-------
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. Billiard, 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 tnethacrylate
Phenol
Propylene glycol
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
3.
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.
2/80 E\aporation Lof> Source* 1.8-3
-------
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
Total 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-Q04g, 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 thylamine
[(CHOtfl]
kg/Mg
NAb
0.15C
1.75C
NAd
NAd
Ib/ton
NAb
0.3C
3.5C
NAd
NAd
Hydrogen sulfide
[H2S]
kg/Mg
NAb
0.005C
0.10C
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.
bAlthough it is known that odors are emitted from canning cookers,
quantitative estimates are not available.
cReference 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
6.8.1 General1"2
Ammonium nitrate (NHi+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 *
FORMATION "]T
ADDITIVE1
»
SOLUTION '
CONCENTRATION ""
^ SOLIDS
FORMATION ~
SOLIDS
FINISHING ~*
1 OFFSIZE RECYCLE
SOLUTIONS
SOLIDS
SCREENING2
I
— ••
SOLIDS
COATING
••
*-
«»-
! BLENDING ',
BAGGING
BULK
SHIPPING
BULK
SHIPPING
1 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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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 %
< 2.5 um < 5 um < 10 um
Solids Formation Operations
Low density prill tower
Rotary drum granulator
Coolers and Dryers
Low density prill cooler
Low density prill predryer
Low density prill dryer
Rotary drum granulator cooler
Pan granuiator 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
inferences 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 distributioas 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 !/84
-------
6.14 UREA
6.14.1 General1
Urea (CO[NH2l2)» 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
(NH2C02NHi+). 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
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 C02 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.^
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.^ 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.1" 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 %)
< 10 um < 5 um < 2.5 u«n
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
NA
NA
84
74
52
18
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 um 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
Particulatesc
Operation
Solution formation
and concentration
Solids formation
Nonfluidized
bed prilling
agricultural grade8
feed grade^
Fluidized bed prilling
agricultural grade^
feed grade-1
k
Drum granulation
Rotary drum cooler
Bagging
Uncontrolled
kg/Mg
0.0105e
1.9h
1.8
3.1
1.8
120
3.72
0.095n
Ib/ton
0.021a
3.8h
3.6
6.2
3.6
241
7.45
0.19°
Controlled
kg/Mg
-
0.032
NA
0.39
0.24
0.115
0.10m
NA
Ib/ton
-
0.064
NA
0.78
0.48
0.234
0.20m
NA
Ammonia
Uncontrolled
kg/Mg
9.12f
0.43
NA
1.46
2.07
1.071
0.0256
NA
Ib/ton
18.24f
0.87
NA
2.91
4.14
2.151
0.051
NA
Exiting Control Device
kg/Mg
-
i
NA
i
1.04
h
NA
NA
Ib/ton
-
i
NA
i
2.08
h
NA
NA
aBased on emissions per unit of production output. Dash - not applicable. NA « not available.
Emission Factor Rating is C for controlled paniculate emissions from rotary drum coolers
and uncontrolled particulate emissions from bagging.
c?articulate test data were collected using a modification of EPA Reference Method 5. 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 Che 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).
MO ammonia control demonstrated by scrubbers installed for particulate control. Some increase in
ammonia emissions exiting the control device was noted.
•'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 (80"F). For fluidized bed prilling,
controlled emission factors are based on use of an entrainment scrubber.
References 14 - 16. Controlled emission factors are based on use of a wet entrainment scrubber.
Wet scrubbers are standard process equipment on drum granulators. 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.
FACTOR RATING: C; Reference 1.
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,"
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. Bernstein 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. Bernstein 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
BAUXITE
TO CONTROL DEVICE
I
SETTLING
CHAMBER
DILUTION
WATER
RED MUD
(IMPURITIES)
DILUTE
SODIUM
HYDROXIDE
TO CONTROL
DEVICE
CRYSTALLIZER
AQUEOUS SODIUM
ALUM1NATE
TO CONTROL DEVICE
I
BAKING
FURNACE
BAKED
ANODES
TO CONTROL DEVICE
1
PREBAKE
REDUCTION
CELL
ANODE PASTE
TO CONTROL DEVICE
HORIZONTAL
OR VERTICAL
SODERBERG
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.^
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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EMISSION FACTORS
4/81
-------
TABLE 7.1-3. REPRESENTATIVE PARTICLE SIZE DISTRIBUTIONS OF UNCONTROLLED
EMISSIONS FROM PREBAKED AND HORIZONTAL STUD SODERBERG CELLS3
Size range ryv
1
5
10
20
a
to
to
to
to
>44
5
10
20
44
Particles (wt Z)
PB
35
25
8
5
5
HSS
44
26
8
6
4
aReference
Emissions from reduction cells also include hydrocarbons or organics,
carbon monoxide and sulfur oxides. Small amounts of hydrocarbons are
released by PB pots, and larger amounts are emitted from HSS and VSS pots.
In vertical cells, these organics are incinerated in integral gas burners.
Sulfur oxides originate from sulfur in the anode coke and pitch. The con-
centrations of sulfur oxides in VSS cell emissions range from 200 to 300 parts
per million. Emissions from PB plants usually have S02 concentrations ranging
from 20 to 30 parts per million.
Emissions from anode bake ovens include the products of fuel combustion;
high boiling organics from the cracking, distillation and oxidation of paste
binder pitch; sulfur dioxide from the sulfur in carbon paste, primarily from
the petroleum coke, fluorides from recycled anode butts; and other partic-
ulate matter. The concentrations of uncontrolled S02 emissions from anode
baking furnaces range from 5 to 47 parts per million (based on 3 percent sulfur
in coke.)^
A variety of control devices has been used to abate emissions from
reduction cells and anode baking furnaces. To control gaseous and partic-
ulate fluorides and particulate emissions, one or more types of wet scrub-
bers (spray tower and chambers, quench towers, floating beds, packed beds,
Venturis, and self induced sprays have been applied to all three types of
reduction cells and to anode baking furnaces. Also, particulate control
methods such as electrostatic precipitators (wet and dry), multiple cyclones
and dry alumina scrubbers (fluid bed, injected, and coated filter types) are
employed with baking furnaces and on all three cell types. Also, the alumina
adsorption systems are being used on all three cell types to control both
gaseous and particulate fluorides by passing the pot offgases through the
entering alumina feed, which adsorbs the fluorides. This technique has an
overall control efficiency of 98 to 99 percent. Baghouses are then used to
collect residual fluorides entrained in the alumina and to recycle them to
the reduction cells. Wet electrostatic precipitators approach adsorption in
particulate removal efficiency but must be coupled to a wet scrubber or
coated baghouse to catch hydrogen fluoride.
Scrubber systems also remove a portion of the S02 emissions. These
emissions could be reduced by wet scrubbing or by reducing the quantity of
sulfur in the anode coke and pitch, i. e., calcining the coke.
4/81
Metallurgical Industry
7.1-7
-------
In the hydrated aluminum oxide calcining, bauxite grinding and materials
handling operations, various dry dust collection devices (centrifugal collec-
tors, multiple cyclones, or electrostatic precipitators and/or wet scrubbers)
have been used.
Potential sources of fugitive particulate emissions in the primary
aluminum industry are bauxite grinding, materials handling, anode baking and
three types of reduction cells (see Table 7.1-2). These fugitives probably
have particle size distributions similar to those presented in Table 7.1-3.
References for Section 7.1
1• Engineering and Cost Effectiveness Study of Fluoride Emissions Control,
Volume I, APTD-0945, U. S. Environmental Protection Agency, Research
Triangle Park, NC, January 1972.
2. Air Pollution Control in the Primary Aluminum Industry, Volume I,
EPA-450/3-73-004a, U. S. Environmental Protection Agency, Research
Triangle Park, NC, July 1973.
3. Particulate Pollutant System Study, Volume I, APTD-0743, U. S. Environ-
mental Protection Agency, Research Triangle Park, NC, May 1971.
4. Emissions from Wet Scrubbing System, Report Number Y-7730-E, York
Research Corp., Stamford, CT, May 1972.
5. Emissions from Primary Aluminum Smelting Plant, Report Number Y-7730-B,
York Research Corp., Stamford, CT, June 1972.
6. Emissions from the Wet Scrubber System, Report Number Y-7730-F, York
Research Corp., Stamford, CT, June 1972.
7. T. R. Hanna and M. J. Pilat, "Size Distribution of Particulates Emitted
from a Horizontal Spike Soderberg Aluminum Reduction Cell", Journal of
the Air Pollution Control Association, 22_:533-536, July 1972.
8. Background Information for Standards of Performance: Primary Aluminum
Industry, Volume 1; Proposed Standards, EPA-450/2-74-020a, U. S.
Environmental Protection Agency, Research Triangle Park, NC, October
1974.
9. Primary Aluminum; Guidelines for Control of Fluoride Emissions from
Existing Primary Aluminum Plants, EPA-450/2-78-049b, U. S. Environmental
Protection Agency, Research Triangle Park, NC, December 1979.
10. Written communication from T. F. Albee, Reynolds Aluminum, Richmond, VA,
to A. A. MacQueen, U. S. Environmental Protection Agency, Research
Triangle Park, NC, October 20, 1982.
11. Environmental Assessment; Primary Aluminum, Interim report, U. S.
Environmental Protection Agency, Cincinnati, OH, October 1979.
7.1-8 EMISSION FACTORS 4/81
-------
7.3 PRIMARY COPPER SMELTING
7.3.1 Process Description^"^
In the United States, copper is produced from sulfide ore concentrates
principally by pyrometallurgical smelting methods. Because the copper ores
usually contain less than 1 percent copper, they must be concentrated before
transport to a smelter. Concentrations of 15 to 35 percent copper are
accomplished at the mine site by crushing, grinding and flotation. Sulfur
content of the concentrate ranges from 25 to 35 percent, and most of the
remainder is iron (25 percent) and water (10 percent). Some concentrates also
contain significant quantities of arsenic, cadmium, lead, antimony and other
heavy metals.
The conventional pyrometallurgical copper smelting process is illustrated
in Figure 7.3-1. The process includes roasting of ore concentrates to produce
calcine, smelting of roasted (calcine feed) or unroasted (green feed) ore
concentrates to produce matte, and converting of the matte to yield blister
copper product (about 99 percent pure). Typically, the blister copper is fire
refined in an anode furnace, cast into "anodes" and sent to an electrolytic
refinery for further impurity elimination.
In roasting, charge material of copper concentrate mixed with a siliceous
flux (often a low grade ore) is heated in air to about 650°C (1,200°F),
eliminating 20 to 50 percent of the sulfur as sulfur dioxide (SC^). Portions
of such impurities as antimony, arsenic and lead are driven off, and some of
the iron is converted to oxide. The roasted product, called calcine, serves
as a dried and heated charge for the smelting furnace. Either multiple
hearth or fluidized bed roasters are used for roasting copper concentrate.
The fluid bed roaster is similar in appearance to a multihearth roaster but has
fewer intricate internal mechanical systems. Multihearth roasters accept
moist concentrate, whereas fluid bed roasters are fed finely ground material
(60 percent minus 200 mesh). With both of these types, the roasting is
autogenous. Because there is less air dilution, higher SC>2 concentrations
are present in fluidized bed roaster gases than in multiple hearth roaster
gases.
In the smelting process, either hot calcines from the roaster or raw
unroasted concentrate are melted with siliceous flux in a smelting furnace to
produce copper matte, a molten mixture of cuprous sulfide (Cu2S) and ferrous
sulfide (FeS) and some heavy metals. The required heat comes from partial
oxidation of the sulfide charge and from burning external fuel. Most of the
iron and some of the impurities in the charge oxidize and combine with the
fluxes to form a slag on top of the molten bath, which is periodically removed
and discarded. Copper matte remains in the furnace until tapped. Mattes
produced by the domestic industry range from 35 to 65 percent copper, with
about 45 percent the most common. This copper content percentage is referred
to as the matte grade. Currently, four smelting furnace technologies are
used in the U.S., reverberatory, electric, Noranda and Outokumpu (flash).
1/84 Metallurgical Industry 7.3-1
-------
ORE CONCENTRATES WITH SILICA FLUXES
FUEL.
AIR-
ROASTING
CONVERTER SLAG (2% Cu)
FUEL-
AIR-
CALCINE
SMELTING
SLAG TO DUMP
(0.5% Cu)
AIR-
MATTE (~40% Cu)
CONVERTING
GREEN POLES OR GAS
~1
FUEL-
AIR-
BLISTER COPPER
(98.5+% Cu)
FIRE REFINING
SLAG TO CONVERTER
ANODE COPPER (99.5% Cu)
TO ELECTROLYTIC REFINERY
-*-OFFGAS
OFFGAS
-^-OFFGAS
-^.OFFGAS
7.3-2
Figure 7.3-1. A conventional copper smelting process.
EMISSION FACTORS
1/84
-------
Reverberatory furnace operation is a continuous process, with frequent
charging of input materials and periodic tapping of matte and skimming of
slag. Reverberatory furnaces typically process from 800 to 1,200 Mg (900 to
1,300 tons) of charge per day. Heat is supplied by combustion of oil, gas or
pulverized coal. Furnace temperatures may exceed 1,500°C (2,730°F).
For smelting in electric arc furnaces, heat is generated by the flow of
an electric current in submerged carbon electrodes lowered through
the furnace roof into the slag layer of the molten bath. The feed generally
consists of dried concentrates or calcines, and charging wet concentrates is
avoided. The chemical and physical changes occurring in the molten bath
are similar to those occurring in the molten bath of a reverberatory furnace.
Also, the matte and slag tapping practices are similar at both furnaces.
Electric furnaces do not produce fuel combustion gases, so flow rates are
lower and S02 concentrations higher in effluent gas than in that of reverber-
atory furnaces.
Flash furnace smelting combines the operations of roasting and smelting
to produce a high grade copper matte from concentrates and flux. In flash
smelting, dried ore concentrates and finely ground fluxes are injected together
with oxygen, preheated air, or a mixture of both into a furnace of special
design, where temperature is maintained at approximately 1,000°C (1,830°F).
Flash furnaces, in contrast to reverberatory and electric furnaces, use the
heat generated from partial oxidation of their sulfide sulfur charge to
provide much or all of the energy (heat) required for smelting. They also
produce offgas streams containing high concentrations of S02-
Slag produced by flash furnace operations contains significantly higher
amounts of copper than does that from reverberatory or electric furnace
operations. As a result, the flash furnace and converter slags produced at
flash smelters are treated in a slag cleaning furnace to recover the copper.
Slag cleaning furnaces usually are small electric arc furnaces. The flash
furnace and converter slags are charged to a slag cleaning furnace and are
allowed to settle under reducing conditions with the addition of coke or iron
sulfide. The copper, which is in oxide form in the slag, is converted to
copper sulfide, subsequently removed from the furnace and charged to a
converter with the regular matte.
The Noranda process, as originally designed, allowed the continuous
production of blister copper in a single vessel, by effectively combining
roasting, smelting and converting into one operation. Metallurgical problems,
however, led to the operation of these reactors for the production of copper
matte. As in flash smelting, the Noranda process takes advantage of the heat
energy available from the copper ore. The remaining thermal energy required
is supplied by oil burners or by coal mixed with the ore concentrates.
The final step in the production of blister copper is converting. The
purpose of converting is to eliminate the remaining iron and sulfur present
in the matte, leaving molten "blister" copper. All but one U. S. smelter use
Fierce-Smith converters, which are refractory lined cylindrical steel shells
mounted on trunnions at either end and rotated about the major axis for
charging and pouring. An opening in the center of the converter functions as
1/84 Metallurgical Industry 7.3-3
-------
a mouth, through which molten matte, siliceous flux and scrap copper are
charged and gaseous products are vented. Air or oxygen rich air is blown
through the molten matte. Iron sulfide (FeS) is oxidized to iron oxide (FeO)
and S02, and the FeO combines with the flux to form a slag on the surface.
At the end of this segment of the converter operation, termed the slag blow,
the slag is skimmed and generally recycled back to the smelting furnace. The
process of charging, blowing and slag skimming is repeated until an adequate
amount of relatively pure Cu2S, called "white metal", accumulates in the
bottom of the converter. A renewed air blast oxidizes the remaining copper
sulfide sulfur to SC^, leaving blister copper in the converter. The blister
copper is subsequently removed and transferred to refining facilities. This
segment of converter operation is termed the finish blow. The SC>2 produced
throughout the operation is vented to pollution control devices.
One smelter uses Hoboken converters, the primary advantage of which lies
in emission control. The Hoboken converter is essentially like a conventional
Fierce-Smith converter, except that this vessel is fitted with a side flue at
one end shaped as an inverted U. This flue arrangement permits siphoning of
gases from the interior of the converter directly to offgas collection,
leaving the converter mouth under a slight vacuum.
Blister copper usually contains from 98.5 to 99.5 percent pure copper.
Impurities may include gold, silver, antimony, arsenic, bismuth, iron, lead,
nickel, selenium, sulfur, tellurium and zinc. To purify blister copper further,
fire refining and electrolytic refining are used. In fire refining, blister
copper is placed in a fire refining furnace, a flux is usually added, and
air is blown through the molten mixture to oxidize remaining impurities,
which are removed as a slag. The remaining metal bath is subjected to a
reducing atmosphere to reconvert cuprous oxide to copper. Temperature in the
furnace is around 1,100°C (2,010°F). The fire refined copper is cast into
anodes and further refined electrolytically. Electrolytic refining separates
copper from impurities by electrolysis in a solution containing copper sulfate
and sulfuric acid. Metallic impurities precipitate from the solution and
form a sludge that is removed and treated to recover precious metals. Copper
is dissolved from the anode and deposited at the cathode. Cathode copper is
remelted and made into bars, ingots or slabs for marketing purpose. The
copper produced is 99.95 to 99.97 percent pure.
7.3.2 Emissions and Controls
Particulate matter and sulfur dioxide are the principal air contaminants
emitted by primary copper smelters. These emissions are generated directly
from the processes involved, as in the liberation of S02 from copper concen-
trate during roasting or in the volatilization of trace elements as oxide fumes.
Fugitive emissions are generated by leaks from major equipment during material
handling operations.
Roasters, smelting furnaces and converters are sources of both particulate
matter and sulfur oxides. Copper and iron oxides are the primary constituents
of the particulate matter, but other oxides such as arsenic, antimony, cadmium,
lead, mercury and zinc may also be present, with metallic sulfates and sulfuric
7.3-4 EMISSION FACTORS 1/84
-------
acid mist. Fuel combustion products also contribute to particulate emissions
from multihearth roasters and reverberatory furnaces.
Single stage electrostatic precipitators (ESP) are widely used in the primary
copper industry for the control of particulate emissions from roasters, smelting
furnaces and converters. Many of the existing ESPs are operated at elevated
temperatures, usually at 200 to 340°C (400 to 650°F) and are termed "hot
ESPs". If properly designed and operated, these ESPs remove 99 percent or
more of the condensed particulate matter present in gaseous effluents. However,
at these elevated temperatures, a significant amount of volatile emissions
such as arsenic trioxide (As203) and sulfuric acid mist is present as vapor in
the gaseous effluent and thus can not be collected by the particulate control
device at elevated temperatures. At these temperatures, the arsenic trioxide
in the vapor state will pass through an ESP. Therefore, the gas stream to be
treated must be cooled sufficiently to ensure that most of the arsenic present
is condensed before entering the control device for collection. At some
smelters, the gas effluents are cooled to about 120°C (250°F) temperature
before entering a particulate control system, usually an ESP (termed "cold
ESP"). Spray chambers or air infiltration are used for gas cooling. Fabric
filters can also be used for particulate matter collection.
Gas effluents from roasters are usually sent to an ESP or spray chamber/ESP
system or are combined with smelter furnace gas effluents before particulate
collection. Overall, the hot ESPs remove only 20 to 80 percent of the total
particulate (condensed and vapor) present in the gas. The cold ESPs may
remove more than 95 percent of the total particulate present in the gas.
Particulate collection systems for smelting furnaces are similar to those for
roasters. Reverberatory furnace off gases are usually routed through waste
heat boilers and low velocity balloon flues to recover large particles and
heat, then are routed through an ESP or spray chamber/ESP system.
In the standard Fierce-Smith converter, flue gases are captured during
the blowing phase by the primary hood over the converter mouth. To prevent
the hood's binding to the converter with splashing molten metal, there is a
gap between the hood and the vessel. During charging and pouring operations,
significant fugitives may be emitted when the hood is removed to allow
crane access. Converter offgases are treated in ESPs to remove particulate
matter and in sulfuric acid plants to remove
Remaining smelter processes handle material that contains very little
sulfur, hence SC>2 emissions from these processes are insignificant.
Particulate emissions from fire refining operations, however, may be of concern
Electrolytic refining does not produce emissions unless the associated sulfuric
acid tanks are open to the atmosphere. Crushing and grinding systems used in
ore, flux and slag processing also contribute to fugitive dust problems.
Control of S02 emissions from smelter sources is most commonly performed
in a single or double contact sulfuric acid plant. Use of a sulfuric acid
plant to treat copper smelter effluent gas streams requires that gas be free
from particulate matter and that a certain minimum inlet S02 concentration be
maintained. Practical limitations have usually restricted sulfuric acid plant
application to gas streams that contain at least 3.0 percent S02» Table 7.3-1
shows typical average S02 concentrations for the various smelter unit offgases.
1/84 Metallurgical Industry 7.3-5
-------
TABLE 7.3-1. TYPICAL SULFUR DIOXIDE CONCENTRATIONS IN
OFFGASES FROM PRIMARY COPPER SMELTING SOURCES
SC>2 concentration
Unit Volume %
Multiple hearth roaster
Fluidized bed roaster
Reverberatory furnace
Electric arc furnace
Flash smelting furnace
Continuous smelting furnace
Fierce-Smith converter
Hoboken converter
Single contact H2S04 plant
Double contact ^804 plant
1
10
0
4
10
5
4
0
.5
.5
.2
_
-
-
-
-
-
-
8
-
0
3
12
1
8
20
15
7
0
.05
.5
.26
Currently, converter gas effluents at most of the smelters are treated
for S02 control in sulfuric acid plants. Gas effluents from some multihearth
roaster operations and all fluid bed roaster operations are also treated in
sulfuric acid plants. The weak S02 content gas effluents from the reverberatory
furnace operations are usually released to the atmosphere with no .reduction of
S02« The gas effluents from the other types of smelter furnaces, due to their
higher contents of S02, are treated in sulfuric acid plants before being
vented. Typically, single contact acid plants achieve 92.5 to 98 percent
conversion of S02 to acid, with approximately 2000 ppm S02 remaining in the
acid plant effluent gas. Double contact acid plants collect from 98 to more
than 99 percent of the S02 and emit about 500 ppm S02« Absorption of the S02
in dimethylaniline (DMA) solution has also been used in U. S. smelters to
produce liquid
Emissions from hydrometallurgical smelting plants generally are small in
quantity and are easily controlled. In the Arbiter process, ammonia gas
escapes from the leach reactors, mixer/settlers, thickeners and tanks. For
control, all of these units are covered and vented to a packed tower scrubber
to recover and recycle the ammonia.
Actual emissions from a particular smelter unit depend upon the configuration
of equipment in that smelting plant and its operating parameters. Table 7.3-2
gives emission factors for the major units for various smelter configurations.
7.3.3 Fugitive Emissions
The process sources of particulate matter and S02 emissions are also the
potential fugitive sources of these emissions, roasting, smelting, converting,
fire refining and slag cleaning. Table 7.3-3 presents the potential fugitive
emission factors for these sources. The actual quantities of emissions
from these sources depend on the type and condition of the equipment and on
the smelter operating techniques. Although emissions from many of these
sources are released inside a building, ultimately they are discharged to the
atmosphere.
Fugitive emissions are generated during the discharge and transfer of hot
calcine from multihearth roasters, and negligible amounts of fugitive emissions
7.3-6 EMISSION FACTORS 1/84
-------
TABLE 7.3-2. EMISSION FACTORS FOR PRIMARY COPPER SMELTERSa>b
EMISSION FACTOR RATING: B
Particulate matter
SO,
Configuration0
Unit
References
Kg/Mg Ib/ton Kg/Mg Ib/ton
Reverberatory furnace (RF)
followed by converters (C)
Multihearth roaster (MHR)
followed by reverberatory
furnace (RF) and converters (C)
Fluid bed roaster (FBR) followed
by reverberatory furnace (RF)
and converters (C)
Concentrate dryer (CD) followed
by electric furnace (EF) and
converters (C)
Fluid bed roaster (FBR) followed
by electric furnace (EF) and
converters (C)
Concentrate dryer (CD) followed
by flash furnace (FF) ,
cleaning furnace (SS) and
converters (C)
Concentrate dryer (CD) followed
by Noranda reactors (NR) and
converters (C)
RF
C
MHR
RF
C
FBR
RF
C
CD
EF
C
FBR
EF
C
CD
FF
ssf
C«
CD
NR
C
25
18
22
25
18
NA
25
18
5
50
18
NA
50
18
5
70
5
NAS
5
NA
NA
50
36
45
50
36
NA
50
36
10
100
36
NA
100
36
10
140
10
NA£
10
NA
NA
160
370
140
90
300
180
90
270
0.5
120
410
180
45
300
0.5
410
0.5
120
0.5
NA
NA
320
740
280
ISO
600
360
160
540
1
240
820
360
90
600
1
820
1
240
1
NA
NA
4-10,
9, 11-15
4-5, 16-17
4-9, 18-19
8, 11-13
20
e
e
21-22
15
3, 11-13, 15
20
15, 23
e
21-22
24
22
22
21-22
aExpressed as units per unit weight of concentrated ore processed by the smelter. Approximately
4 unit weights of concentrate are required to produce 1 unit weight of blister copper. NA -
not available.
''For particulate matter removal, gaseous effluents from roasters, smelting furnaces and converters
are usually treated in hot ESPs at 200 - 340°C (400 - 650°F) or in cold ESPs with gases cooled to
about 120°C (250°F) before ESP. Particulate emissions from copper smelters contain volatile metallic
oxides which remain in vapor form at higher temperatures and which condense to solid particulate at
lower temperatures (120°C or 250°F). Therefore, overall particulate removal in hot ESPs may range
from 20 - 80%, and overall particulate removal in cold ESPs may be 99%. Converter gas effluents
and, at some smelters, roaster gas effluents are treated in single contact acid plants (SCAP) or
double contact acid plants (DCAP) for S02 removal. Typical SCAPs are about 96* efficient, and DCAPs
are up to 99.8 7. efficient in S02 removal. They also remove over 99Z of particulate matter.
cln addition to sources indicated, each smelter configuration contains fire refining anode furnaces
after the converters. Anode furnaces emit negligible 302* No particulate emission data are available
for anode furnaces.
^Factors for all configurations except reverberatory furnace followed by converters were developed by
normalizing test data for several smelters to represent 30% sulfur content in concentrated ore.
eBased on the test data for the configuration multihearth roaster followed by reverberatory furnace
and converters.
'Used to recover copper from furnace slag and converter slag.
SSince the converters at flash furnace and Noranda furnace smelters treat high copper content matte,
converter particulate emissions from flash furnace smelters are expected to be lower than corresponding
emissions from conventional smelters consisting of multihearth roasters, reverberatory furnace, and converters.
may also come from the charging of these roasters. Fluid bed roasting, a
closed loop operation, has negligible fugitive emissions.
Matte tapping and slag skimming operations are sources of fugitive emissions
from smelting furnaces. Fugitive emissions can also result from charging of a
1/84
Metallurgical Industry
7.3-7
-------
TABLE 7.3-3. FUGITIVE EMISSION FACTORS FOR PRIMARY COPPER SMELTERS3
EMISSION FACTOR RATING: B
Source
Particulata matter
Kg/Mg Ib/toa
So2
Kg/Mg
Ib/toa
Roaster calcine discharge
Smelting furnaceb
Converters
Converter slag return
Anode furnace
Slag cleaning £urnacec
1.3
0.2
2.2
NA
0.25
4
2.6
0.4
4.4
HA
0.5
3
0.5
2
65
0.05
0.05
3
1
4
130
0.1
0.1
6
References 16, 22, 25-31. Expressed as mass units per unit weight
of concentrated ore processed by the smelter. Approximately 4 unit
weights of concentrate are required to produce 1 unit weight of copper
metal. Factors for flash furnace smelters and No rand a furnace smelters
may be slightly lower than reported values. NA - not available.
''Includes fugitive emissions from matte tapping and slag skimming
operations. About 50Z of fugitive particulate matter emissions and
about 90% of total SC>2 emissions are from matte tapping operations.
The remainder is from slag skimming.
cUsed to treat slags from smelting furnaces and converters at the flash
furnace smelter.
smelting furnace or from leaks, depending upon the furnace type and condition.
A typical single matte tapping operation lasts from 5 to 10 minutes, and a
single slag skimming operation lasts from 10 to 20 minutes. Tapping frequencies
vary with furnace capacity and type. In an 8 hour shift, matte is tapped 5 to
20 times, and slag is skimmed 10 to 25 times.
Each of the various stages of converter operation, the charging, blowing,
slag skimming, blister pouring, and holding, is a potential source of fugitive
emissions. During blowing, the converter mouth is in stack (i. e., a close
fitting primary hood is over the mouth to capture offgases). Fugitive emissions
escape from the hoods. During charging, skimming and pouring operations, the
converter mouth is out of stack (i. e., the converter mouth is rolled out of
its vertical position, and the primary hood is isolated). Fugitive emissions
are discharged during the rollout.
At times during normal smelting operations, slag or blister copper can
not be transferred immediately from or to the converters. This condition, the
holding stage, may occur for several reasons, including insufficient matte in
the smelting furnace, the unavailability of a crane, and others. Under these
conditions, the converter is rolled out of vertical position and remains in a
holding position, and fugitive emissions may result.
Fugitive emissions from primary copper smelters are captured by applying
either local or general ventilation techniques. Once captured, emissions may
7.3-8
EMISSION FACTORS
1/84
-------
be vented directly to a collection device or be combined with process offgases
before collection. Close fitting exhaust hood capture systems are used for
multihearth roasters, and hood ventilation systems for smelter matte tapping
and slag skimming operations. For converters, secondary hood systems or building
evacuation systems are used.
7.3.4 Lead Emission Factors
Both the process and the fugitive particulate matter emissions from
various equipment at primary copper smelters contain oxides of many inorganic
elements, including lead. The lead content of particulate matter emissions
depends upon both the lead content of concentrate feed into the smelter and
the process offgas temperature. Lead emissions are effectively removed in
particulate control systems operating at low temperatures of about 120°C (250°F).
Table 7.3-4 presents lead emission factors for various operations of
primary copper smelters. These emission factors represent totals of both
process and fugitive emissions.
TABLE 7.3-4. LEAD EMISSION FACTORS FOR PRIMARY COPPER SMELTERS3
EMISSION FACTOR RATING: C
Lead emissions'3
Operation
kg/Mg
IV ton
Roasting0
Smelting*1
Converting6
Refining
0.075
0.036
0.13
HA
0.15
0.072
0.27
NA
Reference 32. Expressed as units per unit weight of concentrated ore
processed by the smelter. Approximately 4 unit weights of concentrate
are required to produce 1 unit weight of copper metal. Based on test
data for several smelters containing from 0.1 to 0.4Z lead in feed
throughput. NA » not available.
"For process and fugitive emissions totals.
cBased on test data on multihearth roasters. Includes the total of
process emissions and calcine transfer fugitive emissions. Calcine
transfer fugitive emissions constitute about 10 percent of the total of
process and fugitive emissions.
dBaaed on test data on reverberatory furnaces. Includes total process
emissions and fugitive emissions from matte tapping and slag skimming
operations. Fugitive emissions from matte tapping and slag skimming
operations amount to about 352 and 2%, respectively.
Includes the total of process and fugitive emissions. Fugitive emissions
constitute about 50 percent of the total.
1/84
Metallurgical Industry
7.3-9
-------
References for Section 7.3
1. Background Information for New Source Performance Standards; Primary
Copper, Zinc, and Lead Smelters, Volume I, Proposed Standards,
EPA-450/2-74-002a, U. S. Environmental Protection Agency, Research Triangle
Park, NC, October 1974.
2. Arsenic Emissions from Primary Copper Smelters - Background Information
for Proposed Standards, Preliminary Draft, EPA Contract No. 68-02-3060,
Pacific Environmental Services, Durham, NG, February 1981.
3. Background Information Document for Revision of New Source Performance
Standards for Primary Copper Smelters, Draft Chapters 3 through 6, EPA
Contract Number 68-02-3056, Research Triangle Institute, Research Triangle
Park, NC, March 31, 1982.
ll" Air Pollution Emission Test; ASARCO Copper Smelter, El Paso, Texas,
EMB-77-CUS-6, U. S. Environmental Protection Agency, Research Triangle
Park, NC, June 1977.
5. Written communication from W. F. Cummins, ASARCO, Inc., El Paso, TX, to
A. E. Vervaert, U. S. Environmental Protection Agency, Research Triangle
Park, NC, August 31, 1977.
6. AP-42 Background Files, Office of Air Quality Planning and Standards,
U. S. Environmental Protection Agency, Research Triangle Park, NC.
7. Source Emissions Survey of Kennecott Copper Corporation, Copper Smelter
Converter Stack Inlet and Outlet and Reverberatory Electrostatic
Precipitator Inlet and Outlet, Hurley, New Mexico, File Number EA-735-09,
Ecology Audits, Inc., Dallas, TX, April 1973.
8. Trace Element Study at a Primary Copper Smelter, EPA-600/2-78-065a
and -065b, U. S. Environmental Protection Agency, Research Triangle Park,
NC, March 1978.
9. Systems Study for Control of Emissions, Primary Nonferrous Smelting
Industry, Volume II: Appendices A and B, PB-184885, National Technical
Information Service, Springfield, VA, June 1969.
10. Design and Operating Parameters For Emission Control Studies: White
Pine Copper Smelter, EPA-600/2-76-036a, U. S. Environmental Protection
Agency, Washington, DC, February 1976.
11. R. M. Statnick, Measurement of Sulfur Dioxide, Particulate and Trace
Elements in Copper Smelter Converter and Roaster/Reverberatory Gas Streams,
PB-238095, National Technical Information Service, Springfield, VA,
October 1974.
12. AP-42 Background Files, Office of Air Quality Planning and Standards,
U. S. Environmental Protection Agency, Research Triangle Park, NC.
7.3-10 EMISSION FACTORS 1/84
-------
13. Design and Operating Parameters For Emission Control Studies, Kennecott -
McGill Copper Smelter, EPA-600/2-76-036c, U. S. Environmental Protection
Agency, Washington, DC, February 1976.
14. Emission Test Report (Acid Plant) of Phelps Dodge Copper Smelter, Ajo,
Arizona, EMB-78-CUS-11, U. S. Environmental Protection Agency, Research
Triangle Park, NC, March 1979.
15. S. Dayton, "Inspiration's Design for Clean Air", Engineering and Mining
Journal, 175:6, June 1974.
16. Emission Testing of ASARCO Copper Smelter, Tacoma, Washington, EMB 78-CUS-
12, U. S. Environmental Protection Agency, Research Triangle Park, NC,
April 1979.
17. Written communication from A. L. Labbe, ASARCO Inc., Tacoma, WA, to S. T.
Cuffe, U. S. Environmental Protection Agency, Research Triangle Park, NC,
November 20, 1978.
18. Design and Operating Parameters for Emission Control Studies: ASARCO -
Hayden Copper Smelter, EPA-600/2-76-036J, U. S. Environmental Protection
Agency, Washington, DC, February 1976.
19. Pacific Environmental Services, Incorporated, Design and Operating
Parameters for Emission Control Studies: Kennecott, Hayden Copper
Smelter, EPA-600/2-76-036b, U. S. Environmental Protection Agency,
Washington, DC, February 1976.
20. R. Larkin, Arsenic Emissions at Kennecott Copper Corporation, Hayden, AZ,
EPA-76-NFS-1, U. S. Environmental Protection Agency, Research Triangle
Park, NC, May 1977.
21. Emission Compliance Status, Inspiration Consolidated Copper Company,
Inspiration, AZ, U. S. Environmental Protection Agency, San Francisco,
CA, 1980.
22. Written communication from M. P. Scanlon, Phelps Dodge Corporation, to
D. R. Goodwin, U. S. Environmental Protection Agency, Research Triangle
Park, NC, October 18, 1978.
23. Written communication from G. M. McArthur, The Anaconda Company, to
D. R. Goodwin, U. S. Environmental Protection Agency, Research Triangle
Park, NC, June 2, 1977.
24. Telephone communication from V. Katari, Pacific Environmental Services,
Inc., Durham, NC, to R. Winslow, Hidalgo Smelter, Phelps Dodge
Corporation, Hidalgo, AZ, April 1, 1982.
25. Emission Test Report, Phelps Dodge Copper Smelter, Douglas, Arizona,
EMB-78-CUS-8, U. S. Environmental Protection Agency, Research Triangle
Park, NC, February 1979.
1/84 Metallurgical Industry 7.3-11
-------
26. Emission Testing of Kennecott Copper Smelter, Magna, Utah, EMB-78-CUS-13,
U. S. Environmental Protection Agency, Research Triangle Park, NC,
April 1979.
27. Emission Test Report, Phelps Dodge Copper Smelter, Ajo, Arizona,
EMB-78-CUS-9, U. S. Environmental Protection Agency, Research Triangle
Park, NC, February 1979.
28. Written communication from R. D. Putnam, ASARCO, Inc., to M. 0. Varner,
ASARCO, Inc., Salt Lake City, UT, May 12, 1980.
•
29. Emission Test Report, Phelps Dodge Copper Smelter, PIayas, New Mexico,
EMB-78-CUS-10, U. S. Environmental Protection Agency, Research Triangle
Park, NC, March 1979.
30. ASARCO Copper Smelter, El Paso, Texas, EMB-78-CUS-7, U. S. Environmental
Protection Agency, Research Triangle Park, NC, April 25, 1978.
31. A. D. Church, et al., "Measurement of Fugitive Particulate and Sulfur
Dioxide Emissions at Inco's Copper Cliff Smelter", Paper A-79-51, The
Metallurgical Society of American Institute of Mining, Metallurgical,
and Petroleum Engineers (AIME), New York, NY.
32. Copper Smelters, Emission Test Report - Lead Emissions, EMB-79-CUS-14,
U. S. Environmental Protection Agency, Research Triangle Park, NC,
September 1979.
7.3-12 EMISSION FACTORS 1/84
-------
Thus, fugitive particulate emissions from hot mix asphalt plants are
mostly dust from aggregate storage, handling and transfer. Stone dust may
range from 0.1 to more than 300 micrometers in diameter. On the average, 5
percent of cold aggregate feed is less than 74 micrometers (minus 200 mesh).
Dust that may escape before reaching primary dust collection generally is 50
to 70 percent less than 74 micrometers. Materials emitted are given in
Tables 8.1-1 and 8.1-4.
Emission factors for various materials emitted from the stack are given
in Table 8.1-1. With the exception of aldehydes, the materials listed in this
Table are also emitted from the mixer, but mixer concentrations are 5 to 100
fold smaller than stack concentrations, lasting only during the discharge of
the mixer.
TABLE 8.1-1.
EMISSION FACTORS FOR SELECTED MATERIALS FROM AN
ASPHALTIC CONCRETE PLANT STACK3
Material emittedb
Particulated
Sulfur oxides (as S02) *®
Nitrogen oxides (as N02)
Volatile organic compounds^
Carbon monoxide^
Polycyclic organic matter^
Aldehydes^
Formaldehyde
2-Methylpropanal
(isobutyraldehyde)
1-Butanal
(n-butyraldehyde )
3-Methylbutanal
(isovaleraldehyde)
Emission factor0
g/Mg
137
146S
18
14
19
0.013
10
0.077
0.63
1.2
8.3
Ib/ton
.274
.2925
.036
.028
.038
.000026
.020
.00015
.0013
.0024
.016
Emission
Factor
Rating
B
C
D
D
D
D
D
D
D
D
D
aReference 16.
bparticulates, carbon monoxide, polycyclics, trace metals and hydrogen
sulfide were observed in the mixer emissions at concentrations that were
small relative to stack concentrations.
°Expressed as g/Mg and Ib/ton of asphaltic concrete produced.
^Mean of 400 plant survey source test results.
Reference 21. S » % sulfur in fuel. S02 may be attenuated >50% by
adsorption on alkaline aggregate.
*Based on limited test data from the single asphaltic concrete plant
described in Table 8.1-2.
4/81
Mineral Products Industry
8.1-7
-------
Reference 16 reports mixer concentrations of SOX, NOX, VOC and
ozone as less than certain values, so they may not be present at
all, while particulates, carbon monoxide, polycyclics, trace metals
and hydrogen sulfide were observed at concentrations that were small
relative to stack amounts. Emissions from the mixer are thus best
treated as fugitive.
The materials listed in Table 8.1-1 are discussed below.
Factor ratings are listed for each material in the table. All emis-
sion factors are for controlled operation, based either on average
industry practice shown by survey or on actual results of testing
in a selected typical plant. The characteristics of this represen-
tative plant are given in Table 8.1-2.
TABLE 8.1-2. CHARACTERISTICS OF AN ASPHALTIC
CONCRETE PLANT SELECTED FOR SAMPLING3
Parameter Plant Sampled
Plant type Conventional permanent
batch plant
Production rate, 160.3 ± 16%
Mg/hr (ton/hr) (177 ± 16%)
Mixer capacity,
Kg (tons) 3.6 (4.0)
Primary collector Cyclone
Secondary collector Wet scrubber (venturi)
Fuel Oil
Release agent Fuel oil
Stack height, m (ft) 15.85 (52)
Reference 16, Table 16.
The industrial survey showed that over 66 percent of operating
hot mix asphalt plants use fuel oil for combustion. Possible sulfur
oxide emissions from the stack were calculated assuming that all
sulfur in the fuel oil is oxidized to SOX. The amount of sulfur
oxides actually released through the stack may be attenuated by
water scrubbers or even by the aggregate itself, if limestone is
being dried. No. 2 fuel oil has an average sulfur content of
0.22 percent.
Emission factors for nitrogen oxides, nonmethane volatile
organics, carbon monoxide, polycyclic organic material and aldehydes
8.1-8 EMISSION FACTORS 4/31
-------
8.4 CALCIUM CARBIDE MANUFACTURING
8.4.1 General
Calcium carbide (CaC2) is manufactured by heating a lime and carbon
mixture to 2,000 to 2,100°C (3,632 to 3,812°F) in an electric arc furnace.
At those temperatures, the lime is reduced by carbon to calcium carbide and
carbon monoxide, according to the following reaction:
CaO + 3C
CaC2 + CO
Lime for the reaction is usually made by reducing limestone in a kiln at the
plant site. The sources of carbon for the reaction are petroleum coke,
metallurgical coke or anthracite coal. Because impurities in the furnace
charge remain in the calcium carbide product, the lime should contain no more
than 0.5 percent each of magnesium oxide, aluminum oxide and iron oxide, and
0.004 percent phosphorous. Also, the coke charge should be low in ash and
sulfur. Analyses indicate that 0.2 to 1.0 percent ash and 5 to 6 percent
sulfur are typical in petroleum coke. About 991 kilograms (2,185 Ib) of
lime, 683 kilograms (1,506 Ib) of coke, and 17 to 20 kilograms (37 to 44 Ib)
of electrode paste are required to produce one megagram (2,205 Ib) of calcium
carbide.
The process for manufacturing calcium carbide is illustrated in
Figure 8.4-1. Moisture is removed from coke in a coke dryer, while lime-
stone is converted to lime in a lime kiln. Fines from coke drying and lime
operations are removed and may be recycled. The two charge materials are
then conveyed to an electric arc furnace, the primary piece of equipment used
to produce calcium carbide. There are two basic types of electric arc
furnaces, the open furnace, in which the carbon monoxide burns to carbon
dioxide when it contacts the air above the charge, and the closed furnace, in
which the gas is collected from the furnace and either used as fuel for other
processes or flared. Electrode paste composed of coal tar pitch binder and
TO FLAR
MARY
EL
(FUEL
*
1
PARTIOJLATE
CONTROL
DEVICE
FURNACE
ROOM
VENTS
COKE
DR"iER
r
LIME
KILN'
~^r
_4
I
ELECTRIC
FURNACE
i
^- TAP FUME
"ENTS
PRIMARY
CRUSHING
SECONDARY
CRUSHING
ALETILES'E GENERATION
Figure 8.4-1. Calcium carbide manufacturing process.
1/84
Mineral Products Industry
i.4-1
-------
anthracite coal is continuously fed into a steel casing where it is baked by
heat from the electric arc furnace before introduction into the furnace. The
baked electrode exits the steel casing just inside the furnace cover and is
consumed in the calcium carbide production process. Molten calcium carbide
is tapped continuously from the furnace into chill cars and is allowed to
cool and solidify. Then, primary crushing of the solidified calcium carbide
by jaw crushers is followed by secondary crushing and screening for size. To
prevent explosion hazards from acetylene generated by reaction of calcium
carbide with ambient moisture, crushing and screening operations may be
performed in an air swept environment before the calcium carbide has
completely cooled or may be carried out in an inert atmosphere. The calcium
carbide product is used primarily in acetylene generation and also as a
desulfurizer of iron.
8.4.2 Emissions and Controls
Emissions from calcium carbide manufacturing include particulate matter,
sulfur oxides, carbon monoxide and hydrocarbons. Particulate matter is
emitted from a variety of equipment and operations in the production of
calcium carbide, including the coke dryer, lime kiln, electric furnace, tap
fume vents, furnace room vents, primary and secondary crushers, and conveying
equipment. (Lime kiln emission factors are presented in Section 8.15.)
Particulate matter emitted from process sources such as the electric furnace
are ducted to a particulate control device, usually fabric filters and wet
scrubbers. Fugitive particulate matter from sources such as tapping opera-
tions, furnace room and conveyors is captured and sent to a particulate
control device. The composition of the particulate matter emissions varies
according to the specific equipment or operation, but the primary components
are magnesium, calcium and carbon compounds. Sulfur oxides are emitted by
the electric furnace from volatilization and oxidation of sulfur in the coke
feed and by the coke dryer and lime kiln from fuel combustion. These process
sources are not controlled specifically for sulfur oxide emissions. Carbon
monoxide is a byproduct of calcium carbide formation in the electric furnace.
Carbon monoxide emissions to the atmosphere are usually negligible. In open
furnaces, carbon monoxide is oxidized to carbon dioxide, thus eliminating
carbon monoxide emissions. In closed furnaces, a portion of the generated
carbon monoxide is burned in the flames surrounding the furnace charge holes,
and the remaining carbon monoxide is used as fuel for other processes or is
flared. The only potential source of hydrocarbon emissions from the manu-
facture of calcium carbide is the coal tar pitch binder in the furnace
electrode paste. Since the maximum volatiles content in the electrode paste
is about 18 percent, the electrode paste represents only a small potential
source of hydrocarbon emissions. In closed furnaces, actual hydrocarbon
emissions from consumption of electrode paste typically are negligible due to
high furnace operating temperature and flames surrounding the furnace charge
holes. Hydrocarbon emissions from open furnaces are also expected to be
negligible because of high furnace operating temperature and the presence of
excess oxygen above the furnace.
Table 8.4-1 gives controlled and uncontrolled emission factors for
various processes in the manufacture of calcium carbide. Controlled factors
are based on test data and permitted emissions for operations with the fabric
filters and wet scrubbers that are typically used to control particulate
emissions in calcium carbide manufacturing.
8.4-2 EMISSION FACTORS 1/84
-------
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Mineral Products Industry
8.4-3
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References for Section 8.4
1. "Permits to Operate: Airco Carbide, Louisville, Kentucky", Jefferson
County Air Pollution Control District, Louisville, KY, December 16,
1980.
2. "Manufacturing or Processing Operations: Airco Carbide, Louisville,
Kentucky", Jefferson County Air Pollution Control District, Louisville,
KY, September 1975.
3. Written communication from A. J. Miles, Radian Corp., Durham, NC, to
Douglas Cook, U. S. Environmental Protection Agency, Atlanta, GA,
August 20, 1981.
4. "Furnace Offgas Emissions Survey: Airco Carbide, Louisville, Kentucky",
Environmental Consultants, Inc., Clarksville, IN, March 17, 1975.
5. J. W. Frye, "Calcium Carbide Furnace Operation", Electric Furnace
Conference Proceedings, American Institute of Mechanical Engineers, New
York, December 9-11, 1970.
6. The Louisville Air Pollution Study, U. S. Department of Health and Human
Services, Robert A. Taft Center, Cincinnati, OH, 1961.
7. R. N. Shreve and J. A. Brink, Jr., Chemical Process Industries, Fourth
Edition, McGraw Hill Company, New York, 1977.
8. J. H. Stuever, "Particulate Emissions - Electric Carbide Furnace Test
Report: Midwest Carbide, Pryor, Oklahoma", Stuever and Associates,
Oklahoma City, OK, April 1978.
9. L. Thomsen, "Particulate Emissions Test Report: Midwest Carbide,
Keokuk, Iowa", Beling Consultants, Inc., Moline, IL, July 1, 1980.
10. D. M. Kirkpatrick, "Acetylene from Calcium Carbide Is an Alternate
Feedstock Route", Oil and Gas Journal, June 7, 1976.
11. L. Clarke and R. L. Davidson, Manual for Process Engineering
Calculations, Second Edition, McGraw-Hill Company, New York, 1962.
8.4-4 EMISSION FACTORS 1/84
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11.2.2 AGRICULTURAL" TILLING
11.2.2.1 General
The two universal objectives of agricultural tilling are the creation of
the desired soil structure to be used as the crop seedbed and the eradication
of weeds. Plowing, the most common method of tillage, consists of some form
of cutting loose, granulating and inverting the soil, and turning under the
organic litter. Implements which loosen the soil and cut off the weeds but
which leave the surface trash in place have recently become more popular for
tilling in dryland farming areas.
During a tilling operation, dust particles from the loosening and pul-
verizing of the soil are injected into the atmosphere as the soil is dropped
to the surface. Dust emissions are greatest during periods of dry soil and
during final seedbed preparation.
11.2.2.2 Emissions and Correction Parameters
The quantity of dust from agricultural tilling is proportional to the
area of land tilled, and to the surface soil texture and moisture content of
the particular field being tilled-
Dust emissions from agricultural tilling have been found to vary
directly with the silt content (defined as particles <75 micrometers in
diameter) of the surface soil depth (0 to 10 centimeters [0 to 4 inches]).
The soil silt content is determined by measuring the proportion of dry soil
that passes a 200 mesh screen, using ASTM-C-136 method. Note that this
definition of silt differs from that customarily used by soil scientists,
for whom silt is particles from 2 to 50 micrometers in diameter.
Field measurements2 indicate that dust emissions from agricultural
tilling are not significantly related to surface soil moisture, although
limited earlier data had suggested such a dependence.1 This is now
believed to reflect the fact that most tilling is performed under dry soil
conditions, as were the majority of the field tests.1"2
Available test data indicate no substantial dependence of emissions on
the type of tillage implement, if operating at a typical speed (8 to
10 kilometers per hour [5 to 6 miles per hour]).1"2
11.2.2.3 Predictive Emission Factor Equation
The quantity of dust emissions from agricultural tilling, per acre of
land tilled, may be estimated with a rating of A or B (see below) using the
following empirical expression2:
E = k(5.38)(s)°-6 (kg/hectare) (1)
E = k(4.80)(s)°'6 (Ib/acre)
5/83 Miscellaneous Sources 11.2.2-1
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where: E = emission factor
k = particle size multipler (dimensionless)
s = silt content of surface soil (%)
The particle size multiplier (k) in the equation varies with aerodynamic
particle size range as follows:
Aerodynamic Particle Size Multiplier for Equation 1
Total
particulate
1.0
< 30 |jm
0.33
< 15 |Jm
0.25
< 10 pm
0.21
< 5 (Jm
0.15
< 2.5 [Jm
0.10
Equation 1 is rated A if used to estimate total particulate emissions,
and B if used for a specific particle size range. The equation retains its
assigned quality rating if applied within the range of surface soil silt
content (1.7 to 88 percent) that was tested in developing the equation.
Also, to retain the quality rating of Equation 1 applied to a specific ag-
ricultural field, it is necessary to obtain a reliable silt value(s) for
that field. The sampling and analysis procedures for determining agricul-
tural silt content are given in Reference 2. In the event that a site spe-
cific value for silt content cannot be obtained, the mean value of 18 per-
cent may be used, but the quality rating of the equation is reduced by one
level.
11.2.2.4 Control Methods3
In general, control methods are not applied to reduce emissions from
agricultural tilling. Irrigation of fields before plowing will reduce
emissions, but in many cases, this practice would make the soil unworkable
and would adversely affect the plowed soil's characteristics. Control
methods for agricultural activities are aimed primarily at reduction of
emissions from wind erosion through such practices as continuous cropping,
stubble mulching, strip cropping, applying limited irrigation to fallow
fields, building windbreaks, and using chemical stabilizers. No data are
available to indicate the effects of these or other control methods on
agricultural tilling, but as a practical matter, it may be assumed that
emission reductions are not significant.
References for Section 11.2.2
1. C. Cowherd, Jr., et al., Development of Emission Factors for Fugitive
Dust Sources. EPA-450/3-74-037, U. S. Environmental Protection Agency,
Research Triangle Park, NC, June 1974.
2. T. A. Cuscino, Jr., et al. , The Role of Agricultural Practices in
Fugitive Dust Emissions, California Air Resources Board, Sacramento,
CA, June 1981.
3. G. A Jutze, et al., Investigation of Fugitive Dust - Sources Emissions
And Control, EPA-450/3-74-036a, U. S. Environmental Protection Agency,
Research Triangle Park, NC, June 1974.
11.2.2-2 EMISSION FACTORS 5/83
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TECHNICAL he. ,
/Please read Instructions on the reverse before complsnni,,
REPORT NO.
AP-42, Supplement 15
2.
3. RSCIPIEN 3 ACCESSION MO.
TITLE ANOSU3TITLS
Supplement 15 to Compilation of Air Pollutant
Emission Factors, AP-42
5 REPORT DATE
January 1984
6. PERFORMING ORGANIZATION CODE
7 AUTHOR(S)
8. PERFORMING ORGANIZATION REPORT NO.
9 PERFORMING ORGANIZATION NAME AND ADDRESS
U. S. Environmental Protection Agency
Office Of Air And Radiation
Office Of Air Quality Planning And Standards
Research Triangle, NC 27711
10. PROGRAM ELEMENT NO.
11. CONTRACT/GRANT NO.
12 SPONSORING AGENCY NAME AND ADDRESS
13. TYPE OF REPORT AND PERIOD COVERED
14. SPONSORING AGENCY CODE
I
15. SUPPLEMENTARY NOTES
EPA Editor: Whitmel M. Joyner
16 ABSTRACT
In this Supplement for AP-42, new, revised or reformatted emissions data are
presented for Stationary Large Bore And Dual Fuel Engines; General Industrial
Surface Coating; Can Coating; Magnet Wire Coating; Other Metal Coating; Flat Wood
Interior Panel Coating; Fabric Coating; Tank And Drum Cleaning; Fish Processing;
Ammonium Nitrate; Urea; Primary Aluminum Production; Primary Copper Smelting;
Asphaltic Concrete Plants; Calcium Carbide Manufacturing; and Agricultural Tilling.
17
KEY WORDS AND DOCUMENT ANALYSIS
!a.
DESCRIPTORS
jb 'OENT|F!ERS/OPEN ENDED TERMS c. COSATI i leid/Group
' Fuel Combustion
Emissions
Emission Factors
Stationary Sources
'9 ScC'_ - IT'' CLASi ~ :'.s .\-.oc,r!\ 21 '•JO OFPAGS6
92
J3 £;i TI3N • 5 CBSCLZ'E
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