\ \ Office of Air Quality Ranning And Standards Research Triangle Ffcrk, NC 27711 EPA-454/R-98-011 •June 1998 United States Environmental Protection Agency ^ EPA LOCATING AND ESTIMATING AIR EMISSIONS FROM Disclaimer This report has been reviewed by the Office of Air Quality Planning and Standards, U.S. Environmental Protection Agency, and has been approved for publication. Mention of trade names and commercial products does not constitute endorsement or recommendation of use. EPA-454/R-98-011 v 11 TABLE OF CONTENTS Section Page LIST OF TABLES.x LIST OF FIGURES. xvi EXECUTIVE SUMMARY .xx 1.0 PURPOSE OF DOCUMENT. 1-1 2.0 OVERVIEW OF DOCUMENT CONTENTS . 2-1 3.0 BACKGROUND INFORMATION.. 3-1 3.1 NATURE OF POLLUTANT. 3-1 3.2 OVERVIEW OF PRODUCTION AND USE. 3-4 3.3 OVERVIEW OF EMISSIONS . 3-8 4.0 EMISSIONS FROM BENZENE PRODUCTION. 4-1 4.1 CATALYTIC REFORMING/SEPARATION PROCESS. 4-7 4.1.1 Process Description for Catalytic Reforming/Separation. 4-7 4.1.2 Benzene Emissions from Catalytic Reforming/Separation. 4-9 4.2 TOLUENE DEALKYLATION AND TOLUENE DISPROPORTIONATION PROCESS . 4-11 4.2.1 Toluene Dealkylation . 4-12 4.2.2 Toluene Disproportionation . 4-13 4.3 ETHYLENE PRODUCTION. 4-16 4.3.1 Process Description . 4-16 4.3.2 Benzene Emissions from Ethylene Plants and Benzene Recovery from Pyrolysis Gasoline. 4-32 4.4 COKE OVEN AND COKE BY-PRODUCT RECOVERY PLANTS . . . 4-36 4.4.1 Process Description . 4-36 4.4.2 Benzene Emissions. 4-46 Cj^lWS% 111 TABLE OF CONTENTS, continued Section Page 4.5 METHODS FOR ESTIMATING BENZENE EMISSIONS FROM EMISSION SOURCES...’. 4-61 4.5.1 Process Vent Emissions, Controls, and Regulations. 4-62 4.5.2 Equipment Leak Emissions, Controls, and Regulations . 4-70 4.5.3 Storage Tank Emissions, Controls, and Regulations. 4-77 4.5.4 Wastewater Collection and Treatment System Emissions, Controls, and Regulations . 4-82 4.5.5 Product Loading and Transport Operations Emissions, Controls, and Regulations. 4-85 5.0 EMISSIONS FROM MAJOR USES OF BENZENE. 5-1 5.1 ETHYLBENZENE AND STYRENE PRODUCTION. 5-2 5.1.1 Process Description for Ethylbenzene and Styrene Production Using Benzene Alkylation and Ethylbenzene Dehydrogenation .... 5-3 5.1.2 Process Description for Ethylbenzene Production from Mixed Xylenes . 5-9 5.1.3 Process Description for Styrene Production from Ethylbenzene Hydroperoxidation. 5-10 5.1.4 Process Description for Styrene Production by an Isothermal Process. 5-12 5.1.5 Benzene Emissions from Ethylbenzene and Styrene Production via Alkylation and Dehydrogenation. 5-14 5.1.6 Control Technology for Ethylbenzene/Styrene Processes . 5-19 5.2 CYCLOHEXANE PRODUCTION. 5-20 5.2.1 Process Description for Cyclohexane Production via Benzene Hydrogenation... 5-21 5.2.2 Benzene Emissions from Cyclohexane Production via Benzene Hydrogenation. 5-23 5.2.3 Process Description for Cyclohexane Production via Separation of Petroleum Fractions . 5-24 5.2.4 Benzene Emissions from Cyclohexane Production via Separation of Petroleum Fractions . 5-26 5.3 CUMENE PRODUCTION . 5_26 5.3.1 Process Descriptions for Cumene Production by Alkylating Benzene with Propylene. 5_27 5.3.2 Benzene Emissions From Cumene Production . 5-34 IV TABLE OF CONTENTS, continued Section Page 5.4 PHENOL PRODUCTION. 5-35 5.4.1 Phenol Production Techniques .. 5-39 5.4.2 Benzene Emissions from Phenol Production. 5-47 5.5 NITROBENZENE PRODUCTION. 5-49 5.5.1 Process Descriptions for Continuous Nitration.. 5-49 5.5.2 Benzene Emissions from Nitrobenzene Production .'. 5-53 5.6 ANILINE PRODUCTION. 5-58 5.6.1 Process Descriptions for Aniline Production for Nitrobenzene ... 5-58 5.6.2 Benzene Emissions from Aniline Production . 5-61 5.7 CHLOROBENZENE PRODUCTION. 5-62 5.7.1 Process Description for Chlorobenzene Production by Direct Chlorination of Benzene. 5-62 5.7.2 Benzene Emissions from Chlorobenzene Production . 5-67 5.8 LINEAR ALKYLBENZENE PRODUCTION. 5-70 5.8.1 Process Description for Production of LAB Using the Olefin Process .. 5-70 5.8.2 Benzene Emissions from LAB Production Using the Olefm Process. 5-74 5.8.3 Process Description for Production of LAB Using the Chlorination Process. 5-74 5.8.4 Benzene Emissions from LAB Production Using the Chlorination Process. 5-78 5.9 OTHER ORGANIC CHEMICAL PRODUCTION. 5-80 5.9.1 Hvdroquinone . 5-80 5.9.2 Benzophenone. 5-81 5.9.3 Benzene Sulfonic Acid. 5-81 5.9.4 Resorcinol . 5-81 5.9.5 Biphenyl. 5-82 5.9.6 Anthraquinone. 5-82 5.10 BENZENE USE AS A SOLVENT .:. 5-82 6.0 EMISSIONS FROM OTHER SOURCES. 6-1 6.1 OIL AND GAS WELLHEADS. 6-1 v TABLE OF CONTENTS, continued Section Esge 6.1.1 Description of Oil and Gas Wellheads. 6-1 6.1.2 Benzene Emissions from Oil and Gas Wellheads. 6-2 6.2 GLYCOL DEHYDRATION UNITS. 6-4 6.2.1 Process Description for Glycol Dehydration Units. 6-5 6.2.2 Benzene Emissions from Glycol Dehydration Units ........... 6-8 6.2.3 Controls and Regulatory Analysis . 6-13 6.3 PETROLEUM REFINERY PROCESSES. 6-14 6.3.1 Description of Petroleum Refineries. 6-14 6.3.2 Benzene Emissions from Petroleum Refinery Processes and Operations . 6-17 6.3.3 Controls and Regulatory Analysis . 6-28 6.4 GASOLINE MARKETING. 6-31 6.4.1 Benzene Emissions from Loading Marine Vessels. 6-34 6.4.2 Benzene Emissions from Bulk Gasoline Plants and Bulk Gasoline Terminals. 6-37 6.4.3 Benzene Emissions from Service Stations . 6-46 6.4.4 Control Technology for Marine Vessel Loading. 6-49 6.4.5 Control Technology for Gasoline Transfer. 6-53 6.4.6 Control Technology for Gasoline Storage . 6-53 6.4.7 Control Technology for Vehicle Refueling Emissions .. 6-56 6.4.8 Regulatory Analysis . 6-58 6.5 PUBLICLY OWNED TREATMENT WORKS . 6-59 6.5.1 Process Description of POTWs. 6-59 6.5.2 Benzene Emissions From POTWs ... 6-68 6.5.3 Control Technologies for POTWs . 6-69 6.5.4 Regulatory Analysis . 6-72 6.6 MUNICIPAL SOLID WASTE LANDFILLS. 6-72 6 .6.1 Process Description of MSW Landfills. 6-73 6.6.2 Benzene Emissions from MSW Landfills. 6-74 6.6.3 Control Technologies for MSW Landfills . 6-80 6.6.4 Regulatory Analysis . 6-81 6.7 PULP, PAPER, AND PAPERBOARD INDUSTRY. 6-81 6.7.1 Process Description for Pulp, Paper, and Paperboard Making Processes . 6 _g 2 6.7.2 Benzene Emissions from Pulp, Paper and Papermaking Processes 6-91 vi TABLE OF CONTENTS, continued Section Page 6.8 SYNTHETIC GRAPHITE MANUFACTURING. 6-93 6.8.1 Process Description for Synthetic Graphite Production. 6-94 6.8.2 Benzene Emissions from Synthetic Graphite Production. 6-97 6.8.3 Control Technologies for Synthetic Graphite Production. 6-99 6.9 CARBON BLACK MANUFACTURE. 6-99 6.9.1 Process Description for Carbon Black Manufacture.6-101 6.9.2 Benzene Emissions from Carbon Black Manufacture.6-104 6 .10 RAYON-BASED CARBON FIBER MANUFACTURE.6-105 6.10.1 Process Description for the Rayon-Based Carbon Fiber Manufacturing Industry.6-106 6.10.2 Benzene Emissions from the Rayon-Based Carbon Fiber Manufacturing Industry.6-107 6.10.3 Controls and Regulatory Analysis .6-107 6.11 ALUMINUM CASTING . . ..6-107 6.11.1 Process Description for Aluminum Casting Facilities.6-107 6.11.2 Benzene Emissions From Aluminum Metal Casting.6-111 6.11.3 Control Technologies for Aluminum Casting Operations .6-112 6.12 ASPHALT ROOFING MANUFACTURING.6-112 6.12.1 Process Description .6-114 6.12.2 Benzene Emissions from Asphalt Roofmg Manufacture .6-127 6.13 CONSUMER PRODUCTS/BUILDING SUPPLIES .6-129 7.0 EMISSIONS FROM COMBUSTION SOURCES. 7-1 7.1 MEDICAL WASTE INCINERATORS. 7-1 7.1.1 Process Description: Medical Waste Incinerators. 7-2 7.1.2 Benzene Emissions From Medical Waste Incinerators . 7-7 7.1.3 Control Technologies for Medical Waste Incinerators . 7-7 7.1.4 Regulatory Analysis . 7-9 7.2 SEWAGE SLUDGE INCINERATORS . 7-10 7.2.1 Process Description: Sewage Sludge Incinerators. 7-11 7.2.2 Benzene Emissions from Sewage Sludge Incineration. 7-19 7.2.3 Control Technologies for Sewage Sludge Incinerators . 7-19 7.2.4 Regulatory Analysis . 7-25 Vll TABLE OF CONTENTS, continued Section Page 7.3 HAZARDOUS WASTE INCINERATION. 7-25 7.3.1 Process Description: Incineration 7-26 7.3.2 Industrial Kilns, Boilers, and Furnaces. 7-36 7.3.3 Benzene Emissions From Hazardous Waste Incineration. 7-37 7.3.4 Control Technologies for Hazardous Waste Incineration. 7-37 7.3.5 Regulatory Analysis . 7-39 7.4 EXTERNAL COMBUSTION OF SOLID, LIQUID, AND GASEOUS FUELS IN STATIONARY SOURCES FOR HEAT AND POWER GENERATION. 7-40 7.4.1 Utility Sector. 7-40 7.4.2 Industrial/Commercial Sector. 7-51 7.4.3 Residential Sector. 7-59 7.5 STATIONARY INTERNAL COMBUSTION . 7-67 7.5.1 Reciprocating Engines. 7-67 7.5.2 Gas Turbines. 7-74 7.6 SECONDARY LEAD SMELTING. 7-79 7.6.1 Process Description . 7-79 7.6.2 Benzene Emissions From Secondary Lead Smelters. 7-91 7.6.3 Control Technologies for Secondary Lead Smelters. 7-95 7.7 IRON AND STEEL FOUNDRIES . 7-95 7.7.1 Process Description for Iron and Steel Foundries . 7-97 7.7.2 Benzene Emissions From Iron and Steel Foundries .7-100 7.7.3 Control Technologies for Iron and Steel Foundries .7-102 7 8 POPTLAND CEMENT PRODUCTION.7-IQ? 7.8.1 Process Description for the Portland Cement Industry .7-104 7.8.2 Benzene Emissions from the Portland Cement Industry and Regulatory Analysis .7-107 7.9 HOT-MIX ASPHALT PRODUCTION. 7 _ 110 7.9.1 Process Description .7-110 7.9.2 Benzene Emissions from the Hot-Mix Asphalt Production.7-119 7.10 OPEN BURNING OF BIOMASS, SCRAP TIRES, AND AGRICULTURAL PLASTIC FILM . 7 _ 121 7.10.1 Biomass Burning . 7-121 7.10.2 Tire Burning. 7-125 7.10.3 Agricultural Plastic Film Burning .7-129 viii TABLE OF CONTENTS, continued Section Page 8.0 BENZENE EMISSIONS FROM MOBILE SOURCES . 8-1 8.1 ON-ROAD MOBILE SOURCES. 8-2 8.2 OFF-ROAD MOBILE SOURCES. 8-5 8.3 MARINE VESSELS. 8-10 8.4 LOCOMOTIVES. 8-13 8.5 AIRCRAFT . 8-14 8.6 ROCKET ENGINES . 8-15 9.0 SOURCE TEST PROCEDURES . 9-1 9.1 EPA METHOD 0030 . 9-2 9.2 EPA METHODS 5040/5041 . 9-4 9.3 EPA METHOD 18. 9-5 9.4 EPA METHOD TO-1. 9-8 9.5 EPA METHOD TO-2. 9-9 9.6 EPA METHOD TO-14. 9-14 9.7 FEDERAL TEST PROCEDURE (FTP). 9-16 9.8 AUTO/OIL AIR QUALITY IMPROVEMENT RESEARCH PROGRAM SPECIATION METHOD. 9-18 10.0 REFERENCES. 10-1 APPENDICES Appendix A Summary of Emission Factors Appendix B United States Petroleum Refineries: Location by State IX ' ' . ■ ' ■ LIST OF TABLES Table Page 3-1 Chemical Identification of Benzene. 3-2 3- 2 Physical and Chemical Properties of Benzene . 3-3 4- 1 Benzene Production Facilities. 4-2 4-2 Ethylene Producers - Location and Capacity. 4-17 4-3 Stream Designations for Figure 4-5, Production of Ethylene from Naphtha and/or Gas-oil Feeds . 4-24 4-4 Benzene Emission Factors for a Hypothetical Ethylene Plant . 4-33 4-5 Coke Oven Batteries Currently Operating in the United States. 4-38 4-6 Summary of Benzene Emission Factors for Furnace and Foundry Coke By-product Recovery Plants. 4-51 4-7 Summary of Benzene Emission Factors for Equipment Leaks at Furnace Coke By-product Recovery Plants. 4-54 4-8 Summary of Benzene Emission Factors for Equipment Leaks at Foundry Coke By-product Recovery Plants . 4-56 4-9 Techniques to Control Benzene Emissions from Equipment Leaks Required by the Benzene NESHAP for Coke By-product Control Recovery Plants. 4-61 4-10 Control Technologies that Form the Basis of Air Pollution Control Standards .. 4-63 4-11 Other Control Technologies that Can be Used to Meet Standards. 4-64 4-12 Comparison of VOC Control Technologies. 4-68 4-13 SOCMI Average Total Organic Compound Emission Factors for Equipment Leak Emissions.,. 4-72 4-14 Refinery Average Emission Factors. 4-73 4-15 Marketing Terminal Average Emission Factors . 4-74 4-16 Oil and Gas Production Operations Average Emission Factors . 4-75 x LIST OF TABLES, continued Table Page 4-17 SOCMI Screening Value Range Total Organic Compound Emission Factors for Equipment Leak Emissions . 4-76 4-18 Refinery Screening Ranges Emission Factors. 4-77 4-19 Marketing Terminal Screening Ranges Emission Factors. 4-78 4-20 Oil and Gas Production Operations Screening Ranges Emission Factors . 4-79 4- 21 Control Techniques and Efficiencies Applicable to Equipment Leak Emissions . . 4-80 5- 1 U.S. Producers of Ethylbenzene and Styrene. 5-4 5-2 Emission Factors for Ethylbenzene/Styrene Production via Alkylation and Dehydrogenation. 5-15 5-3 U.S. Producers of Cyclohexane . 5-21 5-4 U.S. Producers of Cumene . 5-27 5-5 Summary of Emission Factors for Cumene Production at One Facility Using the Aluminum Chloride Catalyst . 5-36 5-6 U.S. Producers of Phenol . 5.37 5-7 Summary of Emission Factors for Phenol Production by the Peroxidation of Cumene...;. 5 _ 4 g 5-8 U.S. Producers of Nitrobenzene. 5_50 5-9 Summary of Emission Factors for Hypothetical Nitrobenzene Production Plants . 5-54 5-10 U.S. Producers of Aniline. 5.59 5-11 U.S. Producers of Mono-, Di-, and Trichlorobenzene. 5-63 5-12 Emission Factors for Chlorobenzene Production by Direct Chlorination of Benzene. ^ 5-13 U.S. Producers of Linear Alkylbenzene (Detergent Alkylates) . 5.71 xi LIST OF TABLES, continued Table Page 5-14 Summary of Emission Factors for Hypothetical Linear Alkylbenzene Plant Using the Olefin Process. 5-75 5-15 Summary of Emission Factors for Hypothetical Linear Alkylbenzene Plant Using the Chlorination Process. 5-79 5-16 Partial List of Manufacturers in Source Categories where Benzene Is Used as a Solvent . 5-84 5-17 U.S. Producers of Ethanol or Isopropanol. 5-86 5-18 U.S. Producers of Caprolactam . 5-89 5- 19 Summary of Emission Factors for Benzene Use as a Solvent. 5-90 6- 1 Benzene and Total Hydrocarbons Equipment Leak Emission Factors for Oil Wellhead Assemblies . 6-3 6-2 Glycol Dehydration Unit Population Data. 6-6 6-3 Reactive Organic Compounds (ROCs) and BTEX Emission Factors for Glycol Dehydration Units. 6-9 6-4 Glycol Dehydration Emission Program Inputs and Outputs. 6-12 6-5 Potential Sources of Benzene Emissions at Petroleum Refineries. 6-18 6-6 Concentration of Benzene in Refinery Process Unit Streams. 6-19 6-7 Concentration of Benzene m Refinery Products . 6-20 6-8 Median Component Counts for Process Units from Small Refineries . 6-22 6-9 Median Component Counts for Process Units from Large Refineries . 6-23 6-10 Model Process Unit Characteristics for Petroleum Refinery Wastewater. 6-25 6-11 Wastewater Emission Factors for Petroleum Refineries. 6-27 6-12 Uncontrolled Volatile Organic Compound and Benzene Emission Factors for Loading, Ballasting, and Transit Losses from Marine Vessels. 6-35 Xll LIST OF TABLES, continued Table Page 6-13 Uncontrolled Total Organic Compound Emission Factors for Petroleum Marine Vessel Sources ... 6-36 6-14 Benzene Emission Factors for Gasoline Loading Racks at Bulk Terminals and Bulk Plants.. 6-38 6-15 Benzene Emission Factors for Storage Losses at a Typical Gasoline Bulk Terminal . 6-41 6-16 Gasoline Vapor and Benzene Emission Factors for a Typical Bulk Plant. 6-43 6-17 Benzene Emission Factors for Storage Losses at a Typical Pipeline Breakout Station 6-44 6-18 Gasoline Vapor and Benzene Emission Factors for a Typical Service Station ... 6-48 6-19 RVP Limits by Geographic Location. 6-50 6-20 Seasonal Variation for Temperature Difference between Dispensed Fuel and Vehicle Fuel Tank. 6-52 6-21 Monthly Average Dispensed Liquid Temperature. 6-52 6-22 Summary of Benzene Emission Factors for POTWs . 6-70 6-23 Summary of Uncontrolled Emission Concentrations of Benzene from Landfills . . 6-77 6-24 Controlled Benzene Emission Factor for Landfills . 6-81 6-25 Distribution of Kraft Pulp Mills in the United States (1993) . 6-83 6-26 List of Common Potential Emission Points within the Kraft Pulp and Papermaking Process . 6 _g 4 6-27 Emission Factors for Synthetic Graphite Production. 6-98 6-28 Locations and Annual Capacities of Carbon Black Producers in 1994 . 6-100 6-29 Stream Codes for the Oil-Furnace Process Illustrated in Figure 6-10 .6-103 6-30 Typical Operating Conditions for Carbon Black Manufacture (High Abrasion Furnace ) .6-105 Xlll LIST OF TABLES, continued Table Page 6-31 Emission Factor for Carbon Black Manufacture.6-105 6-32 Rayon-based Carbon Fiber Manufacturers.6-106 6-33 Emission Factor for Rayon-based Carbon Manufacture.6-108 6-34 Emission Factors for Aluminum Casting.6-113 6-35 Asphalt Roofmg Manufacturers .6-115 6- 36 Emission Factor for Asphalt Roofmg Manufacture.6-128 7- 1 Emission Factor for Medical Waste Incineration. 7-8 7-2 Summary of Emission Factors for Sewage Sludge Incineration . 7-20 7-3 Summary of Emission Factors for One Sewage Sludge Incineration Facility Utilizing a Multiple Hearth Furnace. 7-21 7-4 Summary of Benzene Emission Factors for Hazardous Waste Incineration. 7-38 7-5 Summary of Benzene Emission Factors for Utility Boilers. 7-50 7-6 Summary of Benzene Emission Factors for Industrial and Commercial/Institutional Boilers. 7-57 7-7 Summary of Benzene Emission Factors for Residential Woodstoves. 7-66 7-8 Summary of Benzene Emission Factors for Reciprocating Engines. 7-73 7-9 Summary of Benzene Emission Factors for Gas Turbines. 7-77 7-10 U.S. Secondary Lead Smelters. 7-80 7-11 Summary of Benzene Emission Factors for Secondary Lead Smelting. 7-94 7-12 Benzene Emission Factor for Iron Foundries.7-101 7-13 Summary of Portland Cement Plant Capacity Information .7-105 7-14 Summary of Emission Factors for the Portland Cement Industry.7-109 xiv LIST OF TABLES, continued Table Page 7-15 Emission Factors for Hot-Mix Asphalt Manufacture.,.7-120 7-16 Summary of Benzene Emission Factors for Biomass Burning .7-124 7-17 Summary of Benzene Emission Factors for Biomass Burning by Fuel Type .... 7-126 7-18 Summary of Benzene Emission Factors for Open Burning of Tires.7-128 7- 19 Summary - of Benzene Emission Factors for Open Burning of Agricultural Plastic Film.7-130 8- 1 Benzene Emission Factors for 1990 Taking into Consideration Vehicle Aging ... 8-4 8-2 Off-road Equipment Types and Hydrocarbon Emission Factors Included in the NEVES. 8-6 8-3 Weight Percent Factors for Benzene . . . 8-11 8-4 Benzene Emission Factors for Commercial Marine Vessels . 8-12 8-5 Benzene Emission Factors for Locomotives. 8-13 8-6 Benzene Content in Aircraft Landing and Takeoff Emissions . 8-14 8-7 Emission Factors for Rocket Engines. 8-16 xv LIST OF FIGURES Figure Pa ge 3- 1 Production and Use Tree for Benzene . 3-7 4- 1 Universal Oil Products Platforming (Reforming) Process. 4-8 4-2 Flow Diagram of a Glycol BTX Unit Process . 4-10 4-3 Process Flow Diagram of a Toluene Dealkylation Unit . 4-14 4-4 Toluene Disproportionation Process Flow Diagram (Tatory Process). 4-15 4-5 Process Flow Diagram for Ethylene Production from Naphtha and/or Gas-Oil Feeds . 4-22 4-6 Production of BTX by Hydrogenation of Pyrolysis Gasoline. 4-31 » 4-7 Coke Oven By-Product Recovery, Representative Plant. 4-41 4- 8 Litol Process Flow Diagram. 4-45 5- 1 Basic Operations that May be used in the Production of Ethylbenzene by Benzene Alkylation with Ethylene. 5-6 5-2 Basic Operations that May be used in the Production of Styrene by Ethylbenzene Dehydrogenation. 5-8 5-3 Ethylbenzene Hydroperoxidation Process Block Diagram. 5-11 5-4 Isothermal Processing of Styrene. 5-13 5-5 Process Flow Diagram for Cyclohexane Production using the Benzene Hydrogenation Process. 5-22 5-6 Process Flow Diagram for Cyclohexane from Petroleum Fractions. 5-25 5-7 Process for the Manufacture of Cumene Using Solid Phosphoric Acid Catalyst . . 5-29 5-8 Process for the Manufacture of Cumene Using Aluminum Chloride Catalyst ... 5-31 5-9 Flow Diagram for Phenol Production from Cumene Using the Allied Process . . 5-40 5-10 Flow Diagram for Phenol Production Using the Hercules Process. 5-44 xvi LIST OF FIGURES, continued Figure Page 5-11 Process Flow Diagram for Manufacture of Nitrobenzene. 5-51 5-12 Flow Diagram for Manufacture of Aniline . 5-60 - 5-13 Monochlorobenzene Continuous Production Process Diagram.. 5-64 5-14 Dichlorobenzene and Trichlorobenzene Continuous Production Diagram. 5-66 5-15 Linear Alkylbenzene Production Using the Olefm Process. 5-73 5- 16 Production of Linear Alkylbenzenes Via Chlorination. 5-76 6- 1 Flow Diagram for Glycol Dehydration Unit . 6-7 6-2 Process Flow Diagram for a Model Petroleum Refinery . . . . ; . 6-16 6-3 The Gasoline Marketing Distribution System in the United States . 6-32 6-4 Bulk Plant Vapor Balance System (Stage I). 6-54 6-5 Service Station Vapor Balance System. 6-55 6-6 Process Flow Diagram for a Typical POTW. 6-61 6-7 Typical Kraft Pulp-Making Process with Chemical Recovery . 6-85 6-8 Typical Down-flow Bleach Tower and Washer . 6-92 6-9 Process Flow Diagram for Manufacture of Synthetic Graphite a . 6-95 6-10 Process Flow Diagram for an Oil-furnace Carbon Black Plant.6-102 6-11 Flow Diagram of a Typical Aluminum Casting Facility.6-109 6-12 Asphalt Blowing Process Flow Diagram.6-119 6-13 Asphalt-Saturated Felt Manufacturing Process.6-122 6-14 Organic Shingle and Roll Manufacturing Process Flow Diagram. 6-123 XVII LIST OF FIGURES, continued Figure Page 7-1 Controlled-Air Incinerator. 7-3 7-2 Excess-Air Incinerator . 7-5 7-3 Cross Section of a Multiple Hearth Furnace . 7-12 7-4 Cross Section of a Fluidized Bed Furnace. 7-14 7-5 Cross Section of an Electric Infrared Furnace . 7-17 7-6 Venturi/Impingement Tray Scrubber . 7-23 7-7 General Orientation of Hazardous Waste Incineration Subsystems and Typical Component Options . 7-27 7-8 Typical Liquid Injection Combustion Chamber . 7-30 7-9 Typical Rotary Kiln/Afterburner Combustion Chamber. 7-32 7-10 Typical Fixed Hearth Combustion Chamber . 7-33 7-11 Simplified Boiler Schmatic. 7-42 7-12 Single Wall-fired Boiler . 7-44 7-13 Cyclone Burner. 7-46 7-14 Simplified Atmospheric Fluidized Bed Combustor Process Flow Diagram. 7-47 7-15 Spreader Type Stoker-fired Boiler - Continuous Ash Discharge Grate. 7-48 7-16 Basic Operation of Reciprocating Internal Combustion Engines. 7-69 7-17 Gas Turbine Engine Configuration . 7-75 7-18 Simplified Process Flow Diagram for Secondary Lead Smelting . 7-81 7-19 Cross-sectional View of a Typical Stationary Reverberatory Furnace. 7-84 * 7-20 Cross Section of a Typical Blast Furnace . 7-86 xvm LIST OF FIGURES, continued Fi gure Page 7-21 Side-View of a Typical Rotary Reverbatory Furnace. 7-89 7-22 Cross-sectional View of an Electric Furnace for Processing Slag. 7-92 7-23 Process Flow Diagram for a Typical Sand-Cast Iron and Steel Foundry . 7-98 7-24 Emission Points in a Typical Iron Foundry and Steel Foundry. 7-99 7-25 Process Diagram of Portland Cement Manufacture by Dry Process with Preheater.7-108 7-26 General Process Flow Diagram for Batch Mix Asphalt Paving Plants.7-113 7-27 General Process Flow Diagram for Drum Mix Asphalt Paving Plants.7-116 7-28 General Process Flow Diagram for Counter Flow Drum Mix Asphalt Paving Plants .7-117 9-1 Volatile Organic Sampling Train (VOST). 9-3 9-2 Trap Desorption/Analysis Using EPA Methods 5040/5041 . 9-6 9-3 Integrated Bag Sampling Train. 9-7 9-4 Block Diagram of Analytical System for EPA Method TO-1. 9-10 9-5 Typical Tenax® Cartridge . 9-11 9-6 Carbon Molecular Sieve Trap (CMS) Construction. 9-12 9-7 GC/MS Analysis System for CMS Cartridges . 9-13 9-8 Sampler Configuration for EPA Method TO-14. 9-15 9-9 Vehicle Exhaust Gas Sampling System. 9_17 xix EXECUTIVE SUMMARY The 1990 Clean Air Act Amendments contain a list of 188 hazardous air pollutants (HAPs) which the U.S. Environmental Protection Agency must study, identify sources of, and determine if regulations are warranted. One of these HAPs, benzene, is the subject of this document. This document describes the properties of benzene as an air pollutant, defmes its production and use patterns, identifies source categories of air emissions, and provides benzene emission factors. The document is a part of an ongoing EPA series designed to assist the general public at large, but primarily State/local air agencies, in identifying sources of HAPs and developing emissions estimates. Benzene is primarily used in the manufacture of other organic chemicals, including ethylbenzene/styrene, cumene/phenol, cyclohexane, and nitrobenzene/aniline. Benzene is emitted into the atmosphere from its production, its use as a chemical feedstock in the production of other chemicals, the use of those other chemicals, and from fossil fuel and biomass combustion. Benzene is also emitted from a wide variety of miscellaneous sources including oil and gas wellheads, glycol dehydrators, petroleum refining, gasoline marketing, wastewater treatment, landfills, pulp and paper mills, and from mobile sources. In addition to identifying sources of benzene emissions, information is provided that specifies how’ individual sources of benzene may be tested to quantify- air emissions. xx ' . ’ ■ . * . SECTION 1.0 PURPOSE OF DOCUMENT The U.S. Environmental Protection Agency (EPA), State, and local air pollution control agencies are becoming increasingly aware of the presence of substances in the ambient air that may be toxic at certain concentrations. This awareness, in turn, has led to attempts to identify source/receptor relationships for these substances and to develop control programs to regulate emissions. Unfortunately, limited information is available on the ambient air concentrations of these substances or about the sources that may be discharging them to the atmosphere. To assist groups interested in inventorying air emissions of various potentially toxic substances, EPA is preparing a series of locating and estimating (L&E) documents such as this one that compiles available information on sources and emissions of these substances. Other documents in the series are listed below: Substance Acrylonitrile Arsenic Butadiene Cadmium Carbon Tetrachloride Chlorobenzene (update) Chloroform Chromium (supplement) Chromium EPA Publication Number EPA-450/4-84-007a (Document under revision) EPA-454/R-96-008 EPA-454/R-93-040 EPA-450/4-84-007b EPA-454/R-93-044 EPA-450/4-84-007c EPA-450/2-89-002 EPA-450/4-84-007g 1-1 Substance F.PA Publication Nun Coal and Oil Combustion Sources EPA-450/2-89-001 Cyanide Compounds EPA-454/R-93-041 Dioxins and Furans EPA-454/R-97-003 Epichlorohydrin EPA-450/4-84-007j Ethylene Dichloride EPA-450/4-84-007d Ethylene Oxide EPA-450/4-84-0071 Formaldehyde EPA-450/4-91-012 Lead EPA-454/R-98-006 Manganese EPA-450/4-84-007h Medical Waste Incinerators EPA-454/R-93-053 Mercury and Mercury Compounds (under revision) EPA-453/R-93-023 Methyl Chloroform EPA-454/R-93-045 Methyl Ethyl Ketone EP A-454/R-93-046 Methylene Chloride EPA-454/R-93-006 Municipal Waste Combustors EPA-450/2-89-006 Nickel EPA-450/4-84-007f Perchloroethylene and Trichloroethylene EP A-450/2-89-013 Phosgene EP A-450/4-84-007i Polychlorinated Biphenyls (PCBs) EPA-450/4-84-007n Polycyclic Organic Matter (POM) EPA-450/4-84-007p Sewage Sludge Incinerators EPA-450/2-90-009 Styrene EPA-454/R-93-011 Toluene • EPA-454/R-93-047 Vinylidene Chloride EPA-450/4-84-007k Xylenes EPA-454/R-93-048 This document deals specifically with benzene. Its intended audience includes Federal, State, and local air pollution personnel and others who are interested in locating potential emitters of benzene and estimating their air emissions. 1-2 Because of the limited availability of data on potential sources of benzene emissions and the variability in process configurations, control equipment, and operating procedure among facilities, this document is best used as a primer on (1) types of sources that may emit benzene, (2) process variations and release points that may be expected, and (3) available emissions information on the potential for benzene releases into the air. The reader is cautioned against using the emissions information in this document to develop an ' exact assessment of emissions from any particular facility. Emission estimates may need to be adjusted to take into consideration participation in EPA’s voluntary emission reduction program or compliance with State or local regulations. It is possible, in some cases, that orders-of-magnitude differences may result between actual and estimated emissions, depending on differences in source configurations, control equipment, and operating practices. Thus, in all situations where an accurate assessment of benzene emissions is necessary, the source-specific information should be obtained to confirm the existence of particular emitting operations and the types and effectiveness of control measures, and to determine the impact of operating practices. A source test and/or material balance calculation should be considered as better methods of determining air emissions from a specific operation. In addition to the information presented in this document, another potential source of emissions data for benzene from facilities is the Toxic Chemical Release Inventory (TRI) form required by Title III, Section 313 of the 1986 Superfund Amendments and Reauthorization Act (SARA). 1 Section 313 requires owners and operators of facilities in certain Standard Industrial Classification Codes that manufacture, import, process, or otherwise use toxic chemicals (as listed in Section 313) to report annually their releases of these chemicals to all environmental media. As part of SARA 313, EPA provides public access to the annual emissions data. 1-3 The TRI data include general facility information, chemical information, and emissions data. Air emissions data are reported as total facility release estimates for fugitive emissions and point source emissions. No individual process or stack data are provided to EPA under the program. SARA Section 313 requires sources to use available stack monitoring data for reporting but does not require facilities to perform stack monitoring or other types of emissions measurement. If monitoring data are unavailable, emissions are to be quantified ' based on best estimates of releases to the environment. The reader is cautioned that TRI will not likely provide facility, emissions, and chemical release data sufficient for conducting detailed exposure modeling and risk assessment. In many cases, the TRI data are based on annual estimates of emissions (i.e., on emission factors, material balance calculations, and engineering judgment). The EPA recommends use of TRI data in conjunction with the information provided in this document to locate potential emitters of benzene and to make preliminary estimates of air emissions from these facilities. For mobile sources, more data are becoming available for on-road vehicles. Additionally, the EPA model that generates emission factors undergoes regular update. The on-road mobile sources section in this document should therefore be viewed as an example of how emissions can be determined and the reader should look for more detailed data for the most accurate estimates. Data on off-road vehicles and other stationary sources remain unavailable. However, with EPA’s increased emphasis on air toxics, more benzene data are likely to be generated in the future. As standard procedure, L&E documents are sent to government, industry, and environmental groups wherever EPA is aware of expertise. These groups are given the opportunity to review a document, comment, and provide additional data where applicable. Where necessary, the document is then revised to incorporate these comments. Although this document has undergone extensive review, there may still be shortcomings. Comments 1-4 subsequent to publication are welcome and will be addressed based on available time and resources. In addition, any information on process descriptions, operating parameters, control measures, and emissions information that would enable EPA to improve on the contents of this document is welcome. All comments should be sent to: Group Leader Emission Factor and Inventory Group (MD-14) Office of Air Quality Planning and Standards U. S. Environmental Protection Agency Research Triangle Park, North Carolina 27711 1-5 . - ' SECTION 2.0 OVERVIEW OF DOCUMENT CONTENTS This section briefly outlines the nature, extent, and format of the material presented in the remaining sections of this report. Section 3.0 provides a brief summary of the physical and chemical characteristics of benzene and an overview of its production, uses, and emissions sources. This background section may be useful to someone who needs to develop a general perspective on the nature of benzene, how it is manufactured and consumed, and sources of emissions. Section 4.0 focuses on the production of benzene and the associated air emissions. For each major production source category described in Section 4.0, an example process description and a flow diagram(s) with potential emission points are given. Available emissions estimates are used to calculate emission factors that show the potential for benzene emissions before and after controls employed by industry. Also provided are estimates of emissions from process vents, equipment leaks, storage tanks, and wastewater. Individual companies that are reported in trade publications to produce benzene are named. Section 5.0 describes major source categories that use benzene as a feedstock to produce industrial organic chemicals. For each major production process, a description(s) of the process is given along with a process flow diagram(s). Potential emission points are identified on the diagrams and emission ranges are presented, where available. Individual companies that use benzene as a feedstock are reported. 2-1 Section 6.0 describes emission sources where benzene is emitted as the by-product of a process (such as petroleum refineries) and post-manufacturing activities where releases from benzene-containing products may occur (such as from gasoline distribution). Example process descriptions and flow diagrams are provided in addition to available emission factors for each major industrial category described in this section. Section 7.0 presents information on stationary combustion sources (such as municipal waste combustors) and area combustion sources (such as open burning). Example incinerator, furnace, or boiler diagrams are given, when appropriate. Emission factors are also given, when available. Section 8.0 provides a brief summary on benzene emissions from mobile sources. This section addresses both on-road and off-road sources. Section 9.0 summarizes available procedures for source sampling and analysis of benzene. This section provides an overview of applicable sampling procedures and cites references for those interested in conducting source tests. Section 10.0 presents a list of all the references Cited in this document. Appendix A presents a summary table of the emission factors contained in this document. This table also presents the factor quality rating and the Source Classification Code (SCC) or Area/Mobile Source (AMS) code associated with each emission factor. Appendix B presents a list of all the petroleum refmeries in the United States. Each emission factor listed in Sections 4.0 through 8.0 was assigned an emission factor rating (A, B, C, D, E, or U), based on the criteria for assigning data quality ratings and emission factor ratings as discussed in the document Procedures for Preparing Emission Factor Documents} The criteria for assigning the data quality ratings are as follows: A - Tests are performed by using an EPA reference test method, or when not applicable, a sound methodology. Tests are reported in enough detail for . 2-2 adequate validation, and, raw data are provided that can be used to duplicate the emission results presented in the report. B - Tests are performed by a generally sound methodology, but lacking enough detail for adequate validation. Data are insufficient to completely duplicate the emission result presented in the report. C - Tests are based on an unproven or new methodology, or are lacking a significant amount of background information. D - Tests are based on generally unacceptable method, but the method may provide an order-of-magnitude value for the source. Once the data quality ratings for the source tests had been assigned, these ratings along with the number of source tests available for a given emission point were evaluated. Because of the almost impossible task of assigning a meaningful confidence limit to industry-specific variables (e.g., sample size vs. sample population, industry and facility variability, method of measurement), the use of a statistical confidence interval for establishing a representative emission factor for each source category was not practical. Therefore, some subjective quality rating was necessary. The following emission factor quality ratings were used in the emission factor tables in this document: A - Excellent. Emission factor is developed primarily from A- and B-rated source test data taken from many randomly chosen facilities in the industry population. The source category population is sufficiently specific to minimize variability. E Above average. Emission factor is developed primarily from A- or B-rated test data from a moderate number of facilities. Although no specific bias is evident, it is not clear if the facilities tested represent a random sample of the industry. As with the A rating, the source category population is sufficiently specific to minimize variability. C - Average. Emission factor is developed primarily from A-, B-, and C-rated test data from a reasonable number of facilities. Although no specific bias is evident, it is not clear if the facilities tested represent a random sample of the industry. As with the A rating, the source category population is sufficiently specific to minimize variability. 2-3 D - Below average. Emission factor is developed primarily form A-, B-, and C-rated test data from a small number of facilities, and there may be reason to suspect that these facilities do not represent a random sample of the industry. There also may be evidence of variability within the source population. E - Poor. Factor is developed from C- rated and D-rated test data from a very few number of facilities, and there may be reasons to suspect that the facilities tested do not represent a random sample of the industry. There also may be evidence of variability within the source category population. U - Unrated (Only used in the L&E documents). Emission factor is developed from source tests which have not been thoroughly evaluated, research papers, modeling data, or other sources that may lack supporting documentation. The data are not necessarily “poor,” but there is not enough information to rate the factors according to the rating protocol. This document does not contain any discussion of health or other environmental effects of benzene, nor does it include any discussion of ambient air levels. 2-4 SECTION 3.0 BACKGROUND INFORMATION 3.1 NATURE OF POLLUTANT Benzene is a clear, colorless, aromatic hydrocarbon that has a characteristic sickly sweet odor. It is both volatile and flammable. Chemical identification information for benzene is found in Table-3-1. Selected physical and chemical properties of benzene are presented in Table 3-2 A 7 Benzene contains 92.3 percent carbon and 7.7 percent hydrogen (by mass). The benzene molecule is represented by a hexagon formed by six sets of carbon and hydrogen atoms bonded together with alternating single and double bonds. H I C 3-1 TABLE 3-1. CHEMICAL IDENTIFICATION OF BENZENE Chemical Name Benzene Synonyms Benzol, phenyl hydride, coal naphtha, phene, benxole, cyclohexatriene Molecular formula C 6 H 6 Identification numbers 3 CAS Registry 71-43-2 NIOSH RTECS CY 1400000 DOT/UN/NA UN 1114; Benzene (Benzol) DOT Designation Flammable liquid Source: References 4 and 5. 2 Chemical Abstract Services (CAS); National Institute of Occupational Safety and Health (NIOSH); Registry of Toxic Effects of Chemical Substances (RTECS); Department of Transportation/United Nations/North American (DOT/UN/NA). The chemical behavior of benzene indicates that the benzene molecule is more realistically represented as a resonance-stabilized structure: in which the carbon-to-carbon bonds are identical. The benzene molecule is the cornerstone tor aromatic compounds, all of which contain one or more benzene rings. 6 Because of its resonance properties, benzene is highly stable for an unsaturated hydrocarbon. However, it does react with other compounds, primarily by substitution and, to a lesser degree, by addition. Some reactions can rupture the molecule or result in other groups cleaving to the molecule. Through all these types of reactions, many commercial chemicals are produced from benzene. 8 The most common commercial grade of benzene contains 50 to 3-2 TABLE 3-2. PHYSICAL AND CHEMICAL PROPERTIES OF BENZENE Property Value Molecular weight 0.17 lbs (78.12 g) Melting point 41.9°F(5.5°C) Boiling point at 1 atmosphere (760 mm Hg) 176.18°F (80.1°C) Density, at 68°F (20°C) 0.0141 lb/ft 3 (0.8794 g/cm 3 ) Physical state (ambient conditions) Liquid Color Clear Odor Characteristic Viscosity (absolute) at 68 °F (20 °C) 0.6468 cP Surface tension at 77°F (25 °C) 0.033 g/cm 3 (28.18 dynes/cm 3 ) Heat of vaporization at 176.18°F (80.100°C) 33.871 KJ/Kg-mol (8095 Kcal/Kg-mol) Heat of combustion at constant pressure and 77 °F (25 °C) (liquid C 6 H 6 to liquid H ; 0 and gaseous C0 2 ) 41.836 KJ/g (9.999 Kcal/g) Odor threshold 0.875 ppm Solubility: Water at 77 °F (25 °C) Very slightly soluble (0.180 g/100 mL, 1800 ppm) Organic Solvents Soluble in alcohol, ether, acetone, carbon tetrachloride, carbon disulfide, and acetic acid Vapor pressure at 77 F (25 C) 95.2 mm Hg (12.7 kPaj Auto ignition temperature 1044°F (562°C) Flashpoint 12°F (-11.1°C) (closed cup) Conversion factors (Vapor weight to volume) 1 ppm = 319 mg/m 3 at 77°F (25°C); 1 mg/L = 313 ppm Source: References 4, 5, 6, and 7. 3-3 100 percent benzene, the remainder consisting of toluene, xylene, and other constituents that distill below 248°F (120°C). 4 Laboratory evaluations indicate that benzene is minimally photochemically reactive in the atmosphere compared to the reactivity of other hydrocarbons. Reactivity can be determined by comparing the influence that different hydrocarbons have on the oxidation rate of nitric oxide (NO) to nitrogen dioxide (N0 2 ), or the relative degradation rate of various hydrocarbons when reacted with hydroxyl radicals (OH), atomic oxygen or ozone. For example, based on the NO oxidation test, the photochemical reactivity rate of benzene was determined to be one-tenth that of propylene and one-third that of n-hexane. 9 Benzene shows long-term stability in the atmosphere. 8 Oxidation of benzene will occur only under extreme conditions involving a catalyst or elevated temperature or pressure. Photolysis is possible only in the presence of sensitizers and is dependent oa wavelength absorption. Benzene does not absorb wavelengths longer than l.lxlO' 5 inches (in) (275 nanometers [nm]). 8 In laboratory evaluation, benzene is predicted to form phenols and ring cleavage products when reacted with OH, and to form quinone and ring cleavage products when reacted with aromatic hydrogen. 6 Other products that are predicted to form from indirect reactions with benzene in the atmosphere include aldehydes, peroxides, and epoxides. Photodegradation of NO_ produces atomic oxygen, which can react with atmospheric benzene to form phenols 9 3.2 OVERVIEW OF PRODUCTION AND USE During the eighteenth century, benzene was discovered to be a component of oil, gas, coal tar, and coal gas. The commercial production of benzene from coal carbonization began in the United States around 1941. It was used primarily as feedstock in the chemical manufacturing industry. 10 For United States industries, benzene is currently produced in the United States, the Virgin Islands, and Puerto Rico by 26 companies at 3-4 36 manufacturing facilities. 11 The majority of benzene production facilities in the United States are found in the vicinity of crude oil sources, predominantly located around the Texas and Louisiana Gulf coast. They are also scattered throughout Kentucky, Pennsylvania, Ohio, Illinois, and New Jersey. 11 Domestic benzene production in 1992 was estimated at 2,350 million gallons (gal) (8,896 million L). 11 Production was expected to increase by approximately 3 to 3.5 percent per year through 1994. Exports of benzene in 1993 were about 23 million gal (87 million L), around 1 percent of the total amount produced in the United States. 12 Benzene is produced domestically by five major processes. 12 Approximately 45 percent of the benzene consumed in the United States is produced by the catalytic reforming/separation process. 11 With this process, the naphtha portion of crude oil is mixed with hydrogen, heated, and sent through catalytic reactors. 13 The effluent enters a separator while the hydrogen is flashed off. 13 The resulting liquid is fractionated and the light ends (Cj to C 4 ) are split. Catalytic reformate, from which aromatics are extracted, is the product. 13 Approximately 22 percent of the benzene produced in the United States is derived from ethylene production. 11 Pyrolysis gasoline is a by-product formed from the steam cracking of natural gas concentrates, heavy naphthas, or gas oils to produce ethylene. 14 Toluene dealkylation or toluene disproportionation processes account for another 25 percent of the United States production of benzene. 11 Toluene dealkylation produces benzene and methane from toluene or toluene-rich hydrocarbons through cracking processes using heat and hydrogen. The process may be either fixed-bed catalyst or thermal. Toluene disproportionation produces benzene and xylenes as co-products from toluene using similar processes. 15 Three percent of benzene produced in the United States is derived from coke oven light oil distillation at coke by-product plants. 11 Light oil is recovered from coke oven 3-5 gas, usually by continuous countercurrent absorption in a high-boiling liquid from which it is stripped by steam distillation. 9 A light oil scrubber or spray tower removes the light oil from coke oven gas. 10 Benzene is recovered from the light oil by a number of processes, including fractionating to remove the lighter and heavier hydrocarbons^ hydrogenation, and conventional distillation. Finally, about 2 percent of benzene produced in the United States is derived as a coproduct from xylene isomerization. 11 Figure 3-1 presents a simplified production and use tree for benzene. Each major production process is shown, along with the percent of benzene derived from each process. The primary uses of benzene and the percentage for each use are also given in the figure. The major use of benzene is still as a feedstock for chemical production, as in the manufacture of ethylbenzene (and styrene). In 1992, the manufacture of ethylbenzene (and styrene) accounted for 53 percent of benzene consumption. 12 Ethylbenzene is formed by reacting benzene with ethylene and propylene using a catalyst such as anhydrous aluminum chloride or solid phosphoric acid. 8 Styrene is the product of dehydrogenation of ethylbenzene. 9 Twenty-three percent of the benzene supply is used to produce cumene. 12 Cumene is produced from benzene alkylation with propylene using solid phosphoric acid as a catalyst. 7 Cumene is oxidized to produce phenols and acetone. 12 Phenol is used to make resins and resin intermediates for epoxies and polycarbonates, and caprolactam for nylon. 12 Acetone is used to make solvents and plastics. 16 Cyclohexane production accounts for 13 percent of benzene use. 12 Cyclohexane is produced by reducing benzene hydrogenated vapors using a nickel catalyst at 392°F (200°C). Almost all of cyclohexane is used to make nylon or nylon intermediates. 17 3-6 Benzene Production Proc©**©* 3-7 The production of nitrobenzene, from which aniline is made, accounts for 5 percent of benzene consumption. Nitrobenzene is produced by the nitration of benzene with a concentrated acid mixture of nitric and sulfuric acid. Nitrobenzene is reduced to form aniline. 10 Aniline, in turn, is used to manufacture isocyanates for polyurethane foams, plastics, and dyes. 18 Chlorobenzene production accounts for 2 percent of benzene use. The halogenation of hot benzene with chlorine yields chlorobenzene. Monochlorobenzene and dichlorobenzene are produced by halogenation with chlorine using a molybdenum chloride catalyst. 19 The remainder of the benzene produced is consumed in the production of other chemicals. Other benzene-derived chemicals include linear alkylbenzene, resorcinol, and hydroquinone. Though much of the benzene consumed in the United States is used to manufacture chemicals, another important use is in gasoline blending. Aromatic hydrocarbons, including benzene, are added to vehicle fuels to enhance octane value. As lead content of fuels is reduced, the amount of aromatic hydrocarbons is increased to maintain octane rating, such that the benzene content in gasoline was increased in recent years. 4 The concentration of benzene in refmed gasoline depends on many variables, such as gasoline grade, refinery location and processes, and crude source. 6 The various sources of benzene emissions associated with gasoline marketing are discussed in Section 6.0, and benzene emissions associated with motor vehicles are discussed in Section 8.0 of this document. 3.3 OVERVIEW OF EMISSIONS Sources of benzene emissions from its production and uses are typical of those found at any chemical production facility: • Process vents; 3-8 Equipment leaks; • Waste streams (secondary sources); • Transfer and storage; and • Accidental or emergency releases. These sources of benzene emissions are described in Sections 4.0 and 5.0 of this document. Miscellaneous sources of benzene including oil and gas production, glycol dehydrators, petroleum refineries, gasoline marketing, POTWs, landfills, and miscellaneous manufacturing processes are addressed in Section 6.0. Combustion sources emitting benzene are addressed in Section 7.0. Section 8.0 presents a discussion of benzene emissions from mobile sources. Recent work by the EPA Office of Mobile Sources on benzene in vehicle exhaust resulted in revised emission factors. 20 For off-road vehicles, EPA has also completed a recent study to estimate emissions. 3-9 ■ 1 ■ ■ SECTION 4.0 EMISSIONS FROM BENZENE PRODUCTION This section presents information on the four major benzene production source categories that may discharge benzene air emissions. The four major processes for producing benzene are: • Catalytic reforming/separation; • Toluene dealkylation and disproportionation; • Ethylene production; and • Coke oven light oil distillation. For each of these production source categories, the following information is provided in the sections below: (1) a brief characterization of the national activity in the United States, (2) a process description, (3) benzene emissions characteristics, and (4) control technologies and techniques for reducing benzene emissions. In some cases, the current Federal regulations applicable to the source category are discussed. Table 4-1 lists U. S. producers of benzene and the type of production process used. 11 Following the discussion of the major benzene production source categories, Section 4.5 contains a discussion of methods for estimating benzene emissions from process vents, equipment leaks, storage tanks, wastewater, and transfer operations. These emissions estimation methods are discussed in general terms and can be applied to the source categories in this section as well as the source categories in Section 5.0. 4-1 TABLE 4-1. BENZENE PRODUCTION FACILITIES c/3 C/3 C/3 8 I— a. a .o y 3 ■8 £ CS 3 >, re _ w oo y c 5 /*—s 0“V p—N p—V ^ P*S re q o TT r- > y w > H. D. X re re o. y y re >* >, w C C £ y co re y 5 S Cl. > Cl. re _ 3 w Q. c y rr.s y > y Cl. | re y s 2 re Q. re y 2 F — •- 2 ! § 2 S> § o y k* D- c y iT c y .2 .2 y 'E. 'E 5L « CO •a c re 3 ‘eh x ‘5 u oo y § Z I E o U .2 ■S 3 CO 3 O o U co TD 11 O U CO CO 4J X ■o re L. y E < c ‘5b CO CO y X FT y s 2 re o U E- « O 4> re >*, >-> U •§> c y > o I y o U CO re x E- 3 2 c o a. re CO X 3 co •a 2 5 re a. E o o u 1-4 §. Cr , y c re o • ^4 E y X U re X o a § I § kl re «.s !“■ CO re x y E- U CO re x y E- co X 3 CO 11 Ig o o U o 8 8 8 E re CO y a. 3* O 2 U s ,2 re u- §■ O U re y y x U x s CO y .y > > H. a. re re u y ns « o re x t .oo o s y > o i o U y i— y 73 re CJ >% M y 3 3 y X ob U- 3 X co 2 re U b o "S5 "*o § *o g. c 2 E o 2 3 :g 8.^ E “ re q o y Ul y *3 co £ Ji sfil ° -a 2 111 <0 P- k- y CO 3 y > re o ifUE- »n co re X y E- w CT3 £ X 4k c o * 2 00 c3 3 -C u Mm •o . re s g* .2 o re U I o U y M XI I g X 3 y CL (2 X y £ « s I £ 4-2 TABLE 4-1. CONTINUED co . M J « .= «“ ! g g| < u -a s o CA 3 OJ > H. « u o c flj 35 a -3 « e c —' 4) 4> « 3 w J 2 « o « o U f- U H 00 00 rs m vo m c 00 s “^ ' ^ —- r- «n o tj- m 00 4> > 4> •3 > Cm '& n cl O cq >> u c - ass .. Dm \S 4> CL c3 ~ ov On —> 0 \ r- *"> os '-' N_^ — N_^ —M ■t —■ 77 - «—< CL cq o « 1 -8 0 1 03 4> > ■w CL <£ ° ‘■r « ui 00 u £ £ H. CC cq aj o> cq u CL u 0 * •a u O • •> 4> c 4) 3 * & 13 0 <■* m c 4> 3 £ S « 3 W — £ 2 C s 3 O O cs O cq O H H U H U H r- 00 00 o CN ,77 13 2! ''O OO CN| o vn 2 E CA >, CA cq 4) cq c 0 .1 CO CO CS X X 4) £- CA Lm 4> X 4) ■ H 0 CO *5 A) CL H CA U .2 5 5 0 ‘kS L 3 J= Z '|m J= iT 0 !S O D, 4) X t-M u CA _cu u CA c T3 C 3 3 .2 < 03 E ‘J 2 2 CL c 0 CL B* 0 u CA 4> e*- 0 u O a. CQ C 3 C £ .2 3 CA «a *r V) 4> > cq > .4-3 Dow Chemical U.S. A. Freeport, Texas 25 (95) Pyrolysis gasoline; captive Plaquemine, Louisiana 80 (303) Pyrolysis gasoline; captive _ 120 (454) _ Toluene; captive _ TABLE 4-1. CONTINUED CO OJ CO CO OJ 8 i— Cu c o w u 3 ? & •= * a j 3 a c 5 I cL .2 -2 eI c CL E o 4) o CO CO 3 3 4) 4> > > w • — CL Cl CO co CJ o O 4) O c 1 . c c b* .2 4> i L> 2 g T3 P — .2 .s ! £ o CO co OX) .2 1 E 3) & | 2 E 3 | V) -V O ! .2 o .2 .2 CO *5 8.2 a> c ^ CO Li CO >«>'>'>* L_ W 2222-5 U iCu o m r-- CO CO x a> H U CO 3 e- o u c _o w C 3 u* & o U c o X X LU c _o ]«5 *> . C/5 ca s-g EE o < U - _ eO ^ .y cj S a. eo o b* c 4/ _3 t- r- »/-> »r> 3 >i § CL E o C U .2 ®p CO s -t .3 -a ill 50S 5 ^ E *a 8 2 g -c <2 H. 2 u n C loo cj • •* .2 .s o o ■p c « c ^ u c o ^ S« D CO *o >> o U H X H 0-® £2,22 S^2o «n co 3 .2 C/3 CO CO CO X X ‘5 3 CO C3 X CO co H 4) H 4) OX) 3 £ X H CO 5 w "C JS O c u U OS £ e CO CO c o O 3 3 © & £* & c3 CCJ o O CQ CO 02 U U er cv co T3 ■§ QJ CO CO * ko li II ~ U CO OX) 4> c 11 ^ os ■S 8 o X x 4-4 Mobil Corporation Beaumont, Texas 90(341) Catalytic reformate; no captive use Mobil Oil Corporation 10 (38) Pyrolysis gasoline Mobil Chemical Company, division 20 (76) Catalytic reformate; no captive use Petrochemicals Division Chalmette, Louisiana U.S. Marketing and Refining Division TABLE 4-1. BENZENE PRODUCTION FACILITIES O c/5 CO OJ 8 Ut o. c _o o 3 1 CL I « § .1 ^ zz rz: (S — 8 o ■x (A CO X o t- 3* O >5 co CO W 75 8 c .2 ‘ m '> 5 m U • •“* CO s E 2 2 To < •o O c/] U s C **“ 3 O J o o C/5 i: lo in CO X H) 3 O C/5 3 O I O 3 < C /5 D >5 00 u. 3 W £ (N Tf C/5 co X V H 3 4> OJ £ CO CN , <0 u «Cu S rn Os O 00 © O t OO CO C/5 CO X ■o I i* O. CO o O W c 3 “ 2 «—* .2 «.2 * S * « J3 W co "o co U H U OO (S (N WWW VO — On O Z. © 05 — "3 4> -C U g X CO § CO CO CO O u 3 4-5 (continued) TABLE 4-1. BENZENE PRODUCTION FACILITIES c o • •«—< o 3 *8 >. CO 13 .3 3 O c S § S..2 -2 co ~ U '2 04 >> § Cl eP o U 04 > w 04 > 04 > s. CO (J > CL G. Cl co CO CL o CTS 04 04 CO C o . ^ , „ 04 • « • •. 04 04 — OJ w cS 04 3 o E U <2 <2 C o CO CO OO g 2 1 <2 04 La 04 La 2 c 04 La 04 0) e/5 ‘3 .2 > 04 04 *«—< >> 5v 5s ? 5> c 04 3 2 13 *3 ”3 04 co ^ 2 3 c3 Uc 3 o 2 O U U U U U H r- v© »/■> r~- co co 22 * § £ fed . * o 2 ■3 -S 2 k - o < Q t: UJ c£ CO C/5 X) 3 CO CL E o U 3 o •o 04 3 La I o 04 O J= e U ~ o O O fj “ co X ,44 04 H r* SO TT fS «n © n p* —• )£ fN — o c c o E CL E o U Z UJ > I O z D oo Co s ^ u. >% X3 V CO CO X 04 H U 04 •X 2 O CO VO Ov 00 oo' o W-i ro fS J < H e c o co 04 CO CO 04 8 La CL 2 04 3 CT 04 CO X> 3 co 04 C 04 u. ,04 *La 04 0^ 3 04 2 o oo 04 5 04 > 3 O J= co La 04 •a % 04 ,C0 04 OO x: 04 ^ ;s -a c o 04 04 3 04 OO XX o 8 S’ co co 04 o Z 4-6 existence of particular facilities by consulting current listings or the plants themselves. The level of emissions from any given facility is a function of variables such as throughput and control measures, and should be determined through direct contacts with plant personnel. Reference SRI '93 indicates these data reflect changes made in product locations as of January 1993. 4.1 CATALYTIC REFORMING/SEPARATION PROCESS Production of benzene by reforming/separation is associated with the production of toluene and xylene (BTX plants). Catalytic reforming is used to prepare high-octane blending stocks for gasoline production and for producing aromatics as separate chemicals. The reforming process, shown in Figure 4-1, 22 accounts for about 45 percent of all benzene produced in the United States. 12 In the following description of the reforming process, potential emission points are identified; however, not all of the emission points discussed in this section are always present at plants using this production process. Some companies have indicated that they have closed systems; others have indicated that process vent emissions are well-controlled by flares or scrubbers. 22 4.1.1 Process Description for Catalytic Reforming/Separation The reforming process used at BTX plants (shown in Figure 4-1) can greatly increase the aromatic content of petroleum fractions by such reactions as dehydrogenation, isomerization and dehydrogenation, or cyclization. The usual feedstock in this process is a straight-run, hydrocracked, thermally cracked, or catalytically cracked naphtha. After the naphtha is hydrotreated to remove sulfur (Stream 1), it is mixed with recycled hydrogen (Stream 4) and heated. This feed (Stream 2) is sent through catalytic reactors in which the catalyst, usually platinum or rhenium chloride, converts paraffins to aromatic compounds. The product stream ^Stream 3) consists of excess hydrogen and a reformate nen m aromatics. Products from the reactor (Stream 3) are fed to the separation section, which separates the hydrogen gas from the liquid product. The hydrogen gas can be recycled to the reactor (Stream 4). The liquid product from the separator (Stream 5) is fed to a stabilizer (not shown in the figure). 22 The stabilizer is a fractionator in which more volatile, light hydrocarbons are removed from the high-octane liquid product. The liquid is then sent to a debutanizer (not shown in the figure). Aromatics (benzene, toluene, and mixed xylenes) are then extracted from the stabilized reformate. 22 4-7 © 4-8 Numerous solvents are available for the extraction of aromatics from the stabilized reformate stream. Glycols (tetraethylene glycol) and sulfolane (1,1-tetrahydrothiophene dioxide) are most commonly used. The processes in which these solvents are used are similar, so only the glycol process is described here. In the glycol process shown in Figure 4-2, aromatics are separated from the reformate in the extractor. 22 The raffinate (stream 2) is water-washed and stored. The dissolved aromatics extract (Stream 1) is steam-stripped and the hydrocarbons separated from the solvent. The hydrocarbon stream (Stream 3) is water-washed to remove remaining solvent and is then heated and sent through clay towers to remove olefins (Stream 4). Benzene, toluene, and xylene (Stream 5) are then separated by a series of fractionation steps. 22 4.1.2 Benzene Emissions from Catalytic Reforming/Separation The available information on benzene emissions from process vents, equipment leaks, storage vessels, wastewater collection and treatment systems, and product loading and transport operations associated with benzene production using the catalytic' reforming/separation process is presented below. Where a literature review revealed no source-specific emission factors for uncontrolled or controlled benzene emissions from these emission points from this process, the reader is referred to Section 4.5 of this chapter, which provides a general discussion of methods for estimating uncontrolled and controlled benzene emissions from these emission points. A literature search, a review of materials in the docket (A-79-27) for some National Emission Standards for Hazardous Air Pollutants (NESHAP) efforts on benzene, and information provided by the benzene production industry revealed no source-specific emission factors for benzene from catalytic reforming/separation. 22 However, information provided by the benzene production industry indicates that BTX is commonly produced in closed systems, and that any process vent emissions are well-controlled by flares and/or scrubbers. (See Section 4.5 of this chapter for a discussion of control devices.) 22 Furthermore, some descriptive data were found, indicating that benzene may be emitted from the 4-9 •Jd-Z*~Z9 - Oa3 4-10 Source: Reference 22. catalytic/reforming process during catalyst regeneration or replacement, during recycling of hydrogen gas to the reformer, and from the light gases taken from the separator. These potential emission points are labeled as A, B, and C, respectively, in Figure 4-1. One general estimate of the amount of benzene emitted by catalytic reforming/separation has been reported in the literature. In this reference, it was estimated that 1 percent of total benzene produced by catalytic reforming is emitted. 23 Benzene may be emitted from separation solvent regeneration, raffinate wash water, and raffinate in association with the separation processes following catalytic reforming. These potential sources are shown as A, B, and C, respectively, in Figure 4-2. However, no specific data were found showing emission factors or estimates for benzene emissions from these potential sources. One discussion of the Sulfolane process indicated that 99.9-percent recovery of benzene was not unusual. Therefore, the 0.1 percent unrecovered benzene may be a rough general estimate of the benzene emissions from separation processes. 23 4.2 TOLUENE DEALKYLATION AND TOLUENE DISPROPORTIONATION PROCESS Benzene can also be produced from toluene by hydrodealkylation (HDA) or disproportionation. The amount of benzene produced from toluene depends on the overall demand and price for benzene because benzene produced by HDA costs more than benzene produced through catalytic reforming or pyrolysis gasoline/ 4 At present, benzene production directly from toluene accounts for almost 30 percent of total benzene produced. 11 Growth in demand for toluene in gasoline (as an octane-boosting component for gasoline blending) appears to be slowing because of increased air quality legislation to remove aromatics from gasoline. (At present, gasoline blending accounts for 30 percent of the end use of toluene.) If toluene is removed from the gasoline pool to any great extent, its value is expected to drop because surpluses will occur. In such a scenario, increased use of toluene to produce benzene by HDA or disproportionation would be expected. 24 At present, production of benzene by the HDA and disproportionation processes accounts for 50 percent of toluene end use. 4-11 4.2.1 Toluene Dealkylation Process Description Hydrodealkylation of toluene can be accomplished through thermal or catalytic processes. 25 The total dealkylation capacity is almost evenly distributed between the two ' methods. 10 As shown in Figure 4-3, pure toluene (92 to 99 percent) or toluene (85 to 90 percent) mixed with other heavier aromatics or paraffins from the benzene fractionation column is heated together with hydrogen- containing gas to 1,346°F (730°C) at a specified pressure (Stream 1) and is passed over a dealkylation catalyst in the reactor (Stream 2). Toluene reacts with the hydrogen to yield benzene and methane. The benzene may be separated from methane in a high-pressure separator (Stream 3) by flashing off the methane-containing gas. 25 The product is then established (Stream 4), and benzene is recovered by distillation in the fractionalization column (Stream 5). 10 Recovered benzene is sent to storage (Stream 6). Unreacted toluene and some heavy aromatic by-products are recycled (Stream 7). About 70 to 85 percent conversion of toluene to benzene is accomplished per pass through the system, and the ultimate yield is 95 percent of the theoretical yield. Because there is a weight loss of about 23 percent, the difference in toluene and benzene prices must be high enough to justify use of the HDA process. Benzene Emissions The available information on benzene emissions from process vents, equipment leaks, storage vessels, wastewater collection and treatment systems, and product loading and transport operations associated with benzene production using the toluene dealkylation process was reviewed. No source-specific emission factors were found for benzene emissions from its production through dealkylation of toluene. The reader is referred to Section 4.5 of this 4-12 chapter, which provides a general discussion of methods for estimating uncontrolled and controlled benzene emissions from these emission points. • Potential sources of emissions from the dealkylation process include the separation of benzene and methane, distillation, catalyst regeneration, and stabilization. 23 These potential sources are shown as emission points A, B, C, and D respectively, in Figure 4-3. 10,15,25 4.2.2 Toluene Disproportionation Process Description Toluene disproportionation (or transalkylation) catalytically converts two molecules of toluene to one molecule each of benzene and xylene. 24 As shown in Figure 4-4, the basic process is similar to toluene hydrodealkylation, but can occur under less severe conditions. 15,26 Transalkylation operates at lower temperatures, consumes little hydrogen, and no loss of carbon to methane occurs as with HDA. 24 Toluene material is sent to a separator for removal of off-gases (Stream 3). The product is then established (Stream 4) and sent through clay towers (Stream 5). Benzene, toluene, and xylene are recovered by distillation, and unreacted toluene is recycled (Stream 6). Note that if benzene is the only product required, then HDA is a more economical and feasible process. 27 Benzene Emissions No specific emission factors were found for benzene emissions from its production via toluene disproportionation. Potential sources of benzene emissions from this process are associated with the separation of benzene and xylene, catalyst regeneration, and heavy hydrocarbons that do not break down. 23 These potential sources are shown as points A, B, and C, respectively, in Figure 4-4. 4-13 Fractionation 4-14 Source: References 10, 15, and 25. Recycle Toluene •Jd >**za~oa3 O o v_ CL • £ O x: ** • c c * o I: 3 • Is ^ © Is o * ^ O c « o © Q. 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"3 00 ft o 1— I o U co CS ft ft X P ft. ft n CO ft £ ■'T r~ r~ o“ w OO ON wo ■cr J < £- O H ft ft c a> b. cs w o c Q. II cs ^ “ 2 o >o ft 5 TD s .X w* cS .-3 o • » o c/5 CO CS ft X co b. g 3 ft OX) t? CO cs ft c *—• E CS ■w X c . ft ft O CO b. u. b. c 3 C c ft O X OX) ft ’•o c •a c S o ft "5 cs w bb [3 3 ft a. ft X b- OX. 5 3 H X O CO CS CO ft c- 5 ft ox) X 3 5 ’ft X cs X ,?S <*— "ZB _ Ob3 4-23 Figure 4-5. Process Flow Diagram for Ethylene Production from Naphtha and/or Gas-Oil Feeds, continued TABLE 4-3. STREAM DESIGNATIONS FOR FIGURE 4-5, PRODUCTION OF ETHYLENE FROM NAPHTHA AND/OR GAS-OIL FEEDS Stream Number Stream Description 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 Naphtha or gas oil feed Fuel gas and oil Ethane/propane recycle stream Cracked gas Cracked gas Recycled pyrolysis fuel oil from gasoline fractionator Furnace exhaust Slurry of collected furnace decoking particles Quenched cracked gas Surplus fuel oil Light fractions Overheads from gasoline fractionator Condensed organic phase Raw pyrolysis gasoline to intermediate storage Water phase (saturated with organics) from quench tower Recycled water phase from heat exchangers Surplus water from quench tower Wastewater blowdown from recycle steam generator Overheads from quench tower Water condensed during compression Organic fractions condensed during compression Acid gas stripped in amine stripper Diethanolamine (DEA) Liquid waste stream from caustic wash tower Liquid waste stream from caustic wash tower Process gas stream from caustic wash tower Solid waste stream from drying traps 4-24 (continued) TABLE 4-3. CONTINUED Stream Number 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 Stream Description Process gas Hydrogen rich stream from demethanizer Methane rich stream from demethanizer C 2 components from de-ethanizer C 3 and heavier components from de-ethanizer Hydrogenated acethylene from acetylene convertor Overheads from ethylene fractionator Ethane to recycle pyrolysis furnace Overheads from depropanizer Propylene (purified) Propane to ethane/propane pyrolysis furnace C 4 and heavier components to debutanizer Overheads from debutanizer C 5 and heavier components from debutanizer Combined C 5 components and gasoline stripper bottoms fractions Light ends to cracked gas compressor C 5 and heavier components Superheated stream Stream and hydrocarbons Organic vapor from separator pot Organic vapor from separator pot Organic vapor from separator pot 4-25 which end pyrolysis and simultaneously generate steam. The streams from the transfer-line exchangers (Stream 5) are combined and further quenched by the injection of recycled pyrolysis fuel oil from the gasoline fractionator (Stream 6). The remaining operations shown in Figure 4-5 are required for separation of the various product fractions formed in the cracking of gas oil and/or naphtha; for removal of acid gases (primarily hydrogen sulfide [H 2 S]) and carbon dioxide (CCy and water; and for hydrogenation of acetylene compounds to olefins or paraffins. The quenched cracked gas (Stream 9) passes to the gasoline fractionator, where pyrolysis fuel oil is separated. Most of the fuel oil passes through water-cooled heat exchangers and is recycled (Stream 6) to the preceding oil-quenching operation. The surplus fuel oil (Stream 10), equivalent to the quantity initially present in the cracked gas, passes first to the fuel oil stripper, where light fractions are removed, and then to fuel oil storage. The light fractions (Stream 11) removed in the fuel oil stripper are recycled to the gasoline fractionator. The gasoline fractionator temperatures are well above the vaporization temperature of water, and the contained water remains as superheated steam, with the overhead stream containing the lighter cracked-gas components. The overhead stream from the gasoline fractionator (Stream 12) passes to the quench tower, where the temperature is further reduced, condensing most of the water and part of the C 5 and heavier compounds. The condensed organic phase (Stream 13) is stripped of the lighter components in the gasoline stripper and is passed to raw pyrolysis gasoline intermediate storage (Stream 14). Most of the water phase, which is saturated with organics, is separated in the quench tower (Stream 15), passed through water-cooled heat exchangers (Stream 16), and then recycled to the quench tower to provide the necessary cooling. The surplus water (Stream 17), approximately equivalent to the quantity of steam injected with the pyrolysis furnace feed, passes to the dilution steam generator, where it is vaporized and recycled as steam to the pyrolysis furnaces. Blowdown from the recycle steam generator is removed as a wastewater stream (Stream 18). 4-26 On leaving the quench tower, the pyrolysis gas is compressed to about 3.5 mPa in five stages. 29 The overhead stream from the quench tower (Stream 19) passes to a centrifugal charge-gas compressor (first three stages), where it is compressed. Water (Stream 20) and organic fractions (Stream 21) condensed during compression and cooling are recycled to the quench tower and gasoline stripper. Lubricating oil (seal oil) discharged from the charge-gas compressor is stripped of volatile organics in a separator pot before the oil is recirculated. The organic vapor is vented to the atmosphere (Vent G). Similar separator pots separate volatile organics from lubricating oil from both the ethylene and propylene refrigeration compressors (Streams 48 and 49). Following compression, acid gas (H 2 S and C0 2 ) is removed by absorption in diethanolamine (DEA) or other similar solvents in the amine wash tower followed by a caustic wash step. The amine stripper strips the acid gas (Stream 22) from the saturated DEA and the DEA (Stream 23) is recycled to the amine wash tower. Very little blowdown from the DEA cycle is required. The waste caustic solution, blowdown from the DEA cycle, and wastewater from the caustic wash tower are neutralized, stripped of acid gas, and removed as liquid waste streams (Streams 24 and 25). The acid gas stripped from the DEA and caustic waste (Stream 22) passes to an emission control device (Vent D), primarily to control H 2 S emissions. Following acid gas removal, the remaining process gas stream (Stream 26) is further compressed and passed through drying traps containing a desiccant, where the water content is reduced to the low level necessary to prevent ice or hydrate formation in the low- temperature distillation operations. The drying traps are operated on a cyclic basis, with periodic regeneration necessary to remove accumulated water from the desiccant. The desiccant is regenerated with heated fuel gas and the effluent gas is routed to the fuel system. Fouling of the desiccant by polymer formation necessitates periodic desiccant replacement. 4-27 which results in the generation of a solid waste (Stream 27). However, with a normal desiccant service life of possibly several years, this waste source is relatively minor. With the exception of three catalytic hydrogenation operations, the remaining process steps involve a series of fractionations in which the various product fractions are successively separated. The demethanizer separates a mixture of hydrogen and methane from the C 2 and heavier components of the process gas (Stream 28). The demethanizer overhead stream (hydrogen and methane) is further separated into hydrogen-rich and methane-rich streams (Streams 29 and 30) in the low-temperature chilling section. The methane-rich stream is used primarily for furnace fuel. Hydrogen is required in the catalytic hydrogenation operations. The de-ethanizer separates the C 2 components (ethylene, ethane, and acetylene) (Stream 31) from the C 3 and heavier components (Stream 32). Following catalytic hydrogenation of acetylene to ethylene by the acetylene converter (Stream 33), the ethylene- ethane split is made by the ethylene fractionator. The overhead from the ethylene fractionator (Stream 34) is removed as the purified ethylene product, and the ethane fraction (Stream 35) is recycled to the ethane/propane cracking furnace. For the separation of binary mixtures with close boiling points, such as in the ethylene-ethane fractions, open heat pumps are thermodynamically the most attractive. Both heating and cooling duties have to be incorporated into the cascade refrigeration system for optimum energy utilization. 29 The de-ethanizer bottoms (C 3 and heavier compounds) (Stream 32) pass to the depropanizer, where a C 3 -C 4 split is made. The depropanizer overhead stream (primarily propylene and propane) (Stream 36) passes to a catalytic hydrogenation reactor (C 3 converter), where traces of propadiene and methyl acetylene are hydrogenated. Following hydrogenation, the C 3 fraction passes to the propylene fractionator, where propylene is removed overhead as a purified product (Stream 37). The propane (Stream 38) is recycled to the ethane/propane pyrolysis furnace. 4-28 The C 4 and heavier components (Stream 39) from the depropanizer pass to the debutanizer, where a C 4 -C 5 split is made. The overhead C 4 stream (Stream 40) is removed as feed to a separate butadiene process. The stream containing C 5 and heavier compounds from the debutanizer (Stream 41) is combined with the bottoms fraction from the gasoline stripper as raw pyrolysis gasoline. The combined stream (Stream 42) is hydrogenated in the gasoline treatment section. Following the stripping of lights (Stream 43), which are recycled to the cracked-gas compressor, the C 5 and heavier compounds (Stream 44) are transferred to storage as treated pyrolysis gasoline. This stream contains benzene and other aromatics formed by pyrolysis. The three catalytic hydrogenation reactors for acetylene, C 3 compounds, and pyrolysis gasoline all require periodic regeneration of the catalyst to remove contaminants. The catalyst is generally regenerated every four to six months. At the start of regeneration, as superheated steam (Stream 45) is passed through a reactor, a mixture of steam and hydrocarbons leaving the reactor (Stream 46) is passed to the quench tower. After sufficient time has elapsed for stripping of organics (approximately 48 hours), the exhaust is directed to an atmospheric vent (Vent F) and a steam-air mixture is passed through the catalyst to remove residual carbon. This operation continues for an additional 24 to 48 hours. The presence of air during this phase of the regeneration prevents the vented vapor from being returned to the process. Because the olefms and di-olefms present in pyrolysis gasoline are unstable in motor gasoline and interfere with extraction of aromatics, they are hydrogenated prior to extraction of aromatics. 10 Also, as mentioned before, because the benzene content of pyrolysis gasoline can be high, some plants recover motor gasoline, aromatics (BTX), or benzene from the pyrolysis gasoline. 4-29 Recovery of Benzene from Pyrolysis Gasoline A process flow diagram for a plant producing benzene, toluene, and xylenes by hydrogenation of pyrolysis gasoline is presented in Figure 4-6. Pyrolysis gasoline is fed with make-up hydrogen into the first stage hydrogenation reactor (Stream 1), where olefins are hydrogenated. The reaction conditions are mild (104 to 203 °F [40 to 95 °C] and 147 to 588 lb/in 2 [10 to 40 atmospheres pressure]). 10 The catalyst in the first stage reactor (nickel or palladium) requires more frequent regeneration than most refinery catalysts because of the formation of gums. Catalyst may be regenerated about every 4 months and coke is burned off every 9 to 12 months. 10,30 From the first reactor, the hydrogenated di-olefins and olefins are sent to a second reactor (Stream 2). Reactor effluent is then cooled and discharged into a separator (Stream 3). Part of the gas stream from the separator is recycled back to the reactor (Stream 4) after being scrubbed with caustic solution. The liquid phase from the separator is sent to a coalescer (Stream 5), where water is used to trap particles of coke formed in the reactor. 30 Next, the light hydrocarbons are removed from the liquid in the stabilizer (Stream 6). At this point, the process becomes similar to the solvent extraction of reformate in the catalytic reforming of naphtha. The stabilized liquid is extracted with a solvent, usually Sulfolane or tetraethylene glycol (Stream 7). The raffinate (Stream 8) contains paraffins and may be sent to a cracking furnace to produce olefins. 30 The solvent may be regenerated (Streams 9 and 10). Dissolved aromatics (benzene, toluene, and xylene) are separated from the solvent by distillation (Stream 11) and sent through clay towers (Stream 12). Individual components (benzene, toluene, and xylene) are finally separated (Stream 13) and sent to storage. The above process may vary among facilities. For example. Stream 1 may be passed over additional catalyst, such as cobalt molybdenum, after being passed over a nickel or 4-30 Wastewater 900*8 £ c o CL o «o ^ £ ! | — 1 o . o •2 ® |s O' c c • 5 -o I § e « g £ S 5 C >. .o c E g O tf 8 S • « ^ Q. 5 E 5 8 5 5 a o a « m ° £ • _s o u o m o o c 4J l~ JJ u C* o o U« 3 O CO 4-31 Figure 4-6. Production of BTX by Hydrogenation of Pyrolysis Gasoline palladium catalyst. Also, the olefins produced from the raffinate stream (Stream 8) may be added to a gasoline process or sold as a reformer stock. 31 * 4.3.2 Benzene Emissions from Ethylene Plants and Benzene Recovery from Pyrolysis Gasoline Production of ethylene from naphtha/gas oil does not produce large quantities of volatile organic compounds (VOC) or benzene emissions from process vents during normal operations. 28 Emission factors for benzene from sources at ethylene plants are shown in Table 4-4. The chief source of benzene emissions during normal operations is the charge gas compressor lubricating oil vent (Stream 47, Vent G in Figure 4-5). The emission factors in Table 4-4 were developed from data supplied by ethylene manufacturers. Most benzene emissions from ethylene plants are intermittent and occur during plant startup and shutdown, process upsets, and emergencies (Vent E). For example, benzene may be emitted from pressure relief devices, during intentional venting of off-specification materials, or during depressurizing and purging of equipment for maintenance. 28 Charge gas compressor and refrigeration compressor outages are also potential sources. Emissions from these compressors are generally short term in duration, but pollutants may be emitted at a high rate. In general, intermittent emissions and emissions from all pressure relief devices and emergency vents are routed through the main process vent (Vent E in Figure 4-5). The vent usually is controlled. The relief valve from the demethanizer is usually not routed to the main vent, but the valve is operated infrequently and emits mainly hydrogen and methane. 28 Potential sources of benzene such as flue gas from the cracking furnace (Vent A), pyrolysis furnace decoking (Vent B), acid gas removal (Vent D), and hydrogenation catalyst regeneration (Vent F) generally are not significant sources. 28 Flue gas normally contains products of hydrogen and methane combustion. Emissions from pyrolysis furnace decoking consist of air, steam, C0 2 , CO, and particles of unbumed carbon. 28 Emissions from 4-32 n H Z < J ft- w z w >- X H w < u p U3 H O ft- >- < c£ O u- oo GC O H U < U- z o 07 oo § w w z U4 N z w CQ rf I Tf W CQ < H u. oil o cT re <3 U. Q£ oc D£ 3 o ■w £ 5 c_> re U. C .2 'in to UJ 4 ) 4) ’> c o o c D c 4 > > 4 > .C 3 J O c/3 C/3 a c o U ■3 c D «j i_ H k. o c/3 c/> 3 i— C_ E o U jj oo s c75 o c/3 m 4 > t- Q. E o U i 00 c a u—» 2 - % g 2 > in u 3 v c n I QJ W S >.J! Z§.3 O i m •3 a> c o u c CQ # c <3 k. t- k* o m m 4) k- O. 3 O U "re 3 Q 00 oo 4> 3 V is o Z cc c 12 o o > oc . •£ 00 -g c 3 •c « 3 Q u .« V o I 3 S . 2 * cj u .22 J g ? §f! - UJ ^ o I m 00 C/3 4 > 3 a> a is o Z re > o E 4 > a: 00 re o J3 G < 00 re O ■3 G < t oo c c o re k> o 3 4 > 00 4> e* w 0/5 j>> 2 c3 u oo .E c 3 -s o re ,re k- k— flj 3 3 5 «. re oc ^ 4> 5 s r- *3 On 5^ 7 5- - uj u o I m m >N re rr m S3 o o •3 OJ c O o c D c V E re • 00 > 00 c rt «> o k? u - | | J M gs| ri »i a On >n O i “ 4/ J. LlJ 00 O ro CnI «ri a o 1 00 OO C-4 vi 3 O 1 00 4> 4) 00 •a 3 •3 4> 5 o o O S kj u 4) k> 4J O Q U 3 O 4 ) 3 CD C/3 3 .2 'in in UJ ■s 3 3 E Q. ’5 cr UJ tn 1 E O0 -2 s 1/5 .3 c/3 li ’S'iS a j 5 E ON U O T g E I— — Cu 2 ^'3 *7 3 cr — UJ UJ o I m 4-33 TABLE 4-4. BENZENE EMISSION FACTORS FOR A HYPOTHETICAL ETHYLENE PLANT” 2 F tU QC OD 2 e o w £ c u u. c .2 "t/J t/J uu 03 03 i— 3 O C/3 C _o CO co UJ o V 5 03 Q *o s U u C/3 T3 •o _03 03 o o b. b. C c 03 o 0) o ba u u o ca c cs c U_ D U- D c ■«3 Wm H u. o > ■S 1 tu c c '<5 u. H o co c/} 03 o U 73 3 Q 8 C/3 C/3 2 £ g. u u t U. M 3 CL 4-34 acid gas removal are H 2 S, S0 2 , and C0 2 ; these emissions are generally controlled to recover H 2 S as sulfur or convert H 2 S to S0 2 . As discussed earlier, catalyst regeneration is infrequent and no significant concentrations of benzene have been reported as present in the emissions. 28 Equipment leak benzene emissions at ethylene plants may originate from pumps, valves, process sampling, and continuous process analysis. Refer to Section 4.5.2 of this document, for information on emission estimates procedures, and available emission factors. Regarding equipment leak component counts, totals of 377 and 719 valves for benzene vapor and benzene liquid service respectively had been reported for ethylene plants. 32 Storage of ethylene in salt domes is not a potential source of benzene emissions because the ethylene generally does not contain benzene. The emission factor for benzene from storage vessels shown in Table 4-4 was derived from AP-42 equations. 33 No supporting data showing how the equations were applied were provided by the emission factor reference. Secondary emissions include those associated with handling and disposal of process wastewater. The emission factor in Table 4-4 was derived from estimates of wastewater produced and the estimated percent of the volatile organic compounds (VOC) emitted from the wastewater that is benzene. No data were available concerning benzene emissions from recovering benzene from pyrolysis gasoline. Likely sources include reactor vents, compressors, and any vents on the benzene column (Figure 4-6). The primary control techniques available for intermittent emissions of benzene (pressure relief valves, emergency vents) are flaring and combustion within industrial waste boilers. Other control methods are not as attractive because the emissions are infrequent and of short duration. The estimated control efficiency of flares is 98 percent or greater 34 while control efficiencies for industrial waste boilers vary depending upon design and operation. 28 4-35 For additional discussion on flares and industrial waste boilers as control methods, see Section 4.5.1. One ethylene producer that provided a process description stated that all process vents are connected to flares. However, it was not possible to determine how prevalent such systems are for ethylene production. 35 Equipment leak emissions may be controlled by inspection/maintenance plans or use of equipment such as tandem seal pumps. For additional discussion on equipment leak emissions, see Section 4.5.2. Emissions from sampling lines can be controlled by piping sample line purge gas to the charge gas compressor or to a combustion chamber. Streams from process analyzers may be controlled in the same manner. 28 The primary means of controlling emissions from pyrolysis gasoline or naphtha feedstock storage is floating roof tanks. Emissions can be reduced by 85 percent when internal floating roof devices are used. 28 For additional discussion on storage tank emissions, see Section 4.5.3. 4.4 COKE OVEN AND COKE BY-PRODUCT RECOVERY PLANTS Most coke is produced in the U.S. using the by-product recovery process. In 1994, there was one plant that used a “nonrecovery” process. This section will focus on the by-product recovery process because there are so few nonrecovery facilities in operation. 296 4.4.1 Process Description Although most benzene is obtained from petroleum, some is recovered through distillation of coke oven light oil at coke by-product recovery plants. Light oil is a clear yellow-brown oil that contains coke oven gas components with boiling points between 32 and 392°F (0 and 200°C). 26 Most by-product recovery plants recover light oil, but not all plants refine it. About 3.4 to 4.8 gal (13 to 18 liters [L]) of light oil can be recovered from the coke 4-36 oven gas evolved in coke ovens producing 0.91 ton (1 megagram [Mg]) of furnace coke (3 to 4 gal/ton [10.3 to 13.7 L/Mg]). Light oil itself is 60 to 85 percent benzene. 37 The coke by-product industry recovers various components of coke oven gas including: • Coal tar, a feedstock for producing electrode binder pitch, roofing pitch, road tar, and numerous basic chemicals; • Light oil, a source of benzene and other light aromatic chemicals; • Ammonia or ammonium sulfate, for agriculture and as chemical feedstocks; • Sulfur, a basic chemical commodity; • Naphthalene, used primarily as an intermediate in the production of organic chemicals; and • Coke oven gas, a high-quality fuel similar to natural gas. 38 Because it is contained in the coke oven gas, benzene may be emitted from processes at by-product recovery plants that do not specifically recover or refine benzene. Table 4-5 lists coke oven batteries with by-product recovery plants in the United States. 36 Figure 4-7 shows a process flow diagram for a representative coke by-product recovery plant. 37 39 The figure does not necessarily reflect any given plant, nor does it include all possible operations that could be found at a given facility. The number of units and the types of processes used varies among specific plants. For example, naphthalene recovery is not practiced at all plants, and some plants do not separate benzene from the light oil. Therefore, it is advisable to contact a specific facility to determine which processes are used before estimating emissions based on data in this document. Coal is converted to coke in coke ovens. About 99 percent of the U.S. production of coke uses the slot oven process, also referred to as the Kopper-Becker by-product coking process; the other 1 percent is produced in the original beehive ovens. 4-37 TABLE 4-5. COKE OVEN BATTERIES CURRENTLY OPERATING IN THE UNITED STATES Plant (Location) Battery Identification Number ABC Coke (Tarrant, AL) A 5 6 Acme Steel (Chicago, IL) 1 2 Armco, Inc. (Middletown, OH) 1 2 3 Armco, Inc. (Ashland, KY) 3 4 Bethlehem Steel (Bethlehem, PA) A 2 3 Bethlehem Steel (Bums Harbor, IN) 1 2 Bethlehem Steel (Lackawanna, NY) 7 8 Citizens Gas (Indianapolis, IN) E H 1 Empire Coke (Holt, AL) 1 2 Erie Coke (Erie, PA) A B Geneva Steel (Provo, UT) 1 2 3 4 Gulf States Steel (Gadsden, AL) 2 3 4-38 (continued) TABLE 4-5. CONTINUED Plant (Location) . Battery Identification Number Inland Steel (East Chicago, IN) 6 7 9 10 11 Koppers (Woodward, AL) 1 2A 2B 4A 4B 5 LTV Steel (Cleveland, OH) 6 7 LTV Steel (Pittsburgh, PA) PI P2 P3N • P3S P4 LTV Steel (Chicago, IL) 2 LTV Steel (Warren, OH) 4 National Steel (Ecorse, MI) 5 National Steel (Granite City, IL) A B New Bncton Coke fPortsmouth OH> 1 Sharon Steel (Monessen, PA) IB 2 Shenango (Pittsburgh, PA) 1 4 Sloss Industries (Birmingham, AL) 3 4 5 Toledo Coke (Toledo, OH) C Tonawanda Coke (Buffalo, NY) 1 4-39 (continued) TABLE 4-5. CONTINUED Plant (Location) Battery Identification Number USX (Clairton, PA) 1 2 3 7 8 9 13 14 15 19 20 B USX (Gary, IN) 23 5 7 Wheeling-Pittsburgh (East Steubenville, WV) 1 . 2 3 8 Source: Reference 36. NOTE: This list is subject to change as market conditions change, facility ownership changes, plants are closed, etc. The reader should verify the existence of particular facilities by consulting current lists and/or the plants themselves. The level of benzene emissions from any given facility is a function of variables such as capacity, throughput and control measures, and should be determined through direct contacts with plant personnel. These operating plants and locations were current as of April 1, 1992. 4-40 Primary Coolar 4-41 Source: Reference 37 and 39. Each oven has 3 main parts: coking chambers, heating chambers, and regenerative chambers. All of the chambers are lined with refractory (silica) brick. The coking chamber has ports in the top for charging of the coal. 22 Each oven is typically capable of producing batches of 10 to 55 tons (9.1 to 49.9 Mg) of coke product. A coke oven battery is a series of 20 to 100 coke ovens operated together, with offtake flues on either end of the ovens to remove gases produced. The individual ovens are charged and discharged at approximately equal time intervals during the coke cycle. The resulting constant flow of evolved gas from all the ovens in a battery helps to maintain a balance of pressure in the flues, collecting main, and stack. Process heat comes from the combustion of gases between the coke chambers. Approximately 40 percent of cleaned oven gas (after the removal of its byproducts) is used to heat the coke ovens. The rest is either used in other production processes related to steel production or sold. Coke oven gas is the most common fuel for underfiring coke ovens. 22 The coking time affects the type of coke produced. Furnace coke results when coal is coked for about 15 to 18 hours. Foundry coke, which is less common and is of higher quality (because if is harder and less readily ignited), results when coal is coked for about 25 to 30 hours. 37 The coking process is actually thermal distillation of coal to separate volatile and nonvolatile components. Pulverized coal is charged into the top of an empty, but hot, coke oven. Peaks of coal form under the charging ports and a leveling har smoothes them out. Aficr the leveling bar is withdrawn, the topside charging ports are closed and the coking process begins. Heat for the coke ovens is supplied by a combustion system under the coke oven. The gases evolved during the thermal distillation are removed through the offtake main and sent to the by-product recovery plant for further processing. 4-42 After coking is completed (no volatiles remain), the coke in the chamber is ready to be removed. Doors on both sides of the chamber are opened and a ram is inserted into the chamber. The coke is pushed out of the oven in less than 1 minute, through the coke guide and into a quench car. After the coke is pushed from the oven, the doors are cleaned and repositioned. The oven is then ready to receive another charge of coal. The quench car carrying the hot coke moves along the battery tracks to a quench tower where approximately 270 gallons of water per ton of coke (1,130 L of water per Mg) are sprayed onto the coke mass to cool it from about 2000 to 180°F (1100 to 80°C) and to prevent it from igniting. The quench car may rely on a movable hood to collect particulate emissions, or it may have a scrubber car attached. The car then discharges the coke onto a wharf to drain and continue cooling. Gates on the wharf are opened to allow the coke to fall onto a conveyor that carries it to the crushing and screening station. After sizing, coke is sent to the blast furnace or to storage. As shown in Figure 4-7, coke oven gas leaves the oven at about 1292°F (700 °C) and is immediately contacted with flushing liquor (Stream 1). The flushing liquor reduces the temperature of the gas and acts as a collecting medium for condensed tar. The gas then passes into the suction main. About 80 percent of the tar is separated from the gas in the mains as “heavy” tar and is flushed to the tar decanter (Stream 2). 37 Another 20 percent of the tar is “light” tar, which is cleaner and less viscous, and is condensed and collected in the primary cooler. 39 Smaller amounts of “tar fog” are removed from the gas by collectors (electrostatic precipitators or gas scrubbers) (Stream 4). 37 Light tar and tar fog is collected in the tar intercept sump (stream 6) and is routed to the tar decanter (Stream 5). Depending on plant design, the heavy and light tar streams (Streams 2 and 5) may be merged or separated. The tar is separated from the flushing liquor by gravity in the tar decanter. Recovered flushing liquor is returned to the Flushing Liquor Circulation Tank (Stream7) and re-used. Tar from the decanter is further refined in the tar dewater tank 4-43 (Stream 3). Tar may be sold to coal tar refiners or it may be refined farther on site. Tar and tar products are stored on site in tanks. Wastewater processing can recover phenol (Stream 8) and ammonia, with the ammonia routinely being reinjected into the gas stream (Stream 9). Ammonia salts or ammonia can be recovered by several processes. Traditionally, the ammonia-containing coke oven gas is contacted with sulfuric acid (Stream 10), and ammonium sulfate crystals are recovered (Stream 11). The coke oven gas from which tar and ammonia have been recovered is sent to the final cooler (Stream 12). The final cooler is generally a spray tower, with water serving as the cooling medium. 37 Three types of final coolers and naphthalene recovery technologies are currently used: (1) direct cooling with water and naphthalene recovery by physical separation, (2) direct cooling with water and naphthalene recovery in the tar bottom of the final cooler, and (3) direct cooling with wash oil and naphthalene recovery in the wash oil. 37 Most plants use direct water final coolers and recover naphthalene by physical separation. 37 In this method, naphthalene in the coke oven gas is condensed in the cooling medium and separated by gravity (Stream 13). After the naphthalene is separated, the water is sent to a cooling tower (Stream 14) and recirculated to the final cooler (Stream 15). The coke oven gas that leaves the final cooler is sent to the light oil processing segment of the plant (Stream 16). As shown in Figure 4-7, light oil is primarily recovered from coke oven gas by continuous countercurrent absorption in a high-boiling liquid from which it is stripped by steam distillation. 10 Coke oven gas is introduced into a light oil scrubber (Stream 16). Packed or tray towers have been used in this phase of the process, but spray towers are now commonly used. 10 Wash oil is introduced into the top of the tower (Stream 17) and is circulated through the contacting stages of the tower at around 0.11 to .019 gal/ft 3 (1.5 to 2.5 liters per cubic meter [L/m3]) of coke oven gas. 39 At a temperature of about 86°F (30°C), a light oil scrubber will remove 95 percent of the light oil from coke oven gas. The 4-44 dJ.a-»f-M1d-9800*a £ MS ■C o £ S • •“ s § o ® « g MS = 3 s o ? €> s e o 3 — o o .2 “1 c £ £ o O Cl ° O ® “ I = •? 2 - t <= o O O t2 e g S s ° <• a. • Ja a Z tJ- T3 C « O rf on UNDRY COKE BY-PRODUCT RECOVERY PLANTS 2 .= C3 <3 o. oc a o U d *o c 3 o u. u o- c 4 0 ‘w5 00 £ UJ 0) o U V o co c OJ o > u Q c o U o C/5 CO c _c co CO Ol u CO 4J Q U U c/5 oi oi 01 01 01 01 01 01 h* Os cs ,—^ g */5 00 TT o © 00 d cn ^r Ov Ov CN n 'w' T N■✓ w o VO 8 o o SO © o o TT o o K OV o X o § o © o *ri © r» (N © p- ✓—v as 00 00 fn o K © v> co O Os o I I CO H CQ u< i CO >> CO CQ O to c 2 JJ o "o "o QJ ^4 "o u 5 l_l c B C •2 c o O o CQ o o u CJ (J c a c a D O D o D c 5 W« CS u •a o co > o < c o C3 _ »- ^ Cw « a- w * « 'co CO u C OJ 13 ■3 8 j= £ a. CO z g* TJ * S T3 Q S3 E- ■o £ tu u- OX) O cT w .2 co « u. qc 4J •X O U & ■g i2 1> -X o U u u CO 3 i_ 3 u. OJ o > « Q c o U u o t— 3 O on C/3 C _o ‘Z C/3 E UJ o CO V Q T3 3 cO U U on tu BJ BJ W CU CU BJ BJ BJ BJ bj BJ m oo ___ VO x-x — 8 — § — o o in CN d rn fn © q 00 d cn 'w>' xn o cn 'w' o 'w' cn m d m o X T o VO T o o T o o T o o T o o © X cn id X © X X X X X X X o VO o cn CN CN CN CN CN CN cn cn vd ^X‘ vd —;. VO /- « s ^. ^*v 00 _ cn CN CN CO CO < ■— —" Tj- VO o /C—N in © oo d 00 C d in vd >n ' * in in w "T v *x' T T T o cn O m O' CN o CN © VO © x-x O o X © X o X o X © X © X c4 04 o o o o TT o Tf © r- ri (N CN ■a co 3 T3 co 3 ■a co 3 "O co c •a co c -a — ' *—! _a> u .CD o i— OJ *1 o b. a5 O H 3J 2 "o Ua OJ ■g o u. 3J •g o u c CO 3 co c 3 3 •2 c o o CQ O o © o o 5 O u CQ O u CQ o u 3 C/3 3 C/3 3 e/j 3 CO 3 C/5 c D CO a D CO a D CO o D a D ca a D O QJ U co co u- O 4~> 02 sz 00 •o £ 3J CO CO ka o 3 3 c o u u co co k. © on © 3 © s © CQ 4-52 TABLE 4-6. CONTINUED }r OO 2 e o ‘-3 « CT3 U. OH jo oo( s ^b| a o u re tu c o on 5 W aj o U *o c 3 o 4> O U aj Q c o U u o t— 3 o CO co C U3 o CO o k. c aj o o CQ o o 5 o u 5 o o 5 c D CO 03 c c D CO re o c D CO re o c D CO re O SO ON ra a> o c 4> u. lk« 4> C* V o k. 3 o co f" i rr E c 5 Tj- k. ^ 00 i> re a'l £ ^ c c o •a x S g o § co _ re .5 ft *0 £ 0> O re •5 .a . • S2 "e *7 U « z Tf O M - 3 k. u 3 1; U £: IS ~ oo a I 8 E kk Q aj _i f* re o ft T3 o q aj ao — C c k- k. a> .■2 8.| •o 8 ay o .o • a *« a; C c£ re k. o co o 3 O o k. aj © < o> »-« c r* S * 1® — 4> ft" 0> C ay Jr re .2 Jg £ re co 2 y i- E U- © co •S ay >, S3 c ,re q' c « ^ c 3 .’2 c ° *5. ay .2 >> — 111 2 O 5 1/5 o co W 3 2 re o. aj CO 4-53 TABLE 4-7. SUMMARY OF BENZENE EMISSION FACTORS FOR EQUIPMENT LEAKS AT FURNACE COKE BY-PRODUCT RECOVERY PLANTS >5 T3 44 br u o fa § s % 1 73 Ua 3 O co O c U- CcC &°m| 44 3 > ‘S o .= O ^ o> U 02 * — D O g OO J ® X _ 54 O O £ « CO K >> u c 44 44 C u- 54 c o U 44 o i_ 3 O 4/3 in 3 .2 in in UJ u V) 44 Q U U c /3 D 3 D C4 r4 Os ^r 00 o tj- d T 3 44 3 o a c D oo o o oo o m vO C /5 44 > > D D D D 3 D D D D S o m O /-V Ov u 00 rn © cr co VO co C4 — — ON VO co c4 O i o o d i d , o ■ vo fS| Ov (N vr> CN vn oo V) 00 VO «**s o m —• r- m rs o o i «4 , o 4/ Ov ca o m ON m >. O 13 O E C4) *0 > c "53 c > u 3 w S5 c C/3 c c 0 .2 c 2 03 w. ’E H Utf CO TI ^>5 cu •5 c o 44 C/2 44 CO C o 44 C OJ C 2 5 c 0 0 ■0 0 c^ C O O c OJ — CT3 3 C O QJ -O O co c 0 44 c w C C3 3 3 O 2 44 CO 2 D D O' 2 3 D a 2 D 3 a 5 D C /3 C- E £ C /2 u. 44 co 3 ca •5 w C /2 44 44 ’> 44 Q 4b. .44 13 a: 44 t- 3 co CO 44 •a 44 2 o c o 44 c 3 s o 44 44 C c o U oo c CO T 3 44 3 .3 e o 44 vn 44 ■g s - *8 O u- — 3 0* >> 8 £ “ $ • I co (_> S >» *2 44 ? aa O a co 4-54 Closed-purge sampling _ (100) TABLE 4-7. CONTINUED >> eg •o 03 l- CJ 2 5 g .2 w on >4 £ eg ’2 "o m g i-« D O c/d 2.S* eg p3 u. a u? oo 03 — > -a o ,S o ^ C M a >►> o c .2 'G <— 03 c o U 3 O 00 C/3 c _o '35 C/3 UJ 0) on 03 Q "O c « u u oo 3 © 3 oo m © Tf OO O *o o o u c D a. eg CJ M 3 on 3 C •3 a> T3 c 03 I c 8 . o r> 03 u c 03 U. c2 VI—l 03 £2 2 e cu on 0) i— a. o c — o> c 03 o c u I— eg 3 X> c >* eg eg " 7v _ -a a - 8. « ^ 8 « 3 > O O ® 8 U- U- 8.S 1 c '£ 4j 03 I__ 3 0/ o 03 •o in .2 *0 1) c a. I E 3 .2 o 03 -o c -- 03 d 03 o o o on £ £if $ O rt “ <*- C w O u c 0» t- o 3 <2 ’35 o ^ C/3 C/3 ”Q 1 u O 4> Qu £ 03 ■W ■w 2 •o o> 03 o £ e 03 on 1) on 03 •s eg ■a 0. Cu c 03 03 o on i_ on eg •o 03 03 cn i— Cl. C/3 U eg X O £ 03 o 03 03 2 Uu 0. eg eg c C/3 C/3 .2 1— h. on O o o a "3 eg eg 3 U. U* Ui 4-55 >- Q Z D O pp E- < on < W J H Z PJ c/5 r- Z < ■J Cu >- OS V} PJ g > 2 ° h u ^ PJ < cd D a PJ QC O U- E- U D Q O os a- i >- ca Ph z o on on S pj PJ z PJ PJ N ^ Z O PJ (j co p- O >- os < £ D on oo I PJ CQ < E- >> cs -a « 2 s « 8 .2 ~ to >1 *2 cs 'g "O w 8 H 3 O oo u. M 2 .£ £ « tt. a: CU c si o ^ > u c .2 u £ CU c o U OJ W U- 3 O 00 (A c # o "to C/5 u u C/5 D D D 3 3 O D D D D o r~ i «n 717 C4 o NO T5 ri M-i o o o w o d d cn re > C/5 £ O 2 3 O 3 .O u cu CU 3 O o re cu C/5 73 o '2 re J= CO 05 _> 73 > 3 U*C o U cu 3 ■g W-1CJ - 7 3fi- h £> ^ >, U Q u o > 9 cu o ' i «o cu Jp >5 « 4> 9 OQ O os m NT) 0-5 3 8 3 _o u Ci •3 2 s Cu C/5 C a T3 •o 2 .1 6. Vi C cu flU 3 •3 2 V3 c o o o "o ka Im "c9 u> 3 OJ _c O > u. CU CO CU Q Vt_> .2 "S OS cu h« 3 co CO a> 5 5 CO U* CO •3 U Wm 3 Q. 2 a> CO 4-56 Sampling Connections Uncontrolled 0.51 (0.23) 0.62(0.28) _ Plug or cap _ (100) _--_ - >- cC a z o u- < oo < frl J H Z BJ 2 Cu 00 o U- c/? O t— u < u. z o oo 00 i [U LU z UJ N Z UJ oa a. >- W > O u w H U E> o o cc a. i >- CQ LU o u u- O >■ < O oo oo I W J 03 < H >3 ca •o fe (J 2 B S g I - C^i CT3 1 73 w 8 H 3 O C/3 U- Ofi o c w ?a ca u. as “j i_ Ml Q ■a § U U oo m 3 »n ON OO ro O r- r~ o •a i_ . <4— U OS a> o 3 O 00 3 o ca o. a> > ea 3 i— ea 3 JO o > O o oj u 3 •3 O • i— >i a. ca i 73 £ o u h- .* s ° o o " fr *§ ro E- © TT 0/ CO 1) ej 3 = & OJ OS o i£ E o U M 13 ^ o Cm w ^ c X) -D £ <4- O cd Ui o ^ s ja ea > 200 Btu/scf heating value, • Smoking and 60 ft/sec (18 m/sec) allowed for maximum exit velocity 5 min/2 hr • Air and Steam Assisted • Not used on Flares - > 300 Btu/scf corrosive heating value, and maximum exit velocity based on Btu content formula streams Industrial ^ 98% • Vent stream directly into • Destroys rather Boilers/Process flame than recovers Heaters organics Thermal ^ 98%, or • 1600°F (871 °C) Combustion • Destroys rather Oxidation 20 ppm temperature than recovers • 0.75 sec. residence organics • For halogenated streams • May need vapor 2000°F (1093°C), 1.0 sec. holder on and use a scrubber on outlet intermittent • Proper mixing streams Adsorption a 95% • Adequate quantity and • Most efficient on appropriate quality of carbon streams with low • Gas stream receives relative humidity appropriate conditioning (<50 percent). (cooling, filtering) • Recovers • Appropriate regeneration and cooling of carbon beds before breakthrough occurs organics Source: Reference 45. 4-63 TABLE 4-11. OTHER CONTROL TECHNOLOGIES THAT CAN BE USED TO MEET STANDARDS Type Estimated Control Level Critical Variables That Affect Control Level Comments Catalytic Oxidation up to 98 % • Dependent on compounds, temp, and catalyst bed size • Destroys rather than recovers organics • Technical limitations include particulate or compounds that poison catalysts Absorption 50 to 95 % • Solubility of gas stream in the absorbent • Good contact between absorbent and gas stream • Appropriate absorbent needed may not be readily available • Disposal of spent absorbent may require special treatment procedures, and recovery of organic from absorbent may be time consuming • Preferable on concentrated streams Condensation 50 to 95 % • Proper design of the heat exchanger • Proper flow and temperature of coolant • Preferable on concentrated streams • Recovers organics Source: Reference 45. 4-64 Three types of recovery devices have been identified for controlling benzene emissions: condensation, absorption, and adsorption. With a condensation-type recovery device, all or part of the condensible components of the vapor phase are converted to a liquid phase. Condensation occurs as heat from the vapor phase is transferred to a cooling medium. The most common type of condensation device is a surface condenser, where the coolant and vapor phases are separated by a tube wall and never come in direct contact with each other. Efficiency is dependent upon the type of vapor stream entering the condenser and the flow rate and temperature of the cooling medium. Condenser efficiency varies from 50 to 95 percent. Stream temperature and the organic concentration level in the stream must remain within a certain range to ensure optimal control efficiency. 46 In absorption, one or more components of a gas stream are selectively transferred to a solvent liquid. Control devices in this category include spray towers, venturi scrubbers, packed columns, and plate columns. Absorption efficiency is dependent upon the type of solvent liquid used, as well as design and operating conditions. Absorption is desirable if there is a high concentration of compound in the vent stream that can be recovered for reuse. For example, in the manufacture of monochlorobenzene, absorbers are used to recover benzene for reuse as a feedstock. 46 Stream temperature, specific gravity (the degree of adsorbing liquid saturation), and the organic concentration level must remain within a certain range to ensure optimal control efficiency. 46 Absorbers are generally not used on streams with VOC concentrations below 300 ppmv. 45 Control efficiencies vary from 50 to 95 percent. 45 In adsorption, the process vent gas stream contains a component (adsorbate) that is captured on a solid-phase surface (adsorbent) by either physical or chemical adsorption mechanisms. Carbon adsorbers are the most commonly used adsorption method. With carbon adsorption, the organic vapors are attracted to and physically held on granular activated carbon through intermolecular (van der Waals) forces. The two adsorber designs are fixed-bed and fluidized-bed. Fixed-bed adsorbers must be regenerated periodically to desorb the collected organics. Fluidized-bed adsorbers are continually regenerated. 46 4-65 Adsorption efficiency can be 95 percent for a modem, well-designed system. Removal efficiency depends upon the physical properties of the compounds in the offgas, the gas stream characteristics, and the physical properties of the adsorbent. Stream mass flow during regeneration, the temperature of the carbon bed, and organic concentration level in the stream must remain within a certain range to ensure optimal control efficiency. 46 Adsorbers are not recommended for vent streams with high VOC concentrations. 45 Four types of combustion devices are identified for control of benzene emissions from process vents: flares, thermal oxidizers, boilers and process heaters, and catalytic oxidizers. A combustion device chemically converts benzene and other organics to C0 2 and water. If combustion is not complete, the organic may remain unaltered or be converted to another organic chemical, called a product of incomplete combustion. Combustion temperature and stream flow must remain within a certain range to ensure complete combustion. 46 A flare is an open combustion process that destroys organic emissions with a high-temperature oxidation flame. The oxygen required for combustion is provided by the air around the flame. Good combustion is governed by flame temperature, residence time of the organics in the combustion zone, and turbulent mixing of the components to complete the oxidation reaction. There are two main types of flares: elevated and ground flares. A combustion efficiency of at least 98 percent can be achieved with such control. 46 A thermal oxidizer is usually a refractory-lined chamber containing a burner (or set of burners) at one end. The thermal oxidation process is influenced by residence time, mixing, and temperature. Unlike a flare, a thermal oxidizder operates continuously and is not suited for intermittent streams. Because it operates continuously, auxiliary fuel must be used to maintain combustion during episodes in which the organic concentration in the process vent stream is below design conditions. Based on new technology, it has been determined that all new thermal oxidizers are capable of achieving at least 98 percent destruction efficiency or a 20 parts per million by volume (ppmv) outlet concentration, based on operation at 870°C (1,600°F) with a 0.75-second residence time. 46 4-66 Industrial boilers and process heaters can be designed to control organics by combining the vent stream with the inlet fuel or by feeding the stream into the boiler or stream through a separate burner. An industrial boiler produces steam at high temperatures. A process heater raises the temperature of the process stream as well as the superheating steam at temperatures usually lower than those of an industrial boiler. Greater than 99 percent control efficiency is achievable with these combustion devices. 46 By using catalysts, combustion can occur at temperatures lower than those used in thermal incineration. A catalytic oxidizer is similar to a thermal incinerator except that it incorporates the use of a catalyst. Combustion catalysts include platinum, platinum alloys, copper oxide, chromium, and cobalt. Catalytic oxidizers can achieve destruction efficiencies of 98 percent or greater. 46 Biofiltration is another type of VOC control. In biofiltration, process exhaust gases are passed through soil on compost beds containing micro organisms, which convert VOC to carbon dioxide, water, and mineral salts. 47 Table 4-12 presents a comparison of the VOC control technologies (excluding combustion) that are discussed in this section. 47 Process vents emitting benzene and other VOC that are discussed in Sections 4.1 through 4.4 and in Section 5.0 are affected by one or more of the following six Federal regulations: 1. “National Emission Standards for Organic Hazardous Air Pollutants from the Synthetic Organic Chemical Manufacturing Industry,” promulgated April 22, 1994. 48 2. “National Emission Standards for Hazardous Air Pollutants from Petroleum Refineries,” promulgated August 18, 1995. 49 4-67 TABLE 4 12. COMPARISON OF VOC CONTROL TECHNOLOGIES "O CC t— w c o U s o t/5 4> OX) « c > •o < 5A 3 O Sn SA •3 a e 55 o 4 * 4 / 5 ^ C/5 — >> ca o s s £ y 4> os o > — o CU o 3 Si c _o to *2 2 « •2 3 E "o o £ U Cu uu .ts o a. ox) « c (J cS OS e «j .2 E S « a era i_ *-*1 u o •- C u > 3 tr to fl) 5A g O 3 j CU .52 O >N r~~. u ‘ «U O > — o C. 3 a a o 1 = i 1 U Cu m ON 4> *—* co CA C 4/ T3 C o U o in ;n a , OX) .2 o u- c o a — c o .2 o co CA c o U x; u E— 4> e c3 *o 'x Jn c3 3 3 c3 x 4) •o C o £ O U o U c J C 8 1 5> =: ox) Cu O *- C/5 O O 00 ON •a OO co > T3 < C/3 •S « c ^ o « o ^ c/2 — >N CO O £ § E OJ — 0£ ' ttJ >* J: .ts o u CO rti c- SrJ U g a; «le -5 S3 a X> co •x e a>- n u oo S g E 1 < o 5 U “ >> _ OO o JT w o § 5 <-> £ H QJ co ; 4> •o X 4> “ o CO .- c 3 • = • 1 ST >» a -a 3 CJ 8 u c ,o u CO l_> <*r O a- o u w aj « 3 S > X ^ U- 3 H 3 U C/3 rv X co S’ w- > co > U Q. 6R oo ON I cr> os C o !• o OO J3 < C/3 CJ u. 3 O CO 4-69 3. “Standards of Performance for New Stationary Sources; Volatile Organic Compound (VOC) Emissions from the Synthetic Organic Chemical Manufacturing Industry (SOCMI) Air Oxidation,” promulgated July 1, 1994. 50 4. “Standards of Performance for New Stationary Sources; Volatile Organic Compound (VOC) Emissions from the Synthetic Organic Chemical Manufacturing Industry (SOCMI) Distillation Operations,” promulgated July 1, 1994. 51 5. “Standards of Performance for New Stationary Sources; Volatile Organic Compound (VOC) Emissions from the Synthetic Organic Chemical Manufacturing Industry (SOCMI) Reactor Processes,” promulgated July 1, 1994. 52 6. “National Emission Standards for Benzene Emissions from Coke By-Product Recovery Plants, promulgated October 27, 1993.” 53 In general, for the affected facilities subject to these six regulations, use of the recovery devices and combustion devices discussed above is required. Tables 4-10 and 4-11 present a summary of those controls and the required operating parameters and monitoring ranges needed to ensure that the required control efficiency is being achieved. 4.5.2 Equipment Leak Emissions. Controls, and Regulations Equipment leak emissions occur from process equipment components whenever the liquid or gas streams leak from the equipment. Equipment leaks can occur from the following components: pump seals, process valves, compressor seals and safety relief valves, flanges, open-ended lines, and sampling connections. The following approaches for estimating equipment leak emissions are presented in the EPA publication Protocol for Equipment Leak Emission Estimates i 54 Average emission factor approach; Screening ranges approach; EPA correlation approach; and Unit-specific correlation approach. 4-70 The approaches differ in complexity; however, greater complexity usually yields more accurate emissions estimates. The simplest method, the average emission factor approach, requires that the number of each component type be known. For each component, the benzene content of the stream and the time the component is in service are needed. This information is then multiplied by the EPA's average emission factors for the SOCMI shown in Table 4-13. 54 Refinery average emission factors are shown in Table 4-14; marketing terminal average emission factors are shown in Table 4-15; and oil and gas production average emission factors are shown in Table 4-16. 54 This method is an improvement on using generic emissions developed from source test data, inventory data, and/or engineering judgement. However, this method should only be used if no other data are available because it may result in an overestimation or underestimation of actual equipment leak emissions. For each component, estimated emissions are calculated as follows: No. of equipment components To obtain more accurate equipment leak emission estimates, one of the more complex estimation approaches should be used. These approaches require that some level of emissions measurement for the facility’s equipment components be collected. These are described briefly, and the reader is referred to the EPA protocol document for the calculation details. X Weight % benzene X Component- specific X No. hr/yr in benzene service in the stream _ emission factor j The screening ranges approach (formerly known as the leak/no leak approach) is based on a determination of the number of leaking and non-leaking components. This approach may be applied when screening data are available as either "greater than or equal to 10,000 ppmv" or as "less than 10,000 ppmv." Emission factors for these two ranges of screening values are presented in Table 4-17 for SOCMI screening; Table 4-18 for refinery screening, Table 4-19 for marketing terminal screening, and Table 4-20 for oil and gas production screening. 54 4-71 TABLE 4-13. SOCMI AVERAGE TOTAL ORGANIC COMPOUND EMISSION FACTORS FOR EQUIPMENT LEAK EMISSIONS 3 Equipment Type Service Emission Factor 15 lb/hr/source (kg/hr/source) Valves Gas Light liquid Heavy liquid 0.01313 (0.00597) 0.00887 (0.00403) 0.00051 (0.00023) Pump seals c Light liquid Heavy liquid 0.0438 (0.0199) 0.01896 (0.00862) Compressor seals Gas 0.502 (0.228) Pressure relief valves Gas 0.229 (0.104) Connectors All 0.00403 (0.00183) Open-ended lines All 0.0037 (0.0017) Sampling connections All 0.0330 (0.0150) Source: Reference 54. * The emission factors presented in this table for gas valves, light liquid valves, light liquid pumps, and connectors are revised SOCMI average emission factors. b These factors are for total organic compound emission rates. c The light liquid pump seal factor can be used to estimate the leak rate from agitator seals. The EPA correlation approach offers an additional refinement to estimating equipment leak emissions by providing an equation to predict mass emission rate as a function of screening value for a specific equipment type. The EPA correlation approach is preferred when actual screening values are available. Correlation operations for SOCMI, refinery, marketing terminals, and oil and gas production along with respective correlation curves are provided in Reference 54. The unit-specific correlation approach requires the facility to develop its own correlation equations and requires more rigorous testing, bagging, and analyzing of equipment leaks to determine mass emission rates. Appendix A of the EPA protocol document provides example calculations for each of the approaches described above. 4-72 TABLE 4-14. REFINERY AVERAGE EMISSION FACTORS Equipment type Service Emission Factor (kg/hr/source) a Valves Gas 0.0268 Light Liquid 0.0109 Heavy Liquid 0.00023 Pump seals b Light Liquid 0.114 Heavy Liquid 0.021 Compressor seals Gas 0.636 Pressure relief valves Gas 0.16 Connectors All 0.00025 Open-ended lines All 0.0023 Sampling connections All 0.0150 Source: Reference 54. 1 These factors are for non-methane organic compound emission rates. b The light liquid pump seal factor can be used to estimate the leak rate from agitator seals. Although no specific information on controls of fugitive emissions used by the industry was identified, equipment components in benzene service will have some controls in place. Generally, control of fugitive emissions will require the use of sealless or double mechanical seal pumps and an inspection and maintenance program, as well as replacement of leaking valves and fittings. Typical controls for equipment leaks are listed in Table 4-21. 55 Some leakless equipment is available, such as leakless valves and sealless pumps. 55 Equipment leak emissions are regulated by the National Emission Standard for Equipment Leaks (Fugitive Emission Sources) of Benzene promulgated in June 6, 1984. 56 This standard applies to sources that are intended to operate in benzene service, such as pumps, compressors, pressure relief devices, sampling connection systems, open-ended valves or lines, valves, flanges and other connectors, product accumulator vessels, and control devices or systems required by this subpart. 4-73 TABLE 4-15. MARKETING TERMINAL AVERAGE EMISSION FACTORS Equipment Type Service Emission Factor (kg/hr/source) a Valves Gas 1.3x1 O’ 5 Light Liquid 4.3xl0' 5 Pump seals Gas 6.5xl0' 5 Light Liquid 5.4x10"* Others (compressors and Gas 1.2x10"* others) b Light Liquid 1.3x10"* Fittings (connectors and Gas 4.2x1 O' 5 flanges) c Light Liquid 8.0x1 O' 6 Source: Reference 54. 4 These factors are for total organic compound emission rates (including non-VOC such as methane and ethane). b The "other" equipment type should be applied for any equipment type other than fittings, pumps, or valves. c "Fittings" were not identified as flanges or non-flanged connectors; therefore, the fitting emissions were estimated by averaging the estimates from the connector and the flange correlation equations. Each owner or operator subject to Subpart J shall comply with the requirement of the National Emission Standard for Equipment Leaks promulgated in June 6, 1984. 57 The provisions of this subpart apply to the same sources mentioned above that are intended to operate in volatile hazardous air pollutant (VHAP) service. Benzene is a VHAP. The SOCMI New Source Performance Standards promulgated in October 18, 1983 58 also apply to equipment leak emissions. These standards apply to VOC emissions a f affected facilities that commenced construction, modification, or reconstruction after January 5, 1981. Equipment leak emissions from Coke by-product recovery plants are regulated by the National Emission Standard for Benzene Emissions from Coke By-Product Recovery Plants promulgated in September 14, 1989. 53 These standards apply to the same sources (equipment leak components) as indicated in Subpart J, and V of Part 61. .4-74 TABLE 4-16. OIL AND GAS PRODUCTION OPERATIONS AVERAGE EMISSION FACTORS (kg/hr/source) Equipment Type Service 3 Emission Factor (kg/hr/source) b Valves Gas 4.5xl0' 3 Heavy Oil 8.4x1 O' 6 Light Oil 2.5xl0' 3 Water/Oil 9.8xl0' 5 Pump seals Gas 2.4x1 O' 3 Heavy Oil NA Light Oil 1.3xl0' 2 Water/Oil 2.4x1 O' 5 Others c Gas 8.8x10° Heavy Oil 3.2x1 O' 5 Light Oil 7.5x1 O' 3 Water/Oil 1.4x1 O' 2 Connectors Gas 2.0x10-* Heavy Oil 7.5x1c 6 Light Oil 2.1x10-* Water/Oil ■ LlxlO - * Flanges Gas 3.9x10"* Heavy Oil 3.9xl0' 7 Light Oil 1.1x10"* Water/Oil 2.9X10- 6 Open-ended lines Gas 2.0xlC 3 Heavy Oil 1.4x1 O'* Light Oil 1.4x10' 3 Water/Oil 2.5x10-* Source: Reference 54. 1 Water/Oil emission factors apply to water streams in oil service with a water content greater than 50 percent, from the point of origin to the point where the water content reaches 99 percent. For water streams with a water content greater than 99 percent, the emission rate is considered negligible. b These factors are for total organic compound emission rates (including non-VOC such as methane and ethane) and apply to light crude, heavy crude, gas plant, gas production, and off shore facilities. "NA" indicates that not enough data were available to develop the indicated emission factor. c The "other" equipment type was derived from compressors, diaphrams, drains, dump arms, hatches, instruments, meters, pressure relief valves, polished rods, relief valves, and vents. This "other" equipment type should be applied for any equipment type other than connectors, flanges, open-ended lines, pumps, or valves. 4-75 TABLE 4-17. SOCMI SCREENING VALUE RANGE TOTAL ORGANIC COMPOUND EMISSION FACTORS FOR EQUIPMENT LEAK EMISSIONS* O 1-4 3 O CT •a .c "abl o s 3 O CT H jo » 33 > OX) 3 •- >■% 33 > ox) cn •- cn > u cr cn <4-4 I c D i_ O k- cn CO k- O o V O o 3 c cn CO CL Q. ■a ‘5 cr -C oo CO 4> cn > .2 ‘5 a* •§> CO 4/ _> cn > CO cn 60 cn OJ CO k. O o ’eb cn £ o 4) cn L. jj o •s — CO 4/ 2 n cn | .2 ** m o CO 3 '£ -a S .2 •a 'a. C L_ 3 cn M 1 § .2 «r r* ^ § 2 60 O o 2 2 3 O co 4/ X) 2 CO s .£ 3 a> a u CO u CL co £ 2 O u 8 * OJ > £ 4> cr »== ^ U C c re O © a- — s eo rs — UES ca <75 ^ >N — att o C c C3 O O O. — -.3 re rG — u e s 03 on 04 u O CN C o 'W re o O X ns oc o ON X H >> c re o. s Q WO NO 04 Tt ns on s 00 s r- c4 04 < < Z Z X H >, .« E 04 XS o a o r“ E < 04 04 Os NO NO oo wo © 04 O WO On -'I' Tt NO O' VO WO O O o4 wo Tf 04 £ < Z Da X X u u Xl X u u Z CO ^ E re c O' O' oo On On O o 04 04 in co ca Tf ON NO Tf ON O' o uo 04 NO in o -re- 04 < Z < z < z < u C/3 d x 2 o 04 ~ x. 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Urn Cl W o S qj CT) QJ as g § | 5 Ui y a E CO re 1 f w as w g as oo 8 s w O C C/3 A s re X •3 O & CJ _re •— •a O CD — ,w a. as as* 5 “> b. § o 43 ^ U 3 co re S CO .2 ts ‘•g 2 c c as CO as b. 3 <£ CO re on Cc 3 as oo 3 E O u? ±3 re 3 3 3 § " O Um g 3 g.S op t 2 3 £ u •5 £ . as So ^ >* .3 co as ^ s - n .2 ==2 = y 8 *3 ¥•£ “ re CO — •** 3 4 - CD - 1 .2 i I o as O Z as £ re 5 a. .2 S ^ % s X T3 8 S w co C/3 flj a> 3 3 | ? > a. 5-5 Aluminum Chlorid* Catalyst Poly.thylb.nz.n* R*cycl*d B.nz.n* 5-6 Benzene Alkylation with Ethylbenzene figure) to recover aromatics and to remove hydrogen chloride (HC1) before the remaining inert gases are vented. 69 The crude ethylbenzene (Stream 3) from the settler is washed with water and caustic to remove traces of chlorides and then fed to the ethylbenzene purification section. The crude ethylbenzene contains 40 to 55 percent benzene, 10 to 20 percent poly ethylbenzene (PEB), and high-boiling point materials. The first step in purification is separation of recycled benzene (Stream 4) from the crude ethylbenzene in the benzene recovery column. In the second step, the product ethylbenzene (Stream 5) is separated from the heavier hydrocarbons in the ethylbenzene recovery column. The heavier hydrocarbons are distilled in the polyethylbenzene column to separate the polyethylbenzenes, which are recycled (Stream 7), from the residue oil. 69 Emission points in the purification section include vents from the benzene and ethylbenzene recovery columns (Vent C and D, respectively) and the poly ethylbenzene column (Vent E). 69 Fresh ethylbenzene (Stream 6) from the ethylbenzene purification section is combined with recycled ethylbenzene (Stream 8) from the styrene purification section at the integrated styrene plant and is stored for use as an intermediate for making styrene. 69 Other emission points from the process including storage tanks, are shown in Figure 5-1. pi 110 ii U - A process flow diagram including the basic operations that may be used in the styrene by ethylbenzene dehydrogenation is shown in Figure 5-2. 69 74 Fresh ethylbenzene from the ethylbenzene purification section (ethylbenzene plant) is combined with recycled ethylbenzene (Stream 1) from the styrene purification section. The purified ethylbenzene is preheated in a heat exchanger. The resultant vapor (Stream 2) is then mixed continuously with steam at 1,310°F (710°C) in the dehydrogenation reactor, which contains one of several catalysts. The reaction product (Stream 3) then exits through the heat exchanger and is further cooled in a condenser, where water and crude styrene vapors are condensed. 5-7 E € 55 c o ~~ w CL c c o o a o c ® « CO ?8 £ a • ® D OC 0 3 CO Tf r- T3 § ■'T to 04 a c s <£ 04 cd 04 04 U. 3 O C/3 5-8 Ethylbenzene Dehydrogenation The hydrogen-rich process gas is recovered and used as a fuel (Stream 7) and the process water is purified in a stripper and recycled to the boiler. The remaining crude styrene liquid (Stream 6) goes to a storage tank. Benzene and toluene (Stream 8) are removed from the crude styrene in the benzene/toluene column. They are then typically separated by distillation. The toluene is sold and the benzene is returned to ethylbenzene production section (Stream 10), or it may also be sold. Next, the ethylbenzene column removes ethylbenzene, which is directly recycled (Stream 1). Tars are removed and the product styrene (Stream 9) emerges from the styrene finishing column. In some facilities, an ethylbenzene/benzene/toluene stream is separated from the crude styrene initially and then processed separately. Emission points in this process include vents from the columns for the styrene purification section between the separator and the recovery sections. These include the benzene toluene column (Vent A), the ethylbenzene recycle column (Vent B) and the emergency vent in the styrene finishing column (Vent C). Other emission points from the process including storage tanks and barge loading are shown in Figure 5-2'. 5.1.2 Process Description for Ethylbenzene Production from Mixed Xylenes Ethylbenzene can also be extracted from mixed xylene streams. Proportionately, however, very little ethylbenzene is produced in this fashion. The two major sources of ethylbenzene containing xylenes are catalytic reformate from refineries, and pyrolysis gasoline from ethylene production (see process description for ethylene production in Section 4.3). The amount of ethylbenzene available is dependent on upstream production variables. The ethylene separation occurs downstream of the benzene production. For this reason, the ethylbenzene produced by this process is not considered a source of benzene emissions. Instead, benzene emissions from the entire process train are considered to be emissions from benzene production and are included elsewhere in this document (Section 4.0). 5-9 When combined with the dehydrogenation process previously described to produce styrene (Figure 5-2), the process is similar except that the benzene recycling (Stream 10 in Figure 5-2) cannot be reused directly. 5.1.3 Process Description for Styrene Production from Ethylbenzene Hvdroperoxidation Presently, only one U.S. facility uses the hydroperoxidation process to produce styrene. Figure 5-3 shows a process flow diagram. The four major steps are described below. Ethylbenzene (Stream 1) is oxidized with air to produce ethylene hydroperoxide (Stream 2) and small amounts of a-methyl-benzyl alcohol and acetophenone. The exit gas (principally nitrogen) is cooled and scrubbed to recover aromatics before venting. Unreacted ethylbenzene and low-boiling contaminants are removed in an evaporator. Ethylbenzene is then sent to the recovery section to be treated before reuse. Ethylbenzene hydroperoxide (Stream 3) is combined with propylene over a catalyst mixture and high pressures to produce propylene oxide and acetophenone. Pressure is then reduced and residual propylene and other low-boiling compounds (Stream 4) are separated by distillation. The vent stream containing propane and some propylene can be used as a fuel. Propylene is recycled to the epoxidation reactor. The crude epoxidate (Stream 5) is treated to remove acidic impurities and residual catalyst material and the resultant epoxidate stream is distilled to separate the propylene oxide product for storage. Residual water and propylene are recycled to the process train and liquid distillate is recovered as a fuel. The organic layer is routed (Stream 6) to the ethylbenzene and a-methyl-benzyl alcohol recovery section. Distillation removes any remaining ethylbenzene. Organic waste streams are separated from the a-methyl-benzyl alcohol and acetophenone organic waste liquids are used as fuel. 5-10 Muscoote <€> >K £ o < • > E -NO 2 C c s >* • s«S £ 3 * ui a < 1 id m 3 ,u 2 « 5 o • • if -=: § s 3 o s g C O ■ Q. i s. : a ^ TJ S fc e o o o c c i • E s P € o z ■'T t>- 4> O c 4> i— a o a: aj p 3 O V3 5-11 Figure 5-3. Ethylbenzene Hydroperoxidation Process Block Diagram The mixed stream of a-methyl-benzyl alcohol and acetophenone (Stream 7) is then dehydrated over a solid catalyst to produce styrene. Residual catalyst solids and high-boiling impurities are separated and collected for disposal. The crude styrene goes to a series of distillation columns, where the pure styrene monomer product is recovered. The residual organic stream contains crude acetophenone, catalyst residue, and various impurities. This mixture is treated under pressure with hydrogen gas to convert the acetophenone to a-methyl-benzyl alcohol. Catalyst waste is separated from the a-methyl-benzyl alcohol, which is returned to the recovery section for processing and reuse. Hydrogen and organic vapors are recovered for use as fuel. 5.1.4 Process Description for Stvrene Production bv an Isothermal Process Ethylbenzene may also be converted to styrene by an isothermal process (Figure 5-4). Liquid ethylbenzene is vaporized by condensing steam in a heat exchanger (Stream 1). Process steam (Stream 2) is then introduced into the ethylbenzene stream and the feed mixture is superheated (Stream 3) before it enters the molten-salt reactor (Stream 4) (see Figure 5-4). 75 In the reactor, the ethylbenzene/steam mixture passes through the tubes, where it comes into contact with the catalyst and is dehydrogenated. Heat for the dehydrogenation reaction is supplied by molten salt (preferably a mixture of sodium carbonate, lithium carbonate, and potassium carbonate) surrounding the tubes (Stream 5). The reactor is maintained at a uniform wall temperature by circulating the molten-salt mixture through the heat exchanger of a fired heater (Stream 6). 75 The reaction products are cooled and condensed in a separator (Stream 7). The liquid phase is a mixture of organic products: styrene, unreacted ethylbenzene, and small quantities of benzene, toluene, and high-boiling compounds. Styrene (Stream 8) is separated from the other liquid constituents, which then are recovered and recycled. 75 5-12 Steam Ganarator dia-«f-AA1J-frC00*fl 5-13 The gas phase from the condensation step in the separator consists mainly of hydrogen, with small quantities of C0 2 , CO, and methane.- After these gases are compressed, they are cooled. Condensible products from this fmal cooling stage are then recovered and recycled to the separator. When hydrogen-rich offgas is used as fuel for the heater of the molten-salt reactor, the fuel requirement for this stage of the process is zero. 75 5.1.5 Benzene Emissions from Ethylbenzene and Stvrene Production via Alkylation and Dehydrogenation Emission Estimates from Ethylbenzene Production and Dehydrogenation to Styrene Emission factors have been developed based on an uncontrolled 300-million- kg/yr capacity integrated ethylbenzene/styrene production plant. Major process emission sources are the alkylation reactor area vents (Vent A in Figure 5-1). atmospheric and pressure column vents (Vents B, C, and D in Figure 5-1), vacuum column vents (Vent B in Figure 5-2), and the hydrogen separation vent (Stream 7 in Figure 5-2). Emission factors from these sources are given in Table 5-2. 69,74 The first four process vent streams in Table 5-2 are low- flow, high-concentration streams. The hydrogen separation stream (Stream 7 in Figure 5-2) is high-flow, low-concentration. Other emission sources listed in Table 5-2 include storage losses and shipment losses (Vent G). Fugitive emissions from valves and other equipment leaks are not indicated in Figure 5-1 or 5-2. Reactor area vents remove various inerts plus entrained aromatics (benzene). Inerts include nitrogen or methane used in pressure control, unreacted ethylene, reaction byproducts, and ethylene feed impurities. In typical plants using liquid-phase aluminum chloride catalyst with high-purity ethylene, vent streams are usually cooled and scrubbed to recover aromatics. In plants using the newer solid support catalysts of the UOP or Mobil/Badger process, reactor vent flow rates are very high because of the low-purity ethylene feed. Process economics requires that these vent gases be burned as fuel. 5-14 < > z o * H U D G O Cu W z w O' H CO Z O H < , Z g w Z o w N z til CQ G H til OZ O u- co CC c C oc a > E til a a z < z o u >- < *£ u. j z < o co CO s til ri i u-> til G CQ < H 00 .2 TO ac k. O u to U. o W* 3? £ ^ c w o c Z o ~ 1 £ CQ u Q c o U c _o '35 UJ o C/2 su TO c _o _TO u-> < co O o •o u c o a c D on o I co 00 c *1-1 3 a—i c o O lb > 3 § ka O 2 O TO u c OJ oc » ^2 5 cu < He oo on ^ o o i 1 .o fS rr — OJ o §s 4- cc U* r-V (S ■o ■*r fN •a Cu S C/Q P 11 < U oo c o .TO co O i ON NO 1) c u a JS 3 a ±3 E 3 3 CU TO > I- Cj 5 O i oo c So u > o cu u QC (U 3 (U a > « *5 o 7 id a. CO «> N s ^7 C/0 CQ CO (U c 2 (O I 00 2 CO 2 ^ T 4 £ £ CO ■c /'“s rr U c y o H I c OJ a _ c QJ U CQ > u c ka ^ O I m 5-15 TABLE 5-2. CONTINUED oo c •«—» OS u CO LL 2 S u ~ £ & c ' o c S 2 c/5 ■ UJ 3 o U c CO c _o in c/5 LU u C/5 D Q T5 3 03 U u on cr ■o VO -o D c c o c 3 D 1— _co u. c D > c o CO c_ d CO c D bo T3 3 i D BO > .5 c 3 .2 w <—* O 2 <2 « g s* co CO S C d D OX) c o D u. * i M I 0> o rd co ftJ wo" Tf c o o co CD 3 •o D D > CO u. TD i^T D C O BO CQ T3 O ’ wS •L jj CsL Cm D V- a-» "o BO OS C/5 c u 1— ft 0^ C CO 1— c D 03 o 3 u- y- u D 00 s c co "O c CO D BO o to co D C D i— 5ft -*—• CO VO ^ «>x I D 3 5 a I i D ,C0 D tT Xi ‘tr B0 X £ - X - 00 o £ c CO •o c u * VO Ov CO 1— « - 2 U 2 to r- o — M IS ~ c 2 o CD «-> •C u. 00 D 3 Cl, 2 T3 ■6 2 •s 1 1 s IT ^ >. c > a S'-e E '2, c/5 .X l_ -—' 2 x: O — ,C0 c/5 **“ co ft "3 o aj in in £ D « 3 C/5 C« D u. CL X D D O « S® co U U_ — = oo n Dl- oc ft L- 5 w .2 CD C CO C. x: E 8 co w jO 3 O vO VO D CO CD co D 3 S J D CD D 7? 73 S ^ OJ E 2 « § ^ JZ .O C/5 > o OJ in o c3 D a b> c D C 3 _3 O D u a O o a D 5ft JO l_ ‘■5 f— D > O x: bx D oo 3 D 3 O O D B0 l— D 3 D *" N •a D ft ’>% 3 D ft D s- co CO L- O ■a 3 C/5 D •a ±S D 3 D a D 5ft ^3 D >* ,C0 CO Cfc« QJ s E = loi CO i- - 3 3^ r£ ° — UJ y d -O X3 Cd D D in D5 3 T3 3 3 o D D u- > > CD 00 O0 D 3 c 3 D 'i • p>* i— o _o co o o D rf Cm Ov 3 r~ D VO OJ D D £ D 2 co ft 1/5 g « D •a 3 D 2 a: 2 5-16 styrene Atmospheric and column vents remove non-combustibles in the column feeds, light aliphatic hydrocarbons, and any entrained aromatics. The benzene drying column also removes impurities in the benzene feed. Most emissions occur in the first column of the distillation train (benzene recovery column in Figure 5-1). Vacuum column vents remove air that leaks into the column, light hydrocarbons and hydrogen formed in dehydrogenation, non-combustibles in the column feed, and entrained aromatics. Most emissions occur on the benzene/toluene column (vent A in Figure 5-2). Uncontrolled distillation vents emit 4.2xl0' 3 lb hydrocarbons/lb styrene (4.2xl0' 3 kg hydrocarbons/kg styrene) in one plant where the hydrocarbons are benzene and toluene. Another condenser controlled vent emits 0.4x1 O' 3 lb benzene/lb styrene (0.4x1 O' 3 kg benzene/kg styrene). 9 Following dehydrogenation, a hydrogen-rich gas (Stream 4 in Figure 5-2) containing methane, ethane, ethylene, C0 2 , CO, and aromatics is normally cooled and compressed to recover aromatics. The stream should be vented to the atmosphere (Vent E in Figure 5-2) only during startup, shutdown, and recovery section compressor outages. Some plants may also vent this stream to a flare. Flares are an efficient (99 percent) emission control only when flare diameter and gas flow are closely matched for optimum turbulence and mixing. Emissions can be better controlled when the stream is routed to a manifold and burned with other fuels. Stripper vents have been reported to emit 0.032 lb ethylbenzene/lb styrene (32 g ethylbenzene/kg styrene). 9 This corresponds to 9.6x1 O' 6 lb benzene/lb styrene (9.6x1 O' 3 g benzene/kg styrene). Benzene in shipping and storage (Vent F in Figure 5-1) must also be considered as a source if benzene is not produced on site (in which case these emissions would be considered pan of the benzene production process). 5-17 Benzene Emissions from Styrene Production Using Ethylbenzene Hydroperoxidation Only one U.S. facility currently reports using this method. Emission estimates presented in this section are based on a capacity of 1200 million lb styrene/yr (544 million kg styrene/yr). The three main process emission sources are the ethylbenzene oxidation reactor vent (A in Figure 5-3), the propylene recycle purge vent (B), and the vacuum column vents (C) and (D). Propane vapor (B) is considered a fuel if it is not vented to the atmosphere. Of these sources, only the vacuum vents are large benzene emitters. These emissions result from benzene impurities in the ethylbenzene feed, which may result in minor side reactions in the process train. The ethylbenzene oxidation reactor vent (A) releases CO, light organics, entrained aromatics with nitrogen, oxygen, and C0 2 . The vent gas is scrubbed with oil and water for a 99 percent removal efficiency for organics. The resulting vent stream contains approximately 35 ppm benzene (0.11 mg benzene/1) or 15.9 lb benzene/hr (7.2 kilograms benzene per hour [kg/hr]). 74 The propylene recycle vent (B) releases propane, propylene, ethane, and other impurities. No flow volume data are available but, based on a similar procedure in high-grade propylene production, this stream is a high-Btu gas and would be used as a fuel. No significant benzene emissions are expected. 74 The ethylbenzene hydroperoxidation process contains numerous vacuum columns and evaporators. Vents on these operations (C-l to C-3) release inerts and light organics dissolved in the column feeds, nitrogen used for process pressure control, and entrained aromatics. A combined vent flow is reported to be 264,200 gal/hr (l.OxlO 6 1/hr) containing about 60 lbs benzene/hr (27 kg benzene/hr). 74 5-18 The dehydrogenation vent (D in Figure 5-3) may be an emergency pressure vent similar to the separation vent (C in Figure 5-2). No specific information is available on storage, transport, or fugitive emissions for this process. 5.1.6 Control Technology for Ethvlbenzene/Stvrene Processes Control methods for the two ethylbenzene/styrene processes in use in the United States include condensation, adsorption, flaring, and combustion in boilers or other process heaters. Controls for fugitive emissions from storage tanks, equipment leaks, and others include the use of floating-roof tanks and leak detection/correction programs. No information is available on control methods specific to the two processes mentioned in this report but not in use in the United States. Condensers may be used to control benzene emissions associated with ethylbenzene/styrene production. The control efficiency of a condenser is determined by the temperature and pressure at which the condenser operates and by the concentration and vapor pressure of the organics in the vent stream. At typical pressures of 1 to 3 atmospheres and coil temperatures of 36 to 41 °F (2 to 5°C), condensers can achieve 80 to 90 percent benzene reduction when used on vent streams at 70 to 100 percent saturation in benzene at 104 to 122 °F (40 to 50°C). 74 Higher efficiencies become prohibitively expensive. Condensers have limited use in handling high-volume streams, short duration emergency releases, or cyclic releases such as from the hydrogen separation vent. Furthermore, condensers are inefficient at low saturations such as with the alkylation reactor vents and the column vents of Figure 5-1. In an ethylbenzene/styrene plant, a packed tower can be used to remove benzene. PEB and various ethylbenzene produced during benzene alkylation are good absorbers of benzene and are normally recycled. This system is unsuitable, however, for handling high-volume or intermittent releases of gases beyond the tower design capabilities. 5-19 Absorption systems can maintain 80 to 99 percent benzene removal efficiencies for both saturated and unsaturated benzene streams, depending on the tower design and operating variables. Flare systems can control some streams for which condensation or absorption is not suitable. Flares can efficiently handle highly saturated streams such as ffom the alkylation vents. They can also control upset releases and other irregular releases, although efficiency can be variable. The major difficulty here occurs in manifolding. High-nitrogen or other low- or non-combustible gases may also be problematic. Consequently, there are no conclusive data on flare efficiency. Limited data show benzene destruction efficiencies ranging from 60 to 99 percent. A properly designed flare system must account for a range of flow and gas composition as well as the potential for explosion. Use of vent gases as a fuel combined with regular process fuel is advantageous because vent flow variations can be better accounted for. Also, better gas/air mixing occurs along the entire flare front. As with flares, however, manifolding to ensure optimal combustion characteristics is the major technical problem. Process pressure variations and the possibility of emergency releases are complicating factors. 5.2 CYCLOHEXANE PRODUCTION About 15 percent of the U.S. supply of benzene is used to produce cyclohexane. 10 Table 5-3 lists the location and current capacity for U.S. cyclohexane producers. 11 Two basic methods are used to produce cyclohexane: hydrogenation of benzene and petroleum liquid separation. Most of the cyclohexane produced domestically is produced through hydrogenation of benzene. The following discussions of these two processes are taken from Reference 76. 5-20 TABLE 5-3. U.S. PRODUCERS OF CYCLOHEXANE Company Location Annual Capacity millions of gal (1) Chevron Chemical Company Port Arthur, TX 38 (144) Phillips Petroleum Company Specialty Chemicals Branch Borger, TX 35 (132) Olefins and Cyclics Branch Sweeny, TX ' 90(341) Phillips Puerto Rico Core, Inc. Guayama, PR 100 (379) Texaco Chemical Company Port Arthur, TX 75 (284) CITGO Petroleum Corporation Corpus Christi, TX 30(114) TOTAL 368 (1,393) Source: Reference 11. Note: This list is subject to change as market conditions change, facility ownership changes, plants are closed, etc. The reader should verify the existence of particular facilities by consulting current lists and/or the plants themselves. The level of benzene emissions from any given facility is a function of variables such as capacity, throughput and control measures, and should be determined through direct contacts with plant personnel. These plant locations and capacities were current as of January 1, 1993. 5.2.1 Process Description for Cyclohexane Production via Benzene Hydrogenation Figure 5-5 shows a model flow diagram for the manufacture of cyclohexane by benzene hydrogenation. 76 High-purity benzene (Stream 1) is fed to the catalytic reactors in parallel and hydrogen (Stream 2) is fed into the reactors in series. Part of the cyclohexane separated in the flash separator is recycled (Stream 3) and fed to the reactors in series. Recycling helps to control the reactor temperature, because the reaction is highly exothermic. The temperature is also controlled by generating steam, which is used elsewhere in the petrochemical complex. Both platinum and nickel catalysts are used presently to produce cyclohexane. 5-21 Uquldx-Byproduct to P.Uoch.mlc.l Complox 0....-ByprodueU to Fuol Qa* Syatama dia-*fMld-C£OOM vd r- u c c_> Ui 3 O C/D 5-22 Figure 5-5. Process Flow Diagram for Cyclohexane Production Using the Benzene Hydrogenation Process After leaving the flash separator, the cyclohexane (Stream 4) is sent to a distillation column (stabilizer) for removal of methane, ethane, other light hydrocarbons, and soluble hydrogen gas from the cyclohexane product. These impurities (Stream 6) are routed to the fuel-gas storage system for the facility and used as fuel in process heaters. Cyclohexane (Stream 5) purified in the stabilizer may be greater than 99.9 percent pure. The residual benzene content is typically less than 0.0042 lb/gal (500 mg/1). This pure product is stored in ' large tanks prior to shipment. Gas from the flash separator, largely hydrogen, is not pure enough for direct reuse. Therefore, the stream (8) is purified before being recycled to (Stream 2) the reactor. Typical processes used for hydrogen purification are absorption and stripping of the hydrogen gas and cryogenic separation. Some plants use a combination of the two processes. Organic liquids (Stream 10) that are separated from the hydrogen in the hydrogen purification unit are sent to other petroleum processing units in the petrochemical complex. The separated gases (Stream 9) are used as fuel gas. Depending on the type of hydrogen purification used, inert impurities present in the gas from the flash separator can be purged from the system before the gas enters the hydrogen purification equipment. This stream (7) is sent to the fuel gas system. 5.2.2 Benzene Emissions from Cyclohexane Production via Benzene Hydrogenation There are no process emissions during normal operation. 76 During shutdowns, individual equipment vents are opened as required during final depressurization of equipment. Except for the feed streams, the concentration of benzene in the process equipment is low; therefore, few or no benzene emissions would be expected during a shutdown. 76 Equipment leak emissions from process pumps, valves, and compressors may contain benzene or other hydrocarbons. Storage of benzene (Vent A in Figure 5-5) may also contribute to benzene emissions. 5-23 Other potential sources of emissions are catalyst handling (B) and absorber wastewater (C) (when an aqueous solution is used to purify the recycled hydrogen). Caution is taken to remove the organic compounds from the spent catalyst before it is replaced. The spent catalyst is sold for metal recovery. 76 5.2.3 Process Description for Cyclohexane Production via Separation of Petroleum Fractions Cyclohexane may also be produced by separation of select petroleum fractions. The process used to recover cyclohexane in this manner is shown in Figure 5-6. 76 A petroleum fraction rich in cyclohexane (Stream 1) is fed to a distillation column, in which benzene and methylcyclopentane are removed (Stream 2) and routed to a hydrogenation unit. The bottoms (Stream 3) from the column containing cyclohexane and other hydrocarbons are combined with another petroleum stream (4) and sent to a catalytic reformer, where the cyclohexane is convened to benzene. The hydrogen generated in this step may be used in the hydrogenation step or used elsewhere in the petrochemical complex. The benzene-rich stream (5) leaving the catalytic reformer is sent to a distillation column, where compounds that have vapor pressure higher than benzene (pentanes, etc.) are removed (Stream 6) and used as byproducts. The benzene-rich stream (7) that is left is sent to another distillation column, where the benzene and methylcyclopentane (Stream 8) are removed. The remaining hydrocarbons (largely dimethylpentanes) are used elsewhere in the petrochemical complex as byproducts (Stream 9). Stream 8 (benzene and methylcyclopentane) is combined with Stream 2 and sent to a hydrogenation unit (Stream 10). Hydrogen is fed to this unit and the benzene is converted to cyclohexane. Isomers of cyclohexane, such as methylcyclopentane, are converted to cyclohexane in an isomerization unit (Stream 11) and the effluent from this equipment (Stream 12) is separated in a final distillation step. Pure cyclohexane (Stream 14) is separated from isomers of cyclohexane (Stream 13) and compounds with lower vapor pressures (Stream 15). 5-24 Hexanes Methylcyclopentane diU-«f-M1d-8S00*6 3 O CO 5-25 Note: The stream numbers on the figure correspond to the discussion in the text for this process. Letters correspond to potential sources of benzene emissions. Figure 5-6. Process Flow Diagram for Cyclohexane from Petroleum Fractions 5.2.4 Benzene Emissions from Cyclohexane Production via Separation of Petroleum Fractions There are no process emissions during normal operation. 76 During emergency shutdowns, individual equipment vents are opened as required. Equipment leaks can be sources of benzene, cyclohexane, methane, or other petroleum compound emissions. Leaks from heat exchangers into cooling water or steam production can be a potential fugitive loss. Equipment leak losses have special significance because of the high diffusivity of hydrogen at elevated temperatures and pressures and the extremely flammable nature of the liquid and gas processing streams. 77 No specific emission factors or component counts (valves, flanges, etc.) were found for benzene associated with equipment leak emissions at these plants. A potential source of benzene emissions is catalyst handling. Special efforts are made to remove the organic compounds from the spent catalyst before it is replaced. The spent catalyst is sold for metal recovery. 76 No emission factors were found for benzene as related to catalyst handling. 5.3 CUMENE PRODUCTION Tn the United States, all commercial cumene is produced by the reaction of benzene with propylene. Typically, the catalyst is phosphoric acid, but sulfuric acid or aluminum chloride may be used. Additionally, various new processes based on solid zeolite catalysts were introduced during 1993; however, information about these new processes is limited, and they are not discussed in this section. The location and capacities of U.S. producers of cumene are provided in Table 5-4. 11,78 .5-26 TABLE 5-4. U.S. PRODUCERS OF CUMENE Plant Location Annual Capacity million lb (million kg) Notes Ashland Chemical Company Catlettsburg, KY 550 (249) Cumene is sold BTL Specialty Resins Corporation Blue Island, IL 120 (54) Captive for phenol and acetone Chevron Chemical Company Philadelphia, PA 450 (204) Cumene is sold Port Arthur, TX 450 (204) Cumene is sold Citgo Petroleum Corp. (Champlin) Corpus Christi, TX 825 (374) — Coastal Refining Westville, NJ 150 (68) Cumene is sold Georgia Gulf Corporation Pasadena, TX 1,420 (644) Some cumene transferred to company's phenol/acetone plant Koch Refining Company Corpus Christi, TX 750 (340) Cumene is sold Shell Chemical Company Deer Park, TX 900(408) Captive for phenol/acetone Texaco Chemical Company El Dorado, KS 135 (61) Captive for phenol/acetone Source: References 11 and 78. Note: This list is subject to change as market conditions change, facility ownership changes, plants are closed, etc. The reader should verify the existence of particular facilities by consulting current list and/or the plants themselves. The level of benzene emissions from any given facility is a function of variables such as capacity, throughput, and control measures, and should be determined through direct contacts with plant personnel. These locations, producers, and capacities were current as of November 1993. 5.3.1 Process Descriptions for Cumene Production bv Alkylating Benzene with Propylene Cumene is present in crude oils and refinery streams. However, all commercial cumene is produced by the reaction of benzene and propylene. Benzene and propylene are reacted at elevated temperatures and pressures in the presence of an acidic catalyst. A simplified equation for this reaction is as follows: 5-27 C 6 H 6 + CH^CHCHj [catalyst] (CH 3 ) 2 CHC 6 H 5 (benzene) (propylene) - (cumene) The exothermic reaction is typically conducted using solid phosphoric acid as a catalyst, but the reaction may also be conducted using aluminum chloride or sulfuric acid as the catalyst. The aluminum chloride and sulfuric acid processes are similar; therefore, the sulfuric acid process is not described here. 79 Solid Phosphoric Acid Catalyst Process Figure 5-7 is a typical flow diagram for the manufacture of cumene by the process using phosphoric acid as the catalyst support. 80 Solid phosphoric acid is the most favored catalyst system for manufacturing cumene and is a selective alkylation catalyst that promotes the alkylation of benzene with propylene in a vapor-phase system. 79 Because the catalyst is selective, propylene feedstock for this process does not have to be thoroughly refined before use. Crude propylene streams (Stream 1) from refinery crackers that are fractionated to about 70 percent propylene can be used without further purification. The benzene (Stream 2) used in this process does not have to be dried before use because the catalyst system requires small amounts of water vapor in the reactor stream to activate the catalyst. 79 Propylene and benzene (Streams 1 and 2) are combined in a feed drum and then fed (Stream 3) to a reactor containing the phosphoric acid catalyst. The feed ratio is normally at least four moles of benzene per mole of propylene. An excess of benzene is maintained in order to inhibit side reactions. The propylene is completely consumed. From the reactor, the byproducts, unreacted material, and product are separated by distillation. The reaction products (Stream 4) are sent to a depropanizers where residual hydrocarbons (mostly propane) are removed. The propane (Stream 5) is sent through a condenser, after which some of the 5-28 MuaeooH — c • i • i £ E — c c c o • !! o -O I 8 o a *' Q *o • S 5 a- V O O. 2 s i ° C Q. C O ! 8 2 2 1^ If 5 2 • a © 00 4> U c u u. £ u c L- £ u DC a> u i— 3 O C/i 5-31 Figure 5-8. Process for the Manufacture of Cumene Using Aluminum Chloride Catalyst dried and treated (Stream 1) to remove any residual organic sulfur compounds. The benzene used in this process must be azeotropically dried (Stream 2) to remove dissolved water. The azeotrope drying distillation generates a vent gas (Vent A) that is rich in benzene. 79 Benzene and propylene (Streams 3 and 4) are fed to a catalyst mix tank, where the aluminum chloride powder (Stream 5) is added. This mixture is treated with HC1 gas (Stream 6) to activate the catalyst. The catalyst preparation operation generates a vent gas consisting of inert gases and HC1 gas saturated with vapors of benzene and diisopropylbenzene. A scrubber is typically used to absorb the HC1 gas and the residual vapors are then vented (Vent B). The resulting catalyst suspension (Stream 7) and additional dried benzene (Stream 8) are fed to the alkylation reactor as liquids, and additional dried propylene (Stream 9) is introduced into the bottom of the reactor. The feed ratio to the alkylation reactor is maintained at or above four moles of benzene per mole of propylene to inhibit side reactions. 79 The crude reaction mixture from the alkylation reactor (Stream 10) is sent to a degassing vessel, where hydrocarbons such as propane are released from solution (Stream 11). This vapor stream is scrubbed with a weak caustic solution and then fed (Stream 12) to the diisopropylbenzene (DIPB) scrubber, where the hydrocarbon vapor is recontacted with DIPB to extract residual unreacted propylene. The stream containing the propylene (Stream 13) is sent to the catalyst mix tank. 79 The degassed product (Stream 14) is sent to the acid wash tank, where it is contacted with a weak acid solution that breaks down the catalyst complex and dissolves the aluminum chloride in the water layer. The crude product from the acid wash tank is sent to a decanter tank, where the water is removed. The product is then sent to a caustic wash tank, where any residual acid in the product is extracted and neutralized. The product is decanted again to remove water and then enters a water wash tank, where it is mixed with fresh process water. This process water extracts and removes any residual salt or other water soluble material from the product. The product from the water wash tank is sent to a third decanter tank, where the crude product and water settle and separate. 79 .5-32 The entire wash-decanter system is tied together by one common vent-pad line that furnishes nitrogen for blanketing this series of tanks. A pressure control valve on the end of the vent-pad manifold periodically releases vent gas (Vent C) as levels rise and fall in the various tanks of the wash-decanter system. The vent gas is saturated with water vapor and hydrocarbon vapor (principally benzene) as contained VOC. 79 The washed and decanted product (Stream 15) is stored in a washed-product receiver tank. The crude product from the washed-product tank (Stream 16) is sent to a recovery column, where the excess benzene is stripped out. The recovered benzene (Stream 17) is returned to the benzene feed tank. The vent line associated with the benzene recovery column and with the benzene receiver tank releases some vent gas (Vent D). This vapor is principally inert gas saturated with benzene vapor as contained VOC. 79 The crude cumene (Stream 18) is sent to the cumene distillation column for distillation of the cumene product. The cumene product (Stream 19) is then stored for sale or in-plant use. The cumene distillation column and the associated cumene receiver tank are operated above atmospheric pressure and are blanketed with nitrogen (or methane) to protect the cumene from reacting with oxygen in the air and forming cumene hydroperoxide. The vent line associated with the cumene distillation column and with the cumene receiver tank releases some vent gas (Vent E). This vent gas is nitrogen (or methane) saturated with cumene vapor as the contained VOC. 79 The bottoms from the cumene distillation column contain a small amount of cumene, along with mixed isomers of diisopropylbenzene and a small amount of higher-boiling alkylbenzenes and miscellaneous tars. The bottoms stream (Stream 20) is sent to a DIPB stripping column, where DIPB is recovered and then stored (Stream 21). This stripping column is normally operated under vacuum because of the high-boiling points of the DIPB isomers. The vacuum system on the stripping column draws a vent stream from the column condenser, and this vent stream is air (or inert gas) saturated with cumene and DIPB vapors as 5-33 the contained VOC. Depending on the design and operation of the vacuum system for the column, part or all of the vent gas could be discharged to the atmosphere (Vent F). 79 The bottoms from the DIPB stripper (Stream 22) are stored in a receiver tank and then sent to waste disposal for use as a fuel. The recycle DIPB (Stream 23) is sent to the DIPB scrubber, where it is used to absorb residual propylene from the propane waste gas stream. This recycle DIPB eventually returns to the alkylation reactor, where it is transalkylated with excess benzene to generate additional cumene. 79 5.3.2 Benzene Emissions From Cumene Production Information related to benzene emissions from process vents, equipment leaks, storage vessels, wastewater collection and treatment systems, and product loading and transport operations associated with cumene production is presented below. Where a literature review has revealed no source-specific emission factors for uncontrolled or controlled benzene emissions from these emission points, the reader is referred to Section 5.10 of this chapter, which provides a general discussion of methods for estimating uncontrolled and controlled benzene emissions from these emission points. Benzene Emissions from the Solid Phosphoric Acid Catalyst Process In the solid phosphoric acid process, potential process vent emissions of benzene may be associated with the cumene column vent (Vent A in Figure 5-7). Using methane to pressurize the system, the process operates at a pressure slightly higher than atmospheric pressure to make sure that no air contacts the product. 80 The methane is eventually vented to the atmosphere, carrying with it other hydrocarbon vapors. 80 No specific emission factors were found for benzene emissions from the cumene column. One factor for total VOC emissions indicated that 0.015 lb (0.03 kg) of total VOC are emitted per ton (Mg) of cumene produced, and that benzene constituted a “trace amount” 5-34 of the hydrocarbons in the stream. 80 One cumene producer has indicated that it uses a closed system (all process vents are served by a plant flare system). Thus, it is possible that there are no process vent emissions occurring directly from the production of cumene, although there may be emissions from the flares. 79 Benzene Emissions from the Aluminum Chloride Catalyst Process Process vent emissions of benzene from the production of cumene using an aluminum chloride catalyst are associated with the benzene drying column (Vent A in Figure 5-8), the scrubber or the catalyst mix tank (Vent B), the wash-decanter system (Vent C), the benzene recovery column (Vent D), the cumene distillation system (Vent E), and the DIPB stripping system (Vent F). 80 No specific emission factors were located for benzene emissions from these sources. However, as presented in Table 5-5, one reference provided total VOC emission factors and estimates of benzene percent composition of the emissions. 3,80 The percent (weight) of benzene may be used along with a cumene production volume to calculate an estimate of benzene emissions from these sources. The control technique most applicable to these sources is flaring, with an estimated efficiency of at least 98 percent (see Section 4.5.1 of this chapter for further discussion of this control device). 5.4 PHENOL PRODUCTION Most U.S. phenol (97 percent) is produced by the peroxidation of cumene, a process in which cumene hydroperoxide (CHP) is cleaved to yield acetone and phenol, as well as recoverable by-products a-methylstyrene (AMS) and acetophenone. Phenol is also produced by toluene oxidation and distillation from petroleum operations. 81,82 Table 5-6 shows the locations, capabilities, and production methods of the phenol producers in the United States. 11,81,83 Because benzene may be present in the feedstock, it may be emitted during production of phenol. 5-35 TABLE 5-5. SUMMARY OF EMISSION FACTORS FOR CUMENE PRODUCTION AT ONI FACILITY USING THE ALUMINUM CHLORIDE CATALYST BO c ■+-> CS PC o 03 tu .£ £> o co s f UU co| 3 5 * •I § £ £ w d CJ ’> d Q 3 o U d o O oo C/3 C/3 E w 3 o o C/3 d Q -a c 05 U U in b © X X o o o o Tt c4 ■o D c c o c D d > c r> c/: O u O m m • i o o x x o o o q fN -H d t- — X (N O i X i o i m 1 c g» E .3 3 3 O o u c2 co 3 3 = >> »- S Q D c/3 C/3 D O o 00 c o ,05 C4— 3 C a „ £ co O % 5 3 05 D U > «o 00 ( o O Tf oo q r-,’ rn ■3 D C c o 3 D d t- — U« 3 1 ) > C/3 C/3 D o O i c 1 d g*> a a O c/3 * *5 oo 3 ~ 05 5 S 3 . 8 9 'O a u. 3 4J > C/3 C/3 D O o 3 • E oo £ .5 © 3 U I - ■f Si 1 ° J 2 S c* uo ODD i 3 3 VO D D £ c . 3 D — U CQ © I ro o oo T3 C TO m CO CJ C OJ u- a a OJ CJ b> 3 O OO TO «J (A D •o 4J C CJ ■ — a «j 1 s s. g o u c o •— E c 3 c 5J m a u. C a-^TO 3 0> C 3 O '5 ’oo _ 'S. D ■ = V C 5-36 TABLE 5-6. U.S PRODUCERS OF PHENOL 4J E £ 3 3 3 1-1 ca 3 £ .2 .o .2 .O ca '-t—> <—> ca ca ca ca O ca oc !2 .12 !2 o ;o ~o *x 'x x 13 x 3 c o o 3 o ca hi 4> h- 4) hi 4) ca u. 4) C/5 C/5 cu CU CU E CU 4> 0 ) 4) 4) 3 4) CJ s 3 3 JJ 3 o 4> O H 4> u cu E E E E 3 3 3 aj 3 u u u Cu u 3 3 3 ca ca 3 # o .2 .2 la o la O ca E "ca ' 3 ea 3 13 13 O • u o ."2 ‘x X X •w ca 13 13 ‘x o c c u 3 3 c i~i u. h- ca ca hi 4> 4) 4> X 4> Cu CU cu o E E CU 4) 4) 4> 4) 3 3 4) 3 3 3 3 4) 4) 3 4) 4) 4) 4> *3 o hi 4) E E E J3 E 3 3 3 C 4J E 3 u u u H CU Cu u ca £> cu —' ca c U o r- VO ,_ s ,_„ Ov o «8 „_ v ,_ s — CN VO 00 m if ON CN NO vO r- co w 'n' 'n' 'i' ' s —^ 'n' cn 'n' O O o O O O o CT) c n cn Cv m cn If r- CO oc o oc VO m VO Tf VO < X z in 00 H < X 1—] 3 X H _3 N-H 13 3 Q 7 4) 4> hi o 3 hi 4) 4) 3 < X H *C cu CO H — C/5 J3 u hi 4) > w 3 ca 3 4) 13 E 2 3 3 3 O C/5 4) uu 3 U* ca cu 4) J3 CQ 4) CQ c^ >-> o 3 C ca C/5 ca cu O' ca cu ea ca X 3 3 ca CO o 4) G o ca tu o CJ co in ca • 2 o ca £ ^ ■a g? c •— .HP fc co 2 i o ■8 ‘§> •— c = W ca o E 4> J= u sz o (U c/5 < 3 o ca i— o & o U C/5 c cn > 3 ea 3 _o < a £ E hi d 3 CO O U o & »» 3 ea O (j o CU — ’hi U o E ca o E 4> JZ U o 4) 5 la h. C/5 g w in ea CU VM 3 O ea ’ob E 4) J= u ca E Q E 4> CJ d 3 n 4) c UQ hi o ja • hi u o 4) o 4) C3 4) Q u O X 2 Ci c ca Cu E Q "ca a E 4> sz U >> c ca cu E o *2 o E 5 5-37 Stimson Lumber Company Anacortes, WA <5(<2.3) Petroleum Northwest Petrochemical Corporation, Division _ TABLE 5-6. CONTINUED .2 ‘C M 0.== -2 1 03 c c U o § *c5 “ ~ i e s C w < c .o ’•4—( 03 a o o 03 PU c o «—* es -o X o u. c O S 3 u m «n os oo o •a 03 U- o Q 5 Tt un V oo Os m rn V Sx c 03 cx E Q o . < -O t_ X «■> 3 C 4) H C/3 O co oo •a s oo u U u c 4J i— ,i> O 0> 4J 3 os 5 ex .2 *«—* w o u 'o «N £ o x: *o J3 Si § 1/5 CA OO b* 3 y OJ OJ 1 1 = CX •1*8 O > Q. Q0»« 5-45 cumene (Stream 9) is recycled. The uncondensed vapors from the condenser are vented (Vent C). The concentrated CHP (Stream 10) is transferred through a surge tank to the cleavage reactor (Stream 11). Sulfuric acid, diluted to 5 to 10 percent with acetone (Stream 12), is added to catalyze the decomposition of CHP to acetone and phenol. 80 Uncondensed vapors captured from the cleavage reactor are vented (Vent D). Excess acid in the cleaved mixture (Stream 13) is neutralized with sodium hydroxide solution (Stream 14). The neutralized product (Stream 15) flows through the crude-product surge tank to a multi-column distillation train to produce product-grade acetone, phenol, and AMS. 80 The crude product is separated in the first distillation column into a crude acetone fraction (Stream 16) and a crude phenol stream (Stream 17). The crude acetone (Stream 16) is combined with recycled hydrocarbons from the phenol topping column (Stream 18) and fed through a surge tank to the light-ends column (Stream 19) to strip low-boiling hydrocarbon impurities, such as acetaldehyde and formaldehyde, which are vented to the atmosphere (Vent E). The bottoms stream from the light-ends column (Stream 20) is fed to the acetone finishing column, where the acetone is distilled overhead, condensed (Stream 21), and sent to day tanks and subsequently to acetone product storage and loading. Uncondensed vapors are vented (Vent F). The bottoms stream (Stream 22) is processed to produce AMS (not shown). 80 The crude phenol stream (Stream 17) and the bottoms from the phenol finishing column (Stream 23) are fed to the heavy-ends column and distilled under vacuum to separate tars (Stream 24) from the impure phenol stream (Stream 25). 80 Uncondensed vapors from the condenser following the heavy-ends column are vented (Vent G). The impure phenol is fed to the phenol topping column to remove hydrocarbons such as cumene and AMS. The overhead stream from the phenol topping column (Stream 18) 5-46 may be condensed and recycled to the light-ends column of the acetone process for removal of residual acetone, cumene, and AMS. The uncondensed vapors from the condenser following the phenol topping column are vented (Vent H). The phenolic stream (Stream 26) is then fed to a dehydrating column, where water is removed overhead as a phenol/water azeotrope. * Uncondensed vapors are vented (Vent I). 80 The dried phenol stream (Stream 27) is distilled under vacuum in the phenol finishing column to separate product-quality phenol (Stream 28) from higher boiling components (Stream 23), which are recycled to the heavy ends column. Uncondensed vapors from the condenser after the phenol finishing column are vented (Vent J). The product-quality phenol is stored in tanks for subsequent loading. 80 Toluene Oxidation Process In this process, toluene is oxidized by air to benzoic acid. Following separation, the benzoic acid is catalytically converted to phenol. 5.4.2 Benzene Emissions from Phenol Production Information related to benzene emissions from process vents, equipment leaks, storage vessels, wastewater collection and treatment systems, and product loading and transport operations associated with phenol production is presented below. Where a literature review revealed no source-specific emission factors for uncontrolled or controlled benzene emissions from these emission points, the reader is referred to Section 5.10 of this chapter, which provides a general discussion of methods for estimating uncontrolled and controlled benzene emissions from these types of emission points. “Spent air” from the oxidizer reactor (Vent A, Figure 5-9) is the largest source of benzene emissions at phenol production plants utilizing the Allied process. 87 Table 5-7 provides uncontrolled and controlled (i.e., thermal oxidizer) emission factors from the oxidizer 5-47 TABLE 5-7. SUMMARY OF EMISSION FACTORS FOR PHENOL PRODUCTION BY THE PEROXIDATION OF CUMENE v rj Q c o U aj o t— 3 O CO oo oo C LU c o o c/5 aj Q TD 3 ca U u co CO © 5 8 q ^ 00 C/5 JJ a O 03 23 2 60 c a e 2 o o •— <2 « 3 3 C X (N O o a c (U e 3 0- U CO 5-48 reactor vent from the phenol production process based on the peroxidation of cumene. 88,89 Charcoal adsorption is the most commonly used method to control emissions from the oxidizer reactor vent; however, condensation, absorption, and thermal oxidation have also been used. 90 Recovery devices (i.e., one or more condensers and/or absorbers) are the most commonly used methods to recover product and control emissions from the cleavage (Vent D, Figure 5-9) and product purification distillation columns; however, adsorption and incineration have also been used for emissions reduction. 81,90 5.5 NITROBENZENE PRODUCTION Benzene is a major feedstock in commercial processes used to produce nitrobenzene. Approximately 5 percent of benzene production in the United States is used in the production of nitrobenzene. 12 In these processes, benzene is directly nitrated with a mixture of nitric acid, sulfuric acid, and water. As of February 1991, five companies were producing nitrobenzene in the United States. 91 Their names and plant locations are shown in Table 5-8. 11 In addition to these plants, plans are underway for Miles and First Chemical to start up a possible 250-million-pound (113.4-Gg) aniline plant, along with feedstock nitrobenzene, at Baytown, Texas. 92 A discussion of the nitrobenzene production process, potential sources of benzene emissions, and control techniques is presented in this section. Unless otherwise referenced, the information that follows has been taken directly from Reference 93. 5.5.1 Process Descriptions for Continuous Nitration Nitrobenzene is produced by a highly exothermic reaction in which benzene is reacted with nitric acid in the presence of sulfuric acid. Most commercial plants use a continuous 5-49 TABLE 5-8. PRODUCERS OF NITROBENZENE Company Location Capacity in million Ib/yr (million kg/yr) Rubicon, Inc. Geismar, LA 550 (250) First Chemical Corporation Pascagoula, MS 536 (244) E.I. duPont de Nemours and Company, Inc. Beaumont, TX 350 (160) BASF Corporation (Polymers Division Urethanes) Geisman, LA 250(110) Miles, Inc. (Polymers Division Polyurethane) New Martinsville, WV 100 (45) TOTAL 1,786 (809) Source: Reference 11. Note: This list is subject to change as market conditions change, facility ownership changes, plants are closed, etc. The reader should verify the existence of particular facilities by consulting current lists and/or the plants themselves. The level of benzene emissions from any given facility is a function of variables such as capacity, throughput, and control measures, and should be determined through direct contacts with plant personnel. These data on producers and location were current as of January 1993. nitration process, where benzene and the acids are mixed in a series of continuous stirred- tank reactors. 94 A flow diagram of the basic continuous process is shown in Figure 5-11, 93 As shown in the figure, nitric acid (Stream 1) and sulfuric acid (Stream 2) are mixed before flowing into the reactor. Benzene extract (Stream 6), two recovered and recycled benzene streams (Streams 7 and 8), and as much additional benzene (Stream 9) as is required are combined to make up the benzene charge to the reactor. For the process depicted here, nitration occurs at 131 °F (55°C) under atmospheric pressure. Cooling coils are used to remove the heat generated by the reaction. 5-50 M1J6S00»6 5-51 Figure 5-11. Process Flow Diagram for Manufacture of Nitrobenzene Following nitration, the crude reaction mixture (Stream 3) flows to the decanter, where the organic phase of crude nitrobenzene is separated from the aqueous waste acid. The crude nitrobenzene (Stream 12) subsequently flows to the washer and neutralizer, where mineral (inorganic) and organic acids are removed. The washer and neutralizer effluent are discharged to wastewater treatment. The organic layer (Stream 13) is fed to the nitrobenzene stripper, where water and most of the benzene and other low-boiling-point components are carried overhead. The organic phase carried overhead is primarily benzene and is recycled (Stream 7) to the reactor. The aqueous phase (carried overhead) is sent to the washer. Stripped nitrobenzene (Stream 14) is cooled and then transferred to nitrobenzene storage. The treatment, recycling, or discharge of process streams is also shown in the flow diagram. Aqueous waste acid (Stream 4) from the decanter flows to the extractor, where it is denitrated. There, the acid is treated with fresh benzene from storage (Stream 5) to extract most of the dissolved nitrobenzene and nitric acid. The benzene extract (Stream 6) flow's back to the nitrating reactor, whereas the denitrated acid is stored in the waste acid tank. Benzene is commonly recovered from the waste acid by distillation in the acid stripper. The benzene recovered is recycled (Stream 8), and water carried overhead with the benzene is forwarded (Stream 11) to the washer. The stripped acid (Stream 10) is usually reconcentrated on site but may be sold. 93 Typically, many of the process steps are padded with nitrogen gas to reduce the chances of fire or explosion. This nitrogen padding gas and other inert gases are purged from vents associated with the reactor and separator (Vent A in Figure 5-11), the condenser on the acid stripper (Vent B), the washer and neutralizer (Vent C), and the condenser on the nitrobenzene stripper (Vent D). 5-52 5.5.2 Benzene Emissions from Nitrobenzene Production Benzene emissions may occur at numerous points during the manufacture of nitrobenzene. These emissions may be divided into four types: process emissions, storage emissions, equipment leak emissions, and secondary emissions. Process emissions occur at the following four gas-purge vents: the reactor and separator vent (A), the acid stripper vent (B), the washer and neutralizer vent (C), and the nitrobenzene stripper vent (D). The bulk of benzene emissions occur from the reactor and separator vent. This vent releases about three times the level of benzene released from Vents B and D (Figure 5-11), and about 120 times that released from Vent C. For all of these vents, the majority of VOC emissions is in the form of benzene. Benzene accounts for 99, 100, 76, and 99 percent of total VOC emissions from Vents A, B, C, and D, respectively. Table 5-9 shows estimated emission factors for benzene from these sources. 93 Other emissions include storage, equipment leak, and secondary emissions. Storage emissions (G) occur from tanks storing benzene, waste acid, and nitrobenzene. Equipment leak emissions of benzene can occur when leaks develop in valves, pump seals, and other equipment. Leaks can also occur from corrosion by the sulfuric and nitric acids and can hinder control of fugitive emissions. Secondary emissions can result from the handling and disposal of process waste liquid. Three potential sources of secondary benzene emissions (J) are the wastewater from the nitrobenzene washer, waste caustic from the nitrobenzene neutralizer, and waste acid from the acid stripper. Where waste acid is not stripped before its sale or reconcentration, secondary emissions will be significantly affected (increased) unless the reconcentration process is adequately controlled. Table 5-9 gives benzene emission factors before and after the application of possible controls for two hypothetical plants using the continuous nitration process. The two 5-53 TABLE 5-9. SUMMARY OF EMISSION FACTORS FOR HYPOTHETICAL NITROBENZENE PRODUCTION PLANTS fi u- 60 O cT o S co eq l— JS 2 'ooi g < b mi c ^ .2 § c/3 *-* .2 lo E e w -2 o os C p 2 o I m P P P u ■o m 00 C o o c P • X> «n o Os ■ ■*—* P Z o i m m CN o in oo O 00 _c co 2 c^ Uh O _ o co 04 c t- 4> •w c tl ■a © o o (N T3 CJ C o o c P CO ^ T3 c £ o c g CU on CO U- n o On £ ! 4—1 2 z o i m in CN Os Tf T3 OJ c O O c P C0 o H CO i-i n o On C ’—i .3 2 z o i m P P D D P Os CN Tf Tf T3 V ■o o oT rT rT VO m m CN —* 00 •*$ Tf CN r- VO Tf «n o d o o 0) XL t— o C/3 *o < > c < O *C0 C o o c p a> a. . 2 * *n ,_^ £n cq 2 a 2 o 2 vn CO C s fe a W r Jo m ^ o — Os tJ •- ^ u P z < o § m m o u ■o" u •o' 00 (S VO o o vo r- r^ o in in T3 2 ’o Ui 4—> 3 O O c p <3J JC 1— o c/> T3 < C "O I- flJ _N i 73 « 5 g s a 5 < O 73 i i— 1-1 3 cu I on 3 3 G C 3 3 a a 3 3 X> X s £ g JO z z ON m P P "O* © ON o u ■o’ -o u s T3 X X w V ON 00 rn 00 On O X o m o O • O o u s —^ X X m m O 00 X CN ON ON o o o -o 3 c o O G P 3 6X) 03 t— O ^ Cr> o S £ o •— <- o 3 w to 03 •o o < 3 —> C/3 03 3 C 3 G 3 3 X 0 £| g 2 2 9 g o 2 w On CO P P P P •o 3 c o o G P 1) 03 > •o c 03 CO G- £ 3 0- C/3 CO 3 o o G 3 E a. ’£ cr W C/3 • c 3 O II g E i5 w o £ oo S «3 i •— 3 Z, P On i CO C/3 CO 2 3 C/5 °-73 C* .£ =3 S O x J 8 E •a 3 o 3 ■8 I— C- 4j c 3 s £ o -—co CO k. ^ W ^ 43 C o & •a 43 CO Os 43 CJ c 43 k. A3 <—* 43 a: 43 3 3 O CO U o u_ o 43 Ua 2 c3 t~ S' 43 H CL 3 3 O J 3 CQ £1 43 3 ca i— «3 a. 3 3 3 co 43 3 43 S C 3 • 3 5 = §4 "iS 3 —. n b oox 60 ' / 3 _q k. rr — cfl — CO CO 2 « 5 u. T3 — ,3 3 3 >*- to ,aj 3 CO 3 ^ £ 3 2 a O c >< 55 •3 3 CO 2. 3 ’5 k. 3 C fl 3 O co 3 53 fc m co O ec §82 tu LU CO I £ 3 N iy5 3 c« H o (N OO VO O w OO so TT (N VO CO . •c j> 1 ■o 5 p CO CO 0> u- T3 CO CO CO CO CT3 «3 MM > >• 5-56 plants differ in capacity; one produces 198 million lb/yr (90,000 Mg/yr) and the other 331 million lb/yr (150,000 Mg/yr) of nitrobenzene. Both plants use a vent absorber or thermal oxidizer to control process emissions in conjunction with waste-acid storage and small benzene storage emissions. The values presented for the main benzene storage emissions were calculated by assuming that a contact-type internal floating roof with secondary seals will reduce fixed-roof tank emissions by 85 percent. The values presented for controlled equipment leak emissions are based on the assumption that leaks from valves and pumps, resulting in concentrations greater than 10,000 ppm on a volume basis, are detected, and that appropriate measures are taken to correct the leaks. Secondary emissions and nitrobenzene storage emissions are assumed to be uncontrolled. Uncontrolled emission factors are based on the assumptions given in the footnotes to Table 5-9. The total controlled emission factors for these hypothetical plants range from 0.44 to 0.78 lb/ton (0.22 to 0.39 kg/Mg). Actual emissions from nitrobenzene plants would be expected to vary, depending on process variations, operating conditions, and control methods. 93 A variety of control devices may be used to reduce emissions during nitrobenzene production, but insufficient information is available to determine which devices nitrobenzene producers are using currently. Process emissions may be reduced by vent absorbers, water scrubbers, condensers, incinerators, and/or thermal oxidizers. Storage emissions from the waste-acid storage tank and the small benzene storage tank can be readily controlled in conjunction with the process emissions. (A small storage tank contains approximately one day's supply of benzene; the larger tank is the main benzene storage tank.) In contrast, emissions from the main benzene storage tanks are controlled by using floating-roof storage tanks. 5-57 Equipment leak emissions are generally controlled by leak detection and repair, whereas secondary emissions are generally uncontrolled. 5.6 ANILINE PRODUCTION Almost 97 percent of the nitrobenzene produced in the United States is converted to aniline. 91 Because of its presence as an impurity in nitrobenzene, benzene may be emitted during aniline production. Therefore, a brief discussion of the production of aniline from nitrobenzene and its associated benzene emissions is included in this document. Table 5-10 lists the U.S. producers of aniline and the production method. 11 The mam derivative of aniline (75 percent) is p.p.-methylene diphenyl diisocyanate (MDI). The growth outlook for aniline is expected to remain strong because of its continued use in housing and automobile parts. 95 5.6.1 Process Descriptions for Aniline Production for Nitrobenzene A process flow diagram of the most widely used process for manufacturing of aniline—by hydrogen reduction of nitrobenzene-is shown in Figure 5-12. 96 As shown in the figure, nitrobenzene (Stream 1) is vaporized and fed with excess hydrogen (Stream 2) to a fluidized-bed reactor. The product gases (Stream 3) are passed through a condenser. The condensed materials are decanted (Stream 4), and non-condensible materials are recycled to the reactor (Stream 5). In the decanter, one phase (Stream 6) is crude aniline and the other is an aqueous phase (Stream 7). The crude aniline phase is routed to a dehydration column that operates under vacuum. Aniline is recovered from the aqueous phase by stripping or extraction with nitrobenzene. Overheads from the dehydration column (Stream 8) are condensed and recycled to the decanter. The bottoms from the dehydration column (Stream 9), which contain aniline, 5-58 w 2 j-J 2 < u- O co & a u D Q O 06 P~ CO D © i m W -3 CD < H 4) QS T3 « CO CO o I >> k. i— w ^ "m £■ “if - o .1 3 ^3 HI o ca U- c o _o ca X o c a> j= o. ca c .2 ca k. I O U ca o CL) jz U j= u 4> 4> 4> c c 4> 4) a a •a -a c p o 3 •o 4> ha c V CkO o l>a •o E s CN X c o E 3 ca * X © o s a o o 3 o ■ 3 •o » E o 00 < J ka ca E CO 'S U 3 I V Z « o 73 s 4-1 *•« § >; = i ■o Q- • E “1 o uu u CO 73 CJ 1 u w c o Oa 3 •o ■o § 3 O 4> £ *w CT3 CO rti DO ~ 1 o •S -2 2 £ W E< * ca o V SZ U u- e3 c o 35 g 73 E >> < i £B c o 4—* o 3 •o u U« s o o ca 4> c u _£ CO O I8 Z 3. o rs o ■'1- JJ ’> .1 Ua 2 £ ID z 0) § 5 5 ka , 2 c 3 o 4> .S 44 —a CO o ■a I 4> kg « « 5 CO 4> 35 > g *o c2 w ca ■o u CO 4> J5 > co CO — 0> >» ■s S- s E 4) O _ e* g ~ CO w s 6 .2 « 8 T3 £ 4> o> co O 4) O g Q. 5 u 2 a o o x: co 3 O g a . ^ u. 2*5 J f Da 4> . > CO 2 4) CO 4) ! £ 4) as t« k3a qj J= > s « 4> ^ c E o 5 CO It •= £• ■o 4) C 4) 'O is 3 O x: CO T3 3 ca CO 4) CO ca 4> E CT3 x: -o ° 1 CO S CO .2 •3 ~ c 3 O 4> « fc « 3 m u 3 60 5 3 O _a c tj •a 3 ca 1 *5) 3 O *3 -S S 3 ca co 4) S oc ® I * X2 jd U ^ CO O 0> 8 *3 S’<2 3 T co t; ca CO — — 3 44 U CO •« si (2 4> ca Oa ca o CO ca JS u 3 CO CO 4> 1 1 > o o o 2 o Z 5-59 »n producers and locations were current as of January 1, 1993. c < Mld0900fr6 © B ® re I- re E O 3 13 * O ® O Q c a o ® O o re 05 £T C c k. ® • N N c 'C ® o .o a. o « £ > G c 04 C G 04 04 04 3 N cd o > C/3 z o o nJ £ 0 04 •a cd 04 e c w- Cd 2 04 _3 £ •«—> OX) 2 cd G cd 00 cd 04 04 l-i z Q o c G cd a. c- o C 0- O. <*> 3 § 2 04 1 _I O i— U o M c n O 1 « c o 3 2 o *3 c cd •- S 2 5 aj O S 04 o — 2 u ft, ft. 0 o G c o >v 2 U ^ Q U 2 •3 — G cd b o cd O vU •a c E 04 S E 3 04 cd ■w 00 6 o -c cn U Vi cs OX) S j= u O £ ’Jo 1 3 to 5-63 ownership changes, or plants are closed down. The reader should verify the existence of particular facilities by consulting current lists or the plants themselves. The level of emissions from any given facility is a function of variables such as throughput and control measures, and should be determined through direct contacts with plant personnel. The data on producers and locations were current as of January 1993. T«H-G«s Treatment ON 13 Q "o c c U 13 u l— 3 C OO (fl c on C/3 E UJ 1 re U U C/5 (N i/O s O C/3 *3 < 5 U* CT3 u T3 43 c o u c 3 is -O E c % 3 c/3 U re c oo S — re •- 4) re b. £- H 4) C 4> !i 5 © ro ^ J. U o I m • 3 CO X) •S 2 5 on <2 S3 § .? "I re 2 H fS m s o c o o C/3 •o < 5 u. CT3 U c _c re Vi 5 o u- 4) "S. C/3 w o <2 E c s 4> < > •o 43 c o 13 c 3 c o Vi 4> 5 . a s| 1-4 o © :u2 o I oo Q 2 Q w _ 2 fc 3 43 C 4> C 43 CQ oo c VI V) 43 S *5 «§ = 2 c sll 5 i P d >» o o C > n r ™ 13 J. U 2 3C o i m V 00 8 .2 43 P S| ,« 3 re O © n £ £ J. u S o * ro 43 C 43 | § e 2 •§ 8 = C '3 o C/5 2 5 S o 00 o c .2 & s TO < C 5 Uh u c ^ O W •2 > 5 S “ 43 Vi 00 5 g o 43 •= a 43 § o. m I - § 5 < > ■ •o 43 C o u c 3 i 43 c C O 8 •§ g o | ,2 - 04 vi Tf c o I oo 43 43 00 re a. 43 on 11 13 43 43 O 43 J2 Q 2 72 TO C CJ E . 2 * '5 cr W 04 cri C o I 8 00 ■o 43 a o 43 C D 2 oc 5 .2 i i o £ O § o 2 To § co x: © i co 4= £ u C *a CD 3 .2 *w c o o 5-68 TABLE 5-12. CONTINUED OO .s re OC u re U. s o .5 a u re U. c o '7. "E UJ oo 2 'So t) > u Q c o U u 4> l— 3 O 00 (A c V. in •P E UJ o cn 4 > Q U U oo m I/O T c _o u CO a oo aj 3 O a OJ CQ CO wo Tt" 3 u aj 00 O 3 aj 1-4 <2 oj a aj 8 3 O C/3 *3 g g J 8 .8 flj * *g cn 3 O cn Jr 4> O 3 2 °* «^4 •15 T O O 4> O* S ^ § (N 4> cn 3 O aj •o •o 1) CJ 3 ■g S 1 Q. o o.2 o g 2 P § <9 “i oo Sc O o. 00 o VO ^ w o S 8. ■8 aj 3 aj s IS o _o — SO n Os x: o «TT w OO 3 3 2 *3 i! cn « O re 3 O o •3 4 > CO •o o re u D £ aj aj 3 aj N 3 JS OO P '—' C3 £ e — o c_ J w 5/3 3 •2 & a. T3 re 4> i— v r= C“ re *3 _ 4> 3 cn aj re cn cn 4> 0) Cl K V aj 3 cn w. O w o <2 3 .2 "cn cn 4> 3 4 ) 1 g O B O 2 o •5 « (L cn t Ofi § O SO 8 O ■— cn cn 3 aj N 8 | O _o 2 g 8 O E *3 OO '8 ’in in 4 > cn •O 3 4 ) >> > re 4 > 3 O •3 •3 4 > 8 4 > is 5 u O . • o 2 ^re 3 lt>a flj 3 > ■i i ■i * E o 4) — 4 ) £ QJ D •5 6 00 cn s aj !£> = Cl *3 Cl g re 90 percent) by microorganisms in sewage plants after a relatively short period of time. In comparison, the highly branched alkyl benzene sulfonates have a much lower biological degradability. 100 Dodecylbenzene and tridecylbenzene are the two most common LABs. The locations of the LAB producers in the United States are shown in Table 5-13. 1U01 In the United States, LAB is produced using two different processes. Vista's Baltimore plant uses a monochloroparaffin LAB production process. Vista's Lake Charles plant and Monsanto's Alvin plant use an olefin process, wherein hydrogen fluoride serves as a catalyst. Approximately 64 percent of LAB is produced by the olefm process. The paraffin chlorination process accounts for about 36 percent of LAB production. Both processes are described in the following sections. 5.8.1 Process Description for Production of LAB Using the Olefin Process Production of LAB using the olefin process consists of two steps: a dehydrogenation reaction and an alkylation reaction. The C 10 to C 14 linear paraffins are 5-70 TABLE 5-13. U.S. PRODUCERS OF LINEAR ALKYLBENZENE (DETERGENT ALKYLATES) C ft c/5 OJ CJ O — M % ^ U a _ c cz ‘JT 11 < C .2 CO CJ Q C CT3 CM E o E 33 I I C/3 c IE OJ c > E > £ o- K * D. ea ea i 1 P3 Um CZ CJ C/3 C2 u Ok *o M c "O o c G U. CZ OJ CS w o mm a 8 e c ea JS CJ 13 E 15 J3 O o Um OJ OJ Um OJ E c E oj c > cj oj *o 1 ea OJ c oj oj g - a a JS £ & £ — o ^ T3 l- O g Q c w X H _c > < rt CJ E > c ea C- E Q c ea C/5 c o Q S OJ 1— o E ca CQ Dm 3 O e ca Cm E Q la o E oj J= U eg co So > < CO jlj ca J= u OJ ea u-1 *o oj E c w OJ — a & t o S C 1 * oj u- <-> c5 x OJ oj c w 5-71 changes, or plants are closed down. The reader should verify the existence of particular facilities by consulting current listings or the plants themselves. The level of emissions from any given facility is a function of variables, such as throughput and control measures, and should be determined through direct contacts with plant personnel. These data for producers and locations were current as of January 1993. dehydrogenated to n-olefins, which are reacted with benzene under the influence of a solid, heterogenous catalyst (such as hydrogen fluoride [HF1]) to form LAB. The discussion of LAB production using the olefm process is taken from references 102 and 103. First, n-paraffms are transferred from bulk storage to the linear paraffin feed tank in Stream 1 (Figure 5-15.) 103 The paraffins are heated to the point of vaporization (Stream 2) and passed through a catalyst bed in the Pacol reactor (Stream 3), where the feed is dehydrogenated to form the corresponding linear olefins by the following reaction: R, - CH 2 - CH 2 - R 2 —> Rj CH = CH - R 2 + H 2 The resulting olefins contain from 10 to 30 percent a-olefms, and a mixture of internal olefms, unreacted paraffins, some diolefins, and lower-molecular-weight “cracked materials.” The gas mixture is quickly quenched with a cold liquid stream as it exits to process thermally-promoted side reactions (Stream 4). The hydrogen-rich offgases (e.g., hydrogen, methane, ethane, etc.) are then separated from the olefin liquid phases (Stream 5). The gas is used as process fuel (Stream 6) or vented to a flare stack. Di-olefins in the Pacol separator liquid are selectively converted back to mono-olefins in the Define reactor (Stream 7). The effluent from the reactor is routed to a stripper (Stream 8), where light ends are removed (Stream 9). The olefin-paraffin mixture (Stream 10) is then alkylated with benzene (Stream 11) in the fixed-bed reactor to be blended with a HF1 catalyst. The blend is held at reaction conditions long enough for the alkylation reaction to go to completion as follows: R,CH = CHR 2 + C 6 H 6 — > R t CH 2 - CHR 2 Product from the reactor flows to the benzene stripping column (Stream 12) for separation and recycle of unreacted benzene to the fixed-bed reactor (Stream 13). The liquid HF1 is also separated and recycled to the alkylation vessel to be mixed with fresh HF1. 5-72 Fraah Banzana CD 5 • dia-«f-M1d-«900*6 Pa m O 4J U c a> u- £ 0) 0C 04 Ci c o U 04 o L- 3 O 00 C/3 C/3 C/3 E w c .2 . 2 * *C o C/3 04 Q 13 C 03 u u oo co x Tt O (N w m d cO 0 X O O d X It r- X «o d X it C4 (N 13 04 C o o c D 04 C/3 03 13 04 C/3 D o ' 5 . o u. ■W O 04 N < C 04 > c 04 3 g 1 N w- _ O ^ 3 E E = c O g U op L- C cj pi X) ^■§ o oo CQ c ‘5 eu u- K 04 c fS <1 D CO < u> 04 O ^ C 0 l_i X ' CQ » cl oa 2 < o -J © "eo S?S *S £ 44 c “ . .232 ! 1 ^ oc v Sf 2 g a « & U. c c c 0 JS| *8 60 S « ” 2 •° £ a S O I e« u "O E £ 2 ‘G o> c 8 •- « c« > u u o o 2 o O L. «2 <2 £ C C Ji .2 .2 c /3 «/3 C/3 U* C/3 C/3 Q E £ u UJ tu _J 2 § •a o eii ^ 60 co *a I § O DO g.s C/3 CS •a c /5 a w a 2 4J k- (S -S o. >% >* r .* w o «J «J CO .2 3 « .2 I « a. Cl J' " £ >. 60 E c c X 0 O 4/ k> c 0 "O 1 — 0 L_ O C O u *3 •c > c £ « •0 s c _o « c re 0 «—• & CT3 U4 0 3 60 O0 c X C c 0 E SJ c L. 0 u. 44 03 (4 > C 4/ .60 ’>< 44 C 44 c3 X C. - eo £ .S c I g 1 s Cl — ig i •3 S 3 S. J i g 1 e £ - g 60 O C ^ «S «■> CSV •*C u ■£ 2 o Z 5-75 Alkylbenzene (pure) dl«-»f’MlJ*Z900>e c c s • q. c £ 5 ° m to ° to < o ® Q. c £ o E N * 3 ss» 00 ** O 'C o XT u o o u 8 u i_ 3 O C/0 5-76 Figure 5-16. Production of Linear Alkybenzenes via Chlorination are converted at 212°F (100°C) to a mixture of about 35 percent chlorinated paraffins, and the remainder to paraffins and HC1 as shown in the following reaction:. Ri - CH 2 - R 2 + Cl —> R - CH - R 2 + HC1 + heat Cl Following this reaction, dehydrochlorination (elimination of HC1) of the monochloroalkanes takes place at 392 to 752 °F (200 to 300°C) over an iron catalyst to form olefins (linear alkenes with internal double bonds) (Stream 3). It is necessary to remove all chlorinated paraffins (such as dichloroalkenes) from the process stream because they form other products besides LAB. Therefore, the remaining chlorinated paraffins are dehydrochlorinated to give tar-like products that are easily separated and recycled back to the reactor (Stream 4). HC1 is also removed from the mixture (Stream 5), leaving a mixture of only olefins and paraffins for the alkylation reaction. 100 This olefin-paraffin mixture (Stream 6) is combined with benzene from storage that has been dried in a benzene azeotropic column (Stream 7). These two streams are combined in an alkylation reactor with an aluminum chloride catalyst at 122 °F (50 °C) (Stream 8). The subsequent reaction produces LAB, illustrated below: Rj - CH - R ; + C 6 H 6 —> Rj - CH - R 2 + HC1 + heat, possible olefins, short-chained paraffins, etc. Cl At this point, HC1 gas and some fugitive volatile organics given off during the reaction are treated with adsorbers and excess HC1 is routed to storage (Vent B). Next, the LAB (Stream 9) is routed to a separator where hydrolysis is performed in the presence of HF1 at 50°F (10°C) to separate crude LAB and the organics (benzene, tar, etc.) (Stream 10) from the catalyst sludge (Stream 11). Benzene is recovered in the benzene stripping column and recycled back to the reactor (Stream 12). 5-77 The resulting paraffin-alkylate mixture (Stream 13) is sent through rectification and purification (which includes washing and decanting) to yield pure alkylbenzene and paraffin, which can be recycled as feedstock. 100 5.8.4 Benzene Emissions from LAB Production Using the Chlorination Process Benzene emissions using the LAB chlorination process are shown in Table 5-14. The four major points of benzene emissions are listed below. Emission factors for these points also are presented in Table 5-15. 102 One emission point is the benzene azeotropic column vent, which serves to dry the benzene before it enters the alkylation reactor. Some benzene emissions can escape from the vent in the column (Vent A). The quantity of escaping emissions is dependent on the dryness of the benzene and the design of the column condenser. A second emission point is the hydrochloric acid adsorber vent. Following the alkylation reaction, the HC1 gas and fugitive volatile organics are treated by absorbers. Most of the product goes to hydrochloric acid storage, but some is vented off (Vent B). The amount of benzene emissions given off here is dependent on the fluid temperature in the absorber and the vapor pressure of the mixed absorber fluid. The third type of emission point is the atmospheric wash decanter vents. In the final purification/rectification stage, the crude LAB is washed with alkaline water to neutralize it. Benzene emissions can escape from these atmospheric washer vents (Vent C). Finally, in the benzene stripping column, benzene is recovered and returned to the benzene feed tank. Residual inert gases and benzene emissions can occur at this point (Vent D). The amount of benzene in the stream depends on the quantity of inert gases and the temperature and design of the reflux condenser used. 5-78 TABLE 5-15. SUMMARY OF EMISSION FACTORS FOR HYPOTHETICAL LINEAR ALKYLBENZENE'PLANT USING THE CHLORINATION PROCESS bo C w cs QC o C3 Urn o bfi O *5 cs $ tu oo G •2 g c/3 . c/3 ' s - w U ’> <3 C o U P P oj ! > < i •§ 3 © C o w a ^ Oj CQ a « 3 .e -£ •= On O c/3 P "3 E CO U E u 3 C3 —. s 5 J3 c C. « -tb « o c S o o £ Q c, < a w C/0 03 2“S — OJ C -c ^ Q. Uh C/3 e« o c 00 0 - Oi 3 OJ 1) CQ o> 3 OJ s q oj ^ a c 32 wo <1 u u. 3 O 00 C/3 CO a> 8 I— a. c o « J1 3 U S 5 >, 3 (U CJ 3 n OJ G >? a. DO CQ is O o OX) gs ^ S. c . O 3 ^ 00 ON v W3 3 b> 3 C C a E - .. c ° £ • - •rt TJ g ■® fi & ass Si-’ 0 E kw U o o ® you, <2 a <2 c c a .2 .2 * 00 CO t- U IA U UJ U B «3 3 OJ DO « u, 3 O u c OJ OJ 3 « 3 l— 3 3 W 3 3 J= CO 5 E o c o 3 3 > OJ 3 G CO G O CO i- 3 DO 13 C O 3 CO > OX .s 3 3 ■8 13 3 o CQ < -J G 3 > *s > c < 3 o Z 5-79 contact plant personnel to confirm the existence of emitting operations and control technology at a particular facility prior to estimating emissions therefrom. The most frequently applied control option for all of these sources is to use the emissions for fuel. 5.9 OTHER ORGANIC CHEMICAL PRODUCTION Several additional organic chemicals that are produced using benzene as a feedstock are believed to have benzene emissions. These chemicals include hydroquinone, benzophenone, benzene sulfonic acid, resorcinol, biphenyl, and anthraquinone. 68 A brief summary of the producers, end uses, and manufacturing processes for these chemicals is given below. No emissions data were available for these processes. 5.9.1 Hvdroquinone The primary end use of hydroquinone is in developing black-and-white photographic film (46 percent). A secondary end use is as a raw material for rubber antioxidants (31 percent). 104 A technical grade of hydroquinone is manufactured using benzene and propylene as raw materials by Goodyear Tire and Rubber Company in Bayport, TX,11 million lb/yr (5 million kg/yr) and by the Eastman Chemical Company, Tennessee Eastman Division, in Kingsport, Tennessee, 26 million lb/yr (12 million kg/yr). 11,101 In this process, benzene and recycled cumene are alkylated with propylene in the liquid phase over a fixed-bed silica-alumina catalyst to form a mixture of diisopropylbenzene isomers. The meta isomer is transalkylated with benzene over a fixed bed silica-alumina catalyst to produce cumene for recycle. The para isomer is hydroperoxidized in the liquid phase, using gaseous oxygen, to a mixture of diisopropylbenzene hydroperoxide isomers. The mono isomer is recycled to the hydroperoxidation reactor. The diisopropylbenzene hydroperoxide is cleaved in the liquid phase with sulfuric acid to hydroquinone and acetone. Acetone is produced as a co-product. 104 5-80 5.9.2 Benzophenone Benzophenone (diphenylketone) is used as an intermediate in organic synthesis, and as an odor fixative. Derivatives are used as ultraviolet (UV) absorbers, such as in the UV curing of inks and coatings. 105 Benzophenone is also used as flavoring, soap fragrance, in pharmaceuticals, and as a polymerization inhibitor for styrene. Nickstadt-Moeller, Inc., in Ridgefield, New Jersey, and PMC, Inc., PMC Specialties Group Division in Chicago, Illinois, produce a technical grade of benzophenone. 11 Benzophenone is also produced by Upjohn Company, Fine Chemicals. 101 Benzophenone is produced by acylation of benzene and benzyl chloride. 68 5.9.3 Benzene Sulfonic Acid Benzene sulfonic acid is used as a catalyst for furan and phenolic resins and as a chemical intermediate in various organic syntheses including the manufacture of phenol and resorcinol. 105,106 Benzene sulfonic acid is manufactured by sulfonation—reacting benzene with fuming sulfuric acid. 106 Burroughs Wellcome in Greenville, North Carolina; CL Industries, Inc., in Georgetown, Illinois; and Sloss Industries Corporation in Birmingham, Alabama, produce benzene sulfonic acid. 11 5.9.4 Resorcinol Resorcinol is produced by INDSPEC Chemical Corporation in Petrolia, Pennsylvania. 11 Resorcinol is produced by fusing benzene-m-disulfonic acid with sodium hydroxide. Resorcinol is used in manufacturing resorcinol-formaldehyde resins, dyes, and pharmaceuticals. It is also used as a cross-linking agent for neoprene, as a rubber tackifier, in adhesives for wood veneers and runner-to-textiles composites, and in the manufacture of styphnic acid and cosmetics. 106 5-81 5.9.5 Biphenvl Biphenyl (diphenyl or phenylbenzene) is produced by Chemol Co. in Greensboro, North Carolina; Koch Refining Co. in Corpus Christi, Texas; Monsanto Co. in Anniston, Alabama; Sybron Chemical Inc., in Wellford, South Carolina; and Chevron Chemical Co. of Chevron Corp. 11,101 One method for producing biphenyl is by dehydrogenation-slowly passing benzene through a red-hot iron tube. 106 Biphenyl is used in organic synthesis, as a heat-transfer agent, as a fungistat in packaging citrus fruit, in plant disease control, in the manufacture of benzidine, and as a dyeing assistant for polyesters. 106 In 1991, 8,976 tons (8,143 Mg) of biphenyl were sold. 101 5.9.6 Anthraquinone Anthraquinone is manufactured by heating phthalic anhydride and benzene in the presence of aluminum chloride and dehydrating the product. Anthraquinone is used as an intermediate for dyes and organics, as an organic inhibitor, and as a bird repellent for seeds. 5.10 BENZENE USE AS A SOLVENT Benzene has been used historically as an industrial solvent. Because benzene is readily soluble in a variety of chemicals (including alcohol, ether, and acetone), it has commonly been used as an agent to dissolve other substances. As an industrial solvent, benzene application has included use as an azeotropic agent, distilling agent, reaction solvent, extracting solvent, and recrystallizing agent. However, benzene use as an industrial solvent has been steadily declining over the last few years because of its adverse health effects and increased regulation. The Occupational Safety and Health Administration has cited health risk to workers from exposure to benzene, and EPA has classified benzene as a Group A chemical, a known human carcinogen. 107 5-82 Source categories that currently use benzene as a solvent include pharmaceutical manufacturing; general organic synthesis; alcohol manufacturing; caprolactam production, and plastics, resins, and synthetic rubber manufacturing. Benzene is also used in small quantities (generally less than 0.1 percent) in solvents used in the rubber tire manufacturing industry; however, the amount of emissions generated is variable depending on the amount of solvent used. 108 Facilities in the above-listed source categories indicate that they plan to eliminate benzene solvent use in the next few years. 107 Facilities have been experimenting with substimtes, such as toluene, cyclohexane, and monochlorobenzene. However, those facilities that continue to use benzene indicate that they have been unable to identify a solvent substitute as effective as benzene. 109 Several facilities in the source categories listed above reported benzene emissions in the 1992 TRI. These facilities and their locations are included in Table 5-16. Emissions of benzene from solvent used in the manufacture and use of pesticides, use of printing inks, application of surface coatings, and manufacture of paints are believed to be on the decline or discontinued. 107110 However, several facilities in these source categories reported benzene emissions in the 1992 TRI. 111 These facilities and their locations are also included in Table 5-16. 11 * Benzene continues to be used in alcohol manufacture as a denaturant for ethyl alcohol. It is also used as an azeotropic agent for dehydration of 95 percent ethanol and 91 percent isoproponal. 109 Companies currently producing these alcohols are presented in Table 5-17. lun Benzene is also used as a solvent to extract crude caprolactam. 112 The three major caprolactam facilities currently operating in the United States are listed in 5-83 TABLE 5-16. PARTIAL LIST OF MANUFACTURERS IN SOURCE CATEGORIES WHERE BENZENE IS USED AS A SOLVENT Solvent Use Source Category Location Plastics Materials and Resins * Amoco Chemical Co. Arizona Chemical Co. Chemfax Inc. Exxon Chemical Americas Baton Rouge Resin Finishing Formosa Plastics Corp. Lawter Inti. Inc. Southern Resin Division Neville Chemical Co. Quantum Chemical Corp. La Porte Quantum Chemical Corp. USI Division Rexene Corp. Polypropylene Plant Union Carbide Chemicals & Plastics Co. Texas City Plant Moundville, AL Gulfport, MS Gulfport, MS Baton Rouge, LA Point Comfort, TX Moundville, AL Pittsburgh, PA La Porte, TX Clinton, LA Odessa, TX Texas City, TX Pharmaceutical Manufacturing Warner-Lambert Co. Parke Davis Division Holland, MI Pesticides and Agricultural Chemicals Rhone-Poulenc Ag Co. Agribusiness Maketers, Inc. Institute, WV Baton Rouge, LA Commercial Printing (Gravure) Piedmont Converting, Inc. Lexington T NC (continued) 5-84 TABLE 5-16. CONTINUED ’ ^ Solvent Use Source Category Location ♦Paints and Allied Products - BASF Corporation Inks & Coating v Division St. Louis Paint Manufacturing Co., Inc. Greenville, OH St. Louis, MS Synthetic Rubber DuPont Pontchartrain Works La Place, LA DuPont Beaumont Plant Beaumont, TX Source: Reference 111 5-85 TABLE 5-17. U.S. PRODUCERS OF ETHANOL OR ISOPROPANOL Facility Location Annual Capacity million gal (million L) anol • Archer Daniels Midland Company Cedar Rapids, IA 700 (2,650) ADM Com Processing Division Clinton, LA Decatur, IL Peoria, IL Walhalla, ND 11 (42) Biocom USA Ltd. Jennings, LA 40 (151) Cargill, Incorporated Eddyville, IA 30(113) Domestic Com Milling Division Chief Ethanol Fuels Inc. Hastings, NB 14 (53) Eastman Chemical Company Longview, TX 25 (95) Texas Eastman Division Georgia-Pacific Corporation Bellingham, WA 12 (45) Chemical Division Giant Refining Co. Portales, NM 10 (38) Grain Processing Corporation Muscatine, IA 60 (227) High Plains Corp. Colwich, KS 15 (57) Hubinger-Roquette Americas, Inc. Keokuk, IA 11 (42) Midwest Grain Products, Inc. Atchison, KS 22 (83) Pekin, IL 19 (72) Minnesota Com Processors Columbus. NB NA Marshall, MN 28 (106) New Energy Company of Indiana South Bend, IN 70 (265) Pekin Energy Company Pekin, IL 80 (303) Quantum Chemical Corp. Tuscola, IL 68 (257) USI Division South Point Ethanol South Point, OH 60 (227) A. E. Staley Manufacturing Company Loudon, TN 60 (227) Sweetner Business Group Ethanol Division (continued) 5-86 TABLE 5-17. CONTINUED Facility Location Annual Capacity million gal (million L) Ethanol (continued) • Union Carbide Corporation Solvents and Coatings Materials Division Texas City, TX 123 (466) TOTAL 1,458 (5,519) Isopropanol Exxon Chemical Company Exxon Chemical Americas Baton Rouge, LA 650 (2,460) Lyondell Petrochemical Company Shell Chemical Company Channel view, TX Deer Park, TX 65 (246) 600 (2,271) Union Carbide Corporation Solvents and Coatings Materials Division Texas City, TX 530 (2,006) TOTAL 1,845 (6,984) Source: References 11 and 111. J Emissions listed are those reported in the 1992 TRI. NA = Not available = no emissions reported 5-87 Table 5-18. 11,111 Of the three facilities, DSM and BASF use benzene as a solvent, and Allied Signal produces benzene as a co-product. 113 Benzene is also used as a solvent in the blending and shipping of aluminum alkyls. 113 Emission points identified for solvent benzene are process vents, dryer vents, and building ventilation systems. 107 As shown in Table 5-19, only one emission factor was identified for any of the solvent use categories. 114 The emission factor presented is for the vacuum dryer vent controlled with a venturi scrubber in pharmaceutical manufacturing. 5-88 TABLE 5-18. U.S. PRODUCERS OF CAPROLACTAM cd u. « cd £ £ Cd C6 « XI Cl == * S c U .o o « S S 3 2 3 < c _o ca o o 1 CJ cd tu % >> U U Os CO Os Os SO o o © SO oj £ flj C- o >, .52 X H o c. 5J oj Q e o U u- £ '5 c_> &- co <5 i ^ i 2 Ov c •g •w a. C o oo Q T3 C CB u u oo CO C^) co — on 1_< ^ CU ^ o _ . e O « « c ■ P «- 3 O C g 3 VO cb C o O J= « 05 J- CU o > ro 5-90 SECTION 6.0 EMISSIONS FROM OTHER SOURCES The following activities and manufacturing processes (other than benzene production or use of benzene as a feedstock) were identified as additional sources of benzene emissions: oil and gas wellheads, petroleum refineries, glycol dehydrators, gasoline marketing, publicly owned treatment works (POTWs), landfills, pulp and paper manufacturing, synthetic graphite manufacturing, carbon black manufacturing, rayon-based carbon manufacturing, aluminum casting, asphalt roofing manufacturing, and use of consumer products and building supplies. For each of these categories, the following information is provided in the sections below: (1) a description of the activity or process, (2) a brief characterization of the national activity in the United States, (3) benzene emissions characteristics, and (4) control technologies and techniques for reducing benzene emissions. In some cases, the current Federal regulations applicable to the source category are discussed. 6.1 OIL AND GAS WELLHEADS 6.1.1 Description of Oil and Gas Wellheads Oil and gas production (through wellheads) delivers a stream of oil and gas mixture and leads to equipment leak emissions. Emissions from the oil and gas wellheads. 6-1 including benzene, are primarily the result of equipment leaks from various components at the wellheads (valves, flanges, connections, and open-ended lines). Component configurations for wellheads can vary significantly. Oil and gas well population data are tracked by State and Federal agencies, private oil and gas consulting firms, and oil and gas trade associations. In 1989 a total of 262,483 gas wells and 310,046 oil wells were reported in the United States. 115,116 Reference 117 presents a comprehensive review of information sources for oil and gas well count data. The activity factor data are presented at four levels of resolution: (1) number of wells by county, (2) number of wells by State, (3) number of fields by county, and (4) number of fields by State. 6.1.2 Benzene Emissions from Oil and Gas Wellheads Emissions from oil and gas wellheads can be estimated using the average emission factor approach as indicated in the EPA Protocol for Equipment Leak Emission Estimates. 54 This approach allows the use of average emission factors in combination with wellheads-specific data. These data include: (1) number of each type of components (valves, flanges, etc.), (2) the service type of each component (gas, condensate, mixture, etc.), (3) the benzene concentration of the stream, and (4) the number of wells. A main source of data for equipment leak hydrocarbon emission factors for oil and gas field operations is an API study 118 developed in 1980. Average gas wellhead component count has been reported as consisting of 11 valves, 50 screwed connections, 1 flange, and 2 open-ended lines. 119 No information was found concerning average component counts for oil wellheads. Benzene and total hydrocarbons equipment leak emission factors from oil wellheads are presented in Table 6-1. 120 These emission factors were developed from 6-2 TABLE 6-1. BENZENE AND TOTAL HYDROCARBONS EQUIPMENT LEAK EMISSION FACTORS FOR OIL WELLHEAD ASSEMBLIES" O CO u, c o ‘In m W a o »— euD| '55 2 .g e/5 o *3 «J eo £ Uh psj w CQ T3 03 (U -C lj £ -' TD CO 4> £ 13 £ •= ^ ^ oo — m -a 1 . w W 4> o i— 3 O 00 c o ’55 e/5 s w e o o e/5 £ o- *3 cr W o e/5 •o co oj X 13 £ o i o o I o I m o2 a> o o x xx r- in Tt r- o >_ 3 O cm 2 Field wellhead only. Does not include other field equipment (such as dehydrators, separators, inline heaters, treaters, etc. screening and bagging data obtained in oil production facilities located in California. 120 Over 450 accessible production wellhead assemblies were screened, and a total of 28 wellhead assemblies were selected for bagging. For information about screening and bagging procedures refer to Reference 54. The composition of gas streams varies among production sites. Therefore, when developing benzene emission estimates, the total hydrocarbons emission factors should be modified by specific benzene weight percent, if available. Benzene constituted from less than 0.1 up to 2.3 percent weight of total non-methane hydrocarbons (TNMHC) for water flood wellhead samples from old crude oil production sites in Oklahoma. Also, benzene constituted approximately 0.1 percent weight of TNMHC for gas driven wellhead samples. 121 The VOC composition in the gas stream from old production sites is different than that from a new field. Also, the gas-to-oil ratio for old production sites may be relatively low. 121 The above type of situations should be analyzed before using available emission factors. 6.2 GLYCOL DEHYDRATION UNITS Glycol dehydrators used in the petroleum and natural gas industries have only recently been discovered to be an important source of volatile organic compound (VOC) emissions, including benzene, toluene, ethylbenzene, and xylene (BTEX). Natural gas is typically dehydrated in glycol dehydration units. The removal of water from natural gas may take place in field production, treatment facilities, and in gas processing plants. Glycol dehydration units in field production service have smaller gas throughputs compared with units in gas processing service. It has been estimated that between 30,000 and 40,000 glycol dehydrating units are in operation in the United States. 122 In a survey conducted by the Louisiana Department of Environmental Quality, triethylene glycol (TEG) dehydration units accounted for approximately 95 percent of the total in the United States, with ethylene glycol (EG) and diethylene glycol (DEG) dehydration units accounting for approximately 5 percent. 123 6-4 Data on the population and characteristics of glycol dehydration units nationwide is limited. Demographic data has been collected by Louisiana Department of Environmental Quality, Texas Mid-Continent Oil and Gas Association and Gas Processors Association, Air Quality Service of the Oklahoma Department of Health (assisted by the Oklahoma Mid-Continent Oil and Gas Association), and Air Quality Division of the Wyoming Department of Environmental Quality. 124 Table 6-2 presents population data and characteristics of glycol dehydration units currently available. 124 6.2.1 Process Description for Glvcol Dehydration Units The two basic unit operations occurring in a glycol dehydration unit are absorption and distillation. Figure 6-1 presents a general flow diagram for a glycol dehydration unit. 125 The “wet” natural gas (Stream 1) enters the glycol dehydrator through an inlet separator that removes produced water and liquid hydrocarbons. The gas flows into the bottom of an absorber (Stream 2), where it comes in contact with the “lean” glycol (usually triethylene glycol [TEG]). The water and some hydrocarbons in the gas are absorbed by the glycol. The “dry” gas passes overhead from the absorber through a gas/glycol exchanger (Stream 3), where it cools the incoming lean glycol. The gas may enter a knock-out drum (Stream 4), where any residual glycol is removed. From there, the dry natural gas goes downstream for further processing or enters the pipeline. After absorbing water from the gas in the absorber, the “rich” glycol (Stream 5) is preheated, usually in the still, and the pressure of the glycol is dropped before it enters a three-phase separator (Stream 6). The reduction in pressure produces a flash gas stream from the three-phase separator. Upon exiting the separator (Stream 7), the glycol is filtered to remove panicles. This particular configuration of preheat, flash, and filter steps may vary from unit to unit. The rich glycol (Stream 8) then passes through a glycol/glycol exchanger for further preheating before it enters the reboiler still. 6-5 TABLE 6-2. GLYCOL DEHYDRATION UNIT POPULATION DATA n C/5 ‘3 D o Z o f s « s Cu ^ 03 O U - A ^ ° <2 a S S.S 03 / U $ VI •2 o H c i o o C« on < CU 00 (N «n t-* o\ 2 vO vo 0 “v Ov cs »-< m Ov O ^ (N O o o a >% 3? O a 03 3 , jp ■5 W C nJ W oo oc z DC z m ro co es w O H C/5 03 a 1 Vj « u 33 v- 3 o c u t-4 <4—« CD d=3 3 O C/3 • •« 8 i 03 1 O •§ re O .1 -S oo co *3 # s 3| c o sjf w CO a> w JD TS- E o u CO ■a u i— . 45 .O O •> « z ■s ^ S c - .S CO __ r _ g T3 ^ w 8 §21 (L) J= 4 > 3 A ifl u — •“ w 4> O O •£ >. c u — 2 C 4J BO 3 - C £3 1/5 - 3 5 — _ o £d 2 £ -5 o a i -s 1 s s u s - in £ . -U Caj 2 c c 5 E !r? •■ a '£ a a C50 c § E CO p i ! ° o W» — u U 3 2 2 c « "3 *>L a. E 2 £ p O 4J ^ 4) W3 > >* > — © -a o -g O o U H cf-aS C > O u >% >s >> >» m dj h > a i g c 8. CD O Z 03 Z 6-6 Dry Natural Gas dJ.a-»f-AAld-*Z00*6 O • . .© • 2 S 5-o 6-7 Source: Reference 125. Then, the rich glycol enters the reboiler still (Stream 9) (operating at atmospheric pressure), where the water and hydrocarbons are distilled (stripped) from the glycol making it lean. The lean glycol is pumped back to absorber pressure and sent to the gas/glycol exchanger (Stream 10) before entering the absorber to complete the loop. 6.2.2 Benzene Emissions from Glvcol Dehydration Units The primary source of VOC emissions, including BTEX, from glycol dehydration units is the reboiler still vent stack (Vent A). Because the boiling points of BTEX range from 176°F to 284°F (80 to 140°C), they are not lost to any large extent in the flash tank but are separated from the glycol in the still. These separations in the still result in VOC emissions that contain significant quantities of BTEX. 126 Secondary sources of emissions from glycol dehydration units are the phase separator vent (Vent B) and the reboiler burner exhaust stack (Vent C). Most glycol units have a phase separator between the absorber and the still to remove dissolved gases from the warm rich glycol and reduce VOC emissions from the still. The gas produced from the phase separator can provide the fuel and/or stripping gas required for the reboiler. A large number of small glycol dehydration units use a gas-fired burner as the heat source for the reboiler. The emissions from the burner exhaust stack are considered minimal and are typical of natural gas combustion sources. Reboiler still vent data have been collected by the Louisiana Department of Environmental Quality, 123 and the Ventura County (California) Air Pollution Control District. 127 Table 6-3 presents emission factors for both triethylene glycol (TEG) units and 6-8 TABLE 6 - 3 . REACTIVE ORGANIC COMPOUNDS (ROCs) 1 AND BTEX EMISSION FACTORS FOR GLYCOL DEHYDRATION UNITS C O u. OC| © .2 C/5 O w L- o o cd Uh G O on c/5 s w •q E D z u u oo 03 -o £ 2 o ‘♦o 5/2 11 sd U O O 06 06 V G « 4 _ © >» ox) PO o 2 —' X X so O’ O’ ^ O’" «r> G 1) > 00 t— — "© X> cu 06 2 c^« O C/5 s s X w H CQ ■a E o C/5 2 S X w H CQ 0 33 < 4 -* -o E 0 J 3 L© <*- E -C (4-4 T 3 E 0 CJ v- CJ C /5 O 0 0 C /5 0 C /3 CA C /5 CO C /5 2? S2 ■ »-i >3-^ > OX) £ .x rs > "3. o o 3 S °° £ ^ Os CN o 2 g a rs < *L o o X O’ CN CO X o Os »n U U 0 2 06 06 C 4-1 S|_ O O U. Uc !o OQ — -X 2 ° ^ X 0 £ o- q ^ 00 S s £ X n w w H CQ H CQ x o- X O’ ^ <* CO c 00 u. -E • o J 3 s IS 0 >3 «« >3 x: •— >3 J3 -s O 0) G 03 3 3 O C O *3 3 C/5 w ’S 3 o w u O 06 03 E O CA s s u o 06 o © v. Cm X) M . u> >3 >> > OX) £ -X co o o c • 1 *--1 -* ® 2 ’v* 5 C X x o wo r- — 3 aj > co c C /3 0/ «—* 0 J u L- 3 O C /3 3 CT3 •c j- _ 4 > ^ O S S G 2 4 / C •S -3 O 4 > — (J •age S >*.2 00 5 II 45 5 E 1 c o c < 'n w _ 1 2 o o — •-« I*— - ’’S E u 4 / w a § uj S 2 o w "O 1 45 •a 45 rt u o (X u <2 c o • to to Q J "53 '3 o U oa t- s c u >3 f0 •o u. 8 . 4 > ,45 Cl-. O 2 3 U CQ •o % C o S II 2 8 2 2 6-9 MMsemd = Million standard cubic meter per day. ethylene glycol (EG) units based on the natural gas throughput of the gas treated. The emission factors developed from the LDEQ study were based on responses from 41 companies and 208 glycol dehydration units. The Ventura County, California, factors include testing results at two locations (one for TEG and one for EG). The amount of produced gas treated is thought to be the most important because it largely determines the size of the glycol system. 127 However, the data base does not show a strong correlation because other variables with countervailing influences were not constant. 127 VOC and BTEX emissions from glycol units vary depending upon the inlet feed composition (gas composition and water content) as well as the configuration, size, and operating conditions of the glycol unit (i.e., glycol type, pump type and circulation rate, gas and contactor temperatures, reboiler fire-cycles, and inlet scrubber flash tank efficiencies). 129 The speciation of Total BTEX for TEG units reported by the LDEQ in their study indicated the following composition (% weight): benzene (35); toluene (36); ethylbenzene (5); and xylene (24). For EG units, the following compositions were reported: benzene (48); toluene (30); ethylbenzene (4); and xylene (17). Note that the BTEX composition of natural gas may vary according to geographic areas. Limited information/data on the BTEX composition is available. Four methods for estimating emissions have been reported for glycol dehydration units: (1) rich/lean glycol mass balance, (2) inlet/outlet gas mass balance, (3) unconventional stack measurements (total-capture condensation, and partial stack condensation/flow measurement), and (4) direct stack measurements (conventional stack measurements, and novel stack composition/flow measurement). 129 Sampling of the rich/lean glycol then estimating emissions using mass balance has been the selected method for measuring emissions to date. The Louisiana Department of Environmental Quality requested emission estimates using reboiler mass balances on the rich/lean glycol samples. 6-10 Based upon a set of studies conducted by Oryx Energy Co as part of a task force for the Oklahoma-Kansas Midcontinent Oil & Gas Association, rich/lean glycol mass balance is a highly convenient, cost effective method for estimating air emissions from glycol dehydration units. 129 The following conclusions were addressed in reference 129 regarding this method: (a) good estimates of BTEX can be obtained from rich/lean glycol mass balance, (b) the rich/lean glycol mass balance BTEX estimates are in excellent agreement with total capture condensation method, and (c) rich/lean glycol mass balance is a more reproducible method for emission estimations than nonconventional stack methods. Note that conventional stack methods cannot be used on the stacks of glycol dehydration units because they are too narrow in diameter and have low flow rates. An industry working group consisting of representatives from the American Petroleum Institute, Gas Processors Association, Texas-Midcontinent Oil & Gas Association, Louisiana Mid-Continent Oil and Gas Association, and GRI is conducting field evaluation experiments to determine appropriate and accurate sampling and analytical methods to calculate glycol dehydration unit emissions. 125 GRI has developed a computer tool, entitled GRI-GLYCalc, for estimating emissions from glycol dehydrators. The U.S. EPA has performed their own field study of GRI-GLYCalc and has recommended that it be included in EPA guidance for State/local agency use for development of emission inventories. 130 Atmospheric rich/lean glycol sampling is being evaluated as a screening technique in the above working group program. The goal is to compare these results to the stack and other rich/lean results and determine if a correction factor can be applied to this approach. 125 A second screening technique under study is natural gas sampling and analysis combined with the software program GRI-GLYCalc® to predict emissions. Table 6-4 shows the inputs required of the user and also shows the outputs returned by GRI-GLYCalc®. 132 6-11 TABLE 6-4. GLYCOL DEHYDRATION EMISSION PROGRAM INPUTS AND OUTPUTS Inputs Units Gas Flow Rate MMscfd Gas Composition Volume percent for C r C 6 hydrocarbons and BTEX compounds Gas Pressure psig Gas Temperature °F Dry Gas Water Content 2 lbs/MMscf Number of Equilibrium Stages 2 Dimensionless Lean Glycol Circulation gpm Lean Glycol Composition Weight % H 2 0 Flash Temperature c °F Flash Pressure c psig Gas-Driven Pump Volume Ratio c acffn gas/gpm glycol Outputs Units BTEX Mass Emissions lbs/hr or lb-moles/hr, lbs/day, tpy, vol% Other VOC Emissions lbs/hr or lb-moles/hr, lbs/day, tpy, vol% Flash Gas Composition Dry Gas Water Content 15 Number of Equilibrium Stages' 5 lbs/hr or lb-moles/hr, lbs/day, tpy, vol% lbs/MMscf Dimensionless Source: Reference 132. * Specify ong of these inputs. b Dry Gas Water Content is an output if the Number of Equilibrium Stages is specified and vice versa. c Optional 6-12 6.2.3 Controls and Regulatory Analysis Controls applicable to glycol dehydrator reboiler still vents include hydrocarbon skimmers, condensation, flaring, and incineration. Hydrocarbon skimmers use a three-phase separator to recover gas and hydrocarbons from the liquid glycol prior to its injection into the reboiler. Condensation recovers hydrocarbons from the still vent emissions, whereas flaring and incineration destroy the hydrocarbons present in the still vent emissions. For glycol dehydrators it has been determined by the Air Quality Service, Oklahoma State Department of Health that the Best Available Control Technology (BACT) could include one or more of the following: (1) substitution of glycol, (2) definition of specific operational parameters, such as the glycol circulation rate, reduction of contactor tower temperature, or increasing temperature in the three-phase separator, (3) flaring/incineration, (4) product/vapor recovery, (5) pressurized tanks, (6) carbon adsorption, or (7) change of desiccant system. 128 The Air Quality Division, Wyoming Department of Environmental Quality has stated that facilities will more than likely be required to control emissions from glycol dehydration units. The Division has determined and will accept the use of condensers in conjunction with a vapor recovery system, incinerator, or a flare as representing BACT. 133 Most gas processors have begun to modify existing glycol reboiler equipment to reduce or eliminate VOC emissions. Some strategies and experiences from one natural gas company are presented in Reference 124. For other control technologies refer to Reference 134. Glycol dehydration units are subject to the NSPS for VOC emissions from equipment leaks for onshore natural gas processing plants promulgated in June 1985. 135 The NSPS provides requirements for repair schedules, recordkeeping, and reporting of equipment leaks. 6-13 The Clean Air Act Amendments (CAAA) of 1990 resulted in regulation of glycol dehydration units. Title III of the CAAA regulates the emissions of 188 hazardous air pollutants (HAPs) from major sources and area sources. Title HI has potentially wide-ranging effects for glycol units. The BTEX compounds are included in the list of 188 HAPs and may be emitted at levels that would cause many glycol units to be defined as major sources and subject to Maximum Achievable Control Technology (MACT). 125 Currently, the MACT standard for the oil and natural gas production source category, which includes glycol dehydration units, is being developed under authority of Section 112(d) of the 1990 CAAA and is scheduled for promulgation in May, 1999. In addition to the federal regulations, many states have regulations affecting glycol dehydration units. The State of Louisiana has already regulated still vents on large glycol units, and its air toxics rule may affect many small units. Texas, Oklahoma, Wyoming, and California are considering regulation of BTEX and other VOC emissions from dehydration units. 125 6.3 PETROLEUM REFINERY PROCESSES 6.3.1 Description of Petroleum Refineries Crude oil contains small amounts of naturally occurring benzene. One estimate indicates that crude oil consists of 0.15 percent benzene by volume. 136 Therefore, some processes and operations at petroleum refineries may emit benzene independent of specific benzene recovery processes. Appendix B (Table B-l) lists the locations of petroleum refineries in the U.S. As of January 1995, there were 173 operational petroleum refineries in the United States, with a total crude capacity of 15.14 million barrels per calendar day. 137,138 The majority of refinery capacity is located in Texas, Louisiana, and California. Significant refinery capacities are also found in the Chicago, Philadelphia, and Puget Sound areas. A flow diagram 6-14 of processes likely to be found at a model refinery is shown in Figure 6-2. 139 The arrangement of these processes varies among refineries, and few, if any, employ all of these processes. Processes at petroleum refineries can be grouped into five types: (1) separation processes, (2) conversion processes, (3) treating processes, (4) auxiliary processes and operation, and (5) feedstock/product storage and handling. These are discussed briefly below. The first phase in petroleum refining operations is the separation of crude oil into its major constituents using four separation processes: (1) desalting, (2) atmospheric distillation, (3) vacuum distillation, and (4) light ends recovery. To meet the demands for high-octane gasoline, jet fuel, and diesel fuel, components such as residual oils, fuel oils, and light ends are converted to gasolines and other light fractions using one or more of the following conversion processes: (1) catalytic cracking (fluidized-bed and moving-bed), (2) thermal processes (coking, and visbreaking), (3) alkylation, (4) polymerization, (5) isomerization, and (6) reforming. Petroleum treating processes stabilize and upgrade petroleum products by separating them from less desirable products. Among the treating processes are (1) hydrotreating, (2) chemical sweetening, (3) deasphalting, and (4) asphalt blowing. Auxiliary processes and operations include process heaters, compressor engines, sulfur recovery units, blowdown systems, flares, cooling towers, and wastewater treatment facilities. Finally, all refineries have a feedstock/product storage area (commonly called a “tank farm”) with storage tanks whose capacities range from less than 1,000 barrels to more than 500,000 barrels. Also, feedstock/product handling operations (transfer operations) consist of the loading and unloading of transport vehicles (including trucks, rail cars, and marine vessels). 6-15 Fuel Oat and LPO OS m v o c 4> k. £ es > 3 £ L D 21 w 3 t'ii « a t/5 1 CL 00 VO 00 00 vo vo co CN — CN VO 00 CN CN CN mooN% >-. P .* JX u < 3 00 e vS t> oc u 00 00 c *5 © o U- o •3 >> § 00 c 3 o s X CO 6 o u_ *3 >* X oo c 00 c 00 a 3 £ o © 2 CT3 u il i c © 4/ C/5 (2> JO Cm c 00 o k— 3 >» X J a. a. 3 3 JU CO w L> 3 8 £ a CJ a. u. vS 3 CO c o V) a E 3 3 o CT3 > •2 3 B .2 5 c - ° S> ‘2 9 1 0C u = E 15 o £ — § 1 o CL. O0 .S s V Q U! UJ 2 o g 3 l* a> i o «N W <£ u OC u 6-22 Refineries with crude charge capacities less than 50,000 bbl/sd. TABLE 6-9. MEDIAN COMPONENT COUNTS FOR PROCESS UNITS FROM LARGE REFINERIES 2.2 & 3 E G CO § ill O w >> T3 « g. a j s oo 1) > P5 > OS 3 w -O til o % L — *3 “'ll -> j o o «/s c/3 4> k- o4 E o U T3 £I a> .Z w *3 — J >s TD 51 w 73 Sii j 3 S3 0 O' 'O *^r O' 00 00 »n o 00 VO r* On On % >* P Jd. -* u 5 3 00 c £ * a fN r- fN fN 00 # C *5 e u o © *> >% E oo c O — NO VO O o r- r- oi S 3 fN — — On % x u o 2 CO U 2 oo u .S oo c 2 o o -* CJ CO 00 c § « •€ o J2 I 1 2 S 8 8 l i si £> £ CL c c crs CL c u ffi C W w c/» 5 o 00 o w w o 3 CL u> c 3 L- •o -c CL ■g £ G X £ 3 CO CO > Q § «j ■— 00 ra U. X e o •c 3 c a. oo £ 'I * v Q sd Ul S O J5 5 i— y •5 O 8 c t> 0> a i> u u. 3 c^ 6-23 Refineries with crude charge capacities greater than 50.000 bbl/sd Air emissions from petroleum refinery wastewater collection and treatment are one of the largest sources of VOC emissions at a refinery and are dependent on variables including wastewater throughput, type of pollutants, pollutant concentrations, and the amount of contact wastewater has with the air. Table 6-10 presents model process unit characteristics for petroleum refinery wastewater. 147 The table includes average flow factors, average volatile HAP concentrations, and average benzene concentrations by process unit type to estimate uncontrolled emissions from petroleum refinery wastewater streams. Flow factors were derived from Section 114 questionnaire responses compiled for the Refinery NESHAP study. Volatile HAP and benzene concentrations were derived from Section 114 questionnaire responses, 90-day Benzene Waste Operations NESHAP (BWON) reports, and equilibrium calculations. Uncontrolled wastewater emissions for petroleum refinery process units can be estimated multiplying the average flow factor, the volatile HAP concentrations, and the fraction emitted presented in Table 6-10, for each specific refinery process unit capacity. Wastewater emission factors for oil/water separators, air flotation systems, and sludge dewatering units are presented in Table 6-11. 148151 Another option for estimating emissions of organic compounds from wastewater treatment systems is to use the air emission model presented in the EPA document Compilation of Air Pollutant Emission Factors (AP-42), in Section 4.3, entitled “Wastewater Collection, Treatment, and Storage.” 64 This emission model (referred to as SIMS in AP-42 and now superceded by Water 8) is based on mass transfer correlations and can predict the emissions of individual organic species from a wastewater treatment system. 6-24 cs 3 3 w T 3 in »n in in n in »n in •n »n •n in in m «n 0 .s 00 00 oc 00 00 00 00 00 00 00 00 00 00 00 00 C 0 l_ Uh 2 PJ d d d d d d d d d d d d d d d cu < X n JL) o 2 2 o > 00 08 u. < o O o o o u o ’Sol o CJ 34 (U 3 re c u < 3 'ebl cu 3] (U 3 00 > a £ c OO co 1 — < X 3 "co OXJl 3 D « wo CD O o o TO¬ CS 3 CS • -4, Tt Tt cr cr ^ W W — -H 2 cr —< W cr X 2 • 2 o <*. w c **■' "** O" 2 W - 2 g - w ON OO • m NO (N » O In TO >> Vm 0 Ih to < u X SC X 00 3 CJ eo Wh O o w 3 2 00 U 00 c M O 03 u, O *3 3 00 C c « 2 H o 00 3 o c« 1* o *c3 3 eo 00 3 00 C- 3 2 3 3 -4—* 3 22 C 8 3 O 00 Cu X O M a- flj O C3 3 u. «-> Xi wo > Ih no SC X CU wo < •O O 1-4 Cu 2 3 00 co n o co 3 O wo '•3 B 3 3 o CO > in NO Tt • — “ cr Tt Tt Tt cr cr C8 T3 cr Tt C8 TO C8 TO Tt PJ X ^H t-H r—. X PU 1 O W 1 O 1 O *-H ON On ON in Tt 3 O 3 Ph cr X os rs co 1 —' m in 2 co CO .*3 •—* w 3! 22 •O 00 3 CO 3 .2 ■*—1 08 N *1-1 • 5 < £ E a. •a < CO h. C oj o c o U c 'col £ E CJ o <2 £ .o c _c G J3 < CO 001 a X C/3 C/2 CJ O o o •'O’ m co o o in ni C/2 C 3 O ■'O’ oo >5 CO >> CO > CO •o ~a cr "O o l o W 1 o ON ON ON oo oo o c o 00 C .2 o -t —i ’S •p ’>< d •— .3 00 'w re I * 3 rT co .— D CJ 3 re 3" cx, . w 'Cf cj oo •'t d O 'i u. o 3 D s 3 I o w I CL < X a OC •3 C es 3 _o 03 ns cj E 3 3 CT DO UJ 3 II re w* sg . . nS c E cL V.< z i O o I = CQ 3 >, g. re -P- •O , o 1^ 3 O CJ 3 •3 O C/5 ns DO D •3 OJ CJ 3 IE E 3 « 3 o 3 C/5 3 O OJ 3 < — 6=3 Ci*.*; . . O co « CO C 52 *3 o Q § re *2 £“ O OO a o ss re o o I e Lf> £ £* o | £ 6 S 8 2 ! 3 _o CO ha «—• 3 V o 3 O o oo 5 « o k- Cm ID > oo < < - o 3 C co 3 _o ”c5 DO Cm o m '£ 3 > *Im D > 5o D > '5b D O u. -O' 'ob C/5 C/5 > V5 C/5 e 8. D t_ Um b. k_ o co c 3 O C0 CO o ♦-/ O o M CJ o <2 00 o- o Im O <4— Cm D CJ on .ns £ o -g £ II u = — i ^ Ji *2 C0 Q. -m *3 iC oo ex — H H 6-26 TABLE 6-11. WASTEWATER EMISSION FACTORS FOR PETROLEUM REFINERIES LI CJ C D k. ,l> kk- l> 0 c u. DC 2 c O W CO CO cl a: o CO CL a _o c/3 £ cu £ r~ > o % U Q c/3 co co CO £ CL) u C/3 a> Q li x £ 3 z u u oo uu LX LI w c3 * £ 3 3 JJ LI O O "co os O « —< o ^ — LI S e £ c u c D o ra k- eo r - Ll OO k- 2 co £ w. 2 o eo co Os 3 U D k. «- LI 08 "3 > co ** o ^ QJ CJ <*- ^ f o co — 00 o O g u o H k>_ o X) U O H OX) _-c co _ 8 vC O i co © w*> tu k- LI ,4j o O ax — 3 ^ flj = £ ax 5 s« (LI kk. CQ O kk- OX) o ^ X oo — ^r ^ o •o LI c o o c D 2 C /3 C/3 c o co o c o I co Os rt CQ D LX CO co £ £ •3 "3 LI LI .LI ,D — o o OO o © ^ 2 U ug o H L._. o M £ o o ^9 CO CO c .2 co o 2 CL OX k- C/3 •- >% < OO X X i wo wo u « w>^ ^ 3 C/3 O C /5 ox) iZ >o o u u o o H t- <4-* o o X 0X3 — itf § s o VO •3 Ll O c D OX) c I— OJ CO ^ 3 « c - 3 LI OX) •a J3 OO c 3 OX)| k- L> 'Ll “> co 3 ^ X LI t>0 -3 X X I WO o I CO U. o W0 CN O LI k- 3 co k- £ a> LI 0X) CO k- D > co f— CO co CO LI OX) 3 J3 co "co o ‘5) _o "o X 3 c CO co O C CL < Q C/3 r- c 52 5 CO CO o •O u. U- O < u- c o Cl co CO w- O w c5 c k- ’co ‘o 3 LI O oxi _c 3 ‘C 3 Ll • S CO Un o L) ✓«-> 3 CL C /3 < C /3 LI Q k- CL c k- L> .2 k— £ o 3 C JS 1-4 u- *c3 •o a> E o fS CO CO • —4 3 (S C 0 C/3 LI c O 3 3 3 LI C /3 u co CQ 6-27 6.3.3 Controls and Regulatory Analysis This section presents information on controls for process vents at petroleum refineries, and identifies other sections in this document that may be consulted to obtain information on control technology for storage tanks, and equipment leaks. Applicable Federal regulations to process vents, storage tanks, equipment leaks, transfer operations, and wastewater emissions are briefly described. According to the EPA ICR and Section 114 surveys, the most reported types of control for catalyst regeneration process vents at fluid catalytic cracking units were electrostatic precipitators, carbon monoxide (CO) boilers, cyclones, and scrubbers. Some refineries have reported controlling their emissions with scrubbers at catalytic reformer regeneration vents. For miscellaneous process vents, including miscellaneous equipment in various process units throughout the refinery, the most reported controls were flares, incinerators, and/or boilers. Other controls for miscellaneous process vents reported by refineries include scrubbers, electrostatic precipitators, fabric filters, and cyclones. The process vent provisions included in the Petroleum Refinery NESHAP promulgated on September 18, 1995 affect organic HAP emissions from miscellaneous process vents throughout a refinery. 49 These vents include but are not limited to vent streams from caustic wash accumulators, distillation condensers/accumulators, flash/knock-out drums, reactor vessels, scrubber overheads, stripper overheads, vacuum (steam) ejectors, wash tower overheads, water wash accumulators, and blowdown condensers/accumulators. f For information about controls for storage tanks refer to Section 4.5.3 - Storage Tank Emissions, Controls, and Regulations. ! 6-28 Storage tanks containing petroleum liquids and benzene are regulated by the following Federal rules: 1. “National Emission Standard for Benzene Emissions from Benzene Vessels;” 61 2. “Standards of Performance for Volatile Organic Liquid Storage Vessels (Including Petroleum Liquid Storage Vessels) for which Construction, Reconstruction, or Modification Commenced after July 23, 1984; ” 62 and 3. “National Emission Standards for Hazardous Air Pollutants: Petroleum Refineries.” 49 The Petroleum Refinery NESHAP requires that liquids containing greater than 4 weight percent HAPs at existing storage vessels, and greater than 2 weight percent HAPs at new storage vessels be controlled. There are two primary control techniques for reducing equipment leak emissions: (1) modification or replacement of existing equipment, and (2) implementation of a Leak Detection and Repair (LDAR) program. Equipment leak emissions are regulated by the New Source Performance Standards (NSPS) for Equipment Leaks of VOC in Petroleum Refineries promulgated in May 30, 1984. 152 These standards apply to VOC emissions at affected facilities that commenced construction, modification, or reconstruction after January 4, 1983. The standards regulate compressors, valves, pumps, pressure relief devices, sampling connection systems, open-ended valves or lines, and flanges or other connectors in VOC service. The Benzene Equipment Leaks National Emission Standard for Hazardous Air Pollutants (NESHAP) 56 and the Equipment Leaks NESHAP 57 for fugitive emission sources regulate equipment leak emissions from pumps, compressors, pressure relief devices, sampling connecting systems, open-ended valves or lines, valves, flanges and other connectors, product 6-29 accumulator vessels, and specific control devices or systems at petroleum refineries. These NESHAPs were both promulgated in June 6, 1984. Equipment leak provisions included in the Petroleum Refinery NESHAP require equipment leak emissions to be controlled using the control requirements of the petroleum refinery equipment leaks NSPS or the hazardous organic NESHAP. Any process unit that has no equipment in benzene service is exempt from the equipment leak requirements of the benzene waste NESHAP. “In benzene service” means that a piece of equipment either contains or contacts a fluid (liquid or gas) that is at least 10 percent benzene by weight (as determined according to respective provisions). Any process unit that has no equipment in organic HAP service is exempt from the equipment leak requirements of the petroleum refinery NESHAP. “In organic HAP service” means that a piece of equipment contains or contacts a fluid that is at least 5 percent benzene by weight. Refer to Section 6.4 (Gasoline Marketing) of this L&E document for information on control technologies and regulations for loading and transport operations. For information about controls for wastewater collection and treatment systems, refer to Section 4.5.4 - Wastewater Collection and Treatment System Emissions, Controls, and Regulation. Petroleum refinery wastewater streams containing benzene are regulated by the following Federal rules: 1. “National Emission Standard for Benzene Waste Operations;” 66 2. “New Source Performance Standard for Volatile Organic Compound Emissions from Petroleum Refinery Wastewater Systems;” 153 and 3. “National Emission Standards for Hazardous Air Pollutants: Petroleum Refineries.” 49 6-30 The wastewater provisions in the Petroleum Refinery NESHAP are the same as the Benzene Waste Operations NESHAP. 6-4 GASOLINE MARKETING Gasoline storage and distribution activities represent potential sources of benzene emissions. The benzene content of gasoline ranges from less than 1 to almost 5 percent by liquid volume, but typical liquid concentrations are currently around 0.9 percent by weight. 158 Under Title II of the Clean Air Act as amended in 1990, the benzene content of reformulated gasoline (RFG) will be limited to 1 percent volume maximum (or 0.95 percent volume period average) with a 1.3 percent volume absolute maximum. In California, the “Phase 2 Reformulated Gasoline,” which will be required starting March 1998, also has a 1 percent volume benzene limit (or 0.8 percent volume average) with an absolute maximum of 1.2 percent volume. 20 For this reason, it is expected that the overall average of benzene content in gasoline will decrease over the next few years. Total hydrocarbon emissions from storage tanks, material transfer, and vehicle fueling do include emissions of benzene. This section describes sources of benzene emissions from gasoline transportation and marketing operations. Because the sources of these emissions are so widespread, individual locations are not identified in this section. Instead, emission factors are presented, along with a general discussion of the sources of these emissions. The flow of the gasoline marketing system in the United States is presented in Figure 6-3. 153 The gasoline distribution network includes storage tanks, tanker ships and barges, tank trucks and railcars, pipelines, bulk terminals, bulk plants, and service stations. From refmeries, gasoline is delivered to bulk terminals by way of pipelines, tanker ships, or barges. Bulk terminals may also receive petroleum products from other terminals. From bulk terminals, petroleum products (including gasoline) are distributed by tank trucks to bulk plants. Both bulk terminals and bulk plants deliver gasoline to private, commercial, and retail customers. Daily product at a terminal averages about 250,000 gallons (950,000 liters), in contrast to about 5,000 gallons (19,000 liters) for an average size bulk plant. 154 6-31 Figure 6-3. The Gasoline Marketing Distribution System in the United States Source: Reference 153. Service stations receive gasoline by tank truck from terminals or bulk plants or directly from refineries, and usually store the gasoline in underground storage tanks. Gasoline service stations are establishments primarily selling gasoline and automotive lubricants. Gasoline is by far the largest volume of petroleum product marketed in the United States, with a nationwide consumption of 115 billion gallons (434 billion liters) in 1993. 155 There are presently an estimated 1,300 bulk ter minal s storing gasoline in the United States. 156 About half of these terminals receive products from refineries by pipeline (pipeline breakout stations), and half receive products by ship or barge delivery (bulk gas-line terminals). Most of the terminals (66 percent) are located along the east coast and in the Midwest. The remainder are dispersed throughout the country, with locations largely determined by population patterns. The benzene emission factors presented in the following discussions were derived by multiplying AP-42 VOC emission factors for transportation and marketing 157 times the fraction of benzene in the vapors emitted. The average weight fraction of benzene in gasoline vapors (0.009) was taken from Reference 157. When developing emission estimates, the gasoline vapor emission factors should be modified by specific benzene weight fraction in the vapor, if available. Also a distinction should be made between winter and summer blends of gasoline (a difference in the Reid vapor pressure of the gasoline, which varies from an average of 12.8 psi in the winter to an average of 9.3 in non-winter seasons) to account for the different benzene fractions present in both. 158 The transport of gasoline with marine vessels, distribution at bulk plants, and distribution at service stations, their associated benzene emissions, and their controls are discussed below. 6-33 6.4.1 Benzene Emissions from Loading M arine Vessels Benzene can be emitted while crude oil and refinery products (gasoline, distillate oil, etc.) are loaded and transported by marine tankers and barges. Loading losses are the primary source of evaporative emissions from marine vessel operations. 159 These emissions occur as vapors in “empty” cargo tanks are expelled into the atmosphere as liquid is added to the cargo tank. The vapors may be composed of residual material left in the “empty” cargo tank and/or the material being added to the tank. Therefore, the exact composition of the vapors emitted during the loading process may be difficult to predict. Benzene emissions from tanker ballasting also occur as a result of vapor displacement.. Ballasting emissions occur as the ballast water enters the cargo tanks and displace vapors remaining in the tank from the previous cargo. In addition to loading and ballasting losses, transit losses occur while the cargo is in transit. 157160 Volatile organic compound (VOC) emission factors for petroleum liquids for marine vessel loading are provided in the EPA document Compilation of Air Pollutant Emission Factors (AP-42), Chapter 5 157 and the EPA document VOC/HAP Emissions from Marine Vessel Loading Operations - Technical Support Document for Proposed Standards , 159 Uncontrolled VOC and benzene emission factors for loading gasoline in marine vessels are presented in Table 6-12. This table also presents emission factors for tanker ballasting losses and transit losses from gasoline marine vessels. Table 6-13 presents total organic compound emission factors for marine vessels including loading operations, and transit for crude oil, distillate oil, and other fuels. Emissions of benzene associated with loading distillate fuel and other fuels are very low, due primarily to their low VOC emission factor and benzene content. When developing benzene emission estimates, the total organic compound emission factors presented in Table 6-13 should be multiplied by specific benzene weight fraction in the fuel vapor, if available. 6-34 TABLE 6-12. UNCONTROLLED VOLATILE ORGANIC COMPOUND AND BENZENE EMISSION FACTORS FOR LOADING, BALLASTING, AND TRANSIT LOSSES FROM MARINE VESSELS a •- o « 8 * o U o CT3 tu X) V—« i, i C -g eg h U. <22 e s o 3 •ns u. c/3 r* e UJ u S S 44 02 eg oo ■o u ha ha .44 U— c« % U* H ha 04 M E 1 u u ha 3 o on e o c/3 UJ J5 E 3 z u u co 00 04 ■w' co 04 O •o 44 c eg 04 V3 c _o CQ l— 8. O CO 3 04 04 CO oo 3 O eg CQ 04 04 o "o. eg J= or) o > ■o 04 C/5 eg 13 CQ c/i 3 eg ha K o co 3 T3 04 _04 U CO 3 Jo 3 < 04 o. O CO 3 8 .« ° § £p> .3 04 > 04 ha Q. 04 fd “4, 04 CO co Jj o m £ 2 04 Q. o £ "o- eg S *3 co > eg 04 04 CO CO I S ® > % £ 04 Q. o g o. Jg 3 c/5 o > U > O O - o. *3 Ic o CO o eg 04 £ H • «— •— OX) 5 c3 c3 Ui Uj cS c3 U- CT3 C3 /»\ eg 3. CS 3 w OO .3 w OX) .3 OX) 3 a 2 o. O CO 8 °04 CO £? <5 Q Q Q 00 P r- O) C4 rs ■o OO a«a '•a o C rs o (S >-✓ VQ VO «n 00 r- af O o s o m o o 8 NJ r4 O o o o o o o d o VO VO O VO 00 »o VO »o —a o 00 VO TT CO 04 »—• 04 •er s ^' w w VD !■" in r- 00 Ov o (S —I o i -J ro 04 oo O o 04 co r- C4 eg CQ 04 >> s ^ 8 c O .2 (~i eg 2.2 co 5 JU 5 O > •a 04 8 eg JL4 *04 8 3 co 8 o eg ha 8 . o .3 CO ■g S 5 s °44 .1 00 > eg g 03 3. o oo ha eg C4 So 8 eg 04* 04 CO eg o 8 o c5 t* 8 . O co co .S c to •a — 5 3 « jr- .ts 04 04 co CO 3 e3 H h, 03 H H VO r- Tf VO co ro vo 04 VO 8 o 00 CO Ov 04 CO co O O CO CO CO CO -r CO CO CO O' 04 04 04 04 04 04 04 04 04 04 04 04 04 04 8 8 88 8 8 8 8 8 8 8 8 8 8 8 8 § 8 VO o 8 1 8 8 8 2 i 2 2 Tj- •4 ■4 -r -r -vj- ■4 ov «/0 r- «/-> CO 04 8 04 ha ,04 <*-a 04 oc 04 04 ha 3 o CO 04 c3 co ha o o eg Ua 6-35 b Based on the average weight percent of benzene/VOC ratio of 0.009. 159 c Ocean barge is a vessel with compartment depth of 40 feet; barge is a vessel with compartment depth of 10-12 feet. d Units for this factor are lb/week-1000 gal (mg/week-liter) transported. TABLE 6-13. UNCONTROLLED TOTAL ORGANIC COMPOUND EMISSION FACTORS FOR PETROLEUM MARINE VESSEL SOURCES 3 6.4.2 Benzene Emissions from Bulk Gasoline Plants and Bulk Gasoline Terminals i Each operation in which gasoline is transferred or stored is a potential source of benzene emissions. At bulk terminals and bulk plants, loading, unloading, and storing gasoline are sources of benzene emissions. i Emissions from Gasoline Loading and Unloading The gasoline that is stored in above ground tanks at bulk terminals and bulk plants is pumped through loading racks that measure the amount of product. The loading racks consist of pumps, meters, and piping to transfer the gasoline or other liquid petroleum products. Loading of gasoline into tank trucks can be accomplished by one of three methods: splash, top submerged, or bottom loading. Bulk plants and terminals use the same three methods for loading gasoline into tank trucks. In splash loading, gasoline is introduced into the tank truck directly through a hatch located on the top of the truck. 160 Top submerged loading is done by attaching a downspout to the fill pipe so that gasoline is added to the tank truck near the bottom of the tank. Bottom loading is the loading of product into the truck tank from the bottom. Emissions occur when the product being loaded displaces vapors in the tank being filled. Top submerged loading and bottom loading reduce the amount of material (including benzene) that is emitted by generating fewer additional vapors during the loading process. 160 A majority of facilities loading tank trucks use bottom loading. Table 6-14 lists emission factors for gasoline vapor and benzene from gasoline loading racks at bulk terminals and bulk plants. 160 The gasoline vapor emission factors were taken from Reference 157. The benzene factors were obtained by multiplying the gasoline vapor factor by the average benzene content of the vapor (0.009 percent). 158 6-37 TABLE 6-14. BENZENE EMISSION FACTORS FOR GASOLINE LOADING RACKS AT BULK TERMINALS AND BULK PLANTS c .2 eo ’c/3 C* C/3 • 1 - E O w 0 c<3 U« u co tu c o C/3 W 4) C 4) 2 E cO OUI o o S £ £ W Ml T- E o o w r t "T3 CO > [£. o cO Oil 4) _C o C/3 CO o -o o JS w 4) 2 OX) .£ *5 CO o 4) X> E Z u u co q a 4> a > 4> C 4J OJ 4) 4> CJ C 4) u. , D£ 4) CJ u. 3 a 6-38 Emissions from Storage Tanks Storage emissions of benzene at bulk terminals and bulk plants depend on the type of storage tank used. A typical bulk terminal may have four or five above ground storage tanks with capacities ranging from 400,000 to 4 million gallons (1,500 to 15,000 m 3 ). 160 Most tanks in gasoline service are of an external floating roof design. Fixed-roof tanks, still used in some areas to store gasoline, use pressure-vacuum vents to operate at a slight internal pressure or vacuum and control breathing losses. Some tanks may use vapor balancing or processing equipment to control working losses. The major types of emissions from fixed-roof tanks are breathing and working losses. Breathing loss is the expulsion of vapor from a tank vapor space that has expanded or contracted because of daily changes in temperature and barometric pressure. The emissions occur in the absence of any liquid level change in the tank. Combined filling and emptying losses are called “working losses.” Emptying losses occur when the air that is drawn into the tank during liquid removal saturates with hydrocarbon vapor and is expelled when the tank is filled. A typical external floating-roof tank consists of a cylindrical steel shell equipped with a deck or roof that floats on the surface of the stored liquid, rising and falling with the liquid level. The liquid surface is completely covered by the floating roof except in the small annular space between the roof and the shell. A seal attached to the roof touches the tank wall (except for small gaps in some cases) and covers the remaining area. The seal slides against the tank wall as the roof is raised or lowered. The floating roof and the seal system serve to reduce the evaporative loss of the stored liquid. An internal floating-roof tank has both a permanently affixed roof and a roof that floats inside the tank on the liquid surface (contact roof), or is supported on pontoons several inches above the liquid surface (noncontact roof). The internal floating-roof rises and falls with the liquid level, and helps to restrict the evaporation of organic liquids. 6-39 The four classes of losses that floating roof tanks experience include withdrawal loss, rim seal loss, deck fitting loss, and deck seam loss. Withdrawal losses are caused by the stored liquid clinging to the side of the tank following the lowering of the roof as liquid is withdrawn. Rim seal losses are caused by leaks at the seal between the roof and the sides of the tank. Deck fitting losses are caused by leaks around support columns and deck fittings within internal floating roof tanks. Deck seam losses are caused by leaks at the seams where panels of a bolted internal floating roof are joined. Table 6-15 shows emission factors during both non-winter and winter for storage tanks at a typical bulk terminal. 158 The emission factors were derived from AP-42 equations and a weight fraction of benzene in the vapor of 0.009. 158 Table 6-16 shows uncontrolled emission factors for gasoline vapor and benzene for a typical bulk plant. 160 Table 6-17 shows emission factors during both non-winter and winter months for storage tanks at pipeline breakout stations. 158 The emission factor equations in AP-42 are based on the same equations contained in the EPA’s computer-based program “TANKS.” Since TANKS is regularly updated, the reader should refer to the latest version of the TANKS program (version 3.1 at the time this document was finalized) to calculate the latest emission factors for fixed- and floating-roof storage tanks. The factors in Tables 6-15 and 6-17 were calculated with equations from an earlier version of TANKS and do not represent the latest information available. They are presented to show the type of emission factors that can be developed from the TANKS program. Emissions from Gasoline Tank Trucks Gasoline tank trucks have been demonstrated to be major sources of vapor leakage. Some vapors may leak uncontrolled to the atmosphere from dome cover assemblies, pressure-vacuum (P-V) vents, and vapor collection piping and vents. Other sources of vapor leakage on tank trucks that occur less frequently include tank shell flaws, liquid and vapor transfer hoses, improperly installed or loosened overfill protection sensors, and vapor couplers. This leakage has been estimated to be as high as 100 percent of the vapors w'hich 6-40 TABLE 6-15. BENZENE EMISSION PACTORS FOR STORAGE LOSSES AT A TYPICAL GASOLINE BULK TERMINAL E O u. oflj ‘5? 2 .£ C/3 O w ■3 re co E U- OS UJ o 3 5 H ft. ^ c ^ O 0 £ *v5 ^ 1 J uj 1 I 03 L c E « 1 a ^ u c oa o £ i. © o re U. -X E C 3 H 1— "m re c £ w 3: •- -X C rr % u3 O u o > fd H u- >> o 2 E • £ w g £ I E O Z 2 E O ■5 44 s 44 oc 08 ha o 55 .8 s 3 z u u C/5 UJ os r- co d 00 ON ts o 04 co 04 TT vO tt UJ UJ UJ UJ W w UJ UJ 00 o d Os 5 00 wo 00 wo r» o r~ r-~ o wo 00 o co o © co co O wo CO O 00 3 o 00 3 o CO wo o co © TT CO © © o d 04 Os CO 00 vo wo •O' Os m -g- OO OO TT CO © © o o SO 00 CO 00 q Os 00 at WO vn 00 —- 1 1 aa TT Va- 'w' v^ r 4 1 a. 00 rn 1 SO m CO O'" 00 wo 5 Os WO 3 o O' d TT WO C/3 4 > v. C/5 ^ - «t- «- re E 8 8 .1 *8 * * £ =3 60 , h- •s;§ g 85 o u. 9 ^ 1 « 1 I ?* a 55 & 00 E IS o re E C/3 „ 0) rtj CO w CO £3 ^ C* 60 = «> E ^ .3 •S 44 E ^ S I CT3 — 8 8s “■* § re 4> -a Ij! 1 a* s g 8 x 2 sz UJ C/5 C/5 . *o >> C S3 « E J2 £ 55 iS 8 £ (2 cj 60 .S C/3 00 E •o flJ IS u S3 2 e i § 8 X X 3 * tT -T fS CO CO 88 33 * * Tt TT — (S TT TT T 1 88 3 3 1 1 tt X X 3 TT X X 3 X X 3 1 X X 3 ■4 UJ -a OO TT 8/ O CO 1 U- C/5 1 u- (A C/3 5 8 13 8 ■S 8 Cl OS ^ os E O os _E 60 -a 60 8 60 c ^ .5 _c £ w a "O re •0 0 2 0 c O 2 E 1 £ c3 E "o ■a ^ 13 er 13 la E 1 E 1 E E O 2 0 - £ 2 2 E £ 2 c O E D X X 3 * TT •0 4J 3 C C o o 6-41 TABLE 6-15. CONTINUED e O ^ 60 So 2 .S % u *- •a co eg E u. x BJ 2.1 co U. "Sc c o 8 S 1 [D a 4> CO X> T- § 2 H a| sj co *“• 'r>, — oc ^ o 2 OJ ^ c o co cO O C/3 E £ LU t— of > s UJ vo r- - oo oo 4> c a o Z r-» ON r~ o CN NO VO r~ -3 O •5 4> 2 ul col V- I O •—* i c/3 TO 4> c o u I U- 8 uu C4 NO r~ “ 88 8 8 o d oo (S £ d o m r- o 00 E C/3 00 a 73 c u. 60 c • *N W M E E X U3 i T E 3 Z o u C/2 X 8 i Tf 4) C/2 A4 U 4> Q ■ U. 8 X DC C • m* W cd o E eg c/s 3 4> U oo 4) co S3 x x 00 .s l— o £ « u- 8 x OO c CO o 5 C/3 C 4> C C/3 4» c /3 S3 s I X X 5 Tf o- > x l- « 2 -S c <*. 1 = CO o • * C/3 co b< on 4> 4> | co > CO C/3 CO Ou > cn Tn _• «j ON — cm .2 o „ « -o cc si* ^ T3 C S> O CO CO u co §•£ C .d 4 O 60 o z < H x 60 ’3 x CO •o C/3 l_i 4> cs vri 8 is .3^ ^ 60 r q 2 > § "S5 c o 4> > C/3 4> > u- *o 60 U P a 4> C E cl 2 <*> OOX 2 z o.< c/5 H X 4> Z -S < . ^ *5 f -1 4> & co * CO £ O CL C/3 .* co 8 00 > u- ^ c2 S 1/3 is 3 CO 8 4> Cm o vo 4> 3 T3 CO X) X o VO r—_ NO Zr' E o 00 . NO ) PnT Cl < o CO tT T3 C/3 s E 2 £ 3 M 2 < 0> W C/3 0" V- V3 2 w 52 ’2 2 U S w u. .cd 4) 2 W O o w C/3 U. 3 <2 -S >3 co T3 _o co M u o > 4) e 4) a a E o 4> C/3 c .2 tt . o o cr^ w o P.S C/3 OJ I JO ri 4) c o CL 3 T3 41 C/3 CO X co 3 6 i 2 4/ 1 __ x 23 2 4> co 5 v 2 a Vr O co O 60 ’C X co •O . to I? « >- h 0 co 4> X £ _c TT cn C/3 l-: c CO 4) 4> ,4) X oo x r~. oo Cm 3 o 2 £•5 3 CL 4/ E ^ .2 T3 3 co P 3 4) c X O ~ VO C/3 r~ •“ vo O w 4) C/3 k. •fi X in *3 i— a X .S C/3 c CO 4> ■s x 00 3 O a 3 O 4) 6 a 4) v- 4> X X co c o on "3 o> M CO X C/3 X 3 cO M 4> ■s x 60 3 O p a i-5 w- 3 ^ o O t- 60 Em 2 s 0 CL^ 5 e * c« W Z x < a Z H 4> -f- 2 W- < O H « x s -S ^ 4> c X •— L- M >3 = P C o E c0 on 4) M M CO X c co -M 4) 6 •§> 3 O 3 CL X 60 3 O 4> 5 a 4) i— 4) X >3 'S __ >3 ^3 "So ,£ 2 c o - 2 o q >3^ OOCcmPEPm fw X ^ a x a ° m S X 2 4> |^2s2^^o5S-b- 3 II X II * L. 75 II x II K 5 l- . b • o i: *- •*- “ 2^ aS ^ 2 u w o SPy .co O w xa®l kSkS — - £ co 2 . n ^ p- . — ^ o r- o 'O it co II o .co 00 4/ «o 8 4> L- X 4) U M 3 O on ^5 _ M O .CO 3 * 4)0i;Sfe c3oOOOxxOOOO o W o ^ * w y 4> p .2 cM g 5 a>.§ ^2 ^2 E c -3 -3 £ C = c «oSE 4> o 4) .2 ^ C/3 C/3 ^ ^ 1/5 52 9 -3 «£ « £ E c 3 « o E Ss'SSoSSg2SsS * X li H 8 a &! |'i O ^ 4>4>4)4)MM4J4>y4) C C ^ C ^ ^ Ca ^ C g itin§!ii§i§ ^hCfflOfflUUOCJOcQ 4> X co ‘3 > C0 CO CO •o 8 C/5 C cz I 6-42 VAPOR AND BENZENE EMISSION FACTORS FOR A TYPICAL BULK PLANT Li Z o co < . O so “ I vO Li 03 <22 Cb cn •— I— E ° Li « Ca Li Li d 1) c 'o C/D C3 o § - C/2 C/2 ca CO E o Li : 12 12 t— 3 O CO r— c C/2 C/2 E Li 12 X E 3 z u u co o o VO o »n c o u TO 1) X Li ea H pa Li Li Li O i cn i Tt o I Tt o iO SO Os c o Cri TO 12 0(2 o P3 rat li 1) s O •*—* o "co to os to CS Li E, Tt in o (N d a 12 C c o cn C/2 7a cc o © SO oo © 1 —s Tt co o o r- o d Tt Tt o o co c Li Tt o >w' § o © t_2 CO o o' SO Tt Os Tt Tt »o 'w' CO 00 OS Os CO Tt d Li CO 3 co c* 'iT i> ea o “iT 12 on cn O C/2 3 ea cn on O J co 3 •a ea o hJ *3 ea o ’E 12 cn nJ to 12 CO ’E 12 cn CD 3 H 12 CO 3 CO 3 O. 12 .s X cn 7a l~i 12 3 73 X ca CD ea 1- X u. • Li E Li o cn ^£3 ’H, o c 3 X 3 o 3 12 O o ea co 00 Wh CQ w CO £ O CO c ■5 o hJ TO CO U- 1) E x 3 CO 12 12 12 c /2 TO § 1) X c eS i2 "H. co Tt o I CN Tt O i Tt o »n i CN i Tt o I Tt 6-43 Source: Reference 160. * Typical bulk plant with gasoline throughput of 19,000 liters/day (5,000 gallons/day). b Based on gasoline emission factor and an average benzene/VOC ratio of 0.009. c Calculated using a Stage I control efficiency of 95 percent. TABLE 6-17. BENZENE EMISSION FACTORS FOR STORAGE LOSSES AT A TYPICAL PIPELINE BREAKOUT STATION 3 * 1 C O J- U) 3 .£ C/3 PI w •P «5 « E u. o£ uj 1- J o i o r* re r BU ' c J O ‘K 5 C/3 X5 U3 ’S a> u c C e , re 1— r c c g- ^ >-** 4> C "o C/3 re w C k> 00 00 p /*»s Os ■ G“ V c o m Os' CO © 8 8 © © © (— 'w' —' ' W< t o © OS 00 CO SO — o 1 Os o Z m m o cs •re- s © 8 © 8 © c O C/3 O 4> C c/3 JS on 2.3 8 g> c* -S ■a "S aj re x « .«■ U U. 03 UJ UJ UJ UJ tt UJ UU UJ . © ^^ CN 3 f" 00 •re- Vi (S •^-/ © Vi SO rj , V (S CO SO Os CN CN TT r- o CO CO CO Vi SO CO V cn cn 00 ■re- CN cn o cn CO so os 3 cn X X I X oo r— 12 i— o £ T3 4) C o u c D c*- 8 * «* •O V 2 C/5 3 c/3 •13 X X X 8 3 •re- T3 4/ 1 u- • 12 Ux o o c- ’5 C* a c re *2 > 4> u o > J C/5 O U i 1 C/5 . 5/5 • C/5 C/5 c ■ b*- OJ Efl O C/5 *s S? "re h" r-* 2 13 k> c "re mm E £ c E a E o E a s 1 a o a 2 a a a c E c w E a ‘jr — c. c M D C/3 e/3 C/3 OO .5 E re a> C/3 u 4> 8 o£ oo .5 re £ E "re E 8 a I e o oo re c 4> 12 Z o £ re ■o c o o 4) C/3 OO .S T3 re re 50 Sn 8 Q£ T3 60 % % jK re s o a E .5 re o. E 8 a g c o X X X 8 i S i -re- X X X 8 i 5 •re- X X X 8 i S i •re- X X 3 X X I X 8 i S i -re- X 8 i S x X I X 8 i S i UJ vO /—s —/ d d 1 1 d d 00 00 CO CO (N o 4/ 1 •re- r- so (N m-4 CO vn V CN so SO 00 © r- c rn CO CO © Os r~ CO SO © •re- CN ro •re¬ CN d o CN CN 1 sb •^z ' W " s—^ I ON vs SO •re- © r- os u 1 m — c o vd r- CN o oo SO r- CN Os z ro r-~ CN — © CN CN id sd ■re- oo S _ •o i to > 8 18 * -2 oo cu .5 • re 5g O 55 E g re 4 > E g> 4) 2 X 2 UJ CO X X X 8 i Z i •re- re <4_ "O a _ o ^ o ™ 4> OO 50 .s § «u E 8 re 4 > E g a 2 X 2 U CO X X S •re- T3 CJ 3 c C o u 6-44 TABLE 6-17. CONTINUED C o 5- , ‘S3 2 .S co o S •a cq cq E u. cc\ u i- S o x co E- U. X c ^ 2 OC 'co 5 (A <*C to 4> La a “ 4> a -g 4 v a CQ 2 4> a £ c o Z T- o o co u. a a i H 2 .>> 3 "eo j t. ^ .* > a CO o H a ^ « >! > V o C/5 o 2 a a c Z to r- *n o 5 I o m 8 © u C4 4> a VO s o oo co a I d ■g 6 0> 2 hJ si u. o w I c/3 CO o co so © d to E a Z U U c/3 X X I X S tO c/3 X X I X 3 ■ • u a '% eo •> .25 to a co os 4> ,4> 4> 2 <— O tT <— O o 4) c o X CQ f • p< C/3 as 4) h* CQ X 4> > > CQ CQ •w CO ■o CO 4> CQ £ — 4) i C/3 u. CO CO u oo «n U , o u 3 O C/3 co ’3 u- ctf X) a cO 2 4> 2 2 -S •§> § 13 3 o P • 3 a a. a x 2 op oo a o p E cO _ ob ^2 O £ u> CL flj 1/5 2 C/3 •x C/3 5 X < a OJ Z t“ < H a> 2 e 9J 2 S| e o 2 c — c Q 2 ° 2 u e o u a> CO ”S Ui u eo X a 2 a a> u 4> X £ u ~e CO *93 u u co X .e a 2 4> 2 x OO a o a CL X oo a o 4> 2 a 4> u oj x £ u "oo 5 s J 2 o ' ^ o _ ^ © & * a * a * a * o 1 wo *-u 2x2—2co£ §3 w^do^-doodr^o — 4> w —< w —* w — w — . “ - U 3 II * II * II * II * liu^u-u^u'P •5S 2S2S2^2S d r Po O O 4> r r <2 ii <2 ii <2 ii <2 ii xxoooooooo * 5 M u « o '« o « o ®P .£ <2 •£ -2 3 <2 •£ <2 •S-aCeCcEaEe ilwo^o^o^o 1 i a! al al al n P a ^ 4> ^ 4) CQ > 4, eo’rj*Q^qj^ a>( ^ « w u£2jiuJiui!o5i« 5|IS glSigs S s 3!8gsa§3§a UUOOOBOBOi 6-45 2 x JO CQ > CQ — g 2 CQ •o E should have been captured and to average 30 percent. Because terminal controls are usually found in areas where trucks are required to collect vapors after delivery of product to bulk plants or service stations (balance service), the gasoline vapor emission factor associated with uncontrolled truck leakage was assumed to be 30 percent of the uncontrolled balance service truck loading factor (980 mg/liter x 0.30 = 294 mg/liter). 160 Thus the emission factor for benzene emissions from uncontrolled truck leakage is 2.6 mg/liter, based on a benzene/vapor ratio of 0.009. 6.4.3 Benzene Emissions from Service Stations The discussion on service station operations is divided into two areas: the filling of the underground storage tank (Stage I) and automobile refueling (Stage II). Although terminals and bulk plants also have two distinct operations (tank filling and truck loading), the filling of the underground tank at the service station ends the wholesale gasoline marketing chain. The automobile refueling operations interact directly with the public so that control of these operations can be performed by putting control equipment on either the service station or the automobile. Stage I Emissions at Service Stations Normally, gasoline is delivered to service stations in large tank trucks from bulk terminals or smaller account trucks from bulk plants. Emissions are generated when hydrocarbon vapors in the underground storage tank are displaced to the atmosphere by the gasoline being loaded into the tank. As with other loading losses, the quantity of the service station tank loading loss depends on several variables, including the quantity of liquid transferred, size and length of the fill pipe, the method of filling, the tank configuration and gasoline temperature, vapor pressure, and composition. A second source of emissions from service station tankage is underground tank breathing. Breathing losses tend to be minimal for underground storage tanks due to nearly constant ground temperatures and are primarily the result of barometric pressure changes. 6-46 Stage II Emissions of Service Stations In addition to service station tank loading losses, vehicle refueling operations are considered to be a major source of emissions. Vehicle refueling emissions are attributable to vapor displaced from the automobile tank by dispensed gasoline and to spillage. The major factors affecting the quantity of emissions are dispensed fuel temperature, differential temperature between the vehicle's tank temperature and the dispensed fuel temperature, and fuel Reid vapor pressure (RVP). 161,162 Several other factors that may have an effect upon refueling emissions are: fill rate, amount of residual fuel in the tank, total amount of fill, position of nozzle in the fill-neck, and ambient temperature. However, the magnitude of these effects is much less than that for any of the major factors mentioned above. 161 Spillage loss is made up of configurations from prefill and postfill nozzle drip and from spit-back and overflow from the vehicle's fuel tank filler pipe during filling. Table 6-18 lists the uncontrolled emission factors for a typical gasoline service station. 160,163 This table incudes an emission factor for displacement losses from vehicle refueling. However, the following approach is more accurate to estimate vehicle refueling emissions. Emissions can be calculated using MOBILE 5a, EPA’s mobile source emission factor computer model. MOBILE 5a uses the following equation: 163 E r = 264.2 [(-5.909) - 0.0949 (aT) + 0.0884 (T D ) 4- 0.485 (RVP)] where: E r = Emission rate, mg VOC/0 of liquid loaded RVP = Reid vapor pressure, psia (see Table 6-19) 163 aT = Difference between the temperature of the fuel in the automobile tank and the temperature of the dispensed fuel, °F (see Table 6-20) 161 T d = Dispensed fuel temperature, °F (see Table 6-21) 164 Using this emission factor equation, vehicle refueling emission factors can be derived for specific geographic locations and for different seasons of the year. 6-47 u o PL on C* O H U < tu Z o on oo 2 w w z z o < UJ oo N Z W cq Q Z < O CL < > PL z j o C/5 < o oc I VO w H-J CQ < H W y > c* w oo < u Pu > H < o [2 oc e .ST *4-> O co Pm C/D • £ w e « s s 4> w w w Tfr cs rf O O) vO VO o ^t o m o _ 00 m r* o oo 00 s m m d 4> 4) i— 3 C 00 3 O vi C/3 e w Li c ca H C/5 Li — C X a fcx, H ^ D co OX) « 2 o. o ^ O' 1 C/5 -O 4> c C/5 3 5/5 § 5 V-> i—i OX) v-T O 0 o 9 t- t-J £? 0X) 4) C TD *^S C •- D PL w ON 8 o o £ OX) J2 e« eg 5 CQ oo 1 co T3 4) C 5/5 3 6/5 § 9 &) J o u7 OX) OX) 4) C C *3 13 ••** fisa D pH Ph co Li G <3 H 4) OX) 3 Ui O co w 00 co CO T3 o C <-J 3 „ O OX) I- c OX) .S t-, X e U hE U - D CQ G 4) s 4) O — G- co OX) _c 13 cH 4> PC ja co 4) 4) •3 co •G co 4) O > J 4 ) X) £ 3 rN VO o o 1 O 1 o 7 m cn m u § 8 8 8 1 u vo v6 vO VO on cp o O | O | Tf Tf -o 8 co 4> U e 4> l. U i— 3 O O) co < a. UJ CCJ »n UP J CQ o 2 &> € oo .£ *co 3 b> CQ >> ID 6 o CO CQ 4> CO w C •o rt CO 3 .2 CQ U o J= a. CQ k. C4 O CQ OO .S 60 C w 3! S 13 .2 2 *co (D ?• S 3 £ 4> 00 V, « co g Q *- *G O CQ 4) u 3 3 y 1 i -8 ‘-S H co U > 6-48 mobile source emission factor computer model. In the absence of specific data, Tables 6-19, 6-20, and 6-21 may be used to estimate refueling emissions. Tables 6-19, 6-20, and 6-21 list gasoline RVPs, aT, and T D values respectively for the United States as divided into six regions: Region 1: Connecticut, Delaware, Elinois, Indiana, Kentucky, Maine, Maryland, Massachusetts, Michigan, New Hampshire, New Jersey, New York, Ohio, Pennsylvania, Rhode Island, Virginia, West Virginia, and Wisconsin. Region 2: Alabama. Arkansas, Florida, Georgia, Louisiana, Mississippi, North Carolina, South Carolina, and Tennessee. Region 3: Arizona, New Mexico, Oklahoma, and Texas. Region 4: Colorado, Iowa, Kansas, Minnesota, Missouri, Montana, Nebraska, North Dakota, South Dakota, and Wyoming. Region 5: California, Nevada, and Utah. Region 6: Idaho, Oregon, and Washington. 6.4.4 Control Technology for Marine Vessel Loading Marine vapor control systems can be divided into two categories: vapor recover)' systems and vapor destruction systems. There are a wide variety of vapor recovery systems that can be used with vapor collection systems. Most of the vapor recovery systems installed to date include refrigeration, carbon adsorption/absorption, or lean oil absorption. Three major types of vapor destruction or combustion systems that can operate over the wide flow rate and heat content ranges of marine applications are: open flame flares, enclosed flame flares, and thermal incinerators. 165 When selecting a vapor control system for a terminal, the decision on recovering the commodity depends on the nature of the VOC stream (expected variability in flow rate and hydrocarbon content), and locational factors, such as availability of utilities and distance from the tankship or barge to the vapor control system. The primary reason for selecting incineration is that many marine terminals load more than one commodity. 159164 6-49 TABLE 6-19. RVP LIMITS BY GEOGRAPHIC LOCATION State Summer (Apr.-Sep.) Weighted average Winter (Oct.-Mar.) Annual Alabama 8.6 12.8 10.6 Alaska 13.9 15.0 14.3 Arizona 8.4 11.6 10.0 Arkansas 8.5 13.5 10.7 California 8.6 12.6 10.6 Colorado 8.6 13.1 10.7 Connecticut 9.7 14.5 12.0 Delaware 9.7 14.3 11.9 District of Columbia 8.8 14.1 11.4 Florida 8.7 12.9 10.7 Georgia 8.6 12.8 10.7 Hawaii 11.5 11.5. 11.5 Idaho 9.5 13.2 11.3 Illinois 9.7 14.2 12.0 Indiana 9.7 14.3 11.9 Iowa 9.6 14.2 11.8 Kansas 8.6 13.1 10.8 Kentucky 9.6 14.0 11.7 Louisiana 8.6 12.8 10.6 Maine 9.6 14.5 11.9 Maryland 9.0 14.3 11.6 Massachusetts 9.7 14.5 12.0 Michigan 9.7 14.5 12.0 Minnesota 9.7 14.3 11.8 Mississippi 8.6 12.8 10.7 Missouri 8.7 13.8 11.1 Montana 9.5 14.3 11.7 (continued) 6-50 TABLE 6-19. CONTINUED State Summer (Apr.-Sep.) Weighted average Winter (Oct.-Mar.) Annual Nebraska 9.5 13.5 11.4 Nevada 8.5 12.5 10.4 New Hampshire 9.7 14.5 - 12.0 New Jersey 9.7 14.4 12.1 New Mexico 8.5 12.4 10.3 New York 9.7 14.5 12.0 North Carolina 8.8 13.6 11.1 North Dakota 9.7 14.2 11.7 Ohio 9.7 14.3 11.9 Oklahoma 8.6 12.9 10.7 Oregon 9.0 13.9 11.2 Pennsylvania 9.7 14.5 12.0 Rhode Island • 9.7 14.5 12.1 South Carolina 9.0 13.3 11.0 South Dakota 9.5 13.5 11.3 Tennessee 8.8 13.6 11.1 Texas 8.5 12.5 10.4 Utah 8.7 13.3 10.9 Vermont 9.6 14.5 12.0 Virginia 8.8 14.0 11.3 Washington 9.7 14.3 11.9 West Virginia 9.7 14.3 11.9 Wisconsin 9.7 14.3 11.9 Wyoming 9.5 13.6 11.5 Nationwide Annual Average 9.4 11.4 Nonattainment Annual Averaee 9.2 11.3 Source: Reference 163. 6-51 TABLE 6-20. SEASONAL VARIATION FOR TEMPERATURE DIFFERENCE BETWEEN DISPENSED FUEL AND VEHICLE FUEL TANK 3 Temperature difference (°F) Average annual Summer (Apr.-Sep.) Winter (Oct.-Mar.) 5-Month Ozone Season (May-Sep.) 2-Month Ozone Season (July-Aug.) National average 4.4 8.8 -0.8 9.4 9.9 Region 1 5.7 10.7 -0.3 11.5 12.5 Region 2 4.0 6.8 0.9 7.5 8.2 Region 3 3.7 7.6 -0.4 7.1 7.0 Region 4 5.5 11.7 -2.4 12.1 13.3 Region 5 0.1 3.9 -4.4 5.1 3.2 * , — .—.. , -- -- — .. - . . . . ., Source: Reference 161. a Region 6 was omitted, as well as Alaska and Hawaii. TABLE 6-21. MONTHLY AVERAGE DISPENSED LIQUID TEMPERATURE (T D ) Weighted average Summer (Apr.-Sep.) Winter (Oct.-Mar.) (Annual) National average 74 58 66 Region 1 70 51 61 Region 2 85 76 81 Region 3 79 62 70 Region 4 74 56 65 Region 5 79 63 72 Region 6 64 50 57 Source: Reference 164. 6-52 For additional information on emission controls at marine terminals refer to References 159 and 165. 6.4.5 Control Technology for Gasoline Transfer At many bulk terminals and bulk plants, benzene emissions from gasoline transfer are controlled by CTG, NSPS, and new MACT programs. Control technologies include the use of a vapor processing system in conjunction with a vapor collection system. 160 Vapor balancing systems, consisting of a pipeline between the vapor spaces of the truck and the storage tanks, are closed systems. These systems allow the transfer of displaced vapor into the transfer truck as gasoline is put into the storage tank. 160 Also, these systems collect and recover gasoline vapors from empty, returning tank trucks as they are filled with gasoline from storage tanks. The control efficiency of the balance system ranges from 93 to 100 percent. 1 ' Figure 6-4 shows a Stage I control vapor balance system at a bulk plant. 160 At service stations, vapor balance systems contain the gasoline vapors within the station's underground storage tanks for transfer to empty gasoline tank trucks returning to the bulk terminal or bulk plant. Figure 6-5 shows a diagram of a service station vapor balance system. 160 For more information on Stage II controls refer to Section 6.4.7. 6.4.6 Control Technology for Gasoline Storage The control technologies for benzene emissions from gasoline storage involve upgrading the type of storage tank used or adding a vapor control system. For fixed-roof tanks, emissions are most readily controlled by installation of internal floating roofs. An internal floating roof reduces the area of exposed liquid surface on the tank and, therefore. 6-54 Source: Reference 160. CO 1 I b. £ X E 3 z u u oo W u u CQ 03 U U OQ W 03 03 no TT no © wo © rr wo vC r- © no X- W-) o vO r- o wo o X X OX) OX) TT O WO © © © © o © © o o o o o ““ o *-H »— ▼■H ^-1 *—* »■ ■ H o X X X X X X X X X X X X X X X X X X O X X o as X r- o On r- ON o wo o (N o 00 o Os ON as o wo t" wo 3 Ui —H 3 C C/D o C C C c O C C C C o o O O o CJ o a o o 3 0) 3 3 3 3 3 3 3 3 3 3 O U £ D D D D D D P D o i r» o o i o I wo CJ cd cd TO *—• O Cd 3 aj OX) >* x o 4) 0) OX) 3 o m m i r- o o o I wo CO I r- V JC *C 03 CJ b cd •a 3 O o Q x i r- i © i wo 03 i-i a r- i r-» o i wo 03 45 r\ C o U a O C V- 45 <—> c« 45 .op on cn 45 1 —1 45 oo a *H •a 45 X OX) G "E X3 O • Ou Im w C 45 b OJ - S « 3 « e £ .£ u 3 2 * ? o a cn 'w 5 k. i 4/ .3 45 — 3 | C '"2 ® C 4/ r a CT3 4/ 00 JO c .2 0 •3 'eo £ e k- £> •s & 3 X E £ 45 4/ C C 4/ 45 4J S C 4/ JS S •3 i /-v **- 00 O M ^ w 00 £ b i £ *8 a i! 2 c s U CM a " o S c/d • E w "O 3 3 on 3 O • O. c o £ € 5 00 1 00 S 8 s o r» 3 s CO 03 0*6 1 8 * £ © - . 0 - © ^ "o w o « O " a <• - 11 c * ° 5 o 5 E O w o I ^ o c w (1 © CL * O © © O CL f III?© * Ci ® c e oo © © T> • C C > ^ ° > 11 o O © _ ►" £ o — c X o £ © © - £ E c • — c c c o © 5 ® u -O W» W ^ O S S O 3 — o •o u> §5 a. r; • 1 £ o O O. ° O • — 1 = ® o — CL • © £ © • © © © .o c li c o a. o Z o u c u I— £ dies), nuclear (e.g., moderators, thermal columns, and fuel elements), and miscellaneous (e.g., motion picture projector carbons). 174 6-93 The number of facilities manufacturing synthetic graphite in the United States was not identified. 6.8.1 Process Description for Synthetic Graphite Production Synthetic graphite is produced from calcined petroleum coke and coal tar pitch through a series of processes including crushing, sizing, mixing, cooling, extrudings baking, pitch impregnation, rebaking, and graphitization. Throughout the process of thermal conversion of organic materials to graphite, the natural chemical driving forces cause the growth of larger and larger fused-ring aromatic systems, and ultimately result in the formation of the stable hexagonal carbon network of graphite. A process flow diagram of the synthetic graphite manufacturing process is provided in Figure 6-9. 174,175 Calcined petroleum coke (i.e., raw coke that has been heated to temperatures above 2,200°F (1,200°C) to remove volatiles and shrink the coke to produce a strong, dense particle) is crushed and screened to obtain uniform-sized fractions for the formulation of dry ingredient. Coal tar pitch is stored in heated storage tanks and is pumped to the mixing process, as needed, as the liquid ingredient. The dry ingredient is weighed and loaded, along with a metered amount of coal tar pitch, into a heated mixing cylinder (heated to at least 320°F [160°C]), where they are mixed until they form a homogeneous mixture. During the mixing process, vapors (Vent A in Figure 6-9) are ducted to a stack where they are discharged to the atmosphere. 174,175 The heated mixture is sent to a cooling cylinder which rotates, cooling the mixture with the aid of cooling fans to a temperature slightly above the softening point of the binder pitch. Vapors from the cooling process (Vent B in Figure 6-9) are often vented to a PM control device before being vented to the atmosphere. 174,175 The cooled mixture is charged to a hydraulic press, then pressed through a die to give the mixture the desired shape and size. The extruded mixture is referred to as “green 6-94 dlM-»f-/Vnj-SZ00*8 £ • *. C X o • - 11 si g g S 2 o Cl fc O o °- c © jQ — i • C e : rj- O* w • £ in « ft .x c "Sbl ■I X, C/D in u a a T © *>< TT T o x rJ oo co E in at c/d o Q i Z u u oo •a at C O at c D _Ot c U oo c T3 Ol < « C ^ E nj a> 4: > ^ at -a _e ■h u 0£ E u 4> '.E a. !e Q. <9 i— t— o o at X> at •5 5 E fi S»> C/0 00 X X X X X X X X X X X X I I m m X I X wo r- at at fi 4> t_ At <4— at 0£ at at t- E O C/0 •o at at 3 ■8 i— O. 40 IE Cl c% co O0 8 . ■c a> at at § s £ L—i o w £ CO O <4—i E O "S CO in 6-98 pitch-impregnation processes (Vents C through E in Figure 6-9); however, emission factors could not be developed. 175 6.8.3 Control Technologies for Synthetic Graphite Production 175 As discussed in Section 6.9.1, afterburners may be used to control emissions of unbumed hydrocarbons from the initial baking and rebaking furnace (Vents C and E in Figure 6-9), as well as the preheater and heated storage tank used for the pitch impregnation process (Vent D in Figure 6-9). Data regarding the use of afterburners in this application were not available; however, it is likely that the afterburners would reduce benzene emissions. Additionally, an ESP may be used to control particulate emissions from the cooling cylinder; however, it is unlikely that an ESP would reduce benzene emissions. 6.9 CARBON BLACK MANUFACTURE The chemical carbon black consists of finely divided carbon produced by the thermal decomposition of hydrocarbons in the vapor phase, unlike coke that is produced by the pyrolysis of solids. Carbon black is a major industrial chemical used primarily as a reinforcing agent in rubber compounds, which accounts for over 90 percent of its use. It is used primarily m tires (both original equipment and replacement), which accounts for over 70 percent of its use. 176 Other tire-related applications include inner tubes and retreads. Other uses include automotive hoses and belts, wire and cable, roofing, pigment in inks and coatings and as a plastic stabilizer. 176 As of January 1994, there were 24 carbon black manufacturing facilities in the United States. Over 75 percent of all carbon black production occurs in the States of Texas and Louisiana (36 and 40 percent, respectively). The location of all facilities and their estimated annual production capacities in 1993 are provided in Table 6-28. 177 The manufacture of carbon black is of potential concern for benzene emissions because the predominantly used production process involves the combustion of natural gas and the high-temperature pyrolysis of aromatic liquid hydrocarbons. . 6-99 TABLE 6-28. LOCATIONS AND ANNUAL CAPACITIES OF CARBON BLACK PRODUCERS IN 1994 Company Facility Location Annual Capacity, millions of pounds (millions of kg) Cabot Corporation Franklin, LA 260(118) Pampa, TX 60 (27) Villa Platte, LA 280(127) Waverly, WV 180 (82) Chevron Corporation Cedar Bayou, TX 20 (9) Columbian Chemicals Company El Dorado, AR 120 (54) Moundsville, WV 170 (77) North Bend, LA 220(100) Ulysses, KS 85 (39) Degussa Corporation Arkansas Pass, TX 180 (82) Belpre, OH a 130 (59) New Iberia, LA 200(91) Ebonex Corporation Melvindale, MI 8 (3.6) General Carbon Company Los Angeles, CA 1 (0.45) Hoover Color Corporation Hiwassee, VA 1 (0.45) J.M. Huber Corporation Baytown, TX 225 (102) Borger, TX 175 (79) Orange, TX 135(61) Sid Richardson Carbon and Gasoline Addis, LA 145 (66) Company Big Springs, TX 115 (52) Borger, TX 275 (125) Witco Corporation Phoenix City, AL 60 (27) Ponca City, OK 255(116) Sunray, TX 120(54) TOTAL 3,420(1,551) Source: Reference 177. a Emissions of 81,000 lb/yr (36,741 kg/yr) of benzene reported for 1992. m Note: This listing is subject to change as market conditions change, facility ownership changes, plants are closed ' down, etc. The reader should verify the existence of particular facilities by consulting current listings and/or the plants themselves. The level of benzene emissions from any given facility is a function of variables such as capacity, throughput, and control measures, and should be determined through direct contacts with plant personnel. 6-100 6.9.1 Process Description for Carbon Black Manufacture Approximately 90 percent of all carbon black produced in the United States is manufactured by the oil-fumace process, a schematic of which is given in Figure 6-10. The process streams identified in Figure 6-10 are defined in Table 6-29. 178,179 Generally, all oil-furnace carbon black plants are similar in overall structure and operation. The most pronounced differences in plants are primarily associated with the details of decomposition furnace design and raw product processing. 178 In the oil-fumace process, carbon black is produced by the pyrolysis of an atomized liquid hydrocarbon feedstock in a refractory-lined steel furnace. Processing temperatures in the steel furnace range from 2,408 to 2,804°F (1,320 to 1,540°C). The heat needed to accomplish the desired hydrocarbon decomposition reaction is supplied by the combustion of natural gas. 178 Feed materials used in the oil-fumace process consist of petroleum oil, natural gas, and air. Also, small quantities of alkali metal salts may be added to the oil feed to control the degree of structure of the carbon black. 179 The ideal raw material for the production of modem, high structure carbon blacks is an oil which is highly aromatic; low in sulfur, asphaltenes and high molecular weight resins; and substantially ffeeiDf suspended ash, carbon, and water. To provide maximum efficiency, the furnace and burner are designed to separate, insofar as possible, the heat generating reaction from the carbon forming reaction. Thus, the natural gas feed (Stream 2 in Figure 6-10) is burned to completion with preheated air (Stream 3) to produce a temperature of 2,408 to 2,804°F (1,320 to 1,540°C). The reactor is designed so that this zone of complete combustion attains a swirling motion, and the oil feed (Stream 1), preheated to 392 to 698°F (200 to 370°C), is sprayed into the center of the zone. Preheating is accomplished by heat exchange with the reactor effluent and/or by means of a gas-fired heater. The oil is cracked to carbon and hydrogen with side reactions producing carbon oxides, water, methane, acetylene and other hydrocarbon products. The heat 6-101 ATMOSPHERIC EMISSIONS CO < o CO 5 O'* r~~ o o c u u. £ o 0£ o o u. 3 O C/0 6-102 Figure 6-10. Process Diagram for an Oil-Furnace Carbon Black Plant TABLE 6-29. STREAM CODES FOR THE OIL-FURNACE PROCESS ILLUSTRATED IN FIGURE 6-10 Stream Identification Stream Identification 1 Oil feed 21 Carbon black from cyclone 2 Natural gas feed 22 Surge bin vent 3 Air to reactor 23 Carbon black to pelletizer 4 Quench water 24 Water to pelletizer 5 Reactor effluent 25 Pelletizer effluent 6 Gas to oil preheater 26 Dryer direct heat source vent 7 Water to quench tower 27 Dryer bag filter vent 8 Quench tower effluent 28 Carbon black from dryer bag filter 9 Bag filter effluent 29 Dryer indirect heat source vent 10 Vent gas purge for dryer fuel 30 Hot gases to dryer 11 Main process vent gas 31 Dried carbon black 12 Vent gas to incinerator 32 Screened carbon black 13 Incinerator stack gas 33 Carbon black recvcle j 14 Recovered carbon black 34 Storage bin vent gas 15 Carbon black to micropulverizer 35 Bagging system vent gas 16 Pneumatic conveyor system 36 Vacuum cleanup system vent gas 17 Cyclone vent gas recycle 37 Dryer vent gas 18 Cyclone vent gas 38 Fugitive emissions 19 Pneumatic system vent gas 39 Oil storage tank vent gas 20 Carbon black from bag filter Source: Reference 178. 6-103 transfer from the hot combustion gases to the atomized oil is enhanced by highly turbulent flow in the reactor. 179 The reactor converts 35 to 65 percent of the feedstock carbon content to carbon black, depending on the feed composition and the grade of black being produced. The yields are lower for the smaller particle size grades of black. Variables that can be adjusted to produce a given grade of black include operating temperature, fuel concentration, space velocity in the reaction zone, and reactor geometry (which influences the degree of turbulence in the reactor). A typical set of reactor operating conditions for high abrasion furnace carbon black is given in Table 6-30. 179 The hot combustion gases and suspended carbon black are cooled to about 1004°F (540 °C) by a direct water spray in the quench area, which is located near the reactor outlet. The reactor effluent (Stream 5 in Figure 6-10) is further cooled by heat exchange in the air and oil preheaters. It is then sent to a quench tower where direct water sprays finally reduce the stream temperature to 446 °F (230°C). Carbon black is recovered from the reactor effluent stream by means of a bag filter unit. The raw carbon black collected in the bag filter unit must be further processed to become a marketable product. After passing through the pulverizer, the black has a bulk density of 1.50 to 3.68 lb/ft 3 (24 to 59 kg/m 3 ), and it is too fluffy and dusty to be transported. It is therefore converted into pellets or beads with a bulk density of 6.06 to 10.68 lb/ft 3 (97 to 171 kg/m 3 ). In this form, it is dust-free and sufficiently compacted for shipment. 6.9.2 Benzene Emissions from Carbon Black Manufacture Although no emission factors are readily available for benzene from carbon black manufacture, one carbon black manufacturer with annual capacity of 130 million pounds (59 million kg) using the oil-furnace process reported benzene emissions of 81,000 lb/yr (36,741 kg/yr) for 1992, which translates to 6.23X10* 4 lb (2.83xl0‘ 4 kg) benzene per lb (kg) 6-104 TABLE 6-30. TYPICAL OPERATING CONDITIONS FOR CARBON BLACK MANUFACTURE (HIGH ABRASION FURNACE) Parameter Rate of oil feed Preheat temperature of oil Rate of air feed Rate of natural gas feed Furnace temperature in reaction zone Rate of carbon black production Yield of black (based on carbon in oil feed) Source: Reference 179. Value 27 ft 3 /hr (0.76 m 3 /hr) 550°F (288°C) 234,944 ft 3 /hr (6,653 m 3 /hr) 22,001 ftVhr (623 m 3 /hr) 2,552°F (1,400°C) 860 lb/hr (390 kg/hr) 60 percent carbon black produced. No regulations applicable to carbon black manufacture were identified that would affect benzene emissions. The emission factor is given in Table 6-31. 111 TABLE 6-31. EMISSION FACTOR FOR CARBON BLACK MANUFACTURE SCC Number Description Emission Factor (lb benzene/lb carbon black) Emission Factor Rating Oil Furnace Process 6.23x10"* Source: Reference 111. 6.10 RAYON-BASED CARBON FIBER MANUFACTURE Rayon-based carbon fibers are used primarily in cloth for aerospace applications, including phenolic impregnated heat shields and in carbon-carbon composites for missile parts and aircraft brakes. 180 Due to their high carbon content, these fibers remain stable at very high temperatures. A list of U.S. producers of rayon-based carbon fibers is given in Table 6-32. 177 6-105 TABLE 6-32. RAYON-BASED CARBON FIBER MANUFACTURERS Manufacturer Location Amoco Performance Products, Inc. Greenville, SC BP Chemicals (Hitco) Inc. Gardena, CA Fibers and Materials Division Polycarbon, Inc. Valencia, CA Source: Reference 177. 6.10.1 Process Description for the Ravon-Based Carbon Fiber Manufacturing Industry There are three steps in the production process of rayon-based carbon cloth: • Preparation and heat treating; • Carbonization; and • High heat treatment (optional). 180 In the preparation and heat treating step, the rayon-based cloth is heated at 390 to 660°F (200 to 350°C). Water is driven off (50 to 60 percent weight loss) during this step to form a char with thermal stability. In the carbonization step, the cloth is heated to 1,800 to 3,600°F (1,000 to 2,000°C), where additional weight is lost and the beginnings of a carbon layer structure is formed. To produce a high strength rayon-based fiber, a third step is needed. The cloth is stretched and heat treated at temperatures near 5,400°F (3,000°C). 180 6-106 6 . 10.2 Benzene Emissions from the Ravon-Based Carbon Fiber Manufacturing Industry Benzene emissions occur from the exhaust stack of the carbon fabric dryer, which is used in carbonization of the heat treated rayon. 180 An emission factor for this source is given in Table 6-33. 181 6.10.3 Controls and Regulatory Analysis No controls or regulations were identified for the rayon-based carbon fiber manufacturing industry. 6.11 ALUMINUM CASTING The aluminum casting industry produces aluminum products, such as aluminum pans for marine outboard motors, from cast molds. Sections 6.11.1 through 6.12.3 describe the aluminum casting process, benzene emissions resulting from this process, and air emission control devices utilized in the process to reduce benzene emissions. The number of aluminum casting facilities in the United States was not identified. 6.11.1 Process Description for Aluminum Casting Facilities A common method for making the mold for aluminum motor parts is to utilize polystyrene foam patterns or “positives” of the desired metal part. The basic principle of the casting operation involves the replacement of the polystyrene pattern held within a sand mold with molten metal to form the metal casting. Figure 6-11 presents a simplified flow diagram for a typical aluminum casting facility utilizing polystyrene patterns. 6-107 TABLE 6-33. EMISSION FACTOR FOR RAYON-BASED CARBON MANUFACTURE o P3 u. ooi 3 o ’c/5 Oh (A £ w o 3 "“i Uh ^ 3 ^ o c7 £ C/3- £=2 w CQ T O X r- o X r- OJ CJ ’> E 3 Z u u C/2 OC 4 / o — 3 o 00 o ,re c .2 c/3 g LU 6-108 Polystyrene Pattern Molten Storage Aluminum dia-»f-/vnd-9zoofre j Cl m J • o O o O A » 1c *G C3 u< c U a TJ E ® ^- ° 3 2 O CL ©'— l >* 1 E ? . = St < X c £ o ** « c « c E o ® n © « C 3 C 2 3 £ o 2 S •D « |S «• _ 5 5 O C o © © o D * C6 O z: o ° © « t: is E S E -5 02 Q c o U 02 02 I— 3 o c/5 Li.' 02 CO 02 Q 02 .£2 E 3 z u u m x ^r m ro x oo © c Z 1 E 3 • c co .2 co £ V 3 S < X CO r- CO X r- TT ON On © i CO X on -'T CO O X s NO c oo to = 5 # c *o ■o CO k- c C3 i & o u. w fr* o 3 C 02 v> u CO Q < o CO U. 03 < —*. CO •C To u. CO 73 to CD e :j C 5 ZJ c £ c/5 o > CJ o > CO u X TT r~ C4 X 00 NO w *3 l— "O ZJ 02 OJ 02 a—. _c ~o o ”5 ka ha c ha a c c c c o o 02 02 02 c c >* c D D 73 D s 3 Ja . E 03 £ oJ «5 3 .£ S < £ Ct er >> ha •o >> ha 03 03 U re re ■o •o IZx 73 73 c c (/} C c o o c n o o 02 02 co 02 02 02 02 02 02 c/5 in U C/5 m 3 ■ CO CONTROL DEVICE 6-119 940170-FLW la-FTTP reaction. Oxidizing the asphalt has the effect of raising its softening temperature, reducing penetration, and modifying other characteristics. Inorganic salts such as ferric chloride (FeCl 3 ) may be used as catalysts added to the asphalt flux during air blowing to better facilitate these transformations. 185 The time required for air blowing of asphalt depends on a number of factors including the characteristics of the asphalt flux, the characteristics desired for the finished product, the reaction temperature, the type of still used, the air injection rate, and the efficiency with which the air entering the still is dispersed throughout the asphalt. Blowing times may vary in duration from 30 minutes to 12 hours, with typical times from 1 to 4.5 hours. 185 - 186 Asphalt blowing is a highly temperature-dependent process because the rate of oxidation increases rapidly with increases in temperature. Asphalt is preheated to 400 to 470°F (204 to 2i?°C) before blowing is initiated to ensure that the oxidation process will start an acceptable rate. Conversion does take place at lower temperatures but is much slower. Because of the exothermic nature of the reaction, the asphalt temperature rises as blowing proceeds. This, in turn, further increases the reaction rate. Asphalt temperature is normally kept at about 500 °F (260 °C) during blowing by spraying water onto the surface of the asphalt, although external cooling may also be used to remove the heat of reaction. The allowable upper limit to the reaction temperature is dictated by safety considerations, with the maximum temperature of the asphalt usually kept at least 50°F (28°C) below the flash point of the asphalt being blown. 186 The design and location of the sparger in the blowing still governs how much of the asphalt surface area is physically contacted by the injected air, and the vertical height of the still determines the time span of this contact. Vertical stills, because of their greater head (asphalt height), require less air flow for the same amount of asphalt-air contact. Both vertical and horizontal stills are used for asphalt blowing, but in new construction, the vertical type is preferred by the industry because of the increased asphalt-air contact and consequent reduction 6-120 in blowing times. 186 Also, asphalt losses from vertical stills are reported to be less than those from horizontal stills. All recent blowing still installations have been of the vertical type. Asphalt blowing can be either a batch process or a continuous operation; however, the majority of facilities use a batch process. Asphalt flux is sometimes blown by the oil refiner or asphalt processor to meet the roofing manufacturer's specifications. Many roofmg manufacturers, however, purchase the flux and carry out their own blowing. Blown asphalt (saturant and coating asphalt) is used to produce asphalt felt and coated asphalt roofmg and siding products in the processes depicted in Figures 6-13 and 6-14. 185 The processes are identical up to the point where the material is to be coated. A roll of felt is installed on the felt reel and unwound onto a dry floating looper. The dry floating looper provides a reservoir of felt material to match the intermittent operation of the felt roller to the continuous operation of the line. Felt is unwound from the roll at a faster rate than is reoui r ed hv the line with the excess being stored in the drv looper. The flow of felt to the line A » w v 1 and the tension on the material is kept constant by raising the top set of rollers and increasing looper capacity. The opposite action occurs when a new roll is being put on the felt reel and spliced in, and the felt supply ceases temporarily. There are no benzene emissions generated in this processing step. 186 Following the dry looper, the felt enters the saturator, where moisture is driven out and the felt fibers and intervening spaces are filled with saturant asphalt. (If a fiberglass mat web is used instead of felt, the saturation step and the subsequent drying-in process are bypassed.) The saturator also contains a looper arrangement, which is almost totally submerged in a tank of asphalt maintained at a temperature of 450 to 500 °F (232 to 260 °C). The absorbed asphalt increases the sheet or web weight by about 150 percent. At some plants, the felt is sprayed on one side with asphalt to drive out the moisture prior to dipping. This approach reportedly results in higher benzene emissions than does use of the dip process alone. 186 The saturator is a significant benzene emissions source within the asphalt roofing process. 6-121 VENT TO CONTROL Source: Reference 185. 6-122 940171-FLW-ja-RTP Figure 6-14. Organic Shingle and Roll Manufacturing Process Flow Diagram Source: Reference 185. 6-123 940122-FLW-ja-RTP The saturated felt then passes through drying-in drums and onto the wet looper, sometimes called the hot looper. The drying-in drums press surface saturant into the felt. Depending on the required final product, additional saturant may also be added at this point. The amount of absorption depends on the viscosity of the asphalt and the length of time the asphalt remains fluid. The wet looper increases absorption by providing time for the saturant asphalt to penetrate the felt. The wet looper operation has been shown to be a significant source of organic particulate emissions within the asphalt roofing process; however, the portion that is benzene has not been defined. 186,187 If saturated felt is being produced, the sheet passes directly to the cool-down section. For surfaced roofmg products, however, the saturated felt is carried to the coater station, where a stabilized asphalt coating is applied to both the top and bottom surfaces. Stabilized coating contains a mineral stabilizer and a harder, more viscous coating asphalt that has a higher softening point than saturant asphalt. The coating asphalt and mineral stabilizer are mixed in approximately equal proportions. The mineral stabilizer may consist of finely divided lime, silica, slate dust, dolomite, or other mineral materials. The weight of the fmished product is controlled by the amount of coating used. The coater rollers can be moved closer together to reduce the amount of coating applied to the felt, or separated to increase it. Many modem plants are equipped with automatic scales that weigh the sheets in the process of manufacture and warn the coater operator when the product is running under or over specifications. The coater is a significant emissions source within the roofmg production process. It releases asphalt fumes containing organics, some of which may be benzene compounds. 186,187 The function of the coater-mixer is to mix coating asphalt and a mineral stabilizer in approximately equal proportions. The stabilized asphalt is then piped to the coating pan. The asphalt is piped in at about 450 to 500°F (232 to 260°C), and the mineral stabilizer is delivered by screw conveyor. There is often a preheater immediately ahead of the 6-124 coater-mixer to dry and preheat the material before it is fed into the coater-mixer. This eliminates moisture problems and also helps to maintain the temperature above 320 °F (160°C) in the coater-mixer. The coater-mixer is usually covered or enclosed, with an exhaust pipe for the air displaced by (or carried with) the incoming materials: The coater-mixer is viewed as a potential source of benzene emissions, but not a significant one. 186,187 The next step in the production of coated roofing products is the application of mineral surfacing. The surfacing section of the roofing line usually consists of a multi-compartmented granule hopper, two parting agent hoppers, and two large press rollers. The hoppers are fed through flexible hoses from one or more machine bins above the line. These machine bins provide temporary storage and are sometimes called surge bins. The granule hopper drops colored granules from its various compartments onto the top surface of the moving sheet of coated felt in the sequence necessary to produce the desired color pattern on the roofing. This step is not required for smooth-surfaced products. 186 Parting agents such as talc and sand (or some combination thereof) are applied to the top and back surfaces of the coated sheet from parting agent hoppers. These hoppers are usually of an open-top, slot-type design, slightly longer than the coated sheet is wide, with a screw arrangement for distributing the parting agent uniformly throughout its length. The first hopper is positioned between the granule hopper and the first large press roller, and 8 to 12 inches (0.2 to 0.3 m) above the sheet. It drops a generous amount of parting agent onto the top surface of the coated sheet and slightly over each edge. Collectors are often placed at the edges of the sheet to pick up this overspray, which is then recycled to the parting agent machine bin by open screw conveyor and bucket elevator. The second parting agent hopper is located between the rollers and dusts the back side of the coated sheet. Because of the steep angle of the sheet at this point, the average fall distance from the hopper to the sheet is usually somewhat greater than on the top side, and more of the material falls off the sheet. 186 In a second technique used to apply backing agent to the back side of a coated sheet, a hinged trough holds the backing material against the coated sheet and only material 6-125 that will adhere to the sheet is picked up. When the roofing line is not operating, the trough is tipped back so that no parting agent will escape past its lower lip. Immediately after application of the surfacing material, the sheet passes through the cool-down section. Here the sheet is cooled rapidly by passing it around water-cooled rollers in an abbreviated looper arrangement. Usually, water is also sprayed on the surfaces of the sheet to speed the cooling process. The cool-down section is not a source of benzene emissions. Following cooling, self-sealing coated sheets usually have an asphalt seal-down strip applied. The strip is applied by a roller, which is partially submerged in a pan of hot sealant asphalt. The pan is typically covered to minimize fugitive emissions. No seal-down strip is applied to standard shingle or roll-goods products. Some products are also texturized at this point by passing the sheet over an embossing roll that imparts a pattern to the surface of ,1 _ , _ » -l '186 uic coaicu sneci. The cooling process for both asphalt felt and coated sheets is completed in the next processing station, known as the finish looper. In the finish looper, sheets are allowed to cool and dry gradually. Secondly, the finish looper provides line storage to match the continuous operation of the line to the intermittent operation of the roll winder. It also allows time for quick repairs or adjustments to the shingle cutter and stacker during continuous line operation or, conversely, allows cutting and packaging to continue when the line is down for repair. Usually, this part of the process is enclosed to keep the fmal cooling process from progressing too rapidly. Sometimes, in cold weather, heated air is also used to retard cooling. The finish looper is not viewed as a source of benzene emissions. 186 Following finishing, asphalt felt to be used in roll goods is wound on a mandrel, cut to the proper length, and packaged. When shingles are being made, the material from the finish looper is fed into the shingle-cutting machine. After the shingles have been cut, they are 6-126 moved by roller conveyor to manual or automatic packaging equipment. They are then stacked on pallets and transferred by forklift to storage areas or waiting trucks. 186 6.12.2 Benzene Emissions from Asphalt Roofing Manufacture The primary benzene emission sources associated with asphalt roofing are the asphalt air-blowing stills (and associated oil knockout boxes) and the felt saturators. 186 An emission factor for benzene emissions from the blowing stills or saturators is given in Table 6-36. 189 Additional potential benzene emission sources may include the wet looper, the coater-mixer, the felt coater, the seal-down stripper, and air-blown asphalt storage tanks. Minor fugitive emissions are also possible from asphalt flux and blown asphalt handling and transfer operations. 186 ’ 188,190 Process selection and control of process parameters have been promoted to minimize uncontrolled emissions, including oenzene, rrom asphalt air-blowing stills, asphalt saturators, wet loopers, and coaters. Process controls include the use of: 184 • Dip saturators, rather than spray or spray-dip saturators; • Vertical stills, rather than horizontal stills; • Asphalts that inherently produce low emissions; • Higher-flash-point asphalts; • Reduced temperatures in the asphalt saturant pan; • Reduced asphalt storage temperatures; and • Lower asphalt-blowing temperatures. Dip saturators have been installed for most new asphalt roofing line installations in recent years, and this trend is expected to continue. Recent asphalt blowing still installations have been almost exclusively of the vertical type because of its higher efficiency and lower emissions. Vertical stills occupy less space and require no heating during oxidizing 6-127 w c* z H U i— Z Z < S o z o QC H < oo < cc — u- C3 O H U < U- z o in oo s id m t vO W -) CQ < H t-4 O O 03 n_ oo - c O *S 0* W in s w ^ CO *-* DO _ UU '>v VO — M c ^ w O > 4) Q o 1— e o o t— C o c o D U 4) 4> W» 3 o O C/3 00 C/2 w c o 00 on i— CO O C ~ or . CT3 s 11 uj — a CQ 00 j= c- .2 c 00 > < £ o ■*—» o - ^ 33 C/2 W o in 3 -3 OJ *0 Om a 3 J2 e • 3 DO c £ ,s S OC i; is O 3 4) O W a- o 4 w u - o , 4 > • U x u £ * C^j 00 C 3 i 2 - in " o i m 00 4> o c V- OJ c 2 .8 CO o CT3 c # o ’35 in E w 6-128 (if the temperature of the incoming flux is above 400 °F [204 °C]). Vertical stills are expected to be used in new installations equipped with stills and in most retrofit situations. 186 Asphalt fluxes with lower flash points and softening points tend to have higher emissions of organics because these fluxes generally have been less severely cracked and contain more low-boiling fractions. Many of these light ends can be emitted during blowing. Limiting the minimum softening and flash points of asphalt flux should reduce the amount of benzene-containing fumes generated during blowing because less blowing is required to produce a saturant or coating asphalt. Saturant and coating asphalts with high softening points should reduce benzene emissions from felt saturation and coating operations. However, producing the higher softening point asphalt flux requires more blowing, which increases uncontrolled emissions from the blowing operation . 186 Although these process-oriented emissions control measures are useful, emissions capture equipment and add-on emissions control equipment are also necessary in asphalt roofing material production facilities. The capture of potential benzene emissions from asphalt blowing stills, asphalt storage tanks, asphalt tank truck unloading, and the coater-mixer can and is being achieved in the industry by the use of enclosure systems around the emissions-producing operations. The enclosures are maintained under negative pressure, and the contained emissions are ducted to control devices . 186 Potential emissions from the saturator, wet looper, and coater are generally collected by a single enclosure by a canopy type hood or an enclosure/hood combination. No regulations were identified to control benzene emissions from hot-mix asphalt plants. 6.13 CONSUMER PRODUCTS/BUILDING SUPPLIES This section covers benzene emissions from the application and use of consumer products rather than from the manufacture of such products. Because the types of consumer 6-129 products to which benzene emissions are attributed are so extensive, no list of manufacturers is presented here. Benzene emissions from the use of consumer products and building supplies have been reported in the literature. One indoor air quality data base for organic compounds, shows that indoor benzene levels have been measured in residences, commercial buildings, hospitals, schools, and office buildings. Substantiated sources of these benzene emissions were attributed to tobacco smoke, adhesives (including epoxy resins and latex caulks), spot cleaners, paint removers, particle board, foam insulation, inks, photo film, auto exhaust, and wood stain. 191,192 Although benzene emissions were detected from these consumer sources, no specific benzene emission factors were identified. In addition to these consumer sources, detergents have been identified as another possible source of benzene emissions. 191 In another report, aromatic hydrocarbons (most likely including benzene) were listed as a constituent in certain automotive detailing and cleaning products, including body-cleaning compounds and engine cleaners/degreasers/parts cleaners. However, no specific emission levels were given. 192 Naphtha (CAS number 8030-30-6) is a mixture of a small percentage of benzene, toluene, xylene, and higher homologs derived from coal tar by fractional distillation. Among its applications, naphtha is used as thinner in paints and varnishes and as a solvent in rubber cement. 106 Because naphtha contains a small percentage of benzene, some benzene emissions would be expected from these products. However, no qualifiable benzene emissions from naphtha-containing products were identified. The main control for reducing benzene emissions from consumer products is reformulation, such as substituting water or lower-VOC-emitting alternatives. 192 6-130 The federal government and several states are currently working on regulations for the benzene (or VOC) content of consumer products. Consumer products is a very diverse category and the products are used in a variety of applications. 193 % 6-131 t it* » * SECTION 7.0 EMISSIONS FROM COMBUSTION SOURCES The following stationary point and area combustion source categories have been identified as sources of benzene emissions: medical waste incinerators (MWIs), sewage sludge incinerators (SSIs), hazardous waste incinerators, external combustion sources (e.g., utility boilers, industrial boilers, and residential stoves and furnaces), internal combustion sources, secondary lead smelters, iron and steel foundries, portland cement kilns, hot-mix asphalt plants, and open burning (of biomass, tires, and agricultural plastic). For each combustion source category, the following information is provided in the sections below: (1) a brief characterization of the U.S. population, (2) the process description, (3) benzene emissions characteristics, and (4) control technologies and techniques for reducing benzene emissions. In some cases, the current Federal regulations applicable to the source category are discussed. 7.1 MEDICAL WASTE INCINERATORS MWIs bum wastes produced by hospitals, veterinary facilities, crematories, and medical research facilities. These wastes include both infectious (“red bag” and pathological) medical wastes and non-infectious, general housekeeping wastes. The primary purposes of MWIs are to (1) render the waste innocuous, (2) reduce the volume and mass of the waste, and (3) provide waste-to-energy conversion. The total number and capacity of MWIs in the United States is unknown; however, it is estimated that 90 percent of the 6,872 hospitals (where the majority of MWIs are located) in the nation have some type of on-site incinerator, if only a small unit for incinerating special or pathological waste. 194 The document entitled Locating and Estimating Air Toxic Emissions From Sources of Medical Waste Incinerators , contains a 7-1 more detailed characterization of the MWI industry, including a partial list of the U.S. MWI population. Three main types of incinerators are used for medical waste incineration: controlled-air, excess-air, and rotary kiln. Of the incinerators identified, the majority (> 95 percent) are controlled-air units. A small percentage (<2 percent) are excess-air. Less than 1 percent were identified as rotary kiln. The rotary kiln units tend to be larger, and typically are equipped with air pollution control devices. Approximately 2 percent of the total population identified were found to be equipped with air pollution control devices. 195 7.1.1 Process Description: Medical Waste Incinerators 195 Controlled-Air Incinerators Controlled-air incineration is the most widely used MWI technology and it now dominates the market for new systems at hospitals and similar medical facilities. This technology is also known as starved-air incineration, two-stage incineration, and modular combustion. Figure 7-1 presents a schematic diagram of a typical controlled-air unit. 195 Combustion of waste in controlled-air incinerators occurs in two stages. In the first stage, waste is fed into the primary, or lower, combustion chamber, which is operated with less than the stoichiometric amount of air required for combustion. Combustion air enters the primary chamber from beneath the incinerator hearth (below the burning bed of waste). This air is called primary or underfire air. In the primary (starved-air) chamber, the low air- to-fuel ratio dries and facilitates volatilization of the waste, and most of the residual carbon in the ash bums. At these conditions, combustion gas temperatures are relatively low (1,400 to 1,800°F [760 to 980 °C]). In the second stage, excess air is added to the volatile gases formed in the primary chamber to complete combustion. Secondary chamber temperatures are higher than 7-2 Carbon Dioxide, — Water Vapor and Excess Oxygen and Nitrogen to Atmosphere Main Burner for Minimum Combustion Temperature Volatile Content is Burned in Upper Chamber Excess Air Condition Starved-Air Condition in Lower Chamber Controlled Underfire Air for Burning Down Waste Figure 7-1. Controlled-Air Incinerator Source: Reference 195. 7-3 primary chamber temperatures—typically 1,800 to 2,000°F (980 to 1,095°C). Depending on the heating value and moisture content of the waste, additional heat may be needed. This can be provided by auxiliary burners located at the entrance to the secondary (upper) chamber to maintain desired temperatures. l Waste feed capacities for controlled-air incinerators range from about 75 to 6,500 lb/hour (0.6 to 50 kg/min) (at an assumed fuel heating value of 8,500 Btu/lb [19,700 kJ/kg]). Waste feed and ash removal can be manual or automatic, depending on the unit size and options purchased. Throughput capacities for lower heating value wastes may be higher because feed capacities are limited by primary chamber heat release rates. Heat release rates for controlled-air incinerators typically range from 15,000 to 25,000 Btu/hr-ft 3 (430,000 to 710,000 kJ/hr-m 3 ). Because of the low air addition rates in the primary chamber and corresponding lovv Hue gab velocities (and turbulence), the amount of solids entrained in the gases leaving the primary chamber is low. Therefore, the majority of controlled-air incinerators do not have add-on gas cleaning devices. Excess-Air Incinerators Excess-air incinerators are typically small modular units. They are also referred to as batch incinerators, multiple-chamber incinerators, and “retort” incinerators. Excess-air incinerators are typically a compact cube with a series of internal chambers and baffles. Although they can be operated continuously, they are usually operated in a batch mode. Figure 7-2 presents a schematic for an excess-air unit. 195 Typically, waste is manually fed into the combustion chamber. The charging door is then closed and an afterburner is ignited to bring the secondary chamber to a target temperature (typically 1,600 to 1,800°F [870 to 980°C]). When the target temperature is reached, the primary chamber burner ignites. The waste is dried, ignited, and combusted by heat provided by the primary 7-4 Flame Port Stack Side View Figure 7-2. Excess-Air Incinerator Source: Reference 195. 7-5 ERG Lead 513.cdr chamber burner, as well as by radiant heat from the chamber walls. Moisture and volatile components in the waste are vaporized and pass (along with combustion gases) out of the primary chamber and through a flame port that connects the primary chamber to the secondary or mixing chamber. Secondary air is added through the flame port and is mixed with the volatile components in the secondary chamber. Burners are also installed in the secondary chamber to maintain adequate temperatures for combustion of volatile gases. Gases exiting the secondarv chamber are directed to the incinerator stack or to a control device. When the waste is consumed, the primary burner shuts off. Typically, the afterburner shuts off after a set time. After the chamber cools, ash is manually removed from the primary chamber floor and a new charge of waste can be added. Incinerators designed to bum general hospital waste operate at excess air levels of up to 300 percent. If only pathological wastes are combusted, excess air levels near 100 percent are more common. The lower excess air helps maintain higher chamber temperature when burning high-moisture waste. Waste feed capacities for excess-air incinerators are usually 500 lb/hr (3.8 kg/min) or less. Rotary Kiln Incinerators Rotary kiln incinerators, like the other types, are designed with a primary chamber where the waste is heated and volatilized and a secondary chamber where combustion of the volatile fraction is completed. The primary chamber consists of a slightly inclined, rotating kiln in which waste materials migrate from the feed end to the ash discharge end. The waste throughput rate is controlled by adjusting the rate of kiln rotation and the angle of inclination. Combustion air enters the primary chamber through a port. An auxiliary burner is generally used to start combustion and maintain desired combustion temperatures. Both the primary and secondary chambers are usually lined with acid-resistant refractory brick. Refer to Figure 7-9 of this chapter for a schematic diagram of a typical rotary kiln incinerator. In 7-6 Figure 7-9, the piece of equipment referred to as the “afterburner” is the equivalent of the “secondary chamber” referred to in this section. Volatiles and combustion gases pass from the primary chamber to the secondary chamber. The secondary chamber operates at excess air. Combustion of the volatiles is completed in the secondary chamber. Because of the turbulent motion of the waste in the primary chamber, solids burnout rates and particulate entrainment in the flue gas are higher for rotary kiln incinerators than for other incinerator designs. As a result, rotary kiln incinerators generally have add-on gas cleaning devices. 7.1.2 Benzene Emissions From Medical Waste Incinerators There is limited information currently available on benzene emissions from MWIs. One emission factor for benzene emissions is provided in Table 7-1. 196 This factor represent: benzene emissions during combustion of both general hospital wastes and pathological wastes. 7.1.3 Control Technologies for Medical Waste Incinerators Most control of air emissions of organic compounds is achieved by promoting complete combustion by following good combustion practice (GCP). In general, the conditions of GCP are as follows: 194 Uniform wastefeed; • Adequate supply and good air distribution in the incinerator; Sufficiently high incinerator gas temperatures (> 1,500°F [>815°C]); Good mixing of combustion gas and air in all zones; Minimization of PM entrainment into the flue gas leaving the incinerator; and 7-7 TABLE 7-1 EMISSION FACTOR FOR MEDICAL WASTE INCINERATION e || CS PC i-i G o II O || cs U- o ^ tt WJ £ S n n II o o —H —«— II oc c .X X X o ^ N VO oo C 0\ tT in o • •II is tj* ojl E .c w — 4) O ~a ’> 4> c a m y w- E tf L ) L ) WO c/ 2 9 wo o © (N o wo •o <3 C 4> N C 3 7-8 • Temperature control of the gas entering the air pollution control device to 450 °F (230°C) or less. Failure to achieve complete combustion of organic materials evolved from the waste can result in emissions of a variety of organic compounds. The products of incomplete combustion (PICs) range from low-molecular-weight hydrocarbons (e.g., methane, ethane, or benzene) to high-molecular-weight organic compounds (e.g., dioxins/furans). In general, adequate oxygen, temperature, residence time, and turbulence will minimize emissions of most organics. Control of organics may be partially achieved by using acid gas and PM control devices. To date, most MWIs have operated without add-on air pollution control devices. A small percentage (approximately 2 percent) of MWIs do use air pollution control devices, most frequently wet scrubbers and fabric filters. Fabric filters provide mainly PM control. Other PM control technologies include venturi scrubbers and electrostatic precipitators (ESPs). In addition to wet scrubbing, dry sorbent injection and spray dryer absorbers have also been used for acid gas (i.e., hydrogen chloride [HC1] and sulfur dioxide [S0 2 ]) control. Because it is not documented that acid gas/PM control devices provide reduction in benzene emissions from MWIs, further discussion of these types of control devices is not provided in this section. Locating and Estimating Air Toxic Emissions From Sources of Medical Waste Incinerators , 194 contains a more detailed description of the acid gas/PM air pollution control devices utilized for MWIs, including schematic diagrams. 7.1.4 Re gulatory Analysis Air emissions from MWIs are not currently regulated by Federal standards. However, Section 129 of the CAA requires that standards be established for new and existing MWIs. Standards for MWIs were proposed under Section 129 of the CAA on February 27, 1995 (38 FR 10654). Section 129 requires that the standards include emission limits for HC1, SO : , and CO, among other pollutants. Section 129 also specifies that the standards may require monitoring of surrogate parameters (e.g., flue gas temperature). Thus, 7-9 the standards may require GCP, which would likely result in benzene emissions reduction. Additionally, the standards may require acid gas/PM control device requirements, which may result in some benzene emissions reduction. 7.2 SEWAGE SLUDGE INCINERATORS There are approximately 170 sewage sludge incineration (SSI) plants operating in ihe United Suica. The three main types of SSIs are: multiple-hearth furnaces (MHF). fluidized-bed combustors (FBC), and electric infrared incinerators. Some sludge is co-fired with municipal solid waste in combustors, based on refuse combustion technology. Refuse co-fired with sludge in combustors based on sludge incinerating technology is limited to MHFs only. 197 Over 80 percent of the identified operating sludge incinerators are of the multiple-hearth design. About 15 percent are FBCs and 3 percent are electric infrared incinerators. The remaining combustors co-fire refuse with sludge. Most sludge incinerators are located in the Eastern United States, although there are a significant number on the West Coast. New York has the largest number of facilities, with 33. Pennsylvania and Michigan have the next largest number of facilities, with 21 and 19 sites, respectively. 197,198 Locating and Estimating Air Toxics Emissions for Sewage Sludge Incinerators contains a diagram showing the geographic distribution of the existing population. 198 The three main types of sewage sludge incinerators are described in the following sections. Single hearth cyclone, rotary kiln, wet air oxidation, and co-incineration are also briefly discussed. 7-10 7.2.1 Process Description: Sewage Sludge Incinerators 197 ’ 198 Multiple-Hearth Furnaces A cross-sectional diagram of a typical MHF is shown in Figure 7-3. 198 The basic MHF is a vertically oriented cylinder. The outer shell is constructed of steel, lined with refractory, and surrounds a series of horizontal refractory hearths. A hollow cast-iron rotating shaft runs through the center of the hearths. Cooling air is introduced into the shaft, which extend above the hearths. Attached to the central shaft are the rabble arms, which extend above the hearths. Each rabble arm is equipped with a number of teeth approximately 6 inches in length and spaced about 10 inches apart. The teeth are shaped to rake the sludge in a spiral motion, alternating in direction from the outside in to the inside out, between hearths. Burners are located in the sidewalls of the hearths to provide auxiliary heat. In most MKFs, partially dewatered sludge is fed onto the perimeter of the top hearth. The rabble arms move the sludge through the incinerator by raking the sludge toward the center shaft, where it drops through holes located at the center of the hearth. In the next hearth, the sludge is raked in the opposite direction. This process is repeated in all of the subsequent hearths. The effect of the rabble motion is to break up solid material to allow bener surface contact with heat and oxygen. A sludge depth of about 1 inch is maintained in each hearth at the design sludge flow rate. Scum may also be fed to one or more hearths of the incinerator. Scum is the material that floats on wastewater. It is generally composed of vegetable and mineral oils, grease, hair, waxes, fats, and other materials that will float. Scum may be removed from many treatment units, including pre-aeration tanks, skimming tanks, and sedimentation tanks. Quantities of scum are generally small compared to those of other wastewater solids. Ambient air is first ducted through the central shaft and its associated rabble arms. A portion or all of this air is then taken from the top of the shaft and recirculated into 7-11 COOLING AIR DISCHARGE SCUM AUXILIARY AIR PORTS RABBLE ARM 2 OR 4 PER HEARTH BURNERS SUPPLEMENTAL FUEL COMBUSTION AIR SHAFT COOLING AIR RETURN SOLIDS FLOW DROP HOLES Figure 7-3. Cross Section of a Multiple Hearth Furnace Source: Reference 198. 7-12 940300-kl-DRTP the lower-most hearth as preheated combustion air. Shaft cooling air that is not circulated back into the furnace is ducted into the stack downstream of the air pollution control devices. The combustion air flows upward through the drop holes in the hearths, countercurrent to the flow of the sludge, before being exhausted from the top hearth. Air enters the bottom to cool the ash. Provisions are usually made to inject ambient air directly into the middle hearths as well. i Overall, an MHF can be divided into three zones. The upper hearth comprises the drying znnp where most of the moisture in the sludge is evaporated. The temperature in the drying zone is typically between 800 and 1,400°F (425 and 760°C). Sludge combustion occurs in the middle hearth (second zone) as the temperature is increased to 1,100 to 1,700°F (600 to 930°C). The combustion zone can be further subdivided into the upper-middle hearth, where the volatile gases and solids are burned, and the lower-middle hearth, where most of the fixed carbon is combusted. The third zone, made up of the lower-most hearth, is the cooling zone. In this zone, the ash is cooled as its heat is transferred to the incoming combustion air. Under normal operating conditions. 50 to 100 percent excess air must be added to an MHF in order to ensure complete combustion of the sludge. Besides enhancing contact between fuel and oxygen in the furnace, these relatively high rates of excess air are necessary to compensate for normal variations in both the organic characteristics of the sludge feed and the rate at which it enters the incinerator. When the supply of excess air is inadequate, only partial oxidation of the carbon will occur, with a resultant increase in emissions of CO, soot, and hydrocarbons. Too much excess air, on the other hand, can cause increased entrainment of paniculate and unnecessarily high auxiliary fuel consumption. Fluidized-Bed Combustors Figure 7-4 shows a cross-sectional diagram of an FBC. 198 FBCs consist of a vertically oriented outer shell constructed of steel and lined with refractory. Tuyeres (nozzles designed to deliver blasts of air) are located at the base of the furnace within a refractory-lined grid. A bed of sand, approximately 2.5 feet (0.75 meters) thick, rests upon the grid. Two 7-13 ■ Exhaust and Ash Figure 7-4. Cross Section of a Fluidized Bed Furnace Source: Reference 198. 7-14 general configurations can be distinguished on the basis of how the fluidizing air is injected into the furnace. In the “hot windbox” design, the combustion air is first preheated by passing through a heat exchanger, where heat is recovered from the hot flue gases. Alternatively, ambient air can be injected directly into the furnace from a cold windbox. Partially dewatered sludge is fed into the lower portion of the furnace. Air injected through the tuyeres at a pressure of 3 to 5 pounds per square inch gauge (20 to 35 kilopascals), simultaneously fluidizes the bed of hot sand and the incoming sludge. Temperatures of 1,400 to 1,700°F (750 to 925°C) are maintained in the bed. As the sludge bums, fine ash particles are carried out the top of the furnace. Some sand is also removed in the air stream and must be replaced at regular intervals. Combustion of the sludge occurs in two zones. Within the sand bed itself (the fust zone), evaporation of the water and pyrolysis of the organic materials occur nearly simultaneously as the temperature of the sludge is rapidly raised In the freeboard area (the second zone), the remaining free carbon and combustible gases are burned. The second zone functions essentially as an afterburner. Fluidization achieves nearly ideal mixing between the sludge and the combustion air, and the turbulence facilitates the transfer of heat from the hot sand to the sludge. The most noticeable impact of the better burning atmosphere provided by an FBC is seen in the limited amount of excess air required for complete combustion of the sludge. Typically, FBCs can achieve complete combustion with 20 to 50 percent excess air, about half the excess air required by MHFs. As a consequence, FBCs generally have lower fuel requirements compared to MHFs. Electric Infrared Incinerators Electric infrared incinerators consist of a horizontally oriented, insulated furnace. A woven wire belt conveyor extends the length of the furnace and infrared heating 7-15 elements are located in the roof above the conveyor belt. Combustion air is preheated by the flue gases and is injected into the discharge end of the furnace. Electric infrared incinerators consist of a number of prefabricated modules that can be linked together to provide the necessary furnace length. A cross-section of an electric furnace is shown in Figure 7-5. 198 The dewatered sludge cake is conveyed into one end of the incinerator. An internal roller mechanism levels the sludge into a continuous layer approximately 1 inch thick across the width of the belt. The sludge is sequentially dried and then burned as it moves beneath the infrared heating elements. Ash is discharged into a hopper at the opposite end of the furnace. The preheated combustion air enters the furnace above the ash hopper and is further heated by the outgoing ash. The direction of air flow is countercurrent to the movement of the sludge along the conveyor. Exhaust gases leave the furnace at the feed end. Excess air rates vary from 20 to 70 percent. Other Technologies A number of other technologies have been used for incineration of sewage sludge, including cyclonic reactors, rotary kilns, and wet oxidation reactors. These processes are not in widespread use in the United States and are discussed only briefly. The cyclonic reactor is designed for small-capacity applications and consists of a vertical cylindrical chamber that is lined with refractory. Preheated combustion air is introduced into the chamber tangentially at high velocities. The sludge is sprayed radially toward the hot refractory walls. Combustion is rapid, such that the residence time of the sludge in the chamber is on the order of 10 seconds. The ash is removed with the flue gases. Rotary kilns are also generally used for small capacity applications. The kiln is inclined slightly from the horizontal plane, with the upper end receiving both the sludge feed and the combustion air. A burner is located at the lower end of the kiln. The circumference of 7-16 dJLaa-NT-61.20*6 1 oo On o c a> •4—1 U a: it u u. 3 o C/0 7-17 "igure 7-5. Cross Section of an I Electric Infrared Furnace the kiln rotates at a speed of about 6 inches per second. Ash is deposited into a hopper located below the burner. The wet oxidation process is not strictly one of incineration; it instead utilizes oxidation at elevated temperature and pressure in the presence of water (flameless combustion). Thickened sludge, at about 6-percent solids, is first ground and mixed with a stoichiometric amount of compressed air. The sludge/air mixture is then circulated through a series of heat exchangers before entering a pressurized reactor. The temperature of the reactor is held between 350 and 600°F (175 and 315°C). The pressure is normally 1,000 to 1,800 pounds per square inch grade (7,000 to 12,500 kilopascals). Steam is usually used for auxiliary heat. The water and resulting ash are circulated out the reactor and are separated in a tank or lagoon. The liquid phase is recycled to the treatment plant. Off-gases must be treated to eliminate odors. Co-Incineration and Co-Firing Wastewater treatment plant sludge generally has a high water content and, in some cases, fairly high levels of inert materials. As a result, the net fuel value of sludge is often low. If sludge is combined with other combustible materials in a co-incineration scheme, a furnace feed can be created that has both a low water concentration and a heat value high enough to sustain combustion with little or no supplemental fuel. Virtually any material that can be burned can be combined with sludge in a co-incineration process. Common materials for co-incineration are coal, municipal solid waste (MSW), wood waste, and agricultural waste. There are two basic approaches to combusting sludge with MSW: (1) use of MSW combustion technology by adding dewatered or dried sludge to the MSW combustion unit, and (2) use of sludge combustion technology by adding processed MSW as a supplemental fuel to the sludge furnace. With the latter, MSW is processed by removing noncombustibles, shredding, air classifying, and screening. Waste that is more finely 7-18 processed is less likely to cause problems such as severe erosion of the hearths, poor temperature control, and refractory failures. 7,2.2 Benzene Emissions from Sewage Sludge Incineration Emission factors associated with MHFs and FBCs are provided in Table 7-2. 197 This table provides a comparison of benzene emissions based on no control and control with various PM control devices and an afterburner. However, these emission factors do not reflect the effect of increased operating temperature on reducing benzene emissions. As discussed in Section 7.2.3, increasing the combustion temperature facilitates more complete combustion of organics, resulting in lower benzene emissions. It was not possible in this study to compare the combustor operating conditions of all SSIs for which emissions test data were available to develop the emission factors in Table 7-2. 197 As a result, it was not possible to reflect the effect of combustion temperature on benzene emissions. The emission factors for MHFs •» • nr i — ill 1 UUiw / “— cAa arc based on test data of combustors operated at a variety of combustion temperatures in the primary combustion hearths (1,100 to 1,700°F [600 to 930°C]). Using emissions test data for one sewage sludge combustion facility, it was possible to demonstrate the benzene emission reduction achieved with the practice of increasing operating temperature versus utilizing an afterburner or a scrubber. This comparison is provided m Table 7-3. 199 The emissions test data for the one facility used to develop the emission factors presented in Table 7-3 are also averaged into the emission factors presented in Table 7-2. 7.2.3 Control Technologies for Sewage Sludge Incinerators 197 - 198 Control of benzene emissions from SSIs is achieved primarily by promoting complete combustion by following GCP. The general conditions of GCP are summarized in Section 7.1.3. As with MWIs, failure to achieve complete combustion of organic materials evolved from the waste can result in emissions of a variety of organic compounds, including 7-19 TABLE 7-2. SUMMARY OF EMISSION FACTORS FOR SEWAGE SLUDGE NCINERATION 60 c 1 v- O <—> o cd U- UJ w w o cd U- on C/7 e UJ 60 'Shi c o X r4 oo »n u Q c o U 4) o l— 3 o oo c # o cn c/5 w u u oo *o < x X X k o *n oo w co rf rn ni rn w 3 c > U C/5 U. > G 0) 3 0/ g> 2 C A) a X) &-e - c. o i— on 3 c C u £ -o « S h M =d ^ c M £ 'E. fc £ s x -e X a> •c 2 « 3 O * X on C 4/ > o o o o Tf oi G £ 4/ 60 C '£- G 3 c 4/ > on i~> 4/ X X O C/5 u CQ [X X I «n i © I «n r-~ Ov 4> C 4> u- ,4> o— 4> 02 4> CJ I— 3 $ "O 4> , e3 CO t- O o O—i C O '55 cn E UJ 7-20 MHF = multiple hearth furnace. FBC = fluidized bed combustor. TABLE 7-3. SUMMARY OF EMISSION FACTORS I OR ONE SEWAGE SLUDGE INCINERATION FACILITY UTILIZING A MULTIPLE HEARTH FURNACE V- DC o C o '-5 re 03 U- C* u c c D o 2 £ ex W c o O X D § "d o ‘> Q c 0 c © D u • - 3 E ° W ^ u u 00 m OX m oo D x. X 2 o 00 ta»> G d E d OX) c ‘Eu E C OJ > u D l- 3 03 t~ D ex E d H 00 c re u D c. o •o D —< re > d W d G i— 3 X t~ 0) < "d i— 3 re i-i D ex E — W oo ON l— o OX) £ «N o -ta s —^ Tf o m q X 3 .£ re O- t- c 3 CX ^ E *1 d 5 H * c 2 'X c re d i- o>. d c ex O u C/3 73 3 I ^ CO U- > X) D £Z — N- Q W < 00 iD X X 3 ON On t> c s £ a; cc a u X 3 $ 7-21 benzene, and adequate oxygen, temperature, residence time, and turbulence will generally minimiz e emissions of most organics. Many SSIs have greater variability in their organic emissions than do other waste incinerators because, on average, sewage sludge has a high moisture content and the moisture content can vary widely during operation. 200 Additional reductions in benzene emissions may be achieved by utilizing PM control devices; however, it is not always the case that a PM control device will reduce benzene emissions. In some cases, the incinerator operating conditions (e.g., combustion temperature and temperature at the air pollution control device) may affect the performance of scrubbers. 199 The types of existing SSI PM controls range from low-pressure-drop spray towers and wet cyclones to higher-pressure-drop venturi scrubbers and venturi/impingement tray scrubber combinations. A few ESPs and baghouses are employed, primarily where sludge is co-iired wiui MSW. The most widely used PM control device applied to an MHF is the impingement tray scrubber. Older units use the tray scrubber alone and combination venturi/impingement tray scrubbers are widely applied to newer MHFs and some FBCs. Most electric incinerators and some FBCs use venturi scrubbers only. As indicated in Table 7-3, venturi/impingement tray scrubbers have been demonstrated to reduce benzene emissions from SSIs. A schematic diagram of a typical combination venturi/impingement tray scrubber is presented in Figure 7-6. 198 Hot gas exits the incinerator and enters the precooling or quench section of the scrubber. Spray nozzles in the quench section cool the incoming gas, and the quenched gas then enters the venturi section of the control device. Venturi water is usually pumped into an inlet weir above the quencher. The venturi water enters the scrubber above the throat, completely flooding the throat. Turbulence created by high gas velocity in the converging throat section deflects some of the water 7-22 Gas Exit to Induced Draft Fan and Stack □ Figure 7-6. Venturi/Impingement Tray Scrubber 0 . *- oc □ z o Source: Reference 198. 7-23 traveling down the throat into the gas stream. PM carried along with the gas stream impacts on these water particles and on the water wall. As the scrubber water and flue gas leave the venturi section, they pass into the flooded elbow, where the stream velocity decreases, allowing the water and gas to separate. By restricting the throat area within the venturi, the linear gas velocity is increased and the pressure drop is subsequently increased, increasing PM removal efficiency. At the base of the flooded elbow, the gas stream passes through a connecting duct to the base of the impingement tray tower. Gas velocity is further reduced upon entry to the tower as the gas stream passes upward through the perforated impingement trays. Water usually enters the trays from inlet ports on opposite sides and flows across the tray. As gas passes through each perforation in the tray, it creates a jet that bubbles up the water and further entrains solid particles. At the top of the tower is a mist eliminator to reduce the carryover of water droplets in the stack effluent gas. The impingement section can contain from one to four trays. In the case of MHFs, afterburners may be utilized to achieve additional reduction of organic emissions, including benzene. MHFs produce more benzene emissions because they are designed with countercurrent air flow. Because sludge is usually fed into the top of the furnace, hot air and wet sludge feed are contacted at the top of the furnace, such that any compounds distilled from the solids are immediately vented from the furnace at temperatures too low to completely destroy them. Utilization of an afterburner provides a second opportunity for these unbumed hydrocarbons to be fully combusted. In afterburning, furnace exhaust gases are ducted to a chamber, where they are mixed with supplemental fuel and air and completely combusted. Additionally, some incinerators have the flexibility to allow sludge to be fed to a lower hearth, thus allowing the upper hearth(s) to function essentially as an afterburner. 7-24 7.2.4 Regulatory Analysis Prior to 1993, organic emissions from SSIs were not regulated. On February 19, 1993, Part 503 was added to Subchapter O in Chapter I of Title 40 of the CFR, establishing standards for use or disposal of sewage sludge. Subpart E of Part 503 regulates emissions of total hydrocarbons (THC) from the incineration of SSIs and applies to all SSIs. The THC limit of 100 ppm (measured as a monthly average) is a surrogate for all organic compounds, including benzene. In establishing a standard for organic emissions, EPA had considered establishing a standard for 14 individual organic compounds, including benzene; however, it was concluded that the individual organic pollutants were not significant enough a factor in sewage sludge to warrant requiring individual pollutant limits. Furthermore, based on a long-term demonstration of heated flame ionization detection systems monitoring organic emissions from SSIs, it was concluded that there is an excellent correlation between THC emission levels and organic pollutant emission levels. The THC limit established in Part 503 is an operational standard that would, in general, not require the addition of control devices to existing incinerators, but would require incinerators to adopt good operating practices on a continuous basis. It is expected that FBCs and MHFs will have no difficulty meeting the standard. 200 To ensure the adoption of GCP, the standard requires continuous THC monitoring using a flame ionization detection system, continuous monitoring of the moisture content in the exit gas, and continuous monitoring of combustion temperature. 7.3 HAZARDOUS WASTE INCINERATION Hazardous waste is produced in the form of liquids (e.g., waste oils, halogenated and nonhalogenated solvents, other organic liquids, and pesticides/ herbicides) and sludges and solids (e.g., halogenated and nonhalogenated sludges and solids, dye and paint sludges, resins, and latex). Based on a 1986 study, total annual hazardous waste generation in the United States was approximately 292 million tons (265 million metric tons). 201 Only a 7-25 small fraction of the waste (< 1 percent) was incinerated. The major types of hazardous waste streams incinerated were spent nonhalogenated solvents and corrosive and reactive wastes contaminated with organics. Together, these accounted for 44 percent of the waste incinerated. Other prominent wastes included hydrocyanic acid, acrylonitrile bottoms, and nonlisted ignitable wastes. Hazardous waste can be thermally destroyed through burning under oxidative conditions in incineration systems designed specifically for this purpose and in various types of industrial kilns, boilers, and furnaces. The primary purpose of a hazardous waste incinerator is the destruction of the waste; some systems include energy recovery devices. An estimated 1.9 million tons (1.7 million Mg) of hazardous waste were disposed of in incinerators in 1981. 201 The primary purpose of industrial kilns, boilers, or furnaces is to produce a commercially viable product such as cement, lime, or steam. An estimated 230 million gallons of waste fuel and waste oil were treated at industrial kilns, boilers, and furnaces in 1983. 201 In 1981. it was estimated that industrial kilns, boilers, and furnaces disposed of more than twice the amount of waste that was disposed of via incinerators. 201 7.3.1 Process Description: Incineration Incineration is a process that employs thermal decomposition via thermal oxidation at high temperatures (usually 1,650°F [900°C] or greater) to destroy the organic fraction of the waste and reduce volume. A study conducted in 1986 identified 221 hazardous waste incinerators operating under the Resource Conservation and Recovery Act (RCRA) system in the United States. (See Section 7.3.5 for a discussion of this and other regulations applicable to hazardous waste incineration.) These incinerators are located at 189 separate facilities, 171 of which are located at the site of waste generation. 201 A diagram of the typical process component options in a hazardous waste incineration facility is provided in Figure 7-7. 201 The diagram shows that the major subsystems that may be incorporated into the hazardous waste incineration system are (1) waste 7-26 Waste Preparation Combustion Air Pollution Control c __ TQ C ® c W cn cd x ® _ 15 > 3 O « E ■c ® 5 Q - 2 „ E? 3 o ® £ OCCL c. ® _ ro It If ^3 E 3 ® ® JZ ZO 1 ! i E 05 O c i i >* JZ ® o > E — o ~= C w to o -£055 1 E c ® co o O O 3 ® ® _ ox cr o o ~jir c i ▼ — o _ -o ■-3 £ ® u rt m ® — co 1X1 ‘F'V ® "O — ■“ X ® "O C^-n •— '5 jS ® 12 ombustion hamber(s) ▼ .. Ash Disposal CTO X 3 _ l_l DC Ll Ll i °° 1 O CL C c_-2 ® iss'i to E = 3 ? ® -Q o ® -c iS ® Q O CO CO 05 05 cn.c _c c*E-o g ■o ® -O ~ E 2 ® to _® (J £ ® co co cox i > 3 o CO 7-27 Figure 7-7. General Orientation of Hazardous Waste Incineration Subsystems and Typical Component Options preparation and feeding, (2) combustion chamber(s), (3) air pollution control, and (4) residue/ash handling. These subsystems are discussed in this section, except that air pollution control devices are discussed in Section 7.3.4 of this section. Additionally, energy-recovery equipment may be installed as part of the hazardous waste incineration system, provided that the incinerator is large enough to make energy recovery economically productive (i.e., bigger than about 7 million Btu/hour [7.4 million kJ/hourl) and that corrosive constituents (e.g., HC1) and adhesive particulates are not present at levels that would damage the equipment. 202 Additionally, a few other technologies have been used for incineration of hazardous waste, including ocean incineration vessels and mobile incinerators. These processes are not in widespread use in the United States and are discussed only briefly. Waste Preparation and Feeding^* The feed method is determined by the physical form of the hazardous waste. Waste liquids are blended and then pumped into the combustion chamber through nozzles or via atomizing burners. Liquid wastes containing suspended panicles may need to be screened to avoid clogging of small nozzle or atomizer openings. Liquid wastes may also be blended in order to control the heat content of the liquid to achieve sustained combustion (typically to 8,000 Btu/lb [18,603 kJ/kg]) and to control the chlorine (CL) content of the waste fed to the incinerator (typically to 30 percent or less) to limit the potential for formation of hazardous-free Cl 2 gas in the combustion gas. Waste sludges are typically fed to the combustion chamber using progressive cavity pumps and water-cooled lances. Bulk solid wastes may be shredded to control particle size and may be fed to the combustion chamber via rams, gravity feed, air lock feeders, vibratory or screw feeders, or belt feeders. 7-28 Combustion Chambers 201,202 today: 202 The following five types of combustion chambers are available and operating • Liquid injection; • Rotary kiln; • Fixed-hearth: • Fluidized-bed; and • Fume. These five types of combustion chambers are discussed below. Liquid iniection --Liquid injection combustion chambers are applicable almost exclusively for pumpable liquid waste, including some low-viscosity sludges and slurries. The typical capacity of liquid injection units is about 8 to 28 million Btu/hour (8.4 to 29.5 million kJ/hr). Figure 7-8 presents a typical schematic diagram of a liquid-injection unit. 201 Liquid injection units are usually simple, refractory-lined cylinders (either horizontally or vertically aligned) equipped with one or more waste burners. Vertically aligned units are preferred when wastes are high in organic salts and fusable ash content; horizontal units may be used with low-ash waste. Liquid wastes are injected through the bumer(s), atomized to fme droplets, and burned in suspension. Burners and separate waste injection nozzles may be oriented for axial, radial, or tangential firing. Good atomization, using gas-fluid nozzles with high-pressure air or steam or with mechanical (hydraulic) means, is necessary to achieve high liquid waste destruction efficiency. Rotary Kiln --Rotarv kiln incinerators are applicable to the destruction of solid wastes, slurries, containerized waste, and liquids. Because of their versatility, they are most 7-29 Dischar ■Sp'ZSC* W0d~9U3 o >/■> w «? ^ o © O © (I* a— L a— < QJD C .X X x x x o ^ vo m cn vO ‘35 c vo m CN on o • • * • Tf o ’> x> *o — (U •a La La c o "2 r3 OJ La u i— O o 1— 3 c CJ C O c c r— in • c c c _o .2 .2' or u o C/! 2. 2- r - <*—■ c; ‘ £ .= • — *o ^2 '5 '2 zr cr *P P © o i iA m o o o o 1 c. J rn m c. J 9 o i 1 o in m T3 c/3 O ^ 5 a c3 o O 5J SJ X) c II co C T3 .2 8 a .2 3J C =T •a .-2 5 3 co o“ ZJ *o OJ 3 c5 u. Lai U ZJ C6 u_ c CL 2 o . •a u. X) * u* 3 CO u. O » P c D CO r3 2 0/ "d ** p /*v u. in c O D ZJ or ZJ CaT DX) C P X > JJ | 'e w — 2 1 is if S .S c ° Cl. J, L> CJ •CJ •■= OX) ^ 2 .g .e - '2 co S CO w CO TO X U. h £ u > _c CT 3 OJ 2 2 X La o. *o t» 2 La To L- V C C/3 La i 2 u co C/3 c CO < u c 2 V aj V £ X r- U ■o u 7-38 7.3.5 Regulatory Analysis Organic emissions from hazardous waste incinerators are regulated under 40 CFR 246, Subpart O, promulgated on June 24, 1982. 204 The standards require that in order for a hazardous waste incineration facility to receive a RCRA permit, it must attain a 99.99 percent destruction and removal efficiency (DRE) for each principal organic hazardous constituent (POHC) in the waste feed. Each facility must determine which one or more organic compounds, from a list of approximately 400 organic and inorganic hazardous chemicals (including benzene) in Appendix VIII of 40 CFR 261, 205 are POHCs, based on which are the most difficult to incinerate, considering their concentration or mass in the waste feed. Each facility must then conduct trial bums to determine the specific operating conditions under which 99.99 percent DRE is achieved for each POHC. In order to ensure 99.99 percent DRE, operating limits are established in a permit for each incinera tnr fo r the following conditions* (1) CO level in the stack exhaust gas. (2) waste feed rate, (3) combustion temperature, (4) an appropriate indicator of combustion gas velocity, (5) allowable variations in incinerator system design or operating procedures, and (6) other operating requirements considered necessary to ensure 99.99 percent DRE for the POHCs. Additionally, Subpan 0 of 40 CFR 246 requires that hazardous waste incineration facilities achieve 99-percent emissions reduction of HC1 (if HC1 emissions are greater than 1.8 kg/hr [4.0 lb/hr]) and a limit of 180 milligrams per dry standard cubic meter (0.0787 grains per dry standard cublic foot) for PM emissions. These emission limits would require facilities to apply acid gas/PM control devices. As mentioned in Section 7.3.4, acid gas/PM control devices may result in panial control of emissions of organic compounds. 7-39 7.4 EXTERNAL COMBUSTION OF SOLID, LIQUID, AND GASEOUS FUELS IN STATIONARY SOURCES FOR HEAT AND POWER GENERATION The combustion of solid, liquid, and gaseous fuels such as natural gas, oil, coal, and wood waste has been shown to be a minor source of benzene emissions. This section addresses benzene emissions from the external combustion of these types of fuels by stationary sources that generate heat or power in the utility, industrial/commercial, and residential sectors. 7.4.1 Utility Sector 2 06 Fossil fuel-fired utility boilers comprise about 72 percent (or 1,696,000 million Btu/hr [497,000 megawatts (MW)]) of the generating capacity of U.S. electric power plants. The primary fossil fuels burned in electric utility boilers are coal, natural gas, and oil. Of these fuels, coal is the most widely used, accounting for 60 percent of the U.S. fossil fuel generating capacity. Natural gas represents about 25 percent and oil represents 15 percent of the U.S. fossil fuel generating capacity. Most of the coal-firing capability is east of the Mississippi River, with the significant remainder being in the Rocky Mountain region. Natural gas is used primarily in the South Central States and California. Oil is predominantly used in Florida and the Northeast. Fuel economics and environmental regulations affect regional use patterns. For example, coal is not used m California because of stringent air quality limitations. Information on precise utility plant locations can be obtained by contacting utility trade associations such as the Electric Power Research Institute in Palo Alto, California (415-855-2000); the Edison Electric Institute in Washington, D.C. (202-828-7400); or the U.S. Department of Energy (DOE) in Washington, D.C. Publications by EPA/DOE on the utility industry are also useful in determining specific facility locations, sizes, and fuel use. 7-40 Process Description of Utility Boilers A utility boiler consists of several major subassemblies, as shown in Figure 7-1 1. 206 These subassemblies include the fuel preparation system, the air supply system, burners, the furnace, and the convective heat transfer system. The fuel preparation system, air supply, and burners are primarily involved in converting fuel into thermal energy in the form of hot combustion gases. The last two subassemblies are involved in the transfer of the thermal energy in the combustion gases to the superheated steam required to operate the steam turbine and produce electricity. 206 Three key thermal processes occur in the furnace and convective sections of the boiler. First, thermal energy is released during controlled mixing and combustion of fuel and oxygen in the burners and furnace. Second, a portion of the thermal energy formed by combustion is adsorbed as radiant energy by the furnace walls. The furnace walls are formed oy multiple, closely spaced tubes filled with high-pressure water mat carry water from the bottom of the furnace to absorb radiant heat energy to the steam drum located at the top of the boiler. Third, the gases enter the convective pass of the boiler, and the balance of the energy retained by the high-temperature gases is adsorbed as convective energy by the convective heat transfer system (superheater, reheater, economizer, and air preheater). 206 A number of different furnace configurations are used in utility boilers, including tangentially fired, wall-fired, cyclone-fired, stoker-fired, and FBC boilers. Some of these furnace configurations are designed primarily for coal combustion; others are designed for coal, oil, or natural gas combustion. The types of furnaces most commonly used for firing oil and natural gas are the tangentially fired and wall-fired boiler designs. 207 One of the primary differences between furnaces designed to bum coal versus oil or gas is the furnace size. Coal requires the largest furnace, followed by oil, then gas. 206 The average size of boilers used in the utility sector varies primarily according to boiler type. Cyclone-fired boilers are generally the largest, averaging about 850 to 7-41 Superheaters and Reheaters Flue Gas Air Figure 7-11. Simplified Boiler Schematic Source: Reference 206. 7-42 ERQ_POM_4121 .pr# 1,300 million Btu/hr (250 to 380 MW) generating capacity. Tangentially fired and wall-fired boiler designs firing coal average about 410 to 1,470 million Btu/hr (120 to 430 MW); these designs firing oil and natural gas average about 340 to 920 million Btu/hr (100 to 270 MW). Stoker-fired boilers average about 34 to 58 million Btu/hr (1-0 to 17 MW). 207 Additionally, unit sizes of FBC boilers range from 85 to 1,360 million Btu/hr (25 to 400 MW), with the largest FBC boilers typically closer to 680 million Btu/hr (200 MW). 206 Tangentially Fired Boiler -The tangentially-fired boiler is based on the concept of a single flame zone within the furnace. The fuel-to-air mixture in a tangentially fired boiler projects from the four comers of the furnace along a line tangential to an imaginary cylinder located along the furnace centerline. When coal is used as the fuel, the coal is pulverized in a mill to the consistency of talcum powder (i.e., at least 70 percent of the panicles will pass through a 200-mesh sieve), entrained in primary air, and fired in suspension. 208 As fuel and air are fed to the burners, a rotating “fireball” is formed to control the furnace exit gas ^ ^ A n rtpnr-p f p t-h- p o ■*-q f"» 'rp f f\r fr nl fflTTinCT V9T7Qtir\nC 171 T'VtP ■firp'hq]] mov kWtuuwiuiUi w cms.* jlw Jillx w a. illLli. w \ Hi iOuu. inw lli wU ci.ll ILicLj be moved up and down by tilting the fuel-air nozzle assembly. Tangentially fired boilers commonly bum coal (pulverized). However, oil or gas may also be burned. 206 Wall-Fired Boiler — Wall-fired boilers are characterized by multiple individual burners located on a single wall or on opposing walls of the furnace. Refer to Figure 7-12 for a diagram of a single wall-fired boiler. 206 As with tangentially fired boilers, when coal is used as the fuel, the coal is pulverized, entrained in primary air, and fired in suspension. In contrast to tangentially fired boilers, which produce a single flame envelope or fireball, each of the burners in a wall-fired boiler has a relatively distinct flame zone. Depending on the design and location of the burners, wall-fired boilers consist of various designs, including single-wall, opposed-wall, cell, vertical, arch, and turbo. Wall-fired boilers may bum (pulverized) coal, oil, or natural gas. 206 7-43 Burner B Burner A Air A- AirB- Air C AirD- Fuel A Fuel B Fuel C Fuel D Burner D Burner C Figure 7-12. Single Wall-fired Boiler Source: Reference 206. 7-44 •Jd ezi* - no aj Q 3 o U aj CJ o E c o "cn (/3 s w v U m o i er e fc o = j= cn O — £ 2 £ 1 o 3 3 oo § 3 OJ JxS c3 .O OO 2 3 CO 2 * x> ^ O CO 4J 6 o U. # o •e -a w o> o « && V K] 3 V*- ra u- i_ j- a o > - o -i c C o 0> W .2 U« 0J <2 *5? .2 co •C 3 C 3 ^ g. ■2 £ - e > u- 0*0 t> u 3 w ^ * O ® a. .22 8 CO u — V -g CJ .tS .o 3 c ? P .sp 5 ? — CO cC o u o i2f2|5 £ *- is. ° £ «M 3 t» w «X> 7-50 SCR = selective catalytic reduction. The above control technologies are not intended to reduce benzene emissions from utility boilers. In general, emissions of organic pollutants, including benzene, are reduced by operating the furnace in such as way as to promote complete combustion of the fossil fuel(s) combusted in the furnace. Therefore, any combustion modification that increases the combustion efficiency will most likely reduce benzene emissions. The following conditions can increase combustion efficiency: 211 • Adequate supply of oxygen; • Good air/fuel mixing; • Sufficiently high combustion temperature; • Short combustion gas residence time; and • Uniform fuel load (i.e., consistent combustion intensity). 7 4 2 Industr i al ' C nmmereial Sect or Industrial boilers are widely used in manufacturing, processing, mining, and refining primarily to generate process steam, electricity, or space heat at the facility. However, the industrial generation of electricity is limited, with only 10 to 15 percent of industrial boiler coal consumption and 5 to 10 percent of industrial boiler gas and oil consumption used for electricity' generation. 212 The use of industrial boilers is concentrated in four major industries: pulp and paper, primary metals, chemicals, and minerals. These industries account for 82 percent of the total firing capacity. 213 Commercial boilers are used by commercial establishments, medical institutions, and educational institutions to provide space heating. In collecting survey data to support its Industrial Combustion Coordinated Rulemaking (ICCR), the EPA compiled information on a total of 69,494 combustion boiler units in the industrial and commercial sectors. 213 While this number likely underestimates the total population of boilers in the industrial and commercial sectors (due to unreceived survey 7-51 responses and lack of information on very small units) it provides an indication of the large number of sources included in this category. Of the units included in the ICCR survey database, approximately 70 percent were classified in the natural gas fuel subcategory, 23 percent in the oil (distillate and residual) subcategory, and 6 percent in the coal burning subcategory. These fuel subcategory assignments are based on the units burning only greater than 90 percent of the specified fuel for that subcategnry All other units (accounting for the other 1 percent of assignments) are assigned to a subcategory of “other fossil fuel.” 213 Other fuels burned in industrial boilers are wood wastes, liquified petroleum gas, asphalt, and kerosene. Of these fuels, wood waste is the only non-fossil fuel discussed here because benzene emissions were not characterized for combustion of the other fuels. The burning of wood waste in boilers is confined to those industries where it is available as a byproduct. It is burned both to obtain heat energy and to alleviate possible solid waste disposal problems. Generally, bark is the major type of waste burned in pulp mills. In the lumber, furniture, and plywood industries, either a mixture of wood and bark waste or wood waste alone is most frequently burned. As of 1980, there were approximately 1,600 wood-fired boilers operating in the United States, with a total capacity of over 102,381 million Btu/hour (30,000 MW). 214 Industrial and commercial coal combustion sources are located throughout the United States, but tend to follow industry and population trends. Most of the coal-fired industrial boiler sources are located in the Midwest, Appalachian, and Southeast regions. Industrial wood-fired boilers tend to be located almost exclusively at pulp and paper, lumber products, and furniture industry facilities. These industries are concentrated in the Southeast, Gulf Coast, Appalachian, and Pacific Northwest regions. The Pacific Northwest contains many of the boilers firing salt-laden wood bark. 7-52 Trade associations such as the American Boiler Manufacturers Association in Arlington, Virginia, (703-522-7350) and the Council of Industrial Boiler Owners in Fairfax Station, Virginia, (703-250-9042) can provide information on industrial boiler locations and trends. 215 Process Description of Industrial/Commercial Boilers Some of the same types of boilers used by the utility sector are also used by the industrial/commercial sector; however, the average boiler size used by the industrial/commercial sector is substantially smaller. Additionally, a few types of boiler designs are used only by the industrial sector. For a general description of the major subassemblies of boilers and their key thermal processes, refer to the discussion of utility boilers in Section 7.4.1 and Figure 7-11. The following two sections describe industrial/commercial boilers that fire fossil fuels and wood waste. Fossil Fuel Combustion --All of the boilers used by the utility industry (described in Section 7.4.1) are “water-tube” boilers, which means that the water being heated flows through tubes and the hot gases circulate outside the tubes. Water-tube boilers represent the majority (57 percent) of industrial and commercial boiler capacity (70 percent of industrial boiler capacity). 212 Water-tube boilers are used in a variety of applications, ranging from supplying large amounts of process steam to providing space heat for industrial and commercial facilities. These boilers have capacities ranging from 10 to 1,500 million Btu/hr (3 to 440 MW), averaging about 410 million Btu/hr (120 MW). The most common types of water-tube boilers used in the industrial/ commercial sector are wall-fired and stoker-fired boilers. Tangentially fired and FBC boilers are less commonly used. Refer to Section 7.4.1 for descriptions of these boiler designs. 213 The industrial/commercial sector also uses boilers with two other types of heat transfer methods: fire-tube and cast iron boilers. Because their benzene emissions have not been characterized, these types of boilers are only briefly described below. 7-53 In fire-tube boilers, the hot gas flows through the tubes and the water being heated circulates outside of the tubes. Fire-tube boilers are not available with capacities as large as those of water-tube boilers, but they are also used to produce process steam and space heat. Most fire-tube boilers have a capacity between 1.4 and 24.9 million Btu/hour (0.4 and7.3 MW thermal). Most installed firetube boilers bum oil or gas. 213 In cast iron boilers, the hot gas is also contained inside the tubes, which are surrounded by the water being heated, but the units are constructed of cast iron instead of steel. Cast iron boilers are limited in size and are used only to supply space heat. Cast iron boilers range in size from less than 0.3 to 9.9 million Btu/hour (0.1 to 2.9 MW thermal). 213 Wood Combustion --The burning of wood waste in boilers is mostly confmed to those industries where it is available as a byproduct. It is burned both to obtain heat energy and to alleviate solid waste disposal problems. Wood waste may include large pieces such as slabs, logs and bark strips as well as cuttings, shavings, pellets, and sawdust. 214 Various boiler firing configurations are used in burning wood waste. One common type in smaller operations is the dutch oven or extension type of furnace with a flat grate. This unit is widely used because it can bum fuels with very high moisture. Fuel is fed into the oven through apertures in a firebox and is fired in a cone-shaped pile on a flat grate. The burning is done in two stages: (1) drying and gasification, and (2) combustion of gaseous products. The first stage takes place in a cell separated from the boiler section by a bridge wall. The combustion stage takes place in the main boiler section. 214 In another type of boiler, the fuel-cell oven, fuel is dropped onto suspended fixed grates and fired in a pile. The fuel cell uses combustion air preheating and positioning of secondary and tertiary air injection ports to improve boiler efficiency. 214 In many large operations, more conventional boilers have been modified to bum wood waste. The units may include spreader stokers with traveling grates or vibrating grate 7-54 stokers, as well as tangentially fired or cyclone-fired boilers (see Section 7.4.1 for descriptions of these types of boilers). The most widely used of these configurations is the spreader stoker, which can bum dry or wet wood. Fuel is dropped in front of an air jet that casts the fuel out over a moving grate. The burning is done in three stages: (1) drying, (2) distillation and burning of volatile matter, and (3) burning of fixed carbon. Natural gas or oil is often fired as auxiliary fuel. This is done to maintain constant steam when the wood supply fluctuates or to provide more steam than can be generated from the wood supply alone. 214 Sander dust is often burned in various boiler types at plywood, particle board, and furniture plants. Sander dust contains fine wood particles with low moisture content (less than 20 percent by weight). It is fired in a flaming horizontal torch, usually with natural gas as an ignition aid or supplementary fuel. 214 A recent development in wood firing is the FBC boiler. Refer to Section 7.4.1 for 2 description of this boiler type. Because of the large thermal mass represented by the hot inert bed particles, FBCs can handle fuels with high moisture content (up to 70 percent, total basis). Fluidized beds can also handle dirty fuels (up to 30 percent inert material). Wood material is pyrolyzed more quickly in a fluidized bed than on a grate because of its immediate contact with hot bed material. Combustion is rapid and results in nearly complete combustion of organic matter, minimizing emissions of unbumed organic compounds. 214 Benzene Emissions from Industrial/Commercial Boilers Benzene emissions from industrial/commercial boilers may depend on various factors, including (1) type of fuel burned, (2) type of boiler used, (3) operating conditions of the boiler, and (4) pollution control device(s) used. Conditions that favor more complete combustion of the fuel generally result in lower organic emissions. Additionally, the organic emissions potential of wood combustion is generally thought to be greater than that of fossil fuel combustion because wood waste has a lower heating value, which may decrease 7-55 combustion efficiency. Emission factors for benzene emissions from industrial and commercial/institutional boilers are presented in Table 7-6. 3,216 " 220 Table 7-6 presents emission factors primarily for wood waste combustion. Additionally a few emission factors are presented for fossil fuel (residual oil and coke/coal) and process gas (landfill gas and POTW digester gas) combustion. Most of the emission factors represent emissions from a non-specified type of boiler. Only two boiler types are specified (FBC and spreader-stoker). Additionally, the benzene emission factors presented are emissions following various types of PM and S0 2 emission control systems. In most cases, Table 7-6 specifies the type of wood waste associated with the emission factors for wood combustion boilers. The composition of wood waste may have an impact on benzene emissions. The composition of wood waste depends largely on the industry from which it originates. Pulping operations, for example, produce great quantities of bark that may contain more than 70 percent by weight moisture, along with sand and other noncombustibles. Because of this, bark boilers in pulp mills may emit considerable amounts of organic compounds to the atmosphere unless they are well controlled. On the other hand, some operations, such as furniture manufacturing, produce a clean, dry wood waste, 5 to 50 percent by weight moisture, with relatively low organic emissions when properly burned. Still other operations, such as sawmills, bum a varying mixture of bark and wood waste that results in paniculate emissions somewhere between those of pulp mills and furniture manufacturing. Additionally, when fossil fuels are co-fired with wood waste, the combustion efficiency is typically improved; therefore, organic emissions may decrease. 215 The type of boiler, as well as its operation, affect combustion efficiency and emissions. Wood-fired boilers require a sufficiently large refractory surface to ensure proper drying of high-moisture-content wood waste prior to combustion. Adequately dried fuel is necessary to avoid a decrease in combustion temperatures, which may increase organic emissions because of incomplete combustion. 215 7-56 TABLE 7-6. SUMMARY OF BENZENE EMISSION FACTORS FOR INI iUSTRIAL AND COMMERCIAL/INSTITUTIONAL BOILERS . H Tj 3 U- 3 o i— ,- oo 2 c o ’-S era tu oc o tL o ad a 3, U- ° e 2 O CQ 1 S s § LU X5 0> Q c c U OJ c- >-. —i X X X X X X r-~~ oo OA 00 o o O CN CN wo wo P r- wo CO C/3 3 T3 *2 .2 u. c o 2 o *o w S 3 o C/3 3 O J= 00 CQ •o c C3 © ok i c4 o t 00 TD c O "3 E ° £ o < £ s= o “ ca Cm O0 cq Jr? tn • ^ Cu O 1—1 M ’o *5 00 x> CQ CQ o I r- co O C/3 a. 2 o CJ c 'a. ■o 7-58 Control Technologies for Industrial/Commercial Boilers Control techniques for reducing benzene emissions from industrial and commercial boilers are similar to those used for utility boilers. Refer to Section 7.4.1 for a discussion of control techniques also applicable to commercial and industrial boilers. In Section 7.4.1, various operating conditions are listed that contribute to the combustion efficiency of a boiler (e.g., oxygen supply, good air/fuel mixing, and temperature). It has been demonstrated for a spreader-stoker boiler firing wood that benzene emissions are an order of magnitude lower under good firing conditions than under poor firing conditions (when the boiler was in an unsteady or upset condition). It has also been shown that the ratio of overfire to underfire air plays an important role in benzene emissions. Based on recent test results, the speculation is that if the balance of combustion air heavily favors underfire air, there is insufficient combustion air in the upper furnace to complete the combustion of PTCs (including benzene) Conversely, with excess overfire air. the flame¬ quenching effect of too much combustion air in the upper furnace appears to suppress the combustion of PICs at that stage of the combustion process. 218 7.4.3 Residential Sector The residential sector includes furnaces and boilers burning coal, oil, and natural gas, stoves and fireplaces burning wood, and kerosene heaters. All of these units are designed to heat individual homes. Locations of residential combustion sources are tied directly to population trends. Coal consumption for residential combustion purposes occurs mainly in the Northeast, Appalachian, and Midwest regions. Residential oil consumption is greatest in the Northeast and Mid-Atlantic regions. Wood-fired residential units are generally concentrated in heavily forested areas of the United States, which reflects fuel selection based on availability and price. 215 7-59 Process Description for Residential Furnaces, Boilers, Stoves, and Fireplaces The following sections describe the types of residential furnaces, boilers, stoves, and fireplaces that fire wood, coal, oil, natural gas, kerosene. Wood Combustion —Residential wood combustion generally occurs in either a wood-fired stove or fireplace unit located inside the house. The following discussion describes the specific characterization of woodstoves, followed by a discussion on fireplaces. Woodstoves are commonly used in residences as space heaters. They are used both as the primary source of residential heat and to supplement conventional heating systems. Wood stoves have varying designs based on the use or non-use of baffles and catalysts, the extent of combustion chamber sealing, and differences in air intake and exhaust systems. The EPA has identified five different categories of wood-burning stoves based on differences in both the magnitude and the composition of the emissions: 221 • Conventional woodstoves; • Noncatalytic woodstoves; • Catalytic woodstoves; • Pellet stoves; and • Masonry heaters. Within these categories, there are many variations in device design and operation. The conventional stove category comprises all stoves that do not have catalytic combustors and are not included in the other noncatalytic categories (i.e., noncatalytic and pellet). Conventional stoves do not have any emissions reduction technology or design features and, in most cases, were manufactured before July 1, 1986. Stoves of many different 7-60 airflow designs may be included in this category, such as updraft, downdraft, crossdraft and S-flow. 221 Noncatalytic woodstoves are those units that do not employ catalysts but do have emissions-reducing technology or features. Typical noncatalytic design includes baffles and secondary combustion chambers. 221 Catalytic stoves are equipped with a ceramic or metal honeycomb device, called a combustor or converter, that is coated with a noble metal such as platinum or palladium. The catalyst material reduces the ignition temperature of the unbumed VOC and CO in the exhaust gases, thus augmenting their ignition and combustion at normal stove operating temperatures. As these components bum, the temperamre inside the catalyst increases to a point at which the ignition of the gases is essentially self-sustaining. 221 Pellet stoves axe those fueled with pellets of sawdust, wood products, and other biomass materials pressed into manageable shapes and sizes. These stoves have active air flow systems and unique grate design to accommodate this type of fuel. Some pellet stove models are subject to the 1988 NSPS; others are exempt because of their high air-to-fuel ratio (greater than 35-to-l). 121 Masonry heaters are large, enclosed chambers made of masonry products or a combination of masonry products and ceramic materials. These devices are exempt from the 1988 NSPS because of their weight (greater than 800 kg). Masonry heaters are gaining popularity as a cleaner-burning and heat-efficient form of primary and supplemental heat, relative to some other types of wood heaters. In a masonry heater, a complete charge of wood is burned in a relatively short period of time. The use of masonry materials promotes heat transfer. Thus, radiant heat from the heater warms the surrounding area for many hours after the fire has burned out. 221 7-61 Fireplaces are used primarily for aesthetic effects and secondarily as a supplemental heating source in houses and other dwellings. Wood is the most common fuel for fireplaces, but coal and densified wood “logs” may also be burned. 222 The user intermittently adds fuel to the fire by hand. Fireplaces can be divided into two broad categories: (1) masonry (generally brick and/or stone, assembled on site, and integral to a structure) and (2) prefabricated (usually metal, installed on site as a package with appropriate duct work). Masonry fireplaces typically have large, fixed openings to the fire bed and dampers above the combustion area in the chimney to limit room air and heat losses when the fireplace is not being used. Some masonry fireplaces are designed or retrofitted with doors and louvers to reduce the intake of combustion air during use. 222 Prefabricated fireplaces are commonly equipped with louvers and glass doors to reduce the intake of combustion air, and some are surrounded by ducts through which floor-level air is drawn by natural convection, heated, and returned to the room. Many varieties of prefabricated fireplaces are now on the market. One general class is the freestanding fireplace, the most common of which consists of an inverted sheet metal funnel and stovepipe directly above the fire bed. Another class is the “zero clearance” fireplace, an iron or heavy-gauge steel firebox lined inside with firebrick and surrounded by multiple steel walls with spaces for air circulation. Some zero clearance fireplaces can be inserted into existing masonry fireplace openings, and thus are sometimes called “insens.” Some of these units are equipped with close-fitting doors and have operating and combustion characteristics similar to those of woodstoves. 222 Masonry fireplaces usually heat a room by radiation, with a significant fraction of the combustion heat lost in the exhaust gases and through fireplace walls. Moreover, some of the radiant heat entering the room goes toward warming the air that is pulled into the residence to make up for that drawn up the chimney. The net effect is that masonry fireplaces are usually inefficient heating devices. Indeed, in cases where combustion is poor, where the 7-62 outside air is cold, or where the fire is allowed to smolder (thus drawing air into a residence without producing appreciable radiant heat energy), a net heat loss may occur in a residence using a fireplace. Fireplace heating efficiency may be improved by a number of measures that either reduce the excess air rate or transfer back into the residence some of the heat that would normally be lost in the exhaust gases or through fireplace walls. As noted above, such measures are commonly incorporated into prefabricated units. As a result, the energy efficiencies of prefabricated fireplaces are slightly higher than those of masonry fireplaces. 222 Coal Combustion -Coal is not a widely used source of fuel for residential heating purposes in the United States. Only 0.3 percent of the total coal consumption in 1990 was for residential use. 223 However, combustion units burning coal may be sources of benzene emissions and may be important local sources in areas that have a large number of residential houses tnat rely on tms ruei tor neatmg. There are a wide variety of coal-burning devices in use, including boilers, furnaces, coal-burning stoves, and wood-burning stoves that bum coal. These units may be hand fed or automatic feed. Boilers and warm-air furnaces are usually stoker-fed and are automatically controlled by a thermostat. The stove units are less sophisticated, generally hand fed, and less energy-efficient than boilers and furnaces. Coal-fired heating units are operated at low temperatures and do not efficiently combust fuel. 215 Therefore, the potential for emissions of benzene exists. Distillate Oil Combustion -The most frequently used home heating oil in the United States is No. 2 fuel oil, otherwise referred to as distillate oil. Distillate oil is the second most important home heating fuel behind natural gas. 224 The use of distillate oil-fired heating units is concentrated in the Northeast portion of the United States. Connecticut, Maine, Massachusetts, New Hampshire, Rhode Island, Vermont, Delaware, District of 7-63 Columbia, Maryland, New Jersey, New York, and Pennsylvania accounted for approximately 72 percent of the residential share of distillate oil sales. 225 Residential oil-fired heating units exist in a number of design and operating variations related to burner and combustion chamber design, excess air, heating medium, etc. Residential systems typically operate only in an “on” or “off’ mode, with a constant fuel firing rate, as opposed to commercial and industrial applications, where load modulation is used. 226 In distillate oil-fired heating units, pressure or vaporization is used to atomize fuel oil in an effort to produce finer droplets for combustion. Finer droplets generally mean more complete combustion and less organic emissions. When properly tuned, residential oil furnaces are relatively clean burning, especially as compared to woodstoves. 224 However, another study has shown that in practice not all of the fuel oil is burned and tiny droplets escape the flame and are carried out in the exhaust. 227 This study also concluded that most of the organic emissions from an oil furnace are due to the unbumed oil (as opposed to soot from the combustion process), especially in the more modem burners that use a retention head burner, where over 90 percent of the carbon in the emissions was from unbumed fuel. 227 Natural Gas Combustion -Natural gas is the fuel most widely used for home heating purposes, with more than half of all the homes being heated through natural gas combustion. Gas-fired residential heating systems are generally less complex and easier to maintain than oil-burning units because the fuel bums more cleanly and no atomization is required. Most residential gas burners are typically of the same basic design. They use natural aspiration, where the primary air is mixed with the gas as it passes through the distribution pipes. Secondary air enters the furnace around the burners. Flue gases then pass through a heat exchanger and a stack. As with oil-fired systems, there are usually no pollution control equipment installed on gas systems, and excess air, residence time, flame retention devices, and maintenance are the key factors in the control of emissions from these units. 7-64 Kerosene Combustion —The sale and use of kerosene space heaters increased dramatically during the 1980s and they continue to be sold and used throughout the United States as supplementary and, in some cases, as primary home heating sources. 228 These units are usually unvented and release emissions inside the home. There are two basic types of kerosene space heaters: convective and radiant. Emission Factors for Residential Furnaces, Boilers, Stoves, and Fireplaces The combustion of fossil fuels or wood in residential units is a relatively slow and low-temperature process. Studies do not indicate the cause(s) for benzene formation in the residential sector; however, the mechanism may be similar to that in industrial boilers and utility boilers. Benzene may be formed through incomplete combustion. Because combustion in the residential sector tends to be less efficient than in other sectors, the potential to form benzene may be greater. Table 7-7 presents emission factors for uncontrolled benzene emissions from both catalytic and non-catalytic woodstoves. 3 Benzene emission factors for other types of a residential wood combustion sources are not presented because of limited data. In general, emissions of benzene can vary widely depending on how the units are operated and the how emissions are measured. The following factors may affect benzene emissions measured from residential wood combustion sources: • Unit design and degree of excess air; • Wood type, moisture content, and other wood characteristics; • Bum rate and stage of bum; and • Firebox and chimney temperatures. 7-65 TABLE 7-7. SUMMARY OF BENZENE EMISSION FACTORS FOR RESIDENTIAL WOODSTOVES CJD § - S O W tL3 tL) • tu 0* B 'Si /«—N g s © © SO ^ C 44 Tt X ON X .9 w c r> C CO P o r~ C/2 O *3 w r~ ON e > S —' w — O o r* 6 P ' P U OJ O- >-> T3 "O H O o o o TJ 3 £ £ u- o o o tn o C/3 *o o £ a o o c "(A C/2 o £ *w 13 c3 E o tL _>■» U c 4—> efl o u Z o a. ) ro »r> T 3 9 o C g ^ 9 oo L c/ 8 i 5 S tj- O < C p t CN (N co «J u 3 O to cn > 43 a c o U c 2 ~ X ON «r> —I tj- w OJ G C o c D 4) C OX) c •X 3 S ’O A 3 QJ — 13 ‘5 2 U w _ £ CNJ — o ox) 43 — 2 2 G ' cn G w w OX) o O u, « U cn C 'G "5)1 oj oX) or 1 ^30 CN O i i cn O i CN E CQ S 5 . TO U 43 43 C 43 S £ e to 3 O 5 43 cn k, O o CQ u. 7-73 NSCR = nonselective catalytic reduction. POTW = publically owned treatment works. Other NO x control techniques include internal/external exhaust gas recirculation (EGR), combustion chamber modification, manifold air cooling, and turbocharging. Various other emissions reduction technologies may be applicable to the smaller diesel and gasoline engines. These technologies are categorized into fuel modifications, engine modifications, and exhaust treatments. 7.5.2 Gas Turbines Stationary gas turbines are applied in electric power generators, in gas pipeline pump and compressor drives, and in various process industries. Gas turbines (greater than 3 MW(e)] are used in electrical generation for continuous, peaking, or standby power. 79 In 1990, the actual gas-fired combustion turbine generating capacity for electric utilities was 8,524 MW. 234 The current average size of electricity generation gas turbines is approximately 31 MW. Turbines are also used in industrial applications, but information was not available to estimate their installed capacity. The same fuels used in reciprocating engines are combusted to drive gas turbines. The primary fuels used are natural gas and distillate (No. 2) fuel oil, although residual fuel oil is used in a few applications. 235 The liquid fuel used must be similar in volatility to diesel fuel to produce droplets that penetrate sufficiently far into the combustion chamber to ensure efficient combustion even when a pressure atomizer is used. 230 Process Description for Gas Turbines Gas turbines are so named not because they are gas-fired, but because combustion exhaust gas drives the turbine. Unlike reciprocating engines, gas turbines operate in steady flow. As shown in Figure 7-17, a basic gas turbine consists of a compressor, a combustor, and a turbine. 230 Combustion air enters the turbine through a centrifugal 7-74 Combustion chamber diaa-pt-toeoe o m co co £ UJ U u oo u o o X X co (N —' o T 0* o o X X O CO — f" ON CO — TT a c — u. U u 3 *o 3J 2 C8 u •s s—' _0J 33 ,2 a> ~ .S ° 3 I C/5 *w re c/5 U '-a 5 1 "33 2 c 5/5 .3 C3 .c dc 2 2 C/5 3 re u o I CN © CNJ O i (N 3 ffi 2 8 . •o CJ - u. < o z o u UJ c/o U- 00 0£ o w H U < u* z o -~r oo 2 w UJ re z w u. O > < 2 2 P 00 r- W P CQ < H 0-> Q c o U *o 3 o o c p OJ E 3 Xl i— OJ i O C/5 c/5 a> i) •5 oo .S w- 3 x: CJ c3 X) u. 8 . 3 O x 00 o ■ta-* 0/ "S CO r* c CO U« co <0 = s o •3 ”o£ « X u c o CO X t- « o « r s- © c» T3 Q. « £ 2 ? .' 3 w 52 E s a aj -3 u 4J >> DO C X C | O ’£? •“ o o *5 * o oo £ - e £ E £t'i C 2 4/ .= r: o u 4> ,C0 W eo E |«3 to "O to a> 2 c3 4/ 4J « ui < cq oo u* O O <4— c o *oo oo 7-94 estimated using the THC control efficiency for the given process configuration. These estimates assume that the control efficiency for benzene was equal to the control efficiency for THC. 7.6.3 Control Technologies for Secondary Lead Smelters Controls used to reduce organic emissions from smelting furnaces in the secondary lead smelting industry include afterburners on blast furnaces and combined blast and reverberatory exhausts. Reverberatory and rotary furnaces have minimal benzene emissions because of high exhaust temperatures and turbulence, which promote complete combustion of organics. No controls for THC are necessary for these process configurations. 236 Benzene emissions from blast furnaces are dependent on the type of add-on control used. An afterburner operated at 1,300°F (700°C) achieves about 84 percent destruction efficiency of THC 236 Facilities with blast and reverberatory furnaces usually combine the exhaust streams and vent the combined stream to an afterburner. The higher operating temperature of the reverberatory furnace reduces the fuel needs of the afterburner so that the afterburner is essentially “idling.” Any temperature increase measured across the afterburner is due to the heating value of organic compounds in the blast furnace exhaust. A combined reverberatory and blast furnace exhaust stream ducted to an afterburner with an exit temperature of 1,700°F (930°C) can achieve 99-percent destruction efficiency for THC. 236 Additional controls used by secondary lead smelters include baghouses for paniculate and metal control, hooding and ventilation to a baghouse for process fugitives, and scrubbers for HC1 and S0 2 control. 236 7.7 IRON AND STEEL FOUNDRIES Iron and steel foundries can be defmed as those that produce gray, white, ductile, or malleable iron and steel castings. Cast iron and steels are both solid solutions of 7-95 iron, carbon, and various alloying materials. Although there are many types of each, the iron and steel families can be distinguished by their carbon content. Cast irons typically contain 2 percent carbon or greater; cast steels usually contain less than 2 percent carbon. 242 Iron castings are used in almost all types of equipment, including motor vehicles, farm machinery, construction machinery, petroleum industry equipment, electrical motors, and iron and steel industry equipment. Steel castings are classified on the basis of their composition and heat treatment, which determine their end use. Steel casting classifications include carbon, low-alloy, general-purpose-structural, heat-resistant, corrosion-resistant, and wear-resistant. They are used in motor vehicles, railroad equipment, construction machinery, aircraft, agricultural equipment, ore refining machinery, and chemical manufacturing equipment. ;4: Based on a survey conducted by EPA in support of the iron and steel foundry MACT standard development, there were 756 iron and steel foundries in the United States in 1992. 243 Foundry locations can be correlated with areas of heavy industry and manufacturing and, in general, with the iron and steel production industry (Ohio, Pennsylvania, and Indiana). Additional information on iron and steel foundries and their locations may be obtained from the following trade associations: • American Foundrymen's Society, Des Plaines, Illinois; • National Foundry Association, Des Plaines, Illinois; • Ductile Iron Society, Mountainside, New Jersey; • Iron Casting Society, Warrendale, Pennsylvania; and • Steel Founders' Society of America, Des Plaines, Illinois. / 7-96 7.7.1 Pisces? Description for Iron and Steel Foundries The following four basic operations are performed in all iron and steel foundries: • Storage and handling of raw materials; • Melting of the raw materials; • Transfer of the hoi molten metal into molds, and • Preparation of the molds to hold the molten metal. Other processes present in most, but not all, foundries include: • Sand preparation and handling; • Mold cooling and shakeout; • Casting cleaning, heat treating, and finishing; • Coremaking; and • Pattern making. A generic process flow diagram for iron and steel foundries is given in Figure 7-23. 242 Figure 7-24 depicts the emission points in a typical iron foundry. 244 Iron and steel castings are produced in a foundry by injecting or pouring molten metal into cavities of a mold made of sand, metal, or ceramic material. Input metal is melted by the use of a cupola, an electric arc furnace, or an induction furnace. About 70 percent of all iron castings are produced using cupolas, with lesser amounts produced in electric arc and induction furnaces. However, the use of electric arc furnaces in iron foundries is increasing. Steel foundries rely almost exclusively on electric arc or induction furnaces for melting purposes. With either type of foundry, when the poured metal has solidified, the molds are separated and the castings removed from the mold flasks on a casting shakeout unit. Abrasive 7-97 X3 C =3 O U- OJ •a c C o oo 03 u I T3 C 03 on E 03 b~ CUD 03 s £ O U- on oo 4D O O i— cu ttf o o eg U. *00 © t/5 c C/5 o *2 c X flj CJ > 1) Q o u. c U u <_) u. 3 O co E u U U co O o ON vo rn u S2 o -3 CJj re C2 u X .3 2 O TD S CO 00 ON I m 8 m vo TT (N T3 C re V) (N V) a u a s £ cc o o ka 3 O CO •o o 8 u •o 3 re (A OJj 2 8 . •o 1) 0> OJ c w s .8 oo Jxi X c CA CJ re B- 7-101 benzene emission factor could only be calculated for the sand cooler and belts, as reflected in Table 7-12. 245 - 246 Benzene from sand coolers and belts and casting shakeouts and mixers may be emitted as a result of the heating during mold pouring of the organic binders used to form the casting. During mold pouring, the binder materials in the mold are exposed to temperatures near 2,550°F (1,400°C). At these temperatures, pyrolysis of the chemical binder may release organic chemicals which become trapped in the sand inside the casting. During shakeout and sand cooling, the sand is exposed to the atmosphere and these organic chemicals may be released. 7.7.3 Control Technologies for Iron and Steel Foundries 244 Scrap preparation with heat or solvent degreasers will emit organic compounds. Catalytic incinerators and afterburners can control about 95 percent of organic emissions. Emissions released from melting furnaces include organic compounds. The highest concentrations of furnace emissions occur when furnace doors are open during charging, backcharging, alloying, slag removal, and tapping operations. These emissions can escape into the furnace building or can be collected and vented through roof openings. Emission controls for melting and refining operations involve venting furnace gases and fumes directly to a control device. Canopy hoods or special hoods near furnace doors and tapping points capture emissions and route them to emission control systems. A cupola furnace typically has an afterburner, which achieves up to 95 percent efficiency. The afterburner is located in the furnace stack to oxidize CO and bum organic fumes, tars, and oils. Reducing these contaminants protects the particulate control device from possible plugging and explosion. Toxic emissions from cupolas include both organic and inorganic materials. Cupolas produce the most toxic emissions compared to other melting equipment. During melting in an electric arc furnace, hydrocarbons are emitted from 7-102 vaporization and incomplete combustion of any oil remaining on the scrap iron charge. Electric induction furnaces emit negligible amounts of hydrocarbon emissions, and are typically uncontrolled except during charging and pouring operations. Organic emissions are generated during the refining of molten iron before pouring and from the mold and core materials during pouring. Toxic emissions of halogenated and aromatic hydrocarbons are released in the refining process. Emissions from pouring normally are captured by a collection system and vented, either controlled or uncontrolled, to the atmosphere. Emissions continue as the molds cool. Organics are emitted in mold and core production operations from core baking and mold drying. Afterburners and catalytic incinerators can be used to control organics emissions. In addition to organic binders, molds and cores may be held together in the desired shape by means of a cross-linked organic polymer network. This network of polymers undergoes thermal decomposition when exposed to the very high temperatures of casting, typically 2,550°F (1,400°C). At these temperatures it is likely that pyrolysis of the chemical binder will produce a complex of free radicals that will recombine to form a wide range of chemical compounds having widely differing concentrations. There are many different types of resins currently in use, with diverse and toxic compositions. No data are available for determining the toxic compounds in a particular resin that are emitted to the atmosphere and to what extent these emissions occur. 7.8 PORTLAND CEMENT PRODUCTION Most of the hydraulic cement produced in the United States is Portland cement-a cementitious, crystalline compound composed of metallic oxides. The end-product cement, in its fused state, is referred to as “clinker.” Raw materials used in the process can be 7-103 calcium carbonate- and aluminum-containing limestone, iron, silicon oxides, shale, clay, and sand. 247 As of December 1990, there were 112 Portland cement plants in the United States operating 213 kilns with a total annual clinker capacity of 80 million tons (73.7 million Mg). The kiln population included 80 wet process kilns and 133 dry process kilns. 247 U.S. Portland cement plants are listed in Table 7-13 . 7.8.1 Process Description for the Portland Cement Industry In Portland cement production, most raw materials typically are quarried on site and transferred by conveyor to crushers and raw mills. After the raw materials are reduced to the desired particle size, they are blended and fed to a large rotary kiln. The feed enters the kiln at the elevated end, and the burner is located at the opposite end. The raw materials are then changed into cementitious oxides of metal by a countercurrent heat exchange process. The materials are continuously and slowly moved to the low end by the rotation of the kiln while being heated to high temperatures (2,700°F [1,482°C]) by direct firing (Stream 3 in Figure 7-25). In this stage, chemical reactions occur, and a rock-like substance called “clinker” is formed. This clinker is then cooled, crushed, and blended with gypsum to produce Portland cement. 247 The cement is then either bagged or bulk-loaded and transported Cement may be made via a wet or a dry process. Many older kilns use the wet process. In the past, wet grinding and mixing technologies provided more uniform and consistent material mixing, resulting in a higher quality clinker. Dry process technologies have improved, however, to the point that all of the new kilns since 1975 use the dry process. 249 In the wet process, water is added to the mill while the raw materials are being ground. The resulting slurry is fed to the kiln. In the dry process, raw materials are also ground finely in a mill, but no water is added and the feed enters the kiln in a dry state. More fuel is required for the wet process than the dry process to evaporate the water from the feed. However, for either the wet or dry process, Portland cement production is fuel-intensive. The fuel burned in the kiln may be natural gas, oil, or coal. Many cement 7-104 TABLE 7-13. SUMMARY OF PORTLAND CEMENT PLANT CAPACITY INFORMATION Location Number of Plants (kilns) Capacity 10 3 tons/yr (10 3 Mg/yr) Alabama 5(6) 4,260 (3,873) Alaska 1(0)* 0(0) Arizona 2(7) 1,770(1,609) Arkansas 2(5) 1,314(1,195) California 12 (20) 10,392 (9,447) Colorado 3(5) 1,804 (1,640) Florida 6(8) 3,363 (3,057) Georgia 2(4) 1,378 (1,253) Hawaii KD 263 (239) Idaho 1 (2) 210(191) Illinois 4(8) 2,585 (2,350) Indiana 4(8) 2,830 (2,573) Iowa 4(7) 2,806 (2,551) Kansas 4(11) 1,888 (1,716) Kentucky 1 (1) 724 (658) Maine 1 (1) 455 (414) Maryland 3(7) 1,860 (1,691) Michigan 5(9) 4.898 (4.453) Mississippi KD 504 (458) Missouri 5(7) 4,677 (4,252) Montana 2(2) 592 (538) Nebraska 1(2) 961 (874) Nevada 1(2) 415 (377) New Mexico 1(2) 494 (449) New York 4(5) 3,097 (2,815) Ohio £15) 1,703 (1,548) 7-105 (continued) TABLE 7-13. CONTINUED Location Number of Plants (kilns) Capacity 10 3 tons/yr (10 3 Mg/yr) Oklahoma 3(7) 1,887 (1,715) Oregon KD 480 (436) Pennsylvania 11 (24) 6,643 (6,039) South Carolina 3(7) 2,579 (2,345) South Dakota 766 (696) Tennessee 2(3) 1,050 (955) Texas 12 (20) 8,587 (7,806) Utah 2(3) 928 (844) Virginia 1(5) 1,117 (1,015) Washington i (i) 473 (430) West Virginia 1 (3) 822 (747) ‘ Wyoming KD 461 (419) Source: Reference 247. a Grinding plant only. 7-106 plants bum coal, but supplemental fuels such as waste solvents, chipped rubber, shredded municipal garbage, and coke have been used in recent years. 247 A major trend in the industry is the increased use of waste fuels. In 1989, 33 plants in the United States and Canada reported using waste fuels; the number increased to 55 plants in 1990. 247 The increased use of hazardous waste-derived fuels (HWDFs) for the kilns is attributed to lower cost and increased availability. As waste generators reduce or eliminate solvents from their waste steams, the streams contain more sludge and solids. As a result, two new hazardous waste fueling methods have emerged at cement kilns. The first method pumps solids (either slurried with liquids or dried and ground) into the hot end of the kiln. The second method (patented by cement kiln processor and fuel blender Cadence, Inc.) introduces containers of solid waste into the calcining zone of the kiln. 250 The kiln system for the manufacture of Portland cement by dry process with preheater is shown in Figure 7-25. The raw material enters a four-stage suspension preheater, where hot gases from the kiln heat the raw feed and provide about 40-percent calcination (Stream 1) before the feed enters the kiln. Some installations include a precalcining furnace (Stream 2), which provides about 85 percent calcination before the feed enters the kiln. 247 7.8.2 Benzene Emissions from the Portland Cement Industry and Regulatory Analysis The raw materials used by some facilities may contain organic compounds, which become a source of benzene emissions during the heating step. However, fuel combustion to heat the kiln is believed to be the greater source of benzene emissions. As shown in Table 7-14, benzene is emitted when either fossil fuels or HWDFs are combusted in the kiln. 247 249 - 251 Facilities that bum HWDF are subject to the Boilers and Industrial Furnaces (BIF) rule promulgated February 21, 1991, under the Resource Conservation and Recovery Act (RCRA). The BIF rule requires that a facility that bums hazardous waste demonstrate a 7-107 7-108 ■*r (N o c a> £ a> cc < 1 U > Oh W C/2 p: C/3 C/I C/l P P 03 p O £ o C/l O *o T3 03 *o u CO o OJ Wo CO o cd N v> N N CO 03 C3 03 X u 00 03 QJ 00 c 3 C z P Uh _c ‘£ ■ ■ ’£ ’£ u 73 03 c ”0 ui p X O p c p CQ W CQ 03 CQ i C D ■W i i c 0> C/3 i i c •—* C/D Cd £ 15 £ 2 o vO • i o o a c tu u, A> <4—i OJ ad a> o I— 3 O C/5 7-113 Figure 7-26. General Process Flow Diagram for Batch Mix Asphalt Paving Plants The moisture content of recycled hot-mix asphalt typically ranges from 2 to 3 percent. The different sizes of aggregate are typically transported by front-end loader to separate cold feed bins and metered onto a feeder conveyor belt through gates at thie bottom of the bins. The aggregate is screened before it is fed to the dryer to keep oversize material out of the mix. The screened aggregate is then fed to a rotating dryer with a burner at its lower (discharge) end that is fired with fuel oil, natural gas, or propane. The dryer removes moisture from the agg r egate and heats the aggregate to the proper mix temperature. Inside the dryer are longitudinal flights (metal slats) that lift and tumble the aggregate, causing a curtain of material to be exposed to the heated gas stream. This curtain of material provides greater heat transfer to the aggregate than would occur if the aggregate tumbled along the bottom of the drum towards the discharge end. Aggregate temperature at the discharge end of the dryer is about 300 °F (149°C). The amount of aggregate that a dryer can heat depends on the size of the drum, the size of the burner, and the moisture content of the aggregate. As the amount of moisture to be removed from the aggregate increases, the effective production capacity of the dryer decreases. Vibrating screens segregate the heated aggregate into bins according to size. A weigh hopper meters the desired amount of the various sizes of aggregate into a pugmill mixer. The pugmill typically mixes the aggregate for approximately 15 seconds before hot asphalt cement from a heated tank is sprayed into the pugmill. The pugmill thoroughly mixes the aggregate and hot asphalt cement for 25 to 60 seconds. The finished hot-mix asphalt is either directly loaded into trucks or held in insulated and/or heated storage silos. Depending on the production specifications, the temperature of the hot-mix asphalt product mix can range from 225 to 350°F (107 to 177°C) at the end of the production process. When a hot mix containing RAP is produced, the aggregate is superheated (compared to totally virgin hot-mix asphalt production) to about 600°F (315°C) to ensure sufficient heat transfer to the RAP when it is mixed with the virgin materials. The RAP 7-114 material may be added either to the pugmill mixer or at the discharge end of the dryer. Rarely is more than 30 percent RAP used in batch plants for the production of hot-mix asphalt. Continuous-mix plants are very similar in configuration to batch plants. Continuous-mix plants have smaller hot bins (for holding the heated aggregate) than do batch plants. Little surge capacity is required of these bins because the aggregate is continuously metered and transported to the mixer inlet by a conveyor belt. Asphalt cement is continuously added to the aggregate at the inlet of the mixer. The aggregate and asphalt cement are mixed by the action of rotating paddles as they are conveyed through the mixer. An adjustable dam at the outlet end of the mixer regulates the mixing time and also provides some surge capacity. The finished mix is transported by a conveyor belt to either a storage silo or surge bin. 253 Drum-mix plants dry the aggregate and mix it with the asphalt cement in the same drum, eliminating the need for the extra conveyor belt, hot bins and screens, weigh hopper, and pugmill of batch-mix plants. The drum of a drum-mix plant is much like the drye: of a batch plant, but it typically has more flights than do batch dryers to increase veiling of the aggregate and to improve overall heat transfer. The burner in a drum-mix plant emits a much bushier flame than does the burner in a batch plant. The bushier flame is designed to provide earlier and greater exposure of the virgin aggregate to the heat of the flame. This design also protects the asphalt cement, which is injected away from the direct heat of the flame. 253 Initially, drum-mix plants were designed to be parallel flow as depicted in Figure 7-27. 252 Recently, the counterflow drum-mix plant design shown in Figure 7-28 has become popular. 79 The parallel flow drum-mix process is a continuous mixing type process using proportioning cold-feed controls for the process materials. Aggregate, which has been proportioned by gradations, is introduced to the drum at the burner end. As the drum rotates, the aggregate as well as the combustion products move toward the other end of the drum in parallel. Liquid asphalt cement flow is controlled by a variable flow pump that is electronically linked to the virgin aggregate and RAP weigh scales. The asphalt cement is 7-115 | 1 2 a .-ill z iii m! o UJ o. I 2 « —i g £ 8 <5 ■a • • c l s s | IU O (L O t. ©®(D • Ob o _ UJ 0 \ z 11— > ( •r 2 s< Dl fS on (N c OJ u. £ u oc a o 3 O C/5 7-117 Figure 7-28. General Process Flow Diagram for Counter Flow Drum Mix Asphalt Paving Plants introduced in the mixing zone midway down the drum in a lower temperature zone, along with any RAP and PM from the collectors. The mixture is discharged at the end of the drum and conveyed to a surge bin or storage silos. The exhaust gases also exit the end of the drum and pass on to the collection system. 79 In the counterflow drum-mix type plant, the material flow in the drum is opposite or counterflow to the direction of exhaust gases. In addition, the liquid asphalt cement mixing zone is located behind the burner flame zone so as to keep the materials from direct contact with hot exhaust gases. Liquid asphalt cement flow is still controlled by a variable flow pump and is injected into the mixing zone along with any RAP and PM from primary and secondary collectors. 79 Parallel-flow drum mixers have an advantage in that mixing in the discharge end of the drum captures a substantial portion of the aggregate dust, thereby lowering the load on the downstream collection equipment. For this reason, most parallel flow drum mixers are followed only by primary collection equipment (usually a baghouse or venturi scrubber). However, because the mixing of aggregate and liquid asphalt cement occurs in the hot combustion product flow, organic emissions (gaseous and liquid aerosol) from parallel-flow drum mixers may be greater than in other processes. 79 On the other hand, because the liquid asphalt cement, virgin aggregate, and RAP are mixed in a zone removed from the exhaust gas stream, counterflow drum-mix plants will likely have organic emissions (gaseous and liquid aerosol) that are lower than those from parallel-flow drum-mix plants. A counterflow drum-mix plant can normally process RAP at ratios up to 50 percent with little or no observed effect on emissions. Today's counterflow drum-mix plants are designed for improved thermal efficiencies. 79 Of the 3,600 active hot-mix asphalt plants in the United States, approximately 2,300 are batch-mix plants, 1,000 are parallel-flow drum-mix plants, and 300 are counterflow drum-mix plants. About 85 percent of plants being built today are of the counterflow 7-118 drum-mix design; batch-mix plants and parallel-flow drum-mix plants account for 10 and 5 percent, respectively. 79 One major advantage of both types of drum-mix plants is that they can produce material containing higher percentages of RAP than batch-mix plants can produce. The use of RAP significantly reduces the amount of new (virgin) rock and asphalt cement needed to produce hot-mix asphalt. With the greater veiling of aggregate, drum-mix plants are more efficient than batch-mix plants at transferring heat and achieving proper mixing of recycled asphalt and virgin materials. 253 7.9.2 Benzene Emissions from the Hot-Mix Asphalt Production Emissions of benzene from hot-mix asphalt plants occur from the aggregate rotary dryers and the asphalt heaters (due to fuel combustion). In Figure 7-26, the emission point for the rotary dryer is indicated by SCC 3-05-002-01, and the emission pomt for the heater is indicated by SCC 3-05-002-06, -07, -08, and -09. Note that most of the emission points in Figures 7-26 and 7-27 are sources of paniculate matter. Most plants employ some form of mechanical collection, typically cyclones, to collect aggregate panicle emissions from the rotary dryers. However, these cyclones would have a minimal collection efficiency for benzene. Other types of controls installed at asphalt hot-mix plants, primarily to control PM emissions, include wet scrubbers or baghouses. 253 These controls are expected to have some effect on reducing benzene emissions; however, the control efficiencies are not known. Table 7-15 presents four emission factors for the rotary dryer at a hot-mix asphalt plant. 3,254 " 263 The factors range from 1.41x10^ lb/ton (7.04xl0' 5 kg/Mg) to 1.95x10' 5 lb/ton (9.75x1 O' 6 kg/Mg) and differ in the type of fuel burned to heat the dryer (LPG, oil, natural gas, or diesel) and the type of control device used (cyclone, baghouse, wet scrubber, or uncontrolled). Table 7-15 also presents one emission factor for an 7-119 w oc D H U < u. D Z < £ H < a: Cm 00 < X S i u- O ac c* c u* on DC O H r \ o < u- z o oo oo s LU uo W CQ < H D U c OJ M u— u D£ oc O w . 3 O MJ « «« u. a; u as U. c .2 CO C/2 00 2 w c o w — o o j> a> Q c o U 0) cj t_> 3 O t/3 CO C _o CO CO E cu o oo a> Q •o s U U c/5 NO l/-} r- NO m NO 00 fS (N ■a iU c o u C D 3 4J u. c 6 a. -J a> b C o as *— O U u © © ”x ”x o »/■> r~ oo r-»' rn c "o >% u 3 2 •3 aj a> i— Q l. 03 o Ea • 5 co 3 4> O = J= o go O ,2 >, CQ (j 00 OX) 75 u- 2 ec C © o ”>< *x «r» «n o\ r- — On * c. "3 E JS 2 a w 0> £ C/5 CT3 OX) 75 U 3 CC c uT ^ 4> 2 c -B ea s 2 9 O u. « o T V o o X X o o «n »o — r~ - ■o 4> cS cu S "e3 ■5 *3 CU u < c 7-120 * Emission factors are in lb (kg) of benzene emitted per ton (Mg) of hot-mix asphalt produced. uncontrolled asphalt heater fired with diesel fuel. The source tests from which these emission factors were derived all use CARB Method 401 for sampling. No regulations were identified that require control of benzene emissions at hot mix asphalt plants. 7.10 OPEN BURNING OF BIOMASS, SCRAP TIRES, AND AGRICULTURAL PLASTIC FILM Open burning involves the burning of various materials in open drums or baskets, in fields or yards, and in large open drums or pits. Materials commonly disposed of in this manner include municipal waste, auto body components, landscape refuse, agricultural field refuse, wood refuse, bulky industrial refuse, and leaves. This section describes the open burning of biomass, scrap tires, and agricultural plastic film, and their associated benzene emissions. 7.10.1 Biomass Burning Fires are known to produce respirable PM and toxic substances. Concern has even been voiced regarding the effect of emissions from biomass burning on climate change. 264 Burning wood, leaves, and vegetation can be a source of benzene emissions. In this document, the burning of any wood, leaves, and vegetation is categorized as biomass burning, and includes yard waste burning, land clearing/buming and slash burning, and forest fires/prescribed burning. 265 Part of the complexity of fires as a source of emissions results from the complex chemical composition of the fuel source. Different woods and vegetation are composed of varying amounts of cellulose, lignin, and extractives such as tannins, and other polyphenolics, oils, fats, resins, waxes, and starches. 266 General fuel type categories in the National Fire- Danger Rating (NFDR) System include grasses, brush, timber, and slash (residue that remains on a site after timber harvesting). 266 The flammability of these fuel types depends upon plant 7-121 species, moisture content, whether the plant is alive or dead at the time of burning, weather, and seasonal variations. Pollutants from the combustion of biomass include CO, NO x , sulfur oxides (SO x ), oxidants, polycyclic organic matter (POM), hydrocarbons, and PM. The large number of combustion products is due, in part, to the diversity of combustion processes occurring simultaneously within a fire-flaming, smoldering, and glowing combustion. These processes are distinct combustion processes that involve different chemical reactions that affect when and what pollutants will be emitted during burning. 266 Emission factor models (based on field and laboratory data) have been developed by the U.S. Forest Service. These models incorporate variables such as fuel type and combustion types (flaming or smoldering). Because ratios of toxic air substances are correlated with the release of other primary PICs (such as CO), the models correlate benzene witn CO emissions. 2 " Tnese emission factor models were used to develop emission factors for the biomass burning sub-categories described in the following sections. 265 Because of the potential variety in the fuel source and the limited availability of emission factors to match all possible fuel sources, emissions estimates may not necessarily « represent the combustion practices occurrmg at every location in the United States. Therefore, localized practices of such parameters as type of wood being burned and control strategies should be carefully compared. 265 Yard Waste Burning Yard waste burning is the open burning of such materials as landscape refuse, wood refuse, and leaves in urban, suburban, and residential areas. 265 Yard waste is often burned in open drums, piles, or baskets located in yards or fields. Ground-level open burning emissions are affected by many variables, including wind, ambient temperature, composition and moisture content of the material burned, and compactness of the pile. It should be noted 7-122 that this type of outdoor burning has been banned in certain areas of the United States, thereby reducing emissions from this subcategory. 265 - 267 An emission factor for yard waste is shown in Table 7-16. 265 - 266 Land Clearing and Slash Burning This subcategory includes the burning of organic refuse (field crops, wood, and leaves) in fields (agricultural burning) and wooded areas (slash burning) in order to clear the land. Burning as part of commercial land clearing often requires a permit. 205 Emissions from organic agricultural refuse burning are dependent primarily on the moisture content of the refuse and, in the case of field crops, on whether the refuse is burned in a headfire or a backfire. 26 ' Other variables, such as fuel loading (how much refuse material is burned per unit of land area) and how the refuse is arranged (piles, rows, or spread out), are also important in certain instances. 267 Emission factors for land clearing/buming and slash burning are shown in Table 7-lb 265 - 266 Forest Fires/Prescribed Burning A forest fire (or wildfire) is a large-scale natural combustion process that consumes various ages, sizes, and types of outdoor vegetation. 268 The size, intensity, and even occurrence of a forest fire depend on such variables as meteorological conditions, the species and moisture content of vegetation involved, and the weight of consumable fuel per acre (fuel loading). 268 Prescribed or broadcast burning is the intentional burning of forest acres as part of forest management practices to achieve specific wildland management objectives. Controlled burning can be used to reduce fire hazard, encourage wildlife habitat, control insects, and enhance the vigor of the ecosystem. 266 Prescribed burning occurs thousands of times annually in the United States, and individual fires vary in size from a fraction of an acre 7-123 TABLE 7-16. SUMMARY OF BENZENE EMISSION FACTORS FOR BIOMASS BURNING CUD .£ re 04 o re Uh e o C/3 E w 3J u > Cl> Q o c U •3 - o o o I o co o I NO CM 60 3 CQ 'ob 3 - re u ■a c re O o o I o o m I © I 00 CM o 'o/i ^^ c_> re Uh c © © © © © 'ob © X X X X X o • VO co vO CO C/5 3 m © *n o m C/5 *g U4 O £ •n ON s_^ On •a aj c o o 3 D 01) 3 3 CQ i£ C/3 _re o o O i uo o o i 00 CM ■a 4) E 3 X> co CO re r - H o LS CO c o 4) VO C 4/ VO U c OJ u. A) cm o u. 3 O oo •O .£ 4> i— re CO h* o CJ re CL 1 re 4> on < 7-124 to several thousand acres. Prescribed fire use is often seasonal, which can greatly affect the quantity of emissions produced. 266 HAP emission factors for forest fires and prescribed burning were developed using the same basic approach for yard waste and land clearing burning, with an additional step to further classify fuel types into woody fuels (branches, logs, stumps, and limbs), live vegetation, and duff (layers of partially decomposed organic matter). 265 In addition to the fuel type, the methodology was altered to account for different phases of burning, namely, flaming and smoldering. 265 The resulting emission factors are shown in Table 7-17. 7.10.2 Tire Burning Approximately 240 million vehicle tires are discarded annually. 269 Although viable methods for recycling exist, less than 25 percent of discarded tires are recycled; the remammg 175 million are discarded in landfills, stockpiles, or illegal dumps. 2 '"" Although it is illegal in many states to dispose of tires using open burning, fires often occur at tire stockpiles and through illegal burning activities. 267 These fires generate a huge amount of heat and are difficult to extinguish (some tire fires continue for months). Table 7-18 contains benzene emission factors for chunk tires and shredded tires. 267 When estimating emissions from an accidental tire fire, it should be kept in mind that emissions from burning tires are generally dependent on the bum rate of the tire. A greater potential for emissions exists at lower bum rates, such as when a tire is smoldering rather than burning out of control. 267 The fact that the shredded tires have a lower bum rate indicates that the gaps between tire materials provide the major avenue of oxygen transport. Oxygen transport appears to be a major, if not the controlling mechanism for sustaining the combustion process. 7-125 TABLE 7-17. SUMMARY OE BENZENE EMISSION FACTORS FOR BIOMASS BURNING BY FUEL TYPE O 3 a G O 3 cn oc cn E w t—1 o CTJ o 3 £ Uh G ~ob .x O '^n G cn O • -» e w O c o U > c _o w CS CN NO uo cn CN —< XJ 4J c o o G D OO c X5 *ri CZ — i CJ . . 3 ON o © o o o o X X NO CO NO CO *a i— tZ 00 c 3 c n CQ 3 ^ a ■o *o aj 3 X> O o C/5 3 G • mm W c o O 7-126 Live Uncontrolled 1.48 vegetation _ ( 7.4 x 10 *) TABLE 7-17. COMTINUED O 03 60| c -S O 03 "c/3 0^ C/5 o ca "So o 03 § u. 'ci* c m o • *■* C/3 c C/3 o E w OJ u > > OJ c o o CO c "&G c £ H— CQ V|— OJ c 3 2 Q Q o £ vO vO 15 o E •a 3 re re u oo 2 < 7-127 SNZENE EMISSION FACTORS FOR OPEN BURNING OF TIRES cc U- O >« QZ < S 00 oo i W CQ < H C c3 es o C3 U- c o fA C/5 e UJ c o o 03 U- c o C/5 £ U4 oo ~£b U u U s •e m o cn w -o cn so ON oo CO o c 05 >* •o & 3 H co O > ■— o cn 0) cn >< *5! i— 05 > o *8 £ 3 3 cn 05 cn •— ii — rt >— w- r: ° c & r—- I— ro W» 3 •- 2 ■“ > w - « C 0> 0) O i- >- 3 05 05 •- O. ^3 U ,?8 c o "8 o 3 05 •g cn E 3 — 5 « » w 05 c/5 S 2S i « cn « Cu O r- NO (S 0) o c 05 Ui ,05 05 OC 05 U u> 3 O CO JS oo CO u. Cm 05 O > co 'oo ■o 05 .£ § a 'S Sf 05 b> w 05 e3 cn la o cn 05 3 05 > cn 3 U. > H 7-128 7.10.3 Agricultural Plastic Film Burning Agricultural plastic film is plastic film that has been used for ground moisture and weed control. The open burning of large quantities of plastic film commonly coincides with the burning of field crops. The plastic film may also be gathered into large piles and burned, with or without forced air (an air curtain). 267 Emissions from burning agricultural plastic film are dependent on whether the film is new or has been exposed to vegetation and possibly pesticides. Table 7-19 presents emission factors for benzene emissions from burning new and used plastic film in piles with and without forced air (i.e., air is forced through the pile to simulate an air curtain). 267 7-129 TABLE 7-19. SUMMARY OF BENZENE EMISSION FAC TORS FOR OPEN BURNING OF AGRICULTURAL PLASTIC FILM OXj G •W cc c*. o tu G O w C/2 E w c o o eo U- c o *35 C/2 ‘5 fr> oo £ ~ob U u u u u u~, i/"', v*. w~. © © © © © © o O *“• X X X X X X X X cr> r- U-> r- r- CO 00 ■ O u* •w C w u 5 •-0 C3 ■a aj C/2 c D CN O i o £ c-w r= •o 52 £ jS o 3 O- ••2 c /3 E « 2 4> b a. C *3 2 So 3 c »- — M3 « cj 3 VO fN Um , 4) O u. 3 O C/5 ^<2 3 P CO U u u U Q C, n ft M M i~ u« *“0 0 C W M — O CJ « <2 <2 C3 c C co O O t id c« O co co o 3 '2 3 G U. UU UJ 7-130 SECTION 8.0 BENZENE EMISSIONS FROM MOBILE SOURCES This section quantifies benzene as one component of mobile source hydrocarbon emissions. These emissions occur from mobile sources as evaporative emissions from carburetors, fuel tanks, and crankcases, and as a result of combustion. Benzene is not added to vehicle fuels such as gasoline or diesel, but is formed during their manufacture, either through catalytic reforming or steam cracking. Most vehicle fuel is p T ‘"'ce? c ed usirg catalytic reforming In catalytic reforming, benzene is produced during the reaction that increases the octane rating of the naphtha fraction of the crude oil used as feedstock. Gasoline produced using this process is approximately 0.90 percent benzene (by weight). 158 (See Section 4.1 for an expanded discussion of catalytic reforming.) The other vehicle fuel manufacturing process, the use of steam cracking of naphtha feedstock to obtain ethylene, yields gasoline with a higher benzene content-20 to 50 percent. This fuel is blended with other fuels, before it is sold, in order to comply with the limited maximum concentration of 1.3 percent (by volume). However, steam cracking is considered a minor source of vehicle fuel. (Refer to Section 4.3 for an expanded discussion of pyrolysis gasoline and ethylene plants.) Diesel fuel, on the other hand, is produced by hydrocracking of the gas oil fraction of crude, and contains relatively insignificant amounts of benzene. 8-1 Benzene is emitted in vehicle exhaust as unbumed fuel and as a product of combustion. Higher-molecular-weight aromatics in the fuel, such as ethylbenzene and toluene, can be converted to benzene as products of combustion, accounting for approximately 70 to 80 percent of the benzene in vehicle exhaust. The fraction of benzene in the exhaust varies depending on vehicle type, fuel type, and control technology, but is generally between 3 to 5 percent by weight of the exhaust. The fraction of benzene in the evaporative emissions also depends on control technology and fuel composition, and is generally 1 percent of a vehicle's evaporative emissions. 8.1 ON-ROAD MOBILE SOURCES Results of recent work by the Office of Mobile Sources (OMS) on toxic emissions from on-road motor vehicles are presented in the 1993 report Motor Vehicle-Related Air Toxics Study (MVATS). 20 This report was prepared in response to Section 202(I)(l) of the 1990 amended CAA, which directs EPA to complete a study of the need for, and feasibility of, controlling emissions of toxic air pollutants that are unregulated under the Act and are associated with motor vehicles and motor vehicle fuels. The report presents composite emission factors for several toxic air pollutants, including benzene. The emission factors presented in the MV ATS were developed using currently available emissions data in a modified version of the OMS's MOBILE4.1 emissions model (designated MOBTOX) to estimate toxic emissions as a fraction of total organic gas (TOG) emissions. TOG includes all hydrocarbons as well as aldehydes, alcohols, and other oxygenated compounds. All exhaust mass fractions were calculated on a vehicle-by-vehicle basis for six vehicle types: light-duty gasoline vehicles, light-duty gasoline trucks, heavy-duty gasoline trucks, light-duty diesel vehicles, light-duty diesel trucks, and heavy-duty diesel trucks. 8-2 OMS assumed that light-duty gas and diesel trucks have the same mass fractions as light-duty gas and diesel vehicles, respectively. In developing mass fractions for light-duty gas vehicles and trucks, four different catalytic controls and two different fuel systems (carbureted or fuel injection) were considered. Mass fractions for heavy-duty gas vehicles were developed for carbureted fuel systems with either no emission controls or a three-way catalyst. These mass fractions were applied to TOG emission factors developed to calculate in- use benzene emission factors. These in-use factors take into consideration evaporative and exhaust emissions as well as the effects of vehicle age. A number of important assumptions were made in the development of these on-road benzene emission factors, namely: 1. The increase in emissions due to vehicle deterioration with increased mileage is proportional to the increase in TOG; 2. Toxics fractions remain constant with ambient temperature changes; and 3. The fractions are adequate to use for the excess hydrocarbons that come from malfunction and tampering/misfueling. It should be noted that, in specific situations, EPA mobile methods may over or underestimate actual emissions. The benzene emission factors by vehicle class in grams of benzene emitted per mile driven are shown in Table 8-1. 270 The OMS also performed multiple runs of the MOBTOX program to derive a pollutant-specific, composite emission factor that represented all vehicle classes, based on the percent of total vehicle miles traveled (VMT) attributable to each vehicle class. 20 For traditional gasoline, benzene is typically responsible for 70 to 75 percent of the aggregated toxic emissions. Most of this is associated with engine combustion exhaust. 8-3 TABLE 8-1. BENZENE EMISSION FACTORS FOR 1990 TAKING INTO CONSIDERATION VEHICLE AGING (g/mi) ■o ■C ^ OX) L_ 1 s > > u > Q Q as H Q Q hJ > 5 > o o Q rr H r ^ w Q > O Q oo o m m o TT (N O r- © o m sC a~) Tf tj- C?N o 00 C/3 co 1) cS kH o o. CO > w in o o r-» m o o o o s Tt o o d o d o C/3 60 o J OX) a 13 a o "o3 > C/2 C/2 O U. M -s 'i C/3 c ca > ■o c ca C/3 C. 3 i 4> •C op £ jL) o 2 • C/3 C/3 o ba OX) ■S £ C/3 o <— IS > j«c u 2 H u c OX) .x rx r- OX o © X) 0) 3-Sp o o © C/3 C/3 VO CO CC3 _ O O 2 >3 >3 O 3 3 ‘q Q Q ° I I «—/ «_• -C JO OX) OX) 3 □ II II TO c — ca \q co m Q. oo ? rn ^ o u is ‘EL prj — r- .X H O O Q Q x -J Q X. •o c ca t— o Q J <*- o >3 1— o _ OX) o OX) 3 ca u ■a OJ c 2 E S 4) cn oo 2 u 2 4) > 2 C ft 4> 4) 2 H *4) CM 4) •V 4) 2 H 4) C 2 c^ ca o >3 3 Q * 2 OX) 2 k a j j= 4) > 4) C 2 CO ca U >3 Q 3 >3 Q >3 n 3 3 ^ Q Q >% ^ 2 §§ 2 4> 2 4) > 2 e/3 4) Q « d 4> 2 2 .a Q n • O ST > O ^3 u ® o S S Z P o Q J II II II II II II H ^ > H ^ O O Q Q Q QQQQQU j x j j sc S 8-4 Oxygenated fuels emit less benzene than traditional gasoline mixes but more than diesel fuel. With the introduction of alternative fuels such as methanol blends, compressed natural gas (CNG), and liquified petroleum gas (LPG), formaldehyde is the dominant toxic emission, accounting for 80 to 90 percent of aggregated toxic emissions. 272 Reductions in benzene emissions associated with the use of methanol fuels is dependent upon the methanol content of the fuel. For instance, benzene emissions for M10 (10 percent methanol and 90 percent unleaded gasoline) are reduced by 20 percent compared with traditional fuel, and for M85 (85 percent methanol and 15 percent unleaded gasoline) the reduction is 84 percent (SAE1992). Ml00 (100 percent methanol), ethanol, LPG, and CNG emit minimal amounts of benzene. 273 Furthermore, because both LPG and CNG require closed delivery systems, evaporative emissions are assumed to be zero. 8.2 OFF-ROAD MOBILE SOURCES ror on-roaa mooile sources, EPA prepared me report Nonroad Engine Vehicle Emission Study (NEVES), 274 which presents emission factors for 79 equipment types, ranging from small equipment such as lawn mowers and chain saws to large agricultural, industrial, and construction machinery (see Table 8-2). The equipment types were evaluated based on three engine designs: two-stroke gasoline, four-stroke gasoline, and diesel. Sources for the data include earlier EPA studies and testing and new information on tailpipe exhaust and crankcase emissions supplied by the engine manufacturers. For test data on new engines, OMS made adjustments to better represent in-use equipment emissions taking into consideration evaporative emissions and increases in emissions due to engine deterioration associated with increased equipment age; therefore, new engine data underestimate in-use emissions. 274 Although these emission factors were intended for calculating criteria pollutant (VOC, N0 2 , CO) emissions for SIP emissions inventories, OMS derived emission factors for several HAPs, including benzene, so that national air toxics emissions could be estimated. To estimate benzene emissions, OMS expressed benzene emissions as a weight percent of exhaust 8-5 TABLE 8-2. OFF-ROAD EQUIPMENT TYPES AND HYDROCARBON EMISSION FACTORS INCLUDED IN THE NEVES (g/hp-hr) (FACTOR QUALITY RATING E) Equipment Type, Area and Mobile Source Code (2-stroke gas/4-stroke gas/diesel) 2-Stroke Gasoline Engines 4-Stroke Gasoline Engines Diesel Engines Exhaust Crank Case Exhaust Crank Case Exhaust Crank Case Lawn and Garden, 22-60/65/70-004- 025 Trimmers/Edgers/Brush Cutters 471.58* — 50.78* 7.98* — — 010 Lawn Mowers 436.80* — 79.17* 12.44* — — 030 Leaf Blowers/Vacuums 452.11* — 40.74* 6.40* ~ — 040 Rear-Engine Riding Mowers — — 19.53* 3.07* 1.20 0.02 045 Front Mowers — — 19.53* 3.07* — — 020 Chain Saws <4 hp 625.80* — — — — — 050 Shredders < 5 hp 436.80* — 79.17* 12.44* ~ — 015 Tillers <5 hp 436.80* — 79.17* 12.44* — — 055 Lawn and Garden Tractors — — 19.74* 3.10* 1.20. 0.02 UGvj UVJU SpliwlLri2> -- — *7Q 17* 13 5 hp — — 79.17* 12.44* 1.20 0.02 045 Swathers — — 10.77 b 2.37 b 0.90 0.02 050 Hydro Power Units -- -- 15.08* 2.37* 2.23 0.04 055 Other Agricultural Equipment — — 10.77 b 2.37 b 1.82 0.04 Logging, 22-60/65/70-007- 005 Chain Saws > 4 hp 319.20* — — — — — 010 Shredders >5 hp — — 19.53* 3.07* — — 015 Skidders — — -- — 0.84 c 0.02 c non 'D...- -- -- -- -- 0 £d c 0 02 e * Adjusted for in-use effects using small utility engine data. b Adjusted for m-use effects using heavy-duty engine data. e Exhaust HC adjusted for transient speed and/or transient load operation. d Emission factors for 4-stroke propane-fueled equipment. e g/hr. ' g/gallon. " = Not applicable. 8-9 hydrocarbons plus crank case hydrocarbons. In OMS's analysis, it was assumed that the weight percent of benzene for all off-road sources was 3 percent of exhaust hydrocarbons. 275 A range of OMS-recommended weight percent benzene factors for general categories of off-road equipment are presented in Table 8-3. 274 Note that development of equipment-specific emission factors is underway, and when available, those emission factors should be considered instead. To obtain benzene emission estimates from equipment in these general categories of off-road equipment, the benzene weight percent factors noted in Table 8-3 can be applied to hydrocarbon estimates from the different NEVES equipment types. The NEVES equipment emission factors can be used directly to estimate emissions from specific equipment types if local activity data is available. If general nonroad emission estimates are required, States may choose one of the 33 nonattainment areas, studied in the NEVES report, that is similar in terms of climate and economic activity; the NEVES nonattainment area can be adjusted to estimate emissions in another state by applying a population ratio of the two areas to the NEVES estimate. The NEVES report also has estimates for individual counties of the 33 nonattainment areas such that States or local governments may also produce regional or county inventories by adjusting the NEVES county estimates relative to the population of the different counties. Counties can be chosen from several of the 33 NEVES nonattainment areas if appropriate. For further details on how to calculate emissions from specific equipment types refer to NEVES, for details on calculating emissions of nonroad sources in general see Reference 271. 8.3 MARINE VESSELS For commercial marine vessels, the NEVES report includes VOC emissions for six nonattainment areas taken from a 1991 EPA study Commercial Marine Vessel Contribution to Emission Inventories} 16 This study provided hydrocarbon emission factors for ocean-going commercial vessels and harbor and fishing vessels. The emission factors are shown in Table 8-4. 8-10 TABLE 8-3. WEIGHT PERCENT FACTORS FOR BENZENE As Tested Use Recommended Off-Road Category Benzene % by Weight of FID HC a Diesel Forklift Engine Large Utility Equipment 2.4-3.0 Direct Injection Diesel Automobile Large Utility Equipment (Cyclic) Construction Equipment 3.1-6.5 Indirect Injection Diesel Automobile Large Utility Equipment (Cyclic) Marine, Agricultural Large Utility Construction Equipment - 1.5-2.1 Leaded Gasoline Automobiles Large Utility Equipment (Cyclic) Marine, Agricultural, Large Utility 3.0-3.4 Leaded Gasoline Automobiles (12% Misfire) Large Utility Equipment (Cyclic) Marine, Agricultural, Large Utility 1.1-1.3 1973 Highway Traffic 3.0 Source: Reference 274. lu i u.i uctiimeasured P~lame io niz aiion Detection. Ocean-going marine vessels fall into one of two categories-those with steam propulsion and those with motor propulsion. Furthermore, they emit pollution under two modes of operation: underway and at dockside (hotelling). Most steamships use boilers rather than auxiliary diesel engines while hotelling. Currently, there are no benzene toxic emission fractions for steamship boiler burner emissions. The emission factors for motor propulsion systems are based on emission fractions for heavy-duty diesel vehicle engines. For auxiliary diesel generators, emission factors are available only for 500 KW engines, since the 1991 Booz-Allen and Hamilton report indicated that almost all generators were rated at 500 KW or more. For harbor and fishing vessels, benzene emission factors for diesel engines are provided for the following horsepower categories - less than 500 hp, 500 to 1,000 hp, 1,000 to 1,500 hp, 1,500 to 2,000 hp, and greater than 2,000 hp. In each of these categories, emission factors are developed for full, cruise, and slow operating modes. Toxic emission 8-11 TABLE 8-4. BENZENE EMISSION FACTORS FOR COMMERCIAL MARINE VESSELS Operating Plant (operating mode/rated output) Benzene Emission Factor (lb/1000 gal fuel) 2 Ocean-Going Commercial • Motor Propulsion All underway modes 0.25 Auxiliary Diesel Generators ^ -• - - --- 500 KW (50% load) 0.87 Harbor and Fishing . Diesel Engines < 500 hp Full 0.22 Cruise 0.54 Slow 0.60 500-1000 hp Full 0.25 Cruise 0.18 Slow 0.18 1000-1500 hp Full 0.25 Cruise 0.25 Slow 0.25 1500-2000 hp Full 0.18 Cruise 0.25 Slow 0.25 2000+ hp - Full 0.23 Cruise 0.18 Slow 0.24 Gasoline Engines - all hp ratings Exhaust (g/bhp-hr) 0.35 Evaporative (g/hr) 0.64 1 Benzene exhaust emission factors were estimated by multiplying HC emission factors by benzene TOG fractions. Benzene exhaust emission fractions of HC for all marine diesel engines were assumed to be the same as the TOG emission fraction for heavy-duty diesel vehicles -- 0.0106. The benzene exhaust emission fraction for marine gasoline engines was assumed to be the same as the exhaust TOG emission fraction for heavy duty gasoline vehicles - 0.0527. The benzene evaporative emission fraction was also assumed to be the same as the evaporative emission HC fraction for heavy duty gasoline vehicles -- 0.0104. 8-12 factors are also provided for gasoline engines in this category. These emission factors are not broken down by horsepower rating, and are expressed in grams per. brake horsepower hour rather than pounds per thousand gallons of fuel consumed. 8.4 LOCOMOTIVES As noted in the U.S. EPA's Procedures for Emission Inventory Preparation , Volume IV: Mobile Sources, 271 locomotive activity can be defined as either line haul or yard activities. Line haul locomotives, which perform line haul operation, generally travel between distant locations, such as from one city to another. Yard locomotives, which perform yard operations, are primarily responsible for moving railcars within a particular railway yard. The OMS has included locomotive emissions in its Motor Vehicle-Related Air Toxic Study. 20 The emission factors used for locomotives in this report are derived from the heavy-duty diesel on-road vehicles as there are no emission factors specifically for locomotives. To derive toxic emission factors for heavy diesel on-road vehicles, hydrocarbon emission factors were speciated. The emission factors provided in this study (shown in Table 8-5) are based on g/mile traveled. 20 TABLE 8-5. BENZENE EMISSION FACTORS FOR LOCOMOTIVES Source Toxic Emission Fraction Emission Factor (lb/gal) Line Haul Locomotive 0.0106 a 0.00022 Yard Locomotive 0.0106 a 0.00054 Source: Reference 20. 1 These fractions are found in Appendix B6 of EPA, 1993, and represent toxic emission fractions for heavy-duty diesel vehicles. Toxic fractions for locomotives are assumed to be the same, since no fractions specific for locomotives are available. It should be noted that these fractions are based on g/mile emissions data, whereas emission factors for locomotives are estimated in lb/gal. The toxic emission fractions were multiplied by the HC emission factors to obtain the toxic emission factors. 8.5 AIRCRAFT There are two main types of aircraft engines in use: turbojet and piston. A kerosene-like jet fuel is used in the jet engines, whereas aviation gasoline with a lower vapor pressure than automotive gasoline is used for piston engines. The aircraft fleet in the United States numbers about 198,000, including civilian and military aircraft. 277 Most of the fleet is of the single- and twin-engine piston type and is used for general aviation. However, most of the fuel is consumed by commercial jets and military aircraft; thus, these types of aircraft contribute more to combustion emissions than does general aviation. Most commercial jets have two, three, or four engines. Military aircraft range from single or dual jet engines, as in fighters, to multi-engine transport aircraft with turbojet or turboprop engines. 278 Despite the great diversity of aircraft types and engines, there are considerable data available to aid in calculating aircraft- and engine-specific hydrocarbon emissions, such as the database maintained by the Federal Aviation Administration (FAA) Office of Environment and Energy, FAA Aircraft Engine Emissions Database (FAEED). These hydrocarbon emission factors may be used with weight percent factors of benzene in hydrocarbon emissions to estimate benzene emissions from this source. Benzene weight percent factors in aircraft hydrocarbon emissions are reported in an EPA memorandum 280 concerning toxic emission fractions for aircraft, and are presented in Table 8-6. TABLE 8-6. BENZENE CONTENT IN AIRCRAFT LANDING AND TAKEOFF EMISSIONS Description AMS Code Weight Percent Benzene Factor Quality Military Aircraft 22-75-001-000 2.02 B Commercial Aircraft 22-75-020-000 1.94 B Air Taxi Aircraft 22-75-060-000 3.44 C General Aviation 22-75-050-000 3.91 C Source: Reference 279 and 280. 8-14 Current guidance from EPA for estimating hydrocarbon emissions from aircraft appears in Procedures for Emission Inventory Preparation; Volume IV: Mobile Sources. 271 The landing/takeoff (LTO) cycle is the basis for calculating aircraft emissions. The operating modes in an LTO cycle are (1) approach, (2) taxi/idle in, (3) taxi/idle out, (4) takeoff, and (5) climbout. Emission rates by engine type and operating mode are given in the FAEED. To use this procedure, the aircraft fleet must be characterized and the duration of each operating mode determined. From this information, hydrocarbon emissions can be calculated for one LTO for each aircraft type in the fleet. To determine total hydrocarbon emissions from th? fleet, the emissions from a single LTO for the aircraft type would be multiplied by the number of LTOs for each aircraft type. The emission estimation method noted above is the preferred approach as it takes into consideration differences between new and old aircraft. If detailed aircraft information is unavailable, hydrocarbon emission indices for representative fleet mixes are provided in the emissions inventory guidance document Procedures for Emissions Inventory Preparation ; Volume IV: Mobile Sources. 271 The hydrocarbon emission indices are 0.394 pounds per LTO (0.179 kg per LTO) for general aviation and 1.234 pounds per LTO (0.560 kg per LTO) for air taxis. The benzene fraction of the hydrocarbon total (in terms of total organic gas) can be estimated by using the percent weight factors from Table 8-6. Because air taxis have larger engines and more of the fleet is equipped with turboprop and turbojet engines than is the general aviation fleet, the percent weight factor is somewhat different from the general aviation emission factor. 8.6 ROCKET ENGINES Benzene has also been detected from rocket engines tested or used for space travel. Two types of rocket engines are currently in use: sustainer rocket engines, which provide the main continual propulsion, and booster rocket engines, which provide additional 8-15 force at critical stages of the lift off, such as during the separation of sections of the rocket fuselage. Source testing of booster rocket engines using RP-1 (kerosene) and liquid oxygen have been completed at an engine test site. Tests for benzene were taken for eight test runs sampling at four locations within the plume envelope below the test stand. Results from these tests yielded a range of benzene emission factors—0.31 to 0.561 lb/ton (0.155 to 0.28° kg'Ms) of fu? 1 combusted—providing an average emission factor of 0.431 lb/ton (0.215 kg/Mg) of fuel combusted, as presented in Table 8-7. 282 It should be noted that booster fuel consumption is approximately five times that of sustainer rocket engines. TABLE 8-7. EMISSION FACTORS FOR ROCKET ENGINES AMS Code Emissions Source Emission Factor lb/ton (kg/Mg) Factor Rating 28-10-040-000 Booster rocket engines using 0.431 (0.215) 3 C RP-1 (kerosene) and liquid oxygen as fuel Source: Reference 282. a Emission factors are in lb (kg) of benzene emitted per ton (Mg) of fuel combusted. 8-16 SECTION 9.0 SOURCE TEST PROCEDURES Benzene emissions from ambient air, mobile sources, and stationary sources can be measured utilizing the following test methods: 283 • EPA Method 0030: Volatile Organic Sampling Train (VOST) with EPA Method 5040/5041: Analysis of Sorbent Cartridges from VOST; • EPA Method 18: Measurement of Gaseous Organic Compound Emissions bv Gas ChromatograDhv: • EPA method TO-1: Determination of Volatile Organic Compounds in Ambient Air Using Tenax® Adsorption and Gas Chromatography/Mass Spectrometry (GC/MS); • EPA method TO-2: Determination of Volatile Organic Compounds in Ambient Air by Carbon Molecular Sieve Adsorption and Gas Chromatography/Mass Spectrometry; • EPA Method TO-14: Determination of Volatile Organic Compounds (VOCs) in Ambient Air Using SUMMA® Passivated Canister Sampling and Gas Chromatographic (GC) Analysis; • EPA Exhaust Gas Sampling System, Federal Test Procedure (FTP); and • Auto/Oil Air Quality Improvement Research (AQERP) Speciation Methodology. If applied to stack sampling, the ambient air monitoring methods may require adaptation or modification. To ensure that results will be quantitative, appropriate precautions must be taken to prevent exceeding the capacity of the methodology. Ambient methods that 9-1 require the use of sorbents are susceptible to sorbent saturation if high concentration levels exist. If this happens, breakthrough will occur and quantitative analysis will not be possible. 9.1 EPA METHOD 0030 284 The VOST from SW-846 (third edition) is designed to collect VOCs from the stack gas effluents of hazardous waste incinerators, but it may be used for a variety of stationary sources. The VOST method was designed to collect volatile organics with boiling points in the range of 30°C to 100°C. Many compounds with boiling points above 100°C may also be effectively collected using this method. Because benzene's boiling point is about 80.1 °C, benzene concentrations can be measured using this method. Method 0030 is applicable to benzene concentrations of 10 to 100 or 200 parts per billion by volume (ppbv). If the sample is somewhat above 100 ppbv, saturation of the instrument will occur. In those cases, another method, such as Method 18, should be used. Method 0030 is often used in conjunction with analytical Method 5040/5041. Figure 9-1 presents a schematic of the principal components of the VOST. 241 In most cases, 20 L of effluent stack gas are sampled at an approximate flow rate of 1 L/min, using a glass-lined heated probe. The gas stream is cooled to 20°C by passage through a water-cooled condenser and the volatile organics are collected on a pair of sorbent resin traps. Liquid condensate is collected in the impinger located between the two resin traps. The first resin trap (front trap) contains about 1.6 g Tenax® and the second trap (back trap) contains about 1 g each of Tenax® and petroleum-based charcoal (SKC lot 104 or equivalent), 3:1 by volume. The Tenax® cartridges are then thermally desorbed and analyzed by purge-and-trap GC/MS along with the condensate catch as specified in EPA Methods 5040/5041. Analysis should be conducted within 14 days of sample collection. 9-2 Isolation Valvas 9-3 Figure 9-1. Volatile Organic Sampling Train (VOST) The sensitivity of Method 0030 depends on the level of interferences in the sample and the presence of detectable levels of benzene in the blanks. Interferences arise primarily from background contamination of sorbent traps prior to or after use in sample collection. Many interferences are due to exposure to significant concentrations of benzene in the ambient air at the stationary source site and exposure of the sorbent materials to solvent vapors prior to assembly. To alleviate these problems, the level of the lab blank should be determined in advance. Calculations should be made based on feed concentration to determine if blank level will be a significant problem. Benzene should not be chosen as a target compound at very low feed levels because it is likely there will be significant blank problems. 283 One of the disadvantages of the VOST method is that because the entire sample is analyzed, duplicate analyses cannot be performed. On the other hand, when the entire sample is analyzed, the sensitivity is increased. Anotner advantage is that oreakthrough volume is not greatly affected by humidity. 9.2 EPA METHODS 5040/504l 283 - 284 The contents of the sorbent cartridges (collected using EPA Method 0030) are spiked with an internal standard and thermally desorbed for 10 minutes at 80 °C with organic-free nitrogen or helium gas (at a flow rate of 40 mL/min), bubbled through 5 mL of organic-free water, and trapped on an analytical adsorbent trap. After the 10-minute desorption, the analytical adsorbent trap is rapidly heated to 180°C, with the carrier gas flow reversed so that the effluent flow from the analytical trap is directed into the GC/MS. The volatile organics are separated by temperature-programmed gas chromatography and detected by low-resolution mass spectrometry. The concentrations of the volatile compounds are calculated using the internal standard technique. EPA Methods 5030 and 8420 may be referenced for specific requirements for the thermal desorption unit, purge-and-trap unit, and GC/MS system. 9-4 A diagram of the analytical system is presented in Figure 9-2. The Tenax® cartridges should be analyzed within 14 days of collection. The detection limits for low-resolution MS using this method are usually about 10 to 20 ng or 1 ng/L (3 ppbv). The primary difference between EPA Methods 5040 and 5041 is the fact that Method 5041 utilizes the wide-bore capillary column (such as 30 m DB-624), whereas Method 5040 calls for a stainless steel or glass-packed column (1.8 x 0.25 cm I.D., 1 percent SP'1000 on ^ 0/90 rnesb Carbopack BV 9.3 EPA METHOD 18 285 EPA Method 18 is the preferred method for measuring higher levels of benzene from a source (approximately 1 pan per million by volume [ppmv] to the saturation point of benzene in air). In Method 18, a sample of the exhaust gas to be analyzed is drawn into a stainless steel or glass sampling bulb or a Tedlar® or aluminized Mylar® bag as shown in Figure 9-3. 285 The Tedlar® bag has been used for some time in the sampling and analysis of source emissions for pollutants. The cost of the Tedlar® bag is relatively low, and analysis by gas chromatography is easier than with a stainless steel cylinder sampler because pressurization is not required to extract the air sample in the gas chromatographic analysis process. 286 The bag is placed inside a rigid, leak-proof container and evacuated. The bag is then connected by a Teflon® sampling line to a sampling probe (stainless steel, Pyrex® glass, or Teflon®) at the center of the stack. The sample is drawn into the bag by pumping air out of the rigid container. The sample is then analyzed by gas chromatography coupled with flame ionization detection. Based on field and laboratory validation studies, the recommended time limit for analysis is within 30 days of sample collection. 287 One recommended column is the 8-ft x 1/8 in. O.D. stainless steel column packed with 1 percent SP-1000 in 60/80 carbopack B. However, the GC operator should select the column and GC conditions 9-5 Dssoji Hon S co l 3 u. O § a s h- § o 3 ■ (/) CO c • E a» 3 £ o -C*0 o ■5 9-6 Figure 9-2. Trap Desorption/Analysis Using EPA Methods 5040/5041 Male Quick c © > diy-Bf-M1d-S600^6 © _> a > m oo 00fr6 9-17 Source: Reference 290. The major advantage to using a dilution tube approach is that exhaust gases are allowed to react and condense onto particle surfaces prior to sample collection, providing a truer composition of exhaust emissions as they occur in the atmosphere. Another advantage is that the dilution tube configuration allows simultaneous monitoring of hydrocarbons, CO, C0 2 , and NO x . Back-up sampling techniques, such as filtration/adsorption, are generally recommended for collection of both particulate- and gas-phase emissions. 292 9.8 AUTO/OIL AIR QUALITY IMPROVEMENT RESEARCH PROGRAM SPECIATION METHOD Although there is no EPA-recommended analytical method for measuring benzene from vehicle exhaust, the AQIRP method for the speciation of hydrocarbons and oxygenates is widely used. 292,295 Initially, the AQIRP method included three separate analytical approaches for analyzing different hydrocarbons, but Method 3, the method designated for benzene, was dropped from use because of wandering retention times. Method 2 can be used to measure benzene from auto exhaust but some interferences, which will be discussed later, may occur. This analytical method calls for analyzing the bag samples collected by the FTP method by injecting them into a dual-column GC with an FID. A recommended pre-column is a 2 m x 0.32 mm I.D. deactivated fused silica (J&W Scientific Co.) connected to an analytical column that is 60 m DB-1, 0.32 mm I.D., 1 film thickness. 295 The detection limit for benzene with this method is 0.005 ppmC. The peak areas corresponding to the retention times of benzene are measured and compared to peak areas for a set of standard gas mixtures to determine the benzene concentrations. However, there is a problem with benzene co-eluting with 1-methylcyclopentene. Therefore, the analyst should be aware of this potential interference. 9-18 The amount of benzene in a sample is obtained from the calibration curve in units of micrograms per sample. Collected samples are sufficiently stable to permit 6 days of ambient sample storage before analysis. If samples are refrigerated, they are stable for 18 days. 9-19 ' SECTION 10.0 REFERENCES 1. Toxic Chemical Release Reporting. Community Right-To-Know. 52 FR 21152. June 4, 1987. 2. U.S. EPA. 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Washington, D.C.: U.S. Environmental Protection Agency, Office of Solid Waste and Emergency Response, November 1986. 285. U.S. Code of Federal Regulations. Title 40, Protection of the Environment, Part 60-Standards of Performance for New Stationary Sources, Appendix A—Test Methods, Method 18—Measurement of Gaseous Organic Compound Emissions by Gas Chromatography. Washington, D.C.: Government Printing Office, July 1, 1994. 286. Pau, J.C., J.E. Knoll, and M.R. Midgett. A Tedlar® Bag Sampling System for Toxic Organic Compounds in Source Emission Sampling and Analysis. Journal of Air and Waste Management Association. 41(8): 1095-1097, August 1991. 287. Moody, T.K. (Radian Corporation) and J. Pau (U.S. Environmental Protection Agency). Written communication concerning Emissions Monitoring Systems Laboratory. June 6, 1988. 10-26 288. Entropy Environmentalists, Inc. Sampling and Analysis of Butadiene at a Synthetic Rubber Plant. EPA Contract No. 68-02-4442. Research Triangle Park, North Carolina: U.S. Environmental Protection Agency, Atmospheric Research and Exposure Assessment Laboratory, Quality Assurance Division, October 1988. pp. 3-5. 289. U.S. EPA. Compendium of Methods for the Determination of Toxic Organic Compounds in Ambient Air. EPA-600/4-89-017. Research Triangle Park, North Carolina: U.S. Environmental Protection Agency, Atmospheric Research and Exposure Assessment Laboratory, June 1988. 290. U.S. Code of Federal Regulations, Title 40, Protection of the Environment, Part 86, Subpart B, Emission Regulations for 1977 and Later Model Year New Light-Duty Vehicles and New Light-Duty Trucks; Test Procedures. Washington, D.C.: U.S. Government Printing Office, 1993. 291. Blackley, C. (Radian Corporation) and R. Zweidinger (U.S. Environmental Protection Agency). Teleconference concerning mobile sources testing, May 10, 1994. 292. Blackley, C. (Radian Corporation) and P. Gabele (U.S. Environmental Protection Agency). Teleconference concerning mobile sources testing. May 10, 1994. 293. U.S. EPA. Butadiene Measurement Technology. EPA 460/3-88-005. Ann Arbor, Michigan: U.S. Environmental Protection Agency, Office of Mobile Source Air Pollution Control, 1988. pp. 1-23, Al-15, Bl-5, Cl-3. 294. Lee, F.S., and D. Schuetzle. Sampling, Extraction, and Analysis of Polycyclic Aromatic Hydrocarbons from Internal Combustion Engines. In: Handbook of Polvcyclic Aromatic Hydrocarbons , A. Bjorseth, ed. New York, New York: Marcel Dekker, Inc., 1985. 295. Siegl, W.D., et al. “Improved Emissions Speciation Methodology for Phase II of the Auto/Oil Air Quality Improvement Research Program-Hydrocarbon and Oxygenates.” Presented at the International Congress and Exposition, Detroit, Michigan. SAE Technical Paper Series. Warrendale, Pennsylvania: SAE 930142. March 1993. pp. 63-98. 296. AP-42, op. cit., reference 31. Draft Section 12.2: “Coke Production,” January 1, 1995. 10-27 3 APPENDIX A SUMMARY OF EMISSION FACTORS . TABLE A 1 . SUMMARY OF EMISSION FACTORS 00 0 re QS o re U. cj re U. c .o 05 05 *r~ 3 UJ u Q o U cj — o 00 C/0 < U U in u -a u ZJ \s. v~. ZJ o 3 /— 55 aj jj .3 UJ D D C/5 c _c C/5 00 E rr c u a> c /3 v cj m fS m ■*r 3 cj 0 C/3 4) 0/ C/3 m O O 1 • o C/5 C/5 C C/5 05 D CO c cj CJ Q V CJ «3 3 U o -3 cp c/3 2 /-s c- re > o E 5 J v C /5 5 3 1— 3 re D O re CJ D D <- 00 r- 05 3 00 00 E tu re aj 3 u 3 cr UJ 05 3 O 05 00 E UJ 3 're O 05 00 4) OJ - O .3 U 2 3 — in go re aj > CO 3 „ 12 CO c 3 0 • CO _s 1 CO 3 re • 00 3 1 co 3 re on 0 •i ^ C/5 # 3 re C/5 O •r gj 3 Q 3 1— 3 c _o 1 — 3 re "d 3 E 2 3 _o CJ X 3 O SJ 0 "re cj re 0 U O UJ O '05 05 <2 0 3 2 .re > 3 g ,re L —1 3 k. 0/ 3 <2 3 O kre 3 CC L —1 3 ■a •§ _J 3 i_ 3 E 3 CJ 3 O 3 ^ a UJ u C 00 00 re 3 2 tt* re i> 2 « re 00 0> OS re 00 re S C D .2 i> re V ■*—> CJ Urn u CJ u CJ 3 c/5 5 0 3 C/5 3 3 C • ^ k- Cl 0 ) >5 JJ c Q. 2 i E 3 O >> T3 2 ">5 0 '3 ^ u Si s O X Sr w ^ ■5 '0 •s c3 ■5 u 0 ■5 o - -5 u uj a. u < UJ U UJ CO UJ UJ UJ M D D (N 8 o © o 3 00 2 2 x '00 — juc •O T 3 13 •O 0 •0 •a _ 0 J _ 0 J JJ u _D jj Q O "5 O ~3 0 0 kH 1 — k> i— O 1 — 1 — 3 r- <—■ 3 X 3 3 C O O O CJ D 0 u Q o U •a OJ 3 o o ■o 3 c c a •o OJ c o o oo a •o ja Wrt eg T3 T3 00 _c w •a cq £ o c- U "O OJ QJ "o k> u "o i— o 3 eg CQ c o eg > c o 3 O CQ cn o c o ej j= CJ _c C /5 eg r w — 'v. — ■—■ W •o a> c o o c 00 _c w (U s Cg CQ C /5 eg •O 3 O oo 5J > -a c Q aj OO o 3 H. C * u- Un u t— CJj § c r -c w' o £ 2 CD .£ gj u k* £ ^3 u 5 03 U a; 00 eg k- C r“ c w> o u ►— u. C3 "cb £ a. as cyt SJ CJ O r“ 1 Ui Q Ww 03 D u. 03 Cn kk eg 0 £ i H i z w< a. H H H H o- E 3 00 J= OO c o c~ 'k. C/5 9J Q oo 2 5 eg „ u ffl C ^4 - k- • 52 3 £5^ wo m C<0 O i ro "O aj 3 C C o o A-2 Light Oil Storage Uncontrolled 0.012 Ib/ton (5.8 g/Mg) Gas Blanketing _ 2.4 x 10 4 lb/ton (0.12 g/Mgl TABLE A-1. COMTINUED OO ET re at o re U- u C3 u. s .o ’ -X o U u 3 w CD UJ tu W UJ UJ UJ ID UJ UJ O0 a M oc 'ao /*-V g "Sb ~Sb OX) s ~ob nf) 'Sb ps| vo au 00 o 00 o 00 m (N o in in "W 3 c C c © c o c O o w o jo £ £ £ £ £ CN o VO T O VO T O ’ 1 £4 © X c X X d TT o ni (N ni in oo s ~oc w o o w £ 00 © o 00 00 00 2 00 2 s 00 "eb "ob "ob 00 ~ob vo "eb vo m 00 t-» 00 r- © cn o cn o o o o c a c o c o 3 o w £ o £ o J© !o m in T o T © T o o o X X X VO X VO X VO r- m vn in co re o u .x o U i> u c re c ■§ i— u. cl cl i i 3 CD O t m ■o OJ 3 3 c o CJ m O i m u m a u oo "ab (N c o £ o u Q 00 cz 00 OO 00 oo c z 3 3 3 3 •o T3 T3 •o •a ■o •a "o £ flj _4J u- o 00 c JJ 3J £ «J o JLJ t) jj i— 3 Q o u. •a cz O Ui w C CJ "o Ui 1 re "o u Ltf 3 "o u LC 3 re o u uc 3 re o u u 3 O CQ 3 O O0 O OJ •a 3 O CQ 3 O — CQ 3 O CQ 3 O OQ 3 O U C/5 o u- c u 1/3 u 1/3 u C/3 o V3 a *“ rc 3 w 3 re 3 re 3 re 3 re 3 *—v r ^ ? r"' r"v •—l Vu c o . 3 J u. Q re t- 2 •—* L» o cr 3 i— 3 u. J £ O on 0 ) U u< .2 2£ c re O0 o 3 cd Ux 03 3 O a O OJ u w t; O0 u cr 3 a; n u a> re _E b* o Cn a> 3 J i oo c < 1 C/5 C/5 c r— o 1 op CJ o 5 i X CQ N 3 OJ CQ Flusl Tank OJ o X UJ Tank C 3 "to CC "o o U co co o I = 3 >3 "O "O U. 0 0-0 u. ui e & & 3 • i a >> >3 rT CQ CQ w T3 O 3 C o o m m o I m A-3 -Tar Bottom Uncontrolled 0 10 Ib/ton (51 g/Mg) Light Oil Condenser Vent Uncontrolled 0.096 lb/ton (48 g/Mg) _ Gas Blanketing _ 1.9 x 10 3 Ib/ton (0.97 e/Mg) TABLE A-1. CONTINUED 60 C CO Oi o CO u- B3 uu BJ 60 2 'eb ryf) U* OX) 'eb O o CO ~60 o cn «s o ~eb «T3 "eb Os Um oo d c o • M C/5 C/5 c o c o a o c o 'E £ — £ 3 UJ SO o v/ Os Q o 60 ~eb cs d 60 'So m rJ 60 | "eb d 60 "eb 60 60 2 60 £ 60 60 S 60 60 m c o c o e o ii £ £ = X> -> T O m O o X TT O Q "o c o U co ■a o> ca U •a c o o c CO > 03 c o o c ID e o o c r> 03 jo cq •a 03 co c CD .X C CO •a 03 60 •S -o n \ CXj C 60 a 03 .x c CO •a ■s CO CQ ■a a> co Z ■a c a o OJ Q 03 60 CO i_ O D3 E 3 C/3 o 1 u. O DO o 1 £ 03 60 co u. O D3 X co u. O t/3 03 C 03 N e c u. C- ill CO CO u_ Ui CS H u< CO q 60 J 60 J H CQ 03 CQ o 3 cr 60 c -e ^ -3 CO U« E— 03 .x >,u 23 Lx 52 -o 9 § .x i2 o w <-> C — CO .—, U 3 3 3 0- 43 •0—3 o - - S -S 0- T3 c ■ P O CQ CL u U Q o — /•*■> —/ U c C/3 c o C/5 c/5 C .c 'C o C/5 cj Q on < o r • r 'I u on w LU U1 ID U U D 3 D 3 'So 'So J^V 'So D£> OX) 1 DO S ' 5 b ~ 5 b "no 'ob © 'So "So q OJ O — o — d — o X X X 1 q K fS K (S X 5 eo ■a >> CO 73 ~Sb jc o >5 eo 73 >5 CO 73 'no 4 *; on O >5 co 73 >5 CO 'So u. On >> CO 73 43 l/n ^ S3 i: == ^ ±: £3 (S 7T >5 co •a "So 4C » eo 73 >■. co "no 44 C4 m Sn eo 73 co cj CO c CO c DC c c _c cj cj c. C/5 c c 0 / C/5 =s cj _CJ o CJ _0J a3 _CJ 1) CJ JJ C/5 £ MU •o o c ”o "o c CJ ^GJ u. 2 i— c5 k. j2 l_ CO c o X c o ca c o CQ c o w X c OJ CO C/5 CJ C/5 CJ C/5 CJ C/D CJ CO 1) _c c CS c CO c 3 w c^ To o D a D o D a 2 D > c c _o c CO o CJ U O s CJ — CJ Cj 73 JJ (0 J3 a. V5 _c lo O u. _>5 u _>> —• Q C o CJ M X c o u- O CJ 3 D eo 3 a CJ C/5 D *co a-> oo CO r— o C H < i c/; c/: Gj cj z: x co [zl — aj c CO CJ QJ c/5 co C CO jo =3 a u o c/5 co C/3 Cj > 3 a. CO ■g o _ u -3 -g " o n cj t. w *a 33 CL >, S 73 - “ o' 1 •§ £ 8 o — £— CJ 44 o U cj 33 •o o O X •§ o “ i— a. -jr CQ 03 O un I m 8 i m o I m cj 44 O U » 3 CQ U. on i m 8 ■ m © CO 4= 00 >5 >> CJ > o cj CJ Ct CJ > o CJ CJ 0C A-5 (continued) TABLE A 1. CONTINUED OO c re 02 u re UJ tu E UJ D D 3 > u Q ,_, ■>- re re >> re re *o 5^ re /"N re ■o l re "ob L/n ~ob -X "ob LxC ~ob M ~ob 'ob L*C "ob 00 rs • m o r- «n m CN o o o i ■-—' i ci O ! o re re 2 u3 re 5 2 re 2 2 5^ re 2 2 re *o 2 >% re 2 2 fN ON (N O m ON c/n 1/3 vC CNi CN NO m CN o o o o c o c c c o c o u TJ OJ o u c- (/I c D LI a. CO 3 CO C CO 3 c -*c co 'ft .2 C o c o u c u — re 3 O' s o CO 3 C/5 rtj re Jr oo ** O 5 <*- > o >- 4J a> co CO U O 02 •o L-i c o o c D re 3 o 5 c o 2 Cl 3 02 •a Q x UJ co u E re 00 u X 3 t- o « • ^5 & CQ £ o - Uc! O U u oo u 3 •a o C/0 s w < -9 o U U u on U O re 0. 3 ^3 >) >i l) L. L- 3 a/ a> c > .3 8 - > o u ^ 3 > re •a 00 L*: re •a oo cn © oo U»C fS (N «■ ■O >» re TD ■'d' CC O o On 00 3 3. £ re on a/ OO ■o re > >% re ~o oo JxC 00 o re ■a .£ 00 3 O CJ CL CO 3 u re 3 O' 3 U rj U o l— CL CQ u CQ 1 CO aj re £ o u w O ° u a> > o o C 8 re •a m 3 O o u o. co 3 2 3 O 3 •O O >% • - ©c aj l* O « re > E 8 >* 3 OJ CQ UJ 02 oo 3 J3 3 oo c: ■Jj t> 3 02 *o 3 C C o o cn m m o m Use of Sealed Bellows Valves __ SCC/A MS Code _ Description _ Hmission Source _ Control Device _ Emission Factor _ Factor Rating 3-03-003-15 By-Product Coke - Pumps l ncontrolled 5.1 Ib/day (2.3 kg/day) U Furnace Coke By-Product Recovery Quarterly Inspection 1.5 Ib/day (0.67 kg/day) U -j o 0£ u D D D D D D / ^ s s • >» >% v /■—s >% re CT3 >> >> >> re or 1 w •O -a re cz CS ;a ob ***•»«. ***■»* •o "O CD 00 CO O0 "ob Lx: L* Lx: "So 'cb 'cb Lx: On 00 © lx: t— 3 m v >> >* >% >> >> >> >% >-> re re re re re 5 5 jB 5 o 5 sO LI 8 . to LI re 3 C O CL to C .O c o OC CxT) *35 c C/D (U C3 CD > u> a ‘o > O L O LI to u •a o c o o co u. Zj it rz •C X UJ iO > 2 '£ ao c: 4) 3 OS O = .22 to w O l> u CL to c >> 2 C u L> CL to C tZ Jd Ll CT3 3 C O u 3 H. 3 cc L- g o g 4> to J? ^ — 00 T3 a c o o c 00 c CO 00 l> 00 k. 3 CL I •a li to o •a u c Q u to C o u li c c U CO CL c co 00 c. re U u 3 to li c ■3 Ll ■a c D i c Li CL o A-7 (continued) OO ST eg CC cj eg tt. D G 3 D G ^ 3 3 3 o eg U- E UJ Do eg 5 ~ob Jx: 50 eg 5o eg o Do 5o eg *3 eg eg ;o 'ob jx: "ob jx: 'ob Jx! "ob JxC 'ob Jxi ^ ^ eg eg eg 73 ;o ;3 ~~ "to JXJ 2 8 S «/7 — O CO o CUD CUD JC J< 1/7 *— CA CJ Q u7 co — d x r~_ co XI £ 50 >» >7 eg eg eg ■o ;o ;o XXX 5o 50 eg eg 73 73 DO eg 73 Do eg 73 v© X 07 1/7 CN o CN o 07 — 07 CO ru 07 d c c a Js eg o c o c o o u cj LI CL C/3 s CJ cj CL 1/1 L> X '= .2 -5 7- Do 73 JJ eg u 07 73 cj cj CJ CL 03 s cj L> Cl C/3 3 c o c o O >7 eg 3 a 73 CD CJ u Cl e/3 C u cj CL C/3 s O >7 c o cj c r*\ w u < C3 CC < 3 o 07 U- a> X o CO a-) 3 o a> 1— 4— a: 3 3 O CO > CJ 3 C3 3 ►o. fc— ' *— w X s o 2 c/3 o « « CJ 3 O cj 3 o eg 3 /-v X 3 O OJD 3 CO co C C/3 CJ t— Q ’o Cm > o u. CJ CJ CO C/3 CJ V 3 O ux: C/3 T* -2 G 73 L> CJ LI a. 03 3 u O X' 3 O o 3 LI eg 3 O ■s 3 O 3 O- 3 o£ <*- p o g U co ” 5o D c© 73 L> a eg u 3 O 3 ’ 2 co LI ej > u Q CO 3 O cj l> CJ co u. U LI Q£ L) O u oo 3 _> eg > 3 £. eg X >< UJ 3 C/3 CO LI E eg 07 cj CO D a 07 < u u 07 LI > o o CJ a: cj 3 LI > c CJ CJ LI 73 OC O "O U °T H CD _ >>CQ o CQ — — ^ O u. w 73 £ 73 — °r % § DO O CQ U. w 07 CO co O CO A-8 ' "O aj =3 C C O o TABLE A-1. COMTINUHD OO s re OS u re CL •_> re CL s .o "S3 02 £ UJ u > l> Q o c o U ■_> 3 O V) 3 O 02 02 U Vi U Q on 2 4J < -5 U 0 u on re 3 "ob m m O >* re 3 r-> o v 5J L> CL -o .2 9 e _j 3 w O >. cl ^ D D D D D >% re oo o (N >» re •a o re re 3 3 00 L< r-~ o >% re •a LT. 00 >> re 3 m >» re ~ob u, C4 >» re •a >» re •a 'oo lc VO d re 3 £ — r- 00 : oc >, • re oo c* *rt o >» re ■a rr — > re > v L _> re > or r; O —- a. OJ o tu > o 8 >; U a o w w > ^ 0 0 0 3 3 3 0 0 ■onus o o a: s £ *-> > s <-> s o s OS 02 o ^ 3 u D D D ^ ^ re re re 3 3 3 00 LC on » re 3 on on 02 I— u 02 re •5 CL OO >> re ■a rs o oo Ov o . >. re •a (N o •a aj 3 a o o CO 3 on u 3 3 3 ‘E 3 3. re o (ion o 13 t3 CT3 t3 _C t3 on O Li CJ o o Cl V O- u CL •3 _0 o OO k> •3 _o Vi 3 CL v> _3 v3 rc •3 VD c CL 02 3 ~cz •3 JJ 02 c u. a. "o i_ j>% on "c u 3 c O Um _>% 3 o o ■a o 02 _o 3 O o 3 a> H 3 J3 «— 3 O o OJ C/D alves 3 O o 3 a> u. C3 3 3 O o qj c>n Seals 3 O u 3 ~ re 3 _ '"V — _ '-v a o CL V) C n= >2 o o > o O u ft. a. x i i >% >> t— CO 02 CQ on i m 3 o o V "3 •* P O £ u °r . «- >. os o CO — ■§ >% O CO o ± Z. E q- ^ J= c . 3 >V o 4) 02 CL w OS on c*n O I m m o I co A-9 1 Ise of Degassing Reservoir Vents TABLE A-1. CONTINUED - oo a re CC o re U- D O 3 3 D D 3 o re u- c .2 "co CO E tu >> re ~ob u. «3 "ob — e'¬ en —< *_» £ > li a 3 o U >* re 13 DC VO Sn re 3 cn re "ob «n >* re 3 cn 3 01 li li CL co 3 li 3 C cn c o " co CO CO LI < 3 U u U CO co v CJ > OJ Q 3 o: li CO CO LI V V > o o _ v aj OS 03 o • 3 D 3 ±6 O u °r — >% v CQ •3 >L 2 *1 °r § o CQ U- cn >% re ~ab oo ere d re £ rvJ VO d >-» re "ob cn s d >> re 3 in Ov 3 o 0X3 oo ~ob CO Q LI l-i s CL 3 QC oo s "o. E re r - o c is 3 ... xs co >> cn 3 D 3 o o c CL re U 3 £ ”5 CO LI 00 u> 3 £ re LI I 3 £ "o Urn, 3 £ "o L> 3 £ O ■_> 3 £ "o L> i_ o oo 3 CL V— 3 O u 3 3 CL 1 LI co O U CO CO LI LI O i— 0_ 3 O o 3 ^3 Flare 3 O U 3 D Flare 3 O LI 3 D Flare 3 O LI 3 3 co c .2 — o V c c o OO c E re cn LI LI > k* 3 1— co CO o CO LI LI .E o re k- 0- -co -j LI DC "o 3 3 4 Z u LI r - LI > 3 5 £ 3 CL C LI re is E 3 LI L»i E •§ CL o < < U c LI > E 3 re > u. LI X E 3 Li re > D C V 3 O H • t LI C LI N 3 3 c QJ LI CQ > V > o o LI 111 §= I re L> © J /V o. OD 00 3 k> ,. 3 kl u c *E k. LI 3 — 3 3 3 > O g > O E £ 2 u u— o LI LI 3 . 3 O 3 QC re 2 3 3 LI S % S 3 LI OO -> -n £ g W < g'fr § Q ^ qj £ § Jr a 3 li W CQ CAU 3 > E C S .2 g « C*_ CJ re *o S £ LI LI 3 3 V V u« k- >L >"> Cn Cn cn o i cn 3 O cn £ OO — ere f ere o O Jx: o 8 o s d 3 ere cn 00 ~eb ere ox s w cn a o £ VO 8 o LI k> £ E 3 LI > 3 O re re CL LI CO LI OO c w- •3 •a LI 3 i LI O0 o > .E 3 b o L) .re re 3 CL 3 re cn 2 e LI LI OO 3 O li ±; V- TJ >» 55 DC ere o cn O 3 O ere o 1 cn o 1 1 Ov VO Ov VO Ov VO VC o ere VO o ere i i o i o 1 o O 1 O 1 cn 1 cn cn cn cn A-10 "O 110 — .x C o 3 S '3 2T © *? T 2 o 0* « 2 o r*\ n © © T © ¥0 © X X X X X X X X X X t" VO VO 00 g o O o ?8 VO CN 00 —" *■* 00 CO _J Tf CN VO 2 2 c u re > > 5J OO , ^ ■ *— "o u* c re c 2 o o QL 13 oc c _o "o B O u c o u .2 CJ 2 CJ a> Ua u- 00 _c re 9J Wa _re E OJ Q c u c D O U. o c c0 Cj r s: c 3 OO 3 La - - * La 'vJ E La 3 O 3 3 CJ 3 o U CJ c U c« CJ c 2 oo 3 .£ CLa 3 03 H re 5 ^ *5 crj .« CLa 3 re ^ ^ u. 3 re X 3 3 re re s S Q S S 2 s CJ s CJ CJ CJ w oj n CJ 3 C 3 C /3 c ‘■7 3 OJ CJ CJ 2 x CJ £ 3 E 2 3 E 5/5 3 « E 3 U 3 re cj 3 u m u U > u ^ U CN © c*o © S VO o so VO vo v 6 VO VO VO VO —' —* 1 2 , 2 a © © © © cn CO co CO 3 J3 O U > o o (U D£ cj OJ c u oo c cj 3 3 c CO s 3 o O CO c *a > > > > > c« C/9 C/3 to C/9 C/3 7! C/5 C/3 to 7! C/3 CJ CJ OJ OJ CJ OJ CJ CJ O CJ CJ CJ Q n Q c r* Ua Ua kX La tx a. Cl Oa a- Cl Cu CJ 3 CJ E 3 u oo 3 u ,05 L— I 3 C CO C _o O re e -a CJ •“ X X a. 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