AP-42
Supplement 15e,/
SUPPLEMENT NO. 15
FOR
COMPILATION
OF AIR POLLUTANT
EMISSION FACTORS,
THIRD EDITION
(INCLUDING SUPPLEMENTS 1-7)
U S. Environmental Protection Agency
Region V, Library
230 South Dearborn Street
Chicago, Illinois 60604
U.S. ENVIRONMENTAL PROTECTION AGENCY
Office of Air, Noise and Radiation
Office of Air Quality Planning and Standards
Research Triangie Park, North Carolina 27711
January 1984
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PUBLICATIONS IN SERIES (CONT'D)
Issuance
Supplement No. 13
Release Date
8/82
Section 1.1
Section 1.3
Section 1.4
Section 1.5
Section 1.6
Section 1.7
Section 3.3.4
Section 4.2.2.8
Section 4.2.2.9
Section 4.2.2.10
Section 4
Section 5
Section 5
7
Section
.11
.16
.20
.15
Section 8.23
Bituminous and Subbituminous Coal Combustion
Fuel Oil Combustion
Natural Gas Combustion
Liquefied Petroleum Gas Combustion
Wood Waste Combustion In Boilers
Lignite Combustion
Stationary Large Bore Diesel and Dual Fuel Engines
Automobile and Light Duty Truck Surface Coating
Pressure Sensitive Tapes and Labels
Metal Coil Surface Coating
Textile Fabric Printing
Sodium Carbonate
Synthetic Rubber
Storage Battery Production
Metallic Minerals Processing
Supplement No. 14
Section 1.2 Anthracite Coal Combustion
Section 1.6 Wood Waste Combustion In Boilers
Section 1.9 Residential Fireplaces
Section 1.10 Wood Stoves
Section 2.4 Open Burning
Section 4.2.2.11 Large Appliance Surface Coating
Section 4.2.2.12 Metal Furniture Surface Coating
Section 5.1 Adipic Acid
Section 5.2 Synthetic Ammonia
Section 5.3 Carbon Black
Section 5.4 Charcoal
Section 5.6 Explosives
Section 5.10 Paint And Varnish
Section 5.12 Phthalic Anhydride
Section 5.14 Printing Ink
Section 5.15 Soap And Detergents
Section 5.21 Terephthalic Acid
Section 5.24 Maleic Anhydride
Section 7.1 Primary Aluminum Production
Section 7.5 Iron And Steel Production
Section 8.14 Gypsum Manufacturing
Section 8.19 Construction Aggregate Processing
Section 8.19.1 Sand And Gravel Processing
Section 8.22 Taconite Ore Processing
Section 8.24 Western Surface Coal Mining
Section 11.2 Fugitive Dust Sources
Section 11.2.1 Unpaved Roads
Section 11.2.2 Agricultural Tilling
Section 11.2.3 Aggregate Handling And Storage
Section 11.2.6 Industrial Paved Roads
5/83
ix
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PUBLICATIONS IN SERIES (CONT'D)
Issuance
Supplement 15
Release Date
1/84
Section
Section
Section
Section
Section
Section
Section
Section
Section
Section
Section
Section
Section
Section
Section
Section
Section
3.3.4 Stationary Large Bore Diesel And Dual Fuel Engines
4.2.2.1 General Industrial Surface Coating
4.2.2.2 Can Coating
4.2.2.3 Magnet Wire Coating
4.2.2.4 Other Metal Coating
4.2.2.5 Flat Wood Interior Panel Coating
4.2.2.6 Paper Coating
4.2.2.7 Fabric Coating
4.8 Drum Burning
6.6 Fish Processing
6.8 Ammonium Nitrate
6.14 Urea
7.1 Primary Aluminum Production
7.3 Primary Copper Smelting
8.1 Asphaltic Concrete Plants
8.4 Calcium Carbide Manufacturing
11.2.2 Agricultural Tilling
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3.3.4 STATIONARY LARGE BORE DIESEL AND DUAL FUEL ENGINES
3.3.4.1 General
The primary domestic use of large bore'diesel engines, i.e., those
greater than 560 cubic inch displacement per cylinder (CID/CYL) , is in oil
and gas exploration and production. These engines, in groups of three to
five, supply mechanical power to operate drilling (rotary table), mud pump-
ing and hoisting equipment, and may also operate pumps or auxiliary power
generators. Another frequent application of large bore diesels is elec-
tricity generation for both base and standby service. Smaller uses include
irrigation, hoisting and nuclear power plant emergency cooling water pump
operation.
Dual fuel engines were developed to obtain compression ignition
performance and the economy of natural gas, using a minimum of 5 to 6 percent
diesel fuel to ignite the natural gas. Dual fuel large bore engines (greater
than 560 CID/CYL) have been used almost exclusively for prime electric power
generation .
3.3.4.2 Emissions and Controls
The primary pollutant of concern from large bore diesel and dual fuel
engines is NOx, which readily forms in the high temperature, pressure and
excess air environment found in these engines. Lesser amounts of carbon
monoxide and hydrocarbons are also emitted. Sulfur dioxide emissions will
usually be quite low because of the negligible sulfur content of diesel
fuels and natural gas.
The major variables affecting NOX emissions from diesel engines are
injection timing, manifold air temperature, engine speed, engine load and
ambient humidity. In general, NOX emissions decrease with increasing
humidity.
Because NOx is the primary pollutant from diesel and dual fuel engines ,
control measures to date have been directed mainly at limiting NOX emis-
sions. The most effective NOX control technique for diesel engines is fuel
injection retard, achieving reductions (at eight degrees of retard) of up to
40 percent. Additional NOX reductions are possible with combined retard and
air/fuel ratio change. Both retarded fuel injection (8°) and air/fuel ratio
change of five percent are also effective in reducing NC^ emissions from
dual fuel engines, achieving nominal NOx reductions of about 40 percent and
maximum NC^x reductions of up to 70 percent.
Other NOX control techniques exist but are not considered feasible
because of excessive fuel penalties, capital cost, or maintenance or opera-
tional problems. These techniques include exhaust gas recirculation (EGR) ,
combustion chamber modification, water injection and catalytic reduction.
8/82 Internal Combustion Engine Sources 3.3.4-1
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TABLE 3.3.4-1. EMISSION FACTORS FOR STATIONARY LARGE BORE DIESEL
AND DUAL FUEL ENGINES3
EMISSION FACTOR RATING: C
Engine type
Diesel
lb/103 hph
g/hph
g/kWh
lb/103 galf
g/le
Dual fuel
lb/103 hph
g/hph
g/kWh
Particulateb
2.4
1.1
1.5
50
6
NA
NA
NA
Nitrogen
oxides0
24
11
15
500
60
18
8
11
Carbon
monoxide
6.4
2.9
3.9
130
16
5.9
2.7
3.6
VOC?1
Methane
0.07
0.03
0.04
1
0.2
4.7
2.1
2.9
Nonme thane
0.63
0.29
0.04
*13
1.6
1.5
0.7
0.9
Sulfur
dioxide6
2.8
1.3
1.7
60
7.2
0.70
0.32
0.43
Representative uncontrolled levels for each fuel, determined by weighting data from
several manufactures. Weighting based on I of total horsepower sold by each manu-
facturer during a five year period. NA » not available.
^Emission Factor Rating: E. Approximation based on test of a medium bore diesel.
Emissions are minimum expected for engine operating at 50 - 100Z full rated load.
At OX load, emissions would Increase to 230 g/1.
cMeasured as NOj. Factors are for engines operated at rated load and speed.
dNonmethane VOC is 90% of total VOC from diesel engines but only 252 of total VOC
emissions from dual fuel engines. Individual chemical species within the nonmethane
fraction are not identified. Molecular weight of nonmethane gas stream is assumed
to be that of methane.
eBased on assumed sulfur content of 0.4Z by weight for diesel fuel and 0.46 g/sc
(0.20 gr/scf) for pipeline quality natural gas. Dual fuel 502 emissions based on
5Z oil/95Z gas mix. Emissions should be adjusted for other fuel ratios.
^These factors calculated from the above factors assuming a heating value of 40 MJ/1
(145,000 Btu/gal) for oil, 41 MJ/scm (1100 Btu/scf) for natural gas, and an average
fuel consumption of 9.9 MJ/kWh (7000 Btu/hph).
References for Section 3.3.4
1. Standards Support and Environmental Impact Statement Volume I -
Stationary Internal Combustion Engines, EPA-450/2-78-125a, U. S.
Environmental Protection Agency, Research Triangle Park, NC, July 1979
2. Telephone communication between William H. Lamason, Office of Air
Quality Planning and Standards, U. S. Environmental Protection Agency,
Research Triangle Park, NC, and John H. Wasser, Office of Research and
Development, U. S. Environmental Protection Agency, Research Triangle
Park, NC, July 15, 1983.
3.3.4-2
EMISSION FACTORS
1/84
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4.2.2 INDUSTRIAL SURFACE COATING
4.2.2.1 GENERAL INDUSTRIAL SURFACE COATING1-4
Process Description - Surface coating is the application of decorative or
protective materials in liquid or powder form to substrates. These coatings
normally include general solvent type paints, varnishes, lacquers and water
thinned paints. After application of coating by one of a variety of methods
such as brushing, rolling, spraying, dipping and flow coating, the surface is
air and/or heat dried to remove the volatile solvents from the coated surface.
Powder type coatings can be applied to a hot surface or can be melted after
application and caused to flow together. Other coatings can be polymerized
after application by thermal curing with infrared or electron beam systems.
Coating Operations - There are both "toll" ("independent") and "captive"
surface coating operations. Toll operations fill orders to various manufac-
turer specifications, and thus change coating and solvent conditions more
frequently than do captive companies, which fabricate and coat products within
a single facility and which may operate continuously with the same solvents.
Toll and captive operations differ in emission control systems applicable to
coating lines, because not all controls are technically feasible in toll
situations.
Coating Formulations - Conventional coatings contain at least 30 volume
percent solvents to permit easy handling and application. They typically con-
tain 70 to 85 percent solvents by volume. These solvents may be of one com-
ponent or of a mixture of volatile ethers, acetates, aromatics, cellosolves,
aliphatic hydrocarbons and/or water. Coatings with 30 volume percent of
solvent or less are called low solvent or "high solids" coatings.
Waterborne coatings, which have recently gained substantial use, are of
several types: water emulsion, water soluble and colloidal dispersion, and
electrocoat. Common ratios of water to solvent organics in emulsion and dis-
persion coatings are 80/20 and 70/30.
Two part catalyzed coatings to be dried, powder coatings, hot melts, and
radiation cured (ultraviolet and electron beam) coatings contain essentially
no volatile organic compounds (VOC), although some monomers and other lower
molecular weight organics may volatilize.
Depending on the product requirements and the material being coated, a
surface may have one or more layers of coating applied. The first coat may be
applied to cover surface imperfections or to assure adhesion of the coating.
The intermediate coats usually provide the required color, texture or print,
and a clear protective topcoat is often added. General coating types do not
differ from those described, although the intended use and the material to be
coated determine the composition and resins used in the coatings.
Coating Application Procedures - Conventional spray, which is air atomized
and usually hand operated, is one of the most versatile coating methods. Colors
can be changed easily, and a variety of sizes and shapes can be painted under
4/81 Evaporation Loss Sources 4.2.2.1-1
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many operating conditions. Conventional, catalyzed or waterborne coatings can
be applied with little modification. The disadvantages are low efficiency from
overspray and high energy requirements for the air compressor.
In hot airless spray, the paint is forced through an atomizing nozzle.
Since volumetric flow is less, overspray is reduced. Less solvent is also
required, thus reducing VOC emissions. Care must be taken for proper flow of
the coating, to avoid plugging and abrading of the nozzle orifice. Electro-
static spray is most efficient for low visocity paints. Charged paint par-
ticles are attracted to an oppositely charged surface. Spray guns, spinning
discs or bell shaped atomizers can be used to atomize the paint. Application
efficiencies of 90 to 95 percent are possible, with good "wraparound" and edge
coating. Interiors and recessed surfaces are difficult to coat, however.
Roller coating is used to apply coatings and inks to flat surfaces. If
the cylindrical rollers move in the same direction as the surface to be coated,
the system is called a direct roll coater. If they rotate in the opposite
direction, the system is a reverse roll coater. Coatings can be applied to any
flat surface efficiently and uniformly and at high speeds. Printing and deco-
rative graining are applied with direct rollers. Reverse rollers are used to
apply fillers to porous or imperfect substrates, including papers and fabrics,
to give a smooth uniform surface.
Knife coating is relatively inexpensive, but it is not appropriate for
coating unstable materials, such as some knit goods, or when a high degree of
accuracy in the coating thickness is required.
Rotogravure printing is widely used in coating vinyl imitation leathers
and wallpaper, and in the application of a transparent protective layer over
the printed pattern. In rotogravure printing, the image area is recessed, or
"intaglio", relative to the copper plated cylinder on which the image is
engraved. The ink is picked up on the engraved area, and excess ink is scraped
off the nonimage area with a "doctor blade". The image is transferred directly
to the paper or other substrate, which is web fed, and the product is then
dried.
Dip coating requires that the surface of the subject be immersed in a bath
of paint. Dipping is effective for coating irregularly shaped or bulky items
and for priming. All surfaces are covered, but coating thickness varies, edge
blistering can occur, and a good appearance is not always achieved.
In flow coating, materials to be coated are conveyed through a flow of
paint. Paint flow is directed, without atomization, toward the surface through
multiple nozzles, then is caught in a trough and recycled. For flat surfaces,
close control of film thickness can be maintained by passing the surface
through a constantly flowing curtain of paint at a controlled rate .
Emissions and Controls - Essentially all of the VOC emitted from the sur-
face coating industry is from the solvents which are used in the paint formu-
lations, used to thin paints at the coating facility or used for cleanup. All
unrecovered solvent can be considered potential emissions. Monomers and low
molecular weight organics can be emitted from those coatings that do not include
solvents, but such emissions are essentially negligible.
4.2.2.1-2 EMISSION FACTORS 4/81
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Emissions from surface coating for an uncontrolled facility can be esti-
mated by assuming that all VOC in the coatings is emitted. Usually, coating
consumption volume will be known, and some information about the types of
coatings and solvents will be available. The choice of a particular emission
factor will depend on the coating data available. If no specific information
is given for the coating, it may be estimated from the data in Table 4.2.2.1-2,
TABLE 4.2.2.1-1. VOC EMISSION FACTORS FOR UNCONTROLLED SURFACE COATING3
EMISSION FACTOR RATING: B
Available information on coating
Conventional or waterborne
paints
VOC, wt % (d)
VOC, vol % (V)
Waterborne paint
VOC as weight % of total
volatiles - including water
(X); total volatiles as
weight % of coating (d)
VOC as volume % of total
volatiles - including water
(Y); total volatiles as
volume % of coating (V)
Emissions of
kg/liter of coating Ib/gal of coating
d*coating densityc
100
V-0.
100
d'X'coating density0
100
V-Y-0.88d
100
d*coating densityc
100
V-7.36d
100
d'X'coating densityc
100
V-Y-7.36d
100
aMaterial balance, when coatings volume use is known.
bFor special purposes, factors expressed kg/1 of coating less water may be
desired. These may be computed as follows:
Factor as kg/1 of coating
= Factor as kg/1 of coating less water ]_ _ volume % water
100
clf coating density is not known, it can be estimated from the information
in Table 4.2.2.1-2.
dThe values 0.88 (kg/1) and 7.36 (Ib/gal) use the average density of
solvent in coatings. Use the densities of the solvents in the coatings
actually used by the source, if known.
4/81
Evaporation Loss Source
4.2.2.1-3
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TABLE 4.2.2.1-2. TYPICAL DENSITIES AND SOLIDS CONTENTS OF COATINGS
Type of coating
Enamel , air dry
Enamel , baking
Acrylic enamel
Alkyd enamel
Primer surfacer
Primer, epoxy
Varnish, baking
Lacquer, spraying
Vinyl, roller coat
Polyur ethane
Stain
Sealer
Magnet wire enamel
Paper coating
Fabric coating
Density
kg/liter
0.91
1.09
1.07
0.96
1.13
1.26
0.79
0.95
0.92
1.10
0.88
0.84
0.94
0.92
0.92
Ib/gal
7.6
9.1
8.9
8.0
9.4
10.5
6.6
7.9
7.7
9.2
7.3
7.0
7.8
7.7
7.7
Solids
(volume %)
39.6
42.8
30.3
47.2
49.0
57.2
35.3
26.1
12.0
31.7
21.6
11.7
25.0
22.0
22.0
aReference 1.
All solvents separately purchased as solvent that are used in surface
coating operations and are not recovered subsequently can be considered
potential emissions. Such VOC emissions at a facility can result from onsite
dilution of coatings with solvent, from "makeup solvents" required in flow
coating and, in some instances, dip coating, and from the solvents used for
cleanup. Makeup solvents are added to coatings to compensate for standing
losses, concentration or amount, and thus to bring the coating back to working
specifications. Solvent emissions should be added to VOC emissions from
coatings to get total emissions from a coating facility.
Typical ranges of control efficiencies are given in Table 4.2.2.1-3.
Emission controls normally fall under one of three categories - modification in
paint formula, process changes, or addon controls. These are discussed further
in the specific subsections which follow.
TABLE 4.2.2.1-3. CONTROL EFFICIENCIES FOR
SURFACE COATING OPERATIONS3
Control option
Reduction*3
Substitute waterborne coatings
Substitute low solvent coatings
Substitute powder coatings
Add afterburners/incinerators
60-95
40-80
92-98
95
aReferences 2-4.
^Expressed as % of total uncontrolled emission load.
4.2.2.1-4
EMISSION FACTORS
4/81
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References for Section 4.2.2.1
1. Controlling Pollution from the Manufacturing and Coating of Metal
Products: Metal Coating Air Pollution Control, EPA-625/3-77-009, U. S.
Environmental Protection Agency, Cincinnati, OH, May 1977.
2. H. R. Powers, "Economic and Energy Savings through Coating Selection",
The Sherwin-Williams Company, Chicago, IL, February 8, 1978.
3. Air Pollution Engineering Manual, Second Edition, AP-40, U. S.
Environmental Protection Agency, Research Triangle Park, NC, May 1973.
Out of Print.
4. Products Finishing, 41(6A):4-54, March 1977.
4/81 Evaporation Loss Sources 4.2.2.1-5
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4.2.2.2 CAN COATING1'4
Process Description - Cans may be made from a rectangular sheet (body blank)
and two circular ends (three piece cans), or they can be drawn and wall ironed
from a shallow cup to which an end is attached after the can is filled (two
piece cans). There are major differences in coating practices, depending on
the type of can and the product packaged in it. Figure 4.2.2.2-1 depicts a
three piece can sheet printing operation.
There are both "toll" and "captive" can coating operations. The former
fill orders to customer specifications, and the latter coat the metal for pro-
ducts fabricated within one facility. Some can coating operations do both
toll and captive work, and some plants fabricate just can ends.
Three piece can manufacturing involves sheet coating and can fabricating.
Sheet coating includes base coating and printing or lithographing, followed by
curing at temperatures of up to 220°C (425°F). When the sheets have been
formed into cylinders, the seam is sprayed, usually with a lacquer, to protect
the exposed metal. If they are to contain an edible product, the interiors are
spray coated, and the cans baked up to 220°C (425°F).
Two piece cans are used largely by beer and other beverage industries.
The exteriors may be reverse roll coated in white and cured at 170 to 200°C
(325 to 400°F). Several colors of ink are then transferred (sometimes by
lithographic printing) to the cans as they rotate on a mandrel. A protective
varnish may be roll coated over the inks. The coating is then cured in a
single or multipass oven at temperatures of 180 to 200°C (350 to 400°F). The
cans are spray coated on the interior and spray and/or roll coated on the
exterior of the bottom end. A final baking at 110 to 200°C (225 to 400°F)
completes the process.
Emissions and Controls - Emissions from can coating operations depend on
composition of the coating, coated area, thickness of coat and efficiency of
application. Post-application chemical changes, and nonsolvent contaminants
like oven fuel combustion products, may also affect the composition of emis-
sions. All solvent used and not recovered can be considered potential
emissions.
Sources of can coating VOC emissions include the coating area and the oven
area of the sheet base and lithographic coating lines, the three piece can side
seam and interior spray coating processes, and the two piece can coating and
end sealing compound lines. Emission rates vary with line speed, can or sheet
size, and coating type. On sheet coating lines, where the coating is applied
by rollers, most solvent evaporates in the oven. For other coating processes,
the coating operation itself is the major source. Emissions can be estimated
from the amount of coating applied by using the factors in Table 4.2.2.1-1 or,
if the number and general nature of the coating lines are known, from Table
4.2.2.2-1.
Incineration and the use of waterborne and low solvent coatings both
reduce organic vapor emissions. Other technically feasible control options,
such as electrostatically sprayed powder coatings, are not presently applicable
to the whole industry. Catalytic and thermal incinerators both can be used,
4/81 Evaporation Loss Sources 4.2.2.2-1
-------
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Evaporation Loss Sources
4.2.2.2-3
-------
TABLE 4.2.2.2-2. CONTROL EFFICIENCIES FOR CAN COATING LINES3
Affected facility13
Control option
Reduction0
Two Piece Can Lines
Exterior coating
Interior spray
coating
Three Piece Can Lines
Sheet coating lines
Exterior coating
Interior spray
coating
Can fabricating lines
Side seam spray
coating
Interior spray
coating
End Coating Lines
Sealing compound
Sheet coating
Thermal and catalytic incineration
Waterborne and high solids coating
Ultraviolet curing
Thermal and catalytic incineration
Waterborne and high solids coating
Powder coating
Carbon adsorption
Thermal and catalytic incineration
Waterborne and high solids coating
Ultraviolet curing
Thermal and catalytic incineration
Waterborne and high solids coating
Waterborne and high solids coating
Powder (only for uncemented seams)
Thermal and catalytic incineration
Waterborne and high solids coating
Powder (only for uncemented seams)
Carbon adsorption
Waterborne and high solids coating
Carbon adsorption
Thermal and catalytic incineration
Waterborne and high solids coating
90
60-90
<100
90
60-90
100
90
90
60-90
£100
90
60-90
60-90
100
90
60-90
100
90
70-95
90
90
60-90
aReferenee 3.
bCoil coating lines consist of coaters, ovens and quench areas. Sheet, can
and end wire coating lines consist of coaters and ovens.
cCompared to conventional solvent base coatings used without any added
4.2.2.2-4
EMISSION FACTORS
4/81
-------
primers, backers (coatings on the reverse or backside of the coil), and some
waterborne low to medium gloss topcoats have been developed that equal the
performance of organic solventborne coatings for aluminum but have not yet been
applied at full line speed in all cases. Waterborne coatings for other metals
are being developed.
Available control technology includes the use of addon devices like
incinerators and carbon adsorbers and a conversion to low solvent and ultra-
violet curable coatings. Thermal and catalytic incinerators both may be used
to control emissions from three piece can sheet base coating lines, sheet
lithographic coating lines, and interior spray coating. Incineration is appli-
cable to two piece can coating lines. Carbon adsorption is most acceptable to
low temperature processes which use a limited number of solvents. Such pro-
cesses include two and three piece can interior spray coating, two piece can
end sealing compound lines, and three piece can side seam spray coating.
Low solvent coatings are not yet available to replace all the organic
solventborne formulations presently used in the can industry. Waterborne
basecoats have been successfully applied to two piece cans. Powder coating
technology is used for side seam coating of noncemented three piece cans.
Ultraviolet curing technology is available for rapid drying of the first
two colors of ink on three piece can sheet lithographic coating lines.
References for Section 4.2.2.2
1. T. W. Hughes, et al., Source Assessment: Prioritization of Air Pollution
from Industrial Surface Coating Operations, EPA-650/2-75-019a, U. S.
Environmental Protection Agency, Research Triangle Park, NC, November 1975.
2. Control of Volatile Organic Emissions from Existing Stationary Sources,
Volume I; Control Methods for Surface Coating Operations, EPA-450/2-76-
028, U. S. Environmental Protection Agency, Research Triangle Park, NC,
May 1977.
3. Control of Volatile Organic Emissions from Existing Stationary Sources,
Volume II: Surface Coating of Cans, Coils, Paper Fabrics, Automobiles,
and Light Duty Trucks, EPA-450/2-77-008, U. S. Environmental Protection
Agency, Research Triangle Park, NC, May 1977.
4. Air Pollution Control Technology Applicable to 26 Source of Volatile
Organic Compounds, Office of Mr Quality Planning and Standards, U. S.
Environmental Protection Agency, Research Triangle Park, NC, May 27, 1977.
Unpublished.
4/81 Evaporation Loss Sources 4.2.2.2-5
-------
4.2.2.3 MAGNET WIRE COATING1
Process Description - Magnet wire coating is applying a coat of electrically
insulating varnish or enamel to aluminum or copper wire used in electrical
machinery. The wire is usually coated in large plants that both draw and
insulate it and then sell it to electrical equipment manufacturers. The wire
coating must meet rigid electrical, thermal and abrasion specifications.
Figure 4.2.2.3-1 shows a typical wire coating operation. The wire is
unwound from spools and passed through an annealing furnace. Annealing softens
the wire and cleans it by burning off oil and dirt. Usually, the wire then
passes through a bath in the coating applicator and is drawn through an orifice
or coating die to scrape off the excess. It is then dried and cured in a two
zone oven first at 200°, then 430°C (400 and 806°F). Wire may pass through the
coating applicator and the oven as many as twelve times to acquire the necessary
thickness of coating.
Emissions and Controls - Emissions from wire coating operations depend on
composition of the coating, thickness of coat and efficiency of application.
Postapplication chemical changes, and nonsolvent contaminants such as oven fuel
combustion products, may also affect the composition of emissions. All solvent
used and not recovered can be considered potential emissions.
The exhaust from the oven is the most important source of solvent emissions
in the wire coating plant. Emissions from the applicator are comparatively low,
because a dip coating technique is used. See Figure 4.2.2.3-1.
Volatile organic compound (VOC) emissions may be estimated from the factors
in Table 4.2.2.1-1, if the coating usage is known and if the coater has no
controls. Most wire coaters built since 1960 do have controls, so the infor-
mation in the following paragraph may be applicable. Table 4.2.2.3-1 gives
estimated emissions for a typical wire coating line.
TABLE 4.2.2.3-1
ORGANIC SOLVENT EMISSIONS FROM A TYPICAL WIRE
COATING LINE3
Coating Lineb
kg/hr Ib/hr
12 26
Annual Totalsc
Mg/yr ton/yr
84 93
aReference 1.
^Organic solvent emissions vary from line to line by size and
speed of wire, number of wires per oven, and number of passes
through oven. A typical line may coat 544 kg (1,200 Ib) wire/day.
A plant may have many lines.
cBased upon normal operating conditions of 7,000 hr/yr for one line
without incinerator.
4/81
Evaporation Loss Sources
4.2.2.3-1
-------
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Incineration is the only commonly used technique to control emissions from
wire coating operations. Since about 1960, all major wire coating designers
have incorporated catalytic incinerators into their oven designs, because of
the economic benefits. The internal catalytic incinerator burns solvent fumes
and circulates heat back into the wire drying zone. Fuel otherwise needed to
operate the oven is eliminated or greatly reduced, as are costs. Essentially
all solvent emissions from the oven can be directed to an incinerator with a
combustion efficiency of a least 90 percent.
Ultraviolet cured coatings are available for special systems. Carbon
adsorption is not practical. Use of low solvent coatings is only a potential
control, because they have not yet been developed with properties that meet
industry's requirements.
References for Section 4.2.2.3
1. Control of Volatile Organic Emissions from Existing Stationary Sources,
Volume IV; Surface Coating for Insulation of Magnet Wire, EPA-450/2-77-
033, U. S. Environmental Protection Agency, Research Triangle Park, NC,
December 1977.
2. Controlled and Uncontrolled Emission Rates and Applicable Limitations for
Eighty Processes, EPA Contract Number 68-02-1382, TRC of New England,
Wethersfield, CT, September 1976.
4/81 Evaporation Loss Sources 4.2.2.3-3
-------
4.2.2.4 OTHER METAL COATING1"3
Process Description - Large appliance, metal furniture and miscellaneous metal
part and product coating lines have many common operations, similar emissions
and emission points, and available control technology. Figure 4.2.2.4-1 shows
a typical metal furniture coating line.
Large appliances include doors, cases, lids, panels and interior support
parts of washers, dryers, ranges, refrigerators, freezers, water heaters, air
conditioners, and associated products. Metal furniture includes both outdoor
and indoor pieces manufactured for household, business or institutional use.
"Miscellaneous parts and products" herein denotes large and small farm machin-
ery, small appliances, commercial and industrial machinery, fabricated metal
products and other industries that coat metal under Standard Industrial
Classification (SIC) codes 33 through 39.
Large Appliances - The coatings applied to large appliances are usually
epoxy, epoxy/acrylic or polyester enamels for the primer or single coat, and
acrylic enamels for the topcoat. Coatings containing alkyd resins are also
used. Prime and interior single coats are applied at 25 to 36 volume percent
solids. Topcoats and exterior single coats are applied at 30 to 40 volume
percent. Lacquers may be used to touch up any scratches that occur during
assembly. Coatings contain 2 to 15 solvents, typical of which are esters,
ketones, apliphatics, alcohols, aromatics, ethers and terpenes.
Small parts are generally dip coated, and flow or spray coating is used
for larger parts. Dip and flow coating are performed in an enclosed room
vented either by a roof fan or by an exhaust system adjoining the drain board
or tunnel. Down or side draft booths remove overspray and organic vapors from
prime coat spraying. Spray booths are also equipped with dry filters or a
water wash to trap overspray.
Parts may be touched up manually with conventional or airless spray equip-
ment. Then they are sent to a flashoff area (either open or tunneled) for
about 7 minutes and are baked in a multipass oven for about 20 minutes at 180
to 230°C (350 to 450°F). At that point, large appliance exterior parts go on
to the topcoat application area, and single coated interior parts are moved to
the assembly area of the plant.
The topcoat, and sometimes primers, are applied by automated electrostatic
disc, bell or other types of spray equipment. Topcoats often are more than one
color, changed by automatically flushing out the system with solvent. Both the
topcoat and touchup spray areas are designed with side or down draft exhaust
control. The parts go through about a 10 minute flashoff period, followed by
baking in a multipass oven for 20 to 30 minutes at 140 to 180°C (270 to 350°F).
Metal Furniture - Most metal furniture coatings are enamels, although some
lacquers are used. The most common coatings are alkyds, epoxies and acrylics,
which contain the same solvents used in large appliance coatings, applied at
about 25 to 35 percent solids.
On a typical metal furniture coating line (see Figure 4.2.2.4-1), the
prime coat can be applied with the same methods used for large appliances, but
it may be cured at slightly lower temperatures, 150 to 200°C (300 to 400°F).
4/81 Evaporation Loss Sources 4.2.2.4-1
-------
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EMISSION FACTORS
4/81
-------
The topcoat, usually the only coat, is applied with electrostatic spray or with
conventional airless or air spray. Most spray coating is manual, in contrast
to large appliance operations. Flow coating or dip coating is done, if the
plant generally uses only one or two colors on a line.
The coated furniture is usually baked, but in some cases it is air dried.
If it is to be baked, it passes through a flashoff area into a multizone oven
at temperatures ranging from 150 to 230°C (300 to 450°F).
Miscellaneous Metal Parts and Products - Both enamels (30 to 40 volume
percent solids) and lacquers (10 to 20 volume percent solids) are used to coat
miscellaneous metal parts and products, although enamels are more common.
Coatings often are purchased at higher volume percent solids but are thinned
before application (frequently with aromatic solvent blends). Alkyds are
popular with industrial and farm machinery manufacturers. Most of the coatings
contain several (up to 10) different solvents, including ketones, esters,
alcohols, aliphatics, ethers, aromatics and terpenes.
Single or double coatings are applied in conveyored or batch operations.
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applied by spraying. Electrostatic spraying is common. Spray booths and areas
are kept at a slight negative pressure to capture overspray.
A manual two coat operation may be used for large items like industrial
and farm machinery. The coatings on large products are often air dried rather
than oven baked, because the machinery, when completely assembled, includes
heat sensitive materials and may be too large to be cured in an oven. Miscel-
laneous parts and products can be baked in single or multipass ovens at 150 to
230°C (300 to 450°F).
Emissions and Controls - Volatile organic compounds (VOC) are emitted
from application and flashoff areas and the ovens of metal coating lines. See
Figure 4.2.2.4-1. The composition of emissions varies among coating lines
according to physical construction, coating method and type of coating applied,
but distribution of emissions among individual operations has been assumed to
be fairly constant, regardless of the type of coating line or the specific pro-
duct coated, as Table 4.2.2.4-2 indicates. All solvent used can be considered
potential emissions. Emissions can be calculated from the factors in Table
4.2.2.1-1 if coatings use is known, or from the factors in Table 4.2.2.4-2 if
only a general description of the plant is available. For emissions from the
cleansing and pretreatment area, see Section 4.6, Solvent Degreasing.
• When powder coatings, which contain almost no VOC, are applied to some
metal products as a coating modification, emissions are greatly reduced.
Powder coatings are applied as single coats on some large appliance interior
parts and as topcoat for kitchen ranges. They are also used on metal bed and
chair frames, shelving and stadium seating, and they have been applied as
single coats on small appliances, small farm machinery, fabricated metal pro-
duct parts and industrial machinery components. The usual application methods
are manual or automatic electrostatic spray.
4/81 Evaporation Loss Sources 4.2.2.4-3
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Evaporation Loss Sources
4.2.2.4-5
-------
Improving transfer efficiency is a method of reducing emissions. One
such technique is the electrostatic application of the coating, and another
is dip coating with waterborne paint. For example, many makers of large
appliances are now using electrodeposition to apply prime coats to exterior
parts and single coats to interiors, because this technique increases corrosion
protection and resistance to detergents. Electrodeposition of these waterborne
coatings is also being used at several metal furniture coating plants and at
some farm, commercial machinery and fabricated metal products facilities.
Automated electrostatic spraying is most efficient, but manual and
conventional methods can be used, also. Roll coating is another option on some
miscellaneous parts. Use of higher solids coatings is a practiced technique
for reduction of VOC emissions.
Carbon adsorption is technically feasible for collecting emissions from
prime, top and single coat applications and flashoff areas. However, the
entrained sticky paint particles are a filtration problem, and adsorbers are
not commonly used.
Incineration is used to reduce organic vapor emissions from baking ovens
for large appliances, metal furniture and miscellaneous products, and it is an
option for control of emissions from application and flashoff areas.
Table 4.2.2.4-1 gives estimated control efficiencies for large appliance,
metal furniture and miscellaneous metal part and product coating lines, and
Table 4.2.2.4-2 gives their emission factors.
References for Section 4.2.2.4
1. Control of Volatile Organic Emissions from Existing Stationary Sources,
Volume III; Surface Coating of Metal Furniture, EPA-450/2-77-032, U. S.
Environmental Protection Agency, Research Triangle Park, NC, December 1977.
2. Control of Volatile Organic Emissions from Existing Stationary Sources,
Volume V: Surface Coating of Large Appliances, EPA-450/2-77-034, U. S.
Environmental Protection Agency, Research Triangle Park, NC, December 1977.
3. Control of Volatile Organic Emissions from Existing Stationary Sources,
Volume V: Surface Coating of Miscellaneous Metal Parts and Products,
EPA-450/2-78-015, U. S. Environmental Protection Agency, Research Triangle
Park, NC, June 1978.
4. G. T. Helms, "Appropriate Transfer Efficiencies for Metal Furniture and
Large Appliance Coating", Memorandum, Office of Air Quality Planning and
Standards, U. S. Environmental Protection Agency, Research Triangle Park,
NC, November 28, 1980.
4.2.2.4-6 EMISSION FACTORS 4/81
-------
4.2.2.5 FLAT WOOD INTERIOR PANEL COATING
Process Description^ - Finished flat wood construction products are interior
panels made of hardwood plywoods (natural and lauan), particle board, and
hardboard.
Fewer than 25 percent of the manufacturers of such flat wood products
coat the products in their plants, and in some of the plants that do coat, only
a small percentage of total production is coated. At present, most coating is
done by toll coaters who receive panels from manufacturers and undercoat or
finish them according to customer specifications and product requirements.
Some of the layers and coatings that can be factory applied to flat woods
are filler, sealer, groove coat, primer, stain, basecoat, ink, and topcoat.
Solvents used in organic base flat wood coatings are usually component mix-
tures, including methyl ethyl ketone, methyl isobutyl ketone, toluene, xylene,
butyl acetates, propanol, ethanol, butanol, naphtha, methanol, amyl acetate,
mineral spirits, SoCal I and II, glycols, and glycol ethers. Those most often
used in waterborne coatings are glycol, glycol ethers, propanol and butanol.
Various forms of roll coating are the preferred techniques for applying
coatings to flat woods. Coatings used for surface cover can be applied with
a direct roller coater, and reverse roll coaters are generally used to apply
fillers, forcing the filler into panel cracks and voids. Precision coating
and printing (usually with offset gravure grain printers) are also forms of
roll coating, and several types of curtain coating may be employed, also
(usually for topcoat application). Various spray techniques and brush coating
may be used, too.
Printed interior panelings are produced from plywoods with hardwood
surfaces (primarily lauan) and from various wood composition panels, including
hardboard and particle board. Finishing techniques are used to cover the
original surface and to produce various decorative effects. Figure 4.2.2.5-1
is a flow diagram showing some, but not all, typical production line variations
for printed interior paneling.
Groove coatings, applied in different ways and at different points in the
coating procedure, are usually pigmented low resin solids reduced with water
before use, therefore yielding few, if any, emissions. Fillers, usually applied
by reverse roll coating, may be of various formulations: (1) polyester (which
is ultraviolet cured), (2) water base, (3) lacquer base, (4) polyurethane and
(5) alkyd urea base. Water base fillers are in common use on printed paneling
lines.
Sealers may be of water or solvent base, usually applied by airless spray
or direct roll coating, respectively. Basecoats, which are usually direct roll
coated, generally are of lacquer, synthetic, vinyl, modified alkyd urea,
catalyzed vinyl, or water base.
Inks are applied by an offset gravure printing operation similar to direct
roll coating. Most lauan printing inks are pigments dispersed in alkyd resin,
with some nitrocellulose added for better wipe and printability. Water base
4/81 Evaporation Loss Sources 4.2.2.5-1
-------
inks have a good future for clarity, cost and environmental reasons. After
printing, a board goes through one or two direct or precision roll coaters
for application of the clear protective topcoat. Some topcoats are synthetic,
prepared from solvent soluble alkyd or polyester resins, urea formaldehyde
cross linkings, resins, and solvents.
Natural hardwood plywood panels are coated with transparent or clear
finishes to enhance and protect their face ply of hardwood veneer. Typical
production lines are similar to those for printed interior paneling, except
that a primer sealer is applied to the filled panel, usually by direct roll
coating. The panel is then embossed and "valley printed" to give a "dis-
tressed" or antique appearance. No basecoat is required. A sealer is also
applied after printing but before application of the topcoat, which may be
curtain coated, although direct roll coating remains the usual technique.
Emissions and Controls*~2 - Emissions of volatile organic compounds (VOC) at
flat wood coating plants occur primarily from reverse roll coating of filler,
direct roll coating of sealer and basecoat, printing of wood grain patterns,
direct roll or curtain coating of topcoat(s), and oven drying after one or
more of those operations (see Figure 4.2.2.5-1). All solvent used and not
recovered can be considered potential emissions. Emissions can be calculated
from the factors in Table 4.2.2.1-1, if the coating use is known. Emissions
for interior printed panels can be estimated from the factors in Table
4.2.2.5-1, if the area of coated panels is known.
Waterborne coatings are increasingly used to reduce emissions. They can
be applied to almost all flat wood except redwood and, possibly, cedar. The
major use of waterborne flat wood coatings is in the filler and basecoat
applied to printed interior paneling. Limited use has been made of waterborne
materials for inks, groove coats, and topcoats with printed paneling, and for
inks and groove coats with natural hardwood panels.
Ultraviolet curing systems are applicable to clear or semitransparent
fillers, topcoats on particle board coating lines, and specialty coating oper-
ations. Polyester, acrylic, urethane and alkyd coatings can be cured by this
method.
Afterburners can be used to control VOC emissions from baking ovens, and
there would seem to be ample recovered heat to use. Extremely few flat wood
coating operations have afterburners as addon controls, though, despite the
fact that they are a viable control option for reducing emissions where product
requirements restrict the use of other control techniques.
Carbon adsorption is technically feasible, especially for specific
applications (e. g., redwood surface treatment), but the use of multicomponent
solvents and different coating formulations in several steps along the coating
line has thus far precluded its use to control flat wood coating emissions and
to reclaim solvents. The use of low solvent coatings to fill pores and to seal
wood has been demonstrated.
4.2.2.5-2 EMISSION FACTORS 4/81
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EMISSION FACTORS
4/81
-------
References for Section 4.2.2.5
1. Control of Volatile Organic Emissions from Existing Stationary Sources,
Volume VII; Factory Surface Coating of Flat Wood Interior Paneling, EPA-
450/2-78-032, U. S. Environmental Protection Agency, Research Triangle
Park, NC, June 1978.
2. Air Pollution Control Technology Applicable to 26 Sources of Volatile
Organic Compounds, Office of Air Quality Planning and Standards, U. S.
Environmental Protection Agency, Research Triangle Park, NC, May 27, 1977.
Unpublished.
•
3. Products Finishing, 41(6A):4-54, March 1977.
4/81 Evaporation Loss Sources 4.2.2.5-5
-------
-------
4.2.2.6 PAPER COATING
Process Description^^ - paper is coated for various decorative and functional
purposes with waterborne, organic solventborne, or solvent free extruded mate-
rials. Paper coating is not to be confused with printing operations, which
use contrast coatings that must show a difference in brightness from the paper
to be visible. Coating operations are the application of a uniform layer or
coating across a substrate. Printing results in an image or design on the
substrate.
Waterborne coatings improve printability and gloss but cannot compete
with organic solventborne coatings in resistance to weather, scuff and chem-
icals. Solventborne coatings, as an added advantage, permit a wide range of
surface textures. Most solventborne coating is done by paper converting com-
panies that buy paper from mills and apply coatings to produce a final product.
Among the many products that are coated with solventborne materials are adhesive
tapes and labels, decorated paper, book covers, zinc oxide coated office copier
paper, carbon paper, typewriter ribbons, and photographic film.
Organic solvent formulations generally used are made up of film forming
materials, plasticizers, pigments and solvents. The main classes of film
formers used in paper coating are cellulose derivatives (usually nitrocellu-
lose) and vinyl resins (usually the copolymer of vinyl chloride and vinyl
acetate). Three common plasticizers are dioctyl phthalate, tricresyl phos-
phate and castor oil. The major solvents used are toluene, xylene, methyl
ethyl ketone, isopropyl alcohol, methanol, acetone, and ethanol. Although a
single solvent is frequently used, a mixture is often necessary to obtain the
optimum drying rate, flexibility, toughness and abrasion resistance.
A variety of low solvent coatings, with negligible emissions, has been
developed for some uses to form organic resin films equal to those of con-
ventional solventborne coatings. They can be applied up to 1/8 inch thick
(usually by reverse roller coating) to products like artificial leather goods,
book covers and carbon paper. Smooth hot melt finishes can be applied over
rough textured paper by heated gravure or roll coaters at temperatures from 65
to 230°C (150 to 450°F).
Plastic extrusion coating is a type of hot melt coating in which a molten
thermoplastic sheet (usually low or medium density polyethylene) is extruded
from a slotted die at temperatures of up to 315°C (600°F). The substrate and
the molten plastic coat are united by pressure between a rubber roll and a
chill roll which solidifies the plastic. Many products, such as the polyeth-
ylene coated milk carton, are coated with solvent free extrusion coatings.
Figure 4.2.2.6-1 shows a typical paper coating line that uses organic
solventborne formulations. The application device is usually a reverse roller,
a knife or a rotogravure printer. Knife coaters can apply solutions of much
higher viscosity than roll coaters can, thus emitting less solvent per pound of
solids applied. The gravure printer can print patterns or can coat a solid
sheet of color on a paper web.
4/81 Evaporation Loss Sources 4.2.2.6-1
-------
Ovens may be divided into from two to five temperature zones. The first
zone is usally at about 43°C (110°F), and other zones have progressively higher
temperatures to cure the coating after most solvent has evaporated. The typi-
cal curing temperature is 120°C (250°F), and ovens are generally limited to
200°C (400°F) to avoid damage to the paper. Natural gas is the fuel most often
used in direct fired ovens, but fuel oil is sometimes used. Some of the hea-
vier grades of fuel oil can create problems, because SO and particulate may
contaminate the paper coating. Distillate fuel oil usually can be used satis-
factorily. Steam produced from burning solvent retrieved from an adsorber or
vented to an incinerator may also be used to heat curing ovens.
Emissions and Controls^ - The main emission points from paper coating lines are
the coating applicator and the oven (see Figure 4.2.2.6-1). In a typical paper
coating plant, about 70 percent of all solvents used are emitted from the coat-
ing lines, with most coming from the first zone of the oven. The other 30 per-
cent are emitted from solvent transfer, storage and mixing operations and can
be reduced through good housekeeping practices. All solvent used and not
recovered or destroyed can be considered potential emissions.
TABLE 4.2.2.6-1. CONTROL EFFICIENCIES FOR
PAPER COATING LINES3
Affected facility
Coating line
Control method
Incineration
Carbon adsorption
Low solvent coating
Efficiency (%)
95
90+
80 - 99b
Reference 2.
^Based on comparison with a conventional coating containing 35%
solids and 65% organic solvent, by volume.
Volatile organic compounds (VOC) emissions from individual paper coating
plants vary with size and number of coating lines, line construction, coating
formulation, and substrate composition, so each must be evaluated individually.
VOC emissions can be estimated from the factors in Table 4.2.2.1-1, if coating
use is known and sufficient information on coating composition is available.
Since many paper coating formulas are proprietary, it may be necessary to have
information on the total solvent used and to assume that, unless a control
device is used, essentially all solvent is emitted. Rarely would as much as 5
percent be retained in the product.
Almost all solvent emissions from the coating lines can be collected and
sent to a control device. Thermal incinerators have been retrofitted to a large
number of oven exhausts, with primary and even secondary heat recovery systems
heating the ovens. Carbon adsorption is most easily adaptable to lines which
use single solvent coating. If solvent mixtures are collected by adsorbers,
they usually must be distilled for reuse.
Although available for some products, low solvent coatings are not yet
available for all paper coating operations. The nature of the products, such
4.2.2.6-2
EMISSION FACTORS
4/81
-------
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as some types of photographic film, may preclude development of a low solvent
option. Furthermore, the more complex the mixture of organic solvents in the
coating, the more difficult and expensive to reclaim them for reuse with a
carbon adsorption system.
References for Section 4.2.2.6
1. T. W. Hughes, et al., Source Assessment; Prioritization of Air Pollution
from Industrial Surface Coating Operations, EPA-650/2-75-019a, U. S.
Environmental Protection Agency, Research Triangle Park, NC, February 1975
2. Control of Volatile Organic Emissions from Existing Stationary Sources,
Volume II; Surface Coating of Cans, Coils, Paper Fabrics, Automobiles,
and Light Duty Trucks, EPA-450/2-77-008, U. S. Environmental Protection
Agency, Research Triangle Park, NC, May 1977.
4.2.2.6-4 EMISSION FACTORS 4/81
-------
4.2.2.7 FABRIC COATING1"3
Process Description - Fabric coating imparts to a fabric substrate properties
such as strength, stability, water or acid repellence, or appearance. Fabric
coating is the uniform application of an elastomeric or thermoplastic polymer
solution, or a vinyl plastisol or organosol, across all of at least one side
of a supporting fabric surface or substrate. Coatings are applied by blade,
roll coater, reverse roll coater, and in some instances, by rotogravure coater.
Fabric coating should not be confused with vinyl printing and top coating,
which occur almost exclusively on rotogravure equipment. Textile printing also
should not be considered a fabric coating process.
Products usually fabric coated are rainwear, tents, tarpaulins, substrates
for industrial and electrical tape, tire cord, seals, and gaskets. The industry
is mostly small to medium size plants, many of which are toll coaters, rather
than specialists in their own product lines.
Figure 4.2.2.7-1 is of a typical fabric coating operation. If the fabric
is to be coated with rubber, the rubber is milled with pigments, curing agents
and fillers before being dissolved (mixed) in a suitable solvent. When other
than rubber coatings are used, milling is rarely necessary.
Emissions and Controls1 - The volatile organic compounds (VOC) emissions in a
fabric coating plant originate at the mixer, the coating applicator and the
oven (see Figure 4.2.2.7-1). Emissions from these three areas are from 10 to
25 percent, 20 to 30 percent and 40 to 65 percent, respectively. Fugitive
losses, amounting to a few percent, escape during solvent transfer, storage
tank breathing, agitation of mixing tanks, waste solvent disposal, various
stages of cleanup, and evaporation from the coated fabric after it leaves the
line.
The most accurate method of estimating VOC emissions from a fabric coating
plant is to obtain purchase or use records of all solvents in a specified time
period, add to that the amount of solvent contained in purchased coating solu-
tions, and subtract any stockpiled solvent, such as cleanup solvent, that is
recovered and disposed of in a nonpolluting manner. Emissions from the actual
coating line, without any solvent recovery, can be estimated from the factors
in Section 4.2.2.1, General Industrial Surface Coating, if coating use is known
and sufficient information on coating composition is available. Because many
fabric coatings are proprietary, it may be necessary for the user to supply
information on the total solvent used and to assume that, unless a control
device is used, all solvent is emitted. To calculate total plant emissions,
the coatings mixing losses must be accounted. These losses can be estimated
from the printline losses by using the relative split of plant emissions bet-
ween the mixing area and the printline. For example,
Emissions, = Emissions, /10% loss from mixing \
mixing printline \85% loss from printline'
Incineration is probably the best way to control coating application and
curing emissions on coating lines using a variety of coating formulations.
Primary and secondary heat recovery are likely to be used to help reduce the
fuel requirements of the coating process and, therefore, to increase the economy
4/81 Evaporation Loss Sources 4.2.2.7-1
-------
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EMISSION FACTORS
4/81
-------
of incineration. As with other surface coating operations, carbon adsorption
is most easily accomplished by sources using a single solvent that can be
recovered for reuse. Mixed solvent recovery is, however, in use in other web
coating processes. Fugitive emissions controls include tight covers for open
tanks, collection hoods for cleanup areas, and closed containers for storage
of solvent wiping cloths. Where high solids or waterborne coatings have been
developed to replace conventional coatings, their use may preclude the need for
a control device.
References for Section 4.2.2.7
1. Control of Volatile Organic Emissions from Existing Stationary Sources,
Volume II: Surface Coating of Cans, Coils, Paper Fabrics, Automobiles,
and Light Duty Trucks, EPA-450/2-77-008, U. S. Environmental Protection
Agency, Research Triangle Park, NC, May 1977.
2. B. H. Carpenter and G. K. Hilliard, Environmental Aspects of Chemical Use
in Printing Operations, EPA-560/1-75-005, U. S. Environmental Protection
Agency, Washington, DC, January 1976.
3. J. C. Berry, "Fabric Printing Definition", Memorandum, Office of Air Quality
Planning and Standards, U. S. Environmental Protection Agency, Research
Triangle Park, NC, August 25, 1980.
4/81 Evaporation Loss Sources 4.2.2.7-3
-------
not more than 1000°F (480 - 540°C) to prevent warping of the drum.
Emissions are vented to an afterburner or secondary combustion chamber,
where the gases are raised to at least 1500°F (760°C) for a minimum of
0.5 seconds. The average amount of material removed from each drum is
4.4 Ib (2 kg) .
Table 4.8-2. EMISSION FACTORS FOR TANK TRUCK CLEANING3
EMISSION FACTOR RATING: D
Chemical Class
Compound
Acetone
Perchloroethylene
Methyl methacrylate
Phenol
Propylene glvcol
Vapor
pressure
high
high
medium
low
low
Viscosity
low
low
medium
low
high
Total
emissions
Ib/ truck
0.686
0.474
0.071
0.012
0.002
g/ truck
311
215
32.4
5.5
1.07
Reference 1. One hour test duration.
4.8.2 Emissions and Controls
4.8.2.1 Rail Tank Cars and Tank Trucks - Atmospheric emissions from
tank car and truck cleaning are predominantly volatile organic chemical
vapors. To achieve a practical but representative picture of these
emissions, the organic chemicals hauled by the carriers must be broken
down into classes of high, medium and low viscosities and high, medium
and low vapor pressures. This is because high viscosity materials do
not drain readily, affecting the quantity of material remaining in the
tank, and high vapor pressure materials volatilize more readily during
cleaning and tend to lead to greater emissions.
Practical and economically feasible controls of atmospheric
emissions from tank car and truck cleaning do not exist, except for
containers transporting commodities that produce combustible gases and
water soluble vapors (such as ammonia and chlorine). Gases which are
displaced as tanks are filled are sent to a flare and burned. Water
soluble vapors are absorbed in water and sent to the wastewater system.
Any other emissions are vented to the atmosphere.
Tables 4.8-1 and 4.8-2 give emission factors for representative
organic chemicals hauled by tank cars and trucks.
4.8.2.2 Drums - There is no control for emissions from steaming of
drums. Solution or caustic washing yields negligible air emissions,
because the drum is closed during the wash cycle. Atmospheric emissions
from steaming or washing drums are predominantly organic chemical vapors.
Evaporation Los.- Source*
-------
Air emissions from drum burning furnaces are controlled by proper
operation of the afterburner or secondary combustion chamber, where gases
are raised to at least 1400°F (760°C) for a minimum of 0.5 seconds. This
normally ensures complete combustion of organic materials and prevents the
formation, and subsequent release, of large quantities of NOX, CO and
particulates. In open burning, however, there is no feasible way of con-
trolling the release of incomplete combustion products to the atmosphere.
Conversion of open cleaning operations to closed cycle cleaning and elim-
ination of open air drum burning seem to be the only control alternatives
immediately available.
Table 4.8-3 gives emission factors for representative criteria
pollutants emitted from drum burning and cleaning.
TABLE 4.8-3. EMISSION FACTORS FOR DRUM BURNING3
EMISSION FACTOR RATING: E
Pollutant
"otal Emissions
Controlled
Ib/drum g/drum
Uncontrolled
Ib/drum g/drum
Particulate
NOX
voc
0.02646 12b
0.00004 0.018
negligible
0.035 16
0.002 0.89
negligible
aReference 1. Emission factors are in terms of weight of pollutant
released per drum burned, except for VOC, which are per drum washed.
''Reference 1, Table 17 and Appendix A.
Reference for Section 4.8
1. T. R. Blackwood, et al., Source Assessment; Rail Tank Car, Tank Truck,
and Drum Cleaning, State of the Art, EPA-600/2-78-004g, U. S. Environ-
mental Protection Agency, Research Triangle Park, NC, April 1978.
4.8-4
EMISSION FACTORS
2/80
-------
TABLE 6.6-1. EMISSION FACTORS FOR FISH PROCESSING PLANTS
EMISSION FACTOR RATING: C
Emission source
Cookers , canning
Cookers, fish scrap
Fresh fish
Stale fish
Steam tube dryers
Direct fired dryers
Particulates
kg/Mg
Nega
Nega
Nega
2.5
4d
Ib/ton
Nega
Nega
Nega
5d
8d
Trime thy lamine
[(CHOsN]
kg/Mg
NAb
0.15C
1.75C
NAd
NAd
Ib/ton
NAb
0.3C
3.5C
NAd
NAd
Hydrogen sulfide
[H?S]
kg/Mg
NAb
0.005C
0.10°
NAd
NAd
Ib/ton
NAb
0.01C
0.2C
NAd
NAd
aReference 1. Factors are for uncontrolled emissions, before cyclone.
Neg = negligible. NA = not available.
^Although it is known that odors are emitted from canning cookers,
quantitative estimates are not available.
•^Reference 2.
dReference 1.
References for Section 6.6
1. Air Pollution Engineering Manual, Second Edition, AP-40, U. S. Environ-
mental Protection Agency, Research Triangle Park, NC, May 1973. Out of
Print.
2. W. Summer, Methods of Air Deodorization, New York, Elsevier Publishing
Company, 1963.
4/77
Food and Agricultural Industry
6.6-3
-------
6.8 AMMONIUM NITRATE
1-2
6.8.1 General
Ammonium nitrate (NH^NOs) is produced by neutralizing nitric acid with
ammonia. The reaction can be carried out at atmospheric pressure or at
pressures up to 410 kPa (45 psig) and at temperatures between 405 and 458K
(270 - 365°F). An 83 weight percent solution of ammonium nitrate product
is produced when concentrated nitric acid (56 - 60 weight percent) is
combined with gaseous ammonia in a ratio of from 3.55 to 3.71 to 1, by
weight. When solidified, ammonium nitrate is a hygroscopic colorless
solid.
Ammonium nitrate is marketed in several forms, depending upon its use.
The solution formed from the neutralization of acid and ammonia may be sold
as a fertilizer, generally in combination with urea. The solution may be
further concentrated to form a 95 to 99.5 percent ammonium nitrate melt for
use in solids formation processes. Solid ammonium nitrate may be produced
by prilling, graining, granulation or crystallization. In addition, prills
can be produced in either high or low density form, depending on the
concentration of the melt. High density prills, granules and crystals are
used as fertilizer. Ammonium nitrate grains are used solely in explosives.
Low density prills can be used as either.
The process for manufacturing ammonium nitrate can contain up to seven
major unit operations. These operating steps, shown in Figure 6.8-1, are
solution formation or synthesis, solution concentration, solids formation,
solids finishing, solids screening, solids coating, and bagging and/or bulk
shipping. In some cases, solutions may be blended for marketing as liquid
fertilizers.
AMMONIA'
NITRIC ACID •
1
SOLUTION t
FORMATION T^
ADDITIVE'
t
SOLUTION '
CONCENTRATION
' SOLIDS
*" FORMATION ""*
SOLIDS
*" FINISHING
1 OFFSIZE RECYCLE
SOLUTIONS
^ SOLIDS
SCREENING2
1
••^
SOLIDS
COATING
wm
j SOLUTION J
••
»-
| BLENDING ',
BAGGING
BULK
SHIPPING
BULK
SHIPPING
'ADDITIVE MAY BE ADDED BEFORE. DURING, OR AFTER CONCENTRATION
SCREENING MAY BE BEFORE OR AFTER SOLIDS FINISHING
Figure 6.8-1. Ammonium nitrate manufacturing operations.
The number of operating steps employed is determined by the desired
end product. For example, plants producing ammonium nitrate solutions
alone use only the solution formation, solution blending and bulk shipping
1/84
Food and Agricultural Industry
6.8-1
-------
operations. Plants producing a solid ammonium nitrate product can employ
all of the operations.
All ammonium nitrate plants produce an aqueous ammonium nitrate
solution through the reaction of ammonia and nitric acid in a neutralizer.
To produce a solid product, the ammonium nitrate solution is concentrated
in an evaporator or concentrator heated to drive off water. A melt is
produced containing from 95 to 99.8 percent ammonium nitrate at
approximately 422K (300°F). This melt is then used to make solid ammonium
nitrate products.
Of the various processes used to produce solid ammonium nitrate,
prilling and granulation are the most common. To produce prills, concen-
trated melt is sprayed into the top of a prill tower. Ammonium nitrate
droplets form in the tower and fall countercurrent to a rising air stream
that cools and solidifies the falling droplets into spherical prills.
Prill density can be varied by using different concentrations of ammonium
nitrate melt. Low density prills are formed from a 95 to 97.5 percent
ammonium nitrate melt, and high density prills are formed from a 99.5 to
99.8 percent melt. High density prills are less porous than low density
prills.
In the prilling process, an additive may be injected into the melt
stream. This additive serves three purposes, to raise the crystalline
transition temperature of the solid final product; to act as a desiccant,
drawing water into the final product prills to reduce caking; and to allow
prilling to be conducted at a lower temperature by reducing the freezing
point of molten ammonium nitrate. Magnesium nitrate or magnesium oxide are
examples of additives to the melt stream. Such additives account for 1 to
2.5 weight percent of the final product. While these additives are
effective replacements for conventional coating materials, their use is not
widespread in the industry.
Rotary drum granulators produce granules by spraying a concentrated
ammonium nitrate melt (99.0 to 99.8 percent) onto small seed particles in a
long rotating cylindrical drum. As the seed particles rotate in the drum,
successive layers of ammonium nitrate are added to the particles, forming
granules. Granules are removed from the granulator and screened. Offsize
granules are crushed and recycled to the granulator to supply additional
seed particles or are dissolved and returned to the solution process. Pan
granulators operate on the same principle as drum granulators and produce a
solid product with physical characteristics similar to those of drum
granules, except the solids are formed in a large, rotating circular pan.
The temperature of the ammonium nitrate product exiting the solids
formation process is approximately 339 - 397K (150 - 255°F). Rotary drum
or fluidized bed cooling prevents deterioration and agglomeration of solids
before storage and shipping. Low density prills, which have a high mois-
ture content because of a lower melt concentration, require drying before
cooling, usually in rotary drums or fluidized beds.
Since the solids are produced in a wide variety of sizes, they must be
screened for consistently sized prills or granules. Cooled prills are
screened, and offsize prills are dissolved and recycled to the solution
concentration process. Granules are screened before cooling, undersize
6-8-2 EMISSION FACTORS 1/84
-------
particles are returned directly to the granulator, and oversize granules
may be either crushed and returned to the granulator or sent to the
solution concentration process.
Following screening, products can be coated in a rotary drum to
prevent agglomeration during storage and shipment. The most common coating
materials are clays and diatomaceous earth. However, the use of additives
in the ammonium nitrate melt before prilling may preclude the use of
coatings.
Solid ammonium nitrate is stored and shipped in either bulk or bags.
Approximately 10 percent of solid ammonium nitrate produced in the United
States is bagged.
6.8.2 Emissions and Controls
Emissions from ammonium nitrate production plants are particulate
matter (ammonium nitrate and coating materials), ammonia and nitric acid.
Ammonia and nitric acid are emitted primarily from solution formation and
concentration processes, with ammonia also being emitted from prill towers
and granulators. Particulate matter (largely as ammonium nitrate) is
emitted from most of the process operations and is the primary emission
addressed here.
The emission sources in solution formation and concentration processes
are neutralizers and evaporators, primarily emitting nitric acid and
ammonia. Specific plant operating characteristics, however, make these
emissions vary depending upon use of excess ammonia or acid in the
neutralizer. Since the neutralization operation can dictate the quantity
of these emissions, a range of emission factors is presented in
Table 6.8-1. Particulate emissions from these operations tend to be
smaller in size than those from solids production and handling processes
and generally are recycled back to the process.
Emissions from solids formation processes are ammonium nitrate
particulate matter and ammonia. The sources of primary importance are
prill towers (for high density and low density prills) and granulators
(rotary drum and pan). Emissions from prill towers result from carryover
of fine particles and fume by the prill cooling air flowing through the
tower. These fine particles are from microprill formation, attrition of
prills colliding with the tower or one another, and from rapid transition
of the ammonium nitrate between crystal states. The uncontrolled parti-
culate emissions from prill towers, therefore, are affected by tower
airflow, spray melt temperature, condition and type of melt spray device,
air temperature, and crystal state changes of the solid prills. The amount
of microprill mass that can be entrained in the prill tower exhaust is
determined by the tower air velocity. Increasing spray melt temperature
causes an increase in the amount of gas phase ammonium nitrate generated.
Thus, gaseous emissions from high density prilling are greater than from
low density towers. Microprill formation resulting from partially plugged
orifices of melt spray devices can increase fine dust loading and
emissions. Certain designs (spinning buckets) and practices (vibration of
spray plates) help reduce microprill formation. High ambient air
temperatures can cause increased emissions because of entrainment as a
1/84 Food and Agricultural Industry 6.8-3
-------
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6.8-4
EMISSION FACTORS
1/84
-------
result of the higher air flow required to cool prills and because of
increased fume formation at the higher temperatures.
The granulation process in general provides a larger degree of control
in product formation than does prilling. Granulation produces a solid
ammonium nitrate product that, relative to prills, is larger and has
greater abrasion resistance and crushing strength. The air flow in
granulation processes is lower than that in prilling operations. Granu-
lators, however, cannot produce low density ammonium nitrate economically
with current technology. The design and operating parameters of granula-
tors may affect emission rates. For example, the recycle rate of seed
ammonium nitrate particles affects the bed temperature in the granulator.
An increase in bed temperature resulting from decreased recycle of seed
particles may cause an increase in dust emissions from granule
disintegration.
Cooling and drying are usually conducted in rotary drums. As with
granulators, the design and operating parameters of the rotary drums may
affect the quantity of emissions. In addition to design parameters, prill
and granule temperature control is necessary to control emissions from
disintegration of solids caused by changes in crystal state.
Emissions from screening operations are generated by the attrition of
the ammonium nitrate solids against the screens and against one another.
Almost all screening operations used in the ammonium nitrate manufacturing
industry are enclosed or have a cover over the uppermost screen. Screening
equipment is located inside a building, and emissions are ducted from the
process for recovery or reuse.
Prills and granules are typically coated in a rotary drum. The
rotating action produces a uniformly coated product. The mixing action
also causes some of the coating material to be suspended, creating particu-
late emissions. Rotary drums used to coat solid product are typically kept
at a slight negative pressure, and emissions are vented to a particulate
control device. Any dust captured is usually recycled to the coating
storage bins.
Bagging and bulk loading operations are a source of particulate
emissions. Dust is emitted from each type of bagging process during final
filling when dust laden air is displaced from the bag by the ammonium
nitrate. The potential for emissions during bagging is greater for coated
than for uncoated material. It is expected that emissions from bagging
operations are primarily the kaolin, talc or diatomaceous earth coating
matter. About 90 percent of solid ammonium nitrate produced domestically
is bulk loaded. While particulate emissions from bulk loading are not
generally controlled, visible emissions are within typical state regulatory
requirements (below 20 percent opacity).
Table 6.8-1 summarizes emission factors for various processes involved
in the manufacture of ammonium nitrate. Uncontrolled emissions of particu-
late matter, ammonia and nitric acid are given in the Table. Emissions of
ammonia and nitric acid depend upon specific operating practices, so ranges
of factors are given for some emission sources.
1/84 Food and Agricultural Industry 6.8-5
-------
Emission factors for controlled particulate emissions are also in
Table 6.8-1, reflecting wet scrubbing particulate control techniques. The
particle size distribution data presented in Table 6.8-2 indicate the
applicability of wet scrubbing to control ammonium nitrate particulate
emissions. In addition, wet scrubbing is used as a control technique
because the solution containing the recovered ammonium nitrate can be sent
to the solution concentration process for reuse in production of ammonium
nitrate, rather than to waste disposal facilities.
TABLE 6.8-2.
PARTICLE SIZE DISTRIBUTION DATA FOR UNCONTROLLED EMISSIONS
FROM AMMONIUM NITRATE MANUFACTURING FACILITIES3
CUMULATIVE WEIGHT Z
< 2.5 urn < 5 um < 10 \im
Solids Formation Operations
Low density prill tower
Rotary drum granuiator
Coolers and Dryers
Low density prill cooler
Low density prill predryer
Low density prill dryer
Rotary drum granulator cooler
Pan granulator precooler
56
0.07
0.03
0.03
0.04
0.06
0.3
73
0.3
0.09
0.06
0.04
0.5
0.3
83
2
0.4
0.2
0.15
3
1.5
References 4, 11-12, 22-23. Particle size determinations were not done in
strict accordance with EPA Method 5. A modification was used to handle the
high concentrations of soluble nitrogenous compounds (See Reference 1).
Particle size distributions were not determined for controlled particulate
emissions.
References for Section 6.8
1. Ammonium Nitrate Manufacturing Industry - Technical Document,
EPA-450/3-81-002, U. S. Environmental Protection Agency, Research
Triangle Park, NC, January 1981.
2. W. J. Search and R. B. Reznik, Source Assessment; Ammonium Nitrate
Production, EPA-600/2-77-107i, U. S. Environmental Protection Agency,
Research Triangle Park, NC, September 1977.
3. Memo from C. D. Anderson, Radian Corporation, Durham, NC, to Ammonium
Nitrate file, July 2, 1980.
4. D. P. Becvar, et al., Ammonium Nitrate Emission Test Report; Union
Oil Company of California, EMB-78-NHF-7, U. S. Environmental
Protection Agency, Research Triangle Park, NC, October 1979.
5. K. P. Brockman, Emission Tests for Particulates, Cominco American,
Beatrice, NE, 1974.
6. Written communication from S. V. Capone, GCA Corporation, Chapel Hill,
NC, to E. A. Noble, U. S. Environmental Protection Agency, Research
Triangle Park, NC, September 6, 1979.
6.8-6
EMISSION FACTORS
1/84
-------
7. Written communication from D. E. Cayard, Monsanto Agricultural
Products Company, St. Louis, MO, to E. A. Noble, U. S. Environmental
Protection Agency, Research Triangle Park, NC, December 4, 1978.
8. Written communication from D. E. Cayard, Monsanto Agricultural
Products Company, St. Louis, MO, to E. A. Noble, U. S. Environmental
Protection Agency, Research Triangle Park, NC, December 27, 1978.
9. Written communication from T. H. Davenport, Hercules Incorporated,
Donora, PA, to D. R. Goodwin, U. S. Environmental Protection Agency,
Research Triangle Park, NC, November 16, 1978.
10. R. N. Doster and D. J. Grove, Source Sampling Report; Atlas Powder
Company, Entropy Environmentalists, Inc., Research Triangle Park, NC,
August 1976.
11. M. D. Hansen, et al., Ammonium Nitrate Emission Test Report; Swift
Chemical Company, EMB-79-NHF-11, U. S. Environmental Protection
Agency, Research Triangle Park, NC, July 1980.
12. R. A. Kniskern, et al., Ammonium Nitrate Emission Test Report;
Cominco American, Inc., Beatrice, Nebraska, EMB-79-NHF-9,
U. S. Environmental Protection Agency, Research Triangle Park, NC,
April 1979.
13. Written communication from J. A. Lawrence, C. F. Industries, Long
Grove, IL, to D. R. Goodwin, U. S. Environmental Protection Agency,
Research Triangle Park, NC, December 15, 1978.
14. Written communication from F. D. McCauley, Hercules Incorporated,
Louisiana, MO, to D. R. Goodwin, U. S. Environmental Protection
Agency, Research Triangle Park, October 31, 1978.
15. W. E. Misa, Report of Source Test; Collier Carbon and Chemical
Corporation (Union Oil), Test No. 5Z-78-3, Anaheim, CA,
January 12, 1978.
16. Written communication from L. Musgrove, Georgia Department of Natural
Resources, Atlanta, GA, to R. Rader, Radian Corporation, Durham, NC,
May 21, 1980.
17. Written communication from D. J. Patterson, N-ReN Corporation,
Cincinnati, OH, to E. A. Noble, U. S. Environmental Protection Agency,
Research Triangle Park, NC, March 26, 1979.
18. Written communication from H. Schuyten, Chevron Chemical Company, San
Francisco, CA, to D. R. Goodwin, U. S. Environmental Protection Agency,
March 2, 1979.
19. Emission Test Report: Phillips Chemical Company, Texas Air Control
Board, Austin, TX, 1975.
20. Surveillance Report; Hawkeye Chemical Company, U. S. Environmental
Protection Agency, Research Triangle Park, NC, December 29, 1976.
1/84 Food and Agricultural Industry 6.8-7
-------
21. W. A. Wade and R. W. Cass, Ammonium Nitrate Emission Test Report:
C. F. Industries, EMB-79-NHF-10, U. S. Environmental Protection
Agency, Research Triangle Park, NC, November 1979.
22. W. A. Wade, et al., Ammonium Nitrate Emission Test Report; Columbia
Nitrogen Corporation. EMB-80-NHF-16, U. S. Environmental Protection
Agency, Research Triangle Park, NC, January 1981.
23. York Research Corporation, Ammonium Nitrate Emission Test Report:
N-ReN Corporation, EMB-78-NHF-5, U. S. Environmental Protection
Agency, Research Triangle Park, NC, May 1979.
6.8-8 EMISSION FACTORS j_/84
-------
6.14 UREA
6.14.1 General1
Urea (CO[NH2]2)» also known as carbamide or carbonyl diamide, is
produced by reacting ammonia and carbon dioxide at 448 - 473K (347 - 392°F)
and 13.7 - 23.2 MPa (2,0002 - 3,400 psi) to form ammonium carbamate
(NH2C02NH4). Pressure may be as high as 41.0 MPa (6,000 psi). Urea is
formed by a dehydration decomposition of ammonium carbamate.
Urea is marketed as a solution or in a variety of solid forms. Most
urea solution produced is used in fertilizer mixtures, with a small amount
going to animal feed supplements. Most solids are produced as prills or
granules, for use as fertilizer or protein supplement in animal feeds, and
use in plastics manufacturing. Five U. S. plants produce solid urea in
crystalline form.
The process for manufacturing urea involves a combination of up to
seven major unit operations. These operations, illustrated by the flow
diagram in Figure 6.14-1, are solution synthesis, solution concentration,
solids formation, solids cooling, solids screening, solids coating, and
bagging and/or bulk shipping.
ADDITIVE
AMMONIA
OPTIONAL WITH INDIVIDUAL MANUFACTURING PRACTICES
Figure 6.14-1. Major urea manufacturing operations.
The combination of processing steps is determined by the desired end
products. For example, plants producing urea solution use only the solution
formulation and bulk shipping operations. Facilities producing solid urea
employ these two operations and various combinations of the remaining five
operations, depending upon the specific end product being produced.
In the solution synthesis operation, ammonia and CO^ are reacted to
form ammonium carbamate. The carbamate is then dehydrated to yield 70 to
77 percent aqueous urea solution. This solution can be used as an
1/84
Food and Agricultural Industry
6.14-1
-------
ingredient of nitrogen solution fertilizers, or it can be concentrated
further to produce solid urea.
The concentration process furnishes urea melt for solids formation.
The three methods of concentrating the urea solution are vacuum concentra-
tion, crystallization and atmospheric evaporation. The method chosen
depends upon the level of biuret (NH2CONHCONH2) impurity allowable in the
end product. The most common method of solution concentration is
evaporation.
Urea solids are produced from the urea melt by two basic methods,
prilling and granulation. Prilling is a process by which solid particles
are produced from molten urea. Molten urea is sprayed from the top of a
prill tower, and as the droplets fall through a countercurrent air flow,
they cool and solidify into nearly spherical particles. There are two types
of prill towers, fluidized bed and nonfluidized bed. The major difference
between these towers is that a separate solids cooling operation may be
required to produce agricultural grade prills in a nonfluidized bed prill
tower.4
Granulation is more popular than prilling in producing solid urea for
fertilizer. There are two granulation methods, drum granulation and pan
granulation. In drum granulation, solids are built up in layers on seed
granules in a rotating drum granulator/cooler approximately 14 feet in
diameter. Pan granulators also form the product in a layering process, but
different equipment is used, and pan granulators are not common in this
country.
The solids cooling operation generally is accomplished during solids
formation, but for pan granulation processes and for some agricultural grade
prills, some supplementary cooling is provided by auxiliary rotary drums.
The solids screening operation removes offsize product from solid urea.
The offsize material may be returned to the process in the solid phase or be
redissolved in water and returned to the solution concentration process.
Clay coatings are used in the urea industry to reduce product caking
and urea dust formation, even though they also reduce the nitrogen content
of the product, and the coating operation creates clay dust emissions. The
popularity of clay coating has diminished considerably because of the
practice of injecting formaldehyde additives into the liquid or molten urea
before solids formation.5"6 Additives reduce solids caking during storage
and urea dust formation during transport and handling.
The majority of solid urea product is bulk shipped in trucks, enclosed
railroad cars, or barges, but approximately 10 percent is bagged.
6.14.2 Emissions and Controls
Emissions from urea manufacture include ammonia and particulate matter.
Ammonia is emitted during the solution synthesis and solids production
processes. Particulate matter is the primary emission being addressed here.
There have been no reliable measurements of free gaseous formaldehyde
emissions. The chromotropic acid procedure that has been used to measure
6.14-2 EMISSION FACTORS 1/84
-------
formaldehyde is not capable of distinguishing between gaseous formaldehyde
and methylenediurea, the principle compound formed when the formaldehyde
additive reacts with hot urea.7"8
In the synthesis process, some emission control is inherent in the
recycle process where carbamate gases and/or liquids are recovered and
recycled. Typical emission sources from the solution synthesis process are
noncondensable vent streams from ammonium carbamate decomposers and
separators. Emissions from synthesis processes are generally combined with
emissions from the solution concentration process and are vented through a
common stack. Combined particulate emissions from urea synthesis and
concentration are much less than particulate emissions from a typical solids
producing urea plant. The synthesis and concentration operations are
usually uncontrolled except for recycle provisions to recover ammonia. For
these reasons, no factor for controlled emissions from synthesis and
concentration processes is given in this section.
Uncontrolled emission rates from prill towers may be affected by the
following factors:
- product grade being produced
- air flow rate through the tower
type of tower bed
- ambient temperature and humidity
The total of mass emissions per unit is usually lower for feed grade prill
production than for agricultural grade prills, due to lower airflows.
Uncontrolled particulate emission rates for fluidized bed prill towers are
higher than those for nonfluidized bed prill towers making agricultural
grade prills and are approximately equal to those for nonfluidized bed feed
grade prills.1* Ambient air conditions can affect prill tower emissions.
Available data indicate that colder temperatures promote the formation of
smaller particles in the prill tower exhaust.9 Since smaller particles are
more difficult to remove, the efficiency of prill tower control devices
tends to decrease with ambient temperatures. This can lead to higher
emission levels for prill towers operated during cold weather. Ambient
humidity can also affect prill tower emissions. Air flow rates must be
increased with high humidity, and higher air flow rates usually cause higher
emissions.
The design parameters of drum granulators and rotary drum coolers may
affect emissions.10"11
Drum granulators have an advantage over prill towers in that they are
capable of producing very large particles without difficulty. Granulators
also require less air for operation than do prill towers. A disadvantage of
granulators is their inability to produce the smaller feed grade granules
economically. To produce smaller granules, the drum must be operated at a
higher seed particle recycle rate. It has been reported that, although the
increase in seed material results in a lower bed temperature, the
corresponding increase in fines in the granulator causes a higher emission
rate.10 Cooling air passing through the drum granulator entrains
approximately 10 to 20 percent of the product. This air stream is
1/84 Food and Agricultural Industry 6.14-3
-------
controlled with a wet scrubber which is standard process equipment on drum
granulators.
In the solids screening process, dust is generated by abrasion of urea
particles and the vibration of the screening mechanisms. Therefore, almost
all screening operations used in the urea manufacturing industry are
enclosed or are covered over the uppermost screen. This operation is a
small emission source, and particulate emissions from solids screening are
not treated here.12"13
Emissions attributable to coating include entrained clay dust from
loading, inplant transfer, and leaks from the seals of the coater. No
emissions data are available to quantify this fugitive dust source.
Bagging operations are a source of particulate emissions. Dust is
emitted from each bagging method during the final stages of filling, when
dustladen air is displaced from the bag by urea. Bagging operations are
conducted inside warehouses and are usually vented to keep dust out of the
workroom area, according to OSHA regulations. Most vents are controlled
with baghouses. Nationwide, approximately 90 percent of urea produced is
bulk loaded. Few plants control their bulk loading operations. Generation
of visible fugitive particles is slight.
Table 6.14-1 summarizes the uncontrolled and controlled emission
factors, by processes, for urea manufacture. Table 6.14-2 summarizes
particle sizes for these emissions.
TABLE 6.14-2. UNCONTROLLED PARTICLE SIZE DATA FOR UREA PRODUCTION3
OPERATION
PARTICLE SIZE
(Cummulative Weight Z)
< 10 vm < 5 um < 2.5
urn
Solution Formation and Concentration
Solids Formation
Nonfluidized bed prilling
agricultural grade
feed grade
Fluidized bed prilling
agricultural grade
feed grade
Drum granulation
Rotary Drum Cooler
Bagging
Bulk Loading
NA
90
85
60
24
b
0.70
NA
MA
NA
84
74
52
13
b
0.15
NA
NA
NA
79
50
43
14
b
0.04
NA
NA
not available. No data were available on particle sizes of controlled
emissions. Particle size information was collected uncontrolled in the
ducts and may not reflect particle size in the ambient air.
All particulate matter ^.5.7 urn was collected in the cyclone precollector
sampling equipment.
6.14-4
EMISSION FACTORS
1/84
-------
TABLE 6.14-1. EMISSION FACTORS FOR UREA PRODUCTION*
EMISSION FACTOR RATING: Ab
Particulates0
Operation
Solution formation ,
and concentration
Solids formation
Sonfluidized
bed prilling
agricultural grade*
feed grade^
Fluidized bed prilling
agricultural grade1^
feed grade^
k
Drum granulation
Rotary drum cooler
Bagging
Uncontrolled
kg/Mg Ib/ton
0.0105e O.Q21e
1.9h 3.8h
1.8 3.6
3.1 6.2
1.8 3.6
120 241
3.72 7.45
0.095n 0.19n
Ammonia
Controlled Uncontrolled Exiting Control Device
kg/Mg
-
0.032
NA
0.39
0.24
0.115
0.10m
SA
Ib/ton kg/Mg
9.12f
0.064 0.43
NA NA
0.78 1.46
0.48 2.07
0.234 1.071
0.20m 0.0256
NA NA
Ib/ton kg/Mg
18.24f
0.87 i
NA NA
2.91 i
4.14 1.04
2.151 h
0.051 NA
NA NA
Ib/ton
-
i
NA
i
2.08
h
NA
NA
Based on emissions per unit of production output. Dash * not applicable. NA » not available.
Emission Factor Rating is C for controlled particulate emissions from rotary drum coolers
and uncontrolled particulate emissions from bagging.
'"Particulate test data were collected using a modification of EPA Reference Method 3. Reference 1,
Appendix 3 explains these modifications.
References 14 - 16, 19. Emissions from the synthesis process are generally combined with emissions
from the solution concentration process and vented through a common stack. In the synthesis
process, some emission control is inherent in the recycle process where carbamate gases and/or
liquids are recovered and recycled.
eEPA test data indicated a range of 0.0052 - 0.0150 kg/Mg (0.0104 - 0.0317 Ib/ton).
fEPA test data indicated a range of 3.79 - 14.44 kg/Mg (7.58 - 28.89 Ib/ton).
Reference 20. These factors were determined at an ambient temperature of 288K - 294K
(57°F - 69°F). The controlled emission factors are based on ducting exhaust through a downcomer
and then a wetted fiber filter scrubber achieving a 98.3 percent efficiency. This represents a
higher degree of control than is typical in this industry.
Figures are based on EPA test data. Industry test data ranged from 0.39 - 1.79 kg/'Mg
(0.78 - 3.58 Ib/ton).
TIo ammonia control demonstrated by scrubbers installed for particulate control. Some increase in
ammonia emissions exiting the control device was noted.
J Reference 19. Feed grade factors were determined at an ambient temperature of 302K (85°F) and
agricultural grade factors at an ambient temperature of 299K (30°F) . For fluidized bed prilling,
controlled emission factors are based on use of an entrainment scrubber.
T.eferences 14 - 16. Controlled emission factors are based on use of a wet entrainment scrubber.
Met scrubbers are standard process equipment on drum granulacors. Uncontrolled emissions were
measured at the scrubber inlet.
test data indicated a range of 0.955 - 1.20 kg/Mg (1.91 - 2.40 Ib/ton).
"EMISSION FACTOR RATING: C; Reference 1.
"EMISSION FACTOR RATING: c; Reference i.
1/84
Food and Agricultural Industry
6.14-5
-------
Urea manufacturers presently control particulate matter emissions from
prill towers, coolers, granulators and bagging operations. With the
exception of bagging operations, urea emission sources usually are
controlled with wet scrubbers. The preference of scrubber systems over dry
collection systems is primarily for the easy recycling of dissolved urea
collected in the device. Scrubber liquors are recycled to the solution
concentration process to eliminate waste disposal problems and to recover
the urea collected.1
Fabric filters (baghouses) are used to control fugitive dust from
bagging operations, where humidities are low and blinding of the bags is not
a problem. However, many bagging operations are uncontrolled.1
References for Section 6.14
1. Urea Manufacturing Industry - Technical Document, EPA-450/3-81-001,
U. S. Environmental Protection Agency, Research Triangle Park, NC,
January 1981.
2. D. F. Bress, M. W. Packbier, "The Startup of Two Major Urea Plants/1
Chemical Engineering Progress, May 1977, p. 80.
3. A. V. Slack, "Urea," Fertilizer Development Trends, Noyes Development
Corporation, Park Ridge, NJ, 1968, p. 121.
4. Written communication from J. M. Killen, Vistron Corporation, Lima, OH,
to D. R. Goodwin, U. S. Environmental Protection Agency, Research
Triangle Park, NC, December 21, 1978.
5. Written communication from J. P. Swanburg, Union Oil of California,
Brea, CA, to D. R. Goodwin, U. S. Environmental Protection Agency,
Research Triangle Park, NC, December 20, 1978.
6. Written communication from M. I. Bornstein and S. V. Capone, GCA
Corporation, Bedford, MA, to E. A. Noble, U. S. Environmental
Protection Agency, Research Triangle Park, NC, June 22, 1978.
7. Written communication from Gary McAlister, U. S. Environmental
Protection Agency, Emission Measurement Branch, to Eric Noble, U. S.
Environmental Protection Agency, Industrial Studies Branch, Research
Triangle Park, NC, July 28, 1983.
8. Formaldehyde Use in Urea-Based Fertilizers, Report of the Fertilizer
Institute's Formaldehyde Task Group, The Fertilizer Institute,
Washington, D. C., February 4, 1983.
9. J. H. Cramer, "Urea Prill Tower Control Meeting 20% Opacity,"
Presented at the Fertilizer Institute Environmental Symposium,
New Orleans, LA, April 1980.
10. Written communication from M. I. Bornstein, GCA Corporation, Bedford,
MA, to E. A. Noble, U. S. Environmental Protection Agency, Research
Triangle Park, NC, August 2, 1978.
6.14-6 EMISSION FACTORS
1/84
-------
11. Written communication from M. I. Bornstein and S. V. Capone, GCA
Corporation, Bedford, MA, to E. A. Noble, U. S. Environmental
Protection Agency, Research Triangle Park, NC, June 23, 1978.
12. Written communication from J. P. Alexander, Agrico Chemical Company,
Donaldsonville, LA, to D. R. Goodwin, U. S. Environmental Protection
Agency, NC, December 21, 1978.
13. Written communication from N. E. Picquet, W. R. Grace and Company,
Memphis, TN, to D. R. Goodwin, U. S. Environmental Protection Agency,
Research Triangle Park, NC, December 14, 1978.
14. Urea Manufacture: Agrico Chemical Company Emission Test Report, EMB
Report 79-NHF-13a, U. S. Environmental Protection Agency, Research
Triangle Park, NC, September 1980.
15. Urea Manufacture; Agrico Chemical Company Emission Test Report, EMB
Report 78-NHF-4, U. S. Environmental Protection Agency, Research
Triangle Park, NC, April 1979.
16. Urea Manufacture; CF Industries Emission Test Report, EMB Report
78-NHF-8, U. S. Environmental Protection Agency, Research Triangle
Park, NC, May 1979.
17. Urea Manufacture: Union Oil of California Emission Test Report, EMB
Report 78-NHF-7, U. S. Environmental Protection Agency, Research
Triangle Park, NC, October 1979.
18. Urea Manufacture: Union Oil of California Emission Test Report, EMB
Report 80-NHF-15, U. S. Environmental Protection Agency, Research
Triangle Park, NC, September 1980.
19. Urea Manufacture; W. R. Grace and Company Emission Test Report, EMB
Report 78-NHF-3, U. S. Environmental Protection Agency, Research
Triangle Park, NC, December 1979.
20. Urea Manufacture; Reichhold Chemicals Emission Test Report, EMB Report
80-NHF-14, U. S. Environmental Protection Agency, Research Triangle
Park, NC, August 1980.
1/84 Food and Agricultural Industry 6.14-7
-------
7.1 PRIMARY ALUMINUM PRODUCTION
7.1.1 Process Description^"^
The base ore for primary aluminum production is bauxite, a hydrated
oxide of aluminum consisting of 30 to 70 percent alumina (A1203) and lesser
amounts of iron, silicon and titanium. The bauxite ore is first purified to
alumina by the Bayer process, and this is then reduced to elemental aluminum.
The production of alumina and the reduction of alumina to aluminum are seldom
accomplished at the same facility. A schematic diagram of the primary
production of aluminum is shown at Figure 7.1-1.
In the Bayer process, the ore is dried, ground in ball mills and mixed
with a leaching solution of sodium hydroxide at an elevated temperature and
pressure, producing a sodium aluminate solution which is separated from the
bauxite impurities and cooled. As the solution cools, the hydrated aluminum
oxide (A1203 • 3H20) precipitates. Following separation and washing to
remove iron oxide, silica and other impurities, the hydrated aluminum oxide
is dried and calcined to produce a crystalline form of alumina (A1203),
advantageous for electrolysis.
Aluminum metal is manufactured by the Hall-Heroult process, which
involves the electrolytic reduction of alumina dissolved in a molten salt
bath of cryolite (Na3AlFg) and various salt additives:
2A1203 Electrolysis 4A1 + 302 (!)
Alumina > Aluminum Oxygen
(reduction)
The electrolytic reduction occurs in shallow rectangular cells, or "pots",
which are steel shells lined with carbon. Carbon electrodes extend into the
pot and serve as the anodes, and the carbon lining the steel shell is the cathode.
Molten cryolite functions as both the electrolyte and the solvent for the
alumina. Electrical resistance to the current passing between the electrodes
generates heat that maintains cell operating temperatures between 950° and
1000°C (1730° and 1830°F). Aluminum is deposited at the cathode, where it
remains as molten metal below the surface of the cryolite bath. The carbon
anodes are continuously depleted by the reaction of oxygen (formed during the
reaction) and anode carbon, to produce carbon monoxide and carbon dioxide.
Carbon consumption and other raw material and energy requirements for aluminum
production are summarized in Table 7.1-1. The aluminum product is period-
ically tapped beneath the cryolite cover and is fluxed to remove trace
impurities.
Aluminum reduction cells are distinguished by the anode type and
configuration used in the pots. Three types of pots are currently used,
prebaked (PB), horizontal stud Soderberg (HSS), and vertical stud Soderberg
(VSS). Most of the aluminum produced in the U. S. is processed in PB cells.
Anodes are produced as an ancillary operation at the reduction plant.
In the paste preparation plant, petroleum coke is mixed with a pitch binder
4/81 Metallurgical Industry 7.1-1
-------
SODIUM
HYDROXIDE
TO CONTROL DEVICE
DILUTION
WATER
BAUXITE
SETTLING
CHAMBER
RED MUD
(IMPURITIES)
DILUTE
SODIUM
HYDROXIDE
SPENT
ELECTRODES
TO CONTROL
DEVICE
ALUMINA
ANODE
PASTE
i
ELECTROLYTE
ANODE PASTE
CRYSTALLI2ER
AQUEOUS SODIUM
ALUMINATE
TO CONTROL DEVICE
BAKING
FURNACE
BAKED
ANODES
,, TO CONTROL DEVICE
I
PREBAKE
REDUCTION
CELL
TO CONTROL DEVICE
HORIZONTAL
OR VERTICAL
SOOERBERG
REDUCTION CELL
MOLTEN
ALUMINUM
Figure 7.1-1. Schematic diagram of primary aluminum production process.
7.1-2
EMISSION FACTORS
4/81
-------
to form a paste which is used for Soderberg cell anodes, and for green anodes
for prebake cells. Paste preparation includes crushing, grinding and screen-
ing of coke and cleaned spent anodes (butts), and blending with a pitch binder
in a steam jacketed mixer. For Soderberg anodes, the thick paste mixture is
transferred directly to the potroom for addition to the anode casings. In
prebake anode preparation, the paste mixture is molded to form self supporting
green anode blocks. The blocks are baked in a direct fired ring furnace or an
indirect fired tunnel kiln. Baked anodes are then transferred to the rodding
room, where the electrodes are attached. Volatile organic vapors from the pitch
paste are emitted during anode baking, and most are destroyed in the baking
furnace. The baked anodes, typically 14 to 24 per cell, are attached to metal
rods and serve as replaceable anodes.
TABLE 7.1-1. RAW MATERIAL AND ENERGY REQUIREMENTS FOR ALUMINUM PRODUCTION
Parameter Typical value
Cell operating temperature ~ 950°C (~ 1740°F)
Current through pot line 60,000 - 125,000 amperes
Voltage drop per cell 4.3-5.2
Current efficiency 85 - 90%
Energy required 13.2 - 18.7 kwh/kg aluminum
(6.0 - 8.5 kwh/lb aluminum)
Weight alumina consumed 1.89 - 1.92 kg(lb) Al203/kg(lb) aluminum
Weight electrolyte
fluoride consumed 0.03 - 0.10 kg(lb) fluoride/kg(lb) aluminum
Weight carbon electrode
consumed 0.45 - 0.55 kg(lb) electrode/kg(lb) aluminum
In the electrolytic reduction of alumina, the carbon anodes are lowered
into the cell and consumed at a rate of about 2.5 centimeters (1 inch) per day.
Prebaked cells are preferred over Soderberg cells for their lower power require-
ments, reduced generation of volatile pitch vapors from the carbon anodes,
and provision for better cell hooding to capture emissions.
The second most commonly used reduction cell is the horizontal stud
Soderberg (HSS). This type of cell uses a "continuous" carbon anode. Green
anode paste is periodically added at the top of the anode casing of the pot
and is baked by the heat of the cell to a solid carbon mass as the material
moves down the casing. The cell casing consists of aluminum sheeting and
perforated steel channels, through which electrode connections (studs) are
inserted horizontally into the anode paste. During reduction, as the baking
anode is lowered, the lower row of studs and the bottom channel are removed,
and the flexible electrical connectors are moved to a higher row of studs.
High molecular weight organics from the anode paste are released, along with
other cell emissions. The heavy tars can cause plugging of exhaust ducts,
fans and emission control equipment.
The vertical stud Soderberg (VSS) cell is similar to the HSS cell, except
that the studs are mounted vertically in the anode paste. Gases from the VSS
4/81 Metallurgical Industry 7.1-3
-------
cells can be ducted to gas burners, and the tar and oils combusted. The con- '
struction of the HSS cell prevents the installation of an integral gas collection
device, and hooding is restricted to a canopy or skirt at the base of the cell,
where the hot anode enters the cell bath.
Casting involves pouring molten aluminum into molds and cooling it with
water. At some plants, before casting, the molten aluminum may be batch treated
in furnaces to remove oxide, gaseous impurities and active metals such as
sodium and magnesium. One process consists of adding a flux of chloride and
fluoride salts and then bubbling chlorine gas, usually mixed with an inert
gas, through the molten mixture. Chlorine reacts with the impurities to form
HC1, A1203 and metal chloride emissions. A dross forms and floats on the
molten aluminum and is removed before casting.H
7.1.2 Emissions and Controls1"-* ,10
Controlled and uncontrolled emission factors for total particulate
matter, fluoride and sulfur oxides are presented in Table 7.1-2. Fugitive
particulate and fluoride emission factors for reduction cells are also pre-
sented in this Table.
In the preparation of refined alumina from bauxite, large amounts of
particulates are generated during the calcining of hydrated aluminum oxide,
but the economic value of this dust is such that extensive controls are
employed to reduce emissions to relatively small quantities. Small amounts
of particulates are emitted from the bauxite grinding and materials handling
processes.
Emissions from aluminum reduction processes consist primarily of gaseous
hydrogen fluoride and particulate fluorides, alumina, carbon monoxide, vola-
tile organics, and sulfur dioxide from the reduction cells, and fluorides,
vaporized organics and sulfur dioxide from the anode baking furnaces.
The source of fluoride emissions from reduction cells is the fluoride
electrolyte, which contains cryolite, aluminum fluoride (A1F3), and fluorspar
(CaF2)« For normal operation, the weight, or "bath", ratio of sodium fluo-
ride (NaF) to A1F3 is maintained between 1.36 and 1.43 by the addition of A1F3.
This increases the cell current efficiency and lowers the bath melting point,
permitting lower operating temperature in the cell. Cell fluoride emissions
are decreased by lowering the operating temperature. The ratio of gaseous
(mainly hydrogen fluoride and silicon tetrafluoride) to particulate fluorides
varies from 1.2 to 1.7 with PB and HSS cells, but attains a value of approx-
imately 3.0 with VSS cells.
Particulate emissions from reduction cells consist of alumina and carbon
from anode dusting, cryolite, aluminum fluoride, calcium fluoride, chiolite
(Na5Al3Fi4) and ferric oxide. Representative size distributions for partic-
ulate emissions from PB cells and HSS cells are presented in Table 7.1-3.
Particulates less than 1 micron in diameter represent the largest fraction
(35 - 44 percent) for uncontrolled emissions. In one HSS cell, uncontrolled
particulate emissions from one HSS cell had a mass mean particle diameter of 5.5
microns. Thirty percent by mass of the particles were submicron, and 16 percent
were less than 0.2 microns in diameter.
7.1-4 EMISSION FACTORS 4/81
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