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External Combustion Sources
1.6-15
-------
References For Section 1.6
1. Emission Factor Documentation For AP-42 Section 1.6 — Wood Waste Combustion In Boilers,
Technical Support Division, Office of Air Quality Planning and Standards, U. S. Environmental
Protection Agency, Research Triangle Park, NC, April 1993.
2. Steam, 38th Edition, Babcock and Wilcox, New York, NY, 1972.
3. Atmospheric Emissions From The Pulp And Paper Manufacturing Industry, EPA-450/1-73-002,
U. S. Environmental Protection Agency, Research Triangle Park, NC, September 1973.
4. C-E Bark Burning Boilers, C-E Industrial Boiler Operations, Combustion Engineering, Inc.,
Windsor, CT, 1973.
5. Nonfossil Fuel Fired Industrial Boilers — Background Information, EPA-450/3-82-007, U. S.
Environmental Protection Agency, Research Triangle Park, NC, March 1982.
6. Control Of Particulate Emissions From Wood-Fired Boilers, EPA 340/1-77-026, U. S.
Environmental Protection Agency, Washington, DC, 1977.
7. Background Information Document For Industrial Boilers, EPA 450/3-82-006a, U.S.
Environmental Protection Agency, Research Triangle Park, NC, March 1982.
8. E. F. Aul, Jr. and K. W. Barnett, "Emission Control Technologies For Wood-Fired Boilers",
Presented at the Wood Energy Conference, Raleigh, NC, October 1984.
9. G. Moilanen, et al., "Noncatalytic Ammonia Injection For NOX Reduction on a Waste Wood Fired
Boiler", Presented at the 80th Annual Meeting of the Air Pollution Control Association, New York,
NY, June 1987.
10. "Information On The Sulfur Content Of Bark And Its Contribution To SO2 Emissions When
Burned As A Fuel", H. Oglesby and R. Blosser, Journal Of The Air Pollution Control Agency,
30(T):769-112, July 1980.
11. Written communication from G. Murray, California Forestry Association, Sacramento, CA to E.
Aul, Edward Aul & Associates, Inc., Chapel Hill, NC, Transmittal of Wood Fired Boiler Emission
Test, April, 24, 1992.
12. L. P. Nelson, L. M. Russell, and J. J. Watson, "Global Combustion Sources of Nitrous Oxide
Emissions", Research Project 2333-4 Interim Report, Radian Corporation, Sacramento, CA, 1991.
13. Rebecca L. Peer, Eric P. Epner, and Richard S. Billings, Characterization Of Nitrous Oxide
Emission Sources, EPA Contract No. 68-D1-0031, Research Triangle Park, NC, 1995.
14. Steven D. Piccot, Jennifer A. Buzun, and H. Christopher Frey, Emissions And Cost Estimates For
Globally Significant Anthropogenic Combustion Sources Of NO.,, N2O, CH4, CO, And CO2, EPA
Contract No. 68-02-4288, Research Triangle Park, NC, 1990.
1.6-16 EMISSION FACTORS 8/98
-------
15. G. Marland, and R. M. Rotty, Carbon Dioxide Emissions From Fossil Fuels: A Procedure For
Estimation And Results For 1951-1981, DOE/NBB-0036 TR-003, Carbon Dioxide Research
Division, Office of Energy Research, U.S. Department of Energy, Oak Ridge, TN, 1983.
16. Sector-Specific Issues And Reporting Methodologies Supporting The General Guidelines For The
Voluntary Reporting Of Greenhouse Gases Under Section 1605(b) Of The Energy Policy Act Of
1992, Volume 2 of 3, U.S. Department of Energy, DOE/PO-0028, 1994.
17. R. A. Kester, Nitrogen Oxide Emissions From A Pilot Plant Spreader Stoker Bark Fired Boiler,
Department of Civil Engineering, University of Washington, Seattle, WA, December 1979.
18. A. Nunn, NOX Emission Factors For Wood Fired Boilers, EPA-600/7-79-219, U. S.
Environmental Protection Agency, September 1979.
19. Hazardous Air Emissions Potential From A Wood-Fired Furnace (and Attachments),
A. J. Hubbard, Wisconsin Department of Natural Resources, Madison, WI, July 1991.
20. Environmental Assessment Of A Wood-Waste-Fired Industrial Watertube Boiler, EPA Contract
No. 68-02-3188, Acurex Corporation, Mountain View, CA, March 1984.
21. Evaluation Test On A Wood Waste Fired Incinerator At Pacific Oroville Power Inc., Test Report
No. C-88-050, California Air Resources Board, Sacramento, CA, May 1990.
22. Evaluation Test On Twin Fluidized Bed Wood Waste Fueled Combustors Located In Central
California, Test Report No. C-87-042, California Air Resources Board, Sacramento, CA,
February, 1990.
23. A Polycydic Organic Materials Study For Industrial Wood-Fired Boilers, Technical Bulletin No.
400, National Council of the Paper Industry For Air and Stream Improvement, New York, NY,
May 1983.
24. Compilation Of Air Pollutant Emission Factors, Supplement A, Section 1.6, U. S. Environmental
Protection Agency, Research Triangle Park, NC, 1986.
25. Emission Test Report, Owens-Illinois Forest Products Division, Big Island, Virginia, EMB
Report 80-WFB-2, U. S. Environmental Protection Agency, Research Triangle Park, NC,
February 1980.
26. National Dioxin Study Tier 4, Combustion Sources: Final Test Report, Site 7, Wood Fired
Boiler WFB-A, EPA-450/4-84-014p, U. S. Environmental Protection Agency, Research Triangle
Park, NC, April 1987.
27. A Study Of Nitrogen Oxides Emissions From Wood Residue Boilers, Technical Bulletin No. 102,
National Council of the Paper Industry for Air and Stream Improvement, New York, NY,
November 1979.
28. H. S. Oglesby and R. O. Blosser, "Information On The Sulfur Content Of Bark And Its
Contribution To SO2 Emissions When Burned As A Fuel", Journal Of The Air Pollution Control
Agency, JO(7):769-772, July 1980.
8/98 External Combustion Sources 1.6-17
-------
29. Carbon Monoxide Emissions From Selected Combustion Sources Based On Short-Term
Monitoring Records, Technical Bulletin No. 416, National Council of the Paper Industry For Air
and Stream Improvement, New York, NY, January 1984.
30. Volatile Organic Carbon Emissions From Wood Residue Fired Power Boilers In The Southeast,
Technical Bulletin No. 455, National Council of the Paper Industry For Air and Stream
Improvement, New York, NY, April 1985.
31. A Study Of Formaldehyde Emissions From Wood Residue-Fired Boilers, Technical Bulletin
No. 622, National Council of the Paper Industry For Air and Stream Improvement, New York,
NY, January 1992.
32. Source Emission Testing of the Wood-Fired Boiler Exhaust at Sierra Pacific, Burney, California,
Performed for the Timber Association of California, Galston Technical Services, February 1991.
33. Source Emission Testing of the Wood-fired Boiler #1 Exhaust Stack at Wheelabrator Shasta
Energy Company (TAG Site 9), Anderson, California, Performed for the Timber Association of
California, Galston Technical Services, January 1991.
34. Source Emission Testing of the Wood-fired boiler at Catalyst Hudson, Inc., Anderson California,
Performed for the Timber Association of California, Galston Technical Services, February 1991.
35. Source Emission Testing of the Wood-fired Boiler at Big Valley Timber Company, Bieber,
California, Performed for the Timber Association of California, Galston Technical Services,
February, 1991.
36. Source Emission Testing of the CE Wood-Fired Boiler at Roseburg Forest Products (TAG Site
#3), Performed for the Timber Association of California, Galston Technical Services, January
1991.
37. Source Emission Testing of the Wood-fired Boiler #3 Exhaust at Georgia Pacific, Fort Bragg,
California, Performed for the Timber Association of California, Galston Technical Services,
February 1991.
38. Source Emission Testing of the Wood-fired Boiler "C" Exhaust at Pacific Timber, Scotia,
California, Performed for the Timber Association of California, Galston Technical Services,
February 1991.
39. Source Emission Testing of the Wood-fired Boiler Exhaust at Bohemia, Inc., Rocklin, California,
Prepared for the Timber Association of California, Galston Technical Services, December 1990.
40. Source Emission Testing of the Wood-fired Boiler at Yanke Energy, North Fork, California,
Performed for the Timber Association of California, Galston Technical Services, January 1991.
41. Source Emission Testing of the Wood-fired Boiler Exhaust at Miller Redwood Co., Crescent City,
California, Performed for the Timber Association of California, Galston Technical Services,
February 1991.
42. Emission Test Report, St. Joe Paper Company, Port St. Joe, Florida, EMB Report 80-WFB-5, U.
S. Environmental Protection Agency, Research Triangle Park, NC, May 1980.
1.6-18 EMISSION FACTORS 8/98
-------
43. Source Emission Testing of the Wood-fired Boiler #5 Exhaust at Roseburg Forest Products,
Anderson, California, Performed for the Timber Association of California, Galston Technical
Services, January 1991.
44. Nation Council Of The Paper Industry For Air And Stream Improvement, An Air Emission
Database for Wood Product Plant Combustion Units, Technical Bulletin No. 695. April 1995.
45. Inhalable Paniculate Source Category Report For External Combustion Sources, EPA Contract
No. 68-02-3156, Acurex Corporation, Mountain View, CA, January 1985.
8/98 External Combustion Sources 1.6-19
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2.4 Municipal Solid Waste Landfills
2.4.1 General1'4
A municipal solid waste (MSW) landfill unit is a discrete area of land or an excavation that receives
household waste, and that is not a land application unit, surface impoundment, injection well, or waste pile.
An MSW landfill unit may also receive other types of wastes, such as commercial solid waste,
nonhazardous sludge, and industrial solid waste. The municipal solid waste types potentially accepted by
MSW landfills include (most landfills accept only a few of the following categories):
• MSW,
• Household hazardous waste,
• Municipal sludge,
• Municipal waste combustion ash,
• Infectious waste,
• Waste tires,
• Industrial non-hazardous waste,
• Conditionally exempt small quantity generator (CESQG) hazardous waste,
• Construction and demolition waste,
• Agricultural wastes,
• Oil and gas wastes, and
• Mining wastes.
In the United States, approximately 57 percent of solid waste is landfilled, 16 percent is incinerated,
and 27 percent is recycled or composted. There were an estimated 2,500 active MSW landfills in the
United States in 1995. These landfills were estimated to receive 189 million megagrams (Mg) (208 million
tons) of waste annually, with 55 to 60 percent reported as household waste, and 35 to 45 percent reported
as commercial waste.
2.4.2 Process Description2'5
There are three major designs for municipal landfills. These are the area, trench, and ramp methods.
All of these methods utilize a three step process, which includes spreading the waste, compacting the waste,
and covering the waste with soil. The trench and ramp methods are not commonly used, and are not the
preferred methods when liners and leachate collection systems are utilized or required by law. The area fill
method involves placing waste on the ground surface or landfill liner, spreading it in layers, and
compacting with heavy equipment. A daily soil cover is spread over the compacted waste. The trench
method entails excavating trenches designed to receive a day's worth of waste. The soil from the
excavation is often used for cover material and wind breaks. The ramp method is typically employed on
sloping land, where waste is spread and compacted similar to the area method, however, the cover material
obtained is generally from the front of the working face of the filling operation.
Modern landfill design often incorporates liners constructed of soil (i.e., recompacted clay), or
synthetics (i.e., high density polyethylene), or both to provide an impermeable barrier to leachate (i.e.,
water that has passed through the landfill) and gas migration from the landfill.
8/98 Solid Waste Disposal 2.4-1
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2.4.3 Control Technologyli2'6
The Resource Conservation and Recovery Act (RCRA) Subtitle D regulations promulgated on
October 9, 1991 require that the concentration of methane generated by MSW landfills not exceed
25 percent of the lower explosive limit (LEL) in on-site structures, such as scale houses, or the LEL at the
facility property boundary.
The New Source Performance Standards (NSPS) and Emission Guidelines for air emissions from
MSW landfills for certain new and existing landfills were published in the Federal Register on
March 1, 1996. The regulation requires that Best Demonstrated Technology (BDT) be used to reduce
MSW landfill emissions from affected new and existing MSW landfills emitting greater than or equal to
50 Mg/yr (55 tons/yr) of non-methane organic compounds (NMOCs). The MSW landfills that are affected
by the NSPS/Emission Guidelines are each new MSW landfill, and each existing MSW landfill that has
accepted waste since November 8, 1987, or that has capacity available for future use. The NSPS/Emission
Guidelines affect landfills with a design capacity of 2.5 million Mg (2.75 million tons) or more. Control
systems require: (1) a well-designed and well-operated gas collection system, and (2) a control device
capable of reducing NMOCs in the collected gas by 98 weight-percent.
Landfill gas (LFG) collection systems are either active or passive systems. Active collection systems
provide a pressure gradient in order to extract LFG by use of mechanical blowers or compressors. Passive
systems allow the natural pressure gradient created by the increase in pressure created by LFG generation
within the landfill to mobilize the gas for collection.
LFG control and treatment options include (1) combustion of the LFG, and (2) purification of the LFG.
Combustion techniques include techniques that do not recover energy (i.e., flares and thermal incinerators),
and techniques that recover energy (i.e., gas turbines and internal combustion engines) and generate
electricity from the combustion of the LFG. Boilers can also be employed to recover energy from LFG in
the form of steam. Flares involve an open combustion process that requires oxygen for combustion, and
can be open or enclosed. Thermal incinerators heat an organic chemical to a high enough temperature in
the presence of sufficient oxygen to oxidize the chemical to carbon dioxide (CO2) and water. Purification
techniques can also be used to process raw landfill gas to pipeline quality natural gas by using adsorption,
absorption, and membranes.
2.4.4 Emissions2'7
Methane (CH4) and CO2 are the primary constituents of landfill gas, and are produced by
microorganisms within the landfill under anaerobic conditions. Transformations of CH4 and CO2 are
mediated by microbial populations that are adapted to the cycling of materials in anaerobic environments.
Landfill gas generation, including rate and composition, proceeds through four phases. The first phase is
aerobic [i.e., with oxygen (O2) available] and the primary gas produced is CO2. The second phase is
characterized by O2 depletion, resulting in an anaerobic environment, where large amounts of CO2 and
some hydrogen (H2) are produced. In the third phase, CH4 production begins, with an accompanying
reduction in the amount of CO2 produced. Nitrogen (N2) content is initially high in landfill gas hi the first
phase, and declines sharply as the landfill proceeds through the second and third phases. In the fourth
phase, gas production of CH4, CO2, and N2 becomes fairly steady. The total time and phase duration of
gas generation varies with landfill conditions (i.e., waste composition, design management, and anaerobic
state).
2.4-2 EMISSION FACTORS 8/98
-------
Typically, LFG also contains a small amount of non-methane organic compounds (NMOC). This
NMOC fraction often contains various organic hazardous air pollutants (HAP), greenhouse gases (GHG),
and compounds associated with stratospheric ozone depletion. The NMOC fraction also contains volatile
organic compounds (VOC). The weight fraction of VOC can be determined by subtracting the weight
fractions of individual compounds that are non-photochemically reactive (i.e., negligibly-reactive organic
compounds as defined in 40 CFR 51.100).
Other emissions associated with MSW landfills include combustion products from LFG control and
utilization equipment (i.e., flares, engines, turbines, and boilers). These include carbon monoxide (CO),
oxides of nitrogen (NOX), sulfur dioxide (SO2), hydrogen chloride (HC1), particulate matter (PM) and other
combustion products (including HAPs). PM emissions can also be generated in the form of fugitive dust
created by mobile sources (i.e., garbage trucks) traveling along paved and unpaved surfaces. The reader
should consult AP-42 Volume I Sections 13.2.1 and 13.2.2 for information on estimating fugitive dust
emissions from paved and unpaved roads.
The rate of emissions from a landfill is governed by gas production and transport mechanisms.
Production mechanisms involve the production of the emission constituent in its vapor phase through
vaporization, biological decomposition, or chemical reaction. Transport mechanisms involve the
transportation of a volatile constituent in its vapor phase to the surface of the landfill, through the air
boundary layer above the landfill, and into the atmosphere. The three major transport mechanisms that
enable transport of a volatile constituent in its vapor phase are diffusion, convection, and displacement.
2.4.4.1 Uncontrolled Emissions — To estimate uncontrolled emissions of the various compounds present
in landfill gas, total landfill gas emissions must first be estimated. Uncontrolled CH4 emissions may be
estimated for individual landfills by using a theoretical first-order kinetic model of methane production
developed by the EPA.8 This model is known as the Landfill Air Emissions Estimation model, and can be
accessed from the Office of Air Quality Planning and Standards Technology Transfer Network Website
(OAQPS TTN Web) in the Clearinghouse for Inventories and Emission Factors (CHIEF) technical area
(URL http://www.epa.gov/ttn/chief). The Landfill Air Emissions Estimation model equation is as follows:
QCH, =LR(e-kc -e-kt) (1)
where:
QCH4 = Methane generation rate at time t, m3/yr;
L0 = Methane generation potential, m3 CH4/Mg refuse;
R = Average annual refuse acceptance rate during active life, Mg/yr;
e = Base log, unitless;
k = Methane generation rate constant, yr'1;
c = Time since landfill closure, yrs (c = 0 for active landfills); and
t = Time since the initial refuse placement, yrs.
It should be noted that the model above was designed to estimate LFG generation and not LFG
emissions to the atmosphere. Other fates may exist for the gas generated in a landfill, including capture
and subsequent microbial degradation within the landfill's surface layer. Currently, there are no data that
adequately address this fate. It is generally accepted that the bulk of the gas generated will be emitted
through cracks or other openings in the landfill surface.
8/98 Solid Waste Disposal 2.4-3
-------
Site-specific landfill information is generally available for variables R, c, and t. When refuse
acceptance rate information is scant or unknown, R can be determined by dividing the refuse in place by the
age of the landfill. If a facility has documentation that a certain segment (cell) of a landfill received only
nondegradable refuse, then the waste from this segment of the landfill can be excluded from the calculation
of R. Nondegradable refuse includes concrete, brick, stone, glass, plaster, wallboard, piping, plastics, and
metal objects. The average annual acceptance rate should only be estimated by this method when there is
inadequate information available on the actual average acceptance rate. The time variable, t, includes the
total number of years that the refuse has been in place (including the number of years that the landfill has
accepted waste and, if applicable, has been closed).
Values for variables L0 and k must be estimated. Estimation of the potential CH4 generation capacity
of refuse (L0) is generally treated as a function of the moisture and organic content of the refuse.
Estimation of the CH4 generation constant (k) is a function of a variety of factors, including moisture, pH,
temperature, and other environmental factors, and landfill operating conditions. Specific CH4 generation
constants can be computed by the use of EPA Method 2E (40 CFR Part 60 Appendix A).
The Landfill Air Emission Estimation model includes both regulatory default values and recommended
AP-42 default values for L0 and k. The regulatory defaults were developed for compliance purposes
(NSPS/Emission Guideline). As a result, the model contains conservative L0 and k default values in order
to protect human health, to encompass a wide range of landfills, and to encourage the use of site-specific
data. Therefore, different L0 and k values may be appropriate in estimating landfill emissions for particular
landfills and for use in an emissions inventory.
Recommended AP-42 defaults include a k value of 0.04/yr for areas recieving 25 inches or more of
rain per year. A default k of 0.02/yr should be used in drier areas (<25 inches/yr). An L0 value of
100 m3/Mg (3,530 ft3/ton) refuse is appropriate for most landfills. Although the recommended default k
and L0 are based upon the best fit to 21 different landfills, the predicted methane emissions ranged from 38
to 492% of actual, and had a relative standard deviation of 0.85. It should be emphasized that in order to
comply with the NSPS/Emission Guideline, the regulatory defaults for k and L0 must be applied as
specified in the final rule.
When gas generation reaches steady state conditions, LFG consists of approximately 40 percent by
volume CO2, 55 percent CH4, 5 percent N2 (and other gases), and trace amounts of NMOCs. Therefore,
the estimate derived for CH4 generation using the Landfill Air Emissions Estimation model can also be used
to represent CO2 generation. Addition of the CH4 and CO2 emissions will yield an estimate of total landfill
gas emissions. If site-specific information is available to suggest that the CH4 content of landfill gas is not
55 percent, then the site-specific information should be used, and the CO2 emission estimate should be
adjusted accordingly.
Most of the NMOC emissions result from the volatilization of organic compounds contained in the
landfilled waste. Small amounts may be created by biological processes and chemical reactions within the
landfill. The current version of the Landfill Air Emissions Estimation model contains a proposed
regulatory default value for total NMOC of 4,000 ppmv, expressed as hexane. However, available data
show that there is a range of over 4,400 ppmv for total NMOC values from landfills. The proposed
regulatory default value for NMOC concentration was developed for regulatory compliance purposes and
to provide the most cost-effective default values on a national basis. For emissions inventory purposes,
site-specific information should be taken into account when determining the total NMOC concentration. In
the absence of site-specific information, a value of 2,420 ppmv as hexane is suggested for landfills known
to have co-disposal of MSW and non-residential waste. If the landfill is known to contain only MSW or
2.4-4 EMISSION FACTORS 8/98
-------
have very little organic commercial/industrial wastes, then a total NMOC value of 595 ppmv as hexane
should be used. In addition, as with the landfill model defaults, the regulatory default value for NMOC
content must be used in order to comply with the NSPS/Emission Guideline.
If a site-specific total pollutant concentration is available (i.e., as measured by EPA Reference Method
25C), it must be corrected for air infiltration which can occur by two different mechanisms: LFG sample
dilution, and air intrusion into the landfill. These corrections require site-specific data for the LFG CH4,
CO2, nitrogen (N2), and oxygen (O^ content. If the ratio of N2 to O2 is less than or equal to 4.0 (as found
in ambient air), then the total pollutant concentration is adjusted for sample dilution by assuming that CO2
and CH4 are the primary (100 percent) constituents of landfill gas, and the following equation is used:
Cp (ppmv) (1 x 106)
Cp (ppmv) (corrected for air infiltration) = - (2)
C
co2 CH4
where:
Cp = Concentration of pollutant P in landfill gas (i.e., NMOC as hexane), ppmv;
CO2 concentration in landfill gas, ppmv.
CH4 Concentration in landfill gas, ppmv; and
1 x 106 = Constant used to correct concentration of P to units of ppmv.
If the ratio of N2 to O2 concentrations (i.e., CN , CQ ) is greater than 4.0, then the total pollutant
concentration should be adjusted for air intrusion into the landfill by using equation 2 and adding the
concentration of N2 (i.e., CN ) to the denominator. Values for CQQ . CCH . CN . CQ , can usually be
found in the source test report for the particular landfill along with the total pollutant concentration data.
To estimate emissions of NMOC or other landfill gas constituents, the following equation should be
used:
where:
Qp = Emission rate of pollutant P (i.e. NMOC), m3/yr;
QCH4 = CH4 generation rate, m3/yr (from the Landfill Air Emissions Estimation model);
Cp = Concentration of P in landfill gas, ppmv; and
1.82 = Multiplication factor (assumes that approximately 55 percent of landfill gas is
CH4 and 45 percent is CO2, N2, and other constituents).
8/98 Solid Waste Disposal 2.4-5
-------
Uncontrolled mass emissions per year of total NMOC (as hexane), CO2, CH4, and speciated organic and
inorganic compounds can be estimated by the following equation:
MWD * 1 atm
UMP = QP * P
(4)
(8.205xl(T5 m3-atm/gmol-"K)(1000g/kg)(273 +T"K)
where:
UMp = Uncontrolled mass emissions of pollutant P (i.e., NMOC), kg/yr;
MWp = Molecular weight of P, g/gmol (i.e., 86.18 for NMOC as hexane);
Qp = NMOC emission rate of P, mVyr; and
T = Temperature of landfill gas, °C.
This equation assumes that the operating pressure of the system is approximately 1 atmosphere. If the
temperature of the landfill gas is not known, a temperature of 25°C (77°F) is recommended.
Uncontrolled default concentrations of speciated organics along with some inorganic compounds are
presented in Table 2.4-1. These default concentrations have already been corrected for air infiltration and
can be used as input parameters to equation 3 or the Landfill Air Emission Estimation model for estimating
speciated emissions from landfills when site-specific data are not available. An analysis of the data, based
on the co-disposal history (with non-residential wastes) of the individual landfills from which the
concentration data were derived^ indicates that for benzene, NMOC, and toluene, there is a difference in the
uncontrolled concentrations. Table 2.4-2 presents the corrected concentrations for benzene, NMOC, and
toluene to use based on the site's co-disposal history.
It is important to note that the compounds listed in Tables 2.4-1 and 2.4-2 are not the only compounds
likely to be present in LFG. The listed compounds are those that were identified through a review of the
available literature. The reader should be aware that additional compounds are likely present, such as
those associated with consumer or industrial products. Given this information, extreme caution should be
exercised in the use of the default VOC weight fractions and concentrations given at the bottom of Table
2.4-2. These default VOC values are heavily influenced by the ethane content of the LFG. Available data
have shown that there is a range of over 1,500 ppmv in LFG ethane content among landfills.
2.4.4.2 Controlled Emissions — Emissions from landfills are typically controlled by installing a gas
collection system, and combusting the collected gas through the use of internal combustion engines, flares,
or turbines. Gas collection systems are not 100 percent efficient in collecting landfill gas, so emissions of
CH4 and NMOC at a landfill with a gas recovery system still occur. To estimate controlled emissions of
CH4, NMOC, and other constituents in landfill gas, the collection efficiency of the system must first be
estimated. Reported collection efficiencies typically range from 60 to 85 percent, with an average of
75 percent most commonly assumed. Higher collection efficiencies may be achieved at some sites (i.e.,
those engineered to control gas emissions). If site-specific collection efficiencies are available (i.e., through
a comprehensive surface sampling program), then they should be used instead of the 75 percent average.
Controlled emission estimates also need to take into account the control efficiency of the control device.
Control efficiencies based on test data for the combustion of CH4, NMOC, and some speciated organics
with differing control devices are presented in Table 2.4-3. Emissions from the control devices need to be
added to the uncollected emissions to estimate total controlled emissions.
2.4-6 EMISSION FACTORS 8/98
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Controlled CH4, NMOC, and speciated emissions can be calculated with equation 5. It is assumed that
the landfill gas collection and control system operates 100 percent of the time. Minor durations of system
downtime associated with routine maintenance and repair (i.e., 5 to 7 percent) will not appreciably effect
emission estimates. The first term in equation 5 accounts for emissions from uncollected landfill gas, while
the second term accounts for emissions of the pollutant that were collected but not combusted in the control
or utilization device:
CMp =
UMp *
1 -
100,
100
1 -
•lent
Too,
(5)
where:
CMP
UMp
T)col
Controlled mass emissions of pollutant P, kg/yr;
Uncontrolled mass emissions of P, kg/yr (from equation 4 or the Landfill Air
Emissions Estimation Model);
Collection efficiency of the landfill gas collection system, percent; and
Control efficiency of the landfill gas control or utilization device, percent.
Emission factors for the secondary compounds, CO and NOX, exiting the control device are
presented in Tables 2.4-4 and 2.4-5. These emission factors should be used when equipment vendor
guarantees are not available.
Controlled emissions of CO2 and sulfur dioxide (SO2) are best estimated using site-specific landfill gas
constituent concentrations and mass balance methods.68 If site-specific data are not available, the data in
tables 2.4-1 through 2.4-3 can be used with the mass balance methods that follow.
Controlled CO2 emissions include emissions from the CO2 component of landfill gas (equivalent to
uncontrolled emissions) and additional CO2 formed during the combustion of landfill gas. The bulk of the
CO2 formed during landfill gas combustion comes from the combustion of the CH4 fraction. Small
quantities will be formed during the combustion of the NMOC fraction, however, this typically amounts to
less than 1 percent of total CO2 emissions by weight. Also, the formation of CO through incomplete
combustion of landfill gas will result in small quantities of CO2 not being formed. This contribution to the
overall mass balance picture is also very small and does not have a significant impact on overall CO2
68
emissions.
The following equation which assumes a 100 percent combustion efficiency for CH4 can be used to
estimate CO2 emissions from controlled landfills:
= UM
CO,
UM
CH,
100
* 2.75
(6)
where:
CMCo2 =
UMCQ2 =
UMCH4 =
2.75 =
Controlled mass emissions of CO2, kg/yr;
Uncontrolled mass emissions of CO2, kg/yr (from equation 4 or the Landfill Air
Emission Estimation Model);
Uncontrolled mass emissions of CH4, kg/yr (from equation 4 on the Landfill Air
Emission Estimation Model);
Efficiency of the landfill gas collection system, percent; and
Ratio of the molecular weight of CO2 to the molecular weight of CH4.
8/98
Solid Waste Disposal
2.4-7
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To prepare estimates of SO2 emissions, data on the concentration of reduced sulfur compounds within
the landfill gas are needed. The best way to prepare this estimate is with site-specific information on the
total reduced sulfur content of the landfill gas. Often these data are expressed in ppmv as sulfur (S).
Equations 3 and 4 should be used first to determine the uncontrolled mass emission rate of reduced sulfur
compounds as sulfur. Then, the following equation can be used to estimate SO2 emissions:
CM,n = UM- * — * 2.0 (7)
so2 s 100
where:
= Controlled mass emissions of SO2, kg/yr;
UMg = Uncontrolled mass emissions of reduced sulfur compounds as sulfur, kg/yr (from
equations 3 and 4);
r|CO| = Efficiency of the landfill gas collection system, percent; and
2.0 = Ratio of the molecular weight of SO2 to the molecular weight of S.
The next best method to estimate SO2 concentrations, if site-specific data for total reduced sulfur
compounds as sulfur are not available, is to use site-specific data for speciated reduced sulfur compound
concentrations. These data can be converted to ppmv as S with equation 8. After the total reduced sulfur
as S has been obtained from equation 8, then equations 3, 4, and 7 can be used to derive SO2 emissions.
c = v c * s
^S Z-i = l ^P °P
where:
C§ = Concentration of total reduced sulfur compounds, ppmv as S (for use in equation
3);
Cp = Concentration of each reduced sulfur compound, ppmv;
Sp = Number of moles of S produced from the combustion of each reduced sulfur
compound (i.e., 1 for sulfides, 2 for disulfides); and
n = Number of reduced sulfur compounds available for summation.
If no site-specific data are available, a value of 46.9 ppmv can be assumed for Cs (for use in
equation 3). This value was obtained by using the default concentrations presented in Table 2.4-1 for
reduced sulfur compounds and equation 8.
Hydrochloric acid [Hydrogen Chloride (HC1)] emissions are formed when chlorinated compounds in
LFG are combusted in control equipment. The best methods to estimate emissions are mass balance
methods that are analogous to those presented above for estimating SO2 emissions. Hence, the best source
of data to estimate HC1 emissions is site-specific LFG data on total chloride [expressed in ppmv as the
chloride ion (Cl~)]. If these data are not available, then total chloride can be estimated from data on
individual chlorinated species using equation 9 below. However, emission estimates may be
2.4-8 EMISSION FACTORS 8/98
-------
underestimated, since not every chlorinated compound in the LFG will be represented in the laboratory
report (i.e., only those that the analytical method specifies).
cc, =
where:
CQ
Cp
Clp
C * CI
Concentration of total chloride, ppmv as Cl~ (for use in equation 3);
Concentration of each chlorinated compound, ppmv;
Number of moles of Cl" produced from the combustion of each chlorinated
compound (i.e., 3 for 1,1,1-trichloroethane); and
Number of chlorinated compounds available for summation.
(9)
After the total chloride concentration (CC1) has been estimated, equations 3 and 4 should be used to
determine the total uncontrolled mass emission rate of chlorinated compounds as chloride ion (UMC1). This
value is then used in equation 10 below to derive HC1 emission estimates:
CMHCI = UMQ *
100
* 1.03 *
1
lent
100
(10)
where:
CMHC1
UMC1
rlcol
1.03
Controlled mass emissions of HC1, kg/yr;
Uncontrolled mass emissions of chlorinated compounds as chloride, kg/yr (from
equations 3 and 4);
Efficiency of the landfill gas collection system, percent;
Ratio of the molecular weight of HC1 to the molecular weight of Cl"; and
Control efficiency of the landfill gas control or utilization device, percent.
In estimating HC1 emissions, it is assumed that all of the chloride ion from the combustion of
chlorinated LFG constituents is converted to HC1. If an estimate of the control efficiency, r|cnt, is not
available, then the high end of the control efficiency range for the equipment listed in Table 9 should be
used. This assumption is recommended to assume that HC1 emissions are not under-estimated.
If site-specific data on total chloride or speciated chlorinated compounds are not available, then a
default value of 42.0 ppmv can be used for Ca. This value was derived from the default LFG constituent
concentrations presented in Table 2.4-1. As mentioned above, use of this default may produce
underestimates of HC1 emissions since it is based only on those compounds for which analyses have been
performed. The constituents listed in Table 2.4-1 are likely not all of the chlorinated compounds present in
LFG.
The reader is referred to Sections 11.2-1 (Unpaved Roads, SCC 50100401), and 11-2.4 (Heavy
Construction Operations) of Volume I, and Section II-7 (Construction Equipment) of Volume II, of the
AP-42 document for determination of associated fugitive dust and exhaust emissions from these emission
sources at MSW landfills.
8/98
Solid Waste Disposal
2.4-9
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2.4.5 Updates Since the Fifth Edition
The Fifth Edition was released in January 1995. This is revision includes major revisions of the text
and recommended emission factors conained in the section. The most significant revisions to this section
since publication in the Fifth Edition are summarized below.
• The equations to calculate the CH4, CO2 and other constituents were simplified.
• The default LO and k were revised based upon an expanded base of gas generation data.
• The default ratio of CO2 to CH4 was revised based upon averages observed in available source
test reports.
• The default concentrations of LFG constituents were revised based upon additional data.
• Additional control efficiencies were included and existing efficiencies were revised based upon
additional emission test data.
• Revised and expanded the recommended emission factors for secondary compounds emitted from
typical control devices.
2.4-10 EMISSION FACTORS 8/98
-------
Table 2.4-1. DEFAULT CONCENTRATIONS FOR LFG CONSTITUENTS"
(SCC 50100402, 50300603)
Compound
1,1,1-Trichloroethane (methyl chloroform)3
1 , 1 ,2,2-Tetrachloroethane"
1,1-Dichloroethane (ethylidene dichloride)3
1,1-Dichloroethene (vinylidene chloride)3
1 ,2-Dichloroethane (ethylene dichloride)3
1,2-Dichloropropane (propylene dichloride)"
2-Propanol (isopropyl alcohol)
Acetone
Acrylonitrile3
Bromodichloromethane
Butane
Carbon disulfide3
Carbon monoxideb
Carbon tetrachloridea
Carbonyl sulfide3
Chlorobenzene3
Chlorodifluoromethane
Chloroethane (ethyl chloride)3
Chloroform3
Chloromethane
Dichlorobenzenec
Dichlorodifluoromethane
Dichlorofluoromethane
Dichloromethane (methylene chloride)3
Dimethyl sulfide (methyl sulfide)
Ethane
Ethanol
Ethyl mercaptan (ethanethiol)
Ethylbenzene3
Ethylene dibromide
Fluorotrichloromethane
Hexane3
Hydrogen sulfide
Mercury (total)3''1
Molecular Weight
133.42
167.85
98.95
96.94
98.96
112.98
60.11
58.08
53.06
163.83
58.12
76.13
28.01
153.84
60.07
112.56
86.47
64.52
119.39
50.49
147
120.91
102.92
84.94
62.13
30.07
46.08
62.13
106.16
187.88
137.38
86.18
34.08
200.61
Default
Concentration
(ppmv)
0.48
1.11
2.35
0.20
0.41
0.18
50.1
7.01
6.33
3.13
5.03
0.58
141
0.004
0.49
0.25
1.30
1.25
0.03
1.21
0.21
15.7
2.62
14.3
7.82
889
27.2
2.28
4.61
0.001
0.76
6.57
35.5
2.92X10-4
Emission Factor
Rating
B
C
B
B
B
D
E
B
D
C
C
C
E
B
D
C
C
B
B
B
E
A
D
A
C
C
E
D
B
E
B
B
B
E
8/98
Solid Waste Disposal
2.4-11
-------
Table 2.4-1. (Concluded)
Compound
Methyl ethyl ketonea
Methyl isobutyl ketone"
Methyl mercaptan
Pentane
Perchloroethylene(tetrachloroethylene)a
Propane
t- 1 ,2-dichloroethene
Trichloroethylene (trichloroethene)a
Vinyl chloride2
Xylenes"
Molecular Weight
72.11
100.16
48.11
72.15
165.83
44.09
96.94
131.38
62.50
106.16
Default
Concentration
(ppmv)
7.09
1.87
2.49
3.29
3.73
11.1
2.84
2.82
7.34
12.1
Emission Factor
Rating
A
B
C
C
B
B
B
B
B
B
NOTE: This is not an all-inclusive list of potential LFG constituents, only those for which test data were
available at multiple sites. References 10-67. Source Classification Codes in parentheses.
" Hazardous Air Pollutants listed in Title in of the 1990 Clean Air Act Amendments.
b Carbon monoxide is not a typical constituent of LFG, but does exist in instances involving landfill
(underground) combustion. Therefore, this default value should be used with caution. Of 18 sites where CO
was measured, only 2 showed detectable levels of CO.
c Source tests did not indicate whether this compound was the para- or ortho- isomer. The para isomer is a
Title in-listed HAP.
d No data were available to speciate total Hg into the elemental and organic forms.
2.4-12
EMISSION FACTORS
8/98
-------
Table 2.4-2. DEFAULT CONCENTRATIONS OF BENZENE, NMOC, AND TOLUENE BASED ON
WASTE DISPOSAL HISTORY3
(SCC 50100402, 50300603)
Pollutant
Benzeneb
Co-disposal
No or Unknown co-disposal
NMOC (as hexane)c
Co-disposal
No or Unknown co-disposal
Tolueneb
Co-disposal
No or Unknown co-disposal
Molecular
Weight
78.11
86.18
92.13
Default
Concentration
(ppmv)
11.1
1.91
2420
595
165
39.3
Emission Factor
Rating
D
B
D
B
D
A
a References 10-54. Source Classification Codes in parentheses.
b Hazardous Air Pollutants listed in Title in of the 1990 Clean Air Act Amendments.
c For NSPS/Emission Guideline compliance purposes, the default concentration for NMOC as
specified in the final rule must be used. For purposes not associated with NSPS/Emission
Guideline compliance, the default VOC content at co-disposal sites = 85 percent by weight
(2,060 ppmv as hexane); at No or Unknown sites = 39 percent by weight 235 ppmv as
hexane).
8/98
Solid Waste Disposal
2.4-13
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Table 2.4-3. CONTROL EFFICIENCIES FOR LFG CONSTITUENTS4
Control Device
Boiler/Steam Turbine
(50100423)
Flarec
(50100410)
(50300601)
Gas Turbine
(50100420)
1C Engine
(50100421)
Constituent1"
NMOC
Halogenated Species
Non-Halogenated Species
NMOC
Halogenated Species
Non-Halogenated Species
NMOC
Halogenated Species
Non-Halogenated Species
NMOC
Halogenated Species
Non-Halogenated Species
Control Efficiency (%)
Typical Range Rating
98.0
99.6
99.8
99.2
98.0
99.7
94.4
99.7
98.2
97.2
93.0
86.1
96-99+
87-99+
67-99+
90-99+
91-99+
38-99+
90-99+
98-99+
97-99+
94-99+
90-99+
25-99+
D
D
D
B
C
C
E
E
E
E
E
E
* References 10-67. Source Classification Codes in parentheses.
Halogenated species are those containing atoms of chlorine, bromine, fluorine, or iodine. For any
equipment, the control efficiency for mercury should be assumed to be 0. See section 2.4.4.2 for
methods to estimate emissions of SO2, CO2, and HC1.
c Where information on equipment was given in the reference, test data were taken from enclosed flares.
Control efficiencies are assumed to be equally representative of open flares.
2.4-14
EMISSION FACTORS
8/98
-------
Table 2.4-4. (Metric Units) EMISSION FACTORS FOR SECONDARY COMPOUNDS
EXITING CONTROL DEVICES8
Control Device
Flarec
(50100410)
(50300601)
1C Engine
(50100421)
Boiler/Steam Turbined
(50100423)
Gas Turbine
(50100420)
Pollutant5
Nitrogen dioxide
Carbon monoxide
Particulate matter
Nitrogen dioxide
Carbon monoxide
Particulate matter
Nitrogen dioxide
Carbon monoxide
Particulate matter
Nitrogen dioxide
Carbon monoxide
Particulate matter
Typical Rate,
kg/hr/dscmm
Methane
0.039
0.72
0.016
0.24
0.45
0.046
0.032
5.4 x lO'3
7.9 x 10-3
0.083
0.22
0.021
Emission Factor
Rating
C
C
D
D
C
E
D
E
D
D
E
E
a Source Classification Codes in parentheses.
b No data on PM size distributions were available, however for other gas-fired combustion sources,
most of the paniculate matter is less than 2.5 microns in diameter. Hence, this emission factor can be
used to provide estimates of PM-10 or PM-2.5 emissions. See section 2.4.4.2 for methods to estimate
CO2, SO2, and HC1.
c Where information on equipment was given in the reference, test data were taken from enclosed
flares. Control efficiencies are assumed to be equally representative of open flares.
d All source tests were conducted on boilers, however emission factors should also be representative of
steam turbines. Emission factors are representative of boilers equipped with low-NOx burners and
flue gas recirculation. No data were available for uncontrolled NOX emissions.
8/98
Solid Waste Disposal
2.4-15
-------
Table 2.4-5. (English Units) EMISSION RATES FOR SECONDARY COMPOUNDS
EXITING CONTROL DEVICES3
Control Device
Flarec
(50100410)
(50300601)
1C Engine
(50100421)
Boiler/Steam Turbined
(50100423)
Gas Turbine
(50100420)
Pollutantb
Nitrogen dioxide
Carbon monoxide
Paniculate matter
Nitrogen dioxide
Carbon monoxide
Paniculate matter
Nitrogen dioxide
Carbon monoxide
Paniculate matter
Nitrogen dioxide
Carbon monoxide
Paniculate matter
Typical Rate,
Ib/hr/dscfm
Methane
2.4 x 1C'3
0.045
l.Ox 10'3
0.015
0.028
2.9 x ID'3
2.0 x 10°
3.4 x 10-4
4.9 x 10-4
5.2 x 10'3
0.014
1.3xlO-3
Emission
Factor Rating
C
C
D
D
C
E
E
E
E
D
D
E
a Source Classification Codes in parentheses.
b Based on data for other combustion sources, most of the paniculate matter will be less than
2.5 microns in diameter. Hence, this emission rate can be used to provide estimates of PM-10
or PM-2.5 emissions. See section 2.4.4.2 for methods to estimate CO2, SO2, and HC1.
c Where information on equipment was given in the reference, test data were taken from
enclosed flares. Control efficiencies are assumed to be equally representative of open flares.
d All source tests were conducted on boilers, however emission factors should also be
representative of steam turbines. Emission factors are representative of boilers equipped with
low-NOx burners and flue gas recirculation. No data were available for uncontrolled NOX
emissions.
References for Section 2.4
1. "Criteria for Municipal Solid Waste Landfills," 40 CFR Part 258, Volume 56, No. 196, October 9,
1991.
2. Air Emissions from Municipal Solid Waste Landfills - Background Information for Proposed
Standards and Guidelines, Office of Air Quality Planning and Standards, EPA-450/3-90-011a,
Chapters 3 and 4, U. S. Environmental Protection Agency, Research Triangle Park, NC, March 1991.
3. Characterization of Municipal Solid Waste in the United States: 1992 Update, Office of Solid
Waste, EPA-530-R-92-019, U. S. Environmental Protection Agency, Washington, DC, NTIS
No. PB92-207-166, July 1992.
4. Eastern Research Group, Inc., List of Municipal Solid Waste Landfills, Prepared for the
U. S. Environmental Protection Agency, Office of Solid Waste, Municipal and Industrial Solid Waste
Division, Washington, DC, September 1992.
2.4-16
EMISSION FACTORS
8/98
-------
5. Suggested Control Measures for Landfill Gas Emissions, State of California Air Resources Board,
Stationary Source Division, Sacramento, CA, August 1990.
6. "Standards of Performance for New Stationary Sources and Guidelines for Control of Existing
Sources: Municipal Solid Waste Landfills; Proposed Rule, Guideline, and Notice of Public Hearing,"
40 CFR Parts 51, 52, and 60, Vol. 56, No. 104, May 30, 1991.
7. S.W. Zison, Landfill Gas Production Curves: Myth Versus Reality, Pacific Energy, City of
Commerce, CA, [Unpublished]
8. R.L. Peer, et al., Memorandum Methodology Used to Revise the Model Inputs in the Municipal Solid
Waste Landfills Input Data Bases (Revised), to the Municipal Solid Waste Landfills Docket No. A-
88-09, April 28, 1993.
9. A.R. Chowdhury, Emissions from a Landfill Gas-Fired Turbine/Generator Set, Source Test Report
C-84-33, Los Angeles County Sanitation District, South Coast Air Quality Management District,
June 28, 1984.
10. Engineering-Science, Inc., Report of Stack Testing at County Sanitation District Los Angeles Puente
Hills Landfill, Los Angeles County Sanitation District, August 15, 1984.
11. J.R. Manker, Vinyl Chloride (and Other Organic Compounds) Content of Landfill Gas Vented to an
Inoperative Flare, Source Test Report 84-496, David Price Company, South Coast Air Quality
Management District, November 30, 1984.
12. S. Mainoff, Landfill Gas Composition, Source Test Report 85-102, Bradley Pit Landfill, South Coast
Air Quality Management District, May 22, 1985.
13. J. Littman, Vinyl Chloride and Other Selected Compounds Present in A Landfill Gas Collection
System Prior to and after Flaring, Source Test Report 85-369, Los Angeles County Sanitation
District, South Coast Air Quality Management District, October 9, 1985.
14. W.A. Nakagawa, Emissions from a Landfill Exhausting Through a Flare System, Source Test
Report 85-461, Operating Industries, South Coast Air Quality Management District, October 14,
1985.
15. S. Marinoff, Emissions from a Landfill Gas Collection System, Source Test Report 85-511. Sheldon
Street Landfill, South Coast Air Quality Management District, December 9, 1985.
16. W.A. Nakagawa, Vinyl Chloride and Other Selected Compounds Present in a Landfill Gas
Collection System Prior to and after Flaring, Source Test Report 85-592, Mission Canyon Landfill,
Los Angeles County Sanitation District, South Coast Air Quality Management District, January 16,
1986.
17. California Air Resources Board, Evaluation Test on a Landfill Gas-Fired Flare at the BKK Landfill
Facility, West Covina, CA, ARB-SS-87-09, July 1986.
18. S. Marinoff, Gaseous Composition from a Landfill Gas Collection System and Flare, Source Test
Report 86-0342, Syufy Enterprises, South Coast Air Quality Management District, August 21, 1986.
19. Analytical Laboratory Report for Source Test, Azusa Land Reclamation, June 30, 1983, South Coast
Air Quality Management District.
20. J.R. Manker, Source Test Report C-84-202, Bradley Pit Landfill, South Coast Air Quality
Management District, May 25, 1984.
8/98 Solid Waste Disposal 2.4-17
-------
21. S. Marinoff, Source Test Report 84-315, Puente Hills Landfill, South Coast Air Quality Management
District, February 6, 1985.
22. P.P. Chavez, Source Test Report 84-596, Bradley Pit Landfill, South Coast Air Quality Management
District, March 11, 1985.
23. S. Marinoff, Source Test Report 84-373, Los Angeles By-Products, South Coast air Quality
Management District, March 27, 1985.
24. J. Littman, Source Test Report 85-403, Palos Verdes Landfill, South Coast Air Quality Management
District, September 25, 1985.
25. S. Marinoff, Source Test Report 86-0234, Pacific Lighting Energy Systems, South Coast Air Quality
Management District, July 16, 1986.
26. South Coast Air Quality Management District, Evaluation Test on a Landfill Gas-Fired Flare at the
Los Angeles County Sanitation District's Puente Hills Landfill Facility, [ARB/SS-87-06],
Sacramento, CA, July 1986.
27. D.L. Campbell, et al., Analysis of Factors Affecting Methane Gas Recovery from Six Landfills, Air
and Energy Engineering Research Laboratory, EPA-600/2-91-055, U. S. Environmental Protection
Agency, Research Triangle Park, NC, September 1991.
28. Browning-Ferris Industries, Source Test Report, Lyon Development Landfill, August 21, 1990.
29. X.V. Via, Source Test Report, Browning-Ferris Industries, Azusa Landfill.
30. M. Nourot, Gaseous Composition from a Landfill Gas Collection System and Flare Outlet. Laidlaw
Gas Recovery Systems, to J.R. Farmer, OAQPS:ESD, December 8, 1987.
31. D.A. Stringham and W.H. Wolfe, Waste Management of North America, Inc., to J.R. Farmer,
OAQPS:ESD, January 29, 1988, Response to Section 114 questionnaire.
32. V. Espinosa, Source Test Report 87-0318, Los Angeles County Sanitation District Calabasas
Landfill, South Coast Air Quality Management District, December 16, 1987.
33. C.S. Bhatt, Source Test Report 87-0329, Los Angeles County Sanitation District, Scholl Canyon
Landfill, South Coast Air Quality Management District, December 4, 1987.
34. V. Espinosa, Source Test Report 87-0391, Puente Hills Landfill, South Coast Air Quality
Management District, February 5, 1988.
35. V. Espinosa, Source Test Report 87-0376, Palos Verdes Landfill, South Coast Air Quality
Management District, February 9, 1987.
36. Bay Area Air Quality Management District, Landfill Gas Characterization, Oakland, CA, 1988.
37. Steiner Environmental, Inc., Emission Testing at BFI's Arbor Hills Landfill, Northville, Michigan,
September 22 through 25, 1992, Bakersfield, CA, December 1992.
38. PEI Associates, Inc., Emission Test Report - Performance Evaluation Landfill-Gas Enclosed Flare,
Browning Ferris Industries, Chicopee, MA, 1990.
39. Kleinfelder Inc., Source Test Report Boiler and Flare Systems, Prepared for Laidlaw Gas Recovery
Systems, Coyote Canyon Landfill, Diamond Bar, CA, 1991.
2.4-18 EMISSION FACTORS 8/98
-------
40. Bay Area Air Quality Management District, McGill Flare Destruction Efficiency Test Report for
Landfill Gas at the Durham Road Landfill, Oakland, CA, 1988.
41. San Diego Air Pollution Control District, Solid Waste Assessment for Otay Valley/Annex Landfill.
San Diego, CA, December 1988.
42. PEI Associates, Inc., Emission Test Report - Performance Evaluation Landfill Gas Enclosed Flare,
Rockingham, VT, September 1990.
43. Browning-Ferris Industries, Gas Flare Emissions Source Test for Sunshine Canyon Landfill.
Sylmar,CA, 1991.
44. Scott Environmental Technology, Methane and Nonmethane Organic Destruction Efficiency Tests of
an Enclosed Landfill Gas Flare, April 1992.
45. BCM Engineers, Planners, Scientists and Laboratory Services, Air Pollution Emission Evaluation
Report for Ground Flare at Browning Ferris Industries Greentree Landfill, Kersey, Pennsylvania.
Pittsburgh, PA, May 1992.
46. EnvironMETeo Services Inc., Stack Emissions Test Report for Ameron Kapaa Quarry, Waipahu, HI,
January 1994.
47. Waukesha Pearce Industries, Inc., Report of Emission Levels and Fuel Economies for Eight
Waukesha 12V-AT25GL Units Located at the Johnston, Rhode Island Central Landfill, Houston
TX,July 19, 1991.
48. Mostardi-Platt Associates, Inc., Gaseous Emission Study Performed for Waste Management of
North America, Inc., CID Environmental Complex Gas Recovery Facility, August 8, 1989. Chicago,
IL, August 1989.
49. Mostardi-Platt Associates, Inc., Gaseous Emission Study Performed for Waste Management of
North America, Inc., at the CID Environmental Complex Gas Recovery Facility, July 12-14, 1989.
Chicago, IL, July 1989.
50. Browning-Ferris Gas Services, Inc., Final Report for Emissions Compliance Testing of One
Waukesha Engine Generator, Chicopee, MA, February 1994.
51. Browning-Ferris Gas Services, Inc., Final Report for Emissions Compliance Testing of Three
Waukesha Engine Generators, Richmond, VA, February 1994.
52. South Coast Environmental Company (SCEC), Emission Factors for Landfill Gas Flares at the
Arizona Street Landfill, Prepared for the San Diego Air Pollution Control District, San Diego, CA,
November 1992.
53. Carnot, Emission Tests on the Puente Hills Energy from Landfill Gas (PERG) Facility - Unit 400,
September 1993, Prepared for County Sanitation Districts of Los Angeles County, Tustin, CA,
November 1993.
54. Pape & Steiner Environmental Services, Compliance Testing for Spadra Landfill Gas-to-Energy
Plant, July 25 and 26, 1990, Bakersfield, CA, November 1990.
55. AB2588 Source Test Report for Oxnard Landfill, July 23-27, 1990, by Petro Chem Environmental
Services, Inc., for Pacific Energy Systems, Commerce, CA, October 1990.
8/98 Solid Waste Disposal 2.4-19
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56. AB2588 Source Test Report for Oxnard Landfill, October 16, 1990, by Petro Chem Environmental
Services, Inc., for Pacific Energy Systems, Commerce, CA, November 1990.
57. Engineering Source Test Report for Oxnard Landfill, December 20, 1990, by Petro Chem
Environmental Services, Inc., for Pacific Energy Systems, Commerce, CA, January 1991.
58. AB2588 Emissions Inventory Report for the Salinas Crazy Horse Canyon Landfill, Pacific Energy,
Commerce, CA, October 1990.
59. Newby Island Plant 2 Site 1C Engine's Emission Test, February 7-8, 1990, Laidlaw Gas Recovery
Systems, Newark, CA, February 1990.
60. Landfill Methane Recovery Part II: Gas Characterization, Final Report, Gas Research Institute,
December 1982.
61. Letter from J.D. Thornton, Minnesota Pollution Control Agency, to R. Myers, U.S. EPA, February 1,
1996.
62. Letter and attached documents from M. Sauers, GSF Energy, to S. Thorneloe, U.S. EPA, May 29,
1996.
63. Landfill Gas Particulate and Metals Concentration and Row Rate, Mountaingate Landfill Gas
Recovery Plant, Horizon Air Measurement Services, prepared for GSF Energy, Inc., May 1992.
64. Landfill Gas Engine Exhaust Emissions Test Report in Support of Modification to Existing 1C Engine
Permit at Bakersfield Landfill Unit #1, Pacific Energy Services, December 4, 1990.
65. Addendum to Source Test Report for Superior Engine #1 at Otay Landfill, Pacific Energy Services,
April 2, 1991.
66. Source Test Report 88-0075 of Emissions from an Internal Combustion Engine Fueled by Landfill
Gas, Penrose Landfill, Pacific Energy Lighting Systems, South Coast Air Quality Management
District, February 24, 1988.
67. Source Test Report 88-0096 of Emissions from an Internal Combustion Engine Fueled by Landfill
Gas, Toy on Canyon Landfill, Pacific Energy Lighting Systems, March 8, 1988.
68. Letter and attached documents from C. Nesbitt, Los Angeles County Sanitation Districts, to K. Brust,
E.H. Pechan and Associates, Inc., December 6, 1996.
69. Determination of Landfill Gas Composition and Pollutant Emission Rates at Fresh Kills Landfill,
revised Final Report, Radian Corporation, prepared for U.S. EPA, November 10, 1995.
70. Advanced Technology Systems, Inc., Report on Determination of Enclosed Landfill Gas Flare
Performance, Prepared for Y & S Maintenance, Inc., February 1995.
71. Chester Environmental, Report on Ground Flare Emissions Test Results, Prepared for Seneca
Landfill, Inc., October 1993.
72. Smith Environmental Technologies Corporation, Compliance Emission Determination of the
Enclosed Landfill Gas Flare and Leachate Treatment Process Vents, Prepared for Clinton County
Solid Waste Authority, April 1996.
73. AirRecon®, Division of RECON Environmental Corp., Compliance Stack Test Report for the
Landfill Gas FLare Inlet & Outlet at Bethlehem Landfill, Prepared for LFG Specialties Inc.,
December 3, 1996.
2.4-20 EMISSION FACTORS 8/98
-------
74. ROJAC Environmental Services, Inc., Compliance Test Report, Hartford Landfill Flare Emissions
Test Program, November 19, 1993.
75. Normandeau Associates, Inc., Emissions Testing of a Landfill Gas Flare at Contra Costa Landfill,
Antioch, California, March 22, 1994 and April 22, 1994, May 17, 1994.
76. Roe, S.M., et. al., Methodologies for Quantifying Pollution Prevention Benefits from Landfill Gas
Control and Utilization, Prepared for U.S. EPA, Office of Air and Radiation, Air and Energy
Engineering Laboratory, EPA-600/R-95-089, July 1995.
8/98 Solid Waste Disposal 2.4-21
-------
4.3 Waste Water Collection, Treatment And Storage
4.3.1 General
Many different industries generate waste water streams that contain organic compounds.
Nearly all of these streams undergo collection, contaminant treatment, and/or storage operations before
they are finally discharged into either a receiving body of water or a municipal treatment plant for
further treatment. During some of these operations, the waste water is open to the atmosphere, and
volatile organic compounds (VOC) may be emitted from the waste water into the air.
Industrial waste water operations can range from pretreatment to full-scale treatment processes.
In a typical pretreatment facility, process and/or sanitary waste water and/or storm water runoff is
collected, equalized, and/or neutralized and then discharged to a municipal waste water plant, also
known as a publicly owned treatment works (POTWs), where it is then typically treated further by
biodegradation.
In a full-scale treatment operation, the waste water must meet Federal and/or state quality
standards before it is finally discharged into a receiving body of water. Figure 4.3-1 shows a generic
example of collection, equalization, neutralization, and biotreatment of process waste water in a full-
scale industrial treatment facility. If required, chlorine is added as a disinfectant. A storage basin
contains the treated water until the winter months (usually January to May), when the facility is
allowed to discharge to the receiving body of water. In the illustration, the receiving body of water is
a slow-flowing stream. The facility is allowed to discharge in the rainy season when the facility waste
water is diluted.
Figure 4.3-1 also presents a typical treatment system at a POTW waste water facility.
Industrial waste water sent to POTWs may be treated or untreated. POTWs may also treat waste
water from residential, institutional, and commercial facilities; from infiltration (water that enters the
sewer system from the ground); and/or storm water runoff. These types of waste water generally do
not contain VOCs. A POTW usually consists of a collection system, primary settling, biotreatment,
secondary settling, and disinfection.
Collection, treatment, and storage systems are facility-specific. All facilities have some type of
collection system, but the complexity will depend on the number and volume of waste water streams
generated. As mentioned above, treatment and/or storage operations also vary in size and degree of
treatment. The size and degree of treatment of waste water streams will depend on the volume and
degree of contamination of the waste water and on the extent of contaminant removal desired.
4.3.1.1 Collection Systems -
There are many types of waste water collection systems. In general, a collection system is
located at or near the point of waste water generation and is designed to receive 1 or more waste water
streams and then to direct these streams to treatment and/or storage systems.
A typical industrial collection system may include drains, manholes, trenches, junction boxes,
sumps, lift stations, and/or weirs. Waste water streams from different points throughout the industrial
facility normally enter the collection system through individual drains or trenches connected to a main
sewer line. The drains and trenches are usually open to the atmosphere. Junction boxes, sumps,
9/91 (Reformatted 1/95) Evaporation Loss Sources 4.3-1
-------
w
&
•§
ff
I
=3
*
4f
&
I |t
sit
l.s§
ss:
ii
?.a
.&1
'y
'c
3
T3
13
•£
«
3
t3
I
cd
s
•o
o
o
o
.
a
bO
4.3-2
EMISSION FACTORS
(Reformatted 1/95) 9/91
-------
trenches, lift stations, and weirs will be located at points requiring waste water transport from 1 area or
treatment process to another.
A typical POTW facility collection system will contain a lift station, trenches, junction boxes,
and manholes. Waste water is received into the POTW collection system through open sewer lines
from all sources of influent waste water. As mentioned previously, these sources may convey sanitary,
pretreated or untreated industrial, and/or storm water runoff waste water.
The following paragraphs briefly describe some of the most common types of waste water
collection system components found in industrial and POTW facilities. Because the arrangement of
collection system components is facility-specific, the order in which the collection system descriptions
are presented is somewhat arbitrary.
Waste water streams normally are introduced into the collection system through individual or
area drains, which can be open to the atmosphere or sealed to prevent waste water contact with the
atmosphere. In industry, individual drains may be dedicated to a single source or piece of equipment.
Area drains will serve several sources and are located centrally among the sources or pieces of
equipment that they serve.
Manholes into sewer lines permit service, inspection, and cleaning of a line. They may be
located where sewer lines intersect or where there is a significant change in direction, grade, or sewer
line diameter.
Trenches can be used to transport industrial waste water from point of generation to collection
units such as junction boxes and lift station, from 1 process area of an industrial facility to another, or
from 1 treatment unit to another. POTWs also use trenches to transport waste water from 1 treatment
unit to another. Trenches are likely to be either open or covered with a safety grating.
Junction boxes typically serve several process sewer lines, which meet at the junction box to
combine multiple waste water streams into 1. Junction boxes normally are sized to suit the total flow
rate of the entering streams.
Sumps are used typically for collection and equalization of waste water flow from trenches or
sewer lines before treatment or storage. They are usually quiescent and open to the atmosphere.
Lift stations are usually the last collection unit before the treatment system, accepting waste
water from 1 or several sewer lines. Their main function is to lift the collected waste water to a
treatment and/or storage system, usually by pumping or by use of a hydraulic lift, such as a screw.
Weirs can act as open channel dams, or they can be used to discharge cleaner effluent from a
settling basin, such as a clarifier. When used as a dam, the weir's face is normally aligned
perpendicular to the bed and walls of the channel. Water from the channel usually flows over the weir
and falls to the receiving body of water. In some cases, the water may pass through a notch or
opening in the weir face. With this type of weir, flow rate through the channel can be measured.
Weir height, generally the distance the water falls, is usually no more than 2 meters (6 feet). A
typical clarifier weir is designed to allow settled waste water to overflow to the next treatment process.
The weir is generally placed around the perimeter of the settling basin, but it can also be towards the
middle. Clarifier weir height is usually only about 0.1 meters (4 inches).
9/91 (Reformatted 1/95) Evaporation Loss Sources 4.3-3
-------
4.3.1.2 Treatment And/Or Storage Systems -
These systems are designed to hold liquid wastes or waste water for treatment, storage, or
disposal. They are usually composed of various types of earthen and/or concrete-lined basins, known
as surface impoundments. Storage systems are used typically for accumulating waste water before its
ultimate disposal, or for temporarily holding batch (intermittent) streams before treatment.
Treatment systems are divided into 3 categories: primary, secondary, or tertiary, depending on
their design, operation, and application. In primary treatment systems, physical operations remove
floatable and settleable solids. In secondary treatment systems, biological and chemical processes
remove most of the organic matter in the waste water. In tertiary treatment systems, additional
processes remove constituents not taken out by secondary treatment.
Examples of primary treatment include oil/water separators, primary clarification, equalization
basins, and primary treatment tanks. The first process in an industrial waste water treatment plant is
often the removal of heavier solids and lighter oils by means of oil/water separators. Oils are usually
removed continuously with a skimming device, while solids can be removed with a sludge removal
system.
In primary treatment, clarifiers are usually located near the beginning of the treatment process
and are used to settle and remove settleable or suspended solids contained in the influent waste water.
Figure 4.3-2 presents an example design of a clarifier. Clarifiers are generally cylindrical and are
sized according to both the settling rate of the suspended solids and the thickening characteristics of
the sludge. Floating scum is generally skimmed continuously from the top of the clarifier, while
sludge is typically removed continuously from the bottom of the clarifier.
Equalization basins are used to reduce fluctuations in the waste water flow rate and organic
content before the waste is sent to downstream treatment processes. Flow rate equalization results in a
more uniform effluent quality in downstream settling units such as clarifiers. Biological treatment
performance can also benefit from the damping of concentration and flow fluctuations, protecting
biological processes from upset or failure from shock loadings of toxic or treatment-inhibiting
compounds.
In primary treatment, tanks are generally used to alter the chemical or physical properties of
the waste water by, for example, neutralization and the addition and dispersion of chemical nutrients.
Neutralization can control the pH of the waste water by adding an acid or a base. It usually precedes
biotreatment, so that the system is not upset by high or low pH values. Similarly, chemical nutrient
addition/dispersion precedes biotreatment, to ensure that the biological organisms have sufficient
nutrients.
An example of a secondary treatment process is biodegradation. Biological waste treatment
usually is accomplished by aeration in basins with mechanical surface aerators or with a diffused air
system. Mechanical surface aerators float on the water surface and rapidly mix the water. Aeration of
the water is accomplished through splashing. Diffused air systems, on the other hand, aerate the water
by bubbling oxygen through the water from the bottom of the tank or device. Figure 4.3-3 presents an
example design of a mechanically aerated biological treatment basin. This type of basin is usually an
earthen or concrete-lined pond and is used to treat large flow rates of waste water. Waste waters with
high pollutant concentrations, and in particular high-flow sanitary waste waters, are
typically treated using an activated sludge system where biotreatment is followed by secondary
clarification. In this system, settled solids containing biomass are recycled from clarifier sludge to the
biotreatment system. This creates a high biomass concentration and therefore allows biodegradation to
occur over a shorter residence time. An example of a tertiary treatment process is nutrient
4.3-4 EMISSION FACTORS (Reformatted 1/95) 9/91
-------
Drive Unit
Effluent Weir
Scraper Blades
Sludge Drawoff Pipe
Figure 4.3-2. Example clarifier configuration.
Cable Ties
Surface
Mechanical
Aerators
A
Overflow
Weir
Agitated
Surface
1 Wastewater
1 Inlet Manifold
Figure 4.3-3. Example aerated biological treatment basin.
9/91 (Reformatted 1/95)
Evaporation Loss Sources
4.3-5
-------
removal. Nitrogen and phosphorus are removed after biodegradation as a final treatment step before
waste water is discharged to a receiving body of water.
4.3.1.3 Applications -
As previously mentioned, waste water collection, treatment, and storage are common in many
industrial categories and in POTW. Most industrial facilities and POTW collect, contain, and treat
waste water. However, some industries do not treat their waste water, but use storage systems for
temporary waste water storage or for accumulation of waste water for ultimate disposal. For example,
the Agricultural Industry does little waste water treatment but needs waste water storage systems,
while the Oil and Gas Industry also has a need for waste water disposal systems.
The following are waste water treatment and storage applications identified by type of
industry:
1. Mining And Milling Operations - Storage of various waste waters such as acid mine
water, solvent wastes from solution mining, and leachate from disposed mining wastes.
Treatment operations include settling, separation, washing, sorting of mineral products
from tailings, and recovery of valuable minerals by precipitation.
2. Oil And Gas Industry - One of the largest sources of waste water. Operations treat
brine produced during oil extraction and deep-well pressurizing operations, oil-water
mixtures, gaseous fluids to be separated or stored during emergency conditions, and
drill cuttings and drilling muds.
3. Textile And Leather Industry - Treatment and sludge disposal. Organic species treated
or disposed of include dye carriers such as halogenated hydrocarbons and phenols.
Heavy metals treated or disposed of include chromium, zinc, and copper. Tanning and
finishing wastes may contain sulfides and nitrogenous compounds.
4. Chemical And Allied Products Industry - Process waste water treatment and storage,
and sludge disposal. Waste constituents are process-specific and include organics and
organic phosphates, fluoride, nitrogen compounds, and assorted trace metals.
5. Other Industries - Treatment and storage operations are found at petroleum refining,
primary metals production, wood treating, and metal finishing facilities. Various
industries store and/or treat air pollution scrubber sludge and dredging spoils sludge (i.
e., settled solids removed from the floor of a surface impoundment).
4.3.2 Emissions
VOCs are emitted from waste water collection, treatment, and storage systems through
volatilization of organic compounds at the liquid surface. Emissions can occur by diffusive or
convective mechanisms, or both. Diffusion occurs when organic concentrations at the water surface
are much higher than ambient concentrations. The organics volatilize, or diffuse into the air, in an
attempt to reach equilibrium between aqueous and vapor phases. Convection occurs when air flows
over the water surface, sweeping organic vapors from the water surface into the air. The rate of
volatilization relates directly to the speed of the air flow over the water surface.
Other factors that can affect the rate of volatilization include waste water surface area,
temperature, and turbulence; waste water retention time in the system(s); the depth of the waste water
in the system(s); the concentration of organic compounds in the waste water and their physical
4.3-6 EMISSION FACTORS (Reformatted 1/95) 9/91
-------
properties, such as volatility and diffusivity in water; the presence of a mechanism that inhibits
volatilization, such as an oil film; or a competing mechanism, such as biodegradation.
The rate of volatilization can be determined by using mass transfer theory. Individual gas
phase and liquid phase mass transfer coefficients (k and k«, respectively) are used to estimate overall
mass transfer coefficients (K, Koil, and KD) for each VOC. Figure 4.3-4 presents a flow diagram to
assist in determining the appropriate emissions model for estimating VOC emissions from various
types of waste water treatment, storage, and collection systems. Tables 4.3-1 and 4.3-2, respectively,
present the emission model equations and definitions.
VOCs vary in their degree of volatility. The emission models presented in this section can be
used for high-, medium-, and low-volatility organic compounds. The Henry's law constant (HLC) is
often used as a measure of a compound's volatility, or the diffusion of organics into the air relative to
diffusion through liquids. High-volatility VOCs are HLC > 10"3 atm-m3/gmol; medium-volatility
VOCs are 10'3 < HLC < 1CT atm-m3/gmol; and low-volatility VOCs are HLC < 10~5 atm-m3/ gmol.1
The design and arrangement of collection, treatment, and storage systems are facility-specific;
therefore the most accurate waste water emissions estimate will come from actual tests of a facility
(i. e., tracer studies or direct measurement of emissions from openings). If actual data are unavailable,
the emission models provided in this section can be used.
Emission models should be given site-specific information whenever it is available. The most
extensive characterization of an actual system will produce the most accurate estimates from an
emissions model. In addition, when addressing systems involving biodegradation, the accuracy of the
predicted rate of biodegradation is improved when site-specific compound biorates are input.
Reference 3 contains information on a test method for measuring site-specific biorates, and
Table 4.3-4 presents estimated biorates for approximately 150 compounds.
To estimate an emissions rate (N), the first step is to calculate individual gas phase and liquid
phase mass transfer coefficients k and kj. These individual coefficients are then used to calculate the
overall mass transfer coefficient, K. Exceptions to this procedure are the calculation of overall mass
transfer coefficients in the oil phase, Koil, and the overall mass transfer coefficient for a weir, KD.
Koil requires only k , and KD does not require any individual mass transfer coefficients. The overall
mass transfer coefficient is then used to calculate the emissions rates. The following discussion
describes how to use Figure 4.3-4 to determine an emission rate. An example calculation is presented
in Part 4.3.2.1 below.
Figure 4.3-4 is divided into 2 sections: waste water treatment and storage systems, and waste
water collection systems. Waste water treatment and storage systems are further segmented into
aerated/nonaerated systems, biologically active systems, oil film layer systems, and surface
impoundment flowthrough or disposal. In flowthrough systems, waste water is treated and discharged
to a POTW or a receiving body of water, such as a river or stream. All waste water collection
systems are by definition flowthrough. Disposal systems, on the other hand, do not discharge any
waste water.
Figure 4.3-4 includes information needed to estimate air emissions from junction boxes, lift
stations, sumps, weirs, and clarifier weirs. Sumps are considered quiescent, but junction boxes, lift
stations, and weirs are turbulent in nature. Junction boxes and lift stations are turbulent because
incoming flow is normally above the water level in the component, which creates some splashing.
9/91 (Reformatted 1/95) Evaporation Loss Sources 4.3-7
-------
Wastewater
——<^ System ^>
Treatment and^xAerated^/
../
Equations Used to Obtain.
Kj_ K9 Koil Kp K _N_
aNumbered equations are presented in Table 4.3-1
Kj - Individual liquid phase mass transfer coefficient, m/s
Kg - Individual gas phase mass transfer coefficient, m/s
KJjl - Overall mass transfer coefficient In the oil phase, m/s
Krj - Volatilization - reaeratlon theory mass transfer coefficient
K^ - Overall mass transfer coefficient m/s
N - Emissions, g/s
Wastewater Collection
2 9
2 9
3 2
1 2
5 6
10
7 20
7 19
7 14
7 13
7 16
7 15
7 12
7 11
7 16
7 15
7 12
7 11
18
17
22
23
7 12
7 12
7 12
21
8 24
Figure 4.3.4. Flow diagram for estimating VOC emissions from waste water collection,
treatment, and storage systems.
4.3-8
EMISSION FACTORS
(Reformatted 1/95) 9/91
-------
Table 4.3-1. MASS TRANSFER CORRELATIONS AND EMISSIONS EQUATIONS3
Equation
No. Equation
Individual liquid (kf) and gas (k ) phase mass transfer coefficients
&
1 k{ (m/s) = (2.78 x lO
For: 0 < U10 < 3.25 m/s and all F/D ratios
k, (m/s) = [(2.605 x l(r9)(F/D) + (1.277 x 10-7)](U10)2(Dw^>ether)2/3
For: U10 > 3.25 m/s and 14 < F/D < 51.2
k, (m/s) = (2.61 x 10-7)(U10)2(Dw/Dether)2/3
For: U10 > 3.25 m/s and F/D > 51.2
k, (m/s) = 1.0 x 10'6 + 144 x 10'4 (U*)12 (So,)-0-5; U* < 0.3
k, (m/s) = 1.0 x 10'6 + 34.1 x 10"4 U* (ScL)-°^; U* > 0.3
For: U10 > 3.25 m/s and F/D < 14
where:
U* (m/s) = (0.01)(U10)(6.1 + 0.63(U10))a5
ScL = uL/(pLE > )
F/D = 2 (A/7t)°-5
kg (m/s) = (4.82 x 10-3)(U10)°-78 (ScG)-°-67 (de)-°-n
where:
S'G = MaWJJ
de(m) = 2(A/7t)or5
kc (m/s) = [(8.22 x 10-9)(J)(POWR)(1.024)(T-20)(Ot)(106) *
(MWL)/(VavpL)](Dw/D02iW)°-5
where:
POWR (hp) = (total power to aerators)(V)
Vav(ft ) = (fraction of area agitated)(A)
kg (m/s) = (1.35 x 10'7)(Re)L42 (P)0'4 (ScG)0'5 (Fr)-°'21(Da MWa/d)
where:
Re = d2 w pa/ua
P = [(0.85)(POWR)(550 ft-lb/s-hp)^] gc/(pL(d*)5w3)
ScG = Ma/(Pa?a)
Fr = (d*)w2/gc
k, (m/s) - (fair;C)(Q)/[3600 s/min (hc)(7idc)j
where:
fair,* =
r
= exp [0.77(hc)0-623(Q/7idc)°-66(Dw/D02jW)0-66]
kg (m/s) = 0.001 + (0.0462(U**)(ScG)'a67)
where:
U** (m/s) = [6.1 + (0.63)(U10)]a5(U10/100)
ScG =
9/91 (Reformatted 1/95) Evaporation Loss Sources 4.3-9
-------
Table 4.3-1 (cont.).
Equation
No. Equation
Overall mass transfer coefficients for water (K) and oil (Koil) phases and for weirs (Kp)
7 K= (kf Keq kg)/(Keq kg + k{)
where:
Keq = H/(RT)
8 K (m/s) = [[MWL/(ktpL*(100 cm/m)] + [MWa/(k paH*
55,555(100 cm/m))]]-1 MWL/[(100 cm/m)pL]
9 Koil = kgKeqoil
where:
Keqoil=P*paMWoil/(poilMWaP0)
10 KD = 0.16h (DJDQ2iW)°-75
Air emissions (N)
11 N(g/s) = (1 - Ct/Co) V Co/t
where:
Ct/Co =exp[-KAt/V]
12 N(g/s) = K CL A
where:
CL(g/m3) = Q Co/(KA + Q)
13 N(g/s) = (1 - Ct/Co) V Co/t
where:
Ct/Co = exp[-(KA + KeqQa)t/V]
14 N(g/s) = (KA + QaKeq)CL
where:
CL(g/m3) = QCo/(KA + Q + QaKeq)
15 N(g/s) = (1 - Ct/Co) KA/(KA + Kmax bj V/KS) V Co/t
where:
Ct/Co = exp[-Kmax b; t/Ks - K A t/V]
16 N(g/s) = K CL A
where:
CL(g/m3) = [-b + (b2 - 4ac)°'5]/(2a)
and:
a = KA/Q + 1
b = KS(KA/Q + 1) + Kmax bj V/Q - Co
c = -KsCo
4.3-10 EMISSION FACTORS (Reformatted 1/95) 9/91
-------
Table 4.3-1 (cont.).
Equation
No. Equation
17 N(g/s) = (1 - Ctoil/Cooil)Voi,Cooil/t
where:
Ctoil/C°oil =
and:
Cooil = Kow Co/[l - FO + FO(Kow)]
Voil = (FO)(V)
Doil = (FO)(V)/A
18 N(g/s) = Koi,CL>oilA
where:
C^oilCS/™3) = QoilC'oil^KoilA + Qoil)
and:
Cooi, = Kow Co/[l - FO + FO(Kow)]
Qoil = (FO)(Q)
19 N(g/s) = (1 - Ct/Co)(KA + QaKeq)/(KA + QaKeq + Kmax b; V/KS) V Co/t
where:
Ct/Co = exp[-(KA + KeqQa)t/V - Kmax bj t/KJ
20 N(g/s) = (KA + QaKeq)CL
where:
CL(g/m3) = [-b +(b2 - 4ac)°'5]/(2a)
and:
a = (KA + QaKeq)/Q + 1
b = KS[(KA + QaKeq)/Q + 1] + Kmax bj V/Q - Co
c =-KsCo
21 N (g/s) = (1 - exp[-KD])Q Co
22 N(g/s) = KoilCL>oilA
where:
CuoilCg/™3) = QoilCCOo/MKoilA + Qoil)
and:
Cooii* =Co/FO
Qoil =(FO)(Q)
23 N(g/s) = (1 - Ctoil/Coojl*)(Voil)(Cooil*)/t
where:
Ctoil/Cooil* = exp[-Koil t/Doil]
and:
Cooil* = Co/FO
Voil = (FO)(V)
Doil = (FO)(V)/A
24 -N (g/s) - (1 - exp[-K n dc hc/Q])Q Co
All parameters in numbered equations are defined in Table 4.3-2.
9/91 (Reformatted 1/95) Evaporation Loss Sources 4.3-11
-------
Table 4.3-2. PARAMETER DEFINITIONS FOR MASS TRANSFER CORRELATIONS AND
EMISSIONS EQUATIONS
Parameter
A
bi
CL
CL,oil
Co
oil
oil
Ct
ctoil
d
D
d*
Da
dc
de
Dether
DO2,w
Don
Dw
fairf
F/D
FO
Fr
§c
Definition
Waste water surface area
Biomass concentration (total biological solids)
Concentration of constituent in the liquid phase
Concentration of constituent in the oil phase
Initial concentration of constituent in the liquid
phase
Initial concentration of constituent in the oil phase
considering mass transfer resistance between
water and oil phases
Initial concentration of constituent in the oil phase
considering no mass transfer resistance between
water and oil phases
Concentration of constituent in the liquid phase at
time = t
Concentration of constituent in the oil phase at
time = t
Impeller diameter
Waste water depth
Impeller diameter
Diffusivity of constituent in air
Clarifier diameter
Effective diameter
Diffusivity of ether in water
Diffusivity of oxygen in water
Oil film thickness
Diffusivity of constituent in water
Fraction of constituent emitted to the air,
considering zero gas resistance
Fetch to depth ratio, de/D
Fraction of volume which is oil
Froude number
Gravitation constant (a conversion factor)
Units
m2 or ft2
g/m3
g/m3
g/m3
g/m3
g/m3
g/m3
g/m3
g/m3
cm
m or ft
ft
cm2/s
m
m
cm /s
cm2/s
m
cm2/s
dimensionless
dimensionless
dimensionless
dimensionless
Ibm-ft/s2-lbf
Code2
A
B
D
D
A
D
D
D
D
B
A,B
B
C
B
D
(8.5xl(T6)b
(2.4x1 (T5)b
B
C
D
D
B
D
32.17
4.3-12
EMISSION FACTORS
(Reformatted 1/95) 9/91
-------
Table 4.3-2 (cont.).
Parameter
h
he
H
J
K
KD
Keq
Ke%il
kg
k,
Kmax
Koil
Kow
Ks
MWP
a
MWojl
MWL
N
NI
Ot
P
P*
Po
POWR
Q
Definition
Weir height (distance from the waste water
overflow to the receiving body of water)
Clarifier weir height
Henry's law constant of constituent
Oxygen transfer rating of surface aerator
Overall mass transfer coefficient for transfer of
constituent from liquid phase to gas phase
Volatilization-reaeration theory mass transfer
coefficient
Equilibrium constant or partition coefficient
(concentration in gas phase/concentration in
liquid phase)
Equilibrium constant or partition coefficient
(concentration in gas phase/concentration in oil
phase)
Gas phase mass transfer coefficient
Liquid phase mass transfer coefficient
Maximum biorate constant
Overall mass transfer coefficient for transfer of
constituent from oil phase to gas phase
Octanol-water partition coefficient
Half saturation biorate constant
Molecular weight of air
Molecular weight of oil
Molecular weight of water
Emissions
Number of aerators
Oxygen transfer correction factor
Power number
Vapor pressure of the constituent
Total pressure
Total power to aerators
Volumetric flow rate
Units
ft
m
atm-m /gmol
Ib 02/(hr-hp)
m/s
dimensionless
dimensionless
dimensionless
m/s
m/s
g/s-g biomass
m/s
dimensionless
g/m3
g/gmol
g/gmol
g/gmol
g/s
dimensionless
dimensionless
dimensionless
atm
atm
hp
m3/s
Code3
B
B
C
B
D
D
D
D
D
D
A,C
D
C
A,C
29
B
18
D
A,B
B
D
C
A
B
A
9/91 (Reformatted 1/95)
Evaporation Loss Sources
4.3-13
-------
Table 4.3-2 (cont.).
Parameter
Qa
Qoil
r
R
Re
ScG
ScL
T
t
U*
u**
UIQ
V
Vav
V0il
w
Pa
PL
Poil
ua
HL
Definition
Diffused air flow rate
Volumetric flow rate of oil
Deficit ratio (ratio of the difference between the
constituent concentration at solubility and actual
constituent concentration in the upstream and the
downstream)
Universal gas constant
Reynolds number
Schmidt number on gas side
Schmidt number on liquid side
Temperature of water
Residence time of disposal
Friction velocity
Friction velocity
Wind speed at 10 m above the liquid surface
Waste water volume
Turbulent surface area
Volume of oil
Rotational speed of impeller
Density of air
Density of water
Density of oil
Viscosity of air
Viscosity of water
Units
m3/s
m3/s
dimensionless
atm-m /gmol-K
dimensionless
dimensionless
dimensionless
°C or Kelvin
(K)
s
m/s
m/s
m/s
m3 or ft3
ft2
m3
rad/s
g/cm3
g/cm3 or lb/ft3
g/m3
g/cm-s
g/cm-s
Code3
B
B
D
8.21xlO-5
D
D
D
A
A
D
D
B
A
B
B
B
(1.2xlQ-3)b
lb or 62.4b
B
(1.81xlQ-4)b
(8.93xlO-3)b
a Code:
A = Site-specific parameter.
B = Site-specific parameter. For default values, see Table 4.3-3.
C = Parameter can be obtained from literature. See Attachment 1 for a list of -150 compound
chemical properties at T = 25°C (298°K).
D = Calculated value.
b Reported values at 25°C (298°K).
4.3-14
EMISSION FACTORS
(Reformatted 1/95) 9/91
-------
Table 4.3-3. SITE-SPECIFIC DEFAULT PARAMETERS3
Default Parameter
Definition
Default Value
General
T
Biotreatment Systems
Temperature of water
Windspeed
POWR
W
d(d*)
Va
Biomass concentration (for biologically active
systems)
Quiescent treatment systems
Aerated treatment systems
Activated sludge units
Total power to aerators
(for aerated treatment systems)
(for activated sludge)
Rotational speed of impeller
(for aerated treatment systems)
Impeller diameter
(for aerated treatment systems)
Turbulent surface area
(for aerated treatment systems)
(for activated sludge)
J Oxygen transfer rating to surface aerator
(for aerated treatment systems)
Ot Oxygen transfer correction factor
(for aerated treatment systems)
Nj Number of aerators
Diffused Air Systems
Qa Diffused air volumetric flow rate
Oil Film Layers
Molecular weight of oil
Depth of oil layer
Volume of oil
Volumetric flow rate of oil
Density of oil
V0ii
298°K
4.47 m/s
Qoil
Poll
50 g/m3
300 g/m3
4000 g/m3
0.75 hp/1000 ft3 (V)
2 hp/1000 ft3 (V)
126 rad/s (1200 rpm)
61 cm (2 ft)
0.24 (A)
0.52 (A)
3 Ib O2/hp«hr
0.83
POWR/75
0.0004(V) m3/s
282 g/gmol
0.001 (V/A) m
0.001 (V) m3
0.001 (Q) m3/s
0.92 g/cm3
9/91 (Reformatted 1/95)
Evaporation Loss Sources
4.3-15
-------
Table 4.3-3 (cont.).
Default Parameter
FO
Junction Boxes
D
NI
Lift Station
D
NI
Sump
D
Weirs
dc
h
hc
Definition
Fraction of volume which is oilc
Depth of Junction Box
Number of aerators
Depth of Lift Station
Number of aerators
Depth of sump
Clarifier weir diameter
Weir height
Clarifier weir height6
Default Value
0.001
0.9 m
1
1.5 m
1
5.9m
28.5 m
1.8 m
0.1 m
a Reference 1.
As defined in Table
c Reference 4.
d Reference 2.
e Reference 5.
4.3-2.
Waste water falls or overflows from weirs and creates splashing in the receiving body of water (both
weir and clarifier weir models). Waste water from weirs can be aerated by directing it to fall over
steps, usually only the weir model.
Assessing VOC emissions from drains, manholes, and trenches is also important in
determining the total waste water facility emissions. As these sources can be open to the atmosphere
and closest to the point of waste water generation (i. e., where water temperatures and pollutant
concentrations are greatest), emissions can be significant. Currently, there are no well-established
emission models for these collection system types. However, work is being performed to address this
need.
Preliminary models of VOC emissions from waste collection system units have been
developed.4 The emission equations presented in Reference 4 are used with standard collection system
parameters to estimate the fraction of the constituents released as the waste water flows through each
unit. The fractions released from several units are estimated for high-, medium-, and low-volatility
compounds. The units used in the estimated fractions included open drains, manhole covers, open
trench drains, and covered sumps.
4.3-16
EMISSION FACTORS
(Reformatted 1/95) 9/91
-------
The numbers in Figure 4.3-4 under the columns for kf, k Koil, KD, K, and N refer to the
appropriate equations in Table 4.3-1.3 Definitions for all parameters in these equations are given in
Table 4.3-2. Table 4.3-2 also supplies the units that must be used for each parameter, with codes to
help locate input values. If the parameter is coded with the letter A, a site-specific value is required.
Code B also requires a site-specific parameter, but defaults are available. These defaults are typical or
average values and are presented by specific system in Table 4.3-3.
Code C means the parameter can be obtained from literature data. Table 4.3-4 contains a list
of approximately 150 chemicals and their physical properties needed to calculate emissions from waste
water, using the correlations presented in Table 4.3-1. All properties are at 25°C (77°F).
A more extensive chemical properties data base is contained in Appendix C of Reference 1.)
Parameters coded D are calculated values.
Calculating air emissions from waste water collection, treatment, and storage systems is a
complex procedure, especially if several systems are present. Performing the calculations by hand may
result in errors and will be time consuming. A personal computer program called the Surface
Impoundment Modeling System (SIMS) is now available for estimating air emissions. The program is
menu driven and can estimate air emissions from all surface impoundment models presented in
Figure 4.3-4, individually or in series. The program requires for each collection, treatment, or storage
system component, at a minimum, the waste water flow rate and component surface area. All other
inputs are provided as default values. Any available site-specific information should be entered in
place of these defaults, as the most fully characterized system will provide the most accurate emissions
estimate.
The SIMS program with user's manual and background technical document can be obtained
through state air pollution control agencies and through the U. S. Environmental Protection Agency's
Control Technology Center in Research Triangle Park, NC, telephone (919) 541-0800. The user's
manual and background technical document should be followed to produce meaningful results.
The SIMS program and user's manual also can be downloaded from EPA's Clearinghouse For
Inventories and Emission Factors (CHIEF) electronic bulletin board (BB). The CHIEF BB is open to
all persons involved in air emission inventories. To access this BB, one needs a computer, modem, and
communication package capable of communicating at up to 14,400 baud, 8 data bits, 1 stop bit, and no
parity (8-N-l). This BB is part of EPA's OAQPS Technology Transfer Network system and its
telephone number is (919) 541-5742. First-time users must register before access is allowed.
Emissions estimates from SIMS are based on mass transfer models developed by Emissions
Standards Division (ESD) during evaluations of TSDFs and VOC emissions from industrial waste
water. As a part of the TSDF project, a Lotus® spreadsheet program called CHEMDAT7 was
developed for estimating VOC emissions from waste water land treatment systems, open landfills,
closed landfills, and waste storage piles, as well as from various types of surface impoundments. For
more information about CHEMDAT7, contact the ESD's Chemicals And Petroleum Branch (MD 13),
US EPA, Research Triangle Park, NC 27711.
aAll emission model systems presented in Figure 4.3-4 imply a completely mixed or uniform waste
water concentration system. Emission models for a plug flow system, or system in which there is no
axial, or horizontal mixing, are too extensive to be covered in this document. (An example of plug
flow might be a high waste water flow in a narrow channel.) For information on emission models of
this type, see Reference 1.
9/91 (Reformatted 1/95) Evaporation Loss Sources 4.3-17
-------
4.3.2.1 Example Calculation -
An example industrial facility operates a flowthrough, mechanically aerated biological
treatment impoundment that receives waste water contaminated with benzene at a concentration of
10.29 g/m3.
The following format is used for calculating benzene emissions from the treatment process:
I. Determine which emission model to use
II. User-supplied information
III. Defaults
IV. Pollutant physical property data and water, air, and other properties
V. Calculate individual mass transfer coefficient
VI. Calculate the overall mass transfer coefficients
VII. Calculate VOC emissions
I. Determine Which Emission Model To Use — Following the flow diagram in Figure 4.3-4, the
emission model for a treatment system that is aerated, but not by diffused air, is biologically
active, and is a flowthrough system, contains the following equations:
Equation Nos.
Parameter Definition from Table 4.3-1
K Overall mass transfer coefficient, m/s 7
kf Individual liquid phase mass transfer coefficient, m/s 1,3
k Individual gas phase mass transfer coefficient, m/s 2,4
6
N VOC emissions, g/s 16
II. User-supplied Information — Once the correct emission model is determined, some site-specific
parameters are required. As a minimum for this model, site-specific flow rate, waste water
surface area and depth, and pollutant concentration should be provided. For this example, these
parameters have the following values:
Q = Volumetric flow rate = 0.0623 m3/s
D = Waste water depth = 1.97 m
A = Waste water surface area = 17,652 m2
Co = Initial benzene concentration in the liquid phase = 10.29 g/m3
III. Defaults — Defaults for some emission model parameters are presented in Table 4.3-3.
Generally, site-specific values should be used when available. For this facility, all available
general and biotreatment system defaults from Table 4.3-3 were used:
UJQ = Wind speed at 10 m above the liquid surface = e = 4.47 m/s
T = Temperature of water = 25°C (298°K)
bj = Biomass concentration for aerated treatment systems = 300 g/m3
J = Oxygen transfer rating to surface aerator = 3 Ib O2/hp-hr
POWR = Total power to aerators = 0.75 hp/1,000 ft3 (V)
Ot = Oxygen transfer correction factor = 0.83
Vay = Turbulent surface area = 0.24 (A)
d = Impeller diameter = 61 cm
4.3-18 EMISSION FACTORS (Reformatted 1/95) 9/91
-------
.*
d = Impeller diameter = 2 f t
w = Rotational speed of impeller =126 rad/s
Nj = Number of aerators = POWR/75 hp
IV. Pollutant Physical Property Data, And Water, Air and Other Properties — For each pollutant, the
specific physical properties needed by this model are listed in Table 4.3-4. Water, air, and other
property values are given in Table 4.3-2.
A. Benzene (from Table 4.3-4)
DW benzene = Diffusivity of benzene in water = 9.8 x 10~6 cm2/s
Da benzene = Diffusivity of benzene in air = 0.088 cm2/s
benzene = Henry's law constant for benzene = 0.0055 atm- m /gmol
Kmaxbenzene = Maximum biorate constant for benzene = 5.28 x 10 g/g-s
KS benzene = Half saturation biorate constant for benzene =13.6 g/m
B. Water, Air, and Other Properties (from Table 4.3-3)
pa = Density of air = 1.2 x 103 g/cm3
pL = Density of water = 1 g/cnr (62.4 lbm/ft3)
ua = Viscosity of air = 1.81 x 10"4 g/cm-s
D02 w = Diffusivity of oxygen in water = 2.4 x 10 cm /s
Dether = Diffusivity of ether in water = 8.5 x 10"6 cm2/s
MWL = Molecular weight of water =18 g/gmol
MWa = Molecular weight of air = 29 g/gmol
gp = Gravitation constant = 32.17 lbm-ft/lbrs2
*^v 111 f L «
R = Universal gas constant = 8.21 x 10 atm-m /gmol
V. Calculate Individual Mass Transfer Coefficients — Because part of the impoundment is turbulent
and part is quiescent, individual mass transfer coefficients are determined for both turbulent and
quiescent areas of the surface impoundment.
Turbulent area of impoundment — Equations 3 and 4 from Table 4.3-1.
A. Calculate the individual liquid mass transfer coefficient, k(:
kf(m/s) = [(8.22 x 10-9)(J)(POWR)(1.024)cr-20) *
(Ot)(106)MWL/(VavpL)](DNyD02)W)a5
The total power to the aerators, POWR, and the turbulent surface area, Vav, are calculated
separately [Note: some conversions are necessary.]:
1. Calculate total power to aerators, POWR (Default presented in III):
POWR (hp) = 0.75 hp/1,000 ft3 (V)
V = waste water volume, m
V (m3) = (A)(D) = (17,652 m2)(1.97 m)
V = 34,774 m3
POWR = (0.75 hp/1,000 ft3)(ft3/0.028317 m3)(34,774 m3)
= 921 hp
2. Calculate turbulent surface area, Vav (default presented in III):
Vav (ft2) = 0.24 (A)
= 0.24(17,652 m2)(10.758 ft2/m2)
= 45,576 ft2
9/91 (Reformatted 1/95) Evaporation Loss Sources 4.3-19
-------
Now, calculate kf, using the above calculations and information from II, III, and IV:
kp (m/s) = [(8.22 x 10'9)(3 Ib O2/hp-hr)(921 hp) *
(1.024)(25-2°)(0.83)( 106)( 18 g/gmol)/
((45,576 ft2)(l g/cm3))] *
[(9.8 x 10'6 cm2/s)/(2.4 x 10'5 cm2/s)]a5
= (0.00838)(0.639)
kj = 5.35 x ID'3 m/s
B. Calculate the individual gas phase mass transfer coefficient, k :
kB (m/s) = (1.35 x 10-7)(Re)L42(P)a4(ScG)a5(Fr)-°-21(Da MW_/d)
o
The Reynolds number, Re, power number, P, Schmidt number on the gas side, ScG, and
Froude's number Fr, are calculated separately:
1. Calculate Reynolds number, Re:
Re = d2 w pa/ua
= (61 cm)2(126 rad/s)(1.2 x 10'3 g/cm3)/(1.81 x 10'4 g/cm-s)
= 3.1 x 106
2. Calculate power number, P:
P = [(0.85)(POWR)(550 ft-lb^s-hp)/!^] g^p^d*)5 w3)
Nj = POWR/75 hp (default presented in III)
P = (0.85)(75 hp)(POWR/POWR)(550 ft-lb/s-hp) *
(32.17 lbm-ft/lbrs2)/[(62.4 Ibm/ft3)(2 ft)5(126 rad/s)3]
= 2.8 x 10'4
3. Calculate Schmidt number on the gas side, ScG:
ScG = ua/(paDa)
= (1.81 x 10'4 g/cm-s)/[(1.2 x 10"3 g/cm3)(0.088 cm2/s)]
= 1.71
4. Calculate Froude number, Fr:
Fr = (d*)w2/gc
= (2 ft)(126 rad/s)2/(32.17 lbm-ft/lbrs2)
= 990
Now, calculate kg using the above calculations and information from II, III, and IV:
kg (m/s) = (1.35 x 10'7)(3.1 x 106)L42(2.8 x 10-4)a4(1.71)°-5 *
(990)'0-21 (0.088 cm2/s)(29 g/gmol)/(61 cm)
= 0.109 m/s
Quiescent surface area of impoundment — Equations 1 and 2 from Table 4.3-1
A. Calculate the individual liquid phase mass transfer coefficient, kf:
F/D = 2(A/7i)°'5/D
= 2(17,652 m2/7t)°-5/(1.97 m)
= 76.1
U10 = 4.47 m/s
4.3-20 EMISSION FACTORS (Reformatted 1/95) 9/91
-------
For U10 > 3.25 m/s and F/D > 51.2 use the following:
kp (ra/s) = (2.61 x 10^)(U10)2(D/Dether)2/3
= (2.61 x 10'7)(4.47 m/s)2[(9.8 x 10'6 cm2/s)/
(8.5 x 10'6 cm2/s)]2/3
= 5.74 x 10-6m/s
B. Calculate the individual gas phase mass transfer coefficient, k :
&
kg = (4.82 x 10-3)(U10)a78(ScG)-°-67(de)-ai1
The Schmidt number on the gas side, ScG, and the effective diameter, de, are calculated
separately:
1. Calculate the Schmidt number on the gas side, ScG:
ScG = ua/(paDa) =1.71 (same as for turbulent impoundments)
2. Calculate the effective diameter, de:
de (m) = 2(A/K)0-5
= 2(17,652 m2/K)°-5
= 149.9 m
k (m/s) = (4.82 x 10'3)(4.47 m/s)0-78 (1.71)-°-67 (149.9 m)'0'11
= 6.24 x 10'3 m/s
VI. Calculate The Overall Mass Transfer Coefficient — Because part of the impoundment is
turbulent and part is quiescent, the overall mass transfer coefficient is determined as an area-
weighted average of the turbulent and quiescent overall mass transfer coefficients. (Equation 7
from Table 4.3-1).
Overall mass transfer coefficient for the turbulent surface area of impoundment,KT
KT (m/s) = (k{Keqk )/(Keqk + k,)
Keq = H/RT
= (0.0055 atm-m3/gmol)/[(8.21 x 10'5 atm-m3/ gmol-°K)(298°K)]
= 0.225
KT (m/s) = (5.35 x 10'3 m/s)(0.225)(0.109)/[(0.109 m/s)(0.225) +
(5.35 x 10'6 m/s)]
KT = 4.39 x 10'3 m/s
Overall mass transfer coefficient for the quiescent surface area of impoundment, KQ
KQ (m/s) = (k,Keqk )/(Keqk + k,)
= (5.74 x TO'6 m/s)(0.225)(6.24 x 10'3 m/s)/
[(6.24 X 1C'3 m/s)(0.225) + (5.74 x 10'6 m/s)]
= 5.72 x 10'6 m/s
Overall mass transfer coefficient. K, weighted by turbulent and quiescent surface areas,
AT and AQ
K (m/s) = (KTAT + KQAQ)/A
AT = 0.24(A) (Default value presented in III: AT = Vav)
AQ = (1 - 0.24)A
K (m/s) = [(4.39 x 10'3 m/s)(0.24 A) + (5.72 x 10'6 m/s)(l - 0.24)A]/A
= 1.06 x 10'3 m/s
9/91 (Reformatted 1/95) Evaporation Loss Sources 4.3-21
-------
VII. Calculate VOC Emissions For An Aerated Biological Flowthrough Impoundment — Equation 16
from Table 4.3-1:
N (g/s) = K CL A
where:
CL (g/m3) = [-b + (b2 - 4ac)°'5]/(2a)
and:
a = KA/Q + 1
b = KS(KA/Q + 1) + Kmax b; V/Q - Co
c = -KsCo
Calculate a, b, c, and the concentration of benzene in the liquid phase, CL, separately:
1. Calculate a:
a = (KA/Q + 1) = [(1.06 x 10'3 m/s)(17,652 m2)/(0.0623 m3/s)] + 1
= 301.3
2. Calculate b (V = 34,774 m3 from IV):
b = Ks (KA/Q + 1) + Kmax bj V/Q - Co
= (13.6 g/m^KLOe x 10'3 m/s)(17,652 m2)/(0.0623 m3/s)] +
[(5.28 x 10'6 g/g-s)(300 g/m3)(34,774 m3)/(0.0623 m3/s)] - 10.29 g/m3
= 4,084.6 + 884.1 - 10.29
= 4,958.46 g/m3
3. Calculate c:
c = -KsCo
= -(13.6 g/m3)(10.29 g/m3)
= -139.94
4. Calculate the concentration of benzene in the liquid phase, CL, from a, b, and c above:
CL (g/m3) = [-b + (b2 - 4ac)a5]/(2a)
= [(4,958.46 g/m3) + [(4,958.46 g/m3)2 -
[4(301.3)(-139.94)]]a5]/(2(301.3))
= 0.0282 g/m3
Now calculate N with the above calculations and information from II and V:
N(g/s) =KACL
= (1.06 x 10'3 m/s)(17,652 m2)(0.0282 g/m3)
= 0.52 g/s
4.3.3 Controls
The types of control technology generally used in reducing VOC emissions from waste water
include: steam stripping or air stripping, carbon adsorption (liquid phase), chemical oxidation,
membrane separation, liquid-liquid extraction, and biotreatment (aerobic or anaerobic). For efficient
control, all control elements should be placed as close as possible to the point of waste water
generation, with all collection, treatment, and storage systems ahead of the control technology being
covered to suppress emissions. Tightly covered, well-maintained collection systems can suppress
4.3-22 EMISSION FACTORS (Reformatted 1/95) 9/91
-------
emissions by 95 to 99 percent. However, if there is explosion potential, the components should be
vented to a control device such as an incinerator or carbon adsorber.
The following are brief descriptions of the control technology listed above and of any
secondary controls that may need to be considered for fugitive air emissions.
Steam stripping is the fractional distillation of waste water to remove volatile organic
constituents, with the basic operating principle being the direct contact of steam with waste water.
The steam provides the heat of vaporization for the more volatile organic constituents. Removal
efficiencies vary with volatility and solubility of the organic impurities. For highly volatile
compounds (HLC greater than 10~3 atm-m3/gmol), average VOC removal ranges from 95 to
99 percent. For medium-volatility compounds (HLC between 10"5 and 10~3 atm-m /gmol), average
removal ranges from 90 to 95 percent. For low-volatility compounds (HLC <10"5 atm-m3/gmol),
average removal ranges from less than 50 to 90 percent.
Air stripping involves the contact of waste water and air to strip out volatile organic
constituents. By forcing large volumes of air through contaminated water, the surface area of water in
contact with air is greatly increased, resulting in an increase in the transfer rate of the organic
compounds into the vapor phase. Removal efficiencies vary with volatility and solubility of organic
impurities. For highly volatile compounds, average removal ranges from 90 to 99 percent; for
medium- to low-volatility compounds, removal ranges from less than 50 to 90 percent.
Steam stripping and air stripping controls most often are vented to a secondary control, such as
a combustion device or gas phase carbon adsorber. Combustion devices may include incinerators,
boilers, and flares. Vent gases of high fuel value can be used as an alternate fuel. Typically, vent gas
is combined with other fuels such as natural gas and fuel oil. If the fuel value is very low, vent gases
can be heated and combined with combustion air. It is important to note that organics such as
chlorinated hydrocarbons can emit toxic pollutants when combusted.
Secondary control by gas phase carbon adsorption processes takes advantage of compound
affinities for activated carbon. The types of gas phase carbon adsorption systems most commonly
used to control VOC are fixed-bed carbon adsorbers and carbon canisters. Fixed-bed carbon adsorbers
are used to control continuous organic gas streams with flow rates ranging from 30 to over
3000 m /min. Canisters are much simpler and smaller than fixed-bed systems and are usually installed
to control gas flows of less than 3 m3/min.4 Removal efficiencies depend highly on the type of
compound being removed. Pollutant-specific activated carbon is usually required. Average removal
efficiency ranges from 90 to 99 percent.
Like gas phase carbon adsorption, liquid phase carbon adsorption takes advantage of
compound affinities for activated carbon. Activated carbon is an excellent adsorbent, because of its
large surface area and because it is usually in granular or powdered form for easy handling. Two
types of liquid phase carbon adsorption are the fixed-bed and moving-bed systems. The fixed-bed
system is used primarily for low-flow waste water streams with contact times around 15 minutes, and
it is a batch operation (i. e., once the carbon is spent, the system is taken off line). Moving-bed
carbon adsorption systems operate continuously with waste water typically being introduced from the
bottom of the column and regenerated carbon from the top (countercurrent flow). Spent carbon is
continuously removed from the bottom of the bed. Liquid phase carbon adsorption is usually used for
low concentrations of nonvolatile components and for high concentrations of nondegradable
compounds.5 Removal efficiencies depend on whether the compound is adsorbed on activated carbon.
Average removal efficiency ranges from 90 to 99 percent.
9/91 (Reformatted 1/95) Evaporation Loss Sources 4.3-23
-------
Chemical oxidation involves a chemical reaction between the organic compound and an
oxidant such as ozone, hydrogen peroxide, permanganate, or chlorine dioxide. Ozone is usually added
to the waste water through an ultraviolet-ozone reactor. Permanganate and chlorine dioxide are added
directly into the waste water. It is important to note that adding chlorine dioxide can form chlorinated
hydrocarbons in a side reaction. The applicability of this technique depends on the reactivity of the
individual organic compound.
Two types of membrane separation processes are ultrafiltration and reverse osmosis.
Ultrafiltration is primarily a physical sieving process driven by a pressure gradient across the
membrane. This process separates organic compounds with molecular weights greater than 2000,
depending on the size of the membrane pore. Reverse osmosis is the process by which a solvent is
forced across a semipermeable membrane because of an osmotic pressure gradient. Selectivity is,
therefore, based on osmotic diffusion properties of the compound and on the molecular diameter of the
compound and membrane pores.
Liquid-liquid extraction as a separation technique involves differences in solubility of
compounds in various solvents. Contacting a solution containing the desired compound with a solvent
in which the compound has a greater solubility may remove the compound from the solution. This
technology is often used for product and process solvent recovery. Through distillation, the target
compound is usually recovered, and the solvent reused.
Biotreatment is the aerobic or anaerobic chemical breakdown of organic chemicals by
microorganisms. Removal of organics by biodegradation is highly dependent on the compound's
biodegradability, its volatility, and its ability to be adsorbed onto solids. Removal efficiencies range
from almost zero to 100 percent. In general, highly volatile compounds such as chlorinated
hydrocarbons and aromatics will biodegrade very little because of their high-volatility, while alcohols
and other compounds soluble in water, as well as low-volatility compounds, can be almost totally
biodegraded in an acclimated system. In the acclimated biotreatment system, the microorganisms
easily convert available organics into biological cells, or biomass. This often requires a mixed culture
of organisms, where each organism utilizes the food source most suitable to its metabolism. The
organisms will starve and the organics will not be biodegraded if a system is not acclimated, i. e., the
organisms cannot metabolize the available food source.
4.3.4 Glossary Of Terms
Basin - an earthen or concrete-lined depression used to hold liquid.
Completely mixed - having the same characteristics and quality throughout or at all times.
Disposal - the act of permanent storage. Flow of liquid into, but not out of a device.
Drain - a device used for the collection of liquid. It may be open to the atmosphere or
be equipped with a seal to prevent emissions of vapors.
Flowthrough - having a continuous flow into and out of a device.
Plug flow - having characteristics and quality not uniform throughout. These will change
in the direction the fluid flows, but not perpendicular to the direction of flow
(i. e., no axial movement)
4.3-24 EMISSION FACTORS (Reformatted 1/95) 9/91
-------
Storage - any device to accept and retain a fluid for the purpose of future discharge.
Discontinuity of flow of liquid into and out of a device.
Treatment - the act of improving fluid properties by physical means. The removal of
undesirable impurities from a fluid.
VOC - volatile organic compounds, referring to all organic compounds except the
following, which have been shown not to be photochemically reactive:
methane, ethane, trichlorotrifluoroethane, methylene chloride,
1,1,1 ,-trichloroethane, trichlorofluoromethane, dichlorodifluoromethane,
chlorodifluoromethane, trifluoromethane, dichlorotetrafluoroethane, and
chloropentafluoroethane.
9/91 (Reformatted 1/95) Evaporation Loss Sources 4.3-25
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EMISSION FACTORS
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Evaporation Loss Sources
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4.3-38
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(Reformatted 1/95) 9/91
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9/91 (Reformatted 1/95)
Evaporation Loss Sources
4.3-39
-------
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4.3-40
EMISSION FACTORS
(Reformatted 1/95) 9/9\
-------
4.3.5 Waste Water—Greenhouse Gases
Greenhouse gases are emitted from both domestic and industrial waste water treatment operations.
When biological processes such as suspended-growth and attached-growth units operate in anaerobic
conditions with high biochemical oxygen demand (BOD) loading, the dominant greenhouse gas emitted is
methane (CH4), though lesser quantities of carbon dioxide (CO2) and nitrous oxide (N2O) may also be
emitted. Methane generated from waste water treatment plants may also be collected and utilized as a source
of energy, or flared. An anaerobic process is any treatment process that operates in the absence of oxygen.
The chemical reactions that occur in anaerobic conditions are mitigated by biological activities, such that they
are affected by many different factors (i.e., BOD loading, oxygen concentration, phosphorus and nitrogen
levels, temperature, redox potential, and retention time) which may significantly impact emissions.
4.3.5.1 Domestic Waste Water Treatment Processes -
Publicly owned treatment works (POTWs) are treatment facilities that treat waste water from
residences and businesses of a defined community. Aerobic treatment, which is rapid and relatively low in
odor, is used by a majority of POTWs in the U.S. The most common aerobic treatment process is activated
sludge, where raw waste water is mixed with a sludge of living aerobic microorganisms (the sludge is
activated in a mechanically aerated tank). The microorganisms rapidly adsorb and biologically oxidize the
organic solids suspended in the waste water, producing CO2.6 POTWs use a wide range of chemical and
biological processes. A POTW usually consists of a number of aerobic, anaerobic, and physical processes.
Those facilities that use biological processes under anaerobic conditions with high BOD loading emit CH4,
and, to a lesser extent, N2O and CO2. None of the data currently available on N2O and CO2 emissions are
useful for developing emission factors for this source. Emissions of CO2 from this source as well as other
biogenic sources are part of the carbon cycle, and as such are typically not included in greenhouse gas
emission inventories. To estimate uncontrolled CH4 emissions from a typical waste water treatment plant,
the following equation can be used:
lbBOD5 (365
capita/day/
yr
0.22 Ib CH4
Ib BOD.
Fraction 1 lb CH
Anaerobically =
Digested J Yr
(1)
where:
P is the population of the community served by the POTW.
Note: To convert from lb CH4/yr to kg CH4/yr, multiply by 0.454.
BOD5 is a standardized measurement for BOD. This 5-day BOD test is a measure of the "strength"
of the waste water; waste water with a high BOD5 is considered "strong." The BOD5-CH4
conversion (0.22 lb CH4/lb BOD5) is taken from Metcalf & Eddy8 and Orlich.9 The domestic BOD loading
rate (lb BOD5/capita/day) varies from one population group to the next, usually ranging from 0.10 to 0.17 lb,
with a typical value of 0.13 lb BOD5/capita/day.10 To obtain the exact domestic BOD loading rate for a
specific community, contact the local waste water treatment plant operator for that community. It has been
hypothesized that emission factors based on chemical oxygen demand (COD) are more accurate than those
based on BOD. Research is currently being conducted by the U. S. EPA relevant to this hypothesis.
02/98
Evaporation Loss Sources
4.3-41
-------
The fraction of the domestic waste water treated anaerobically is calculated by considering which
treatment processes are anaerobic and what percent of the total hydraulic retention time the waste water
spends in these treatment processes. This fraction is dependent on the treatment processes used and the
operating conditions of a specific plant. This information can also be provided by contacting local waste
water treatment plant operators. If treatment activity data are not available from local wastewater treatment
1 2
plant operators, a default value of 15 percent of domestic water treated anaerobically may also be used. A
default value of 15 percent is also recommended in the Intergovernmental Panel on Climate Change (IPCC)
Greenhouse Gas Inventory Reference Manual.^
If aBOD5 value of 0.13 Ib BOD5 is assumed, the IPCC assumption is used that
15 percent of waste water is anaerobically digested, and none of the gas is recovered for energy or flared, then
equation 1 reduces to the following equation:
j Ib CH4 1 CH,
(P) * 1.56 1 = Ib i (2)
\ capita/yry yr
4.3.5.2 Industrial Waste Water Treatment Processes -
An industrial waste water system uses unit processes similar to those found in POTWs. Such a
treatment system may discharge into a water body or may pretreat the waste water for discharge into a sewer
system leading to a POTW. To estimate uncontrolled CH4 methane emissions from a typical industrial waste
water treatment plant the following equation can be used:
( Ib BOD, ^ ( 0.22 Ib CH.) | Fraction
* 1— * 1 * Anaerobically
V ft3 wastewater/ { Ib BOD5 J ^ Digested
(3)
Ho,,cA Ib CH.
365
days \ _ lbCH4
yr ; yr
where:
Q! = daily waste water flow (ft3/day).
Flow rates for individual industrial waste water treatment facilities (Qj) can be provided by the
operator of the industrial waste water treatment plant or by reviewing a facility's National Pollution Discharge
Elimination System (NPDES) discharge permit.
Industrial BOD loading rates (Ib BOD5/ft waste water) vary depending upon the source of the waste
water contamination. Some contaminants have very high BOD5, such as contaminants in food and beverage
manufacturers' waste water. Table 4.3-5 provides a list of typical industrial BOD loading rates for major
industrial sources. To obtain the exact BOD loading rate for a specific facility, contact the facility's waste
water treatment plant operator or review the facility's NPDES discharge permit.
4.3-42 EMISSION FACTORS 02/98
-------
The fraction of the industrial waste water treated anaerobically is dependent on the treatment
processes used in specific plants. The composition of an industrial waste stream is more diverse than
municipal wastewater. The difference makes it very difficult to provide a default fraction of anaerobically
treated wastewater that would be representative of facilities in a specific inventory area. This information can
also be provided by contacting individual waste water treatment plant operators.
4.3.5.3 Controls
Waste water treatment plant operators (domestic as well as industrial) can also provide information
on gas recovery and utilization. If a gas recovery system is in place, uncontrolled CH4 emissions estimates
should be adjusted based on operator estimates of the efficiency of the gas collection system and the
destruction of the collected gas. For more information on control efficiencies, see Section 4.3.3.
4.3.6 Updates Since the Fifth Edition
The Fifth Edition was released in January 1995. In February 1998, this section was revised by the
addition of 4.3.5 which addresses Greenhouse Gas emissions. The revisions made in February 1998 are to be
included in Supplement D.
02/98 Evaporation Loss Sources 4.3-43
-------
Table 4.3-5. BIOCHEMICAL OXYGEN DEMAND (BOD) ESTIMATES FOR VARIOUS
INDUSTRIAL WASTE WATERS
Industry
Fertilizer
Food and
beverages
Beer
Beet sugar
Butter
Cane sugar
Cereals
Cheese
Fruits and
vegetables'1
Meats
Milk
Wine
Iron and steel
Non-ferrous
metals
Petroleum
refining
(Petrochemical)
Pharmaceutical
Pulp and paper
Rubber
Textiles
BOD5 (Ib/ft3)3
0.04
5.31
0.41
0.19
0.08
0.06
1.9
40.27
1.3
7.6
8.43
0.04
0.04
0.25
0.08
0.17
0.04
0.04
Reference
Number
14
15
15,16
17
15
18
17
15
19
15
15
14
14
14
14
14,20
14
14
Range
0.03-0.05b
4.99-5.62c
0.34-0.47C
0.07-0.09C
Average of BOD values for processing 35 different
fruits an vegetables. The BOD values ranged from
4.370 to 1747.979 lbs/ft3. For the BOD5 value it
was assumed that biodegradation was high such that
the BOD5 value was considered to be 75% of the
BOD value.
—
6.24-8.93c
7.49-9.36c
0.03-0.05b
0.03-0.05b
Average of values reported in Carmichael and
Strzepek (1987).
0.07-0.09C
0.14-0.19
0.03-0.05b
0.03-0.05C
To convert Ib/fr to kg/m^ multiply by 16.0185.
A BOD5 value was not provided in the literature. The range of BOD5 values was derived from the ultimate
BOD value from the textile industry, which should have a similar, relatively small value. BOD5 is 55 to 75
percent of ultimate BOD, depending on the biodegradability of the waste stream. The midpoint of the
extrapolated range is presented in the second column as BOD5.
c A range of values is given for BOD5 because a specific BOD5 value was not provided in the literature. The
range of BOD5 values was derived from the ultimate BOD value from the literature. BOD5 is 55 to 75
percent of ultimate BOD, depending on the biodegradability of the waste stream. If the waste stream
contains a large amount of material that does not biodegrade easily, then a value closer to the lower value
should be used. If the waste stream contains a large amount of material that does biodegrade easily, then a
value closer to the higher value should be used. If it is unclear how biodegradable the material is, and
BOD5 data for a specific facility is not available, then a value at the midpoint of the range should be used.
The midpoint of the range is presented in the second column as BOD5.
d For a more complete list of BOD5 values see reference 15.
4.3-44
EMISSION FACTORS
02/98
-------
References For Section 4.3
1. Hazardous Waste Treatment, Storage, And Disposal Facilities (TSDF) — Air Emission Models,
EPA-450/3-87-026, U. S. Environmental Protection Agency, Research Triangle Park, NC,
April 1989.
2. Waste Water Treatment Compound Property Processor Air Emissions Estimator (WATER 7), U. S.
Environmental Protection Agency, Research Triangle Park, NC, available early 1992.
3. Evaluation Of Test Method For Measuring Biodegradation Rates Of Volatile Organics, Draft,
EPA Contract No. 68-D90055, Entropy Environmental, Research Triangle Park, NC,
September 1989.
4. Industrial Waste Water Volatile Organic Compound Emissions — Background Information For
BACT/LAER Determinations, EPA-450/3-90-004, U. S. Environmental Protection Agency,
Research Triangle Park, NC, January 1990.
5. Evan K. Nyer, Ground Water Treatment Technology, Van Nostrand Reinhold Company, New York,
1985.
6. J. Mangino and L. Sutton. Evaluation of Greenhouse Gas Emissions From Wastewater Treatment
Systems. Contract No. 68-D1-0117, Work Assignment 22, U. S. Environmental Protection Agency,
Office of Research and Development, Air and Energy Engineering Research Laboratory, Research
Triangle Park, NC. April 1992.
7. L.C. Huff. Wastewater Methane Emission Estimates-Report to Congress. Contract
No. 68-D1-0117. U. S. Environmental Protection Agency, Office of Research and Development, Air
and Energy Engineering Research Laboratory, Research Triangle Park, NC. July 1992.
8. Metcalf & Eddy, Inc., Waste Water Engineering: Treatment, Disposal, And Reuse, McGraw-Hill
Book Company, p. 621, 1979.
9. Dr. J. Orlich, "Methane Emissions From Landfill Sites And Waste Water Lagoons", Presented in
Methane Emissions And Opportunities For Control, 1990.
10. Viessman, Jr. and M.J. Hammer. 1985. Water Supply And Pollution Control. Harper & Row
Publishers, New York, NY.
11. U. S. Environmental Protection Agency. International Anthropogenic Methane Emissions Report
to Congress. Office of Policy Planning and Evaluation, EPA 230-R-93-010. 1994.
12. M.J. Lexmond and G. Zeeman. Potential Of Uncontrolled Anaerobic Wastewater Treatment In
Order To Reduce Global Emissions Of The Greenhouse Gases Methane And Carbon Dioxide.
02/98 Evaporation Loss Sources 4.3-45
-------
Department of Environmental Technology, Agricultural University of Wageningen, the Netherlands.
Report Number 95-1. 1995.
13. Intergovernmental Panel on Climate Control, Greenhouse Gas Inventory Reference Manual, Vol. 3,
IPCC/OECD, p. 6.28, 1994.
14. J. B. Carmichael and K.M. Strzepek, Industrial Water Use And Treatment Practices, United
Nations Industrial Development Organization, Cassell Tycooly, Philadelphia, PA, pp. 33, 36, 49, 67
and 85, 1987.
15. D. Barnes, et al., "Surveys In Industrial Waste Water Treatment", Vol. 1, Food And Allied
Industries, Pitman Publishing Inc., Marshfield, Massachusetts, pp. 12, 73, 213 and 316, 1984.
16. Development Document For Effluent Limitations Guidelines And New Source Performance
Standards For The Beet Sugar Processing Subcategory Of The Sugar Processing Point Source
Category, EPA 40/l-74/002b, U. S. Environmental Protection Agency, Effluent Guidelines
Division, Office Of Waste And Hazardous Materials, Washington, DC, January 1974.
17. Development Document For Effluent Limitations Guidelines And New Source Performance
Standards For The Dairy Product Processing Point Source Category, EPA 440/1 -74/021 a,
U. S. Environmental Protection Agency, Effluent Guidelines Division, Office Of Waste And
Hazardous Materials, Washington, DC, p. 59, May 1974.
18. Development Document For Effluent Limitations Guidelines And New Source Performance
Standards For The Animal Feed, Breakfast Cereal, And Wheat Starch Segments Of The Grain
Mills Points Source Category, EPA 440/1-74/039a, U. S. Environmental Protection Agency,
Effluent Guidelines Division, Office Of Waste And Hazardous Materials, Washington, DC, pp.
39-40, December 1974.
19. Development Document For Effluent Limitations Guidelines And New Source Performance
Standards For The Rendering Segment Of The Meat Products And Rendering Processing Point
Source Category, EPA 400/l-4/031d, U. S. Environmental Protection Agency, Effluent Guidelines
Division, Office of Waste And Hazardous Materials, Washington, DC, pp. 58, 60, January 1975.
20. E. R. Hall (editor), "Anaerobic Treatment For Pulp And Paper Waste Waters", Anaerobic Treatment
Of Industrial Waste Water, Noyes Data Corporation, Park Ridge, New Jersey
pp. 15-22, 1988.
4.3-46 EMISSION FACTORS 02/98
-------
7.1 Organic Liquid Storage Tanks
1 9
7.1.1 Process Description
Storage vessels containing organic liquids can be found in many industries, including
(1) petroleum producing and refining, (2) petrochemical and chemical manufacturing, (3) bulk storage
and transfer operations, and (4) other industries consuming or producing organic liquids. Organic
liquids in the petroleum industry, usually called petroleum liquids, generally are mixtures of
hydrocarbons having dissimilar true vapor pressures (for example, gasoline and crude oil). Organic
liquids in the chemical industry, usually called volatile organic liquids, are composed of pure
chemicals or mixtures of chemicals with similar true vapor pressures (for example, benzene or a
mixture of isopropyl and butyl alcohols).
Six basic tank designs are used for organic liquid storage vessels: fixed roof (vertical and
horizontal), external floating roof, domed external (or covered) floating roof, internal floating roof,
variable vapor space, and pressure (low and high). A brief description of each tank is provided below.
Loss mechanisms associated with each type of tank are provided in Section 7.1.2.
The emission estimating equations presented in Section 7.1 were developed by the American
Petroleum Institute (API). API retains the copyright to these equations. API has granted permission
for the nonexclusive; noncommercial distribution of this material to governmental and regulatory
agencies. However, API reserves its rights regarding all commercial duplication and distribution of its
material. Therefore, the material presented in Section 7.1 is available for public use, but the material
cannot be sold without written permission from the American Petroleum Institute and the U. S.
Environmental Protection Agency.
7.1.1.1 Fixed Roof Tanks-
A typical vertical fixed roof tank is shown in Figure 7.1-1. This type of tank consists of a
cylindrical steel shell with a permanently affixed roof, which may vary in design from cone- or dome-
shaped to flat. Losses from fixed roof tanks are caused by changes in temperature, pressure, and
liquid level.
Fixed roof tanks are either freely vented or equipped with a pressure/vacuum vent. The latter
allows the tanks to operate at a slight internal pressure or vacuum to prevent the release of vapors
during very small changes in temperature, pressure, or liquid level. Of current tank designs, the fixed
roof tank is the least expensive to construct and is generally considered the minimum acceptable
equipment for storing organic liquids.
Horizontal fixed roof tanks are constructed for both above-ground and underground service
and are usually constructed of steel, steel with a fiberglass overlay, or fiberglass-reinforced polyester.
Horizontal tanks are generally small storage tanks with capacities of less than 40,000 gallons.
Horizontal tanks are constructed such that the length of the tank is not greater than six times the
diameter to ensure structural integrity. Horizontal tanks are usually equipped with pressure-vacuum
vents, gauge hatches and sample wells, and manholes to provide access to these tanks. In addition,
underground tanks may be cathodically protected to prevent corrosion of the tank shell. Cathodic
protection is accomplished by placing sacrificial anodes in the tank that are connected to an impressed
current system or by using galvanic anodes in the tank. However, internal cathodic protection against
9/97 Liquid Storage Tanks 7.1-1
-------
corrosion is no longer widely used in the petroleum industry, due to corrosion inhibitors that are now
found in most refined petroleum products.
The potential emission sources for above-ground horizontal tanks are the same as those for
vertical fixed roof tanks. Emissions from underground storage tanks are associated mainly with
changes in the liquid level in the tank. Losses due to changes in temperature or barometric pressure
are minimal for underground tanks because the surrounding earth limits the diurnal temperature
change, and changes in the barometric pressure result in only small losses.
7.1.1.2 External Floating Roof Tanks -
A typical external floating roof tank (EFRT) consists of an open- topped cylindrical steel shell
equipped with a roof that floats on the surface of the stored liquid. The floating roof consists of a
deck, fittings, and rim seal system. Floating decks that are currently in use are constructed of welded
steel plate and are of two general types: pontoon or double-deck. Pontoon-type and double-deck-type
external floating roof tanks are shown in Figures 7.1-2 and 7.1-3, respectively. With all types of
external floating roof tanks, the roof rises and falls with the liquid level in the tank. External floating
decks are equipped with a rim seal system, which is attached to the deck perimeter and contacts the
tank wall. The purpose of the floating roof and rim seal system is to reduce evaporative loss of the
stored liquid. Some annular space remains between the seal system and the tank wall. The seal
system slides against the tank wall as the roof is raised and lowered. The floating deck is also
equipped with fittings that penetrate the deck and serve operational functions. The external floating
roof design is such that evaporative losses from the stored liquid are limited to losses from the rim
seal system and deck fittings (standing storage loss) and any exposed liquid on the tank walls
(withdrawal loss).
7.1.1.3 Internal Floating Roof Tanks -
An internal floating roof tank (IFRT) has both a permanent fixed roof and a floating roof
inside. There are two basic types of internal floating roof tanks: tanks in which the fixed roof is
supported by vertical columns within the tank, and tanks with a self-supporting fixed roof and no
internal support columns. Fixed roof tanks that have been retrofitted to use a floating roof are
typically of the first type. External floating roof tanks that have been converted to internal floating
roof tanks typically have a self-supporting roof. Newly constructed internal floating roof tanks may be
of either type. The deck in internal floating roof tanks rises and falls with the liquid level and either
floats directly on the liquid surface (contact deck) or rests on pontoons several inches above the liquid
surface (noncontact deck). The majority of aluminum internal floating roofs currently in service have
noncontact decks. A typical internal floating roof tank is shown in Figure 7.1-4.
Contact decks can be (1) aluminum sandwich panels that are bolted together, with a
honeycomb aluminum core floating in contact with the liquid; (2) pan steel decks floating in contact
with the liquid, with or without pontoons; and (3) resin-coated, fiberglass reinforced polyester (FRP),
buoyant panels floating in contact with the liquid. The majority of internal contact floating decks
currently in service are aluminum sandwich panel-type or pan steel-type. The FRP decks are less
common. The panels of pan steel decks are usually welded together.
Noncontact decks are the most common type currently in use. Typical noncontact decks are
constructed of an aluminum deck and an aluminum grid framework supported above the liquid surface
by tubular aluminum pontoons or some other buoyant structure. The noncontact decks usually have
bolted deck seams. Installing a floating roof minimizes evaporative losses of the stored liquid. Both
contact and noncontact decks incorporate rim seals and deck fittings for the same purposes previously
described for external floating roof tanks. Evaporative losses from floating roofs may come from deck
7.1-2 EMISSION FACTORS 9/97
-------
fittings, nonwelded deck seams, and the annular space between the deck and tank wall. In addition,
these tanks are freely vented by circulation vents at the top of the fixed roof. The vents minimize the
possibility of organic vapor accumulation in the tank vapor space in concentrations approaching the
flammable range. An internal floating roof tank not freely vented is considered a pressure tank.
Emission estimation methods for such tanks are not provided in AP-42.
7.1.1.4 Domed External Floating Roof Tanks -
Domed external (or covered) floating roof tanks have the heavier type of deck used in external
floating roof tanks as well as a fixed roof at the top of the shell like internal floating roof tanks.
Domed external floating roof tanks usually result from retrofitting an external floating roof tank with a
fixed roof. This type of tank is very similar to an internal floating roof tank with a welded deck and a
self supporting fixed roof. A typical domed external floating roof tank is shown in Figure 7.1-5.
As with the internal floating roof tanks, the function of the fixed roof is not to act as a vapor
barrier, but to block the wind. The type of fixed roof most commonly used is a self supporting
aluminum dome roof, which is of bolted construction. Like the internal floating roof tanks, these
tanks are freely vented by circulation vents at the top of the fixed roof. The deck fittings and rim
seals, however, are identical to those on external floating roof tanks. In the event that the floating
deck is replaced with the lighter IFRT-type deck, the tank would then be considered an internal
floating roof tank.
7.1.1.5 Variable Vapor Space Tanks-
Variable vapor space tanks are equipped with expandable vapor reservoirs to accommodate
vapor volume fluctuations attributable to temperature and barometric pressure changes. Although
variable vapor space tanks are sometimes used independently, they are normally connected to the
vapor spaces of one or more fixed roof tanks. The two most common types of variable vapor space
tanks are lifter roof tanks and flexible diaphragm tanks.
Lifter roof tanks have a telescoping roof that fits loosely around the outside of the main tank
wall. The space between the roof and the wall is closed by either a wet seal, which is a trough filled
with liquid, or a dry seal, which uses a flexible coated fabric.
Flexible diaphragm tanks use flexible membranes to provide expandable volume. They may
be either separate gasholder units or integral units mounted atop fixed roof tanks.
Variable vapor space tank losses occur during tank filling when vapor is displaced by liquid.
Loss of vapor occurs only when the tank's vapor storage capacity is exceeded.
7.1.1.6 Pressure Tanks-
Two classes of pressure tanks are in general use: low pressure (2.5 to 15 psig) and high
pressure (higher than 15 psig). Pressure tanks generally are used for storing organic liquids and gases
with high vapor pressures and are found in many sizes and shapes, depending on the operating
pressure of the tank. Pressure tanks are equipped with a pressure/vacuum vent that is set to prevent
venting loss from boiling and breathing loss from daily temperature or barometric pressure changes.
High-pressure storage tanks can be operated so that virtually no evaporative or working losses occur.
In low-pressure tanks, working losses can occur with atmospheric venting of the tank during filling
operations. No appropriate correlations are available to estimate vapor losses from pressure tanks.
9/97 Liquid Storage Tanks 7.1-3
-------
7.1.2 Emission Mechanisms And Control
Emissions from organic liquids in storage occur because of evaporative loss of the liquid
during its storage and as a result of changes in the liquid level. The emission sources vary with tank
design, as does the relative contribution of each type of emission source. Emissions from fixed roof
tanks are a result of evaporative losses during storage (known as breathing losses or standing storage
losses) and evaporative losses during filling and emptying operations (known as working losses).
External and internal floating roof tanks are emission sources because of evaporative losses that occur
during standing storage and withdrawal of liquid from the tank. Standing storage losses are a result of
evaporative losses through rim seals, deck fittings, and/or deck seams. The loss mechanisms for fixed
roof and external and internal floating roof tanks are described in more detail in this section. Variable
vapor space tanks are also emission sources because of evaporative losses that result during filling
operations. The loss mechanism for variable vapor space tanks is also described in this section.
Emissions occur from pressure tanks, as well. However, loss mechanisms from these sources are not
described in this section.
7.1.2.1 Fixed Roof Tanks -
The two significant types of emissions from fixed roof tanks are storage and working losses.
Storage loss is the expulsion of vapor from a tank through vapor expansion and contraction, which are
the results of changes in temperature and barometric pressure. This loss occurs without any liquid
level change in the tank.
The combined loss from filling and emptying is called working loss. Evaporation during
filling operations is a result of an increase in the liquid level in the tank. As the liquid level increases,
the pressure inside the tank exceeds the relief pressure and vapors are expelled from the tank.
Evaporative loss during emptying occurs when air drawn into the tank during liquid removal becomes
saturated with organic vapor and expands, thus exceeding the capacity of the vapor space.
Fixed roof tank emissions vary as a function of vessel capacity, vapor pressure of the stored
liquid, utilization rate of the tank, and atmospheric conditions at the tank location.
Several methods are used to control emissions from fixed roof tanks. Emissions from fixed
roof tanks can be controlled by installing an internal floating roof and seals to minimize evaporation of
the product being stored. The control efficiency of this method ranges from 60 to 99 percent,
depending on the type of roof and seals installed and on the type of organic liquid stored.
Vapor balancing is another means of emission control. Vapor balancing is probably most
common in the filling of tanks at gasoline stations. As the storage tank is filled, the vapors expelled
from the storage tank are directed to the emptying gasoline tanker truck. The truck then transports the
vapors to a centralized station where a vapor recovery or control system is used to control emissions.
Vapor balancing can have control efficiencies as high as 90 to 98 percent if the vapors are subjected to
vapor recovery or control. If the truck vents the vapor to the atmosphere instead of to a recovery or
control system, no control is achieved.
Vapor recovery systems collect emissions from storage vessels and convert them to liquid
product. Several vapor recovery procedures may be used, including vapor/liquid absorption, vapor
compression, vapor cooling, vapor/solid adsorption, or a combination of these. The overall control
efficiencies of vapor recovery systems are as high as 90 to 98 percent, depending on the methods used,
the design of the unit, the composition of vapors recovered, and the mechanical condition of the
system.
7.1-4 EMISSION FACTORS 9/97
-------
In a typical thermal oxidation system, the air/vapor mixture is injected through a burner
manifold into the combustion area of an incinerator. Control efficiencies for this system can range
from 96 to 99 percent.
7.1.2.2 Floating Roof Tanks2'7 -
Total emissions from floating roof tanks are the sum of withdrawal losses and standing storage
losses. Withdrawal losses occur as the liquid level, and thus the floating roof, is lowered. Some
liquid remains on the inner tank wall surface and evaporates. For an internal floating roof tank that
has a column supported fixed roof, some liquid also clings to the columns and evaporates.
Evaporative loss occurs until the tank is filled and the exposed surfaces are again covered. Standing
storage losses from floating roof tanks include rim seal and deck fitting losses, and for internal floating
roof tanks also include deck seam losses for constructions other than welded decks. Other potential
standing storage loss mechanisms include breathing losses as a result of temperature and pressure
changes.
Rim seal losses can occur through many complex mechanisms, but for external floating roof
tanks, the majority of rim seal vapor losses have been found to be wind induced. No dominant wind
loss mechanism has been identified for internal floating roof or domed external floating roof tank rim
seal losses. Losses can also occur due to permeation of the rim seal material by the vapor or via a
wicking effect of the liquid, but permeation of the rim seal material generally does not occur if the
correct seal fabric is used. Testing has indicated that breathing, solubility, and wicking loss
mechanisms are small in comparison to the wind-induced loss. The rim seal factors presented in this
section incorporate all types of losses.
The rim seal system is used to allow the floating roof to rise and fall within the tank as the
liquid level changes. The rim seal system also helps to fill the annular space between the rim and the
tank shell and therefore minimize evaporative losses from this area. A rim seal system may consist of
just a primary seal or a primary and a secondary seal, which is mounted above the primary seal.
Examples of primary and secondary seal configurations are shown in Figures 7.1-6, 7.1-7, and 7.1-8.
The primary seal serves as a vapor conservation device by closing the annular space between
the edge of the floating deck and the tank wall. Three basic types of primary seals are used on
external floating roofs: mechanical (metallic) shoe, resilient filled (nonmetallic), and flexible wiper
seals. Some primary seals on external floating roof tanks are protected by a weather shield. Weather
shields may be of metallic, elastomeric, or composite construction and provide the primary seal with
longer life by protecting the primary seal fabric from deterioration due to exposure to weather, debris,
and sunlight. Internal floating roofs typically incorporate one of two types of flexible, product-
resistant seals: resilient foam-filled seals or wiper seals. Mechanical shoe seals, resilient filled seals,
and wiper seals are discussed below.
A mechanical shoe seal uses a light-gauge metallic band as the sliding contact with the shell of
the tank, as shown in Figure 7.1-7. The band is formed as a series of sheets (shoes) which are joined
together to form a ring, and are held against the tank shell by a mechanical device. The shoes are
normally 3 to 5 feet deep, providing a potentially large contact area with the tank shell. Expansion
and contraction of the ring can be provided for as the ring passes over shell irregularities or rivets by
jointing narrow pieces of fabric into the ring or by crimping the shoes at intervals. The bottoms of the
shoes extend below the liquid surface to confine the rim vapor space between the shoe and the floating
deck.
9/97 Liquid Storage Tanks 7.1-5
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The rim vapor space, which is bounded by the shoe, the rim of the floating deck, and the
liquid surface, is sealed from the atmosphere by bolting or clamping a coated fabric, called the primary
seal fabric, that extends from the shoe to the rim to form an "envelope". Two locations are used for
attaching the primary seal fabric. The fabric is most commonly attached to the top of the shoe and the
rim of the floating deck. To reduce the rim vapor space, the fabric can be attached to the shoe and the
floating deck rim near the liquid surface. Rim vents can be used to relieve any excess pressure or
vacuum in the vapor space.
A resilient filled seal can be mounted to eliminate the vapor space between the rim seal and
liquid surface (liquid mounted) or to allow a vapor space between the rim seal and the liquid surface
(vapor mounted). Both configurations are shown in Figures 7.1-6 and 7.1-7. Resilient filled seals
work because of the expansion and contraction of a resilient material to maintain contact with the tank
shell while accommodating varying annular rim space widths. These rim seals allow the roof to move
up and down freely, without binding.
Resilient filled seals typically consist of a core of open-cell foam encapsulated in a coated
fabric. The seals are attached to a mounting on the deck perimeter and extend around the deck
circumference. Polyurethane-coated nylon fabric and polyurethane foam are commonly used materials.
For emission control, it is important that the attachment of the seal to the deck and the radial seal
joints be vapor-tight and that the seal be in substantial contact with the tank shell.
Wiper seals generally consist of a continuous annular blade of flexible material fastened to a
mounting bracket on the deck perimeter that spans the annular rim space and contacts the tank shell.
This type of seal is depicted in Figure 7.1-6. New tanks with wiper seals may have dual wipers, one
mounted above the other. The mounting is such that the blade is flexed, and its elasticity provides a
sealing pressure against the tank shell.
Wiper seals are vapor mounted; a vapor space exists between the liquid stock and the bottom
of the seal. For emission control, it is important that the mounting be vapor-tight, that the seal extend
around the circumference of the deck and that the blade be in substantial contact with the tank shell.
Two types of materials are commonly used to make the wipers. One type consists of a cellular,
elastomeric material tapered in cross section with the thicker portion at the mounting. Rubber is a
commonly used material; urethane and cellular plastic are also available. All radial joints in the blade
are joined. The second type of material that can be used is a foam core wrapped with a coated fabric.
Polyurethane on nylon fabric and polyurethane foam are common materials. The core provides the
flexibility and support, while the fabric provides the vapor barrier and wear surface.
A secondary seal may be used to provide some additional evaporative loss control over that
achieved by the primary seal. Secondary seals can be either flexible wiper seals or resilient filled
seals. For external floating roof tanks, two configurations of secondary seals are available: shoe
mounted and rim mounted, as shown in Figure 7.1-8. Rim mounted secondary seals are more
effective in reducing losses than shoe mounted secondary seals because they cover the entire rim vapor
space. For internal floating roof tanks, the secondary seal is mounted to an extended vertical rim
plate, above the primary seal, as shown in Figure 7.1-8. However, for some floating roof tanks, using
a secondary seal further limits the tank's operating capacity due to the need to keep the seal from
interfering with fixed roof rafters or to keep the secondary seal in contact with the tank shell when the
tank is filled.
7.1-6 EMISSION FACTORS 9/97
-------
In a typical thermal oxidation system, the air/vapor mixture is injected through a burner
manifold into the combustion area of an incinerator. Control efficiencies for this system can range
from 96 to 99 percent.
7.1.2.2 Floating Roof Tanks2"7 -
Total emissions from floating roof tanks are the sum of withdrawal losses and standing storage
losses. Withdrawal losses occur as the liquid level, and thus the floating roof, is lowered. Some
liquid remains on the inner tank wall surface and evaporates. For an internal floating roof tank that
has a column supported fixed roof, some liquid also clings to the columns and evaporates.
Evaporative loss occurs until the tank is filled and the exposed surfaces are again covered. Standing
storage losses from floating roof tanks include rim seal and deck fitting losses, and for internal floating
roof tanks also include deck seam losses for constructions other than welded decks. Other potential
standing storage loss mechanisms include breathing losses as a result of temperature and pressure
changes.
Rim seal losses can occur through many complex mechanisms, but for external floating roof
tanks, the majority of rim seal vapor losses have been found to be wind induced. No dominant wind
loss mechanism has been identified for internal floating roof or domed external floating roof tank rim
seal losses. Losses can also occur due to permeation of the rim seal material by the vapor or via a
wicking effect of the liquid, but permeation of the rim seal material generally does not occur if the
correct seal fabric is used. Testing has indicated that breathing, solubility, and wicking loss
mechanisms are small in comparison to the wind-induced loss. The rim seal factors presented in this
section incorporate all types of losses.
The rim seal system is used to allow the floating roof to rise and fall within the tank as the
liquid level changes. The rim seal system also helps to fill the annular space between the rim and the
tank shell and therefore minimize evaporative losses from this area. A rim seal system may consist of
just a primary seal or a primary and a secondary seal, which is mounted above the primary seal.
Examples of primary and secondary seal configurations are shown in Figures 7.1-6, 7.1-7, and 7.1-8.
The primary seal serves as a vapor conservation device by closing the annular space between
the edge of the floating deck and the tank wall. Three basic types of primary seals are used on
external floating roofs: mechanical (metallic) shoe, resilient filled (nonmetallic), and flexible wiper
seals. Some primary seals on external floating roof tanks are protected by a weather shield. Weather
shields may be of metallic, elastomeric, or composite construction and provide the primary seal with
longer life by protecting the primary seal fabric from deterioration due to exposure to weather, debris,
and sunlight. Internal floating roofs typically incorporate one of two types of flexible, product-
resistant seals: resilient foam-filled seals or wiper seals. Mechanical shoe seals, resilient filled seals,
and wiper seals are discussed below.
A mechanical shoe seal uses a light-gauge metallic band as the sliding contact with the shell of
the tank, as shown in Figure 7.1-7. The band is formed as a series of sheets (shoes) which are joined
together to form a ring, and are held against the tank shell by a mechanical device. The shoes are
normally 3 to 5 feet deep, providing a potentially large contact area with the tank shell. Expansion
and contraction of the ring can be provided for as the ring passes over shell irregularities or rivets by
jointing narrow pieces of fabric into the ring or by crimping the shoes at intervals. The bottoms of the
shoes extend below the liquid surface to confine the rim vapor space between the shoe and the floating
deck.
9/97 Liquid Storage Tanks 7.1-5
-------
The rim vapor space, which is bounded by the shoe, the rim of the floating deck, and the
liquid surface, is sealed from the atmosphere by bolting or clamping a coated fabric, called the primary
seal fabric, that extends from the shoe to the rim to form an "envelope". Two locations are used for
attaching the primary seal fabric. The fabric is most commonly attached to the top of the shoe and the
rim of the floating deck. To reduce the rim vapor space, the fabric can be attached to the shoe and the
floating deck rim near the liquid surface. Rim vents can be used to relieve any excess pressure or
vacuum in the vapor space.
A resilient filled seal can be mounted to eliminate the vapor space between the rim seal and
liquid surface (liquid mounted) or to allow a vapor space between the rim seal and the liquid surface
(vapor mounted). Both configurations are shown in Figures 7.1-6 and 7.1-7. Resilient filled seals
work because of the expansion and contraction of a resilient material to maintain contact with the tank
shell while accommodating varying annular rim space widths. These rim seals allow the roof to move
up and down freely, without binding.
Resilient filled seals typically consist of a core of open-cell foam encapsulated in a coated
fabric. The seals are attached to a mounting on the deck perimeter and extend around the deck
circumference. Polyurethane-coated nylon fabric and polyurethane foam are commonly used materials.
For emission control, it is important that the attachment of the seal to the deck and the radial seal
joints be vapor-tight and that the seal be in substantial contact with the tank shell.
Wiper seals generally consist of a continuous annular blade of flexible material fastened to a
mounting bracket on the deck perimeter that spans the annular rim space and contacts the tank shell.
This type of seal is depicted in Figure 7.1-6. New tanks with wiper seals may have dual wipers, one
mounted above the other. The mounting is such that the blade is flexed, and its elasticity provides a
sealing pressure against the tank shell.
Wiper seals are vapor mounted; a vapor space exists between the liquid stock and the bottom
of the seal. For emission control, it is important that the mounting be vapor-tight, that the seal extend
around the circumference of the deck and that the blade be in substantial contact with the tank shell.
Two types of materials are commonly used to make the wipers. One type consists of a cellular,
elastomeric material tapered in cross section with the thicker portion at the mounting. Rubber is a
commonly used material; urethane and cellular plastic are also available. All radial joints in the blade
are joined. The second type of material that can be used is a foam core wrapped with a coated fabric.
Polyurethane on nylon fabric and polyurethane foam are common materials. The core provides the
flexibility and support, while the fabric provides the vapor barrier and wear surface.
A secondary seal may be used to provide some additional evaporative loss control over that
achieved by the primary seal. Secondary seals can be either flexible wiper seals or resilient filled
seals. For external floating roof tanks, two configurations of secondary seals are available: shoe
mounted and rim mounted, as shown in Figure 7.1-8. Rim mounted secondary seals are more
effective in reducing losses than shoe mounted secondary seals because they cover the entire rim vapor
space. For internal floating roof tanks, the secondary seal is mounted to an extended vertical rim
plate, above the primary seal, as shown in Figure 7.1-8. However, for some floating roof tanks, using
a secondary seal further limits the tank's operating capacity due to the need to keep the seal from
interfering with fixed roof rafters or to keep the secondary seal in contact with the tank shell when the
tank is filled.
7.1-6 EMISSION FACTORS 9/97
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The deck fitting losses from floating roof tanks can be explained by the same mechanisms as
the rim seal losses. However, the relative contribution of each mechanism is not known. The deck
fitting losses identified in this section account for the combined effect of all of the mechanisms.
Numerous fittings pass through or are attached to floating roof decks to accommodate
structural support components or allow for operational functions. Internal floating roof deck fittings
are typically of different configuration than those for external floating roof decks. Rather than having
tall housings to avoid rainwater entry, internal floating roof deck fittings tend to have lower profile
housings to minimize the potential for the fitting to contact the fixed roof when the tank is filled.
Deck fittings can be a source of evaporative loss when they require openings in the deck. The most
common components that require openings in the deck are described below.
1. Access hatches. An access hatch is an opening in the deck with a peripheral vertical well
that is large enough to provide passage for workers and materials through the deck for construction or
servicing. Attached to the opening is a removable cover that may be bolted and/or gasketed to reduce
evaporative loss. On internal floating roof tanks with noncontact decks, the well should extend down
into the liquid to seal off the vapor space below the noncontact deck. A typical access hatch is shown
in Figure 7.1-9.
2. Gauge-floats. A gauge-float is used to indicate the level of liquid within the tank. The
float rests on the liquid surface and is housed inside a well that is closed by a cover. The cover may
be bolted and/or gasketed to reduce evaporation loss. As with other similar deck penetrations, the well
extends down into the liquid on noncontact decks in internal floating roof tanks. A typical gauge-float
and well are shown in Figure 7.1-9.
3. Gauge-hatch/sample ports. A gauge-hatch/sample port consists of a pipe sleeve equipped
with a self-closing gasketed cover (to reduce evaporative losses) and allows hand-gauging or sampling
of the stored liquid. The gauge-hatch/sample port is usually located beneath the gauger's platform,
which is mounted on top of the tank shell. A cord may be attached to the self-closing gasketed cover
so that the cover can be opened from the platform. A typical gauge-hatch/sample port is shown in
Figure 7.1-9.
4. Rim vents. Rim vents are used on tanks equipped with a seal design that creates a vapor
pocket in the seal and rim area, such as a mechanical shoe seal. A typical rim vent is shown in
Figure 7.1-10. The vent is used to release any excess pressure or vacuum that is present in the vapor
space bounded by the primary-seal shoe and the floating roof rim and the primary seal fabric and the
liquid level. Rim vents usually consist of weighted pallets that rest on a gasketed cover.
5. Deck drains. Currently two types of deck drains are in use (closed and open deck drains)
to remove rainwater from the floating deck. Open deck drains can be either flush or overflow drains.
Both types consist of a pipe that extends below the deck to allow the rainwater to drain into the stored
liquid. Only open deck drains are subject to evaporative loss. Flush drains are flush with the deck
surface. Overflow drains are elevated above the deck surface. Typical overflow and flush deck drains
are shown in Figure 7.1-10. Overflow drains are used to limit the maximum amount of rainwater that
can accumulate on the floating deck, providing emergency drainage of rainwater if necessary. Closed
deck drains carry rainwater from the surface of the deck though a flexible hose or some other type of
piping system that runs through the stored liquid prior to exiting the tank. The rainwater does not
come in contact with the liquid, so no evaporative losses result. Overflow drains are usually used in
conjunction with a closed drain system to carry rainwater outside the tank.
9/97 Liquid Storage Tanks 7.1-7
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6. Deck legs. Deck legs are used to prevent damage to fittings underneath the deck and to
allow for tank cleaning or repair, by holding the deck at a predetermined distance off the tank bottom.
These supports consist of adjustable or fixed legs attached to the floating deck or hangers suspended
from the fixed roof. For adjustable legs or hangers, the load-carrying element passes through a well or
sleeve into the deck. With noncontact decks, the well should extend into the liquid. Evaporative
losses may occur in the annulus between the deck leg and its sleeve. A typical deck leg is shown in
Figure 7.1-10.
7. Unslotted guidepoles and wells. A guidepole is an antirotational device that is fixed to the
top and bottom of the tank, passing through a well in the floating roof. The guidepole is used to
prevent adverse movement of the roof and thus damage to deck fittings and the rim seal system. In
some cases, an unslotted guidepole is used for gauging purposes, but there is a potential for differences
in the pressure, level, and composition of the liquid inside and outside of the guidepole. A typical
guidepole and well are shown in Figure 7.1-11.
8. Slotted (perforated) guidepoles and wells. The function of the slotted guidepole is similar
to the unslotted guidepole but also has additional features. Perforated guidepoles can be either slotted
or drilled hole guidepoles. A typical slotted guidepole and well are shown in Figure 7.1-11. As
shown in this figure, the guide pole is slotted to allow stored liquid to enter. The same can be
accomplished with drilled holes. The liquid entering the guidepole is well mixed, having the same
composition as the remainder of the stored liquid, and is at the same liquid level as the liquid in the
tank. Representative samples can therefore be collected from the slotted or drilled hole guidepole.
However, evaporative loss from the guidepole can be reduced by modifying the guidepole or well or
by placing a float inside the guidepole. Guidepoles are also referred to as gauge poles, gauge pipes, or
stilling wells.
9. Vacuum breakers. A vacuum breaker equalizes the pressure of the vapor space across the
deck as the deck is either being landed on or floated off its legs. A typical vacuum breaker is shown
in Figure 7.1-10. As depicted in this figure, the vacuum breaker consists of a well with a cover.
Attached to the underside of the cover is a guided leg long enough to contact the tank bottom as the
floating deck approaches. When in contact with the tank bottom, the guided leg mechanically opens
the breaker by lifting the cover off the well; otherwise, the cover closes the well. The closure may be
gasketed or ungasketed. Because the purpose of the vacuum breaker is to allow the free exchange of
air and/or vapor, the well does not extend appreciably below the deck.
Fittings used only on internal floating roof tanks include column wells, ladder wells, and stub
drains.
1. Columns and wells. The most common fixed-roof designs are normally supported from
inside the tank by means of vertical columns, which necessarily penetrate an internal floating deck.
(Some fixed roofs are entirely self-supporting and, therefore, have no support columns.) Column wells
are similar to unslotted guide pole wells on external floating roofs. Columns are made of pipe with
circular cross sections or of structural shapes with irregular cross sections (built-up). The number of
columns varies with tank diameter, from a minimum of 1 to over 50 for very large diameter tanks. A
typical fixed roof support column and well are shown in Figure 7.1-9.
The columns pass through deck openings via peripheral vertical wells. With noncontact decks,
the well should extend down into the liquid stock. Generally, a closure device exists between the top
of the well and the column. Several proprietary designs exist for this closure, including sliding covers
and fabric sleeves, which must accommodate the movements of the deck relative to the column as the
7.1-8 EMISSION FACTORS 9/97
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liquid level changes. A sliding cover rests on the upper rim of the column well (which is normally
fixed to the deck) and bridges the gap or space between the column well and the column. The cover,
which has a cutout, or opening, around the column slides vertically relative to the column as the deck
raises and lowers. At the same time, the cover slides horizontally relative to the rim of the well. A
gasket around the rim of the well reduces emissions from this fitting. A flexible fabric sleeve seal
between the rim of the well and the column (with a cutout or opening, to allow vertical motion of the
seal relative to the columns) similarly accommodates limited horizontal motion of the deck relative to
the column.
2. Ladders and wells. Some tanks are equipped with internal ladders that extend from a
manhole in the fixed roof to the tank bottom. The deck opening through which the ladder passes is
constructed with similar design details and considerations to deck openings for column wells, as
previously discussed. A typical ladder well is shown in Figure 7.1-12.
3. Stub drains. Bolted internal floating roof decks are typically equipped with stub drains to
allow any stored product that may be on the deck surface to drain back to the underside of the deck.
The drains are attached so that they are flush with the upper deck. Stub drains are approximately
1 inch in diameter and extend down into the product on noncontact decks.
Deck seams in internal floating roof tanks are a source of emissions to the extent that these
seams may not be completely vapor tight if the deck is not welded. Generally, the same loss
mechanisms for fittings apply to deck seams. The predominant mechanism depends on whether or not
the deck is in contact with the stored liquid. The deck seam loss equation accounts for the effects of
all contributing loss mechamisms.
7.1.3 Emission Estimation Procedures
The following section presents the emission estimation procedures for fixed roof, external
floating roof, domed external floating roof, and internal floating roof tanks. These procedures are
valid for all petroleum liquids, pure volatile organic liquids, and chemical mixtures with similar true
vapor pressures. It is important to note that in all the emission estimation procedures the physical
properties of the vapor do not include the noncondensibles (e. g., air) in the gas but only refer to the
condensible components of the stored liquid. To aid in the emission estimation procedures, a list of
variables with their corresponding definitions was developed and is presented in Table 7.1-1.
The factors presented in AP-42 are those that are currently available and have been reviewed
and approved by the U. S. Environmental Protection Agency. As storage tank equipment vendors
design new floating decks and equipment, new emission factors may be developed based on that
equipment. If the new emission factors are reviewed and approved, the emission factors will be added
to AP-42 during the next update.
The emission estimation procedures outlined in this chapter have been used as the basis for the
development of a software program to estimate emissions from storage tanks. The software program
entitled "TANKS" is available through the Technology Transfer Network (TTN) Bulletin Board
System maintained by the U. S. Environmental Protection Agency.
7.1.3.1 Total Losses From Fixed Roof Tanks4'8'14 -
The following equations, provided to estimate standing storage and working loss emissions,
apply to tanks with vertical cylindrical shells and fixed roofs. These tanks must be substantially
liquid- and vapor-tight and must operate approximately at atmospheric pressure. The equations are not
9/97 Liquid Storage Tanks 7.1-9
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intended to be used in estimating losses from unstable or boiling stocks or from mixtures of
hydrocarbons or petrochemicals for which the vapor pressure is not known or cannot be readily
predicted. Total losses from fixed roof tanks are equal to the sum of the standing storage loss and
working loss:
LT = LS + LW (1-1)
where:
Ly = total losses, Ib/yr
Ls = standing storage losses, Ib/yr
Lw = working losses, Ib/yr
Standing Storage Loss - Fixed roof tank breathing or standing storage losses can be estimated from:
Ls = 365 VVWVKEKS (1-2)
where:
Ls = standing storage loss, Ib/yr
Vy = vapor space volume, ft3
T
Wy = vapor density, Ib/ft
KE = vapor space expansion factor, dimensionless
Ks = vented vapor saturation factor, dimensionless
365 = constant, oVyr
Tank Vapor Space Volume. Vy - The tank vapor space volume is calculated using the following
equation:
VV=*D2HVO (1-3)
where:
o
Vy = vapor space volume, ft
D = tank diameter, ft, see Note 1 for horizontal tanks
HyQ = vapor space outage, ft
The vapor space outage, Hvo is the height of a cylinder of tank diameter, D, whose volume is
equivalent to the vapor space volume of a fixed roof tank, including the volume under the cone or
dome roof. The vapor space outage, Hvo, is estimated from:
7.1-10 EMISSION FACTORS 9/97
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Hvo = Hs - HL + HRO (1-4)
where:
HyO = vapor space outage, ft
Hs = tank shell height, ft
HL = liquid height, ft
HRO = roof outage, ft; see Note 2 for a cone roof or Note 3 for a dome roof
Notes:
1. The emission estimating equations presented above were developed for vertical fixed roof
tanks. If a user needs to estimate emissions from a horizontal fixed roof tank, some of the tank
parameters can be modified before using the vertical tank emission estimating equations. First, by
assuming that the tank is one-half filled, the surface area of the liquid in the tank is approximately
equal to the length of the tank times the diameter of the tank. Next, assume that this area represents a
circle, i. e., that the liquid is an upright cylinder. Therefore, the effective diameter, DE, is then equal
to:
LD (1-5)
. 0.785
where:
DE = effective tank diameter, ft
L = length of tank, ft
D = actual diameter of tank, ft
One-half of the actual diameter of the horizontal tank should be used as the vapor space outage, Hvo.
This method yields only a very approximate value for emissions from horizontal storage tanks. For
underground horizontal tanks, assume that no breathing or standing storage losses occur (Ls = 0)
because the insulating nature of the earth limits the diurnal temperature change. No modifications to
the working loss equation are necessary for either above-ground or underground horizontal tanks.
2. For a cone roof, the roof outage, HRO, is calculated as follows:
HRO=1/3HR (1-6)
where:
HRQ = roof outage (or shell height equivalent to the volume contained under the roof), ft
HR = tank roof height, ft
9/97 Liquid Storage Tanks 7.1-11
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The tank roof height, HR, is equal to SR RS
where:
SR - tank cone roof slope, if unknown, a standard value of 0.0625 ft/ft is used, ft/ft
Rs = tank shell radius, ft
3. For a dome roof, the roof outage, HRO, is calculated as follows:
HRO ~ HR
1/2 + 1/6
(1-7)
where:
HRO = roof outage, ft
HR = tank roof height, ft
RS = tank shell radius, ft
The tank roof height, HR, is calculated:
HR - RR '
' RS ) '
(1-8)
where:
HR = tank roof height, ft
RR = tank dome roof radius, ft
R§ = tank shell radius, ft
The value of RR usually ranges from 0.8D - 1.2D, where D = 2 RS. If RR is unknown, the tank
diameter is used in its place. If the tank diameter is used as the value for RR, Equations 1-7 and 1-8
reduce to HR = 0.268 Rs and HRO = 0.137 RS.
Vapor Density. Wy - The density of the vapor is calculated using the following equation:
Wv =
MyPyA
RT
(1-9)
LA
where:
Wy = vapor density, Ib/ft
My = vapor molecular weight, Ib/lb-mole; see Note 1
7.1-12
EMISSION FACTORS
9/97
-------
R = the ideal gas constant, 10.731 psia-ft /lb-mole-°R
PVA = vapor pressure at daily average liquid surface temperature, psia; see Notes 1 and 2
TLA = daily average liquid surface temperature, °R; see Note 3
Notes:
1. The molecular weight of the vapor, Mv, can be determined from Table 7.1-2 and 7.1-3 for
selected petroleum liquids and volatile organic liquids, respectively, or by analyzing vapor samples.
Where mixtures of organic liquids are stored in a tank, My can be calculated from the liquid
composition. The molecular weight of the vapor, Mv, is equal to the sum of the molecular weight,
M;, multiplied by the vapor mole fraction, y;, for each component. The vapor mole fraction is equal
to the partial pressure of component i divided by the total vapor pressure. The partial pressure of
component i is equal to the true vapor pressure of component i (P) multiplied by the liquid mole
fraction, (x;). Therefore,
Mv =IMiyi =
Px
PVA
(1-10)
where:
PVA, total vapor pressure of the stored liquid, by Raoult's Law, is:
PVA = IPXj (1-11)
For more detailed information, please refer to Section 7.1.4.
2. True vapor pressure is the equilibrium partial pressure exerted by a volatile organic liquid,
as defined by ASTM-D 2879 or as obtained from standard reference texts. Reid vapor pressure is the
absolute vapor pressure of volatile crude oil and volatile nonviscous petroleum liquids, except liquified
petroleum gases, as determined by ASTM-D-323. True vapor pressures for organic liquids can be
determined from Table 7.1-3. True vapor pressure can be determined for crude oils using
Figures 7.1-13a and 7.1-13b. For refined stocks (gasolines and naphthas), Table 7.1-2 or
Figures 7.1-14a and 7.1-14b can be used. In order to use Figures 7.1-13a, 7.1-13b, 7.1-14a, or
7.1-14b, the stored liquid surface temperature, TLA, must be determined in degrees Fahrenheit. See
Note 3 to determine TLA.
Alternatively, true vapor pressure for selected petroleum liquid stocks, at the stored liquid
surface temperature, can be determined using the following equation:
PVA = exp [A - (B/TLA)] (l-12a)
where:
exp = exponential function
A = constant in the vapor pressure equation, dimensionless
B = constant in the vapor pressure equation, °R
9/97 Liquid Storage Tanks 7.1-13
-------
TLA = daily average liquid surface temperature, °R
PVA = true vapor pressure, psia
For selected petroleum liquid stocks, physical property data are presented in Table 7.1-2. For
refined petroleum stocks, the constants A and B can be calculated from the equations presented in
Figure 7.1-15 and the distillation slopes presented in Table 7.1-4. For crude oil stocks, the constants
A and B can be calculated from the equations presented in Figure 7.1-16. Note that in
Equation l-12a, TLA is determined in degrees Rankine instead of degrees Fahrenheit.
The true vapor pressure of organic liquids at the stored liquid temperature can be estimated by
Antoine's equation:
PVA
where:
A = constant in vapor pressure equation
B = constant in vapor pressure equation
C = constant in vapor pressure equation
TLA = daily average liquid surface temperature, °C
PVA = vapor pressure at average liquid surface temperature, mm Hg
For organic liquids, the values for the constants A, B, and C are listed in Table 7.1-5. Note
that in Equation l-12b, TLA is determined in degrees Celsius instead of degrees Rankine. Also, in
Equation l-12b, PVA is determined in mm of Hg rather than psia (760 mm Hg = 14.7 psia).
3. If the daily average liquid surface temperature, TLA, is unknown, it is calculated using the
following equation:
TLA = °-44TAA + 0.56TB + 0.0079 ttl (1-13)
where:
TLA = daily average liquid surface temperature, °R
TAA = daily average ambient temperature, °R; see Note 4
TB = liquid bulk temperature, °R; see Note 5
a = tank paint solar absorptance, dimensionless; see Table 7.1-6
I = daily total solar insolation factor, Btu/ft2-d; see Table 7.1-7
If TLA is used to calculate PVA from Figures 7.1-13a, 7.1-13b, 7.1-14a, or 7.1-14b, TLA must be
converted from degrees Rankine to degrees Fahrenheit (°F = °R - 460). If TLA is used to calculate
PVA from Equation l-12b, TLA must be converted from degrees Rankine to degrees Celsius
7.1-14 EMISSION FACTORS 9/97
-------
(°C = [°R - 492J/1.8). Equation 1-13 should not be used to estimate liquid surface temperature from
insulated tanks. In the case of insulated tanks, the average liquid surface temperature should be based
on liquid surface temperature measurements from the tank.
4. The daily average ambient temperature, TAA, is calculated using the following equation:
TAA = (TAX + TAN)'2 (1-14)
where:
TAA = daily average ambient temperature, °R
TAX = daily maximum ambient temperature, °R
TAN = daily minimum ambient temperature, °R
Table 7.1-7 gives values of TAX and TAN for selected U. S. cities.
5. The liquid bulk temperature, TB, is calculated using the following equation:
TB = TAA + 6a-l (1-15)
where:
TB = liquid bulk temperature, °R
TAA = daily average ambient temperature, °R, as calculated in Note 4
a = tank paint solar absorptance, dimensionless; see Table 7.1-6.
Vapor Space Expansion Factor, KE - The vapor space expansion factor, KE, is calculated using the
followin euation:
following equation:
p
LA A ~ FVA
where:
ATV = daily vapor temperature range, °R; see Note 1
APV = daily vapor pressure range, psi; see Note 2
APB = breather vent pressure setting range, psi; see Note 3
PA = atmospheric pressure, psia
ATV^APV-APB
9/97 Liquid Storage Tanks 7.1-15
-------
PVA = vapor pressure at daily average liquid surface temperature, psia; see Notes 1 and 2 for
Equation 1-9
TLA = daily average liquid surface temperature, °R; see Note 3 for Equation 1-9
Notes:
1. The daily vapor temperature range, ATy, is calculated using the following equation:
ATy = 0.72 ATA + 0.028 cd (1-17)
where:
ATy = daily vapor temperature range, °R
ATA = daily ambient temperature range, °R; see Note 4
a = tank paint solar absorptance, dimensionless; see Table 7.1-6
I = daily total solar insolation factor, Btu/ft2-d; see Table 7.1-7
2. The daily vapor pressure range, APV, can be calculated using the following equation:
APV = Pvx - PVN (1-18)
where:
APy = daily vapor pressure range, psia
PyX = vapor pressure at the daily maximum liquid surface temperature, psia; see Note 5
PVN = vapor pressure at the daily minimum liquid surface temperature, psia; see Note 5
The following method can be used as an alternate means of calculating APV for petroleum
liquids:
0.50 BPVA ATV
APy = — I (1-19)
where:
APy = daily vapor pressure range, psia
B = constant in the vapor pressure equation, °R; see Note 2 to Equation 1-9
PVA = vapor pressure at the daily average liquid surface temperature, psia; see Notes 1 and 2
to Equation 1-9
TLA = daily average liquid surface temperature, °R; see Note 3 to Equation 1-9
ATy = daily vapor temperature range, °R; see Note 1
7.1-16 EMISSION FACTORS 9/97
-------
3. The breather vent pressure setting range, APB, is calculated using the following equation:
APB = PBP-PBV
where:
APg = breather vent pressure setting range, psig
Pgp = breather vent pressure setting, psig
PBV = breather vent vacuum setting, psig
If specific information on the breather vent pressure setting and vacuum setting is not
available, assume 0.03 psig for PBp and -0.03 psig for PBV as typical values. If the fixed roof tank is
of bolted or riveted construction in which the roof or shell plates are not vapor tight, assume that
APg = 0, even if a breather vent is used. The estimating equations for fixed roof tanks do not apply
to either low or high pressure tanks. If the breather vent pressure or vacuum setting exceeds 1.0 psig,
the standing storage losses could potentially be negative.
4. The daily ambient temperature range, ATA, is calculated using the following equation:
ATA = TAX - TAN d'21)
where:
ATA = daily ambient temperature range, °R
TAX = daily maximum ambient temperature, °R
TAN = daily minimum ambient temperature, °R
Table 7.1-7 gives values of TAX and TAN for selected cities in the United States.
5. The vapor pressures associated with daily maximum and minimum liquid surface
temperature, PVX and PVN> respectively are calculated by substituting the corresponding temperatures,
TLX and TLN, into the vapor pressure function discussed in Notes 1 and 2 to Equation 1-9. If TLX
and TLN are unknown, Figure 7.1-17 can be used to calculate their values.
Vented Vapor Saturation Factor. Ks - The vented vapor saturation factor, Ks, is calculated using the
following equation:
Ko = _ ! _ (1-22)
S 1 + 0.053 PVAHVO
where:
Ks = vented vapor saturation factor, dimensionless
PVA = vapor pressure at daily average liquid surface temperature, psia; see Notes 1 and 2 to
Equation 1-9
HYQ = vapor space outage, ft, as calculated in Equation 1-4
9/97 Liquid Storage Tanks 7.1-17
-------
Working Loss - The working loss, Lw, can be estimated from:
Lw = 0.0010 MvPVAQKNKp, (1-23)
where:
Lw = working loss, Ib/yr
My = vapor molecular weight, Ib/lb-mole; see Note 1 to Equation 1-9
PyA = vapor pressure at daily average liquid surface temperature, psia; see Notes 1 and 2 to
Equation 1-9
Q = annual net throughput (tank capacity [bbl] times annual turnover rate), bbl/yr
KN = turnover factor, dimensionless; see Figure 7.1-18
for turnovers > 36, KN = (180 + N)/6N
for turnovers < 36, KN = 1
N = number of turnovers per year, dimensionless
N = -v
where:
N = number of turnovers per year, dimensionless
Q = annual net throughput, bbl/yr
VLX = tank maximum liquid volume, ft
and
where:
D = diameter, ft
HLX - maximum liquid height, ft
Kp = working loss product factor, dimensionless, 0.75 for crude oils. For all other organic
liquids, Kp = 1
7.1.3.2 Total Losses From Floating Roof Tanks3'5'13'15"17 -
Total floating roof tank emissions are the sum of rim seal, withdrawal, deck fitting, and deck
seam losses. The equations presented in this subsection apply only to floating roof tanks. The
equations are not intended to be used in the following applications:
1. To estimate losses from unstable or boiling stocks or from mixtures of hydrocarbons or
petrochemicals for which the vapor pressure is not known or cannot readily be predicted;
7.1-18 EMISSION FACTORS 9/97
-------
2. To estimate losses from closed internal or closed domed external floating roof tanks (tanks
vented only through a pressure/vacuum vent); or
3. To estimate losses from tanks in which the materials used in the rim seal and/or deck
fittings are either deteriorated or significantly permeated by the stored liquid.
Total losses from floating roof tanks may be written as:
Lj = LR + LWQ + Lp + LD (2-1)
where:
Lj = total loss, Ib/yr
LR = rim seal loss, Ib/yr; see Equation 2-2
LWD = withdrawal loss, Ib/yr; see Equation 2-4
LF = deck fitting loss, Ib/yr; see Equation 2-5
LD = deck seam loss (internal floating roof tanks only), Ib/yr; see Equation 2-9
Rim Seal Loss - Rim seal loss from floating roof tanks can be estimated using the following equation:
LR = (KRa + KRb vn)DP*MvKc (2-2)
where:
LR = rim seal loss, Ib/yr
KRa = zero wind speed rim seal loss factor, lb-mole/ft-yr; see Table 7.1-8
KRb = wind speed dependent rim seal loss factor, lb-mole/(mph)nft-yr; see Table 7.1-8
v = average ambient wind speed at tank site, mph; see Note 1
n = seal-related wind speed exponent, dimensionless; see Table 7.1-8
P = vapor pressure function, dimensionless; see Note 2
P /P
P*= VA A (2-3)
[1+(1-[PVA/PA])°-5]2
where:
PVA = vapor pressure at daily average liquid surface temperature, psia;
See Notes 1 and 2 to Equation 1-9 and Note 3 below
PA = atmospheric pressure, psia
9/97 Liquid Storage Tanks 7.1-19
-------
D = tank diameter, ft
My = average vapor molecular weight, Ib/lb-mole; see Note 1 to Equation 1-9,
Kc = product factor; Kc = 0.4 for crude oils; K£ = 1 for all other organic liquids.
Notes:
1. If the ambient wind speed at the tank site is not available, use wind speed data from the
nearest local weather station or values from Table 7.1-9. If the tank is an internal or domed external
floating roof tank, the value of v is zero.
2. P* can be calculated or read directly from Figure 7.1-19.
3. The API recommends using the stock liquid temperature to calculate PVA for use in
Equation 2-3 in lieu of the liquid surface temperature. If the stock liquid temperature is unknown,
API recommends the following equations to estimate the stock temperature:
Average Annual Stock
Tank Color Temperature, Ts (°F)
White TAA + Oa
Aluminum TAA + 2.5
Gray TAA + 3.5
Black TAA + 5.0
aTAA is the average annual ambient temperature in degrees Fahrenheit.
Withdrawal Loss - The withdrawal loss from floating roof storage tanks can be estimated using
Equation 2-4.
L
WD
(0.943)QCW1
D
1 +
D
(2-4)
where:
LWD = withdrawal loss, Ib/yr
Q = annual throughput (tank capacity [bbl] times annual turnover rate), bbl/yr
C = shell clingage factor, bbl/1,000 ft2; see Table 7.1-10
WL = average organic liquid density, Ib/gal; see Note 1
D = tank diameter, ft
0.943 = constant, 1,000 ft3-gal/bbl2
Nc = number of fixed roof support columns, dimensionless; see Note 2
Fc = effective column diameter, ft (column perimeter [ft]/Ji); see Note 3
7.1-20 EMISSION FACTORS 9/97
-------
Notes:
1 . A listing of the average organic liquid density for select petrochemicals is provided in
Tables 7.1-2 and 7.1-3. If WL is not known for gasoline, an average value of 6.1 Ib/gal can be
assumed.
2. For a self-supporting fixed roof or an external floating roof tank:
For a column-supported fixed roof:
N£ = use tank-specific information or see Table 7.1-11.
3. Use tank-specific effective column diameter or
FQ = 1.1 for 9-inch by 7-inch built-up columns, 0.7 for 8-inch-diameter pipe
columns, and 1.0 if column construction details are not known
Deck Fitting Loss - Deck fitting losses from floating roof tanks can be estimated by the following
equation:
LF = FF P*MVKC (2-5)
where:
Lp = the deck fitting loss, Ib/yr
FF = total deck fitting loss factor, Ib-mole/yr
FF = [(NFi KFi) + (NF2KF2) + ... +(Npn Kpn )] (2-6)
where:
NF = number of deck fittings of a particular type (i = 0,1,2,. ..,nf), dimensionless
i
KF. = deck fitting loss factor for a particular type fitting
(i - 0,1,2,. ..,nf), Ib-mole/yr; see Equation 2-7
nf = total number of different types of fittings, dimensionless
P*, My, K£ are as defined for Equation 2-2.
The value of Fp may be calculated by using actual tank-specific data for the number of each
fitting type (Np) and then multiplying by the fitting loss factor for each fitting (Kp).
The deck fitting loss factor, Kp for a particular type of fitting, can be estimated by the
following equation: '
9/97 Liquid Storage Tanks 7.1-21
-------
KFj = KFa; + KFbj (Kvv)m' (2-7)
where:
KF = loss factor for a particular type of deck fitting, Ib-mole/yr
KFa = zero wind speed loss factor for a particular type of fitting, Ib-mole/yr
Kpb = wind speed dependent loss factor for a particular type of fitting, lb-mole/(mph)m-yr
nij = loss factor for a particular type of deck fitting, dimensionless
i = 1,2, ..., n, dimensionless
Ky = fitting wind speed correction factor, dimensionless; see below
v = average ambient wind speed, mph
For external floating roof tanks, the fitting wind speed correction factor, Kv, is equal to 0.7.
For internal and domed external floating roof tanks, the value of v in Equation 2-7 is zero and the
equation becomes:
KF; = KF3i (2-8)
Loss factors Kpa, Kp^, and m are provided in Table 7.1-12 for the most common deck fittings
used on floating roof tanks. These factors apply only to typical deck fitting conditions and when the
average ambient wind speed is below 15 miles per hour. Typical numbers of deck fittings for floating
roof tanks are presented in Tables 7.1-11, 7.1-12, 7.1-13, 7.1-14, and 7.1-15.
Deck Seam Loss - Neither welded deck internal floating roof tanks nor external floating roof tanks
have deck seam losses. Internal floating roof tanks with bolted decks may have deck seam losses.
Deck seam loss can be estimated by the following equation:
LD = KDSDD2P*MVKC (2-9)
where:
KD = deck seam loss per unit seam length factor, Ib-mole/ft-yr
= 0.0 for welded deck
= 0.14 for bolted deck; see Note
f\
SD = deck seam length factor, ft/ft
gf^TT)
Adeck
7.1-22 EMISSION FACTORS 9/97
-------
where:
Lseam = total length of deck seams, ft
Adeck = area of deck, ft2 - n D2/4
D, P , My, and Kc are as defined for Equation 2-2
If the total length of the deck seam is not known, Table 7.1-16 can be used to determine SD.
For a deck constructed from continuous metal sheets with a 7-ft spacing between the seams, a value of
0.14 ft/ft can be used. A value of 0.33 ft/ft can be used for SD when a deck is constructed from
rectangular panels 5 ft by 7.5 ft. Where tank-specific data concerning width of deck sheets or size of
deck panels are unavailable, a default value for SD can be assigned. A value of 0.20 ft/ft can be
assumed to represent the most common bolted decks currently in use.
Note: Recently vendors of bolted decks have been using various techniques, such as gasketing the
deck seams, in an effort to reduce deck seam losses. However, emission factors are not
currently available in AP-42 that represent the emission reduction, if any, achieved by these
techniques. Some vendors have developed specific factors for their deck designs; however,
use of these factors is not recommended until approval has been obtained from the governing
regulatory agency or permitting authority.
7.1.3.3 Variable Vapor Space Tanks18 -
Variable vapor space filling losses result when vapor is displaced by liquid during filling
operations. Since the variable vapor space tank has an expandable vapor storage capacity, this loss is
not as large as the filling loss associated with fixed roof tanks. Loss of vapor occurs only when the
tank's vapor storage capacity is exceeded. Equation 3-1 assumes that one-fourth of the expansion
capacity is available at the beginning of each transfer.
Variable vapor space system filling losses can be estimated from:
Lv=(2.40 x lO'2) (MVPVA/V{) [(VL) - (0.25 V2N2)] (3-1)
where:
Lv = variable vapor space filling loss, lb/1,000 gal throughput
My = molecular weight of vapor in storage tank, Ib/lb-mole; see Note 1 to Equation 1-9
PYA - true vapor pressure at the daily average liquid surface temperature, psia; see Notes 1
and 2 to Equation 1-9
Vj = volume of liquid pumped into system, throughput, bbl/yr
V2 = volume expansion capacity of system, bbl; see Note 1
N2 = number of transfers into system, dimensionless; see Note 2
9/97 Liquid Storage Tanks 7.1-23
-------
Notes:
1. V2 is the volume expansion capacity of the variable vapor space achieved by roof lifting or
diaphragm flexing.
2. N2 is the number of transfers into the system during the time period that corresponds to a
throughput of Vj.
The accuracy of Equation 3-1 is not documented. Special tank operating conditions may result
in actual losses significantly different from the estimates provided by Equation 3-1. For example, if
one or more tanks with interconnected vapor spaces are filled while others are emptied simultaneously,
all or part of the expelled vapors will be transferred to the tank, or tanks, being emptied. This is
called balanced pumping. Equation 3-1 does not account for balanced pumping, and will overestimate
losses under this condition. It should also be noted that, although not developed for use with heavier
petroleum liquids such as kerosenes and fuel oils, the equation is recommended for use with heavier
petroleum liquids in the absence of better data.
7.1.3.4 Pressure Tanks -
Losses occur during withdrawal and filling operations in low-pressure (2.5 to 15 psig) tanks
when atmospheric venting occurs. High-pressure tanks are considered closed systems, with virtually
no emissions. Vapor recovery systems are often found on low-pressure tanks. Fugitive losses are also
associated with pressure tanks and their equipment, but with proper system maintenance, these losses
are considered insignificant. No appropriate correlations are available to estimate vapor losses from
pressure tanks.
7.1.3.5 Variations Of Emission Estimation Procedures -
All of the emission estimation procedures presented in Section 7.1.3 can be used to estimate
emissions for shorter time periods by manipulating the inputs to the equations for the time period in
question. For all of the emission estimation procedures, the daily average liquid surface temperature
should be based on the appropriate temperature and solar insolation data for the time period over
which the estimate is to be evaluated. The subsequent calculation of the vapor pressure should be
based on the corrected daily liquid surface temperature. For example, emission calculations for the
month of June would be based only on the meteorological data for June. It is important to note that a
1-month time frame is recommended as the shortest time period for which emissions should be
estimated.
In addition to the temperature and vapor pressure corrections, the constant in the standing
storage loss equation for fixed roof tanks would need to be revised based on the actual time frame
used. The constant, 365, is based on the number of days in a year. To change the equation for a
different time period, the constant should be changed to the appropriate number of days in the time
period for which emissions are being estimated. The only change that would need to be made to the
working loss equation for fixed roof tanks would be to change the throughput per year to the
throughput during the time period for which emissions are being estimated.
Other than changing the meteorological data and the vapor pressure data, the only changes
needed for the floating roof rim seal, deck fitting, and deck seam losses would be to modify the time
frame by dividing the individual losses by the appropriate number of days or months. The only
change to the withdrawal losses would be to change the throughput to the throughput for the time
period for which emissions are being estimated.
7.1-24 EMISSION FACTORS 9/97
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Another variation that is frequently made to the emission estimation procedures is an
adjustment in the working or withdrawal loss equations if the tank is operated as a surge tank or
constant level tank. For constant level tanks or surge tanks where the throughput and turnovers are
high but the liquid level in the tank remains relatively constant, the actual throughput or turnovers
should not be used in the working loss or withdrawal loss equations. For these tanks, the turnovers
should be estimated by determining the average change in the liquid height. The average change in
height should then be divided by the total shell height. This adjusted turnover value should then be
multiplied by the actual throughput to obtain the net throughput for use in the loss equations.
Alternatively, a default turnover rate of four could be used based on data from these type tanks.
7.1.4 Hazardous Air Pollutants (HAP) Speciation Methodology
In some cases it may be important to know the annual emission rate for a component (e. g.,
HAP) of a stored liquid mixture. There are two basic approaches that can be used to estimate
emissions for a single component of a stored liquid mixture. One approach involves calculating the
total losses based upon the known physical properties of the mixture (i. e., gasoline) and then
determining the individual component losses by multiplying the total loss by the weight fraction of the
desired component. The second approach is similar to the first approach except that the mixture
properties are unknown; therefore, the mixture properties are first determined based on the composition
of the liquid mixture.
Case 1 — If the physical properties of the mixture are known (Py^. My ML and WL), the
total losses from the tank should be estimated using the procedures described previously for the
particular tank type. The component losses are then determined from either Equation 4-1 or 4-2. For
fixed roof tanks, the emission rate for each individual component can be estimated by:
LT =(ZV)(LT) (4-1)
M vi 1
where:
LT = emission rate of component i, Ib/yr
M
Zy = weight fraction of component i in the vapor, Ib/lb
Lp = total losses, Ib/yr
For floating roof tanks, the emission rate for each individual component can be estimated by:
LT. = (Zv XLR + LF +LD) + (ZL.)(LWD) (4-2)
where:
Lj = emission rate of component i, Ib/yr
Zy = weight fraction of component i in the vapor, Ib/lb
LR = rim seal losses, Ib/yr
Lp = deck fitting losses, Ib/yr
9/97 Liquid Storage Tanks 7.1-25
-------
LD = deck seam losses, Ib/yr
ZL. = weight fraction of component i in the liquid, Ib/lb
LWD = withdrawal losses, Ib/yr
If Equation 4-1 is used in place of Equation 4-2 for floating roof tanks, the value obtained will be
approximately the same value as that achieved with Equation 4-2 because withdrawal losses are
typically minimal for floating roof tanks.
In order to use Equations 4-1 and 4-2, the weight fraction of the desired component in the
liquid and vapor phase is needed. The liquid weight fraction of the desired component is typically
known or can be readily calculated for most mixtures. In order to calculate the weight fraction in the
vapor phase, Raoult's Law must first be used to determine the partial pressure of the component. The
partial pressure of the component can then be divided by the total vapor pressure of the mixture to
determine the mole fraction of the component in the vapor phase. Raoult's Law states that the mole
fraction of the component in the liquid (xj) multiplied by the vapor pressure of the pure component (at
the daily average liquid surface temperature) (P) is equal to the partial pressure (P;) of that component:
Pi = (P)(Xj) (4-3)
where:
Pj = partial pressure of component i, psia
P = vapor pressure of pure component i at the daily average liquid surface temperature,
psia
Xj = liquid mole fraction, Ib-mole/lb-mole
The vapor pressure of each component can be calculated from Antoine's equation or found in
standard references, as shown in Section 7.1.3.1. In order to use Equation 4-3, the liquid mole
fraction must be determined from the liquid weight fraction by:
x; = (ZL.)(ML) / (Mj) (4-4)
where:
Xj = liquid mole fraction of component i, Ib-mole/lb-mole
ZL = weight fraction of component i in the liquid, Ib/lb
ML = molecular weight of liquid stock, Ib/lb-mole
M; = molecular weight of component i, Ib/lb-mole
If the molecular weight of the liquid is not known, the liquid mole fraction can be determined by
assuming a total weight of the liquid mixture (see Example 1 in Section 7.1.5).
7.1-26 EMISSION FACTORS 9/97
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The liquid mole fraction and the vapor pressure of the component at the daily average liquid
surface temperature can then be substituted into Equation 4-3 to obtain the partial pressure of the
component. The vapor mole fraction of the component can be determined from the following
equation:
y. -
<4-5'
where:
YJ = vapor mole fraction of component i, Ib-mole/lb-mole
PJ = partial pressure of component i, psia
PVA - total vapor pressure of liquid mixture, psia
The weight fractions in the vapor phase are calculated from the mole fractions in the vapor phase.
(4-6)
¥i Mv
where:
Zv = vapor weight fraction of component i, Ib/lb
y; = vapor mole fraction of component i, Ib-mole/lb-mole
M; = molecular weight of component i, Ib/lb-mole
My = molecular weight of vapor stock, Ib/lb-mole
The liquid and vapor weight fractions of each desired component and the total losses can be
substituted into either Equations 4-1 or 4-2 to estimate the individual component losses.
Case 2 — For cases where the mixture properties are unknown but the composition of the
liquid is known (i. e., nonpetroleum organic mixtures), the equations presented above can be used to
obtain a reasonable estimate of the physical properties of the mixture. For nonaqueous organic
mixtures, Equation 4-3 can be used to determine the partial pressure of each component. If
Equation 4-4 is used to determine the liquid mole fractions, the molecular weight of the liquid stock
must be known. If the molecular weight of the liquid stock is unknown, then the liquid mole fractions
can be determined by assuming a weight basis and calculating the number of moles (see Example 1 in
Section 7.1.5). The partial pressure of each component can then be determined from Equation 4-3.
For special cases, such as wastewater, where the liquid mixture is a dilute aqueous solution,
Henry's Law should be used instead of Raoult's Law in calculating total losses. Henry's Law states
that the mole fraction of the component in the liquid phase multiplied by the Henry's Law constant for
the component in the mixture is equal to the partial pressure (P;) for that component. For wastewater,
Henry's Law constants are typically provided in the form of atm-m /g-mole.
9/97 Liquid Storage Tanks 7.1-27
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Therefore, the appropriate form of Henry's Law equation is:
Pj = (HA) (Cj) (4-7)
where:
P; = partial pressure of component i, atm
HA = Henry's Law constant for component i, atm-m3/g-mole
C; = concentration of component i in the waste water, g-mole/m3; see Note
Section 4.3 of AP-42 presents Henry's Law constants for selected organic liquids. The partial pressure
calculated from Equation 4-7 will need to be converted from atmospheres to psia (1 atm = 14.7 psia).
Note: Typically wastewater concentrations are given in mg/liter, which is equivalent to g/m3. To
convert the concentrations to g-mole/m divide the concentration by the molecular weight of
the component.
The total vapor pressure of the mixture can be calculated from the sum of the partial pressures:
PVA = I Pi (4-8)
where:
PVA = vapor pressure at daily average liquid surface temperature, psia
Pj = partial pressure of component i, psia
This procedure can be used to determine the vapor pressure at any temperature. After
computing the total vapor pressure, the mole fractions in the vapor phase are calculated using
Equation 4-5. The vapor mole fractions are used to calculate the molecular weight of the vapor, My.
The molecular weight of the vapor can be calculated by:
Mv = I Mjy; (4-9)
where:
My = molecular weight of the vapor, Ib/lb-mole
Mj = molecular weight of component i, Ib/lb-mole
yj = vapor mole fraction of component i, Ib-mole/lb-mole
Another variable that may need to be calculated before estimating the total losses, if it is not
available in a standard reference, is the density of the liquid, WL. If the density of the liquid is
unknown, it can be estimated based on the liquid weight fractions of each component (see
Section 7.1.5, Example 3).
7.1-28 EMISSION FACTORS 9/97
-------
All of the mixture properties are now known (PVA> Mv, and WL). These values can now be
used with the emission estimation procedures outlined in Section 7.1.3 to estimate total losses. After
calculating the total losses, the component losses can be calculated by using either Equations 4-1 or
4-2. Prior to calculating component losses, Equation 4-6 must be used to determine the vapor weight
fractions of each component.
9/97 Liquid Storage Tanks 7.1-29
-------
Pressure/Vacuum Vent
Fixed Roo f
Float Gauge
Roo f Column
Liquid Level
Ind i ca tor
Inlet Nozzle
Outlet Nozzle
Roo f ManhoIe
Gauge-Ha t ch/
Sample Wei I
Gauger's Platforr
Sp i raI St a i rway
Cylindrical Shell
Shell Manhole
Figure 7.1-1. Typical fixed-roof tank.
7.1-30
EMISSION FACTORS
9/97
-------
Overflow drain
Deck leg
(center area)
Rim seal —i
(mechanical-shoe}
Open top (no fixed roof)
Access hatch
Gauge hatch/
sample port
Solid guidepote
(unslotted)
Tank shell
Rim vent
Figure 7.1-2. External floating roof tank (pontoon type).
20
9/97
Liquid Storage Tanks
7.1-31
-------
- Peripheral roof vents
Fixed-roof center vent
Fixed roof
(column-
supported)
-Rim seal
(vapor-mounted)
Sample port
Deck leg
Gauge float
Fixed-roof
support column
Tank shell
Access hatch
Deck drain
7.1-32
Figure 7.1-4. Internal floating roof tank.20
EMISSION FACTORS
9/97
-------
Fixed-roof center vent
Fixed roof
(self-supporting
^ aluminum
dome)
Peripheral venting typically
provided at the eaves
Rim seal
(mechanical-shoe)
Rim vent
Tank shell
Gauge float
Deck leg
(pontoon area)
Deck leg
(center area)
Solid guidepole
(unslotted)
Gauge hatch/
sample port
Overflow drain
Access hatch
9/97
Figure 7.1-5. Domed external floating roof tank.20
Liquid Storage Tanks
7.1-33
-------
V\r—Tank shell
\ Ju f— Floating roof deck
" Liquid surface-
Tank.
•hell
ResilenMOIed seal
(not In contact with the liquid surface)
(see section view below)
Bastomerio-coated
fabric envelope
Resilient
foam core
Flexible-wiper seal
(wiper position may vary with the
floating roofs direction of travel)
(see section views below)
Rim vapor
space
Liquid
surface
Floating
roof
deck
Tank-
shell
Rim vapor
space -^
Liquid
surface
Haatomeric blade
Floating
roof
deck
Elastomaric-coated
fabric envelope
•Foam core
Floating
roof
deck
Liquid
surface
7.1-34
Figure 7.1-6. Vapor-mounted primary seals.20
EMISSION FACTORS
9/97
-------
Floating roof deck
Resilient-filled seal
(bottom of seal in contact with the liquid surface)
(see section view below)
Tank
shell
Elastomeric-
coated
fabric
envelope
Liquid
surface
Weattiershield
(not shown above)
Resilient core
(foam or liquid-filled)
-Floating
roof
deck
Floating roof deck
Primary-seal
fabric
(see section view below)
Metallic
shoe
Rim vapor
space
Liquid
surface
•Tank shell
Primary-seal fabric
•Floating
roof
deck
9/97
Figure 7.1-7. Liquid-mounted and mechanical shoe primary seals.20
Liquid Storage Tanks
7.1-35
-------
Tank
shell
Rim-mounted secondary seal
over
resilient-filled primary seal
Secondary seal
> oeconaary seal
^ (flexible wiper shown)
Rim extender
Primary seal—v
(resilient-filled)
Liquid
surface
Tank
shell
Rim-mounted secondary seal
over
flexible-wiper primary seal
Secondary seal
(flexible wiper shown)
Rim extender
Primary seal—
(ftexiblfl-wiper)
Liquid
surface
Shoe-mounted secondary seal
over
mechanical-shoe primary seal
•Tank shell
Primary seal
(mechanical
shoe-
Secondary-seal
(shoe-mounted)
Liquid
surface
Rim-mounted secondary seal
over
mechanical-shoe primary seal
•Tank shell
Primary seal
(mechanical
shoe'
Liquid
surface
Secondary-seal
(rim-mounted)
Floating
roof
deck
7.1-36
Figure 7.1-8. Secondary rim seals.20
EMISSION FACTORS
9/97
-------
Floating
roof
deck
Well
(see section view below)
Handle
Removable cover
Gasket
Well
Liquid
surface
Bolted
closed
Floating
roof
deck
Access Hatch
Cable
Removable
cover
Floating
roof
deck
Well
(see section view below)
Removable cover
Bolted
closed
Floating
roof
deck
Float
Gauge float
Floating
roof
Pipe column
Sliding
cover
(see section view below)
Well
Sliding
cover
'Floating
roof
deck
(noncontact
type shown)
Fixed-Roof Support Column
Funnel
and slit-
fabric seal
Self- Cord
closing
cover
Pipe
sleeve
tnrougryf
the F-'
deck
Slit-
fsbric
Gauge-hatch/ / -^v.p^ sample port
sample port ' (internal floating roofs only)
(see section view below)
Cord
(shown pulling
coveropen)
Gasket
Pipe
sleeve
Liquid
surface
Funnel
Floating
roof
deck
Sample Ports
9/97
Figure 7.1-9. Deck fittings for floating roof tanks.20
Liquid Storage Tanks
7.1-37
-------
Leg-activated
cover
Floating
roof
deck
Well
(see section view below)
Adjustable leg ^^ "IS Alternative pinhole
^^•^IH
Cover . TL-- Pin
^v ti**r
Gasket _ ^k f, —Floating
roof
Leg guide-^jh=Jl Kj J ^ \ deck
Liquid r^J>Hrr (noncontact
swSISw vT^Mlil type shown)
Screened
cover
Pipe
sleeve
drain
Screened
cover
surface
Rush Floating
drain roof
deck
(see section view below)
Pipe stub
Rush drain
Floating
roof
deck
(noncontact
type shown
this side)
Vacuum Breaker
Deck Drains
Floating
roof
deck
(see section view below)
Adjustable leg
Leg sleeve
lative pinhote
Pin
Boating
roof
deck
Deck Leg
Tank
shell-si
Mechanical-
shoe seal
(see section view below)
Mechanical-
shoe seal—v
Liquid
surface
Rim Vent
7.1-38
Figure 7.1-10. Deck fittings for floating roof tanks.20
EMISSION FACTORS
Rim vent
Floating
roof
deck
Rim vent
Pipe
sleeve
Floating
roof
deck
9/97
-------
Solid gukiepole
Sliding
cover
Roller assembly
Floating
roof
deck
Solid guidepole
Roller assembly
Sliding
cover
Gasket-
Well
Liquid
surface
Solid guidepole
Roller assembly
(see section views below)
Unslotted (solid) Guidepole
Slotted guidepole
Roller assembly
Sliding
cover
Slots In guidepole
(2 staggered rows
on opposite sides)
Floating
roof
deck
Slotted guidepole
Roller assembly.
Sliding cover
Removable
gasketed
float
Well
Uquld
surface
(see section views below)
Jotted guidepole
Roller assembly
Pole
sleeve
r loafing
roof
deck
Slotted (perforated) Guidepole
Figure 7.1-11. Slotted and unslotted guidepoles.
20
9/97
Liquid Storage Tanks
7.1-39
-------
Floating
roof
deck
Ladder
Sliding
cover
Well
(see section view below)
Ladder
Liquid
surface
Sliding
cover
Floating
roof
deck
(noncontact
type shown)
Figure 7.1-12. Ladder well.20
7.1-40
EMISSION FACTORS
9/97
-------
I— 0.5
• 9
10
11
12
13
14
IS
20
,— 2
— 3
— 5
— 10
I—IS
140
130 —
120 —=
110
100 —E
90
70
60
SO
40
30
20 —=
10
9/97
Figure 7.1-13a. True vapor pressure of crude oils with a Reid vapor
pressure of 2 to 15 pounds per square inch.
Liquid Storage Tanks
7.1-41
-------
— 0.20
— 0.30
— 0.40
0.50
0.60
0.70
0.80
0.90
1.00
— 1.50
— 2.00
2.50
3.00
3.50
4.00
5.00^.
6.00
7.00
^- 8.00
=- 9.00
— 10.0
— 11.0
-12.0
-13.0
-14.0
-15.0
-16.0
-17.0
-18.0
-19.0
-20.0
-21.0
-22.0
-23.0
-24.0
120-]
100-H
90-
80-3
50-3
40-3
10-3
Notes:
1.5- slope of the ASTM distillation curve at 10 percent evaporated, in degrees
Fahrenheit per percent
- [(T at 15 percent) - (T at 5 percem)]/(10 percent).
In the absence of distillation data, the following average values of 5 may be used:
Motor gasoline—3.0.
Aviation gasoline—2.0.
Light naphtha (RVP of 9-14 pounds per square inch)—3.5.
Naphtha (RVP of 2-8 pounds per square inch)—2.5.
2. The broken line illustrates a sample problem for a gasoline stock (5 = 3.0) with a
Reid vapor pressure of 10 pounds per square inch and a stock temperature of 62.5T.
Figure 7.1-14a. True vapor pressure of refined petroleum stocks with a Reid vapor
pressure of 1 to 20 pounds per square inch.
7.1-42
EMISSION FACTORS
9/97
-------
P = exp
2,799 1_000,1. m^ _ 7,261
-2.227 Iog10 (RVP) - _±^_ U 12.82
T + 459.6 '" T + 459.6
Where:
P = stock true vapor pressure, in pounds per square inch absolute.
T = stock temperature, in degrees Fahrenheit.
RVP = Reid vapor pressure, in pounds per square inch.
Note: This equation was derived from a regression analysis of points read off Figure 7.1-13a over the full
range of Reid vapor pressures, slopes of the ASTM distillation curve at 10 percent evaporated, and
stock temperatures. In general, the equation yields P values that are within +0.05 pound per square
inch absolute of the values obtained directly from the nomograph.
Figure 7.1-13b. Equation for true vapor pressure of crude oils
with a Reid vapor pressure of 2 to 15 pounds per square inch.4
0.7553 - | 413"° I S°'5login (RVP) - 11.854 -
T + 459.6 10 '
2,416
+ 459.6
- 2.013
loglo(RVP) -
51°
8,742
T + 459.6
Where:
P = stock true vapor pressure, in pounds per square inch absolute.
T = stock temperature, in degrees Fahrenheit.
RVP = Reid vapor pressure, in pounds per square inch.
S = slope of the ASTM distillation curve at 10 percent evaporated, in degrees Fahrenheit per percent.
Note: This equation was derived from a regression analysis of points read off Figure 7.1-14a over the full range of
Reid vapor pressures, slopes of the ASTM distillation curve at 10 percent evaporated, and stock temperatures.
In general, the equation yields P values that are within +0.05 pound per square inch absolute of the values
obtained directly from the nomograph.
Figure 7.1-14b. Equation for true vapor pressure of refined
petroleum stocks with a Reid vapor pressure of
1 to 20 pounds per square inch.
A = 15.64 - 1.854 S°'5 - (0.8742-0.3280 Sa5)ln(RVP)
B = 8,742 - 1,042 S°'5 - (1,049-179.4 S°'5)ln(RVP)
where:
RVP = stock Reid vapor pressure, in pounds per square inch
In = natural logarithm function
S = stock ASTM-D86 distillation slope at 10 volume percent
evaporation (°F/vol %)
Figure 7.1-15. Equations to determine vapor pressure constants A and B for refined
petroleum stocks.8
9/97 Liquid Storage Tanks 7.1-43
-------
A = 12.82 - 0.9672 In (RVP)
B = 7,261 - 1,216 In (RVP)
where:
RVP = Reid vapor pressure, psi
In = natural logarithm function
Figure 7.1-16. Equations to determine vapor pressure Constants A and B for crude oil stocks.
Daily Maximum and Minimum Liquid Surface Temperature, (°R)
TLX = TLA + °-25 ATV
TLN = TLA - ^ ATV
where:
TLX = daily maximum liquid surface temperature, °R
TLA is as defined in Note 3 to Equation 1-9
ATy is as defined in Note 1 to Equation 1-16
TLN = daily minimum liquid surface temperature, °R
Figure 7.1-17. Equations for the daily maximum and minimum liquid surface temperatures.
7.1-44 EMISSION FACTORS 9/97
-------
1.0
0.8
p Q.6
£• °-4
1
2 0.2
100
200
300
400
TURNOVER PER YEAR » ANNUAL THROUGHPUT
TANK CAPACITY
Note: For 36 turnovers per year or leu, K* = 1.0
Figure 7.1-18. Turnover factor (KN) for fixed roof tanks.
9/97
Liquid Storage Tanks
7.1-45
-------
l.U
0.9
0.8
0.7
0.6
0.5
0.4
0.3
0.2
0.1
0.09
0.08
O.OT
0.06
0.05
0.04
0.03
0.02
0.01
«.
-
-
-
-
-
=
5
*--
-
-
-
-
-
-
[/
= /
~l
/
/
i
/
/
i
/
/
I
X
I
X
»
{i
i
X
•f [1
/
i
X
i
/
/
/-
i_
/-
/ _
-
-
=
5
••
-
-
-
-
-
-
i
^
-
r.u
0.9
0.8
0.7
0.6
0.5
0.4
0.3
0.2
0.1
0.09
0.08
0.07
0.08
0.05
0.04
0.03
0.02
0.01
3 4 5 87 8 9 10 11 12 13 14
Stock tnw vapor pranur*. P (pounds p«r square Inch sbsokit*)
15
Notes:
1. Broken line illustrates sample problem for P = 5.4 pounds per square inch absolute.
2. Curve is for atmospheric pressure, Pv equal to 14.7 pounds per square inch absolute.
7.1-46
Figure 7.1-19. Vapor pressure function.
EMISSION FACTORS
9/97
-------
ption
Description
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Cu >
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0? CU
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9/97
Liquid Storage Tanks
7.1-47
-------
o
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Description
fill! l
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ption
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£
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«
cxu
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7.1-48
EMISSION FACTORS
9/97
-------
CO
Q
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§
U
O
H
U
Q
P
U
w
w
CO
PH
0
^
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u
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CO
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CS
CO
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OS
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,>>>%>.>,>,><>,>>
''-----''
*~ *r^
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Pi
9/97
Liquid Storage Tanks
7.1-51
-------
Table 7.1-4. ASTM DISTILLATION SLOPE FOR SELECTED REFINED
PETROLEUM STOCKS3
Refined Petroleum Stock
Aviation gasoline
Naphtha
Motor gasoline
Light naphtha
Reid Vapor Pressure, RVP
(psi)
ND
2-8
ND
9-14
ASTM-D86 Distillation Slope
At 10 Volume Percent
Evaporated, (°F/vol%)
2.0
2.5
3.0
3.5
a Reference 8. ND = no data.
7.1-52
EMISSION FACTORS
9/97
-------
Table 7.1-5.
VAPOR
FOR
PRESSURE EQUATION CONSTANTS
ORGANIC LIQUIDS3
Name
Acetaldehyde
Acetic acid
Acetic anhydride
Acetone
Acetonitrile
Acrylamide
Acrylic acid
Acrylonitrile
Aniline
Benzene
Butanol (iso)
Butanol-(l)
Carbon disulfide
Carbon tetrachloride
Chlorobenzene
Chloroform
Chloroprene
Cresol(-M)
Cresol(-O)
Cresol(-P)
Cumene (isopropylbenzene)
Cyclohexane
Cyclohexanol
Cyclohexanone
Dichloroethane(l,2)
Dichloroethylene(l ,2)
Diethyl (N,N) anilin
Dimethyl formamide
Dimethyl hydrazine (1,1)
Dimethyl phthalate
Dinitrobenzene
Dioxane(l,4)
Epichlorohydrin
Ethanol
Ethanolamine(mono-)
Ethyl acetate
Ethyl acrylate
Ethyl benzene
Ethyl chloride
Ethyl ether
Formic acid
Furan
Furfural
Heptane(iso)
Hexane(-N)
Vapor Pressure Equation Constants
A
(Dimensionless)
8.005
7.387
7.149
7.117
7.119
11.2932
5.652
7.038
7.32
6.905
7.4743
7.4768
6.942
6.934
6.978
6.493
6.161
7.508
6.911
7.035
6.963
6.841
6.255
7.8492
7.025
6,965
7.466
6.928
7.408
4.522
4.337
7.431
8.2294
8.321
7.456
7.101
7.9645
6.975
6.986
6.92
7.581
6.975
6.575
6.8994
6.876
B
(°C)
1600.017
1533.313
1444.718
1210.595
1314.4
3939.877
648.629
1232.53
1731.515
1211.033
1314.19
1362.39
1169.11
1242.43
1431.05
929.44
783.45
1856.36
1435.5
1511.08
1460.793
1201.53
912.87
2137.192
1272.3
1141.9
1993.57
1400.87
1305.91
700.31
229.2
1554.68
2086.816
1718.21
1577.67
1244.95
1897.011
1424.255
1030.01
1064.07
1699.2
1060.87
1198.7
1331.53
1171.17
C
(°C)
291.809
222.309
199.817
229.664
230
273.16
154.683
222.47
206.049
220.79
186.55
178.77
241.59
230
217.55
196.03
179.7
199.07
165.16
161.85
207.78
222.65
109.13
273.16
222.9
231.9
218.5
196.43
225.53
51.42
-137
240.34
273.16
237.52
173.37
217.88
273.16
213.21
238.61
228.8
260.7
227.74
162.8
212.41
224.41
9/97
Liquid Storage Tanks
7.1-53
-------
Table 7.1-5 (cont.).
"Reference 12.
Name
Hexanol(-l)
Hydrocyanic acid
Methanol
Methyl acetate
Methyl ethyl ketone
Methyl isobutyl ketone
Methyl methacrylate
Methyl styrene (alpha)
Methylene chloride
Morpholine
Naphthalene
Nitrobenzene
Pentachloroethane
Phenol
Picoline(-2)
Propanol (iso)
Propylene glycol
Propylene oxide
Pyridine
Resorcinol
Styrene
Tetrachloroethane( 1,1,1,2)
Tetrachloroethane( 1 , 1 ,2,2)
Tetrachloroethylene
Tetrahydrofuran
Toluene
Trichloro( 1 , 1 ,2)trifluoroethane
Trichloroethane( 1,1,1)
Trichloroethane( 1,1,2)
Trichloroethylene
Trichlorofluoromethane
Trichloropropane( 1,2,3)
Vinyl acetate
Vinylidene chloride
Xylene(-M)
Xylene(-O)
Vapor Pressure Equation Constants
A
(Dimensionless)
7.86
7.528
7.897
7.065
6.9742
6.672
8.409
6.923
7.409
7.7181
7.01
7.115
6.74
7.133
7.032
8.117
8.2082
8.2768
7.041
6.9243
7.14
6.898
6.631
6.98
6.995
6.954
6.88
8.643
6.951
6.518
6.884
6.903
7.21
6.972
7.009
6.998
B
(°C)
1761.26
1329.5
1474.08
1157.63
1209.6
1168.4
2050.5
1486.88
1325.9
1745.8
1733.71
1746.6
1378
1516.79
1415.73
1580.92
2085.9
1656.884
1373.8
1884.547
1574.51
1365.88
1228.1
1386.92
1202.29
1344.8
1099.9
2136.6
1314.41
1018.6
1043.004
788.2
1296.13
1099.4
1426.266
1474.679
C
(°C)
196.66
260.4
229.13
219.73
216
191.9
274.4
202.4
252.6
235
201.86
201.8
197
174.95
211.63
219.61
203.540
273.16
214.98
186.060
224.09
209.74
179.9
217.53
226.25
219.48
227.5
302.8
209.2
192.7
236.88
243.23
226.66
237.2
215.11
213.69
7.1-54
EMISSION FACTORS
9/97
-------
Table 7.1-6. PAINT SOLAR ABSORPTANCE FOR FIXED ROOF TANKS3
Paint Color
Aluminum
Aluminum
Gray
Gray
Red
White
Paint Shade Or Type
Specular
Diffuse
Light
Medium
Primer
NA
Paint Factors (a)
Paint Condition
Good Poor
0.39 0.49
0.60 0.68
0.54 0.63
0.68 0.74
0.89 0.91
0.17 0.34
a Reference 8. If specific information is not available, a white shell and roof, with the paint in good
condition, can be assumed to represent the most common or typical tank paint in use. If the tank
roof and shell are painted a different color, a is determined from a = (aR + as)/2; where aR is the
tank roof paint solar absorptance and as is the tank shell paint solar absorptance. NA = not
applicable.
9/97
Liquid Storage Tanks
7.1-55
-------
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7.1-56
EMISSION FACTORS
9/97
-------
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7.1-58
EMISSION FACTORS
9/97
-------
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9/91
Liquid Storage Tanks
7.1-61
-------
Table 7.1-8. RIM-SEAL LOSS FACTORS, KRa, KRb, and n,
FOR FLOATING ROOF TANKS^
Tank Construction And
Rim-Seal System
Average-Fitting Seals
KRa
(lb-mole/ft-yr)
;-,,;{ \^--f^;".<4ft^'>H\^3v;^ .-•"~'-:-*?:?*&^'Wd^?T&
Mechanical-shoe seal
Primary onlyb
Shoe-mounted secondary
Rim-mounted secondary
Liquid-mounted seal
Primary only
Weather shield
Rim-mounted secondary
Vapor-mounted seal
Primary only
Weather shield
Rim-mounted secondary
5.8
1.6
0.6
1.6
0.7
0.3
6.7C
3.3
2.2
KRb
[lb-mole/(mph)n-ft-yr]
nks-'V £':'& -^,4',%vr;H,v
0.3
0.3
0.4
0.3
0.3
0.6
0.2
0.1
0.003
n
(dimensionless)
vViV'-.W. y •"--;'-
2.1
1.6
1.0
1.5
1.2
0.3
3.0
3.0
4.3
- --^;>>iS;rv^r':-.^:?.\r: - !.--'
Mechanical-shoe seal
Primary only
Shoe-mounted secondary
Rim-mounted secondary
10.8
9.2
1.1
0.4
0.2
0.3
2.0
1.9
1.5
Note: The rim-seal loss factors KRa, KRb, and n may only be used for wind speeds below 15 miles
per hour.
a Reference 15.
b
If no specific information is available, a welded tank with an average-fitting mechanical-shoe
primary seal can be used to represent the most common or typical construction and rim-seal system
in use for external and domed external floating roof tanks.
c If no specific information is available, this value can be assumed to represent the most common or
typical rim-seal system currently in use for internal floating roof tanks.
7.1-62
EMISSION FACTORS
9/97
-------
Table 7.1-9. AVERAGE ANNUAL WIND SPEED (v) FOR SELECTED U. S. LOCATIONS3
Location
Alabama
Birmingham
Huntsville
Mobile
Montgomery
Alaska
Anchorage
Annette
Barrow
Barter Island
Bethel
Bettles
Big Delta
Cold Bay
Fairbanks
Gulkana
Homer
Juneau
King Salmon
Kodiak
Kotzebue
McGrath
Nome
St. Paul Island
Talkeetna
Valdez
Yakutat
Arizona
Flagstaff
Phoenix
Tucson
Wind
Speed
(mph)
7.2
8.2
9.0
6.6
6.9
10.6
11.8
13.2
12.8
6.7
8.2
17.0
5.4
6.8
7.6
8.3
10.8
10.8
13.0
5.1
10.7
17.7
4.8
6.0
7.4
6.8
6.3
8.3
Location
Arizona (continued)
Winslow
Yuma
Arkansas
Fort Smith
Little Rock
California
Bakersfield
Blue Canyon
Eureka
Fresno
Long Beach
Los Angeles (City)
Los Angeles Int'l. Airport
Mount Shasta
Sacramento
San Diego
San Francisco (City)
San Francisco Airport
Santa Maria
Stockton
Colorado
Colorado Springs
Denver
Grand Junction
Pueblo
Connecticut
Bridgeport
Hartford
Wind
Speed
(mph)
8.9
7.8
7.6
7.8
6.4
6.8
6.8
6.3
6.4
6.2
7.5
5.1
7.9
6.9
8.7
10.6
7.0
7.5
10.1
8.7
8.1
8.7
12.0
8.5
Location
Delaware
Wilmington
District of Columbia
Dulles Airport
National Airport
Florida
Apalachicola
Daytona Beach
Fort Meyers
Jacksonville
Key West
Miami
Orlando
Pensacola
Tallahassee
Tampa
West Palm Beach
Georgia
Athens
Atlanta
Augusta
Columbus
Macon
Savannah
Hawaii
Hilo
Honolulu
Kahului
Lihue
Wind
Speed
(mph)
9.1
7.4
9.4
7.8
8.7
8.1
8.0
11.2
9.3
8.5
8.4
6.3
8.4
9.6
7.4
9.1
6.5
6.7
7.6
7.9
7.2
11.4
12.8
12.2
9/97
Liquid Storage Tanks
7.1-63
-------
Table 7.1-9 (cont.).
Location
Idaho
Boise
Pocatello
Illinois
Cairo
Chicago
Moline
Peoria
Rockford
Springfield
Indiana
Evansville
Fort Wayne
Indianapolis
South Bend
Iowa
Des Moines
Sioux City
Waterloo
Kansas
Concordia
Dodge City
Goodland
Topeka
Wichita
Kentucky
Cincinnati Airport
Jackson
Lexington
Louisville
Wind
Speed
(mph)
8.8
10.2
8.5
10.3
10.0
10.0
10.0
11.2
8.1
10.0
9.6
10.3
10.9
11.0
10.7
12.3
14.0
12.6
10.0
12.3
9.1
7.2
9.3
8.4
Location
Louisiana
Baton Rouge
Lake Charles
New Orleans
Shreveport
Maine
Caribou
Portland
Maryland
Baltimore
Massachusetts
Blue Hill Observatory
Boston
Worcester
Michigan
Alpena
Detroit
Flint
Grand Rapids
Houghton Lake
Lansing
Muskegon
Sault Sainte Marie
Minnesota
Duluth
International Falls
Minneapolis-Saint Paul
Rochester
Saint Cloud
Wind
Speed
(mph)
7.6
8.7
8.2
8.4
11.2
8.8
9.2
15.4
12.5
10.1
8.1
10.4
10.2
9.8
8.9
10.0
10.7
9.3
11.1
8.9
10.6
13.1
8.0
Location
Mississippi
Jackson
Meridian
Missouri
Columbia
Kansas City
Saint Louis
Springfield
Montana
Billings
Glasgow
Great Falls
Helena
Kalispell
Missoula
Nebraska
Grand Island
Lincoln
Norfolk
North Platte
Omaha
Scottsbuff
Valentine
Nevada
Elko
Ely
Las Vegas
Reno
Winnemucca
Wind
Speed
(mph)
7.4
6.1
9.9
10.8
9.7
10.7
11.2
10.8
12.8
7.8
6.6
6.2
11.9
10.4
11.7
10.2
10.6
10.6
9.7
6.0
10.3
9.3
6.6
8.0
7.1-64
EMISSION FACTORS
9/97
-------
Table 7.1-9 (cont.).
Location
New Hampshire
Concord
Mount Washington
New Jersey
Atlantic City
Newark
New Mexico
Albuquerque
Roswell
New York
Albany
Birmingham
Buffalo
New York (Central Park)
New York (JFK Airport)
New York (La Guardia
Airport)
Rochester
Syracuse
North Carolina
Asheville
Cape Hatteras
Charlotte
Greensboro-High Point
Raleigh
Wilmington
North Dakota
Bismark
Fargo
Williston
Wind
Speed
(mph)
6.7
35.3
10.1
10.2
9.1
8.6
8.9
10.3
12.0
9.4
12.0
12.2
9.7
9.5
7.6
11.1
7.5
7.5
7.8
8.8
10.2
12.3
10.1
Location
Ohio
Akron
Cleveland
Columbus
Dayton
Mansfield
Toledo
Youngstown
Oklahoma
Oklahoma City
Tulsa
Oregon
Astoria
Eugene
Medford
Pendleton
Portland
Salem
Sexton Summit
Pennsylvania
Allentown
Avoca
Erie
Harrisburg
Philadelphia
Pittsburgh Int'l
Airport
Williamsport
Puerto Rico
San Juan
Wind
Speed
(mph)
9.8
10.6
8.5
9.9
11.0
9.4
9.9
12.4
10.3
8.6
7.6
4.8
8.7
7.9
7.1
11.8
9.2
8.3
11.3
7.6
9.5
9.1
7.8
8.4
Location
Rhode Island
Providence
South Carolina
Charleston
Columbia
Greenville-
Spartanburg
South Dakota
Aberdeen
Huron
Rapid City
Sioux Falls
Tennessee
Bristol-Johnson
City
Chattanooga
Knoxville
Memphis
Nashville
Oak Ridge
Texas
Abilene
Amarillo
Austin
Brownsville
Corpus Christi
Dallas-Fort Worth
Del Rio
El Paso
Galveston
Houston
Lubbock
Wind
Speed
(mph)
10.6
8.6
6.9
6.9
11.2
11.5
11.3
11.1
5.5
6.1
7.0
8.9
8.0
4.4
12.0
13.6
9.2
11.5
12.0
10.8
9.9
8.9
11.0
7.9
12.4
9/97
Liquid Storage Tanks
7.1-65
-------
Table 7.1-9 (cont.).
Location
Texas (continued)
Midland-Odessa
Port Arthur
San Angelo
San Antonio
Victoria
Waco
Wichita Falls
Utah
Salt Lake City
Vermont
Burlington
Virginia
Lynchburg
Norfolk
Richmond
Roanoke
Washington
Olympia
Quillayute
Seattle Int'l. Airport
Spokane
Walla Walla
Yakima
West Virginia
Belkley
Charleston
Elkins
Huntington
Wind
Speed
(mph)
11.1
9.8
10.4
9.3
10.1
11.3
11.7
8.9
8.9
7.7
10.7
7.7
8.1
6.7
6.1
9.0
8.9
5.3
7.1
9.1
6.3
6.2
6.6
Location
Wisconsin
Green Bay
La Crosse
Madison
Milwaukee
Wyoming
Casper
Cheyenne
Lander
Sheridan
Wind
Speed
(mph)
10.0
8.8
9.9
11.6
12.9
13.0
6.8
8.0
a Reference 13.
7.1-66
EMISSION FACTORS
9/97
-------
Table 7.1-10. AVERAGE CLINGAGE FACTORS, Ca
(bbl/103 ft2)
Product Stored
Gasoline
Single-component stocks
Crude oil
Shell Condition
Light Rust
0.0015
0.0015
0.0060
Dense Rust
0.0075
0.0075
0.030
Gunite Lining
0.15
0.15
0.60
a Reference 3. If no specific information is available, the values in this table can be assumed to
represent the most common or typical condition of tanks currently in use.
Table 7.1-11. TYPICAL NUMBER OF COLUMNS AS A FUNCTION OF TANK
DIAMETER FOR INTERNAL FLOATING ROOF TANKS WITH COLUMN-
SUPPORTED FIXED ROOFS3
Tank Diameter Range D, (ft)
0 < D < 85
85 < D < 100
100 < D < 120
120 < D < 135
135
-------
Table 7.1-12. DECK-FITTING LOSS FACTORS, KFa, K^,
AND m, AND TYPICAL NUMBER OF DECK FITTINGS, NFa
Fitting Type And Construction Details
Access hatch (24-inch diameter well)
Bolted cover, gasketedb
Unbolted cover, ungasketed
Unbolted cover, gasketed
Fixed roof support column welld
Round pipe, ungasketed sliding cover
Round pipe, gasketed sliding cover
Round pipe, flexible fabric sleeve seal
Built-up column, ungasketed sliding cover0
Built-up column, gasketed sliding cover
Unslotted guide-pole and well (8-inch
diameter unslotted pole, 21-inch
diameter well)
Ungasketed sliding cover5
Ungasketed sliding cover w/pole sleeve
Gasketed sliding cover
Gasketed sliding cover w/pole wiper
Gasketed sliding cover w/pole sleeve
Slotted guide-pole/sample well (8-inch
diameter slotted pole, 21 -inch
diameter well)6
Ungasketed or gasketed sliding cover
Ungasketed or gasketed sliding cover,
with float8
Gasketed sliding cover, with pole wiper
Gasketed sliding cover, with pole sleeve
Gasketed sliding cover, with pole sleeve
and pole wiper
Gasketed sliding cover, with float and
pole wiper6
Gasketed sliding cover, with float, pole
sleeve, and pole wiper11
Gauge-float well (automatic gauge)
Unbolted cover, ungasketed
Unbolted cover, gasketed
Bolted cover, gasketed
Gauge-hatch/sample port
Weighted mechanical actuation,
gasketedb
Weighted mechanical actuation,
ungasketed
Slit fabric seal, 10% open area0
Vacuum breaker
Weighted mechanical actuation,
ungasketed
Weighted mechanical actuation, gasketedb
KFa
(Ib-mole/yr)
1.6
36C
31
31
25
10
47
33
31
25
25
14
8.6
43
31
41
11
8.3
21
11
14°
4.3
2.8
0.47
2.3
12
7.8
6.2C
Loss Factors
KFb m
(lb-mole/(mph)m-yr)
0
5.9
5.2
150
2.2
13
3.7
12
270
36
48
46
4.4
7.9
9.9
5.4
17
0
0.02
0
0.01
1.2
m
(dimensionless)
0
1.2
1.3
1.4
2.1
2.2
0.78
0.81
1.4
2.0
1.4
1.4
1.6
1.8
0.89
1.1
0.38
0
0.97
0
4.0
0.94
Typical Number Of
Fittings, NF
1
Nc
(Table 7.1-11)
1
f
1
1
Nvb(Table7.1-13y
7.1-68
EMISSION FACTORS
9/97
-------
Table 7.1-12 (cont).
Fitting Type And Construction Details
Deck drain (3-inch diameter)
Openb
90% closed
Stub drain (1-inch diameter)k
Deck leg (3-inch diameter)
Adjustable, internal floating deckc
Adjustable, pontoon area - ungasketedb
Adjustable, pontoon area - gasketed
Adjustable, pontoon area - sock
Adjustable, center area - ungasketedb
Adjustable, center area - gasketed"1
Adjustable, center area - sockm
Adjustable, double-deck roofs
Fixed
Rim vent"
Weighted mechanical actuation, ungasketed
Weighted mechanical actuation, gasketed
Ladder well
Sliding cover, ungasketed0
Sliding cover, gasketed
Loss Factors
(lb-mole/yr) (lb-mole/(mph)m-yr)
1.5 0.21
1.8 0.14
1.2
7.9
2.0 0.37
1.3 0.08
1.2 0.14
0.82 0.53
0.53 0.11
0.49 0.16
0.82 0.53
0 0
0.68 1.8
0.71 0.10
76
56
m Typical Number Of
(dimensionless) Fittings, Np
Nd (Table 7. 1-13)
1.7
1.1
Nd (Table 7. 1-1 5)
N, (Table 7.1-15),
(Table 7. 1-14)
0.91
0.65
0.65
0.14
0.13
0.14
0.14
0
1
1.0
1.0
ld
, and m, may only be used for wind speeds below
Note: The deck-fitting loss factors, Kpa,
15 miles per hour.
a Reference 5, unless otherwise indicated.
If no specific information is available, this value can be assumed to represent the most common or
typical deck fitting currently in use for external and domed external floating roof tanks.
c If no specific information is available, this value can be assumed to represent the most common or
typical deck fitting currently in use for internal floating roof tanks.
d Column wells and ladder wells are not typically used with self supported fixed roofs.
e References 16,19.
A slotted guide-pole/sample well is an optional fitting and is not typically used.
g Tests were conducted with floats positioned with the float wiper at and 1 inch above the sliding
cover. The user is cautioned against applying these factors to floats that are positioned with the
wiper or top of the float below the sliding cover ("short floats"). The emission factor for such a
float is expected to be between the factors for a guidepole without a float and with a float,
depending upon the position of the float top and/or wiper within the guidepole.
h Tests were conducted with floats positioned with the float wiper at varying heights with respect to
the sliding cover. This fitting configuration also includes a pole sleeve which restricts the airflow
from the well vapor space into the slotted guidepole. Consequently, the float position within the
guidepole (at, above, or below the sliding cover) is not expected to significantly affect emission
levels for this fitting configuration, since the function of the pole sleeve is to restrict the flow of
vapor from the vapor space below the deck into the guidepole.
J Nvb = 1 for internal floating roof tanks.
Stub drains are not used on welded contact internal floating decks.
m These loss factors were derived using the results from pontoon-area deck legs with gaskets and
socks.
n Rim vents are used only with mechanical-shoe primary seals.
9/97
Liquid Storage Tanks
7.1-69
-------
Table 7.1-13. EXTERNAL FLOATING ROOF TANKS: TYPICAL NUMBER OF
VACUUM BREAKERS, Nvb, AND DECK DRAINS, Nda
Tank Diameter
D (feet)b
50
100
150
200
250
300
350
400
Number Of Vacuum Breakers, Nvb
Pontoon Roof
1
1
2
3
4
5
6
7
Double-Deck Roof
1
1
2
2
3
3
4
4
Number Of Deck drains, Nd
1
1
2
3
5
7
ND
ND
a Reference 3. This table was derived from a survey of users and manufacturers. The actual number
of vacuum breakers may vary greatly depending on throughput and manufacturing prerogatives. The
actual number of deck drains may also vary greatly depending on the design rainfall and
manufacturing prerogatives. For tanks more than 350 feet in diameter, actual tank data or the
manufacturer's recommendations may be needed for the number of deck drains. This table should
not be used when actual tank data are available. ND = no data.
If the actual diameter is between the diameters listed, the closest diameter listed should be used. If
the actual diameter is midway between the diameters listed, the next larger diameter should be used.
7.1-70
EMISSION FACTORS
9/97
-------
Table 7.1-14. EXTERNAL FLOATING ROOF TANKS: TYPICAL NUMBER OF
ROOF LEGS, N,a
Tank Diameter, D (feet)b
30
40
50
60
70
80
90
100
110
120
130
140
150
160
170
180
190
200
210
220
230
240
250
260
270
280
290
300
310
320
330
340
350
360
370
380
390
400
Pontoon
Number Of Pontoon
Legs
4
4
6
9
13
15
16
17
18
19
20
21
23
26
27
28
29
30
31
32
33
34
35
36
36
37
' 38
38
39
39
40
41
42
44
45
46
47
48
Roof
Number Of Center Legs
2
4
6
7
9
10
12
16
20
24
28
33
38
42
49
56
62
69
77
83
92
101
109
118
128
138
148
156
168
179
190
202
213
226
238
252
266
281
Number Of Legs On
Double-Deck Roof
6
7
8
10
13
16
20
25
29
34
40
46
52
58
66
74
82
90
98
107
115
127
138
149
162
173
186
200
213
226
240
255
270
285
300
315
330
345
a Reference 3. This table was derived from a survey of users and manufacturers. The actual number
of roof legs may vary greatly depending on age, style of floating roof, loading specifications, and
manufacturing prerogatives. This table should not be used when actual tank data are available.
If the actual diameter is between the diameters listed, the closest diameter listed should be used. If
the actual diameter is midway between the diameters listed, the next larger diameter should be used.
9/97
Liquid Storage Tanks
7.1-71
-------
Table 7.1-15. INTERNAL FLOATING ROOF TANKS: TYPICAL NUMBER
OF DECK LEGS, Nj, AND STUB DRAINS, Nda
Deck fitting type
Deck leg or hanger well
Stub drain (1-inch diameter) >c
Typical Number Of Fittings, Np
D
10 600
a Reference 4
D = tank diameter, ft
c Not used on welded contact internal floating decks.
Table 7.1-16. DECK SEAM LENGTH FACTORS (SD) FOR TYPICAL DECK
CONSTRUCTIONS FOR INTERNAL FLOATING ROOF TANKS3
Deck Construction
Continuous sheet construction13
5 ft wide
6 ft wide
7 ft wide
Panel constructiond
5 x 7.5 ft rectangular
5 x 12 ft rectangular
Typical Deck Seam Length Factor,
SD (ft/ft2)
0.20C
0.17
0.14
0.33
0.28
a Reference 4. Deck seam loss applies to bolted decks only.
b SD = 1/W, where W = sheet width (ft).
0 If no specific information is available, this value can be assumed to represent the most common
bolted decks currently in use.
d SD = (L+W)/LW, where W = panel width (ft) and L = panel length (ft).
7.1-72
EMISSION FACTORS
9/97
-------
7.1.5 Sample Calculations
Example 1 - Chemical Mixture in a Fixed Roof Tank
Determine the yearly emission rate of the total product mixture and each component for a chemical
mixture stored in a vertical cone roof tank in Denver, Colorado. The chemical mixture contains (for
every 3,171 Ib of mixture) 2,812 Ib of benzene, 258 Ib of toluene, and 101 Ib of cyclohexane. The
tank is 6 ft in diameter, 12 ft high, usually holds about 8 ft of product, and is painted white. The tank
working volume is 1,690 gallons. The number of turnovers per year for the tank is five (i. e., the
throughput of the tank is 8,450 gal/yr).
Solution
1. Determine tank type. The tank is a fixed-cone roof, vertical tank.
2. Determine estimating methodology. The product is made up of three organic liquids, all of which
are miscible in each other, which makes a homogenous mixture if the material is well mixed. The
tank emission rate will be based upon the properties of the mixture. Raoult's Law (as discussed in the
HAP Speciation Section) is assumed to apply to the mixture and will be used to determine the
properties of the mixture.
3. Select equations to be used. For a vertical, fixed roof storage tank, the following equations apply:
LJ^LS + LW (i-i)
Ls = 365 WVVVKEKS (1-2)
Lw = 0.0010 MvPVAQKNKp (1-23)
where:
Lq- = total loss, Ib/yr
Ls = standing storage loss, Ib/yr
Lw = working loss, Ib/yr
Vv = tank vapor space volume, ft3
Vv = K/4 D2 Hvo (1-3)
9/97 Liquid Storage Tanks 7.1-73
-------
Wy = vapor density, lb/ft3
WV = ^ d-9)
v
KE = vapor space expansion factor, dimensionless
RE _ *Tv ^ AFV-AFB (M6)
TLA PA ~ PVA
Ks = vented vapor space saturation factor, dimensionless
Ks = 1 (1-22)
S 1 + 0.053 PVAHVO
D = diameter, ft
HVO= vapor space outage, ft
My = molecular weight of vapor, Ib/lb-mole
PVA = vapor pressure at the daily average liquid surface temperature, psia
r, -A , t t 10.731 psia • ft3
R = ideal gas constant = _
Ib-mole • °R
TLA = daily average liquid surface temperature, °R
ATy = daily vapor temperature range, °R
APy = daily vapor pressure range, psia
APB = breather vent pressure setting range, psi
PA = atmospheric pressure, psia
Q = annual net throughput, bbl/yr
KN = working loss turnover factor, dimensionless
Kp = working loss product factor, dimensionless
4. Calculate each component of the standing storage loss and working loss functions.
a. Tank vapor space volume, Vy:
Vv = Ti/4 D2 Hvo (1-3)
D = 6 ft (given)
7.1-74 EMISSION FACTORS 9/97
-------
For a cone roof, the vapor space outage, HVQ is calculated by:
Hvo = Hs - HL + HRO (1-4)
Hs = tank shell height, 12 ft (given)
HL = stock liquid height, 8 ft (given)
HRQ = roof outage, 1/3 HR = 1/3(SR)(RS) (1-6)
SR = tank cone roof slope, 0.0625 ft/ft (given) (see Note 1 to Equation 1-4)
Rs = tank shell radius = 1/2 D = 1/2 (6) = 3
Substituting values in Equation 1-6 yields,
HRO = I (0.0625X3) = 0.0625 ft
3
Then use Equation 1-4 to calculate Hvo,
Hvo = 12 - 8 + 0.0625 = 4.0625 ft
Therefore,
Vv = 1 (6)2 (4.0625) = 114.86 ft3
4
b. Vapor density, Wv:
Ww = V VA (1-9)
R = ideal gas constant = 10.731 psia-ft3
lb-mole-°R
My = stock vapor molecular weight, Ib/lb-mole
PVA = stock vapor pressure at the daily average liquid surface temperature, psia
TLA = daily average liquid surface temperature, °R
First, calculate TLA using Equation 1-13.
TLA = 0.44 TAA + 0.56 TB + 0.0079 a I (1-13)
9/97 Liquid Storage Tanks 7.1-75
-------
where:
TAA = daily average ambient temperature, °R
TB = liquid bulk temperature, °R
I = daily total solar insolation, Btu/ft2-d = 1,568 (see Table 7.1-7)
a = tank paint solar absorptance = 0.17 (see Table 7.1-6)
TAA and TB must be calculated from Equations 1-14 and 1-15.
T _ TAX + TAN (1-14)
*AA ~ j
from Table 7.1-7, for Denver, Colorado:
TAX = ^a^v maximum ambient temperature = 64.3°F
TAN = daily minimum ambient temperature = 36.2°F
Converting to °R:
TAX = 64.3 + 460 = 524.3°R
TAN = 36.2 + 460 = 496.2°R
Therefore,
TAA = (524.3 + 496.2)/2 = 510.25 °R
TB = liquid bulk temperature = TAA + 6cc - 1 (1-15)
TAA = 510.25 °R from previous calculation
a = paint solar absorptance = 0.17 (see Table 7.1-6)
I = daily total solar insolation on a horizontal surface = 1,568 Btu/ft2-d (see
Table 7.1-7)
Substituting values in Equation 1-15
TB = 510.25 + 6 (0.17) - 1 = 510.27 °R
Using Equation 1-13,
TLA = (°-44) (510.25°R) + 0.56 (510.27°R) + 0.0079 (0.17) (1,568) = 512.36°R
Second, calculate PVA using Raoult's Law.
7.1-76 EMISSION FACTORS 9/97
-------
According to Raoult's Law, the partial pressure of a component is the product of its pure vapor
pressure and its liquid mole fraction. The sum of the partial pressures is equal to the total vapor
pressure of the component mixture stock.
The pure vapor pressures for benzene, toluene, and cyclohexane can be calculated from Antoine's
equation. Table 7.1-5 provides the Antoine's coefficients for benzene, which are A = 6.905,
B = 1,211.033, and C = 220.79. For toluene, A = 6.954, B = 1,344.8, and C = 219.48. For
cyclohexane, A = 6.841, B = 1,201.53, and C = 222.65. Therefore:
log P = A - B
6 T + C
TLA, average liquid surface temperature (°C) = (512.36 - 492)/1.8 = 11
For benzene,
log P = 6.905 -
1,211.033
(11°C + 220.79)
P = 47.90 mmHg = 0.926 psia
Similarly for toluene and cyclohexane,
P = 0.255 psia for toluene
P = 0.966 psia for cyclohexane
In order to calculate the mixture vapor pressure, the partial pressures need to be calculated for each
component. The partial pressure is the product of the pure vapor pressures of each component
(calculated above) and the mole fractions of each component in the liquid.
The mole fractions of each component are calculated as follows:
Component
Benzene
Toluene
Cyclohexane
Total
Amount, Ib
2,812
258
101
-M,
78.1
92.1
84.2
Moles
36.0
2.80
1.20
40.0
xi
0.90
0.07
0.03
1.00
where:
MJ = molecular weight of component
X; = liquid mole fraction
The partial pressures of the components can then be calculated by multiplying the pure vapor pressure
by the liquid mole fraction as follows:
9/97
Liquid Storage Tanks
7.1-77
-------
Component
Benzene
Toluene
Cyclohexane
Total
P at 52°F
0.926
0.255
0.966
Xj
0.90
0.07
0.03
1.0
p
partial
0.833
0.018
0.029
0.880
The vapor pressure of the mixture is then 0.880 psia.
Third, calculate the molecular weight of the vapor, My. Molecular weight of the vapor depends upon
the mole fractions of the components in the vapor.
where:
Mv =
M; = molecular weight of the component
y; = vapor mole fraction
The vapor mole fractions, yj, are equal to the partial pressure of the component divided by the total
vapor pressure of the mixture.
Therefore,
Vbenzene = PpartiaAotal = 0.833/0.880 = 0.947
Similarly, for toluene and cyclohexane,
ycyclohexane =
The mole fractions of the vapor components sum to 1 .0.
The molecular weight of the vapor can be calculated as follows:
= 0.033
Component
Benzene
Toluene
Cyclohexane
Total
M,
78.1
92.1
84.2
Yi
0.947
0.020
0.033
1.0
Mv
74.0
1.84
2.78
78.6
7.1-78
EMISSION FACTORS
9/97
-------
Since all variables have now been solved, the stock density, Wv, can be calculated:
v
(78.6) (0.880) _ -2 b
(10.731) (512.36) ft 3
c. Vapor space expansion factor, KE:
TLA PA PVA
where:
ATy = daily vapor temperature range, °R
APy = daily vapor pressure range, °R
APB = breather vent pressure setting range, psia
PA = atmospheric pressure, 14.7 psia (given)
PyA = vapor pressure at daily average liquid surface temperature, psia = 0.880 psia (from
Step 4b)
TLA = daily average liquid surface temperature, °R = 512.36°R (from Step 4b)
First, calculate the daily vapor temperature range from Equation 1-17:
ATV = 0.72ATA + 0.028ccl (1-17)
where:
ATV = daily vapor temperature range, °R
ATA = daily ambient temperature range = TAX - TAN
a = tank paint solar absorptance, 0.17 (given)
I = daily total solar insolation, 1,568 Btu/ft -d (given)
from Table 7.1-7, for Denver, Colorado:
TAX = 64.3°F
T= 36.2°F
9/97 Liquid Storage Tanks 7.1-79
-------
Converting to °R,
TAX = 64.3 + 460 = 524.3°R
TAN= 36.2 + 460 = 496.2°R
From equation 1-17 and ATAX = TAX - TAN
ATA = 524.3 - 496.2 = 28.TR
f\
Therefore,
ATV = 0.72 (28.1) + (0.028)(0.17)(1568) = 27.7°R
Second, calculate the daily vapor pressure range using Equation 1-18:
APV = PVX-PVN (1-18)
PVX, PyN = vapor pressures at the daily maximum, minimum liquid temperatures can be calculated
in a manner similar to the PVA calculation shown earlier.
TLX = maximum liquid temperature, TLA + 0.25 ATy (from Figure 7.1-17)
TLN = minimum liquid temperature, TLA - 0.25 ATV (from Figure 7.1-17)
TLA = 512.36 (from Step 4b)
ATV= 27.7°R
TLX = 512.36 + (0.25) (27.7) = 519.3°R or 59°F
TLN = 512.36 - (0.25) (27.7) = 505.4°R or 45°F
Using Antoine's equation, the pure vapor pressures of each component at the minimum liquid surface
temperature are:
Pbenzene = 0.758 psia
Ptoluene = °-203 Psia
Pcyclohexane = 0.794 psia
7.1-80 EMISSION FACTORS 9/97
-------
The partial pressures for each component at TLN can then be calculated as follows:
Component
Benzene
Toluene
Cyclohexane
Total
P at 45°F
0.758
0.203
0.794
xi
0.90
0.07
0.03
1.0
P
partial
0.68
0.01
0.02
0.71
Using Antoine's equation, the pure vapor pressures of each component at the maximum liquid
surface temperature are:
Pbenzene= L14 Psia
Ptoluene= °'32 P*ia
Pcyclohexane = U8 Psia
The partial pressures for each component at TLX can then be calculated as follows:
Component
Benzene
Toluene
Cyclohexane
Total
P
1.14
0.32
1.18
Xj
0.90
0.07
0.03
1.0
p
partial
1.03
0.02
0.04
1.09
Therefore, the vapor pressure range, APV = PLx " PLN = 1-09 - 0.710 = 0.38 psia.
Next, calculate the breather vent pressure, APB, from Equation 1-20:
~ PBP " PBV
(1-20)
where:
PBp = breather vent pressure setting = 0.03 psia (given) (see Note 3 to Equation 1-16)
PBV = breather vent vacuum setting = -0.03 psig (given) (see Note 3 to Equation 1-16)
APB = 0.03 - (-0.03) = 0.06 psig
Finally, KE, can be calculated by substituting values into Equation 1-16.
K = (27.7) + 0.38 - 0.06 psia =
E (512.36) 14.7 psia - 0.880 psia
9/97
Liquid Storage Tanks
7.1-81
-------
d. Vented vapor space saturation factor, Ks:
Ko = ! (1-22)
S 1 + 0.053 PVA Hvo
where:
PVA = 0.880 psia (from Step 4b)
Hvo = 4.0625 ft (from Step 4a)
Ko = ! = 0.841
s 1 -i- 0.053(0.880)(4.0625)
5. Calculate standing storage losses.
Ls = 365 WVVVKEKS
Using the values calculated above:
Wv = 1.26 x 10'2 Ib (from Step 4b)
ft3
Vv = 114.86 ft3 (from Step 4a)
KE = 0.077 (from Step 4c)
Ks =0.841 (from Step 4d)
Ls = 365 (1.26 x 10-2)(114.86)(0.077)(0.841) = 34.2 Ib/yr
6. Calculate working losses.
The amount of VOCs emitted as a result of filling operations can be calculated from the
following equation:
Lw = (0.0010) (Mv)(PVA)(Q)(KN)(Kp) (1-23)
From Step 4:
Mv = 78.6 (from Step 4b)
PVA = 0.880 psia (from Step 4b)
Q = 8,450 gal/yr x 2.381 bbl/100 gal = 201 bbl/yr (given)
Kp = product factor, dimensionless = 1 for volatile organic liquids, 0.75 for crude oils
KN = 1 for turnovers <36 (given)
N = turnovers per year = 5 (given)
7.1-82 EMISSION FACTORS 9/97
-------
Lw - (0.0010)(78.6)(0.880)(201)(1)(1) = 13.9 Ib/yr
7. Calculate total losses, L
= Ls + Lw
where:
Ls = 34.2 Ib/yr
Lw = 13.9 Ib/yr
LT= 34.7 + 13.9 = 48.1 Ib/yr
8. Calculate the amount of each component emitted from the tank.
The amount of each component emitted is equal to the weight fraction of the component in the
vapor times the amount of total VOC emitted. Assuming 100 moles of vapor are present, the number
of moles of each component will be equal to the mole fraction multiplied by 100. This assumption is
valid regardless of the actual number of moles present. The vapor mole fractions were determined in
Step 4b. The weight of a component present in a mixture is equal to the product of the number of
moles and molecular weight, Mj, of the component. The weight fraction of each component is
calculated as follows:
„, . , . - .. pounds;
Weight traction = -c — : — ' .
total pounds
Therefore,
Component
Benzene
Toluene
Cyclohexane
Total
No. of moles x M{ = PoundSj
(0.947 x 100) = 94.7
(0.02 x 100) = 2.0
(0.033 x 100) = 3.3
100
78.1
92.1
84.3
7,396
184
278
7,858
Weight
fraction
0.94
0.02
0.04
1.0
The amount of each component emitted is then calculated as:
Emissions of componentj = (weight fractiorijXLj)
Component
Benzene
Toluene
Cyclohexane
Total
Total VOC emitted,
Weight fraction x Ib/yr =
0.94
0.02
0.04
48.1
48.1
48.1
Emissions, Ib/yr
45.2
0.96
1.92
48.1
9/97
Liquid Storage Tanks
7.1-83
-------
Example 2 - Chemical Mixture in a Horizontal Tank - Assuming that the tank mentioned in
Example 1 is now horizontal, calculate emissions. (Tank diameter is 6 ft and length is 12 ft.)
Solution:
Emissions from horizontal tanks can be calculated by adjusting parameters in the fixed roof equations.
Specifically, an effective diameter, DE, is used in place of the tank diameter, D. The vapor space
height, HYQ, is assumed to be half the actual tank diameter.
1. Horizontal tank adjustments. Make adjustments to horizontal tank values so that fixed roof tank
equations can be used. The effective diameter, DE, is calculated as follows:
PL
0.785
= (6H12) = 9 5?7 ft
E ^ 0.785
The vapor space height, Hvo is calculated as follows:
Hvo = 1/2 D = 1/2 (6) = 3 ft
2. Given the above adjustments the standing storage loss, Ls, can be calculated.
Calculate values for each effected variable in the standing loss equation.
Ls = 365 VVWVKEKS
Vy and Kg depend on the effective tank diameter, DE, and vapor space height, Hvo.
These variables can be calculated using the values derived in Step 1:
Vv = JL (9.577)2 (3) = 216.10 ft
1 + (0.053) (PVA) (Hvo)
1
1 + (0.053) (0.880) (3)
= 0.877
7.1-84 EMISSION FACTORS 9/97
-------
3. Calculate standing storage loss using the values calculated in Step 2.
Ls = 365 VVWVKEKS
Vv = 216.10 ft3 (from Step 2)
Wv = 1.26 x 1CT2 lb/ft3 (from Step 4b, example 1)
KE = 0.077 (from Step 4c, example 1)
Ks = 0.877 (from Step 2)
Ls = (365)(1.26 x 10-2)(216.10)(0.077)(0.877)
Ls = 67.1 Ib/yr
4. Calculate working loss. Since the parameters for working loss do not depend on diameter or vapor
space height, the working loss for a horizontal tank of the same capacity as the tank in Example 1 will
be the same.
Lw = 13.9 Ib/yr
5. Calculate total emissions.
Lq. = Ls + Lw
Lp = 67.1 + 13.9 = 81 Ib/yr
9/97 Liquid Storage Tanks 7.1-85
-------
Example 3 - Chemical Mixture in an External Floating Roof Tank - Determine the yearly emission
rate of a mixture that is 75 percent benzene, 15 percent toluene, and 10 percent cyclohexane, by
weight, from a 100,000-gallon external floating roof tank with a pontoon roof. The tank is 20 feet in
diameter. The tank has 10 turnovers per year. The tank has a mechanical shoe seal (primary seal) and
a shoe-mounted secondary seal. The tank is made of welded steel and has a light rust covering the
inside surface of the shell. The tank shell is painted white, and the tank is located in Newark, New
Jersey. The floating deck is equipped with the following fittings: (1) an ungasketed access hatch with
an unbolted cover, (2) an unspecified number of ungasketed vacuum breakers with weighted
mechanical actuation, and (3) ungasketed gauge hatch/sample ports with weighted mechanical
actuation.
Solution:
1. Determine tank type. The tank is an external floating roof storage tank.
2. Determine estimating methodology. The product consists of three organic liquids, all of which are
miscible in each other, which make a homogenous mixture if the material is well mixed. The tank
emission rate will be based upon the properties of the mixture. Because the components have similar
structures and molecular weights, Raoult's Law is assumed to apply to the mixture.
3. Select equations to be used. For an external floating roof tank,
LT = Lyyj-) + LR + Lp + LJ-J (2-1)
LWD = (0.943) QCWL/D (2-4)
LR = (KRa + KRbvn)P*DMvKc (2-2)
LF = FFP*MVKC (2-5)
LD = KDSDD2P*MVKC (2-9)
where:
Ly = total loss, Ib/yr
LWD = withdrawal loss, Ib/yr
LR = rim seal loss from external floating roof tanks, Ib/yr
Lp = deck fitting loss, Ib/yr
LD = deck seam loss, Ib/yr = 0 for external floating roof tanks
Q - product average throughput, bbl/yr
C = product withdrawal shell clingage factor, bbl/1,000 ft2; see Table 7.1-10
WL = density of liquid, Ib/gal
7.1-86 EMISSION FACTORS 9/97
-------
D = tank diameter, ft
KRa = zero wind speed rim seal loss factor, lb-mole/ft-yr; see Table 7.1.8
KRb = wind speed dependent rim seal loss factor, lb-mole/(mph)nft-yr; see Table 7.1-
v = average ambient wind speed for the tank site, mph
n = seal wind speed exponent, dimensionless
P = the vapor pressure function, dimensionless
= (PVA/PA)/(! + [HPvA/PA)]0'5)2
where:
PVA= the true vapor pressure of the materials stored, psia
PA = atmospheric pressure, psia = 14.7
My = molecular weight of product vapor, Ib/lb-mole
KC = product factor, dimensionless
Fp = the total deck fitting loss factor, Ib-mole/yr
nf
= I (NF.Kp.) = [(NFiKFi) + (Np2KF2) + ... + ^ Kp^)]
where:
Np = number of fittings of a particular type, dimensionless. Np is determined for the
specific tank or estimated from Tables 7.1-12, 7.1-13, or 7\1-14
KF = deck fitting loss factor for a particular type of fitting, Ib-mole/yr. KF is determined
for each fitting type from Equation 2-7 and the loss factors in Table 7.1-12
nf = number of different types of fittings, dimensionless; nf = 3 (given)
KD = deck seam loss per unit seam length factor, Ib-mole/ft/yr
SD = deck seam length factor, ft/ft2
4. Identify parameters to be calculated/determined from tables. In this example, the following
parameters are not specified: WL, Fp, C, KRa, KRb, v, n, PVA> P*, Mv, and Kc. The following values
are obtained from tables or assumptions:
9/97 Liquid Storage Tanks 7.1-87
-------
Kc = 1.0 for volatile organic liquids (given in Section 7.1.3.2)
C = 0.0015 bbl/1,000 ft2 for tanks with light rust (from Table 7.1-10)
KRa = 1.6 (from Table 7.1-8)
KRb = 0.3 (from Table 7.1-8)
n= 1.6 (from Table 7.1-8)
Since the wind speed for the actual tank site is not specified, the wind speed for Newark, New
Jersey is used:
v= 10.2 mph (see Table 7.1-9)
Fp, WL, PVA, P , and My still need to be calculated.
Fp is estimated by calculating the individual Kp and Np for each of the three types of deck
fittings used in this example. For the ungasketed access hatches' with unbolted covers, the KF value
can be calculated using information from Table 7.1-12. For this fitting, KFa = 36, K^ = 5.9, and
m = 1.2. The value for KV for external floating roof tanks is 0.7 (see Section 7.1.3, Equation 2-7).
There is normally one access hatch. So,
KFaccess hatch = KFa + KFt>(Kvv)m
= 36 + 5.9 [(0.7)(10.2)]L2
KFaccess hatch = 98-4 lb-mole/yr
Faccess hatch ~
The number of vacuum breakers can be taken from Table 7.1-13. For a tank with a diameter
of 20 feet and a pontoon roof, the typical number of vacuum breakers is one. Table 7.1-12 provides
fitting factors for weighted mechanical actuation, ungasketed vacuum breakers when the average wind
speed is 10.2 mph. Based on this table, KFa = 7.8, Kp^ = 0.01, and m = 4. So,
KFvacuum breaker = KFa + KFb (Kvv)
KFvacuum breaker = 7.8 + 0.01 [(0.7)(10.2)]4
KFvacuum breaker = 33-8 lb-mole/yr
N — 1
Fvacuum breaker
For the ungasketed gauge hatch/sample ports with weighted mechanical actuation, Table 7.1-12
indicates that floating roof tanks normally have only one. This table also indicates that KFa = 2.3, Kpb
= 0, and m = 0. Therefore,
7.1-88 EMISSION FACTORS 9/97
-------
Ty" K ± K (K v^^
^Fgauge hatch/sample port ~ Fa r Fb ^ v '
K =9^+0
Fgauge hatch/sample port
KFgauge hatch/sample port = 2'3 lb-mole/yr
N =1
Fgauge hatch/sample port
'P can be calculated from Equation 2-6:
3
FF=
(Kp.)(Np.)
= 134.5 lb-mole/yr
5. Calculate mole fractions in the liquid. The mole fractions of components in the liquid must be
calculated in order to estimate the vapor pressure of the liquid using Raoult's Law. For this example,
the weight fractions (given as 75 percent benzene, 15 percent toluene, and 10 percent cyclohexane) of
the mixture must be converted to mole fractions. First, assume that there are 1,000 Ib of liquid
mixture. Using this assumption, the mole fractions calculated will be valid no matter how many
pounds of liquid actually are present. The corresponding amount (pounds) of each component is equal
to the product of the weight fraction and the assumed total pounds of mixture of 1,000. The number
of moles of each component is calculated by dividing the weight of each component by the molecular
weight of the component. The mole fraction of each component is equal to the number of moles of
each component divided by the total number of moles. For this example the following values are
calculated:
Component
Benzene
Toluene
Cyclohexane
Total
Weight
fraction
0.75
0.15
0.10
1.00
Weight, Ib
750
150
100
1,000
Molecular
weight, Mj,
Ib/lb-mole
78.1
92.1
84.2
Moles
9.603
1.629
1.188
12.420
Mole
fraction
0.773
0.131
0.096
1.000
For example, the mole fraction of benzene in the liquid is 9.603/12.420 = 0.773.
6. Determine the daily average liquid surface temperature. The daily average liquid surface
temperature is equal to:
TLA = 0.44 TAA + 0.56 TB + 0.0079 a I
9/97
Liquid Storage Tanks
7.1-89
-------
TAA = (TAX + TAN)/2
For Newark, New Jersey (see Table 7.1-7):
TAX = 62.5°F = 522.2°R
TAN = 45.9°F = 505.6°R
I = 1,165 Btu/ft2-d
From Table 7.1-6, a = 0.17
Therefore;
TAA = (522.2 + 505.6)72 = 513.9°R
TB = 513.9°R + 6 (0.17) - 1 = 513.92°R
TLA = 0.44 (513.9) + 0.56 (513.92) + 0.0079 (0.17)0,165)
= 515.5°R = 55.8°F = 56°F
7. Calculate partial pressures and total vapor pressure of the liquid. The vapor pressure of each
component at 56°F can be determined using Antoine's equation. Since Raoult's Law is assumed to
apply in this example, the partial pressure of each component is the liquid mole fraction (x;) times the
vapor pressure of the component (P).
Component
Benzene
Toluene
Cyclohexane
Totals
P at 56°F
1.04
0.29
1.08
xi
0.773
0.131
0.096
1.00
p
partial
0.80
0.038
0.104
0.942
The total vapor pressure of the mixture is estimated to be 0.942 psia.
8. Calculate mole fractions in the vapor. The mole fractions of the components in the vapor phase
are based upon the partial pressure that each component exerts (calculated in Step 7).
So for benzene:
where:
ybenzene = PpartiaAotal = 0-80/0.942 = 0.85
vbenzene = mo^e fracti°n °f benzene in the vapor
7.1-90
EMISSION FACTORS
9/97
-------
^partial = Partia' pressure of benzene in the vapor, psia
Ptotal = total vapor pressure of the mixture, psia
Similarly,
Ytoluene = 0.038/0.942 = 0.040
ycyclohexane = 0.104/0.942 = 0.110
The vapor phase mole fractions sum to 1.0.
9. Calculate molecular weight of the vapor. The molecular weight of the vapor depends upon the
mole fractions of the components in the vapor.
Mv =
where:
My = molecular weight of the vapor, Ib/lb-mole
M; = molecular weight of component i, Ib/lb-mole
Vj = mole fraction of component i in the vapor, Ib-mole/lb-mole
Component
Benzene
Toluene
Cyclohexane
Total
M,
78.1
92.1
84.2
y\
0.85
0.040
0.110
1.00
My = Z(Mj)(yj)
66.39
3.68
9.26
79.3
The molecular weight of the vapor is 79.3 Ib/lb-mole.
10. Calculate weight fractions of the vapor. The weight fractions of the vapor are needed to calculate
the amount (in pounds) of each component emitted from the tank. The weight fractions are related to
the mole fractions calculated in Step 7 and total molecular weight calculated in Step 9:
9/97
Liquid Storage Tanks
7.1-91
-------
Mv
(0.85)(78.1) no. . ,
= v /v i. = 0.84 for benzene
79.3
z = (0.040X92.1) _
79.3
Z
V
(0.110)(84.2) _ ,. , . ,
= =0.12 for cyclohexane
79.3
11. Calculate total VOC emitted from the tank. The total VOC emitted from the tank is calculated
using the equations identified in Step 3 and the parameters calculated in Steps 4 through 9.
a. Calculate withdrawal losses:
LWD = 0.943 QCWL/D
where:
Q = 100,000 gal x 10 turnovers/yr (given)
= 1,000,000 gal x 2.381 bbVlOO gal = 23,810 bbl/yr
C = 0.0015 bbl/103 ft2 (from Table 7.1-10)
WL = 1/E (wt fraction in liquid)/(liquid component density from Table 7.1-3)]
Weight fractions
Benzene = 0.75 (given)
Toluene = 0.15 (given)
Cyclohexane = 0.10 (given)
Liquid densities
Benzene = 7.4 (see Table 7.1-3)
Toluene = 7.3 (see Table 7.1-3)
Cyclohexane = 6.5 (see Table 7.1-3)
WL = l/[(0.75/7.4) + (0.15/7.3) + (0.10/6.5)]
= 1/(0.101 + 0.0205 + 0.0154)
= 1/0.1369
7.1-92 EMISSION FACTORS 9/97
-------
= 7.3 Ib/gal
D = 20 ft (given)
LWD = 0.943 QCWL/D
= [0.943(23,810)(0.0015)(7.3)/20]
= 12 Ib of VOC/yr from withdrawal losses
b. Calculate rim seal losses:
LR = (KRa + KRbvn)DP*MvKc
where:
KRa= 1.6 (from Step 4)
KRb = 0.3 (from Step 4)
v = 10.2 mph (from Step 4)
n = 1.6 (from Step 4)
Kc = 1 (from Step 4)
PVA = 0.942 psia (from Step 7) (formula from Step 3)
D = 20 ft
P* = (PVA/PAW + tHPvA/PA)]0'5)2
= (0.942/14.7)/(l+[l-(0.942/14.7)]a5)2 = 0.017
Mv = 79.3 Ib/lb-mole (from Step 9)
LR - [(1.6 + (0.3)(10.2)L6)](0.017)(20)(79.3)(1.0)
= 376 Ib of VOC/yr from rim seal losses
c. Calculate deck fitting losses:
LF = FFP*MVKC
where:
FF = 134.5 Ib-mole/yr (from Step 4)
P* = 0.017
9/97 Liquid Storage Tanks 7.1-93
-------
Mv = 79.3 Ib/lb-mole
Kc = 1.0 (from Step 4)
LF = (134.5)(0.017)(79.3)(1.0)
= 181 Ib/yr of VOC emitted from deck fitting losses
d. Calculate total losses:
= 12 + 376+ 181
= 569 Ib/yr of VOC emitted from tank
12. Calculate amount of each component emitted from the tank. For an external floating roof tank,
the individual component losses are determined by Equation 4-2:
L^ = (ZV.)(LR + LF) + (ZL.)(LWD)
Therefore,
L-Tbenzene = (0.84)(557) + (0.75)(12) = 477 Ib/yr benzene
L-rtoluene = (0.040)(557) + (0.15)(12) = 24 Ib/yr toluene
Lrcyclohexane = (0.12)(557) + (0.10)(12) = 68 Ib/yr cyclohexane
7.1-94 EMISSION FACTORS 9/97
-------
Example 4 - Gasoline in an Internal Floating Roof Tank - Determine emissions of product from a
1 million gallon, internal floating roof tank containing gasoline (RVP 13). The tank is painted white
and is located in Tulsa, Oklahoma. The annual number of turnovers for the tank is 50. The tank is
70 ft in diameter and 35 ft high and is equipped with a liquid-mounted primary seal plus a secondary
seal. The tank has a column-supported fixed roof. The tank's deck is welded and equipped with the
following: (1) two access hatches with unbolted, ungasketed covers; (2) an automatic gauge float well
with an unbolted, ungasketed cover; (3) a pipe column well with a flexible fabric sleeve seal; (4) a
sliding cover, gasketed ladder well; (5) adjustable deck legs; (6) a slotted sample pipe well with a
gasketed sliding cover; and (7) a weighted, gasketed vacuum breaker.
Solution:
1. Determine tank type. The following information must be known about the tank in order to use the
floating roof equations:
— the number of columns
— the effective column diameter
— the rim seal description (vapor- or liquid-mounted, primary or secondary seal)
— the deck fitting types and the deck seam length
Some of this information depends on specific construction details, which may not be known.
In these instances, approximate values are provided for use.
2. Determine estimating methodology. Gasoline consists of many organic compounds, all of which
are miscible in each other, which form a homogenous mixture. The tank emission rate will be based
on the properties of RVP 13 gasoline. Since vapor pressure data have already been compiled, Raoult's
Law will not be used. The molecular weight of gasoline also will be taken from a table and will not
be calculated. Weight fractions of components will be assumed to be available from SPECIATE data
base.
3. Select equations to be used.
L-p — L^yj-) + LR + Lp + LQ (2-1)
_ (0.943) QCWL
D D
LR= (KRa + KRbvn)DP*MvKc (2-2)
LF= FFP*MVKC (2-5)
LD= KDSDD2P*MVKC (2-9)
where:
L-p = total loss, Ib/yr
LWD = withdrawal loss, Ib/yr
LR = rim seal loss, Ib/yr
LF = deck fitting loss, Ib/yr
9/97 Liquid Storage Tanks 7.1-95
-------
LD = deck seam loss, Ib/yr
Q = product average throughput (tank capacity [bbl] times turnovers per year),
bbl/yr
f\
C = product withdrawal shell clingage factor, bbl/ 1,000 ft
WL = density of liquid, Ib/gal
D = tank diameter, ft
N£ = number of columns, dimensionless
Fc = effective column diameter, ft
KRa = zero wind speed rim seal loss factor, lb-mole/ft-yr
KRb = wind speed dependent rim seal loss factor, lb-mole/(mph)nft-yr
v = average ambient site wind speed (zero for internal floating roof tanks), mph
My = the average molecular weight of the product vapor, Ib/lb-mole
K£ = the product factor, dimensionless
P = the vapor pressure function, dimensionless
and
PVA = the vapor pressure of the material stored, psia
PA = average atmospheric pressure at tank location, psia
Fp = the total deck fitting loss factor, Ib-mole/yr
= I (Np.Kp.) = [(NFiKFi) + (NF2KF2) + ... + (NF^)]
and:
NF. = number of fittings of a particular type, dimensionless. NF is determined
for the specific tank or estimated from Table 7.1-12
Kp = deck fitting loss factor for a particular type of deck fitting, Ib-mole/yr.
Kp.is determined for each fitting type using Table 7.1-12
nf = number of different types of fittings, dimensionless
KD = the deck seam loss factor, lb-mole/ft-yr
= 0.14 for non welded decks
= 0 for welded decks
7.1-96 EMISSION FACTORS 9/97
-------
SD = deck seam length factor, ft/ft2
~ Lseam/Adeck
and:
Lseam = total length of deck seams, ft
Adeck = area of deck, ft2 = 7iD2/4
4. Identify parameters to be calculated or determined from tables. In this example, the following
parameters are not specified: Nc, FC, P, Mv, KRa, KRb, v, P , KC, FF, KD, and SD. The density of
the liquid (WL) and the vapor pressure of the liquid (P) can be read from tables and do not need to be
calculated. Also, the weight fractions of components in the vapor can be obtained from speciation
manuals. Therefore, several steps required in preceding examples will not be required in this example.
In each case, if a step is not required, the reason is presented.
The following parameters can be obtained from tables or assumptions:
K£ = 1.0 for volatile organic liquids
Nc= 1 (from Table 7.1-11)
FC = 1.0 (assumed)
KRa = 0.3 (from Table 7.1-8)
KRb = 0.6 (from Table 7.1-8)
v = 0 for internal floating roof tanks
Mv = 62 Ib/lb-mole (from Table 7.1-2)
WL = 5.6 Ib/gal (from Table 7.1-2)
C = 0.0015 bbl/1,000 ft2 (from Table 7.1-10)
KD = 0 for welded decks so SD is not needed
FF = I (KF Np.)
11
5. Calculate mole fractions in the liquid. This step is not required because liquid mole fractions are
only used to calculate liquid vapor pressure, which is given in this example.
6. Calculate the daily average liquid surface temperature. The daily average liquid surface
temperature is equal to:
TLA = °-44 TAA + °-56 TB + °-0079 a T
TAA = (TAX + TAN)/2
9/97 Liquid Storage Tanks 7.1-97
-------
TB = TAA + 6« - 1
For Tulsa, Oklahoma (see Table 7.1-7):
TAX= 71.3°F = 530.97°R
TAN = 49.2°F = 508.87°R
I = 1,373 Btu/ft2-d
From Table 7.1-6, a = 0.17
Therefore,
TAA = (530.97 + 508.87)72 = 519.92°R
TB = 519.92 + 6(0.17) - 1 = 519.94°R
TLA = 0.44 (519.92) + 0.56 (519.94) + 0.0079(0.17)0,373)
TLA= 228.76 + 291.17 + 1.84
TLA= 521.77°Ror62°F
7. Calculate partial pressures and total vapor pressure of the liquid. The vapor pressure of gasoline
RVP 13 can be interpolated from Table 7.1-2. The interpolated vapor pressure at 62°F is equal to
7.18 psia. Therefore,
P*= PVA/PA
[1 + (1 - [PVA/PA])a5]2
P* = (7.18/14.7)/[1 + (1-(7.18/14.7))0-5]2
P* = 0.166
8. Calculate mole fractions of components in the vapor. This step is not required because vapor mole
fractions are needed to calculate the weight fractions and the molecular weight of the vapor, which are
already specified.
9. Calculate molecular weight of the vapor. This step is not required because the molecular weight of
gasoline vapor is already specified.
10. Calculate weight fractions of components of the vapor. The weight fractions of components in
gasoline vapor can be obtained from a VOC speciation manual.
7.1-98 EMISSION FACTORS 9/97
-------
11. Calculate total VOC emitted from the tank. The total VOC emitted from the tank is calculated
using the equations identified in Step 3 and the parameters specified in Step 4.
^T = LWD + LR + LF + LD
a. Calculate withdrawal losses:
LWD = [(0.943)QCWL]/D [1 + (NCFC)/D]
where:
Q = (1,000,000 gal)(50 turnovers/yr)
= (50,000,000 gal)(2.381 bbl/100 gal) = 1,190,500 bbl/yr
C = 0.0015 bbl/1,000 ft2
WL = 5.6 Ib/gal
D = 70 ft
LWD = [(0.943)(1,190,500)(0.0015)(5.6)]/70[1 + (1)(1)/70] = 137 Ib/yr VOC for withdrawal
losses
b. Calculate rim seal losses:
LR = (KRa + KRbvn)DP*MvKc
Since v = 0 for IFRT's:
LR = KRaDP MVKC
where:
KRa = 0.3 lb-mole/ft-yr
D = 70 ft
P* = 0.166
Mv = 62 Ib/lb-mole
KC= 1.0
LR = (0.3)(0.166)(70)(62)(1.0) = 216 Ib/yr VOC from rim seals
9/97 Liquid Storage Tanks 7.1-99
-------
c. Calculate deck fitting losses:
LF = FFP*MVKC
where:
FF = I (KF.Np.)
KF. = KFa. for internal floating roof tanks since the wind speed is zero (see Equation 2-8).
Substituting values for Kp taken from Tables 7.1-12 and 7.1-15 for access hatches, gauge float well,
pipe column well, ladder well, deck legs, sample pipe well, and vacuum breaker, respectively, yields:
FF = (36)(2) + (14)(1) + (10)(1) + (56)(1) + 7.9[5 + (70/10) + (702/600)] + (4
= 361 Ib-mole/yr
P* = 0.166
Mv = 62 Ib/lb-mole
c =
LF = (361)(0.166)(62)(1.0) = 3,715 Ib/yr VOC from deck fittings
d. Calculate deck seam losses:
LD = KDSDD2P*MvKc
Since KD = 0 for IFRT's with welded decks,
LD = 0 Ib/yr VOC from deck seams
e. Calculate total losses:
= 137 + 216 + 3,715 + 0 = 4,068 Ib/yr of VOC emitted from the tank
12. Calculate amount of each component emitted from the tank. The individual component losses are
equal to:
IT. = (ZV.)(LR + LF + LD) + (ZL.)(LWD)
Since the liquid weight fractions are unknown, the individual component losses are calculated based on
the vapor weight fraction and the total losses. This procedure should yield approximately the same
values as the above equation because withdrawal losses are typically low for floating roof tanks. The
amount of each component emitted is the weight fraction of that component in the vapor (obtained
from a VOC species data manual and shown below) times the total amount of VOC emitted from the
tank. The table below shows the amount emitted for each component in this example.
7.1-100 EMISSION FACTORS 9/97
-------
Constituent
Air toxics
Benzene
Toluene
Ethylbenzene
O-xylene
Nontoxics
Isomers of pentane
N-butane
Iso-butane
N-pentane
Isomers of hexane
3 -methyl pentane
Hexane
Others
Total
Weight Percent In Vapor
0.77
0.66
0.04
0.05
26.78
22.95
9.83
. 8.56
4.78
2.34
1.84
21.40
100
Emissions, Ib/yr
31.3
26.8
1.6
2.0
1,089
934
400
348
194
95.2
74.9
871
4,068
Source: SPECIATE Data Base Management System, Emission Factor and Inventory Group, U. S.
Environmental Protection Agency, Research Triangle Park, NC, 1993.
References for Section 7.1
1. Laverman, R.J., Emission Reduction Options For Floating Roof Tanks, Chicago Bridge and Iron
Technical Services Company, Presented at the Second International Symposium on Aboveground
Storage Tanks, Houston, TX, January 1992.
2. VOC Emissions From Volatile Organic Liquid Storage Tanks-Background Information For
Proposed Standards, EPA-450/3-81-003a, U. S. Environmental Protection Agency, Research
Triangle Park, NC, July 1984.
3. Evaporative Loss From External Floating Roof Tanks, Third Edition, Bulletin No. 2517, American
Petroleum Institute, Washington, DC, 1989.
4. Evaporation Loss From Internal Floating Roof Tanks, Third Edition, Bulletin No. 2519, American
Petroleum Institute, Washington, DC, 1982.
5. Manual Of Petroleum Measurement Standards: Chapter 19: Evaporative Loss Measurement,
Section 2, Evaporative Loss From Floating Roof Tanks, Preliminary Draft, American Petroleum
Institute, Washington, DC, December 1994.
6. Ferry, R.L., Estimating Storage Tank Emissions—Changes Are Coming, TGB Partnership, 1994.
7. Benzene Emissions From Benzene Storage Tanks-Background Information For Proposed
Standards, EPA-450/3-80-034a, U. S. Environmental Protection Agency, Research Triangle Park,
NC, December 1980.
8. Evaporative Loss From Fixed Roof Tanks, Second Edition, Bulletin No. 2518, American
Petroleum Institute, Washington, D.C., October 1991.
9/97
Liquid Storage Tanks
7.1-101
-------
9. Estimating Air Toxics Emissions From Organic Liquid Storage Tanks, EPA-450/4-88-004, U. S.
Environmental Protection Agency, Research Triangle Park, NC, October 1988.
10. Barnett, H.C., et ai, Properties Of Aircraft Fuels, NACA-TN 3276, Lewis Flight Propulsion
Laboratory, Cleveland, OH, August 1956.
11. Petrochemical Evaporation Loss From Storage Tanks, First Edition, Bulletin No. 2523, American
Petroleum Institute, Washington, D.C., 1969.
12. SIMS Data Base Management System, Version 2.0, U. S. Environmental Protection Agency,
Research Triangle Park, NC, 1990.
13. Comparative Climatic Data Through 1990, National Oceanic and Atmospheric Administration,
Asheville, NC, 1990.
14. Input For Solar Systems, U. S. Department of Commerce, National Oceanic and Atmospheric
Administration, Environmental and Information Service, National Climatic Center, Asheville, NC,
prepared for the U. S. Department of Energy, Division of Solar Technology, November 1978
(revised August 1979).
15. Ferry, R.L., Documentation Of Rim Seal Loss Factors For The Manual Of Petroleum
Measurement Standards: Chapter 19--Evaporative Loss Measurement: Section 2-Evaporative
Loss From Floating Roof Tanks, preliminary draft, American Petroleum Institute, April 5, 1995.
16. Written communication from R. Jones, et al., Midwest Research Institute, to D. Beauregard, U. S.
Environmental Protection Agency, Final Fitting Loss Factors For Internal And External Floating
Roof Tanks, May 24, 1995.
17. Written communication from A. Parker and R. Neulicht, Midwest Research Institute, to
D. Beauregard, U. S. Environmental Protection Agency, Fitting Wind Speed Correction Factor For
External Floating Roof Tanks, September 22, 1995.
18. Use Of Variable Vapor Space Systems To Reduce Evaporation Loss, Bulletin No. 2520, American
Petroleum Institute, New York, NY, 1964.
19. Written communication from A. Parker, Midwest Research Institute, to D. Beauregard, U. S.
Environmental Protection Agency, Final Deck Fitting Loss Factors for AP-42 Section 7.1,
February 23, 1996.
20. Courtesy of R. Ferry, TGB Partnership, Hillsborough, NC.
7.1-102 EMISSION FACTORS 9/97
-------
8.8 Nitric Acid
8.8.1 General1'2
In 1991, there were approximately 65 nitric acid (HNO3) manufacturing plants in the U. S. with a
total capacity of 11 million tons of HNO3 per year. The plants range in size from 6,000 to 700,000 tons per
year. About 70 percent of the nitric acid produced is consumed as an intermediate in the manufacture of
ammonium nitrate (NH4NO3), which in turn is used in fertilizers. The majority of the nitric acid plants are
located in agricultural regions such as the Midwest, South Central, and Gulf States because of the high
demand for fertilizer in these areas. Another 5 to 10 percent of the nitric acid produced is used for organic
oxidation in adipic acid manufacturing. Nitric acid is also used in organic oxidation to manufacture
terephthalic acid and other organic compounds. Explosive manufacturing utilizes nitric acid for organic
nitrations. Nitric acid nitrations are used in producing nitrobenzene, dinitrotoluenes, and other chemical
intermediates.1 Other end uses of nitric acid are gold and silver separation, military munitions, steel and
brass pickling, photoengraving, and acidulation of phosphate rock.
8.8.2 Process Description1'3"4
Nitric acid is produced by 2 methods. The first method utilizes oxidation, condensation, and
absorption to produce a weak nitric acid. Weak nitric acid can have concentrations ranging from 30 to 70
percent nitric acid. The second method combines dehydrating, bleaching, condensing, and absorption to
produce a high-strength nitric acid from a weak nitric acid. High-strength nitric acid generally contains more
than 90 percent nitric acid. The following text provides more specific details for each of these processes.
8.8.2.1 Weak Nitric Acid Production1'3"4 -
Nearly all the nitric acid produced in the U. S. is manufactured by the high-temperature catalytic
oxidation of ammonia as shown schematically in Figure 8.8-1. This process typically consists of 3 steps: (1)
ammonia oxidation, (2) nitric oxide oxidation, and (3) absorption. Each step corresponds to a distinct
chemical reaction.
Ammonia Oxidation -
First, a 1:9 ammonia/air mixture is oxidized at a temperature of 1380 to 1470°F as it passes through
a catalytic converter, according to the following reaction:
4NH3 + 5O2 - 4NO + 6Hp (1)
The most commonly used catalyst is made of 90 percent platinum and 10 percent rhodium gauze constructed
from squares of fine wire. Under these conditions the oxidation of ammonia to nitric oxide (NO) proceeds in
an exothermic reaction with a range of 93 to 98 percent yield. Oxidation temperatures can vary from 1380 to
1650°F. Higher catalyst temperatures increase reaction selectivity toward NO production. Lower catalyst
temperatures tend to be more selective toward less useful products: nitrogen (N2) and nitrous oxide (N2O).
Nitric oxide is considered to be a criteria pollutant and nitrous oxide is known to be a global warming gas.
The nitrogen dioxide/dimer mixture then passes through a waste heat boiler and a platinum filter.
02/98 Inorganic Chemical Industry
-------
EMISSION
POINT
COMPRESSOR
EXPANDER
(SCC 3-01-013-02)
EFFLUENT
STACK
AMMONIA
NO EMISSIONS 1
I "CONTROL
I CATALYTIC REDUCTION
I
J 2
ENTRAINED
MIST
SEPARATOR
COOLER
CONDENSER
PRODUCT
(50 - 70%
HNO 3)
Figure 8.8-1. Row diagram of typical nitric acid plant using single-pressure process
(high-strength acid unit not shown).
(Source Classification Codes in parentheses.)
EMISSION FACTORS
02/98
-------
Nitric Oxide Oxidation -
The nitric oxide formed during the ammonia oxidation must be oxidized. The process stream is
passed through a cooler/condenser and cooled to 100°F or less at pressures up to 116 pounds per square inch
absolute (psia). The nitric oxide reacts noncatalytically with residual oxygen to form nitrogen dioxide (NO2)
and its liquid dimer, nitrogen tetroxide:
2NO + O2 - 2NO2 «. N2O4 (2)
This slow, homogeneous reaction is highly temperature- and pressure-dependent. Operating at low
temperatures and high pressures promotes maximum production of NO2 within a minimum reaction time.
Absorption -
The final step introduces the nitrogen dioxide/dimer mixture into an absorption process after being
cooled. The mixture is pumped into the bottom of the absorption tower, while liquid dinitrogen tetroxide is
added at a higher point. Deionized process water enters the top of the column. Both liquids flow
countercurrent to the nitrogen dioxide/dimer gas mixture. Oxidation takes place in the free space between the
trays, while absorption occurs on the trays. The absorption trays are usually sieve or bubble cap trays. The
exothermic reaction occurs as follows:
3NO2 + Hp - 2HNO3 + NO (3)
A secondary air stream is introduced into the column to re-oxidize the NO that is formed in Reaction
3. This secondary air also removes NO2 from the product acid. An aqueous solution of 55 to 65 percent
(typically) nitric acid is withdrawn from the bottom of the tower. The acid concentration can vary from 30 to
70 percent nitric acid. The acid concentration depends upon the temperature, pressure, number of absorption
stages, and concentration of nitrogen oxides entering the absorber.
There are 2 basic types of systems used to produce weak nitric acid: (1) single-stage pressure
process, and (2) dual-stage pressure process. In the past, nitric acid plants have been operated at a single
pressure, ranging from atmospheric pressure to 14.7 to 203 psia. However, since Reaction 1 is favored by
low pressures and Reactions 2 and 3 are favored by higher pressures, newer plants tend to operate a dual-
stage pressure system, incorporating a compressor between the ammonia oxidizer and the condenser. The
oxidation reaction is carried out at pressures from slightly negative to about
58 psia, and the absorption reactions are carried out at 116 to 203 psia.
In the dual-stage pressure system, the nitric acid formed in the absorber (bottoms) is usually sent to
an external bleacher where air is used to remove (bleach) any dissolved oxides of nitrogen. The bleacher
gases are then compressed and passed through the absorber. The absorber tail gas (distillate) is sent to an
entrainment separator for acid mist removal. Next, the tail gas is reheated in the ammonia oxidation heat
exchanger to approximately 392°F. The final step expands the gas in the power-recovery turbine. The
thermal energy produced in this turbine can be used to drive the compressor.
8.8.2.2 High-Strength Nitric Acid Production1'3 -
A high-strength nitric acid (98 to 99 percent concentration) can be obtained by concentrating the
weak nitric acid (30 to 70 percent concentration) using extractive distillation. The weak nitric acid cannot be
concentrated by simple fractional distillation. The distillation must be carried out in the presence of a
dehydrating agent. Concentrated sulfuric acid (typically 60 percent sulfuric acid) is most commonly used for
this purpose. The nitric acid concentration process consists of feeding strong sulfuric acid and 55 to 65
percent nitric acid to the top of a packed dehydrating column at approximately atmospheric pressure. The
acid mixture flows downward, countercurrent to ascending vapors. Concentrated nitric acid leaves the top of
the column as 99 percent vapor, containing a small amount of NO2 and oxygen (O2) resulting from
dissociation of nitric acid. The concentrated acid vapor leaves the column and goes to a bleacher and a
countercurrent condenser system to effect the condensation of strong nitric acid and the separation of oxygen
02/98 Inorganic Chemical Industry 8.8-3
-------
and oxides of nitrogen (NOX) byproducts. These byproducts then flow to an absorption column where the
nitric oxide mixes with auxiliary air to form NO2, which is recovered as weak nitric acid. Inert and unreacted
gases are vented to the atmosphere from the top of the absorption column. Emissions from this process are
relatively minor. A small absorber can be used to recover NO2. Figure 8.8-2 presents a flow diagram of
high-strength nitric acid production from weak nitric acid.
H2so4
50-70%
HNO,
INERT,
UNREACTED
GASES
WEAK
NITRIC ACID
Figure 8.8-2. Flow diagram of high-strength nitric acid production from weak nitric acid.
8.8.3 Emissions And Controls3"5
Emissions from nitric acid manufacture consist primarily of NO, NO2 (which account for visible
emissions), trace amounts of HNO3 mist, and ammonia (NH3). By far, the major source of nitrogen oxides
(NOX) is the tailgas from the acid absorption tower. In general, the quantity of NOX emissions is directly
related to the kinetics of the nitric acid formation reaction and absorption tower design. NOX emissions can
increase when there is (1) insufficient air supply to the oxidizer and absorber, (2) low pressure, especially in
the absorber, (3) high temperatures in the cooler-condenser and absorber, (4) production of an excessively
high-strength product acid, (5) operation at high throughput rates, and (6) faulty equipment such as
compressors or pumps that lead to lower pressures and leaks, and decrease plant efficiency.
The 2 most common techniques used to control absorption tower tail gas emissions are extended
absorption and catalytic reduction. Extended absorption reduces NOX emissions by increasing the efficiency
of the existing process absorption tower or incorporating an additional absorption tower. An efficiency
increase is achieved by increasing the number of absorber trays, operating the absorber at higher pressures, or
cooling the weak acid liquid in the absorber. The existing tower can also be replaced with a single tower of a
larger diameter and/or additional trays. See Reference 5 for the relevant equations.
In the catalytic reduction process (often termed catalytic oxidation or incineration), tail gases from
the absorption tower are heated to ignition temperature, mixed with fuel (natural gas, hydrogen, propane,
butane, naphtha, carbon monoxide, or ammonia) and passed over a catalyst bed. In the presence of the
catalyst, the fuels are oxidized and the NOX are reduced to N2. The extent of reduction of NO2 and NO to N2
is a function of plant design, fuel type, operating temperature and pressure, space velocity through the
8.8-4
EMISSION FACTORS
02/98
-------
reduction catalytic reactor, type of catalyst, and reactant concentration. Catalytic reduction can be used in
conjunction with other NOX emission controls. Other advantages include the capability to operate at any
pressure and the option of heat recovery to provide energy for process compression as well as extra steam.
Catalytic reduction can achieve greater NOX reduction than extended absorption. However, high fuel costs
have caused a decline in its use.
Two seldom-used alternative control devices for absorber tailgas are molecular sieves and wet
scrubbers. In the molecular sieve adsorption technique, tailgas is contacted with an active molecular sieve
that catalytically oxidizes NO to NO2 and selectively adsorbs the NO2. The NO2 is then thermally stripped
from the molecular sieve and returned to the absorber. Molecular sieve adsorption has successfully controlled
NOX emissions in existing plants. However, many new plants elect not to install this method of control
because its implementation incurs high capital and energy costs. Molecular sieve adsorption is a cyclic
system, whereas most new nitric acid plants are continuous systems. Sieve bed fouling can also cause
problems.
Wet scrubbers use an aqueous solution of alkali hydroxides or carbonates, ammonia, urea, potassium
permanganate, or caustic chemicals to "scrub" NOX from the absorber tailgas. The NO and NO2 are
absorbed and recovered as nitrate or nitrate salts. When caustic chemicals are used, the wet scrubber is
referred to as a caustic scrubber. Some of the caustic chemicals used are solutions of sodium hydroxide,
sodium carbonate, or other strong bases that will absorb NOX in the form of nitrate or nitrate salts. Although
caustic scrubbing can be an effective control device, it is often not used due to its incurred high costs and the
necessity of treating its spent scrubbing solution.
Comparatively small amounts of nitrogen oxides are also lost from acid concentrating plants. These
losses (mostly NO2) are from the condenser system, but the emissions are small enough to be controlled
easily by inexpensive absorbers.
Acid mist emissions do not occur from the tailgas of a properly operated plant. The small amounts
that may be present in the absorber exit gas streams are removed by a separator or collector prior to entering
the catalytic reduction unit or expander.
The acid production system and storage tanks are the only significant sources of visible emissions at
most nitric acid plants. Emissions from acid storage tanks may occur during tank filling.
Nitrogen oxides and N2O emission factors shown in Table 8.8-1 vary considerably with the type of
control employed and with process conditions. For comparison purposes, the New Source Performance
Standard on nitrogen emissions expressed as NO2 for both new and modified plants is 3.0 pounds of NO2
emitted per ton (Ib/ton) of 100 percent nitric acid produced.
8.8.4 Changes Since July, 1993
• Reformatted for the Fifth Edition, released in January 1995
• Supplement D update (February 1998) - added a N2O emission factor for weak acid plant tailgas.
02/98 Inorganic Chemical Industry 8.8-5
-------
Table 8.8-1. NITROGEN OXIDE EMISSIONS FROM
NITRIC ACID PLANTS
EMISSION FACTOR RATING: E
Source
Weak acid plant tailgas
Uncontrolled15'0
Catalytic reduction0
Natural gasd
Hydrogen6
Natural gas/hydrogen (25%/75%)f
Extended absorption
Single-stage process8
Dual-stage process
Chilled absorption and caustic
scrubber1
High-strength acid plantk
Control
Efficiency
%
0
99.1
97 - 98.5
98 - 98.5
95.8
ND
ND
NOX,
Ib/ton
Nitric Acid
Produced3
57
0.4
0.8
0.9
1.9
2.1
2.2
10
N20,
Ib/ton Nitric
Acid Produced"1
11.70
ND
ND
ND
ND
ND
ND
ND
a Assumes 100% acid. Production rates are in terms of total weiSht of product (water and acid). A plant
producing 500 tons per day of 55 weight % nitric acid is calculated as producing
275 tons/day of 100% acid. To convert Ib/ton to kg/Mg, multiply by 0.5. ND = no data.
b Reference 6. Based on a study of 12 plants, with average production rate of 230 tons
(100% HNO3)/day (range 55 - 750 tons) at average rated capacity of 97% (range 72 -100%).
c Single-stage pressure process.
d Reference 4. Fuel is assumed to be natural gas. Based on data from 7 plants, with average production rate
of 340 tons (100% HNO3)/day (range 55 -1077 tons).
e Reference 6. Based on data from 2 plants, with average production rate of 160 tons (100% HNO3)/day
(range 120 - 210 tons) at average rated capacity of 98% (range 95 -100%). Average absorber exit
temperature is 85°F (range 78 - 90°F), and the average exit pressure is
85 psig (range 80 - 94 psig).
f Reference 6. Based on data from 2 plants, with average production rate of 230 tons (100% HNO3)/day
(range 185 - 279 tons) at average rated capacity of 110% (range 100 -119%). Average absorber exit
temperature is 91 °F (range 83 - 98°F), and average exit pressure is 79 psig (range 79 - 80 psig).
g Reference 4. Based on data from 5 plants, with average production rate of 540 tons (100%HNO3)/day
(range 210- 1050 tons).
h Reference 4. Based of data from 3 plants, with average production rate of 590 tons (100% HNO3)/day
(range 315-940 tons).
•i Reference 4. Based on data from 1 plant, with a production rate of 700 tons (100% HNO3)/day.
k Reference 2. Based on data from 1 plant, with a production rate of 1.5 tons (100% HNO3)/hour at 100%
rated capacity, of 98% nitric acid.
m Reference 7.
8.8-6
EMISSION FACTORS
02/98
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References For Section 8.8
1. Alternative Control Techniques Document: Nitric And Adipic Acid Manufacturing Plants, EPA-
450/3-91-026, U. S. Environmental Protection Agency, Research Triangle Park, NC, December
1991.
2. North American Fertilizer Capacity Data, Tennessee Valley Authority, Muscle Shoals, AL,
December 1991.
3. Standards Of Performance For Nitric Acid Plants, 40 CFR 60 Subpart G.
4. Marvin Drabkin, A Review Of Standards Of Performance For New Stationary Sources — Nitric
Acid Plants, EPA-450/3-79-013, U. S. Environmental Protection Agency, Research Triangle Park,
NC, March 1979.
5. Unit Operations Of Chemical Engineering, 3rd Edition, McGraw-Hill, Inc., New York, 1976.
6. Atmospheric Emissions From Nitric Acid Manufacturing Processes, 999-AP-27, U. S. Department
of Health, Education, And Welfare, Cincinnati, OH, December 1966.
7. R. L. Peer, et al., Characterization Of Nitrous Oxide Emission Sources, U. S. Environmental
Protection Agency, Office of Research and Development, Research Triangle Park, NC,
pp. 2-15, 1995.
02/98 Inorganic Chemical Industry 8.8-7
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9.9.1 Grain Elevators And Processes
9.9.1.1 Process Description1"14
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 types. Operations other than storage, such as
cleaning, drying, and blending, often are performed at elevators. The principal grains and oilseeds handled
include wheat, corn, oats, rice, soybeans, and sorghum.
Country elevators are generally smaller elevators that receive grain by truck directly from farms
during the harvest season. These elevators sometimes clean or dry grain before it is transported to terminal
elevators or processors. Terminal elevators dry, clean, blend, and store grain before shipment to other
terminals or processors, or for export. These elevators may receive grain by truck, rail, or barge, and
generally have greater grain handling and storage capacities than do country elevators. Export elevators are
terminal elevators that load grain primarily onto ships for export.
Regardless of whether the elevator is a country or terminal, there are two basic types of elevator
design: traditional and modern. Traditional grain elevators are typically designed so the majority of the grain
handling equipment (e.g., conveyors, legs, scales, cleaners) are located inside a building or structure, normally
referred to as a headhouse. The traditional elevator often employs belt conveyors with a movable tripper to
transfer the grain to storage in concrete or steel silos. The belt and tripper combination is located above the
silos in an enclosed structure called the gallery or bin deck. Grain is often transported from storage using belt
conveyors located in an enclosed tunnel beneath the silos. Particulate emissions inside the elevator structure
may be controlled using equipment such as cyclones, fabric filters, dust covers, or belt wipers; grain may be
oil treated to reduce emissions. Controls are often used at unloading and loading areas and may include
cyclones, fabric filters, baffles in unloading pits, choke unloading, and use of deadboxes or specially designed
spouts for grain loading. The operations of traditional elevators are described in more detail in Section 2.2.1.
Traditional elevator design is generally associated with facilities built prior to 1980.
Country and terminal elevators built in recent years have moved away from the design of the
traditional elevators. The basic operations performed at the elevators are the same; only the elevator design
has changed. Most modern elevators have eliminated the enclosed headhouse and gallery (bin decks). They
employ a more open structural design, which includes locating some equipment such as legs, conveyors,
cleaners, and scales, outside of an enclosed structure. In some cases, cleaners and screens may be located in
separate buildings. The grain is moved from the unloading area using enclosed belt or drag conveyors and, if
feasible, the movable tripper has been replaced with enclosed distributors or turn-heads for direct spouting
into storage bins and tanks. The modern elevators are also more automated, make more use of computers,
and are less labor-intensive. Some traditional elevators have also been partially retrofitted or redesigned to
incorporate enclosed outside legs, conveyors, cleaners, and other equipment. Other techniques used to reduce
emissions include deepening the trough of the open-belt conveyors and slowing the conveyor speed, and
increasing the size of leg belt buckets and slowing leg velocity. At loading and unloading areas of modern
elevators, the controls cited above for traditional elevators can also be used to reduce emissions.
The first step at a grain elevator is the unloading of the incoming truck, railcar, or barge. A truck or
railcar discharges its grain into a hopper, from which the grain is conveyed to the main part of the elevator.
Barges are unloaded by a bucket elevator (marine leg) that is extended down into the barge hold or by cranes
using clam shell buckets. The main building at an elevator, where grain is elevated and distributed, is called
5/98 Food And Agricultural Industry 9.9.1-1
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the "headhouse". In the headhouse, grain is lifted on one of the elevator legs and is typically discharged onto
the gallery belt, which conveys the grain to the storage bins. A "tripper" diverts grain off the belt and into the
desired bin. Other modes of transfer include augers and screw conveyors. Grain is often cleaned, dried, and
cooled for storage. Once in storage, grain may be transferred one or more times to different storage bins or
may be emptied from a bin, treated or dried, and stored in the same or a different bin. For shipping, grain is
discharged from bins onto the tunnel belt below, which conveys it to the scale garner and to the desired
loadout location (possibly through a surge bin). Figure 9.9.1-1 presents the major process operations at a
grain elevator.
A grain processing plant or mill receives grain from an elevator and performs various manufacturing
steps that produce a finished food product. The grain receiving and handling operations at processing plants
and mills are basically the same as at grain elevators. Examples of processing plants are flour mills, oat
mills, rice mills, dry corn mills, and animal feed mills. The following subsections describe the processing of
the principal grains. Additional information on grain processing may be found in AP-42 Section 9.9.2,
Cereal Breakfast Food, and AP-42 Section 9.9.7, Corn Wet Milling.
9.9.1.1.1 Flour Milling2'5-
Most flour mills produce wheat flour, but durum wheat and rye are also processed in flour mills. The
wheat flour milling process consists of 5 main steps: (1) grain reception, preliminary cleaning, and storage;
(2) grain cleaning; (3) tempering or conditioning; (4) milling the grain into flour and its byproducts; and
(5) storage and/or shipment of finished product. A simplified diagram of a typical flour mill is shown in
Figure 9.9.1-2. Wheat arrives at a mill and, after preliminary cleaning, is conveyed to storage bins. As grain
is needed for milling, it is withdrawn and conveyed to the mill area where it first enters a separator (a
vibrating screen), then, an aspirator to remove dust and lighter impurities, and then passes over a magnetic
separator to remove iron and steel particles. From the magnetic separator, the wheat enters a disc separator
designed to catch individual grains of wheat and reject larger or smaller material and then to a stoner for
removal of stones, sand, flints, and balls of caked earth or mud. The wheat then moves into a scourer which
buffs each kernel and removes more dust and loose bran (hull or husk). Following the scouring step, the
grain is sent to the tempering bins where water is added to raise the moisture of the wheat to make it easier to
grind. When the grain reaches the proper moisture level, it is passed through an impact machine as a final
cleaning step. The wheat flows into a grinding bin and then into the mill itself.
The grain kernels are broken open in a system of breaks by sets of corrugated rolls, each set taking
feed from the preceding one. After each break, the grain is sifted. The sifting system is a combination of
sieving operations (plansifters) and air aspiration (purifiers). The flour then passes through the smooth
reducing rolls, which further reduce the flour-sized particles and facilitate the removal of the remaining bran
and germ particles. Plansifters are used behind the reducing rolls to divide the stock into over-sized particles,
which are sent back to the reducing rolls, and flour, which is removed from the milling system. Flour stock is
transported from the milling system to bulk storage bins and subsequently packaged for shipment.
Generally, durum wheat processing comprises the same steps as those used for wheat flour milling.
However, in the milling of durum, middlings rather than flour are the desired product. Consequently, the
break system, in which middlings are formed, is emphasized over the part of the reduction system in which
flour is formed. Grain receiving, cleaning, and storage are essentially identical for durum and flour milling.
The tempering step varies only slightly between the two processes. The tempering of durum uses the same
equipment as wheat, but the holding times are shorter. Only the grain milling step differs significantly from
the comparable flour milling step.
The break system in a durum mill generally has at least five sets of rolls for a gradual reduction of
the stock to avoid producing large amounts of break flour. The rolls in the reduction system are used for
9.9.1-2 EMISSION FACTORS 5/98
-------
INTERMEDIATE
STORAGE BIN
(VENT)
• = POTENTIAL PM/PM-10 EMISSION SOURCE
A = POTENTIAL VOC EMISSION SOURCE
5/98
Figure 9.9.1-1. Major process operations at a grain elevator.
Food And Agricultural Industry
9.9.1-3
-------
9.9.1-4
GRAIN
RECEIVING
TRUCK
BARGE
RAIL
SHIP
GRAIN
HANDLING
• = POTENTIAL PM/PM-10 EMISSION SOURCE
A = POTENTIAL VOC EMISSION SOURCE
PRELIMINARY (
CLEANING
STORAGE
CLEANING HOUSE
SEPARATORS I J AQPIRATOH I J MAGNETIC
(SCREENS) ASMHAIUH SEPARATOR
DISC
SEPARATOR
SURGE L I O™,,D^ L 1 STONER
BIN
i
OPTIONAL
TFMPFRINP "I J MAGNETIC i J IMPACT
TEMPERING | -» SEPARATOR j 1 MACHINE
i
GRINDING
BIN/HOPPER A
MILLING !
AIR
AIR '' '
BULK
STORAGE
BAGGING
BULK
LOADING
TRUCK
RAIL
Figure 9.9.1-2. Simplified process flow diagram of a typical flour mill.
EMISSION FACTORS
5/98
-------
sizing only, and not to produce flour. The sizing produces a uniform product for sale. The sifting system
differs from that in a wheat flour mill in that it relies heavily on purifiers. In place of plansifters,
conventional sieves are more common and are used to make rough separations ahead of the purifiers.
Rye milling and wheat flour milling are quite similar processes. The purpose of both processes is to
make flour that is substantially free of bran and germ. The same basic machinery and process are employed.
The flow through the cleaning and tempering portions of a rye mill is essentially the same as the flow through
the wheat flour mill. However, because rye is more difficult to clean than wheat, this cleaning operation must
be more carefully controlled.
In contrast to wheat milling, which is a process of gradual reduction with purification and
classification, rye milling does not employ gradual reduction. Both the break and reduction roller mills in a
rye mill are corrugated. Following grinding, the screening systems employ plansifters like those used in
wheat flour mills. There is little evidence of purifier use in rye mills.
The wheat milling and rye milling processes are very similar because flour is the product of the break
rolling system. In durum wheat flour milling, the intent is to produce as little flour as possible on the break
rolls. As in wheat flour milling, the intent in rye milling is to make as much rye flour as possible on the break
rolls. Consequently, there are more break rolls in proportion to reduction rolls in a rye mill than in a durum
wheat flour mill.
9.9.1.1.2 Oat Milling2-7-
The milling process for oats consists of the following steps: (1) reception, preliminary cleaning, and
storage; (2) cleaning; (3) drying and cooling; (4) grading and hulling; (5) cutting; (6) steaming; and
(7) flaking. A simplified flow diagram of the oat milling process is shown in Figure 9.9.1-3. The receiving
and storage operations are comparable to those described for grain elevators and for the wheat flour milling
process. Preliminary cleaning removes coarse field trash, dust, loose chaff, and other light impurities before
storage. After the oats are removed from storage, they flow to a milling separator combining coarse and fine
screening with an efficient aspiration. In the next sequence of specialized cleaning operations, the oats are
first routed to a disk separator for stick removal, and then are classified into three size categories. Each size
category is subjected to a variety of processes (mechanical and gravitational separation, aspiration, and
magnetic separation) to remove impurities. Large and short hulled oats are processed separately until the last
stages of milling.
The next step in the oat processing system is drying and cooling. Oats are dried using pan dryers,
radiator column dryers, or rotary steam tube dryers. Oats typically reach a temperature of 88° to 98°C (190°
to 200 °F) here, and the moisture content is reduced from 12 percent to 7 to 10 percent. After drying and
cooling, the oats are ready for hulling; hulled oats are called groats. Some mills are now hulling oats with no
drying or conditioning, then drying the groats separately to develop a toasted flavor. Hulling efficiency can
be improved by prior grading or sizing of the oats. The free hulls are light enough that aspirators remove
them quite effectively.
Generally, the final step in the large oat system is the separation of groats totally free of whole oats
that have not had the hulls removed. These groats bypass the cutting operation and are directed to storage
prior to flaking. The rejects are sent to the cutting plant. The cutting plant is designed to convert the groats
into uniform pieces while producing a minimum of flour. The cut material is now ready for the flaking plant.
First, the oats are conditioned by steaming to soften the groats thereby promoting flaking with a minimum of
breakage. The steamed groats pass directly from the steamer into the flaking rolls. Shakers under the rolls
remove fines and overcooked pieces are scalped off. The flakes generally pass
5/98 Food And Agricultural Industry 9.9.1-5
-------
GRAIN '
RECEIVING
OPTION 1
DRYING/ •
COOLING A
GRADING /
SIZING
HULLING
GROATS FOR
REGULAR
OAT FLAKES
FLAKING
ROLLS
CLEANING
ASPIRATION
STORAGE
DISC •
SEPARATOR
ASPIRATION
,, ASPIRATION
MILLING •
SEPARATOR
MAGNETIC
SEPARATOR
OPTION 2
(NOTE: OATS MAY FOLLOW
THE SEQUENCE OF
PROCESSES IN EITHER
OPTIONS 1 OR 2-
MILL-SPECIFIC.)
GRADING /
SIZING
HULLING
DRYING/ •
COOLING A
CELL
MACHINES
GROATS FOR QUICK OAT FLAKES
CUTTING
• = POTENTIAL PM/PM-10 EMISSION SOURCE
A = POTENTIAL VOC EMISSION SOURCE
SEPARATOR
ASPIRATOR
A
CONDITIONING
STEAM
SCREEN
COOLER
PACKAGING
9.9.1-6
Figure 9.9.1-3. Flow diagram for oat processing operations.
EMISSION FACTORS
5/98
-------
through a dryer and cooler to quickly reduce moisture content and temperature which ensures acceptable shelf
life. The cooled flakes are then conveyed to the packaging system.
9.9.1.1.3 Rice Milling2'8'10-
The first step in rice processing after harvest is drying using either fixed-bed or continuous-flow
dryers to reduce the wet basis moisture content (MCwb) from 24 to 25 percent to 13 to 14 percent MCwb.
Essentially all of the rice is dried either on the farm or at commercial drying facilities prior to shipping to the
rice mill. After the rice is dried, it is stored and subsequently shipped to either conventional or parboil rice
mills for further processing. There are three distinct stages in both mills: (1) rough rice receiving, cleaning,
drying, and storage; (2) milling; and (3) milled rice and byproduct bagging, packaging, and shipping. A
simplified flow diagram of the rice milling process is shown in Figure 9.9.1-4.
Grain is received primarily by truck and rail. The rough rice is precleaned using combinations of
scalpers, screens, aspirators, and magnetic separators and then passed through a stoner, or gravity separator,
to remove stones from the grain. The cleaned rice is transported to a disk huller where the rice is dehulled.
The rice then passes through a sieve to remove bran and small brokens and to an aspirator to remove hulls.
The unshelled rice grains (commonly called paddy) and brown rice are separated in a paddy separator. The
unshelled paddy is then fed into another pair of shellers set closer together than the first set, and the process
of shelling, aspiration, and separation is repeated.
From the paddy machines, the rice is conveyed to a sequence of milling machines called whitening
cones, which scour off the outer bran coats and the germ from the rice kernels. Milling may be accomplished
by a single pass through a mill or by consecutive passages through multiple whitening cones. The discharge
from each stage is separated by a sieve. After the rice is milled, it passes through a polishing cone, which
removes the inner bran layers and the proteinaceous aleurone layer. Because some of the kernels are broken
during milling, a series of classifiers, known as trieurs, is used to separate the different size kernels. The rice
may be sold at this point as polished, uncoated rice, or it may be conveyed to machines known as trumbels, in
which the rice is coated with talc and glucose to give the surface a gloss. The rice is transferred to bulk
storage prior to packing and shipping. For packing, the rice is transported to a packing machine where the
product is weighed and placed in burlap sacks or other packaging containers.
In parboiling mills, the cleaned rough rice is steamed and dried prior to the milling operations.
Pressure vessels are used for the steaming step, and steam tube dryers are used to dry the rice to 11 to
13 percent MCwb. Following the drying step, the rice is milled in conventional equipment to remove hull
(bran), and germ.
9.9.1.1.4 Corn Dry Milling2'12'13-
Corn is dry milled by either a degerming or a nondegerming system. Because the degerming system
is the principal system used in the United States, it will be the focus of the dry corn milling process
description here. A simplified flow diagram of the corn dry milling process is shown in Figure 9.9.1-5. The
degerming dry corn milling process is more accurately called the tempering degerminating (TD) system. The
degerming system involves the following steps after receiving the grain: (1) dry cleaning, and if necessary,
wet cleaning; (2) tempering; (3) separation of hull, germ, and tip cap from the endosperm in the
degerminator; (4) drying and cooling of degermer product; (5) multistep milling of degermer product through
a series of roller mills, sifters, aspirators, and purifiers; (6) further drying of products, if necessary; (7)
processing of germ fraction for recovery of crude corn oil; and (8) packaging and shipping of products.
Unloading and dry cleaning of corn is essentially the same as described for wheat. However, for
corn, surface dirt and spores can best be removed by wet cleaning, which involves a washing-destoning unit
followed by a mechanical dewatering unit. After cleaning, the corn is sent through the tempering or
5/98 Food And Agricultural Industry 9.9.1 -7
-------
TRUCK RAIL
OPTIONAL
MAGNETIC
SEPARATOR
WEIGHING
DISK
HULLER
STONER
1
A
•
DRYING ^
i
A
STEAMING
SIEVE
PARBOILING
•
4
; Mil
i i i/-\i
i nvjv.
i
ASPIRATION
^ PADDY
SEPARATOR
LL
JSE
POLISHED UNCOATED
RICE
-TALC GLUCOSE
• = POTENTIAL PM/PM-10 EMISSION SOURCE
A = POTENTIAL VOC EMISSION SOURCE
STORAGE
WEIGH
PACKING / •
SHIPPING
9.9.1-8
Figure 9.9.1-4. Row diagram for conventional and parboil rice mills.
EMISSION FACTORS
5/98
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TRUCK
BARGE-
RAIL
GRAIN
RECEIVING
PRELIMINARY
CLEANING
WET CLEANING
TEMPERING
DEGERMING
TAIL STOCK
DRYER
COOLER
ASPIRATOR
SIFTER
ASPIRATOR
ROLLER MILL
SIFTER
DRYER
COOLER
STORAGE
DRYER
• = POTENTIAL PM/PM-10 EMISSION SOURCE
A = POTENTIAL VOC EMISSION SOURCE
THROUGH STOCK
• FLAKING GRITS
DEGERMER
STOCK
ASPIRATOR • •*
SIFTER
BULK LOADING
DRYER
COOLER
ASPIRATOR
GRAVITY TABLE
GERM FRACTION
EXPELLER '
(OR HEXANE
EXTRACTION)
SPENT
GERM
CRUDE CORN OIL
TO REFINER
PACKAGING
Figure 9.9.1-5. Simplified process flow diagram for a corn dry milling operation with degerming.
5/98 Food And Agricultural Industry 9.9.1 -9
-------
conditioning step, which raises the moisture content of the corn to 21 to 25 percent. After tempering, the corn
is degermed, typically in a Beall degermer and corn huller. The Beall degermer is essentially an attrition
device built in the form of a cone mill. The product exits in two streams, thru-stock and tail stock. Rotary
steam-tube dryers are often used to dry the degermer product, because its moisture content must be in the 15
to 18 percent range for proper milling. After drying, the product is cooled to 32° to 37°C (90° to 100°F).
After drying and cooling, the degermer stock is sifted or classified by particle size and is fed into the
conventional milling system.
The milling section in a dry corn mill consists of sifting, classifying, milling, purifying, aspirating,
and possibly, final drying operations. The feed to each pair of rolls consists of selected mill streams produced
during the steps of sifting, aspirating, roller milling, and gravity table separating. For the production of
specific products, various streams are withdrawn at appropriate points in the milling process. A number of
process streams are often blended to produce a specific product. The finished products are stored temporarily
in working bins, dried and cooled if necessary, and rebolted (sifted) before packaging or shipping in bulk.
Oil is recovered from the germ fraction either by mechanical screw presses or by a combination of
screw presses and solvent extraction. A more detailed discussion of the corn oil extraction process is
included in AP-42 Section 9.11.1, Vegetable Oil Processing.
9.9.1.1.5 Animal Feed Mills2-5'u-
The manufacture of feed begins with receiving of ingredients at the mill. A simplified flow diagram
of the animal feed manufacturing process is shown in Figure 9.9.1-6. Over 200 ingredients may be used in
feed manufacture, including grain, byproducts (e.g., meat meal, bone meal, beet and tomato pulp), and
medicinals, vitamins, and minerals (used in very small portions). Grain is usually received at the mill by
hopper bottom truck and/or rail cars, or in some cases, by barge. Most mills pass selected feed ingredients,
primarily grains, through cleaning equipment prior to storage. Cleaning equipment includes scalpers to
remove coarse materials before they reach the mixer. Separators, which perform a similar function, often
consist of reciprocating sieves that separate grains of different sizes and textures. Magnets are installed
ahead of the grinders and at other critical locations in the mill system to remove pieces of metal, bits of wire,
and other foreign metallic matter, which could harm machinery and contaminate the finished feed. From the
cleaning operation, the ingredients are directed to storage.
Upon removal from storage, the grain is transferred to the grinding area, where selected whole grains,
primarily corn, are ground prior to mixing with other feed components. The hammermill is the most widely
used grinding device. The pulverized material is forced out of the mill chamber when it is ground finely
enough to pass through the perforations in the mill screen.
Mixing is the most important process in feed milling and is normally a batch process. Ingredients are
weighed on bench or hopper scales before mixing. Mixers may be horizontal or vertical type, using either
screws or paddles to move the ingredients. The material leaving the mixer is meal, or mash, and may be
marketed in this form. If pellets are to be made, the meal is conditioned with steam prior to being pelleted.
Pelleting is a process in which the conditioned meal is forced through dies. Pellets are usually 3.2 to
19 mm (1/8 to 3/4 in.) in diameter. After pelleting, pellets are dried and cooled in pellet coolers. If pellets
are to be reduced in size, they are passed through a crumbier, or granulator. This machine is a roller mill with
corrugated rolls. Crumbles must be screened to remove fines and oversized materials. The product is sent to
storage bins and then bagged or shipped in bulk.
9.9.1-10 EMISSION FACTORS 5/98
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TRUCK
RAIL •
BARGE
GRAIN
RECEIVING
GRAIN CLEANING
GRAIN STORAGE
(ELEVATOR)
MAGNETIC
SEPARATOR
MILLING
MIXER
SURGE HOPPER
STORAGE
CONDITIONING
PELLETING
PELLET COOLER
GRUMBLER/
GRANULATOR
(ROLLER MILL)
SCREEN
STORAGE
• = POTENTIAL PM/PM-10 EMISSION SOURCE
A = POTENTIAL VOC EMISSION SOURCE
OTHER
INGREDIENT
RECEIVING
STORAGE
STORAGE
WEIGH
MEAL / MASH
STEAM
PELLETS TO STORAGE
•BAGGING
5/98
BULK SHIPPING
TRUCK, RAIL
Figure 9.9.1-6. Typical animal feed milling process flow diagram.
Food And Agricultural Industry
9.9.1-11
-------
In modern feed mills, transport equipment is connected with closed spouting and turnheads, covered
drag and screw conveyors, and tightly sealed transitions between adjoining equipment to reduce internal dust
loss and consequent housekeeping costs. Also many older facilities have upgraded to these closed systems.
9.9.1.1.6 Malted Barley Production36'37 -
Barley is shipped by railcar or truck to malting facilities. A screw conveyor or bucket elevator
typically transports barley to storage silos or to the cleaning and sizing operations. The barley is cleaned and
separated by size (using screens) and is then transferred to a malthouse where it is rinsed in steeping tanks
(steeped) and is allowed to germinate. Following steeping and germination, "green" malt is dried, typically in
an indirect-, natural gas-fired malt kiln. Malt kilns typically include multiple levels, called beds or layers.
For a two-level kiln, green malt, with a moisture content of about 45 percent, enters the upper deck of the kiln
and is dried, over a 24-hour period, to between 15 and 20 percent. The barley is then transferred to the lower
deck of the kiln, where it is dried to about 4 percent over a second 24-hour period. Some facilities burn sulfur
in a sulfur stove and exhaust the stove into the kiln at selected times during the kiln cycle. The sulfur dioxide
serves as a fungicide, bactericide, and preservative. Malted barley is then transferred by screw conveyor to a
storage elevator until it is shipped.
9.9.1.2 Emissions And Controls2'5'14'39
The main pollutant of concern in grain storage, handling, and processing facilities is particulate
matter (PM). Organic emissions (e.g., hexane) from certain operations at corn oil extraction facilities may
also be significant. These organic emissions (and related emissions from soybean and other oilseed
processing) are discussed in AP-42 Section 9.11.1. Also, direct fired grain drying operations and product
dryers in grain processing plants may emit small quantities of VOC's and other combustion products; no data
are currently available to quantify the emission of these pollutants. The following sections focus primarily on
PM sources at grain elevators and grain milling/processing facilities.
9.9.1.2.1 Grain Elevators -
Except for barge and ship unloading and loading activities, the same basic operations take place at
country elevators as at terminal elevators, only on a smaller scale and with a slower rate of grain movement.
Emission factors for various grain elevator operations are presented later in this subsection. Because PM
emissions at both types of elevators are similar, they will be discussed together in this subsection.
In trying to characterize emissions and evaluate control alternatives, potential PM emission sources
can be classified into three groups. The first group includes external emission sources (grain receiving and
grain shipping), which are characterized by direct release of PM from the operations to the atmosphere.
These operations are typically conducted outside elevator enclosures or within partial enclosures, and
emissions are quickly dispersed by wind currents around the elevator. The second group of sources are
process emission sources that may or may not be vented to the atmosphere and include grain cleaning and
headhouse and internal handling operations (e.g., garner and scale bins, elevator legs, and transfer points such
as the distributor and gallery and tunnel belts). These operations are typically located inside the elevator
structure. Dust may be released directly from these operations to the internal elevator environment, or
aspiration systems may be used to collect dust generated from these operations to improve internal
housekeeping. If aspiration systems are used, dust is typically collected in a cyclone or fabric filter before the
air stream is discharged to the atmosphere. Dust emitted to the internal environment may settle on internal
elevator surfaces, but some of the finer particles may be emitted to the environment through doors and
windows. For operations not equipped with aspiration systems the quantity of PM emitted to the atmosphere
depends on the tightness of the enclosures around the operation and internal elevator housekeeping practices.
The third group of sources includes those processes that emit PM to the atmosphere in a well-defined exhaust
stream (grain drying and storage bin vents). Each of these operations is discussed in the paragraphs below.
9.9.1-12 EMISSION FACTORS 5/98
-------
The amount of dust emitted during the various grain-handling operations may depend upon the type
of grain being handled, the quality or grade of the grain, the moisture content of the grain, the speed of the
belt conveyors used to transport the grain, and the extent and efficiency of dust containment systems (i.e.,
hoods, sheds, etc.) in use at an elevator. Part of the dust liberated during the handling of grain at elevators
gets into the grain during the harvesting operation. However, most of these factors have not been studied in
sufficient detail to permit the delineation of their relative importance to dust generation rates.
Grain dust emitted from grain elevator handling operations comprises about 70 percent organic
material, about 17 percent free silica (silicon dioxide), and specific materials in the dust, which may include
particles of grain kernels, spores of smuts and molds, insect debris, pollens, and field dust. Data recently
collected on worker exposure to grain dust indicate that the characteristics of the dust released from
processing operations to the internal elevator environment vary widely. The fraction of respirable dust (i.e.,
those dust particles equal to or less than 10 um in diameter) ranged from about 1 percent to over 60 percent
with an average of 20 and 26 percent for country and export elevators respectively. Those elevators handling
primarily wheat had an average respirable fraction of about 30 percent while those handling primarily corn
and soybeans had an average respirable fraction of slightly less than 20 percent. Because these dusts have a
high organic content and a substantial suspendible fraction, concentrations above the minimum explosive
concentration (MEC) pose an explosion hazard. Housekeeping practices instituted by the industry have
reduced explosion hazards, and this situation is rarely encountered in work areas.
Elevators in the United States receive grain by truck, railroad hopper car, and barge. The two
principal factors that contribute to dust generation during bulk unloading are wind currents and dust
generated when a falling stream of grain strikes the receiving pit. Falling or moving streams of grain initiate
a column of air moving in the same direction. Grain unloading is an intermittent source of dust occurring
only when a truck or car is unloaded. For country elevators it is a significant source during the harvest season
and declines sharply or is nonexistent during other parts of the year. At terminal elevators, however,
unloading is a year-round operation.
Trucks, except for the hopper (gondola) type, are generally unloaded by the use of some type of truck
dumping platform. Hopper trucks discharge through the bottom of the trailer. Elevators are often designed
with the truck unloading dump located in a drive-through tunnel. These drive-through areas are sometimes
equipped with a roll-down door on one end, although, more commonly they are open at both ends so that the
trucks can enter and leave as rapidly as possible. The drive-through access can act as a "wind-tunnel" in that
the air may blow through the unloading area at speeds greater than the wind in the open areas away from the
elevator. However, the orientation of the facility to the prevailing wind direction can moderate this effect.
Many facilities have installed either roll-down or bi-fold doors to eliminate this effect. The use of these doors
can greatly reduce the "wind tunnel" effect and enhance the ability to contain and capture the dust.
The unloading pit at a grain elevator usually consists of a heavy grate approximately
3.05 m x 3.05 m (10 ft x 10 ft) through which the grain passes as it falls into the receiving pit. This pit will
often be partially filled with grain as the truck unloads because the conveyor beneath the pit does not carry off
the grain as fast as it enters. The dust-laden air emitted by the truck unloading operation results from
displacement of air out of the pit plus the aspiration of air caused by the falling stream of grain. The dust
itself is composed of field dirt and grain particles. Unloading grain from hopper trucks with choke
flow-practices can provide a substantial reduction in dust emissions.
Similarly, a hopper railcar can be unloaded with minimal dust generation if the material is allowed to
form a cone around the receiving grate (i.e., choke feed to the receiving pit). This situation will occur when
either the receiving pit or the conveying system serving the pit are undersized in comparison to the rate at
which material can be unloaded from the hopper car. In such cases, dust is generated primarily during the
5/98 Food And Agricultural Industry 9.9.1-13
-------
initial stage of unloading, prior to establishment of the choked-feed conditions. Dust generated by wind
currents can be minimized by the use of a shed enclosed on two sides with a manual or motorized door on one
end or a shroud around the hopper discharge.
In most cases, barges are unloaded by means of a retractable bucket type elevator that is lowered into
the hold of the barge. There is some generation of dust in the hold as the grain is removed and also at the top
of the leg where the grain is discharged onto the transfer belt. This latter source is more appropriately
designated a transfer point.
The loadout of grain from elevators into railcar, truck, barge, or ship is another important source of
PM emissions and is difficult to control. Gravity is usually used to load grain from bins above the loading
station or from the scale in the headhouse. The main causes of dust emissions when loading bulk grain by
gravity into trucks or railcars is the wind blowing through the loading sheds and dust generated when the
falling stream of grain strikes the truck or railcar hopper. The grain leaving the loading spout is often
traveling at relatively high velocity and librates a considerable amount of dust as the grain is deposited in the
car or truck. Dust emitted during loading of barges and ships can be at least equal to, or maybe greater than,
PM generated during loading of trucks or railcars. The openings for the holds in these vessels are large,
making it very hard to effectively capture the emissions. The use of deadboxes, aspiration, socks, tents, or
other means are often used to reduce dust emissions.
Grain dryers present a difficult problem for air pollution control because of the large volumes of air
exhausted from the dryer, the large cross-sectional area of the exhaust, the low specific gravity of the emitted
dust, and the high moisture content of the exhaust stream. The rate of emission of PM from grain dryers is
primarily dependent upon the type of grain, the dustiness of the grain, and the dryer configuration (rack or
column type). The particles emitted from the dryers, although relatively large, may be very light and difficult
to collect. However, during corn drying the characteristic "bees wing" is emitted along with normal grain
dust. "Bees wing," a light flaky material that breaks off from the corn kernel during drying and handling, is a
troublesome PM emission. Essentially, all bees wing emissions are over 50 u.m in diameter, and the mass
mean diameter is probably in the region of 150 urn. In addition to the bees wings, the dust discharged from
grain dryers consists of hulls, cracked grain, weed seeds, and field dust. Effluent from a corn dryer may
consist of 25 percent bees wing, which has a specific gravity of about 0.70 to 1.2. Approximately 95 percent
of the grain dust is larger than 50 um.2
Cross-flow column dryers have a lower emission rate than rack dryers because some of the dust is
trapped by the column of grain. In order to control the dust emitted from the columns, it is necessary to build
an enclosure. This enclosure also serves as a relatively inefficient settling chamber. New grain dryers being
sold today do not require the use of enclosures. In rack dryers, the emission rate is higher because the turning
motion of the grain generates more bees wings and the design facilitates dust escape. Some rack dryers are
exhausted only from one or two points and are thus better suited for control device installation. The EPA's
New Source Performance Standards (NSPS) for grain elevators established visible emission limits for grain
dryers by requiring 0 percent opacity for emissions from column dryers with column plate perforations not to
exceed 2.4 mm diameter (0.094 in.) or rack dryers with a screen filter not to exceed 50 mesh openings.
Equipment used to clean grain varies from simple screening devices to aspiration-type cleaners.
Both types of systems potentially generate substantial quantities of PM depending on the design and extent of
enclosure.
Both country and terminal elevators are usually equipped with garner and scale bins for weighing of
grain. A country elevator may have only one garner bin and scale bin. However, a terminal elevator has
multiple scale and garner bin systems, each with a capacity ranging from 42.3 to 88.1 m3 (1,200 to 2,500 bu)
9.9.1-14 EMISSION FACTORS 5/98
-------
to process 1,233 to 2,643 m3/hr (35,000 to 75,000 bu/hr). Dust may be emitted from both the scale and
garner bin whenever grain is admitted. The incoming stream of grain displaces air from the bin, and the
displaced air entrains dust. The potential for emissions depends on the design of the system. For example,
some facilities employ a relief duct that connects the two pieces of equipment to provide a path for displaced
air. Also, in some cases, the bins are completely open at the top while some systems are completely enclosed.
The leg may be aspirated to remove dust created by the motion of the buckets and the grain flow. A
variety of techniques are used to aspirate elevator legs. For example, some are aspirated at both the top and
bottom; others are fitted with ducting from the top to the bottom in order to equalize the pressure, sometimes
including a small blower to serve this purpose. The collected dust is discharged to a cyclone or filter. Leg
vents may emit small amounts of dust under some operating conditions. However, these vents are often
capped or sealed to prevent dust emissions. The sealing or capping of the vent is designed to act as an
explosion relief vent after a certain internal pressure is reached to prevent damage to the equipment.
When grain is handled, the kernels scrape and strike against each other and the conveying medium.
This action tends to rub off small particles of chaff and to fragment some kernels. Dust is continuously
generated, and the grain is never absolutely clean. Belt conveyors have less rubbing friction than either screw
or drag conveyors, and therefore, generate less dust. Dust emissions usually occur at belt transfer points as
materials fall onto or away from a belt. Belt speed has a strong effect on dust generation at transfer points.
Examples of transfer points are the discharge from one belt conveyor or the discharge from a bin onto a
tunnel belt.
Storage bin vents, which are small screen-covered openings located at the top of the storage bins, are
used to vent air from the bins as the grain enters. The grain flow into a bin induces a flow of air with the
grain, and the grain also displaces air out of the bin. The air pressure that would be created by these
mechanisms is relieved through the vents. The flow of grain into the bin generates dust that may be carried
out with the flow of air through the bin vents. The quantity of dust released through the vents increases as the
level of the grain in the bin increases. Bin vents are common to both country and terminal elevators, although
the quantity of dust emitted is a function of the grain handling rate, which is considerably higher in terminal
elevators.
The three general types of measures that are available to reduce emissions from grain handling and
processing operations are process modifications designed to prevent or inhibit emissions, capture/ collection
systems, and oil suppression systems that inhibit release of dust from the grain streams. The following
paragraphs describe the general approaches to process controls, capture systems, and oil suppression. The
characteristics of the collection systems most frequently applied to grain handling and processing plants
(cyclones and fabric filters) are then described, and common operation and maintenance problems found in
the industry are discussed.
Because emissions from grain handling operations are generated as a consequence of mechanical
energy imparted to the dust by the operations themselves and local air currents in the vicinity of the
operations, an obvious control strategy is to modify the process or facility to limit the effects of those factors
that generate emissions. The primary preventive measures that facilities have used are construction and
sealing practices that limit the effect of air currents and minimizing grain free fall distances and grain
velocities during handling and transfer. Some construction and sealing practices that minimize emissions are
enclosing the receiving area to the degree practicable, preferably with doors at both ends of a receiving shed;
specifying dust-tight cleaning and processing equipment; using lip-type shaft seals at bearings on conveyor
5/98 Food And Agricultural Industry 9.9.1-15
-------
and other equipment housings; using flanged inlets and outlets on all spouting, transitions, and miscellaneous
hoppers; and fully enclosing and sealing all areas in contact with products handled.
A substantial reduction in emissions from receiving, shipping, handling, and transfer areas can be
achieved by reducing grain free fall distances and grain velocities. Choke unloading reduces free fall distance
during hopper car unloading. The same principle can be used to control emissions from grain transfer onto
conveyor belts and from loadout operations. An example of a mechanism that is used to reduce grain
velocities is a "dead box" spout, which is used in grain loadout (shipping) operations. The dead box spout
slows down the flow of grain and stops the grain in an enclosed area. The dead box is mounted on a
telescoping spout to keep it close to the grain pile during operation. In principle, the grain free falls down the
spout to an enclosed impact dead box, with grain velocity going to zero. It then falls onto the grain pile.
Typically, the entrained air and dust liberated at the dead box is aspirated back up the spout to a dust
collector. Finally, several different types of devices are available that, when added to the end of the spout,
slow the grain flow and compress the grain discharge stream. These systems entrap the dust in the grain
stream, thereby providing a theoretical reduction in PM emissions. There are few, if any, test data from
actual ship or barge loading operations to substantiate this theoretical reduction in emissions.
While the preventive measures described above can minimize emissions, most facilities also require
ventilation, or capture/collection, systems to reduce emissions to acceptable levels. In fact, air aspiration
(ventilation) is a part of the dead box system described above. Almost all grain handling and processing
facilities, except relatively small grain elevators, use capture/collection on the receiving pits, cleaning
operations, and elevator legs. Generally, milling and pelletizing operations at processing plants are
ventilated, and some facilities use hooding systems on all handling and transfer operations.
Grain elevators that rely primarily on aspiration typically duct many of the individual dust sources to
a common dust collector system, particularly for dust sources in the headhouse. Thus, aspiration systems
serving elevator legs, transfer points, bin vents, etc., may all be ducted to one collector in one elevator and to
two or more individual systems in another. Because of the myriad possibilities for ducting, it is nearly
impossible to characterize a "typical" grain elevator from the standpoint of delineating the exact number and
types of air pollution sources and the control configurations for those sources.
The control devices typically used in the grain handling and processing industry are cyclones (or
mechanical collectors) and fabric filters. Cyclones are generally used only on country elevators and small
processing plants located in sparsely populated areas. Terminal elevators and processing plants located in
densely populated areas, as well as some country elevators and small processing plants, normally use fabric
filters for control. Both of these systems can achieve acceptable levels of control for many grain handling and
processing sources. Although cyclone collectors can achieve acceptable performance in some scenarios, and
fabric filters are highly efficient, both devices are subject to failure if they are not properly operated and
maintained. Also, malfunction of the ventilation system can lead to increased emissions at the source.
The emission control methods described above rely on either process modifications to reduce dust
generation or capture collection systems to control dust emissions after they are generated. An alternative
control measure that has developed over the last 10 years is dust suppression by oil application. The driving
forces for developing most such dust suppression systems have been grain elevator explosion control as well
as emission control. Consequently, few data have been published on the amount of emission reduction
achieved by such systems. Recent studies, however, have indicated that a PM reduction of approximately 60
to 80 percent may be achievable (see References 57 and 61 in Section 4 of the Background Report).
Generally, these oil application dust suppression systems use either white mineral oil, soybean oil, or
some other vegetable oil. Currently the Food and Drug Administration restricts application rates of mineral
9.9.1-16 EMISSION FACTORS 5/98
-------
oil to 0.02 percent by weight. Laboratory testing and industry experience have shown that oil additives
applied at a rate of 60 to 200 parts per million by weight of grain, or 0.5 to 1.7 gallons of oil per thousand
bushels of grain can provide effective dust control.39 The effectiveness of the oil suppression system
depends to some extent on how well the oil is dispersed within the grain stream after it is applied. Several
options are available for applying oil additives.
1. As a top dressing before grain enters the bucket elevator or at other grain transfer points.
2. From below the grain stream at a grain transfer point using one or more spray nozzles.
3. In the boot of the bucket elevator leg.
4. At the discharge point from a receiving pit onto a belt or other type conveyor.
5. In a screw conveyor.
9.9.1.2.2 Grain Processing Plants -
Several grain milling operations, such as receiving, conveying, cleaning, and drying, are similar to
those at grain elevators. In addition, applications of various types of grinding operations to the grain, grain
products, or byproducts are further sources of emissions. The hammermill is the most widely used grinding
device at feed mills. Some product is recovered from the hammermill with a cyclone collector or baghouse.
Mills, similar to elevators, use a combination of cyclones and fabric filters to conserve product and to control
emissions. Several types of dryers are used in mills, including the traditional rack or column dryers, fluidized
bed dryers (soybean processing), and flash-fired or direct-fired dryers (corn milling). These newer dryer
types might have lower emissions, but data are insufficient at this time to quantify the difference. The grain
precleaning often performed before drying also likely serves to reduce emissions.
Because of the operational similarities, emission control methods used in grain milling and
processing plants are similar to those in grain elevators. Cyclones or fabric filters are often used to control
emissions from the grain handling operations (e. g., unloading, legs, cleaners, etc.) and also from other
processing operations. Fabric filters are used extensively in flour mills. However, certain operations within
milling operations are not amenable to the use of these devices and alternatives are needed. Wet scrubbers,
for example, are applied where the effluent gas stream has a high moisture content. A few operations have
been found to be difficult to control by any method. Various emission control systems have been applied to
operations within the grain milling and processing industry.
Grain processing facilities also have the potential to emit gaseous pollutants. Natural gas-fired
dryers and boilers are potential sources of combustion byproducts and VOC. The production of various
modified starches has the potential for emissions of hydrochloric acid or ethylene oxide. However, no data
are available to confirm or quantify the presence of these potential emissions. Neither are there any data
available concerning the control of these potential emissions.
Table 9.9.1-1 presents emission factors for filterable PM and PM-10 emissions from grain elevators.
Table 9.9.1-2 presents emission factors for filterable PM; PM-10; inorganic, organic and total condensible
PM emissions from grain processing facilities.
The most recent source test data for grain elevators either does not differentiate between country and
inland terminal elevators or does not show any significant difference in emission factors between these two
types of elevators. There are no current emission source test data for export terminal elevators. Because
there is no significant difference in emission factors between different types of elevators, the emission factors
presented in Table 9.9.1-1 are for grain elevators, without any distinction between elevator types.
5/98 Food And Agricultural Industry 9.9.1-17
-------
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In Tables 9.9.1-1 and 9.9.1-2, a number of potential emission sources are presented for each type of
facility. The number and type of processes that occur within a specific elevator or grain processing plant will
vary considerably from one facility to another. The total emissions from a specific facility will be dependent
upon the different types of processes and the number of times a process or operation occurs within each
facility. Not all processes occur at every facility; therefore, the specific emission sources and number of
sources must be determined for each individual facility. It is not appropriate to sum emission factors for all
sources and assume that total factor for all facilities.
References For Section 9.9.1
1. Emission Factor Documentation For AP-42 Section 9.9.1, Grain Elevators And Processing Plants,
Contract No. 68-D2-0159 and Purchase Order No. 8D-1993-NANX, Midwest Research Institute,
Gary, NC, March 1998.
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. Environmental Protection Agency, Research Triangle
Park, NC, December 1973.
3. V. Ramanthan and D. Wallace, Review Of Compliance Monitoring Programs With Respect To
Gain Elevators, Final Report, EPA Contract 68-01-4139, Tasks 12 and 14, Midwest Research
Institute, March 1980.
4. G. A. LaFlam, Emission Factor Documentation For AP-42 Section 6.9.1, Grain Elevators And
Processing Plants, Pacific Environmental Services Inc., Durham, NC, September 1987.
5. D. Wallace, Grain Handling And Processing, Part of Chapter 13, "Food And Agricultural Industry",
in Air Pollution Engineering Manual, Van Nostrand Reinhold, NY, 1992.
6. Letter from Thomas C. O'Connor, National Grain and Feed Association, to Dallas Safriet, U. S.
Environmental Protection Agency, Research Triangle Park, NC. November 24, 1993.
7. Francis H. Webster, Oats: Chemistry And Technology, American Association Of Cereal Chemists,
St. Paul, MN, 1986.
8. Bienvenido O. Juliano, Rice Chemistry And Technology, American Association Of Cereal Chemists,
St. Paul, MN, 1985.
9. Bor S. Luk, Rice, Volume I, Production, Second Edition, Van Nostrand Reinhold, New York, NY,
1991.
10. Bor S. Luk, Rice, Volume n, Utilization, Second Edition, Van Nostrand Reinhold, New York, NY,
1991.
11. Samuel R. Aldrich, Walter O. Scott, and Robert G. Hoeft, Modern Corn Production, Third Edition,
A. & L. Publications, Champaign, IL, 1986.
12. G. F. Spraque and J. W. Dudgley, Corn And Corn Improvement, Third Edition, American Society
Of Agronomy, Inc., Crop Science Society Of America, Inc., and Soil Science Society Of America,
Inc., Madison, WI, 1988.
5/98 Food And Agricultural Industry 9.9.1 -25
-------
13. S. A. Watson and P. E. Ramstad, Corn Chemistry And Technology, American Association Of Cereal
Chemists, Inc., St. Paul, MN, 1987.
14. R. R. McElhiney, Feed Manufacturing Technology III, American Feed Manufacturers Association,
Arlington, VA, 1985.
15. Health and Hygiene, Inc., Worker Exposure To Dust In The Grain Industry, Unpublished report for
the National Grain And Feed Association, Washington, DC, September 1991.
16. Tests Of Oil Suppression OfPM-lOAt Grain Elevators, Test Report, Midwest Research Institute,
Kansas City, MO, November 1994.
17. F. S. Lai, et al., Examining The Use Of Additives To Control Grain Dust, Final Report To The
National Grain And Feed Association, Washington, DC, June 1982.
18. P. Kenkel and R. Noyes, "Grain Elevator Dust Emission Study", Oklahoma State University,
Stillwater, OK, October 21, 1994 and "Clarifying Response To MRI Report On OSU Dust Emission
Study", Oklahoma State University, Stillwater, OK, February 13, 1995.
19. Emission Factors For Grain Elevators, Final Report to National Grain and Feed Foundation,
Midwest Research Institute, Kansas City, Missouri, January, 1997.
20. F. J. Belgea, Dust Control Systems Performance Test, Pollution Curbs, Inc., St. Paul, Minnesota,
July 15, 1976.
21. A. L. Trowbridge, Participate Emissions Testing, ERC Report No. 4-7683, Environmental Research
Corporation, St. Paul, MN, January 16, 1976.
22. C. S. Hulburt, Paniculate Emissions Evaluation And Performance Test Of The Dust Control
Systems At Farmers Coop Elevator In Enderlin, North Dakota, Pollution Curbs Inc., St. Paul, MN,
October 23, 1974.
23. 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.
24. F. J. Belgea, Cyclone Emissions And Efficiency Evaluation, Pollution Curbs Inc., St. Paul, MN,
March 10, 1972.
25. P. Lonnes, Results Of Paniculate Emission Compliance Testing At The Peavey Company In Valley
City, North Dakota, Conducted March 16-18, 1977, Interpoll Inc., St. Paul, MN, April 15,1977.
26. R. W. Gerstle and R. S. Amick, Test Number 73-GRN-l, Ralston Purina Company, Louisville,
Kentucky, Final Report, EPA Contract No. 68-02-0237, Task 17, U. S. Environmental Protection
Agency, Research Triangle Park, NC, 1972.
27. Environmental Engineering Inc., Source Test Report On Measurement Of Emissions From Cargill,
Inc., Sioux City, Iowa, Test No. 72-Cl-28(GRN), U. S. Environmental Protection Agency, Research
Triangle Park, NC, 1972.
9.9.1-26 EMISSION FACTORS 5/98
-------
28. W. D. Snowden, Atmospheric Emission Evaluation, Mayflower Farms Grain And Feed Milling
Plant, Portland, Oregon, Test No. 72-Cl-34(GRN), U. S. Environmental Protection Agency,
Research Triangle Park, NC, February 8, 1973.
29. Particvlate Emission Testing For Wayne Farms Sandersville, Mississippi, Air Systems Testing,
Inc., Marietta, GA, September 1-2, 1992.
30. Report Of Particulate Emissions Tests For Wayne Farms Laurel Feed Mill, Environmental
Monitoring Laboratories, Ridgeland, MS, August 29 and September 20, 1994.
31. Written communication from Paul Luther, Purina Mills, Inc., St. Louis, MO, to Greg LaFlam, Pacific
Environmental Service Inc., Durham, NC, March 11 and August 28, 1987.
32. Report Of Particulate Emissions Tests For Stockton Hay And Grain Company, Environmental
Research Group, Inc., Emeryville, CA, September 1983.
33. H. J. Taback, ef al, Fine Particle Emissions From Stationary And Miscellaneous Sources In The
South Coast Air Basin, Final Report, PB-293-923, California Air Resources Board, Sacramento,
CA, February 1979.
34. Written communication from W. James Wagoner, Butte County Air Pollution Control Agency,
Durham, CA, to Dallas Safriet, U. S. Environmental Protection Agency, Research Triangle Park, NC,
October 11, 1993.
35. Thomas Rooney, Emission Performance Testing Of A Rice Mill, Western Environmental Services,
Redondo Beach, CA, March 1992.
36. H. J. Beaulieu, Final Report Atmospheric Emission Testing Busch Agricultural Resources, Inc.,
Idaho Falls Malt Plant, Industrial Hygiene Resources, Ltd., Boise, Idaho, October, 1991.
37. M. J. Huenink, Total Particulate Emissions Stack Testing Of The Kiln 6 Operations At Busch
Agricultural Resources, Inc., Manitowoc, Wisconsin, Environmental Technology and Engineering
Corp., Elm Grove, Wisconsin, May 8, 1996.
38. Emission Factors For Grain Receiving And Feed Loading Operations At Feed Mills, for National
Cattleman's Beef Association, Texas A&M University, College Station, Texas, September 17, 1996.
39. Letter from Thomas C. O'Connor, National Grain and Feed Association, to Dallas Safriet, U. S.
Environmental Protection Agency, Research Triangle Park, North Carolina, June 30, 1997.
5/98 Food And Agricultural Industry 9.9.1 -27
-------
10.5 Plywood Manufacturing
10.5.1 General
Plywood is a building material consisting of veneers (thin wood layers or plies) bonded with an
adhesive. The outer layers (face and back) surround a core that is usually lumber, veneer, or particleboard.
Plywood has many uses, including wall siding, sheathing, roof decking, concrete formboards, floors, and
containers.
10.5.2 Process Description1"3'15
The manufacture of plywood consists of seven main processes: log debarking and bucking, heating
the logs, peeling the logs into veneers, drying the veneers, gluing the veneers together, pressing the veneers in
a hot press, and finishing processes such as sanding and trimming. Figure 10.5-1 provides a generic process
flow diagram for a plywood mill.
The initial step of debarking is accomplished by feeding logs through one of several types of
debarking machines. The purpose of this operation is to remove the outer bark of the tree without
substantially damaging the wood. Although the different types of machines function somewhat differently,
emissions from the different machines are comparable. After the bark is removed, the logs are cut to
appropriate lengths in a step known as bucking.
The logs (now referred to as blocks) then are heated to improve the cutting action of the veneer lathe
or slicer, thereby generating a product from the lathe or slicer with better surface finish. Blocks are heated to
around 93 °C (200 °F) using a variety of methods-hot water baths, steam heat, hot water spray, or a
combination of the three.
After heating, the logs are processed to generate veneer. For most applications, a veneer lathe is
used, but some decorative, high quality veneer is generated with a veneer slicer. The slicer and veneer lathe
both work on the same principle; the wood is compressed with a nosebar while the veneer knife cuts the
blocks into veneers that are typically 3 mm (1/8 in.) thick. These pieces are then clipped to a useable width,
typically 1.37 m (54 in.), to allow for shrinkage and trim.
Veneers are taken from the clipper to a veneer dryer where they are dried to moisture contents that
range from less than 1 to 15 percent. Target moisture contents depend on the type of resin used in
subsequent gluing steps. The typical drying temperature ranges from 150° to 200°C (300° to 400°F). The
veneer dryer may be a longitudinal dryer, which circulates air parallel to the veneer, or a jet dryer. The jet
dryers direct hot, high velocity air at the surface of the veneers in order to create a more turbulent flow of air.
The increased turbulence provides more effective use of dryer energy, thereby reducing drying time. In direct-
heated wood-fired dryers, the combustion gases are blended with recirculated exhaust from the dryer to
reduce the combustion gas temperature. In such cases, the gases entering the dryer generally are maintained
in the range of 316° to 427°C (600° to 800°F).
When the veneers have been dried to their specified moisture content, they are glued together with a
thermosetting resin. The two main types of resins are phenol-formaldehyde, which is used for softwood and
exterior grades of hardwood, and urea-formaldehyde, which is used to glue interior grades of hardwood. The
resins are applied by glue spreaders, curtain coalers, or spray systems. Spreaders have a
9/97 Wood Products Industry 10.5-1
-------
LOG
STORAGE
(SCC 3-07-008-95)
PM EMISSIONS
ORGANIC
EMISSIONS
VENEER
LAYOUT AND
GLUE
SPREADING
ORGANIC
EMISSIONS
LOG DEBARKING
(SCC 3-07-008-01)
AND BUCKING
(SCC 3-07-008-02)
ORGANIC
PM EMISSIONS EMISSIONS
LOG STEAMING
(SCC 3-07-007-30)
i
VENEER DRYER
(SCC 3-07-007-27)
(SCC 3-07-007-11 TO -20)
(SCC 3-07-007-40 TO -70)
VENEER CUTTING
(SCC 3-07-007-25)
OTHER SOURCES
PLYWOOD RESIDUE HANDLING AND
TRANSFER (SCC 3-07-007- )
PLYWOOD RESIDUE STORAGE PILES
(SCC 3-07-007-.
ORGANIC
EMISSIONS
PM EMISSIONS
PM EMISSIONS
i
PLYWOOD CUTTING
PLYWOOD PRESSING (SCC 3-07-007-10)
(SCC 3-07-007-80 TO -81)
PLYWOOD SANDING
(SCC 3-07-007-02)
FINISHED
PRODUCT
Figure 10.5-1. Generic process flow diagram for a plywood mill.
(SCC = Source Classification Code.)
10.5-2
EMISSION FACTORS
9/97
-------
series of rubber-covered grooved application rolls that apply the resin to the sheet of veneer. Generally, resin
is spread on two sides of one ply of veneer, which is then placed between two plies of veneer that are not
coated with resin.
Assembly of the plywood panels must be symmetrical on either side of a neutral center in order to
avoid excessive warpage. For example, a five-ply panel would be laid up in the following manner. A back,
with the grain direction parallel to the long axis of the panel, is placed on the assembly table. The next veneer
has a grain direction perpendicular to that of the back, and is spread with resin on both sides. Then, the
center is placed, with no resin, and with the grain perpendicular to the previous veneer (parallel with the
back). The fourth veneer has a grain perpendicular to the previous veneer (parallel with the short axis of the
panel) and is spread with resin on both sides. The final, face, veneer with no resin is placed like the back with
the grain parallel to the long axis of the plywood panel.
The laid-up assembly of veneers then is sent to a hot press in which it is consolidated under heat and
pressure. Hot pressing has two main objectives: (1) to press the glue into a thin layer over each sheet of
veneer; and (2) to activate the thermosetting resins. Typical press temperatures range from 132° to 165° C
(270° to 330°F) for softwood plywood, and 107° to 135°C (225° to 275°F) for hardwood plywood. Press
times range from 2 to 7 minutes. The time and temperature vary depending on the wood species used, the
resin used, and the press design.
The plywood then is taken to a finishing process where edges are trimmed; the face and back may or
may not be sanded smooth. The type of finishing depends on the end product desired.
10.5.3 Emissions and Controls2'20
The primary emissions from the manufacture of plywood include filterable particulate matter (PM)
and PM less than 10 micrometers in aerodynamic diameter (PM-10) from log debarking and bucking, and
plywood cutting and sanding; filterable and condensible PM/PM-10 from drying and pressing; organic
compounds from steaming and drying operations; and organic compounds, including formaldehyde and other
hazardous air pollutants (HAPs), from gluing and hot pressing. However, trace amounts of combustion by-
products, which may include HAPs (e. g., aldehydes), may be present in direct-fired, veneer dryer exhausts as
a result of fossil fuel or wood combustion gases being passed through the dryer. Fuel combustion for
material drying also can generate carbon monoxide (CO), carbon dioxide (CO2), sulfur dioxide (SO2), and
nitrogen oxide (NOX) emissions.
The main source of emissions is the veneer dryer, which emits significant quantities of organic
compounds. The quantity and type of organic compounds emitted varies depending on the wood species, the
dryer type, and its method of operation. The two discernible fractions released from the dryer are
condensibles and volatiles. The condensible organic compounds consist largely of sesqui-terpenes, resin
acids, fatty acids, and alcohols. As these condensible compounds cool after being emitted from the stack,
they often combine with water vapor to form aerosols, which can cause a blue haze. The other fraction,
volatile organic compounds (VOCs), comprises terpenes along with small quantities of volatile combustion
by-products where direct-fired dryers are used.
Measurement of VOC and condensible PM emission rates are highly dependent on stack gas and
sampling train filter temperatures. When the sampling train filter temperature is higher than the stack gas
temperature, the rate of VOC and condensible PM emissions measured will increase with increasing filter
temperature, because as filter temperature increases less organic material will condense on the sampling train
filter. The available data are inadequate to determine the effect on emissions of recirculating the exhaust
from wood-fired veneer dryers to a combustion gas blend box.
9/97 Wood Products Industry 10.5-3
-------
The hot pressing operation is also a source of organic emissions. The quantity and composition of
emissions from this operation are expected to vary with wood species and resin components. However, few
test data are available for hot presses to characterize this variability.
Significant quantities of sawdust and other small wood particles are generated by plywood cutting
and sanding operations. Sanders and trim saws typically have control devices to recover the material for use
as a fuel in the dryer or boiler. However, small amounts of PM may be released from cutting and sanding.
Log debarking, log bucking, and sawdust handling are additional sources of PM emissions. Finally, fugitive
dust emissions are generated from open sources such as sawdust storage piles and vehicular traffic.
Emissions from these operations are discussed in more detail in AP-42 Chapter 13.
Particulate matter and PM-10 emissions from log debarking, sawing, sanding, and material handling
operations can be controlled through capture in an exhaust system connected to a sized cyclone and/or fabric
filter collection system. These wood dust capture and collection systems are used not only to control
atmospheric emissions, but also to collect the dust as a by-product fuel for a boiler or dryer.
Methods of controlling PM emissions from the veneer dryer include multiple spray chambers, a
packed tower combined with a cyclonic collector, a sand filter scrubber, an ionizing wet scrubber (IWS), an
electrified filter bed (EFB), and a wet electrostatic precipitator (WESP). The first three devices are older
technologies that are being replaced with newer technologies that combine electrostatic processes with other
scrubbing or filtration processes. Wet PM controls, such as IWS and WESP systems also may reduce VOC
emissions from veneer dryers, but to a lesser extent than PM emissions are reduced by such systems.
In multiple spray chamber systems, the dryer exhaust is routed through a series of chambers in which
water is used to capture pollutants. The water is then separated from the exhaust stream in a demisting zone.
Multiple spray chambers are the most common control technology used on veneer dryers today. However,
because they provide only limited removal of PM, PM-10, and condensible organic emissions, they are being
replaced with newer, more effective techniques. The packed tower/cyclonic collector comprises a spray
chamber, a cyclonic collector, and a packed tower in series. Applications of this system are also limited as
newer, more efficient controls are applied. The sand filter scrubber incorporates a wet scrubbing section
followed by a wet-sand filter and mist eliminator. The larger PM is removed in the scrubber, while a portion
of the remaining organic material is collected in the filter bed or the mist eliminator. This scrubbing system is
also becoming obsolete as newer, more efficient controls are applied.
Three newer technologies for controlling veneer dryer emissions are the IWS, the EFB, and the
WESP. Because applications of these systems are relatively recent, there are limited data on their
performance for veneer dryer emission control. The IWS combines electrostatic forces with packed bed
scrubbing techniques to remove pollutants from the exhaust stream. The EFB uses electrostatic forces to
attract pollutants to an electrically charged gravel bed. The WESP uses electrostatic forces to attract
pollutants to either a charged metal plate or a charged metal tube. The collecting surfaces are continually
rinsed with water to wash away the pollutants.
Little information is available on control devices for plywood pressing operations, as these
operations are generally uncontrolled. However, one test report indicates that hot press emissions at one
facility are captured by a large hood placed over and around the hot press and cooling station. The captured
emissions are ducted to a packed-bed caustic scrubber. Formaldehyde collected in the scrubber is converted
to sodium formate and discharged to the sewer.
A VOC control technology gaining popularity in the wood products industry for controlling both
dryer and press exhaust gases is regenerative thermal oxidation. Thermal oxidizers destroy VOCs, CO, and
10.5-4 EMISSION FACTORS 9/97
-------
condensible organics by burning them at high temperatures. Regenerative thermal oxidizers (RTOs) are
designed to preheat the inlet emission stream with heat recovered from the incineration exhaust gases. Up to
98 percent heat recovery is possible, although 95 percent is typically specified. Gases entering an RTO are
heated by passing through pre-heated beds packed with a ceramic media. A gas burner brings the preheated
emissions up to an incineration temperature between 788° and 871 °C (1450° and 1600°F) in a combustion
chamber with sufficient gas residence time to complete the combustion. Combustion gases then pass through
a cooled ceramic bed where heat is extracted. By reversing the flow through the beds, the heat transferred
from the combustion exhaust air preheats the gases to be treated, thereby reducing auxiliary fuel
requirements. Industry experience has shown that RTOs typically achieve 95 percent reduction for VOC
(except at inlet concentrations below 20 parts per million by volume as carbon [ppm-vC]), 70 to 80 percent
reduction for CO, and typical NOX increase of 10 to 20 ppm.
Biofiltration systems can be used effectively for control of a variety of pollutants including organic
compounds (including formaldehyde and benzene), NOX, CO, and PM from both dryer and press exhaust
streams. Data from pilot plant studies in U. S. oriented strandboard mills indicate that biofilters can achieve
VOC control efficiencies of 70 to 90 percent, formaldehyde control efficiencies of 85 to 98 percent, CO
control efficiencies of 30 to 50 percent, NOX control efficiencies of 80 to 95 percent, and resin/fatty acid
control efficiencies of 83 to 99 percent.
Other potential control technologies for plywood veneer dryers and presses include exhaust gas
recycle, regenerative catalytic oxidation (RCO), absorption systems (scrubbers), and adsorption systems.
Table 10.5-1 presents emission factors for veneer dryer emissions of PM, including filterable PM
and condensible PM. Table 10.5-2 presents emission factors for veneer dryer emissions of SO2, NOX, CO,
and CO2. Table 10.5-3 presents emission factors for veneer dryer emissions of organic pollutants.
Table 10.5-4 presents emission factors for plywood press emissions of PM, including filterable PM and
condensible PM. Table 10.5-5 presents emission factors for plywood press emissions of formaldehyde and
VOC. Table 10.5-6 presents emission factors for plywood manufacturing miscellaneous sources.
9/97 Wood Products Industry 10.5-5
-------
Table 10.5-1. EMISSION FACTORS FOR PLYWOOD VENEER DRYERS--
PARTICULATE MATTER3
Source
Direct wood-fired
Douglas fir
(SCC-3-07-007-47)
Direct natural gas-fired
Unspecified pines6
(SCC-3-07-007-50)
Indirect heated
Unspecified pines6
(SCC-3-07-007-60)
Douglas fir
(SCC-3-07-007-67)
Douglas fir
(SCC-3-07-007-67)
Unspecified firs8
(SCC-3-07-007-66)
Radio frequency heated
Unspecified pines6
(SCC-3-07-007-70)
Emission
Control0
WESP
None
None
None
WESP
WESP
None
Filterable15
PM
0.26
0.079
0.35
0.070f
0.040
0.034
0.0050
EMISSION
FACTOR
RATING
D
E
D
D
E
E
E
PM-10
ND
ND
ND
ND
ND
ND
ND
EMISSION
FACTOR
RATING
Condensibled
0.045
0.42
1.0
0.82f
0.11
0.065
0.0060
EMISSION
FACTOR
RATING
D
E
D
D
E
E
E
a Emission factor units are pounds per thousand square feet of 3/8-inch thick veneer (Ib/MSF 3/8). One
Ib/MSF 3/8 = 0.5 kg/m3. SCC = source classification code. Reference 19 except where noted otherwise.
ND = no data available.
b Filterable PM is that PM collected on or prior to the filter of an EPA Method 5 (or equivalent) sampling
train.
c Emission control device: WESP = wet electrostatic precipitator.
d Condensible PM is that PM collected in the impinger portion of a PM sampling train.
e Based on data on the drying of mixed pine species or the drying of veneers which are identified only as
pines.
f References 11,14.
g Based on data on the drying of mixed fir species or the drying of veneers which are identified only as firs.
10.5-6
EMISSION FACTORS
9/97
-------
Table 10.5-2. EMISSION FACTORS FOR PLYWOOD VENEER DRYERS--SO2, NOX>
CO, AND CO2a
Source
Direct wood-fired
(SCC-3-07-007-40 to
-46)
Direct natural gas-fired
(SCC-3-07-007-50)
Indirect heated
(SCC-3-07-007-60 to
-69)
Radio-frequency heated
(SCC-3-07-007-70)
Emission
Control
None
None
None
None
SO2
0.058
ND
NA
ND
EMISSION
FACTOR
RATING
D
NOX
0.24
0.012
NA
ND
EMISSION
FACTOR
RATING
D
E
CO
5.1
0.57
NA
ND
EMISSION
FACTOR
RATING
D
E
C02C
ND
ND
ND
ND
EMISSION
FACTOR
RATING
a Factors represent uncontrolled emissions. SCC = Source Classification Code. ND = no data available.
NA = not applicable. All emission factors in units of pounds per thousand square feet of 3/8-inch thick
veneer (Ib/MSF 3/8). One Ib/MSF 3/8 = 0.5 kg/m3. Reference 19.
9/97
Wood Products Industry
10.5-7
-------
Table 10.5-3. EMISSION FACTORS FOR PLYWOOD VENEER DRYERS-ORGANICSa
Source
Direct wood-fired
Unspecified pinesd
(SCC 3-07-007-40)
Hemlock
(SCC 3-07-007-44)
Douglas fir
(SCC 3-07-007-47)
Unspecified firs8
(SCC 3-07-007-46)
Direct natural gas-fired
Unspecified pinesd
(SCC 3-07-007-50)
Indirect heated
Unspecified pines
(SCC 3-07-007-60)
Douglas fir
(SCC 3-07-007-67)
Poplar
(SCC 3-07-007-69)
Radio-frequency heated
Unspecified pinesd
(SCC 3-07-007-70)
Emission
Control"
None
None
WESP
rws
None
None
None
None
None
VOCC
3.3e
0.70e-f
0.50e
0.61e-f
2.1e
27e,h
1.3eJ
0.033k-m
0.22e
EMISSION
FACTOR
RATING
E
E
D
E
E
D
D
E
E
Formaldehyde
ND
ND
ND
ND
ND
ND
ND
0.0023k
ND
EMISSION
FACTOR
RATING
E
a Factors represent uncontrolled emissions unless noted. SCC = Source Classification Code. ND = no data
available. All emission factors in units of pounds per thousand square feet of 3/8-inch thick veneer
(Ib/MSF 3/8). One Ib/MSF 3/8 = 0.5 kg/m3. Reference 19 except where noted.
b Emission control device: WESP = wet electrostatic precipitator; IWS = ionizing wet scrubber.
c Volatile organic compounds as propane.
d Based on data on the drying of mixed pine species or on the drying of veneers which are identified only as
pines.
e Emission factor may not account for formaldehyde, which is suspected to be present; VOC factor indicated
is likely to be biased low.
f Reference 10.
h References 10,19.
J References 10,14.
s Based on data on the drying of mixed fir species or on the drying of veneers which are identified only as
firs.
k Reference 12.
m Emission factor calculated as the sum of the factor for VOC and the factor for formaldehyde, based on a
separate measurement.
10.5-8
EMISSION FACTORS
9/97
-------
Table 10.5-4. EMISSION FACTORS FOR PLYWOOD PRESSES--PARTICULATE MATTER3
Source
Plywood press
PF resin
(SCC 3-07-007-80)
Filterable6
PM
0.12
EMISSION
FACTOR
RATING
D
PM-10
ND
EMISSION
FACTOR
RATING
Condensible0
0.083
EMISSION
FACTOR
RATING
D
a Reference 19. Emission factors units are pounds per thousand square feet of 3/8-inch thick panel (Ib/MSF
3/8). One Ib/MSF 3/8 = 0.5 kg/m3. SCC = Source Classification Code. ND = no data available. Factors
represent uncontrolled emissions. PF = phenol-formaldehyde.
b Filterable PM is that PM collected on or prior to the filter of an EPA Method 5 (or equivalent) sampling
train.
c Condensible PM is that PM collected in the impinger portion of a PM sampling train.
Table 10.5-5. EMISSION FACTORS FOR PLYWOOD PRESSES-FORMALDEHYDE AND VOCa
Source
Plywood press
PF resin
(SCC 3-07-007-80)
UF resin
(SCC 3-07-007-81)
UF resin, wet scrubber
(SCC 3-07-007-81)
FORMALDEHYDE
ND
0.0042
0.0025
EMISSION
FACTOR
RATING
E
E
vocb
0.33c'd
0.0216
0.0186
EMISSION
FACTOR
RATING
D
E
E
a Factors represent uncontrolled emissions unless noted. SCC = Source Classification Code. Reference 12
unless otherwise noted. ND = no data available. Emission factor units are pounds per thousand square feet
of 3/8-inch thick panel (Ib/MSF 3/8). One Ib/MSF 3/8 = 0.5 kg/m3. PF = phenol-formaldehyde; UF =
urea-formaldehyde.
Volatile organic compounds on a propane basis.
c Reference 19.
d Emission factor may not account for formaldehyde, which is suspected to be present; VOC factor indicated
is likely to be biased low.
e Emission factor calculated as the sum of the factor for VOC and the factor for formaldehyde, based on a
separate measurement.
9/97
Wood Products Industry
10.5-9
-------
Table 10.5-6. EMISSION FACTORS FOR PLYWOOD MANUFACTURING--
MISCELLANEOUS SOURCES3
Source
Log storage
(SCC 3-07-008-95)
Log debarking
(SCC 3-07-008-01)
Log bucking
(SCC 3-07-008-02)
Log steaming
(SCC 3-07-007-30)
Veneer cutting
(SCC 3-07-007-25)
Veneer layout and glue spreading
(SCC 3-07-007-27)
Plywood cutting
(SCC 3-07-007-10)
Plywood sanding
(SCC 3-07-007-02)
Plywood residue handling and transfer
(SCC 3-07-007- )
Plywood residue storage piles
(SCC 3-07-007- )
Pollutant
ND
ND
ND
ND
ND
ND
ND
ND
ND
ND
Emission
factor
EMISSION
FACTOR
RATING
SCC = Source Classification Code; ND = no data available.
10.5-10
EMISSION FACTORS
9/97
-------
References For Section 10.5
1. C. B. Hemming, Plywood, Kirk-Othmer Encyclopedia Of Chemical Technology, Second Edition,
Volume 15, John Wiley & Sons, Inc., New York, NY, 1968, pp. 896-907.
2. F. L. Monroe, et al., Investigation Of Emissions From Plywood Veneer Dryers, Washington State
University, Pullman, WA, February 1972.
3. T. Baumeister, ed., Plywood, Standard Handbook For Mechanical Engineers, Seventh Edition,
McGraw-Hill, New York, NY, 1967, pp. 6-162 through 6-169.
4. A. Mick, and D. McCargar, Air Pollution Problems In Plywood, Particleboard, And Hardboard
Mills In The Mid-Willamette Valley, Mid-Willamette Valley Air Pollution Authority, Salem, OR,
March 24, 1969.
5. Controlled And Uncontrolled Emission Rates And Applicable Limitations For Eighty Processes ,
Second Printing, EPA-340/1-78-004, U. S. Environmental Protection Agency, Research Triangle
Park, NC, April 1978, pp. X-l - X-6.
6. J. A. Danielson, ed., Air Pollution Engineering Manual, AP-40, Second Edition,
U. S. Environmental Protection Agency, Research Triangle Park, NC, May 1973, pp. 372-374.
7. Assessment Of Fugitive Particulate Emission Factors For Industrial Processes ,
EPA-450/3-78-107, U. S. Environmental Protection Agency, Research Triangle Park, NC,
September 1978.
8. C. T. Van Decar, Plywood Veneer Dryer Control Device, Journal Of The Air Pollution Control
Association, 22:968, December 1972.
9. Alternative Control Technology Document—PM-10 Emissions From The Wood Products Industry:
Plywood Manufacturing, Draft, U. S. Environmental Protection Agency, Research Triangle Park,
NC, September 1992.
10. A Study Of Organic Compound Emissions From Veneer Dryers And Means For Their Control,
Technical Bulletin No. 405, National Council of the Paper Industry for Air and Stream Improvement,
New York, August 1983.
11. Emission Test Report—Georgia-Pacific Springfield Plant, Springfield, Oregon , EMB
Report 81-PLY-4, U. S. Environmental Protection Agency, Research Triangle Park, NC, June 1981.
12. Source Test Report—Woodtech, Inc., Bluefield, Virginia, prepared for Woodtech, Inc., by
Environmental Quality Management, Inc., and Pacific Environmental Services, January 1992.
13. Emission Factor Documentation For AP-42 Section 10.5, U. S. Environmental Protection Agency,
Research Triangle Park, NC, July 1997.
14. Emission Test Report—Champion International Lebanon Plant, Lebanon, Oregon , EMB
Report 81-PLY-2, U. S. Environmental Protection Agency, Research Triangle Park, NC, May 1982.
15. Written communication from John Pinkerton, National Council of the Paper Industry for Air and
Stream Improvement, Inc., to Dallas Safriet, U. S. Environmental Protection Agency, Research
Triangle Park, NC, April 13, 1993.
9/97 Wood Products Industry 10.5-11
-------
16. Written communication from John Pinkerton, National Council of the Paper Industry for Air and
Stream Improvement, Inc., to Dallas Safriet, U. S. Environmental Protection Agency, Research
Triangle Park, NC, June 8, 1993.
17. Written communication and attachments from T. A. Crabtree, Smith Engineering Company,
Broomall, PA, to P. E. Lassiter, U. S. Environmental Protection Agency, Research Triangle Park,
NC, July 26, 1996.
18. Technical Memorandum, Minutes of the October 12-13, 1993 BACT Technologies Workshop,
Raleigh, NC, sponsored by the American Forest and Paper Association, K. D. Bullock, Midwest
Research Institute, Gary, NC, October 1993.
19. Oriented Strandboard And Plywood Air Emission Databases, Technical Bulletin No. 694 , the
National Council of the Paper Industry for Air and Stream Improvement, New York, NY,
April 1995.
20. A. E. Cavadeas, RTO Experience In The Wood Products Industry, Presented at Environmental
Challenges: What's New in the Wood Products Industry?, workshop sponsored by the American
Forest and Paper Association, Research Triangle Park, NC, February 4-5, 1997.
10.5-12 EMISSION FACTORS 9/97
-------
APPENDIX A
EMISSION FACTOR CALCULATION SPREADSHEETS
This appendix presents printouts of the detailed spreadsheets that were constructed in order to
calculate emission factors for plywood veneer dryers and presses. Table A-l presents the calculations for
plywood veneer dryers. Table A-2 presents the calculations for plywood presses. Table A-3 presents a
summary of Method 25 and Method 25A VOC data and available formaldehyde data for plywood veneer
dryers and presses.
As discussed in Section 4.3.1 of this report, the data available for some of the specific emission
factors developed included the results of multiple tests on the same emission source. In such cases, the test-
specific emission factors for the same source were averaged first, and that average emission factor then was
averaged with the factors for the other sources to yield the candidate emission factors for AP-42. In Table A-
1, the emission factor column is divided into two subcolumns, "Test," and "Dryer". The emission factor
column labeled "Test" includes the available test-specific emission factors. The emission factor column
labeled "Dryer" includes averages of test-specific emission factors for the same dryer. For dryers where only
one test-specific emission factor was available, that emission factor appears in both the "Test" and "Dryer"
columns. The AP-42 candidate emission factors were developed by averaging the dryer average emission
factors in the "Dryer" column. A parallel structure applies to Table A-2 for plywood presses.
A-l
-------
11.17 Lime Manufacturing
11.17.1 Process Description' "5
Lime is the high-temperature product of the calcination of limestone. Although limestone deposits
are found in every state, only a small portion is pure enough for industrial lime manufacturing. To be
classified as limestone, the rock must contain at least 50 percent calcium carbonate. When the rock contains
30 to 45 percent magnesium carbonate, it is referred to as dolomite, or dolomitic limestone. Lime can also be
produced from aragonite, chalk, coral, marble, and sea shells. The Standard Industry Classification (SIC)
code for lime manufacturing is 3274. The six-digit Source Classification Code (SCC) for lime manufacturing
is 3-05-016.
Lime is manufactured in various kinds of kilns by one of the following reactions:
CaCO3 + heat -* CO2 + CaO (high calcium lime)
CaCO3-MgCO3 + heat - 2CO2 + CaOMgO (dolomitic lime)
In some lime plants, the resulting lime is reacted (slaked) with water to form hydrated lime. The basic
processes in the production of lime are: (1) quarrying raw limestone; (2) preparing limestone for the kilns by
crushing and sizing; (3) calcining limestone; (4) processing the lime further by hydrating; and
(5) miscellaneous transfer, storage, and handling operations. A generalized material flow diagram for a lime
manufacturing plant is given in Figure 11.17-1. Note that some operations shown may not be performed in
all plants.
The heart of a lime plant is the kiln. The prevalent type of kiln is the rotary kiln, accounting for
about 90 percent of all lime production in the United States. This kiln is a long, cylindrical, slightly inclined,
refractory-lined furnace, through which the limestone and hot combustion gases pass countercurrently. Coal,
oil, and natural gas may all be fired in rotary kilns. Product coolers and kiln feed preheaters of various types
are commonly used to recover heat from the hot lime product and hot exhaust gases, respectively.
The next most common type of kiln in the United States is the vertical, or shaft, kiln. This kiln can
be described as an upright heavy steel cylinder lined with refractory material. The limestone is charged at the
top and is calcined as it descends slowly to discharge at the bottom of the kiln. A primary advantage of
vertical kilns over rotary kilns is higher average fuel efficiency. The primary disadvantages of vertical kilns
are their relatively low production rates and the fact that coal cannot be used without degrading the quality of
the lime produced. There have been few recent vertical kiln installations in the United States because of high
product quality requirements.
Other, much less common, kiln types include rotary hearth and fluidized bed kilns. Both kiln types
can achieve high production rates, but neither can operate with coal. The "calcimatic" kiln, or rotary hearth
kiln, is a circular kiln with a slowly revolving doughnut-shaped hearth. In fluidized bed kilns, finely divided
limestone is brought into contact with hot combustion air in a turbulent zone, usually above a perforated
2/98 Mineral Products Industry 11.17-1
-------
!
3
'
i
i
LIMEST
HIGH CALCIUM AND DOLOMITIC LIMESTONE 1
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QUARRY AND MINE OPERATIONS
(DRILLING. BLASTING. AND
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SCC DESCRIPTION
(A) =306018-01
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(5) =305-016-07
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©=305016-09
@ =305016-10
© =306016-11
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© = 3O5O16-13
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(5) =3O5O16-27
n RA-R < rm 1 lUPCTrVJC
FOR ROTARY KILNS
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PRIMARY CRUSHING
SECONDARY CRUSHING/SCREENING
i CALCINING
RAW MATERIAL TRANSFER
RAW MATERIAL UNLOADING
HYDRATOR ATMOSPHERIC
RAW MATERIAL STORAGE PILES
PRODUCT COOLER
PRESSURE HYDRATOR
LIME SILOS
PACKAGING/SHIPPING
PRODUCT TRANSFER
PRIMARY SCREENING
CONVEYOR TRANSFER, PRIMARY
CRUSHED MATERIAL
SECONDARY/TERTIARY SCREENING
PRODUCT LOADING. ENCLOSED TRUCK
PRODUCT LOADING, OPEN TRUCK
FUEL
, 1
CLASSIFICATION ©[— ^STONE^ >-| CALCINATION (£)|
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STORAGE. PACKAGING. AND SHIPPING (*)
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Figure 11.17-1. Process flow diagram for lime manufacturing.4
(SCC = Source Classification Code.)
11.17-2
EMISSION FACTORS
2/98
-------
grate. Because of the amount of lime carryover into the exhaust gases, dust collection equipment must be
installed on fluidized bed kilns for process economy.
Another alternative process that is beginning to emerge in the United States is the parallel flow
regenerative (PR) lime kiln. This process combines 2 advantages. First, optimum heating conditions for lime
calcining are achieved by concurrent flow of the charge material and combustion gases. Second, the multiple-
chamber regenerative process uses the charge material as the heat transfer medium to preheat the combustion
air. The basic PR system has 2 shafts, but 3 shaft systems are used with small size grains to address the
increased flow resistance associated with smaller feed sizes.
In the 2-shaft system, the shafts alternate functions, with 1 shaft serving as the heating shaft and the
other as the flue gas shaft. Limestone is charged alternatively to the 2 shafts and flows downward by gravity
flow. Each shaft includes a heating zone, a combustion/burning zone, and a cooling zone. The 2 shafts are
connected in the middle to allow gas flow between them. In the heating shaft, combustion air flows
downward through the heated charge material. After being preheated by the charge material, the combustion
air combines with the fuel (natural gas or oil), and the air/fuel mixture is fired downward into the combustion
zone. The hot combustion gases pass from the combustion zone in the heating shaft to the combustion zone
in the flue gas shaft. The heated exhaust gases flow upward through the flue gas shaft combustion zone and
into the preheating zone where they heat the charge material. The function of the 2 shafts reverses on a 12-
minute cycle. The bottom of both shafts is a cooling zone. Cooling air flows upward through the shaft
countercurrently to the flow of the calcined product. This air mixes with the combustion gases in the
crossover area providing additional combustion air. The product flows by gravity from the bottom of both
shafts.
About 15 percent of all lime produced is converted to hydrated (slaked) lime. There are 2 kinds of
hydrators: atmospheric and pressure. Atmospheric hydrators, the more prevalent type, are used in
continuous mode to produce high-calcium and dolomitic hydrates. Pressure hydrators, on the other hand,
produce only a completely hydrated dolomitic lime and operate only in batch mode. Generally, water sprays
or wet scrubbers perform the hydrating process and prevent product loss. Following hydration, the product
may be milled and then conveyed to air separators for further drying and removal of coarse fractions.
The major uses of lime are metallurgical (aluminum, steel, copper, silver, and gold industries),
environmental (flue gas desulfurization, water softening, pH control, sewage-sludge destabilization, and
hazardous waste treatment), and construction (soil stabilization, asphalt additive, and masonry lime).
11.17.2 Emissions And ControlsM-6
Potential air pollutant emission points in lime manufacturing plants are indicated by SCC in
Figure 11.17-1. Except for gaseous pollutants emitted from kilns, particulate matter (PM) is the only
dominant pollutant. Emissions of filterable PM from rotary lime kilns constructed or modified after May 3,
1977 are regulated to 0.30 kilograms per megagram (kg/Mg) (0.60 pounds per ton [lb/ton]) of stone feed
under 40 CFR Part 60, subpart HH.
The largest ducted source of particulate is the kiln. The properties of the limestone feed and the ash
content of the coal (in coal-fired kilns) can significantly affect PM emission rates. Of the various kiln types,
fluidized beds have the highest levels of uncontrolled PM emissions because of the very small feed rate
combined with the high air flow through these kilns. Fluidized bed kilns are well controlled for maximum
product recovery. The rotary kiln is second worst in uncontrolled PM emissions because of the small feed
rate and relatively high air velocities and because of dust entrainment caused by the rotating chamber. The
calcimatic (rotary hearth) kiln ranks third in dust production primarily because of the larger feed rate and the
2/98 Mineral Products Industry 11.17-3
-------
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, the relatively low air velocities, and the slow
movement of material through the kiln. In coal-fired kilns, the properties of the limestone feed and the ash
content of the coal can significantly affect PM emissions.
Some sort of particulate control is generally applied to most kilns. Rudimentary fallout chambers
and cyclone separators are commonly used to control the larger particles. Fabric and gravel bed filters, wet
(commonly venturi) scrubbers, and electrostatic precipitators are used for secondary control.
Carbon monoxide (CO), carbon dioxide (CO2), sulfur dioxide (SO2), and nitrogen oxides (NOX) are
all produced in kilns. Sulfur dioxide emissions are influenced by several factors, including the sulfur content
of the fuel, the sulfur content and mineralogical form (pyrite or gypsum) of the stone feed, the quality of lime
being produced, and the type of kiln. Due to variations in these factors, plant-specific SO2 emission factors
are likely to vary significantly from the average emission factors presented here. The dominant source of
sulfur emissions is the kiln's fuel, and the vast majority of the fuel sulfur is not emitted because of reactions
with calcium oxides in the kiln. Sulfur dioxide emissions may be further reduced if the pollution equipment
uses a wet process or if it brings CaO and SO2 into intimate contact.
Carbon dioxide is emitted from the kiln as a result of the carbonate in the limestone being reduced to
CO2 gas, and the carbon in the fuel oxidizing. If CO2 emissions from the fuel combustion are estimated
using data from Chapter 1 (External Combustion Sources) only non-combustion CO2 emission factors should
be used (915 kg/Mg (1830 Ib/ton) lime produced for dolomitic limestone and 785 kg/Mg (1570 Ib/ton) lime
produced for calcitic limestone). These estimates are theoretical, based on the production of two moles of
CO2 for each mole of limestone produced. In some facilities a portion of the CO2 generated is recovered for
use in sugar refining.
In sugar refining, a suspension of hydrated lime in water is used to adjust the pH of the product
stream and precipitate colloidal impurities. The lime is then removed by reaction with carbon dioxide.
Product coolers are emission sources only when some of their exhaust gases are not recycled through
the kiln for use as combustion air. The trend is away from the venting of product cooler exhaust, however, to
maximize fuel use efficiencies. Cyclones, baghouses, and wet scrubbers have been used 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 operation, particulate emissions may also result from drilling and blasting. Emission factors for some
of these operations are presented in Sections 11.19 and 13.2 of this document.
Tables 11.17-1 (metric units) and 11.17-2 (English units) present emission factors for PM emissions
from lime manufacturing calcining, cooling, and hydrating. Tables 11.17-3 (metric units) and 11.17-4
(English units) include emission factors for the mechanical processing (crushing, screening, and grinding) of
limestone and for some materials handling operations. Section 11.19, Construction Aggregate Processing,
also includes stone processing emission factors that are based on more recent testing, and, therefore, may be
more representative of emissions from stone crushing, grinding, and screening. In addition, Section 13.2,
Fugitive Dust Sources, includes emission factors for materials handling that may be more representative of
materials handling emissions than the emission factors in Tables 11.17-3 and 11.17-4.
Emission factors for emissions of SO2, NOX, CO, and CO2 from lime manufacturing are presented in
Tables 11.17-5 and 11.17-6. Particle size distribution for rotary lime kilns is provided in Table 11.17-7.
11.17-4 EMISSION FACTORS 2/98
-------
Because of differences in the sulfur content of the raw material and fuel and in process operations, a
mass balance on sulfur may yield a more representative emission factor for a specific facility than the SO2
emission factors presented in Tables 11.17-5 and 11.17-6. In addition, CO2 emission factors estimated using
a mass balance on carbon may be more representative for a specific facility than the CO2 emission factors
presented in Tables 11.17-5 and 11.17-6. Additional information on estimating emission factors for CO2
emissions from lime kilns can be found in the background report for this AP-42 section.
11.17.3 Updates Since the Fifth Edition
The Fifth Edition was released in January 1995. Revisions to this section since that date are
summarized below. For further detail, consult the memoranda describing each supplement or the background
report for this section. These and other documents can be found on the EFIG home page
(http ://w ww.epa. go v/ttn/chief).
Supplement D.June 1998
• Revision made to distinguish between the carbon dioxide that is emitted from a kiln as a result of the
carbonate in the limestone being reduced to CO2 gas, and the carbon in the fuel oxidizing (based on
information already contained in the background report).
• Note added to indicate that some of the CO2 created in lime manufacturing is used in sugar refining.
• The report cited for the above information was added to the reference section as reference number 7.
This changed the numbering for the subsequent references.
• The background document was not revised.
2/98 Mineral Products Industry 11.17-5
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FACTOR
RATING
CU
U
B
o
Q
Z
Q
Z
Q
Z
a
N
S
o
(N
5>o
•3 g
(U CO
gy
*-* ^^
o S
"to ^
•S'-s
fl
a
Q
Q
o
°
Q
Z
Q
§
r~
S
o
1
X)
o
on
5
^
'?
o ^,
II
J3 O
•eg
o — <
-------
Table 11.17-3 (Metric Units). EMISSION FACTORS FOR LIME MANUFACTURING
RAW MATERIAL AND PRODUCT PROCESSING AND HANDLING2
Source
Primary crushed
(SCC 3-05-016-01)
Scalping screen and hammermill (secondary crusher)0
(SCC 3-05-0 16-02)
Primary crusher with fabric filterd
(SCC 3-05-016-01)
Primary screen with fabric filter6
(SCC 3-05-0 16- 16)
Crushed material conveyor transfer with fabric filte/
(SCC 3-05-016-24)
Secondary and tertiary screen with fabric filter8
(SCC 3-05-016-25)
Product transfer and conveying
(SCC3-05-016-15)h
Product loading, enclosed truck
(SCC 3-05-0 16-26)h
Product loading, open truck
(SCC3-05-016-27)h
Filterableb
PM
0.0083
0.31
0.00021
0.0030
4.4x1 0'5
6.5xlO'5
1.1
0.31
0.75
EMISSION
FACTOR
RATING
E
E
D
D
D
D
E
D
D
PM-10
ND
ND
ND
ND
ND
ND
ND
ND
ND
EMISSION
FACTOR
RATING
a Factors represent uncontrolled emissions unless otherwise noted. Factors are kg/Mg of material
processed unless noted. ND = no data. SCC = Source Classification Code.
b Filterable PM is that PM collected on or before the filter of an EPA Method 5 (or equivalent)
sampling train.
c Reference 8; units of kg/Mg of stone processed.
d Reference 35. Emission factors in units of kg/Mg of material processed. Includes scalping screen,
scalping screen discharges, primary crusher, primary crusher discharges, and ore discharge.
e Reference 35. Emission factors in units of kg/Mg of material processed. Includes primary screening,
including the screen feed, screen discharge, and surge bin discharge.
Reference 35. Emission factors in units of kg/Mg of material processed. Based on average of three
runs each of emissions from two conveyor transfer points on the conveyor from the primary crusher
to the primary stockpile.
g Reference 35. Emission factors in units of kg/Mg of material processed. Based on sum of emissions
from two emission points that include conveyor transfer point for the primary stockpile underflow to
the secondary screen, secondary screen, tertiary screen, and tertiary screen discharge.
Reference 12; units of kg/Mg of product loaded.
11.17-10
EMISSION FACTORS
2/98
-------
Table 11.17-4 (English Units). EMISSION FACTORS FOR LIME MANUFACTURING
RAW MATERIAL AND PRODUCT PROCESSING AND HANDLING3
Source
Primary crushed
(SCC 3-05-016-01)
Scalping screen and hammermill (secondary crusher)
(SCC 3-05-016-02)c
Primary crusher with fabric filterd
(SCC 3-05-016-01)
Primary screen with fabric filter6
(SCC 3-05-016-16)
Crushed material conveyor transfer with fabric filter
(SCC 3-05-016-24)
Secondary and tertiary screen with fabric filter8
(SCC 3-05-016-25)
Product transfer and conveying
(SCC3-05-016-15)h
Product loading, enclosed truck
(SCC3-05-016-26)h
Product loading, open truck
(SCC3-05-016-27)h
Filterable15
PM
0.017
0.62
0.00043
0.00061
8.8xlO'5
0.00013
2.2
0.61
1.5
EMISSION
FACTOR
RATING
E
E
D
D
D
D
E
D
D
PM-10
ND
ND
ND
ND
ND
ND
ND
ND
ND
EMISSION
FACTOR
RATING
a Factors represent uncontrolled emissions unless otherwise noted. Factors are Ib/ton of material
processed unless noted. ND = no data. SCC = Source Classification Code.
b Filterable PM is that PM collected on or before the filter of an EPA Method 5 (or equivalent)
sampling train.
c Reference 8; factors are Ib/ton.
d Reference 35. Factors are Ib/ton of material processed. Includes scalping screen, scalping screen
discharges, primary crusher, primary crusher discharges, and ore discharge.
e Reference 35. Factors are Ib/ton of material processed. Includes primary screening, including the
screen feed, screen discharge, and surge bin discharge.
Reference 35. Factors are Ib/ton of material processed. Based on average of three runs each of
emissions from two conveyor transfer points on the conveyor from the primary crusher to the primary
stockpile.
Reference 35. Emission factors in units of kg/Mg of material processed. Based on sum of emissions
from two emission points that include conveyor transfer point for the primary stockpile underflow to
the secondary screen, secondary screen, tertiary screen, and tertiary screen discharge.
Reference 12; units are Ib/ton of product loaded.
f
2/98
Mineral Products Industry
11.17-11
-------
c
D
o
•fi
ID
3
i
u
o
o
z
CO
CO
1
ft p
< <
O
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EMISSION
FACTOR
RATING
O
Z
1
II
o
(2
"S
•w
o
c
u
GO
1
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•S
o
GO
GO
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ssions
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w —
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Factors rep
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Mass balan
References
References
CJ "O
-------
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o
o
•3
co
CO
O\ O ,—1
CO
ID
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DUD
O O O
G C C
ESS
G> (D D D O D O
O O O O O O
C C C C C C
a a H a a a
O u U u u o
U 1)
u o
2/98
Mineral Products Industry
11.17-13
-------
D
00
*yr
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u
6
u
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o
u
^* ^^ f *•)
2 o z
GO H ft
§ < <
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oo (J H
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ogo
co H a
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6
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00
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0
m
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Q
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10
C s-*.
32
3 S
S iA
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U CO
(S U
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Q
Z
Q
Q-
r-
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i_2 ^^
>•* *^o
3 o
Is
u to
^8
o 52
U
Q
Q
Z
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Z
tIJ
S
o
Q
"S
m
O
u.
1
Be
'i
c ^^
~ 22
2 o
S ^
•o 9
u m
Coal-fired rotary preheater kiln with di
PM controls (SCC 3-05-016-22)
U
8
u
m
VO
Q
Z
Q
Z
u
•^
M3
S
Coal-fired rotary preheater kiln with
multiclone, water spray, and fabric fi
(SCC 3-05-016-22)
a
8
cs
Q
Z
Q
in
O
Q
Q
1 Gas-fired calcimatic kiln
(SCC 3-05-016-05)
Q
Q
-
Tf
0
Q
•^
o
Q
Z
Q
"(S
8
o
c
12 -^
•* ro
0 ts,
•a ^>
cs ^-*
s s
GO i
D m
i§
S B
03 o
"*? -S
ca '>
O
m
•So
Q
Z
Q
Z
Q
Z
Q
Z
Product cooler
(SCC 3-05-0 16-11)
ontrolled emissions unless otherwise noted. Factors are Ib/ton of lime produced unless noted. ND = no data. SCC = Source
CJ
E
3
B
U
00
D,
a*
oo
i_<
O
^
UH
•o
o
U
B
• P-<
lassifical
U
ur may yield a more representative emission factor for a specific facility.
"3
00
0
U
O
B
13
.0
oo
oo
s
ion may yield a more representative emission factor for a specific facility.
t i
O
B
O
u
o
B
oa
JO
oo
s
O
CN
'-^
00
eference
&
CO
m^
CO
o"
(N
CO
t— 1
00
eference
OS
R.
o"
(M
oo
eference
&
11.17-14
EMISSION FACTORS
2/98
-------
o
o
ro
-------
Table 11.17-7. AVERAGE PARTICLE SIZE DISTRIBUTION FOR ROTARY
LIME KILNS3
Particle Size
Gum)
2.5
5.0
10.0
15.0
20.0
Cumulative Mass Percent Less Than Stated Particle Size
Uncontrolled Rotary
Kiln
1.4
2.9
12
31
ND
Rotary Kiln With
Multiclone
6.1
9.8
16
23
31
Rotary Kiln With
ESP
14
ND
50
62
ND
Rotary Kiln With
Fabric Filter
27
ND
55
73
ND
a Reference 4, Table 4-28; based on A- and C-rated particle size data. Source Classification Codes 3-05-
016-04, and -18 to -21. ND = no data.
References For Section 11.17
1. Screening Study For Emissions Characterization From Lime Manufacture, EPA Contract
No. 68-02-0299, Vulcan-Cincinnati, Inc., Cincinnati, OH, August 1974.
2. Standards Support And Environmental Impact Statement, Volume I: Proposed Standards Of
Performance For Lime Manufacturing Plants, EPA-450/2-77-007a, U. S. Environmental Protection
Agency, Research Triangle Park, NC, April 1977.
3. National Lime Association, Lime Manufacturing, Air Pollution Engineering Manual, Buonicore,
Anthony J. and Wayne T. Davis (eds.), Air and Waste Management Association, Van Nostrand
Reinhold, New York, 1992.
4. J. S. Kinsey, Lime And Cement Industry-Source Category Report, Volume I: Lime Industry,
EPA-600/7-86-031, U. S. Environmental Protection Agency, Cincinnati, OH, September 1986.
5. Written communication from J. Bowers, Chemical Lime Group, Fort Worth, TX, to R. Marinshaw,
Midwest Research Institute, Gary, NC, October 28, 1992.
6. Written communication from A. Seeger, Morgan, Lewis & Bockius, to R. Myers, U. S.
Environmental Protection Agency, Research Triangle Park, NC, November 3, 1993.
7. Minerals Yearbook: Lime Annual Report, U. S. Department of Interior, Washington, DC, 1993.
8. Air Pollution Emission Test, J. M. Brenner Company, Lancaster, PA, EPA Project No. 75-STN-7,
U. S. Environmental Protection Agency, Office of Air Quality Planning and Standards, Research
Triangle Park, NC, November 1974.
9. D. Crowell et al, Test Conducted at Marblehead Lime Company, Bellefonte, PA, Report on the
Particulate Emissions from a Lime Kiln Baghouse, Marblehead, Lime Company, Chicago, IL,
July 1975.
10. Stack Sampling Report of Official Air Pollution Emission Tests Conducted on Kiln No. 1 at
J. E. Baker Company, Millersville, OH, Princeton Chemical Research, Inc., Princeton, NJ,
March 1975.
11.17-16
EMISSION FACTORS
2/98
-------
11. W. R. Feairheller, and T. L. Peltier, Air Pollution Emission Test, Virginia Lime Company,
Ripplemead, VA, EPA Contract No. 68-02-1404, Task 11, (EPA, Office of Air Quality Planning and
Standards), Monsanto Research Corporation, Dayton, OH, May 1975.
12. G. T. Cobb et al., Characterization oflnhalable Particulate Matter Emissions from a Lime Plant,
Vol. I, EPA-600/X-85-342a, Midwest Research Institute, Kansas City, MO, May 1983.
13. W. R. Feairheller et al., Source Test of a Lime Plant, Standard Lime Company, Woodville, OH,
EPA Contract No. 68-02-1404, Task 12 (EPA, Office of Air Quality Planning and Standards),
Monsanto Research Corporation, Dayton, OH, December 1975.
14. Air Pollution Emission Test, Dow Chemical, Freeport, TX, Project Report No. 74-LIM-6,
U. S. Environmental Protection Agency, Office of Air Quality Planning and Standards, Research
Triangle Park, NC, May 1974.
15. J. B. Schoch, Exhaust Gas Emission Study, J. E. Baker Company, Millersville, OH, George D.
Clayton and Associates, Southfield, MI, June 1974.
16. Stack Sampling Report of Official Air Pollution Emission Tests Conducted on Kiln No. 2 Scrubber
atj. E. Baker Company, Millersville, OH, Princeton Chemical Research, Inc., Princeton, NJ, May
1975.
17. R. L. Maurice and P. F. Allard, Stack Emissions on No. 5 Kiln, Paul Lime Plant, Inc., Engineers
Testing Laboratories, Inc., Phoenix, AZ, June 1973.
18. R. L. Maurice, and P. F. Allard, Stack Emissions Analysis, U.S. Lime Plant, Nelson, AZ, Engineers
Testing Laboratories, Inc., Phoenix, AZ, May 1975.
19. T. L. Peltier, Air Pollution Emission Test, Allied Products Company, Montevallo, AL, EPA
Contract No. 68-02-1404, Task 20 (EPA, Office of Air Quality Planning and Standards), Monsanto
Research Corporation, Dayton, OH, September 1975.
20. T. L. Peltier, Air Pollution Emission Test, Martin-Marietta Corporation, Calera, AL, (Draft), EMB
Project No. 76-LIM-9, U. S. Environmental Protection Agency, Office of Air Quality Planning and
Standards, Research Triangle Park, NC, September 1975.
21. Report on the Particulate Emissions from a Lime Kiln Baghouse (Exhibit 1 supplied by the
National Lime Association), August 1977.
22. Report on the Particulate Emissions from a Lime Kiln Baghouse (Exhibit 2 supplied by the
National Lime Association), May 1977.
23. Report on the Particulate Emissions from a Lime Kiln Baghouse (Exhibit 3 supplied by the
National Lime Association), May 1977.
24. Air Pollution Emission Test, U.S. Lime Division, Flintkote Company, City of Industry, CA, Report
No. 74-LIM-5, U. S. Environmental Protection Agency, Office of Air Quality Planning and
Standards, Research Triangle Park, NC, October 1974.
25. T. L. Peltier and H. D. Toy, Particulate and Nitrogen Oxide Emission Measurements from Lime
Kilns, EPA Contract No. 68-02-1404, Task No. 17, (EPA, National Air Data Branch, Research
Triangle Park, NC), Monsanto Research Corporation, Dayton, OH, October 1975.
26. Air Pollution Emission Test, Kilns 4, 5, and 6, Martin-Marietta Chemical Corporation, Woodville,
OH, EMB Report No. 76-LIM-12, U. S. Environmental Protection Agency, Office of Air Quality
Planning and Standards, Research Triangle Park, NC, August 1976.
2/98 Mineral Products Industry 11.17-17
-------
27. Air Pollution Emission Test, Kilns 1 and 2. J. E. Baker Company. Millersville. OH, EMB Project
No. 76-LIM-l 1, U. S. Environmental Protection Agency, Office of Air Quality Planning and
Standards, Research Triangle Park, NC, August 1976.
28. Particulate Emission Tests Conducted on the Unit #2 Lime Kiln in Alabaster, Alabama, for Allied
Products Corporation, Guardian Systems, Inc., Leeds, AL, October 1990.
29. Particulate Emission Tests Conducted on #1 Lime Kiln in Alabaster, Alabama, for Allied Products
Corporation, Guardian Systems, Inc., Leeds, AL, October 1991.
30. Mass Emission Tests Conducted on the #2 Rotary Lime Kiln in Saginaw, Alabama, For SI Lime
Company, Guardian Systems, Inc., Leeds, AL, October 1986.
31. Flue Gas Characterization Studies Conducted on the #4 Lime Kiln in Saginaw, Alabama, for
Dravo Lime Company, Guardian Systems, Inc., Leeds, AL, July 1991.
32. R. D. Rovang, Trip Report, Paul Lime Company, Douglas, AZ, U. S. Environmental Protection
Agency, Office of Air Quality Planning and Standards, Research Triangle Park, NC, January 1973.
33. T. E. Eggleston, Air Pollution Emission Test, Bethlehem Mines Corporation Annville, PA, EMB
Test No. 74-LIM-l, U. S. Environmental Protection Agency, Office of Air Quality Planning and
Standards, Research Triangle Park, NC, August 1974.
34. Air Pollution Emission Test, Marblehead Lime Company, Gary, Indiana, Report No. 74-LIM-7,
U. S. Environmental Protection Agency, Office of Air Quality Planning and Standards, Research
Triangle Park, NC, 1974.
35. Emissions Survey Conducted at Chemstar Lime Company, Located in Bancroft, Idaho, American
Environmental Testing Company, Inc., Spanish Fork, Utah, February 26, 1993.
11.17-18 EMISSION FACTORS 2/98
-------
12.1 Primary Aluminum Production
12.1.1 General1
Primary aluminum refers to aluminum produced directly from mined ore. The ore is refined and
electrolytically reduced to elemental aluminum. There are 13 companies operating 23 primary aluminum
reduction facilities in the U. S. In 1991, these facilities produced 4.5 million tons of primary aluminum.
12.1.2 Process Description2"3
Primary aluminum production begins with the mining of bauxite ore, a hydrated oxide of aluminum
consisting of 30 to 56 percent alumina (A12O3) and lesser amounts of iron, silicon, and titanium. The ore is
refined into alumina by the Bayer process. The alumina is then shipped to a primary aluminum plant for
electrolytic reduction to aluminum. The refining and reducing processes are seldom accomplished at the same
facility. A schematic diagram of primary aluminum production is shown in Figure 12.1-1.
12.1.2.1 Bayer Process Description -
In the Bayer process, crude bauxite ore is dried, ground in ball mills, and mixed with a preheated
spent leaching solution of sodium hydroxide (NaOH). Lime (CaO) is added to control phosphorus content
and to improve the solubility of alumina. The resulting slurry is combined with sodium hydroxide and
pumped into a pressurized digester operated at 221 to 554°F. After approximately 5 hours, the slurry of
sodium aluminate (NaAl2OH) solution and insoluble red mud is cooled to 212°F and sent through either a
gravity separator or a wet cyclone to remove coarse sand particles. A flocculent, such as starch, is added to
increase the settling rate of the red mud. The overflow from the settling tank contains the alumina in solution,
which is further clarified by filtration and then cooled. As the solution cools, it becomes supersaturated with
sodium aluminate. Fine crystals of alumina trihydrate (A12O3 • 3H2O) are seeded in the solution, causing the
alumina to precipitate out as alumina trihydrate. After being washed and filtered, the alumina trihydrate is
calcined to produce a crystalline form of alumina, which is advantageous for electrolysis.
12.1.2.2 Hall-Heroult Process -
Crystalline A12O3 is used in the Hall-Heroult process to produce aluminum metal. Electrolytic
reduction of alumina occurs in shallow rectangular cells, or "pots", which are steel shells lined with carbon.
Carbon electrodes extending into the pot serve as the anodes, and the carbon lining serves as the cathode.
Molten cryolite (Na3AlF6) functions as both the electrolyte and the solvent for the alumina. The electrolytic
reduction of A12O3 by the carbon from the electrode occurs as follows:
2A12O3 + 3C - 4A1 + 3CO2 (1)
Aluminum is deposited at the cathode, where it remains as molten metal below the surface of the
cryolite bath. The carbon anodes are continuously depleted by the reaction. The aluminum product is tapped
every 24 to 48 hours beneath the cryolite cover, using a vacuum siphon. The aluminum is then transferred to
a reverberatory holding furnace where it is alloyed, fluxed, and
2/98 Metallurgical Industry 12.1-1
-------
Figure 12.1-1. Schematic diagram of aluminum production process. (Source Classification
Codes in parentheses.)
12.1-2
EMISSION FACTORS
2/98
-------
degassed to remove trace impurities. (Aluminum reverberatory furnace operations are discussed in detail in
Section 12.8, "Secondary Aluminum Operations".) From the holding furnace, the aluminum is cast or
transported to fabricating plants.
Three types of aluminum reduction cells are now in use: prebaked anode cell (PB), horizontal stud
Soderberg anode cell (HSS), and vertical stud Soderberg anode cell (VSS). Most of the aluminum produced
in the U. S. is processed using the prebaked cells.
All three aluminum cell configurations require a "paste" (petroleum coke mixed with a pitch binder).
Paste preparation includes crushing, grinding, and screening of coke and blending with a pitch binder in a
steam jacketed mixer. For Soderberg anodes, the thick paste mixture is added directly to the anode casings.
In contrast, the prebaked ("green") anodes are produced as an ancillary operation at a reduction plant.
In prebake anode preparation, the paste mixture is molded into green anode blocks ("butts") that are
baked in either a direct-fired ring furnace or a Reid Hammer furnace, which is indirectly heated. After
baking, steel rods are inserted and sealed with molten iron. These rods become the electrical connections to
the prebaked carbon anode. Prebaked cells are preferred over Soderberg cells because they are electrically
more efficient and emit fewer organic compounds.
12.1.3 Emissions And Controls2"10
Controlled and uncontrolled emission factors for total paniculate matter, gaseous fluoride, and
particulate fluoride are given in Table 12.1-1. Table 12.1-2 gives available data for size-specific paniculate
matter emissions for primary aluminum industry processes.
In bauxite grinding, hydrated aluminum oxide calcining, and materials handling operations, various
dry dust collection devices (centrifugal collectors, multiple cyclones, or Electrostatic precipitators (ESPs)
and/or wet scrubbers) have been used. Large amounts of particulate are generated during the calcining of
hydrated aluminum oxide, but the economic value of this dust leads to the use of extensive controls which
reduce emissions to relatively small quantities.
Emissions from aluminum reduction processes are primarily gaseous hydrogen fluoride and
particulate fluorides, alumina, carbon monoxide, carbon dioxide (CO2), volatile organics, and sulfur dioxide
(SO2) from the reduction cells. The source of fluoride emissions from reduction cells is the fluoride
electrolyte, which contains cryolite, aluminum fluoride (A1F3), and fluorospar (CaF2). The dissociation of the
molten cryolite is the source of the perfluorinated carbons (PFCs) —
tetrafluoromethane (CF4) and hexafluoroethane (C2F6) — which are formed during anode effects. The
factors related to the formation of PFCs are not currently well understood, but they can be formed either by
direct reaction of the fluorine with the carbon anode or electrochemically.J1 The emission factors for CF4 and
C2F6 presented here should be used with caution due to the lack of information on their formation.
Table 12.1-3 presents emission factors for greenhouse gases. The CO2 emission factors shown in
Table 12.1-3 assume that all of the carbon used in the production process is emitted as CO2. While some of
the carbon is emitted as CO, there is insufficient data to develop emission factors for CO. Therefore, the
carbon emitted as CO is treated here as CO2 because it is assumed that it will eventually be oxidized to CO2
after being emitted. Because the primary source of carbon in the anodes is petroleum coke (some is also from
the pitch binder), care must be taken not to double count CO2 emissions in a greenhouse gas emissions
inventory if the CO2 emissions from aluminum production are also accounted for as a non-fuel use of
petroleum coke.
2/98 Metallurgical Industry 12.1-3
-------
Particulate emissions from reduction cells include alumina and carbon from anode dusting, and
cryolite, aluminum fluoride, calcium fluoride, chiolite (Na5Al3F14), and ferric oxide. Representative size
distributions for fugitive emissions from PB and HSS plants, and for particulate emissions from HSS cells,
are presented in Table 12.1-2.
Emissions from reduction cells also include hydrocarbons or organics, carbon monoxide, and sulfur
oxides. These emission factors are not presented here because of a lack of data. Small amounts of
hydrocarbons are released by PB pots, and larger amounts are emitted from HSS and VSS pots. In vertical
cells, these organics are incinerated in integral gas burners. Sulfur oxides originate from sulfur in the anode
coke and pitch, and concentrations of sulfur oxides in VSS cell emissions range from 200 to 300 parts per
million. Emissions from PB plants usually have SO2 concentrations ranging from 20 to 30 parts per million.
Emissions from anode bake ovens include the products of fuel combustion; high boiling organics
from the cracking, distillation, and oxidation of paste binder pitch; sulfur dioxide from the sulfur in carbon
paste, primarily from the petroleum coke; fluorides from recycled anode butts; and other particulate matter.
Emission factors for these components are not included in this document due to insufficient data.
Concentrations of uncontrolled SO2 emissions from anode baking furnaces range from 5 to 47 parts per
million (based on 3 percent sulfur in coke).
High molecular weight organics and other emissions from the anode paste are released from HSS and
VSS cells. These emissions can be ducted to gas burners to be oxidized, or they can be collected and recycled
or sold. If the heavy tars are not properly collected, they can cause plugging of exhaust ducts, fans, and
emission control equipment.
A variety of control devices has been used to abate emissions from reduction cells and anode baking
furnaces. To control gaseous and particulate fluorides and particulate emissions, 1 or more types of wet
scrubbers (spray tower and chambers, quench towers, floating beds, packed beds, Venturis) have been applied
to all 3 types of reduction cells and to anode baking furnaces. In addition, particulate control methods such as
wet and dry electrostatic precipitators (ESPs), multiple cyclones, and dry alumina scrubbers (fluid bed,
injected, and coated filter types) are used on all 3 cell types and with anode baking furnaces.
The fluoride adsorption system is becoming more prevalent and is used on all 3 cell types. This
system uses a fluidized bed of alumina, which has a high affinity for fluoride, to capture gaseous and
particulate fluorides. The pot offgases are passed through the crystalline form of alumina, which was
generated using the Bayer process. A fabric filter is operated downstream from the fluidized bed to capture
the alumina dust entrained in the exhaust gases passing through the fluidized bed. Both the alumina used in
the fluidized bed and that captured by the fabric filter are used as feedstock for the reduction cells, thus
effectively recycling the fluorides. This system has an overall control efficiency of 99 percent for both
gaseous and particulate fluorides. Wet ESPs approach adsorption in particulate removal efficiency, but they
must be coupled to a wet scrubber or coated baghouse to catch hydrogen fluoride.
Scrubber systems also remove a portion of the SO2 emissions. These emissions could be reduced by
wet scrubbing or by reducing the quantity of sulfur in the anode coke and pitch (i.e., calcining the coke).
The molten aluminum may be batch treated in furnaces to remove oxide, gaseous impurities, and
active metals such as sodium and magnesium. One process consists of adding a flux of chloride and fluoride
salts and then bubbling chlorine gas, usually mixed with an inert gas, through the molten mixture. Chlorine
12.1-4 EMISSION FACTORS 2/98
-------
reacts with the impurities to form HC1, ALjO-j and metal chloride emissions. A dross forms on the molten
aluminum and is removed before casting.
Potential sources of fugitive particulate emissions in the primary aluminum industry are bauxite
grinding, materials handling, anode baking, and the 3 types of reduction cells (see
Table 12.1-1). These fugitive emissions probably have particulate size distributions similar to those
presented in Table 12.1-2.
12.1.4 Changes to Section Since 10/86
>• Reformatted in 1995 for the 5th Edition.
>• For Supplement D to the 5th Edition, the tables with metric units were removed and some text and
emission factors were added for the Greenhouse gases (CO2, CF4, and C2F6).
2/98 Metallurgical Industry 12.1-5
-------
Table 12.1-1. EMISSION FACTORS FOR PRIMARY ALUMINUM
PRODUCTION PROCESSES (Ib/ton Al produced)3
EMISSION FACTOR RATING: A
Operation
Bauxite grinding0
(SCC 3-03-000-01)
Uncontrolled
Spray tower
Floating bed scrubber
Quench tower and spray
screen
Aluminum hydroxide calciningd
(SCC 3-03-002-01)
Uncontrolled6
Spray tower
Floating bed scrubber
Quench tower
ESP
Anode baking furnace
(SCC 3-03-001-05)
Uncontrolled
Fugitive (SCC 3-03-001-11)
Spray tower
ESP
Dry alumina scrubber
Prebake cell
(SCC 3-03-001-01)
Uncontrolled
Fugitive (SCC 3-03-001-08)
Emissions to collector
Multiple cyclones
Dry alumina scrubber
Dry ESP plus spray tower
Spray tower
Floating bed scrubber
Coated bag filter dry scrubber
Crossflow packed bed
Dry plus secondary scrubber
Total
Paniculate5
6.0
1.8
1.7
1.0
200.0
60.0
56.0
34.0
4.0
3.0
ND
0.75
0.75
0.06
94.0
5.0
89.0
19.6
1.8
4.5
112.8
112.8
1.8
26.3
0.7
Gaseous
Fluoride
Neg
Neg
Neg
Neg
Neg
Neg
Neg
Neg
Neg
0.9
ND
0.04
0.04
0.009
24.0
1.2
22.8
22.8
0.2
1.4
1.4
0.5
3.4
6.7
0.4
Particulate
Fluoride
Neg
Neg
Neg
Neg
Neg
Neg
Neg
Neg
Neg
0.1
ND
0.03
0.03
0.002
20.0
1.0
19.0
4.2
0.4
3.4
3.8
3.8
0.4
5.6
0.3
Reference
1,3
1,3
1,3
1,3
1,3
1,3
1,3
1,3
1,3
2,12-13
NA
12
2
2,12
1-2,12-13
2,12
2
2
2,12
2,12
2
2
2
12
12
12.1-6
EMISSION FACTORS
2/98
-------
Table 12.1-1 (Cont.)
Operation
Vertical Soderberg stud cell
(SCC 3-03-001-03)
Uncontrolled
Fugitive (SCC 3-03-001-10)
Emissions to collector
Spray tower
Venturi scrubber
Multiple cyclones
Dry alumina scrubber
Scrubber plus ESP plus spray
screen and scrubber
Horizontal Soderberg stud cell
(SCC 3-03-001 -02)
Uncontrolled
Fugitive (SCC 3-03-001-09)
Emissions to collector
Spray tower
Floating bed scrubber
Scrubber plus wet ESP
Wet ESP
Dry alumina scrubber
Total
Particulateb
78.0
12.0
66.0
16.5
2.6
33.0
1.3
7.7
98.0
10.0
88.0
22.0
19.4
1.8
1.8
1.8
Gaseous
Fluoride
33.0
4.9
28.1
0.3
0.3
28.1
0.3
1.5
22.0
2.2
19.8
7.5
0.4
0.2
1.0
0.4
Particulate
Fluoride
11.0
1.7
9.3
2.3
0.4
4.7
0.2
1.3
12.0
1.2
10.8
2.7
2.4
0.2
0.2
0.2
Reference
2,12
12
12
2
2
2
2
2
2,12
2,12
2,12
2,12
2
2,12
12
12
a To convert from Ib/ton to kg/Mg, multiply by 0.5. SCC = Source Classification Code. Neg = negligible.
ND = no data. NA = not applicable. Sulfur oxides may be estimated, with an EMISSION FACTOR
RATING of C, by the following calculations.
Anode baking furnace, uncontrolled SO2 emissions (excluding furnace fuel
combustion emissions):
40(C)(S)(1-0.01 K) Ib/ton
Prebake (reduction) cell, uncontrolled SO2 emissions:
0.4(C)(S)(K) Ib/ton
where:
C = Anode consumption during electrolysis, Ib anode consumed/lb Al
produced
S = % sulfur in anode before baking
K = % of total SO2 emitted by prebake (reduction) cells.
Anode consumption weight is weight of anode paste (coke + pitch)
before baking.
b Includes paniculate fluorides, but does not include condensible organic particulate.
c For bauxite grinding, units are Ib of pollutant/ton of bauxite processed.
d For aluminum hydroxide calcining, units are Ib of pollutant/ton of alumina produced.
e After multicyclones.
2/98
Metallurgical Industry
12.1-7
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2/98
Metallurgical Industry
12.1-9
-------
References For Section 12.1
1. Mineral Commodity Summaries 1992, U. S. Bureau Of Mines, Department Of The Interior,
Washington, DC.
2. Engineering And Cost Effectiveness Study Of Fluoride Emissions Control, Volume I, APTD-0945,
U. S. Environmental Protection Agency, Research Triangle Park, NC,
January 1972.
3. Air Pollution Control In The Primary Aluminum Industry, Volume I, EPA-450/3-73-004a,
U. S. Environmental Protection Agency, Research Triangle Park, NC, July 1973.
4. Particulate Pollutant System Study, Volume I, APTD-0743, U. S. Environmental Protection
Agency, Research Triangle Park, NC, May 1971.
5. Inhalable Particulate Source Category Report For The Nonferrous Industry, Contract No. 68-02-
3159, Acurex Corporation, Mountain View, CA, October 1985.
6. Emissions From Wet Scrubbing System, Y-7730-E, York Research Corporation, Stamford, CT,
May 1972.
7. Emissions From Primary Aluminum Smelting Plant, Y-7730-B, York Research Corporation,
Stamford, CT, June 1972.
8. Emissions From The Wet Scrubber System, Y-7730-F, York Research Corporation, Stamford, CT,
June 1972.
9. T. R. Hanna and M. J. Pilat, "Size Distribution Of Particulates Emitted From A Horizontal Spike
Soderberg Aluminum Reduction Cell", Journal Of The Air Pollution Control Association, 22:533-
5367,July 1972.
10. Written communication from T. F. Albee, Reynolds Aluminum, Richmond, VA, to A. A. McQueen,
U. S. Environmental Protection Agency, Research Triangle Park, NC, October 20, 1982.
11. In ventory Of U. S. Greenhouse Gas Emissions And Sinks: 1990-1993, EPA 230-R-94-014,
U. S. Environmental Protect in Agency, Office of Policy, Planning and Evaluation, Washington, DC,
p. 27, 1994.
12. Background Information For Standards Of Performance: Primary Aluminum Industry: Volume I,
Proposed Standards, EPA-450/2-74-020a, U. S. Environmental Protection Agency, Research
Triangle Park, NC, October 1974.
13. Primary Aluminum: Guidelines For Control Of Fluoride Emissions From Existing Primary
Aluminum Plants, EPA-450/2-78-049b, U. S. Environmental Protection Agency, Research Triangle
Park, NC, December 1979.
14. Inventory Methods Manual For Estimating Canadian Emissions Of Greenhouse Gases, prepared
by Ortech Corporation, for Environment Canada, Ottawa, Ontario, pp. A.29.4-5, 1994.
12.1-10 EMISSION FACTORS 2/98
-------
15. Greenhouse Gas Emissions In Norway—Inventories, And Estimation Methods, Norwegian State
Pollution Control Authority, Rapport 94.02, p. 22, 1994.
16. Canada's Greenhouse Gas Emissions: Estimations for 1990, Report EPS 5/AP14, prepared by
A.P. Jaques, Environment Canada, Ottawa, Ontario, p. 56, 1992.
17. Air Pollution Engineering Manual, Chapter 14, Metallurgical Industry, Primary Aluminum
Industry, M. Wei, A. Buonicore, and W. Davies, eds., Van Nostrand Reinhold, New York, NY, 1992.
2/98 Metallurgical Industry 12.1-11
-------
13.2.1 Paved Roads
13.2.1.1 General
Particulate emissions occur whenever vehicles travel over a paved surface, such as a road or parking
lot. Particulate emissions from paved roads are due to direct exhaust from vehicles and resuspension of loose
material on the road surface. In general terms, particulate emissions from paved roads originate from the
loose material present on the surface. In turn, that surface loading, as it is moved or removed, is continuously
replenished by other sources. At industrial sites, surface loading is replenished by spillage of material and
trackout from unpaved roads and staging areas. Figure 13.2.1-1 illustrates several transfer processes
occurring on public streets.
Various field studies have found that public streets and highways, as well as roadways at industrial
facilities, can be major sources of the atmospheric particulate matter within an area.1"9 Of particular interest
in many parts of the United States are the increased levels of emissions from public paved roads when the
equilibrium between deposition and removal processes is upset. This situation can occur for various reasons,
including application of snow and ice controls, carryout from construction activities in the area, and wind
and/or water erosion from surrounding unstabilized areas. In the absence of continuous addition of fresh
material (through localized trackout or application of antiskid material), paved road surface loading should
reach equilibrium values in which the amount of material resuspended matches the amount replenished. The
equilibrium sL value depends upon numerous factors. It is believed that the most important factors are:
mean speed of vehicles traveling the road; the average daily traffic (ADT); the number of lanes and ADT per
lane; the fraction of heavy vehicles (buses and trucks); and the presence/absence of curbs, storm sewers and
parking lanes.
13.2.1.2 Emissions And Correction Parameters
Dust emissions from paved roads have been found to vary with what is termed the "silt loading"
present on the road surface as well as the average weight of vehicles traveling the road. The term silt loading
(sL) refers to the mass of silt-size material (equal to or less than 75 micrometers [um] in physical diameter)
per unit area of the travel surface.4"5 The total road surface dust loading is that of loose material that can be
collected by broom sweeping and vacuuming of the traveled portion of the paved road. The silt fraction is
determined by measuring the proportion of the loose dry surface dust that passes through a 200-mesh screen,
using the ASTM-C-136 method. Silt loading is the product of the silt fraction and the total loading, and is
abbreviated "sL". Additional details on the sampling and analysis of such material are provided in AP-42
Appendices C.I and C.2.
The surface sL provides a reasonable means of characterizing seasonal variability in a paved road
emission inventory.9 In many areas of the country, road surface loadings are heaviest during the late winter
and early spring months when the residual loading from snow/ice controls is greatest. As noted earlier, once
replenishment of fresh material is eliminated, the road surface loading can be expected to reach an
equilibrium value, which is substantially lower than the late winter/early spring value.
10/97 Miscellaneous Sources 13.2.1-1
-------
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13.2.1-2
EMISSION FACTORS
10/97
-------
13.2.1.3 Predictive Emission Factor Equations10
The quantity of dust emissions from vehicle traffic on a paved road may be estimated using the
following empirical expression:
E=k(sL/2)°-65(W/3)L5 (1)
where:
E = paniculate emission factor (having units matching the units of k)
k = base emission factor for particle size range and units of interest (see below)
sL = road surface silt loading (grams per square meter) (g/m2)
W = average weight (tons) of the vehicles traveling the road
It is important to note that Equation 1 calls for the average weight of all vehicles traveling the road.
For example, if 99 percent of traffic on the road are 2 Mg cars/trucks while the remaining 1 percent consists
of 20 Mg trucks, then the mean weight "W" is 2.2 Mg. More specifically, Equation 1 is not intended to be
used to calculate a separate emission factor for each vehicle weight class. Instead, only one emission factor
should be calculated to represent the "fleet" average weight of all vehicles traveling the road.
The particle size multiplier (k) above varies with aerodynamic size range as shown in Table 13.2.1-1.
To determine particulate emissions for a specific particle size range, use the appropriate value of k shown in
Table 13.2.1-1.
Table 13.2-1.1. PARTICLE SIZE MULTIPLIERS FOR PAVED ROAD EQUATION
Size range3
PM-2.5C
PM-10
PM-15
PM-30d
Multiplier kb
g/VKT
1.1
4.6
5.5
24
g/VMT
1.8
7.3
9.0
38
Ib/VMT
0.0040
0.016
0.020
0.082
a Refers to airborne particulate matter (PM-x) with an aerodynamic diameter equal to or less than
x micrometers.
b Units shown are grams per vehicle kilometer traveled (g/VKT), grams per vehicle mile traveled (g/VMT),
and pounds per vehicle mile traveled (Ib/VMT). The multiplier k includes unit conversions to produce
emission factors in the units shown for the indicated size range from the mixed units required in
Equation 1.
c Ratio of PM-2.5 to PM-10 taken from Reference 22.
PM-30 is sometimes termed "suspendable particulate" (SP) and is often used as a surrogate for TSP.
The above equation is based on a regression analysis of numerous emission tests, including 65 tests
for PM-10. Sources tested include public paved roads, as well as controlled and uncontrolled industrial
paved roads. All sources tested were of freely flowing vehicles on relatively level roads and at constant
speed. No tests of "stop-and-go" traffic or vehicles under load were available for inclusion in the data base.
The equations retain the quality rating of A (B for PM-2.5), if applied within the range of source conditions
that were tested in developing the equation as follows:
10/97
Miscellaneous Sources
13.2.1-3
-------
Silt loading: 0.02 - 400 g/m2
0.03 - 570 grains/square foot (ft2)
Mean vehicle weight: 1.8-38 megagrams (Mg)
2.0 - 42 tons
Mean vehicle speed: 16-88 kilometers per hour (kph)
10-55 miles per hour (mph)
To retain the quality rating for the emission factor equation when it is applied to a specific paved
road, it is necessary that reliable correction parameter values for the specific road in question be determined.
With the exception of limited access roadways, which are difficult to sample, the collection and use of site-
specific sL data for public paved road emission inventories are strongly recommended. The field and
laboratory procedures for determining surface material silt content and surface dust loading are summarized
in Appendices C.I and C.2. In the event that site-specific values cannot be obtained, an appropriate value for
a paved public road may be selected from the values given in Table 13.2.1-2, but the quality rating of the
equation should be reduced by 2 levels. Also, recall that Equation 1 refers to emissions due to freely flowing
(not stop-and-go) traffic at constant speed on level roads.
During the preparation of the background document (Reference 10), public road silt loading values
from 1992 and earlier were assembled into a data base. This data base is available in the file "oldsldatzip"
located at the Internet URL "http://www.epa.gov/ttn/chief/ap42back.html" on the World Wide Web.
Although hundreds of public paved road sL measurements had been collected, there was no uniformity in
sampling equipment and analysis techniques, in roadway classification schemes, and in the types of data
reported. Not surprisingly, the data set did not yield a coherent relationship between sL and road class,
average daily traffic (ADT), etc., even though an inverse relationship between sL and ADT has been found
for a subclass of curbed paved roads in urban areas. Further complicating the analysis is the fact that, in
many parts of the country, paved road sL varies greatly over the course of the year, probably because of
cyclic variations in mud/dirt carryout and in use of anti-skid materials. Although there were strong reasons to
suspect that the assembled data base was skewed towards high values, independent data were not available to
confirm the suspicions.
Since the time that the background document was prepared, new field sampling programs have
shown that the assembled sL data set is biased high for "normal" situations. Just as importantly, however,
the newer programs confirm that substantially higher than "normal" silt loadings can occur on public paved
roads. As a result, two sets of default values are provided in Table 13.2.1-2, one for "normal" conditions and
another for worst-case conditions (such as after winter storm seasons or in areas with substantial mud/dirt
trackout). The newer sL data base is available as in the file "newsldatzip" located at the Internet URL
"http://www.epa.gov/ttn/chief/ap42back.html" on the World Wide Web.
13.2.1-4 EMISSION FACTORS 10/97
-------
Table 13.2.1-2 (Metric Units). RECOMMENDED DEFAULT SILT LOADING (g/m2)
VALUES FOR PUBLIC PAVED ROADS3
Normal conditions
Worst-case conditions0
High ADT roadsb
0.1
0.5
Low ADT roads
0.4
3
a Excluding limited access roads. See discussion in text. 1 g/n? is equal to 1.43
grains/ft2
b High ADT refers to roads with at least 5,000 vehicles per day.
c For conditions such as post-winter-storm or areas with substantial mud/dirt
carryout.
The range of sL values in the data base for normal conditions is 0.01 to 1.0 for high-ADT roads and
0.054 to 6.8 for low-ADT roads. Consequently the use of a default value from Table 13.2.1-2 should be
expected to yield only an order-of-magnitude estimate of the emission factor. Public paved road silt loadings
are dependent upon: traffic characteristics (speed, ADT, and fraction of heavy vehicles); road characteristics
(curbs, number of lanes, parking lanes); local land use (agriculture, new residential construction) and
regional/seasonal factors (snow/ice controls, wind blown dust). As a result, the collection and use of site-
specific silt loading data is highly recommended. In the event that default sL values are used, the quality
ratings for the equation should be downgraded 2 levels.
Limited access roadways pose severe logistical difficulties in terms of surface sampling, and few sL
data are available for such roads. Nevertheless, the available data do not suggest great variation in sL for
limited access roadways from one part of the country to another. For annual conditions, a default value of
0.015 g/m is recommended for limited access roadways. ' Even fewer of the available data correspond to
worst-case situations, and elevated loadings are observed to be quickly depleted because of high traffic
speeds and high ADT rates. A default value of 0.2 g/m is recommended for short periods of time following
application of snow/ice controls to limited access roads.22
The limited data on silt loading values for industrial roads have shown as much variability as public
roads. Because of the greater variation of traffic conditions, the use of preventive controls and the use of
mitigative controls at industrial roads, the data probably do not reflect the potential extent of this variation.
However, the collection of site specific silt loading data from industrial roads is easier and safer than for
public roads. Therefore, the collection and use of site-specific silt loading data is preferred and is highly
recommended. In the event that site-specific values cannot be obtained, an appropriate value for an industrial
road may be selected from the mean values given in Table 13.2.1-3, but the quality rating of the equation
should be reduced by 2 levels.
13.2.1.4 Controls6'23
Because of the importance of the surface loading, control techniques for paved roads attempt either
to prevent material from being deposited onto the surface (preventive controls) or to remove from the travel
lanes any material that has been deposited (mitigative controls). Regulations requiring the covering of loads
in trucks, or the paving of access areas to unpaved lots or construction sites, are preventive measures.
Examples of mitigative controls include vacuum sweeping, water flushing, and broom sweeping and flushing.
10/97
Miscellaneous Sources
13.2.1-5
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EMISSION FACTORS
10/97
-------
It is particularly important to note that street sweeping of gutters and curb areas may actually increase the silt
loading on the traveled portion of the road. Redistribution of loose material onto the travel lanes will
actually produce a short-term increase in the emissions.
In general, preventive controls are usually more cost effective than mitigative controls. The cost-
effectiveness of mitigative controls falls off dramatically as the size of an area to be treated increases. The
cost-effectiveness of mitigative measures is also unfavorable if only a short period of time is required for the
road to return to equilibrium silt loading condition. That is to say, the number and length of public roads
within most areas of interest preclude any widespread and routine use of mitigative controls. On the other
hand, because of the more limited scope of roads at an industrial site, mitigative measures may be used quite
successfully (especially in situations where truck spillage occurs). Note, however, that public agencies could
make effective use of mitigative controls to remove sand/salt from roads after the winter ends.
Because available controls will affect the sL, controlled emission factors may be obtained by
substituting controlled silt loading values into the equation. (Emission factors from controlled industrial
roads were used in the development of the equation.) The collection of surface loading samples from treated,
as well as baseline (untreated), roads provides a means to track effectiveness of the controls over time.
13.2.1.5 Changes since Fifth Edition
The following changes were made since the publication of the Fifth Edition of AP-42:
1) The particle size multiplier was reduced by approximately 55% as a result of emission testing
specifically to evaluate the PM-2.5 component of the emissions.
2) Default silt loading values were included in Table 13.2.1-2 replacing the Tables and Figures
containing silt loading statistical information.
3) Editorial changes within the text were made indicating the possible causes of variations in the silt
loading between roads within and among different locations. The uncertainty of using the default silt
loading value was discussed.
References For Section 13.2.1
1. D. R. Dunbar, Resuspension Of'Participate Matter, EPA-450/2-76-031, U. S. Environmental
Protection Agency, Research Triangle Park, NC, March 1976.
2. 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.
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. C. Cowherd, Jr., ef al., Quantification Of Dust Entrainment From Paved Roadways,
EPA-450/3-77-027, U. S. Environmental Protection Agency, Research Triangle Park, NC, July 1977.
5. Size Specific Particula te Emission Factors For Uncontrolled Industrial And Rural Roads, EPA
Contract No. 68-02-3158, Midwest Research Institute, Kansas City, MO, September 1983.
10/97 Miscellaneous Sources 13.2.1-7
-------
6. 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.
7. J. P. Reider, Size-specific Particulate Emission Factors For Uncontrolled Industrial And Rural
Roads, EPA Contract 68-02-3158, Midwest Research Institute, Kansas City, MO, September 1983.
8. C. Cowherd, Jr., and P. J. Englehart, Paved Road Particulate Emissions, EPA-600/7-84-077, U. S.
Environmental Protection Agency, Cincinnati, OH, July 1984.
9. C. Cowherd, Jr., and P. J. Englehart, Size Specific Particulate Emission Factors For Industrial And
Rural Roads, EPA-600/7-85-038, U. S. Environmental Protection Agency, Cincinnati, OH, September
1985.
10. Emission Factor Documentation ForAP-42, Sections 11.2.5 and 11.2.6 — Paved Roads, EPA
Contract No. 68-DO-0123, Midwest Research Institute, Kansas City, MO, March 1993.
11. 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.
12. PM-10 Emission Inventory Of Landfills In The Lake Calumet Area, EPA Contract No. 68-02-3891,
Midwest Research Institute, Kansas City, MO, September 1987.
13. Chicago Area Particulate Matter Emission Inventory — Sampling And Analysis, Contract
No. 68-02-4395, Midwest Research Institute, Kansas City, MO, May 1988.
14. Montana Street Sampling Data, Montana Department Of Health And Environmental Sciences, Helena,
MT, July 1992.
15. Street Sanding Emissions And Control Study, PEI Associates, Inc., Cincinnati, OH, October 1989.
16. Evaluation Of PM-10 Emission Factors For Paved Streets, Harding Lawson Associates, Denver, CO,
October 1991.
17. Street Sanding Emissions And Control Study, RTP Environmental Associates, Inc., Denver, CO, July
1990.
18. Post-storm Measurement Results — Salt Lake County Road Dust Silt Loading Winter 1991/92
Measurement Program, Aerovironment, Inc., Monrovia, CA, June 1992.
19. Written communication from Harold Glasser, Department of Health, Clark County (NV).
20. PM-10 Emissions Inventory Data For The Maricopa And Pima Planning Areas, EPA Contract No.
68-02-3888, Engineering-Science, Pasadena, CA, January 1987.
21. Characterization Of PM-10 Emissions From Antiskid Materials Applied To Ice- And Snow-Covered
Roadways, EPA Contract No. 68-DO-0137, Midwest Research Institute, Kansas City, MO, October
1992.
22. Fugitive Particulate Matter Emissions, EPA Contract No. 68-D2-0159, Work Assignment No. 4-06,
Midwest Research Institute, Kansas City, MO, April 1997.
13.2.1-8 EMISSION FACTORS 10/97
-------
23. C. Cowherd, Jr., ef a/., Control Of Open Fugitive Dust Sources, EPA-450/3-88-008,
U. S. Environmental Protection Agency, Research Triangle Park, NC, September 1988.
24. Written communication from G. Muleski, Midwest Research Institute, Kansas City, MO, to R. Myers,
U. S. Environmental Protection Agency, Research Triangle Park, NC, September 30, 1997.
10/97 Miscellaneous Sources 13.2.1-9
-------
13.2.6 Abrasive Blasting
13.2.6.1 General1'2
Abrasive blasting is the use of abrasive material to clean or texturize a material such as metal or
masonry. Sand is the most widely used blasting abrasive. Other abrasive materials include coal slag, smelter
slags, mineral abrasives, metallic abrasives, and synthetic abrasives. Industries that use abrasive blasting
include the shipbuilding industry, automotive industry, and other industries that involve surface preparation
and painting. The majority of shipyards no longer use sand for abrasive blasting because of concerns about
silicosis, a condition caused by respiratory exposure to crystalline silica. In 1991, about 4.5 million tons of
abrasives, including 2.5 million tons of sand, 1 million tons of coal slag, 500 thousand tons of smelter slag,
and 500 thousand tons of other abrasives were used for domestic abrasive blasting operations.
13.2.6.2 Process Description1"9
Abrasive blasting systems typically include three essential components: an abrasive container (i. e.,
blasting pot); a propelling device; and a blasting nozzle or nozzles. The exact equipment used depends to a
large extent on the specific application and type(s) of abrasive.
Three basic methods can be used to project the abrasive towards the surface being cleaned: air
pressure; centrifugal wheels; or water pressure. Air blast (or dry) systems use compressed air to propel the
abrasive using either a suction-type or pressure-type process. Centrifugal wheel systems use a rotating
impeller to mechanically propel the abrasive by a combination of centrifugal and inertial forces. Finally, the
water (or wet) blast method uses either air pressure or water pressure to propel an abrasive slurry towards the
cleaned surface.
Abrasive materials used in blasting can generally be classified as sand, slag, metallic shot or grit,
synthetic, or other. The cost and properties associated with the abrasive material dictate its application. The
following discusses the general classes of commonly used abrasives.
Silica sand is commonly used for abrasive blasting where reclaiming is not feasible, such as in
unconfmed abrasive blasting operations. Sand has a rather high breakdown rate, which can result in
substantial dust generation. Worker exposure to free crystalline silica is of concern when silica sand is used
for abrasive blasting.
Coal and smelter slags are commonly used for abrasive blasting at shipyards. Black Beauty™,
which consists of crushed slag from coal-fired utility boilers, is a commonly used slag. Slags have the
advantage of low silica content, but have been documented to release other contaminants, including
hazardous air pollutants (HAP), into the air.
Metallic abrasives include cast iron shot, cast iron grit, and steel shot. Cast iron shot is hard and
brittle and is produced by spraying molten cast iron into a water bath. Cast iron grit is produced by crushing
oversized and irregular particles formed during the manufacture of cast iron shot. Steel shot is produced by
blowing molten steel. Steel shot is not as hard as cast iron shot, but is much more durable. These materials
typically are reclaimed and reused.
9/97 Metallurgical Industry 13.2.6-1
-------
Synthetic abrasives, such as silicon carbide and aluminum oxide, are becoming popular substitutes
for sand. These abrasives are more durable and create less dust than sand. These materials typically are
reclaimed and reused.
Other abrasives include mineral abrasives (such as garnet, olivine, and staurolite), cut plastic, glass
beads, crushed glass, and nutshells. As with metallic and synthetic abrasives, these other abrasives are
generally used in operations where the material is reclaimed. Mineral abrasives are reported to create
significantly less dust than sand and slag abrasives.
The type of abrasive used in a particular application is usually specific to the blasting method. Dry
blasting is usually done with sand, metallic grit or shot, aluminum oxide (alumina), or silicon carbide. Wet
blasters are operated with either sand, glass beads, or other materials that remain suspended in water.
13.2.6.3 Emissions And Controls1'3'5'11
Emissions —
Paniculate matter (PM) and particulate HAP are the major concerns relative to abrasive blasting.
Table 13.2.6-1 presents total PM emission factors for abrasive blasting as a function of wind speed. Higher
wind speeds increase emissions by enhanced ventilation of the process and by retardation of coarse particle
deposition.
Table 13.2.6-1 also presents fine particulate emission factors for abrasive blasting. Emission factors
are presented for PM-10 and PM-2.5, which denote particles equal to or smaller than 10 and 2.5 microns in
aerodynamic diameter, respectively. Emissions of PM of these size fractions are not significantly wind-speed
dependent. Table 13.2.6-1 also presents an emission factor for controlled emissions from an enclosed
abrasive blasting operation controlled by a fabric filter; the blasting media was 30/40 mesh garnet.
Limited data from Reference 3 give a comparison of total PM emissions from abrasive blasting using
various media. The study indicates that, on the basis of tons of abrasive used, total PM emissions from
abrasive blasting using grit are about 24 percent of total PM emissions from abrasive blasting with sand.
The study also indicates that total PM emissions from abrasive blasting using shot are about 10 percent of
total PM emissions from abrasive blasting with sand.
Hazardous air pollutants, typically particulate metals, are emitted from some abrasive blasting
operations. These emissions are dependent on both the abrasive material and the targeted surface.
Controls —
A number of different methods have been used to control the emissions from abrasive blasting.
Theses methods include: blast enclosures; vacuum blasters; drapes; water curtains; wet blasting; and reclaim
systems. Wet blasting controls include not only traditional wet blasting processes but also high pressure
water blasting, high pressure water and abrasive blasting, and air and water abrasive blasting. For wet
blasting, control efficiencies between 50 and 93 percent have been reported. Fabric filters are used to control
emissions from enclosed abrasive blasting operations.
13.2.6-2 EMISSION FACTORS 9/97
-------
Table 13.2.6-1. PARTICULATE EMISSION FACTORS FOR ABRASIVE BLASTING3
EMISSION FACTOR RATING: E
Source
Sand blasting of mild steel
panels'3
(SCC 3-09-002-02)
Abrasive blasting of unspecified
metal parts, controlled with a
fabric filter'1
(SCC 3-09-002-04)
Particle size
Total PM
5 mph wind speed
10 mph wind speed
15 mph wind speed
PM-10C
PM-2.5C
Total PM
Emission factor,
lb/1 ,000 Ib abrasive
27
55
91
13
1.3
0.69
a One Ib/1,000 Ib is equal to 1 kg/Mg. Factors represent uncontrolled emissions, unless noted.
SCC = Source Classification Code.
b Reference 10.
c Emissions of PM-10 and PM-2.5 are not significantly wind-speed dependent.
d Reference 11. Abrasive blasting with garnet blast media.
References For Section 13.2.6
1. C. Cowherd and J. Kinsey, Development Of Paniculate And Hazardous Emission Factors For
Outdoor Abrasive Blasting, EPA Contract No. 68-D2-0159, Midwest Research Institute, Kansas
City, MO, June 1995.
2. Written communication from J. D. Hansink, Barton Mines Corporation, Golden, CO, to Attendees of
the American Waterways Shipyard Conference, Pedido Beach, AL, October 28, 1991.
3. South Coast Air Quality Management District, Section 2: Unconflned Abrasive Blasting, Draft
Document, El Monte, CA, September 8, 1988.
4. A. W. Mallory, "Guidelines For Centrifugal Blast Cleaning", J. Protective Coatings And Linings,
1(1), June 1984.
5. B. Baldwin, "Methods Of Dust-Free Abrasive Blast Clearing", Plant Engineering, 32(4),
February 16, 1978.
6. B. R Appleman and J. A, Bruno, Jr., "Evaluation Of Wet Blast Cleaning Units", /. Protective
Coatings And Linings, 2(8), August 1985.
9/97
Metallurgical Industry
13.2.6-3
-------
7. M. K. Snyder and D. Bendersky, Removal Of Lead-Based Bridge Paints, NCHRP Report 265,
Transportation Research Board, Washington, DC, December 1983.
8. J. A. Bruno, "Evaluation Of Wet Abrasive Blasting Equipment", Proceedings Of The 2nd Annual
International Bridge Conference, Pittsburgh, PA, June 17-19, 1985.
9. J. S. Kinsey, Assessment Of Outdoor Abrasive Blasting, Interim Report, EPA Contract
No. 68-02 4395, Work Assignment No. 29, U. S. Environmental Protection Agency, Research
Triangle Park, NC, September 11, 1989.
10. J. S. Kinsey, S. Schliesser, P. Murowchick, and C. Cowherd, Development Of Paniculate Emission
Factors For Uncontrolled Abrasive Blasting Operations, EPA Contract No. 68-D2-0159, Midwest
Research Institute, Kansas City, MO, February 1995.
11. Summary Of Source Test Results, Poly Engineering, Richmond, CA , Bay Area Air Quality
Management District, San Francisco, CA, November 19, 1990.
12. Emission Factor Documentation For AP-42 Section 13.2.6, Abrasive Blasting, Final Report,
Midwest Research Institute, Gary, NC, September 1997.
13.2.6-4 EMISSION FACTORS 9/97
-------
14.4 Enteric Fermentation—Greenhouse Gases
14.4.1 General
The description of this source is drawn from a report by Gibbs and Leng.l The methodology and
factors presented in this section are drawn directly from the methodology description in the State Workbook:
Methodologies for Estimating Greenhouse Gas Emissions, prepared by the U. S. EPA Office of Policy,
Planning and Evaluation (OPPE),2 International Anthropogenic Methane Emissions: Estimates for 1990?
and Crutzen, et al. (1986).4 A more detailed discussion of biology and variables affecting methane (CH4)
generation from ruminant digestion can be found in those volumes.
Enteric fermentation is fermentation that takes place in the digestive systems of animals. In
particular, ruminant animals (cattle, buffalo, sheep, goats, and camels) have a large "fore-stomach," or rumen,
within which microbial fermentation breaks down food into soluble products that can be utilized by the
animal. ' Approximately 200 species and strains of microorganisms are present in the anaerobic rumen
environment, although only a small portion, about 10 to 20 species, are believed to play an important role in
ruminant digestion. The microbial fermentation that occurs in the rumen enables ruminant animals to digest
coarse plant material that monogastric animals cannot digest.3
Methane is produced in the rumen by bacteria as a by-product of the fermentation process. This CH4
is exhaled or belched by the animal and accounts for the majority of emissions from ruminants. Methane also
is produced in the large intestines of ruminants and is expelled.1'2
There are a variety of factors that affect CH4 production in ruminant animals, such as: the physical
and chemical characteristics of the feed, the feeding level and schedule, the use of feed additives to promote
production efficiency, and the activity and health of the animal. It has also been suggested that there may be
genetic factors that affect CH4 production. Of these factors, the feed characteristics and feed rate have the
most influence.2
To describe CH4 production by ruminant animals, it is convenient to refer to the portion of feed
energy (food caloric value) intake that is converted to CH4. Higher levels of conversion translate into higher
emissions, given constant feed energy intake. Similarly, higher levels of intake translate into higher
emissions, given constant conversion. There are, however, interactions between level of intake and
1 O
conversion to CH4, so these values are not independent. '
Methane production as a fraction of the animal's gross energy intake generally will decrease as daily
intake increases for the same diet, but the actual quantity of CH4 produced may increase due to the greater
amount of fermentable material. Because of the complex relationship between the quantity of feed and the
CH4 yield percentage, emission factors and straightforward emission equations can be used for general
approximations only. In cases where the animal type, feed quality, and feed quantity are narrowly
characterized and matched to reliable CH4 yield percent values, CH4 emission factors are much more
accurate. In addition, feed intake changes over time with animal performance. Periodic updates to the
emission factors are required to reflect changes in animal management characteristics.
As a result of the various interrelationships among feed characteristics, feed intake, and conversion
rates to CH4, most well-fed ruminant animals in temperate agriculture systems will convert about 5.5-6.5
percent of their feed energy intake to CH4. Given this range for the rate of CH4 formation, CH4 emissions
a Monogastric animals have a single-chambered stomach, unlike the multi-chambered stomachs of ruminants.
Examples of monogastric animals include swine, dogs, monkeys, and humans.
2/98 Greenhouse Gas Biogenic Sources 14.4-1
-------
can be estimated based on the feed energy consumed by the animals. Because feed energy intake is related
to production level (e.g., weight gain or milk production), the feed energy intake can be estimated for these
regions based on production statistics.1'2
The rates of conversion of feed energy to CH4 for non-ruminant animals are much lower than those
for ruminants. For swine on good quality grain diets, about 0.6 percent of feed consumed is converted to
CH4. For horses, mules, and asses the estimate is about 2.5 percent. While these estimates are also
uncertain and likely vary among regions, the global emissions from these species are much smaller than the
emissions from ruminant animals. Consequently, the uncertainty in these values does not contribute
significantly to the uncertainty in the estimates of total CH4 emissions from livestock.2-4
14.4.2 Emissions
Given their population and size, cattle account for the majority of CH4 emissions in the United
States for this source category. Cattle characteristics and emissions vary significantly by region.
Therefore, it was important to develop a good model for cattle which takes into account the diversity of
cattle types and cattle feeding systems in the United States. The variability in emission factors among
regions for other animals is much smaller than the variability in emission factors for cattle.2
The emission factors presented here were developed using a validated mechanistic modelb of rumen
digestion and CH4 production for cattle feeding systems in the United States.5 The digestion model
estimates the amount of CH4 formed and emitted as a result of microbial fermentation in the rumen. The
model is linked to an animal production model that predicts growth, pregnancy, milk production, and other
production variables as a function of digestion products. The model evaluates the relationships between
feed input characteristics and animal outputs including weight gain, lactation, heat production, pregnancy,
and CH4 emissions.5 The model has been validated for a wide range of feeding conditions encountered in
the United States; a total of 32 diets were simulated for 8 animal types in 5 regions.5 Figure 14.4-1 shows
which states are assigned to each region. Table 14.4-1 provides regional emission factors for typical types
of dairy and beef cattle. The use of these emission factors requires detailed information on cattle
production characteristics.2
For example, emissions from beef cattle in Kansas from a 1,000 head (animal) operation using the
yearling system are calculated using the figures and tables of this section, in the following manner:
2,000
(1,000 head) (103.4 Ib CH4/head-yr)
EF =
2,000 Ib/ton
EF = 5.17 ton CH4/year
where: EF = CH4 emission factor for a livestock operation or facility (ton CH4/yr)
b The mechanistic model is outlined in the U. S. EPA Report to Congress entitled "Anthropogenic
Methane Emissions in the United States: Estimates for 1990."5
14.4-2 EMISSION FACTORS 2/98
-------
F = the individual animal methane emission factor from Table 14.4-1 and Figure 14.4-1
(Ib CH4/head-yr). In this example Kansas is in the north central zone according to
Figure 14.4-1 and yearling operations in the north central zone have an "F" value of 103.4 Ib
CH4 per head-yr.
Emission factors for other animals were developed using a simple functional relationship between
feed intake and feed intake released as CH4.3'4 This approach is reasonable given that feed characteristics of
other animals are more or less homogeneous. Table 14.4-2 provides emission factors for sheep, goats, swine,
horses, mules, and asses in developing and developed countries. Note that emission factors differ for sheep
and swine for developed and developing countries, and the emission factor for water buffalos is unique for
India.
Emission factors for cattle outside of the United States were also developed based on a model of feed
intake and methane conversion. Table 14.4-3 provides emission factors for dairy cattle in Western Europe,
Eastern Europe, Oceania, Latin America, Asia, Africa and the Middle East, and the Indian Subcontinent.
Table 14.4-4 provides emission factors for non-dairy cattle in the same regions.
Although much study and measurement of this source has been done, the potential variation for the
parameters used to develop the emission factors introduce a considerable amount of uncertainty, as would be
the case for any source that relies on biological processes, which are highly variable by nature.
2/98 Greenhouse Gas Biogenic Sources 14.4-3
-------
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I
t-H
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00
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National
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u
South
Atlantic
North
Atlantic
National
Average*5
O
(
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-------
Table 14.4-2. ENTERIC FERMENTATION EMISSION FACTORS FOR OTHER ANIMALS3
EMISSION FACTOR RATING: E
Animal Type
Sheep
Goats
Swine
Horses
Mules/Asses
Water Buffalo
Emission Factors
Developing
Countries (Ibs)
11.0
11.0
2.2
39.6
22.0
116.8b
Developing
Countries (kg)
5.0
5.0
1.0
18.0
10.0
53.0
Developed
Countries (Ibs)
17.6
11.0
3.3
39.6
22.0
127.9
Developed
Countries (kg)
8.0
5.0
1.5
18.0
10.0
58.0
3 References 3 and 4. Units are Ibs/head/year or kg/head/year.
b India only. Emission factor for developed countries applies to other developing countries.
Table 14.4-3. ENTERIC FERMENTATION EMISSION FACTORS FOR DAIRY CATTLE3
EMISSION FACTOR RATING: E
Region
Western Europe
Eastern Europe
Oceania
Latin America
Asia
Africa and Middle East
Indian Subcontinent
CH4 Emission
Factor
(Ib/head/yr)
220
178
150
125
123
72
101
CH4 Emission
Factor
(kg/head/yr)
100
81
68
57
56
36
46
Average Milk
Production
(Ib/yr)
9240
5610
3740
1760
3630
1045
1980
Average Milk
Production
(kg/yr)
4200
2550
1700
800
1650
475
900
a Reference 6.
14.4-6
EMISSION FACTORS
9/97
-------
Table 14.4-4. ENTERIC FERMENTATION EMISSION FACTORS
FOR NON-DAIRY CATTLE3
EMISSION FACTOR RATING: E
Type
Western Europe
Mature Males
Replacement/growing
Calves on milk
Calves on forage
Eastern Europeb
Mature Females
Mature Males
Young
Oceania0
Mature Females
Mature Males
Young
Latin America*1
Mature Females
Mature Males
Young
Asia6
Mature Females — Farming
Mature Females — Grazing
Mature Males — Farming
Mature Males — Grazing
Young
Indian Subcontinentf
Mature Females
Mature Males
Young
Africa
Mature Females
Draft Bullocks
Mature Females — Grazing
Bulls — Grazing
Young
CH4 Emission Factors
(Ib/head/yr)
132
185
0
73
163
143
88
139
121
86
128
125
92
106
90
128
97
68
68
90
37
68
88
101
121
31
CH4 Emission Factors
(kg/head/yr)
60
84
0
6.3
73.7
65
40.2
63.2
54.6
38.8
58.2
56.7
42.3
48.3
41.3
57.5
44.3
31.2
30
46.1
17
31.2
39.7
46
55.2
14.2
a Reference 3.
b Based on estimates for the former U.S.S.R.
c Based on estimates for Australia.
Based on estimates for Brazil.
e Based on estimates for China.
f Based on estimates for India.
9/97
Greenhouse Gas Biogenic Sources
14.4-7
-------
References For Section 14.4
1. M. J. Gibbs and R. A. Leng, "Methane Emissions From Livestock", Methane And Nitrous Oxide,
Proceedings Of The International IPCC Workshop, Amersfoort, The Netherlands, pp. 73-79,
February 1993.
2. State Workbook: Methodology For Estimating Greenhouse Gas Emissions, EPA 230-B-92-002,
U. S. Environmental Protection Agency, Office of Policy, Planning and Evaluation, Washington, DC,
1995.
3. International Anthropogenic Methane Emissions: Estimates for 1990, EPA-230-R-93-010.
U. S. Environmental Protection Agency, Global Change Division, Office of Air and Radiation,
Washington, DC, 1994.
4. P. Crutzen, et al, Methane Production By Domestic Animals, Wild Ruminants, Other Herbivorous
Fauna, and Humans, Tellus, 38B(3-4): 271-284, 1986.
5. Anthropogenic Methane Emissions In The United States: Estimates For 1990, Report to Congress,
U. S. Environmental Protection Agency, Office of Air and Radiation, Washington, DC, 1993.
6. Greenhouse Gas Inventory Workbook, Intergovernmental Panel On Climate Change/Organization
For Economic Cooperation And Development, Paris, France, pp. 4.1-4.5,1995.
14.4-8 EMISSION FACTORS 9/97
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