CONTROL TECHNIQUES
FOR CARBON MONOXIDE
EMISSIONS
FROM STATIONARY SOURCES
U.S. DEPARTMENT OF HEALTH, EDUCATION, AND WELFARE
Public Health Service
Environmental Health Service
-------
CONTROL TECHNIQUES
FOR
CARBON MONOXIDE 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
For sale by the Superintendent of Documents, U.S. Government Printing Office, Washington, B.C., 20402 - Price 70 cents
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National Air Pollution Control Administration Publication No. AP-65
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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 informa-
tion is a vital step in a program designed to
assist the States in taking responsible techno-
logical, social, and political action to protect
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
setting limitations on concentrations of at-
mospheric 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 pollutants.
Once these steps have been taken for any
region, and for any pollutant or combination
of pollutants, then the State or States re-
sponsible for the designated region are on
notice to develop ambient air quality stan-
dards applicable to the region for the pol-
lutants involved, 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 Adminis-
tration has established appropriate programs
to carry out the several Federal responsibil-
ities specified in the legislation.
Control Techniques for Carbon Monoxide
Emissions from Stationary Sources is one of a
series of documents to be produced under the
program established to carry out the responsi-
bility for developing and distributing control
technology information. Previously, on
February 11, 1969, control technique infor-
mation 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 indus-
try, universities, and all levels of government.
The committee, whose members are listed
-------
following this discussion, provided invaluable
advice in identifying the best possible meth-
ods for controlling the pollution sources,
assisted in determining the costs involved,
and gave major assistance in drafting this
document.
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
consultation 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
suggestions. In addition, certain consultants
to the National Air Pollution Control Admin-
istration also revised and assisted in preparing
portions of this document. These also are
listed 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
methods 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
Divison 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 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
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
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
Engineering
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
Manufacturing 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
Vll
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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, Pennsylvania
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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TABLE OF CONTENTS
Section Page
LIST OF FIGURES xi
LIST OF TABLES xii
SUMMARY xiii
1. INTRODUCTION 1-1
2. SOURCES OF CARBON MONOXIDE 2-1
2.1 REFERENCES FOR SECTION 2 2-2
3. STATIONARY COMBUSTION SOURCES 3-1
3.1 SOURCES 3-1
3.2 EMISSIONS 3-2
3.2.1 Quantity of Emissions 3—2
3.2.2 Formation of Carbon Monoxide 3—2
3.2.3 Effect of Design on Emissions 3—2
3.2.4 Emission Rates 3—3
3.3 CONTROL TECHNIQUES 3-3
3.3.1 Good Practice 3-3
3.3.2 Energy Source Substitution 3—7
3.4 REFERENCES FOR SECTION 3 3-8
4. INDUSTRIAL PROCESS SOURCES 4-1
4.1 IRON AND STEEL INDUSTRY 4-1
4.1.1 Iron Ore Benefication (Sinter Plants) 4-1
4.1.2 Blast Furnaces 4-2
4.1.2.1 Emissions 4—2
4.1.2.2 Control Techniques 4-3
4.1.3 Basic Oxygen Furnaces 4—3
4.1.3.1 Emissions 4—3
4.1.3.2 Control Techniques 4—3
4.1.4 Iron Cupolas 4—5
4.1.4.1 Emissions 4—6
4.1.4.2 Control Techniques 4—6
4.1.5 Electric Furnaces 4—7
4.1.5.1 Emissions 4—7
4.1.6 Coke Ovens 4_8
4.1.6.1 Emissions 4_9
4.1.6.2 Control Techniques 4_9
4.1.7 Cost of Controls 4_9
IX
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4.2 PETROLEUM REFINERIES 4-10
4.2.1 Catalytic Operations 4-10
4.2.1.1 Emissions 4-10
4.2.1.2 Control Techniques 4-11
4.2.2 Fluid Cokers 4-13
4.2.2.1 Emissions 4-13
4.2.2.2 Control Techniques 4-13
4.2.3 Cost of Controls 4-13
4.3 CHEMICAL INDUSTRY 4-14
4.3.1 Synthesis Gases 4-14
4.3.2 Methanol 4-15
4.3.3 Ammonia 4—15
4.3.4 Phosgene 4-16
4.3.5 Organic Acids 4-16
4.3.6 Aldehydes 4-17
4.3.7 Other Organic Compounds 4—17
4.3.8 Emissions 4—18
4.3.9 Control Techniques 4—18
4.3.10 Cost of Controls 4-21
4.4 CARBON BLACK MANUFACTURING PLANTS 4-21
4.4.1 Channel Black 4-21
4.4.1.1 Emissions 4—22
4.4.1.2 Control Techniques 4-23
4.4.2 Thermal Black 4_23
4.4.2.1 Emissions 4—23
4.4.2.2 Control Techniques 4-23
4.4.3 Furnace Black 4—23
4.4.3.1 Emissions 4-23
4.4.3.2 Control Techniques 4—24
4.5 PULP AND PAPER INDUSTRY 4_24
4.5.1 Kraft Pulp Mill Recovery Furnaces 4—24
4.5.1.1 Emissions 4—24
4.5.1.2 Control Techniques 4—24
4.5.2 Lime Kilns 4-24
4.5.2.1 Emissions 4—24
4.5.2.2 Control Techniques 4—24
4.5.3 Cost of Controls 4-25
4.6 MISCELLANEOUS INDUSTRIAL SOURCES 4-25
4.6.1 Electrometallurgical Furnaces 4—25
4.6.2 Silicon Carbide Furnaces 4—26
4.6.3 Calcium Carbide Furnaces 4—26
4.6.4 Elemental Phosphorus Furnaces 4—27
4.6.5 Aluminum Reduction Cells 4—27
4.7 REFERENCES FOR SECTION 4 4-28
5. WASTE INCINERATION AND OTHER BURNING 5-1
5.1 EMISSIONS 5-l
5.2 CONTROL TECHNIQUES 5-5
5.2.1 Waste Disposal 5~5
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5.2.2 Incineration 5—5
5.2.3 Forest Wildfires 5-6
5.2.4 Controlled Vegetation-Burning 5-6
5.2.5 Coal-Refuse Fires 5-6
5.2.6 Structural Fires 5-7
5.3 COST OF CONTROLS 5-7
5.4 REFERENCES FOR SECTION 5 5-7
6. CARBON MONOXIDE EMISSION FACTORS 6-1
6.1 REFERENCES FOR SECTION 6 6-3
SUBJECT INDEX 1-1
LIST OF FIGURES
4-1. Basic Oxygen Furnace With Closed Hood and Gas-Cleaning and Storage
System 4-4
4-2. Basic Oxygen Furnace With Open Hood and Gas-Cleaning System 4—4
4-3. Open-Hood System With Steam-Generating Hoods 4—5
4-4. Integral Afterburner With Inverted Cone Installed in Top Part of Cupola To Create
Turbulance To Ensure Complete Combustion 4—6
4-5. Diagram of Afterburner System Showing Flame Introduced at Most Favorable Loca-
tion to Ignite Cupola Gases 4—7
4-6. Diagram of Flame in Afterburner System That Is Neither Extinguished Nor
Affected by Cupola Charge 4—7
4-7. Water-Cooled, Carbon Monoxide Waste-Heat Boiler 4-11
4-8. Corner-Fired Burners of a Carbon Monoxide Waste-Heat Boiler: (left)
Elevation View Showing a Typical Set of Burners for One Corner; (right)
Plan View of Firebox Showing Location of the Four Sets of Burners 4—12
4-9. Slowdown and Relief Collection System 4—20
4-10. Typical Diagram for Carbon Black Manufacture 4—22
4-11. Electric Furnace for Ferroalloys Industry 4—26
4-12. Electric Furnace for Production of Silicon Carbide 4—26
4-13. Diagram of Electric Furnace for Production of Elemental Phosphorus 4—27
5-1. Domestic Gas-Fired Incinerator 5—1
5-2. Single-Chamber Incinerator 5—2
5-3. Cutaway of In-Line Multiple-Chamber Incinerator 5—2
5-4. Section of Flue-Fed Incinerator 5—3
5-5. Section of Chute-Fed Apartment Incinerator 5—3
5-6. Section of Pathological Incinerator 5—4
5-7. Section of Municipal Incinerator 5—4
XI
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LIST OF TABLES
Table Page
2—1. Summary of Estimated Carbon Monoxide Emissions in the United States During
1968 2-1
3—1. Estimated United States Fuel Consumption For Selected Stationary Combustion
Sources in 1966 3 — 1
3—2. Estimated United States Power Generation For Various Energy Sources 3—1
3—3. Bond Energies of Some Simple Chemical Substances 3—2
3—4. Carbon Monoxide Emissions From Suspension Coal-Fired Boiler Units 3—3
3—5. Carbon Monoxide Emissions From Grate-Fired Coal-Burning Units 3—3
3—6. Classification of Oil Burners According To Application and List of Possible Defects. 3—5
3—7. Estimated Carbon Monoxide Emission Rates From Fossil Fuels at Duty of 107
Btu/hr 3-7
4—1. Gaseous Emissions From Sintering Operations 4—1
4—2. Historical Statistics of Coke Industry in the United States 4—8
4—3. Catalytic Cracking Capacity in the United States 4—11
4—4. Synthesis Gas Components 4—15
4—5. Carbon Monoxide and Hydrogen Content In Some Industrial Gases 4—15
4-6. Cost of Flares 4-21
4—7. Electric Furnace Production of Ferroalloys in the United States, 1967 4—25
5—1. Estimated National Emissions in 1968 From Incineration and Other Burning 5—4
6—1. Carbon Monoxide Emission Factors 6—1
Xll
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SUMMARY
Carbon monoxide (CO) is a colorless, odor-
less, tasteless gas, about 97 percent as heavy
as air. It is a major pollutant, by quantity,
having a current annual emission rate within
the United States of about 100 million tons.
Carbon monoxide is formed when carbona-
ceous fuels are burned with insufficient oxy-
gen to form carbon dioxide (CO2). It is also
copiously formed from CO2 at high tempera-
tures under reducing conditions. It is the first
product in the oxidation of the carbon in a
fuel. Even if there is sufficient oxygen for
complete reaction to form CO2, the latter
may still break down to form CO, owing to
the dissociation brought about by high tem-
peratures. Dissociation of CO2 to CO for the
temperatures cited are listed in Table 1.
Table 1. DISSOCIATION OF CO, TO CO
Temperature, °F
1,340
2,060
2,780
2,960
3,140
3,495
Percentage dissociation
2 X 10"s
1.5X ID'2
5.5 X 10"1
1.0
1.8
5.0
Some CO can, therefore, form in high-
temperature furnaces, even from CO2 itself. If
the equilibrium, CO2 < > CO + O, is
"frozen" by rapid cooling, some of the CO
does not have time to recombine and persists.
Low cooling rates reduce CO emissions. Lean
fuel-air mixtures favor low CO concentra-
tions. CO emissions would be increased, how-
ever, by recycling cold flue gas to lean
mixtures.
SOURCES OF CARBON MONOXIDE
Estimated emissions of CO within the
United States during 1968 are given in Table 2.
Table 2. ESTIMATED CO EMISSIONS IN THE
UNITED STATES DURING 1968 (106 tons)
Source
Transportation
Fuel combustion in stationary sources
Solid waste burning
Industrial processes
Forest and structural fires
Prescribed agricultural and forest
burning
Coal refuse fires
Total
Emissions
63.8
1.8
7.8
9.7
5.0
10.7
1.2
100.0
Table 2 does not include estimates of emis-
sions from use of explosives and some rela-
tively small sources such as the electrochem-
ical and electrometallurgical industries.
By far the greatest source of CO emissions is
the automobile. Automobile emissions are
covered in detail in a companion document,
AP-66, Control Techniques for Carbon Mon-
oxide, Nitrogen Oxide, and Hydrocarbon
Emissions from Mobile Sources.
Major emissions include forest fires, struc-
tural fires, and burning banks of coal refuse.
Industrial sources include foundries, petro-
leum refineries, and kraft pulp mills. Burning
of solid waste produces more CO than all the
conventional stationary fuel combustion
sources. Tables 3 and 4 are summaries of the
methods employed for controlling CO emis-
sions.
xm
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Table 3. SUMMARY OF METHODS FOR CONTROLLING CARBON MONOXIDE EMISSIONS
FROM STATIONARY COMBUSTION SOURCES
Control method
Remarks
Change of fuel or energy source
Change to gas from oil and coal
Change to nuclear power or hydroelectric
generation
Replace industrial, commercial, and household
thermal requirements with central power
Combustion control
Air supply
Residence time
Temperature
Mixing
Flame contact
Change of waste disposal method
Sanitary landfill
Various treatments for coal-waste piles
Accepted emission factors for burning of coal, oil, and gas
show decreasing CO emissions for these three fuels, in the
order given. But CO emissions from boilers and furnaces are
so low a fraction of total CO emissions that fuel change is
not justified.
Use of nuclear power is expected to grow; hydroelectric
generation will grow slowly. Nuclear power involves genera-
tion of some CO due to the periodic test operation of stand-
by power-generating units employing conventional fuels.
Generation of electric power is increasing. CO emissions are
easier to control at a central power plant than at small in-
stallations and households. Efficiency is lower for indirect
use of fuel through electricity than for direct burning. Re-
duction in local CO concentrations may result in increased
oxides of nitrogen (NOX) emissions at distant power plants.
A well-adjusted gas-fired boiler may emit less than 1 ppm of
CO, but may emit more than 50,000 ppm if insufficient
combustion air is supplied. Insufficient air always causes CO
formation; too much air may do the same by flame quench.
Short residence times tend to cause more CO in exit gases.
Proper residence time allows the use of less excess air.
High temperature is desirable, but dissociation of C02 into
CO becomes noticeable at 2,800°F. Rapid cooling and low
oxygen concentration tend to hinder recombination of C02.
Flame temperatures above 3,000°F are conducive to forma-
tion of oxides of nitrogen (NOX).
Good mixing is very important for burning of CO; appliance
and burner design should facilitate mixing.
Contact of flame with cold surfaces tends to form CO by
quenching, i.e., it reduces residence time at effective oxida-
tion temperature.
Replaces open-burning and incineration.
These are not deliberately burned, but ignite by spontaneous
combustion or accident. See AP-52, Control Techniques for
Sulfur Oxide Air Pollutants.
xiv
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Table 4. SUMMARY OF METHODS FOR CONTROLLING CARBON MONOXIDE EMISSIONS
FROM STATIONARY PROCESS SOURCES
Source
Control method
Remarks
Iron and steel industry
Blast furnace
Grey iron cupola
Basic oxygen steel furnace
Sintering furnace
Coke oven
Petroleum industry
Petroleum catalytic cracking
unit
Petroleum fluid coker
Chemical industry
CO generated is burned as fuel
Flame afterburner
Burned inside hood and dis-
persed by stack
None
Proper design, scheduling,
operation, and maintenance
Burned as fuel in CO boiler
Burned as fuel in CO boiler
Most commonly burned
waste
as
Emissions can be produced by faulty equipment
and accidents.
Not all controlled.
Collection for use as fuel not common in
United States.
Controls are same as those to control particu-
lates and SO2. See AP-52, Control Techniques
for Sulfur Oxide Air Pollutants.
CO produced during regeneration of catalyst.
Burning as fuel usually requires supplementary
fuel for stability.
Gas produced in coker burning section of coking
unit is rich in CO.
Moderate amounts generated in chemical in-
dustry as a whole, but this actually occurs only
in specified segments of the industry. Emissions
are from gas purging, leaks, abnormal operations
such as startup, upsets and shutdown, or relief
of overpressure.
COSTS OF CONTROLS
Determining the costs involved in control of
CO emissions is seldom straightforward, and is
often impossible.
Enormous amounts of CO are generated in a
blast furnace, but this gas is cleaned and used
as fuel. Cleaning entails removing particulate
matter; and if costs were to be allocated to air
pollution control, it would be logical to
allocate them to particulate removal rather
than to CO removal. Particulates also consti-
tute the real air pollution problem in the
operation of the basic oxygen furnace. The
CO generated is usually burned, or it can be
collected for use as fuel. If the CO is collected
for fuel, the cost of the gasholder and
associated piping could be allocated to util-
ities rather than to CO air pollution control.
Total costs are, of course, not necessarily
recovered in the heating value of the CO
collected.
The chemical industry generates a moderate
amount of CO in reforming operations that
usually has to be removed by suitable pro-
cesses in order to make the desired product-
hydrogen, or a mixture of hydrogen and
nitrogen. If CO is burned in a waste-gas flare*
the costs of flare operation could be allocated
to CO control unless the flare is used to burn
various waste gases from other chemical pro-
cesses.
The economics of a CO boiler serving a
petroleum catalytic cracking unit are sepa-
rable from those of any equipment required to
clean the boiler feed gas. In this case, the
boiler handles only clean CO-rich gas, and
abates only CO emissions. Costs of such a
boiler and its auxiliaries should, however, be
based on engineering study and cost quota-
tions from CO boiler suppliers.
Cost estimates for CO control, when appli-
cable, may be made by the general methods
described in AP-51, Control Techniques for
Particulate Air Pollutants.
xv
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CONTROL TECHNIQUES
FOR CARBON MONOXIDE EMISSIONS
FROM STATIONARY SOURCES
1. INTRODUCTION
Pursuant to authority delegated to the
Commissioner of the National Air Pollution
Control Administration, Control Techniques
For Carbon Monoxide Emissions From Sta-
tionary Sources is issued in accordance with
Section 107c of the Clean Air Act, as
amended (42 U.S.C. 1857-18571).
This document has been prepared to sum-
marize current information on sources of
carbon monoxide (CO) emissions, methods of
control, and costs and cost-effectiveness of
controls.
Carbon monoxide is a chemical compound
of carbon and oxygen. A gas at all tempera-
tures above -218°F, CO has a density 96.5
percent of that of air, is quite stable up to
very high temperatures, is odorless, and is
toxic. Carbon monoxide is one of the products
of incomplete combustion of carbonaceous
fuels and is formed whenever carbon-bearing
materials burn, if the oxygen furnished is less
than that required to form carbon dioxide
(CO2). Carbon monoxide is also readily
formed from CO2 in the presence of hot
carbon-bearing materials.
Carbon monoxide in the atmosphere may
have adverse effects upon health, and reduc-
tion of emissions of this pollutant may be of
importance to an effective air pollution abate-
ment program. Carbon monoxide originates
from a variety of sources, and the available
control techniques vary in type, application,
effectiveness, and cost.
The control techniques described herein
represent a broad spectrum of information
from many engineering and other technical
fields. The devices, methods, and principles
have been developed and used over many
years, and much experience has been gained
in their application. They are recommended
as the techniques generally applicable to the
broad range of CO emission control problems.
Many agricultural, commercial, industrial,
and municipal processes and activities that
generate CO are described individually in this
document. Various techniques that can be
applied to control emissions of CO from these
sources are reviewed and compared, and
equipment costs are included, also.
Although exhaust from automobiles consti-
tutes by far the greatest source of CO in the
atmosphere, this emission category is not
discussed comprehensively in this document.
It is, however, treated extensively in a sepa-
rate document, AP—66, Control Techniques
For Carbon Monoxide, Nitrogen Oxide, and
Hydrocarbon Emissions From Mobile
Sources.
While some data are presented on quantities
of CO emitted to the atmosphere, the effects
of CO on health and welfare are considered in
a companion document AP—62, Air Quality
Criteria for Carbon Monoxide.
1-1
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2. SOURCES OF CARBON MONOXIDE
Carbon monoxide is one of the products
produced by the incomplete combustion of
carbonaceous material; it is formed, for in-
stance, when carbonaceous material is burned
in a reducing atmosphere, in which the
available oxygen is not sufficient to burn the
material completely to carbon dioxide. Be-
cause such conditions exist in the cylinders of
the gasoline internal-combustion engine, and
because of the large number of automobiles in
use, CO emissions from this source conspicu-
ously exceed those from any combination of
other sources.
Table 2—1 is a summary of estimated
annual emissions of CO within the United
States during 1968. No figures are available
for a few operations, such as certain metallur-
gical operations and the use of explosives.
Table 2-1 shows that the sum of the CO
emissions was approximately 100 million
tons.
Large amounts of CO are produced and
handled by industry; but, in most cases, this is
used as fuel or raw material, and emissions
result only from leaks or abnormal operation.
Based on data from Section 4.1, total produc-
tion of CO by pig-iron blast furnaces, for
instance, was estimated to be about 90
million tons in 1968—even more than that
generated by the gasoline internal-combustion
engine, but only a small fraction of this CO
escapes from the blast furnace operations.
Almost 60 percent of the CO emissions
summarized in Table 2— 1 is due to the motor
vehicle; it is also interesting to note the
relatively large contribution that still arises
from the use of wood as fuel. The small values
of CO emissions indicated for burning natural
gas must not convey the impression that
complete combustion necessarily takes place
when gas is burned; actually, copious quanti-
ties of CO can be formed if this fuel is burned
with too little air.
Most of the emissions given in Table 2—1
were estimated by the National Inventory of
Air Pollutant Emission Control Section of the
National Air Pollution Control Administra-
tion, using emission factors from reference 1
or as developed in this document. Derivation
of a few of the emissions is illustrated in some
of the sections of this document.
Table 2-1. SUMMARY OF ESTIMATED
CARBON MONOXIDE EMISSIONS2
IN THE UNITED STATES DURING 1968
(tons/year)
Source
Mobile fuel combustion
Motor vehicles
Gasoline
Diesel
Aircraft3
Railroad
Vessels
Non-highway users
Stationary fuel combustion
Coal
Fuel oil
Natural gas
Wood
Solid waste
Incineration
Open burning
Conical burners
Coal-refuse fires
Structural fires
Forest fires
Wild fires
Prescribed burning
Agricultural burning
Emissions
59,000,000
160,000
2,400,000
120,000
310,000
1,800,000
770,000
50,000
3,000
1,010,000
800,000
3,400,000
3,600,000
1,200,000
250,000
4,740,000
2,480,000
8,250,000
2-1
-------
Table 2-1 (continued). SUMMARY OF
ESTIMATED CARBON MONOXIDE
EMISSIONS2 IN THE UNITED STATES
DURING 1968
(tons/year)
Source
Industrial processes
Blast-furnace sinter plants
Gray-iron cupolas
Basic oxygen furnaces
Beehive coke ovens
Kraft recovery furnaces, lime kilns
Carbon black
Petroleum catalytic cracking units
Fluid coking burners
Methanol
Formaldehyde
Subtotal
Ammonia
Metallurgical electric furnaces
Zinc and lead reduction
Aluminum reduction
Calcium carbide furnaces
Silicon carbide furnaces
Phosphorus furnaces
Explosions (blasting, etc.)
Emissions
2,400,000
3,600,000
100,000
20,000
830,000
350,000
2,200,000
160,000
4,000
34,000
100,041,000
b
b
b
b
b
b
b
b
This includes emissions during cruising.
bAlthough these sources are thought to be emitters of
CO, no data are available and no emission factors-
have been developed.
2.1 REFERENCES FOR SECTION 2
1. Duprey, R. L. Compilation of Air Pollutant
Emission Factors. U.S. DHEW, PHS, CPEHS,
National Center for Air Pollution Control. Dur-
ham, N. C. PHS Publication 999-AP-42. 1968.
67 p.
2. National Air Pollution Control Administration,
Reference Book of Nationwide Emissions. U.S.
DHEW, PHS, CPEHS, NAPCA. Durham, N. C.
2-2
-------
3. STATIONARY COMBUSTION SOURCES
3.1 SOURCES
Stationary combustion sources include
steam-electric generating plants and industrial,
commercial, and domestic combustion units.
These sources burn large quantities of coal,
fuel oil, and natural gas, and lesser amounts of
other fuels such as coke oven gas or tar, coke,
refinery gas, blast furnace gas, wood, bagasse,
or other waste- or byproduct-type fuels.
Estimated fossil fuel consumption for various
stationary combustion sources is shown in
Table 3-1.
The nearly 1,000 steam-electric generating
plants in the United States4 burn coal, re-
sidual fuel oil, or natural gas. Projections of
United States power generation for various
energy sources are shown in Table 3—2.
The steam boiler is the most common
industrial stationary combustion device.
Other types of boilers or heaters used by
industry employ hot water, molten salt, or-
Table 3-2. ESTIMATED UNITED STATES POWER
GENERATION FOR VARIOUS
ENERGY SOURCES4
(109 kw-hr)
Energy source
Coal
Oil
Gas
Hydroelectric
Nuclear
Total
1968
683
104
305
222
12
1,326
1980
1,225
205
485
274
901
3,090
1990
1,630
220
620
316
3,066
5,852
ganic liquids, and mercury. Fired stills,
heaters, ovens, and furnaces are also used. The
fuels most commonly used in these devices
are: coal, natural gas, or petroleum-derived
fuel oils. Industrial sources burning other
fuels are often considered to be industrial
process sources or incineration sources; there
is, however, no fundamental difference be-
Table 3-1. ESTIMATED UNITED STATES FUEL CONSUMPTION FOR
SELECTED STATIONARY COMBUSTION SOURCES IN 1966
(1012 Btu)
Fuel
Coal, including3
anthracite and
lignitea
Fuel oilb
Natural gasf
Total
Type of use
Domestic and
commercial
610
4,440C
5,760
10,810
Industrial
2,600
l,840d
6,9608
11,400
Power
generation
6,400
'
910e
2,610
9,920
Total
9,610
7,190
15,330
32,130
aBased on reference 1 and heating value of
12,000 Btu/lb.
bfiased on reference 2 and heating values as
indicated.
^Heating value of 142,000 Btu/gal.
dHeating value of 150,000 Btu/gal; includes
military fuel.
eHeating value of 150,000 Btu/gal.
ffiased on reference 3 and heating value of
1,000 Btu/ft3.
SIncludes refinery and pipeline fuel.
3-1
-------
tween these and stationary combustion
sources.
There are more than 30 million domestic
and commercial space-heating plants in the
United States.5 These plants burn coal, na-
tural gas, or petroleum fuel oil. A few
space-heating plants burn liquefied petroleum
or natural gas products, and more than 2.5
million homes are heated by electrical energy.
Other minor domestic stationary combustion
sources include kitchen ranges, clothes driers,
and hot water heaters. Commercial heating
systems are commonly steam-type systems.
Hot water and warm air systems are also used.
3.2 EMISSIONS
3.2.1 Quantity of Emissions
Nationally, the quantity of CO emissions
from oil-fired and gas-fired stationary com-
bustion sources is estimated to be negligible in
comparison with the 100 million tons emitted
from all sources. Emissions from coal-fired
sources are estimated at less than 1 percent of
total United States CO emissions.
3.2.2 Formation of Carbon Monoxide
Carbon monoxide is formed as an inter-
mediate product of reactions between carbo-
naceous fuels and oxygen.6 When less than
the theoretical amount of oxygen required for
complete combustion is supplied, CO is a final
product of the reaction. Under these condi-
tions, CO concentrations may exceed 50,000
ppm.
Formation of the oxides of carbon is a
simple process only when pure carbon and
pure oxygen are involved. The burning of
carbonaceous fuels, in general, is a very
complicated process involving formation of
CO before CO2 is formed.6 If the tempera-
ture of combustion is high enough, dissocia-
tion of the CO2 begins:
Table 3-3. BOND ENERGIES OF SOME
SIMPLE CHEMICAL SUBSTANCES7
CO,
co + o
Actually, CO is a very stable substance at high
temperature, as indicated by Table 3—3.
In order for a chemical reaction to take place,
chemical bonds must be broken and formed.
Bond energies are a measure of the difficulty
in breaking a chemical bond. Table 3-3
Substance
Carbon monoxide
Carbon dioxide
Propane
Acetylene
Bond
C-0
0=C-0
C3H7-H
HC^CH
Bond energy,
Kcal/mol
256.7
128
98
230
indicates a higher bond energy for CO than
for acetylene, which is notorious for its
stability at electric arc temperatures; CO is
indeed known to be stable at very high
temperature. Conversely, propane is easily
cracked or decomposed at moderate tempera-
tures, and the bond energy is seen to be low.
The bond energy for CO2 is moderately low,
and experience shows that it is not difficult to
remove an atom of oxygen from CO2 by
dissociation to form CO. For these reasons
then, a second mechanism of CO formation is
high-temperature dissociation of CO2, or
hindering of the combination of CO and
oxygen by virtue of temperature. Thus, rais-
ing the temperature increases the concentra-
tion of CO in the thermodynamic sense.
The reaction rates increase with tempera-
ture. Increase of oxygen concentration tends
to decrease the CO concentration by afford-
ing a greater chance for collision of CO and
oxygen molecules (actually, hydroxyl radi-
cals) to form CO2.6
3.2.3 Effect of Design on Emissions
For minimum CO emissions, combustion
equipment is designed for rapid reaction rates
and long reaction time. Rapid reaction rates
are promoted by providing for intimate con-
tact between fuel and air, furnishing sufficient
air for combustion, increasing combustion
temperature by preheating the fuel and air,
limiting the amount of excess air, and mini-
mizing heat loss during oxidation of the fuel.
After complete oxidation of the fuel, slow
cooling of the combustion gases promotes
more complete oxidation of CO to CO2.
Some of the conditions favorable to complete
fuel combustion tend to promote formation
of nitrogen oxides. High flame temperatures
are the most effective of these conditions.
3-2
-------
For units firing powdered coal, the effect of
method of boiler-firing on CO emissions is
given in Table 3-4.
Table 3-4. CARBON MONOXIDE EMISSIONS
FROM SUSPENSION COAL-FIRED
BOILER UNITS8
(lb/106 Btu)
Type of firing
Vertical
Corner
Front wall
Spreader stoker
Horizontally opposed
CO emissions
0.017
0.011
0.005
0.029
0.044
Emissions from some grate-fired coal-burning
units are given in Table 3—5.
Table 3-5. CARBON MONOXIDE EMISSIONS
FROM GRATE-FIRED COAL-BURNING UNITS8
Type unit
Chain grate
Spreader stoker
Underfeed stoker
Underfeed stoker
Underfeed stoker
Hand-fired stoker
Unit size,
106 Btu/hr
147
59.2
4.4
3.0
0.066
0.115
CO emissions,
lb/106 Btu
0.51
<0.1
0.16
0.14
1.1
3.5
The data in Tables 3—4 and 3—5 indicate
that furnace design and firing method can
affect the quantity of CO emissions.
3.2.4 Emission Rates
Although emission factors are used for
estimating CO emissions from various kinds of
stationary combustion sources, the accuracy
of the numbers used is insufficient for other
than a qualitative comparison among various
fuels and equipment. It is not firmly estab-
lished that there are differences among CO
emissions from coal-, gas-, and oil-fired power
boilers. Coal-fired stoker or grate-type com-
mercial or industrial combustion equipment
probably emits more CO per unit of heat
input than equivalent oil- or gas-fired units; it
is firmly established that well-adjusted,
domestic coal-fired units emit more CO than
well-adjusted, equivalent-sized oil- or gas-fired
equipment.
When coal-, oil-, or gas-fired stationary
combustion equipment is operated with an
insufficient air supply, CO emission rates can
be several thousand times as great as emissions
from well-adjusted units. Under these condi-
tions, oil-fired and coal-fired units emit dense
smoke, but gas-fired equipment must be badly
out of adjustment to emit smoke.
3.3 CONTROL TECHNIQUES
The following techniques are known for
control of carbon monoxide emissions from
stationary combustion sources:
1. Good practice.
2. Energy conservation.
3. Energy source substitution.
4. Source relocation.
5. Source shutdown.
6. Gas cleaning.
3.3.1 Good Practice
Good practice is the most practical tech-
nique for reduction of CO emissions from
stationary combustion sources. Good practice
involves proper design, application, installa-
tion, operation, and maintenance of the com-
bustion equipment and auxiliary systems.
Guidelines for good practice are published
by the fuel industry, equipment manufac-
turers, engineering associations, and govern-
ment agencies. Stationary combustion units
should be operated within their design limits
and according to the recommendations of the
manufacturer or other authority on proper
operating practices. Combustion units and
components should be kept in good repair to
continue to meet design specifications. Sensi-
tive CO monitoring systems are helpful in
indicating the need for combustion system
repair. Other sources of information on good
practice are:
1. Air Pollution Control Association.
2. American Boiler Manufacturers Associ-
ation.
3. American Petroleum Institute.
4. American Society of Heating, Refriger-
ating, and Air-Conditioning Engineers.
5. American Society of Mechanical En-
gineers.
6. Edison Electrical Institute.
7. The Institute of Boiler and Radiator
Manufacturers.
3-3
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8. Insurance agencies.
9. Mechanical Contractors Association of
America.
10. National Academy of Sciences-Na-
tional Research Council.
11. National Coal Association.
12. National Fire Protection Association.
13. National Oil Fuel Institute.
14. National Warm Air Heating and Air-
Conditioning Association.
15. U.S. Bureau of Mines.
16. State and local air pollution control
agencies.
Proper fuel-air ratio adjustment is of major
importance for reduction of CO emissions
from stationary combustion sources. Flue
gases from the best-designed combustion unit
may contain substantial concentrations of CO
if insufficient air is provided for combustion.
Carbon monoxide emissions also increase
when excessive air is admitted to cool com-
bustion temperature below the optimum for
maximum oxidation of fuel and CO. As a rule
of thumb, coal- and oil-fired units may be
adjusted for 10 to 12 percent CO2 on a dry
basis, and natural-gas-fired units may be ad-
justed for 8 to 10 percent CO2 on a dry basis.
Since many units are designed to perform best
at values outside these ranges, the combustion
equipment manufacturer or other combustion
experts should be consulted on proper fuel-air
ratio adjustments for individual combustion
units.
As an alternative to using CO2 as a cri-
terion, oil-, gas-, or pulverized-coal-fired units
may be adjusted for 0.2 to 3.0 percent
oxygen for well-designed combustion units. It
should be noted, however, that operation at
very high combustion temperatures may yield
excessive oxides of nitrogen. Examples of this
are well known in the boiler industry.
Carbon monoxide emissions can be mini-
mized by designing for (1) a high combustion
temperature; (2) intimate contact among fuel,
oxygen, and combustion gases; (3) sufficient
reaction time; and (4) low effluent tempera-
ture.
Combustion systems should be selected on
the basis of application and designed to meet
specified load requirements. In addition, the
3-4
fuel-handling system, draft system, fuel-
burning system, flues and stacks, ash-handling
system, and combustion controls must be
properly selected, integrated, and designed to
handle the load and the fuel to be burned.
Selection of the size, number, and type of
burners depends upon the type of furnace.
For systems involving new furnace installa-
tions, the combustion space and heat distribu-
tion pattern can be arranged to suit any
particular type of burner, whereas on existing
combustion systems, the burner must be
selected to fit the existing design.
Stationary combustion units are designed to
operate within a specific range of load condi-
tions. In systems requiring a wide range of
heat releases, it may be desirable to utilize
multiple burners, since there is a limitation to
the burner-turndown ratio available. If such a
unit is operated outside design limits, exces-
sive emissions of CO or excessive oxygen in
the flue gas may result. It is, therefore,
necessary that the load be accurately esti-
mated before stationary combustion systems
are selected and installed.
Firing in excess of the design rate of the
combustion system—overloading—is perhaps
the greatest cause of excessive CO emissions
from a stationary combustion source. Com-
monly available oil burners and defects of
operation that may result in CO pollution are
noted in Table 3—6.
Before any fuel can be ignited, it must first
become a vapor. Thus, the extent of atomiza-
tion of oil is extremely important to efficient
burner operation and CO emission abatement.
For a given quantity of oil, the smaller the oil
particle, the greater will be the area exposed
to the air, and the more readily the proper
air-fuel mixture can be ignited. High-
combustion efficiency, rapid ignition, and
higher flame temperature are produced when
the proper amount of air necessary for com-
plete combustion is supplied. The degree of
fineness of atomization is, therefore, of prime
importance in the proper functioning of an oil
burner. With the complete atomization of oil,
complete combustion can be secured with the
stoichiometric amount of air. Any air in
excess of that required for complete combus-
tion causes fuel waste, because waste-gas
-------
Table 3-6. CLASSIFICATION OF OIL BURNERS ACCORDING TO APPLICATION AND
LIST OF POSSIBLE DEFECTS9
Burner type
Domestic
Pressure atomizing
Rotary
Vaporizing
Commercial, Industrial
Pressure atomizing
Horizontal rotary
cup
Steam atomizing
Air atomizing
Applications
Residential furnaces,
water heaters
Residential furnaces,
water heaters
Residential furnaces,
water heaters
Steam boilers,
process furnaces
Steam boilers,
process furnaces
Steam boilers,
process furnaces
Steam boilers,
process furnaces
Oil type
usually used
No. 1 or 2
No. 1 or 2
No. 1
No. 4, 5
No. 4,5,6
No. 5,6
No. 5
Defects that cause excessive CO emissions
Increased viscosity of oil, nozzle wear, clogged
flue gas passages or chimney, clogged air inlet,
oil rate in excess of design
Increased viscosity of oil, clogged nozzle or air
supply, oil rate in excess of design
Fuel variations, clogged flue gas passages or
chimney, clogged air supply
Oil preheat too low or too high, nozzle wear,
nozzle partly clogged, impaired air supply,
clogged flue gas passages, poor draft, overload-
ing
Oil preheat too low or too high, burner partly
clogged or dirty, impaired air supply, clogged
flue gas passages, poor draft, overloading
Oil preheat too low or too high, burner partly
clogged or dirty, impaired air supply, clogged
flue gas passages, poor draft, overloading, insuf-
ficient atomizing pressure
Oil preheat too low or too high, burner partly
clogged or dirty, impaired air supply, clogged
flue gas passages, poor draft, overloading, insuf-
ficient atomizing pressure
volume increases and the additional fuel
required to heat it represents a loss.
The flue area or vent opening in a furnace
or boiler serves to deliver the products of
combustion to the atmosphere. A second
function is to maintain the desired furnace
pressure. In some furnaces, it is desirable to
maintain a positive pressure; in others, a zero
or slightly negative pressure is desired.
Efficiency of combustion depends partly on
flue area. In order to maintain the desired
combustion rate, it is necessary to correctly
size the flue or vent opening. Too small a flue
opening acts as an impediment to the flow of
gases and products of combustion attempting
to escape. This restriction produces a back
pressure, which hinders the flow of fresh air
to the combustion chamber and thereby
reduces the quantity of fuel that can be
burned efficiently. When this happens, all
attempts to increase the rate of burning
beyond the limit imposed by the restriction
result in the creation of CO. In addition, a
drop in furnace temperature results, with
possible flame extinguishment.
When flue-area openings are excessively
large, the products of combustion leave the
furnace too fast under fixed chimney draft,
and the furnace pressure decreases. This pres-
sure drop results in an infiltration of excess
air, with consequent fuel waste, variation in
furnace atmosphere, difficulty in maintaining
desired temperature and uniform heat distri-
bution, and possible ignition failure. This,
too, may result in an increase in CO emissions
when coal or oil is being burned.
Exclusive of the selection of fuel, the most
important feature to consider for purposes of
3-5
-------
CO abatement in stationary fuel combustion
sources is the combustion control system.
Major innovations in combustion equipment
design have taken place in this area. Combus-
tion control equipment is primarily concerned
with two functional aspects, namely, adjust-
ment of the fuel supply under variation of
load demand, and correction and control of
the fuel-air ratio corresponding to the fuel
supply.
Generally, any form of automatic combus-
tion control of the fuel-air ratio offers the
potential of increased efficiency, lower CO
emissions, and lower operating costs than
does a manually operated system. The more
complex and larger the installation or the
greater the load fluctuation, the more com-
plex and comprehensive are the controls that
can be justified. The primary purpose of such
controls is to limit fuel consumption, follow
load demands without lags, increase safety
and reduce ambient air pollution. Variations
in load are very rapidly reflected in operating
conditions, which may not elicit sufficiently
rapid response from an operator in a manually
operated system.
Control systems are of the following three
general types:
1. The on-off control system is the sim-
plest control system available. This system
regulates the fuel and air flow to the boiler
burner system by a pressure signal from a
steam header or the boiler drum. As the
steam pressure varies between set limits,
the burners either light off or shut down.
This method of control is the least effec-
tive for maintaining a well-balanced fuel-
air ratio. The CO emission or excess air is,
therefore, usually higher from boilers using
this control system. This occurs because
the boiler is constantly being heated or
cooled, an even combustion temperature is
not maintained, and complete combustion
of the fuel is achieved during only part of
the cycle. This type of control is used on
small fire-tube boilers, heaters, etc., where
simple controls are specified to minimize
investment.
2. The position-control system will adjust
the fuel-air ratio to the boiler require-
ments. Like on-off control, position con-
3-6
trol regulates by steam pressure. As the
boiler pressure varies due to supply and
demand, the control system adjusts the
dampers in the air system as well as the
fuel valve. The system can follow a slightly
fluctuating load and produce a more ac-
ceptable fuel-air ratio over the operating
range.
This type of control system would be
most common on package and medium-
sized boilers.
3. The most elaborate system for combus-
tion control is the metering system. This
system anticipates load, and is found
almost exclusively on utility boilers. The
system measures steam flow and pressure,
fuel flow, and air flow, and compares
steam requirements with the feed-water
input to determine the correct firing rate.
A feedback control system provides rapid
response. When operating properly, this
system offers the best continuous fuel-air
ratio for the desired operating range.
In summary, although the on-off combus-
tion control system is simplest, it offers the
least amount of control over the fuel-air ratio
of the three general types of combustion
systems. The position-control system is more
complicated, and it can vary the fuel-air ratio
to produce a more efficient firing rate over a
range of loads. Of the three systems, the
metering system is the most sensitive to load
variation, and is able to control the fuel-air
ratio over constant, as well as fluctuating,
load conditions.
The following example illustrates how the
proper application of basic engineering princi-
ples to furnace design can facilitate the
lowering of overall fuel requirements and
substantially lessen the likelihood of ambient
air pollution by CO from two major sources,
fuel and CO-bearing offgases. The example
points up the importance of refractory selec-
tion and combustion chamber design.
To maintain ignition stability during tran-
sient events accompanying operating-load
fluctuations on CO boilers for fluid catalytic
cracking units, equilibrium temperatures in
the range of 1,800 °F are desirable to assure
complete consumption of the CO-bearing
offgas. Combustion can be achieved with
-------
stable ignition, however, in a temperature
range as low as 1,500° to 1,600°F in hot
refractory combustors under proper condi-
tions. If the combustion chamber design
promotes thorough mixing of auxiliary fuel
and gas, and if the chamber is sized to provide
adequate residence time, CO combustion can
take place at lower temperatures and less
auxiliary fuel will be used because of the
efficiency of combustion.
To insure gas ignition during the transient
flows accompanying load changes and varying
rates of coke burn, the combustion chamber
construction should assure complete conver-
sion of CO to CO2 over the widest possible
operating temperature range. Unsuited to this
purpose are low-heat-capacity furnace settings
of typical insulating firebrick and combustion
volumes surrounded by cold, heat-absorbing
surfaces. In contrast, it is desirable to provide
refractory furnace enclosures having maxi-
mum heat storage or thermal "fly wheel"
effect, to protect from loss of ignition and
pulsating detonation. Stable operation is pro-
moted by adequate size of the combustion
chamber, which insures sufficient gas resi-
dence time, and by high heat capacity setting,
which enhances stable operation.
In addition, maximum contact of the hot
refractory walls and the fuel gases greatly
accelerates the rate of combustion. The more
hot refractory that is available, the less will be
the dependence on auxiliary burners for
ignition. In the ideal design, ignition is sus-
tained by stored radiant heat energy in the
refractory setting, rather than by direct mix-
ing with hot gases generated by the auxiliary
burners. When sufficient hot refractory is
provided, the CO continues to burn stably,
even if the auxiliary burners are out of
service.
From the above, it follows that the presence
of any heat sink, particularly a relatively cold
surface, in contact with the combustion
chamber, greatly increases the difficulty of
obtaining good CO combustion and, thus,
increases CO emissions.
In order to ignite the CO, the temperature
of the air-CO mixture must be raised to at
least 1,200° F. After this substantial addi-
tional heat energy is brought into the system,
the CO ignites and contributes to a turtner
increase in temperature.
If, however, the combustion chamber and
burner ports are of sufficient number and
arrangement that the CO is fed gradually and
at an increasing rate into a stream of much
hotter combustion gases, without any major
chilling effect, then a much more reliable and
complete conversion of CO to CO2 can be
achieved with a minimum auxiliary fuel re-
quirement. Many small burners, coordinated
with well-distributed CO ports, enhance com-
bustion conditions.
3.3.2 Energy Source Substitution
CO emissions can be reduced by substitu-
tions among fossil fuels. Table 3—7 gives
emission factors for the small heat-release rate
of 10 million Btu per hour. The table data
were estimated from data in reference 10.
Table 3-7. ESTIMATED CARBON MONOXIDE
EMISSION RATES FROM FOSSIL FUELS AT
DUTY OF 107 Btu/hr
(lb/hr)
Fuel
Coal
Oil
Natural gas
CO
20
0.134
0.0038
The relative emission rate from coal com-
bustion decreases with increasing size of
combustion unit. Substitution of gas- or
oil-fired units for coal-burning grate- or
stoker-type units can reduce CO emissions.
Hydroelectric power is too limited in
growth potential in the United States to be
considered as a substitute for fossil-fuel en-
ergy. Nuclear power generation would not
entirely eliminate CO emissions, because of
the need for standby fossil-fuel power-
generating facilities at these stations.
The subject of fuel substitution is probably
academic for large, well-operated units like
power plants, because of their low CO emis-
sion rates; however, conversion from coal to
oil or gas can reduce emissions from homes
and other numerous small users concentrated
in very limited areas.
3-7
-------
3.4 REFERENCES FOR SECTION 3
1. Minerals Yearbook 1966, Vol. I-II. U. S. Dept.
of Interior, Bureau of Mines. Washington, D. C.
1967. p. 686, 728.
2. Fuel Oil Shipments, 1967. U. S. Dept. of
Interior, Bureau of Mines. Washington, D. C.
August 1,1967. 12 p.
3. Minerals Yearbook 1966, Vol. I-II. U. S. Dept.
of Interior, Bureau of Mines. Washington, D. C.
1967. p. 774.
4. Preliminary National Power Survey Estimates.
Federal Power Commission. December 1969.
5. Dunphy, B. 1966 Oilheating Sales Analysis.
Installations up 2.5% to 558,965. Fueloil & Oil
Heat. 2<5:29-35, January 1967.
6. Fristrom, R. M. The Mechanism of Combustion
in Flames. Chem. Eng. News. 41 (41): 150-160,
October 14,1963.
7. Handbook of Chemistry and Physics, 47th ed.
Cleveland, The Chemical Rubber Co., 1966.
1856 p.
8. Smith, W. A. and C. W. Gruber. Atmospheric
Emissions from Coal Combustion-An Inventory
Guide. U. S. DHEW, PHS, National Air Pollution
Control Administration. Cincinnati, Ohio. Publi-
cation Number 999-AP-24. April 1966. 112 p.
9. Air Pollution, Stern, A. C. (ed.) Vol. III. New
York, Academic Press, Inc., 1968. p. 22.
10. Steam-Electric Plant Factors. Washington, D. C.,
National Coal Association, 1967. p. 81-90.
-------
4. INDUSTRIAL PROCESS SOURCES
4.1 IRON AND STEEL INDUSTRY
Carbon monoxide is generated during sev-
eral stages in the production of iron and steel,
beginning with the sinter plant for beneficiat-
ing iron ore; the blast furnace for producing
hot metal; and the basic oxygen, open-hearth,
and electric furnaces for producing steel.
Emissions from sinter plants are significant.
Blast furnaces generate large amounts of CO,
but emissions are insignificant since the gases
are cleaned and used as fuel. Some recent
basic oxygen furnace designs also have provis-
ions to cool and clean the offgas, which could
then be used as fuel. In the open-hearth
furnace, excess air supplied to the end-fired
burners completely consumes the CO released
from the metal bath. The small amount of CO
released from electric furnaces burns at the
electrode ports. Coke ovens generate a signifi-
cant amount of CO, but most of it is collected
with the coke oven-gas and used as fuel.
Cupola furnaces also produce a significant
amount of CO, and only a few are being
controlled. The heating furnaces and boilers
used in the steel mills are subject to the same
problems as other boiler operations.
4.1.1 Iron Ore Beneficiation (Sinter Plants)
Iron ore is beneficiated by grinding, con-
centrating it magnetically, and sintering of the
concentrate in the form of coke or pellets
suitable for use as a burden for blast furnaces.
The total sinter plant capacity in the United
States in 1960 was 65 million tons of sinter
Table 4-1. GASEOUS EMISSIONS FROM SINTERING OPERATIONS2
Experiment
No.
A-l
A-2
B
C-l
C-2
D
E
F
Fuel
Nature
Coke -1/8 in.
Coke-1/8 in.
Charcoal-1/8 in.
Coke-lOOmesh
Coke-lOOmesh
Charcoal-1/8 in.
Graphitized
electrode— 1/8 in.
Flue dust
(16.3%C)
y
4
4
3.5
4
4
3.5
3.5
21.5
Water,
%
3.5
3.5
3.5
3.5
3.5
3.5
3.5
3.5
Atmos-
phere
Air
Air
Air
Air
Air
02 9%
N2 91%
Air
Air
Specific
volume ,a
ft3 /ton
31,500
32,100
31,400
32,000
31,600
34,400
35,800
37,800
Mean
temperature
of lower
bed,°C
1,440
1,440
1,090
1,380
1,370
1,290
1,520
1,250
Gas, %
C02
4.7
4.6
4.7
6.6
6.8
3.9
4.8
2.5
CO
1.1
1.1
2.5
1.7
1.8
1.9
0.5
1.05
Composition
02,
15.2
15.0
13.9
12.8
12.6
4.2
15.0
17.5
CO
CO + C02
0.19
0.19
0.35
0.21
0.21
0.33
0.095
0.30
aSpecific volume per ton of raw sinter mix or approximately 0.75 ton finished sinter.
4-1
-------
coke and 15 million tons of pellets. Capacity
in 1970 is expected to be 75 million tons of
sinter and 40 million tons of pellets.1
Carbon monoxide emissions from sintering
operations can be estimated from Table 4—1.
A typical value is taken as 450 cubic feet per
ton of raw sinter mix or 600 cubic feet per
ton of finished sinter. This is about 33 pounds
of CO per ton of raw sinter mix or 44 pounds
of CO per ton of finished sinter. Carbon
monoxide emissions from firing pellets can be
expected to be approximately the same.
From the previously cited capacity projec-
tions, 1968 production of sinter is estimated
as 73 million tons and pellet production as 35
million tons. Carbon monoxide emissions
from 1968 production are calculated to be
1.62 million tons per year for sinter and
780,000 tons per year for pellets.
4.1.2 Blast Furnaces
A blast furnace is a large cylindrical struc-
ture, approximately 100 feet high, made of
steel, and lined with refractory brick. Iron
ore, coke, and limestone are charged at the
top, and heated air is blown in at the bottom.
The coke is preheated by the hot gases
ascending from the hearth so that, when it
reaches the lower portion of the furnace and
comes in contact with the air of the hot blast,
it will burn with great intensity. At the high
temperatures that exist at this location (above
3,000°F), CO2 is not stable because of the
large quantity of carbon present as coke. For
this reason, if any CO2 forms, it reacts
immediately with C to form CO.
Consequently, the combustion of coke in the
blast furnace can be expressed by the follow-
ing chemical equation:
C+ 1/2 O2— CO
In modern blast-furnace operations, between
600 and 900 pounds of carbon react in this
manner for every ton of hot metal produced.3
This forms between 1,400 and 2,100 pounds
of CO. Carbon monoxide reduces the iron
oxides to metallic iron. Chemical equilibrium
prevents all the CO from being used. Gases
leaving the furnace contain about 25 to 30
percent CO.4
The CO content of the blast-furnace gas
gives the gas a heating value of about 100 Btu
per cubic foot. Furnace gas can thus be used
as fuel, but first, must be cleaned, since it
contains 7 to 30 grains of dust per standard
cubic foot. The usual cleaning system is
composed of a dust catcher (settling
chamber), a primary cleaner, and a secondary
cleaner. The primary cleaner usually consists
of some type of medium-efficiency scrubber.
The secondary cleaner may consist of a
high-pressure-drop venturi scrubber, a rotary
disintegrator, or an electrostatic precipitator.
The venturi scrubber is more likely to be used
with a blast furnace that can operate at
relatively high top-pressure.
Blast-furnace gas is used to preheat the blast
air, before its injection into the furnace
through the tuyeres, to intensify and speed up
the burning of the coke required for the
smelting operation. The air blast is heated in
"stoves," which are cylindrical steel vessels,
lined with a refractory. They have an upward
passage for combustion and downward pas-
sage filled with checkerwork to absorb the
heat. There are usually three stoves per
furnace, and they are alternately "on gas" and
"on blast." Modem stoves for large furnaces
are 26 to 28 feet in diameter and about 120
feet high.3
Only a part of the blast-furnace gas is
required for heating the stoves. The remainder
is used for steam generation, heating of
soaking pits, underfiring of coke ovens, and
other miscellaneous heating uses.
4.1.2.1 Emissions
As stated above, all the CO generated in the
blast furnace is normally used for fuel; ab-
normal conditions, however, can cause emis-
sions of dust and CO. "Slips" are the principal
cause of such emissions. A slip is caused by an
initial wedging or bridging of the stock in the
furnace. When this occurs, the material under-
neath continues to move downward, and a
void is created. The void tends to increase in
size until the "bridge" collapses. Accompany-
ing the sudden downward movement of the
4-2
-------
stock above the bridge is a rush of gas to the
top of the furnace.3 This occurrence causes
abnormally high pressures—much greater than
can be handled through the gas-cleaning
equipment.4 When this happens, bleeders or
safety valves open to release the pressure, and
a cloud of dust and CO is emitted into the
atmosphere.
4.1.2.2 Control Techniques
Blast furnace operators are constantly striv-
ing to reduce the incidence of slips and,
thereby, increase efficiency and production
and reduce air pollutant emissions. Further-
more, with increased understanding of the
cause of slips, further steps are being taken to
utilize practices and procedures to eliminate
them. The use of sinter, with a reduction in
the amount of fines fed to blast furnaces, has
resulted in smoother operations.
The improvements made in blast-furnace
feed materials and in instrumentation have
reduced the number of malfunctions known
as "slips" occurring in blast furnaces almost
to the vanishing point. In addition, a change
in the piping system and in the permissible
top pressure has made it possible to contain
the emissions from most slips that actually do
occur. As a result, it is very rare today for a
slip of such magnitude to occur as to spring
the escape valves high on the furnace and
allow the heavily dust-laden gases to escape to
the outside.5
4.1.3 Basic Oxygen Furnaces
The basic oxygen process is employed to
produce steel from hot blast-furnace metal
and some added scrap metal, by use of a
stream of commercially pure oxygen to oxi-
dize the impurities, principally carbon and
silicon.
The basic oxygen furnace is an unheated,
pear-shaped vessel, mounted on trunnions. It
is in the upright position during the blowing
cycle. The charge, which occupies only a
small portion of the total volume of the
vessel, is refined by a high-velocity oxygen jet
from a water-cooled lance that is lowered
vertically through the vessel mouth to within
a predetermined distance above the surface of
the bath. The distance between lance and
surface varies during the blow from 7 to 2.5
feet in various plants.6
Dark brown smoke evolves, at the start of
the blow, from oxidation of the iron. It
persists until the silicon, manganese, and
phosphorus begin to oxidize; then these ox-
ides enter the slag. Next, carbon is oxidized
and evolved, chiefly as CO. An excess of air is
usually mixed with the gases to burn the CO
as the offgasses are collected. This eliminates
the possibility of an explosion from ignition
within the exhaust system. Many furnaces are
equipped with waste-heat boilers for thermal
recovery from burning of the CO.7
4.1.3.1 Emissions
The charge to a basic oxygen furnace
usually consists of hot metal and scrap in the
ratio of 70 to 30, plus burnt lime. Based on
this charge, the offgas will produce about 124
to 152 pounds of CO per ton of steel. After
aspirated air is added to the offgas, the weight
of dry gas will increase to about 1,800 to
2,000 pounds per ton of steel and will contain
from 0 to about 2.6 pounds of CO after
combustion.
During the normal operation of an iron and
steel plant, only small amounts of CO would
reach the atmosphere from this source.7
4.1.3.2 Control Techniques
The high-velocity oxygen stream impinging
on the surface of the molten iron in a basic
oxygen furnace generates extreme heat, and
causes the formation of large amounts of iron
oxide fumes. A gas-cleaning system for the
effluent must, therefore, be provided. These
systems utilize high-energy scrubbers or elec-
trostatic precipitators as the final collecting
device.
The fume collecting hoods are of two
types—closed hoods and open hoods. The
closed hoods are designed to reduce infil-
trated air to a minimum. After cleaning, the
gas enters a gas-collecting and -holding system
and is subsequently used for fuel or as a raw
material for chemical manufacturing. A dia-
gram of the system is shown in Figure 4— 1.
4-3
-------
•BURNER
MAIN COOLER
UPPER HOOD
LOWER HOOD
SKIRT
TOP COOLER
PRIMARY VENTURI
ELBOW
SEPARATOR
STACK
ELBOW SEPARATOR
SECONDARY VENTURI
INDUCED-
DRAFT FAN
Rl
*
t
CO HOLDING TANK
WATER SEAL
CHECK VALVE
Figure 4-1. Basic oxygen furnace with closed hood and gas-cleaning and storage system.
In open-hood systems, sufficient air is ad-
mitted to completely burn the CO in the
hood. An excess of air is usually provided, for
safety reasons, and the effluent volume is as
much as 25 times the volume of the oxygen
used. The length of the hood should be
sufficient to assure complete combustion of
the CO before the gas is cooled below the
ignition temperature in the quench chamber,
which precedes the dust-collection equip-
ment. Figure 4—2 illustrates an open-hood
system.
In this diagram, gases generated at the
furnace are burned with excess air and cooled
with water sprays in a water-jacketed hood
and chamber. The spray header acts as a
baffle and causes some of the large particles in
the gas stream to fall into the spark box and,
from there, to a settling tank. The gas is
further cooled by radiation in the flue con-
EMERGENCY
STACK DAMPER
COMBUSTION
AIR AND
EXCESS AIR
WATER JACKETED
SPRAY CHAMBER
BASIC OXYGEN
FURNACE VESSEL
STACK
Figure 4-2. Basic oxygen furnace with open hood and gas-cleaning system.
4-4
-------
necting the spray chamber to the gas inlet of
the precipitator. This inlet decreases the gas
flow, permitting more of the large particles to
drop into the expansion chamber before the
gas enters a plate precipitator for final clean-
ing.
Hoods are water-cooled because satisfactory
refactory linings for this type of application
have not been developed to date.8 They may
use cold water, hot water, or steam. Cold-
water hoods are usually of parallel wall-panel
recirculation is not necessary, cold-water
hoods are usually lowest in capital cost.
Hot-water or steam hoods should be supplied
with treated boiler feedwater. Hot-water
hoods may serve as a source of hot water for
other uses, or the water may be recirculated
through a water-cooling tower or some type
of heat exchanger. In view of the large
quantity of heat available, the use of steam
generated in a steam hood should be con-
sidered. Steam is generated on a cyclical basis,
C
ACCUMULATOR
BOILER-SUPERHEATER
PLANT ST^AM
275 psi, 55
-------
placed on top of the burning coke bed. The
heat generated melts the metal, which is
drawn off through the tap hole.
4.1.4.1 Emissions
As in the blast furnace, blowing air into an
incandescent bed of coke results in the
formation of a considerable amount of CO.
The gases from cupolas contain from 10 to 13
percent CO.9 On the basis of iron melted, this
is from 220 to 370 pounds of CO generated
per ton of iron.
A questionnaire survey of the 1,680 United
States foundries has been completed by the
National Air Pollution Control Administra-
tion and the Department of Commerce. Re-
sults show that the 14.6 million tons of iron
castings shipments produced by cupolas in
1966 required 32.4 million tons of melt.
Based on this survey, approximately 10 to 20
percent of this production was subject to
flame afterburner control, which was about
90 percent efficient for CO reduction. With
an emission factor of 250 pounds of CO per
ton of melt for uncontrolled cupolas and 10
pounds of CO per ton of melt (or charge), for
controlled cupolas, an estimated 3.467 mil-
lion tons of CO was emitted from iron
cupolas in 1966.
4.1.4.2 Control Techniques
Many cupolas operate without any effluent
control measures; they emit CO, dust, and
fumes directly to the atmosphere. Cupolas
equipped with efficient particulate collecting
systems have afterburners for burning CO in
order to avoid handling explosive gas mix-
tures. The afterburner also burns the combus-
tible particulates, such as coke breeze and any
smoke and oil vapors, that may originate from
oily scrap in the charge.
While afterburners may be installed as sepa-
rate units, the common practice is to use the
upper portion of the cupola above the
charging door as the afterburner. When this is
done, the height of the standard cupola must
be increased to provide adequate retention
time to complete the combustion in the
afterburner.
An afterburner should be designed with
adequate capacity to raise the temperature of
the combustibles, inspirated air, and cupola
gases to at least 1,200°F.9 The geometry of
the secondary combustion zone should be
such that the products to be incinerated have
a retention time of at least 1/4 second.
Enough turbulence must be created in the gas
stream for thorough mixing of combustibles
and air. In large-diameter cupola furnaces,
stratification of the gas stream may make this
a major problem. One device, proved to be
successful in promoting mixing in large-
diameter cupolas, is the inverted cone10
shown in Figure 4-4. The combustion air is
inspirated through the charging door.
GAS BURNERS
Figure 4-4. Integral afterburner with inverted
cone installed in top part of cupola to create
turbulence to ensure complete combustion.
Other necessary afterburner design features
are:
4-6
-------
1. A steady flame that does not go out and
is not affected by the cupola charge. If
the flame is extinguished, it relights
automatically.
2. An automatic modulating control system
of the main burners, controlled from a
thermocouple in the stack, which cuts
off the main burner flame, but not the
pilot, if cupola gases have sufficient CO
to affect the control temperature.
3. No interference with the cupola charging
system or melting process.
These features are illustrated in Figures 4—5
and 4—6.
FLAME
_T
I
CHARGE
OPENING
Figure 4-5. Diagram of afterburner system
showing flame introduced at most favorable
location to ignite cupola gases.
(Courtesy of American Foundryman's Society
The balanced-blast cupola represents a de-
sign that is capable of reducing CO in the exit
gas from the cupola preheat zone. This cupola
differs from the conventional cupola, mainly,
in having three or more rows of tuyeres to
admit air at several levels, instead of at only
one or two levels.'1 By proper adjustment of
air to the individual tuyeres, CO can be
maximized in the bottom of the cupola where
needed, and minimized at the top preheat
zone. Uniform melting and reduction in bridg-
BURNER
COMBUSTOR
LOCATED
OUT OF WAY
OF CHARGING
SYSTEM
Figure 4-6. Diagram of flame in afterburner
system that is neither extinguished nor af-
fected by cupola charge.
(Courtesy of American Foundryman's Society)
ing can be obtained; also, freezing near a
tuyere can be prevented by temporary shutoff
of air at that tuyere. These factors decrease
both coke consumption and CO emissions.
The conventional cold-blast cupola is fed with
ambient blast air. The hot-blast cupola is fed
with preheated blast air.1 * The airfeed is
preheated to about 1,000°F before going to
the tuyeres. The resultant increase in heat
input to the cupola decreases the amount of
coke required for melting, decreases the
amount of combustion products, and tends to
decrease CO emissions.
4.1.5 Electric Furnaces
In 1967, 15 million tons or 11.8 percent of
the U. S. annual steel production was made in
electric-arc furnaces.' 2 The electric furnace is
particularly well adapted to the production of
steel from cold scrap. Since the basic oxygen
process has a limited scrap-handling capacity,
and a plentiful supply of inexpensive scrap is
available, the production rate of steel from
electric furnaces continues to increase.
4.1.5.1 Emissions
When steel is made in the electric furnace,
excess carbon is added to the charge to create
a carbon boil, which serves to stir and purge
the metal bath. The excess carbon rarely
exceeds 0.5 percent. This amount of carbon,
when oxidized, yields 18 pounds of CO per
ton. Perhaps half of the oxygen in the CO
reacts to CO2 within the furnace.13 Essen-
4-7
-------
tially all of the remainder oxidizes to CO2 at
the electrode ports.
4.1.6 Coke Ovens
Coke is produced by carbonization, the
destructive distillation of coal. This process is
carried out in either beehive or by-product
ovens, both of which are carefully heated to
coking temperature, then kept hot for the 20-
to 30-year lifetime of the oven. A battery is
made up of as many as 100 individual coke
ovens side by side in a continuous structural
unit. Coke production figures are given in
Table 4-2.
The use of beehive ovens has declined to the
extent that only about 1.2 percent of the
annual U. S. coke supply is produced in
them.12 These ovens are far worse air pol-
luters than are by-product ovens. About 6.5
tons of coal per batch is charged through an
opening in the dome-like roof. Products of
distillation and combustion escape through
the same opening. A door in the front is used
to regulate the amount of air admitted during
coking and to discharge the finished coke.
Enough heat is retained by the oven be-
tween charges to drive off volatile gases from
a new charge of coal. The gases ignite at the
surface of the charge to provide heat for the
coking process. As heat builds up, the coal is
transformed into a pasty, semifused state, and
expands appreciably. When coking is finished,
the bricks placed in the door are torn away
and the coke is sprayed with water. The rapid
cooling causes the charge to break into
irregular pieces having a column-like struc-
ture, a characteristic of beehive coke. When
cooled, the coke is screened.
In by-product ovens, coal is heated in the
absence of air. Volatile matter is ducted to
equipment that extracts valuable ingredients,
such as tar, ammonia liquor, and light oil,
from the gas. Approximately 36 percent of
the coke oven gas (heating value, 550 Btu/ft3)
produced during coking is used to heat the
coke ovens. *2 The remainder of the gas is
usually used for heat in other processes in the
steel plant.
From 16 to 20 tons of coal is charged from
ports in the top of the rectangular oven. The
ports are sealed, and the coal begins to fuse,
starting at the oven walls, which are heated by
coal gas combustion. The fusing works toward
Table 4-2. HISTORICAL STATISTICS OF COKE INDUSTRY IN UNITED STATES
14
Coke production, 106 net tons
Year
1880
1890
1900
1910
1920
1930
1940
1944
1950
1955
1960
1966a
1967a
1968
By-product
ovens
1.1
7.1
30.8
45.2
54.0
67.0
66.9
73.6
56.2
66.0
63.8
63.3
Beehive
ovens
3.3
11.5
19.4
34.6
20.5
2.8
3.1
7.0
5.8
1.7
1.0
1.4
0.8
0.8
Total
3.3
11.5
20.5
41.7
51.3
48.0
57.1
74.0
72.7
75.3
57.2
67.4
64.6
64.1
Production from
by-product
ovens, %
5.2
17.1
60.0
94.2
94.6
90.6
92.0
97.7
98.2
97.9
98.8
98.8
Yield of
coke from
coal, %
63.7
63.9
63.9
66.1
67.4
68.7
70.1
70.3
69.9
69.9
70.3
69.9
69.6
70.2
aData are from Reference 12, p. 400
4-8
-------
me center irom both walls; a crack forms
down the middle of the charge when the two
fused zones meet. In about 20 hours, when
carbonization is finished, the charge is shoved
out into quench cars, cooled, and screened.
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.
The hot coal gas is first cooled with an
aqueous solution of ammonia. Condensed tar
and fixed salts, such as ammonium chloride,
are removed. Further cooling and an electro-
static precipitator remove any remaining tar.
The ammonia is recovered by a weak solution
of sulfuric acid; an acid separator then re-
moves sulfuric acid mist. Liquid oil, removed
in a series of scrubbing towers, is distilled and
treated to yield benzene, toluene, and other
products.
4.1.6.1 Emissions
About 15,000 cubic feet of coal gas is
recovered from the production of a ton of
coke in a by-product oven.14 Carbon monox-
ide makes up about 6 percent, by volume, of
this gas.15 Efficient combustion of the gas, to
provide heat for coking or other processes,
oxidizes the CO to CO2. Some CO emissions
occur during charging and discharging of the
by-product ovens. No data are available, but
the quantity is probably insignificant.
Coal gas formed during beehive-oven opera-
tions is burned inefficiently inside the ovens
to provide the heat required for coking.
Combustion products and unburned coal gas
are allowed to escape to the atmosphere. If
the figures cited above for by-product ovens
are assumed to apply to the gases escaping
from beehive ovens, then CO emissions (based
on 1967 coke production figures) from all
beehive ovens in the United States would
total 5.4 X 108 cubic feet, or 20,000 tons,
per year.
4.1.6.2 Control Techniques
Carbon monoxide emissions can be reduced
by the same methods that can be used to
reduce particulate emissions, as detailed in a
companion NAPCA volume, AP-51, Control
Techniques for Particulate Air Pollutants.
These methods consist of techniques used to
reduce emissions during charging of coal into
the ovens, and of methods to minimize leaks.
Emissions during charging can be reduced
by steam-jet aspirators in by-product header
ducts, charging-car volumetric sleeves, me-
chanical removal of charging-hole lids, and
sealing sleeves for levelling bars. Leaks can be
minimized by gas-tight, self-sealing oven
doors, which require a minimum of manual
sealing with clay; mechanical cleaners or
self-sealers for doors and charging-hole covers;
and improved refractories, with less spalling
and cracking, which cause warping of metal
parts and gas leaks into flue systems and
chimneys.
4.1.7 Cost of Controls
Afterburners are usually installed on cupo-
las to burn CO. Their cost is insignificant
when compared to dust-collector costs. For
example, 1968 installed costs for after-
burners, with necessary controls and air
blower for a typical-size cupola (54-inch,
inside diameter) amounted to $2,400.16 The
cost for a venturi-scrubber system for dust
collection, on the other hand, amounted to
approximately $200,000.' ° Fuel for the after-
burner cost approximately $5,000 for the
54-inch cupola (assuming a cost of 60^ per
106 Btu for the fuel) in 1968.
A gas-cleaning system for a basic oxygen
furnace must be considered as a multiple-
pollutant-control system, i.e., for collection
of particulates as well as CO. The components
of such a system include the hood, gas cooler,
duct work, collectors, fans, instrumentation,
and collected-waste-handling equipment. Sev-
eral distinct fume-hood schemes could be
considered, based on whether CO is burned or
collected, and the degree of heat recovery
employed. In the United States, collection of
CO as fuel is rare, and, therefore, the cost of
CO control is rarely separable from that of
dust abatement.
A very good discussion on costs of control
equipment for the steel industry is given in A
Systems Analysis Study of the Integrated Iron
4-9
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and Steel Industry.1 The general points cov-
ered on cost derivation are helpful, but, for
reasons already given, no costs in the study
apply to CO emission abatement.
4.2 PETROLEUM REFINERIES
The sources of CO in a petroleum refinery
include: catalyst regenerators, coking opera-
tions, blanketing gas generators, flares, boil-
ers, and process heaters. Only moving-bed
catalyst regenerators and fluid cokers emit
significant amounts of CO.
4.2.1 Catalytic Operations
In petroleum processing, catalysts are em-
ployed in the operations of cracking, reform-
ing, hydrotreating, isomerization, hydrocrack-
ing, alkylation, and polymerization. Most of
the catalysts used are in the form of solid
beads, pellets, and powders, which become
coated with carbon from coking reactions of
the feed materials. To maintain catalyst activ-
ity, these carbon deposits must be periodi-
cally burned off the catalyst surface. Burning
carbon at a controlled temperature and at a
set combustion air rate leads to the formation
of CO. In some processes, the catalyst parti-
cles circulate continuously between the reac-
tion zone and the regeneration zone, resulting
in the regeneration process being continuous.
Sulfur and nitrogen compounds are also re-
moved in the regeneration process. Cracking
catalysts are the only types that require
regeneration frequently enough to produce
significant amounts of CO.
Catalytic cracking units are of two types:
fluid catalytic cracking (FCC) units and Ther-
mofor catalytic cracking (TCC) units. FCC
units utilize a powdered catalyst, and TCC
units utilize bead or pelleted catalysts.
The reactor of an FCC unit is a large verticle
cylinder in which a bed of powdered catalyst
is kept in a fluidized state by the flow of
vaporized feed material. The regenerator is a
similar vessel, which may be placed above,
below, or beside the reactor. The catalyst
circulates continuously between the reactor
and regenerator. The catalyst stream from the
reactor is stripped of hydrocarbon vapors by
steam and is conveyed to the regenerator by
airflow. Additional air is injected into the
regenerator to burn off the carbon deposits.
The temperature is maintained in the range of
1,050° to 1,100°F. Coke-burnoff rates vary
with the size of the unit from 5,000 to
34,000 pounds per hour. A stream of regener-
ated catalyst is continuously returned to the
reactor. Its sensible heat furnishes the re-
quired heat for the cracking reactions.
Thermofor catalytic cracking and Houdri-
flow units utilize beaded or pelleted catalyst.
Regenerated catalyst and vaporized feed enter
the top of the reactor chamber and travel
concurrently downward through the vessel.
The catalyst is purged with steam at the base
of the reactor and travels by gravity into the
regenerator chamber. Combustion air is ad-
mitted at a controlled rate to burn off carbon
deposits. From the bottom of the regenerator,
the catalyst is returned by an airlift to a surge
hopper above the reactor. Older units utilized
a bucket elevator for catalyst return. An
average-sized TCC unit regenerator has a coke-
burnoff rate of 3,500 pounds per hour.
4.2.1.1 Emissions
When the carbon deposits are burned off
the cracking catalyst, the temperature must
be kept below about 1,100°F to avoid heat
deactivation of the catalyst and to preserve
the structural integrity of the equipment.
Temperature is regulated by control of the
combustion-air-flow rate. Large amounts of
CO are formed in this process. The emission
rates from different units show considerable
variation, but average emission factors have
been determined as follows: from FCC units,
13,700 pounds of CO per 1,000 barrels of
fresh feed; and for TCC units, 3,800 pounds
of CO per 1,000 barrels of fresh feed.17
A recent study gave the total 1967 rated
capacity of the catalytic cracking units in the
United States, as shown in Table 4—3.
Using the preceding emission factors, the
above capacity figures, and a factor of 0.9 to
relate capacity per stream day to charge per
calendar day, the CO generated is calculated
to be:
FCC units: 7.4 million tons per year of CO
4-10
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Table 4-3. CATALYTIC CRACKING CAPACITY
IN UNITED STATES18
Type unit
FCC
TCC
Houdriflow
Total feed,
bbl/stream day
4,655,570
748,600
199,000
Recycle,%
29.9
29.0
29.2
TCC and Houdriflow units: 422,000 tons
per year of CO
4.2.1.2 Control Techniques
The CO waste-heat boiler affords a means of
utilizing the heat of combustion of CO and
the sensible heat of the regeneration gases.
The CO and other combustibles, mainly
hydrocarbons, are oxidized to CO2 and water,
Figure 4-7. Water-cooled, carbon monoxide waste-heat boiler.
(Courtesy of Combustion Engineering, Inc., Windsor, Conn.)
4-11
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Figure 4-8. Corner-fired burners of a carbon monoxide waste-heat boiler: (left; Elevation
view showing a typical set of burners for one corner; (right) plan view of firebox showing
location of the four sets of burners.
(Courtesy of Combustion Engineering, Inc., Windsor, Conn.)
-------
and are, thereby, eliminated as air pollutants.
Thus, regenerator gas from catalytic cracking
is commonly burned to recover its heating
value.
In most cases, supplementary fuel is re-
quired to insure stable operation. This fuel
may be fuel oil, refinery process gas, or
natural gas. The boiler does not contain an
oxidation catalyst chamber for conversion of
the CO to CO2. It depends, instead, upon the
maintenance of a minimum CO gas-
combustion temperature of 1,800°F within
the primary furnace section, provided by the
introduction of supplementary fuel.19
The CO boiler may be a vertical structure
with either a rectangular or circular cross
section with water-cooled walls, as shown in
Figure 4—7. The outer dimensions of a typical
rectangular boiler are 32 feet wide by 44 feet
deep by 64 feet high, with a 200-foot-high
stack.2 ° The boiler is equipped with a forced-
draft fan and four sets of fixed, tangential-
type burners (one set for each corner). A
typical set of burners includes two CO com-
partments, four fuel gas nozzles, and two
steam-atomized oil burners, as shown in Fig-
ure 4—8. The burners are approximately 1-1/2
feet wide by 6 feet high. A tangential-type
mixing of the gases for more nearly complete
combustion is achieved by arranging the
burners slightly off center.
Regeneration gases from the FCC unit are
normally delivered to the inlet of the CO
boiler duct work at about 1,100°F and 2
pounds per square inch (gauge). Whenever the
regenerator gases first pass through an electri-
cal precipitator, the inlet gas to the precipita-
tor must be cooled below 500°F. The CO
boiler would then receive regeneration flue
gas at a temperature between 450° and
500°F.
4.2.2 Fluid Cokers
A fluid-coking unit resembles an FCC unit
in that a bed of fluidized solids is used to
transfer heat to the partially vaporized feed
material. It differs in that the solid particles
are coke, which is a product of the cracking
reaction. Coking occurs in a thin, liquid film
on circulating, fluidized, seed coke agitated
by rising gaseous products in the reactor.2 1
Reactor temperature is 900° to 1,050°F.
A stream of coke particles is continuously
withdrawn, steam-stripped, and transported
to another vessel called a burner. A controlled
amount of air is injected into the burner, and
sufficient coke is burned to maintain the coke
bed at a temperature of 1,110° to 1,200°F. A
stream of coke at this temperature is returned
to the reactor. More coke is formed in the
reactor than is burned; consequently, a coke-
product stream is withdrawn.
4.2.2.1 Emissions
In the burner, coke is burned under condi-
tions of limited air with respect to the
amount of carbon present. Hence, the flue gas
is very rich in CO. It is estimated that CO
emissions average 30 pounds per barrel of
fresh feed.22 In 1960, the total capacity of
the fluid-coking plants in the United States
was 100,000 barrels per day.2 3 On this basis,
the total CO generated in 1960 from fluid-
coking units was 550,000 tons per year.
Estimated CO emissions (shown in Table
2-1) indicate that CO boilers are often used
to burn the CO generated in fluid coking.
4.2.2.2 Control Techniques
The flue gas from the burner can be burned
in CO boilers similar to those used for catalyst
regenerator flue gas.
4.2.3 Cost of Controls
The economics of a CO boiler installation in
conjunction with a catalytic-cracking unit are
specific for a given refinery. The economics
may be generalized sufficiently, however, to
determine a range of catalytic-cracking unit
sizes that can pay out a CO boiler.19 The
basic variable used in determining the size of
the catalytic-cracking unit is coke-burning
rate. Other variables that affect payout in-
clude the following in the order of decreasing
importance: (1) fuel value, (2) CO2/CO
ratio, (3) flue gas temperatures, (4) excess
oxygen in CO gas, and (5) hydrogen content
of regenerator coke.
On the assumption that additional steam is
required in the refinery, a coke-burning rate
of 10,000 pounds per hour or more can be
4-13
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economically attractive for installation of a
CO boiler when fuel has a value of 20$ per
106 Btu. If additional steam is not required,
the minimum coke-burning rate to provide a
reasonable payout for a CO boiler is about
18,000 pounds per hour. A payout of 6 years
after taxes is assumed.19 In some areas, the
reduction in air contaminants is sufficiently
important to justify a payout longer than 6
years.
No figures are available for a CO boiler for a
fluid-coking unit, but economic consider-
ations would be similar to those given above
for the catalytic cracking unit CO boiler. This
would be true, however, only for a new fluid
coking unit when the CO boiler is built
integral with the unit during construction.
The installation of duct work, blower, and
other accessories for adding a CO boiler to an
existing unit usually cannot be economically
justified.
4.3 CHEMICAL INDUSTRY
Carbon monoxide is used directly in the
chemical industry as a raw material for
synthesizing other chemicals, such as metha-
nol and phosgene. It is also produced, and has
a transitory existence, as one of the gaseous
products of the reformer, where hydrogen or
a mixture of hydrogen and nitrogen is desired.
In these cases, CO is removed as such or, more
commonly, is oxidized to CO2 or reduced to
methane.
The production of CO by the chemical
industry of the United States is estimated at
somewhat greater than 6.6 million tons per
year. This includes the CO that has only a
transitory existence in the vessels and pipe-
lines of the reforming plants. This production
does not loom large, by comparison, with the
60 million tons per year emitted to the
atmosphere from gasoline engines (Table
2—1), or with the 90 million tons per year
produced in pig-iron blast furnaces and mostly
used as fuel therein.
4.3.1 Synthesis Gases
Most of the hydrogen used by the chemical
industry in the United States is made by the
steam-reforming process. Hydrocarbons fur-
nish the source of hydrogen, and the basic
reaction is:
CnHm+nH20
H
Natural gas is the hydrocarbon most often
used in this country:
CH4 +H20-
-CO + 3H2
These reactions, the main sources of CO
within the chemical industry, are used exten-
sively to generate synthesis gases, which are
used to make such products as methanol and
ammonia. The manufacture of hydrogen by
this method always involves, therefore, the
generation and handling of CO. The above
reaction is favored by higher temperature and
lower pressure, but modern plants operate at
pressures of 450 pounds per square inch
(gauge) or more, for economic reasons.
The gas reformer is a furnace having alloy
tubes containing a nickel-base catalyst. The
reforming process requires heat, and tempera-
tures of 1,400° to 1,800°F are commonly
used.24
The gases most often needed are hydrogen,
or a mixture of hydrogen and nitrogen for
ammonia synthesis. For these uses, the water
gas shift reaction is employed to remove CO:
CO2
CO + H2O-
This reaction is not affected by pressure, but
is favored by lower temperatues, which, how-
ever, reduce the reaction rate. Highly active
low-temperature catalysts of recent develop-
ment allow operation under 500°F and re-
move most of the CO at a reasonable rate in
one shift stage. The CO2 formed is removed
by scrubbing.
Small residual amounts of CO and CO2 can
be removed by methanation:
3H, +CO-
-*CH4 +H,O
This reaction is carried out at elevated tem-
peratures over a nickel catalyst and can
reduce CO to less than 10 ppm.24
4-14
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Another type of reforming is partial oxida-
tion, for which there are several processes.
Hydrocarbons are burned under reducing con-
ditions:
Naphtha or natural gas are the hydrocarbons
generally fed. The percentage of CO in the
raw synthesis gas increases with the C/H ratio
in the feed hydrocarbon. Typical results for
conversion of the hydrocarbon, using 95
percent oxygen as oxidant, are given in Table
4-4.
Table 4-4. SYNTHESIS GAS COMPONENTS25
(vol. %)
Synthesis gas
Natural gas
Naphtha
Heavy fuel oil
H2
60.9
51.6
46.1
CO
34.5
41.8
46.9
Table 4—5 compares various industrial gases
according to their typical contents of CO and
Table 4-5. CARBON MONOXIDE AND HYDRO-
GEN CONTENT IN SOME INDUSTRIAL GASES26
(vol. %)
Gas
Coke oven
Blast furnace
Water gas
Methane reformer
Methane partial combustion
Oil partial combustion
CO
6.3
27.5
42.8
15.5
35.6
47
H2
53
49.8
75.7
61.5
47
hydrogen. The last three gases listed in Table
4—5 are the raw unpurified synthesis gases.
Steam-reforming of methane tends to be fav-
ored where there is a plentiful supply of cheap
natural gas, as in the United States.24 Partial
oxidation is more often used in Europe.
4.3.2 Methanol
The production of synthetic methanol in
the United States in 1968 was about 3.750
billion pounds.27 Theoretically, this produc-
tion would require a feed of 1.65 million tons
of CO, which represents the minimum known
requirement for this production. Methanol is
synthesized as follows:
CO + 2H2-
-CH3OH.
This reaction is favored by high pressure and
by lower temperatures, and it is exothermic.
In practice, pressures of 4,500 pounds per
square inch (gauge) and temperatures up to
700°F have been used in the presence of a
suitable catalyst. Temperature control of the
methanol converter is by dilution with
quench gas or CO2. The methanol produced
contains some impurities, which must be
removed by flashing on pressure letdown,
followed by distillation. The unreacted gas is
recycled by the recycle compressor and com-
bined with fresh feed; inert gases are pre-
vented from building up in the system by
purging. The methanol converters of some
recent methanol plants utilize new copper-
based catalysts permitting operation at pres-
sures and temperatures as low as 700 pounds
per square inch (gauge) and 500°F, respec-
tively.2 8
Synthesis gas can be produced for use
directly in methanol synthesis, without the
separations or adjustments required for mak-
ing phosgene, ammonia, and other products.
4.3.3 Ammonia
The production of ammonia in the United
States in 1968 was about 12.5 million tons,27
From the data given in Table 4—5 for the
methane reformer, the CO associated with the
production of this amount of ammonia can be
calculated to be over 4 million tons, if the
ammonia synthesis gas were made by the
steam-methane reforming process. For ammo-
nia manufacture, the CO is removed to a
residue of less than 20 parts per million, since
it poisons the catalyst. This removal is done
by the gas shift and methanation reactions
described previously.
Ammonia is synthesized by the following
reaction:
N, + 3H,
•2NH,
4-15
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This reaction is favored by high pressure and
by lower temperatures. Pressures of 100 to
1,000 atmospheres and temperatures of 750°
to 900°F have been used. In order to secure
the required nitrogen-hydrogen mixture, a
hydrocarbon gas is reacted in two stages. In
the first stage, part of the hydrocarbon is
reformed with steam; in the second stage, the
unreacted hydrocarbon is partially oxidized
with sufficient air to yield the proper
hydrogen-nitrogen ratios.
4.3.4 Phosgene
Phosgene is made from CO and chlorine by
the reaction:
CO + C12
-COCL2.
This exothermic reaction is carried out in
water-cooled tubes filled with activated-
carbon catalyst. Only a slight excess of CO is
used to insure complete reaction of the
chlorine, and the yield is over 99 percent.
In 1967 there were 17 phosgene-manufactur-
ing establishments in the United States29
having a combined annual capacity of over
400,000 tons, much of which was for in-plant
use only. Theoretically, 1 14,000 tons of CO is
required to make the above quantity of
phosgene. Phosgene itself is such a dangerous
material and is so hazardous to life, that leaks
anywhere in the phosgene system are made
improbable by careful design and watchful
operation.
The CO manufacturing system employing
phosgene is similar to that required for
making methanol, in that it has a reformer; it
differs, however, in having the requirement
for relatively pure hydrogen-free CO. The CO
in raw synthesis gas is therefore purified by
absorption and desorption or by cryogenic
methods. A commonly used purification
method involves high-pressure absorption of
CO in a special copper liquor containing
cuprous and cupric chlorides and ammonium
carbonate:
The CO is liberated on release of pressure.
Absorption is carried out at near ambient
temperatures, and the temperature is raised to
aid desorption. This is quite a complicated
system; the ratio of cupric to cuprous copper
must be held within a certain range, and CO2
and sulfides should be removed.30 This re-
moval is done ahead of the copper-liquor
system by, first, passing the gas through an
ethanolamine absorber-stripper system. Cool
mono- or diethanolamine absorbs the acidic
hydrogen sulfide and CO2, and these are both
driven off later by heating the amine solution
in a stripping tower, which regenerates the
amine. In the following copper-liquor system,
the separation and purification of the CO
takes place.
There may be three CO-handling units in
phosgene manufacture: the reformer, the
ethanolamine absorber-stripper unit, and the
copper liquor CO absorption-purification
equipment. Nevertheless, the relatively small
usage of phsogene relegates this industry to
one of minor potential CO emissions.
4.3.5 Organic Acids3'
Carbon monoxide can be made to react
with certain alcohols and unsaturated hydro-
carbons to form organic acids. Perhaps the
most important of such processes is the
synthesis of acetic acid from CO and metha-
nol as shown by the following reaction:
CH3OH + CO-
-*CH3COOH
Cu2 (NH3 )4~+ 2 CO
Cu2(NH3)6(CO)-2-
2NH3
The synthesis takes place in the presence of
aqueous cobaltous iodide at about 250°C and
10,000 pounds per square inch.25 Published
yield figures show that at one large plant, CO
requirements are 21,000 tons per year, exclu-
sive of that required for making methanol.25
The vent gases are expanded to about 150
pounds per square inch (gauge) and washed
with methanol feed before being piped to the
fuel supply. By-products other than gas are
also formed in the reaction and are separated
from the acetic acid by distillation.
Other types of organic acids can be synthe-
sized in accordance with the following general
equation:
4-16
-------
RCH=CH2+CO+H,O-
-RCH2CH2COOH
Acrylic,25 pivalic,32 succinic,33-34 and mo-
nobasic unsaturated acids2 5 are among those
that may be made.
4.3.6 Aldehydes
Carbon monoxide can be made to react
with certain olefms to form aldehydes.
Among patented processes are the following:
C2 H4 + CO + H2 -C2 Hs CHO
This reaction takes place at 600 pounds per
square inch and 130°C with a catalyst of
cobalt on kieselguhr, and the yield of pro-
pionaldehyde is over 75 percent.35 Normal
butyraldehyde is formed in the presence of
cobalt naphthenate catalyst at 150°C and 500
pounds per square inch in accordance with
the following reaction:3 6
C3H6 + CO + H2 C3 H7 CHO
The Oxo process is of commercial impor-
tance, expecially in Europe; with this process,
aldehydes can be made from olefins, CO, and
hydrogen.2 5 The Oxo process is illustrated by
the following reaction:
RCH=CH2 + CO + H2 -RCH2CH2CHO
This reaction is carried out at about 150°C
and 250 atmospheres with a cobalt catalyst.
There are some by-products, which are sepa-
rated by distillation. If alcohols are desired,
they are made by hydrogenation in a separate
process step. Olefin conversion is over 95
percent.
Formaldehyde (HCHO) manufacture con-
sumes about 40 percent of all the methanol
produced annually in the United States.27
Methanol vapor and air are passed over a hot
catalyst at 1 atmosphere, and the gases are
absorbed in water. The following reactions
may occur, depending on the type of catalyst
used:
CH,OH-
HCHO + H2
CH3OH+ 1/2 O2
Since HCHO is thermodynamically unstable
and tends to decompose under the reaction
conditions into CO and H2, some CO is
always formed by partial decomposition of
HCHO. The product gases go directly to the
scrubbers, and CO leaves in the scrubber
off-gas.
4.3.7 Other Organic Compounds
A number of miscellaneous organic synthe-
ses involving CO have been worked out or
patented.
At least one plant abroad makes butanol as
follows:25
C3H6 +3CO + 2H2O-
C4 Ho OH+ 2 CO,
This reaction is carried out at 100°C and 220
pounds per square inch (gauge) with a catalyst
mixture containing iron pentacarbonyl.
By-products include propane, CO2, and
hydrogen; these are bled off, along with some
CO, through a scrubber. Most of the CO is
recycled back to the reactor.
The versatile and powerful solvent, di-
methyl formamide, can be made by the
following reaction involving CO37
(CH3)2NH + CO-
(CH3)2NOCH
This reaction is carried out at a temperature
of about 60°C and a pressure of 90 pounds
per square inch in the presence of sodium
methylate catalyst.
Diethyl ketone can be made by a reaction
involving CO:38
2C2H4+CO
CO C, H,
The yield given for this particular synthesis
was rather low, at only 20 percent.31
The preceding discussion has indicated that
CO is an important petrochemical feedstock;
its use may greatly increase at some future
time. It is available in enormous amounts in
the steel industry at a current rate of about
90 million tons per year from pig iron blast
furnaces, and 2.3 million tons per year from
basic oxygen furnaces. A variety of synthesis
gases could be made from these gases, using
steam and hot coke.
4.3.8 Emissions
All CO emissions in the chemical process
4-17
-------
industry come directly or indirectly from
processes involving synthesis gas. The various
synthesis gases always contain some inert
gases. As the reactive gases are consumed,
inert gases build up. They are commonly
purged from the system by continuously
bleeding off a small percentage of the total
gas stream. The reacting gas forms a consid-
erable percentage of this purge stream; and if
the reacting gas is CO, the purge represents a
potential emission of CO. One leading manu-
facturer of methanol, for instance, estimates
that emissions —including those from
purging—range from 0.2 pound of CO per ton
of methanol produced in a modern single-line
plant, to 15 pounds of CO per ton produced in
a relatively old multiple-line plant.39 If 70
percent of the 1968 methanol was produced in
modern, single-line plants, the CO emission
from all plants would have been less than
4,000 tons. In addition to the above emissions,
methanol plants may vent CO from high stacks
during periods of startup, shutdown, or circuit
upset. A 600-ton-per-day methanol plant may
vent a mixture of the H2 and CO containing
about 10,000 standard cubic feet per minute
of CO, under such conditions, for periods up
to several hours.
Carbon monoxide emissions from formal-
dehyde manufacture are about 0.05 pound
for each pound of formaldehyde produced.39
Based on production figures, CO emissions
amounted to 34,000 tons in 1967.
Carbon monoxide is not one of the easiest
materials to burn; thus, emissions often are
released when it is used as fuel, or is inciner-
ated.40'4 1 The lower and upper flammability
limits are 12.5 and 74 percent by volume.
Leaks, a source of emissions and a source of
economic loss to the industry, are a continu-
ous problem to engineering and maintenance
personnel.42 Leaks occur from shaft seals,
such as the stuffing boxes for agitators and
pumps, and at fan and compressor shafts.
Valves can leak from stem-packing or faulty
seating. Flanges and gaskets are prone to
develop leaks, especially if all of the loading
conditions were not recognized and investi-
gated during design.
Operation of safety valves may release large
amounts of CO for a short time, and poor
reseating of the blown valve can prolong the
emission. Rupture discs, sometimes installed
to protect equipment from overpressure, re-
lease all the gas in a given system, if ruptured.
Safety valves and rupture discs are usually
manifolded to a relief system having a flare or
stack. In the event of a line break, gas is
released just as in the case of a rupture disc,
except that this release is directly to the
atmosphere.
Operating areas and compressor houses are
often monitored continuously for CO. Un-
scheduled shutdowns, such as those caused by
power failures, sometimes result in sudden
releases of gases.
On high-pressure systems, these gases oper-
ate the safety valves, as just noted. Systems
operating near atmospheric pressure may re-
lease CO and other gases at a temporarily high
rate through water seal pots.
4.3.9 Control Techniques
Although significant amounts of CO are
generated and handled by the chemical in-
dustry of the United States, the emissions are
minor. This is because any appreciable emis-
sion would cause loss of the desired raw
material, regardless of whether the material is
CO itself, or hydrogen. Emission of these
gases would also constitute a toxic or fire
hazard.
The chemical industry adapted earlier refin-
ery and oil-processing know-how in making
equipment adaptations to satisfy its own
special needs. The result is that syntheses of
the type described herein are generally made
in continuous, automatically controlled pro-
cess plants. Such plants feature seamless pipe
and welded pressure vessels—made, assembled,
and tested strictly according to code.43'44
Piping and pressure vessel codes still reflect
the historic technical interdependence be-
tween the two industries. Continuous process-
ing was not developed to reduce air pollution;
but, as an incidental benefit, emissions of all
kinds tend to be less from continuous pro-
cesses than they are from batch processes.
4-18
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Design codes are mainly responsible for low
CO emissions in the chemical process indus-
tries.45'46 The code followed for piping has
been the United States of America Standards
Institute Code B 31.3 for Petroleum Refinery
Piping. This code gives minimum standards,
but acts as a guide to chemical construction
firms and engineering staffs of the chemical
industry. A piping code for the chemical
industry is now nearing completion, and
publication4 s is planned for 1970. This will
be Code B 31.6 for Chemical Plant Piping.46
It differs from the old Code B 31.3, mainly,
in that it includes provision for handling
lethal fluids (such as HCN gas) and design
rules for piping items that are damageable
mechanically, such as glass.
Another important code is the American
Society of Mechanical Engineers (ASME)
Code for Unfired Pressure Vessels, Section
VIII. Vessels are an important part of most
chemical plants and include reactors, surge
tanks, separators, and many other kinds of
equipment. Approximately 25 of the states
currently require compliance with this code.
The code is long and complicated: in addition
to many details of design and strength of
materials, it considers such things as pneu-
matic and hydrostatic tests, inspection of
welds, and qualification and testing of weld-
ers. For these reasons, vessel failures are
extremely rare when vessels are used as
designed in accordance with this code. In the
case of synthesis gas, the hydrogen, not the
CO, is the difficult component to contain.
The type of steel used retains the hydrogen.
The steel is specified for the process condi-
tions expected.4 7
Purge gas composition depends upon the
use to which the original synthesis gas was
put, and may be high in CO. One methanol
manufacturer reports that he sends methanol
synthesis purge gas to the reformers that
make ammonia synthesis gas. A common
method of control for purge gas is to send it
to the plant fuel system48 or to pipe it
directly to a boiler.2 4 It may also be burned
in a flare.
Flaring is often used to burn miscellaneous
waste vapors, and, also, to control emergency
vapor releases. A flare is a flame maintained
out of doors at the end of a waste-gas-collec-
tion system; it burns both regular and emer-
gency emissions.
Pressure vessels, heat exchangers, and pipe-
lines are commonly protected against over-
pressure by safety (or relief) valves or rupture
discs.49'50 These devices are specified in a
manner consistent with the requirements of
the piping and pressure-vessel codes men-
tioned above. The spring-loaded safety valve
opens to relieve pressure in the system and
then reseats itself. The rupture disc is a thin
metal diaphragm installed between flanges
and carefully designed to rupture at a certain
difference in pressure on the two sides.
Normally, the outside pressure on the disc is
atmospheric. Rupture discs are available in
many metals, from aluminum to platinum,
and in many alloys. Discs must be made of
corrosion-resistant materials because the rup-
ture strength is altered by only slight metal
attack.
Safety valves are normally required to pro-
tect individual vessels, heat exchangers, and
even sections of piping that can be blocked
off for any reason. To specify safety-valve
protection, each equipment piece or plant
section to be protected is carefully examined
with respect to what can go wrong. Typical of
conditions investigated would be: (1) chemi-
cal reaction out of control, (2) failure of
cooling water, (3) bursting of an exchanger
tube, (4) blocking off a vessel or line, and (5)
fire. These conditions may all give rise to gas
evolution and overpressure. Fire is often the
governing condition through which the most
vapor is generated. Fire is often, therefore,
the basis of design of the safety valve or
rupture disc.
After the safety valves are sized and speci-
fied, the vapor-collection system is designed.
This system receives gas and liquid from the
discharge side of the safety valves and rupture
discs, and conveys the gases to a flare or
stack. At least one knockout drum51 is
commonly furnished to separate liquid from
4-19
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the gas stream. The flare itself is commonly
an elevated stack having a pilot burner to
ignite the discharged gas. In designing the
collection system, allowance is made for the
variation from normal to emergency flow: a
small bypass can take care of normal gas flow
and a water seal can accommodate very large
gas flows. Actually, water seal pots have been
used in reformer plants to limit pressure in
the system and to release sudden gas accumu-
lations.
Figure 4—9 illustrates a typical blowdown
and relief-collection system and flare, such as
may be used in a chemical plant or complex.
The collection header for blowdown and
relief, discharges into a separator drum51 to
remove liquid droplets before going to the
stack. Separated liquid is pumped off to
disposal. An inert purge gas, such as nitrogen,
prevents flame flashback. Safe operation can
be obtained by purging at such a rate that the
.oxygen concentration in the stack 25 feet
from the top is less than 6 percent.5 2 Purging
is costly, and molecular seals5 3 are now
commonly used to reduce purge-gas require-
ments and reduce emissions to the at-
mosphere. During startup, the headers may be
purged with fuel gas, prior to igniting the
flare; the flare is ignited by a pilot gas flame
at the flare tip. The flame arrester, shown at
the base of the flare stack in Figure 4—9 is
included for added insurance against flame
flashback. The flare can be extinguished by
flame blowout due to too-high-flare-gas veloc-
ity. This would release CO, but blowout is
prevented by designing within certain stack
velocities. If blowout occurs, remote re-
ignition is accomplished by the pilot burner.
Safety and the effect of heat radiation are
important considerations in flare design.54
Because a large flare may radiate enormous
amounts of heat, it may have to be elevated
and distant from structures and personnel.
Many flare stacks are 200 feet high or more.
PURGE GAS
INLETS FROM RELIEF
VALVES AND
BLOWDOWN
GLASS
LIQUID TO WASTE
-RESTRICTION
ORIFICE
SEPARATOR
DRUM
3-
FLARE STACK, TOP 20
FEET TO BE HEAT •
RESISTING METAL
FLAME ARRESTOR
(ELECTRICALLY
HEATED IN
SEVERELY COLD
REGIONS)
PILOT LIGHT
_ FUEL
*~ GAS
WASTE PUMP'
DRAIN
DRAIN
Figure 4-9. Blowdown and relief collection system.
4-20
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4.3.10 Cost of Control
The following installed costs of flares 100
feet high, presented in Table 4-6, include:
guying, caged ladder, pilot and ignition sys-
tem, and engineering. They do not include
separator drum, flare piping, gas piping, elec-
tric lighting, and real estate. The given costs
are for smoking-type flares, suitable for dis-
posing of the CO-containing gases previously
discussed; by contrast, oil refinery flares
should be the smokeless type, because they so
often burn smoke-producing material. Op-
erating costs estimates are based on a natural
gas cost of $0.35 per 1,000 cubic feet. Flares
Table 4-6 COST OF FLARES5 5
Flare-stack
diameter, inches
12
24
Costs
Capital
$48,000
60,000
Annual operating
Pilot gas
$1,000
1,000
Purge gas
$1,000
4,000
are low-mainteance items, with replacements
most commonly being in the ignition system.
Flares suitable for upset conditions in am-
monia and methanol plants will be closer to
the 24-inch-diameter size. The above capital
costs do not take into account the piping runs
to the flare; for remote flare locations, the
capital costs of these piping runs can be
substantial.
Control of CO emissions from all of the
processes described in this section is inherent
in the design and construction of the plants.
Capital cost of control would be a sum
subjectively arrived at by allocation of facil-
ities. The difficulties in allocation are obvious,
and it is perhaps for this reason that there is
no information in the literature about costs of
control for the plants described above.
4.4 CARBON BLACK MANUFACTURING
PLANTS
The carbon black industry in the United
States has grown at a rate of 4 percent per
year56 from 1945 through 1965. At the end
of 1967, the industry's nine producers had 35
plants whose yearly production capability
totaled 3.102 billion pounds.57 Actual total
production in 1967 was 2.484 billion pounds
of carbon black. In 1968, two more large plants
were put in operation; each has a capacity of
100 million pounds per year.5 8 •5 9
Most of the carbon black produced (93
percent) is used in the rubber industry to
reinforce rubber. Essentially, it provides abra-
sion resistance to retard wear in products such
as tires. In the paint and ink industries,
carbon black is used as a colorant. It is also
used in the food, plastics, and paper indus-
tries.
Carbon monoxide is evolved in the produc-
tion of carbon black. Carbon black is pro-
duced by the partial breakdown of certain
hydrocarbons to elemental carbon and other
by-products, including CO. This hydrocarbon
breakdown is usually accomplished by
thermal cracking (thermal process) or by
incomplete combustion (furnace and channel
processes). All of these methods can produce
CO.
In the United States, 6 percent of the
carbon black is produced by the channel
process, 12 percent by the thermal process,
and 82 percent by the furnace process. Figure
4—10 is a flow diagram of a typical carbon
black plant. As shown in Figure 4— 10, CO is
produced in the carbon black process. CO can
be emitted from leaks in the cyclones, bag
filter, exhaust system after the fan, or from
connecting duct work. Some CO, trapped
between carbon black particles, might escape
in the grinder or in storage, but this amount
would probably be very minor, compared to
that from the exhaust system.
4.4.1 Channel Black
Channel black is produced by impinging a
natural gas flame on a relatively cool iron
plate or channel. Because the distance be-
tween the gas tip and the channel is too short
to allow complete combustion, the unburned
carbon is deposited on the channel as carbon
black. Channel black is made on a continuous
basis in buildings called "hot houses," con-
taining 2,000 to 4,000 flames, which impinge
4-21
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A
OIL OR GAS-
AIR
FURNACE
COMBUSTION
GASES
CONTAINING
CO TO
ATMOSPHERE
BAG FILTER
SECONDARY
CYCLONE
NOTE: CO EMISSIONS CAN
COME FROM LEAKS IN DUCT-
WORK, CYCLONES, FILTER
JPELLETIZER]-->£
STORAGE
FOR
CARBON
BLACK
Figure 4-10. Typical diagram for carbon black manufacture.
on moving channels. The black is then auto-
matically scraped from the channels and
conveyed to the product-handling system.
Each hot house uses 150,000 to 260,000
cubic feet of natural gas per day.60 The
temperature of the hot house is kept at about
1,000°F by the natural draft created in the
building. The yield of carbon black in the
channel process is about 2.5 pounds per 1,000
cubic feet of gas.60 Recently, because of the
rising cost of natural gas, the gas has been
enriched with cracked recycle and cracked
distillate oil. The yield from these oils is
about 2.5 pounds of black per gallon.
4.4.1.1 Emissions
The channel black process emits CO directly
to the atmosphere from the hot houses;
therefore, there is no practical method for
accurately determining the amount of CO
emitted. All of the CO produced in this
process goes to the atmosphere as CO because
it does not oxidize readily at process condi-
tions. A gross estimate of the CO emissions
4--22
-------
from the channel black process is 59,500 tons
per year.60
4.4.1.2 Control Techniques
Channel black is used as the colorant in ink
black6! because its properties cannot be
duplicated in the other two processes. The
channel process must have a natural draft
through the hot house. Any attempt to
confine the emissions from these hot houses
would disturb the natural draft and, thus,
reduce the yield and quality of the black. The
only control used is the moving of the entire
plant if the problem gets too bad in a
particular area. The particulate problems
would probably necessitate a move before the
CO would reach high enough levels to cause a
problem.
4.4.2 Thermal Black
Thermal black is produced by the decompo-
sition of natural gas in the absence of air or
flame. This thermal-cracking process takes
place in a checkerwork furnace or generator.
First, the furnace is heated to 2,400° to
2,800°F; then, the flue is closed, and the
natural gas is admitted to the generator. The
gas is decomposed principally to carbon and
hydrogen, with smaller quantities of CO,
CO2, methane, and nitrogen. The thermal
carbon black passes from the furnace, is
cooled, and is then collected. When the
furnace becomes cool, the gas is shut off and
the furnace is reheated with the gases (prin-
cipally hydrogen) produced in the cracking
process. The full cycle for this process takes
about 10 minutes, with the time being divided
about equally between heating and crack-
ing.60 Theoretically, if the natural gas were
all methane, 31.82 pounds of carbon black
and 2,000 cubic feet of hydrogen would be
produced per thousand cubic feet of methane.
The actual yield for the thermal process is 40
to 50 percent (up to 16 pounds of black per
thousand cubic feet of natural gas).60
Thermal black is coarse and does not have the
reinforcing properties or color of channel
black.
4.4.2.1 Emissions
Emissions from the thermal process are
estimated at 47 pounds of CO per ton of
thermal black or a yearly value of 3,500 tons
of CO. Since the gas given off during the
cracking process is used to reheat the checker-
work, however, much of this CO may be
further oxidized to CO2 during the reheating
phase.
4.4.2.2 Control Techniques
The thermal process emits a comparatively
small amount of CO when the exit gases are
reused to heat the checkerwork. The amount
is probably not enough to make it econom-
ically feasible to control the CO pollution.
4.4.3 Furnace Black
Furnace black, which can be divided into
gas-furnace black and oil-furnace black, is
produced by the incomplete combustion of
fuel (oil or gas) in a specially designed
furnace. To produce gas-furnace black, a
turbulent mixture of air and natural gas is
burned at 2,200°F. The ratio of air to gas
(4.5:1) does not allow complete combustion,
and results in the production of black. After
the black leaves the furnace, it is cooled,
agglomerated, and collected. The yield from
the gas furnace is 25 to 30 percent for the
larger-particle-size furnace black and 10 to 15
percent for the smaller-particle black.60
Sometimes the gas is enriched with oil.
To produce oil-furnace black, the oil is first
preheated to 550° to 700°F; then the air and
gas are fed at a constant ratio while the
weight of oil is varied to keep the furnace at
2,500°F. Different grades of black can be
produced by varying the temperature and
velocity in the furnace, or the geometry of
the furnace. A yield of 55 percent can be
expected from oil furnace black.60 Oil fur-
nace black tends to predominate in the
industry because of advanced technology and
the increasing cost of gas.5 6
4.4.3.1 Emissions
Carbon monoxide emissions from furnace-
black production vary from 5 to 11 percent
by volume in the exit gases.60 On the average,
560 pounds of CO is emitted per ton of
furnace black produced.60 This gives an
4-23
-------
estimated yearly emission of 285,000 tons of
CO from the production of furnace black.
4.4.3.2 Control Techniques
The furnace process may at some time have
to be controlled in the United States. Two
furnace plants in the United Kingdom are
now required to control their CO emis-
sions.60 A flare on the stack is being used
successfully to incinerate the CO.
Catalytic incineration is not practical for
CO concentrations in the 5 to 10 percent
range because the operating temperatures
would exceed 1,000°F, which is well above
the permissible operating temperature range
of the catalysts.62
4.5 PULP AND PAPER INDUSTRY
Carbon monoxide emissions from kraft pulp
mills are often overlooked. Potential sources
of CO emissions from these mills are recovery
furnaces and lime kilns. Bark-fired and fossil
fuel-fired boilers are other potential sources
of CO emissions. Carbon monoxide emissions
from boilers and control techniques for boiler
emissions are discussed in Section 3, "Indus-
trial Stationary Combustion Sources."
4.5.1 Kraft Pulp Mill Recovery Furnaces
All kraft pulp mills use one or more
recovery furnaces to recovery valuable chem-
icals and heat energy from the black liquor
produced in the wood digestion process. The
materials recovered or burned would other-
wise create a waste disposal problem and
represent an economic loss.
The kraft recovery furnace is a highly
specialized unit. Design of these units and
modification of design or modification of
operating conditions, therefore, require exten-
sive specialized knowledge and experience.
4.5.1.1 Emissions
Carbon monoxide emissions from United
States kraft recovery furnaces are estimated at
700,000 tons per year.63'64'65 CO emission
rates are estimated at 60 pounds per ton of
pulp produced.6 3 '6 5
Emissions of CO from individual furnaces
vary from as much as 2 percent when insuf-
ficient air is supplied, to a negligible level
when sufficient air is admitted.66
The kraft recovery furnace recovers the salt
content of waste cooking liquor. A reducing
atmosphere must be maintained in the fur-
nace to reduce the sodium sulfate content of
the liquor to sodium sulfide.67 This reduction
must take place so that the sodium ion can
remain soluble in the following lime caustici-
zation step. Reducing conditions form much
CO in the furnace, which would escape as
such were it not for the fact that additional
air is admitted above the furnace reducing
zone to oxidize CO. Thus, if the furnace is
operated as designed, very little CO is emit-
ted.
4.5.1.2 Control Techniques
With proper control of kraft-recovery fur-
nace combustion, CO emission levels are
below the range detectable with Orsat-type
instruments (0.2 percent).66 Combustion is
controlled by adjustment of primary and
secondary air and by monitoring the CO and
oxygen content of the combustion gases.
Many recovery furnaces operate with mini-
mum CO emissions when the oxygen content
of the combustion gases is adjusted to about 3
percent.
Since most kraft recovery furnaces are
designed by experienced manufacturers, fur-
nace design is seldom the cause of excessive
CO emissions. Almost invariably, the cause of
CO emissions is furnace operation well above
rated capacity—a situation wherein it is im-
possible to maintain oxidizing conditions in
the exit gas.
4.5.2 Lime Kilns
All kraft pulp mills use one or more lime
kilns to regenerate lime from calcium car-
bonate produced in the causticizing process.
4.5.2.1 Emissions
Carbon monoxide emissions from kraft pulp
mill lime kilns are estimated at 130,000 tons
per year. Carbon monoxide emission rates are
estimated at 10 pounds per ton of pulp
produced.6 4
4.5.2.2 Control Techniques
Because of the specialized nature of the
kraft pulp mill lime process, and the lack of
accurate data on CO emissions from the lime
4-24
-------
kilns, no proved CO emissions control tech-
niques are available for these specific sources.
These emissions could possibly be reduced,
however, through variations in the kiln air
supply, kiln temperatures, and increased tur-
bulence and reaction time. Kiln design modifi-
cation is a good possibility for new installa-
tions.
4.5.3 Costs
If CO emissions from kraft pulp mill re-
covery furnaces and lime kilns can be con-
trolled solely by increasing the quantity of air
admitted to the furnace or kiln, the cost of
reduction would be the cost of developing the
control technique and the cost of the heat
energy lost with the increased volume of stack
gases.
4.6 MISCELLANEOUS INDUSTRIAL
SOURCES
4.6.1 Electrometallurgical Furnaces
The submerged arc electric furnace is used
in the production of ferroalloys; Table 4—7
shows United States production in 1967.
Table 4-7. ELECTRIC FURNACE PRODUCTION
OF FERROALLOYS EM THE
UNITED STATES,7 1967.
(tons/year)
Ferroalloy
Ferromanganese
Ferrosilicon
Ferrochromium
Ferrochromsilicon
Ferrophosphorus
Silicomanganese
All others
Total
Production
280,000
528,000
263,000
154,000
1 1 1 ,000
230,000
259,000
1,825,000
Ferroalloys are made by reduction of suita-
ble oxides in the electric arc furnace. For
example, in making ferrochromium the charge
may consist of chrome ore, limestone, quartz
(silica), coal and wood chips, along with
scrap iron. In this case, the silica and lime
form a slag. For ferrosilicon, the charge would
consist mainly of iron scrap, silica, and coke.
In every case, CO is formed copiously and
escapes through the pores and channels in the
charge. The escaping gas carries large quanti-
ties of particulates, which are essentially
submicron in size (50 percent less than 0.1
micron), and which present a notoriously
difficult control problem. Particulate abate-
ment requires control equipment that bears
little relation to that required for the compar-
atively minor control problem presented by
CO.
The ferroalloy furnace, may be hooded for
collection of the off-gases, which will contain
as much as 85 percent CO, 2.5 percent CO2,
0.5 percent O2,10 percent H2, and 2 to 2.5
percent each CH4 and N2. Utilization of this
gas even as boiler fuel (approximate heating
value, 340 Btu per cubic foot) requires
scrubbing for removal of dust and is only
marginally economical. Most furnaces operate
with an open top and allow the CO to burn as
it escapes through the charge. Temperature of
the escaping CO is normally about 750°F, but
may be as much as 1,500°F. Residual CO
concentrations of several percent may be
present because of incomplete combustion
and the high equilibrium CO concentration at
flame temperatures.
Adequate ventilation is necessary in the
furnace areas to hold CO levels within safe
limits. CO monitors are employed to warn of
buildup of hazardous concentrations.
Figure 4— 11 illustrates an electric arc fur-
nace with dust control system typical of the
ferroalloy industry. The fan draws dilution air
into the system through the gap between
furnace body and cover. If a baghouse is used
instead of a wet scrubber, dilution air is even
more necessary, to lower the temperature of
the gas going to the bags. The CO burns inside
the furnace cover when it mixes with the
admitted air. Unburned CO goes through the
particulate control device and up the stack.
No emission factors are presently available for
these furnaces. With a tight hood, the CO
content of scrubbed gas will be 80 to 90
percent, and the gas can be used as boiler fuel
if a user is nearby; otherwise, the gas would
be flared.
Because these furnaces are extremely dusty,
there will be increasing pressure in the future
for particulate controls. Baghouses and other
4-25
-------
STACK
AIR IN AT
FURNACE
GAP -*
WATER PUMP
Figure 4-11. Electric furnace for
ferroalloys industry.
control devices would be lower in cost if the
furnace offgases could be cooled by radiation
or other methods, instead of by air dilution,
which increases the gas volume handled. This
would mean the use of closed systems, han-
dling and emitting relatively concentrated CO.
Potential CO emissions would be greatly
increased, but it might be possible to use the
gas as fuel or to flare it.
4.6.2 Silicon Carbide Furnaces
Silicon carbide is an important abrasive
manufactured by heating a mixture of sand
(SiO2) and coke to about 2,200°C in an
electric resistance furnace. The heat is gener-
ated by the resistance of the charge to a flow
of electric current passed through it. The
silicon-carbide furnace is illustrated in Figure
4-12. At these temperatures the reaction
proceeds as follows:
SiO, + 3C
-SiC + 2CO
The walls of the furnace are temporary, so
that they can be torn away from the charge
after completion of heating. The gases that
are formed work their way out of the porous
charge and escape to the atmosphere. Because
the surface of the charge is relatively cool,
some CO may escape unburned.
For every pound of silicon carbide formed,
1.4 pounds, or about 18 cubic feet of CO, is
formed. Although much of the released CO
burns above the furnace, the combustion is
uncontrolled and, undoubtedly, a considera-
ble portion dissipates into the ambient atmo-
sphere. Silicon carbide furnaces are not nor-
mally hooded for collecting CO or for provid-
ing excess air to dilute its concentration.
4.6.3 Calcium Carbide Furnaces
Calcium carbide is manufactured by heating
a mixture of quicklime (CaO) and carbon in
an electric arc furnace. The reaction proceeds
at about 2,100°C as follows:
CaO + 3C-
-Ca C2 + CO
ELECTRIC BUS BARS
POROUS CHARGE
CONDUCTING CORE
1 I I I I I I I I I I
I I I I I I I I I I I
Figure 4-12. Electric furnace for production of silicon carbide.
4-26
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The gases that are formed escape through the
porous charge. The use of high-grade raw
materials is necessary, because few impurities
are eliminated in manufacture. Metallurgical
coke, petroleum coke, or anthracite coal is
used as the source of carbon. The actual
reaction occurs between solid carbon and
liquid lime in the melt below the electrode
tips. The calcium carbide product is removed
from the bottom of the furnace as a liquid.
Calcium carbide furnaces are essentially the
same as ferroalloy furnaces, and may be
hooded to collect the CO evolved. Because
the offgas must be cleaned, even for utiliza-
tion as boiler fuel, the economics of recovery
is marginal. Adquate ventilation and monitor-
ing are necessary to prevent hazardous con-
centrations of CO in operating areas.
Competitive combustion processes for man-
ufacture of acetylene have largely supplanted
calcium carbide as a source material for
acetylene. The further burden of investment
and expense for pollution control is probably
not recoverable by increasing calcium carbide
prices.
4.6.4 Elemental Phosphorus Furnaces
Elemental phosphorus is made entirely by
an electric furnace process. A mixture of
phosphate rock, sand, and coke is heated in a
three-electrode (three phase) electric furnace
to about 1,500°C. The following equation
represents the overall reactions occurring:
4 Cas F (PO4)3 + 18 SiO2 + 30C
18 [CaO • SiO2 • 1/9 CaF2 ] + 30 CO + 3P4
Excess carbon is necessary to reduce iron,
which may be present in the charge; a small
fraction of the silicon is also reduced.6 8
The furnace (Figure 4—13) is operated at,
or very slightly under, atmospheric pressure.
The escaping gases are primarily CO, but they
do contain all of the P4 (gas), some dust, and
some SiF4 (gas). The dust is removed in an
electrostatic precipitator, after which the P4
is condensed as a liquid (m.p. 111°F) in a
water condenser. The residual gas is about 90
percent CO, the balance being H2, O2, and
CH4. This gas is burned as fuel in phosphate-
rock-drying kilns, or is flared if the kilns are
out of service.
Escape of CO from the furnace involves
simultaneous escape of P4, which is very
undesirable. CO emissions would, therefore,
be either accidental and temporary in dura-
tion, or due to incomplete combustion of the
washed gas.
GAS
OFFTAKE
RE-
FRACTORY
LINING
FEED
SPOUT
ELECTRODE
WATER-
COOLED
SEALING
— RING
Figure 4-13. Diagram of electric furnace for
production of elemental phosphorus.
4.6.5 Aluminum Reduction Cells
Aluminum is manufactured by the electro-
lysis of alumina (A12 O3) dissolved in a bath
of molten cryolite (Na3AlF6). Impurities are
removed from bauxite ore in the first step of
the process to avoid deposition in the metallic
aluminum. The cryolite renders the bath
electrically conducting; small amounts of
other fluorides are then added to lower the
melting point so that the cell operating
temperature is about 950°C. Both the cell
anode and cathode are made of carbon.
Metallic aluminum separates at the cathode,
and oxygen is released at the anode. Depend-
ing on the operating conditions in the elec-
trolytic cell, between 500 and 1,200 pounds
of CO is formed per ton of aluminum
produced.65 For a 1968 production of about
3.2 million tons of aluminum, 0.8 to 1.9
million tons of CO was formed. Much of the
CO burns upon exposure to the atmosphere
or in the afterburner of cells so equipped.
4-27
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4.7 REFERENCES FOR SECTION 4
1. Greaves, M. J. and A. English. Engineering
Contributions to New Techniques of Iron Ore
Agglomeration. In: Agglomeration, Knepper, W.
A. (ed.), New York, Interscience Publishers,
1962. p. 419453.
2. Voice, E. W. and R. Wild. The Influence of
Fundamental Factors on the Sintering Process.
In: Sintering Symposium, Port Pirie, Australia,
1958. Melbourne, The Australasian Institute of
Mining and Metallurgy, 1958. p. 21-59.
3. McGannon, H. E. The Making, Shaping and
Treating of Steel. 8th ed. Pittsburgh, United
States Steel Company, 1964. 1300 p.
4. Schueneman, J. J., M. D. High, and W. E. Bye.
Air Pollution Aspects of the Iron and Steel
Industry. U.S. DHEW, PHS, Division of Air Pollu-
tion. Washington, D. C. PHS Publication No.
999-AP-l. June 1963. 118 p.
5. Brandt, A. D. Current Status and Future
Prospects-Steel Industry Air Pollution Control.
In: Proceedings of the 3rd National Conference
on Air Pollution, December 12-14,1966. Wash-
ington, D. C. PHS Publication No. 1649. 1967. p.
236-241.
6. Jackson, A. Oxygen Steelmaking for Steel-
makers. London, George Newnes Ltd., 1964. 258
P-
7. A Systems Analysis Study of the Integrated Iron
and Steel Industry. Battelle Memorial Institute.
May 1969. Clearing House for Scientific and
Technical Information. Accession No. PB
184576, PB 184577. Springfield, Va.
8. Wheeler, D. H. Fume Control in L-D Plants. J.
Air Pollution Control Assoc. 75:98-101, Feb-
ruary 1968.
9. 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.
10. Foundry Air Pollution Control Manual. 2d. ed.
Des Plaines, American Foundrymen's Society,
1967.66 p.
11. The Cupola and Its Operation. 3d. ed. Des
Plaines, American Foundrymen's Society, 1965.
322 p.
12. Minerals Yearbook 1967, Vol. I-II. U. S. Dept.
of Interior, Bureau of Mines. Washington, D. C.
1968. p. 608.
13. Electric Furnace Steelmaking, Vol. II. Theory
and Fundamentals, Sims, C. E. (ed.). New York,
Interscience Publishers, 1963. p. 301.
14. DeCarlo, J. A., T. W. Hunter, and M. M. Otero.
Coke and Coal Chemicals. In: Minerals Yearbook
1961. U.S. Dept. of Interior, Bureau of Mines.
Washington, D.C. 1962. p. 205-267.
15. Powell, A. R. Gas From Coal Carbonization-
Preparation and Properties. In: Chemistry of
Coal Utilization, Lowry, H. H. (ed.). Vol. II. New
York, John Wiley & Sons, 1945. p. 921 -946.
16. North American Manufacturing Company Esti-
mate.
17. Ozolins, G. and R. Smith. A Rapid Survey
Technique for Estimating Community Air Pollu-
tion Emissions. U.S. DHEW, PHS, National Cen-
ter for Air Pollution Control. Cincinnati, Ohio.
PHS Publication No. 999-AP-29. 1967. p. 69.
18. Stormont, D. H. Crude Capacity in U. S. Sets a
Near-Record Pace for 1967. Oil Gas J.
66(14): 126-130+, April 1,1968.
19. Alexander, W. H. and R. L. Bradley. Can You
Justify a CO Boiler? Petrol. Refiner.
57:107-112, August 1958.
20. 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.
21. Petroleum Processing Handbook, Bland, W. F.
and R. L. Davidson (eds.). New York, McGraw-
Hill Book Co., 1097 p.
22. National Air Pollution Control Administration,
Reference Book of Nationwide Emissions. U.S.
DHEW, PHS, CPEHS, NAPCA. Durham, N. C.
23. Saxton, A. L., H. N. Weinberg, and R. 0. Wright.
Get Cheaper Coking Now with this New Design.
Petrol. Refiner. 59:157-160, May 1960.
24. Noyes, R. Ammonia and Synthesis Gas 1967.
Park Ridge, Noyes Development Corp., 1967.
177 p.
25. Synthesis Gas—Shell Development Co. Hydro-
carbon Processing. 46:227, November 1967.
26. Kirk-Othmer Encyclopedia of Chemical Technol-
ogy, Standen, A. (ed.). 2d ed. New York,
Interscience Publishers, 1963.
27. Elsbree, John J. Organic Chemicals. Chemical
Engineering News. 46(37), September 2,1968. p.
92A-94A.
28. 25th Inventory of New Processes and Technol-
ogy. Chem. Eng. 75(15): 104, July 15,1968.
29. Oil Paint and Drug Reporter, May 4,1964.
30. Egalon, R., R. Vanhille, and M. Willemyns.
Purification of Carbon Monoxide by Cupram-
monium Carbonate Solutions. Removal of Car-
bon Monoxide by Cuprammonium Carbonate
4-28
-------
Solutions. Ind. Eng. Chem. 47:887-899, May
1955.
31. Sittig, M. Organic Chemical Process Encyclopedia
1967. Park Ridge, Noyes Development Corp.,
1967.590 p.
32. Friedman, B. S. and S. M. Cotton. Production of
Acids and Esters. Sinclair Refining Co., U. S.
Patent No. 3,005,846). Official Gazette. U. S.
Patent Office. 777(4): 1081, October 1961.
33. Kurhajec, G. A., D. L. Johnston, and K. E.
Furman. Production of Carboxylic Acids (Shell
Oil Co., U. S. Patent No. 3,047,622). Official
Gazette U. S. Patent Office. 7S0(5):1731, July
1962.
34. Natta, G. and P. Pino. Preparation of Succinic
Acids (Lonza Electric and Chemical Works, Ltd.
U.S. Patent No. 2,851,486). Official Gazette U.S.
Patent Office. 7?4(2):484, September 1958.
35. Hagemeyer, H. J., Jr. and D. C. Hull. Process of
Producing Oxygenated Organic Compounds
(Eastman Kodak Co., U. S. Patent No.
2,784,167). Official Gazette U. S. Patent Office.
706(5): 1221, May 1956.
36. Jaros, S. and C. Roming, Jr. Production of
Aldehydes and Alcohols. Esso Research and
Engineering Co., U. S. Patent No. 3,119,876).
Official Gazette U. S. Patent Office. 79
-------
59. Del Gatto, J. V. Cabot Carbon Black Plant Goes
Commercial. Rubber World. A5
-------
5. WASTE INCINERATION AND OTHER BURNING
5.1 EMISSIONS
Preliminary results of a survey conducted
by the Public Health Service indicate that
household, commercial, and industrial solid-
waste production in the U. S. 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
collected for disposal, the remainder being
either disposed of onsite or handled by the
household or establishment itself.l
An estimated 177 million tons of this
material is burned in the open or in incinera-
tors.2 An additional 550 million tons of
agriculture waste and 1.1 billion ton.s of
mineral wastes are generated each year.l It is
estimated that half of the agricultural wastes
are burned in the open. Except for the
estimated 48 million tons of coal refuse
consumed by fire each year, no other mineral
wastes are burned.2 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.2
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, CO, and
smog-forming compounds such as aldehydes,
hydrocarbons, and organic acids—which
typify open burning—but tends to increase
nitrogen oxides emissions.
Figures 5—1 through 5—7 show various
basic types of incinerators. In a multiple-
chamber design, as illustrated in Figure 5—3,
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
CHARGING DOOR
-r /
COMBUSTION AIR
INLET OPENINGS
PRIMARY COMBUSTION -
CHAMBER
WASTE ^
PRIMARY BURNER ^
^ H ^ BAROMETRIC DAMPER
// 1
^OOO //
//\
/ " \
^ / // »
I
^
\
^^•GSJm&k
*:^^^^^^#v
v^tH?TsHM3Ss^w-*v-i^5
X ""->-
0_
GRATED
1
-u — u — Ln_r-Ln_r
1
1
1
I
1
i
I
i_r<,H
{/-- -3>
l
i
k
\m
rm
' )
-j~}i
-^^r
ASH PAN /
- SECONDARY COMBUSTION
CHAMBER
— SECONDARY BURNER
- FLUE GAS FLOW
Figure 5-1. Domestic gas-fired incinerator.
5-1
-------
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. Auxiliary
burners are sometimes installed in the mixing
chamber to increase combustion temperature
to about 1,400° to 1,800° F. As much as 150
percent excess air may be supplied in order to
promote oxidation of combustibles. Sizes and
configurations of incinerators vary with the
service for which they are designed. Refer-
ences 3 and 4 contain information on design
parameters for incinerators.
Estimated CO emissions from incineration
and other burning are shown in Table 5—1.
AIR DISTRIBUTION MANIFOLD
SELF-SUSTAINING AFTERBURNER SECTIONS
GAS SUPPLIED ONLY
DURING STARTUP
FORCED AIR BLOWER
CHARGING DOOR
WASTE
Figure 5-2. Single-chamber incinerator.
CHARGING DOOR WITH
OVERFIRE AIR PORT
IGNITION CHAMBER
FLAME PORT
SECONDARY AIR PORT'
CURTAIN WALL
GRATES
CLEANOUT DOORS WITH UNDERGRAT
AIR PORTS
LOCATION OF SECONDARY
BURNER
SECONDARY COMBUSTION
CHAMBER
BREECHING TO STACK
MIXING CHAMBER.
CURTAIN WALL PORT
CLEANOUT DOORS
Figure 5-3. Cutaway of in-line multiple-chamber incinerator.
5-2
-------
CHARGING DOOR-II OVERFIRE /
PRIMARY BURNER ~~
ASH PIT DOOR
60°
HEARTH
INCINERATOR
SIDE VIEW
Figure 5-4. Section of flue-fed incinerator.
MOTOR OPERATED
DAMPER
CHARGING CHUTE
ROOF
SAMPLING POINT
EXHAUST FLUE
SECONDARY BURNER
PRIMARY BURNER
CHARGING DOOR
PRIMARY DRAFT
ASH PIT DOOR
INCINERATOR
Figure 5-5. Section of chute-fed apartment incinerator.
5-3
-------
STORAGE
PIT
Figure 5-6. Section of pathological incinerator.
(Courtesy of Silent Glow Oil Burner Corp.)
SECONDARY
COMBUSTION
CHAMBER
TO GAS CLEANER
AND STACK
Figure 5-7. Section of municipal incinerator.
Table 5-1. ESTIMATED NATIONAL EMISSIONS IN 1968 FROM
INCINERATION AND OTHER BURNING2
(tons/year)
Source
Onsite incineration
Municipal incineration
Conical-burner incineration
Open burning
Agricultural burning
Prescribed forest burning
Forest wildfires
Structural fires
Coal-refuse fires
Total
Quantity burned
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
Carbon monoxide
emissions
780,000
20,000
3,600,000
3,400,000
8,250,000
2,480,000
4,740,000
250,000
1,200,000
24,720,000
5-4
-------
5.2 CONTROL TECHNIQUES
High-temperature incineration using excess
air, or alternative waste-disposal methods not
involving burning, are the most likely means
for reducing CO emissions. Some of these
methods are discussed in the following sec-
tions.
5.2.1 Waste Disposal
From the standpoint of air pollution con-
trol, the most satisfactory methods of waste
disposal are those that do not involve burning.
Sanitary landfills are good alternatives if land
for this purpose is available. Approximately
1.2 acre-feet of volume is required per 1,000
persons per year of operation when waste
production is 5.3 pounds per day per capita.5
In addition, cover material approximating 20
percent by volume, of the compacted waste is
required. Availability of fill material limits the
use of sanitary landfills.
Unusual local factors may ameliorate the
landfill site problem. For example, reference
6 indicates that a project is under way in
which the refuse is shredded and baled for
loading on rail cars for shipment to aban-
doned strip-mine landfill sites. Non-
combustion alternatives may have application
in some localities. Composting has been con-
sidered and is being tested on a practical
scale7 for disposal of garbage. 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 or unless
properly prepared. Such practices are now
forbidden by the United States Government.
A recent report8 states that refuse has been
ground and compressed into bales, which are
wrapped in chicken wire and coated with
asphalt. The high-density bales sink to the
bottom in the deeper ocean areas and, re-
portedly, remain intact. The practice of grind-
ing garbage in kitchen units and flushing it
down the sewer has been increasing. This, in
turn, increases the load on sewage-disposal
plants and the amount of sewage sludge.
5.2.2 Incineration
Although no exact criteria are set for
temperature, excess air, or residence time for
incinerators, incineration temperatures greater
than 1,600°F, excess air in a quantity of
more than 150 percent, and heat-release rates
less than 18,000 Btu per hour per cubic foot
of total combustion space are sometimes used
as design parameters for CO emission reduc-
tion. When these conditions are achieved, CO
emission rates are less than 1 pound per ton
of waste incinerated.9
Where the most effective CO emission con-
trol is desired, auxiliary burners are used to
increase incineration temperature to 1,600°
to 1,800° F. At temperatures above 1,800° F,
slagging of refractories is often a problem.
Even when dry, combustible wastes that will
burn at temperatures exceeding 1,600°F are
incinerated, auxiliary burners are useful for
preheating the secondary combustion sections
of the incinerator before the waste is ignited.
Temperature-control systems promote con-
sistent emission reduction. These usually con-
sist of on-off type controls for smaller units,
and modulating-type controls for larger incin-
erators.
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.1 ° For the most effective control, air
is passed through the grates (underfire air),
admitted over the burning waste (overfire air),
and admitted into chambers where auxiliary
burners are located (secondary air). The ratio
among these air supplies varies, 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 automatically regulated and, at
times, the ratio between air supply at various
points is automatically controlled. 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 heat-
release of 18,000 Btu per hour for each cubic
5-5
-------
foot of total combustion space is sometimes
used as a design parameter for determining
required combustion space. Contact between
gaseous combustibles and air is promoted
through the design by providing baffles,
bridge walls, checkerwork, curtain walls,
down passes, drop arches, and mixing cham-
bers; by introducing air at strategic locations;
and by locating auxiliary burners to promote
mixing.
Differences among CO emissions from var-
ious types of incinerators are caused by
differences in incineration conditions. Al-
though insufficient air, combustion space, and
mixing increase emission rates, the most
common cause of increased CO emission rates
is low incineration temperature. Estimates of
emission factors from various types of inciner-
ators are given in Section 6.
Another way of reducing total CO emis-
sions from incineration and combustion is by
recovering heat in a boiler, and thereby elim-
inating the need for combustion of some
fossil fuels. This means of refuse disposal has
already received considerable attention in
Europe,11"15 and has been tried in the
United States.16
5.2.3 Forest WUdfires
About 4.7 million tons of CO is emitted
annually from forest wildfires.2 These fires
are caused by natural elements such as light-
ning, or by careless practices. Considerable
activity has been and is being directed toward
reducing the frequency of occurrence and the
severity of these fires. These activities include
publishing 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 U.S. Department
of Interior and state and local agencies.
5.2.4 Controlled Vegetation-Burning
Forest debris, crop residues, scrub, brush,
weeds, grass, and other vegetation are burned
for one or more of the following purposes:
1. To control vegetation, insects, or organ-
isms harmful to plant life.
2. To reduce the volume of waste.
3. To minimize fire hazards.
4. To improve land.
Carbon monoxide emissions from this burn-
ing are estimated at about 10.7 million tons
per year.2
Collection and incineration of these wastes
in properly controlled incinerators would re-
duce emission rates from an estimated 60 to 65
pounds per ton to as little as 1 pound per ton.2
Other alternatives to incineration are aban-
donment or onsite-burial, transport and dis-
posal in remote areas, and utilization. Aban-
donment or onsite-burial is practical in cases
where no other harmful effects will ensue.
Since abandoned or buried vegetation can have
harmful effects upon plant life—e.g., hosting
harmful insects or organisms—agricultural
agencies such as the U.S. Department of Agri-
culture, state, and local agencies should be
consulted before these techniques are recom-
mended. Other harmful aspects, such as odor
or water pollution potential or fire hazards,
should also be considered. Collection and
transport of these materials for disposal in
areas where harmful effects are avoided is pos-
sible, 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 are used
as raw materials for kraft pulp mills or
processes producing fiberboard, charcoal bri-
quettes, or synthetic firewood.17 Composting
or animal-feeding are other possible alterna-
tives to burning.
5.2.5 Coal-Refuse Fires
An estimated 1.2 million tons of CO is
emitted each year from 19 billion cubic feet
of burning coal refuse.2 Extinguishing or
preventing such fires are the techniques used
for eliminating these emissions. These meth-
ods involve cooling and repiling the refuse,
sealing refuse with impervious material, inject-
ing slurries of non-combustibles into the
refuse, minimizing the quantity of combusti-
bles in the refuse, and preventing ignition of
the refuse. The above techniques and the
status of future plans and research are de-
scribed and discussed in AP—52, Control
Techniques for Sulfur Oxide Air Pollutants.18
5-6
-------
5.2.6 Structural Fires
Structural fires emit an estimated 250,000
tons of CO annually.2 Fire prevention and
control techniques are used to minimize these
expensive sources of emissions. Some of the
techniques used to prevent fires are: use of
fireproof construction; proper handling, stor-
age, and packaging of flammable materials;
and publishing and advertising information on
fire prevention. Fire control techniques in-
clude the various methods for promptly extin-
guishing fires, such as by the use of sprinklers,
foam, and inert gas systems. Also included is
the provision of adequate fire-fighting fa-
cilities, personnel, and alarm systems. Infor-
mation on these and other techniques for fire
prevention and control are available from
agencies, such as:
1. Local fire departments.
2. National Fire Protection Association.
3. National Safety Council.
4. Insurance companies.
5.3 COSTS OF CONTROLS
Costs of controls are primarily a function of
the relative costs of the various methods of
incineration and the costs of non-combustion
waste disposal. Because cost comparisons vary
widely with locality, they should be made on
an individual basis.
The average community budgets $5.39 per
capita per year for waste collection. Com-
munities operating their own facilities budget
about $6.80 per capita per year for semi-
weekly collection and about $5.60 per capita
per year for weekly collection.1 Sanitary
landfill costs—including amortization—have
been reported as $1.05 per ton for 27,000
tons of waste per year, and $1.27 per ton for
11,000 tons per year.1 Operating costs for
municipal incinerators are estimated at $4 to
$8 per ton of waste, and capital costs are
estimated at $6,000 to $13,000 per ton per
day capacity.19 Estimated capital costs of
smaller incinerators are given in AP—51,
Control Techniques for Paniculate Air Pollu-
tants.
20
Installed auxiliary burner costs range from
$2 to $6 per pound per hour incinerator
capacity.2 l Fuel requirements for increasing
incineration temperatures to 1,600°F with
150 percent excess air range from none for
dry combustible wastes, to an estimated
15,000 Btu per pound for a 3,500 Btu-per-
pound-gross-heating-value waste containing 75
percent free moisture.
5.4 REFERENCES FOR SECTION 5
1. Black, R. J. et al. The National Solids Wastes
Survey. Presented at 1968 Annual Meeting of the
Institute for Solid Wastes of the American Public
Works Association. Miami Beach, Fla. Oct. 1968,
53 p.
2. National Air Pollution Control Administration,
Reference Book of Nationwide Emissions. U.S.
DREW, PHS, CPEHS, NAPCA. Durham, N.C.
3. Incineration. In: 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. p. 413-503.
4. De Marco, Jack et al. Incinerator
Guidelines-1969. U.S. DHEW, PHS, CPEHS,
Environmental Control Administration.
Cincinnati, Ohio. SW-13TS. 176 p.
5. Kirsh, J. B. Sanitary Landfill. In: Element of
Solid Waste Management Training Course Man-
ual. Public Health Service. Cincinnati, Ohio.
1968. p. 1-4.
6. Air Pollution Problems from Refuse Disposal
Operations in the Delaware Valley. Dept. of
Public Health, Air Management Services. Phila-
delphia, Pa. February 1969.
7. Wiley, J. S. et al. Composting Developments in
the U. S. Combust. Sci. 6:2, 5-9, Summer 1965.
8. Kurker, C. Reducing Emissions from Refuse
Disposal. J. Air Pollution Control Assoc.
19:69-72, February 1969.
9. Stenburg, R. L. et al. Effects of High Volatile
Fuel on Incinerator Effluents. J. Air Pollution
Control Assoc., 5:376-384, August 1961.
10. IIA Incinerator Standards. New York, Incinera-
tor Institute of America, November 1968.
11. 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.
12. Eberhardt, H. European Practice in Refuse and
Sewage Sludge Disposal by Incineration. In:
Proceedings of 1966 National Incinerator Confer-
ence. New York, American Society of Mechani-
cal Engineers, 1966. p. 124-143
5-7
-------
13. Rogus, C. A. An Appraisal of Refuse Incineration
in Western Europe. In: Proceedings of 1966
National Incinerator Conference. New York,
American Society of Mechanical Engineers,
1966. p. 114-123.
14. 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.
15. Rousseau, H. The Large Plants for Incineration
of Domestic Refuse in the Paris Metropolitan
Area. In: Proceedings of the 1968 National
Incinerator Conference. New York, American
Society of Mechanical Engineers, 1968. p.
225-231.
16. Moore, H. C. and F. X. Reardon. A Salvage Fuel
Boiler Plant for Maximum Steam Production. In:
Proceedings of 1966 National Incinerator Confer-
ence. New York, American Society of Mechani-
cal Engineers, 1966. p. 252-258.
17. Private Communication with E. K. Taylor.
Southwest Air Pollution Control Authority,
State of Washington. October 1969.
18. Control Techniques for Sulfur Oxide Air
Pollutants. U.S. DHEW, PHS, CPEHS, National
Air Pollution Control Administration. Washing-
ton, D.C. AP-52. January 1969. p. 87-91.
19. Private Communication with H. L. Hickman.
Division of Technical Operations, Bureau of
Solid Waste Management. Rockville, Maryland.
November 1, 1968.
20. Control Techniques for Particulate Air Pollu-
tants. U.S. DHEW, PHS, CPEHS, National Air
Pollution Control Administration. Washington,
D.C. AP-51. January 1969. 215 p.
21. Private Survey of Incinerator Manufacturers.
National Air Pollution Control Administration.
October 1969.
5-i
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6. CARBON MONOXIDE 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. This
determination—together with meteorological,
air quality and effects sampling programs, and
strong enforcement actions—fulfills the re-
quirements for local, state, and Federal air
pollution control activities.
An adequate emission investigation will
provide evidence of source emissions and
define the location, magnitude, frequency,
duration, and relative contribution of these
emissions. This emission survey of pollutants
will include emission rates from fuel combus-
tion at stationary and mobile sources, solid
waste disposal, and industrial process losses.
Ideally, to determine emission rates, a stack
analysis of each source of interest would be
necessary. This is impractical, of course, when
an air pollution survey must cover a large land
area that could contain many thousands of
sources. Emissions must be estimated from
sources that do not have accurate stack-gas
analyses. Estimates are arrived at by the use
of emission factors, which are estimates of
pollutant emission rates based on past stack-
sampling data, material balances, and engi-
neering appraisals of sources that are similar
to those in question.
Table 6—1 is a compilation of available
emission factors for CO from various types of
Table 6-1. CARBON MONOXIDE EMISSION FACTORS
Source
Emission factor2
Reference
Stationary fuel combustion
Coal
Less than 10 x 106 Btu/hr capacity
10 to 100 x 106 Btu/hr capacity
Greater than 100 x 106 Btu/hr
capacity
Fuel oil
Less than 100 x 106 Btu/hr
capacity
More than 100 x 106 Btu/hr
capacity
Natural gas
Less than 100 x 106 Btu/hr
capacity
More than 100 x 106 Btu/hr
capacity
Wood
Solid waste disposal
Open burning onsite of leaves,
brush, paper, etc.
Open-burning dump
Municipal incinerator
50 Ib/ton of coal burned
3 Ib/ton of coal burned
0.5 Ib/ton of coal burned
2 lb/1,000 gal of oil burned
0.04 lb/1,000 gal of oil burned
0.41b/106 ft3 of gas burned
Negligible lb/106 ft3 of gas burned
30—65 Ib/ton of wood burned
60 Ib/ton of waste burned
85 Ib/ton of waste burned
1 Ib/ton of waste burnedd
6-1
1,2,3
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Table 6-1. CARBON MONOXIDE EMISSION FACTORS cont.
Source
Emission factor4
Reference
Commercial and industrial multiple
chamber incinerator
Commercial and industrial single
chamber incinerator
Flue-fed incinerator
Domestic incinerator
Process industries (specific examples)
Gray iron foundry
Cupola
Uncontrolled
Controlled with afterburner
Iron and steel manufacture
Blast furnace
Basic oxygen furnace
Petroleum refinery
Fluid catalytic unit
Moving-bed catalytic cracking
unit
10 Ib/ton of waste burned
44 Ib/ton of waste burned
27 Ib/ton of waste burned
200 Ib/ton of waste burned
250 Ib/ton of charge
8 Ib/ton of charge
1,700-250 Ib/ton of pig iron produced0
124-152 Ib/ton of steel produced*1
13,700 lb/1,000 bbl fresh feed6
3,800 lb/1,000 bbl fresh feed6
5,6
5,6,7
aThese emissions are from uncontrolled sources, unless otherwise noted.
bThis represents excellent design and operation.
cPractically all of the CO is burned for heating purposes or in waste gas flares.
dGases emitted from a basic oxygen furnace during the blowing period contain 87 percent CO. After ignition of the gases above
the furnace, the CO amounts to 0.0-0.3 percent.
eThese emissions are completely controlled when CO waste heat boilers are utilized.
sources. These emission rates represent uncon-
trolled sources, unless otherwise noted. These
emission factors apply best to areas, rather
than to specific sources; actual measurements
are preferable when calculations are made for
specific sources, but emission factors can be
used when data are lacking. For a specific
source where control equipment is utilized,
the listed uncontrolled process source emis-
sion rates must be multiplied by 1 minus the
percent efficiency of the equipment expressed
in hundredths. Except where noted, emission
factors are from a Public Health Service
Publication.1
There are of course, many other process
sources of CO emissions. Emission factors for
other miscellaneous process sources can be
found through literature searches, stack-gas
testing, and material balances on the process
in question. It must be remembered that the
emission factors listed herein are average
values and can vary, depending on operating
conditions and other factors.
Examples of how to use emission factors are
given below.
1. Fuel oil combustion:
Given: Power plant burns 50,000,000 gal-
lons of fuel oil per year
(50,000,000^) (0.04 !!L°nC?)
yr 1000 gal
=2,000
IbofCO
yr
2. Petroleum refinery:
Given: 50,000 bbl/day catalytic cracking
unit operating 355 days/yr with
CO boiler having 99.7% control.
x 355
days =
yr
QQQ
Ib CO
yr
3. Solid waste disposal:
Given: Apartment complex having flue-
fed incinerator which burns 5,000
tons per year
6-2
-------
(5,000^5) (27
1 b ot CO
yr ton of waste
IbofCO
135,000
6.1 REFERENCES FOR SECTION 6
1. Duprey, R. L. Compilation of Air Pollutant
Emission Factors. U.S. DHEW, PHS, National
Center for Air Pollution Control. Durham, N.C.
PHS Publication No. 999-AP-42.
2. Procedure for Conducting Comprehensive Air
Pollution Surveys. New York State Dept. of
Health, Bureau of Air Pollution Control Services.
Albany, N.Y. August 18,1965.
3. Gerstle, R. W. and D. A. Kemnitz. Amospheric
Emissions From Open Burning. J. Air Pollution
Control Assoc. 17:324-327, May 1967.
4. Lozano, E. R. et al. Air Pollution Emissions trom
Jet Engines. Presented at the Air Pollution Control
Association Meeting. Cleveland, Ohio. June 1967.
5. Schueneman, J. J., M. D. High, and W..E. Bye. Air
Pollution Aspects of the Iron and Steel Industry.
U.S. DHEW, PHS, Division of Air Pollution.
Washington, D.C. PHS Publication Number
999-AP-I.June 1963. 118 p.
6. A Systems Analysis Study of the Integrated Iron
and Steel Industry. Battelle Memorial Institute.
May 1969. Clearing House for Scientific and
Technical Information. Accession No. PB 184576,
PB 184577. Springfield, Virginia.
7. Wheeler, D. H. Fume Control in L-D Plants. J. Air
Pollution Control Assoc.75:98-101, February
1968.
6-3
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SUBJECT INDEX
Aldehydes, 4-17
Aluminum reduction cells, 4-27
Ammonia, 4-15-4-16
B
Basic oxygen furnaces, 4-3—4-5
Blast furnaces, 4-2-4-3
Calcium carbide furnaces, 4-26—4-27
Carbon black manufacturing plants,
4-21-4-24
Carbon monoxide emission factors, 6-1—6-3
Catalytic operations, 4-10—4-13
Channel black production, 4-21—4-23
Chemical industry, 4-14—4-21
Coal-burning units (See Grate-fired coal-
burning units)
Coal-refuse fires, 5-6
Coke ovens, 4-8-4-9
Combustion equipment (See Design of com-
bustion equipment)
Controlled vegetation burning, 5-6
Control techniques
basic oxygen furnaces, 4-3—4-5
blast furnaces, 4-3
calcium carbide furnaces, 4-26
channel black production, 4-23
chemical industry, 4-18—4-20
coal-refuse fires, 5-6
coke ovens, 4-9
controlled vegetation burning, 5-6
electrometallurgical furnaces, 4-25—4-26
energy source substitution, 3-7
fluid cokers, 4-13
forest wildfires, 5-6
furnace black production 4-24
good practice, 3-3—3-7
iron cupolas, 4-6—4-7
kraft pulp mill recovery furnaces, 4-24
lime kilns, 4-24-4-25
petroleum refineries, 4-11-4-13
silicon carbide furnaces, 4-26
structural fires, 5-7
waste incineration and other burning,
5-5-5-7
Cost of controls
calcium carbide furnaces, 4-27
chemical industry, 4-21
iron and steel industry, 4-9—4-10
kraft pulp mill recovery furnaces, 4-25
petroleum refineries, 4-13—4-14
waste incineration and other burning, 5-7
D
Design of combustion equipment
effect on emissions, 3-2—3-3
E
Electric furnaces, 4-7
Electrometallurgical furnaces, 4-25—4-26
Elemental phosphorus furnaces, 4-27
Emission factors (See Carbon monoxide emis-
sion factors)
Emissions of carbon monoxide
aluminum reduction cells, 4-27
basic oxygen furnaces, 4-3
blast furnaces, 4-2—4-3
calcium carbide furnaces, 4-26—4-27
carbon black manufacturing plants,
4-21-4-24
channel black production, 4-22—4-23
chemical industry, 4-18
coal-refuse fires, 5-6
coke ovens, 4-9
controlled vegetation burning, 5-6
electric furnaces, 4-7—4-8
electrometallurgical furnaces, 4-25—4-26
elemental phosphorus furnaces, 4-27
fluid cokers, 4-13
forest wildfires, 5-6
furnace black production, 4-23—4-24
general, 2-1-2-2,3-2-3-3
grate-fired coal-burning units, 3-3
iron cupolas, 4-6
kraft pulp mill recovery furnaces, 4-24
lime kilns, 4-24
petroleum refineries, 4-10—4-11
1-1
-------
pulp and paper industry, 4-24
silicon carbide furnaces, 4-26
sintering operations, 4-1—4-2
structural fires, 5-7
suspension coal-fired boiler units, 3-3
thermal black production, 4-23
waste incineration and other burning,
5-1-5-4
Energy source substitution, 3-7
Fluid cokers, 4-13
Forest wildfires, 5-6
Fuel consumption
stationary combustion sources, 3-1
Furnace black production, 4-23—4-24
Grate-fired coal-burning units, 3-3
I
Incineration (See Waste incineration and
other burning)
Iron and steel industry, 4-1—4-10
Iron cupolas, 4-5—4-7
K
Kraft pulp mill recovery furnaces, 4-24
L
Lime kilns, 4-24-4-25
Methanol, 4-15
M
O
Organic acids, 4-16—4-17
Organic compounds, 4-17—4-18
Petroleum refineries, 4-10—4-14
Phosgene, 4-16
Phosphorus furnaces (See Elemental phos-
phorus furnaces)
Power generation for various energy sources,
3-1
Pulp and paper industry, 4-24—4-25
R
Refineries (See Petroleum refineries)
S
Silicon carbide furnaces, 4-26
Sinter plants, 4-1-4-2
Sources of carbon monoxide
aluminum reduction cells, 4-27
basic oxygen furnaces, 4-3
blast furnaces, 4-2—4-3
calcium carbide furnaces, 4-26—4-27
carbon black manufacturing plants,
4-21-4-24
channel black production, 4-21 —4-22
chemical industry, 4-14—4-21
coal-refuse fires, 5-6
coke ovens, 4-8—4-9
controlled vegetation burning, 5-6
electric furnaces, 4-7—4-8
electrometallurgical furnaces, 4-25—4-26
elemental phosphorus furnaces, 4-27
fluid cokers, 4-13
forest wildfires, 5-6
furnace black, 4-23-4-24
general, 2-1-2-2
iron and steel industry, 4-1—4-10
iron cupolas, 4-5—4-7
kraft pulp mill recovery furnaces, 4-24
petroleum refineries, 4-10—4-14
pulp and paper industry, 4-24-4-25
silicon carbide furnaces, 4-26
sinter plants, 4-1
stationary combustion sources, 3-1—3-2
structural fires, 5-7
thermal black production, 4-23
waste incineration and other burning,
5-1-5-7
Steam-electric generating plants, 3-1
Structural fires, 5-7
Suspension coal-fired boiler units, 3-3
Synthesis gases, 4-14—4-15
1-2
-------
T
Thermal black production, 4-23
V
Vegetation burning (See Controlled vegatation
burning)
W
Waste incineration and other burning,
5-1-5-7
1-3
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