-------
Figure 2.5-4. Cumulative Particle Size Distribution and
Size-Specific Emission Factors for
Multiple-Health Incinerators
,0.18
5 0
Figure 2.5-5. Cumulative Particle Size Distribution and
Size-Specific Emission Factors for Fluidized-Bed Incinerators
j.i
18"
0.24
0.20
T.
0.16 %
0.12 3
0.08 'J
-3
II
o.oi 2
w
o
100
7/93
Solid Waste Disposal
2.5-47
-------
Figure 2.5-6, Cumulative Particle Size Distribution and
Size-Specific Emission Factors for Electric
(infrared) Incinerators
r
ae
. 5
•j
9
o
-4
: 3
o
o
o
L.50 *,
r
L.25
o
U
1.0 2
o
0.75 |
"a
-JO.50 .3
o
0.25 ^
c
o
1 0
100
»«rt«l« 4I4W
2.5-48
EMISSION FACTORS
7/93
-------
References for Section 2.5
1. Second Review of Standards of Performance for Sewage Sludge Incinerators, EPA-450/3-84-
010, U. S. Environmental Protection Agency, Research Triangle Park, North Carolina,
March 1984.
2. Process Design Manual for Sludge Treatment and Disposal, EP A-625/1 -79-011, U. S.
Environmental Protection Agency, Cincinnati, Ohio, September 1979.
3. Control Techniques for Paniculate Emissions From Stationary Sources - Volume 1,
EPA-450/3-81-005a, U. S. Environmental Protection Agency, Research Triangle Park,
North Carolina, September 1982.
4. Final Draft Test Report-Site 01 Sewage Sludge Incinerator SSI-A, National Dioxin Study.
Tier 4: Combustion Sources. EPA Contract No. 68-03-3148, U. S. Environmental
Protection Agency, Research Triangle Park, North Carolina, July 1986.
5. Final Draft Test Report-Site 03 Sewage Sludge Incinerator SSI-B, National Dioxin Study.
Tier 4: Combustion Sources. EPA Contract No. 68-03-3148, U. S. Environmental
Protection Agency, Research Triangle Park, North Carolina, July 1986.
6. Draft Test Report-Site 12 Sewage Sludge Incinerator SSI-C, EPA Contract No. 68-03-3138,
U. S. Environmental Protection Agency, Research Triangle Park, North Carolina, April
1986.
7. M. Trichon and R. T. Dewling, The Fate of Trace Metals in a Fluidized-Bed Sewage Sludge
Incinerator, (Port Washington). (GCA).
8. Engineering-Science, Inc., Paniculate and Gaseous Emission Tests at Municipal Sludge
Incinerator Plants "O", "P", "Q", and "R" (4 tests), EPA Contract No. 68-02-2815,
U. S. Environmental Protection Agency, McLean, Virginia, February 1980.
9. Organics Screening Study Test Repon. Sewage Sludge Incinerator No. 13, Detroit Water and
Sewer Department, Detroit, Michigan, EPA Contract No. 68-02-3849, PEI Associates, Inc.,
Cincinnati, Ohio, August 1986.
10. Chromium Screening Study Test Repon. Sewage Sludge Incinerator No. 13, Detroit Water
and Sewer Department, Detroit Michigan, EPA Contract No. 68-02-3849, PEI Associates,
Inc., Cincinnati, Ohio, August 1986.
11. Results of the October 24, 1980, Paniculate Compliance Test on the No. 1 Sludge Incinerator
Wet Scrubber Stack, MWCC St. Paul Wastewater Treatment Plant in St. Paul, Minnesota,
[STAPPA/ALAPCO/05/27/86-No. 02], Interpoll Inc., Circle Pines, Minnesota, November
1980.
12. Results of the June 6, 1983, Emission Compliance Test on the No. 10 Incinerator System in
the F&I 2 Building, MWCC Metro Plant, St. Paul, Minnesota, [STAPPA/ALAPCO/05/27/86-
No. 02], Interpoll Inc., Circle Pines, Minnesota, June 1983.
7/93 Solid Waste Disposal 2.5-49
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13. Results of the May 23, 1983, Emission Compliance Test on the No. 9 Incinerator System in
the F&I 2 Building, MWCC Metro Plant, St. Paul, Minnesota, [STAPPA/ALAPCO/05/27/86-
No. 02], Interpoll Inc., Circle Pines, Minnesota, May 1983.
14. Results of the November 25, 1980, Paniculate Emission Compliance Test on the No. 4 Sludge
Incinerator Wet Scrubber Stack, MWCC St. Paul Wastewater Treatment Plant, St. Paul,
Minnesota, [STAPPA/ALAPCO/05/27/86-No. 02], Interpoll Inc., Circle Pines, Minnesota,
December, 1980.
15. Results of the March 28, 1983, Paniculate Emission Compliance Test on the No. 8
Incinerator, MWCC Metro Plant, St. Paul, Minnesota, [STAPPA/ALAPCO/05/28/86-
No. 06], Interpoll Inc., Circle Pines, Minnesota, April 1983.
16. Paniculate Emission Test Reponfor a Sewage Sludge Incinerator, City of Shelby Wastewater
Treatment Plant, [STAPPA/ALAPCO/07/28/86-No. 06], North Carolina Department of
Natural Resources, February 1979.
17. Source Sampling Evaluation for Rocky River Wastewater Treatment Plant, Concord,
Nonh Carolina, [STAPPA/ALAPCO/05/28/86-No. 06], Mogul Corp., Charlotte,
North Carolina, July 1982.
18. Performance Test Report: Rocky Mount Wastewater Treatment Facility,
[STAPPA/ALAPCO/07/28/86-No. 06], Envirotech, Belmont, California, July 1983.
19. Performance Test Reponfor the Incineration System at the Honolulu Wastewater Treatment
Plant, Honolulu, Oahu, Hawaii, [STAPPA/ALAPCO/05/22/86-No. 11], Zimpro, Rothschild,
Wisconsin, January 1984.
20. (Test Results) Honolulu Wastewater Treatment Plant, Ewa, Hawaii, [STAPPA/ALAPCO/05/
22/86-No. 11], Zimpro, Rothschild, Wisconsin, November 1983.
21. Air Pollution Source Test. Sampling and Analysis of Air Pollutant Effluent from Wastewater
Treatment Facility-Sand Island Wastewater Treatment Plant in Honolulu, Hawaii, [STAPPA/
ALAPCO/05/22/86-No. 11], Ultrachem, Walnut Creek, California, December 1978.
22. Air Pollution Source Test. Sampling and Analysis of Air Pollutant Effluent From Wastewater
Treatment Facility—Sand Island Wastewater Treatment Plant in Honolulu, Hawaii—Phase II,
[STAPPA/ALAPCO/05/22/86-No. 11], Ultrachem, Walnut Creek, California, December
1979.
23. Stationary Source Sampling Repon, EEI Reference No. 2988, at the Osborne Wastewater
Treatment Plant, Greensboro, Nonh Carolina, [STAPPA/ALAPCO/07/28/86-No. 06],
Particulate Emissions and Particle Size Distribution Testing. Sludge Incinerator Scrubber
Inlet and Scrubber Stack, Entropy, Research Triangle Park, North Carolina, October 1985.
24. Metropolitan Sewer District-Little Miami Treatment Plant (three tests: August 9, 1985,
September 16, 1980, and September 30, 1980) and Mill Creek Treatment Plant (one test:
January 9, 1986), [STAPPA/ALAPCO/05/28/86-No. 14], Southwestern Ohio Air Pollution
Control Agency.
2.5-50 EMISSION FACTORS 7/93
-------
25. Paniculate Emissions Compliance Testing, at the City of Milwaukee South Shore Treatment
Plant, Milwaukee, Wisconsin, [STAPPA/ALAPCO/06/12/86-No. 19], Entropy, Research
Triangle Park, North Carolina, December 1980.
26. Paniculate Emissions Compliance Testing, at the City of Milwaukee South Shore Treatment
Plant, Milwaukee, Wisconsin, [STAPPA/ALAPCO/06/12/86-No. 19], Entropy, Research
Triangle Park, North Carolina, November 1980.
27. Stack Test Repon-Bayshore Regional Sewage Authority, in Union Beach, New Jersey,
[STAPPA/ALAPCO/05/22/86-No. 12], New Jersey State Department of Environmental
Protection, Trenton, New Jersey, March 1982.
28. Stack Test Repon-Jersey City Sewage Authority, in Jersey City, New Jersey,
[STAPPA/ALAPCO/05/22/86-No. 12], New Jersey State Department of Environmental
Protection, Trenton, New Jersey, December 1980.
29. Stack Test Repon-Nonhwest Bergen County Sewer Authority, in Waldwick, New Jersey,
[STAPPA/ALAPCO/05/22/86-No. 12], New Jersey State Department of Environmental
Protection, Trenton, New Jersey, March 1982.
30. Stack Test Repon-Pequannock, Lincoln Park, and Fairfield Sewerage Authority, in Lincoln
Park, New Jersey, [STAPPA/ALAPCO/05/22/86-No. 12], New Jersey State Department of
Environmental Protection, Trenton, New Jersey, December 1975.
31. Atmospheric Emission Evaluation, of the Anchorage Water and Wastewater Utility Sewage
Sludge Incinerator, ASA, Bellevue, Washington, April 1984.
32. Stack Sampling Reponfor Municipal Sewage Sludge Incinerator No. 1, Scrubber Outlet
(Stack), Providence, Rhode Island, Recon Systems, Inc., Three Bridges, New Jersey,
November 1980.
33. Stack Sampling Repon, Compliance Test No. 3, at the Attleboro Advanced Wastewater
Treatment Facility, in Attleboro, Massachusetts, David Gordon Associates, Inc., Newton
Upper Falls, Massachusetts, May 1983.
34. Source Emission Survey, at the Rowlett Creek Plant, North Texas Municipal Water District,
Piano, Texas, Shirco, Inc., Dallas, Texas, November 1978.
35. Emissions Data for Infrared Municipal Sewage Sludge Incinerators (Five tests), Shirco, Inc.,
Dallas, Texas, January 1980.
37. Electrostatic Precipitator Efficiency on a Multiple Heanh Incinerator Burning Sewage Sludge,
Contract No. 68-03-3148, U. S. Environmental Protection Agency, Research Triangle Park,
North Carolina, August 1986.
38. Baghouse Efficiency on a Multiple Heanh Incinerator Burning Sewage Sludge, Contract
No. 68-03-3148, U. S. Environmental Protection Agency, Research Triangle Park, North
Carolina, August 1986.
7/93 Solid Waste Disposal 2.5-51
-------
39. J.B. Farrell and H. Wall, Air Pollution Discharges from Ten Sewage Sludge Incinerators,
U. S. Environmental Protection Agency, Cincinnati, Ohio, August 1985. ^B
40. Emission Test Report. Sewage Sludge Incinerator, at the Davenport Wastewater Treatment
Plant, Davenport, Iowa, [STAPPA/ALAPCO/ll/04/86-No. 119], PEDCo Environmental,
Cincinnati, Ohio, October 1977.
41. Sludge Incinerator Emission Testing. Unit No. 1 for City of Omaha, Papillion Creek Water
Pollution Control Plant, [STAPPA/ALAPCO/10/28/86-No. 100], Particle Data Labs, Ltd.,
Elmhurst, Illinois, September 1978.
42. Sludge Incinerator Emission Testing. Unit No. 2 for City of Omaha, Papillion Creek Water
Pollution Control Plant, [STAPPA/ALAPCO/10/28/86-No. 100], Particle Data Labs, Ltd.,
Elmhurst, Illinois, May 1980.
43. Paniculate and Sulfur Dioxide Emissions Test Report for Zimpro on the Sewage Sludge
Incinerator Stack at the Cedar Rapids Water Pollution Control Facility, [STAPPA/ALAPCO/
11/04/86-No. 119], Serco, Cedar Falls, Iowa, September 1980.
44. Newport Wastewater Treatment Plant, Newport, Tennessee. (Nichols; December 1979).
[STAPPA/ALAPCO/lO/27/86-No. 21].
45. Maryville Wastewater Treatment Plant Sewage Sludge Incinerator Emission Test Report,
[STAPPA/ALAPCO/lO/27/86-No. 21], Enviro-measure, Inc., Knoxville, Tennessee, August
1984.
46. Maryville Wastewater Treatment Plant Sewage Sludge Incinerator Emission Test Report,
[STAPPA/ALAPCO/lO/27/86-No. 21], Enviro-measure, Inc., Knoxville, Tennessee, October
1982.
47. Southerly Wastewater Treatment Plant, Cleveland, Ohio, Incinerator No. 3, [STAPPA/
ALAPCO/ll/12/86-No. 124], Envisage Environmental, Inc., Richfield, Ohio, May 1985.
48. Southerly Wastewater Treatment Plant, Cleveland, Ohio. Incinerator No. 1, [STAPPA/
ALAPCO/ll/12/86-No. 124], Envisage Environmental, Inc., Richfield, Ohio, August 1985.
49. Final Report for an Emission Compliance Test Program (July 1, 1982), at the City of
Waterbury Wastewater Treatment Plant Sludge Incinerator, Waterbury, Connecticut,
[STAPPA/ALAPCO/12/17/86-No. 136], York Services Corp, July 1982.
50. Incinerator Compliance Test, at the City of Stratford Sewage Treatment Plant, Stratford,
Connecticut, [STAPPA/ALAPCO/12/17/86-No. 136], Emission Testing Labs, September
1974.
51. Emission Compliance Tests at the Norwalk Wastewater Treatment Plant in South Smith Street,
Norwalk, Connecticut, [STAPPA/ALAPCO/12/17/86-No. 136], York Research Corp,
Stamford, Connecticut, February 1975.
2.5-52 EMISSION FACTORS 7/93
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52. Final Report-Emission Compliance Test Program at the East Shore Wastewater Treatment
Plant in New Haven, Connecticut, [STAPPA/ALAPCO/12/17/86-No. 136], York Services
Corp., Stamford, Connecticut, September 1982.
53. Incinerator Compliance Test at the Enfield Sewage Treatment Plant in Enfield, Connecticut,
[STAPPA/ALAPCO/12/17/86-No. 136], York Research Corp., Stamford, Connecticut, July
1973.
54. Incinerator Compliance Test at The Glastonbury Sewage Treatment Plant in Glastonbury,
Connecticut, [STAPPA/ALAPCO/12/17/86-No. 136], York Research Corp., Stamford,
Connecticut, August 1973.
55. Results of the May 5, 1981, Paniculate Emission Measurements of the Sludge Incinerator, at
the Metropolitan District Commission Incinerator Plant, [STAPPA/ALAPCO/12/17/86-
No. 136], Henry Souther Laboratories, Hartford, Connecticut.
56. Official Air Pollution Tests Conducted on the Nichols Engineering and Research Corporation
Sludge Incinerator at the Wastewater Treatment Plant in Middletown, Connecticut,
[STAPPA/ALAPCO/12/17/86-No. 136], Rossnagel and Associates, Cherry Hill, New Jersey,
November 1976.
57. Measured Emissions From the West Nichols-Neptune Multiple Hearth Sludge Incinerator at the
Naugatuck Treatment Company in Naugatuck, Connecticut, [STAPPA/ALAPCO/12/17/86-
No. 136], The Research Corp., East Hartford, Connecticut, April 1985.
58. Compliance Test Report-(August 27, 1986), at the Mattabasset District Pollution Control
Plant Main Incinerator in Cromwell, Connecticut, [STAPPA/ALAPCO/12/17/86-No. 136],
ROJAC Environmental Services, Inc., West Hartford, Connecticut, September 1986.
59. Stack Sampling Report (May 21, 1986) City of New London No. 2 Sludge Incinerator Outlet
Stack Compliance Test, [STAPPA/ALAPCO/12/17/86-No. 136], Recon Systems, Inc., Three
Bridges, New Jersey, June 1986.
60. Paniculate Emission Tests, at the Town of Vernon Municipal Sludge Incinerator in Vernon,
Connecticut, [STAPPA/ALAPCO/12/17/86-No. 136], The Research Corp., Wethersfield,
Connecticut, March 1981.
61. Non-Criteria Emissions Monitoring Program for the Envirotech Nine- Hearth Sewage Sludge
Incinerator, at the Metropolitan Wastewater Treatment Facility in St. Paul, Minnesota, ERT
Document No. P-E081-500, October 1986.
62. D.R. Knisley, et al., Site 1 Revised Draft Emission Test Report, Sewage Sludge Test Program,
U. S. Environmental Protection Agency, Water Engineering Research Laboratory, Cincinnati,
Ohio, February 9, 1989.
63. D.R. Knisley, et al., Site 2 Final Emission Test Report, Sewage Sludge Test Program, U. S.
Environmental Protection Agency, Water Engineering Research Laboratory, Cincinnati, Ohio,
October 19, 1987.
7/93 Solid Waste Disposal 2.5-53
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64. D.R. Knisley, et al., Site 3 Draft Emission Test Report and Addendum, Sewage Sludge Test
Program. Volume 1: Emission Test Results, U. S. Environmental Protection Agency, Water
Engineering Research Laboratory, Cincinnati, Ohio, October 1, 1987.
65. D.R. Knisley, et al., Site 4 Final Emission Test Report, Sewage Sludge Test Program, U. S.
Environmental Protection Agency, Water Engineering Research Laboratory, Cincinnati, Ohio,
May 9, 1988.
66. R.C. Adams, et al., Organic Emissions from the Exhaust Stack of a Multiple Hearth Furnace
Burning Sewage Sludge, U.S. Environmental Protection Agency, Water Engineering
Research Laboratory, Cincinnati, Ohio, September 30, 1985.
67. R.C. Adams, et al., Paniculate Removal Evaluation of an Electrostatic Precipitator Dust
Removal System Installed on a Multiple Hearth Incinerator Burning Sewage Sludge, U.S.
Environmental Protection Agency, Water Engineering Research Laboratory, Cincinnati, Ohio,
September 30, 1985.
68. R.C. Adams, et al., Paniculate Removal Capability of a Baghouse Filter on the Exhaust of a
Multiple Hearth Furnace Burning Sewage Sludge, U.S. Environmental Protection Agency,
Water Engineering Research Laboratory, Cincinnati, Ohio, September 30, 1985.
69. R.G. Mclnnes, et al., Sampling and Analysis Program at the New Bedford Municipal Sewage
Sludge Incinerator, GCA Corporation/Technology Division. U. S. Environmental Protection
Agency, Research Triangle Park, North Carolina, November 1984.
70. R.T. Dewling, et al., "Fate and Behavior of Selected Heavy Metals in Incinerated Sludge."
Journal of the Water Pollution Control Federation, Vol. 52, No. 10, October 1980.
71. R.L. Bennet, et al., Chemical and Physical Characterization of Municipal Sludge Incinerator
Emissions, Report No. EPA 600/3-84-047, NTIS No. PB 84-169325, U. S. Environmental
Protection Agency, Environmental Sciences Research Laboratory, Research Triangle Park,
North Carolina, March 1984.
72. Acurex Corporation. 1990 Source Test Data for the Sewage Sludge Incinerator,
Project 6595, Mountain View, California, April 15, 1991.
73. Emissions of Metals, Chromium, and Nickel Species, and Organicsfrom Municipal
Wastewater Sludge Incinerators, Volume I: Summary Repon, U.S. Environmental Protection
Agency, Cincinnati, Ohio, 1992.
74. L.T. Hentz, et al., Air Emission Studies of Sewage Sludge, Incinerators at the Western Branch
Wastewater Treatment Plan, Water Environmental Research, Vol. 64, No. 2, March/April,
1992.
75. Source Emissions Testing of the Incinerator #2 Exhaust Stack at the Central Costa Sanitary
District Municipal Wastewater Treatment Plan, Mortmez, California, Galson Technical
Services, Berkeley, California, October, 1990.
2.5-54 EMISSION FACTORS 7/93
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76. R.R. Segal, et al., Emissions of Metals, Chromium and Nickel Species, and Organicsfrom
Municipal Wastewater Sludge Incinerators, Volume II: Site 5 Test Report - Hexavalent
Chromium Method Evaluation, EPA 600/R-92/003a, March 1992.
77. R.R. Segal, et al., Emissions of Metals, Chromium and Nickel Species, and Organicsfrom
Municipal Wastewater Sludge Incinerators, Volume III: Site 6 Test Report,
EPA 600/R-92/003a, March 1992.
78. A.L. Cone et al., Emissions of Metals, Chromium, Nickel Species, and Organicsfrom
Municipal Wastewater Sludge Incinerators. Volume 5: Site 7 Test Report CEMS, Entropy
Environmentalists, Inc., Research Triangle Park, North Carolina, March 1992.
79. R.R. Segal, et al., Emissions of Metals, Chromium and Nickel Species, and Organicsfrom
Municipal Wastewater Sludge Incinerators, Volume VI: Site 8 Test Report,
EPA 600/R-92/003a, March 1992.
80. R.R. Segal, et al., Emissions of Metals, Chromium and Nickel Species, and Organicsfrom
Municipal Wastewater Sludge Incinerators, Volume VII: Site 9 Test Report,
EPA 600/R-92/003a, March 1992.
81. Stack Sampling for THC and Specific Organic Pollutants at MWCC Incinerators. Prepared
for the Metropolitan Waste Control Commission, Mears Park Centre, St. Paul, Minnesota,
July 11, 1991, QC-91-217.
7/93 Solid Waste Disposal 2.5-55
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2.6 MEDICAL WASTE INCINERATION
Medical waste incineration involves the burning of wastes produced by hospitals, veterinary
facilities, and medical research facilities. These wastes include both infectious ("red bag") medical
wastes as well as non-infectious, general housekeeping wastes. The emission factors presented here
represent emissions when both types of these wastes are combusted rather than just infectious wastes.
Three main types of incinerators are used: controlled air, excess air, and rotary kiln. Of the
incinerators identified in this study, the majority (>95 percent) are controlled air units. A small
percentage (<2 percent) are excess air. Less than one percent were identified as rotary kiln. The
rotary kiln units tend to be larger, and typically are equipped with air pollution control devices.
Approximately 2 percent of the total population identified in this study were found to be equipped
with air pollution control devices.
2.6.1 Process Description1"6
Types of incineration described in this section include:
• Controlled air,
• Excess air, and
• Rotary kiln.
2.6.1.1 Control led-Air Incinerators - Controlled-air incineration is the most widely used medical
waste incinerator (MWI) technology, and now dominates the market for new systems at hospitals and
similar medical facilities. This technology is also known as starved-air incineration, two-stage
incineration, or modular combustion. Figure 2.6-1 presents a typical schematic diagram of a
controlled air unit.
Combustion of waste in controlled air incinerators occurs in two stages. In the first stage,
waste is fed into the primary, or lower, combustion chamber, which is operated with less than the
stoichiometric amount of air required for combustion. Combustion air enters the primary chamber
from beneath the incinerator hearth (below the burning bed of waste). This air is called primary or
underfire air. In the primary (starved-air) chamber, the low air-to-fuel ratio dries and facilitates
volatilization of the waste, and most of the residual carbon in the ash burns. At these conditions,
combustion gas temperatures are relatively low [760 to 980°C (1,400 to 1,800°F)].
In the second stage, excess air is added to the volatile gases formed in the primary chamber to
complete combustion. Secondary chamber temperatures are higher than primary chamber
temperatures-typically 980 to 1,095°C (1,800 to 2,000°F). Depending on the heating value and
moisture content of the waste, additional heat may be needed. This can be provided by auxiliary
burners located at the entrance to the secondary (upper) chamber to maintain desired temperatures.
Waste feed capacities for controlled air incinerators range from about 0.6 to 50 kg/min (75 to
6,500 Ib/hr) [at an assumed fuel heating value of 19,700 kj/kg (8,500 Btu/lb)]. Waste feed and ash
removal can be manual or automatic, depending on the unit size and options purchased. Throughput
7/93 Solid Waste Disposal 2.6-1
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Carbon Dioxide,
Water Vapor
Oxygen and Nitrogen
and Excess
to Atmosphere
Air
Air
Main Burner for
Minimum Combustion
Temperature
Starved-Alr
Condition in
Lower Chamber
Controlled
Underfire Air
for Burning
Down Waste
Volatile Content
is Burned In
Upper Chamber
Excess Air
Condition
2.6-2
Figure 2.6-1. Controlled Air Incinerator
EMISSION FACTORS
7/93
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capacities for lower heating value wastes may be higher, since feed capacities are limited by primary
chamber heat release rates. Heat release rates for controlled air incinerators typically range from
about 430,000 to 710,000 kJ/hr-m3 (15,000 to 25,000 Btu/hr-ft3).
Because of the low air addition rates in the primary chamber, and corresponding low flue gas
velocities (and turbulence), the amount of solids entrained in the gases leaving the primary chamber is
low. Therefore, the majority of controlled air incinerators do not have add-on gas cleaning devices.
2.6.1.2 Excess Air Incinerators — Excess air incinerators are typically small modular units. They
are also referred to as batch incinerators, multiple chamber incinerators, or "retort" incinerators.
Excess air incinerators are typically a compact cube with a series of internal chambers and baffles.
Although they can be operated continuously, they are usually operated in a batch mode.
Figure 2.6-2 presents a schematic for an excess air unit. Typically, waste is manually fed
into the combustion chamber. The charging door is then closed, and an afterburner is ignited to bring
the secondary chamber to a target temperature [typically 870 to 980°C (1600 to 1800°F)]. When the
target temperature is reached, the primary chamber burner ignites. The waste is dried, ignited, and
combusted by heat provided by the primary chamber burner, as well as by radiant heat from the
chamber walls. Moisture and volatile components in the waste are vaporized, and pass (along with
combustion gases) out of the primary chamber and through a flame port which connects the primary
chamber to the secondary or mixing chamber. Secondary air is added through the flame port and is
mixed with the volatile components in the secondary chamber. Burners are also installed in the
secondary chamber to maintain adequate temperatures for combustion of volatile gases. Gases exiting
the secondary chamber are directed to the incinerator stack or to an air pollution-control device.
When the waste is consumed, the primary burner shuts off. Typically, the afterburner shuts off after
a set time. Once the chamber cools, ash is manually removed from the primary chamber floor and a
new charge of waste can be added.
Incinerators designed to burn general hospital waste operate at excess air levels of up to
300 percent. If only pathological wastes are combusted, excess air levels near 100 percent are more
common. The lower excess air helps maintain higher chamber temperature when burning high
moisture waste. Waste feed capacities for excess air incinerators are usually 3.8 kg/min (500 Ib/hr)
or less.
2.6.1.3 Rotary Kiln Incinerators — Rotary kiln incinerators, like the other types, are designed with a
primary chamber, where the waste is heated and volatilized, and a secondary chamber, where
combustion of the volatile fraction is completed. The primary chamber consists of a slightly inclined,
rotating kiln in which waste materials migrate from the feed end to the ash discharge end. The waste
throughput rate is controlled by adjusting the rate of kiln rotation and the angle of inclination.
Combustion air enters the primary chamber through a port. An auxiliary burner is generally used to
start combustion and maintain desired combustion temperatures. Both the primary and secondary
chambers are usually lined with acid-resistant refractory brick, as shown in the schematic drawing,
Figure 2.6-3.
7/93 Solid Waste Disposal 2.6-3
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RamePort
Charging
Door
Ignition
Chamber
Stack
Secondary
/Air Ports
Secondary
X" Burner Port
Mixing
Chamber
First
Underneath Port
i
Hearth
Side View
Secondary
Combustion
Chamber
Mixing
Chamber
Cleanout
Doors
Charging Door
Hearth
Primary
Burner Port
Secondary
Underneath Port
Figure 2.6-2. Excess Air Incinerator
2.6-4
EMISSION FACTORS
7/93
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Figure 2.6-3. Rotary Kiln Incinerator
i
I
7/93
Solid Waste Disposal
2.6-5
-------
Volatiles and combustion gases pass from the primary chamber to the secondary chamber.
The secondary chamber operates at excess air. Combustion of the volatiles is completed in the
secondary chamber. Due to the turbulent motion of the waste in the primary chamber, solids burnout
rates and paniculate entrainment in the flue gas are higher for rotary kiln incinerators than for other
incinerator designs. As a result, rotary kiln incinerators generally have add-on gas cleaning devices.
2.6.2 Emissions and Controls2'4'7'43
Medical waste incinerators can emit significant quantities of pollutants to the atmosphere.
These pollutants include: 1) paniculate matter (PM), 2) metals, 3) acid gases, 4) oxides of nitrogen
(NOX), 5) carbon monoxide (CO), 6) organics, and 7) various other materials present in medical
wastes, such as pathogens, cytotoxins, and radioactive diagnostic materials.
Paniculate matter is emitted as a result of incomplete combustion of organics (i.e., soot) and
by the entrainment of noncombustible ash due to the turbulent movement of combustion gases.
Paniculate matter may exit as a solid or an aerosol, and may contain heavy metals, acids, and/or trace
organics.
Uncontrolled paniculate emission rates vary widely, depending on the type of incinerator,
composition of the waste, and the operating practices employed. Entrainment of PM in the
incinerator exhaust is primarily a function of the gas velocity within the combustion chamber
containing the solid waste. Controlled air incinerators have the lowest turbulence and, consequently,
lowest PM emissions; rotary kiln incinerators have highly turbulent combustion, and thus have the
highest PM emissions.
The type and amount of trace metals in the flue gas are directly related to the metals
contained in the waste. Metals emissions are affected by the level of PM control and the flue gas
temperature. Most metals (except mercury) exhibit fine-particle enrichment and are removed by
maximizing small particle collection. Mercury, due to its high vapor pressure, does not show
significant particle enrichment, and removal is not a function of small particle collection in gas
streams at temperatures greater than 150°C (SOOT).
Acid gas concentrations of hydrogen chloride (HC1) and sulfur dioxide (SO2) in MWI flue
gases are directly related to the chlorine and sulfur content of the waste. Most of the chlorine, which
is chemically bound within the waste in the form of polyvinyl chloride (PVC) and other chlorinated
compounds, will be converted to HC1. Sulfur is also chemically bound within the materials making
up medical waste and is oxidized during combustion to form SO2.
Oxides of nitrogen (NOX) represent a mixture of mainly nitric oxide (NO) and nitrogen
dioxide (NO2). They are formed during combustion by: 1) oxidation of nitrogen chemically bound
in the waste, and 2) reaction between molecular nitrogen and oxygen in the combustion air. The
formation of NOX is dependent on the quantity of fuel-bound nitrogen compounds, flame temperature,
and air/fuel ratio.
Carbon monoxide is a product of incomplete combustion. Its presence can be related to
insufficient oxygen, combustion (residence) time, temperature, and turbulence (fuel/air mixing) in the
combustion zone.
Failure to achieve complete combustion of organic materials evolved from the waste can result
in emissions of a variety of organic compounds. The products of incomplete combustion (PICs) range
2.6-6 EMISSION FACTORS 7/93
-------
from low molecular weight hydrocarbon (e.g., methane or ethane) to high molecular weight
compounds [e.g., polychlorinated dibenzo-p-dioxins and dibenzofurans (CDD/CDF)]. In general,
combustion conditions required for control of CO (i.e., adequate oxygen, temperature, residence
time, and turbulence) will also minimize emissions of most organics.
Emissions of CDD/CDF from MWIs may occur as either a vapor or as a fine particulate.
Many factors are believed to be involved in the formation of CDD/CDF and many theories exist
concerning the formation of these compounds. In brief, the best supported theories involve four
mechanisms of formation.2 The first theory states that trace quantities of CDD/CDF present in the
refuse feed are carried over, unburned, to the exhaust. The second theory involves formation of
CDD/CDF from chlorinated precursors with similar structures. Conversion of precursor material to
CDD/CDF can potentially occur either in the combustor at relatively high temperatures or at lower
temperatures such as are present in wet scrubbing systems. The third theory involves synthesis of
CDD/CDF compounds from a variety of organics and a chlorine donor. The fourth mechanism
involves catalyzed reactions on fly ash particles at low temperatures.
To date, most MWIs have operated without add-on air pollution control devices (APCDs). A
small percentage (approximately 2 percent) of MWIs do use APCDs. The most frequently used
control devices are wet scrubbers and fabric filters (FFs). Fabric filters provide mainly PM control.
Other PM control technologies include venturi scrubbers and electrostatic precipitators (ESPs). In
addition to wet scrubbing, dry sorbent injection (DSI) and spray dryer absorbers have also been used
for acid gas control.
Wet scrubbers use gas-liquid absorption to transfer pollutants from a gas to a liquid stream.
Scrubber design and the type of liquid solution used largely determine contaminant removal
efficiencies. With plain water, removal efficiencies for acid gases could be as high as 70 percent for
HC1 and 30 percent for SO2. Addition of an alkaline reagent to the scrubber liquor for acid
neutralization has been shown to result in removal efficiencies of 93 to 96 percent.
Wet scrubbers are generally classified according to the energy required to overcome the
pressure drop through the system. Low-energy scrubbers (spray towers) are primarily used for acid
gas control only, and are usually circular in cross-section. The liquid is sprayed down the tower
through the rising gas. Acid gases are absorbed/neutralized by the scrubbing liquid. Low energy
scrubbers mainly remove particles larger than 5-10 micrometers (jim) in diameter.
Medium-energy scrubbers can be used for particulate matter and/or acid gas control. Medium
energy devices rely mostly on impingement to facilitate removal of PM. This can be accomplished
through a variety of configurations, such as packed columns, baffle plates, and liquid impingement
scrubbers.
Venturi scrubbers are high-energy systems that are used primarily for PM control. A typical
venturi scrubber consists of a converging and a diverging section connected by a throat section. A
liquid (usually water) is introduced into the gas stream upstream of the throat. The flue gas impinges
on the liquid stream in the converging section. As the gas passes through the throat, the shearing
action atomizes the liquid into fine droplets. The gas then decelerates through the diverging section,
resulting in further contact between particles and liquid droplets. The droplets are then removed from
the gas stream by a cyclone, demister or swirl vanes.
A fabric filtration system (baghouse) consists of a number of filtering elements (bags) along
with a bag cleaning system contained in a main shell structure with dust hoppers. Particulate-Iaden
7/93 Solid Waste Disposal 2.6-7
-------
gas passes through the bags so that the particles are retained on the upstream side of the fabric, thus
cleaning the gas. A FF is typically divided into several compartments or sections. In a FF, both the
collection efficiency and the pressure drop across the bag surface increase as the dust layer on the bag
builds up. Since the system cannot continue to operate with an increasing pressure drop, the bags are
cleaned periodically. The cleaning processes include reverse flow with bag collapse, pulse jet
cleaning, and mechanical shaking. When reverse flow and mechanical shaking are used, the
particulate matter is collected on the inside of the bag; paniculate matter is collected on the outside of
the bag in pulse jet systems. Generally, reverse flow FFs operate with lower gas flow per unit area
of bag surface (air-to-cloth ratio) than pulse jet systems and, thus, are larger and more costly for a
given gas flow-rate or application. Fabric filters can achieve very high (>99.9 percent) PM removal
efficiencies. These systems are also very effective in controlling fine particulate matter, which results
in good control of metals and organics entrained on fine particulate.
Particulate collection in an ESP occurs in three steps: (1) suspended particles are given an
electrical charge; (2) the charged particles migrate to a collecting electrode of opposite polarity; and
(3) the collected PM is dislodged from the collecting electrodes and collected in hoppers for disposal.
Charging of the particles is usually caused by ions produced in high voltage corona. The
electric fields and the corona necessary for particle charging are provided by converting alternating
current to direct current using high voltage transformers and rectifiers. Removal of the collected
particulate matter is accomplished mechanically by rapping or vibrating the collecting electrode plates.
ESPs have been used in many applications due to their high reliability and efficiency in controlling
total PM emissions. Except for very large and carefully designed ESPs, however, they are less
efficient than FFs at control of fine particulates and metals.
Dry sorbent injection (DSI) is another method for controlling acid gases. In the DSI process,
a dry alkaline material is injected into the flue gas into a dry venturi within the ducting or into the
duct ahead of a particulate control device. The alkaline material reacts with and neutralizes acids in
the flue gas. Fabric filters are employed downstream of DSI to: 1) control the PM generated by the
incinerator, 2) capture the DSI reaction products and unreacted sorbent, and 3) increase sorbent/acid
gas contact time, thus enhancing acid gas removal efficiency and sorbent utilization. Fabric filters are
commonly used with DSI because they provide high sorbent/acid gas contact. Fabric filters are less
sensitive to PM loading changes or combustion upsets than other PM control devices since they
operate with nearly constant efficiency. A potential disadvantage of ESPs used in conjunction with
DSI is that the sorbent increases the electrical resistivity of the PM being collected. This
phenomenon makes the PM more difficult to charge and, therefore, to collect. High resistivity can be
compensated for by flue gas conditioning or by increasing the plate area and size of the ESP.
The major factors affecting DSI performance are flue gas temperature, acid gas dew point
(temperature at which the acid gases condense), and sorbent-to-acid gas ratio. DSI performance
improves as the difference between flue gas and acid dew point temperatures decreases and the
sorbent-to-acid gas ratio increases. Acid gas removal efficiency with DSI also depends on sorbent
type and the extent of sorbent mixing with the flue gas. Sorbents that have been successfully applied
include hydrated lime [Ca(OH)2], sodium hydroxide (NaOH), and sodium bicarbonate (NaHCO3).
For hydrated lime, DSI can achieve 80 to 95 percent of HC1 removal and 40 to 70 percent removal of
SO2 under proper operating conditions.
The primary advantage of DSI compared to wet scrubbers is the relative simplicity of the
sorbent preparation, handling, and injection systems as well as the easier handling and disposal of dry
2.6-8 EMISSION FACTORS 7/93
-------
solid process wastes. The primary disadvantages are its lower sorbent utilization rate and
correspondingly higher sorbent and waste disposal rates.
In the spray drying process, lime slurry is injected into the SD through either a rotary
atomizer or dual-fluid nozzles. The water in the slurry evaporates to cool the flue gas, and the lime
reacts with acid gases to form calcium salts that can be removed by a PM control device. The SD is
designed to provide sufficient contact and residence time to produce a dry product before leaving the
SD adsorber vessel. The residence time in the adsorber vessel is typically 10 to IS seconds. The
participates leaving the SD (fly ash, calcium salts, and unreacted hydrated lime) are collected by a FF
or ESP.
Emission factors and emission factor ratings for controlled air incinerators are presented in
Tables 2.6-1 through 2.6-15. For emissions controlled with wet scrubbers, emission factors are
presented separately for low, medium, and high energy wet scrubbers. Particle size distribution data
for controlled air incinerators are presented in Table 2.6-15 for uncontrolled emissions and controlled
emissions following a medium-energy wet scrubber/FF and a low-energy wet scrubber. Emission
factors and emission factor ratings for rotary kiln incinerators are presented in Tables 2.6-16
through 2.6-18. Emissions data are not available for pathogens because there is not an accepted
methodology for measurement of these emissions. Refer to References 8, 9, 11, 12, and 19 for more
information.
7/93 Solid Waste Disposal 2.6-9
-------
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Table 2.6-15. PARTICLE SIZE DISTRIBUTION FOR
CONTROLLED AIR MEDICAL WASTE INCINERATOR
PARTICULATE MATTER EMISSIONS*
(SCC 50100505, 50200505)
EMISSION FACTOR RATING = E
Cut Diameter
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Size
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a References 7-43. SCC = Source Classification Code.
2.6-24
EMISSION FACTORS
7/93
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Solid Waste Disposal
2.6-27
-------
References for Section 2.6
1. Locating and Estimating Air Toxic Emissions from Medical Waste Incinerators, U.S. ^^
Environmental Protection Agency, Rochester, New York, September 1991.
2. Hospital Waste Combustion Study: Data Gathering Phase, EPA-450/3-88-017, U. S.
Environmental Protection Agency, Research Triangle Park, North Carolina, December 1988.
3. C.R. Brunner, "Biomedical Waste Incineration", presented at the 80th Annual Meeting of the
Air Pollution Control Association, New York, New York, June 21-26, 1987. p. 10.
4. Flue Gas Cleaning Technologies for Medical Waste Combustors, Final Report, U.S.
Environmental Protection Agency, Research Triangle Park, North Carolina, June 1990.
5. Municipal Waste Combustion Study; Recycling of Solid Waste, U. S. Environmental Protection
Agency, EPA Contract 68-02-433, pp.5-6.
6. S. Black and J. Netherton, Disinfection, Sterilization, and Preservation. Second Edition,
1977, p.729.
7. J. McCormack, et al., Evaluation Test on a Small Hospital Refuse Incinerator at Saint
Bernardine's Hospital in San Bernardino, California, California Air Resources Board, July
1989.
8. Medical Waste Incineration Emission Test Report, Cape Fear Memorial Hospital, Wilmington,
North Carolina, U. S. Environmental Protection Agency, December 1991.
9. Medical Waste Incineration Emission Test Report, Jordan Hospital, Plymouth, Massachusetts,
U. S. Environmental Protection Agency, February 1992.
10. J.E. McCormack, Evaluation Test of the Kaiser Permanente Hospital Waste Incinerator in
San Diego, California Air Resources Board, March 1990.
11. Medical Waste Incineration Emission Test Report, Lenoir Memorial Hospital, Kinston,
North Carolina, U. S. Environmental Protection Agency, August 12, 1991.
12. Medical Waste Incineration Emission Test Report, AMI Central Carolina Hospital, Sanford,
North Carolina, U. S. Environmental Protection Agency, December 1991.
13. A. Jenkins, Evaluation Test on a Hospital Refuse Incinerator at Cedars Sinai Medical Center,
Los Angeles, California, California Air Resources Board, April 1987.
14. A. Jenkins, Evaluation Test on a Hospital Refuse Incinerator at Saint Agnes Medical Center,
Fresno, California, California Air Resources Board, April 1987.
15. A. Jenkins, et al., Evaluation Retest on a Hospital Refuse Incinerator at Sutter General
Hospital, Sacramento, California, California Air Resources Board, April 1988.
2.6-28 EMISSION FACTORS 7/93
-------
16. Test Report for Swedish American Hospital Consumat Incinerator, Beling Consultants,
Rockford, Illinois, December 1986.
17. J.E. McCormack, ARE Evaluation Test Conducted on a Hospital Waste Incinerator at Los
Angeles County-USC Medical Center, Los Angeles, California, California Air Resources
Board, January 1990.
18. M.J. Bumbaco, Report on a Stack Sampling Program to Measure the Emissions of Selected
Trace Organic Compounds, Particulates, Heavy Metals, and HClfrom the Royal Jubilee
Hospital Incinerator, Victoria, British Columbia, Environmental Protection Programs
Directorate, April 1983.
19. Medical Waste Incineration Emission Test Report, Borgess Medical Center, Kalamazoo,
Michigan, EMB Report 91-MWI-9, U.S. Environmental Protection Agency, Office of Air
Quality Planning and Standards, December 1991.
20. Medical Waste Incineration Emission Test Report, Morristown Memorial Hospital,
Morristown, New Jersey, EMB Report 91-MWI-8, U. S. Environmental Protection Agency,
Office of Air Quality Planning and Standards, December 1991.
21. Report of Emission Tests, Burlington County Memorial Hospital, Mount Holly, New Jersey,
New Jersey State Department of Environmental Protection, November 28, 1989.
22. Results of the November 4 and 11, 1988 Paniculate and Chloride Emission Compliance Test
on the Morse Boulger Incinerator at the Mayo Foundation Institute Hills Research Facility
Located in Rochester, Minnesota, HDR Techserv, Inc., November 39, 1988.
23. Source Emission Tests at ERA Tech, North Jackson, Ohio, Custom Stack Analysis
Engineering Report, CSA Company, December 28, 1988.
24. Memo to Data File, Hershey Medical Center, Derry Township, Pennsylvania, from Thomas
P. Bianca, Environmental Resources, Commonwealth of Pennsylvania, May 9, 1990.
25. Stack Emission Testing, Erlanger Medical Center, Chattanooga, Tennessee, Report 1-6299-2,
Campbell & Associates, May 6, 1988.
26. Emission Compliance Test Program, Nazareth Hospital, Philadelphia, Pennsylvania, Ralph
Manco, Nazareth Hospital, September 1989.
27. Report of Emission Tests, Hamilton Hospital, Hamilton, New Jersey, New Jersey State
Department of Environmental Protection, December 19, 1989.
28. Report of Emission Tests, Raritan Bay Health Services Corporation, Perth Amboy,
New Jersey, New Jersey State Department of Environmental Protection, December 13, 1989.
29. K.A. Hansen, Source Emission Evaluation on a Rotary Atomizing Scrubber at Klamath Falls,
Oregon, AM Test, Inc., July 19, 1989.
30. A.A. Wilder, Final Report for Air Emission Measurements from a Hospital Waste Incinerator,
Safeway Disposal Systems, Inc., Middletown, Connecticut.
7/93 Solid Waste Disposal 2.6-29
-------
31. Stack Emission Testing, Erlanger Medical Center, Chattanooga, Tennessee, Report 1-6299,
Campbell & Associates, April 13, 19SS. ^B
32. Compliance Emission Testing for Memorial Hospital, Chattanooga, Tennessee, Air Systems
Testing, Inc., July 29, 1988.
33. Source Emission Tests at ERA Tech, Northwood, Ohio, Custom Stack Analysis Engineering
Report, CSA Company, July 27, 1989.
34. Compliance Testing for Southland Exchange Joint Venture, Hampton, South Carolina, ETS,
Inc., July 1989.
35. Source Test Report, MEGA of Kentucky, Louisville, Kentucky, August, 1988.
36. Report on Paniculate and HCL Emission Tests on Therm-Tec Incinerator Stack, Elyra, Ohio,
Maurice L. Kelsey & Associates, Inc., January 24, 1989.
37. Compliance Emission Testing for Paniculate and Hydrogen Chloride at Bio-Medical Service
Corporation, Lake City, Georgia, Air Techniques Inc., May 8, 1989.
38. Paniculate and Chloride Emission Compliance Test on the Environmental Control Incinerator
at the Mayo Foundation Institute Hills Research Facility, Rochester, Minnesota, HDR
Techserv, Inc., November 30, 1988.
39. Report on Paniculate and HCL Emission Tests on Therm-Tec Incinerator Stack, Cincinnati,
Ohio, Maurice L. Kelsey & Associates, Inc., May 22, 1989.
40. Report on Compliance Testing, Hamot Medical Center, Erie, Pennsylvania, Hamot Medical
Center, July 19, 1990.
41. Compliance Emission Testing for HCA North Park Hospital, Hixson, Tennessee, Air Systems
Testing, Inc., February 16, 1988.
42. Compliance Paniculate Emission Testing on the Pathological Waste Incinerator, Humana
Hospital-East Ridge, Chattanooga, Tennessee, Air Techniques, Inc., November 12, 1987.
43. Report of Emission Tests, Helene Fuld Medical Center, Trenton, New Jersey, New Jersey
State Department of Environmental Protection, December 1, 1989.
2.6-30 EMISSION FACTORS 7/93
-------
2.7 MUNICIPAL SOLID WASTE LANDFILLS
2.7.1 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:
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.
Municipal solid waste management in the United States is dominated by disposal in landfills.
Approximately 67 percent of solid waste is landfilled, 16 percent is incinerated, and 17 percent is
recycled or composted. There were an estimated 5,345 active MSW landfills in the United States in
1992. In 1990, active landfills were receiving an estimated 118 million megagrams (Mg) (130 million
tons) of waste annually, with 55 to 60 percent reported as household waste, and 35 to 45 percent
reported as commercial waste.
2.7.2 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 (e.g., recompacted clay),
or synthetics (e.g., 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.
7/93 Solid Waste Disposal 2.7-1
-------
2.7.3 Control Technology1-2'6
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.
Proposed 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 May 30, 1991. The regulation, if adopted, will require 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 150 Mg/yr (165 tons/yr) of non-methanogenic organic
compounds (NMOCs). The MSW landfills that would be affected by the proposed NSPS would be
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. Control systems would 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 collection systems are either active or passive systems. Active collection systems
provide a pressure gradient in order to extract landfill by use of mechanical blowers or compressors.
Passive systems allow the natural pressure gradient created by the increase in landfill pressure from
landfill gas generation to mobilize the gas for collection.
Landfill gas control and treatment options include (1) combustion of the landfill gas, and (2)
purification of the landfill gas. 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 landfill gas. Boilers
can also be employed to recover energy from landfill gas 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.
2.7.4 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 [e.g., 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 in 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 (e.g.,
waste composition, design management, and anaerobic state).
2.7-2 EMISSION FACTORS 7/93
-------
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.
2.7.4.1 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.2 This model is known as the Landfill Air Emissions
Estimation model, and can be accessed from the EPA's Control Technology Center bulletin board.
The Landfill Air Emissions Estimation model equation is as follows:
QCH4 = L0 R (e'kc - e-ty
where:
QCH = 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.
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. Also, nondegradable refuse should be subtracted from the mass of
acceptance rate to prevent overestimation of CH4 generation. The average annual acceptance rate
should only be estimated by this method when there is inadequate information available on the actual
average acceptance rate.
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 use of the EPA Method 2E.
The Landfill Air Emission Estimation model uses the proposed regulatory default values for
L0 and k. However, the defaults were developed for regulatory compliance purposes. As a result, it
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.
7/93 Solid Waste Disposal 2.7-3
-------
A k value of 0.04/yr is appropriate for areas with normal or above normal precipitation rather
than the default value of 0.02/yr. For landfills with drier waste, a k value of 0.02/yr is more
appropriate. An L0 value of 125 m3/Mg (4,411 ft3/Mg) refuse is appropriate for most landfills. It
should be emphasized that in order to comply with the NSPS, the model defaults for k and L0 must
be applied as specified in the final rule.
Landfill gas consists of approximately 50 percent by volume CO2, 50 percent CH4, and trace
amounts of NMOCs when gas generation reaches steady state conditions. 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 50 percent, then the site specific information should be used, and the CO2 emission
estimate should be adjusted accordingly.
Emissions of NMOCs result from NMOCs contained in the landfilled waste, and from their
creation from biological processes and chemical reactions within the landfill cell. The Landfill Air
Emissions Estimation model contains a proposed regulatory default value for total NMOCs of
8000 ppmv, expressed as hexane. However, there is a wide range for total NMOC values from
landfills. The proposed regulatory default value for NMOC concentration was developed for
regulatory compliance and to provide the most cost-effective default values on a national basis. For
emissions inventory purposes, it would be preferable that site-specific information be taken into
account when determining the total NMOC concentration. A value of 4,400 ppmv as hexane is
preferable for landfills known to have co-disposal of MSW and commercial/industrial organic wastes.
If the landfill is known to contain only MSW or have very little organic commercial/industrial wastes,
then a total NMOC value of 1,170 ppmv as hexane should be used.
If a site-specific total NMOC concentration is available (i.e., as measured by EPA Reference
Method 25C), it must be corrected for air infiltration into the collected landfill gas before it can be
combined with the estimated landfill gas emissions to estimate total NMOC emissions. The total
NMOC concentration is adjusted for air infiltration by assuming that CO2 and CH4 are the primary
(100 percent) constituents of landfill gas, and the following equation is used:
(PPmv as hexane) (1 x 106) = Cj^MOC PPmv as hexane
(corrected for air
CcO2 (PPmv) + CCH4 (PPmv) infiltration)
where:
CjsfMOC = Total NMOC concentration in landfill gas, ppmv as hexane;
= CO2 concentration in landfill gas, ppmv.
= CH4 Concentration in landfill gas, ppmv; and
1 x 106 = Constant used to correct NMOC concentration to units of ppmv.
Values for CCQ and CCH4 can be usually be found in the source test report for the particular
landfill along with the total NMOC concentration data.
2.7-4 EMISSION FACTORS 7/93
-------
To estimate total NMOC emissions, the following equation should be used:
QNMOC = 2 QCH4 * CNMQC'O x io6)
where:
QNMOC = NMOC emission rate, m3/yr;
QCH = CH4 generation rate, m3/yr (from the Landfill Air Emissions Estimation
model);
= Total NMOC concentration in landfill gas, ppmv as hexane; and
2 = Multiplication factor (assumes that approximately SO percent of landfill
gas is
The mass emissions per year of total NMOCs (as hexane) can be estimated by the following equation:
,. _ n .
MNMOC = QNMOC
f 1050.2 "I
[(273+T)J
where:
= NMOC (total) mass emissions (Mg/yr);
QNMOC = NMOC emission rate (m3/yr); and
T = Temperature of landfill gas (°C).
This equation assumes that the operating pressure of the system is approximately 1 atmosphere, and
represents total NMOC based on the molecular weight of hexane. If the temperature of the landfill
gas is not known, a temperature of 25°C (75°F) is recommended.
Uncontrolled emission concentrations of individual NMOCs along with some inorganic
compounds are presented in Table 2.7-1. These individual NMOC and inorganic concentrations have
already been corrected for air infiltration and can be used as input parameters in the Landfill Air
Emission Estimation model for estimating individual NMOC emissions from landfills when site-
specific data are not available. An analysis of the data based on the co-disposal history (with
hazardous wastes) of the individual landfills from which the concentration data were derived indicates
that for benzene and toluene, there is a difference in the uncontrolled concentration. Table 2.7-2
presents the corrected concentrations for benzene and toluene to use based on the site's co-disposal
history.
Similar to the estimation of total NMOC emissions, individual NMOC emissions can be
estimated by the following equation:
QNMOC = 2 QcH4 * cNMOC/(i * io6)
where:
QNMOC = NMOC emission rate, m3/yr;
QCH4 = CH4 generation rate, m3/yr (from the Landfill Air Emission Estimation
model);
d-NMOC = NMOC concentration in landfill gas, ppmv; and
2 = Multiplication factor (assumes that approximately 50 percent of landfill
gas is
7/93
Solid Waste Disposal
2.7-5
-------
Table 2.7-1. UNCONTROLLED LANDFILL GAS CONCENTRATIONS8
(SCC 50200602)
Compound
1,1,1 -Trichloroethane (methyl chloroform)*
1 , 1 ,2,2-Tetrachloroethane*
1 , 1 ,2-Trichloroethane*
1,1-Dichloroethane (ethylidene dichloride)*
1,1-Dichloroethene (vinyl idene chloride)*
1 ,2-Dichloroethane (ethylene dichloride)*
1,2-Dichloropropane (propylene dichloride)*
Acetone
Acrylonitrile*
Bromodichloromethane
Butane
Carbon disulfide*
Carbon monoxide
Carbon tetrachloride*
Carbonyl sulfide*
Chlorobenzene*
Chlorodiflouromethane
Chloroethane (ethyl chloride)*
Chloroform*
Chloromethane
Dichlorodifluoromethane
Dichlorofluoromethane
Dichloromethane (methylene chloride)*
Dimethyl sulfide
Ethane
Ethyl mercaptan
Ethylbenzene*
Fluorotrichloromethane
Hexane*
Hydrogen sulfide
Methyl ethyl ketone
Methyl isobutyl ketone*
Methyl mercaptan
Median
ppmv
0.27
0.20
0.10
2.07
0.22
0.79
0.17
8.89
7.56
2.06
3.83
1.00
309.32
0.00
24.00
0.20
1.22
1.17
0.27
1.14
12.17
4.37
14.30
76.16
227.65
0.86
4.49
0.73
6.64
36.51
6.13
1.22
10.43
Emission
Factor
Rating
B
C
E
B
B
B
C
B
D
C
B
E
C
B
E
D
B
B
B
B
B
C
C
B
D
C
B
B
B
B
B
B
B
2.7-6
EMISSION FACTORS
7/93
-------
Table 2.7-1. (Cont.).
Compound
NMOC (as hexane)
Pentane
Perchloroethylene (tetrachloroethene)*
Propane
Trichloroethene*
t-1 ,2-dichloroethene
Vinyl chloride*
Xylene*
Median
ppmv
1170
3.32
3.44
10.60
2.08
4.01
7.37
12.25
Emission
Factor
Rating
D
B
B
B
B
B
B
B
a References 9-35. SCC = Source Classification Code
* = Hazardous Air Pollutants listed in Title I of the 1990 Clean Air
Act Amendments.
Table 2.7-2. UNCONTROLLED CONCENTRATIONS OF BENZENE AND TOLUENE
BASED ON HAZARDOUS WASTE DISPOSAL HISTORY*
(SCC 50200602)
Benzene*
Co-disposal
Unknown
No co-disposal
Toluene*
Co-disposal
Unknown
No co-disposal
Concentration
ppmv
24.99
2.25
0.37
102.62
31.63
8.93
Emission
Factor
Rating
D
B
D
D
B
D
a References 9-35. SCC = Source Classification Code.
* = Hazardous Air Pollutants listed in Title I of the 1990
Clean Air Act Amendments.
The mass emissions per year of each individual landfill gas compound can be estimated by the
following equation:
7/93
Solid Waste Disposal
2.7-7
-------
= QNMOC *(Molecular weight of compound)
(8.205xlO'5 m3-atm/mol-°K) (1000 g)(273 + T)
where:
= Individual NMOC mass emissions (Mg/yr);
QNMOC = NMOC emission rate (m3/yr); and
T = Temperature of landfill gas (°C).
2.7.4.2 Controlled Emissions — Emissions from landfills are typically controlled by installing a gas
collection system, and destroying 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 NMOCs at a landfill with a gas recovery system still occur. To estimate
controlled emissions of CH4, NMOCs, 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. If site-specific collection
efficiencies are available, they should be used instead of the 75 percent average.
Uncollected CH4, CO2, and NMOCs can be calculated with the following equation:
< _ Collection Efficiency
Too
Controlled emission estimates also need to take into account the control efficiency of the
control device. Control efficiencies of CH4 and NMOCs with differing control devices are presented
in Table 2.7-3. Emissions from the control devices need to be added to the uncollected emissions to
estimate total controlled emissions.
Emission factors for secondary compounds (CO2, CO, and NOX) exiting the control device
are presented in Tables 2.7-4 and 2.7-5.
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 (Heavy-duty Construction Equipment)
of Volume II, of the AP-42 document for determination of associated dust and exhaust emissions from
these emission sources at MSW landfills.
2.7-8 EMISSION FACTORS 7/93
-------
Table 2.7-3. CONTROL EFFICIENCIES FOR LANDFILL GAS CONSTITUENTS*
Control
Device
1C Engine
(no SCC)
Turbine
(no SCC)
Flare
(50200601)
(50300601)
Compound
Benzene
Trichloroethylene
Perchloroethylene
NMOCs (as hexane)
1,1,1 -Trichloroethane
Chloroform
Toluene
Carbon tetrachloride
Perchloroethylene
Toluene
1,1,1 -Trichloroethane
Trichloroethylene
Vinyl chloride
Chloroform
Perchloroethylene
Toluene
Xylene
1,1,1 -Trichloroethane
1,2-Dichloroethane
Benzene
Carbon tetrachloride
Methylene chloride
NMOCs (as hexane)
Trichloroethylene
t-1 ,2-dichloroethene
Vinyl chloride
Average
Control
Efficiency
83.83
89.60
89.41
79.75
92.47
99.00
79.71
98.50
99.97
99.91
95.18
99.92
98.00
93.04
85.02
93.55
99.28
85.24
88.68
89.50
95.05
97.60
83.16
96.20
99.59
97.61
Emission
Factor
Rating
E
E
E
E
E
E
E
E
E
E
E
E
E
D
C
C
E
C
E
C
D
E
E
C
E
C
References 9-35. Source Classification Codes in parenthesis.
7/93
Solid Waste Disposal
2.7-9
-------
Table 2.7-4. (Metric Units) EMISSION RATES FOR SECONDARY COMPOUNDS
EXITING CONTROL DEVICES*
Average Rate,
kg/hr/dscmm
Control Device Compound Uncontrolled Methane
Flare
(50200601)
(50300601)
ICE
(no SCC)
Turbine
(no SCC)
Carbon dioxide
Carbon monoxide
Nitrogen dioxide
Methane
Sulfur dioxide
Carbon dioxide
Nitrogen dioxide
Carbon dioxide
Carbon monoxide
135.4
0.80
0.11
1.60
0.03
182.37
0.80
49.36
0.32
Emission
Factor
Rating
B
B
C
C
E
E
E
E
E
a Source Classification Codes in parenthesis.
Table 2.7-5. (English Units) EMISSION RATES FOR SECONDARY COMPOUNDS
EXITING CONTROL DEVICES'
Control Device
Flare
(50200601)
(50300601)
1C Engine
(no SCC)
Turbine
(no SCC)
Compound
Carbon dioxide
Carbon monoxide
Nitrogen dioxide
Methane
Sulfur dioxide
Carbon dioxide
Nitrogen dioxide
Carbon dioxide
Carbon monoxide
Average Rate,
Ib/hr/dscfm
Uncontrolled Methane
8.450
0.050
0.007
0.105
0.002
11.380
0.050
3.080
0.021
Emission
Factor
Rating
B
B
C
C
E
E
E
D
E
a Source Classification Codes in parenthesis.
2.7-10
EMISSION FACTORS
7/93
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References for Section 2.7
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, U. S.
Environmental Protection Agency. Research Triangle Park, North Carolina.
EPA-450/3-90-011a. Chapters 3 and 4. March 1991.
3. Characterization of Municipal Solid Waste in the United States: 1992 Update. Office of
Solid Waste, U. S. Environmental Protection Agency, Washington, D.C.
EPA-530-R-92-019. 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, D.C. September 1992.
5. Suggested Control Measures for Landfill Gas Emissions. State of California Air Resources
Board, Stationary Source Division, Sacramento, California. 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, California. [Unpublished]
8. R.L. Peer, et al., Development of an Empirical Model of Methane Emissions from Landfills.
U.S. Environmental Protection Agency, Office of Research and Development.
EPA-600/R-92-037. 1992.
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.
7/93 Solid Waste Disposal 2.7-11
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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 BBK
Landfill Facility. West Covina, California, 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.
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, California, July 1986.
2.7-12 EMISSION FACTORS 7/93
-------
27. D.L. Campbell, et al., Analysis of Factors Affecting Methane Gas Recovery from Six
Landfills. Air and Energy Engineering Research Laboratory, U.S. Environmental Protection
Agency, Research Triangle Park, North Carolina. EPA-600/2-91-055. 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. Fanner, 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.
7/93 Solid Waste Disposal 2.7-13
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3.1 STATIONARY GAS TURBINES FOR ELECTRICITY GENERATION
3.1.1 General
Stationary gas turbines are applied in electric power generators, in gas pipeline pump and
compressor drives, and in various process industries. Gas turbines (greater than 3 MW(e)) are used in
electrical generation for continuous, peaking, or standby power. The primary fuels used are natural
gas and distillate (No. 2) fuel oil, although residual fuel oil is used in a few applications.
3.1.2 Emissions
Emission control technologies for gas turbines have advanced to a point where all new and
most existing units are complying with various levels of specified emission limits. For these sources,
the emission factors become an operational specification rather than a parameter to be quantified by
testing. This section treats uncontrolled (i.e., baseline) emissions and controlled emissions with specific
control technologies.
The emission factors presented are for simple cycle gas turbines. These factors also apply to
cogeneration/combined cycle gas turbines. In general, if the heat recovery steam generator (HRSG) is
not supplementary fired, the simple cycle input specific emission factors (Ib/MMBtu) will apply to
cogeneration/combined cycle systems. The output specific emissions (g/hp-hr) will decrease according
to the ratio of simple cycle to combined cycle power output. If the HRSG is supplementary fired, the
emissions and fuel usage must be considered to estimate stack emissions. Nitrogen Oxide (NOX)
emissions from regenerative cycle turbines (which account for only a small percentage of turbines in
use) are greater than emissions from simple cycle turbines because of the increased combustion air
temperature entering the turbine. The carbon monoxide (CO) and hydrocarbon (HC) emissions may be
lower with the regenerative system for a comparable design. More power is produced from the same
energy input, so the input specific emissions factor will be affected by changes in emissions, while
output specific emissions will reflect the increased power output.
Water/steam injection is the most prevalent NOX control for cogeneration/combined cycle gas
turbines. The water or steam is injected with the air and fuel into the turbine combustion can in order
to lower the peak temperatures which, in turn, decreases the thermal NOX produced. The lower
average temperature within (he combustor can may produce higher levels of CO and HC as a result of
incomplete combustion.
Selective catalytic reduction (SCR) is a post-combustion control which selectively reduces NOX
by reaction of ammonia and NO on a catalytic surface to form N2 and H2O. Although SCR systems
can be used alone, all existing applications of SCR have been used in conjunction with water/steam
injection controls. For optimum SCR operation, the flue gas must be within a temperature range of
600-800°F with the precise limits dependent on the catalyst. Some SCR systems also utilize a CO
catalyst to give simultaneous catalytic CO/NOX control.
Advanced combustor can designs are currently being phased into production turbines. These
dry techniques decrease turbine emissions by modifying the combustion mixing, air staging, and flame
stabilization to allow operation at a much leaner air/fuel ratio relative to normal operation. Operating
at leaner conditions will lower peak temperatures within the primary flame zone of the combustor.
The lower temperatures may also increase CO and HC emissions.
7/93 Stationary Internal Combustion Sources 3.1-1
-------
With the proliferation and advancement of NOX control technologies for gas turbines during
the past 15 years, the emission factors for the installed gas turbine population are quite different than
uncontrolled turbines. However, uncontrolled turbine emissions have not changed significantly.
Therefore a careful review of specific turbine details should be performed before applying uncontrolled
emission factors. Today most gas turbines are controlled to meet local, state, and/or federal
regulations.
The average gaseous emission factors for uncontrolled gas turbines (firing natural gas and fuel
oil) are presented in Tables 3.1-1 and 3.1-2. There is some variation in emissions over the population
of large uncontrolled gas turbines because of the diversity of engine designs and models. Tables 3.1-3
and 3.1-4 present emission factors for gas turbines controlled for NOX using water injection, steam
injection or SCR. Tables 3.1-5 and 3.1-6 present emission factors for large distillate oil-fired turbines
controlled for NOX using water injection.
Gas turbines firing distillate or residual oil may emit trace metals carried over from the metals
content of the fuel. If the fuel analysis is known, the metals content of the fuel should be used for
flue gas emission factors assuming all metals pass through the turbine. If the fuel analysis is not
known, Table 3.1-7 provides order of magnitude levels of trace elements for turbines fired with
distillate oil.
i
3.1.2 EMISSION FACTORS 7/93
-------
TABLE 3.1-1. (ENGLISH UNITS)
EMISSION FACTORS FOR LARGE UNCONTROLLED GAS TURBINES'
(Source Classification Codes)
Pollutant
Emission
Factor
Rating"
Natural Gas
(SCC 20100201)
tgrams/hr-hp]c [Ib/MMBtu]
(power output) (fuel input)
Fuel Oil (i.e. Distillate)
(SCC 20100101)
[grams/hp-hr]c [Ib/MMBtu]
(power output) (fuel input)
NO,
CO
CO2d
TOC(as
methane)
SO, (as SO2)e
PM (solids)
PM
(condensables)
PM Sizing %
< .05 microns
< .10 microns
< .15 microns
< .20 microns
< .25 microns
< 1 micron
C 1.6
D .39
B 407
D .087
B 3.41S
E .070
E .082
D
D
D
D
D
D
0.44
.11
112
.024
.94S
.0193
.0226
15%
40%
63%
78%
89%
100%
2.54
.174
596
.062
3.67S
.138
.084
.698
.048
164
.017
1.01S
.038
.023
16%
48%
72%
85%
93%
100%
•References 1-8.
b"D" and "E" rated emission factors are due to limited data and/or a lack of documentation of test results,
may not be suitable for specific facilities or populations and should be used with care.
"Calculated from Ib/MMBtu assuming an average heat rate of 8,000 Btu/hp-hr (x 3.632).
•"Based on 100 percent conversion of the fuel carbon to CO2. CO2 [Ib/MMBtu] = 3.67*C/E,
where C = carbon content of fuel by weight (0.7), and E = energy content of fuel, (0.0023 MMBtu/lb).
The uncontrolled CO2 emission factors are also applicable to controlled gas turbines.
"All sulfur in the fuel is converted to SO2. S = percent sulfur in fuel.
7/93
Stationary Internal Combustion Sources
3.1-3
-------
TABLE 3.1-2. (METRIC UNITS)
EMISSION FACTORS FOR LARGE UNCONTROLLED GAS TURBINES"
(Source Classification Codes)
i
Pollutant
Emission
factor
Rating11
Natural Gas
(SCC 20100201)
[grams/kW-hr* [ng/J]
(power output) (fuel input)
Fuel Oil (i.e. Distillate)
(SCC 20100101)
[grams/kW-hr]c [ng/J]
(power output) (fuel input)
NOX
CO
C02d
TOC (as methane)
SOX (as SOjT
PM (solids)
PM (condensables)
PM Sizing %
< .05 microns
< .10 microns
< .15 microns
< .20 microns
< .25 microns
< 1 micron
C
D
B
D
B
E
E
D
D
D
D
D
D
2.15
.52
546
.117
4.57S
.094
.11
190
46
48160
10.32
404S
8.30
9.72
15%
40%
63%
78%
89%
100%
3.41
.233
799
.083
4.92S
.185
.113
300
20.6
70520
7.31
434.3S
16.3
9.89
16%
48%
72%
85%
93%
100%
"References 1-8.
b"D" and "E" rated emission factors are due to limited data and/or a lack of documentation of test results,
may not be suitable for specific facilities or populations and should be used with care.
"Calculated from ng/J assuming an average heat rate of 11,318 kJ/kW-hr.
•teased on 100 percent conversion of the fuel carbon to CO2. CO2 [Ib/MMBtu] = 3.67*C/E,
where C = ratio of carbon in the fuel by weight, and E = energy content of fuel, MMBtu/lb.
The uncontrolled C02 emission factors are also applicable to controlled gas turbines.
'All sulfur in the fuel is assumed to be converted to SO2.
3.1-4
EMISSION FACTORS
7/93
-------
TABLE 3.1-3. (ENGLISH UNITS)
EMISSION FACTORS FOR LARGE GAS-FIRED CONTROLLED GAS TURBINES"
(Source Classification Code: 20100201)
EMISSION FACTOR RATING: C
Pollutant
Water Injection
(.8 water/fuel ratio)
[grams/hr-hp]
(power
output)
NO, .50
CO .94
TOC (as methane)
NH3
NMHC
Formaldehyde
[Ib/MMBtu]
(fuel
input)
Steam Injection
(1.2 water/fuel ratio)
[grams/hr-hp]
(power
output)
.14 .44
.28 .53
[Ib/MMBtu]
(fuel
input)
.12
.16
Selective
Catalytic
Reduction (with
water injection)
[Ib/MMBtu]
(fuel
input)
.03b
.0084
.014
.0065
.0032
.0027
"References 3, 10 - 15. All data are averages of a limited number of tests and may not be typical of
those reductions which can be achieved at a specific location.
bAverage of 78 percent reduction of NO., through the SCR catalyst.
7/93
Stationary Internal Combustion Sources
3.1-5
-------
TABLE 3.14. (METRIC UNITS)
EMISSION FACTORS FOR LARGE GAS-FIRED CONTROLLED GAS TURBINES"
(Source Classification Code: 20100201)
EMISSION FACTOR RATING: C
Pollutant
Water Injection
(0.8 water/fuel ratio)
[grams/kW-hr]
(power output)
NOX .66
CO 1.3
TOC (as methane)
NH3
NMHC
Formaldehyde
[ng/J]
(fuel input)
Steam Injection
(1.2 water/fuel ratio)
[grams/kW-hr]
(power output)
61 .59
120 .71
[ngfl]
(fuel input)
52
69
Selective
Catalytic
Reduction (with
water injection)
[ng/J]
(fuel input)
3.78"
3.61
6.02
2.80
1.38
1.16
"References 3, 10 - 15. All data are averages of a limited number of tests and may not be typical of
those reductions which can be achieved at a specific location.
""Average of 78 percent reduction of NO, through the SCR catalyst.
3.1-6
EMISSION FACTORS
7/93
-------
TABLE 3.1-5. (ENGLISH UNITS) EMISSION FACTORS FOR LARGE
DISTILLATE OIL-FIRED CONTROLLED GAS TURBINES1
(Source Classification Code: 20100101)
Pollutant
NO,
CO
TOC (as methane)
SOx
PM
Emission Factor Rating
Water Injection
(.8 water/fuel ratio)
[grams/hr-hp]b
(power output)
E 1.05
E .067
E .017
B
E .135
[Ib/MMBtu]
(fuel input)
.290
.0192
.0048
C
.0372
"Reference 16.
Calculated from fuel input assuming an average heat rate of 8,000 Btu/hp-hr (x 3.632).
CA11 sulfur in the fuel is assumed to be converted to SO,.
TABLE 3.1-6. (METRIC UNITS) EMISSION FACTORS FOR LARGE
DISTILLATE OIL-FIRED CONTROLLED GAS TURBINES"
(Source Classification Code: 20100101)
Pollutant
NOX
CO
TOC (as methane)
sox
PM
Emission Factor Rating
Water Injection
(.8 water/fuel ratio)
[grams/kW-hr]b
(power output)
E 1.41
E .090
E .023
B
E .181
[ng/H
(fuel input)
125
8.26
2.06
C
16.00
"Reference 16.
Calculated from fuel input assuming an average heat rate of 8,000 Btu/hp-hr (x 3.632).
CA11 sulfur in the fuel is assumed to be converted to SO*.
7/93
Stationary Internal Combustion Sources
3.1-7
-------
TABLE 3.1-7. TRACE ELEMENT EMISSION FACTORS FOR DISTILLATE OIL-FIRED GAS TURBINES8
(Source Classification Code: 20100101)
EMISSION FACTOR RATING: Eb
Trace Element
Ib/MMBtu
Aluminum
Antimony
Arsenic
Barium
Beryllium
Boron
Bromine
Cadmium
Calcium
Chromium
Cobalt
Copper
Iron
Lead
Magnesium
Manganese
Mercury
Molybdenum
Nickel
Phosphorus
Potassium
Selenium
Silicon
Sodium
Tin
Vanadium
Zinc
64
9.4
2.1
8.4
.14
28
1.8
1.8
330
20
3.9
578
256
25
100
145
.39
3.6
526
127
185
2.3
575
590
35
1.9
294
1.5 E-04
2.2 E-05
4.9 E-06
2.0 E-05
3.3 E-07
6.5 E-05
4.2 E-06
4.2 E-06
7.7 E-04
4.7 E-05
9.1 E-06
1.3 E-03
6.0 E-04
5.8 E-05
2.3 E-04
3.4 E-04
9.1 E-07
8.4 E-06
1.2 E-03
3.0 E-04
4.3 E-04
5.3 E-06
1.3 E-03
1.4 E-03
8.1 E-05
4.4 E-06
6.8 E-04
"Reference 1.
""Emission factor rating of "E" indicates that the data are from a limited data
set and may not be representative of a specific source or population of sources.
3.1-8
EMISSION FACTORS
7/93
-------
REFERENCES FOR SECTION 3.1
1. Shih, C.C., J.W. Hamersma, and D.G. Ackerman, R.G. Beimer, M.L. Kraft, and M.M.
Yamada, Emissions Assessment of Conventional Stationary Combustion Systems; Vol. II
Internal Combustion Sources. Industrial Environmental Research Laboratory,
EPA-600/7-79-029c, U.S. Environmental Protection Agency, Research Triangle Park, NC,
February 1979.
2. Final Report - Gas Turbine Emission Measurement Program, prepared by General Applied
Science Laboratories for Empire State Electric Energy Research Corp., August 1974, GASL
TR787.
3. Malte, P.C, S., Bernstein, F. Bahlmann, and J. Doelman, NO, Exhaust Emissions for Gas-Fired
Turbine Engines. ASME 90-GT-392, June 1990.
4. Standards Support and Environmental Impact Statement; Volume 1: Proposed Standards of
Performance for Stationary Gas Turbines. EPA-450/2-77-017a, September 1977.
5. Hare, C.T. and K.J. Springer, Exhaust Emissions from Uncontrolled Vehicles and Related
Equipment using Internal Combustion Engines: Part - 6 Gas Turbines, Electric Utility Power
Plant, SWRI for EPA report APTD-1495, U.S. Environmental Protection Agency, Research
Triangle Park, NC, NTIS PB-235751.
6. Lieferstein, M., Summary of Emissions from Consolidated Edison Gas Turbine, prepared by
the Department of Air Resources, City of New York, November 5, 1975.
7. Hurley, J.F. and S. Hersh, Effect of Smoke and Corrosion Suppressant Additives on Paniculate
and Gaseous Emissions from Utility Gas Turbine: prepared by KVB Inc., for Electric Power
Research Institute, EPRI FP-398, March 1977.
8. Crawford, A.R., E.H. Mannym M.W. Gregory and W. Bartok, The Effect of Combustion
Modification on Pollutants and Equipment Performance of Power Generation Equipment," in
Proceedings of the Stationary Source Combustion Symposium Vol. Ill - Field Testing and
Surveys, U.S. EPA-600/2-76-152c, NTIS PB-257 146, June 1976.
9. Carl, D.E., E.S. Obidinski, and C.A. Jersey, Exhaust Emissions from a 25-MW Gas Turbine
FiruiR Heavy and Light Distillate Fuel Oils and Natural Gas, paper presented at the Gas
Turbine Conference and Products Show, Houston, Texas, March 2-6, 1975.
10. Shareef, G.S. and D.K. Stone, Evaluation of SCR NOT Controls for Small Natural Gas-Fueled
Prime Movers - Phase I. prepared by Radian Corp. (DCN No.: 90-209-028-11) for the Gas
Research Institute, GRI-90/0138, July 1990.
11. Pease, R.R., SCAQMD Engineering Division Report - Status Report on SCR for Gas Turbines
South Coast Air Quality Management District, July 1984.
7/93 Stationary Internal Combustion Sources 3.1-9
-------
REFERENCES FOR SECTION 3.1 (concluded)
12. GEMS Certification and Compliance Testing at Chevron USA. Inc.'s Gaviota Gas Plant
Report PS-89-1837/Project G569-89, Chevron USA, Inc., Goleta, CA, 93117, June 21, 1989.
13. Emission Testing at the Bonneville Pacific Cogeneration Plant. Report PS-92-2702/Project
7141-92, Bonneville Pacific Corporation, Santa Maria, CA, 95434, March 1992.
14. Compliance test report on a production gas-fired 1C engine, ESA, 19770-462, Proctor and
Gamble, Sacramento, CA, December 1986.
15. Compliance test report on a cogeneration facility, CR 75600-2160, Proctor and Gamble,
Sacramento, CA, May, 1990.
16. Larkin, R. and E.B. Higginbotham, Combustion Modification Controls For Stationary Gas
Turbines Vol. II. Utility Unit Field Test EPA 600/7-81-122, U.S. Environmental Protection
Agency, Research Triangle Park, NC, July 1981.
i
3.1-10 EMISSION FACTORS 7/93
-------
3.2 HEAVY DUTY NATURAL GAS FIRED PIPELINE COMPRESSOR ENGINES
3.2.1 General
Engines in the natural gas industry are used primarily to power compressors used for pipeline
transportation, field gathering (collecting gas from wells), underground storage, and gas processing
plant applications, i.e. prime movers. Pipeline engines are concentrated in the major gas producing
states (such as those along the Gulf Coast) and along the major gas pipelines. Gas turbines emit
considerably smaller amounts of pollutants than do reciprocating engines; however, reciprocating
engines are generally more efficient in their use of fuel.
Reciprocating engines are separated into three design classes: 2-stroke lean burn, 4-stroke lean
burn and 4-stroke rich burn. Each of these have design differences which affect both baseline
emissions as well as the potential for emissions control. Two-stroke engines complete the power cycle
in a single engine revolution compared to two revolutions for 4-stroke engines. With the two-stroke
engine, the fuel/air charge is injected with the piston near the bottom of the power stroke. The valves
are all covered or closed and the piston moves to the top of the cylinder compressing the charge.
Following ignition and combustion, the power stroke starts with he downward movement of the piston.
Exhaust ports or valves are then uncovered to remove the combustion products, and a new fuel/air
charge is ingested. Two stroke engines may be turbocharged using an exhaust powered turbine to
pressurize the charge for injection into the cylinder. Non-turbocharged engines may be either blower
scavenged or piston scavenged to improve removal of combustion products.
Four stroke engines use a separate engine revolution for the intake/compression stroke and the
power/exhaust stroke. These engines may be either naturally aspirated, using the suction from the
piston to entrain the air charge, or turbocharged, using a turbine to pressurize the charge.
Turbocharged units produce a higher power output for a given engine displacement, whereas naturally
aspirated units have lower initial cost and maintenance. Rich burn engines operate near the fuel-air
stoichiometric limit with exhaust excess oxygen levels less than 4 percent. Lean burn engines may
operate up to the lean flame extinction limit, with exhaust oxygen levels of 12 percent or greater.
Pipeline population statistics show a nearly equal installed capacity of turbines and reciprocating
engines. For reciprocating engines, two stroke designs contribute approximately two-thirds of installed
capacity.
3.2.2 Emissions and Controls
The primary pollutant of concern is NOX, which readily forms in the high temperature,
pressure, and excess air environment found in natural gas fired compressor engines. Lesser amounts
of carbon monoxide and hydrocarbons are emitted, although for each unit of natural gas burned,
compressor engines (particularly reciprocating engines) emit significantly more of these pollutants than
do external combustion boilers. Sulfur oxides emissions are proportional to the sulfur content of the
fuel and will usually be quite low because of the negligible sulfur content of most pipeline gas. This
section will also discuss the major variables affecting NOX emissions and the various control
technologies that will reduce uncontrolled NOX emissions.
The major variables affecting NOX emissions from compressor engines include the air fuel
ratio, engine load (defined as the ratio of the operating horsepower to the rated horsepower), intake
(manifold) air temperature and absolute humidity. In general, NOX emissions increase with increasing
7/93 Stationary Internal Combustion Sources 3.2-1
-------
load and intake air temperature and decrease with increasing absolute humidity and air fuel ratio. (The ^^
latter already being, in most compressor engines, on the "lean" side of that air fuel ratio at which
maximum NOX formation occurs). Quantitative estimates of the effects of these variables are presented
in Reference 10.
Because NOX is the primary pollutant of significance emitted from pipeline compressor
engines, control measures to date have been directed mainly at limiting NOX emissions. Reference 11
summarizes control techniques and emission reduction efficiencies. For gas turbines, the early control
applications used water or steam injection. New applications of dry low NOX combustor can designs
and selective catalytic reduction are appearing. Water injection has achieved reductions of 70 to 80
percent with utility gas turbines. Efficiency penalties of 2 to 3 percent are typical due to the added
heat load of the water. Turbine power outputs typically increase, however. Steam injection may also
be used, but the resulting NOX reductions may not be as great as with water injection, and it has the
added disadvantage that a supply of steam must be readily available. Water injection has not been
applied to pipeline compressor engines because of the lack of water availability.
The efficiency penalty and operational impacts associated with water injection have led
manufacturers to develop dry low NOX combustor can designs based on lean bum and/or staging to
suppress NOX formation. These are entering the market in the early 1990's. Stringent gas turbine NOX
limits have been achieved in California in the late 1980's with selective catalytic reduction. This is an
ammonia based post-combustion technology which can achieve in excess of 80 percent NOX
reductions. Water or steam injection is frequently used in combination with selective catalytic
reduction (SCR) to minimize ammonia costs.
For reciprocating engines, both combustion controls and post-combustion catalytic reduction
have been developed. Controlled rich bum engines have mostly been equipped with non-selective
catalytic reduction which uses unreacted hydrocarbons and CO to reduce NOX by 80 to 90 percent.
Some rich-burn engines can be equipped with prestratified charge which reduces the peak flame
temperature in the NOX forming regions. Lean burn engines have mostly met NOX reduction
requirements with lean combustion controls using torch ignition or chamber redesign to enhance flame
stability. NOX reductions of 70 to 80 percent are typical for numerous engines with retrofit or new
unit controls. Lean burn engines may also be controlled with selective catalytic reductions (SCR), but
the operational problems associated with engine control under low NOX operation have been a
deterrent.
Emission factors for natural gas fired pipeline compressor engines are presented in Tables 3.2-
1 and 3.2-2 for baseline operation and in 3.2-4 through 3.2-7 for controlled operation. The factors for
controlled operation are taken from a single source test. Table 3.2-3 lists non-criteria (organic)
emission factors.
3.2-2 EMISSION FACTORS 7/93
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EMISSION FACTORS
7/93
-------
TABLE 3.2-3. (ENGLISH AND METRIC UNITS) NON-CRITERIA EMISSION FACTORS
FOR UNCONTROLLED NATURAL GAS PRIME MOVERS*
(Source Classification Code: 20200202)
EMISSION FACTOR RATING: Eb
Pollutant
2-Cycle Lean Burn
[grams/kW-hr]
[ng/J]
Formaldehyde 1.78 140
Benzene 2.2E-3 0.17
Toluene 2.2E-3 0.17
Ethylbenzene 1.1E-3 0.086
Xylenes 3.3E-3 0.26
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7/93 Stationary Internal Combustion Sources 3.2-5
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References for Section 3.2
1. Engines, Turbines, and Compressors Directory, American Gas Association, Catalog #XF0488.
2. Martin, N.L. and R.H. Thring, Computer Database of Emissions Data for Stationary
Reciprocating Natural Gas Engines and Gas Turbines in use by the Gas Pipeline Transmission
Industry Users Manual (Electronic Database Included), prepared by South West Research
Institute for the Gas Research Institute, GRI-89/0041.
3. Air Pollution Source Testing for California AB2588 on an Oil Platform Operated by Chevron
USA. Inc. Platform Hope, California, Chevron USA, Inc., Ventura, CA, August 29, 1990.
4. Air Pollution Source Testing for California AB2588 of Engines at the Chevron USA, Inc.
Carpinteria Facility. Chevron USA, Inc., Ventura, CA, August 30, 1990.
5. Pooled Source Emission Test Report: Gas Fired 1C Engines in Santa Barbara County, ARCO,
Bakersfield, CA, July, 1990.
6. Castaldini, C., Environmental Assessment of NO, Control on a Spark-Ignited Large Bore
Reciprocating Internal Combustion Engine, U.S. Environmental Protection Agency, Research
Triangle Park, NC, April 1984.
7. Castaldini, C. and L.R. Waterland, Environmental Assessment of a Reciprocating Engine
Retrofitted with Nonselective Catalytic Reduction, EPA-600/7-84-073B, U.S. Environmental
Protection Agency, Research Triangle Park, NC, June 1984.
8. Castaldini, C. and L.R. Waterland, Environmental Assessment of a Reciprocating Engine
Retrofitted with Selective Catalytic Reduction. EPA Contract No. 68-02-3188, U.S.
Environmental Protection Agency, Research Triangle Park, NC, December 1984.
9. Fanick, R.E., H.E. Dietzmann, and C.M. Urban, Emissions Data for Stationary Reciprocating
Engines and Gas Turbines in Use by the Gas Pipeline Transmission Industry - Phase I&II,
prepared by South West Research Institute for the Pipeline Research Committee of the
American Gas Association, April 1988, Project PR-15-613.
10. Standards Support and Environmental Impact Statement, Volume I: Stationary Internal
Combustion Engines. EPA-450/2-78-125a, U.S. Environmental Protection Agency, Office of
Air Quality Planning and Standards, Research Triangle Park, NC, July 1979.
11. Castaldini, C., NQV Reduction Technologies for Natural Gas Industry Prime Movers, prepared
by Acurex Corp., for the Gas Research Institute, GRI-90/0215, August 1990.
7/93 Stationary Internal Combustion Sources 3.2-9
-------
3.3 GASOLINE AND DIESEL INDUSTRIAL ENGINES
3.3.1 General
The engine category addressed by this section covers a wide variety of industrial applications
of both gasoline and diesel internal combustion engines such as, aerial lifts, fork lifts, mobile
refrigeration units, generators, pumps, industrial sweepers/scrubbers, material handling equipment (such
as conveyors), and portable well-drilling equipment. The rated power of these engines covers a rather
substantial range; up to 186 kW (250 hp) for gasoline engines and up to 447 kW (600 hp) for diesel
engines. (Diesel engines greater than 600 hp are covered in Section 3.4: Large Stationary Diesel and
All Stationary Dual Fuel Engines). Understandably, substantial differences in engine duty cycles exist
It was necessary, therefore, to make reasonable assumptions concerning usage in order to formulate
some of the emission factors.
3.3.2 Process Description
All reciprocating internal combustion (1C) engines operate by the same basic process. A
combustible mixture is first compressed in a small volume between the head of a piston and its
surrounding cylinder. The mixture is then ignited, and the resulting high pressure products of
combustion push the piston through the cylinder. This movement is converted from linear to rotary
motion by a crankshaft. The piston returns, pushing out exhaust gases, and the cycle is repeated.
There are two methods used for stationary reciprocating 1C engines: compression ignition (CI)
and spark ignition (SI). Section 3.3 deals with both types of reciprocating internal combustion
engines.
In compression ignition engines, combustion air is first compression heated in the cylinder,
and diesel fuel oil is then injected into the hot air. Ignition is spontaneous as the air is above the auto-
ignition temperature of the fuel. Spark ignition engines initiate combustion by the spark of an
electrical discharge. Usually the fuel is mixed with the air in a carburetor (for gasoline) or at the
intake valve (for natural gas), but occasionally the fuel is injected into the compressed air in the
cylinder. All diesel fueled engines are compression ignited and all gasoline fueled engines are spark
ignited.
CI engines usually operate at a higher compression ratio (ratio of cylinder volume when the
piston is at the bottom of its stroke to the volume when it is at the top) than SI engines because fuel is
not present during compression; hence there is no danger of premature auto-ignition. Since engine
thermal efficiency rises with increasing pressure ratio (and pressure ratio varies directly with
compression ratio), CI engines are more efficient than SI engines. This increased efficiency is gained
at the expense of poorer response to load changes and a heavier structure to withstand the higher
pressures.
3.3.3 Emissions and Controls
The best method for calculating emissions is on the basis of "brake specific" emission factors
(g/hp-hr or g/kW-hr). Emissions are calculated by taking the product of the brake specific emission
factor, the usage in hours (that is, hours per year or hours per day), the power available (rated power),
and the load factor (the power actually used divided by the power available).
7/93 Stationary Internal Combustion Sources 3.3-1
-------
Once reasonable usage and duty cycles for this category were ascertained, emission values
were aggregated to arrive at the factors presented in Tables 3.3-1 (English units) and 3.3-2 (Metric
units) for criteria and organic pollutants. Emissions data for a specific design type were weighted
according to estimated material share for industrial engines. The emission factors in this table are
most appropriately applied to a population of industrial engines rather than to an individual power
plant because of their aggregate nature. Table 3.3-3 shows unweighted speciated organic compound
and air toxic emissions factors based upon only two engines. Their inclusion in this section is
intended only for rough order of magnitude estimates.
Table 3.3-4 shows a summary of various diesel emission reduction technologies (some which
may be applicable to gasoline engines). These technologies are categorized into fuel modifications,
engine modifications, and exhaust after treatments. Current data are insufficient to quantify the results
of the modifications. Table 3.3-4 provides general information on the trends of changes on selected
parameters.
3.3.2 EMISSION FACTORS 7/93
-------
TABLE 3.3-1. (ENGLISH UNITS) EMISSION FACTORS FOR UNCONTROLLED GASOLINE
AND DIESEL INDUSTRIAL ENGINES"
(Source Classification Codes)
Pollutant
[Rating]"
NOX [D]
CO[D]
SOX [D]
Paniculate [D]
C02 [BY
Aldehydes [D]
Hydrocarbons
Exhaust [D]
Evaporative [E]
Crankcase [E]
Refueling [E]
Gasoline Fuel
(SCC 20200301, 20300301)
[grams/hp-hr]
(power output)
5.16
199
0.268
0.327
493
0.22
6.68
0.30
2.20
0.49
[Ib/MMBtu]
(fuel input)
1.63
62.7
0.084
0.10
155
0.07
2.10
0.09
0.69
0.15
Diesel Fuel
(SCC 20200102, 20300101)
[grams/hp-hr]
(power output)
14.0
3.03
0.931
1.00
525
0.21
1.12
0.00
0.02
0.00
[Ib/MMBtu]
(fuel input)
4.41
0.95
0.29
0.31
165
0.07
0.35
0.00
0.01
0.00
"Data based on uncontrolled levels for each fuel from References 1, 3 and 6.
When necessary, the average brake specific fuel consumption (BSFC) value was
used to convert from g/hp-hr to Ib/MMBtu was 7000 Btu/hp-hr.
b"D" and "E" rated emission factors are most appropriate when applied to a
population of industrial engines rather than to an individual power plant, due
to the aggregate nature of the emissions data.
"Based on assumed 100 percent conversion of carbon in fuel to CO2 with 87 weight
percent carbon in diesel, 86 weight percent carbon in gasoline, average brake
specific fuel consumption of 7000 Btu/hp-hr, diesel heating value of 19300 Btu/lb,
and gasoline heating value of 20300 Btu/lb.
7/93
Stationary Internal Combustion Sources
3.3-3
-------
TABLE 3.3-2. (METRIC UNITS) EMISSION FACTORS FOR UNCONTROLLED GASOLINE
AND DIESEL INDUSTRIAL ENGINES*
(Source Classification Codes)
Pollutant
[Rating]"
NOX [D]
CO[D]
SOX [D]
Paniculate [D]
CO2 [B]c
Aldehydes [D]
Hydrocarbons
Exhaust [D]
Evaporative [E]
Crankcase [E]
Refueling [E]
Gasoline Fuel
(SCC 20200301, 20300301)
[grams/kW-hr]
(power output)
6.92
267
0.359
0.439
661
0.30
8.96
0.40
2.95
0.66
[ng/J]
(fuel input)
699
26,947
36
44
66,787
29
905
41
298
66
Diesel Fuel
(SCC 20200102, 20300101)
[grams/kW-hr]
(power output)
18.8
4.06
1.25
1.34
704
0.28
1.50
0.00
0.03
0.00
[ng/J]
(fuel input)
1,896
410
126
135
71,065
28
152
0.00
2.71
0.00
"Data based on uncontrolled levels for each fuel from References 1, 3 and 6.
b"D" and "E" rated emission factors are most appropriate when applied to a
population of industrial engines rather than to an individual power plant,
due to the aggregate nature of the emissions data.
"Based on assumed 100 percent conversion of carbon in fuel to CO2 with 87 weight
percent carbon in diesel, 86 weight percent carbon in gasoline, average brake
specific fuel consumption of 7000 Btu/hp-hr, diesel heating value of 19300 Btu/lb,
and gasoline heating value of 20300 Btu/lb.
3.3-4
EMISSION FACTORS
7/93
-------
TABLE 3.3-3. (ENGLISH AND METRIC UNITS) SPECIATED ORGANIC COMPOUNDS AND
AIR TOXIC EMISSION FACTORS FOR UNCONTROLLED DIESEL ENGINES3
(Source Classification Codes: 20200102, 20300101)
(ALL EMISSION FACTORS ARE RATED: E)b
Pollutant
Benzene
Toluene
Xylenes
Propylene
1,3 Butadiene"
Formaldehyde
Acetaldehyde
Acrolein
Polycyclic Aromatic Hydrocarbons (PAH)
Naphthalene
Acenaphthylene
Acenaphthene
Fluorene
Phenanthrene
Anthracene
Fluoranthene
Pyrene
Benz(a)anthracene
Chrysene
Benzo(b)fluoranthene
Benzo(k)fluoranthene
Benzo(a)pyrene
Indeno(l ,2,3-cd)pyrene
Dibenz(a,h)anthracene
Benzo(g,h,l)perylene
Total PAH
[Ib/MMBtu]
(fuel input)
9.33 E-04
4.09 E-04
2.85 E-04
2.58 E-03
< 3.91 E-05
1.18 E-03
7.67 E-04
< 9.25 E-05
8.48 E-05
< 5.06 E-06
< 1.42 E-06
2.92 E-05
2.94 E-05
1.87 E-06
7.61 E-06
4.78 E-06
1.68 E-06
3.53 E-07
< 9.91 E-08
< 1.55 E-07
< 1.88 E-07
< 3.75 E-07
< 5.83 E-07
< 4.89 E-07
1.68 E-04
[ng/J]
(fuel input)
0.401
0.176
0.122
1.109
< 0.017
0.509
0.330
< 0.040
3.64 E-02
< 2.17 E-03
< 6.11 E-04
1.26 E-02
1.26 E-02
8.02 E-04
3.27 E-03
2.06 E-03
7.21 E-04
1.52 E-04
< 4.26 E-05
< 6.67 E-05
< 8.07 E-05
< 1.61 E-04
< 2.50 E-04
< 2.10 E-04
7.22 E-02
"Data are based on the uncontrolled levels of two diesel engines from References 6 and 7.
b"E" rated emission factors are due to limited data sets, inherent variability in the
population and/or a lack of documentation of test results. "E" rated emission factors
may not be suitable for specific facilities or populations and should be used with care.
"Data are based on one engine.
7/93 Stationary Internal Combustion Sources 3.3.5
-------
TABLE 3.3-4. DIESEL EMISSION CONTROL TECHNOLOGIES8
Technology
Affected Parametei*
Increase
Decrease
Fuel Modifications
Sulfur Content Increase
Aromatic Content Increase
Cetane Number
10 percent and 90 percent Boiling Point
Fuel Additives
Water/Fuel Emulsions
Engine Modifications
Injection Timing
Fuel Injection Pressure
Injection Rate Control
Rapid Spill Nozzles
Electronic Timing & Metering
Injector Nozzle Geometry
Combustion Chamber Modifications
Turbocharging
Charge Cooling
Exhaust Gas Recirculation
Oil Consumption Control
Exhaust After Treatment
Paniculate Traps
Selective Catalytic Reduction
Oxidation Catalysts
PM, Wear
PM, NOX
NOX, PM, BSFC,
Power
PM, NOX
PM, Power
PM, Power, Wear
PM, NOX
PM
PM, NOX
NOX
NOT
NOX, PM
PM
NOX, PM
PM
NOX, PM
NOX
NOX
NOX
PM, Wear
PM
NOX
HC, CO, PM
"Reference 4.
"NO, = Nitrogen oxides; PM = Paniculate matter, HC = Hydrocarbons;
CO = Carbon monoxide; BSFC = Brake specific fuel consumption.
3.3-6
EMISSION FACTORS
7/93
-------
References for Section 3.3
1. Hare, C.T. and K.J. Springer, Exhaust Emissions from Uncontrolled Vehicles and Related
Equipment using Internal Combustion Engines. Part 5: Farm, Construction, and Industrial
Engines, U.S. Environmental Protection Agency, Research Triangle Paric, NC, Publication
APTD-1494, October 1973, pp. 96-101.
2. Lips, H.I., J.A. Gotterba, and KJ. Lira, Environmental Assessment of Combustion
Modification Controls for Stationary Internal Combustion Engines. EPA-600/7-81-127,
Industrial Environmental Research Laboratory, Office of Environmental Engineering and
Technology, Office of Air Quality Planning and Standards, U.S. Environmental Protection
Agency, Research Triangle Park, NC, July 1981.
3. Standards Support and Environmental Impact Statement. Volume I: Stationary Internal
Combustion Engines, EPA-450/2-78-125a, Emission Standards and Engineering Division,
Office of Air, Noise, and Radiation, Office of Air Quality Planning and Standards, U.S.
Environmental Protection Agency, Research Triangle Park, NC, July 1979.
4. Technical Feasibility of Reducing NOT and Paniculate Emissions from Heavv-Duty Engines.
Draft Report by Acurex Environmental Corporation for the California Air Resources Board,
Sacramento, CA, March 1992, CARB Contract A132-085.
5. Nonroad Engine and Vehicle Emission Study-Report. EPA-460/3-91-02, Certification Division,
Office of Mobile Sources, Office of Air & Radiation, U.S. Environmental Protection Agency,
Research Triangle Park, NC, November 1991.
6. Pooled Source Emission Test Report: Oil and Gas Production Combustion Sources. Fresno
and Ventura Counties, California, Report prepared by ENSR Consulting and Engineering for
Western States Petroleum Association (WSPA), Bakersfield, CA, December 1990, ENSR
7230-007-700.
7. Osborn, W.E., and M.D. McDannel, Emissions of Air Toxic Species: Test Conducted Under
AB2588 for the Western States Petroleum Association. Report prepared by Carnot for Western
States Petroleum Association (WSPA), Glendale, CA, May 1990, CR 72600-2061.
7/93 Stationary Internal Combustion Sources 3.3.7
-------
3.4 LARGE STATIONARY DIESEL AND ALL STATIONARY DUAL FUEL ENGINES
3.4.1 General
The primary domestic use of large stationary diesel engines (greater than 600 hp) is in oil and
gas exploration and production. These engines, in groups of three to five, supply mechanical power to
operate drilling (rotary table), mud pumping and hoisting equipment, and may also operate pumps or
auxiliary power generators. Another frequent application of large stationary diesels is electricity
generation for both base and standby service. Smaller uses include irrigation, hoisting and nuclear
power plant emergency cooling water pump operation.
Dual fuel engines were developed to obtain compression ignition performance and the
economy of natural gas, using a minimum of 5 to 6 percent diesel fuel to ignite the natural gas. Large
dual fuel engines have been used almost exclusively for prime electric power generation. This section
includes all dual fuel engines.
3.4.2 Process Description
All reciprocating internal combustion (1C) engines operate by the same basic process. A
combustible mixture is first compressed in a small volume between the head of a piston and its
surrounding cylinder. The mixture is then ignited, and the resulting high pressure products of
combustion push the piston through the cylinder. This movement is converted from linear to rotary
motion by a crankshaft. The piston returns, pushing out exhaust gases, and the cycle is repeated.
There are two methods used for stationary reciprocating 1C engines: compression ignition (CI)
and spark ignition (SI). Section 3.4 deals only with compression ignition engines.
In compression ignition engines, combustion air is first compression heated in the cylinder,
and diesel fuel oil is then injected into the hot air. Ignition is spontaneous as the air is above the auto-
ignition temperature of the fuel. Spark ignition engines initiate combustion by the spark of an
electrical discharge. Usually the fuel is mixed with the air in a carburetor (for gasoline) or at the
intake valve (for natural gas), but occasionally the fuel is injected into the compressed air in the
cylinder. Although all diesel fueled engines are compression ignited and all gasoline and gas fueled
engines are spark ignited, gas can be used in a compression ignition engine if a small amount of diesel
fuel is injected into the compressed gas/air mixture to burn any mixture ratio of gas and diesel oil
(hence the name dual fuel), from 6- to 100-percent diesel oil.
CI engines usually operate at a higher compression ratio (ratio of cylinder volume when the
piston is at the bottom of its stroke to the volume when it is at the top) than SI engines because fuel is
not present during compression; hence there is no danger of premature auto-ignitioa Since engine
thermal efficiency rises with increasing pressure ratio (and pressure ratio varies directly with
compression ratio), CI engines are more efficient than SI engines. This increased efficiency is gained
at the expense of poorer response to load changes and a heavier structure to withstand the higher
pressures.
7/93 Stationary Internal Combustion Sources 3.4-1
-------
3.4.3 Emissions and Controls
Most of the pollutants from 1C engines are emitted through the exhaust However, some
hydrocarbons escape from the crankcase as a result of blowby (gases which are vented from the oil
pan after they have escaped from the cylinder past the piston rings) and from the fuel tank and
carburetor because of evaporation. Nearly all of the hydrocarbons from diesel compression ignition
(CI) engines enter the atmosphere from the exhaust Crankcase blowby is minor because hydrocarbons
are not present during compression of the charge. Evaporative losses are insignificant in diesel
engines due to the low volatility of diesel fuels. In general, evaporative losses are also negligible in
engines using gaseous fuels because these engines receive their fuel continuously from a pipe rather
than via a fuel storage tank and fuel pump.
The primary pollutants from internal combustion engines are oxides of nitrogen (NOJ, organic
compounds (hydrocarbons), carbon monoxide (CO), and particulates, which include both visible
(smoke) and nonvisible emissions. The other pollutants are primarily the result of incomplete
combustion. Ash and metallic additives in the fuel also contribute to the paniculate content of the
exhaust Oxides of sulfur (SOX) also appears in the exhaust from 1C engines.
The primary pollutant of concern from large stationary diesel and all stationary dual fuel
engines is NOX, which readily forms in the high temperature, pressure, nitrogen content of the fuel,
and excess air environment found in these engines. Lesser amounts of CO and organic compounds are
emitted. The sulfur compounds, mainly SO2, are directly related to the sulfur content of the fuel. SOX
emissions will usually be quite low because of the negligible sulfur content of diesel fuels and natural
gas.
Tables 3.4-1 (English units) and 3.4-2 (Metric units) contain gaseous emission factors.
Table 3.4-3 shows the speciated organic compound emission factors and Table 3.4-4 shows the
emission factors for polycyclic aromatic hydrocarbons (PAH). These tables do not provide a complete
speciated organic compound and PAH listing since they are based only on a single engine test; they
are to be used for rough order of magnitude comparisons.
Table 3.4-5 shows the particulate and particle sizing emission factors.
Control measures to date have been directed mainly at limiting NOX emissions because NOX is
the primary pollutant from diesel and dual fuel engines. Table 3.4-6 shows the NOX reduction and fuel
consumption penalties for diesel and dual fueled engines based on some of the available control
techniques. All of these controls are engine control techniques except for the selective catalytic
reduction (SCR) technique, which is a post-combustion control. The emission reductions shown are
those which have been demonstrated. The effectiveness of controls on an particular engine will
depend on the specific design of each engine and the effectiveness of each technique could vary
considerably. Other NOX control techniques exist but are not included in Table 3.4-6. These
techniques include internal/external exhaust gas recirculation (EGR), combustion chamber
modification, manifold air cooling, and turbocharging.
3.4-2 EMISSION FACTORS 7/93
-------
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Stationary Internal Combustion Sources
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EMISSION FACTORS
4/93
-------
TABLE 3.4-3. (ENGLISH AND METRIC UNITS) SPECIATED ORGANIC COMPOUND
EMISSION FACTORS FOR LARGE STATIONARY DIESEL ENGINES"
(Source Classification Code: 20200401)
(Emission Factor Rating: E)b
Pollutant
Benzene
Toluene
Xylenes
Propylene
Formaldehyde
Acetaldehyde
Acrolein
[Ib/MMBtu]
(fuel input)
7.76 E-04
2.81 E-04
1.93 E-04
2.79 E-03
7.89 E-05
2.52 E-05
7.88 E-06
[ng/J]
(fuel input)
3.34 E-01
1.21 E-01
8.30 E-02
1.20 E-00
3.39 E-02
1.08 E-02
3.39 E-03
"Data based on the uncontrolled levels of one diesel engine from reference 5. There was enough
information to compute the input specific emission factors of Ib/MMBtu, but not enough to calculate
the output specific emission factor of g/hp-hr. There was enough information to compute the input
specific emission factors of ng/J, but not enough to calculate the output specific emission factor of
g/kW-hr.
b"E" rating for emission factors are due to limited data sets, inherent variability in the population
and/or a lack of documentation of test results. "E" rated emission factors may not be suitable for
specific facilities or populations and should be used with care.
7/93 Stationary Internal Combustion Sources 3.4.5
-------
TABLE 3.4-4. (ENGLISH AND METRIC UNITS) POLYCYCLIC AROMATIC HYDROCARBON
(PAH) EMISSION FACTORS FOR LARGE STATIONARY DIESEL ENGINES"
(Source Classification Code: 20200401)
(Emission Factor Rating: E)b
Pollutant
Polycyclic Aromatic Hydrocarbons (PAH)
Naphthalene
Acenaphthylene
Acenaphthene
Fluorene
Phenanthrene
Anthracene
Fluoranthene
Pyrene
Benz(a)anthracene
Chrysene
Benzo(b)fluoranthene
Benzo(k)fluoranthene
Benzo(a)pyrene
Indeno(l ,2,3-cd)pyrene
Dibenz(a,h)anthracene
Benzo(g,h,l)perylene
Total PAH
[Ib/MMBru]
(fuel input)
1.30 E-04
9.23 E-06
4.68 E-06
1.28 E-05
4.08 E-05
1.23 E-06
4.03 E-06
3.71 E-06
6.22 E-07
1.53 E-06
1.11 E-06
< 2.18 E-07
< 2.57 E-07
< 4. 14 E-07
< 3.46 E-07
< 5.56 E-07
2.12 E-04
[ng/J]
(fuel input)
5.59 E-02
3.97 E-03
2.01 E-03
5.50 E-03
1.75 E-02
5.29 E-04
1.73 E-03
1.60 E-03
2.67 E-04
6.58 E-04
4.77 E-04
< 9.37 E-05
< 1.10 E-04
< 1.78 E-04
< 1.49 E-04
< 2.39 E-04
9.09 E-02
"Data are based on the uncontrolled levels of one diesel engine from reference 5. There was enough
information to compute the input specific emission factors of Ib/MMBtu and ng/J but not enough to
calculate the output specific emission factor of g/hp-hr and g/kW-hr.
b"E" rating for emission factors is due to limited data sets, inherent variability in the population and/or
a lack of documentation of test results. "E" rated emission factors may not be suitable for specific
facilities or populations and should be used with care.
3.4-6 EMISSION FACTORS 7/93
-------
TABLE 3.4-5. (ENGLISH AND METRIC UNITS) PARTICULATE AND PARTICLE SIZING
EMISSION FACTORS FOR LARGE STATIONARY DIESEL ENGINES"
(Source Classification Code: 20200401)
(Emission Factor Rating: E)b
Pollutant
Paniculate Size Distribution
<1 urn
1-3 um
3-10 urn
>10um
Total PM-10 (£10 um)
TOTAL
Paniculate Emissions
Solids
Condensables
TOTAL
Power Output
[grams/hp-hr] [grams/kW-hr]
0.1520 0.2038
0.0004 0.0005
0.0054 0.0072
0.0394 0.0528
0.1578 0.2116
0.1972 0.2644
0.2181 0.2925
0.0245 0.0329
0.2426 0.3253
Fuel Input
[Ib/MMBtu]
0.0478
0.0001
0.0017
0.0124
0.0496
0.0620
0.0686
0.0077
0.0763
[ng/J]
20.56
0.05
0.73
5.33
21.34
26.67
29.49
3.31
32.81
"Data are based on the uncontrolled levels of one diesel engine from reference 6. The data for the
paniculate emissions were collected using Method 5 and the particle size distributions were
collected using a Source Assessment Sampling System (SASS).
b"E" rating for emission factors is due to limited data sets, inherent variability in the population and/or
a lack of documentation of test results. "E" rated emission factors may not be suitable for specific
facilities or populations and should be used with care.
7/93
Stationary Internal Combustion Sources
3.4-7
-------
TABLE 3.4-6. NOX REDUCTION AND FUEL CONSUMPTION PENALTIES FOR
LARGE STATIONARY DIESEL AND DUAL FUEL ENGINES3
(Source Classification Codes)
Control Approach
Diesel
(SCC 20200401)
Percent NOX
Reduction
ABSFC,b
Percent
Dual Fuel
(SCC 20200402)
Percent
NOX
Reduction
ABSFC,"
Percent
Derate
Retard
Air-to-Fuel
Water Injection (H20/fuel ratio)
Selective Catalytic Reduction (SCR)
10%
20%
25%
2°
4°
8°
3%
±10%
50%
<20
5-23
<20
<40
28-45
7-8
25-35
80-95
4
1-5
4
4
2-8
3
2-4
0
<20
1-33
<20
<40
50-73
<20
25-40
80-95
4
1-7
3
1
3-5
0
1-3
0
"Data are based on references 1, 2, and 3. The reductions shown are typical and will vary depending
on the engine and duty cycle.
bBSFC = Brake Specific Fuel Consumption.
3.4-8
EMISSION FACTORS
7/93
-------
References for Section 3.4
1. Lips, H.I., J.A. Gotterba, and K.J. Lim, Environmental Assessment of Combustion Modification
Controls for Stationary Internal Combustion Engines. EPA-600/7-81-127, Industrial Environmental
Research Laboratory, Office of Environmental Engineering and Technology, Office of Air Quality
Planning and Standards, U.S. Environmental Protection Agency, Research Triangle Park, NC, July
1981,
2. Campbell, L.M., D.K. Stone, and G.S. Shareef, Sourcebook: NOT Control Technology Data,
Control Technology Center. EPA-600/2-91-029, Emission Standards Division, Office of Air
Quality Planning and Standards, U.S. Environmental Protection Agency, Research Triangle Park,
NC, July 1991.
3. Catalysts for Air Pollution Control, brochure by the Manufacturers of Emission Controls
Association (MECA), Washington, DC, March 1992.
4. Standards Support and Environmental Impact Statement. Volume I: Stationary Internal
Combustion Engines. EPA-450/2-78-125a, Emission Standards and Engineering Division, Office of
Air, Noise, and Radiation, Office of Air Quality Planning and Standards, U.S. Environmental
Protection Agency, Research Triangle Park, NC, July 1979.
5. Pooled Source Emission Test Report: Oil and Gas Production Combustion Sources. Fresno and
Ventura Counties. California. Report prepared by ENSR Consulting and Engineering for Western
States Petroleum Association (WSPA), Bakersfield, CA, December 1990, ENSR # 7230-007-700.
6. Castaldini, C., Environmental Assessment of NOT Control on a Compression Ignition Large Bore
Reciprocating Internal Combustion Engine. Volume I: Technical Results. EPA-600/7-86/001a,
Combustion Research Branch of the Energy Assessment and Control Division, Industrial
Environmental Research Laboratory, Office of Research and Development, U.S. Environmental
Protection Agency, Washington, DC, April 1984.
7/93 Stationary Internal Combustion Sources 3.4-9
-------
5.2 SYNTHETIC AMMONIA
5.2.1 General1'2
Synthetic ammonia (NH3) refers to ammonia that has been synthesized (SIC 2873) from natural
gas. Natural gas molecules are reduced to carbon and hydrogen. The hydrogen is then purified and
reacted with nitrogen to produce ammonia. Approximately 75 percent of the ammonia produced is
used as fertilizer, either directly as ammonia or indirectly after synthesis as urea, ammonium nitrate,
and monoammonium or diammonium phosphates. The remaining is used as raw material in the
manufacture of polymeric resins, explosives, nitric acid, and other products.
Synthetic ammonia plants are located throughout the U. S. and Canada. Synthetic ammonia is
produced in 25 states by 60 plants which have an estimated combined annual production capacity of
15.9 million megagrams (17.5 million tons) in 1991. Ammonia plants are concentrated in areas with
abundant supplies of natural gas. Seventy percent of U. S. capacity is located in Louisiana, Texas,
Oklahoma, Iowa and Nebraska.
5.2.2 Process Description1'3"4
Anhydrous ammonia is synthesized by reacting hydrogen with nitrogen at a molar ratio of 3 to
1, then compressing the gas and cooling it to -33°C (-27°F). Nitrogen is obtained from the air, while
hydrogen is obtained from either the catalytic steam reforming of natural gas (methane) or naphtha, or
the electrolysis of brine at chlorine plants. In the U. S., about 98 percent of synthetic ammonia is
produced by catalytic steam reforming of natural gas. Figure 5.2-1 shows a general process flow
diagram of a typical ammonia plant.
Six process steps are required to produce synthetic ammonia using the catalytic steam reforming
method: 1) natural gas desulfurization, 2) catalytic steam reforming, 3) carbon monoxide shift, 4)
carbon dioxide removal, 5) methanation and 6) ammonia synthesis. The first, third, fourth, and fifth
steps remove impurities such as sulfur, CO, CO2 and water from the feedstock, hydrogen and
synthesis gas streams. In the second step, hydrogen is manufactured and nitrogen (air) is introduced
into this two stage process. The sixth step produces anhydrous ammonia from the synthetic gas.
While all ammonia plants use this basic process, details such as operating pressures, temperatures,
and quantities of feedstock vary from plant to plant.
5.2.2.1 Natural Gas Desulfurization
In this step, the sulfur content (as H2S) in natural gas is reduced to below 280 micrograms per
cubic meter to prevent poisoning of the nickel catalyst in the primary reformer. Desulfurization can
be accomplished by using either activated carbon or zinc oxide. Over 95 percent of the ammonia
plants in the U. S. use activated carbon fortified with metallic oxide additives for feedstock
desulfurization. The remaining plants use a tank filled with zinc oxide for desulfurization. Heavy
hydrocarbons can decrease the effectiveness of an activated carbon bed. This carbon bed also has
another disadvantage in that it cannot remove carbonyl sulfide. Regeneration of carbon is
accomplished by passing superheated steam through the carbon bed. A zinc oxide bed offers several
advantages over the activated carbon bed. Steam regeneration to use as energy is not required when
using a zinc oxide bed. No air emissions are created by the zinc oxide bed, and the higher
7/93 Chemical Process Industry 5.2-1
-------
NATURAL GAS
FUEL
STEAM
AIR
EMISSIONS
3-01-003-09
PROCESS
CONDENSATE
FEEDSTOCK
DESULFURIZATION
PRIMARY REFORMER
SECONDARY
REFORMER
HIGH TEMPERATURE
SHIFT
LOW TEMPERATURE
SHIFT
I
CO2 ABSORBER
1
METHANATION
AMMONIA SYNTHESIS
NH
EMISSIONS DURING
REGENERATION
3-01-003-05
FUEL COMBUSTION
EMISSIONS
t
3-01-003-06 (natural gas)
3-01-003-07 (oil fired)
EMISSIONS
3-01-003-008
CO2 SOLUTION
REGENERATION
STEAM
PURGE GAS VENTED TO
PRIMARY REFORMER
FOR FUEL
Figure 5.2-1 General flow diagram of a typical ammonia plant.
molecular weight hydrocarbons are not removed. Therefore, the heating value of the natural gas is
not reduced.
5.2.2.2 Catalytic steam reforming
Natural gas leaving the desulfurization tank is mixed with process steam and preheated to
540°C (1004°F). The mixture of steam and gas enters the primary reformer (natural gas fired
primary reformer and oil fired primary reformer tubes, which are filled with a nickel-based reforming
5.2-2
EMISSION FACTORS
7/93
-------
catalyst. Approximately 70 percent of the methane (CH4) is converted to hydrogen and carbon
dioxide (CO2). An additional amount of CH4 is converted to CO. This process gas is then sent to
the secondary reformer, where it is mixed with compressed air that has been preheated to about
540°C (1004°F). Sufficient air is added to produce a final synthesis gas having a hydrogen-to-
nitrogen mole ratio of 3 to 1. The gas leaving the secondary reformer is then cooled to 360 °C
(680°F) in a waste heat boiler.
5.2.2.3 Carbon monoxide shift
After cooling, the secondary reformer effluent gas enters a high temperature CO shift converter
which is filled with chromium oxide initiator and iron oxide catalyst. The following reaction takes
place in the carbon monoxide converter:
CO + H2O -» CO2 + H2 (1)
The exit gas is then cooled in a heat exchanger. In some plants, the gas is passed through a bed of
zinc oxide to remove any residual sulfur contaminants that would poison the low temperature shift
catalyst. In other plants, excess low temperature shift catalyst is added to ensure that the unit will
operate as expected. The low temperature shift converter is filled with a copper oxide/zinc oxide
catalyst. Final shift gas from this converter is cooled from 210 to 110°C (410 to 230°F) and enters
the bottom of the carbon dioxide absorption system. Unreacted steam is condensed and separated
from the gas in a knockout drum. This condensed steam (process condensate) contains ammonium
carbonate ([(NH4)2 CO3 • H2O]) from the high temperature shift converter, methanol (CH3OH) from
the low temperature shift converter, and small amounts of sodium, iron, copper, zinc, aluminum and
calcium.
Process condensate is sent to the stripper to remove volatile gases such as ammonia, methanol,
and carbon dioxide. Trace metals remaining in the process condensate are removed by the ion
exchange unit.
5.2.2.4 Carbon dioxide removal
In this step, CO2 in the final shift gas is removed. CO2 removal can be done by using two
methods: monoethanolamine (C2H4NH2OH) scrubbing and hot potassium scrubbing. Approximately
80 percent of the ammonia plants use monoethanolamine (MEA) to aid in removing CO2. The CO2
gas is passed upward through an adsorption tower countercurrent to a 15 to 30 percent solution of
MEA in water fortified with effective corrosion inhibitors. After absorbing the CO2, the amine
solution is preheated and regenerated (carbon dioxide regenerator) in a reactivating tower. This
reacting tower removes CO2 by steam stripping and then by heating. The CO2 gas (98.5 percent CO2)
is either vented to the atmosphere or used for chemical feedstock in other parts of the plant complex.
The regenerated MEA is pumped back to the absorber tower after being cooled in a heat exchanger
and solution cooler.
5.2.2.5 Methanation
Residual CO2 in the synthesis gas is removed by catalytic methanation which is conducted over
a nickel catalyst at temperatures of 400 to 600°C (752 to 1112°F) and pressures up to 3,000 kPa (435
psia) according to the following reactions:
CO + 3H2 - CH4 + H20 (2)
7/93 Chemical Process Industry 5.2-3
-------
CO2 + H2 -» CO + H2O (3)
CO2 + 4H2 -* CH4 + 2H2O (4)
Exit gas from the methanator, which has a 3:1 mole ratio of hydrogen and nitrogen, is then cooled to
38°C (100°F).
5.2.2.6 Ammonia Synthesis
In the synthesis step, the synthesis gas from the methanator is compressed at pressures ranging
from 13,800 to 34,500 kPa (2000 to 5000 psia), mixed with recycled synthesis gas, and cooled to
0°C (32°F). Condensed ammonia is separated from the unconverted synthesis gas in a liquid-vapor
separator and sent to a let-down separator. The unconverted synthesis is compressed and preheated to
180°C (356°F) before entering the synthesis converter which contains iron oxide catalyst. Ammonia
from the exit gas is condensed and separated, then sent to the let-down separator. A small portion of
the overhead gas is purged to prevent the buildup of inert gases such as argon in the circulating gas
system.
Ammonia in the let-down separator is flashed to 100 kPa (14.5 psia) at -33°C (-27°F) to
remove impurities from the liquid. The flash vapor is condensed in the let-down chiller where
anhydrous ammonia is drawn off and stored at low temperature.
5.2.3 Emissions And Controls1'3
Pollutants from the manufacture of synthetic anhydrous ammonia are emitted from four process
steps: 1) regeneration of the desulfurization bed, 2) heating of the catalytic steam, 3) regeneration of
carbon dioxide scrubbing solution, and 4) steam stripping of process condensate.
More than 95 percent of the ammonia plants in the U. S. use activated carbon fortified with
metallic oxide additives for feedstock desulfurization. The desulfurization bed must be regenerated
about once every 30 days for an average period of 8 to 10 hours. Vented regeneration steam contains
sulfur oxides (SOX) and hydrogen sulfide (H2S), depending on the amount of oxygen in the steam.
Regeneration also emits hydrocarbons and carbon monoxide (CO). The reformer, heated with natural
gas or fuel oil, emits combustion products such as NOX, CO, SOX, hydrocarbons, and particulates.
Carbon dioxide (CO^ is removed from the synthesis gas by scrubbing with MEA or hot
potassium carbonate solution. Regeneration of this CO2 scrubbing solution with steam produces
emission of water, NH3, CO, CO2 and monoethanolamine.
Cooling the synthesis gas after low temperature shift conversion forms a condensate containing
NH3, CO2, methanol (CH3OH), and trace metals. Condensate steam strippers are used to remove
NH3 and methanol from the water, and steam from this is vented to the atmosphere, emitting NH3,
CO2, and methanol.
Some processes have been modified to reduce emissions and to improve utility of raw materials
and energy. One such technique is the injection of the overheads into the reformer stack along with
the combustion gases to eliminate emissions from the condensate steam stripper.
5.2-4 EMISSION FACTORS 7/93
-------
"
Q
W
_!
i
H
2
8
fc
D
o"
u
o
Total Organic Compounds
o"
V)
O
o
c
O *H 60
|t2 «
I
a
60
S
>
|| 60
|l<5
I
£
60
S
J?
fg b 60
« fc *"
I
i
60
J?
C
.2 g 60
gM § s
wfc*
1
.c
60
1 S "
Jl*
I
i
60
1
Emission Point
(SCC)
Desulfurization unit
regeneration1* 6.9 13.8 E 0.0288c>d 0.0576c'd E 3.6 7.2 E
(SCC 3-01-003-05)
Carbon dioxide regenerator
(SCC 3-01-003-008) l.O11 2.011 E 0.52e 1.04 E 1.0 2.0 E 1220 2440 E
Condensate steam stripper
(SCC 3-01-003-09 0.6f 1.2 E 1.1 2.2 E 3.48 6.88 E
«
•-
a
i-
- =2
ot X> O T3 O <*- 60 J3
7/93
Chemical Process Industry
5.2-5
-------
References for Section 5.2
1. Source Category Survey: Ammonia Manufacturing Industry, EPA-450/3-80-014, U.S.
Environmental Protection Agency, Research Triangle Park, NC, August 1980.
2. North American Fertilizer Capacity Data, Tennessee Valley Authority, Muscle Shoals, AL,
December 1991.
3. G.D. Rawlings and R.B. Reznik, Source Assessment: Synthetic Ammonia Production, EPA-
600/2-77-107m, U. S. Environmental Protection Agency, Research Triangle Park, NC,
November 1977.
4. AIRS Facility Subsystem Source Classification Codes and Emission Factor Listing For Criteria
Pollutants. EPA-450/4-90-003, U. S. Environmental Protection Agency, Research Triangle
Park, NC 27711, March 1990.
5.2-6 EMISSION FACTORS 7/93
-------
5.5 CHLOR-ALKALI
5.5.1 General1'2
The chlor-alkali electrolysis process is used in the manufacture of chlorine, hydrogen and
sodium hydroxide (caustic) solution. Of these three, the primary product is chlorine.
Chlorine is one of the more abundant chemicals produced by industry and has a wide variety of
industrial uses. Chlorine was first used to produce bleaching agents for the textile and paper industries
and for general cleaning and disinfecting. Since 1950, chlorine has become increasingly important as
a raw material for synthetic organic chemistry. Chlorine is an essential component of construction
materials, solvents, and insecticides. Annual production from U. S. facilities was 9.9 million
megagrams (10.9 million tons) in 1990 after peaking at 10.4 million megagrams (11.4 million tons) in
1989.
5.5.2 Process Description1"3
There are three types of electrolytic processes used in the production of chlorine: 1) the
diaphragm cell process, 2) the mercury cell process, and 3) the membrane cell process. In each
process, a salt solution is electrolyzed by the action of direct electric current which converts chloride
ions to elemental chlorine. The overall process reaction is:
2NaCl + 2H2O -» C12 + H2 + 2NaOH (1)
In all three methods the chlorine (C12) is produced at the positive electrode (anode) and the caustic
soda (NaOH) and hydrogen (H2) are produced, directly or indirectly, at the negative electrode
(cathode). The three processes differ in the method by which the anode products are kept separate
from the cathode products.
Of the chlorine produced in the U. S. in 1989, 94 percent was produced either by the
diaphragm cell or mercury cell process. Therefore, these will be the only two processes discussed in
this section.
5.5.2.1 Diaphragm Cell
Figure 5.5-1 shows a simplified block diagram of the diaphragm cell process. Water and
sodium chloride (NaCl) are combined to create the starting brine solution. The brine undergoes
precipitation and filtration to remove impurities. Heat is applied and more salt is added. Then the
nearly saturated, purified brine is heated again before direct electric current is applied. The anode is
separated from the cathode by a permeable asbestos-based diaphragm to prevent the caustic soda from
reacting with the chlorine. The chlorine produced at the anode is removed, and the saturated brine
flows through the diaphragm to the cathode chamber. The chlorine is then purified by liquefaction and
evaporation to yield a pure liquified product.
The caustic brine produced at the cathode is separated from salt and concentrated in an
elaborate evaporative process to produce commercial caustic soda. The salt is recycled to saturate the
dilute brine. The hydrogen removed in the cathode chamber is cooled and purified by removal of
7/93 Chemical Process Industry 5.5-1
-------
oxygen, then used in other plant processes or sold.
5.5.2.2 Mercury Cell
Figure 5.5-2 shows a simplified block diagram for the mercury cell process. The recycled brine
from the electrolysis process (anolyte) is dechlorinated and purified by a precipitation-filtration
process. The liquid mercury cathode and the brine enter the cell flowing concurrently. The
electrolysis process creates chlorine at the anode and elemental sodium at the cathode. The chlorine is
removed from the anode, cooled, dried, and compressed. The sodium combines with mercury to form
a sodium amalgam. The amalgam is further reacted with water in a separate reactor called the
decomposer to produce hydrogen gas and caustic soda solution. The caustic and hydrogen are then
separately cooled and the mercury removed before proceeding to storage, sales or other processes.
5.5.3 Emissions And Controls4
Table 5.5-1 is a summary of chlorine emission factors for chlor-alkali plants. Emissions from
diaphragm and mercury cell plants include chlorine gas, carbon dioxide (CO2), carbon monoxide
(CO), and hydrogen. Gaseous chlorine is present in the blow gas from liquefaction, from vents in
tank cars and tank containers during loading and unloading, and from storage tanks and process
transfer tanks. Carbon dioxide emissions result from the decomposition of carbonates in the brine feed
when contacted with acid. Carbon monoxide and hydrogen are created by side reactions within the
production cell. Other emissions include mercury vapor from mercury cathode cells and chlorine from
compressor seals, header seals, and the air blowing of depleted brine in mercury-cell plants.
Emissions from these locations are, for the most part, controlled through the use of the gas in other
parts of the plant, neutralization in alkaline scrubbers, or recovery of the chlorine from effluent gas
streams.
Table 5.5-2 presents mercury emission factors based on two source tests used to substantiate the
mercury national emission standard for hazardous air pollutants (NESHAP). Due to insufficient data,
emission factors for CO, CO2, and hydrogen are not presented here.
5.5-2 EMISSION FACTORS 7/93
-------
WATER
SALT
(BRINE)
SALT
BRINE
SATURATION
RAW BRINE
PRECIPITATION
FILTRATION
CHLORINE
PURIFIED BRINE
HEAT
EXCHANGE
SALT
BRINE
SATURATION
HEAT
EXCHANGE
HYDROGEN
SALT
ELECTROLYSIS
CONCENTRATION
COOLING
STORAGE
SODIUH HYDROXIDE
HYDROGEH
OXYGEH
REMOVAL
HYDROGEN
PRECIPITANTS
RESIDUE
CHLORINE GAS
DRYING
COMPRESSION
LIQUEFACTION
EVAPORATION
CHLORINE
7/93
Figure 5.5-1 Simplified diagram of the diaphragm cell process
Chemical Process Industry
5.5-3
-------
SALT
DILUTED BRINE
CAUSTIC
SOLUTION
BRINE
SATURATION
RAW BRINE
PRECIPITATION
DECHLORINATION
HYDRO-
CHLORIC
ACID
PRECIPITANTS
FILTRATION
RESIDUE
COOLING
ANOLYTE
HYDROCHLORIC ACID
ELECTROLYSIS
WATER AMALGAM
CAUSTIC
SOLUTION
CHLORINE GAS
MERCURY
AMALGAM
DECOMPOSITION
COOLING
HYDROGEN
COOLING
MERCURY
REMOVAL
COOLING
MERCURY
REMOVAL
STORAGE
SODIUM HYDROXIDE
DRYING
COMPRESSION
HYDROGEN
CHLORINE
5.5-4
Figure 5.5-2 Simplified diagram of the mercury cell process
EMISSION FACTORS
7/93
-------
Table 5.5-1 (Metric Units).
EMISSION FACTORS FOR CHLORINE FROM CHLOR-ALKALI PLANTS'
Source (SCC)
Chlorine Gas
kg/Mg
of Chlorine
Produced
Emission
Factor
Rating
Liquefaction blow gases
Diaphragm cell (SCC 3-01-008-01)
Mercury cell (SCC 3-01-008-02)
Water absorbed (SCC 3-01-008-99)
Caustic scrubbed (SCC 3-01-008-99)
Chlorine Loading
Returned tank car vents (SCC 3-01-008-03)
Shipping container vents (SCC 3-01-008-04)
Mercury Cell Brine Air Blowing (SCC 3-01-008-05)
10 to 50
20 to 80
0.830
0.006
4.1
8.7
2.7
E
E
E
E
E
E
E
'Reference 4. SCC = Source Classification Code.
bControl devices.
Table 5.5-1 (English Units).
EMISSION FACTORS FOR CHLORINE FROM CHLOR-ALKALI PLANTS*
Source (SCC) .*!
of C
Prc
Liquefaction blow gases
Diaphragm cell (SCC 3-01-008-01) 20
Mercury cell (SCC 3-01-008-02) 40
Water absorbed (SCC 3-01-008-99)
Caustic scrubber13 (SCC 3-01-008-99) 0
Chlorine Gas
g/Mg Emission
"hlorine Factor
>duced Rating
to 100 E
to 160 E
1.66 E
.012 E
Chlorine Loading
Returned tank car vents (SCC 3-01-008-03) 8.2 E
Shipping container vents (SCC 3-01-008-04) 17.3 E
Mercury Cell Brine Air Blowing (SCC 3-01-008-05)
5.4 E
'Reference 4. Units are Ib of pollutant/ton .
bControl devices.
7/93
Chemical Process Industry
5.5-5
-------
Table 5.5-2 (Metric and English Units).
EMISSION FACTORS FOR MERCURY FROM MERCURY CELL CHLOR-ALKALI PLANTS*
Type of Source (SCC)
Mercury Gas
kg/Mg
of Clorine
Produced
Hydrogen Vent (SCC 3-01-008-02)
Uncontrolled 0.0017
Controlled 0.0006
End Box (SCC 3-01-008-02) 0.005
Ib/ton
of Clorine
Produced
0.0033
0.0012
0.010
Emission
Factor
Rating
E
E
E
* SCC = Source Classification Code
References for Section 5.5
1. Ullmann's Encyclopedia of Industrial Chemistry, VCH Publishers, New York, 1989.
2. The Chlorine Institute, Inc., Washington, DC, January 1991.
3. 1991 Directory Of Chemical Producers, Menlo Park, California: Chemical Information
Services, Stanford Research Institute, Stanford, CA, 1991.
4. Atmospheric Emissions from Chlor-A^kali Manufacture, AP-80, U. S. EPA, Office of Air
Quality Planning and Standards, Research Triangle Park, NC, January 1971.
5. B. F. Goodrich Chemical Company Chlor-Alkali Plant Source Tests, Calvert City, Kentucky,
EPA Contract No. CPA 70-132, Roy F. Weston, Inc., May 1972.
6. Diamond Shamrock Corporation Chlor-Alkali Plant Source Tests, Delaware City, Delaware,
EPA Contract No. CPA 70-132, Roy F. Weston, Inc., June 1972.
5.5-6
EMISSION FACTORS
7/93
-------
5.7 Hydrochloric Acid
5.7.1 General1
Hydrochloric acid (HC1) is listed as a Title III Hazardous Air Pollutant (HAP). Hydrochloric
acid is a versatile chemical used in a variety of chemical processes, including hydrometallurgical
processing (e.g., production of alumina and/or titanium dioxide), chlorine dioxide synthesis, hydrogen
production, activation of petroleum wells, and miscellaneous cleaning/etching operations including
metal cleaning (e.g., steel pickling). Also known as muriatic acid, HC1 is used by masons to clean
finished brick work, is also a common ingredient in many reactions, and is the preferred acid for
catalyzing organic processes. One example is a carbohydrate reaction promoted by hydrochloric acid,
analogous to those in the digestive tracts of mammals.
Hydrochloric acid may be manufactured by several different processes, although over 90
percent of the HC1 produced in the U.S. is a byproduct of the chlorination reaction. Currently, U.S.
facilities produce approximately 2.3 million megagrams (2.5 million tons) of HC1 annually, a slight
decrease from the 2.5 million megagrams (2.8 million tons) produced in 1985.
5.7.2 Process Description1"4
Hydrochloric acid can be produced by one of the five following processes:
1) Synthesis from elements:
H2 + C12 - 2HC1 (1)
2) Reaction of metallic chlorides, particularly sodium chloride (NaCl), with sulfuric acid
(H2SO4) or a hydrogen sulfate:
NaCl + H2SO4 -* NaHSO4 + HC1 (2)
NaCl + NaHS04 -» Na2SO4 + HC1 (3)
2NaCl + H2SO4 - NajSC^ + 2HC1 (4)
3) As a byproduct of chlorination, e.g. in the production of dichloromethane,
trichloroethylene, perchloroethylene, or vinyl chloride:
C12 - C2H4C12 (5)
- C2H3C1 + HC1 (6)
4) By thermal decomposition of the hydrated heavy-metal chlorides from spent pickle liquor
in metal treatment:
2FeCl3 + 6H2O -» Fe2O3 + 3H2O + 6HC1 (7)
7/93 Chemical Process Industry 5.7-1
-------
5) From incineration of chlorinated organic waste:
C4H6C12 + 5O2 -» 4CO2 + 2H2O + 2HC1 (8)
Figure 5.7-1 is a simplified diagram of the steps used for the production of byproduct HC1 from the
chlorination process.
CHLORINATION GASES
VENT GAS
- HCI
- CHLORINE
CHLORINATION
PROCESS
t
HCI
ABSORPTION
SCRUBBER
CONCENTRATED
LIQUID HCI
DILUTE HCI
Figure 5.7-1 HCI production from chlorination process
After leaving the chlorination process, the HCl-containing gas stream proceeds to the absorption
column, where concentrated liquid HCI is produced by absorption of HCI vapors into a weak solution
of hydrochloric acid. The HCl-free chlorination gases are removed for further processing. The liquid
acid is then either sold or used elsewhere in the plant. The final gas stream is sent to a scrubber to
remove the remaining HCI prior to venting.
5.7.3 Emissions4'5
According to a 1985 emission inventory, over 89 percent of all HCI emitted to the atmosphere
resulted from the combustion of coal. Less than one percent of the HCI emissions came from the
direct production of HCI. Emissions from HCI production result primarily from gas exiting the HCI
purification system. The contaminants are HCI gas, chlorine and chlorinated organic compounds.
Emissions data are only available for HCI gas. Table 5.7-1 lists estimated emission factors for
systems with and without final scrubbers.
5.7-2
EMISSION FACTORS
7/93
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TABLE 5.7-1 (METRIC UNITS)
EMISSION FACTORS FOR HYDROCHLORIC ACID MANUFACTURE5
Type of Process
(SCC)
HC1 Emissions
kg/Mg
HC1
Produced
Emission
Factor
Rating
Byproduct hydrochloric acid
With final scrubber (3-011-01-99) 0.08 E
Without final scrubber (3-011-01-99) 0.90 E
TABLE 5.7-1 (ENGLISH UNITS)
EMISSION FACTORS FOR HYDROCHLORIC ACID MANUFACTURE5
Type of Process
(SCC)
HC1 Emissions
Ib/ton HC1
Produced
Emission
Factor
Rating
Byproduct hydrochloric acid
With final scrubber (3-011-01-99) 0.15 E
Without final scrubber (3-011-01-99) 1.8 E
7/93
Chemical Process Industry
5.7-3
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References for Section 5.7
1. Encyclopedia of Chemical Technology, Third Edition, Volume 12, John Wiley and Sons, New
York, 1978.
2. Ullmann's Encyclopedia of Industrial Chemistry, Volume A, VCH Publishers, New York,
1989.
3. Encyclopedia of Chemical Processing and Design, Marcel Dekker, Inc., New York, 1987.
4. Hydrogen Chloride and Hydrogen Fluoride Emission Factors for the NAPAP (National Acid
Precipitation Assessment Program) Emission Inventory, U.S. EPA, PB86-134040. October
1985.
5. Atmospheric Emissions from Hydrochloric Acid Manufacturing Processes. U.S. DHEW, PHS,
CPEHS, National Air Polluting Control Administration. Durham, N.C. Publication Number
AP-54. September 1969.
5.7-4 EMISSION FACTORS 7/93
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5.8 HYDROFLUORIC ACID
5.8.1 General5'6
Hydrogen fluoride (HF) is listed as a Title III Hazardous Air Pollutant (HAP). Hydrogen
fluoride is produced in two forms, as anhydrous hydrogen fluoride and as aqueous hydrofluoric acid.
The predominate form manufactured is hydrogen fluoride, a colorless liquid or gas which fumes on
contact with air and is water soluble.
Traditionally, hydrofluoric acid has been used to etch and polish glass. Currently, the largest
use for HF is in aluminum production. Other HF uses include uranium processing, petroleum
alkylation, and stainless steel pickling. Hydrofluoric acid is also used to produce fluorocarbons used
in aerosol sprays and in refrigerants. Although fluorocarbons are heavily regulated due to
environmental concerns, other applications for fluorocarbons include manufacturing of resins,
solvents, stain removers, surfactants, and Pharmaceuticals.
5.8.2 Process Description1'3'6
Hydrofluoric acid is manufactured by the reaction of acid-grade fluorspar (CaF2) with sulfuric
acid (H2SO4) as shown below:
CaF2 + H2SO4 -» CaSO4 + 2HF (1)
A typical HF plant is shown schematically in Figure 5.8-1. The endothermic reaction requires
30 to 60 minutes in horizontal rotary kilns externally heated to 200 to 250°C (390 to 480°F). Dry
fluorspar ("spar") and a slight excess of sulfuric acid are fed continuously to the front end of a
stationary prereactor or directly to the kiln by a screw conveyor. The prereactor mixes the
components prior to charging to the rotary kiln. Calcium sulfate (CaSO4) is removed through an air
lock at the opposite end of the kiln. The gaseous reaction products—hydrogen fluoride and excess
H2SO4 from the primary reaction, silicon tetrafluoride (SiF4), sulfur dioxide (SO2), carbon dioxide
(CO2), and water produced in secondary reactions—are removed from the front end of the kiln along
with entrained particulate. The particulates are removed from the gas stream by a dust separator and
returned to the kiln. Sulfuric acid and water are removed by a precondenser. Hydrogen fluoride
vapors are then condensed in refrigerant condensers forming "crude HF", which is removed to
intermediate storage tanks. The remaining gas stream passes through a sulfuric acid absorption tower
or acid scrubber, removing most of the remaining hydrogen fluoride and some residual sulfuric acid,
which are also placed in intermediate storage. The gases exiting the scrubber then pass through water
scrubbers, where the SiF4 and remaining HF are recovered as fluosilicic acid (H2SiF6). The water
scrubber tailgases are passed through a caustic scrubber before being released to the atmosphere. The
hydrogen fluoride and sulfuric acid are delivered from intermediate storage tanks to distillation
columns, where the hydrofluoric acid is extracted at 99.98 percent purity. Weaker concentrations
(typically 70 to 80 percent) are prepared by dilution with water.
5.8.3 Emissions And Controls1"2'4
Emission factors for various HF process operations are shown in Table 5.8-1. Emissions are
suppressed to a great extent by the condensing, scrubbing, and absorption equipment used in the
recovery and purification of the hydrofluoric and fluosilicic acid products. Particulate in the gas
7/93 Chemical Process Industry 5.8-1
-------
5.8-2
Figure 5.8-1. Hydrofluoric acid process flow diagram.
EMISSION FACTORS
7/93
-------
stream is controlled by a dust separator near the outlet of the kiln and is recycled to the kiln for
further processing. The precondenser removes water vapor and sulfuric acid mist, and the condensers,
acid scrubber and water scrubbers remove all but small amounts of HF, SiF4, SO2, and CO2 from the
tailgas. A caustic scrubber is employed to further reduce the levels of these pollutants in the tailgas.
Particulates are emitted during handling and drying of the fluorspar. They are controlled with
bag filters at the spar silos and drying kilns. Fugitive dust emissions from spar handling and storage
are controlled with flexible coverings and chemical additives.
Hydrogen fluoride emissions are minimized by maintaining a slight negative pressure in the kiln
during normal operations. Under upset conditions, a standby caustic scrubber or a bypass to the tail
caustic scrubber are used to control HF emissions from the kiln.
7/93 Chemical Process Industry 5.8-3
-------
Table 5.8-1 (Metric Units).
EMISSION FACTORS FOR HYDROFLUORIC ACID MANUFACTURE*
Operation And Controls
Control
efficiency
Emissions
Gases
kg/Mg
Acid
Produced
Emission
Factor
Rating
Paniculate (Spar)
kg/Mg
Fluorspar
Produced
Emission
Factor
Rating
Spar Dryingb (SCC 3-01-012-03)
Uncontrolled
Fabric filter
Spar Handling Silos0
Uncontrolled
Fabric filter
(SCC 3-01-012-04)
Transfer Operations (SCC 3-01-012-05)
Uncontrolled
Covers, additives
TailGasc (SCC 3-01-012-06)
Uncontrolled
0
99
0
99
0
80
0
37.5
0.4
30.0
0.3
3.0
0.6
E
E
E
E
E
E
12.5 (HF)
15.0
Caustic Scrubber
99
22.5
(S02)
0.1 (HF)
0.2 (SiF4)
0.3 (S02)
E
E
E
E
E
E
aSCC = Source Classification Code.
bReference 1. Averaged from information provided by 4 plants. Hourly fluorspar input calculated
from reported 1975 year capacity, assuming stoichiometric amount of calcium fluoride and 97.5%
content in fluorspar. Hourly emission rates calculated from reported baghouse controlled rates.
Values averaged are as follows:
Plant 1975 Capacity Emissions fluorspar (kg/Mg)
1 13,600 Mg HF 53
2 18,100 MgHF 65
3 45,400 Mg HF 21
4 10,000 Mg HF 15
"Reference 1. Four plants averaged for silo emissions, 2 plants for transfer operations emissions.
dThree plants averaged from Reference 1. Hydrogen fluoride and SiF4 factors from Reference 4.
5.8-4
EMISSION FACTORS
7/93
-------
Table 5.8-1 (English Units).
EMISSION FACTORS FOR HYDROFLUORIC ACID MANUFACTURE*
Operation And Control
Control
efficiency
Emissions
Gases
Ib/ton
Acid
Produced
Emission
Factor
Rating
Particulate (Spar)
Ib/ton
Fluorspar
Produced
Emission
Factor
Rating
Spar Dryingb (SCC 3-01-012-03)
Uncontrolled
Fabric filter
Spar handling silosc
Uncontrolled
Fabric Filter
(SCC 3-01-012-04)
Transfer operations (SCC 3-01-012-05)
Uncontrolled
Covers, additives
Tail Gasd (SCC 3-01-012-06)
Uncontrolled
0
99
0
99
0
80
0
75.0
0.8
60.0
0.6
6.0
1.2
E
E
E
E
E
E
Caustic Scrubber
99
25.0 (HF)
30.0
(SiF4)
45.0 (SO^
0.2 (HF)
0.3 (SiF^
0.5 (SO2)
E
E
E
E
E
E
*SCC = Source Classification Code
bReference 1. Averaged from information provided by 4 plants. Hourly fluorspar input calculated
from reported 1975 year capacity, assuming stoichiometric amount of calcium fluoride and 97.5%
content in fluorspar. Hourly emission rates calculated from reported baghouse controlled rates.
Values averaged are as follows:
Plant 1975 Capacity Emissions fluorspar flb/ton)
1 15,000 ton HF 106
2 20,000 ton HF 130
3 50,000 ton HF 42
4 11,000 ton HF 30
Reference 1. Four plants averaged for silo emissions, 2 plants for transfer operations emissions.
dThree plants averaged from Reference 1. Hydrogen fluoride and SiF4 factors from Reference 4.
7/93
Chemical Process Industry
5.8-5
-------
References for Section 5.8
1. Screening Study On Feasibility Of Standards Of Performance For Hydrofluoric Acid
Manufacture, EPA-450/3-78-109, U. S. Environmental Protection Agency, Research Triangle
Park, NC, October 1978.
2. "Hydrofluoric Acid", Kirk-Othmer Encyclopedia Of Chemical Technology, Interscience
Publishers, New York, NY, 1965.
3. W. R. Rogers and K. Muller, "Hydrofluoric Acid Manufacture", Chemical Engineering
Progress, 59(5): 85-8, May 1963.
4. J. M. Robinson, et al., Engineering And Cost Effectiveness Study Of Fluoride Emissions
Control, Vol. 1, PB 207 506, National Technical Information Service, Springfield, VA, 1972.
5. "Fluorine", Encyclopedia Of Chemical Processing And Design, Marcel Dekker, Inc., New
York, NY, 1985.
6. "Fluorine Compounds, Inorganic", Kirk-Othmer Encyclopedia Of Chemical Technology, John
Wiley & Sons, New York, NY, 1980.
5.8-6 EMISSION FACTORS 7/93
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5.9 NITRIC ACID
5.9.1 General1'2
In 1991, there were approximately 65 nitric acid (HNO3) manufacturing plants in the
U.S. with a total capacity of 10 million megagrams (11 million tons) of acid per year. The
plants range in size from 5,400 to 635,000 megagrams (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 in order to accommodate the high concentration of fertilizer
use. Another five to ten 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.
5.9.2 Process Description1'3"4
Nitric acid is produced by two 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.
5.9.2.1 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 5.9-1. This
process typically consists of three steps: 1) ammonia oxidation, 2) nitric oxide oxidation, 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 750 to 800°C (1380 to 1470°F) as it passes through a catalytic converter, according to the
following reaction:
4NH3 + 5O2 -» 4NO + 6H2O (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 proceeds in an exothermic reaction with a range of 93 to 98 percent
yield. Oxidation temperatures can vary from 750 to 900°C (1380 to 1650°F). Higher
catalyst temperatures increase reaction selectivity toward nitric oxide (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
-------
EMISSION
POINT
TAIL
COMPRESSOR
EXPANDER
L.GAS
301-01342
EFFLUENT
STACK
AMMONIA
,— NOV EMISSIONS
XCONTROL
2
FUEr
.. AIR
PREHEATER
oncuuuiiun >
NITSx-N !
Ml l.
A V / i r
T ^^ \ ••
^ r i
NITRIC OXIDE
GAS
I
c
4
/
)
)
\ /
WATER
ENTRAINED
MIST
SEPERATOR
COOLER
CONDENSER
PRODUCT
(50-70%
HNOo
Figure 5.9-1. Flow diagram of typical nitric acid plant
using single-pressure process (high-strength acid unit not shown).
5.9-2
EMISSION FACTORS
7/93
-------
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.
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 38°C
(100°F) or less at pressures up to 800 kPa (116 psia). The nitric oxide reacts noncatalytically
with residual oxygen to form nitrogen dioxide 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 promote 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
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 + H2O -* 2HNO3 + NO (3)
A secondary air stream is introduced into the column to re-oxidize the NO which 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 two 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 1400 kPa (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 400 kPa (58 psia), and the
absorption reactions are carried out at 800 to 1,400 kPa (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 200 °C
(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.
5.9.2.2 High Strength Acid Nitric 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
7/93 Chemical Process Industry 5.9-3
-------
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 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 and nitrogen oxide by-products. 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 5.9-2 presents a flow diagram
of high-strength nitric acid production from weak nitric acid.
H2S04
50-70% HNOg.N
HNO,
3 V 1'
DEHYDRATING
COLUMN
COOLING
WATER
o2.o2 i
ICONOENSI
*• )
—* BLEACHER < ,
( fc
STRONG
NITRIC ACI[
DR
AIR
L-»
OJ.NO
)
INEI
fc UNR
r~* QAS
ABSORPTION
COLUMN
*T,
EACTED
.ES
I w WEAK
* NITRIC ACID
Figure 5.9-2. Flow diagram of high-strength nitric acid production
from weak nitric acid.
5.9.3 Emissions And Controls3"5
Emissions from nitric acid manufacture consist primarily of NO, NO2 (which account
for visible emissions) and trace amounts of HNO3 mist and NH3. By far, the major source of
nitrogen oxides is the tail gas from the acid absorption tower. In general, the quantity of NOX
emissions are directly related to the kinetics of the nitric acid formation reaction and
absorption tower design. NOX emissions can increase when there is (1) insuffficient 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 which lead to lower pressures and leaks and decrease plant efficiency.
The two most common techniques used to control absorption tower tail gas emissions
are extended absorption and catalytic reduction. Extended absorption reduces nitrogen oxide
emissions by increasing the efficiency of the existing process absorption tower or
incorporating an additional absorption tower. An efficiency increase is achieved by increasing
5.9-4
EMISSION FACTORS
7/93
-------
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 nitrogen oxides 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 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 tail gas are molecular sieves
and wet scrubbers. In the molecular sieve adsorption technique, tail gas is contacted with an
active molecular sieve which 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 do not install this method of control. 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 tail
gas. 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
to treat 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 tail gas of a properly operated plant. The
small amounts that may be present in the absorber exit gas streams are removed by a
separator or collector prior to entering the catalytic reduction unit or expander.
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 oxide emission factors shown in Table 5.9-1 vary considerably with the type
of control employed and with process conditions. For comparison purposes, the New Source
Performance Standard on nitrogen emission expressed as NO2 for both new and modified
7/93 Chemical Process Industry 5.9-5
-------
plants is 1.5 kilograms of NO2 emitted per megagram (3.0 Ib/ton) of 100 percent nitric acid
produced.
Table 5.9-1 (Metric and English Units).
NITROGEN OXIDE EMISSIONS FROM NITRIC ACID PLANTS*
Control k
Source Efficiency Nit
% Pr
Weak Acid Plant Tailgas
Uncontrolled1*'0 0
Catalytic reduction0
Natural gasd 99.1
Hydrogen6 97-98.5
Natural gas/hydrogen (25%/75%)f 98-98.5
Extended absorption 95.8
Single-Stage Process8
Dual-Stage Process*1
Chilled Absorption and Caustic Scrubbed N/A
High Strength Acid Plantk N/A
NOX
g/Mg Ib/ton Emission
ric Acid Nitric Acid Factor
oduced Produced Rating
28 57 E
0.2 0.4 E
0.4 0.8 E
0.5 0.9 E
0.95 1.9 E
1.1 2.1 E
1.1 2.2 E
5 10 E
'Assumes 100% acid. Production rates are in terms of total weight of product (water and acid). A plant producing
454 Mg (500 tons) per day of 55 weight % nitric acid is calculated as producing 250 Mg (275 tons)/day of 100%
acid. NA = Not available.
bReference 6. Based on a study of 12 plants, with average production rate of 207 Mg (100% HNO3)/day (range
50 - 680) 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
309 Mg (100% HNO3Vday (range 50 - 977 Mg).
eReference 6. Based on data from 2 plants, with average production rate of 145 Mg (100% HNO3)/day (range
109 - 190 Mg) at average rated capacity of 98% (range 95 - 100%). Average absorber exit temperature is 29 °C
(85 op) {range 25 - 32°C (78 - 90op)}, and the average exit pressure is 586 kPa (85 psig) {range 552 - 648 kPa
(80 - 94 psig)}.
Reference 6. Based on data from 2 plants, with average production rate of 208 Mg (100% HNO3)/day (range
168 - 249 Mg) at average rated capacity of 110% (range 100 - 119%). Average absorber exit temperature is 33°C
(91 °F) {range 28 - 37°C (83 - 98°F)}, and average exit pressure is 545 kPa (79 psig) {range 545 - 552 kPa
(79-80 psig)}.
^Reference 4. Based on data from 5 plants, with average production rate of 492 Mg (100% HNO3)/day
(range 190 - 952 Mg).
hReference 4. Based of data from 3 plants, with average production rate of 532 Mg (100% HNO3)/day (range
286 - 850 Mg).
JReference 4. Based of data from 1 plant, with a production rate of 628 Mg (100% HNO3)/day.
kReference 2. Based on data from 1 plant, with a production rate of 1.4 Mg (100% HNO3)/hour at 100%
rated capacity, of 98% nitric acid.
5.9-6
EMISSION FACTORS
7/93
-------
References for Section 5.9
1. Alternative Control Techniques Document: Nitric And Adipic Acid Manufacturing
Plants, EPA-450/3-91-026, U.S. Environmental Protection Agency, OAQPS, 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. 1976.
6. Atmospheric Emissions From Nitric Acid Manufacturing Processes, 999-AP-27,
U. S. Department of Health, Education, and Welfare, Cincinnati, OH,
December 1966.
7/93 Chemical Process Industry 5.9-7
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5.11 PHOSPHORIC ACID
5.11.1 General1'2
Phosphoric acid (H3PO4) is produced by two commercial methods: wet process and thermal
process. Wet process phosphoric acid is used in fertilizer production. Thermal process phosphoric
acid is of a much higher purity and is used in the manufacture of high grade chemicals,
pharmaceutical, detergents, food products, beverages and other nonfertilizer products. In 1987 over 9
million megagrams (9 million tons) of wet process phosphoric acid was produced in the form of
phosphorus pentoxide (P2O5). Only about 363,000 megagram (400,000 tons) of P2O5 was produced
from the thermal process. Demand for phosphoric acid has increased approximately 2.3 to 2.5 percent
per year.
The production of wet process phosphoric acid generates a considerable quantity of acidic
cooling water with high concentrations of phosphorus and fluoride. This excess water is collected in
cooling ponds which are used to temporarily store excess precipitation for subsequent evaporation and
to allow recirculation of the process water to the plant for re-use. Leachate seeping is therefore a
potential source of ground water contamination. Excess rainfall also results in water overflows from
settling ponds. However, cooling water can be treated to an acceptable level of phosphorus and
fluoride if discharge is necessary.
5.11.2 Process Description3"5
5.11.2.1 Wet Process Acid Production
In a wet process facility (see Figures 5.11-1A and 5.11-1B), phosphoric acid is produced by
reacting sulfuric acid (H2SO4) with naturally occurring phosphate rock. The phosphate rock is dried,
crushed and then continuously fed into the reactor along with sulfuric acid. The reaction combines
calcium from the phosphate rock with sulfate, forming calcium sulfate (CaSO4), commonly referred
to as gypsum. Gypsum is separated from the reaction solution by filtration. Facilities in the U. S.
generally use a dihydrate process that produces gypsum in the form of calcium sulfate with two
molecules of water (CaSO4 • 2 H2O or calcium sulfate dihydrate). Japanese facilities use a
hemihydrate process which produces calcium sulfate with a half molecule of water (CaSO4 • Vz
H2O). This one-step hemihydrate process has the advantage of producing wet process phosphoric acid
with a higher P2O5 concentration and less impurities than the dihydrate process. Due to these
advantages, some U. S. companies have recently converted to the hemihydrate process. However,
since most wet process phosphoric acid is still produced by the dihydrate process, the hemihydrate
process will not be discussed in detail here. A simplified reaction for the dihydrate process is as
follow:
Ca3(PO4)2 + 3H2SO4 + 6H2O -«• 2H3PO4 + 3[CaSO4 • 2H2O]1 (1)
In order to make the strongest phosphoric acid possible and to decrease evaporation costs, 93
percent sulfuric acid is normally used. Because the proper ratio of acid to rock in the reactor is
critical, precise automatic process control equipment is employed in the regulation of these two feed
streams.
7/93 Chemical Process Industry 5.11-1
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Figure 5.11-1A. Flow diagram of a wet process phosphoric acid plant.
5.11-2 EMISSION FACTORS 7/93
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*- VACUUM
TO VACUUM*
AND HOT WELL
TO ACID PLANT
HYDROFLUOSIUC ACID
Figure 5.11-1B. Flow diagram of a wet process phosphoric acid plant (cont.).
During the reaction, gypsum crystals are precipitated and separated from the acid by filtration.
The separated crystals must be washed thoroughly to yield at least a 99 percent recovery of the
filtered phosphoric acid. After washing, the slurried gypsum is pumped into a gypsum pond for
storage. Water is syphoned off and recycled through a surge cooling pond to the phosphoric acid
process. Approximately 0.7 acres of cooling and settling pond area is required for every ton of daily
P2O5 capacity.
Considerable heat is generated in the reactor. In older plants, this heat was removed by blowing
air over the hot slurry surface. Modern plants vacuum flash cool a portion of the slurry, and then
recycle it back into the reactor.
Wet process phosphoric acid normally contains 26 to 30 percent P2O5- In most cases, the acid
must be further concentrated to meet phosphate feed material specifications for fertilizer production.
Depending on the types of fertilizer to be produced, phosphoric acid is usually concentrated to 40 to
55 percent P2O5 by using two or three vacuum evaporators.
5.11.2.2 Thermal Process Acid Production
Raw materials for the production of phosphoric acid by the thermal process are elemental
(yellow) phosphorus, air and water. Thermal process phosphoric acid manufacture, as shown
schematically in Figure 5.11-2, involves three major steps: 1) combustion, 2) hydration, and 3)
demisting.
In combustion, the liquid elemental phosphorus is burned (oxidized) in ambient air in a
combustion chamber at temperatures of 1650 to 2760°C (3000 to 5000°F) to form phosphorus
pentoxide (Reaction 2). The phosphorus pentoxide is then hydrated with dilute phosphoric acid
(H3PO4) or water to produce strong phosphoric acid liquid (Reaction 3). Demisting, the final step,
removes the phosphoric acid mist from the combustion gas stream before release to the atmosphere.
7/93
Chemical Process Industry
5.11-3
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Figure 5.11-2. Flow diagram of a thermal process phosphoric acid plant.
5.11-4 EMISSION FACTORS 7/93
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This is usually done with high-pressure drop demistors.
P4 + 502 ->• 2P205 (2)
2P2O5 + 6H2O -» 4H3PO4 (3)
Concentration of phosphoric acid (H3PO4) produced from thermal process normally ranges
from 75 to 85 percent. This high concentration is required for high grade chemical production and
other nonfertilizer product manufacturing. Efficient plants recover about 99.9 percent of the elemental
phosphorus burned as phosphoric acid.
5.11.3 Emissions And Controls 3"6
Emission factors for controlled and uncontrolled wet phosphoric acid production are shown in
Tables 5.11-1 and 5.11-2, respectively. Emission factors for controlled thermal phosphoric acid
production are shown in Table 5.11-3.
5.11.3.1 Wet Process
Major emissions from wet process acid production includes gaseous fluorides, mostly silicon
tetrafluoride (SiF4) and hydrogen fluoride (HF). Phosphate rock contains 3.5 to 4.0 percent fluorine.
In general, part of the fluorine from the rock is precipitated out with the gypsum, another part is
leached out with the phosphoric acid product, and the remaining portion is vaporized in the reactor or
evaporator. The relative quantities of fluorides in the filter acid and gypsum depend on the type of
rock and the operating conditions. Final disposition of the volatilized fluorine depends on the design
and operation of the plant.
Scrubbers may be used to control fluorine emissions. Scrubbing systems used in phosphoric
acid plants include venturi, wet cyclonic and semi-cross flow scrubbers. The leachate portion of the
fluorine may be deposited in settling ponds. If the pond water becomes saturated with fluorides,
fluorine gas may be emitted to the atmosphere.
The reactor in which phosphate rock is reacted with sulfuric acid is the main source of
emissions. Fluoride emissions accompany the air used to cool the reactor slurry. Vacuum flash
cooling has replaced the air cooling method to a large extent, since emissions are minimized in the
closed system.
Acid concentration by evaporation is another source of fluoride emissions. Approximately 20 to
40 percent of the fluorine originally present in the rock vaporizes in this operation.
Total particulate emissions from process equipment were measured for one digester and for one
filter. As much as 5.5 kilograms of particulate per megagram (11 pounds per ton) of P2O5 were
produced by the digester, and approximately 0.1 kilograms per megagram (.2 pounds per ton) of
P2O5 were released by the filter. Of this particulate, three to six percent were fluorides.
Particulate emissions occurring from phosphate rock handling are discussed in Section 8.18,
Phosphate Rock Processing.
7/93 Chemical Process Industry 5.11-5
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5.11.3.2 Thermal Process
The major source of emissions from the thermal process is phosphoric acid mist
contained in the gas stream from the hydrator. The particle size of the acid mist ranges from 1.4 to
2.6 micrometers (/*m). It is not uncommon for as much as half of the total phosphorus pentoxide
(P2O5) to be present as liquid phosphoric acid particles suspended in the gas stream. Efficient plants
are economically motivated to control this potential loss with various control equipment. Control
equipment commonly used in thermal process phosphoric acid plants includes venturi scrubbers,
cyclonic separators with wire mesh mist eliminators, fiber mist eliminators, high energy wire mesh
contractors, and electrostatic precipitators.
Table 5.11-1. (Metric and English Units).
CONTROLLED EMISSION FACTORS FOR WET PHOSPHORIC ACID PRODUCTION4
Source (SCC Code)
Fluorine
kg/Mg
P205
Produced
Ib/ton
P205
Produced
Emission
Factor
Rating
Reactorb (SCC 3-01-016-01)
Evaporator0 (SCC 3-01-016-99)
Belt Filter0 (SCC 3-01-016-99)
Belt Filter Vacuum Pump0 (SCC 3-01-016-99)
Gypsum settling and cooling pondsd'e (SCC 3-01-016-02)
1.9 x 10'3 3.8 x 10'3 A
0.022 x 10'3 0.044 x 10'3 B
0.32 x 10'3 0.64 x 10'3 B
0.073 xlO'3 O.lSxlO'3 B
Site specific Site specific
*SCC = Source Classification Code
b Reference 8-13
0 Reference 13
d Reference 18. Site specific. Acres of cooling pond required: ranges from 0.10 acre per daily ton
P2O5 produced in the summer in the southeastern United States to zero in the colder locations in
the winter months when the cooling ponds are frozen.
e Reference 19 states "Based on our findings concerning the emissions of fluoride from gypsum
ponds, it was concluded than no investigator had as yet established experimentally the fluoride
emission from gypsum ponds."
5.11-6
EMISSION FACTORS
7/93
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Table 5.11-2. (Metric and English Units).
UNCONTROLLED EMISSION FACTORS FOR WET PHOSPHORIC ACID PRODUCTION"
Source (SCC Code)
Nominal
Percent
Control
Efficiency
kg/Mg
P20s
Produced
Reactorb (SCC 3-01-016-01) 99 0.19
Evaporator0 (SCC 3-01-016-99) 99 0.00217
Belt Filter0 (SCC 3-01-016-99) 99 0.032
Belt Filter Vacuum Pump0 (SCC 3-01-016-99)
99 0.0073
Gypsum settling and cooling pondsd'e (SCC 3-01-016-02) N/A Site
specific
Fluoride
Ib/ton
P205
Produced
0.38
0.0044
0.064
0.015
Site
specific
Emission
Factor
Rating
B
C
C
C
* SCC = Source Classification Code.
b Reference 8-13
c Reference 13
d Reference 18. Site specific. Acres of cooling pond required: ranges from 0.04 hectare per daily
Mg (0.10 acre per daily ton) P2O5 produced in the summer in the southeastern U. S. to zero in
the colder locations in the winter months when the cooling ponds are frozen.
e Reference 19 states "Based on our findings concerning the emissions of fluoride from gypsum
ponds, it was concluded than no investigator had as yet established experimentally the fluoride
emission from gypsum ponds."
7/93
Chemical Process Industry
5.11-7
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Table 5.11-3. (Metric and English Units).
CONTROLLED EMISSION FACTORS FOR THERMAL PHOSPHORIC ACID PRODUCTION*
Source (SCC Code)
Nominal
Percent
Control
Efficiency
Particulateb
kg/Mg
P205
Produced
Packed tower (SCC 3-01-017-03) 95.5 1.07
Venturi scrubber (SCC3-01-017-04) 97.5 1.27
Glass fiber mist eliminator (SCC 3-01-017-05) 96-99.9 0.35
Wire mesh mist eliminator (SCC 3-01-017-06) 95 2.73
High pressure drop mist (SCC 3-01-017-07) 99.9 0.06
Electrostatic precipitator (3-01-017-08) 98-99 0.83
Ib/ton
P2°5
Produced
2.14
2.53
0.69
5.46
0.11
1.66
Emission
Factor
Rating
E
E
E
E
E
E
* SCC = Source Classification Code.
b Reference 6.
References for Section 5.11
1. "Phosphoric Acid", Chemical and Engineering News. March 2, 1987.
2. SulJuric/Phosphoric Acid Plant Operation, American Institute Of Chemical Engineers, New
York, 1982.
3. P. Becker, Phosphates And Phosphoric Acid, Raw Materials, Technology, And Economics Of
The Wet Process, 2nd Edition, Marcel Dekker, Inc., New York, 1989.
4. Atmospheric Emissions from Wet Process Phosphoric Acid Manufacture, AP-57, U. S.
Environmental Protection Agency, Research Triangle Park, NC, April 1970.
5. Atmospheric Emissions From Thermal Process Phosphoric Acid Manufacture, AP-48, U.S.
Environmental Protection Agency, Research Triangle Park, NC, October 1968.
6. Control Techniques For Fluoride Emissions, Unpublished, U. S. Public Health Service,
Research Triangle Park, NC, September 1970.
7. Final Guideline Document: Control Of Fluoride Emissions From Existing Phosphate Fertilizer
Plants, EPA-450/2-77-005, U. S. Environmental Protection Agency, Research Triangle Park,
NC, March 1977.
8. Summary Of Emission Measurements - East Phos Acid, International Minerals And Chemical
Corporation, Polk County, FL, August 1990.
5.11-8
EMISSION FACTORS
7/93
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9. Summary Of Emission Measurements - East Phos Add, International Minerals And Chemical
Corporation, Polk County, FL, February 1991.
10. Summary Of Emission Measurements - East Phos Acid, International Minerals And Chemical
Corporation, Polk County, FL, August 1991.
11. Source Test Repon, Seminole Fertilizer Corporation, Bartow, FL, September 1990.
12. Source Test Report, Seminole Fertilizer Corporation, Bartow, FL, May 1991.
13. Stationary Source Sampling Report, Texasgulf Chemicals Company, Aurora, NC, Entropy
Environmentalists, Inc., Research Triangle Park, NC, December 1987.
14. Stationary Source Sampling Report, Texasgulf Chemicals Company, Aurora, NC, Entropy
Environmentalists, Inc., Research Triangle Park, NC. March 1987.
15. Sulfur Dioxide Emissions Test. Phosphoric Add Plant, Texasgulf Chemicals Company,
Aurora, NC, Entropy Environmentalists, Inc., Research Triangle Park, NC, August 1988.
16. Stationary Source Sampling Report, Texasgulf Chemicals Company, Aurora, NC, Entropy
Environmentalists, Inc., Research Triangle Park, NC, August 1987.
17. Source Test Report, FMC Corporation, Carteret, NJ, Princeton Testing Laboratory,
Princeton, NJ, March 1991.
18. A. J. Buonicore and W. T. Davis, eds., Air Pollution Engineering Manual, Van Nostrand
Reinhold, New York, NY, 1992.
19. Evaluation Of Emissions And Control Techniques For Reducing Fluoride Emission From
Gypsum Ponds In The Phosphoric Add Industry, EPA-600/2-78-124, U. S. Environmental
Protection Agency, Research Triangle Park, NC, 1978.
7/93 Chemical Process Industry 5.11-9
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5.15 SOAP AND DETERGENTS
5.15.1 General
5.15.1.1 Soap Manufacturing1'3'6
The term "soap" refers to a particular type of detergent in which the water-solubilized group is
carboxylate and the positive ion is usually sodium or potassium. The largest soap market is bar soap
used for personal bathing. Synthetic detergents replaced soap powders for home laundering in the late
1940s, because the carboxylate ions of the soap react with the calcium and magnesium ions in the
natural hard water to form insoluble materials called lime soap. Some commercial laundries that have
soft water continue to use soap powders. Metallic soaps are alkali-earth or heavy-metal long-chain
carboxylates which are insoluble in water but soluble in nonaqueous solvents. They are used as
additives in lubricating oils, greases, rust inhibitors, and jellied fuels.
5.15.1.2 Detergent Manufacturing1'3'6'8
The term "synthetic detergent products" applies broadly to cleaning and laundering compounds
containing surface-active (surfactant) compounds along with other ingredients. Heavy-duty powders
and liquids for home and commercial laundry detergent comprise 60 to 65 percent of the U. S. soap
and detergent market and were estimated at 2.6 megagrams (2.86 million tons) in 1990.
Until the early 1970s, almost all laundry detergents sold in the U. S. were heavy-duty powders.
Liquid detergents were introduced that utilized sodium citrate and sodium silicate. The liquids offered
superior performance and solubility at a slightly increased cost. Heavy-duty liquids now account for
40 percent of the laundry detergents sold in the U. S., up from 15 percent in 1978. As a result, 50
percent of the spray drying facilities for laundry granule production have closed since 1970. Some
current trends, including the introduction of superconcentrated powder detergents, will probably lead
to an increase in spray drying operations at some facilities. Manufacturers are also developing more
biodegradable surfactants from natural oils.
5.15.2 Process Descriptions
5.15.2.1 Soap 1'3-6
From American colonial days to the early 1940s, soap was manufactured by an alkaline
hydrolysis reaction called saponification. Soap was made in huge kettles into which fats, oils, and
caustic soda were piped and heated to a brisk boil. After cooling for several days, salt was added,
causing the mixture to separate into two layers with the "neat" soap on top and spent lye and water on
the bottom. The soap was pumped to a closed mixing tank called a crutcher where builders,
perfumes, and other ingredients were added. Builders are alkaline compounds which improve the
cleaning performance of the soap. Finally, the soap was rolled into flakes, cast or milled into bars, or
spray-dried into soap powder.
An important modern process (post 1940s) for making soap is the direct hydrolysis of fats by
water at high temperatures. This permits fractionation of the fatty acids, which are neutralized to soap
7/93 Chemical Process Industry 5.15-1
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in a continuous process as shown in Figure 5.15-1. Advantages for this process include close control
of the soap concentration, the preparation of soaps of certain chain lengths for specific purposes, and
easy recovery of glycerin, a byproduct. After the soap is recovered, it is pumped to the crutcher and
treated the same as the product from the kettle process.
5.15.2.2 Detergent1'3'6'8
The manufacture of spray-dried detergent has three main processing steps: 1) slurry
preparation, 2) spray drying and 3) granule handling. The three major components of detergent are
surfactants (to remove dirt and other unwanted materials), builders (to treat the water to improve
surfactant performance) and additives to improve cleaning performance. Additives may include
bleaches, bleach activators, antistatic agents, fabric softeners, optical brighteners, antiredeposition
agents, and fillers.
The formulation of slurry for detergent granules requires the intimate mixing of various liquid,
powdered, and granulated materials. Detergent slurry is produced by blending liquid surfactant with
powdered and liquid materials (builders and other additives) in a closed mixing tank called a soap
crutcher. Premixing of various minor ingredients is performed in a variety of equipment prior to
charging to the crutcher or final mixer. Figure 5.15-2 illustrates the various operations. Liquid
surfactant used in making the detergent slurry is produced by the sulfonation of either a linear alkylate
or a fatty acid, which is then neutralized with a caustic solution containing sodium hydroxide
(NaOH). The blended slurry is held in a surge vessel for continuous pumping to a spray dryer. The
slurry is atomized by spraying through nozzles rather than by centrifugal action. The slurry is sprayed
at pressures of 4.100 to 6.900 kPa (600 to 1000 pounds per square inch) in single-fluid nozzles and at
pressures of 340 to 690 kPa (50 to 100 psi) in two-fluid nozzles. Steam or air is used as the atomizing
fluid in the two-fluid nozzles. The slurry is sprayed at high pressure into a vertical drying tower
having a stream of hot air of from 315 to 400°C (600 to 750°F). All spray drying equipment
designed for detergent granule production incorporates the following components: spray drying tower,
air heating and supply system, slurry atomizing and pumping equipment, product cooling equipment,
and conveying equipment. Most towers designed for detergent production are countercurrent, with
slurry introduced at the top and heated air introduced at the bottom. The towers are cylindrical with
cone bottoms and range in size from 4 to 7 meters (12 to 24 feet) in diameter and 12 to 38 meters (40
to 125 feet) in height. The detergent granules are conveyed mechanically or by air from the tower to
a mixer to incorporate additional dry or liquid ingredients, and finally to packaging and storage.
5.15.3 Emissions And Controls
5.15.3.1 Soap1'3'6
The main atmospheric pollution problem in soap manufacturing is odor. The storage and
handling of liquid ingredients (including sulfonic acids and salts) and sulfates are some of the sources
of this odor. Vent lines, vacuum exhausts, raw material and product storage, and waste streams are
all potential odor sources. Control of these odors may be achieved by scrubbing exhaust fumes and, if
necessary, incinerating the remaining VOCs. Odors emanating from the spray dryer may be
controlled by scrubbing with an acid solution. Blending, mixing, drying, packaging and other
physical operations may all involve
dust emissions. The production of soap powder by spray drying is the single largest source of dust in
the manufacture of synthetic detergents. Dust emissions from other finishing operations can be
controlled by dry filters such as baghouses. The large sizes of the paniculate from synthetic detergent
drying means that high efficiency cyclones installed in series can achieve satisfactory control.
5.15-2 EMISSION FACTORS 7/93
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7/93
Figure 5.15-1. Continuous process for fatty acids and soaps.
Chemical Process Industry
5.15-3
-------
Currently, no emission factors are available for soap manufacturing. No information on hazardous air
pollutants (HAPs), volatile organic compounds (VOCs), ozone depleters, or heavy metal emissions
information were found for soap manufacturing.
5.15.3.2 Detergent1'3'4-6-8
The exhaust air from detergent spray drying towers contains two types of air contaminants: 1)
fine detergent particles and 2) organics vaporized in the higher temperature zones of the tower.
Emission factors for particulates from spray drying operations are shown in Table 5.15-1.
Dust emissions are generated at scale hoppers, mixers, and crutchers during the batching and
mixing of fine dry ingredients to form slurry. Conveying, mixing, and packaging of detergent
granules can also cause dust emissions. Pneumatic conveying of fine materials causes dust emissions
when conveying air is separated from bulk solids. For this process, fabric filters are generally used,
not only to reduce or to eliminate dust emissions, but also to recover raw materials. The dust
emissions principally consist of detergent compounds, although some of the particles are uncombined
phosphates, sulfates, and other mineral compounds.
Dry cyclones and cyclonic impingement scrubbers are the primary collection equipment
employed to capture the detergent dust in the spray dryer exhaust for return to processing. Dry
cyclones are used in parallel or in series to collect this paniculate and recycle it back to the crutcher.
The dry cyclone separators can remove 90 percent or more by weight of the detergent product fines
from the exhaust air. Cyclonic impinged scrubbers are used in parallel to collect the paniculate from
a scrubbing slurry and to recycle it to the crutcher.
Secondary collection equipment is used to collect fine particulates that escape from primary
devices. For example, cyclonic impingement scrubbers are often followed by mist eliminators, and
dry cyclones are followed by fabric filters or scrubber/electrostatic precipitator units. Several types of
scrubbers can be used following the cyclone collectors. Venturi scrubbers have been used but are
being replaced with packed bed scrubbers. Packed bed scrubbers are usually followed by wet-pipe-
type electrostatic precipitators built immediately above the packed bed in the same vessel. Fabric
filters have been used after cyclones but have limited applicability, especially on efficient spray
dryers, due to condensing water vapor and organic aerosols binding the fabric filter.
In addition to paniculate emissions, volatile organics may be emitted when the slurry contains
organic materials with low vapor pressures. The VOCs originate primarily from the surfactants
included in the slurry. The amount vaporized depends on many variables such as tower temperature,
and the volatility of organics used in the slurry. These vaporized organic materials condense in the
tower exhaust airstream into droplets or particles. Paraffin alcohols and amides in the exhaust stream
can result in a highly visible plume that persists after the condensed water vapor plume has dissipated.
Opacity and the organics emissions are influenced by granule temperature and moisture at the
end of drying, temperature profiles in the dryer, and formulation of the slurry. A method for
controlling visible emissions would be to remove offending organic compounds (i. e., by substitution)
from the slurry. Otherwise, tower production rate may be reduced thereby reducing air inlet
temperatures and exhaust temperatures. Lowering production rate will also reduce organic emissions.
Some of the hazardous air pollutants (HAPs) and volatile organic compounds (VOCs) identified
from the VOC/PM Speciate Database Management System (SPECIATE) are: hexane, methyl alcohol,
1,1,1-trichloroethane, perchloroethylene, benzene, and toluene. Lead was identified from SPECIATE
5.15-4 EMISSION FACTORS 7/93
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7/93
Figure 5.15-2. Manufacture of spray-dried detergents.
Chemical Process Industry
5.15-5
-------
data as the only heavy metal constituent. No numerical data are presented for lead, HAP, or VOC
emissions due to the lack of sufficient supporting documentation.
Table 5.15-1. (English and Metric Units).
PARTICULATE EMISSION FACTORS FOR DETERGENT SPRAY DRYING*
Control Device Efficiency
(%)
Uncontrolled
Cyclone 85
Cyclone with:
Spray chamber 92
Packed scrubber 95
Venturi scrubber 97
Wet scrubber 99
Wet scrubber/ESP 99.9
Packed bed/ESP 99
Fabric filter 99
Paniculate
kg/Mg Ib/ton
of Product of Product
45 90
7 . 14
3.5 7
2.5 5
1.5 3
0.544 1.09
0.023 0.046
0.47 0.94
0.54 1.1
Emission
Factor
Rating
Eb
Eb
Eb
Eb
Eb
Eb
Eb
Ec
Eb
aSome type of primary collector, such as a cyclone, is considered integral to a spray drying system.
ESP = Electrostatic Precipitator.
bEmission Factors are estimations and are not supported by current test data.
cEmission factor has been calculated from a single source test. An efficiency of 99% has been
estimated.
5.15-6
EMISSION FACTORS
7/93
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References for Section 5.15
1. Source Category Survey: Detergent Industry. EPA Contract No. 68-02-3059, June 1980.
2. A. H. Phelps, "Air Pollution Aspects Of Soap And Detergent Manufacture", APCA Journal,
17, (8): 505-507. August 1967.
3. R. N. Shreve, Third Edition: Chemical Process Industries, McGraw-Hill Book Company, New
York, NY.
4. J. H. Perry, Fourth Edition: Chemical Engineers Handbook, McGraw-Hill Book Company,
New York, NY.
5. Soap And Detergent Manufacturing: Point Source Category, EPA-440/1 -74-018-a, U.S.
Environmental Protection Agency, Research Triangle Park, NC, April 1974.
6. J. A. Danielson, Air Pollution Engineering Manual (2nd Edition), AP-40, U. S. Environmental
Protection Agency, Research Triangle Park, NC. May 1973. Out of Print.
7. A. Lanteri, "Sulfonation And Sulfation Technology". Journal Of The American Oil Chemists
Society, 55, 128-132, January 1978.
8. A. J. Buonicore and W. T. Davis, eds., Air Pollution Engineering Manual, Van Nostrand
Reinhold, New York, NY, 1992.
9. Emission Test Report, Procter And Gamble, Augusta, GA, Georgia Department Of Natural
Resources, Atlanta, GA, July 1988.
10. Emission Test Report, Time Products, Atlanta, GA, Georgia Department Of Natural Resources,
Atlanta, GA, November 1988.
11. AIRS Facility Subsystem Source Classification Codes And Emission Factor Listing For Criteria
Air Pollutants, U. S. Environmental Protection Agency, Research Triangle Park, NC,
EPA-450/4-90-003, March 1990.
7/93 Chemical Process Industry 5.15-7
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5.16 SODIUM CARBONATE
5.16.1 General
Sodium carbonate (Na2CO3), commonly referred to as soda ash, is one of the largest-volume
mineral products in the U.S., with 1991 production of over 9 million Mg (10.2 million tons). Over
85 percent of this soda ash originates in Wyoming, with the remainder coming from Searles Valley,
California. Soda ash is used primarily in the production of glass, chemicals, soaps and detergents, and
by consumers. Demand depends to great extent upon the price of, and environmental issues
surrounding, caustic soda, which is interchangeable with soda ash in many uses and is widely co-
produced with chlorine (see section 5.5 Chlor-Alkali).
5.16.2 Process Description
Soda ash may be manufactured synthetically or from naturally occurring raw materials such as
ore. Only one U.S. facility recovers small quantities of Na2CO3 synthetically as a byproduct of
cresylic acid production. Other synthetic processes include the Solvay process, which involves
saturation of brine with ammonia (NH4) and carbon dioxide (CO2) gas, and the Japanese ammonium
chloride (NH4C1) coproduction process. Both of these synthetic processes result in ammonia
emissions. Natural processes include the calcination of sodium bicarbonate (NaHCO3), or nahcolite, a
naturally-occurring ore found in vast quantities in Colorado.
The two processes presently used to produce natural soda ash differ only in the recovery and
primary treatment of the raw material used. The raw material for Wyoming soda ash is mined trona
ore, while California soda ash is derived from sodium carbonate-rich brine extracted from Searles
Lake.
There are four distinct methods used to mine the Wyoming trona ore: 1) solution mining, 2)
room-and-pillar, 3) longwall, and 4) shortwall. In solution mining, dilute sodium hydroxide (NaOH),
commonly called caustic soda, is injected into the trona to dissolve it. This solution is treated with
carbon dioxide gas in carbonation towers to convert the sodium carbonate (Na2CO3) in solution to
sodium bicarbonate (NaHCO3), which precipitates and is filtered out. The crystals are again dissolved
in water, precipitated with carbon dioxide, and filtered. The product is calcined to produce dense soda
ash. Brine extracted from below Searles Lake in California is treated similarly.
For the room-and-pillar, longwall, and shortwall methods, the conventional blasting agent is
prilled ammonium nitrate (NH4NO3) and fuel oil, or ANFO (see section 11.3 "Explosives
Detonation"). Beneficiation is accomplished with either of two methods called the sesquicarbonate and
the monohydrate processes. In the sesquicarbonate process, shown schematically in Figure 5.16-1,
trona ore is first dissolved in water and then treated as brine. The liquid is filtered to remove
insoluble impurities before the sodium sesquicarbonate (Na2CO3 • NaHCO3 • 2H2O) is precipitated out
using vacuum crystallizers. The result is centrifuged to remove remaining water, and can be sold as a
finished product or further calcined to yield soda ash of light to intermediate density. In the
monohydrate process, shown schematically in Figure 5.16-2, the crushed trona is calcined in a rotary
kiln, yielding dense soda ash and carbon dioxide and water as by-products. The calcined material is
combined with water to allow settling out or filtering of impurities such as shale, and is then
7/93 Chemical Process Industry 5.16-1
-------
CONTROL
DEVICE
CONTROL
DEVICE
TRONA_
ORE
1
CRUS
AN
SCRE
HERS
D
:ENS
DISSOLVER
VACUUM
CRYSTALUZER
j
i
DRY
SODIUM
CARBONATE
Figure 5.16-1 Flow diagram for sesquicarbonate sodium carbonate processing
DRY
SODIUM
CARBONATE
Figure 5.16-2 Flow diagram for monohydrate sodium carbonate processing
concentrated by triple-effect evaporators and/or mechanical vapor recompression crystallizers to
precipitate sodium carbonate monohydrate (Na2CO3-H2O). Impurities such as sodium chloride
(NaCl) and sodium sulfate (Na2SO4)remain in solution. The crystals and liquor are centrifuged, and
the recovered crystals are calcined again to remove remaining water. The product must then be
cooled, screened, and possibly bagged before shipping.
5.16.3 Emissions and Controls
The principal air emissions from the sodium carbonate production methods presently used in the
U.S. are paniculate emissions from the ore calciners; soda ash coolers and dryers; ore crushing,
screening, and transporting operations; and product handling and shipping operations. Emissions of
products of combustion, such as carbon monoxide, nitrogen oxides, sulfur dioxide, and carbon
dioxide occur from direct-fired process heating units such as ore calcining kilns and soda ash dryers.
With the exception of carbon dioxide, which is suspected of contributing to global climate change,
insufficient data are available to quantify these emissions with a reasonable level of confidence, but
similar processes are addressed in various sections of Chapter 8 of AP-42 (Mineral Products
Industries). Emissions of filterable and total paniculate matter from individual processes and process
5.16-2
EMISSION FACTORS
7/93
-------
components are quantified in Table 5.16-1 on a controlled (as-measured) basis. Emissions of total
paniculate matter from these same processes are quantified in Table 5.16-2 on an uncontrolled basis.
No data quantifying emissions of organic condensible paniculate matter from sodium carbonate
manufacturing processes are available, but this portion of the paniculate matter can be assumed to be
negligible. Emissions of carbon dioxide from selected processes are quantified in Table 5.16-3.
Emissions from combustion sources such as boilers, and from evaporation of hydrocarbon fuels used
to fire these combustion sources, are covered in other chapters of AP-42.
Paniculate emissions from calciners and dryers are typically controlled by venturi scrubbers,
electrostatic precipitators, and/or cyclones. Baghouse filters are not well suited to applications such as
these, due to the high moisture content of the effluent gas. Paniculate emissions from the ore and
product handling operations are typically controlled by either venturi scrubbers or baghouse filters.
These control devices are an integral part of the manufacturing process, capturing raw materials and
product for economic reasons. Due to a lack of suitable emissions data for uncontrolled processes,
controlled emission factors are presented for this industry in addition to uncontrolled emission factors.
The uncontrolled emission factors have been calculated by applying nominal control efficiencies to the
controlled emission factors.
7/93 Chemical Process Industry 5.16-3
-------
Table 5.16-1 (Metric Units)
PARTICULATE MATTER: CONTROLLED BASIS
kg
Process (SCC Code) Pn
Filterable8
/Mg Emission
of Factor
aduct Rating
Ore mining0 (3-01-023-99) 0.0016 C
Ore crushing and screening0 (3-01-023-99) 0.0010 D
Ore transfer0 (3-01-023-99) 0.00008 E
Monohydrate process: rotary ore calciner
(3-01-023-04/05) 0
091 A
Sesquicarbonate process: rotary calciner
(3-01-023-99) 0.36 B
Sesquicarbonate process: fluid-bed calciner
(3-01-023-99) 0
021 C
Rotary soda ash dryers (3-01-023-06) 0.25 C
Fluid-bed soda ash dryers/coolers (3-01-023-07) 0.015 C
Soda ash screening (3-01-023-99) 0.0097 E
Soda ash storage/loading and unloading0
(3-01-023-99) 0.0021 E
Totalb
kg/Mg
of
Product
N/Ad
0.0018
0.0001
0.12
0.36
N/Ad
0.25
0.019
0.013
0.0026
Emission
Factor
Rating
N/Ad
C
E
B
C
N/Ad
D
D
E
E
8 Filterable participate matter is that material collected in the probe and filter of a method 5 or Method
17 sampler
b Total particulate matter includes filterable particulate and inorganic condensible particulate.
0 For ambient temperature processes, all particulate matter emissions can be assumed to be filterable at
ambient conditions; however, particulate sampling according to EPA Reference Method 5 involves the
heating of the front half of the sampling train to temperatures that may vaporize some portion of this
particulate matter, which will then recondense in the back half of the sampling train. For consistency,
particulate matter measured as condensible according to Method 5 is reported as such.
d N/A = data not available.
5.16-4
EMISSION FACTORS
7/93
-------
Table 5.16-1 (English Units)
PARTICULATE MATTER: CONTROLLED BASIS
Filterable
Ib/ton Em
of Fa
Process (SCC Code) Product Ra
Ore mining0 (3-01-023-99)
0.0033
Ore crushing and screening0 (3-01-023-99) 0.0021
Ore transfer0 (3-01-023-99)
0.0002
" Totalb
ssion Ib/ton Emission
ctor of Factor
Lting Product Rating
C N/Ad N/Ad
D 0.0035 C
E 0.0002 E
Monohydrate process: rotary ore calciner 0.18 A 0.23 B
(3-01-023-04/05)
Sesquicarbonate process: rotary calciner 0.72
(3-01-023-99)
Sesquicarbonate process: fluid-bed
(3-01-023-99)
calciner 0.043
Rotary soda ash dryers (3-01-023-06) 0.50
Fluid-bed soda ash dryers/coolers
Soda ash screening (3-01-023-99)
(3-01-023-07) 0.030
0.019
Soda ash storage/loading and unloading0 0.0041
(3-01-023-99)
B 0.73 C
C N/Ad N/Ad
C 0.52 D
C 0.39 D
E 0.026 E
E 0.0051 E
" Filterable particulate matter is that material collected in the probe and filter of a method 5 or Method
17 sampler
b Total particulate matter includes filterable particulate and inorganic condensible particulate.
0 For ambient temperature processes, all particulate matter emissions can be assumed to be filterable at
ambient conditions; however, particulate sampling according to EPA Reference Method 5 involves the
heating of the front half of the sampling train to temperatures that may vaporize some portion of this
particulate matter, which will then recondense in the back half of the sampling train. For consistency,
particulate matter measured as condensible according to Method 5 is reported as such.
d N/A = data not available.
7/93
Chemical Process Industry
5.16-5
-------
TABLE 5.16-2
PARTICULATE MATTER: UNCONTROLLED BASIS
Process (SCC
Ore mining (3-01-023-99)
Nominal -
Control
Efficiency
Code) (percent) ]
Ore crushing and screening (3-01-023-99)
Ore transfer (3-01-023-99)
Monohydrate process: rotary ore calciner (3-01-023-04/05) 99 9
Sesquicarbonate process: rotary calciner (3-01-023-99)
Sesquicarbonate process: fluid-bed
calciner (3-01-023-99)
Rotary soda ash dryers (3-01-023-06)
Fluid-bed soda ash dryers/coolers
Soda ash screening (3-01-023-99)
(3-01-023-07) 99
Soda ash storage/loading and unloading (3-01-023-99) 99 9
Total8
cg/Mg Ib/ton Emission
of of Factor
Jroduct Product Rating
1.6 3.3 D
1.7 3.5 E
0.1 0.2 E
90 180 B
36 72 D
2.1 4.3 D
25 50 E
1.5 3.0 E
10 19 E
2.6 5.2 E
8 Values for total particulate matter on an uncontrolled basis can be assumed to include filterable
particulate and both organic and inorganic condensible particulate. For processes operating at
significantly greater than ambient temperatures, these factors have been calculated by applying the
nominal control efficiency to the controlled (as-measured) filterable particulate emission factors above.
TABLE 5.16-3 (METRIC UNITS)
CARBON DIOXIDE"
Process
(SCC Code)
Monohydrate process: rotary ore calciner
Sesquicarbonate process
Sesquicarbonate process
Rotary soda ash dryers
: rotary calciner
Carbon Dioxide
kg/Mg
of
Product
(3-01-023-04/05) 200
(3-01-023-99) 150
: fluid-bed calciner (3-01-023-99) 90
(3-01-023-06)
63
Ib/ton
of
Product
400
310
180
130
Emission
Factor
Rating
E
E
E
E
a Emission factors for carbon dioxide are derived from ORSAT analyses during emission
tests for criteria pollutants, rather than from fuel analyses and material balances.
5.16-6
EMISSION FACTORS
7/93
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References for Section 5.16
1. D.S. Kostick, "Soda Ash," Mineral Commodity Summaries 1992, pp. 162-163, U.S Department
of the Interior, Bureau of Mines, 1992.
2. D.S. Kostick, "Soda Ash," Minerals Yearbook 1989, Volume I: Metals and Minerals, pp. 951-
968, U.S Department of the Interior, Bureau of Mines, 1990.
3. SRI International, 1990 Directory of Chemical Producers: United States.
4. L. Gribovicz, Wyoming Department of Environmental Quality, Air Quality Division, "FY 91
Annual Inspection Report: FMC-Wyoming Corporation, Westvaco Soda Ash Refinery," 11
June 1991.
5. L. Gribovicz, Wyoming Department of Environmental Quality, Air Quality Division, "FY 92
Annual Inspection Report: General Chemical Partners, Green River Works," 16 September
1991.
6. L. Gribovicz, Wyoming Department of Environmental Quality, Air Quality Division, "FY 92
Annual Inspection Report: Rh6ne-Poulenc Chemical Company, Big Island Mine and Refinery,"
17 December 1991.
7. L. Gribovicz, Wyoming Department of Environmental Quality, Air Quality Division, "FY 91
Annual Inspection Report: Texasgulf Chemical Company, Granger Trona Mine & Soda Ash
Refinery," 15 July 1991.
8. "Stack Emissions Survey: General Chemical, Soda Ash Plant, Green River, Wyoming,"
Western Environmental Services and Testing, Inc., Casper, WY, February 1988.
9. "Stack Emissions Survey: General Chemical, Soda Ash Plant, Green River, Wyoming,"
Western Environmental Services and Testing, Inc., Casper, WY, November 1989.
10. "Rh6ne-Poulenc Wyoming Co. Paniculate Emission Compliance Program," TRC
Environmental Measurements Division, Englewood, CO, 21 May 1990.
11. "Rhone-Poulenc Wyoming Co. Particulate Emission Compliance Program," TRC
Environmental Measurements Division, Englewood, CO, 6 July 1990.
12. "Stack Emissions Survey: FMC-Wyoming Corporation, Green River, Wyoming," FMC-
Wyoming Corporation, Green River, WY, October 1990.
13. "Stack Emissions Survey: FMC-Wyoming Corporation, Green River, Wyoming," FMC-
Wyoming Corporation, Green River, WY, February 1991.
14. "Stack Emissions Survey: FMC-Wyoming Corporation, Green River, Wyoming," FMC-
Wyoming Corporation, Green River, WY, January 1991.
15. "Stack Emissions Survey: FMC-Wyoming Corporation, Green River, Wyoming," FMC-
Wyoming Corporation, Green River, WY, October 1990.
7/93 Chemical Process Industry 5.16-7
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16. "Compliance Test Report: FMC-Wyoming Corporation, Green River, Wyoming," FMC-
Wyoming Corporation, Green River, WY, 6 June 1988.
17. "Compliance Test Report: FMC-Wyoming Corporation, Green River, Wyoming," FMC-
Wyoming Corporation, Green River, WY, 24 May 1988.
18. "Compliance Test Report: FMC-Wyoming Corporation, Green River, Wyoming," FMC-
Wyoming Corporation, Green River, WY, 28 August 1985.
19. "Stack Emissions Survey: FMC-Wyoming Corporation, Green River, Wyoming," FMC-
Wyoming Corporation, Green River, WY, December 1990.
20. "Emission Measurement Test Report of GR3A Crusher," The Emission Measurement People,
Inc.," Canon City, CO, 16 October 1990.
21. "Stack Emissions Survey: TG Soda Ash, Inc., Granger, Wyoming," Western Environmental
Services and Testing, Inc., Casper, WY, August 1989.
22. "Compliance Test Reports," Tenneco Minerals, Green River, WY, 30 November 1983.
23. "Compliance Test Reports," Tenneco Minerals, Green River, WY, 8 November 1983.
24. "Particulate Stack Sampling Reports," Texasgulf, Inc., Granger, WY, October 1977-September
1978.
25. "Fluid Bed Dryer Emissions Certification Report," Texasgulf Chemicals Co., Granger, WY, 18
February 1985.
26. "Stack Emissions Survey: General Chemical, Soda Ash Plant, Green River, Wyoming,"
Western Environmental Services and Testing, Inc., Casper, WY, May 1987.
5.16-8 EMISSION FACTORS 7/93
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5.17 SULFURICACID
5.17.1 General1'2
Sulfuric acid (H2SO4) is a basic raw material used in a wide range of industrial processes and
manufacturing operations. Almost 70 percent of sulfuric acid manufactured is used in the production
of phosphate fertilizers. Other uses include copper leaching, inorganic pigment production, petroleum
refining, paper production, and industrial organic chemical production.
Sulfuric acid may be manufactured commercially by either the lead chamber process or the
contact process. Because of economics, all of the sulfuric acid produced in the U. S. is now produced
by the contact process. U. S. facilities produce approximately 42 million megagrams (46.2 million
tons) of H2SO4 annually. Growth in demand was about 1 percent per year from 1981 to 1991 and is
projected to continue to increase at about 0.5 percent per year.
5.17.2 Process Description3"5
Since the contact process is the only process currently used, it will be the only one discussed in
this section. Contact plants are classified according to the raw materials charged to them: elemental
sulfur burning, spent sulfuric acid and hydrogen sulfide burning, and metal sulfide ores and smelter
gas burning. The contributions from these plants to the total acid production are 81, 8 and 11 percent,
respectively.
The contact process incorporates three basic operations, each of which corresponds to a distinct
chemical reaction. First, the sulfur in the feedstock is oxidized (burned) to sulfur dioxide:
S + O2 -* SO2 (1)
The resulting sulfur dioxide is fed to a process unit called a converter, where it is catalytically
oxidized to sulfur trioxide:
2SO2 + O2 -» 2SO3 (2)
Finally, the sulfur trioxide is absorbed in a strong sulfuric acid (98 percent) solution:
SO3 + H2O •* H2SO4 (3)
5.17.2.1 Elemental Sulfur Burning Plants
Figure 5.17-1 is a schematic diagram of a dual absorption contact process sulfuric acid plant
that burns elemental sulfur. In the Frasch process, elemental sulfur is melted, filtered to remove ash,
and sprayed under pressure into a combustion chamber. The sulfur is burned in clean air that has
been dried by scrubbing with 93 to 99 percent sulfuric acid. The gases from the combustion chamber
cool by passing through a waste heat boiler and then enter the catalyst (vanadium pentoxide)
converter. Usually, 95 to 98 percent of the sulfur dioxide from the combustion chamber is converted
to sulfur trioxide, with an accompanying large evolution of heat. After being cooled, again by
7/93 Chemical Process Industry 5.17-1
-------
Figure 5.17-1. Typical contact process sulfuric acid plant burning elemental sulfur.
5.17-2 EMISSION FACTORS 7/93
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generating steam, the converter exit gas enters an absorption tower. The absorption tower is a packed
column where acid is sprayed in the top and where the sulfur trioxide enters from the bottom. The
sulfur trioxide is absorbed in the 98 to 99 percent sulfuric acid. The sulfur trioxide combines with the
water in the acid and forms more sulfuric acid.
If oleum (a solution of uncombined SO3 dissolved in H2SO4) is produced, SO3 from the
converter is first passed to an oleum tower that is fed with 98 percent acid from the absorption
system. The gases from the oleum tower are then pumped to the absorption column where the
residual sulfur trioxide is removed.
In the dual absorption process shown in Figure 5.17-1, the SO3 gas formed in the primary
converter stages is sent to an interpass absorber where most of the SO3 is removed to form H2SO4.
The remaining unconverted sulfur dioxide is forwarded to the final stages in the converter to remove
much of the remaining SO2 by oxidation to SO3, whence it is sent to the final absorber for removal of
the remaining sulfur trioxide. The single absorption process uses only one absorber, as the name
implies.
5.17.2.2 Spent Acid And Hydrogen Sulfide Burning Plants
A schematic diagram of a contact process sulfuric acid plant that burns spent acid is shown in
Figure 5.17-2. Two types of plants are used to process this type of sulfuric acid. In one, the sulfur
dioxide and other products from the combustion of spent acid and/or hydrogen sulfide with undried
atmospheric air are passed through gas cleaning and mist removal equipment. The gas stream next
passes through a drying tower. A blower draws the gas from the drying tower and discharges the
sulfur dioxide gas to the sulfur trioxide converter, then to the oleum tower and/or absorber.
In a "wet gas plant", the wet gases from the combustion chamber are charged directly to the
converter, with no intermediate treatment. The gas from the converter flows to the absorber, through
which 93 to 98 percent sulfuric acid is circulated.
5.17.2.3 Sulfide Ores And Smelter Gas Plants
The configuration of this type of plant is essentially the same as that of a spent acid plant
(Figure 5.17-2), with the primary exception that a roaster is used in place of the combustion furnace.
The feed used in these plants is smelter gas, available from such equipment as copper
converters, reverberatory furnaces, roasters and flash smelters. The sulfur dioxide in the gas is
contaminated with dust, acid mist and gaseous impurities. To remove the impurities, the gases must
be cooled and passed through purification equipment consisting of cyclone dust collectors,
electrostatic dust and mist precipitators, and scrubbing and gas cooling towers. After the gases are
cleaned and the excess water vapor is removed, they are scrubbed with 98 percent acid in a drying
tower. Beginning with the drying tower stage, these plants are nearly identical to the elemental sulfur
plants shown in Figure 5.17-1.
5.17.3 Emissions4'6-7
5.17.3.1 Sulfur Dioxide
Nearly all sulfur dioxide emissions from sulfuric acid plants are found in the exit stack gases.
Extensive testing has shown that the mass of these SO2 emissions is an inverse function of the sulfur
7/93 Chemical Process Industry 5.17-3
-------
Ill
Figure 5.17-2. Basic flow diagram of contact process sulfuric acid plant burning spent acid.
5.17-4 EMISSION FACTORS 7/93
-------
conversion efficiency (SO2 oxidized to SO3). This conversion is always incomplete, and is affected by
the number of stages in the catalytic converter, the amount of catalyst used, temperature and pressure,
and the concentrations of the reactants (sulfur dioxide and oxygen). For example, if the inlet SO2
concentration to the converter were 9 percent by volume (a representative value), and the conversion
temperature was 430°C (806°F), the conversion efficiency would be 98 percent. At this conversion,
Table 5.17-1 shows that the uncontrolled emission factor for SO2 would be 13 kg/Mg (26 pounds per
ton) of 100 percent sulfuric acid produced. (For purposes of comparison, note that the Agency's new
source performance standard (NSPS) for new and modified plants is 2 kg/Mg (4 pounds per ton) of
100 percent acid produced, maximum 2 hour average). As Table 5.17-1 and Figure 5.17-3 indicate,
achieving this standard requires a conversion efficiency of 99.7 percent in an uncontrolled plant, or
the equivalent SO2 collection mechanism in a controlled facility.
Dual absorption, as discussed above, has generally been accepted as the Best Available Control
Technology (BACT) for meeting NSPS emission limits. There are no by-products or waste scrubbing
materials created, only additional sulfuric acid. Conversion efficiencies of 99.7 percent and higher are
achievable, whereas most single absorption plants have SO2 conversion efficiencies ranging only from
95 to 98 percent. Furthermore, dual absorption permits higher converter inlet sulfur dioxide
concentrations than are used in single absorption plants, because the final conversion stages effectively
remove any residual sulfur dioxide from the interpass absorber.
In addition to exit gases, small quantities of sulfur oxides are emitted from storage tank vents
and tank car and tank truck vents during loading operations, from sulfuric acid concentrators, and
through leaks in process equipment. Few data are available on the quantity of emissions from these
sources.
Table 5.17-1 (Metric and English Units).
SULFUR DIOXIDE EMISSION FACTORS FOR SULFURIC ACID PLANTS*
s
SO2 to SO3 kg
Conversion Efficiency
(%) Pn
O2 Emissions1*
/Mg Ib/ton
of of
)duct Product
93 (SCC 3-01-023-18) 48.0 96
94 (SCC 3-01-023-16) 41.0 82
95 (SCC 3-01-023-14) 35.0 70
96 (SCC 3-01-023-12) 27.5 55
97 (SCC 3-01-023-10) 20.0 40
98 (SCC 3-01-023-08) 13.0 26
99 (SCC 3-01-023-06) 7.0 14
99.5 (SCC 3-01-023-04) 3.5 7
99.7 2.0 4
100 (SCC 3-01-023-01) 0.0 0.0
Emission
Factor
Rating
E
E
E
E
E
E
E
E
E
E
Reference 3. SCC = Source Classification Code.
bThis linear interpolation formula can be used for calculating emission factors for conversion efficiencies
between 93 and 100%: emission factor = -13.65 (% conversion efficiency) + 1365.
7/93
Chemical Process Industry
5.17-5
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SULFUR CONVERSION, % feedstock sulfur
99.92 99.7 99.0 98.0 97.0 96.0 95.0
10,000
92.9
100
1.5 2 2.5 3 4 5 6 78 910 15 20 2530 40 6070 90
80
SO2 EMISSIONS, Ib/ton of 100% h^SC^ produced
Figure 5.17-3. Sulfuric acid plant feedstock conversion versus volumetric and mass SO2 emissions at
various inlet SO2 concentrations by volume.
5.17-6
EMISSION FACTORS
7/93
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5.17.3.2 Acid Mist
Nearly all the acid mist emitted from sulfuric acid manufacturing can be traced to the absorber exit
gases. Acid mist is created when sulfur trioxide combines with water vapor at a temperature below the
dew point of sulfur trioxide. Once formed within the process system, this mist is so stable that only a
small quantity can be removed in the absorber.
In general, the quantity and particle size distribution of acid mist are dependent on the type of
sulfur feedstock used, the strength of acid produced, and the conditions in the absorber. Because it
contains virtually no water vapor, bright elemental sulfur produces little acid mist when burned.
However, the hydrocarbon impurities in other feedstocks (i. e., dark sulfur, spent acid and hydrogen
sulfide) oxidize to water vapor during combustion. The water vapor, in turn, combines with sulfur
trioxide as the gas cools in the system.
The strength of acid produced, whether oleum or 99 percent sulfuric acid, also affects mist
emissions. Oleum plants produce greater quantities of finer more stable mist. For example, an
unpublished report found that uncontrolled mist emissions from oleum plants burning spent acid range
from 0.5 to 5.0 kg/Mg (1.0 to 10.0 pounds per ton), while those from 98 percent acid plants burning
elemental sulfur range from 0.2 to 2.0 kg/Mg (0.4 to 4.0 pounds per ton).4 Furthermore, 85 to 95 weight
percent of the mist particles from oleum plants are less than two microns in diameter, compared with only
30 weight percent that are less than two microns in diameter from 98 percent acid plants.
The operating temperature of the absorption column directly affects sulfur trioxide absorption and,
accordingly, the quality of acid mist formed after exit gases leave the stack. The optimum absorber
operating temperature depends on the strength of the acid produced, throughput rates, inlet sulfur trioxide
concentrations, and other variables peculiar to each individual plant. Finally, it should be emphasized that
the percentage conversion of sulfur trioxide has no direct effect on acid mist emissions.
Table 5.17-2 presents uncontrolled acid mist emission factors for various sulfuric acid plants. Table
5.17-3 shows emission factors for plants that use fiber mist eliminator control devices. The three most
commonly used fiber mist eliminators are the vertical tube, vertical panel, and horizontal dual pad types.
They differ from one another in the arrangement of the fiber elements, which are composed of either
chemically resistant glass or fluorocarbon, and in the means employed to collect the trapped liquid. Data
are available only with percent oleum ranges for two raw material categories.
5.17.3.3 Carbon Dioxide
The nine source tests mentioned above were also used to determine the amount of carbon dioxide
(CO2), a global warming gas, emitted by sulfuric acid production facilities. Based on the tests, a CO2
emission factor of 4.05 kg emitted per Mg produced (8.10 Ib/ton) was developed, with an emission factor
rating of C.
7/93 Chemical Process Industry 5.17-7
-------
Table 5.17-2 (Metric and English Units).
UNCONTROLLED ACID MIST EMISSION FACTORS FOR SULFURIC ACID PLANTS*
Raw Material
Oleum
Produced,
% total
output
Emissions'*
kg/Mg of
Product
Recovered sulfur (SCC 3-01-023-22) 0 to 43 0.174-0.4
Bright virgin sulfur (SCC 3-01-023-22) 0 0.85
Dark virgin sulfur (SCC 3-01-023-22) 0 to 100 0.16-3.14
Spent acid (SCC 3-01-023-22) 0 to 77 1.1-1.2
Ib/ton of
Product
Emission
Factor
Rating
0.348 - 0.8 E
1.7 E
0.32 - 6.28 E
2.2 - 2.4 E
"Reference 3. SCC = Source Classification Code.
b Emissions are proportional to the percentage of oleum in the total product. Use low end of ranges
for low oleum percentage and high end of ranges for high oleum percentage.
Table 5.17-3 (Metric and English Units).
CONTROLLED ACID MIST EMISSION FACTORS FOR SULFURIC ACID PLANTS
Raw Material
Oleum
produced,
% total
output
Emissions
kg/Mg of
Product
Elemental Sulfur* (SCC 3-01-023-22) - 0.064
Dark Virgin Sulfurb (SCC 3-01-023-22) Otol3 0.26-1.8
Spent Acid (SCC 3-01-023-22) 0 to 56 0.014-0.20
Ib/ton of
Product
Emission
Factor
Rating
0.128 C
0.52 - 3.6 E
0.28 - 0.40 E
Reference 8-13, 15-17. SCC = Source Classification Code.
bReference 3.
References for Section 5.17
1. Chemical Marketing Reporter, Schnell Publishing Company, Inc., New York, 240:8,
September 16, 1991.
2. Final Guideline Document: Control Of Sulfuric Acid Mist Emissions From Existing Sulfuric Acid
Production Units, EPA-450/2-77-019, U. S. Environmental Protection Agency, Research
Triangle Park, NC, September 1977.
3. Atmospheric Emissions From Sulfuric Add Manufacturing Processes, 999-AP-13,
U. S. Department of Health, Education and Welfare, Washington, DC, 1966.
4. Unpublished report on control of air pollution from sulfuric acid plants, U. S. Environmental
Protection Agency, Research Triangle Park, NC, August 1971.
5.17-8
EMISSION FACTORS
7/93
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5. Review Of New Source Performance Standards For Suljuric Acid Plants, EPA-450/3-85-012,
U. S. Environmental Protection Agency, Research Triangle Park, NC, March 1985.
6. Standards Of Performance For New Stationary Sources, 36 FR 24875, December 23, 1971.
7. "Sulfuric Acid", Air Pollution Engineering Manual, Air And Water Management Association,
1992.
8. Source Emissions Compliance Test Report, Sulfuric Acid Stack, Roy F. Weston, Inc., West
Chester, PA, October 1989.
9. Source Emissions Compliance Test Report, Sulfuric Acid Stack, Roy F. Weston, Inc., West
Chester, PA, February 1988.
10. Source Emissions Compliance Test Report, Sulfuric Acid Stack, Roy F. Weston, Inc., West
Chester, PA, December 1989.
11. Source Emissions Compliance Test Report, Suljuric Acid Stack, Roy F. Weston, Inc.; West
Chester, PA, December 1991.
12. Stationary Source Sampling Report, Sulfuric Acid Plant, Entropy Environmentalists, Inc.,
Research Triangle Park, NC, January 1983.
13. Source Emissions Test: Sulfuric Acid Plant, Ramcon Environmental Corporation, Memphis, TN,
October 1989.
14. Mississippi Chemical Corporation, Air Pollution Emission Tests, Sulfuric Acid Stack,
Environmental Science and Engineering, Inc., Gainesville, FL, September 1973.
15. Kennecott Copper Corporation, Air Pollution Emission Tests, Sulfuric Acid Stack - Plant 6,
Engineering Science, Inc., Washington, DC, August 1972.
16. Kennecott Copper Corporation, Air Pollution Emission Tests, Sulfuric Acid Stack - Plant 7,
Engineering Science, Inc., Washington, DC, August 1972.
17. American Smelting Corporation, Air Pollution Emission Tests, Suljuric Acid Stack, Engineering
Science, Inc., Washington, DC, June 1972.
7/93 Chemical Process Industry 5.17-9
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5.18 SULFUR RECOVERY
5.18.1 General1"2
Sulfur recovery refers to the conversion of hydrogen sulfide (H2S) to elemental sulfur.
Hydrogen sulfide is a byproduct of processing natural gas and refining high-sulfur crude oils. The
most common conversion method used is the Claus process. Approximately 90 to 95 percent of
recovered sulfur is produced by the Claus process. The Claus process typically recovers 95 to 97
percent of the hydrogen sulfide feedstream.
Over 5.9 million megagrams (6.5 million tons) of sulfur were recovered in 1989, representing
about 63 percent of the total elemental sulfur market in the U.S. The remainder was mined or
imported. The average production rate of a sulfur recovery plant in the U.S. varies from 51 to 203
megagrams (56 to 224 tons) per day.
5.18.2 Process DescriptionJ "2
Hydrogen sulfide, a byproduct of crude oil and natural gas processing, is recovered and
converted to elemental sulfur by the Claus process. Figure 5.18-1 shows a typical Claus sulfur
recovery unit. The process consists of multistage catalytic oxidation of hydrogen sulfide according to
the following overall reaction:
2H2S + O2 - 2S + 2H2O (1)
Each catalytic stage consists of a gas reheater, a catalyst chamber and a condenser.
The Claus process involves burning one third of the hydrogen sulfide (H2S) with air in a
reactor furnace to form sulfur dioxide (SO2) according to the following reaction:
2H2S + 3O2 -* 2SO2 + 2H2O + heat " (2)
The furnace normally operates at combustion chamber temperatures ranging from 980 to 1540°C
(1800 to 2800°F) with pressures rarely higher than 70 kPa (10 psia). Before entering a sulfur
condenser, hot gas from the combustion chamber is quenched in a waste heat boiler that generates
high to medium pressure steam. About 80 percent of the heat released could be recovered as useful
energy. Liquid sulfur from the condenser runs through a seal leg into a covered pit from which it is
pumped to trucks or railcars for shipment to end users. Approximately 65 to 70 percent of the sulfur
is recovered. The cooled gases exiting the condenser are then sent to the catalyst beds.
The remaining uncombusted two-thirds of the hydrogen sulfide undergoes Claus reaction (reacts
with SO2) to form elemental sulfur as follows:
2H2S + SO2 ^—3S + 2H20 + heat (3)
The catalytic reactors operate at lower temperatures, ranging from 200 to 315°C (400 to 600°F).
Alumina or bauxite is sometimes used as a catalyst. Because this reaction represents an equilibrium
chemical reaction, it is not possible for a Claus plant to convert all the incoming sulfur compounds to
elemental sulfur. Therefore, two or more stages are used in series to recover the sulfur. Each catalytic
stage can recover half to two-thirds of the incoming sulfur. The number of catalytic stages depends
upon the level of conversion desired. It is estimated that 95 to 97 percent overall recovery can be
7/93 Chemical Process Industry 5.18-1
-------
SULFUR
SPENT
CATALYST
ADDITIONAL CONVERTERS/CONDENSERS TO
ACHIEVE ADDITIONAL RECOVERY OF
ELEMENTAL SULFUR ARE OPTIONAL AT THIS
POINT
SULFUR
Figure 5.18-1 Typical Claus sulfur recovery unit
achieved depending on the number of catalytic reaction stages and the type of reheating method used.
If the sulfur recovery unit is located in a natural gas processing plant, the type of reheat employed is
typically either auxiliary burners or heat exchangers, with steam reheat being used occasionally. If the
sulfur recovery unit is located in a crude oil refinery, the typical reheat scheme uses 3536 to 4223
kPa (500 to 600 psig) steam for reheating purposes. Most plants are now built with two catalytic
stages, although some air quality jurisdictions require three. From the condenser of the final catalytic
stage, the process stream passes to some form of tailgas treatment process. The tailgas, containing
H2S, SO2, sulfur vapor and traces of other sulfur compounds formed in the combustion section,
escapes with the inert gases from the tail end of the plant. Thus, it is frequently necessary to follow
the Claus unit with a tailgas cleanup unit to achieve higher recovery.
5.18-2
EMISSION FACTORS
7/93
-------
In addition to the oxidation of H2S to SO2 and the reaction of SO2 with H2S in the reaction
furnace, many other side reactions can and do occur in the furnace. Several of these possible side
reactions are:
CO2 + H2S -* COS + H2O (4)
COS + H2S -» CS2 + H20 (5)
2 COS -» CO2 + CS2 (6)
5.18.3 Emissions and Controls1"4
Table 5.18-1 shows emission factors and recovery efficiencies for modified Claus sulfur
recovery plants. Emissions from the Claus process are directly related to the recovery efficiency.
Higher recovery efficiencies mean less sulfur emitted in the tailgas. Older plants, or very small Claus
plants producing less than 20 megagrams (22 tons) per day of sulfur without tailgas cleanup, have
varying sulfur recovery efficiencies. The efficiency depends upon several factors, including the
number of catalytic stages, the concentrations of H2S and contaminants in the feed stream,
stoichiometric balance of gaseous components of the inlet, operating temperature, and catalyst
maintenance.
A two-bed catalytic Claus plant can achieve 94 to 96 percent efficiency. Recoveries range from
96 to 97.5 percent for a three-bed catalytic plant and range from 97 to 98.5 percent for a four-bed
catalytic plant. At normal operating temperatures and pressures, the Claus reaction is
thermodynamically limited to 97 to 98 percent recovery. Tailgas from the Claus plant still contains
0.8 to 1.5 percent sulfur compounds.
Existing new source performance standard (NSPS) limits sulfur emissions from Claus sulfur
recovery plants of greater than 20.32 megagrams (22.40 ton) per day capacity to 0.025 percent (250
ppmv) by volume. This limitation is effective at zero percent oxygen on a dry basis if emissions are
controlled by an oxidation control system or a reduction control system followed by" incineration. This
is comparable to the 99.8 to 99.9 percent control level for reduced sulfur.
7/93 Chemical Process Industry 5.18-3
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Table 5.18-1 (Metric and English Units).
EMISSION FACTORS FOR MODIFIED CLAUS SULFUR RECOVERY PLANTS
Number of
Catalytic Stages
Average Percent
Sulfur Recovery*
SO2 Emissions
kg/Mg of
Sulfur
Produced
Two, uncontrolled 93.5C 139b'c
Three, uncontrolled 95. 5d 94b>d
Four, uncontrolled 96.5e 73b'e
Two, controlledf 98.6 29
Three, controlled8 96.8 65
Ib/ton of
Sulfur
Produced
278b>c
188b'd
145b,e
57
129
Emission
Factor
Rating
E
E
E
B
B
"Efficiencies are for feedgas streams with high H2S concentrations. Gases with lower H2S concentrations would
have lower efficiencies. For example, a 2- or 3-stage plant could have a recovery efficiency of 95% for a 90%
H2S stream, 93% for 50% H2S, and 90% for 15% H2S.
bReference 5. Based on net weight of pure sulfur produced. The emission factors were determined using the
average of the percentage recovery of sulfur. Sulfur dioxide emissions are calculated from percentage sulfur
recovery by one of the following equations:
S02 emissions (kg/Mg) = (100-% recovery) x
% recovery
S02 emissions (Ib/ton) = (1 <*>-**** very) x
% recovery
Typical sulfur recovery ranges from 92 to 95 percent.
dTypical sulfur recovery ranges from 95 to 96 percent.
'Typical sulfur recovery ranges from 96 to 97 percent.
^Reference 6. Test data indicated sulfur recovery ranges from 98.3 to 98.8 percent.
References 7, 8 and 9. Test data indicated sulfur recovery ranges from 95 to 99.8 percent.
Emissions from the Claus process may be reduced by: 1) extending the Claus reaction into a lower
temperature liquid phase, 2) adding a scrubbing process to the Claus exhaust stream, or 3)
incinerating the hydrogen sulfide gases to form sulfur dioxide.
Currently, there are five processes available that extend the Claus reaction into a lower temperature
liquid phase including the BSR/selectox, Sulfreen, Cold Bed Absorption, Maxisulf, and IFP-1
processes. These processes take advantage of the enhanced Claus conversion at cooler temperatures in
the catalytic stages. All of these processes give higher overall sulfur recoveries of 98 to 99 percent
when following downstream of a typical two- or three-stage Claus sulfur recovery unit, and therefore
reduce sulfur emissions.
5.18-4
EMISSION FACTORS
7/93
-------
Sulfur emissions can also be reduced by adding a scrubber at the tail end of the plant. There are
essentially two generic types of tailgas scrubbing processes: oxidation tailgas scrubbers and reduction
tailgas scrubbers. The first scrubbing process is used to scrub sulfur dioxide (SO2) from incinerated
tailgas and recycle the concentrated SO2 stream back to the Claus process for conversion to elemental
sulfur. There are at least three oxidation scrubbing processes: the Wellman-Lord, Stauffer Aquaclaus
and IFP-2. Only the Wellman-Lord process has been applied successfully to U.S. refineries.
The Wellman-Lord process uses a wet generative process to reduce stack gas sulfur dioxide
concentration to less than 250 parts per million volume (ppmv) and can achieve approximately 99.9
percent sulfur recovery. Claus plant tailgas is incinerated and all sulfur species are oxidized to form
sulfur dioxide (SO2) in the Wellman-Lord process. Gases are then cooled and quenched to remove
excess water and to reduce gas temperature to absorber conditions. The rich SO2 gas is then reacted
with a solution of sodium sulfite (Na2SO3) and sodium bisulfite (NaHSO3) to form the bisulfite:
SO2 + Na2SO3 + H2O -» 2NaHSO3 (7)
The offgas is reheated and vented to the atmosphere. The resulting bisulfite solution is boiled in an
evaporator-crystallizer, where it decomposes to SO2 and H2O vapor and sodium sulfite is precipitated:
2NaHSO3 -» Na2SO3* + H2O + SO2t (8)
Sulfite crystals are separated and redissolved for reuse as lean solution in the absorber. The wet SO2
gas is directed to a partial condenser where most of the water is condensed and reused to dissolve
sulfite crystals. The enriched SO2 stream is then recycled back to the Claus plant for conversion to
elemental sulfur.
In the second type of scrubbing process, sulfur in the tailgas is converted to H2S by hydrogenation
in a reduction step. After hydrogenation, the tailgas is cooled and water is removed. The cooled
tailgas is then sent to the scrubber for H2S removal prior to venting. There are at least four reduction
scrubbing processes developed for tailgas sulfur removal: Beavon, Beavon MDEA, S.COT and
ARCO. In the Beavon process, H2S is converted to sulfur outside the Claus unit using a lean H2S-to-
sulfur process (the Strefford process). The other three processes utilize conventional amine scrubbing
and regeneration to remove H2S an recycle back as Claus feed.
Emissions from the Claus process may also be reduced by incinerating sulfur-containing tailgases to
form sulfur dioxide. In order to properly remove the sulfur, incinerators must operate at a
temperature of 650°C (1,200°F) or higher if all the H2S is to be combusted. Proper air-to-fuel ratios
are needed to eliminate pluming from the incinerator stack. The stack should be equipped with
analyzers to monitor the SO2 level.
7/93 Chemical Process Industry 5.18-5
-------
References for Section 5.18
1. B. Goar et al., "Sulfur Recovery Technology," Energy Progress, Vol. 6(2): 71-75, June, 1986.
2. Written communication from Bruce Scott, Bruce Scott, Inc. to David Hendricks, Pacific
Environmental Services, Inc., February 28, 1992.
3. Review of New Source Performance Standards for Petroleum Refinery Claus Sulfur Recovery
Plants, EPA-450/3-83-014, U. S. Environmental Protection Agency, Research Triangle Park,
NC, August 1983.
4. Standards Support and Environmental Impact Statement, Volume 1: Proposed Standards of
Performance for Petroleum Refinery Sulfur Recovery Plants. EPA-450/2-76-016a, U. S.
Environmental Protection Agency, Research Triangle Park, NC, September 1976.
5. D. K. Beavon, "Abating Sulfur Plant Gases," Pollution Engineering, January/February 1972,
pp. 34-35.
6. "Compliance Test Report: Collett Ventures Company, Chatom, Alabama," Environmental
Science & Engineering, Inc., Gainesville, FL, May 1991.
7. "Compliance Test Report: Phillips Petroleum Company, Chatom, Alabama," Environmental
Science & Engineering, Inc., Gainesville, FL, July 1991.
8. "Compliance Test report: Mobil Exploration and Producing Southeast, Inc., Coden, Alabama,"
Cubix Corporation, Austin, TX, September 1990.
9. "Emission Test Report: Getty Oil Company, New Hope, TX," EMB Report No. 81-OSP-9,
July 1981.
5.18-6 EMISSION FACTORS 7/93
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6.8 AMMONIUM NITRATE
6.8.1 General1'3
Ammonium nitrate (NH4NO3) is produced by neutralizing nitric acid (HNO3) with ammonia
(NH3). In 1991, there were 58 U.S. ammonium nitrate plants located in 22 states producing about 8.2
million megagrams (nine million tons) of ammonium nitrate. Approximately 15 to 20 percent of this
amount was used for explosives and the balance for fertilizer.
Ammonium nitrate is marketed in several forms, depending upon its use. Liquid ammonium
nitrate may be sold as a fertilizer, generally in combination with urea. Liquid ammonium nitrate may
be concentrated to form an ammonium nitrate "melt" for use in solids formation processes. Solid
ammonium nitrate may be produced in the form of prills, grains, granules or crystals. Prills can be
produced in either high or low density form, depending on the concentration of the melt. High density
prills, granules and crystals are used as fertilizer, grains are used solely in explosives, and low
density prills can be used as either.
6.8.2 Process Description1'2
The manufacture of ammonium nitrate involves several major unit operations including solution
formation and concentration; solids formation, finishing, screening and coating; and product bagging
and/or bulk shipping. In some cases, solutions may be blended for marketing as liquid fertilizers.
These operations are shown schematically in Figure 6.8-1.
The number of operating steps employed depends on the end product desired. For example,
plants producing ammonium nitrate solutions alone use only the solution formation, solution blending
and bulk shipping operations. Plants producing a solid ammonium nitrate product may employ all of
the operations.
All ammonium nitrate plants produce an aqueous ammonium nitrate solution through the
reaction of ammonia and nitric acid in a neutralizer as follows:
NH3 + HNO3 -» NH4NO3 (1)
Approximately 60 percent of the ammonium nitrate produced in the U.S. is sold as a solid
product. To produce a solid product, the ammonium nitrate solution is concentrated in an evaporator
or concentrator. The resulting "melt" contains about 95 to 99.8 percent ammonium nitrate at
approximately 149°C (300°F). This melt is then used to make solid ammonium nitrate products.
Prilling and granulation are the most common processes used to produce solid ammonium
nitrate. To produce prills, concentrated melt is sprayed into the top of a prill tower. In the tower,
ammonium nitrate droplets fall countercurrent to a rising air stream that cools and solidifies the
falling droplets into spherical prills. Prill density can be varied by using different concentrations of
ammonium nitrate melt. Low density prills, in the range of 1.29 specific gravity, are formed from a
95 to 97.5 percent ammonium nitrate melt, and high density prills, in the range of 1.65 specific
7/93 Chemical Process Industry 6.8-1
-------
SOLIDS
INISHING
DRYING
COOLING
SOLIDS
FORMATI
PRILLING
GRANULA
ON
£ z
O d
Z
O CO
o 9
_j
O
1 g
Q 2
UJ
LU- »
O O
" ^
ui 2
m cv
O
0 !t
tn \sL
g S
< u,
m
UJ
:i
(5
z
6.8-2
Figure 6.8-1 Ammonium nitrate manufacturing operations
EMISSION FACTORS
7/9
-------
gravity, are formed from a 99.5 to 99.8 percent melt. Low density prills are more porous than high
density prills. Therefore, low density prills are used for making blasting agents because they will
absorb oil. Most high density prills are used as fertilizers.
Rotary drum granulators produce granules by spraying a concentrated ammonium nitrate melt
(99.0 to 99.8 percent) onto small seed particles of ammonium nitrate in a long rotating cylindrical
drum. As the seed particles rotate in the drum, successive layers of ammonium nitrate are added to
the particles, forming granules. Granules are removed from the granulator and screened. Offsize
granules are crushed and recycled to the granulator to supply additional seed particles or are dissolved
and returned to the solution process. Pan granulators operate on the same principle as drum
granulators, except the solids are formed in a large, rotating circular pan. Pan granulators produce a
solid product with physical characteristics similar to those of drum granules.
Although not widely used, an additive such as magnesium nitrate or magnesium oxide may be
injected directly into the melt stream. This additive serves three purposes: to raise the crystalline
transition temperature of the final solid product; to act as a desiccant, drawing water into the final
product to reduce caking; and to allow solidification to occur at a low temperature by reducing the
freezing point of molten ammonium nitrate.
The temperature of the ammonium nitrate product exiting the solids formation process is
approximately 66 to 124°C (150 to 255°F). Rotary drum or fluidized bed cooling prevents
deterioration and agglomeration of solids before storage and shipping. Low density prills have a high
moisture content because of the lower melt concentration, and therefore require drying in rotary
drums or fluidized beds before cooling.
Since the solids are produced in a wide variety of sizes, they must be screened for consistently
sized prills or granules. Cooled prills are screened and offsize prills are dissolved and recycled to the
solution concentration process. Granules are screened before cooling. Undersize particles are returned
directly to the granulator and oversize granules may be either crushed and returned to the granulator
or sent to the solution concentration process.
Following screening, products can be coated in a rotary drum to prevent agglomeration during
storage and shipment. The most common coating materials are clays and diatomaceous earth.
However, the use of additives in the ammonium nitrate melt before solidification, as described above,
may preclude the use of coatings.
Solid ammonium nitrate is stored and shipped in either bulk or bags. Approximately ten percent
of solid ammonium nitrate produced in the U.S. is bagged.
6.8.3 Emissions and Controls
Emissions from ammonium nitrate production plants are paniculate matter (ammonium nitrate
and coating materials), ammonia and nitric acid. Ammonia and nitric acid are emitted primarily from
solution formation and granulators. Paniculate matter (largely as ammonium nitrate) is emitted from
most of the process operations and is the primary emission addressed here.
The emission sources in solution formation and concentration processes are neutralizes and
evaporators, primarily emitting nitric acid and ammonia. The vapor stream off the top of the
7/93 Chemical Process Industry 6.8-3
-------
neutralization reactor is primarily steam with some ammonia and NH4NO3 participates present.
Specific plant operating characteristics, however, make these emissions vary depending upon use of
excess ammonia or acid in the neutralizes Since the neutralization operation can dictate the quantity
of these emissions, a range of emission factors is presented in Table 6.8-1. Paniculate emissions from
these operations tend to be smaller in size than those from solids production and handling processes
and generally are recycled back to the process.
Emissions from solids formation processes are ammonium nitrate participate matter and
ammonia. The sources of primary importance are prill towers (for high density and low density prills)
and granulators (rotary drum and pan). Emissions from prill towers result from carryover of fine
particles and fume by the prill cooling air flowing through the tower. These fine particles are from
microprill formation, attrition of prills colliding with the tower or one another, and from rapid
transition of the ammonia nitrate between crystal states. The uncontrolled paniculate emissions from
prill towers, therefore, are affected by tower airflow, spray melt temperature, condition and type of
melt spray device, air temperature, and crystal state changes of the solid prills. The amount of
microprill mass that can be entrained in the prill tower exhaust is determined by the tower air
velocity. Increasing spray melt temperature causes an increase in the amount of gas phase ammonium
nitrate generated. Thus, gaseous emissions from high density prilling are greater than from low
density towers.
6.8-4 EMISSION FACTORS 7/9
-------
Table 6.8-1 (Metric Units)
EMISSION FACTORS FOR PROCESSES IN
AMMONIUM NITRATE MANUFACTURING PLANTS4
Participate Matter
I
Process kg/
Pr
Uncontrolled
Mg of Factor
oduct Rating
Neutralizer 0.045-4.3 B
Controlled15
kg/Mg of
Product
0.002-0.22
Factor
Rating
B
Evaporation/concentration operations 0.26 A
Solids Formation Operations
High density prill towers '.
.59 A
Low density prill towers 0.46 A
Rotary drum granulators 146 A
Pan granulators '.
Coolers and dryers
.34 A
High density prill coolers6 0.8 A
Low density prill coolers6 25.8 A
Low density prill dryers6 57.2 A
Rotary drum granulator coolers6 8.1 A
Pan granulator coolers6 18.3 A
Coating operations* < 2.0 B
Bulk loading operations* <,
0.01 B
0.60
0.26
0.22
0.02
0.01
0.26
0.57
0.08
0.18
<: 0.02
A
A
A
A
A
A
A
A
B
B
Ammonia '.
Uncontrolled0
kg/Mg of
Product
0.43-18.0
0.27-16.7
28.6
0.13
29.7
0.07
0.02
0.15
0-1.59
kj
Factor
Rating Pr
Citric Acid
;/Mg
of Factor
oduct Rating
B 0.042-ld B
A
A
A
A
A
A
A
A
(See Reference 1).
bBased on the following control efficiencies for wet scrubbers, applied to uncontrolled emissions: neutralizes,
95 percent; high density prill towers, 62 percent; low density prill towers, 43 percent; rotary drum granulators,
99.9 percent; pan granulators, 98.5 percent; coolers, dryers, and coaters, 99%.
°Given as ranges because of variation in data and plant operations. Factors for controlled emissions not
presented due to conflicting results on control efficiency.
BBased on 95 percent recovery in a granulator recycle scrubber.
6Factors for coolers represent combined precooler and cooler emissions, and factors for dryers represent
combined predryer and dryer emissions.
'Fugitive participate emissions arise from coating and bulk loading operations.
7/93
Chemical Process Industry
6.8-5
-------
TABLE 6.8-1 (ENGLISH UNITS)
EMISSION FACTORS FOR PROCESSES IN
AMMONIUM NITRATE MANUFACTURING PLANTS4
All Emission Factors are in
Ratings (A-E) Follow Each Factor
Particulate Matter
\
Itv
Process Pi
Jncontrolled
ton of Factor
•oduct Rating
Neutralizer 0.09-8.6 B
Controlled15
Ib/ton of
Product
0.004-0.43
Factor
Rating
B
Evaporation/concentration operations 0.52 A
Solids Formation Operations
High density prill towers 3.18 A
Low density prill towers 0.92 A
Rotary drum granulators
392 A
Pan granulators 2.68 A
Coolers and dryers
High density prill coolers6
1.6 A
Low density prill coolers6 51.6 A
Low density prill dryers8 114.4 A
Rotary drum granulator coolers6
16.2 A
Pan granulator coolers6 36.6 A
Coating operations <
~ 4.0 B
1.20
0.52
0.44
0.04
0.02
0.52
1.14
0.16
0.36
<, 0.04
A
A
A
A
A
A
A
A
B
B
Ammonia
Uncontrolled0
Ib/ton of
Product
0.86-36.0
0.54-33.4
57.2
0.26
59.4
0.14
0.04
0.30
0-3.18
Factor lb/
Rating Pi
Nitric Acid
ton of Factor
•oduct Rating
B 0.084-2d B
A
A
A
A
A
A
A
A
Bulk loading operationsf < 0.02 B
8Some ammonium nitrate emission factors are based on data gathered using a modification of EPA Method 5
(See Reference 1).
bBased on the following control efficiencies for wet scrubbers, applied to uncontrolled emissions: neutralizes,
95 percent; high density prill towers, 62 percent; low density prill towers, 43 percent; rotary drum granulators,
99.9 percent; pan granulators, 98.5 percent; coolers, dryers, and coaters, 99%.
cGiven as ranges because of variation hi data and plant operations. Factors for controlled emissions not
presented due to conflicting results on control efficiency.
dBased on 95 percent recovery in a granulator recycle scrubber.
6Factors for coolers represent combined precooler and cooler emissions, and factors for dryers represent
combined predryer and dryer emissions.
^Fugitive particulate emissions arise from coating and bulk loading operations.
6.8-6
EMISSION FACTORS
7/9
-------
Microprill formation resulting from partially plugged orifices of melt spray devices can increase
fine dust loading and emissions. Certain designs (spinning buckets) and practices (vibration of spray
plates) help reduce microprill formation. High ambient air temperatures can cause increased emissions
because of entrainment as a result of higher air flow required to cool prills and because of increased
fume formation at the higher temperatures.
The granulation process in general provides a larger degree of control in product formation
than does prilling. Granulation produces a solid ammonium nitrate product that, relative to prills, is
larger and has greater abrasion resistance and crushing strength. The air flow in granulation processes
is lower than that in prilling operations. Granulators, however, cannot produce low density
ammonium nitrate economically with current technology. The design and operating parameters of
granulators may affect emission rates. For example, the recycle rate of seed ammonium nitrate
particles affects the bed temperature in the granulator. An increase in bed temperature resulting from
decreased recycle of seed particles may cause an increase in dust emissions from granule
disintegration.
Cooling and drying are usually conducted in rotary drums. As with granulators, the design and
operating parameters of the rotary drums may affect the quantity of emissions. In addition to design
parameters, prill and granule temperature control is necessary to control emissions from disintegration
of solids caused by changes in crystal state.
Emissions from screening operations are generated by the attrition of the ammonium nitrate
solids against the screens and against one another. Almost all screening operations used in the
ammonium nitrate manufacturing industry are enclosed or have a cover over the uppermost screen.
Screening equipment is located inside a building and emissions are ducted from the process for
recovery or reuse.
Prills and granules are typically coated in a rotary drum. The rotating action produces a
uniformly coated product. The mixing action also causes some of the coating material to be
suspended, creating paniculate emissions. Rotary drums used to coat solid product are typically kept
at a slight negative pressure and emissions are vented to a paniculate control device. Any dust
captured is usually recycled to the coating storage bins.
Bagging and bulk loading operations are a source of paniculate emissions. Dust is emitted from
each type of bagging process during final filling when dust laden air is displaced from the bag by the
ammonium nitrate. The potential for emissions during bagging is greater for coated than for uncoated
material. It is expected that emissions from bagging operations are primarily the kaolin, talc or
diatomaceous earth coating matter. About 90 percent of solid ammonium nitrate produced
domestically is bulk loaded. While paniculate emissions from bulk loading are not generally
controlled, visible emissions are within typical state regulatory requirements (below 20 percent
opacity).
Table 6.8-1 summarizes emission factors for various processes involved in the manufacture of
ammonium nitrate. Uncontrolled emissions of paniculate matter, ammonia and nitric acid are given in
the Table. Emissions of ammonia and nitric acid depend upon specific operating practices, so ranges
of factors are given for some emission sources.
Emission factors for controlled paniculate emissions are also in Table 6.8-1, reflecting wet
7/93 Chemical Process Industry 6.8-7
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scrubbing paniculate control techniques. The particle size distribution data presented in Table 6.8-2
indicate the emissions. In addition, wet scrubbing is used as a control technique because the solution
containing the recovered ammonium nitrate can be sent to the solution concentration process for reuse
in production of ammonium nitrate, rather than to waste disposal facilities.
Table 6.8-2
PARTICLE SIZE DISTRIBUTION DATA FOR UNCONTROLLED EMISSIONS
FROM AMMONIUM NITRATE MANUFACTURING FACILITIES8
Operation
Cumulative Weight %
<; 2.5
< 5 /on
< 10 jim
Solids Formation Operations
Low density prill tower 56
Rotary drum granulator 0.07
Coolers and Dryers
Low density prill cooler 0.03
Low density prill predryer 0.03
Low density prill dryer 0.04
Rotary drum granulator cooler 0.06
Pan granulator precooler 0.3
73
0.3
0.09
0.06
0.04
0.5
0.3
83
2
0.4
0.2
0.15
3
1.5
*References 5, 12, 13, 23 and 24. Particle size determinations were not done in strict
accordance with EPA Method 5. A modification was used to handle the high
concentrations of soluble nitrogenous compounds (See Reference 1). Particle size
distributions were not determined for controlled particulate emissions.
References for Section 6.8
1. Ammonium Nitrate Manufacturing Industry: Technical Document, EPA-450/3-81-002,
U.S. Environmental Protection Agency, Research Triangle Park, NC, January 1981.
2. W.J. Search and R.B. Reznik, Source Assessment: Ammonium Nitrate Production,
EPA-600/2-77-107i, U.S. Environmental Protection Agency, Research Triangle Park,
NC, September 1977.
3. North American Fertilizer Capacity Data, Tennessee Valley Authority, Muscle Shoals,
AL, December, 1991.
4. Memo from C.D. Anderson, Radian Corporation, Durham, NC, to Ammonium Nitrate
file, July 2, 1980.
6.8-8
EMISSION FACTORS
7/9
-------
5. D.P. Becvar, et al., Ammonium Nitrate Emission Test Report: Union Oil Company of
California, EMB-78-NHF-7, U.S. Environmental Protection Agency, Research Triangle
Park, NC, October 1979.
6. K.P. Brockman, Emission Tests for Participates, Cominco American, Beatrice, NE,
1974.
7. Written communication from S.V. Capone, GCA Corporation, Chapel Hill, NC, To
E.A. Noble, U.S. Environmental Protection Agency, Research Triangle Park, NC,
September 6, 1979.
8. Written communication from D.E. Cayard, Monsanto Agricultural Products Company,
St. Louis, MO, to E.A. Noble, U.S. Environmental Protection Agency, Research
Triangle Park, NC, December 4, 1978.
9. Written communication from D.E. Cayard, Monsanto Agricultural Products Company,
St. Louis, MO, to E.A. Noble, U.S. Environmental Protection Agency, Research
Triangle Park, NC, December 27, 1978.
10. Written communication from T.H. Davenport, Hercules Incorporated, Donora, PA, to
D.R. Goodwin, U.S. Environmental Protection Agency, Research Triangle Park, NC,
November 16, 1978.
11. R.N. Doster and D.J. Grove, Source Sampling Report: Atlas Powder Company,
Entropy Environmentalists, Inc., Research Triangle Park, NC, August 1976.
12. M.D. Hansen, et al., Ammonium Nitrate Emission Test Report: Swift Chemical
Company, EMB-79-NHF-11, U.S. Environmental Protection Agency, Research
Triangle Park, NC, July 1980.
13. R.A. Kniskern, et al., Ammonium Nitrate Emission Test Report: Cominco American,
Inc., Beatrice, NE, EMB-79-NHF-9, U.S. Environmental Protection Agency, Research
Triangle Park, NC, April 1979.
14. Written communication from J.A. Lawrence, C.F. Industries, Long Grove, IL, to D.R.
Goodwin, U.S. Environmental Protection Agency, Research Triangle Park, NC,
December 15, 1978.
15. Written communication from F.D. McLauley, Hercules Incorporated, Louisiana, MO,
to D.R. Goodwin, U.S. Environmental Protection Agency, Research Triangle Park,
NC, October 31, 1978.
16. W.E. Misa, Report of Source Test: Collier Carbon and Chemical Corporation (Union
Oil), Test No. 5Z-78-3, Anaheim, CA, January 12, 1978.
17. Written communication from L. Musgrove, Georgia Department of Natural Resources,
7/93 Chemical Process Industry 6.8-9
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Atlanta, GA, to R. Rader, Radian Corporation, Durham, NC, May 21, 1980.
18. Written communication from D.J. Patterson, Nitrogen Corporation, Cincinnati, OH, to
E.A. Noble, U.S. Environmental Protection Agency, Research Triangle Park, NC,
March 26, 1979.
19. Written communication from H. Schuyten, Chevron Chemical Company, San
Francisco, CA, to D.R. Goodwin, U.S. Environmental Protection Agency, March 2,
1979.
20. Emission Test Report: Phillips Chemical Company, Texas Air Control Board, Austin,
TX, 1975.
21. Surveillance Report: Hawkeye Chemical Company, U.S. Environmental Protection
Agency, Research Triangle Park, NC, December 29, 1976.
22. W.A. Wade and R.W. Cass, Ammonium Nitrate Emission Test Report: C.F. Industries,
EMB-79-NHF-10, U.S. Environmental Protection Agency, Research Triangle Park,
NC, November 1979.
23. W.A. Wade, et al., Ammonium Nitrate Emission Test Report: Columbia Nitrogen
Corporation, EMB-80-NHF-16, U.S. Environmental Protection Agency, Research
Triangle Park, NC, January, 1981.
24. York Research Corporation, Ammonium Nitrate Emission Test Report: Nitrogen
Corporation, EMB-78-NHF-5, U.S. Environmental Protection Agency, Research
Triangle Park, NC, May 1979.
6.8-10 EMISSION FACTORS 7/9
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6.10 PHOSPHATE FERTILIZERS
Phosphate fertilizers are classified into three groups of chemical compounds. Two of these
groups are known as superphosphates and are defined by the percentage of phosphorous as P2O5.
Normal superphoshate contains between 15 and 21 percent phosphorous as P2O5 wheras triple
superphosphate contains over 40 percent phosphorous. The remaining group is Ammonium
Phosphate (NH4H2PO4).
7/93 Chemical Process Industry 6.10-1
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6.10.1 NORMAL SUPERPHOSPHATES
6.10.1.1 General1'3
Normal superphosphate refers to fertilizer material containing 15 to 21 percent phosphorous as
phosphorous pentoxide (P2O5). As defined by the Census Bureau, normal superphosphate contains not
more than 22 percent of available P2Os- There are currently about eight fertilizer facilities producing
normal superphosphates in the U.S. with an estimated total production of about 273,000 megagrams
(300,000 tons) per year.
6.10.1.2 Process Description1
Normal superphosphates are prepared by reacting ground phosphate rock with 65 to 75 percent
sulfuric acid. An important factor in the production of normal superphosphates is the amount of iron
and aluminum in the phosphate rock. Aluminum (as A12O3) and iron (as Fe2O3) above five percent
imparts an extreme stickiness to the superphosphate and makes it difficult to handle.
The two general types of sulfuric acid used in superphosphate manufacture are virgin and spent
acid. Virgin acid is produced from elemental sulfur, pyrites, and industrial gases and is relatively
pure. Spent acid is a recycled waste product from various industries that use large quantities of
sulfuric acid. Problems encountered with using spent acid include unusual color, unfamiliar odor, and
toxicity.
A generalized flow diagram of normal superphosphate production is shown in Figure 6.10.1-1.
Ground phosphate rock and acid are mixed in a reaction vessel, held in an enclosed area for about 30
minutes until the reaction is partially completed, and then transferred, using an enclosed conveyer
known as the den, to a storage pile for curing (the completion of the reaction). Following curing, the
product is most often used as a high-phosphate additive in the production of granular fertilizers. It can
also be granulated for sale as granulated superphosphate or granular mixed fertilizer. To produce
granulated normal superphosphate, cured superphosphate is fed through a clod breaker and sent to a
rotary drum granulator where steam, water, and acid may be added to aid in granulation. Material is
processed through a rotary drum granulator, a rotary dryer, a rotary cooler, and is then screened to
specification. Finally, it is stored in bagged or bulk form prior to being sold.
6.10.1.3 Emissions and Controls1'6
Sources of emissions at a normal superphosphate plant include rock unloading and feeding,
mixing operations (in the reactor), storage (in the curing building), and fertilizer handling operations.
Rock unloading, handling and feeding generate particulate emissions of phosphate rock dust. The
mixer, den and curing building emit gases in the form of silicon tetrafluoride (SiF4), hydrogen
fluoride (HF) and particulates composed of fluoride and phosphate material. Fertilizer handling
operations release fertilizer dust. Emission factors for the production of normal superphosphate are
presented in Table 6.10.1-1.
At a typical normal superphosphate plant, emissions from the rock unloading, handling and
feeding operations are controlled by a baghouse. Baghouse cloth filters have reported efficiencies of
-------
Figure 6.10.1-1 Normal superphosphate process flow diagram1
6.10.1-2
EMISSION FACTORS
7/93
-------
over 99 percent under ideal conditions. Collected dust is recycled. Emissions from the mixer and den
are controlled by a wet scrubber. The curing building and fertilizer handling operations normally are
not controlled.
Silicon tetrafluoride (SiF^ and hydrogen fluoride (HF) emissions, and paniculate from the
mixer, den and curing building are controlled by scrubbing the offgases with recycled water. Gaseous
silicon tetrafluoride in the presence of moisture reacts to form gelatinous silica, which has a tendency
to plug scrubber packings. The use of conventional packed-countercurrent scrubbers and other
contacting devices with small gas passages for emissions control is therefore limited. Scrubbers that
can be used are cyclones, venturi, impingement, jet ejector and spray-crossflow packed scrubbers.
Spray towers are also used as precontactors for fluorine removal at relatively high concentration
levels of greater than 4.67 g/m3 (3000 ppm).
Air pollution control techniques vary with particular plant designs. The effectiveness of
abatement systems in removing fluoride and paniculate also varies from plant to plant, depending on
a number of factors. The effectiveness of fluorine abatement is determined by the inlet fluorine
concentration, outlet or saturated gas temperature, composition and temperature of the scrubbing
liquid, scrubber type and transfer units, and the effectiveness of entrainment separation. Control
efficiency is enhanced by increasing the number of scrubbing stages in series and by using a fresh
water scrub in the final stage. Reported efficiencies for fluoride control range from less than 90
percent to over 99 percent, depending on inlet fluoride concentrations and the system employed. An
efficiency of 98 percent for paniculate control is achievable.
The emission factors have not been adjusted by this revision, but they have been downgraded to
an "E" quality rating based on the absence of supporting source tests. The PM-10 emission factors
have been added to the table, but were taken from the AIRS Listing for Criteria Air Pollutants, which
is also rated "E." No additional or recent data were found concerning fluoride emissions from
gypsum ponds. A number of hazardous air pollutants (HAPs) have been identified by SPECIATE as
being present in the phosphate manufacturing process. Some HAPs identified include hexane, methyl
alcohol, formaldehyde, MEK, benzene, toluene, and styrene. Heavy metals such as lead and mercury
are present in the phosphate rock. The phosphate rock is mildly radioactive due to the presence of
some radionuclides. No emission factors are included for these HAPs, heavy metals, or radionuclides
due to the lack of sufficient data.
7/93 Chemical Process Industry 6.10.1-3
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Table 6.10.1-1. (Metric and English Units)
EMISSION FACTORS FOR THE PRODUCTION OF NORMAL SUPERPHOSPHATE
Emission point
Rock unloading1*
Rock feeding1*
Mixer and denc
Emission Factor
kg
of
Pollutant Pro
/Mg Ib/ton
P2O5 of P2O5
duced Produced
Paniculate 0.28 0.56
PM-10 0.15 0.29
Paniculate 0.06 0.11
PM-10 0.03 0.06
Paniculate 0.26 0.52
Fluoride 0.10 0.2
PM-10 0.22 0.44
Curing building*1
Paniculate 3.60 7.20
Fluoride 1.90 3.80
PM-10 3.0 6.1
Emission
Factor
Rating
Ea
Ee
Ea
Ee
Ea
E»
Ee
E*
Ea
Ee
Reference 1, pp. 74-77, 169.
bFactors are for emissions from baghouse with an estimated collection efficiency of 99%.
°Factors are for emissions from wet scrubbers with a reported 97% control efficiency.
dUncontrolled.
from AIRS Listing for Criteria Air Pollutants.
References for Section 6.10.1
1. J.M. Nyers, et al., Source Assessment: Phosphate Fertilizer Industry, EPA-600/2-79-019c, U.
S. Environmental Protection Agency, Research Triangle Park, NC, May 1979.
2. H.C. Mann, Normal Superphosphate, National Fertilizer & Environmental Research Center,
Tennessee Valley Authority, Muscle Shoals, Alabama, February 1992.
3. North American Fertilizer Capacity Data (including supplement). Tennessee Valley Authority,
Muscle Shoals, Alabama, December 1991.
4. Background Information for Standards of Performance: Phosphate Fertilizer Industry: Volume
1: Proposed Standards. EPA-450/2-74-019a, U. S. Environmental Protection Agency, Research
Triangle Park, NC, October 1974.
5. Background Information for Standards of Performance: Phosphate Fertilizer Industry: Volume
2: Test Data Summary. EPA-450/2-74-019b, U. S. Environmental Protection Agency, Research
Triangle Park, NC, October 1974.
6. Final Guideline Document: Control of Fluoride Emissions from Existing Phosphate Fertilizer
Plants. EPA-450/2-77-005, U. S. Environmental Protection Agency, Research Triangle Park,
NC, March 1977.
6.10.1-4
EMISSION FACTORS
7/93
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6.10.2 TRIPLE SUPERPHOSPHATES
6.10.2.1 General2'3
Triple superphosphate, also known as double, treble, or concentrated superphosphate, is a
fertilizer material with a phosphorus content of over 40 percent, measured as phosphorus pentoxide
(P2O5). Triple superphosphate is produced in only six fertilizer facilities in the U. S. In 1989, there
were an estimated 3.2 million megagrams (3.5 million tons) of triple superphosphate produced.
Production rates from the various facilities range from 23 to 92 megagrams (25 to 100 tons) per hour.
6.10.2.2 Process Description1'2
Two processes have been used to produce triple superphosphate: run-of-the-pile (ROP-TSP) and
granular (GTSP). At this time, no facilities in the U. S. are currently producing ROP-TSP, but a
process description is given.
The ROP-TSP material is essentially a pulverized mass of variable particle size produced in a
manner similar to normal superphosphate. Wet-process phosphoric acid (50 to 55 percent P2O5) is
reacted with ground phosphate rock in a cone mixer. The resultant slurry begins to solidify on a slow
moving conveyer en route to the curing area. At the point of discharge from the den, the material
passes through a rotary mechanical cutter that breaks up the solid mass. Coarse ROP-TSP product is
sent to a storage pile and cured for three to five weeks. The product is then mined from the storage
pile to be crushed, screened, and shipped in bulk.
Granular triple superphosphate yields larger, more uniform particles with improved storage and
handling properties. Most of this material is made with the Dorr-Oliver slurry granulation process,
illustrated in Figure 6.10.2-1. In this process, ground phosphate rock or limestone is reacted with
phosphoric acid in one or two reactors in series. The phosphoric acid used in this process is
appreciably lower in concentration (40 percent P2O5) than that used to manufacture ROP-TSP
product. The lower strength acid maintains the slurry in a fluid state during a mixing period of one to
two hours. A small sidestream of slurry is continuously removed and distributed onto dried, recycled
fines, where it coats the granule surfaces and builds up its size.
Pugmills and rotating drum granulators have been used in the granulation process. Only one
pugmill is currently operating in the U. S. A pugmill is composed of a u-shaped trough carrying twin
counter-rotating shafts, upon which are mounted strong blades or paddles. The blades agitate, shear
and knead the liquified mix and transport the material along the trough. The basic rotary drum
granulator consists of an open-ended, slightly inclined rotary cylinder, with retaining rings at each end
and a scraper or cutter mounted inside the drum shell. A rolling bed of dry material is maintained in
the unit while the slurry is introduced through distributor pipes set lengthwise in the drum under the
bed. Slurry-wetted granules are then discharged onto a rotary dryer, where excess water is evaporated
and the chemical reaction is accelerated to completion by the dryer heat. Dried granules are then sized
on vibrating screens. Oversize particles are crushed and recirculated to the screen, and undersize
particles are recycled to the granulator. Product-size granules are cooled in a countercurrent rotary
drum, then sent to a storage pile for curing. After a curing period of three to five days, granules are
removed from storage, screened, bagged and shipped.
7/93 Chemical Process Industry 6.10.2-1
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^
WEIGHER
FEEDER
Figure 6.10.2-1. Dorr-Oliver process for granular triple superphosphate production1
6.10.2-2 EMISSION FACTORS 7/93
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6.10.2.3 Emissions and Controls1"6
Controlled emission factors for the production of GTSP are given in Table 6.10.2-1. Emission
factors for ROP-TSP are not given since it is not being produced currently in the U. S.
Sources of paniculate emissions include the reactor, granulator, dryer, screens, cooler, mills,
and transfer conveyors. Additional emissions of paniculate result from the unloading, grinding,
storage, and transfer of ground phosphate rock. One facility uses limestone, which is received in
granulated form and does not require additional milling.
TABLE 6.10.2-1 (METRIC UNITS)
CONTROLLED EMISSION FACTORS FOR THE PRODUCTION
OF TRIPLE SUPERPHOSPHATES
Process
Pollutant
Granular triple superphosphate
Rock unloading1* Paniculate
PM-10
Rock feeding13 Paniculate
PM-10
Reactor,
screens0
granulator, dryer, cooler and Paniculate
Fluoride
PM-10
Curing building0 Paniculate
Fluoride
PM-10
Controlled emission factor
kg/Mg Ib/ton Emission
of of Factor
Product Product Rating
0.09 0.18 Ea
0.04 0.08 Ed
0.02 0.04 Ea
0.01 0.02 Ed
0.05 0.10 Ea
0.12 0.24 Ea
0.04 0.08 Ed
0.10 0.20 Ea
0.02 0.04 Ea
0.08 0.17 Ed
Reference 1, pp. 77-80, 168, 170-171.
bFactors are for emissions from baghouses with an estimated collection efficiency of 99 percent.
cFactors are for emissions from wet scrubbers with an estimated 97 percent control efficiency.
dBased on AIRS Listing For Criteria Air Pollutants.
Emissions of fluorine compounds and dust particles occur during the production of GTSP triple
superphosphate. Silicon tetrafluoride (SiF4) and hydrogen fluoride (HF) are released by the
acidulation reaction and they evolve from the reactors, den, granulator, and dryer. Evolution of
fluoride is essentially finished in the dryer and there is little fluoride
evolved from the storage pile in the curing building.
At a typical plant, baghouses are used to control the fine rock particles generated by the rock
grinding and handling activities. Emissions from the reactor, den and granulator are controlled by
7/93
Chemical Process Industry
6.10.2-3
-------
scrubbing the effluent gas with recycled gypsum pond water in cyclonic scrubbers. Emissions from
the dryer, cooler, screens, mills, product transfer systems, and storage building are sent to a cyclone
separator for removal of a portion of the dust before going to wet scrubbers to remove fluorides.
Particulate emissions from ground rock unloading, storage and transfer systems are controlled
by baghouse collectors. These baghouse cloth filters have reported efficiencies of over 99 percent.
Collected solids are recycled to the process. Emissions of silicon tetrafluoride, hydrogen fluoride, and
paniculate from the production area and curing building are controlled by scrubbing the offgases with
recycled water. Exhausts from the dryer, cooler, screens, mills, and curing building are sent first to a
cyclone separator and then to a wet scrubber. Tailgas wet scrubbers perform final cleanup of the plant
offgases.
Gaseous silicon tetrafluoride in the presence of moisture reacts to form gelatinous silica, which
has the tendency to plug scrubber packings. Therefore, the use of conventional packed countercurrent
scrubbers and other contacting devices with small gas passages for emissions control is not feasible.
Scrubber types that can be used are 1) spray tower, 2) cyclone, 3) venturi, 4) impingement, 5) jet
ejector, and 6) spray-crossflow packed.
The effectiveness of abatement systems for the removal of fluoride and paniculate varies from
plant to plant, depending on a number of factors. The effectiveness of fluorine abatement is
determined by: 1) inlet fluorine concentration, 2) outlet or saturated gas temperature, 3) composition
and temperature of the scrubbing liquid, 4) scrubber type and transfer units, and 5) effectiveness of
entrainment separation. Control efficiency is enhanced by increasing the number of scrubbing stages
in series and by using a fresh water scrub in the final stage. Reported efficiencies for fluoride control
range from less than 90 percent to over 99 percent, depending on inlet fluoride concentrations and the
system employed. An efficiency of 98 percent for paniculate control is achievable.
The paniculate and fluoride emission factors are identical to the previous revisions, but have
been downgraded to "E" quality because no documented, up-to-date source tests were available and
previous emission factors could not be validated from the references which were given. The PM-10
emission factors have been added to the table, but were derived from the AIRS Database, which also
has an "E" rating. No additional or recent data were found concerning fluoride emissions from
gypsum ponds. A number of hazardous air pollutants (HAPs) have been identified by SPECIATE as
being present in the phosphate fertilizer manufacturing process. Some HAPs identified include
hexane, methyl alcohol, formaldehyde, MEK, benzene, toluene, and styrene. Heavy metals such as
lead and mercury are present in the phosphate rock. The phosphate rock is mildly radioactive due to
the presence of some radionuclides. No emission factors are included for these HAPs, heavy metals,
or radionuclides due to the lack of sufficient data.
6.10.2-4 EMISSION FACTORS 7/93
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References for Section 6.10.2
1. J. M. Nyers, et al., Source Assessment: Phosphate Fertilizer Industry, EPA-600/2-79-019c,
U. S. Environmental Protection Agency, Research Triangle Park, NC, May 1979.
2. H.C. Mann, Triple Superphosphate, National Fertilizer & Environmental Research Center,
Tennessee Valley Authority, Muscle Shoals, Alabama, February 1992.
3. North American Fertilizer Capacity Data (including supplement). Tennesee Valley Authority,
Muscle Shoals, Alabama, December 1991.
4. Background Information for Standards of Performance: Phosphate Fertilizer Industry:
Volume 1: Proposed Standards. EPA-450/2-74-019a, U. S. Environmental Protection Agency,
Research Triangle Park, NC, October 1974.
5. Background Information for Standards of Performance: Phosphate Fertilizer Industry:
Volume 2: Test Data Summary. EPA-450/2-74-019b, U. S. Environmental Protection Agency,
Research Triangle Park, NC, October 1974.
6. Final Guideline Document: Control of Fluoride Emissions from Existing Phosphate Fertilizer
Plants. EPA-450/2-77-005, U. S. Environmental Protection Agency, Research Triangle Park,
NC, March 1977.
7/93 Chemical Process Industry 6.10.2-5
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6.10.3 AMMONIUM PHOSPHATE
6.10.3.1 General1
Ammonium phosphate (NH4H2PO4) is produced by reacting phosphoric acid (H-jPO^ with
anhydrous ammonia (NH3). Ammoniated superphosphates are produced by adding normal
superphosphate or triple superphosphate to the mixture. The production of liquid ammonium
phosphate and ammoniated superphosphates in fertilizer mixing plants is considered a separate
process. Both solid and liquid ammonium phosphate fertilizers are produced in the U.S. This
discussion covers only the granulation of phosphoric acid with anhydrous ammonia to produce
granular fertilizer. Total ammonium phosphate production in the U.S. in 1992 was estimatd to be 7.7
million megagrams (8.5 million tons).2
6.10.3.2 Process Description1
Two basic mixer designs are used by ammoniation-granulation plants: the pugmill ammoniator
and the rotary drum ammoniator. Approximately 95 percent of ammoniation-granulation plants in the
United States use a rotary drum mixer developed and patented by the Tennessee Valley Authority
(TVA). The basic rotary drum ammoniator-granulator consists of a slightly inclined open-end rotary
cylinder with retaining rings at each end, and a scrapper or cutter mounted inside the drum shell. A
rolling bed of recycled solids is maintained in the unit.
Ammonia-rich offgases pass through a wet scrubber before exhausting to the atmosphere.
Primary scrubbers use raw materials mixed with acids (such as scrubbing liquor), and secondary
scrubbers use gypsum pond water.
In the TVA process, phosphoric acid is mixed in an acid surge tank with 93 percent sulfuric
acid (H2SO4), which is used for product analysis control, and with recycled acid from wet scrubbers.
(A schematic diagram of the ammonium phosphate process flow diagram is shown in Figure
6.10.3-1.) Mixed acids are then partially neutralized with liquid or gaseous anhydrous ammonia in a
brick-lined acid reactor. All of the phosphoric acid and approximately 70 percent of the ammonia are
introduced into this vessel. A slurry of ammonium phosphate and 22 percent water are produced and
sent through steam-traced lines to the ammoniator-granulator. Slurry from the reactor is distributed on
the bed, the remaining ammonia (approximately 30 percent) is sparged underneath. Granulation, by
agglomeration and by coating particulate with slurry, takes place in the rotating drum and is
completed in the dryer. Ammonia-rich offgases pass through a wet scrubber before exhausting to the
atmosphere. Primary scrubbers use raw materials mixed with acid (such as scrubbing liquor), and
secondary scrubbers use pond water.
Moist ammonium phosphate granules are transferred to a rotary concurrent dryer and then to
a cooler. Before being exhausted to the atmosphere, these offgases pass through cyclones and wet
scrubbers. Cooled granules pass to a double-deck screen, in which oversize and undersize particles
are separated from product particles. The product ranges in granule size from 1 to 4 millimeters
(mm). The oversized granules are crushed, mixed with the undersized, and recycled back to the
ammoniator-granulator.
-------
Figure 6.10.3-1. Ammonium phosphate process flow diagram
6.10.3-2
EMISSION FACTORS
7/93
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6.10.3.3 Emissions and Controls1
Sources of air emissions from the production of ammonium phosphate fertilizers include the
reactor, the ammoniator-granulator, the dryer and cooler, product sizing and material transfer, and
the gypsum pond. The reactor and ammoniator-granulator produce emissions of gaseous ammonia,
gaseous fluorides such as hydrogen fluoride (HF) and silicon tetrafluoride (SiF^, and paniculate
ammonium phosphates. These two exhaust streams are generally combined and passed through
primary and secondary scrubbers.
Exhaust gases from the dryer and cooler also contain ammonia, fluorides and particulates and
these streams are commonly combined and passed through cyclones and primary and secondary
scrubbers. Paniculate emissions and low levels of ammonia and fluorides from product sizing and
material transfer operations are controlled the same way.
Emissions factors for ammonium phosphate production are summarized in Table 6.10.3-1.
These emission factors are averaged based on recent source test data from controlled phosphate
fertilizer plants in Tampa, Florida.
Table 6.10.3-1. (Metric Units)
AVERAGE CONTROLLED EMISSION FACTORS FOR
THE PRODUCTION OF AMMONIUM PHOSPHATES*
Emission Point
Fluoride as F
kg/Mg
of
Product
Reactor/ammoniator-
granulator 0.02
Dryer/cooler 0.02
Product sizing and
material transfer*1 0.001
Total plant emissions 0.02C
Factor
Rating
Particulate
kg/Mg
of
Product
E 0.76
E 0.75
E 0.03
A 0.34d
Factor
Rating
Ammonia
kg/Mg
of
Product
Factor
Rating
S02
kg/Mg Factor
of Rating
Product
E
E
E
A 0.07 E 0.04e E
a Reference 1, pp. 80-83, 173
b Represents only one sample.
c References 7, 8, 10, 11, 13-15. EPA has promulgated a fluoride emission guideline of 0.03 kg/Mg
P2O5 input.
d References 7, 9, 10, 13-15.
eBased on limited data from only one plant, Reference 9.
7/93
Food and Agricultural Industry
6.10.3-3
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Table 6.10.3-1. (English Units)
AVERAGE CONTROLLED EMISSION FACTORS FOR
THE PRODUCTION OF AMMONIUM PHOSPHATES*
Emission Point
Fluoride as F
Ib/ton of
Product
Reactor/ammoniator-
granulator 0.05
Dryer/cooler 0.04
Product sizing and
material transferb 0.002
Total plant emissions 0.04C
Factor
Rating
Particulate
Ib/ton
of
Product
E 1.52
E 1.50
E 0.06
A 0.68d
Factor
Rating
Ammonia
Ib/ton
of
Product
Factor
Rating
SO2
Ib/ton
of Factor
Product Rating
E
E
E
A 0.14 E 0.08° E
"Reference 1, pp. 80-83, 173
b Represents only one sample.
c References 7, 8, 10, 11, 13-15. EPA has promulgated a fluoride emission guideline of 0.03 kg/Mg
P2O5 input.
d References 7, 9, 10, 13-15.
eBased on limited data from only one plant, Reference 9.
Exhaust streams from the reactor and ammoniator-granulator pass through a primary scrubber,
in which phosphoric acid is used to recover ammonia and paniculate. Exhaust gases from the dryer,
cooler and screen first go to cyclones for paniculate recovery, and then to primary scrubbers.
Materials collected in the cyclone and primary scrubbers are returned to the process. The exhaust is
sent to secondary scrubbers, where recycled gypsum pond water is used as a scrubbing liquid to
control fluoride emissions. The scrubber effluent is returned to the gypsum pond.
Primary scrubbing equipment commonly includes venturi and cyclonic spray towers.
Impingement scrubbers and spray-crossflow packed bed scrubbers are used as secondary controls.
Primary scrubbers generally use phosphoric acid of 20 to 30 percent as scrubbing liquor, principally
to recover ammonia. Secondary scrubbers generally use gypsum and pond water for fluoride control.
Throughout the industry, however, there are many combinations and variations. Some plants
use reactor-feed concentration phosphoric acid (40 percent P2Os) in both primary and secondary
scrubbers, and some use phosphoric acid near the dilute end of the 20 to 30 percent P2O5 range in
only a single scrubber. Existing plants are equipped with ammonia recovery scrubbers on the reactor,
ammoniator-granulator and dryer, and paniculate controls on the dryer and cooler. Additional
scrubbers for fluoride removal exist, but they are not typical. Only 15 to 20 percent of installations
contacted in an EPA survey were equipped with spray-crossflow packed bed scrubbers or their
equivalent for fluoride removal.
6.10.3-4
EMISSION FACTORS
7/93
-------
Emission control efficiencies for ammonium phosphate plant control equipment are reported as
94 to 99 percent for ammonium, 75 to 99.8 percent for particulates, and 74 to 94 percent for
fluorides.
References for Section 6.10.3
1. J.M. Nyers, et al., Source Assessment: Phosphate Fertilizer Industry, EPA-600/2-79-019c, U.S.
Environmental Protection Agency, Research Triangle Park, NC, May 1979.
2. North American Fertilizer Capacity Data, Tennessee Valley Authority, Muscle Shoals, AL,
December 1991.
3. Compliance Source Test Report: Texasgulf Inc., Granular Triple Super Phosphate Plant,
Aurora, NC, May 1987.
4. Compliance Source Test Report: Texasgulf Inc., Diammonium Phosphate Plant No.2, Aurora,
NC, August 1989.
5. Compliance Source Test Report: Texasgulf Inc., Diammonium Phosphate Plant #2, Aurora,
NC, December 1991.
6. Compliance Test Report: Texasgulf, Inc., Diammonium Phosphate #7, Aurora, NC, September
1990.
7. Compliance Source Test Report: Texasgulf Inc., Ammonium Phosphate Plant #2, Aurora, NC,
November 1990.
8. Compliance Source Test Report: Texasgulf Inc., Diammonium Phosphate Plant #2, Aurora,
NC, November 1991.
9. Compliance Source Test Report: IMC Fertilizer, Inc., #1 DAP plant, Western Polk County, FL,
October 1991.
10. Compliance Source Test Report: IMC Fertilizer, Inc., #2 DAP Plant, Western Polk County, FL,
June 1991.
11. Compliance Source Test Report: IMC Fertilizer, Inc., Western Polk County, FL, April 1991.
7/93 Food and Agricultural Industry 6.10.3-5
-------
6.14 UREA
6.14.1 General1'14
Urea [ CO(NH2)2 ], also known as carbamide or carbonyl diamide, is marketed as a solution or
in solid form. Most urea solution produced is used in fertilizer mixtures, with a small amount going to
animal feed supplements. Most solids are produced as prills or granules, for use as fertilizer or protein
supplement in animal feed, and in plastics manufacturing. Five U.S. plants produce solid urea in
crystalline form. About 7.3 million megagrams (8 million tons) of urea were produced in the U.S. in
1991. About 85 percent was used in fertilizers (both solid and solution forms), 3 percent in animal feed
supplements and the remaining 12 percent in plastics and other uses.
6.14.2 Process Description1'2
The process for manufacturing urea involves a combination of up to seven major unit operations.
These operations, illustrated by the flow diagram in Figure 6.14-1, are solution synthesis, solution
concentration, solids formation, solids cooling, solids screening, solids coating and bagging and/or bulk
shipping.
The combination of processing steps is determined by the desired end products. For example, plants
producing urea solution use only the solution formulation and bulk shipping operations. Facilities
producing solid urea employ these two operations and various combinations of the remaining five
operations, depending upon the specific end product being produced.
In the solution synthesis operation, ammonia (NH3) and carbon dioxide (CO2) are reacted to form
ammonium carbamate (NH2CO2NH4). Typical operating conditions include temperatures from 180 to
20°C (356 to 392°F), pressures from 140 to 250 atm, NH3:CO2 molar ratios from 3:1 to 4:1, and a
retention time of 20 to 30 minutes. The carbamate is then dehydrated to yield 70 to 77 percent aqueous
urea solution. These reactions are as follows:
2NH3 + CO2 -» NH2CO2NH4 (1)
NH2CO2NH4 -» NH2CONH2 + H2O (2)
The urea solution can be used as an ingredient of nitrogen solution fertilizers, or it can be concentrated
further to produce solid urea.
The three methods of concentrating the urea solution are vacuum concentration, crystallization and
atmospheric evaporation. The method chosen depends upon the level of biuret (NH2CONHCONH2)
impurity allowable in the end product. Aqueous urea solution begins to decompose at 60°C (140°F) to
biuret and ammonia. The most common method of solution concentration is evaporation.
The concentration process furnishes urea "melt" for solids formation. Urea solids are produced
from the urea melt by two basic methods: prilling and granulation. Prilling is a process by which solid
particles are produced from molten urea. Molten urea is sprayed from the top of a prill tower. As the
droplets fall through a countercurrent air flow, they cool and solidify into nearly spherical particles.
There are two types of prill towers, fluidized bed and nonfluidized bed. The major difference is that a
separate solids cooling operation may be required to produce agricultural grade prills in a nonfluidized
bed prill tower.
7/93 Chemical Process Industry 6.14-1
-------
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6.14-2
Figure 6.14-1 Major urea manufacturing operations
EMISSION FACTORS
7/93
-------
Granulation is used more frequently than prilling in producing solid urea for fertilizer. Granular
urea is generally stronger than prilled urea, both in crushing strength and abrasion resistance. There are
two granulation methods, drum granulation and pan granulation. In drum granulation, solids are built up
in layers on seed granules placed in a rotating drum granulator/cooler approximately 4.3 meters (14 feet)
in diameter. Pan granulators also form the product in a layering process, but different equipment is used
and pan granulators are not commonly used in the U.S.
The solids cooling operation is generally accomplished during solids formation, but for pan
granulation processes and for some agricultural grade prills, some supplementary cooling is provided by
auxiliary rotary drums.
The solids screening operation removes offsize product from solid urea. The offsize material may
be returned to the process in the solid phase or be redissolved in water and returned to the solution
concentration process.
Clay coatings are used in the urea industry to reduce product caking and urea dust formation. The
coating also reduces the nitrogen content of the product. The use of clay coating has diminished
considerably, being replaced by injection of formaldehyde additives into the liquid or molten urea before
solids formation. Formaldehyde reacts with urea to from methylenediurea, which is the conditioning
agent. Additives reduce solids caking during storage and urea dust formation during transport and
handling.
The majority of solid urea product is bulk shipped in trucks, enclosed railroad cars or barges, but
approximately ten percent is bagged.
6.14.3 Emissions and Controls1'3"7
Emissions from urea manufacture are mainly ammonia and paniculate matter. Formaldehyde and
methanol, hazardous air pollutants (HAPs) may be emitted if additives are used. Formalin™, used as a
formaldehyde additive, may contain up to 15 percent methanol. Ammonia is emitted during the solution
synthesis and solids production processes. Paniculate matter is emitted during all urea processes. There
have been no reliable measurements of free gaseous formaldehyde emissions. The chromotropic acid
procedure that has been used to measure formaldehyde is not capable of distinguishing between gaseous
formaldehyde and methylenediurea, the principle compound formed when the formaldehyde additive
reacts with hot urea.
Table 6.14-1 summarizes the uncontrolled and controlled emission factors, by processes, for urea
manufacture. Table 6.14-2 summarizes particle sizes for these emissions.
In the synthesis process, some emission control is inherent in the recycle process where carbamate
gases and/or liquids are recovered and recycled. Typical emission sources from the solution synthesis
process are noncondensable vent streams from ammonium carbamate decomposers and separators.
Emissions from synthesis processes are generally combined with emissions from the solution
concentration process and are vented through a common stack. Combined paniculate emissions from urea
synthesis and concentration operations are small compared to paniculate emissions from a typical solids-
producing urea plant. The synthesis and concentration operations are usually uncontrolled except for
recycle provisions to recover ammonia. For these reasons, no factor for controlled emissions from
synthesis and concentration processes is given in this section.
Uncontrolled emission rates from prill towers may be affected by the following factors: 1) product
grade being produced, 2) air flow rate through the tower, 3) type of tower bed, and 4) ambient
temperature and humidity.
7/93 Chemical Process Industry 6.14-3
-------
The total of mass emissions per unit is usually lower for feed grade prill production than for
agricultural grade prills, due to lower airflows. Uncontrolled particulate emission rates for fluidized bed
prill towers are higher than those for nonfluidized bed prill towers making agricultural grade prills, and
are approximately equal to those for nonfluidi/ed bed feed grade prills. Ambient air conditions can affect
prill tower emissions. Available data indicate that colder temperatures promote the formation of smaller
particles in the prill tower exhaust. Since smaller particles are more difficult to remove, the efficiency
of prill tower control devices tends to decrease with ambient temperatures. This can lead to higher
emission levels for prill towers operated during cold weather. Ambient humidity can also affect prill
tower emissions. Air flow rates must be increased with high humidity, and higher air flow rates usually
cause higher emissions.
The design parameters of drum granulators and rotary drum coolers may affect emissions. Drum
granulators have an advantage over prill towers in that they are capable of producing very large particles
without difficulty. Granulators also require less air for operation man do prill towers. A disadvantage of
granulators is their inability to produce the smaller feed grade granules economically. To produce smaller
granules, the drum must be operated at a higher seed particle recycle rate. It has been reported that,
although the increase in seed material results in a lower bed temperature, the corresponding increase in
fines in the granulator causes a higher emission rate. Cooling air passing through the drum granulator
entrains approximately 10 to 20 percent of the product. This air stream is controlled with a wet scrubber
which is standard process equipment on drum granulators.
In the solids screening process, dust is generated by abrasion of urea particles and the vibration
of the screening mechanisms. Therefore, almost all screening operations used in the urea manufacturing
industry are enclosed or are covered over the uppermost screen. This operation is a small emission
source, therefore particulate emission factors from solids screening are not presented.
Emissions attributable to coating include entrained clay dust from loading, inplant transfer and leaks
from the seals of the coater. No emissions data are available to quantify this fugitive dust source.
Bagging operations are sources of particulate emissions. Dust is emitted from each bagging method
during the final stages of filling, when dust-laden air is displaced from the bag by urea. Bagging
operations are conducted inside warehouses and are usually vented to keep dust out of the workroom area,
as mandated by OSHA regulations. Most vents are controlled with baghouses. Nationwide, approximately
90 percent of urea produced is bulk loaded. Few plants control their bulk loading operations. Generation
of visible fugitive particles is negligible.
Urea manufacturers presently control particulate matter emissions from prill towers, coolers,
granulators and bagging operations. With the exception of bagging operations, urea emission sources are
usually controlled with wet scrubbers. Scrubber systems are preferred over dry collection systems
primarily for the easy recycling of dissolved urea collected in the device. Scrubber liquors are recycled
to the solution concentration process to eliminate waste disposal problems and to recover the urea
collected.
Fabric filters (baghouses) are used to control fugitive dust from bagging operations, where
humidities are low and binding of the bags is not a problem. However, many bagging operations are
uncontrolled.
6.14-4 EMISSION FACTORS 7/93
-------
TABLE 6.14-1 (METRIC UNITS)
EMISSION FACTORS FOR UREA PRODUCTION
All Emission Factors are in
Ratings (A-E) Follow Each Factor
Type of Operation
Solution formation and
concentration*1
Nonfluidized bed prilling
Agricultural grade*
Feed gradeh
Fluidized bed prilling
Agricultural grade*1
Feed grade*1
Drum granulation1
Rotary drum cooler
Bagging
Particulate*
Uncontrolled
kg/Mg
of
Product
0.0105C
1.9
1.8
3.1
1.8
120
3.89k
0.0951
Factor
Rating
A
A
A
A
A
A
A
E
Controlled
kg/Mg
of
Product
0.032f
0.39
0.24
0.115
0.101
Factor
Rating
A
A
A
A
E
Ammonia
Uncontrolled
kg/Mg
of
Product
9.23d
0.43
1.46
2.07
1.07*
0.0256k
kg
Factor
Rating Pn
A
A
A
A 1
A
A
Controlled*
/Mg
of Factor
xluct Rating
.04 A
"Particulate test data were collected using a modification of EPA Reference Method 3. Reference 1, Appendix B
explains these modifications.
References 9 and 11. Emissions from the synthesis process are generally combined with emissions from the
solution concentration process and vented through a common stack. In the synthesis process, some emission
control is inherent hi the recycle process where carbamate gases and/or liquids are recovered and recycled.
'EPA test data indicated a range of 0.005 to 0.016 kg/Mg (0.010 to 0.032 Ib/ton).
'fePA test data indicated a range of 4.01 to 14.45 kg/Mg (8.02 to 28.90 Ib/ton).
'Reference 12. These factors were determined at an ambient temperature of 14 to 21 °C (57° to 69°F). The
controlled emission factors are based on ducting exhaust through a downcomer and then a wetted fiber filter
scrubber achieving a 98.3 percent efficiency. This represents a higher degree of control than is typical in this
industry.
fOnly runs two and three were used (test Series A).
^No ammonia control demonstrated by scrubbers installed for particulate control. Some increase in ammonia
emissions exiting the control device was noted.
Reference 11. Feed grade factors were determined at an ambient temperature of 29°C (85°F) and agricultural
grade factors at an ambient temperature of 27°C (80°F). For fluidized bed prilling, controlled emission factors
are based on use of an entrainment scrubber.
'References 8 and 9. Controlled emission factors are based on use of a wet entrainment scrubber. Wet scrubbers
are standard process equipment on drum granulators. Uncontrolled emissions were measured at the scrubber
inlet.
JEPA test data indicated a range of 0.955 to 1.20 kg/Mg (1.90 to 2.45 Ib/ton).
Reference 10.
Reference 1. Data were provided by industry.
7/93
Chemical Process Industry
6.14-5
-------
Table 6.14-1. (English Units)
EMISSION FACTORS FOR UREA PRODUCTION
Type of Operation
Solution formation and
concentration
Nonfluidized bed prilling
Agricultural grade6
Feed grade*1
Fluidized bed prilling
Agricultural gradeh
Feed gradeh
Drum granulation1
Rotary drum cooler
Bagging
Particulate"
Uncontrolled
Ib/ton
of
Product
0.021°
3.8
3.6
6.2
3.6
241
7.78k
0.191
Factor
Rating
A
A
A
A
A
A
A
E
Controlled
Ib/ton
of
Product
0.063f
0.78
0.48
0.234
0.201
Factor
Rating
A
A
A
A
E
Ammonia
Uncontrolled
Ib/ton
of
Product
18.46d
0.87
2.91
4.14
2.15J
0.05 lk
Ib
Factor
Rating Pr<
A
A
Controlled^
/ton
of Factor
iduct Rating
A
A 2.08 A
A
A
"Particulate test data were collected using a modification of EPA Reference Method 3. Reference 1, Appendix B
explains these modifications.
^References 9 and 11. Emissions from the synthesis process are generally combined with emissions from the
solution concentration process and vented through a common stack. In the synthesis process, some emission
control is inherent in the recycle process where carbamate gases and/or liquids are recovered and recycled.
"EPA test data indicated a range of 0.005 to 0.016 kg/Mg (0.010 to 0.032 Ib/ton).
"fePA test data indicated a range of 4.01 to 14.45 kg/Mg (8.02 to 28.90 Ib/ton).
Reference 12. These factors were determined at an ambient temperature of 14 to 21 °C (57° to 69°F). The
controlled emission factors are based on ducting exhaust through a downcomer and then a wetted fiber filter
scrubber achieving a 98.3 percent efficiency. This represents a higher degree of control than is typical in this
industry.
Only runs two and three were used (test Series A).
SNo ammonia control demonstrated by scrubbers installed for particulate control. Some increase in ammonia
emissions exiting the control device was noted.
Reference 11. Feed grade factors were determined at an ambient temperature of 29°C (85°F) and agricultural
grade factors at an ambient temperature of 27°C (80°F). For fluidized bed prilling, controlled emission factors
are based on use of an entrainment scrubber.
References 8 and 9. Controlled emission factors are based on use of a wet entrainment scrubber. Wet scrubbers
are standard process equipment on drum granulators. Uncontrolled emissions were measured at the scrubber
inlet.
JEPA test data indicated a range of 0.955 to 1.20 kg/Mg (1.90 to 2.45 Ib/ton).
Reference 10.
'Reference 1. Data were provided by industry.
6.14-6
EMISSION FACTORS
7/93
-------
TABLE 6.14-2
UNCONTROLLED PARTICLE SIZE DATA FOR UREA PRODUCTION
Particle size
(cumulative weight %)
Solid
Type of Operation <
Formation
Nonfluidized bed prilling
Agricultural grade
Feed grade
Fluidized bed prilling
Agricultural grade
Feed grade
Drum granulation
Rotary drum cooler
10 /tm < 5 /im
90 84
85 74
60 52
24 18
a a
0.70 0.15
<: 2.5 fim
79
50
43
14
a
0.04
' All particulate matter ^5.7 /tm was collected in the cyclone precollector sampling equipment.
References for Section 6.14
1. Urea Manufacturing Industry: Technical Document, EPA-450/3-81-001, U.S. Environmental
Protection Agency, Research Triangle Park, NC, January 1981.
2. D.F. Bress, M.W. Packbier, "The Startup of Two Major Urea Plants," Chemical Engineering
Progress, May 1977, p. 80.
3. Written communication from Gary McAlister, U.S. Environmental Protection Agency,
Emission Measurement Branch, to Eric Noble, U.S. Environmental Protection Agency,
Emission, Industrial Studies Branch, Research Triangle Park, NC, July 28, 1983.
4. Formaldehyde Use in Urea-Based Fertilizers, Report of the Fertilizer Institute's Formaldehyde
Task Group, The Fertilizer Institute, Washington, DC, February 4, 1983.
5. J.H. Cramer, "Urea Prill Tower Control Meeting 20% Opacity." Presented at the Fertilizer
Institute Environment Symposium, New Orleans, LA, April 1980.
6. Written communication from M.I. Bornstein, GCA Corporation, Bedford, MA, to E.A. Noble,
U.S. Environmental Protection Agency, Research Triangle Park, NC, August 2, 1978.
7. Written communication from M.I. Bornstein and S.V. Capone, GCA Corporation, Bedford,
MA, to E.A. Noble, U.S. Environmental Protection Agency, Research Triangle Park, NC,
June 23, 1978.
8. Urea Manufacture: Agrico Chemical Company Emission Test Report, EMB Report 78-NHF-4,
U.S. Environmental Protection Agency, Research Triangle Park, NC, April 1979.
7/93
Chemical Process Industry
6.14-7
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9. Urea Manufacture: CF Industries Emission Test Report, EMB Report 78-NHF-8, U.S.
Environmental Protection Agency, Research Triangle Park, NC, May 1979.
10. Urea Manufacture: Union Oil of California Emission Test Report, EMB Report 80-NHF-15,
U.S. Environmental Protection Agency, Research Triangle Park, NC, September 1980.
11. Urea Manufacture: W.R. Grace and Company Emission Test Report, EMB Report 80-NHF-3,
U.S. Environmental Protection Agency, Research Triangle Park, NC, December 1979.
12. Urea Manufacture: Reichhold Chemicals Emission Test Report, EMB Report 80-NHF-14, U.S.
Environmental Protection Agency, Research Triangle Park, NC, August 1980.
13. North American Fertilizer Capacity Data, Tennessee Valley Authority, Muscle Shoals, AL,
December 1991.
6.14-8 EMISSION FACTORS 7/93
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6.18 AMMONIUM SULFATE MANUFACTURE
6.18. General1'2
Ammonium sulfate [ (NH4)2SO4 ] is commonly used as a fertilizer. In 1991, U. S. facilities
produced about 2.7 million megagrams (three million tons) of ammonium sulfate in about 35 plants.
Production rates at these plants range from 1.8 to 360 megagrams (2 to 400 tons) per year.
6.18.2 Process Description1
About 90 percent of ammonium sulfate is produced by three different processes: 1) as a
byproduct of caprolactam [ (CK^COHN ] production, 2) from synthetic manufacture, and 3) as a
coke oven byproduct. The remainder is produced as a byproduct of either nickel or methyl
methacrylate manufacture, or from ammonia scrubbing of tail gas at sulfuric acid (H2SO4) plants.
These minor sources are not discussed here.
Ammonium sulfate is produced as a byproduct from the caprolactam oxidation process stream
and the rearrangement reaction stream. Synthetic ammonium sulfate is produced by combining
anhydrous ammonia and sulfuric acid in a reactor. Coke oven byproduct ammonium sulfate is
produced by reacting the ammonia recovered from coke oven off-gas with sulfuric acid. Figure 6.18-1
is a diagram of typical ammonium sulfate manufacturing for each of the three primary commercial
processes.
After formation of the ammonium sulfate solution, manufacturing operations of each process
are similar. Ammonium sulfate crystals are formed by circulating the ammonium sulfate liquor
through a water evaporator, which thickens the solution. Ammonium sulfate crystals are separated
from the liquor in a centrifuge. In the caprolactam byproduct process, the product is first transferred
to a settling tank to reduce the liquid load on the centrifuge. The saturated liquor is returned to the
dilute ammonium sulfate brine of the evaporator. The crystals, which contain about 1 to 2.5 percent
moisture by weight after the centrifuge, are fed to either a fluidized-bed or a rotary drum dryer.
Fluidized-bed dryers are continuously steam heated, while the rotary dryers are fired directly with
either oil or natural gas or may use steam-heated air.
At coke oven byproduct plants, rotary vacuum filters may be used in place of a centrifuge and
dryer. The crystal layer is deposited on the filter and is removed as product. These crystals are
generally not screened, although they contain a wide range of particle sizes. They are then carried by
conveyors to bulk storage.
At synthetic plants, a small quantity (about 0.05 percent) of a heavy organic (i.e., high
molecular weight organic) is added to the product after drying to reduce caking.
Dryer exhaust gases pass through a paniculate collection device, such as a wet scrubber. This
collection controls emissions and reclaims residual product. After being dried, the ammonium sulfate
crystals are screened into coarse and fine crystals. This screening is done in an enclosed area to
restrict fugitive dust in the building.
7/93 Chemical Process Industry 6.18-1
-------
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6.18-2
EMISSION FACTORS
7/93
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6.18.3 Emissions And Controls1
Ammonium sulfate paniculate is the principal emission from ammonium sulfate manufacturing
plants. The gaseous exhaust of the dryers contains nearly all the emitted ammonium sulfate. Other
plant processes, such as evaporation, screening and materials handling, are not significant sources of
emissions.
The paniculate emission rate of a dryer is dependent on gas velocity and particle size
distribution. Gas velocity, and thus emission rates, varies according to the dryer type. Generally, the
gas velocity of fluidized-bed dryers is higher than for most rotary drum dryers. Therefore, the
paniculate emission rates are higher for fluidized-bed dryers. At caprolactam byproduct plants,
relatively small amounts of volatile organic compounds (VOC) are emitted from the dryers.
Some plants use baghouses for emission control, but wet scrubbers, such as venturi and
centrifugal scrubbers, are more suitable for reducing paniculate emissions from the dryers. Wet
scrubbers use the process streams as the scrubbing liquid so that the collected paniculate can be easily
recycled to the production system.
Tables 6.18-1 and 6.18-2 shows uncontrolled and controlled paniculate and VOC emission
factors for various dryer types. The VOC emissions shown apply only to caprolactam byproduct
plants.
Table 6.18-1 (Metric Units).
EMISSION FACTORS FOR AMMONIUM SULFATE MANUFACTURE*
Dryer Type
Rotary dryers
Uncontrolled
Wet scrubber
Fluidized-bed dryers
Uncontrolled
Wet scrubber
Paniculate
kg/MG
23
0.02C
109
0.14
Emission
Factor Rating
C
A
C
C
vocb
kg/Mg
0.74
0.11
0.74
0.11
Emission
Factor Rating
C
C
C
C
a Reference 3. Units are kg of pollutant/Mg of ammonium sulfate produced.
b VOC emissions occur only at caprolactam plants. The emissions are caprolactam vapor.
c Reference 4.
7/93
Chemical Process Industry
6.18-3
-------
Table 6.18-2 (English Units).
EMISSION FACTORS FOR AMMONIUM SULFATE MANUFACTURE8
Dryer Type
Rotary dryers
Uncontrolled
Wet scrubber
Fluidized-bed dryers
Uncontrolled
Wet scrubber
Paniculate
Ib/ton
46
0.04°
218
0.28
Emission
Factor Rating
C
A
C
C
vocb
Ib/ton
1.48
0.22
1.48
0.22
Emission
Factor Rating
B
B
B
B
a Reference 3. Units are Ibs. of pollutant/ton of ammonium sulfate produced
b VOC emissions occur only at caprolactam plants. The emissions are caprolactam vapor.
c Reference 4.
References for Section 6.18
1. Ammonium Sulfate Manufacture: Background Information for Proposed Emission Standards,
EPA-450/3-79-034a, U. S. Environmental Protection Agency, Research Triangle Park, NC,
December 1979.
2. North American Fertilizer Capacity Data, Tennessee Valley Authority, Muscle Shoals, AL,
December 1991.
3. Emission Factor Documentation For Section 6.18, Ammonium Sulfate Manufacture, Pacific
Environmental Services, Inc., Research Triangle Park, NC, March 1981.
4. Compliance Test Report: J.R. Simplot Company, Pocatello, ID, February, 1990.
6.18-4
EMISSION FACTORS
7/93
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7.7 PRIMARY ZINC SMELTING
7.7.1 General1-2
Zinc is found in the earth's crust primarily as zinc sulfide (ZnS). Primary uses for zinc
include galvanizing of all forms of steel, as a constituent of brass, for electrical conductors,
vulcanization of rubber and in primers and paints. Most of these applications are highly
dependent upon zinc's resistance to corrosion and its light weight characteristics. In 1991,
approximately 260 thousand megagrams of zinc were refined at the tour U. S. primary zinc
smelters. The annual production volume has remained constant since the 1980s. Three of these
four plants, located in Illinois, Oklahoma, and Tennessee) utilize electrolytic technology, and the
one plant in Pennsylvania uses electrothermic process. This annual production level
approximately equals production capacity, despite a mined zinc ore recovery level of 520
megagrams, a domestic zinc demand of 1190 megagrams, and a secondary smelting production
level of only 110 megagrams. As a result, the
U. S. is a leading exporter of zinc concentrates as well as the world's largest importer of refined
zinc.
Zinc ores typically may contain from three to eleven percent zinc, along with cadmium,
copper, lead, silver, and iron. Bcncficiation, or the concentration of the zinc in the recovered ore,
is accomplished at or near the mine by crushing, grinding, and flotation process. Once
concentrated, the zinc ore is transferred to smelters for the production of zinc or zinc oxide. The
primary product of most zinc companies is slab zinc, which is produced in five grades: special high
grade, high grade, intermediate, brass special, and prime western. The four U. S. primary smelters
also produce sulfuric acid as a byproduct.
7.7.2 Process Description'
Reduction of zinc sulfide concentrates to metallic zinc is accomplished through either
electrolytic deposition from a sulfate solution or by distillation in retorts or furnaces. Both of
these methods begin with the elimination of most of the sulfur in the concentrate through a
roasting process, which is described below. A generalized process diagram depicting primary zinc
smelting is presented in Figure 7.7-1.
Roasting is a high-temperature process that converts zinc sulfide concentrate to an impure
zinc oxide called calcine. Roaster types include multiple-hearth, suspension or fluidized bed. The
following reactions occur during roasting:
2ZnS + 3O2 -»• 2ZnO + SO2 [1]
2SO2 + O2 -> 2SO3 |2)
In a multiple-hearth roaster, the concentrate drops through a series of nine or more
hearths stacked inside a brick lined cylindrical column. As the feed concentrate drops through
the furnace, it is first dried by the hot gases passing through the hearths and then oxidized to
produce calcine. The reactions are slow and can be sustained only by the addition of fuel.
7/93 Metallurgical Industry 7.7-1
-------
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EMISSION FACTORS
7/93
-------
Multiple hearth roasters are unpressurized and operate at about 690°C (1300T). Operating time
depends upon the composition of concentrate and amount of the sulfur removal required.
Multiple hearth roasters have the capability of producing a high-purity calcine.
In a suspension roaster, the concentrates are blown into a combustion chamber very
similar to that of a pulverized coal furnace. The roaster consists of a refractory-lined cylindrical
steel shell, with a large combustion space at the top and two to four hearths in the lower portion,
similar to those of a multiple hearth furnace. Additional grinding, beyond that required for a
multiple hearth furnace, is normally required to assure that heat transfer to the material is
sufficiently rapid for the desulfurization and oxidation reactions to occur in the furnace chamber.
Suspension roasters are unpressurized and operate at about 980°C (1800°F).
In a fluidized-bed roaster, finely ground sulfide concentrates are suspended and oxidized in
a feedstock bed supported on an air column. As in the suspension roaster, the reaction rates for
desulfurization are more rapid than in the older multiple-hearth processes. Fluidized-bed roasters
operate under a pressure slightly lower than atmospheric and at temperatures averaging 1000°C
(1800°F). In the fluidized-bed process, no additional fuel is required after ignition has been
achieved. The major advantages of this roaster arc greater throughput capacities and greater
sulfur removal capabilities.
Electrolytic processing of desulfurized calcine consists of three basic steps, leaching,
purification and electrolysis. Leaching occurs in an aqueous solution of sulfuric acid, yielding a
zinc sulfate solution as shown in Equation 3 below.
ZnO + SO3 -*• ZnSO4 [3]
In double leaching, the calcine is first leached in a neutral or slightly alkaline solution, then in an
acidic solution, with the liquid passing countcrcurrent to the flow of calcine. In the neutral
leaching solution, sulfatcs from the calcine dissolve, but only a portion of the zinc oxide enters
into solution. The acidic leaching solution dissolves the remainder of the zinc oxide, along with
metallic impurities such as arsenic, antimony, cobalt, germanium, nickel, and thallium. Insoluble
zinc ferrite, formed during concentrate roasting by the reaction of iron with zinc,-remains in the
leach residue, along with lead and silver. Lead and silver typically are shipped to a lead smelter
for recovery, while the zinc is extracted from the zinc ferrile to increase recovery efficiency.
In the purification process, a number of various reagents are added to the zinc-laden
electrolyte in a sequence of steps designed to precipitate the metallic impurities, which otherwise
will interfere with deposition of zinc. After purification, concentrations of these impurities are
limited to less than 0.05 milligram per liter (4 x 10 pounds per gallon). Purification is usually
conducted in large agitated tanks. The process takes place at temperatures ranging from 40 to
85°C (104 to 185°F), and pressures ranging from atmospheric to 240 kilopascals (Kpa) (2.4
atmospheres).
In electrolysis, metallic zinc is recovered from the purified solution by passing current
through an electrolyte solution, causing zinc to deposit on an aluminum cathode. As the
electrolyte is slowly circulated through the cells, water in the electrolyte dissociates, releasing
oxygen gas at the anode. Zinc metal is deposited at the cathode and sulfuric acid is regenerated
for recycle to the leach process. The sulfuric acid acts as a catalyst in the process as a whole.
Electrolytic zinc smelters contain as many as several hundred cells. A portion of the
electrical energy is converted into heat, which increases the temperature of the electrolyte.
7/93 Metallurgical Industry 7.7-3
-------
Electrolytic cells operate at temperature ranges from 30 to 35°C (86 to 95°F) and at atmospheric
pressure. A portion of the electrolyte is continuously circulated through the cooling towers both
to cool and concentrate the electrolyte through evaporation of water. The cooled and
concentrated electrolyte is then recycled to the cells. Every 24 to 48 hours, each cell is shut
down, the zinc-coated cathodes are removed and rinsed, and the zinc is mechanically stripped
from the aluminum plates.
The electrothermic distillation retort process, as it exists at one U. S. plant, was developed
by the St. Joe Minerals Corporation in 1930. The principal advantage of this pyrometallurgical
technique over electrolytic processes is its ability to accommodate a wide variety of zinc-bearing
materials, including secondary items such as calcine derived from electric arc furnace (EAF) dust.
Electrothermic processing of desulfurized calcine begins with a down draft sintering operation, in
which grate pallets are joined to form a continuous conveyor system. The sinter feed is essentially
a mixture of roaster calcine and EAF calcine. Combustion air is drawn down through the
conveyor, and impurities such as lead, cadmium, and halides in the sinter feed are driven off and
collected in a bag filter. The product sinter typically includes 48 percent zinc, 8 percent iron, 5
percent aluminum, 4 percent silicon, 2.5 percent calcium, and smaller quantities of magnesium,
lead, and other metals.
Electric retorting with its greater thermal efficiency than externally heated furnaces, is the
only pyrometallurgical technique utilized by the U. S. primary zinc industry, now and in the future.
Product sinter and, possibly, secondary zinc materials are charged with coke to an electric retort
furnace. The charge moves downward from a rotary feeder in the furnace top into a refractory-
lined vertical cylinder. Paired graphite electrodes protrude from the top and bottom of this
cylinder, producing a current flow. The coke serves to provide electrical resistance, producing
heat and generating the carbon monoxide required for the reduction process. Temperatures of
1400°C (2600°F) are attained, immediately vaporizing zinc oxides according to the following
reaction:
ZnO + CO -* Zn (vapor) + CO2 [4]
The zinc vapor and carbon dioxide pass to a vacuum condenser, where zinc is recovered by
bubbling through a molten zinc bath. Over 95 percent of the zinc vapor leaving the retort is
condensed to liquid zinc. The carbon dioxide is regenerated with carbon, and the carbon
monoxide is recycled back to the retort furnace.
7.7.3 Emissions And Controls
Each of the two smelting processes generates emissions along the various process steps.
The roasting process in a zinc smelter is typically responsible for more than 90 percent of the
potential SO2 emissions. About 93 to 97 percent of the sulfur in the feed is emitted as sulfur
oxides. Concentrations of SO2 in the offgas vary with the type of roaster operation. Typical SO2
concentrations for multiple hearth, suspension, and fluidizcd bed roasters are 4.5 to 6.5 percent,
10 to 13 percent, and 7 to 12 percent, respectively. Sulfur dioxide emissions from the roasting
processes at all four U. S. primary zinc processing facilities are recovered at on-site sulfuric acid
plants. Much of the particulate matter emitted from primary zinc processing facilities is also
attributable to the concentrate roasters. The amount and composition of particulate varies with
operating parameters, such as air How rate and equipment configuration. Various combinations
of control devices such as cyclones, electrostatic precipitators (ESP), and baghouses can be used
on roasters and on sintering machines, achieving 94 to 99 percent emission reduction.
7.7-4 EMISSION FACTORS 7/93
-------
Controlled and uncontrolled participate emission factors for points within a zinc smelting
facility are presented in Tables 7.7-1 and 7.7-2. Fugitive emission factors are presented in Tables
7.7-3 and 7.7-4. These emission factors should be applied carefully. Emission factors for sintering
operations are derived from data from a single facility no longer operating. Others are estimated
based on similar operations in the steel, lead and copper industries. Testing on one
electrothcrmic primary zinc smelting facility indicates that cadmium, chromium, lead, mercury,
nickel, and zinc arc contained in the offgases from both the sintering machine and the retort
furnaces.
Table 7.7-1 (Metric Units).
PARTICULATE EMISSION FACTORS FOR ZINC SMELTING11
Process
Roasting
Multiple hearth1"1 (SCC 3-03-030-02)
Suspension0 (SCC 3-03-030-07)
Fluidizcd bed"1 (SCC 3-03-030-08)
Sinter plant (SCC 3-03-030-03)
Uncontrolled0
With cyclonef
With cyclone and ESP8
Electric retort11 (SCC 3-03-030-21)
Electrolytic process1 (SCC 3-03-030-06)
Uncontrolled
113
2000
2167
62.5
10.0
3.3
Emission
Factor
Rating
E
E
E
E
E
E
Controlled
4
24.1
8.25
Emission
Factor
Rating
E
E
E
''Factors are for kg/Mg of zinc produced. SCC = Source Classification Code.
ESP = Electrostatic precipitalor.
bRcfcrcnces 2,4. Averaged from an estimated 10% of feed released as particulate, zinc
production rate at 60% of roaster feed rate, and other estimates.
cRcferences 2,4. Based on an average 60% of feed released as particulate emission and a zinc
production rate at 60% of roaster feed rate. Controlled emissions based on 20% dropout in
waste heat boiler and 99.5% dropout in cyclone and ESP.
dRefercnces 4,7. Based on an average 65% of feed released as particulate emissions and a zinc
production rale of 60 percent of roaster feed rate.
cRcfcrence 4. Based on unspecified industrial source data.
Reference 8. Data not necessarily compatible with uncontrolled emissions.
gRcfcrencc 8.
hRcfcrcnce 1. Based on unspecified industrial source data.
J Reference 2.
7/93
Metallurgical Industry
7.7-5
-------
Table 7.7-2 (English Units).
PARTICULATE EMISSION FACTORS FOR ZINC SMELTING3
Process
Roasting
Multiple hearthb (SCC 3-03-030-02)
Suspension0 (SCC 3-03-030-07)
Fluidized becT (SCC 3-03-030-08)
Sinter plant (SCC 3-03-030-03)
Uncontrolled6
With cyclonef
With cyclone and ESP8
Electric retort*1 (SCC 3-03-030-21)
Electrolytic processJ (SCC 3-03-030-06)
Uncontrolled
227
2000
2167
125
20.0
6.6
Emission
Factor
Rating
E
E
E
E
E
E
Controlled
8
48.2
16.5
Emission
Factor
Rating
E
E
E
aFactors are for Ib/ton of zinc produced. SCC = Source Classification Code.
ESP = Electrostatic precipitator.
bReferences 2,4. Averaged from an estimated 10% of feed released as particulate, zinc
production rate at 60% of roaster feed rate, and other estimates.
cReferences 2,4. Based on an average 60% of feed released as particulate emission and a zinc
production rate at 60% of roaster feed rate. Controlled emissions based on 20% dropout in
waste heat boiler and 99.5% dropout in cyclone and ESP.
References 4,7. Based on an average 65% of feed released as particulate emissions and a zinc
production rate of 60 percent of roaster feed rate.
eReference 4. Based on unspecified industrial source data.
Reference 8. Data not necessarily compatible with uncontrolled emissions.
8Reference 8.
hReference 1. Based on unspecified industrial source data.
^Reference 2.
7.7-6
EMISSION FACTORS
7/93
-------
Table 7.7-3 (Metric Units).
UNCONTROLLED FUGITIVE PARTICULATE EMISSION FACTORS
FOR SLAB ZINC SMELTING3
Process
Roasting
Sinter plantb
Wind box (SCC 3-03-030-19)
Discharge screens (SCC 3-03-030-20)
Retort building0 (SCC 3-03-030-24)
Caslingd (SCC 3-03-030-1 1)
Emissions
Negligible
0.12 - 0.55
0.28 - 1.22
1.0 - 2.0
1.26
Emission
Factor
Rating
E
E
E
E
''Reference 9. Factors are in kg/Mg of product. SCC = Source Classification Code.
bFrom steel industry operations for which there are emission factors. Based on quantity of sinter
produced.
cFrom lead industry operations.
dFrom copper industry operations.
Table 7.7-4 (English Units).
UNCONTROLLED FUGITIVE PARTICULATE EMISSION FACTORS
FOR SLAB ZINC SMELTING
Process
Roasting
Sinter plantb
Wind box (SCC 3-03-030-19)
Discharge screens (SCC 3-03-030-20)
Retort building0 (SCC 3-03-030-24)
Castingd (SCC 3-03-030-1 1)
Emissions
Negligible
0.24- 1.10
0.56 - 2.44
2.0 - 4.0
2.52
Emission
Factor
Rating
E
E
E
E
"Reference 9. Factors are in Ib/ton of product. SCC = Source Classification Code.
bFrom steel industry operations for which there arc emission factors. Based on quantity of sinter
produced.
°From lead industry operations.
From copper industry operations.
7/93
Metallurgical Industry
7.7-7
-------
References for Section 7.7
1. J. H. Jolly, "Zinc", Mineral Commodity Summaries 1992, U. S. Department Of The Interior,
Washington, DC, 1992.
2. J. H. Jolly, "Zinc", Minerals Yearbook 1989, U. S. Department Of The Interior, Washington,
DC, 1990.
3. R. L. Williams, "The Monaca Electrothermic Smelter - The Old Becomes The New", Lead-
Zinc '90, The Minerals, Metals & Materials Society, Philadelphia, PA, 1990.
4. Environmental Assessment Of The Domestic Primary Copper, Lead And Zinc Industries,
EPA-600/2-82-066, U. S. Environmental Protection Agency, Cincinnati, OH, October 1978.
5. Paniculate Pollutant System Study, Volume I: Mass Emissions, APTD-0743, U. S.
Environmental Protection Agency, Research Triangle Park, NC, May 1971.
6. G. Sallee, Personal Communication, Midwest Research Institute, Kansas City, MO, June
1970.
7. Systems Study For Control Of Emissions In The Primary Nonfeirous Smelting Industry,
Volume I, APTD-1280, U. S. Environmental Protection Agency, Research Triangle Park,
NC, June 1969.
8. R. B. Jacko and D. W. Ncvendorf, "Trace Metal Emission Test Results From A Number Of
Industrial And Municipal Point Sources", Journal Of The Air Pollution Control Association,
27(10):989-994, October 1977.
9. Technical Guidance For Control Of Industrial Process Fugitive Paniculate Emissions, EPA-
450/3-77-010, U. S. Environmental Protection Agency, Research Triangle Park, NC, March
1977.
10. Background Information For New Source Performance Standards: Primary Copper, Zinc And
Lead Smelters, Volume I: Proposed Standards, EPA-450/2-74-002a, U. S. Environmental
Protection Agency, Research Triangle Park, NC, October 1974.
11. Written communication from J. D. Reese, Zinc Corporation Of America, Monaca, PA, to
C. M. Campbell, Pacific Environmental Services, Inc., Research Triangle Park, NC, 18
November 1992.
12. Emission Study Performed For Zinc Coloration Of America At The Monaca Facilities, 14-30
May 1991, EMC Analytical, Inc., Gilberts, IL, 27 April 1992.
7.7-8 EMISSION FACTORS 7/93
-------
7.14 SECONDARY ZINC PROCESSING
7.14.1 General1'2
The secondary zinc industry processes scrap metals for the recovery of zinc in the form of in
the form of zinc slabs, zinc oxide, or zinc dust. There are currently 10 secondary zinc recovery
plants operating in the U. S., with an aggregate capacity of approximately 60 megagrams (60 tons)
per year.
7.14.2 Process Description
Zinc recovery involves three general operations performed on scrap, pretreatment, melting,
and refining. Processes typically used in each operation are shown in Figure 7.14-1.
7.14.2.1 Scrap Pretreatment
Scrap metal is delivered to the secondary zinc processor as ingots, rejected castings, flashing
and other mixed metal scrap containing zinc. Scrap pretreatment includes: (1) sorting, (2)
cleaning, (3) crushing and screening, (4) sweating, and (5) leaching.
In the sorting operation, zinc scrap is manually separated according to zinc content and any
subsequent processing requirements. Cleaning removes foreign materials to improve product
quality and recovery efficiency. Crushing facilitates the ability to separate the zinc from the
contaminants. Screening and pneumatic classification concentrates the zinc metal for further
processing.
A sweating furnace (rotary, rcvcrbcratory, or muffle furnace) slowly heats the scrap
containing zinc and other metals to approximately 364°C (787°F). This temperature is sufficient
to melt zinc but is still below the melting point of the remaining metals. Molten zinc collects at
the bottom of the sweat furnace and is subsequently recovered. The remaining scrap metal is
cooled and removed to be sold to other secondary processors.
Leaching with sodium carbonate solution converts dross and skimmings to zinc oxide, which
can be reduced to zinc metal. The zinc containing material is crushed and washed with water,
separating contaminants from zinc-containing metal. The contaminated aqueous stream is treated
with sodium carbonate to convert zinc chloride into sodium chloride (NaCl) and insoluble zinc
hydroxide (ZnOH). The NaCl is separated from the insoluble residues by filtration and settling.
The precipitate zinc hydroxide is dried and calcined (dehydrated into a powder at high
temperature) to convert it into crude zinc oxide (ZnO). The ZnO product is usually refined to
zinc at primary zinc smelters. The washed zinc-containing metal portion becomes the raw
material for the melting process.
7/93 Metallurgical Industry 7.14-1
-------
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7.14-2
EMISSION FACTORS
7/93
-------
7.14.2.2 Melting
Zinc scrap is melted in kettle, crucible, reverberatory, and electric induction furnaces. Flux
is used in these furnaces to trap impurities from the molten zinc. Facilitated by agitation, flux and
impurities float to the surface of the melt as dross, and is skimmed from the surface. The
remaining molten zinc may be poured into molds or transferred to the refining operation in a
molten state.
Zinc alloys are produced from pretreated scrap during sweating and melting processes. The
alloys may contain small amounts of copper, aluminum, magnesium, iron, lead, cadmium and tin.
Alloys containing 0.65 to 1.25 percent copper are significantly stronger than unalloyed zinc.
7.14.2.3 Refining
Refining processes remove further impurities in clean zinc alloy scrap and in zinc vaporized
during the melt phase in retort furnaces, as shown in Figure 7.14-2.
Molten zinc is heated until it vaporizes. Zinc vapor is condensed and recovered in several forms,
depending upon temperature, recovery time, absence or presence of oxygen, and equipment used
during zinc vapor condensation. Final products from refining processes include zinc ingots, zinc
dust, zinc oxide, and zinc alloys.
Distillation retorts and furnaces are used cither to reclaim zinc from alloys or to refine
crude zinc. Bottle retort furnaces consist of a pear-shaped ceramic retort (a long-necked vessel
used for distillation). Bottle retorts are filled with zinc alloys and heated until most of the zinc is
vaporized, sometimes as long as 24 hours. Distillation involves vaporization of zinc at
temperatures from 982 to 1249°C (1800 to 2280°F) and condensation as zinc dust or liquid zinc.
Zinc dust is produced by vaporization and rapid cooling, and liquid zinc results when the vaporous
product is condensed slowly at moderate temperatures. The melt is cast into ingots or slabs.
A muffle furnace is a continuously charged retort furnace, which can operate lor several
days at a time.
Molten zinc is charged through a feed well that also acts as an airlock. Muffle furnaces
generally have a much greater vaporization capacity than bottle retort furnaces. They produce
both zinc ingots and zinc oxide of 99.8 percent purity.
Pot melting, unlike bottle retort and muffle furnaces, does not incorporate distillation as a
part of the refinement process. This method merely monitors the composition of the intake to
control the composition of the product. Specified die-cast scraps containing zinc are melted in a
steel pot. Pot melting is a simple indirect heat melting operation where the final alloy cast into
zinc alloy slabs is controlled by the scrap input into the pot.
Furnace distillation with oxidation produces zinc oxide dust. These processes are similar to
distillation without the condenser. Instead of entering a condenser, the zinc vapor discharges
directly into an air stream leading to a refractory-lined combustion chamber. Excess air completes
the oxidation and cools the zinc oxide dust before it is collected in a fabric filter.
Zinc oxide is transformed into zinc metal though a retort reduction process using coke as a
reducing agent. Carbon monoxide produced by the partial oxidation of the coke reduces the zinc
oxide to metal and carbon dioxide. The zinc vapor is recovered by condensation.
7/93 Metallurgical Industry 7.14-3
-------
t
PURE
METAL
TAPHOLE '
Figure 7.14-2. Zinc retort distillation furnace.
STACK
MOLTEN METAL
TAPHOLE
FLAME PORT
AIR IN
DUCT FOR OXIDE
COLLECTION
RISER CONDENSER
UNIT
MOLTEN METAL
TAPHOLE
Figure 7.14-3. Muffle furnace and condenser.
7.14-4
EMISSION FACTORS
7/93
-------
7.14.3 Emissions1"4
Process and fugitive emission factors for secondary zinc operations are tabulated in Tables
7.14-1 through 7.14-4. Emissions from sweating and melting operations consist of particulate, zinc
fumes, other volatile metals, flux fumes, and smoke generated by the incomplete combustion of
grease, rubber and plastics in zinc scrap. Zinc fumes are negligible at low furnace temperatures.
Flux emissions may be minimized by using a nonfuming flux. In production requiring special
fluxes that do generate fumes, fabric filters may be used to collect emissions. Substantial
emissions may arise from incomplete combustion of carbonaceous material in the zinc scrap.
These contaminants are usually controlled by afterburners.
Particulate emissions from sweating and melting are most commonly recovered by fabric
filter. In one application on a muffle sweating furnace, a cyclone and fabric filter achieved
particulate recovery efficiencies in excess of 99.7 percent. In one application on a reverberatory
sweating furnace, a fabric filter removed 96.3 percent of the particulate. Fabric filters show
similar efficiencies in removing particulate from exhaust gases of melting furnaces.
Crushing and screening operations are also sources of dust emissions. These emissions are
composed of zinc, aluminum, copper, iron, lead, cadmium, tin, and chromium. They can be
recovered by hooded exhausts used as capture devices and can be controlled with fabric filters.
The sodium carbonate leaching process emits zinc oxide dust during the calcining operation
(oxidizing precipitate into powder at high temperature). This dust can be recovered in fabric
filters, although zinc chloride in the dust may cause plugging problems.
Emissions from refining operations are mainly metallic fumes. Distillation/oxidation
operations emit their entire zinc oxide product in the exhaust gas. Zinc oxide is usually recovered
in fabric filters with collection efficiencies of 98 to 99 percent.
7/93 Metallurgical Industry 7.14-5
-------
Table 7.14-1 (Metric Units).
UNCONTROLLED PARTICULATE EMISSION FACTORS FOR
SECONDARY ZINC SMELTING3
Operation
Reverberatory sweating*3 (in mg/Mg feed material)
Clean metallic scrap (SCC 3-04-008-18)
General metallic scrap (SCC 3-04-008-28)
Residual scrap (SCC 3-04-008-38)
Rotary sweating0 (SCC 3-04-008-09)
Muffle sweating0 (SCC 3-04-008-10)
Kettle sweating15
Clean metallic scrap (SCC 3-04-008-14)
General metallic scrap (SCC 3-04-008-24)
Residual scrap (SCC 3-04-008-34)
Electric resistance sweating0 (SCC 3-04-008-11)
Sodium carbonate leaching calciningd (SCC 3-04-008-06)
Kettle potd, mg/Mg product (SCC 3-04-008-03)
Crucible melting (SCC 3-04-008-42)
Reverberatory melting (SCC 3-04-008-42)
Electric induction melting (SCC 3-04-008-43)
Alloying (SCC 3-04-008-40)
Retort and muffle distillation, in kg/Mg of product
Pouring0 (SCC 3-04-008-51)
Casting0 (SCC 3-04-008-52)
Muffle distillation*1 (SCC 3-04-008-02
Graphite rod distillation0'6 (SCC 3-04-008-53)
Retort distillation/oxidationf (SCC 3-04-008-54)
Muffle distillation/oxidationf (SCC 3-04-008-55)
Retort reduction (SCC 3-04-008-01)
Galvanizingd (SCC 3-04-008-05)
Emissions
Negligible
6.5
16
5.5 - 12.5
5.4 - 16
Negligible
5.5
12.5
< 5
44.5
0.05
ND
ND
ND
ND
0.2 - 0.4
0.1 - 0.2
22.5
Negligible
10- 20
10 - 20
23.5
2.5
Emission Factor
Rating
C
C
C
C
C
C
C
C
C
C
C
C
C
C
C
C
C
a Factors are for kg/Mg of zinc used, except as noted. SCC = Source Classification Code.
ND = no data.
b Reference 3.
c Reference 4.
d References 5-7.
e Reference 1.
f Reference 4. Factors are for kg/Mg of ZnO produced. All product zinc oxide dust is carried
over in the exhaust gas from the furnace and is recovered with 98 - 99 percent efficiency.
7.14-6
EMISSION FACTORS
7/93
-------
Table 7.14-2 (English Units).
UNCONTROLLED PARTICULATE EMISSION FACTORS FOR
SECONDARY ZINC SMELTING3
Operation
Reverberatory sweating15 (in mg/Mg feed material)
Clean metallic scrap (SCC 3-04-008-18)
General metallic scrap (SCC 3-04-008-28)
Residual scrap (SCC 3-04-008-38)
Rotary sweating0 (SCC 3-04-008-09)
Muffle sweating0 (SCC 3-04-008-10)
Kettle sweating11
Clean metallic scrap (SCC 3-04-008-14)
General metallic scrap (SCC 3-04-008-24)
Residual scrap (SCC 3-04-008-34)
Electric resistance sweating0 (SCC 3-04-008-11)
Sodium carbonate leaching calciningd (SCC 3-04-008-06)
Kettle potd, mg/Mg product (SCC 3-04-008-03)
Crucible melting (SCC 3-04-008-42)
Reverberatory melting (SCC 3-04-008-42)
Electric induction melting (SCC 3-04-(K)8-43)
Alloying (SCC 3-04-W8-40)
Retort and muffle distillation, in Ib/ton of product
Pouring0 (SCC 3-04-008-51)
Casting0 (SCC 3-04-008-52)
Muffle distillation11 (SCC 3-04-008-02
Graphite rod distillation0'0 (SCC 3-04-008-53)
Retort distillation/oxidation1' (SCC 3-04-008-54)
Muffle distillation/oxidation' (SCC 3-04-008-55)
Retort reduction (SCC 3-04-008-01)
Galvanizingd (SCC 3-04-008-05)
Emissions
Negligible
13
32
11 -25
10.8 - 32
Negligible
11
25
< 10
89
0.1
ND
ND
ND
ND
0.4 - 0.8
0.2 - 0.4
45
Negligible
20 - 40
20 - 40
47
5
Emission Factor
Rating
C
C
C
C
C
C
C
C
C
C
C
C
C
C
C
C
C
a Factors are for Ih/ton of zinc used, except as noted. SCC = Source Classification Code.
ND = no data.
b Reference 3.
c Reference 4.
d References 5-7.
e Reference 1.
Reference 4. Factors are for Ib/ton of ZnO produced. All product zinc oxide dust is carried
over in the exhaust gas from the furnace and is recovered with 98 - 99 percent efficiency.
7/93
Metallurgical Industry
7.14-7
-------
Table 7.14-3 (Metric Units).
FUGITIVE PARTICULATE EMISSION FACTORS FOR
SECONDARY ZINC SMELTING3
Operation
Reverberatory sweating15 (SCC 3-04-008-61)
Rotary sweating15 (SCC 3-04-008-62)
Muffle sweating15 (SCC 3-04-008-63)
Kettle (pot) sweating15 (SCC 3-04-008-64)
Electrical resistance sweating, per kg processed15
(SCC 3-04-008-65)
Crushing/screening0 (SCC 3-04-008-12)
Sodium carbonate leaching (SCC 3-04-008-66)
Kettle (pot) melting furnace15 (SCC 3-04-008-67)
Crucible melting furnaced (SCC 3-04-008-68)
Reverberatory melting furnace15 (SCC 3-04-008-69)
Electric induction meltingb (SCC 3-04-008-70)
Alloying retort distillation (SCC 3-04-008-71)
Retort and muffle distillation (SCC 3-04-008-72)
Casting15 (SCC 3-04-008-73)
Graphite rod distillation (SCC 3-04-008-74)
Retort distillation/oxidation (SCC 3-04-008-75)
Muffle distillation/oxidation (SCC 3-04-008-76)
Retort reduction (SCC 3-04-008-77)
Emissions
0.63
0.45
0.54
0.28
0.25
2.13
ND
0.0025
0.0025
0.0025
0.0025
ND
1.18
0.0075
ND
ND
ND
ND
Emission
Factor
Rating
E
E
E
E
E
E
E
E
E
E
E
E
aReference 8. Factors are kg/Mg of end product, except as noted. SCC — Source Classification
Code. ND = no data.
Estimate based on stack emission factor given in Reference 1, assuming fugitive emissions to be
equal to five % of stack emissions.
cReference 1. Factors are for kg/Mg of scrap processed. Average of reported emission factors.
Engineering judgment, assuming fugitive emissions from crucible melting furnace to be equal to
fugitive emissions from kettle (pot) melting furnace.
7.14-8
EMISSION FACTORS
7/93
-------
Table 7.14-4 (English Units).
FUGITIVE PARTICULATE EMISSION FACTORS FOR
SECONDARY ZINC SMELTING21
Operation
Revcrhcratory sweating13 (SCC 3-04-008-61)
Rotary sweat ingh (SCC 3-04-008-62)
Muffle sweating11 (SCC 3-04-008-63)
Kettle (pot) sweatingb (SCC 3-04-008-64)
Electrical resistance sweating, per ton processed15
(SCC 3-04-008-65)
Crushing/scrccningc (SCC 3-04-008-12)
Sodium carbonate leaching (SCC 3-04-008-66)
Kettle (pot) melting furnace11 (SCC 3-04-008-67)
Crucible melting furnaced (SCC 3-04-008-68)
Rcvcrberatory melting furnace11 (SCC 3-04-008-69)
Electric induction melting11 (SCC 3-04-008-70)
Alloying retort distillation (SCC 3-04-008-71)
Retort and muffle distillation (SCC 3-04-008-72)
Casting11 (SCC 3-04-008-73)
Graphite rod distillation (SCC 3-04-008-74)
Retort distillation/oxidation (SCC 3-04-008-75)
Muffle distillation/oxidation (SCC 3-04-008-76)
Retort reduction (SCC 3-04-008-77)
Emissions
1.30
0.90
1.07
0.56
0.50
4.25
ND
0.005
0.005
0.005
0.005
2.36
0.015
ND
ND
ND
ND
Emission
Factor
Rating
E
E
E
E
E
E
E
E
E
E
E
E
"Reference 8. Factors are Ib/ton of end product, except as noted. SCC = Source Classification
Code. ND = no data.
Estimate based on stack emission factor given in Reference 1, assuming fugitive emissions to be
equal to five % of stack emissions.
cRefcrcncc 1. Factors arc for Ib/ton of scrap processed. Average of reported emission factors.
Engineering judgment, assuming fugitive emissions from crucible melting furnace to be equal to
fugitive emissions from kettle (pot) melting furnace.
7/93
Metallurgical Industry
7.14-9
-------
References for Section 7.14
1. William M. Coltharp, et al, Multimedia Environmental Assessment Of The Secondary
Nonferrous Metal Industry, Draft, EPA Contract No. 68-02-1319, Radian Corporation,
Austin, TX, June 1976.
2. John A. Danielson, Air Pollution Engineering Manual, 2nd Edition, AP-40, U. S.
Environmental Protection Agency, Research Triangle Park, NC, 1973. Out of Print.
3. W. Herring, Secondary Zinc Industry Emission Control Problem Definition Study (Part I),
APTD-0706, U. S. Environmental Protection Agency, Research Triangle Park, NC, May
1971.
4. H. Nack, et al., Development Of An Approach To Identification Of Emerging Technology And
Demonstration Opportunities, EPA-650/2-74-048, U. S. Environmental Protection Agency,
Cincinnati, Ohio, May 1974.
5. G. L. Allen, et al, Control Of Metallurgical And Mineral Dusts And Fumes In Los Angeles
County, Report Number 7627, U. S. Department Of The Interior, Washington, DC, April
1952.
6. Restricting Dust And Sulfur Dioxide Emissions From Lead Smelters, VDI Number 2285, U. S.
Department Of Health And Human Services, Washington, DC, September 1961.
7. W. F. Hammond, Data On Nonferrous Metallurgical Operations, Los Angeles County Air
Pollution Control District, Los Angeles, CA, November 1966.
8. Assessment Of Fugitive Paniculate Emission Factors For Industrial Processes, EPA-450/3-78-
107, U. S. Environmental Protection Agency, Research Triangle Park, NC, September 1978.
9. Source Category Survey: Secondary Zinc Smelting And Refining Industry, EPA-450/3-80-012,
U. S. Environmental Protection Agency, Research Triangle Park, NC, May 1980.
7.14-10 EMISSION FACTORS 7/93
-------
7.16 LEAD OXIDE AND PIGMENT PRODUCTION
7.16.1 General1'2'7
Lead oxide is a general term and can be cither lead monoxide, or "litharge" (PbO); lead
tetroxide, or "red lead" (Pb3O4); or black, or "gray", oxide which is a mixture of 70 percent lead
monoxide and 30 percent metallic lead. Black lead is made for specific use in the manufacture of
lead acid storage batteries. Because of the size of the lead acid battery industry, lead monoxide is
the most important commercial compound of lead, based on volume. Total oxide production in 1989
was 57,984 megagrams (64,000 tons).
Litharge is used primarily in the manufacture of various ceramic products. Because of its
electrical and electronic properties, litharge is also used in capacitors, Vidicon® tubes, and
electrophotographic plates, as well as in ferromagnetic and ferroelectric materials. It is also used as
an activator in rubber, a curing agent in elastomers, a sulfur removal agent in the production of
thioles and in oil refining, and an oxidation catalyst in several organic chemical processes. It also has
important markets in the production of many lead chemicals, dry colors, soaps (i. e., lead stearate),
and driers for paint. Another important use of litharge is the production of lead salts, particularly
those used as stabilizers for plastics, notably polyvinyl chloride materials.
The major lead pigment is red lead (Pb^O4), which is used principally in ferrous metal
protective paints. Other lead pigments include white lead and lead chromates. There are several
commercial varieties of white lead including leaded zinc oxide, basic carbonate white lead, basic
sulfate white lead, and basic lead silicates. Of these, the most important is leaded zinc oxide, which
is used almost entirely as white pigment for exterior oil-based paints.
7.16.2 Process Description8
Black oxide is usually produced by a Barton Pot process. Basic carbonate white lead
production is based on the reaction of litharge with acetic acid or acetate ions. This product is then
reacted with carbon dioxide will form lead carbonate. While leads (other than carbonates) are made
cither by chemical, fuming, or mechanical blending processes. Red lead is produced by oxidizing
litharge in a revcrberatory furnace. Chromalc pigments are generally manufactured by precipitation
or calcination as in the following equation:
Pb(NO3)2 + Na2(CrO4) -+ PbCrO4 + 2 NaNO3 [1]
Commercial lead oxides can all be prepared by wet chemical methods. With the exception
of lead dioxide, lead oxides arc produced by thermal processes in which lead is directly oxidized with
air. The processes may be classified according to the temperature of the reaction: 1) low
temperature, below the melting point of lead; 2) moderate temperature, between the melting points
of lead and of lead monoxide; and 3) high temperature, above the melting point of lead monoxide.
Low Temperature Oxidation - Low temperature oxidation of lead is accomplished by tumbling
slugs of metallic lead in a ball mill equipped with an air How. The air How provides oxygen and is
used as a coolant. If some form of cooling were not supplied, the heat generated by the oxidation
of the lead plus the mechanical heat of the tumbling charge would raise the charge temperature
above the melting point of lead. The ball mill product is a "Icady" oxide with 20 to 50 percent free
lead.
7/93 Metallurgical Industry 7.16-1
-------
Moderate Temperature Oxidation - Three processes are used commercially in the moderate
temperature range: 1) refractory furnace, 2) rotary tube furnace, and 3) the Barton Pot process. In
the refractory furnace process, a cast steel pan is equipped with a rotating vertical shaft and a
horizontal crossarm mounted with plows. The plows move the charge continuously to expose fresh
surfaces for oxidation. The charge is heated by a gas flame on its surface. Oxidation of the charge
supplies much of the reactive heat as the reaction progresses. A variety of products can be
manufactured from pig lead feed by varying the feed temperature, and time of furnacing. Yellow
litharge (orthorhombic) can be made by cooking for several hours at 600 to 700°C (1112 to 1292°F)
but may contain traces of red lead and/or free metallic lead.
In the rotary tube furnace process, molten lead is introduced into the upper end of a
refractory-lined inclined rotating tube. An oxidizing flame in the lower end maintains the desired
temperature of reaction. The tube is long enough so that the charge is completely oxidized when it
emerges from the lower end. This type of furnace has been used commonly to produce lead
monoxide (tetragonal type), but it is not unusual for the final product to contain traces of both free
metallic and red lead.
The Barton Pot process (Figure 7.16-1) uses a cast iron pot with an upper and lower stirrer
rotating at different speeds. Molten lead is fed through a port in the cover into the pot, where it is
broken up into droplets by high-speed blades. Heat is supplied initially to develop an operating
temperature from 370 to 4SO°C (698 to 896°F). The exothermic heat from the resulting oxidation
of the droplets is usually sufficient to maintain the desired temperature. The oxidized product is
swept out of the pot by an air stream.
The operation is controlled by adjusting the rate of molten lead feed, the speed of the stirrers,
the temperature of the system, and the rate of air How through the pot. The Barton Pot produces
either litharge or leady litharge (litharge with 50 percent free lead). Since it operates at a higher
temperature than a ball mill unit, the oxide portion will usually contain some orthorhombic litharge.
It may also be operated to obtain almost entirely orthorhombic product.
High Temperature Oxidation - High temperature oxidation is a fume-type process. A very
fine particle, high-purity orthorhombic litharge is made by burning a fine stream of molten lead in
a special blast-type burner. The flame temperature is around 1200°C (2192°F). The fume is swept
out of the chamber by an air stream, cooled in a series of "goosenecks" and collected in a baghouse.
The median particle diameter is from 0.50 to 1.0 microns, as compared with 3.0 to 16.0 microns for
lead monoxide manufactured by other methods.
7.16.3 Emissions And Controls '6
Emission factors for lead oxide and pigment production processes are given in Tables 7.16.3-1
and 7.16.3-2. The emission factors were assigned an E rating because of high variabilities in test run
results and nonisokinetic sampling. Also, since Storage battery production facilities produce lead
oxide using the Barton Pot process, a comparison of the lead emission factors from both industries
has been performed. The lead oxide emission factors from the battery plants were found to be
considerably lower than the emission factors from the lead oxide and pigment industry. Since lead
battery production plants arc covered under federal regulations, one would expect lower emissions
from these sources.
7.16-2 EMISSION FACTORS 7/93
-------
LEAD
FEED
LEAD OXIDE
LEAD
CONVEYER
(PRODUCT TO STORAGE)
Figure 2.2.2-1. Lead oxide Barton Pot process.
Automatic shaker-type fabric filters, often preceded by cyclone mechanical collectors or
settling chambers, are the common choice for collecting lead oxides and pigments. Control
efficiencies of 99 percent are achieved with these control device combinations. Where fabric filters
are not appropriate scrubbers may be used, to achieve control efficiencies from 70 to 95 percent.
The ball mill and Barton Pot processes of black oxide manufacturing recover the lead product by
these two means. Collection of dust and fumes from the production of red lead is likewise an
economic necessity, since particulate emissions, although small, are about 90 percent lead. Emissions
data from the production of white lead pigments are not available, but they have been estimated
because of health and safety regulations. The emissions from dryer exhaust scrubbers account for
over 50 percent of the total lead emitted in lead chromate production.
7/93
Metallurgical Industry
7.16-3
-------
Table 7.16-1 (Metric Units).
CONTROLLED EMISSIONS FROM LEAD OXIDE AND PIGMENT PRODUCTION8
Process
Lead Oxide Production
Barton Potb
(SCC 3-01-035-06)
Calcining
(SCC 3-01-035-07)
Baghouse Inlet
Baghouse Outlet
Pigment Production
Red leadb
(SCC 3-0 1-035- 10)
White leadb
(SCC 3-01-035-15)
Chrome pigments
(SCC 3-01 -035-20)
Particulate
Emissions
0.21 - 0.43
7.13
0.032
0.5C
Emission
Factor
Rating
E
E
E
B
Lead
Emissions
0.22
7.00
0.024
0.50
0.28
0.065
Emission
Factor
Rating
E
E
E
B
B
B
References
4,6
6
6
4-5
4-5
4-5
aFactors are for kg/Mg of product. SCC = Source Classification Code.
bMeasured at baghousc outlet. Baghouse is considered process equipment.
cOnly PbO and oxygen are used in red lead production, so particulate emissions are assumed to be
about 90% lead.
7.16-4
EMISSION FACTORS
7/93
-------
Table 7.16-2 (English Units).
CONTROLLED EMISSIONS FROM LEAD OXIDE AND PIGMENT PRODUCTION"
Process
Lead Oxide Production
Barton Potb
(SCC 3-01-035-06)
Calcining
(SCC 3-01-035-07)
Baghouse Inlet
Baghouse Outlet
Pigment Production
Red leadb
(SCC 3-0 1-035- 10)
White leadb
(SCC 3-0 1-035- 15)
Chrome pigments
(SCC 3-0 1-035-20)
Particulate
Emissions
0.43 - 0.85
14.27
0.064
1.0C
Emission
Factor
Rating
E
E
E
B
Lead
Emissions
0.44
14.00
0.05
0.90
0.55
0.13
Emission
Factor
Rating
E
E
E
B
B
B
References
4,6
6
6
4-5
4-5
4-5
"Factors arc tor Ih/ton of product. SCC = Source Classification Code.
Measured at haghouse outlet. Baghouse is considered process equipment.
°Only PhO and oxygen are used in red lead production, so particulate emissions are assumed to be
about 90% lead.
7/93
Metallurgical Industry
7.16-5
-------
References for Section 7.16
1. E. J. Ritchie, Lead Oxides, Independent Battery Manufacturers Association, Inc., Largo, FL,
1974.
2. W. E. Davis, Emissions Study Of Industrial Sources Of Lead Air Pollutants, 1970, EPA Contract
No. 68-02-0271, W. E. Davis and Associates, Leawood, KS, April 1973.
3. Background Information In Support Of The Development Of Performance Standards For The
Lead Additive Industry, EPA Contract No. 68-02-2085, PEDCo Environmental Specialists, Inc.,
Cincinnati, OH, January 1976.
4. Control Techniques For Lead Air Emissions, EPA-450/2-77-012A. U. S. Environmental
Protection Agency, Research Triangle Park, NC, December 1977.
5. R. P. Betz, et ai, Economics Of Lead Removal In Selected Industries, EPA Contract No. 68-02-
0299, Battclle Columbus Laboratories, Columbus OH, December 1972.
6. Air Pollution Emission Test, Contract No. 74-PB-O-l, Task No. 10, Office Of Air Quality
Planning And Standards, U. S. Environmental Protection Agency, Research Triangle Park, NC,
August 1973.
7. Mineral Yearbook, Volume 1: Metals And Minerals, Bureau Of Mines, U.S. Department Of
The Interior, Washington, DC, 1989.
8. Harvey E. Brown, Lead Oxide: Properties and Applications, International Lead Zinc Research
Organization, Inc., New York, NY, 1985.
7.16-6 EMISSION FACTORS 7/93
-------
8.8 CLAY AND FLY ASH SINTERING
NOTE: Clay and fly ash sintering operations are no longer conducted in the United States.
However, this section is being retained for historical purposes.
8.8.1 Process Description1"3
Although the process for sintering fly ash and clay are similar, there are some distinctions that
justify a separate discussion of each process. Fly ash sintering plants are generally located near the
source, with the fly ash delivered to a storage silo at the plant. The dry fly ash is moistened with a
water solution of lignin and agglomerated into pellets or balls. This material goes to a traveling-grate
sintering machine where direct contact with hot combustion gases sinters the individual particles of
the pellet and completely burns off the residual carbon in the fly ash. The product is then crushed,
screened, graded, and stored in yard piles.
Clay sintering involves the driving off of entrained volatile matter. It is desirable that the
clay contain a sufficient amount of volatile matter so that the resultant aggregate will not be too
heavy. It is thus sometimes necessary to mix the clay with finely pulverized coke (up to 10 percent
coke by weight). In the sintering process, the clay is first mixed with pulverized coke, if necessary,
and then pelletized. The clay is next sintered in a rotating kiln or on a traveling grate. The sintered
pellets are then crushed, screened, and stored, in a procedure similar to that for fly ash pellets.
8.8.2 Emissions and Controls1
In fly ash sintering, improper handling of the fly ash creates a dust problem. Adequate
design features, including fly ash wetting systems and paniculate collection systems on all transfer
points and on crushing and screening operations, would greatly reduce emissions. Normally, fabric
filters are used to control emissions from the storage silo, and emissions are low. The absence of this
dust collection system, however, would create a major emission problem. Moisture is added at the
point of discharge from silo to the agglomerator, and very few emissions occur there. Normally,
there are few emissions from the sintering machine, but if the grate is not properly maintained, a dust
problem is created. The consequent crushing, screening, handling, and storage of the sintered
product also create dust problems.
In clay sintering, the addition of pulverized coke presents an emission problem because the
sintering of coke-impregnated dry pellets produces more particulate emissions than the sintering of
natural clay. The crushing, screening, handling, and storage of the sintered clay pellets creates dust
problems similar to those encountered in fly-ash sintering. Emission factors for both clay and fly-ash
sintering are shown in Table 8.8-1.
2/72 Mineral Products Industry 8.8-1
-------
TABLE 8.8-1 (METRIC UNITS)
EMISSION FACTORS FOR CLAY AND FLY ASH SINTERING*
k
Source (SSC) M
Fly ash crushing,
screening, sintering,
and storage
(3-05-009-01)d
Clay/coke mixture
sintering
(3-05-009-02)e
Clay/coke mixture
crushing, screening,
and storage
(3-05-009-07)f
Natural clay
sintering
(3-05-009-03)«
Natural clay
crushing, screening,
and storage
(3-05-009-04)f
Filterable13
PM
g/Mg Emission
of Factor
aterial Rating
55 E
20 E
7.5 E
6 E
6 E
PM-10
kg/Mg Emissi
of Facto
Material Ratin
ND
ND
ND
ND
ND
Condensible PMC
Inorganic
on kg/Mg Emiss
r of Fact
g Material Ratii
ND
ND
ND
ND
ND
Organic
sion kg/Mg
or of
ng Material
ND
ND
ND
ND
ND
Emission
Factor
Rating
ND = No data.
"Factors represent uncontrolled emissions unless otherwise noted.
bFilterable PM is that PM collected on or prior to the filter of an EPA Method 5 (or equivalent)
sampling train.
cCondensible PM is that PM collected in the impinger portion of a PM sampling train.
dReference 1.
References 3 to 5; for 90 percent clay, 10 percent pulverized coke; traveling grate, single pass,
up-draft sintering machine.
fBased on data in Section 8.19-2.
gReference 2; rotary dryer sinterer.
8.8-2
EMISSION FACTORS
2/72
-------
TABLE 8.8-1 (ENGISH UNITS)
EMISSION FACTORS FOR CLAY AND FLY ASH SINTERING*
Source
(SSC)
Filterable15
PM
lb/ton
of
Material
Emission
Factor
Rating
PM-10
lb/ton
of
Material
Emission
Factor
Rating
Condensible PMC
Inorganic
lb/ton
of
Material
Emission
Factor
Rating
Organic
lb/ton
of
Material
Emission
Factor
Rating
Fly ash crushing, 110
screening, sintering, and
storage
(3-05-009-01)d
Clay/coke mixture 40
sintering
(3-05-009-02)e
Clay/coke mixture 15
crushing, screening, and
storage
(3-05-009-07)f
Natural clay sintering 12
(3-05-009-03)*
Natural clay crushing, 12
screening, and storage
(3-05-009-04/
ND
ND
ND
ND
ND
ND
ND
ND
ND
E
E
ND
ND
ND
ND
ND
ND
ND = No data.
aFactors represent uncontrolled emissions unless otherwise noted.
bFilterable PM is that PM collected on or prior to the filter of an EPA Method 5 (or equivalent)
sampling train.
cCondensible PM is that PM collected in the impinger portion of a PM sampling train.
Reference 1.
References 3 to 5; for 90 percent clay, 10 percent pulverized coke; traveling grate, single pass,
up-draft sintering machine.
fBased on data in Section 8.19-2.
gReference 2; rotary dryer sinterer.
2/72
Mineral Products Industry
8.8-3
-------
References for Section 8.8
1. Air Pollutant Emission Factors, Final Report, Resources Research, Inc., VA. Prepared for
National Air Pollution Control Administration, Durham, N.C., under Contract
No. (PA-22-68-119). April 1970.
2. Communication between Resources Research, Inc., Reston, VA, and a clay sintering firm.
October 2, 1969.
3. Communication between Resources Research, Inc., Reston, VA., and an anonymous Air
Pollution Control Agency. October 16, 1969.
4. J. J. Henn, et al., Methods for Producing Alumina from Clay: An Evaluation of Two Lime
Sinter Processes, Department of the Interior, U.S. Bureau of Mines. Washington, DC, Report
of Investigation No. 7299. September 1969.
5. F. A. Peters, et al., Methods for Producing Alumina from Clay: An Evaluation of the Lime-
Soda Sinter Process, Department of the Interior, U. S. Bureau of Mines, Washington, DC.
Report of Investigation No. 6927. 1967.
8.8-4 EMISSION FACTORS 2/72
-------
8.10 CONCRETE BATCHING
8.10-1 Process Description1"4
Concrete is composed essentially of water, cement, sand (fine aggregate) and coarse
aggregate. Coarse aggregate may consist of gravel, crushed stone or iron blast furnace slag. Some
specialty aggregate products could be either heavyweight aggregate (of barite, magnetite, limonite,
ilmenite, iron or steel) or lightweight aggregate (with sintered clay, shale, slate, diatomaceous shale,
perlite, vermiculite, slag, pumice, cinders, or sintered fly ash). Concrete batching plants store,
convey, measure and discharge these constituents into trucks for transport to a job site. In some
cases, concrete is prepared at a building construction site or for the manufacture of concrete products
such as pipes and prefabricated construction parts. Figure 8.10-1 is a generalized process diagram for
concrete batching.
The raw materials can be delivered to a plant by rail, truck or barge. The cement is
transferred to elevated storage silos pneumatically or by bucket elevator. The sand and coarse
aggregate are transferred to elevated bins by front end loader, clam shell crane, belt conveyor, or
bucket elevator. From these elevated bins, the constituents are fed by gravity or screw conveyor to
weigh hoppers, which combine the proper amounts of each material.
Truck mixed (transit mixed) concrete involves approximately 75 percent of U. S. concrete
batching plants. At these plants, sand, aggregate, cement and water are all gravity fed from the
weigh hopper into the mixer trucks. The concrete is mixed on the way to the site where the concrete
is to be poured. Central mix facilities (including shrink mixed) constitute the other one fourth of the
industry. With these, concrete is mixed and then transferred to either an open bed dump truck or an
agitator truck for transport to the job site. Shrink mixed concrete is concrete that is partially mixed at
the central mix plant and then completely mixed in a truck mixer on the way to the job site. Dry
batching, with concrete mixed and hauled to the construction site in dry form, is seldom, if ever,
used.
8.10-2 Emissions and Controls5"7
Emission factors for concrete batching are given in Tables 8.10-1 and 8.10-2, with potential
air pollutant emission points shown. Paniculate matter, consisting primarily of cement dust but
including some aggregate and sand dust emissions, is the only pollutant of concern. All but one of
the emission points are fugitive in nature. The only point source is the transfer of cement to the silo,
and this is usually vented to a fabric filter or "sock". Fugitive sources include the transfer of sand
and aggregate, truck loading, mixer loading, vehicle traffic, and wind erosion from sand and
aggregate storage piles. The amount of fugitive emissions generated during the transfer of sand and
aggregate depends primarily on the surface moisture content of these materials. The extent of fugitive
emission control varies widely from plant to plant.
Types of controls used may include water sprays, enclosures, hoods, curtains, shrouds,
movable and telescoping chutes, and the like. A major source of potential emissions, the movement
of heavy trucks over unpaved or dusty surfaces in and around the plant, can be controlled by good
maintenance and wetting of the road surface.
10/86 Mineral Products Industry 8.10-1
-------
i,
.f
o
o
oo
fi
g.
8.10-2
EMISSION FACTORS
10/86
-------
TABLE 8.10-1 (METRIC UNITS)
EMISSION FACTORS FOR CONCRETE BATCHING*
All Emission Factors in kg/Mg of Material Mixed Unless Noted
Ratings (A-E) Follow Each Emission Factor
Source
(SSC)
Filterableb
PM
PM-10
Condensible PMC
Inorganic
Organic
Sand and aggregate transfer to elevated bin 0.014
(3-05-01 l-06)d
Cement unloading to elevated storage silo
Pneumatic6
Bucket elevato/
(3-05-011-07)
Weigh hopper loading 0.01
(3-05-011-08)8
Mixer loading (central mix) 0.02
(3-05-011-09)8
Truck loading (truck mix) 0.01
(3-05-011-108
Vehicle traffic (unpaved roads)
(3-05-01 l-_j*
Wind erosion from sand and aggregate storage
piles
(3-05-01!-_)'
Total process emissions (truck mix) 0.05
(3-05-01 l-_ji
E ND
0.13 D ND
0.12 E ND
E ND
E ND
E ND
4.5 C ND
3.9 D ND
E ND
ND
ND
ND
ND
ND
ND
ND
ND
ND
ND
ND
ND
ND
ND
ND
ND
ND
ND
ND = No data.
'Factors represent uncontrolled emissions unless otherwise noted.
^Filterable PM is that PM collected on or prior to the filter of an EPA Method 5 (or equivalent) sampling train.
°Condensible PM is that PM collected in the impinger portion of a PM sampling train.
dReference 6.
eFor uncontrolled emissions measured before filter. Based on two tests on pneumatic conveying controlled by a fabric
filter.
Reference 7. From test of mechanical unloading to hopper and subsequent transport of cement by enclosed bucket
elevator to
elevated bins with fabric socks over bin vent.
^Reference 5. Engineering judgement, based on observations and emissions tests of similar controlled sources.
hFrom Section 11.2.1, with k = 0.8, s = 12, S = 20, W = 20, w = 14, and p = 100; units of kg/vehicle kilometers
traveled.
'From Section 8.19.1, for emissions <30 micrometers from inactive storage piles; units of kg/hectare/day
JBased on pneumatic conveying of cement at a truck mix facility. Does not include vehicle traffic or wind erosion from
storage
piles.
10/86
Mineral Products Industry
8.10-3
-------
Table 8.10-2 (English Units)
EMISSION FACTORS FOR CONCRETE BATCHING*
All Emission Factors in the Ib/ton (lb/yd3) of Material Mixed Unless Notedb
Ratings (A-E) Follow Each Emission Factor
Source
(SSC)
Filterable6
PM
PM-10
Condensible PMd
Inorganic
Organic
Sand and aggregate transfer to elevated bin 0.029 E ND ND ND
(3-05-01 l-06)e (0.05)
Cement unloading to elevated storage silo
Pneumaticf 0.27 D ND ND ND
(0.07)
Bucket elevator* 0.24 E ND ND ND
(3-05-011-07) (0.06)
Weigh hopper loading 0.02 E ND ND ND
(3-05-011-OSp (0.04)
Mixer loading (central mix) 0.04 E ND ND ND
(3-05-011-09? (0.07)
Truck loading (truck mix) 0.02 E ND ND ND
(3-05-011-1011 (0.04)
Vehicle traffic (unpaved roads) 16 C ND ND ND
(3-05-01!-__)' (0.02)
Wind erosion from sand and aggregate storage piles 3.5k D ND ND ND
(3-05-01 !-_)> (O.I)1
Total process emissions (truck mix) 0.1 E ND ND ND
(3-05-01 l-_)m (0.2)
ND = No data.
'Factors represent uncontrolled emissions unless otherwise noted.
bBased on a typical yd3 weighing 1.818 kg (4,000 Ib) and containing 227 kg (500 Ib) cement, 564 kg (1,240 Ib) sand,
864 kg (1,900 Ib) coarse aggregate and 164 kg (360 Ib) water.
cFilterable PM is that PM collected on or prior to the filter of an EPA Method 5 (or equivalent) sampling train.
dCondensible PM is that PM collected in the impinger portion of a PM sampling train.
'Reference 6.
fFor uncontrolled emissions measured before filter. Based on two tests on pneumatic conveying controlled by a fabric
filter.
^Reference 7. From test of mechanical unloading to hopper and subsequent transport of cement by enclosed bucket
elevator to elevated bins with fabric socks over bin vent.
Reference 5. Engineering judgement, based on observations and emission tests of similar controlled sources.
'From Section 11.2.1, with k = 0.8, s = 12, S = 20, W = 20, w = 14, and p = 100; units of Ib/vehicle miles traveled;
based on facility producing 23,100 m3/yr (30,000 yd3/yr) of concrete, with average truck load of 6.2 m3 (8 yd3) and
plant road length of 161 meters (0.1 mile).
JFrom Section 8.19.1, for emissions <30 micrometers from inactive storage piles.
kUnits of lb/acre/day.
'Assumes 1,011 m2 (1/4 acre) of sand and aggregate storage at plant with production of 23,000 m3/yr (30,000 yr'lyr).
"Based on pneumatic conveying of cement at a truck mix facility; does not include vehicle traffic or wind erosion from
storage piles.
8.10-4
EMISSION FACTORS
10/86
-------
Predictive equations that allow for emission factor adjustment based on plant specific
conditions are given in Chapter 11. Whenever plant specific data are available, they should be used
in lieu of the fugitive emission factors presented in Table 8.10-1.
References for Section 8.10
1. Air Pollutant Emission Factors, APTD-0923, U. S. Environmental Protection Agency, Research
Triangle Park, NC, April 1970.
2. Air Pollution Engineering Manual, 2nd Edition, AP-40, U. S. Environmental Protection Agency,
Research Triangle Park, NC, 1974. Out of Print.
3. Telephone and written communication between Edwin A. Pfetzing, PEDCo Environmental., Inc.,
Cincinnati, OH, and Richard Morris and Richard Meininger, National Ready Mix Concrete
Association, Silver Spring, MD, May 1984.
4, Development Document for Effluent Limitations Guidelines and Standards of Performance, The
Concrete Products Industries, Draft, U. S. Environmental Protection Agency, Washington, DC,
August 1975.
5. Technical Guidance for Control of Industrial Process Fugitive Particulate Emissions,
EPA-450/3-77-010, U. S. Environmental Protection Agency, Research Triangle Park, NC,
March 1977.
6. Fugitive Dust Assessment at Rock and Sand Facilities in the South Coast Air Basin, Southern
California Rock Products Association and Southern California Ready Mix Concrete Association,
Santa Monica, CA, November 1979.
7. Telephone communication between T. R. Black wood, Monsanto Research Corp., Dayton, OH,
and John Zoller, Pedco Environmental, Inc., Cincinnati, OH, October 18, 1976.
10/86 Mineral Products Industry 8.10-5
-------
8.11 GLASS FIBER MANUFACTURING
8.11.1 General1'4
Glass fiber manufacturing is the high-temperature conversion of various raw materials
(predominantly borosilicates) into a homogeneous melt, followed by the fabrication of this melt into
glass fibers. The two basic types of glass fiber products, textile and wool, are manufactured by
similar processes. A typical diagram of these processes is shown in Figure 8.11-1. Glass fiber
production can be segmented into three phases: raw materials handling, glass melting and refining,
and wool glass fiber forming and finishing, this last phase being slightly different for textile and
wool glass fiber production.
Raw Materials Handling - The primary component of glass fiber is sand, but it also includes
varying quantities of feldspar, sodium sulfate, anhydrous borax, boric acid, and many other materials.
The bulk supplies are received by rail car and truck, and the lesser-volume supplies are received in
drums and packages. These raw materials are unloaded by a variety of methods, including drag
shovels, vacuum systems, and vibrator/gravity systems. Conveying to and from storage piles and
silos is accomplished by belts, screws, and bucket elevators. From storage, the materials are weighed
according to the desired product recipe and then blended well before their introduction into the
melting unit. The weighing, mixing, and charging operations may be conducted in either batch or
continuous mode.
Glass Melting and Refining - In the glass melting furnace, the raw materials are heated to
temperatures ranging from 1500° to 1700°C (2700° to 3100°F) and are transformed through a
sequence of chemical reactions to molten glass. Although there are many furnace designs, furnaces
are generally large, shallow, and well-insulated vessels that are heated from above. In operation, raw
materials are introduced continuously on top of a bed of molten glass, where they slowly mix and
dissolve. Mixing is effected by natural convection, gases rising from chemical reactions, and, in
some operations, by air injection into the bottom of the bed.
Glass melting furnaces can be categorized, by their fuel source and method of heat
application, into four types: recuperative, regenerative, unit, and electric melter. The recuperative,
regenerative, and unit melter furnaces can be fueled by either gas or oil. The current trend is from
gas-fired to oil-fired. Recuperative furnaces use a steel heat exchanger, recovering heat from the
exhaust gases by exchange with the combustion air. Regenerative furnaces use a lattice of brickwork
to recover waste heat from exhaust gases. In the initial mode of operation, hot exhaust gases are
routed through a chamber containing a brickwork lattice, while combustion air is heated by passage
through another corresponding brickwork lattice. About every 20 minutes, the airflow is reversed, so
that the combustion air is always being passed through hot brickwork previously heated by exhaust
gases. Electric furnaces melt glass by passing an electric current through the melt. Electric furnaces
are either hot-top or cold-top. The former use gas for auxiliary heating, and the latter use only the
electric current. Electric furnaces are currently used only for wool glass fiber production because of
the electrical properties of the glass formulation. Unit melters are used only for the "indirect" marble
melting process, getting raw materials from a continuous screw at the back of the furnace adjacent to
the exhaust air discharge. There are no provisions for heat recovery with unit melters.
9/85 Mineral Products Industry 8.11-1
-------
Raw materials
receiving and handling
I
Raw materials storage
Crushing, weighing, mixing
Melting and refining
Direct
process
Wool glass fiber
Indirect
process
Marble forming
Annealing
Marble storage, shipment
Marble melting
Textile glass fiber
Forming
Forming
Binder addition
Sizing, binding addition
Compression
Winding
Oven curing
Oven drying
Cooling
Oven curing
Fabrication
Fabrication
Packaging
Packaging
Raw
material
handling
Glass
melting
and
forming
Fiber
forming
and
finishing
Figure 8.11-1. Typical flow diagram of the glass fiber production process.
8.11-2
EMISSION FACTORS
9/85
-------
In the "indirect" melting process, molten glass passes to a forehearth, where it is drawn off,
sheared into globs, and formed into marbles by roll-forming. The marbles are then stress-relieved in
annealing ovens, cooled, and conveyed to storage or to other plants for later use. In the "direct"
glass fiber process, molten glass passes from the furnace into a refining unit, where bubbles and
particles are removed by settling, and the melt is allowed to cool to the proper viscosity for the fiber
forming operation.
Wool Glass Fiber Forming and Finishing - Wool fiberglass is produced for insulation and is
formed into mats that are cut into batts. (Loose wool is primarily a waste product formed from mat
trimming, although some is a primary product, and is only a small part of the total wool fiberglass
produced. No specific emission data for loose wool production are available.) The insulation is used
primarily in the construction industry and is produced to comply with ASTM C167-64, the "Standard
Test Method for Thickness and Density of Blanket- or Batt-Type Thermal Insulating Material."
Wool fiberglass insulation production lines usually consist of the following processes:
(1) preparation of molten glass, (2) formation of fibers into a wool fiberglass mat, (3) curing the
binder-coated fiberglass mat, (4) cooling the mat, and (5) backing, cutting, and packaging the
insulation. Fiberglass plants contain various sizes, types, and numbers of production lines, although a
typical plant has three lines. Backing (gluing a flat flexible material, usually paper, to the mat),
cutting, and packaging operations are not significant sources of emissions to the atmosphere.
The trimmed edge waste from the mat and the fibrous dust generated during the cutting and
packaging operations are collected by a cyclone and either are transported to a hammer mill to be
chopped into blown wool (loose insulation) and bulk packaged or are recycled to the forming section
and blended with newly formed product.
During the formation of fibers into a wool fiberglass mat (the process known as "forming" in
the industry), glass fibers are made from molten glass, and a chemical binder is simultaneously
sprayed on the fibers as they are created. The binder is a thermosetting resin that holds the glass
fibers together. Although the binder composition varies with product type, typically the binder
consists of a solution of phenol-formaldehyde resin, water, urea, lignin, silane, and ammonia.
Coloring agents may also be added to the binder. Two methods of creating fibers are used by the
industry. In the rotary spin process, depicted in Figure 8.11-2, centrifugal force causes molten glass
to flow through small holes in the wall of a rapidly rotating cylinder to create fibers that are broken
into pieces by an air stream. This is the newer of the two processes and dominates the industry
today. In the flame attenuation process, molten glass flows by gravity from a furnace through
numerous small orifices to create threads that are then attenuated (stretched to the point of breaking)
by high velocity, hot air, and/or a flame. After the glass fibers are created (by either process) and
sprayed with the binder solution, they are collected by gravity on a conveyor belt in the form of a
mat.
The conveyor carries the newly formed mat through a large oven to cure the thermosetting
binder and then through a cooling section where ambient air is drawn down through the mat.
Figure 8.11-3 presents a schematic drawing of the curing and cooling sections. The cooled mat
remains on the conveyor for trimming of the uneven edges. Then, if product specifications require it,
a backing is applied with an adhesive to form a vapor barrier. The mat is then cut into batts of the
desired dimensions and packaged.
9/85 Mineral Products Industry 8.11-3
-------
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8.11-4
EMISSION FACTORS
9/85
-------
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9/85
Mineral Products Industry
8.11-5
-------
Textile Glass Fiber Forming and Finishing - Molten glass from either the direct melting
furnace or the indirect marble melting furnace is temperature-regulated to a precise viscosity and
delivered to forming stations. At the forming stations, the molten glass is forced through heated
platinum bushings containing numerous very small openings. The continuous fibers emerging from
the openings are drawn over a roller applicator, which applies a coating of a water-soluble sizing
and/or coupling agent. The coated fibers are gathered and wound into a spindle. The spindles of
glass fibers are next conveyed to a drying oven, where moisture is removed from the sizing and
coupling agents. The spindles are then sent to an oven to cure the coatings. The final fabrication
includes twisting, chopping, weaving, and packaging the fiber.
8.11.2 Emissions and Controls1'3'4
Emissions and controls for glass fiber manufacturing can be categorized by the three
production phases with which they are associated. Emission factors for the glass fiber manufacturing
industry are given in Tables 8.11-1 through 8.11-3.
Raw Materials Handling - The major emissions from the raw materials handling phase are
fugitive dust and raw material particles generated at each of the material transfer points. Such a point
would be where sand pours from a conveyor belt into a storage silo. The two major control
techniques are wet or moist handling and fabric filters. When fabric filters are used, the transfer
points are enclosed, and air from the transfer area is continuously circulated through the fabric filters.
Glass Melting and Refining - The emissions from glass melting and refining include volatile
organic compounds from the melt, raw material particles entrained in the furnace flue gas, and, if
furnaces are heated with fossil fuels, combustion products. The variation in emission rates among
furnaces is attributable to varying operating temperatures, raw material compositions, fuels, and flue
gas flow rates. Of the various types of furnaces used, electric furnaces generally have the lowest
emission rates, because of the lack of combustion products and of the lower temperature of the melt
surface caused by bottom heating. Emission control for furnaces is primarily fabric filtration. Fabric
filters are effective on paniculate matter (PM) and sulfur oxides (SOX) and, to a lesser extent, on
carbon monoxide (CO), nitrogen oxides (NOX), and fluorides. The efficiency of these compounds is
attributable to both condensation on filterable PM and chemical reaction with PM trapped on the
filters. Reported fabric filter efficiencies on regenerative and recuperative wool furnaces are for PM,
954- percent; SOX, 99+ percent; CO, 30 percent; and fluoride, 91 to 99 percent. Efficiencies on
other furnaces are lower because of lower emission loading and pollutant characteristics.
Wool Fiber Forming and Finishing - Emissions generated during the manufacture of wool
fiberglass insulation include solid particles of glass and binder resin, droplets of binder, and
components of the binder that have vaporized. Glass particles may be entrained in the exhaust gas
stream during forming, curing, or cooling operations. Test data show that approximately 99 percent
of the total emissions from the production line are emitted from the forming and curing sections.
Even though cooling emissions are negligible at some plants, cooling emissions at others may include
fugitives from the curing section. This commingling of emissions occurs because fugitive emissions
from the open terminal end of the curing oven may be induced into the cooling exhaust ductwork and
be discharged into the atmosphere. Solid particles of resin may be entrained in the gas stream in
either the curing or cooling sections. Droplets of organic binder may be entrained in the gas stream
in the forming section or may be a result of condensation of gaseous pollutants as the gas stream is
cooled. Some of the liquid binder used in the forming section is vaporized by the elevated
temperatures in the forming and curing processes. Much of the vaporized material will condense
8.11-6 EMISSION FACTORS 9/85
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Mineral Products Industry
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EMISSION FACTORS
9/85
-------
when the gas stream cools in the ductwork or in the emission control device.
Paniculate matter is the principal pollutant that has been identified and measured at wool
fiberglass insulation manufacturing facilities. It was known that some fraction of the PM emissions
results from condensation of organic compounds used in the binder. Therefore, in evaluating
emissions and control device performance for this source, a sampling method, EPA Reference
Method SE, was used that permitted collection and measurement of both solid particles and condensed
PM.
Tests were performed during the production of R-ll building insulation, R-19 building
insulation, ductboard, and heavy-density insulation. These products, which account for 91 percent of
industry production, had densities ranging from 9.1 to 12.3 kilograms per cubic meter (kg/m3) (0.57
to 0.77 pounds per cubic foot Db/ft3]) for R-ll, 8.2 to 9.3 kg/m3 (0.51 to 0.58 Ib/ft3) for R-19, and
54.5 to 65.7 kg/m3 (3.4 to 4.1 Ib/ft3) for ductboard. The heavy-density insulation had a density of
118.5 kg/m3 (7.4 Ib/ft3). (The remaining 9 percent of industry wool fiberglass production is a variety
of specialty products for which qualitative and quantitative information is not available.) The loss on
ignition (LOI) of the product is a measure of the amount of binder present. The LOI values ranged
from 3.9 to 6.5 percent, 4.5 to 4.6 percent, and 14.7 to 17.3 percent for R-ll, R-19, and ductboard,
respectively. The LOI for heavy-density insulation is 10.6 percent. A production line may be used
to manufacture more than one of these product types because the processes involved do not differ.
Although the data base did not show sufficient differences in mass emission levels to establish
separate emission standards for each product, the uncontrolled emission factors are sufficiently
different to warrant their segregation for AP-42.
The level of emissions control found in the wool fiberglass insulation manufacturing industry
ranges from uncontrolled to control of forming, curing, and cooling emissions from a line. The
exhausts from these process operations may be controlled separately or in combination. Control
technologies currently used by the industry include wet ESP's, low- and high-pressure-drop wet
scrubbers, low- and high-temperature thermal incinerators, high-velocity air filters, and process
modifications. These added control technologies are available to all firms in the industry, but the
process modifications used in this industry are considered confidential. Wet ESP's are considered to
be best demonstrated technology for the control of emissions from wool fiberglass insulation
manufacturing lines. Therefore, it is expected that most new facilities will be controlled in this
manner.
Textile Fiber Forming and Finishing - Emissions from the forming and finishing processes
include glass fiber particles, resin particles, hydrocarbons (primarily phenols and aldehydes), and
combustion products from dryers and ovens. Emissions are usually lower in the textile "fiber glass
process than in the wool fiberglass process because of lower turbulence in the forming step, roller
application of coatings, and use of much less coating per ton of fiber produced.
References for Section 8.11
1. J. R. Schorr et al., Source Assessment: Pressed and Blown Glass Manufacturing Plants,
EPA-600/2-77-005, U.S. Environmental Protection Agency, Research Triangle Park, NC,
January 1977.
2. Annual Book ofASTM Standards, Part 18, ASTM Standard C167-64 (Reapproved 1979),
American Society for Testing and Materials, Philadelphia, PA.
9/85 Mineral Products Industry 8.11-15
-------
3. Standard of Performance For Wool Fiberglass Insulation Manufacturing Plants, 50 FR 7700,
February 25, 1985.
4. Wool Fiberglass Insulation Manufacturing Industry: Background Information for Proposed
Standards, U. S. Environmental Protection Agency, Research Triangle Park, NC, EPA-
450/3-83-022a, December 1983.
5. Screening Study to Determine Need for Standards of Performance for New Sources in the Fiber
Glass Manufacturing Industry—Draft, U. S. Environmental Protection Agency, Research Triangle
Park, NC, December 1976.
8.11-16 EMISSION FACTORS 9/85
-------
8.14 GYPSUM PROCESSING
8.14.1 Process Description1"2
Gypsum is calcium sulfate dihydrate (CaSO4 • 2H2O), a white or gray naturally occurring
mineral. Raw gypsum ore is processed into a variety of products such as a portland cement additive,
soil conditioner, industrial and building plasters, and gypsum wallboard. To produce plasters or
wallboard, gypsum must be partially dehydrated or calcined to produce calcium sulfate hemihydrate
(CaSO4 • l£H2O), commonly called stucco.
A flow diagram for a typical gypsum process producing both crude and finished gypsum
products is shown in Figure 8.14-1. In this process gypsum is crushed, dried, ground, and calcined.
Not all of the operations shown in Figure 8.14-1 are performed at all gypsum plants. Some plants
produce only wallboard, and many plants do not produce soil conditioner.
Gypsum ore, from quarries and underground mines, is crushed and stockpiled near a plant.
As needed, the stockpiled ore is further crushed and screened to about 50 millimeters (2 inches) in
diameter. If the moisture content of the mined ore is greater than about 0.5 weight percent, the ore
must be dried in a rotary dryer or a heated roller mill. Ore dried in a rotary dryer is conveyed to a
roller mill, where it is ground to the extent that 90 percent of it is less 149 micrometers (100 mesh).
The ground gypsum exits the mill in a gas stream and is collected in a product cyclone. Ore is
sometimes dried in the roller mill by heating the gas stream, so that drying and grinding are
accomplished simultaneously and no rotary dryer is needed. The finely ground gypsum ore is known
as landplaster, which may be used as a soil conditioner.
In most plants, landplaster is fed to kettle calciners or flash calciners, where it is heated to
remove three-quarters of the chemically bound water to form stucco. Calcination occurs at
approximately 120° to 150°C (250° to 300°F), and 0.908 megagrams (Mg) (1 ton) of gypsum
calcines to about 0.77 Mg (0.85 ton) of stucco.
In kettle calciners, the gypsum is indirectly heated by hot combustion gas passed through flues
in the kettle, and the stucco product is discharged into a "hot pit" located below the kettle. Kettle
calciners may be operated in either batch or continuous mode. In flash calciners, the gypsum is
directly contacted with hot gases, and the stucco product is collected at the bottom of the calciner.
At some gypsum plants, drying, grinding, and calcining are performed in heated impact mills.
In these mills hot gas contacts gypsum as it is ground. The gas dries and calcines the ore and then
conveys the stucco to a product cyclone for collection. The use of heated impact mills eliminates the
need for rotary dryers, calciners, and roller mills.
Gypsum and stucco are usually transferred from one process to another by means of screw
conveyors or bucket elevators. Storage bins or silos are normally located downstream of roller mills
and calciners but may also be used elsewhere.
7/93 Mineral Products Industry 8.14-1
-------
Crushed rock
storage bins
m
© ©
1 /
©
i
Product
cyclone
Key to Source Classification Codes
S) 3-05-015-05, -06
11 3-05-015-08
E 3-05-015-07
IS 3-06-015-09
(E] 3-05-015-01
E 3-05-015-02
fi2 3-05-O15-04
(H 3-06-015-tt, -12
ID 3-06-015-14
E 3-05-015-18
IB 3-05-015-17
O 3-05-015-21. -22
9
Conveying
ea
storage bins
99
Conveying
SI
Calciner
m
©
Sold as
industrial
and
building
plaster
Key to Emission Sources ;
(T) Point source PM emissions j
(2) Combustion emissions
(3> Fugitive PM emissions
Sold as
prefabricate
Paper roll*
I . Water, foam \ boe
<•" / ' ^\ ^^-—- paper and/or \ prod
(7} T •' ^-^\^"^ pulpwood ^ ^__
Scoring and
chamfering
\,
\ Pan mixer / t - !
i 1 1
t t t v-, [ Multi-deck j
1 Roardline convevor I"""1 ^,u.u'-""»| ^
ird I
ucts/
9
Board end !
sawing j
1 Kiln ' ^ IM
Figure 8.14-1. Overall process flow diagram for gypsum processing/
8.14-2
EMISSION FACTORS
7/93
-------
In the manufacture of plasters, stucco is ground further in a tube or ball mill and then batch-
mixed with retarders and stabilizers to produce plasters with specific setting rates. The thoroughly
mixed plaster is fed continuously from intermediate storage bins to a bagging operation.
In the manufacture of wallboard, stucco from storage is first mixed with dry additives such as
perlite, starch, fiberglass, or vermiculite. This dry mix is combined with water, soap foam,
accelerators and shredded paper, or pulpwood in a pin mixer at the head of a board forming line.
The slurry is then spread between two paper sheets that serve as a mold. The edges of the paper are
scored, and sometimes chamfered, to allow precise folding of the paper to form the edges of the
board. As the wet board travels the length of a conveying line, the calcium sulfate hemihydrate
combines with the water in the slurry to form solid calcium sulfate dihydrate, or gypsum, resulting in
rigid board. The board is rough-cut to length, and it enters a multideck kiln dryer, where it is dried
by direct contact with hot combustion gases or by indirect steam heating. The dried board is
conveyed to the board end sawing area and is trimmed and bundled for shipment.
8.14.2 Emissions and Controls2'7
Potential emission sources in gypsum processing plants are shown in Figure 8.14-1. While
paniculate matter (PM) is the dominant pollutant in gypsum processing plants, several sources may
emit gaseous pollutants also. The major sources of PM emissions include rotary ore dryers, grinding
mills, calciners, and board end sawing operations. Paniculate matter emission factors for these
operations are shown in Table 8.14-1. In addition, emission factors for PM less than or equal to 10
microns in aerodynamic diameter (PM10) emissions from selected processes are presented in
Table 8.14-1. All of these factors are based on output production rates. Particle size data for ore
dryers, calciners, and board end sawing operations are shown in Tables 8.14-2 and 8.14-3.
The uncontrolled emission factors presented in Table 8.14-1 represent the process dust
entering the emission control device. It is important to note that emission control devices are
frequently needed to collect the product from some gypsum processes and, thus, are commonly
thought of by the industry as process equipment and not as added control devices.
Emissions sources in gypsum plants are most often controlled with fabric filters. These
sources include:
- rotary ore dryers (SCC 3-05-015-01) - board end sawing (SCC 3-05-015-21,-22)
- roller mills (SCC 3-05-015-02) - scoring and chamfering (SCC 3-05-015-_)
- impact mills (SCC 3-05-015-13) - plaster mixing and bagging (SCC 3-05-015-16,-17)
- kettle calciners (SCC 3-05-015-11) - conveying systems (SCC 3-05-015-04)
- flash calciners (SCC 3-05-015-12) - storage bins (SCC 3-05-015-09,-10,-14)
Uncontrolled emissions from scoring and chamfering, plaster mixing and bagging, conveying systems,
and storage bins are not well quantified.
Emissions from some gypsum sources are also controlled with electrostatic precipitators
(ESP's). These sources include rotary ore dryers, roller mills, kettle calciners, and conveying
systems. Although rotary ore dryers may be controlled separately, emissions from roller mills and
conveying systems are usually controlled jointly with kettle calciner emissions. Moisture in the kettle
calciner exit gas improves the ESP performance by lowering the resistivity of the dust.
7/93 Mineral Products Industry 8.14-3
-------
TABLE 8.14-1 (METRIC UNITS)
EMISSION FACTORS FOR GYPSUM PROCESSING*
All Emission Factors in kg/Mg of Output Rate
Ratings (A-E) follow Each Emission Factor
Process (SCC)
Crushers, screens, stockpiles, and roads
(3-05-015-05,-06,-07,-08)
Rotary ore dryers (3-05-015-01)
Rotary ore dryers w/ fabric filters
(3-05-015-01)
Roller mills w/ cyclones (3-05-015-02)
Roller mills w/ fabric filters
(3-05-015-02)
Roller mill and kettle calciner
w/electrostatic precipitators
(3-05-015-02,-! 1)
Continuous kettle calciners and hot pit
(3-05-015-11)
Continuous kettle calciners and hot pit
w/ fabric filters (3-05-015-11)
Continuous kettle calciners w/ cyclones
and electrostatic precipitators
(3-05-015-11)
Flash calciners (3-05-015-12)
Flash calciners w/fabric filters
(3-05-015-12)
Impact mills w/cyclones (3-05-015-13)
Impact mills w/ fabric filters
(3-05-015-13)
Board end sawing— 2.4-m boards
(3-05-015-21)
Board end sawing~3.7-m boards
(3-05-015-22)
Board end sawing w/ fabric filters-2.4-
and 3.7-m boards (3-05-015-21, -22)
Filterable PMb
d
0.0042(FFF)1-7e
0.020S
1.3h
0.06011
O.OSO11''
21J
0.0030J
0.050*
19k
0.020k
50m
0.010m
0.040"
0.030"
36°
D
D
D
D
D
D
D
D
D
D
D
D
D
D
D
PM10
d
0.00034(FFF)1-7
0.0052
ND
ND
ND
13
ND
ND
7.2
0.017
ND
ND
ND
ND
27
D
D
D
D
D
D
CO2C
NA
12f
NA
NA
NA
ND
ND
NA
NA
551
ND
NA
NA
NA
NA
NA
D
D
8.14-4
EMISSION FACTORS
7/93
-------
Table 8.14-1 (METRIC UNITS) (continued)
ND = No data available. NA = Not applicable.
"Factors represent uncontrolled emissions unless otherwise specified.
bFilterable PM is that PM collected on or prior to an EPA Method 5 (or equivalent) sampling train.
Typical pollution control devices generally have a negligible effect on CO2 emissions.
dFactors for these operations are in Sections 8.19 and 11.2.
References 3-4, 8, 11-12. Equation is for the emission rate upstream of any process cyclones and
applies only to concurrent rotary ore dryers with flowrates of 7.5 cubic meters per second (m3/s) or
less. FFF in the uncontrolled emission factor equation is "flow feed factor," the ratio of gas mass
rate per unit dryer cross section area to the dry mass feed rate, in the following units: (kg/hr-m2 of
gas flow)/(Mg/hr dry feed). Measured uncontrolled emission factors for 4.2 and 5.7 m3/s range
from 5 to 60 kg/Mg.
References 3-4.
References 3-4, 8, 11-12. Applies to rotary dryers with and without cyclones upstream of fabric
filter.
hReferences 11-14. Applies to both heated and unheated roller mills.
'References 11-14. Factor is for combined emissions from roller mills and kettle calciners, based on
the sum of the roller mill and kettle calciner output rates.
^References 4-5, 11, 13-14. Emission factors based on the kettle and the hot pit do not apply to batch
kettle calciners.
References 3, 6, 10.
'References 3, 6, 9.
""References 9, 15. As used here, an impact mill is a process unit used to dry, grind, and calcine
gypsum simultaneously.
"References 4-5, 16. Emission factor units = kg/m2. Based on 13 mm board thickness and 1.2 m
board width. For other thicknesses, multiply the appropriate emission factor by 0.079 times board
thickness in mm.
°References 4-5, 16. Emission factor units = kg/106 m2.
7/93 Mineral Products Industry 8.14-5
-------
TABLE 8.14-1 (ENGLISH UNITS)
EMISSION FACTORS FOR GYPSUM PROCESSING'
All Emission Factors in Rate
Ratings (A-E) follow Each Emission Factor
Process (SCC)
Crushers, screens, stockpiles, and roads
(3-05-015-05,-06,-07,-08)
Rotary ore dryers (3-05-015-01)
Rotary ore dryers w/fabric filters
(3-05-015-01)
Roller mills w/cyclones (3-05-015-02)
Roller mills w/ fabric filters
(3-05-015-02)
Roller mill and kettle calciner w/
electrostatic precipitators
(3-05-015-02,-H)
Continuous kettle calciners and hot pit
(3-05-015-11)
Continuous kettle calciners and hot pit
w/ fabric filters (3-05-015-11)
Continuous kettle calciners w/ cyclones
and electrostatic precipitators
(3-05-015-11)
Flash calciners (3-05-015-12)
Flash calciners w/fabric filters
(3-05-015-12)
Impact mills w/ cyclones (3-05-015-13)
Impact mills w/ fabric filters
(3-05-015-13)
Board end sawing~8-ft boards
(3-05-015-21)
Board end sawing- 12-ft boards
(3-05-015-22)
Board end sawing w/ fabric filters-S-
and 12-ft boards (3-05-015-21, -22)
Filterable PMb
d
0.16(FFF)1/77e
0.0408
2.6h
0.12h
O.CWO11'1
41J
0.0060'
0.090*
37k
0.040*
100m
0.020m
0.80"
0.50n
7.5°
D
D
D
D
D
D
D
D
D
D
D
D
D
D
D
PM10
d
O.OlStFFF)1-7
0.010
ND
ND
ND
26
ND
ND
14
0.034
ND
ND
ND
ND
5.7
D
D
D
D
D
D
C02C
NA
23f
NA
NA
NA
ND
ND
NA
NA
no1
ND
NA
NA
NA
NA
NA
D
D
8.14-6
EMISSION FACTORS
7/93
-------
Table 8.14-1 (ENGLISH UNITS) (continued)
ND = No data available. NA = Not applicable.
"Factors represent uncontrolled emissions unless otherwise specified.
bFilterable PM is that particulate collected on or prior to an EPA Method 5 (or equivalent) sampling
train.
"Typical pollution control devices generally have a negligible effect on CO2 emissions.
dFactors for these operations are in Sections 8.19 and 11.2.
References 3-4, 8, 11-12. Equation is for the emission rate upstream of any process cyclones and
applies only to concurrent rotary ore dryers with flowrates of 16,000 actual cubic feet per minute
(acfrn) or less. FFF in the uncontrolled emission factor equation is "flow feed factor," the ratio of
gas mass rate per unit dryer cross section area to the dry mass feed rate, in the following units:
(lb/hr-ft2 of gas flow)/(ton/hr dry feed). Measured uncontrolled emission factors for 9,000 and
12,000 acfrn range from 10 to 120 Ib/ton.
References 3-4.
gReferences 304, 8, 11-12. Applies to rotary dryers with and without cyclones upstream of fabric
filter.
References 11-14. Applies to both heated and unheated roller mills.
'References 11-14. Factor is for combined emissions from roller mills and kettle calciners, based on
the sum of the roller mill and kettle calciner output rates.
••References 4-05, 11, 13-14. Emission factors based on the kettle and the hot pit do not apply to
batch kettle calciners.
References 3, 6, 10.
'References 3, 6, 9.
""References 9, 15. As used here, an impact mill is a process unit used to dry, grind, and calcine
gypsum simultaneously.
"References 4-5, 16. Emission factor units = lb/100 ft2. Based on 1/2-in. board thickness and 4-ft
board width. For other thicknesses, multiply the appropriate emission factor by 2 times board
thickness in inches.
°References 4-5, 16. Emission factor units = lb/106 ft2.
7/93 Mineral Products Industry 8.14-7
-------
TABLE 8.14-2. SUMMARY OF PARTICLE SIZE DISTRIBUTION DATA FOR
UNCONTROLLED PM EMISSIONS FROM GYPSUM PROCESSING*
EMISSION FACTOR RATING: D
Diameter
(microns)
Cumulative % less than diameter
Rotary ore
dryerb
Rotary ore dryer
with cyclone0
Continuous kettle
calcinerd
Flash calciner6
2.0 1 12 17 10
10.0 8 45 63 38
*Weight percent given as filterable PM. Diameter is given as aerodynamic diameter, except for
continuous kettle calciner, which is given as equivalent diameter, as determined by Banco and
Sedigraph analyses.
Reference 3.
°Reference 4.
References 4, 5.
References 3, 6.
TABLE 8.14-3. SUMMARY OF PARTICLE SIZE DISTRIBUTION DATA FOR
FABRIC FILTER-CONTROLLED PM EMISSIONS FROM GYPSUM MANUFACTURING*
EMISSION FACTOR RATING: D
Diameter
(microns)
Cumulative % less than diameter
Rotary ore dryerb
2.0 9
10.0 26
Flash calciner0
52
84
Board end sawing0
49
76
"Aerodynamic diameters, Andersen analysis.
bReference 3.
°Reference 3, 6.
8.14-8
EMISSION FACTORS
7/93
-------
Other sources of PM emissions in gypsum plants are primary and secondary crushers,
screens, stockpiles, and roads. If quarrying is part of the mining operation, PM emissions may also
result from drilling and blasting. Emission factors for some of these sources are presented in
Sections 8.19 and 11.2. Gaseous emissions from gypsum processes result from fuel combustion and
may include nitrogen oxides, sulfur oxides, carbon monoxide, and carbon dioxide (CO2). Processes
using fuel include rotary ore dryers, heated roller mills, impact mills, calciners, and board drying
kilns. Although some plants use residual fuel oil, the majority of the industry uses clean fuels such as
natural gas or distillate fuel oil. Emissions from fuel combustion may be estimated using emission
factors presented in Sections 1.3 and 1.4 and fuel consumption data in addition to those emission
factors presented in Table 8.14-1.
REFERENCES FOR SECTION 8.14
1. Kirk-Othmer Encyclopedia of Chemical Technology, Volume 4, John Wiley & Sons, Inc., New
York, 1978.
2. Gypsum Industry - Background Information for Proposed Standards (Draft), U.S. Environmental
Protection Agency, Research Triangle Park, NC, April 1981.
3. Source Emissions Test Report, Gold Bond Building Products, EMB-80- GYP-1,
U. S. Environmental Protection Agency, Research Triangle Park, NC, November 1980.
4. Source Emissions Test Report, United States Gypsum Company, EMB-80- GYP-2,
U. S. Environmental Protection Agency, Research Triangle Park, NC, November 1980.
5. Source Emission Tests, United States Gypsum Company Wallboard Plant, EMB-80-GYP-6,
U. S. Environmental Protection Agency, Research Triangle Park, NC, January 1981.
6. Source Emission Tests, Gold Bond Building Products, EMB-80-GYP-5, U. S. Environmental
Protection Agency, Research Triangle Park, NC, December 1980.
7. S. Oglesby and G. B. Nichols, A Manual of Electrostatic Precipitation Technology, Part II:
Application Areas, APTD-0611, U. S. Environmental Protection Agency, Cincinnati, OH,
August 25, 1970.
8. Official Air Pollution Emission Tests Conducted on the Rock Dryer and No. 3 Calcidyne Unit,
Gold Bond Building Products, Report No. 5767, Rosnagel and Associates, Medford, NJ,
August 3, 1979.
9. Particulate Analysis ofCalcinator Exhaust at Western Gypsum Company, Kramer, Callahan and
Associates, Rosario, NM, April 1979. Unpublished.
10. Official Air Pollution Tests Conducted on the #7 Calcidyner Baghouse Exhaust at the National
Gypsum Company, Report No. 2966, Rossnagel and Associates, Atlanta, GA, April 10, 1978.
11. Report to United States Gypsum Company on Particulate Emission Compliance Testing,
Environmental Instrument Systems, Inc., South Bend, IN, November 1975. Unpublished.
7/93 Mineral Products Industry 8.14-9
-------
12. Paniculate Emission Sampling and Analysis, United States Gypsum Company, Environmental
Instrument Systems, Inc., South Bend, IN, July 1973. Unpublished.
13. Written communication from Wyoming Air Quality Division, Cheyenne, WY, to M. Palazzolo,
Radian Corporation, Durham, NC, 1980.
14. Written communication from V. J. Tretter, Georgia-Pacific Corporation, Atlanta, GA, to
M. E. Kelly, Radian Corporation, Durham, NC, November 14, 1979.
15. Telephone communication between M. Palazzolo, Radian Corporation, Durham, NC, and
D. Louis, C. E. Raymond Company, Chicago, IL, April 23, 1981.
16. Written communication from M. Palazzolo, Radian Corporation, Durham, NC, to B. L. Jackson,
Weston Consultants, West Chester, PA, June 19, 1980.
17. Telephone communication between P. J. Murin, Radian Corporation, Durham, NC, and
J. W. Pressler, U. S. Department of the Interior, Bureau of Mines, Washington, DC,
November 6, 1979.
8.14-10 EMISSION FACTORS 7/93
-------
8.16 MINERAL WOOL MANUFACTURING
8.16.1 General1'2
Mineral wool often is defined as any fibrous glassy substance made from minerals (typically
natural rock materials such as basalt or diabase) or mineral products such as slag and glass. Because
glass wool production is covered separately in AP-42 (Section 8.11), this section deals only with the
production of mineral wool from natural rock and slags such as iron blast furnace slag, the primary
material, and copper, lead, and phosphate slags. These materials are processed into insulation and
other fibrous building materials that are used for structural strength and fire resistance. Generally,
these products take one of four forms: "blowing" wool or "pouring" wool, which is put into the
structural spaces of buildings; batts, which may be covered with a vapor barrier of paper or foil and
are shaped to fit between the structural members of buildings; industrial and commercial products
such as high-density fiber felts and blankets, which are used for insulating boilers, ovens, pipes,
refrigerators, and other process equipment; and bulk fiber, which is used as a raw material in
manufacturing other products, such as ceiling tile, wall board, spray-on insulation, cement, and
mortar.
Mineral wool manufacturing facilities are included in Standard Industrial Classification (SIC)
Code 3296, mineral wool. This SIC code also includes the production of glass wool insulation
products, but those facilities engaged in manufacturing textile glass fibers are included in SIC
Code 3229. The six digit source category code (SCC) for mineral wool manufacturing is 3-05-017.
8.16.2 Process Description1'4'5
Most mineral wool produced in the United States today is produced from slag or a mixture of
slag and rock. Most of the slag used by the industry is generated by integrated iron "and steel plants
as a blast furnace byproduct from pig iron production. Other sources of slag include the copper,
lead, and phosphate industries. The production process has three primary components—molten
mineral generation in the cupola, fiber formation and collection, and final product formation.
Figure 8.16-1 illustrates the mineral wool manufacturing process.
The first step in the process involves melting the mineral feed. The raw material (slag and
rock) is loaded into a cupola in alternating layers with coke at weight ratios of about 5 to 6 parts
mineral to 1 part coke. As the coke is ignited and burned, the mineral charge is heated to the molten
state at a temperature of 1300° to 1650°C (2400° to 3000°F). Combustion air is supplied through
tuyeres located near the bottom of the furnace. Process modifications at some plants include air
enrichment and the use of natural gas auxiliary burners to reduce coke consumption. One facility also
reported using an aluminum flux byproduct to reduce coke consumption.
The molten mineral charge exits the bottom of the cupola in a water-cooled trough and falls
onto a fiberization device. Most of the mineral wool produced in the United States is made by
variations of two fiberization methods. The Powell process uses groups of rotors revolving at a high
rate of speed to form the fibers. Molten material is distributed in a thin film on the surfaces of the
rotors and then is thrown off by centrifugal force. As the material is discharged from the rotor, small
globules develop on the rotors and form long, fibrous tails as they travel horizontally. Air or steam
7/93 Mineral Products Industry 8.16-1
-------
Slag, Coka,
Additives
,
&nlsslon
Control
equipment
]
J Cupola
N
CSCC' 3-D3-017-013
From Proceselng
Granulated
Products
8.16-2
Figure 8.16-1. Mineral wool manufacturing process flow diagram.
EMISSION FACTORS
7/93
-------
may be blown around the rotors to assist in fiberizing the material. A second fiberization method, the
Downey process, uses a spinning concave rotor with air or steam attenuation. Molten material is
distributed over the surface of the rotor, from which it flows up and over the edge and is captured
and directed by a high-velocity stream of air or steam.
During the spinning process, not all globules that develop are converted into fiber. The
nonfiberized globules that remain are referred to as "shot." In raw mineral wool, as much as half of
the mass of the product may consist of shot. As shown in Figure 8.16-1, shot is usually separated
from the wool by gravity immediately following fiber ization.
Depending on the desired product, various chemical agents may be applied to the newly
formed fiber immediately following the rotor. In almost all cases, an oil is applied to suppress dust
and, to some degree, anneal the fiber. This oil can be either a proprietary product or a medium-
weight fuel or lubricating oil. If the fiber is intended for use as loose wool or bulk products, no
further chemical treatment is necessary. If the mineral wool product is required to have structural
rigidity, as in batts and industrial felt, a binding agent is applied with or in place of the oil treatment.
This binder is typically a phenol-formaldehyde resin that requires curing at elevated temperatures.
Both the oil and the binder are applied by atomizing the liquids and spraying the agents to coat the
airborne fiber.
After formation and chemical treatment, the fiber is collected in a blowchamber.
Resin-and/or oil-coated fibers are drawn down on a wire mesh conveyor by fans located beneath the
collector. The speed of the conveyor is set so that a wool blanket of desired thickness can be
obtained.
Mineral wool containing the binding agent is carried by conveyor to a curing oven, where the
wool blanket is compressed to the appropriate density and the binder is baked. Hot air, at a
temperature of 150° to 320°C (300° to 600°F), is forced through the blanket until the binder has set.
Curing time and temperature depend on the type of binder used and the mass rate through the oven.
A cooling section follows the oven, where blowers force air at ambient temperatures through the wool
blanket.
To make batts and industrial felt products, the cooled wool blanket is cut longitudinally and
transversely to the desired size. Some insulation products are then covered with a vapor barrier of
aluminum foil or asphalt-coated kraft paper on one side and untreated paper on the other side. The
cutters, vapor barrier applicators, and conveyors are sometimes referred to collectively as a batt
machine. Those products that do not require a vapor barrier, such as industrial felt and some
residential insulation batts, can be packed for shipment immediately after cutting.
Loose wool products consist primarily of blowing wool and bulk fiber. For these products,
no binding agent is applied, and the curing oven is eliminated. For granulated wool products, the
fiber blanket leaving the blowchamber is fed to a shredder and pelletizer. The pelletizer forms small,
1-inch diameter pellets and separates shot from the wool. A bagging operation completes the
processes. For other loose wool products, fiber can be transported directly from the blowchamber to
a baler or bagger for packaging.
7/93 Mineral Products Industry 8.16-3
-------
8.16.3 Emissions and Controls1'13
The sources of emissions in the mineral wool manufacturing industry are the cupola; binder
storage, mixing, and application; the blow chamber; the curing oven; the mineral wool cooler;
materials handling and bagging operations; and wastewater treatment and storage. With the exception
of lead, the industry emits the full range of criteria pollutants. Also, depending on the particular
types of slag and binding agents used, the facilities may emit both metallic and organic hazardous air
pollutants (HAP's).
The primary source of emissions in the mineral wool manufacturing process is the cupola. It
is a significant source of particulate matter (PM) emissions and is likely to be a source of PM less
than 10 micrometers (/tin) in diameter (PM-10) emissions, although no particle size data are available.
The cupola is also a potential source of HAP metal emissions attributable to the coke and slags used
in the furnace. Coke combustion in the furnace produces carbon monoxide (CO), carbon dioxide
(CO2), and nitrogen oxide (NOX) emissions. Finally, because blast furnace slags contain sulfur, the
cupola is also a source of sulfur dioxide (SO2) and hydrogen sulfide (H2S) emissions.
The blowchamber is a source of PM (and probably PM-10) emissions. Also, the annealing
oils and binders used in the process can lead to VOC emissions from the process. Other sources of
VOC emissions include batt application, the curing oven, and wastewater storage and treatment.
Finally, fugitive PM emissions can be generated during cooling, handling, and bagging operations.
Tables 8.16-1 and 8.16-2 present emission factors for filterable PM emissions from various mineral
wool manufacturing processes; Tables 8-16.3 and 8.16-4 show emission factors for CO, CO2, SO2,
and sulfates; and Tables 8.16-5 and 8.16-6 present emission factors for NOX, N2O, H2S and
fluorides.
Mineral wool manufacturers use a variety of air pollution control techniques, but most are
directed toward PM control with minimal control of other pollutants. The industry has given greatest
attention to cupola PM control, with two-thirds of the cupolas in operation having fabric filter control
systems. Some cupola exhausts are controlled by wet scrubbers and electrostatic precipitators
(ESP's); cyclones are also used for cupola PM control either alone or in combination with other
control devices. About half of the blow chambers in the industry also have some level of PM
control, with the predominant control device being low-energy wet scrubbers. Cyclones and fabric
filters have been used to a limited degree on blow chambers. Finally, afterburners have been used to
control VOC emissions from blow chambers and curing ovens and CO emissions from cupolas.
8.16-4 EMISSION FACTORS 7/93
-------
Table 8.16-1. (Metric Units)
EMISSION FACTORS FOR MINERAL WOOL MANUFACTURING*
Process (SCC) kg
P
Cupola0 (30501701)
Cupola with fabric filterd (30501701)
Reverberatory ftirnacee (30501702)
Batt curing oven6 (30501704)
Batt curing oven with ESPf (30501704)
Blow chamber0 (30501703)
Blow chamber with wire mesh
Cooler6 (30501705)
filter^ (30501703)
Filterable PMb
/Mg of Emission
roduct Factor Rating
8.2 E
0.051 D
2.4 E
1.8 E
0.36 D
6.0 E
0.45 D
1.2 E
"Factors represent uncontrolled emissions unless otherwise noted.
bFilterable PM is that PM collected on or prior to the filter of an EPA
Method 5 (or equivalent) sampling train.
"References 1, 12. Activity level is assumed to be total feed charged.
References 6, 7, 8, 10, and 11. Activity level is total feed charged.
Reference 12.
'Reference 9.
^Reference 7. Activity level is mass of molten mineral feed charged.
7/93
Mineral Products Industry
8.16-5
-------
Table 8.16-2. (English Units)
EMISSION FACTORS FOR MINERAL WOOL MANUFACTURING*
Process (SCC)
Cupola0 (30501701)
Cupola with fabric filterd (30501701)
Reverberatory furnace6 (30501702)
Batt curing ovene (30501704)
Batt curing oven with ESPf (30501704)
Blow chamber0 (30501703)
Blow chamber with wire mesh filter^ (30501703)
Cooler6 (30501705)
Filterable PMb
Ib/ton of
product
16
0.10
4.8
3.6
0.72
12
0.91
2.4
Emission
Factor Rating
E
D
E
E
D
E
D
E
"Factors represent uncontrolled emissions unless otherwise noted.
bFilterable PM is that PM collected on or prior to the filter of an EPA
Method 5 (or equivalent) sampling train.
Reference 1, 12. Activity level is assumed to be total feed charged.
dReferences 6, 7, 8, 10, and 11. Activity level is total feed charged.
6Reference 12.
Reference 9.
gReference 7. Activity level is mass of molten mineral feed charged.
8.16-6
EMISSION FACTORS
7/93
-------
Table 8.16-3 (Metric Units)
EMISSION FACTORS FOR MINERAL WOOL MANUFACTURING*
Source (SCC)
C0b
kg/Mg of
total feed
charged
Cupola (30501701) 125
Cupola with fabric NA
filter (30501701)
Batt curing oven ND
(30501704)
Blow chamber ND
(30501703)
Cooler (30501705) ND
Emission
Factor
Rating
C02b
kg/Mg of
total feed
charged
D 260
NA
ND
80e
ND
Emissio
n Factor
Rating
S02
kg/Mg of
total feed
charged
D 4.0C
NA
0.58d
E 0.43d
0.034d
Emission
Factor
Rating
SO3
kg/Mg of
total feed
charged
D 3.2d
0.077b
E ND
E ND
E ND
Emissio
n Factor
Rating
E
E
NA = Not applicable.
ND = No data available.
*Factors represent uncontrolled emissions unless otherwise noted.
Reference 6.
cReferences 6,10, and 11.
dReference 12.
Reference 9.
7/93
Mineral Products Industry
8.16-7
-------
Table 8.16-4 (English Units)
EMISSION FACTORS FOR MINERAL WOOL MANUFACTURING*
Source (SCC)
C0b
lb/ton of
total feed
charged
Cupola (30501701) 250
Cupola with fabric filter NA
(30501701)
Batt curing oven ND
(30501704)
Blow chamber ND
(30501703)
Cooler (30501705) ND
Emission
Factor
Rating
C02b
lb/ton of
total feed
charged
D 520
NA
ND
160e
ND
Emission
Factor
Rating
SO2
lb/ton of
total feed
charged
D 8.0*
NA
1.2d
E 0.087d
0.068d
Emission
Factor
Rating
SO3
lb/ton of
total feed
charged
D 6.3d
0.15b
E ND
E ND
E ND
Emission
Factor
Rating
E
E
NA = Not applicable.
ND = No data available.
"Factors represent uncontrolled emissions unless otherwise noted.
Reference 6.
References 6, 10, and 11.
Reference 12.
Reference 9.
8.16-8
EMISSION FACTORS
7/93
-------
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Mineral Products Industry
8.16-9
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REFERENCES FOR SECTION 8.16
1. Source Category Survey: Mineral Wool Manufacturing Industry, EPA-450/3-80-016, U. S.
Environmental Protection Agency, Research Triangle Park, NC, March 1980.
2. The Facts on Rocks and Slag Wool, Pub. No. N 020, North American Insulation
Manufacturers Association, Alexandria, VA, Undated.
3. ICF Corporation, Supply Response to Residential Insulation Retrofit Demand, Report to the
Federal Energy Administration, Contract No. P-14-77-5438-0, Washington, D.C.,
June 1977.
4. Personal communication between F. May, U.S.G. Corporation, Chicago, Illinois, and
R. Marinshaw, Midwest Research Institute, Gary, NC, June 5, 1992.
5. Memorandum from K. Schuster, N.C. Department of Environmental Management, to M.
Aldridge, American Rockwool, April 25, 1988.
6. Sulfur Oxide Emission Tests Conducted on the #7 and #2 Cupola Stacks in Leeds, Alabama
for Rock Wool Company, November 8 & 9, 1988, Guardian Systems, Inc., Leeds, AL,
Undated.
7. Paniculate Emissions Tests for U.S. Gypsum Company on the Number 4 Dry Filter and
Cupola Stack Located in Birmingham, Alabama on January 14, 1981, Guardian Systems,
Inc., Birmingham, AL, Undated.
8. Untitled Test Report, Cupolas Nos. 1, 2, and 3, U.S. Gypsum, Birmingham, AL, June 1979.
9. Paniculate Emission Tests on Batt Curing Oven for U.S. Gypsum, Birmingham, Alabama on
October 31-November 1, 1977, Guardian Systems, Inc., Birmingham, AL, Undated.
10. J.V. Apicella, Paniculate, Sulfur Dioxide, and Fluoride Emissions from Mineral Wool
Emission, with Varying Charge Compositions, American Rockwool, Inc. Spring Hope, N. C.
27882, Alumina Company of America, Alcoa Center, PA, June 1988.
11. J.V. Apicella, Compliance Repon on Paniculate, Sulfur Dioxide, Fluoride, and Visual
Emissions from Mineral Wool Production, American Rockwool, Inc., Spring Hope, NC
27882, Aluminum Company of America, Alcoa Center, PA, February 1988.
12. J.L. Spinks, "Mineral Wool Furnaces," In: Air Pollution Engineering Manual, J.A.
Danielson, ed., U. S. DHEW, PHS, National Center for Air Pollution Control, Cincinnati,
OH. PHS Publication Number 999-AP-40, 1967, pp. 343-347.
13. Personal communication between M. Johnson, U. S. Environmental Protection Agency,
Research Triangle Park, NC, and D. Bullock, Midwest Research Institute, Gary, NC,
March 22, 1993.
7/93 Mineral Products Industry 8.16-11
-------
8.17 PERLITE PROCESSING
8.17.1 Process Description1 >2
Perlite is a glassy volcanic rock with a pearl-like luster. It usually exhibits numerous
concentric cracks that cause it to resemble an onion skin. A typical perlite sample is composed of 71
to 75 percent silicon dioxide, 12.5 to 18.0 percent alumina, 4 to 5 percent potassium oxide, 1 to
4 percent sodium and calcium oxides, and trace amounts of metal oxides.
Crude perlite ore is mined, crushed, dried in a rotary dryer, ground, screened, and shipped to
expansion plants. Horizontal rotary or vertical stationary expansion furnaces are used to expand the
processed perlite ore.
The normal size of crude perlite expanded for use in plaster aggregates ranges from plus
250 micrometers (/*m) (60 mesh) to minus 1.4 millimeters (mm) (12 mesh). Crude perlite expanded
for use as a concrete aggregate ranges from 1 mm (plus 16 mesh) to 0.2 mm (plus 100 mesh).
Ninety percent of the crude perlite ore expanded for horticultural uses is greater than 841 /*m
(20 mesh).
Crude perlite is mined using open-pit methods and then is moved to the plant site, where it is
stockpiled. Figure 8.17-1 is a flow diagram of crude ore processing. The first processing step is to
reduce the diameter of the ore to approximately 1.6 centimeters (cm) (0.6 inch [in.]) in a primary jaw
crusher. The crude ore is then passed through a rotary dryer, which reduces the moisture content
from between 4 and 10 percent to less than 1 percent.
After drying, secondary grinding takes place in a closed-circuit system using screens, air
classifiers, hammer mills, and rod mills. Oversized material produced from the secondary circuit is
returned to the primary crusher. Large quantities of fines, produced throughout the processing
stages, are removed by air classification at designated stages. The desired size processed perlite ore
is stored until it is shipped to an expansion plant.
At the expansion plants, the processed ore is either preheated or fed directly to the furnace.
Preheating the material to approximately 430 °C (800 °F) reduces the amount of fines produced in the
expansion process, which increases usable output and controls the uniformity of product density. In
the furnace, the perlite ore reaches a temperature of 760° to 980°C (1400° to 1800°F), at which
point it begins to soften to a plastic state where the entrapped combined water is released as steam.
This causes the hot perlite particles to expand 4 to 20 times their original size. A suction fan draws
the expanded particles out of the furnace and transports them pneumatically to a cyclone classifier
system to be collected. The air-suspended perlite particles are also cooled as they are transported to
the collection equipment. The cyclone classifier system collects the expanded perlite, removes the
excessive fines, and discharges gases to a baghouse or wet scrubber for air pollution control.
The grades of expanded perlite produced can also be adjusted by changing the heating cycle,
altering the cutoff points for size collection, and blending various crude ore sizes. All processed
products are graded for specific uses and are usually stored before being shipped. Most production
rates are less than 1.8 megagrams per hour (Mg/hr) megagrams (2 tons/hr), and expansion furnace
7/93 Mineral Products Industry 8.17-1
-------
STORAGE
DRYER
STORAGE
SCREENING
AND SIZING
BAGHOUSE OR
WET SCRUBBER
STORAGE
BINS
EXPANSION
FURNACE
CSCC 3-05-018-01)
BAGGING
.AND
SHIPPING
O D C)
SHIPPING
TO EXPANSION
PLANT
8.17-2
Figure 8.17-1. Flow diagram for perlite processing.1
EMISSION FACTORS
7/93
-------
temperatures range from 870° to 980°C (1600° to 1800°F). Natural gas is typically used for fuel,
although No. 2 fuel oil and propane are occasionally used. Fuel consumption varies from 2,800 to
8,960 kilojoules per kilogram (Id/kg) (2.4 x 106 to 7.7 x 106 British thermal units per ton [Btu/ton])
of product.
8.17.2 Emissions and Controls1'3'11
The major pollutant of concern emitted from perlite processing facilities is particulate matter
(PM). The dryers, expansion furnaces, and handling operations can all be sources of PM emissions.
Emissions of nitrogen oxides from perlite expansion and drying generally are negligible. When
sulfur-containing fuels are used, sulfur dioxide (SO2) emissions may result from combustion sources.
However, the most common type of fuel used in perlite expansion furnaces and dryers is natural gas,
which is not a significant source of SO2 emissions.
Test data from one perlite plant indicate that perlite expansion furnaces emit a number of trace
elements, including aluminum, calcium, chromium, fluorine, iron, lead, magnesium, manganese,
mercury, nickel, titanium, and zinc. However, because the data consist of a single test run, emission
factors were not developed for these elements. The sample also was analyzed for beryllium, uranium,
and vanadium, but these elements were not detected.
To control PM emissions from both dryers and expansion furnaces, the majority of perlite
plants use baghouses, some use cyclones either alone or in conjunction with baghouses, and a few use
scrubbers. Frequently, PM emissions from material handling processes and from the dryers are
controlled by the same device. Large plants generally have separate fabric filters for dryer emissions,
whereas small plants often use a common fabric filter to control emissions from dryers and materials
handling operations. In most plants, fabric filters are preceded by cyclones for product recovery.
Wet scrubbers are also used in a small number of perlite plants to control emissions from perlite
milling and expansion sources.
Table 8.17-1 presents emission factors for filterable PM and CO2 emissions from the
expanding and drying processes.
7/93 Mineral Products Industry 8.17-3
-------
Table 8.17-1 (Metric Units). EMISSION FACTORS FOR PERLITE PROCESSING8
Process
Filterable PN
kg/Mg Em
Perlite Fa
(SCC) Expanded Ra
Expansion furnace (3-05-0 18-01) ND
Expansion furnace with
(3-05-018-01)
lb CO2
ssion kg/Mg Emission
ctor Perlite Factor
iting Expanded Rating
420C D
wet cyclone l.ld D NA
Expansion furnace with cyclone 0.15e D NA
and baghouse (3-05-018-01)
Dryer (3-05-01 8-_J
ND
16f D
Dryer with baghouse (3-05-0 18-_J 0.64f D NA
Dryer with cyclones and baghouses
(3-05-01 8-_J 0.1 3«
D NA
Table 8.17-1 (English Units). EMISSION FACTORS FOR PERLITE PROCESSING3
lb
Pe
Process (SCC) Exp
Filterable PMb
/ton Emission
srlite Factor
anded Rating
Expansion furnace (3-05-0 18-01) ND
Expansion furnace with wet cyclone 2
(3-05-018-01)
.ld D
Expansion furnace with cyclone 0.29e D
and baghouse (3-05-018-01)
Dryer (3-05-01 8-_J ND
Dryer with baghouse (3-05-0 18-_) 1.28f D
Dryer with cyclones and baghouses 0
(3-05-018-_)
258 D
C02
Ib/ton
Perlite
Expanded
850C
NA
NA
31f
NA
NA
Emission
Factor
Rating
D
D
ND = no data available. NA = not applicable.
*A11 emission factors represent controlled emissions.
bFilterable PM is that PM collected on or prior to the filter of an EPA Method 5 (or equivalent)
sampling train.
°Reference 4.
Reference 11.
References 4, 8.
Reference 10.
^References 7, 9.
8.17-4
EMISSION FACTORS
7/93
-------
REFERENCES FOR SECTION 8.17
1. Calciners and Dryers in Mineral Industries - Background Information for Proposed Standards,
EPA-450/3-85-025a, U.S. Environmental Protection Agency, Research Triangle Park, NC,
October 1985.
2. Perlite: US Minerals Yearbook 1989, Volume I: Metals and Minerals, U.S. Department of the
Interior, Bureau of Mines, Washington, DC, pp. 765 - 767.
3. Perlite Industry Source Category Survey, EPA-450/3-80-005, U. S. Environmental Protection
Agency, Research Triangle Park, NC, February 1980.
4. Emission Test Report (Perlite): W.R. Grace and Company, Irondale, Alabama, EMB Report
83-CDR-4, U. S. Environmental Protection Agency, Research Triangle Park, NC,
February 1984.
5. Paniculate Emission Sampling and Analysis: United States Gypsum Company, East Chicago,
Indiana, Environmental Instrument Systems, Inc., South Bend, IN, July 1973.
6. Air Quality Source Sampling Report #216: Grefco, Inc., Perlite Mill, Socorro, New Mexico,
State of New Mexico Environmental Improvement Division, Santa Fe, NM, January 1982.
7. Air Quality Source Sampling Report #198: Johns Manville Perlite Plant, No Agua, New Mexico,
State of New Mexico Environmental Improvement Division, Santa Fe, NM, February 1981.
8. Stack Test Report, Perlite Process: National Gypsum Company, Roll Road, Clarence Center,
New York, Buffalo Testing Laboratories, Buffalo, NY, December 1972.
9. Particulate Analyses of Dryer and Mill Baghouse Exhaust Emissions at Silbrico Perlite Plant, No
Agua, New Mexico, Kramer, Callahan & Associates, NM, February 1980.
10. Stack Emissions Survey for U.S. Gypsum, Perlite Mill Dryer Stack, Grants, New Mexico, File
Number EA 7922-17, Ecology Audits, Inc., Dallas, TX, August 1979.
11. Sampling Observation and Report Review, Grefco, Incorporated, Perlite Insulation Board Plant,
Florence, Kentucky, Commonwealth of Kentucky Department for Natural Resources and
Environmental Protection, Bureau of Environmental Protection, Frankfort, KY, January 1979.
7/93 Mineral Products Industry 8.17-5
-------
8.18 PHOSPHATE ROCK PROCESSING
8.18.1 Process Description1"5
The separation of phosphate rock from impurities and nonphosphate materials for use in
fertilizer manufacture consists of beneficiation, drying or calcining at some operations, and grinding.
The Standard Industrial Classification (SIC) code for phosphate rock processing is 1475. The six-
digit Source Classification Code (SCC) for phosphate rock processing is 3-05-019.
Because the primary use of phosphate rock is in the manufacture of phosphatic fertilizer, only
those phosphate rock processing operations associated with fertilizer manufacture are discussed here.
Florida and North Carolina accounted for 94 percent of the domestic phosphate rock mined and
89 percent of the marketable phosphate rock produced during 1989. Other States in which phosphate
rock is mined and processed include Idaho, Montana, Utah, and Tennessee. Alternative flow
diagrams of these operations are shown in Figure 8.18-1.
Phosphate rock from the mines is first sent to beneficiation units to separate sand and clay and
to remove impurities. Steps used in beneficiation depend on the type of rock. A typical beneficiation
unit for separating phosphate rock mined in Florida begins with wet screening to separate pebble
rock, which is larger than 1.43 millimeters (mm) (0.056 inch [in.]), or 14 mesh, and smaller than
6.35 mm (0.25 in.) from the balance of the rock. The pebble rock is shipped as pebble product. The
material that is larger than 0.85 mm (0.033 in.), or 20 mesh, and smaller than 14 mesh is separated
using hydrocyclones and finer mesh screens and is added to the pebble product. The fraction smaller
than 20 mesh is treated by two-stage flotation. The flotation process uses hydrophilic or hydrophobic
chemical reagents with aeration to separate suspended particles. Phosphate rock mined in North
Carolina does not contain pebble rock. In processing this type of phosphate, 2-mm (0.078 in.) or
10-mesh screens are used. Like Florida rock, the fraction that is less than 10 mesh is treated by two-
stage flotation, and the fraction larger than 10 mesh is used for secondary road building.
Phosphate rock mined in North Carolina does not contain pebble rock. In processing this
type of phosphate, 10-mesh screens are used. Like Florida rock, the fraction that is less than
10 mesh is treated by two-stage flotation, and the fraction larger than 10 mesh is used for secondary
road building.
The two major western phosphate rock ore deposits are located in southeastern Idaho and
northeastern Utah, and the beneficiation processes used on materials from these deposits differ
greatly. In general, southeastern Idaho deposits require crushing, grinding, and classification.
Further processing may include filtration and/or drying, depending on the phosphoric acid plant
requirements. Primary size reduction generally is accomplished by crushers (impact) and grinding
mills. Some classification of the primary crushed rock may be necessary before secondary grinding
(rod milling) takes place. The ground material then passes through hydrocyclones that are oriented in
a three-stage countercurrent arrangement. Further processing in the form of chemical flotation may
be required. Most of the processes are wet to facilitate material transport and to reduce dust.
Northeastern Utah deposits are lower grade and harder than the southeastern Idaho deposits
and requiring processing similar to that of the Florida deposits. Extensive crushing and grinding is
7/93 Mineral Products Industry 8.18-1
-------
Amber Acid Production
Phosphate rock fc
from mine
Benefication
f
Rock
Transfer
SCO: 3-05-019-03
(D PM emissions
(D Gaseous emissions
To phosphoric
acid manufacturing
Green Acid Production
Phosphate rock
from rnine
Benefication
Drying
SCO: 3-05-01 9-01
or
Calcining
SCO: 3-05-019-05
t t
Fuel Air
Rock
Transfer
SCC: 3-05*019-03
, To phosphoric
acid production
Granular Triple Super Phosphate Production (GTSP)
Phosphate rock _^
from mine
Grinding
SCC: 3-05-19-02
Rock
Transfer
SCC: 3-05-019-03
^ To GTSP
production
Figure 8.18-1. Alternative process flow diagrams for phosphate rock processing.
8.18-2 EMISSION FACTORS
7/93
-------
necessary to liberate phosphate from the material. The primary product is classified with 150- to
200-mesh screens, and the finer material is disposed of with the tailings. The coarser fraction is
processed through multiple steps of phosphate flotation and then diluent flotation. Further processing
may include filtration and/or drying, depending on the phosphoric acid plant requirements. As is the
case for southeastern Idaho deposits, most of the processes are wet to facilitate material transport and
to reduce dust.
The wet beneficiated phosphate rock may be dried or calcined, depending on its organic
content. Florida rock is relatively free of organics and is for the most part no longer dried or
calcined. The rock is maintained at about 10 percent moisture and is stored in piles at the mine
and/or chemical plant for future use. The rock is slurried in water and wet-ground in ball mills or
rod mills at the chemical plant. Consequently, there is no significant emission potential from wet
grinding. The small amount of rock that is dried in Florida is dried in direct-fired dryers at about
120°C (250°F), where the moisture content of the rock falls from 10 to 15 percent to 1 to 3 percent.
Both rotary and fluidized bed dryers are used, but rotary dryers are more common. Most dryers are
fired with natural gas or fuel oil (No. 2 or No. 6), with many equipped to burn more than one type of
fuel. Unlike Florida rock, phosphate rock mined from other reserves contains organics and must be
heated to 760° to 870°C (1400° to 1600°F) to remove them. Fluidized bed calciners are most
commonly used for this purpose, but rotary calciners are also used. After drying, the rock is usually
conveyed to storage silos on weather-protected conveyors and, from there, to grinding mills. In
North Carolina, a portion of the beneficiated rock is calcined at temperatures generally between 800°
and 825°C (1480° and 1520°F) for use in "green" phosphoric acid production, which is used for
producing super phosphoric acid and as a raw material for purified phosphoric acid manufacturing.
To produce "amber" phosphoric acid, the calcining step is omitted, and the beneficiated rock is
transferred directly to the phosphoric acid production processes. Phosphate rock that is to be used for
the production of granular triple super phosphate (GTSP) is beneficiated, dried, and ground before
being transferred to the GTSP production processes.
Dried or calcined rock is ground in roll or ball mills to a fine powder, typically specified as
60 percent by weight passing a 200-mesh sieve. Rock is fed into the mill by a rotary valve, and
ground rock is swept from the mill by a circulating air stream. Product size classification is provided
by a "revolving whizzer, which is mounted on top of the ball mill," and by an air classifier. Oversize
particles are recycled to the mill, and product size particles are separated from the carrying air stream
by a cyclone.
8.18.2 Emissions and Controls1'3"9
The major emission sources for phosphate rock processing are dryers, calciners, and grinders.
These sources emit paniculate matter (PM) in the form of fine rock dust and sulfur dioxide (SO2).
Beneficiation has no significant emission potential, because the operations involve slurries of rock and
water. The majority of mining operations in Florida handle only the beneficiation step at the mine;
all wet grinding is done at the chemical processing facility.
Emissions from dryers depend on several factors, including fuel types, air flow rates, product
moisture content, speed of rotation, and the type of rock. The pebble portion of Florida rock receives
much less washing than the concentrate rock from the flotation processes. It has a higher clay content
and generates more emissions when dried. No significant differences have been noted in gas volume
or emissions from fluid bed or rotary dryers. A typical dryer processing 230 megagrams per hour
(Mg/hr) (250 tons per hour [tons/hr]) of rock will discharge between 31 and 45 dry normal cubic
7/93 Mineral Products Industry 8.18-3
-------
meters per second (dry nm3/sec) (70,000 and 100,000 dry standard cubic feet per minute [dscfm]) of
gas, with a PM loading of 1,100 to 11,000 milligrams per nm3 (mg/nm3) (0.5 to 5 grains per dry
standard cubic feet [gr/dscf]). Emissions from calciners consist of PM and SO2 and depend on fuel
type (coal or oil), air flow rates, product moisture, and grade of rock.
Phosphate rock contains radionuclides in concentrations that are 10 to 100 times the
radionuclide concentration found in most natural material. Most of the radionuclides consist of
uranium and its decay products. Some phosphate rock also contains elevated levels of thorium and its
daughter products. The specific radionuclides of significance include uranium-238, uranium-234,
thorium-230, radium-226, radon-222, lead-210, and polonium-210.
The radioactivity of phosphate rock varies regionally, and within the same region the
radioactivity of the material may vary widely from deposit to deposit. Table 8.18-1 summarizes data
TABLE 8.18-1. RADIONUCLIDE CONCENTRATIONS OF
DOMESTIC PHOSPHATE ROCK"
Origin
Florida
Tennessee
South Carolina
North Carolina
Arkansas, Oklahoma
Western States
Typical values, pCi/g
48 to 143
5.8 to 12.6
267
5.86b
19 to 22
80 to 123
"Reference 8, except where indicated otherwise.
bReference 9.
on radionuclide concentrations for domestic deposits of phosphate rock. Materials handling and
processing operations can emit radionuclides either as dust, or in the case of radon-222, which is a
decay product of uranium-238, as a gas. Phosphate dust particles generally have the same specific
activity as the phosphate rock from which the dust originates.
Scrubbers are most commonly used to control emissions from phosphate rock dryers, but
electrostatic precipitators are also used. Fabric filters are not currently being used to control
emissions from dryers. Venturi scrubbers with a relatively low pressure loss (3,000 pascals [Pa]
[12 in. of water]) may remove 80 to 99 percent of PM 1 to 10 micrometers (jj.m) in diameter, and 10
to 80 percent of PM less than 1 fxm. High-pressure-drop scrubbers (7,500 Pa [30 in. of water]) may
have collection efficiencies of 96 to 99.9 percent for PM in the size range of 1 to 10 /-cm and 80 to
86 percent for particles less than 1 fim. Electrostatic precipitators may remove 90 to 99 percent of all
PM. Another control technique for phosphate rock dryers is use of the wet grinding process. In this
process, rock is ground in a wet slurry and then added directly to wet process phosphoric acid
reactors without drying.
A typical 45 Mg/hr (50 ton/hr) calciner will discharge about 13 to 27 dry nm3/sec (30,000 to
60,000 dscfm) of exhaust gas, with a PM loading of 0.5 to 5 gr/dscf. As with dryers, scrubbers are
8.18-4
EMISSION FACTORS
7/93
-------
the most common control devices used for calciners. At least one operating calciner is equipped with
a precipitator. Fabric filters could also be applied.
Oil-fired dryers and calciners have a potential to emit sulfur oxides when high-sulfur residual
fuel oils are burned. However, phosphate rock typically contains about 55 percent lime (CaO), which
reacts with the SO2 to form calcium sulfites and sulfates and thus reduces SO2 emissions. Dryers and
calciners also emit fluorides.
A typical grinder of 45 Mg/hr (50 ton/hr) capacity will discharge about 1.6 to 2.5 dry
nm3/sec (3,500 to 5,500 dscfm) of air containing 0.5 to 5.0 gr/dscf of PM. The air discharged is
"tramp air," which infiltrates the circulating streams. To avoid fugitive emissions of rock dust, these
grinding processes are operated at negative pressure. Fabric filters, and sometimes scrubbers, are
used to control grinder emissions. Substituting wet grinding for conventional grinding would reduce
the potential for PM emissions.
Emissions from material handling systems are difficult to quantify because several different
systems are used to convey rock. Moreover, a large part of the emission potential for these
operations is fugitives. Conveyor belts moving dried rock are usually covered and sometimes
enclosed. Transfer points are sometimes hooded and evacuated. Bucket elevators are usually
enclosed and evacuated to a control device, and ground rock is generally conveyed in totally enclosed
systems with well defined and easily controlled discharge points. Dry rock is normally stored in
enclosed bins or silos, which are vented to the atmosphere, with fabric filters frequently used to
control emissions.
Table 8.18-2 summarizes emission factors for controlled emissions of SO2 from phosphate
rock calciners and for uncontrolled emissions of CO and CO2 from phosphate rock dryers and
calciners. Emission factors for PM emissions from phosphate rock dryers, grinders, and calciners are
presented in Table 8.18-3. Particle size distribution for uncontrolled filterable PM emissions from
phosphate rock dryers and calciners are presented in Table 8.18-4. As shown in Table 8.18-4, the
size distribution of the uncontrolled calciner emissions is very similar to that of the dryer emissions.
Table 8.18-5 summarizes emission factors for emissions of water-soluble and total fluorides from
phosphate rock dryers and calciners. Emission factors for controlled and uncontrolled radionuclide
emissions from phosphate rock grinders also are presented in Table 8.18-5. Emission factors for PM
emissions from phosphate rock ore storage, handling, and transfer can be developed using the
equations presented in Section 11.3.
The new source performance standard (NSPS) for phosphate rock plants was promulgated in
April 1982 (40 CFR 60 Subpart NN). This standard limits PM emissions and opacity for phosphate
rock calciners, dryers, and grinders and limits opacity for handling and transfer operations. The
national emission standard for radionuclide emissions from elemental phosphorus plants was
promulgated in December 1989 (40 CFR 61 Subpart K). This standard limits emissions of
polonium-210 from phosphate rock calciners and nodulizing kilns at elemental phosphorus plants and
requires annual compliance tests.
7/93 Mineral Products Industry 8.18-5
-------
Table 8.18-2 (Metric Units)
EMISSION FACTORS FOR PHOSPHATE ROCK PROCESSING*
Process (SCC)
SO2
kg/Mg
of Total
Feed
Emission
Factor
Rating
CO2
kg/Mg
of Total
Feed
Emissio
n Factor
Rating
CO
kg/Mg
of Total
Feed
Emission
Factor
Rating
Dryer (3-05-019-01) ND 43b D 0.17C D
Calciner with scrubber 0.0034d D 115e D ND
(3-05-019-05)
Table 8.18-2 (English Units)
EMISSION FACTORS FOR PHOSPHATE ROCK PROCESSING*
Process (SCC)
SO2
lb/ton of
Total
Feed
Emission
Factor
Rating
CO2
lb/ton
of Total
Feed
Emission
Factor
Rating
CO
lb/ton
of Total
Feed
Emission
Factor
Rating
Dryer (3-05-019-01) ND 86b D 0.34° D
Calciner with scrubber 0.0069 D 230e D ND
(3-05-019-05)
ND = no data available.
'Factors represent uncontrolled emissions unless otherwise noted.
bReferences 10, 11.
"Reference 10.
References 13, 15.
"References 14 to 22.
8.18-6
EMISSION FACTORS
7/93
-------
Table 8.18-3 (Metric Units)
EMISSION FACTORS FOR PHOSPHATE ROCK PROCESSING*
k|
of
Process (SCC) *
Filterable PMb
PM
j/Mg Emission
Total Factor
3eed Rating
Dryer (3-05-019-01)d 2.90 D
Dryer with scrubber 0.035 D
(3-05-019-Olf
Dryer with ESP 0.016 D
(3-05-019-01)d
Grinder (3-05-019-02)d 0.8 C
Grinder with fabric filter (3- 0.0022 D
05-019-02/
Calciner (3-05-0 19-05)d 7.7 D
Calciner with scrubber (3-05- 0.
019-05)
Transfer and storage 2
(3-05-019-_Jd
10« C
E
PM-10
kg/Mg Emiss
of Total Fact*
Feed Radii
2.4 E
ND
ND
ND
ND
7.4 E
ND
ND
Condensible PMC
Inorganic
ion kg/Mg
>r of Total
ig Feed
ND
0.015
0.004
ND
0.0011
ND
0.0079
g
ND
Emission
Factor
Rating
D
D
D
D
C
Organic
kg/Mg
of Total
Feed
ND
ND
ND
ND
ND
ND
0.044h
ND
Emission
Factor
Rating
D
ND = No data available.
aFactors represent uncontrolled emissions unless otherwise noted.
bFilterable PM is that PM collected on or prior to the filter of an EPA Method 5 (or
equivalent) sampling train. PM-10 values are based on cascade impaction particle size distribution.
cCondensible PM is that PM collected in the impinger portion of a PM sampling train.
dReference 1.
Reference 1, 10, and 11
References 1, 11 and 12
^References 1, 14 to 22.
hReference 14 to 22.
7/93
Mineral Products Industry
8.18-7
-------
Table 8.18-3 (English Units)
EMISSION FACTORS FOR PHOSPHATE ROCK PROCESSING*
Process (SCC)
Dryer (3-05-019-01)d
Dryer with scrubber
(3-05-019-01)6
Dryer with ESP
(3-05-019-01)d
Grinder (3-05-0190-2)d
Grinder with fabric filter
(3-05-019-02)f
Filterable PMb
PM
lb/ton
of Total
Feed
5.70
0.070
0.033
1.5
0.0043
Calciner (3-05-019-05)d 15.4
Calciner with scrubber
(3-05-019-05)
Transfer and storage
(3-05-019-_)d
0.13S
1
Emission
Factor
Rating
D
D
D
C
D
D
C
E
PM-10
lb/ton of Emissi
Total Factc
Feed Ratin
4.8 E
ND
ND
ND
ND
15 E
ND
ND
Condensible PM
Inorganic
on lb/ton of
>r Total
g Feed
ND
0.030
0.008
ND
0.0021
ND
0.02
ND
Emission
Factor
Rating
D
D
D
D
C
C
Organic
lb/ton
of Total
Feed
ND
ND
ND
ND
ND
ND
0.088h
ND
Emission
Factor
Rating
D
ND = No data available.
"Factors represent uncontrolled emissions unless otherwise noted.
bFilterable PM is that PM collected on or prior to the filter of an EPA Method 5 (or
equivalent) sampling train. PM-10 values are based on cascade impaction particle size distribution.
cCondensible PM is that PM collected in the impinger portion of a PM sampling train.
dReference 1.
References 8, 10 and 11.
^References 1, 11, and 12.
^References 1, 14 to 22.
hReferences 14 to 22.
8.18-8
EMISSION FACTORS
7/93
-------
Table 8.18-4. PARTICLE SIZE DISTRIBUTION OF FILTERABLE PARTICULATE
EMISSIONS FROM PHOSPHATE ROCK DRYERS AND CALCINERS1
RATING: E
Diameter, /im
10
5
2
1
0.8
0.5
Percent less than size
Dryers
82
60
27
11
7
3
Calciners
96
81
52
26
110
5
7/93
Mineral Products Industry
8.18-9
-------
Table 8.18-5 (Metric Units)
EMISSION FACTORS FOR PHOSPHATE ROCK PROCESSING4
Process (SCC)
Dryer (3-05-019-01)°
Dryer with scrubber
(3-05-019-01)d
Grinder (3-05-0 19-02)e
Grinder with fabric filter
(3-05-019-02)e
Calciner with scrubber
(3-05-019-05)f
Fluoride, H
kg/Mg
of Total
Feed
0.0009
0.00048
ND
ND
ND
2O-soluble
Emission
Factor
Rating
D
D
Fluoride, total
kg/Mg
of Total
Feed
0.037
0.0048
ND
ND
0.00081
Emission
Factor
Rating
D
D
D
Radionuclidesb
kg/Mg
of Total
Feed
ND
ND
800R
5.2R
ND
Emission
Factor
Rating
E
E
Table 8.18-5 (English Units)
EMISSION FACTORS FOR PHOSPHATE ROCK PROCESSING8
Process (SCC)
Dryer (3-05-019-01)°
Dryer with scrubber
(3-05-019-01)d
Grinder (3-05-0 19-02)e
Grinder with fabric filter
(3-05-019-02)6
Calciner with scrubber
(3-05-019-05/
Fluoride, H2O-soluble
lb/ton
of Total
Feed
0.0017
0.00095
ND
ND
ND
Emission
Factor
Rating
D
D
Fluoride, total
lb/ton
of Total
Feed
0.073
0.0096
ND
ND
0.0016
Emission
Factor
Rating
D
D
D
Radionuclidesb
lb/ton
of Total
Feed
ND
ND
730R
4.7R
ND
Emission
Factor
Rating
E
E
ND = No data available.
"Factors represent uncontrolled emissions unless otherwise noted.
bln units of pCi/Mg of feed.
Reference 10.
References 10 and 11.
References 7 and 8.
Reference 1.
8.18-10
EMISSION FACTORS
7/93
-------
REFERENCES FOR SECTION 8.18
1. Background Information: Proposed Standards for Phosphate Rock Plants (Draft),
EPA-450/3-79-017, U. S. Environmental Protection Agency, Research Triangle Park, NC,
September 1979.
2. Minerals Yearbook, Volume I, Metals and Minerals, Bureau of Mines, U. S. Department of the
Interior, Washington D.C., 1991.
3. Written communication from B. S. Batts, Florida Phosphate Council, to R. Myers, Emission
Inventory Branch, U.S. Environmental Protection Agency, Research Triangle Park, NC,
March 12, 1992.
4. Written communication from K. T. Johnson, The Fertilizer Institute, to R. Myers, Emission
Inventory Branch, U. S. Environmental Protection Agency, Research Triangle Park, NC,
April 30, 1992.
5. Written communication for K. T. Johnson, The Fertilizer Institute to R. Myers, Emission
Inventory Branch, U.S. Environmental Protection Agency, Research Triangle Park, NC,
February 12, 1989.
6. "Sources of Air Pollution and Their Control," Air Pollution, Volume III, 2nd Ed., Arthur Stern,
ed., New York, Academic Press, 1968, pp. 221-222.
7. Background Information Document: Proposed Standards for Radionuclides, EPA 520/1-83-001,
U. S. Environmental Protection Agency, Office of Radiation Programs, Washington, D.C.,
March 1983.
8. R. T. Stula et al., Control Technology Alternatives and Costs for Compliance-Elemental
Phosphorus Plants, Final Report, EPA Contract No. 68-01-6429, Energy Systems Group, Science
Applications, Incorporated, La Jolla, CA, December 1, 1983.
9. Telephone communication from B. Peacock, Texasgulf, Incorporated, to R. Marinshaw, Midwest
Research Institute, Cary, NC, April 4, 1993.
10. Emission Test Report: International Minerals and Chemical Corporation, Kingsford, Florida,
EMB Report 73-ROC-l, U. S. Environmental Protection Agency, Research Triangle Park, NC,
February 1973.
11. Emission Test Report: Occidental Chemical Company, White Springs, Florida, EMB
Report 73-ROC-3, U. S. Environmental Protection Agency, Research Triangle Park, NC,
January 1973.
12. Emission Test Report: International Minerals and Chemical Corporation, Norafyn, Florida, EMB
Report 73-ROC-2, U. S. Environmental Protection Agency, Research Triangle Park, NC,
February 1973.
13. Sulfur Dioxide Emission Rate Test, No. I Calciner, Texasgulf, Incorporated, Aurora, North
Carolina, Texasgulf Environmental Section, Aurora, NC, May 1990.
7/93 Mineral Products Industry 8.18-11
-------
14. Source Performance Test, Calciner Number 4, Texasgulf, Inc., Phosphate Operations, Aurora,
NC, August 28, 1991, Texasgulf, Incorporated, Aurora, NC, September 25, 1991.
15. Source Performance Test, Calciner Number 6, Texasgulf, Inc., Phosphate Operations, Aurora,
NC, August 5 and 6, 1992, Texasgulf, Incorporated, Aurora, NC, September 17, 1992.
16. Source Performance Test, Calciner Number 4, Texasgulf, Inc., Phosphate Operations, Aurora,
NC, June 30, 1992, Texasgulf, Incorporated, Aurora, NC, July 16, 1992.
17. Source Performance Test, Calciner Number 1, Texasgulf, Inc., Phosphate Operations, Aurora,
NC, June 10, 1992, Texasgulf, Incorporated, Aurora, NC, July 8, 1992.
18. Source Performance Test, Calciner Number 2, Texasgulf, Inc., Phosphate Operations, Aurora,
NC, July 7, 1992, Texasgulf, Incorporated, Aurora, NC, July 16, 1992.
19. Source Performance Test, Calciner Number 5, Texasgulf, Inc., Phosphate Operations, Aurora,
NC, June 16, 1992, Texasgulf, Incorporated, Aurora, NC, July 8, 1992.
20. Source Performance Test, Calciner Number 6, Texasgulf, Inc., Phosphate Operations, Aurora,
NC, August 4 and 5, 1992, Texasgulf, Incorporated, Aurora, NC, September 21, 1992.
21. Source Performance Test, Calciner Number 3, Texasgulf, Inc., Phosphate Operations, Aurora,
NC, August 27, 1992, Texasgulf, Incorporated, Aurora, NC, September 21, 1992.
22. Source Performance Test, Calciner Number 2, Texasgulf, Inc., Phosphate Operations, Aurora,
NC, August 21 and 22, 1992, Texasgulf, Incorporated, Aurora, NC, September 20, 1992.
8.18-12 EMISSION FACTORS 7/93
-------
8.23 METALLIC MINERALS PROCESSING
8.23.1 Process Description1"6
Metallic mineral processing typically involves the mining of ore, from either open pit or
underground mines; the crushing and grinding of ore; the separation of valuable minerals from matrix
rock through various concentration steps; and at some operations, the drying, calcining, or pelletizing
of concentrates to ease further handling and refining. Figure 8.23-1 is a general flow diagram for
metallic mineral processing. Very few metallic mineral processing facilities will contain all of the
operations depicted in this figure, but all facilities will use at least some of these operations in the
process of separating valued minerals from the matrix rock.
The number of crushing steps necessary to reduce ore to the proper size vary with the type of
ore. Hard ores, including some copper, gold, iron, and molybdenum ores, may require as much as a
tertiary crushing. Softer ores, such as some uranium, bauxite, and titanium/zirconium ores, require
little or no crushing. Final comminution of both hard and soft ores is often accomplished by grinding
operations using media such as balls or rods of various materials. Grinding is most often performed
with an ore/water slurry, which reduces paniculate matter emissions to negligible levels. When dry
grinding processes are used, paniculate matter emissions can be considerable.
After final size reduction, the beneficiation of the ore increases the concentration of valuable
minerals by separating them from the matrix rock. A variety of physical and chemical processes is
used to concentrate the mineral. Most often, physical or chemical separation is performed in an
aqueous environment, which eliminates paniculate matter emissions, although some ferrous and
titaniferous minerals are separated by magnetic or electrostatic methods in a dry environment.
The concentrated mineral products may be dried to remove surface moisture. Drying is most
frequently done in natural gas-fired rotary dryers. Calcining or pelletizing of some products, such as
alumina or iron concentrates, is also performed. Emissions from calcining and pelletizing operations
are not covered in this section.
8.23.2 Process Emissions7'9
Paniculate matter emissions result from metallic mineral plant operations such as crushing and
dry grinding ore; drying concentrates; storing and reclaiming ores and concentrates from storage bins;
transferring materials; and loading final products for shipment. Paniculate matter emission factors
are provided in Table 8.23-1 for various metallic mineral process operations, including primary,
secondary, and tertiary crushing; dry grinding; drying; and material handling and transfer. Fugitive
emissions are also possible from roads and open stockpiles, factors for which are in Section 11.2.
The emission factors in Table 8.23-1 are for the process operations as a whole. At most
metallic mineral processing plants, each process operation requires several types of equipment. A
single crushing operation likely includes a hopper or ore dump, screen(s), crusher, surge bin, apron
feeder, and conveyor belt transfer points. Emissions from these various pieces of equipment are often
ducted to a single control device. The emission factors provided in Table 8.23-1 for primary,
8/82 Minerals Products Industry 8.23-1
-------
ORE
MINING
SCO: 3-05-
PRIMARY CRUSHING
SCC: 3-03-024-01,05
SECONDARY CRUSHING
SCC: 3-03-024-02,06
STORAGE
SCC: 3-05-
TERTIARY CRUSHING
SCC: 3-03-024-03, 07
STORAGE
SCC: 3-05-
GRINDING
SCC: 3-03-024-09,10
BENEFICIATION
Tailings
DRYING
SCC: 3-03-024-11
i i
PACKAGING AND
SHIPPING
SCC: 3-05-024-04, 08
KEY
PM emissions
Gaseous emissions
Figure 8.23-1. Process flow diagram for metallic mineral processing.
8.23-2
EMISSION FACTORS
8/82
-------
Table 8.23-1 (Metric Units)
EMISSION FACTORS FOR METALLIC MINERALS PROCESSING*
All Emission Factors in the kg/Mg of Material Processed Unless Notedb
Ratings (A-E) Follow Each Emission Factor
Source (SCC)
Low moisture orec
Primary crushing (3-03-024-0 l)d
Secondary crushing (3-03-024-02)d
Tertiary crushing (3-03-024-03)d
Wet grinding
Dry grinding with air conveying and/or air classification (3-03-024-09)e
Dry grinding without air conveying and/or air classification (3-03-024-10)6
Drying—all minerals except titanium/zirconium sands (3-03-024-1 l)f
Drying—titanium/zirconium with cyclones (3-03-024-1 l)f
Material handling and transfer— all minerals except bauxite (3-03-024-04)*
Material handling and transfer-bauxite/alumina (3-03-024-04)«'h
High moisture ore0
Primary crushing (3-03-024-05)d
Secondary crushing (3-03-024-06)d
Tertiary crushing (3-03-024J07)d
Wet grinding
Dry grinding with air conveying and/or air classification (3-03-024-09)6
Dry grinding without air conveying and/or air classification (3-03-024-10)°
Drying— all minerals except titanium/zirconium sands (3-03-024-1 l)f
Drying— titanium/zirconium with cyclones (3-03-024-1 l)f
Material handling and transfer— all minerals except bauxite (3-03-024-08)*
Material handling and transfer-bauxite/alumina (3-03-024-08)8'h
Filterable0
PM
0.2
0.6
1.4
Neg.
14.4
1.2
9.8
0.3
0.06
0.6
0.01
0.03
0.03
Neg.
14.4
1.2
9.8
0.3
0.005
NA
C
D
E
C
D
C
C
C
C
C
D
E
C
D
C
C
C
PM-10
0.02
NA
0.08
Neg.
13
0.16
5.9
NA
0.03
NA
0.004
0.012
0.01
Neg.
13
0.16
5.9
NA
0.002
NA
C
D
E
C
D
C
C
C
C
D
E
C
D
C
C
C
NA = not available
Neg. = negligible
"References 9 to 12; factors represent uncontrolled emissions unless otherwise noted; controlled emission
factors are discussed in Section 8.23.3.
bFilterable PM is that PM collected on or prior to the filter of an EPA Method 5 (or equivalent) sampling
tram.
cDefined in Section 8.23.2.
dBased on weight of material entering primary crusher.
"Based on weight of material entering grinder; emission factors are the same for both low moisture and high
moisture ore because material is usually dried before entering grinder.
Based on weight of material exiting dryer; emission factors are the same for both high moisture and low
moisture ores; SOX emissions are fuel dependent (see Chapter 1); NOX emissions depend on burner design
and combustion temperature (see Chapter 1).
gBased on weight of material transferred; applies to each loading or unloading operation and to each conveyor
belt transfer point.
hBauxite with moisture content as high as 15 to 18 percent can exhibit the emission characteristics of low
moisture ore; use low moisture ore emission factor for bauxite unless material exhibits obvious sticky,
nondusting characteristics.
8/82
Minerals Products Industry
8.23-3
-------
Table 8.23-1 (English Units)
EMISSION FACTORS FOR METALLIC MINERALS PROCESSING8
All Emission Factors in the Ib/ton of Material Processed Unless Notedb
Ratings (A-E) Follow Each Emission Factor
Source (SCC)
Low moisture orec
Primary crushing (3-03-024-01)d
Secondary crushing (303-024-02)d
Tertiary crushing (3-03-024-03)4
Wet grinding
Dry grinding with air conveying and/or air classification (3-03-024-09)6
Dry grinding without air conveying and/or air classification (3-03-024-10)*
Drying— all minerals except titanium/zirconium sands (3-03-024-1 l)f
Drying-titanium/zirconium with cyclones (3-03-024-1 l)f
Material handling and transfer— all minerals except bauxite (3-03-024-04)3
Material handling and transfer-bauxite/alumina (3-03-024-04)g'h
High moisture orec
Primary crushing (3-03-024-05)d
Secondary crushing (3-03-024-06)d
Tertiary crushing (3-03-024-07)d
Wet grinding
Dry grinding with air conveying and/or air classification (3-03-024-09)6
Dry grinding without air conveying and/or air classification (3-03-024- 10)e
Drying—all minerals except titanium/zirconium sands (3-03-024-1 l)f
Drying-titanium/zirconium with cyclones (3-03-024-1 l)f
Material handling and transfer— all minerals except bauxite (3-03-024-08)8
Material handling and transfer-bauxite/alumina (3-03-024-08)g'h
Filterable0
PM
0.5
1.2
2.7
Neg.
28.8
2.4
19.7
0.5
0.12
1.1
0.02
0.05
0.06
Neg.
28.8
2.4
19.7
0.5
0.01
NA
C
D
E
C
D
C
C
C
C
C
D
E
C
D
C
C
C
PM-10
0.05
NA
0.16
Neg.
26
0.31
12
NA
0.06
NA
0.009
0.02
0.02
Neg.
26
0.31
12
NA
0.004
NA
C
D
E
C
D
C
C
C
C
D
E
C
D
C
C
C
NA = not available
Neg. = negligible
'References 9 to 12; factors represent uncontrolled emissions unless otherwise noted; controlled emission
factors are discussed in Section 8.23.3.
bFilterable PM is that PM collected on or prior to the filter of an EPA Method 5 (or equivalent) sampling
train.
cDefined in Section 8.23.2.
dBased on weight of material entering primary crusher.
'Based on weight of material entering grinder; emission factors are the same for both low moisture and high
moisture ore because material is usually dried before entering grinder.
%ased on weight of material exiting dryer; emission factors are the same for both high moisture and low
moisture ores; SOX emissions are fuel dependent (see Chapter 1); NOX emissions depend on burner design
and combustion temperature (see Chapter 1).
gBased on weight of material transferred; applies to each loading or unloading operation and to each conveyor
belt transfer point.
^Bauxite with moisture content as high as 15 to 18 percent can exhibit the emission characteristics of low
moisture ore; use low moisture ore emission factor for bauxite unless material exhibits obvious sticky,
nondusting characteristics.
8.23-4
EMISSION FACTORS
8/82
-------
secondary, and tertiary crushing operations are for process units that are typical arrangements of the
above equipment.
Emission factors are provided in Table 8.23-1 for two types of dry grinding operations: those
that involve air conveying and/or air classification of material and those that involve screening of
material without air conveying. Grinding operations that involve air conveying and air classification
usually require dry cyclones for efficient product recovery. The factors in Table 8.23-1 are for
emissions after product recovery cyclones. Grinders in closed circuit with screens usually do not
require cyclones. Emission factors are not provided for wet grinders because the high moisture
content in these operations can reduce emissions to negligible levels.
The emission factors for dryers in Table 8.23-1 include transfer points integral to the drying
operation. A separate emission factor is provided for dryers at titanium/zirconium plants that use dry
cyclones for product recovery and for emission control. Titanium/zirconium sand-type ores do not
require crushing or grinding, and the ore is washed to remove humic and clay material before
concentration and drying operations.
At some metallic mineral processing plants, material is stored in enclosed bins between
process operations. The emission factors provided in Table 8.23-1 for the handling and transfer of
material should be applied to the loading of material into storage bins and the transferring of material
from the bin. The emission factor will usually be applied twice to a storage operation: once for the
loading operation and once for the reclaiming operation. If material is stored at multiple points in the
plant, the emission factor should be applied to each operation and should apply to the material being
stored at each bin. The material handling and transfer factors do not apply to small hoppers, surge
bins, or transfer points that are integral with crushing, drying, or grinding operations.
At some large metallic mineral processing plants, extensive material transfer operations, with
numerous conveyor belt transfer points, may be required. The emission factors for material handling
and transfer should be applied to each transfer point that is not an integral part of another process
unit. These emission factors should be applied to each such conveyor transfer point and should be
based on the amount of material transferred through that point.
The emission factors for material handling can also be applied to final product loading for
shipment. Again, these factors should be applied to each transfer point, ore dump, or other point
where material is allowed to fall freely.
Test data collected in the mineral processing industries indicate that the moisture content of
ore can have a significant effect on emissions from several process operations. High moisture
generally reduces the uncontrolled emission rates, and separate emission rates are provided for
primary crushers, secondary crushers, tertiary crushers, and material handling and transfer operations
that process high-moisture ore. Drying and dry grinding operations are assumed to produce or to
involve only low-moisture material.
For most metallic minerals covered in this section, high-moisture ore is defined as ore whose
moisture content, as measured at the primary crusher inlet or at the mine, is 4 weight percent or
greater. Ore defined as high-moisture at the primary crusher is presumed to be high moisture ore at
any subsequent operation for which high moisture factors are provided, unless a drying operation
precedes the operation under consideration. Ore is defined as low-moisture when a dryer precedes
8/82 Minerals Products Industry 8.23-5
-------
the operation under consideration or when the ore moisture at the mine or primary crusher is less than
4 weight percent.
Separate factors are provided for bauxite handling operations because some types of bauxite
with a moisture content as high as 15 to 18 weight percent can still produce relatively high emissions
during material handling procedures. These emissions could be eliminated by adding sufficient
moisture to the ore, but bauxite then becomes so sticky that it is difficult to handle. Thus, there is
some advantage to keeping bauxite in a relatively dusty state, and the low-moisture emission factors
given represent conditions fairly typical of the industry.
Paniculate matter size distribution data for some process operations have been obtained for
control device inlet streams. Since these inlet streams contain paniculate matter from several
activities, a variability has been anticipated in the calculated size-specific emission factors for
paniculate matter.
Emission factors for paniculate matter equal to or less than 10 pm in aerodynamic diameter
(PM-10), from a limited number of tests performed to characterize the processes, are presented in
Table 8.23-1.
In some plants, paniculate matter emissions from multiple pieces of equipment and operations
are collected and ducted to a control device. Therefore, examination of reference documents is
recommended before applying the factors to specific plants.
Emission factors for PM-10 from high-moisture primary crushing operations and material
handling and transfer operations were based on test results usually in the 30 to 40 weight percent
range. However, high values were obtained for high-moisture ore at both the primary crushing and
the material handling and transfer operations, and these were included in the average values in the
table. A similarly wide range occurred in the low-moisture drying operation.
Several other factors are generally assumed to affect the level of emissions from a particular
process operation. These include ore characteristics such as hardness, crystal and grain structure, and
friability. Equipment design characteristics, such as crusher type, could also affect the emissions
level. At this time, data are not sufficient to quantify each of these variables.
8.23.3 Controlled Emissions7'9
Emissions from metallic mineral processing plants are usually controlled with wet scrubbers
or baghouses. For moderate to heavy uncontrolled emission rates from typical dry ore operations,
dryers, and dry grinders, a wet scrubber with pressure drop of 1.5 to 2.5 kilopascals (6 to 10 inches
of water) will reduce emissions by approximately 95 percent. With very low uncontrolled emission
rates typical of high-moisture conditions, the percentage reduction will be lower (approximately 70
percent).
Over a wide range of inlet mass loadings, a well-designed and maintained baghouse will
reduce emissions to a relatively constant outlet concentration. Such baghouses tested in the mineral
processing industry consistently reduce emissions to less than 0.05 gram per dry standard cubic meter
(g/dscm) (0.02 grains per dry standard cubic foot [gr/dscf]), with an average concentration of
0.015 g/dscm (0.006 gr/dscf). Under conditions of moderate to high uncontrolled emission rates of
typical dry ore facilities, this level of controlled emissions represents greater than 99 percent removal
8.23-6 EMISSION FACTORS 8/82
-------
of participate matter emissions. Because baghouses reduce emissions to a relatively constant outlet
concentration, percentage emission reductions would be less for baghouses on facilities with a low
level of uncontrolled emissions.
References for Section 8.23
1. D. Kram, "Modem Mineral Processing: Drying, Calcining and Agglomeration", Engineering
and Mining Journal, 181(6): 134-151, June 1980.
2. A. Lynch, Mineral Crushing and Grinding Circuits, Elsevier Scientific Publishing Company,
New York, 1977.
3. "Modern Mineral Processing: Grinding", Engineering and Mining Journal, 787(161): 106-113,
June 1980.
4. L. Mollick, "Modern Mineral Processing: Crushing", Engineering and Mining Journal,
787(6):96-103, June 1980.
5. R. H. Perry, et al., Chemical Engineer's Handbook, 4th Ed., McGraw-Hill, New York, 1963.
6. R. Richards and C. Locke, Textbook of Ore Dressing, McGraw-Hill, New York, 1940.
7. "Modern Mineral Processing: Air and Water Pollution Controls", Engineering and Mining
Journal, 181 (6): 156-171, June 1980.
8. W. E. Horst and R. C. Enochs, "Modern Mineral Processing: Instrumentation and Process
Control", Engineering and Mining Journal, 787(6):70-92, June 1980.
9. Metallic Mineral Processing Plants - Background Information for Proposed Standards (Draft).
EPA Contract No. 68-02-3063, TRW, Research Triangle Park, NC, 1981.
10. Telephone communication between E. C. Monnig, TRW, Environmental Division, and R. Beale,
Associated Minerals, Inc., May 17, 1982.
11. Written communication from W. R. Chalker, DuPont, Inc., to S. T. Cuffe, U.S. Environmental
Protection Agency, Research Triangle Park, NC, December 21, 1981.
12. Written communication from P. H. Fournet, Kaiser Aluminum and Chemical Corporation, to S.
T. Cuffe, U. S. Environmental Protection Agency, Research Triangle Park, NC, March 5, 1982.
8/82 Minerals Products Industry 8.23-7
-------
8.25 LIGHTWEIGHT AGGREGATE MANUFACTURING
8.25.1 Process Description1 >2
Lightweight aggregate is a type of coarse aggregate that is used in the production of
lightweight concrete products such as concrete block, structural concrete, and pavement. The
Standard Industrial Classification (SIC) code for lightweight aggregate manufacturing is 3295; there
currently is no Source Classification Code (SCC) for the industry.
Most lightweight aggregate is produced from materials such as clay, shale, or slate. Blast
furnace slag, natural pumice, vermiculite, and perlite can be used as substitutes, however. To
produce lightweight aggregate, the raw material (excluding pumice) is expanded to about twice the
original volume of the raw material. The expanded material has properties similar to natural
aggregate, but is less dense and therefore yields a lighter concrete product.
The production of lightweight aggregate begins with mining or quarrying the raw material.
The material is crushed with cone crushers, jaw crushers, hammermills, or pugmills and is screened
for size. Oversized material is returned to the crushers, and the material that passes through the
screens is transferred to hoppers. From the hoppers, the material is fed to a rotary kiln, which is
fired with coal, coke, natural gas, or fuel oil, to temperatures of about 1200°C (2200°F). As the
material is heated, it liquefies and carbonaceous compounds in the material form gas bubbles, which
expand the material; in the process, volatile organic compounds (VOC's) are released. From the kiln,
the expanded product (clinker) is transferred by conveyor into the clinker cooler, where it is cooled
by air, forming a porous material. After cooling, the lightweight aggregate is screened for size;
crushed, if necessary; stockpiled; and shipped. Figure 8.25-1 illustrates the lightweight aggregate
manufacturing process.
Although the majority (approximately 90 percent) of plants use rotary kilns, traveling grates
are also used to heat the raw material. In addition, a few plants process naturally occurring
lightweight aggregate such as pumice.
8.25.2 Emissions and Controls1
Emissions from the production of lightweight aggregate consist primarily of particulate
matter (PM), which is emitted by the rotary kilns, clinker coolers, and crushing, screening, and
material transfer operations. Pollutants emitted as a result of combustion in the rotary kilns include
sulfur oxides (SO2), nitrogen oxides (NOX), carbon monoxide (CO), carbon dioxide (CO2), and
VOC's. Chromium, lead, and chlorides also are emitted from the kilns. In addition, other metals,
including aluminum, copper, manganese, vanadium, and zinc, are emitted in trace amounts by the
kilns. However, emission rates for these pollutants have not been quantified. In addition to PM,
clinker coolers emit CO2 and VOC's. Emission factors for crushing, screening, and material transfer
operations can be found in AP-42 Section 8.19.
7/93 Mineral Products Industry 8.25-1
-------
Oversize
Material
Figure 8.25-1. Process flow diagram for lightweight aggregate manufacturing.
8.25-2
EMISSION FACTORS
7/93
-------
Some lightweight aggregate plants fire kilns with material classified as hazardous waste under
the Resource Conservation and Recovery Act. Emission data are available for emissions of hydrogen
chloride, chlorine, and several metals from lightweight aggregate kilns burning hazardous waste.
However, emission factors developed from these data have not been incorporated in the AP-42 section
because the magnitude of emissions of these pollutants is largely a function of the waste fuel
composition, which can vary considerably.
Emissions from rotary kilns generally are controlled with wet scrubbers. However, fabric
filters and electrostatic precipitators (ESP's) are also used to control kiln emissions. Multiclones and
settling chambers generally are the only types of controls for clinker cooler emissions.
Table 8.25-1 summarizes uncontrolled and controlled emission factors for PM emissions (both
filterable and condensible) from rotary kilns and clinker coolers. Emission factors for SO2, NOX,
CO, and CO2 emissions from rotary kilns are presented in Table 8.25-2. An emission factor for CO2
emissions from clinker coolers is included in Table 8.25-2. Table 8.25-3 presents emission factors
for total VOC (TVOQ, emissions from rotary kilns. Size-specific PM emission factors for rotary
kilns and clinker coolers are presented in Table 8.25-4.
7/93 Mineral Products Industry 8.25-3
-------
TABLE 8.25-1 (METRIC UNITS)
EMISSION FACTORS FOR LIGHTWEIGHT AGGREGATE PRODUCTION*
kg/
1
Process
Rotary kiln
(3-05 )
Rotary kiln with scrubber 0
(3-05 )
Filterableb
PM
Mg of Emission
-eed Factor
Rating
65d D
.398 c
Rotary kiln wilh fabric filter 0.13' C
(3-05 )
Rotary kiln with ESP 0.34k D
(3-05 )
Clinker cooler with 0.141 D
settling chamber
(3-05 )
Clinker cooler with multiclone 0
(3-05 )
15m D
PM-10
kg/Mg Emiss
of Feed Fact<
Ratir
ND
0.15b D
ND
ND
0.0551 D
0.060m D
Condensible PMC
Inorganic
ion kg/Mg
w of Feed
'g
0.41C
0.1011
0.070*
0.015k
0.00851
0.0013m
Emission
Factor
Rating
D
D
D
D
D
D
Organic
kg/Mg of
Feed
0.0080f
0.0046h
ND
ND
0.000341
0.0014m
Emission
Factor
Rating
D
D
D
D
ND = No data available.
"Factors represent uncontrolled emissions unless otherwise noted.
bFilterable PM is that PM collected on or prior to the filter of an EPA Method 5 (or equivalent) sampling train.
PM-10 values are based on cascade impaction particle size distribution.
°Condensible PM is mat PM collected in the impinger portion of a PM sampling train.
dReferences 3,7,14. Average of 3 tests that ranged from 6.5 to 170 kg/Mg.
Reference 3,14.
Reference 3.
^References 3,5,10,12-14.
hReferences 3,5.
|References7,14, 17-19.
JReference 14.
kReferences 15,16.
'References 3,6.
"Reference 4.
8.25-4
EMISSION FACTORS
7/93
-------
TABLE 8.25-1 (ENGLISH UNITS)
EMISSION FACTORS FOR LIGHTWEIGHT AGGREGATE PRODUCTION8
All Emission Factors in Unless Noted
Ratings (A-E) Follow Each Emission Factor
Filterable13
PM
Ib/ton
of Feed
Process (SCC)
Emission
Factor
Rating
PM-10
Ib/ton
of Feed
Emission
Factor
Rating
Condensible PMC
Inorganic
Ib/ton of
Feed
Emission
Factor
Rating
Organic
Ib/ton
of Feed
Emission
Factor
Rating
ISC'1
0.788
0.261
Rotary kiln
(3-05 )
Rotary kiln with scrubber
(3-05 )
Rotary kiln with fabric filter
(3-05 )
Rotary kiln with ESP
(3-05 )
Clinker cooler with settling chamber 0.28
(3-05 )
Clinker cooler with multiclone
(3-05 )
D ND
0.29"
0.82e
0.016*
0.67*
C
D
ND
ND
0.30m
D 0.11
D 0.12"
D 0.19h D 0.0092h
0.14* D ND
0.03 lk D ND
D 0.0171 D 0.000671
D 0.0025111 D 0.0027m
D
D
D
D
ND = No data available.
'Factors represent uncontrolled emissions unless otherwise noted.
bFilterable PM is mat PM collected on or prior to the filter of an EPA Method 5 (or equivalent) sampling train.
PM-10 values are based on cascade impaction particle size distribution.
°Condensible PM is that PM collected in the impinger portion of a PM sampling train.
dReferences 3,7,14. Average of 3 tests that ranged from 13 to 340 Ib/ton.
Reference 3,14.
fReference3.
^References 3,5,10,12-14.
hReferences 3,5.
|References7,14, 17-19.
JReference 14.
^References 15,16.
'References 3,6.
•"Reference 4.
7/93
Mineral Products Industry
8.25-5
-------
Table 8.25-2 (Metric Units)
EMISSION FACTORS FOR LIGHTWEIGHT AGGREGATE PRODUCTION"
Process
(SCC)
SOX
kg/Mg
of
Product
Rotary kiln 2.8b
(3-05 )
Rotary kiln 1.7e
with scrubber
(3-05 )
Clinker cooler with ND
dry multicyclone
(3-05 )
Emission
Factor
Rating
NOX
kg/Mg
of
Product
C ND
C 1.0f
ND
Emission
Factor
Rating
CO
kg/Mg
of
Product
0.29C
D ND
ND
Emission
Factor
Rating
C02
kg/Mg
of
Product
C 240**
ND
228
Emission
Factor
Rating
C
D
TABLE 8.25-2 (ENGLISH UNITS)
EMISSION FACTORS FOR LIGHTWEIGHT AGGREGATE PRODUCTION*
Process (SCC)
SOX
Ib/ton
of
Product
Rotary kiln 5.6b
(3-05 )
Rotary kiln 3.4e
with scrubber
(3-05 )
Clinker cooler with ND
dry multicyclone
(3-05 )
Emission
Factor
Rating
NOX
Ib/ton
of
Product
C ND
C 1.9f
ND
Emission
Factor
Rating
CO
Ib/ton
of
Product
0.59C
D ND
ND
Emission
Factor
Rating
CO2
Ib/ton
of
Product
C 480d
ND
438
Emission
Factor
Rating
C
D
ND = No data available.
"Factors represent uncontrolled emissions unless otherwise noted.
bReferences 3, 4, 5, 8.
References 17, 18, 19.
References 3, 4, 5, 12, 13, 14, 17, 18, 19
References 3, 4, 5, 9.
^References 3, 4, 5.
gReference 4.
8.25-6
EMISSION FACTORS
7/93
-------
TABLE 8.25-3 (METRIC UNITS)
EMISSION FACTORS FOR LIGHTWEIGHT AGGREGATE PRODUCTION*
Process
(SCC)
TVOC's
kg/Mg
of
Product
Emission
Factor
Rating
Rotary kiln (3-05 ) ND
Rotary kiln with scrubber 0.39b D
(3-05 )
TABLE 8.25-3 (ENGLISH UNITS)
EMISSION FACTORS FOR LIGHTWEIGHT AGGREGATE PRODUCTION'
All Emission Factors in Unless Noted
Ratings (A-E) Follow Each Emission Factor
Process
(SCC)
TVOC's
Ib/ton
of
Product
Emission
Factor
Rating
Rotary kiln (3-05 ) ND
Rotary kiln with scrubber 0.78b D
(3-05 )
ND = No data available.
'Factors represent uncontrolled emissions unless otherwise noted.
bReference 3.
7/93
Mineral Products Industry
8.25-7
-------
TABLE 8.25-4. PARTICULATE MATTER SIZE-SPECIFIC EMISSION FACTORS
FOR EMISSIONS FROM ROTARY KILNS AND CLINKER COOLERS*
Rotary Kiln with Scrubbed
EMISSION FACTOR RATING:
D
Diameter,
microns
Cumulative %
less than
diameter
Emission factor
kg/Mg
2.5 35 0.10
6.0 46 0.13
10.0 50 0.14
15.0 55 0.16
20.0 57 0.16
Ib/ton
0.20
0.26
0.28
0.31
0.32
Clinker Cooler with Settling Chamber0
EMISSION FACTOR RATING: D
Diameter,
microns
Cumulative %
less than
diameter
Emission factor
kg/Mg
2.5 9 0.014
6.0 21 0.032
10.0 35 0.055
15.0 49 0.080
20.0 58 0.095
Ib/ton
0.027
0.063
0.11
0.16
0.19
i
Clinker Cooler with Multicloned
EMISSION FACTOR RATING: D
Diameter,
microns
Cumulative %
less than
diameter
Emission factor
kg/Mg
2.5 19 0.029
6.0 31 0.047
10.0 40 0.060
15.0 48 0.072
20.0 53 0.080
Ib/ton
0.057
0.093
0.12
0.14
0.16
aEmission factors based on total feed.
bReferences 3, 5.
cReferences 3, 6.
Reference 4.
8.25-8
EMISSION FACTORS
7/93
-------
REFERENCES FOR SECTION 8.25
1. Caldners and Dryers in Mineral Industries-Background Information for Proposed Standards,
EPA-450/3-85-025a, U.S. Environmental Protection Agency, Research Triangle Park, NC,
October 1985.
2. B. H. Spratt, The Structural Use of Lightweight Aggregate Concrete, Cement and Concrete
Association, United Kingdom, 1974.
3. Emission Test Report: Vulcan Materials Company, Bessemer, Alabama, EMB Report 80-LWA-4,
U. S. Environmental Protection Agency, Research Triangle Park, NC, March 1982.
4. Emission Test Report: Arkansas Lightweight Aggregate Corporation, West Memphis, Arkansas,
EMB Report 80-LWA-2, U.S. Environmental Protection Agency, Research Triangle Park, NC,
May 1981.
5. Emission Test Report: Plant K6, from Caldners and Dryers in Mineral Industries - Background
Information Standards, EPA-450/3-85-025a, U.S. Environmental Protection Agency, Research
Triangle Park, NC, October 1985.
6. Emission Test Report: Galite Corporation, Rockmart, Georgia, EMB Report 80-LWA-6, U. S.
Environmental Protection Agency, Research Triangle Park, NC, February 1982.
7. Summary of Emission Measurements on No. 5 Kiln, Carolina Solite Corporation, Aquadale,
North Carolina, Sholtes & Koogler Environmental Consultants, Inc., Gainesville, FL, April
1983.
8. Sulfur Dioxide Emission Measurements, Lightweight Aggregate Kiln No. 5 (Inlet), Carolina Solite
Corporation, Aquadale, North Carolina, Sholtes & Koogler Environmental Consultants, Inc.,
Gainesville, FL, May 1991.
9. Sulfur Dioxide Emission Measurements, Lightweight Aggregate Kiln No. 5 (Outlet), Carolina
Solite Corporation, Aquadale, North Carolina, Sholtes & Koogler Environmental Consultants,
Inc., Gainesville, FL, May 1991.
10. Summary of Particulate Matter Emission Measurements, No. 5 Kiln Outlet, Florida Solite
Corporation, Green Cove Springs, Florida, Sholtes and Koogler Environmental Consultants,
Gainesville, FL, June 19, 1981.
11. Summary of Particulate Matter Emission Measurements, No. 5 Kiln Outlet, Florida Solite
Corporation, Green Cove Springs, Florida, Sholtes and Koogler Environmental Consultants,
Gainesville, FL, September 3, 1982.
12. Particulate Emission Source Test Conducted on No.l Kiln Wet Scrubber at Tombigbee
Lightweight Aggregate Corporation, Livingston, Alabama, Resource Consultants, Brentwood, TN,
November 12, 1981.
7/93 Mineral Products Industry 8.25-9
-------
13. Paniculate Emission Source Test Conducted on No.2 Kiln Wet Scrubber at Tombigbee
Lightweight Aggregate Corporation, Livingston, Alabama, Resource Consultants, Brentwood, TN,
November 12, 1981.
14. Report of Simultaneous Efficiency Tests Conducted on the Orange Kiln and Baghouse at Carolina
Stalite, Gold Hill, N.C., Rossnagel & Associates, Charlotte, NC, May 9, 1980.
15. Stack Test Report No. 85-1, Lehigh Lightweight Aggregate Plant, Dryer-Kiln No. 2, Woodsboro,
Maryland, Division of Stationary Source Enforcement, Maryland Department of Health and
Mental Hygiene, Baltimore, MD, February 1, 1985.
16. Stack Test Report No. 85-7, Lehigh Lightweight Aggregate Plant, Dryer-Kiln No. 1, Woodsboro,
Maryland, Division of Stationary Source Enforcement, Maryland Department of Health and
Mental Hygiene, Baltimore, MD, May 1985.
17. Emission Test Results for No. 2 and No. 4 Aggregate Kilns, Solite Corporation, Leaksville Plant,
Cascade, Virginia, IEA, Research Triangle Park, NC, August 8, 1992.
18. Emission Test Results for No. 2 Aggregate Kiln, Solite Corporation, Hubers Plant, Brooks,
Kentucky, IEA, Research Triangle Park, NC, August 12, 1992.
19. Emission Test Results for No. 7 and No. 8 Aggregate Kilns, Solite Corporation, A. F. Old Plant,
Arvonia, Virginia, IEA, Research Triangle Park, NC, August 8, 1992.
8.25-10 EMISSION FACTORS 7/93
-------
8.27 FELDSPAR PROCESSING
8.27.1 General1
Feldspar consists essentially of aluminum silicates combined with varying percentages of
potassium, sodium, and calcium, and it is the most abundant mineral of the igneous rocks. The two
types of feldspar are soda feldspar (7 percent or higher Na2O) and potash feldspar (8 percent or
higher K2O). Feldspar-silica mixtures can occur naturally, such as in sand deposits, or can be
obtained from flotation of mined and crushed rock.
8.27.2 Process Description l'2
Conventional open-pit mining methods including removal of overburden, drilling and blasting,
loading, and transport by trucks are used to mine ores containing feldspar. A froth flotation process
is used for most feldspar ore beneficiation. Figure 8.27-1 shows a process flow diagram of the
flotation process. The ore is crushed by primary and secondary crushers and ground by jaw crushers,
cone crushers, and rod mills until it is reduced to less than 841 /im (20 mesh). Then the ore passes
to a three-stage, acid-circuit flotation process.
An amine collector that floats off and removes mica is used in the first flotation step. Also,
sulfuric acid, pine oil, and fuel oil are added. After the feed is dewatered in a classifier or cyclone to
remove reagents, sulfuric acid is added to lower the pH. Petroleum sulfonate (mahogany soap) is
used to remove iron-bearing minerals. To finish the flotation process, the discharge from the second
flotation step is dewatered again, and a cationic amine is used for collection as the feldspar is floated
away from quartz in an environment of hydrofluoric acid (pH of 2.5 to 3.0).
If feldspathic sand is the raw material, no size reduction may be required. Also, if little or no
mica is present, the first flotation step may be bypassed. Sometimes the final flotation stage is
omitted, leaving a feldspar-silica mixture (often referred to as sandspar), which is usually used in
glassmaking.
From the completed flotation process, the feldspar float concentrate is dewatered to 5 to 9
percent moisture. A rotary dryer is then used to reduce the moisture content to 1 percent or less.
Rotary dryers are the most common dryer type used, although fluid bed dryers are also used. Typical
rotary feldspar dryers are fired with No. 2 oil or natural gas, operate at about 230°C (450°F), and
have a retention time of 10 to 15 minutes. Magnetic separation is used as a backup process to
remove any iron minerals present. Following the drying process, dry grinding is sometimes
performed to reduce the feldspar to less than 74 /*m (200 mesh) for use in ceramics, paints, and tiles.
Drying and grinding are often performed simultaneously by passing the dewatered cake through a
rotating gas-fired cylinder lined with ceramic blocks and charged with ceramic grinding balls.
Material processed in this manner must then be screened for size or air classified to ensure proper
particle size.
7/93 Mineral Products Industry 8.27-1
-------
•20 MESH
OVERFLOW SLIME
TO WASTE
AMINE, H 2SO« .
PINE OIL, FUEL OIL
OVERFLOW
H SQ, , PETROLEUM SULFONATE
OVERFLOW (GARNET)
sec
DRYER
3-05-034-02
GLASS PLANTS
FLOTATION
CELLS
DRYER
SCC: 3-05-034-02
GLASS PLANTS
MAGNET 1 C
SEPARAT 1 ON
PEBBLE
MILLS
T
POTTERY
8.27-2
Figure 8.27-1. Feldspar flotation process.1
EMISSION FACTORS
7/93
-------
8.27.2 Emissions and Controls
The primary pollutant of concern that is emitted from feldspar processing is paniculate matter
(PM). Paniculate matter is emitted by several feldspar processing operations, including crushing,
grinding, screening, drying, and materials handling and transfer operations.
Emissions from dryers typically are controlled by a combination of a cyclone or a multiclone
and a scrubber system. Paniculate matter emissions from crushing and grinding generally are
controlled by fabric filters.
Table 8.27-1 presents controlled emission factors for filterable PM from the drying process.
Table 8.27-2 presents emission factors for CO2 from the drying process. The controls used in
feldspar processing achieve only incidental control of CO2.
Table 8.27-1 (Metric Units).
EMISSION FACTORS FOR FILTERABLE PARTICULATE MATTER*
Process (SCC)
Dryer with
Dryer with
Filterable Paniculate
kg/Mg Emission
Feldspar Factor
Dried Rating
scrubber and demisterb (SCC 3-05-034-02) 0.60 D
mechanical collector and scrubberc>d (SCC 3-05-034-02) 0.041 D
Table 8.27-1 (English Units).
EMISSION FACTORS FOR FILTERABLE PARTICULATE MATTER8
Process (SCC)
Dryer with
Dryer with
Filterable Paniculate
Ib/Ton
Feldspar Dried
Emission
Factor
Rating
scrubberb (SCC 3-05-034-02) 1.2 D
mechanical collector and scrubberc'd (SCC 3-05-034-02) 0.081 D
a SCC = Source Classification Code
b Reference 4.
c Reference 3.
d Reference 5.
7/93
Mineral Products Industry
8.27-3
-------
Table 8.27-2 (Metric Units).
EMISSION FACTOR FOR CARBON DIOXIDE*
Process (SCQ
Dryer with
Carbon Dioxide
kg/Mg
Feldspar
Dried
Emission
Factor
Rating
multiclone and scrubbed (SCC 3-05-034-02) 51 D
Table 8.27-2 (English Units).
EMISSION FACTOR FOR CARBON DIOXIDE*
Process (SCC)
Dryer with
Carbon Dioxide
Ib/Ton
Feldspar
Dried
Emission
Factor
Rating
multiclone and scrubbed (SCC 3-05-034-02) 102 D
* SCC = Source Classification Code.
b Scrubbers may achieve incidental control of CO2 emissions. Multiclones do not control CO2
emissions.
REFERENCES FOR SECTION 8.27
1. Calciners and Dryers in Mineral Industries-Background Information for Proposed Standards,
EPA-450/3-85-025a, U.S. Environmental Protection Agency, Research Triangle Park, NC,
October 1985.
2. US Minerals Yearbook 1989: Feldspar, Nepheline syenite, and Aplite: US Minerals Yearbook
1989, pp. 389-396.
3. Source Sampling Report for The Feldspar Corporation: Spruce Pine, NC, Environmental Testing
Inc., Charlotte, NC, May 1979.
4. Paniculate Emission Test Report for a Scrubber Stack at International Minerals Corporation:
Spruce Pine, NC, North Carolina Department of Natural Resources & Community Development,
Division of Environmental Management, September 1981.
5. Paniculate Emission Test Report for Two Scrubber Stacks at Lawson United Feldspar & Mineral
Company: Spruce Pine, NC, North Carolina Department of Natural Resources & Community
Development, Division of Environmental Management, October 1978.
8.27-4
EMISSION FACTORS
7/93
-------
STORAGE OF ORGANIC LIQUIDS
12.1 PROCESS DESCRIPTION1'2
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).
Five basic tank designs are used for organic liquid storage vessels: fixed roof
(vertical and horizontal), external 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 12.2.
The emission estimating equations presented in Chapter 12 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
Chapter 12 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.
Fixed Roof Tanks - A typical vertical fixed roof tank is shown in Figure 12.1-1. 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.
Fixed roof tanks are either freely vented or equipped with a pressure/vacuum vent.
The latter allows them 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 are cathodically protected to
prevent corrosion of the tank shell. Cathodic protection is accomplished by placing
07/93 Storage of Organic Liquids 12-1
-------
sacrificial anodes in the tank that are connected to an impressed current system or by using
galvanic anodes in the tank.
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.
External Floating Roof Tanks - A typical external floating roof tank consists of an open-
topped cylindrical steel shell equipped with a roof that floats on the surface of the stored
liquid. Floating roof tanks 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 roofs are shown in Figures 12.1-2 and 12.1-3, respectively. With aU types
of external floating roof tanks, the roof rises and falls with the liquid level in the tank.
External floating roof tanks are equipped with a seal system, which is attached to the roof
perimeter and contacts the tank wall. The purpose of the floating roof and 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 roof is also equipped with roof fittings that penetrate the floating
roof and serve operational functions. The external floating roof design is such that
evaporative losses from the stored liquid are limited to losses from the seal system and roof
fittings (standing storage loss) and any exposed liquid on the tank walls (withdrawal loss).
Internal Floating Roof Tanks - An internal floating roof tank has both a permanent fixed roof
and a floating deck inside. The terms "deck" and "floating roof can be used
interchangeably in reference to the structure floating on the liquid inside the tank. 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 deck 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 are noncontact decks. Typical contact
deck and noncontact deck internal floating roof tanks are shown in Figure 12.1-4.
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 roofs currently in service are aluminum sandwich panel-type or pan
steel-type. The FRP roofs are less common. The panels of pan steel decks are usually
welded together.
12-2 EMISSION FACTORS 07/93
-------
Typical noncontact decks have 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
or deck minimizes evaporative losses of the stored liquid. As with the external floating roof
tanks, both contact and noncontact decks incorporate rim seals and deck fittings for the same
purposes previously described for external floating roof tanks. Evaporation losses from
decks may come from deck 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
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.
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.
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
07/93 Storage of Organic Liquids 12-3
-------
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.
Pressure/Vocuum Vent
F i xed Rao f
Float Gauge
Roof Column
L i c|u i d Leve I
Indicator
Inlet Nozzl•
Outlet Nozzl*
Roo f ManhoI•
Gauge-Ha t ch/
Sample Wei I
Gauger's
PI a t f orm
Spiral Stairway
Cy I indrical She I I
ShelI Manhole
Figure 12.1-1. Typical fixed-roof tank.1
12-4
EMISSION FACTORS
07/93
-------
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07/93
Storage of Organic Liquids
12-39
-------
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EMISSION FACTORS
10/92
-------
Appendix D
Procedures For Sampling Surface And Bulk Materials
This appendix presents procedures recommended for the collection of material samples from paved
and unpaved roads and from bulk storage piles. (AP-42 Appendix E, "Procedures For Analyzing
Surface And Bulk Materials Samples", presents analogous information for the analysis of the samples.)
These recommended procedures are based on a review of American Society For Testing And Materials
(ASTM) methods, such as C-136 (sieve analysis) and D-2216 (moisture content). The
recommendations follow ASTM standards where practical, and where not, an effort has been made to
develop procedures consistent with the intent of the pertinent ASTM standards.
This appendix emphasizes that, before starting any field sampling program, one must first define
the study area of interest and then determine the number of samples that can be collected and analyzed
within the constraints of time, labor, and money available. For example, the study area could be
defined as an individual industrial plant with its network of paved/unpaved roadways and material
piles. In that instance, it is advantageous to collect a separate sample for each major dust source in
the plant. This level of resolution is useful in developing cost-effective emission reduction plans. On
the other hand, if the area of interest is geographically large (say a city or county, with a network of
public roads), collecting at least one sample from each source would be highly impractical. However,
in such an area, it is important to obtain samples representative of different source types within the
area.
D.I Samples From Unpaved Roads
Objective
The overall objective in an unpaved road sampling program is to inventory the mass of paniculate
matter (PM) emissions from the roads. This is typically done by
1. Collecting "representative" samples of the loose surface material from the road,
2. Analyzing the samples to determine silt fractions, and,
3. Using the results in the predictive emission factor model given in AP-42 Section 11.2.1,
Unpaved Roads, together with traffic data (e. g., number of vehicles traveling the road each
day).
Before any field sampling program, it is necessary to define the study area of interest and to
determine the number of unpaved road samples that can be collected and analyzed within the
constraints of time, labor, and money available. For example, the study area could be defined as a
very specific industrial plant having a network of roadways. Here it is advantageous to collect a
separate sample for each major unpaved road in the plant. This level of resolution is useful in
developing cost-effective emission reduction plans involving dust suppressants or traffic rerouting. On
the other hand, the area of interest may be geographically large, and well-defined traffic information
may not be easily obtained. In this case, resolution of the PM emission inventory to specific road
7/93 Appendix D D-l
-------
segments would not be feasible, and it would be more important to obtain representative road-type
samples within the area by aggregating several sample increments.
Procedure
For a network consisting of many relatively short roads contained in a well-defined study area (as
would be the case at an industrial plant), it is recommended that one collect a sample for each 0.8
kilometers (km) (0.5 miles [mi]) length, or portion thereof, for each major road segment. Here, the
term "road segment" refers to the length of road between intersections (the nodes of the network) with
other paved or unpaved roads. Thus, for a major segment 1 km (0.6 mi) long, two samples are
recommended.
For longer roads in study areas that are spatially diverse, it is recommended that one collect a
sample for each 4.8 km (3 mi) length of the road. Composite a sample from a minimum of three
incremental samples. Collect the first sample increment at a random location within the first 0.8 km
(0.5 mi), with additional increments taken from each remaining 0.8 km (0.5 mi) of the road, up to a
maximum length of 4.8 km (3 mi). For a road less than 1.5 mi in length, an acceptable method for
selecting sites for the increments is based on drawing three random numbers (xl, x2, x3) between zero
and the length. Random numbers may be obtained from tabulations in statistical reference books, or
scientific calculators may be used to generate pseudorandom numbers. See Figure D-l.
The following steps describe the collection method for samples (increments).
1. Ensure that the site offers an unobstructed view of traffic and that sampling personnel are
visible to drivers. If the road is heavily traveled, use one person to "spot" and route traffic safely
around another person collecting the surface sample (increment).
2. Using string or other suitable markers, mark a 0.3 meters (m) (1 foot [ft]) wide portion across
the road. (WARNING: Do not mark the collection area with a chalk line or in any other method
likely to introduce fine material into the sample.)
3. With a whisk broom and dustpan, remove the loose surface material from the hard road base.
Do not abrade the base during sweeping. Sweeping should be performed slowly so that fine surface
material is not injected into the air. NOTE: Collect material only from the portion of the road over
which the wheels and carriages routinely travel (i. e., not from berms or any "mounds" along the road
centerline).
4. Periodically deposit the swept material into a clean, labeled container of suitable size, such as
a metal or plastic 19 liter (L) (5 gallon [gal]) bucket, having a scalable polyethylene liner. Increments
may be mixed within this container.
5. Record the required information on the sample collection sheet (Figure D-2).
Sample Specifications
For uncontrolled unpaved road surfaces, a gross sample of 5 kilograms (kg) (10 pounds [lb]) to
23 kg (50 Ib) is desired. Samples of this size will require splitting to a size amenable for analysis (see
D-2 EMISSION FACTORS 7/93
-------
Appendix E). For unpaved roads having been treated with chemical dust suppressants (such as
petroleum resins, asphalt emulsions, etc.), the above goal may not be practical in well-defined study
areas because a very large area would need to be swept. In general, a minimum of 400 grams (g)
(1 Ib) is required for silt and moisture analysis. Additional increments should be taken from heavily
controlled unpaved surfaces, until the minimum sample mass has been achieved.
D.2 Samples From Paved Roads
Objective
The overall objective in a paved road sampling program is to inventory the mass of paniculate
emissions from the roads. This is typically done by
1. Collecting "representative" samples of the loose surface material from the road,
2. Analyzing the sample to determine the silt fraction, and,
3. Combining the results with traffic data in a predictive emission factor model.
The remarks above about definition of the study area and the appropriate level of resolution for
sampling unpaved roads are equally applicable to paved roads. Before a field sampling program, it is
necessary first to define the study area of interest and then to determine the number of paved road
samples that can be collected and analyzed. For example, in a well-defined study area (e. g., an
industrial plant), it is advantageous to collect a separate sample for each major paved road, because
the resolution can be useful in developing cost-effective emission reduction plans. Similarly, in
geographically large study areas, it may be more important to obtain samples representative of road
types within the area by aggregating several sample increments.
Compared to unpaved road sampling, planning for a paved road sample collection exercise
necessarily involves greater consideration as to types of equipment to be used. Specifically, provisions
must be made to accommodate the characteristics of the vacuum cleaner chosen. For example, paved
road samples are collected by cleaning the surface with a vacuum cleaner with "tared" (i. e., weighed
before use) filter bags. Upright "stick broom" vacuums use relatively small, lightweight filter bags,
while bags for industrial-type vacuums are bulky and heavy. Because the mass collected is usually
several times greater than the bag tare weight, uprights are thus well suited for collecting samples from
lightly loaded road surfaces. On the other hand, on heavily loaded roads, the larger industrial-type
vacuum bags are easier to use and can be more readily used to aggregate incremental samples from all
road surfaces. These features are discussed further below.
Procedure
For a network of many relatively short roads contained in a well-defined study area (as would be
the case at an industrial plant), it is recommended that one collect a sample for each 0.8 km (0.5 mi)
length, or portion thereof, for each major road segment. For a 1 km long (0.6 mi) segment, then, two
samples are recommended. As mentioned, the term "road segment" refers to the length of road
between intersections with other paved or unpaved roads (the nodes of the network).
7/93 Appendix D D-3
-------
For longer roads in spatially heterogeneous study areas, it is recommended that one collect a
sample for each 4.8 km (3 mi) of sampled road length. Create a composite sample from a minimum
of three incremental samples. Collect the first increment at a random location within the first 0.8 km
(0.5 mi), with additional increments taken from each remaining 0.8 km (0.5 mi) of the road, up to a
maximum length of 4.8 km (3 mi.) For a road less than 2.4 km (1.5 mi) long, an acceptable method
for selecting sites for the increments is based on drawing three random numbers (xl, x2, x3) between
zero and the length (See Figure D-3). Random numbers may be obtained from tabulations in
statistical reference books, or scientific calculators may be used to generate pseudorandom numbers.
The following steps describe the collection method for samples (increments).
1. Ensure that the site offers an unobstructed view of traffic and that sampling personnel are
visible to drivers. If the road is heavily traveled, use one crew member to "spot" and route traffic
safely around another person collecting the surface sample (increment).
2. Using string or other suitable markers, mark the sampling portion across the road.
(WARNING: Do not mark the collection area with a chalk line or in any other method likely to
introduce fine material into the sample.) The widths may be varied between 0.3 m (1 ft) for visibly
dirty roads and 3 m (10 ft) for clean roads. When an industrial-type vacuum is used to sample lightly
loaded roads, a width greater than 3 m (10 ft) may be necessary to meet sample specifications, unless
increments are being combined.
3. If large, loose material is present on the surface, it should be collected with a whisk broom
and dustpan. NOTE: Collect material only from the portion of the road over -which the wheels and
carriages routinely travel (i. e., not from berms or any "mounds" along the road centerline). On roads
with painted side markings, collect material "from white line to white line" (but avoid centerline
mounds). Store the swept material in a clean, labeled container of suitable size, such as a metal or
plastic 19 L (5 gal) bucket, with a scalable polyethylene liner. Increments for the same sample may
be mixed within the container.
4. Vacuum the collection area using a portable vacuum cleaner fitted with an empty tared
(preweighed) filter bag. NOTE: Collect material only from the portion of the road over which the
wheels and carriages routinely travel (i. e., not from berms or any "mounds" along the road
centerline). On roads with painted side markings, collect material "from white line to white line" (but
avoid centerline mounds). The same filter bag may be used for different increments for one sample.
For heavily loaded roads, more than one filter bag may be needed for a sample (increment).
5. Carefully remove the bag from the vacuum sweeper and check for tears or leaks. If necessary,
reduce samples (using the procedure in Appendix E) from broom sweeping to a size amenable to
analysis. Seal broom-swept material in a clean, labeled plastic jar for transport (alternatively, the
swept material may be placed in the vacuum filter bag). Fold the unused portion of the filter bag,
wrap a rubber band around the folded bag, and store the bag for transport.
6. Record the required information on the sample collection sheet (Figure D-4).
D-4 EMISSION FACTORS 7/93
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Sample Specifications
When broom swept samples are collected, they should be at least 400 g (1 Ib) for silt and moisture
analysis. Vacuum swept samples should be at least 200 g (0.5 Ib). Also, the weight of an "exposed"
filter bag should be at least 3 to 5 times greater than when empty. Additional increments should be
taken until these sample mass goals have been attained.
D.3 Samples From Storage Piles
Objective
The overall objective of a storage pile sampling and analysis program is to inventory particulate
matter emissions from the storage and handling of materials. This is done typically by
1. Collecting "representative" samples of the material,
2. Analyzing the samples to determine moisture and silt contents, and,
3. Combining analytical results with material throughput and meteorological information in an
emission factor model.
As initial steps in storage pile sampling, it is necessary to decide (a) what emission mechanisms -
material load-in to and load-out from the pile, wind erosion of the piles - are of interest and (b) how
many samples can be collected and analyzed, given time and monetary constraints. (In general, annual
average PM emissions from material handling can be expected to be much greater than those from
wind erosion.) For an industrial plant, it is recommended that at least one sample be collected for
each major type of material handled within the facility.
In a program to characterize load-in emissions, representative samples should be collected from
material recently loaded into the pile. Similarly, representative samples for load-out emissions should
be collected from areas that are worked by load-out equipment such as front end loaders or clamshells.
For most "active" piles (i. e., those with frequent load-in and load-out operations), one sample may be
considered representative of both loaded-in and loaded-out materials. Wind erosion material samples
should be representative of the surfaces exposed to the wind.
In general, samples should consist of increments taken from all exposed areas of the pile (i. e., top,
middle, and bottom). If the same material is stored in several piles, it is recommended that piles with
at least 25% of the amount in storage be sampled. For large piles that are common in industrial
settings (e. g., quarries, iron and steel plants), access to some portions may be impossible for the
person collecting the sample. In that case, increments should be taken no higher than it is practical for
a person to climb carrying a shovel and a pail.
Procedure
The following steps describe the method for collecting samples from storage piles.
7/93 Appendix D D-5
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1. Sketch plan and elevation views of the pile. Indicate if any portion is not accessible. Use the
sketch to plan where the N increments will be taken by dividing flie perimeter into N-l roughly
equivalent segments.
a. For a large pile, collect a minimum of 10 increments, as near to mid-height of the pile as
practical.
b. For a small pile, a sample should be a minimum of 6increments, evenly distributed among
the top, middle, and bottom.
"Small" or "large" piles, for practical purposes, may be defined as those piles which can or
cannot, respectively, be scaled by a person carrying a shovel and pail.
2. Collect material with a straight-point shovel or a small garden spade, and store the increments
in a clean, labeled container of suitable size (such as a metal or plastic 19 L [5 gal] bucket) with a
scalable polyethylene liner. Depending upon the ultimate goals of the sampling program, choose one
of the following procedures:
a. To characterize emissions from material handling operations at an active pile, take
increments from the portions of the pile which most recently had material added and
removed. Collect the material with a shovel to a depth of 10 to 15 centimeters (cm) (4 to
6 inches [in]). Do not deliberately avoid larger pieces of aggregate present on the surface.
b. To characterize handling emissions from an inactive pile, obtain increments of the core
material from a 1 m (3 ft) depth in the pile. A sampling tube 2 m (6 ft) long, with a
diameter at least 10 times the diameter of the largest particle being sampled, is
recommended for these samples. Note that, for piles containing large particles, the
diameter recommendation may be impractical.
c. If characterization of wind erosion , rather than material handling is the goal of the
sampling program, collect the increments by skimming the surface in an upwards direction.
The depth of the sample should be 2.5 cm (1 in), or the diameter of the largest particle,
whichever is less. Do not deliberately avoid collecting larger pieces of aggregate present
on the surface.
In most instances, collection method "a" should be selected.
3. Record the required information on the sample collection sheet (Figure D-5). Note the space
for deviations from the summarized method.
Sample Specifications
For any of the procedures, the sample mass collected should be at least 5 kg (10 Ib). When most
materials are sampled with procedures 2.a or 2.b, ten increments will normally result in a sample of at
least 23 kg (50 Ib). Note that storage pile samples usually require splitting to a size more amenable to
laboratory analysis.
D-6 EMISSION FACTORS 7/93
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7/93
Appendix D
D-7
-------
i
Date Collected
SAMPLING DATA FOR UNPAVED ROADS
Recorded by
Road Material (e.g., gravel, slag, dirt,
etc.):*
Site of sampling:
METHOD:
1. Sampling device: whisk broom and dustpan
2. Sampling depth: loose surface material (do not abrade road base)
3. Sample container: bucket with sealable liner
4. Gross sample specifications:
a. Uncontrolled surfaces -- 5 kg (10 Ib) to 23 kg (50 Ib)
b. Controlled surfaces -- minimum of 400 g (1 Ib) is required for analysis
Refer to AP-42 Appendix D for more detailed instructions.
Indicate any deviations from the above:.
SAMPLING DATA COLLECTED:
Sample
No.
Time
Location +
Surf.
Area
Depth
Mass of
Sample
* Indicate and give details if roads are controlled.
+ Use code given on plant or road map for segment identification. Indicate sampling
location on map.
D-8
Figure D-2. Example data form for unpaved road samples.
EMISSION FACTORS
7/93
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SAMPLING DATA FOR PAVED ROADS
Date Collected
Sampling location*
Recorded by
No. of Lanes
Surface type (e.g., asphalt, concrete, etc.)_
Surface condition (e.g., good, rutted, etc.).
* Use code given on plant or road map for segment identification. Indication sampling
location on map.
METHOD:
1. Sampling device: portable vacuum cleaner (whisk broom and dustpan if heavy
loading present)
2. Sampling depth: loose surface material (do not sample curb areas or other
untravelled portions of the road)
3. Sample container: tared and numbered vacuum cleaner bags (bucket with sealable
liner if heavy loading present)
4. Gross sample specifications: Vacuum swept samples should be at least 200 g
(0.5 Ib), with the exposed filter bag weight should be at least 3 to 5 times greater
than the empty bag tare weight.
Refer to AP-42 Appendix D for more detailed instructions.
Indicate any deviations from the above:_
SAMPLING DATA COLLECTED:
Sample
No.
Vacuum Bag
ID Tare Wgt (g)
Sampling
Surface Dimensions
(Ixw)
Time
Mass of
Broom-Swept
Sample +
+ Enter "0" if no broom sweeping is performed.
Figure D-4. Example data form for paved roads.
D-10
EMISSION FACTORS
7/93
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Date Collected
SAMPLING DATA FOR STORAGE PILES
Recorded by
Type of material sampled
Sampling location*
METHOD:
1. Sampling device: pointed shovel (hollow sampling tube if inactive pile is to be
sampled)
2. Sampling depth:
For material handling of active piles: 10-15 cm (4-6 in)
For material handling of inactive piles: 1 m (3 ft)
For wind erosion samples: 2.5 cm (1 in) or depth of the largest particle (whichever
is less)
3. Sample container: bucket with sealable liner
4. Gross sample specifications:
For material handling of active or inactive piles: minimum of 6 increments with total
sample weight of 5 kg (10 Ib) [10 increments totalling 23 kg (50 Ib) are
recommended]
For wind erosion samples: minimum of 6 increments with total sample weight of
5kg(10lb)
Refer to AP-42 Appendix D for more detailed instructions.
Indicate any deviations from the above:
SAMPLING DATA COLLECTED:
Sample
No.
Time
Location* of
Sample Collection
Device Used
S/T**
Depth
Mass of
Sample
* Use code given of plant or area map for pile/sample identification. Indicate each sampling location
on map.
"Indicate whether shovel or tube.
Figure D-5. Example data form for storage piles.
7/93
Appendix D
D-ll
-------
Appendix E
Procedures For Analyzing Surface And Bulk Material Samples
This appendix discusses procedures recommended for the analysis of samples collected from paved
and unpaved surfaces and from bulk storage piles. (AP-42 Appendix D, "Procedures For Sampling
Surface And Bulk Materials", presents procedures for the collection of these samples.) These
recommended procedures are based on a review of American Society For Testing And Materials
(ASTM) methods, such as C-136 (sieve analysis) or D-2216 (moisture content). The recommendations
follow ASTM standards where practical, and where not, an effort has been made to develop
procedures consistent with the intent of the pertinent ASTM standards.
E.I Sample Splitting
Objective
The collection procedures presented in Appendix D can result in samples that need to be reduced
in size before laboratory analysis. Samples are often unwieldy, and field splitting is advisable before
transporting the samples.
The size of the laboratory sample is important. Too small a sample will not be representative, and
too much sample will be unnecessary as well as unwieldy. Ideally, one would like to analyze the
entire gross sample in batches, but that is not practical. While all ASTM standards acknowledge this
impracticality, they disagree on the exact optimum size, as indicated by the range of recommended
samples, extending from 0.05 to 27 kilograms (kg) (0.1 to 60 pounds [lb]).
Splitting a sample may be necessary before a proper analysis. The principle in sizing a laboratory
sample for silt analysis is to have sufficient coarse and fine portions both to be representative of the
material and to allow sufficient mass on each sieve to assure accurate weighing. A laboratory sample
of 400 to 1,600 grams (g) is recommended because of the capacity of normally available scales (1.6 to
2.6 kg). A larger sample than this may produce "screen blinding" for the 20 centimeter (cm) (8 inch
[in]) diameter screens normally available for silt analysis. Screen blinding can also occur with small
samples of finer texture. Finally, the sample mass should be such that it can be spread out in a
reasonably sized drying pan to a depth of < 2.5cm (1 in).
Two methods are recommended for sample splitting: riffles, and coning and quartering. Both
procedures are described below.
Procedures
Figure E-l shows two riffles for sample division. Riffle slot widths should be at least three times
the size of the largest aggregate in the material being divided. The following quote from ASTM
Standard Method D2013-72 describes the use of the riffle.
7/93 Appendix E E-l
-------
Feed Chute
SAMPLE DIVIDERS (RIFFLES)
Rolled
Edges
Riffle Sampler
(b)
Riffle Bucket and
Separate Feed Chute Stand
(b)
Figure E-l. Sample riffle dividers.
CONING AND QUARTERING
Figure E-2. Procedure for coning and quartering.
E-2
EMISSION FACTORS
7/93
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Divide the gross sample by using a riffle. Riffles properly used will reduce sample
variability but cannot eliminate it. Riffles are shown in [Figure E-l]. Pass the material
through the riffle from a feed scoop, feed bucket, or riffle pan having a lip or opening the full
length of the riffle. When using any of the above containers to feed the riffle, spread the
material evenly in the container, raise the container, and hold it with its front edge resting on
top of the feed chute, then slowly tilt it so that the material flows in a uniform stream through
the hopper straight down over the center of the riffle into all the slots, thence into the riffle
pans, one-half of the sample being collected in a pan. Under no circumstances shovel the
sample into the riffle, or dribble into the riffle from a small-mouthed container. Do not allow
the material to build up in or above the riffle slots. If it does not flow freely through the slots,
shake or vibrate the riffle to facilitate even flow.
Coning and quartering is a simple procedure useful with all powdered materials and with sample
sizes ranging from a few grams to several hundred pounds. Oversized material, defined as > 0.6
millimeters (mm) (3/8 in) in diameter, should be removed before quartering and be weighed in a
"tared" container (one for which its empty weight is known).
Preferably, perform the coning and quartering operation on a floor covered with clean 10 mil
(mm) plastic. Take care that the material is not contaminated by anything on the floor or that any
portion is not lost through cracks or holes. Samples likely affected by moisture or drying must be
handled rapidly, preferably in a controlled atmosphere, and sealed in a container to prevent further
changes during transportation and storage.
The procedure for coning and quartering is illustrated in Figure E-2. The following procedure
should be used:
1. Mix the material and shovel it into a neat cone.
2. Flatten the cone by pressing the top without further mixing.
3. Divide the flat circular pile into equal quarters by cutting or scraping out two diameters at
right angles.
4. Discard two opposite quarters.
5. Thoroughly mix the two remaining quarters, shovel them into a cone, and repeat the quartering
and discarding procedures until the sample is reduced to 0.4 to 1.8 kg (1 to 4 Ib).
E.2 Moisture Analysis
Paved road samples generally are not to be oven dried because vacuum filter bags are used to
collect the samples. After a sample has been recovered by dissection of the bag, it is combined with
any broom swept material for silt analysis. All other sample types are oven dried to determine
moisture content before sieving.
7/93 Appendix E E-3
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Procedure
1. Heat the oven to approximately 110°C (230°F). Record oven temperature. (See Figure E-3.)
2. Record the make, capacity, and smallest division of the scale.
3. Weigh the empty laboratory sample containers which will be placed in the oven to determine
their tare weight. Weigh any lidded containers with the lids. Record the tare weight(s). Check zero
before each weighing.
4. Weigh the laboratory sample(s) in the container(s). For materials with high moisture content,
assure that any standing moisture is included in the laboratory sample container. Record the combined
weight(s). Check zero before each weighing.
5. Place sample in oven and dry overnight. Materials composed of hydrated minerals or organic
material such as coal and certain soils should be dried for only 1.5 hours.
6. Remove sample container from oven and (a) weigh immediately if uncovered, being careful of
the hot container; or (b) place a tight-fitting lid on the container and let it cool before weighing.
Record the combined sample and container weight(s). Check zero before weighing.
7. Calculate the moisture, as the initial weight of the sample and container, minus the oven-dried
weight of the sample and container, divided by the initial weight of the sample alone. Record the
value.
8. Calculate the sample weight to be used in the silt analysis, as the oven-dried weight of the
sample and container, minus the weight of the container. Record the value.
Date:
Sample No:
Material:
Split Sample Balance:
Make
Capacity
Smallest division
Total Sample Weight:
(Excl. Container)
Number of Splits:
MOISTURE ANALYSIS
By:
Split Sample Weight (before drying)
Pan + Sample:
Pan:
Wet Sample:
Oven Temperature:
Date In
Time In
Drying Time
Date Out _
Time Out
Sample Weight (after drying)
Pan + Sample:
Pan:
Dry Sample:
MOISTURE CONTENT:
(A) Wet Sample Wt.
(B) Dry Sample Wt.
(C) Difference Wt.
Cx 100
A = % Moisture
Figure E-3. Example moisture analysis form.
E-4
EMISSION FACTORS
7/93
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E.3 Silt Analysis
Objective
Several open dust emission factors have been found to be correlated with the silt content (< 200
mesh) of the material being disturbed. The basic procedure for silt content determination is
mechanical, dry sieving. For sources other than paved roads, the same sample which was oven-dried
to determine moisture content is then mechanically sieved.
For paved road samples, the broom-swept particles and the vacuum-swept dust are individually
weighed on a beam balance. The broom-swept particles are weighed in a container, and the vacuum-
swept dust is weighed in the bag of the vacuum, which was tared before sample collection. After
weighing the sample to calculate total surface dust loading on the traveled lanes, combine the broom-
swept particles and the vacuumed dust. Such a composite sample is usually small and may not require
splitting in preparation for sieving.
Procedure
1. Select the appropriate 20-cm (8-in) diameter, 5-cm (2-in) deep sieve sizes. Recommended U.
S. Standard Series sizes are 3/8 in, No. 4, No. 40, No. 100, No. 140, No. 200, and a pan. Comparable
Tyler Series sizes can also be used. The No. 20 and the No. 200 are mandatory. The others can be
varied if the recommended sieves are not available, or if buildup on one paniculate sieve during
sieving indicates that an intermediate sieve should be inserted.
2. Obtain a mechanical sieving device, such as a vibratory shaker or a Roto-Tap® without the
tapping function.
3. Clean the sieves with compressed air and/or a soft brush. Any material lodged in the sieve
openings or adhering to the sides of the sieve should be removed, without handling the screen roughly,
if possible.
4. Obtain a scale (capacity of at least 1600 grams [g] or 3.5 Ib) and record make, capacity,
smallest division, date of last calibration, and accuracy. (See Figure E-4.)
5. Weigh the sieves and pan to determine tare weights. Check the zero before every weighing.
Record the weights.
6. After nesting the sieves in decreasing order of size, and with pan at the bottom, dump dried
laboratory sample (preferably immediately after moisture analysis) into the top sieve. The sample
should weigh between ~ 400 and 1600 g (~ 0.9 and 3.5 Ib). This amount will vary for finely textured
materials, and 100 to 300 g may be sufficient when 90% of the sample passes a No. 8 (2.36 mm)
sieve. Brush any fine material adhering to the sides of the container into the top sieve and cover the
top sieve with a special lid normally purchased with the pan.
7. Place nested sieves into the mechanical sieving device and sieve for 10 minutes (min.).
Remove pan containing minus No. 200 and weigh. Repeat the sieving at 10-min. intervals until the
7/93 Appendix E E-5
-------
difference between two successive pan sample weighings (with the pan tare weight subtracted) is less
than 3.0%. Do not sieve longer than 40 min.
8. Weigh each sieve and its contents and record the weight. Check the zero before every
weighing.
9. Collect the laboratory sample. Place the sample in a separate container if further analysis is
expected.
10. Calculate the percent of mass less than the 200 mesh screen (75 micrometers [um]). This is
the silt content.
E.4 References
1. "Standard Method Of Preparing Coal Samples For Analysis", Annual Book OfASTM Standards,
1977, D2013-72, American Society For Testing And Materials, Philadelphia, PA, 1977.
2. L. Silverman, et al., Particle Size Analysis In Industrial Hygiene, Academic Press, New York,
1971.
E-6 EMISSION FACTORS 7/93
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SILT ANALYSIS
Date
Sample No:
Material:
By
Sample Weight (after drying)
Pan + Sample:
Pan:
Split Sample Balance:
Make
Smallest Division
SIEVING
Dry Sample:
Capacity
Final Weight:
Net Weight <200 Mesh
% Silt = Total Net Weight x 100 = %
Time: Start:
Initial (Tare):
10 min:
20 min:
30 min:
40 min:
Weight (Pan Only)
Screen
3/8 in.
4 mesh
10 mesh
20 mesh
40 mesh
100 mesh
140 mesh
200 mesh
Pan
Tare Weight
(Screen)
Final Weight
(Screen + Sample)
Net Weight (Sample)
%
Figure E-4. Example silt analysis form.
7/93
Appendix E
E-7
-------
TECHNICAL REPORT DATA
(Please read Instructions on the reverse before completing)
1. REPORT NO.
AP-42
2.
Volume I, Supplement F
3. RECIPIENT'S ACCESSION NO
4. TITLE AND SUBTITLE
Supplement F To Compilation Of Air Pollutant Emission
Factors, Volume I
5. REPORT DATE
July 1993
6. PERFORMING ORGANIZATION CODE
7. AUTHOR(S)
8. PERFORMING ORGANIZATION REPORT NO
9. PERFORMING ORGANIZATION NAME AND ADDRESS
10. PROGRAM ELEMENT NO.
U. S. Environmental Protection Agency
Office Of Air Quality Planning And Standards (MD 14)
Research Triangle Park, NC 27711
11. CONTRACT/GRANT NO.
12. SPONSORING AGENCY NAME AND ADDRESS
13. TYPE OF REPORT AND PERIOD COVERED
14. SPONSORING AGENCY CODE
15. SUPPLEMENTARY NOTES
16. ABSTRACT
This supplement to the AP-42 series contains new or revised emission information on Bituminous And
Subbituminous Coal Combustion; Anthracite Coal Combustion; Fuel Oil Combustion; Natural Gas Combustion;
Liquefied Petroleum Gas Combustion; Wood Waste Combustion In Boilers; Lignite Combustion; Bagasse
Combustion In Sugar Mills; Residential Fireplaces; Residential Wood Stoves; Waste Oil Combustion; Refuse
Combustion; Sewage Sludge Incineration; Medical Waste Incineration; Landfills; Stationary Gas Turbines For
Electricity Generation; Heavy Duty Natural Gas Fired Pipeline Compressor Engines; Gasoline And Diesel
Industrial Engines; Large Stationary Diesel And All Stationary Dual Fuel Engines; Synthetic Ammonia; Chlor-
Alkali; Hydrochloric Acid; Hydrofluoric Acid; Nitric Acid; Phosphoric Acid; Soap And Detergents; Sodium
Carbonate; Sulfuric Acid; Sulfur Recovery; Ammonium Nitrate; Normal Superphosphates; Triple
Superphosphates; Ammonium Phosphate; Urea; Ammonium Sulfate; Zinc Smelting; Secondary Zinc
Processing; Lead Oxide And Pigment Production; Clay And Fly Ash Sintering; Concrete Batching; Glass Fiber
Manufacturing; Gypsum Processing; Mineral Wool Processing; Perlite Processing; Phosphate Rock Processing;
Metallic Minerals Processing; Lightweight Aggregate Manufacturing; Feldspar Processing; Storage Of Organic
Liquids; Procedures For Sampling Surface And Bulk Materials; and Procedures For Analyzing Surface And
Bulk Material Samples.
This information is necessary for developing State Implementation Plans, emission inventories and
operating permits.
17.
KEY WORDS AND DOCUMENT ANALYSIS
DESCRIPTORS
b.IDENTIFIERS/OPEN ENDED TERMS C COSATI Field/Group
Stationary Sources
Point Sources
Area Sources
Emissions
Emission Factors
Air Pollutants
18. DISTRIBUTION STATEMENT
19. SECURITY CLASS (ThisReport)
21. NO. OF PAGES
628
20. SECURITY CLASS (Thispage)
22. PRICE
EPA Form 2220-1 (R«v. 4-77) PREVIOUS EDITION is OBSOLETE
*U.S. G.P.O.:1993-728-090:87002
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