-------
per hour. Wastes are burned on a hearth in the combustion chamber. The
units are equipped with combustion controls and afterburners to ensure good
combustion and minimal emissions.
2.1.2.2 Emissions and Controls
Operating conditions, refuse composition, and basic combustor design
have a pronounced effect on emissions. The manner in which air is supplied
to the combustion chamber or chambers has a significant effect on the
quantity of particulate emissions. Air may be introduced from beneath the
chamber, from the side, or from the top of the combustion chamber. As
underfire air is increased, an increase in fly-ash emissions occurs.
Erratic refuse charging causes a disruption of the combustion bed and a
subsequent release of large quantities of particulates. Large quantities of
uncombusted particulate matter and carbon monoxide are also emitted for an
extended period after charging of batch-fed units because of interruptions
in the combustion process. In continuously fed units, furnace particulate
emissions are strongly dependent upon grate type. The use of a rotary kiln
and reciprocating grates results in higher particulate emissions than the
use of a rocking or traveling grate. Emissions of oxides of sulfur are
dependent on the sulfur content of the refuse. Carbon monoxide and unburned
hydrocarbon emissions may be significant and are caused by poor combustion
resulting from improper combustor design or operating conditions. Nitrogen
oxide emissions increase with an increase in the temperature of the
combustion zone, an increase in the residence time in the combustion zone
before quenching, and an increase in the excess air rates to the point where
dilution cooling overcomes the effect of increased oxygen concentration.
9/88 Solid Waste Disposal 2.1-13
-------
References for Section 2.1.2
1. Air Pollutant Emission Factors, Final Report, Resources Research,
Incorporated, Reston, VA, prepared for National Air Pollution Control
Administration, Durham, NC, under Contract Number CPA-2269-119,
April 1970.
2. Control Techniques for Carbon Monoxide Emissions from Stationary
Sources, U.S. DHEW, PHS, EHS, National Air Pollution Control
Administration, Washington, DC, Publication Number AP-65, March 1970.
3. Air Pollution Engineering Manual, U.S. DHEW, PHS, National Center for
Air Pollution Control, Cincinnati, OH, Publication Number 999-AP-40,
1967, p. 413-503.
4. J. DeMarco. et al., Incinerator Guidelines 1969, U.S. DHEW, Public
Health Service, Cincinnati, OH, SW. 13TS, 1969, p. 176.
5. J. 0. Brukle, J. A. Dorsey, and B. T. Riley, The Effects of Operating
Variables and Refuse Types on Emissions from a Pilot-Scale Trench
Incinerator, Proceedings of the 1968 Incinerator Conference, American
Society of Mechanical Engineers, New York, NY, May 1968, p. 34-41.
6. Walter R. Nessen, Systems Study of Air Pollution from Municipal
Incineration, Arthur D. Little, Inc. Cambridge, MA, prepared for
National Air Pollution Control Administration, Durham, NC, under
Contract Number CPA-22-69-23, March 1970.
7. C. V. Ranter, R. G. Lunche, and A. P. Fururich, Techniques for Testing
Air Contaminants from Combustion Sources, J. Air Pol. Control Assoc.,
6(4): 191-199, February 1957.
8. J. L. Stear, Municipal Incineration; A Review of Literature, U. S.
Environmental Protection Agency, Office of Air Programs, Research
Triangle Park, NC, OAP Publication Number AP-79, June 1971.
9. E. R. Kaiser, Refuse Reduction Processes in Proceedings of Surgeon
General's Conference on Solid Waste Management, Public Health Service,
Washington, DC, PHS Report Number 1729, July 10-20, 1967.
10. Unpublished source test data on incinerators, Resources Research,
Incorporated, Reston, VA, 1966-1969.
11. E. R. Kaiser, et al., Modifications to Reduce Emissions from a Flue-Fed
Incinerator, New York University, College of Engineering, Report
Number 552.2, June 1959, p. 40 and 49.
12. Communication between Resources Research, Incorporated, Reston, VA, and
Maryland State Department of Health, Division of Air Quality Control,
Baltimore, MD, 1969.
2.1-14 EMISSION FACTORS 9/88
-------
13. Unpublished data on incinerator testing. U.S. DHEW, PHS, EHS, National
Air Pollution Control Administration, Durham, NC, 1970.
9/88 Solid Waste Disposal 2.1-15
-------
2.5 SEWAGE SLUDGE INCINERATION
2.5.1 Process Description
In sewage sludge incineration, materials generated by wastewater
treatment plants are oxidized to reduce the volume of solid waste.
In the first step in the process, the sludge is dewatered until it is
15 to 30 percent solids so that it will burn without auxiliary fuel.
Dewatered sludge is conveyed to a combustion device where thermal oxidation
occurs. The unburned residual ash is removed from the combustion device,
usually on a continuous basis, and disposed. The exhaust gas stream is
directed to an air pollution control device, typically a wet scrubber.
Approximately 95 percent of sludge incinerators are multiple-hearth and
fluidized-bed designs. Multiple-hearth incinerators are vertically oriented
cylindrical shells containing from 4 to 14 refractory hearths stacked one
above the other. Sludge typically enters at the periphery of the top hearth
and is raked inward by the teeth on a rotating rabble arm to a drop hole
leading to the second hearth. The teeth on the rabble arm above the second
hearth are positioned in the opposite direction to move the sludge
outward. This outside-in, inside-out pattern is repeated on alternate
hearths. Fluidized-bed incinerators also are vertically oriented
cylindrical shells. A bed of sand approximately 0.7-meters (2.5-feet) thick
rests on the grid and is fluidized by air injected through the tuyeres
located at the base of the furnace within a refractory-lined grid. Sludge
is introduced directly into the bed. Temperatures in a multiple-hearth
furnace are 320°C (600°F) in the lower, ash-cooling hearth; 760° to 1100°C
(1400° to 2000°F) in the central combustion hearths; and 540° to 650°C
(1000° to 1200°F) in the upper, drying hearths. Temperatures in a
fluidized-bed reactor are fairly uniform, from 680" to 820°C (1250° to
1500°F). In both types of furnaces, an auxiliary fuel may be required
either during startup or when the moisture content of the sludge is too high
to support combustion.
Electric (infrared) furnaces are the newest of the technologies
currently in use for sludge incineration. The sludge is conveyed into one
end of the horizontally oriented incinerator where it is first dried and
then burned as it travels beneath the infrared heating elements.
Other sludge incineration technologies that are no longer in widespread
use include cyclonic reactors, rotary kilns, and wet oxidation reactors.
Some sludge is coincinerated with refuse.
124
2.5.2 Emissions and Controls ' '
Sludge incinerators have the potential to emit significant quantities
of pollutants to the atmosphere. One of these pollutants is particulate
matter, which is emitted because of the turbulent movement of the combustion
gases with respect to the burning sludge and resultant ash. The particle
size distribution and concentration of the particulate emissions leaving the
incinerator vary widely, depending on the composition of the sludge being
burned and the type and operation of the incineration process.
9/88 Solid Waste Disposal 2.5-1
-------
Total particulate emissions are usually highest for a fluidized-bed
incinerator because the combustion gas velocities required to fluidize the
bed result in entrainment of large quantities of ash in the flue gas.
Particulate emissions from multiple-hearth incinerators are usually less
than those from fluidized-bed incinerators because the agitation of ash and
gas velocity through the bed are lower in the multiple-hearth
incinerators. Electric furnaces have the lowest particulate matter
emissions because the sludge is not stirred or mixed during incineration and
air flows through the unit generally are quite low, resulting in minimal
entrainment.
Incomplete combustion of sludge can result in emissions of intermediate
products (e.g., volatile organic compounds and carbon monoxide). Other
potential emissions include sulfur dioxide, nitrogen oxides, metals, acid
gases, and toxic organic compounds.
Wet scrubbers are commonly used to control particulate and gaseous
(e.g., S02, NOx, CO, and VOC's) emissions from sludge incinerators. There
are two practical reasons for this: (1) a wastewater treatment plant is a
source of relatively inexpensive scrubber water (plant effluent) and (2) a
system for the treatment of the scrubber effluent is available (spent
scrubber water is sent to the head of the treatment plant for solids removal
and pH adjustment). The most widely used scrubber types are venturi and
impingement-tray. Cyclone wet scrubbers and systems combining all three
types of scrubbers are also used.
Pressure drops for venturi, impingement tray, and cyclone scrubbers are
1 to 40 kPa, .0.4 kPa per stage, and 1 to 2 kPa, respectively. Collection
efficiency can range from 60 to 99 percent depending on the scrubber
pressure drop, particle size distribution, and particulate concentration.
Emission factors and emission factor ratings for sludge incinerators
are shown in Table 2.5-1. Table 2.5-2 shows the cumulative particle size
distribution and size specific emission factors for sewage sludge
incinerators. Figures 2.5-1, 2.5-2, and 2.5-3 show the cumulative particle
size distribution and size-specific emission factors for multiple-hearth,
fluidized-bed, and electric infrared incinerators, respectively.
2.5-2 EMISSION FACTORS
9/88
-------
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9/88
Solid Waste Disposal
2.5-3
-------
TABLE 2.5-2. CUMULATIVE PARTICLE SIZE DISTRIBUTION AND SIZE SPECIFIC
EMISSION FACTORS FOR SEWAGE SLUDGE INCINERATORS3
Particle
size.
microns
15
10
5.0
2.5
1.0
0.625
TOTAL
^Reference
Cumulative mass % < stated size
Uncontrolled Controlled
MHD Fbc Ela MHD Pbc Ela
15 NA 43 30 7.7 60
10 NA 30 27 7.3 50
5.3 NA 17 25 6.7 35
2.8 NA 10 22 6.0 25
1.2 NA 6.0 20 5.0 18
0.75 NA 5.0 17 2.7 15
100 100 100 100 100 100
5.
Cumu 1 at i ve
Uncontrol
MH° Fbc
6.0 NA
(12)
4.1 NA
(8.2)
2.1 NA
(4.2)
1.1 NA
(2.2)
0.47 NA
(0.94)
0.30 NA
(0.60)
40 NA
(80)
emission
led
El«
4.3
(8.6)
3.0
(6.0)
1.7
(3.4)
1.0
(2.0)
0.60
(1.2)
0.50
(1.0)
10
(20)
factor, kg/Mg (Ib/ton)
Control led
MHD Fbc
0.12 0.23
(0.24) (0.46)
0.11 0.22
(0.22) (0.44)
0.10 0.20
(0.20) (0.40)
0.09 0.18
(0.18) (0.36)
0.08 0.15
(0.16) (0.30)
0.07 0.08
(0.14) (0.16)
0.40 3.0
(0.80) (6.0)
Ela
1.2
(2.4)
1.0
(2.0)
0.70
(1.4)
0.50
(1.0)
0.35
(0.70)
0.30
(0.60)
2.0
(4.0)
Kfrl = mul-tiple hearth.
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0
100
2.5-4
Figure 2.5-1. Cumulative particle size distribution
size-specific emission factors for
multiple-hearth incinerators.
EMISSION FACTORS
and
9/88
-------
0.1
nr
Pirtlelt dUwtttr (m»)
0.24
0.20
0.08
O.OA
100
60
s
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J-i
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0.12 °
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cn
to
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cu
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Figure 2.5-2. Cumulative particle size distribution and
size-specific emission factors for
fluidized-bed incinerators.
60
f&
60
J4
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u
o
u
y
«9 .
tfl
(0
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Uncontrolled
Illl Ill
1.0 10
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Figure 2.5-3. Cumulative particle size distribution and
size-specific emission factors for
electric (infrared) incinerators.
9/88
Solid Waste Disposal
2.5-5
-------
REFERENCES FOR SECTION 2.5
1. Environmental Regulations and Technology; Use and Disposal of Municipal
Wastewater Sludge, EPA-625/10-84-003, U. S. Environmental Protection
Agency, Cincinnati, OH, September 1984.
2. Seminar Publication; Municipal Wastewater Sludge Combustion Technology,
EPA-625/4-85/015, U. S. Environmental Protection Agency, Cincinnati,
OH, September 1985.
3. Written communication from C. Hester, Midwest Research Institute, Cary,
NC, to J. Crowder, Office of Air Quality Planning and Standards, U. S.
Environmental Protection Agency, Research Triangle Park, NC, September
1985.
4. Control Techniques for Particulate Emissions From Stationary Sources
Volume 1, EPA-45/3-81-005a, U. S. Environmental Protection Agency,
Research Triangle Park, NC, September 1982.
5. Draft report. Emission Factor Documentation for AP-42 Section 2.5—
Sewage Sludge Incineration, Monitoring and Data Analysis Division,
Office of Air Quality Planning and Standards, U. S. Environmental
Protection Agency, Research Triangle Park, NC, September 1987.
2.5-6 EMISSION FACTORS 9/88
-------
4.2.2.7 Polymeric Coating of Supporting Substrates
"Polymeric coating of supporting substrates" is defined as a web coating
process other than paper coating that applies an elastomer or other polymeric
material onto a supporting substrate. Typical substrates include woven, knit,
and nonwoven textiles; fiberglass; leather; yarn; and cord. Examples of
polymeric coatings are natural and synthetic rubber, urethane, polyvinyl
chloride, acrylic, epoxy, silicone, phenolic resins, and nitrocellulose.
Plants have from 1 to more than 10 coating lines. Most plants are commission
coaters where coated substrates are produced according to customer
specifications. Typical products include rainwear, conveyor belts, V-belts,
diaphragms, gaskets, printing blankets, luggage, and aircraft and military
products. This industrial source category has been retitled from "Fabric
Coating" to that listed above to reflect the general use of polymeric coatings
on substrate materials including but not limited to conventional textile
fabric substrates.
Process description ~ - The process of applying a polymeric coating to a
supporting substrate consists of mixing the coating ingredients (including
solvents), conditioning the substrate, applying the coating to the substrate,
drying/curing the coating in a drying oven, and subsequent curing or
vulcanizing if necessary. Figure 4.2.2.7-1 is a schematic of a typical
solvent-borne polymeric coating operation identifying volatile organic
compound (VOC) emission locations. Typical plants have one or two small
(<38 m or 10,000 gallons) horizontal or vertical solvent storage tanks which
are operated at atmospheric pressure, however, some plants have as many as
five. Coating preparation equipment includes the mills, mixers, holding
tanks, and pumps used to prepare polymeric coatings for application. Urethane
coatings typically are purchased premixed and require little or no mixing at
the coating plant. The conventional types of equipment for applying organic
solvent-borne and waterborne coatings include knife-over-roll, dip, and
reverse-roll coaters. Once applied to the substrate, liquid coatings are
solidified by evaporation of the solvent in a steam-heated or direct-fired
oven. Drying ovens usually are of forced-air convection design in order to
maximize drying efficiency and prevent a dangerous localized buildup of vapor
concentration or temperature. For safe operation, the concentration of
organic vapors is usually held between 10 and 25 percent of the lower
explosive limit (LEL). Newer ovens may be designed for concentrations of up
to 50 percent of the LEL through the addition of monitors, alarms, and fail-
safe shutdown systems. Some coatings require subsequent curing or vulcanizing
in separate ovens.
Emissions sources ~ - The significant VOC emission sources in a
polymeric coating plant include the coating preparation equipment, the coating
application and flashoff area, and the drying ovens. Emissions from the
solvent storage tanks and the cleanup area are normally only a small
percentage of the total.
In the mixing or coating preparation area, VOC's are emitted from the
individual mixers and holding tanks during the following operations: filling
of mixers, transfer of the coating, intermittent activities such as changing
9/88 Evaporation Loss Sources 4.2.2.7-1
-------
4.2.2.7-2
EMISSION FACTORS
9/88
-------
the filters in the holding tanks, and mixing (if mix equipment is not equipped
with tightly fitting covers). The factors affecting emissions in the mixing
area include tank size, number of tanks, solvent vapor pressure, throughput,
and the design and performance of tank covers.
Emissions from the coating application area result from the evaporation
of solvent around the coating application equipment during the application
process and from the exposed substrate as it travels from the coater to the
drying oven entrance (flashoff). The factors affecting emissions are the
solvent content of the coating, line width and speed, coating thickness,
volatility of the solvent(s), temperature, distance between coater and oven,
and air turbulence in the coating area,
Emissions from the drying oven result from the fraction of the remaining
solvent that is driven off in the oven. The factors affecting uncontrolled
emissions are the solvent content of the coating and the amount of solvent
retained in the finished product. Fugitive emissions due to the opening of
oven doors also may be significant in some operations. Some plasticizers and
reaction by-products may be emitted if the coating is subsequently cured or
vulcanized. However, emissions from the curing or vulcanizing of the coating
are usually negligible compared to the total emissions from the operation.
Solvent type and quantity are the common factors affecting emissions from
all the operations in a polymeric coating facility. The rate of evaporation
or drying is dependent upon solvent vapor pressure at a given temperature and
concentration. The most commonly used organic solvents are toluene, dimethyl
formamide (DMF), acetone, methyl ethyl ketone (MEK), isopropyl alcohol,
xylene, and ethyl acetate. Factors affecting solvent selection are cost,
solvency, toxicity, availability, desired rate of evaporation, ease of use
after solvent recovery, and compatibility with solvent recovery equipment.
1 2 U —7
Emissions control ' ' - A control system for evaporative emissions
consists of two components: a capture device and a control device. The
efficiency of the control system is determined by the efficiencies of the two
components.
A capture device is used to contain emissions from a process operation
and direct them to a stack or to a control device. Covers, vents, hoods, and
partial and total enclosures are alternative capture devices used on coating
preparation equipment. Hoods and partial and total enclosures are typical
capture devices for use in the coating application area. A drying oven can be
considered a capture device because it both contains and directs VOC emissions
from the process. The efficiency of capture devices is variable and depends
upon the quality of design and the level of operation and maintenance.
A control device is any equipment that has as its primary function the
reduction of emissions. Control devices typically used in this industry are
carbon adsorbers, condensers, and incinerators. Tightly fitting covers on
coating preparation equipment may be considered both capture and control
devices.
Carbon adsorption units use activated carbon to adsorb VOC's from a gas
stream; the VOC's are later recovered from the carbon. Two types of carbon
9/88 Evaporation Loss Sources 4.2.2.7-3
-------
adsorbers are available: fixed bed and fluidized bed. Fixed-bed carbon
adsorbers are designed with a steam-stripping technique to recover the VOC
material and regenerate the activated carbon. The fluidized-bed units used in
this industry are designed to use nitrogen for VOC vapor recovery and carbon
regeneration. Both types achieve typical VOC control efficiencies of
95 percent when properly designed, operated, and maintained.
Condensation units control VOC emissions by cooling the solvent laden gas
to the dew point of the solvent(s) and collecting the droplets. There are two
condenser designs commercially available: nitrogen (inert gas) atmosphere and
air atmosphere. These systems differ in the design and operation of the
drying oven (i.e., use of nitrogen or air in the oven) and in the method of
cooling the solvent laden air (i.e., liquified nitrogen or refrigeration).
Both design types can achieve VOC control efficiencies of 95 percent.
Incinerators control VOC emissions through oxidation of the organic
compounds into carbon dioxide and water. Incinerators used to control VOC
emissions may be of thermal or catalytic design and may use primary or
secondary heat recovery to reduce fuel costs. Thermal incinerators operate at
approximately 890°C (1600°F) to assure oxidation of the organic compounds.
Catalytic incinerators operate in the range of 315° to 430°C (600° to 800°F)
while using a catalyst to achieve comparable oxidation of VOC's. Both design
types achieve a typical VOC control efficiency of 98 percent.
Tightly fitting covers control VOC emissions from mix vessels by reducing
evaporative losses. Airtight covers can be fitted with conservation vents to
avoid excessive internal pressure or vacuum. The parameters affecting the
efficiency of these controls are solvent vapor pressure, cyclic temperature
change, tank size, throughput, and the pressure and vacuum settings on the
conservation vents. A good system of tightly fitting covers on mixing area
vessels is estimated to reduce emissions by approximately 40 percent. Control
efficiencies of 95 or 98 percent can be obtained by directing the captured
VOC's to an adsorber, condenser, or incinerator.
When the efficiencies of the capture device and control device are known,
the efficiency of the control system can be computed by the following
equation:
(capture efficiency)x(control efficiency)=(control system efficiency).
The terms of this equation are fractional efficiencies rather than
percentages. For instance, a system of hoods delivering 60 percent of VOC
emissions to a 90 percent efficient carbon adsorber would result in a control
system efficiency of 54 percent (0.60x0.90=0.54). Table 4.2.2.7-1 summarizes
the control system efficiencies that may be used in the absence of measured
data on mix equipment and coating operations.
4.2.2.7-4 EMISSION FACTORS 9/88
-------
TABLE 4.2.2.7-1. SUMMARY OF CONTROL EFFICIENCIES*
Overall control
Control technology efficiency, %"
Coating Preparation Equipment
Uncontrolled 0
Sealed covers with conservation vents 40
Sealed covers with carbon adsorber/condenser _ 95
Coating Operation0
Local ventilation with carbon adsorber/condenser 81
Partial enclosure with carbon adsorber/condenser 90
Total enclosure with carbon adsorber/condenser 93
Total enclosure with incinerator 96
aReference 1. To be used in the absence of measured data.
To be applied to uncontrolled emissions from indicated process area, not
from entire plant.
clncludes coating application/flashoff area and drying oven.
1 l4_8
Emissions estimation techniques ' - In this diverse industry,
realistic estimates of emissions require solvent usage data. Due to the wide
variation found in coating formulations, line speeds, and products, no
meaningful inferences can be made based simply on the equipment present.
Plant-wide emissions can be estimated by performing a liquid material
balance in uncontrolled plants and in those where VOC's are recovered for
reuse or sale. This technique is based on che assumption that all solvent
purchased replaces VOC's which have been emitted. Any identifiable and
quantifiable side streams should be subtracted from this total. The general
formula for this is:
•\
r solvent i r quantifiable •>_/• VOC
^•purchased' ^-solvent output1^ ^emitted''*
The first term encompasses all solvent purchased including thinners, cleaning
agents, and the solvent content of any premixed coatings as well as any
solvent directly used in coating formulation. From this total, any
quantifiable solvent outputs are subtracted. These outputs may include
solvent retained in the finished product, reclaimed solvent sold for use
outside the plant, and solvent contained in waste streams. Reclaimed solvent
which is reused at the plant is not subtracted.
9/88 Evaporation Loss Sources 4.2.2.7-5
-------
The advantages of this method are that it is based on data that are
usually readily available, it reflects actual operations rather than
theoretical steady state production and control conditions, and it includes
emissions from all sources at the plant. However, care should be taken not to
apply this method over too short a time span. Solvent purchases, production,
and waste removal occur in their own cycles, which may not coincide exactly.
Occasionally, a liquid material balance may be possible on a smaller
scale than the entire plant. Such an approach may be feasible for a single
coating line or group of lines served by a dedicated mixing area and a
dedicated control and recovery system. In this case, the computation begins
with total solvent metered to the mixing area instead of solvent purchased.
Reclaimed solvent is subtracted from this volume whether or not it is reused
onsite. Of course, other solvent input and output streams must be accounted
for as previously indicated. The difference between total solvent input and
total solvent output is then taken to be the quantity of VOC's emitted from
the equipment in question.
The configuration of meters, mixing areas, production equipment, and
controls usually will not make this approach possible. In cases where control
devices destroy potential emissions or a liquid material balance is
inappropriate for other reasons, plant-wide emissions can be estimated by
summing the emissions calculated for specific areas of the plant. Techniques
for these calculations are presented below.
Estimating VOC emissions from a coating operation (application/flashoff
area and drying oven) starts with the assumption that the uncontrolled
emission level is equal to the quantity of solvent contained in the coating
applied. In other words, all the VOC in the coating evaporates by the end of
the drying process. This quantity should be adjusted downward to account for
solvent retained in the finished product in cases where it is quantifiable and
significant.
Two factors are necessary to calculate the quantity of solvent applied:
the solvent content of the coating and the quantity of coating applied.
Coating solvent content can be directly measured using EPA Reference
Method 24. Alternative ways of estimating the VOC content include the use of
either data on coating formulation that are usually available from the plant
owner/operator or premixed coating manufacturer or, if these cannot be
obtained, approximations based on the information in Table 4.2.2.7-2. The
amount of coating applied may be directly metered. If it is not, it must be
determined from production data. These should be available from the plant
owner/operator. Care should be taken in developing these two factors to
assure that they are in compatible units.
When an estimate of uncontrolled emissions is obtained, the controlled
emissions level is computed by applying a control system efficiency factor:
/•uncontrolled i r. , _ rr. . i r VOC i
I „/,« Jxll-control system efficiencyl = l . ,1.
*• VOC ' ^ J '' '•emitted'
4.2.2.7-6 EMISSION FACTORS 9/88
-------
TABLE 4.2.2.7-2. SOLVENT AND SOLIDS CONTENT OF POLYMERIC COATINGS3
Typical percentage, by weight
Polymer type % solvent % solids
Rubber
Urethanes
Acrylics
Vinylc
Vinyl Plastisol
Organisol
Epoxies
Silicone
Nitrocellulose
50-70
50-60
b
60-80
5
15-40
30-40
50-60
70
30-50
40-50
50
20-40
95
60-85
60-70
40-50
30
Reference 1.
Organic solvents are generally not used in the formulation of acrylic
coatings. Therefore, the solvent content for acrylic coatings represents
nonorganic solvent use (i.e., water).
cSolvent-borne vinyl coating.
As previously explained, the control system efficiency is the product of the
efficiencies of the capture device and the control device. If these values
are not known, typical efficiencies for some combinations of capture and
control devices are presented in Table 4.2.2.7-1. It is important to note
that these control system efficiencies are applicable only to emissions that
occur within the areas served by the systems. Emissions from such sources as
process wastewater or discarded waste coatings may not be controlled at all.
In cases where emission estimates from the mixing area alone are desired,
a slightly different approach is necessary. Here, uncontrolled emissions will
be only that portion of total solvent that evaporates during the mixing
process. A liquid material balance across the mixing area (i.e., solvent
entering minus solvent content of coating applied) would provide a good
estimate. In the absence of any measured value, it may be assumed that
approximately 10 percent of the total solvent entering the mixing area is
emitted during the mixing process, but this can vary widely. When an estimate
of uncontrolled mixing area emissions has been made, the controlled emission
rate can be calculated as discussed previously. Table 4.2.2.7-1 lists typical
overall control efficiencies for coating mix preparation equipment.
Solvent storage tanks of the size typically found in this industry are
regulated by only a few States and localities. Tank emissions are generally
9/88 Evaporation Loss Sources 4.2.2.7-7
-------
small (<125 kg/yr). If an estimate of emissions is desired, it can be
computed using the equations, tables, and figures provided in Section 4.3.2.
REFERENCES FOR SECTION 4.2.2.7
1. Polymeric Coating of Supporting Substrates—Background Information for
Proposed Standards, EPA-450/3-85-022a, U. S. Environmental Protection
Agency, Research Triangle Park, NC, October 1985.
2. Control of Volatile Organic Emissions From Existing Stationary Sources—
Volume II; Surface Coating of Cans, Coils, Paper, Fabrics, Automobiles,
and Light Duty Trucks, EPA-450/2-77-008, U. S. Environmental Protection
Agency, Research Triangle Park, NC, May 1977.
3. E. J. Maurer, "Coating Operation Equipment Design and Operating
Parameters," Memorandum to Polymeric Coating of Supporting Substrates
File, MRI, Raleigh, NC, April 23, 1984.
4. Control of Volatile Organic Emissions From Existing Stationary Sources—
Volume I; Control Methods for Surface-Coating Operations, EPA-450/2-76-
028, U. S. Environmental Protection Agency, Research Triangle Park, NC,
November 1976.
5. G. Crane, Carbon Adsorption for VOC Control, U. S. Environmental
Protection Agency, Research Triangle Park, NC, January 1982.
6. D. Moscone, "Thermal Incinerator Performance for NSPS," Memorandum, Office
of Air Quality Planning and Standards, U. S. Environmental Protection
Agency, Research Triangle Park, NC, June 11, 1980.
7. D. Moscone, "Thermal Incinerator Performance for NSPS, Addendum,"
Memorandum, Office of Air Quality Planning and Standards, U. S.
Environmental Protection Agency, Research Triangle Park, NC, July 22,
1980.
8. C. Beall, "Distribution of Emissions Between Coating Mix Preparation Area
and the Coating Line," Memorandum to Magnetic Tape Coating Project File,
MRI, Raleigh, NC, June 22, 1984.
4.2.2.7-8 . EMISSION FACTORS
9/88
-------
4.12 POLYESTER RESIN PLASTICS PRODUCT FABRICATION
4.12.1 General Description1"2
A growing number of products are fabricated from liquid polyester resin
reinforced with glass fibers and extended with various inorganic filler
materials such as calcium carbonate, talc, mica or small glass spheres.
These composite materials are often referred to as fiberglass reinforced
plastic (FRP), or simply "fiberglass". The Society Of The Plastics Industry
designates these materials as "reinforced plastics/composites" (RP/C). Also,
advanced reinforced plastics products are now formulated with fibers other
than glass, such as carbon, aramid and aramid/carbon hybrids. In some
processes, resin products are fabricated without fibers. One major product
using resins with fillers but no reinforcing fibers is^the synthetic marble
used in manufacturing bathroom countertops, sinks and related items. Other
applications of nonreinforced resin plastics include automobile body filler,
bowling balls and coatings.
Fiber reinforced plastics products have a wide range of application in
industry, transportation, home and recreation. Industrial uses include stor-
age tanks, skylights, electrical equipment, ducting, pipes, machine compo-
nents, and corrosion resistant structural and process equipment. In
transportation, automobile and aircraft applications are increasing rapidly.
Home and recreational items include bathroom tubs and showers, boats (build-
ing and repair), surfboards and skis, helmets, swimming pools and hot tubs,
and a variety of sporting goods.
The thermosetting polyester resins considered here are complex polymers
resulting from the cross-linking reaction of a liquid unsaturated polyester
with a vinyl type monomer, most often styrene. The unsaturated polyester is
formed from the condensation reaction of an unsaturated dibasic acid or
anhydride, a saturated dibasic acid or anhydride, and a polyfunctional
alcohol. Table 4.12-1 lists the most common compounds used for each compo-
nent of the polyester "backbone", as well as the principal cross-linking
monomers. The chemical reactions that form both the unsaturated polyester
and the cross-linked polyester resin are shown in Figure 4.12-1. The emis-
sion factors presented here apply to fabrication processes that use the
finished liquid resins (as received by fabricators from chemical manufac-
turers), and not to the chemical processes used to produce these resins.
(See Chapter 5, Chemical Process Industry.)
In order to be used in the fabrication of products, the liquid resin
must be mixed with a catalyst to initiate polymerization into a solid thermo-
set. Catalyst concentrations generally range from 1 to 2 percent by original
weight of resin; within certain limits, the higher the catalyst concentration,
the faster the cross-linking reaction proceeds. Common catalysts are organic
peroxides, typically methyl ethyl ketone peroxide or benzoyl peroxide.
Resins may contain inhibitors, to avoid self curing during resin storage,
and promoters, to allow polymerization to occur at lower temperatures.
9/88 Evaporation Loss Sources 4.12-1
-------
TABLE 4.12-1. TYPICAL COMPONENTS OF RESINS
To Form the Unsaturated Polyester
Unsaturated Acids Saturated Acids Polyfunctional Alcohols
Maleic anhydride Phthalic anhydride Propylene glycol
Fumaric acid Isophthalic acid Ethylene glycol
Adipic acid Diethylene glycol
Dipropylene glycol
Neopentyl glycol
Pentaerythritol
Cross-linking Agents (Monomers)
Styrene
Methyl methacrylate
Vinyl toluene
Vinyl acetate
Diallyl phthalate
Acrylamide
2-ethyl hexylacrylate
The polyester resin/fiberglass industry consists of many small faci-
lities (such as boat repair and small contract firms) and relatively few
large firms that consume the major fraction of the total resin. Resin
usage at these operations ranges from less than 5,000 kilograms per year
to over 3 million kilograms per year.
Reinforced plastics products are fabricated using any of several
processes, depending on their size, shape and other desired physical
characteristics. The principal processes include hand layup, spray layup
(sprayup), continuous lamination, pultrusion, filament winding and various
closed molding operations.
Hand layup, using primarily manual techniques combined with open
molds, is the simplest of the fabrication processes. Here, the reinforce-
ment is manually fitted to a mold wetted with catalyzed resin mix, after
which it is saturated with more resin. The reinforcement is in the form
of either a chopped strand mat, a woven fabric or often both. Layers of
reinforcement and resin are added to build the desired laminate thickness.
Squeegees, brushes and rollers are used to smooth and compact each layer
as it is applied. A release agent is usually first applied to the mold
to facilitate removal of the composite. This is often a wax, which can
be treated with a water soluble barrier coat such as polyvinyl alcohol to
promote paint adhesion on parts that are to be painted. In many operations,
4.12-2 EMISSION FACTORS 9/88
-------
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Evaporation Loss Sources
4.12-3
-------
the mold is first sprayed with gel coat, a clear or pigmented resin mix
that forms the smooth outer surface of many products. Gel coat spray
systems consist of separate sources of resin and catalyst, with an airless
hand spray gun that mixes them together into an atomized resin/catalyst
stream. Typical products are boat hulls and decks, swimming pools, bathtubs
and showers, electrical consoles and automobile components.
Spray layup, or "sprayup", is another open mold process, differing from
hand layup in that it uses mechanical spraying and chopping equipment for
depositing the resin and glass reinforcement. This process allows a greater
production rate and more uniform parts than does hand layup, and often uses
more complex molds. As in hand layup, gel coat is frequently applied to the
mold before fabrication to produce the desired surface qualities. It is
common practice to combine hand layup and sprayup operations.
For the reinforced layers, a device is attached to the sprayer system to
chop glass fiber "roving" (uncut fiber) into predetermined lengths and pro-
ject it to merge with the resin mix stream. The stream precoats the chop,
and both are deposited simultaneously to the desired layer thickness on the
mold surface (or on the gel coat that was applied to the mold). Layers are
built up and rolled out on the mold as necessary to form the part. Products
manufactured by sprayup are similar to those made by hand layup, except that
more uniform and complex parts can generally be produced more efficiently with
sprayup techniques. However, compared to hand layup, more resin generally is
used to produce similar parts by spray layup because of the inevitable over-
spray of resin during application.
Continuous lamination of reinforced plastics materials involves impreg-
nating various reinforcements with resins on an in-line conveyor. The
resulting laminate is cured and trimmed as it passes through the various con-
veyor zones. In this process, the resin mix is metered onto a bottom carrier
film, using a blade to control thickness. This film, which defines the pa-
nel's surface, is generally polyester, cellophane or nylon, and may have a
smooth, embossed or matte surface. Methyl methacrylate is sometimes used as
the cross-linking agent, either alone or in combination with styrene, to
increase strength and weather resistance. Chopped glass fibers free-fall
into the resin mix and are allowed to saturate with resin, or "wet out". A
second carrier film is applied on top of the panel before subsequent forming
and curing. The cured panel is then stripped of its films, trimmed and cut
to the desired length. Principal products include translucent industrial sky-
lights and greenhouse panels, wall and ceiling liners for food areas, garage
doors and cooling tower louvers. Figure 4.12-2 shows the basic elements of
a continuous laminating production line.
Pultrusion, which can be thought of as extrusion by pulling, is used to
produce continuous cross-sectional llneals similar to those made by extrud-
ing metals such as aluminum. Reinforcing fibers are pulled through a liquid
resin mix bath and into a long machined steel die, where heat initiates an
exothermic reaction to polymerize the thermosetting resin matrix. The compo-
site profile emerges from the die as a hot, constant cross-sectional that
cools sufficiently to be fed into a clamping and pulling mechanism. The pro-
duct can then be cut to desired lengths. Example products include electrical
insulation materials, ladders, walkway gratings, structural supports, and
rods and antennas.
4.12-4 EMISSION FACTORS 9/88
-------
Resin metering device -*
Cure area
Cross cut saw or shear
rewind
"9 Ed9e'T o
Inspection area
Stacking device II ii
Figure 4.12-2. Typical continuous lamination production process.
Filament winding is the process of laying a band of resin impregnated
fibers onto a rotating mandrel surface in a precise geometric pattern, and
curing them to form the product. This is an efficient method of producing
cylindrical parts with optimum strength characteristics suited to the
specific design and application. Glass fiber is most often used for the
filament, but aramid, graphite, and sometimes boron and various metal wires
may be used. The filament can be wetted during fabrication, or previously
impregnated filament ("prepreg") can be used. Figure 4.12-3 shows the
filament winding process, and indicates the three most common winding
patterns. The process illustration depicts circumferential winding, while
the two smaller pictures show helical and polar winding. The various wind-
ing patterns can be used alone or in combination to achieve the desired
strength and shape characteristics. Mandrels are made of a wide variety of
materials and, in some applications, remain inside the finished product as
a liner or core. Example products are storage tanks, fuselages, wind
turbine and helicopter blades, and tubing and pipe.
Helical Winding
Polar Winding
Figure 4.12-3. Typical filament winding process.-^
9/88
Evaporation Loss Sources
4.12-5
-------
Closed, such as compression or injection, molding operations involve
the use of two matched dies to define the entire outer surface of the part.
When closed and filled with a resin mix, the matched die mold is subjected
to heat and pressure to cure the plastic. For the most durable production
configuration, hardened metal dies are used (matched metal molding).
Another closed molding process is vacuum or pressure bag molding. In bag
molding, a hand layup or sprayup is covered with a plastic film, and vacuum
or pressure is applied to rigidly define the part and improve surface
quality. The range of closed molded parts includes tool and appliance
housings, cookware, brackets and other small parts, and automobile body and
electrical components.
Synthetic marble casting, a large segment of the resin products indus-
try, involves production of bathroom sinks, vanity tops, bathtubs and
accessories using filled resins that have the look of natural marble. No
reinforcing fibers are used in these products. Pigmented or clear gel coat
can either be applied to the mold itself or sprayed onto the product after
casting to simulate the look of natural polished marble. Marble casting
can be an open mold process, or it may be considered a semiclosed process
if cast parts are removed from a closed mold for subsequent gel coat spray-
ing.
4.12.2 Emissions And Controls
Organic vapors consisting of volatile organic compounds (VOC) are emit-
ted from fresh resin surfaces during the fabrication process and from the
use of solvents (usually acetone) for cleanup of hands, tools, molds and
spraying equipment. Cleaning solvent emissions can account for over 36
percent of the total plant VOC emissions.^ There also may be some release
of particulate emissions from automatic fiber chopping equipment, but these
emissions have not been quantified.
Organic vapor emissions from polyester resin/fiberglass fabrication
processes occur when the cross-linking agent (monomer) contained in the
'liquid resin evaporates into the air during resin application and curing.
Styrene, methyl methacrylate and vinyl toluene are three of the principal
monomers used as cross-linking agents. Styrene is by far the most common.
Other chemical components of resins are emitted only at trace levels,
because they not only have low vapor pressures but also are substantially
converted to polymers.-^"6
Since emissions result from evaporation of monomer from the uncured
resin, they depend upon the amount of resin surface exposed to the air and
the time of exposure. Thus, the potential for emissions varies with the
manner in which the resin is mixed, applied, handled and cured. These fac-
tors vary among the different fabrication processes. For example, the
spray layup process has the highest potential for VOC emissions because the
atomization of resin into a spray creates an extremely large surface area
from which volatile monomer can evaporate. By contrast, the emission
potential in synthetic marble casting and closed molding operations is
considerably lower, because of the lower monomer content in the casting
resins (30 to 38 percent, versus about 43 percent) and of the enclosed
nature of these molding operations. It has been found that styrene
4.12-6 EMISSION FACTORS 9/88
-------
evaporation increases with increasing gel time, wind speed and ambient
temperature, and that increasing the hand rolling time on a hand layup or
sprayup results in significantly higher styrene losses. 1 Thus, production
changes that lessen the exposure of fresh resin surfaces to the air should
be effective in reducing these evaporation losses.
In addition to production changes, resin formulation can be varied to
affect the VOC emission potential, In general, a resin with lower monomer
content should produce lower emissions. Evaluation tests with low-styrene-
emission laminating resins having a 36 percent styrene content found a 60
to 70 percent decrease in emission levels, compared to conventional resins
(42 percent styrene), with no sacrifice in the physical properties of the
laminate. Vapor suppressing agents also are sometimes added to resins to
reduce VOC emissions. Most vapor suppressants are paraffin waxes, stearates
or polymers of proprietary composition, constituting up to several weight
percent of the mix. Limited laboratory and field data indicate that vapor
suppressing resins reduce styrene losses by 30 to 70 percent. °
Emission factors for several fabrication processes using styrene con-
tent resins have been developed from the results of facility source tests (B
Rating) and laboratory tests (C Rating), and through technology transfer
estimations (D Rating).* Industry experts also provided additional infor-
mation that was used to arrive at the final factors presented in Table
4,12-2.6 Since the styrene content varies over a range of approximately 30
to 50 weight percent, these factors are based on the quantity of styrene
monomer used in the process, rather than on the total amount of resin used.
The factors for vapor-suppressed resins are typically 30 to 70 percent of
those for regular resins. The factors are expressed as ranges, because of
the observed variability in source and laboratory test results and of the
apparent sensitivity of emissions to process parameters.
Emissions should be calculated using actual resin monomer contents.
When specific information about the percentage of styrene is unavailable,
the representative average values in Table 4.12-3 should be used. The sam-
ple calculation illustrates the application of the emission factors.
Sample Calculation - A fiberglass boat building facility
consumes an average of 250 kg per day of styrene-containing
resins using a combination of hand layup (75%) and spray layup
(25%) techniques. The laminating resins for hand and spray lay-
up contain 41.0 and 42.5 weight percent, respectively, of styrene.
The resin used for hand layup contains a vapor-suppressing agent.
From Table 4.12-2, the factor for hand layup using a vapor-suppresed
resin is 2 - 7 (0.02 to 0.07 fraction of total styrene emitted);
the factor for spray layup is 9 - 13 (0.09 to 0.13 fraction emit-
ted). Assume the midpoints of these emission factor ranges.
Total VOC emissions are:
(250 kg/day) [(0.41)(0.045)(0.75) + (0.425)(0.11)(0.25)]
= 6.4 kg/day.
9/88 Evaporation Loss Sources 4.12-7
-------
TABLE 4.12-2. EMISSION FACTORS FOR UNCONTROLLED POLYESTER RESIN
PRODUCT FABRICATION PROCESSES3
(100 x mass of VOC emitted/mass of monomer input)
Process
Hand layup
Spray layup
Continuous lamination
Pultrusiond
Filament winding6
Marble casting
Closed moldingg
Resin
NVS
5-10
9-13
4-7
4-7
5-10
1 - 3
1 - 3
VSb
2-7
3-9
1 - 5
1 - 5
2-7
1 - 2
1 - 2
Emission
Factor
Rating
C
B
B
D
D
B
D
Gel Coat
NVS
26 - 35
26 - 35
c
c
c
f
c
VSb
8-25
8-25
c
c
c
f
c
Emission
Factor
Rating
D
B
—
—
—
—
—
aReference 9. Ranges represent the variability of processes and sensiti-
vity of emissions to process parameters. Single value factors should be
selected with caution. NVS = nonvapor-suppressed resin. VS = vapor-sup-
pressed resin.
^Factors are 30-70% of those for nonvapor-suppressed resins.
cGel coat is not normally used in this process.
^Resin factors for the continuous lamination process are assumed to apply.
eResin factors for the hand layup process are assumed to apply.
fFactors unavailable. However, when cast parts are subsequently sprayed
with gel coat, hand and spray layup gel coat factors are assumed to apply.
gResin factors for marble casting, a semiclosed process, are assumed to
apply.
TABLE 4.12-3. TYPICAL RESIN STYRENE PERCENTAGES
Resin Application
Resin Styrene Content3
(wgt. %)
Hand layup
Spray layup
Continuous lamination
Filament winding
Marble casting
Closed molding
Gel coat
43
43
40
40
32
35
35
4.12-8
aMay vary by at least +5 percentage points.
EMISSION FACTORS
9/88
-------
Emissions from use of gel coat would be calculated in the same manner.
If the monomer content of the resins were unknown, a representative value
of 43 percent could be selected from Table 4.12-3 for this process combina-
tion. It should be noted that these emissions represent evaporation of
styrene monomer only, and not of acetone or other solvents used for clean-
up.
In addition to process changes and materials substitution, add-on con-
trol equipment can be used to reduce vapor emissions from styrene resins.
However, control equipment is infrequently used at RP/C fabrication facili-
ties, due to low exhaust VOC concentrations and the potential for contami-
nation of adsorbent materials. Most plants use forced ventilation techni-
ques to reduce worker exposure to styrene vapors, but vent the vapors
directly to the atmosphere with no attempt at collection. At one contin-
uous lamination facility where incineration was applied to vapors vented
from the impregnation table, a 98.6 percent control efficiency was mea-
sured. 1 Carbon adsorption, absorption and condensation also have been
considered for recovering styrene and other organic vapors, but these tech-
niques have not been applied to any significant extent in this industry.
Emissions from cleanup solvents can be controlled through good house-
keeping and use practices, reclamation of spent solvent, and substitution
with water based solvent substitutes.
References for Section 4.12
1. M. B. Rogozen, Control Techniques for Organic Gas Emissions from Fiber-
glass Impregnation and Fabrication Processes, ARB/R-82/165, California
Air Resources Board, Sacramento, CA, (NTIS PB82-251109), June 1982.
2. Modern Plastics Encyclopedia, 1986-1987, J33 (10A), October 1986.
3. C. A. Brighton, G. Pritchard and G. A. Skinner, Styrene Polymers;
Technology and Environmental Aspects, Applied Science Publishers, Ltd.,
London, 1979.
4. M. Elsherif, Staff Report, Proposed Rule 1162 - Polyester Resin
Operations, South Coast Air Quality Management District, Rule Develop-
ment Division, El Monte, CA, January 23, 1987.
5. M. S. Crandall, Extent of Exposure to Styrene in the Reinforced Plastic
Boat Making Industry, Publication No. 82-110, National Institute For
Occupational Safety And Health, Cincinnati, OH, March 1982.
6. Written communication from R. C. Lepple, Aristech Chemical Corporation,
Polyester Unit, Linden, NJ, to A. A. MacQueen, U.S. Environmental Pro-
tection Agency, Research Triangle Park, NC, September 16, 1987.
7. L. Walewski and S. Stockton, "Low-Styrene-Emission Laminating Resins
Prove It in the Workplace", Modern Plastics, 62(8):78-80, August 1985.
9/88 Evaporation Loss Sources 4.12-9
-------
8. M. J. Duffy, "Styrene Emissions - How Effective Are Suppressed
Polyester Resins?", Ashland Chemical Company, Dublin, OH, presented
at 34th Annual Technical Conference, Reinforced Plastics/Composites
Institute, The Society Of The Plastics Industry, 1979.
9. G. A. LaFlam, Emission Factor Documentation for AP-42 Section 4.12;
Polyester Resin Plastics Product Fabrication, Pacific Environmental
Services, Inc., Durham, NC, November 1987.
4.12-10 EMISSION FACTORS 9/88
-------
5.15 SOAP AND DETERGENTS
5.15.1 Soap Manufacture
Process Description^ - Soap may be manufactured by either 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, method
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", which is precipitating the soft curds of soap
out of the aqueous lye solution by adding sodium chloride (salt). The soap so-
lution then is washed to remove glycerine and color body impurities, to leave
the "neat" soap to form during a settling period. Continuous alkaline saponi-
fication 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 varied forms as liquid,
powder, granule, chip, flake or bar.
Emissions And Controls^ - The main atmospheric pollution problem in the manu-
facture 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, inciner-
ating the remaining compounds. Odors emanating from the spray dryer may be
controlled by scrubbing with an acid solution.
Blending, mixing, drying, packaging and other physical operations all may
involve 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
other finishing operations can be controlled by dry filters such as baghouses.
The large sizes of the particulate from soap drying mean that high efficiency
cyclones installed in series can give satisfactory control.
5.15.2 Detergent Manufacture
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 sulfa-
tion by sulfuric acid, of either 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 a spray dryer. The slurry is sprayed at
high pressure 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 air introduced
at the bottom. The detergent granules thus formed are conveyed mechanically
or by air from the tower to a mixer, to incorporate additional dry or liquid
ingredients, and finally to packaging and storage.
9/88 Chemical Process Industry 5.15-1
-------
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5.15-2
EMISSION FACTORS
9/88
-------
Emissions And Controls^ •* - In the batching and mixing of fine dry ingredients
to form slurry, dust emissions are generated at scale hoppers, mixers and
crutchers. Fabric filters are used, not only to reduce or to eliminate the
dust emissions but also to recover raw materials. Emission factors for parti-
culate from spray drying operations are shown in Table J.15-1. Tabie 5.15-2
and Figure 5.15-2 give size specific particulate emission factors for operations
on which information is available. 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 it back to the crutcher. Cyclonic
impinged scrubbers are used, in parallel, to collect the particulate from a
scrubbing slurry and to recycle it to the crutcher. Secondary collection equip-
ment is used to collect the fine particulate that has 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, fabric filters provide the best control.
TABLE 5.15-1. PARTICULATE EMISSION FACTORS FOR DETERGENT SPRAY DRYING^
EMISSION FACTOR RATING: B
Particulate
Control
device
Uncontrolled
Cyclone^
Cyclone
w/Spray chamber
w/Packed scrubber
w/Venturi scrubber
w/Wet scrubber
w/Wet scrubber/ESP
Fabric filter
Efficiency
-
85
92
95
97
99
99.9
99
kg/Mg of
product
45
7
3.5
2.5
1.5
0.544
0.023
0.54
Ib/ton of
product
90
14
7
1.08
0.046
'.1
aReferences 4-8. VOC emissions data have not been reported in the
literature. Dash = not applicable. ESP = electrostatic precipitator.
t>Some type of primary collector, such as a cyclone, is considered integral
to a spray drying system.
9/88 Chemical Process Industry 5.15-3
-------
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5.15-4
EMISSION FACTORS
9/88
-------
References for Section 5.15
1. Air Pollutant Emission Factors, APTD-0923, U. S. Environmental Protection
Agency, Research Triangle Park, NC, April 1970.
2. Air Pollution Engineering Manual, AP-40, U. S. Environmental Protection
Agency, Research Triangle Park, NC, May 1973. Out Of Print.
3. Source Category Survey; Detergent Industry, EPA-450/3-80-030, U. S, Envi-
ronmental Protection Agency, Research Triangle Park, NC, June 1980.
4. A. H. Phelps, "Air Pollution Aspects Of Soap And Detergent Manufacture",
Journal Of The Air Pollution Control Association, j^CS):505-507, August
1967.
5. R. N. Shreve, Chemical Process Industries, Third Edition, New York, McGraw-
Hill, 1967.
6. G. P. Larsen, et al. , "Evaluating Sources Of Air Pollution", Industrial And
Engineering Chemistry. 4_5:1070-1074, May 1953.
7. P. Y. McCormick, et al. , "Gas-solid Systems", Chemical Engineer's Handbook,
McGraw-Hill Book Company, New York, 1963.
8. Communication from Maryland State Department Of Health, Baltimore, MD,
November 1969.
9. Emission Test Report, Witco Chemical Corporation, Patterson, NJ, EMB-73-
DET-6, U. S. Environmental Protection Agency, Research Triangle Park, NC,
July 1973.
10. Emission Test Report, Lever Brothers, Los Angeles, CA, EMB-73-DET-2, U. S.
Environmental Protection Agency, Research Triangle Park, NC, April 1973.
11. Emission Test Report, Procter and Gamble, Augusta, GA, EMB-72-MM-10, U. S.
Environmental Protection Agency, Research Triangle Park, NC, June 1972.
12. Emission Test Report, Procter and Gamble, Long Beach, CA, EMB-73-DET-4,
U. S. Environmental Protection Agency, Research Triangle Park, NC, April
1973.
13. Emission Test Report, Colgate-Palmolive, Jeffersonville, IN, EMB-73-DET-7,
U. S. Environmental Protection Agency, Research Triangle Park, NC, June
1973.
14. Emission Test Report, Lever Brothers, Edgewater, NJ, EMB-72-MM-9, U. S.
Environmental Protection Agency, Research Triangle Park, NC, June 1972.
9/88 Chemical Process Industry 5.15-5
-------
6.4 GRAIN ELEVATORS AND PROCESSING PLANTS
6.4.1 General1"3
Grain elevators are facilities at which grains are received, stored, and
then distributed for direct use, process manufacturing, or export. They can
be classified as either "country" or "terminal" elevators, with terminal
elevators further categorized as inland or export (marine) types. Operations
other than storage often are performed at elevators, such as cleaning, drying
and blending. The principal grains handled include wheat, milo, corn, oats,
rice and soybeans.
Country elevators are generally smaller elevators that receive grain by
truck directly from farms during the harvest season. These elevators some-
times clean or dry grain before it is transported to terminal elevators or
processors. Terminal elevators dry, clean, blend and store grain for ship-
ment to other terminals or processors, or for export. These elevators may
receive grain by truck, rail or barge, and they have significantly greater
grain handling and storage capacities than do country elevators. Export
elevators are terminal elevators that load grain primarily onto ships for
export.
The first step at a grain elevator is the unloading of the incoming
truck, railcar or barge. A truck discharges its grain into a hopper, usually
below grade, from which the grain is conveyed to the main part of the eleva-
tor. Barges are unloaded by a bucket elevator (marine leg) that is extended
down into the hold. The main building at an elevator, where grain is elevated
and distributed, is called the "headhouse". In the headhouse, grain is lifted
on one of the elevator legs and discharged onto the gallery belt, which con-
veys the grain to the storage bins, or silos. A "tripper" diverts grain into
the desired bin. Grain is often cleaned and/or dried before storage. When
ready for shipping, grain is discharged from bins onto the tunnel belt below,
which conveys it to the scale garner and on to the desired loadout location.
Figure 6.4-1 illustrates the basic elements of an export terminal elevator.
A grain processing plant (mill) receives grain from an elevator and per-
forms various manufacturing steps that produce a finished food product.
Examples of these plants are flour mills, animal feed mills, and producers of
edible oils, starch, corn syrup, and cereal products. The elevator operations
of unloading, conveying and storing also are performed at mills.
6.4.2 Emissions And Controls1
The only pollutant emitted in significant quantities from grain eleva-
tors and processing operations is particulate matter. Small amounts of
combustion products from natural gas fired grain dryers also may be emitted.
Grain elevators and grain processing operations can be considered separate
categories of the industry when considering emissions.
9/88 Food And Agricultural Industry 6.4-1
-------
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6.4-2
EMISSION FACTORS
9/88
-------
6.4.2.1 Grain Elevators - Emissions of fugitive dust occur whenever quanti-
ties of grain are set into motion during loading, conveying, transfer, drying
or cleaning operations at a grain elevator. The emission rate can be
affected by the quantity of foreign material in the grain (dirt, seeds,
sticks, stones, etc., known as "dockage") and by the type of grain. While it
is difficult to quantify the effect of dockage, observations indicate that
soybeans, oats and sorghum are usually very dusty, whereas wheat and corn are
comparatively clean.4 Total particulate emission factors for the principal
operations at grain elevators are presented in Table 6.4-1. Since data dif-
ferentiating these emission factors by grain type are sparse, all of these
factors are approximate average values intended to apply to a variety of
grains. Tables 6.4-2, 6.4-3 and 6.4-4, and Figures 6.4-2, 6.4-3 and 6.4-4,
show particle size distributions and size specific emission factors for three
operations at grain elevators.
The emission factors in Table 6.4-1 represent the amount of dust genera-
ted per unit weight of grain processed through each uncontrolled operation.
Since the amount of grain passing through each individual operation is often
difficult to determine, it is sometimes convenient to express the emission
factors in terms of the quantity of grain received or shipped by the eleva-
tor. (It is assumed that the amounts shipped and received are equal over the
long run.) Therefore, the factors in Table 6.4-1 have been modified and are
expressed in Table 6.4-5 as a function of the amount of grain received or
shipped. The ratios shown in Table 6.4-5 are approximate values based on
averages for bin turning, cleaning and drying in each elevator category.
However, because operating practices at individual elevators are different,
these ratios, like the emission factors themselves, may lack precision
when applied to an individual elevator.
The factors in Tables 6.4-1 and 6.4-5 should not be added together in
order to obtain a single overall emission factor for a grain elevator
because, in most elevators, the emissions from some operations are controlled
and others are not. Therefore, emissions estimations generally should be
undertaken for each operation and its associated control device.
Several methods are available to reduce or control dust emissions at
grain elevators. Since most emissions are generated when air passes swiftly
through a mass of grain, measures that slow down grain transfer (conveying)
rates or that reduce free fall distances will reduce emissions. Bulk grain,
especially when falling through' the air, should be protected from significant
air currents or wind sources. Many operations at elevators are partially or
totally enclosed (e. g., screw conveyors, drag conveyors, elevator legs) to
isolate generated dust from the atmosphere. Hooding in the vicinity of some
operations (e. g., grain unloading, conveyor transfer points) collects gener-
ated dust by creating a negative pressure area (through suction, or air
aspiration) near the center of activity and then ducting the dusty air to a
control device. Recent developments in the control of ship and' barge loading
operations include the use of "dead boxes" and tent controls. The dead box
is a baffled attachment on the loading spout that serves to reduce the speed
of the falling grain before it reaches the open air and strikes the grain
pile. Aspiration to a control device often accompanies the use of the dead
box. Large flexible covers connected to the loading spout and aspiration
ducting, called tents, are used to cover the holds of ships during most of a
loading operation. The tent must be removed during topping off (usually
9/88 Food And Agricultural Industry 6.4-3
-------
TABLE 6.4-1. TOTAL PARTICULATE EMISSION FACTORS FOR
UNCONTROLLED GRAIN ELEVATORS3
EMISSION FACTOR RATING: B
Type of Operation
Country elevators
Unloading (receiving)
Loading (shipping)
Removal from bins (tunnel belt)
Dryingb
Cleaning0
Headhouse (legs)
Inland terminal elevators
Unloading (receiving)
Loading (shipping)
Removal from bins (tunnel belt)
Drying^3
Cleaning0
Headhouse ( legs )
Tripper (gallery belt)
Export elevators
Unloading (receiving)
Loading (shipping)
Removal from bins (tunnel belt)
Dryingb
Cleaning0
He adhou se ( le gs )
Tripper (gallery belt)
Total particulate
kg/Mg
0.3
0.2
0.5
0.4
1.5
0.8
0.5
0.2
0.7
0.6
1.5
0.8
0.5
0.5
0.5
0.7
0.5
1.5
0.8
0.5
Ib/ton
0.6
0.3
1.0
0.7
3.0
1.5
1.0
0.3
1.4
1.1
3.0
1.5
1.0
1.0
1.0
1.4
1.1
3.0
1.5
1.0
^Expressed as weight of dust emitted/unit weight of grain handled by each
operation. For inland terminal and export elevators, Reference 5; for dry-
ing, References 2, 6; for country elevators, Reference 5 and additional test
data in References 7-10.
^References 6, 11. Based on 0.9 kg/Mg for uncontrolled rack dryers and 0.15
kg/Mg for uncontrolled column dryers, prorated on the basis of the distribu-
tion of these two types of dryers.
^Reference 11. Average of values, from < 0.3 kg/Mg for wheat to 3.0 kg/Mg
for corn.
6.4-4
EMISSION FACTORS
9/88
-------
TABLE 6.4-2. PARTICLE SIZE DISTRIBUTION AND EMISSION
FACTORS FOR UNCONTROLLED RICE DRYERSa
EMISSION FACTOR RATING: D
Aerodynamic particle
diameter (urn)
Cumulative weight %
< stated size
Emission factor*1
(kg/Mg)
2.5
6.0
10.0
15.0
Total particulate
0.8
2.6
7.7
24.5
0.0012
0.0039
0.012
0.037
0.15C
References 1, 12.
^Expressed as cumulative weight of particulate _< corresponding
particle size/unit weight of rice dried.
cReference 11.
99.9
31 90
•8
M
V
50
0.01
UNCONTROLLED
— Uaighc percent
___ EmUiion factor
0.04
0.03
3!
09
0.01
5 10 20 50
Particle diameter, urn
100
Figure 6.4-2. Cumulative size distribution and
emission factors for uncontrolled rice dryers.
9/88
Food And Agricultural Industry
6.4-5
-------
TABLE 6.4-3. PARTICLE SIZE DISTRIBUTION AND EMISSION
FACTORS FOR CONTROLLED BARGE UNLOADING/CONVEYING3
EMISSION FACTOR RATING: D
Aerodynamic particle
diameter (urn)
Cumulative weight %
< stated size
Emission factor**
(kg/Mg)
2.5
6.0
10.0
4.0
11.0
18.0
0.00013
0.00037
0.00054
Total particulate
0.003C
aReference 13. Control is by fabric filter.
^Expressed as cumulative weight of particulate _<_ corresponding
particle size/unit weight of grain unloaded/conveyed.
cTotal mass emission factor is from Reference 1.
99.9
0)
N
•H 95
-O 90
01
50
CONTROLLED
- Weight percent
- Emission factor
0.1 0.2 0.5 1 2 5 10
Particle diameter, urn
Figure 6.4-3. Cumulative size distribution and
emission factors for controlled barge unloading/conveying.
6.4-6
EMISSION FACTORS
9/88
-------
TABLE 6.4-4. PARTICLE SIZE DISTRIBUTION AND EMISSION
FACTORS FOR UNCONTROLLED SHIPLOADING3
EMISSION FACTOR RATING: C
Aerodynamic particle
diameter (um)
2.5
6.0
10.0
15.0
Total particulate
Cumulative weight %
< stated size
10.4
27.0
42.0
53.0
Emission factor^5
(kg/Mg)
0.05
0.13
0.21
0.26
0.50C
References 1, 14-15.
^Expressed as cumulative weight of particulate <_ corresponding
particle size/unit weight of grain loaded onto ships.
cReference 11.
99.9
99
95
-a
o>
u
a
0.01
UNCONTROLLED
• Weight parcenc
—^K— Emission factor
0.35
0.20
0.15
oo
3f
00
0.10
0.05
2 5 10 20 50 100
Particle diameter, um
Figure 6.4-4. Cumulative size distribution and
emission factors for uncontrolled shiploading.
9/88
Food And Agricultural Industry
6.4-7
-------
TABLE 6.4-5. TOTAL PARTICULATE EMISSION FACTORS FOR
GRAIN ELEVATORS, BASED ON AMOUNT OF GRAIN RECEIVED OR SHIPPED3
EMISSION FACTOR RATING: C
Type of Operation
Country elevators
Unloading (receiving)
Loading (shipping)
Removal from bins (tunnel belt) ,
Drylngd
Cleaning6
Headhouse (legs)
Inland terminal elevators
Unloading (receiving)
Loading (shipping)
Removal from bins (tunnel belt)
Dryingd
Cleaning6
Headhouse (legs)
Tripper (gallery belt)
Export elevators
Unloading (receiving)
Loading (shipping)
Removal from bins (tunnel belt)
Drying^
Cleaning6
Headhouse (legs)
Tripper (gallery belt)
Emission factor,
kg/Mg handled15
0.3
0.2
0.5
0.4
1.5
0.8
0.5
0.2
0.7
0.6
1.5
0.8
0.5
0.5
0.5
0.7
0.5
1.5
0.8
0.5
X
Typical ratio of grain
processed to grain
received or shipped0
1.0
1.0
2.1
0.3
0.1
3.1
1.0
1.0
2.0
0.1
0.2
3.0
1.7
1.0
1.0
1.2
0.01
0.2
2.2
l.l
=
Emission factor,
kg/Mg received
or shipped
0.3
0.2
1.0
0.1
0.2
2.5
0.5
0.2
1.4
0.1
0.3
2.3
0.8
0.5
0.5
0.8
0.01
0.3
1.7
0.6
aAssumes amount received is approximately equal to the amount shipped.
bTo obtain units of Ib/ton, multiply factors by 2.0.
cReference 6. Average values from a survey of elevators across the U. S.
for any Individual elevator or group of elevators in the same locale.
dSee Note b In Table 6.4-1.
eSee Note c in Table 6.4-1.
Can be considerably different
6.4-8
EMISSION FACTORS
9/88
-------
about 25 percent of the total loading), allowing essentially uncontrolled
emissions to escape.
Most elevators utilize particulate control devices on at least some of
their operations. The traditional form of control at elevators has been
mechanical collectors, or cyclones. Cyclones collect particles larger than
about 10 microns with only 85 to 95 percent control efficiency, often
producing visible emissions. Hence, fabric filters are usually selected in
areas having more stringent control requirements. Typical efficiencies for
well operated fabric filters exceed 99 percent, with no visible emissions.
The air aspirated from enclosed equipment and hoods is ducted to a fabric
filter or, in some cases, one or more cyclones. Rarely are other particulate
control devices, such as wet scrubbers and electrostatic precipitators,
applied at elevators. Grain dryers present a different sort of control
problem because of the large volumes of warm, moist air exhausted. Most
dryers are enclosed with a continuously vacuumed polyester or stainless steel
screening to collect particulate, with the vacuum usually discharged to a
cyclone. Two principal dryer configurations, rack and column, are in use.
The majority of dryers manufactured today are of the column type, which has
considerably lower emissions than the rack type.'6
6.4.2.2 Grain Processing Plants - Several grain milling operations, such as
receiving, conveying, cleaning and drying, are similar to those at grain
elevators. In addition to these, breaking down (milling) the grain or grain
by-products for processing through various types of grinding operations is a
further source of emissions. The hammermill is the most widely used grinding
device at feed mills. Product is recovered from the hammermill with a
cyclone collector, which can be a major source of dust emissions. Again,
like elevators, mills use a combination of cyclones and fabric filters to
conserve product and to control emissions. Drying at a grain mill is accom-
plished using several types of dryers, including fluidized bed dryers (soy-
bean processing) and flash fired or direct fired dryers (corn milling).
These newer dryer types might have lower emissions than the traditional rack
or column dryers, but data are insufficient at this time to quantify the
difference. The grain pre-cleaning often performed before drying also likely
serves to reduce emissions. Emission factors for various grain milling and
other processing operations are presented in Table 6.4-6, and the particle
size distribution and size specific emission factor for a roaster operation
are shown in Table 6.4-7 and Figure 6.4-5. The origins of these emission
factors are discussed below. ^
Emission factor data for feed mill operations are sparse. The factors
for receiving, shipping and handling are based on estimates made by experts
within the feed industry.17 The remaining feed mill factors are based on test
data in References 2, 18 and 19.
The roasting of carob kibble (or pods), which are ground and used as a
chocolate substitute, is similar to coffee roasting. The emission factor and
particle size distribution for this operation were derived from References 20
and 21.
Three emission areas for wheat mill processing operations are grain
receiving and handling, cleaning house and milling operations. Data from
Reference 5 were used to estimate emission factors for grain receiving and
9/88 Food And Agricultural Industry 6.4-9
-------
TABLE 6.4-6. TOTAL PARTICULATE EMISSION FACTORS FOR
UNCONTROLLED GRAIN PROCESSING OPERATIONS21
EMISSION FACTOR RATING: D
Type of Operation
Feed mills
Receiving
Shipping
Handling
Grinding
Hamme rmil li ngb
Flakingb
Crackingb
Pellet coolerb
Carob kibble roasting
Wheat milling
Receiving
Precleaning and handling
Cleaning house
Mill house
Durum milling
Receiving
Precleaning and handling
Cleaning house
Mill house
Rye milling
Receiving
Precleaning and handling
Cleaning house
Mill house
e
Oat milling
Rice milling
Receiving
Precleaning and handling
Dryingf
Cleaning and mill house
Emission factor
kg/Mg
1.3
0.5
2.7
O.lc»d
O.lc
0.01c»d
0.2C
3.0
0.5
2.5
-
35.0
0.5
2.5
—
"~
0.5
2.5
—
35.0
1 ?S
J. . t, _J
0.32
2.5
0.15
—
Ib/ton
2.5
1.0
5.5
0.2c«d
0.2d
0.02c«d
0.4C
6.0
1.0
5.0
-
70.0
1.0
5.0
—
«
1.0
5.0
—
70.0
2 S
&• . ~j
0.64
5.0
0.30
—
6.4-10
EMISSION FACTORS
9/88
-------
TABLE 6.4-6 (concluded).
/
Type of Operation
Soybean milling
Receiving
Handling
Cleaning
DryingS
Cracking and dehulling
Hull grinding
Bean conditioning
Flaking
Meal dryer
Meal cooler
Bulk loading
Dry corn milling
Receiving
DryingS
Precleaning and handling
Cleaning house
Degerming and milling
Wet corn milling
Receiving
Hand li ng
Cleaning
Dryingh
Bulk loading
Emission factor
kg/Mg
0.8
2.5
-
3.6
1.7
1.0
0.05
0.29
0.75
0.9
0.14
0.5
0.25
2.5
3.0
~
0.5
2.5
3.0
0.24
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1.6
5.0
-
7.2
3.3
2.0
0.1
0.57
1.5
1.8
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1.0
0.5
5.0
6.0
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1.0
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6.0
0.48
"
aMost emission factors are expressed as weight of dust emitted/unit weight of
grain entering the plant, not necessarily the same as amount of material
processed by each operation. Dash = no data.
^Expressed as weight of dust emitted/unit weight of grain processed.
GWith cyclones.
"Measured on corn processing operations at feed mills.
eRepresents several sources at one plant, some controlled with cyclones and
others with fabric filters.
fAverage for uncontrolled column dryers; see Table 6.4-2.
SDryer types unknown.
"For rotary steam tube dryers.
9/88
Food And Agricultural Industry
6.4-11
-------
TABLE 6.4-7. PARTICLE SIZE DISTRIBUTION AND EMISSION
FACTORS FOR UNCONTROLLED CAROB KIBBLE ROASTERS3
EMISSION FACTOR RATING: E
Aerodynamic particle
diameter (urn)
Cumulative weight %
< stated size
Emission factor'3
(kg/Mg)
2.5
6.0
10.0
15.0
Total particulate
0.6
0.7
2.0
11.5
0.018
0.021
0.060
0.35
3.0^
^Reference 18.
^Expressed as cumulative weight of particulate jC corresponding
particle size/unit weight of carob kibble roasted.
Reference 21.
01
.2 M
UNCONTROLLED
— Height percent
.__ Emission factor
i iti
0.40 3
0.30 31
0.20
0.10
2 5 10 20 50 100
Particle diameter, urn
Figure 6.4-5. Cumulative size distribution and
emission factors for uncontrolled carob kibble roasters,
6.4-12
EMISSION FACTORS
9/88
-------
handling. Data for the cleaning house are insufficient to estimate an emis-
sion factor, and information contained in Reference 2 was used to estimate the
emission factor for milling operations. The large emission factor for the
milling operation applies to uncontrolled operations. Almost all of the
sources involved, however, are equipped with control devices to prevent
product losses. Fabric filters are widely used for this purpose.
Durum and rye milling operations are similar to those for 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 mill-
ing 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 before storage. An estimate of the emission factor for drying
was 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 unavail-
able, and no emission factors for other grains are considered applicable
because oats are reported to be dustier than many other grains. The only
emission factor data available are for controlled emissions.
Emission factors for rice milling are based on those for similar opera-
tions in other grain handling facilities. Insufficient information is avail-
able 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 wet corn milling is generally unavailable, in
part because of 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. The drying emission factor is from
tests at a wet corn milling plant producing animal feed.22
Due to operational similarities between grain milling and processing
plants and grain elevators, the control methods used are similar. Both 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 the 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.
The various emission control systems that have been applied to operations
within the grain milling and processing industry are described in Reference
2.
9/88 Food And Agricultural Industry 6.4-13
-------
References for Section 6.4
1. G. A. LaFlam, Documentation for AP-42 Emission Factors; Section 6.4,
Grain Elevators and Processing Plants, Pacific Environmental Services,
Inc., Durham, NC, September 1987.
2. L. J. Shannon, et al., Emissions Control in the Grain and Feed Industry,
Volume I - Engineering and Cost Study, EPA-450/3-73-003a, U.S. Environ-
mental Protection Agency, Research Triangle Park, NC, December 1973.
3. The Storage and Handling of Grain, PEI, Inc., Cincinnati, OH, for
U. S. EPA Region V, Contract No. 68-02-1355, March 1974.
4. Technical Guidance for Control of Industrial Process Fugitive Particu-
late Emissions, PEI, Inc., for U. S. Environmental Protection Agency,
Research Triangle Park, NC, Contract No. 68-02-1375, March 1977.
5. P. G. Gorman, Potential Dust Emission from a Grain Elevator in Kansas
City, Missouri, MRI for U. S. Environmental Protection Agency, Research
Triangle Park, NC, Contract No. 68-02-0228, May 1974.
6. L. J. Shannon, et al., Emission Control in the Grain and Feed Industry,
Volume II - Emission Inventory, EPA-450/3-73-003b, MRI for U. S.
Environmental Protection Agency, Research Triangle Park, NC, September
1974.
7. W. H. Maxwell, Stationary Source Testing of a Country Grain Elevator at
Overbrook, Kansas, MRI for U. S. Environmental Protection Agency,
Research Triangle Park, NC, Contract No. 68-02-1403, February 1976.
8. W. H. Maxwell, Stationary Source Testing of a Country Grain Elevator at
Great Bend, Kansas, MRI for U. S. Environmental Protection Agency,
Research Triangle Park, NC, Contract No. 68-02-1403, April 1976.
9. F. J. Belgea, Cyclone Emissions and Efficiency Evaluation, (Tests at
elevators in Edinburg and Thompson, North Dakota), Pollution Curbs,
Inc., St. Paul, MN, March 10, 1972.
10. F. J. Belgea, Grain Handling Dust Collection Systems Evaluation for
Farmer's Elevator Company, Minot, North Dakota, Pollution Curbs, Inc.,
St. Paul, MN, August 28, 1972.
11. M. P. Schrag, etal., Source Test Evaluation for Feed and Grain Indus-
try, EPA-450/3-76-043, U. S. Environmental Protection Agency, Research
Triangle Park, NC, December 1976.
12. Emission test data from Environmental Assessment Data Systems, Fine
Particle Emission Information System (FPEIS), Series No. 228, U. S.
Environmental Protection Agency, Research Triangle Park, NC, June 1983.
13. Air Pollution Emission Test, Bunge Corporation, Destrehan, LA, EMB-
74-GRN-7, U. S. Environmental Protection Agency, Research Triangle Park,
NC, January 1974.
6.4-14 EMISSION FACTORS 9/88
-------
14. W. Battye and R. Hall, Particulate Emission Factors and Feasibility of
Emission Controls for Shiploading Operations at Portland, Oregon Grain
Terminals, Volume I, GCA Corporation, Bedford, MA., June 1979.
15. Emission Factor Development for Ship and Barge Loading of Grain, GCA
Corporation for U. S. Environmental Protection Agency, Research Triangle
Park, NC, Contract No. 68-02-3510, October 1984.
16. J. M. Appold, "Dust Control for Grain Dryers," in Dust Control for Grain
Elevators, presented before the National Grain and Feed Association, St.
Louis, MO, May 7-8, 1981.
17. Written communication from D. Bossman, American Feed Industry Associa-
tion, Arlington, VA, to F. Noonan, U. S. Environmental Protection
Agency, Research Triangle Park, NC, July 24, 1987.
18. Written communication from P. Luther, Purina Mills, Inc., St. Louis, MO,
to G. LaFlam, PES, Inc., Durham, NC, March 11, 1987.
19. Written communication from P. Luther, Purina Mills, Inc., St. Louis, MO,
to F. Noonan, U. S. Environmental Protection Agency, Research Triangle
Park, NC, July 8, 1987.
20. Emission test data from FPEIS Series No. 229, U. S. Environmental
Protection Agency, Research Triangle Park, NC, June 1983.
21. H. J. Taback, Fine Particle Emissions from Stationary and Miscellaneous
Sources in the South Coast Air Basin, KVB, Inc., Tustin, CA, for the
California Air Resources Board, February 1979.
22. Source Category Survey; Animal Feed Dryers. EPA-450/3-81-017, U. S.
Environmental Protection Agency, Research Triangle Park, NC, December
1981.
9/88 Food And Agricultural Industry 6.4-15
-------
About 10 percent of all lime produced is converted to hydrated (slaked)
lime. There are two kinds of hydrators, atmospheric and pressure. Atmo-
spheric hydrators, the more prevalent type, are used in continuous mode to
produce high calcium and normal doloraitic hydrates. Pressure hydrators, on
the other hand, produce only a completely hydrated dolomitic lime and oper-
ate only in batch mode. Generally, water sprays or wet scrubbers perform
the hydrating process, to prevent product loss. Following hydration, the
product may be milled and then conveyed to air separators for further drying
and removal of coarse fractions.
In the United States, lime plays a major role in chemical and metal-
lurgical operations. Two of the largest uses are as steel flux and in
alkali production. Lesser uses include construction, refractory and agri-
cultural applications.
8.15.2 Emissions And Controls3"5
Potential air pollutant emission points in lime manufacturing plants
are shown in Figure 8.15-1. Except for gaseous pollutants emitted from
kilns, particulate is the only pollutant of concern from most of the opera-
tions .
The largest ducted source of particulate is the kiln. Of the various
kiln types, fluidized beds have the most uncontrolled particulate emissions,
because of the very small feed size combined with high air flow through
these kilns. Fluidized bed kilns are well controlled for maximum product
recovery. The rotary kiln is second worst in uncontrolled particulate emis-
sions, also because of the small feed size and relatively high air veloci-
ties and dust entrainment caused by the rotating chamber. The calcimatic
(rotary hearth) kiln ranks third in dust production, primarily because of
the larger feed size and the fact that, during calcination, the limestone
remains stationary relative to the hearth. The vertical kiln has the lowest
uncontrolled dust emissions, due to the large lump feed and the relatively
low air velocities and slow movement of material through the kiln.
Some sort of particulate control is generally applied to most kilns.
Rudimentary fallout chambers and cyclone separators are commonly used for
control of the larger particles. Fabric and gravel bed filters, wet (com-
monly venturi) scrubbers, and electrostatic precipitators are used for sec-
ondary control.
Nitrogen oxides, carbon monoxide and sulfur oxides are all produced in
kilns, although the last are the only gaseous pollutant emitted in signifi-
cant quantities. Not all of the sulfur in the kiln fuel is emitted as sul-
fur oxides, since 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.
Product coolers are emission sources only when some of their exhaust
gases are not recycled through the kiln for use as combustion air. The
10/86 Mineral Products Industry 8.15-3
-------
trend is away from the venting of product cooler exhaust, however, to maxi-
mize fuel use efficiencies. Cyclones, baghouses and wet scrubbers have been
employed on coolers for particulate control.
Hydrator emissions are low, because water sprays or wet scrubbers are
usually installed 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, making
control more difficult.
Other particulate sources in lime plants include primary and secondary
crushers, mills, screens, mechanical and pneumatic transfer operations,
storage piles, and roads. If quarrying is a part of the lime plant opera-
tion, particulate may also result from drilling and blasting. Emission
factors for some of these operations are presented in Sections 8.19 and 11.2
of this document.
Controlled and uncontrolled emission factors and particle size data for
lime manufacturing are given in Tables 8.15-1 through 8.15-3. The size dis-
tributions of particulate emissions from controlled and uncontrolled rotary
kilns and uncontrolled product loading operations are shown in Figures
8.15-2 and 8.15-3.
1.15-4 EMISSION FACTORS 10/86
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,.15-5
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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.
9/88 Mineral Products Industry 8.19.2-1
-------
FIGURE 8.19.2-1. Typical stone processing plant.
8.19.2-2
EMISSION FACTORS
9/88
-------
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 con-
sumer after secondary or tertiary crushing.
8.19.2.2 Emissions And Controls1"3
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
9/88 Mineral Products Industry 8.19.2-3
-------
higher than those based upon plume profiling tests, but they have a greater
degree of reliability. Some test data for primary crushing indicate higher
emissions than from secondary crushing, although factors affecting emission
rates and visual observations suggest that the secondary crushing emission
factor, on a throughput basis, should be higher. Table 8.19.2-1 shows single
factors for either primary or secondary crushing reflecting a combined data
base. An emission factor for tertiary crushing is given, but it is based on
extremely limited data. All factors are rated low because of the limited and
highly variable data base.
TABLE 8.19.2-1.
UNCONTROLLED PARTICIPATE EMISSION FACTORS
FOR CRUSHING OPERATIONS3
Type of crushing'5
Primary or secondary
Dry material
Wet material0
Tertiary dry materiald
Particulate
< 30 urn
kg/Mg (Ib/ton)
0.14 (0.28)
0.009 (0.018)
0.93 (1.85)
< 10 urn
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. Typical control efficiencies for cyclone, 70 - 80%;
fabric filter, 99%; wet spray systems, 70 - 90%.
°References 5-6. Refers to crushing of rock either naturally wet or
moistened to 1.5 - 4 weight % with wet suppression techniques.
^Range of values used to calculate emission factor is 0.0008 - 1.38 kg/Mg.
Emission factor estimates for stone quarry blasting operations are not
presented here because of the sparsity and unreliability of available test
data. While a procedure for estimating blasting emissions is presented in
Section 8.24, Western Surface Coal Mines, that procedure should not be applied
to stone quarries because of dissimilarities in blasting techniques, material
blasted and size of blast areas.
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
8.19.2-4
EMISSION FACTORS
9/88
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Mineral Products Industry
8.19.2-5
-------
through tests at various quarries and processing plants.""' 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
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., e t a1., 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.
8.19.2-6 EMISSION FACTORS 9/88
-------
8.24 WESTERN SURFACE COAL MINING
8.2A.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
SUBBITUMINOUSC3
BITUMINOUS
1
2
3
it
5
6
7
9
9
10
11
12
Coal field
Fore Union
Powder River
North Central
Bighorn Basin
Wind River
Bams Fork
Uinta
Southwestern Utah
San Juan River
Raton Mesa
Denver
Green River
Strippable reserves
CIO6 tons)
23,529
56,727
All underground
j All underground
3
1,000
308
224
2,318
All underground
All underground
2,120
9/88
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 9/88
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Mineral Products Industry
8.24-5
-------
The equations were developed through field sampling of 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 equations,
given in Table 8.24-3. However, the equations are derated one letter 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
Number
Source Correction of test
factor samples
Coal loading
Bulldozers
Coal
Overburden
Dragline
Scraper
Grader
Light/medium
duty vehicle
Haul truck
Moisture
Moisture
Silt
Moisture
Silt
Drop distance
ii ii
Moisture
Silt
Weight
Speed
Moisture
Wheels
Silt loading
7
3
3
8
8
19
7
10
15
7
7
2,9
26
Range Geometric
mean
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
- 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
- 2270
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
Units
%
%
%
%
%
m
ft
%
Mg
ton
kph
mph
%
number
g/m2
Ib/ac
aReference
In using the equations to estimate emissions from sources found in a
specific western surface mine, it is necessary that reliable values for
correction parameters be determined for the specific sources of interest,
if the assigned quality ranges of the equations are to be applicable.
For example, actual silt content of coal or overburden measured at a facility
8.24-6
EMISSION FACTORS
9/88
-------
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.
9/88 Mineral Products Industry 8.24-7
-------
TABLE 8.24-4. UNCONTROLLED PARTICULATE EMISSION FACTORS FOR
OPEN DUST SOURCES AT WESTERN SURFACE COAL MINES
Source
Drilling
Topsoil removal by
scraper
Overburden
replacement
Truck loading by
power shovel
(batch drop)
Train loading (batch
or continuoui drop)
Bottom dump truck
unloading
(batch drop)
End dump truck
unloading
(batch drop)
Scraper unloading
(batch drop)
Wind erosion of
expoted area>
Material Mine
location
Overburden
Coal
Topsoil
Overburden
Overburden
Coal
Overburden
Coal
Coal
Topaoil
Seeded land,
(tripped over-
burden, graded
overburden
Any
V
Any
IV
Any
V
Any
III
V
IV
III
II
I
Any
V
IV
Any
TSP
emission
factor
1.3
0.59
0.22
0.10
0.058
C.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
0.027
0.014
0.005
0.002
0.020
0.010
0.0)4
0.0070
0.066
0.033
0.007
0.004
0.04
0.02
0.38
0.85
Emission
Units Factor
Rating
Ib/hole
kg/bole
Ib/hole
kg/hole
Ib/T
kg/Hg
Ib/T
kg/Hg
Ib/T
kg/Hg -
Ik/T
kg/Kg
Ib/T
kg/Hg
Ib/T
kg/Hg
Ib/T
kg/T
Ib/T
kg/Hg
Ib/T
kg/Hg
Ib/T
kg/Hg
Ib/T
kg/Hg
Ib/T
kg/Hg
Ib/T
kg/Hg
Ib/T
kg/Hg
T
(acreKyr)
Hfr
*1K
(oectareHyr)
B
B
E
E
I
I
D
0
C
c
C
c
D
D
D
D
E
E
E
E
E
E
E
E
D
D
D
D
E
E
C
C
C
c
Roman nuaterals I through V refer to specific nine locations for whicfc the
corresponding emission factors were developed (Reference 4). Table* 8.24-4
and 8.24-5 present characteristics of each of these nines. See text for
correct use of these "mine specific" emission factors. The other factors
(from Reference 5 except for overburden drilling from Reference 1) can be
applied to any western surface coal mine.
Total suspended particulate (TSP) denotes what is measured by i 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
9/88
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EMISSION FACTORS
9/88
-------
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. IJ. 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.
9/88 Mineral Products Industry 8.24-11
-------
CHAPTER 11. MISCELLANEOUS SOURCES
This chapter contains emission factor information on those source cate-
gories that differ substantially from, and hence cannot be grouped with, the
other "stationary" sources discussed in this publication. These miscellaneous
emitters, both natural and manmade, are almost exclusively area sources, with
their pollutant generating process(es) dispersed over large land areas. Another
characteristic of these sources is the inapplicability, in most cases, of con-
ventional 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 stabiliation of dirt roads. Finally,
miscellaneous sources generally emit pollutants intermittently, when compared
to most stationary point sources. For example, a wildfire may emit large
quantities of particulate and carbon monoxide for several hours or even days.
But, when measured against a continuous emitter, such as a sulfuric acid plant,
over a long period of time, its emissions may seem relatively minor. Effects
on air quality may also be of relatively short duration.
9/88 Miscellaneous Sources 11-1
-------
11.1 Wildfires And Prescribed Burning
11.1.1 General1
A wildfire is a large scale natural combustion process that consumes
various ages, size and types of flora growing outdoors in a geographical area.
Consequently, wildfires are potential sources of large amounts of air pollut-
ants that should be considered when trying to relate emissions to air quality.
The size and intensity, even the occurrence, of a wildfire depend
directly on such variables as meteorological conditions, the species of vege-
tation involved and their moisture content, and the weight of consumable fuel
per acre (available fuel loading). Once a fire begins, the dry combustible
material is consumed first. 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. Under proper environmental and fuel conditions,
this process may initiate a chain reaction that results in a widespread
conflagration.
The complete combustion of wildland fuels (forests, grasslands, wetlands)
require a heat flux (temperature gradient), adequate oxygen supply, and
sufficient burning time. The size and quantity of wildland fuels, meteo-
rological conditions, and topograhic features interact to modify the burning
behavior as the fire spreads, and the wildfire will attain different degrees
of combustion efficiency during its lifetime.
The importance of both fuel type and fuel loading on the fire process
can not be overemphasized. To meet the pressing need for this kind of infor-
mation, the U. S. Forest Service is developing a model of a nationwide fuel
identification system that will provide estimates of fuel loading by size
class. 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 (NFDRS). This system considers
five classes of fuel, the components of which are selected on the basis of
combustibility, response of dead fuels to moisture, and whether the living
fuels are herbaceous (grasses, brush) or woody (trees, shrubs).
Most fuel loading figures are based on values for "available fuel," that
is, combustible material that will be consumed in a wildfire under specific
weather conditions. Available fuel values must not be confused with corres-
ponding values for either "total fuel" (all the combustible material that
would burn under the most severe weather and burning 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, fuel loadings are estimated
for the vegetation in the U. S. Forest Service Regions are presented in
Table 11.1-1. Figure 11.1-1 illustrates these areas and regions.
9/88 Miscellaneous Sources 11.1-1
-------
TABLE 11.1-1. SUMMARY OF ESTIMATED FUEL CONSUMED BY WILDFIRES*
National region*5
Rocky Mountain
Region 1: Northern
Region 2: Rocky Mountain
Region 3: Southwestern
Region 4: Intermountain
Pacific
Region 5: California
Region 6: Pacific Northwest
Region 10: Alaska
Coastal
Interior
Southern
Region 8: Southern
Eastern
North central
Region 9: Conifers
Ha rdwo ods
Estimated average fuel loading
Mg /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
aReference 1.
Figure 11.1-1 for region boundaries
11.1-2
EMISSION FACTORS
9/88
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Miscellaneous Sources
11.1-3
-------
11.1.2 Emissions And Controls*
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 are 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, relative humidity); (2) fuels
(fuel type, fuel bed array, moisture content, 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 emissions data on actual
wildfires, so that it is not possible to verify or disprove the hypothesis.
Therefore, until such measurements are made, the only available information is
that obtained from burning experiments in the laboratory. These data, for 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:
Ft - PjL (1)
E± - F-tA - Pi LA (2)
where: F^ = Emission factor (mass of pollutant/unit area of
forest consumed)
P! = Yield for pollutant "i" (mass of pollutant/unit
mass of forest fuel consumed)
= 8.5 kg/Mg (17 Ib/ton) for total particulate
70 kg/Mg (140 Ib/ton) for carbon monoxide
= 12 kg/Mg (24 Ib/ton) for total hydrocarbon (as Cfy)
= 2 kg/Mg (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 pollutant)
For example, suppose that is is necessary to estimate the total particu-
late 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 megagrams per
hectare (9 tons per acre). Further, the pollutant yield for particulates is
8.5 kilograms per megagram (17 Ib/ton). Therefore, the emissions are:
11.1-4 EMISSION FACTORS
9/88
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E - (8.5 kg/Mg of fuel) (20 Mg of fuel hectare) (10,000 hectares)
E - 1.700,000 kg - 1,700 Mg
The most effective method of controlling wildfire emissions is, of course,
to prevent the occurrence of wildfires, by various means at the land manager'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 to prevent fuel buildup under controlled
conditions, thus reducing the danger of a wildfire. Although some air pollution
is generated by this preventive burning, the net amount is believed to be a
relatively smaller quantity than that produced by wildfires.
11.1.3 Prescribed Burning1
Prescribed burning is a land treatment, used under controlled conditions,
to accomplish natural resource management objectives. It is one of several
land treatments, used individually or in combination, including chemical and
mechanical methods. Prescribed fires are conducted within the limits of a fire
plan and prescription which describes both the acceptable range of weather,
moisture, fuel and fire behavior parameters and the ignition method to achieve
the desired effects. Prescribed fire is a cost effective and ecologically
sound tool for forest, range and wetland management. Its use reduces the
potential for destructive wildfires and thus maintains long term air quality.
Also, the practice removes logging residues, controls insects and disease,
improves wildlife habitat and forage production, increases water yield, main-
tains natural succession of plant communities, and reduces the need for pes-
ticides and herbicides. The major air pollutant concern is the smoke produced.
Smoke from prescribed fires is a complex mixture of carbon, tars, liquids
and different gases. This open combustion source produces particles of widely
ranging size, depending to some extent on the rate of energy release of the
fire. For example, total particulate and particulate less than 2.5 micrometers
mean mass cutpoint diameter are produced in different proportions, depending on
rates of heat release by the fire.^ This difference is greatest for the highest
intensity fires, and particle volume distribution is bimodal, with peaks near
0.3 micrometers and exceeding 10 micrometers.-' Particles over about 10 microns,
probably of ash and partially burned plant matter, are extrained by the turbu-
lent nature of high intensity fires.
Burning methods differ with fire objectives and with fuel and weather
conditions. For example, the various ignition techniques used to burn under
standing trees include 1) heading fire, a line of fire that runs with the wind;
2) backing fire, a line of fire that moves into the wind; 3) spot fires, which
burn from a number of fires ignited along a line or in a pattern; and 4) flank
fire, a line of fire that is lit into the wind, to spread laterally to the
direction of the wind. Methods of igniting the fires depend on forest manage-
ment objectives and the size of the area. Often, on areas of 50 or more acres,
helicopters with aerial ignition devices are used to light broadcast burns.
Broadcast fires may involve many lines of fire in a pattern that allows the
strips of fire to burn together over a sizeable area.
11.1-6 EMISSION FACTORS 9/88
-------
In discussing prescribed burning, the combustion process is divided into
preheating, flaming, glowing and smoldering phases. The different phases of
combustion greatly affect the amount of emissions produced. 5~7 The preheating
phase seldom releases significant quantities of material to the atmosphere.
Glowing combustion is usually associated with burning of large concentrations
of woody fuels such as logging residue piles. The smoldering combustion phase
is a very inefficient and incomplete combustion process that emits pollutants
at a much higher ratio to the quantity of fuel consumed than does the flaming
combustion of similar materials.
The amount of fuel consumed depends on the moisture content of the
For most fuel types, consumption during the smoldering phase is much greatest
when the fuel is driest. When lower layers of the fuel are moist, the fire
usually is extinguished rapidly. 10
The major pollutants from wildland burning are particulate, carbon monoxide
and volatile organics. Nitrogen oxides are emitted at rates of from 1 to 4
grams per kilogram burned, depending on combustion temperatures. Emissions of
sulfur oxides are negligible. ^
Particulate emissions depend on the mix of combustion phase, the rate of
energy release, and the type of fuel consumed. All of these elements must be
considered in selecting the appropriate emission factor for a given fire and
fuel situation. In some cases, models developed by the U. S. Forest Service
have been used to predict particulate emission factors and source strength. *• •*
These models address fire behavior, fuel chemistry, and ignition technique, and
they predict the mix of combustion products. There is insufficient knowledge
at this time to describe the effect of fuel chemistry on emissions.
Table 11.1-3 presents emission factors from various pollutants, by fire
and fuel configuration. Table 11.1-4 gives emission factors for prescribed
burning, by geographical area within the United States. Estimates of the
percent of total fuel consumed by region were compiled by polling experts
from the Forest Service. The emission factors are averages and can vary by
as much as 50 percent with fuel and fire conditions. To use these factors,
multiply the mass of fuel consumed per hectare by the emission factor for the
appropriate fuel type. The mass of fuel consumed by a fire is defined as the
available fuel. Local forestry officials often compile information on fuel
consumption for prescribed fires and have techniques for estimating fuel
consumption under local conditions. The Southern Forestry Smoke Management
Guidebook-* and the Prescribed Fire Smoke Management Guide *^ should be consulted
when using these emission factors.
The regional emission factors in Table 11.1-4 should be used only for
general planning purposes. Regional averages are based on estimates of the
acreage and vegetation type burned and may not reflect prescribed burning
activities in a given state. Also, the regions identified are broadly defined,
and the mix of vegetation and acres burned within a given state may vary
considerably from the regional averages provided. Table 11.1-4 should not be
used to develop emission inventories and control strategies.
To develop state emission inventories, the user is strongly urged to con-
tact that state's federal land management agencies and state forestry agencies
that conduct prescribed burning to obtain the best information on such activities.
Q/88
Miscellaneous Sources 11.1-7
-------
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11.1-8
EMISSION FACTORS
9/88
-------
TABLE 11.1-4.
EMISSION FACTORS FOR PRESCRIBED BURNING
BY U. S. REGION
Regional
configuration and
fuel type8
Pacific Northwest
Logging slash
Piled slash
Douglas fir/
Western hemlock
Mixed conifer
Ponderosa pine
Ha rdwo od
Underburning pine
Average for region
Pacific Southwest
Sagebrush
Chaparral
Pi nyon/ Juniper
Underburing pine
Grassland
Average for region
Southeast
Palme t to/ gal Iberry
Underburning pine
Logging slash
Grassland
Other
Average for region
Rocky Mountain
Logging slash
Underburning pine
Grassland
Other
Average for region
North Central and Eastern
Logging slash
Grassland
Underburning pine
Other
Average for region
Percent
of fuelb
42
24
19
6
4
5
100
35
20
20
15
10
100
35
30
20
'10
5
100
50
20
20
10
100
50
30
10
10
100
Pollutant0
Part icul ate
(g/k«)
PM2.5
4
12
12
13
11
30
9.4
8
PM10
5
13
13
13
12
30
10.3
9
9
13
30
10
13.0
15
30
13
10
17
4 18.8
4
30
10
17
11.9
13
10
30
17
14
PM
6
17
17
20
18
35
13.3
15
15
17
35
10
17.8
16
35
20
10
17
21.9
6
35
10
17
13.7
17
10
35
17
16.5
CO
37
175
175
126
112
163
111.1
62
62
175
163
75
101.0
125
163
126
75
175
134
37
163
75
175
83.4
175
75
163
175
143.8
aRegional areas are generalized, e. g., the Pacific Northwest includes
Oregon, Washington and parts of Idaho and California. Fuel types
generally reflect the ecosystems of a region, but users should seek
advice on fuel type mix for a given season of the year. An average
factor for Northern California could be more accurately described as
chaparral, 25%; underburning pine, 15%; sagebrush, 15%; grassland,
5%; mixed conifer, 25%*, and Douglas fir/Western hemlock, 15%.
Dash • no data.
''Based on the judgment of forestry experts.
cAdapted from Table 11.1-3 for the dominant fuel types burned.
9/88
Miscellaneous Sources
11.1-9
-------
References for Section 11.1
1. Development Of Emission Factors For Estimating Atmospheric Emissions From
Forest Fires, EPA-450/3-73-009, U. S. Environmental Protection Agency,
Research Triangle Park, NC, October 1973.
2. D. E. Ward and C. C. Hardy, Advances In The Characterization And Control
Of Emissions From Prescribed Broadcast Fires Of Coniferous Species Logging
Slash On Clearcut Units, EPA DW12930110-01-3/DOE DE-A179-83BP12869, U. S.
Forest Service, Seattle, WA, January 1986.
3. L. F. Radke, et al., Airborne Monitoring And Smoke Characterization Of
Prescribed Fires On Forest Lands In Western Washington and Oregon,
EPA-600/X-83-047, U. S. Environmental Protection Agency, Cincinnati, OH,
July 1983.
4. H. E. Mobley, et al., A Guide For Prescribed Fire In Southern Forests,
U. S. Forest Service, Atlanta, GA, 1973.
5. Southern Forestry Smoke Management Guidebook, SE-10, U. S. Forest Service,
Asheville, NC, 1976.
6. D. E. Ward and C. C. Hardy, "Advances In The Characterization And Control
Of Emissions From Prescribed Fires", Presented at the 77th Annual Meeting
of the Air Pollution Control Association, San Francisco, CA, June 1984.
7. C. C. Hardy and D. E. Ward, "Emission Factors For Particulate Matter By
Phase Of Combustion From Prescribed Burning", Presented at the Annual
Meeting of the Air Pollution Control Association Pacific Northwest
International Section, Eugene, OR, November 19-21, 1986.
8. D. V. Sandberg and R. D. Ottmar, "Slash Burning And Fuel Consumption In
The Douglas Fir Subregion", Presented at the 7th Conference On Fire And
Forest Meteorology, Fort Collins, CO, April 1983.
9. D. V. Sandberg, "Progress In Reducing Emissions From Prescribed Forest
Burning In Western Washington And Western Oregon", Presented at the Annual
Meeting of the Air Pollution Control Association Pacific Northwest
International Section, Eugene, OR, November 19-21, 1986.
10. R. D. Ottmar and D. V. Sandberg, "Estimating 1000-hour Fuel Moistures In
The Douglas Fir Subregion", Presented at the 7th Conference On Fire And
Forest Meteorology, Fort Collins, CO, April 25-28, 1983.
11. D. V. Sandberg, et al. , Effects Of Fire On Air - A State Of Knowledge
Review, WO-9, U. S. Forest Service, Washington, DC, 1978. -
12. C. K. McMahon, "Characteristics Of Forest Fuels, Fires, And Emissions",
Presented at the 76th Annual Meeting of the Air Pollution Control
Association, Atlanta, GA, June 1983.
13. D. E. Ward, "Source Strength Modeling Of Particulate Matter Emissions From
Forest Fires", Presented at the 76th Annual Meeting of the Air Pollution
Control Association, Atlanta, GA, June 1983.
11.1-10 EMISSION FACTORS 9/88
-------
14. D. E. Ward, et al., "Particulate Source Strength Determination For Low-
intensity Prescribed Fires", Presented at the Agricultural Air Pollutants
Specialty Conference, Air Pollution Control Association, Memphis, TN,
March 18-19, 1974.
15. Prescribed Fire Smoke Management Guide, 420-1, BIFC-BLM Warehouse, 3905
Vista Avenue, Boise, ID, February 1985.
9/88 Miscellaneous Sources 11.1-11
-------
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 Calculation 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.1~~^
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.^ 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, generally nonporous surface that usually dries
quickly after a rainfall. The temporary reduction in emissions caused by
precipitation 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 rating of A:
E=k(1.7) — — — — (kg/VKT)
(Ib/VMT)
Miscellaneous Sources
11.2.1-1
-------
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-------
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 the equation varies with aerodynamic particle
size range as follows:
Aerodynamic Particle Size Multiplier For Equation
<30 uma
1.0
<30 urn
0.80
£15 urn
0.50
<10 urn
0.36
_<5um
0.20
<2.5 urn
0.095
a Stokes diameter
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
geographical distribution of the mean annual number of wet days per year in the
United States.
The equation 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
Road silt
content
(wgt. %)
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 when addressing a specific
unpaved road, it is necessary that reliable correction parameter values be
determined for the road in question. The field and laboratory procedures for
determining road surface silt content are given in Reference 4. In the event
that site specific values for correction parameters cannot be. obtained, the
appropriate mean values from Table 11.2.1-1 may be used, but the quality rating
of the equation is reduced to B.
The equation was developed for calculating 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 for
the equation. Worst case emissions, corresponding to dry road conditions, may
be calculated by setting p = 0 in the equation (equivalent to dropping the last
9/88
Miscellaneous Sources
11.2.1-3
-------
0)
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11.2.1-4
EMISSION FACTORS
9/88
-------
terra 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
average period (usually 24 hours). Similarly, in using the equation to calcu-
late emissions for a 91 day season of the year, replace the term (365-p)/365
with the terra (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 Controls
Common control techniques for unpaved roads are paving, surface treating
with penetration chemicals, working into the roadbed of stabilization 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 treat-
ment 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 calcu-
lated using the predictive emission factor equation given above.
The control efficiencies achievable by paving can be estimated by comparing
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 stabilization
chemicals are much more difficult to estimate. The application parameters
which determine control efficiency include dilution ratio, application intensity
(mass of diluted chemical per road area) and application frequency. Other
factors that affect the performance of chemical stabilizers include vehicle
characteristics (e. g., traffic volume, average weight) and road characteristics
(e. g., bearing strength).
Besides water, petroleum resin products have historically been the dust
suppressants most widely used on industrial unpaved roads. Figure 11.2.1-2
presents a method to estimate average control efficiencies associated with
petroleum resins applied to unpaved roads. Several items should be noted:
1. The term "ground inventory" represents the total volume (per
unit area) of petroleum resin concentrate (not solution)
applied since the start of the dust control season.
2. Because petroleum resin products must be periodically reapplied
to unpaved roads, the use of a time-averaged control efficiency
value is appropriate. Figure 11.2.1-2 presents control effi-
ciency values averaged over two common application intervals,
two weeks and one month. Other application intervals will
require interpolation.
9/88 Miscellaneous Sources 11.2.1-5
-------
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11.2.1-6
EMISSION FACTORS
9/88
-------
3. Note that zero efficiency is assigned until the ground inventory
reaches 0.2 liters per square meter (0.05 gallons per square yard).
As an example of the use of Figure 11.2.1-2, suppose that the equation has
been used to estimate an emission factor of 2.0 kilograms per vehicle kilometer
traveled for particles equal to or less than 10 microns from a particular road.
Also, suppose that, starting on May 1, the road is treated with 1 liter per
square meter of a (1 part petroleum resin to 5 parts water) solution on the
first of each month until October. Then, the following average controlled
emission factors are found:
Period
May
June
July
August
September
Ground
Inventory
(L/m2)
0.17
0.33
0.50
0.67
0.83
Average Control
Efficiency3
(%)
0
62
68
74
80
Average Controlled
Emission Factor
(kg/VKT)
2.0
0.76
0.64
0.52
0.40
aFrom Figure 11.2.1-2, j£ 10 urn. Zero efficiency assigned if ground
inventory is less than 0.2 L/m2 (0.05 gal/yd2).
Newer dust suppressants have been successful in controlling emissions from
unpaved roads. Specific test results for those chemicals, as well as for petro-
leum resins, are provided in References 14 through 16.
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-600/2-79-013, U. S. Environmental Protection
Agency, Cincinnati, OH, 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, Cincinnati, OH,
March 1978.
9/88 Miscellaneous Sources 11.2.1-7
-------
6. R. Bohn, Evaluation Of Open Dust Sources In The Vicinity Of Buffalo, New
York, EPA Contract No. 68-02-2545, Midwest Research Institute, Kansas
City, MO, March 1979.
7. C. Cowherd, Jr., and T. Cuscino, Jr., Fugitive Emissions Evaluation,
MRI-4343-L, Midwest Research Institute, Kansas City, MO, 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, PEI, Inc., Kansas City, MO, July 1981.
10. 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, Cincinnati, OH, 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, Cincinnati, OH, September 1985.
13. .Climatic Atlas Of The United States, U. S. Department Of Commerce,
Washington, DC, June 1968.
14. G. E. Muleski, et al., Extended Evaluation Of Unpaved Road Dust Suppres-
sants In The Iron And Steel Industry, EPA-600/2-84-027, U. S. Environmental
Protection Agency, Cincinnati, OH, February 1984.
15. C. Cowherd, Jr., and J. S. Kinsey, Identification, Assessment And Control
Of Fugitive Particulate Emissions, EPA-600/8-86-023, U. S. Environmental
Protection Agency, Cincinnati, OH, August 1986.
16. G. E. Muleski and C. Cowherd, Jr., Evaluation Of The Effectiveness Of
Chemical Dust Suppressants On Unpaved Roads, EPA-600/X-XX-XXX, U. S.
Environmental Protection Agency, Cincinnati, OH, November 1986.
11.2.1-8 EMISSION FACTORS 9/88
-------
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 uncovered,
partially because of the need for frequent material transfer into or out of
storage.
Dust emissions occur at several points in the storage cycle, such as
during material loading onto the pile, disturbances by strong wind currents,
and loadout from the pile. The movement of trucks and loading 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 varies
with the volume of aggregate passing through the storage cycle. Also, emis-
sions depend on three parameters of the condition of a particular storage pile:
age of Che 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 disaggregated
and released to the atmosphere upon exposure to air currents, either from aggre-
gate transfer itself or from high winds. As the aggregate weathers, however,
potential for dust emissions is greatly reduced. Moisture causes aggregation
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.
Silt (particles equal to or less than 75 microns in diameter) content is
determined by measuring the portion of dry aggregate material that passes
through a 200 mesh screen, using ASTM-C-136 method. Table 11.2.3-1 summarizes
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).
Adding aggregate material to a storage pile or removing it both usually
involve 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 exam-
ples of batch drop operations. Adding material to the pile by a conveyor
stacker is an example of a continuous drop operation.
9/88 Miscellaneous Sources 11.2.3-1
-------
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EMISSION FACTORS
9/88
-------
The quantity of particulate emissions generated by either type of drop
operation, per ton of material transferred, may be estimated, with a rating of
A, using the following empirical expression^:
E = k(0.0016)
(kg/Mg)
E = k(0.0032)
(Ib/ton)
where: E = emission factor
k = particle size multiplier (dimensionless)
U = mean wind speed, m/s (mph)
M = material moisture content (%)
The particle size multiplier, k, varies with aerodynamic particle diameter, as
shown in Table 11.2.3-2.
TABLE 11.2.3-2. AERODYNAMIC PARTICLE SIZE MULTIPLIER (k)
<30 urn
0.74
<15 urn
0.48
<10 urn
0.35
<5 urn
0.20
<2.5 urn
0.11
The equation retains the assigned quality rating if applied within the
ranges of source conditions that were tested in developing the equation, as
given in Table 11.2.3-3. Note that silt content is included in Table 11.2.3-3,
even though silt content does not appear as a correction parameter in the equa-
tion. While it is reasonable to expect that silt content and emission factors
are interrelated, no significant correlation between the two was found during
the derivation of the equation, probably because most tests with high silt
contents were conducted under lower winds, and vice versa. It is recommended
that estimates from the equation be reduced one quality rating level, if the
silt content used in a particular application falls outside the range given in
Table 11.2.3-3.
9/88
Miscellaneous Sources
11.2.3-3
-------
TABLE 11.2.3-3. RANGES OF SOURCE CONDITIONS FOR EQUATION 1
Silt
Content
0.44 - 19
Moisture
Content
0.25 - 4.8
Wind Speed
(m/s) (mph)
0.6 - 6.7 1.3 - 15
Also, to retain the equation's quality rating when applied to a specific
facility, it is necessary that reliable correction parameters be determined for
the specific sources of interest. The field and laboratory procedures for
aggregate sampling are given in Reference 3. In the event that site specific
values for correction parameters cannot be obtained, the appropriate mean
values from Table 11.2.3-1 may be used, but, in that case, the quality rating
of the equation is reduced by one level.
For emissions from equipment traffic (trucks, front end loaders, dozers,
etc.) traveling between or on piles, it is recommended that the equations 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 among the piles
(which may differ from the silt values for the stored materials) should be used.
Worst case emissions from storage pile areas occur under dry windy condi-
tions. Worst case emissions from materials handling operations may be calcu-
lated by substituting into the equation 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), centering on 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 Controls
Watering and chemical wetting agents are the principal means for control
of aggregate storage pile emissions. Enclosure or covering of inactive 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 technique is to apply chemical wet-
ting agents for better wetting of fines and 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.9
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.
11.2.3-4 EMISSION FACTORS 9/88
-------
2. R. Bohn, e t al., Fugitive Emissions From Integrated Iron And Steel Plants,
EPA-600/2-78-050, U. S. Environmental Protection Agency, Cincinnati, OH,
March 1978.
3. 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, Cincinnati, OH, May 1979.
4. R. Bohn, Evaluation Of Open Dust Sources In The Vicinity Of Buffalo,
New York, EPA Contract No. 68-02-2545, Midwest Research Institute, Kansas
City, MO, March 1979,
5. C. Cowherd, Jr., and T. Cuscino, Jr., Fugitive Emissions Evaluation,
MRI-4343-L, Midwest Research Institute, Kansas City, MO, 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, PEI, Inc., Kansas City, MO, July 1981.
8. E. T. Brookman, et al., Determination of Fugitive Coal Dust Emissions From
Rotary Railcar Dumping. 1956-L81-00, TRC, Hartford, CT, May 1984.
9. 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.
9/88 Miscellaneous Sources 11.2.3-5
-------
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 road-
way 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 open truck bodies.
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 asso-
ciated vehicle traffic.
Dust emissions from industrial paved roads have been found to vary in
direct proportion to the fraction of silt (particles equal to or less than 75
microns in diameter) in the road surface material. The silt fraction is deter-
mined 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. The 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^:
E = 0.022 I ( | \ |\ H 1 (kg/VKT) (1)
V280
L \ /W \0-7
0.0771 [ | ( ]( | (Ib/VMT)
1000 I \ 3
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)
11/88 Miscellaneous Sources 11.2.6-1
-------
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EMISSION FACTORS
9/88
-------
The industrial road augmentation factor (I) in Equation 1 takes into account
higher emissions from industrial roads than from urban roads. I = 7.0 for a
paved 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 on-e set of wheels on the shoulder. I = 1.0
for cases in which traffic travels only on paved 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
(%)
5.1-92
Surface loading
kg/km Ib/mile
42.0 - 2000 149 - 7100
No. of
lanes
2-4
Vehicle weight
Mg tons
2.7 - 12 3-13
If I is less than 1.0, the rating of the equation drops to D, because of the
subjectivity in the guidelines for estimating I.
The quantity of particle emissions in the finer size ranges 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 equation:
0.3
k(3.5)
(kg/VKT)
(Ib/VMT)
(2)
where: E = emission factor
sL = road surface silt loading, g/m^ (oz/yd^)
The particle size multiplier (k) above varies with aerodynamic size range
as follows:
Aerodynamic Particle Size
Multiplier (k) For Equation 2
(Dimensionless)
<15 urn
<10 urn
<2.5 urn
0.28
0.22
0.081
9/88
Miscellaneous Sources
11.2.6-3
-------
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 particle emissions in the finer size ranges 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
<15 urn
<10 urn
0.12 kg/VKT
(0.41 Ib/VMT)
0.093 kg/VKT
(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,
-------
Although there are relatively few quantitative data on emissions from
controlled paved roads, those that are available indicate that adequate esti-
mates generally may be obtained by substituting controlled loading values into
Equations 1 and 2. The major exception to this is water flushing combined
with broom sweeping. In that case, the equations tend to overestimate emis-
sions substantially (by an average factor of 4 or more).
On a paved road with moderate traffic (500 vehicles per day), to achieve
control efficiencies on the order of 50 percent, 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 depo-
sition 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 eliminating 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. Bohn, et al., Fugitive Emissions From Integrated Oron And Steel Plants,
EPA-600/2-78-050, U. S. Environmental Protection Agency, Cincinnati, OH,
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, Cincinnati, OH, May 1979.
3. R. Bohn, Evaluation Of Open Dust Sources In The Vicinity Of Buffalo,
New York, EPA Contract No. 68-02-2545, Midwest Research Institute, Kansas
City, MO, March, 1979.
4. T. Cuscino, Jr., et al., Iron And Steel Plant Open Source Fugitive Emission
Control Evaluation, EPA-600/2-83-110, U. S. Environmental Protection Agency,
Cincinnati, OH, 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.
6. 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, Cincinnati, OH, September 1985.
9/88 Miscellaneous Sources 11.2.6-5
-------
11.2.7 INDUSTRIAL WIND EROSION
11.2.7.1 General1"3
Dust emissions may be generated by wind erosion of open aggregate storage
piles and exposed areas within an industrial facility. These sources typically
are characterized by nonhomogeneous surfaces impregnated with nonerodible ele-
ments (particles larger than approximately 1 cm in diameter). Field testing of
coal piles and other exposed materials using a portable wind tunnel has shown
that (a) threshold wind speeds exceed 5 m/s (11 mph) at 15 cm above the surface
or 10 m/s (22 mph) at 7 m above the surface, and (b) particulate emission rates
tend to decay rapidly (half life of a few minutes) during an erosion event. In
other words, these aggregate material surfaces are characterized by finite
availability of erodible material (mass/area) referred to as the erosion
potential. Any natural crusting of the surface binds the erodible material,
thereby reducing the erosion potential.
11.2.7.2 Emissions And Correction Parameters
If typical values for threshold wind speed at 15 cm are corrected to
typical wind sensor height (7-10 m), the resulting values exceed the upper
extremes of hourly mean wind speeds observed in most areas of the country. In
other words, mean atmospheric wind speeds are not sufficient to sustain wind
erosion from flat surfaces of the type tested. However, wind gusts may quickly
deplete a substantial portion of the erosion potential. Because erosion poten-
tial has been found to increase rapidly with increasing wind speed, estimated
emissions should be related to the gusts of highest magnitude.
The routinely measured meteorological variable which best reflects the
magnitude of wind gusts is the fastest mile- This quantity represents the wind
speed corresponding to the whole mile of wind movement which has passed by the
1 mile contact anemometer in the least amount of time. Daily measurements of
the fastest mile are presented in the monthly Local Climatological Data (LCD)
summaries. The duration of the fastest mile, typically about 2 min (for a
fastest mile of 30 mph), matches well with the half life of the erosion
process, which ranges between 1 and 4 min. It should be noted, however, that
peak winds can significantly exceed the daily fastest mile.
The wind speed profile in the surface boundary layer is found to follow a
logarithmic distribution:
u(z) = u* In z_ (z > z0) (1)
0.4 ZQ
where u = wind speed, cm/sec
u* = friction velocity, cm/sec
z = height above test surface, cm
zo = roughness height, cm
0.4 = von Karman's constant, dimensionless
The friction velocity (u*) is a measure of wind shear stress on the erodible
surface, as determined from the slope of the logarithmic velocity profile. The
roughness height (zo) is a measure of the roughness of the exposed surface as
determined from the y intercept of the velocity profile, i.e. , the height at
9/88 Miscellaneous Sources '^1.2.7-1
-------
which the wind speed is zero. These parameters are illustrated in Figure
11.2.7-1 for a roughness height of 0.1 cm.
Emissions generated by wind erosion are also dependent on the frequency of
disturbance of the erodible surface because each time that a surface is dis-
turbed, its erosion potential is restored. A disturbance is defined as an
action which results in the exposure of fresh surface material. On a storage
pile, this would occur whenever aggregate material is either added to or
removed from the old surface. A disturbance of an exposed area may also result
from the turning of surface material to a depth exceeding the size of the
largest pieces of material present.
11.2.7.3 Predictive Emission Factor Equation4
The emission factor for wind generated particulate emissions from mixtures
of erodible and nonerodible surface material subject to disturbance may be
expressed in units of g/or-yr as follows:
N
Emission factor - k P (2)
i
where k = particle size multiplier
N = number of disturbances per year
Pi = erosion potential corresponding to the observed (or probable)
fastest mile of wind for the ith period between disturbances,
g/m2
The particle size multiplier (k) for Equation 2 varies with aerodynamic
particle size, as follows:
AERODYNAMIC PARTICLE SIZE MULTIPLIERS FOR EQUATION 2
<30 um <15 urn <10 urn <2.5 urn
1.0 0.6 0.5 0.2
This distribution of particle size within the <30um fraction is comparable
to the distributions reported for other fugitive dust sources where wind speed
is a factor. This is illustrated, for example, in the distributions for batch
and continuous drop operations encompassing a number of test aggregate materials
(see Section 11.2.3).
In calculating emission factors, each area of an erodible surface that is sub-
ject to a different frequency of disturbance should be treated separately. For
a surface disturbed daily, N = 365/yr, and for a surface disturbance once
every 6 months, N = 2/yr.
Equations 2 and 3 apply only to dry, exposed materials with limited erosion
potential. The resulting calculation is valid only for a time period as long
or longer than the period between disturbances. Calculated emissions repre-
sent intermittent events and should not be input directly into dispersion
models that assume steady state emission rates.
11.2.7-2 EMISSION FACTORS 9/88
-------
°
V) $
I
K
ki
9/88
Figure 11.2.7-1. Illustration of logarithmic velocity profile.
Miscellaneous Sources 11.2.7-3
-------
The erosion potential function for a dry, exposed surface is:
P = 58 (u* - u*)2 25 (u* - u*)
fc t (3)
P - 0 for u* < u*
~ t
where u* = friction velocity (m/s)
ut = threshold friction velocity (m/s)
Because of the nonlinear form of the erosion potential function, each erosion
event must be treated separately.
For uncrusted surfaces, the threshold friction velocity is best estimated from
the dry aggregate structure of the soil. A simple hand sieving test of surface
soil (adapted from a laboratory procedure published by W. S. Chepil) can be
used to determine the mode of the surface aggregate size distribution by
inspection of relative sieve catch amounts, following the procedure described
below. Alternatively, the threshold friction velocity for erosion can be
determined from the mode of the aggregate size distribution, as described by
Gillette. 5~6
Threshold friction velocities for several surface types have been determined
by field measurements with a portable wind tunnel. These values are presented
in Table 11.2.7-1.
TABLE 11.2.7-1. FIELD PROCEDURE FOR DETERMINTION OF THRESHOLD
FRICTION VELOCITY
Tyler
sieve no.
5
9
16
32
60
Opening
(mm)
4
2
1
0.5
0.25
Midpoint
(mm)
3
1.5
0.75
0.375
u* (cm/sec)
t
100
72
58
43
FIELD PROCEDURE FOR DETERMINATION OF THRESHOLD FRICTION VELOCITY
(from a 1952 laboratory procedure published by W. S. Chepil)
1. Prepare a nest of sieves with the following openings: 4 mm, 2 mm, 1 mm,
0.5 mm, 0.25 mm. Place a collector pan below tti crhhrj-ftaga *5M36
2. Collect a sample representing the surface layer of loose particles
(approximately 1 cm in depth, for an encrusted surface), removing any rocks
11.2.7-4 EMISSION FACTORS 9/88
-------
larger than about 1 cm in average physical diameter.
sampled should be not less than 30 cm.
The area to be
3. Pour the sample into the top sieve (4 mm opening), and place a lid on the
top.
4. Move the covered sieve/pan unit by hand, using a broad circular arm motion
in the horizontal plane. Complete 20 circular movements at a speed just
necessary to achieve some relative horizontal motion between the sieve and
the particles.
5. Inspect the relative quantities of catch within each sieve, and determine
where the mode in the aggregate size distribution lies, i. e., between the
opening size of the sieve with the largest catch and the opening size of
the next largest sieve.
6. Determine the threshold friction velocity from Figure 1.
The fastest mile of wind for the periods between disturbances may be obtained
from the monthly LCD summaries for the nearest reporting weather station that
is representative of the site in question. These summaries report actual
fastest mile values for each day of a given month. Because the erosion
potential is a highly nonlinear function of the fastest mile, mean values of
the fastest mile are inappropriate. The anemometer heights of reporting
weather stations are found in Reference 8, and should be corrected to a 10 m
reference height using Equation 1.
TABLE 11.2.7-2. THRESHOLD FRICTION VELOCITIES
Material
Overburden3
Scoria (roadbed
material)3
Ground coal3
(surrounding coal
pile)
Uncrusted coal pilea
Scraper tracks on
coal pilea»b
Fine coal dust on
concrete padc
a Western surface coal
b Lightly crusted.
c Eastern power plant.
Threshold
friction
velocity
(m/s)
1.02
1.33
0.55
1.12
0.62
0.54
mine.
Roughness
height
(cm)
0.3
0.3
0.01
0.3
0.06
0.2
Threshold wind
velocity at 10
zo = Actual zo
21
27
16
23
15
11
m (m/s)
= 0.5 cm
19
25
10
21
12
10
Ref.
2
2
2
2
2
3
9/88
Miscellaneous Sources
11.2.7-5
-------
To convert the fastest mile of wind (u+) from a reference anemometer height of
10 m to the equivalent friction velocity (u*), the logarithmic wind speed
profile may be used to yield the following equation:
u* = 0.053 u+10 (4)
where u* = friction velocity (m/s)
u iQ = fastest mile of reference anemometer for period between
disturbances (m/s)
This assumes a typical roughness height of 0.5 cm for open terrain.
Equation 4 is restricted to large relatively flat piles or exposed areas with
little penetration into the surface wind layer.
If the pile significantly penetrates the surface wind layer (i.e., with a
height-to-base ratio exceeding 0.2), it is necessary to divide the pile area
into subareas representing different degrees of exposure to wind. The results
of physical modeling show that the frontal face of an elevated pile is exposed
to wind speeds of the same order as the approach wind speed at the top of the
pile.
For two representative pile shapes (conical and oval with flattop, 37 degree
side slope), the ratios of surface wind speed (ug) to approach wind speed (ur)
have been derived from wind tunnel studies.^ The results are shown in
Figure 11.2.7-2 corresponding to an actual pile height of 11 m, a reference
(upwind) anemometer height of 10 m, and a pile surface roughness height (zo)
of 0.5 cm. The measured surface winds correspond to a height of 25 cm above
the surface. The area fraction within each contour pair is specified in
Table 11.2.7-3.
The profiles of us/ur in Figure 11.2.7-2 can be used to estimate the surface
friction velocity distribution around similarly shaped piles, using the
following procedure:
1. Correct the fastest mile value (u+) for the period of interest from the
anemometer height (z) to a reference height of 10 m (u ^Q) using a
variation of Equation 1:
u+1Q = u+ In (10/0.005) (5)
In (z/0.005)
where a typical roughness height of 0.5 cm (0.005 m) has been assumed.
If a site specific roughness height is available, it should be used.
2. Use the appropriate part of Figure 11.2.7-2 based on the pile shape and
orientation to the fastest mile of wind, to obtain the corresponding sur-
face wind speed distribution (u ):
»3
u+ = (M u+ (6)
11.2.7-6 EMISSION FACTORS 9/88
-------
Flow
Direction
Pile A
Pile B1
Pile B2
Pile B3
Figure 11.2.7-2. Contours of Normalized Surface Wind Speeds, us/ur
9/88
Miscellaneous Sources
11.2.7-7
-------
3. For any subarea of the pile surface having a narrow range of surface wind
speed, use a variation of Equation 1 to calculate the equivalent friction
velocity (u*):
0.4 u+
u* = =0.10 u+
s
_
Im0.5
From this point on, the procedure is identical to that used for a flat pile,
as described above.
Implementation of the above procedure is carried out in the following steps:
1. Determine threshold friction velocity for erodible material of interest
(see Table 11.2.7-2 or determine from mode of aggregate size
distribution).
2. Divide the exposed surface area into subareas of constant frequency of
disturbance (N).
TABLE 11.2.7-2. SUBAREA DISTRIBUTION FOR REGIMES OF us/ur
Percent of pile surface area (Figure
Pile subarea
0.2a
0.2b
0.2c
0.6a
0.6b
0.9
1.1
Pile A
5
35
-
48
-
12
™
Pile Bl
5
2
29
26
24
14
~
Pile B2
3
28
-
29
22
15
3
11.2.7-2)
Pile B3
3
25
-
28
26
14
4
3. Tabulate fastest mile values (u+) for each frequency of disturbance and
correct them to 10 m (U+IQ) using Equation 5.
4. Convert fastest mile values (U+IQ) to equivalent friction velocities (u*),
taking into account (a) the uniform wind exposure of nonelevated surfaces,
using Equation 4, or (b) the nonuniform wind exposure of elevated surfaces
(piles), using Equations 6 and 7.
5. For elevated surfaces (piles), subdivide areas of constant N into sub-
areas of constant u* (i.e., within the isopleth values of ug/ur in Figure
11.2.7-2 and Table 11.2.7-3) and determine the size of each subarea.
6. Treating each subarea (of constant N and u*) as a separate source,
calculate the erosion potential (P^) for each period between disturbances
using Equation 3 and the emission factor using Equation 2.
11.2.7-8 EMISSION FACTORS 9/88
-------
7. Multiply the resulting emission factor for each subarea by the size of
the subarea, and add the emission contributions of all subareas. Note
that the highest 24-hr emissions would be expected to occur on the
windiest day of the year. Maximum emissions are calculated assuming a
single event with the highest fastest mile value for the annual period.
The recommended emission factor equation presented above assumes that all of
the erosion potential corresponding to the fastest mile of wind is lost during
the period between disturbances. Because the fastest mile event typically
lasts only about 2 min, which corresponds roughly to the halflife for the
decay of actual erosion potential, it could be argued that the emission factor
overestimates particulate emissions. However, there are other aspects of the
wind erosion process which offset this apparent conservatism:
1. The fastest mile event contains peak winds which substantially exceed the
mean value for the event.
2. Whenever the fastest mile event occurs, there are usually a number of
periods of slightly lower mean wind speed which contain peak gusts of the
same order as the fastest mile wind speed.
Of greater concern is the likelihood of overprediction of wind erosion
emissions in the case of surfaces disturbed infrequently in comparison to the
rate of crust formation.
11.2.7.4 Example calculation for wind erosion emissions from conically shaped
coal pile
A coal burning facility maintains a conically shaped surge pile 11 m in height
and 29.2 m in base diameter, containing about 2000 Mg of coal, with a bulk
density of 800 kg/m3 (50 lb/ft3). The total exposed surface area of the pile
is calculated as follows:
S = r r2 + h2
= 3.14(14.6) (14.6)2 + (11.O)2
= 838 m2
Coal is added to the pile by means of a fixed stacker and reclaimed by front-
end loaders operating at the base of the pile on the downwind side. In addi-
tion, every 3 days 250 Mg (12.5% of the stored capacity of coal) is added back
to the pile by a topping off operation, thereby restoring the full capacity of
the pile. It is assumed that (a) the reclaiming operation disturbs only a
limited portion of the surface area where the daily activity is occurring,
such that the remainder of the pile surface remains intact, and (b) the top-
ping off operation creates a fresh surface on the entire pile while restoring
its original shape in the area depleted by daily reclaiming activity.
Because of the high frequency of disturbance of the pile, a large number of
calculations must be made to determine each contribution to the total annual
wind erosion emissions. This illustration will use a single month as an
example.
9/88 Miscellaneous Sources 11.2.7-9
-------
Prevailing
Wind
Direction
Circled values
refer to us/ur
* A portion of C£ is disturbed daily by reclaiming activities.
m ea
ID
A
B
Ci + C?
us
"uT
0.9
0.6
0.2
%
12
48
40
Area (m^)
101
402
335
838
Figure 11.2.7-3. Example 1: Pile surface areas within each wind speed regime.
11.2.7-10
EMISSION FACTORS
9/88
-------
Step 1: In the absence of field data for estimating the threshold friction
velocity, a value of 1.12 m/s is obtained from Table 11.2.7-2.
Step 2: Except for a small area near the base of the pile (see
Figure 11.2.7-3), the entire pile surface is disturbed every 3 days, corre-
sponding to a value of N - 120/yr. It will be shown that the contribution of
the area where daily activity occurs is negligible so that it does not need to
be treated separately in the calculations.
Step 3: The calculation procedure involves determination of the fastest mile
for each period of disturbance. Figure 11.2.7-4 shows, a representative set of
values (for a 1 month period) that are assumed to be applicable to the geographic
area of the pile location. The values have been separated into 3 day periods,
and the highest value in each period is indicated. In this example, the
anemometer height is 7 m, so that a height correction to 10 m is needed for the
fastest mile values. From Equation 5,
In (10/0.005)
u+io = u+7 In (7.0.005)
u+io = 1*05 u+7
Step 4: The next step is to convert the fastest mile value for each 3 day
period into the equivalent friction velocities for each surface wind regime
(i. e., us/ur ratio) of the pile, using Equations 6 and 7. Figure 11.2.7-3
shows the surface wind speed pattern (expressed as a fraction of the approach
wind speed at a height of 10 m). The surface areas lying within each wind
speed regime are tabulated below the figure.
The calculated friction velocities are presented in Table 11.2.7-4. As
indicated, only three of the periods contain a friction velocity which exceeds
the threshold value of 1.12 m/s for an uncrusted coal pile. These three values
all occur within the Ug/ur =0.9 regime of the pile surface.
Step 5: This step is not necessary because there is only one frequency of
disturbance used in the calculations. It is clear that the small area of
daily disturbance (which lies entirely within the Ug/ur =0.2 regime) is never
subject to wind speeds exceeding the threshold value.
9/88 Miscellaneous Sources 11.2.7-11
-------
Local Climatological Data
MONTHLY SUMMARY
WIND
ex
o
3
V
a
\
30
0
10
13
12
20
29
29
22
1 4
29
I 7
2 1
10
10
0 1
33
27
32
24
22
32
29
07
31
30
30
33
34
29
_»
_J O
9 UJ
cn UJ
UJ Q.
ec en
14
5.3
10.5
2.4
1 1 .0
11.3
M.l
19.6
10.9
3.0
14.6
22.3
7.9
7.7
4.5
6.7
3.7
1 .2
4.3
9.3
7.5
0.3
7. 1
2.4
5.9
1 .3
2. 1
8.3
8.2
5.0
3. 1
4.9
0
UJ
a
en
o 3
a: o.
UJ
>. je
15
6.9
10.6
6.0
11.4
1 1 .9
19.0
19.8
1 1 .2
8. 1
5. 1
23.3
3.5
5.5
9.6
8.8
3.8
1 .5
5.8
0.2
7.8
0.6
7.3
8.5
8.8
1 . 7
2.2
8.5
8.3
6.6
5.2
5.5
FASTEST
MILE
o ~"
UJO.
a. z
in
16
Q
(H
10
16
1C
6j
q^
1 7
15
23
v^
23
18
^y
13
Qj
T"5
12
1 4
©
1 6
5^
TA
i 5
\J>
16
16
1J)
10
9
8
o
o
cr
o
17
36
01
02
13
1 1
30
30
30
13
12
29
1 7
18
1 3
1 1
35
34
31
35
24
20
32
13
02
32
32
26
32
32
31
25
FOR THE MONTH:
30
—
3.3
^•HMk*. t
1 . 1
[
31
29
)*TE: 1 1
o
22
i
2
3
5
6
7
g
9
f,
I
12
3
1 4
15
16
1 7
18
'19
20
21
22
23
24
25
26
27
25
29
30
3'.
Figure 11.2.7-4. Daily fastest miles of wind for periods of interest.
11.2.7-12
EMISSION FACTORS
9/88
-------
TABLE 11.2.7-4. EXAMPLE 1: CALCULATION OF FRICTION VELOCITIES
u+7
3 Day
period
1
2
3
4
5
6
7
8
9
10
(mph)
14
29
30
31
22
21
16
25
17
13
(m/s)
6.3
13.0
13.4
13.9
9.8
9.4
7.2
11.2
7.6
5.8
u+10
(mph)
15
31
32
33
23
22
17
26
18
14
(m/s) Us/ur
6.6
13.7
14.1
14.6
10.3
9.9
7.6
11.8
8.0
6.1
u* -
0.2
0.13
0.27
0.28
0.29
0.21
0.20
0.15
0.24
0.16
0.12
0.1 u+8
0.6
0.40
0.82
0.84
0.88
0.62
0.59
0.46
0.71
0.48
0.37
(m/s)
0.9
0.59
1.23
1.27
1.31
0.93
0.89
0.68
1.06
0.72
0.55
Steps 6 and 7: The final set of calculations (shown in Table 11.2.7-5)
involves the tabulation and summation of emissions for each disturbance period
and for the affected subarea. The erosion potential (P) is calculated from
Equation 3.
TABLE 11.2.7-5. EXAMPLE 1: CALCULATION OF PM10 EMISSIONS3
Pile Surface
3 Day
period
2
3
4
u* (m/s)
1.23
1.27
1.31
u* - u*fc (m/s)
0.11
0.15
0.19
P (g/m2)
3.45
5.06
6.84
ID
A
A
A
Total PMjo
Area
(m2)
101
101
101
emissions
kPA
(g)
170
260
350
. 780
where u*t = 1.12 m/s for uncrusted coal and k • 0.5 for
For example, the calculation for the second 3 day period is:
P2 - 58(1.23 - 1.12)2 + 25(1.23 - 1.12)
- 0.70 + 2.75 - 3.45 g/m2
The PM].o emissions generated by each event are found as the product of the
PMio multiplier (k - 0.5), the erosion potential (P), and the affected area
of the pile (A).
9/88 Miscellaneous Sources 11.2.7-13
-------
As shown in Table 11.2.7-5, the results of these calculations indicate a
monthly PM^Q emission total of 780 g.
11.2.7.5 Example calculation for wind erosion from flat area covered with coal
dust
A flat circular area of 29.2 m in diameter is covered with coal dust left over
from the total reclaiming of a conical coal pile described in the example
above. The total exposed surface area is calculated as follows:
S = _ d2 = 0.785 (29. 2)2 = 670 m2
4
This area will remain exposed for a period of 1 month when a new pile will be
formed.
Step 1: In the absence of field data for estimating the threshold friction
velocity, a value of 0.54 m/s is obtained from Table 11.2.7-2.
Step 2: The entire surface area is exposed for a period of 1 month after
removal of a pile and N = 1/yr.
Step 3: From Figure 11.2.7-5, the highest value of fastest mile for the
30 day period (31 mph) occurs on the llth day of the period. In this example,
the reference anemometer height is 7 m, so that a height correction is needed
for the fastest mile value. From Step 3 of the previous example, U+IQ = 1.05
u+7, so that u+io = 33 mph.
Step 4: Equation 4 is used to convert the fastest mile value of 33 mph
(14.6 m/s) to an equivalent friction velocity of 0.77 m/s. This value exceeds
the threshold friction velocity from Step 1 so that erosion does occur.
Step 5: This step is not necessary because there is only one frequency of
disturbance for the entire source area.
Steps 6 and 7: The PM^Q emissions generated by the erosion event are
calculated as the product of the PM^Q multiplier (k = 0.5), the erosion
potential (P) and the source area (A). The erosion potential is calculated
from Equation 3 as follows:
P = 58(0.77 - 0.54)2 + 25(0.77 - 0.54)
= 3.07 + 5.75
= 8.82 g/m2
Thus the PM^Q emissions for the 1 month period are found to be:
E = (0.5X8.82 g/m2)(670 m2)
= 3.0 kg
11.2.7-14 EMISSION FACTORS 9/88
-------
References for Section 11.2.7
1. C. Cowherd Jr., "A New Approach to Estimating Wind Generated Emissions
from Coal Storage Piles", Presented at the APCA Specialty Conference on
Fugitive Dust Issues in the Coal Use Cycle, Pittsburgh, PA, April 1983.
2. K. Axtell and C. Cowherd, Jr., Improved Emission Factors for Fugitive Dust
from Surface Coal Mining Sources, EA-600/7-84-048, U. S. Environmental
Protection Agency, Cincinnati, OK, March 1984.
3. G. E. Muleski, "Coal Yard Wind Erosion Measurement", Midwest Research
Institute, Kansas City, MO, March 1985.
4. Update of Fugitive Dust Emissions Factors in AP-42 Section 11.2 - Wind
Erosion, MRI No. 8985-K, Midwest Research Institute, Kansas City, MO, 1988.
5. W. S. Chepil, "Improved Rotary Sieve for Measuring State and Stability
of Dry Soil Structure", Soil Science Society of America Proceedings,
16_: 113-117, 1952.
6. D. A. Gillette, e t al., "Threshold Velocities for Input of Soil
Particles Into the Air By Desert Soils", Journal of Geophysical Research,
85_(C10):5621-5630.
7. Local Climatological Data, National Climatic Center, Asheville, NC.
8. M. J. Changery, National Wind Data Index Final Report, HCO/T1041-01 UC-60,
National Climatic Center, Asheville, NC, December 1978.
9. B. J. B. Stunder and S. P. S. Arya, "Windbreak Effectiveness for Storage
Pile Fugitive Dust Control: A Wind Tunnel Study", Journal of the Air
Pollution Control Association. 38:135-143, 1988.
9/88 Miscellaneous Sources 11.2.7-15
-------
APPENDIX C.3
SILT ANALYSIS PROCEDURES
1. Select the appropriate 8 inch diameter 2 inch deep sieve sizes.
Recommended standard series sizes are 3/8 inch No. 4, No. 20, No. 40,
No. 100, No. 140, No. 200, and a pan. .The No. 20 and the No. 200 are
mandatory. Comparable Tyler Series sizes can also be used.
2. Obtain a mechanical sieving device such as a vibratory shaker or a
Roto-Tap (without the tapping function).
3. Clean the sieves with compressed air and/or a soft brush. Material lodged
in the sieve openings or adhering to the sides of the sieve should be
removed without handling the screen roughly, if possible.
4. Obtain a scale with capacity of at least 1600 grams, and record its make,
capacity, smallest increment, date of last calibration, and accuracy.
5. Record the tare weight of sieves and pan, and check the zero before every
.weighing.
6. After nesting the sieves in decreasing order of hole size, and with the
pan at the bottom, dump dried laboratory sample into the top sieve,
preferably immediately after moisture analysis. The sample should weigh
between 800 and 1600 grams (1.8 and 3.5 pounds). Brush fine material
adhering to the sides of the container into the top sieve, and cover the
top sieve with a special lid normally purchased with the pan.
7. Place nested sieves into the mechanical device, and sieve for 10 minutes.
Remove pan containing minus No. 200 and weigh its contents. Repeat the
sieving in 10 minute intervals until the difference between two successive
pan sample weights is less than 3.0 percent when the tare of the pan has
been substracted. Do not sieve longer than 40 minutes.
8. Weigh each sieve and its contents, and record the weight.
check the zero before every weighing.
Remember to
9. Collect the laboratory sample, and place it in a separate container if
further analysis is expected.
10. Calculate the percent of mass less than the 200 mesh screen (75 micro-
meters). This is the silt content.
u. s. ocwEHwan1 ttasnsa OFFICE i988/526-090/87oos
9/88
Appendix C.3
C.3-1
-------
-------
TECHNICAL REPORT DATA
(Please read Instructions on the reverse before completing)
1. REPORT NO.
AP 42, Supplement B
2.
3. RECIPIENT'S ACCESSION NO.
4. TITLE AND SUBTITLE
Supplement B to Compilation of Air Pollutant Emission
Factors, AP-42, Fourth Edition
5. REPORT DATE
September 1988
6. PERFORMING ORGANIZATION CODE
7. AUTHOR(S)
8. PERFORMING ORGANIZATION REPORT NO.
9. PERFORMING ORGANIZATION NAME AND ADDRESS
U.S. Environmental Protection Agency
Office of Air And Radiation
Office Of Air Quality Planning And Standards
Research Triangle Park, NC 27711
10. PROGRAM ELEMENT NO.
11. CONTRACT/GRANT NO.
12. SPONSORING AGENCY NAME AND ADDRESS
13. TYPE OF REPORT AND PERIOD COVERED
14. SPONSORING AGENCY CODE
15. SUPPLEMENTARY NOTES
EPA Editor: Whitmel M. Joyner
16. ABSTRACT
In this Supplement to the Fourth Edition of AP-42, new or revised emissions data
are presented for Bituminous And Subbituminous Coal Combustion; Anthracite Coal
Combustion; Residential Wood Stoves; Waste Oil Combustion; Refuse Combustion; Sewage
Sludge Incineration; Surface Coating; Polyester Resin Plastics Product Fabrication;
Soap And Detergents; Grain Elevators And Processing Plants; Lime Manufacturing; Crushec
Stone Processing; Western Surface Coal Mining; Wildfires And Prescribed Burning;
Unpaved Roads; Aggregate Handling And Storage Piles; Industrial Paved Roads; Industrial
Wind Erosion; and Appendix C.3, "Silt Analysis Procedures".
17.
KEY WORDS AND DOCUMENT ANALYSIS
DESCRIPTORS
b.IDENTIFIERS/OPEN ENDED TERMS c. COSATI F;ield/Group
Stationary Sources
Point Sources
Area Sources
Emission Factors
Emissions
18. DISTRIBUTION STATEMENT
19. SECURITY CLASS (ThisReport)
21. NO. OF PAGES
182
20 SECURITY CLASS (This page)
22. PRICE
EPA Form 2220-1 (Rev. 4-77) PREVIOUS EDITION IS OBSOLETE
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