CONTROL TECHNIQUES
FOR HYDROCARBON
AND ORGANIC SOLVENT
EMISSIONS
FROM STATIONARY SOURCES
U.S. DEPARTMENT OF HEALTH, EDUCATION, AND WELFARE
Public Health Service
Environmental Health Service
-------
CONTROL TECHNIQUES FOR HYDROCARBON
AND ORGANIC SOLVENT EMISSIONS
FROM STATIONARY SOURCES
U. S. DEPARTMENT OF HEALTH, EDUCATION, AND WELFARE
Public Health Service
Environmental Health Service
National Air Pollution Control Administration
Washington, D.C.
March 1970
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National Air Pollution Control Administration Publication No. AP-68
For sale by the Superintendent of Documents, U.S. Government Printing Office
Washington, B.C., 20402 - Price $1
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PREFACE
Throughout the development of Federal air
pollution legislation, the Congress has con-
sistently found that the States and local
governments have the primary responsibility
for preventing and controlling air pollution at
its source. Further, the Congress has con-
sistently declared that it is the responsibility
of the Federal government to provide tech-
nical and financial assistance to State and
local governments so that they can undertake
these responsibilities.
These principles were reiterated in the
1967 amendments to the Clean Air Act. A
key element of that Act directs the Secretary
of Health, Education, and Welfare to collect
and make available information on all aspects
of air pollution and its control. Under the
Act, the issuance of control techniques infor-
mation is a vital step in a program designed to
assist the States in taking responsible tech-
nological, social, and political action to pro-
tect the public from the adverse effects of air
pollution.
Briefly, the Act calls for the Secretary of
Health, Education, and Welfare to define the
broad atmospheric areas of the Nation in
which climate, meteorology, and topography,
all of which influence the capacity of air to
dilute and disperse pollution, are generally
homogeneous.
Further, the Act requires the Secretary to
define those geographical regions in the
country where air pollution is a problem—
whether interstate or intrastate. These air
quality control regions are designated on the
basis of meteorological, social, and political
factors which suggest that a group of com-
munities should be treated as a unit for set-
ting limitations on concentrations of atmos-
pheric pollutants. Concurrently, the Secretary
is required to issue air quality criteria for
those pollutants he believes may be harmful
to health or welfare, and to publish related
information on the techniques which can be
employed to control the sources of those pol-
lutants.
Once these steps have been taken for any
region, and for any pollutant or combination
of pollutants, then the State or States respon-
sible for the designated region are on notice
to develop ambient air quality standards ap-
plicable to the region for the pollutants in-
volved, and to develop plans of action for
meeting the standards.
The Department of Health, Education, and
Welfare will review, evaluate, and approve
these standards and plans and, once they are
approved, the States will be expected to take
action to control pollution sources in the
manner outlined in their plans.
At the direction of the Secretary, the
National Air Pollution Control Administra-
tion has established appropriate programs to
carry out the several Federal responsibilities
specified in the legislation.
Control Techniques for Hydrocarbon and
Organic Solvent Emissions from Stationary
Sources is one of a series of documents to be
produced under the program established to
carry out the responsibility for developing
and distributing control technology informa-
tion. Previously, on February 11, 1969, con-
trol technique information was published for
sulfur oxides and particulate matter.
In accordance with the Clean Air Act, a
National Air Pollution Control Techniques
Advisory Committee was established, having a
membership broadly representative of in-
dustry, universities, and all levels of govern-
ment. The committee, whose members are
listed following this discussion, provided in-
valuable advice in identifying the best possible
methods for controlling the pollution sources,
assisted in determining the costs involved, and
111
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gave major assistance in drafting this docu-
ment.
As further required by the Act, appropriate
Federal departments and agencies, also listed
on the following pages, were consulted prior
to issuance of this document. A Federal con-
sultation committee, comprising members
designated by the heads of 17 departments
and agencies, reviewed the document, and
met with staff personnel of the National Air
Pollution Control Administration to discuss
its contents.
During 1967, at the initiation of the Secre-
tary of Health, Education, and Welfare, sev-
eral government-industry task groups were
formed to explore mutual problems relating
to air pollution control. One of these, a task
group on control technology research and
development, looked into ways that industry
representatives could participate in the review
of the control techniques reports. Accord-
ingly, several industrial representatives, listed
on the following pages, reviewed this docu-
ment and provided helpful comments and sug-
gestions. In addition, certain consultants to
the National Air Pollution Control Adminis-
tration also revised and assisted in preparing
portions of this document. These also are
listed on the following pages.
The Organic Solvents Advisory Committee
also provided invaluable assistance by review-
ing and commenting on the material in this
document. Committee membership is indi-
cated on the following pages.
The Administration is pleased to acknowl-
edge efforts of each of the persons specifically
named, as well as those of the many not so
listed who contributed to the publication of
this volume. In the last analysis, however, the
National Air Pollution Control Administra-
tion is responsible for its content.
The control of air pollutant emissions is a
complex problem because of the variety of
sources and source characteristics. Technical
factors- frequently make necessary the use of
different control procedures for different
types of sources. Many techniques are still in
the development stage, and prudent control
strategy may call for the use of interim meth-
ods until these techniques are perfected.
Thus, we can expect that we will continue to
improve, refine, and periodically revise the
control techniques information so that it will
continue to reflect the most up-to-date
knowledge available.
John T. Middleton,
Commissioner,
National Air Pollution
Control Administration.
IV
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NATIONAL AIR POLLUTION CONTROL TECHNIQUES ADVISORY
COMMITTEE
Chairman
Mr. Robert L. Harris, Jr., Director
Bureau of Abatement and Control
National Air Pollution Control Administration
MEMBER
Mr. Herbert J. Dunsmore
Assistant to Administrative
Vice President of Engineering
U. S. Steel Corporation
Pittsburgh, Pennsylvania
Mr. John L. Gilliland
Technical Director
Ideal Cement Company
Denver, Colorado
Dr. August T. Rossano
Department of Civil Engineering
Air Resource Program
University of Washington
Seattle, Washington
Mr. Jack A. Simon
Principal Geologist
Illinois State Geological Survey
Urbana, Illinois
Mr. Victor H. Sussman, Director
Division of Air Pollution Control
Pennsylvania Department of Health
Harrisburg, Pennsylvania
Dr. Harry J. White, Head
Department of Applied Science
Portland State College
Portland, Oregon
CONSULTANT
Mr. Robert L. Chass
Chief Deputy Air Pollution
Control Officer
Los Angeles County Air Pollution
Control District
Los Angeles, California
Mr. C. G. Cortelyou
Coordinator of Air & Water
Conservation
Mobil Oil Corporation
New York, New York
Mr. Charles M. Heinen
Assistant Chief Engineer
Chemical Engineering Division
Chrysler Corporation
Highland Park, Michigan
Mr. William Monroe
Chief, Air Pollution Control
Division of Clean Air & Water
State Department of Health
Trenton, New Jersey
Mr. William W. Moore
Vice President, and Manager of
Air Pollution Control Division
Research-Cottrell, Inc.
Bound Brook, New Jersey
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FEDERAL AGENCY LIAISON REPRESENTATIVES
Department of Agriculture
Dr. Theodore C. Byerly
Assistant Director of Science
and Education
Department of Commerce
Mr. Paul T. O'Day
Staff Assistant to the Secretary
Department of Defense
Mr. Thomas R. Casberg
Office of the Deputy Assistant Secretary
(Properties and Installations)
Department of Housing & Urban Development
Mr. Samuel C. Jackson
Assistant Secretary for Metropolitan
Development
Department of the Interior
Mr. Harry Perry
Mineral Resources Research Advisor
Department of Justice
Mr. Walter Kiechel, Jr.
Assistant Chief
General Litigation Section
Land and Natural Resources Division
Department of the Treasury
Mr. Gerard M. Brannon
Director
Office of Tax Analysis
Atomic Energy Commission
Dr. Martin B. Biles
Director
Division of Operational Safety
Federal Power Commission
Mr. F. Stewart Brown
Chief
Bureau of Power
General Services Administration
Mr. Thomas E. Crocker
Director
Repair and Improvement Division
Public Buildings Service
National Aeronautics and Space
Administration
Major General R. H. Curtin, USAF
(Ret.)
Director of Facilities
Department of Labor
Dr. Leonard R. Linsenmayer
Deputy Director
Bureau of Labor Standards
Post Office Department
Mr. W. Norman Meyers
Chief, Utilities Division
Bureau of Research & Engineering
Department of Transportation
Mr. William H. Close
Assistant Director for Environmental
Research
Office of Noise Abatement
National Science Foundation
Dr. Eugene W. Bierly
Program Director for Meteorology
Division of Environmental Sciences
Tennessee Valley Authority
Dr. F. E. Gartrell
Assistant Director of Health
Veterans Administration
Mr. Gerald M. Hollander
Director of Architecture and Engi-
neering
Office of Construction
VI
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CONTRIBUTORS
Dr. William G. Agnew, Head
Fuels & Lubricants Department
Research Laboratories
General Motors Corporation
Warren, Michigan
Dr. A. D. Brandt
Manager, Environmental Quality Control
Bethlehem Steel Corporation
Bethlehem, Pennsylvania
Mr. John M. Depp, Director
Central Engineering Department
Monsanto Company
St. Louis, Missouri
Mr. Stewart S. Fritts
Operations Consultant
Lone Star Cement Corporation
New York, New York
Mr. J. C. Hamilton
Vice President for Administration
Director of Engineering
Owens-Illinois, Inc.
Toledo, Ohio
Mr. Richard B. Hampson
Manager, Technical Services
Freeman Coal Mining Corporation
Chicago, Illinois
Mr. C. William Hardell
Coordinator, Eastern Region
Air & Water Conservation
Atlantic Richfield Company
New York, New York
Mr. James F. Jonakin
Manager, Air Pollution Control Systems
Combustion Engineering, Inc.
Windsor, Connecticut
Mr. James R. Jones, Director
Coal Utilization Services
Peabody Coal Company
St. Louis, Missouri
Mr. John F. Knudsen
MMD-ED Industrial Hygiene Engineer
Kennecott Copper Corporation
Salt Lake City, Utah
Mr. Edward Largent
Manager, Environmental & Industrial
Hygiene, Medical Dept.
Reynolds Metals Company
Richmond, Virginia
Mr. Walter Lloyd
Director, Coal & Ore Services Dept.
Pennsylvania Railroad Company
Philadelphia, Pennsylvania
Mr. Michael Lorenzo
General Manager
Environmental Systems Department
Westinghouse Electric Corporation
Washington, D. C.
Mr. J. F. McLaughlin
Executive Assistant
Union Electric Company
St. Louis, Missouri
Mr. Robert Morrison
President, Marquette Cement Manufac-
turing Company
Chicago, Illinois
Dr. Clarence A. Neilson
Director of Laboratories & Manager
Of Technical Services
Laboratory Refining Dept.
Continental Oil Company
Ponca City, Oklahoma
Mr. James L. Parsons
Consultant Manager
Environmental Control
E. I. duPont de Nemours & Co., Inc.
Wilmington, Delaware
vn
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Mr. James H. Rook
Director of Environmental Control
Systems
American Cyanamid Company
Wayne, New Jersey
Mr. K. J. Schatzlein
Chemical Engineer
Lehigh Portland Cement Company
Allentown, Penna.
Mr. T. W. Schroeder
Manager of Power Supply
Illinois Power Company
Decatur, Illinois
Mr. Robert W. Scott
Coordinator for Conservation Technology
Esso Research & Engineering Company
Linden, New Jersey
Mr. Bruce H. Simpson
Executive Engineer, Emissions Planning
Ford Motor Company
Dearborn, Michigan
Mr. Samuel H. Thomas
Director of Environmental Control
Owens-Corning Fiberglas Corporation
Toledo, Ohio
Mr. A. J. Von Frank
Director, Air & Water Pollution Control
Allied Chemical Corporation
New York, New York
Mr. Earl Wilson, Jr.
Manager, Industrial Gas Cleaning Dept.
Koppers Company, Inc.
Baltimore, Maryland
Mr. Wayne Wingert
Environmental Improvement Engineer
The Detroit Edison Company
Detroit, Michigan
Vlll
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ORGANIC SOLVENTS ADVISORY COMMITTEE
Dr. Sidney W. Benson, Chairman
Department of Thermochemistry and
Chemical Kinetics
Stanford Research Institute
Menlo Park, California
Lt. Col. Abel M. Dominquez
Assistant Chief, Toxicology Branch
Armed Forces Institute of Pathology
Washington, D. C.
Dr. William L. Faith
Consulting Chemical Engineer
San Marino, California
Mr. Walter J. Hamming
Chief Air Pollution Analyst
Los Angeles County Air
Pollution Control District
Los Angeles, California
Dr. Charles E. Kircher
Research Manager
Detrex Chemical Industries, Inc.
Detroit, Michigan
Mr. Arthur Levy
Chief, Physical Chemistry &
Solid State Materials Department
Battelle Memorial Institute
Columbus, Ohio
Mr. Elgin D. Sallee, Manager
Safety & Industrial Hygiene
American Can Company
New York, New York
Mr. Francis Scofield
Vice President, Technical Affairs
National Paint, Varnish & Lacquer Assoc.
Washington,,©C C.
Mr. Jerome Wilkenfeld
Director, Environmental Health
Hooker Chemical Corporation
New York, New York
IX
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TABLE OF CONTENTS
Section page
LIST OF FIGURES xiv
LIST OF TABLES xv
SUMMARY xvii
1. INTRODUCTION 1-1
2. BACKGROUND INFORMATION 2-1
2.1 DEFINITIONS 2-1
2.2 PHOTOCHEMICAL REACTIONS 2-1
2.3 STATIONARY SOURCES OF HYDROCARBON EMISSIONS .... 2-1
2.4 REFERENCES FOR SECTION 2 2-2
3. CONTROL TECHNIQUES AND EQUIPMENT FOR STATIONARY SOURCES 3-1
3.1 INTRODUCTION 3-1
3.2 INCINERATION 3-1
3.2.1 Basic Operating Principles and Equipment 3-2
3.2.1.1 Direct Flame 3-2
3.2.1.2 Catalytic Afterburners ' 3-3
3.2.1.3 Process Heaters and Boilers 3-6
3.2.2 Selection of an Afterburner 3-6
3.3 ADSORPTION 3-7
3.3.1 Introduction 3-7
3.3.2 Basic Operating Principles 3-7
3.3.3 Applications of Adsorption 3-8
3.3.3.1 Types of Adsorbents 3-9
3.3.4 Types of Adsorption Equipment 3-9
3.3.4.1 Description of an Adsorption Process 3-9
3.3.4.2 Factors Involved in Selection of an Adsorber ... 3-12
3.3.5 Instruments for Control of Adsorption Process 3-13
3.4 ABSORPTION 3-14
3.4.1 Introduction 3-14
3.4.2 Applications 3-14
3.4.3 Selection of an Absorbent 3-14
3.4.4 Types of Absorbers 3-14
3.4.5 Principles of Operation 3-16
3.5 CONDENSATION 3-19
3.5.1 Introduction 3-19
3.5.2 Basic Operating Principles and Types of Equipment 3-21
3.5.3 Design Factors and Applications 3-21
3.6 USE OF LESS PHOTOCHEMICALLY REACTIVE MATERIALS . . . 3-23
3.6.1 General Considerations 3-23
3.6.2 Regulations Based on Photochemical Reactivity 3-24
3.6.3 Rule 66 of Los Angeles County 3-24
3.6.4 Background of Rule 66 3-24
xi
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Section
3.6.5 Applicability of Rule 66 to Other Areas 3"26
3.6.6 Regulation 3 of San Francisco Bay Area Air Pollution
Control District 3"26
3.6.7 Photochemical Reactivity of Trichloroethylene 3-26
3.7 REFERENCES FOR SECTION 3 3"26
4. CONTROL SYSTEMS FOR INDUSTRIAL PROCESSES 4"1
4.1 PETROLEUM REFINERIES 4'1
4.1.1 Introduction 4'1
4.1.2 Storage 4'3
4.1.3 Waste-Gas Disposal Systems 4-4
4.1.3.1 Pressure-Relief Systems 4-4
4.1.3.2 Flares 4-5
4.1.4 Oil-Water Effluent Systems 4-5
4.1.5 Cracking Catalyst Regeneration 4-6
4.1.6 Pumps 4-6
4.1.7 Airblowing of Asphalt 4-7
4.1.8 Valves 4-8
4.1.9 Loading Facilities 4-8
4.1.10 Vacuum Jets 4-8
4.1.11 Boilers and Process Heaters 4-8
4.1.12 Chemical Treating Processes 4-8
4.2 GASOLINE DISTRIBUTION SYSTEMS 4-8
4.2.1 Introduction 4-8
4.2.2 Emissions 4-9
4.2.3 Controls 4-10
4.2.3.1 Overhead Loading 4-10
4.2.3.2 Bottom Loading 4-11
4.2.3.3 Vapor Disposal 4-12
4.2.4 Regulations and Costs 4-13
4.3 CHEMICAL PLANTS 4-13
4.3.1 Introduction 4-13
4.3.2 Processes 4-14
4.3.3 Emission Control 4-16
4.3.3.1 Collection of Vented Gases 4-17
4.3.3.2 Halogenation 4-17
4.3.3.3 Disposal of Waste Gases 4-18
4.4 PAINT, LACQUER, AND VARNISH MANUFACTURE 4-18
4.4.1 Introduction 4-18
4.4.2 Paint Manufacturing 4-18
4.4.3 Lacquer Manufacturing 4-20
4.4.4 Varnish Manufacturing 4-21
4.4.4.1 Introduction 4-21
4.4.4.2 Manufacturing Processes and Emissions 4_21
4.4.4.3 Controls 4-23
4.5 RUBBER AND PLASTIC PRODUCTS MANUFACTURE 4.25
4.5.1 Introduction 4-25
4.5.2 Rubber Manufacture 4.25
xii
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Section Pase
4.6 SURFACE COATING APPLICATIONS 4-26
4.6.1 Introduction 4-26
4.6.2 Emissions 4-27
4.6.3 Control Techniques and Costs 4-27
4.7 DECREASING OPERATIONS 4-28
4.7.1 Introduction 4-28
4.7.2 Vapor Degreasing Equipment 4-30
4.8 DRY CLEANING 4-31
4.8.1 Introduction 4-31
4.8.2 Process Description 4-31
4.8.3 Solvent Emissions 4-32
4.8.4 Control Techniques and Costs 4-32
4.9 STATIONARY FUEL COMBUSTION 4-33
4.9.1 Introduction 4-33
4.9.2 Processes and Emissions 4-33
4.9.3 Control Techniques 4-33
4.9.3.1 Operating Practices 4-33
4.9.3.2 Improved Equipment Design 4-34
4.9.3.3 Fuel Substitution 4-34
4.9.4 Control Costs 4-34
4.10 METALLURGICAL COKE PLANTS 4-34
4.10.1 Process Descriptions 4-34
4.10.2 Emissions 4-35
4.10.3 Control of Emissions 4-35
4.11 SEWAGE TREATMENT 4-37
4.11.1 Introduction 4-37
4.11.2 Process Description and Emissions 4-37
4.11.3 Control Techniques and Costs 4-37
4.12 WASTE INCINERATION AND OTHER BURNING 4-38
4.12.1 Introduction 4-38
4.12.2 Emissions 4-38
4.12.3 Controls 4-42
4.12.3.1 Waste Disposal 4-42
4.12.3.2 Incineration 4-42
4.12.3.3 Forest Wildfires 4-43
4.12.3 A Controlled Vegetation Burning 4-44
4.12.3.5 Coal Refuse Fires 4-44
4.12.3.6 Structural Fires 4-44
4.12.4 Costs 4-44
4.13 MISCELLANEOUS 4-45
4.13.1 Introduction 4-45
4.13.2 Fermentation Processes 4-45
4.13.3 Food Processing 4-45
4.13.4 Charcoal Manufacture 4-46
4.13.5 Drug Manufacture 4-46
4.14 REFERENCES FOR SECTION 4 4-46
xiii
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Section
Page
5. EMISSION FACTORS 5
5.1 REFERENCES FOR SECTION 5 5
6. ECONOMICS 6"!
6.1 INTRODUCTION 6~*
6.2 DEFINITION OF ALTERNATIVES 6~l
6.3 IDENTIFICATION OF COSTS 6-1
6.3.1 Capital Investment 6-2
6.3.2 Maintenance and Operation 6-2
6.3.3 Annualized Costs 6-2
6.4 COST CURVES BY EQUIPMENT TYPES 6-3
6.4.1 Afterburners 6-3
6.4.2 Activated-Carbon Adsorbers 6-3
6.4.3 Absorption Equipment 6-4
6.4.4 Condensers 6-5
6.5 VALUE OF RECOVERED MATERIALS 6-5
6.6 REFERENCES FOR SECTION 6 6-6
7. CURRENT RESEARCH 7-1
7.1 RESEARCH PROJECTS APPLICABLE TO HYDROCARBONS
ANDORGANICS 7-1
7.2 RESEARCH ON CONTROL EQUIPMENT AND TECHNIQUES ... 7-1
7.3 CURRENT RESEARCH PROJECTS 7-2
7.4 REFERENCES FOR SECTION 7 7-3
8. SUBJECT INDEX 1-1
LIST OF FIGURES
Figure
3—1. Typical Multijet Burner Arrangement Used in Direct-Flame
Afterburner 3-3
3—2. Direct-Flame Afterburner, Vertical Arrangement 3-4
3—3. Raw Gas Burner and Multiple Jet Grid 3-4
3—4. Afterburner With Heat Exchanger 3-5
3-5. Catalytic Afterburner 3-6
3-6. Diagrammatic Sketch of Two-Unit Fixed-Bed Adsorber 3-11
3—7. Diagrammatic Sketch of Vertical Adsorber with Two Cones,
Permitting Studies on Different Depths of Carbon Beds 3-11
3-8. Standard Skid-Mounted Vapor-Recovery Unit 3-12
3-9. Schematic Diagram of a Bubble-Cap Tray Tower 3-15
3-10. Packed Tower 3-15
3-11. Spray Tower 3-15
3-12. Venturi Scrubber 3-16
3—13. Driving Force for Absorption 3-16
3—14. Common Tower Packing Materials 3-17
3—15. Number of Transfer Units for Absorbers or Strippers With
Constant Absorption Stripping Factor 3_17
3—16. Types of Condensers 3-22
xiv
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Figure Page
4— 1. Processing Plan for Typical Complete Refinery 4-2
4—2. Representation of Gasoline Distribution System 4-9
4-3. View of Bottom-Loading Station 4-10
4—4. View of Mobil Oil Corporation Vapor Closure 4-11
4—5. Chiksan Pneumatically Operated Loading Assembly With
Integrated Vapor Closure and Return Line 4-11
4—6. View of Greenwood Vapor Closure 4-12
4-7. SOCO Vapor Closure Device in Filling Position 4-12
4—8. Small Capacity Vaporsaver Gasoline Absorption Unit 4-13
4—9. Automatic Jet Compressor 4-17
4—10. Direct-Fired Afterburner for Control of Emissions from
Two Phthalic Anhydride Production Units 4-19
4—11. Schematic Plan for Varnish-Cooking Control System 4-25
4—12. Self-Recuperating Heat Recovery: Single Efficiency Heat
Exchange 4-29
4—13. Self-Recuperating Heat Recovery: Variable Heat Exchange 4-29
4—14. Self-Recuperating Heat Recovery: Variable Efficiency Heat Exchange . 4-29
4—15. Domestic Gas-Fired Incinerator 4-39
4—16. Single-Chamber Incinerator 4-39
4—17. Cutaway of an In-Line Multiple-Chamber Incinerator 4-40
4—18. Section of the Flue-Fed Incinerator 4-40
4—19. Section of Chute-Fed Apartment Incinerator 4-40
4—20. Section of Pathological Incinerator 4-41
4—21. Section of Municipal Incinerator 4-41
4-22. Land Waste-Disposal Costs 4-45
4-23. Cost of Incinerator at Three Levels of Control of
Particulate Emissions 4-45
6-1. Purchase Cost of Afterburners, 1968 6-3
6—2. Adsorption System Installed Costs, 1969 Basis 6-4
6—3. Packed Tower Costs, with Raschig Rings as Packing, 1969 Basis .... 6-4
6—4. Purchase Costs of Condensers 6-5
LIST OF TABLES
Table
2—1. Summary of Nationwide Hydrocarbon Emissions, 1968 2-2
3—1. Gases and Vapors Selectively Adsorbed By Activated Carbon 3-10
3—2. Constants For Use in Determining Gas-Phase Height of
Transfer Units 3-18
3—3. Constants for Use in Determining Liquid-Phase Height of
Transfer Units 3-19
3—4. Pressure Drop Constants for Tower Packing 3-20
3—5. Representative Applications of Condensers in Air Pollution
Control 3-23
4—1. Typical Analysis of Vapors From Loading of Gasoline into
Tank Trucks 4-9
xv
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Table Page
4—2. Quantities of Raw Materials and Intermediate Products Converted to
Synthetic Organic Chemicals in 1967 4-14
4—3. Calculation of Hydrocarbon Losses From Process Equipment
500-Million-lb/yr Ethylene Plant 4-16
4—4. Average Hydrocarbon Emissions From Stationary Fuel
Combustion Sources 4-33
4—5. Trends in Overall Efficiency of Steam-Electric Generating Plants .... 4-34
4—6. Typical Composition and Amounts of Compounds Removed
Per Ton of Coal 4-36
4—7. Organic Vapor Concentrations Emitted From An
Activated Sludge Plant 4-37
4—8. Estimated National Emissions From Incineration and
Other Burning 4-42
5—1. Emission Factors for Hydrocarbons 5-1
xvi
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SUMMARY
The effects of hydrocarbon and organic
solvent emissions are of two types, direct and
indirect. Direct effects are caused by the origi-
nal, unaltered emissions, and indirect effects
are caused by substances formed by photo-
chemical reactions of the original emissions
with other substances in the atmosphere. The
purpose of this document is to make informa-
tion available on techniques for the control of
organic emissions from stationary sources.
STATIONARY SOURCES OF HYDROCAR-
BON AND ORGANIC SOLVENT EMISSIONS
Sources of hydrocarbon emissions include
petroleum refining, gasoline distribution and
marketing, chemical manufacturing, coal
coking, fuel burning, waste disposal, and food
processing. Sources of organic solvent emis-
sions include manufacture and application of
protective coatings, manufacture of rubber
and plastic products, degreasing and cleaning
of metal parts, dry cleaning operations, print-
ing, and manufacture of chemicals.
CONTROL TECHNIQUES
AND EQUIPMENT
Methods used to control hydrocarbon and
organic solvent emissions are (1) operational
or process changes, (2) substitution of materi-
als, and (3) installation of control equipment.
The techniques used in control devices are of
four classifications: incineration, adsorption,
absorption, and condensation.
Incineration devices are of two types,
direct-flame afterburners and catalytic after-
burners. Direct-flame afterburners utilize a
flame to complete oxidation of the organic
emissions. Flame coverage, turbulence, efflu-
ent residence time, and temperature are im-
portant in the design of an afterburner. Tem-
peratures of 1200° to 1400°F and residence
times of 0.3 to 0.6 second are usually re-
quired. Removal efficiencies of direct-flame
afterburners can be high; organic particulates
are removed effectively; and no secondary dis-
posal problems are encountered. Operational
costs are high unless heat- recovery equipment
is installed.
Catalytic afterburners utilize a catalyst so
that emissions can be oxidized at a lower tem-
perature than could otherwise be done. Fuel
costs are thus lower, but removal efficiencies
are also lower. Catalysts are subject to poison-
ing and deactivation from the heat present.
Activated-carbon adsorbers collect organic
vapors in the capillary surface of the solid
adsorbent. After the carbon bed has adsorbed
the optimum amount of organic material, the
gas stream is stopped and the carbon bed is
steam stripped to remove the organic materi-
al. The carbon bed is then ready for reuse.
The steam and organic material are con-
densed, and the organic is recovered by decan-
tation or distillation. Two or more carbon-
containing vessels are used, one adsorbing
while the other is desorbing.
Costs of adsorbing systems and their opera-
tions are high, but recovery of valuable ma-
terials enhances the feasibility of such opera-
tions. High removal efficiencies are possible.
Streams containing resin-forming gases cannot
be handled by carbon adsorbers because the
resins plug the carbon beds.
Absorption is the transfer of a soluble
component of a gas phase into a relatively
nonvolatile liquid absorbent. Common ab-
sorbents are water, mineral oil, nonvolatile
hydrocarbons, and aqueous solutions such as
solutions of oxidizing agents or alkalis. Con-
tact between gas and liquid is provided in
bubble-plate columns, packed towers, jet
scrubbers, spray towers, and venturi scrub-
bers.
Absorbers are widely used when gas and
vapor concentrations are high; however, such
xvn
-------
equipment is usually classified as production
equipment, and not as emission control equip-
ment. Absorbers are not widely used when
concentrations are low since large and expen-
sive equipment would be required to achieve
good removal efficiencies.
Condensers collect organic emissions by
lowering the temperature of the gaseous
stream to the condensation point of that ma-
terial. Condensers are of two types, contact
and surface. In contact condensers, the gase-
ous stream is brought into direct contact with
the cooling liquid, the condensed material
mixing with the coolant. In a surface con-
denser, the vapor to be condensed and the
cooling fluid are separated by a metal wall.
Condensers used in the petroleum and
chemical industries to condense concentrated
vapors are classified as production equipment.
High removal efficiency cannot be achieved
with low concentrations; condensers are,
therefore, useful as preliminary devices to be
followed by a more efficient device such as an
afterburner or adsorber.
Use of Less Photochemically
Reactive Materials
Collection of organic emissions from the
painting of buildings and structures is im-
practical. In operations wherever collection is
possible but is not financially feasible, substi-
tution of less reactive materials is a possible
control technique.
Los Angeles County limits the emissions
from organic solvents by Rule 66. All the
normally used solvents are divided into two
groups, those classified as photochemically re-
active and those not photochemically reac-
tive. Emissions from the reactive group are
restricted, but emissions from the nonreactive
group are not limited, except when flame con-
tact, baking, or heat-curing is involved. Many
solvents with more than the allowed amount
of reactive materials have been reformulated
by the manufacturer with materials in the
nonreactive group.
The San Francisco Bay Area Air Pollution
Control District limits emission of only very
reactive compounds. These are defined as ole-
fins, substituted aromatics, and aldehydes.
Control Systems for Industrial Processes
Petroleum Refining
Evaporation losses during storage are min-
imized by use of floating roof tanks, pressure
tanks, and vapor conservation or recovery
systems. Hydrocarbons from catalyst regener-
ators can be controlled by waste heat boilers.
Leakage from valves, pumps, and compressors
can be reduced by systematic maintenance of
connections and seals. Waste water separators
can be controlled by enclosing the separator
tanks. Vapor recovery systems or smokeless
flares are utilized to control hydrocarbon
vapors from blowdown systems. Stripping
gases from acid treating, doctor treating, and
caustic treating and air-blowing effluents can
be controlled by incineration.
Gasoline Distribution Systems
Vapors emitted during the loading of gaso-
line tank trucks can be collected and delivered
to a vapor disposal system. The collection
system consists of a tight fitting hatch and a
vapor delivery line. For top-loading tanks, the
vapor delivery line is an annular space around
the gasoline delivery line. For bottom-loading
tanks, the vapor line is a separate line con-
nected at the top of the tank. Vapors can be
delivered to a gas-blanketed vapor holder and
used as fuel in boilers and heaters where the
load rack is adjacent to the refinery. For stor-
age and loading facilities at other locations,
packaged vapor recovery units have been de-
veloped in which the vapors are compressed
and reabsorbed in gasoline.
Chemical Plants
The principal raw materials for synthetic
organic products are derived mostly from
petroleum and to a lesser extent from the
by-products of the coking of coal. These ma-
terials are processed through the following
types of conversions: alkylation, hydrogena-
tion, dehydrogenation, dehydration, esteri-
fication, halogenation and dehalogenation
oxidation, nitration, and polymerization.
xvm
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Waste gases from processing units can be
collected and delivered to a burner, to a gas
holder, or into a fuel header system. Waste
gases from units producing chlorinated hydro-
carbons can be processed to recover by-
product hydrochloric acid. Direct flame and
catalytic afterburners are used to eliminate
organic vapors and mists from many off-gases.
Paint, Lacquer, and Varnish Manufacture
Emissions from paint and lacquer manu-
facture occur during mixing, grinding, and
thinning operations. Varnish ingredients must
be "cooked" to promote such reactions as de-
polymerization, esterification, isomerization,
melting, and bodying. Emissions contain fatty
acids, aldehydes, acrolein, glycerol, acetic
acid, formic acid, and complex residues of
thermal decomposition. Control systems con-
sist of condensers, scrubbers, and after-
burners.
Rubber and Plastic Products Manufacture
Emissions from rubber product manu-
facture occur during heat plasticization,
chemical plasticization, and vulcanization.
Control techniques include carbon adsorp-
tion, direct-flame and catalytic incineration,
and reformulation to nonphotochemically
reactive materials. In plastic products manu-
facture, emissions can occur trom curing
ovens, particularly when dioctyl phthalate is
used as a plasticizer. Such mists can be
controlled with high-energy scrubbers or with
afterburners.
Surface Coating Applications
Emissions of hydrocarbons from the ap-
plication of paint, varnish, and similar
coatings are due to the evaporation of the
solvents, diluents, and thinners. Where con-
trols are required, reformulation with non-
photochemically reactive solvents is a method
of control. Afterburners have been used to
control emissions from paint bake ovens.
These ovens can sometimes be redesigned to
reduce the volume of gases to be handled, ef-
fecting considerable savings. Heat recovery
systems can lower operating costs by reducing
fuel requirements.
Decreasing Operations
Most vapor-phase degreasers use chlori-
nated hydrocarbon solvents, principally
trichloroethylene. Less photochemically
reactive 1,1,1-trichloroethane (methyl chloro-
form) and perchloroethylene can be sub-
stituted. Activated-carbon adsorbers can be
used to control emissions in some applica-
tions. Solvent emissions can be minimized by
elimination of drafts, good drainage of work
items, controlled speed of work entering and
leaving work zone, and covering of tank
whenever possible.
Dry Cleaning
Dry cleaning is done by two processes:
those using petroleum solvents and those
using perchloroethylene or other halogenated
solvents. In plants using perchloroethylene,
vapor is recovered by water-cooled condens-
ers, which may be followed by activated-
carbon adsorbers. The value of the solvent
makes recovery economically feasible. Plants
using petroleum solvents can be controlled, if
necessary, by using solvents reformulated to
be nonphotochemically reactive. Control by
activated carbon may be feasible.
Stationary Fuel Combustion
Hydrocarbons may be emitted if com-
bustion is not complete. When properly
designed and operated, stationary fuel com-
bustion equipment is not a serious source of
organic emissions.
Metallurgical Coke Plants
The hydrocarbons from the coking of coal
are collected to recover by-products. Emis-
sions occur during charging operations and
from improperly fitting doors and other leaks.
Emissions during charging can be reduced by
steam-jet aspirators in the collection pipes.
Self-sealing doors and good maintenance
programs can reduce emissions.
Sewage Treatment Plants
Primary sewage plants emit hydrocarbons
from the screening and grit chambers, and
from the settling tanks. Activated-sludge
xix
-------
plants emit gas from the aeration tanks. Trick-
ling filter plants emit organic gas from the
filters, the clarifiers, and from the sludge-
digestion tanks. Control of emissions can be
accomplished by covering or enclosing the
various treating units and oxidizing or com-
busting the effluent gases.
Waste Disposal
Burning of waste materials can cause emis-
sions of hydrocarbons. Open burning and
inefficient incinerators are the predominant
sources of such emissions. Control can be
achieved by the use of multiple-chamber in-
cinerators or by disposing of the waste in san-
itary landfills.
Miscellaneous Operations
Emissions from deep fat fryers and coffee
roasters can be controlled by afterburners. Fish
cookers can .be controlled by condensers.
Evaporators of liquids from fish processing
can be controlled by condensers and scrub-
bers, and fish meal driers by scrubbing with
chlorinated water. Noncondensible gases from
charcoal manufacturing can be burned.
ECONOMICS
Economic considerations in air pollution
control include: (1) the selection of control
techniques and equipment; (2) the assessment
of the impact of control on product prices,
profits, investments, and value added to the
product; and (3) the identification of the
many direct and indirect costs of installing
and operating air pollution control equip-
ment. Process alterations or substitutions are
usually considered first in selecting a control
technique. If control equipment is necessary,
the required emission reduction, process
stream characteristics, and plant facilities are
evaluated in order to select the system that
will optimize costs and benefits. Value of
recovered materials may be a significant cost
offset.
xx
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CONTROL TECHNIQUES FOR
HYDROCARBON AND ORGANIC SOLVENT
EMISSIONS FROM STATIONARY SOURCES
1. INTRODUCTION
Pursuant to authority delegated to the
Commissioner of the National Air Pollution
Control Administration, Control Techniques
for Hydrocarbon and Organic Solvent Emis-
sions From Stationary Sources is issued in
accordance with Section 107(c) of the Clean
Air Act as amended (42 U.S.C. 1857-18571).
This document has been prepared to sum-
marize current information on stationary
sources of hydrocarbons and organic solvent
emissions, methods of control, and the costs
and cost-effectiveness of controls.
The available control techniques for these
emissions vary in type, application, effective-
ness, and cost. By far the most important
technique for controlling air pollution is in
the basic design of equipment to utilize
efficiently or consume completely the proc-
essed materials. Failing this, control equip-
ment can be used to reduce emissions. Operat-
ing principles, design characteristics,
advantages, disadvantages, applications, and
costs of the various control equipment and
techniques are described herein.
The control techniques described in this
document represent a broad spectrum of
information from many technical fields. The
devices, methods, and principles have been
developed and used over many years and are
constantly being revised and improved. They
are recommended as the techniques generally
available to control hydrocarbon and organic
solvent emissions.
The many industrial processes involved are
described individually in this document. The
various techniques and control systems that
can be applied to remove the pollutants from
these processes are reviewed and compared.
Sections are included on emission factors,
equipment costs and cost-effectiveness anal-
ysis, and current research and development.
The proper choice of a method, or combi-
nation of methods, to control emissions from
a specific source depends on many factors
other than the source characteristics alone.
For this reason, no attempt is made here to
review all possible combinations of control
techniques that may be required to com-
pletely remove a certain emission.
In some applications, it would be unwise to
attempt to control organic vapors by a
method that may be the preferred one for
other organics. For example, if combustion is
used to control organic vapors that contain
halogens, sulfur, or nitrogen, the combustion
products may be less desirable and more
corrosive than the original emission. Another
type of control system such as a scrubber may
then be required in series with the burner to
remove the harmful components from these
combustion products.
Mobile sources of hydrocarbon and organic
emissions are described in AP-66, Control
Techniques for Carbon Monoxide, Nitrogen
Oxide, and Hydrocarbon Emissions from
Mobile Sources, which is being published
simultaneously with this and other documents
on control techniques for air pollutant emis-
sions.
While some data are presented on quan-
tities of hydrocarbons and organic solvents
emitted to the atmosphere, the effects upon
health and welfare of hydrocarbons and sec-
ondary atmospheric reaction products are
considered in two companion documents,
AP-64, Air Quality Criteria for Hydrocarbons
and AP-63, Air Quality Criteria for Photo-
chemical Oxidants.
1-1
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2. BACKGROUND INFORMATION
2.1 DEFINITIONS
Hydrocarbons contain only the elements
hydrogen and carbon. Organic solvents may
contain, in addition to hydrogen and carbon,
one or more of the following elements:
oxygen, nitrogen, sulfur, and halogens. In this
document the term "organic solvents" is
intended to include such other materials as
diluents and thinners.
A discussion of the nomenclature of or-
ganic compounds is beyond the scope of this
work; the reader may find information of this
nature in a reference book.1 A definition of
generic names of some of the more important
compounds and types of compounds is perti-
nent, however.
The major divisions of hydrocarbons are
(1) aromatic, (2) aliphatic, and (3) alicyclic. If
within the structure of the molecule there is a
benzene structure ( ^^> , a six-carbon ring
containing three double bonds), the hydro-
carbon is aromatic. If no ring structure exists,
the compound is said to be aliphatic. If a ring
structure other than the benzene ring is
present, the compound is said to be alicylic.
Many further subdivisions exist within these
divisions.
Aliphatic hydrocarbons include both satu-
rated paraffinic compounds (CnH2n+2) and
unsaturated compounds. Unsaturated com-
pounds are compounds with carbon-carbon
double (alkenes) or triple (alkynes) bonds.
Alkenes are perhaps better known as olefins
and have the type formula CnH2n. Olefins are
generally regarded as being the most reactive
of the organic compounds in photochemical
smog formation, although reactivity varies
widely with chemical structure.
2.2 PHOTOCHEMICAL REACTIONS
Gaseous organic compounds in the atmos-
phere may undergo chemical and physical
processes that produce other substances with
greatly altered properties. These reactions are
photochemical in nature. A description of
these processes and the effects of the prod-
ucts are given in AP-63, Air Quality Criteria
for Photochemical Oxidants, U.S. Department
of Health, Education, and Welfare, National
Air Pollution Administration, and in AP-64,
Air Quality Criteria for Hydrocarbons, U.S.
Department of Health, Education, and Wel-
fare, National Air Pollution Control Adminis-
tration.
2.3 STATIONARY SOURCES OF
HYDROCARBON EMISSIONS
Atmospheric hydrocarbons and other or-
ganic compounds can be thought of as having
four origins: petroleum, coal, natural gas, and
biological products. Organic gases can escape
to the atmosphere at many points during the
production, processing, storage, transport,
and ultimate use of the originating organic
material.
Potential sources of hydrocarbon emissions
in petroleum production and product process-
ing include leakage from oil field operations,
refining, gasoline storage tanks, gasoline load-
ing facilities, blowing of asphalt, blowdown
systems, catalyst regenerators, processing ves-
sels, flares, compressors, pumps, vacuum jets,
waste-effluent handling equipment, and turn-
around operations.
Gasoline distribution and marketing sys-
tems emit hydrocarbon vapors from tank-
truck loading racks, service station tank-filling
operations, and automobile tank-filling opera-
tions.
Organic solvents are derived mainly but not
exclusively from petroleum. They are used in
many kinds of operations. Chemical, drug,
and pharmaceutical manufacturing plants can
be sources of organic emissions from those
2-1
-------
operations involving the use of organic sol-
vents. Rubber and plastic product manufac-
turing often involves the use of organic-
solvent-based-adhesives and other solvent uses
that lead to organic emissions. Paint and
varnishes, lacquers, under-coatings, etc., are
composed of 40 to 80 percent organic sol-
vents, which evaporate during or after the
application of the coating. Degreasing and
cleaning of metal items can cause significant
organic emissions. Vapor-phase degreasing is
the most widely used method, but spray
degreasing is also used. Dry cleaning of cloth-
ing utilizes organic solvents and contributes to
emissions. The manufacturing processes for
solvents and solvates are also potential
sources.
Metallurgical coke plants emit varying
amounts of hydrocarbons, depending on type
of furnace, operating methods, maintenance
practices, and other factors.
Fuel-burning equipment of all types can
emit organics if it is not properly adjusted,
not adequately maintained, or not operated
correctly.
Waste disposal by burning can cause organ-
ic emissions from incomplete combustion.
Open burning of refuse is the greatest of-
fender in this category. Inefficient incinerators
are also significant sources. Carbonaceous
material from many sources is disposed of by
burning.
Miscellaneous sources of organic gases from
biological sources include fermentation proc-
esses, food processing, organic fertilizer proc-
essing, wood distillation, and soap manufac-
turing.
Estimates for total United States organic
emissions from stationary sources are pre-
sented in Table 2-1. These estimates in general
were made from emission factors and quan-
tities of fuels consumed, quantities of refuse
burned, and quantities of raw materials proc-
essed. Although they represent only gross
approximations, they are the best estimates
currently available.
Table 2-1. SUMMARY OF NATIONWIDE
HYDROCARBON EMISSIONS, 19682
(106 tons/year)
Source
Transportation
Motor vehicles
Gasoline
Diesel
Aircraft
Railroads
Vessels
Nonhighway use, motor fuels
Fuel combustion— stationary
Coal
Fuel oil
Natural gas
Wood
Industrial processes
Solid waste disposal
Miscellaneous
Forest fires
Structural fires
Coal refuse
Agricultural burning
Organic solvent evaporation3
Gasoline marketing
Total
Emissions
15.2
0.4
0.3
0.3
0.1
0.3
0.2
0.1
Negligible
0.4
4.6
1.6
2.2
0.1
0.2
1.6
3.2
1.2
32.0
a Includes estimated 25 percent aldehydes, ketones,
and esters, and 10 percent chlorinated solvents.
2.4 REFERENCES FOR SECTION 2
1. Introduction, with Key and Discussion of the
Naming of Chemical Compounds for Indexing.
Chem, Abstracts Subject Index. 56: 1N-98N,
Jan-June, 1962.
2. National Air Pollution Control Administration,
Reference Book of Nationwide Emissions. U.S.
DHEW, PHS, CPEHS, NAPCA. Durham, N.C.
2-2
-------
3. CONTROL TECHNIQUES AND EQUIPMENT
FOR STATIONARY SOURCES
3.1 INTRODUCTION
Methods now employed commercially to
control the emission of organic air pollutants
are (1) operational or process changes, (2)
substitution of a higher-boiling- point material
and/or a less reactive compound in the proc-
ess, and (3) installation of control equipment
to capture of destroy the organic vapors
emitted from the process. By far the most
important technique for controlling air pollu-
tion is to design basic equipment for utilizing
efficiently or consuming completely the mate-
rials being processed. Failing this, control
equipment must be used in order to reduce
organic emissions. Commercially available
control techniques may be divided into five
general classifications: incineration, adsorp-
tion, absorption, condensation, and substitu-
tion of other materials. These techniques are
discussed in this chapter. Basic operating
principles of equipment employed are ex-
plained, and their areas of application are
indicated. The significant factors affecting
their operation are outlined, and general cost
information is provided.
3.2 INCINERATION
Incineration is the control of organic emis-
sions by combustion. The objective is to
oxidize completely the organic vapors and
gases from a process or operation that emits
them. Some emissions, of course, include
particulate as well as gaseous matter. If the
particulates are combustible, they may also be
handled by the combustion process. Incinera-
tion devices have been widely and successfully
used for reducing organic emissions. They
offer the potential of heat recovery.
Devices in which dilute concentrations of
organic vapors are burned by the use of added
fuel are known as afterburners. Devices used
to burn waste gases having sufficient heating
value to burn without added fuel are known
as flares if there is no air premixing or as
incinerators if there is air premixing. Flares
are discussed in Section 4.1, Petroleum Re-
fineries.
Afterburners are gas-cleaning devices that
incinerate organic emissions. Combustion is
accomplished either by direct-flame incinera-
tion or by catalytic oxidation. Under the
proper conditions, the firebox of a process
heater or boiler may also be used as an
afterburner.
In practice, it would usually be unwise to
attempt to control, solely by combustion,
organic vapors that contain halogens or sulfur,
since the combustion products of such mate-
rials are usually less desirable and often
corrosive. A secondary control system such as
a scrubber may be required in series with the
afterburner to remove these contaminants.
Industrial processes for which control by
afterburners is satisfactory include solvent
operations, drying, baking, and curing opera-
tions performed in ovens, dryers, and kilns.
Successful combustion control devices have
been applied to aluminum chip dryers, petro-
leum processing, animal blood dryers, auto-
motive brakeshoe debonding ovens, citrus
pulp dryers, coffee roasters, wire enameling
ovens, incinerators, foundry core ovens, meat
smokehouses, paint-baking ovens, varnish
cookers, paper printing and impregnating,
pharmaceutical manufacturing, sewage dis-
posal, chemical processing, and textile finish-
ing. In many of these operations, the after-
burners reduce the amount of particulate
matter as well as the organic vapors present in
the gas stream, and thereby reduce the opac-
ity of the exhaust gas.
3-1
-------
3.2.1 Basic Operating Principles
and Equipment
3.2.1.1 Direct Flame
For combustion of organic vapors and
liquids, the concentrations of vapor and air
must be within the limits of flammability.
These limits are the mixture ratios of vapor
and air that are either too rich or too lean to
ignite. These limits exist because flammation
proceeds by accumulation of thermal energy.
Their value for different mixtures will be
determined by the heat of reaction, the ther-
mal conductivities, rates of diffusion, and
specific heats of the components.
In order that a flame be self-sustaining, the
mixture of air and combustibles must provide
enough heat to maintain the combustion
temperature. The energy contained in a mix-
ture of air and most organic materials at the
lower flammable limit is, generally, equivalent
to approximately 52 British thermal units
(Btu) per standard cubic foot (scf). At am-
bient temperature, then, the organic vapors
and liquids in the air must provide at least 52
Btu per scf in order that a flame may be
initiated by a high-temperature source and be
self-sustaining. The oxidation reaction rate is
a function of temperature, and oxidation can
be carried out either above or below the
auto-ignition temperature of a given vapor.
An outside source of heat energy must be
provided, however, to maintain the tempera-
ture and a specific reaction rate, unless (1) the
concentration of the vapor is high enough to
support self-sustained combustion and (2) an
ignition source is maintained. Generally, high
concentrations of combustibles are diluted to
25 percent or less of the lower flammability
limit for safety. The required heat is then
provided by independently burning a second
source of fuel. The required technique, there-
fore, is to inject enough fuel gas into the
air-rich effluent to bring a portion of the mass
into the combustible range and thereby heat
the remainder to the ignition temperature.
The external energy thus added starts a chain
reaction wherein heat from the burning
vapors supplies a portion of the total heat
3-2
required to complete the chemical reaction.
Figures 3-1 and 3-2 show a direct-flame
afterburner with provision for auxiliary heat.
Burning time is an important factor in
afterburner design. This time period is called
the "dwell time" or "residence time." It
varies with the type of effluent and the
method of incineration, being on the order of
0.3 to 0.6 second at 1,200° to 1,400°F.
Burner type and arrangement have a consider-
able effect on burning time. The more
thorough the flame contact is with the efflu-
ent gases, the shorter is the time required to
achieve complete combustion. Turbulence in
the combustor zone achieves much the same
benefit of reducing required retention time, as
actual flame contact. Multijet burners have
been found to be very effective in securing
good flame contact.
Figure 3-1 shows a burner arrangement
wherein the effluent gases are used as both
primary and secondary air for the multijet
burners. Figure 3-2 shows a complete after-
burner with this type of burner. Figure 3-3
illustrates a multijet burner arrangement in
which no air is mixed with the gas prior to its
injection into the combustion zone. The
photograph shows the multiple small raw gas
jets distributed over the duct area. This
deployment of the jets results in efficient
mixing of the effluent with the flame. Figure
3-4 shows an afterburner that incorporates a
heat exchanger in which the afterburner exit
gases are used to preheat the gas stream
containing the pollutants that are to be
burned.
If the combustion reaction is arrested by
insufficient temperature, insufficient resi-
dence time, or poor mixing, CO, aldehydes,
and other products of incomplete combustion
may be produced. To achieve complete com-
bustion, thorough mixing of the organic
vapors and oxygen is required. Maintaining
high turbulence or injecting steam promotes
this intimate contact.
Properly designed and operated direct-
flame afterburners usually achieve organic
vapor removal efficiencies in excess of 95
-------
ADJUSTABLE
CONTROL
LOUVERS
GAS
CONNECTION
FUME INLET
CONNECTION
PATH OF FUME FLOW (FUME ITSELF IS
USED AS SOURCE OF BURNER COMBUSTION
OXYGEN, ELIMINATING NEED FOR OUTSIDE
AIR ADMISSION AND INCREASED Btu LOAD.)
r
REMOVABLE
PILOT
ASSEMBLY |
INCINERATION
CHAMBER /
FUME INLET PLENUM
J
REFRACTORY-LINED
IGNITION CHAMBER
Figure 3-1. Typical multijet burner arrangement used in direct-flame afterburners.
(Courtesy Hirt Combustion Engineers)
percent. In the design of afterburners, burner
utilization in conjunction with the overall
combustor design must be considered to
achieve the optimum and necessary time,
temperature, and turbulence. The materials of
construction, thicknesses, weights, etc., must,
of course, be structurally adequate or thermal
stress will lead to equipment failure.
3.2.1.2 Cataly tic Afterburners
Catalytic afterburners are designed much
like direct-flame types, but employ a solid
active surface whereon the combustion reac-
tion takes place, usually at a significantly
lower temperature than would be required for
combustion by direct flame. Since they can
be operated at temperatures much lower than
those required for direct-flame combustion,
catalytic afterburners have the advantage of
lower fuel costs in some applications. One
type of catalytic afterburner is shown in
Figure 3-5. Since fuel requirements for a
direct-flame afterburner can be lowered by
means of a heat exchanger, the total cost of
operating a direct-flame afterburner may be
comparable to the cost of operating the
catalytic type.
Catalytic incineration can be applied to
very low concentrations of contaminants,
being limited only by the prescribed operating
temperature limits of the catalyst and related
equipment.
The primary problems with catalytic after-
burners are their higher maintenance costs
and their susceptibility to catalyst poisons.
They will not function if the catalyst has
become fouled by particulate matter, or if it
3-3
-------
Figure 3-2. Direct-flame afterburner, vertical arrangement.
(Courtesy Hirt Combustion Engineers.)
GAS
a.
I ' f I I I
b.
Figure 3-3. Raw gas burner and multiple-jet grid. a. Diagram showing location of burner,
b. PhOtOgraph Of burner during Operation. (Courtesy North American Manufacturing Company)
-------
Figure 3-4. Afterburner with heat exchanger. (Courtesy The Air Preheater Company)
has been coated by polymers during low-
temperature operation. Catalytic units there-
fore are not always inherently functional, and
because of this, they may not meet prescribed
standards of performance. An afterburner
that does not achieve substantially complete
combustion of the organic emissions can
produce CO, aldehydes, and other partially
oxidized substances. These materials may be
less desirable than the emissions would be
without an afterburner.
Catalyst life is, in general, greater than 2
years. Catalysts do, however, gradually lose
activity through fouling and erosion of the
surface. Loss of surface area and consequent
reduction in activity can also be caused by
heat effects.
Combustion catalysts consist of various
shapes of basic material coated with a metallic
compound. The variety of shapes and cata-
lytic materials provide a multitude of cata-
lysts for each application. As a result, a good
general rule to follow is to consult with a
catalyst manufacturer on the most suitable
catalytic equipment configuration. Metallic
and metallic compound coatings include plati-
num, platinum alloys, copper chromite,
copper oxides, chromium, manganese, nickel,
and cobalt. Base materials may be ceramic or
metallic pellets or honeycombed forms.
Catalytic incineration has application in
petroleum refining, chemical processing,
foundry core baking, fabric coating, baking
ovens, and others.
3-5
-------
OXIDIZED GAS OUTLET
CATALYST
ELEMENTS
BLOWER
FUME ENTRY
FROM OVEN
PREHEAT
BURNER
Figure 3-5. Catalytic afterburner. (Courtesy
Catalytic Combustion Corporation)
3.2.1.3 Process Heaters and Boilers
Fireboxes of heaters and boilers can
approximate the conditions of well-designed
afterburners, providing the temperature, tur-
bulence, and flame contact are adequate. If
the gas stream to be treated contains appre-
ciable heat, special fireboxes (waste heat
boilers) are used. On the other hand, if the
heat content is low, common types of steam
and hot water heaters and boilers are used.
Completely satisfactory adaptations of
boilers for use as afterburners are not
common. All aspects of operation should be
throughly evaluated before this method of air
pollution control is used. The primary func-
tion of a boiler is to supply steam or hot
water; and whenever its use as a control
device conflicts with this function, one or
both of its purposes suffer.
The use of a boiler as an afterburner
requires that the following conditions1 exist:
1. The air contaminants to be controlled
must be almost wholly combustible
3-6
since a boiler firebox cannot be ex-
pected to control noncombustible pol-
lutants. Inorganic dusts and fumes
deposit on heat transfer surfaces and
foul them with resulting losses in
boiler efficiency and steam-generating
capacity.
2. The volumes of contaminated gases
must not be excessive or they will
reduce thermal efficiencies in much
the same way as excess combustion
air does. The additional volume of
products of combustion will also
cause higher pressure drops through
the system, in some cases exceeding
the draft provided by existing boiler
auxiliaries.
3. The oxygen content of the contami-
nated gases when used as combustion
air must be similar to that of air to
insure adequate combustion. Incom-
plete combustion can form tars or
resins which will deposit on heat-
transfer surfaces and result in reduc-
tion of boiler efficiency. When these
contaminants exceed air pollution
control standards for gas- or oil-fired
boilers, tube fouling will already have
become a major maintenance problem.
4. An adequate flame must be main-
tained continuously in the boiler fire-
box. High-low or modulating burner
controls are satisfactory, providing the
minimum firing rate is sufficient to
incinerate the maximum volume of
effluent expected in the boiler fire-
box. Obviously a burner equipped
with on-off controls would not be
feasible.
3.2.2 Selection of an Afterburner
If an afterburner is being considered.as a
means of controlling organic contaminants,
the following information about the applica-
tion must be determined:
1. The chemical contaminant must be
identified or tested to make sure it
will burn completely, without yielding
objectionable products of combus-
tion. When objectionable products are
-------
formed, the control system must em-
ploy equipment in addition to after-
burners.
2. The concentration and physical form
of the contaminant must be deter-
mined. These determinations help pro-
vide estimates of the available heat to
be supplied. If liquid mists or solid
materials are present, they may pre-
clude the use of catalytic afterburners,
or fireboxes of heaters and boilers.
3. The temperature of the effluent to be
controlled is required, to help deter-
mine the needed auxiliary heat and
fuel and the final volume of gases in
the afterburners.
4. The volume rate of the effluent is
required to set the rate of auxiliary
fuel and determine the dimensions of
the afterburner. Throat velocities of
15 to 25 feet per second (ft/sec) have
been found to provide adequate mix-
ing of contaminated gases with flames
of burner combustion products.
Where a single-nozzle burner is used,
velocities of 40 ft/sec have been used
to enhance turbulence and mixing.
Combustion-chamber velocities, on
the other hand, are usually held at 10
to 15 ft/sec to allow sufficient resi-
dence time and sufficient turbulence
for complete combustion while main-
taining a reasonable length for the
afterburner.
5. The oxygen content of the effluent
must be known to determine whether
there will be sufficient quantity for
complete combustion of the contam-
inants and any extra fuel.
6. The space limitations must be con-
sidered in designing the afterburner.
7. Weight limitations must be con-
sidered, because afterburners may be
large enough and heavy enough to
require additional structural support.
8. The recovery of heat should be con-
sidered, since this heat is the only
thing of value that can be recovered
from an incinerator.
9. The cost of electric power and gaseous
fuels must be considered because they
contribute significantly to the total
operating costs of the equipment.
3.3 ADSORPTION
3.3.1 Introduction
The property of a surface to collect vapors
is known as adsorption. Gas-purification
processes involving this principle are based
upon the physical properties of certain granu-
lar solids, known as adsorbents, by which
they attract selected components of a fluid
and retain them on their surfaces. The
amount of adsorption on the surface of most
solids is small; however, certain materials
(e.g., activated alumina, silica gel, and acti-
vated carbon) have been developed to adsorb
substantial quantities of gases and vapors on
their surfaces. These materials are highly
porous and have a very large surface-
to-volume ratio. A fluid is able to penetrate
the material and contact the large surface area
available for adsorption.
Complete package adsorption systems are
available from a number of manufacturers for
use in processes involving volatile solvents.
This section presents the basic operating
principles and applications of adsorption.
Types of adsorbents and equipment are also
discussed.
3.3.2 Basic Operating Principles
There are two main types of adsorption:
(1) physical adsorption in which the gas is
attracted to the surface of the adsorbent and
(2) chemical adsorption in which the gas
interacts with the adsorbent in the manner of
a chemical reaction.2 The surface attraction is
due to van der Waals' forces, the intermolecu-
lar forces that produce normal condensation
to the liquid state. On a smooth surface, van
der Waals' adsorption gives a layer not more
than a few molecules thick. Within the capil-
laries of a porous solid, however, this surface
adsorption is supplemented by capillary con-
densation. As a result, the total amount ad-
sorbed is substantially increased.
3-7
-------
In vapor-phase adsorption, essentially an
exothermic gas-solid equilibrium process, the
approach to equilibrium is governed by the
rate of adsorption. As such, conditions that
shift the equilibrium toward saturation usu-
ally improve the process. Consequently, the
system is more efficient near the dew point of
the adsorbate (substance being absorbed), and
a vapor-phase adsorption system generally
should operate at the highest pressure and the
lowest temperature within the process limi-
tations.3
After some period of usage, the adsorbent
will become saturated with the contaminant
and will no longer function. When this occurs,
it must be regenerated or replaced. Regenera-
tion may be done in a number of ways. The
temperature of the adsorbent may be raised
until the vapor pressure of the adsorbed gas
exceeds atmospheric pressure. The adsorbed
gas will then be evolved and may be collected
at atmospheric pressure. The most common
method is to withdraw the adsorbed gas in a
stream of easily condensable gas such as
steam. The stripped gas is then recovered by
condensing the mixture. Thus by regenera-
tion, the adsorbent is restored to activity, and
the adsorbed material is removed for disposal
or recovery. An inert gas can also be used as a
stripping agent.
If the gas or vapors to be adsorbed consist
of not one but several compounds, the ad-
sorption of the various components is not
uniform. Generally, these components are
adsorbed in an approximate inverse relation-
ship to their volatilities. Hence, when air
containing a mixture of organic vapors is
passed through a bed of adsorbent, the vapors
are equally adsorbed at the start; but as the
amount of the higher-boiling constituent re-
tained in the bed increases, the more volatile
component revaporizes. The point at which
the rate of adsorption of the more volatile
component starts to decrease is called a
"breakpoint." After this breakpoint is
reached, the exit vapor consists largely of the
more volatile material. The higher-boiling
component has displaced the lower-boiling
3-8
component, and this is repeated for each
additional component.
The main function of the adsorption equip-
ment is to bring the gas and solid adsorbent
into direct contact to facilitate adsorption.
Two or more adsorbers are required for
continuous adsorption, one or more being in
operation while the other is being regen-
erated. Fluidized bed and moving bed equip-
ment may be used for large-scale continuous
operation.
3.3.3 Applications of Adsorption
While, in general, fixed-bed adsorbers have
not been installed to recover organic solvent
vapors when the vapor-laden stream con-
tained less than 0.2 pound of solvent per
1,000 scf of gas (2,700 ppm), much lower
concentrations can be actually recovered very
efficiently. This is because adsorption is virtu-
ally complete and independent of concentra-
tion; however, the maximum bed loading
(saturation point) is dependent on initial
concentration.
There is a range of vapor concentration for
which profitable recovery of organics cannot
be obtained with either regenerative or non-
regenerative adsorption. This range, between a
few ppm and about 1,000 ppm, is often
unsuitable for nonregenerative systems be-
cause of the high cost of adsorbent re-
placement. It is also uneconomical for regen-
erative systems because adsorbate recovery
costs generally exceed the value of the ma-
terial recovered.4 For such a range, instead of
desorption, newly developed oxidative de-
struction of the adsorbate is suggested. The
carbon is impregnated with a small amount of
catalyst, which is inactive during adsorption.
It may be activated by heating the air stream,
thus bringing about catalytic oxidation of the
adsorbate.
For satisfactory adsorption, a substance
should have a molecular weight greater than
45. Methanol is the only common organic
solvent that does not meet this requirement.
Since corrosion is a problem in some
applications, especially when steam is used for
-------
regeneration, systems are sometimes con-
structed of stainless steel.
Despite its disadvantages, adsorption ap-
pears to be the most economical control
method for organic vapors in the concentra-
tion range of 100 to 200 ppm when compared
to other methods of emission control.5
Processes that discharge organic vapors that
can be controlled by adsorption include dry
cleaning; degreasing; paint spraying; tank dip-
ping; solvent extracting; metal foil coating;
plastics, chemical, pharmaceutical, rubber,
linoleum, and transparent wrapping manufac-
turing; and, fabric impregnation. In the manu-
facture of paints and varnishes, adsorption of
the solvents followed by their recovery is not
feasible alone, because of the fouling of the
absorbent with coating solids. Scrubbing with
water to remove the paint solids and conden-
sables should precede adsorption of the sol-
vent by carbon.6
3.3.3.1 Types of Adsorbents
The most important characteristics of solid
adsorbents are their large surface-to-volume
ratios and their preferential affinity for cer-
tain specific substances. The preferential
adsorption characteristics and physical prop-
erties of industrial adsorbents determine the
applications for each type. All the adsorbents
are capable of adsorbing organic solvents,
impurities, and water vapor from gas streams,
but each has a particular affinity for either
polar or nonpolar vapors.7
Water vapor is an example of a polar
compound, and organic vapors are nonpolar.
The siliceous and metal oxide adsorbents have
an affinity for polar compounds; activated
carbon is the most commonly used nonpolar
adsorbent.
Silica gel and aluminum oxide preferen-
tially adsorb water from a gas mixture con-
taining water vapor and organic solvents. This
is a serious disadvantage in emission control
where the water content of the gas stream is
often greater than the organic vapor content.
Silica gel and activated alumina disintegrate in
the presence of liquid water, hence wet steam
may not be used for desorption. These ad-
sorbents are used successfully, in the drying
of water-saturated solvents recovered by de-
cantation.
Activated carbons adsorb organic vapors
from gases selectively, even in the presence of
water vapor, and, therefore, are widely used
for gas purification and organic vapor re-
covery. The great advantage that activated
carbon has over other adsorbents in the field
of emission control is its outstanding ability
to recover organic solvents from low concen-
trations in the presence of water vapor. A list
of vapors that can be adsorbed by activated
carbon is presented in Table 3-1.
Activated carbons for use as gas adsorbents
are manufactured from coconut shells, fruit
pits, coal, peat, and petroleum residues.8 The
raw materials are first carbonized by selective
oxidation of the carbonaceous material by air
at low temperature. The hard materials are
crushed to size and activated directly to give
hard dense granules of carbon. The softer
materials are ground to a powder, formed into
briquettes or pellets with a tar or pitch
binder, calcined, crushed to size, and then
activated. Activation consists of heating to
1560° to 1740° F with steam, carbon di-
oxide, or flue gas.
Gas purification application, involving the
removal of small quantities of impurities such
as those listed, include deodorizing of air, the
removal of odors in ventilation systems of
buildings, and the removal of dangerous toxic
vapors from air streams.
3.3.4 Types of Adsorption Equipment
3.3.4.1 Description of an Adsorption Process
A typical adsorption process is shown dia-
grammatically in Figure 3-6. One adsorber
handles the vapor-laden stream while the
other is undergoing regeneration. When the
first, or onstream, adsorbent bed approaches
the break-through point, the second adsorber,
which meanwhile has been regenerated, is
placed on stream. This procedure insures that
the vapor is removed from the air continu-
ously. Caution must be exercised to insure
that an adsorber is adequately cooled after
desorption before it is placed on stream again.
Contact of organic vapors with a hot carbon
3-9
-------
Table 3-1. REPRESENTATIVE GASES AND VAPORS SELECTIVELY
ADSORBED BY ACTIVATED CARBON
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.
acetaldehyde
acetone
benzene
isobutane
normal butane
normal butene
butyne
carbon dioxide
carbon disulfide
carbon tetrachloride
carbonyl sulfide
chloroform
cumene
cyclohexane
cyclohexanone
cyclopentadiene
dichloroethane
dichloroethylene
dimethyl formamide
ethane
ethanol
ethyl acetate
ethyl chloride
ethyl mercaptan
ethylene
ethylene oxide
freon 12
28.
29.
30.
31.
32.
33.
34.
35.
36.
37.
38.
39.
40.
41.
42.
43.
44.
45.
46.
47.
48.
49.
50.
51.
52.
53.
heptane
normal hexane
hexanol
hydrogen cyanide
hydrogen sulfide
isopentane
isoprene (methyl butadiene 1 ,3)
isovaleric acid
simulated kerosene (Ci4H3o)
methane
methyl ethyl ketone
methyl mercaptan
mineral spirits
neopentane
normal pentane
perchloroethylene
propane
propylene
propyl mercaptan
pyridine
tetrahydrofuran
tetrahydrothiamine
toluene
trichloroethylene
vinyl chloride
metaxylene
bed may promote decomposition or partial
oxidation and thereby result in the discharge
of odorous or irritating gases to the atmos-
phere.4
Adsorbers may be classified as regenerative
or nonregenerative. Regenerative systems are
used when the adsorbent is to be reactivated
by desorption and the desorbed vapors re-
covered for reuse or disposal. Nonregenerative
systems are used when the adsorbent is to be
replaced with fresh material, the displaced
material usually being returned to the vendor
for regeneration. Nonregenerative adsorption
is often employed in air-conditioning systems
for large buildings.
3-10
Adsorbers can have fixed, moving, or fluid-
ized beds. They can be set vertically or
horizontally. A single fixed-bed unit is satis-
factory if process downtime is available for
regeneration of the adsorbent. For example,
an adsorber for a spray-paint booth that is in
use only 6 hours a day can be designed to
extract the total emission for this period and
to be desorbed after the operating period.
The simplest equipment for a fixed-bed
adsorber is a vertical cylindrical vessel fitted
with perforated screens that support the
carbon. Another type of fixed bed is arranged
in the shape of a cone, as shown in Figure 3-7.
The cone shape allows more surface area for
-------
I
VAPOR-
LADEN
AIR
ADSORBER 1
ADSORBER 2
STEAM
EXHAUST AIR
TO ATMOSPHERE
J\
I
I
I STEAM PLUS
I SOLVENT VAPORS
CONDENSER
TOP-PHASE
LIQUID
BOTTOM-PHASE
LIQUID
DECANTER
Figure 3-6. Diagrammatic sketch of two-unit fixed-bed adsorber.
VAPOR-
LADEN
AIR IN
CYLINDRICAL
SHELL
HOUSING
VAPOR-
FREE
OUT
Figure 3-7. Left: Diagrammatic sketch of vertical adsorber with two cones, permitting
studies on different depths of carbon beds. Right: Vertical cone adsorber in operation.
3-11
-------
gas fiov. and accommodates higher air rates at
lower pressure drops than does a flat bed of
the same diameter using the same total weight
of adsorbent. Where the cone shape will
provide adequate adsorption, its use tends to
reduce costs of moving the gases through the
system. A commercially available, skid-
mounted unit is shown in Figure 3-8.
Moving-bed adsorbers actually move the
adsorbent into and out of the adsorption
zone. The fluidized-bed adsorber contains a
number of shallow fluidized beds of activated
adsorbent. The air flows upward through
these beds and fluidizes them; the solvent is
progressively adsorbed onto the carbon. Sol-
vent-free air is finally discharged into the
atmosphere through dust collectors at the top
of the adsorber vessel. Fresh adsorber is fed
onto the top tray of the adsorber, into the
fluidized bed. It flows across the tray, over a
weir, and down a downcomer to the tray
beneath, progresssively becoming loaded with
solvent as it moves through the adsorber.
Because the carbon circulation rate can be
closely matched to the solvent feed rates, very
high loading of solvent on carbon can be
achieved. This can result in lower steam
consumption for desorption. The fluidized
state, if properly used, tends to avoid the
channeling problem sometimes encountered
with fixed beds.
3.3.4.2 Factors Involved in Selection
of an Adsorber
Consideration of the proper type of ad-
sorber begins with identifying the compo-
nents of the air stream to be treated, the
stream temperature, pressure, water content,
and flow rate. If any solids are present, they
may have to be removed to prevent fouling of
the adsorbent surface.
With this information, a general idea of the
amount of adsorbent required can be ob-
tained from "adsorption isotherms," graphs
of amount adsorbed versus vapor pressure.
These relationships, often available in the
literature, actually show the quantity ad-
sorbed per unit weight of adsorbent under
true static equilibrium conditions. In air
pollution control, however, most organic
emissions are very dilute vapors that flow over
Figure 3-8. Standard skid-mounted vapor-recovery unit. (Courtesy vuican-Cmci,-,
-------
the adsorbent and are in contact with the
surface only momentarily. Consequently, this
removal process involves mass transfer as well
as adsorption, and no adequate design and
scale-up procedure is available.1
In actual practice, the adsorptive capacity,
height of bed, and stripping conditions for a
given adsorption problem are obtained experi-
mentally in laboratory (or pilot) units. For
example, pilot plant studies have shown that
for optimum use of activated carbon to
control toluene vapors, stripping should be
taken to the point where 8'/2 pounds of
toluene is recovered from each 100 pounds of
carbon instead of attempting to remove 20
pounds, which is possible under very pro-
longed and uneconomic contacting and strip-
ping.9
When the basic information concerning the
stream to be treated is established and the
adsorbent to treat it is selected, the type and
size of adsorber can be determined. For many
processes that discharge organic vapors into
the air, the packaged equipment available is
suitable if certain precautions are taken.
3.3.5 Instruments for Control
of Adsorption Process
Vapor concentration and adsorber tempera-
ture are the most important factors in the
control of an adsorption process. The concen-
tration of the vapor fed to the adsorber must
be kept at a safe level, which may be
calculated from a knowledge of the quantity
of air or gas being drawn through the adsorp-
tion system. In most cases, the rate of solvent
evaporation is measurable, and a simple ori-
fice-type flow meter is sufficient to enable
calculation and maintenance of the desired
concentration.
The low concentrations in the effluent of
the adsorber may be measured in a number of
ways, depending upon the physical and chem-
ical properties of the solvent:
1. The vapor may be adsorbed. A small
measured volume of the vapor-laden
air is passed through a small test
adsorber; the adsorbent is then
steamed, and the solvent is condensed,
collected, and weighed.
2. Vapors may be detected by qualitative
analysis. For example, chlorinated
vapors may be decomposed by passing
them through a quartz tube heated to
more than 400° C; the chlorine is then
detected with a 2 percent potassium
iodide solution.
3. Vapors may be measured quantita-
tively. The solvent is taken into solu-
tion and titrated, using an appropriate
indicator.
4. The vapors may be measured by in-
strumental methods such as infrared
absorption, gas chromatography, or
atomic-absorption spectroscopy. Un-
like chemical quantitative analysis,
which is often lengthy and unsuitable
for routine or continuous control,
these methods are capable of accu-
rately detecting a few-part-per-million
concentration in a gas mixture.
The instrumental methods are best for
pollution control purposes. Some instru-
mental analyzers may be used continuously to
monitor selected components from one or
several process streams such as measurement
of solvent concentration at various points, in
the plant and building, as well as the concen-
tration at the inlet and outlets of the ad-
sorbers.
The temperature should be measured by
placing temperature sensors at strategic points
in the solvent air line and in the carbon bed.
Recording temperature devices may be used
so that temperature variations may be noticed
by the operators. Generally, a change in the
condition of the adsorbent is reflected as a
change in the operating temperature.
The ventilation system and recovery units
must be designed by experienced contractors
to insure as safe a final system as possible,
because adsorption is the process often used
to collect flammable or toxic substances. All
usual precautions for handling toxic or flam-
mable solvents must be observed. If necessary,
flame arresters should be placed so as to
3-13
-------
prevent the spread of flame or an explosion
through feed lines to the adsorber.
If raised to the ignition temperatures and
exposed to oxidizing conditions, activated
carbon burns readily. The majority of carbons
are safe, however, for operation in air temper-
atures below 300° F.7
3.4 ABSORPTION
3.4.1 Introduction
In the absorption process a soluble com-
ponent of a gas mixture is dissolved into a
relatively nonvolatile liquid. In addition to
being simply dissolved, the gas mixture may
react chemically with the liquid. This tech-
nique is quite common and profitable as a
step in petroleum and petrochemical opera-
tions in which a gas has a relatively high
concentration of solvent vapor. From an air
pollution standpoint, absorption has been
used primarily to control inorganic com-
pounds, rather than organic vapors, because
low concentrations of organic vapors tend to
require long contact time and large quantities
of absorbent. The economics of the method
under these circumstances are often unfavor-
able unless the absorbent can be regenerated
or the solution can be used as a process
make-up stream. Otherwise, the absorbent
stream can present an additional disposal
problem. In emission control applications,
absorption is best used in conjunction with
other control techniques such as incineration
or adsorption, as required, to achieve the
prescribed degree of emissions removal.
3.4.2 Applications
Absorption of hydrocarbons in the petro-
leum and petrochemical industries is an im-
portant manufacturing step. Products often
absorbed in a product-recovery step in indus-
trial processes include light hydrocarbons
(e.g., acetylene, butadiene), acetic acid,
methanol, ethanol, propanol, chloroform,
formaldehyde, formic acid, amines, and
ketones. Actually, this type of absorption
must be considered as a preliminary step in air
pollution control as it does not usually re-
move as much of the material as would be
required for emission control.
3-14
Absorption has been employed in scrubbers
to remove condelisable vapors and particulate
matter from the following sources: asphalt
batch plants, ceramic tile manufacture, cof-
fee roasters, chromium-plating units, petro-
leum coker units, fish meal systems, pipe
coating, smoke generators and smoke houses,
and varnish and resin cookers.10'12
3.4.3 Selection of an Absorbent
The ideal absorbent should meet six re-
quirements:
1. The gas should be quite soluble to en-
hance the rate of absorption and to
decrease the quantity of absorbent re-
quired. Solvents that are chemically
similar to the solute generally provide
good solubility.
2. The solvent should be relatively non-
volatile.
3. The solvent should be noncorrosive, if
possible, to reduce equipment costs.
4. The solvent should be inexpensive and
readily available.
5. The solvent should have low viscosity
to increase absorption and reduce
flooding.
6. The solvent should be low in toxicity,
nonflammable, and chemically stable,
and have a low freezing point.1
The common absorbents for organic vapors
are water, mineral oil, nonvolatile hydro-
carbon oils, and aqueous solutions (e.g., solu-
tions of oxidizing agents, sodium carbonate,
or sodium hydroxide).
3.4.4 Types of Absorbers
Gas absorption equipment is designed to
provide thorough contact between the gas and
the liquid solvent to permit interphase diffu-
sion of the materials. This contact is provided
by several types of equipment; namely,
bubble-plate columns, jet scrubbers, packed
towers, spray towers, and venturi scrub-
bers.1 3 Bubble-plate columns employ step-
wise contact by means of a number of plates
or trays arranged so that the gas is dispersed
through a layer of liquid on each plate, as
shown in Figure 3-9. Each plate is more or
less a separate stage, and the number of plates
-------
SHELL-*
TRAY*
DOWNSPOUT,
TRAY
SUPPORT,,
RING
TRAY —
STIFFENER
VAPOR
RISER ~
FROTH J
•><
K
,«^
--^B^y^r
! S ' '•
' , :.2-'r-jf^ •'"
•'X, '^-?->- ^~ 1
iil
•**
•*"
•>\
•i
M «U ««i. 1 1
^•LIQUID IN
-BUBBLE CAP
. SIDESTREAM
^"WITHDRAWAL
^•'< •'.,-• ^INTERMEDIATE
tojj- ™
:•'•'. :•'?»••':'["
"^^M
L
^-GAS IN
^LIQUID OUT
Figure 3-9. Schematic diagram of a bubble-cap tray
tower. 14
(Courtesy of McGraw-Hill Book Co.)
required depends upon the difficulty of the
mass transfer operation and the degree of
separation desired. Jet scrubbers are basically
spray nozzles. Packed towers are filled with a
packing material having a large surface-to-
volume ratio; the packing is wetted by the
absorbent to provide a large surface area of
liquid film for continuous contacting of the
gases (Figure 3-10). Spray towers (Figure
3-11) dispense the liquid in the form of a
spray and pass the gas through this spray.
Venturi scrubbers contact the gas and the
absorbent in the throat of a venturi nozzle
(Figure 3-12). The gas-liquid mixture then
enters an entrainment separator tangentially,
and centrifugal force separates the liquid
droplets from the gas.
Packed and spray towers are most often
used because they introduce relatively lower
pressure losses than the bubble-plate columns.
Low pressure losses are important because
large volumes of exhaust gases with relatively
low concentrations of contaminants are
treated in many air pollution control installa-
tions. Spray chambers have the advantage of
LIQUID
IN
LIQUID
DISTRIBUTOR
PACKING
RESTRAINER
SHELL
RANDOM
PACKING
LIQUID
RE-DISTRIBUTOR
PACKING
SUPPORT
— GAS IN
—-LIQUID
OUT
Figure 3-10. Packed tower.
(Courtesy of McGraw-Hill Book Co.)
CLEAN
GAS
OUTLET
EXHAUST
GAS
INLET
LIQUID
SPRAY
MOISTURE
•ELIMINATORS
LIQUID
ABSORBENT
INLET
ABSORBENT-
CONTAMINANT
SOLUTION
OUTLET
Figure 3-11. Spray tower.
3-15
-------
CLEAN GAS
OUTLET
ENTRAINMENT
LIQUID SEPARATOR
ABSORBENT INLET
EXHAUST
GAS
INLET
ABSORBENT.
CONTAMINANT
SOLUTION
OUTLET
Figure 3-12. Venturi scrubber.
being able to handle exhaust gases containing
participate matter without plugging. The
spray chamber is, however, the least effective
of the various types of absorption equipment.
Since very fine droplets of liquid are neces-
sary for good contact, spray noz/les operated
with high pressure drop are required. These
fine droplets tend to be entrained in the gas
and must be separated.
3.4.5 Principles of Operation
Absorption of a gaseous component by a
liquid occurs when the liquid contains less
than the equilibrium concentration of the
component. This departure of the liquid
stream from equilibrium provides the driving
force for absorption.15 As illustrated in
Figure 3-13, for a given liquid concentration,
the gas concentration in the tower is always
greater than the corresponding equilibrium
concentration.
The rate of absorption depends upon (1)
the temperature, diffusivity, viscosity, and
density of the substance; (2) the tower condi-
tions, particularly the gas and liquid mass
flow rates; and (3) the kind of packing em-
ployed. These factors and equilibrium data
have been correlated to give two key measures
of tower performance, the number of transfer
units and the height of a transfer unit.14 The
number of transfer units is the number of
times the driving force (the departure from
3-16
0.020
- 0.016 -
z
o
U
<
Qi
Ll_
UJ
_l
O
0.012 -
0.008 —
0.004 —
OK^
0 0.002 0.004 0.0060.008 0.0100.012 0.014
X =MOLE FRACTION IN LIQUID
Figure 3-13. Driving force for absorption.
equilibrium) must be divided into the pre-
scribed change in gas concentration. The
height of a transfer unit is the depth of pack-
ing needed to effect one transfer unit. When
the height of a transfer unit is multiplied by
the number of units, the required height of
packing in the absorption tower is estimated.
Procedures for carrying out these calculations
are given in the Air Pollution Engineering
Manual.1 A simple countercurrent tower is
limited in effectiveness to one transfer unit,
and enrichment of the liquid phase is equal to
the driving force producing the enrichment.
Packed towers can provide as many transfer
units as is practical. The gases and liquids are
normally contacted in counter flow to achieve
maximum absorption efficiency, but they can
also be contacted in parallel flow.
The packing should provide a large surface
area and should give enough void space when
packed to permit good liquid flow. The mate-
rial should not break easily in handling and
should be light in weight; it should be chem-
ically inert enough to prevent deterioration.
Manufactured packing has various shapes, as
shown in Figure 3-14. Raschig rings, consist-
ing of hollow cylinders having an external dia-
meter equal to the length, are the most com-
mon type of packing.
In most emission control cases, the concen-
trations involved range so low that the equili-
brium curve and the operating curves are
essentially straight lines. An estimate of the
-------
BERL SADDLE
RASCHIG RING
INTALOX SADDLE
PALL RING
TELLERETTE
Figure 3-14. Common tower packing
materials.
size of an absorber can usually be made under
these circumstances in three steps:
1. The mass flow rates per square foot of
tower area are determined by using in-
formation supplied for the packing
selected (Table 3-2). These prescribed
flows will permit the tower to operate
without flooding. From these values
and the quantity of exhaust stream to
be treated, the tower cross-sectional
area is obtained.
2. The number of transfer units, N, is de-
termined through the use of Figure
3-15. First, convert the liquid and the
gas flows, L and G, from pounds per
hour to moles per hour; then take
their ratio (liquid/gas). Divide this by
the slope of the equilibrium line
(shown as m, Figure 3-13). The result
is the value "A" used as a label for
each curve of Figure 3-15. The re-
quired ordinate is simply the outlet
gas concentration (in mole fraction
units) divided by the inlet concentra-
tion, since the incoming absorbent
usually contains no absorbate (X2~0).
GAS ABSORPTION
1 2 3 4 5 6 8 10 20 30 40 SO
NUMBER OF TRANSFER UNITS,
NtrjG (absorption) or NrQl_ (stripping)
Figure 3-15. Number of transfer units for
absorbers or strippers with constant absorp-
tion stripping factor.
3. The height of a transfer unit is calcu-
lated as follows:
Height of a gas-phase transfer unit:
where:
Htg =
a(gas rate, lb/hr-ft2 )
(liquid rate, lb/hr-ft2
D =
(gas viscosity, lb/hr-ft)
(gas density, lb/ft3 ) (diffusivity, ft2 /hr)
3-17
-------
Table 3-2. CONSTANTS FOR USE IN DETERMINING GAS-PHASE HEIGHT OF TRANSFER UNITS a'14
Packing
Raschig rings
3/8 in.
1 in.
1-1/2 in.
2 in.
Bed saddles
1/2 in.
1 in.
1-1/2 in.
Partition rings
Sin.
Spiral rings (stacked staggered)
3 in. single spiral
3 in. triple spiral
Drip-point grids
No. 6146
No. 6295
a
2.32
7.00
6.41
17.30
2.58
3.82
32.40
0.81
1.97
5.05
650
2.38
15.60
3.91
4.56
&
0.45
0.39
0.32
0.38
0.38
0.41
0.30
0.30
0.36
0.32
0.58
0.35
0.38
0.37
0.17
7
0.47
0.58
0.51
0.66
0.40
0.45
0.74
0.24
0.40
0.45
1.06
0.29
0.60
0.39
0.27
Gas flow rate,
lb/hr-ft2
200 to 500
200 to 800
200 to 600
200 to 700
200 to 700
200 to 800
200 to 700
200 to 700
200 to 800
200 to 1,000
150 to 900
130 to 700
200 to 1,000
130 to 1,000
100 to 1,000
Liquid flow rate,
lb/hr-ft2
500 to 1,500
400 to 500
500 to 4,500
500 to 1,500
1,500 to 4,500
500 to 4,500
500 to 1,500
1,500 to 4,500
400 to 4,500
400 to 4,500
3,000 to 10,000
3,000 to 10,000
500 to 3,000
3,000 to 6,500
2, 000 to 11,500
aCourtesy of McGraw-Hill Book Co.
The diffusivity is that of the component in
the gas stream. Height of liquid-phase transfer
unit:
HtL =
where:
_ 1" (liquid rate, lb/hr-ft2 )
F =
|_ (liquid viscosity, Ib/ft-hr)
(viscosity of the liquid, poises)
(liquid density, g/cm3) (comp. liq. dif-
fusivity, cm2 /sec)
With the number of transfer units estimated,
and the height of each, the packing height is
then estimated as the product of the two:
Packing height = (N)(Hto)
The packed column requires a blower and
motor to overcome its pressure drop. Pres-
sure drop data show considerable variation,
presumably due to differences in packing den-
sity. An empirical correlation has been devel-
oped to estimate the pressure drop per foot
of packed height, using empirical constants
fitted to the data for different types of packi
ing.14 The formula is as follows:
Values for a, 0, 7 are given in Table 3-2. Val-
ues for 0 and 77 are given in Table 3-3.
From these, the height of an overall transfer
unit is:
AP
— = m(10"8)(10'lL
Z
C"2
-
PG
where:
H
tO
HtL/A
AP = Pressure drop in packed tower
3-18
-------
Z - Packed height of tower, in feet
m and n = Pressure-drop constants
L' = Superficial mass liquid velocity
lb/hr-ft2
G' = Superficial mass gas velocity, lb/
hr-ft2
PL - Liquid density, lb/ft3
PG = Gas density, lb/ft3
Constants for the above factors are given in
Table 3-4.
3.5 CONDENSATION
3.5.1 Introduction
Condensation and subsequent removal of
organic compounds is a proved method of
reducing organic emission. Many organic com-
pounds, because of their relatively high boil-
ing points, readily condense even though they
are not highly concentrated. Thus at a given
temperature, if the partial pressure of a com-
pound is increased until it is equal to or
greater than its vapor pressure at that temper-
ature, the compound will condense. Alterna-
tively, if the temperature of a gaseous mixture
is reduced to the saturation temperature, at
which the vapor pressure equals the partial
Table 3-3. CONSTANTS FOR USE IN DETERMINING LIQUID-PHASE
HEIGHT OF TRANSFER UNITSa'14
Packing
Raschig rings
3/8 in.
1/2 in.
1 in.
1-1/2 in.
2 in.
Berl saddles
1/2 in.
1 in.
1-1/2 in.
Partition rings
3 in.
Spiral rings (stacked staggered)
3-in. single spiral
3-in. triple spiral
Drip-point grids
No. 6146
No. 6295
*
0.00182
0.00357
0.0100
0.0111
0.0125
0.00666
0.00588
0.00625
0.0625
0.00909
0.0116
0.0154
0.00725
V
0.46
0.35
0.22
0.22
0.22
0.28
0.28
0.28
0.09
0.28
0.28
0.23
0.31
L' range, Ib/hr-ft2
400 to 15,000
400 to 15,000
400 to 15,000
400 to 15,000
400 to 15,000
400 to 15,000
400 to 15,000
400 to 15,000
3, 000 to 14,000
400 to 15,000
3,000 to 14,000
3,500 to 30,000
2,500 to 22,000
aCourtesy of McGraw-Hill Book Co.
3-19
-------
Table 3-4. PRESSURE DROP CONSTANTS FOR TOWER PACKING a-14
Packing
Raschig rings
1/2 in.
3/4 ir,.
1 in.
1-1/2 in.
2 in.
Berl saddles
1/2 in.
3/4 in.
1 in.
1-1/2 in.
Intalox saddles
1 in.
1-1/2 in.
Drip-point grid
No. 6146
Continuous flue
Cross flue
No. 6295
Continuous flue
Cross flue
m
139.00
32.90
32.10
12.08
11.13
60.40
f\
0.00720
0.00450
0.00434
0.00398
0.00295
0.00340
24.10 0.00295
16.01 0.00295
8.01
12.44
5.66
1.045
0.00225
0.00277
0.00225
0.00214
1.218 0.00227
i
1.088
1.435
0.00224
0.00167
L' range, Ib/hr-ft2
300 to 8,600
1,800 to 10,800
360 to 27,000
720 to 18,000
720 to 21,000
300 to 14,100
360 to 14,400
720 to 78,800
720 to 21,600
2,520 to 14,400
2,520 to 14,400
3,000 to 17,000
300 to 17,500
850 to 12,500
900 to 12,500
P/Z range, Ib/ft2-ft
Oto2.6
Oto2.6
0 to 2.6
0 to 2.6
0 to 2.6
0 to 2.6
0 to 2.6
0 to 2.6
0 to 2.6
0 to 2.6
0 to 2.6
0 to 0.5
0 to 0.5
0 to 0.5
0 to 0.5
aCourtesy of McGraw-Hill Book Co.
pressure of one of the constituents, condensa-
tion will also occur. Condensation can thus be
accomplished in two ways, by decreasing the
temperature or by increasing the system pres-
sure. In most air pollution control applica-
tions, condensation is effected by decreasing
the temperature. Condensation by increasing
pressure is possible, but usually not practical.
Condensers have found a wide range of
application in the organic chemical industry
where their purpose has been to condense
concentrated vapors in the primary process,
rather than to reduce contaminant emissions.
Applied in the primary process, they recover
valuable products and reduce the volume of
effluent gas.
3-20
Control of organic emissions by condensa-
tion is limited by the equilibrium partial pres-
sure of the component. As condensation
occurs, the partial pressure of the material
remaining in the gas phase decreases rapidly,
and complete condensation is not possible.
For example, even at 32° R toluene has a
vapor pressure of about 6 millimeters of
mercury (mm Hg); at atmospheric pressure
(760 mm Hg), a gas stream saturated with
toluene would still contain about 8000 ppm
of that gas. Thus, condensers must usually be
followed by a secondary air pollution control
system such as an afterburner, which treats
the noncondensible gases and achieves a high
degree of overall efficiency. For this reason,
-------
condensers have not been used as much as
afterburners ajid adsorbers to control organic
gas emissions.
3.5.2 Basic Operating Principles and
Types of Equipment
Since condensation is usually accomplished
by decreasing the temperature of the vapor, a
cold surface or a cooling liquid is deployed in
the gas stream to induce condensation.
Condensers may be classified into two
groups; namely, surface and contact. In a sur-
face condenser, the vapor to be condensed
and the cooling medium are separated by a
metal wall; in a contact condenser, the vapor
and cooling medium are brought into direct
contact.
Surface condensers include the common
shell-and-tube-type heat exchangers, as shown
in Figure 3-16. In these devices, the cooling
medium, usually water, flows through the
tubes, and vapor condenses on the outside
surface. The condensed vapor forms a film on
the cool tubes and drains away to storage or
disposal. Air-cooled condensers are usually
constructed with finned tubes, and the vapor
condenses inside the tubes.
Contact condensers cool the vapor by
spraying a cold liquid, usually water, directly
into the gas stream. The condensed vapor and
water mixture are then usually treated and
disposed, or they may be recovered. Contact
condensers are, in general, less expensive,
more flexible, and more efficient in removing
organic compounds than surface condensers.
Many variations of the contact condenser
exist in addition to the spray tower shown in
Figure 3-16. These include the steam or water
ejector, and barometric condenser in which
the condensing vapors create a negative pres-
sure, which serves to induce the flow of addi-
tional vapor from the process.
3.5.3 Design Factors and Applications
The main design factors to be considered in
condensing organic compounds are the
type(s) of compounds and their temperature,
volume, concentration, vapor pressure, and
specific heat. When a surface condenser is uti-
lized, knowledge of the heat transfer coeffi-
cients on both the vapor and liquid sides is
also required. The temperature and amount of
coolant available are also important considera-
tions.
In the design of a contact condenser, the
amount of cooling water to be used is the
critical design factor. This may be computed
by calculating the heat to be removed from
the condensing vapor: Heat in Btu/hour =
(pounds of vapor to be condensed per hour)
X (latent heat of vaporization) + (heat
capacity of the liquid) X (degrees of sub-
cooling required). The amount of heat that
must be removed from the noncondensible
gases must also be included. The amount of
cooling water required is this heat load
divided by the allowable difference in water
temperature (inlet water temperature - outlet
water temperature).
In a contact type of condenser, about 15
pounds of water (1.8 gallons) at 60° F is re-
quired to condense 1 pound of steam at 212°
F and cool the condensate to 140° F. Dilu-
tion and subcooling of the condensate pre-
vents release of volatile compounds.
In a typical cylindrical contact-spray-
chamber condenser, contact times on the order
of 1 second with a cross-sectional velocity of
about 400 to 500 feet per minute have been
used. Pressure drops on the order of 1 inch of
water are typical of these units. The use of a
contact condenser can result in a water pollu-
tion problem, a factor that sometimes re-
stricts the use of this type of condenser.
In the design of a surface condenser, the
area of heat exchange is the critical factor.
This area is computed by the following
equation:
A UT
m
Where: A=Heat transfer area, ft2
Q=Heat to be removed, Btu/hr
U=Overall heat transfer coefficient,
Btu/hr-ft2-°F
T =Mean temperature difference, °F
lm
3-21
-------
INLET OUTLET
INLET
OUTLET
CT*
VAPOR
SPRAY
DISCHARGE
Figure 3-16. Types of condensers. Surface condensers: (a) Shell and tube, Schutte and Koerting Co.,
Cornwell Heights, Penn.; (b) fin fan, Hudson Products Corp., Houston, Texas; (c) finned hairpin
section, Brown Fintube Co., Tulsa, Okla.; (d) integral finned section, UOP Wolverine Tube, Allen
Park, Mich.; and (e) tubular, Hudson Products Corp., Houston, Texas. Contact condensers; (f) Spray;
(g) jet, Schutte and Koerting Co., Cornwell Heights, Penn.; and (h) barometric, Schutte and Koerting
Co., Cornwell Heights, Penn.
3-22
-------
The solution of this equation is difficult
since U depends on many parameters of the
condensing and cooling streams. A value for U
may be estimated by means of a heat balance
or may be determined experimentally.16'17
Condensers have found a wide range of
applications in controlling organic com-
pounds, as shown in Table 3-5. Their applica-
tion in any specific process depends on the
amount and type of coolant available, liquid
disposal problems, and the volume of the
recovered compounds. Condensers are usually
used as preliminary devices and for best con-
trol are followed by a more efficient device
such as an afterburner or absorber.
3.6 USE OF LESS PHOTOCHEMICALLY
REACTIVE MATERIALS
3.6.1 General Considerations
Emission of organic air pollutants from
some operations cannot be reduced by the in-
stallation of control equipment. For example,
solvent evaporation from decorative and pro-
tective coatings of buildings and structures
cannot be confined for disposal. Industrial
surface-coating operations, vapor degreasing,
dry cleaning, certain electronic and electrical
manufacturing procedures, and some rubber
and plastic manufacturing procedures emit
organic vapors that can be minimized, how-
ever, by installing control equipment, but the
cost may be prohibitive. An alternative to
these "mechanical" techniques for controlling
organic emissions from industrial operations is
to reformulate the solvent being used so that
the emitted material is less reactive.
Photochemical reactivity, or simply "reac-
tivity," is the tendency of an atmospheric
system containing the organic compound in
question and nitrogen oxides to undergo,
under the influence of ultraviolet radiation
(sunlight) and appropriate meteorological
conditions, a series of chemical reactions that
result in the various manifestations associated
with photochemical air pollution. These in-
clude eye irritation, vegetation damage, and
visibility reduction.
All organic compounds, in principle, can be
ranked according to their relative ability to
undergo photochemical reactions character-
istic of smog. For many, however, the data
are not available. Furthermore, the ranking of
a number of organic compounds on the basis
of their rates of disappearnace during photo-
lysis would not necessarily be the same rank-
ing of those same compounds on the basis of
their ability to produce eye irritation. Also,
these two rankings would be different from
the ranking of the same compounds on the
basis of their abilities to reduce visibility. A
ranking on their ability to cause plant damage
would be different still, and so forth. Thus,
there are great difficulties in classifying or-
ganic compounds according to a photo-
chemical reactivity scale that would be cor-
rect for all occasions. 18 > '9
Table 3-5. REPRESENTATIVE APPLICATIONS OF CONDENSERS
IN AIR POLLUTION CONTROL
Petroleum refining
Petrochemical
manufacturing
Basic chemical
Miscellaneous
industries
Gasoline accumulator
vents
Storage vessels
Lube oil refining
Polyethylene gas
accumulator vents
Styrene
Copper naphthenates
Insecticides
Phthalic anhydride
Resin reactors
Solvent recovery
Ammonia
Chlorine solutions
Drycleaning
Degreasers
Tar dipping
3-23
-------
3.6.2 Regulations Based on Photochemical
Reactivity
In order to regulate organic emissions on
the basis of photochemical reactivities, a defi-
nition of photochemical reactivity must be
adopted. To date, two areas, Los Angeles
County and San Francisco Bay Area, have en-
acted regulations of this type. Both regula-
tions based their definitions of reactivity on
the chemical structure of specified materials.
The definitions differ because the goals of the
two rules differ in degree. The San Francisco
Bay Area rule seeks only to limit emissions.of
very reactive materials, while Los Angeles
County's rule also seeks to limit emissions of
moderately reactive materials. In order to
illustrate this control technique, the principal
provisions of both of these rules are given in
the following sections. Because the Los
Angeles rule was a pioneering effort, some
background information leading up to the
adoption of the rule is given.
3.6.3 Rule 66 of Los Angeles County
Los Angeles County, which has a severe
photochemical air pollution problem, in 1966
enacted a regulation to limit certain organic
emissions on the basis of photochemical reac-
tivity. This regulation, entitled Rule 66, ap-
plies to organic solvent emissions. Section "k"
of this rule20 defines a photochemically reac-
tive solvent as follows:
"For the purposes of this rule, a photo-
chemically reactive solvent is any solvent
with an aggregate of more than 20 per-
cent of its total volume composed of the
chemical compounds classified below or
which exceeds any of the following in-
dividual percentage composition limita-
tions, referred to the total volume of sol-
vent:
(1) A combination of hydrocarbons,
alcohols, aldehydes, esters, ethers,
or ketones having an olefinic or
cyclo-olefinic type of unsaturation:
5 percent;
(2) A combination of aromatic com-
pounds with eight or more carbon
3-24
atoms to the molecule except ethyl-
benzene: 8 percent;
(3) A combination of ethylbenzene,
ketones having branched hydro-
carbon structures, trichloroethyl-
ene, or toluene: 20 percent."
Section "a" limits the emissions from paint
baking ovens or heat-curing operations to 15
pounds per day or requires that they be re-
duced by 85 percent, regardless of the type of
solvent used.
Section "b" limits emissions from all other
operations using photochemically reactive sol-
vents to 40 pounds per day or requires that
they be reduced by 85 percent.
Rule 66.1 prohibits the sale or use of archi-
tectural coatings that contain photochemi-
cally reactive solvents, as defined above.
Specifically exempt from the provisions of
Rule 66"b" are: saturated halogenated hydro-
carbons; perchloroethylene; applications of
insecticides, pesticides, or herbicides; and the
manufacture, transport, or storage of organic
solvents.
Rule 66 provides that emission reduction
must be accomplished by (1) incineration
with at least 90 percent of the carbon in the
solvent being oxidized to carbon dioxide, or
(2) adsorption, or (3) a method determined to
be not less effective than (1) or (2).
The experimental procedures and the evalu-
ation of the results obtained which led up to
the provisions of Rule 66 have been described
by Hamming.2 l
The control techniques used to secure com-
pliance with Rule 66 have been described by
Krenz et al.2 2 Some of the methods used are
reformulation of the solvents used in the man-
ufacture of paints and other protective coat-
ings, use of direct-fired afterburners to con-
trol emissions from paint baking ovens, use of
trichloroethane and perchloroethylene in
vapor degreasers, and reformulation of petro-
leum dry-cleaning solvents.
3.6.4 Background of Rule 66
This section was extracted from material
prepared by personnel of the Los Angeles
-------
County Air Pollution Control District to ex-
plain the need for Rule 66, its scope, history
of its development, methodology used in eval-
uating reactivity of solvents, and implementa-
tion of the Rule.
Specific types of hydrocarbons, such as are
found in gasoline, had been demonstrated to
be active participants in atmospheric reactions
responsible for typical smog effects. Addi-
tional extensive research by the Los Angeles
County Air Pollution Control District has
since demonstrated that many organic solvent
materials are highly reactive when irradiated
in the presence of oxides of nitrogen, and that
some of these organic solvents can produce
even more ozone and eye irritation than irradi-
ation of auto exhaust. It has also been shown
that partial oxidation of solvent vapors prior
to their emission to the atmosphere, which
occurs in many solvent-using processes, en-
hances its photochemical reactivity. It is thus
apparent that organic solvent emissions con-
tribute significantly to photochemical smog in
Los Angeles County.
Several surveys were made to determine the
types and quantities of organic solvents used
in Los Angeles County. Methods of usage
and estimated emissions were obtained from
the data obtained.
Preliminary screening of the solvents was
accomplished on the basis of eye irritation
tests performed by irradiating diluted por-
tions of each solvent in a 50-liter flask.
More extensive tests were performed in
larger chambers of 1180-cubic-foot capacity.
Solvent vapor concentrations of 2 to 16 ppm
were used with 1 or 2 ppm of oxides of nitro-
gen and irradiation times of 4 to 6 hours. The
photochemical reactions were followed by
analyzing for hydrocarbons, nitric oxide,
nitrogen dioxide, total oxidant, ozone,
aldehydes, carbon monoxide, sulfur dioxide,
and aerosols.
In evaluating the air pollution potential of
a solvent or other test substance, its contribu-
tion to any photochemical effect was con-
sidered. Such effects include:
1. Eye irritation.
2. Ozone formation.
3. Aerosol formation.
4. Total aldehyde formation.
5. Effect on NOX reaction.
These criteria were selected as being among
the most significant in relation to natural
photochemical smog incidents, though not
necessarily in the order named. Each solvent
or mixture tested was evaluated in terms of
these criteria and compared, on the same
basis, with auto exhaust in various concen-
trations, pure olefins, and a "blank" chamber.
If a substance being judged equalled or ex-
ceeded (the most dilute concentration of)
auto exhaust or pure olefins in their ability to
produce any of the cited effects, it was con-
sidered to be reactive. If it failed to produce
any of the cited effects to a degree compa-
rable with that produced by auto exhaust or
pure olefins, but greater than that produced
by a "blank" or "background" irradiation, it
was judged to be nonreactive or inert. Sol-
vents in the "reactive" classification were con-
sidered as probably requiring control; those in
the "slightly or moderately reactive" classifi-
cation were regarded as possibly requiring
control, but to a lesser extent than those in
the "reactive" category; and the "nonreac-
tive" substances were regarded as requiring
little or no control.
The efficacy of Rule 66 is attested to by
the reduction in the emission of organic sol-
vents since its enactment. By 1969 the emis-
sions of organic solvents would have exceeded
a calculated 600 tons per day if uncontrolled.
Because of Rule 66, the emission of organic
solvents in 1969 not only was reduced to 500
tons per day, but many of the emissions were
of the slightly reactive or nonreactive type
and, therefore, do not contribute in any great
measure to the photochemical smog problem.
Future reductions may be confidently ex-
pected since it has been demonstrated that
compliance with the Los Angeles County sol-
vent control legislation can be achieved by (1)
treatment of the organic emissions resulting
from solvent usage, (2) converting to less
photochemically reactive solvents, or (3)
changing the process. An engineering permit
3-25
-------
system and an enforcement inspection pro-
gram insure that control equipment to treat
the effluent is designed for the required effi-
ciency and operated in compliance with the
law.
3.6.5 Applicability of Rule 66 to Other
Areas
Rule 66 was designed to alleviate a condi-
tion in a specific area. Louis J. Fuller,23 Air
Pollution Control Officer of Los Angeles
County, had this to say concerning its appli-
cability to other areas:
"It has been said that Rule 66 is the
most talked about local air pollution
legislation in the country. It is true that
many communities both from this
nation and abroad have inquired about
it. I would, therefore, like to caution
these communities first to learn the char-
acter and extent of their local problems,
and then work to resolve them. This rule
covers thousands of products, processes,
combinations of equipment, production
lines, and applications and is framed
only for Los Angeles County. It may
prove to be unrelated to other areas."
3.6.6 Regulation 3 of San Francisco Bay Area
Air Pollution Control District
In 1967, the San Francisco Bay Area Air
Pollution Control District adopted a regula-
tion to restrict the emissions of reactive or-
ganic materials. Reactive organic compounds
are defined as olefins, substituted aromatics,
and aldehydes. Not included as olefins are
compounds in which all olefinic groups con-
tain three or more halogen atoms. A com-
plying solvent is defined as any organic sol-
vent which emits to the atmosphere organic
compounds which on condensation contain 8
percent or less of reactive organic compounds
provided that an additional 12 percent of the
organic compounds from the emission may be
mono-substituted aromatic compounds.24
The rule limits organic emissions to 50
ppm, calculated as hexane, unless one of the
following requirements is met:
1. A complying material is being used
and no heat is applied, or if heat is
3-26
used and the emission contains fewer
than 5 ppm of aldehydes.
2. There are fewer than 5 percent
reactives in the organic fraction of the
emission.
3. There are fewer than 10 pounds per
day reactive organic compounds, or
less than 20 pounds per day total or-
ganic compounds emitted.
4. The reactive compounds in the emis-
sion have been reduced by 85 percent
overall.
If heat is applied and the emission contains
more than 5 ppm aldehydes, the total or-
ganics must be fewer than 50 ppm, or the
emission must meet one of requirements 2, 3,
or 4 above.
The purpose of this rule is to control the
emissions of very reactive compounds only.25
3.6.7 Photochemical Reactivity of
Trichloroethylene
Los Angeles County Air Pollution Control
District, on the basis of studies, divided the
common solvents into classes: (1) reactive, (2)
slightly or moderately reactive, and (3) nonre-
active. Trichloroethylene was placed in cate-
gory 2.
Stanford Research Institute, under the
sponsorship of a group of manufacturers of
trichloroethylene, conducted a 2-year smog-
chamber study to develop additional data on
the photochemical reactivity of trichloro-
ethylene. The summary report of this study,
by Katherine W. Wilson,2 6 was issued in Sep-
tember 1969. Different experimental condi-
tions and different indices of reactivity from
those used in the Los Angeles studies were
used in these studies. On the basis of their
results, the Stanford group attributed a low
photochemical reactivity rating to trichloro-
ethylene.
3.7 REFERENCES FOR SECTION 3
1. Air Pollution Engineering Manual, Danielson, J.
A. (ed.). U.S. DHEW, PHS. National Center for
Air Pollution Control. Cincinnati, Ohio. PHS
Publication No. 999-AP-40. 1967. 892 p.
-------
2. Glasstone, S. Textbook of Physical Chemistry.
2d ed. New York, D. Van Nostrand Co 1946
1320 p.
3. Vapor Phase Adsorption. Pittsburgh Activated
Carbon Co. Pittsburgh, Pa. 1969.
4. Turk, A. Source Control by Solid Adsorption.
In: Air Pollution. Stern, A. C. (ed.). Vol. II. New
York, Academic Press, 1962. p. 367-386.
5. Chass, R. L., C. V. Kanter, and J. H. Elliott.
Contribution of Solvents to Air Pollution and
Methods for Controlling Their Emissions. J. Air
Pollution Control Assoc. 75:64-72 February
1963.
6. Hardison, L. C. Controlling Combustible Emis-
sions. Paint Varn. Prod. 57:41-47, July 1967.
7. Fulker, R. D. Adsorption. Great Britain, George
Newnes, Ltd., 1964. p. 5-15.
8. Doying, E. G. Activated Carbon. In: Kirk-
Othmer Encyclopedia of Chemical Technology,
Standen, A. (ed.). Vol. 4, 2d ed. New York, In-
terscience Publishers, 1964. p. 149-150.
9. Elliott,!. H., N. Kayne, and M. F. Le Due. Ex-
perimental Program for the Control Organic
Emissions from Protective Coating Operations.
Air Pollution Control District. Los Angeles, Cal.,
Final Report Number 8, June 1962. 147 p.
10. Lunche, R. G., et al. Air Pollution Engineering in
Los Angeles County. Air Pollution Control Dis-
trict. Los Angeles, Cal. July 1, 1966.
11. Kropp, E. P. Scrubbing Devices for Air Pollution
Control. Paint, Oil, Chem. Rev. 775(14): 13-16,
July 3, 1952.
12. Hardison, L. C. Disposal of Gaseous Wastes. UOP
Air Correction Division, Greenwich, Conn. Pre-
sented at Seminar on Waste Disposal Sponsored
by East Ohio Gas Co. Cleveland. May 18, 1967.
13. How to Control Gases and Vapors to Abate Air
Pollution. Heating, Piping, Air Conditioning.
57:113-126, December 1959.
14. Treybal, R. E. Mass-Transfer Operations. New
York, McGraw-Hill Book Co., 1955, 666 p.
15. Eckert, J. S. et al. Absorption Processes Utilizing
Packed Towers. Ind. Eng. Chem. 59:41-47, Feb-
ruary 1967.
16. Rubin, F. L. et al. Heat-Transfer Equipment. In:
Chemical Engineer's Handbook, Perry, J. H.
(ed.). 4th ed. New York, McGraw-Hill Book Co.,
1963. p. 11/1-11/49.
17. Votta, F. Condensing From Vapor-Gas Mixtures.
Chem. Eng. 77(12):223-228, June 8, 1964.
18. Altshuller, A. P. Reactivity of Organic Sub-
stances in Atmospheric Photooxidation Reac-
tions. U. S. DHEW, PHS. Division of Air Pollu-
tion. Cincinnati, Ohio. PHS Publication Number
999-AP-14. July 1965. 29 p.
19. Altshuller, A. P. An Evaluation of Techniques for
the Determination of the Photochemical Reactiv-
ity of Organic Emissions. J. Air Pollution Control
Assoc. 75:257-260, May 1966.
20. Los Angeles Air Pollution Control District. Rules
and Regulations. Regulation IV. Prohibition. In:
A Compilation of Selected Air Pollution Emis-
sion Control Regulations and Ordinances.
National Center for Air Pollution Control. Wash-
ington, D. C. PHS Publication Number
999-AP-43. 1968. p. 24, 55, 90, 103, 109.
21. Hamming, W. J. Photochemical Reactivity of
Solvents (Paper No. 670809). S.A.E. Transac-
tions. 76:159, 1968.
22. Krenz, W. B., J. E. Dickinson, and R. L. Chass.
An Appraisal of Rule 66 of the Los Angeles
County Air Pollution Confrol District. J. Air Pol-
lution Control Assoc. 75:743-747, November
1968.
23. Fuller, L. J. The Need for Rule 66 in Los Angeles
County. Presented at Society of Automotive
Engineers, Aeronautic and Space Engineering and
Manufacturing Meeting, Los Angeles. October
2-6, 1967. p. 3.
24. San Francisco Bay Area Air Pollution Control
District Regulation 3 (adopted January 4, 1967).
In: A Compilation of Selected Air Pollution
Emission Control Regulations and Ordinances.
National Center for Air Pollution Control. Wash-
ington, D.C. PHS Publication Number 999-AP-
43. 1968. p. 106-109.
25. Feldstein, M. and W. R. Grouse. The Application
of the Bay Area Air Pollution Control District
Regulation 3 to Solvent Emission Control. Pre-
sented at 61st Annual Meeting of the Air Pollu-
tion Control Association. St. Paul. June 1968. p.
2.
26. Wilson, K. W. Photoreactivity of Trichloroethy-
lene. Stanford Research Institute. Menlo Park,
Cal. September 1969. p. 2-3.
3-27
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4, CONTROL SYSTEMS FOR INDUSTRIAL PROCESSES
Currently, air pollutants can only be con-
trolled at the source. Industrial sources of
emissions are controlled by improvement of
plant housekeeping or operation, substitution
of process or material, and direct prevention
of material from escaping to the atmosphere.
The process valves in an oil refinery, for
example, can be repaired, or furnaces in a mill
can be adjusted to give more efficient com-
bustion. A sanitary landfill can be used
instead of incineration for disposing of some
types of waste materials, or a relatively inert
organic solvent can be used to replace a
photochemically reactive solvent. Operations
that do not directly influence the basic
process can sometimes be controlled directly
by afterburning, adsorption, absorption, or
condensation techniques to prevent the
escape of emissions to the atmosphere. At
times, the control methods may overlap, or an
industry or installation may use more than
one of the four basic techniques.
4.1 PETROLEUM REFINERIES
4.1.1 Introduction
From the production of crude oil to the
marketing of finished products, the petroleum
industry has the potential for emitting signifi-
cant quantities of hydrocarbon gases and
vapors. These emissions are often undesirable;
they may also be precursors of photochemical
smog. Crude oil is first produced from the
ground. Then the liquid hydrocarbons are
separated from the gases, light hydrocarbon
vapors, and water. Finally, the crude oil is
stored until it is removed to the refinery
where it is converted to saleable products. In
crude oil production, most of the emissions
are due to evaporation of hydrocarbons from
storage tanks.
The design of a refinery depends on the
kind of crude oil it processes and on the final
products it manufactures. Refinery opera-
tions are most easily discussed, therefore, in
terms of their similar functions. Figure 4—1 is
a schematic diagram of a typical refining
process.
Since crude oil as it is produced has few
uses, it is processed to obtain saleable prod-
ucts, such as gasoline, kerosene, fuel oil,
petrochemical raw materials, waxes, lubri-
cating oils, and asphalt. Processing involves
four major steps: separation, conversion,
treatment, and blending.
The first refining step, separation by distil-
lation within a specific temperature range,
yields fractions, the relative volumes of which
are determined by the nature of the crude oil.
These fractions are usually further refined to
meet the demands for the various petroleum
products. These processes are outlined below:
Conversion by cracking is employed to
convert high-molecular-weight hydrocarbons
into products of lower molecular weights. For
example, cracking partially converts heavy gas
oil to gasoline. If a catalyst is used (the more
usual case), it is called catalytic cracking; if
not, it is thermal cracking. Thermal cracking
requires higher temperatures and pressures
than those required to catalytic cracking.
Gasoline yield and quality can be improved
by several other processes. In catalytic re-
forming, the molecules of the gasoline feed
stock are rearranged and dehydrogenated to
produce high-octane gasoline blending stocks.
Isomerization rearranges molecules to increase
the octane number; it also increases molecular
branching, but it does not add to or remove
anything from the original material. In still
other conversion processes, liquid gasoline is
made from the hydrocarbon gases generated
during cracking. Polymerization joins two or
more olefin molecules. Alkylation joins an
4-1
-------
DRY GAS
*- FUEL GAS
GAS
PLANTS
SATURATE
AND
UNSATURATE
LIGHT
NAPHTHA
POLY) GASOLINE
STRAIGHT RUN GASOLINE
HYDROCRACKED GASOLINE
AVIATION
GASOLINE
HEAVY
NAPHTHA
MIDDLE
DITILLATES
HYDROGEN
PLANT
HYDROCRACKED
GASOLINE
HEAVY GAS OIL
HYDROGEN
SULFIDE
CATALYTIC
GASOLINE
CATALYTIC
CRACKING
UNIT
LIGHT FUEL OIL
COKER
GASOLINE
LUBES
WAXES
>- GREASES
REDUCED
CRUDE^
LUBE DISTILLATES
OLEFINS TO
CHEMICAL
>. LIGHT FUEL
OIL
HEAVY FUEL
Figure 4-1. Processing plan for typical complete refinery1 (Courtesy of Academic Press, inc.)
-------
olefin with a branched chain paraffin to yield
a saturated hydrocarbon.
Treatment steps are used to purify the
material or to prevent an undesirable reaction
with an impurity. For example, during selec-
tive hydrogenation, sulfur and nitrogen as
impurities in the feed stocks are converted to
hydrogen sulfide and ammonia, respectively.
In addition, olefins and aromatic compounds
may be hydrogenated to partial or complete
saturation. Three types of treatment em-
ployed are acid treatment, "sweetening," and
solvent extraction. Petroleum fractions may
be brought into contact with concentrated
sulfuric acid to remove sulfur, nitrogen, and
undesirable unsaturated compounds and to
improve color and odor. Sweetening converts
mercaptans to disulfides and thus improves
odor. Sodium plumbite (doctor), lead sulfide,
hyprochlorite, and copper chloride are
common sweetening agents. In solvent extrac-
tion, solvents are used to remove undesired
contaminants or to concentrate desired com-
ponents.
Physical treatments such as absorption,
air-blowing, electrical coalescence, and filtra-
tion are used in intermediate refining proc-
esses to remove contaminants.
Another commonplace activity at refineries
is the blending of base stocks to produce a
wide variety of finished products.
A list of equipment, facilities, and proc-
esses likely to produce organic emissions in
crude oil production and in refining includes:
1. Storage.
2. Catalyst regeneration.
3. Pipeline valves.
4. Pressure relief valves.
5. Pump and compression seals.
6. Loading facilities.
7. Drain and waste separators.
8. Blowdown systems.
9. Boilers and process heaters.
10. Vacuum jets.
11. Chemical treatment.
4.1.2 Storage
Storage is potentially the most important
source of hydrocarbon emissions in the petro-
leum industry. Vapors can be emitted when
storage tanks "breathe," when vapors are
displaced during filling, and when liquids
evaporate. Tanks "breathe" due to the expan-
sion and contraction of their contents with
the heat of the day and the cool of the night.
When the contents expand, air mixed with
hydrocarbon vapors is forced out of the tank.
Methods have been developed to estimate
losses and to minimize these losses from
storage tanks.2'5
Pressure tanks, fixed-roof tanks, floating-
roof tanks, and conservation tanks provide
closed storage. Pressure tanks will withstand
pressures exerted by their contents and are
themselves a control measure. Fixed-roof
tanks are vertical cylinders with a flat, coni-
cal, or domed roof; they often have open
vents to the atmosphere. Floating-roof tanks
have pan, pontoon, or double-deck floating
roofs. Pan-floating roofs have flat metal plates
for the roofs; they may buckle and lose
vapors or sink. In many tanks, pontoon
sections have been added to the exposed
decks to overcome some of these losses.
Center drains can be used to handle the
drainage. Pontoon roofs are often used on
large-diameter tanks; some have a vapor trap
on the underside. Double-deck roofs provide
compartmented dead-air space over the entire
liquid surface; the bottom deck is often coned
upward to trap vapors. Conservation tanks are
connected to gas storage systems and have
internal flexible diaphragms, or floating
plastic blankets.
Floating roofs normally have a sealing
element between the roof and tank wall. The
floating section is usually about 8 inches
smaller in diameter than the tank wall. The
space between is usually sealed by vertical
shoes (metal plates) connected by braces to
the floating roof. The shoes, suspended so
that they exert force against the tank wall, are
fixed with a suitable fabric between the shoes
and the floating roof. The fabric seal extends
from the top of the sealing plates to the inner
surface of the tank, and its flexibility permits
it to seal even riveted areas. A secondary seal
can be employed to act as a wiper blade,
4-3
-------
reducing the wicking action associated with
floating roofs. Another type of sealing device
is a flexible tube, filled with air or liquid,
which rests on the hydrocarbon surface and
keeps contact with both the roof and the tank
shell. Fixed-roof tanks can often be converted
to floating-roof construction by use of com-
mercially available internal elements.
Floating plastic blankets or tiny plastic
spheres have been developed to function as
floating roofs.6 These coverings have proved
to be effective controls for fixed-roof crude
oil tanks. They do not reduce emissions of
gasoline or one-component fractions as effec-
tively as the other devices.
A good reflecting paint can reduce evapora-
tion by lowering the temperature of petro-
leum in storage. Vaporized material can be
contained using a vapor-balance system
wherein the vapor spaces of all tanks contain-
ing the same general classification of products
are manifolded together and fed to a reservoir
tank from which any excesses can be fed to a
flare or a boiler. Vapor recovery systems
recover all hydrocarbon vapors, by compres-
sion and absorption, as liquid product or as
fuel gas.
Tanks may lose vapors at gaging hatches,
sample hatches, and relief vents unless these
are designed and maintained for proper clo-
sure.
4.1.3 Waste-Gas Disposal Systems7
Large volumes of hydrocarbon gases are
produced in modern refineries and petro-
chemical plants. Generally, these gases are
collected and used as fuel or as raw material
for further processing. Sudden or unexpected
upsets in process units and scheduled shut-
downs, however, can produce gas in excess of
the capacity of the gas-recovery system.
Emergencies that can cause the sudden vent-
ing of excessive amounts of gases and vapors
include fires, compressor failures, over-
pressures in process vessels, line breaks, leaks,
and power failures.
A system for disposal of emergency and
waste refinery gases normally consists of a
4-4
manifolded pressure-relieving or blowdown
system and a blowdown recovery system, a
system of flares for the combustion of the
excess gases, or both. In addition to disposing
of emergency and excess gas flows, these
systems are used in the evacuation of units
during shutdowns and turnarounds. Normally,
a unit is shut down by depressuring into a fuel
gas or vapor recovery system with further
depressuring to essentially atmospheric pres-
sure by venting to a low-pressure flare system.
Thus, overall emissions of refinery hydro-
carbons are substantially reduced.
A blowdown or pressure-relieving system
consists of relief valves, safety valves, manual
bypass valves, blowdown headers, knockout
vessels, and holding tanks. A blowdown re-
covery system also includes compressors and
vapor surge vessels such as gas holders or
vapor spheres. Flares are usually considered as
part of the blowdown system in a modern
refinery.
4.1.3.1 Pressure-Relief Systems
A pressure-relief system can consist of one
relief.valve, safety valve, or rupture disc or of
several relief devices manifolded to a common
header. Usually the systems are segregated
according to the type of material handled,
that is, liquid or vapor, as well as to the
operating pressure involved. The following
definitions are taken from reference 8:
1. A relief valve is one which automati-
cally opens when the static pressure
exceeds a preset value. It opens
further with an increase of pressure
over the set pressure. It is used pri-
marily for liquid service.
2. A safety valve opens fully when the
static pressure exceeds the set pres-
sure. It is used for gas or vapor service.
3. A rupture disc consists of a thin metal
diaphragm held between flanges. It is
fabricated to rupture at a predeter-
mined pressure.
In a vapor blowdown system a knockout
drum is used to remove entrained liquids from
the gas stream. This is particularly important
if the gas is to be burned in a smokeless flare.
-------
4.1.3.2 Flares1
Smokeless flares are of two types, elevated
flares and ground-level flares. Flares are ele-
vated in order to safely dissipate the heat
released and diffuse any vapors that may be
emitted.
Smoke is a by-product of incomplete com-
bustion. Smokeless combustion can be
achieved if there is (1) sufficient fuel values in
the gas mixture to obtain the minimum
theoretical combustion temperature, (2) ade-
quate combustion air, and (3) adequate mix-
ing of the fuel and air.
Smokeless combustion can be obtained in
an elevated flare by the injection of an inert
gas to the combustion zone to provide turbu-
lence and inspirate air. A mechanical air-
mixing system would be ideal, but is not
economical in view of the large volume of
gases handled. The most commonly used
air-inspirating material for an elevated flare is
steam. Three main types of steam-injected
elevated flares are in use. The difference
among them is the manner in which the steam
is injected into the combustion zone.
In the first type, steam is injected by
several small jets placed concentrically around
the flare tip. These jets, installed at an angle,
cause the steam to discharge in a converging
pattern immediately above the flare tip.
A second type has a flare tip with no
obstruction to flow; that is, the flare tip is the
same diameter as the stack. The steam is
injected by a single nozzle located concentri-
cally within the burner tip. In this type of
flare, the steam is premixed with the gas
before ignition and discharge.
A third type is equipped with a flare tip
constructed to cause the gases to flow
through several tangential openings to pro-
mote turbulence. A steam ring at the top of
the stack has numerous equally spaced holes
about 1 /8 inch in diameter for injecting steam
into the gas stream.
Steam injection is generally believed to
result in the following benefits: (1) energy
available at relatively low cost can be used to
inspirate air and provide turbulence within
the flame, (2) steam reacts with the fuel to
form oxygenated compounds that burn
readily at relatively low temperatures, (3)
water-gas reactions also occur with this same
end result, and (4) steam reduces the partial
pressure of the fuel and retards polymeriza-
tion.
The injection of steam into a flare can be
controlled either manually or automatically.
In some installations, the steam is supplied at
maximum rates, and manual throttling of a
steam valve is required for adjusting the steam
flow to the particular gas flow rate. For best
combustion at the minimum steam consump-
tion, instrumentation should be provided to
automatically proportion the steam rate to
the rate of gas flow. A pressure-sensing
element located in the gas line as a control
system actuates a control valve in the steam
supply line. A small bypass valve is usually
used to permit a small, continuous flow of
steam to keep the steam holes open and
permit smokeless burning of small gas flows.
Ground-level flares are of four principal
types: horizontal venturi, water injection,
multijet, and vertical venturi.
A horizontal venturi-type flare system uti-
lizes groups of standard venturi burners. In
this type of burner, the gas pressure inspirates
combustion air for smokeless operation.
A water-injection flare consists of a single
burner with a water spray ring around the
burner nozzle. The water spray inspirates air
and provides water vapor for the smokeless
combustion of gases. Water is not as effective
as steam for controlling smoke with high
gas-flow rates, unsaturated materials, or wet
gases.
A multijet ground flare uses two sets of
burners, one for normal gas release rates and
both for higher flaring rates.
A vertical, venturi-type ground flare also
uses commercial-type venturi burners. This
type of flare is suitable for relatively small
flows of gas at a constant rate.
4.1.4 Oil-Water Effluent Systems
A typical waste-water gathering system for
a modern refinery usually includes gathering
4-5
-------
lines, drain seals, junction boxes, and pipes of
vitrified clay or concrete for transmitting
waste water from processing units to large
basins or ponds used as oil-water separators.
These basins are sized to receive all effluent
water, sometimes even rain runoff; they are
constructed as earthen pits, concrete-lined
basins, and steel tanks.
Liquid wastes discharging to these systems
originate at a wide variety of sources such as
pump glands, accumulators, spills, cleanouts,
sampling lines, and relief valves.
Organic compounds can escape to the
atmosphere from openings in the sewer
system, channels, vessels, and oil-water separa-
tors. The large exposed surface area of these
separators can result in large hydrocarbon
emissions to the atmosphere.
The most effective means of control of
hydrocarbon emissions from oil-water separa-
tors has been the covering of forebays or
primary separator sections.7 Either fixed
roofs or floating roofs are acceptable covers.
Separation and skimming of over 80 percent
of the floatable oil layer takes place in the
covered sections. Thus, only a small amount
of oil is contained in the effluent water,
which flows under concrete curtains to the
open afterbays or secondary separator sec-
tions.
Satisfactory fixed roofs have been con-
structed by using wooden beams for struc-
tural support and asbestos paper as a cover. A
mastic-type sealing compound is then used to
seal all joints and cracks. Although this form
of roof is acceptable for the control of
pollutants, in practice a completely vaportight
roof is difficult to achieve. The resultant
leakage of air into the vapor space, and vapor
leakage into the atmosphere are not desirable
from standpoints of air pollution or safety.
The explosion hazard associated with fixed
roofs is not present in a floating-roof installa-
tion. These roofs are similar to those de-
veloped for storage tanks. The floating covers
are built to fit into bays with about 1 inch of
clearance around the perimeter. Fabric or
rubber may be used to seal the gap between
4-6
the roof edge and the container wall. The
roofs are fitted with access manholes, skim-
mers, gage hatches, and supporting legs. In
operation, skimmed oil flows through lines
from the skimmers to a covered tank (floating
roof or connected to vapor recovery) or sump
and then is pumped to demulsifying proces-
sing facilities. Effluent water from the oil-
water separator is handled in the manner
described previously.
In addition to covering the separator, open
sewer lines that may carry volatile products
can be converted to closed, underground lines
with water-seal-type vents. Junction boxes
can also be vented to vapor recovery facilities,
and steam can be used to blanket the sewer
lines to inhibit formation of explosive mix-
tures.
4.1.5 Cracking Catalyst Regeneration
Petroleum fractions are cracked to produce
compounds of lower molecular weight. Cata-
lysts in the form of powders or beads are
utilized. The catalyst particles become coated
with carbon and high-molecular-weight com-
pounds. These materials must be burned off
the catalyst in order to maintain its activity.
The catalyst continuously circulates from the
reactor chamber to the regenerator chamber.
In the regenerator, a controlled amount of air
is admitted to burn off the coatings. This
causes the formation of CO and hydro-
carbons. These emissions can be controlled by
incineration using a waste heat boiler. These
boilers are commonly referred to as CO
boilers.7
4.1.6 Pumps
Pumps are used in every phase of the
petroleum industry. Leakage from pumps can
cause organic emissions wherever organic
liquids are handled. The opening in the
cylinder or fluid end through which the
connecting rod actuates the piston is the
major potential source of emissions from a
reciprocating pump. In centrifugal pumps, the
usual source of leakage is the point at which
the drive shaft passes through the impeller
casing.
-------
Several means have been devised for sealing
the annular clearance between pump shafts
and fluid casings to retard leakage. For most
refinery applications, packed seals and me-
chanical seals are widely used.
Packed seals can be used on both positive-
displacement and centrifugal-type pumps.
Typical packed seals generally consist of a
stuffing box filled with sealing material that
encases the moving shaft. The stuffing box is
fitted with a takeup ring which is made to
compress the packing and cause it to tighten
around the shaft. Materials commonly used
for packing are metal, rubber, leather, wood,
and plastics.
The contact surfaces of the packing and
shaft are lubricated by a controlled amount of
product leakage to the atmosphere. This
feature makes packing seals undesirable in
applications where the product can cause a
pollution problem. The packing may also be
saturated with some material such as graphite
or oil that acts as a lubricant.
The second commonly used means of
sealing is the mechanical seal. This type of
seal can be used only in pumps that have a
rotary shaft motion. A simple mechanical seal
consists of two rings with wearing surfaces at
right angles to the shaft. One ring is stationary
while the other is attached to the shaft and
rotates with it. A spring and the action of
fluid pressure keep the two faces in contact.
The wearing faces are lubricated by a thin
film of the material being pumped. The
wearing faces, usually made of carbon, are
precisely finished to insure perfectly flat
surfaces.
Emissions to the atmosphere from centrif-
ugal-type pumps may be controlled in some
cases by use of the described mechanical-type
seals instead of packing glands. For cases that
cannot be controlled with mechanical seals,
special pumps, such as canned or diaphragm
pumps, are required.
The canned pump is totally enclosed, with
its motor built as an integral part of the
pump. Seals and attendant leakage are elimi-
nated. The diaphragm pump is another type
devoid of seals. It has no moving parts except
a flexible diaphragm whose back-and-forth
motion coupled with intake and discharge
valves effects a pumping action.
Other than the direct methods used to
control leakage, operational changes may min-
imize release of emissions to the atmosphere.
One desirable change is to bleed off pump
casings during shutdown to the fuel gas
system, vapor recovery facilities, or a flare
instead of directly to the atmosphere.
4.1.7 Air-blowing of Asphalt
Asphalt is normally obtained from select
crude oils by means of vacuum distillation or
solvent extraction. To make it suitable for
paving, roofing, or pipe coating, asphalt is
sometimes reacted with air. Air-blowing is
mainly a dehydrogenation process. Oxygen in
the air combines with hydrogen in the oil
molecules to form water vapor. The progres-
sive loss of hydrogen results in polymerization
or condensation of the asphalt to the desired
consistency.
Blowing is usually carried out in batches",
starting with the asphalt at a temperature of
300° to 400° F. Little additional heat is
needed since the reaction becomes exo-
thermic.
Effluents from the asphalt air-blowing stills
include oxygen, nitrogen, water vapor, sulfur
compounds, and hydrocarbons in the forms
of gases, odors, and aerosols. Discharge of
these odors and airborne oil particles can be
disagreeable.
Control of emissions from asphalt air-blow-
ing stills has been accomplished by scrubbing
and incineration, singly or in combination.7
Most installations use the combination. For
scrubbing alone to be effective, a very high
water-to-gas ratio of about 100 gallons per
1,000 standard cubic feet per minute is neces-
sary.
Where removal of most of the potential air
pollutants is not feasible by scrubbing alone,
the noncondensibles must be incinerated.
Essential to effective incineration is direct-
flame contact with the effluents, a minimum
retention time of 0.3 second in the combus-
tion zone, and maintenance of a minimum
4-7
-------
combustion chamber temperature of 1,200°F.
Other desirable features include turbulent
mixing of vapors in the combustion chamber,
and adequate instrumentation. Primary con-
densation of steam and water vapor allows use
of smaller incinerators and results in fuel
savings. Some of the heat released by incin-
eration of the waste gases may be recovered
by using it to generate steam.
4.1.8 Valves
Valves are employed in every phase of the
petroleum industry where petroleum or petro-
leum products are transferred by piping from
one point to another. Pressure relief valves are
discussed in Section 4.1.3.1.
Manual and automatic flow control valves
are used to regulate the flow of fluids through
a system. These valves are subject to product
leakage from the valve stem as" a result of the
actions of vibration, heat, pressure, and corro-
sion or improper maintenance of valve stem
packing.
Obviously, the controlling factor in pre-
venting leakage from valves is maintenance.
An effective schedule of inspection and pre-
ventive maintenance can keep leakage at a
minimum. Minor leaks that might not be
detected by casual observation can be located
and eliminated by thorough periodic inspec-
tions.
4.1.9 Loading Facilities
Losses from refinery loading facilities can
be handled similarly to losses from distribu-
tion facilities, as discussed in Section 4.2.
4.1.10 Vacuum Jets
Emissions of hydrocarbons from vacuum
jets can be controlled by venting the discharge
to blowdown or vapor-recovery systems.
These hydrocarbon emissions may also be
vented to the firebox of a boiler or heater.
4.1.11 Boilers and Process Heaters
Proper maintenance of burner equipment is
essential to proper control of boilers and
process heaters to assure efficiency of com-
bustion and minimum emission of unburned
hydrocarbons. Choice of fuel is important in
some types of equipment, which may be
4-8
designed for preferential use of gas, oil, or
solid fuels. In many types of fireboxes, how-
ever, provision is made for manual or auto-
matic switching from one fuel to another or
from the simultaneous burning of different
fuels. Close attention to the operation of the
equipment is important in maintaining opti-
mum burning conditions.
4.1.12 Chemical Treating Processes
In acid treatment, emissions can be reduced
by substituting continuous mechanical mixing
for batch-type agitators that employ air-blow-
ing for mixing. Acid regeneration can also be
used instead of the hydrolysis-concentration
method of acid recovery. Gases emitted dur-
ing acid-sludge recovery can be vented to
caustic scrubbers to remove sulfur dioxide
and odorants. Gases from scrubbers can then
be vented to a firebox or flare. For new instal-
lations, acid treatment can also be replaced by
catalytic hydrogenation or by other pro-
cessing techniques that may prove to be more
effective.
In doctor treating, the doctor solution can
be steam-stripped to recover hydrocarbons
prior to air-blowing for regeneration. The
effluent from air-blowing can then be incin-
erated to destroy hydrocarbon vapors.
In the disposal of spent caustic, entrained
hydrocarbons are often removed by stripping
with inert gases. The vapors removed in this
stripping operation can be vented to a flare or
to a furnace firebox.
Whenever hydrocarbons are removed in air-
or gas-blowing operations, the effluent hydro-
carbons can be destroyed by incineration.
4.2 GASOLINE DISTRIBUTION SYSTEMS
4.2.1 Introduction
Gasoline and other petroleum products are
distributed from the refinery to the consumer
by pipelines, trucks and trailers, railroad tank-
cars, and ocean-going tankers, all of which
form a distribution network, as shown in
Figure 4—2. Intermediate storage and loading
stations that receive products from refineries
by pipeline or tanker are called terminals;
-------
REFINERY STORAGE
REFINERY
LOADING
1
RAILROAD
TANKCARS,
TRUCKS,
AND
TRAILERS
PIPE MARINE
TRANSPORT TERMINAL
i
TERMINAL
I
1
TRUCKS
AND
TRAILERS
1
\
, BULK PLANT
STORAGE
MARINE
TRANSPORT
1 '
TERMINAL
TRUCKS
AND
TRAILERS
SERVICE STATION
OR
CONSUMER
AIRPORT
STORAGE
Figure 4-2. Representation of gasoline dis-
tribution system, showing flow of gasoline
and other petroleum products from refinery
to consumer.
those supplied by trucks and trailers are called
bulk plants.
Marine terminals are bulk storage installa-
tions adjacent to docks; petroleum products
are stored in them prior to being loaded into
ocean-going tankers. Petroleum products are
loaded into trucks, trailers, and tankcars at
bulk installations by means of loading racks.
These racks contain equipment to meter and
deliver the various products into vehicles from
storage.
4.2.2 Emissions
When a tank truck or tanker is filled
through an open overhead hatch or a bottom
connection, the incoming liquid displaces the
contained vapors. The displaced vapors, which
are forced out into the atmosphere, usually
consist of a mixture of air and hydrocarbons.
Ordinarily, when gasoline is loaded, the
hydrocarbon concentration of the vapors is
30 to 50 percent by volume and the hydro-
carbons consist of gasoline fractions ranging
from propane through hexane. Table 4—1
shows a typical analysis of the vapors emitted
during the loading of motor gasoline into tank
vehicles.9
The volume of vapors produced during
loading operations, as well as the composi-
tion, is greatly influenced by the type of load-
ing or filling employed.9 Overhead loading,
presently the most widely used, may be fur-
ther divided into splash and submerged filling.
In splash filling, the outlet of the delivery
tube is above the liquid surface during all or
most of the loading. In submerged filling, the
outlet of the delivery tube is extended to
Table 4-1. TYPICAL ANALYSIS OF VAPORS FROM LOADING OF GASOLINE
INTO TANK TRUCKS
Fraction
Air
Hydrocarbon
Propane
Iso-butane
Butene
N-butane
Iso-pentene
Pentene
N-pentane
Hexane
Volume, %
58.1
41.9
0.6
2.9
3.2
17.4
7.7
5.1
2.0
3.0
Weight, %
37.6
62.4
0.6
3.8
4.0
22.5
12.4
8.0
3.1
8.0
4-9
-------
within 6 inches of the bottom and is sub-
merged beneath the liquid during most of the
loading. Bottom loading is accomplished by
connecting a swing-type loading arm or hose
at ground level to a matching fitting on the
underside of the tank vehicles (Figure 4—3).
Splash filling generates more turbulence and
therefore more hydrocarbon vapors than sub-
merged filling. In bottom loading, all the load-
ing is submerged, thus turbulence is mini-
mized and less vapor is produced.
Loading and unloading operations are the
primary sources of emissions in the distri-
bution of gasoline and petroleum products.
4.2.3 Controls
To control vapor emission from loading
operations, devices can be installed to collect
the vapors at the tank vehicle hatch.
4.2.3.1 Overhead Loading
Four types of vapor collectors have been
developed for use during overhead loading
operations. All are essentially plug-shaped
devices that are inserted into a fitting for the
hatch opening. Gasoline flows through a cen-
tral channel in the device into the tank vehicle
compartment. This central channel is sur-
rounded by an annular space into which
vapors enter through openings on the bottom
of the hatch fitting. The annular space is in
turn connected to a hose or pipe leading to a
vapor disposal system.
The Mobile Oil Corporation device, shown
in Figure 4—4, is connected to a vapor cham-
ber with a transparent section to allow the
operator to see the calibrated capacity mark-
ers located within the tank compartment.
This closure has adjustable height. It requires
a constant downward force to keep it firmly
in place during filling. It is built to fit only
hatches 8 to 10 inches in diameter.
The Chiksan device in Figure 4—5 incorpo-
rates the hatch closure, the vapor return line,
Figure 4-3. View Of bOttOm-IOading Station. (Courtesy Standard Oil Company of California. Western Operations.
Inc., San Francisco, Cal.)
4-10
-------
Figure 4-4. View of Mobil Oil Corporation
vapor closure.
(Courtesy of Mobil Oil Corporation, Los Angeles, Cal.)
and the fill line into an assembled unit. This
unit has features to prevent overfills, topping
off, or filling unless the assembly is properly
seated in the tank hatch.
The Greenwood vapor closure, shown in
Figure 4—6, developed by the Vernon Tool
Company, also requires downward force dur-
ing filling. It ordinarily does not have a trans-
parent vapor chamber. This closure has an
adapter for hatches larger than 10 inches.
Developed by the Standard Oil Company
of California, the device shown in Figure 4—7
has a positive clamp for the hatch opening,
which, when closed automatically actuates
the vapor chamber. It also has a safety shutoff
float that senses the gas level and prevents
overfilling. These SOCO devices can be used
with adapters for hatches larger than 8 inches
in diameter.
The slide positioner of the Mobile Oil Corp-
oration device can be a source of vapor leaks
and requires close attention by the operator
during adjustments for fitting and submerged
Figure 4-5. Chiksan pneumatically operated
loading assembly with integrated vapor
closure and return line.
(Courtesy of Chiksan Co., Brea, Cal.)
loading. The inner valves of the SOCO devices
make them considerably heavier than other
types. This device increases pressure drop and
slows the loading rates. Mobil and Greenwood
devices both require check valves in the vapor-
gathering lines to prevent the vapor from
discharging back to the atmosphere when the
assembly is withdrawn. In addition, these
devices require nearly vertical entry of the
loading tube into the hatch opening in order
to provide a tight seal against vapor leaks. An
assembly is available to assure that the Green-
wood device maintains this vertical position.
4.2.3.2 Bottom Loading
Bottom loading permits easier collection of
displaced vapors. Because the filling line and
the vapor collection line are independent of
each other, collection during bottom loading
is relatively easy. The vapor collection line
consists of a flexible hose or swing-type arm
connected to a quick-acting valve fitting on
the dome of the vehicle. A check valve must,
of course, be installed on the vapor collection
4-11
-------
Figure 4-6. View of Greenwood vapor closure.
(Courtesy of At Ian ti c-Ri ch f i el d Oil Corporation, Los
An gel es, Ca I.)
line to prevent backflow of vapors to the
atmosphere when the connection to the tank
is broken.
4.2.3.3 Vapor Disposal
Vapors collected during loading operations
may be used as fuel or may be recovered as a
product. When fired heaters or boilers are
available, the displaced vapors may be
directed through a drip pot to a small vapor
holder, which is gas-blanketed to prevent
formation of explosive mixtures. The vapors
are drawn from this holder by a compressor
and discharged to the fuel gas system.
If the loading facility is near the refinery,
the vapor line can be connected from the
loading facility to an existing vapor recovery
system through a regulator valve. If not, pack-
aged units may be used to recover vapors.
Figure 4—8 shows an absorption unit devel-
oped by the Superior Tank and Construction
Company. It includes a tank equipped with a
flexible membrane diaphragm, a saturator, an
Figure 4-7. SOCO vapor closure device in
filling position.
(Courtesy of American Airlines, Los Angeles, Cal.)
absorber, compressors, pumps, and instru-
ments. These units use the gasoline product as
the absorbent. In operation, these units avoid
the accumulation of explosive mixtures by
passing the vapors displaced at the loading
rack through a saturator countercurrently to
gasoline pumped from storage. The saturated
vapors then flow to the vaporsphere, where a
diaphragm controls a compressor, which
draws the vapors from the sphere and injects
them at about 200 pounds per square inch
(guage) into the absorber. Gasoline used to
absorb the hydrocarbon vapors is returned to
storage, while the remaining gases, mostly air,
are released to the atmosphere through a
back-pressure regulator. Some difficulty has
been experienced with air entrained in the
gasoline returning to storage. Any such air
released in the storage tank is saturated with
hydrocarbon vapors as it is discharged. This
air can be properly removed by flashing the
liquid gasoline from the absorbed in one or
more additional vessels operating at succes-
sively lower pressures.
4-12
-------
Figure 4-8. Small-capacity vaporsaver gasoline absorption unit.
(Courtesy of American Airlines, Los Angeles, Cal.)
4.2.4 Regulations and Costs
Regulations pertaining to gasoline loading
systems have been applied primarily in Los
Angeles County, where about 8 percent of the
total petroleum refining capacity of the
United States is concentrated. Rule 61,
adopted in 1956, requires control on large
bulk-gasoline loading installations. Com-
pliance with this rule by the industry has re-
sulted in an estimated reduction of hydro-
carbon emissions of about 50 tons daily in
Los Angeles County.10 Emissions from bulk
loading without controls would be about 145
tons per day.
These controls represent investments of
more than $3 million by the petroleum in-
dustry, and payouts are estimated at 30
months to 5 years. Besides recovery of pro-
ducts in some of the control systems, other
benefits have resulted, such as better working
conditions for operating personnel. Gasoline
losses from spills, overfills, and loading arm
drainage have also been minimized.
The cost of a bulk storage control system
in 1968 was proportional to the gasoline
throughput. A system consisting of loading
arms, a vapor holding tank, and a Vaporsaver
unit for absorption, costs approximately
$90,000 for a terminal with a throughput of
somewhat less than 300,000 gallons per day,
and approximately $125,000 for a terminal
with a throughput of 750,000 gallons per day.
4.3 CHEMICAL PLANTS
4.3.1 Introduction
Manufacturers of synthetic organic chemi-
cals such as elastomers, dyes, flavors, per-
fumes, plastics, resins, plasticizers, pigments,
pesticides, rubber processing chemicals, and
4-13
-------
miscellaneous solvents have the problems of
controlling emissions of hydrocarbons from
raw materials and from products made from
these materials. According to the U.S. Tariff
Commission, 3,092 million gallons of raw
materials was consumed by the chemical in-
dustry in 1967.ll These raw materials were
obtained from coal (coke oven gas, coal tar,
water-gas, and oil-gas tar) and from petro-
leum. The quantities of the most important
raw materials—benzene, toluene, xylene,
naphthalene, and creosote oil—are shown in
Table 4—2. The total of crude products pro-
duced from petroleum and natural gas
amounted to 54,436 million pounds in 1967,
an increase of 8 percent over 1966. The quan-
tity of each product is itemized in Table 4-2.
From these crude products, a total of 80,256
million pounds of synthetic organic chemicals
was produced, as itemized in the same table.
4.3.2 Processes
Organic chemicals, or petrochemicals, are
largely manufactured by conversion processes.
Many of the conversions involve complicated
reactions; most involve (1) continuous pro-
cessing in large volume and (2) control by
Table 4-2. QUANTITIES OF RAW MATERIALS AND INTERMEDIATE PRODUCTS
CONVERTED TO SYNTHETIC ORGANIC CHEMICALS IN 1967
Raw materials produced from
coala and petroleum
Benzene
Toluene
Xylene
Naphthalene
Creosote Oil
Total
90,642
19,357
5,488
520,991
126,234
762,712
Quantity, 1000 gal.
878,704
624,454
449,349
376,679
—
2,329,186
Crude products produced from natural
gas and petroleum
C2 hydrocarbons: acetylene
ethane
ethylene
C3 hydrocarbons: propane
propylene
propane-propylene
€4 hydrocarbons
C5 hydrocarbons
All other aliphatics and derivatives
Aromatics and naphthenes
Total
Synthetic organic chemical produced
Miscellaneous chemicals and solvents
Dyes
Elastomers
Flavor and perfume materials
Pesticides and related products
Pigments
Placticizers
Plastics and resins
Rubber processing chemicals
Total
Quantity, 1000 gal.
16,455
429
1,557
11,855
4,123
5,771
617
8,227
784
4,618
54,436
Quantity, 1000 gal.
59,695
206
3,822
112
1,049
53
1,262
13,793
264
80,256
aThe U.S. Tariff Commission figures for coal are for coke oven gas, coal, water gas, and oil-gas
tar.
4-14
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automated instrumentation. Many are sys-
tems-controlled through computers. Gener-
ally, the type of emission is identified by the
type of raw material and auxiliary raw
material, and the type of conversion.
Pipelines, barges, and ships, by facilitating
the delivery of raw materials and products,
have provided fundamental stimulation of the
growth and geographic spread of petro-
chemical manufacturing.
Of the thousands of chemical manufactur-
ing processes, each has unique control prob-
lems. The types of chemical conversions uti-
lized in these processes are classified below.
Alkylation is the union of an olefin with an
aromatic or paraffinic hydrocarbon. Ethyl
benzene is produced by alkylating benzene
with ethylene,1 2 and naphthalene, by dealky-
lation of a petroleum fraction.13
In amination, an amino compound is
formed by using ammonia (or a substituted
ammonia) as the agent. Other amines are
made by reducing a nitro compound. Ethanol-
amines, for example, are obtained when eth-
ylene oxide is bubbled through an ammonia
solution.
Hydrogenation, the addition of hydrogen,
is used to manufacture a broad range of pro-
ducts. For example, methanol is made by
reacting CO with hydrogen.
Dehydrogenation, the removal of hydro-
gen, produces unsaturated compounds. Ben-
zene is made by dehydrogenation of substi-
tuted cyclohexanes.
Dehydration, the removal of water, pro-
duces ethers from alcohols. Hydration, the
addition of water, produces ethyl alcohol
from ethylene.
In esterification, an alcohol reacts with an
organic acid to form an ester. Ethyl alcohol
reacts with acetic acid to form ethyl acetate,
an important solvent.
Halogenation and dehalogenation are the
addition or removal of a halogen. Methyl
chloride is made by chlorination of methane.
Chlorine, bromine, iodine, and fluorine are
the halogenation agents.
Oxidation, the addition of oxygen, is one
of the most valuable conversion processes^
Ethylene oxide is made by oxidation of eth-
ylene. The cheapest oxidizing agent is air, but
pure oxygen has advantages in many applica-
tions.
Nitration introduces nitrogen into hydro-
carbons. Nitrobenzene is an important pro-
duct of nitration.
Polymerization is the reaction of simple
molecules to form more complex polymers.
For example, ethylene is polymerized to poly-
ethylene.
The raw materials and the products are
potential sources of emissions in any chemical
conversion operation. Chemical reactions for
production of a desired product usually result
in several by-products. Although the forma-
tion of by-products is minimized by adjusting
the conversion conditions, the quantities
formed must be either recovered for use or be
properly disposed of as wastes. Waste disposal
is a primary problem, complicated by the fact
that wastes may be highly toxic. Thus air-
cleaning methods that merely transfer the
emissions to streams or other waters are not
satisfactory.
The major sources of emissions to the air
are streams of waste gases, vapors from distil-
lation columns, and leakage from feed and
product transport lines. Many chemical plants
generate their own steam for use in refining
and for supplying power; therefore, emissions
characteristic of power plants are an inherent
part of the total. The manufacture or regener-
ation of catalysts usually results in nonhydro-
carbon emissions.
Many plants that produce their own crude
products have emissions similar to those from
petroleum plants. Annual total emissions were
estimated for a plant producing 500 million
pounds per year of ethylene. Emission
factors, taken from Public Health Service
Publication No. 763,14 were used for indi-
vidual pieces of equipment, to derive the re-
sults shown in Table 4-3. For these esti-
mates, all pumps, compressors, valves, etc.,
were counted and the composition of the
process streams were delineated.
4-15
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Table 4-3. CALCULATION OF HYDROCARBON LOSSES FROM PROCESS
EQUIPMENT IN 500 MILLION-LB/YR ETHYLENE PL ANT15
Emission source
Loss factor3
Number of capacity
Emissions,
Ib/day
Valves
Pumps (mech. seal)
Compressors (centrifugal,
mechanical seal)
Compressors (reciprocating,
packed seal)
Cooling water
Process drains and waste
water separators
Slowdown systems
Relief valves (operating
vessels)
Relief valves (storage tanks)
Storage tanks
(floatingroof)(VP1.5 psi)
Miscellaneous losses
0.15 Ib/day-valve
3.2 Ib/day-seal
3.2 Ib/day-seal
5.4 Ib/day-seal
6.0 lb/106gal
150 lb/1000 bbl capacity
100 lb/1000 bbl capacity
2.9 Ib/day-valve
0.6 Ib/day-valve
4.8 Ib/day-1000 bbl cap.
1.7 Ib/day-lOOObblcap.
10 Ib/day-lOObblcap.
4500 valves x 0.15
150 pumps x 3.2
10 comp. x 2 x 3.2
1 comp. x 5.4
50,000 gpm x 60 x 24 x 6
1,000,000
20,000 bbl x 150
1,000
20,000 bbl x 150
1,000
400 valves x 2.9
14 tanks x 2 valves x 0.6
500,000 bbl x. 4.8
5,000 bbl x 1.7
1,000
20,000 bbl x 10
= 675
= 480
= 64
5
= 430
=3000
=2000
= 1150
= 17
=2400
= 9
= 200
1,000
Total calculated hydrocarbon emission 10,430 Ib/day
Loss on plant feed^ 10,430 =021wt%
20,000x250
aThese loss factors are applicable to plants practicing extensive hydrocarbon control.
"The range of emissions from hydrocarbon processing plants may range from 0.1 to 0.6% by weight
of plant throughout. The lower value calculated here is applicable to an area such as Los Angeles
County where stringent control is practiced.
4.3.3 Emission Controls
Often, control of emissions by the chemical
industry is based on economic incentives. In
other words, condensers are used to recover
vapors containing usable reactants, and wastes
are burned to recover heat value. Thus, since
the prevention of losses is usually considered
a part of the process, investment data from
contractors include the cost of such conven-
tional controls. Investment data do not, how-
ever, ordinarily include controls such as cata-
lytic fume burner systems, thermal inciner-
4-16
ators, or special adsorbers required to remove
contaminants from exhaust gas streams.
Catalytic oxidations are seldom, if ever,
free of odor. Large quantities of air pumped
through the reaction system to provide the
oxygen necessary for the conversion. Low
concentrations of the main reactants are car-
ried into the air. Existing methods for re-
covery of these low concentrations are often
unattractive economically, in the sense that
the recovered material does not pay for the
-------
cost of recovery. Recently, however, new de-
velopments in recovery methods have begun
to reduce the economic burden of recovery or
disposal and, in some cases, have begun to
indicate a profit potential. These are discussed
below.
4.3.3.1 Collection of Ven ted Gases
Frequently, waste gases from columns,
partial condensers, or other equipment pol-
lute air or produce smog when they are
vented to the atmosphere. It is not profitable
to use conventional reciprocating or centrif-
ugal compressors to collect these streams for
incineration. In addition, some waste gases
with a low heating value may not give the
desired heat release because of inert materials
present. This problem can be overcome by
using automated jet-compressors, which use a
good fuel as the motive gas and can be oper-
ated to give good combustible exhausts.16
The automated jet-compressor is a special
type of jet ejector, made of five basic parts as
shown in Figure 4-9. First, the secondary or
waste gases enter body A where they are
entrained by high-pressure motive gases from
nozzle B; then this mixture is discharged at an
intermediate pressure from diffuser C. Spindle
operator D can move spindle E to vary the
SPINDLE OPERATOR, D
SPINDLE, E
WASTE GASES, W
BODY, A
NOZZLE, B
MOTIVE GASES,
DIFFUSER, C
o
DISCHARGED GASES, Wd
Figure 4-9. Automatic jet compressor.
motive gas rates so that the required pneu-
matic relationships are maintained. The device
can operate at constant suction pressure, con-
stant discharge pressure, or constant ratio of
motive gas to waste gas. The gases can be dis-
charged directly to a burner with automatic
throttling and flaring, to a gas holder for
intermediate storage, or into a fuel header
system.
4.3.3.2 Halogenation
Organic emissions containing a halogen
(primarily chlorine) are a special problem,
because the halogen atoms are not combusti-
ble. Accordingly, incineration of chlorine-
containing organic compounds can produce
HC1, elemental chlorine, or other chlorinated
compounds.
The problem is to design an incineration
system that will first produce the hydrogen
halide gas and then absorb it. Experimenta-
tion has shown that if the hydrogen-to-
halogen ratio is high enough, approximately 5
to 1, essentially all of the halogen in the
products of combustion will be in the form of
the hydrogen halide.
To maintain this ratio for substances like
ethylene or propylene dichloride, some
hydrocarbon fuel must be added to the com-
bustion system to supply hydrogen. A
technique developed to do this for organic
chlorides recovers up to 99 percent of the
hydrogen chloride as 18° Baume' acid from
gas streams containing as little as 3 percent
hydrogen chloride.17
In this recovery system, the .waste is incin-
erated in a vortex-type burner and im-
mediately quenched in a graphite- or carbon-
lined tower; the resulting vapors are processed
through a series of impervious, graphite, tubu-
lar cascade absorbers, which are designed to
produce 18° Baume'acid, with up to 100 ppm
of hydrogen chloride in the vent gas. If ad-
ditional treatment is required, another scrub-
bing station is provided to produce very weak
hydrochloric acid to be used as make-up
liquor in the main absorption equipment. The
4-17
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remaining vapors usually contain fewer than
50 ppm hydrogen chloride. This recovery
system, depending on the disposal rate, can
produce a positive return on investment.
4.3.3.3 Disposal of Waste Gases
Catalytic vapor incinerators at an ethylene
producing plant eliminate essentially all
ethylene contained in a relatively cool waste
gas stream. The heart of the system is a
catalyst that makes it possible to burn ethyl-
ene that is present in concentrations too low
to support normal incineration. The treated
stream does not contain catalyst poisons.
Part of the equipment operating costs are
recouped by recovering energy released when
the ethylene is burned. This energy is recov-
ered in two stages: first, the hot gas stream
powers expansion turbines, which drive com-
pressors; then, the stream is reduced to an
acceptable heat level for use in power recov-
ery turbines, while the heat recovered is used
to super-heat the process steam.
Some plants have adopted other types of
incinerators to abate gases and vapors. A
direct-flame incinerator is shown in Figure
4—10. The two units burn the organic gases,
vapors, and particulate matter in the effluent
gases from a phthalic anhydride manufactur-
ing plant.
4.4 PAINT, LACQUER, AND VARNISH
MANUFACTURE
4.4.1 Introduction
Paints, lacquers, and varnishes have been
used for years for decorative and protective
purposes and, in some instances, for electrical
insulation and chemical resistance. Present-
day coatings are the products of precisely
controlled chemical reactions and accurately
proportioned formulations, which may in-
clude natural or synthetic drying oils,
pigments, volatile solvents, resins, driers, thin-
ners, plasticizers, and antioxidants.1 8
Coatings may be divided into two general
types: pigmented or nonpigmented. The
4-18
vehicle (or binder) is common to both types.
Most of the materials other than pigments are
of organic composition, with varying degrees
of volatility. Thus handling, mixing, and
processing operations produce different
amounts of atmospheric pollution depending
on which raw materials are used, the com-
binations of these materials, and the con-
ditions to which they are subjected.18
The paint or varnish manufacturer usually
produces his own vehicles by either chemical
reactions and/or cooking operations which
vaporize part of the ingredients. Other losses
result from (1) thinning operations that use
volatile solvents and thinners to produce
proper consistency for the finished product
and (2) the handling and storage of raw
materials and intermediate products.18
Even with the atmospheric losses involved
in manufacture of paints and varnishes, more
hydrocarbons usually are emitted from the
application of these coatings than from the
manufacturing process itself. This source of
pollution is covered in Section 4.6.
Production of varnish appears to be the
largest contributor of atmospheric hydro-
carbon emissions in this industry and thus will
be discussed in considerably more detail than
paint and lacquer production.
4.4.2 Paint Manufacturing
Paint can be defined as a pigmented liquid
composition that is converted to a relatively
opaque solid film after application as a thin
layer.19 Enamels are paints which form an
especially smooth and glossy film.
Paint manufacturing consists of the fol-
lowing operations:
1. Mixing pigment with sufficient vehicle
to make a paste of proper grinding
consistency.
2. Grinding the paste on a mill until ag-
gregates are broken down.
3. Letting down (diluting) the ground
paste with the remaining materials.
4. Tinting to required color.
5. Testing.
6. Straining, filling, and packaging.
-------
Figure 4-10. Direct-fired afterburner for control of emissions from two phthalic anhydride
production Units. (Courtesy Reichhold Chemicals, Inc., Azusa, Cal.)
In some cases the mixing and grinding
operations are done in one step. Although
"grinding" is the term commonly used in the
industry, actual grinding or reduction in size
of particles of pigment does not occur in the
majority of cases.1 9
Paint manufacturing is still largely a batch
process because of the large number of raw
4-19
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materials and finished products required,
many of which must be custom formulated
and processed.2 °
The two sources of hydrocarbon emissions
in paint manufacturing are the grinding op-
eration, during which the batch may heat up
considerably and lead to vaporization of
certain ingredients, and the thinning
operation, during which vaporization of sol-
vents occurs. A small amount of pigment fines
is emitted from the mixing operation. Thin-
ning of premixed paint pastes to the required
consistency for application involves dilution
with aliphatic or aromatic hydrocarbons,
alcohols, ketones, esters, and other highly
volatile materials.18 Because of the volatility
of most thinners, mixing must be done in
totally enclosed tanks to prevent losses of
these expensive solvents and, more recently,
to prevent air pollution from these materials.
A recent estimate of the hydrocarbon emis-
sions from paint manufacture is that about
0.5 percent of the weight of the paint is emit-
ted as hydrocarbons. Another estimate is that
the solvent loss to the atmosphere from mix-
ing operations generally amounts to no more
than 1 to 2 percent of the solvent used.18
Methods of controlling atmospheric emis-
sions from paint manufacture include: (1)
reformulation of the paint to replace a photo-
chemically reactive solvent such as xylene
with a less photochemically reactive solvent,
(2) production of water-base coatings, (3)
condensation and absorption by scrubbing
with water, (4) condensation and absorption
by scrubbing with alkali or acid washes, (5)
scrubbing and adsorption by activated
charcoal or other adsorbents, (6) combustion,
and (7) dispersal from high stacks. McFadden
states that no one control method is
satisfactory for all applications.2 l
The preferred method of controlling the
hydrocarbon emissions would be reformula-
tion since this would serve to reduce the
reactive solvent emissions during the manufac-
turing process and during application. Baking
enamels cannot, however, meet the require-
ments of Los Angeles County's Rule 66 by
reformulation since baking-oven emissions
4-20
must be controlled regardless of the solvent
used.
4.4.3 Lacquer Manufacturing
Lacquers are solutions of resins in organic
solvents that harden as a result of evaporation
of the solvent rather than oxidation or
polymerization.20 Present-day lacquers are
primarily nitrocellulose coatings, which may
be either clear or pigmented. If pigment is
added, the lacquer is then called lacquer
enamel or pigmented lacquer and is more
resistant to weather.
Nitrocellulose is made from cotton linters,
which are short fibers remaining on cotton
seeds after the long fibers have been removed
by cotton gins for textile purposes.22 Filters
are purified by boiling in caustic solution
until they become pure white. These fibers
are nitrated to produce nitrocellulose, which
is the basic film-forming ingredient in lac-
quers. It is blended with resins, plasticizers,
volatile solvents, and diluents to produce lac-
quers with various properties such as desirable
elasticity, good adhesion to surfaces, depth or
body of the film, luster, and good drying
characteristics. For pigmented lacquers, a sep-
arate pigment grinding or milling step is re-
quired. Mixing and tinting operations are
usually carried out in totally enclosed agitator
tanks to decrease the amount of solvent
vaporization.
Solvents are the materials that provide the
proper consistency for application of lac-
quers. The solid ingredients of the lacquer as
well as the method of application dictate the
selection of solvents. The solvents used in lac-
quer manufacture are mainly the esters,
ketones, etc.; the latent solvents used are the
alcohols, ethyl, butyl, and amyl; the diluents
are the petroleum thinners and coal tar sol-
vents.22 Usually, blends of several solvents
are required to produce satisfactory lacquers.
Resins used in lacquers must be soluble in
mixtures of esters, alcohols, and hydro-
carbons. Some of the resins used are shellac,
elimi, dammar, ester gum, and alkyds.2 2
Hydrocarbon emissions from lacquer
manufacture consist of vaporized solvents and
-------
diluents; but unless temperatures become
elevated, the losses are small. The best
method of controlling these emissions is re-
formulation to replace reactive solvents with
less reactive ones. Other methods include con-
densers, afterburners, scrubbers, absorbers,
and adsorbers, or combinations of several of
them. For instance, if an activated-carbon
adsorber is used, a scrubber should be in-
stalled in front of it to remove pitch or a tarry
material, which may collect on the carbon
and decrease its efficiency.
4.4.4 Varnish Manufacturing
4.4.4.1 Introduction
Varnish has been defined in various ways
by the technical societies and several au-
thors.9'19-22 Some authorities say varnish is
a colloid; others say it is a solution. The one
common definition, however, is that varnish is
unpigmented, consists of resins, oils, thin-
ners, and driers, and dries by evaporation of
the solvents and by oxidation and
polymerization of the remaining constituents.
The most common varnishes are the
oleoresinous ones, which can be broken down
into minor classes such as oil plus resins, oil,
and oil-modified. They are all solutions of one
or more (natural or synthetic) resins in a dry-
ing oil and a volatile solvent. All oleoresinous
varnishes dry by oxidation; or oxidation and
condensation; or oxidation, condensation,
and polymerization.22 The other major type
of varnish is spirit varnish, which consists of
alcohol solvents plus either natural or syn-
thetic resins with little or no oil. Shellac is the
most common example of this type of
varnish. Spirit varnishes dry either by evapora-
tion or by evaporation and some polymeriza-
tion.
Other important types of varnish developed
more recently include: alkyd resin varnish,
which is a solution of alkyd resin (a synthetic
polyester co-reacted with a vegetable oil) in a
volatile solvent with added drier; asphalt
varnish, which is a solution of asphalt in a
volatile solvent; and lithograph varnish, which
is used as a vehicle in pigmented lithographing
printing ink.
4.4.4.2 Manufacturing Processes and
Emissions
The various steps in varnish manufacturing
include cooking, thinning, mixing, filtering,
storing and aging (if necessary), testing, and
packaging. The most important step in this
process is cooking. The cooking process per-
forms many functions; some of the most
important ones are:
1. Depolymerization of resins and oils.
Natural resins are insoluble in many
oils, such as linseed, tung, and castor,
that are the film-forming materials in
oleoresinous varnishes. Thus, the resin
must be heated to a temperature
above its softening point for decom-
position and depolymerization to take
place. The resulting resin is then
soluble or reacts with the oils.
2. Bodying of natural and synthetic oils.
3. Melting materials to accelerate solubil-
ity and reaction.
4. Esterification of rosin, phthalic
anhydride, maleic anhydride, or tall
oil with a polyhydric alcohol such as
glycerol or pentaerythritol.
5. Isomerization to eliminate extreme
reactivity in some oils during
oxidation.
6. Preparation of alkyd resins.
7. Distillation and evaporation to remove
undesirable constituents such as
volatiles in resins.
All or part of the above operations take place
during the cooking process but differ depend-
ing upon the particular batch being processed.
Cooking temperatures in varnish kettles
range from 200° to 600° F and are usually
maintained for several hours. The average
batch starts to give off vapors at about 350°
F; the rate of vaporization rises with a
temperature increase and reaches its max-
imum at approximately, or shortly after, the
maximum processing temperature is
reached.18'22 Vapor emission continues as
long as heating is continued but slowly
decreases after the maximum is reached.
There are two types of kettles used for
cooking varnish, the open kettle, which is
4-21
-------
heated over an open flame, and the newer
totally enclosed kettle, which is set over or
within a totally enclosed source of heat.
Naturally, the open kettle allows vaporized
material to be emitted to the atmosphere un-
less hooding and ventilation systems are pro-
vided.
The vapors emitted from varnish cookers
possess penetrating and disagreeable odors
and other irritating characteristics. These
vapors consist of (1) low-melting-temperature
constituents of natural gums, synthetic acids,
and rosins, some of which are purposely
driven off for process reasons; (2) thermal de-
composition and oxidation products
volatilized during bodying of oils; and (3)
volatile thinners, which distill off during thin-
ning of hot varnish.22 The composition of
these vapors is a function of the raw
materials, cooking formulas, and heating
cycle. Some of the raw materials used include
(1) oils such as linseed, castor, fish, tall, soya,
tung, oiticica, and perilla; (2) resins such as
phenolics, rosin, copal, dammar, manila and
East India, alkyd, ester gum, acrylates, sili-
cones, epoxies, and polyurethanes; (3) sol-
vents and thinners such as turpentine, xylol,
toluol, alcohols, aromatic and aliphatic
naphthas, and dipentine; and (4) dryers such
as Co, Mn, Pb, and Zn naphthenates;
resinates; tallates; and linoleates.
The major constituents of the emissions
from varnish cookers are stated to be largely
fatty acids and aldehydes, mixed with water
vapor, acrolein, glycerol, acetic acid, formic
acid, and complex residues of thermal decom-
position.22 The most unpleasant of these is
acrolein because of its pungent, disagreeable
odor, very low odor threshold, and eye-irri-
tating characteristics. In addition to the air
contaminants listed above, some highly of-
fensive sulfur compounds such as hydrogen
sulfide, butyl mercaptan, thiophene, and allyl
sulfide are emitted when tall oil is esterified
with glycerine and pentaerythritol.7
Total emissions to the atmosphere depend
on the composition of the batch, rate of
temperature application, maximum tempera-
ture of the process, method of adding solvents
4-22
and driers, amount of stirring employed, ex-
tent of air-blowing, length of cooking time,
and amount of pollution or other process con-
trol equipment employed. Typical losses from
various cooking processes1 8 are as follows:
1. Total loss from oleoresinous varnish
cooks average 3 to 6 percent, with
some losses as high as 10 to 12
percent.
2. Losses from alkyd resin cooks range
from 4 to 6 percent.
3. Cooking and blowing of oils produce
losses of 1 to 3 percent.
4. Heat polymerization of acrylic resins
produces losses of less than 1 percent
unless the reaction gets out of control.
For the process of gum-running of natural
copals, the amount of vapor liberated is
stated to vary from 12 to 35 percent of the
original weight of copal, depending upon the
type of copal, temperature, and duration of
the running process.23 A reasonable average
is stated to be a 25 percent loss.
The second largest source of emissions
from varnish manufacture is the thinning
operation. Many processes require the ad-
dition of solvents and thinners during the
cooking process which is near the boiling
point of the solvents. The amount of solvent
lost to the atmosphere in this case will be
considerable if the open kettle operations are
used. However, other factors controlling the
solvent loss include its volatility, the tem-
perature of the material to which it is added,
the amount of additional heat applied, if any,
and the degree of stirring employed. Because
of the volatility of most solvents, most thin-
ning operations must be done in totally en-
closed tanks to prevent large losses of the sol-
vents. This is necessary because most of these
solvents are not only pollution problems, but
are quite expensive. The method of thinning
also affects the total solvent loss because if a
small amount of cold solvent is poured into a
large mass of hot varnish, more solvent is
vaporized and lost than if a small amount of
hot varnish is poured into a large volume of
cold solvent.
-------
Losses of solvents during thinning can
range from 5 to 50 percent of the total added
in open thinning tanks, depending upon the
method used and the amount of time the
thinned mixture is left open.23 However,
since most manufacturers use totally enclosed
thinning tanks, the amount of solvent lost to
the atmosphere amounts to no more than 1 to
2 percent of the solvent used.1 8
4.4.4.3 Controls
It is apparent from the foregoing survey of
varnish-making and synthetic resin-making
'processes that there are many opportunities
for release of gaseous materials, which for
various reasons it is desirable to control.
Generally, the varnish industry has practiced
control of emissions because of economic rea-
sons. In fact, integral condensers reduce emis-
sions from many processes considerably.
Other methods of controlling these emissions
include scrubbers, absorbers, adsorbers, after-
burners, reformulation of solvents, and
sublimation.
In designing condensers to control emis-
sions from varnish-making operations, the
standard design factors such as the type(s) of
compounds and their physical properties,
such as temperature, volume, concentration,
vapor pressure, and specific heat must be
considered. In addition, in many of these
processes noncondensible substances must be
removed by other means. Many of the lower-
boiling-point noncondensible hydrocarbons
are very inflammable, and provision must be
made to remove the risk of flashes. For
example, to remove copal vapors, a satisfac-
tory condensation unit should include the fol-
lowing:23
1. A condenser to remove most of the
vapors, followed by scrubbing and
combustion, charcoal adsorption, or a
ventilating stack to remove the traces.
2. Means for vapor withdrawal.
3. Provision for cooling and collecting a
large volume of distillate.
4. Corrosion-resistant materials of
construction.
5. Precaution against flashes.
6. Provision for overflow between cook-
ing kettle and first condenser.
7. Recirculation of cooling water to
reduce quantities required.
8. Separate unit for each kettle if
possible.
Both surface-type and direct-contact-type
condensers have been employed in this in-
dustry.
Several different types of scrubbers have
been used by the varnish industry.23 These
include (1) a countercurrent device in which
the vapors enter at the bottom against a
descending water stream and leave through
the top, (2) a parallel-current water scrubber
succeeded by smaller counter-current scrub-
bers, (3) water jet scrubbers, and a (4) scrub-
ber with spinning discs located on a revolving
vertical spindle.
Adsorbers used in this industry are very ef-
ficient at removing solvents and odors from
varnish-making processes; however, to
maintain high efficiencies, the gas streams
entering these units must be essentially free of
solids and entrained oil droplets. In varnish-
making, the effluent is not free of these
materials, and in practice a pitchy deposit
forms on the charcoal absorbent. This deposit
resists removal by steam during desorption.2 3
In another case this pitchy material was also
found and assumed to consist of tarry
materials that found their way past the pre-
liminary scrubber plus low-molecular-weight
materials undergoing polymerization.
In controlling varnish vapors, it appears
that adsorption by charcoal or other solid
adsorbents would be most useful after the
bulk of condensible matter has been removed
by condensers, scrubbers, etc. Sevard states
that adsorption, following revivification,
provides concentrated vapors, which may be
burned more economically than when mixed
with large volumes of air.24
At present, the most effective means of
controlling emissions from varnish-making
operations has been combustion. Vapor
disposal by combustion has several advantages
over other control methods because it
requires a minimum of equipment, assures
4-23
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complete vapor elimination from the atmos-
phere, and consumes very little fuel in cor-
rectly designed furnaces. Incineration, of
these hot combustible vapors calls, however,
for special devices to protect against flame
propagation in the opposite direction of the
flow of vapors between the kettle and the
incinerating furnace. In some systems, a series
of water jets or a water scrubber are inter-
posed between the varnish kettle and the
furnace.2 3 In another system, the vapors are
passed first through a water-cooled condenser
and then to a combustion hearth.2 3 In still
another, the varnish vapors are assisted from
the kettle by means of a steam nozzle. The
mixture of steam and vapor is condensed. The
reduced pressure, which results from the
vapor condensation pulls the vapors from the
kettle. The noncondensibles are then
burned.2 3
In designing afterburners to control emis-
sions in a process where the ratio of non-
cumbustibles to combustibles is relatively
large, five interrelated variables25 must be
considered: reaction temperature, particle size
of combustibles, mixing, flame contact, and
residence time. The importance of these
variables is apparent since theories of flame
propagation propose that a flame is maintain-
ed by continuous autoignition at the flame
front.2 s
In designing an afterburner control system
for varnish kettles, the following items should
be considered:
1. Hooding. Hoods should be tight fit-
ting, should be easy to clean, and
should prevent condensate drippage
into the kettle.
2. Ductwork. Ducts should be sloped
away from the hoods, and low spots
should be eliminated. Corrosion-
resistant materials with provisions for
cleaning should be used.
3. Flashback Protection and Precleaning.
A water spray leg is recommended for
precleaning and flashback protection.
A high-velocity section at inlet
provides additional fire protection.
4-24
4. Afterburner. A minimum gas temper-
ature of 1200°F should be used with
provisions for temperatures of
1400°F. Intimate mixing with
luminous flame should be provided.
Combustion chamber should be re-
fractory lined and should provide
residence time of 0.5 second. The
velocity through the chamber should
not be less than 15 feet per second.
5. Controls. Burner controls should be of
modulating type to insure a contin-
uous and uninterrupted flame.
6. Safety. Protection must be provided
for all possible types of failure of the
control system to prevent fires.
An example of a typical control system used
in a Los Angeles varnish manufacturing plant
is shown in Figure 4-11.
Two afterburner installations at varnish
manufacturing plants have been tested.25 A
tangentially fired system was found to pro-
vide over 99 percent efficiency with regard to
gaseous organic matter calculated as hexane.
This unit cost $6,500 when it was installed in
1956. Fuel requirements are 1,980,000 Btu
per hour, which amounts to a cost of $0.90
per hour to incinerate 950 standard cubic feet
per minute of contaminated air. An axially
fired afterburner had an efficiency of 96
percent when removing gaseous hydrocarbons
as indicated by the modified Beckman Model
2 infrared spectrophotometer. This after-
burner cost $2,500 installed. Fuel require-
ments are 570,000 Btu per hour, which
amounts to a cost of $0.26 per hour.
Catalytic combustion units have also been
considered in the varnish industry. However,
one test showed that a temperature of 950°F
was required to remove all odors.7 Since this
temperature is near the 1200°F required in
the direct-flame type, the advantage in fuel
saving of using this type unit is questionable.
Solvents emitted from thinning operations
can be controlled by the methods discussed
under paint manufacture. Again, the best
method is to reformulate the mixture to
-------
\
TANGENTIALLY FIRED AFTERBURNER
EXHAUST BLOWER
PORTABLE
COOKERS
WITH
iHOODS
RECIRCULATING
WATER BASIN
WATER-RECIRCULATING PUMP
Figure 4-11. Schematic pTan for varnish-cooking control system.
substitute a less reactive solvent for a reactive
one.
4.5 RUBBER AND PLASTIC PRODUCTS
MANUFACTURE
4.5.1 Introduction
The rubber and plastic industries are similar
in that many ingredients other than the base
material are added to produce desired proper-
ties of the final product. The ingredients are
classified according to the part they play in
the finished product. Some of the ingredients,
however, may have several functions, so this
classification is arbitrary. The compounding
ingredients added to rubber are as follows: (1)
plasticizers or softeners, (2) vulcanizing
agents, (3) accelerators, (4) activators and
retarders, (5) antioxidants, (6) fillers, and (1)
miscellaneous ingredients such as pigments,
rubber substitutes, odorants, abrasives, stif-
feners, and blowing agents.
Vinyl chloride polymers and copolymers
are thermoplastics that are naturally hard, but
can be changed to permanently pliable
materials by addition of suitable plasticizers.
The most common plasticizer used for this
purpose is dioctyl phthalate (DOP), but some-
times diisoactyl phthalate (DIOP) is used. For
flexible plastics and sponges, there are 50 or
more parts of placticizers per 100 parts of
resin. These products are cured at high tem-
peratures, which volatilize the placticizers and
produce air pollutants.
4.5.2 Rubber Manufacture
The most important operations in the
manufacture of rubber are as follows: (1)
physical treatment of raw rubber to prepare it
for addition of compounding ingredients; (2)
incorporation of various substances, especially
fillers; (3) pretreatment of mix to make it
satisfactory for preparing the final product;
(4) forming the final product; and (5)
vulcanization or curing the molded article.
The first step in this process is
plasticization which can be done in several
ways. Mechanical plasticization is ac-
complished on a mixing mill or internal mixer
which rolls the rubber and makes it soft and
plastic. Heat plasticization is accomplished by
4-25
-------
heating in ovens for about 24 hours at 300°
to 400°F. Chemical plasticization is ac-
complished by adding peptizing agents on the
mills and is more rapid and economical than
other means under certain conditions. Typical
peptizing agents are naphthyl mercaptan,
xylyl mercaptan, zinc salt of pentachloro-
thiophenol, and dithio-bis-benzanilide.
Typical antioxidants that create hydro-
carbon and organic pollutants are aromatic
amines, aldehyde-amine condensation
products, derivatives of secondary
naphthylamines, aromatic diamine derivatives,
and ketone-amine condensation products.
To vulcanize or cure the molded article, the
material is held at elevated temperatures of
200° to 300° F from a few seconds to several
hours. This is the operation during which
many of the plasticizers, accelerators, and
other organics are volatilized and driven off as
air pollutants. One of the major problems as-
sociated with rubber production is odor.
The principal methods used to control air
pollutants from rubber manufacture are those
discussed in Section 4.4 for solvent recovery:
reformulation, condensation, adsorption,
absorption, and incineration. Many of the
rubber manufacturers have been recovering
solvents for economic reasons. In one case, a
rubber company installed an activated-carbon
adsorption system and found that with a 65
percent recovery figure for a base, the system
could save them up to $39,000 in the first full
12 months of operation.2 6
In reformulation, use of nonreactive sol-
vents in place of reactive ones would alleviate
hydrocarbons and odor problems.
Direct-flame incineration has proved to be
very successful in controlling both hydro-
carbons and odors. In one rubber processing
plant, tests of a direct-flame incineration
system showed that for a total system flow of
31,000 pounds per hour, and an incineration
temperature of 1,120° F, total hydrocarbons
were reduced from 1,305 to 207 ppm by
weight with an efficiency of 84 percent27
(calculations based on reduction of total
hydrocarbons in pounds per hour). With al-
lowance for the contribution of fuel oil, as
4-26
established during the blank run, the ef-
ficiency of process contamination removal
became 89 percent. This was stated to be
closer to the overall efficiency expected if the
incinerator were fired with natural gas.
In a similar run at an incineration tem-
perature of 1,190° F, total hydrocarbons
were reduced from 1,155 to 89 ppm by
weight for an efficiency of 92 percent. Al-
lowing for fuel oil contribution would
increase this efficiency to 97 percent.
Catalytic-type combustion has been
investigated thoroughly for removing pol-
lutants from rubber plants. In some cases,
however, it has been found that temperatures
only 100°F below those required for direct-
flame incineration were required, and thus
increased costs of catalyst-type operations
would not be justified. In other tests,27 this
type of combustion was abandoned because
of (1) the danger of poisoning of the catalyst
and (2) the impairment of its effectiveness as
the catalyst became coated with carbonaceous
deposits.
4.6 SURFACE COATING APPLICATIONS
4.6.1 Introduction
Coatings applied to surfaces for protection
and decoration can be broadly divided into
two classes: convertible and non-
convertible.2 8 The convertible class includes
oil paints and oil varnishes in which the coat-
ing dries and hardens primarily through
oxidation and polymerization reactions
induced by the surrounding air. The non-
convertible coatings are those in which a
resinous film-forming material is dissolved in a
volatile solvent. When applied to a surface,
the solvent evaporates and leaves a resin film,
which does not undergo any significant
chemical change on continued exposure.
Solvents facilitate the use of the varnishes
and resins that form both classes of coatings
noted above. In coatings use, the quantity of
solvent purchased generally coincides with the
quantity emitted into the atmosphere.
Materials referred to in the trade as diluents
and thinners are also included in the general
-------
category of solvents for coatings applications.
Most of the organic solvents in commercial or
industrial use can be classified as aliphatic
hydrocarbons, aromatic hydrocarbons,
alcohols, ketones, esters, halogenated hydro-
carbons, or mixtures of these categories of
compounds.
4.6.2 Emissions
When coatings are applied, no attempt is
usually made to collect emissions, and es-
sentially all of the solvents used find their
way into the atmosphere.
Certain coating operations are amenable to
control. These include industrial finishes
requiring baking, coating coils, enameling
wire, painting automobiles, painting other
sheet metal products, and drying in lithograph
ovens.
4.6.3 Control Techniques and Costs
The use of nonreactive formulation (e.g.,
water-base and formulations with nonreactive
organic solvents) is the best approach to
control of these emissions in general. Organic
emissions from the multitude of painting and
baking operations employed in metal finishing
can be reduced or suitably controlled by a
variety of methods. The methods that warrant
consideration are modification of equipment,
reformulation of solvents, adsorption,
absorption, and incineration.
The possibility of reducing or eliminating
air pollution through equipment or process
modification should be thoroughly evaluated.
This method offers an opportunity for
significant cost savings either by eliminating
the need for special control equipment or by
reducing the size of the control equipment
ultimately required.
When the possibilities for modification of
equipment and process have been exhausted,
the recovery or control of the remaining sol-
vent emissions can theoretically be ac-
complished by one or more of the following
processes: condensation by cooling or
compression, absorption, chemical modifica-
tion including incineration, and adsorption.
All these systems were studied in detail in
order to select and investigate experimentally
the method that appeared to have the greatest
promise of feasibility for control of solvent
emissions where the concentrations range
from 100 to 200 parts per million.2 9
It has been shown that for condensation of
organic vapors by cooling, refrigeration
requirements would be very costly. For
example, to obtain 90 percent recovery of
toluene vapors being emitted at a rate of 250
pounds per day with a concentration of 1
pound per 40,000 cubic feet of air would
require over 500 tons of refrigeration.
The use of compression to accomplish
condensation would require high pressure and
large power consumption. In the toluene
example above, over 800 atmospheres pres-
sure and 70 horsepower per thousand cubic
feet per minute handled would be required.
Absorption involves the scrubbing of the
vapor-laden gases with a liquid in which the
solvent is soluble. With organic vapors,
mineral oil would be a possible absorbing
agent. In this case, also, impractically large
absorption equipment would be required for
organic vapors in the 100- to 200-ppm range.
Chemical destruction or modification of
organic vapors would require impractically
large equipment because of difficulties similar
to those involved in absorption. Destruction
of organic vapors by incineration becomes
very costly for the range of concentration of
organic vapors occurring in surface coating
operations. With higher concentrations, such
as are emitted from paint baking ovens, incin-
eration has been used with success because of
lower fuel requirements and some heat recov-
ery.
The control of organic solvent emissions
from protective coating operations was in-
vestigated in a pilot plant study by Elliot3 ° et
al. It was concluded that the control of
organic emissions from spraying operations
was technically feasible using adsorption on
activated carbon. By using the data obtained
in the pilot plant adsorber, estimates were
made of costs for larger units. These estimates
ranged from $8.00 per cfm for a 1,000-cfm
4-27
-------
spray booth to $1.54 per cfm for a
50,000-cfm spray booth.
For baking ovens and other operations that
can use afterburners, several factors are
important in the selection of a proper system.
Because an afterburner, or almost any other
air pollution equipment, does not yield a
profit, the tendency in some cases is to buy
the cheapest equipment on the market. The
cheapest equipment may not always be the
most economical to operate over an extended
period.
One way to reduce the cost of an after-
burner is to reduce the amount of exhaust air
to be treated. Fire underwriters' standards
require that vapor concentrations inside the
oven be kept at not more than 25 percent of
the lower explosive limit of the vapor. When
an afterburner is to be added to an existing
oven, a check should be made to determine
whether the amount of dilution air actually
being used is substantially more than that re-
quired by the underwriters' standards, as is
sometimes the case. The afterburner can then
be designed or selected for the required
volume. When a new oven is to be designed
for afterburner control, the oven and after-
burner can be designed as an integral unit,
with the afterburner furnishing all or part of
the heat required to operate the oven.
Afterburners generate a lot of waste heat,
and the need for heat recovery systems is ap-
parent. For afterburners handling large air
volumes (3,000 cfm or more), the addition of
heat recovery systems is almost a necessity. In
principle, there are three types of heat recov-
ery systems: self-recuperating heat recovery,
heat recovery to provide hot process air for
the ovens, and heat recovery to provide heat
for auxiliary use. The most common system is
the self-recuperating heat exchanger, which
can be built into the incinerator as a neat
package. Three types are in use, as shown in
Figures 4-12, 4-13, and 4-14. In Figure
4-12, all the exhaust air passes through the
heat exchanger. With this arrangement, only
one heat exchanger efficiency can be obtain-
ed. The system shown in Figure 4-13 allows
part of the incinerated air to be bypassed.
4-28
Heat exchange efficiency is controlled by con-
trolling the bypass volume. The system in
Figure 4-14 employs a variable-type heat ex-
changer (for example, Ljungstrom), which al-
lows the efficiency of heat exchange to be
varied. Self-recuperating heat exchangers
should be sized to take over most of the heat
load, but they should not be too large. Even
at maximum loading, the incineration tem-
perature should be controlled by the burner
and not by the concentration of solvents.
An incinerator system can be designed in
many ways. For this reason, some basis for
comparison of designs is necessary. While
direct comparison is not possible, a few rules
should be applied to their comparison.
4.7 DECREASING OPERATIONS
4.7.1 Introduction
In many industrial operations, metal parts
must be thoroughly cleaned of all grease and
oil before they can be plated, painted, or
further processed. In this connection, it is
important to recognize the terminology used
by industry to differentiate between various
cleaning processes in which organic solvents
are used as cleaning agents. For example,
certain types of process equipment operate
with little or no built-in control of solvent
losses, while others operate with a relatively
high degree of control with regard to solvent
losses. In general, "degreasing" merely implies
the use of an organic solvent to dissolve and
remove soils from metals, etc., by any type of
process. If the solvent used for cleaning is at
or near room temperature and if the equip-
ment used is not designed to control solvent
losses, then such a process is referred to as
"solvent cleaning" or "cold solvent cleaning."
The solvents used in these processes may be
halogenated, nonhalogenated, or mixtures of
them. If the solvent used for cleaning is main-
tained by heat input at its atmospheric boiling
point in the process equipment, and if this
equipment is designed to control and
minimize solvent losses to the air, then the
cleaning process is called "vapor degreasing".
In other words, vapor degreasing is a specific
-------
;/vHAUST
GAS
1
EFFLUENT
FROM
PROCESS
HEAT
EXCHANGER
INCINERATOR
Figure 4-12. Self-recuperating heat recovery: single efficiency heat exchange.
EXHAUST
GAS
EXHAUST
GAS
EFFLUENT
FROM
PROCESS
I
t
HEAT
EXCHANGER
INCINERATOR
Figure 4-13. Self-recuperating heat recovery: variable heat exchange.
EXHAUST
GAS
I
EFFLUENT
FROM
PROCESS
1
1
VARIABLE '
HEAT 1- -
EXCHANGER [
1
i
IKIPIN FR A TOR
Figure 4-14. Self-recuperating heat recovery: variable efficiency heat exchange.
4-29
-------
type of cleaning process designed to use only
halogenated solvents, which are essentially
nonflammable and have a relatively high
vapor density. Complete descriptions of
"solvent cleaning" and "vapor degreasing" are
presented in the chapter on metal cleaning in
the Metals Handbook.31
With respect to "vapor degreasing"
operations using trichloroethylene, for
example, industrial experience indicates the
following general guidelines can be used in
estimating solvent vapor losses from a proper-
ly designed and operated machine:
1. Based on the open cross-section area
of the degreaser, estimate the
operating solvent loss as 0.25 (± 50
percent) pound per hour per square
foot of open area.
2. Based on the work load processed
through the unit, estimate solvent loss
as 0.5 to 1.5 gallons per hour per ton
of metal cleaned.
3. Based on the solvent turnover in the
unit (boil-up rate), estimate solvent
loss as 1 to 2 percent of the vapor
generation rate in pounds per hour.
Emissions from all types of degreasing
operations consist of vapors of the solvent or
solvents used in the cleaning process. While
daily emissions from a single unit vary from a
few pounds to as high as 1,300 pounds for a
spray degreasing booth, the total emissions
from such sources in an industrialized area
may be quite large.7 It has been estimated
that in Los Angeles County, degreasing vapors
amounted to 95 tons per day in 1967.32
4.7.2 Vapor Degreasing Equipment
The usual vapor degreaser includes a heat-
ing system on one end of the tank to create a
vapor that condenses on the metal parts.
Condensation continues until the metal is
heated to the vapor temperature. The upper
portion of the tank contains water-cooled
condensers to prevent excessive loss of vapors.
Because of the high density of the vapors,
they do not tend to rise from the tank if
excessive drafts are prohibited.
4-30
Because of the specialized equipment
design features required for satisfactory
operation and control of vapor degreasers,
commercial rather than "handmade" units
should be used. In general, suppliers of vapor
degreasing equipment can provide so-called
"standard" units, or can design specific equip-
ment for almost any process requirement. The
vapor degreasing process lends itself equally
well to batch and continuous type operation.
Also, a variety of different cleaning cycles
(using the separate vapor and liquid phases, as
well as liquid sprays) may be incorporated in
any given vapor degreaser as required by the
cleaning process.33 A thorough discussion of
vapor degreaser design, operation, main-
tenance, and safety are presented in the
ASTM Handbook of Vapor Degreasing.3 4
A relatively new development in control-
ling vapor loss from a vapor degreaser is the
incorporation of an additional lower tem-
perature cooling surface (chiller) in the free-
board section of the machine. This is claimed
to reduce operating solvent loss by as much as
35 to 50 percent.
A review article on the industrial safety ex-
perience of trichloroethylene as a vapor
degreasing solvent is available.35
Degreasing tanks can be equipped with slid-
ing or guillotine-type covers, which can be
closed when not in use.
Since most degreasing solvents are slightly
toxic, some degreaser tanks are provided with
an exhaust system to capture escaped vapors.
These lateral exhaust hoods should be de-
signed in accordance with the ventilation rate
outlined in the American Standard Safety
Code for Ventilation and Operation of Open-
Surface Tanks, Standard #Z9.1-1951. The
ventilation rates should be for Class B-3 oper-
ations, and the ventilation rates should not
exceed those specified in Tables 3 and 4 of
the standard.
4.7.3 Control Systems and Costs
In general, no auxiliary control systems are
used on vapor degreasers, and in Los Angeles
County most processors have switched to
noncontrolled solvents to comply with the
-------
organic emission regulations. Switching, for
example, to a less reactive, higher-boiling-
point solvent such as perchloroethylene has
made it possible for vapor degreasing opera-
tions to operate within the law.
To minimize solvent losses from vapor
degreasers, the following techniques34 should
be followed:
1. A degreaser should not be subject to
drafts from open windows, doors, unit
heaters, exhaust fans, and so forth;
therefore, if possible, a 12-to 18-inch-
high shield should be placed on the
windward side of the unit.
2. Work items should be placed in the
basket in such a way as to allow effi-
cient drainage and prevent carryout of
solvent.
3. Metal construction should be used for
all baskets, hangers, separators, and so
forth; use of rope and fabric that
absorb solvent should be avoided.
4. The speed of work entering and leav-
ing the vapor zone should be held to
11 feet per minute or less; the rapid
movement of work through the vapor
zone causes vapor to be lifted out of
the machine.
5. Spraying above the vapor level should
be avoided; the spray nozzle should be
positioned in the vapor space where it
will not create disturbances in the
contents of the vapor.
6. Work should be held in the vapor until
it reaches the vapor temperature at
which all condensation ceases; re-
moval before condensation has ceased
causes the work to come out wet with
liquid solvent.
7. When the metal articles are of such
construction that liquid collects in
pockets, the work should be suspend-
ed in the free-board area above the
tank to allow further liquid drainage.
8. The degreaser tank should be kept
covered whenever possible.
In general, carbon adsorption is not used
on exhaust systems from vapor degreasers.
Adsorbers are used more extensively on
exhaust streams from other types of solvent
cleaning processes for both halogenated and,
in particular, nonhalogenated organic sol-
vents.36'37 In one case, a system consisting
of two parallel-flow carbon chambers re-
moved 1,100 gallons of solvent per month
from the vapor-laden air exhaust from spray
degreasing booths.7 This unit cost about
$9,000 and has a flow capacity of 3,000 cubic
feet per minute.38
4.8 DRY CLEANING
4.8.1 Introduction
Clothing and other textiles may be cleaned
by treating them with organic solvents. This
treatment process involves agitating the cloth-
ing in a solvent bath, rinsing with clean sol-
vent, and drying with warm air.
There are basically two types of dry-clean-
ing installations: those using petroleum sol-
vents (Stoddard and 140°F), and those using
chlorinated synthetic solvents (perchloroeth-
ylene). Early dry-cleaning plants used petro-
leum solvents. Because of the inherent fire
hazard, most zoning laws prohibit the opera-
tion of cleaning plants that use petroleum
solvents in residential and commercial areas.
Nonflammable, chlorinated solvents were
developed for use in residential installations.
Chlorinated solvents do, however, have several
disadvantages: higher costs (tenfold more
expensive), greater toxicity, more corrosive to
metals, and more deleterious to some dyes
and fabrics. Nevertheless, the trend is toward
synthetic solvent plants both for small and
large installations.7
Based on an average per capita emission
rate of 3.9 pounds per year,39 total organic
emissions from dry cleaning are on the order
of 400,000 tons per year in the United States.
4.8.2 Process Description
In a petroleum-solvent dry-cleaning plant,
the equipment generally consists of a washer,
centrifuge (extractor), tumbler, filter, and
often a batch still. The centrifuge is used to
recover solvent by spinning it from the
4-31
-------
clothes. The clothes then enter a tumbler
where they are dried with warm air. The
tumbler is usually vented through a lint trap
to the atmosphere in this type of plant.
In synthetic solvent plants, the washer and
extractor are a single unit. The tumbler oper-
ates as a closed system, having a condenser for
vapor recovery. The tumbler is vented to the
atmosphere or to a carbon adsorber only dur-
ing a short deodorizing period.
4.8.3 Solvent Emissions
The major source of solvent emissions in
dry cleaning is the tumbler through which hot
air is circulated to dry the clothes. Drying
leads to vaporization of the solvent and emis-
sions to the atmosphere, unless control equip-
ment is used. Because of the volatility of the
solvents used, additional emissions occur
when storage tanks are loaded, equipment
doors are opened, ductwork or equipment
leaks, and solvent-soaked textiles are removed
from equipment. These latter sources are
more of a problem in petroleum plants
because the low cost of the solvent does not
give much economic incentive for conserving
the solvent during handling operations.
Since dry cleaning is only a physical proc-
ess, solvent emissions consist of the respec-
tive evaporated solvents. Chemical composi-
tion of petroleum solvents is about 46 percent
paraffins, 42 percent naphthenes, and 12
percent aromatic compounds. In Los Angeles,
Rule 66 led to reformulation of the solvents
to reduce the aromatic content to less than 8
percent.
Emissions from synthetic plants using
separate vessels for cleaning and drying are
about 10 gallons per 1,000 pounds of textiles
cleaned. This drops to 2.5 to 3.5 gallons per
1,000 pounds for older plants in good condi-
tion but with carbon adsorbers, and down to
only 1-1.5 gallons per 1,000 pounds of tex-
tiles for new integrated plants with activated-
carbon adsorbers.38 The rate for units using
the same vessel for cleaning and drying units
is in the range of 5 gallons per 1,000 pounds
of textiles cleaned without adsorption units.
Emissions from petroleum-solvent plants are
4-32
about 15 gallons per 1,000 pounds of tex-
tiles.7 The relative emission contribution on a
solvent tonnage basis is somewhat smaller,
because a gallon of synthetic solvent is about
twice as heavy as a gallon of petroleum sol-
vent.
4.8.4 Control Techniques and Costs
Both adsorption and condensation systems
may be used to control solvent emissions
from dry-cleaning plants using synthetic sol-
vents. Solvent recovery systems are not only
commercially available as part of a synthetic
solvent cleaning plant, but they are also eco-
nomically attractive. The primary control
element is a water-cooled condenser, which is
an integral part of the closed cycle in the
tumbler or drying system. Up to 95 percent
of the solvent that is evaporated from the
clothing is recovered here. About half of the
remaining solvent is then recovered in an acti-
vated-carbon adsorber, giving an overall con-
trol efficiency of 97-98 percent. Because of
the value of the recovered solvent, the adsorp-
tion unit pays for itself within 1 to 2 years in
all except the very smallest units.7 A double-
bed activated-carbon unit handling 700 cubic
feet per minute and equipped with low-pres-
sure steam regeneration costs about
$2,300.38 Despite this economic advantage,
only about half of all synthetic solvent clean-
ing units are thought to have carbon adsorb-
ers. In Los Angeles County, it is estimated
that 50-75 percent of all units have adsorbers
and that these account for 25 percent of total
dry-cleaning volume.
There are no commercially available con-
trol units for solvent recovery in petroleum-
solvent plants because it is less economical to
recover the vapors. The vaporized solvent is
not condensible at the temperatures
employed, and thus the whole solvent recov-
ery burden would fall on an adsorption sys-
tem, necessitating equipment up to 20 times
larger than that used in a comparable syn-
thetic solvent plant. One recent estimate
shows the solvent recovery cost to be about
1.7^ per pound of clothing;4' however, even
with this cost, it would appear that petroleum
-------
plants could install solvent collection equip-
ment and remain competitive with synthetic
plant operations, since total operating costs
account for only about 20 percent of the
overall dry-cleaning cost.
Another way of controlling solvent emis-
sions from petroleum plants is through direct-
fired afterburners. Estimates show that a
saving in capital cost could be achieved, but
an increase in operating costs would also be
incurred compared to carbon adsorbers.4 *
Afterburners are not suitable for synthetic
chlorinated hydrocarbons because of the
danger of producing hydrogen chloride, phos-
gene, or other toxic gases.
4.9 STATIONARY FUEL COMBUSTION
4.9.1 Introduction
The combustion of fuels may result in the
emission of hydrocarbons and other organic
material if combustion is not complete. When
properly operated and designed, however,
stationary fuel combustion equipment is not a
large source of organic emissions, and c'ontrol
equipment is not required.
4.9.2 Processes and Emissions
Fuels are burned in a wide variety of equip-
ment ranging from small hand-fired coal
furnaces to large oil, gas, and coal-fired steam-
electric generating plants. Due to variations in
combustion efficiency and type of fuel,
hydrocarbon emissions will depend on the
particular type of combustion device. Table
4—4 presents the average hydrocarbon emis-
sions for various types of fuels and furnace
sizes. Considerable variation in these emis-
sions can occur, however, depending on the
operation of an individual unit.
4.9.3 Control Techniques
Hydrocarbon emissions from fuel combus-
tion can be reduced or eliminated by essen-
tially three techniques: improved operating
practices, improved equipment design, and
fuel substitution.
4.9.3.1 Operating Practices
Good operating practice is the most prac-
tical technique for reducing hydrocarbon
emissions from existing stationary combus-
tion sources. Even the best equipment will
perform poorly if improperly applied, in-
stalled, operated, or maintained and emit
hydrocarbons, smoke, and other pollutants.
Hydrocarbon emissions are directly related to
the three common combustion parameters of
time, temperature, and turbulence. A high
degree of fuel and air turbulence will greatly
reduce hydrocarbon emissions, increase com-
bustion efficiency, and reduce fuel
consumption.
Guidelines for good combustion practice
are published by the fuel industry, equipment
manufacturers, engineering association, and
government agencies. Stationary combustion
units should be operated within their design
limits at all times and according to the recom-
mendations of the manufacturer in order to
achieve a high degree of combustion effi-
ciency. Combustion units and components
should be kept in good repair to meet design
Table 4-4. AVERAGE HYDROCARBON EMISSIONS FROM STATIONARY
FUEL COMBUSTION SOURCES3 (lb/109 Btu)
Fuel
Coal
Oil
Gas
Size range
Steam-electric
7.7
Neg.
Industrial
38
12.5
Neg.
Domestic and
commercial
380
12.5-19
Neg.
aExpressed as methane; based on data from reference39, except as noted.
^Datum from reference 40.
4-33
-------
specifications. Flue gas monitoring systems
such as oxygen and smoke recorders are help-
ful in indicating the operation of the furnace
and are useful in keeping emissions at a mini-
mum.
Source of information on good operating
practice include:
1. American Boiler Manufacturers Asso-
ciation.
2. American Gas Association.
3. American Petroleum Institute.
4. American Society of Heating, Refrig-
erating, and Air-Conditioning Engi-
neers.
5. American Society of Mechanical Engi-
neers.
6. The Institute of Boiler and Radiator
Manufacturers.
7. Mechanical Contractors Association of
America.
8. National Academy of Sciences
National Research Council.
9. National Coal Association.
10. National Fire Protection Association.
11. National Oil Fuel Institute.
12. National Warm Air Heating and Air-
Conditioning Association.
13. U. S. Bureau of Mines.
4.9.3.2 Improved Equipment Design
Hydrocarbon emissions may be reduced by
upgrading combustion processes through
improving designs to reduce emissions or
through redesign to reduce the quantity of
fuel required for a given energy output.
Improvements in the combustion of pulver-
ized coal and better mixing of highly turbu-
lent secondary air into the primary combus-
tion zone have improved combustion efficien-
cies and reduced emissions of hydrocarbons
from steam-electric generating plants. The
trend toward better steam utilization in these
plants has also improved the efficiency of
conversion of thermal energy from fossil fuels
into electrical energy. Table 4—5 shows recent
improvements in efficiency of fossil fuel
combustion for electric generation.
4-34
Table 4-5. TRENDS IN OVERALL EFFICIENCY
OF STEAM-ELECTRIC GENERATING
PLANTS 42'43 (Btu per kw-hr)
Year
1956
1957
1963
1964
1965
1966
Coal
11,257
11,191
10,258
10,241
10,218
10,301
Oil
12,828
12,512
11,278
11,138
11,097
11,247
Gas
12,245
12,238
11,066
10,962
10,868
10,774
Continued research in the areas of magne-
tohydrodynamics, electrogas dynamics, and
fuel cells, solar energy, etc., offers the prom-
ise of reduced fuel requirements and reduced
hydrocarbon emissions.
4.9.3.3 Fuel Substitution
The substitution of gas for coal or oil in
any type of furnace reduces the emissions of
organic gases when good combustion tech-
niques are used. A switch from coal to oil will
reduce organic emissions on smaller industrial
furnaces and on commercial and domestic fur-
naces. This reduction in organic emissions is
largely effected by the better mixing and
firing characteristics of a liquid or gaseous
fuel as compared to those of a solid.
4.9.4 Control Costs
Costs for reducing hydrocarbon emissions
from combustion processes are low and may
sometimes show an overall profit due to
increased combustion efficiency. Switching to
another type of fuel may sometimes be more
expensive on a cost-per-Btu basis; but when
operation, maintenance, and combustion
efficiency savings are included, the overall
cost may be moderate. In addition, other
atmospheric emission problems will be
reduced when a more easily burned fuel is
used.
Average fuel cost data have been com-
piled.43
4.10 METALLURGICAL COKE PLANTS
4.10.1 Process Descriptions
Coke is mainly produced by the destructive
distillation of coal in long rows of narrow
-------
rectangular ovens.43 From 16 to 25 tons of
coal is charged through ports in the top of the
ovens. The ports are sealed, and the coking
period begins because of the intense heat in
the oven. In about 16 to 20 hours, when the
volatile matter has been driven off and carbo-
nization is complete, the charge is pushed out
into quench cars, cooled, and screened.1 3 The
high-temperature process, during which the
coal is heated to temperatures ranging from
1,650° to 2,150°F, is used almost exclusively
in the United States.
In the most commonly used by-product
ovens, this volatile matter is ducted to equip-
ment that extracts from the gas components
such as tar, ammonia liquor, and light oil.
Approximately 35 percent of the coke oven
gas (heating value, 550 Btu/ft3) produced
during coking is used to heat the coke
ovens.44 Although the remainder of the gas is
usually used for heat in other nearby pro-
cesses, it is sometimes flared.
Coke is also manufactured in beehive-type
ovens in which no attempt is made to recover
the volatile matter; it is simply vented to the
atmosphere. In 1966, only about 2 percent of
the total metallurgical coke production of
67.4 million tons was produced in beehive
ovens.45
4.10.2 Emissions
Visible smoke, hydrocarbons, CO, and
other emissions originate from the following
by-product coking operations: (1) charging of
coal into the red-hot ovens, (2) oven leakage
during the coking or carbonization period, (3)
pushing the coke out of the ovens, and (4)
quenching the hot coke. There are organic
emissions, from the last two operations only
where the material is undercoked. Although
organic compounds are only a part of these
emissions, they will also decrease when meas-
ures are taken to reduce the more notice-
able pollutants.
Soon after an oven has been emptied at the
end of the coking cycle, it is refilled with a
new charge of pulverized coal. Since the oven
interior is at a temperature of 1,500° to
1,800°F, volatilization of gases from the coal
mass begins at once. Unless controlled, these
gases escape to the atmosphere as visible
clouds of yellow-brown smoke.
Because of the nature of the coking pro-
cess, hydrocarbons and other organic com-
pounds are generated and emitted from the
furnaces. Very few quantitative data on
organic emissions are available, however.
4.10.3 Control of Emissions46
Progress has been made over the years in
reducing the quantity of emissions released
during the coking process. Improvements in
both coke-oven design and operating prac-
tices, such as shortening the time required for
charging, are responsible for reduced emis-
sions.
One potential improvement over older
plants consists of aspirating gases from the
interior of the oven by means of steam jet
aspirators during charging periods. In older
units, the oven interior was sealed off from
the gas-collecting duct during charging, and
enormous quantities of smoke were emitted.
Despite the use of an aspirator during charg-
ing, some smoke escapes from openings at the
opposite end of the oven because of the
distance the gases must travel and because of
partial obstruction caused by piling up of
coal. One arrangement for minimizing this
emission provides two gas-collecting ducts
(mains) with a gas ascension pipe and aspi-
rator at each end of the oven. Effective con-
trol with this arrangement is greatly depend-
ent on the operators who must regulate the
stem valves supplying the jet aspirators.
The use of a leveling bar during the filling
operations prevents uneven piling of the coal
and assists in keeping the gas-collecting ducts
unobstructed.
Emission control systems mounted on the
larry car itself have been installed. These
systems collect, ignite, and wash the escaping
oven gases during the charging process.47
The development of volumetric sleeves on
the top of the larry car hoppers has made it
possible to adjust the bulk of coal in each
hopper to match the requirements of ovens of
different capacity. This makes it possible to
4-35
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charge the correct volume of coal and thereby
minimizes resistance to the passage of gas over
the coke within the oven.
Appropriate spacing of the charging holes
in relation to oven volume also reduces emis-
sions during charging. Proper spacing elimi-
nates piling up of coal in the oven in such a
manner as to obstruct free passage of gases to
the gas takeoff flue. In addition, if the
bottom ends of the charging holes are flared
outward, more space is provided between the
coal and the top of the oven for free passage
of gases.
Any arrangements that reduce the time
required for transfer of the coal charge from
the larry car hopper to the oven interior will
also reduce the total escape of smoke and
organics. Several mechanical devices for this
purpose are available, including (1) hopper
vibrating mechanisms used in conjunction
with smooth stainless steel liners, (2) cylin-
drical hoppers and bottom turn-table feeders,
and (3) a screw-feed mechanism.
Another device, consisting of drop sleeves
and shear gates, provides an enclosure be-
tween the hopper of the larry car and the top
of the charging hole to prevent the escape of
gases from the charging hole.
Control of the bulk density of the coal
mass is one of the factors contributing to coal
feed rate. In coke plants where the coal is
pulverized and blended, it has become increas-
ingly common to control the moisture con-
tent and, by the addition of small quantities
of oil to the coal, to modify the bulk density
further. Oil-sprayed coal moves out of the
larry car hoppers more easily and can thus be
charged faster.
Operation of the steam jet aspirator in the
ascension pipe of the oven being serviced is
not entirely successful in preventing the
escape of smoke. Each oven, however, can be
equipped with a smoke seal box, which sur-
rounds the leveling bar opening. In conjunc-
tion with the effect of the steam jet aspirator,
the seal box greatly reduces the escape of gas
from the opening.
The by-product recovery system, which
receives the fumes from the gas collecting
4-36
main, is largely an enclosed process consisting
of scrubbers, separators, and distillation col-
umns. The organic compounds shown in
Table 4-6 are removed from the coke-oven
gas, and the remaining stripped gas is used as
fuel. Organic emission may occur from the
recovery process because of leaking equip-
ment, pump seals, valve seals, vents, storage
tanks, and other relatively minor sources.
Table 4-6. TYPICAL COMPOSITION AND
AMOUNTS OF COMPOUNDS REMOVED
FROM COKE-OVEN GAS PER TON OF
COAL48
Compound
Amount, gallons
Benzene 1.85
Toluene 0.45
Xylene and light solvent naphtha 0.30
Acid washing losses 0.16
Heavy hydrocarbons and naphthalene 0.24
Wash oil 0.20
During the carbonization period, leakage
may also occur around the oven doors. In
older ovens, the joint between the door and
the jamb was sealed by luting, that is, by
hand-troweling a wet mixture of clay and
coke breeze into a channel between the doors
and the jamb. Newer oven designs feature self-
sealing doors in which metal-to-metal contact
between a machined surface and knife edge
together with mechanical arrangements for
exerting pressure provide the seal. A superior
maintenance program must be applied to this
equipment since damage to the seal inevitably
allows leaks to develop. An optimum main-
tenance program for self-sealing doors, pro-
posed by coke-oven operators in Allegheny
County, Pennsylvania, includes use of stain-
less steel as the knife-edge material and adop-
tion of systems for (1) keeping a complete
history of each door and (2) informing the
maintenance force of the reason that a par-
ticular door has been taken out of service.
For luted doors, the luting should be
tamped immediately after charging is com-
pleted in order to prevent emissions.
The quantity of smoke arising from the
coke during transportation to the quenching
station is dependent on the degree of coking.
-------
Adequately carbonized coke will not smoke
when exposed to the air; however, poorly
carbonized coke will emit some smoke and
hydrocarbons during the short trip to the
quenching tower.
The measures discussed above can do much
to minimize emissions from coking opera-
tions, but no combination of these measures
provides a completely satisfactory control
method for coke-oven emissions. A satis-
factory solution to the problem of emissions
during charging has not been developed.4 9
4.11 SEWAGE TREATMENT
4.11.1 Introduction
Municipal sewage is generally treated in a
primary treatment plant, an activated-sludge
plant, or a trickling filter plant. All of the
treatment plants emit organic gases, many of
which are odorous. Quantitative data on the
nature or amount of emissions, however, are
generally lacking and difficult to obtain be-
cause sewage treatment plants are essentially
outside operations.
Hydrocarbon emissions vary widely from
plant to plant, depending on the type of plant
and treatment process, the condition and
composition of the influent, and the size of
the plant.
4.11.2 Process Description and Emissions
A primary sewage treatment plant basically
removes only solid material through sedimen-
tation or screening processes. Hydrocarbon
emissions therefore only occur from the
screening and grit chamber, and from the
settling tank itself.
The activated-sludge treatment plant is
probably the largest emitter of hydrocarbons
when compared with the other two processes.
In the activated-sludge plant, the sewage,
after passing through screens and a primary
clarifier (settling tank), is aerated with com-
pressed air. Additional sludge, now biologi-
cally activated by the air, is settled out in a
final clarifier and recycled to the aeration
chamber.50 Various volatile oils, fats, and
other organic compounds present in the sew-
age are partially stripped from the liquid.
Table 4-7 shows the organic vapor con-
centrations measured in the ambient air above
the various treating units at a single activated-
sludge plant.
Table 4-7. ORGANIC VAPOR CONCENTRATIONS
EMITTED FROM AN ACTIVATED-SLUDGE
PLANT51
Process
Bar screen
Aeration tank
Final clarifier
Concentration,
/Jg/liter
35.2
20
6.7
In a trickling filter plant, the primary treat-
ment plant is followed by the trickling filter
and a final clarifier. The trickling filter is a
large bed of coarse, impervious material over
which the sewage is sprayed. The sewage
trickles down through the-bed and comes into
contact with the ambient air, which promotes
bacterial action.50 Odors and other organic
materials are emitted from the clarifiers and
the filter itself.
Sludge collected in the clarifiers is fre-
quently digested in order to render it more
innocuous. Sludge digestion generates a
methane-rich gas, which may contain trace
amounts of hydrocarbons and other odorous
material. Digester gas contains approximately
75 percent methane, 20 percent carbon diox-
ide, and a balance of oxygen, nitrogen, and
trace contaminants. Since the gas has a heat-
ing value of about 670 Btu per cubic foot, it
is frequently burned in a boiler or in an
internal combustion engine at the plant.50
Direct venting or improper combustion of this
gas will result in organic emissions.
4.11.3 Control Techniques and Costs
The basic hydrocarbon and odor control
techniques at any sewage treatment plant con-
sist of adequate and careful plant design,
proper operation, and diligent maintenance of
the treating equipment. Proper plant design
calls for the reduction of odor and hydro-
carbon emission by eliminating the emission
source. Hydrocarbon emissions arising from
septic sewage can be reduced by pretreatment
4-37
-------
with an oxidizing agent such as a chlorate.
Frequent cleaning of screens and grit cham-
bers, and preventing the buildup of sludge on
walls also reduces organic emissions.
The covering of various treating units such
as settling tanks, aeration chambers, and
trickling filters and the oxidizing or combust-
ing of effluent gases also serve to reduce emis-
sions.5 2 At the Owl's Head Plant in New
York City, the gases drawn from the covered
settling tanks are treated with ozone to
reduce organic emissions and odors. At
Mamaroneck, New York, gases vented from
the bar screens, grit removal unit, and settling
chamber are all treated with ozone.5 3 A
Sarasota, Florida, plant utilizes a plastic cover
over its trickling filter to minimize emis-
sions.5 2 Sludge drying beds could also be
covered, and the air drawn over the beds for
drying could be incinerated before it is re-
leased.
Adequate organic emission control involves
additional plant construction costs to provide
covers for the various processing units. In
addition, air blowers, ozone generators, or
other gas-oxidizing systems must be installed.
Oxidation ponds are also used to dispose of
sewage in some rural areas. These ponds or
lagoons are simply holding areas where the
natural oxidation processes through surface
contact with the air achieve biological break-
down of the sewage. These ponds may emit
odorous compounds such as mercaptans and
amines, but the main organic gas emitted is
methane. This gas is emitted at a rate of about
5 cubic feet per pound of BOD destroyed
under a pond loading condition of 55 pounds
of BOD per acre per day.34
4.12 WASTE INCINERATION AND OTHER
BURNING
4.12.1 Introduction
Preliminary results of a survey conducted
by the Public Health Service indicate that
household, commercial, and industrial solid
waste production in the United States is
about 10 pounds per capita per day, or 360
million tons per year. About 190 million tons
per year (or 5.3 pounds per day per capita) is
4-38
collected for disposal, and the remainder is
either disposed of on site or handled by the
household or establishment itself.5 5
An estimated 177 million tons of this
material is burned in the open or in inciner-
ators.56 An additional 550 million tons of
agricultural waste and 1.1 billion tons of
mineral wastes are generated each year.5 5 It is
estimated that half of the agricultural wastes
are burned in the open. Except for the esti-
mated 48 million tons of coal refuse con-
sumed by fire each year, no other mineral
wastes are burned.5 6 The quantity of material
consumed by forest burning and structural
fires is estimated to total about 220 million
and 8 million tons a year, respectively.5 6
Incineration and open burning are used to
reduce the weight and volume of solid waste.
High-temperature incineration with excess air
reduces emissions of particulates; carbon
monoxide; and smog-forming compounds
such as aldehydes, hydrocarbons, and organic
acids, which typify open burning. Nitrogen
oxides emissions, however, increase.
Figures 4—15 through 4—21 show various
basic types of incinerators. In a multiple-
chamber design as illustrated in Figure 4—17,
combustion products are formed by contact
between underfire air and waste on the grates
in the primary chamber. Additional air (over-
fire air) is admitted above the burning waste
to promote gas phase combustion. Gases from
the primary chamber flow to a small mixing
chamber where more air is admitted and then
to a larger secondary chamber where more
complete oxidation occurs. At times, auxil-
iary burners are installed in the mixing
chamber to increase combustion temperature
to about 1,400° to 1,800°F. A total of 150
percent excess air is sometimes supplied to
promote oxidation of combustibles. Sizes and
configurations of incinerators vary with the
service for which they are designed. Refer-
ences 7 and 57 contain information on design
parameters for incinerators.
4.12.2 Emissions
Hydrocarbon emissions from incineration
and other burning are estimated as shown in
Table 4-8.
-------
CHARGING DOOR
COMBUSTION AIR
INLET OPENINGS
PRIMARY COMBUSTION
CHAMBER
WASTE
PRIMARY BURNER
{
GRATE
BAROMETRIC DAMPER
SECONDARY COMBUSTION
CHAMBER
SECONDARY BURNER
FLUE GAS FLOW
Figure 4-15. Domestic gas-fired incinerator.
^ HEAT EXCHANGER
SELF-SUSTAINING AFTERBURNER SECTIONS
GAS SUPPLIED ONLY
DURING STARTUP
FORCED AIR BLOWER
Figure 4-16. Single-chamber incinerator.
CHARGING DOOR
.•WASTE
4-39
-------
CHARGING DOOR WITH
OVERFIRE AIR PORT
IGNITION CHAMBER
-FLAME PORT
SECONDARY AIR PORT
CURTAIN WALL
GRATES
CLEANOUTDOORS WITH
UNDERGRATE AIR PORTS
SECONDARY COMBUSTION
CHAMBER
BREECHING TO STACK
LOCATION OF SECONDARY
BURNER
MIXING CHAMBER
CURTAIN WALL PORT
CLEANOUT DOORS
Figure 4-17. Cutaway of an in-line multiple-chamber incinerator.
BYPASS FLUE~
OVERFIRE AIR
CHARGING GATE
PRIMARY BURNER
ASH PIT DOOR
CHARGING CHUTE
MOTOR
OPERATED
DAMPER
CHARGING
CHUTE
CHARGING DOOR
60-degree
HEARTH
ROOF
SAMPLING POINT
EXHAUST FLUE
SECONDARY
BURNER
PRIMARY
BURNER
CHARGING
•DOOR
PRIMARY
DRAFT
ASH PIT
DOOR
Figure 4-18. Section of the flue-fed incinerator.
Figure 4-19. Section of chute-fed apartmen
incinerator.
4-40
-------
STACK GAS OUT
REBURNED
Figure 4-20. Section of pathological incinerator.
(Courtesy of Silent'Glow Oil Burner Corp.)
INCINERATOR _.
BUILDING
WATER BRIDGE
COOLED CRANE
HOPPER
CHARGING
HOPPER
PRIMARY
COMBUSTION
CHAMBER
STORAGE
PIT -
TO GAS CLEANER
AND STACK
SECONDARY
COMBUSTION
CHAMBER
Figure 4-21. Section of municipal incinerator.
4-41
-------
Table 4-8. ESTIMATED NATIONAL EMISSIONS FROM INCINERATION
AND OTHER BURNING, 196857
Onsite incineration
Municipal incineration
Conical burner incineration
Open burning
Agricultural burning
Controlled forest burning
Forest wildfires
Structural fires
Coal refuse fires
Total
Quantity,
tons/yr
57,000,000
16,000,000
27,000,000
77,000,000
275,000,000
76,000,000
146,000,000
8,000,000
48,000,000
730,000,000
Hydrocarbon emissions,
tons/yr
29,000
2,000
150,000
1,150,000
1,650,000
760,000
1,460,000
80,000
240,000
5,521,000
4.12.3 Controls
High temperature-excess air incineration
and substitution of noncombustion alterna-
tive waste dispositions are the most likely
means for reducing hydrocarbon emissions.
Some of these methods are discussed below.
4.12.3.1 Waste Disposal
From the standpoint of air pollution,
burning is not a satisfactory method of waste
disposal. The sanitary landfill is a good alter-
native if land for this purpose is available.
Approximately 1 acre-foot of land is required
per 1,000 persons per year of operation when
waste production is 4.5 pounds per day per
capita.58 In addition, soil approximating 20
percent by volume of the compacted waste is
required. At times, unavailability of soil limits
the use of sanitary landfill.
Unusual local factors may lead to solution
of the landfill site problem. Reference 59 indi-
cates that a project is under way in which the
refuse is shredded and baled for loading onto
rail cars for shipment to abandoned strip-mine
landfill sites.
4-42
Other alternatives may have application in
some localities. Composting has been con-
sidered and is being tested on a practical
scale.60 Dumping at sea has been practiced by
some seacoast cities, but some of the garbage
floats and returns to shore unless dumped far
out at sea. Such practices are now forbidden
by the United States Government. The
Japanese have ground and compressed refuse
into bales,6 l which are wrapped in chicken
wire and coated with asphalt. The high-den-
sity bales sink to the bottom in the deeper
ocean areas and reportedly remain intact. The
practice of grinding garbage in kitchen units
and flushing down the sewer has been increas-
ing. This in turn increases the load of sewage
disposal plants and the amount of sewage
sludge.
4.12.3.2 Incineration
Although no exact criteria are set for
temperature, excess air, or residence time for
incinerators, incineration temperatures greater
than 1,600°F, more than 150 percent excess
air, and heat release rates less than 1,800 Btu
-------
per hour per cubic foot of total combustion
space are sometimes used as design parameters
for hydrocarbon emission reduction. When
these conditions are achieved, hydrocarbon
emission rates are less than 0.3 pound per ton
of waste incinerated.6 2
Where the most effective hydrocarbon
emission control is desired, auxiliary burners
are used to increase incineration temperature
to 1,600°-1,800°F. At temperatures above
1,800°F, slagging of refractories is often a
problem. Even when dry combustible wastes
are incinerated, auxiliary burners are useful
for preheating the secondary combustion sec-
tions of the incinerator before the waste is
ignited. Temperature control systems promote
consistent emission reduction. These are usual-
ly on-off-type controls for smaller units and
modulating-type controls for larger incinera-
tors.
Incineration air may be supplied by natural
or mechanical draft. Recommended stack or
chimney dimensions, barometric damper
dimensions, and induced-draft fan capacities
for various incinerators, air flow, and wastes
are published by the Incinerator Institute of
America.6 3 For the most effective control, air
is passed through the grates (underfire air),
admitted over the burning waste (overfire air),
and admitted in chambers where auxiliary
burners are located (secondary air). The ratios
between these air supplies vary, depending
upon the design of the incinerator. For small
incinerators, combustion air is regulated by
manual adjustment of air ports at the various
points of entry. For larger incinerators, admis-
sion of air is regulated automatically, and at
times the ratio between air supply at various
points is controlled automatically. For 150
percent excess air, the oxygen content of the
undiluted gases at the incinerator outlet
ranges between 12 and 14 percent, depending
upon the type of waste incinerated and the
type of auxiliary fuel used.
Sufficient residence time for oxidation of
combustibles is provided by furnishing insu-
lated combustion space. A maximum waste
and auxiliary fuel heat release of 18,000 Btu
per hour for each cubic foot of total combus-
tion space is sometimes used as a design
parameter for determining required combus-
tion space. Contact between combustibles in
the gas phase and air is promoted (1) by
providing baffles, bridge walls, checkerwork,
curtain walls, down passes, drop arches, and
mixing chambers; (2) by introducing air at
strategic locations; and (3) by locating auxil-
iary burners to promote mixing.
Differences between hydrocarbon emis-
sions from various types of incinerators are
caused by differences in incineration condi-
tions. Although insufficient air, combustion
space, and mixing increase emission rates, the
most common cause of increased hydro-
carbon emission rates is low incineration
temperature. Estimates of emission rates from
various types of incinerators are given in Sec-
tion 5.
Another way of reducing total hydro-
carbon emissions from incineration and com-
bustion is to recover heat in a boiler. That
heat would eliminate the need for combustion
of some fossil fuels. This means of refuse dis-
posal has already received considerable atten-
tion in Europe.64'68
In 1966, two 50,000 pound-per-hour steam
generators were installed at the Navy Public
Works Center in Norfolk, Virginia.69 They
were designed to burn 180 tons of mixed
refuse per day in each of two furnaces. The
heating value of the mixed refuse is estimated
at 5,000 Btu per pound with a 25 percent
moisture content and 12.5 percent noncom-
bustibles. Steam is generated from the com-
bustion of the refuse. The waste firing is
supplemented by oil firing as required. The
furnace walls are water-cooled and integral
with the boiler, which reportedly increases
steam production by 38 percent.
4.12.3.3 Forest Wildfires
About 1.5 million tons of hydrocarbons is
emitted annually from uncontrolled forest
fires.5 6 These fires are caused by natural
elements such as lightning or by careless
practices. Considerable activity has been and
is being directed toward reducing the fre-
quency of occurrence and the severity of
these fires. These activities include publishing
443
-------
and advertising information on fire prevention
and control, surveillance of forest areas where
fires are likely to occur, and various fire-
fighting and control activities. Information on
forest fire prevention and control is available
from the United States Department of
Interior, and state and local agencies.
4.12.3.4 Controlled Vegetation Burning
Forest debris, crop residue, scrub, brush,
weeds, grass, and other vegetation are burned
for one or more of the following purposes:
l.To control vegetation, insects, or
organisms harmful to plant life.
2. To reduce the volume of waste.
3. To minimize fire hazards.
4. To improve land.
Hydrocarbon emissions from this burning are
estimated to be 2.4 million tons per year.5 6
Collection and incineration of these wastes
in properly controlled incinerators would
reduce emission rates from an estimated 12 to
20 pounds per ton to less than 0.3 pound per
ton.56
Other alternatives to incineration are aban-
donment or burying at the site, transport and
disposal in remote areas, and utilization.
Abandonment or burying at the site is practi-
cal in cases where no harmful effects will
ensue. Because abandoned or buried vegeta-
tion can have harmful effects upon plant life,
such as hosting harmful insects or organisms,
agricultural agencies such as the U.S. Depart-
ment of Agriculture or state and local agen-
cies should be consulted before these tech-
niques are employed. Other harmful aspects
such as odor, potential water pollution, and
fire hazards should also be considered. Collec-
tion and transport of these materials for
disposal in areas where the effects of burning
will cause no problem is possible, but not
commonly practiced.
At times it is possible to use some of these
waste materials. Large forest scraps are pro-
cessed by chipping or crushing and used as
raw materials for kraft pulp mills or processes
producing fiberboard, charcoal briquettes, or
synthetic firewood. Composting and animal
feeding are other possible alternatives to
burning.60
4-44
4.12.3.5 Coal Refuse Fires
An estimated 240,000 tons of hydro-
carbons is emitted each year from 19 billion
cubic feet of burning coal refuse.57 Extin-
guishing and preventing these fires are the
techniques used for eliminating emissions
from them. These techniques involve cooling
and repiling the refuse, sealing refuse with
impervious material, injecting slurries of non-
combustibles into the refuse, minimizing the
quantity of combustibles in the refuse, and
preventing ignition of the refuse. These tech-
niques and the status of future plans and
research are described and discussed in the
document Control Techniques for Sulfur
Oxide Air Pollutants.7 °
4.12.3.6 Structural Fires
Structural fires emit an estimated 80,000
tons of hydrocarbons annually.5 6 Prevention
and control techniques are used to reduce
these emissions. Use of fireproof construc-
tion, proper handling, storage, and packaging
of flammable materials and information
programs on fire prevention are some of the
techniques used to prevent fires. Fire control
techniques include the various methods for
promptly extinguishing fires such as the use
of sprinklers, foam, and inert gas systems;
provision of adequate fire fighting facilities
and personnel; and provision of adequate
alarm systems. Information on these and
other techniques for fire prevention and
control are available from agencies such as
insurance companies, local fire departments,
National Fire Protection Association, and the
National Safety Council.
4.12.4 Costs
The cost of controls is primarily a function
of the relative costs of the various methods of
incineration and the cost of noncombustion
disposition. As cost comparisons vary widely
from locality to locality, comparisons should
be made on an individualized basis. Informa-
tion that may be useful for guiding cost
comparisons is presented below.
According to a recent survey, the average
community budgets $5.39 per capita per year
-------
for waste collection. Communities operating
their own facilities budget about $6.80 per
capita per year for twice-a-week collection
and about $5.60 per capita per year for once-
a-week collection.55 Sanitary landfill costs
including amortization have been reported as
$1.05 per ton for 27,000 tons per year of
waste and $1.27 per ton for 11,000 tons per
year.5 s Figure 4-22 shows average operating
costs for sanitary landfill and open-dump
waste-disposal methods.5 5
o 2'°
z
il
Q-*t 1.0
\-
o
I
I
0 10 30 20 40
REFUSE HANDLED. 1,000 tons/year
Figure 4-22. Land waste-disposal costs.56
Operating costs for municipal incinerators
are estimated at $4 to $8 per ton of waste, and
capital costs are estimated at from $6,000 to
$13,000 per ton per day capacity. Estimated
capital costs of incinerators are shown in
Figure 4-23.
Auxiliary fuel requirements for increasing
the incineration temperature to 1,600°F with
150 percent excess air vary from zero for dry
combustible waste to an estimated 15,000
Btu per pound for wastes containing 75 per-
cent moisture and having a heating value of
3,500 Btu per pound.
4.13 MISCELLANEOUS
4.13.1 Introduction
Almost any processing of organic matter
results in the emission of hydrocarbons. Such
diverse activities as chocolate manufacturing,
bread baking, pharmaceutical manufacturing,
leather tanning, coffee roasting, food process-
ing, fermentation, tobacco aging, and charcoal
manufacture all result in the emission of some
organic compound. The following processes
illustrate the sources and nature of hydro-
100 500 1,000 1,500 2,000
CAPACITY OF INCINERATOR, Ib/hr
Figure 4-23. Cost of incinerator at three
levels of control of particula'te emissions.73
carbon emissions. Quantitative emission infor-
mation is not generally available.
4.13.2 Fermentation Processes
The manufacture of beer, wine, whiskey,
and other fermented beverages results in the
emission of organic compounds, largely
alcohols. These emissions come from distilling
operations, cooking or brewing kettles, vac-
uum systems, fermenters, and aging or storage
processes. Air pollution controls for organic
emissions, other than condensers, which are
an integral part of the process, are not used.
In the manufacture of distilled liquors (whis-
key, gin, etc.), one of the larger sources of
organic emissions is the aging warehouse
where the liquor is kept for 1 to 5 years in
wooden barrels. During this time, evaporation
occurs through the barrel staves.12 The dry-
ing of the "slop" or still bottoms, which are
used for animal feed, also results in organic
emissions. This drying is accomplished in
either rotary or vacuum drum driers.
4.13.3 Food Processing
Many food processing operations emit
organic compounds. Deep fat frying (French
4-45
-------
frying) of various baked goods, vegetables,
fish, and meat results in the vaporization of
various oils in the material being fried. Exces-
sive heating of the cooking oil vaporizes some
of the oil itself.7 Objectionable organic emis-
sions from these processes are best controlled
by afterburners.
Coffee roasting also releases odorous organ-
ic compounds, which derive from the volatile
matter present in the green coffee beans.
Because of the relatively high boiling point of
many of these compounds (saturated and
unsaturated fats, furfural compounds, etc.),
they tend to condense after leaving the
roaster and form particulate matter. Control
of organic and smoke emissions may be
accomplished by venting part of the exit gases
back through the roaster, or by installing an
afterburner.73'74
The canning of fish and other perishable
foods results in organic emissions from the
oils and fats present in the food. The canning
of fish is probably most objectionable because
of the malodorous organic compounds
emitted. Fish may be either precooked before
canning (usually confined to large fishes like
tuna) or canned and cooked before sealing
(sardines, anchovies, etc.). After the cans are
sealed, they are pressure-cooked. Condensed
steam, oils, and juices collected during the
cooking processes are collected for by-prod-
uct recovery. In addition to the collected
oils and juices, the inedible parts of fish are
also processed into by-products such as fish
meal, high-protein concentrates, and fish sol-
ubles. This reduction of the inedibles pro-
duces the major organic odorous emissions in
the form of trimethylamine, (CH3)3N.
Many types of equipment are employed to
control gases at a fish canning and reduction
plant. These devices include condensers on
the cooking processers, condensers and after-
burners on the evaporators, and afterburners
or chlorinated water scrubbers on the fish
meal drier gases.1 2
4.13.4 Charcoal Manufacture
The destructive distillation of wood to
produce charcoal, wood alcohol, and acetic
4-46
acid is accomplished by heating hard wood in
an enclosed retort. Approximately 44 pounds
of methane and other noncondensible organic
compounds is emitted for each cord of wood
(4,000 lb).12 Since this gas also contains
about 27 percent carbon monoxide, and has a
heating value of 150 to 250 Btu per cubic
foot, it is usually burned as fuel at the plant.
Combustion of this wood gas effectively con-
trols the hydrocarbon emissions.
4.13.5 Drug Manufacture
Drugs and Pharmaceuticals encompass a
broad spectrum of materials, ranging from
purified anesthetic-grade ethers and other
anesthetics to the extraction and purification
of cod-liver oil. "Biological" odors are con-
ventionally controlled by incineration. Sol-
vents may be recovered by adsorption. Pill
coating, with chocolate or other taste-con-
trolling materials, can emit odors that are not
unpleasant, but are annoying if persistent.
Incineration and adsorption are the most
effective means of control. Usually there is no
provision for recovery of the adsorbed
materials. Frequently, the use of packaged
replaceable adsorption units is feasible.
REFERENCES FOR SECTION 4
1. Air Pollution, Stern, A. C. (ed.). Vol. Ill, 2d. ed.
New York, Academic Press, 1968. p. 103.
2. Evaporation Loss in the Petroleum Industry-
Causes and Control. American Petroleum Insti-
tute. New York. Bulletin 2513. 1959. 59 p.
3. Evaporation Loss from Low-Pressure Tanks.
American Petroleum Institute. New York. Bulle-
tin 2516. 1962. 15 p.
4. Evaporation Loss from Floating-Roof Tanks.
American Petroleum Institute. New York. Bulle-
tin 2517. 1962. 26 p.
5. Evaporation Loss from Fixed-Roof Tanks.
American Petroleum Institute. New York. Bulle-
tin 2518. 1962.41 p.
6. Use of Plastic Foam to Reduce Evaporation Loss.
American Petroleum Institute. New York. Bulle-
tin 2515. 1961. 15 p.
7. Air Pollution Engineering Manual, Danielson, J.
A. (ed.). National Center for Air, Pollution Con-
trol. Cincinnati, Ohio. PHS Publication No.
999-AP-40. 1967. 892 p.
-------
8. Recommended Practices for the Design and
Installation of Pressure-Relieving Systems in
Refineries, Part 1, 2d ed. American Petroleum
Institute. New York. November, 1967.
9. Deckert, I. S., R. G. Lunche, and R. C. Murray.
Control Vapors from Bulk Gasoline Loading. J.
Air Pollution Control Assoc.
-------
42. Steam-Electric Plant Factors/1966. National Coal
Association. Washington, D. C. 1967. p. 81-90.
43. Control Techniques for Sulfur Oxide Air Pollut-
ants. National Air Pollution Control Administra-
tion. Washington, D. C. Publication Number
AP-52. January 1968. p. 3-11.
44. Russell, C. C. Carbonization. In: Kirk-Othmer
Encyclopedia of Chemical Technology, Standen,
A. (ed.). Vol. 4, 2d ed. New York, Interscience
Publishers, 1964. p. 400-423.
45. Coke and Coal Chemicals. In: Minerals Year-
book, 1966, Vol. HI, Metals, Minerals, and
Fuels. U. S. Dept. of Interior, Bureau of Mines.
Washington, D. C. 1967. p. 731-764.
46. Air Pollution Problems of the Steel Industry-
Information Report, Section II—Smoke in Coke
Oven Operation, Hemeon, W. C. L. (ed.). J. Air
Pollution Control Assoc. 70(3):208-210, June
1960.
47. C. E. News Feature. Chem. Eng. 7J(3):32, Janu-
ary 29, 1968.
48. Porter, H. C, Coal Carbonization. New York, The
Chemical Catalog Co., 1924. 442 p.
49. A Systems Analysis Study of the Integrated Iron
and Steel Industry. Battelle Memorial Institute.
Columbus, Ohio. May 1969. p. V-3.
50. Babbitt, H. E. and E. R. Baumann. Sewerage and
Sewage Treatment. 8th ed. New York, John
Wiley and Sons, Inc., 1958. p. 526.
51. Glaser, J. R. and J. O. Ledbetter. Air Pollution
from Sewage Treatment (Paper No. 69-44).
Presented at 62nd Air Pollution Control Associa-
tion Meeting. New York. June 22-26, 1969.
52. Eliassen, R. and C. A. Vath. Air Pollution Con-
trol in Sewage Treatment Plants. J. Water Pollu-
tion Control Federation. 52:424-427, April
1960.
53. Ozone Newsletter. Welsbach Corp., Philadelphia,
Pa. January 1967.
54. Nelson, R. Y. and J. O. Ledbetter. Atmospheric
Emissions from Oxidation Ponds. J. Air Pollution
Control Assoc. 14:50-52, February 1964.
55. Black, R. J. et at. The National Solids Wastes
Survey. Presented at Annual Meeting of the
Institute for Solid Wastes of the American Public
Works Association. 1968.
56. National Air Pollution Control Administration,
Reference Book of Nationwide Emissions. U.S.
DHEW, PHS, CPEHS, NAPCA. Durham, N. C.
57. Guidelines for Design and Operation of a Muni-
cipal Solid Waste Incinerator. Environmental
Control Administration. Cincinnati, Ohio, (to be
published).
58. Kirsh, J. B. Sanitary Landfill. In: Element of
Solid Waste Management Training Course
Manual. Public Health Service. Cincinnati, Ohio.
1968. p. 1-14.
4-48
59. Air Pollution Problems from Refuse Disposal
Operations in the Delaware Valley. Dept. of
Public Health, Air Management Services. Phila-
delphia, Pa. February 1969.
60. Wiley, J. S. et at. Composting Developments in
the U. S. Combust. Sci. 6:2, 5-9, Summer 1965.
61. Kurker, C. Reducing Emissions from Refuse
Disposal. J. Air Pollution Control Assoc.
19:69-72, February 1969.
62. Stenburg, R. L. at al. Effects of High Volatile
Fuel on Incinerator Effluents. J. Air Pollution
Control Assoc. 8:376-384, August 1961.
63. IIA Incinerator Standards. Incinerator Institute
of America. New York November 1968.
64. Stabenow, G. Performance and Design Data for
Large European Refuse Incinerators with Heat
Recovery. In: Proceedings of 1968 National
Incinerator Conference. New York, American
Society of Mechanical Engineers, 1968. p.
278-286.
65. Ebernhardt, H. European Practice in Refuse and
Sewage Sludge Disposal by Incineration. In:
Proceedings of 1966 National Incinerator Con-
ference. New York, American Society of Me-
chanical Engineers, 1966. p. 124.
66. Rogers, C. A. An Appraisal of Refuse Incinera-
tion in Western Europe. In: Proceedings of 1966
National Incinerator Conference. New York,
American Society of Mechanical Engineers,
1966. p. 114-123.
67. Stabenow. G. Survey of European Experience
with High Pressure Boiler Operation Burning
Wastes and Fuel. In: Proceedings of 1966
National Incinerator Conference. New York,
American Society of Mechanical Engineers,
1966. p. 144-160.
68. Rousseau, H. The Large Plants for Incineration
of Domestic Refuse in the Paris Metropolitan
Area. In: Proceedings of 1968 National Incinera-
tor Conference. New York, American Society of
Mechanical Engineers, 1968. p. 225-231.
69. Moore, H. C. and F. X. Reardon. A Salvage Fuel
Boiler Plant for Maximum Steam Production. In:
Proceedings of 1966 National Incinerator Con-
ference. New York, American Society of
Mechanical Engineers, 1966. p. 252-258.
70. Control Techniques for Sulfur Oxide Air Pollut-
ants. National Air Pollution Control Administra-
tion. Washington, D. C. January 1969. No.
AP-52. p. 91-93.
71. Private Communication with H. L. Hickman.
Bureau of Solid Wastes Management. Rockville,
Md. November 1, 1968.
72. Control Techniques for Particulate Air Pollut-
ants. National Air Pollution Control Administra-
tion. Publication No. AP-51. Washington, D.C.
January 1969. 215 p.
-------
73. Partee, F. Air Pollution in the Coffee Roasting 74. Loquercio, P. A. and W. J. Stanley. Air Pollution
Industry. National Air PoUution Control Admin- Potential for Coffee Roasting. Air Eng. 9:22-29,
istration. Cincinnati, Ohio. PHS Publication No. November 1967.
999-AP-9. September 1964. 15 p.
4-49
-------
5. EMISSION FACTORS
For an accurate air pollution survey,
whether for a single source or for a metro-
politan area, pollutant emissions must be
identified by type and quantity.
Ideally, in order to determine emission
rates, a stack analysis of all sources of possible
emission would be necessary; but this is
impossible, of course, when an air pollution
survey must cover a large area, which could
contain several thousand sources. Emissions
from sources that have not been measured
and analyzed must, therefore, be estimated.
Estimates are determined by the use of emis-
sion factors, which are pollutant emission
rates based on stack-sampling data, material
balances, and engineering appraisals of the
same type of sources.
Because emission factors may at times be
based on limited or variable data, emission
factors should be used with caution unless the
data upon which the factor is based have been
studied or reviewed.
Table 5-1 is a compilation of available emis-
sion factors for hydrocarbons from various
types of sources. These emissions rates are for
uncontrolled sources unless otherwise noted.
Except where noted, emission factors were
compiled from a Public Health Service publi-
cation.1 For some cases in which a range of
emission factors is given, the range reflects the
figures given by different sources.
Table 5-1. EMISSION FACTORS FOR HYDROCARBONS
Source
Fuel combustion-stationary sources
Coal combustion unit
<10 x 106 Btu/hr capacity
10 to 100 x 106 Btu/hr capacity
Greater than 100 x 10° Btu/hr
capacity
Fuel Oil
<10 x 1Q6 Btu/hr capacity
10 to 100 x 106 Btu/hr capacity
Greater than 100 x 1Q6 Btu/hr
capacity
Solid waste disposal
Open burning on site of leaves, brush,
paper, etc.
Open burning dump
Municipal incinerator
Multiple-chamber incinerator
Single-chamber incinerator
Flue-fed incinerator
Domestic incinerator
No control
Afterburner
Hydrocarbon emissions,
Ib/unit given
10
1
0.2
3
2
0.8
12
30
0.3
0.5
0.8
2
2
1
Unit
ton of coal
ton of coal
ton of coal
1 ,000 gal of oil
1 ,000 gal of oil
1 ,000 gal of oil3
ton of waste
ton of waste
ton of waste
ton of waste
ton of waste
ton of waste
ton of waste
ton of waste
5-1
-------
Table 5-1 (continued). EMISSION FACTORS FOR HYDROCARBONS
Source
Hydrocarbon emissions,
Ib/unit given
Unit
Process industries
Phthalic anhydride plant
Oxidation of napthalene vapors
with excess air over catalyst
Petroleum refinery (as total
hydrocarbons)
Boilers and process heaters
Fluid catalytic unit
Moving-bed catalytic cracking
unit
Compressor internal combustion engines
Slowdown system
With control
Without control
Process drains
With control
Without control
Vacuum jets
With control
Without control
Cooling towers
Pipeline valves and flanges
Vessel relief valves
Pump seals
Compressor seals
Air blowing, blend changing, and
sampling
Storage
V.P.M.5 psia-fixed roof
V.P.>1.5 psia-floating roof
V.P.<1.5 psia-fixed roofb
Commercial operations
Dry cleaning
Chlor-hydrocarbons
Hydrocarbon vapors
Gasoline handling (evaporation)
Filling tank vehicles
Splash filling
Submerge filling
Filling service station tanks
Splash filling
Submerge filling
Filling automobile tanks
32
140
220
87
1.2
5
300
210
Negligible
130
28
11
17
5
10
47
4.8
1.6
1.7
2.2
8.2
4.9
11.5
7.3
11.6
ton of product
l,000bbloil
1,000 bbl fresh feed
1,000 bbl fresh feed
1,000 ft3 fuel gas
1,000 bbl refinery capacity
1,000 bbl refinery capacity
1,000 bbl waste water
1,000 bbl waste water
1,000 bbl vacuum distillation
capacity
1,000 bbl vacuum distillation
capacity
1Q6 gal cooling water capacity
1,000 bbl refinery capacity
1,000 bbl refinery capacity
1,000 bbl refinery capacity
1,000 bbl refinery capacity
1,000 bbl refinery capacity
1,000 bbl refinery capacity
1,000 bbl storage capacity
1,000 bbl storage capacity
per capita per year
per capita per year
1,000 gal throughput
1,000 gal throughput
1,000 gal throughput
1,000 gal throughput
1,000 gal throughput
aFrom reference 2.
bprom reference 3.
5-2
-------
Examples of how emission factors are used are given below:
1. Coal combustion:
Given: Power plant burns 100,000 tons per year of coal in a steam
generator of 450 x 106 Btu/hr capacity.
Find: Annual hydrocarbon emissions.
(100,000 tons/yr.) (0.2 -~) = 20,000 Ib of HC/yr
2. Petroleum refinery, fluid catalytic cracking unit:
Given: Fluid catalytic cracking unit with 10,000 barrels per day of
fresh feed; operates 350 days per year and has no CO boiler.
Find: Annual hydrocarbon emissions.
(10,000 barrels/day) () (350 day/year)
- 770,000 Ib of HC/year.
5.1 REFERENCES FOR SECTION 5 2. Smith, W. S., Atmospheric Emissions from Fuel
Oil Combustion, U.S. DHEW. Public Health
Service Publication No. 999-AP-2. Cincinnati,
Ohio. 1962.
1. Duprey, R. L. Compilation of Air Pollutant 3. Atmospheric Emissions from Petroleum Refin-
Emission Factors. U.S. DHEW. PHS. National eries. U.S. DHEW. PHS. Division of Air Pollu-
Center for Air Pollution Control. Durham, N. C. tion. Washington, D. C. PHS Publication Number
PHS Publication Number 999-AP-42. 1968. 67 p. 763. 1960. 56 p.
5-3
-------
6. ECONOMICS
6.1 INTRODUCTION
Economic considerations in air pollution
control include: (1) definition of alternatives,
(2) identification of costs, (3) cost curves by
equipment types, (4) value of recovered
materials, (5) selection of control systems,
and (6) assessment of economic impact. Each
of these if discussed below.
6.2 DEFINITION OF ALTERNATIVES
The process of selecting a control system
should be begun by identifying the total con-
trol needs of a plant. Usually more than one
problem exists, and attacking pollution prob-
lems together is more economical than trying
to handle each one separately. The advantages
and disadvantages of the substitution of fuels
or raw materials, and the modification or even
replacement of the processes can best be
assessed with the total needs in view, since
these methods tend to reduce or eliminate
more than one problem. Such methods also
tend to have an effect on solid waste disposal
and water pollution problems. If process alter-
ations or substitutions are not feasible, then
effluent control equipment is necessary. In
most cases, the problems can be remedied in
several ways. The economic analysis of the
different ways is an approach to the selection
of one of them for a given problem. Other
considerations are the effects that the emis-
sions may have on the company's relations
with the public and the growth potential for
the plant or process.
An important factor in making the choice
among control equipment alternatives is the
degree of reduction of emissions required to
meet emission standards. The degree of emis-
sion reduction or collection efficiency re-
quired depends upon the reduction required
before the level of emission falls below the
level permitted. The usual ranges of collection
efficiency for various types of control equip-
ment are discussed in Section 3.
Factors to be considered next are the
process stream characteristics: flow rate,
temperature, moisture content, explosiveness,
particle content, odor, corrosiveness, and igni-
tion point. For consideration of afterburners,
the quantity of auxiliary fuel must be deter-
mined. The temperature modifications (heat
transfer) necessary if adsorption is to be
applied must be defined. The conditions for
absorption must be determined. Power
requirements for pumps, compressors, or
blowers must be estimated. Space required for
the control system is often an important con-
sideration.
Plant facilities should be planned to include
equipment for waste treatment, product
recovery, and heat recovery.
Each alternative that meets all require-
ments can then be evaluated in terms of cost.
6.3 IDENTIFICATION OF COSTS
Cost estimates, useful in comparing alterna-
tive control systems, are best developed using
techniques available for preliminary capital
cost estimating. An excellent source of such a
method, together with equipment cost rela-
tionships, is the "Capital Cost Estimating"
procedure, published in Chemical Engineering
on March 24, 1969.1
The definable control costs are those that
are directly associated with the installation
and operation of control systems. These
expenditures have a breakdown for account-
ing purposes as follows:
1. Capital investment
Engineering studies, design costs, land,
structural modification, construction over-
head, dismantlement, rearrangement, lost
production, control hardware, auxiliary
equipment, installation, and startup.
6-1
-------
2. Maintenance and operation
Utilities, labor, supplies and materials,
treatment and disposal of collected mate-
rial, supervision, plant overhead, and
employee benefits.
3. Capital charges
Taxes, insurance, interest, and deprecia-
tion.
Some of these expenditures vary from
place to place and are therefore not discussed
further. Typical costs are engineering studies,
land acquisition, structural modifications, and
operating supply inventory. The others are
discussed as a group.
6.3.1 Capital Investment
The "installed costs," often quoted by
manufacturers on the basis of their engineer-
ing studies, include control hardware, auxil-
iary equipment, and installation costs. These
costs vary with the rate of exhaust to be
treated and with the collection efficiency of
the control device. Installed costs include a
reasonable increment for erection, insulation
material, transportation of equipment, site
preparation, clarifiers and liquid treatment
systems, and auxiliary items such as fans,
ductwork, motors, and control instrumen-
tation.
According to a recent survey conducted by
the American Institute of Plant Engineers,
installation added an average of 49.7 percent
to the cost of control equipment.2 The lowest
average installation cost, 16 percent of equip-
ment price, was in the aerospace industry.
The highest, 81 percent, was in the chemical
industry.
6.3.2 Maintenance and Operation
Maintenance cost is the expenditure
required to sustain the operation of control
devices at their designed efficiency with a
scheduled maintenance program and neces-
sary replacement parts. The costs of operation
and maintenance depend upon the quality
and suitability of the control equipment, the
user's understanding of its operation, and his
vigilance in maintaining it. Maintenance labor
takes an average of 16 percent of a plant's
6-2
control budget, and spare parts and materials
account for 10 percent.2
Annual operating cost is the expense of
operating a control device at its designed
collection efficiency. This cost depends upon
the gas volume cleaned, the pressure drop
across the system, the operating time, the elec-
tricity consumed, the mechanical efficiency of
the fan, the scrubbing liquor consumed, and
axuliary fuel used. About 43 percent of a
pollution control operating budget is spent
for power, fuel, and water; collected waste
disposal accounts for 31 percent.2
6.3.3 Annualized Costs
Annualized capital costs are estimated by
depreciating the capital investment (total
installed cost) over the expected life of the
control equipment, and adding the capital
charges (taxes, interest, and insurance).
Adding the recurring maintenance and opera-
tion costs to this figure gives the total annu-
alized cost of control. Operation costs include
disposal of collected materials, if this opera-
tion incurs added costs. In some cases these
materials will have value. The control system
sometimes adds value to the primary products
by improving their quality.
Certain simplifying assumptions allow the
annualized cost to be estimated, if more
specific information pertinent to a given case
is not available.3 These assumptions are as
follows:
1. Purchase and installation costs are
depreciated over 15 years, a period
assumed to be a reasonable economic
life for control devices.
2. The straight-line method of deprecia-
tion (6-2/3 percent per year) is the
easiest to use in cost formulas since it
has the simplicity of a constant annual
writeoff.
3. Other capital costs—interest, property
taxes, insurance, and miscellaneous-
are assumed to be equal to the
amount of depreciation, 6-2/3 percent
of the initial capital cost of the con-
trol equipment installed. Thus depre-
ciation plus these other annual charges
-------
amount to 13-1/3 percent of the
initial capital cost of the equipment.
4. Electric power costs reflect electricity
used by all systems directly associated
with the control equipment, and are
computed on the marginal rate classes
on a constant usage basis at a specified
gas volume.
5. The user of control equipment is
assumed to establish a scheduled pre-
ventive maintenance program de-
signed to maintain equipment at its
optimum collection efficiency.
Unscheduled maintenance, such as
replacement of defective parts, is
undertaken as required.
Some business firms use an interest rate to
compute capital costs as in item 3 above only
when money is actually borrowed. When
capital is supplied from company assets, the
"cost of capital" is the before-tax earnings,
which could be obtained by investing the
capital in some other opportunity.4 This is
frequently called the "opportunity cost of
capital" and varies widely by industries and
individual firms. It is usually higher than the
cost of borrowed capital.
6.4 COST CURVES BY EQUIPMENT
TYPES
For the convenience of those who may use
the cost information described in this section,
a series of control equipment cost curves are
provided (Figures 6-1 through 6-4). These
curves represent costs in a normal situation. If
the installation requires special measures in
site preparation, supporting structures, utility
installations, or if other unusual costs are
incurred, the total cost of the control installa-
tion can be substantially higher than indicated
by these curves.
6.4.1 Afterburners
For control of particulates, puchase costs
have been correlated with afterburner capac-
ity using data from the literature, from
personal experiences, and from questioning
users, installers, and suppliers of pollution
control equipment.3 Assuming no basic
change in costs for afterburners to control
organic liquids and vapors, the "purchase
cost" curve in Figure 6-1 may be used to esti-
mate equipment costs from the volume-flow
rate of the gas to be treated. The curve may
be updated by means of the Chemical Engi-
neering Plant Cost Index. Costs of heat
exchangers do not appear in the curve and are
therefore an extra cost item if used.
CO
o
1/5
O
O
40
30
20
10
_ l^ I I
3:
u
o:
CATALYTIC
AFTERBURNER
DIRECT FLAME-
?ife- I I I I I I I I I
1.5 2 3 4 5 6 8 10 20 30
GAS VOLUME THROUGH COLLECTOR, 103 X acfm
Figure 6-1. Purchase cost of afterburners,
1968.
Given the equipment-cost estimate, the
other cost components can be estimated by
suitable relation thereto. Depending upon
local conditions, installation costs range from
10 to 50 percent of the equipment costs, and,
rarely, as high as 100 percent. Annual mainte-
nance costs run approximately 6ft per cubic
foot per minute (cfm) and 20^ per cfm for
catalytic afterburners.
6.4.2 Activated-Carbon Adsorbers
Adsorption systems have been installed, in
many cases, to recover a valuable component
economically. Economic return depends on
the amount of material that can be recovered.
Where organic vapors exist at very low con-
centrations, the value of the recovered
material may be sufficient to cover operating
costs only if the recovery unit is relatively
large. The value of recovered material weighed
against investment and operating costs deter-
mines the least expensive method of removing
6-3
-------
organic vapors whether the system pays for
itself or not.
Figure 6-2 shows the installed-cost esti-
mates of adsorbers versus the flow rate of the
stream to be treated. Based on the results of
pilot plant experiments by Elliot5 et al., in
which vapors from protective coating opera-
tions were treated, these costs include super-
heater, condenser, decanter, blower, blower
motor, cooling tower, water pump, filters,
filter housing, initial carbon charge, carbon
vessel and screens, and ducts. The installation
costs were set equal to the total cost of all
equipment; therefore, the installed costs
shown are twice the equipment costs.
100,000 rr
1,000 10,000 100,000
EXHAUST GAS RATE AT 60 ° F, ft3/min
Figure 6-2. Adsorption system installed
costs, 1969 basis.
Installed cost estimates are $6.80 to $8.00
per cfm for a 1000-cfm system. For
50,000-cfm systems, the cost ranges from
$1.54 to $1.70 per cfm.5 The estimates for
the higher ranges are based on extrapolation
of pilot plant data. Since no units of these
sizes have been built, the projections are con-
jectural.
Operating cost estimates have been re-
ported by Mantell6 and by Barnebey and
Davis.7 According to Mantell, the recovery
expense for typical activated-carbon systems,
operating with a solvent vapor concentration
of 30 to 50 percent of the lower explosive
6-4
limit, may be less than 0.2e! per pound of sol-
vent recovered and seldom more than 10 per
pound, based on the 1951 economy.
Barnebey and Davis report operating costs up
to 40 a gallon without distillation of the re-
covered product (1959). Neither author in-
cluded maintenance expense in arriving at
operating costs.
6.4.3 Absorption Equipment
The cost of absorption equipment can only
be estimated by an engineering study of each
particular problem, since, as has been shown,
the nature of the component to be absorbed
determines the materials of construction and
the kind of packing.8 It is recommended that
each case be referred to professional engineers
and vendors of control equipment for actual
cost quotations.
For a first estimate of the primary costs of
a packed tower, however, Figure 6-3 may be
used together with an estimate of the tower
height required, as discussed in Section 3.4.5.
This figure shows the installed cost per foot
of height of packed tower versus the flow rate
of gas to be treated.
10 SO 100 5001,0005,00010,000
EXHAUST GAS RATE AT 120°F, ft3/min
Figure 6-3. Packed tower costs, with
Raschig rings as packing, 1969 basis.9
Costs are shown for carbon steel and for stain-
less steel. Raschig rings were assumed to be
-------
the packing material. For these, gas flow rates
can range from 50 to 150 cubic feet per
minute per square foot (air at 80°F). These
limits are shown in the figure.
6.4.4 Condensers
The basic costs for both contact-type and
surface condensers (shell and tube) are shown
in Figure 6-4. The data for these curves were
obtained from the reference given on each
curve. The cost of surface condensers is based
on the critical factor in sizing these units,
namely, the heat transfer area. The cost of
contact-type condensers is based on the
average gas volume through the unit. Both
types of condensers are available as package
units and thus require a minimum of field
labor for installation.
Operating costs for condensers are not ex-
cessive. Pressure drop of the vapor passing
through these units is on the order of 1 inch
of water. Costs of water consumed, pumping,
disposal, and, in some cases, operation of a
cooling tower must be included in the annual
operating charge.
6.5 VALUE OF RECOVERED MATERIALS
Numerous industrial plants throughout the
country are proving that the pollution prob-
lem can be solved and that the recovered
materials are worth more than their recovery
costs. Whether the recovered materials will
pay for the cost of control depends largely
upon the size of the operation and the value
of the particular materials.
Pollution abatement systems can result in
recovery of raw materials and energy or the
production of saleable by-products. The value
of these items should be utilized in an eco-
nomic analysis by estimating their dollar
100
50
10
CO
O
S 10
(J
X
u
SHELL AND TUBE CONDENSER AREA, ft2
100 1,000
10,000
10 100
AVERAGE GAS VOLUME THROUGH CONDENSER, acfm
1.000
Figure 6-4. Purchase costs of condensers.1'3'10
6-5
-------
values and applying the values as credits to
the annualized cost of the systems under
study. In some cases the control system in-
creases the value of the primary products by
improving their quality.
6.6 References For Section 6
1. Guthrie, K. M. Capital Cost Estimating. Chem.
Eng. 7<5(6):122, March 24, 1969.
2. AIPE Survey of Air Pollution Control Costs.
Modern Mfg. 126:186-188, June 1968.
3. Control Techniques for Particulate Air Pollut-
ants. U.S. DHEW. PHS. CPEHS. National Air
Pollution Control Administration. Washington,
D.C. Publication No. AP-51. January 1969. 215
P-
4. Barish, N. N. Economic Analysis. New York,
McGraw-Hill Book Co., 1962. p. 225-226.
5. Elliott, J. H., N. Kayne, and M. F. LeDuc.
Experimental Program for the Control of Organic
Emissions from Protective Coating Operations.
Air Pollution Control District. Co. Los Angeles,
Calif. Final Report. June 1962. p. 3-6.
6. Mantell, C. L. Adsorption, 2d ed., New York,
McGraw-Hill Book Co., 1951. 634 p.
1. Barnebey, H. L. and W. L. Davis. Costs of Sol-
vent Recovery Systems. Chem. Eng. 65(26): 54,
December 29, 1958.
8. Spencer, E. F. et al. An Evaluation of Methods
for Controlling Organic Emissions from Protec-
tive Coating and Spraying Operations. Air Pollu-
tion Control District. Los Angeles, Calif. Report
No. 2. July 1, 1958.
9. Teller, A. J. Absorption with Chemical Reaction.
Chem. Eng. 67(14):! 11-124, July 11, 1960.
10. Teller, A. J., S. A. Miller, and E. G. Scheibel.
Liquid-Gas Systems. In: Chemical Engineer's
Handbook, Perry, J. H. (ed.) 4th ed., New York,
McGraw-Hill Book Co., 1963. p. 18/1-18/91.
6-6
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7. CURRENT RESEARCH
7.1 RESEARCH PROJECTS APPLICABLE
TO HYDROCARBONS AND
ORGANICS
A summary of 800 air pollution research
projects active during Fiscal Year 1967 is
given in reference 1. All projects that were
applicable to hydrocarbons and organics from
stationary sources are listed in Section 7.3.
The projects are listed in alphabetical order
by the reference 2 code number and are
categorized according to various subject areas.
The control equipment and techniques sec-
tion is divided into various subheadings such
as absorption, adsorption, incineration, scrub-
bing, halogenation, catalysis, and pyrolysis.
The increase in research on air pollution
can be seen by comparing the approximately
800 research projects active during Fiscal
Year 1967 with the 501 projects active during
Calendar Year 1966. A summary of the 1966
air pollution research can be found in refer-
ence 3. This report shows that 22 percent of
the total funding was applied to control de-
vices or methods, 13 percent was applied to
source and source emission studies, and 16
percent was applied to health effects.
7.2 RESEARCH ON CONTROL
EQUIPMENT AND TECHNIQUES
There is a continuing effort to improve
equipment for controlling hydrocarbons and
organics. In addition to research being spon-
sored by the industries that create air pollut-
ants, the companies that make the equipment
are continuously striving to improve their
product or are trying to develop new and
better control techniques.
One study sponsored by the National Air
Pollution Control Administration during
1967-1968 was a $212,230 contract to Pope,
Evans, and Robbins to study fluidized-bed
combustion.4
One major part of industrial air pollution
results from exhausting large volumes of air
that are contaminated with organic vapors at
concentrations too small to recover economi-
cally. A process called the Zorbcin Process is
said to purify the air to the extent that it can
be recycled back into the plant air. This could
give the added benefit of reducing large heat-
ing and air-conditioning loads in process
plants that require frequent air changes.
The Zorbcin Process consists of forcing
plant exhaust air through one or more acti-
vated-carbon beds to remove the organic con-
taminant. The purified air is either discharged
to the atmosphere or returned to the plant
area. When the carbon bed becomes saturated
with organics, it is removed from the adsorp-
tion cycle and regenerated by circulating hot
air through the bed. Regenerating air flow is
appreciably lower than contaminated air flow
to each adsorber. A slip stream from the
regenerating air is sent to an air incinerator or
a catalytic combustion chamber where the
stripped organic vapor is burned. The slip
stream is less than one-tenth of the contami-
nated air flow. A small amount of natural gas
is burned in the incinerator to insure com-
plete combustion of the organics and to
supply any additional heat required for car-
bon regeneration. Direct mixing or heat
exchange transfer this heat to the regenerating
air.
At the end of the regenerating cycle, the
remaining regenerating gas is purged and
exhausted either to the atmosphere or into
the contaminated air stream. Since the regen-
erating air and exhaust from the incinerator
are ultimately cleaned by passing through an
activated adsorber, complete combustion in
the incinerator is not required to guarantee
high-purity air leaving the system.
7-1
-------
The system is adaptable to moving-bed or
fixed-bed adsorption systems. Also since the
vapors are held above their dew point, no
corrosive condensate will be involved. Thus
inexpensive construction materials can be
used.
The developers of the Zorbcin Process state
that some development work is still needed
before an optimum commercial unit can be
delivered. Desorption characteristics data for
various organic vapors at different concen-
trations and regenerating air temperatures are
lacking.
A new platinum catalyst has been designed
especially for air pollution problems.2 This
catalyst was originally developed for nitric
acid tail-gas decolorization, but has proved
effective for the elimination of hydrocarbon
and organic vapor contaminants.
The new family of ceramic catalysts are in
the form of a honeycomblike structure. The
advantages of these honeycomb catalysts are
stated to be:
1. A much lower pressure drop (for a gas
flow of 10 scfm per square inch of
catalyst bed, the pressure drop through
the honeycomb was 1 inch of water
per inch of bed depth and compared
with 24 inches of water through a
standard pellet bed of 1 /8-inch pellets).
2. A more uniform gas distribution.
3. A greater structural strength.
4. No attrition or loss of fines.
5. No channeling or hot spots.
When tested on various hydrocarbons and
organics, the ceramic catalysts were found to
be effective for completely oxidizing N-hep-
tane and other solvents such as xylene,
methyl ethyl ketone, acetone, and alcohols.
In absorption research, a new method of
increasing interfacial area for gas-liquid con-
tacting in cocurrent flow employs screen
packings.5 Interfacial area was found to be
increased twofold to fourfold by the presence
of a screen packing. Liquid-phase mass trans-
fer coefficient was found to be virtually inde-
pendent of gas flow, but dependent on liquid
flow rate.
7.3 CURRENT RESEARCH PROJECTS
This section is a summary of current air
pollution research projects that apply to
hydrocarbons and other organics from station-
ary sources. This following list, compiled
from reference 1, includes both foreign and
domestic projects, and the reference codes
given in alphabetical order were taken directly
from it. The first six letters of the code are
the first six letters of the last name of the
principal investigator. The two digits in the
middle of the code indicate the organization
supporting the research and may be obtained
from reference 1. The projects were categor-
ized by subject and include all projects active
or begun during the Fiscal Year 1968. If
information on the location and address of
the organization conducting the research is
desired, the reader is referred to reference 1.
Reference Code
Battig -50-SLA
Crietz -09-CP
Grumer-11-FCC
Grumer-13-FCC
Hangeb-11-CER
Long-10-RHD
Newhal-10-CPA
Parris-18-APG
Powers-17-APE
Powers-17-APE
Robiso-11-CCA
Subject
Combustion
Safe Limits of Air Pollu-
tion From Products of
Fuel Combustion
Combustion Products
Flame Characteristics
Causing Air Pollution
Flame Characteristics
Causing Air Pollution
Combustion Emission
Reduction
Reduction of Hydrocar-
bons During Incomplete
Combustion
Combustion Process An-
alysis
Air Pollution-Generating
Stations
Aerodynamic Properties
of Engine Exhaust
Plumes
The Aerodynamic Prop-
erties of Engine Exhaust
Plumes
Characterization and Con-
trol of Air Pollutants
7-2
-------
Starkm-10-CGC
Tebben-10-ABC
Unknow-11-AEO
Engel -96-CGA
Low-10-FAC
Moore -10-SAP
Saffer -72-DAC
Shulma-10-KAM
Zwiebe-10-MEA
Satter-10-HCA
Cote-11-GGP
Dorsey -11-MIC
Essenh-10-IPE
Gitsen -53-IOS
Kaiser -10-CIM
Kaiser-10-SIB
Sables-11-GGP
Seifer-10-IWT
From a Fluidized Bed
Combustion Unit
Combustion Gas Compo-
sition
Aromatic By-Products of
Combustion
Atmospheric Emissions
from Oil-Fired Power
Plants Control Equip-
ment and Techniques
Cycled Gas Absorption
Fundamentals of Air
Cleaning by Sorption
Processes
Study of Air Pollutants
by Absorption Spectro-
scopy
Development of Activat-
ed Carbon for Air Condi-
tioners
Kinetics of Adsorption
by Molecular Sieves
Multicomponent Equilib-
rium Adsorption - Air
Pollution
Hetero-Homogeneous
Catalysis of Air Pollut-
ants
Guide to Good Practice
for Flue Fed Incinerators
Municipal Incinerator
Control Development
Incineration Processes
and Emissions
Incineration of Organic
Sludge
Continuous Incineration
of Municipal Refuse
Smokeless Incineration
of Bulky Refuse
Guide to Good Practice
for Direct-Fed Multiple
Chamber Incinerators
Incinerator Water Treat-
ment System and Air Pol-
lution Scrubber Test
Smith-10-DII
Stengl-51-MI
Unknow-11-AEM
Waid -64-FIA
Kaiser -10-PMR
Chandl -05-CFF
Krotch-11-CSD
Margol-11-NPR
Neal-10-ACD
Ozolin-11-MIP
Ryan -09-FSP
Unknow-11-AEP
Demonstration of Im-
proved Incinerator Tech-
nology for a Small Com-
munity
Municipal Incinerator
Atmospheric Emission
from Municipal Incinera-
tors
Fume Incineration Appli-
cations
Pyrolisis of Municipal
Refuse Industrial proc-
esses and hydrocarbon
sources
The Contribution of For-
est Fires to Atmospheric
Pollution
Cooperative Study to De-
velop Control Devices
New Process Research
Atmospheric Carcinogens
in a Dense Petro-Chemi-
cal Area
Major Industry and Proc-
ess Emission Surveys
Field Studies Planned
Fires
Atmospheric Emissions
from Petroleum Refiner-
ies
7.4 REFERENCES FOR SECTION 7
1. Burd, P. A. Index to Air Pollution Research.
Pennsylvania State University, Center for Air
Environment Studies. State College, Pa. July
1968.
2. Platinum Catalysts and Systems for Air Pollution
Control, Part 1. Matthey Bishop, Inc. Malvern,
Pa. Bulletin No. THT-3000. 1969.
3. Guide to Research in Air Pollution: Projects Act-
ive in Calendar Year 1966. 6th ed. Division of
Air Pollution. Washington, D. C. PHS Publication
No. 981. December 1966. 82 p.
Bender, R. J. Pollution Control Makes Steady
4.
5.
Progress. Power. 772:88-89, October 1968.
Voyer, R. D. and A. I. Miller. Improved Gas-
liquid Contacting in Co-current Flow. Can. J.
Chem. Eng. 46(5): 335-341, October 1968.
7-3
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SUBJECT INDEX
Absorbents
selection criteria, 3-14
Absorbers
types of, 3-14-3-16
Absorption
applications of, 3-14
costs of equipment, 6-4-6-5
principles of operation, 3-16-3-19
selection of absorbents, 3-14
types of absorbers, 3-14-3-16
Adsorbents.
types of, 3-9
Adsorbers
cost of, 6-3
factors in the selection of, 3-12-3-13
Adsorption
applications of, 3-8—3-9
basic operating principles, 3-7-3-8
control of the process, 3-13-3-14
description of the process, 3-9
selection of an adsorber, 3-12—3-13
types of adsorbents, 3-9
Afterburners
basic operating principles, 3-2—3-5
criteria for selection of, 3-6—3-7
costs of, 6-3
Air-blowing of asphalt
in petroleum refining, 4-7—4-8
Catalytic afterburners, 3-3-3-5
Charcoal manufacture, 4-46
Chemical plants
collection of vented gases, 4-17
disposal of waste gases, 4-18
halogenation, 4-17-4-18
Chemical treating system, 4-8
Coal refuse fires, 4-44
Condensation
basic operating principles and equipment,
3-21
condenser design factors, 3-21-3-23
general discussion of, 3-19-3-21
Condensers
costs of, 6-5
design factors and applications, 3-21-3-23
operating principle, 3-21
types of, 3-21
Control systems (industrial processes)
chemical plants, 4-16—4-18
degreasing operations, 4-30—4-31
dry cleaning, 4-32—4-33
gasoline distribution systems, 4-8—4-13
lacquer manufacture, 4-18—4-21
metallurgical coke plants, 4-35—4-37
paint manufacture, 4-18—4-20
petroleum refineries, 4-1—4-8
rubber and plastic products manufacture,
4-25-4-26
sewage treatment, 4-37—4-38
stationary fuel combustion, 4-33—4-34
surface coating application, 4-27—4-28
varnish manufacture, 4-23—4-25
waste incineration and other burning,
4-42-4-45
Costs
annualized costs, 6-2—6-3
capital investments, 6-2
control system alternatives, 6-1
degreasing operations, 4-30—4-31
dry cleaning, 4-32—4-33
equipment cost curves, 6-3—6-5
gasoline distribution systems, 4-13
maintenance and operation costs, 6-2
sewage treatment, 4-37—4-38
stationary fuel combustion, 4-34
surface coating applications, 4-27—4-28
waste incineration, 4-44—4-45
1-1
-------
Cracking catalyst regeneration
in petroleum refineries, 4-6
D
Degreasing operations, 4-28—4-31
Direct flame afterburners, 3-2—3-3
Drug manufacture, 4-46
Dry cleaning, 4-31 -4-33
Economics
of pollution control, 6-1—6-6
Emission factors, 5-1—5-3
Emissions
charcoal manufacture, 4-46
chemical plants, 4-13-4-16
degreasing operations, 4-28—4-30
drug manufacture, 4-46
dry cleaning, 4-32
fermentation processes, 4-45
food processing, 4-45—4-46
gasoline distribution systems, 4-9—4-10
metallurgical coke plants, 4-35
paint, lacquer, and varnish manufacture,
4-18-4-22
petroleum refineries, 4-1—4-8
rubber and plastic products manufacture,
4-25-4-26
sewage treatment, 4-37
stationary fuel combustion, 4-33
surface coating applications, 4-27
waste incineration, 4-38—4-42
controls, 4-10-4-12
costs, 4-13
emissions, 4-9—4-10
overhead loading, 4-10—4-11
regulations and costs, 4-13
vapor disposal, 4-12
H
Hydrocarbon emission sources, 2-1—2-2
I
Incineration
basic operating principles and equipment,
3-1-3-6
selection of an afterburner, 3-6—3-7
waste disposal, 4-42—4-43
Lacquer manufacturing, 4-20—4-21
Los Angeles County
rule 66, 3-24-3-26
M
Metallurgical coke plants, 4-34—4-37
Fermentation processes, 4-45
Food processing, 4-45—4-46
Forest wildfires, 4-43—4-44
Fuel substitution
control of stationary fuel combustion, 4-34
Gasoline distribution systems
bottom loading, 4-11 —4-12
O
Oil-water effluent systems, 4-5—4-6
Operating principles and equipment
absorption, 3-16-3-19
adsorption, 3-7-3-8
catalytic after burners, 3-3—3-5
condensation, 3-21
direct flame afterburners, 3-2—3-3
process heaters and boilers, 3-6
stationary fuel combustion, 4-33—4-34
1-2
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Paint, lacquer, and varnish manufacture,
4-18-4-25
Paint manufacturing, 4-18-4-20
Petroleum refinery emission sources
air-blowing of asphalt, 4-7-4-8
boilers and process heaters, 4-8
chemical treating processes, 4-8
cracking catalyst regeneration, 4-6
flares, 4-5
general discussion, 4-1—4-3
loading facilities, 4-8
oil-water effluent systems, 4-5—4-6
pressure relief systems, 4-4
pumps, 4-6—4-7
storage, 4-3—4-4
vacuum jets, 4-8
valves, 4-8
waste gas disposal systems, 4-4—4-5
Photochemical reactions
discussion of, 2-1
Photochemical reactivity
of trichloroethylene, 3-26
regulation 3 of San Francisco Bay Area,
3-26
regulations based on reactivities, 3-24—3-26
rule 66 of Los Angeles County, 3-24-3-26
use of in controlling organic emissions,
3-23-3-26
Plastics manufacture (See Rubber and plastics
products manufacture)
Process heaters and boilers, 3-6
Pumps
petroleum refineries, 4-6—4-7
R
Recovery
of raw materials, 6-5—6-6
Regulation 3
San Francisco Bay Area, 3-26
Research, 7-1 -7-3
Rubber and plastic products manufacture,
4-25-4-26
Rule 66 of Los Angeles County
background of, 3-24-3-26
provisions of, 3-24
San Francisco Bay Area Control District
regulation 3, 3-26
Sewage treatment, 4-37—4-38
Sources
hydrocarbon emissions general discussion,
2-1-2-2
organic solvent emissions general dis-
cussion, 2-1—2-2
Stationary fuel combustion, 4-33—4-34
Storage emissions, 4-3—4-4
Surface coating operations, 4-26—4-28
costs, 4-27-4-28
Trichloro ethylene
photochemical reactivity of, 3-26
Vapor degreasing equipment, 4-30—4-31
Varnish manufacturing, 4-21—4-25
Vegetation burning, 4-44
W
Waste-gas disposal systems
flares, 4-5
pressure relief systems, 4-4
Waste incineration and other burning,
4-38-4-45
1-3
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