-------
washed to remove free acid, and the wash water (yellow water) is recycled to
the early nitration stages. The washed TNT is then neutralized with soda ash
and treated with a 16 percent aqueous sodium sulfite (Sellite) solution to
remove contaminating isomers. The Sellite waste solution (red water) from the
purification process is discharged directly as a liquid waste stream, is
collected and sold, or is concentrated to a slurry and incinerated. Finally,
the TNT crystals are melted and passed through hot air dryers, where most of
the water is evaporated. The dehydrated product is solidified, and the TNT
flakes packaged for transfer to a storage or loading area.
TOLUENE
SPENT ACID
1st
NITRATION
NITRO-
TOLUENE
*
60%HN03
OLEUM
t
2nd
NITRATION
DNT
1
60% HN03
3rd
NITRATION
PRODUCT
1
97% HN03
Figure 5.6-2. Nitration of toluene to form trinitrotoluene.
5.6.3 Nitrocellulose Production
1,6
Nitrocellulose is commonly prepared by the batch type mechanical dipper
process. A newly developed continuous nitration processing method is also
being used. In batch production, cellulose in the form of cotton linters,
fibers or specially prepared wood pulp is purified by boiling and bleaching.
The dry and purified cotton linters or wood pulp are added to mixed nitric and
sulfuric acid in metal reaction vessels known as dipping pots. The reaction
is represented by:
) + 3HONO^ + rUSO, — (C,H.,0
Cellulose Nitric Sulfuric Nitrocellulose
Ac id Ac id
Water
Sulfuric
Acid
Following nitration, the crude NC is centrifuged to remove most of the spent
nitrating acids and is put through a series of water washing and boiling
treatments to purify the final product.
TABLE 5.6-1.
EMISSION FACTORS FOR THE OPEN BURNING OF TNT
(Ib pollution/ton TNT burned)
a,b
Type of
Explosive
Participates Nitrogen
Oxides
Carbon
Monoxide
Volatile
Organic
Compounds
TNT
180.0
150.0
56.0
1.1
a
5/83
Reference 7. Particulate emissions are soot. VOC is nonmethane.
The burns were made on very small quantities of TNT, with test
apparatus designed to simulate open burning conditions. Since
such test simulations can never replicate actual open burning, it
is advisable to use the factors in this Table with caution.
Chemical Process Industry
5.6-3
-------
Process
TABLE 5.6-2. EMISSION FACTORS FOR
EMISSION FACTOR
Particulates
kg/Mg Ib/ton
I
Sulfur oxides
(S02)
kg/Mg
Ib/ton
TNT - Batch Process
Nitration reactors
Fume recovery
Acid recovery
Nitric acid concentrators
Sulfuric acid concentrators
Electrostatic
precipator (exit)
Electrostatic precipitator
w/scrubber
Red water incinerator
Uncontrolled
g
Wet scrubber
Selllte exhaust
TNT - Continuous Process
Nitration reactors
Fume recovery
Acid recovery
12.5
(0.015 - 63)
0.5
25
(0.03 - 126)
1
7
(2 - 20)
Neg.
1
(0.025 - 1.75)
1
(0.025 - 1.75)
29.5
(0.005 - 88)
14
(4 - 40)
Neg.
(0.05 - 3.5)
2
(0.05 - 3.5)
59
(0.01 - 177)
Red water incinerator 0.13 0.25
(0.015 - 0.25) (0.03 - 0.5)
Nitrocellulose*1 ±
Nitration reactors — —
Nitric acid concentrator — —
Sulfuric acid concentrator — —
Boiling tubs — —
0.12
(0.025 - 0.22)
0.7
(0.4 - 1)
—
34
(0.2 - 67)
~~
0.24
(0.05 - 0.
1.4
(0.8 - 2)
—
68
(0.4-135)
~
43)
I
For some processes, considerable variations in emissions have been reported. Average of reported values
is shown first, ranges in parentheses. Where only one number is given, only one source test was
available. Emission factors are in units of kg of pollutant per Mg and pounds of pollutant per ton of TNT
.or Nitrocellulose produced.
Significant emissions of volatile organic compounds have not been reported for the explosives industry.
However, negligible emissions of toluene and trinitromethane (TNM) from nitration
reactors have been reported in TNT manufacture. Also, fugitive VOC emissions may result from
various solvent recovery operations. See Reference 6.
Reference 5.
dActd mist emissions influenced by nitrobody levels and type of furnace fuel.
eNo data available for NO emissions after scrubber. NO emissions are assumed unaffected by scrubber.
5..6-4
EMISSION FACTORS
5/R1
-------
EXPLOSIVES MANUFACTURING
RATING: C
,a,b
Nitrogen oxides Nitric acid mist Sulfuric acid mist
(NO ) (100% HNO ) (100% H SO )
kg/Mg Ib/ton kg/Mg Ib/ton kg/ ton Ib/ton
12.5
(3 - 19)
27.5
(0.5 - 68)
18.5
(8 - 36)
20
(1 - 40)
20
(1 - 40)
13
(0.75 - 50)
2.5
25 0.5 1 - -
(6 - 38) (0.15 - 0.95) (0.3 - 1.9)
55 46 92 - -
(1 - 136) (0.005 - 137) (0.02 - 275)
37 - - 4.5 9
(16 - 72) (0.15 - 13.5) (0.3 - 27)
40 - - 32.5 65
(2 - 80) (0.5 - 94) (1 - 188)
40 - - 2.5 5
(2 - 80) (2 - 3) (4 - 6)
26 - - - -
(1.5 - 101)
e — . __
(0.3 - 8)
(0.6 - 16)
4
(3.35 - 5)
1.5
(0.5 - 2.25)
3.5
(3 - 4.2)
7
(1.85 - 17)
7
(5 - 9)
—
1
8
(6.7
3
(1 -
7
(6.1
14
(3.7
14
(10 -
—
2
- 10)
4.5)
- 8.4)
- 34)
18)
0.5 1 - -
(0.15 - 0.95 (0.3 - 1.9)
0.01 0.02 - -
(0.005 - 0.015) (0.01 - 0.03)
— — — —
9.5 19 -
(0.25 - 18) (0.5 - 36)
_ — — _
- - 0.3 0.6
_ _ _
Use low end of range for modern efficient units, high end fur less efficient units.
^Apparent reductions in NO and particulate after control may not be significant, because these values are
based on only one test result.
Reference 4.
For product with low nitrogen content (12Z), use high end of range. For products wit'i higher
nitrogen content, use lower end of range.
5/83
Chemical Process Industry
5.6-5
-------
2-3 5-7
b.6.4 Emissions and Controls" '
Oxides of nitrogen (NUX) and sulfur (SOX) are the major emissions from
the processes involving the manufacture, concentration and recovery of acids
in the nitration process of explosives manufacturing. Emissions from the
manufacture of nitric and sulfuric acid are discussed in othi.-r Sections of
this publication. Trinitromethane (TNM) is a gaseous byproduct of the
nitration process of TNT manufacture. Volatile organic compound emissions
result primarily from fugitive vapors from various solvent recovery
operations. Explosive wastes and contaminated packaging material are
regularly disposed of by open burning, and such results in uncontrolled
emissions, mainly of NOX and particulate matter. Experimental burns of
several explosives to determine "typical" emission factors for the open
burning of TNT are presented in Table 5.6-1.
In the manufacture of TNT, emissions from the nitrators containing NO,
N02, N2U, trinitromethane (TNM) and some toluene are passed through a fume
recovery system to extract NOX as nitric acid, and then are vented through
scrubbers to the atmosphere. Final emissions contain quantities of unabsorbed
NOX and TNM. Emissions may also come from the production of Sellite solution
and the incineration of red water. Red water incineration results in
atmospheric emissions of NO , SO and ash (primarily Na~SO..)
X L- Z, ^\
In the manufacture of nitrocellulose, emissions from reactor pots and
centrifuge are vented to an NOX water absorber. The weak HNOj solution is
transferred to the acid concentration system. Absorber emissions are mainly
NOX. Another possible source of emissions is the boiling tubs, where steam
and acid vapors vent to the absorber.
The most important fact affecting emissions from explosives manufacture
is the type and efficiency of the manufacturing process. The efficiency of
the acid and fume recovery systems for TNT manufacture will directly affect
the atmospheric emissions. In addition, the degree to which acids are exposed
to the atmosphere during the manufacturing process affects the NOX and SOX
emissions. For nitrocellulose production, emissions are influenced by the
nitrogen content and the desired product quality. Operating conditions will
also affect emissions. Both TNT and nitrocellulose can be produced in batch
processes. Such processes may never reach steady state, and emission
concentrations may vary considerably with time, and fluctuations in emissions
will influence the efficiency of control methods.
Several measures may be taken to reduce emissions from explosive
manufacturing. The effects of various control devices and process changes,
along with emission factors for explosives manufacturing, are shown in
Table 5.6-2. The emission factors are all related to the amount of product
produced and are appropriate either for estimating long term emissions or for
evaluating plant operation at full production conditions. For short time
periods, or for plants with internu ttent operating schedules, the emission
5.. 6-6 EMISSION FACTORS 5/83
-------
factors in Table 5.6-2 should be used with caution, because processes not
associated with the nitration step are often not in operation at the same time
as the nitration reactor.
References for Section 5.6
1. R. N. Shreve, Chemical Process Industries, 3rd Ed., McGraw-Hill Book
Company, New York, 1967.
2. Unpublished data on emissions from explosives manufacturing, Office of
Criteria and Standards, National Air Pollution Control Administration,
Durham, NC, June 1970.
3. F. B. Higgins, Jr., et al., "Control of Air Pollution From TNT
Manufacturing", Presented at 60th annual meeting of Air Pollution Control
Association, Cleveland, OH, June 1967.
4. Air Pollution Engineering Source Sampling Surveys, Radford Army
Ammunition Plant, U. S. Army Environmental Hygiene Agency, Edgewood
Arsenal, MD, July 1967, July 1968.
5. Air Pollution Engineering Source Sampling Surveys, Volunteer Army
Ammunition Plant and Joliet Army Ammunition Plant, U. S. Army Environmental
Hygiene Agency, Edgewood Arsenal, MD, July 1967, July 1968.
6. Industrial Process Profiles for Environmental Use; The Explosives Industry,
EPA-600/2-77-0231, U. S. Environmental Protection Agency, Research Triangle
Park, NC, February 1977.
7. Specific Air Pollutants from Munitions Processing and Their Atmospheric
Behavior, Volume 4: Open Burning and Incineration of Waste Munitions,
Research Triangle Institute, Research Triangle Park, NC, January 1978.
5/83 Chemical Process Industry 5.6-7
-------
5.7 HYDROCHLORIC ACID
Hydrochloric acid is manufactured by a number of different chemical processes. Approximately 80 percent of
the hydrochloric acid, however, is produced by the by-product hydrogen chloride process, which will be the only
process discussed in this section. The synthesis process and the Mannheim process are of secondary importance.
5.7.1 Process Description1
By-product hydrogen chloride is produced when chlorine is added to an organic compound such as benzene,
toluene, and vinyl chloride. Hydrochloric acid is produced as a by-product of this reaction. An example of a
process that generates hydrochloric acid as a by-product is the direct chlorination of benzene. In this process
benzene, chlorine, hydrogen, air, and some trace catalysts are the raw materials that produce chlorobenzene. The
gases from the reaction of benzene and chlorine consist of hydrogen chloride, benzene, chlorobenzenes, and air.
These gases are first scrubbed in a packed tower with a chilled mixture of monochlorobenzene and
dichlorobenzene to condense and recover any benzene or chlorobenzene. The hydrogen chloride is then absorbed
in a falling film absorption plant.
5.7.2 Emissions
The recovery of the hydrogen chloride from the chlorination of an organic compound is the major source of
hydrogen chloride emissions. The exit gas from the absorption or scrubbing system is the actual source of the
hydrogen chloride emitted. Emission factors for hydrochloric acid produced as by-product hydrogen chloride are
presented in Table 5.7-1.
Table 5.7-1. EMISSION FACTORS FOR HYDROCHLORIC
ACID MANUFACTURING'
EMISSION FACTOR RATING: B
Type of process
By-product hydrogen chloride
With final scrubber
Without final scrubber
Hydrogen chloride emissions
Ib/ton
0.2
3
kg/MT
0.1
1.5
aReference 1.
Reference for Section 5.7
1. Atmospheric Emissions from Hydrochloric Acid Manufacturing Processes. U.S. DHEW, PHS, CPEHS,
National Air Pollution Control Administration. Durham, N.C. Publication Number AP-S4. September 1969.
2/72 Chemical Process Industry 5.7-1
-------
5.8 HYDROFLUORIC ACID
1-3
5.8.1 Process Description
Nearly all of the hydrofluoric acid, or hydrogen fluoride, currently
produced in the United States is manufactured by the reaction of acid-
grade fluorospar with sulfuric acid in the reaction:
CaF2 + E2SOi^ > CaSOi^ + 2 HF
Calcium Sulfuric Calcium Hydrogen
Fluoride Acid Sulfate Fluoride
(Fluorospar) (Anhydrite) (Hydrofluoric
Acid)
The fluorospar typically contains 97.5 percent or more calcium fluoride,
1 percent or less silicon dioxide (Si02), and 0.05 percent or less
sulfur, with calcium carbonate (CaCOa) as the principal remainder. See
Figure 5.8-1 for a typical process flow diagram.
The reaction to produce the acid is endothermic and is usually
carried out in externally heated horizontal rotary kilns for 30 to 60
minutes at 390 to 480°F (200-250°C). Dry fluorospar and a slight excess
of sulfuric acid are fed continuously to the front end of the kiln.
Anhydrite is removed through an air lock at the opposite end. The
gaseous reaction products - hydrogen fluoride, excess sulfuric acid from
the primary reaction, silicon tetrafluoride, sulfur dioxide, carbon
dioxide, and water produced in secondary reactions - are removed from
the front end of the kiln with entrained particulate materials. The
particulates are removed from the gas stream by a dust separator, and
the sulfuric acid and water are removed by a precondenser. The hydrogen
fluoride vapors are condensed in refrigerant condensers and are delivered
to an intermediate storage tank. The uncondensed gases are passed
through a sulfuric acid absorption tower to remove most of the remaining
hydrogen fluoride, which is also delivered with the residual sulfuric
acid to the intermediate storage tank. The remaining gases are passed
through water scrubbers, where the silicon tetrafluoride and remaining
hydrogen fluoride are recovered as fluosilicic acid (^SiFg). The
hydrogen fluoride and sulfuric acid are delivered to distillation
columns, where the hydrofluoric acid is extracted at 99.98 percent
purity. Weaker concentrations (typically 70-80 percent) are prepared by
dilution with water.
124
5.8.2 Emissions and Controls ' '
Air polluting emissions are suppressed to a great extent by the
condensing, scrubbing and absorption equipment used in the recovery and
purification of the hydrofluoric and fluosilicic acid products. Partic-
ulate material in the process gas stream is controlled by a dust separator
near the outlet of the kiln and is recycled to the kiln for further
2/80 Chemical Process Industry 5.8-1
-------
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.•5.8-3
-------
processing. The precondenser removes water vapor and sulfuric acid
mist, and the condenser, acid scrubber and water scrubbers remove all
but small amounts of hydrogen fluoride, silicon tetrafluoride, sulfur
dioxide and carbon dioxide from the tail gas. A caustic scrubber is
employed to reduce further the levels of these pollutants in the tail
gas.
Dust emissions result from the handling and drying of the fluorospar,
and they are controlled with bag filters at the spar storage silos and
drying kilns, their principal emission points.
Hydrogen fluoride emissions are minimized by maintaining a slight
negative pressure in the kiln during normal operations. Under upset
conditions, a standby caustic scrubber or a bypass to the tail gas
caustic scrubber are used to control hydrogen fluoride emissions from
the kiln.
Fugitive dust emissions from spar handling and storage are con-
trolled with flexible coverings and chemical additives.
Table 5.8-1 lists the emission factors for the various process
operations. The principal emission locations are shown in the process
flow diagram, Figure 5.8-1.
References for Section 5.8
1. Screening Study on Feasibility of Standards of Performance for
Hydrofluoric Acid Manufacture, EPA-450/3-78-109, U.S. Environmental
Protection Agency, Research Triangle Park, NC, October 1978.
2. "Hydrofluoric Acid", Kirk-Othmer Encyclopedia of Chemical
Technology, Vol. 9, Interscience Publishers, New York, 1965.
3. W. R. Rogers and K. Muller, "Hydrofluoric Acid Manufacture",
Chemical Engineering Progress, 59(5);85-8. May 1963.
4. J. M. Robinson, et al., Engineering and Cost Effectiveness Study
of Fluoride Emissions Control, Vol. 1, PB 207 506, National Technical
Information Service, Springfield, VA, 1972.
5.8-4 EMISSION FACTORS 2/80
-------
5.9 NITRIC ACID
5.9.1 Process Description
Weak Acid Production - Nearly all the nitric acid produced in the
United States is manufactured by the catalytic oxidation of ammonia
(Figure 5.9-1). This process typically consists of three steps, each of
which corresponds to a distinct chemical reaction. First, a 1:9 ammonia/
air mixture is oxidized at high temperature (1380 - 1470°F or
750 - 800°C) as it passes through a platinum/rhodium catalyst, according
to the reaction:
4NH3 + 502 ->• 4NO + 6H20 (1)
Ammonia Oxygen Nitric Water
oxide
After the process stream is cooled to 100°F (38°C) or less by passage
through a cooler/condenser, the nitric oxide reacts with residual oxygen
to form nitrogen dioxide:
2NO + 02 + 2N02 £
Nitrogen Nitrogen (2)
dioxide tetroxide
Finally, the gases are introduced into a bubble cap plate absorption
column for contact with a countercurrent stream of water. The exothermic
reation that occurs is:
3N02 + H20 -»• 2HN03 + NO (3)
The production of nitric oxide in Reaction 3 necessitates the intro-
duction of a secondary air stream into the column to oxidize it into
nitrogen dioxide, thereby perpetuating the absorption operation.
In the past, nitric acid plants have been operated at a single
pressure, ranging from 14.7 to 176 pounds per square inch (100 - 1200 kPa),
However, since Reaction 1 is favored by low pressures and Reactions 2
and 3 are favored by higher pressures, newer plants tend to be operating
two pressure systems, incorporating a compressor between the oxidizer
and the condenser.
The spent gas flows from the top of the absorption tower to an
entrainment separator for acid mist removal, through a heat exchanger in
the ammonia oxidation unit for energy absorption by the ammonia stream,
through an expander for energy recovery, and finally to the stack. In
most plants, however, the tail gas is treated to remove residual nitrogen
oxides before release to the atmosphere.
Hdgh Strength Acid Production - The nitric acid concentration
process consists of feeding strong sulfuric acid and 50 - 70 percent
nitric acid to the top of a packed dehydrating column at approximately
atmospheric pressure. The acid mixture flows downward counter to ascend-
ing vapors. Concentrated nitric acid leaves the top of the column as 98
10/80 Chemical Process Industry 5.9-1
-------
AIR
EMISSION
POINT
COMPRESSOR
EXPANDER
— NOX EMISSIONS—
CONTROL
CATALYTIC REDUCTION
2
I
WASTE
HEAT
BOILER
ENTRAINED
MIST
SEPARATOR
PLATINUM
FILTER
NITRIC
SECONDARY AIR
c
AS
r
t
AIR
(COOLING
WATER
)
(
)
c
-^
L-^-
ABSORPTION
TOWER
^^^^^— <^^^
— —
COOLER
CONDENSER
N02
L
PRODUCT
(50 • 70%
HN03)
Figure 5.9-1. Flow diagram of typical nitric acid plant using pressure process (high strength
acid unit not shown).
5.9-2
EMISSION FACTORS
10/80
-------
percent vapor, containing a small amount of N02 and 62 from dissociation
of nitric acid. The concentrated acid vapor leaves the column and goes
to a bleacher and countercurrent condenser system to effect the conden-
sation of strong nitric acid and the separation of oxygen and nitrogen
oxide byproducts. These byproducts then flow to an absorption column
where the nitric oxide mixes with auxiliary air to form N02, which is
recovered as weak nitric acid. Unreacted gases are vented to the atmo-
sphere from the top of the absorption column.
TABLE 5.9-1. NITROGEN OXIDE EMISSIONS FROM NITRIC ACID PLANTS3
EMISSION FACTOR RATING: B
Control Emissions
Source Efficiency. % Ib/ton Acid kg/MT Acid
Weak Acid Plant Tail Gas
0
(14 - 86) (7 - 43)
Uncontrolled1* 0 43 22
Catalytic reduction
Natural gas
Hydrogen
Natural gas/hydrogen
(25%/75%)a
Extended absorption
High Strength Acid Plant6
99.1
97 - 99.8
98 - 98.5
95.8
NAf
0.4
(0.05 - 1.2)
0.8
(0 - 1.5)
1.0
(0.8 - 1.1)
1.8
(0.8 - 2.7)
10
0.2
(0.03 - 0.6)
0.4
(0 - 0.8)
0.5
(0.4 - 0.6)
0.9
(0.4 - 1.4)
5
o
Based on 100% acid. Production rates are in terms of total weight of
product (water and acid). A plant producing 500 tons (454 MT)/day of
55 wt. % nitric acid is calculated as producing 275 tons (250 MT)/day
, of 100% acid. Ranges in parentheses. NA: Not Applicable.
Reference 3. Based on a study of 18 plants.
References 1 and 2. Based on data from 2 plants with these process
conditions: production rate, 130 tons (118 MT)/day at 100% rated
capacity; absorber exit temperature, 90°F (32°C); absorber exit
,pressure, 87 psig (600 kPa); acid strength, 57%.
References 1 and 2. Based on data from 2 plants with these process
conditions: production rate, 208 tons (188 MT)/day at 100% rated
capacity; absorber exit temperature, 90°F (32°C); absorber exit
presure, 80 psig (550 kPa); acid strength, 57%.
eReferences 1 and 2. Based on a unit that produces 3000 Ib/hr (6615
kg/hr) at 100% rated capacity, of 98% nitric acid.
10/80 Chemical Process Industry 5.9-3
-------
The two most common techniques used to control absorption tower
tail gas emissions are extended absorption and catalytic reduction. The
extended absorption technique reduces emissions by increasing the effi-
ciency of the absorption tower. This efficiency increase is achieved by
increasing the number of absorber trays, operating the absorber at
higher pressures, or cooling the weak acid liquid in the absorber.
In the catalytic reduction process (often termed catalytic oxidation),
tail gases are heated to ignition temperature, mixed with fuel (natural
gas, hydrogen, carbon monoxide or ammonia) and passed over a catalyst.
In the presence of the catalyst, the fuels are oxidized, and the nitrogen
oxides are reduced to N2. The extent of reduction of NC>2 and NO to N2
is a function of plant design, fuel type operating temperature and
pressure, space velocity through the reduction catalytic reactor, type
of catalyst, and reactant concentration. See Table 5.9-1.
Two seldom used alternative control devices for absorber tail gas
are molecular sieves and wet scrubbers. In the molecular sieve technique,
tail gas is contacted with an active molecular sieve which catalyticly
oxidizes NO to N02 and selectively adsorbs the N02. The N02 is then
thermally stripped from the molecular sieve and returned to the absorber.
In the scrubbing technique, absorber tail gas is scrubbed with an aqueous
solution of alkali hydroxides or carbonates, ammonia, urea or potassium
permanganate. The NO and N02 are absorbed and recovered as nitrate or
nitrite salts.
Comparatively small amounts of nitrogen oxides are also lost from
acid concentrating plants. These losses (mostly N02) are from the
condenser system, but the emissions are small enough to be controlled
easily by inexpensive absorbers.
Acid mist emissions do not occur from the tail gas of a properly
operated plant. The small amounts that may be present in the absorber
exit gas streams are removed by a separator or collector prior to entering
the catalytic reduction unit or expander.
Emissions from acid storage tanks may occur during tank filling.
The displaced gases are equal in volume to the quantity of acid added to
the tanks.
Nitrogen oxide emissions (expressed as N02) are presented for weak
nitric acid plants in Table 5.9-1. The emission factors vary consider-
ably with the type of control employed and with process conditions. For
comparison purposes, the EPA New Source Performance Standard for both
new and modified plants is 3.0 pounds per ton (1.5 kg/MT) of 100 percent
acid produced, maximum 3 hour average, expressed as N02.
5.9-4 EMISSION FACTORS 10/80
-------
Emissions from nitric acid manufacture consist primarily of nitric
oxide, nitrogen dioxide (which accounts for visible emissions) and trace
amounts of nitric acid mist. By far, the major source of nitrogen
oxides is the tail gas from the acid absorption tower (Table 5.9-1). In
general, the quantity of NOjj emissions is directly related to the
kinetics of the nitric acid formation reaction and absorption tower
design.
The two most common techniques used to control absorption tower
tail gas emissions are extended absorption and catalytic reduction. The
extended absorption technique reduces emissions by increasing the effi-
ciency of the absorption tower. This efficiency increase is achieved by
increasing the number of absorber trays, operating the absorber at
higher pressures, or cooling the weak acid liquid in the absorber.
In the catalytic reduction process (often termed catalytic oxidation),
tail gases are heated to ignition temperature, mixed with fuel (natural
gas, hydrogen, carbon monoxide or ammonia) and passed over a catalyst.
In the presence of the catalyst, the fuels are oxidized, and the nitrogen
oxides are reduced to N£. The extent of reduction of NC>2 and NO to N£
is a function of plant design, fuel type operating temperature and
pressure, space velocity through the reduction catalytic reactor, type
of catalyst, and reactant concentration. See Table 5.9-1.
Two seldom used alternative control devices for absorber tail gas
are molecular sieves and wet scrubbers. In the molecular sieve technique,
tail gas is contacted with an active molecular sieve which catalyticly
oxidizes NO to N02 and selectively adsorbs the N02- The N02 is then
thermally stripped from the molecular sieve and returned to the absorber.
In the scrubbing technique, absorber tail gas is scrubbed with an aqueous
solution of alkali hydroxides or carbonates, ammonia, urea or potassium
permanganate. The NO and N02 are absorbed and recovered as nitrate or
nitrite salts.
Comparatively small amounts of nitrogen oxides are also lost from
acid concentrating plants. These losses (mostly N02) are from the
condenser system, but the emissions are small enough to be controlled
easily by inexpensive absorbers.
Acid mist emissions do not occur from the tail gas of a properly
operated plant. The small amounts that may be present in the absorber
exit gas streams are removed by a separator or collector prior to entering
the catalytic reduction unit or expander.
Emissions from acid storage tanks may occur during tank filling.
The displaced gases are equal in volume to the quantity of acid added to
the tanks.
Nitrogen oxide emissions (expressed as N02) are presented for weak
nitric acid plants in Table 5.9-1. The emission factors vary consider-
ably with the type of control employed and with process conditions. For
comparison purposes, the EPA New Source Performance Standard for both
10/80 Chemical Process Industry 5.9-5
-------
new and modified plants is 3.0 pounds per ton (1.5 kg/MT) of 100 percent
acid produced, maximum 3 hour average, expressed as N02-
References for Section 5.9
1. Control of Air Pollution from Nitric Acid Plants. Office of Air
Quality Planning and Standards, U.S. Environmental Protection
Agency, Research Triangle Park, NC, August 1971. Unpublished.
2. Atmospheric Emissions from Nitric Acid Manufacturing Processes,
999-AP-27, U.S. Department of Health, Education and Welfare,
Cincinnati, OH, 1966.
3. Marvin Drabkin, A Review of Standards of Performance for New
Stationary Sources - Nitric Acid Plants, EPA-450/3-79-013, U.S.
Environmental Protection Agency, Research Triangle Park, NC, March
1979.
4. "Standards of Performance for Nitric Acid Plants", 40 CFR 60. G.
5.9-6 EMISSION FACTORS 10/80
-------
5.10 PAINT AND VARNISH
5.10.1 Paint Manufacturing
The manufacture of paint involves the dispersion of a colored oil or
pigment in a vehicle, usually an oil or resin, followed by the addition of an
organic solvent for viscosity adjustment. Only the physical processes of
weighing, mixing, grinding, tinting, thinning and packaging take place. No
chemical reactions are involved.
These processes take place in large mixing tanks at approximately room
temperature.
The primary factors affecting emissions from paint manufacture are care
in handling dry pigments, types of solvents used and mixing temperature.
About 1 or 2 percent of the solvent is lost even under well controlled
conditions. Particulate emissions amount to 0.5 to 1.0 percent of the pigment
handled.
Afterburners can reduce emitted volatile organic compounds (VOC) by
99 percent and particulates by about 90 percent. A water spray and oil filter
system can reduce particulate emissions from paint blending by 90 percent.
5.10.2 Varnish Manufacturing1"3'5
The manufacture of varnish also involves the mixing and blending of
various ingredients to produce a wide range of products. However in this
case, chemical reactions are initiated by heating. Varnish is cooked in
either open or enclosed gas fired kettles for periods of 4 to 16 hours at
temperatures of 93 to 340°C (200 to 650°F).
Varnish cooking emissions, largely in the form of volatile organic
compounds, depend on the cooking temperatures and times, the solvent used, the
degree of tank enclosure and the type of air pollution controls used.
Emissions from varnish cooking range from 1 to 6 percent of the raw material.
To reduce organic compound emissions from the manufacture of paint and
varnish, control techniques include condensers and/or adsorbers on solvent
handling operations, and scrubbers and afterburners on cooking operations.
Afterburners can reduce volatile organic compounds by 99 percent. Emission
factors for paint and varnish are shown in Table 5.10-1.
5/83 Chemical Process Industry 5.10-1
-------
TABLE 5.10-1. UNCONTROLLED EMISSION FACTORS FOR PAINT AND
VARNISH MANUFACTURING3'
EMISSION FACTOR RATING: C
Particulate
Type of
product
Paintd
Varnish
Bodying oil
Oleoresinous
Alkyd
Acrylic
kg/Mg
pigment
10
-
-
-
—
Ib/ton
pigment
20
-
-
-
—
Nonmethane VOCC
kg/Mg
of product
15
20
75
80
10
Ib/ton
of product
30
40
150
160
20
References 2, 4-8.
Afterburners can reduce VOC emissions by 99% and
particulates by about 90%. A water spray and oil filter
system can reduce particulates by about 90%.
Expressed as undefined organic compounds whose composition depends
upon the type of solvents used in the manfacture of paint and
varnish.
Reference 4. Particulate matter (0.5 - 1.0 %) is emitted from
pigment handling.
References for Section 5.10
1. Air Pollutant Emission Factors, APTD-0923, U. S. Environmental Protection
Agency, Research Triangle Park, NC, April 1970.
2. R. L. Stenburg, "Controlling Atmospheric Emissions from Paint and Varnish
Operations, Part I", Paint and Varnish Production, September 1959.
3. Private Communication between Resources Research, Inc., Reston, VA, and
National Paint, Varnish and Lacquer Association, Washington, DC.,
September 1969.
4. Unpublished engineering estimates based on plant visits in Washington,
DC, Resources Research, Inc., Reston, VA, October 1969.
5. Air Pollution Engineering Manual, Second Edition, AP-40, U. S.
Environmental Protection Agency, Research Triangle Park, NC, May 1973.
6. E. G. Lunche, et al., "Distribution Survey of Products Emitting Organic
Vapors in Los Angeles County", Chemical Engineering Progress,
53(8):371-376, August 1957.
5.10-2 EMISSION FACTORS 5/33
-------
7. Communication on emissions from paint and varnish operations between
Resources Research, Inc., Reston, VA, and G. Sallee, Midwest Research
Institute, Kansas City, MO, December 17, 1969.
8. Communication between Resources Research, Inc., Reston, VA, and Roger
Higgins, Benjamin Moore Paint Company, June 25, 1968.
5/83 Chemical Process Industry 5.10-3
-------
5.11 PHOSPHORIC ACID
Phosphoric acid is produced by two principal methods, the wet
process and the thermal process. The wet process is employed when the
acid is to be used for fertilizer production. Thermal process phos-
phoric acid is of higher purity and is used in the manufacture of high
grade chemical and food products.
1 2
5.11.1 Process Description '
5.11.1.1 Wet Process Acid Production - In modern wet process phosphoric
acid plants, as shown in Figure 5.11-1, finely ground phosphate rock,
which contains 31 to 35.5 percent phosphorus pentoxide (P20s), is
continuously fed into a reactor with sulfuric acid which decomposes the
phosphate rock. In order to malce the strongest phosphoric acid possible
and to decrease later evaporation costs, 93 or 98 percent sulfuric acids
are normally used. Because the proper ratio of acid to rock in the
reactor must be maintained as closely as possible, precise automatic
process control equipment is employed in the regulation of these two
feed streams.
Gypsum crystals (CaSOt,. . 2^0) are precipitated by the phosphate
rock and sulfuric acid reaction. There is little market for the gypsum,
so it is handled as waste, filtered out of the acid and sent to settling
ponds. Approximately 0.7 acres of cooling and settling pond are required
for every ton of daily P20s production.
Considerable heat is generated in the reactor, which must be
removed. In older plants, this is done by blowing air over the hot
slurry surface. Modern plants use vacuum flash cooling of part of the
slurry, then sending it back into the reactor.
The reaction slurry is held in the reactor for periods of up to
eight hours, depending on the rock and reactor design, and is then sent
to be filtered. This produces a 32 percent acid solution, which gener-
ally needs concentrating for further use. Current practice is to
concentrate it in two or three vacuum evaporators to about 54 percent
5.11.1.2 Thermal Process Acid Production - Raw materials for the
production of phosphoric acid by the thermal process are elemental
(yellow) phosphorus, air and water. Thermal process phosphoric acid
manufacture, as shown in Figure 5.11-2, typically involves three steps.
First, the liquid elemental phosphorus is burned (oxidized) in a
combustion chamber at temperatures of 3000 to 5000°F (1650 - 2760°C) to
form phosphorus pentoxide. Then, the phosphorus pentoxide is hydrated
with dilute acid or water to produce phosphoric acid liquid and mist.
The final step is to remove the phosphoric acid mist from the gas
stream.
2/80 Chemical I'roco* liuluslr> 5.1 I-1
-------
WASH _
WATER
GYPSUM
POND WATER"
H2SO,
TO VACUUM •
"AND HOT WELL
GYPSUM SLURRY
TO POND
•TO SCRUBBER
HYDROFLUOSILICIC ACID
Figure 5.11-1. Flow diagram of wet process phosphoric acid plant.
STACK
EFFLUENT
(AIR + H3PO MIST)
ACID TREATING PLANT
STACK EFFLUENT
(AIR + H2S)
HYDROGEN SULFIDE.
SODIUM HYDROSULFIDE,
OR SODIUM SULFIDE
PHOSPHORUS HYDRATOR- i
COMBUSTION ABSORBER COOLING WATER
CHAMBER
BURNING AND HYDRATION SECTION
f
BLOWER PUMP
ACID TREATING SECTION
(USED IN THE MANUFACTURE OF ACID
FOR FOOD AND SPECIAL USES)
Figure 5.11-2. Flow diagram of thermal process phosphoric acid plant.
5.11-2
EMISSION FACTORS
2/80
-------
The reactions involved are:
Pit + 5 02 + Pi+010
Pit010 + 6 H20 -> 4
Thermal process acid normally contains 75 to 85 percent phosphoric
acid (HsPOit). In efficient plants, about 99.9 percent of the phosphorus
burned is recovered as acid.
1-3
5.11.2 Emissions and Controls
5.11.2.1 Wet Process Emissions and Controls - Gaseous fluorides, mostly
silicon tetrafluoride and hydrogen fluoride, are the major emissions
from wet process acid. Phosphate rock contains 3.5 to 4.0 percent
fluorine, and the final distribution of this fluorine in wet process
acid manufacture varies widely. In general, part of the fluorine goes
with the gypsum, part with the phosphoric acid product, and the rest is
vaporized in the reactor or evaporator. The proportions and amounts
going with the gypsum and acid depend on the nature of the rock and
process conditions. Disposition of the volatilized fluorine depends on
the design and operation of the plant. Substantial amounts can pass off
into the air, unless effective scrubbers are used. Some of the fluorine
which is carried to the settling ponds with the gypsum will get into the
atmosphere, once the pond water is saturated with fluorides.
The reactor, where phosphate rock is decomposed by sulfuric acid,
is the main source of atmospheric contaminants. Fluoride emissions
accompany the air used to cool the reactor slurry. Vacuum flash cooling
has replaced the air cooling method to a large extent, since emissions
are minimized in the closed system.
Acid concentration by evaporation provides another source of
fluoride emissions. It has been estimated that 20 to 40 percent of the
fluorine originally present in the rock vaporizes in this operation.
Total particulate emissions directly from process equipment were
measured for one digester and for one filter. As much as 11 pounds of
particulates per ton of P20s were produced by the digester, and approxi-
mately 0.2 pounds per ton of ?205 were released by the filter. Of this
particulate, 3 to 6 percent was fluorides.
Particulate emissions occurring from phosphate rock handling are
covered in Section 8.18.
5.11.2.2 Thermal Process Emissions and Controls - The principal
atmospheric emission from the thermal process is phosphoric acid mist
(t^POit) contained in the gas stream from the hydrator. The particle
size of the acid mist ranges from 0.4 to 2.6 micrometers. It is not
uncommon for as much as half of the total phosphorus pentoxide to be
present as liquid phosphoric acid particles suspended in the gas stream.
2/80 Chemical Process Industry 5.11-3
-------
Economical operation of the process demands that this potential loss be
controlled, so all plants are equipped with some type of emission
control equipment.
Control equipment commonly used in thermal process phosphoric acid
plants includes venturi scrubbers, cyclonic separators with wire mesh
mist eliminators, fiber mist eliminators, high energy wire mesh contactors,
and electrostatic precipitators.
Table 5.11-1. EMISSION FACTORS FOR PHOSPHORIC
ACID PRODUCTION
EMISSION FACTOR RATING: B
Source
Wet Process
Reactor, uncontrolled
Gypsum settling and
cooling ponds
Condenser, uncontrolled
a
Particulates
Ib/ton
_
kg/MT
_
Fluorine
Ib/ton
56.4
1.12
61.2
kg/MT
28.2
0.56
30.6
Typical controlled
emissions'1 - - .02-. 07 .01-. 04
Thermal Process '
Packed tower (95.5%)
Venturi scrubber (97.5%)
Glass fiber mist
eliminator
(96.0 - 99.9%)
Wire mesh mist eliminator
(95.0%)
High pressure drop mist
eliminator (99.9%)
Electrostatic precipitator
(98 - 99%)
2.14
2.53
0.69
5.46
0.11
1.66
1.07
1.27
0.35
2.73
0.06
0.83
- -
- -
-
-
- -
- -
fAcid mist particulates (0.4 - 2.6 pm).
References 1 and 3. Pounds of fluorine (as gaseous fluorides) per
ton of T?2°5 produced. Based on a material balance of fluorine from
phosphate rock of 3.9% fluorine and 33% P20s.
Approximately 0.7 acres (0.3 hectares) of cooling and settling pond are
required to produce 1 ton of P20s daily. Emissions in terms of pond
area would be 1.60 Ib/acre per day (1.79 kg/hectare per day).
Reference 5.
^Reference 3. Pounds of particulate per ton of P205.
Numbers in parentheses indicate the control efficiency associated with
each device.
5.11-4 EMISSION FACTORS 2/80
-------
References for Section 5.11
1. Atmospheric Emissions from Wet Process Phosphoric Acid
Manufacture, AP-57, National Air Pollution Control Administration,
Raleigh, NC, April 1970.
2. Atmospheric Emissions from Thermal Process Phosphoric Acid
Manufacture, AP-48, National Air Pollution Control Administration,
Durham, NC, October 1968.
3. Control Techniques for Fluoride Emissions, Unpublished, U.S. Public
Health Service, Research Triangle Park, NC, September 1970.
4. W.R. King, "Fluorine Air Pollution from Wet Process Phosphoric Acid
Plants - Water Ponds", Doctoral Thesis, Supported by EPA Research
Grant No. R-800950, North Carolina State University, Raleigh, NC,
1974.
5. Final Guideline Document; Control of Fluoride Emissions from
Existing Phosphate Fertilizer Plants. EPA-450/2-77-005, U.S.
Environmental Protection Agency, Research Triangle Park, NC, March
1977.
2/80 Chemical Process Industry 5.1 1-5
-------
5.12 PHTHALIC ANHYDRIDE
5.12.1 General1
Phthalic anhydride (PAN) production in the United States in 1972 was 0.9 billion pounds per year,
this total is estimated to increase to 2.2 billion pounds per year by 1985. Of the current production, 50
percent is used for plasticizers, 25 percent for alkyd resins, 20 percent for unsaturated polyester resins,
I and 5 percent for miscellaneous and exports. PAN is produced by catalytic oxidation of either ortho-
xylene or naphthalene. Since naphthalene is a higher priced feedstock and has a lower feed utilization
. (about 1.0 Ib PAN/lb o-xylene versus 0.97 Ib PAN/lb naphthalene), future production growth is pre-
dicted to utilize o-xylene. Because emission factors are intended for future as well as present applica-
I tion, this report will focus mainly on PAN production utilizing o-xylene as the main feedstock.
The processes for producing PAN by o-xylene or naphthalene are the same except for reactors,
' catalyst handling, and recovery facilities required for fluid bed reactors.
In PAN production using o-xylene as the basic feedstock, filtered air is preheated, compressed, and
mixed with vaporized o-xylene and fed into the fixed-bed tubular reactors. The reactors contain the
catalyst, vanadium pentoxide, and are operated at 650 to 725° F (340 to 385° C). Small amounts of
' sulfur dioxide are added to the reactor feed to maintain catalyst activity. Exothermic heat is removed
by a molten salt bath circulated around the reactor tubes and transferred to a steam generation system.
Naphthalene-based feedstock is made up of vaporized naphthalene and compressed air. It is
transferred to the fluidized bed reactor and oxidized in the presence of a catalyst, vanadium pent-
oxide, at 650' to 725° F (340 to 385° C). Cooling tubes located in the catalyst bed remove the exothermic ',
heat which is used to produce high-pressure steam. The reactor effluent consists of PAN vapors, en-
trained catalyst, and various by-products and non-reactant gas. The catalyst is removed by filtering and
returned to the reactor.
1
! The chemical reactions for air oxidation of o-xylene and naphthalene are as follows.
302
3H20
o-xylene + oxygen
phthalic
anhydride
water
4% 02
naphthalene
oxygen
5/83
/
2H20 + 2C02
C
II
0
pi
anhydride
• Chemical Process Industry ^ A ^ . .
phthalic , water , carbon
dioxide
-------
r
' The reactor effluent containing crude PAN plus products from side reactions and excess oxygen passes
1 to a series of switch condensers where the crude PAN cools and crystallizes. The condensers are alter-
nately cooled and then heated, allowing PAN crystals to form and then melt from the condenser tube
fins.
The crude liquid is transferred to a pretreatment section in which phthalic acid is dehydrated to
anhydride. Water, maleic anhydride, and benzoic acid are partially evaporated. The liquid then goes
' to a vacuum distillation section where pure PAN (99.8 wt. percent pure) is recovered. The product can
be stored and shipped either as a liquid or a solid (in which case it is dried, flaked, and packaged in
multi-wall paper bags). Tanks for holding liquid PAN are kept at 300°F (150°C) and blanketed with
dry nitrogen to prevent the entry of oxygen (fire) or water vapor (hydrolysis to phthalic acid).
Maleic anhydride is currently the only by-product being recovered.
Figures 1 and 2 show the process flow for air oxidation of o-xylene and naphthalene, respectively.
5.12.2 Emissions and Controls1
Emissions from o-xylene and naphthalene storage are small and presently are not controlled.
The major contributor of emissions is the reactor and condenser effluent which is vented from the
condenser unit. Particulate, sulfur oxides (for o-xylene-based production), and carbon monoxide
make up the emissions, with carbon monoxide comprising over half the total. The most efficient (96
percent) system of control is the combined usage of a water scrubber and thermal incinerator. A
thermal incinerator alone is approximately 95 percent efficient in combustion of pollutants for o-
xylene-based production, and 80 percent efficient for naphthalene-based production. Thermal incin-
erators with steam generation show the same efficiencies as thermal incinerators alone. Scrubbers
have a 99 percent efficiency in collecting particulates, but are practically ineffective in reducing car-
bon monoxide emissions. In naphthalene-based production, cyclones can be used to control catalyst
dust emissions with 90 to 98 percent efficiency.
Pretreatment and distillation emissions—particulates and hydrocarbons—are normally processed
, through the water scrubber and/or incinerator used for the main process stream (reactor and con-
j denser) or scrubbers alone, with the same efficiency percentages applying.
I
Product storage in the liquid phase results in small amounts of gaseous emissions. These gas
streams can either be sent to the main process vent gas control devices or first processed through
sublimation boxes or devices used to recover escaped PAN. Flaking and bagging emissions are negli-
gible, but can be sent to a cyclone for recovery of PAN dust. Exhaust from the cyclone presents no
problem. ^
_. « - t^g"""*
Table 5.12-1 gives emission factors for controlled and uncontrolled emissions from the production;
•• — -
5.12-2 EMISSION FACTORS 5/83
-------
"5
II
OOCj
O O O
ii
ac °
A
\~n
/il
EC
UJ
M
8
I
in
(Q
0)
X
6
O)
'35
c
(0
o
O
H-
(0
•o
O
CM
ID
Q)
O)
"J I-
CC Z
5/83
Chemical Process Industry
5.12-3
-------
5.12-4
EMISSION FACTORS
5/83
I
-------
TABLE 5.12-1. EMISSION FACTORS FOR PHTHALIC ANHYDRIDE
a
EMISSION FACTOR RATING: B
Particulate
Process
Oxidation of o-xylenec
Main process stream
Uncontrolled
W/sc rubber and thermal
incinerator
W/ thermal incinerator
W/ incinerator with
steam generator
Pre treatment
Uncontrol led
W/ scrubber and thermal
incinerator
W/ thermal Incinerator
Distillation
Uncontrolled
W/ scrubber and thermal
incinerator
W/ thermal incinerator
Oxidation of naphthalene0
Main process stream
Uncontrolled
W/ thermal Incinerator
W/sc rubber
Pretreatment
Uncontrolled
W/ thermal incinerator
W/sc rubber
Distillation
Uncontrol led
W/ thermal incinerator
W/scrubber
kg/Mg
69e
3
4
4
6.48
0.3
0.4
45e
2
2
1 V
281'
6
0.3
2.5J
0.5
<0.1
191
4
0.2
Ib/ton
138e
6
7
7
13g
0.5
0.7
89e
4
4
1 k
56 *
11
0.6
5J
1
<0.1
38*
8
0.4
SO
kg/Mg
f
4.7f
4.7
4.7
4.7
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
Ib/ton
9.4f
9.4
9.4
9.4
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
Nonmethane VOCb
CO
kg/Mg Ib/ton kg/Mg
0
0
0
0
0
0
0
1.2e>h
< 0. 1
< 0. 1
0
0
0
0
0
0
5h,i
1
<0.1
0
0
0
0
0
0
0
2.4e'h
< 0.1
0.1
0
0
0
0
0
0
loh.l
2
0.1
151
6
8
8
0
0
0
0
0
0
50
10
50
0
0
0
0
0
0
Ib/ton
301
12
15
15
0
0
0
0
0
0
100
20
100
0
0
0
0
0
0
Reference 1. Factors are in kg of pollutant/Mg (Ib/ton) of phthalic anhydride produced.
Emissions contain no methane.
°Control devices listed are those currently being used by phthalic anhydride plants.
nain process stream includes reactor and multiple switch condensers as vented through condenser unit.
eConsists of phthalic anhydride, maleic anhydride, benzole acid.
Value shown corresponds to relatively fresh catalyst, which can change with catalyst age. Can be 9.5 - 13 kg/Mg
(19 - 25 Ib/ton) for aged catalyst.
^Consists of phthalic anhydride and maleic anhydride.
Normally a vapor, but can be present as a particulate at low temperature.
Consists of phthalic anhydride, maleic anhydride, naphthaquinone.
^Particulate is phthalic anhydride.
Does not include catalyst dust, controlled by cyclones with efficiency of 90 - 98Z.
Reference for Section 5.12
1. Engineering and Cost Study of Air Pollution Control for the
Petrochemical Industry, Vol. 7; Phthalic Anhydride Manufacture
from Ortho-xylene, EPA-450/3-73-006g, U. S. Environmental Protection
Agency, Research Triangle Park, NC, July 1975.
5/83
Chemical Process Industry
5.12-5
-------
5.13 PLASTICS
5.13.1 Process Description1
The manufacture of most resins or plastics begins with the polymerization or linking of the basic compound
(monomer), usually a gas or liquid, into high molecular weight noncrystalline solids. The manufacture of the
basic monomer is not considered part of the plastics industry and is usually accomplished at a chemical or
petroleum plant.
The manufacture of most plastics involves an enclosed reaction or polymerization step, a drying step, and a
final treating and forming step. These plastics are polymerized or otherwise combined in completely enclosed
stainless steel or glass-lined vessels. Treatment of the resin after polmerization varies with the proposed use.
Resins for moldings are dried and crushed or ground into molding powder. Resins such as the alkyd resins that are
to be used for protective coatings are normally transferred to an agitated thinning tank, where they are thinned
with some type of solvent and then stored in large steel tanks equipped with water-cooled condensers to prevent
loss of solvent to the atmosphere. Still other resins are stored in latex form as they come from the kettle.
5.13.2 Emissions and Controls1
The major sources of air contamination in plastics manufacturing are the emissions of raw materials or
monomers, emissions of solvents or other volatile liquids during the reaction, emissions of sublimed solids such as
phthalic anhydride in alkyd production, and emissions of solvents during storage and handling of thinned resins.
Emission factors for the manufacture of plastics are shown in Table 5.13-1.
Table 5.13-1. EMISSION FACTORS FOR PLASTICS
MANUFACTURING WITHOUT CONTROLS8
EMISSION FACTOR RATING: E
Type of plastic
Polyvinyl chloride
Polypropylene
General
Paniculate
Ib/ton
35b
3
5to10
kg/MT
17.5b
1.5
2.5 to 5
Ga
Ib/ton
17C
0.7d
—
ses
kg/MT
8.5C
0.35d
—
"References 2 and 3.
bUsually controlled with a fabric filter efficiency of 98 to 99
percent.
cAs vinyl chloride.
dAs propylene.
Much of the control equipment used in this industry is a basic part of the system and serves to recover a
reactant or product. These controls include floating roof tanks or vapor recovery systems on volatile material,
storage units, vapor recovery systems (adsorption or condensers), purge lines that vent to a flare system, and
recovery systems on vacuum exhaust lines.
2/72
Chemical Process Industry
5.13-1
-------
References for Section 5.13
1. Air Pollutant Emission Factors. Final Report. Resources Research, Inc. Reston, Va. Prepared for National
Air Pollution Control Administration, Durham, N.C., under Contract Number CPA-22-69-119. April 1970.
2. Unpublished data from industrial questionnaire. U.S. DHEW, PHS, National Air Pollution Control
Administration, Division of Air Quality and Emissions Data. Durham, N.C. 1969.
3. Private Communication between Resources Research, Incorporated, and Maryland State Department of
Health, Baltimore, Md. November 1969.
5.13-2 EMISSION FACTORS 2/72
i
-------
5.14 PRINTING INK
5.14.1 Process Descriptionl
There are four major classes of printing ink: letterpress and lithographic inks, commonly called oil or paste
inks; and flexographic and rotogravure inks, which are referred to as solvent inks. These inks vary considerably in
physical appearance, composition, method of application, and drying mechanism. Flexographic and rotogravure
inks have many elements in common with the paste inks but differ in that they are of very low viscosity, and they
almost always dry by evaporation of highly volatile solvents.2
There are three general processes in the manufacture of printing inks: (1) cooking the vehicle and adding dyes,
(2) grinding of a pigment into the vehicle using a roller mill, and (3) replacing water in the wet pigment pulp by
an ink vehicle (commonly known as the flushing process).-' The ink "varnish" or vehicle is generally cooked in
large kettles at 200° to 600°F (93° to 315°C) for an average of 8 to 12 hours in much the same way that regular
varnish is made. Mixing of the pigment and vehicle is done in dough mixers or in large agitated tanks. Grinding is
most often carried out in three-roller or five-roller horizontal or vertical mills.
5.14.2 Emissions and Controls1'4
Varnish or vehicle preparation by heating is by far the largest source of ink manufacturing emissions. Cooling
the varnish components — resins, drying oils, petroleum oils, and solvents - produces odorous emissions. At
about 350° F (175°C) the products begin to decompose, resulting in the emission of decomposition products
from the cooking vessel. Emissions continue throughout the cooking process with the maximum rate of emissions
occuring just after the maximum temperature has been reached. Emissions from the cooking phase can be
reduced by more than 90 percent with the use of scrubbers or condensers followed by afterburners.4'5
Compounds emitted from the cooking of oleoresinous varnish (resin plus varnish) include water vapor, fatty
acids, glycerine, acrolein, phenols, aldehydes, ketones, terpene oils, terpenes, and carbon dioxide. Emissions of
thinning solvents used in flexographic and rotogravure inks may also occur.
The quantity, composition, and rate of emissions from ink manufacturing depend upon the cooking
temperature and time, the ingredients, the method of introducing additives, the degree of stirring, and the extent
of air or inert gas blowing. Particulate emissions resulting from the addition of pigments to the vehicle are
affected by the type of pigment and its particle size. Emission factors for the manufacture of printing ink are
presented in Table 5.14-1.
5/83 Chemical Process Industry 5.14-1
-------
TABLE 5.14-1. EMISSION FACTORS FOR PRINTING INK
MANUFACTURING3
EMISSION FACTOR RATING: E
Nonme thane ,
volatile organic compounds
Type of process
Vehicle cooking
General
Oils
Oleoresinous
Alkyds
Pigment mixing
kg/Mg
of product
60
20
75
80
NA
Ib/ton
of product
120
40
150
160
NA
Particulates
kg/Mg
of pigment
NA
NA
NA
NA
1
Ib/ton
of pigment
NA
NA
NA
NA
2
Based on data from Section 5.10, Paint and Varnish. NA = not applicable.
The nonmethane VOC emissions are a mix of volatilized vehicle components,
cooking decomposition products and ink solvent.
References for Section 5.14
1. Air Pollutant Emission Factors. APTD-0923, U. S. Environmental
Protection Agency, Research Triangle Park, NC, April 1970.
2. R. N. Shreve, Chemical Process Industries, 3rd Ed., New York, McGraw
Hill Book Co., 1967.
3. L. M. Larsen, Industrial Printing Inks, New York, Reinhold Publishing
Company, 1962.
4. Air Pollution Engineering Manual, 2nd Edition, AP-40, U. S. Environmental
Protection Agency, Research Triangle Park, NC, May 1973.
5. Private communication with Ink Division of Interchemical Corporation,
Cincinnati, Ohio, November 10, 1969.
5.14-2
EMISSION FACTORS
5/83
-------
5.15 SOAP AND DETERGENTS
5.15.1 Soap Manufacture
Process Description ' - Soap may be manufactured by either a batch or
continuous process, using either the alkaline saponification of natural fats
and oils or the direct saponification of fatty acids. The kettle, or full
boiled, process is a batch process of several steps in either a single kettle
or a series of kettles. Fats and oils are saponified by live steam boiling in
a caustic solution, followed by "graining", or precipitating, the soft curds
of soap out of the aqueous lye solution by adding sodium chloride (salt). The
soap solution then is washed to remove glycerine and color body impurities, to
leave the "neat" soap to form during a settling period. Continuous alkaline
saponification of natural fats and oils follows the same steps as batch
processing, but it eliminates the need for a lengthy process time. Direct
saponification of fatty acids is also accomplished in continuous processes.
Fatty acids obtained by continuous hydrolysis usually are continuously
neutralized with caustic soda in a high speed mixer/neutralizer to form soap.
All soap is finished for consumer use in such various forms as liquid,
powder, granule, chip, flake or bar.
Emissions and Controls - The main atmospheric pollution problem in the
manufacture of soap is odor. Vent lines, vacuum exhausts, product and raw
material storage, and waste streams are all potential odor sources. Control
of these odors may be achieved by scrubbing all exhaust fumes and, if
necessary, incinerating the remaining compounds. Odors emanating from the
spray drier may be controlled by scrubbing with an acid solution.
Blending, mixing, drying, packaging and other physical operations are
subject to dust emissions. The production of soap powder by spray drying is
the largest single source of dust in the manufacture of soap. Dust emissions
from finishing operations other than spray drying can be controlled by dry
filters and baghouses. The large size of the particulates in soap drying
means that high efficiency cyclones installed in series can be satisfactory in
controlling emissions.
5.15.2 Detergent Manufacture
1 7_Q
Process Description ' - The manufacture of spray dried detergent has three
main processing steps, slurry preparation, spray drying and granule handling.
Figure 5.15-1 illustrates the various operations. Detergent slurry is produced
by blending liquid surfactant with powdered and liquid materials (builders and
other additives) in a closed mixing tank called a crutcher. Liquid surfactant
used in making the detergent slurry is produced by the sulfonation or sulfation
by sulfuric acid of a linear alkylate or a fatty acid, which is then neutralized
with caustic solution (NaOH). The blended slurry is held in a surge vessel
for continuous pumping to the spray dryer. The slurry is sprayed at high
pressure through nozzles into a vertical drying tower having a stream of hot
air of from 315° to 400°C (600° to 750°F). Most towers designed for detergent
production are countercurrent, with slurry introduced at the top and heated
5/83 Chemical Process Industry 5.15-1
-------
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5.15-2
EMISSION FACTORS
5/83
-------
air introduced at the bottom. A few towers are concurrent and have both hot
air and slurry introduced at the top. The detergent granules are mechanically
or air conveyed from the tower to a mixer to incorporate additional dry or
liquid ingredients and finally sent to packaging and storage.
7—8
Emissions and Controls - In the batching and mixing of fine dry ingredients
to form slurry, dust emissions are generated at scale hoppers, mixers and the
crutcher. Baghouses and/or fabric filters are used not only to reduce or to
eliminate the dust emissions but to recover raw materials. The spray drying
operation is the major source of particulate emissions from detergent manu-
facturing. Particulate emissions from spray drying operations are shown in
Table 5.15-1. There is also a minor source of volatile organics when the
product being sprayed contains organic materials with low vapor pressures.
These vaporized organic materials condense in the tower exhaust air stream
into droplets or particles. Dry cyclones and cyclonic impingement scrubbers
are the primary collection equipment employed to capture the detergent dust in
the spray dryer exhaust for return to process. Dry cyclones are used in
parallel or in series, to collect particulate (detergent dust) and to recycle
the dry product back to the crutcher. Cyclonic impinged scrubbers are used in
parallel to collect the particulate in a scrubbing slurry which is recycled
back to the crutcher. Secondary collection equipment is used to collect the
fine particulates that have escaped from the primary devices. Cyclonic
impingement scrubbers are often followed by mist eliminators, and dry cyclones
are followed by fabric filters or scrubber/electrostatic precipitator units.
Conveying, mixing and packaging of detergent granules can cause dust emissions.
Usually baghouses and/or fabric filters provide the best control.
TABLE 5.15-1. PARTICULATE EMISSION FACTORS FOR SPRAY DRYING
DETERGENTS3
EMISSION FACTOR RATING: B
Particulate Emissions
Control
Device
Uncontrolled
Cyclone
Cyclone
w/Spray chamber
w/Packed scrubber
w/Venturi scrubber
Overall
Efficiency, %
_
85
92
95
97
kg/Mg of
product
45
7
3.5
2.5
1.5
Ib/ton of
product
90
14
7
5
3
a
References 2-6. Emissions data for volatile organic compounds has
.not been reported in the literature.
Some type of primary collector, such as a cyclone, is considered
an integral part of the spray drying system.
5/83 Chemical Process Industry 5.15-3
-------
References for Section 5.15
1. Air Pollutant Emission Factors, APTD-0923, U. S. Environmental Protection
Agency, Research Triangle Park, NC, April 1970.
2. A. H. Phelps, "Air Pollution Aspects of Soap and Detergent Manufacture",
Journal of the Air Pollution Control Association, _17_(8): 505-507, August
1967.
3. R. N. Shreve, Chemical Process Industries, Third Edition, New York,
McGraw-Hill Book Company, 1967.
4. G. P. Larsen, et al., "Evaluating Sources of Air Pollution", Industrial
and Engineering Chemistry, 45_: 1070-1074, May 1953.
5. P. Y. McCormick, et al., "Gas-solid Systems", Chemical Engineer's Handbook,
J. H. Perry (ed.), New York, McGraw-Hill Book Company, 1963.
6. Communication with Maryland State Department of Health, Baltimore, MD,
November 1969.
7. J. A. Danielson, Air Pollution Engineering Manual, AP-40, U. S.
Environmental Protection Agency, May 1973.
8. Source Category Survey; Detergent Industry, EPA-450/3-80-030, U. S.
Environmental Protection Agency, Research Triangle Park, NC, June 1980.
5.15-4 ' EMISSION FACTORS 5/83
-------
5.16 SODIUM CARBONATE
5.16.1 General1'2
Processes used to produce sodium carbonate (Na2C03), or soda ash, are
classified as either natural or synthetic. Natural processes recover sodium
carbonate from naturally occurring deposits of trona ore (sodium sesquicar-
bonate) or from brine containing sodium sesquicarbonate and sodium carbonate.
The synthetic process (Solvay process) produces sodium carbonate by reacting
ammoniated sodium chloride with carbon dioxide. For about a century, almost
all sodium carbonate production was by the Solvay process. However, since
the mid-1960s, Solvay process production has declined substantially, and
natural production has grown by 500 percent. Only one plant in the U.S. now
uses the Solvay process. Available data on emissions from the Solvay process
are also presented, but because the natural processes are more prevalent in
this country, this discussion will focus on emissions from the natural
processes.
Three different natural processes are currently in use. These are the
monohydrate, sesquicarbonate and direct carbonation processes. The sesqui-
carbonate process was the first natural process used, but it is used at only
one plant and is not expected to be used at future plants. And since data
on uncontrolled emissions from this process are not available, emissions
from the sesquicarbonate process are not discussed. The monohydrate and
direct carbonation processes and emissions are described below, the differ-
ences in these two processes being in raw materials processing.
In the monohydrate process, sodium carbonate is produced from trona
ore, which consists of 86 to 95 percent sodium sesquicarbonate
(Na2C03 * NaHCOs • 21^0), 5 to 12 percent gangues (clays and other insoluble
impurities) and water. The mined trona ore is crushed and screened and
calcined to drive off carbon dioxide and water, forming crude sodium carbon-
ate. Rotary gas fired calciners currently are most commonly used, but the
newest plants use coal fired calciners, and future plants are also likely to
use coal fired calciners because of the economics and the limited avail-
ability of natural gas.
The crude sodium carbonate is dissolved and separated from the insoluble
impurities. Sodium carbonate monohydrate (Na2C03 • H20) is crystallized
from the purified liquid by multiple effect evaporators. The sodium carbon-
ate monohydrate is then dried, to remove the free and bound water and to
produce the final product. Rotary steam tube, fluid bed steam tube, and
rotary gas fired dryers are used, with steam tube dryers more likely in
future plants.
In the direct carbonation process, sodium carbonate is produced from
brine containing sodium sesquicarbonate, sodium carbonate and other salts.
The brine is prepared by pumping liquor into salt deposits, where the salts
Q /QO
Chemical Process Industry 5^16-1
-------
are dissolved into a liquor. The recovered brine is carbonated by contact
with carbon dioxide to convert all of the sodium carbonate that is present
to sodium bicarbonate. The sodium bicarbonate is then recovered from the
brine by vacuum crystallizers. The crystal slurry is filtered, and the
crystals enter steam heated predryers to evaporate some of the moisture.
The partially dried sodium bicarbonate goes to a steam heated calciner where
carbon dioxide and the remaining water are driven off, forming impure sodium
carbonate. The carbon dioxide evolved is recycled to the brine carbonators.
The impure sodium carbonate is bleached with sodium nitrate in a gas fired
rotary bleacher to remove discoloring impurities. The bleached sodium
carbonate is then dissolved and recrystallized. The resulting crystals of
sodium carbonate monohydrate are dried, as in the monohydrate process.
In the Solvay process, ammonia, calcium carbonate (limestone), coal and
sodium chloride (brine) are the basic raw materials. The brine is purified
in a series of reactors and clarifiers by precipitating the magnesium and
calcium ions with soda ash and sodium hydroxide. Sodium bicarbonate is
formed by carbonating a solution of ammonia and purified brine which is fed
to either steam or gas rotary dryers where it is converted (calcined) to
sodium carbonate.
5.16.2 Emissions and Controls
The principal emission points in the monohydrate and direct carbonation
processes are shown in Figures 5.16-1 and 5.16-2. The major emission sources
in the monohydrate process are calciners and dryers, and the major sources
in the direct carbonation process are bleachers, dryers and predryers.
Emission factors for the emission sources are presented in Table 5.16-1, and
emission factors for the Solvay process are presented in Table 5.16-2.
In addition to the major emission points, emissions may also arise from
crushing and dissolving operations, elevators, conveyor transfer points,
product loading and storage piles. Emissions from these sources have not
been quantified.
Particulate matter is the only pollutant of concern from sodium carbon-
ate plants. Emissions of sulfur dioxide (862) arise from calciners fired
with coal, but reaction of the evolved S02 with the sodium carbonate in the
calciner keeps SC>2 emissions low. Small amounts of volatile organic com-
pounds (VOC) may also be emitted from calciners, possibly from oil shale
associated with the trona ore, but these emissions have not been quantified.
The particulate matter emission rates from calciners, dryers, predryers
and bleachers are affected by the gas velocity through the unit and by the
particle size distribution of the feed material. The latter affects the
emission rate because small particles are more easily entrained in a moving
stream of gas than are large particles. Gas velocity through the unit
affects the degree of turbulence and agitation. As the gas velocity
increases, so does the rate of increase in total particulate matter emis-
sions. Thus, coal fired calciners may have higher particulate emission
factors than gas fired calciners because they have higher gas flow rates.
The additional particulate emissions contributed by the coal fly ash repre-
sent less than one percent of total particulate emissions, and the emission
5.16-2 EMISSION FACTORS 8/82
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Chemical Process Industry
5.16-3
-------
TABLE 5.16-1.
UNCONTROLLED EMISSION FACTORS FOR NATURAL PROCESS
SODIUM CARBONATE PLANTS3
EMISSION FACTOR RATING: B
Source
Particulate emissions
Gas fired calciner .
Coal fired calciner
Rotary steam tube dryer
Fluid bed steam tube dryer ,
Rotary steam heater predryer
Rotary gas fired bleacher
kg/Mg
184.0
195.0
33.0
73.0
1.0
155.0
Ib/ton
368.0
390.0
67.0
146.0
3.1
311.0
References 3-5. Values are averages of 2 - 3 test runs.
Factor is in kg/Mg (Ib/ton) of ore fed to calciner. Includes particulate
emissions from coal fly ash. These represent < 1% of the total emissions.
Emissions of S02 from the coal are roughly 0.0007 kg/Mg (0.014 Ib/ton) of
feed.
"Factor is in kg/Mg (Ib/ton) of dry product from dryer.
a Factor is in kg/Mg (Ib/ton) of dry NaHC03 feed.
"Factor is in kg/Mg (Ib/ton) of dry feed to bleacher.
TABLE 5.16-2.
UNCONTROLLED EMISSION FACTORS FOR A SYNTHETIC
SODA ASH (SOLVAY) PLANT3
EMISSION FACTOR RATING: D
Emissions
Ammonia losses
Particulate
kg/Mg
2
25
Ib/ton
4
50
.Reference 6.
Calculated by subtracting measured ammonia effluent discharges from ammonia
purchases.
GMaximum uncontrolled emissions, from New York State process certificates to
operate. Does not include emissions from fugitive or external combustion
sources.
5.16-4
EMISSION FACTORS
8/82
-------
factor for coal fired calciners is about 6 percent higher than that for gas
fired calciners. Fluid bed steam tube dryers have higher gas flow rates and
particulate emission factors than do rotary steam tube dryers. No data on
uncontrolled particulate emissions from gas fired dryers are available, but
these dryers also have higher gas flow rates than do rotary steam tube
dryers and would probably have higher particulate emission factors.
The particulate emission factors presented in Table 5.16-1 represent
emissions measured at the inlet to the control devices. However, even in
the absence of air pollution regulations requiring emission control, these
emissions should be controlled to some degree to prevent excessive loss of
product. Because the level of control needed for product recovery is
difficult to define, the emission factors do not account for this recovery.
Cyclones in series with electrostatic precipitators (ESP) are most
commonly used to control particulate emissions from calciners and bleachers.
Venturi scrubbers are also used, but they are not as effective. Cyclone/ESP
combinations have achieved removal efficiencies ranging from 99.5 to 99.96
percent for new coal fired calciners, and 99.99 percent for bleachers. Com-
parable efficiencies should be possible for new gas fired calciners. Venturi
scrubbers are most commonly used to control emissions from dryers and pre-
dryers, because of the high moisture content of the exit gas. Cyclones are
used in series with the scrubbers for predryers and fluid bed steam tube
dryers. Removal efficiencies averaging 99.88 percent have been achieved for
venturi scrubbers on rotary steam tube dryers at a pressure drop of 6.2 kPa
(25 inches water), and acceptable collection efficiences may be achieved
with lower pressure drops. Efficiencies of 99.9 percent have been achieved
for a cyclone/venturi scrubber on a fluid bed steam tube dryer at a pressure
drop of 9.5 kPa (38 inches water). Efficiencies over 98 percent have been
achieved for a cyclone/venturi scrubber on a predryer.
Fugitive emissions originating from limestone handling/processing oper-
ations, product drying operations and dry solids handling (conveyance and
bulk loading) are a significant source of emissions from the manufacture of
soda ash by the Solvay process. These fugitive emissions have not been
quantified. Ammonia losses also occur because of leaks at pipe fittings,
gasket flanges, pump packing glands, discharges of absorber exhaust, and
exposed bicarbonate cake on filter wheels and on feed floor prior to
calcifying.
References for Section 5.16
1. Sodium Carbonate Industry - Background Information for Proposed
Standards, EPA-450/3-80-029a, U. S. Environmental Protection Agency,
Research Triangle Park, NC, August 1980.
2. Air Pollutant Emission Factors, Final Report, HEW Contract Number
CPA-22-69-119, Resources Research, Inc., Reston, VA, April 1970.
3. Sodium Carbonate Manufacturing Plant, EPA-79-SOD-1, U. S. Environ-
mental Protection Agency, Research Triangle Park, NC, August 1979.
8/82 Chemical Process Industry 5.16-5
-------
4. Sodium Carbonate Manufacturing Plant, EPA-79-SOD-2, U. S. Environ-
mental Protection Agency, Research Triangle Park, NC, March 1980.
5. Particulate Emissions from the Kerr-McGee Chemical Corporation Sodium
Carbonate Plant, EPA-79-SOD-3, U. S. Environmental Protection Agency,
Research Triangle Park, NC, March 1980.
6. Written communication from W. S. Turetsky, Allied chemical Company,
Morristown, NJ, to Frank Noonan, U.S. Environmental Protection Agency,
Research Triangle Park, NC, June 17, 1982.
5.16-6 EMISSION FACTORS 8/82
-------
5.17 SULFURIC ACID
5.17.1 General
All sulfuric acid is made by either the lead chamber process
or the contact process. Because the contact process accounts for
more than 97 percent of the total sulfuric acid production in the
United States, it is the only process discussed in this Section.
Contact plants are generally classified according to the raw materials
charged to them - (1) elemental sulfur burning, (2) spent acid and
hydrogen sulfide burning, and (3) sulfide ores and smelter gas
burning. The contributions from these plants to the total acid
production are 68, 18.5 and 13.5 percent respectively.
All contact processes incorporate three basic operations, each
of which corresponds to a distinct chemical reaction. First, the
sulfur in the feedstock is burned to sulfur dioxide:
S + 02 —^ S02
Sulfur Oxygen Sulfur (1)
dioxide
Then, the sulfur dioxide is catalytically oxidized to sulfur trioxide:
2S02 + 02 —>• 2S03
Sulfur Oxygen Sulfur (2)
dioxide trioxide
Finally, the sulfur trioxide is absorbed in a strong aqueous solution
of sulfuric acid:
S03 + H20 —+* H2S04
Sulfur Water Sulfuric (3)
trioxide acid
1 2
Elemental Sulfur Burning Plants ' - Elemental sulfur, such as
Frasch process sulfur from oil refineries, is melted, settled or
filtered to remove ash and is fed into a combustion chamber. The
sulfur is burned in clean air that has been dried by scrubbing with
93 - 99 percent sulfuric acid. The gases from the combustion chamber
cool and then enter the solid catalyst (vanadium pentoxide) con-
verter. Usually, 95 - 98 percent of the sulfur dioxide from the
combustion chamber is converted to sulfur trioxide, with an accompany-
ing large evolution of heat. After being cooled, the converter exit
gas enters an absorption tower, where the sulfur trioxide is absorbed
with 98 - 99 percent sulfuric acid. The sulfur trioxide combines
with the water in the acid and forms more sulfuric acid.
If oleum, a solution of uncombined 803 in H2SO^, is produced,
803 from the converter is first passed to an oleum tower that is
fed with 98 percent acid from the absorption system. The gases
4/81 Chemical Process Industry 5.17-1
-------
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5.17-2
EMISSION FACTORS
4/81
-------
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Figure 5.17-2. Basic flow diagram of contact process sulfuric acid plant burning spent acid.
4/81
Chemical Process Industry
5.17-3
-------
from the oleum tower are then pumped to the absorption column where
the residual sulfur trioxide is removed.
A schematic diagram of a contact process sulfuric acid plant
that burns elemental sulfur is shown in Figure 5.17-1.
1 2
Spent Acid and Hydrogen Sulfide Burning Plants ' - Two types of
plants are used to process this type of sulfuric acid. In one, the
sulfur dioxide and other combustion products from the combustion of
spent acid and/or hydrogen sulfide with undried atmospheric air are
passed through gas cleaning and mist removal equipment. The gas
stream next passes through a drying tower. A blower draws the gas
from the drying tower and discharges the sulfur dioxide gas to the
sulfur trioxide converter. A schematic diagram of a contact process
sulfuric acid plant that burns spent acid is shown in Figure 5.17-2.
In a "wet gas plant", the wet gases from the combustion chamber
are charged directly to the converter with no intermediate treatment.
The gas from the converter flows to the absorber, through which
93 - 98 percent sulfuric acid is circulating.
Sulfide Ores and Smelter Gas Plants - The configuration of this
type of plant is essentially the same as that of a spent acid plant
(Figure 5.17-2), with the primary exception that a roaster is used
in place of the combustion furnace.
The feed used in these plants is smelter gas, available from
such equipment as copper converters, reverberatory furnaces,
roasters and flash smelters. The sulfur dioxide in the gas is con-
taminated with dust, acid mist and gaseous impurities. To remove
the impurities, the gases must be cooled and passed through purifi-
cation equipment consisting of cyclone dust collectors, electrostatic
dust and mist precipitators, and scrubbing and gas cooling towers.
After the gases are cleaned and the excess water vapor is removed,
they are scrubbed with 98 percent acid in a drying tower. Beginning
with the drying tower stage, these plants are nearly identical to
the elemental sulfur plants shown in Figure 5.17-1.
5.17.2 Emissions and Controls
1-3
Sulfur Dioxide - Nearly all sulfur dioxide emissions from
sulfuric acid plants are found in the exit gases. Extensive testing
has shown that the mass of these SO2 emissions is an inverse func-
tion of the sulfur conversion efficiency (S02 oxidized to SO^).
This conversion is always incomplete, and is affected by the number
of stages in the catalytic converter, the amount of catalyst used,
temperature and pressure, and the concentrations of the reactants
(sulfur dioxide and oxygen). For example, if the inlet S02 concen-
tration to the converter were 8 percent by volume (a representative
value), and the conversion temperature were 473°C (883°F), the con-
version efficiency would be 96 percent. At this conversion, the
5.17-4 EMISSION FACTORS 4/81
i
i
-------
uncontrolled emission factor for 802 would be 27.5 kg/Mg (55 pounds
per ton) of 100 percent sulfuric acid produced, as shown in
Table 5.17-1. For purposes of comparison, note that the Environ-
mental Protection Agency performance standard for new and modified
plants is 2 kg/Mg (4 pounds per ton) of 100 percent acid produced,
maximum 2 hour average. As Table 5.17-1 and Figure 5.17-3 indicate,
achieving this standard requires a conversion efficiency of 99.7
percent in an uncontrolled plant or the equivalent S02 collec-
tion mechanism in a controlled facility. Most single absorption
plants have SO. conversion efficiencies ranging from 95 - 98 percent.
In addition to exit gases, small quantities of sulfur oxides
are emitted from storage tank vents and tank car and tank truck vents
during loading operations, from sulfuric acid concentrators, and
through leaks in process equipment. Few data are available on the
quantity of emissions from these sources.
Of the many chemical and physical means for removing SO2 from
gas streams, only the dual absorption and the sodium sulfite/bisul-
fite scrubbing processes have been found to increase acid production
without yielding unwanted byproducts.
TABLE 5.17-1. EMISSION FACTORS FOR SULFURIC
ACID PLANTSS
EMISSION FACTOR RATING: A
S02 Emissions
Conversion of SO2 kg/Mg of 100% Ib/ton of 100%
to S03 (%) H2S04 H2S04
93
94
95
96
97
98
99
99.5
99.7
100
48.0
41.0
35.0
27.5
20.0
13.0
7.0
3.5
2.0
0.0
96
82
70
55
40
26
14
7
4
0
.Reference 1.
This linear interpolation formula can be used for calculating
emission factors for conversion efficiencies between 93 and 100%:
emission factor =-13.65 (% conversion efficiency) + 1365.
4/81 Chemical Process Industry 5.17-5
-------
99.92
10,000
SULFUR CONVERSION, % feedstock sulfur
99.7 99.0
98.0
97.0 96.0 95.0
1.5
2.5 3
40 50 60708090100
4 5 6 7 8 9 10 15 20 25 30
SUBMISSIONS, Ib/ton of 100% H2S04 produced
Figure 5.17-3. Sulfuric acid plant feedstock sulfur conversion versus volumetric and
mass SC>2 emissions at various inlet SC>2 concentrations by volume.
5.17-6
EMISSION FACTORS
4/81
-------
In the dual absorption process, the 803 gas formed in the
primary converter stages is sent to a primary absorption tower where
most of the 863 is removed to form H^SC^. The remaining unconverted
sulfur dioxide is forwarded to the final stages in the converter to
remove much of the remaining 802 by oxidation to 863, from whence
it is sent to the secondary absorber for final sulfur trioxide
removal. The result is the conversion of a much higher fraction of
802 to 803 (a conversion of 99.7 percent or higher, on the average,
which meets the performance standard). Furthermore, dual absorption
permits higher converter inlet sulfur dioxide concentrations than
are used in single absorption plants, because the secondary conver-
sion stages effectively remove any residual sulfur dioxide from the
primary absorber.
Where dual absorption reduces sulfur dioxide emissions by
increasing the overall conversion efficiency, the sodium sulfite/
bisulfite scrubbing process removes sulfur dioxide directly from
the absorber exit gases. In one version of this process, the sul-
fer dioxide in the waste gas is absorbed in a sodium sulfite solution,
is separated, and is recycled to the plant. Test results from a
680 Mg (750 ton per day) plant equipped with a sulfite scrubbing
system indicated an average SO emission factor of 1.35 kg/Mg
(2.7 pounds per ton) of 100 percent acid.
1-3
Acid Mist - Nearly all the acid mist emitted from sulfuric acid
manufacturing can be traced to the absorber exit gases. Acid mist
is created when sulfur trioxide combines with water vapor at a
temperature below the dew point of sulfur trioxide. Once formed
within the process system, this mist is so stable that only a small
quantity can be removed in the absorber.
In general, the quantity and particle size distribution of
acid mist are dependent on the type of sulfur feedstock used, the
strength of acid produced, and the conditions in the absorber.
Because it contains virtually no water vapor, bright elemental
sulfur produces little acid mist when burned. However, the hydro-
carbon impurities in other feedstocks - dark sulfur, spent acid
and hydrogen sulfide - oxidize to water vapor during combustion.
The water vapor, in turn, combines with sulfur trioxide as the gas
cools in the system.
The strength of acid produced - whether oleum or 99 percent
sulfuric acid - also affects mist emissions. Oleum plants produce
greater quantities of finer more stable mist. For example, uncon-
trolled mist emissions from oleum plants burning spent acid range
from 0.5 to 5.0 kg/Mg (1.0 to 10.0 pounds per ton), while those
from 98 percent acid plants burning elemental sulfur range from
0.2 to 2.0 kg/Mg (0.4 to 4.0 pounds per ton). Furthermore,
85 - 95 weight percent of the mist particles from oleum plants are
less than 2 microns in diameter, compared with only 30 weight
percent that are less than 2 microns in diameter from 98 percent
acid plants.
4/81 Chemical Process Industry 5.17-7
-------
The operating temperature of the absorption column directly
affects sulfur trioxide absorption and, accordingly, the quality of
acid mist formed after exit gases leave the stack. The optimum
absorber operating temperature depends on the strength of the acid
produced, throughput rates, inlet sulfur trioxide concentrations,
and other variables peculiar to each individual plant. Finally,
It should be emphasized that the percentage conversion of sulfur
trioxide has no direct effect on acid mist emissions. In
Table 5.17-2, uncontrolled acid mist emissions are presented for
various sulfuric acid plants.
TABLE 5.17-2. ACID MIST EMISSION FACTORS FOR SULFURIC
ACID PLANTS WITHOUT CONTROLS3
EMISSIONS FACTOR RATING: B
Emissions
Oleum produced,
Raw material % total output kg/Mg acid Ib/ton acid
Recovered sulfur
Bright virgin sulfur
Dark virgin sulfur
Sulfide ores
Spent acid
0 to 43
0
33 to 100
0 to 25
0 to 77
0.175 - 0.4
0.85
0.16 - 3.15
0.6 - 3.7
1.1 - 1.2
0.35 - 0.8
1.7
0.32 - 6.3
1.2 - 7.4
2.2 - 2.4
^Reference 1.
Emissions are proportional to the percentage of oleum in the total
product. Use low end of ranges for low oleum percentage and high
end of ranges for high oleum percentage.
Two basic types of devices, electrostatic precipitators and
fiber mist eliminators, effectively reduce the acid mist concentra-
tion from contact plants to less than the EPA New Source Performance
Standard, which is 0.075 kg/Mg (0.15 pound per ton) of acid. Pre-
cipitators, if properly maintained, are effective in collecting the
mist particles at efficiencies up to 99 percent (see Table 5.17-3).
The three most commonly used fiber mist eliminators are the
vertical tube, vertical panel, and horizontal dual pad types. They
differ from one another in the arrangement of the fiber elements,
which are composed of either chemically resistant glass or fluoro-
carbon, and in the means employed to collect the trapped liquid.
The operating characteristics of these three types are compared with
electrostatic precipitators in Table 5.17-3.
5.17-8 EMISSION FACTORS 4/81
-------
TABLE 5.17-3. EMISSION COMPARISON AND COLLECTION EFFICIENCY OF
TYPICAL ELECTROSTATIC PRECIPITATOR AND FIBER MIST ELIMINATORS3
Control device
Particle size
collection
efficiency, %
>3 |jm <3^m
Acid mist emissions
98% acid plants Oleum plants
kg/Mg Ib/ton kg/Mg Ib/ton
Electrostatic
precipitator
Fiber mist
eliminator
99
100
0.05
0.10
0.06
0.12
Tabular
Panel
Dual pad
100
100
100
95-99
90-98
93-99
0.01
0.05
0.055
0.02
0.10
0.11
0.01
0.05
0.055
0.02
0.10
0.11
/Reference 2.
Based on manufacturers' generally expected results. Calculated for !
SO^ concentration in gas converter.
References for Section 5.17
1. Atmospheric Emissions from Sulfuric Acid Manufacturing Processes,
999-AP-13, U.S. Department of Health, Education and Welfare,
Washington, DC, 1966.
2. Unpublished report on control of air pollution from sulfuric
acid plants, U.S. Environmental Protection Agency, Research
Triangle Park, NC, August 1971.
3. Standards of Performance for New Stationary Sources, 36 FR 24875,
December 23, 1971.
4. M. Drabkin and Kathryn J. Brooks, A Review of Standards of
Performance for New Stationary Sources - Sulfuric Acid Plants,
EPA Contract No. 68-02-2526, Mitre Corporation, McLean, VA,
June 1978.
5. Final Guideline Document; Control of Sulfuric Acid Mist
Emissions from Existing Sulfuric Acid Production Units,
EPA 450/2-77-019, U.S. Environmental Protection Agency,
Research Triangle Park, NC, September 1977.
4/81
Chemical Process Industry
5.17-9
-------
5.18 SULFUR RECOVERY
1 2
5.18.1 Process Description '
Most of the elemental sulfur produced from hydrogen sulfide (H2S)
is made by the modified Glaus process. A simplified flow diagram of
this process is shown in Figure 5.18-1. The process consists of the
multistage catalytic oxidation of hydrogen sulfide according to the
following overall Reaction:
2H2S + 02 •* 2S + 2H20
In the first step, one third of the H2S is reacted with air in a furnace
and combusted to S02 according to Reaction (2):
H2S + 1.502 •* S02 + H20 (2)
The heat of the reaction is recovered in a waste heat boiler or sulfur
condenser.
For gas streams with low concentrations of H2S (20 - 60%), approxi-
mately one third of the gas stream is fed to the furnace and the H2S is
nearly completely combusted to S02, while the remainder of the gas is
bypassed around the furnace. This is the "split stream" configuration.
For gas streams with higher H2S concentrations, the entire gas stream is
fed to the furnace with just enough air to combust one third of the H2S
to S02. This is the "partial combustion" configuration. In this
configuration, as much as 50 to 60 percent conversion of the hydrogen
sulfide to elemental sulfur takes place in the initial reaction chamber
by Reaction (1). In extremely low concentrations of H2S (<25 - 30%), a
Claus process variation known as "sulfur recycle" may be used, where
product sulfur is recycled to the furnace and burned, raising the
effective sulfur level where flame stability may be maintained in the
furnaces.
After the reaction furnace, the gases are cooled to remove
elemental sulfur and then reheated. The remaining H2S in the gas stream
is then reacted with the S02 over a bauxite catalyst at 500 - 600°F
(260 - 316°C) to produce elemental sulfur according to Reaction 3:
2H2S + S02 £ 3S + 2H20 (3)
Because this is a reversible reaction, equilibrium requirements limit
the conversion. Lower temperatures favor elemental sulfur formation,
but at too low a temperature, elemental sulfur fouls the catalyst.
Because the reaction is exothermic, the comversion attainable in one
stage is limited. Therefore, two or more stages are used in series,
with interstage cooling to remove the heat of reaction and to condense
the sulfur.
2/80 Chemical Proross Industry .>.!«-1
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EMISSION FACTORS
2/80
i
-------
Carbonyl sulfide (COS) and carbon disulfide (CS2) are formed in the
reaction furnace in the presence of carbon dioxide and hydrocarbons:
C02 + H2S £ H2° + cos
COS + H2S j H20 + CS2 (5)
CHij + 4S j CS2 + 2H2S (6)
About 0.25 to 2.5 percent of the sulfur fed may be lost in this way.
Additional sulfur may be lost as vapor, mist or droplets.
5.18.2 Emissions and Controls
Tail gas from a Claus sulfur recovery unit contains a variety of
pollutants, including sulfur dioxide, hydrogen sulfide, other reduced
sulfur compounds (such as COS and CS2), carbon monoxide, and volatile
organic compounds. If no other controls are used, the tail gas is
incinerated, so that the emissions consist mostly of sulfur dioxide.
Smaller amounts of carbon monoxide are also emitted.
The emissions of S02 (along with H2S and sulfur vapor) depend
directly on the sulfur recovery efficiency of the Claus plant. This
efficiency is dependent upon many factors, including the following:
- Number of catalytic conversion stages
- Inlet feed stream composition
- Operating temperatures and catalyst maintenance
- Maintenance of the proper stoichiometric ratio of H2S/S02
- Operating capacity factor
Recovery efficiency increases with the number of catalytic stages
used. For example, for a Claus plant fed with 90 percent H2S, sulfur
recovery is approximately 85 percent for one catalytic stage and 95
percent for two or three stages.
Recovery efficiency also depends on the inlet feed stream compo-
sition. Sulfur recovery increases with increasing H2S concentration in
the feed stream. For example, a plant having two or three catalytic
stages would have a sulfur recovery efficiency of approximately 90
percent when treating a 15 mole percent H2S feed stream, 93 percent for
a 50 mole percent H2S stream, and 95 percent for a 90 mole percent H2S
stream. Various contaminants in the feed gas reduce Claus sulfur
recovery efficiency. Organic compounds in the feed require extra air
for combustion, and added water and inert gas from burning these organics
decrease sulfur concentrations and thus lower sulfur recovery. Higher
molecular weight organics also reduce efficiencies because of soot
formation on the catalyst. High concentrations of C02 in the feed gas
reduce catalyst life.
2/80 Chemical Process Industry 5.18-3
-------
Since the Glaus reactions are exothermic, sulfur recovery is
enhanced by removing heat and operating the reactors at as low a tern-
perature as practicable without condensing sulfur on the catalyst.
Recovery efficiency also depends on catalyst performance. One to 2
percent loss in recovery efficiency over the period of catalyst life has
been reported. Maintenance of the 2:1 stoichiometric ratio of I^S and
SC>2 is essential for efficient sulfur recovery. Deviation above or
below this ratio results in a loss of efficiency. Operation of a Glaus
plant below capacity may also impair Glaus efficiency somewhat.
Removal of sulfur compounds from Glaus plant tail gas is possible
by three general schemes:
1) Extension of the Glaus reaction to increase overall sulfur
recovery,
2) Conversion of sulfur gases to S02, followed by S02 removal
technology,
3) Conversion of sulfur gases to H2S, followed by t^S removal
technology.
Processes in the first scheme remove additional sulfur compounds by
carrying out the Glaus reaction at lower temperatures to shift equi-
librium of the Glaus reactions toward formation of additional sulfur.
The IFP-1, BSR/Selectox, Sulfreen, and Amoco CBA processes use this
technique to reduce the concentration of tail gas sulfur compounds to
1500 - 2500 ppm, thus increasing the sulfur recovery of the Glaus plant
to 99 percent.
In the second class of processes, the tail gas is incinerated to
convert all sulfur compounds to SOj. The S02 is then recovered by one
of several processes, such as the Wellman-Lord. In the Wellman-Lord and
certain other processes, the S02 absorbed from the tail gas is recycled
to the Glaus plant to recover additional sulfur. Processes in this
class can reduce the concentration of sulfur compounds in the tail gas
to 200 - 300 ppm or less, for an overall sulfur recovery efficiency
(including the Glaus plant) of 99.9+ percent.
The third method for removal of sulfur compounds from Glaus tail
gas involves converting the sulfur compounds to H^S by mixing the tail
gas with a reducing gas and passing it over a reducing catalyst. The
H2S is then removed, by the Stretford process (in the Beavon and Clean
Air processes) or by an amine absorption system (SCOT process). The
Beavon and Clean Air processes recover the l^S as elemental sulfur, and
the SCOT process produces a concentrated H2S stream which is recycled to
the Glaus process. These processes reduce the concentration of sulfur
compounds in the tail gas to 200 - 300 ppm or less and increase the
overall recovery efficiency of the Glaus plant to 99.9+ percent.
i
5.18-4 EMISSION FACTORS 2/80
-------
A New Source Performance Standard for Glaus sulfur recovery plants
in petroleum refineries was promulgated in March 1978. This standard
limits emissions to 0.025 percent by volume (250 ppm) of SC>2 on a dry
basis and at zero percent oxygen, or 0.001 percent by volume of H2S and
0.03 percent by volume of H2S, COS, and 682 on a dry basis and at zero
percent oxygen.
Table 5.18-1. EMISSION FACTORS FOR MODIFIED GLAUS SULFUR RECOVERY
PLANTS
EMISSION FACTOR RATING: D
Number of Catalytic Stages
Two, uncontrolled
Three, uncontrolled
Four , uncontrolled
Controlled
Typical
Recovery
of Sulfur, %£
92 to 95
95 to 97.5
96 to 99
99 to 99.9
S0_ Emissions
1 Ib/ton
348 to 211
211 to 167
167 to 124
40 to 4
kg/MT
174 to 105
106 to 84
84 to 62
20 to 2
Q
Efficiencies are for feed gas streams with high I^S concentrations.
Gases with lower H2S concentrations would have lower efficiencies.
For example, a 2 or 3 stage plant could have a recovery efficiency of
95% for a 90% H2S stream, 93% for 50% H2S, and 90% for 15% H2S.
Based on net weight of pure sulfur produced. The range in emission
fractors corresponds to the range in percentage recovery of sulfur.
S02 emissions calculated from percentage sulfur recovery by following
equation:
S02 emissions (kg/MT) = (10g-* ™c°™ry) X 2000
^ ° % recovery
Lower percent recovery is for control by extended Glaus, and higher
percent is for conversion to and removal of H2S or S02 .
References for Section 5.18
1. E. C. Cavanaugh, et al. , Environmental Assessment Data Base for
Low/Medium Btu Gasification Technology, Volume II, EPA Contract No.
68-02-2147, Radian Corporation, Austin, TX, September 1977.
2. Standards Support and Environmental Impact Statement, Volume 1;
Proposed Standards of Performance for Petroleum Refinery Sulfur
Recovery Plants. EPA-450/2-76-016a, U. S. Environmental Protection
Agency, Research Triangle Park, NC, September 1976.
3. B. Goar and T. Arrington, "Guidelines for Handling Sour Gas",
Oil and Gas Journal, 76(26); 160-164, June 26, 1978.
2/80 Chemical Profess Industry .">.
-------
5.19 SYNTHETIC FIBERS
5.19.1 Process Descriptionl
Synthetic fibers are classified into two major categories, semi-synthetic and "true" synthetic. Semi-synthetics,
such as viscose rayon and acetate fibers, result when natural polymeric materials such as cellulose are brought into
a dissolved or dispersed state and then spun into fine filaments. True synthetic polymers, such as Nylon, * Orion,
and Dacron, result from addition and other polymerization reactions that form long chain molecules.
True synthetic fibers begin with the preparation of extremely long, chain-like molecules. The polymer is spun
in one of four ways:2 (1) melt spinning, in which molten polymer is pumped through spinneret jets, the polymer
solidifying as it strikes the cool air; (2) dry spinning, in which the polymer is dissolved in a suitable organic
solvent, and the resulting solution is forced through spinnerets; (3) wet spinning, in which the solution is
coagulated in a chemical as it emerges from the spinneret; and (4) core spinning, the newest method, in which a
continuous filament yarn together with short-length "hard" fibers is introduced onto a spinning frame in such a
way as to form a composite yarn.
5.19.2 Emissions and Controls'
In the manufacture of viscose rayon, carbon disulfide and hydrogen sulfide are the major gaseous emissions.
Air pollution controls are not normally used to reduce these emissions, but adsorption in activated carbon at an
efficiency of 80 to 95 percent, with subsequent recovery of theCS2 can be accomplished.3 Emissions of gaseous
hydrocarbons may also occur from the drying of the finished fiber. Table 5.19-1 presents emission factors for
semi-synthetic and true synthetic fibers.
Table 5.19-1. EMISSION FACTORS FOR SYNTHETIC FIBERS MANUFACTURING
EMISSION FACTOR RATING: E
Type of fiber
Semi-synthetic
Viscose rayona-b
True synthetic0
Nylon
Dacron
Hydrocarbons
Ib/ton
—
7
—
kg/MT
—
3.5
—
Carbon
disulfide
Ib/ton
55
-
—
kg/MT
27.5
-
—
Hydrogen
sulfide
Ib/ton
6
-
—
kg/MT
3
-
—
Oil vapor
or mist
Ib/ton
—
15
7
kg/MT
-
7.5
3.5
Reference 4.
"May be reduced by 80 to 95 percent adsorption in activated charcoal.
cReference 5.
*Mention of company or product names does not constitute endorsement by the Environmental Protection
Agency.
2/72
Chemical Process Industry
5.19-1
-------
References for Section 5.19
1. Air Pollutant Emission Factors. Final Report. Resources Research, Inc. Reston, Va. Prepared for National
Air Pollution Control Administration, Durham, N.C., under Contract Number CPA-22-69-119. April 1970.
2. Fibers, Man-Made. In: Kirk-Othmer Encyclopedia of Chemical Technology. New York, John Wiley and Sons,
Inc. 1969.
3. Fluidized Recovery System Nabs Carbon Disulfide. Chem. Eng. 70(8):92-94, April 15,1963.
4. Private communication between Resources Research, Incorporated, and Rayon Manufacturing Plant.
December 1969.
5. Private communication between Resources Research, Incorporated, and E.I. Dupont de Nemours and
Company. January 13,1970.
5.19-2 EMISSION FACTORS 2/72
-------
5.20 SYNTHETIC RUBBER
5.20.1. Emulsion Styrene-Butadiene Copolymers
General - Two types of polymerization reaction are used to produce styrene-
butadiene copolymers, the emulsion type and the solution type. This Section
addresses volatile organic compound (VOC) emissions from the manufacture of
copolymers of styrene and butadiene made by emulsion polymerization processes.
The emulsion products can be sold in either a granular solid form, known as
crumb, or in a liquid form, known as latex.
Copolymers of styrene and butadiene can be made with properties ranging
from those of a rubbery material to those of a very resilient plastic.
Copolymers containing less than 45 weight percent styrene are known as
styrene-butadiene rubber (SBR). As the styrene content is increased over 45
weight percent, the product becomes increasingly more plastic.
Emulsion Crumb Process - As shown in Figure 5.20-1, fresh styrene and
butadiene are piped separately to the manufacturing plant from the storage
area. Polymerization of styrene and butadiene proceeds continuously though
a train of reactors, with a residence time in each reactor of approximately
1 hour. The reaction product formed in the emulsion phase of the reaction
mixture is a milky white emulsion called latex. The overall polymerization
reaction ordinarily is not carried out beyond a 60 percent conversion of
monomers to polymer, because the reaction rate falls off considerably beyond
this point and product quality begins to deteriorate.
Because recovery of the unreacted monomers and their subsequent purifi-
cation are essential to economical operation, unreacted butadiene and styrene
from the emulsion crumb polymerization process normally are recovered. The
latex emulsion is introduced to flash tanks where, using vacuum flashing, the
unreacted butadiene is removed. The butadiene is then compressed, condensed
and pumped back to the tank farm storage area for subsequent reuse. The
condenser tail gases and noncondensibles pass through a butadiene adsorber/
desorber unit, where more butadiene is recovered. Some noncondensibles and
VOC vapors pass to the atmosphere or, at some plants, to a flare system.
The latex stream from the butadiene recovery area is then sent to the styrene
recovery process, usually taking place in perforated plate steam stripping
columns. From the styrene stripper, the latex is stored in blend tanks.
From this point in the manufacturing process, latex is processed
continuously. The latex is pumped from the blend tanks to coagulation
vessels, where dilute sulfuric acid (I^SO^ of pH 4 to 4.5) and sodium
chloride solution are added. The acid and brine mixture causes the emulsion
to break, releasing the styrene-butadiene copolymer as crumb product. The
coagulation vessels are open to the atmosphere.
8/82 Chemical Process Industry
5.20-1
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5.20-3
-------
TABLE 5.20-1. EMISSION FACTORS FOR EMULSION STYRENE-BUTADIENE
COPOLYMER PRODUCTION3
EMISSION FACTOR RATING: B
Process Volatile Organic Emissions
g/kg Ib/ton
Emulsion Crumb
Monomer recovery, uncontrolled0 2.6 5.2
Absorber vent , 0.26 0.52
Blend/coagulation tank, uncontrolled 0.42 0.84
Dryers6 2.51 5.02
Emulsion Latex
Monomer removal ,.
Condenser vent 8.45 16.9
Blend tanks ,.
Uncontrolled 0.1 0.2
Nonmethane VOC, mainly styrene and butadiene. For emulsion crumb and
emulsion latex processes only. Factors for related equipment and
operations (storage, fugitives, boilers, etc.) are presented in other
Sections of AP-42.
Expressed as units per unit of copolymer produced.
^Average of 3 industry supplied stack tests.
Average of 1 industry stack test and 2 industry supplied emission
estimates.
No controls available. Average of 3 industry supplied stack tests and 1
findustry estimate.
EPA estimates from industry supplied data, confirmed by industry.
Leaving the coagulation process, the crumb and brine acid slurry is
separated by screens into solid and liquid. The crumb product is processed
in rotary presses that squeeze out most of the entrained water. The liquid
(brine/acid) from the screening area and the rotary presses is cycled to the
coagulation area for reuse.
The partially dried crumb is then processed in a continuous belt dryer
which blows hot air at approximately 93°C (200°F) across the crumb to com-
plete the drying of the product. Some plants have installed single pass
dryers, where space permits, but most plants still use the triple pass dryers
which were installed as original equipment in the 1940s. The dried product
is baled and weighed before shipment.
Emulsion Latex Process - Emulsion polymerization can also be used to
produce latex products. These latex products have a wider range of pro-
perties and uses than do the crumb products, but the plants are usually much
smaller. Latex production, shown in Figure 5.20-2, follows the same basic
processing steps as emulsion crumb polymerization, with the exception of
final product processing.
5.20-4 EMISSION FACTORS 8/82
i
-------
As in emulsion crumb polymerization, the monomers are piped to the
processing plant from the storage area. The polymerization reaction is
taken to near completion (98 to 99 percent conversion), and the recovery of
unreacted monomers is therefore uneconomical. Process economy is directed
towards maximum conversion of the monomers in one process trip.
Because most emulsion latex polymerization is done in a batch process,
the number of reactors used for latex production is usually smaller than for
crum production. The latex is sent to a blowdown tank where, under vacuum,
any unreacted butadiene and some unreacted styrene are removed from the
latex. If the unreacted styrene content of the latex has not been reduced
sufficiently to meet product specifications in the blowdown step, the latex
is introduced to a series of steam stripping steps to reduce the content
further. Any steam and styrene vapor from these stripping steps is taken
overhead and is sent to a water cooled condenser. Any uncondensibles leaving
the condenser are vented to the atmosphere.
After discharge from the blowdown tank or the styrene stripper, the
latex is stored in process tanks. Stripped latex is passed through a series
of screen filters to remove unwanted solids and is stored in blending tanks,
where antioxidants are added and mixed. Finally, latex is pumped from the
blending tanks to be packaged into drums or to be bulk loaded into railcars
or tank trucks.
Emissions and Controls - Emission factors for emulsion styrene-butadiene
copolymer production processes are presented in Table 5.20-1.
In the emulsion crumb process, uncontrolled noncondensed tail gases
(VOC) pass through a butadiene absorber control device, which is 90 percent
efficient, to the atmosphere or, in some plants, to a flare stack.
No controls are presently employed for the blend tank and/or coagul-
ation tank areas, on either crumb or latex facilities. Emissions from
dryers in the crumb process and the monomer removal part of the latex
process do not employ control devices.
Individual plant emissions may vary from the average values listed in
Table 5.20-1 with facility age, size and plant modification factors.
References for Section 5.20
1. Control Techniques Guideline (Draft), EPA Contract No. 68-02-3168,
GCA, Inc., Chapel Hill, NC, April 1981.
2. Emulsion Styrene-Butadiene Copolymers; Background Document , EPA
Contract No. 68-02-3063, TRW Inc., Research Triangle Park, NC, May 1981.
3. Confidential written communication from C. Fabian, U.S. Environmental
Protection Agency, Research Triangle Park, NC, to Styrene-Butadiene
Rubber File (76/15B), July 16, 1981.
8/82 Chemical Process Industry 5.20-5
-------
5.21 Terephthalic Acid
5.21.1 Process Description
Terephthalic acid (TPA) is made by air oxidation of jv-xylene and requires
purification for use in polyester fiber manufacture. A typical continuous
process for the manufacture of crude terephthalic acid (C-TPA) is shown in
Figure 5.21-1. The oxidation and product recovery portion essentially
consists of the Mid-Century oxidation process, whereas the recovery and
recycle of acetic acid and recovery of methyl acetate are essentially as
practiced by dimethyl terephthalate (DMT) technology. The purpose of the
DMT process is to convert the terephthalic acid contained in C-TPA to a form
that will permit its separation from impurities. C-TPA is extremely insoluble
in both water and most common organic solvents. Additionally, it does not
melt, it sublimes. Some products of partial oxidation of £-xylene, such as
_p_-toluic acid and _p_-formyl benzoic acid, appear as impurities in TPA.
Methyl acetate is also formed in significant amounts in the reaction.
0 0
OCAT " / — S. I'
CH3 + 302 - » HO-C-/ \-C— OH + 2H20
tAUCIIUAUU "X. ^ - '
SOLVENT) (g-XYLENE) (AIR) \. (TEREPHTHALIC ACID) (WATER)
CO + C02 + H20
C-TPA Production
Oxidation of £-xylene - ^-xylene (stream 1 of Figure 5.21-1), fresh acetic
acid (2), a catalyst system, such as manganese or cobalt acetate and sodium
bromide (3) , and recovered acetic acid are combined into the liquid feed
entering the reactor (5). Air (6), compressed to a reaction pressure of
about 2000 kPa (290 psi) , is fed to the reactor. The temperature of the
exothermic reaction is maintained at about 200°C (392°F) by controlling the
pressure at which the reaction mixture is permitted to boil and form the
vapor stream leaving the reactor (7).
Inert gases, excess oxygen, CO, C02» and volatile organic compounds
(VOC) (8) leave the gas/ liquid separator and are sent to the high pressure
absorber. This stream is scrubbed with water under pressure, resulting in a
gas stream (9) of reduced VOC content. Part of the discharge from the
high pressure absorber is dried and is used as a source of inert gas (IG),
and the remainder is passed through a pressure control valve and a noise
silencer before being discharged to the atmosphere through process vent A.
The underflow (23) from the absorber is sent to the azeotrope still for
recovery of acetic acid .
Crystallization and Separation - The reactor liquid containing TPA (10)
flows to a series of crystallizers, where the pressure is relieved and the
5/83 Chemical Process Industry 5.21-1
-------
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liquid is cooled by the vaporization and return of condensed VOC and water.
The partially oxidized impurities are more soluble in acetic acid and tend
to remain in solution, while TPA crystallizes from the liquor. The inert
gas that was dissolved and entrained in the liquid under pressure is
released when the pressure is relieved and is subsequently vented to the
atmosphere along with the contained VOC (B). The slurry (11) from the
crystallizers is sent to solid/liquid separators, where the TPA is recovered
as a wet cake (14). The mother liquor (12) from the solid/liquid separators
is sent to the distillation section, while the vent gas (13) is discharged
to the atmosphere (B).
Drying, Handling and Storage - The wet cake (14) from solid/liquid
separation is sent to dryers, where with the use of heat and IG, the
moisture, predominately acetic acid, is removed, leaving the product, C-TPA,
as dry free flowing crystals (19). IG is used to convey the product (19) to
storage silos. The transporting gas (21) is vented from the silos to bag
dust collectors to reduce its particulate loading, then is discharged to the
atmosphere (D). The solids (S) from the bag filter can be forwarded to
purification or can be incinerated.
Hot VOC laden IG from the drying operation is cooled to condense and
recover VOC (18). The cooled IG (16) is vented to the atmosphere (B), and
the condensate (stream 18) is sent to the azeotrope still for recovery of
acetic acid.
Distillation and Recovery - The mother liquor (12) from solid/liquid
separation flows to the residue still, where acetic acid, methyl acetate and
water are recovered overhead (26) and product residues are discarded. The
overhead (26) is sent to the azeotrope still where dry acetic acid is
obtained by using ji-propyl acetate as the water removing agent.
The aqueous phase (28) contains saturation amounts of n-propyl acetate and
methyl acetate, which are stripped from the aqueous matter in the wastewater
still. Part of the bottoms product is used as process water in absorption,
and the remainder (N) is sent to wastewater treatment. A purge stream of
the organic phase (30) goes to the methyl acetate still, where methyl
acetate and saturation amounts of water are recovered as an overhead product
(31) and are disposed of as a fuel (M). n-propyl acetate, obtained as the
bottoms product (32), is returned to the azeotrope still. Process losses of
ri-propyl acetate are made up from storage (33). A small amount of inert
gas, which is used for blanketing and instrument purging, is emitted to the
atmosphere through vent C.
C-TPA Purification
The purification portion of the Mid-Century oxidation process involves
the hydrogenation of C-TPA over a palladium containing catalyst at about
232°C (450°F). High purity TPA is recrystallized from a high pressure water
solution of the hydrogenated material.
The Olin-Mathieson manufacturing process is similar to the Mid-Century
process except the former uses 95 percent oxygen, rather than air, as the
oxidizing agent. The final purification step consists essentially of a
5/83 Chemical Process Industry 5.21-3
-------
continuous sublimation and condensation procedure. The C-TPA is combined
with small quantities of hydrogen and a solid catalyst, dispersed in steam,
and transported to a furnace. There the C-TPA is vaporized and certain of
the contained impurities are catalytically destroyed. Catalyst and non-
volatile impurities are removed in a series of filters, after which the pure
TPA is condensed and transported to storage silos.
1-3
5.21.2 Emissions and Controls
A general characterization of the atmospheric emissions from the
production of C-TPA is difficult, because of the variety of processes.
Emissions vary considerably, both qualitatively and quantitatively. The
Mid-Century oxidation process appears to be one of the lowest polluters, and
its predicted preeminence will suppress future emissions totals.
The reactor gas at vent A normally contains nitrogen (from air oxidation);
unreacted oxygen; unreacted £-xylene; acetic acid (reaction solvent); carbon
monoxide, carbon dioxide, and methyl acetate from oxidation of _p_-xylene and
acetic acid not recovered by the high pressure absorber; and water. The
quantity of VOC emitted at vent A can vary with absorber pressure and the
temperature of exiting vent gases. During crystallization of terephthalic
acid and separation of crystalized solids from the solvent (by centrifuge or
filters), noncondensible gases carrying VOC are released. These vented
gases and the C-TPA dryer vent gas are combined and released to the atmosphere
at vent B. Different methods used in this process can affect the amounts of
noncondensible gases and accompanying VOC emitted from this vent.
Gases released from the distillation section at ve.nt C are the small
amount of gases dissolved in the feed stream to distillation; the inert gas
used in inert blanketing, instrument purging pressure control; and the VOC
vapors carried by the noncondensable gases. The quantity of this discharge
is usually small.
The gas vented from the bag filters on the product storage tanks (silos)
(D) is dry, reaction generated inert gas containing the VOC not absorbed in
the high pressure absorber. The vented gas stream contains a small quantity
of TPA particulate that is not removed by the bag filters.
Performance of carbon adsorption control technology for a VOC gas
stream similar to the reactor vent gas (A) and product transfer vent gas (D)
has been demonstrated, but, carbon monoxide (CO) emissions will not be
reduced. An alternative to the carbon adsorption system is a thermal oxidizer
which provides reduction of both CO and VOC.
Emission sources and factors for the C-TPA process are presented in
Table 5.21-1.
5.21-4 EMISSION FACTORS 5/83
i
-------
TABLE 5.21-1. UNCONTROLLED EMISSION FACTORS FOR
CRUDE TEREPHTHALIC ACID MANUFACTURE41
EMISSION FACTOR RATING: C
Emission Source
Reactor vent
Crystallization,
separation, drying
Distillation and
recovery vent
Product transfer
vent
Stream
Designation
(Figure 5.21-1)
A
vent B
C
D
Emissions (g/kg)
Nonme thane VOC ' CO
15 17
1.9
1.1
1.8 2
«3
Factors are expressed as g of pollutant/kg of product produced.
.Dash = not applicable.
Reference 1. VOC gas stream consists of methyl acetate, £-xylene,
and acetic acid. No methane was found.
CReference 1. Typically, thermal oxidation results in >99% reduction
of VOC and CO. Carbon adsorption gives a 97% reduction of VOC
.only (Reference 1).
Stream contains 0.7 g of TPA particulates/kg. VOC and CO emissions
originated in reactor offgas (IG) used for transfer.
References for Section 5.21
1. S. W. Dylewski, Organic Chemical Manufacturing, Volume 7; Selected
Processes, EPA-450/3-80-028b, U. S. Environmental Protection Agency,
Research Triangle Park, NC, January 1981.
2. D. F. Durocher, et al., Screening Study To Determine Need for Standards
of Performance for New Sources of Dimethyl Terephthalate and Terephthalic
Acid Manufacturing, EPA Contract No. 68-02-1316, Radian Corporation,
Austin, TX, July 1976.
3. J. W. Pervier, et al., Survey Reports on Atmospheric Emissions from the
Petrochemical Industry, Volume II, EPA-450/3-73-005b, U. S. Environmental
Protection Agency, Research Triangle Park, NC, April 1974.
5/83 Chemical Process Industry 5.21-5
-------
5.22 LEAD ALKYL
5.22.1 Process Description-*-
Two alkyl lead compounds, tetraethyl lead (TEL) and tetramethyl lead
(TML), are used as antiknock gasoline additives. Over 75 percent of the 1973
additive production was TEL, more than 90 percent of which was made by alkyl-
ation of sodium/lead alloy.
Lead alkyl is produced in autoclaves by the reaction of sodium/lead
alloy with an excess of either ethyl (for TEL) or methyl (for TML) chloride in
the presence of acetone catalyst. The reaction mass is distilled to separate
the product, which is then purified, filtered and mixed with chloride/bromide
additives. Residue is sluiced to a sludge pit, from which the bottoms are
sent to an indirect steam dryer, and the dried sludge is fed to a reverberatory
furnace to recover lead.
Gasoline additives are also manufactured by the electrolytic process, in
which a solution of ethyl (or methyl) magnesium chloride and ethyl (or methyl)
chloride is electrolyzed, with lead metal as the anode.
5.22 Emissions and Controls *
Lead emissions from the sodium/lead alloy process consist of particulate
lead oxide from the recovery furnace (and, to a lesser extent, from the melting
furnace and alloy reactor), alkyl lead vapor from process vents, and fugitive
emissions from the sludge pit.
Emissions from the lead recovery furnace are controlled by fabric filters
or wet scrubbers. Vapor streams rich in lead alkyl can either be incinerated
and passed through a fabric filter or be scrubbed with water prior to incinera-
ting.
Emissions from electrolytic process vents are controlled by using an elev-
ated flare and a liquid incinerator, while a scrubber with toluene as the scrubb-
ing medium controls emissions from the blending and tank car loading/unloading
systems.
12/81 Chemical Process Industry 5.22-1
-------
TABLE 5.22-1. LEAD ALKYL MANUFACTURE LEAD EMISSION FACTORS3
EMISSION FACTOR RATING: B
Process
Electrolytic15
Sodium/lead alloy
Recovery furnace0
Process vents, TEL**
Process vents, TMLd
Sludge pitsd
kg/Mg
0.5
28
2
75
0.6
Lead
Ib/ton
1.0
55
4
150
1.2
aNo information on other emissions from lead alkyl
manufacturing is available. Emission factors are
expressed as weight per unit weight of product.
References 1-3.
References 1-2, 4.
^Reference 1.
TABLE 5.22-2. LEAD ALKYL MANUFACTURE CONTROL EFFICIENCIES3
Process Control Percent reduction
Sodium/lead alloy Fabric filter 99+
Low energy wet scrubber 80-85
High energy wet scrubber 95-99
aReference 1.
References for Section 5.22
1. Background Information in Support of the Development of Performance
Standards for the Lead Additive Industry, EPA Contract No. 68-02-2085,
PEDCo-Environmental Specialists, Inc., Cincinnati, OH, January 1976.
2. Control Techniques for Lead Air Emissions, EPA-450/2-77-012, U. S. En-
vironmental Protection Agency, Research Triangle Park, NC, December 1977.
3. W. E. Davis, Emissions Study of Industrial Sources of Lead Air Pollutants,
1970, EPA Contract No. 68-02-0271, W. E. Davis and Associates, Leawood,
KS, April 1973.
4. R. P. Betz, et al., Economics of Lead Removal in Selected Industries,
EPA Contract No. 68-02-0611, Batelle Columbus Laboratories, Columbus,
OH, August 1973.
5.22-2 EMISSION FACTORS 12/81
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5.23 PHARMACEUTICALS PRODUCTION
5.23.1 Process Description
Thousands of individual products are categorized as Pharmaceuticals.
These products usually are produced in modest quantities in relatively
small plants using batch processes. A typical pharmaceutical plant will
use the same equipment to make several different products at different
times. Rarely is equipment dedicated to the manufacture of a single
product.
Organic chemicals are used as raw materials and as solvents, and
some chemicals such as ethanol, acetone, isopropanol and acetic anhyd-
ride are used in both ways. Solvents are almost always recovered and
used many times.
In a typical batch process, solid reactants and solvent are charged
to a reactor where they are held (and usually heated) until the desired
product is formed. The solvent is distilled off, and the crude residue
may be treated several times with additional solvents to purify it. The
purified material is separated from the remaining solvent by centrifuge
and finally is dried to remove the last traces of solvent. As a rule,
solvent recovery is practiced for each step in the process where it is
convenient and cost effective to do so. Some operations involve very
small solvent losses, and the vapors are vented to the atmosphere through
a fume hood. Generally, all operations are carried out inside buildings,
so some vapors may be exhausted through the building ventilation system.
Certain Pharmaceuticals - especially antibiotics - are produced by
fermentation processes. In these instances, the reactor contains an
aqueous nutrient mixture with living organisms such as fungi or bacteria.
The crude antibiotic is recovered by solvent extraction and is purified
by essentially the same methods described above for chemically synthe-
sized Pharmaceuticals. Similarly, other pharmaceuticals are produced by
extraction from natural plant or animal sources. The production of
insulin from hog or beef pancreas is an example. The processes are not
greatly different from those used to isolate antibiotics from fermen-
tation broths.
5.23.2 Emissions and Controls
Emissions consist almost entirely of organic solvents that escape
from dryers, reactors, distillation systems, storage tanks and other
operations. These emissions are exclusively nonmethane organic compounds.
Emissions of other pollutants are negligible (except for particulates in
unusual circumstances) and are not treated here. It is not practical to
attempt to evaluate emissions from individual steps in the production
process or to associate emissions with individual pieces of equipment,
because of the great variety of batch operations that may be carried out
10/80 Chemical Process Industry 5.23-1
-------
at a single production plant. It is more reasonable to obtain data on
total solvent purchases by a plant and to assume that these represent
replacements for solvents lost by evaporation. Estimates can be refined
by subtracting the materials that do not enter the air because of being
incinerated or incorporated into the pharmaceutical product by chemical
reaction.
If plant-specific information is not available, industrywide data
may be used instead. Table 5.23-1 lists annual purchases of solvents by
U.S. pharmaceutical manufacturers and shows the ultimate disposition of
each solvent. Disposal methods vary so widely with the type of solvent
that it is not possible to recommend average factors for air emissions
from generalized solvents. Specific information for individual solvents
must be used. Emissions can be estimated by obtaining plant-specific
data on purchases of individual solvents and computing the quantity of
each solvent that evaporates into the air, either from information in
Table 5.23-1 or from information obtained for the specific plant under
consideration. If solvent volumes are given, rather than weights,
liquid densities in Table 5.23-1 can be used to compute weights.
Table 5.23-1 gives for each plant the percentage of each solvent
that is evaporated into the air and the percentage that is flushed into
the sewer. Ultimately, much of the volatile material from the sewer
will evaporate and will reach the air somewhere other than the pharma-
ceutical plant. Thus, for certain applications it may be appropriate to
include both the air emissions and the sewer disposal, in an emissions
inventory that covers a broad geographic area.
Since solvents are expensive and must be recovered and reused for
economic reasons, solvent emissions are controlled as part of the normal
operating procedures in a pharmaceutical industry. In addition, most
manufacturing is carried out inside buildings, where solvent losses must
be minimized to protect the health of the workers. Water or brine
cooled condensers are the most common control devices, with carbon
adsorbers in occasional use. With each of these methods, solvent can be
recovered. Where the main objective is not solvent reuse but is the
control of an odorous or toxic vapor, scrubbers or incinerators are
used. These control systems are usually designed to remove a specific
chemical vapor and will be used only when a batch of the corresponding
drug is being produced. Usually, solvents are not recovered from
scrubbers and reused, and of course, no solvent recovery is possible
from an incinerator.
It is difficult to make a quantitative estimate of the efficiency
of each control method, because it depends on the process being con-
trolled, and pharmaceutical manufacture involves hundreds of different
processes. Incinerators, carbon adsorbers and scrubbers have been
reported to remove greater than 90 percent of the organics in the
control equipment inlet stream. Condensers are limited, in that they
can only reduce the concentration in the gas stream to saturation at the
5.23-2 EMISSION FACTORS 10/80
-------
condenser temperature, but not below that level. Lowering the temper-
ature will, of course, lower the concentration at saturation, but it is
not possible to operate at a temperature below the freezing point of one
of the components of the gas stream.
TABLE 5.23-1.
SOLVENT PURCHASES AND ULTIMATE DISPOSITION BY
PHARMACEUTICAL MANUFACTURERS3
Solvent
Acetic Acid
Acetic Anhydride
Acetone
Aceton1tr11e
Amyl Acetate
Amyl Alcohol
Benzene
Blender (AMOCO)
Butanol
Carbon Tetrachloride
Chloroform
Cyclohexylamine
o-D1chloro benzene
Dlethylamine
Dlethyl Carbonate
Dimethyl Acetamide
Dimethyl Formamlde
Dlmethylsulfoxlde
l.4-D1oxane
Etna no 1
Ethyl Acetate
Ethyl Bromide
Ethylene Glycol
Ethyl Ether
Formaldehyde
Formamlde
Freons
Hexane
Isobutyraldehyde
Isopropanol
Isopropyl Acetate
Isopropyl Ether
Nethanol
Methyl Cellosolve
Hethylene Chloride
Methyl Ethyl Ketone
Methyl Formate
Methyl Isobutyl Ketone
Polyethylene Glycol 600
Pyrldlne
Skelly Solvent B (hexanes)
Tetrahydrofuran
Toluene
Trlchloroethane
Xylene
Annual
Purchase
(metric tons)
930
1.265
12,040
35
285
1.430
1.010
530
320
1.850
500
3.930
60
50
30
95
1,630
750
43
13.230
2.380
45
60
280
30
440
7,150
530
85
3,850
480
25
7.960
195
10,000
260
415
260
3
3
1,410
4
6,010
135
3,090
Ultimate Disposition (percent)
" A1r
Emissions
1
1
14
83
42
99
29
-
24
11
57
.
2
94
4
7
71
1
5
10
30
.
-
85
19
.
0.1
17
50
14
28
50
31
47
53
65
-
80
-
~
29
-
31
100
6
Sewer
82
57
22
17
58
-
37
-
8
7
5
.
98
6
71
-
3
28
-
6
47
100
100
4
77
67
.
.
50
17
11
50
45
53
5
12
74
-
-
100
2
-
14
.
19
Incineration
_
-
38
-
-
-
16
-
1
82
-
-
-
-
-
-
20
71
-
7
20
-
-
-
-
-
-
15
-
17
61
-
14
.
20
23
-
-
-
-
69
100
26
.
70
Solid Waste or
Contract Haul
_
-
7
-
-
-
8
-
36
-
38
-
-
-
-
93
6
-
95
1
3
-
-
11
-
26
•
68
-
7
-
-
6
>
22
-
12
29
.
5
Product
17
42
19
-
.
1
10
100
31
.
-
100
-
-
25
-
-
-
-
76
-
-
-
-
4
7
99.9
-
-
45
-
-
4
-
-
-
14
20
100
-
-
-
-
-
~
Liquid Density
Ib/gal 9 68°F
8.7
9.0
6.6
6.6
7.3
6.8
7.3
NA
6.8
13.3
12.5
7.2
10.9
5.9
8.1
7.9
7.9
11.1
8.6
6.6
7.5
12.1
9.3
6.0
b
9.5
c
5.5
6.6
6.6
7.3
6.0
6.6
8.7
11.1
6.7
8.2
6.7
9.5
8.2
5.6
7.4
7.2
11.3
7.2
These data were reported by 26 member companies of the Pharmaceutical
Manufacturers Association, accounting for 53 percent of pharmaceutical
sales in 1975.
Sold as aqueous solutions containing 37% to 50% formaldehyde by weight.
Some Freons are gases, and others are liquids weighing 12 - 14 Ib/gal.
10/80
Chemical Process Industry
5.23-3
-------
Reference for Section 5.23
1. Control of Volatile Organic Emissions from Manufacture of
Synthesized Pharmaceutical Products, EPA-450/2-78-029, U. S.
Environmental Protection Agency, Research Triangle Park, NC,
December 1978.
5.23-4 EMISSION FACTORS 10/80
I
-------
5.24 MALE1C ANHYDRIDE
5.24.1 General1
The dominant end use of maleic anhydride (MA) is in the production of
unsaturated polyester resins. These laminating resins, which have high
structural strength and good dielectric properties, have a variety of
applications in automobile bodies, building panels, molded boats, chemical
storage tanks, lightweight pipe, machinery housings, furniture, radar
domes, luggage and bathtubs. Other end products are fumaric acid,
agricultural chemicals, alkyd resins, lubricants, copolymers, plastics,
succinic acid, surface active agents, and more. In the United States, one
plant uses only n-butane and another uses n-butane for 20 percent of its
feedstock, but the primary raw material used in the production of MA is
benzene. The MA industry is converting old benzene plants and building new
plants to use n-butane. MA also is a byproduct of the production of
phthalic anhydride. It is a solid at room temperature but is a liquid or
gas during production. It is a strong irritant to skin, eyes and mucous
membranes of the upper respiratory system.
The model MA plant, as described in this Section, has a benzene to MA
conversion rate of 94.5 percent, has a capacity of 22,700 megagrams
(25,000 tons) of MA produced per year, and runs 8000 hours per year.
Because of a lack of data on the n-butane process, this discussion
covers only the benzene oxidation process.
2
5.24.2 Process Description
Maleic anhydride is produced by the controlled air oxidation of
benzene, illustrated by the following chemical reaction:
VO
2 C6H6 + 9 02 —^ 2 C4H203 + HO + 4 C02
MoO
Cst^il v^ t
Benzene Oxygen Maleic Water Carbon
anhydride dioxide
Vaporized benzene and air are mixed and heated before entering the
tubular reactor. Inside the reactor', the benzene/air mixture is reacted in
the presence of a catalyst which contains approximately 70 percent vanadium
pentoxide (V^O^), with usually 25 to 30 percent molybdenum trioxide (MoOg),
forming a vapor of MA, water and carbon dioxide. The vapor, which may also
contain oxygen, nitrogen, carbon monoxide, benzene, maleic acid,
formaldehyde, formic acid and other compounds from side reactions, leaves
the reactor and is cooled and partially condensed so that about 40 percent
of the MA is recovered in a crude liquid state. The effluent is then passed
through a separator which directs the liquid to storage and the remaining
vapor to the product recovery absorber. The absorber contacts the vapor
with water, producing a liquid of about 40 percent maleic acid. The
5/83 . Chemical Process Industry 5.24-1
-------
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EMISSION FACTORS
5/83
-------
40 percent mixture is converted to MA, usually by azeotropic distillation
with xylene. Some processes may use a double effect vacuum evaporator at
this point. The effluent then flows to the xylene stripping column where
the xylene is extracted. This MA is then combined in storage with that from
the separator. The molten product is aged to allow color forming impurities
to polymerize. These are then removed in a fractionation column, leaving
the finished product. Figure 5.24-1 represents a typical process.
MA product is usually stored in liquid form, although it is sometimes
flaked and pelletized into briquets and bagged.
2
5.24.3 Emissions and Controls
Nearly all emissions from MA production are from the main process vent
of the product recovery absorber, the largest vent in the process. The
predominant pollutant is unreacted benzene, ranging from 3 to 10 percent of
the total benzene feed. The refining vacuum system vent, the only other
exit for process emissions, produces 0.28 kilograms (0.62 Ib) per hour of MA
and xylene.
Fugitive emissions of benzene, xylene, MA and maleic acid also arise
from the storage (see Section 4.3) and handling (see Section 9.1.3) of
benzene, xylene and MA. Dust from the briquetting operations can contain
MA, but no data are available on the quantity of such emissions.
TABLE 5.24-1.
COMPOSITION OF UNCONTROLLED EMISSIONS FROM PRODUCT
RECOVERY ABSORBER3
Component
kg/Mg
Ib/ton
Nitrogen
Oxygen
Water
Carbon dioxide
Carbon monoxide
Benzene
Formaldehyde
Maleic acid
Formic acid
Total
73.37
16.67
4.00
3.33
2.33
0.33
0.05
0.01
0.01
21,406.0
4,863.0
1,167.0
972.0
680.0
67.0
14.4
2.8
2.8
29,175.0
42,812.0
9,726.0
2,334.0
1,944.0
1,360.0
134.0
28.8
5.6
5.6
58,350.0
Reference 2.
Potential sources of secondary emissions are spent reactor catalyst,
excess water from the dehydration column, vacuum system water, and
fractionation column residues. The small amount of residual organics in the
spent catalyst after washing has low vapor pressure and produces a small
percentage of total emissions. Xylene is the principal organic contaminant
in the excess water from the dehydration column and in the vacuum system
water. The residues from the fractionation column are relatively heavy
5/83
Chemical Process Industry
5.24-3
-------
organics, with a molecular weight greater than 116, and they produce
a small percentage of total emissions.
Benzene oxidation process emissions can be controlled at the main vent
by means of carbon adsorption, thermal incineration or catalytic incineration.
Benzene emissions can be eliminated by conversion to the n-butane process.
Catalytic incineration and conversion from the benzene process to the n-butane
process are not discussed for lack of data. The vent from the refining
vacuum system is combined with that of the main process, as a control for
refining vacuum system emissions. A carbon adsorption system or an incine-
ration system can be designed and operated at a 99.5 percent removal
efficiency for benzene and volatile organic compounds with the operating
parameters given in Appendix D of Reference 2.
TABLE 5.24-2. EMISSION FACTORS FOR MALEIC ANHYDRIDE PRODUCTION3
EMISSION FACTOR RATING: C
Nonmethane VOC Benzene
Source kg/Mg Ib/ton kg/Mg Ib/ton
Product vents
(recovery absorber and
refining vacuum system
combined vent)
Uncontrolled 87 174 67.0 134.0
With carbon adsorption0 0.34 0.68 0.34 0.68
With incineration 0.43 0.86 0.34 0.68
Storage and handling
emissions - -
Q
Fugitive emissions - - -
Secondary emissions N/A N/A N/A N/A
No data are available for catalytic incineration or for plants producing MA
from n-butane. Dash: see footnote. N/A: not available.
VOC also includes the benzene. For recovery absorber and refining vacuum,
VOC can be MA and xylene; for storage and handling, MA, xylene and dust
from briquetting operations; for secondary emissions, residual organics
from spent catalyst, excess water from dehydration column, vacuum system
water, and fractionation column residues. VOC contains no methane.
«
Before exhaust gas stream goes into carbon adsorber, it is scrubbed with
caustic to remove organic acids and water soluble organics. Benzene is the
only likely VOC remaining.
dSee Section 4.3.
eSee Section 9.1.3.
Secondary emission sources are excess water from dehydration column, vacuum
system water, and organics from fractionation column. No data are available
on the quantity of these emissions.
5.24-4 EMISSION FACTORS 5/83
-------
Fugitive emissions from pumps and valves may be controlled by an
appropriate leak detection system and maintenance program. No control
devices are presently being used for secondary emissions.
References for Section 5.24
1. B. Dmuchovsky and J. E. Franz, "Maleic Anhydride", Kirk-Othmer
Encyclopedia of Chemical Technology, Volume 12, John Wiley and
Sons, Inc., New York, NY, 1967, pp. 819-837.
2. J. F. Lawson, Emission Control Options for the Synthetic Organic
Chemicals Manufacturing Industry; Maleic Anhydride Product Report,
EPA Contract No. 68-02-2577, Hydroscience, Inc., Knoxville, TN,
March 1978.
5/83 Chemical Process Industry 5.24-5
-------
6. FOOD AND AGRICULTURAL INDUSTRY
Before food and agricultural products are used by the consumer they undergo a number of processing steps,
such as refinement, preservation, and product improvement, as well as storage and handling, packaging, and
shipping. This section deals with the processing of food and agricultural products and the intermediate steps that
present air pollution problems. Emission factors are presented for industries where data were available. The
primary pollutant emitted from these processes is particulate matter.
6.1 ALFALFA DEHYDRATING
6.1.1 General13
Dehydrated alfalfa is a meal product resulting from the rapid drying of alfalfa by artifical means at
temperatures above 212°F (100°C). Alfalfa meal is used in chicken rations, cattle feed, hog rations, sheep feed,
turkey mash, and other formula feeds. It is important for its protein content, growth and reproductive factors,
pigmenting xanthophylls, and vitamin contributions.
A schematic of a generalized alfalfa dehydrator plant is given in Figure 6.1-1. Standing alfalfa is mowed and
chopped in the field and transported by truck to a dehydrating plant, which is usually located within 10 miles of
the field. The truck dumps the chopped alfalfa (wet chops) onto a self-feeder, which carries it into a direct-fired,
rotary drum. Within the drum, the wet chops are dried from an initial moisture content of about 60 to 80 percent
(by weight) to about 8 to 16 percent. Typical combustion gas temperatures within the oil- or gas-fired drums
range from 1800 to 2000°F (980 to 1092°C) at the inlet to 250 to 300°F (120 to 150°C) at the outlet.
From the drying drum, the dry chops are pneumatically conveyed into a primary cyclone that separates them
from the high-moisture, high-temperature exhaust stream. From the primary cyclone, the chops are fed into a
hammermill, which grinds the dry chops into a meal. The meal is pneumatically conveyed from the hammermill
into a meal collector cyclone in which the meal is separated from the airstream and discharged into a holding bin.
Meal is then fed into a pellet mill where it is steam conditioned and extruded into pellets.
From the pellet mill, the pellets are either pneumatically or mechanically conveyed to a cooler, through which
air is drawn to cool the pellets and, in some cases, remove fines. Fines removal is more commonly effected in
shaker screens following or ahead of the cooler, with the fines being conveyed back into the meal collector
cyclone, meal bin, or pellet mill. Cyclone separators may be employed to separate entrained fines in the cooler
exhaust and to collect pellets when the pellets are pneumatically conveyed from the pellet mill to the cooler.
Following cooling and screening, the pellets are transferred to bulk storage. Dehydrated alfalfa is most often
stored and shipped in pellet form; however, in some instances, the pellets may be ground in a hammermill and
shipped in meal form. When the finished pellets or ground pellets are pneumatically transferred to storage or
loadout, additional cyclones may be employed for product airstream separation at these locations.
6.1.2 Emissions and Controls ''3
Particulate matter is the primary pollutant of concern from alfalfa dehydrating plants although some odors
arise from the organic volatiles driven off during drying. Although the major source is the primary cooling
cyclone, lesser sources include the downstream cyclone separators and the bagging and loading operations.
4/76 6.1-1
-------
Emission factors for the various cyclone separators utilized in alfalfa dehydrating plants are given in Table
6.1-1. Note that, although these sources are common to many plants, there will be considerable variation from
the generalized flow diagram in Figure 6.1-1 depending on the desired nature of the product, the physical layout
of the plant, and the modifications made for air pollution control. Common variations include ducting the
exhaust gas stream from one or more of the downstream cyclones back through the primary cyclone and ducting
a portion of the primary cyclone exhaust back into the furnace. Another modification involves ducting a part of
the meal collector cyclone exhaust back into the hammermill, with the remainder ducted to the primary cyclone
or discharged directly to the atmosphere. Also, additional cyclones may be employed if the pellets are
pneumatically rather than mechanically conveyed from the pellet mill to the cooler or if the finished pellets or
ground pellets are pneumatically conveyed to storage or loadout.
Table 6.1-1. PARTICULATE EMISSION FACTORS FOR ALFALFA DEHYDRATING PLANTS
EMISSION FACTOR RATING: PRIMARY CYCLONES: A
ALL OTHER SOURCES: C
Sources3
Primary cyclone
Meal collector cyclone^
Pellet collector cyclone6
Pellet cooler cyclone*
Pellet regrind cycloneS
Storage bin cyclone"
Emissions
Ib/ton of product"
10C
2.6
Not available
3
8
Neg.
kg/MT of product'3
5C
1.3
Not available
1.5
4
Neg.
^he cyclones used for product/airstream separation are the air pollution sources in alfalfa dehydrating plants.
All factors are based on References 1 and 2.
"Product consists of meal or pellets. These factors can be applied to the quantity of incoming wet chops by
dividing by a factor of four.
cThis average factor may be used even when other cyclone exhaust streams are ducted back into the primary
cyclone. Emissions from primary cyclones may range from 3 to 35 Ib/ton (1.5 to 17.5 kg/MT) of product
and are more a function of the operating procedures and process modifications made for air pollution control
than whether other cyclone exhausts are ducted back through the primary cyclone. Use 3 to 15 Ib/ton (1.5 to
7.5 kg/MT) for plants employing good operating procedures and process modifications for air pollution control.
Use higher values for older, unmodified, or less well run plants.
dThis cyclone is also called the air meal separator or hammermill cyclone. When the meal collector exhaust is
ducted back to the primary cyclone and/or the hammermill, this cyclone is no longer a source.
^his cyclone will only be present if the pellets are pneumatically transferred from the pellet mill to the pellet
cooler.
fThis cyclone is also called the pellet meal air separator or pellet mill cyclone. When the pellet cooler cyclone
exhaust is ducted back into the primary cyclone, it is no longer a source.
9This cyclone is also called the pellet regrind air separator. Regrind operations are more commonly found at
terminal storage facilities than at dehydrating plants.
"Small cyclone collectors may be used to collect the finished pellets when they are pneumatically transferred
to storage.
Air pollution control (and product recovery) is accomplished in alfalfa dehydrating plants in a variety of ways.
A simple, yet effective technique is the proper maintenance and operation of the alfalfa dehydrating equipment.
Particulate emissions can be reduced significantly if the feeder discharge rates are uniform, if the dryer furnace is
operated properly, if proper airflows are employed in the cyclone collectors, and if the hammermill is well
maintained and not overloaded. It is especially important in this regard not to overdry and possibly burn the
chops as this results in the generation of smoke and increased fines in the grinding and pelletizing operations.
6.1-2
EMISSION FACTORS
4/76
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Food and Agricultural Industry
6.1-3
-------
Equipment modification provides another means of particulate control. Existing cyclones can be replaced with
more efficient cyclones and concomitant air flow systems. In addition, the furnace and burners can be modified
or replaced to minimize flame impingement on the incoming green chops. In plants where the hammermill is a
production bottleneck, a tendency exists to overdry the chops to increase throughput, which results in increased
emissions. Adequate hammermill capacity can reduce this practice.
Secondary control devices can be employed on the cyclone collector exhaust streams. Generally, this practice
has been limited to the installation of secondary cyclones or fabric filters on the meal collector, pellet collector,
or pellet cooler cyclones. Some measure of secondary control can also be effected on these cyclones by ducting
their exhaust streams back into the primary cyclone. Primary cyclones are not controlled by fabric filters because
of the high moisture content in the resulting exhaust stream. Medium energy wet scrubbers are effective in
reducing particulate emissions from the primary cyclones, but have only been installed at a few plants.
Some plants employ cyclone effluent recycle systems for particulate control. One system skims off the
particulate-laden portion of the primary cyclone exhaust and returns it to the furnace for incineration. Another
system recycles a large portion of the meal collector cyclone exhaust back to the hammermill. Both systems can
be effective in controlling particulates but may result in operating problems, such as condensation in the recycle
lines and plugging or overheating of the hammermill.
References for Section 6.1
1. Source information supplied by Ken Smith of the American Dehydrators Association, Mission, Kan.
December 1975.
2. Gorman, P.G. et al. Emission Factor Development for the Feed and Grain Industry. Midwest Research
Institute. Kansas City, Mo. Prepared for Environmental Protection Agency, Research Triangle Park, N.C.
under Contract No. 68-02-1324. Publication No. EPA450/3-75-054. October 1974.
3. Smith, K.D. Particulate Emissions from Alfalfa Dehydrating Plants - Control Costs and Effectiveness. Final
Report. American Dehydrators Association. Mission, Kan. Prepared for Environmental Protection Agency,
Research Triangle Park, N.C. Grant No. R801446. Publication No. 650/2-74-007. January 1974.
6.1-4 EMISSION FACTORS 4/76
-------
6.2 COFFEE ROASTING
6.2. 1 Process Description l -2
Coffee, which is imported in the form of green beans, must be cleaned, blended, roasted, and packaged
being sold. In a typical coffee roasting operation, the green coffee beans are freed of dust and chaff by dropping
the beans into a current of air. The cleaned beans are then sent to a batch or continuous roaster. During the
roasting, moisture is driven off, the beans swell, and chemical changes take place that give the roasted beans their
typical color and aroma. When the beans have reached a certain color, they are quenched, cooled, and stoned.
6.2.2 Emissions1-2
Dust, chaff, coffee bean oils (as mists), smoke, and odors are the principal air contaminants emitted from
coffee processing. The major source of particulate emissions and practically the only source of aldehydes,
nitrogen oxides, and organic acids is the roasting process. In a direct-fired roaster, gases are vented without
recirculation through the flame. In the indirect-fired roaster, however, a portion of the roaster gases are
recirculated and particulate emissions are reduced. Emissions of both smoke and odors from the roasters can be
almost completely removed by a properly designed afterburner.1'2
Particulate emissions also occur from the stoner and cooler. In the stoner, contaminating materials heavier
than the roasted beans are separated from the beans by an air stream. In the cooler, quenching the hot roasted
beans with water causes emissions of large quantities of steam and some particulate matter.3 Table 6.2-1
summarizes emissions from the various operations involved in coffee processing.
Table 6.2-1. EMISSION FACTORS FOR ROASTING PROCESSES WITHOUT CONTROLS
EMISSION FACTOR RATING: B
Type of process
Roaster
Direct-fired
Indirect-fired
Stoner and cooler0
Instant coffee spray dryer
Pollutant
Particulates3
Ib/ton
7.6
4.2
1.4
1.4d
kg/MT
3.8
2.1
0.7
0.7d
N0xb
Ib/ton
0.1
0.1
—
-
kg/IVIT
0.05
0.05
_
-
Aldehydes13
Ib/ton
0.2
0.2
_
-
kg/MT
0.1
0.1
—
—
Organic acids'3
Ib/ton
0.9
0.9
—
—
kg/MT
0.45
0.45
_
-
Reference 3.
b
Reference 1.
clf cyclone is used, emissions can be reduced by 70 percent.
"Cyclone plus wet scrubber always used, representing a controlled factor.
2/72
Food and Agricultural Industry
6.2-1
-------
References for Section 6.2
1. Polglase, W.L., H.F. Dey, and R.T. Walsh. Coffee Processing. In: Air Pollution Engineering Manual.
Danielson, J.A. (ed.). U.S. DHEW, PHS, National Center for Air Pollution Control. Cincinnati, Ohio.
Publication Number 999-AP-40. 1967. p. 746-749.
2. Duprey, R.L. Compilation of Air Pollutant Emission Factors. U.S. DHEW, PHS, National Center for Air
Pollution Control. Durham, N.C. PHS Publication Number 999-AP-42. 1968. p. 19-20.
3. Partee, F. Air Pollution in the Coffee Roasting Industry. Revised Ed. U.S. DHEW, PHS, Division of Air
Pollution. Cincinnati, Ohio. Publication Number 999-AP-9. 1966.
i
6.2-2 EMISSION FACTORS 2/72
-------
6.3 COTTON GINNING
6.3.1 General1
The primary function of a cotton gin is to separate seed from the lint of raw seed cotton. Approximately one
500-pound bale of cotton can be produced from 1 ton of seed cotton. During ginning, lint dust, fine leaves, and
other trash are emitted into the air. The degree of pollution depends on the seed cotton trash content, which
depends on the method used to harvest the cotton. Handpicked cotton has a lower trash content than machine-
stripped cotton.
6.3.2 Process Description2
Figure 6.3-1 is a flow diagram of the typical cotton ginning process. Each of the five ginning steps and
associated equipment is described in the following sections.
6.3.2.1 Unloading System — Trucks and trailers transport seed cotton from the field to the gin. Pneumatic
systems convey the seed cotton from the vehicles or storage houses to a separator and feed control unit. (Some
gins utilize a stone and green boll trap for preliminary trash removal.) The screen assembly in the separator
collects the seed cotton and allows it to fall into the feed control unit. The conveying air flows from the separator
to a cyclone system where it is cleaned and discharged to the atmosphere.
6.3.2.2 Seed Cotton Cleaning System — Seed cotton is subjected to three basic conditioning processes — drying,
cleaning, and extracting — before it enters the gin stand for separation of lint from seed. To ensure adequate
conditioning, cotton gins typically use two conditioning systems in series (see Figure 6.3-1).
Cotton dryers are designed to reduce the moisture content of the seed cotton to an optimum level of 6.5 to 8.0
percent. A push-pull high-pressure fan system conveys seed cotton through the tower dryer to the cleaner, which
loosens the cotton and removes fine particles of foreign matter such as leaf trash, sand, and dirt. Large pieces of
foreign matter (e.g., sticks, stems, and burrs) are removed from the seed cotton by a different process, referred to
as "extracting.'' Several types of extractors are used at cotton gins: burr machines, stick machines, stick and burr
machines, stick and green leaf extractors, and extractor-feeders. The burr machine removes burrs and
pneumatically conveys them to the trash storage area. The seed cotton then enters a stick (or a stick and green
leaf) machine, which removes sticks, leaves, and stems. Afterwards, the seed cotton is pneumatically conveyed to
the next processing step.
6.3.2.3 Overflow System — From the final conditioning unit, the seed cotton enters a screw conveyor distributor,
which apportions the seed cotton to the extractor-feeders at a controlled rate. When the flow of seed cotton
exceeds the limit of the extractor-feeders, the excess seed cotton flows into the overflow hopper. A pneumatic
system transfers seed cotton from the overflow hopper back to the extractor-feeder as required.
6.3.2.4 Lint Cotton Handling System — Cotton enters the gin stand through a "huller front," which performs
some cleaning. A saw grasps the locks of cotton and draws them through a widely spaced set of "huller ribs,"
which strip off hulls and sticks. The cotton locks are then drawn into the roll box, where seeds are separated from
the fibers. As the seeds are removed, they slide down the face of the ginning ribs and fall to the bottom of the gin
stand for subsequent removal to storage. Cotton lint is removed from the saw by a brush or a blast of air and
conveyed pneumatically to the lint cleaning system for final cleaning and combing. The lint cotton is separated
from the conveying air stream by a separator that forms the lint into a batt. This batt is fed into the first set of lint
cleaners, where saws comb the lint cotton and remove leaf particles, grass, and motes.
12/77 Food and Agricultural Industry 6.3-1
-------
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12/77
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6.3.2.5 Battery Condenser and Baling System — Lint cotton is pneumatically transported from the lint cleaning
system to a battery condenser, which consists of drums equipped with screens that separate the lint cotton from
the conveying air. The conveying air is then discharged through an in-line filter or cyclones before being
exhausted to the atmosphere. The batt of lint cotton is then fed into the baling press, which packs it into uniform
bales of cotton.
6.3.3 Emissions and Controls
The major sources of participates from cotton ginning can be arranged into 10 emission source
categories based on specific ginning operations (Figure 6.3-2). Three primary methods of particulate
control are in use: (1) high efficiency cyclones on the high-pressure fan discharges with collection
efficiencies greater than 99 percent,2 (2) in-line filters on low-pressure fan exhaust vents with
efficiencies of approximately 80 percent, and (3) fine screen coverings on condenser drums in the low-
pressure systems with efficiencies of approximately 50 percent.*'4 The unifilter is a new concept for
collecting all wastes from cotton gins. It is designed to replace all cyclones, in-line filters, and covered
condenser drums, and has a collection efficiency of up to 99 percent.5
Table 6.3-1 presents emission factors from uncontrolled cotton ginning operations.1
Table 6.3-2 presents emission factors for a typical cotton gin equipped with available control
devices; the data base involved cotton gins with a variety of different control devices, including
cyclones, in-line filters, screen coverings, and unifilters.2.6-9 The total emission factor can be expected
to vary by roughly a factor of two, depending on the type of seed cotton, the trash content of the seed
cotton, the maintenance of control devices, and the plant operation procedures.
12/77 Food and Agricultural Industry 6.3-3
-------
UNLOADING
SYSTEM
SEED COTTON
CLEANING
SYSTEM
N0.1 DRYER AND
CLEANER
(4) EMISSIONS-
IB) EMISSIONS
TRASH FAN
I HANDLING
* SYSTEM
EXTRACTOR
NO. 2 DRYER AND
CLEANER
EXTRACTOR/FEEDER
PUNT COTTON
GIN STAND
--K
MOTE FAN
NO. 1 LINT
CLEANER
NO. 2 LINT
CLEANER
L.
BATTERY CONDENSER
AND
BALING PRESS
*• EMISSIONS (1)
DEMISSIONS (2)
DEMISSIONS (3)
-EMISSIONS (5)
DEMISSIONS (6)
*» EMISSIONS (7)
DEMISSIONS (9)
(10) EMISSIONS •
MASTER
TRASH
FAN
TRASH STORAGE
6.3-4
Figure 6.3-2. Emissions from a typical ginning operation.
EMISSION FACTORS 12/77
-------
Table 6.3-1. EMISSION FACTORS FOR COTTON GINNING
OPERATIONS WITHOUT CONTROL"*
EMISSION FACTOR RATING: C
Process
Unloading fan
Seed cotton
cleaning system
Cleaners
and dryersd
Stick and burr
machine
Miscellaneous6
Total
Estimated total
paniculate
Ib/bale
5
1
3
3
12
kg/bale
2.27
0.45
1.36
1.36
5.44
Particulates
>100|mm
settled out, %c
0
70
95
50
—
Estimated emission
factor (released
to atmosphere)
Ib/bale
5.0
0.3
0.2
1.5
7.0
kg/bale
2.27
0.14
0.09
0.68
3.2
aReference 1.
bOne bale weighs 500 pounds (226 kilograms).
Percentage of the particles that settle out in the plant.
^Corresponds to items 1 and 2 in Table 6.3-2.
Corresponds to items 4 through 9 in Table 6.3-2.
Table 6.3-2. PARTICULATE EMISSION FACTORS
FOR COTTON GINS WITH CONTROLS*
EMISSION FACTOR RATING: C
Emission sourceb
1. Unloading fan
2. No. 1 dryer and cleaner
3. No. 2 dryer and cleaner
4. Trash fan
5. Overflow fan
6. No. 1 lint cleaner condenser
7. No. 2 lint cleaner condenser
8. Mote fan
9. Battery condenser
10. Master trash fan
Total
lb/balec
0.32
0.18
0.10
0.04
0.08
0.81
0.15
0.20
0.19
0.17
2.24
g/kg
0.64
0.36
0.20
0.08
0.16
1.62
0.30
0.40
0.38
0.34
4.48
Emission factor
12/77
"References 2,6-9.
Numbers correspond to those in Figure 6.3-2.
CA bale of cotton weighs 500 pounds (227 Kilograms).
Food and Agricultural Industry
6.3-5
-------
References for Section 6.3
1. Air-borne Particulate Emissions from Cotton Ginning Operations. U.S. Department of Health,
Education and Welfare, Public Health Service, Taft Sanitary Engineering Center. Cincinnati,
Oh. 1960.
2. Source Assessment Document No. 27, Cotton Gins. Monsanto Research Corporation. Dayton, Oh.
Prepared for U.S. Environmental Protection Agency, Research Triangle Park, N.C. Publication
No. EPA-600/2-78-004a. December 1975.
3. McCaskill, O.L. and R. A. Wesley. The Latest in Pollution Control. Texas Cotton Ginners' Journal
and Yearbook. 1974.
4. Baker, Roy. F.|and,Calvin B. Parnell, Jr. Three Types of Condenser Filters for Fly Lint and Dust
Control at Cotton Gins. U.S. Department of Agriculture, Agriculture Research Service. Beltsville,
Md. ARS-42-192. September 1971.
5. McCaskill, O.L. and R.A. Wesley. Unifilter Collecting System for Cotton-gin Waste Materials.
U.S. Department of Agriculture, Agriculture Research Service. New Orleans, La. ARS-S-144.
September 1976.
6. Parnell, C.B., Jr. and Roy V. Baker. Particulate Emissions of a Cotton Gin in the Texas Stripper
Area. U.S. Department of Agriculture, Agriculture Research Service. Washington, D.C.
Production Research Report No. 149. May 1973.
7. Kirk, I.W., T.E. Wright, and K.H. Read. Particulate Emissions from Commercial Cotton Ginning
Operations. Southwestern Cotton Ginning Research Laboraory, Mesilla Park, New Mexico.
Presented at ASAE 1976 Winter Meeting, Chicago, Illinois. December 1976.
8. Cotton Gin Emission Tests, Marana Gin, Producers Cotton Oil Company, Marana, Arizona.
National Enforcement Investigations Center, Denver, Colo, and EPA Region IX. Publication No.
EPA-330/2-78-008. May 1978.
9. Emission Test Report, Westside Farmers' Cooperative Gin #5, Tranquility, California. PEDCo
Environmental, Inc., Cincinnati, Ohio. Prepared for U.S. EPA Division of Stationary Source
Enforcement, Contract No. 68-01-4147, Task No. 47, PN 3370-2-D. February 1978.
6.3-6 EMISSION FACTORS 12/77
-------
6.4 FEED AND GRAIN MILLS AND ELEVATORS
6.4.1 General1-3
Grain elevators are buildings in which grains are gathered, stored, and discharged for use, further
processing, or shipping. They are classified as "country," "terminal," and "export" elevators, according
to their purpose and location. At country elevators, grains are unloaded, weighed, and placed in
storage as they are received from farmers residing within about a 20-mile radius of the elevator. In
addition, country elevators sometimes dry or clean grain before it is shipped to terminal elevators or
processors.
Terminal elevators receive most of their grain from country elevators and ship to processors, other
terminals, and exporters. The primary functions of terminal elevators are to store large quantities of
grain without deterioration and to dry, clean, sort, and blend different grades of grain to meet buyer
specifications.
Export elevators are similar to terminal elevators except that they mainly load grain on ships for!
export.
Processing of grain in mills and feed plants ranges' from very simple mixing steps to complex!
industrial processes. Included are such diverse processes as: (1) simple mixing operations in feed mills,
(2) grain milling in flour mills, (3) solvent extracting in soybean processing plants, and (4) a complex
. series of processing steps in a corn wet-milling plant. ;
6.4.2 Emissions and Controls
Grain handling, milling, and processing include a variety of operations from the initial receipt of
the grain at either a country or terminal elevator to the delivery of a finished product. Flour, livestock
feed, soybean oil, and corn syrup are among the products produced from plants in the grain and feed
industry. Emissions from the feed and grain industry can be separated into two general areas, those
occurring at grain elevators and those occurring at grain processing operations.
6.4.2.1 Grain Elevators - Grain elevator emissions can occur from many different operations in the
elevator including unloading (receiving), loading (shipping), drying, cleaning, headhouse (legs),
tunnel belt, gallery belt, and belt trippers. Emission factors for these operations at terminal, country,
and export elevators are presented in Table 6.4-1. All of these emission factors are approximate average
values intended to reflect a variety of grain types. Actual emission factors for a specific source may be
considerably different, depending on the type of grain, i.e., corn, soybeans, wheat, and other factors
such as grain quality.
The emission factors shown in Table 6.4-1 represent the amount of dust generated per ton of grain
processed through each of the designated operations (i.e., uncontrolled emission factors). Amounts of
grain processed through each of these operations in a given elevator are dependent on such factors as
the amount of grain turned (interbin transfer), amount dryed, and amount cleaned, etc. Because the
amount of grain passing through each operation is often difficult to determine, it may be more useful
to express the emission factors in terms of the amount of grain shipped or received, assuming these
amounts are about the same over the long term. Emission factors from Table 6.4-1 have been modified
accordingly and are shown in Table 6.4-2 along with the appropriate multiplier that was used as repre-
sentative of typical ratios of throughput at each operation to the amount of grain shipped or received.
This ratio is an approximate value based on average values for turning, cleaning, and drying in each
4/77 Food and Agricultural Industry 6.4-1
-------
type of elevator. However, because operating practices in individual elevators are different, tKesS
ratios, like the basic emission factors themselves, are more valid when applied to a group of elevators!
rather than individual elevators. !
Table 6.4-1. PARTICULATE EMISSION FACTORS
FOR UNCONTROLLED GRAIN ELEVATORS
EMISSION FACTOR RATING: B
Type of source
Terminal elevators
Unloaded (receiving)
Loading (shipping)
Removal from bins (tunnel belt)
Dryingb
Cleaning0
Headhouse (legs)
Tripper (gallery belt)
Country elevators
Unloading (receiving)
Loading (shipping)
Removal from bins
Drying'3
Cleaning0
Headhouse (legs)
Export elevators
Unloading (receiving)
Loading (shipping)
Removal from bins (tunnel belt)
Drying13
Cleaning0
Headhouse (legs)
Tripper (gallery belts)
Emission factor3
Ib/ton
1.0
0.3
1.4
1.1
3.0
1.5
1.0
0.6
0.3
1.0
0.7
3.0
1.5
1.0
1.0
1.4
1.1
3.0
1.5
1.0
kg/MT
0.5
0.2
1.7
0.6
1.5
0.8
0.5
0.3
0.2
0.5
0.4
1.5
0.8
0.5
0.5
0.7
0.5
1.5
0.8
0.5
aEmission factors are in terms of pounds of dust emitted per ton of
grain processed by each operation. Most of the factors for terminal
and export elevators are based on Reference 1. Emission factors
for drying are based on References 2 and 3. The emission factors
for country elevators are based on Reference 1 and specific country
elevator test data in References 4 through 9.
bEmission factors for drying are based on 1.8 Ib/ton for rack dryers
and 0.3 Ib/ton for column dryers prorated on the basis of distribu-
tion of these two types of dryers in each elevator category, as
discussed in Reference 3.
"-Emission factor of 3.0 for cleaning is an average value which may
range from <0.5 for wheat up to 6.0 for corn.
The factors in Tables 6.4-1 or 6.4-2 should not be added together in an attempt to obtain a single
emission factor value for grain elevators because in most elevators some of the operations are
equipped with control devices and some are not. Therefore, any estimation of emissions must be
directed to each operation and its associated control device, rather than the elevator as a whole, unless
the purpose was to estimate total potential (i.e., uncontrolled) emissions. An example of the use of
emission factors in making an emission inventory is contained in Reference 3.
6.4-2
EMISSION FACTORS
4/77
-------
Table 6.4-2. PARTICULATE EMISSION FACTORS FOR GRAIN ELEVATORS BASED ON
AMOUNT OF GRAIN RECEIVED OR SHIPPED3
Type of source
Terminal elevators
Unloading (receiving)
Loading (shipping)
Removal from bins (tunnel belt)
Drying13
Cleaning0
Headhouse (legs)
Tripper (gallery belt)
Country elevators
Unloading (receiving)
Loading (shipping)
Removal from bins
Drying*5
Cleaning0
Headhouse (legs)
Export elevators
Unloading (receiving)
Loading (shipping)
Removal from bins (tunnel belt)
Drymgb
Cleaning0
Headhouse (legs)
Tripper (gallery belt)
Emission factor,
Ib/ton processed
1.0
0.3
1.4
1.1
3.0
1.5
1.0
0.6
0.3
1.0
0.7
30
1.5
1.0
1.0
1.4
1.1
3.0
1.5
1.0
X
Typical ratio of tons processed
to tons received or shipped"
1.0
1.0
2.0
0.1
0.2
3.0
1 7
1.0
1.0
2.1
0.3
0 1
3.1
1.0
1.0
1 2
001
0.2
2.2
1.1
=
Emission factor,
Ib/ton received or shipped
1.0
0.3
2.8
0.1
0.6
4.5
1.7
0.6
0.3
2.1
0.2
0.3
4.7
1 0
1 0
1.7
001
06
33
1 1
aAssume that over the long term the amount received is approximately equal to amount shipped.
bSeeNoteb in Table 6.4-1.
°See Notec in Table 6.4-1. i
H 1
Ratios shown are average values taken from a survey of many elevators across the U.S. These ratios can be considerably different
for any individual elevator or group of elevators in the same locale.
Some of the operations listed in the table, such as the tunnel belt and belt tripper, are internal or
in-house dust sources which, if uncontrolled, might show lower than expected atmospheric emissions
because of internal settling of dust. The reduction in emissions via internal settling is not known,
although it is possible that all of this dust is eventually emitted to the atmosphere due to subsequent
external operations, internal ventilation, or other means.
Many elevators utilize control devices on at least some operations. In the past, cyclones have com-
monly been applied to legs in the headhouse and tunnel belt hooding systems. More recently, fabric
filters have been utilized at many elevators on almost all types of operations. Unfortunately, some
sources in grain elevators present control problems. Control of loadout operations is difficult because
of the problem of containment of the emissions. Probably the most difficult operation to control,
because of the large flow rate and high moisture content of the exhaust gases, is the dryers. Screen-
houses or continuously vacuumed screen systems are available for reducing dryer emissions and have
been applied at several facilities. Detailed descriptions of dust control systems for grain elevator oper-
ations are contained in Reference 2.
6.4.2.2 Grain Processing Operations - Grain processing operations include many of the operations
performed in a grain elevator in addition to milling and processing of the grain. Emission factors for
different grain milling and processing operations are presented in Table 6.4-3. Brief discussions of
these different operations and the methods used for arriving at the emission factor values shown in
Table 6.4-3 are presented below.
4/77
Food and Agricultural Industry
6.4-3
-------
Table 6.4-3. PARTICULATE EMISSION FACTORS
FOR GRAIN PROCESSING OPERATIONSL2,3
EMISSION FACTOR RATING: D
Type of source
Feed mills
Receiving
Shipping
Handling
Grinding
Pellet coolers
Wheat mills
Receiving
Precleaning and handling
Cleaning house
Millhouse
Durum mills
Receiving
Precleaning and handling
Cleaning house
Millhouse
Rye milling
Receiving
Precleaning and handling
Cleaning house
Millhouse
Dry corn milling
Receiving
Drying
Precleaning and handling
Cleaning house
Degerming and milling
Oat milling
Total
Rice milling
Receiving
Handling and precleaning
Drying
Cleaning and millhouse
Soybean mills
Receiving
Handling
Cleaning
Drying
Cracking and dehulling
Hull grinding
Emission factor3-0
(uncontrolled except where indicated)
Ib/ton
1.30
0.50
3.00
0.1 QC
0.1 OC
1.00
5.00
70.00
1.00
5.00
-
-
1.00
5.00
70.00
1.00
0.50
5.00
6.00
-
2.50d
0.64
5.00
-
-
1.60
5.00
-
7.20
3.30
2.00
kg/MT
0.65
0.25
1.50
0.05C
0.05C
0.50
2.50
-
35.00
0.50
2.50
-
0.50
2.50
-
35.00
0.50
0.25
2.50
3.00
-
1.25d
0.32
2.50
-
-
0.80
2.50
-
3.60
1.65
1.00
6.4-4
EMISSION FACTORS
4/77
-------
Table 6.4-3 (continued). PARTICULATE EMISSION FACTORS
FOR GRAIN PROCESSING OPE RATIONS'! .2,3
EMISSION FACTOR RATING: D
Type of source
Bean conditioning
Flaking
Meal dryer
Meal cooler
Bulk loading
Corn wet milling
Receiving
Handling
Cleaning
Dryers
Bulk loading
Emission factor3,'3
(uncontrolled except where indicated)
Ib/ton
0.10
0.57
1.50
1.80
0.27
1.00
5.00
6.00
-
-
kg/MT
0.05
0.29
0.75
0.90
0.14
0.50
2.50
3.00
-
-
aEmission factors are expressed in terms of pounds of dust emitted per ton of grain
entering the plant (i.e., received), which is not necessarily the same as the amount
of material processed by each operation.
Blanks indicate insufficient information.
""Controlled emission factor (controlled with cyclones).
Controlled emission factor.CThis represents several sources in one plant; some
controlled with cyclones and others controlled with fabric filters.)
Emission factor data for feed mill operations are sparse. This is partly due to the fact that many
ingredients, whole grain and other dusty materials (bran, dehydrated alfalfa, etc.), are received by
both truck and rail and several unloading methods are employed. However, because some feed mill
operations (handling, shipping, and receiving) are similar to operations in a grain elevator, an emis-
sion factor for each of these different operations was estimated on that basis. The remaining
operations are based on information in Reference 2.
Three emission areas for wheat mill processing operations are grain receiving and handling, clean-
ing house, and milling operations. Data from Reference 1 are used to estimate emissions factors for
grain receiving and handling. Data for the cleaning house are insufficient to estimate an emission
factor, and information contained in Reference 2 is used to estimate the emission factor for milling
operations. The large emission factor for the milling operation is somewhat misleading because almost
all of the sources involved are equipped with control devices to prevent product losses; fabric filters
are widely used for this purpose.
Operations for durum mills and rye milling are similar to those of wheat milling. Therefore, most
of these emission factors are assumed equal to those for wheat mill operations.
The grain unloading, handling, and cleaning operations for dry corn milling are similar to those in
other grain mills, but the subsequent operations are somewhat different. Also, some drying of corn
received at the mill may be necessary prior to storage. An estimate of the emission factor for drying is
obtained from Reference 2. Insufficient information is available to estimate emission factors for
degerming and milling.
Information necessary to estimate emissions from oat milling is unavailable, and no emission
factor for another grain is considered applicable because oats are reported to be dustier than many,
other grains. The only emission factor data available are for controlled emissions.2 An overall con-
trolled emission factor of 2.5 Ib/ton is calculated from these data.
4/77
Food and Agricultural Industry
6.4-5
-------
Emission factors for rice milling are based on those for similar operations in other grain handling
facilities. Insufficient information is available to estimate emission factors for drying, cleaning, and
mill house operations.
Information contained in Reference 2 is used to estimate emission factors for soybean mills.
Emissions information on corn wet-milling is unavailable in most cases due to the wide variety of
products and the diversity of operations. Receiving, handling, and cleaning operations emission
factors are assumed to be similar to those for dry corn milling.
Many of the operations performed in grain milling and processing plants are the same as those in
grain elevators, so the control methods are similar. As in the case of grain elevators, these plants often
use cyclones or fabric filters to control emissions from the grain handling operations (e.g.', unloading,
legs, cleaners, etc.). These same devices are also often used to control emissions from other processing
operations; a good example of this is the extensive use of fabric filters in flour mills. However, there are
also certain operations within some milling operations that are not amenable to use of these devices.
Therefore, wet scrubbers have found some application, particularly where the effluent gas stream has
a high moisture content. Certain other operations have been found to be especially difficult to control,
such as rotary dryers in wet corn mills. Descriptions of the emission control systems that have been
applied to operations within the grain milling and processing industries are contained in Reference 2.
This section was prepared for EPA by Midwest Research Institute.10
References for Section 6.4
1. Gorman, P.G. Potential Dust Emission from a Grain Elevator in Kansas City, Missouri. Prepared
by Midwest Research Institute for Environmental Protection Agency, Research Triangle Park,
N.C. under Contract No. 68-02-0228, Task Order No. 24. May 1974.
2. Shannon, L.J. et al. Emission Control in the Grain and Feed Industry , Volume I - Engineering
and Cost Study. Final Report. Prepared for Environmental Protection Agency by Midwest
Research Institute. Document No. EPA-450/3-73-003a. Research Triangle Park, N.C. December
1973.
3. Shannon, L.J. et al. Emission Control in the Grain and Feed Industry, Volume II - Emission
Inventory. Final Report. Prepared by Midwest Research Institute for Environmental Protection
Agency, Research Triangle Park, N.C. Report No. EPA-450/3-73-003b. September 1974
4. Maxwell, W.H. Stationary Source Testing of a Country Grain Elevator at Overbrook, Kansas.
Prepared by Midwest Research Institute for Environmental Protection Agency under EPA
Contract No. 68-02-1403. Research Triangle Park, N.C. February 1976.
5. Maxwell, W.H. Stationary Source Testing of a Country Grain Elevator at Great Bend, Kansas.
Prepared by Midwest Research Institute for Environmental Protection Agency under EPA
Contract No. 68-02-1403. Research Triangle Park, N.C. April 1976.
6. Belgea, F.J. Cyclone Emissions and Efficiency Evaluation. Report submitted to North Dakota
State Department of Health on tests at an elevator in Edenburg, North Dakota, by Pollution
Curbs, Inc. St. Paul, Minnesota. March 10, 1972.
7. Trowbridge, A.L. Particulate Emission Testing - ERC Report No. 4-7683. Report submitted to
North Dakota State Department of Health on tests at an elevator in Egeland, North Dakota, by
Environmental Research Corporation. St. Paul, Minnesota. January 16, 1976.
6.4-6 EMISSION FACTORS 4/77
-------
8. Belgea, F. J. Grain Handling Dust Collection Systems Evaluation for Farmers Elevator Company,
Minot, North Dakota. Report submitted to North Dakota State Department of Health, by
Pollution Curbs, Inc. St. Paul, Minnesota. August 28, 1972.
9. Belgea, F.J. Cyclone Emission and Efficiency Evaluation. Report submitted to North Dakota
State Department of Health on tests at an elevator in Thompson, North Dakota, by Pollution
Curbs, Inc. St. Paul, Minnesota. March 10, 1972.
10. Schrag, M.P. et al. Source Test Evaluation for Feed and Grain Industry. Prepared by Midwest
Research Institute, Kansas City, Mo., for Environmental Protection Agency, Research Triangle
Park, N.C., under Contract No. 68-02-1403, Task Order No. 28. December 1976. Publication No.
EPA-450/3-76-043.
4/77 Food and Agricultural Industry 6.4-7
-------
6.5 FERMENTATION
6.5.1 Process Description1
For the purpose of this report only the fermentation industries associated with food will be considered. This
includes the production of beer, whiskey, and wine.
The manufacturing process for each of these is similar. The four main brewing production stages and their
respective sub-stages are: (1) brewhouse operations, which include (a) malting of the barley, (b) addition of
adjuncts (corn, grits, and rice) to barley mash, (c) conversion of starch in barley and adjuncts to maltose sugar by
enzymatic processes, (d) separation of wort from grain by straining, and (e) hopping and boiling of the wort; (2)
fermentation, which includes (a) cooling of the wort, (b) additional yeast cultures, (c) fermentation for 7 to 10
days, (d) removal of settled yeast, and (e) filtration and carbonation; (3) aging, which lasts from 1 to 2 months
under refrigeration; and (4) packaging, which includes (a) bottling-pasteurization, and (b) racking draft beer.
The major differences between beer production and whiskey production are the purification and distillation
necessary to obtain distilled liquors and the longer period of aging. The primary difference between wine making
and beer making is that grapes are used as the initial raw material in wine rather than grains.
2/72 Food and Agricultural Industry 6.5-1
-------
Table 6.5-1. EMISSION FACTORS FOR FERMENTATION PROCESSES
EMISSION f ACTOR RATING: E
Type
/
of product
Particulates
Ib/ton I kg/MT
Hydrocarbons
Ib/ton I kg/MT
Beer
Grain handling3
Drying spent grains, etc.3
Whiskey
Grain handling3
Drying spent grains, etc.3
Aging
Wine
See Subsection 6.5.1
1.5
2.5
NA
10°
NA
0.024d
See Subsection 6.5.2
3Based on section on gram processing
bNo emission factor available, but emiss.ons do occur.
cPounds per year per barrel of whiskey stored.
^Kilograms per year per liter of whiskey stored.
eNo significant emissions.
References for Section 6.5
\. Air Pollutan* Emission Factors. Final Report. Resources Research, Inc. Reston, Va. Prepared for National
Air Pollution Control Administration, Durham, N.C., under Contract Number CPA-22-69-119. April 1970.
2. Shreve, R.N. Chemical Process Industries, 3rd Ed. New York, McGraw-Hill Book Company. 1967. p.
591-608.
6.5-2
EMISSION FACTORS
2/72
i
-------
6.5.1. BEER MAKING
6.5.1.1 General1"3
Beer is a beverage of low alcoholic content (2-7 percent)
made by the fermentation of malted starchy cereal grains. Barley
is the principal grain used. The production of beer is carried out
in four major stages, brewhouse operations, fermentation, aging and
packaging. These processes are shown in Figure 6.5.1-1.
Brewhouse operations include malting of the barley, addition
of adjuncts to the barley mash, conversion of the starch in the
barley and adjuncts to maltose sugar, separation of wort from the
grain, and hopping and boiling of the wort.
In malting, barley is continuously moistened to cause it to
germinate. With germination, enzymes are formed which break down
starches and proteins to less complex water soluble compounds. The
malted barley is dried to arrest the enzyme formation and is ground
in a malt or roll mill. Adjuncts, consisting of other grains
(ground and unmalted), sugars and syrups, are added to the ground
malted barley and, with a suitable amount of water, are charged to
the mash tun (tank-like vessel). Conversion of the complex
carbohydrates (starch and sugars) and proteins to simpler water
soluble fermentable compounds by means of enzyme action takes
place in the mash tun, a process called mashing. The mash is sent
to a filter press or straining tub (lauter tun) where the wort
(unfermented beer) is separated from the spent grain solids. Hops
are added to the wort in a brew kettle, where the wort is boiled
one and a half to three hours to extract essential substances from
the hops, to concentrate the wort, and to destroy the malt enzymes.
The wort is strained to remove hops, and sludge is removed by a
filter or centrifuge.
Wort is cooled to 10°C (50°F) or lower. During cooling, it
absorbs air necessary to start fermentation. The yeast is added
and mixed with the wort in line to the fermentation starter tanks.
Fermentation, the conversion of the simple sugars in the wort to
ethanol and carbon dioxide, is completed in a closed fermenter.
The carbon dioxide gas released by the fermentation is collected
and later used for carbonating the beer. Cooling to maintain
proper fermentation temperature is required because the reaction is
exothermic.
After fermentation is complete, beer is stored to age for
several weeks at 0°C (32°F) in large closed tanks. It is recar-
bonated, pumped through a pulp filter, pasteurized at 60°C (140°F)
to make it biologically stable, and packaged in bottles and cans.
Beer put in kegs for draft sale is not pasteurized.
4/81 Food and Agricultural Industry 6.5.1-1
-------
i
(Pasteurizer
v
/ Packager /
Figure 6.5.1-1. Flow diagram of a beer making process.
2-7
6.5.1.2 Emissions and Controls
The major emissions from beer making and their sources are
particulates and volatile organics, mainly ethanol, from spent
grain drying, and particulates from grain handling. Volatile
organics (VOC) from fermentation are negligible, and they are
fugitive because the fermenters are closed to provide for collecting
carbon dioxide. Other brewery processes are minor sources of
volatile organics, ethanol and related compounds, such as boiling
6.5.1-2
EMISSION FACTORS
4/81
i
-------
wort in the brew kettle and malt drying. An estimate of these
emissions is not available.
Fugitive particulate emissions from grain handling and milling
at breweries are reduced by operating in well ventilated, low
pressure conditions. At grain handling and milling operations,
fabric filters are most often used for dust collection. Organics
and organic particulate matter from spent grain drying can be
controlled by mixing the dryer exhaust with the combustion air of a
boiler. A centrifugal fan wet scrubber is the most commonly used
control.
TABLE 6.5.1-1. EMISSION FACTORS FOR BEER BREWING3
EMISSION FACTOR RATING: D
Source
Grain handling
Brew kettle
Spent grain drying
Cooling units
Fermentation
Particulate
1.5 (3)b
2.5 (5)b
Volatile Organic Compounds
NA°
1.31 (2.63)d
NAC
e
Neg
a 6
Expressed in terms of kg/10 g (Ib/ton) of grain handled. Blanks
.indicate no emissions.
Reference 6.
O
Factors not available, but negligible amounts of ethanol emissions
.are suspected.
Reference 4. Mostly ethanol.
Negligible amounts of ethanol, ethyl acetate, isopropyl alcohol,
n-propyl alcohol, isoamyl alcohol, and isoamyl acetate emissions
are suspected.
References for Section 6.5.1
1. H.E. H^yrup, "Beer and Brewing", Kirk-Othmer Encyclopedia of
Chemical Technology, Volume 3, John Wiley and Sons, Inc.,
New York, 1964, pp. 297-338.
2. R. Norris Shreve, Chemical Process Industries, 3rd Ed.,
McGraw-Hill Book Company, New York, 1967, pp. 603-605.
3. E.G. Cavanaugh, et al., Hydrocarbon Pollutants from Stationary
Sources, EPA-600/7-77-110, U.S. Environmental Protection Agency,
Research Triangle Park, NC, September 1977.
4/81 Food and Agricultural Industry 6.5.1-3
-------
4. H.W. Bucon, et al., Volatile Organic Compound (VOC) Species
Data Manual, Second Edition, EPA-450/4-80-015, U.S. Environmental
Protection Agency, Research Triangle Park, NC, December 1978.
5. Melvin W. First, et al., "Control of Odors and Aerosols from
Spent Grain Dryers", Journal of the Air Pollution Control
Association, 24_(7): 653-659, July 1974.
6. AEROS Manual Series, Volume V; AEROS Manual of Codes,
EPA-450/2-76-005, U.S. Environmental Protection Agency, Research
Triangle Park, NC, April 1976.
7. Peter N. Formica, Controlled and Uncontrolled Emission Rates
and Applicable Limitations for Eighty Processes, EPA-340/1-78-004,
U.S. Environmental Protection Agency, Research Triangle Park,
NC, April 1978.
i
6.5.1-4 EMISSION FACTORS 4/81
-------
6.5.2 WINE MAKING
6.5.2.1 General1"4
Wine is made by the fermentation of the juice of certain fruits,
chiefly grapes. The grapes are harvested when the sugar content is
right for the desired product, generally around 20 percent sugar by
weight. The industry term for grape sugar content is Degrees Brix, with
1 °Brix equal to 1 gram of sugar per 100 grams of juice.
The harvested grapes are stemmed and crushed, and the juice is
extracted. Sulfurous acid, potassium metabisulfite or liquefied S(>2 is
used to produce 50 to 200 mg of S02, which is added to inhibit the
growth of undesirable bacteria and yeasts. For the making of a white
wine, the skins and solids are removed from the juice before fermen-
tation. For a red wine, the skins and solids, which color the wine, are
left in the juice through the fermentation stage. The pulpy mixture of
juice, skins and solids is called a "must".
White wine is generally fermented at about 52°F (11°C), and red
wine at about 80°F (27°C). Fermentation takes a week to ten days for
white wine and about two weeks for red. Fermentation is conducted in
tanks ranging in size from several thousand gallons to larger than
500,000 gallons.
The sugar of the fruit juice is converted into ethanol by the
reaction:
C6H1206 ->• 2 C2H5OH + 2 C02
(sugar) (ethanol)
This process takes place in the presence of a specially cultivated
yeast. Theoretically, the yield of ethanol should be 51.1 percent by
weight of the initial sugar. The actual yield is found to be around 47
percent. The remaining sugar is lost as alcohol or byproducts of complex
chemical mechanisms, or it remains in the wine as the result of incomplete
fermentation.
When fermentation is complete, the wine goes through a finishing
process for clarification. Common clarification procedures are filtr-
ation, fining refrigeration, pasteurization and aging. The wine is then
bottled, corked or capped, labeled and cased. The finer red and white
table wines are aged in the bottle.
1 2
6.5.2.2 Emissions and Controls '
Large amounts of CC>2 gas are liberated by the fermentation process.
The gas is passed into the atmosphere through a vent in the top of the
tank. Ethanol losses occur chiefly as a result of entrainment in the
2/80 Food and Agricultural Industry 6.5.2-1
-------
C02- Factors which affect the amount of ethanol lost during fermen-
tation are temperature of fermentation, initial sugar content, and
whether a juice or a must is being fermented (i.e., a white or red wine
being made).
Emission factors for wine making are given in Table 6.5.2-1.
These emission factors are for juice fermentation (white wine) with an
initial sugar content of 20 °Brix. Emission factors are given for two
temperatures commonly used for fermentation.
Table 6.5.2-1. ETHANOL EMISSION FACTORS FOR UNCONTROLLED WINE
FERMENTATION
EMISSION FACTOR RATING: B
a b
Ethanol Emissions '
Fermentation
temperature
52°F (11.1°C)C
80°F (26.7°C)C'd
Other conditions
lb/103 gal
fermented
1.06
4.79
e
g/kl
fermented
127.03
574.04
e
Due primarily to entrainment in C02, not evaporation. H2S, mercaptans
and other componments may be emitted in limited quantities, but no
, test or other information is available.
C2H5OH lost in production.
^References 1 and 2. For white wine with initial 20° Brix.
For red wine, add correction term for must fermentation (2.4 lb/103 gal
or 287.62 g/kl).
See Equation 1.
Emission factors for wines produced under other conditions can be
approximated with the following equation:
EF - [0.136T - 5.91] + [(B - 20.4)(T - 15.21)(0.00685)] + [C] (1)
where: EF = emission factor, pounds of ethanol lost per
thousand gallons of wine made
T = fermentation temperature, °F
B = initial sugar content, °Brix
C = correction term, 0 (zero) for white wine or
2.4 lb/103 gal for red wine
Although no testing has been done on emissions from wine fermen-
tation without grapes, it is expected that ethanol is also emitted from
these operations.
d.o.2-2 EMISSION FACTORS 2/80
-------
There is potential alcohol loss at various working and storage
stages in the production process. Also, fugitive alcohol emissions
could occur from disposal of fermentation solids. Ethanol is considered
to be a reactive precursor of photochemical oxidants (ozone). Emissions
would be highest during the middle of the fermentation season and would
taper off towards the end. Since wine facilities are concentrated in
certain areas, these areas would be more affected.
Currently, the wine industry uses no means to control the ethanol
lost during fermentation.
References for Section 6.5.2
1. Source Test Report and Evaluation on Emissions from a
Fermentation Tank at E. & J. Gallo Winery, C-8-050, California Air
Resources Board, Sacramento, CA, October 31, 1978.
2. H. W. Zimmerman, et al., "Alcohol Losses from Entrainment in
Carbon Dioxide Evolved during Fermentation", American Journal
of Enology. 15:63-68, 1964.
3. R. N. Shreve, Chemical Process Industries, 3rd Ed.,
McGraw-Hill Book Company, New York, 1967, pp. 591-608.
4. M. A. Amerine, "Wine", Kirk-Othmer Encyclopedia of Chemical
Technology, Volume 22, John Wiley and Sons, Inc., New York, 1^70,
pp. 307-334.
2/80 Food and Agricultural Industry
-------
6.6 FISH PROCESSING
6.6.1 Process Description
Fish processing includes the canning of fish and the manufacturing of by-products such as fish oil;
and fish meal. The manufacturing of fish oil and fish meal are known as reduction processes. A general-
ized fish processing operation is presented in Figure 6.6-1 .
Two types of canning operations are used. One is the "wet fish" method in which trimmed and
eviscerated fish are cooked directly in open cans. The other operation is the "pre-cooked" process in
which eviscerated fish are cooked whole and portions are hand selected and packed into cans. The pre-
cooked process is used primarily for larger fish such as tuna.
By-product manufacture of rejected whole fish and scrap requires several steps. First, the fish scrap
mixture from the canning line is charged to a live steam cooker. After the material leaves the cooker,
it is pressed to remove water and oil. The resulting press cake is broken up and dried in a rotary drier.
Two types of driers are used to dry the press cake: direct-fired and steam-tube driers. Direct-fired
driers contain a stationary firebox ahead of the rotating section. The hot products of combustion from
the firebox are mixed with air and wet meal inside the rotating section of the drier. Exhaust gases are
generally vented to a cyclone separator to recover much of the entrained fish meal product. Steam-
tube driers contain a cylindrical bank of rotating tubes through which hot, pressurized steam is
passed. Heat is indirectly transferred to the meal and the air from the hot tubes. As with direct-fired
driers, the exhaust gases are vented to a cyclone for product recovery.
6.6.2 Emissions and Controls
Although smoke and dust can be a problem, odors are the most objectionable emissions from fish
processing plants. By-product manufacture results in more of these odorous contaminants than
cannery operations because of the greater state of decomposition of the materials processed. In gener-
al, highly decayed feedstocks produce greater concentrations of odors than do fresh feedstocks.
The largest odor sources are the fish meal driers. Usually, direct-fired driers emit more odors than
steam-tube driers. Direct-fired driers will also emit smoke, particularly if the driers are operated
under high temperature conditions. Cyclones are frequently employed on drier exhaust gases for
product recovery and particulate emission control.
Odorous gases from reduction cookers consist primarily of hydrogen sulfide [H2S] and trimethyl-
amine [(CH3),NJ. Odors from reduction cookers are emitted in volumes appreciably less than from fish
meal driers. There are virtually no particulate emissions from reduction cookers.
Some odors are also produced by the canning processes. Generally, the pre-cooked process emits
less odorous gases than the wet-fish process. This is because in the pre-cooked process, the odorous
exhaust gases are trapped in the cookers, whereas in the wet-fish process, the steam and odorous
offgases are commonly vented directly to the atmosphere.
Fish cannery and fish reduction odors can be controlled with afterburners, chlorinator-scrubbers,
and condensers. Afterburners are most effective, providing virtually 100 percent odor control; how-
ever they are costly from a fuel-use standpoint. Chlbrinator-scrubbers have been found to be 95 to 99
percent effective in controlling odors from cookers and driers. Condensers are the least effective
control device. Generally, centrifugal collectors are satisfactory for controlling excessive dust emis-
sions from driers.
Emission factors for fish processing are presented in Table 6.6-1.
4/77 Food and Agricultural Industry 6.6-1
-------
E
2
en
2
8
Q.
T3
0>
_N
"(5
OJ
I
CD
CD
0)
6.6-2
EMISSION FACTORS
4/77
-------
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
Tr ime thy lamine
[(CHOlN]
kg/Mg
NAb
0.15C
1.75C
NAd
NAd
Ib/ton
NAb
0.3C
3.5C
NAd
NAd
Hydrogen sulfide
[H?S]
kg/Mg
NAb
0.005C
0.10C
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.
^Although 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 Deodorlzation, New York, Elsevier Publishing
Company, 1963.
4/77
Food and Agricultural Industry
6.6-3
-------
6.7 MEAT SMOKEHOUSES
6.7.1 Process Description1
Smoking is a diffusion process in which food products are exposed to an atmosphere of hardwood smoke.
causing various organic compounds to be absorbed by the food. Smoke is produced commerically in the United
States by three major methods: (1) by burning dampened sawdust (20 to 40 percent moisture), (2) by burning
dry sawdust (5 to 9 percent moisture) continuously, and (3) by friction. Burning dampened sawdust and
kiln-dried sawdust are the most widely used methods. Most large, modern, production meat smokehouses are the
recirculating type, in which smoke is circulated at reasonably high temperatures throughout the smokehouse.
6.7.2 Emissions and Controls1
Emissions from smokehouses are generated from the burning hardwood rather than from the cooked product
itself. Based on approximately 110 pounds of meat smoked per pound of wood burned (110 kilograms of meat
per kilogram of wood burned), emission factors have been derived for meat smoking and are presented in Table
6.7-1.
Emissions from meat smoking are dependent on several factors, including the type of wood, the type of smoke
generator, the moisture content of the wood, the air supply, and the amount of smoke recirculated. Both
low-voltage electrostatic precipitators and direct-fired afterburners may be used to reduce particulate and organic
emissions. These controlled emission factors have also been shown in Table 6.7-1.
Table 6.7-1. EMISSION FACTORS FOR MEAT SMOKINGa-b
EMISSION FACTOR RATING: D
Pollutant
Particulates
Carbon monoxide
Hydrocarbons (CH4)
Aldehydes (HCHO)
Organic acids (acetic)
Uncontrolled
Ib/ton of meat
0.3
0.6
0.07
0.08
0.2
kg/MT of meat
0.15
0.3
0.035
0.04
0.10
Controlled0
Ib/ton of meat
0.1
Negd
Neg
0.05
0.1
kg/MT of meat
0.05
Neg
Neg
0.025
0.05
aBased on 110 pounds of meat smoked per pound of wood burned (110 kg meat/kg wood burned).
^References 2, 3, and section on charcoal production.
cControls consist of either a wet collector and low-voltage precipitator in series or a direct-fired afterburner.
dWith afterburner.
2/72
Food and Agricultural Industry
6.7-1
-------
References for Section 6.7
1. Air Pollutant Emission Factors. Final Report. Resources Research, Inc. Reston, Va. Prepared for National
Air Pollution Control Administration, Durham, N.C., under Contract Number CPA-22-69-119. April 1970.
2. Carter, E. Private communication between Maryland State Department of Health and Resources Research,
Incorporated. November 21, 1969.
3. Polglase, W.L., H.F. Dey, and R.T. Walsh. Smokehouses. In: Air Pollution Engineering Manual. Danielson, J.
A. (ed.). U.S. DHEW, PHS, National Center for Air Pollution Control. Cincinnati, Ohio. Publication Number
999-AP-40. 1967. p. 750-755.
6.7-2 EMISSION FACTORS 2/72 ^
-------
6.8 AMMONIUM NITRATE
1-2
6.8.1 General
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 t
FORMATION TT"
ADDITIVE
*
SOLUTION '
CONCENTRATION
SOLIDS SOLIDS
FORMATION FINISHING
1 OFFSIZE RECYCLE
SOLIDS SOLIDS 1
SCREENING2 COATING \
SOLUTIONS r^moTj
•-
»•
| BLENDING !
BAGGING
BULK
SHIPPING
BULK
SHIPPING
ADDITIVE MAY BE ADDED BEFORE. DURING. OR AFTER CONCENTRATION
SCREENING MAY BE BEFORE OR AFTER SOLIDS FINISHING
Figure 6.8-1. Ammonium nitrate manufacturing operations.
The number of operating steps employed is determined by the desired
end product. For example, plants producing ammonium nitrate solutions
alone use only the solution formation, solution blending and bulk shipping
1/84
Food and Agricultural Industry
6.8-1
-------
operations. Plants producing a solid ammonium nitrate product can employ
all of the operations.
All ammonium nitrate plants produce an aqueous ammonium nitrate
solution through the reaction of ammonia and nitric acid in a neutralizer.
To produce a solid product, the ammonium nitrate solution is concentrated
in an evaporator or concentrator heated to drive off water. A melt is
produced containing from 95 to 99.8 percent ammonium nitrate at
approximately 422K (300°F). This melt is then used to make solid ammonium
nitrate products.
Of the various processes used to produce solid ammonium nitrate,
prilling and granulation are the most common. To produce prills, concen-
trated melt is sprayed into the top of a prill tower. Ammonium nitrate
droplets form in the tower and fall countercurrent to a rising air stream
that cools and solidifies the falling droplets into spherical prills.
Prill density can be varied by using different concentrations of ammonium
nitrate melt. Low density prills are formed from a 95 to 97.5 percent
ammonium nitrate melt, and high density prills are formed from a 99.5 to
99.8 percent melt. High density prills are less porous than low density
prills.
In the prilling process, an additive may be injected into the melt
stream. This additive serves three purposes, to raise the crystalline
transition temperature of the solid final product; to act as a desiccant,
drawing water into the final product prills to reduce caking; and to allow
prilling to be conducted at a lower temperature by reducing the freezing
point of molten ammonium nitrate. Magnesium nitrate or magnesium oxide are
examples of additives to the melt stream. Such additives account for 1 to
2.5 weight percent of the final product. While these additives are
effective replacements for conventional coating materials, their use is not
widespread in the industry.
Rotary drum granulators produce granules by spraying a concentrated
ammonium nitrate melt (99.0 to 99.8 percent) onto small seed particles in a
long rotating cylindrical drum. As the seed particles rotate in the drum,
successive layers of ammonium nitrate are added to the particles, forming
granules. Granules are removed from the granulator and screened. Offsize
granules are crushed and recycled to the granulator to supply additional
seed particles or are dissolved and returned to the solution process. Pan
granulators operate on the same principle as drum granulators and produce a
solid product with physical characteristics similar to those of drum
granules, except the solids are formed in a large, rotating circular pan.
The temperature of the ammonium nitrate product exiting the solids
formation process is approximately 339 - 397K (150 - 255°F). Rotary drum
or fluidized bed cooling prevents deterioration and agglomeration of solids
before storage and shipping. Low density prills, which have a high mois-
ture content because of a lower melt concentration, require drying before
cooling, usually in rotary drums or fluidized beds.
Since the solids are produced in a wide variety of sizes, they must be
screened for consistently sized prills or granules. Cooled prills are
screened, and offsize prills are dissolved and recycled to the solution
concentration process. Granules are screened before cooling, undersize
6-8-2 EMISSION FACTORS 1/84
-------
particles are returned directly to the granulator, and oversize granules
may be either crushed and returned to the granulator or sent to the
solution concentration process.
Following screening, products can be coated in a rotary drum to
prevent agglomeration during storage and shipment. The most common coating
materials are clays and diatomaceous earth. However, the use of additives
in the ammonium nitrate melt before prilling may preclude the use of
coatings.
Solid ammonium nitrate is stored and shipped in either bulk or bags.
Approximately 10 percent of solid ammonium nitrate produced in the United
States is bagged.
6.8.2 Emissions and Controls
Emissions from ammonium nitrate production plants are particulate
matter (ammonium nitrate and coating materials), ammonia and nitric acid.
Ammonia and nitric acid are emitted primarily from solution formation and
concentration processes, with ammonia also being emitted from prill towers
and granulators. Particulate matter (largely as ammonium nitrate) is
emitted from most of the process operations and is the primary emission
addressed here.
The emission sources in solution formation and concentration processes
are neutralizers and evaporators, primarily emitting nitric acid and
ammonia. Specific plant operating characteristics, however, make these
emissions vary depending upon use of excess ammonia or acid in the
neutralizer. Since the neutralization operation can dictate the quantity
of these emissions, a range of emission factors is presented in
Table 6.8-1. Particulate emissions from these operations tend to be
smaller in size than those from solids production and handling processes
and generally are recycled back to the process.
Emissions from solids formation processes are ammonium nitrate
particulate matter and ammonia. The sources of primary importance are
prill towers (for high density and low density prills) and granulators
(rotary drum and pan). Emissions from prill towers result from carryover
of fine particles and fume by the prill cooling air flowing through the
tower. These fine particles are from microprill formation, attrition of
prills colliding with the tower or one another, and from rapid transition
of the ammonium nitrate between crystal states. The uncontrolled parti-
culate emissions from prill towers, therefore, are affected by tower
airflow, spray melt temperature, condition and type of melt spray device,
air temperature, and crystal state changes of the solid prills. The amount
of microprill mass that can be entrained in the prill tower exhaust is
determined by the tower air velocity. Increasing spray melt temperature
causes an increase in the amount of gas phase ammonium nitrate generated.
Thus, gaseous emissions from high density prilling are greater than from
low density towers. Microprill formation resulting from partially plugged
orifices of melt spray devices can increase fine dust loading and
emissions. Certain designs (spinning buckets) and practices (vibration of
spray plates) help reduce microprill formation. High ambient air
temperatures can cause increased emissions because of entrainment as a
1/84 Food and Agricultural Industry 6.8-3
-------
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6.8-4
EMISSION FACTORS
1/84
-------
result of the higher air flow required to cool prills and because of
increased fume formation at the higher temperatures.
The granulation process in general provides a larger degree of control
in product formation than does prilling. Granulation produces a solid
ammonium nitrate product that, relative to prills, is larger and has
greater abrasion resistance and crushing strength. The air flow in
granulation processes is lower than that in prilling operations. Granu-
lators, however, cannot produce low density ammonium nitrate economically
with current technology. The design and operating parameters of granula-
tors may affect emission rates. For example, the recycle rate of seed
ammonium nitrate particles affects the bed temperature in the granulator.
An increase in bed temperature resulting from decreased recycle of seed
particles may cause an increase in dust emissions from granule
disintegration.
Cooling and drying are usually conducted in rotary drums. As with
granulators, the design and operating parameters of the rotary drums may
affect the quantity of emissions. In addition to design parameters, prill
and granule temperature control is necessary to control emissions from
disintegration of solids caused by changes in crystal state.
Emissions from screening operations are generated by the attrition of
the ammonium nitrate solids against the screens and against one another.
Almost all screening operations used in the ammonium nitrate manufacturing
industry are enclosed or have a cover over the uppermost screen. Screening
equipment is located inside a building, and emissions are ducted from the
process for recovery or reuse.
Prills and granules are typically coated in a rotary drum. The
rotating action produces a uniformly coated product. The mixing action
also causes some of the coating material to be suspended, creating particu-
late emissions. Rotary drums used to coat solid product are typically kept
at a slight negative pressure, and emissions are vented to a particulate
control device. Any dust captured is usually recycled to the coating
storage bins.
Bagging and bulk loading operations are a source of particulate
emissions. Dust is emitted from each type of bagging process during final
filling when dust laden air is displaced from the bag by the ammonium
nitrate. The potential for emissions during bagging is greater for coated
than for uncoated material. It is expected that emissions from bagging
operations are primarily the kaolin, talc or diatomaceous earth coating
matter. About 90 percent of solid ammonium nitrate produced domestically
is bulk loaded. While particulate emissions from bulk loading are not
generally controlled, visible emissions are within typical state regulatory
requirements (below 20 percent opacity).
Table 6.8-1 summarizes emission factors for various processes involved
in the manufacture of ammonium nitrate. Uncontrolled emissions of particu-
late matter, ammonia and nitric acid are given in the Table. Emissions of
ammonia and nitric acid depend upon specific operating practices, so ranges
of factors are given for some emission sources.
1/84 Food and Agricultural Industry 6.8-5
-------
Emission factors for controlled particulate emissions are also in
Table 6.8-1, reflecting wet scrubbing particulate control techniques. The
particle size distribution data presented in Table 6.8-2 indicate the
applicability of wet scrubbing to control ammonium nitrate particulate
emissions. In addition, wet scrubbing is used as a control technique
because the solution containing the recovered ammonium nitrate can be sent
to the solution concentration process for reuse in production of ammonium
nitrate, rather than to waste disposal facilities.
i
TABLE 6.8-2.
PARTICLE SIZE DISTRIBUTION DATA FOR UNCONTROLLED EMISSIONS
FROM AMMONIUM NITRATE MANUFACTURING FACILITIES3
CUMULATIVE WEIGHT %
< 2.5 um < 5 um < 10 urn
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 granulator precooler
56
0.07
0.03
0.03
0.04
0.06
0.3
73
0.3
0.09
0.06
0.04
0.5
0.3
83
2
0.4
0.2
0.15
3
1.5
References 4, 11-12, 22-23. Particle size determinations were not done in
strict accordance with EPA Method 5. A modification was used to handle the
high concentrations of soluble nitrogenous compounds (See Reference 1).
Particle size distributions were not determined for controlled particulate
emissions.
References for Section 6.8
1. Ammonium Nitrate Manufacturing Industry - Technical Document,
EPA-450/3-81-002, U. S. Environmental Protection Agency, Research
Triangle Park, NC, January 1981.
2. W. J. Search and R. B. Reznik, Source Assessment: Ammonium Nitrate
Production, EPA-600/2-77-107i, U. S. Environmental Protection Agency,
Research Triangle Park, NC, September 1977.
3. Memo from C. D. Anderson, Radian Corporation, Durham, NC, to Ammonium
Nitrate file, July 2, 1980.
4. D. P. Becvar, et al., Ammonium Nitrate Emission Test Report; Union
Oil Company of California, EMB-78-NHF-7, U. S. Environmental
Protection Agency, Research Triangle Park, NC, October 1979.
5. K. P. Brockman, Emission Tests for Particulates, Cominco American,
Beatrice, NE, 1974.
6. Written communication from S. V. Capone, GCA Corporation, Chapel Hill,
NC, to E. A. Noble, U. S. Environmental Protection Agency, Research
Triangle Park, NC, September 6, 1979.
6.8-6
EMISSION FACTORS
1/84
-------
7. Written communication from D. E. Cayard, Monsanto Agricultural
Products Company, St. Louis, MO, to E. A. Noble, U. S. Environmental
Protection Agency, Research Triangle Park, NC, December 4, 1978.
8. Written communication from D. E. Cayard, Monsanto Agricultural
Products Company, St. Louis, MO, to E. A. Noble, U. S. Environmental
Protection Agency, Research Triangle Park, NC, December 27, 1978.
9. Written communication from T. H. Davenport, Hercules Incorporated,
Donora, PA, to D. R. Goodwin, U. S. Environmental Protection Agency,
Research Triangle Park, NC, November 16, 1978.
10. R. N. Doster and D. J. Grove, Source Sampling Report; Atlas Powder
Company, Entropy Environmentalists, Inc., Research Triangle Park, NC,
August 1976.
11. M. D. Hansen, et al., Ammonium Nitrate Emission Test Report; Swift
Chemical Company, EMB-79-NHF-11, U. S. Environmental Protection
Agency, Research Triangle Park, NC, July 1980.
12. R. A. Kniskern, et al., Ammonium Nitrate Emission Test Report;
Cominco American, Inc., Beatrice, Nebraska, EMB-79-NHF-9,
U. S. Environmental Protection Agency, Research Triangle Park, NC,
April 1979.
13. Written communication from J. A. Lawrence, C. F. Industries, Long
Grove, IL, to D. R. Goodwin, U. S. Environmental Protection Agency,
Research Triangle Park, NC, December 15, 1978.
14. Written communication from F. D. McCauley, Hercules Incorporated,
Louisiana» MO, to D. R. Goodwin, U. S. Environmental Protection
Agency, Research Triangle Park, October 31, 1978.
15. W. E. Misa, Report ofSource 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
1/84
-------
6.9 ORCHARD HEATERS
6.9.1 General1"*
Orchard heaters are commonly used in various areas of the United States to prevent frost damage to fruit and
fruit trees. The five common types of orchard heaters-pipeline, lazy flame, return stack, cone, and solid fuel-are
shown in Figure 6.9-1. The pipeline heater system is operated from a central control and fuel is distributed by a
piping system from a centrally located tank. Lazy flame, return stack, and cone heaters contain integral fuel
reservoirs, but can be converted to a pipeline system. Solid fuel heaters usually consist only of solid briquettes,
which are placed on the ground and ignited.
The ambient temperature at which orchard heaters are required is determined primarily by the type of fruit
and stage of maturity, by the daytime temperatures, and by the moisture content of the soil and air.
During a heavy thermal inversion, both convective and radiant heating methods are useful in preventing frost
damage; there is little difference in the effectiveness of the various heaters. The temperature response for a given
fuel rate is about the same for each type of heater as long as the heater is clean and does not leak. When there is
little or no thermal inversion, radiant heat provided by pipeline, return stack, or cone heaters is the most effective
method for preventing damage.
Proper location of the heaters is essential to the uniformity of the radiant heat distributed among the trees.
Heaters are usually located in the center space between four trees and are staggered from one row to the next.
Extra heaters are used on the borders of the orchard.
6.9.2 Emissions1'6
Emissions from orchard heaters are dependent on the fuel usage rate and the type of heater. Pipeline heaters
have the lowest participate emission rates of all orchard heaters. Hydrocarbon emissions are negligible in the
pipeline heaters and in lazy flame, return stack, and cone heaters that have been converted to a pipeline system.
Nearly all of the hydrocarbon losses are evaporative losses from fuel contained in the heater reservoir. Because of
the low burning temperatures used, nitrogen oxide emissions are negligible.
Emission factors for the different types of orchard heaters are presented in Table 6.9-1 and Figure 6.9-2.
4/73 Food and Agricultural Industry 6.9-1
-------
PIPELINE HEATER
CONE STACK
RETURN STACK
SOLID FUEL
Figure 6.9-1. Types of orchard heaters.
6.9-2
EMISSION FACTORS
4/73
-------
s
S 8
SMteaq OOOI-JM/QI 'SNOISSIIN3
12/75
Food and Agricultural Industry
6.9-3
-------
Table 6.9-1. EMISSION FACTORS FOR ORCHARD HEATERS8
EMISSION FACTOR RATING: C
Pollutant
Part icu late
Ib/htr-hr
kg/htr-hr
Sulfur oxides0
Ib/htr-hr
kg/htr-hr
Carbon monoxide
Ib/htr-hr
kg/htr-hr
Hydrocarbons'
Ib/htr-yr
kg/htr-yr
Nitrogen oxidesh
Ib/htr-hr
kg/htr-hr
Type of heater
Pipeline
b
b
0.1 3Sd
0.06S
6.2
2.8
Neg9
Neg
Neg
Neg
Lazy
flame
b
b
0.11S
0.05S
NA
NA
16.0
7.3
Neg
Neg
Return
stack
b
b
0.1 4S
0.06S
NA
NA
16.0
7.3
Neg
Neg
Cone
b
b
0.1 4S
0.06S
NA
NA
16.0
7.3
Neg
Neg
Solid
fuel
0.05
0.023
NAe
NA
NA
NA
Neg
Neg
Neg
Neg
aReferences 1,3,4, and 6.
bParticulate emissions for pipeline, lazy flame, return stack, and cone heaters are
shown in Figure 6.9-2.
c Based on emission factors for fuel oil combustion in Section 1.3.
dS - sulfur content.
eNot available.
* Reference 1. Evaporative losses only. Hydrocarbon emissions from combustion
are considered negligible. Evaporative hydrocarbon losses for units that are
part of a pipeline system are negligible.
Negligible.
"Little nitrogen oxide is formed because of the relatively low combustion
temperatures.
References for Section 6.9
1. Air Pollution in Ventura County. County of Ventura Health Department, Santa Paula, CA, June 1966.
2. Frost Protection in Citrus. Agricultural Extension Service, University of California, Ventura, CA, November
1967.
3. Personal communication with Mr. Wesley Snowden. Valentine, Fisher, and Tomlinson, Consulting Engineers,
Seattle, WA, May 1971.
4. Communication with the Smith Energy Company, Los Angeles, CA, January 1968.
5. Communication with Agricultural Extension Service, University of California, Ventura, CA. October 1969.
6. Personal communication with Mr. Ted Wakai. Air Pollution Control District, County of Ventura, Ojai, CA,
May 1972.
6.9-4
EMISSION FACTORS
7/79
-------
6.10 PHOSPHATE FERTILIZERS
6.10.1 NORMAL SUPERPHOSPHATES1
6.10.1.1 General
The term "normal superphosphate" is used to designate a fertilizer
material containing 15 - 21 percent P20s. It is prepared by reacting
ground phosphate rock with 65 - 75 percent sulfuric acid. Rock and acid
are mixed in a reaction vessel, held in an enclosed area (den) while the
reaction mixture solidifies, and transferred to a storage pile for
curing. Following curing, the product is most often ground and bagged
for sale as run-of-the-pile product. It can also be granulated, for
sale as granulated superphosphate or granular mixed fertilizer. However,
this accounts for less than 5 percent of total production. To produce a
granular normal superphosphate material, run-of-the-pile material is
first fed to a pulverizer to be crushed, ground, and screened. Screened
material is sent to a rotary drum granulator and then through a rotary
dryer. The material goes through a rotary cooler and on to storage bins
for sale as bagged or bulk product. Superphosphate fertilizers are
produced at 79 plants in the United States. A generalized flow diagram
of the process for the production of normal superphosphate is shown in
Figure 6.10.1-1.
6.10.1.2 Emissions and Controls
Sources of emissions at a normal superphosphate plant include rock
unloading and feeding, mixer (reactor), den, curing building, and fertil-
izer handling operations. Rock unloading, handling and feeding generate
particulate emissions of phosphate rock dust. The mixer, den and
curing building emit gaseous fluorides (HF and SiF^) and particulates
composed of fluoride and phosphate material. Fertilizer handling oper-
ations release fertilizer dust.
At a typical normal superphosphate plant, the rock unloading,
handling and feeding operations are controlled by a baghouse. The mixer
and den are controlled by a wet scrubber. The curing building and
fertilizer handling operations normally are not controlled.
Emission factors for the production of normal superphosphate are
presented in Table 6.10.1-1. These emission factors are averages based
on recent source test data from controlled phosphate fertilizer plants
in Florida.
10/80 Food and Agricultural Industry 6.10.1-1
-------
PARTICULATE
EMISSIONS
BAGHOUSE
ROCK FEEDER
SYSTEM
ROCK BIN PARI|CULATE
EMISSIONS
*
I
BAG HOUSE
DUST
WEIGHER
RECYCLED TO
ROCK BIN
SULFUR! C-
ACID
:io
TROL
J~
1 _ WET
JL
_/CONE
~j MIXER
PUG MILL
SCRUBBER
CUTTER
TO GYPSUM
POND
PARTICULAR
-AND FLUORIDE
EMISSIONS
RECYCUD
WATER
DEN
PARTICULAR
AND RUORIDC
-*• EMISSIONS
I UNCONTROLLED I
•PRODUCT
Figure 6.10.1-1. Normal superphosphate process flow diagram.
6.10.1-2
E11ISSION FACTORS
10/80
-------
TABLE 6.10.1-1. EMISSION FACTORS FOR THE PRODUCTION OF
NORMAL SUPERPHOSPHATE3
EMISSION FACTOR RATING: A
Emission factor
Emission point Pollutant Ib/ton P 0 kg/MT
Rock unloading
Rock feeding
Mixer and den
Curing building
Particulate
Particulate
Particulate
Fluoride
Particulate
Fluoride
0.56
0.11
0.52
0.20
7.20
3.80
0.28
0.06
0.26
0.10
3.60
1.90
^Reference 1, pp. 74-77, 169.
Factors are for emissions from baghouse with an estimated collection
cefficiency of 99%.
Factors are for emissions from wet scrubbers with a reported 97%
.control efficiency.
Uncontrolled.
Particulate emissions from ground rock unloading, storage and
transfer systems are controlled by baghouse collectors. These cloth
filters have reported efficiencies of over 99 percent. Collected solids
are recycled to the process.
Silicon tetrafluoride and hydrogen fluoride emissions, and partic-
ulate from the mixer, den and curing building are controlled by scrubbing
the offgases with recycled water. Gaseous silicon tetrafluoride in the
presence of moisture reacts to form gelatinous silica which has the
tendency to plug scrubber packings. The use of conventional packed
countercurrent scrubbers and other contacting devices with small gas
passages for emissions control is therefore limited. Scrubber types
that can be used are cyclonic^venturi, impingement, jet ejector and
spray crossflow packed. Spray towers also find use as precontactors for
fluorine removal at relatively high concentration levels (greater than
3,000 ppm, or 4.67 g/m3).
Air pollution control techniques vary with particular plant designs.
The effectiveness of abatement systems in removal of fluoride and
particulate also varies from plant to plant, depending on a number of
factors. The effectiveness of fluorine abatement is determined by (1)
inlet fluorine concentration, (2) outlet or saturated gas temperature,
(3) composition and temprature of the scrubbing liquid, (4) scrubber
type and transfer units, and (5) effectiveness of entrainment separation.
Control efficiency is enhanced by increasing the number of scrubbing
10/80 Food and Agricultural Industry 6.10.1-3
-------
stages in series and by using a fresh water scrub in the final stage.
Reported efficiencies for fluoride control range from less than 90
percent to over 99 percent, depending on inlet fluoride concentrations
and the system employed. An efficiency of 98 percent for particulate
control is achievable.
Reference for Section 6.10.1
1. J. M. Nyers, et al., Source Assessment; Phosphate Fertilizer
Industry, EPA-600/2-79-019c, U. S. Environmental Protection Agency,
Research Triangle Park, NC, May 1979.
i
6.10.1-4 EMISSION FACTORS 10/80
-------
6.10.2 TRIPLE SUPERPHOSPHATES
6.10.2.1 General
Triple superphosphate is a fertilizer material of PZ^S content over
40 percent, made by reacting phosphate rock and phosphoric acid. The
two principal types of triple superphosphate are run-of-the-pile (40
percent of total production) and granular (60 percent of total produc-
tion) . Run-of-the-pile material is essentially a pulverized mass of
variable particle size produced in a manner similar to normal super-
phosphate. Thus, phosphoric acid (50 percent PZ^S) is reacted in a cone
mixer with ground phosphate rock. The resultant slurry begins to
solidify on a slow moving conveyer (den) en route to the curing area.
At the point of discharge from the den, the material passes through a
rotary mechanical cutter that breaks up the solid mass. Coarse run-of-
the-pile product is sent to a storage pile and cured for a period of 3
to 5 weeks. The final product is then mined from the "pile" in the
curing shed, and then crushed, screened, and shipped in bulk. Granular
triple superphosphate yields larger, more uniform particles with improved
storage and handling properties. Most of this material is made with the
Dorr-Oliver slurry granulation process, illustrated in Figure 6.10.2-1.
In this process, ground phosphate rock is mixed with phosphoric acid in
a reactor or mixing tank. The phosphoric acid used in this process is
appreciably lower in concentration (40 percent PaOs) than that used to
manufacture run-of-the-pile product, because the lower strength acid
maintains the slurry in a fluid state during a mixing period of 1 to 2
hours. A thin slurry is continuously removed and distributed onto
dried, recycled fines, where it coats the granule surfaces and builds up
its size.
Pugmills and rotating drum granulators are used in the granulation
process. A pugmill is composed of a u-shaped trough carrying twin
contrarotating shafts, upon which are mounted strong blades or paddles.
Their action agitates, shears and kneads the solid/liquid mix and trans-
ports the material along the trough. The basic rotary drum granulator
consists of an open ended slightly inclined rotary cylinder, with retain-
ing rings at each end and a scraper or cutter mounted inside the drum
shell. A rolling bed of dry material is maintained in the unit while
the slurry is introduced through distributor pipes set lengthwise in the
drum under the bed. Slurry-wetted granules then discharge onto a
rotary dryer, where excess water is evaporated and the chemical reaction
is accelerated to completion by the dryer heat. Dried granules are then
sized on vibrating screens. Oversize particles are crushed and recircu-
lated to the screen, and undersize particles are recycled to the granu-
lator. Product size granules are cooled in a countercurrent rotary
drum, then sent to a storage pile for curing. After a curing period of
3 to 5 days, granules are removed from storage, screened, bagged and
shipped.
10/80 Food and Agricultural Industry 6.10.2-1
-------
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6.10.2.2 Emissions and Controls
Emissions of fluorine compounds and dust particles occur during the
production of granular triple superphosphate. Silicon tetrafluoride and
hydrogen fluoride are released by the acidulation reaction and they
evolve from the reactors, den, granulator, dryer and cooler. Evolution
of fluorides continues at a lower rate in the curing building, as the
reaction preceeds. Sources of particulate emissions include the reactor,
granulator, dryer, cooler, screens, mills, and transfer conveyors.
Additional emissions of particulate result from the unloading, storage
and transfer of ground phosphate rock.
At a typical plant, emissions from the reactor, den and granulator
are controlled by scrubbing the effluent gas with recycled gypsum pond
water. Emissions from the dryer, cooler, screens, mills, product trans-
fer systems, and storage building are sent to a cyclone separator for
removal of a portion of the dust before going to wet scrubbers. Bag-
houses are used to control the fine rock particles generated by the
preliminary ground rock handling activities.
Emission factors for the production of run-of-the-pile and granular
triple superphosphate are given in Table 6.10.2-1. These emission
factors are averages based on recent source test data from controlled
phosphate fertilizer plants in Florida.
Particulate emissions from ground rock unloading, storage and
transfer systems are controlled by baghouse collectors. These cloth
filters have reported efficiencies of over 99 percent. Collected solids
are recycled to the process. Emissions of silicon tetrafluoride, hydrogen
fluoride, and particulate from the production area and curing building
are controlled by scrubbing the offgases with recycled water. Exhausts
from the dryer, cooler, screens, mills, and curing building are sent
first to a cyclone separator and then to a wet scrubber.
Gaseous silicon tetrafluoride in the presence of moisture reacts to
form gelatinous silica, which has the tendency to plug scrubber packings.
The use of conventional packed countercurrent scrubbers and other con-
tacting devices with small gas passages for emissions control is there-
fore limited. Scrubber types that can be used are (1) spray tower, (2)
cyclonic, (3) venturi, (4) impingement, (5) jet ejector, and (6) spray-
crossflow packed.
Spray towers are used as precontactors for fluorine removal at
relatively high concentration levels (greater than 3,000 ppm, or 4.67
g/m3).
Air pollution control techniques vary with particular plant designs.
The effectiveness of abatement systems for the removal of fluoride and
particulate also varies from plant to plant, depending on a number of
factors. The effectiveness of fluorine abatement is determined by (1)
10/80 Food and Agricultural Industry 6.10.2-3
-------
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EMISSION FACTORS
10/80
-------
inlet fluorine concentration, (2) outlet or saturated gas temperature,
(3) composition and temperature of the scrubbing liquid, (4) scrubber
type and transfer units, and (5) effectiveness of entrainment separation.
Control efficiency is enhanced by increasing the number of scrubbing
stages in series and by using a fresh water scrub in the final stage.
Reported efficiencies for fluoride control range from less than 90
percent to over 99 percent, depending on inlet fluoride concentrations
and the system employed. An efficiency of 98 percent for particulate
control is achievable.
Reference for Section 6.10.2
1. J. M. Nyers, et al., Source Assessment; Phosphate Fertilizer
Industry, EPA-600/2-79-019c, U. S. Environmental Protection Agency,
Research Triangle Park, NC, May 1979.
10/80 Food and Agricultural Industry 6.10.2-5
-------
6.10.3 AMMONIUM PHOSPHATES
6.10.3.1 General
Ammonium phosphates are produced by reacting phosphoric acid with
anhydrous ammonia. Both solid and liquid ammonium phosphate fertilizers
are produced in the United States. Ammoniated superphosphates are also
produced, by adding normal superphosphate or triple superphosphate to
the mixture. This discussion covers only the granulation of phosphoric
acid with anhydrous ammonia to produce granular fertilizers. The produc-
tion of liquid ammonium phosphates and ammoniated superphosphates in
fertilizer mixing plants is considered a separate process. Two basic
mixer designs are used by ammoniation-granulation plants, the pugmill
ammoniator and the rotary drum ammoniator. Approximately 95 percent of
ammoniation-granulation plants in the United States use a rotary drum
mixer developed and patented by the Tennessee Valley Authority (TVA).
In the TVA process, phosphoric acid is mixed in an acid surge tank with
93 percent sulfuric acid (used for product analysis control) and with •
recycle and acid from wet scrubbers (see Figure 6.10.3-1). Mixed acids
are then partially neutralized with liquid or gaseous anhydrous ammonia
in a brick lined acid reactor. All phosphoric acid and approximately 70
percent of ammonia are introduced into this vessel.
A slurry of NHitH2POit and 22 percent water is produced and sent
through steam-traced lines to the ammoniator-granulator. Ammonia rich
offgases from the reactor are wet scrubbed before exhausting to the
atmosphere. Primary scrubbers use raw material-mixed acids as scrubbing
liquor, and secondary scrubbers use gypsum pond water.
The basic rotary drum ammoniator-granulator consists of a slightly
inclined open end rotary cylinder with retaining rings at each end, and
a scraper or cutter mounted inside the drum shell. A rolling bed of
recycled solids is maintained in the units. Slurry from the reactor is
distributed on the bed, and the remaining ammonia (approximately 30
percent) is sparged underneath. Granulation, by agglomeration and by
coating particules with slurry, takes place in the rotating drum and is
completed in the dryer. Ammonia rich offgases pass through a wet
scrubber before exhausting to the atmosphere.
Moist ammonium phosphate granules are transferred to a rotary
cocurrent dryer and then to a cooler. Before exhausting to the atmo-
sphere, these offgases pass through cyclones and wet scrubbers. Cooled
granules pass to a double deck screen, in which oversize and undersize
particles are separated from product particles.
6.10.3.2 Emissions and Controls
Air emissions from production of ammonium phosphate fertilizers by
ammoniation granulation of phosphoric acid and ammonia result from five
process operations. The reactor and ammoniator granulator produce
10/80 Food and Agricultural Industry 6.10.3-1
-------
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E11ISSION FACTORS
10/80
-------
emissions of gaseous ammonia, gaseous fluorides (HF and SiF^) and partic-
ulate ammonium phosphates. These two exhaust streams generally are
combined and passed through primary and secondary scrubbers.
Exhaust gases from the dryer and cooler also contain ammonia,
fluorides and particulates, and these streams commonly are combined and
passed through cyclones and primary and secondary scrubbers. Partic-
ulate emissions and low levels of ammonia and fluorides from product
sizing and material transfer operations are controlled the same way.
Emission factors for ammonium phosphate production are summarized
in Table 6.10.3-1. These emission factors are averages based on recent
source test data from controlled phosphate fertilizer plants in Florida.
Exhaust streams from the reactor and ammoniator-granulator pass
through a primary scrubber, in which phosphoric acid recovers ammonia
and particulate. Exhaust gases from the dryer, cooler and screen go
first to cyclones for particulate recovery, and from there to primary
scrubbers. Materials collected in the cyclone and primary scrubbers are
returned to the process. The exhaust is sent to secondary scrubbers,
where recycled gypsum pond water is used as a scrubbing liquid to control
fluoride emissions. The scrubber effluent is returned to the gypsum
pond.
Primary scrubbing equipment commonly includes venturi and cyclonic
spray towers, while cyclonic spray towers, impingement scrubbers, and
spray-crossflow packed bed scrubbers are used as secondary controls.
Primary scrubbers generally use phosphoric acid of 20 to 30 percent as
scrubbing liquor, principally to recover ammonia. Secondary scrubbers
generally use gypsum and pond water, for fluoride control.
Throughout the industry, however, there are many combinations and
variations. Some plants use reactor-feed concentration phosphoric acid
(40 percent P2°s) i*1 both primary and secondary scrubbers, and some use
phosphoric acid near the dilute end of the 20 to 30 percent P£OS range
in only a single scrubber. Existing plants are equipped with ammonia
recovery scrubbers on the reactor, ammoniator-granulator and dryer, and
particulate controls on the dryer and cooler. Additional scrubbers for
fluoride removal are common but not typical. Only 15 to 20 percent of
installations contacted in an EPA survey were equipped with spray-
crossflow packed bed scrubbers or their equivalent for fluoride removal.
Emission control efficiencies for ammonium phosphate plant control
equipment have been reported as 94 - 99 percent for ammonium, 75 - 99.8
percent for particulates, and 74 - 94 percent for fluorides.
10/80 Food and Agricultural Industry 6.10.3-3
-------
TABLE 6.10.3-1. AVERAGE CONTROLLED EMISSION FACTORS FOR THE
PRODUCTION OF AMMONIUM PHOSPHATES3
EMISSION FACTOR RATING: A
Emission Point
Reactor/ammoniator-granulator
Fluoride (as F)
Particulates
Ammonia
Dryer/cooler
Fluoride (as F)
Particulates
Ammonia
Product sizing and material transfer
Fluoride (as F)C
Particulates
Ammonia
Total plant emissions
Fluoride (as F)
Particulates
Ammonia
Controlled
Ib/ton P20r
0.05
1.52
b
0.03
1.50
b
0.01
0.06
b
0.08
0.30
0.14
Emission Factors
. kg/MT P205
0.02
0.76
b
0.02
0.75
b
0.01
0.03
b
0.04
0.15
0.07
^Reference 1, pp. 80-83, 173.
No information available. Although ammonia is emitted from these unit
operations, it is reported as a total plant emission.
^Represents only one sample.
EPA has promulgated a fluoride emission guideline of 0.03 g/kg P20c
input.
eBased on limited data from only 2 plants.
Reference for Section 6.10.3
1. J. M. Nyers, et al., Source Assessment; Phosphate Fertilizer
Industry, EPA-600/2-79-019c, U.S. Environmental Protection Agency,
Research Triangle Park, NC, May 1979.
6.10.3-4 EMISSION FACTORS 10/80
f
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6.11 STARCH MANUFACTURING
6.11.1 Process Description1
The basic raw material in the manufacture of starch is dent corn, which contains starch. The starch in the
corn is separated from the other components by "wet milling."
The shelled grain is prepared for milling in cleaners that remove both the light chaff and any heavier foreign
material. The cleaned corn is then softened by soaking (steeping) it in warm water acidified with sulfur dioxide.
The softened corn goes through attrition mills that tear the kernels apart, freeing the germ and loosening the hull.
The remaining mixture of starch, gluten, and hulls is finely ground, and the coarser fiber particles are removed by
screening. The mixture of starch and gluten is then separated by centrifuges, after which the starch is filtered and
washed. At this point it is dried and packaged for market.
6.11.2 Emissions
The manufacture of starch from corn can result in significant dust emissions. The various cleaning, grinding,
and screening operations are the major sources of dust emissions. Table 6.11-1 presents emission factors for starch
manufacturing.
Table 6.11-1. EMISSION FACTORS
FOR STARCH MANUFACTURING3
EMISSION FACTOR RATING: D
Type of operation
Uncontrolled
Controlledb
Particulates
Ib/ton
8
0.02
kg/MT
4
0.01
aReference 2.
Based on centrifugal gas scrubber.
References for Section 6.11
1. Starch Manufacturing. In: Kirk-Othmer Encyclopedia of Chemical Technology, Vol. IX. New York, John
Wiley and Sons, Inc. 1964.
2. Storch, H. L. Product Losses Cut with a Centrifugal Gas Scrubber. Chem. Eng. Progr. (52:51-54. April 1966.
2/72 Food and Agricultural Industry 6.11-1
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6.12 SUGAR CANE PROCESSING
6.12.1 General13
Sugar cane is burned in the field prior to harvesting to remove unwanted foliage as well as to control rodents
and insects. Harvesting is done by hand or, where possible, by mechanical means.
After harvesting, the cane goes through a series of processing steps for conversion to the final sugar product. It
is first washed to remove dirt and trash; then crushed and shredded to reduce the size of the stalks. The juice is
next extracted by one of two methods, milling or diffusion. In milling, the cane is pressed between heavy rollers
to squeeze out the juice; in diffusion, the sugar is leached out by water and thin juices. The raw sugar then goes
through a series of operations including clarification, evaporation, and crystallization in order to produce the final
product. The fibrous residue remaining after sugar extraction is called bagasse.
All mills fire some or all of their bagasse in boilers to provide power necessary in their milling operation. Some,
having more bagasse than can be utilized internally, sell the remainder for use in the manufacture of various
chemicals such as furfural.
6.12.2 Emissions 2>3
The largest sources of emissions from sugar cane processing are the openfield burning in the harvesting of the
crop and the burning of bagasse as fuel. In the various processes of crushing, evaporation, and crystallization,
relatively small quantities of particulates are emitted. Emission factors for sugar cane field burning are shown in
Table 2.4-2. Emission factors for bagasse firing in boilers are included in Chapter 1.
References for Section 6.12
1. Sugar Cane. In: Kirk-Othmer Encyclopedia of Chemical Technology, Vol. IX. New York, John Wiley and
Sons, Inc. 1964.
2. Darley, E. F. Air Pollution Emissions from Burning Sugar Cane and Pineapple from Hawaii. In: Air Pollution
from Forest and Agricultural Burning. Statewide Air Pollution Research Center, University of California,
Riverside, Calif. Prepared for Environmental Protection Agency, Research Triangle Park, N.C. under Grant
No. R800711. August 1974.
3. Background Information for Establishment of National Standards of Performance for New Sources. Raw Cane
Sugar Industry. Environmental Engineering, Inc. Gainesville, Fla. Prepared for Environmental Protection
Agency, Research Triangle Park, N.C. under Contract No. CPA 70-142, Task Order 9c. July 15, 1971.
4/76 Food and Agricultural Industry 6.12-1
-------
6.13 BREAD BAKING
6.13.1 General1'2
Bakery products generally can be divided into two groups—products leavened by yeast and products
chemically leavened by baking powder. Other than yeast bread, which comprises the largest fraction of
all yeast leavened baking production, leavened products include sweet rolls, crackers, pretzels, etc.
Examples of chemically leavened baking products are cakes, cookies, cake doughnuts, corn bread and
baking powder biscuits.
Brea,d is generally produced by either the straight-dough process or the sponge-dough process. In the
straight-dough process, the ingredients are mixed, allowed to ferment, and then baked. In the sponge-
dough process, only part of the ingredients are initially mixed and allowed to ferment, with the remainder
added to the mix and fermented just prior to baking. The sponge-dough process is more often used by
commercial bakeries.
In a commercial bakery, bread dough is fermented from two to four hours prior to baking at about
450T (232°C). The temperature inside the bread does not exceed 212°F (100°C). The ovens used are pre-
dominately direct fired by natural gas. In such ovens, any vapors driven off the bread and any combustion
product gases are removed through the same exhaust vent.
6.13.2 Emissions1'2
In the leavening process, yeast metabolizes the sugars and starches in the bread dough. During this
fermentation stage, various chemical reactions take place, with the end products being primarily carbon
dioxide (CO^ and ethanol (C2HSOH). The carbon dioxide is necessary to leaven the dough, thereby in-
creasing its volume. The byproduct ethanol, however, evaporates and leaves the dough. The rate of ethanol
production depends on dough temperature, quantity of sweetner and type of yeast.
Laboratory experiments1 and theoretical estimates2 suggest that ethanol emissions from the sponge-
dough process may range from 5 to 8 pounds per 1000 pounds of bread produced, whereas ethanol
emissions from the straight-dough process- are only 0.5 pounds per 1000 pounds produced. These factors
include ethanol evaporation from all phases of bread production, although most of the emissions occur
during baking. Negligible quantities of ethanol remain in the bread following baking. Several other non-
methane volatile organic compounds are also emitted from bread production, but in much smaller amounts.
The reader should consult References 1 and 2 for details on how these emission factors are derived.
No controls or process modifications are employed to reduce ethanol emissions from bakeries. Some
fraction of the ethanol emitted during baking could potentially be destroyed in the direct fired gas ovens,
but since the ethanol does not come into contact with the flame zone, this fraction is thought to be in-
significant.
References for Section 6.13
1. R..M. Keller, \onmethane Organic Emissions from Bread Producing Operations, EPA-450/4-79-001. U.S.
Environmental Protection Agency. Research Triangle Park. NC. December 1978.
2. D.C. Henderson. "Commercial Bakeries as a Major Source of Reactive Volatile Organic Gases". Emission
Im-entorylF actor Workshop: Volume I, EPA-450/3-78-042a, U.S. Environmental Protection Agency. Research
Triangle Park. NC. August 1978.
7/79 Food and Agricultural Industry 6.13-1
-------
-------
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
(NH2C02NHit). 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.
AMMONIA-
CARBON.
DIOXIDE
ADDITIVE*
j-
\
SOLUTION
CONCENTRATION
SOLIDS
FORMATION
SOLIDS
COOLING
COATING* U
|
1
OFFSIZE RECYCLE
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.1*
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.
i
TABLE 6.14-2. UNCONTROLLED PARTICLE SIZE DATA FOR UREA PRODUCTION'
OPERATION
PARTICLE SIZE
(Cummulative Weight %)
< 10 urn < 5 um < 2.5 \im
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
13
b
0.15
NA
NA
NA
79
50
43
14
b
0.04
NA
NA
not available. No data were available on particle sizes of controlled
emissions. Particle size information was collected uncontrolled in the
ducts and may not reflect particle size in the ambient air.
All particulate matter ^.5.7 um was collected in the cyclone precollector
sampling equipment.
6.14-4
EMISSION FACTORS
1/84
-------
TABLE 6.14-1. EMISSION FACTORS FOR UREA PRODUCTION3
EMISSION FACTOR RATING: Ab
Participates
Ammonia
Operation
Solution formation ,
and concentration
Uncontrolled
kg/Mg
0.0105*
Ib/ton
0.021e
Controlled Uncontrolled Exiting Control Device
kg/Mg Ib/ton kg/Mg
9.12f
Ib/ton kg/Mg
18.24f
Ib/ton
Solids formation
Nonfluidized
bed prilling
agricultural grade8
feed grade^
Fluidlzed bed prilling
agricultural grade-1
feed grade^
Drum granulation
Rotary drum cooler
Bagging
1
1
3
1
120
3
0
.9n
.8
.1
.8
.72
.095°
3
3
6
3
241
7
0
,8n
.6
.2
.6
.45
.19°
0.032
NA
0.39
0.24
0.115
0.101"
MA
0
0
0
0
0
.064
NA
.78
.48
.234
.20n
NA
0.43
NA
1.46
2.07
1.071
0.0256
NA
0.87
NA
2.91
4.14
2.151
0.051
NA
i
NA
i
1.04
h
NA
NA
i
NA
i
2.08
h
NA
MA
aBased on emissions per unit of production output. Dash - not applicable. NA * not available.
Emission Factor Rating Is C for controlled particulate emissions from rotary drum coolers
and uncontrolled particulate emissions from bagging.
cParticulate test data were collected using a modification of EFA Reference Method 5. Reference 1,
Appendix B explains these modifications.
References 14 - 16, 19. Emissions from the synthesis process are generally combined with emissions
from the solution concentration process and vented through a common stack. In the synthesis
process, some emission control is inherent in the recycle process where carbamate gases and/or
liquids are recovered and recycled.
eEPA test data indicated a range of 0.0052 - 0.0150 kg/Mg (0.0104 - 0.0317 Ib/ton).
fEPA test data indicated a range of 3.79 - 14.44 kg/Mg (7.58 - 28.89 Ib/ton).
^Reference 20. These factors were determined at an ambient temperature of 288K - 294K
(57*F - 69°F). The controlled emission factors are based on ducting exhaust through a downcomer
and then a wetted fiber filter scrubber achieving a 98.3 percent efficiency. This represents a
higher degree of control than is typical in this industry.
figures are based on EFA test data. Industry test data ranged from 0.39 - 1.79 kg/Mg
(0.78 - 3.58 Ib/ton).
TIo ammonia control demonstrated by scrubbers installed for particulate control. Some Increase in
ammonia emissions exiting the control device was noted.
-"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.
^PA test data indicated a range of 0.955 - 1.20 kg/Mg (1.91 - 2.40 Ib/ton).
"EMISSION FACTOR RATING-, c; Reference i.
"EMISSION FACTOR RATING: c; Reference i.
1/84
Food and Agricultural Industry
6.14-5
-------
Urea manufacturers presently control particulate matter emissions from
prill towers, coolers, granulators and bagging operations. With the
exception of bagging operations, urea emission sources usually are
controlled with wet scrubbers. The preference of scrubber systems over dry
collection systems is primarily for the easy recycling of dissolved urea
collected in the device. Scrubber liquors are recycled to the solution
concentration process to eliminate waste disposal problems and to recover
the urea collected.1
Fabric filters (baghouses) are used to control fugitive dust from
bagging operations, where humidities are low and blinding of the bags is not
a problem. However, many bagging operations are uncontrolled.1
References for Section 6.14
1. Urea Manufacturing Industry - Technical Document, EPA-450/3-81-001,
U. S. Environmental Protection Agency, Research Triangle Park, NC,
January 1981.
2. D. F. Bress, M. W. Packbier, "The Startup of Two Major Urea Plants/'
Chemical Engineering Progress, May 1977, p. 80.
3. A. V. Slack, "Urea," Fertilizer Development Trends? Noyes Development
Corporation, Park Ridge, NJ, 1968, p. 121.
4. Written communication from J. M. Killen, Vistron Corporation, Lima, OH,
to D. R. Goodwin, U. S. Environmental Protection Agency, Research
Triangle Park, NC, December 21, 1978.
5. Written communication from J. P. Swanburg, Union Oil of California,
Brea, CA, to D. R. Goodwin, U. S. Environmental Protection Agency,
Research Triangle Park, NC, December 20, 1978.
6. Written communication from M. I. Bornstein and S. V. Capone, GCA
Corporation, Bedford, MA, to E. A. Noble, U. S. Environmental
Protection Agency, Research Triangle Park, NC, June 22, 1978.
7. Written communication from Gary McAlister, U. S. Environmental
Protection Agency, Emission Measurement Branch, to Eric Noble, U. S.
Environmental Protection Agency, Industrial Studies Branch, Research
Triangle Park, NC, July 28, 1983.
8. Formaldehyde Use in Urea-Based Fertilizers, Report of the Fertilizer
Institute's Formaldehyde Task Group, The Fertilizer Institute,
Washington, D. C., February 4, 1983.
9. J. H. Cramer, "Urea Prill Tower Control Meeting 20% Opacity,"
Presented at the Fertilizer Institute Environmental Symposium,
New Orleans, LA, April 1980.
10. Written communication from M. I. Bornstein, GCA Corporation, Bedford,
MA, to E. A. Noble, U. S. Environmental Protection Agency, Research
Triangle Park, NC, August 2, 1978.
6.14-6 EMISSION FACTORS
1/84
-------
11. Written communication from M. I. Bornstein and S. V. Capone, GCA
Corporation, Bedford, MA, to E. A. Noble, U. S. Environmental
Protection Agency, Research Triangle Park, NC, June 23, 1978.
12. Written communication from J. P. Alexander, Agrico Chemical Company,
Donaldsonville, LA, to D. R. Goodwin, U. S. Environmental Protection
Agency, NC, December 21, 1978.
13. Written communication from N. E. Picquet, W. R. Grace and Company,
Memphis, TN, to D. R. Goodwin, U. S. Environmental Protection Agency,
Research Triangle Park, NC, December 14, 1978.
14. Urea Manufacture; Agrico Chemical Company Emission Test Report, EMB
Report 79-NHF-13a, U. S. Environmental Protection Agency, Research
Triangle Park, NC, September 1980.
15. Urea Manufacture; Agrico Chemical Company Emission Test Report, EMB
Report 78-NHF-4, U. S. Environmental Protection Agency, Research
Triangle Park, NC, April 1979.
16. Urea Manufacture; CF Industries Emission Test Report, EMB Report
78-NHF-8, U. S. Environmental Protection Agency, Research Triangle
Park, NC, May 1979.
17. Urea Manufacture; Union Oil of California Emission Test Report, EMB
Report 78-NHF-7, U. S. Environmental Protection Agency, Research
Triangle Park, NC, October 1979.
18. Urea Manufacture; Union Oil of California Emission Test Report, EMB
Report 80-NHF-15, U. S. Environmental Protection Agency, Research
Triangle Park, NC, September 1980.
19. Urea Manufacture; W. R. Grace and Company Emission Test Report, EMB
Report 78-NHF-3, U. S. Environmental Protection Agency, Research
Triangle Park, NC, December 1979.
20. Urea Manufacture; Reichhold Chemicals Emission Test Report, EMB Report
80-NHF-14, U. S. Environmental Protection Agency, Research Triangle
Park, NC, August 1980.
1/84 Food and Agricultural Industry 6.14-7
-------
6.15 BEEF CATTLE FEEDLOTS
6.15.1 General1
A beef cattle feedlot is an area in which beef animals are confined for fattening prior to marketing.
This fattening, or finish feeding, typically lasts four to five months, during which time the cattle are fed
a high energy ration of feed grains and/or forage.
Cattle feedlots range in capacity from several head up to 100,000 cattle. Of the 146,000 beef cattle feed-
lots in the U.S. in 1973, 2,040 feedlots had a capacity of more than 1,000 head, marketing 65 percent of all
finish fed beef cattle. Animal density in feedlots is generally in the range of 12,500 to 125,000 head/km2.
During its stay in a feedlot, a beef animal will produce over 450 kg of manure (dry weight). Wet manure
production is typically about 27 kg per day per head, usually deposited on less than 20 m2 of surface.
Because of the prodigious quantity of manure produced in a feedlot, periodic removal is necessary to
prevent unacceptable accumulations. Most cattle manure is applied to nearby land as fertilizer for feed
grain production, while some is lagooned, dumped on wastelands, or disposed of through incineration.
liming, or pitting. Manure removal frequencies are dictated in part by climatic conditions, animal comfort.
labor scheduling, and air and water pollution control potentials. Typically, manure removal is conducted
from one to three times per year. When disposal is not immediately possible after removal, the manure may
be stockpiled on a nearby open site.
The leading states in the industry are Texas, Nebraska, Iowa, Kansas, Colorado. California, and
Illinois. These states contribute 75 percent of all feed cattle marketed and contain 72 percent of the feedlots
greater than 1000 head capacity. Feedlots are generally located in low population density regions with
access to major transportation routes.
6.15.2 Emissions and Controls1
Air pollution from feedlots originates from several points in a feedlot operation, including the holding
pens, runoff holding ponds, and alleyways among pens. Major pollutants of concern include fugitive par-
ticulate, ammonia and various malodorous gases.
Fugitive particulate is generated several ways. Cattle movement within the holding pens is a primary
source. Dust is also generated by wind acting on the dried surfaces and by vehicular traffic on alleyways
among the pens. Fugitive particulate emissions from feedlots are composed largely of soil dust and dried
manure. The potential for dust generation is greatly increased during prolonged dry periods (e.g., from late
spring to midsummer in the Southwest), and when a loose, dry pad of soil and manure is allowed to build
up in the pens.
Ammonia is the predominant gaseous pollutant emitted from feedlots. Ammonia is a result of anaerobic
decomposition of feedlot surfaces as well as volatilization from urine. Ammonia emissions are generally
increased when conditions favor anaerobic decay. For example, although 25 to 40 percent moisture levels
are necessary on feedlot surfaces for aerobic decomposition (which is odorless), too much rain or
watering, resulting in puddling and wet spots, can trigger increased ammonia production. Ammonia forma-
tion may also occur when anaerobic conditions exist in the manure stockpiles and runoff holding ponds.
In general, higher ammonia emissions are associated with higher temperatures and humidity, overly wet
conditions, and feedlot disturbances such as mounding or manure removal.
A number of extremely odorous compounds (amines, sulfides. mercaptans) may also result from
anaerobic decomposition of solid manure beneath the feedlot surface as well as in the runoff holding ponds.
7/79 Food and Agricultural Industry 6.15-1
-------
Generally, the same conditions that favor ammonia production will enhance the evolution of these other
gases, as well.
No air pollutant control devices are applied to feedlots because of the fugitive nature of the emissions.
The most effective controls involve various housekeeping measures designed to eliminate conditions that
favor the generation of dust and odors. For example, measures that help to maintain sufficient moisture
levels in the feedlot surface areas and manure stockpiles will reduce the generation of dust. One of the most
effective dust control techniques is periodic application of water to the dry feedlot surface, by either per-
manent sprinkling systems or mobile tank trucks. However, care must be taken to avoid overwatering,
which can cause wet spots conducive to anaerobic decay and subsequent malodors. Increasing the cattle
density in the pens may also help maintain high enough moisture levels to limit paniculate generation.
In addition, some dust control is effected by minimizing the accumulation of dry and pulverized manure on
the surfaces of the feedlots. A maximum depth of 2 to 8 cm of loose, dry manure is recommended for
increasing the effectiveness of dust control procedures.
Odor and ammonia control are best effected by housekeeping measures that enhance aerobic rather
than anaerobic decomposition of the cattle wastes. For example, besides reducing dust emissions.
sprinkling provides moisture for aerobic biodegradation of the manure. Good drainage must be provided,
however, and overwatering must be avoided. Deep accumulations of manure of slurry consistency can
optimize anaerobic conditions. Hence, feedlot surfaces should be periodically scraped to remove such
accumulations. Scraping should be done carefully, so that only the surface layer is disturbed. Manure
stockpiles should not be allowed to get too large, too wet, or encrusted, and they should be disposed of
within four or five days. If the stockpiles are composted, the manure should be piled in long narrow win-
drows to allow access for turning the piles to promote aerobic conditions and to enable rapid control of
spontaneous combustion fires. Anaerobic conditions can be reduced in runoff holding ponds by removing
solids from the runoff, by adding more water to the ponds to dilute the nutrient content, and by aeration
of the surface. Runoff water also may be treated chemically to suppress the release of malodorous gases.
Emission factors for feedlot operations are shown in Table 6.15-1. These factors should be considered
at best to be crude estimates of potential emissions from feedlots where no measures are employed to
control dust or odors. The limitations of these factors are more fully discussed in the footnote to Table
6.15-1. The reader should consult Reference 1 for a detailed discussion of the emissions and control
information available on beef cattle feedlots.
6.15-2 EMISSION FACTORS 7/79
-------
Table 6.15-1. EMISSION FACTORS FOR BEEF CATTLE FEEDLOTS8
EMISSION FACTOR RATING: E
Pollutant
Particulateb
Ammonia0
Aminesc
Total sulfur compounds0
Feedlot capacity basis
Ib (kg) per day per
1000 head capacity
280 (130)
11 (5)
0.4 (0.2)
1.7(0.8)
Feedlot throughput basis
ton (metric ton) per
1000 head throughput
27 (25)
1.1 (1)
0.044 (0.04)
0.15 (0.14)
"These factors represent general feedlot operations with no housekeeping measures for air pollution control.
Because of the limited data available on emissions and the nature of the techniques utilized to develop emission
factors, Table 6.15-1 should only be used to develop order-of-magnitude estimates of feedlot emissions. AH factors
are based on information compiled in Reference 1.
bThese factors represent emissions during a dry season at a feedlot where watering as a dust control measure would
not be a common practice. No data are available to estimate emission factors for feedlots during periods of abundant
precipitation or where watering and other housekeeping measures are employed for dust control.
cThese factors represent emission factors for feedlots that have not been chemically treated and where no special
housekeeping measures are employed for odor control.
Reference for Section 6.15
1. J.A. Peters and T.R. Blackwood, Source Assessment: Beef Cattle Feedlots, EPA-600/2-77-107, U.S. Environ-
mental Protection Agency. Research Triangle Park, NC. June 1977.
7/79
Food and Agricultural Industry
6.15-3
-------
6.16 DEFOLIATION AND HARVESTING OF COTTON
6.16.1 General
Wherever it is grown in the U.S., cotton is defoliated or disiccated prior to harvest. Defoliants are used
on the taller varieties of cotton which are machine picked for lint and seed cotton, while desiccants usually
are used on short, stormproof cotton varieties of lower yield that are harvested by mechanical stripper
equipment. More than 99 percent of the national cotton area is harvested mechanically. The two principal
harvest methods are machine picking, with 70 percent of the harvest from 61 percent of the area, and
machine stripping, with 29 percent of the harvest from 39 percent of the area. Picking is practiced through-
out the cotton regions of the U.S., while stripping is limited chiefly to the dry plains of Texas and Oklahoma.
Defoliation may be defined as the process by which leaves are abscised from the plant. The process may
be initiated by drought stress, low temperatures or disease, or it may be chemically induced by topically
applied defoliant agents or by overfertilization. The process helps lodged plants to return to an erect posi-
tion, removes the leaves which can clog the spindles of the picking machine and strain the fiber, accelerates
the opening of mature bolls, and reduces boll rots. Desiccation by chemicals is the drying or rapid killing
of the leaf blades and petioles, with the leaves remaining in a withered state on the plant. Harvest-aid
chemicals are applied to cotton as water-based spray, either by aircraft or by a ground machine.
Mechanical cotton pickers, as the name implies, pick locks of seed cotton from open cotton bolls and
leave the empty burs and unopened bolls on the plant. Requiring only one operator, typical modern pickers
are self propelled and can simultaneously harvest two rows of cotton at a speed of 1.1 to 1.6 meters per
second (2.5 - 3.6 mph). When the picker basket gets filled with seed cotton, the machine is driven to a
cotton trailer at the edge of the field. As the basket is hydraulically raised and tilted, the top swings open.
allowing the cotton to fall into the trailer. When the trailer is full, it is pulled from the field, usually by pick-
up truck, and taken to a cotton gin.
Mechanical cotton strippers remove open and unopened bolls, along with burs, leaves and stems from
cotton plants, leaving only bare branches. Tractor-mounted, tractor-pulled or self propelled, strippers
require only one operator. They harvest from one to four rows of cotton at speeds of 1.8 to 2.7 m/s (4.0 -
6.0 mph). After the cotton is stripped, it enters a conveying system that carries it from the stripping unit to
an elevator. Most conveyers utilize either augers or a series of rotating spike-toothed cylinders to move the
cotton, accomplishing some cleaning by moving the cotton over perforated, slotted or wire mesh screen.
Dry plant material (burs, stems and leaves) is crushed and dropped through openings to the ground. Blown
air is sometimes used to assist cleaning.
6.16.2 Emissions and Controls
Emission factors for the drifting of major chemicals applied to cotton are compiled from literature and
reported in Reference 1. In addition, drift losses from arsenic acid spraying were developed by field
testing. Two off-target collection stations, with six air samplers each, were located downwind from the
ground spraying operations. The measured concentration was applied to an infinite line source atmosphere
diffusion model (in reverse) to calculate the drift emission rate. This was in turn used for the final emission
factor calculation. The emissions occur from July to October, preceding by two weeks the period of harvest
in each cotton producing region. The drift emission factor for arsenic acid is eight times lower than pre-
viously estimated, since Reference 1 used a ground rig rather than an airplane, and because of the low vola-
tility of arsenic acid. Various methods of controlling drop size, proper timing of application, and modifica-
tion of equipment are practices which can reduce drift hazards. Fluid additives have been used that in-
crease the viscosity of the spray formulation, and thus decrease the number of fine droplets (<100 /im).
7/79 Food and Agricultural Industry 6.16-1
-------
Spray nozzle design and orientation also control the droplet size spectrum. Drift emission factors for the
defoliation of desiccation of cotton are listed in Table 6.16-1.
Table 6.16-1. EMISSION FACTORS FOR
DEFOLIATION OR DESICCATION OF COTTON3
EMISSION FACTOR RATING: C
Pollutant
Sodium chlorate
DEF
Arsenic acid
Paraquat
Emission factorb
Ib/ton
20.0
20.0
12.2
20.0
g/kg
10.0
10.0
6.1
10.0
aReference 1
bFactor is in terms of quantity of drift per quantity applied
Three unit operations are involved in mechanical harvesting of cotton: harvesting, trailer loading (basket
dumping) and transport of trailers in the field. Emissions from these operations are in the form of solid
particulates. Particulate emissions (<7 /j.m mean aerodynamic diameter) from these operations were de-
veloped in Reference 2. The particulates are composed mainly of raw cotton dust and solid dust, which
contains free silica. Minor emissions include small quantities of pesticide, defoliant and desiccant residues
that are present in the emitted particulates. Dust concentrations from harvesting were measured by
following each harvesting machine through the field at a constant distance directly downwind from the
machine, while staying in the visible plume centerline. The procedure for trailer loading was the same,
but since the trailer is stationary while being loaded, it was necessary only to stand a fixed distance
directly downwind from the trailer while the plume or puff passed over. Readings were taken upwind of all
field activity to get background concentrations. Particulate emission factors for the principal types of
cotton harvesting operations in the U.S. are shown in Table 6.16-2. The factors are based on average
machine speed of 1.34 m/s (3.0 mph) for pickers and 2.25 m/s (5.03 mph) for strippers, on a basket capacity
of 109 kg (240 Ib), on a trailer capacity of 6 baskets, on a lint cotton yield of 63.0 metric tons/km2 (1.17 bale/
acre) for pickers and 41.2 metric tons/km2 (.77 bale/acre) for strippers, and on a transport speed of 4.47 m/s
(10.0 mph). Analysis of particulate samples showed average free silica content of 7.9 percent for mechan-
ical cotton picking and 2.3 percent for mechanical cotton stripping. Estimated maximum percentages for
pesticides, defoliants and desiccants from harvesting are also noted in Table 6.16-2. No current cotton
harvesting equipment or practices provide for control of emissions. In fact, equipment design and operat-
ing practices tend to maximize emissions. Preharvest treatment (defoliation and desiccation) and harvest
practices are timed to minimize moisture and trash content, so they also tend to maximize emissions. Soil
dust emissions from field transport can be reduced by lowering vehicle speed.
6.16-2
EMISSION FACTORS
7/79
-------
Table 6.16-2. PARTICULATE EMISSION FACTORS FOR COTTON HARVESTING OPERATIONS*
EMISSION FACTOR RATING: C
Type of harvester
Picker0
Two-row, with basket
Stripped
Two-row, pulled trailer
Two-row, with basket
Four-row, with basket
Weighted average6
Harvesting
_kg_
km2
.46
7.4
2.3
2.3
4.3
Ib
ml2
2.6
42
13
13
24
Trailer
loading
-^
km5
.070
_b
.092
.092
.056
It
m
.4
-
.5
.5
.3
5-
Transport
J
-------
6.17 HARVESTING OF GRAIN
6.17.1 General1
Harvesting of grain refers to the activities performed to obtain
the cereal kernels of the plant for grain or the entire plant for forage
and/or silage uses. These activities are accomplished by machines that
cut, thresh, screen, clean, bind, pick, and shell the crops in the
field. Harvesting also includes loading harvested crops into trucks and
transporting crops on the grain field.
Crops harvested for their cereal kernels are cut as close as
possible to the inflorescence (the flowering portion containing the
kernels). This portion is threshed, screened and cleaned to separate
the kernels. The grain is stored in the harvest machine while the
remainder of the plant is discharged back onto the field.
Combines perform all of the above activities in one operation.
Binder machines only cut the grain plants and tie them into bundles or
leave them in a row in the field (called a windrow). The bundles are
allowed to dry for threshing later by a combine with a pickup
attachment.
Corn harvesting requires the only exception to the above
procedures. Corn is harvested by mechanical pickers, picker/shellers,
and combines with corn head attachments. These machines cut and husk
the ears from the standing stalk. The sheller unit also removes the
kernels from the ear. After husking, a binder is sometimes used to
bundle entire plants into piles (called shocks) to dry.
For forage and/or silage, mowers, crushers, windrowers, field
choppers, binders, and similar cutting machines are used to harvest
grasses, stalks and cereal kernels. These machines cut the plants as
close to the ground as possible and leave them in a windrow. The plants
are later picked up and tied by a baler.
Harvested crops are loaded onto trucks in the field. Grain kernels
are loaded through a spout from the combine, and forage and silage bales
are manually or mechanically placed in the trucks. The harvested crop
is then transported from the field to a storage facility.
6.17.2 Emissions and Controls
Emissions are generated by three grain harvesting operations,
(1) crop handling by the harvest machine, (2) loading of the harvested
crop into trucks, and (3) transport by trucks on the field. Particulate
matter, composed of soil dust and plant tissue fragments (chaff) may be
entrained by wind. Particulate emissions from these operations (<7ym
mean aerodynamic diameter) are developed in Reference 1. For this
study, collection stations with air samplers were located downwind
(leeward) from the harvesting operations, and dust concentrations were
2/80 Food and Agrirultural Industry 6.17-1
-------
measured at the visible plume centerline and at a constant distance
behind the combines. For product loading, since the trailer is station-
ary while being loaded, it was necessary only to take measurements a
fixed distance downwind from the trailer while the plume or puff passed
over. The concentration measured for harvesting and loading was applied
to a point source atmospheric diffusion model to calculate the source
emission rate. For field transport, the air samplers were again placed
a fixed distance downwind from the path of the truck, but this time the
concentration measured was applied to a line source diffusion model.
Readings taken upwind of all field activity gave background concen-
trations. Particulate emission factors for wheat and sorghum harvesting
operations are shown in Table 6.17-1.
There are no control techniques specifically implemented for the
reduction of air pollution emissions from grain harvesting. However,
several practices and occurences do affect emission rates and concen-
tration. The use of terraces, contouring, and stripcropping to inhibit
soil erosion will suppress the entrainment of harvested crop fragments
in the wind. Shelterbelts, positioned perpendicular to the prevailing
wind, will lower emissions by reducing the wind velocity across the
field. By minimizing tillage and avoiding residue burning, the soil
will remain consolidated and less prone to disturbance from transport
activities.
Table 6.17-1. EMISSION RATES/FACTORS FROM THE HARVESTING
GRAIN3
EMISSION FACTOR RATING: D
Operation
Harvest
machine
Truck
loading
Field
transport
Ib/hr
0.027
0.014
0.37
Emission rate
Wheat Sorghum
mg/sec
3.4
1.8
47.0
Ib/hr mg/sec
0.18 23.0
0.014 1.8
0.37 47.0
Q
Emission factor
Wheat Sorghum
lb/mi2
0.96
0.07
0.65
g/km
170.0
12.0
110.0
2 2
lb/mi g/km
6.5 1100.0
0.13 22.0
1.2 200.0
rReference 1.
Assumptions from Reference 1 are an average combine speed of 3.36
meters per second, combine swath width of 6.07 meters, and a field
transport speed of 4.48 meters per second.
In addition to Note b, assumptions are a truck loading time of six
minutes, a truck capacity of .052 km2 for wheat and .029 km2 for
sorghum, and a filed truck travel time of 125 seconds per load.
6.17-2
EMISSION FACTORS
2/80
-------
Reference for Section 1.14
1. R. A. Wachten and T. R. Blackwood, Source Assessment: Harvesting
of Grain, State of the Art, EPA-600/2-79-107f, U. S. Environmental
Protection Agency, Research Triangle Park, NC, July 1977.
2/80 Food and Agricultural Industry 6.17-3
-------
6.18 AMMONIUM SULFATE MANUFACTURE
6.18.1 General
Ammonium sulfate, [NH4]2S04, is commonly used as a fertilizer.
About 90 percent of ammonium sulfate is produced by three types of
facilities, caprolactam byproduct, synthetic, and coke oven byproduct
plants. The remainder is produced as a byproduct of nickel manu-
facture from ore concentrates, methyl methacrylate manufacture, and
ammonia scrubbing of tail gas at sulfuric acid plants.
During the manufacture of caprolactam, [CI^lsCOHN, ammonium
sulfate is produced from the oximation process stream and the
rearrangement reaction stream. Synthetic ammonium sulfate is
produced by the direct combination of ammonia and sulfuric acid in
a reactor. Coke oven byproduct ammonium sulfate is produced by
reacting ammonia recovered from coke oven offgas with sulfuric
acid. Figure 6.18-1 is a process flow diagram for each of the
three primary commercial processes.
After formation of the ammonium sulfate solution, operations
of each process are similar. Ammonium sulfate crystals are formed
by continuously circulating an ammonium sulfate liquor through an
evaporator to thicken the solution. Ammonium sulfate crystals are
separated from the liquor in the centrifuge. The saturated liquor
is returned to the dilute ammonium sulfate brine of the evaporator.
The crystals, with about 1 to 2.5 percent moisture by weight after
the centrifuge, are fed to either a fluidized bed or rotary drum
dryer. Fluidized bed dryers are continuously steam heated, and
rotary dryers are either directly fired with oil or natural gas, or
they use steam heated air. At coke oven byproduct plants, rotary
drum dryers may be used in place of a centrifuge and dryer. On the
filter of these dryers, a crystal layer is deposited which is
removed from the drum by a scraper or a knife.
The volume of ammonium sulfate in the dryer exhaust gas varies
according to production process and dryer type. A gas flow rate of
620 scm/Mg of product (20,000 scf/ton) is considered representative
of a direct fired rotary drum dryer. A gas flow of 2,500 scm/Mg of
product (80,000 scf/ton) is considered representative of a steam
heated fluidized bed dryer. Dryer exhaust gases are passed through
a particulate collection device, usually a wet scrubber, for product
recovery and for pollution control.
The ammonium sulfate crystals are conveyed from the dryer to
an enclosure where they are screened to product specifications,
generally to coarse and fine products. The screening is enclosed
to control dust in the building.
4/81 Food and Agricultural Industry 6.18-1
-------
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EMISSION FACTORS
4/81
-------
6.18.2 Emissions and Controls
Ammonium sulfate particulate is the principal pollutant emitted
to the atmosphere from the manufacturing plants, nearly all of it
being contained in the gaseous exhaust of the dryers. Other plant
processes, such as evaporation, screening, and materials handling,
are not significant sources of emissions.
The particulate emission rate of a dryer depends on the gas
velocity and the particle size distribution. Since gas velocity
varies according to the dryer type, emission rates also vary.
Generally, the gas velocity of fluidized bed dryers is higher than
for most rotary drum dryers, and particulate emission rates are
also higher. The smaller the particle, the easier it is removed by
the gas stream of either type of dryer.
At caprolactam byproduct plants, volatile organic compounds
(VOC) are emitted from the dryers. Emissions of caprolactam vapor
are at least two orders of magnitude lower than the particulate
emissions.
Wet scrubbers, such as venturi and centrifuge, are most suitable
for reducing particulate emissions from the dryers. Wet scrubbers
use process streams as the scrubbing liquid. This allows the
collected particulate to be recycled easily to the production
system.
Table 6.18-1 shows the uncontrolled and controlled emission
factors for the various dryer types. The VOC emissions shown in
Table 6.18-1 apply only to caprolactam byproduct plants which may
use either a fluidized bed or rotary drum dryer.
TABLE 6.18-1. EMISSION FACTORS FOR AMMONIUM SULFATE MANUFACTURE3
EMISSION FACTOR RATING: B
Particulates Volatile Organic Compounds
Dryer Type & Controls kg/MgIb/ton kg/MgIb/ton
Rotary dryers
Uncontrolled 23 46 0.74 1.48
Wet scrubber 0.12 0.24 0.11 0.22
Fluidized bed dryers
Uncontrolled
Wet scrubber
109
0.14
218
0.28
0.74
0.11
1.48
0.22
•a
Expressed as emissions by weight per unit of ammonium sulfate
, production by weight.
VOC emissions occur only at caprolactam plants using either type
of dryer. The emissions are caprolactam vapor.
4/81 Food and Agricultural Industry 6.18-3
-------
Reference for Section 6.18
1. Ammonium Sulfate Manufacture - Background Information for Proposed
Emission Standards, EPA-450/3-79-034a, U.S. Environmental Protection
Agency, Research Triangle Park, NC, December 1979.
c
6.18-4 EMISSION FACTORS 4/81
-------
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 (1)
Alumina > Aluminum Oxygen
(reduction)
The electrolytic reduction occurs in shallow rectangular cells, or "pots",
which are steel shells lined with carbon. Carbon electrodes extend into the
pot and serve as the anodes, and the carbon lining the steel shell is the cathode.
Molten cryolite functions as both the electrolyte and the solvent for the
alumina. Electrical resistance to the current passing between the electrodes
generates heat that maintains cell operating temperatures between 950° and
1000°C (1730° and 1830°F). Aluminum is deposited at the cathode, where it
remains as molten metal below the surface of the cryolite bath. The carbon
anodes are continuously depleted by the reaction of oxygen (formed during the
reaction) and anode carbon, to produce carbon monoxide and carbon dioxide.
Carbon consumption and other raw material and energy requirements for aluminum
production are summarized in Table 7.1-1. The aluminum product is period-
ically tapped beneath the cryolite cover and is fluxed to remove trace
impurities.
Aluminum reduction cells are distinguished by the anode type and
configuration used in the pots. Three types of pots are currently used,
prebaked (PB), horizontal stud Soderberg (HSS), and vertical stud Soderberg
(VSS). Most of the aluminum produced in the U. S. is processed in PB cells.
Anodes are produced as an ancillary operation at the reduction plant.
In the paste preparation plant, petroleum coke is mixed with a pitch binder
4/81 Metallurgical Industry 7.1-1
-------
SODIUM
HYDROXIDE
TO CONTROL DEVICE
»
DILUTION
WATER
RED MUD
(IMPURITIES)
I
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SODIUM
HYDROXIDE
TO CONTROL
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I
ALUMINUM
HYDROXIDE
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SPENT
ELECTRODES
ALUMINA
ANODE
PASTE
ELECTROLYTE
ANODE PASTE
CRYSTALLIZER
AQUEOUS SODIUM
ALUMINATE
TO CONTROL DEVICE
I
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BAKED
ANODES
TO CONTROL DEVICE
I
PREBAKE
REDUCTION
CELL
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OR VERTICAL
SODERBERG
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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, A12C-3 and metal chloride emissions. A dross forms and floats on the
molten aluminum and is removed before casting.^
7.1.2 Emissions and Controls1"3>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
(NasAl3Fi4) 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
1 to 5
5 to 10
10 to 20
20 to 44
>44
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PB
35
25
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5
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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.)8
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. ParticulatePollutant 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
-------
7.2 COKE MANUFACTURING
7.2.1 Process Description
Coking is the process of destructive distillation, or the heating
of coal in an atmosphere of low oxygen content. During this process,
organic compounds in the coal break down to yield gases and a relatively
involatile residue. The primary method for the manufacture of coke is
the byproduct method, which accounts for more than 98 percent of U.S.
coke production.
The byproduct method is oriented to the recovery of gases produced
during the coking cycle. Narrow rectangular slot-type coking ovens are
constructed of silica brick, and a battery is commonly made up of a
series of 40 to 70 of these ovens interspaced with heating flues. A
larry car runs along the top of the coke battery, charging the ovens
with coal through ports. After each charging, the ports are sealed, and
heat is supplied to the ovens by combustion of gases passing through the
flues between the ovens. The fuels used in the combustion process are
natural gas, coke oven gas or blast furnace gas. In the ovens, coke is
formed first near the brick walls and then toward the center, where
temperatures are 2000° - 2100°F (1100° - 1150°C). After a period of
16 - 20 hours, the coking process is complete. Coke is pushed by a ram
from the oven into a quenching car. The quenching car of hot coke is
moved by rail to the quench tower, where several thousand gallons of
water are used to cool the coke. The coke is allowed to dry and is
separated into various sizes for future use. See Figure 7.5-1 of this
document for a flow diagram of an integrated iron and steel plant which
contains the coking operations.
7.2.2 Emissions
Particulates, volatile organic compounds, carbon monoxide and other
emissions originate from the following byproduct coking operations: (1)
coal preheating (if used), (2) charging of coal into the incandescent
ovens, (3) oven leakage during the coking period, (4) pushing the coke
out of the ovens, (5) quenching the hot coke and (6) combustion stacks.
Gaseous emissions from the byproduct ovens during the coking process are
drawn off to a collecting main and are subjected to various operations
for separating ammonia, coke oven gas, tar, phenol, light oil (benzene,
toluene, xylene) and pyridine. These unit operations are potential
sources of volatile organic compounds.
Oven charging operations and leakage around poorly sealed coke oven
doors and lids are major sources of emissions from byproduct ovens.
Emissions also occur when finished coke is pushed into the quench cars
and during the quenching operation. The combustion process is also a
source of pollutant emissions. As the combusting gases pass through the
coke oven heating flues, emissions from the ovens may leak into the
stream. Also, if the coke oven gas is not desulfurized, the combustion
process will emit sulfur dioxide. Figure 7.2-1 is a depiction of a coke
oven battery showing the major air pollution sources.
10/80 Metallurgical Industry 7.2-1
-------
7.2-2
EMISSION FACTORS
10/30
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Metallurgical Industry
7.2-3
-------
Associated with the byproduct coke oven process are open source fugit-
ive dust operations. These include material handling operations of unload-
ing, storing, grinding and sizing of coal, and the screening, crushing,
storing and loading of coke. Fugitive emissions also come from vehicles
traveling on paved and unpaved surfaces. These emissions and the parameters
that influence them are discussed in more detail in Section 7.5 and Chapter
11 of this document. The emission factors for coking operations are summar-
ized in Table 7.2-1. Extensive information on the data used to develop the
particulate emission factors is found in Reference 1.
References for Section 7.2
1. Particulate Emission Factors Applicable to the Iron and Steel In-
dustry, EPA-450/4-79-028, U.S. Environmental Protection Agency,
Research Triangle Park, NC, September 1979.
2. Air Pollution by Coking Plants, United Nations Report: Economic Com-
mission for Europe, ST/ECE/Coal/26, 1968.
3. R. W. Fullerton, "Impingement Baffles To Reduce Emissions from Coke
Quenching", Journal of the Air Pollution Control Association,
J7:807-809, December 1967.
4. R. B. Jacko, et al., By-product Coke Oven Pushing Operation; Total
and Trace Metal Particulate Emissions, Purdue University, West
Lafayette, IN, June 27, 1976.
5. Control Techniques for Lead Air Emissions, EPA-450/2-770-012, U.S.
Environmental Protection Agency, Research Triangle Park, NC, December
1977.
6. Mineral Industry Surveys: Weekly Coal Report No. 3056, Bureau of
Mines, U.S. Department of the Interior, Washington, DC, undated.
7. J. Varga and H. W. Lownie, Jr., Final Technological Report on: A
Systems Analysis Study of the Integrated Iron and Steel Industry,
HEW Contract No. PH 22-68-65, Battelle Memorial Institute, Columbus,
OH, May 1969.
f
7.2-4 EMISSION FACTORS 12/81
-------
7.3 PRIMARY COPPER SMELTING
7.3.1 Process Descriptionl~3
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 (802). 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 S02 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 (Cu£S) 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-
FUEL-
AIR-
BLISTER COPPER
(98.5t% Cu)
FIRE REFINING
SLAG TO CONVERTER-
ANODE COPPER (99.5% Cu)
TO ELECTROLYTIC REFINERY
•OFFGAS
OFFGAS
•OFFGAS
OFFGAS
Figure 7.3-1. A conventional copper smelting process.
7.3-2 EMISSION FACTORS
-------
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 S02, 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 S02 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 off gases 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 S02 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 S(>2 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 off gases.
1/84 Metallurgical Industry 7.3-5
-------
TABLE 7.3-1. TYPICAL SULFUR DIOXIDE CONCENTRATIONS IN
OFFGASES FROM PRIMARY COPPER SMELTING SOURCES
S02 concentration
Unit Volume %
i
Multiple hearth roaster
Fluidlzed bed roaster
Reverberatory furnace
Electric arc furnace
Flash smelting furnace
Continuous smelting furnace
Fierce-Smith converter
Hoboken converter
Single contact H2S04 plant
Double contact H2S04 plant
1.5
10
0.5
4
10
5
4
0.2
- 3
- 12
- 1.5
- 8
- 20
- 15
- 7
8
- 0.26
0.05
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 S0£ 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 S02-
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
Configuration0
Particulate matter
SO,
Unit
References
Kg/Mg Ib/ton Kg/Mg Ib/ton
Reverberatory furnace (RF)
followed by converters (C)
Mult inearth 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
ce
CD
NR
C
25
18
22
25
18
MA
25
18
5
50
18
HA
50
18
5
70
5
NA2
5
NA
NA
50
36
45
50
36
NA
50
36
10
100
36
NA
100
36
10
140
10
MAS
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
180
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
8, 11-13, 15
20
15, 23
e
21-22
24
22
22
21-22
^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 blister copper. NA -
not available.
''For particulate matter removal, gaseous effluents from roasters, smelting furnaces and converters
are usually treated in hot ESP3 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 99X. 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 % efficient in SC>2 removal. They also remove over 99% of particulate matter.
cln addition to sources indicated, each smelter configuration contains fire refining anode furnaces
after the converters. Anode furnaces emit negligible SC>2. 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
Particulate matter
Kg/Mg Ib/ton
S02
Kg/Mg
lb/ton
Roaster calcine discharge
Smelting furnace*5
Converters
Converter slag return
Anode furnace
Slag cleaning furnacac
1.3
0.2
2.2
NA
0.25
4
2.6
0.4
4.4
NA
0.5
8
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 50% 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.
i
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 Ib/ton
Roasting0 0.075 0.15
Smeltlngd 0.036 0.072
Converting6 0.13 0.27
Refining NA 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 0.4% lead in feed
throughput. NA - not available.
bFor 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.
dBased 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 35% and 2%, respectively.
elncludes 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, NC, 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.
4. 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
^recipitator 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, Playas, 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
-------
7.4 FERROALLOY PRODUCTION
7.4.1 Process Description1'2
Ferroalloy is the generic term for alloys consisting of iron and one or more other metals. Ferroalloys are used
in steel production as alloying elements and deoxidants. There are three basic types of ferroalloys: (1)
silicon-based alloys, including ferrosilicon and calciumsilicon; (2) manganese-based alloys, including fer-
romanganese and silicomanganese; and (3) chromium-based alloys, including ferrochromium and ferrosilico-
chrome.
The four major procedures used to produce ferroalloy and high-purity metallic additives for steelmaking are:
(1) blast furnace, (2) electrolytic deposition, (3) alumina silico-thermic process, and (4) electric smelting furnace.
Because over 75 percent of the ferroalloys are produced in electric smelting furnaces, this section deals only with
that type of furnace.
The oldest, simplest, and most widely used electric furnaces are the submerged-arc open type, although
semi-covered furnaces are also used. The alloys are made in the electric furnaces by reduction of suitable oxides.
For example, in making ferrochromium the charge may consist of chrome ore, limestone, quartz (silica), coal and
wood chips, along with scrap iron.
7.4.2 Emissions3
The production of ferroalloys has many dust- or fume-producing steps. The dust resulting from raw material
handling, mix delivery, and crushing and sizing of the solidified product can be handled by conventional
techniques and is ordinarily not a pollution problem. By far the major pollution problem arises from the
ferroalloy furnaces themselves. The conventional submerged-arc furnace utilizes carbon reduction of metallic
oxides and continuously produces large quantities of carbon monoxide. This escaping gas carries large quantities
of particulates of submicron size, making control difficult.
In an open furnace, essentially all of the carbon monoxide burns with induced air at the top of the charge, and
CO emissions are small. Particulate emissions from the open furnace, however, can be quite large. In the
semi-closed furnace, most or all of the CO is withdrawn from the furnace and burns with dilution air introduced
into the system. The unburned CO goes through particulate control devices and can be used as boiler fuel or can
be flared directly. Particulate emission factors for electric smelting furnaces are presented in Table 7.4-1. No
carbon monoxide emission data have been reported in the literature.
2/72 Metallurgical Industry 7.4-1
-------
TABLE 7.4-1. EMISSION FACTORS FOR FERROALLOY PRODUCTION IN
ELECTRIC SMELTING FURNACESa
EMISSION FACTOR RATING: C
Type of furnace and
product
Open furnace
50% FeSic
75% FeSid
90% FeSic
Silicon metal6
Silicomanganese^
Ferrochrome-Silicon
High Carbon ferrochrome
Semi-covered furnace
Ferromanganese^
Particulates
kg/Mg
100
157.5
282.5
312.5
97.5
—
22.5
Ib/ton
200
315
565
625
195
—
45
Leadb
kg/Mg
0.15
0.0015
—
0.0015
0.0029
0.04
0.17
0.06
Ib/ton
0.29
0.0031
-
0.0031
0.0057
0.08
0.34
0.11
aEmission factors expressed as weight per unit weight of specified
product. Dash indicates no available data.
^References 1-5.
cReference 8.
References 10-11.
References 9, 12.
^Reference 11.
REFERENCES FOR SECTION 7.4
1. R. A. Pearson, "Control of Emissions from Ferroalloy Furnace Processing",
presented at the 27th Electric Furnace Conference, Detroit, MI, December
1969.
2. J. 0. Dealy and A. M. Killin, Air Pollution Control Engineering and Cost
Study of the Ferroalloy Industry, EPA-450/2-74-008, U.S.Envir o nmental
Protection Agency, Research Triangle Park, NC, May 1974.
3. A. E. Vandergrift, et al., Particulate Pollutant System Study - Mass
Emissions, PB-203-128, PB-203-522 and PB-203-521, U.S. Environmental
Protection Agency, Research Triangle Park, NC, May 1971.
4. Control Techniques for Lead Air Emissions, EPA-450/2-77-012, U.S. Environ-
mental Protection Agency, Research Triangle Park, NC, December 1977.
5. W. E. Davis, Emissions Study of Industrial Sources of Lead Air Pollutants,
1970, EPA-APTD-1543, W. E. Davis and Associates, Leawood, KS, April 1973.
6. Air Pollutant Emission Factors, Final Report, Resources Research, Inc.,
Reston, VA, prepared for National Air Pollution Control Administration,
Durham, NC, under Contract Number CPA-22-69-119, April 1970.
7.4-2
EMISSION FACTORS
12/81
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7. Ferroalloys; Steel's All-purpose Additives, The Magazine of Metals
Producing, February 1967.
8. R. A. Person, Control of Emissions from Ferroalloy Furnace Processing,
Niagara Falls, NY, 1969.
9. Unpublished stack test results, Resources Research, Incorporated,
Reston, VA.
10. R. Ferrari, Experiences in Developing an Effective Pollution Control
System for a Submerged-Arc Ferroalloy Furnace Operation, J. Metals,
p. 95-104, April 1968.
11. Fredriksen and Nestaas, Pollution Problems by Electric Furnace
Ferroalloy Production, United Nations Economic Commission for Europe,
September 1968.
12. R. W. Gerstle and J. L. McGinnity, Plant Visit Memorandum, U.S.
DREW, PHS, National Center for Air Pollution Control, Cincinnati,
OH, June 1967.
12/81 Metallurgical Industry 7.4-3
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7.5 IRON AND STEEL PRODUCTION
1-2
7.5.1 Process Description and Emissions
Iron and steel manufacturing may be grouped into eight generic process
operations: 1) coke production, 2) sinter production, 3) iron production,
4) steel production, 5) semifinished product preparation, 6) finished prod-
uct preparation, 7) heat and electricity supply and 8) handling and trans-
port of raw, intermediate and waste materials. Figure 7.5-1, a general
flow diagram of the iron and steel industry, interrelates these categories.
Coke production is discussed in detail in Section 7.2 of this publication,
and more information on the handling and transport of materials is found in
Chapter 11.
Sinter Production - The sintering process converts fine raw materials like
fine iron ore, coke breeze, fluxstone, mill scale and flue dust into an ag-
glomerated product of suitable size for charging into a blast furnace. The
materials are mixed with water to provide cohesion in a mixing mill and are
placed on a continuous moving grate called the sinter strand. A burner
hood above the front third of the sinter strand ignites the coke in the
mixture. Once ignited, combustion is self supporting and provides suffi-
cient heat, 1300 to 1480°C (2400 to 2700°F), to cause surface melting and
agglomeration of the mix. On the underside of the sinter machine lie wind-
boxes that draw the combusted air through the material bed into a common
duct to a particulate control device. The fused sinter is discharged at
the end of the sinter machine, where it is crushed and screened, and any
undersize portion is recycled to the mixing mill. The remaining sinter is
cooled in open air by water spray or by mechanical fan to draw off the heat
from the sinter. The cooled sinter is screened a final time, with the
fines being recycled and the rest being sent to charge the blast furnaces.
Emissions occur at several points in the sintering process. Points of
particulate generation are the windbox, the discharge (sinter crusher and
hot screen), the cooler and the cold screen. In addition, inplant transfer
stations generate emissions which can be controlled by local enclosures.
All the above sources except the cooler normally are vented to one or two
control systems.
Iron Production - Iron is produced in blast furnaces, which are large re-
fractory lined chambers into which iron (as natural ore or as agglomerated
products such as pellets or sinter, coke and limestone) is charged and al-
lowed to react with large amounts of hot air to produce molten iron. Slag
and blast furnace gases are byproducts of this operation. The average
charge to produce one unit weight of iron requires 1.7 unit weights of iron
bearing charge, 0.55 unit weights of coke, 0.2 unit weights of limestone,
and 1.9 unit weights of air. Average blast furnace byproducts consist of
0.3 unit weights of slag, 0.05 unit weights of flue dust, and 3.0 unit
weights of gas per unit of iron produced. The flue dust and other iron ore
fines from the process are converted into useful blast furnace charge by
the sintering operation.
5/83 Metallurgical Industry 7.5-1
-------
CO
3
13
a
QJ
-------
Because of its high carbon monoxide content, this blast furnace gas
has a low heating value, about 2790 to 3350 joules per cubic liter (75 to
90 BTU/ft3) and is used as a fuel within the steel plant. Before it can be
efficiently oxidized, however, the gas must be cleaned of particulate.
Initially, the gases pass through a settling chamber or dry cyclone to re-
move about 60 percent of the particulate. Next, the gases undergo a one or
two stage cleaning operation. The primary cleaner is normally a wet scrub-
ber, which removes about 90 percent of the remaining particulate. The sec-
ondary cleaner is a high energy wet scrubber (usually a venturi) or an
electrostatic precipitator, either of which can remove up to 90 percent of
the particulate that eludes the primary cleaner. Together these control
devices provide a clean fuel of less than 0.05 grams per cubic meter (0.02
gr/ft3) for use in the steel plant.
Emissions occur during the production of iron when there is a blast
furnace "slip" and during hot metal transfer operations in the cast house.
All gas generated in the blast furnace is normally cleaned and used for
fuel. Conditions such as "slips", however, can cause instant emissions of
carbon monoxide and particulates. Slips occur when a stratum of the mate-
rial charged to a blast furnace does not settle with the material below it,
thus leaving a gas filled space between the two portions of the charge.
When this unsettled stratum of charge collapses, the displaced gas may
cause the top gas pressure to increase above the safety limit, thus opening
a counter weighted bleeder valve to the atmosphere.
Steel Production (Basic Oxygen Furnace) - The basic oxygen process is used
to produce steel from a furnace charge typically composed of 70 percent
molten blast furnace metal and 30 percent scrap metal by use of a stream of
commercially pure oxygen to oxidize the impurities, principally carbon and
silicon. Most of the basic oxygen furnaces (EOF) in the United States have
oxygen blown through a lance in the top of the furnace. However, the
Quelle Basic Oxygen Process (QBOP), which is growing in use, has oxygen
blown through tuyeres in the bottom of the furnace. Cycle times for the
basic oxygen process range from 25 to 45 minutes.
The large quantities of carbon monoxide (CO) produced by the reactions
in the BOF can be combusted at the mouth of the furnace and then vented to
gas cleaning devices, as with open hoods, or the combustion can be sup-
pressed at the furnace mouth, as with closed hoods. The term "closed hood"
is actually a misnomer, since the opening at the furnace mouth is large
enough to allow approximately 10 percent of theoretical air to enter. Al-
though most furnaces installed before 1975 are of the open hood design,
nearly all the QBOPs in the United States have closed hoods, and most of
the new top blown furnaces are being designed with closed hoods.
There are several sources of emissions in the basic oxygen furnace
steel making process, 1) the furnace mouth during refining - with collec-
tion by local full (open) or suppressed (closed) combustion hoods, 2) hot
metal transfer to charging ladle, 3) charging scrap and hot metal, 4) dump-
ing slag and 5) tapping steel.
Steel Production (Electric Arc Furnaces) - Electric arc furnaces (EAF) are
used to produce carbon and alloy steels. The charge to an EAF is nearly
5/83 Metallurgical Industry 7.5-3
-------
always 100 percent scrap. Direct arc electrodes through the roof of the
furnace melt the scrap. An oxygen lance may or may not be used to speed
the melting and refining process. Cycles range from 1-1/2 to 5 hours for
carbon steel and from 5 to 10 hours for alloy steel.
Sources of emissions in the electric arc furnace steel making process
are 1) emissions from melting and refining, often vented through a hole in
the furnace roof, 2) charging scrap, 3) dumping slag and 4) tapping steel.
In interpreting and using emission factors for EAFs, it is important to
know what configuration one is dealing with. For example, if an EAF has a
building evacuation system, the emission factor before the control device
would represent all melting, refining, charging, tapping and slagging emis-
sions which ascend to the building roof. Reference 2 has more details on
various configurations used to control electric arc furnaces.
Steel Production (Open Hearth Furnaces) - In the open hearth furnace (OHF),
a mixture of iron and steel scrap and hot metal (molten iron) is melted in
a shallow rectangular basin or "hearth". Burners producing a flame above
the charge provide the heat necessary for melting. The mixture of scrap
and hot metal can vary from all scrap to all hot metal, but a half and half
mixture is a reasonable industry average. The process may or may not be
oxygen lanced, with process cycle times approximately 8 hours and 10 hours,
respectively.
Sources of emissions in the open hearth furnace steel making process
are 1) transferring hot metal, 2) melting and refining the heat, 3) charg-
ing of scrap and/or hot metal, 4) dumping slag and 5) tapping steel.
Semifinished Product Preparation - After the steel has been tapped, the
molten metal is teemed into ingots which are later heated to form blooms,
billets or slabs. (In a continuous casting operation, the molten metal may
bypass this entire process.) The product next goes through a process of
surface preparation of semifinished steel (scarfing). A scarfing machine
removes surface defects before shaping or rolling of the steel billets,
blooms and slabs by applying jets of oxygen to the surface of the steel,
which is at orange heat, thus removing a thin layer of the metal by rapid
oxidation. Scarfing can be performed by machine on hot semifinished steel
or by hand on cold or slightly heated semifinished steel. Emissions occur
during teeming as the molten metal is poured, and when the semifinished
steel products are manually or machine scarfed to remove surface defects.
Miscellaneous Combustion Sources - Iron and steel plants require energy
(heat or electricity) for every plant operation. Some energy operations on
plant property that produce emissions are boilers, soaking pits and slab
furnaces which burn coal, No. 2 fuel oil, natural gas, coke oven gas or
blast furnace gas. In soaking pits, ingots are heated until the tempera-
ture distribution over the cross section of the ingots is acceptable and
the surface temperature is uniform for further rolling into semifinished
products (blooms, billets and slabs). In slab furnaces, a slab is heated
before being rolled into finished products (plates, sheets or strips). The
emissions from the combustion of natural gas, fuel oil or coal for boilers
7.5-4 EMISSION FACTORS 5/83
-------
can be found in Chapter 1 of this document. Estimated emissions from these
same fuels used in soaking pits or slab furnaces can be the same as those
for boilers, but since it is estimation, the factor rating drops to D.
Emission factor data for blast furnace gas and coke oven gas are not
available and must be estimated. There are three facts available for mak-
ing the estimation. First, the gas exiting the blast furnace passes
through primary and secondary cleaners and can be cleaned to less than 0.05
grams per cubic meter (0.02 gr/ft3). Second, nearly one third of the coke
oven gas is methane. Third, there are no blast furnace gas constituents
that generate particulate when burned. The combustible constituent of
blast furnace gas is CO, which burns clean. Based on facts one and three,
the emission factor for combustion of blast furnace gas is equal to the
particulate loading of that fuel, 0.05 grams per cubic meter (2.9 lb/106
ft3).
Emissions for combustion of coke oven gas can be estimated in the same
fashion. Assume that cleaned coke oven gas has as much particulate as
cleaned blast furnace gas. Since one third of the coke oven gas is meth-
ane, the main component of natural gas, it is assumed that the combustion
of this methane in coke oven gas generates 0.06 grams per cubic meter (3.3
lb/106 ft3) of particulate. Thus, the emission factor for the combustion
of coke oven gas is the sum of the particulate loading and that generated
by the methane combustion, or 0.1 grams per cubic meter (6.2 lb/106 ft3).
Open Dust Sources - Like process emission sources, open dust sources con-
tribute to the atmospheric particulate burden. Open dust sources include
1) vehicle traffic on paved and unpaved roads, 2) raw material handling
outside of buildings and 3) wind erosion from storage piles and exposed
terrain. Vehicle traffic consists of plant personnel and visitor vehicles;
plant service vehicles; and trucks handling raw materials, plant deliver-
ables, steel products and waste materials. Raw materials are handled by
clamshell buckets, bucket/ladder conveyors, rotary railroad dumps, bottom
railroad dumps, front end loaders, truck dumps, and conveyor transfer sta-
tions, all of which disturb the raw material and expose fines to the wind.
Even fine materials resting on flat areas or in storage piles are exposed
and are subject to wind erosion. It is not unusual to have several million
tons of raw materials stored at a plant and to have in the range of 10 to
100 acres of exposed area there.
Open dust source emission factors for iron and steel production are
presented in Table 7.5-1. These factors were determined through source
testing at various integrated iron and steel plants.
As an alternative to the single valued open dust emission factors
given in Table 7.5-1, empirically derived emission factor equations are
presented in Chapter 11 of this document. Each equation was developed for
a source operation defined on the basis of a single dust generating mecha-
nism which crosses industry lines, such as vehicle traffic on unpaved
roads. The predictive equation explains much of the observed variance in
measured emission factors by relating emissions to parameters which charac-
terize source conditions. These parameters may be grouped into three cate-
gories: 1) measures of source activity or energy expended (e.g., the speed
5/83 Metallurgical Industry 7.5-5
-------
TABLE 7.5-1. UNCONTROLLED PARTICIPATE EMISSION FACTORS FOR
OPEN DUST SOURCES AT IRON AND STEEL MILLS3
Operation
Continuous drop
Conveyor transfer station
Sinterc
Emissions by
<
13
30 M>
0.026
Pile formation -
stacker
Pellet ore
Lump ore
A
Coald
Batch drop
Front end loader/truck0
High silt slag
Low silt slag
Vehicle travel on
unpaved roads ,
Light duty vehicle
A
Medium duty vehicle
u
Heavy duty vehicle
Vehicle travel on
paved roads
Light/heavy vehicle mix
Predictive emission factor
. seated in Chapter 11.
1
0
0
0
0
0
13
0
4
0
0
1
2
7
3
14
0
0
.2
.0024
.15
.00030
.055
.00011
.026
.4
.0088
.51
.8
.1
.3
.9
.22
.78
equations,
Units/unit of material transferred.
. Reference 3. Interpolation to other
Reference 4. Interpolation to other
<
9.
0.
0.
0.
0.
0.
particle
15 Mm
0
018
75
0015
095
00019
0.034
0.
8.
0.
2.
0.
0.
1.
1.
5.
2.
9.
0.
0.
000069
5
017
9
0058
37
3
5
2
7
7
16
56
size range
6
0
0
0
0
0
0
0
6
0
2
0
0
1
1
4
2
7
0
0
which generally
Units/unit of
particle sizes
particle sizes
< 10 Mm
.5
.013
.55
.0011
.075
.00015
.026
.000052
.5
.013
.2
.0043
.28
.0
.2
.1
.1
.6
.12
.44
provide
(aerodynamic
< 5 Mm
4.2
0.0084
0.32
0.00064
0.040
0.000081
0.014
0.000029
4.0
0.0080
1.4
0.0028
0.18
0.64
0.70
2.5
1.4
4.8
0.079
0.28
more accurate
diameter)
< 2
2.
0.
0.
0.
0.
0.
0.
0.
2.
0.
0.
0.
0.
0.
0.
1.
0.
2.
0.
0.
.5 M"
3
0046
17
00034
022
000043
0075
000015
3
0046
80
0016
10
37
42
5
76
7
042
15
estimates of
V
Units"
g/Mg
Ib/T
g/Mg
Ib/T
g/Mg
Ib/T
g/Mg
Ib/T
g/Mg
Ib/T
g/Mg
Ib/T
kg/VKT
Ib/VMT
kg/VKT
Ib/VMT
kg/VKT
Ib/VMT
kg/VKT
Ib/VMT
emissions,
Emission
Factor
Rating
0
D
B
B
C
C
E
E
C
C
C
C
C
C
C
C
B
B
C
C
are pre-
distance traveled.
will be approximate.
will be approximate.
and weight of a vehicle traveling on an unpaved road), 2) properties of the
material being disturbed (e.g., the content of suspendible fines in the
surface material on an unpaved road) and 3) climatic parameters (e.g., num-
ber of precipitation free days per year, when emissions tend to a maximum).
Because the predictive equations allow for emission factor adjustment
to specific source conditions, the equations should be used in place of the
factors in Table 7.5-1, if emission estimates for sources in a specific
iron and steel facility are needed. However, the generally higher quality
ratings assigned to the equations are applicable only if 1) reliable values
of correction parameters have been determined for the specific sources of
interest and 2) the correction parameter values lie within the ranges
tested in developing the equations. Chapter 11 lists measured properties
of aggregate process materials and road surface materials in the iron and
steel industry, which can be used to estimate correction parameter values
for the predictive emission factor equations, in the event that site spe-
cific values are not available. Use of mean correction parameter values
from Chapter 11 reduces the quality ratings of the emission factor equation
by one level.
7.5-6
EMISSION FACTORS
5/83
-------
Particulate emission factors for iron and steel plant processes are in
Table 7.5-2. These emission factors are a result of an extensive investi-
gation by EPA and the American Iron and Steel Institute.2 Carbon monoxide
emission factors are in Table 7.5-3.5
TABLE 7.5-2. PARTICULATE EMISSION FACTORS FOR IRON AND STEEL MILLS3
Source
Blast furnaces
Slips
Uncontrolled cast house emissions
Monitor
Tap hole and trough (not runners)
Sintering
Windbox emissions
Uncontrolled
Leaving grate
After coarse particulate removal
Controlled by dry ESP
Controlled by wet ESP
Controlled by scrubber
Controlled by cyclone
Sinter discharge (breaker and hot
screens)
Uncontrolled
Controlled by baghouse
Controlled by orifice scrubber
Windbox and discharge
Controlled by baghouse
Basic oxygen furnaces
Top blown furnace melting and refining
Uncontrolled
Controlled by open hood vented to:
ESP
Scrubber
Controlled by closed hood vented to:
Scrubber
QBOP melting and refining
Controlled by scrubber
Charging
At source
At building monitor
Tapping
At source
At building monitor
Hot metal transfer
At source
At building monitor
EOF monitor (all sources)
Electric arc furnaces
Melting and refining
Uncontrolled
Carbon steel
Charging, tapping and slagging
Uncontrolled emissions escaping
monitor
Melting, refining, charging, tapping
and slagging
Uncontrolled
Alloy steel
Carbon steel
Units
kg (lb)/slip
kg/Mg
kg/Mg
(Ib/ton) hot metal
(Ib/ton) finished
Emissions Emission Factor
Rating
39
0
0
.5
.3
.15
(87)
(0.6)
(0.3)
D
B
B
sinter
5.56
kg/Mg
(Ib/ton) finished
4
0
0
0
0
.35
.8
.085
.235
.5
(11.1)
(8.7)
(1.6)
(0.17)
(0.47)
U)
B
A
B
B
B
B
sinter
kg/Mg
(Ib/ton) finished
slater
kg/Mg
kg/Mg
kg/Mg
kg/Mg
kg/Mg
kg/Mg
kg/Mg
kg/Mg
kg/Mg
(Ib/ton) steel
(Ib/ton) steel
(Ib/ton) hot metal
(Ib/ton) steel
(Ib/ton) hot metal
(Ib/ton) steel
(Ib/ton) steel
(Ib/ton) steel
(Ib/ton) steel
3
0
0
0
14
0
0
0
0
0
0
0
0
0
0
0
19
0
5
25
.it
.05
.295
.15
.25
.065
.045
.0034
.028
.3
.071
.46
.145
.095
.028
.25
.7
.65
(6.8)
(0.1)
(0.59)
(0.3)
(28.5)
(0.13)
(0.09)
(0.0068)
(0.056)
(0.6)
(0.142)
(0.92)
(0.29)
(0.19)
(0.056)
(0.5)
(38)
(1.4)
(11.3)
(50)
B
B
A
A
B
A
B
A
A
A
B
A
B
A
B
B
C
C
A
C
Controlled by:
Configuration 1
(building evacuation to baghouse
for alloy steel)
Configuration 2
(DSE plus charging hood vented
to common baghouse for carbon
steel)
0.15 (0.3)
0.0215 (0.043)
(continued)
5/83
Metallurgical Industry
7.5-7
-------
TABLE 7.5-2.
PARTICULATE EMISSION FACTORS FOR IRON AND
STEEL MILLS3 (continued)
Source Units
Open hearth furnaces
Melting and refining kg/Mg (Ib/ton) steel
Uncontrolled
Controlled by ESP
Roof monitor emissions
Teeming
Leaded steel kg/Mg (Ib/ton) steel
Uncontrolled fas measured at the
source)
Controlled by side draft hood vented
to baghouse
Unleaded steel
Uncontrolled (as measured at the
source)
Controlled by side draft hood vented
to baghouse
Machine scarfing
Uncontrolled kg/Kg (Ib/ton) metal
through scarfer
Controlled by ESP
Miscellaneous combustion sources
Boilers, soaking pits and slab reheat kg/108 J (lb/106 BTU)
furnaces
Blast furnace gas
Coke oven gas
Emissions Emission Factor
Rating
10.55
0.14
0.084
0.405
0.0019
0.035
0.0008
0.05
0.0115
0.015
0.0052
(21.1)
(0.28)
(0.168)
(0.81)
(0.0038)
(0.07)
(0.0016)
(0.1)
(0.023)
(0.035)
(0.012)
A
A
C
A
A
A
A
B
A
D
D
J Reference 2. ESP - electrostatic precipitator. DSE = direct shell evacuation.
For fuels such as coal, fuel oil and natural gas, use the emission factors presented in Chapter 1. of
this document.. The factor rating for these fuels in boilers is A, and in soaking pits and slab re-
heat furnaces is D.
TABLE 7.5-3. UNCONTROLLED CARBON MONOXIDE
EMISSION FACTORS FOR IRON
AND STEEL MILLS3
EMISSION FACTOR RATING: C
Source
kg/Mg
Ib/ton
Sintering windbox
Basic oxygen furnace
Electric arc furnace
22
69
9
44
138
18
, Reference 5.
of finished sinter.
7.5-8
EMISSION FACTORS
5/83
-------
References for Section 7.5
1. H. E. McGannon, ed. , The Making, Shaping and Treating of Steel, U. S.
Steel Corporation, Pittsburgh, PA, 1971.
2. T. A. Cuscino, Jr., Particulate Emission Factors Applicable to the
Iron and Steel Industry, EPA-450/4-79-029, U. S. Environmental Protec-
tion Agency, Research Triangle Park, NC, September 1979.
3. R. Bohn, et al. , Fugitive Emissions from Integrated Iron and Steel
Plants, EPA-600/2-78-050, U. S. Environmental Protection Agency,
Research Triangle Park, NC, March 1978.
4. C. Cowherd, Jr., et al. , Iron and Steel Plant Open Source Fugitive
Emission Evaluation, EPA-600/2-79-103, U. S. Environmental Protection
Agency, Research Triangle Park, NC, May 1979.
5. Control Techniques for Carbon Monoxide Emissions from Stationary
Sources, AP-65, U. S. Department of Health, Education and Welfare,
Washington, DC, March 1970.
5/83 Metallurgical Industry 7.5-9
-------
7.6 PRIMARY LEAD SMELTING
1-3
7.6.1 Process Description
Lead is usually found naturally as a sulfide ore containing small
amounts of copper, iron, zinc and other trace elements. It is normally
concentrated at the mine from an ore of 3 to 8 percent lead to an ore
concentrate of 55 to 70 percent lead, containing from 13 to 19 percent,
by weight, free and uncombined sulfur. A typical flow sheet for the
production of lead metal from ore concentrate is shown in Figure 7.6-1.
Processing involves three major steps:
- Sintering, in which the concentrated lead and sulfur are
oxidized to produce lead oxide and sulfur dioxide. (Simulta-
neously, the charge concentrates, recycled sinter, sand and other
inert materials are agglomerated to form a dense, permeable
substance called sinter.)
- Reducing the lead oxide contained in the sinter to produce
molten lead bullion.
- Refining the lead bullion to eliminate any impurities.
7.6.1.1 Sintering - Sinter is produced by a sinter machine, a contin-
uous steel pallet cpnveyor belt moved by gears and sprockets. Each
pallet consists of perforated or slotted grates, beneath which are
windboxes connected to fans that provide a draft through the moving
sinter charge. Depending on the direction of this draft, the sinter
machine is either of the updraft or downdraft type. Except for the
draft direction, however, all machines are similar in design,
construction and operation.
The sintering reaction is autogenous, occuring at a temperature of
approximately 1800°F (1000°C):
2PbS + 302 -»• 2PbO + 2S02 (1)
Operating experience has shown that system operation and product quality
are optimum when the sulfur content of the sinter charge is between 5
and 7 percent by weight. To maintain this desired sulfur content,
sulfide-free fluxes such as silica and limestone, plus large amounts of
recycled sinter and smelter residues, are added to-the mix. The quality
of the product sinter is usually determined by its Ritter Index hardness,
which is inversely proportional to the sulfur content. Hard quality
sinter (low sulfur content) is preferred, because it resists crushing
during discharge from the sinter machine. Undersized sinter usually
results from insufficient desulfurization and is recycled for further
processing.
2/80 Metallurgical Industry 7.6-1
-------
Of the two kinds of sintering machines used, the updraft design is
superior for many reasons. First, the sinter bed thickness is more
permeable (and hence can be larger), thereby permitting a higher pro-
duction rate than that of a downdraft machine of similar dimensions.
Secondly, the small amounts of elemental lead that form during sintering
will solidify at their point of formation in updraft machines, whereas,
in downdraft operation, the metal tends to flow downward and collect on
the grates or at the bottom of the sinter charge, thus causing increased
pressure drop and attendant reduced blower capacity. In addition, the
updraft system exhibits the capability of producing sinter of higher
lead content and requires less maintenance than the downdraft machine.
Finally, and most important from an air pollution control standpoint,
updraft sintering can produce a single strong SC>2 effluent stream from
the operation, by use of weak gas recirculation. This, in turn, permits
more efficient and economical use of control methods such as sulfuric
acid recovery devices.
7.6.1.2 Reduction - Lead reduction is carried out in a blast furnace,
basically a water jacketed shaft furnace supported by a refractory base.
Tuyeres, through which combustion air is admitted under pressure, are
located near the bottom and are evenly spaced on either side of the
furnace .
The furnace is charged with a mixture of sinter (80 - 90 percent of
charge) , metallurgical coke (8 - 14 percent of charge) , and other
materials, such as limestone, silica, litharge, slag-forming constit-
uents, and various recycled and cleanup materials. In the furnace, the
sinter is reduced to lead bullion by reactions (2) through (6).
PbO -f CO -»- Pb + C02 (2)
C + 02 •* C02 (3)
C + C02 -> 2CO (4)
2PbO + PbS ->• 3Pb + SO (5)
+ PbS -> 2Pb + 2S0 (6)
Carbon monoxide and heat required for reduction are supplied by the
combustion of coke. Most of the impurities are eliminated in the slag.
Solid products from the blast furnace generally separate into four
layers: speiss, the lightest material (basically arsenic and antimony),
matte (copper sulf ide and other metal sulf ides) , slag (primarily
silicates), and lead bullion. The first three layers are combined as
slag, which is continually collected from the furnace and either processed
at the smelter for its metal content or shipped to treatment facilities.
r.6-2 EMISSION FACTORS 2/80
-------
Sulfur oxides are also generated in blast furnaces from small
quantities of residual lead sulfide and lead sulfates in the sinter
feed. The quantity of these emissions is a function not only of the
residual sulfur content in the sinter, but also of the amount of sulfur
that is captured by copper and other impurities in the slag.
Rough lead bullion from the blast furnace usually requires pre-
liminary treatment (dressing) in kettles before undergoing refining
operations. First, the bullion is cooled to 700 to 800°F (370 - 430°C).
Copper and small amounts of sulfur, arsenic, antimony and nickel are
removed from solution, collecting on the surface as a dross. This
dross, in turn, is treated in a reverberatory furnace where the copper
and other metal impurities are further concentrated before being routed
to copper smelters for their eventual recovery. Drossed lead bullion is
treated for further copper removal by the addition of sulfurbearing
material and zinc, and/or aluminum, to lower the copper content to
approximately 0.01 percent.
7.6.1.3 Refining - The third and final phase of smelting, the refining
of the bullion in cast iron kettles, occurs in five steps:
- Removal of antimony, tin and arsenic.
- Removal of precious metals by Parke's Process, in which zinc
combines with gold and silver to form an insoluble intermetallic at
operating temperatures.
- Vacuum removal of zinc.
- Removal of bismuth using the Betterson Process, which is the
addition of calcium and magnesium to form an insoluble compound
with the bismuth that is skimmed from the kettle.
- Removal of remaining traces of metal impurities by addition
of NaOH and NaN03.
The final refined lead, commonly of 99.990 to 99.999 percent purity,
is then cast into 100 pound pigs for shipment.
1 2
7.6.2 Emissions and Controls '
Each of the three major lead smelting process steps generates
substantial quantities of particulates and/or sulfur dioxide.
Nearly 85 percent of the sulfur present in the lead ore concentrate
is eliminated in the sintering operation. In handling process offgases,
either a single weak stream is taken from the machine hood at less than
2 percent 862, or two streams are taken, one strong stream (5-7
percent 802) from the feed end of the machine and one weak stream (<0.5
percent 862) from the discharge end. Single stream operation has been
2/80 M<>lallur
-------
used when there is little or no market for recovered sulfur, so that the un-
controlled weak SC>2 stream is emitted to the atmosphere. When sulfur removal
is required, however, dual stream operation is preferred. The strong stream
is sent to a sulfuric acid plant, and the weak stream is vented to the atmos-
phere after removal of particulates.
TABLE 7.6-1. EMISSION FACTORS FOR PRIMARY LEAD SMELTING
PROCESSES WITHOUT CONTROLSa
EMISSION FACTOR RATING: B
Total
Particulates
Process
Ore crushing"
Sintering (updraft)c
Blast furnaced
Dross reverberatory
furnace6
kg/Mg
1.0
106.5
180.5
10.0
Ib/ton
2.0
213.0
361.0
20.0
Sulfur dioxide Lead
kg/Mg Ib/ton kg/Mg
0.15
275.0 550.0 87
(4.2-170)
22.5 45.0 29
(8.7-50)
Neg Neg 2.4
(1.3-3.5)
Ib/ton
0.3
174
(8.4-340)
59
(17.5-100)
4.8
(2.6-7.0)
Materials handlingf 2.5 5.0
aOre crushing emission factors expressed as kg/Mg (Ib/ton) of crushed ore. All other
emission factors expressed as kg/Mg (Ib/ton) of lead product. Dash indicates no
available data.
bReferences 2, 13.
^References 1, 4-6, 11, 14-17, 21-22.
^References 1-2, 7, 12, 14, 16-17, 19.
^References 2, 11-12, 14, 18, 20.
^Reference 2.
When dual gas stream operation is used with updraft sinter machines, the
weak gas stream can be recirculated through the bed to mix with the strong gas
stream, resulting in a single stream with an S02 concentration of about 6 per-
cent. This technique has the overall effect of decreasing machine production
capacity, but permits a more convenient and economical recovery of the 862
by sulfuric acid plants and other control methods.
Without weak gas recirculation, the latter portion of the sinter machine
acts as a cooling zone for the sinter and, consequently, assists in the reduc-
tion of dust formation during product discharge and screening. However,
when recirculation is used, the sinter is usually discharged in a relatively
hot state, 400 - 500° C (745 to 950° F), with an attendant increase in partic-
ulates. Methods for reducing these dust quantities include recirculation of
off gases through the sinter bed, relying upon the filtering effect of the
bed or the ducting of gases from the discharge through a particulate collection
device and then to the atmosphere. Because reaction activity has ceased in
the discharge area, these latter gases contain little
7.6-4 EMISSION FACTORS 12/81
-------
The particulate emissions from sinter machines range from 5 to 20
percent of the concentrated ore feed. When expressed in terms of
product weight, a typical emission is estimated to be 213 Ib/ton (106.5
kg/MT) of lead produced. This value, along with other particulate and
S02 factors, appears in Table 7.6-1.
Table 7.6-2. PARTICLE SIZE DISTRIBUTION OF FLUE DUST
FROM UPDRAFT SINTERING MACHINES
Size (ym)
20 - 40
10 - 20
5-10
<5
Percent by weight
15 - 45
9-30
4-19
1-10
Typical material balances from domestic lead smelters indicate that
about 15 percent of the sulfur in the ore concentrate fed to the sinter
machine is eliminated in the blast furnace. However, only half of this
amount (about 7 percent of the total sulfur in the ore) is emitted as
S02. The remainder is captured by the slag. The concentration of this
S02 stream can vary from 500 to 2500 ppm, by volume (1.4 - 7.2 g/m3),
depending on the amount of dilution air injected to oxidize the carbon
monoxide and to cool the stream before baghouse particulate removal.
Particulate emissions from blast furnaces contain many different
kinds of material, including a range of lead oxides, quartz, limestone,
iron pyrites, iron-lime-silicate slag, arsenic, and other metal-containing
compounds associated with lead ores. These particles readily agglom-
erate and are primarily submicron in size, difficult to wet, and cohesive.
They will bridge and arch in hoppers. On the average, this dust loading
is quite substantial (see Table 7.6-1).
Virtually no sulfur dioxide emissions are associated with the
various refining operations. However, a small amount of particulate is
generated by the dross reverberatory furnace, about 20 Ib/ton (10 kg/MT)
of lead.
Finally, minor quantities of particulates are generated by ore
crushing and materials handling operations. These emission factors are
also presented in Table 7.6-1.
Table 7.6-2 is a listing of size distributions of flue dust from
updraft sintering machine effluent. Though these are not fugitive
emissions, the size distributions may closely resemble those of the
fugitive emissions. Particulate fugitive emissions from the blast
furnace consist basically of lead oxides, 92 percent of which are less
than 4 ym in size. Uncontrolled emissions from a lead dross rever-
beratory furnace are mostly less than 1 ym, and this may also be the
case with the fugitive emissions.
2/80 Metallurgical Industry 7.6-5
-------
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r.6-6
EMISSION FACTORS
2/80
-------
Table 7.6-4. POTENTIAL FUGITIVE EMISSION FACTORS FOR PRIMARY
LEAD SMELTING PROCESSES WITHOUT CONTROLS3'b
EMISSION FACTOR RATING: E
Particulates
Process Ib/ton kg/MT
Ore mixing and pelletizing (crushing) 2.26 1.13
Car charging (conveyor loading and
transfer) of sinter 0.50 0.25
Sinter machine leakage0 0.68 0.34
Sinter return handling 9.00 4.50
Sinter machine discharge, sinter crushing
Q
and screening 1.50 0.75
Sinter transfer to dump area 0.20 0.10
Sinter product dump area 0.01 0.005
Blast furnace (charging, blow condition,
tapping) 0.16 0.08
Lead pouring to ladle, transferring, and
slag pouring
Slag cooling
Zinc fuming furnace vents
Dross kettle
Reverberatory furnace leakage
Silver retort building
Lead casting
0.93
0.47
4.60
0.48
3.00
1.80
0.87
0.47
0.24
2.30
0.24
1.50
0.90
0.44
a
All factors are expressed in units per end product lead produced,
except sinter operations, which are expressed in units per sinter or
, sinter handled/transferred/charged.
Reference 8, except where noted.
References 9 and 10. Engineering judgement using steel sinter machine
, leakage emission factor.
Reference 2.
Q
Reference 2. Engineering judgement, estimated to be half the magnitude
of lead pouring and ladling -operations.
2/80 Metallurgical Industry 7.6-1
-------
Emission controls on lead smelter operations are for particulates
and sulfur dioxide. The most commonly employed high efficiency parti-
culate control devices are fabric filters and electrostatic precip-
itators, which often follow centrifugal collectors and tubular coolers
(pseudogravity collectors). Three of the 6 lead smelters presently
operating in the United States use single absorption sulfuric acid
plants for control of sulfur dioxide emissions from sinter machines and,
occasionally, from blast furnaces. Single stage plants can attain SO
levels of 2000 ppm (5.7 g/m3), and dual stage plants can attain levels
of 550 ppm (1.6 g/m3). Typical efficiencies of dual stage sulfuric acid
plants in removing sulfur oxides can exceed 99 percent. Other techni-
cally feasible S02 control methods are elemental sulfur recovery plants
and dimethylaniline (DMA) and ammonia absorption processes. These
methods and their representative control efficiencies are listed in
Table 7.6-3.
References for Section 7.6
1. Charles Darvin and Fredrick Porter, Background Information for New
Source Peformance Standards: Primary Copper, Zinc, and Lead
Smelters, Volume I, EPA-450/2-74-002a, U.S. Environmental
Protection Agency, Research Triangle Park, NC, October 1974.
2. A. E. Vandergrift, et al., Handbook of Emissions, Effluents, and
Control Practices for Stationary Particulate Pollution Sources,
Three volumes, HEW Contract No. CPA 22-69-104, Midwest Research
Institute, Kansas City, MO, November 1970 - May 1971.
3. A. Worcester and D. H. Beilstein, "The State of the Art: Lead
Recovery", Presented at the 10th Annual Meeting of the Metallurgical
Society, AIME, New York, March 1971.
4. T. J. Jacobs, "Visit to St. Joe Minerals Corporation Lead Smelter,
Herculaneum, MO", Memorandum to Emission Standards and Engineering
Division, Office of Air Quality Planning and Standards, U.S.
Environmental Protection Agency, Research Triangle Park, NC,
October 21, 1971.
5. T. J. Jacobs, "Visit to Amax Lead Company, Boss, MO", Memorandum to
Emission Standards and Engineering Division, Office of Air Quality
Planning and Standards, U.S. Environmental Protection Agency,
Research Triangle Park, NC, October 28, 1971.
6. Written Communication from R. B. Paul, American Smelting and
Refining Co., Glover, MO, to Regional Administrator, U.S.
Environmental Protection Agency, Kansas City, MO, April 3, 1973.
f.6-8 EMISSION FACTORS 2/80
-------
7. Emission Test No. 72-MM-14, Office of Air Quality Planning and Standards,
U. S. Environmental Protection Agency, Research Triangle Park, NC, May
1972.
8. Silver Valley/Bunker Hill Smelter Environmental Investigation (Interim
Report), EPA Contract No. 68-02-1343, PEDCo Environmental, Specialists,
Inc., Cincinnati, OH, February 1975.
9. R. E. Iversen, "Meeting with U. S. Environmental Protection Agency and
AISI on Steel Facility Emission Factors", Memorandum, Office of Air
Quality Planning and Standards, U. S. Environmental Protection Agency,
Research Triangle Park, NC, June 7, 1976.
10. G. E. Spreight, "Best Practical Means in the Iron and Steel Industry",
The Chemical Engineer, London, 271;132-139, March 1973.
11. Control Techniques for Lead Air Emissions, EPA-450/2-77-012, U. S. En-
vironmental Protection Agency, Research Triangle Park, NC, January 1978.
12. Systems Study for Control of Emissions: Primary Nonferrous Smelting In-
dustry, U. S. Department of Health, Education and Welfare, Washington,
DC, June 1969.
13. Environmental Assessment of the Domestic Primary Copper, Lead, and Zinc
Industry, EPA Contract No. 68-02-1321, PEDCo-Environmental Specialists,
Inc., Cincinnati, OH, September 1976.
14. H. R. Jones, Pollution Control in the Nonferrous Metals Industry, Noyes
Data Corporation, Park Ridge, NJ, 1972.
15. L. J. Duncan and E. L. Keitz, "Hazardous Particulate Pollution from Typi-
cal Operations in the Primary Nonferrous Smelting Industry", presented
at the 67th Annual Meeting of the Air Pollution Control Association,
Denver, CO, June 1974.
16. E. P. Shea, Source Sampling Report; Emissions from Lead Smelters, EPA
Contract No. 68-02-0228, Midwest Research Institute, Kansas City, MO,
1973.
17. R. C. Hussy, Source Testing; Emissions from a Primary Lead Smelter, EPA
Contract No. 68-02-0228, Midwest Research Institute, Kansas City, MO,
1973.
18. Emission Test No. 73-PLD-l, Office of Air Quality Planning and Standards,
U. S. Environmental Protection Agency, Research Triangle Park, NC, Octo-
ber 1973.
19. Interim Report on Control Techniques for Lead Air Emissions, Development
of Lead Emission Factors, and 1975 National Lead Emission Inventory, EPA
Contract No. 68-02-1375, PEDCo-Environmental Specialists, Inc., Cincin-
nati, OH, June 1976.
12/81 Metallurgical Industry 7.6-9
-------
20. S. Wyatt, et al., Preferred Standards Path Analysis on Lead Emissions
from Stationary Sources, Office of Air Quality Planning and Standards,
Research Triangle Park, NC, September 1974.
21. A. E. Vandergrift, et al., Particulate Pollutant System Study - Mass
Emissions, PB-203-128, PB-203-522 and PB-203-521, U. S. Environmental
Protection Agency, Research Triangle Park, NC, May 1971.
22. V. S. Katari, et al., Trace Pollutant Emissions from the Processing of
Metallic Ores, EPA-650/2-74-115, U. S. Environmental Protection Agency,
Research Triangle Park, NC, October 1974.
7.6-10 EMISSION FACTORS 12/81
4
-------
7.7 ZINC SMELTING
7.7.1 Process Description1*^
As stated previously, most domestic zinc comes from zinc and lead ores.
Another important source of raw material for zinc metal has been zinc oxide
from fuming furnaces. For efficient recovery of zinc, sulfur must be removed
from concentrates to a level of less than 2 percent. This is done by fluid-
ized beds or multiple-hearth roasting occasionally followed by sintering.
Metallic zinc can be produced from the roasted ore by the horizontal or
vertical retort process or by the electrolytic process if a high-purity zinc
is needed.
7.7.2 Emissions and Controls1»2
Dust, fumes, and sulfur dioxide are emitted from zinc concentrate roast-
ing or sintering operations. Particulates may be removed by electrostatic
precipitators or baghouses. Sulfur dioxide may be converted directly into
sulfuric acid or vented. Emission factors for zinc smelting are presented
in Table 7.7-1.
TABLE 7.7-1. EMISSION FACTORS FOR PRIMARY ZINC
SMELTING WITHOUT CONTROLS3
EMISSION FACTOR RATING: B
Type of operation Particulates Sulfur oxides Lead*3
kg/Mg Ib/ton kg/Mg Ib/ton kg/Mg Ib/ton
Ore unloading, storage
and transfer
Roasting (multiple-
hearth)0
Sinteringd
Horizontal retorts^
Vertical retorts^
Electrolytic process
-
60
45
4
50
1.5
_ - -
120 550 1100
90 e e
8 - -
100
3
1.95
(1-2.9)
19.25
(13.5-25)
1.2
2.25
(2-2.5)
—
3.85
(2.0-5.7)
38.5
(27-50)
2.4
4.5
(4-5)
~
Approximately 2 unit weights of concentrated ore are required to produce
1 unit weight of zinc metal. Emission factors expressed as units per unit
weight of concentrated ore produced. Dash indicates no available data.
^References 1-3.
References 4-5.
^References 5-6.
elncluded in SO, losses from roasting.
fReference 3.
12/81 Metallurgical Industry 7.7-1
-------
References for Section 7.7
1. Control Techniques for Lead Air Emissions, EPA-450/2-77-012, U. S. Envi-
ronmental Protection Agency, Research Triangle Park, NC, December 1977.
2. H. R. Jones, Pollution Control in the Nonferrous Metals Industry, Noyes
Data Corporation, Park Ridge, NJ, 1972.
3. G. B. Carne, Control Techniques for Lead Emissions, Draft Report, U. S.
Environmental Protection Agency, Research Triangle Park, NC, February
1971.
4. R. L. Duprey, Compilation of Air Pollutant Emission Factors, U. S. DHEW,
PHS, National Center for Air Pollution Control, Durham, NC, PHS Pub-
lication Number 999-AP-42, 1968, p. 26-28.
5. A. Stern (ed), "Sources of Air Pollution and Their Control, Air Pollution,
Vol III, 2nd Ed., New York, NY, Academic Press, 1968, p. 182-186.
6. G. Sallee, Private communication on Particulate Pollutant Study, Midwest
Research Institute, Kansas City, MO, prepared for National Air Pollution
Control Administration, Durham, NC, under Contract Number 22-69-104,
June 1970.
7. Systems Study for Control of Emissions in the Primary Nonferrous Smelting
Industry, 3 Volumes, San Francisco, Arthur G. McKee and Company, June
1969.
7.7-2 EMISSION FACTORS 12/81
-------
7.8 SECONDARY ALUMINUM OPERATIONS
*
7.8.1 General
Secondary aluminum operations involve the cleaning, melting,
refining and pouring of aluminum recovered from scrap. The processes
used to convert scrap aluminum to secondary aluminum products such
as lightweight metal alloys for industrial castings and ingots are
presented in Figure 7.8-1. Production involves two general classes
of operation, scrap treatment and smelting/refining.
Scrap treatment involves receiving, sorting and processing
scrap to remove contaminants and to prepare the material for smelting.
Processes based on mechanical, pyrometallurgical and hydrometal-
lurgical techniques are used, and those employed are selected to
suit the type of scrap processed.
The smelting/refining operation generally involves the following
steps:
• charging • mixing
• melting • demagging
• fluxing • degassing
• alloying • skimming
• pouring
All of these steps may be involved in each operation, with process
distinctions being in the furnace type used and in emission charac-
teristics. However, as with scrap treatment, not all of these
steps are necessarily incorporated into the operations at a
particular plant. Some steps may be combined or reordered, depending
on furnace design, scrap quality, process inputs and product
specifications.
Scrap treatment - Purchased aluminum scrap undergoes inspection
upon delivery. Clean scrap requiring no treatment is transported
to storage or is charged directly into the smelting furnace. The
bulk of the scrap, however, must be manually sorted as it passes
along a steel belt conveyor. Free iron, stainless steel, zinc,
brass and oversized materials are removed. The sorted scrap then
goes to appropriate scrap treating processes or is charged directly
to the smelting furnace.
Sorted scrap is conveyed to a ring crusher or hammer mill,
where the material is shredded and crushed, with the iron torn away
from the aluminum. The crushed material is passed over vibrating
screens to remove dirt and fines, and tramp iron is removed by
magnetic drums and/or belt separators. Baling equipment compacts
bulky aluminum scrap into 1x2 meter (3x6 foot) bales.
4/81 Metallurgical Industry 7.8-1
-------
7.8-2
EMISSION FACTORS
4/81
-------
Pure aluminum cable with steel reinforcement or insulation is
cut by alligator type shears and granulated or further reduced in
hammer mills, to separate the iron core and the plastic coating
from the aluminum. Magnetic processing accomplishes iron removal,
and air classification separates the insulation.
Borings and turnings, in most cases, are treated to remove
cutting oils, greases, moisture and free iron. The processing
steps involved are (a) crushing in hammer mills or ring crushers,
(b) volatilizing the moisture and organics in a gas or oil fired
rotary dryer, (c) screening the dried chips to remove aluminum
fines, (d) removing iron magnetically and (e) storing the clean
dried borings in tote boxes.
Aluminum can be recovered from the hot dross discharged from a
refining furnace by batch fluxing with a salt/cryolite mixture in a
mechanically rotated, refractory lined barrel furnace. The metal
is tapped periodically through a hole in its base. Secondary
aluminum recovery from cold dross and other residues from primary
aluminum plants is carried out by means of this batch fluxing in a
rotary furnace. In the dry milling process, cold aluminum laden
dross and other residues are processed by milling, screening and
concentrating to obtain a product containing at least 60-70 percent
aluminum. Ball, rod or hammer mills can be used to reduce oxides
and nonmetallies to fine powders. Separation of dirt and other
unrecoverables from the metal is achieved by screening, air
classification and/or magnetic separation.
Leaching involves (a) wet milling, (b) screening, (c) drying
and (d) magnetic separation to remove fluxing salts and other non-
recoverables from drosses, skimmings and slags. First, the raw
material is fed into a long rotating drum or an attrition or ball
mill where soluble contaminants are leached. The washed material
is then screened to remove fines and dissolved salts and is dried
and passed through a magnetic separator to remove ferrous materials.
The nonmagnetics then are stored or charged directly to the smelting
furnace.
In the roasting process, carbonaceous materials associated
with aluminum foil are charred and then separated from the metal
product.
Sweating is a pyrometallurgical process used to recover
aluminum from high iron content scrap. Open flame reverberatory
furnaces may be used. Separation is accomplished as aluminum and
other low melting constituents melt and trickle down the hearth,
through a grate and into air cooled molds or collecting pots. This
product is termed "sweated pig". The higher melting materials,
including iron, brass and oxidation products formed during the
sweating process, are periodically removed from the furnace.
4/81 Metallurgical Industry 7.8-3
-------
Smelting/refining - In reverberatory (chlorine) operations,
reverberatory furnaces are commonly used to convert clean sorted
scrap, sweated pigs or some untreated scrap to specification ingots,
shot or hot metal. The scrap is first charged to the furnace by
some mechanical means, often through charging wells designed to
permit introduction of chips and light scrap below the surface of a
previously melted charge ("heel"). Batch processing is generally
practiced for alloy ingot production, and continuous feeding and
pouring are generally used for products having less strict
specifications.
Cover fluxes are used to prevent air contact with and consequent
oxidation of the melt. Solvent fluxes react with nonmetallics such
as burned coating residues and dirt to form insolubles which float
to the surface as part of the slag.
Alloying agents are charged through the forewell in amounts
determined by product specifications. Injection of nitrogen or
other inert gases into the molten metal can be used to aid in
raising dissolved gases (typically hydrogen) and intermixed solids
to the surface.
Demagging reduces the magnesium content of the molten charge
from approximately 0.3 to 0.5 percent (typical scrap value) to
about 0.1 percent (typical product line alloy specification). When
demagging with chlorine gas, chlorine is injected under pressure
through carbon lances to react with magnesium and aluminum as it
bubbles to the surface. Other chlorinating agents, or fluxes, are
sometimes used, such as anhydrous aluminum chloride or chlorinated
organics.
In the skimming step, contaminated semisolid fluxes (dross,
slag or skimmings) are ladled from the surface of the melt and
removed through the forewell. The melt is then cooled before
pouring.
The reverberatory (fluorine) process is similar to the
reverberatory (chlorine) smelting/refining process, except that
aluminum fluoride (AlFn) is employed in the demagging step instead
of chlorine. The A1F-} reacts with magnesium to produce molten
metal aluminum and solid magnesium fluoride salt which floats to
the surface of the molten aluminum and is skimmed off.
The crucible smelting/refining process is used to melt small
batches of aluminum scrap, generally limited to 500 kg (1000 Ib) or
less. The metal treating process steps are essentially the same as
those of reverberatory furnaces.
The induction smelting/refining process is designed to produce
hardeners by blending pure aluminum and hardening agents in an
electric induction furnace. The process steps include charging
scrap to the furnace, melting, adding and blending the hardening
agent, skimming, pouring and casting into notched bars.
7.8-4 EMISSION FACTORS 4/81
-------
7.8.2 Emissions and Controls
Table 7.8-1 presents emission factors for the principal
emission sources in secondary aluminum operations. Although each
step in scrap treatment and smelting/refining is a potential source
of emissions, emissions from most of the processing operations are
either not characterized here or emit only small amounts of
pollutants.
Crushing/ screening produces small amounts of metallic and
nonmetallic dust. Baling operations produce particulate emissions,
primarily dirt and alumina dust resulting from aluminum oxidation.
Shredding/classifying also emits small amounts of dust. Emissions
from these processing steps are normally uncontrolled.
Burning/drying operations emit a wide range of pollutants.
Afterburners are used generally to convert unburned hydrocarbons to
C02 and H20. Other gases potentially present, depending on the
composition of the organic contaminants, include chlorides, fluo-
rides and sulfur oxides. Oxidized aluminum fines blown out of the
dryer by the combustion gases comprise particulate emissions. Wet
scrubbers are sometimes used in place of afterburners.
Mechanically generated dust from the rotating barrel dross
furnace constitutes the main air emission of hot dross processing.
Some fumes are produced from the fluxing reactions. Fugitive emis-
sions are controlled by enclosing the barrel in a hood system and
by ducting the stream to a baghouse. Furnace off gas emissions,
mainly fluxing salt fume, are controlled by a venturi scrubber.
In dry milling, large amounts of dust are generated from the
crushing, milling, screening, air classification and materials
transfer steps. Leaching operations may produce particulate emis-
sions during drying. Emissions from roasting are particulates from
the charring of carbonaceous materials.
Emissions from sweating furnaces vary with the feed scrap
composition. Smoke may result from incomplete combustion of organic
contaminants (e.g., rubber, oil and grease, plastics, paint, card-
board, paper) which may be present. Fumes can result from oxidation
of magnesium and zinc contaminants and from fluxes in recovered
drosses and skims.
Atmospheric emissions from reverberatory (chlorine) smelting/
refining represent a significant fraction of the total particulate
and gaseous effluents generated in the secondary aluminum industry.
Typical furnace effluent gases contain combustion products, chlorine,
hydrogen chloride and metal chlorides of zinc, magnesium and aluminum,
aluminum oxide and various metals and metal compounds, depending on
the quality of scrap charged. Particulate emissions from one
secondary aluminum smelter have a size distribution of D^Q « 0.4H.
4/81 Metallurgical Industry 7.8-5
-------
TABLE 7.8-1. PARTICIPATE EMISSION FACTORS FOR SECONDARY
ALUMINUM OPERATIONS3
Electrostatic Emission
Uncontrolled
Operation
Sweating furnace
Smelting
b
Crucible furnace
Reverberatory furnace
Chlorination station
kg/Mg
7.25
0.95
; 2.15
500
Ib/ton
14.5
1.9
4.3
1000
Baghouse precipitator Factor
kg/Mg
1.65
_
0.65e
25
Ib/ton kg/Mg
3.3
-
1.3e 0.65
50
Ib/ton Rating
C
_ r
1.3 B
B
aReference 2. Emission factors expressed as units per unit weight of metal
.processed. Factors apply only to Al metal recovery operations.
Based on averages of two source tests.
Based on averages of ten source tests. Standard deviation of uncontrolled
emission factor is 17.5 kg/Mg (3.5 Ib/ton), that of controlled factor is 0.15 kg/Mg
d(0.3 Ib/ton).
Expressed as kg/Mg (Ib/ton) of chlorine used. Based on averages of ten source tests.
Standard deviation of uncontrolled emission factor is 215 kg/Mg (430 Ib/ton), of
controlled factor, 18 kg/Mg (36 Ib/ton).
This factor may be lower if a coated baghouse is used.
Emissions from reverberatory (fluorine) smelting/refining are
similar to those from reverberatory (chlorine) smelting/refining.
The use of AlF-j rather than chlorine in the demagging step reduces
demagging emissions. Fluorides are emitted as gaseous fluorides
(hydrogen fluoride, aluminum and magnesium fluoride vapors, and
silicon tetrafluoride) or as dusts. Venturi scrubbers are usually
used for fluoride emission control.
References for Section 7.8
1. W.M. Coltharp, et al., Multimedia Environmental Assessment of
the Secondary Nonferrous Metal Industry, Draft Final Report,
2 vols., EPA Contract No. 68-02-1319, Radian Corporation,
Austin, TX, June 1976.
2. W.F. Hammond and S.M. Weiss, Unpublished report on air
contaminant emissions from metallurgical operations in Los
Angeles County, Los Angeles County Air Pollution Control
District, July 1964.
3. R.A. Baker, et al., Evaluation of a Coated Baghouse at a
Secondary Aluminum Smelter, EPA Contract No. 68-02-1402,
Environmental Science and Engineering, Inc., Gainesville, FL,
October 1976.
4. Air Pollution Engineering Manual, 2d Edition, AP-40, U.S.
Environmental Protection Agency, Research Triangle Park, NC,
May 1973. Out of Print.
7.8-6 EMISSION FACTORS 4/81
I
-------
5. E.J. Petkus, "Precoated Baghouse Control for Secondary Aluminum
Smelting", Presented at the 71st Annual Meeting of the Air
Pollution Control Association, Houston, TX, June 1978.
4/81 Metallurgical Industry 7.8-7
-------
7.9 SECONDARY COPPER SMELTING AND ALLOYING
7.9.1 Process Description1'2
The secondary copper industry processes scrap metals for the recovery of copper. Products include
refined copper or copper alloys in forms such as ingots, wirebar, anodes, and shot. Copper alloys are combinations
of copper with other materials, notably, tin, zinc, and lead. Also, for special applications, combinations include
such metals as cobalt, manganese, iron, nickel, cadmium, and beryllium and nonmetals such as arsenic and
silicon.
The principal processess involved in copper recovery are scrap metal pretreatment and smelting.
Pretreatment includes cleaning and concentration to prepare the material for the smelting furnace. Smelting
involves heating and treating the scrap to achieve separation and purification of specific metals.
The feed material used in the recovery process can be any metallic scrap containing a useful amount of
copper, bronze (copper and tin), or brass (copper and zinc). Traditional forms are punchings, turnings and
borings, defective or surplus goods, metallurgical residues such as slags, skimmings, and drosses, and obsolete,
worn out, or damaged articles including automobile radiators, pipe, wire, bushings, and bearings.
The type and quality of the feed material determines the processes the smelter will use. Due to the large
variety of possible feed materials available, the method of operation varies greatly between plants. Generally, a
secondary copper facility deals with less pure raw materials and produces a more refined product, whereas brass
and bronze alloy processors take cleaner scrap and do less purification and refining. Figure 7.9-1 is a flowsheet
depicting the major processes that can be expected in a secondary copper smelting operation. A brass and bronze
alloying operation is shown in Figure 7.9-2.
Pretreatment of the feed material can be accomplished using several different procedures, either
separately or in combination. Feed scrap is concentrated by manual and mechanical methods such as sorting,
stripping, shredding, and magnetic separation. Feed scrap is sometimes briquetted in a hydraulic press.
Pyrometallurgical pretreatment may include sweating, burning of insulation (especially from wire scrap), and
drying (burning off oil and volatiles) in rotary kilns. Hydrometallurgical methods include flotation and leaching,
with chemical recovery.
In smelting, low-grade scrap is melted in a cupola furnace, producing "black copper" (70 to 80 percent Cu)
and slag; these are often separated in a reverberatory furnace, from which the melt is transferred to a converter or
electric furnace to produce "blister" copper, which is 90 to 99 percent Cu.
Blister copper may be poured to produce shot or castings, but is often further refined electrolytically or by
fire refining. The fire-refining process is essentially the same as that described for the primary copper smelting
industry (Section 7.3.1). The sequence of events in fire-refining is (1) charging, (2) melting in an oxidizing
atmosphere, (3) skimming the slag, (4) blowing with air or oxygen, (5) adding fluxes, (6) "poling" or otherwise
providing a reducing atmosphere, (7) reskimming, and (8) pouring.
To produce bronze or brass rather than copper, an alloying operation is required. Clean, selected bronze
and brass scrap is charged to a melting furnace with alloys to bring the resulting mixture to the desired final
composition. Fluxes are added to remove impurities and to protect the melt against oxidation by air. Air or oxygen
may be blown through the melt to adjust the composition by oxidizing excess zinc.
With zinc-rich feed such as brass, the zinc oxide concentration in the exhaust gas is sometimes high
enough to make recovery for its metal value desirable. This process is accomplished by vaporizing the zinc from
the melt at high temperature and capturing the oxide downstream in a process baghouse.
Metallurgical Industry 7.9-1
4
•f
-------
ENTERING THE SYSTEM
LEAVING THE SYSTEM
LOW-GRADE SCRAP
(SLAGS, SKIMMINGS,
DROSSES. CHIPS,
BORINGS)
FUEL
AIR
PYROMETALLURGICAL
PRETREATMENT
(DRYING)
GASES, OUST, METAL OXIDES
•** TO CONTROL EQUIPMENT
TREATED
SCRAP
FLUX »
FUEL »
AIR »
CUPOLA
BLACK 1
COPPER T
CARBON MONOXIDE, PARTICULATE DUST,
». METAL OXIDES, TO AFTERBURNER AND
PARTICULATE CONTROL
SLAG
FLUX-
FUEL-
AIR —
SMELTING FURNACE
(REVERBERATORY)
GASES AND METAL OXIDES
' TO CONTROL EQUIPMENT
SEPARATED
COPPER
SLAG
FLUX-
FUEL-
AIR—
CONVERTER
BLISTER
COPPER
AIR.
FUEL.
REDUCING MEDIUM,
(POLING)
GASES AND METAL OXIDES
' TO CONTROL EQUIPMENT
BLISTER
COPPER
i
CASTINGS AND SHOT
PRODUCTION
SLAG
FIRE REFINING
T
FUGITIVE METAL OXIDES FROM
. POURING TO EITHER HOODING
OR PLANT ENVIRONMENT
GASES, METAL DUST,
'TO CONTROL DEVICE
REFINED
COPPER
7.9-2
7.9-1. Low-grade copper recovery.
EMISSION FACTORS
12,
-------
ENTERING THE SYSTEM
LEAVING THE SYSTEM
HIGH-GRADE SCRAP
(WIRE, PIPE, BEARINGS,
PUNCHINGS, RADIATORS)
MANUAL AND MECHANICAL
PRETREATMENT
(SORTING)
DESIRED
COPPER SCRAP
FUEL
AIR
COPPER
FLUX
FUEL
ALLOY MATERIAL-
IZING, TIN, ETC)
-» FUGITIVE DUST TO ATMOSPHERE
DESIRED BRASS
AND BRONZE SCRAP
>
WIRE Bl
l
FUEL + SW£
AIR +
BRA
BR
MELTING AND
ALLOYING FURNACE
ALLOY
MATERIAL
-*-UNDESIRED SCRAP TO SALE
»- GASES, METAL OXIDES TO
CONTROL EQUIPMENT
• LEAD, SOLDER, BABBITT METAL
•PARTICULATES, HYDROCARBONS,
ALDEHYDES, FLUORIDES, AND
CHLORIDES TO AFTERBURNER
AND PARTICULATE CONTROL
—ft, METAL OXIDES TO
CONTROL EQUIPMENT
—»-SLAG TO DISPOSAL
CASTING
.FUGITIVE METAL OXIDES GENERATED
DURING POURING TO EITHER PLANT
ENVIRONMENT OR HOODING
12/77
7.9-2. High-grade brass and bronze alloying.
Metallurgical Industry
7.9-3
-------
The final step is always casting of the suitably alloyed or refined metal into a desired form, i.e, shot, wirebar,
anodes, cathodes, ingots, or other cast shapes. The metal from the melt is usually poured into a ladle or a small
pot, which serves the functions of a surge hopper and a flow regulator, then into a mold.
7.9.2 Emissions and Controls
The principal pollutants emitted from secondary copper smelting activities are particulate matter in
various forms. Removal of insulation from wire by burning causes particulate emissions of metal oxides and
unburned insulation. Drying of chips and borings to remove excess oils and cutting fluids can cause discharges of
large amounts of dense smoke consisting of soot and unburned hydrocarbons. Particulate emissions from the top
of a cupola furnace consist of metal oxide fumes, dirt, and dust from limestone and coke.
The smelting process utilizes large volumes of air to oxidize sulfides, zinc, and other undesirable consti-
tuents of the feed. This procedure generates much particulate matter in the exit gas stream. The wide variation
among furnace types, charge types, quality, extent of pretreatment, and size of charge is reflected in a broad spec-
trum of particle sizes and variable grain loadings in the escaping gases. One major factor contributing to differ-
ences in emission rates is the amount of zinc present in scrap feed materials; the low-boiling zinc evaporates and
combines with air oxygen to give copious fumes of zinc oxide.
Metal oxide fumes from furnaces used in secondary smelters have been controlled by baghouses,
electrostatic precipitators, or wet scrubbers. Efficiency of control by baghouses may be better than 99 percent,
but cooling systems are needed to prevent the hot exhaust gases from damaging or destroying the bag filters. A
two-stage system employing both water jacketing and radiant cooling is common. Electrostatic precipitators are
not as well suited to this application, having a low collection efficiency for dense particulates such as oxides of
lead and zinc. Wet scrubber installations are also relatively ineffective in the secondary copper industry.
Scrubbers are useful mainly for particles larger than 1 micron, (jum) but the metal oxide fumes generated are
generally submicron in size.
Particulate emissions associated with drying kilns can be similarly controlled. Drying temperatures up to
150° C (300° F) produce relatively cool exhaust gases, requiring no precooling for control by baghouses.
Wire burning generates much particulate matter, largely unburned combustibles. These emissions can be
effectively controlled by direct-flame afterburners, with an efficiency of 90 percent or better if the afterburner
combustion temperature is maintained above 1000° C (1800° F). If the insulation contains chlorinated organics
such as poly vinyl chloride, hydrogen chloride gas will be generated and will not be controlled by the afterburner.
One source of fugitive emissions in secondary smelter operations is charging of scrap into furnaces
containing molten metals. This often occurs when the scrap being processed is not sufficiently compact to allow a
full charge to fit into the furnace prior to heating. The introduction of additional material onto the liquid metal
surface produces significant amounts of volatile and combustible materials and smoke, which can escape through
the charging door. Briquetting the charge offers a possible means of avoiding the necessity of such fractional
charges. When fractional charging cannot be eliminated, fugitive emissions are reduced by turning off the
furnace burners during charging. This reduces the flow of exhaust gases and enhances the ability of the exhaust
control system to handle the emissions.
Metal oxide fumes are generated not only during melting, but also during pouring of the molten metal into
the molds. Other dusts may be generated by the charcoal, or other lining, used in association with the mold.
Covering the metal surface with ground charcoal is a method used to make "smooth-top" ingots. This process
creates a shower or sparks, releasing emissions into the plant environment at the vicinity of the furnace top and
the molds being filled.
Emission factor averages and ranges for six different types of furnaces are presented in Table 7.9-1.
7.9-4 EMISSION FACTORS 12/77
-------
TABLE 7.9-1.
PARTICULATE EMISSION FACTORS FOR FURNACES USED IN SECONDARY
COPPER SMELTING AND ALLOYING PROCESSES*»b
EMISSION FACTOR RATING: B
Participate Lead*1
Control kg/Mg Ib/ton kg/Mg Ib/ton
Furnace and charge type equipment average
range average range
Cupola
Scrap Iron
Insulated copper wire
Scrap copper and brass
Reverberatory
High lead alloy (58%
Lead
Red/yellow brass (15%
Lead
Other alloys (7Z lead)
Copper
Brass and bronze
Rotary
Brass and bronze
Crucible and pot
Brass and bronze
Electric Arc
Copper
Brass and bronze
Electric Induction
None
None
ESPC
None
ESP
None
None
None
None
Baghouse
None
•Baghouse
None
ESP
None
ESP
None
Baghouse
None
Baghouse
0.002
120
.5
15
1.2
30-40
1-1.4
0.003
230
10
70
2.4
60-80
2-2.8
25
6.6
2.5
50
13.2
5.0
2.6
0.2
18
•1.3
150
7
11
0.5
2.5
0.5
5.5
3
0.4-15
0.1-0.3
0.3-35
0.3-2.5
50-250
3-10
1-20
3-10
1-4
0.02-1
2-9
5.1
0.4
36
2.6
300
13
21
1
5
1
11
6
0.8-30
0.3-0.6
0.6-70
0.6-5
100-500
6-19
2-40
6-19
2-8
0.04-2
4-18
Copper
Brass and bronze
None
Baghouse
None
Baghouse
3.5
0.25
10
0.35
-
-
0.3-20
6.01-0.65
7
0.5
20
0.7
-
-
0.5-40
0.01-1.3
-
-
- —
-
aFactors for high lead alloy (58 percent lead), red and yellow brass (15 percent lead), and other
alloys (7 percent lead) produced In the reverberator/ furnace are based on unit weight produced.
All other factors given in terms of raw materials charged to unit. Dash Indicates ho available
information.
bThe information for partlculate in Table 7.9-1 was based on unpublished data furnished by the
following:
Philadelphia Air Management Services, Philadelphia, PA.
New Jersey Department of Environmental Protection, Trenton, NJ.
New Jersey Department of Environmental Protection, Metro Field Office, Springfield, NJ.
New Jersey Department of Environmental Protection, Newark Field Office, Newark, NJ.
New York State Department of Environmental Conservation, New York, NY.
The City of New York Department of Air Resources, New York, NY.
Cook County Department of Environmental Control, Maywood, IL.
Wayne County Department of Health, Air Pollution Control Division, Detroit, MI.
City of Cleveland Department of Public Health and Welfare, Division of Air Pollution
Control, Cleveland, OH.
State of Ohio Environmental Protection Agency, Columbus, OH.
City of Chicago Department of Environmental Control, Chicago, IL.
South Coast Air Quality Management District, Los Angeles, CA.
CESP equals electrostatic preclpltator.
^References 1, 5-6.
10/80
Metallurgical Industry
7.9-5
-------
References for Section 7.9
1. Air Pollution Aspects of Brass and Bronze Smelting and Refining Industry,
U.S. Department of Health, Education and Welfare, National Air Pollution
Control Administration, Raleigh, NC, Publication No. AP-58, November 1969.
2. J. A. Danielson (ed.), Air Pollution Engineering Manual (2nd Ed.), AP-40,
U.S. Environmental Protection Agency, Research Triangle Park, NC, 1973.
Out of Print.
3. Emission Factors and Emission Source Information for Primary and Secondary
Copper Smelters, U.S. Environmental Protection Agency, Research Triangle
Park, NC, Publication No. EPA-450/3-77-051, December 1977.
4. Control Techniques for Lead Air Emissions, EPA-450-2/77-012, U.S. Environ-
mental Protection Agency, Research Triangle Park, NC, December 1977.
5. H. H. Fukubayashi, et al., Recovery of Zinc and Lead fromBrass Smelter
Dust, Report of Investigation No. 7880, Bureau of Mines, U.S. Department
of the Interior, Washington, DC, 1974.
6. "Air Pollution Control in the Secondary Metal Industry", Presented at the
First Annual National Association of Secondary Materials Industries Air
Pollution Control Workshop, Pittsburgh, PA, June 1967.
I
7.9-6 EMISSION FACTORS 12/81
1
-------
7.10 GRAY IRON FOUNDRIES
7.10.1 General
Gray iron foundries produce gray iron castings by melting,
alloying and molding pig iron and scrap iron. The process flow
diagram of a typical gray iron foundry is presented in Figure 7.10-1.
The four major processing operations of the typical gray iron
foundry are raw materials handling, metal melting, mold and core
production, and casting and finishing.
Raw Materials Handling - The raw material handling operations
include the receiving, unloading, storage and conveying of all raw
materials for the foundry. The raw materials used by gray iron
foundries are pig iron, iron and steel scrap, foundry returns,
metal turnings, alloys, carbon additives, coke, fluxes (limestone,
soda ash, fluorspar, calcium carbide), sand, sand additives, and
binders. These raw materials are received in ships, railcars,
trucks and containers, transferred by truck, loaders and conveyers
to both open piles and enclosed storage areas, and then transferred
by similar means from storage to the processes.
Metal Melting - Generally the first step in the metal melting
operations is scrap preparation. Since scrap is normally purchased
in the proper size for furnace feed, scrap preparation primarily
consists of scrap degreasing. This is very important for electric
induction furnaces, as organics on scrap can cause an explosion.
Scrap may be degreased with solvents, by centrifugation or by
combustion in an incinerator or heater, or it may be charged with-
out treatment, as is often the case with cupola furnaces. After
preparation, the scrap, iron, alloy and flux are weighed and charged
to the furnace.
The cupola furnace is the major type of furnace used in the
gray iron industry today. It is typically a vertical refractory
lined cylindrical steel shell, charged at the top with alternate
layers of metal, coke and flux. Larger cupolas are water cooled
instead of refractory lined. Air introduced at the bottom of the
cupola burns the coke to melt the metal charge. Typical melting
capacities range from 0.5 to 14 Mg (1 - 27 tons) per hour, with a
few larger units approaching 50 Mg (100 tons) per hour. Cupolas
can be tapped either continuously or intermittently from a side
tap hole at the bottom of the furnace.
Electric arc furnaces, used to a lesser degree in the gray
iron industry, are large refractory lined steel pots fitted with a
refractory lined roof through which three graphite electrodes are
inserted. The metal charge is heated to melting by electrical arcs
produced by the current flowing between the electrodes and the
charge. Electric arc furnaces are charged with raw material through
the removed lid, by a chute through the lid, or through a door in
4/81 Metallurgical Industry 7.10-1
-------
RAW MATERIALS
UNLOADING, STORAGE,
TRANSFER
• FLUX
• METALLICS
• CARBON SOURCES
• SAND
• BINDER
i— -^HYDROCARBONS
SAND
FUGITIVE
DUST
t
i
' FUMES AND'
FUGITIVE
SCRAP
PREPARATION
AND SMOKE
-»-FURNANCE
VENT
FUGITIVE
DUST
4
MIXING
"• PREPARATION
OUST
ir— -^FUGITIVE
! DUST
MOLD
MAKING
SAND
FURNANCE
•CUPOLA
• ELECTRIC ARC
• INDUCTION
•OTHER
1
• SAND
• BINDER
. -»- FUGITIVE FUMES ,
I AND OUST
TAPPING,
TREATING
r~
i
CORE MAKING
i .----»- FUGITIVE FUMES ,
i AND DUST 1
MOLD POURING,
COOLING
1
CASTING
SHAKEOUT
— — — -fe» EIIPITIVC
DUST
f r
CORE BAKING
-^FUGITIVE
DUST
OVEN VENT
COOLING
CLEANING,
FINISHING
FUMES AND
FUGITIVE
DUST
FUGITIVE
DUST
SHIPPING
Figure 7.10-1. Typical flow diagram of a grey iron foundry.
7.10-2
EMISSION FACTORS
4/81
-------
the side. The molten metal is tapped by tilting and pouring through
a hole in the side. Melting capacities range up to 10 Mg (20 tons)
per hour.
A third furnace type used in the gray iron industry is the
electric induction furnace. Induction furnaces are vertical refrac-
tory lined cylinders surrounded by electrical coils energized with
alternating current. The resulting fluctuating magnetic field
heats the metal. Induction furnaces are kept closed except when
charging, skimming and tapping. The molten metal is tapped by
tilting and pouring through a hole in the side. Induction furnaces
are also used with other furnaces to hold and superheat the charge
after melting and refining in another furnace.
A small percentage of melting in the gray iron industry is
also done in air furnaces, reverberatory furnaces, pot furnaces and
indirect arc furnaces.
The basic melting process operations are 1) furnace charging,
in which the metal, scrap, alloys, carbon and flux are added to the
furnace, 2) melting, during which the furnace remains closed,
3) backcharging, which involves the addition of more metal and,
possibly, alloys, 4) refining and treating, during which the chemis-
try is adjusted, 5) slag removing, and 6) tapping molten metal into
a ladle or directly into molds.
Mold and Core Production - Cores are molded sand shapes used to
make the internal voids in castings, and molds are forms used to
shape the exterior of castings. Cores are made by mixing sand with
organic binders, molding the sand into a core, and baking the core
in an oven. Molds are prepared by using a mixture of wet sand,
clay and organic additives to make the mold shapes, and then by
drying with hot air. Increasingly, cold setting binders are being
used in both core and mold production. Used sand from shakeout
operations is recycled to the sand preparation area to be cleaned,
screened and reused to make molds.
Casting and Finishing — When the melting process is complete, the
molten metal is tapped and poured into a ladle. At this point, the
molten metal may be treated by addition of magnesium to produce
ductile iron by the addition of soda ash or lime to remove sulfur.
At times, graphite may be innoculated to adjust carbon levels. The
treated molten metal is then poured into molds and allowed partially
to cool. The partially cooled castings are placed on a vibrating
grid where the mold and core sand is shaken away from the casting.
The sand is returned to the mold manufacturing process, and the
castings are allowed to cool further in a cooling tunnel.
In the cleaning and finishing process, burrs, risers and gates
are broken off or ground off to match the contours of the castings,
after which the castings are shot blasted to remove remaining mold
sand and scale.
4/81 Metallurgical Industry 7.10-3
-------
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4/81
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4/81
Metallurgical Industry
7.10-5
-------
7.10.2 Emissions and Controls
Emissions from the raw materials handling operations consist
of fugitive particulates generated from the receiving, unloading,
storage and conveying of all raw materials for the foundry. These
emissions are controlled by enclosing the major emission points and
routing the air from the enclosures through fabric filters or wet
collectors.
Scrap preparation using heat will emit smoke, organics and
carbon monoxide, and preparation using solvent degreasers will emit
organics. (See Section 4.6, Solvent Degreasing.) Catalytic incinera-
tors and afterburners can be applied to control about 95 percent of
the organics and carbon monoxide.
Emissions from melting furnaces consist of particulates,
carbon monoxide, organics, sulfur dioxide, nitrogen oxides and
small quantities of chlorides and fluorides. The particulates,
chlorides and fluorides are generated by flux, incomplete combustion
of coke, carbon additives, and dirt and scale on the scrap charge.
Organics on the scrap and the reactivity of the coke effect carbon
monoxide emissions. Sulfur dioxide emissions, characteristic of
cupola furnaces, are attributable to sulfur in the coke.
The highest concentration of furnace emissions occurs during
charging, backcharging, alloying, slag removal, and tapping opera-
tions, when the furnace lids and doors are opened. Generally,
these emissions have escaped into the furnace building and have
been vented through roof vents. Controls for emissions during the
melting and refining operations usually concern venting the furnace
gases and fumes directly to a collection and control system.
Controls for fugitive furnace emissions involve the use of roof
hoods or special hoods in the proximity of the furnace doors, and
of tapping ladles to capture emissions and to route them to emission
control systems.
High energy scrubbers and bag filters with respective effi-
ciencies greater than 95 percent and 98 percent are used to control
particulate emissions from cupolas and electric arc furnaces in the
U.S. Afterburners achieving 95 percent control are used for reducing
organics and carbon monoxide emissions from cupolas. Normally,
induction furnaces are uncontrolled.
The major pollutants from mold and core production are particu-
lates from sand reclaiming, sand preparation, sand mixing with
binders and additives, and mold and core forming. There are organics,
CO and particulate emissions from core baking, and organic emissions
from mold drying. Bag filters and high energy scrubbers can be
used to control particulates from mold and core production.
Afterburners and catalytic incinerators can be used to control
organics and carbon monoxide emissions.
7.10-6 EMISSION FACTORS 4/81
-------
TABLE 7.10-3. SIZE DISTRIBUTION FOR PARTICULATE EMISSIONS FROM
THREE ELECTRIC ARC FURNACE INSTALLATIONS3
Particle Size (n)
<1
<2
<5
<10
<15
<20
<50
Foundry A
5
15
28
41
55
68
98
Foundry B
8
54
80
89
93
96
99
Foundry C
18
61
84
91
94
96
99
aReference 1, p. 111-39.
TABLE 7.10-4. SIZE DISTRIBUTION FOR PARTICULATE
EMISSIONS FROM EIGHTEEN CUPOLA FURNACE INSTALLATIONS21
Cumulative % Less
Particle Size (n) Than Indicated Size
<2
<5
<10
<20
<50
<100
<200
14
24
34
44
61
78
93
aReference 1, p. 111-33.
4/81 Metallurgical Industry 7.10-7
-------
In the casting operations, large quantities of particulates
can be generated in the treating and innoculation steps before
pouring. Emissions from pouring consist of fumes, carbon monoxide,
organics, and particulates evolved from the mold and core materials
when contacted with molten iron. These emissions continue to
evolve as the mold cools. A significant quantity of particulate
emissions is also generated during the casting shakeout operation.
Particulate emissions from shakeout can be controlled by either
high energy scrubbers or bag filters. Emissions from pouring are
normally uncontrolled or are ducted into other exhaust streams.
Emissions from finishing operations are of large particulates
emitted during the removal of burrs, risers and gates, and during
the blasting process. Particulates from finishing operations are
usually large in size and are easily controlled by cyclones.
Emission factors for melting furnaces are presented in
Table 7.10-1, and emission factors for fugitive particulates are
presented in Table 7.10-2. Typical particle size distributions for
emissions from electric arc and cupola furnaces are presented in
Table 7.10-3 and Table 7.10-4.
References for Section 7.10
1. J.A. Davis, et al., Screening Study on Cupolas and Electric
Furnaces in Gray Iron Foundries, EPA Contract No. 68-01-0611,
Battelle Laboratories, Columbus, OH, August 1975.
2. W.F. Hammond and S.M. Weiss, "Air Contaminant Emissions from
Metallurgical Operations in Los Angeles County", Presented at
Air Pollution Control Institute, Los Angeles, CA, July 1964.
3. H.R. Crabaugh, et al., "Dust and Fumes from Gray Iron Cupolas:
How They Are Controlled in Los Angeles County", Air Repair,
4/3): 125-130, November 1954.
4. Air Pollution Engineering Manual, Second Edition, AP-40, U.S.
Environmental Protection Agency, Research Triangle Park, NC,
May 1973. Out of Print.
5. J.M. Kane, "Equipment for Cupola Control", American Foundryman's
Society Transactions, (A:525-531, 1956.
6. Air Pollution Aspects of the Iron Foundry Industry, APTD-0806,
U.S. Environmental Protection Agency, Research Triangle Park,
NC, February 1971.
7. John Zoller, et al., Assessment of Fugitive Particulate Emission
Factors for Industrial Processes, EPA-450/3-78-107, U.S.
Environmental Protection Agency, Research Triangle Park, NC,
September 1978.
7.10-8 EMISSION FACTORS 4/81
-------
8. P.F. Fennelly and P.D. Spawn, Air Pollutant Control Techniques
for Electric Arc Furnaces in the Iron and Steel Foundry Industry,
EPA 450/2-78-024, U.S. Environmental Protection Agency, Research
Triangle Park, NC, June 1978.
9. Control Techniques for lead Air Emissions, Volumes 1 and 2,
EPA-450/2-77-012, U.S. Environmental Protection Agency, Research
Triangle Park, NC, December 1977.
10. W.E. Davis, Emissions Study of Industrial Sources of Lead Air
Pollutants, 1970, APTD-1543, U.S. Environmental Protection
Agency, Research Triangle Park, NC, April 1973.
11. Emission Test No. 71-CI-27, Office of Air Quality Planning and
Standards, U.S. Environmental Protection Agency, Research
Triangle Park, NC, February 1972.
12. Emission Test No. 71-CI-30, Office of Air Quality Planning
and Standards, U.S. Environmental Protection Agency, Research
Triangle Park, NC, March 1972.
4/81 Metallurgical Industry 7.10-9
-------
7.11 SECONDARY LEAD PROCESSING
1—7
7.11.1 Process Description
The secondary lead industry processes a variety of leadbearing
scrap and residue to produce lead and lead alloy ingots, battery lead
oxide, and lead pigments (PbsO^ and PbO). Processing may involve scrap
pretreatment, smelting and refining/casting. Processes typically used
in each operation are shown in Figure 7.11-1.
7.11.1.1 Scrap pretreatment is the partial removal of metal and non-
metal contaminants from leadbearing scrap and residue. Processes used
for scrap pretreatment include battery breaking, crushing and sweating.
Battery breaking is the draining and crushing of batteries followed by
manual screening to separate the lead from nonmetallic materials. This
separated lead scrap is then mixed with other scraps and smelted in
reverberatory or blast furnaces. Oversize pieces of scrap and residues
are usually crushed by jaw crushers. Sweating separates lead from high-
melting metals in direct gas or oil fired rotary or reverberatory
furnaces. Rotary furnaces are typically used to process low lead content
scrap and residue, while reverberatory furnaces are used to process high
lead content scrap. The partially purified lead is periodically tapped
for further processing in smelting furnaces or pot furnaces.
7.11.1.2 Smelting is the production of purified lead by melting and
separating lead from metal and nonmetallic contaminants and by reducing
oxides to elemental lead. Reverberatory smelting furnaces are used to
produce a semisoft lead product that typically contains 3-4 percent
antimony. Blast furnaces produce hard or antimonial lead containing
about 10 percent antimony.
A reverberatory furnace produces semisoft lead from a charge of
lead scrap, metallic battery parts, oxides, drosses and other residues.
The furnace consists of a rectangular shell lined with refractory brick
and fired directly with oil or gas to a temperature of 2300°F (1250°C).
The material to be melted is heated by direct contact with combustion
gases. The furnace can process about 50 tons per day (45 MT/day).
About 47 percent of the charge is typically recovered as lead product
and is periodically tapped into molds or holding pots. Forty-six
percent of the charge is removed as slag and subsequently processed in
blast furnaces. The remaining 7 percent of the furnace charge escapes
as dust or fume.
Blast furnaces produce hard lead from charges containing siliceous
slag from previous runs (typically about 4.5 percent of the charge),
scrap iron (about 4.5 percent), limestone (about 3 percent), coke (about
5.5 percent), and oxides, pot furnace refining drosses, and reverberatory
slag (comprising the remaining 82.5 percent of the charge). The propor-
tions of rerun slags, limestone and coke vary respectively to as high as
8 percent, 10 percent, and 8 percent of the charge. Processing capacity
of the blast furnace ranges from 20 - 80 tons per day (18 - 73 MT/day).
10/80 Metallurgical Industry 7.11-1
-------
Similar to iron cupolas, the furnaces consist of vertical steel cyl-
inders lined with refractory brick. Combustion air at 0.5 - 0.75 psig
is introduced at the bottom of the furnace through tuyeres. Some of the
coke combusts to melt the charge, while the remainder reduces lead
oxides to elemental lead. The furnace exhausts at temperatures of
1200 - 1350°F (650 - 730°C).
As the lead charge melts, limestone and iron float to the top of
the molten bath and form a flux that retards oxidation of the product
lead. The molten lead flows from the furnace into a holding pot at a
nearly continuous rate. The product lead constitutes roughly 70 percent
of the charge. From the holding pot, the lead is usually cast into
large ingots, called pigs or sows.
About 18 percent of the charge is recovered as slag, with about 60
percent of this being a sulfurous slag called matte. Roughly 5 percent
of the charge is retained for reuse, and the remaining 7 percent of the
charge escapes as dust or fume.
7.11.1.3 Refining/ cast ing is the use of kettle type furnaces in remelt-
ing, alloying, refining and oxidizing processes. Materials charged for
remelting are usually lead alloy ingots which require no further process
ing before casting. The furnaces used for alloying, refining and oxidiz
ing are usually gas fired, and operating temperatures range from
700 - 900°F (375 - 485°C).
Alloying furnaces simply melt and mix ingots of lead and alloy
material. Antimony, tin, arsenic, copper and nickel are the most common
alloying materials.
Refining furnaces remove copper and antimony to produce soft lead,
and they remove arsenic, copper and nickel to produce hard lead. Sulfur
may be added to the molten lead bath to remove copper. Copper sulfide
skimmed off as dross may subsequently be processed in a blast furnace to
recover residual lead. Aluminum chloride flux may be used to remove
copper, antimony and nickel. The antimony content can be reduced to
about 0.02 percent by bubbling air through the molten lead. Residual
antimony can be removed by adding sodium nitrate and sodium hydroxide to
the bath and skimming off the resulting dross. Dry dressing consists of
adding sawdust to the agitated mass of molten metal. The sawdust
supplies carbon to help separate globules of lead suspended in the dross
and to reduce some of the lead oxide to elemental lead.
Oxidizing furnaces are either kettle or reverberatory furnaces
which oxidize lead and entrain the product lead oxides in the combustion
air stream. The product is subsequently recovered in baghouses at high
efficiency.
7.11-2 EMISSION FACTORS 10/80
-------
145
7.11.2 Emissions and Controls ' '
Emission factors for uncontrolled processes and fugitive partic-
ulate emissions are in Tables 7.11-1 and 7.11-2, respectively.
Reverberatory and blast furnaces account for about 88 percent of
the total lead emissions from the secondary lead industry. Most of the
remaining processes are small emission sources with undefined emission
characteristics.
Emissions from battery breaking mainly consist of sulfuric acid
mist and dusts containing dirt, battery case material and lead com-
pounds. Emissions from crushing are also mainly dusts.
Emissions from sweating operations consist of fume, dust, soot
particulates and combustion products, including sulfur dioxide. The
sulfur dioxide emissions are from the combustion of sulfur compounds in
the scrap and fuel. Dusts range in size from 5-20 ym, while unagglom-
erated lead fumes range in size from 0.07 - 0.4 ym, with an average
diameter of 0.3 ym. Particulate loadings in the stack gas from rever-
beratory sweating range from 1.4 - 4.5 grains per cubic foot (3.2 - 10.3
g/m3). Baghouses usually control sweating emissions, with removal
efficiencies exceeding 99 percent. The emission factors for lead sweat-
ing in Table 7.11-1 are based on measurements at similar sweating furnaces
in other secondary metals processing industries, and are not based on
measurements at lead sweating furnaces.
Reverberatory smelting furnaces emit particulates and oxides of
sulfur and nitrogen. Particulates consist of oxides, sulfides and
sulfates of lead, antimony, arsenic, copper and tin, as well as unagglom-
erated lead fume. Particulate loadings range from 7-22 grains per
cubic foot (16 - 50 g/m3). Emissions are generally controlled with
settling and cooling chambers followed by a baghouse. Control efficien-
cies generally exceed 99 percent, as shown in Table 7.11-3. Wet scrub-
bers are sometimes used to reduce sulfur dioxide emissions. However,
because of the small particles emitted, scrubbers are not as widely used
as baghouses for particulate control.
Two chemical analyses by electron spectroscopy showed the part-
iculates to consist of 38 - 42 percent lead, 20 - 30 percent tin, and
about 1 percent zinc.16 Typically, particulates from reverberatory
smelting furnaces comprise about 20 percent lead.
Emissions from blast furnaces occur at charging doors, the slag
tap, the lead well, and the furnace stack. The emissions are combustion
gases (including carbon monoxide, hydrocarbons, and oxides of sulfur and
nitrogen) and particulates. Emissions from the charging doors and the
slag tap are hooded and routed to the devices treating the furnace stack
emissions. Reverberatory furnace particulates are larger than those
emitted from blast furnaces and are thus suitable for control by scrubbers
10/80 Metallurgical Industry 7.11-3
-------
CD
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7.11-4
EMISSION FACTORS
10/30
-------
Table 7.11-2. FUGITIVE EMISSION FACTORS FOR SECONDARY LEAD PROCESSING
EMISSION FACTOR RATING: E
a
Particulates
Source
Sweating
Smelting
Kettle
Refining
Casting
Ib/ton
1.6 - 3.5
2.8 - 15.7
0.04
0.88
kg/MT
0.8 - 1.8
1.4 - 7.9
0.02
0.44
Ib/ton
0.4 - 1.
0.6 - 3.
0.01
0.2
Lead
kg/MT
8 0.2 - 0.4
6 0.3 - 1.8
0.005
0.1
a
of the uncontrolled stack emissions. All factors except that for
casting are based on the amount of charge to the process. The casting
,factor is based on the amount of lead cast. Reference 14.
Factors are based on an approximation that particulate emissions
,contain 23% lead. References 3 and 5.
"Factors based on limited tests of a roof monitor over casting operations
at a primary smelter.
10/80
Metallurgical Industry
7.11-5
-------
or fabric filters downstream of coolers. Efficiencies for various
control devices are shown in Table 7.11-3. In one application, fabric
filters alone captured over 99 percent of the blast furnace particulate
emissions.
Table 7.11-3. EFFICIENCIES OF PARTICULATE CONTROL EQUIPMENT
ASSOCIATED WITH SECONDARY LEAD SMELTING FURNACES
i
Control device
Fabric filter3
o
Dry cyclone plus fabric filter
Wet cyclone plus fabric filter
Settling chamber plus dry
cyclone plus fabric filter
Venturi scrubber plus demister
Furnace Particulate control
type efficiency, %
Blast
Reverberatory
Blast
Reverberatory
Reverberatory
Blast
98.4
99.2
99.0
99.7
99.8
99.3
a
, Reference 8.
Reference 9.
, Reference 10.
Reference 12.
The size distribution for blast furnace particulates recovered by
an efficient fabric filter is reported in Table 7.11-4. Particulates
recovered from another blast furnace contained about 80 - 85 percent
lead sulfate and lead chloride, 4 percent tin, 1 percent cadmium, 1
percent zinc, 0.5 percent each antimony and arsenic, and less than 1
percent organic matter.17
Kettle furnaces for melting, refining and alloying are relatively
minor emission sources. The kettles are hooded, with fumes and dusts
typically vented to baghouses and recovered with efficiencies exceeding
99 percent. Twenty measurements of the uncontrolled particulates from
kettle furnaces showed a mass median aerodynamic particle diameter of
18.9 ym, with particle size ranging from 0.05 - 150 ym. Three chemical
analyses by electron spectroscopy showed the composition of particulates
to vary from 12 - 17 percent lead, 5-17 percent tin, and 0.9 - 5.7
percent zinc.16
Emissions from oxidizing furnaces are economically recovered with
baghouses. The particulates are mostly lead oxide, but they also
contain amounts of lead and other metals. The oxides range in size from
0.2 - 0.5 ym. Controlled emissions have been reported to be as low as
0.2 - 2.8 pounds per ton (0.1 - 1.4 kg/MT).
7.11-6 EMISSION FACTORS 10/80
-------
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10/80
Metallurgical Industry
7.11-7
-------
Table 7.11-4. PARTICLE SIZE DISTRIBUTION OF PARTICULATES
RECOVERED FROM A COMBINED BLAST AND REVERBERATORY
FURNACE GAS STREAM WITH BAGHOUSE CONTROL3
i
Particle Size Range, ym
Fabric filter catch, wt %
0 to 1
1 to 2
2 to 3
3 to 4
4 to 16
13.3
45.2
19.1
14.0
8.4
Reference 4, Table 86.
References for Section 7.11
1. William M. Coltharp, et al., Multimedia Environmental Assessment
of the Secondary Nonferrous Metal Industry (Draft), 2 Volumes, EPA
Contract No. 68-02-1319, Radian Corporation, Austin, TX, June 1976.
2. H. Nack, et al., Development of an Approach to Identification of
Emerging Technology and Demonstration Opportunities, EPA-650/2-74-
048, U.S. Environmental Protection Agency, Research Triangle Park,
NC, May 1974.
3. J. M. Zoller, et al., A Method of Characterization and QuantIfi-
cajiion of Fugitive Lead Emissions from Secondary Lead Smelters,
Ferroalloy Plants and Gray Iron Foundries (Revised), EPA-450/3-78-
003 (Revised), U.S. Environmental Protection Agency, Research
Triangle Park, NC, August 1978.
4. John A. Danielson, editor, Air Pollution Engineering Manual, Second
Edition, AP-40, U.S. Environmental Protection Agency, Research
Triangle Park, NC, May 1973, pp. 299-304. Out of Print.
5. Control Techniques for Lead Air Emissions, EPA-450/2-77-012, U.S.
Environmental Protection Agency, Research Triangle Park, NC,
January 1978.
6. Background Information for Proposed New Source Performance Standards,
Volume I: Secondary Lead Smelters and Refineries, APTD-1352, U.S.
Environmental Protection Agency, Research Triangle Park, NC, June
1973.
7.11-8
EMISSION FACTORS
10/80
i
-------
7. J. W. Watson and K. J. Brooks, A Review of Standards of Performance
for New Stationary Sources - Secondary Lead Smelters (Draft), EPA
Contract No. 68-02-2526, The Mitre Corporation, McLean, VA, June
1978.
8. John E. Williamson, et al., A Study of Five Source Tests on Emissions
from Secondary Lead Smelters, EPA Order No. 2PO-68-02-3326, County
of Los Angeles Air Pollution Control District, Los Angeles, CA,
February 1972.
9. Emission Test No. 72-CI-8, Office of Air Quality Planning and
Standards, U.S. Environmental Protection Agency, Research Triangle
Park, NC, July 1972.
10. Emission Test No. 72-CI-7, Office of Air Quality Planning and
Standards, U.S. Environmental Protection Agency, Research Triangle
Park, NC, August 1972.
11. A. E. Vandergrift, et al., Particulate Pollutant Systems Study,
Volume I; Mass Emissions, APTD-0743, U.S. Environmental Protection
Agency, Research Triangle Park, NC, May 1971.
12. Emission Test No. 71-CI-33, Office of Air Quality Planning and
Standards, U.S. Environmental Protection Agency, Research Triangle
Park, NC, August 1972.
13. Emission Test No. 71-CI-34, Office of Air Quality Planning and
Standards, U.S. Environmental Protection Agency, Research Triangle
Park, NC, July 1972.
14. Technical Guidance for Control of Industrial Process Fugitive
Particulate Emissions, EPA-450/3-77-010, U.S. Environmental
Protection Agency, Research Triangle Park, NC, March 1977.
15. Silver Valley/Bunker Hill Smelter Environmental Investigation
(Interim Report), EPA Contract No. 68-02-1343, PEDCo-Environmental
Specialists, Inc., Cincinnati, OH, February 1975.
16. E. I. Hartt, An Evaluation of Continuous Particulate Monitors at a
Secondary Lead Smelter, M.S. Report No. O.R.-16, Environmental
Protection Service, Environment Canada.
17. J. E. Howes, et al., Evaluation of Stationary Source Particulate
Measurement Methods, Volume V: Secondary Lead Smelters, EPA Contract
No. 68-02-0609, Battelle Columbus Laboratories, Columbus, OH,
January 1979.
10/80 Metallurgical Industry 7.11-9
-------
7.12 SECONDARY MAGNESIUM SMELTING
7.12.1 Process Descriptionl
Magnesium smelting is carried out in crucible or pot-type furnaces that are charged with magnesium scrap
and fired by gas, oil, or electric heating. A flux is used to cover the surface of the molten metal because
magnesium will burn in air at the pouring temperature (approximately 1500 F or 815°C). The molten
magnesium, usually cast by pouring into molds, is annealed in ovens utilizing an atmosphere devoid of oxygen.
7.12.2 Emissions1
Emissions from magnesium smelting include particulate magnesium (MgO) from the melting, nitrogen oxides
from the fixation of atmospheric nitrogen by the furnace temperatures, and sulfur dioxide losses from annealing
oven atmospheres. Factors affecting emissions include the capacity of the furnace; the type of flux used on the
molten material; the amount of lancing used; the amount of contamination of the scrap, including oil and other
hydrocarbons; and the type and extent of control equipment used on the process. The emission factors for a pot
furnace are shown in Table 7.12-1.
Table 7.12-1. EMISSION FACTORS
FOR MAGNESIUM SMELTING
EMISSION FACTOR RATING: C
Type of furnace
Pot furnace
Uncontrolled
Controlled
Particulates3
Ib/ton
4
0.4
kg/MT
2
0.2
References 2 and 3. Emission factors
expressed as units per unit weight of
metal processed.
2/72
Metallurgical Industry
7.12-1
-------
References for Section 7.12
1. Air Pollutant Emission Factors. Final Report. Resources Research, Inc. Reston, Va. Prepared for National
Air Pollution Control Administration, Durham, N.C., under Contract Number CPA-22-69-119. April 1970.
2. Allen, G. L. et al. Control of Metallurgical and Mineral Dusts and Fumes in Los Angeles County. Department
of the Interior, Bureau of Mines. Washington, D.C. Information Circular Number 7627. April 1952.
3. Hammond, W. F. Data on Non-Ferrous Metallurgical Operations. Los Angeles County Air Pollution Control
District. November 1966.
7.12-2 EMISSION FACTORS 2/72
-------
7.13 STEEL FOUNDRIES
7.13.1 Process Description
Steel foundries produce steel castings by the melting, alloying
and molding of pig iron and steel scrap. The process flow diagram
of a typical steel foundry is presented in Figure 7.13-1. The
major processing operations of the typical steel foundry are raw
materials handling, metal melting, mold and core production, and
casting and finishing.
Raw Materials Handling - The raw material handling operations
include the receiving, unloading, storage and conveying of all raw
materials for the foundry. Some of the raw materials used by steel
foundries are pig iron, iron and steel scrap, foundry returns,
metal turnings, alloys, carbon additives, fluxes (limestone, soda
ash, fluorspar, calcium carbide), sand, sand additives, and binders.
These raw materials are received in ships, railcars, trucks, and
containers, and are transferred by trucks, loaders, and conveyors
to both open pile and enclosed storage areas. They are then
transferred by similar means from storage to the subsequent processes.
Metal Melting - Generally, the first step in the metal melting
operations is scrap preparation. Since scrap is normally purchased
in the proper size for furnace feed, preparation primarily consists
of scrap degreasing. This is very important for electric induction
furnaces, as organics on scrap can be explosive. Scrap may be
degreased with solvents, by centrifugation or by incinerator or
preheater combustion. After preparation, the scrap, metal, alloy,
and flux are weighed and charged to the furnace.
Electric arc furnaces are used almost exclusively in the steel
foundry for melting and formulating steel. Electric arc furnaces
are large refractory lined steel pots, fitted with a refractory
roof through which three graphite electrodes are inserted. The
metal charge is melted with resistive heating generated by electrical
current flowing among the electrodes and through the charge.
Electric arc furnaces are charged with raw materials by removing
the lid, through a chute opening in the lid, or through a door in
the side. The molten metal is tapped by tilting and pouring
through a hole in the side. Melting capacities range up to
10 megagrams (11 tons) per hour.
A second, less common, furnace used in steel foundries is the
open hearth furnace, a very large shallow refractory lined vessel
which is operated in a batch manner. The open hearth furnace is
fired at alternate ends, using the heat from the waste combustion
gases to heat the incoming combustion air.
A third furnace used in the steel foundry is the induction
furnace. Induction furnaces are vertical refractory lined cylinders
4/81 Metallurgical Industry 7.13-1
-------
RAW MATERIALS
UNLOADING, STORAGE,
TRANSFER
• FLUX
• METALLICS
• CARBON SOURCES
• SAND
• BINDER
FUGITIVE
DUST
I
i
1 FUMES AND'
FUGITIVE
DUST
j—•>-HYDROCARBONS
I AND SMOKE
SCRAP
PREPARATION
1 *
FURNANCE
• ELECTRIC ARC
• INDUCTION
•OTHER
•FURNANCE
VENT
FUGITIVE
DUST
I
, •*-FUGITIVE FUMES
I AND DUST
TAPPING,
TREATING
,---•*• FUGITIVE FUMES
j AND DUST
MOLD POURING,
COOLING
SAND
OVEN VENT
CASTING
SHAKEOUT
•*- FUGITIVE
DUST
COOLING
»> FUMES AND
FUGITIVE
DUST
CLEANING,
FINISHING
-^FUGITIVE
DUST
SHIPPING
Figure 7.13-1. Typical flow diagram of a steel foundry.
7.13-2
HUSSION FACTORS
4/81
-------
surrounded by electrical coils energized with alternating current.
The resulting fluctuating magnetic field heats the metal. Induction
furnaces are kept closed except when charging, skimming and tapping.
The molten metal is tapped by tilting and pouring through a hole in
the side. Induction furnaces are also used with other furnaces, to
hold and superheat a charge melted and refined in the other furnaces.
A very small fraction of the secondary steel industry also uses
crucible and pneumatic converter furnaces.
The basic melting process operations are 1) furnace charging,
in which metal, scrap, alloys, carbon, and flux are added to the
furnace, 2) melting, during which the furnace remains closed,
3) backcharging, which is the addition of more metal and possibly
alloys, 4) refining, during which the carbon content is adjusted,
5) oxygen lancing, which is injecting oxygen into the molten steel
to dislodge slag and to adjust the chemistry of the metal, 6) slag
removal, and 7) tapping the molten metal into a ladle or directly
into molds.
Mold and Core Production - Cores are forms used to make the internal
voids in castings, and molds are forms used to shape the casting
exterior. Cores are made of sand with organic binders, molded into
a core and baked in an oven. Molds are made of wet sand with clay
and organic additives, dried with hot air. Increasingly, coal
setting binders are being used in both core and mold production.
Used sand from castings shakeout operations is recycled to the sand
preparation area, where it is cleaned, screened and reused.
Casting and Finishing - When the melting process is complete, the
molten metal is tapped and poured into a ladle. At this time, the
molten metal may be treated by adding alloys and/or other chemicals.
The treated metal is then poured into molds and is allowed partially
to cool under carefully controlled conditions. Molten metal may be
poured directly from the furnace to the mold.
When partially cooled, the castings are placed on a vibrating
grid, and the sand of the mold and core are shaken away from the
casting. The sand is recycled to the mold manufacturing process,
and the casting is allowed to cool further.
In the cleaning and finishing process, burrs, risers and gates
are broken or ground off to match the contour of the casting.
Afterward, the castings are usually shot blasted to remove remaining
mold sand and scale.
7.13.2 Emissions and Controls
Emissions from the raw materials handling operations are
fugitive particulates generated from receiving, unloading, storage
and conveying all raw materials for the foundry. These emissions
are controlled by enclosing the major emission points and routing
the air from the enclosures through fabric filters.
4/81 Metallurgical Industry 7.13-3
-------
Emissions from scrap preparation consist of hydrocarbons if
solvent degreasing is used, and consist of smoke, organics and
carbon monoxide if heating is used. Catalytic incinerators and
afterburners of approximately 95 percent control efficiency for
carbon monoxide and organics can be applied to these sources.
Emissions from melting furnaces are particulates, carbon
monoxide, organics, sulfur dioxide, nitrogen oxides, and small
quantities of chlorides and fluorides. The particulates, chlorides
and fluorides are generated by the flux, the carbon additives, and
dirt and scale on the scrap charge. Organics on the scrap and the
carbon additives effect CO emissions. The highest concentrations
of furnace emissions occur during charging, backcharging, alloying,
oxygen lancing, slag removal, and tapping operations, when the
furnace lids and doors are opened. Characteristically, these
emissions have escaped into the furnace building and have been
vented through roof vents. Controls for emissions during the
melting and refining operations focus on venting the furnace gases
and fumes directly to an emission collection duct and control
system. Controls for fugitive furnace emissions involve either the
use of building roof hoods or of special hoods near the furnace
doors, to collect emissions and route them to emission control
systems. Emission control systems commonly used to control partic-
ulate emissions from electric arc and induction furnaces are bag
filters, cyclones and venturi scrubbers. The capture efficiencies
of the collection systems, presented in Table 7.13-1, range from
80 to 100 percent. Usually, induction furnaces are uncontrolled.
The major pollutants from mold and core production are
particulates from sand reclaiming, sand preparation, sand mixing
with binders and additives, and mold and core forming. There are
volatile organics (VOC), CO and particulate emissions from core
baking, and VOC emissions from mold drying. Bag filters and high
energy scrubbers can be used to control particulates from mold and
core production. Afterburners and catalytic incinerators can be
used to control VOC and CO emissions.
In the casting operations, large quantities of particulates
can be generated in the steps prior to pouring. Emissions from
pouring consist of fumes, CO, VOC, and particulates from the mold
and core materials when contacted by the molten steel. As the mold
cools, emissions continue. A significant quantity of particulate
emissions is also generated during the casting shakeout operation.
The particulate emissions from the shakeout operations can be
controlled by either high efficiency cyclones or bag filters.
Emissions from pouring are usually uncontrolled.
Emissions from finishing operations consist of large particulates
from the removal of burrs, risers and gates, and during shot blasting.
Particulates from finishing operations typically are large and are
generally controlled by cyclones.
7.13-4 EMISSION FACTORS 4/81
-------
TABLE 7.13-1. EMISSION FACTORS FOR STEEL FOUNDRIES
EMISSION FACTOR RATING: A
Nitrogen
Particulates3 oxides
Process kg/Mg Ib/ton kg/Mg Ib/ton
Melting
Electric arcb'c 6.5 (2 to 20) 13 (4 to 40) 0.1 0.2
Open hearthd'6 5.5 (1 to 10) 11 (2 to 20) 0.005 0.01
Open hearth oxygen lanced '8 5 (4 to 5.5) 10 (8 to 11)
Electric induction11 0.05 0.1
a
Expressed as units per unit weight of metal processed. If the scrap metal
is very dirty or oily, or if increased oxygen lancing is employed, the
.emission factor should be chosen from the high side of the factor range.
Electrostatic precipitator, 92 - 98% control efficiency; baghouse
(fabric filter), 98 - 99% control efficiency; venturi scrubber, 94 - 98%
control efficiency.
.References 2-10.
Electrostatic precipitator, 95 - 98.5% control efficiency; baghouse, 99.9%
control efficiency; venturi scrubber, 96 - 99% control efficiency.
^References 2, 11 - 13.
Electrostatic precipitator, 95 - 98% control efficiency; baghouse, 99% control
efficiency; venturi scrubber, 95 - 98% control efficiency.
^References 6 and 14.
Usually not controlled.
Emission factors for melting furnaces in the steel foundry are
presented in Table 7.13-1.
Although no emission factors are available for nonfurnace
emission sources in steel foundries, they are very similar to those
in iron foundries .* Nonfurnace emission factors and particle size
distributions for iron foundry emission sources are presented in
Section 7.10, Gray Iron Foundries.
References for Section 7.13
1. Paul F. Fennelly and Peter D. Spawn, Air Pollutant Control
Techniques for Electric Arc Furnaces in the Iron and Steel
Foundry Industry, EPA-450/2-78-024, U.S. Environmental
Protection Agency, Research Triangle Park, NC, June 1978.
4/81 Metallurgical Industry 7.13-5
-------
2. J.J. Schueneman, et al., Air Pollution Aspects of the Iron and
Steel Industry, National Center for Air Pollution Control,
Cincinnati, OH, June 1963.
3. Foundry Air Pollution Control Manual, 2nd Ed., Foundry Air
Pollution Control Committee, Des Plaines, II, 1967.
4. R.S. Coulter, "Smoke, Dust, Fumes Closely Controlled in Electric
Furnaces", Iron Age, 173;107-110, January 14, 1954.
5. Air Pollution Aspects of the Iron and Steel Industry, p. 109.
6. J.M. Kane and R.V. Sloan, "Fume Control Electric Melting
Furnaces", American Foundryman, 18_:33-34, November 1950.
7. Air Pollution Aspects of the Iron and Steel Industry, p. 109.
8. C.A. Faist, "Electric Furnace Steel", Proceedings of the
American Institute of Mining and jletallurgical Engineers,
_U: 160-161, 1953.
9. Air Pollution Aspects of the Iron and Steel Industry, p. 109.
10. I.H. Douglas, "Direct Fume Extraction and Collection Applied
to a Fifteen Ton Arc Furnace", Special Report on Fume Arrestment,
Iron and Steel Institute, 1964, pp. 144, 149.
11. Inventory of Air Contaminant Emissions, New York State Air
Pollution Control Board, Table XI, pp. 14-19. Date unknown.
12. A.C. Elliot and A.J. Freniere, "Metallurgical Dust Collection
in Open Hearth and Sinter Plant", Canadian Mining and Metal-
lurgical Bulletin, 21(606):724-732, October 1962.
13. C.L. Hemeon, "Air Pollution Problems of the Steel Industry",
JAPCA, H)(3):208-218, March 1960.
14. D.W. Coy, Unpublished data, Resources Research, Incorporated,
Reston, VA.
7.13-6 EMISSION FACTORS 4/81
-------
7.14 SECONDARY ZINC PROCESSING
1 2
7.14.1 Process Description '
The secondary zinc industry processes obsolete and scrap
materials to recover zinc as slabs, dust and zinc oxide. Pro-
cessing involves three operations, scrap pretreatment, melting and
refining. Processes typically used in each operation are shown in
Figure 7.14-1. Molten product zinc may be used in zinc galvanizing.
Scrap Pretreatment - Pretreatment is the partial removal of metal
and other contaminants from scrap containing zinc. Sweating
separates zinc from high melting metals and contaminants by melting
the zinc in kettle, rotary, reverberatory, muffle or electric
resistance furnaces. The product zinc then is usually directly
used in melting, refining or alloying processes. The high melting
residue is periodically raked from the furnace and further processed
to recover zinc values. These residues may be processed by crushing/
screening to recover impure zinc or by sodium carbonate leaching to
produce zinc oxide.
In crushing/screening, zinc bearing residues are pulverized or
crushed to break the physical bonds between metallic zinc and
contaminants. The impure zinc is then separated in a screening or
pneumatic classification step.
In sodium carbonate leaching, the zinc bearing residues are
converted to zinc oxide, which can be reduced to zinc metal. They
are crushed and washed to leach out zinc from contaminants. The
aqueous stream is then treated with sodium carbonate, precipitating
zinc as the hydroxide or carbonate. The precipitate is then dried
and calcined to convert zinc hydroxide into crude, zinc oxide. The
ZnO product is usually refined to zinc at primary zinc smelters.
Melting - Zinc is melted at 425-590°C (800-1100°F) in kettle,
crucible, reverberatory and electric induction furnaces. Zinc to
be melted may be in the form of ingots, reject castings, flashing
or scrap. Ingots, rejects and heavy scrap are generally melted
first, to provide a molten bath to which light scrap and flashing
are added. Before pouring, a flux is added and the batch agitated
to separate the dross accumulating during the melting operation.
The flux floats the dross and conditions it so it can be skimmed
from the surface. After skimming, the melt can be poured into
molds or ladles.
Refining/Alloying - Additional processing steps may involve alloying,
distillation, distillation and oxidation, or reduction. Alloying
produces mainly zinc alloys from pretreated scrap. Often the
alloying operation is combined with sweating or melting.
Distillation retorts and furnaces are used to reclaim zinc
from alloys or to refine crude zinc. Retort distillation is the
4/81 Metallurgical Industry 7.14-1
-------
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TABLE 7.14-1.
UNCONTROLLED PARTLCULATE EMLSSION FACTORS
FOR SECONDARY ZLNC SMELTING3
EMISSION FACTOR RATING: C
Emissions
Operation
b
Reverberatory sweating
clean metallic scrap
general metallic scrap
residual scrap
Rotary sweating0
Muffle sweating0
Kettle sweating
clean metallic scrap
general metallic scrap
residual scrap
Electric resistance sweating0
Crushing/ screening
Sodium carbonate leaching
crushing/ screening0
calcining"*
Kettle (pot) melting
Crucible melting
Reverberatory melting
Electric induction melting
Al loying
Retort and muffle distillation
pouring0
casting0 ,
muffle distillation
Graphite rod distillation0'6
Retort distillation/oxidation
Muffle distillation/oxidatlonf
Retort reduction
Galvanizing
kg/Mg
Negligible
6.5
16
5.5-12.5
5.4-16
Negligible
5.5
12.5
<5
0.5-3.8
0.5-3.8
44.5
0.05
DNA
DNA
DNA
DNA
0.2-0.4
0.1-0.2
22.5
Negligible
10-20
10-20
23.5
2.5
Ib/ton
Negligible
13
32
11-25
10.8-32
Negligible
11
25
<10
1.0-7.5
1.0-7.5
89
0.1
DNA
DNA
DNA
DNA
0.4-0.8
0.2-0.4
45
Negligible
20-40
20-40
47
5
Expressed as units per unit weight of feed material processed for
crushing/screening, skimming/residues processed; for kettle (pot)
melting and retort and muffle distillation operations, metal
product. Galvanizing factor expressed in units per unit weight
.of zinc used. DNA: Data not available.
Reference 3.
.Reference 4.
References 5-7.
-Reference 1.
Reference 4. Factor units per unit weight of ZnO produced. The
product zinc oxide dust is totally carried over in the exhaust gas
from the furnace and is recovered with 98-99% efficiency.
4/81
Metallurgical Industry
7.14-3
-------
vaporization at 980-1250°C (1800-2280°F) of elemental zinc with its
subsequent condensation as zinc dust or liquid zinc. Rapid cooling
of the vapor stream below the zinc melting point produces zinc
dust, which can be removed from the condenser and packaged. If
slab zinc is the desired product, the vapors are condensed slowly
at a higher temperature. The resultant melt is cast into ingots or
slabs. Muffle distillation furnaces produce principally zinc
ingots, and graphite rod resistance distillation produces zinc
dust.
Retort and muffle furnace distillation and oxidation processes
produce zinc oxide dust. These processes are similar to distillation
through the vaporization step. In contrast, for distillation/oxi-
dation, the condenser is omitted, and the zinc vapor is discharged
directly into an air stream leading to a refractory lined combustion
chamber. Excess air is added to complete oxidation and to cool the
product. The zinc oxide product is usually collected in a baghouse.
In retort reduction, zinc metal is produced by the reaction of
carbon monoxide and zinc oxide to yield zinc and carbon dioxide.
Carbon monoxide is supplied by the partial oxidation of the coke.
The zinc is recovered by condensation.
Zinc Galvanizing - Zinc galvanizing is the coating of clean oxide
free iron or steel with a thin layer of zinc by immersion in molten
zinc. The galvanizing occurs in a vat or in dip tanks containing
molten zinc and cover flux.
1,2
7.14.2 Emissions and Controls
Factors for uncontrolled point source and fugitive particulate
emissions are tabulated in Tables 7.14-1 and 7.14-2 respectively.
Emissions from sweating and melting operations consist
principally of particulates, zinc fumes, other volatile metals,
flux fumes and smoke generated by the incomplete combustion of
grease, rubber and plastics in the zinc bearing feed material.
Zinc fumes are negligible at low furnace temperatures, for they
have a low vapor pressure even at 480°C (900°F), With elevated
temperatures, however, heavy fuming can result. Flux emissions are
minimized by the use of a nonfuming flux. Substantial emissions
may arise from incomplete combustion of carbonaceous material in
the zinc scrap. These contaminants are usually controlled by
afterburners. Further emissions are the products of combustion of
the furnace fuel. Since the furnace fuel is usually natural gas,
these emissions are minor. In reverberatory furnaces, the products
of fuel combustion are emitted with the other emissions. Other
furnaces emit the fuel combustion products as a separate emission
stream.
Particulates from sweating and melting are mainly hydrated
ZnCl2 and ZnO, with small amounts of carbonaceous material. Chemical
7.14-4 EMISSION FACTORS 4/81
-------
TABLE 7.14-2. FUGITIVE PARTICULATE UNCONTROLLED EMISSION
FACTORS FOR SECONDARY ZINC SMELTING
EMISSION FACTOR RATING: E
Particulate
Operation
b
Reverberatory sweating
b
Rotary sweating
Muffle sweating
Kettle (pot) sweating
Electric resistance sweating
Q
Crushing/ screening
Sodium carbonate leaching
Kettle (pot) melting furnace
Crucible melting furnace
Reverberatory melting furnace
Electric induction melting
Alloying retort distillation
Retort and muffle distillation
Casting
Graphite rod distillation
Retort distillation/oxidation
Muffle distillation/oxidation
Retort reduction
kg/Mg
0.63
0.45
0.54
0.28
0.25
2.13
DNA
0.0025
0.0025
0.0025
0.0025
DNA
1.18
0.0075
DNA
DNA
DNA
DNA
Ib/ton
1.30
0.90
1.07
0.56
0.50
4.25
DNA
0.005
0.005
0.005
0.005
DNA
2.36
0.015
DNA
DNA
DNA
DNA
Reference 8. Expressed as units per end product, except factors
for crushing/screening and electric resistance furnaces, which are
expressed as units per unit of scrap processed. DNA: Data not
.available.
Estimate based on stack emission factor given in Reference 1,
assuming fugitive emissions to be equal to 5% of stack emissions.
Reference 1. Average of reported emission factors.
Engineering judgement, assuming fugitive emissions from crucible
melting furnace to be equal to fugitive emissions from kettle
(pot) melting furnace.
4/81
Metallurgical Industry
7.14-5
-------
analyses of particulate emissions from kettle sweat are shown in
Table 7.14-3.
TABLE 7.14-3. COMPOSITION OF PARTICULATE EMISSIONS
FROM KETTLE SWEAT PROCESSING3
Component Percent
ZnCl2 14.5 - 15.3
ZnO 46.9 - 50.0
NH4C1 1.1 - 1.4
A1203 1.0 - 2.7
Fe20 0.3 - 0.6
PbO 0.2
H20 (in ZnCl2 • 41^0) 7.7-8.1
Oxide of Mg, Sn, Ni, Si, Ca, Na 2.0
Carbonaceous material 10.0
Moisture (deliquescent) 5.2 - 10.2
a
Reference 3 .
These particulates also contain Cu, Cd, Mn and Cr. Another
analysis showed the following composition: 4 percent ZnCl2 , 77 percent
ZnO, 4 percent H20, 4 percent metal chlorides and 10 percent carbona-
ceous matter.^ These particulates vary widely in size. Particulates
from kettle sweating of residual zinc scrap had the following size
distributions:
60% 0 -
17% 11 - 20n
23%
Particulates from kettle sweating of metallic scrap had mean particle
size distributions ranging from Dp5Q = 1.1 /n to Dp5Q = 1.6|a. Emissions
from a reverberatory sweat furnace had an approximate Dp^Q = l|a.
Baghouses are most commonly used to recover particulate emissions
from sweating and melting. In one application on a muffle sweating
7.14-6 EMISSION FACTORS 4/81
-------
furnace, a cyclone and baghouse achieved particulate recovery
efficiencies in excess of 99.7 percent. In another application on
a reverberatory sweating furnace, a baghouse removed 96.3 percent
of the particulates, reducing the dust loading from 0.513 g/Nm3 to
0.02 g/Nm . Baghouses show similar efficiencies in removing
particulates from exhaust gases of melting furnaces.
Crushing and screening operations are also sources of dust
emissions. These particulates are composed of Zn, Al, Cu, Fe, Pb,
Cd, Sn and Cr, and they can be recovered from hooded exhausts by
baghouses.
The sodium carbonate leaching process produces particulate
emissions of ZnO dust during the calcining operation. This dust
can be recovered in baghouses, although ZnCl2 in the dust may cause
plugging problems.
Emissions from refining operations are mainly metallic fumes.
These fume and dust particles are quite small, with sizes ranging
from 0.05 - l|a.2 Distillation/oxidation operations emit their
entire ZnO product in the exhaust gas. The ZnO has a very small
particle size (0.03 to 0.5(i) and is recovered in baghouses with
typical collection efficiencies of 98-99 percent.^
Some emissions of zinc oxide occur during galvanizing, but
these emissions are small because of the bath flux cover and the
relatively low temperature maintained in the bath.
Data describing the particle size distribution of fugitive
emissions are unavailable. These emissions are probably similar in
size to stack emissions.
References for Section 7.14
1. William M. Coltharp, et al., Multimedia Environmental Assessment
of the Secondary Nonferrous Metal Industry, Draft Final Report,
2 vols., EPA Contract No. 68-02-1319, Radian Corporation,
Austin, TX, June 1976.
2. John A. Danielson, Air Pollution Engineering Manual, 2nd
Edition, AP-A2, U.S. Environmental Protection Agency, Research
Triangle Park, NC, 1973. Out of Print.
3. W. Herring, Secondary Zinc Industry Emission Control Problem
Definition Study(Part I), APTD-0706, U.S. Environmental
Protection Agency, Research Triangle Park, NC, May 1971.
4. H. Nack, et al., Development of an Approach to Identification
of Emerging Technology and Demonstration Opportunities, EPA-650/
2-74-048, U.S. Environmental Protection Agency, Research
Triangle Park, NC, May 1974.
4/81 Metallurgical Industry 7.14-7
-------
5. G.L. Allen, et al., Control of Metallurgical and Mineral Dusts
and Fumes in Los Angeles County, Number 7627, U.S. Department
of the Interior, Washington, DC, April 1952.
6. Restricting Dust and Sulfur Dioxide Emissions from Lead Smelters,
translated from German, VDI Number 2285, U.S. Department of
Health, Education and Welfare, Washington, DC, September 1961.
7. W.F. Hammond, Data on Nonferrous Metallurgical Operations, Los
Angeles County Air Pollution Control District, Los Angeles,
CA, November 1966.
8. Assessment of Fugitive Particulate Emission Factors for
Industrial Processes, EPA-450/3-78-107, U.S. Environmental
Protection Agency, Research Triangle Park, NC, September 1978.
i
7.14-8 EMISSION FACTORS 4/81
-------
7.15 STORAGE BATTERY PRODUCTION
7.15.1 Process Description1
Lead acid storage batteries are produced from lead alloy ingots and lead
oxide. The lead oxide may be prepared by the battery manufacturer or may be
purchased from a supplier. See Section 7.16.
Lead alloy ingots are charged to a melting pot, from which the molten
lead flows into molds that form the battery grids. Pasting machines force a
paste into the interstices of the grids, after which they are referred to as
plates. The grids are often cast in doublets and split apart (slitting)
after they have been pasted and cured. The paste is made in a batch type
process. Mixing lead oxide powder, water and sulfuric acid produces a
positive paste, and the same ingredients in slightly different proportions
plus an expander (generally a mixture of barium sulfate, carbon black and
organics) make the negative paste.
After the plates are cured, they are sent to the three process operation
of plate stacking and burning and element assembly in the battery case.
Doublet plates are cut apart and stacked in an alternating positive and
negative block formation, with insulators between them. These insulators are
of materials such as wood, treated paper, plastic or rubber. Then, in the
burning operation, leads are welded to tabs on each positive or negative
plate. An alternative to this operation is the cast-on strap process, in
which molten lead is poured around the plate tabs to form the connection, and
positive and negative terminals are then welded to each such connected
element. The completed elements are assembled in battery cases either before
(wet batteries) or after (dry batteries) the formation step.
Formation is the immersing of plates in a dilute sulfuric acid solution
and the connecting of positive plates to the positive pole of a direct
current (dc) source and the negative plates to the negative pole of the dc
source. In the wet formation process, this is done in the battery case.
After forming, the acid is dumped, fresh acid is added, and a boost charge is
applied to complete the battery. In dry formation, the individual plates may
be formed in tanks of sulfuric acid before assembly. Also, they may be
assembled first and then formed in tanks. The formed elements from either
method are then placed in the battery cases, and the batteries are shipped
dry. Figure 7.15-1 is a process flow diagram for lead acid battery
manufacture.
Defective parts are either reclaimed at the battery plant or are sent to
a secondary lead smelter (See Section 7.11). Lead reclamation facilities at
battery plants generally are small pot furnaces. Approximately 1 percent of
the lead processed at a typical lead acid battery plant is recycled through
the reclamation operation.
Lead acid storage battery plants range in production capacity from less
than 500 batteries per day to about 10,000 batteries per day. Lead acid
storage batteries are produced in many sizes, but the majority is produced
for use in automobiles and falls into a standard size range. A standard
8/82 Metallurgical Industry 7.15-1
-------
•H
4J
O
3
-a
o
M
0)
cd
cu
00
cd
M
o
14-4
•H
•a
to
co
-------
TABLE 7.15-1. STORAGE BATTERY PRODUCTION EMISSION FACTORS*
Process
Grid casting
Paste mixing
Lead oxide mill ,
(baghouse outlet)
Three process operation
Lead reclaim furnace
Dry formation
Total production
Particulate
kg(lb)/103
batteries
1.42
(3.13)
1.96
(4.32)
0.05
(0.11)
42.0
(92.6)
3.03
(6.68)
14.7
(32.4)
63.2
(139)
Lead
kg(lb)/103
batteries
0.35
(0.77)
1.13
(2.49)
0.05
(0.11)
4.79
(10.6)
0.63
(1.38)
NA
6.94
(15.3)
Emission
Factor
Rating
B
B
C
B
B
B
References 1-7. NA » not applicable. Based on standard automotive
batteries of about 11.8 kg (26 Ib) of lead, of which approximately half is
present in the lead grids and half in the lead oxide paste. Particulate
emissions include lead and its compounds, as well as other substances.
Lead emission factors are expressed as emissions of elemental lead.
Reference 5. Emissions measured for a well controlled facility (fabric
filters with an average air:cloth ratio of 3:1) were 0.025 kg (0.055 Ib)
particulate/1000 batteries and 0.024 kg (0.053 Ib) lead/1000 batteries.
Factors represent emissions from a facility with typical controls (fabric
filtration with an air:cloth ratio of about 4:1). Emissions from a
facility with typical controls are estimated to be about twice those from
a well controlled facility (Reference 1).
°Based on the assumption that about 1% of the lead processed at a typical
battery plant is processed by the reclaim operation.
For sulfates in aerosol form, expressed as sulfuric acid, and not account-
ing for water and other substances which might be present.
8/82
Metallurgical Industry
7.15-3
-------
battery contains about 11.8 kilograms (26 Ib) of lead, of which about half is
present in the lead grids and half in the lead oxide paste.
7.15.2 Emissions and Controls*"^
Lead oxide emissions result from the discharge of air used in the lead
oxide production process. In addition, particulate matter and lead
particulate are generated in the grid casting, paste mixing, lead reclamation,
three process operations, and other operations such as slitting and small
parts casting. These particulates are usually collected by ventilation
systems to reduce employee exposure to airborne lead. Sulfuric acid mist
emissions are generated during the formation step. Acid mist emissions are
significantly higher for dry formation processes than for wet formation
processes, because wet formation is conducted in battery cases, while dry
formation is conducted in open tanks. Table 7.15-1 presents average
uncontrolled emission factors for grid casting, paste mixing, lead reclamation,
dry formation, and three process operations, and an average controlled
emission factor for lead oxide production. The particulate emission factors
presented in the Table include lead and its compounds. The lead emission
factors represent emissions of lead in element and compound form, expressed
as elemental lead.
A fabric filter is used as part of the process equipment to collect
product from the lead oxide facility. Typical air to cloth ratios of fabric
filters used for this facility are about 4 to 1. It is estimated that
emissions from a facility controlled by a fabric filter with a 3 to 1 air to
cloth ratio are about 50 percent less than those from a facility with a
typical collection system.1
Fabric filters can also be used to control emissions from slitting and
three process operations. The paste mixing operation consists of two phases.
The first, in which dry ingredients are charged to the mixer, results in
major emissions of lead oxide and is usually vented to a baghouse. For the
second phase of the cycle, when moisture is present in the exhaust stream,
the paste mixer generally is vented to an impingement scrubber. Grid casting
machines are sometimes vented to an impingement scrubber. Lead reclamation
facilities generally are also vented to impingement scrubbers.
Emission reductions of 99 percent and above can be obtained where fabric
filtration is used to control slitting, paste mixing and three process
operations. Application of scrubbers to paste mixing, grid casting and lead
reclamation facilities can result in emission reductions from 85 percent to
over 90 percent.
Wet formation processes usually do not require control. Emissions of
sulfuric acid mist from dry formation processes can be reduced by over
95 percent with mist eliminators. Surface foaming agents are also used
commonly in dry formation baths to control acid mist emissions.
References for Section 7.15
1. Lead Acid Battery Manufacture - Background Information for Proposed
Standards, EPA 450/3-79-028a, U.S. Environmental Protection Agency,
Research Triangle Park, NC, November 1979.
1•15-4 EMISSION FACTORS 8/82
-------
2. Source Test EPA-74-BAT-1, U.S. Environmental Protection Agency, Research
Triangle Park, NC, March 1974.
3. Source Testing of Lead Acid Battery Manufacturing Plant - Globe-Union,
Inc., Canby. OR, EPA-76-BAT-4, U.S. Environmental Protection Agency,
Research Triangle Park, NC, 1976.
4. R.C. Fulton and G.W. Zolna, Report of Efficiency Testing Performed
April 30, 1976, on American Air Filter Roto-Clone, Spotts, Stevens and
McCoy, Inc., Wyomissing, PA, June 1, 1976.
5. Source Testing at a Lead Acid Battery Manufacturing Company - ESB, Canada,
Ltd., Mississauga, Ontario, EPA-76-3, U.S. Environmental Protection
Agency, Research Triangle Park, NC, 1976.
6. Emissions Study at a Lead Acid Battery Manufacturing Company - ESB, Inc.,
Buffalo, NY, EPA-76-BAT-2, U.S. Environmental Protection Agency,
Research Triangle Park, NC, 1976.
7. Test Report - Sulfuric Acid Emissions from ESB Battery Plant Forming Room,
Allentown, PA, EPA-77-BAT-5. U.S. Environmental Protection Agency,
Research Triangle Park, NC, 1977.
8/82 Metallurgical Industry 7.15-5
-------
7.16 LEAD OXIDE AND PIGMENT
PRODUCTION
7.16.1 General
Lead oxide is used in the manufacture of lead/acid storage batteries (Section 7.15) and as a pigment in
paints. Black oxide, which is used exclusively in storage batteries, contains 60 to 80 percent litharge (PbO)
the remainder being finely divided metallic lead.1 The major lead pigment is red lead (Pb3O4), which is used
principally in ferrous metal protective paints. Other lead pigments include white lead and lead chromates.
Most lead oxides and many lead pigments are derived from lead monoxide (PbO) in the form of litharge,
which is produced by (1) partially oxidizing lead and milling it into a powder, which is then completely oxi-
dized in a reverberatory furnace; (2) oxidizing and stirring pig lead in a reverberatory furnace or rotary kiln;
(3) running molten lead into a cupelling furnace; or (4) atomizing •molten lead in a flame. The product must
be cooled quickly to below 300°C (572T) to avoid formation of red lead.2
Black oxide is usually produced (in the same furnace in which the litharge is made) by either the ball
mill or Barton process. Cyclones and fabric filters collect the product. Red lead is produced by oxidizing
litharge in a reverberatory furnace. Basic carbonate white lead production is based on the reaction of
litharge with acetic acid or acetate ions. White leads other than carbonates are made either by chemical
or fuming processes. Chromate pigments are generally manufactured by precipitation or calcination.
7.16.2 Emissions and Controls
Automatic shaker type fabric filters, often preceded by cyclone mechanical collectors or settling cham-
bers, are the almost universal choice for collecting lead oxides and pigments. Where fabric filters are not
appropriate, scrubbers are used, resulting in higher emissions. The ball mill and Barton processes of black
oxide manufacturing recover the lead product by these two means. Collection of dust and fumes from the
production of red lead is likewise an economic necessity, since particulate emissions, although small, are
about 90 percent lead. Data on emissions from the production of white lead pigments are not available, but
they have been estimated because of health and safety regulations. The emissions from dryer exhaust
scrubbers account for over 50 percent of the total lead emitted in lead chromate production.
7/79 Metallurgical Industry 7.16-1
-------
Table 7.16-1. LEAD OXIDE AND PIGMENT PRODUCTION EMISSION FACTORS8
EMISSION FACTOR RATING: B
Process
Lead oxide
production:
Barton potb
Calcining
furnace
Pigment
production:
Red leadb
White leadb
Chrome
pigments:
Particulate
Ib/ton
produced
0.43-0.85
c
1.0*
c
c
kg/103 kg
produced
0.21-0.43
c
0.5d
c
c
Lead emission factor
Ib/ton
produced
0.44
14.0
0.9
0.55
0.13
kg/103 kg
produced
0.22
7.0
0.5
0.28
0.065
References
4,6,7
6
4,5
4,5
4,5
"Reference 4, pp. 4-283 and 4-287.
bMeasured at baghouse outlet. Baghouse is considered process equipment.
cData not available.
dOnly PbO and oxygen used in red lead production, so paniculate emissions assumed to be about 90% lead.
Table 7.16-2. LEAD OXIDE AND PIGMENT PRODUCTION CONTROL EFFICIENCIES
Process.
Control
Percent
reduction
Lead oxide and
pigment production
Mechanical shaker fabric
filter (preceded by dry
cyclone or settling chamber)
Scrubber
99a
70-95b
"Reference 3.
"Reference 4
7.16-2
EMISSION FACTORS
7/79
-------
References for Section 7.16
1. E. J. Ritchie, Lead Oxides, Independent Battery Manufacturers Association, Inc., Largo. FL. 1974.
2. W. E. Davis, Emissions Study of Industrial Sources of Lead Air Pollutants, 1970, EPA Contract No.
68-02-0271, W. E. Davis and Associates, Leawood, KS, April 1973.
3. Background Information in Support of the Development of Performance Standards for the Lead Addi-
tive Industry, EPAContract No. 68-02-2085, PEDCo-Environmental Specialists, Inc., Cincinnati. OH,
January 1976.
4. Control Techniques for Lead Air Emissions, EPA-450/2-77-012. U.S. Environmental Protection
Agency, Research Triangle Park, NC, December 1977.
5. R. P. Betz, et al., Economics of Lead Removal in Selected Industries, EPA Contract No. 68-02-0299,
Battelle Columbus Laboratories. Columbus, OH, December 1972.
6. Emission Test No. 74-PB-O-l. Office of Air Quality Planning and Standards, U.S. Environmental
Protection Agency, Research Triangle Park, NC, August 1973.
Metallurgical Industry 7.16-3
-------
7.17 MISCELLANEOUS LEAD PRODUCTS
7.17.1 Type Metal Production
7.17.1.1 General — Lead type, used primarily in the letterpress segment of the printing industry, is cast
from a molten lead alloy and remelted after use. Linotype and monotype processes produce a mold, while
the stereotype process produces a plate for printing. All type metal is an alloy consisting of 60 to 85 percent
recovered lead, with antimony, tin and a small amount of virgin metal.
7.17.1.2 Emissions and Controls — The melting pot is the major source of emissions, containing hydro-
carbons as well as lead particulates. Pouring the molten metal into the molds involves surface oxidation of
the metal, possibly producing oxidized fumes, while the trimming and finishing operations emit lead par-
ticles. It is estimated that 35 percent of the total emitted particulate is lead.1
Approximately half of the current lead type operations control lead emissions, by about 80 percent. The
other operations are uncontrolled.2 The most frequently controlled sources are the main melting pots and
dressing areas. Linotype equipment does not require controls when operated properly. Devices in current
use on monotype and stereotype lines include rotoclones. wet scrubbers, fabric filters, and electrostatic
precipitators, all which can be used in various combinations.
7.17.2 Can Soldering
7.17.2.1 Process Description — Side seams of cans are soldered on a machine consisting of a solder-
coated roll operating in a bath of molten solder, typically containing 98 percent lead. After soldering, excess
is wiped away by a rotating cloth buffer, which creates some dust (Table 7.17-1).3
7.17.2.2 Emissions and Controls - Hoods, exhaust ducts and mechanical cyclones (Table 7.17-2) collect
the large flakes generated at the wiping station, but some dust escapes in the form of particles 20 microns or
smaller, with a lead content of 3 to 38 percent. Maintaining a good flux cover is the most effective means
of controlling lead emissions from the solder batch. Low energy wet collectors or fabric filters can also con-
trol lead emissions from can soldering.
7.17.3 Cable Covering
7.17.3.1 Process Description — About 90 percent of the lead cable covering produced in the United States
is lead cured jacketed cables, and 10 percent is on lead sheathed cables. In preparation of the former type.
an unalloyed lead cover applied in the vulcanizing treatment during the manufacture of rubber-insulated
cable must be stripped from the cable and remelted.
Lead coverings are applied to insulated cable by hydraulic extrusion of solid lead around the cable.
Molten lead is continuously fed into an extruder or screw press, where it solidifies as it progresses. A melt-
ing kettle supplies lead to the press.
7.17.3.2 Emissions and Controls — The melting kettle is the only source of atmospheric lead emissions.
and it is generally uncontrolled.4 Average particle size is approximately 5 microns, with a lead content of
about 70 to 80 percent.3-5
Cable covering processes do not usually include particulate collection devices, although fabric filters.
rotoclone wet collectors and dry cyclone collectors can reduce lead emissions (Table 7.17-2). Lowering and
controlling the melt temperature, enclosing the melting unit and using fluxes to provide a cover on the melt
can also minimize emissions.
7/79 Metallurgical Industry 7.17-1
-------
Table 7.17-1 EMISSION FACTORS FOR MISCELLANEOUS SOURCES8
EMISSION FACTOR RATING: C
Process
Type metal
production
Can soldering
Cable covering
Metallic lead
products
Ammunition
Bearing metals
Other sources
of lead
Particulate emission factor
Metric
0.4 kg/103 kg
Pb procb
0.8 x 106
baseboxes
prod0
0.3 kg/103 kg
Pb procd
e
e
e
English
0.7 Ib/ton Pb
procb
0.9 ton/106
baseboxes
prod0
0.6 Ib/ton Pb
procd
e
e
e
Lead emission factor
Metric
0.13 kg/103
kg Pb proc
160 kg/106
baseboxes
prod'
0.25 kg/103
kg Pb proc
<0.5 kg/106
kg Pb proc
negligible
0.8 kg/103 kg
Pb proc
English
0.25 Ib/ton
Pb proc
0.1 8 ton/106
baseboxes
prod
0.5 Ib/ton Pb
proc
1.0lb/103ton
Pb proc
negligible
1.5 Ib/ton Pb
proc
References
2,7
7
3,5,7
3,7
3,7
3,7
aProc = processed; prod = produced.
Calculated on the basis of 35% of the total (Reference 1).
'Reference 7, pp. 4-297 and 4-298.
"Reference 7, p. 4-301.
"Data not available.
'Basebox = 20.23 m2 (217.8 ft2), standard tin plate sheet area.
Table 7.17-2. CAN SOLDERING AND CABLE COVERING
CONTROL EFFICIENCIES
Process
Can soldering
Cable covering
Control
Mechanical cyclone
Fabric filter
Rotoclone wet collector
Dry cyclone collector
Percent
reduction
75 +
99.9
75-85
45 +
'Reference 7
7.17-2
EMISSION FACTORS
7/79
-------
7.17.4 Metallic Lead Products
7.17.4.1 General - Lead is consumed and emitted in the manufacture of ammunition, bearing metals
and other lead products. Lead used in the manufacture of ammunition is melted and alloyed before it is
cast, sheared, extruded, swaged or mechanically worked. Some lead is also reacted to form lead azide, a
detonating agent. Lead is used in bearing manufacture by alloying it with copper, bronze, antimony and tin.
Other lead products include terne metal (a plating alloy), weights and ballasts, caulking lead, plumbing
supplies, roofing materials, casting metal foil, collapsible metal tubes and sheet lead. Lead is also used for
galvanizing, annealing and plating. It is usually melted and cast prior to mechanical forming operations.
7.17.4.2 Emissions and Controls — Little or no air pollution control equipment is currently used by manu-
facturers of metallic lead products.6 Emissions from bearing manufacture are negligible, even without
controls.3
References for Section 7.17
1. N. J. Kulujian, Inspection Manual for the Enforcement of New Source Performance Standards:
Portland Cement Plants, EPA Contract No. 68-02-1355, PEDCo-Environmental Specialists, Inc.,
Cincinnati, OH, January 1975.
2. Atmospheric Emissions from Lead Typesetting Operation Screening Study, EPA Contract No. 68-02-
2085, PEDCo-Environmental Specialists, Inc., Cincinnati, OH, January 1976.
3. W. E. Davis, Emissions Study of Industrial Sources of Lead Air Pollutants, 1970, EPA Contract No.
68-02-0271, W. E. Davis Associates, Leawood, KS, April 1973.
4. R. P. Betz, et al., Economics of Lead Removal in Selected Industries, EPA Contract No. 68-02-0611,
Battelle Columbus Laboratories, Columbus, OH, August 1973.
5. E. P. Shea, Emissions from Cable Covering Facility, EPA Contract No. 68-02-0228, Midwest Re-
search Institute, Kansas City, MO. June 1973.
6. Mineral Industry Surveys: Lead Industry in May 1976, Bureau of Mines, U.S. Department of the
Interior, Washington, DC, August 1976.
7. Control Techniques for Lead Air Emissions, EPA-450/2-77-012, U.S. Environmental Protection
Agency, Research Triangle Park. NC. December 1977.
Metallurgical Industry 7.17-3
-------
7.18 LEADBEARING ORE CRUSHING
AND GRINDING
7.18.1 Process Description
Lead and zinc ores are normally deep mined, whereas copper ores are open pit mined. Lead, zinc and
copper are usually found together (in varying percentages) in combination with sulfur and/or oxygen.
In underground mines, the ore is disintegrated by percussive drilling machines, run through a primary
crusher, and then conveyed to the surface. In open pit mines, ore and gangue are loosened and pulverized
by explosives, scooped up by mechanical equipment, and transported to the concentrator.
Standard crushers, screens, and rod and ball mills classify and reduce the ore to powders in the 65 to 325
mesh range. The finely divided particle* are separated from the gangue and are concentrated in a liquid
medium by gravity and/or selective flotation, then cleaned, thickened and filtered. The concentrate is dried
prior to shipment to the smelter.
7.18.2 Emissions and Controls
Lead emissions are basically fugitive, caused by drilling, blasting, loading, conveying, screening.
unloading, crushing and grinding. The primary means of control are good mining techniques and equip-
ment maintenance. These practices include enclosing the truck loading operation, wetting or covering
truck loads and stored concentrates, paving the road from mine to concentrator, sprinkling the unloading
area, and preventing leaks in the crushing and griding enclosures. Cyclones and fabric filter? can be used
in the milling operations.
('articulate and lead emi —ion fat tor- lor Ic.id ore cni>liin<; ami material- handling operation-
are ghen in Table 7.18-1. Lead emi—ion-. I'roni the mining and milling of copper ore- are
negligible.
7/79 Metallurgical Industry 7.18-1
-------
Table 7.18-1. EMISSION FACTORS FOR ORE CRUSHING AND
GRINDING
EMISSION FACTOR RATING: B
Type of
ore
Pbc
Zn
Cu
Pb-Zn
Cu-Pb
Cu-Zn
Cu-Pb-Zn
Participate
emission factor3
Ib/ton
processed
6.0
6.0
6.4
6.0
6.4
6.4
6.4
kg/103 kg
processed
3.0
3.0
3.2
3.0
3.2
3.2
3.2
Lead
emission factorb
Ib/ton
processed
0.3
' 0.012
0.012
0.12
0.12
0.012
0.12
kg/103 kg
processed
0.15
0.006
0.006
0.06
0.06
0.006
0.06
"Reference 1, pp. 4-39
"^References 1-5
cRe
-------
8. MINERAL PRODUCTS INDUSTRY
This section involves the processing and production of various minerals. Mineral processing is characterized
by particulate emissions in the form of dust. Frequently, as in the case of crushing and screening, this dust is
identical to the material being handled. Emissions also occur through handling and storing the finished product
because this material is often dry and fine. Particulate emissions from some of the processes such as quarrying,
yard storage, and dust from transport are difficult to control. Most of the emissions from themanufacturingpro-
cesses discussed in this section, however, can be reduced by conventional particulate control equipment such as
cyclones, scrubbers, and fabric filters. Because of the wide variety in processing equipment and final product,
emissions cover a wide range; however, average emission factors have been presented for general use.
4/81
Mineral Products Industry
8.0-1
-------
8.1 ASPHALTIC CONCRETE PLANTS
8.1.1 General
Asphaltic concrete (asphaltic hot mix) is a paving material
which consists of a combination of graded aggregate that is dried,
heated and evenly coated with hot asphalt cement.
Asphalt hot mix is produced by mixing hot, dry aggregate with
hot liquid asphalt cement, in batch or continuous processes. Since
different applications require different aggregate size distribu-
tions, the aggregate is segregated by size and is proportioned into
the mix as required. In 1975, about 90 percent of total U.S.
production was conventional batch process, and most of the remainder
was continuous batch. The dryer drum process, another method of
hot mix asphalt production, in which wet aggregate is dried and
mixed with hot liquid asphalt cement simultaneously in a dryer,
comprised less than 3 percent of the total, but most new construc-
tion favors this design. Plants may be either permanent or portable.
Conventional Plants - Conventional plants produce finished asphaltic
concrete through either batch (Figure 8.1-1) or continuous
(Figure 8.1-2) aggregate mixing operations. Raw aggregate is
normally stockpiled near the plant, at a location where the moisture
content will stabilize to between 3 and 5 percent by weight.
As processing for either type of operation begins, the aggregate
is hauled from the storage piles and is placed in the appropriate
hoppers of the cold feed unit. The material is metered from the
hoppers onto a conveyor belt and is transported into a gas or oil
fired rotary dryer. Because a substantial portion of the heat is
transferred by radiation, dryers are equipped with flights designed
to tumble the aggregate to promote drying.
As it leaves the dryer, the hot material drops into a bucket
elevator and is transferred to a set of vibrating screens, where it
is classified into as many as four different grades (sizes). The
classified hot materials then enter the mixing operation.
In a batch plant, the classified aggregate drops into one of
four large bins. The operator controls the aggregate size distri-
bution by opening individual bins and allowing the classified
aggregate to drop into a weigh hopper until the desired weight is
obtained. After all the material is weighed, the sized aggregates
are dropped into a mixer and mixed dry for about 30 seconds. The
asphalt, a solid at ambient temperatures, is pumped from heated
storage tanks, weighed and injected into the mixer. The hot mix is
then dropped into a truck and hauled to the job site.
In a continuous plant, the classified aggregate drops into a
set of small bins which collect and meter the classified aggregate
to the mixer. From the hot bins, the aggregate is metered through
4/81 Mineral Products Industry 8.1-1
-------
'5
a
o
'w
w
0)
o
o
0)
T3
c
_eg
Q.
"5
Q.
(O
co
x
E
.
o
*-•
(0
m
oo
8.L2
EMISSION FACTORS
4/81
-------
I
I
o
1
Q)
-------
a set of feeder conveyors to another bucket elevator and into the
mixer. Asphalt is metered through the inlet end of the mixer, and
retention time is controlled by an adjustable dam at the end of the
mixer. The mix flows out of the mixer into a hopper from which
trucks are loaded.
Dryer Drum Plants - The dryer drum process simplifies the conven-
tional process by using proportioning feed controls in place of hot
aggregate storage bins, vibrating screens and the mixer.
Figure 8.1-3 is a diagram of the dryer drum process. Both
aggregate and asphalt are introduced near the flame end of the
revolving drum. A variable flow asphalt pump is linked electron-
ically to the aggregate belt scales to control mix specifications.
Dryer drum plants generally use parallel flow design for hot
burner gases and aggregate flow. Parallel flow has the advantage
of giving the mixture a longer time to coat and to collect dust in
the mix, thereby reducing particulate emissions to the atmosphere.
The amount of particulates generated within the dryer in this
process is lower than that generated within conventional dryers,
but because asphalt is heated to high temperatures for a long
period of time, organic emissions are greater.
The mix is discharged from the revolving dryer drum into surge
bins or storage silos.
22
Recycle Process for Drum Mix - Asphalt injected directly into the
dryer in the drum mix process is uniquely suited for the new, fast
developing technology of recycling asphalt pavement. Many drum mix
plants are now sold with a "recycle kit", which allows the plant to
be converted to process blends of virgin and recycled material.
In a recycling process, salvaged asphalt pavement (or base
material) that has been crushed and screened is introduced into the
dryer drum at a point somewhere downstream of the virgin aggregate
inlet. The amount of recycled pavement that can be successfully
processed has not yet been determined, but eventually, as the tech-
nology is developed, the blends may approach 100 percent recycled
material. Current blends range from about 20 percent to a maximum
of 50 percent recycled material.
The advantages of the recycling process are that blended
recycled material and virgin aggregate are generally less expensive
than 100 percent virgin aggregate, liquid asphalt requirements are
less due to residual asphalt in the recycled material, and the
recycled material requires less drying than the virgin aggregate.
The chief problem with recycling is opacity standards, because of
emissions of blue smoke (an aerosol of submicron organic droplets
volatilized from the asphalt and subsequently condensed before
exiting the stack). However, current recycle plant designs have
8.1-4 EMISSION FACTORS 4/81
-------
c
£
Q.
*^
CO
Q.
o
-C
E
3
•D
CD
ID
Q.
>s
s
I
CO
CO
06
4/81
Mineral Products Industry
8.1-5
-------
reduced blue smoke emissions greatly by preventing direct contact
of flame and liquid asphalt as it is injected.
8.1.2 Emissions and Controls
Emission points at batch, continuous and drum dryer hot mix
asphalt plants numbered below refer to Figures 8.1-1, 2 and 3,
respectively.
Emissions from the various sources in an asphaltic concrete
plant are vented either through the dryer vent or the scavenger
vent. The dryer vent stream goes to the primary collector. The
outputs of the primary collector and the scavenger vent go to the
secondary collector, then to the stack (1) for release to the atmos-
phere. The scavenger vent carries releases from the hot aggregate
elevator (5), vibrating screens (5), hot aggregate storage bins
(5), weigh hopper and mixer (2). The dryer vent carries emissions
only from the dryer. In the dryer drum process, the screens, weigh
hopper and mixer are not in a separate tower. Dryer emissions in
conventional plants contain mineral fines and fuel combustion
products, and the mixer assembly (2) also emits materials from the
hot asphalt. In dryer drum plants, both types of emissions arise
in the drum.
Emissions from drum mix recycled asphalt plants are similar
to emissions from regular drum mix plants, except for greater vola-
tile organics due to direct flame volatilization of petroleum deriva-
tives contained in used asphalt. Control of liquid organic emissions
in the drum mix recycle process is by (1) introduction of recycled
material at the center of the drum or farther toward the discharge
end, coupled with a flight design that causes a dense curtain of
aggregate between the flame and the residual asphalt, (2) protection
of the material from the flame by a heat shield, or (3) insulation
of the recycled material from the combustion zone entirely by a
drum-within-a-drum arrangement in which virgin material is dried
and coated in the inner drum, recycled material is indirectly heated
in the annular space surrounding the inner drum, and the materials
oo
are mixed at discharge of the inner drum/
Potential fugitive particulate emission sources from asphaltic
concrete plants include unloading of aggregate to storage bins (5),
conveying aggregate by elevators (5), and aggregate screening
operations (5). Another source of particulate emissions is the
mixer (2), which, although it is generally vented into the secondary
collector, is open to the atmosphere when a batch is loaded onto a
truck. This is an intermittent operation, and ambient conditions
(wind, etc.) are quite variable, so these emissions are best regarded
as fugitive. The open truck (4) can also be a source of fugitive
VOC emissions, as can the asphalt storage tanks (3), which may also
emit small amounts of polycyclics.
8.1-6 EMISSION FACTORS 4/81
-------
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 emitted**
Particulated
Sulfur oxides (as S02)d'^
Nitrogen oxides (as N02)
Volatile organic compounds^
Carbon monoxide^
Polycyclic organic matter^
Aldehydes^
Formaldehyde
2-Methylpropanal
(isobutyraldehyde)
1-Butanal
(n-butyraldehyde )
3-Me thy Ibutanal
(isovaleraldehyde)
Emission factor0
g/Mg
137
146S
18
14
19
0.013
10
0.077
0.63
1.2
8.3
Ib/ton
.274
.2923
.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.
cExpressed as g/Mg and Ib/ton of asphaltic concrete produced.
^Mean of 400 plant survey source test results.
eReference 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,
Mg (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 4/81
-------
were determined by sampling stack gas at the representative asphalt
hot mix plant.
The choice of applicable control equipment ranges from dry
mechanical collectors to scrubbers and fabric collectors. Attempts
to apply electrostatic precipitators have met with little success.
Practically all plants use primary dust collection equipment such
as large diameter cyclones, skimmers or settling chambers. These
chambers are often used as classifiers to return collected material
to the hot aggregate elevator combine it with the dryer aggregate
load. The primary collector effluent is ducted to a secondary
collection device because of high emission levels if vented to the
atmosphere.
TABLE 8.1-3. PARTICULATE EMISSION FACTORS FOR
CONVENTIONAL HOT MIX ASPHALTIC PLANTS3
EMISSION FACTOR RATING: B
Emission Factor
Type of Control kg/Mg Ib/ton
c d
Uncontrolled '
Precleaner"
High efficiency cyclone
Spray tower
Baffle spray tower
Multiple centrifugal scrubber
Orifice scrubber
Venturi scrubber^
Baghouse^
22.5
7.5
0.85
0.20
0.15
0.035
0.02
0.02
0.01
45.0
15.0
1.7
0.4
0.3
0.07
(.007-. 138)
0.04
0.04
(.025-. 053)
0.02
(0. 07-. 036)
^References 1, 2, 5-10 and 14-16.
Expressed in terms of emissions per unit weight of asphalt
concrete produced.
Almost all plants have at least a cleaner following the
,rotary dryer.
Reference 16. These factors differ from those given in
Table 8.1-1 because they are for uncontrolled emissions and
are from an earlier survey.
eReference 15. Average emission from a properly designed,
installed, operated and maintained scrubber, based on a
fstudy to develop New Source Performance Standards.
References 14 and 15.
References 14 and 15. Emissions from a properly designed,
installed, operated and maintained baghouse, based on a study
to develop New Source Performance Standards.
4/81 Mineral Products Industry 8.1-9
-------
Particulate emission factors for conventional asphaltic concrete
plants are presented in Table 8.1-3. Particle size distribution
information has not been included, because the particle size distri-
bution varies with the aggregate being used, the mix being made and
the type of plant operation. Potential fugitive particulate emis-
sion factors for conventional asphaltic concrete plants are shown
in Table 8.1-4.
Particulate emission factors for dryer drum plants are presented
in Table 8.1-5. (There are no data for other pollutants released
from the dryer drum hot mix process.) Particle size distribution
has not been included, because it varies with the aggregate used,
the mix made and the type of plant operation. Emission factors for
particulates in an uncontrolled plant can vary by a factor of 10,
depending upon the percent of fine particles in the aggregate.
References for Section 8.1
1. Asphaltic^ Concrete Plants Atmospheric Emissions Study,
EPA Contract No. 68-02-0076, Valentine, Fisher, and Tomlinson,
Seattle, WA, November 1971.
2. Guide for Air Pollution Control of Hot Mix Asphalt Plants,
Information Series 17, National Asphalt Pavement Association,
Riverdale, MD.
3. J.A. Danielson, "Control of Asphaltic Concrete Batching Plants
in Los Angeles County", JAPCA, ^£(2):29-33, 1960.
4. H.E. Friedrich, "Air Pollution Control Practices and Criteria
for Hot Mix Asphalt Paving Batch Plants", JAPCA, 19(12);424-8,
December 1969.
5. Air Pollution Engineering Manual, AP-40, U.S. Environmental
Protection Agency, Research Triangle Park, NC, 1973. Out of
Print.
6. G.L. Allen, et al., "Control of Metallurgical and Mineral Dust
and Fumes in Los Angeles County, California", Information
Circular 7627, U.S. Department of Interior, Washington, DC,
April 1952.
7. P.A. Kenline, Unpublished report on control of air pollutants
from chemical process industries, Robert A. Taft Engineering
Center, Cincinnati, OH, May 1959.
8. G. Sallee, Private communication on particulate pollutant study
between Midwest Research Institute and National Air Pollution
Control Administration, Durham, NC, June 1970.
8.1-10 EMISSION FACTORS 4/81
i
-------
TABLE 8.1-4. POTENTIAL UNCONTROLLED FUGITIVE
PARTICULATE EMISSION FACTORS FOR CONVENTIONAL
ASPHALTIC CONCRETE PLANTS
EMISSION FACTOR RATING: E
Q
Particulates
Type of Operation kg/Mg Ib/ton
Unloading coarse and fine
aggregate to storage bins*3 0.05 0.10
Cold and dried (and hot)
aggregate elevatorb 0.10 0.20
Screening hot aggregate0 0.013 0.026
a
Expressed as units per unit weight of aggregate.
Reference 18. Assumed equal to similar sources.
Reference 19. Asssumed equal to similar crushed
granite processes.
TABLE 8.1-5. PARTICULATE EMISSION FACTORS
FOR DRYER DRUM HOT MIX ASPHALT PLANTS3
EMISSION FACTOR RATING: B
Type of Control
Uncontrolled
Cyclone or multicyclone
Low energy wet scrubber
Venturi scrubber
Emission Factor
kg/Mg Ib/ton
2.45 4.9
0.34 0.67
0.04 0.07
0.02 0.04
fReference 11.
Expressed in terms of emissions per unit weight of
asphalt concrete produced. These factors differ
from those for conventional asphaltic concrete
plants because the aggregate contacts, and is coated
with, asphalt early in the dryer drum process.
Either stack sprays where water droplets are
injected into the exit stack, or a dynamic scrubber
that incorporates a wet fan.
4/81 Mineral Products Industry 8.1-11
-------
9. J.A. Danielson, Unpublished test data from asphalt batching
plants, Los Angeles County Air Pollution Control District,
Presented at Air Pollution Control Institute, University of
Southern California, Los Angeles, CA, November 1966.
10. M.E. Fogel et al., Comprehensive Economic Study of Air Pollution
Control Costs for Selected Industries and Selected Regions,
R-OU-455, U.S. Environmental Protection Agency, Research
Triangle Park, NC, February 1970.
11. Preliminary Evaluation of Air Pollution Aspects of the Drum
Mix Process, EPA-340/1-77-004, U.S. Environmental Protection
Agency, Research Triangle Park, NC, March 1976.
12. R.W. Beaty and B.M. Bunnell, "The Manufacture of Asphalt
Concrete Mixtures in the Dryer Drum", Presented at the Annual
Meeting of the Canadian Technical Asphalt Association, Quebec
City, Quebec, November 19-21, 1973.
13. J.S. Kinsey, An Evaluation of Control Systems and Mass Emission
Rates from Dryer Drum Hot Asphalt Plants, Colorado Air Pollution
Control Division, Denver, CO, December 1976.
14. Background Information for Proposed New Source Performance
Standards, APTD-1352A and B, U.S. Environmental Protection
Agency, Research Triangle Park, NC, June 1973.
15. Background Information for New Source Performance Standards,
EPA 450/2-74-003, U.S. Environmental Protection Agency, Research
Triangle Park, NC, February 1974.
16. Z.S. Kahn and T.W. Hughes, Source Assessment; Asphalt Paving
Hot Mix, EPA Contract No. 68-02-1874, Monsanto Research
Corporation, Dayton, OH, July 1977.
17. V.P. Puzinauskas and L.W. Corbett, Report on Emissions from
Asphalt Hot Mixes, RR-75-1A, The Asphalt Institute, College
Park, MD, May 1975.
18. Evaluation of Fugitive Dust from Mining, EPA Contract
No. 68-02-1321, Pedco Environmental Specialists, Inc., Cincinnati,
OH, June 1976.
19. J.A. Peters and P.K. Chalekode, "Assessment of Open Sources",
Presented at the Third National Conference on Energy and the
Environment, College Corner, OH, October 1, 1975.
20. Illustration of Dryer Drum Hot Mix Asphalt Plant, Pacific
Environmental Services, Inc., Santa Monica, CA, 1978.
8.1-12 EMISSION FACTORS 4/81
-------
21. Herman H. Forsten, "Applications of Fabric Filters to Asphalt
Plants", Presented at the 71st Annual Meeting of the Air Pol-
lution Control Association, Houston, TX, June 1978.
22. Emission of Volatile Organic Compounds from Drum Mix Asphalt
Plants, EPA Contract No. 68-01-2585, JACA Corporation, Fort
Washington, PA, September 1980.
4/81 Mineral Products Industry 8.1-13
-------
8.2 ASPHALT ROOFING
8.2.1 General1
The asphalt roofing industry manufactures asphalt saturated felt
rolls, shingles, roll roofing with mineral granules on the surface, and
smooth roll roofing that may contain a small amount of mineral dust or
mica on the surface. Most of these products are used in roof construc-
tion, with small quantities used in walls and other building applications.
8.2.2 Process Description
The manufacturing of asphalt felt, roofing, and shingles involves
the saturating and coating of felt with heated asphalt (saturant asphalt
and/or coating asphalt) by means of dipping and/or spraying. The process
can be divided into (1) asphalt storage, (2) asphalt blowing, (3) felt
saturation, (4) coating and (5) mineral surfacing. Glass fiber is
sometimes used in place of the paper felt, in which case the asphalt
saturation step is bypassed.
Preparation of the asphalt is an integral part of the production of
asphalt roofing. This preparation, called "blowing", involves the
oxidation of asphalt flux by bubbling air through liquid asphalt flux at
260°C (500°F) for 1 to 4.5 hours, depending on the desired characteristics
of the asphalt, such as softening point and penetration rate.2 A typical
plant will blow from four to six batches per 16 hour day, and the roofing
line will operate for 16 hours per day and 5 days per week. Blowing may
be done either in vertical tanks or in horizontal chambers. Inorganic
salts such as ferric chloride (FeCls) may be used as catalysts to achieve
desired properties and to increase the rate of reaction in the blowing
still, thus decreasing the time required for each blow.3 Air blowing of
asphalt may be conducted at oil refineries, asphalt processing plants,
and asphalt roofing plants. Figure 8.2-1 illustrates an asphalt blowing
operation.
Figure 8.2-2 shows a typical line for the manufacture of
asphalt-saturated felt, which consists of a paper feed roll, a dry looper
section, a saturator spray section (if used), a saturator dipping section,
steam-heated drying-in drums, a wet looper, water cooled rollers, a
finish floating looper, and a roll winder.
Organic felt may weigh from 25 to 55 pounds per 480 square feet (a
common unit in the paper industry), depending upon the intended product.
The felt is unrolled from the unwind stand into the dry looper, which
maintains a constant tension on the material. From the dry looper, the
felt may pass into the spray section of the saturator (not used in all
plants), where asphalt at 205° to 250°C (400° to 480°F) is sprayed onto
one side of the felt through several nozzles. In the saturator dip
section, the saturated felt is drawn over a series of rollers, with the
bottom rollers submerged in hot asphalt at 205° to 250°C (400° to 480°F).
4/81 Mineral Products Industry 8.2-1
-------
i
»
WATER VAPOR, OIL
AND PARTICIPATE
I
.NOCKOUT BOX
OR CYCLONE
>. s
WATER VAPOR
— ^. TO
PARTICULATE CONTROL
DEVICE
ASPHALT
FLUX -7
125°-1500F
BLOWING
STILL
CONTAINING
ASPHALT
/ft
RECOVERED OIL
WATER
AIR
FUEL
ASPHALT HEATER
AIR BLOWER
-*• BLOWN ASPHALT
Figure 8.2.-1. Air blowing of asphalt.3
At the next step, steam heated drying-in drums and the wet looper provide
the heat and time, respectively, for the asphalt to penetrate the felt.
The saturated felt then passes through water cooled rolls and onto the
finish floating looper, and then is rolled and cut on the roll winder to
product size. Two common weights of asphalt felt are 15 and 30 pounds
per 108 square feet (108 square feet of felt covers exactly 100 square
feet of roof).
A typical process for manufacturing asphalt shingles, mineral
surfaced rolls and smooth rolls is illustrated in Figure 8.2-3. This
line is similar to the felt line, except that following the wet looper are
a coater, a granule applicator, a press section, water cooled rollers, a
finish floating looper, and either a roll winder or a shingle cutter and
stacker. After leaving the wet looper, the saturated felt passes through
the coater. Filled asphalt coating at 180° to 205°C (355° to 400°F) is
released through a valve onto the felt just as it passes into the coater.1
Filled asphalt is prepared by mixing coating asphalt at 205°C (400°F) and
8.2-2
EMISSION FACTORS
4/81
-------
VENT TO CONTROL
EQUIPMENT
BURNER
ROLLWINOER
FOR ASPHALT
FELT
PUW>
8.2-2. Schematic of line for manufacturing asphalt saturated felt.1
4/81
Mineral Products Industry
8.2-3
-------
TANK
TRUCK
7T?T
PUMP
GRANULES |
STORAGE
TANK
TRUCK
YW
.^JLAJ^A^t-yAjAjAA-^A
SCREW CONVEYOR
TO CONTROL
EQUIPMENT GAS
BURNER
r
PUMP
VENT
VENT TO JCRE
CONTROL CONVEYOR
EQUIPMENT
t
SHINGLE STACKER
8.2-3. Schematic of line for manufacturing asphalt shingles, mineral surfaced rolls, and smooth
rolls.'
8.2-4
EMISSION FACTORS
4/81
-------
a mineral stabilizer (filler) in approximately equal proportions. The
filled asphalt is pumped to the coater. Sometimes the mineral stabilizer
is dried at about 120°C (250°F) in a dryer before mixing with the coating
asphalt. Heated squeeze rollers in the coater distribute the coating
evenly upon the felt surface, to form a thick base coating to which rock
granules, sand, talc, or mica can adhere. After leaving the coater, a
felt to be made into shingles or mineral surfaced rolls passes through
the granules applicator where granules are fed onto the hot, coated
surface. The granules are pressed into the coating as it passes through
squeeze rollers. Sand, talc or mica is applied to the back, or opposite,
side of the felt and is also pressed into the felt surface. Following
the application of the granules, the felt is cooled rapidly and is
transferred through the finish flowing looper to a roll winder or shingle
cutter.
8.2.3 Emissions and Controls
The atmospheric emissions from asphalt roofing manufacturing are:
1. gaseous and particulate organic compounds that include small
amounts of particulate polycyclic organic matter (PPOM),
2. emissions of small amounts of aldehydes, carbon monoxide and
sulfur dioxide, and
3. particulate emissions from mineral handling and storage.
The sources of the above pollutants are the asphalt blowing stills,
the saturator and coater, the asphalt storage tanks, and the mineral
handling and storage facilities. Emission factors from uncontrolled
blowing and saturating processes for particulate, carbon monoxide, and
volatile organic carbon as methane and nonmethane are summarized in
Table 8.2-1.
A common method to control emissions at asphalt roofing plants is
completely to enclose the saturator, wet looper and coater and then to
vent the emissions to one or more control devices (see Figures 8.2-2 and
8.2-3). Fugitive emissions from the saturator may pass through roof
vents and other openings in the building, if the saturator enclosure is
not properly installed and maintained. Control devices used in the
industry include afterburners, high velocity air filters, low voltage
electrostatic precipitators, and wet scrubbers. Blowing operations are
controlled by afterburners. Table 8.2-2 presents emission factors for
controlled blowing and saturating processes.
Particulate emissions associated with mineral handling and storage
operations are captured by enclosures, hoods or pickup pipes and are
controlled by using cyclones and/or fabric filters with removal
efficiencies of approximately 80-99 percent.
4/81 Mineral Products Industry 8.2-5
-------
TABLE 8.2-1. EMISSION FACTORS FOR ASPHALT ROOFING MANUFACTURING
WITHOUT CONTROLS3
EMISSION FACTOR RATING: PARTICULATE- A
OTHER- D
Volatile
Carbon
Particulates
Operation
Asphalt
blowing
c
Saturant
Coatii
ig
kg/Mg
3.6
13.4
Ib/ton
7.
26.
2
7
monoxide
kg/Mg
0.14d
Ib/ton
0.
27d
organic
methane
kg/Mg
e
0.94
Ib/ton
e
1.88
compounds
nonme thane
kg/Mg
e
0.93
Ib/ton
e
1.86
Shingle
saturation^ 0.25
0.50 0.01 0.02 0.04 0.08 0.01 0.02
Shingle ,
saturation
1.57
3.14 0.13 0.25 0.11 0.22 0.02 0.03
.References 2 and 4.
Expressed as kg/Mg (Ib/ton) of asphalt processed.
^Saturant blow of 1.5 hours.
Reference 2. CO data for uncontrolled emissions from stills was not
obtained during latest test program.
6Species data not available for saturant blow. Total organics (as CH4) for
saturant blow are 0.73 kg/Mg (1.460 Ib/ton).
Coating blow of 4.5 hours.
^Expressed as kg/Mg (Ib/ton) of 106.5 kg (235 Ib) shingle produced. Data
.from dip saturators.
Data from spray/dip saturator.
NOTES: -Particulate polycyclic organic matter is about 0.3 % of
particulate for blowing stills and 0.1 % of particulate for saturators.
-Aldehyde emission measurements made during coating blows:
4.6x10~5 kg/Mg (9.2xlO~5 Ib/ton).
-Aldehyde emissions data taken from one saturator only, with
afterburner the control device: 0.004 kg/Mg (0.007 Ib/ton).
-Species data not obtained for uncontrolled VOC, assumed same
percentage methane/nonmethane as in controlled emissions.
8.2-6
EMISSION FACTORS
4/81
-------
TABLE 8.2-2. EMISSION FACTORS FOR ASPHALT ROOFING MANUFACTURING
WITH CONTROLS3
EMISSION FACTOR RATING: PARTICULATE- A
OTHER- D
Particulates
Operation
Asphalt blowing
Saturant
£
Coating
Shingle
saturation
kg/Mg
0.25
0.45
0.03
Ib/ton
0.50
0.89
0.06
monoxide
kg/Mg
0.6
4.4
0.45
Ib/ton
1.2
8.8
0.898
methane
kg/Mg
d
0.05
0.08
Ib/ton
d
0.10
0.15
nonme thane
kg/Mg
d
0.05
0.01
Ib/ton
d
0.09
0.02
ft
.References 2 and 4.
Expressed as kg/Mg (Ib/ton) of asphalt processed.
.Saturant blow of 1.5 hours.
Species data not available for saturant blow. Total organics (as CH4) for
saturant blow are 0.015 kg/Mg (0.03 Ib/ton).
..Coating blow of 4.5 hours.
Expressed as kg/Mg (Ib/ton) of 106.5 kg (235 Ib) shingle produced
(averages of test data from four plants).
CO emissions data taken from one plant only, with afterburner the
control device. Temperature of afterburner not high enough to convert
CO to C02.
NOTE: Particulate polyclic organic matter is about 0.03 % of particulate
for blowing stills and about 1.1 % of particulate for saturators.
4/81 Mineral Products Industry 8.2-7
-------
In this industry, closed silos are used for mineral storage, so open
storage piles are not a problem. To protect the minerals from moisture
pickup, all conveyors that are outside the buildings are enclosed.
Fugitive mineral emissions may occur at the unloading point, depending on
the type of equipment used. The discharge from the conveyor to the silos
is controlled by either a cyclone or a fabric filter.
References for Section 8.2
1. John A. Danielson, Air Pollution Engineering Manual (2d Ed.), AP-40,
U.S. Environmental Protection Agency, Research Triangle Park, NC,
May 1973. Out of print.
2. Atmospheric Emissions from Asphalt Roofing Processes, EPA Contract
No. 68-02-1321, Pedco Environmental, Cincinnati, OH, October 1974.
3. L. W. Corbett, "Manufacture of Petroleum Asphalt", Bituminous
Materials: Asphalts, Tars, and Pitches, Vol. 2, Part 1, New York,
Interscience Publishers, 1965.
4. Background Information for Proposed Standards Asphalt Roofing
Manufacturing Industry, EPA 450/3-80-021a, U.S. Environmental
Protection Agency, Research Triangle Park, NC, June 1980.
i
8.2-8 EMISSION FACTORS 4/81
-------
8.3 BRICKS AND RELATED CLAY PRODUCTS
8.3.1 Process Description
The manufacture of brick and related products such as clay pipe, pottery, and some types of refractory brick
involves the mining, grinding, screening, and blending of the raw materials, and the forming, cutting or shaping,
drying or curing, and firing of the final product.
Surface clays and shales are mined in open pits; most fine clays are found underground. After mining, the
material is crushed to remove stones and stirred before it passes onto screens that are used to segregate the
particles by size.
At the start of the forming process, clay is mixed with water, usually in a pug mill. The three principal
processes for forming brick are: stiff-mud, soft-mud, and dry-process. In the stiff-mud process, sufficient water is
added to give the clay plasticity; bricks are then formed by forcing the clay through a die and using cutter wire to
separate the bricks. All structural tile and most brick are formed by this process. The soft-mud process is usually
used when the clay contains too much water for the stiff-mud process. The clay is mixed with water until the
moisture content reaches 20 to 30 percent, and the bricks are formed in molds. In the dry-press process, clay is
mixed with a small amount of water and formed in steel molds by applying a pressure of 500 to 1500 psi. The
brick manufacturing process is shown in Figure 8.3-1.
Before firing, the wet clay units that have been formed are almost completely dried in driers that are usually
heated by waste heat from the kilns. Many types of kilns are used for firing brick; however, the most common are
the tunnel kiln and the periodic kiln. The downdraft periodic kiln is a permanent brick structure that has a
number of fireholes where fuel is fired into the furnace. The hot gases from the fuel are drawn up over the bricks,
down through them by underground flues, and out of the oven to the chimney. Although fuel efficiency is not as
high as that of a tunnel kiln because of lower heat recovery, the uniform temperature distribution through the
kiln leads to a good quality product. In most tunnel kilns, cars carrying about 1200 bricks each travel on rails
through the kiln at the rate of one 6-foot car per hour. The fire zone is located near the middle of the kiln and
remains stationary.
In all kilns, firing takes place in six steps: evaporation of free water, dehydration, oxidation, vitrification,
flashing, and cooling. Normally, gas or residual oil is used for heating, but coal may be used. Total heating time
varies with the type of product; for example, 9-inch refractory bricks usually require 50 to 100 hours of firing.
Maximum temperatures of about 2000°F (1090°C) are used in firing common brick.
8.3.2 Emissions and Controls1'3
Particulate matter is the primary emission in the manufacture of bricks. The main source of dust is the
materials handling procedure, which includes drying, grinding, screening, and storing the raw material.
Combustion products are emitted from the fuel consumed in the curing, drying, and firing portion of the process.
Fluorides, largely in gaseous form, are also emitted from brick manufacturing operations. Sulfur dioxide may be
emitted from the bricks when temperatures reach 2500°F (1370°C) or greater; however, no data on such
emissions are available.4
4/73 Mineral Products Industry 8.3-1
-------
(P)
PULVERIZING
SCREENING
(
)
GLAZING
•
(P)
DRYING
HOT
GASES
«
FUEL
w-
\
(P)
KILN
(P)
STORAGE
AND
SHIPPING
Figure 8.3-1. Basic flow diagram of brick manufacturing process.
source of paniculate emissions.
'P" denotes a major
A variety of control systems may be used to reduce both particulate and gaseous emissions. Almost any type
of particulate control system will reduce emissions from the material handling process, but good plant design and
hooding are also required to keep emissions to a minimum.
The emissions of fluorides can be reduced by operating the kiln at temperatures below 2000°F (1090°C) and
by choosing clays with low fluoride content. Satisfactory control can be achieved by scrubbing kiln gases with
water; wet cyclonic scrubbers are available that can remove fluorides with an efficiency of 95 percent, or higher.
Emission factors for brick manufacturing are presented in Table 8.3-1. Insufficient data are available to present
particle size information.
8.3-2
EMISSION FACTORS
4/73
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Mineral Products Industry
8.3-3
-------
References for Section 8.3
1. Air Pollutant Emission Factors. Final Report. Resources Research, Inc., Reston, Virginia. Prepared for
National Air Pollution Control Administration, Durham, N.C., under Contract Number CPA-22-69-119. April
1970.
2. Technical Notes on Brick and Tile Construction. Structural Clay Products Institute. Washington, D.C.
Pamphlet Number 9. September 1961.
3. Unpublished control techniques for fluoride emissions. Environmental Protection Agency, Office of Air
Programs, Research Triangle Park, N.C.
4. Allen, M. H. Report on Air Pollution, Air Quality Act of 1967 and Methods of Controlling the Emission of
Particulate and Sulfur Oxide Air Pollutants. Structural Clay Products Institute, Washington, D. C. September
1969.
5. Norton, F. H. Refractories, 3rd Ed. New York, McGraw-Hill Book Company. 1949.
6. Semran, K. T. Emissions of Fluorides from Industrial Processes: A Review. J. Air Pol. Control Assoc.
7(2):92-108. August 1957.
7. Kirk-Othmer. Encyclopedia of Chemical Technology, Vol. V, 2nd Ed. New York, Interscience (John Wiley
and Sons, Inc.), 1964. p. 561-567.
8. Wentzel, K. F. Fluoride Emissions in the Vicinity of Brickworks. Staub. 25(3):45-50. March 1965.
9. Allen, G. L. et al. Control of Metallurgical and Mineral Dusts and Fumes in Los Angeles County. U. S.
Department of Interior, Bureau of Mines. Washington, D.C. Information Circular Number 7627. April 1952.
10. Private communication between Resources Research, Inc. Reston, Va. and the State of New Jersey Air
Pollution Control Program, Trenton. July 20, 1969.
8.3-4 EMISSION FACTORS 4/73
-------
8.4 CALCIUM CARBIDE MANUFACTURING
8.4.1 General
Calcium carbide (CaC£) 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 •> CaC£ + 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
1/84
Figure 8.4-1. Calcium carbide manufacturing process.
Mineral Products Industry
8.4-1
-------
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
-------
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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8.5 CASTABLE REFRACTORIES
8.5.1 Process Description1 "3
Castable or fused-cast refractories are manufactured by carefully blending such components as alumina,
zirconia, silica, chrome, and magnesia; melting the mixture in an electric-arc furnace at temperatures of 3200 to
4500°F (1760 to 2480°C); pouring it into molds; and slowly cooling it to the solid state. Fused refractories are
less porous and more dense than kiln-fired refractories.
8.5.2 Emissions and Controls1
Particulate emissions occur during the drying, crushing, handling, and blending of the components; during the
actual melting process; and in the molding phase. Fluorides, largely in the gaseous form, may also be emitted
during the melting operations.
The general types of particulate controls may be used on the materials handling aspects of refractory
manufacturing. Emissions from the electric-arc furnace, however, are largely condensed fumes and consist of very
fine particles. Fluoride emissions can be effectively controlled with a scrubber. Emission factors for castable
refractories manufacturing are presented in Table 8.5-1.
Table 85-1. PARTICULATE EMISSION FACTORS FOR CASTABLE
REFRACTORIES MANUFACTURING8
EMISSION FACTOR RATING: C
Type of process
Raw material dryerb
Raw material crushing
and processing0
Electric-arc meltingd
Curing oven6
Molding and shakeoutb
Type of control
Baghouse
Scrubber
Cyclone
Baghouse
Scrubber
-
Baghouse
Uncontrolled
Ib/ton
30
120
50
0.2
25
kg/MT
15
60
25
0.1
12.5
Controlled
Ib/ton
0.3
7
45
0.8
10
-
0.3
kg/MT
0.15
3.5
22.5
0.4
5
-
0.15
aFluoride emissions from the melt average about 1.3 pounds of HF per ton of melt (0.65 kg
HF/MT melt). Emission factors expressed as units per unit weight of feed material.
Reference 4.
cReferences 4 and 5.
"References 4 through 6.
6Reference 5.
2/72
Mineral Products Industry
8.5-1
-------
References for Section 8.5
1. Air Pollutant Emission Factors. Final Report. Resources Research, Inc. Reston, Va. Prepared for National
Air Pollution Control Administration, Durham, N.C., under Contract Number CPA-22-69-119. April 1970.
2. Brown, R. W. and K. H. Sandmeyer. Applications of Fused-Cast Refractories. Chem. Eng. 76:106-114, June
16, 1969.
3. Shreve, R.N. Chemical Process Industries, 3rd Ed. New York, McGraw-Hill Book Company. 1967. p. 158.
4. Unpublished data provided by a Corhart Refractory. Kentucky Department of Health, Air Pollution Control
Commission. Frankfort, Kentucky. September 1969.
5. Unpublished stack test data on refractories. Resources Research, Incorporated. Reston, Virginia. 1969.
6. Unpublished stack test data on refractories. Resources Research, Incorporated. Reston, Virginia. 1967.
8.5-2 EMISSION FACTORS 2/72
-------
8.6 PORTLAND CEMENT MANUFACTURING
8.6.1 Process Description l ~3
Portland cement manufacture accounts for about 98 percent of the cement production in the United States.
The more than 30 raw materials used to make cement may be divided into four basic components: lime
(calcareous), silica (siliceous), alumina (argillaceous), and iron (ferriferous). Approximately 3200 pounds of dry
raw materials are required to produce 1 ton of cement. Approximately 35 percent of the raw material weight is
removed as carbon dioxide and water vapor. As shown in Figure 8.6-1, the raw materials undergo separate
crushing after the quarrying operation, and, when needed for processing, are proportioned, ground, and blended
using either the wet or dry process.
In the dry process, the moisture content of the raw material is reduced to less than 1 percent either before or
during the grinding operation. The dried materials are then pulverized into a powder and fed directly into a rotary
kiln. Usually, the kiln is a long, horizontal, steel cylinder with a refractory brick lining. The kilns are slightly
inclined and rotate about the longitudinal axis. The pulverized raw materials are fed into the upper end and travel
slowly to the lower end. The kilns are fired from the lower end so that the hot gases pass upward and through the
raw material. Drying, decarbonating, and calcining are accomplished as the material travels through the heated
kiln, finally burning to incipient fusion and forming the clinker. The clinker is cooled, mixed with about 5
percent gypsum by weight, and ground to the final product fineness. The cement is then stored for later
packaging and shipment.
With the wet process, a slurry is made by adding water to the initial grinding operation. Proportioning may
take place before or after the grinding step. After the materials are mixed, the excess water is removed and final
adjustments are made to obtain a desired composition. This final homogeneous mixture is fed to the kilns as a
slurry of 30 to 40 percent moisture or as a wet filtrate of about 20 percent moisture. The burning, cooling,
addition of gypsum, and storage are carried out as in the dry process.
8.6.2 Emissions and Controls1'2-4
Particulate matter is the primary emission in the manufacture of portland cement. Emissions also include the
normal combustion products of the fuel used to supply heat for the kiln and drying operations, including oxides
of nitrogen and small amounts of oxides of sulfur.
Sources of dust at cement plants include: (1) quarrying and crushing, (2) raw material storage, (3) grinding and
blending (dry process only), (4) clinker production, (5) finish grinding, and (6) packaging. The largest source of
emissions within cement plants is the kiln operation, which may be considered to have three units: the feed
system, the fuel-firing system, and the clinker-cooling and handling system. The most desirable method of
disposing of the collected dust is injection into the burning zone of the kiln and production of clinkers from the
dust. If the alkali content of the raw materials is too high, however, some of the dust is discarded or leached
before returning to the kiln. In many instances, the maximum allowable alkali content of 0.6 percent (calculated
as sodium oxide) restricts the amount of dust that can be recycled. Additional sources of dust emissions are raw
material storage piles, conveyors, storage silos, and loading/unloading facilities.
The complications of kiln burning and the large volumes of materials handled have led to the adoption of
many control systems for dust collection. Depending upon the emission, the temperature of the effluents in the
4/73 Mineral Products Industry 8.6-1
-------
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plant in question, and the particulate emission standards in the community, the
cement industry generally uses mechanical collectors, electrical precipitators,
fabric filter (baghouse) collectors, or combinations of these devices to control
emissions.
Table 8.6-1 summarizes emission factors for cement manufacturing and also
includes in footnote d typical control efficiencies of particulate emissions.
Table 8.6-2 indicates the particle size distribution for particulate emissions
from kilns and cement plants before control systems are applied.
TABLE 8.6-1.
EMISSION FACTORS FOR CEMENT MANUFACTURING
WITHOUT CONTROLS3>b»c»d
EMISSION FACTOR RATING: B
12/81
Pry Process
Wet Process
Pollutant
Kilns
Dryers,
grinders, etc.
Kilns
Dryers,
grinders, etc.
Particulate6
kg/Mg
Ib/ton
Sulfur dioxidef
Mineral source
kg/Mg
Ib/ton
Gas combustion
kg/Mg
Ib/ton
Oil combustion
kg/Mg
Ib/ton
Coal combustion
kg/Mg
Ib/ton
Nitrogen oxides
kg/Mg
Ib/ton
Lead
kg/Mg
Ib/ton
122.0
245.0
5.1
10.2
Negh
Neg
2.1S1
4.2S
3.4S
6.8S
1.3
2.6
0.06
0.12
48.0 114.0
96.0 228.0
5.1
10.2
Neg
Neg
2. IS
4.2S
3.4S
6.8S
1.3
2.6
0.02 0.05
0.04 0.10
16.0
32.0
-
-
-
-
-
-
-
—
-
-
0.01
0.02
aOne barrel of cement weighs 171 kg (376 pounds).
"These emission factors include emissions from fuel combustion, which should not
be calculated separately.
References 1-2.
^Emission factors expressed in weight per unit weight of cement produced. Dash
indicates no available data.
eTypical collection efficiencies for kilns, dryers, grinders, etc., are: multi-
cyclones, 80%; electrostatic precipitators, 95%; electrostatic precipitators with
multicyclones, 97.5%; fabric filter units, 99.8%.
^The sulfur dioxide factors presented take into account the reactions with the alk-
aline dusts when no baghouses are used. With baghouses, approximately 50% more SO2
is removed because of reactions with the alkaline particulate filter cake. Also
note that the total S02 from the kiln is determined by summing emission contribu-
tions from the mineral source and the appropriate fuel.
SThese emissions are the result of sulfur being present in the raw materials and are
thus dependent upon source of the raw materials used. The 5.1 kg/Mg (10.2 Ib/ton)
factors account for part of the available sulfur remaining behind in the product
because of its alkaline nature and affinity for S02«
"Negligible.
1S - % sulfur in fuel.
JReferences 7-8.
Mineral Products Industry
8.6-3
-------
TABLE 8.6-2. SIZE DISTRIBUTION OF DUST EMITTED
FROM UNCONTROLLED KILN OPERATIONS1*5
Particle size, Kiln dust finer than corresponding
microns particle size»%
60 93
50 90
40 84
30 74
20 58
10 38
5 23
1 3
Sulfur dioxide may be generated from the sulfur compounds in the ores as
well as from combusion of fuel. The sulfur content of both ores and fuels will
vary from plant to plant and with geographic location. The alkaline nature of
the cement, however, provides for direct absorption of S02 into the product.
The overall control inherent in the process is approximately 57 percent or
greater of the available sulfur in ore and fuel if a baghouse that allows the
S02 to come in contact with the cement dust is used. Control, of course, will
vary according to the alkali and sulfur content of the raw materials and fuel."
References for Section 8.6
1. T. E. Kreichelt, D. A. Kemnitz, and S. T. Cuffe, AtmosphericEmissions
from the Manufacture of Portland Cement, U.S. DHEW, Public Health Service,
Cincinnati, OH, PHS Publication Number 999-AP-17, 1967.
2. Unpublished standards of performance for new and substantially modified
Portland cement plants, U.S. Environmental Protection Agency, Bureau of
Stationary Source Pollution Control, Research Triangle Park, NC, August
1971.
3« A Study of the Cement Industry in the State of Missouri, Resources Re-
search Inc., Reston, VA, prepared for the Air Conservation Commission of
the State of Missouri, December 1967.
4. Standards of Performance for New Stationary Sources, U.S. Environmental
Protection Agency, Federal Register 36(247,Pt II): December 23, 1971.
5. Particulate Pollutant System Study, Midwest Research Institute, Kansas
City, MO, prepared for U.S. Environmental Protection Agency, Air Pollution
Control Office, Research Triangle Park, NC, under Contract Number CPA-22-
69-104, May 1971.
6. Restriction of Emissions from Portland Cement Works, VDI Richtlinien,
Dusseldorf, Germany, February 1967.
7. Emission Tests Nos. 71-MM-02, 71-MM-03 and 71-MM-05, Office of Air Quality
Planning and Standards, Research Triangle Park, NC, March-April 1972.
8. Control Techniques for Lead Air Emissions, EPA 450/2-77-012, U. S. Environ-
mental Protection Agency, Research Triangle Park, NC, December 1972.
8.6-4 EMISSION FACTORS 12/81
-------
8.7 CERAMIC CLAY MANUFACTURING
8.7.1 Process Description1
The manufacture of ceramic clay involves the conditioning of the basic ores by several methods. These include
the separation and concentration of the minerals by screening, floating, wet and dry grinding, and blending of the
desired ore varieties. The basic raw materials in ceramic clay manufacture are kaolinite (Al2O3'2Si02*2H20)
and montmorillonite [(Mg, Ca) OA^C^'SSiC^'nr^O] clays. These clays are refined by separation and
bleaching, blended, kiln-dried, and formed into such items as whiteware, heavy clay products (brick, etc.),
various stoneware, and other products such as diatomaceous earth, which is used as a filter aid.
8.7.2 Emissions and Controls1
Emissions consist primarily of particulates, but some fluorides and acid gases are also emitted in the drying
process. The high temperatures of the firing kilns are also conducive to the fixation of atmospheric nitrogen and
the subsequent release of NO, but no published information has been found for gaseous emissions. Particulates
are also emitted from the grinding process and from storage of the ground product.
Factors affecting emissions include the amount of material processed, the type of grinding (wet or dry), the
temperature of the drying kilns, the gas velocities and flow direction in the kilns, and the amount of fluorine in
the ores.
Common control techniques include settling chambers, cyclones, wet scrubbers, electrostatic precipitators, and
bag filters. The most effective control is provided by cyclones for the coarser material, followed by wet scrubbers,
bag filters, or electrostatic precipitators for dry dust. Emission factors for ceramic clay manufacturing are
presented in Table 8.7-1.
Table 8.7-1. PARTICULATE EMISSION FACTORS FOR CERAMIC CLAY MANUFACTURING3
EMISSION FACTOR RATING: A
Type of process
Drying01
Grinding6
Storaged
Uncontrolled
Ib/ton
70
76
34
kg/MT
35
38
17
Cyclone13
Ib/ton
18
19
8
kg/MT
9
9.5
4
Multiple-unit
cyclone and scrubber0
Ib/ton
7
-
-
kg/MT
3.5
-
-
aEmission factors expressed as units per unit weight of input to process.
Approximate collection efficiency: 75 percent.
cApproximate collection efficiency: 90 percent.
References 2 through 5.
eReference 3,
2/72
Mineral Products Industry
8.7-1
-------
References for Section 8.7-1
1. Air Pollutant Emission Factors. Final Report. Resources Research, Inc. Reston, Va. Prepared for National
Air Pollution Control Administration, Durham, N.C., under Contract Number CPA-22-69-119. April 1970.
2. Allen, G. L. et al. Control of Metallurgical and Mineral Dusts and Fumes in Los Angeles County. Department
of Interior, Bureau of Mines. Washington, D.C. Information Circular Number 7627. April 1952.
3. Private Communication between Resources Research, Incorporated, Reston, Virginia, and the State of New
Jersey Air Pollution Control Program, Trenton, New Jersey. July 20,1969.
4. Henn, J. J. et al. Methods for Producing Alumina from Clay: An Evaluation of Two Lime Sinter Processes.
Department of Interior, Bureau of Mines. Washington, D.C. Report of Investigations Number 7299.
September 1969.
5. Peters, F. A. et al. Methods for Producing Alumina from Clay: An Evaluation of the Lime-Soda Sinter
Process. Department of Interior, Bureau of Mines. Washington, D.C. Report of Investigation Number 6927.
1967.
8.7-2 EMISSION FACTORS 2/72
-------
8.8 CLAY AND FLY-ASH SINTERING
8.8.1 Process Description1
Although the processes for sintering fly ash and clay are similar, there are some distinctions that justify a
separate discussion of each process. Fly-ash sintering plants are generally located near the source, with the fly ash
delivered to a storage silo at the plant. The dry fly ash is moistened with a water solution of lignin and
agglomerated into pellets or balls. This material goes to a traveling-grate sintering machine where direct contact
with hot combustion gases sinters the individual particles of the pellet and completely burns off the residual
carbon in the fly ash. The product is then crushed, screened, graded, and stored in yard piles.
Clay sintering involves the driving off of entrained volatile matter. It is desirable that the clay contain a
sufficient amount of volatile matter so that the resultant aggregate will not be too heavy. It is thus sometimes
necessary to mix the clay with finely pulverized coke (up to 10 percent coke by weight).2'3 In the sintering
process the clay is first mixed with pulverized coke, if necessary, and then pelletized. The clay is next sintered in
a rotating kiln or on a traveling grate. The sintered pellets are then crushed, screened, and stored, in a procedure
similar to that for fly ash pellets.
8.8.2 Emissions and Controls1
In fly-ash sintering, improper handling of the fly ash creates a dust problem. Adequate design features,
including fly-ash wetting systems and participate collection systems on all transfer points and on crushing and
screening operations, would greatly reduce emissions. Normally, fabric filters are used to control emissions from
the storage silo, and emissions are low. The absence of this dust collection system, however, would create a major
emission problem. Moisture is added at the point of discharge from the silo to the agglomerator, and very few
emissions occur there. Normally, there are few emissions from the sintering machine, but if the grate is not
properly maintained, a dust problem is created. The consequent crushing, screening, handling, and storage of the
sintered product also create dust problems.
In clay sintering, the addition of pulverized coke presents an emission problem because the sintering of
coke-impregnated dry pellets produces more particulate emissions than the sintering of natural clay. The crushing,
screening, handling, and storage of the sintered clay pellets creates dust problems similar to those encountered in
fly-ash sintering. Emission factors for both clay and fly-ash sintering are shown in Table 8.8-1.
2/72 Mineral Products Industry 8.8-1
-------
Table 8.8-1. PARTICULATE EMISSION FACTORS FOR
SINTERING OPERATIONS8
EMISSION FACTOR RATING: C
Type of material
Fly ashd
Clay mixed with cokef -9
Natural clay*1-'
Sintering operation13
Ib/ton
110
40
12
kg/MT
55
20
6
Crushing, screening.
and yard storage13'0
Ib/ton
e
15
12
kg/MT
e
7.5
6
aEmission factors expressed as units per unit weight of finished product.
bCyclones would reduce this emission by about 80 percent.
Scrubbers would reduce this emission by about 90 percent.
cBased on data in section on stone quarrying and processing.
dReference 1.
elncluded in sintering losses.
90 percent clay, 10 percent pulverized coke; traveling-grate, single-pass, up-draft sintering
machine.
9References 3 through 5.
Rotary dryer sinterer.
1 Reference 2.
References for Section 8.8
1. Air Pollutant Emission Factors. Final Report. Resources Research, Inc. Reston, Va. Prepared for National
Air Pollution Control Administration, Durham, N.C., under Contract Number CPA-22-69-119. April 1970.
2. Communication between Resources Research, Incorporated, Reston, Virginia, and a clay sintering firm.
October 2, 1969.
3. Communication between Resources Research, Incorporated, Reston, Virginia, and an anonymous Air
Pollution Control Agency. October 16, 1969.
4. Henn, J. J. et al. Methods for Producing Alumina from Clay: An Evaluation of Two Lime Sinter Processes.
Department of the Interior, Bureau of Mines. Washington, D.C. Report of Investigation Number 7299.
September 1969.
5. Peters, F. A. et al. Methods for Producing Alumina from Clay: An Evaluation of the Lime-Soda Sinter
Process. Department of the Interior, Bureau of Mines. Washington, D.C. Report of Investigation Number
6927.1967.
8.8-2
EMISSION FACTORS
2/72
-------
8.9 COAL CLEANING
1 2
8.9.1 Process Description '
Coal cleaning is a process by which impurities such as sulfur, ash
and rock are removed from coal to upgrade its value. Coal cleaning
processes are categorized as either physical cleaning or chemical clean-
ing. Physical coal cleaning processes, the mechanical separation of
coal from its contaminants using differences in density, are by far the
major processes in use today. Chemical coal cleaning processes are not
commercially practical and are therefore not included in this discussion.
The scheme used in physical coal cleaning processes varies among
coal cleaning plants but can generally be divided into four basic phases:
initial preparation, fine coal processing, coarse coal processing, and
final preparation. A sample process flow diagram for a physical coal
cleaning plant is presented in Figure 8.9-1.
In the initial preparation phase of coal cleaning, the raw coal is
unloaded, stored, conveyed, crushed, and classified by screening into
coarse and fine coal fractions. The size fractions are then conveyed to
their respective cleaning processes.
Fine coal processing and coarse coal processing use very similar
operations and equipment to separate the contaminants. The primary
differences are the severity of operating parameters. The majority of
coal cleaning processes use upward currents or pulses of a fluid such as
water to fluidize a bed of crushed coal and impurities. The lighter
coal particles rise and are removed from the top of the bed. The
heavier impurities are removed from the bottom. Coal cleaned in the wet
processes then must be dried in the final preparation processes.
Final preparation processes are used to remove moisture from coal,
thereby reducing freezing problems and weight, and raising the heating
value. The first processing step is dewatering, in which a major por-
tion of the water is removed by the use of screens, thickeners and
cyclones. The second step is normally thermal drying, achieved by any
one of three dryer types: fluidized bed, flash and multilouvered. In
the fluidized bed dryer, the coal is suspended and dried above a per-
forated plate by rising hot gases. In the flash dryer, coal is fed into
a stream of hot gases, for instantaneous drying. The dried coal and wet
gases are drawn up a drying column and into a cyclone for separation.
In the multilouvered dryer, hot gases are passed through a falling
curtain of coal. The coal is raised by flights of a specially designed
conveyor.
1 2
8.9.2 Emissions and Controls '
Emissions from the initial coal preparation phase of either wet or
dry processes consist primarily of fugitive particulates, as coal dust,
from roadways, stock piles, refuse areas, loaded railroad cars, conveyor
2/80 Mineral Product* Industry 8.9-1
-------
+-» c
M O
« o
7
E
2
O)
o
O
c
03
O)
'E
03
-SJ
o
"J5
8
8
'5.
o>
00
3
05
EMISSION FACTORS
2/80
-------
belt pouroffs, crushers, and classifiers. The major control technique
used to reduce these emissions is water wetting. Another technique
applicable to unloading, conveying, crushing, and screening operations
involves enclosing the process area and circulating air from the area
through fabric filters.
Table 8.9-1. EMISSION FACTORS FOR COAL CLEANING3
EMISSION FACTOR RATING: B
*• — - _0ger at ion
Pollutant^—- — ~__
Particulates
Before Cyclone
After Cyclone
After Scrubber
S098
z
After Cyclone
After Scrubber
NO ^
X
After Scrubber
vock
After Scrubber
Fluidized
Ib/ton
20b
12e
0.09e
0.43h
0.25
0.14
0.10
Bed Flash Multilouvered
kg/MT
iob
6e
0.05e
0.22h
0.13
0.07
0.05
Ib/ton kg/MT
16b 8b
10f 5f
0.4f 0.2f
_i
-
-
-
Ib/ton kg/MT
25° 13C
8C 4°
O.lf 0.05C
-
-
-
- -
, Emission factors expressed as units per weight of coal dried.
References 3 and 4.
,Reference 5.
Cyclones are standard pieces of process equipment for product collection.
^References 6, 7, 8, 9 and 10.
Reference 1.
References 7 and 8. The control efficiency of venturi scrubbers
on S02 emissions depends on the inlet S02 loading, ranging from 70 to
80% removal for low sulfur coals (.7% S) down to 40 to 50% removal for
high sulfur coals (3% S).
References 7, 8 and 9.
.Not available.
•^Reference 8. The control efficiency of venturi scrubbers on NO.
. emissions is approximately 10 to 25%.
volatile organic compounds as Ibs of carbon/ton of coal dried.
The major emission source in the fine or coarse coal processing
phases is the air exhaust from the air separation processes. For the
dry cleaning process, this is where the coal is stratified by pulses of
air. Particulate emissions from this source are normally controlled
with cyclones followed by fabric filters. Potential emissions from wet
cleaning processes are very low.
x
2/80
Mineral Product* Industry
8.9-3
-------
The major source of emissions from the final preparation phase is
the thermal dryer exhaust. This emission stream contains coal particles
entrained in the drying gases, in addition to the standard products of
coal combustion resulting from burning coal to generate the hot gases.
Factors for these emissions are presented in Table 8.9-1. The most
common technologies used to control this source are venturi scrubbers
and mist eliminators downstream from the product recovery cyclones. The
particulate control efficiency of these technologies ranges from 98 to
99.9 percent. The venturi scrubbbers also have an NOX removal efficiency
of 10 to 25 percent, and an S02 removal efficiency ranging from 70 to 80
percent for low sulfur coals to 40 to 50 percent for high sulfur coals.
References for Section 8.9
1. Background Information for Establishment of National Standards of
Performance for New Sources: Coal Cleaning Industry, Environmental
Engineering, Inc., Gainesville, FL, EPA Contract No. CPA-70-142,
July 1971.
2. Air Pollutant Emissions Factors, National Air Pollution Control
Administration, Contract No. CPA-22-69-119, Resources Research
Inc., Reston, VA, April 1970.
3. Stack Test Results on Thermal Coal Dryers (Unpublished), Bureau of
Air Pollution Control, Pennsylvania Department of Health,
Harrisburg, PA.
4. "Amherst's Answer to Air Pollution Laws", Coal Mining and
Processing, 7(2);26-29, February 1970.
5. D. W. Jones, "Dust Collection at Moss No. 3", Mining Congress
Journal, 55(7);53-56, July 1969.
6. Elliott Northcott, "Dust Abatement at Bird Coal", Mining Congress
Journal, 53^26-29, November 1967.
7. Richard W. Kling, Emissions from the Island Creek Coal Company Coal
Processing Plant, York Research Corporation, Stamford, CT,
February 14, 1972.
8. Coal Preparation Plant Emission Tests, Consolidation Coal Company,
Bishop, West Virginia, EPA Contract No. 68-02-0233, Scott Research
Laboratories, Inc., Plumsteadville, PA, November 1972.
9. Coal Preparation Plant Emission Tests, Westmoreland Coal Company,
Wentz Plant, EPA Contract No. 68-02-0233, Scott Research
Laboratories, Inc., Plumsteadville, PA, April 1972.
10. Background Information for Standards of Performance; Coal
Preparation Plants, Volume 2: Test Data Summary,
EPA-450/2-74-021b, U. S. Environmental Protection Agency, Research
Triangle Park, NC, October 1974.
8.9-1 EMISSION FACTORS 2/80
-------
8.10 CONCRETE BATCHING
8.10.1 Process Description 1 - 3
Concrete batching involves the proportioning of sand, gravel, and cement by means of weigh hoppers and
conveyors into a mixing receiver such as a transit mix truck. The required amount of water is also discharged into
the receiver along with the dry materials. In some cases, the concrete is prepared for on-site building construction
work or for the manufacture of concrete products such as pipes and prefabricated construction parts.
8.10.2 Emissions and Controls1
Particulate emissions consist primarily of cement dust, but some sand and aggregate gravel dust emissions do
occur during batching operations. There is also a potential for dust emissions during the unloading and conveying
of concrete and aggregates at these plants and during the loading of dry-batched concrete mix. Another source of
dust emissions is the traffic of heavy equipment over unpaved or dusty surfaces in and around the concrete
batching plant.
Control techniques include the enclosure of dumping and loading areas, the enclosure of conveyors and
elevators, filters on storage bin vents, and the use of water sprays. Table 8.10-1 presents emission factors for
concrete batch plants.
Table 8.10-1. PARTICULATE EMISSION FACTORS
FOR CONCRETE BATCHING3
EMISSION FACTOR RATING: C
Concrete
batching13
Uncontrolled
Good control
Emission
Ib/yd3 of
concrete
0.2
0.02
kg/m3 of
concrete
0.12
0.012
aOne cubic yard of concrete weighs 4000 pounds (1 m3 = 2400 kg).
The cement content varies with the type of concrete mixed, but
735 pounds of cement per yard (436 kg/m3) may be used as a typi-
cal value.
bReference 4.
2/72 Mineral Products Industry 8.10-1
-------
References for Section 8.10
1. Air Pollutant Emission Factors. Final Report. Resources Research Inc. Reston, Va. Prepared for National Air
Pollution Control Administration, Durham, N.C., under Contract Number CPA-22-69-119. April 1970.
2. Vincent, E. J. and J. L. McGinnity. Concrete Batching Plants. In: Air Pollution Engineering Manual.
Danielson, J. A. (ed.). U.S. DHEW, PHS, National Center for Air Pollution Control. Cincinnati, Ohio. PHS
Publication Number 999-AP-40. 1967. p. 334-335.
3. Communication between Resources Research, Incorporated, Reston, Virginia, and the National Ready-Mix
Concrete Association. September 1969.
4. Allen, G. L. et al. Control of Metallurgical and Mineral Dusts and Fumes in Los Angeles County. Department
of the Interior, Bureau of Mines. Washington, D.C. Information Circular Number 7627. April 1952.
8.10-2 EMISSION FACTORS 2/72
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8.11 GLASS FIBER MANUFACTURING
8.11.1 General
Glass fiber manufacturing is the high temperature conversion of various
raw materials (predominantly borosilicates) into a homogeneous melt, followed
by the fabrication of this melt into glass fibers. The two basic types of
glass fiber products, textile and wool, are manufactured by similar pro-
cesses. A typical diagram of these processes is shown in Figure 8.11-1.
Glass fiber production can be segmented into three phases: raw materials
handling, glass melting and refining, and fiber forming and finishing, this
last phase being slightly different in textile and the wool glass fiber
production.
Raw Materials Handling - The primary component of glass fiber is sand,
but it also includes varying quantities of feldspar, sodium sulfate, an-
hydrous borax, boric acid, and many other materials. The bulk supplies are
received by rail car and truck, and the lesser volume supplies are received
in drums and packages. These raw materials are unloaded by a variety of
methods, including drag shovels, vacuum systems and vibrator/gravity systems.
Conveying to and from storage piles and silos is accomplished by belts,
screws and bucket elevators. From storage, the materials are weighed
according to the desired product recipe and then blended well before their
introduction into the melting unit. The weighing, mixing and charging
operations may be conducted in either batch or continuous mode.
Glass Melting And Refining - In the glass melting furnace, the raw
materials are heated to temperatures ranging from 1500° to 1700°C (2700° to
3100°F) and are transformed through a sequence of chemical reactions to
molten glass. Although there are many furnace designs, furnaces are gener-
ally large, shallow and well insulated vessels which are heated from above.
In operation, raw materials are introduced continuously on top of a bed of
molten glass, where they slowly mix and dissolve. Mixing is effected by
natural convection, gases rising from chemical reactions, and in some
operations, by air injection into the bottom of the bed.
Glass melting furnaces can be categorized, by their fuel source and
method of heat application, into four types: recuperative, regenerative,
unit, and electric melter. The recuperative, regenerative, and unit melter
furnaces can be fueled by either gas or oil. The current trend is from gas
fired to oil fired. Recuperative furnaces use a steel heat exchanger,
recovering heat from the exhaust gases by exchange with the combustion air.
Regenerative furnaces use a lattice of brickwork to recover waste heat from
exhaust gases. In the initial mode of operation, hot exhaust gases are
routed through a chamber containing a brickwork lattice, while combustion
air is heated by passage through another corresponding brickwork lattice.
About every twenty minutes, the air flow is reversed, so that the combustion
air is always being passed through hot brickwork previously heated by exhaust
gases. Electric furnaces melt glass by passing an electric current through
the melt. Electric furnaces are either hot top or cold top. The former use
gas for auxiliary heating, and the latter use only the electric current.
9/85 Mineral Products Industry 8.11-1
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Forming
Binder addition
Compression
Oven curing
Cooling
Fabrication
Packaging
Raw materials
receiving and handling
Raw materials storage
Crushing, weighing, mixing
Raw
material
hand 1 ing
Melting and refining
Direct
process
Wool glass fiber
Indirect
process
Marble forming
Anneal ing
Marble storage, shipment
Marble melting
Textile glass fiber
Forming
Sizing, binding addition
Winding
Oven drying
Oven curing
Fabrication
Packaging
Glass
melt' ing
and
forming
Fiber
fonting
and
finishing
Figure 8.11-1.
Typical flow diagram of the glass fiber
production process.
8.11-2
EMISSION FACTORS
9/85
-------
Electric furnaces are currently used only for wool glass fiber production,
because of the electrical properties of the glass formulation. Unit raelters
are used only for the "indirect" marble melting process, getting raw
materials from a continuous screw at the back of the furnace adjacent to the
exhaust air discharge. There are no provisions for heat recovery with unit
melters.
In the "indirect" melting process, molten glass passes to a forehearth,
where it is drawn off, sheared into globs, and formed into marbles by roll
forming. The marbles are then stress relieved in annealing ovens, cooled,
and conveyed to storage or to other plants for later use. In the "direct"
glass fiber process, molten glass passes from the furnace into a refining
unit, where bubbles and particles are removed by settling, and the melt is
allowed to cool to the proper viscosity for the fiber forming operation.
Wool Glass Fiber Forming And Finishing - Wool fiberglass is produced
for insulation and is formed into mats that are cut into batts. (Loose wool
is primarily a waste product formed from mat trimming, although some is a
primary product, and is only a small part of the total wool fiberglass pro-
duced. No specific emission data for loose wool production are available.)
The insulation is used primarily in the construction industry and is
produced to comply with ASTM C167-64, the "Standard Test Method for
Thickness and Density of Blanket or Batt Type Thermal Insulating Material."2
Wool fiberglass insulation production lines usually consist of the
following processes: (1) preparation of molten glass, (2) formation of
fibers into a wool fiberglass mat, (3) curing the binder coated fiberglass
mat, (4) cooling the mat, and (5) backing, cutting and packaging the insula-
tion. Fiberglass plants contain various sizes, types, and numbers of
production lines, although a typical plant has three lines. Backing (appli-
cation of a flat flexible material, usually paper, glued to the mat),
cutting and packaging operations are not significant sources of emissions to
the atmosphere.
The trimmed edge waste from the mat and the fibrous dust generated
during the cutting and packaging operations are collected by a cyclone and
are either transported to a hammer mill to be chopped into blown wool (loose
insulation) and bulk packaged or recycled to the forming section and blended
with newly forming product.
During the formation of fibers into a wool fiberglass mat (the process
known as forming in the industry), glass fibers are made from molten glass,
and a chemical binder is simultaneously sprayed on the fibers as they are
created. The binder is a thermosetting resin that holds the glass fibers
together. Although the binder composition varies with product type, typi-
cally the binder consists of a solution of phenol-formaldehyde resin, water,
urea, lignin, silane and ammonia. Coloring agents may also be added to the
binder. Two methods of creating fibers are used by the industry. In the
rotary spin process, depicted in Figure 8.11-2, centrifugal force causes
molten glass to flow through small holes in the wall of a rapidly rotating
cylinder to create fibers that are broken into pieces by an air stream.
This is the newer of the two processes and dominates the industry today.
In the flame attenuation process, molten glass flows by gravity from a
furnace through numerous small orifices to create threads that are then
9/85 Mineral Products Industry 8.11-3
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55
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-------
attenuated (stretched to the point of breaking) by high velocity, hot air
and/or a flame. After the glass fibers are created (by either process) and
sprayed with the binder solution, they are collected by gravity on a conveyor
belt in the form of a mat.
The conveyor carries the newly formed mat through a large oven for
curing of the thermosetting binder and then through a cooling section where
ambient air is drawn down through the mat. Figure 8.11-3 presents a
schematic drawing of the curing and cooling sections. The cooled mat remains
on the conveyor for trimming of the uneven edges. Then, if product specifi-
cations require it, a backing is applied with an adhesive to form a vapor
barrier. The mat is then cut into batts of the desired dimensions and
packaged.
Textile Glass Fiber Forming And Finishing - Molten glass from either
the direct melting furnace or the indirect marble melting furnace is tempera-
ture regulated to a precise viscosity and delivered to forming stations. At
the forming stations, the molten glass is forced through heated platinum
bushings containing numerous very small orifices. The continuous fibers
emerging from the orifices are drawn over a roller applicator which applies
a coating of water soluble sizing and/or coupling agent. The coated fibers
are gathered and wound into a spindle. The spindles of glass fibers are next
conveyed to a drying oven, where moisture is removed from the sizing and
coupling agents. The spindles are then sent to an oven to cure the coatings.
The final fabrication includes twisting, chopping, weaving and packaging of
the fiber.
8.11.2 Emissions And Controls
Emissions and controls for glass fiber manufacturing can be categorized
by the three production phases with which they are associated. Emission
factors for the glass fiber manufacturing industry are given in Tables 8.11-1
and 8.11-2.
Raw Materials Handling - The major emissions from the raw materials
handling phase are fugitive dust and raw material particles generated at each
of the material transfer points. Such a point would be where sand pours from
a conveyor belt into a storage silo. The two major control techniques are
wet or very moist handling and fabric filters. When fabric filters are used,
the transfer points are enclosed, and air from the transfer area is
continuously circulated through the fabric filters.
Glass Melting And Refining - The emissions from glass melting and
refining include volatile organic compounds from the melt, raw material
particles entrained in the furnace flue gas and, if furnaces are heated with
fossil fuels, combustion products. The variation in emission rates among
furnaces is attributable to varying operating temperature, raw material com-
position, fuels, and flue gas flow rates. Electric furnaces generally have
the lowest emission rates, because of the lack of combustion products and of
the lower temperature of the melt surface caused by bottom heating. Emission
control for furnaces is primarily fabric filtration. Fabric filters are
effective on particulates and SO and, to a lesser extent, on CO, NO and
fluorides. Efficiency on these compounds is attributable to both condensa-
tion on filterable particulates and chemical reaction with particulates
9/85 Mineral Products Industry 8.11-5
-------
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trapped on the filters. Reported fabric filter efficiencies on regenerative
and recuperative wool furnaces are for particulates, 95+ percent; SO ,
99+ percent; CO, 30 percent; and fluoride, 91 to 99 percent. Efficiencies
on other furnaces are lower because of lower emission loading and pollutant
characteristics.
Wool Fiber Forming And Finishing - Emissions generated during the
manufacture of wool fiberglass insulation include solid particles of glass
and binder resin, droplets of binder, and components of the binder that have
vaporized. Glass particles may be entrained in the exhaust gas stream during
forming, curing or cooling operations. Test data show that approximately
99 percent of the total emissions from the production line is emitted from
the forming and curing sections. Even though cooling emissions are negli-
gible at some plants, cooling emissions at others may include fugitives from
the curing section. This commingling of emissions occurs because fugitive
emissions from the open terminal end of the curing oven may be induced into
the cooling exhaust ductwork and be discharged into the atmosphere. Solid
particles of resin may be entrained in the gas stream in either the curing
or cooling sections. Droplets of organic binder may be entrained in the gas
stream in the forming section or may be a result of condensation of gaseous
pollutants as the gas stream is cooled. Some of the liquid binder used in
the forming section is vaporized by the elevated temperatures in the forming
and curing processes. Much of the vaporized material will condense when the
gas stream cools in the ductwork or in the emission control device.
Particulate matter is the principal pollutant that has been identified
and measured at wool fiberglass insulation manufacturing facilities. It was
known that some fraction of the particulate emissions results from condensa-
tion of organic compounds used in the binder. Therefore, in evaluating
emissions and control device performance for this source, a sampling method,
EPA Reference Method 5E, was used that permitted collection and measurement
of both solid particles and condensed particulate material.3
Tests were performed during the production of R-ll building insulation,
R-19 building insulation, ductboard and heavy density insulation.4 These
products, which account for 91 percent of industry production, had densities
ranging from 9.1 to 12.3 kilograms per cubic meter (kg/m3) for R-ll, 8.2 to
9.3 kg/m3 for R-19, and 54.5 to 65.7 kg/m3 for ductboard. The heavy density
insulation had a density of 118.5 kg/m3. (The remaining 9 percent of
industry wool fiberglass production is a variety of specialty products for
which qualitative and quantitative information is not available.) The loss
on ignition (LOI) of the product is a measure of the amount of binder
present. The LOI values ranged from 3.9 to 6.5 percent, 4.5 to 4.6 percent,
and 14.7 to 17.3 percent, respectively. The LOI for heavy density is
10.6 percent. A production line may be used to manufacture more than one of
these product types because the processes involved do not differ. Although
the data base did not show sufficient differences in mass emission levels to
establish separate emission standards for each product, the uncontrolled
emission factors are sufficiently different to warrant their segregation for
AP-42.
The level of emissions control found in the wool fiberglass insulation
manufacturing industry ranges from uncontrolled to control of forming, curing
9/85 Mineral Products Industry 8.11-7
-------
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EMISSION FACTORS
9/85
-------
and cooling emissions from a line. The exhausts from these process opera-
tions may be controlled separately or in combination. Control technologies
currently used by the industry include wet ESPs, low and high pressure drop
wet scrubbers, low and high temperature thermal incinerators, high velocity
air filters, and process modifications. These added control technologies
are available to all firms in the industry, but the process modifications
used in this industry are considered confidential. Wet ESPs are considered
to be best demonstrated technology for the control of emissions from wool
fiberglass insulation manufacturing lines.4 Therefore, it is expected that
most new facilities will be controlled in this manner.
Textile Fiber Forming And Finishing - Emissions from the forming and
finishing processes include glass fiber particles, resin particles, hydro-
carbons (primarily phenols and aldehydes), and combustion products from
dryers and ovens. Emissions are usually lower in the textile fiber glass
process than in the wool fiberglass process because of lower turbulence in
the forming step, roller application of coatings, and use of much less
coating per ton of fiber produced.
TABLE 8.11-2.
UNCONTROLLED EMISSION FACTORS FOR ROTARY SPIN WOOL GLASS
FIBER MANUFACTURING3
EMISSION FACTOR RATING: B
Particulate
Organic compounds
Products Front half
R-19
R-ll
Ductboard
Heavy
density
17.81
(36.21)
19.61
(39.21)
27.72
(55.42)
4.91
(9.81)
Back half
4.25
(8.52)
3.19
(6.37)
8.55
(17.08)
1.16
(2.33)
Total
22.36
(44.72)
22.79
(45.59)
36.26
(72.50)
6.07
(12.14)
Phenolics
3.21
(6.92)
6.21
(12.41)
10.66
(21.31)
0.88
(1.74)
Phenol Formaldehyde
0.96
(1-92)
0.92
(1.84)
3.84
(7.68)
0.53
(1.04)
0.75
(1.50)
1.23
(2.46)
1.80
(3.61)
0.43
(0.85)
Reference 4. Expressed in kg/Mg (Ib/ton) of finished product. Gas stream
did not pass through any added primary control device (wet ESP, venturi
.scrubber, etc.).
Included in total particulate catch. These organics are collected as con-
densible particulate matter and do not necessarily represent the entire
organics present in the exhaust gas stream.
Includes phenol.
References for Section 8.11
1. J. R. Schorr, et al., Source Assessment: Pressed and Blown Glass
Manufacturing Plants, EPA-600/2-77-005, U. S. Environmental Protection
Agency, Research Triangle Park, NC, January 1977.
9/85
Mineral Products Industry
8.11-9
-------
2. Annual Book of ASTM Standards, Part 18, ASTM Standard C167-64
(Reapproved 1979), American Society for Testing and Materials,
Philadephia, Pa.
3. Standard of Performance For Wool Fiberglass Insulation Manufacturing
Plants, 50 FR 7700, February 25, 1985.
4. Wool Fiberglass Insulation Manufacturing Industry: Background
Information for Proposed Standards, U. S. Environmental Protection
Agency, Research Triangle Park, NC, EPA-450/3-83-022a, December 1983.
8.11-10 EMISSION FACTORS 9/85
-------
8.12 FRIT MANUFACTURING
8.12.1 Process Description1 -2
Frit is used in enameling iron and steel and in glazing porcelain and pottery. In a typical plant, the raw
materials consist of a combination of materials such as borax, feldspar, sodium fluoride or fluorspar, soda ash,
zinc oxide, litharge, silica, boric acid, and zircon. Frit is prepared by fusing these various minerals in a smelter,
and the molten material is then quenched with air or water. This quenching operation causes the melt to solidify
rapidly and shatter into numerous small glass particles, called frit. After a drying process, the frit is finely ground
in a ball mill where other materials are added.
8.12.2 Emissions and Controls2
Significant dust and fume emissions are created by the frit-smelting operation. These emissions consist
primarily of condensed metallic oxide fumes that have volatilized from the molten charge. They also contain
mineral dust carryover and sometimes hydrogen fluoride. Emissions can be reduced by not rotating the smelter
too rapidly (to prevent excessive dust carry-over) and by not heating the batch too rapidly or too long (to prevent
volatilizing the more fusible elements).
The two most feasible control devices for frit smelters are baghouses and venturi water scrubbers. Emission
factors for frit smelters are shown in Table 8.12-1. Collection efficiencies obtainable for venturi scrubbers are also
shown in the table.
4/73 Mineral Products Industry 8.12-1
-------
Table 8.12-1. EMISSION FACTORS FOR FRIT SMELTERS
WITHOUT CONTROLS3
EMISSION FACTOR RATING: C
Type of furnace
Rotary
Participates6
Ib/ton
16
kg/MT
8
Fluorides6
Ib/ton
5
kg/MT
2.5
aReference 2. Emission factors expressed as units per unit weight of charge.
^A venturi scrubber with a 21-inch (535-mm) water-gauge pressure drop can reduce par-
ticulate emissions by 67 percent and fluorides by 94 percent.
References for Section 8.12
1. Duprey, R. L. Compilation of Air Pollutant Emission Factors. U.S. DHEW, PHS, National Center for Air
Pollution Control. Durham, N.C. PHS Publication Number 999-AP-42. 1968. p. 37-38.
2. Spinks, J. L. Frit Smelters. In: Air Pollution Engineering Manual. Danielson, J. A. (ed.), U.S. DHEW, PHS,
National Center for Air Pollution Control. Cincinnati, Ohio. PHS Publication Number 999-AP-40. 1967. p.
738-744.
8.12-2
EMISSION FACTORS
2/72
-------
8.13 GLASS MANUFACTURING
8.13.1 General l~s
Commercially produced glass can be classified as either soda-lime, lead, fused silica, borosilicate, or 96
percent silica. Soda-lime glass, which constitutes 77 percent of total glass production, will be discussed in this
section. Soda-lime glass consists of sand, limestone, soda ash, and cullet (broken glass). The manufacture of glass
can be broken down into four phases: (1) preparation of raw material, (2) melting in a furnace, (3) forming, and
(4) finishing. Figure 8.13-1 shows an overall flow diagram for glass manufacturing.
The products of the glass manufacturing industry are flat glass, container glass, or pressed and blown glass.
The procedure for manufacturing glass is the same for all three categories except for forming and finishing. Flat
glass, which comprises 24 percent of total glass production, is formed by either the float, drawing, or rolling
process. Container glass and pressed and blown glass, which comprise 51 and 25 percent, respectively, of total
glass production, utilize either pressing, blowing, or pressing and blowing to form the desired product.
As raw materials are received, they are crushed and stored in separate elevated bins. The raw materials are
transferred through a gravity feed system to the weigher and mixer, where the material and cullet are mixed to
ensure homogeneous melting. The mixture is then transferred by conveyor to the batch storage bin where it
remains until being dropped into the furnace feeder, which supplies the raw material to the melting furnace. All
equipment used in handling and preparing the raw material is housed separately from the furnace and is usually
referred to as the batch plant. Figure 8.13-2 shows a flow diagram of a batch plant.
The furnace most commonly utilized is a continuous regenerative furnace capable of producing between 50
and 300 tons (45 and 272 metric tons) of glass per day. A furnace may have either side or end ports connecting
brick checkers to the inside of the melter. The purpose of the checkers is to conserve fuel by utilizing the heat of
the combustion products in one side of the furnace to preheat combustion air in the other side. As material enters
the melting furnace through the feeder, it floats on the top of the molten glass already in the furnace. As it melts,
it passes to the front of the melter and eventually flows through a throat connecting the melter and the refiner. In
the refiner, the molten glass is heat conditioned for delivery to the forming process. Figures 8.13-3 and 8.13-4
show side-port and end-port regenerative furnaces.
RAW
MATERIAL
MELTING
FURNACE
FINISHING
FINISHING
GLASS
FORMING
ANNEALING
1
INSPECTION
AND
TESTING
CULLET
CRUSHING
RECYCLE UNDESIRABLE
GLASS
PACKING
STORAGE
OR
SHIPPING
12/77
8.13-1. Flow diagram for glass manufacturing.
Mineral Products Industry
8.13-1
-------
GULLET
RAW MATERIALS
RECEIVING
HOPPER
SCREW
CONVEYOR
FILTER
VENTS
STORAGE BINS
MAJOR RAW MATERIALS
MINOR
INGREDIENT
STORAGE
BINS
BELT CONVEYOR
BATCH
STORAGE
BIN
FURNACE
FEEDER
GLASS-
MELTING
FURNACE
8.13-2. Flow diagram of a batch plant.1
After refining, the molten glass leaves the furnace through forehearths (except for the float process in which
molten glass goes directly to the tin bath) and goes to be shaped by either pressing, blowing, pressing and blowing,
drawing, rolling, or floating, depending upon the desired product. Pressing and blowing are preformed
mechanically using blank molds and glass cut into sections (gobs) by a set of shears. In the drawing process,
molten glass is drawn upward through rollers that guide the sheet glass. The thickness of the sheet is determined
by the speed of the draw and the configuration of the draw bar. The rolling process is similar to the drawing
process except that the glass is drawn horizontally by plain or patterned rollers and, for plate glass, requires
grinding and polishing. The float process utilizes a molten tin bath over which the glass is drawn and formed into a
finely finished surface requiring no grinding or polishing. The product undergoes finishing (decorating or
coating) and annealing (removing unwanted stress areas in the glass), and is then inspected and prepared for
shipment to market. Any damaged or undersirable glass is transferred back to the batch plant to be used as cullet.
8.13.2 Emissions and Controls1'5
Table 8.13-1 lists controlled and uncontrolled emission factors for glass manufacturing.
The main pollutant emitted by the batch plant is particulates in the form of dust. This can be controlled, with
99 to 100 percent efficiency, by enclosing all possible dust sources and using baghouses or cloth filters. Another
way to control dust emissions, also with an efficiency approaching 100 percent, is to treat the batch to reduce the
amount of fine particles present. Forms of preparation are presintering, briquetting, pelletizing, or liquid alkali
treatment.
8.13-2
EMISSION FACTORS
12/77
-------
GLASS SURFACE IN MEL1EH
ATURAL DRIFT STACK
BACK IALL
REFINER SIDE WALLj
BELTER SIDE §ALL THROAT.
GLASS SURFACE IN REFINER
8.13-3. Side-port continuous regenerative furnace.1
REFINER SIDE WALL
SURFACE IN REFINER
INDUCED DRAFT FAN
• RIDER ARCHES
12/77
8.13-4. End-port continuous regenerative furnace.1
MINERAL PRODUCTS INDUSTRY
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8.13-4
EMISSION FACTORS
1/82
-------
The melting furnace contributes over 99 percent of the total emissions
from the glass plant. In the furnace, both particulates and gaseous pollutants
are emitted. Particulates result from volatilization of materials in the melt
that combine with gases to form condensates. These are either collected in the
checker-work and gas passages or escape to the atmosphere. Serious problems
arise when the checkers are not properly cleaned in that slag can form, clog-
ging the passages and eventually deteriorating the condition and efficiency
of the furnace. Nitrogen oxides form when nitrogen and oxygen react in the
high temperatures of the furnace. Sulfur oxides result from the decomposition
of the sulfates in the batch and the fuel. Proper maintenance and firing of
the furnace can control emissions and also add to the efficiency of the
furnace and reduce operational costs. Low-pressure wet centrifugal scrubbers
have been used to control particulates and sulfur oxides, but their low
efficiency (approximately 50 percent) indicates their inability to collect
particulates of submicron size. High-energy venturi scrubbers are approx-
imately 95 percent effective in reducing particulate and sulfur oxide emis-
sions; their effect on nitrogen oxide emissions is unknown. Baghouses,
which have up to 99 percent particulate collection efficiency, have been
used on small regenerative furnaces, but due to fabric corrosion, require
careful temperature control. Electrostatic precipitators have an efficiency
of up to 99 percent in the collection of particulates.
Emissions from the forming and finishing phase depend upon the type of
glass being manufactured. For container, press, and blow machines, the major-
ity of emissions result from the gob coming into contact with the machine
lubricant. Emissions in the form of a dense white cloud, which can exceed
40 percent opacity, are generated by flash vaporization of hydrocarbon greases
and oils. Grease and oil lubricants are being replaced by silicone emulsions
and water-soluble oils, which may virtually eliminate the smoke. For flat
glass, the only contributor to air pollutant emissions is gas combustion in
the annealing lehr, which is totally enclosed except for entry and exit
openings. Since emissions are small and operational procedures are efficient,
no controls are utilized.
References for Section 8.13
1. J. A. Danielson (ed.)., Air Pollution Engineering Manual (2nd Ed.), AP-40,
U.S. Environmental Protection Agency, Research Triangle Park, NC, 1973.
Out of Print.
2. Richard B. Reznik, Source Assessment: Flat Glass Manufacturing Plants,
EPA-600/20-76-032b, U. S. Environmental Protection Agency, Research Tri-
angle Park, NC, March 1976.
3. J. R. Schoor, D. T. Hooie, P. R. Sticksel, and Clifford Brockway, Source
Assessment; Glass Container Manufacturing Plants, EPA-600/2-76-269, U.S.
Environmental Protection Agency, Washington, DC, October 1976.
12/81 Mineral Products Industry 8.13-5
-------
4. A. B. Tripler, Jr. and G. R. Smithson, Jr., A Review of Air Pollution Prob-
lems and Control in the Ceramic Industries, Battelle Memorial Institute,
Columbus, OH, presented at 72nd Annual Meeting of the American Ceramic
Society, May 1970.
5. J. R. Schorr, D. T. Hooie, M. C. Brockway, P. R. Sticksel, and D. E. Niesz,
Source Assessment: Pressed and Blown Glass Manufacturing Plants, prepared
for U. S. Environmental Protection Agency, Research Triangle Park, NC,
Publication Number EPA-600/2-77-005, January 1977.
6. Control Techniques for Lead Air Emissions, EPA-450/2-77-012, U. S. Environ-
mental Protection Agency, Research Triangle Park, NC, December 1977.
7. Confidential test data, PEDCo-Environmental Specialists, Inc., Cincinnati,
OH.
8.13-6 EMISSION FACTORS 12/81
-------
8.14 GYPSUM MANUFACTURING
1-2
8.14.1 Process Description
Gypsum is calcium sulfate dihydrate (CaSO • 2H?0), a white or gray
naturally occurring mineral. Raw gypsum ore is processed into a variety of
products such as a Portland cement additive, soil conditioner, industrial
and building plasters, and gypsum wallboard. To produce plasters or
wallboard, gypsum must first be partially dehydrated or calcined to produce
calcium sulfate hemihydrate (CaSO,• ^H 0), commonly called stucco.
A flow diagram for a typical gypsum process producing both crude and
finished gypsum products is shown in Figure 8.14-1. In this process, gypsum
is crushed, dried, ground and calcined. Some of the operations shown in
Figure 8.14-1 are not performed at all gypsum plants. Some plants produce
only wallboard, and many plants do not produce soil conditioner.
Gypsum ore, from quarries and/or underground mines, is crushed and
stockpiled near a plant. As needed, the stockpiled ore is further crushed
and screened to about 50 millimeters (2 inches) in diameter. If the
moisture content of the mined ore is greater than about 0.5 weight percent,
the ore must be dried in a rotary dryer or a heated roller mill. Ore dried
in a rotary dryer is conveyed to a roller mill where it is ground to
90 percent less 149 micrometers (100 mesh). The ground gypsum exits the
mill in a gas stream and is collected in a product cyclone. Ore is
sometimes dried in the roller mill by heating the gas stream, so that drying
and grinding are accomplished simultaneously and no rotary dryer is needed.
The finely ground gypsum ore is known as landplaster, which may be used as
soil conditioner.
In most plants, landplaster is fed to kettle calciners or flash
calciners, where it is heated to remove three quarters of the chemically
bound water to form stucco. Calcination occurs at approximately 120 to
150°C (250 to 300°F), and 0.908 megagrams (Mg) (one ton) of gypsum calcines
to about 0.77 Mg (0.85 ton) of stucco.
In kettle calciners, the gypsum is indirectly heated by hot combustion
gas passed through flues in the kettle, and the stucco product is discharged
into a "hot pit" located below the kettle. Kettle calciners may be operated
in either batch or continuous modes. In flash calciners, the gypsum is
directly contacted with hot gases, and the stucco product is collected at
the bottom of the calciner. A major gypsum manufacturer holds a patent on
the design of the flash calciner.
At some gypsum plants, drying, grinding and calcining are performed in
heated impact mills. In these mills, hot gas contacts gypsum as it is
ground. The gas dries and calcines the ore and then conveys the stucco to a
product cyclone for collection. The use of heated impact mills eliminates
the need for rotary dryers, calciners and roller mills.
5/83 Mineral Products Industry 8.14-1
-------
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EMISSION FACTORS
5/83
-------
Gypsum and stucco usually are transferred from one process to another
in screw conveyors or bucket elevators. Storage bins or silos are normally
located downstream of roller mills and calciners but may also be used
elsewhere.
In the manufacture of plasters, stucco is ground further in a tube or
ball mill and then batch mixed with retarders and stabilizers to produce
plasters with specific setting rates. The thoroughly mixed plaster is fed
continuously from intermediate storage bins to a bagging operation.
In the manufacture of wallboard, stucco from storage is first mixed
with dry additives such as perlite, starch, fiberglass or vermiculite. This
dry mix is combined with water, soap foam, accelerators and shredded paper
or pulpwood in a pin mixer at the head of a board forming line. The slurry
is then spread between two paper sheets that serve as a mold. The edges of
the paper are scored, and sometimes chamfered, to allow precise folding of
the paper to form the edges of the board. As the wet board travels the
length of a conveying line, the calcium sulfate hemihydrate combines with
the water in the slurry to form solid calcium sulfate dihydrate or gypsum,
resulting in rigid board. The board is rough cut to length, and it enters a
multideck kiln dryer where it is dried by direct contact with hot combustion
gases or by indirect steam heating. The dried board is conveyed to the
board end sawing area and is trimmed and bundled for shipment.
2
8.14.2 Emissions and Controls
Potential emission sources in gypsum manufacturing plants are shown in
Figure 8.14-1. Although several sources may emit gaseous pollutants,
particulate emissions are of greatest concern. The major sources of
particulate emissions include rotary ore dryers, grinding mills, calciners
and board end sawing operations. Particulate emission factors for these
operations are shown in Table 8.14-1. All these factors are based on output
production rates. Particle size data for ore dryers, calciners and board
end sawing operations are shown in Tables 8.14-2 and 8.14-3.
The uncontrolled emission factors presented in Table 8.14-1 represent
the process dust entering the emission control device. It is important to
note that emission control devices are frequently needed to collect the
product from some gypsum processes and, thus, are commonly thought of by the
industry as process equipment and not added control devices.
Emissions sources in gypsum plants are most often controlled with
fabric filters. These sources include:
- rotary ore dryers - board end sawing
- roller mills - scoring and chamfering
- impact mills - plaster mixing and bagging
- kettle calciners - conveying systems
- flash calciners - storage bins
Uncontrolled emissions from scoring and chamfering, plaster mixing and
bagging, conveying systems, and storage bins are not well quantified.
5/83 Mineral Products Industry 8.14-3
-------
TABLE 8.14-1. PARTICULATE EMISSION FACTORS FOR GYPSUM PROCESSING*
EMISSION FACTOR RATING: B
Process Uncontrolled
kg/Mg Ib/ton
With
fabric
filter0
kg/Mg Ib/ton
With
electrostatic
precipitator
kg/Mg Ib/ton
Crushers, screens,
stockpiles, roads
Rotary ore dryers
Roller mills1
.Impact mills6*1
Plash calciners8'"
Continuous kettle
calciners
e.f.g
0.0042(FFF)
1.3J
1.77
50'
19
21*1
,8.3
0.16(FFF)
2.6*
I008ti
37
1.77
0.02"
0.06
0.01
0.02
0.04
0.12
0.02
0.04
0.003P 0.006P
NA
0.05k 0.09k
KA
NA
0.05J
0.09J
kg/a'
lb/100 ft
kg/106 m2 lb/106 ft2
Board end saving
2.4 m (8 ft) boards
3.7 m (12 ft) boards
0.04
0.03
0.8
0.5
36
36
7.5
7.5
*Based on process output production rate. Rating applies to all factors except vhere otherwise noted.
Dash » not applicable. NA - not available.
Factors represent any dust entering the emission control device.
References 3-6, 8-11. Factors for sources controlled with fabric filters are based on pulse jet fabric
filters with actual air/cloth ratios ranging from 2.3:1 - 7.0:1, mechanical shaker fabric filters with
ratios from 1.5:1 - 4.6:1, and a reverse flow fabric filter with a ratio of 2.3:1.
Factors for these operations are in Sections 8.19 and 11.2.
elncludes particulate matter from fuel combustion.
References 3-4, 8, 11-12. Equation Is for emission rate upstream of any process cyclones and is
applicable only to concurrent rotary ore dryers with flowrates of 7.5 m /s (16,000 acfm) or less.
FFF in the uncontrolled emission factor equation is "flow feed factor", the ratio of gas mass
rate per unit dryer cross sectional area to the dry mass feed rate, in the following units:
kg/hr - m2 of gas flow Ib/hr - ft2 of gas flow
Mg/hr dry feedton/hr dry feed
Measured uncontrolled emission factors for 4.2 and 5.7 m /s (9000 and 12,000 acfm) range from 5 -
60 kg/Mg (10 - 120 Ib/ton).
8EMISSION FACTOR RATING: C.
Applicable to rotary dryers with and without process cyclones upstream of the fabric filter.
References 11-14. Factors apply to both heated and unheated roller mills.
•'Factors represent emissions downstream of the product cyclone.
Factor is for combined emissions from roller mills and kettle calciners, based on the sum of the roller
mill and kettle calciner output production rates.
References 9,15. As used here, an impact mill is a process unit with process cyclones and is
used to dry, grind and calcine gypsum simultaneously.
""References 3, 6, 10. A flash calciner is a process unit used to calcine gypsum through direct contact
with hot gas. No grinding is performed in this unit.
"References 4-5, 11, 13-14.
pBased on emissions from both the kettle and the hot pit. Not applicable to batch kettle calciners.
^References 4-5, 16. Based on 13 mm (*j in.) board thickness and 1.2 m (4 ft)
board width. For other board thicknesses, multiply the appropriate emission factor by 0.079 times
board thickness in millimeters, or by 2 times board thickness in Inches.
8.14-4
EMISSION FACTORS
5/83
-------
TABLE 8.14-2. UNCONTROLLED PARTICLE SIZE DATA
FOR GYPSUM PROCESSING
Process Weight Percent
10 ym 2 ym
Rotary ore dryer . .
with cyclones 45 12
without cyclones 8 1
Continuous kettle calciners 63 17
Flash calcinersf 38b 10b
.Reference 4.
Aerodynamic diameter, Andersen analysis.
.Reference 3.
References 4-5.
fEquivalent diameter, Bahco and Sedigraph analyses.
References3, 6.
TABLE 8.14-3. PARTICLE SIZE DATA FOR GYPSUM PROCESSING
OPERATIONS CONTROLLED WITH FABRIC FILTERS8
Process
Rotary ore dryer.
with cyclones ,
without cyclones
Flash calciners
Board end sawing6
Weight Percent
10 ym 2 ym
c 9
26 9
84 52
76 49
3,
.Aerodynamic diameters, Andersen analysis.
Reference 4.
.Not available
Reference 3.
a
^References 3, 6.
References 4-5.
5/83 Mineral Products Industry 8.14-5
-------
Emissions from some gypsum sources are also controlled with
electrostatic precipitators (ESP). These sources include rotary ore dryers,
roller mills, kettle calciners and conveying systems. Although rotary ore
dryers may be controlled separately, emissions from roller mills and
conveying systems are usually controlled jointly with kettle calciner
emissions. Moisture in the kettle calciner exit gas improves the ESP
performance by lowering the resistivity of the dust.
Other sources of particulate emissions in gypsum plants are primary and
secondary crushers, screens, stockpiles and roads. If quarrying is part of
the mining operation, particulate emissions may also result from drilling
and blasting. Emission factors for some of these sources are presented in
Sections 8.19 and 11.2.
Gaseous emissions from gypsum processes result from fuel combustion and
may include nitrogen oxides, carbon monoxide and sulfur oxides. Processes
using fuel include rotary ore dryers, heated roller mills, impact mills,
calciners and board drying kilns. Although some plants use residual fuel
oil, the majority of.the industry uses clean fuels such as natural gas or
distillate fuel oil. Emissions from fuel combustion may be estimated
using emission factors presented in Sections 1.3 and 1.4.
References for Section 8.14
1. Kirk-Othmer Encyclopedia of Chemical Technology, Volume 4, John Wiley &
Sons, Inc., New York, 1978.
2. Gypsum Industry - Background Information for Proposed Standards
(Draft), U. S. Environmental Protection Agency, Research Triangle Park,
NC, April 1981.
3. Source Emissions Test Report, Gold Bond Building Products, EMB-80-
GYP-1, U. S. Environmental Protection Agency, Research Triangle Park,
NC, November 1980.
4. Source Emissions Test Report, United States Gypsum Company, EMB-80-
GYP-2, U. S. Environmental Protection Agency, Research Triangle Park,
NC, November 1980.
5. Source Emission Tests, United States Gypsum Company Wallboard Plant,
EMB-80-GYP-6, U. S. Environmental Protection Agency, Research Triangle
Park, NC, January 1981.
6. Source Emission Tests, Gold Bond Building Products, EMB-80-GYP-5, U. S.
Environmental Protection Agency, Research Triangle Park, NC,
December 1980.
7. S. Oglesby and G. B. Nichols, A Manual of Electrostatic Precipitation
Technology, Part II: Application Areas, APTD-0611, U. S. Environmental
Protection Agency, Cincinnati, OH, August 25, 1970.
8. Official Air Pollution Emission Tests Conducted on the Rock Dryer
"and #3 Calcidyne Unit, Gold Bond Building Products. Report No. 5767,
Rosnagel and Associates, Medford, NJ, August 3, 1979.
8.14-6 EMISSION FACTORS 5/83
-------
9. Particulate Analysis of Calcinator Exhaust at Western Gypsum Company,
Kramer, Callahan and Associates, Rosario, NM, April 1979. Unpublished.
10. Official Air Pollution Tests Conducted on the #1 Calcidyner Baghouse
Exhaust at the National Gypsum Company, Report No. 2966, Rossnagel and
Associates, Atlanta, GA, April 10, 1978.
11. Report to United States Gypsum Company on Particulate Emission
Compliance Testing, Environmental Instrument Systems, Inc., South
Bend, IN, November 1975. Unpublished.
12. Particulate Emission Sampling and Analysis, United States Gypsum
Company, Environmental Instrument Systems, Inc., South Bend, IN,
July 1973. Unpublished.
13. Written communication from Wyoming Air Quality Division, Cheyenne, WY,
to Michael Palazzolo, Radian Corporation, Durham, NC, 1980.
14. Written communication from V. J. Tretter, Georgia-Pacific Corporation,
Atlanta, GA, to M. E. Kelly, Radian Corporation, Durham, NC,
November 14, 1979.
15. Telephone communication between Michael Palazzolo, Radian Corporation,
Durham, NC, and D. Louis, C. E. Raymond Company, Chicago, IL, April 23,
1981.
16. Written communication from Michael Palazzolo, Radian Corporation,
Durham, NC, to B. L. Jackson, Weston Consultants, West Chester, PA,
June 19,
1980.
17. Telephone communication between P. J. Murin, Radian Corporation,
Durham, NC, and J. W. Pressler, U. S. Department of the Interior,
Bureau of Mines, Washington, DC, November 6, 1979.
5/83 Mineral Products Industry 8.14-7
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8.15 LIME MANUFACTURING
8.15.1 General1-4
Lime is the high-temperature product of the calcination of limestone. There are two kinds of lime:
high-calcium lime (CaO) and dolomitic lime (CaO • MgO). Lime is manufactured in various kinds of
kilns by one of the following reactions:
CaCOs + heat —> CO2 + CaO (high calcium lime)
CaCOa . MgCO3 + heat -> CCh + CaO . MgO (dolomitic lime)
In some lime plants, the resulting lime is reacted (slaked) with water to form hydrated lime.
The basic processes in the production of lime are (1) quarrying the raw limestone, (2) preparing the
limestone for the kilns by crushing and sizing, (3) calcining the limestone, (4) processing the quicklime
further by hydrating, and (5) miscellaneous transfer, storage, and handling operations. A generalized
material flow diagram for a lime manufacturing plant is given in Figure 8.15-1. Note that some of the
operations shown may not be performed in all plants.
The heart of a lime plant is the kiln. The most prevalent type of kiln is the rotary kiln, accounting
for about 90 percent of all lime production in the United States. This kiln is a long, cylindrical, slightly
inclined, refractory-lined furnace through which the limestone and hot combustion gases pass count-
ercurrently. Coal, oil, and natural gas may all be fired in rotary kilns. Product coolers and kiln-feed
preheaters of various types are commonly employed to recover heat from the hot lime product and
and hot exhaust gases, respectively.
The next most prevalent type of kiln in the United States is the vertical, or shaft, kiln. This kiln can
be described as an upright heavy steel cylinder lined with refractory material. The limestone is
charged at the top and calcined as it descends slowly to the bottom of the kiln where it is discharged. A
primary advantage of vertical kilns over rotary kilns is the higher average fuel efficiency. The primary
disadvantages of vertical kilns are their relatively low production rates and the fact that coal cannot
be used without degrading the quality of the lime produced. Although still prevalent in Europe, there
have been few recent vertical kiln installations in the United States because of the high production
requirements of domestic manufacturers.
Other, much less common, kiln types include rotary hearth and fluidized-bed kilns. The rotary
hearth kiln, or "calcimatic" kiln, is a circular-shaped kiln with a slowly revolving donut-shaped hearth.
In fluidized-bed kilns, finely divided limestone is brought into direct contact with hot combustion
air in a turbulent zone, usually above a perforated grate. Dust collection equipment must be installed
on fluidized-bed kilns for process economics because of the high lime carryover into the exhaust gases.
Both kiln types can achieve high production rates, but neither can operate with coal.
About 10 percent of all lime produced is converted to hydrated (slaked) lime. There are two kinds
of hydrators: atmospheric and pressure. Atmospheric hydrators, the most prevalent kind, are used to
produce high calcium and normal dolomitic hydrates. Pressure hydrators, on the other hand, are only
employed when a completely hydrated dolomitic lime is needed. Atmospheric hydrators operate
continuously, whereas pressure hydrators operate in a batch mode. Generally, water sprays or wet
scrubbers are employed as an integral part of the hydrating process to prevent product losses. Follow-
ing hydration, the resulting product may be milled and conveyed to air separators for further drying
and for removal of the coarse fractions. ,
4/77 Mineral Products Industry 8.15-1
-------
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Figure 8.15-1. Generalized lime manufacturing plant.
8.15-2
EMISSION FACTORS
4/77
-------
1
In the United States, the major use of lime is in chemical and metallurgical applications. Two of the '
largest uses in these areas are as steel flux and in alkali production. Other lesser uses include con-
struction, refractory, and agricultural applications.
8.15.2 Emissions and Controls3'5
Potential air pollutant emitting points in lime manufacturing plants are shown in Figure 8.15-1.
Particulate is the only pollutant of concern from most of the operations; however, gaseous pollutants
are also emitted from kilns.
The largest source or particulate is the kiln. Of the various kiln types in use, fluidized-bed kilns
have the highest uncontrolled particulate emissions. This is due primarily to the very small feed size
combined with the high air flow through these kilns. Fluidized-bed kilns are well controlled for
maximum product recovery.' The rotary kiln is second to the fluidized-bed kiln in uncontrolled
particulate emissions. This is attributed to the small feed size and relatively high air velocities and
dust entrainment caused by the rotating chamber. The rotary hearth, or "calcimatic" kiln ranks third
in dust production, primarily because of the larger feed size combined with the fact that the limestone
remains in a stationary position relative to the hearth during calcination. The vertical kiln has the
lowest uncontrolled dust emissions due to the large lump-size feed and the relatively slow air velocities
and slow movement of material through the kiln.
Some sort of particulate control is generally employed on most kilns. Rudimentary fallout chamb-
ers and cyclone separators are commonly used for control of the larger particles; fabric and gravel bed
filters, wet (commonly venturi) scubbers, and electrostatic precipitators are employed for secondary
control. Table 8.15-1 yields approximate efficiencies of each type of control on the various types of
kilns.
Nitrogen oxides, carbon monoxide, and sulfur oxides are all produced in kilns, although the latter
are the only gaseous pollutant emitted in significant quantities. Not all of the sulfur in the kiln fuel is
emitted as sulfur oxides because some fraction reacts with the materials in the kiln. Some sulfur oxide
reduction is also effected by the various equipment used for secondary particulate control. Estimates
of the quantities of sulfur oxides emitted from kilns, both before and after controls, are presented in
Table 8.15-1.
Hydrator emissions are low because water sprays or wet scrubbers are usually installed for econom-
ic reasons to prevent product loss in the exhaust gases. Emissions from pressure hydrators may be
higher than from the more common atmospheric hydrators because the exhaust gases are released
intermittently oxer short time intervals, makim.: control more difficult.
Product coolers are emission sources only when some of their exhaust gases are not recycled
through the kiln for use as combustion air. The trend is away from the venting of product cooler ex-
haust, however, to maximize fuel use efficiencies. Cyclones, baghouses, and wet scrubbers have been
employed on coolers for particulate control.
Other particulate sources in lime plants include primary and secondary crushers, mills, screens,
mechanical and pneumatic transfer operations, storage piles, and unpaved roads. If quarrying is a part
of the lime plant operation, particulate may also result from drilling and blasting. Emission factors
for some of these operations are presented in Sections 8.20 and 11.2.
Emission factors for lime manufacturing are presented in Table 8.15-1.
4/77 Mineral Products Industry 8.15-3
-------
Table 8.15-1. EMISSION FACTORS FOR LIME MANUFACTURING
EMISSION FACTOR RATING: B
Source
Crushers, screens.
conveyors, storage
piles, unpaved roads
Rotary kilns
Uncontrolled*-
After settling chamber
or large diameter
cyclone
After multiple cyclones
After secondary dust
collection*
Vertical kilns
Uncontrolled
Calcimatic kilns'
Uncontrolled
After multiple cyclones
After secondary dust
collection]
Fluidized-bed kilns
Product coolers
Uncontrolled
Hydrators
Emissions3
Paniculate
Ib/ton
b
340
200
85e
1
8
50
6
NA
NAk
401
0.1m
kg/MT
b
170
100
43e
0.5
4
25
3
NA
NAk
201
0.05m
Sulfur dioxide
Ib/ton
Neg.
d
d
d
g
NAh
NA
NA
NA
NA
Neg.
Neg.
kg/MT
Neg.
d
d
d
g
NAh
NA
NA
NA
NA
Neg.
Neg.
Nitrogen oxides
Ib/ton
Neg.
3
3
3
3
NA
0.2
0.2
0.2
NA
Neg.
Neg.
kg/MT
Neg.
1.5
1.5
1.5
1.5
NA
0.1
0.1
0.1
NA
Neg.
Neg.
Carbon monoxide
Ib/ton
Neg.
2
2
2
2
NA
NA
NA
NA
NA
Neg.
Neg.
kg/MT
Neg.
1
1
1
1
NA
NA
NA
NA
NA
Neg.
Neg.
aAII emission factors for kilns and coolers are per unit of lime produced. Divide by two to obtain factors per unit of limestone feed to the kiln.
Factors for hydrators are per unit of hydrated lime produced. Multiply by 1 25 to obtain factors per unit of lime feed to the hydrator. All
emissions data are based on References 4 Jhrough 6. _____
''Emission factors for these operations are presented in Sections 8.20 and 1 1 .2.
°No paniculate control except for settling that may occur in the stack breeching and chimney base.
en low-sulfur (less than 1 percent, by weight) fuels are used, only about 10 percent of the fuel sulfur is emitted as SO2- When high-
sulfur fuels are used, approximately 50 percent of the fuel sulfur is emitted as SC>2.
eThis factor should be used when coal is fired in the kiln. Limited data suggest that when only natural gas or oil is fired, particulate
emissions after multiple cyclones may be as low as 20 to 30 Ib/ton (10 to 15 kg/MT).
'Fabric or gravel bed filters, electrostatic precipitators, or wet (most commonly venturi) scrubbers. Particulate concentrations as low as
0.2 Ib/ton (0.1 kg/MT) have been achieved using these devices.
"When scrubbers are used, less than 5 percent of the fuel sulfur will be emitted as SC>2, even with high-sulfur coal. When other secondary
collection devices are used, about 20 percent of the fuel sulfur will be emitted as SC>2 with high-sulfur fuels and less than 10 percent
with low-sulfur fuels.
"Not available.
'Calcimatic kilns generally employ stone preheaters. All factors represent emissions after the kiln exhaust passes through a preheater.
'Fabric filters and venturi scrubbers have been employed on calcimatic kilns. No data are available on particulate emissions after
secondary control.
^Fluidized-bed kilns must employ sophisticated dust collection equipment for process economics; hence, particulate emissions will
depend on the efficiency of the control equipment installed.
'Some or all of the cooler exhaust is typically used in the kiln as combustion air. Emissions will result only from that fraction that
is not recycled to the kiln.
mThis is a typical particulate loading for atmospheric hydrators following water sprays or wet scrubbers. Limited data suggest
paniculate emissions from pressure hydrators may be approximately 2 Ib/ton (1 kg/MT) of hydrate produced, after wet collectors.
8.15-4
EMISSION FACTORS
4/77
-------
References for Section 8.15
1. Lewis, C. J. and B.B. Crocker. The Lime Industry's Problem of Airborne Dust. J. Air Pol. Control
Asso. Vol. 19, No. 1. January 1969.
2. Kirk-Othmer Encyclopedia of Chemical Technology. 2nd Ed. Vol 12. New York, John Wiley and
Sons. 1967. p. 414-459.
3. Screening Study for Emissions Characterization From Lime Manufacture. Vulcan-Cincinnati.
Cincinnati, Ohio. Prepared for U.S. Environmental Protection Agency, Research Triangle Park,
N.C. Under Contract No. 68-02-0299. August 1974.
4. Evans, L.B. et al. An Investigation of the Best Systems of Emission Reduction For Rotary Kilns
and Lime Hydrators in the Lime Industry. Standards Support and Environmental Impact •
Statement. Office of Air Quality Planning and Standards. U.S. Environmental Protection
Agency. Research Triangle Park, N.C. February 1976.
5. Source Test Data on Lime Plants from Office of Air Quality Planning and Standards. U.S.
Environmental Protection Agency. Research Triangle Park, N.C. 1976.
6. Air Pollutant Emission Factors. TRW Systems Group. Reston, Virginia. Prepared for the
National Air Pollution Control Administration, U.S. Department of Health,. Education, and
Welfare. Washington, D.C. under Contract No. CPA 22-69-119. April 1970. P. 2-2 through 2-19.
4/77 Mineral Products Industry 8.15-5
-------
8.16 MINERAL WOOL MANUFACTURING
8.16.1 Process Description1 >2
The product mineral wool used to be divided into three categories: slag wool, rock wool, and glass wool.
Today, however, straight slag wool and rock wool as such are no longer manufactured. A combination of slag and
rock constitutes the charge material that now yields a product classified as a mineral wool, used mainly for
thermal and acoustical insulation.
Mineral wool is made primarily in cupola furnaces charged with blast-furnace slag, silica rock, and coke. The
charge is heated to a molten state at about 3000°F (1650°C) and then fed to a blow chamber, where steam
atomizes the molten rock into globules that develop long fibrous tails as they are drawn to the other end of the
chamber. The wool blanket formed is next conveyed to an oven to cure the binding agent and then to a cooler.
8.16.2 Emissions and Controls
The major source of emissions is the cupola or furnace stack. Its discharge consists primarily of condensed
fumes that have volatilized from the molten charge and gases such as sulfur oxides and fluorides. Minor sources of
particulate emissions include the blowchamber, curing oven, and cooler. Emission factors for various stages of
mineral wool processing are shown in Table 8.16-1. The effect of control devices on emissions is shown in
footnotes to the table.
2/72 Mineral Products Industry 8.16-1
-------
Table 8.16-1. EMISSION FACTORS FOR MINERAL WOOL PROCESSING
WITHOUT CONTROLS3
EMISSION FACTOR RATING: C
Type of process
Cupola
Reverberatory furnace
Blow chamber0
Curing ovend
Cooler
Particulates
Ib/ton
22
5
17
4
2
kg/MT
11
2.5
8.5
2
1
Sulfur oxides
Ib/ton
0.02
Negb
Neg
Neg
Neg
kg/MT
0.01
Neg
Neg
Neg
Neg
"Reference 2. Emission factors expressed as units per unit weight of charge.
"^Negligible.
°A centrifugal water scrubber can reduce paniculate emissions by 60 percent.
dA direct-flame afterburner can reduce paniculate emissions by 50 percent.
References for Section 8.16
1. Duprey, R. L. Compilation of Air Pollutant Emission Factors. U.S. DHEW, PHS, National Center for Air
Pollution Control. Durham, N. C. PHS Publication Number 999-AP-42. 1968. p. 39-40.
2. Spinks, J. L. Mineral Wool Furnaces. In: Air Pollution Engineering Manual. Danielson, J. A. (ed.). U.S.
DHEW, PHS, National Center for Air Pollution Control. Cincinnati, Ohio. PHS Publication Number
999-AP-40. 1967. p. 343-347.
8.16-2
EMISSION FACTORS
2/72
-------
8.17 PERLITE MANUFACTURING
8.17.1 Process Description1 '2
Perlite is a glassy volcanic rock consisting of oxides of silicon and aluminum combined as a natural glass by
water of hydration. By a process called exfoliation, the material is rapidly heated to release water of hydration
and thus to expand the spherules into low-density particles used primarily as aggregate in plaster and concrete. A
plant for the expansion of perlite consists of ore unloading and storage facilities, a furnace-feeding device, an
expanding furnace, provisions for gas and product cooling, and product-classifying and product-collecting
equipment. Vertical furnaces, horizontal stationary furnaces, and horizontal rotary furnaces are used for the
exfoliation of perlite, although the vertical types are the most numerous. Cyclone separators are used to collect
the product.
8.17.2 Emissions and Controls2
A fine dust is emitted from the outlet of the last product collector in a perlite expansion plant. The fineness of
the dust varies from one plant to another, depending upon the desired product. In order to achieve complete
control of these particulate emissions, a baghouse is needed. Simple cyclones and small multiple cyclones are not
adequate for collecting the fine dust from perlite furnaces. Table 8.17-1 summarizes the emissions from perlite
manufacturing.
Table 8.17-1. PARTICULATE EMISSION FACTORS
FOR PERLITE EXPANSION FURNACES
WITHOUT CONTROLS3
EMISSION FACTOR RATING: C
Type of furnace
Vertical
Emissions'3
Ib/ton
21
kg/MT
10.5
a Reference 3. Emission factors expressed as units per unit weight of
charge.
^Primary cyclones will collect 80 percent of the particulates above
20 micrometers, and baghouses will collect 96 percent of the particles
above 20 micrometers.2
2/72 Mineral Products Industry 8.17-1
-------
References for Section 8.17
1. Duprey, R. L. Compilation of Air Pollutant Emission Factors. U.S. DHEW, PHS, National Center for Air
Pollution Control. Durham, N.C. PHS Publication Number 999-AP-42. 1968. p. 39.
2. Vincent, E. J. Perlite-Expanding Furnaces. In: Air Pollution Engineering Manual. Danielson, J. A. (ed.). U.S.
DHEW, PHS, National Center for Air Pollution Control. Cincinnati, Ohio. PHS Publication Number
999-AP-40. 1967. p. 350-352.
3. Unpublished data on perlite expansion furnace. National Center for Air Pollution Control. Cincinnati, Ohio.
July 1967.
8.17-2 EMISSION FACTORS 2/72
-------
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5 grams/dscf (1.2 - 12 grams/dry nm3). A particle size distribution of
the uncontrolled dust emissions is given in Table 8.18-2.
Scrubbers are most commonly used to control emissions from phosphate
rock dryers, but electrostatic precipitators are also used. Fabric
filters are not currently being used to control emissions from dryers.
Venturi scrubbers with a relatively low pressure loss (12 inches of
water, or 3000 Pa) may remove 80 to 99 percent of particulates 1 to 10
micrometers in diameter, and 10 to 80 percent of particulates less than
1 micrometer. High pressure drop scrubbers (30 inches of water, or 7500
Pa) may have collection efficiencies of 96 to 99.9 percent for 1-10
micrometer particulates and 80 to 86 percent for particles less than 1
micrometer. Electrostatic precipitators may remove 90 to 99 percent of
all particulates. Another control technique for phosphate rock dryers
is use of the wet grinding process, in which the drying step is
eliminated.
A typical 50 ton per hour (45 MT/hour) calciner will discharge
about 30,000 to 60,000 dscfm (13 - 27 dry nm3/sec) of exhaust gas, with
a particulate loading of 0.5 to 5 g/dscf (1.2 - 12 g/dry nm3). As
shown in Table 8.18-2, the size distribution of the uncontrolled calciner
emissions is very similar to that of the dryer emissions. As with
dryers, scrubbers are the most common control devices used for calciners.
At least one operating calciner is equipped with a precipitator. Fabric
filters could also be applied.
Oil fired dryers and calciners have a potential to emit sulfur
oxides when high sulfur residual fuel oils are burned. However, phos-
phate rock typically contains about 55 percent CaO, which reacts with
the SOX to form calcium sulfites and sulfates and thus reduces SOX
emissions.
Low levels of gaseous fluoride emissions (0.002 Ib/ton or 0.001
kg/MT) of rock processed from calciners have been reported, although
other reports indicate that the calcination temperature is too low to
drive off gaseous fluorides. Fluoride emissions from dryers are
negligible.
A typical grinder of 50 tons per hour (45 MT/hr) capacity will
discharge about 3500 to 5500 dscfm (1.6 - 2.5 dry nm3/sec) of air
containing 0.5 to 5.0 gr/dscf (1.2 - 12 g/dry nm3) of particulates. The
air discharged is "tramp air" which infiltrates the circulating streams.
To avoid fugitive emissions of rock dust, these streams are operated at
negative pressure. Fabric filters, and sometimes scrubbers, are used to
control grinder emissions. Substituting wet grinding for conventional
grinding would reduce the potential for particulate emissions.
Emissions from material handling systems are difficult to quantify,
since several different systems are employed to convey rock. Moreover,
a large part of the emission potential for these operations is fugitives.
Conveyor belts moving dried rock are usually covered and sometimes
«.!«-! EMISSION FACTORS 2/80
-------
8.18 PHOSPHATE ROCK PROCESSING
8.18.1 General
The processing of phosphate rock for use in fertilizer manufacture
consists of beneficiation, drying or calcining, and grinding stages.
Since the primary use of phosphate rock is in the manufacture of phos-
phatic fertilizer, only those phosphate rock processing operations
associated with fertilizer manufacture are discussed here. A flow
diagram of these operations is shown in Figure 8.18-1.
Phosphate rock from the mines is first sent to beneficiation units
to remove impurities. Steps used in beneficiation depend on the type of
rock. A typical beneficiation unit for processing phosphate rock mined
in Florida (about 78 percent of United States plant capacity in 1978)
begins with wet screening to separate pebble rock (smaller than 1/4 inch
and larger than 14 mesh) from the balance of the rock. The pebble rock
is sent to the rock dryer, and the fraction smaller than 14 mesh is
slurried and treated by two-stage flotation. The flotation process uses
hydrophilic or hydrophobic chemical reagents with aeration to separate
suspended particles. Phosphate rock mined in North Carolina (about 8
percent of United States capacity in 1978) does not contain pebble rock.
In processing this type of phosphate, the fraction larger than 1/4 inch
is sent to a hammer mill and then recycled to the screens, and the
fraction less than 14 mesh is treated by two-stage floation, like
Florida rock. The sequence of beneficiation steps at plants processing
Western hard phosphate rock (about 10 percent of United States capacity
in 1978) typically includes crushing, classification and filtration.
The size reduction is carried out in several steps, the last of which is
a slurry grinding process using a wet rod mill to reduce the rock to
particles about the size of beach sand. The slurry is then classified
by size in hydroclones to separate tailings (clay and particles smaller
than about 100 mesh), and the rock is then filtered from the slurry.
Beneficiated rock is commonly stored in open wet piles. It is reclaimed
from these piles by one of several methods (including skip loaders,
underground conveyor belts, and aboveground reclaim trolleys) and is
then conveyed to the next processing step.
The wet beneficiated phosphate rock is then dried or calcined,
depending on its organic content. Florida rock is relatively free of
organics and is dried in direct fired dryers at about 250°F (120°C),
where the moisture content of the rock falls from 10-15 percent to 1-3
percent. Both rotary and fluidized bed dryers are used, but rotary
dryers are more common. Most dryers are fired with natural gas or fuel
oil (No. 2 or No. 6), with many equipped to burn more than one type of
fuel. Unlike Florida rock, phosphate rock mined from other reserves
contains organics and must be heated to 1400° - 1600°F (760°C - 870°C)
to remove them. Fluidized bed calciners are most commonly used for this
purpose, but rotary calciners are also used. After drying, the rock is
usually conveyed to storage silos on weather protected conveyors and,
from there, to grinding mills.
2/80 Mint-nil PrmluclH IniliiMln 8.18-1
-------
Table 8.18-1. UNCONTROLLED PARTICULATE EMISSION FACTORS
FOR PHOSPHATE ROCK PROCESSING3
EMISSION FACTOR RATING: B
Type of Source
T> . b
Drying
Calcining
Grinding13
Transfer and storage
Open storage piles
Ib/ton
5.7
(1.4 - 14.0)
15.4
(3.8 - 38.0)
1.5
(0.4 - 4.0)
2
40
Emissions
kg/MT
2.9
(0.7 - 7.0)
7.7
(1.9 - 19.0)
0.8
(0.2 - 2.0)
1
20
Emission factors expressed as units per unit weight of processed
phosphate rock. Ranges in parentheses.
Reference 1.
,Reference 3.
Reference 4.
Dried or calcined rock is ground in roll or ball mills to a fine
powder, typically specified as 60 percent by weight passing a 200 mesh
sieve. Rock is fed into the mill by a rotary valve, and ground rock is
swept from the mill by a circulating air stream. Product size classi-
fication is provided by "revolving whizzers" and by an air classifier.
Oversize particles are recycled to the mill, and product size particles
are separated from the carrying air stream by a cyclone.
8.18.2 Emissions and Controls
The major emission sources for phosphate rock processing are
dryers, calciners and grinders. These sources emit particulates in the
form of fine rock dust. Emission factors for these sources are pre-
sented in Table 8.18-1. Beneficiation has no significant emission
potential, since the operations involve slurries of rock and water.
Emissions from dryers depend on several factors, including fuel
types, air flow rates, product moisture content, speed of rotation, and
the type of rock. The pebble portion of Florida rock receives much less
washing than the concentrate rock from the floation processes. It has a
higher clay content and generates more emissions when dried. No signi-
ficant differences have been noted in gas volume or emissions from fluid
bed or rotary dryers. A typical dryer processing 250 tons per hour (230
metric tons per hour) of rock will discharge between 70,000 and 100,000
dscfm (31 - 45 dry nm3/sec) of gas, with a particulate loading of 0.5 to
«.l«-2 EMISSION FACTORS 2/80
-------
enclosed. Transfer points are sometimes hooded and evacuated. Bucket
elevators are usually enclosed and evacuated to a control device, and
ground rock is generally conveyed in totally enclosed systems with well
defined and easily controlled discharge points. Dry rock is normally
stored in enclosed bins or silos which are vented to the atmosphere,
with fabric filters frequently used to control emissions.
Table 8.18-2. PARTICLE SIZE DISTRIBUTION OF EMISSIONS
FROM PHOSPHATE ROCK DRYERS AND CALCINERSa
Diameter (pm)
10.0
5.0
2.0
1.0
0.8
0.5
Percent Less
Dryers
82
60
27
11
7
3
Than Size
Calciners
96
81
52
26
10
5
Reference 1.
References for Section 8.18
1. Background Information; Proposed Standards for Phosphate Rock
Plants (Draft), EPA-450/3-79-017, U. S. Environmental Protection
Agency, Research Triangle Park, NC, September 1979.
2. "Sources of Air Pollution and Their Control", Air Pollution,
Volume III, 2nd Ed., Arthur Stern, ed., New York, Academic Press,
1968, pp. 221-222.
3. Unpublished data from phosphate rock preparation plants in Florida,
Midwest Research Institute, Kansas City, MO, June 1970.
4. Control Techniques for Fluoride Emissions, Internal document,
Office of Air Quality Planning and Standards, U. S. Environmental
Protection Agency, Research Triangle Park, NC, pp. 4-34, 4-36 and
4-46.
2/80 Mineral Product* Iiidu*tr> 8.18-5
-------
8.19 CONSTRUCTION AGGREGATE PROCESSING
General1"^
The construction aggregate industry covers a range of subclassifications
of the nonmetallic minerals industry (see Section 8.23, Metallic Minerals
Processing, for information on that similar activity). Many operations and
processes are common to both groups, including mineral extraction from the
earth, loading, unloading, conveying, crushing, screening, and loadout. Other
operations are restricted to specific subcategories. These include wet and dry
fine milling or grinding, air classification, drying, calcining, mixing, and
bagging. The latter group of operations is not generally associated with the
construction aggregate industry but can be conducted on the same raw materials
used to produce aggregate. Two examples are processing of limestone and sand-
stone. Both substances can be used as construction materials and may be pro-
cessed further for other uses at the same location. Limestone is a common
source of construction aggregate, but it can be further milled and classified
to produce agricultural limestone. Sandstone can be processed into construction
sand and also can be wet and/or dry milled, dried, and air classified into
industrial sand.
The construction aggregate industry can be categorized by source, mineral
type or form, wet versus dry, washed or unwashed, and end uses, to name but a
few. The industry is divided in this document into Section 8.19.1, Sand And
Gravel Processing, and Section 8.19.2, Crushed Stone Processing. Sections on
other categories of the industry will be published when data on these processes
become available.
Uncontrolled construction aggregate processing can produce nuisance pro-
blems and can have an effect upon attainment of ambient particulate standards.
However, the generally large particles produced often can be controlled readily.
Some of the individual operations such as wet crushing and grinding, washing,
screening, and dredging take place with "high" moisture (more than about 1.5 to
4.0 weight percent). Such wet processes do not generate appreciable particulate
emissions.
References for Section 8.19
1. Air Pollution Control Techniques for Nonmetallic Minerals Industry,
EPA-450/3-82-014, U. S. Environmental Protection Agency, Research
Triangle Park, NC, August 1982.
2. Review Emissions Data Base And Develop Emission Factors For The
Construction Aggregate Industry, Engineering-Science, Inc., Arcadia,
CA, September 1984.
9/85 Mineral Products Industry 8.19-1
-------
8.19.1 SAND AND GRAVEL PROCESSING
8.19.1.1 Process Description1"3
Deposits of sand and gravel, the consolidated granular materials result-
ing from the natural disintegration of rock or stone, are generally found in
near-surface alluvial deposits and in subterranean and subaqueous beds. Sand
and gravel are products of the weathering of rocks and unconsolidated or poorly
consolidated materials and consist of siliceous and calcareous components.
Such deposits are common throughout the country.
Depending upon the location of the deposit, the materials are excavated
with power shovels, draglines, front end loaders, suction dredge pumps or other
apparatus. In rare situations, light charge blasting is done to loosen the
deposit. The materials are transported to the processing plant by suction
pump, earth mover, barge, truck or other means. The processing of sand and
gravel for a specific market involves the use of different combinations of
washers, screens and classifiers to segregate particle sizes; crushers to
reduce oversize material; and storage and loading facilities. Crushing oper-
ations, when used, are designed to reduce production of fines, which often
must be removed by washing. Therefore, crusher characteristics, size reduction
ratios and throughput, among other factors, are selected to obtain the desired
product size distribution.
In many sand and gravel plants, a substantial portion of the initial feed
bypasses any crushing operations. Some plants do no crushing at all. After
initial screening, material is conveyed to a portion of the plant called the
wet processing section, where wet screening and silt removal are conducted to
produce washed sand and gravel. Negligible air emissions are expected from the
wet portions of a sand and gravel plant.
Industrial sand processing is similar to that of construction sand, insofar
as the initial stages of crushing and screening are concerned. Industrial sand
has a high (90 to 99 percent) quartz or silica content and is frequently obtained
from quartz rich deposits of sand or sandstone. At some plants, after initial
crushing and screening, a portion of the sand may be diverted to construction
sand use. Industrial sand processes not associated with construction sand
include wet milling, scrubbing, desliming, flotation, drying, air classifica-
tion and cracking of sand grains to form very fine sand products.
8.19.1.2 Emissions and Controls1
Dust emissions can occur from many operations at sand and gravel proces-
sing plants, such as conveying, screening, crushing, and storing operations.
Generally, these materials are wet or moist when handled, and process emissions
are often negligible. A substantial portion of these emissions may consist of
heavy particles that settle out within the plant. Emission factors (for process
or fugitive dust sources) from sand and gravel processing plants are shown in
Table 8.19.1-1. (If processing is dry, expected emissions could be similar to
those given in Section 8.19.2, Crushed Stone Processing).
Emission factors for crushing wet materials can be applied directly or
on a dry basis, with a control efficiency credit being given for use of wet
8.19.1-1 EMISSION FACTORS 9/85
-------
materials (defined as 1.5 to 4.0 percent moisture content or greater) or wet
suppression. The latter approach is more consistent with current practice.
The single valued fugitive dust emission factors given in Table 8.19.1-1
may be used for an approximation when no other information exists. Empirically
derived emission factor equations presented in Section 11.2 of this document
are preferred and should be used when possible. Each of those equations has
been developed for a single source operation or dust generating mechanism which
crosses industry lines, such as vehicle traffic on unpaved roads. The predic-
tive equation explains much of the observed variance in measured emission
factors by relating emissions to the differing source variables. These vari-
ables may be grouped as (1) measures of source activity or expended energy
(e. g., feed rate, or speed and weight of a vehicle traveling on an unpaved
road), (2) properties of the material being disturbed (e. g., moisture content,
or content of suspendable fines in the material) and (3) climate (e. g., number
of precipitation free days per year, when emissions tend to a maximum).
Because predictive equations allow for emission factor adjustment to
specific conditions, they should be used instead of the factors given in Table
8.19.1-1 whenever emission estimates are needed for sources in a specific sand
and gravel processing facility. However, the generally higher quality ratings
assigned to these equations are applicable only if (1) reliable values of cor-
rection parameters have been determined for the specific sources of interest,
and (2) the correction parameter values lie within the ranges found in develop-
ing the equations. Section 11.2 lists measured properties of aggregate materials
used in operations similar to the sand and gravel industry, and these properties
can be used to approximate correction parameter values for use in the predictive
emission factor equations, in the event that site specific values are not avail-
able. Use of mean correction parameter values from Chapter 11 reduces the
quality ratings of the emission factor equations by at least one level.
Since emissions from sand and gravel operations usually are in the form
of fugitive dust, control techniques applicable to fugitive dust sources are
appropriate. Some successful control techniques used for haul roads are
application of dust suppressants, paving, route modifications, soil stabiliza-
tion, etc.; for conveyors, covering and wet suppression; for storage piles, wet
dust suppression, windbreaks, enclosure and soil stablizers; and for conveyor
and batch transfer points (loading and unloading, etc.), wet suppression and
various methods to reduce freefall distances (e. g., telescopic chutes, stone
ladders, and hinged boom stacker conveyors); for screening and other size
classification, covering and wet suppression.
Wet suppression techniques include application of water, chemicals and/or
foam, usually at crusher or conveyor feed and/or discharge points. Such spray
systems at transfer points and on material handling operations have been esti-
mated to reduce emissions 70 to 95 percent.' Spray systems can also reduce
loading and wind erosion emissions from storage piles of various materials 80
to 90 percent.8 Control efficiencies depend upon local climatic conditions,
source properties and duration of control effectiveness. Wet suppression has
a carryover effect downstream of the point of application of water or other
wetting agents, as long as the surface moisture content is high enough to cause
the fines to adhere to the larger rock particles.
9/85 Mineral Products Industry 8.19.1-2
-------
TABLE 8.19.1-1. UNCONTROLLED PARTICULATE EMISSION FACTORS
FOR SAND AND GRAVEL PROCESSING PLANTS3
Uncontrolled Operation
Process Sources0
Primary or secondary
crushing (wet)
Open Dust Sources0
Screening"
Flat screens
(dry product)
Continous drop0
Transfer station
Pile formation - stacker
Batch drop0
Bulk loading
Active storage pllesS
Active day
Inactive day (wind
erosion only)
Unpaved haul roads
Wet materials
Emissions by Particle Size Range (aerodynamic diameter)1"
Total
Particulate
NA
NA
0.014 (0.029)
NA
0.12 (0.024)
NA
NA
1
TSP
(< 30 pm)
0.009 (0.018)
0.08 (0.16)
NA
0.065 (0.13)
0.028 (0.056)f
14.8 (13.2)
3.9 (3.5)
1
PM10
(£ 10 pm)
NA
0.06 (0.12)
NA
0.03 (0.06)e
0.0012 (0.0024)f
7.1 (6.3)e
1.9 (1.7)e
1
Units
kg/Mg (Ib/ton)
kg/Mg (Ib/ton)
kg/Mg (Ib/ton)
kg/Mg (Ib/ton)
kg/Mg (Ib/ton)
kg/hectare/day11
(Ib/acre/day)
kg/hectare/day11
(Ib/acre/day)
Emission
Factor
Rating
D
C
E
E
E
D
D
D
aNA • not available. TSP » total suspended particulate. Predictive emission factor equations, which general!;
provide more accurate estimates of emissions under specific conditions, are presented in Chapter 11. Factor
for open dust sources are not necessarily representative of the entire industry or of a "typical" situtation
bTotal particulate Is airborne particles of all sizes in the source plume. TSP is what is measured by a standar
high volume sampler (see Section 11.2).
cReferences 5-9.
dReferences 4-5. For completely wet operations, emissions are likely to be negligible.
Extrapolation of data, using k factors for appropriate operation from Chapter 11.
fpor physical, not aerodynamic, diameter.
SReference 6. Includes the following distinct source operations in the storage cycle: (1) loading of aggregate
onto storage piles (batch or continuous drop operations), (2) equipment traffic In storage areas, (3) wini
erosion of pile (batch or continuous drop operations). Assumes 8 to 12 hours of activity/24 hours.
^Kg/hectare (Ib/acre) of storage/day (Includes areas among piles).
*See Section 11.2 for empirical equations.
References for Section 8.19.1
1 . Air Pollution Control Techniques For Nonmetallic Minerals Industry,
EPA-450/3-82-014, U. S. Environmental Protection Agency, Research
Triangle Park, NC, August 1982.
2. S. Walker, "Production of Sand and Gravel", Circular Number 57, National
Sand and Gravel Association, Washington, DC, 1954.
3. Development Document For Effluent Limitations Guidelines And Standards -
Mineral Mining And Processing Industry, EPA-440/l-76-059b, U. S. Environ
mental Protection Agency, Washington, DC, July 1979.
9/85
EMISSION FACTORS
8.19.1-3
-------
4. Review Emissions Data Base And Develop Emission Factors For The Construc-
tion Aggregate Industry, Engineering-Science, Inc., Arcadia, CA, September
1984.
5. "Crushed Rock Screening Source Test Reports on Tests Performed at Conrock
Corp., Irwindale and Sun Valley, CA Plants", Engineering-Science, Inc.,
Arcadia, CA, August 1984.
6. 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.
7. R. Bohn, et al., Fugitive Emissions From Integrated Iron And Steel Plants,
EPA-600/2-78-050, U. S. Environmental Protection Agency, Washington, DC,
March 1978.
8. G. A. Jutze and K. Axetell, Investigation Of Fugitive Dust, Volume I;
Sources, Emissions and Control, EPA-450/3-74-036a, U. S. Environmental
Protection Agency, Research Triangle Park, NC, June 1974.
9. Fugitive Dust Assessment At Rock And Sand Facilities In The South Coast
Air Basin, Southern California Rock Products Association and Southern
California Ready Mix Concrete Association, P.E.S., Santa Monica, CA,
November 1979.
i
8.19.1-4 Mineral Products Industry 9/85
-------
8.19.2 CRUSHED STONE PROCESSING
8.19.2.1 Process Description1
Major rock types processed by the rock and crushed stone industry include
limestone, dolomite, granite, traprock, sandstone, quartz and quartzite. Minor
types include calcareous marl, marble, shell and slate. Industry classifica-
tions vary considerably and, in many cases, do not reflect actual geological
definitions.
Rock and crushed stone products generally are loosened by drilling and
blasting, then are loaded by power shovel or front end loader and transported
by heavy earth moving equipment. Techniques used for extraction vary with the
nature and location of the deposit. Further processing may include crushing,
screening, size classification, material handling, and storage operations. All
of these processes can be significant sources of dust emissions if uncontrolled.
Some processing operations also include washing, depending on rock type and
desired product.
Quarried stone normally is delivered to the processing plant by truck and
is dumped into a hoppered feeder, usually a vibrating grizzly type, or onto
screens, as illustrated in Figure 8.19.2-1. These screens separate or scalp
large boulders from finer rocks that do not require primary crushing, thus
reducing the load to the primary crusher. Jaw, or gyratory, crushers are
usually used for initial reduction. The crusher product, normally 7.5 to 30
centimeters (3 to 12 inches) in diameter, and the grizzly throughs (undersize
material) are discharged onto a belt conveyor and usually are transported either
to secondary screens and crushers or to a surge pile for temporary storage.
Further screening generally separates the process flow into either two
or three fractions (oversize, undersize and throughs) ahead of the secondary
crusher. The oversize is discharged to the secondary crusher for further
reduction, and the undersize usually bypasses the secondary crusher. The
throughs sometimes are separated, because they contain unwanted fines, and are
stockpiled as crusher run material. Gyratory crushers or cone crushers are
commonly used for secondary crushing, although impact crushers are sometimes
found.
The product of the secondary crushing stage, usually 2.5 centimeters (1
inch) diameter or less, is transported to secondary screens for further sizing.
Oversize material is sent back for recrushing. Depending on rock type and
desired product, tertiary crushing or grinding may be necessary, usually using
cone crushers or hammermills. (Rod mills, ball mills and hammer mills normally
are used in milling operations, which are not considered a part of the construc-
tion aggregate industry.) The product from tertiary crushing may be conveyed
to a classifier, such as a dry vibrating screen system, or to an air separator.
Any oversize is returned to the tertiary crusher for further reduction. At this
point, end products of the desired grade are conveyed or trucked directly to
finished product bins or to open area stockpiles.
9/85
Mineral Products Industry
8.19.2-1
-------
FIGURE 8.19.2-1. TYPICAL STONE PROCESSING PLANT
8.19.2-2
EMISSION FACTORS
9/85
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Mineral Products Industry
8.19.2-5
-------
specific source conditions, these equations should be used instead of those in
Table 8.19.2-2, whenever emission estimates applicable to specific stone quarry-
Ing and processing facility sources are needed. Chapter 11.2 provides measured
properties of crushed limestone, as required for use in the predictive emission
factor equations.
References for Section 8.19.2
1. Air Pollution Control Techniques for Nonmetallic Minerals Industry,
EPA-450/3-82-014, U. S. Environmental Protection Agency, Research
Triangle Park, NC, August 1982.
2. P. K. Chalekode, et al., Emissions from the Crushed Granite Industry;
State of the Art, EPA-600/2-78-021, U. S. Environmental Protection
Agency, Washington, DC, February 1978.
3. T. R. Blackwood, et al., Source Assessment; Crushed Stone, EPA-600/2-78-
004L, U. S. Environmental Protection Agency, Washington, DC, May 1978.
4. F. Record and W. T. Harnett, Particulate Emission Factors for the
Construction Aggregate Industry, Draft Report, GCA-TR-CH-83-02, EPA
Contract No. 68-02-3510, GCA Corporation, Chapel Hill, NC, February 1983.
5. Review Emission Data Base and Develop Emission Factors for the Con-
struction Aggregate Industry, Engineering-Science, Inc., Arcadia, CA,
September 1984.
6. 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.
7. R. Bohn, et al., Fugitive Emissions from Integrated Iron and Steel Plants,
EPA-600/2-78-050, U. S. Environmental Protection Agency, Washington, DC,
March 1978.
t
8.19.2-6 EMISSION FACTORS 9/85
-------
In certain cases, stone washing is required to meet particular end product
specifications or demands, as with concrete aggregate processing. Crushed and
broken stone normally are not milled but are screened and shipped to the consumer
after secondary or tertiary crushing.
8.19.2.2 Emissions and Controls^-"^
Dust emissions occur from many operations in stone quarrying and pro-
cessing. A substantial portion of these emissions consists of heavy particles
that may settle out within the plant. As in other operations, crushed stone
emission sources may be categorized as either process sources or fugitive dust
sources. Process sources include those for which emissions are amenable to
capture and subsequent control. Fugitive dust sources generally involve the
reentrainment of settled dust by wind or machine movement. Factors affecting
emissions from either source category include the type, quantity and surface
moisture content of the stone processed; the type of equipment and operating
practices employed; and topographical and climatic factors.
Of geographic and seasonal factors, the primary variables affecting uncon-
trolled particulate emissions are wind and material moisture content. Wind
parameters vary with geographical location, season and weather. It can be
expected that the level of emissions from unenclosed sources (principally fugi-
tive dust sources) will be greater during periods of high winds. The material
moisture content also varies with geographic location, season and weather.
Therefore, the levels of uncontrolled emissions from both process emission
sources and fugitive dust sources generally will be greater in arid regions
of the country than in temperate ones, and greater during the summer months
because of a higher evaporation rate.
The moisture content of the material processed can have a substantial
effect on uncontrolled emissions. This is especially evident during mining,
initial material handling, and initial plant process operations such as primary
crushing. Surface wetness causes fine particles to agglomerate on, or to adhere
to, the faces of larger stones, with a resulting dust suppression effect. How-
ever, as new fine particles are created by crushing and attrition, and as the
moisture content is reduced by evaporation, this suppressive effect diminishes
and may disappear. Depending on the geographic and climatic conditions, the
moisture content of mined rock may range from nearly zero to several percent.
Since moisture content is usually expressed on a basis of overall weight per-
cent, the actual moisture amount per unit area will vary with the size of the
rock being handled. On a constant mass fraction basis, the per unit area mois-
ture content varies inversely with the diameter of the rock. Therefore, the
suppressive effect of the moisture depends on both the absolute mass water con-
tent and the size of the rock product. Typically, a wet material will contain
1.5 to 4 percent water or more.
There are a large number of material, equipment and operating factors
which can influence emissions from crushing. These include: (1) rock type,
(2) feed size and distribution, (3) moisture content, (4) throughput rate, (5)
crusher type, (6) size reduction ratio, and (7) fines content. Insufficient
data are available to present a matrix of rock crushing emission factors
detailing the above classifications and variables. Data available from which
to prepare emission factors also vary considerably, for both extractive testing
and plume profiling. Emission factors from extractive testing are generally
9/85 Mineral Products Industry 8.19.2-3
-------
higher than those based upon
degree of reliability. Some
emissions than from secondary
rates and visual observations
factor, on a throughput basis
factors for either primary or
base. An emission factor for
extremely limited data. All
highly variable data base.
plume profiling tests, but they have a greater
test data for primary crushing indicate higher
crushing, although factors affecting emission
suggest that the secondary crushing emission
should be higher. Table 8.19.2-1 shows single
secondary crushing reflecting a combined data
tertiary crushing is given, but it is based on
factors are rated low because of the limited and
TABLE 8.19.2-1.
UNCONTROLLED PARTICULATE EMISSION FACTORS
FOR CRUSHING OPERATIONS3
Type of Crushing^
Primary or secondary
Dry material
Wet material0
Tertiary, dry material**
Particulate Matter
< 30 ym
kg/Mg (Ib/ton)
0.14 (0.28)
0.009 (0.018)
0.93 (1.85)
< 10 ym
kg/Mg (Ib/ton)
0.0085 (0.017)
-
-
Emission
Factor
Rating
D
D
E
aBased on actual feed rate of raw material entering the particular operation.
Emissions will vary by rock type, but data available are insufficient to
characterize these phenomena. Dash = no data.
References 4-5. Factors are uncontrolled. Typical control efficiencies:
cyclone, 70 - 80%; fabric filter, 99%; wet spray systems, 70 - 90%.
"^References 5-6. Refers to crushing of rock either naturally wet or after
moistened to 1.5 to 4 weight % by use of wet suppression techniques.
dRange of values used to calculate emission factor was 0.0008 - 1.38 kg/Mg.
There are no screening emission factors presented in this Section. How-
ever, the screening emission factors given in Section 8.19.1, Sand and Gravel
Processing, should be similar to those expected from screening crushed rock.
Milling of fines is also not included in this Section as this operation is
normally associated with non construction aggregate end uses and will be covered
elsewhere in the future when information is adequate.
Open dust source (fugitive dust) emission factors for stone quarrying and
processing are presented in Table 8.19.2-2. These factors have been determined
through tests at various quarries and processing plants.6~7 The single valued
open dust emission factors given in Table 8.19.2-2 may be used when no other
information exists. Empirically derived emission factor equations presented
in Section 11.2 of this document are preferred and should be used when possible.
Because these predictive equations allow the adjustment of emission factors for
8.19.2-4
EMISSION FACTORS
9/85
-------
SECTION 8.20
This Section is reserved for future use.
9/85 Mineral Products Industry 8.20-1
-------
8.21 COAL CONVERSION
In addition to its direct use for combustion, coal can be converted
to organic gases and liquids, thus allowing the continued use of conven-
tial oil and gas fired processes when oil and gas supplies are not
available. Currently, there is little commercial coal conversion in the
United States. Consequently, it is very difficult to determine which of
the many conversion processes will be commercialized in the future. The
following sections provide general process descriptions and general
emission discussions for high-, medium- and low-Btu gasification (gasi-
faction) processes and for catalytic and solvent extraction liquefaction
processes.
1-2
8.21.1 Process Description
8.21.1.1 Gasification - One means of converting coal to an alternate
form of energy is gasification. In this process, coal is combined with
oxygen and steam to produce a combustible gas, waste gases, char and
ash. The more than 70 coal gasification systems currently available or
being developed (1979) can be classified by the heating value of the gas
produced and by the type of gasification reactor used. High-Btu gasi-
fication systems produce a gas with a heating value greater than 900
Btu/scf (33,000 J/m3). Medium-Btu gasifiers produce a gas having a
heating value between 250 - 500 Btu/scf (9,000 - 19,000 J/m3). Low-Btu
gasifiers produce a gas having a heating value of less than 250 Btu/scf
(9,000 J/m3).
The majority of the gasification systems consist of four operations:
coal pretreatment, coal gasification, raw gas cleaning and gas beneficia-
tion. Each of these operations consists of several steps. Figure
8.21-1 is a flow diagram for an example coal gasification facility.
Generally, any coal can be gasified if properly pretreated. High
moisture coals may require drying. Some caking coals may require
partial oxidation to simplify gasifier operation. Other pretreatment
operations include crushing, sizing, and briqueting of fines for feed to
fixed bed gasifiers. The coal feed is pulverized for fluid or entrained
bed gasifiers.
After pretreatment, the coal enters the gasification reactor, where
it reacts with oxygen and steam to produce a combustible gas. Air is
used as the oxygen source for making low-Btu gas, and pure oxygen is
used for making medium- and high-Btu gas (inert nitrogen in the air
dilutes the heating value of the product). Gasification reactors are
classified by type of reaction bed (fixed, entrained or fluidized), the
operating pressure (pressurized or atmospheric), the method of ash
removal (as molten slag or dry ash), and the number of stages in the
gasifier (one or two). Within each class, gasifiers have similar
emissions.
Mineral Products Industry 8.21-1
-------
The raw gas from the gasifier contains varying concentrations of
carbon monoxide, carbon dioxide, hydrogen, methane, other organics,
hydrogen sulfide, miscellaneous acid gases, nitrogen (if air was used as
the oxygen source), particulates and water. Four gas purification proc-
esses may be required to prepare the gas for combustion or further
beneficiation: particulate removal, tar and oil removal, gas quenching
and cooling, and acid gas removal. The primary function of the partic-
ulate removal process is the removal of coal dust, ash and tar aerosols
in the raw product gas. During tar and oil removal and gas quenching
and cooling, tars and oils are condensed, and other impurities such as
ammonia are scrubbed from raw product gas using either aqueous or
organic scrubbing liquors. Acid gases such as H2S, COS, CS2, mercap-
tans, and C02 can be removed from gas by an acid gas removal process.
Acid gas removal processes generally absorb the acid gases in a solvent,
from which they are subsequently stripped, forming a nearly pure acid
gas waste stream with some hydrocarbon carryover. At this point, the
raw gas is classified as either a low-Btu or medium-Btu gas.
To produce high-Btu gas, the heating value of the medium-Btu gas is
raised by shift conversion and methanation. In the shift conversion
process, K^O and a portion of the CO are catalytically reacted to form
C02 and H2 . After passing through an absorber for C02 removal, the
remaining CO and H2 in the product gas are reacted in a methanation
reactor to yield CHi,. and
There are also many auxiliary processes accompanying a coal gasi-
fication facility, which provide various support functions. Among the
typical auxiliary processes are oxygen plant, power and steam plant,
sulfur recovery unit, water treatment plant, and cooling towers.
8.21.1.2 Liquefaction - Liquefaction is a conversion process designed
to produce synthetic organic liquids from coal. This conversion is
achieved by reducing the level of impurities and increasing the hydrogen
to carbon ratio of coal to the point that is becomes fluid. Currently,
there are over 20 coal liquefaction processes in various stages of
development by both industry and Federal agencies (1979) . These
processes can be grouped into four basic liquefaction techniques:
- Indirect liquefaction
- Pyrolysis
- Solvent extraction
- Catalytic liquefaction
Indirect liquefaction involves the gasification of coal followed by the
catalytic conversion of the product gas to a liquid. Pyrolysis lique-
faction involves heating coal to very high temperatures, thereby crack-
ing the coal into liquid and gaseous products. Solvent extraction uses
a solvent generated within the process to dissolve the coal and to
transfer externally produced hydrogen to the coal molecules. Catalytic
liquefaction resembles solvent extraction, except that hydrogen is added
to the coal with the aid of a catalyst.
8.21-2 EMISSION FACTORS 2/80
-------
Steam
Oxygen or
Air
Coal Preparation
"Drying
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"Partial Oxidaticjn
"Briqueting
Coal
preparation
*Coal Hopper Gas
Tar
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Sulfur
Gasification
Raw gas
cleaning
Gas
beneficiation
product gas
High-Btu
Product Gas
Figure 8.21-1. Flow diagram of typical coal gasification plant.
2/80
Mineral Products Industry
8.21-:*
-------
Figure 8.21-2 presents the flow diagram of a typical solvent extrac-
tion or catalytic liquefaction plant. These coal liquefaction processes
consist of four basic operations: coal pretreatment, dissolution and
liquefaction, product separation and purification, and residue
gasification.
Coal pretreatment generally consists of coal pulverizing and
drying. The dissolution of coal is best effected if the coal is dry and
finely ground. The heater used to dry coal is typically coal fired, but
it may also combust low-BTU value product streams or may use waste heat
from other sources.
The dissolution and liquefaction operations are conducted in a
series of pressure vessels. In these processes, the coal is mixed with
hydrogen and recycled solvent, heated to high temperatures, dissolved
and hydrogenated. The order in which these operations occur varies
among the liquefaction processes and, in the case of catalytic liquefac-
tion, involves contact with a catalyst. Pressures in these processes
range up to 2000 psig (14,000 Pa), and temperatures range up to 900°F
(480°C). During the dissolution and liquefaction process, the coal is
hydrogenated to liquids and some gases, and the oxygen and sulfur in the
coal are hydrogenated to H20 and H2S.
After hydrogenation, the liquefaction products are separated,
through a series of flash separators, condensers, and distillation
units, into a gaseous stream, various product liquids, recycle solvent,
and mineral residue. The gases from the separation process are separ-
ated further by absorption into a product gas stream and a waste acid
gas stream. The recycle solvent is returned to the dissolution/lique-
faction process, and the mineral residue of char, undissolved coal and
ash is used in a conventional gasification plant to produce hydrogen.
The residue gasification plant closely resembles a convential high-
Btu coal gasifaction plant. The residue is gasified in the presence of
oxygen and steam to produce CO, H2, H20, other waste gases, and partic-
ulates. After treatment for removal of the waste gases and particulates,
the CO and H20 go into a shift reactor to produce C02 and additional H2 •
The H2 enriched product gas from the residue gasifier is used subsequently
in the hydrogenation of the coal.
There are also many auxiliary processes accompanying a coal lique-
faction facility which provide various support functions. Among the
typical auxiliary processes are oxygen plant, power and steam plant,
sulfur recovery unit, water treatment plant, cooling towers, and sour
water strippers.
1-3
8.21.2 Emissions and Controls
Although characterization data are availabe for some of the many
developing coal conversion processes, describing these data in detail
would require a more extensive discussion than possible here. So, this
8.21-4 EMISSION FACTORS 2/80
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Mineral Products Industry
8.21-9
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Section will cover emissions and controls for coal conversion processes
on a qualitative level only.
8.21.2.1 Gasification - All of the major operations associated with
low-, medium- and high-Btu gasification technology (coal pretreattnent,
gasification, raw gas cleaning, and gas beneficiation) can produce
potentially hazardous air emissions. Auxiliary operations, such as
sulfur recovery and combustion of fuel for electricity and steam genera-
tion, could account for a major portion of the emissions from a gasifica-
tion plant. Discharges to the air from both major and auxiliary operations
are summarized and discussed in Table 8.21-1.
Dust emissions from coal storage, handling and crushing/sizing can
be controlled with available techniques. Controlling air emissions from
coal drying, briqueting and partial oxidation processes is more difficult
because of the volatile organics and possible trace metals liberated as
the coal is heated.
The coal gasification process itself appears to be the most serious
potential source of air emissions. The feeding of coal and the with-
drawal of ash release emissions of coal or ash dust and organic and
inorganic gases that are potentially toxic and carcinogenic. Because of
their reduced production of tars and condensable organics, slagging
gasifiers pose less severe emission problems at the coal inlet and ash
outlet.
Gasifiers and associated equipment also will be sources of potenti-
ally hazardous fugitive leaks. These leaks may be more severe from
pressurized gasifiers and/or gasifiers operating at high temperatures.
Raw gas cleaning and gas beneficiation operations appear to be
smaller sources of potential air emissions. Fugitive emissions have not
been characterized but are potentially large. Emissions from the acid
gas removal process depend on the kind of removal process employed at a
plant. Processes used for acid gas removal may remove both sulfur
compounds and carbon dioxide or may be operated selectively to remove
only the sulfur compounds. Typically, the acid gases are stripped from
the solvent and processed in a sulfur plant. Some processes, however,
directly convert the absorbed hydrogen sulfide to elemental sulfur.
Emissions from these direct conversion processes (e.g., the Stretford
process) have not been characterized but are probably minor, consisting
of CC-2, air, moisture and small amounts of
i
Emission controls for two auxiliary processes (power and steam
generation and sulfur recovery) are discussed elsewhere in this document
(Sections 1.1 and 5.18, respectively). Gases stripped or desorbed from
process wastewaters are potentially hazardous, since they contain many
of the components found in the product gas. These include sulfur and
nitrogen species, organics, and other species that are toxic and potenti
ally carcinogenic. Possible controls for these gases include incinera-
tion, byproduct recovery, or venting to the raw product gas or inlet
8.21-10 EMISSION FACTORS 2/80
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air. Cooling towers are usually minor emission sources, unless the
cooling water is contaminated.
8.21.2.2 Liquefaction - The potential exists for generation of signifi-
cant levels of atmospheric pollutants from every major operation in a
coal liquefaction facility. These pollutants include coal dust, combust-
ion products, fugitive organics and fugitive gases. The fugitive
organics and gases could include carcinogenic polynuclear organics and
toxic gases such as metal carbonyls, hydrogen sulfides, ammonia, sulfu-
rous gases, and cyanides. Many studies are currently underway to charac-
terize these emissions and to establish effective control methods.
Table 8.21-2 presents information now available on liquefaction emissions.
Emissions from coal preparation include coal dust from the many
handling operations and combustion products from the drying operation.
The most significant pollutant from these operations is the coal dust
from crushing, screening and drying activities. Wetting down the surface
of the coal, enclosing the operations, and venting effluents to a
scrubber or fabric filter are effective means of particulate control.
A major source of emissions from the coal dissolution and lique-
faction operation is the atmospheric vent on the slurry mix tank. The
slurry mix tank is used for mixing feed coal and recycle solvent. Gases
dissolved in the recycle solvent stream under pressure will flash from
the solvent as it enters the unpressurized slurry mix tank. These gases
can contain hazardous volatile organics and acid gases. Control tech-
niques proposed for this source include scrubbing, incineration or
venting to the combustion air supply for either a power plant or a
process heater.
Emissions from process heaters fired with waste process gas or
waste liquids will consist of standard combustion products. Industrial
combustion emission sources and available controls are discussed in
Section 1.1.
The major emission source in the product separation and purifi-
cation operations is the sulfur recovery plant tail gas. This can
contain significant levels of acid or sulfurous gases. Emission factors
and control techniques for sulfur recovery tail gases are discussed in
Section 5.18.
Emissions from the residue gasifier used to supply hydrogen to the
system are very similar to those for coal gasifiers previously discussed
in this Section.
Emissions from auxiliary processes include combustion products from
onsite steam/electric power plant and volatile emissions from the
wastewater system, cooling towers and fugitive emission sources.
Volatile emissions from cooling towers, wastewater systems and fugitive
emission sources possibly can include every chemical compound present in
the plant. These sources will be the most significant and most difficult
2/80 Mineral Products Industry 8.21-13
\ ' (
-------
to control in a coal liquefaction facility. Compounds which can be
present include hazardous organics, metal carbonyls, trace elements such
as mercury, and toxic gases such as CO, H2S, HCN, NH3, COS and CS2.
Emission controls for wastewater systems involve minimizing the
contamination of water with hazardous compounds, enclosing the waste
water systems, and venting the wastewater systems to a scrubbing or
incineration system. Cooling tower controls focus on good heat exchanger
maintenance, to prevent chemical leaks into the system, and on surveil-
lance of cooling water quality. Fugitive emissions from various valves,
seals, flanges and sampling ports are individually small but collec-
tively very significant. Diligent housekeeping and frequent maintenance,
combined with a monitoring program, are the best controls for fugitive
sources. The selection of durable low leakage components, such as
double mechanical seals, is also effective.
References for Section 8.21
1. C. E. Burklin and W. J. Moltz, Energy Resource Development System,
EPA Contract No. 68-01-1916, Radian Corporation and The University
of Oklahoma, Austin, TX, September 1978.
2. E. C. Cavanaugh, et al., Environmental Assessment Data Base for
Low/Medium-BTU Gasification Technology, Volume 1.
EPA-600/7-77-125a, U. S. Environmental Protection Agency, Research
Triangle Park, NC, November 1977.
3. P. W. Spaite and G. C. Page, Technology Overview; Low- and Medium-
BTU Coal Gasification Systems. EPA-600/7-78-061, U.S. Environmental
Protection Agency, Research Triangle Park, NC, March 1978.
8.21-14 EMISSION FACTORS 2/80
-------
8.22 TACONITE ORE PROCESSING
8.22.1 General1'2
More than two thirds of the iron ore produced in the United States for
making iron consists of taconite concentrate pellets. Taconite is a low
grade iron ore, largely from deposits in Minnesota and Michigan, but from
other areas as well. Processing of taconite consists of crushing and
grinding the ore to liberate ironbearing particles, concentrating the ore
by separating the particles from the waste material (gangue), and pelletiz-
ing the iron ore concentrate. A simplified flow diagram of these process-
ing steps is shown in Figure 8.22-1.
Liberation - The first step in processing crude taconite ore is crushing
and grinding. The ore must be ground to a particle size sufficiently close
to the grain size of the ironbearing mineral, to allow for a high degree of
mineral liberation. Most of the taconite used today requires very fine
grinding. The grinding is normally performed in three or four stages of
dry crushing, followed by wet grinding in rod mills and ball mills. Gy-
ratory crushers are generally used for primary crushing, and cone crushers
are used for secondary and tertiary fine crushing. Intermediate vibrating
screens remove undersize material from the feed to the next crusher and al-
low for closed circuit operation of the fine crushers. The rod and ball
mills are also in closed circuit with classification systems such as cy-
clones. An alternative is to feed some coarse ores directly to wet or dry
semiautogenous or autogenous grinding mills, then to pebble or ball mills.
Ideally, the liberated particles of iron minerals and barren gangue should
be removed from the grinding circuits as soon as they are formed, with
larger particles returned for further grinding.
Concentration - As the iron ore minerals are liberated by the crushing
steps, the ironbearing particles must be concentrated. Since only about 33
percent of the crude taconite becomes a shippable product for iron making,
a large amount of gangue is generated. Magnetic separation and flotation
are most commonly used for concentration of the taconite ore.
Crude ores in which most of the recoverable iron is magnetite (or, in
rare cases, maghemite) are normally concentrated by magnetic separation.
The crude ore may contain 30 to 35 percent total iron by assay, but theo-
retically only about 75 percent of this is recoverable magnetite. The re-
maining iron becomes part of the gangue.
Nonmagnetic taconite ores are concentrated by froth flotation or by a
combination of selective flocculation and flotation. The method is deter-
mined by the differences in surface activity between the iron and gangue
particles. Sharp separation is often difficult.
Various combinations of magnetic separation and flotation may be used
to concentrate ores containing various iron minerals (magnetite and hema-
tite, or maghemite) or wide ranges of mineral grain sizes. Flotation is
also often used as a final polishing operation on magnetic concentrates.
5/83 Mineral Products Industry 8.22-1
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Pelletization - Iron ore concentrates must be coarser than about No. 10
mesh to be acceptable as blast furnace feed without further treatment. The
finer concentrates are agglomerated into small "green" pellets. This is
normally accomplished by tumbling moistened concentrate with a balling drum
or balling disc. A binder additive, usually powdered bentonite, may be
added to the concentrate to improve ball formation and the physical quali-
ties of the "green" balls. The bentonite is lightly mixed with the care-
fully moistened feed at 4.5 to 9 kilograms per megagram (10 to 20 Ib/ton).
The pellets are hardened by a procedure called induration, the drying
and heating of the green balls in an oxidizing atmosphere at incipient fu-
sion temperature [1290 to 1400°C (2350 to 2550°F), depending on the compo-
sition of the balls] for several minutes and then cooling. Four general
types of indurating apparatus are currently used. These are the vertical
shaft furnace, the straight grate, the circular grate and grate/kiln. Most
of the large plants and new plants use the grate/kiln. Natural gas is most
commonly used for pellet induration now, but probably not in the future.
Heavy oil is being used at a few plants, and coal may be used at future
plants.
In the vertical shaft furnace, the wet green balls are distributed
evenly over the top of the slowly descending bed of pellets. A rising
stream of gas of controlled temperature and composition flows counter to
the descending bed of pellets. Auxiliary fuel combustion chambers supply
hot gases midway between the top and bottom of the furnace. In the
straight grate apparatus, a continuous bed of agglomerated green pellets is
carried through various up and down flows of gases at different tempera-
tures. The grate/kiln apparatus consists of a continuous traveling grate
followed by a rotary kiln. Pellets indurated by the straight grate appara-
tus are cooled on an extension of the grate or in a separate cooler. The
grate/kiln product must be cooled in a separate cooler, usually an annular
cooler with countercurrent airflow.
1-3
8.22.2 Emissions and Controls
Emission sources in taconite ore processing plants are indicated in
Figure 8.22-1. Particulate emissions also arise from ore mining opera-
tions. Uncontrolled emission factors for the major processing sources are
presented in Table 8.22-1, and control efficiencies in Table 8.22-2.
The taconite ore is handled dry through the crushing stages. All
crushers, size classification screens and conveyor transfer points are ma-
jor points of particulate emissions. Crushed ore is normally ground in wet
rod and ball mills. A few plants, however, use dry autogenous or semi-
autogenous grinding and have higher emissions than do conventional plants.
The ore remains wet through the rest of the beneficiation process, so par-
ticulate emissions after crushing are generally insignificant.
The first source of emissions in the pelletizing process is the trans-
fer and blending of bentonite. There are no other significant emissions in
the balling section, since the iron ore concentrate is normally too wet to
cause appreciable dusting. Additional emission points in the pelletizing
process include the main waste gas stream from the indurating furnace,
5/83 Mineral Products Industry 8.22-3
-------
TABLE 8.22-1. UNCONTROLLED PARTICIPATE EMISSION
FACTORS FOR TACONITE ORE
PROCESSING3
EMISSION FACTOR RATING: D
Source Emissions
kg/Mg Ib/ton
Fine crushing
Waste gas
Pellet handling
Grate discharge
Grate feed
Bentonite blending
Coarse crushing
Ore transfer
Bentonite transfer
39.9
14.6
1.7
0.66
0.32
0.11
0.10
0.05
0.02
79.8
29.2
3.4
1.32
0.64
0.22
0.20
0.10
0.04
, Reference 1. Median
D r, , . .
values.
£• _ _ 1 1 _ J
produced.
pellet handling, furnace transfer points (grate feed and discharge), and
for plants using the grate/kiln furnace, annular coolers. In addition,
tailings basins and unpaved roadways can be sources of fugitive emissions.
Fuel used to fire the indurating furnace generates low levels of sul-
fur dioxide emissions. For a natural gas fired furnace, these emissions
are about 0.03 kilograms of S02 per megagram of pellets produced (0.06 lb/
ton). Higher S02 emissions (about 0.6 to 0.7 kg/Mg, or 0.12 to 0.14 lb/
ton) would result from an oil or coal fired furnace.
Particulate emissions from taconite ore processing plants are con-
trolled by a variety of devices, including cyclones, multiclones, roto-
clones, scrubbers, baghouses and electrostatic precipitators. Water sprays
are also used to suppress dusting. Annular coolers are generally left un-
controlled, because their mass loadings of particulates are small, typi-
cally less than 0.11 grams per cubic meter (0.05 g/scf).
The largest source of particulate emissions in taconite ore mines is
traffic on unpaved haul roads.3 Table 8.22-3 presents size specific emis-
sion factors for this source determined through source testing at one taco-
nite mine. Other significant particulate emission sources at taconite
mines are wind erosion and blasting.3
As an alternative to the single valued emission factors for open dust
sources given in Tables 8.22-1 and 8.22-3, empirically derived emission
8.22-4 Mineral Products Industry 5/83
-------
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Mineral Products Industry
8.22-5
-------
TABLE 8.22-3. UNCONTROLLED PARTICIPATE EMISSION FACTORS FOR
HEAVY DUTY VEHICLE TRAFFIC ON HAUL ROADS AT
TACONITE MINES3
material
Crushed rock
and gla-
cial till
Crushed
taconite
and waste
Emission factor
< 30 [Jm
3.1
11.0
2.6
9.3
< 15 Mm
2.2
7.9
1.9
6.6
by aerodynamic diameter
< 10 Mm
1.7
6.2
1.5
5.2
< 5 Mm
1.1
3.9
0.90
3.2
< 2.5 [Jm
0.62
2.2
0.54
1.9
Tim* t c
kg/VKT
Ib/VMT
kg/VKT
Ib/VMT
Emission
Rating
C
C
D
D
Reference 3. Predictive emission factor equations, which generally pro-
vide more accurate estimates of emissions, are presented in Chapter 11.
VKT = Vehicle kilometers traveled. VMT = Vehicle miles traveled.
factor equations are presented in Chapter 11 of this document. Each equa-
tion was developed for a source operation defined on the basis of a single
dust generating mechanism which crosses industry lines, such as vehicle
traffic on unpaved roads. The predictive equation explains much of the ob-
served variance in measured emission factors by relating emissions to pa-
rameters which characterize source conditions. These parameters may be
grouped into three categories: 1) measures of source activity or energy
expended (e.g., the speed and weight of a vehicle traveling on an unpaved
road), 2) properties of the material being disturbed (e.g., the content of
suspendable fines in the surface material on an unpaved road), 3) climatic
parameters (e.g., number of precipitation free days per year, when emis-
sions tend to a maximum).
Because the predictive equations allow for emission factor adjustment
to specific source conditions, the equations should be used in place of
the single valued factors for open dust sources, in Tables 8.22-1 and
8.22-3, if emission estimates for sources in a specific taconite ore mine
or processing facility are needed. However, the generally higher quality
ratings assigned to the equations are applicable only if 1) reliable values
of correction parameters have been determined for the specific sources of
interest and 2) the correction parameter values lie within the ranges
tested in developing the equations. Chapter 11 lists measured properties
of aggregate process materials and road surface materials found in taconite
mining and processing facilities, which can be used to estimate correction
parameter values for the predictive emission factor equations, in the event
that site specific values are not available. Use of mean correction param-
eter values from Chapter 11 reduces the quality ratings of the emission
factor equations by one level.
8.22-6
EMISSION FACTORS
5/83
-------
References for Section 8.22
1. J. P. Pilney and G. V. Jorgensen, Emissions from Iron Ore Mining, Ben-
ficiation and Palletization, Volume 1, EPA Contract No. 68-02-2113,
Midwest Research Institute, Minnetonka, MN, June 1978.
2. A. K. Reed, Standard Support and Environmental Impact Statement for
the Iron Ore Beneficiation Industry (Draft), EPA Contract No. 68-02-
1323, Battelle Columbus Laboratories, Columbus, OH, December 1976.
3. T. A. Cuscino, et al., Taconite Mining Fugitive Emissions Study,
Minnesota Pollution Control Agency, Roseville, MN, June 1979.
5/83 Mineral Products Industry 8.22-7
-------
8.23 METALLIC MINERALS PROCESSING
8.23.1 Process Description1-6
Metallic mineral processing typically involves the mining of ore,
either from open pit or underground mines; the crushing and grinding of ore;
the separation of valuable minerals from matrix rock through various concen-
tration steps; and at some operations, the drying, calcining or pelletizing
of concentrates to ease further handling and refining. Figure 8.23-1 is a
general flow diagram for metallic mineral processing. Very few metallic
mineral processing facilities will contain all of the operations depicted in
this Figure, but all facilities will use at least some of these operations
in the process of separating valued minerals from the matrix rock.
The number of crushing steps necessary to reduce ore to the proper size
will vary with the type of ore. Hard ores, including some copper, gold, iron
and molybdenum ores, may require as much as a tertiary crushing. Softer
ores, such as some uranium, bauxite and titanium/zirconium ores, require
little or no crushing. Final comminution of both hard and soft ores is often
accomplished by grinding operations using media such as balls or rods of var-
ious materials. Grinding is most often performed with an ore/water slurry,
which reduces particulate emissions to negligible levels. When dry grinding
processes are used, particulate emissions can be considerable.
After final size reduction, the beneficiation of the ore increases the
concentration of valuable minerals by separating them from the matrix rock.
A variety of physical and chemical processes is used to concentrate the
mineral. Most often, physical or chemical separation is performed in an
aqueous environment which eliminates particulate emissions, although some
ferrous and titaniferous minerals are separated by magnetic or electrostatic
methods in a dry environment.
The concentrated mineral products may be dried to remove surface
moisture. Drying is most frequently done in natural gas fired rotary
dryers. Calcining or pelletizing of some products, such as alumina or iron
concentrates, are also performed. Emissions from calcining and pelletizing
operations are not covered in this Section.
8.23.2 Process Emissions7-9
Particulate emissions result from metallic mineral plant operations
such as crushing and dry grinding of ore; drying of concentrates; storing
and reclaiming of ores and concentrate's from storage bins; transfer of
materials; and loading of final products for shipment. Particulate emission
factors are provided in Table 8.23-1 for various metallic mineral process
operations, including primary, secondary and tertiary crushing; dry grinding;
drying; and material handling and transfer. Fugitive emissions are also
possible from roads and open stockpiles, factors for which are in Section
11.2.
8/82 Mineral Products Industry 8.23-1
-------
—Ore From Mines
Primary
Crushers
Storage
Bin(s)
Storage
Bin(s)
Secondary
Crushers
Tertiary
Crushers
Grinders
Product
Loadout
Dryers
Beneficiation
Tailings
Figure 8.23-1. A metallic mineral processing plant.
The emission factors in Table 8.23-1 are for the process operations as
the above equipment.
product recovery. The fac tors
to negligible levels.
8.23
8.23-2
EMISSION FACTORS
8/82
-------
The emission factors for dryers in Table 8.23-1 include transfer points
integral with the drying operation. A separate emission factor is provided
for dryers at titanium/zirconium plants that use dry cyclones for product
recovery and for emission control. Titanium/zirconium sand type ores do not
require crushing or grinding, and the ore is washed to remove humic and clay
material before concentration and drying operations.
At some metallic mineral processing plants, material is stored in
enclosed bins between process operations. The emission factors provided in
Table 8.23-1 for the handling and transfer of material should be applied to
the loading of material into storage bins and the transferring of material
from the bin. The emission factor will usually be applied twice to a storage
operation, once for the loading operation and once for the reclaiming oper-
ation. If material is stored at multiple points in the plant, the emission
factor should be applied to each operation and should apply to the material
being stored at each bin. The material handling and transfer factors do not
apply to small hoppers, surge bins or transfer points that are integral with
crushing, drying or grinding operations.
At some large metallic mineral processing plants, extensive material
transfer operations, with numerous conveyor belt transfer points, may be
required. The emission factors for material handling and transfer should be
applied to each transfer point that is not an integral part of another
process unit. These emission factors should be applied to each such conveyor
transfer point and should be based on the amount of material transferred
through that point.
The emission factors for material handling can also be applied to final
product loading for shipment. Again, these factors should be applied to
each transfer point, ore dump or other point where material is allowed to
fall freely.
Test data collected in the mineral processing industries indicate that
the moisture content of ore can have a significant effect on emissions from
several process operations. High moisture generally reduces the uncon-
trolled emission rates, and separate emission rates are provided for primary
crushers, secondary crushers, tertiary crushers, and material handling and
transfer operations that process high moisture ore. Drying and dry grinding
operations are assumed to produce or to involve only low moisture material.
For most metallic minerals covered in this Section, high moisture ore
is defined as ore whose moisture content, as measured at the primary crusher
inlet or at the mine, is 4 weight percent or greater. Ore defined as high
moisture at the primary crusher is presumed to be high moisture ore at any
subsequent operation for which high moisture factors are provided, unless a
drying operation precedes the operation under consideration. Ore is defined
as low moisture when a dryer precedes the operation under consideration or
when the ore moisture at the mine or primary crusher is less than 4 weight
percent.
Separate factors are provided for bauxite handling operations, in that
some types of bauxite with a moisture content as high as 15 to 18 weight
percent can still produce relatively high emissions during material handling
8/82 Mineral Products Industry 8.23-3
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8.23-4
EMISSION FACTORS
8/82
-------
procedures. These emissions could be eliminated by adding sufficient mois-
ture to the ore, but bauxite then becomes so sticky that it is difficult to
handle. Thus, there is some advantage to keeping bauxite in a relatively
dusty state, and the low moisture emission factors given represent condi-
tions fairly typical of the industry.
Particulate matter size distribution data for some process operations
have been obtained for control device inlet streams. Since these inlet
streams contain particulate matter from several activities, a variability
has been anticipated in the calculated size specific emission factors for
particulates.
Emission factors for particulate matter equal to or less than lOym
aerodynamic diameter, from a limited number of tests performed to charac-
terize the processes, are presented in Table 8.23-1.
In some plants, particulate emissions from multiple pieces of equipment
and operations are collected and ducted to a control device. Therefore,
examination of reference documents is recommended before application of the
factors to specific plants.
Emission factors for particulate matter equal to or less than lOym from
high moisture primary crushing operations and material handling and transfer
operations were based on test results usually in the 30 to 40 weight percent
range. However, high values were obtained for high moisture ore at both the
primary crushing and the material handling and transfer operations, and
these were included in the average values in the Table. A similarly wide
range occurred in the low moisture drying operation.
Several other factors are generally assumed to affect the level of
emissions from a particular process operation. These include ore character-
istics such as hardness, crystal and grain structure, and friability.
Equipment design characteristics, such as crusher type, could also affect
the emissions level. At this time, data are not sufficient to quantify each
of these variables.
8.23.3 Controlled Emissions7-9
Emissions from metallic mineral processing plants are usually controlled
with wet scrubbers or baghouses. For moderate to heavy uncontrolled emis-
sion rates from typical dry ore operations, dryers and dry grinders, a wet
scrubber with pressure drop of 1.5 to 2.5 kilopascals (6 to 10 inches of
water) will reduce emissions by approximately 95 percent. With very low
uncontrolled emission rates typical of high moisture conditions, the
percentage reduction will be lower (approximately 70 percent).
Over a wide range of inlet mass loadings, a well designed and main-
tained baghouse will reduce emissions to a relatively constant outlet
concentration. Such baghouses tested in the mineral processing industry
consistently reduce emissions to less than 0.05 grams per dry standard cubic
meter (0.02 grains per dry standard cubic foot), with an average concentra-
tion of 0.015 g/dscm (0.006 gr/dscf). Under conditions of moderate to high
uncontrolled emission rates of typical dry ore facilities, this level of
8/82 Mineral Products Industry 8.23-5
-------
controlled emissions represents greater than 99 percent removal of partic-
ulate emissions. Because baghouses reduce emissions to a relatively constant
outlet concentration, percentage emission reductions would be less for
baghouses on facilities with a low level of uncontrolled emissions.
References for Section 8.23
1. D. Kram, "Modern Mineral Processing: Drying, Calcining and Agglo-
meration", Engineering and Mining Journal. 181(6);134-151. June 1980.
2. A. Lynch, Mineral Crushing and Grinding Circuits. Elsevier Scientific
Publishing Company, New York, 1977.
3. "Modern Mineral Processing: Grinding", Engineering and Mining Journal.
181(161):106-113, June 1980.
4. L. Mollick, "Modern Mineral Processing: Crushing", Engineering and
Mining Journal. ^81(6):96-103, June 1980.
5. R. H. Perry, et al., Chemical Engineer's Handbook. 4th Ed, McGraw-Hill,
New York, 1963.
6. R. Richards and C. Locke, Textbook of Ore Dressing, McGraw-Hill, New
York, 1940.
7. "Modern Mineral Processing: Air and Water Pollution Controls",
Engineering and Mining Journal. 1.81(6) : 156-171, June 1980.
8. W. E. Horst and R. C. Enochs, "Modern Mineral Processing: Instru-
mentation and Process Control", Engineering and Mining Journal.
181(6):70-92, June 1980.
9. Metallic Mineral Processing Plants - Background Information for Proposed
Standards (Draft). EPA Contract No. 68-02-3063, TRW, Research Triangle
Park, NC, 1981.
10. Telephone communication between E. C. Monnig, TRW Environmental
Division, and R. Beale, Associated Minerals, Inc., May 17, 1982.
11. Written communication from W. R. Chalker, DuPont, Inc., to S. T. Cuffe,
U. S. Environmental Protection Agency, Research Triangle Park, NC,
December 21, 1981.
12. Written communication from P. H. Fournet, Kaiser Aluminum and Chemical
Corporation, to S. T. Cuffe, U. S. Environmental Protection Agency,
Research Triangle Park, NC, March 5, 1982.
8.23-6 EMISSION FACTORS 8/82
-------
8.24 WESTERN SURFACE COAL MINING
8.24.1 General1
There are 12 major coal fields in the western states (excluding the
Pacific Coast and Alaskan fields), as shown in Figure 8.24-1. Together,
they account for more than 64 percent of the surface minable coal reserves
COAL TYPE
LIGNITE
SUBBITUMINOUSCD
BITUMINOUS
1
2
3
4
5
6
7
8
9
10
11
12
Coal field
Fort Union
Powder River
North Central
Bighorn Basin
Wind River
Hams Fork
Uinta
Southwestern Utah
San Juan River
Raton Mesa
Denver
Green River
Strippable reserves
(IP6 tons)
23,529
56,727
All underground
All underground
3
1,000
308
224
2,318
All underground
All underground
2.120
5/83
Figure 8.24-1. Coal fields of the western U.S.3
Mineral Products Industry
8.24-1
-------
in the United States.2 The 12 coal fields have varying characteristics
which may influence fugitive dust emission rates from mining operations,
including overburden and coal seam thicknesses and structure, mining equip-
ment, operating procedures, terrain, vegetation, precipitation and surface
moisture, wind speeds and temperatures. The operations at a typical west-
ern surface mine are shown in Figure 8.24-2. All operations that involve
movement of soil, coal, or equipment, or exposure of erodible surfaces,
generate some amount of fugitive dust.
The initial operation is removal of topsoil and subsoil with large
scrapers. The topsoil is carried by the scrapers to cover a previously
mined and regraded area as part of the reclamation process or is placed in
temporary stockpiles. The exposed overburden, the earth which is between
the topsoil and the coal seam, is leveled, drilled and blasted. Then the
overburden material is removed down to the coal seam, usually by a dragline
or a shovel and truck operation. It is placed in the adjacent mined cut,
forming a spoils pile. The uncovered coal seam is then drilled and
blasted. A shovel or front end loader loads the broken coal into haul
trucks, and it is taken out of the pit along graded haul roads to the tip-
ple, or truck dump. Raw coal sometimes may be dumped onto a temporary
storage pile and later rehandled by a front end loader or bulldozer.
At the tipple, the coal is dumped into a hopper that feeds the primary
crusher, then is conveyed through additional coal preparation equipment
such as secondary crushers and screens to the storage area. If the mine
has open storage piles, the crushed coal passes through a coal stacker onto
the pile. The piles, usually worked by bulldozers, are subject to wind
erosion. From the storage area, the coal is conveyed to a train loading
facility and is put into rail cars. At a captive mine, coal will go from
the storage pile to the power plant.
During mine reclamation, which proceeds continuously throughout the
life of the mine, overburden spoils piles are smoothed and contoured by
bulldozers. Topsoil is placed on the graded spoils, and the land is pre-
pared for revegetation by furrowing, mulching, etc. From the time an area
is disturbed until the new vegetation emerges, all disturbed areas are sub-
ject to wind erosion.
8.24.2 Emissions
Predictive emission factor equations for open dust sources at western
surface coal mines are presented in Tables 8.24-1 and 8.24-2. Each equa-
tion is for a single dust generating activity, such as vehicle traffic on
unpaved roads. The predictive equation explains much of the observed vari-
ance in emission factors by relating emissions to three sets of source pa-
rameters: 1) measures of source activity or energy expended (e.g., speed
and weight of a vehicle traveling on an unpaved road); 2) properties of the
material being disturbed (e.g., suspendable fines in the surface material
of an unpaved road); and 3) climate (in this case, mean wind speed).
The equations may be used to estimate particulate emissions generated
per unit of source extent (e.g., vehicle distance traveled or mass of mate-
rial transferred).
8.24-2 EMISSION FACTORS 5/83
-------
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5/83
Mineral Products Industry
8.24-3
-------
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8.24-4
EMISSION FACTORS
5/83
-------
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5/83
Mineral Products Industry
8.24-5
-------
The equations were developed through field sampling various western surface
mine types and are thus applicable to any of the surface coal mines located
in the western United States.
In Tables 8.24-1 and 8.24-2, the assigned quality ratings apply within
the ranges of source conditions that were tested in developing the equa-
tions, given in Table 8.24-3. However, the equations are derated one let-
ter value (e.g., A to B) if applied to eastern surface coal mines.
TABLE 8.24-3.
TYPICAL VALUES FOR CORRECTION FACTORS APPLICABLE TO THE
PREDICTIVE EMISSION FACTOR EQUATIONS3
Source
Blasting
Coal loading
Bulldozers
Coal
Overburden
Dragline
Scraper
Grader
Light/medium
duty vehicles
Haul truck
Correction Number
factor of test
samples
Moisture
Depth
Area
Moisture
Moisture
Silt
Moisture
Silt
Drop distance
Moisture
Silt
Weight
Speed
Moisture
Wheels
Silt loading
5
18
18
7
3
3
8
8
19
7
10
15
7
7
29
26
Range
7.2
6
20
90
1,000
6.6
4.0
6.0
2.2
3.8
1.5
5
0.2
7.2
33
36
8.0
5.0
0.9
6.1
3.8
34
- 38
- 41
- 135
- 9,000
- 100,000
- 38
- 22.0
- 11.3
- 16.8
- 15.1
- 30
- 100
- 16.3
-25.2
- 64
- 70
-19.0
- 11.8
- 1.7
- 10.0
- 254
- 2,270
Geometric
mean Units
17.2
7.9
25.9
1,800
19,000
17.8
10.4
8.6
7.9
6.9
8.6
28.1
3.2
16.4
48.8
53.8
11.4
7.1
1.2
8.1
40.8
364
%
m
ft
m2
ft2
%
%
%
I
I
m
ft
%
%
Mg
tons
kph
mph
%
number
g/m2
Ib/acre
Reference 1.
In using the equations to estimate emissions from sources in a spe-
cific western surface coal mine, it is necessary that reliable values for
correction parameters be determined for the specific sources of interest,
if the assigned quality ratings of the equations are to apply. For exam-
ple, actual silt content of coal or overburden measured at a facility
8.24-6
EMISSION FACTORS
5/83
-------
should be used instead of estimated values. In the event that site spe-
cific values for correction parameters cannot be obtained, the appropriate
geometric mean values from Table 8.24-3 may be used, but the assigned qual-
ity rating of each emission factor equation is reduced by one level (e.g.,
A to B).
Emission factors for open dust sources not covered in Table 8.24-3 are
in Table 8.24-4. These factors were determined through source testing at
various western coal mines.
The factors in Table 8.24-4 for mine locations I through V were devel-
oped for specific geographical areas. Tables 8.24-5 and 8.24-6 present
characteristics of each of these mines (areas). A "mine specific" emission
factor should be used only if the characteristics of the mine for which an
emissions estimate is needed are very similar to those of the mine for
which the emission factor was developed. The other (nonspecific) emission
factors were developed at a variety of mine types and thus are applicable
to any western surface coal mine.
As an alternative to the single valued emission factors given in Table
8.24-4 for train or truck loading and for truck or scraper unloading, two
empirically derived emission factor equations are presented in Section
11.2.3 of this document. Each equation was developed for a source opera-
tion (i.e., batch drop and continuous drop, respectively), comprising a
single dust generating mechanism which crosses industry lines.
Because the predictive equations allow emission factor adjustment to
specific source conditions, the equations should be used in place of the
factors in Table 8.24-4 for the sources identified above, if emission esti-
mates for a specific western surface coal mine are needed. However, the
generally higher quality ratings assigned to the equations are applicable
only if 1) reliable values of correction parameters have been determined
for the specific sources of interest and 2) the correction parameter values
lie within the ranges tested in developing the equations. Table 8.24-3
lists measured properties of aggregate materials which can be used to esti-
mate correction parameter values for the predictive emission factor equa-
tions in Chapter 11, in the event that site specific values are not avail-
able. Use of mean correction parameter values from Table 8.24-3 reduces
the quality ratings of the emission factor equations in Chapter 11 by one
level.
5/83 Mineral Products Industry 8.24-7
-------
TABLE 8.24-4. UNCONTROLLED PARTICULATE EMISSION FACTORS FOR
OPEN DUST SOURCES AT WESTERN SURFACE COAL MINES
i
Source
Material
Mine
location
TSP
emission
factor1"
Units
Emission
Factor
Rating
Drilling
Topsoil removal by
scraper
Overburden
replacement
Truck loading by
power shovel
(batch drop)
Overburden
Coal
Topsoil
Overburden
Overburden
Train loading (batch Coal
or continuous drop)
Any
V
Any
IV
Anv
Any
III
Bottom dump truck
unloading
(batch drop)
Overburden
1.3
0.59
0.22
0.10
0.058
0.029
0.44
0.22
0.012
0.0060
0.037
0.018
0.028
0.014
0.0002
0.0001
0.002
0.001
Ib/hole
kg/hole
Ib/hole
kg/hole
Ib/T
kg/Mg
Ib/T
kg/Mg
Ib/T
kg/Mg
Ib/T
kg/Mg
Ib/T
kg/Mg
Ib/T
kg/Mg
Ib/T
kg/T
End duap truck
unloading
(batch drop)
Scraper unloading
(batch drop)
Wind erosion of
exposed areas
Coal
Coal
Topsoil
Seeded land,
stripped over-
burden, graded
overburden
IV
III
II
I
Any
V
IV
Any
0.027
0.014
0.005
0.002
0.020
0.010
0.014
0.0070
0.066
0.033
0.007
0.004
0.04
0.02
0.38
0.85
Ib/T
kg/Mg
Ib/T
kg/Mg
Ib/T
kg/Mg
Ib/T
kg/Mg
Ib/T
kg/Ms
Ib/T
kg/Mg
Ib/T
kg/Mg
T
(acre)(yr)
Ho
**K
(hectare) (yr)
E
E
E
E
E
E
D
P
D
D
E
E
C
C
C
C
Roaan numerals I through V refer to specific nine locations for which the
corresponding eaiission factors were developed (Reference 4). Tables 8.24-4
and 8.24-5 present characteristics of each of these Bines. See text for
correct use of these "mine specific" enission factors. The other factors
(fron Reference 5 except for overburden drilling fron Reference 1) can be
applied to any western surface coal nine.
Total suspended particulate (TSP) denotes what is measured by a standard high
volume sampler (see Section 11.2).
Predictive emission factor equations, which generally provide more accurate
estimates of emissions, are presented in Chapter 11.
8.24-8
EMISSION FACTORS
5/83
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References for Section 8.24
1. K. Axetell and C. Cowherd, Improved Emission Factors for Fugitive Dust
from Western Surface Coal Mining Sources, 2 Volumes, EPA Contract No.
68-03-2924, U. S. Environmental Protection Agency, Cincinnati, OH,
July 1981.
2. Reserve Base of U. S. Coals by Sulfur Content: Part 2, The Western
States, IC8693, Bureau of Mines, U. S. Department of the Interior,
Washington, DC, 1975.
3. Bituminous Coal and Lignite Production and Mine Operations - 1978,
DOE/EIA-0118(78), U. S. Department of Energy, Washington, DC, June
1980.
4. K. Axetell, Survey of Fugitive Dust from Coal Mines, EPA-908/1-78-003,
U. S. Environmental Protection Agency, Denver, CO, February 1978.
5. I). L. Shearer, et al., Coal Mining Emission Factor Development and
Modeling Study, Amax Coal Company, Carter Mining Company, Sunoco
Energy Development Company, Mobil Oil Corporation, and Atlantic
Richfield Company, Denver, CO, July 1981.
5/83 Mineral Products Industry 8.24-11
-------
PETROLEUM INDUSTRY
9.1 PETROLEUM REFINING'
9.1.1 General Description
The petroleum refining industry converts crude oil into more than 2500 refined products, including liquefied
petroleum gas, gasoline, kerosene, aviation fuel, diesel fuel, fuel oils, lubricating oils, and feedstocks for the
petrochemical industry. Petroleum refinery activities start with receipt of crude for storage at the refinery,
include all petroleum handling and refining operations, and terminate with storage preparatory to shipping the
refined products from the refinery.
The petroleum refining industry employs a wide variety of processes. A refinery's processing flow
scheme is largely determined by the composition of the crude oil feedstock and the chosen slate of petroleum
products. The example refinery flow scheme presented in Figure 9.1-1 shows the general processing arrangement
used by refineries in the United States for major refinery processes. The arrangement of these processes will vary
among refineries, and few, if any, employ all of these processes. Petroleum refining processes having direct
emission sources are presented in bold-line boxes on the figure.
Listed below are five categories of general refinery processes and associated operations:
1.
Separation processes
a. atmospheric distillation
b. vacuum distillation
light ends recovery (gas processing)
c.
2. Petroleum conversion processes
a. cracking (thermal and catalytic)
b. reforming
c. alkylation
d. polymerization
e. isomerization
f. coking
g. visbreaking
3. Petroleum treating processes
a. hydrodesulfurization
b. hydrotreating
c. chemical sweetening
d. acid gas removal
e. deasphalting
4. Feedstock and product handling
a. storage
b. blending
c. loading
d. unloading
5. Auxiliary facilities
a. boilers
b. wastewater treatment
c. hydrogen production
12/77 9.1-1
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d. sulfur recovery plant
e. cooling towers
f. blowdown system
g. compressor engines
These refinery processes are defined in the following section and their emission characteristics and applicable
emission control technology are discussed.
9.1.1.1. Separation Processes — The first phase in petroleum refining operations is the separation of crude oil into
its major constituents using three petroleum separation processes: atmospheric distillation, vacuum distillation,
and light ends recovery (gas processing). Crude oil consists of a mixture of hydrocarbon compounds including
paraffinic, naphthenic, and aromatic hydrocarbons plus small amounts of impurities including sulfur, nitrogen,
oxygen, and metals. Refinery separation processes separate these crude oil constituents into common-boiling-
point fractions.
9.1.1.2. Conversion Processes—To meet the demands for high-octane gasoline, jet fuel, and diesel fuel,
components such as residual oils, fuel oils, and light ends are converted to gasolines and other light fractions.
Cracking, coking, and visbreaking processes are used to break large petroleum molecules into smaller petroleum
molecules. Polymerization and alkylation processes are used to combine small petroleum molecules into larger
ones. Isomerization and reforming processes are applied to rearrange the structure of petroleum molecules to
produce higher-value molecules of a similar molecular size.
9.1.1.3. Treating Processes—Petroleum treating processes stabilize and upgrade petroleum products by
separating them from less desirable products and by removing objectionable elements. Undesirable elements
such as sulfur, nitrogen, and oxygen are removed by hydrodesulfurization, hydrotreating.chemical sweetening
and acid gas removal. Treating processes employed primarily for the separation of petroleum products include
such processes as deasphalting. Desalting is used to remove salt, minerals, grit, and water from crude oil feed
stocks prior to refining. Asphalt blowing is used for polymerizing and stabilizing asphalt to improve its weathering
characteristics.
9.1.1.4. Feedstock and Product Handling—The refinery feedstock and product handling operations consist of
unloading, storage, blending, and loading activities.
9.1.1.5. Auxiliary Facilities—A wide assortment of processes and equipment not directly involved in the refining
of crude oil are used in functions vital to the operation of the refinery. Examples are boilers, wastewater treatment
facilities, hydrogen plants, cooling towers, and sulfur recovery units. Products from auxiliary facilities (clean
water, steam, and process heat) are required by most refinery process units throughout the refinery.
9.1.2 Process Emission Sources and Control Technology
This section presents descriptions of those refining processes that are significant air pollutant contributors.
Process flow schemes, emission characteristics, and emission control technology are discussed for each process.
Table 9.1-1 lists the emission factors for direct-process emissions in petroleum refineries. The following process
emission sources are discussed in this section on petroleum refining emissions:
1. Vacuum distillation.
2. Catalytic cracking.
3. Thermal cracking processes.
4. Utility boilers.
5. Heaters.
12/77 Petroleum Industry 9.1-3
-------
6. Compressor engines.
7. Slowdown systems.
8. Sulfur recovery.
9.1.2.1. Vacuum Distillation—Topped crude withdrawn from the bottom of the atmospheric distillation column
is composed of high-boiling-point hydrocarbons. When distilled at atmospheric pressures, the crude oil
decomposes and polymerizes to foul equipment. To separate topped crude into components, it must be distilled in a
vacuum column at a very low pressure and in a steam atmosphere.
In the vacuum distillation unit, topped crude is heated with a process heater to temperatures ranging from
700 to 800° F (370 to 425° C). The heated topped crude is flashed into a multi-tray vacuum distillation column
operating at vacuums ranging from 0.5 to 2 psia (350 to 1400 kg/m2). In the vacuum column, the topped crude is
separated into common-boiling-point fractions by vaporization and condensation. Stripping steam is normally
injected into the bottom of the vacuum distillation column to assist in the separation by lowering the effective
partial pressures of the components. Standard petroleum fractions withdrawn from the vacuum distillation
column include lube distillates, vacuum oil, asphalt stocks, and residual oils. The vacuum in the vacuum
distillation column is normally maintained by the use of steam ejectors but may be maintained by the use of
vacuum pumps.
The major sources of atmospheric emissions from the vacuum distillation column are associated with the
steam ejectors or vacuum pumps. A major portion of the vapors withdrawn from the column by the ejectors or
pumps are recovered in condensers. Historically, the noncondensable portion of the vapors has been vented to the
atmosphere from the condensers. There are approximately 50 pounds (23 kg) of noncondensable hydrocarbons
per 1000 barrels of topped crude processed in the vacuum distillation column.2'12'13 A second source of
atmospheric emissions from vacuum distillation columns is combustion products from the process heater.
Process heater requirements for the vacuum distillation column are approximately 37,000 Btu per barrel (245
Joules/cm3) of topped crude processed in the vacuum column. Process heater emissions and their control are
discussed later in this section. Fugitive hydrocarbon emissions from leaking seals and fittings are also associated
with the vacuum distillation unit, but these are minimized by the low operating pressures and low vapor pressures
in the unit. Fugitive emission sources are also discussed later in this section.
Control technology applicable to the noncondensable emissions vented from the vacuum ejectors or pumps
include venting into blowdown systems or fuel gas systems, and incineration in furnaces or waste heat
boilers.2'12'13 These control techniques are generally greater than 99 percent efficient in the control of
hydrocarbon emissions, but they also contribute to the emission of combustion products.
9.1.2.2. Catalytic Cracking—Catalytic cracking, using heat, pressure, and catalysts, converts heavy oils into
lighter products with product distributions favoring the more valuable gasoline and distillate blending
components. Feedstocks are usually gas oils from atmospheric distillation, vacuum distillation, coking, and
deasphalting processes. These feedstocks typically have a boiling range of 650 to 1000° F (340 to 540° C). All of the
catalytic cracking processes in use today can be classified as either fluidized-bed or moving-bed units.
Fluidized-bed Catalytic Cracking (FCC) — The FCC process uses a catalyst in the form of very fine particles
that act as a fluid when aerated with a vapor. Fresh feed is preheated in a process heater and introduced into the
bottom of a vertical transfer line or riser with hot regenerated catalyst. The hot catalyst vaporizes the feed
bringing both to the desired reaction temperature,880 to 980° F (470 to 525° Q.The high activity of modern
catalysts causes most of the cracking reactions to take place in the riser as the catalyst and oil mixture flows
upward into the reactor. The hydrocarbon vapors are separated from the catalyst particles by cyclones in the
reactor. The reaction products are sent to a fractionator for separation.
9.1-4 EMISSION FACTORS 12/77
-------
The spent catalyst falls to the bottom of the reactor and is steam stripped as it exists the reactor bottom to
remove absorbed hydrocarbons. The spent catalyst is then conveyed to a regenerator. In the regenerator, coke
deposited on the catalyst as a result of the cracking reactions is burned off in a controlled combustion process with
preheated air. Regenerator temperature is usually 1100 to 1250° F (590 to 675° C). The catalyst is then recycled to
be mixed with fresh hydrocarbon feed.
Moving-bed Catalytic Cracking (TCC)— In the TCC process, catalyst beads (~ 0.5 cm) flow by gravity into the
top of the reactor where they contact a mixed-phase hydrocarbon feed. Cracking reactions take place as the
catalyst and hydrocarbons move concurrently downward through the reactor to a zone where the catalyst is
separated from the vapors. The gaseous reaction products flow out of the reactor to the fractionation section of
the unit. The catalyst is steam stripped to remove any adsorbed hydrocarbons. It then falls into the regenerator
where coke is burned from the catalyst with air. The regenerated catalyst is separated from the flue gases and
recycled to be mixed with fresh hydrocarbon feed. The operating temperatures of the reactor and regenerator in
the TCC process are comparable to those in the FCC process.
Air emissions from catalytic cracking processes are (1) combustion products from process heaters and (2)
flue gas from catalyst regeneration. Emissions from process heaters are discussed later in this section. Emissions
from the catalyst regenerator include hydrocarbons, oxides of sulfur, ammonia, aldehydes, oxides of nitrogen,
cyanides, carbon monoxide, and particulates (Table 9.1-1). The paniculate emissions from FCC units are much
greater than those from TCC units because of the higher catalyst circulation rates used.2'3'5
FCC particulate emissions are controlled by cyclones and/or electrostatic precipitators. Particulate control
efficiencies are as high as 80 to 85 percent.3' 5 Carbon monoxide wasteheat boilers reduce the carbon monoxide
and hydrocarbon emissions from FCC units to negligible levels.3 TCC catalyst regeneration produces similar
pollutants to FCC units but in much smaller quantities (Table 9.1-1). The particulate emissions from a TCC unit
are normally controlled by high-efficiency cyclones. Carbon monoxide and hydrocarbon emissions from a TCC
unit are incinerated to negligible levels by passing the flue gases through a process heater fire-box or smoke plume
burner. In some installations, sulfur oxides are removed by passing the regenerator flue gases through a water or
caustic scrubber.2'3'5
9.1.2.3 Thermal Cracking — Thermal cracking processes include visbreaking and coking, which break heavy oil
molecules by exposing them to high temperatures.
Visbreaking — Topped crude or vacuum residuals are heated and thermally cracked (850 to 900° F, 50 to 250
psig) (455 to 480° C, 3.5 to 17.6 kg/cm2) in the visbreaker furnace to reduce the viscosity or pour point of the
charge. The cracked products are quenched with gas oil and flashed into a fractionator. The vapor overhead from
the fractionator is separated into light distillate products. A heavy distillate recovered from the fractionator
liquid can be used as a fuel oil blending component or used as catalytic cracking feed.
Coking — Coking is a thermal cracking process used to convert low value residual fuel oil to higher value gas
oil and petroleum coke. Vacuum residuals and thermal tars are cracked in the coking process at high temperature
and low pressure. Products are petroleum coke, gas oils, and lighter petroleum stocks. Delayed coking is the most
widely used process today, but fluid coking is expected to become an important process in the future.
In the delayed coking process, heated charge stock is fed into the bottom section of a fractionator where light
ends are stripped from the feed. The stripped feed is then combined with recycle products from the coke drum and
rapidly heated in the coking heater to a temperature of 900 to 1100° F (480 to 590° C). Steam injection is used to
control the residence time in the heater. The vapor-liquid feed leaves the heater, passing to a coke drum where,
with controlled residence time, pressure (25 to 30 psig) (1.8 to2.1 kg/cm2), and temperature (750°F) (400° C), it
is cracked to form coke and vapors. Vapors from the drum return to the fractionator where the thermal cracking
products are recovered.
12/77 Petroleum Industry 9.1-5
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In the fluid coking process, typified by Flexicoking, residual oil feeds are injected into the reactor where they
are thermally cracked, yielding coke and a wide range of vapor products. Vapors leave the reactor and are
quenched in a scrubber where entrained coke fines are removed. The vapors are then fractionated. Coke from the
reactor enters a heater and is devolatilized. The volatiles from the heater are treated for fines and sulfur removal
to yield a particulate free, low-sulfur fuel gas. The devolatilized coke is circulated from the heater to a gasifier
where 95 percent of the reactor coke is gasified at high temperature with steam and air or oxygen. The gaseous
products and coke from the gasifier are returned to the heater to supply heat for the devolatilization. These gases
exit the heater with the heater volatiles through the same fines and sulfur removal processes.
From available literature, it is unclear what emissions are released and where they are released. Air
emissions from thermal cracking processes include coke dust from decoking operations, combustion gases from
the visbreaking and coking process heaters, and fugitive emissions. Emissions from the process heaters are
discussed later in this section. Fugitive emissions from miscellaneous leaks are significant because of the high
temperatures involved, and are dependent upon equipment type and configuration, operating conditions, and
general maintenance practices. Fugitive emissions are also discussed later in this section. Particulate emissions
from delayed coking operations are potentially very significant. These emissions are associated with removing the
coke from the coke drum and subsequent handling and storage operations. Hydrocarbon emissions are also
associated with cooling and venting the coke drum prior to coke removal. However, comprehensive data for
delayed coking emissions have not been included in available literature. 4'5
Particulate emission control is accomplished in the decoking operation by wetting down the coke.5
Generally, there is no control of hydrocarbon emissions from delayed coking. However, some facilities are now
collecting coke drum emissions in an enclosed system and routing them to a refinery flare.4'5
9.1.2.4 Utilities Plant — The utilities plant supplies the steam necessary for the refinery. Although the steam can
be used to produce electricity by throttling through a turbine, it is primarily used for heating and separating
hydrocarbon streams. When used for heating, the steam usually heats the petroleum indirectly in heat
exchangers and returns to the boiler. In direct contact operations, the steam can serve as a stripping medium or a
process fluid. Steam may also be used in vacuum ejectors to produce a vacuum. Emissions from boilers and
applicable emission control technology are discussed in much greater detail in Chapter 1.0.
9.1.2.5 Sulfur Recovery Plant — Sulfur recovery plants are used in petroleum refineries to convert hydrogen
sulfide (HsS) separated from refinery gas streams into the more disposable by-product, elemental sulfur.
Emissions from sulfur recovery plants and their control are discussed in Section 5.18.
9.1.2.6 Slowdown System — The blowdown system provides for the safe disposal of hydrocarbons (vapor and
liquid) discharged from pressure relief devices.
Most refining processing units and equipment subject to planned or unplanned hydrocarbon discharges are
manifolded into a collection unit, called the blowdown system. By using a series of flash drums and condensers
arranged in decreasing pressure, the blowdown is separated into vapor and liquid cuts. The separated liquid is
recycled into the refinery. The gaseous cuts can either be smokelessly flared or recycled.
Uncontrolled blowdown emissions primarily consist of hydrocarbons, but can also include any of the other
criteria pollutants. The emission rate in a blowdown system is a function of the amount of equipment manifolded
into the system, the frequency of equipment discharges, and the blowdown system controls.
Emissions from the blowdown system can be effectively controlled by combustion of the noncondensables in
a flare. To obtain complete combustion or smokeless burning (as required by most states), steam is injected in the
combustion zone of the flare to provide turbulence and to inspirate air. Steam injection also reduces emissions of
nitrogen oxides by lowering the flame temperature. Controlled emissions are listed in Table 9.1-1.2'11
9.1-8 EMISSION FACTORS 12/77
-------
9.1.2.7 Process Heaters - Process heaters (furnaces) are used
extensively in refineries to supply the heat necessary to raise the
temperature of feed materials to reaction or distillation level. They
are designed to raise petroleum fluid temperatures to a maximum of about
950°F (510°C). The fuel burned may be refinery gas, natural gas, residual
fuel oils, or combinations, depending on economics, operating conditions
and emission requirements. Process heaters may also use carbon monoxide-
rich regenerator flue gas as fuel.
All the criteria pollutants are emitted from process heaters. The
quantity of these emissions is a function of the type of fuel burned,
the nature of the contaminants in the fuel, and the heat duty of the
furnace. Sulfur oxide can be controlled by fuel desulfurization or flue
gas treatment. Carbon monoxide and hydrocarbons can be limited by more
combustion efficiency. Currently, four general techniques or modifi-
cations for the control of nitrogen oxides are being investigated:
combustion modification, fuel modification, furnace design and flue gas
treatment. Several of these techniques are presently being applied to
large utility boilers, but their applicability to process heaters has
not been established.2*14
9.1.2.8 Compressor Engines - Many older refineries run high pressure
compressors with reciprocating and gas turbine engines fired with natural
gas. Natural gas has usually been a cheap, abundant source of energy.
Examples of refining units operating at high pressure include hydro-
desulfurization, isomerization, reforming and hydrocracking. Internal
combustion engines are less reliable and harder to maintain than steam
engines or electric motors. For this reason, and because of increasing
natural gas costs, very few such units have been installed in the last
few years.
The major source of emissions from compressor engines is combustion
products in the exhaust gas. These emissions include carbon monoxide,
hydrocarbons, nitrogen oxides, aldehydes and ammonia. Sulfur oxides may
also be present, depending on the sulfur content of the natural gas.
All these emissions are significantly higher in exhaust of reciprocating
engines than from turbine engines.
The major emission control technique applied to compressor engines
is carburetion adjustment similar to that applied on automobiles.
Catalyst systems similar to those applied to automobiles may also be
effective in reducing emissions, but their use has not been reported.
9.1.2.9 Sweetening - Sweetening of distillates is accomplished by the
conversion of mercaptans to alkyl disulfides in the presence of a
catalyst. Conversion may be followed by an extraction step for the
removal of the alkyl disulfides. In the conversion process, sulfur is
added to the sour distillate with a small amount of caustic and air.
The mixture is then passed upward through a fixed bed catalyst counter
to a flow of caustic entering at the top of the vessel. In the conversion
and extraction process, the sour distillate is washed with caustic and
then is contacted in the extractor with a solution of catalyst and
10/80 Petroleum Industry 9.1-9
-------
Table 9.1-2. FUGITIVE EMISSION FACTORS FOR PETROLEUM REFINERIES*
Emission
Source
Pipeline valves
Open ended valves
Process
Stream
Type*
II
III
IV
V
•e I
Emission
Factor
Units
Ib/hr-source
kg/day-source
»
"
"
"
"
"
..
"
Emission Factors
Uncontrolled
Emissions0
0.059
0.64
0.024
0.26
0.0005
0.005
0.018
0.20
0.005
0.05
(0.030 -
(0.32 -
(0.017 -
(0.18 -
(0.0002-
(0.002 -
(0.007 -
(0.08 -
(0.0016-
(0.017 -
0.110)
1.19)
0.036)
0.39)
0.0015)
0.016)
0.045)
0.49)
0.016)
0.17)
Controlled
Emissions
NA
NA
NA
NA
NA
Emission
Applicable Control Technology Factor
Rating
Monitoring and maintenance programs A
A
A
A
Installation of cap or plug on open end A
of valve/line
Flanges
0.00056 (0.0002- 0.0025)
0.0061 (0.002 - 0.027)
Monitoring and maintenance programs
Pump seals
0.25
2.7
(0.16 - 0.37)
(1.7 - 4.0)
0.046 (0.019 - 0.11)
0.50 (0.21 - 1.2)
Mechanical seals, dual seals, purged
seals, monitoring and maintenance
programs, controlled degassing vents
Compressor seals II
1.4
15
0.11
1.2
(0.66 - 2.9)
(7.1 - 31)
(0.05 - 0.23)
(0.5 - 2.5)
Mechanical seals, dual seals, purged
seals, monitoring and maintenance
programs, controlled degassing vents
Process drains
0.070 (0.023 - 0.20)
0.76 (0.25 - 2.2)
Traps and covers
Pressure vessel
relief valves . ,
(gas service) *
Cooling towers
0.36
3.9
Oil/water separators -
Storage
Loading
lb/106 gal cooling
water
kg/106 liters cooling
water
lb/103 bbl refinery
feed8
kg/103 liters
refinery feed
lb/103 gal wastewater
kg/103 liter waste
water
lb/103 bbl refinery
feed
kg/103 liters refinery
feed
See Section 4.3
See Section 4.4
(0.10 - 1.3)
(1.1 - 14)
0.7
10
0.03
5
0.6
200
0.6
Negligible Rupture disks upstream of relief
valves and/or venting to a flare
0.70 Minimization of hydrocarbon leaks
into cooling water system. Monitoring
of cooling water for hydrocarbons
0.083
1.2
0.004
0.2
0.024
10
0.03
Covered separators and/or vapor recovery
Systems
aData from References 2, 4, 12 and 13 except as noted. Overall, less than 1% by weight of the total VOC emissions are methane.
NA - Not Available.
The volatility and hydrogen content of the process streams have a substantial effect on the emission rate of some fugitive emission sources.
The stream identification numerals and group names and descriptions are:
Stream
Identification
Numeral
I
II
III
Stream
Name
All streams
Gas streams
Light liquid and
gas/liquid streams
Stream Group Description
Al 1 s t reams
Hydrocarbon gas/vapor at process
volume)
Liquid or gas/liquid stream with
kerosene (> 0.1 psia @ 100°F or
present at > 20% by volume
conditions (conti
lining less than
a vapor pressure greater than th«
689 Pa @ 38CC), based on the most
50% hydrogen, by
it of
volatile class
Heavy liquid streams
Hydrogen streams
Liquid stream with a vapor pressure equal to or less than that of kerosene (^ 0.1
psia @ 1000F or 689 Pa @ 38°C), based on the most volatile class present at > 20%
by volume
Gas streams containing more than 50% hydrogen by volume
^Numbers in parentheses are the upper and lower bounds of the 95% confidence interval for the emission factor.
Data from Reference 17.
fThe downstream side of these valves is open to Che atmosphere. Emissions are through the valve seat of the closed valve.
Emission factor for relief valves in gas service is for leakage, not for emissions caused by vessel pressure relief.
^Refinery rate is defined as the crude oil feed rate to the atmospheric distillation column.
,.1-10
EMISSION FACTORS
10/80
-------
caustic. The extracted distillate is then contacted with air to convert
mercaptans to disulfides. After oxidation, the distillate is settled,
inhibitors are added, and the distillate is sent to storage. Regeneration
is accomplished by mixing caustic from the bottom of the extractor with
air arid then separating the disulfides and excess air.
The major emission problem is hydrocarbons from contact between
the distillate product and air in the "air blowing" step. These emissions
are related to equipment type and configuration, as well as to operating
conditions and maintenance practices.4
9.1.2.10 Asphalt Blowing - The asphalt blowing process polymerizes
asphaltic residual oils by oxidation, increasing their melting temper-
ature and hardness to achieve an increased resistance to weathering.
The oils, containing a large quantity of polycyclic aromatic compounds
(asphaltic oils), are oxidized by blowing heated air through a heated
batch mixture or, in continuous process, by passing hot air counter-
current to the oil flow. The reaction is exothermic, and quench steam
is sometimes needed for temperature control. In some cases, ferric
chloride or phosphorus pentoxide is used as a catalyst to increase the
reaction rate and to impart special characteristics to the asphalt.
Air emissions from asphalt blowing are primarily hydrocarbon vapors
vented with the blowing air. The quantities of emissions are small
because of the prior removal of volatile hydrocarbons in the distilla-
tion units, but the emissions may contain hazardous polynuclear organics.
Emission are 60 pounds per ton of asphalt.13 Emissions from asphalt
blowing can be controlled to negligible levels by vapor scrubbing,
incineration, or both4.13
9.1.3 Fugitive Emissions and Controls
Fugitive emission sources are generally defined as volatile organic
compound (VOC) emission sources not associated with a specific process
but scattered throughout the refinery. Fugitive emission sources
include valves of all types, flanges, pump and compressor seals, process
drains, cooling towers, and oil/water separators. Fugitive VOC emissions
are attributable to the evaporation of leaked or spilled petroleum
liquids and gases. Normally, control of fugitive emissions involves
minimizing leaks and spills through equipment changes, procedure changes,
and improved monitoring, housekeeping and maintenance practices.
Controlled and uncontrolled fugitive emission factors for the following
sources are listed in Table 9.1-2.
0 valves (pipeline, open ended, vessel relief)
0 flanges
0 seals (pump, compressor)
0 process drains
0 oil/water separators (wastewater treatment)
0 storage
0 transfer operations
0 cooling towers
10/80 Petroleum Industry 9.1-11
-------
9.1.3.1 Valves, Flanges, Seals and Drains - For these .sources, a very
high correlation has been found between mass emission rates and the type
of stream service in which the sources are employed. Kxcept for com-
pressed gases, streams are classified into one of three stream groups,
(1) gas/vapor streams, (2) light liquid/two phase streams, and (3)
kerosene and heavier liquid streams. Gases passing through compressors
are classified as either hydrogen or hydrocarbon service. It is found that
sources in gas/vapor stream service have higher emission rates than
those in heavier stream service. This trend is especially pronounced
for valves and pump seals. The size of sources like valves, flanges,
pump seals, compressor seals, relief valves and process drains does not
affect the leak rates.17 The emission factors are independent of process
unit or refinery throughput.
Emission factors are given for compressor seals in each of the two
gas service classifications. Valves, because of their number and relatively
high emission factor, are the major emission source among the source
types. This conclusion is based on an analysis of a hypothetical refinery
coupled with the emission rates. The total quantity of fugitive VOC
emissions in a typical oil refinery with a capacity of 330,000 barrels
(52,500 m3) per day is estimated as 45,000 pounds (20.4 MT) per day.
See Table 9.1-3.
9.1.3.2 Storage - All refineries have a feedstock and product storage
area, termed a "tank farm", which provides surge storage capacity to
assure smooth, uninterrupted refinery operations. Individual storage
tank capacities range from less than 1000 barrels to more than 500,000
barrels (160 - 79,500 m3). Storage tank designs, emissions and emission
control technologies are discussed in detail in Section 4.3.
9.1.3.3 Transfer Operations - Although most refinery feedstocks and
products are transported by pipeline, some are transported by trucks,
rail cars and marine vessels. They are transferred to and from these
transport vehicles in the refinery tank farm area by specialized pumps
and piping systems. The emissions from transfer operations and appli-
cable emission control technology are discussed in much greater detail
in Section 4.4.
9.1.3.4 Wastewater Treatment Plant - All refineries employ some form of
wastewater treatment so water effluents can safely be returned to the
environment or reused in the refinery. The design of wastewater treat-
ment plants is complicated by the diversity of refinery pollutants,
including oil, phenols, sulfides, dissolved solids, and toxic chemicals.
Although the wastewater treatment processes employed by refineries vary
greatly, they generally include neutralizers, oil/water separators,
settling chambers, clarifiers, dissolved air flotation systems, coagu-
lators, aerated lagoons, and activated sludge ponds. Refinery water
effluents are collected from various processing units and are conveyed
through sewers and ditches to the wastewater treatment plant. Most of
the wastewater treatment occurs in open ponds and tanks.
9.1-12 EMISSION FACTORS 10/80
-------
The main components of atmospheric emissions from wastewater treat-
ment plants are fugitive VOC and dissolved gases that evaporate from the
surfaces of wastewater residing in open process drains, wastewater
separators, and wastewater ponds (Table 9.1-2). Treatment processes
that involve extensive contact of wastewater and air, such as aeration
ponds and dissolved air flotation, have an even greater potential for
atmospheric emissions.
The control of wastewater treatment plant emissions involves cov-
ering wastewater systems where emission generation is greatest (such as
covering American Petroleum Institute separators and settling basins)
and removing dissolved gases from wastewater streams with sour water
strippers and phenol recovery units prior to their contact with the
atmosphere. These control techniques potentially can achieve greater
than 90 percent reduction of wastewater system emissions.13
TABLE 9.1-3. FUGITIVE VOC EMISSIONS FROM AN OIL REFINERY17
Source
Valves
Flanges
Pump Seals
Compressors
Relief Valves
Drains
•a
Cooling Towers
Oil/Water Separators
(uncovered)
TOTAL
Number
11,500
46,500
350
70
100
650
VOC
Ib/day
6,800
600
1,300
1,100
500
1,000
1,600
32,100
45,000
Emissions
kg /day
3,084
272
590
499
227
454
726
14,558
20,408
o
Emissions from the cooling towers and oil/water separators are based on
limited data. EPA is currently involved in further research to provide
better data on wastewater system fugitive emissions.
9.1.3.5 Cooling Towers - Cooling towers are used extensively in refinery
cooling water systems to transfer waste heat from the cooling water to
the atmosphere. The only refineries not employing cooling towers are
those with once-through cooling. The increasing scarcity of large water
supplies required for once-through cooling is contributing to the disappear-
ance of that form of refinery cooling. In the cooling tower, warm
cooling water returning from refinery processes is contacted with air by
cascading through packing. Cooling water circulation rates for refineries
commonly range from 0.3 to 3.0 gallons (1.1 - 11.0 liters) per minute
per barrel per day of refinery capacity.2* lf>
Atmospheric emissions from the cooling tower consist of fugitive
VOC and gases stripped from the cooling water as the air and water come
into contact. These contaminants enter the cooling water system from
10/80 Petroleum Industry 9.1-13
-------
leaking heat exchangers and condensers. Although the predominant conta-
minant in cooling water is VOC, dissolved gases such as hydrogen sulfide
and ammonia may also be found (Table 9.1-2) ^j1*'17
Control of cooling tower emissions is accomplished by reducing
contamination of cooling water through the proper maintenance of heat
exchangers and condensers. The effectiveness of cooling tower controls
is highly variable, depending on refinery configuration and existing
maintenance practices.
References for Section 9.1
1. C. E. Burklin, et al., Revision of Emission Factors for Petroleum
Refining, EPA-450/3-77-030, U.S. Environmental Protection Agency,
Research Triangle Park, NC, October 1977.
2. Atmospheric Emissions from Petroleum Refineries: A Guide for Measure-
ment and Control, PHS No. 763, Public Health Service, U.S. Depart-
ment of Health, Education and Welfare, Washington, DC, 1960.
3. Background Information for Proposed New Source Standards; Asphalt
Concrete Plants, Petroleum Refineries, Storage Vessels, Secondary
Lead Smelters and Refineries, Brass or Bronze Ingot Production Plants,
Iron and Steel Plants, Sewage Treatment Plants, APTD-1352a, U.S.
Environmental Protection Agency, Research Triangle Park, NC, 1973.
4. John A. Danielson (ed.), Air Pollution Engineering Manual (2nd Ed.),
AP-40, U.S. Environmental Protection Agency, Research Triangle
Park, NC, 1973. Out of Print.
5. Ben G. Jones, "Refinery Improves Particulate Control", Oil and Gas
Journal, 69(26);60-62, June 28, 1971.
6. "Impurities in Petroleum", Petreco Manual, Petrolite Corp., Long
Beach, CA, 1958.
7. Control Techniques for Sulfur Oxide in Air Pollutants, AP-52, U.S.
Environmental Protection Agency, Research Triangle Park, NC,
January 1969.
8. H. N. Olson and K. E. Hutchinson, "How Feasible Are Giant, One-
train Refineries?", Oil and Gas Journal, 70(1);39-43, January 3,
1972.
9. C. M. Urban and K. J. Springer, Study of Exhaust Emissions from
Natural Gas Pipeline Compressor Engines, American Gas Association,
Arlington, VA, February 1975.
10. H. E. Dietzmann and K. J. Springer, Exhaust Emissions from Piston
and Gas Turbine Engines Used in Natural Gas Transmission, American
Gas Association, Arlington, VA, January 1974.
9.1-14 EMISSION FACTORS 10/80
-------
11. M. G. Klett and J. B. Galeski, Flare Systems Study, EPA-600/2-76-
079, U.S. Environmental Protection Agency, Research Triangle Park,
NC, March 1976.
12. Evaporation Loss in the Petroleum Industry, Causes and Control,
API Bulletin 2513, American Petroleum Institute, Washington, DC,
1959.
13. Hydrocarbon Emissions from Refineries, API Publication No. 928,
American Petroleum Institute, Washington, DC, 1973.
14. R. A. Brown, et al., Systems Analysis Requirements for Nitrogen
Oxide Control of Stationary Sources, EPA-650/2-74-091, U.S.
Environmental Protection Agency, Research Triangle Park, NC, 1974.
15. R. P. Hangebrauck, et al., Sources of Polynuclear Hydrocarbons in
the Atmosphere, 999-AP-33, Public Health Service, U.S. Department
of Health, Education and Welfare, Washington, DC, 1967.
16. W. S. Crumlish, "Review of Thermal Pollution Problems, Standards,
and Controls at the State Government Level", Presented at the
Cooling Tower Institute Symposium, New Orleans, LA, January 30, 1966.
17. Assessment of Atmospheric Emissions from Petroleum Refining,
EPA-600/2-80-075a through -075d, U.S. Environmental Protection
Agency, Research Triangle Park, NC, 1980.
10/80 Petroleum Industry 9.1-15
-------
9.2 NATURAL GAS PROCESSING
9.2.1 General1
Natural gas from high-pressure wells is usually passed through field separators to remove hydrocarbon
condensate and water at the well. Natural gasoline, butane, and propane are usually present in the gas, and gas
processing plants are required for the recovery of these liquefiable constituents (see Figure 9.2-1). Natural gas is
considered "sour" if hydrogen sulfide is present in amounts greater than 0.25 grain per 100 standard cubic feet.
The hydrogen sulfide (H2S) must be removed (called "sweetening" the gas) before the gas can be utilized. If F^jS
is present, the gas is usually sweetened by absorption of the H2S in an amine solution. Amine processes are used
for over 95 percent of all gas sweetening in the United States. Processes such as carbonate processes, solid bed
absorbents, and physical absorption methods are employed in the other sweetening plants. Emissions data for
sweetening processes other than amine types are very meager.
The major emission sources in the natural gas processing industry are compressor engines and acid gas wastes
from gas sweetening plants. Compressor engine emissions are discussed in section 3.3.2; therefore, only gas
sweetening plant emissions are discussed here.
9.2.2 Process Description2'3
Many chemical processes are available for sweetening natural gas. However, at present, the most widely used
method for H2S removal or gas sweetening is the amine type process (also known as the Girdler process) in which
various amine solutions are utilized for absorbing H2S. The process is summarized in reaction 1 and illustrated in
Figure 9.2-2.
2 RNH2 + H2S «-(RNH3)2S 0)
where: R = mono, di, or tri-ethanol
N = nitrogen
H = hydrogen
S = sulfur
The recovered hydrogen sulfide gas stream may be (1) vented, (2) flared in waste gas flares or modern
smokeless flares, (3) incinerated, or (4) utilized for the production of elemental sulfur or other commercial
products. If the recovered H2S gas stream is not to be utilized as a feedstock for commercial applications, the gas
is usually passed to a tail gas incinerator in which the H2S is oxidized to sulfur dioxide and then passed to the
atmosphere via a stack. For more details, the reader should consult Reference 8.
9.2.3 Emissions4'5
Emissions will only result from gas sweetening plants if the acid waste gas from the amine process is flared or
incinerated. Most often, the acid waste gas is used as a feedstock in nearby sulfur recovery or sulfuric acid plants.
When flaring or incineration is practiced, the major pollutant of concern is sulfur dioxide. Most plants employ
elevated smokeless flares or tail gas incinerators to ensure complete combustion of all waste gas constituents,
including virtually 100 percent conversion of H2S to S02. Little particulate, smoke, or hydrocarbons result from
these devices, and because gas temperatures do not usually exceed 1200°F (650°C), significant quantities of
nitrogen oxides are not formed. Emission factors for gas sweetening plants with smokeless flares or incinerators
are presented in Table 9.2-1.
4/76 Petroleum Industry 9.2-1
-------
•o
CO
l_
4->
CO
c
OJ
*J
H-
o
E
CO
O)
CO
73
o
T3
0}
Nl
CD
0>
O
CN
05
-------
Table 9.2-1. EMISSION FACTORS FOR GAS SWEETENING PLANTS8
EMISSION FACTOR RATING: SULFUR OXIDES: A
ALL OTHER FACTORS: C
Process*5
Amine
lb/106 ft3 gas processed
kg/103 m3 gas processed
Particulates
Neg.
Neg.
Sulfur oxides0
(S02)
1685Sd
26.98 Sd
Carbon
monoxide
Neg.
Neg.
Hydrocarbons
Neg.
Neg.
Nitrogen
oxides
Neg.
Neg.
aEmission factors are presented in this section only for smokeless flares and tail gas incinerators on the amine gas sweetening
process. Too little emissions information exists to characterize emissions from older, less efficient waste gas flares on the
amine process or from other, less common gas sweetening processes. Emission factors for various internal combustion engines
utilized in a gas processing plant are given in section 3.3.2. Emission factors for sulfuric acid plants and sulfur recovery plants
are given in sections 5.17 and 5.18, respectively.
''These factors represent emissions after smokeless flares (with fuel gas and steam injection) or tail gas incinerators and are based
on References 2 and 4 through 7.
cThese factors are based on the assumptions that virtually 100 percent of all HoS in the acid gas waste is converted to SO% during
flaring or incineration and that the sweetening process removes essentially 100 percent of the H^ present in the feedstock.
dS is the (-(28 content, on a mole percent basis, in the sour gas entering the gas sweetening plant. For example, if the H^S content
is 2 percent, the emission factor would be 1685 times 2, or 3370 Ib SO2 per million cubic feet of sour gas processed. If the
H2S mole percent is unknown, average values from Table 9.2-2 may be substituted.
Note: If H2$ contents are reported in grains per 100 scf or ppm, use the following factors to convert to mole percent:
0.01 mol % HjS = 6.26 gr HjS/lOO scf at 60°F and 29.92 in. Hg
1 gr/100 scf = 16 ppm (by volume)
To convert to or from metric units, use the following factor:
0.044 gr/100 scf = 1 mg/Um3
ACID GAS
PURIFIED
GAS
*1 STEAM
ylREBOILER
-^
4/76
HEAT EXCHANGER
Figure 9.2-2. Flow diagram of the amine process for gas sweetening.
Petroleum Industry
9.2-3
-------
Table 9.2-2. AVERAGE HYDROGEN SULFIDE CONCENTRATIONS
IN NATURAL GAS BY AIR QUALITY CONTROL REGION3
State
Alabama
Arizona
Arkansas
California
Colorado
Florida
Kansas
Louisiana
Michigan
Mississippi
Montana
New Mexico
North Dakota
Oklahoma
AQCR name
Mobile-Pensacola-Panama City -
Southern Mississippi (Fla., Miss.)
Four Corners (Colo., N.M., Utah)
Monroe-El Dorado (La.)
Shreveport-Texarkana-Tyler
(La., Okla., Texas)
Metropolitan Los Angeles
San Joaquin Valley
South Central Coast
Southeast Desert
Four Corners (Ariz., N.M., Utah)
Metropolitan Denver
Pawnee
San Isabel
Yampa
Mobile-Pensacola-Panama City -
Southern Mississippi (Ala., Miss.)
Northwest Kansas
Southwest Kansas
Monroe-El Dorado (Ariz.)
Shreveport-Texarkana-Tyler
(Ariz., Okla., Texas)
Upper Michigan
Mississippi Delta
Mobile-Pensacola-Panama City -
Southern Mississippi (Ala., Fla.)
Great Falls
Miles City
Four Corners (Ariz., Colo., Utah)
Pecos-Permian Basin
North Dakota
Northwestern Oklahoma
Shreveport-Texarkana-Tyler
(Ariz., La., Texas)
Southeastern Oklahoma
AQCR
number
5
14
19
22
24
31
32
33
14
36
37
38
40
5
97
100
19
22
126
134
5
141
143
14
155
172
187
22
188
Average
H2S, mol %
3.30
0.71
0.15
0.55
2.09
0.89
3.66
1.0
0.71
0.1
0.49
0.3
0.31
3.30
0.005
0.02
0.15
0.55
0.5
0.68
3.30
3.93
0.4
0.71
0.83
1.74b
1.1
0.55
0.3
9.2-4
EMISSION FACTORS
4/76
-------
Table 9.2-2 (continued). AVERAGE HYDROGEN SULFIDE CONCENTRATIONS
IN NATURAL GAS BY AIR QUALITY CONTROL REGION3
State
Texas
Utah
Wyoming
AQCR name
Abilene-Wichita Falls
Amarillo-Lubbock
Austin-Waco
Corpus Christi-Victoria
Metropolitan Dallas-Fort Worth
Metropolitan San Antonio
Midland-Odessa-San Angelo
Shreveport-Texarkana-Tyler
(Ariz., La., Okla.)
Four Corners (Ariz., Colo., N.M.)
Casper
Wyoming (except Park, Bighorn
and Washakie Counties)
AQCR
number
210
211
212
214
215
217
218
22
14
241
243
Average
H2S, mol %
0.055
0.26
0.57
0.59
2.54
1.41
0.63
0.55
0.71
1.262
2.34
Reference 9.
bSour gas only reported for Burke, Williams, and McKenzie Counties.
°Park, Bighorn, and Washakie Counties report gas with an average 23 mol % HjS content.
Some plants still use older, less efficient waste gas flares. Because these flares usually burn at temperatures
lower than necessary for complete combustion, some emissions of hydrocarbons and particulates as well as higher
quantities of I^S can occur. No data are available to estimate the magnitude of these emissions from waste gas
flares.
Emissions from sweetening plants with adjacent commercial plants, such as sulfuric acid plants or sulfur
recovery plants, are presented in sections 5.17 and 5.18, respectively. Emission factors for internal combustion
engines used in gas processing plants are given in section 3.3.2.
Background material for this section was prepared for EPA by Ecology Audits, Inc.**
References for Section 9.2
1. Katz, D.L., D. Cornell, R. Kobayashi, F.H. Poettmann, J.A. Vary, J.R. Elenbaas, and C.F. Weinaug.
Handbook of Natural Gas Engineering. New York, McGraw-Hill Book Company. 1959. 802 p.
2. Maddox, R.R. Gas and Liquid Sweetening. 2nd Ed. Campbell Petroleum Series, Norman, Oklahoma. 1974.
298 p.
3. Encyclopedia of Chemical Technology. Vol. 7. Kirk, R.E. and D.F. Othmer (eds.). New York, Interscience
Encyclopedia, Inc. 1951.
4. Sulfur Compound Emissions of the Petroleum Production Industry. M.W. Kellogg Co., Houston, Texas.
Prepared for Environmental Protection Agency, Research Triangle Park, N.C. under Contract No. 68-02-1308.
Publication No. EPA-650/2-75-030. December 1974.
5. Unpublished stack test data for gas sweetening plants. Ecology Audits, Inc., Dallas, Texas. 1974.
4/76
Petroleum Industry
9.2-5
-------
6. Control Techniques for Hydrocarbon and Organic Solvent Emissions from Stationary Sources. U.S. DHEW,
PHS, EHS, National Air Pollution Control Administration, Washington, D.C. Publication No. AP-68. March
1970. p. 3-1 and 4-5.
7. Control Techniques for Nitrogen Oxides from Stationary Sources. U.S. DHEW, PHS, EHS, National Air
Pollution Control Administration, Washington, D.C. Publication No. AP-67. March 1970. p. 7-25 to 7-32.
8. Mullins, B.J. et al. Atmospheric Emissions Survey of the Sour Gas Processing Industry. Ecology Audits, Inc.,
Dallas, Texas. Prepared for Environmental Protection Agency, Research Triangle Park, N.C. under Contract
No. 68-02-1865. Publication No. EPA-450/3-75-076. October 1975.
9. Federal Air Quality Control Regions. Environmental Protection Agency, Research Triangle Park, N.C.
Publication No. AP-102. January 1972.
i
4/76 EMISSION FACTORS 9.2-6
-------
10. WOOD PRODUCTS INDUSTRY
Wood processing involves the conversion of raw wood to either pulp, pulpboard, or one of several types of
wallboard including plywood, particleboard, or hardboard. This section presents emissions data for chemical
wood pulping, for pulpboard and plywood manufacturing, and for woodworking operations. The burning of wood
waste in boilers and conical burners is not included as it is discussed in Chapters 1 and 2 of this publication.
10.1 CHEMICAL WOOD PULPING
10.1.1 Generali
Chemical wood pulping involves the extraction of cellulose from wood by dissolving the lignin that binds the
cellulose fibers together. The principal processes used in chemical pulping are the kraft, sulfite, neutral sulfite
semichemical (NSSC), dissolving, and soda; the first three of these display the greatest potential for causing air
pollution. The kraft process accounts for about 65 percent of all pulp produced in the United States; the sulfite
and NSSC processes, together, account for less than 20 percent of the total. The choice of pulping process is de-
termined by the product being made, by the type of wood species available, and by economic considerations.
10.1.2 Kraft Pulping
10.1.2.1 Process Descriptionl»2—The kraft process (see Figure 10.1.2-1) involves the cooking of wood chips
under pressure in the presence of a cooking liquor in either a batch or a continuous digester. The cooking liquor,
or "white liquor," consisting of an aqueous solution of sodium sulfide and sodium hydroxide, dissolves the lignin
that binds the cellulose fibers together.
When cooking is completed, the contents of the digester are forced into the blow tank. Here the major portion
of the spent cooking liquor, which contains the dissolved lignin, is drained, and the pulp enters the initial stage of
washing. From the blow tank the pulp passes through the knotter where unreacted chunks of wood are removed.
The pulp is then washed and, in some mills, bleached before being pressed and dried into the finished product.
It is economically necessary to recover both the inorganic cooking chemicals and the heat content of the spent
"black liquor," which is separated from the cooked pulp. Recovery is accomplished by first concentrating the
liquor to a level that will support combustion and then feeding it to a furnace where burning and chemical recovery
take place.
Initial concentration of the weak black liquor, which contains about 15 percent solids, occurs in the multiple-
effect evaporator. Here process steam is passed countercurrent to the liquor in a series of evaporator tubes that
increase the solids content to 40 to 55 percent. Further concentration is then effected in the direct contact
evaporator. This is generally a scrubbing device (a cyclonic or venturi scrubber or a cascade evaporator) in which
hot combustion gases from the recovery furnace mix with the incoming black liquor to raise its solids content to
55 to 70 percent.
The black liquor concentrate is then sprayed into the recovery furnace where the organic content supports
combustion. The inorganic compounds fall to the bottom of the furnace and are discharged to the smelt dissolving
tank to form a solution called "green liquor." The green liquor is then conveyed to a causticizer where slaked
lime (calcium hydroxide) is added to convert the solution back to white liquor, which can be reused in subsequent
cooks. Residual lime sludge from the causticizer can be recycled after being dewatered and calcined in the hot
lime kiln.
Many mills need more steam for process heating, for driving equipment, for providing electric power, etc., than
can be provided by the recovery furnace alone. Thus, conventional industrial boilers that burn coal, oil, natural
gas, and in some cases, bark and wood waste are commonly employed.
4/76 Wood Products Industry 10.1-1
-------
w
CO
>
O
73
C
03
cn
c
OB
13
CO
TO
o
Q.
O
o>
O
10.1-2
EMISSION FACTORS
4/76
-------
10.1.2.2. Emission and Controls1 -6-Participate emissions from the kraft process occur primarily from the re-
covery furnace, the lime kiln, and the smelt dissolving tank. These emissions consist mainly of sodium salts but
include some calcium salts from the lime kiln. They are caused primarily by the carryover of solids plus the sub-
limation and condensation of the inorganic chemicals.
Paniculate control is provided on recovery furnaces in a variety of ways. In mills where either a cyclonic
scrubber or cascade evaporator serves as the direct contact evaporator, further control is necessary as these devices
are generally only 20 to 50 percent efficient for particulates. Most often in these cases, an electrostatic precipitator
is employed after the direct contact evaporator to provide an overall particulate control efficiency of 85 to > 99
percent. In a few mills, however, a venturi scrubber is utilized as the direct contact evaporator and simultaneously
provides 80 to 90 percent particulate control. In either case auxiliary scrubbers may be included after the
precipitator or the venturi scrubber to provide additional control of particulates.
Particulate control on lime kilns is generally accomplished by scrubbers. Smelt dissolving tanks are commonly
controlled by mesh pads but employ scrubbers when further control is needed.
The characteristic odor of the kraft mill is caused in large part by the emission of hydrogen sulfide. The major
source is the direct contact evaporator in which the sodium sulfide in the black liquor reacts with the carbon
dioxide in the furnace exhaust. The lime kiln can also be a potential source as a similar reaction occurs involving
residual sodium sulfide in the lime mud. Lesser amounts of hydrogen sulfide are emitted with the noncondensible
off-gasses from the digesters and multiple-effect evaporators.
The kraft-process odor also results from an assortment of organic sulfur compounds, all of which have extremely
low odor thresholds. Methyl mercaptan and dimethyl sulfide are formed in reactions with the wood component
lignin. Dimethyl disulfide is formed through the oxidation of mercaptan groups derived from the lignin. These
compounds are emitted from many points within a mill; however, the main sources are the digester/blow tank
systems and the direct contact evaporator.
Although odor control devices, per se, are not generally employed in kraft mills, control of reduced sulfur
compounds can be accomplished by process modifications and by optimizing operating conditions. For example,
black liquor oxidation systems, which oxidize sulfides into less reactive thiosulfates, can considerably reduce
odorous sulfur emissions from the direct contact evaporator, although the vent gases from such systems become
minor odor sources themselves. Noncondensible odorous gases vented from the digester/blow tank system and
multiple-effect evaporators can be destroyed by thermal oxidation, usually by passing them through the lime
kiln. Optimum operation of the recovery furnace, by avoiding overloading and by maintaining sufficient oxygen
residual and turbulence, significantly reduces emissions of reduced sulfur compounds from this source. In addi-
tion, the use of fresh water instead of contaminated condensates in the scrubbers and pulp washers further reduces
odorous emissions. The effect of any of these modifications on a given mill's emissions will vary considerably.
Several new mills have incorporated recovery systems that eliminate the conventional direct contact evaporators.
In one system, preheated combustion air rather than flue gas provides direct contact evaporation. In the other,
the multiple-effect evaporator system is extended to replace the direct contact evaporator altogether. In both of
these systems, reduced sulfur emissions from the iccovery furnace/direct contact evaporator reportedly can be
reduced by more than 95 percent from conventional uncontrolled systems.
Sulfur dioxide emissions result mainly from oxidation of reduced sulfur compounds in the recovery furnace.
It is reported that the direct contact evaporator absorbs 50 to 80 percent of these emissions; further scrubbing, if
employed, can reduce them another 10 to 20 percent.
Potential sources of carbon monoxide emissions from the kraft process include the recovery furnace and lime
kilns. The major cause of carbon monoxide emissions is furnace operation well above rated capacity, making it
impossible to maintain oxidi/mg conditions.
4/77 Wood Products Industry 10.1-3
-------
Some nitrogen oxides fere also emitted from the recovery furnace and lime kilns although the
amounts are relatively small. Indications are that nitrogen oxides emissions from each of these sources
-are on the order of 1 pound per air-dried ton (0.5 kg/air-dried MT) of pulp produced.5 6
A major source of emissions in a kraft mill is the boiler for generating auxiliary steam and power.
The fuels used are coal, oil, natural gas, or bark/wood waste. Emission factors for boilers are presented
in Chapter 1.
Table 10.1.2-1 presents emission factors for a conventional kraft mill. The most widely used
paniculate controls devices are shown along with the odor reductions resulting from black liquor
oxidation and incint, .ition of noncondensible off-gases.
10.1.3 Acid Sulfite Pulping
10.1.3.1 Process Description14 - The production of acid sulfite pulp proceeds similarly to kraft pulp-
ing except that different chemicals are used in the cooking liquor. In place of the caustic solution used
to dissolve the lignin in the wood, sulfurous acid is employed. To buffer the cooking solution, a bisul-
fite of sodium, magnesium, calcium, or ammonium is used. A simplified flow diagram of a magnesium-
base process is shown in Figure 10.1.3-1.
r
Digestion is carried out under high pressure and high temperature in either batch-mode of coif
^tinuous digesters in the presence of a sulfurous acid-bisulfite cooking liquor. When cooking is com-
leted, the digester is either discharged at high pressure into a blow pit or its contents are pumped out
at a lower pressure into a dump tank. The spent sulfite liquor (also called red liquor) then drains
through the bottom of the tank and is either treated and disposed, incinerated, or sent to a plant for
recovery of heat and chemicals. The pulp is then washed and processed through screens and centri-
fuges for removal of knots, bundles of fibers, and other materials. It subsequently may be bleached,
pressed, and dried in paper-making operations.
Because of the variety of bases employed in the cooking liquor, numerous schemes for heat and/or
chemical recovery have evolved. In calcium-base systems, which are used mostly in older mills, chemi-
cal recovery is not practical, and the spent liquor is usually discarded or incinerated. In ammonium-
base operations, heat can be recovered from the spent liquor through combustion, but the ammonium
base is consumed in the process. In sodium- or magnesium-base operations heat, sulfur, and base
recovery are all feasible.
If recovery is practiced, the spent weak red liquor (which contains more than half of the raw
materials as dissolved organic solids) is concentrated in a multiple-effect evaporator and direct contact
evaporator to 55 to 60 percent solids. Strong liquor is sprayed into a furnace and burned, producing
steam for the digesters, evaporators, etc., and to meet the mills power requirements.
When magnesium base liquor is burned, a flue gas is produced from which magnesium oxide is
recovered in a multiple cyclone as fine white powder. The magnesium oxide is then water-slaked and
used as circulating liquor in a series of venturi scrubbers which are designed to absorb sulfur dioxide
from the flue gas and form a bisulfite solution for use in the cook cycle. When sodium-base liquor is
burned, the inorganic compounds are recovered as a molten smelt containing sodium sulfide and
sodium carbonate. This smelt may be processed further and used to absorb sulfur dioxide from the
flue gas and sulfur burner. In some sodium-base mills, however, the smelt may be sold to a nearby kraft
mill as raw material for producing green liquor.
10.1-4 EMISSION FACTORS 4/"< '
-------
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-------
10.1-6
EMISSION FACTORS
4/77
-------
, If recovery is not practiced, an acid plant of sufficient capacity to fulfill the mill's total sulfite
-requirement is necessary. Normally, sulfur is burned in a rotary or spray burner. The gas produced is
'then cooled by heat exchangers plus a water spray and then absorbed in a variety of different scrubbers'
containing either limestone or a solution of the base chemical. Where recovery is practiced, fortifica-^
:tion is accomplished similarly, although a much smaller amount of, sulfur dioxide must be produced :
to make up for that lost in the process.
10.1.3.2 Emissions and Controls14 - Sulfur dioxide is^enerally considered the major pollutant ojj
concern from sulfite pulp mills. The characteristic "kraft" odor is not emitted because volatile re-
^duced sulfur compounds are not products of the lignin-bisulfite reaction.
One of the major SQj,sources is the digester and blow pit or dump tank system. Sulfur dioxide is
present in the intermittent digester relief gases as well as in the gases given off at the end of the cook
when the digester contents are discharged into the blow pit or dump tank. The quantity of sulfur oxide
{evolved and emitted to the atmosphere in these gas streams depends on the pH of the cooking liquor,
.the pressure at which the digester contents are discharged, and the effectiveness of the absorption
(systems employed for SOa recovery. Scrubbers can be installed that reduce SO? from this source by as
jmuch as 99 percent.
Another source of sulfur dioxide emissions is the recovery system. Since magnesium-, sodium-, and
ammonium-base recovery systems all utilize absorption systems to recover SO2 generated in the re-
covery furnace, acid fortification towers, multiple-effect evaporators, etc., the magnitude of SO^
emissions depends on the desired.efficiency of these systems. Generally, such absorption systems
provide better than 95 percent sulfur recovery to minimize sulfur makeup needs.
The various pulp washing, screening, and cleaning operations are also potential sources of SO?.
These operations are numerous and may account for a significant fraction of a mill's SO2 emissions if
not controlled.
The only significant particulate source in the pulping and recovery process is the absorption system
handling the recovery furnace exhaust. Less particulate is generated in ammonium-base systems than
magnesium- or sodium-base systems as the combustion productions are mostly nitrogen, water vapor,
and sulfur dioxide.
Other major sources of emissions in a sulfite pulp mill include the auxiliary power boilers. Emis-
sion factors for these boilers are presented in Chapter 1.
i Emission factors for the various sulfite pulping operations are shown in Table 10.1.3-1.
10.1.4 Neutral Sulfite Semichemical (NSSC) Pulping
10.1.4.1 Process Description1*7!15'16 - In this process, the wood chips are cooked in a neutral solution of
sodium sulfite and sodium bicarbonate. The sulfite ion reacts with the lignin in the wood, and the
sodium bicarbonate acts as a buffer to maintain a neutral solution. The major difference between this
process (as well as all semichemical techniques) and the kraft and acid sulfite processes is that only a
portion of the lignin is removed during the cook, after which the pulp is further reduced by mechani-
cal disintegration. Because of this, yields as high as 60 to 80 percent can be achieved as opposed to 50 |o
55 percent for other chemical processes.
4/77 Wood Products Industry 10.1-7
-------
Table 10.1.3-1. EMISSION FACTORS FOR SULFITE PULPING3
Source
Digester/blow pit or
dump tankc
Recovery system'
Acid plantS
Other sources'
Base
All
MgO
MgO
MgO
MgO
NH3
NH3
Na
Ca
MgO
NHs
Na
NH3
Na
Ca
All
Control
None
Process change6
Sciubber
Process change
and scrubber
All exhaust
vented through
recovery system
Process change
Process change
and scrubber
Process change
and scrubber
Unknown
Multicloneand
venturi
scrubbers
Ammonia
absorption and
mist eliminator
Sodium carbonate
scrubber
Scrubber
Unknownn
Jenssen
scrubber
None
Emission factor"3
Paniculate
Ib/ADUT
Negd
Neg
Neg
Neg
Neg
Neg
Neg
Neg
Neg
2
0 7
4
Neg
Neg
Neg
Neg
kg/ADUMT
Neg
Neg
Neg
Neg
Neg
Neg
Neg
Neg
Neg
1
0.35
2
Neg
Neg
Neg
Neg
Sulfur Dioxide
Ib/ADUT
1070
2-6
1
0.2
0
25
04
2
67
9
7
2
0.3
0.2
8
12
kg/ADUMT
5-35
1-3
0.5
0.1
0
12.5
0.2
1
33.5
4.5
3.5
1
0.2
0.1
4
6
Emission
factor
rating
C
C
B
B
A
D
B
C
C
A
B
C
C
D
C
D
aAM emission factors represent long-term average emissions.
^Factors expressed in terms of Ib (kg) of pollutant per air dried unbleached ton (MT) of pulp. All factors are based on data
in Reference 14.
cThese factors represent emissions that occur after the cook is completed and when the digester contents are discharged in-
to the blow pit or dump tank. Some relief gases are vented from the digester during the cook cycle, but these are usually
transferred to pressure accumulators, and the SC>2 therein is reabsorbed for use in the cooking liquor. These factors repre-
sent long-term average emissions; in some mills, the actual emissions will be intermittent and for short time periods.
^Negligible emissions.
eProcess changes may include such measures as raising the pH of the cooking liquor, thereby lowering the free SC>2, reliev-
ing the pressure in the digester before the contents are discharged, and pumping out the digester contents instead of blow-
ing them out.
f The recovery system at most mills is a closed system that includes the recovery furnace, direct contact evaporator, multi-
ple-effect evaporator, acid fortification tower, and SC>2 absorption scrubbers. Generally, there will only be one emission
point for the entire recovery system. These factors are long-term averages and include the high SC>2 emissions during the
periodic purging of the recovery system.
9Acid plants are necessary in mills that have no or insufficient recovery systems.
^Control is practiced, but type of control is unknown.
' Includes miscellaneous pulping operations such as knotters, washers, screens, etc.
10.1-8
EMISSION FACTORS
4/77
-------
The NSSC process varies from mill to mill. Some mills dispose of their spent liquor, some mills recover the
cooking chemicals, and some, which are operated in conjunction with kraft mills, mix their spent liquor with the
kraft liquor as a source of makeup chemicals. When recovery is practiced, the steps involved parallel those of the
sulfite process.
10.1.4.2 Emissions and ControlsV,'*,'<>-Paniculate emissions are a potential problem only when recovery
systems are employed. Mills that do practice recovery, but are not operated in conjunction with kraft operations
often utilize fluidized bed reactors to burn their spent liquor. Because the flue gas contains sodium sulfate and
sodium carbonate dust, efficient particulate collection may be included to facilitate chemical recovery.
A potential gaseous pollutant is sulfur dioxide. The absorbing towers, digester/blow tank system, and recovery
furnace are the main sources of this pollutant with the amounts emitted dependent upon the capability of the
scrubbing devices installed for control and recovery.
Hydrogen sulfide can also be emitted from NSSC mills using kraft-type recovery furnaces. The main potential
source is the absorbing tower where a significant quantity of hydrogen sulfide is liberated as the cooking liquor is
made. Other possible sources include the recovery furnace, depending on the operating conditions maintained, as
well as the digester/blow tank system in mills where some green liquor is used in the cooking process. Where green
liquor is used, it is also possible that significant quantities of mercaptans will be produced. Hydrogen sulfide
emissions can be eliminated if burned to sulfur dioxide prior to entering the absorbing systems.
Because the NSSC process differs greatly from mill to mill, and because of the scarcity of adequate data, no
emission factors are presented.
References for Section 10.1
1. Hendrickson, E. R. et al. Control of Atmospheric Emissions in the Wood Pulping Industry. Vol. I. U.S.
Department of Health, Education and Welfare, PHS, National Air Pollution Control Administration, Wash-
ington, D.C. Final report under Contract No. CPA 22-69-18. March 15,1970.
2. Britt, K. W. Handbook of Pulp and Paper Technology. New York, Reinhold Publishing Corporation, 1964.
p. 166-200.
3. Hendrickson, E. R. et al. Control of Atmospheric Emissions in the Wood Pulping Industry. Vol. III. U.S.
Department of Health, Education, and Welfare, PHS, National Air Pollution Control Administration, Wash-
ington, D.C. Final report under Contract No. CPA 22-69-18. March 15,1970.
4. Walther, J. E. and H. R. Amberg. Odor Control in the Kraft Pulp Industry. Chem. Eng. Progress. 66:73-
80, March 1970.
5. Galeano, S. F. and K. M. Leopold. A Survey of Emissions of Nitrogen Oxides in the Pulp Mill. TAPPI.
56(3):74-76, March 1973.
6. Source test data from the Office of Air Quality Planning and Standards, U.S. Environmental Protection
Agency, Research Triangle Park, N.C. 1972.
7. Atmospheric Emissions from the Pulp and Paper Manufacturing Industry. U.S. Environmental Protection
Agency, Research Triangle Park, N.C. Publication No. EPA-450/1-73-002. September 1973.
4/77 Wood Products Industry 10.1-9
-------
8. Blosser, R. O. and H. B. Cooper. Paniculate Matter Reduction Trends in the Kraft Industry. NCASI paper,
Corvallis, Oregon.
9. Padfield, D. H. Control of Odor from Recovery Units by Direct-Contact Evaporative Scrubbers with
Oxidized Black-Liquor. TAPPI. 56:83-86, January 1973.
10. Walther, J. E. and H. R. Amberg. Emission Control at the Kraft Recovery Furnaces. TAPPI. 55(3): 1185-
1188, August 1972.
11. Control Techniques for Carbon Monoxide Emissions from Stationary Sources. U.S. Department of Health
Education and Welfare, PHS, National Air Pollution Control Administration, Washington, D.C. Publication
No. AP-65. March 1970. p. 4-24 and 4-25.
12. Blosser, R. 0. et al. An Inventory of Miscellaneous Sources of Reduced Sulfur Emissions from the Kraft
Pulping Process. (Presented at the 63rd APCA Meeting. St. Louis. June 14-18, 1970.)
13. Factors Affecting Emission of Odorous Reduced Sulfur Compounds from Miscellaneous Kraft Process
Sources. NCASI Technical Bulletin No. 60. March 1972.
14. Background Document: Acid Sulfite Pulping. Prepared by Environmental Science and Engineering, Inc.,
Gainesville, Fla., for Environmental Protection Agency under Contract No. 68-02-1402, Task Order No. 14.
Document No. EPA-450/3-77-005. Research Triangle Park, N.C. January 1977.
15. Benjamin, M. et al. A General Description of Commercial Wood Pulping and Bleaching Processes. J. Air
Pollution Control Assoc. 79(3): 155-161, March 1969.
16. Galeano, S. F. and B. M. Dillard. Process Modifications for Air Pollution Control in Neutral Sulfite Semi-
Chemical Mills. J. Air Pollution Control Assoc. 22(3): 195-199, March 1972.
,10.1-10 •< EMISSION FACTORS 4/77
-
-------
10.2 PULPBOARD
10.2.1 General"
Pulpbouul manufacturing involves the fabncation of fibrous boaids from a pulp slmiy. This includes two dis-
tinct types of product, papcrboard and fibcrboard Papeiboard is a geneial term that descnbes u sheet 0.012 nidi
(0.30 mm) or more in thickness made of fibious material on a paper-lorming machine.2 |- iberboard. also referred
to as particle board, is thicker than paperboard and is made somewhat differently.
There are two distinct phases in the conversion of wood to pulpboaid (I) the manufacture of pulp from raw
wood and (2) the manufacture of pulpboard from the pulp. This section deals only with the latter as the former
is covered under the section on the wood pulping industry.
10.2.2 Process Description1
In the in , lufacture of paperboard, the slock is sent through screens into the head box, from which it flows
onto a mo- • c screen. Approximately 15 percent of the wutcr is removed by suction boxes located under the
screen. Vinilicr 50 to 60 percent of the moisture content is removed in the drying section. The dried board
then enters the calendar stack, which imparts the final surface to the product.
In the manufacture of fibcrboard, the slurry that remains after pulping is washed and sent to the stock chests
where sizing is added. The refined fiber from the stock chests is fed to the head box of the board machine. The
stock is next fed onto the forming screens and sent to dryers, after which the dry product is finally cut and
fabricated.
10.2.3 Emissions'
Emissions from the paperboard machine consist mainly of water vapor: little or no paniculate matter is emit-
ted from the dryers.3-5 Particulates are emitted, however, from the fibcrboaid drying opeiation Additional
particulate emissions occur from the cutting and sanding operations. Emission factors for these operations are
given in section 10.4. Emission factors for pulpboard manufacturing are shown in Table 10.2-1.
Table 10.2-1. PARTICULATE EMISSION FACTORS FOR
PULPBOARD MANUFACTURING3
EMISSION FACTOR RATING: E
Type of product
Paperboard
Fiberboardb
Emissions
Ib/ton
Neg
0.6
kg/MT
Neg
0.3
aEmissiOn factors expressed as units per unit weight of finished product.
bReference 1.
References for Section 10.2
1. Air Pollutant Emission Factors. Resources Research, Inc., Rcston, Virginia. Prepaied foi National An
Pollution Control Administration, Washington, D.C. under Contract No. CPA-22-61)-! I1). Apnl lc)70.
2. The Dictionary of Paper. New York, American Paper and Pulp Association, ll)40.
4/76 Wood Products Industry 10.2-1
-------
3. Hough, (I. W. and L. J. (jross. Air knmsion Control in ;i Modem I'ulp ;ind Papei Mill. Ainci. Papei Indusliy.
51:36, February 1969.
4. Pollution Control Progress. J. Air Pollution Control Assoc. /7:410, June 1967.
5. Private communication between I. Gcllman and the National Council of the Papei Industry lor Clean Air
and Stream Improvement. New York,October 2X, 1969.
10.2-2 EMISSION FACTORS 4/76
-------
10.3 PLYWOOD VENEER AND LAYOUT OPERATIONS
10.3.1 General1"3
Plywood is a building material consisting of veneers (thin wood
layers or plies) bonded with an adhesive. The outer layers (faces)
surround a core which is usually lumber, veneer or particle board.
Plywood uses are many, including wall siding, sheathing, roof decking,
concrete formboards, floors, and containers. Most plywood is made from
Douglas Fir or other softwoods, and the majority of plants are in the
Pacific Northwest. Hardwood veneers make up only a very small portion
of total production.
In the manufacture of plywood, logs are sawed to the desired
length, debarked and peeled into veneers of uniform thickness. Veneer
thicknesses of less than one half inch or one centimeter are common.
These veneers are then transported to veneer dryers with one or more
decks, to reduce their moisture content. Dryer temperatures are held
between about 300 and 400°F (150 - 200°C). After drying, the plies go
through the veneer layout operation, where the veneers are sorted,
patched and assembled in perpendicular layers, and a thermosetting resin
adhesive applied. The veneer assembly is then transferred to a hot
press where, under pressure and steam heat, the product is formed.
Subsequently, all that remains is trimming, face sanding, and possibly
some finishing treatment to enhance the usefulness of the product.
Plywood veneer and layout operations are shown in Figure 10.3-1.
O_Q
10.3.2 Emissions and Controls
Emissions from the manufacture of plywood include particulate
matter and organic compounds. The main source of emissions is the
veneer dryer, with other sources producing negligible amounts of organic
compound emissions or fugitive emissions. The log steaming and veneer
drying operations produce combustion products, and these emissions
depend entirely on the type of fuel and equipment used.
Uncontrolled fugitive particulate matter, in the form of sawdust
and other small wood particles, comes primarily from the plywood cutting
and sanding operations. To be considered additional sources of fugitive
particulate emissions are log debarking, log sawing and sawdust handling.
The dust that escapes into the air from sanding, sawing and other wood-
working operations may be controlled by collection in an exhaust system
and transport through duct work to a sized cyclone. Section 10.4
discusses emissions from such woodworking waste collection operations.
Estimates of uncontrolled particulate emission factors for log debarking
and sawing, sawdust pile handling, and plywood sanding and cutting are
given in Table 10.3-1. From the veneer dryer, and at stack temperatures,
the only particulate emissions are small amounts of wood fiber particles
in concentrations of less than 0.002 grams per dry standard cubic foot.
2/80 Woo«l Product* In«lustr> 10.3-1
-------
fugitive
particulate
LOG
STORAGE
LOG
DEBARKING
AND
SAWING
LOG
STEAMING
fugitive
particulate
organic
compounds
VENEER
LAYOUT
AND
3LUE SPREADINd
organic
compounds
PLYWOOD
PRESSING
fugitive
particulate
PLYWOOD
CUTTING
fugitive
particulate
Figure 10.3-1. Plywood veneer and layout operations
4,5
10.3-2
EMISSION FACTORS
2/80
-------
Table 10.3-1. UNCONTROLLED FUGITIVE PARTICULATE EMISSION
FACTORS FOR PLYWOOD VENEER AND LAYOUT OPERATONS
EMISSION FACTOR RATING: E
Source
•a
Log debarking
a
Log sawing
Sawdust handling
Q
Veneer lathing
Particulates
0.024 Ib/ton
0.350 Ib/ton
1.0 Ib/ton
NA
0.012 kg/MT
0.175 kg/MT
0.5 kg/MT
NA
Plywood cutting and
j^ d
sanding
0.1 Ib/ft
0.05 kg/m
Reference 7. Emission factors are expressed as units per unit weight
, of logs processed.
Reference 7. Emission factors are expressed as units per unit weight
of sawdust handled, including sawdust pile loading, unloading and
storage.
.Estimates not available.
Reference 5. Emission factors are expressed as units per surface area
of plywood produced. These factors are expressed as representative
values for estimated values ranging from 0.066 to 0.132 Ib/ft2
(0.322 to 0.644 kg/m2).
The major pollutants emitted from veneer dryers are organic compounds.
The quantity and type of organics emitted vary, depending on the wood
species and on the dryer type and its method of operation. There are
two discernable fractions which are released, condensibles and volatiles.
The condensible organic compounds consist largely of wood resins, resin
acids and wood sugars, which cool outside the stack to temperatures
below 70°F (21°C) and combine with water vapor to form a blue haze, a
water plume or both. This blue haze may be eliminated by condensing the
organic vapors in a finned tube matrix heat exhanger condenser. The
other fraction, volatile organic compounds, is comprised of terpenes and
natural gas components (such as unburned methane), the latter occurring
only when gas fired dryers are used. The amounts of organic compounds
released because of adhesive use during the plywood pressing operation
are negligible. Uncontrolled organic process emission factors are given
in Table 10.3-2.
2/80
Wood Products Indiistn
10.3-3
-------
Table 10.3-2. UNCONTROLLED ORGANIC COMPOUND PROCESS EMISSION
FACTORS FOR PLYWOOD VENEER DRYERS3
EMISSION FACTOR RATING: B
Volatile
Organic Compounds
Species
Douglas Fir
sapwood
steam fired
gas fired
heartwood
Larch
Southern pine
Otherb
lb/104 ft2
0.45
7.53
1.30
0.19
2.94
0.03-3.00
kg/104 m2
2.3
38.6
6.7
1.0
15.1
0.15-15.4
Condensible
Organic Compounds
lb/104 ft2
4.64
2.37
3.18
4.14
3.70
0.5-8.00
4 2
kg/10* m
23.8
12.1
16.3
21.2
18.9
2.56-41
.0
f\
Reference 2. Emission factors are expressed in pounds of pollutant
per 10,000 square feet of 3/8 inch thick veneer dried, and kilograms
of pollutant per 10,000 square meters of 1 centimeter thick veneer
-dried. All dryers are steam fired unless otherwise specified.
These ranges of factors represent results from one source test for
each of the following species (in order from least to greatest
emissions): Western Fir, Hemlock, Spruce, Western Pine and
Ponderosa Pine.
References for Section 10.3
1. C.B. Hemming, "Plywood", Kirk-Othmer Encyclopedia of Chemical
Technology, Second Edition, Volume 15, John Wiley & Sons, Inc., New
York, NY, 1968, pp. 896-907.
2. F. L. Monroe, et al., Investigation of Emissions from Plywood
Veneer Dryers, Washington State University, Pullman, WA, February
1972.
3. Theodore Baumeister, ed., "Plywood", Standard Handbook for
Mechanical Engineers, Seventh Edition, McGraw-Hill, New York, NY,
1967, pp. 6-162 - 6-169.
4. Allen Mick and Dean McCargar, Air Pollution Problems in Plywood,
Particleboard, and Hardboard Mills in the Mid-Willamette Valley.
Mid-Willamette Valley Air Pollution Authority, Salem, OR,
March 24, 1969.
10.3-1 EMISSION FACTORS 2/80
i
-------
5. Controlled and Uncontrolled Emission Rates and Applicable
Limitations for Eighty Processes, Second Printing,
EPA-340/1-78-004, U.S. Environmental Protection Agency, Research
Triangle Park, NC, April 1978, pp. X-l - X-6.
6. John A. Danielson, ed., Air Pollution Engineering Manual,
AP-40, Second Edition, U.S. Environmental Protection Agency,
Research Triangle Park, NC, May 1973, pp. 372-374.
7. Assessment of Fugitive Particulate Emission Factors for
Industrial Processes, EPA-450/3-78-107, U.S. Environmental
Protection Agency, Research Triangle Park, NC, September 1978.
8. C. Ted Van Decar, "Plywood Veneer Dryer Control Device",
Journal of the Air Pollution Control Association, 22:968,
December 1972.
2/80 Wood Products Imlustn,
-------
10.4 WOODWORKING WASTE COLLECTION OPERATIONS
10.4.1 General1'5
Woodworking, as defined in this section, includes any operation that involves the generation of small wood
waste particles (shavings, sanderdust, sawdust, etc.) by any kind of mechanical manipulation of wood, bark, or
wood byproducts. Common woodworking operations include sawing, planing, chipping, shaping, moulding,
hogging, lathing, and sanding. Woodworking operations are found in numerous industries, such as sawmills,
plywood, particleboard, and hardboard plants, and furniture manufacturing plants.
Most plants engaged in woodworking employ pneumatic transfer systems to remove the generated wood waste
from the immediate proximity of each woodworking operation. These systems are necessary as a housekeeping
measure to eliminate the vast quantity of waste material that would otherwise accumulate. They are also a
convenient means of transporting the waste material to common collection points for ultimate disposal. Large
diameter cyclones have historically been the primary means of separating the waste material from the airstreams
in the pneumatic transfer systems, although baghouses have recently been installed in some plants for this
purpose.
The waste material collected in the cyclones or baghouses may be burned in wood waste boilers, utilized in the
manufacture of other products (such as pulp or particleboard), or incinerated in conical (teepee/wigwam)
burners. The latter practice is declining with the advent of more stringent air pollution control regulations and
because of the economic attractiveness of utilizing wood waste as a resource.
10.4.2 Emissions1'6
The only pollutant of concern in woodworking waste collection operations is particulate matter. The major
emission points are the cyclones utilized in the pneumatic transfer systems. The quantity of particulate emis-
sions from a given cyclone will depend on the dimensions of the cyclone, the velocity of the airstream, and the
nature of the operation generating the waste. Typical large diameter cyclones found in the industry will only
effectively collect particles greater than 40 micrometers in diameter. Baghouses, when employed, collect essen-
tially all of the waste material in the airstream. The wastes from numerous pieces of equipment often feed into
the same cyclone, and it is common for the material collected in one or several cyclones to be conveyed to
another cyclone. It is also possible for portions of the waste generated by a single operation to be directed to
different cyclones.
Because of this complexity, it is useful when evaluating emissions from a given facility to consider the waste
handling cyclones as air pollution sources instead of the various woodworking operations that actually generate
the particulate matter. Emission factors for typical large diameter cyclones utilized for waste collection in
woodworking operations are given in Table 10.4-1.
Emission factors for wood waste boilers, conical burners, and various drying operations—often found in
facilities employing woodworking operations—are given in Sections 1.6, 2.3, 10.2, and 10.3.
2/80 Wood Products Induslr\ 10.4-1
-------
Table 10.4.1. PARTICULATE EMISSION FACTORS FOR LARGE DIAMETER
CYCLONES IN WOODWORKING WASTE COLLECTION SYSTEMS3
EMISSION FACTOR RATING: D
Types of waste handled
Sanderdust0*
Other6
Particulate emissions'3'0
gr/scf
0.055
(0.005-0.16)
0.03
(0.001-0.16)
g/Nm3
0.126
(0.0114-0.37)
0.07
(0.002-0.37)
Ib/hr
5
(0.2-30.0)
2
(0.03-24.0)
kg/hr
2.3
(0.09-13.6)
0.91
(0.014-10.9)
aTypical waste collection cyclones range from 4 to 16 feet (1.2 to 4.9 meters) in diameter
and employ airflows ranging from 2,000 to 26,000 standard cubic feet (57 to 740 normal
cubic meters) per minute. Note: if baghouses are used for waste collection, paniculate
emissions will be negligible.
bReferences 1 through 3.
cObserved value ranges are in parentheses.
'These factors should be used whenever waste from sanding operations is fed directly into
the cyclone in question.
eThese factors should be used for cyclones handling waste from all operations other than
sanding. This includes cyclones that handle waste (including sanderdust) already collected
by another cyclone.
References for Section 10.4
1. Source test data supplied by Robert Harris, Oregon Department of Environmental Quality, Portland, OR,
September 1975.
2. J.W. Walton, et al., "Air Pollution in the Woodworking Industry", Presented at the 68th Annual Meeting of
the Air Pollution Control Association, Boston, MA, June 1975.
3. J.D. Patton and J.W. Walton, "Applying the High Volume Stack Sampler To Measure Emissions from Cotton
Gins, Woodworking Operations, and Feed and Grain Mills", Presented at 3rd Annual Industrial Air Pollution
Control Conference, Knoxville, TN, March 29-30,1973.
4. C.F. Sexton, "Control of Atmospheric Emissions from the Manufacturing of Furniture", Presented at 2nd
Annual Industrial Air Pollution Control Conference, Knoxville, TN, April 20-21,1972.
5. A. Mick and D. McCargar, "Air Pollution Problems in Plywood, Particleboard, and Hardboard Mills in the
Mid-Willamette Valley", Mid-Williamette Valley Air Pollution Authority, Salem, OR, March 24,1969.
6. Information supplied by the North Carolina Department of Natural and Economic Resources, Raleigh, NC,
December 1975.
10.1-2
EMISSION FACTORS
2/80
-------
10.4.3 Fugitive Emission Factors
Since most woodworking operations control emissions out of necessity, fugitive emissions are seldom a
problem. However, the wood waste storage bins are a common source of fugitive emissions. Table 10.4-2
shows these emission sources and their corresponding emission factors.
Information concerning size characteristics is very limited. Data collected in a western red cedar furni-
ture factory equipped with exhaust ventilation on most woodworking equipment showed most suspended
particles in the working environment to be less than 2 /xm in diameter.7
Table 10.4-2. POTENTIAL UNCONTROLLED
FUGITIVE PARTICULATE EMISSION FACTORS
FOR WOODWORKING OPERATIONS
EMISSION FACTOR RATING: C
Type of operation
Wood waste storage bin ventb
Wood waste storage bin loadoutb
Participates3
Ib/ton
1.0
2.0
kg/MT
0.5
1.0
"Factors expressed as units per unit weight of wood waste handled.
bEngineermg judgment based on plant visits.
Additional Reference for Section 10.4
7. Lester V. Cralley, et a/., Industrial Enivronmental Health, the Worker and the Community, Academic
Press, New York and London, 1972.
7/79
Wood Processing
10.4-3
-------
MISCELLANEOUS SOURCES
This chapter contains emission factor information on those source categories that differ substantially from—and
hence cannot be grouped with—the other "stationary" sources discussed in this publication. These "miscellaneous"
emitters (both natural and man-made) are almost exclusively "area sources", that is, their pollutant generating
process(es) are dispersed over large land areas (for example, hundreds of acres, as in the case of forest wildfires), as
opposed to sources emitting from one or more stacks with a total emitting area of only several square feet. Another
characteristic these sources have in common is the nonapplicability, in most cases, of conventional control
methods, such as wet/dry equipment, fuel switching, process changes, etc. Instead, control of these emissions,
where possible at all, may include such techniques as modification of agricultural burning practices, paving with
asphalt or concrete, or stabilization of dirt roads. Finally, miscellaneous sources generally emit pollutants
intermittently, when compared with most stationary point sources. For example, a forest fire may emit large
quantities of particulates and carbon monoxide for several hours or even days, but when measured against the
emissions of a continuous emitter (such as a sulfuric acid plant) over a long period of time (1 year, for example), its
emissions may seem relatively minor. Effects on air quality may also be of relatively short-term duration.
11.1 FOREST WILDFIRES
11.1.1 General1
A forest "wildfire" is a large-scale natural combustion process that consumes various ages, sizes, and types of
botanical specimens growing outdoors in a defined geographical area. Consequently, wildfires are potential sources
of large amounts of air pollutants that should be considered when trying to relate emissions to air quality.
The size and intensity (or even the occurrence) of a wildfire is directly dependent on such variables as the local
meteorological conditions, the species of trees and their moisture content, and the weight of consumable fuel per
acre (fuel loading). Once a fire begins, the dry combustible material (usually small undergrowth and forest floor
litter) is consumed first, and if the energy release is large and of sufficient duration, the drying of green, live
material occurs with subsequent burning of this material as well as the larger dry material. Under proper
environmental and fuel conditions, this process may initiate a chain reaction that results in a widespread
conflagration.
The complete combustion of a forest fuel will require a heat flux (temperature gradient), an adequate oxygen
supply, and sufficient burning time. The size and quantity of forest fuels, the meteorological conditions, and the
topographic features interact to modify and change the burning behavior as the fire spreads; thus, the wildfire will
attain different degrees of combustion during its lifetime.
The importance of both fuel type and fuel loading on the fire process cannot be overemphasized. To meet the
pressing need for this kind of information, the U.S. Forest Service is developing a country-wide fuel identification
system (model) that will provide estimates of fuel loading by tree-size class, in tons per acre. Further, the
environmental parameters of wind, slope, and expected moisture changes have been superimposed on this fuel
model and incorporated into a National Fire Danger Rating System (NFDR). This system considers five classes of
fuel (three dead and two living), the components of which are selected on the basis of combustibility, response to
moisture (for the dead fuels), and whether the living fuels are herbaceous (plants) or ligneous (trees).
Most fuel loading figures are based on values for "available fuel" (combustible material that will be consumed in
a wildfire under specific weather conditions). Available fuel values must not be confused with corresponding values
for either "total fuel" (all the combustible material that would burn under the most severe weather and burning
11.1-1
-------
conditions) or "potential fuel" (the larger woody material that remains even after an extremely high intensity
wildfire). It must be emphasized, however, that the various methods of fuel identification are of value only when
they are related to the existing fuel quantity, the quantity consumed by the fire, and the geographic area and
conditions under which the fire occurs.
For the sake of conformity (and convenience), estimated fuel loadings were obtained for the vegetation in the
National Forest Regions and the wildlife areas established by the U.S. Forest Service, and are presented in Table
11.1-1. Figure 11.1-1 illustrates these areas and regions.
Table 11.1-1. SUMMARY OF ESTIMATED FUEL
CONSUMED BY FOREST FIRES3
Area and
Region'3
Rocky Mountain group
Region 1 :
Region 2:
Region 3:
Region 4:
Northern
Rocky Mountain
Southwestern
Intermountain
Pacific group
Region 5:
Region 6:
Region 10:
California
Pacific Northwest
Alaska
Coastal
Interior
Southern group
Region 8:
Southern
Eastern group
North Central group
Region 9:
Conifers
Hardwoods
Estimated average fuel loading
MT/hectare
83
135
67
22
40
43
40
135
36
135
25
20
20
25
25
22
27
ton/acre
37
60
30
10
8
19
18
60
16
60
11
9
9
11
11
10
12
a
Reference 1.
See Figure 11.1-1 for regional boundaries.
11.1.2 Emissions and Controlsl
It has been hypothesized (but not proven) that the nature and amounts of air pollutant emissions are directly
related to the intensity and direction (relative to the wind) of the wildfire, and indirectly related to the rate at
which the fire spreads. The factors that affect the rate of spread are (1) weather (wind velocity, ambient
temperature, and relative humidity), (2) fuels (fuel type, fuel bed array, moisture content, and fuel size), and (3)
topography (slope and profile). However, logistical problems (such as size of the burning area) and difficulties in
safely situating personnel and equipment close to the fire have prevented the collection of any reliable
experimental emission data on actual wildfires, so that it is presently impossible to verify or disprove the
above-stated hypothesis. Therefore, until such measurements are made, the only available information is that
11.1-2
EMISSION FACTORS
1/75
-------
• HEADQUARTERS
REGIONAL BOUNDARIES
Figure 11.1-1. Forest areas and U.S. Forest Service Regions.
obtained from burning experiments in the laboratory. These data, in the forms of both emissions and emission
factors, are contained in Table 11.1-2. It must be emphasized that the factors presented here are adequate for
laboratory-scale emissions estimates, but that substantial errors may result if they are used to calculate actual
wildfire emissions.
The emissions and emission factors displayed in Table 11.1-2 are calculated using the following formulas:
p. = P.I
ri riL
EJ = FjA^PjLA
where: Fj = Emission factor (mass of pollutant/unit area of forest consumed)
PJ = Yield for pollutant "i" (mass of pollutant/unit mass of forest fuel consumed)
= 8.5 kg/MT (17 Ib/ton) for total particulate
= 70 kg/MT (140 Ib/ton) for carbon monoxide
= 12 kg/MT (24 Ib/ton) for total hydrocarbon (as CH4)
1/75
Internal Combustion Engine Sources
(1)
(2)
11.1-3
-------
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EMISSION FACTORS
1/7
-------
= 2 kg/MT (4 Ib/ton) for nitrogen oxides (NOX)
= Negligible for sulfur oxides (SOX)
L = Fuel loading consumed (mass of forest fuel/unit land area burned)
A = Land area burned
EJ = Total emissions of pollutant "i" (mass of pollutant)
For example, suppose that it is necessary to estimate the total particulate emissions from a 10,000 hectare
wildfire in the Southern area (Region 8). From Table 11.1-1 it is seen that the average fuel loading is 20
MT/hectare (9 ton/acre). Further, the pollutant yield for particulates is 8.5 kg/MT (17 Ib/ton). Therefore, the
emissions are:
E = (8.5 kg/MT of fuel) (20 MT of fuel/hectare) (10,000 hectares)
E = 1,700,000 kg = 1,700MT
The most effective method for controlling wildfire emissions is, of course, to prevent the occurrence of forest
fires using various means at the forester's disposal. A frequently used technique for reducing wildfire occurrence is
"prescribed" or "hazard reduction" burning. This type of managed burn involves combustion of litter and
underbrush in order to prevent fuel buildup on the forest floor and thus reduce the danger of a wildfire. Although
some air pollution is generated by this preventative burning, the net amount is believed to be a relatively smaller
quantity than that produced under a wildfire situation.
Reference for Section 11.1
1. Development of Emission Factors for Estimating Atmospheric Emissions from Forest Fires. Final Report. IIT
Research Institute, Chicago, 111. Prepared for Office of Air Quality Planning and Standards, Environmental
Protection Agency, Research Triangle Park, N.C., under Contract No. 68-02-0641, October 1973. (Publication
No. EPA-450/3-73-009).
1/75 Internal Combustion Engine Sources 11.1-5
-------
11.2 FUGITIVE DUST SOURCES
Significant atmospheric dust arises from the mechanical disturbance of
granular material exposed to the air. Dust generated from these open
sources is termed "fugitive" because it is not discharged to the atmosphere
in a confined flow stream. Common sources of fugitive dust include unpaved
roads, agricultural tilling operations, aggregate storage piles, and heavy
construction operations.
For the above categories of fugitive dust sources, the dust generation
process is caused by two basic physical phenomena:
1. Pulverization and abrasion of surface materials by application of
mechanical force through implements (wheels, blades, etc.).
2. Entrainment of dust particles by the action of turbulent air cur-
rents, such as wind erosion of an exposed surface by wind speeds over 19
kilometers per hour (12 miles/hr).
The air pollution impact of a fugitive dust source depends on the
quantity and drift potential of the dust particles injected into the atmo-
sphere. In addition to large dust particles that settle out near the
source (often creating a local nuisance problem), considerable amounts of
fine particles are also emitted and dispersed over much greater distances
from the source.
The potential drift distance of particles is governed by the initial
injection height of the particle, the particle's terminal settling veloc-
ity, and the degree of atmospheric turbulence. Theoretical drift dis-
tances, as a function of particle diameter and mean wind speed, have been
computed for fugitive dust emissions.1 These results indicate that, for a
typical mean wind speed of 16 kilometers per hour (10 miles/hr), particles
larger than about 100 micrometers are likely to settle out within 6 to 9
meters (20 to 30 ft) from the edge of the road. Particles that are 30 to
100 micrometers in diameter are likely to undergo impeded settling. These
particles, depending upon the extent of atmospheric turbulence, are likely
to settle within a few hundred feet from the road. Smaller particles, par-
ticularly those less than 10 to 15 micrometers in diameter, have much
slower gravitational settling velocities and are much more likely to have
their settling rate retarded by atmospheric turbulence. Thus, based on the
presently available data, it appears appropriate to report only those par-
ticles smaller than 30 micrometers. Future updates to this document are
expected to define appropriate factors for other particle sizes.
Several of the emission factors presented in this Section are ex-
pressed in terms of total suspended particulate (TSP). TSP denotes what
is measured by a standard high volume sampler. Recent wind tunnel studies
have shown that the particle mass capture efficiency curve for the high
volume sampler is very broad, extending from 100 percent capture of parti-
cles smaller than 10 micrometers to a few percent capture of particles as
large as 100 micrometers. Also, the capture efficiency curve varies with
5/83 Miscellaneous Sources 11.2-1
-------
wind speed and wind direction, relative to roof ridge orientation. Thus,
high volume samplers do not provide definitive particle size information
for emission factors. However, an effective cutpoint of 30 micrometers
aerodynamic diameter is frequently assigned to the standard high volume
sampler.
Control techniques for fugitive dust sources generally involve water-
ing, chemical stabilization, or reduction of surface wind speed with wind-
breaks or source enclosures. Watering, the most common and generally least
expensive method, provides only temporary dust control. The use of chemi-
cals to treat exposed surfaces provides longer dust suppression but may be
costly, have adverse effects on plant and animal life, or contaminate the
treated material. Windbreaks and source enclosures are often impractical
because of the size of fugitive dust sources.
11.2-2 EMISSION FACTORS
4
-------
11.2.1 UNPAVED ROADS
11.2.1.1 General
Dust plumes trailing behind vehicles traveling on unpaved roads are a
familiar sight in rural areas of the United States. When a vehicle travels an
unpaved road, the force of the wheels on the road surface causes pulverization
of surface material. Particles are lifted and dropped from the rolling wheels,
and the road surface is exposed to strong air currents in turbulent shear with
the surface. The turbulent wake behind the vehicle continues to act on the
road surface after the vehicle has passed.
11.2.1.2 Emissions And Correction Parameters
The quantity of dust emissions from a given segment of unpaved road varies
linearly with the volume of traffic. Also, field investigations have shown
that emissions depend on correction parameters (average vehicle speed, average
vehicle weight, average number of wheels per vehicle, road surface texture and
road surface moisture) that characterize the condition of a particular road and
the associated vehicle traffic.!"^
Dust emissions from unpaved roads have been found to vary in direct
proportion to the fraction of silt (particles smaller than 75 micrometers in
diameter) in the road surface materials.1 The silt fraction is determined by
measuring the proportion of loose dry surface dust that passes a 200 mesh
screen, using the ASTM-C-136 method. Table 11.2.1-1 summarizes measured silt
values for industrial and rural unpaved roads.
The silt content of a rural dirt road will vary with location, and it
should be measured. As a conservative approximation, the silt content of the
parent soil in the area can be used. However, tests show that road silt con-
tent is normally lower than in the surrounding parent soil, because the fines
are continually removed by the vehicle traffic, leaving a higher percentage
of coarse particles.
Unpaved roads have a hard nonporous surface that usually dries quickly
after a rainfall. The temporary reduction in emissions because of precipita-
tion may be accounted for by not considering emissions on "wet" days (more than
0.254 millimeters [0.01 inches] of precipitation).
The following empirical expression may be used to estimate the quantity of
size specific particulate emissions from an unpaved road, per vehicle kilometer
traveled (VKT) or vehicle mile traveled (VMT), with a rAtins o£ A:
9/85 Miscellaneous Sources 11.2.1-1
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EMISSION FACTORS
9/85
-------
where: E = emission factor
k = particle size multiplier (dimensionless)
s = silt content of road surface material (%)
S = mean vehicle speed, km/hr (mph)
W = mean vehicle weight, Mg (ton)
w = mean number of wheels
p = number of days with at least 0.254 mm
(0.01 in.) of precipitation per year
The particle size multiplier, k, in Equation 1 varies with aerodynamic particle
size range as follows:
Aerodynamic Particle Size Multiplier For Equation 1
<30 ym
0.80
<15 ym
0.50
<10 ym
0.36
<5 ym
0.20
<2.5 ym
0.095
The number of wet days per year, p, for the geographical area of interest
should be determined from local climatic data. Figure 11.2.1-1 gives the geo-
graphical distribution of the mean annual number of wet days per year in the
United States.
Equation 1 retains the assigned quality rating if applied within the ranges
of source conditions that were tested in developing the equation, as follows:
RANGES OF SOURCE CONDITIONS FOR EQUATION 1
Equation
1
Road silt
content
(%, w/w)
4.3 - 20
Mean vehicle weight
Mg
2.7 - 142
ton
3 - 157
Mean vehicle speed
km/hr
21 - 64
mph
13 - 40
Mean no.
of wheels
4-13
Also, to retain the quality rating of the equation applied to a specific unpaved
road, it is necessary that reliable correction parameter values for the specific
road in question be determined. The field and laboratory procedures for deter-
mining road surface silt content are given in Reference 4. In the event that
site specific values for correction parameters cannot be obtained, the appro-
priate mean values from Table 11.2.1-1 may be used, but the quality rating of
the equation is reduced to B.
Equation 1 was developed for calculation of annual average emissions, and
thus, is to be multiplied by annual vehicle distance traveled (VDT). Annual
average values for each of the correction parameters are to be substituted into
9/85
Miscellaneous Sources
11.2.1-3
-------
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EMISSION FACTORS
9/85
-------
the equation. Worst case emissions, corresponding to dry road conditions,
may be calculated by setting p = 0 in the equation (which is equivalent to
dropping the last term from the equation). A separate set of nonclimatic
correction parameters and a higher than normal VDT value may also be justified
for the worst case averaging period (usually 24 hours). Similarly, to calc-
ulate emissions for a 91 day season of the year using Equation 1, replace the
term (365-p)/365 with the term (91-p)/91, and set p equal to the number of wet
days in the 91 day period. Also, use appropriate seasonal values for the
nonclimatic correction parameters and for VDT.
11.2.1.3 Control Methods
Common control techniques for unpaved roads are paving, surface treating
with penetration chemicals, working into the roadbed of chemical stabiliza-
tion chemicals, watering, and traffic control regulations. Chemical stabilizers
work either by binding the surface material or by enhancing moisture retention.
Paving, as a control technique, is often not economically practical. Surface
chemical treatment and watering can be accomplished with moderate to low costs,
but frequent retreatments are required. Traffic controls, such as speed limits
and traffic volume restrictions, provide moderate emission reductions but may
be difficult to enforce. The control efficiency obtained by speed reduction
can be calculated using the predictive emission factor equation given above.
The control efficiencies achievable by paving can be estimated by com-
paring emission factors for unpaved and paved road conditions, relative to
airborne particle size range of interest. The predictive emission factor
equation for paved roads, given in Section 11.2.6, requires estimation of the
silt loading on the traveled portion of the paved surface, which in turn depends
on whether the pavement is periodically cleaned. Unless curbing is to be
installed, the effects of vehicle excursion onto shoulders (berms) also must be
taken into account in estimating control efficiency.
The control efficiencies afforded by the periodic use of road stabili-
zation chemicals are much more difficult to estimate. The application para-
meters which determine control efficiency include dilution ratio, application
intensity (mass of diluted chemical per road area) and application frequency.
Between applications, the control efficiency is usually found to decay at a
rate which is proportional to the traffic count. Therefore, for a specific
chemical application program, the average efficiency is inversely proportional
to the average daily traffic count. Other factors that affect the performance
of chemical stabilizers include vehicle characteristics (e. g., average weight)
and road characteristics (e. g., bearing strength).
Water acts as a road dust suppressant by forming cohesive moisture films
among the discrete grains of road surface material. The average moisture level
in the road surface material depends on the moisture added by watering and
natural precipitation and on the moisture removed by evaporation. The natural
evaporative forces, which vary with geographic location, are enhanced by the
movement of traffic over the road surface. Watering, because of the frequency
of treatments required, is generally not feasible for public roads and is used
effectively only where water and watering equipment are available and where
roads are confined to a single site, such as a construction location.
9/85 Miscellaneous Sources 11.2.1-5
-------
References for Section 11.2.1
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. R. J. Dyck and J. J. Stukel, "Fugitive Dust Emissions from Trucks on
Unpaved Roads", Environmental Science and Technology, 10(10):1046-1048,
October 1976.
3. R. 0. McCaldin and K. J. Heidel, "Particulate Emissions from Vehicle
Travel over Unpaved Roads", Presented at the 71st Annual Meeting of the
Air Pollution Control Association, Houston, TX, June 1978.
4. C. Cowherd, Jr., et al., Iron and Steel Plant Open Dust Source Fugitive
Emission Evaluation, EPA-600/2-79-103, U. S. Environmental Protection
Agency, Research Triangle Park, NC, May 1979.
5. R. Bohn, et al., Fugitive Emissions from Integrated Iron and Steel Plants,
EPA-600/2-78-050, U. S. Environmental Protection Agency, Research Triangle
Park, NC, March 1978.
6. R. Bohn, Evaluation of Open Dust Sources in the Vicinity of Buffalo, New
York, U. S. Environmental Protection Agency, New York, NY, March 1979.
7. C. Cowherd, Jr., and T. Cuscino, Jr., Fugitive Emissions Evaluation,
Equitable Environmental Health, Inc., Elmhurst, IL, February 1977.
8. T. Cuscino, Jr., et al., Taconite Mining Fugitive Emissions Study,
Minnesota Pollution Control Agency, Roseville, MN, June 1979.
9. K. Axetell and C. Cowherd, Jr., Improved Emission Factors for Fugitive
Dust from Western Surface Coal Mining Sources, 2 Volumes, EPA Contract
No. 68-03-2924, PEDCo Environmental, Inc., Kansas City, MO, July 1981.
10. T. Cuscino, Jr., et al., Iron and Steel Plant Open Source Fugitive
Emission Control Evaluation, EPA-600/2-83-110, U. S. Environmental Pro-
tection Agency, Research Triangle Park, NC, October 1983.
11. J. Patrick Reider, Size Specific Emission Factors for Uncontrolled Indus-
trial and Rural Roads, EPA Contract No. 68-02-3158, Midwest Research
Institute, Kansas City, MO, September 1983.
12. C. Cowherd, Jr., and P. Englehart, Size Specific Particulate Emission
Factors for Industrial and Rural Roads, EPA-600/7-85-038, U. S. Environ-
mental Protection Agency, Research Triangle Park, NC, September 1985.
13. Climatic Atlas of the United States, U. S. Department of Commerce,
Washington, DC, June 1968.
11.2.1-6 EMISSION FACTORS 9/85
-------
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 eradi-
cation 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 that loosen the soil and cut off the
weeds but leave the surface trash in place have recently become more popu-
lar for tilling in dryland farming areas.
During a tilling operation, dust particles from the loosening and pul-
verization 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. Also, emissions depend on surface soil texture and
surface soil moisture content, conditions of a particular field being
tilled.
Dust emissions from agricultural tilling have been found to vary di-
rectly with the silt content (defined as particles < 75 micrometers in di-
ameter) of the surface soil depth (0 to 10 cm [0 to 4 in.]). 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 be-
lieved 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 (for exam-
ple, 8 to 10 km/hr [5 to 6 mph]).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)0'6 (kg/hectare) (1)
E = k(4.80)(s)°'6 (Ib/acre)
5/83 Miscellaneous Sources 11.2.2-1
-------
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 Mm
0.33
< 15 Mm
0.25
< 10 pro
0.21
< 5 Mm
0.15
< 2.5 Mm
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
-------
11.2.3 AGGREGATE HANDLING AND STORAGE PILES
11.2.3.1 General
Inherent in operations that use minerals in aggregate form is the
maintenance of outdoor storage piles. Storage piles are usually left un-
covered, partially because of the need for frequent material transfer into
or out of storage.
Dust emissions occur at several points in the storage cycle, during
material loading onto the pile, during disturbances by strong wind cur-
rents, and during loadout from the pile. The movement of trucks and load-
ing equipment in the storage pile area is also a substantial source of
dust.
11.2.3.2 Emissions and Correction Parameters
The quantity of dust emissions from aggregate storage operations var-
ies with the volume of aggregate passing through the storage cycle. Also,
emissions depend on three correction parameters that characterize the con-
dition of a particular storage pile: age of the pile, moisture content and
proportion of aggregate fines.
When freshly processed aggregate is loaded onto a storage pile, its
potential for dust emissions is at a maximum. Fines are easily disaggre-
gated and released to the atmosphere upon exposure to air currents from ag-
gregate transfer itself or high winds. As the aggregate weathers, how-
ever, potential for dust emissions is greatly reduced. Moisture causes ag-
gregation and cementation of fines to the surfaces of larger particles.
Any significant rainfall soaks the interior of the pile, and the drying
process is very slow.
Field investigations have shown that emissions from aggregate storage
operations vary in direct proportion to the percentage of silt (particles
< 75 |Jtn in diameter) in the aggregate material.1 3 The silt content is de-
termined by measuring the proportion of dry aggregate material that passes
through a 200 mesh screen, using ASTM-C-136 method. Table 11.2.3-1 summa-
rizes measured silt and moisture values for industrial aggregate materials.
11.2.3.3 Predictive Emission Factor Equations
Total dust emissions from aggregate storage piles are contributions of
several distinct source activities within the storage cycle:
1. Loading of aggregate onto storage piles (batch or continuous drop
operations).
2. Equipment traffic in storage area.
3. Wind erosion of pile surfaces and ground areas around piles.
4. Loadout of aggregate for shipment or for return to the process
stream (batch or continuous drop operations).
5/33 Miscellaneous Sources 11.2.3-1
-------
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11.2.3-2
EMISSION FACTORS
5/83
-------
Adding aggregate material to a storage pile or removing it usually in-
volves dropping the material onto a receiving surface. Truck dumping on
the pile or loading out from the pile to a truck with a front end loader
are examples of batch drop operations. Adding material to the pile by a
conveyor stacker is an example of a continuous drop operation.
The quantity of particulate emissions generated by a batch drop opera-
tion, per ton of material transferred, may be estimated, with a rating of
C, using the following empirical expression2:
E = k(0.00090)
E = k(0.0018)
(I)
(I)
(Hf)
0.33
(kg/Mg)
(1)
0.33
(Ib/ton)
whe re:
E = emission factor
k = particle size multipler (dimensionless)
s = material silt content (%)
U = mean wind speed, m/s (mph)
H = drop height, m (ft)
M = material moisture content (%)
Y = dumping device capacity, m3 (yd3)
The particle size multipler (k) for Equation 1 varies with aerodynamic par-
ticle size, shown in Table 11.2.3-2.
TABLE 11.2.3-2.
AERODYNAMIC PARTICLE SIZE
MULTIPLIER (k) FOR
EQUATIONS 1 AND 2
Equation < 30 < 15 < 10 < 5 < 2.5
(Jm |Jm |Jm (Jtn |Jm
Batch drop 0.73 0.48 0.36 0.23 0.13
Continuous
drop
0.77 0.49 0.37 0.21 0.11
The quantity of particulate emissions generated by a continuous drop
operation, per ton of material transferred, may be estimated, with a rating
of C, using the following empirical expression3:
5/83
Miscellaneous Sources
11.2.3-3
-------
E = k(0.00090)
E = k(0.0018)
/s\ /JL\ /JL\
V57 \2.27 \3.07
(I)2
(!) (!) (if)
(kg/Mg)
(2)
(Ib/ton)
where: E = emission factor
k = particle size multiplier (dimensionless)
s = material silt content (%)
U = mean wind speed, m/s (mph)
H = drop height, m (ft)
M = material moisture content (%)
The particle size multiplier (k) for Equation 2 varies with aerodynamic
particle size, as shown in Table 11.2.3-2.
Equations 1 and 2 retain the assigned quality rating if applied within
the ranges of source conditions that were tested in developing the equa-
tions, as given in Table 11.2.3-3. Also, to retain the quality ratings of
Equations 1 or 2 applied to a specific facility, it is necessary that reli-
able correction parameters be determined for the specific sources of inter-
est. The field and laboratory procedures for aggregate sampling are given
in Reference 3. In the event that site specific values for correction pa-
rameters cannot be obtained, the appropriate mean values from Table
11.2.3-1 may be used, but in that case, the quality ratings of the equa-
tions are reduced by one level.
TABLE 11.2.3-3.
RANGES OF SOURCE CONDITIONS FOR
EQUATIONS 1 AND 2a
Silt Moisture
Equation content content
(%) (%)
Dumping capacity
yda
Drop height
m ft
Batch drop
1.3 - 7.3 0.25 - 0.70 2.10 - 7.6 2.75 - 10
NA
NA
Continuous
drop
1.4-19 0.64-4.8 NA
NA 1.5 - 12 4.8 - 39
NA = not applicable.
For emissions from equipment traffic (trucks, front end loaders, doz-
ers, etc.) traveling between or on piles, it is recommended that the equa-
tions for vehicle traffic on unpaved surfaces be used (see Section 11.2.1).
For vehicle travel between storage piles, the silt value(s) for the areas
11.2.3-4
EMISSION FACTORS
5/83
-------
among the piles (which may differ from the silt values for the stored mate-
rials) should be used.
For emissions from wind erosion of active storage piles, the following
total suspended particulate (TSP) emission factor equation is recommended:
E = 1'9 (iTs) Pi?) (if) (kg/ day/hectare) (3)
(if) <">/day/acre)
E = J'7
where: E = total suspended particulate emission factor
s = silt content of aggregate (%)
p = number of days with § 0.25 mm (0.01 in.) of precipitation
per year
f = percentage of time that the unobstructed wind speed ex-
ceeds 5.4 m/s (12 mph) at the mean pile height
The coefficient in Equation 3 is taken from Reference 1, based on sam-
pling of emissions from a sand and gravel storage pile area during periods
when transfer and maintenance equipment was not operating. The factor from
Test Report 1, expressed in mass per unit area per day, is more reliable
than the factor expressed in mass per unit mass of material placed in stor-
age, for reasons stated in that report. Note that the coefficient has been
halved to adjust for the estimate that the wind speed through the emission
layer at the test site was one half of the value measured above the top of
the piles. The other terms in this equation were added to correct for
silt, precipitation and frequency of high winds, as discussed in Refer-
ence 2. Equation 3 is rated C for application in the sand and gravel in-
dustry and D for other industries.
Worst case emissions from storage pile areas occur under dry windy
conditions. Worst case emissions from materials handling (batch and con-
tinuous drop) operations may be calculated by substituting into Equations 1
and 2 appropriate values for aggregate material moisture content and for
anticipated wind speeds during the worst case averaging period, usually
24 hours. The treatment of dry conditions for vehicle traffic (Section
11.2.1) and for wind erosion (Equation 3), centering around parameter p,
follows the methodology described in Section 11.2.1. Also, a separate set
of nonclimatic correction parameters and source extent values corresponding
to higher than normal storage pile activity may be justified for the worst
case averaging period.
11.2.3.4 Control Methods
Watering and chemical wetting agents are the principal means for con-
trol of aggregate storage pile emissions. Enclosure or covering of in-
active piles to reduce wind erosion can also reduce emissions. Watering is
useful mainly to reduce emissions from vehicle traffic in the storage pile
area. Watering of the storage piles themselves typically has only a very
temporary slight effect on total emissions. A much more effective tech-
nique is to apply chemical wetting agents for better wetting of fines and
5/83 Miscellaneous Sources 11.2.3-5
-------
longer retention of the moisture film. Continuous chemical treatment of
material loaded onto piles, coupled with watering or treatment of roadways,
can reduce total particulate emissions from aggregate storage operations by
up to 90 percent.
References for Section 11.2.3
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. R. Bohn, et al. , Fugitive Emissions from Integrated Iron and Steel
Plants, EPA-600/2-78-050, U. S. Environmental Protection Agency,
Research Triangle Park, NC, March 1978.
3. C. Cowherd, Jr., et al., Iron and Steel Plant Open Dust Source Fugi-
tive Emission Evaluation, EPA-600/2-79-103, U. S. Environmental Pro-
tection Agency, Research Triangle Park, NC, May 1979.
4. R. Bohn, Evaluation of Open Dust Sources in the Vicinity of Buffalo,
New York, U. S. Environmental Protection Agency, New York, NY, March
1979.
5. C. Cowherd, Jr., and T. Cuscino, Jr., Fugitive Emissions Evaluation,
Equitable Environmental Health, Inc., Elmhurst, IL, February 1977.
6. T. Cuscino, et al., Taconite Mining Fugitive Emissions Study,
Minnesota Pollution Control Agency, Roseville, MN, June 1979.
7. K. Axetell and C. Cowherd, Jr., Improved Emission Factors for Fugitive
Dust from Western Surface Coal Mining Sources, 2 Volumes, EPA Contract
No. 68-03-2924, PEDCo Environmental, Inc., Kansas City, MO, July 1981.
8. 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.
11.2.3-6 EMISSION FACTORS 5/83
-------
11.2.4 Heavy Construction Operations
11.2.4.1 General — Heavy construction is a source of dust emissions that may have substantial temporary impact
on local air quality. Building and road construction are the prevalent construction categories with the highest
emissions potential. Emissions during the construction of a building or road are associated with land clearing,
blasting, ground excavation, cut and fill operations, and the construction of the particular facility itself. Dust
emissions vary substantially from day to day depending on the level of activity, the specific operations, and the
prevailing weather. A large portion of the emissions result from equipment traffic over temporary roads at the
construction site.
11.2.4.2 Emissions and Correction Parameters — The quantity of dust emissions from construction operations
are proportional to the area of land being worked and the level of construction activity. Also, by analogy to the
parameter dependence observed for other similar fugitive dust sources,1 it is probable that emissions from heavy
construction operations are directly proportional to the silt content of the soil (that is, particles smaller than 75
jum in diameter) and inversely proportional to the square of the soil moisture, as represented by Thornthwaite's
precipitation-evaporation (PE) index.2
11.2.4.3 Emission Factor — Based on field measurements of suspended dust emissions from apartment and
shopping center construction projects, an approximate emission factor for construction operations is:
1.2 tons per acre of construction per month of activity
This value applies to construction operations with: (1) medium activity level, (2) moderate silt content ('vSO
percent), and (3) semiarid climate (PE V>0; see Figure 11.2-2). Test data are not sufficient to derive the specific
dependence of dust emissions on correction parameters.
The above emission factor applies to particles less than about 30 urn in diameter, which is the effective cut-off
size for the capture of construction dust by a standard high-volume filtration sampler1, based on a particle
density of 2.0-2.5 g/cm3 .
11.2.4.4 Control Methods — Watering is most often selected as a control method because water and necessary
equipment are usually available at construction sites. The effectiveness of watering for control depends greatly on
the frequency of application. An effective watering program (that is, twice daily watering with complete
coverage) is estimated to reduce dust emissions by up to 50 percent.3 Chemical stabilization is not effective in
reducing the large portion of construction emissions caused by equipment traffic or active excavation and cut and
fill operations. Chemical stabilizers are useful primarily for application on completed cuts and fills at the
construction site. Wind erosion emissions from inactive portions of the construction site can be reduced by about
80 percent in this manner, but this represents a fairly minor reduction in total emissions compared with emissions
occurring during a period of high activity.
References for Section 11.2.4
1. Cowherd, C., Jr., K. Axetell, Jr., C. M. Guenther, and G. A. Jutze. Development of Emissions Factors for
Fugitive Dust Sources. Midwest Research Institute, Kansas City, Mo. Prepared for Environmental Protection
Agency, Research Triangle Park, N.C. under Contract No. 68-02-0619. Publication No. EPA-450/3-74-037.
June 1974.
2. Thornthwaite, C. W. Climates of North America According to a New Classification. Geograph. Rev. 21'
633-655,1931.
3. Jutze, G. A., K. Axetell, Jr., and W. Parker. Investigation of Fugitive Dust-Sources Emissions and Control,
PEDCo Environmental Specialists, Inc., Cincinnati, Ohio. Prepared for Environmental Protection Agency,
Research Triangle Park, N.C. under Contract No. 68-02-0044. Publication No. EPA-450/3-74-036a. June 1974.
12/75 Miscellaneous Sources 11.2.4-1
-------
11.2.5 PAVED URBAN ROADS
11.2.5.1 General
Various field studies have indicated that dust emissions from paved street
are a major component of the material collected by high volume samplers. Reen-
trained traffic dust has been found to consist primarily of mineral matter
similar to common sand and soil, mostly tracked or deposited onto the roadway
by vehicle traffic itself. Other particulate matter is emitted directly by the
vehicles from, for example, engine exhaust, wear of bearings and brake linings,
and abrasion of tires against the road surface. Some of these direct emissions
may settle to the street surface, subsequently to be reentrained. Appreciable
emissions from paved streets are added by wind erosion when the wind velocity
exceeds a threshold value of about 20 kilometers per hour (13 miles per hour).
Figure 11.2.5-1 illustrates particulate transfer processes occurring on urban
streets.
11.2.5.2 Emission Factors And Correction Parameters
Dust emission rates may vary according to a number of factors. The most
important are thought to be traffic volume and the quantity and particle size
of loose surface material on the street. On a normal paved street, an equili-
brium is reached whereby the accumulated street deposits are maintained at a
relatively constant level. On average, vehicle carryout from unpaved areas
may be the largest single source of street deposit. Accidental spills, street
cleaning and rainfall are activities that disrupt the street loading equili-
brium, usually for a relatively short duration.
The lead content of fuels also becomes a part of reentrained dust from
vehicle traffic. Studies have found that, for the 1975-76 sampling period,
the lead emission factor for this source was approximately 0.03 grams per
vehicle mile traveled (VMT) . With the reduction of lead in gasoline and the
use of catalyst equipped vehicles, the lead factor for reentrained dust was
expected to drop below 0.01 grams per mile by I960.3
The quantity of dust emissions of vehicle traffic on a paved roadway may
be estimated using the following empirical expression4 :
e = k i P (g/VKT)
e = k = (Ib/VMT)
where: e = particulate emission factor, g/VKT (Ib/VMT)
L = total road surface dust loading, g/m2 (grains/ft2 )
s = surface silt content, fraction of particles
_< 75 ym diameter (American Association of
State Highway Officials)
k = base emission factor, g/VKT (Ib/VMT)
p = exponent (dimensionless)
9/85 Miscellaneous Sources 11.2.5-1
-------
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2 s
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11.2.5-2
EMISSION FACTORS
9/85
-------
The total loading (excluding litter) is measured by sweeping and vacuuming
lateral strips of known area from each active travel lane. The silt fraction
is determined by measuring the proportion of loose dry road dust that passes a
200 mesh screen, using the ASTM-C-136 method. Silt loading is the product of
total loading and silt content.
The base emission factor coefficients, k, and exponents, p, in the equation
for each size fraction are listed in Table 11.2.5-1. Total suspended particulate
(TSP) denotes that particle size fraction of airborne particulate matter that
would be collected by a standard high volume sampler.
TABLE 11.2.5-1. PAVED URBAN ROAD EMISSION FACTOR EQUATION PARAMETERS3
Particle Size Fraction**
TSP
_< 15 um
£ 10 pm
< 2.5 ym
k
g/VKT (Ib/VMT)
5.87 (0.0208)
2.54 (0.0090)
2.28 (0.0081)
1.02 (0.0036)
P
0.9
0.8
0.8
0.6
Reference 4. See page 11.2.5-1 for equation. TSP
particulate.
Aerodynamic diameter.
total suspended
Microscopic analysis indicates the origin of material collected on high
volume filters to be about 40 weight percent combustion products and 59 per-
cent mineral matter, with traces of biological matter and rubber tire particles.
The small particulate is mainly combustion products, while most of the large
material is of mineral origin.
11.2.5.3 Emissions Inventory Applications^
For most emissions inventory applications involving urban paved roads,
actual measurements of silt loading will probably not be made. Therefore, to
facilitate the use of the previously described equation, it is necessary to
characterize silt loadings according to parameters readily available to per-
sons developing the inventories. It is convenient to characterize variations
in silt loading with a roadway classification system, and this is presented
in Table 11.2.5-2. This system generally corresponds to the classification
systems used by transportation agencies, and thus the data necessary for an
emissions inventory - number of road kilometers per road category and traffic
counts - should be easy to obtain. In some situations, it may be necessary to
combine this silt loading information with sound engineering judgment in order
to approximate the loadings for roadway types not specifically included in
Table 11.2.5-2.
9/85
Miscellaneous Sources
11.2.5-3
-------
TABLE 11.2.5-2. PAVED URBAN ROADWAY CLASSIFICATION3
Roadway Category
Freeways/expressways
Major streets/highways
Collector streets
Local streets
Average Dally Traffic
(Vehicles)
> 50,000
> 10,000
500 - 10,000
< 500
Lanes
>_ 4
> 4
aReference 4.
kRoad width >_ 32 ft.
cRoad width < 32 ft.
A data base of 44 samples analyzed according to consistent procedures may
be used to characterize the silt loadings for each roadway category.4 These
samples, obtained during recent field sampling programs, represent a broad range
of urban land use and roadway conditions. Geometric means for this data set are
given by sampling location and roadway category in Table 11.2.5-3.
TABLE 11.2.5-3. SUMMARY OF SILT LOADINGS (sL) FOR PAVED URBAN ROADWAYS3
Roadway Category
Local Collector Major Streets/
Streets Streets Highways
City
Baltimore
Buffalo
Granite City (IL)
Kansas City
St. Louis
All
Xg (g/m2) n Xg (g/m2) n Xg (g/m2)
1.42 2 0.72 4 0.39
1.41 5 0.29 2 0.24
- - - 0.82
2.11 4 0.41
- - - - 0.16
1.41 7 0.92 10 0.36
n
3
4
3
13
3
26
Freeways/
Expressways
Xg (g/m2) n
-
-
-
-
0.022 1
0.022 1
aReference 4. Xg = geometric mean based on corresponding n sample size.
Dash = not available. To convert g/m2to grains/ft2 multiply g/m2 by 1.4337.
11.2.5-4
EMISSION FACTORS
9/85
-------
These sampling locations can be considered representative of most large
urban areas in the United States, with the possible exception of those in the
Southwest. Except for the collector roadway category, the mean silt loadings
do not vary greatly from city to city, though the St. Louis mean for major
roads is somewhat lower than those of the other four cities. The substantial
variation within the collector roadway category is probably attributable to the
effects of land use around the specific sampling locations. It should also be
noted that an examination of data collected at three cities in Montana during
early spring indicates that winter road sanding may produce loadings five to
six times higher than the means of the loadings given in Table 11.2.5-3 for the
respective road categories.5
Table 11.2.5-4 presents the emission factors by roadway category and par-
ticle size. These were obtained by inserting the above mean silt loadings into
the equation on page 11.2.5-1. These emission factors can be used directly for
many emission inventory purposes. It is important to note that the paved road
emission factors for TSP agree quite well with those developed from previous
testing of roadway sites in the major street and highway category, yielding
mean TSP emission factors of 4.3 grams/VKT (Reference 6) and 2.6 grams/VKT
(Reference 7).
TABLE 11.2.5-4. RECOMMENDED PARTICULATE EMISSION FACTORS FOR SPECIFIC
ROADWAY CATEGORIES AND PARTICLE SIZE FRACTIONS
Emission Factor
Roadway
Category
TSP
g/VKT (Ib/VMT)
1 15 um
g/VKT (Ib/VMT)
< 10 urn
g/VKT (Ib/VMT)
< 2.5 ym
g/VKT (Ib/VMT)
Local streets 15 (0.053)
10 (0.035)
Collector
streets
Major streets/
highways 4.4 (0.016)
Freeways/
expressways 0.35 (0.0012)
5.8 (0.021) 5.2 (0.018) 1.9 (0.0067)
4.1 (0.015) 3.7 (0.013) 1.5 (0.0053)
2.0 (0.0071) 1.8 (0.0064) 0.84 (0.0030)
0.21 (0.00074) 0.19 (0.00067) 0.16 (0.00057)
References for Section 11.2.5
1. D. R. Dunbar, Resuspension of Particulate Matter, EPA-450/2-76-031, U. S.
Environmental Protection Agency, Research Triangle Park, NC, March 1976.
2. M. P. Abel, "The Impact of Refloatation on Chicago's Total Suspended
Particulate Levels", Purdue University, Purdue, IN, August 1974.
3. C. M. Maxwell and D. W. Nelson, A Lead Emission Factor for Reentrained
Dust from a Paved Roadway, EPA-450/3-78-021, U. S. Environmental Pro-
tection Agency, Research Triangle Park, NC, April 1978.
9/85
Miscelleanous Sources
11.2.5-5
-------
4. Chatten Cowherd, Jr. and Phillip J. Englehart, Paved Road Particulate
Emissions, EPA-600/7-84-077, U. S. Environmental Protection Agency, Wash-
ington, DC, July 1984.
5. R. Bohn, Update and Improvement of the Emission Inventory for MAPS Study
Areas, State of Montana, Helena, MT, August 1979.
6. C. Cowherd, Jr., et al., Quantification of Dust Entrainment from Paved
Roadways, EPA-450/3-77-027, U. S. Environmental Protection Agency,
Research Triangle Park, NC, July 1977.
7. K. Axetell and J. Zell, Control of Reentrained Dust from Paved Streets,
EPA-907/9-77-077, U. S. Environmental Protection Agency, Kansas City,
MO, August 1977.
11.2.5-6 EMISSION FACTORS 9/85
-------
11.2.6 INDUSTRIAL PAVED ROADS
11.2.6.1 General
Various field studies have indicated that dust emissions from industrial
paved roads are a major component of atmospheric particulate matter in the
vicinity of industrial operations. Industrial traffic dust has been found to
consist primarily of mineral matter, mostly tracked or deposited onto the
roadway by vehicle traffic itself when vehicles enter from an unpaved area or
travel on the shoulder of the road, or when material is spilled onto the paved
surface from haul truck traffic.
11.2.6.2 Emissions And Correction Parameters
The quantity of dust emissions from a given segment of paved road varies
linearly with the volume of traffic. In addition, field investigations have
shown that emissions depend on correction parameters (road surface silt content,
surface dust loading and average vehicle weight) of a particular road and
associated vehicle
Dust emissions from industrial paved roads have been found to vary in
direct proportion to the fraction of silt (particles ^75 ym in diameter) in
the road surface material. ^~2 The silt fraction is determined by measuring the
proportion of loose dry surface dust that passes a 200 mesh screen, using the
ASTM-C-136 method. In addition, it has also been found that emissions vary in
direct proportion to the surface dust loading. ^-"^ fhe road surface dust loading
is that loose material which can be collected by broom sweeping and vacuuming of
the traveled portion of the paved road. Table 11.2.6-1 summarizes measured silt
and loading values for industrial paved roads.
11.2.6.3 Predictive Emission Factor Equations
The quantity of total suspended particulate emissions generated by vehicle
traffic on dry industrial paved roads, per vehicle kilometer traveled (VKT) or
vehicle mile traveled (VMT) may be estimated, with a rating of B or D (see below),
using the following empirical expression^:
i?
where: E = emission factor
I = industrial augmentation factor (dimensionless) (see below)
n = number of traffic lanes
s = surface material silt content (%)
L * surface dust loading, kg/km (Ib/mile) (see below)
W = average vehicle weight, Mg (ton)
9/85 Miscellaneous Sources 11.2.6-1
-------
TABLE 11.2.6-1.
TYPICAL SILT CONTENT AND LOADING VALUES FOR PAVED ROADS
AT INDUSTRIAL FACILITIES3
No. of
Indu»try Plant Sites
Copper melting 1
Iron and steel
production 6
Asphalt batching 1
Concrete batching 1
Sand and gravel
processing 1
No. of
No. of Silt (X, H/V) Travel Total loading
Samples Range Mean Lanes Range
3 [15.4-21.7) 119.0) 2 112.9-19.5)
[45.8-69.2]
2 0.006-4.77
20 1.1-35.7 12.5 2 0.020-16.9
4 [2.6-4.6] [3.6] 1 [12.1-18.0J
(43.0-64.0]
3 [5.2-6.0] [5.5] 2 (1.4-1.8)
(5.0-6.4)
3 [6.4-7.9) (7.1J 1 [2.8-5.5)
(9. 9-19 .4]
Mean
(15-9]
155.4]
0.495
1.75
(15.7]
155.7)
(1.7)
15.9]
(3.8J
113-3]
Silt loading
(8/« >
Units b Range
kg/ka [188-400]
lb/Bl
kg/ka <1 .0-2 .3
Ib/al
kg/ka (76-193)
Ib/ml
kg/km [11-12]
lb/Bl
kg/ka [53-95]
Ib/ml
Mean
(292 J
7
1138]
(12)
[70]
"Reference* 1-5. Brackets Indicate values based on samples obtained at only one plant site.
bMultlply entries by 1,000 to obtain atated units.
The industrial road augmentation factor (I) in the Equation 1 takes into
account higher emissions from industrial roads than from urban roads. I » 7.0
for an industrial roadway which traffic enters from unpaved areas. I - 3.5 for
an industrial roadway with unpaved shoulders where 20 percent of the vehicles
are forced to travel temporarily with one set of wheels on the shoulder. I = 1.0
for cases in which traffic does not travel on unpaved areas. A value between 1.0
and 7.0 which best represents conditions for paved roads at a certain industrial
facility should be used for I in the equation.
The equation retains the quality rating of B if applied to vehicles
traveling entirely on paved surfaces (I » 1.0) and if applied within the range
of source conditions that were tested in developing the equation as follows:
Silt
content
1.0, the rating of the equation drops to D because of the subjectivity
in the guidelines for estimating I.
The quantity of fine particle emissions generated by traffic consisting
predominately of medium and heavy duty vehicles on dry Industrial paved roads,
per vehicle unit of travel, may be estimated, with a rating of A, using the
11.2.6-2
EMISSION FACTORS
9/85
-------
/sL\ 0.3
\12
,,! fea
E = k (5|) ' (kg/VKT) (2)
sL\ 0-3
(Ib/VMT)
where: E » emission factor
sL - road surface silt loading, g/m2 (oz/yd2)
The particle size multiplier (k) above varies with aerodynamic size range
as follows:
Aerodynamic Particle Size
Multiplier (k) For Equation 2
(Dimensionless)
ym <10 ym <2.5 ym
0.28 0.22 0.081
To determine particulate emissions for a specific particle size range, use the
appropriate value of k above.
The equation retains the quality rating of A, if applied within the range
of source conditions that were tested in developing the equation as follows:
silt loading, 2 - 240 g/m2 (0.06 - 7.1 oz/yd2)
mean vehicle weight, 6 - 42 Mg (7 - 46 tons)
The following single valued emission factors** may be used in lieu of
Equation 2 to estimate fine particle emissions generated by light duty vehicles
on dry, heavily loaded industrial roads, with a rating of C:
Emission Factors For Light Duty
Vehicles On Heavily Loaded Roads
ym ym
0.12 kg/VKT 0.093 kg/VKT
(0.41 Ib/VMT) (0.33 Ib/VMT)
These emission factors retain the assigned quality rating, if applied within
the range of source conditions that were tested in developing the factors, as
follows:
silt loading, 15 - 400 g/m2 (0.44 - 12 oz/yd2)
mean vehicle weight, <4 Mg (<4 tons)
Also, to retain the quality ratings of Equations 1 and 2 when applied to a
specific industrial paved road, it is necessary that reliable correction para-
meter values for the specific road in question be determined. The field and
9/85 Miscellaneous Sources 11.2.6-3
-------
laboratory procedures for determining surface material silt content and surface
dust loading are given in Reference 2. In the event that site specific values
for correction parameters cannot be obtained, the appropriate mean values from
Table 11.2.6-1 may be used, but the quality ratings of the equations should be
reduced by one level.
11.2.6.4 Control Methods
Common control techniques for industrial paved roads are broom sweeping,
vacuum sweeping and water flushing, used alone or in combination. All of
these techniques work by reducing the silt loading on the traveled portions of
the road. As indicated by a comparison of Equations 1 and 2, fine particle
emissions are less sensitive than total suspended particulate emissions to the
value of silt loading. Consistent with this, control techniques are generally
less effective for the finer particle sizes.^ The exception is water flushing,
which appears preferentially to remove (or agglomerate) fine particles from the
paved road surface. Broom sweeping is generally regarded as the least effec-
tive of the common control techniques, because the mechanical sweeping process
is inefficient in removing silt from the road surface.
To achieve control efficiencies on the order of 50 percent on a paved road
with moderate traffic ( 500 vehicles per day) requires cleaning of the surface
at least twice per week.^ This is because of the characteristically rapid
buildup of road surface material from spillage and the tracking and deposition
of material from adjacent unpaved surfaces, including the shoulders (berms) of
the paved road. Because industrial paved roads usually do not have curbs, it
is important that the width of the paved road surface be sufficient for vehicles
to pass without excursion onto unpaved shoulders. Equation 1 indicates that
elimination of vehicle travel on unpaved or untreated shoulders would effect a
major reduction in particulate emissions. An even greater effect, by a factor
of 7, would result from preventing travel from unpaved roads or parking lots
onto the paved road of interest.
References for Section 11.2.6
1. R. Bonn, et al., Fugitive Emissions from Integrated Iron and Steel Plants,
EPA-600/2-78-050, U. S. Environmental Protection Agency, Research Triangle
Park, NC, March 1978.
2. C. Cowherd, Jr., et al., Iron and Steel Plant Open Dust Source Fugitive
Emission Evaluation, EPA-600/2-79-103, U. S. Environmental Protection
Agency, Research Triangle Park, NC, May 1979.
3. R. Bonn, Evaluation of Open Dust Sources in the Vicinity of Buffalo,
New York, U. S. Environmental Protection Agency, New York, NY, March 1979.
4. T. Cuscino, Jr., et al., Iron and Steel Plant Open Source Fugitive Emis-
sion Control Evaluation, EPA-600/2-83-110, U. S. Environmental Protection
Agency, Research Triangle Park, NC, October 1983.
5. J. Patrick Reider, Size Specific Particulate Emission Factors for Uncon-
trolled Industrial and Rural Roads, EPA Contract No. 68-02-3158, Midwest
Research Institute, Kansas City, MO, September 1983.
11.2.6-4 EMISSION FACTORS 9/85
-------
6. C. Cowherd, Jr. and P. Englehart, Size Specific Particulate Emission
Factors For Industrial And Rural Roads, EPA-600/7-85-051, U. S. Environ-
mental Protection Agency, Washington, DC, September 1985.
9/85 Miscellaneous Sources 11.2.6-5
-------
11.3 EXPLOSIVES DETONATION
11.3.1 General 1~5
This section deals mainly with pollutants resulting from the
detonation of industrial explosives and firing of small arms. Military
applications are excluded from this discussion. Emissions associated
with the manufacture of explosives are treated in Section 5.6,
Explosives.
An explosive is a chemical material that is capable of extremely
rapid combustion resulting in an explosion or detonation. Since an
adequate supply of oxygen cannot be drawn from the air, a source of
oxygen must be incorporated into the explosive mixture. Some explo-
sives, such as trinitrotoluene (TNT), are single chemical species, but
most explosives are mixtures of several ingredients. "Low explosive"
and "high explosive" classifications are based on the velocity of
explosion, which is directly related to the type of work the explosive
can perform. There appears to be no direct relationship between the
velocity of explosions and the end products of explosive reactions.
These end products are determined primarily by the oxygen balance of the
explosive. As in other combustion reactions, a deficiency of oxygen
favors the formation of carbon monoxide and unburned organic compounds
and produces little, if any, nitrogen oxides. An excess of oxygen
causes more nitrogen oxides and less carbon monoxide and other unburned
organics. For ammonium nitrate and fuel oil mixtures (ANFO), a fuel oil
content of more than 5.5 percent creates a deficiency of oxygen.
There are hundreds of different explosives, with no universally
accepted system for classifying them. The classification used in Table
11.3-1 is based on the chemical composition of the explosives, without
regard to other to other properties, such as rate of detonation, which
relate to the applications of explosives but not to their specific end
products. Most explosives are used in two-, three-, or four-step trains
that are shown schematically in Figure 11.3-1. The simple removal of a
tree stump might be done with a two-step train made up of an electric
blasting cap and a stick of dynamite. The detonation wave from the
blasting cap would cause detonation of the dynamite. To make a large
hole in the earth, an inexpensive explosive such as ammonium nitrate and
fuel oil (ANFO) might be used. In this case, the detonation wave from
the blasting cap is not powerful enough to cause detonation, so a
booster must be used in a three- or four-step train. Emissions from the
blasting caps and safety fuses used in these trains are usually small
compared to those from the main charge, because the emissions are
roughly proportional to the weight of explosive used, and the main
charge makes up most of the total weight. No factors are given for
computing emissions from blasting caps or fuses, because these have not
been measured, and because the uncertainties are so great in estimating
emissions from the main and booster charges that a precise estimate of
all emissions is not practical.
2/80 Miscellaneous Sources 11.3-1
-------
2. DYNAMITE
1 ELECTRIC
BLASTING CAP
PRIMARY I
HIGH EXPLOSIVE SECONDARY HIGH EXPLOSIVE
a. Two-step explosive train
3 DYNAMITE
1. SAFETY FUSE
2 NONELECTRIC
BLASTING CAP
LOW EXPLOSIVE PRIMARY
(BLACK POWDER) HIGH
EXPLOSIVE
SECONDARY HIGH EXPLOSIVE
b. Three-step explosive train
f
. «.«,-„ 2. NONELECTRIC
FUSE BLASTING CAP
i n
LOW
^ SXP
PRIMAR
.OSIVE HIGH E
Y
c. Four-step explosive train
Figure 11.3-1. Two-, three-, and four-step explosive trains.
i
I 1.3-2
EMISSION FACTORS
2/80
-------
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2 4-6
11.3.3 Emissions and Controls '
Carbon monoxide is the pollutant produced in greatest quantity from
explosives detonation. TNT, an oxygen deficient explosive, produces
more CO than most dynamites, which are oxygen balanced. But all explo-
sives produce measurable amounts of CO. Particulates are produced as
well, but such large quantities of particulate are generated in the
shattering of the rock and earth by the explosive that the quantity of
particulates from the explosive charge cannot be distinguished. Nitrogen
oxides (both NO and N02) are formed, but only limited data are available
on these emissions. Oxygen deficient explosives are said to produce
little or no nitrogen oxides, but there is only a small body of data to
confirm this. Unburned hydrocarbons also result from explosions, but in
most instances, methane is the only species that has been reported.
Hydrogen sulfide, hydrogen cyanide and ammonia all have been
reported as products of explosives use. Lead is emitted from the firing
of small arms ammunition with lead projectiles and/or lead primers, but
the explosive charge does not contribute to the lead emissions.
The emissions from explosives detonation are influenced by many
factors such as explosive composition, product expansion, method of
priming, length of charge, and confinement. These factors are difficult
to measure and control in the field and are almost impossible to duplicate
in a laboratory test facility. With the exception of a few studies in
underground mines, most studies have been performed in laboratory test
chambers that differ substantially from the actual environment. Any
estimates of emissions from explosives use must be regarded as approxi-
mations that cannot be made more precise, because explosives are not
used in a precise, reproducible manner.
To a certain extent, emissions can be altered by changing the
composition of the explosive mixture. This has been practiced for many
years to safeguard miners who must use explosives. The U. S. Bureau of
Mines has a continuing program to study the products from explosives and
to identify explosives that can be used safely underground. Lead
emissions from small arms use can be controlled by using jacketed soft
point projectiles and special leadfree primers.
Emission factors are given in Table 11,3-1.
References for Section 11.3
1. C. R. Newhouser, Introduction to Explosives, National Bomb Data
Center, International Association of Chiefs of Police, Gaithersburg,
MD (undated).
2. Roy V. Carter, "Emissions from the Open Burning or Detonation of
Explosives", Presented at the 71st Annual Meeting of the Air
Pollution Control Association, Houston, TX, June 1978.
••'*-1 EMISSION FACTORS 2/80
-------
3. Melvin A. Cook, The Science of High Explosives. Reinhold Publishing
Corporation, New York, 1958.
4. R. F. Chaiken, et al., Toxic Fumes from Explosives; Ammonium
Nitrate Fuel Oil Mixtures, Bureau of Mines Report of Investigations
7867, U. S. Department of Interior, Washington, DC, 1974.
5. Sheridan J. Rogers, Analysis of Noncoal Mine Atmospheres; Toxic
Fumes from Explosives, Bureau of Mines, U. S. Department of Interior,
Washington, DC, May 1976.
6. A. A. Juhasz, "A Reduction of Airborne Lead in Indoor Firing
Ranges by Using Modified Ammunition", Special Publication 480-26,
Bureau of Standards, U. S. Department of Commerce, Washington, DC,
November 1977.
2/80 MiwHIaneoiiK Soiirres 11.3-5
-------
APPENDIX A
MISCELLANEOUS DATA
A-l
-------
SOME USEFUL WEIGHTS AND MEASURES
grain
gram
ounce
kilogram
pound
0.002
0.04
28.35
2.21
0.45
ounces
ounces
grams
pounds
kilograms
pound (troy)
ton (short)
ton (long)
ton (metric)
ton (shipping)
12 ounces
2000 pounds
2240 pounds
2200 pounds
40 feet3
centimeter
inch
foot
meter
yard
mile
0.39 inches
2.54 centimeters
30.48 centimeters
1.09 yards
0.91 meters
1.61 kilometers
centimeter2
inch2
foot2
meter2
yard2
mile2
cord
cord
peck
bushel
0.16 inches2
6.45 centimeters2
0.09 meters2
1.2 yards2
0.84 meters2
2.59 kilometers2
128 feet3
4 meters3
8 quarts
(dry) 4 pecks
bushel 2150.4 inches3
centimeter-'
inch3
foot3
foot3
meter3
yard3
gallon (U.S.)
barrel
hogshead
township
hectare
0.061 inches3
16.39 centimeters3
centimeters3
inches3
yards3
283.17
1728
1.31
0.77
meters;
i
231 inches3
31.5 gallons
2 barrels
36 miles2
2.5 acres
MISCELLANEOUS DATA
One cubic foot of anthracite coal weighs about S3 pounds.
One cubic foot of bituminous coal weighs from 47 to 50 pounds.
One ton of coal is equivalent to two cords of wood for steam purposes.
A gallon of water (U.S. Standard) weighs 8.33 Ibs. and contains 231
cubic inches.
There are 9 square feet of heating surface to each square foot of grate
surface.
A cubic foot of water contains 7.5 gallons and 1728 cubic inches, and
weighs 62.5 Ibs.
Each nominal horsepower of a boiler requires 30 to 35 Ibs. of water per
hour.
A horsepower is equivalent to raising 33,000 pounds one foot per minute,
or 550 pounds one foot per second.
To find the pressure in pounds per square inch of column of water,
multiply the height of the column in feet by 0.434.
A-2
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A-3
-------
THERMAL EQUIVALENTS FOR VARIOUS FUELS
Type of fuel
Btu (gross)
kcal
Solid fuels
Bituminous coal
Anthracite coal
Lignite
Wood
Liquid fuels
Residual fuel oil
Distillate fuel oil
Gaseous fuels
Natural gas
Liquefied petroleum gas
Butane
Propane
(21 .0 to 28.0) x
106/ton
25.3 x
16.0 x
21 .Ox
6.3 x 106/bbl
5.9 x 1Q«/bbl
1,050/ft3
97,400/gal
90,500/gal
(5.8 to 7.8) x
106/MT
7.03 x
4.45 x K^/MT
1.47x 106/m3
10 x 103/liter
9.35 x 103/liter
9,350/m3
6,480/liter
6,030/liter
WEIGHTS OF SELECTED
SUBSTANCES
Type of substance
Asphalt
Butane, liquid at 60° F
Crude oil
Distillate oil
Gasoline
Propane, liquid at 60° F
Residual orl
Water
Ib/gal
a57
4.84
7.08
7.05
6.17
4.24
7.88
8.4
g/liter
1030
579
850
845
739
507
944
1000
A-4
-------
DENSITIES OF SELECTED SUBSTANCES
Substance
Fuels
Crude Oil
Residual Oil
Distillate Oil
Gasoline
Natural Gas
Butane
Propane
Wood (Air dried)
Elm
Fir, Douglas
Fir, Balsam
Hemlock
Hickory
Maple , Sugar
Maple, White
Oak, Red
Oak, White
Pine , Southern
Agricultural Products
Corn
Milo
Oats
Barley
Wheat
Cotton
Mineral Products
Brick
Cement
Cement
Concrete
Glass , Common
Gravel, Dry Packed
Gravel, Wet
Gypsum, Calcined
Lime, Pebble
Sand, Gravel (Dry, loose)
Density
874 kg/m3
944 kg/m3
845 kg/m3
739 kg/m3
673 kg/m3
579 kg/m3
507 kg/m3
561 kg/m3
513 kg/m3
400 kg/m3
465 kg/m3
769 kg/m3
689 kg/m3
529 kg/m3
673 kg/m3
769 kg/m3
641 kg/m3
25.4 kg/bu
25.4 kg/bu
14.5 kg/bu
21.8 kg/bu
27.2 kg/bu
226 kg/ bale
2.95 kg/brick
170 kg/bbl
1483 kg/m3
2373 kg/m3
2595 kg/m3
1600-1920 kg/m3
2020 kg/m3
880-960 kg/m3
850-1025 kg/m3
1440-1680 kg/m3
7.3 Ib/gal
7.88 Ib/gal
7.05 Ib/gal
6.17 Ib/gal
1 lb/23.8 ft3
4.84 Ib/gal (liquid)
4.24 Ib/gal (liquid)
35 lb/ft3
32 lb/ft3
25 lb/ft3
29 lb/ft3
48 lb/ft3
43 lb/ft3
33 lb/ft3
42 lb/ft3
48 lb/ft3
40 lb/ft3
56 Ib/bu
56 Ib/bu
32 Ib/bu
48 Ib/bu
60 Ib/bu
500 Ib/bale
6.5 Ib/brick
375 Ib/bbl
2500 lb/yd3
4000 lb/yd3
162 lb/ft3
100-120 lb/ft3
126 lb/ft3
55-60 lb/ft3
53-64 lb/ft3
90-105 lb/ft3
A-5
-------
CONVERSION FACTORS
The table of conversion factors on the following pages contains factors
for converting English to metric units and metric to English units as well as
factors to manipulate units within the same system. The factors are arranged
alphabetically by unit within the following property groups.
o Area
o Density
o Energy
o Force
o Length
o Mass
o Pressure
o Velocity
o Volume
o Volumetric Rate
To convert a number from one unit to another:
1) Locate the unit in which the number is currently expressed in the
left hand column of the table,
2) Find the desired unit in the center column, and
3) Multiply the number by the corresponding conversion factor
in the right hand column.
A-7
-------
CONVERSION FACTORS3
To convert from to multiply by
Area
Acres Sq feet 4.356 x 104
Acres Sq kilometers 4.0469 x 10~3
Acres Sq meters 4.0469 x 103
Acres Sq miles(statute) 1.5625 x 10~3
Acres Sq yards 4.84 x 103
Sq feet Acres 2.2957 x 10~5
Sq feet Sq cm 929.03
Sq feet Sq inches 144.0
Sq feet Sq meters 0.092903
Sq feet Sq miles 3.587 x 10~8
Sq feet Sq yards 0.111111
Sq inches Sq feet 6.9444 x 10~3
Sq inches Sq meters 6.4516 x 10"^
Sq inches Sq mm 645.16
Sq kilometers Acres 247.1
Sq kilometers Sq feet 1.0764 x 107
Sq kilometers Sq meters 1.0 x 10^
Sq kilometers Sq miles 0.386102
Sq kilometers Sq yards 1.196xl06
Sq meters.............. Sq cm 1.0 x 10^
Sq meters Sq feet 10.764
Sq meters Sq inches 1.55 x 103
Sq meters Sq kilometers 1.0 x 10~6
Sq meters Sq miles 3.861 x 10~7
Sq meters Sq mm 1.0xlO&
Sq meters Sq yards 1.196
Sq miles Acres. 640.0
Sq miles.. Sq feet 2.7878 x 107
Sq miles Sq kilometers 2.590
Sq miles Sq meters 2.59 x 106
Sq miles Sq yards 3.0976 x 106
Sq yards Acres 2.0661 x 10~4
Sq yards Sq cm 8.3613 x 103
Sq yards Sq ft.. 9.0
Sq yards Sq inches 1.296xl03
Sq yards Sq meters 0.83613
Sq yards Sq miles 3.2283 x 10~7
aWhere appropriate the conversion factors appearing in this table
have been rounded to four to six significant figures for ease in
use. The accuracy of these numbers is considered suitable for use
with emissions data; if a more accurate number is required, tables
containing exact factors should be consulted.
A-8
-------
To convert from
Density
CONVERSION FACTORS Contd.
to
multiply by
Dynes/cu cm
Grains/cu foot
Grams /cu cm
Grams/cu cm
Grams/cu cm............
Grams/cu cm............
Grams/cu cm
Grams/cu cm
Grams/cu cm
Grams/cu cm
Grams/cu cm.
Grams/cu meter
Grams/liter
Kilograms/cu meter.....
Kilograms/cu meter
Kilograms/cu meter.....
Pounds/cu foot
Pounds/cu foot
Pounds/cu inch
Pounds/cu inch
Pounds/cu inch.
Pounds/gal (U.S., liq).
Pounds/gal (U.S., liq).
Energy
Btu
Btu
Btu
Btu
Btu
Btu
Btu
Btu/hr
Btu/hr
Btu/hr
Btu/hr
Btu/hr
Btu/hr
Btu/hr
Btu/hr
Btu/lb
Btu/lb
Btu/lb
Calories,kg(mean).
Calories,kg(mean).
Grams/cu cm 1.0197 x 10~3
Grams/cu meter 2.28835
Dynes/cu cm 980.665
Grains/milliliter 15.433
Grams/milliliter 1.0
Pounds/cu inch.. 1.162
Pounds/cu foot 62.428
Pounds/cu inch 0.036127
Pounds/gal (Brit.) 10.022
Pounds/gal(U.S., dry) 9.7111
Pounds/gal(U.S., liq.) 8.3454
Grains/cu foot 0.4370
Pounds/gal (U.S.) 8.345 x 10~3
Grams/cu cm 0.001
Pounds/cu ft 0.0624
Pounds/cu in 3.613 x 10"5
Grams/cu cm 0.016018
Kg/cu meter 16.018
Grams/cu cm 27.68
Grams/liter 27.681
Kg/cu meter 2.768 x 104
Grams/cu cm 0.1198
Pounds/cu ft 7.4805
Cal.,gm (1ST.) 251.83
Ergs 1.05435 x 1010
Foot-pounds 777.65
Hp-hours 3.9275 x 10~4
Joules(Int. ) 1054.2
Kg-meters 107.51
Kw-hours(Int.) 2.9283 x 10~4
Cal. ,kg/hr 0.252
Ergs/sec 2.929 x 106
Foot-pounds/hr 777.65
Horsepower (mechanical).... 3.9275 x 10~4
Horsepower (boiler) 2.9856 x 10~5
Horsepower (electric) 3.926 x 10~4
Horsepower (metric) 3.982 x 10~4
Kilowatts 2.929 x 10~4
Foot-pounds/lb 777.65
Hp-hr/lb 3.9275 x 10~4
Joules/gram 2.3244
Btu(lST.) 3.9714
Ergs 4.190 x 1010
A-9
-------
CONVERSION FACTORS Contd.
To convert from
Calories ,kg_(mean)
Calories, kj>( mean)
Calories, jtg_( mean)
Calories,kg_(mean)
Calories,jcg(mean)......
Ergs
Ergs
Ergs
Ergs
Ergs
Ergs
Foot-pounds
Foot-pounds
Foot-pounds
Foot-pounds
Foot-pounds
Foot-pounds
Foot-pounds
Foot-pounds
Foot-pounds
Foot-pounds/hr.
Foot-pounds/hr
Foot-pounds/hr
Foot-pounds/hr
Foot-pounds/hr
Horsepower (mechanical)
Horsepower (mechanical)
Horsepower (mechanical)
Horsepower (mechanical)
Horsepower (mechanical)
Horsepower (mechanical)
Horsepower (mechanical)
Horsepower (mechanical)
Horsepower (boiler)....
Horsepower (boiler)....
Horsepower (boiler)....
Horsepower (boiler)....
Horsepower (boiler)....
Horsepower (boiler)....
Horsepower (boiler)....
Horsepower (boiler)....
Horsepower (electric)..
Horsepower (electric)..
Horsepower (electric)..
Horsepower (electric)..
Horsepower (electric)..
Horsepower (electric)..
Horsepower (electric)..
to
Foot-pounds
Hp-hours
Joules
Kg-meters
Kw-hours(lnt.)
Btu
Foot-poundals
Foot-pounds
Joules (Int.)
Kw-hours
Kg-meters
Btu(IST.)
Cal.,kg_ (1ST.)
Ergs
Foot-poundals
Hp-hours
Joules
Kg-meters
Kw-hours(Int.)
Newton-meters..............
Btu/min
Ergs/min
Horsepower (mechanical)....
Horsepower (metric)
Kilowatts
Btu(mean)/hr
Ergs/sec
Foot-pounds/hr
Horsepower (boiler)
Horsepower (electric)
Horsepower (metric)
Joules/sec
Kilowatts(Int.)
Btu(raean)/hr
Ergs/sec
Foot-pounds/min
Horsepower (mechanical)....
Horsepower (electric)
Horsepower (metric)
Joules/sec
Kilowatts
Btu(mean)/hr
Cal. ,kg_/hr.
Ergs/sec.
Foot-pounds/min
Horsepower (boiler)
Horsepower (metric)
Joules/sec
multiply by
3.0904 x 103
1.561 x 10~3
4.190 x 103
427.26
1.1637 x 10~3
9.4845 x 10"11
2.373 x 10~6
7.3756 x 10-8
9.99835 x 10~8
2.7778 x 10~14
x 10~8
0197
2851 x 10~3
3.2384 x 10~4
1.3558 x 107
32.174
5.
1.
0.
0505 x
3558
138255
10
-7
5.
3,
2,
7,
1,
3.76554 x 10~7
1.3558
2.1432 x 10~5
2.2597 x 105
5.0505 x 10~7
121 x 10~7
766 x 10"7
5425 x 103
457 x 109
980 x 106
0.07602
0.9996
1.0139
745.70
0.74558
3.3446 x 104
9.8095 x 1010
4.341 x 105
13.155
13.15
13.337
9.8095 x 103
9.8095
2.5435 x 103
641.87
7.46 x 109
3.3013 x 104
0.07605
1.0143
746.0
A-10
-------
CONVERSION FACTORS Contd.
To convert from
Horsepower (electric).
Horsepower (metric)...
Horsepower (metric)...
Horsepower (metric)...
Horsepower (metric)...
Horsepower (metric)...
Horsepower (metric)...
Horsepower (metric)...
Horsepower (metric)...
Horsepower-hours
Horsepower-hours
Horsepower-hours
Horsepower-hours
Horsepower-hours
Joules (Int.)
Joules (Int.)
Joules (Int.)
Joules (Int.)
Joules (Int.)
Joules (Int.)/sec
Joules (Int.)/sec
Joules (Int.)/sec
Kilogram-meters.......
Kilogram-meters.......
Kilogram-meters
Kilogram-meters
Kilogram-meters
Kilogram-meters
Kilogram-meters
Kilogram-meters
Kilogram-meters/sec...
Kilowatts (Int.)
Kilowatts (Int.)
Kilowatts (Int.)
Kilowatts (Int.)
Kilowatts (Int.)
Kilowatts (Int.)
Kilowatts (Int.)
Kilowatts (Int.)
Kilowatts (Int.)
Kilowatts (Int.)
Kilowatts (Int.)
Kilowatt-hours (Int.).
Kilowatt-hours (Int.).
Kilowatt-hours (Int.).
Kilowatt-hours (Int.).
Kilowatt-hours (Int.).
to
Kilowatts
Btu(mean)/hr
Ergs/sec.
Foot-pounds/min.
Horsepower (mechanical)....
Horsepower(boller).
Horsepower (electric)......
Kg-meters/sec
Kilowatts
Btu(mean)
Foot-pounds
Joules
Kg-meters
Kw-hours
Btu (1ST.)
Ergs
Foot-poundals
Foot-pounds
Kw-hours
Btu(mean)/min
Cal. ,kg^/min.
Horsepower
Btu (mean)
Cal. ,kg (mean)
Ergs
Foot-poundals..............
Foot-pounds
Hp-hours
Joules (Int.)
Kw-hours
Watts
Btu (!ST.)/hr
Cal,kg_ (1ST. )/hr
Ergs/sec
Foot-poundals/min
Foot-pounds/min
Horsepower (mechanical)....
Horsepower (boiler)
Horsepower (electric)
Horsepower (metric)
Joules (Int.)/hr
Kg-meters/hr.
Btu (mean)
Foot-pounds
Hp-hours
Joules (Int.)
Kg-meters
multiply by
0.746
2.5077 x 103
7.355 x 109
3.255 x 104
0.98632
0.07498
0.9859
75.0
0.7355
2.5425 x 103
1.98 x 106
2.6845 x 106
2.73745 x 105
0.7457
9.4799 x 10~4
1.0002 x 107
12.734
0.73768
2.778 x 10~7
0.05683
0.01434
1.341 x 10~3
9.2878 x 10~3
2.3405 x 10~3
9.80665 x 107
232.715
7.233
3.653 x 10~6
9.805
2.724 x 10~6
9.80665
3.413 x 103
860.0
1.0002 x 1010
1.424 x 106
4.4261 x 104
1.341
0.10196
1.3407
1.3599
3.6 x 106
3.6716 x 105
3.41 x 103
2.6557 x 106
1.341
3.6 x 106
3.6716 x 105
A-ll
-------
CONVERSION FACTORS Contd.
To convert from to multiply by
Newton-meters.......... Gram-cm 1.01972 x
Newton-meters Kg-meters 0.101972
Newton-meters Pound-feet 0.73756
Force
Dynes Newtons 1.0 x 10"^
Dynes Poundals 7.233 x 10~5
Dynes Pounds 2.248 x 10~6
Newtons Dynes 1.0 x 10~^
Newtons Pounds (avdp.) 0.22481
Poundals Dynes 1.383xl04
Poundals Newtons 0.1383
Poundals Pounds (avdp.) 0.03108
Pounds (avdp.) Dynes 4.448 x 10->
Pounds (avdp.)......... Newtons 4.448
Pounds (avdp.) Poundals 32.174
Length
Feet Centimeters 30.48
Feet Inches 12
Feet Kilometers 3.048 x 10~4
Feet Meters 0.3048
Feet Miles (statute) 1.894xlO~^
Inches Centimeters 2.540
Inches Feet 0.08333
Inches Kilometers 2.54 x 10~5
Inches Meters 0.0254
Kilometers Feet 3.2808 x 103
Kilometers Meters 1000
Kilometers Miles (statute) 0.62137
Kilometers Yards 1.0936 x 103
Meters Feet 3.2808
Meters Inches 39.370
Micrometers Angstrom units 1.0 x 10^
Micrometers Centimeters 1.0 x 10~3
Micrometers Feet 3.2808xlO~6
Micrometers Inches 3.9370 x 10~5
Micrometers Meters 1.0 x 10~6
Micrometers Millimeters 0.001
Micrometers.... Nanometers. 1000
Miles (statute) Feet 5280
Miles (statute) Kilometers 1.6093
Miles (statute) Meters.. 1.6093 x 103
Miles (statute). Yards 1760
Millimeters Angstrom units 1.0 x 10'
Millimeters Centimeters 0.1
Millimeters Inches 0.03937
Millimeters Meters 0.001
A-12
-------
CONVERSION FACTORS Contd.
To convert from to multiply by
Millimeters Micrometers 1000
Millimeters Mils 39.37
Nanometers Angstrom units 10
Nanometers Centimeters 1.0 x 10"'
Nanometers Inches 3.937 x 10~°
Nanometers Micrometers 0.001
Nanometers Millimeters 1.0 x 10~6
Yards Centimeters 91.44
Yards Meters 0.9144
Mass
Grains Grams 0.064799
Grains Milligrams 64.799
Grains. Pounds (apoth. or troy).... 1.7361 x 10~4
Grains Pounds (avdp.) 1.4286 x 10"4
Grains Tons (metric) 6.4799 x 10~8
Grams Dynes 980.67
Grams Grains 15.432
Grams Kilograms 0.001
Grams Micrograms •• 1 x 10"
Grams Pounds (avdp.) 2.205 x 10~3
Grams Tons, metric (megagrams)... 1 x 10"°
Kilograms Grains 1.5432 x 104
Kilograms Poundals 70.932
Kilograms Pounds (apoth.or troy)..... 2.679
Kilograms Pounds (avdp.) 2.2046
Kilograms Tons (long) 9.842 x 10~4
Kilograms Tons (metric) 0.001
Kilograms Tons (short) 1.1023 x 10~3
Megagrams. Tons (metric) 1.0
Milligrams Grains 0.01543
Milligrams Grams 1.0 x 10~3
Milligrams Ounces (apoth. or troy).... 3.215 x 10~^
Milligrams Ounces (avdp.) 3.527 x 10~5
Milligrams Pounds (apoth. or troy).... 2.679 x 10~6
Milligrams Pounds (avdp.) 2.2046 x 10~6
Ounces (apoth. or troy) Grains 480
Ounces (apoth. or troy) Grams 31.103
Ounces (apoth. or troy) Ounces (advp. ) 1.097
Ounces (avdp.) Grains 437.5
Ounces (avdp.) Grams 28.350
Ounces (avdp.) Ounces (apoth. or troy).... 0.9115
Ounces (avdp.) Pounds (apoth. or troy).... 0.075955
Ounces (avdp.) Pounds (avdp.) 0.0625
Pounds (avdp.) Poundals..... 32.174
Pounds (avdp.) Pounds (apoth. or troy).... 1.2153
A-13
-------
CONVERSION FACTORS Contd.
To convert from
to
Pounds (avdp.) Tons (long)
Pounds (avdp.) Tons (metric)
Pounds (avdp.) Tons (short)
Pounds (avdp.) Grains
Pounds (avdp.) Grams
Pounds (avdp.) Ounces (apoth. or troy)....
Pounds (avdp. ) Ounces (avdp.) ,
Tons (long) Kilograms
Tons (long) Pounds (apoth. or troy)....
Tons (long) Pounds (avdp.) ,
Tons (long) Tons (metric) ,
Tons (long) Tons (short) ,
Tons (metric)... Grams ,
Tons (metric) Megagrams
Tons (metric) Pounds (apoth. or troy)...,
Tons (metric) Pounds (avdp.) ,
Tons (metric).......... Tons (long)
Tons (metric) Tons (short)
Tons (short) Kilograms
Tons (short) Pounds (apoth. or troy)...
Tons (short) Pounds (avdp.) ,
Tons (short) Tons (long)
Tons (short) Tons (metric)
multiply by
4.4643 x 10~4
4.5359 x 10~4
5.0 x 10-4
7000
453.59
14.583
16
1.016 x 103
2.722 x 103
2.240 x 103
1.016
.12
0 x
0
106
Pressure
Atmospheres
Atmospheres
Atmospheres
Atmospheres
Atmospheres.
Atmospheres............
Inches of Hg (60°F)....
Inches of Hg (60°F)....
Inches of Hg (60°F)....
Inches of Hg (60°F)....
Inches of H.,0 (4°C)....
Inches of H20 (4°C)....
Inches of H20 (4°C)....
Inches of H20 (4°C)....
Inches of H20 (4°C)....
Kilograms/sq cm
Kilograms/sq cm........
Kilograms/sq cm
Kilograms/sq cm
Kilograms/sq cm.
Millimeters of Hg (0°C)
Millimeters of Hg (0°C)
Cm of H20 (4°C)....
Ft of H20 (39.2°F),
In of Hg (32°F)...,
Kg/sq cm
Mm of Hg (0°C)
Pounds/sq inch.....
Atmospheres
Grams/sq cm.
Mm of Hg (60°F)...,
Pounds/sq ft
Atmospheres
In of Hg (32°F)
Kg/sq meter........
Pounds/sq ft
Pounds/sq inch
Atmospheres
Cm of Hg (0°C)
Ft of H20 (39.2°F).
In of Hg (32°F)
Pounds/sq inch....,
Atmospheres........
Grams/sq cm ,
2.6792 x 103
2.2046 x 103
0.9842
1.1023
907.18
2.4301 x 103
2000
0.8929
0.9072
1.033 x 10^
33.8995
29.9213
1.033
760
14.696
0.03333
34.434
25.4
70.527
2.458 x 10~J
0.07355
25.399
5.2022
0.036126
0.96784
73.556
32.809
28.959
14.223
1.3158 x 10~3
1.3595
A-14
-------
CONVERSION FACTORS Contd.
To convert from to multiply by
Millimeters of Hg (0°C) Pounds/sq inch 0.019337
Pounds/sq inch......... Atmospheres 0.06805
Pounds/sq inch Cm of Hg (0°C) 5.1715
Pounds/sq inch Cm of H20 (4°C) 70.309
Pounds/sq inch In of Hg (32°F) 2.036
Pounds/sq inch In of ^0 (39. 2F) 27.681
Pounds/sq inch Kg/sq cm 0.07031
Pounds/sq inch Mm of Hg (0°C) 51.715
Velocity
Centimeters/sec Feet/min 1.9685
Centimeters/sec Feet/sec 0.0328
Centimeters/sec Kilometers/hr 0.036
Centimeters/sec Meters/min 0.6
Centimeters/sec Miles/hr 0.02237
Feet/minute Cm/sec 0.508
Feet/minute Kilometers/hr 0.01829
Feet/minute Meters/min 0.3048
Feet/minute... Meters/sec 5.08 x 10" 3
Feet/minute Miles/hr 0.01136
Feet/sec Cm/sec 30.48
Feet/sec Kilometers/hr 1.0973
Feet/sec Meters/min 18.288
Feet/sec Miles/hr 0.6818
Kilometers/hr Cm/sec 27.778
Kilometers/hr Feet/hr 3.2808 x 103
Kilometers/hr Feet/min 54.681
Kilometers/hr Meters/sec 0.27778
Kilometers/hr Miles (statute)/hr 0.62137
Meters/min Cm/sec 1.6667
Meters/min Feet/min 3.2808
Meters/min Feet/sec 0.05468
Meters/min Kilometers/hr 0.06
Miles/hr Cm/sec 44.704
Miles/hr Feet/hr 5280
Miles/hr Feet/min 88
Miles/hr.... Feet/sec. 1.4667
Miles/hr Kilometers/hr 1.6093
Miles/hr Meters/min 26.822
Volume
Barrels (petroleum,US). Cu feet 5.6146
Barrels (petroleum,US). Gallons (US) 42
Barrels (petroleum,US). Liters 158.98
Barrels (US, liq.) Cu feet 4.2109
Barrels (US, liq.) Cu inches 7.2765 x 103
A-15
-------
CONVERSION FACTORS Contd.
To convert from
Barrels (US, liq.)....
Barrels (US, liq.)....
Barrels (US, liq.)....
Cubic centimeters ,
Cubic centimeters.....
Cubic centimeters
Cubic cent imeters
Cubic centimeters
Cubic centimeters ,
Cubic feet
Cubic feet
Cubic feet
Cubic feet
Cubic inches
Cubic inches
Cubic inches
Cubic inches
Cubic inches
Cubic inches
Cubic inches
Cubic meters
Cubic meters
Cubic meters
Cubic meters..........
Cubic meters
Cubic meters
Cubic meters
Cubic yards
Cubic yards
Cubic yards
Cubic yards
Cubic yards
Cubic yards
Cubic yards
Cubic yards
Cubic yards.
Cubic yards
Cubic yards
Cubic yards
Cubic yards
Gallons (US, liq.)....
Gallons (US, liq.)....
Gallons (US, liq.)....
Gallons (US, liq.)....
to
multiply by
Gallons (US, liq.),
(US, liq.),
Gallons
Gallons
Gallons (US, liq.),
(US, liq.)..,
Cu meters 0.1192
Gallons (US, liq.) 31.5
Liters 119.24
Cu feet 3.5315 x 10~5
Cu inches 0.06102
Cu meters 1.0 x 10~6
Cu yards 1.308 x 10~6
Gallons (US, liq.) 2.642 x 10~4
Quarts (US, liq.) 1.0567 x 10~3
Cu centimeters 2.8317 x 104
Cu meters 0.028317
Gallons (US, liq.) 7.4805
Liters 28.317
Cu cm 16.387
Cu feet 5.787 x 10~4
Cu meters 1.6387 x 10~5
Cu yards 2.1433 x 10"5
Gallons (US, liq.) 4.329 x 10~3
Liters 0.01639
Quarts (US, liq.) 0.01732
Barrels (US, liq) 8.3864
Cu cm 1.0 x 106
Cu feet 35.315
Cu inches 6.1024 x 104
Cu yards 1.308
Gallons (US, liq.) 264.17
Liters 1000
Bushels (Brit.) 21.022
Bushels (US) 21.696
Cu cm 7.6455 x 105
Cu feet 27
Cu inches 4.6656 x 104
Cu meters... 0.76455
Gallons 168.18
Gallons 173.57
Gallons 201.97
Liters 764.55
Quarts 672.71
Quarts 694. 28
Quarts 807.90
Barrels (US, liq.) 0.03175
Barrels (petroleum,US) 0.02381
Bushels (US) 0.10742
Cu centimeters 3.7854 x 103
Cu feet 0.13368
Cu inches 231
Cu meters 3.7854 x 10~3
Cu yards 4.951 x 10~3
A-16
-------
To convert from
CONVERSION FACTORS Contd.
to
multiply by
Gallons (US, liq.) Gallons (wine) 1.0
Gallons (US, liq.) Liters 3.7854
Gallons (US, liq.) Ounces (US, fluid) 128.0
Gallons (US, liq.) Pints (US, liq.) 8.0
Gallons (US, liq.) Quarts (US, liq.) 4.0
Liters Cu centimeters 1000
Liters Cu feet 0.035315
Liters Cu inches 61.024
Liters Cu meters 0.001
Liters Gallons (US, liq.) 0.2642
Liters Ounces (US, fluid) 33.814
Volumetric Rate
Cu ft/min Cu cm/sec 471.95
Cu ft/min Cu ft/hr 60.0
Cu ft/min Gal (US)/min 7.4805
Cu ft/min Liters/sec 0.47193
Cu meters/min Gal (US)/min 264.17
Cu meters/min Liters/min 999.97
Gallons (US)/hr Cu ft/hr 0.13368
Gallons (US)/hr Cu meters/min 6.309 x 10~5
Gallons (US)/hr Cu yd/min 8.2519 x 10~5
Gallons (US)/hr Liters/hr 3.7854
Liters/min Cu ft/min 0.0353
Liters/min Gal (US, liq.)/min 0.2642
A-17
-------
CONVERSION FACTORS FOR COMMON AIR POLLUTION MEASUREMENTS
AIRBORNE PARTICULATE MATTER
To convert from
Mllligrams/cu m
Grams/cu ft
Grams/cu m
Mlcrograms/cu in
Mlcrograms/cu ft
Pounds/1000 cu ft
To
Grams/cu ft
Grams/cu m
Mlcrograms/cu m
Micrograms/cu ft
Pounds/1000 cu ft
Mllligrams/cu m
Grams/cu m
Micrograms/cu m
Mlcrograms/cu ft
Pounds/1000 cu ft
Milligrams/cu m
Grams/cu ft
Micrograms/cu m
Micrograms/cu ft
Pounds/1000 cu ft
Mllllgrams/cu m
Grams/cu ft
Grams/cu m
Micrograms/cu ft
Pounds/1000 cu ft
Milligrams/cu m
Grams/cu ft
Grams/cu m
Micrograms/cu m
Pounds/1000 cu ft
Milligrams/cu m
Grams/ cu ft
Micrograms/cu m
Grams/cu m
Mlcrograms/cu ft
Multiply by
283.2 x 10~6
0.001
1000.0
28.32
62.43 x 10-6
35.3145 x 103
35.314
35.314 x 106
1.0 x 106
2.2046
1000.0
0.02832
1.0 x 106
28.317 x 103
0.06243
0.001
28.317 x 10-9
1.0 x 10~6
0.02832
62.43 x 10-9
35.314 x 10~3
1.0 x 10-6
35.314 x 10-6
35.314
2.2046 x ID"6
16.018 x 103
0.35314
16.018 x 106
16.018
353.14 x 103
SAMPLING PRESSURE
To convert from
Millimeters of mercury
(0°C)
Inches of mercury
(0°C)
Inches of water (60°F)
To
Inches of water (60°F)
Inches of water (60°F)
Millimeters of mercury
(0°C)
Inches of mercury (0°C)
Multiply by
0.5358
13.609
1.8663
73.48 x 10-3
A-18
-------
CONVERSION FACTORS FOR COMMON AIR POLLUTION MEASUREMENTS
ATMOSPHERIC GASES
To convert from
To
Multiply by
Mllligrams/cu m
Micrograms/cu m
Micrograms/Hter
Ppm by volume (20°C)
Ppm by weight
Pounds/cu ft
Micrograms/cu m
Micrograms/liter
Ppm by volume (20°C)
Ppm by weight
Pounds/cu ft
Milligrams/cu m
Micrograms/liter
Ppm by volume (20°C)
Ppm by weight
Pounds/cu ft
Milligrams/cu ra
Micrograms/cu m
Ppm by volume (20°C)
Ppm by weight
Pounds/cu ft
Milllgrams/cu m
Micrograms/cu m
Micrograms/liter
Ppm by weight
Pounds/cu ft
Milligrams/cu m
Micrograms/cu m
Mlcrograms/li ter
Ppm by volume (20°C)
Pounds/cu ft
Milligrams/cu m
Micrograms/cu m
Micrograms/liter
Ppm by volume (20°C)
Ppm by weight
1000.0
1.0
24 .04
M
0.8347
62.43 x 10-9
0.001
0.001
0.02404
M
834.7 x 10-6
62.43 x 10-12
1.0
1000.0
24.04
M
0.8347
62.43 x 10~9
M
24.04
M
0.02404
M
24.04
M
28.8
M
385.1 x 106
1.198
1.198 x 10-3
1.198
28.8
M
7.48 x 10-6
16.018 x 106
16.018 x 109
16.018 x 106
385 .1 x 1Q6
M
133.7 x 103
M » Molecular weight of gas.
A-19
-------
CONVERSION FACTORS FOR COMMON AIR POLLUTION MEASUREMENTS
VELOCITY
To convert from
Meters/sec
Kilometers/hr
Feet/ sec
Miles/hr
To
Kilometers/hr
Feet/ sec
Miles/hr
Meters/sec
Feet/ sec
Miles/hr
Meters/sec
Kilometers/hr
Miles/hr
Meters/ sec
Kilometers/hr
Feet/ sec
Multiply by
3.6
3.281
2.237
0.2778
0.9113
0.6214
0.3048
1.09728
0.6818
0.4470
1.6093
1.4667
ATMOSPHERIC PRESSURE
To convert from
Atmospheres
Millimeters of mercury
Inches of mercury
Millibars
To
Millimeters of mercury
Inches of mercury
Millibars
Atmospheres
Inches of mercury
Millibars
Atmospheres
Millimeters of mercury
Millibars
Atmospheres
Millimeters of mercury
Inches of mercury
Multiply by
760.0
29.92
1013.2
1.316 x 10~3
39.37 x 10~3
1.333
0.03333
25.4005
33.35
0.00987
0.75
0.30
VOLUME EMISSIONS
To convert from
Cubic m/min
Cubic ft/min
To
Cubic ft/min
Cubic m/min
Multiply by
35.314
0.0283
A-20
-------
BOILER CONVERSION FACTORS
1 Megawatt » 10.5 x I06 BTU/hr
(8 to 14 x 106 BTU/hr)
1 Megawatt - 8 x 103 Ib steam/hr
(6 to 11 x 103 Ib steam/hr)
1 BHP - 34.5 Ib steam/hr
1 BHP » 45 x 103 BTU/hr
(40 to 50 x lO3 BTU/hr)
1 Ib steam/hr - 1.4 x 103 BTU/hr
(1.2 to 1.7 x 103 BTU/hr)
NOTES: In the relationships,
Megawatt is the net electric power production of a steam
electric power plant.
BHP is boiler horsepower.
Lb steam/hr is the steam production rate of the boiler.
BTU/hr la the heat Input rate to the boiler (based on the
gross or high heating value of the fuel burned).
For less efficient (generally older and/or smaller) boiler operations,
use the higher values expressed. For more efficient operations
(generally newer and/or larger), use the lower vlaues-
VOLUME
Cubic Inches
Mllllliters
Liters
Ounces (U. S. fl.)
Gallons (U. S.)*..
Barrels (U. S.)...
Cubic feet
cu. in.
0.061024
61 .024
1 .80469
231
7276.5
1728
ml.
16.3868
1000
29.5729
3785.3
1 .1924xl05
2 .8316x10*
liters
.0163868
0.001
0.029573
3.7853
119.2369
28.316
ounces
(U. S. fl.)
0.5541
0.03381
33.8147
128
4032.0
957.568
gallons
(U. S.)
4.3290xlO-3
2.6418x10-4
0.26418
7. 8125xlO-3
31.5
7.481
barrels
(U. S.)
1.37429xlO-4
8.387x10-6
8.387x10-3
2.48xlO-4
0.031746
0.23743
cu. ft.
5.78704x10-*
3.5316x10-5
0.035316
1 .0443x10-3
0.13368
4.2109
1U. S. gallon of water at 16.7°C (62°F) weighs 3.780 kg. or 8.337 pounds (avoir.)
MASS
Ounces (avoir . ) . . .
Pounds (avoir.)*..
Tons (U. S.)
Milligrams
grams
1000
28.350
453.59
0.06480
9.072xl05
0.001
kilograms
0.001
0.028350
0.45359
6.480x10-5
907.19
lx!0~6
ounces
(avoir.)
3.527xlO-2
35.274
16.0
2.286x10-3
3.200xl04
3.527x10-5
pounds
(avoir.)
2.205x10-3
2 .2046
0.0625
1 .429x10-*
2000
2 .205x10-6
grains
15.432
15432
437.5
7000
1 .4xl07
0.015432
tons
(U. S.)
1 .102xlO~6
1.102x10-3
3.125x10-5
5.0x10-*
7. 142xlO-8
1.102x10-9
milligrams
1000
1x10*
2.8350x10*
4.5359x105
64.799
9.0718xl08
*Mass of 27.692 cubic inches water weighed in air at 4.0°C, 760 mm mercury pressure.
A-21
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CONVERSION FACTORS FOR VARIOUS SUBSTANCES3
Type of substance Conversion factors
Fuel
Oil
Natural gas
Gaseous Pollutants
°3
N02
so2
H2S
CO
HC (as methane)
Agricultural products
Corn
Milo
Oats
Barley
Wheat
Cotton
Mineral products
Brick
Cement
Cement
Concrete
Mobile sources, fuel efficiency
Motor vehicles
Water born vessels
Miscellaneous liquids
1 bbl = 159 liters (42 gal)
1 therm = 100,000 Btu (approx.
25000 kcal)
1 ppm, volume
1 ppm, volume
1 ppm, volume
1 ppm, volume
1 ppm, volume
1 ppm, volume
1960
1880 /ig/m3
2610 /'g/m3
1390 ng/m3
1.14 mg/m3
0.654 mg/m3
1 bu = 25.4 kg = 56 Ib
1 bu = 25.4 kg = 56 Ib
1 bu = 14.5 kg = 32 Ib
1 bu = 21.8 kg = 48 Ib
1 bu = 27.2 kg = 60 Ib
1 bale = 226 kg = 500 Ib
1 brick = 2.95 kg = 6.5 Ib
1 bbl = 170 kg = 375 Ib
1 yd3 - 1130 kg = 2500 Ib
1 yd3 = 1820 kg = 4000 Ib
1.0 mi/gal = 0.426 km/liter
1.0 gal/naut mi = 2.05 liters/km
Beer
Paint
Varnish
Whiskey
Water
1 bbl = 31.5 gal
1 gal = 4.5 to 6.82 kg = 10 to
1 gal = 3.18 kg = 7 Ib
1 bbl = 190 liters = 50.2 gal
1 gal = 3.81 kg = 8.3 Ib
15 Ib
aMany of the conversion factors in this table represent average values and
approximations and some of the values vary with temperature and pressure.
These conversion factors should, however, be sufficiently accurate for
general field use.
I
A-24
-------
TECHNICAL REPORT DATA
(Please read Instructions en th.- reverse before cumpltiinf;)
(' AP-42 Fourth Edition, Volume I
J. TITLE AND SUBTITLE
COMPILATION OF AIR POLLUTANT EMISSION FACTORS,
VOLUME I: STATIONARY POINT AND AREA SOURCES
7.
9.
12
15
16
AUTHOR(S)
PERFORMING ORGANIZATION NAME AND ADDRESS
Source Analysis Section, MDAD (MD 14)
Office Of Air Quality Planning And Standards
U. S. Environmental Protection Agency
Research Triangle Park, NC 27711
. SPONSORING AGENCY NAME AND ADDRESS
3 RECIPIENT'S ACCESSION NO.
5. REPORT DATE
September 1985
6, PERFORMING ORGANIZATION CODE
8. PERFORMING ORGANIZATION REPORT NO.
10. PROGRAM ELEMENT NO.
11. CONTRACT/GRANT NO.
13. TYPE OF REPORT AND PERIOD COVERED
14 SPONSORING AGENCY CODE
. SUPPLEMENTARY NOTES *
EPA Editor: Whitmel M. Joyner
. ABSTRACT
Emission data obtained from source tests, material balance studies,
responsible for conducting air pollution emission inventories. Emission factors
given in this document cover most of the common stationary and area source emission
categories: fuel combustion; combustion of solid wastes; evaporation of fuels,
solvents and other volatile substances; various industrial processes; and
miscellaneous sources. When no specific source test data are available, these
factors can be used to estimate the quantities of pollutants being released from a
source or source group.
Volume II of this document provides emission factors for mobile sources, both
on and off highway types. This information is available from EPA's Office Of Mobile
Sources, 2565 Plymouth Road, Ann Arbor, MI 48105.
17.
DESCRIPTORS
KEY WORDS AND DOCUMENT ANALYSIS
b IDENTIFIERS/OPEN ENDED TERMS
Emissions
Emission Factors
Stationary Sources
Area Sources
Fuel Combustion
Emission Inventories
18. DISTRIBUTION STATEMENT
c. COSATl Held/Group
19 SECURITY CLASS (This Report) 21 NO. OF PAGES
! 888
120 SECURITY ' LASS (Vtisp
EPA Form 2220-1 (Rev. 4-77) Previous EDITION is OBSOLETE
-------
U.S. Environmental Protection Agency
Region V. Library
230 South Dearborn Street
Chicago, Illinois 60604
-------
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