-------
•a
"on
a
i
o
I
,
a
oo
ed
EMISSION
FACTOR
RATING
MISSION
FACTOR
RATING
1
1
60
Po
000000000
WWWWWWWWW*
r>i'53Vi"OT)-i/S-*— its
000000000
[UULUWPJWWtUllJ^
Q
SSSSSSSf
C4*O
00
00
S
o oo
CM vo
p
SSSSgSS
^— < en oo o oo
^HOOOo
crn'-'
+ ooo099 +
UUtUWpjpJWU
O O
00
UtUtUPJU
y
0 cT b o §
I-S^Q
<§J*6I
10/96
Solid Waste Disposal
2.1-27
-------
Table 2.1-9 (Metric And English Units). EMISSION FACTORS FOR
MODULAR STARVED-AIR COMBUSTORSa'b
Pollutant
PM"
As'
Cd"
Ci>
Hg«'f
Ni'
Pbe
S02
HC1«
NO,*
CO
C02h
CDD/CDFj
Uncontrolled
kg/Mg
1.72 E+00
3.34 E-04
1.20E-03
1.65E-03
2.8 E-03
2.76 E-03
ND
1.61 E+00
1.08E+00
1.58 E+00
1.50E-01
9.85 E+02
1.47E-06
Ib/ton
3.43 E+00
6.69 E-04
2.41 E-03
3.31 E-03
5.6 E-03
5.52 E-03
ND
3.23 E+00
2.15 E+00
3.16 E+00
2.99 E-01
1.97E+03
2.94 E-06
EMISSION
FACTOR
RATING
B
C
D
C
A
D
NA
E
D
B
B
D
D
ESP"
kg/Mg
1.74 E-01
5.25 E-05
2.30 E-04
3.08 E-04
2.8 E-03
5.04 E-04
1.41 E-03
*
*
*
*
*
1.88 E-06
Ib/ton
3.48 E-01
1.05 E-04
4.59 E-04
6. 16 E-04
5.6 E-03
1.01 E-03
2.82 E-03
*
He
*
*
*
3.76 E-06
EMISSION
FACTOR
RATING
B
D
D
D
A
E
C
C
* Emission factors were calculated from concentrations using an F-factor of 0.26 dscm/J (9,570 dscf/MBtu) and a
heating value of 10,466 J/g (4,500 Btu/lb). Other heating values can be substituted by multiplying the emission factor
by the new heating value and dividing by 10,466 J/g (4,500 Btu/lb). Source Classification Codes 5-01-001-01, 5-03-
001-14. ND = no data. NA = not applicable. * = Same as "uncontrolled" for these pollutants.
b Emission factors should be used for estimating long-term, not short-term, emission levels. This particularly applies to
pollutants measured with a continuous emission monitoring system (e. g., CO, NO,).
c ESP = Electrostatic Precipitator
d PM = total participate matter, as measured with EPA Reference Method 5.
" Hazardous air pollutants listed in the Clean Air Act.
* Mercury levels based on emission levels measured at mass burn, MOD/EA, and MOD/SA combustors.
8 Control of NO, and CO is not tied to traditional acid gas/PM control devices.
h Calculated assuming a dry carbon content of 26.8% for feed refuse.126'135 CO2 emitted from this source may not
increase total atmospheric CO2 because emissions may be offset by the uptake of CO2 by regrowing biomass.
j CDD/CDF = total tetra- through octa- chlorinated dibenzo-p-dioxin/chlorinated dibenzofurans,
2,3,7,8-tetrachlorodibenzo-p-dioxin, and dibenzofurans are hazardous air pollutants listed in the Clean Air Act.
2.1-28
EMISSION FACTORS
10/96
-------
Another point to keep in mind when using emission factors is that certain control
technologies, specifically ESPs and DSI systems, are not all designed with equal performance
capabilities. The ESP and DSI-based emission factors are based on data from a variety of facilities
and represent average emission levels for MWCs equipped with these control technologies. To
estimate emissions for a specific ESP or DSI system, refer to either the AP-42 background report for
this section or the NSPS and EG BIDs to obtain actual emissions data for these facilities. These
documents should also be used when conducting risk assessments, as well as for determining removal
efficiencies. Since the AP-42 emission factors represent averages from numerous facilities, the
uncontrolled and controlled levels frequently do not correspond to simultaneous testing and should not
be used to calculate removal efficiencies.
Emission factors for MWCs were calculated from flue gas concentrations using an F-factor of
0.26 dry standard cubic meters per joule (dscm/J) (9,570 dry standard cubic feet per million British
thermal units [Btu]) and an assumed heating value of the waste of 10,466 J/g (4,500 Btu per pound
[Btu/lb]) for all combustors except RDF, for which a 12,792 J/g (5,500 Btu/lb) heating value was
assumed. These are average values for MWCs; however, a particular facility may have a different
heating value for the waste. In such a case, the emission factors shown in the tables can be adjusted
by multiplying the emission factor by the actual facility heating value and dividing by the assumed
heating value (4,500 or 5,500 Btu/lb, depending on the combustor type). Also, conversion factors to
obtain concentrations, which can be used for developing more specific emission factors or making
comparisons to regulatory limits, are provided in Tables 2.1-10 and 2.1-11 for all combustor types
(except RDF) and RDF combustors, respectively.
Also note that the values shown in the tables for PM are for total PM, and the CDD/CDF
data represent total tetra- through octa-CDD/CDF. For SO2, NO,,, and CO, the data presented in the
tables represent long-term averages, and should not be used to estimate short-term emissions. Refer
to the EPA BIDs which discuss achievable emission levels of SO2, NOX, and CO for different
averaging times based on analysis of continuous emission monitoring data. Lastly, for PM and
metals, levels for MB/WW, MB/RC, MB/REF, and MOD/EA were combined to determine the
emission factors, since these emissions should be the same for these types of combustors. For
controlled levels, data were combined within each control technology type (e. g., SD/FF data, ESP
data). For Hg, MOD/SA data were also combined with the mass burn and MOD/EA data.
2.1.7 Other Types Of Combustors122-134
2.1.7.1 Industrial/Commercial Combustors -
The capacities of these units cover a wide range, generally between 23 and 1,800 kilograms
(50 and 4,000 pounds) per hour. Of either single- or multiple-chamber design, these units are often
manually charged and intermittently operated. Some industrial combustors are similar to municipal
combustors in size and design. Emission control systems include gas-fired afterburners, scrubbers, or
both. Under Section 129 of the CAAA, these types of combustors will be required to meet emission
limits for the same list of pollutants as for MWCs. The EPA has not yet established these limits.
2.1.7.2 Trench Combustors -
Trench combustors, also called air curtain incinerators, forcefully project a curtain of air
across a pit in which open burning occurs. The air curtain is intended to increase combustion
efficiency and reduce smoke and PM emissions. Underfire air is also used to increase combustion
efficiency.
10/96 Solid Waste Disposal 2.1-29
-------
Table 2.1-10. CONVERSION FACTORS FOR ALL COMBUSTOR TYPES EXCEPT RDF
a At 7% O,
Divide
For As, Cd,
For PM:
For HC1:
For SO2:
For NOX:
For CO:
For CO2:
Cr, Hg, Ni, Pb, and CDD/CDF:
kg/Mg refuse
Ib/ton refuse
kg/Mg refuse
Ib/ton refuse
kg/Mg refuse
Ib/ton refuse
kg/Mg refuse
Ib/ton refuse
kg/Mg refuse
Ib/ton refuse
kg/Mg refuse
Ib/ton refuse
kg/Mg refuse
Ib/ton refuse
By
4.03 x 10-6
8.06 x ID'6
4.03 x 10-3
8.06 x 10'3
6.15X10'3
1.23x 1C'2
1.07x 10-2
2.15x 1C'2
7.70 x 10-3
1.54x 10-2
4.69 x 10-3
9.4 x 10-3
7.35 x 10'3
1.47x ID'2
To Obtain'
/ig/dscm
rng/dscm
ppmv
ppmv
ppmv
ppmv
ppmv
2.1-30
EMISSION FACTORS
10/96
-------
Table 2.1-11. CONVERSION FACTORS FOR REFUSE-DERIVED FUEL COMBUSTORS
Divide
For As, Cd,
For PM:
For HC1:
For SO2:
For NOX:
For CO:
For CO2:
Cr, Hg, Ni, Pb, and CDD/CDF:
kg/Mg refuse
Ib/ton refuse
kg/Mg refuse
Ib/ton refuse
kg/Mg refuse
Ib/ton refuse
kg/Mg refuse
Ib/ton refuse
kg/Mg refuse
Ib/ton refuse
kg/Mg refuse
Ib/ton refuse
kg/Mg refuse
Ib/ton refuse
By
4.92 x ID'6
9.85 x ID'6
4.92 x ID'3
9.85 x 10'3
7.5 x ID'3
1.5x ID'2
1.31 x ID'2
2.62 x 10-2
9.45 x ID'3
1.89x ID'2
5.75 x ID'3
U5x 10-2
9.05 x 10-3
1.81 x ID'2
To Obtain"
/ig/dscm
mg/dscm
ppmv
ppmv
ppmv
ppmv
ppmv
At 7% O,
10/96
Solid Waste Disposal
2.1-31
-------
Trench combustors can be built either above- or below-ground. They have refractory walls
and floors and are normally 8-feet wide and 10-feet deep. Length varies from 8 to 16 feet. Some
units have mesh screens to contain larger particles of fly ash, but other add-on pollution controls are
normally not used.
Trench combustors burning wood wastes, yard wastes, and clean lumber are exempt from
Section 129, provided they comply with opacity limitations established by the Administrator. The
primary use of air curtain incinerators is the disposal of these types of wastes; however, some of
these combustors are used to burn MSW or construction and demolition debris.
In some states, trench combustors are often viewed as a version of open burning and the use
of these types of units has been discontinued in some States.
2.1.7.3 Domestic Combustors -
This category includes combustors marketed for residential use. These types of units are
typically located at apartment complexes, residential buildings, or other multiple family dwellings,
and are generally found in urban areas. Fairly simple in design, they may have single or multiple
refractory-lined chambers and usually are equipped with an auxiliary burner to aid combustion. Due
to their small size, these types of units are not currently covered by the MWC regulations.
2.1.7.4 Flue-fed Combustors-
These units, commonly found in large apartment houses or other multiple family dwellings,
are characterized by the charging method of dropping refuse down the combustor flue and into the
combustion chamber. Modified flue-fed incinerators utilize afterburners and draft controls to improve
combustion efficiency and reduce emissions. Due to their small size, these types of units are not
currently covered by the MWC regulations.
Emission factors for industrial/commercial, trench, domestic, and flue-fed combustors are
presented in Table 2.1-12.
2.1-32 EMISSION FACTORS 10/96
-------
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b Expressed as mei
10/96
Solid Waste Disposal
2.1-33
-------
References For Section 2.1
1. Written communication from D. A. Fenn and K. L. Nebel, Radian Corporation, Research
Triangle Park, NC, to W. H. Stevenson, U. S. Environmental Protection Agency, Research
Triangle Park, NC. March 1992.
2. J. Kiser, "The Future Role Of Municipal Waste Combustion", Waste Age, November 1991.
3. September 6, 1991. Meeting Summary: Appendix 1 (Docket No. A-90-45, Item
Number II-E-12).
4. Municipal Waste Combustion Study: Combustion Control Of Organic Emissions,
EPA/530-SW-87-021c, U. S. Environmental Protection Agency, Washington, DC, June 1987.
5. M. Clark, "Minimizing Emissions From Resource Recovery", Presented at the International
Workshop on Municipal Waste Incineration, Quebec, Canada, October 1-2, 1987.
6. Municipal Waste Combustion Assessment: Combustion Control At Existing Facilities,
EPA 600/8-89-058, U. S. Environmental Protection Agency, Research Triangle Park, NC,
August 1989.
7. Municipal Waste Combustors - Background Information For Proposed Standards: Control Of
NOX Emissions, EPA-450/3-89-27d, U. S. Environmental Protection Agency, Research
Triangle Park, NC, August 1989.
8. Municipal Waste Combustors - Background Information For Proposed Standards: Post
Combustion Technology Performance, U. S. Environmental Protection Agency, August 1989.
9. Municipal Waste Combustion Study - Flue Gas Cleaning Technology, EPA/530-SW-87-021c,
U. S. Environmental Protection Agency, Washington, DC, June 1987.
10. R. Bijetina, et al., "Field Evaluation of Methane de-NOx at Olmstead Waste-to-Energy
Facility", Presented at the 7th Annual Waste-to-Energy Symposium, Minneapolis, MN,
January 28-30, 1992.
11. K. L. Nebel and D. M. White, A Summary Of Mercury Emissions And Applicable Control
Technologies For Municipal Waste Combustors, Research Triangle Park, NC, September,
1991.
12. Emission Test Report: OMSS Field Test On Carbon Injection For Mercury Control,
EPA-600/R-92-192, Office of Air Quality Planning and Standards, U. S. Environmental
Protection Agency, Research Triangle Park, NC, September 1992.
13. J. D. Kilgroe, et al., "Camden Country MWC Carbon Injection Test Results", Presented at
the International Conference on Waste Combustion, Williamsburg, VA, March 1993.
14. Meeting Summary: Preliminary Mercury Testing Results For The Stanislaus County
Municipal Waste Combustor, U. S. Environmental Protection Agency, Research Triangle
Park, NC, November 22, 1991.
2.1-34 EMISSION FACTORS 10/96
-------
15. R. A. Zurlinden, et al., Environmental Test Report, Alexandria/Arlington Resources Recovery
Facility, Units 1, 2, And 3, Report No. 144B, Ogden Martin Systems of
Alexandria/Arlington, Inc., Alexandria, VA, March 9, 1988.
16. R. A. Zurlinden, et al., Environmental Test Report, Alexandria/Arlington Resource Recovery
Facility, Units I, 2, And 3, Report No. 144A (Revised), Ogden Martin Systems of
Alexandria/Arlington, Inc., Alexandria, VA, January 8, 1988.
17. Environmental Test Report, Babylon Resource Recovery Test Facility, Units 1 And 2, Ogden
Martin Systems of Babylon, Inc., Ogden Projects, Inc., March 1989.
18. Ogden Projects, Inc. Environmental Test Report, Units 1 And 2, Babylon Resource Recovery
Facility, Ogden Martin Systems for Babylon, Inc., Babylon, NY, February 1990.
19. PEI Associates, Inc. Method Development And Testing For Chromium, No. Refuse-to-Energy
Incinerator, Baltimore RESCO, EMB Report 85-CHM8, EPA Contract No. 68-02-3849,
U.S. Environmental Protection Agency, Research Triangle Park, NC, August 1986.
20. Entropy Environmentalists, Inc. Paniculate, Sulfur Dioxide, Nitrogen Oxides, Chlorides,
Fluorides, And Carbon Monoxide Compliance Testing, Units 1, 2, And 3, Baltimore RESCO
Company, L. P., Southwest Resource Recovery Facility, RUST International, Inc., January
1985.
21. Memorandum. J. Perez, AM/3, State of Wisconsin, to Files. "Review Of Stack Test
Performed At Barron County Incinerator," February 24, 1987.
22. D. S. Beachler, et al., "Bay County, Florida, Waste-To-Energy Facility Air Emission Tests.
Westinghouse Electric Corporation", Presented at Municipal Waste Incineration Workshop,
Montreal, Canada, October 1987.
23. Municipal Waste Combustion, Multi-Pollutant Study. Emission Test Report. Volume I,
Summary Of Results, EPA-600/8-89-064a, Maine Energy Recovery Company, Refuse-Derived
Fuel Facility, Biddeford, ME, July 1989.
24. S. Klamm, et al., Emission Testing At An RDF Municipal Waste Combustor, EPA Contract
No. 68-02-4453, U. S. Environmental Protection Agency, NC, May 6, 1988. (Biddeford)
25. Emission Source Test Report — Preliminary Test Report On Cattaraugus County, New York
State Department of Environmental Conservation, August 5, 1986.
26. Permit No. 0560-0196 For Foster Wheeler Charleston Resource Recovery, Inc. Municipal
Solid Waste Incinerators A & B, Bureau of Air Quality Control, South Carolina Department
of Health and Environmental Control, Charleston, SC, October 1989.
27. Almega Corporation. Unit 1 And Unit 2, EPA Stack Emission Compliance Tests, May 26, 27,
And 29, 1987, At The Signal Environmental Systems, Claremont, NH, NH/VT Solid Waste
Facility, Prepared for Clark-Kenith, Inc. Atlanta, GA, July 1987.
10/96 Solid Waste Disposal 2.1-35
-------
28. Entropy Environmentalists, Inc. Stationary Source Sampling Report, Signal Environmental
Systems, Inc., At The Claremont Facility, Claremont, New Hampshire, Dioxins/Furans
Emissions Compliance Testing, Units 1 And 2, Reference No. 5553-A, Signal Environmental
Systems, Inc., Claremont, NH, October 2, 1987.
29. M. D. McDannel, et al, Air Emissions Tests At Commerce Refuse-To-Energy Facility
May 26 - June 5, 1987, County Sanitation Districts of Los Angeles County, Whittier, CA,
July 1987.
30. M. D. McDannel and B. L. McDonald, Combustion Optimization Study At The Commerce
Refuse-To-Energy Facility. Volume /, ESA 20528-557, County Sanitation Districts of
Los Angeles County, Los Angeles, CA, June 1988.
31. M. D. McDannel et al., Results Of Air Emission Test During The Waste-to-Energy Facility,
County Sanitation Districts Of Los Angeles County, Whittier, CA, December 1988.
(Commerce)
32. Radian Corporation. Preliminary Data From October - November 1988 Testing At The
Montgomery County South Plant, Dayton, Ohio.
33. Written communication from M. Hartman, Combustion Engineering, to D. White,
Radian Corporation, Detroit Compliance Tests, September 1990.
34. Interpoll Laboratories. Results Of The November 3-6, 1987 Performance Test On The No. 2
RDF And Sludge Incinerator At The WLSSD Plant In Duluth, Minnesota, Interpoll Report
No. 7-2443, April 25, 1988.
35. D. S. Beachler, (Westinghouse Electric Corporation) and ETS, Inc, Dutchess County
Resource Recovery Facility Emission Compliance Test Report, Volumes 1-5, New York
Department of Environmental Conservation, June 1989.
36. ETS, Inc. Compliance Test Report For Dutchess County Resource Recovery Facility, May
1989.
37. Written communication and enclosures from W. Harold Snead, City of Galax, VA, to
Jack R. Farmer, U.S. Environmental Protection Agency, Research Triangle Park, NC,
July 14, 1988.
38. Cooper Engineers, Inc., Air Emissions Tests Of Solid Waste Combustion A Rotary
Combustion/Boiler System At Gallatin, Tennessee, West County Agency of Contra Costa
County, CA, July 1984.
39. B. L. McDonald, et al., Air Emissions Tests At The Hampton Refuse-Fired Stream Generating
Facility, April 18-24, 1988, Clark-Kenith, Incorporated, Bethesda, MD, June 1988.
40. Radian Corporation for American Ref-Fuel Company of Hempstead, Compliance Test Report
For The Hempstead Resource Recovery Facility, Westbury, NY, Volume I, December 1989.
41. J. Campbell, Chief, Air Engineering Section, Hillsborough County Environmental Protection
Commission, to E. L. Martinez, Source Analysis Section/AMTB, U. S. Environmental
Protection Agency, May 1, 1986.
2.1-36 EMISSION FACTORS 10/96
-------
42. Mitsubishi SCR System for Municipal Refuse Incinerator, Measuring Results At Tokyo-
Hikarigaoka And Iwatsuld, Mitsubishi Heavy Industries, Ltd, July 1987.
43. Entropy Environmentalists, Inc. for Honolulu Resource Recovery Venture, Stationary Source
Sampling Final Report, Volume I, Oahu, HI, February 1990.
44. Ogden Projects, Inc., Environmental Test Report, Indianapolis Resource Recovery Facility,
Appendix A And Appendix B, Volume I, (Prepared for Ogden Martin Systems of Indianapolis,
Inc.), August 1989.
45. D. R. Knisley, et al. (Radian Corporation), Emissions Test Report, Dioxin/Furan Emission
Testing, Refuse Fuels Associates, Lawrence MA, (Prepared for Refuse Fuels Association),
Haverhill, MA, June 1987.
46. Entropy Environmentalists, Inc. Stationary Source Sampling Report, Ogden Martin Systems of
Haverhill, Inc., Lawrence, MA Thermal Conversion Facility. Paniculate, Dioxins/Furans and
Nitrogen Oxides Emission Compliance Testing, September 1987.
47. D. D. Ethier, et al. (TRC Environmental Consultants), Air Emission Test Results At The
Southeast Resource Recovery Facility Unit I, October - December, 1988, Prepared for Dravo
Corporation, Long Beach, CA, February 28, 1989.
48. Written communication from from H. G. Rigo, Rigo & Rigo Associates, Inc., to
M. Johnston, U. S. Environmental Protection Agency. March 13, 1989. 2 pp. Compliance
Test Report Unit No. 1 - South East Resource Recovery Facility, Long Beach, CA.
49. M. A. Vancil and C. L. Anderson (Radian Corporation), Summary Report CDD/CDF,
Metals, HCl, SO2, NOX, CO And Particulate Testing, Marion County Solid Waste-To-Energy
Facility, Inc., Ogden Martin Systems Of Marion, Brooks, Oregon, U. S. Environmental
Protection Agency, Research Triangle Park, NC, EMB Report No. 86-MIN-03A, September
1988.
50. C. L. Anderson, et al. (Radian Corporation), Characterization Test Report, Marion County
Solid Waste-To-Energy Facility, Inc., Ogden Martin Systems Of Marion, Brooks, Oregon,
U.S. Environmental Protection Agency, Research Triangle Park, NC, EMB Report
No. 86-MIN-04, September 1988.
51. Letter Report from M. A. Vancil, Radian Corporation, to C. E. Riley, EMB Task Manager,
U.S. Environmental Protection Agency. Emission Test Results for the PCDD/PCDF Internal
Standards Recovery Study Field Test: Runs 1, 2, 3, 5, 13, 14. July 24, 1987. (Marion)
52. C. L. Anderson, et al., (Radian Corporation). Shutdown/Startup Test Program Emission Test
Report, Marion County Solid Waste-To-Energy Facility, Inc., Ogden Martin Systems Of
Marion, Brooks, Oregon, U. S. Environmental Protection Agency, Research Triangle Park,
NC, EMB Report No. 87-MIN-4A, September 1988.
53. Clean Air Engineering, Inc., Report On Compliance Testing For Waste Management, Inc. At
. The McKay Bay Refuse-to-Energy Project Located In Tampa, Florida, October 1985.
10/96 Solid Waste Disposal 2.1-37
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54. Alliance Technologies Corporation, Field Test Report - MTEP 111. Mid-Connecticut Facility,
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55. C. L. Anderson, (Radian Corporation), CDD/CDF, Metals, And Paniculate Emissions
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56. Entropy Environmentalists, Inc., Municipal Waste Combustion Multi-Pollutant Study,
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57. Entropy Environmentalists, Inc., Emissions Testing Report, Wheelabrator Millbury, Inc.
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through 12, 1988, Prepared for Rust International Corporation. Reference No. 5605-B.
August 5, 1988.
58. Entropy Environmentalists, Inc., Stationary Source Sampling Report, Wheelabrator Millbury,
Inc., Resource Recovery Facility, Millbury, Massachusetts, Mercury Emissions Compliance
Testing, Unit No. 1, May 10 And 11, 1988, Prepared for Rust International Corporation.
Reference No. 5892-A, May 18, 1988.
59. Entropy Environmentalists, Inc., Emission Test Report, Municipal Waste Combustion
Continuous Emission Monitoring Program, Wheelabrator Resource Recovery Facility,
Millbury, Massachusetts, U.S. Environmental Protection Agency, Research Triangle Park,
NC, Emission Test Report 88-MIN-07C, January 1989.
60. Entropy Environmentalists, Municipal Waste Combustion Multipollutant Study: Emission Test
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61. Entropy Environmentalists, Emission Test Report, Municipal Waste Combustion, Continuous
Emission Monitoring Program, Wheelabrator Resource Recovery Facility, Millbury,
Massachusetts, Prepared for the U. S. Environmental Protection Agency, Research Triangle
Park, NC. EPA Contract No. 68-02-4336, October 1988.
62. Entropy Environmentalists, Emissions Testing At Wheelabrator Millbury, Inc. Resource
Recovery Facility, Millbury, Massachusetts, Prepared for Rust International Corporation.
February 8-12, 1988.
63. Radian Corporation, Site-Specific Test Plan And Quality Assurance Project Plan For The
Screening And Parametric Programs At The Montgomery County Solid Waste Management
Division South Incinerator - Unit #3, Prepared for U. S. EPA, OAQPS and ORD, Research
Triangle Park, NC, November 1988.
64. Written communication and enclosures from John W. Norton, County of Montgomery, OH,
to Jack R. Farmer, U. S. Environmental Protection Agency, Research Triangle Park, NC.
May 31, 1988.
2.1-38 EMISSION FACTORS 10/96
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65. J. L. Hahn, et al., (Cooper Engineers) and J. A. Finney, Jr., et al., (Belco Pollution Control
Corp.), "Air Emissions Tests Of A Deutsche Babcock Anlagen Dry Scrubber System At The
Munich North Refuse-Fired Power Plant", Presented at: 78th Annual Meeting of the Pollution
Control Association, Detroit, MI, June 1985.
66. Clean Air Engineering, Results Of Diagnostic And Compliance Testing At NSP French Island
Generating Facility Conducted May 17-19, 1989, July 1989.
67. Preliminary Report On Occidental Chemical Corporation EFW. New York State Department
Of Environmental Conservation, (Niagara Falls), Albany, NY, January 1986.
68. H. J. Hall, Associates, Summary Analysis On Precipitator Tests And Performance Factors,
May 13-15, 1986 At Incinerator Units 1,2- Occidental Chemical Company, Prepared for
Occidental Chemical Company EFW, Niagara Falls, NY, June 25, 1986.
69. C. L. Anderson, et al. (Radian Corporation), Summary Report, CDD/CDF, Metals and
Paniculate, Uncontrolled And Controlled Emissions, Signal Environmental Systems, Inc.,
North Andover RESCO, North Andover, MA, U.S. Environmental Protection Agency,
Research Triangle Park, NC, EMB Report No. 86-MINO2A, March 1988.
70. York Services Corporation, Final Report For A Test Program On The Municipal Incinerator
Located At Northern Aroostook Regional Airport, Frenchville, Maine, Prepared for Northern
Aroostook Regional Incinerator Frenchville, ME, January 26, 1987.
71. Radian Corporation, Results From The Analysis Of MSW Incinerator Testing At Oswego
County, New York, Prepared for New York State Energy Research and Development
Authority, March 1988.
72. Radian Corporation, Data Analysis Results For Testing At A Two-Stage Modular MSW
Combustor: Oswego County ERF, Fulton, New York, Prepared for New York State's Energy
Research and Development Authority, Albany, NY, November 1988.
73. A. J. Fossa, et al., Phase I Resource Recovery Facility Emission Characterization Study,
Overview Report, (Oneida, Peekskill), New York State Department of Environmental
Conservation, Albany, NY, May 1987.
74. Radian Corporation, Results From The Analysis Of MSW Incinerator Testing At Peekskill,
New York, Prepared for New York State Energy Research and Development Authority,
DCN:88-233-012-21, August 1988.
75. Radian Corporation, Results from the Analysis of MSW Incinerator Testing at Peekskill, New
York (DRAFT), (Prepared for the New York State Energy Research and Development
Authority), Albany, NY, March 1988.
76. Ogden Martin Systems of Pennsauken, Inc., Pennsauken Resource Recovery Project, BACT
Assessment For Control Of NO,. Emissions, Top-Down Technology Consideration, Fairfield,
NJ, pp. 11, 13, December 15, 1988.
77. Roy F. Weston, Incorporated, Penobscot Energy Recovery Company Facility, Orrington,
Maine, Source Emissions Compliance Test Report Incinerator Units A And B (Penobscot,
Maine), Prepared for GE Company, September 1988.
10/96 Solid Waste Disposal 2.1-39
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78. S. Zaitlin, Air Emission License Finding Of Fact And Order, Penobscot Energy Recovery
Company, Orrington, ME, State of Maine, Department of Environmental Protection, Board of
Environmental Protection, February 26, 1986.
79. R. Neulicht, (Midwest Research Institute), Emissions Test Report: City Of Philadelphia
Northwest And East Central Municipal Incinerators, Prepared for the U. S. Environmental
Protection Agency, Philadelphia, PA, October 31, 1985.
80. Written communication with attachments from Philip Gehring, Plant Manager (Pigeon Point
Energy Generating Facility), to Jack R. Farmer, Director, BSD, OAQPS, U. S.
Environmental Protection Agency, June 30, 1988.
81. Entropy Environmentalists, Inc., Stationary Source Sampling Report, Signal RESCO, Pinellas
County Resource Recovery Facility, St. Petersburg, Florida, CARB/DER Emission Testing,
Unit 3 Precipitator Inlets and Stack, February and March 1987.
82. Midwest Research Institute, Results Of The Combustion And Emissions Research Project At
The Vicon Incinerator Facility In Pittsfield, Massachusetts, Prepared for New York State
Energy Research and Development Authority, June 1987.
83. Response to Clean Air Act Section 114 Information Questionnaire, Results of Non-Criteria
Pollutant Testing Performed at Pope-Douglas Waste to Energy Facility, July 1987, Provided
to EPA on May 9, 1988.
84. Engineering Science, Inc., A Report On Air Emission Compliance Testing At The Regional
Waste Systems, Inc. Greater Portland Resource Recovery Project, Prepared for Dravo Energy
Resources, Inc., Pittsburgh, PA, March 1989.
85. D. E. Woodman, Test Report Emission Tests, Regional Waste Systems, Portland, ME,
February 1990.
86. Environment Canada, The National Incinerator Testing And Evaluation Program: Two State
Combustion, Report EPS 3/up/l, (Prince Edward Island), September 1985.
87. Statistical Analysis Of Emission Test Data From Fluidized Bed Combustion Boilers At Prince
Edward Island, Canada, U. S. Environmental Protection Agency, Publication No.
EPA-450/3-86-015, December 1986.
88. The National Incinerator Testing And Evaluation Program: Air Pollution Control Technology,
EPS 3/UP/2, (Quebec City), Environment Canada, Ottawa, September 1986.
89. Lavalin, Inc., National Incinerator Testing And Evaluation Program: The Combustion
Characterization Of Mass Burning Incinerator Technology; Quebec City (DRAFT), (Prepared
for Environmental Protection Service, Environmental Canada), Ottawa, Canada,
September 1987.
90. Environment Canada, NITEP, Environmental Characterization Of Mass Burning Incinerator
Technology at Quebec City. Summary Report, EPS 3/UP/5, June 1988.
2.1-40 EMISSION FACTORS 10/96
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91. Interpoll Laboratories, Results Of The March 21 - 26, 1988, Air Emission Compliance Test On
The No. 2 Boiler At The Red Wing Station, Test IV (High Load), Prepared for Northern States
Power Company, Minneapolis, MN, Report No. 8-2526, May 10, 1988.
92. Interpoll Laboratories, Results Of The May 24-27, 1988 High Load Compliance Test On
Unit 1 And Low Load Compliance Test On Unit 2 At The NSP Red Wing Station, Prepared for
Northern States Power Company, Minneapolis, MN, Report No. 8-2559, July 21, 1988.
93. Cal Recovery Systems, Inc., Final Report, Evaluation Of Municipal Solid Waste Incineration.
(Red Wing, Minnesota facility) Submitted To Minnesota Pollution Control Agency, Report
No. 1130-87-1, January 1987.
94. Eastmount Engineering, Inc., Final Report, Waste-To-Energy Resource Recovery Facility,
Compliance Test Program, Volumes II-V, (Prepared for SEMASS Partnership.), March 1990.
95. D. McClanahan, (Fluor Daniel), A. Licata (Dravo), and J. Buschmann (Flakt, Inc.).,
"Operating Experience With Three APC Designs On Municipal Incinerators". Proceedings of
the International Conference on Municipal Waste Combustion, pp. 7C-19 to 7C-41,
(Springfield), April 11-14, 1988.
96. Interpoll Laboratories, Inc., Results Of The June 1988 Air Emission Performance Test On The
MSW Incinerators At The St. Croix Waste To Energy Facility In New Richmond, Wisconsin,
Prepared for American Resource Recovery, Waukesha, WI, Report No. 8-2560,
September 12, 1988.
97. Interpoll Laboratories, Inc, Results Of The June 6, 1988, Scrubber Performance Test At The
St. Croix Waste To Energy Incineration Facility In New Richmond, Wisconsin, Prepared for
Interel Corporation, Englewood, CO, Report No. 8-25601, September 20, 1988.
98. Interpoll Laboratories, Inc., Results Of The August 23, 1988, Scrubber Performance Test At
The St. Croix Waste To Energy Incineration Facility In New Richmond, Wisconsin, Prepared
for Interel Corporation, Englewood, CO, Report No. 8-2609, September 20, 1988.
99. Interpoll Laboratories, Inc., Results Of The October 1988 Paniculate Emission Compliance
Test On The MSW Incinerator At The St. Croix Waste To Energy Facility In New Richmond,
Wisconsin, Prepared for American Resource Recovery, Waukesha, WI, Report No. 8-2547,
November 3, 1988.
100. Interpoll Laboratories, Inc., Results Of The October 21, 1988, Scrubber Performance Test At
The St. Croix Waste To Energy Facility In New Richmond, Wisconsin, Prepared for Interel
Corporation, Englewood, CO, Report No. 8-2648, December 2, 1988.
101. J. L. Hahn, (Ogden Projects, Inc.), Environmental Test Report, Prepared for Stanislaus Waste
Energy Company Crows Landing, CA, OPI Report No. 177R, April 7, 1989.
102. J. L. Hahn, and D. S. Sofaer, "Air Emissions Test Results From The Stanislaus County,
California Resource Recovery Facility", Presented at the International Conference on
Municipal Waste Combustion, Hollywood, FL, pp. 4A-1 to 4A-14, April 11-14, 1989.
10/96 Solid Waste Disposal 2.1-41
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103. R. Seelinger, et al. (Ogden Products, Inc.), Environmental Test Report, Walter B. Hall
Resource Recovery Facility, Units 1 And 2, (Prepared for Ogden Martin Systems of Tulsa,
Inc.), Tulsa, OK, September 1986.
104. PEI Associates, Inc, Method Development And Testing for Chromium, Municipal Refuse
Incinerator, Tuscaloosa Energy Recovery, Tuscaloosa, Alabama, U.S. Environmental
Protection Agency, Research Triangle Park, NC, EMB Report 85-CHM-9, January 1986.
105. T. Guest and O. Knizek, "Mercury Control At Burnaby's Municipal Waste Incinerator",
Proceedings of the 84th Annual Meeting and Exhibition of the Air and Waste Management
Association, Vancouver, British Columbia, Canada, June 16-21, 1991.
106. Trip Report, Burnaby MWC, British Columbia, Canada. White, D., Radian Corporation,
May 1990.
107. Entropy Environmentalists, Inc. for Babcock & Wilcox Co. North County Regional Resource
Recovery Facility, West Palm Beach, FL, October 1989.
108. P. M. Maly, et al., Results Of The July 1988 Wilmarth Boiler Characterization Tests, Gas
Research Institute Topical Report No. GRI-89/0109, June 1988-March 1989.
109. J. L. Hahn, (Cooper Engineers, Inc.), Air Emissions Testing At The Martin GmbH Waste-To-
Energy Facility In Wurzburg, West Germany, Prepared for Ogden Martin Systems, Inc.,
Paramus, NJ, January 1986.
110. Entropy Environmentalists, Inc. for Westinghouse RESD, Metals Emission Testing Results,
Conducted At The York County Resource Recovery Facility, February 1991.
111. Entropy Environmentalists, Inc. for Westinghouse RESD, Emissions Testing For: Hexavalent
Chromium, Metals, Paniculate. Conducted At The York County Resource Recovery Facility,
July 31 -August 4, 1990.
112. Interpoll Laboratories, Results of the July 1987 Emission Performance Tests Of The
Pope/Douglas Waste-To-Energy Facility MSW Incinerators In Alexandria, Minnesota,
(Prepared for HDR Techserv, Inc.), Minneapolis, MN, October 1987.
113. D. B. Sussman, Ogden Martin System, Inc., Submittal to Air Docket (LE-131), Docket
No. A-89-08, Category IV-M, Washington, DC, October 1990.
114. F. Ferraro, Wheelabrator Technologies, Inc., Data package to D. M. White, Radian
Corporation, February 1991.
115. D. R. Knisley, et al. (Radian Corporation), Emissions Test Report, Dioxin/Furan Emission
Testing, Refuse Fuels Associates, Lawrence, Massachusetts, (Prepared for Refuse Fuels
Association), Haverhill, MA, June 1987.
116. Entropy Environmentalists, Inc., Stationary Source Sampling Report, Ogden Martin Systems
Of Haverhill, Inc., Lawrence, Massachusetts Thermal Conversion Facility. Paniculate,
Dioxins/Furans And Nitrogen Oxides Emission Compliance Testing, September 1987.
2.1-42 EMISSION FACTORS 10/96
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117. A. J. Fossa, et al., Phase I Resource Recovery Facility Emission Characterization Study,
Overview Report, New York State Department of Environmental Conservation, Albany, NY,
May 1987.
118. Telephone communciation between D. DeVan, Oneida ERF, and M. A. Vancil, Radian
Corporation. April 4, 1988. Specific collecting area of ESPs.
119. G. M. Higgins, An Evaluation Of Trace Organic Emissions From Refuse Thermal Processing
Facilities (North Little Rock, Arkansas; Mayport Naval Station, Florida; And Wright Patterson
Air Force Base, Ohio), Prepared for U. S. Environmental Protection Agency/Office of Solid
Waste by Systech Corporation, July 1982.
120. R. Kerr, et al., Emission Source Test Report—Sheridan Avenue RDF Plant, Answers (Albany,
New York), Division of Air Resources, New York State Department of Environmental
Conservation, August 1985.
121. U. S. Environmental Protection Agency, Emission Factor Documentation for AP-42
Section 2.1, Refuse Combustion, Research Triangle Park, NC, May 1993.
122. Air Pollutant Emission Factors, APTD-0923, U. S. Environmental Protection Agency,
Research Triangle Park, NC, April 1970.
123. Control Techniques For Carbon Monoxide Emissions From Stationary Sources, AP-65,
U. S. Environmental Protection Agency, Research Triangle Park, NC, March 1970.
124. Air Pollution Engineering Manual, AP-40, U. S. Environmental Protection Agency, Research
Triangle Park, NC, 1967.
125. J. DeMarco, et al., Incinerator Guidelines 1969, SW. 13TS, U. S. Environmental Protection
Agency, Research Triangle Park, NC, 1969.
126. Municipal Waste Combustors - Background Information For Proposed Guidelines For Existing
Facilities, U. S. Environmental Protection Agency, Research Triangle Park, NC,
EPA-450/3-89-27e, August 1989.
127. Municipal Waste Combustors - Background Information for Proposed Standards: Control Of
NOX Emissions U. S. Environmental Protection Agency, Research Triangle Park, NC,
EPA-450/3-89-27d, August 1989.
127. J. O. Brukle, et al., "The Effects Of Operating Variables And Refuse Types On Emissions
From A Pilot-scale Trench Incinerator," Proceedings of the 1968 Incinerator Conference,
American Society of Mechanical Engineers, New York, NY, May 1968.
128. W. R. Nessen, Systems Study Of Air Pollution From Municipal Incineration, Arthur D. Little,
Inc., Cambridge, MA, March 1970.
130. C. R. Brunner, Handbook Of Incineration Systems, McGraw-Hill, Inc., pp. 10.3-10.4, 1991.
131. Telephone communication between K. Quincey, Radian Corporation, and E. Raulerson,
Florida Department of Environmental Regulations, February 16, 1993.
10/96 Solid Waste Disposal 2.1-43
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132. Telephone communication between K. Nebel and K. Quincey, Radian Corporation, and
M. McDonnold, Simonds Manufacturing, February 16, 1993.
133. Telephone communication between K. Quincey, Radian Corporation, and R. Crochet, Crochet
Equipment Company, February 16 and 26, 1993.
134. Telephone communication between K. Quincey, Radian Corporation, and T. Allen, NC
Division of Environmental Management, February 16, 1993.
135. John Pacy, Methane Gas In Landfills: Liability Or Asset?, Proceedings of the Fourth
National Congress of the Waste Management Technology and Resource and Energy
Recovery, Co-sponsored by the National Solid Wastes Management Association and
U. S. EPA, November 12-14, 1975.
2.1-44 EMISSION FACTORS 10/96
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2.2 Sewage Sludge Incineration
There are approximately 170 sewage sludge incineration (SSI) plants in operation in the
United States. Three main types of incinerators are used: multiple hearth, fluidized bed, and electric
infrared. Some sludge is co-fired with municipal solid waste in combustors based on refuse
combustion technology (see Section 2.1). Refuse co-fired with sludge in combustors based on sludge
incinerating technology is limited to multiple hearth incinerators only.
Over 80 percent of the identified operating sludge incinerators are of the multiple hearth
design. About 15 percent are fluidized bed combustors and 3 percent are electric. The remaining
combustors co-fire refuse with sludge. Most sludge incinerators are located in the Eastern
United States, though there are a significant number on the West Coast. New York has the largest
number of facilities with 33. Pennsylvania and Michigan have the next-largest numbers of facilities
with 21 and 19 sites, respectively.
Sewage sludge incinerator emissions are currently regulated under 40 CFR Part 60, Subpart O
and 40 CFR Part 61, Subparts C and E. Subpart O in Part 60 establishes a New Source Performance
Standard for particulate matter. Subparts C and E of Part 61—National Emission Standards for
Hazardous Air Pollutants (NESHAP)—establish emission limits for beryllium and mercury,
respectively.
In 1989, technical standards for the use and disposal of sewage sludge were proposed as
40 CFR Part 503, under authority of Section 405 of the Clean Water Act. Subpart G of this
proposed Part 503 proposes to establish national emission limits for arsenic, beryllium, cadmium,
chromium, lead, mercury, nickel, and total hydrocarbons from sewage sludge incinerators. The
proposed limits for mercury and beryllium are based on the assumptions used in developing the
NESHAPs for these pollutants, and no additional controls were proposed to be required. Carbon
monoxide emissions were examined, but no limit was proposed.
2.2.1 Process Description1'2
Types of incineration described in this section include:
- Multiple hearth,
- Fluidized bed, and
- Electric.
Single hearth cyclone, rotary kiln, and wet air oxidation are also briefly discussed.
2.2.1.1 Multiple Hearth Furnaces -
The multiple hearth furnace was originally developed for mineral ore roasting nearly a
century ago. The air-cooled variation has been used to incinerate sewage sludge since the 1930s.
A cross-sectional diagram of a typical multiple hearth furnace is shown in Figure 2.2-1. The basic
multiple hearth furnace (MHF) is a vertically oriented cylinder. The outer shell is constructed of
steel, lined with refractory, and surrounds a series of horizontal refractory hearths. A hollow cast
iron rotating shaft runs through the center of the hearths. Cooling air is introduced into the shaft
1/95 Solid Waste Disposal 2.2-1
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COOLING AIR DISCHARGE
FLOATING DAMPER
SLUDGE INLET
FLUE GASES OUT
DRYING ZONE
COMBUSTION ZONE
COOLING ZONE
ASH DISCHARGE
RABBLE ARM
'AT EACH HEARTH
COMBUSTION
AIR RETURN
RABBLE ARM
DRIVE
COOLING AIR FAN
Figure 2.2-1. Cross Section of a Multiple Hearth Furnace
2.2-2
EMISSION FACTORS
1/95
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which extend above the hearths. Each rabble arm is equipped with a number of teeth, approximately
6 inches in length, and spaced about 10 inches apart. The teeth are shaped to rake the sludge in a
spiral motion, alternating hi direction from the outside in, to the inside out, between hearths.
Typically, the upper and lower hearths are fitted with four rabble arms, and the middle hearths are
fitted with two. Burners, providing auxiliary heat, are located in the sidewalls of the hearths.
In most multiple hearth furnaces, partially dewatered sludge is fed onto the perimeter of the
top hearth. The rabble arms move the sludge through the incinerator by raking the sludge toward the
center shaft where it drops through holes located at the center of the hearth. In the next hearth the
sludge is raked hi the opposite direction. This process is repeated in all of the subsequent hearths.
The effect of the rabble motion is to break up solid material to allow better surface contact with heat
and oxygen. A sludge depth of about 1 inch is maintained in each hearth at the design sludge flow
rate.
Scum may also be fed to one or more hearths of the incinerator. Scum is the material that
floats on wastewater. It is generally composed of vegetable and mineral oils, grease, hair, waxes,
fats, and other materials that will float. Scum may be removed from many treatment units including
preaeration tanks, skimming tanks, and sedimentation tanks. Quantities of scum are generally small
compared to those of other wastewater solids.
Ambient air is first ducted through the central shaft and its associated rabble arms. A
portion, or all, of this air is then taken from the top of the shaft and recirculated into the lowermost
hearth as preheated combustion air. Shaft cooling air which is not circulated back into the furnace is
ducted into the stack downstream of the air pollution control devices. The combustion air flows
upward through the drop holes in the hearths, countercurrent to the flow of the sludge, before being
exhausted from the top hearth. Air enters the bottom to cool the ash. Provisions are usually made to
inject ambient air directly into the middle hearths as well.
From the standpoint of the overall incineration process, multiple hearth furnaces can be
divided into three zones. The upper hearths comprise the drying zone where most of the moisture in
the sludge is evaporated. The temperature in the drying zone is typically between 425 and 760°C
(800 and 1400°F). Sludge combustion occurs in the middle hearths (second zone) as the temperature
is increased to about 925°C (1700°F). The combustion zone can be further subdivided into the
upper-middle hearths where the volatile gases and solids are burned, and the lower-middle hearths
where most of the fixed carbon is combusted. The third zone, made up of the lowermost hearth(s), is
the cooling zone. In this zone the ash is cooled as its heat is transferred to the incoming combustion
ah-.
Multiple hearth furnaces are sometimes operated with afterburners to further reduce odors and
concentrations of unburned hydrocarbons. In afterburning, furnace exhaust gases are ducted to a
chamber where they are mixed with supplemental fuel and air and completely combusted. Some
incinerators have the flexibility to allow sludge to be fed to a lower hearth, thus allowing the upper
hearth(s) to function essentially as an afterburner.
Under normal operating condition, 50 to 100 percent excess air must be added to an MHF in
order to ensure complete combustion of the sludge. Besides enhancing contact between fuel and
oxygen in the furnace, these relatively high rates of excess air are necessary to compensate for normal
variations in both the organic characteristics of the sludge feed and the rate at which it enters the
incinerator. When an inadequate amount of excess air is available, only partial oxidation of the
carbon will occur, with a resultant increase in emissions of carbon monoxide, soot, and hydrocarbons.
1/95 Solid Waste Disposal 2.2-3
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Too much excess air, on the other hand, can cause increased entrainment of paniculate and
unnecessarily high auxiliary fuel consumption.
Multiple hearth furnace emissions are usually controlled by a venturi scrubber, an
impingement tray scrubber, or a combination of both. Wet cyclones and dry cyclones are also used.
Wet electrostatic precipitators (Wet ESPs) are being installed as retrofits where tighter limits on
paniculate matter and metals are required by State regulations.
2.2.1.2 Fluidized Bed Incinerators -
Fluidized bed technology was first developed by the petroleum industry to be used for catalyst
regeneration. Figure 2.2-2 shows the cross section diagram of a fluidized bed furnace. Fluidized bed
combustors (FBCs) consist of a vertically oriented outer shell constructed of steel and lined with
refractory. Tuyeres (nozzles designed to deliver blasts of air) are located at the base of the furnace
within a refractory-lined grid. A bed of sand, approximately 0.75 meters (2.5 feet) thick, rests upon
the grid. Two general configurations can be distinguished on the basis of how the fluidizing air is
injected into the furnace. In the "hot windbox" design the combustion air is first preheated by
passing through a heat exchanger where heat is recovered from the hot flue gases. Alternatively,
ambient air can be injected directly into the furnace from a cold windbox.
Partially dewatered sludge is fed into the lower portion of the furnace. Air injected through
the tuyeres, at pressures of from 20 to 35 kilopascals (3 to 5 pounds per square inch gauge),
simultaneously fluidizes the bed of hot sand and the incoming sludge. Temperatures of 750 to 925 °C
(1400 to 1700°F) are maintained in the bed. Residence times are typically 2 to 5 seconds. As the
sludge burns, fine ash particles are carried out the top of the furnace. Some sand is also removed in
the air stream; sand make-up requirements are on the order of 5 percent for every 300 hours of
operation.
Combustion of the sludge occurs in two zones. Within the bed itself (Zone 1), evaporation of
the water and pyrolysis of the organic materials occur nearly simultaneously as the temperature of the
sludge is rapidly raised. In the second zone (freeboard area), the remaining free carbon and
combustible gases are burned. The second zone functions essentially as an afterburner.
Fluidization achieves nearly ideal mixing between the sludge and the combustion air and the
turbulence facilitates the transfer of heat from the hot sand to the sludge. The most noticeable impact
of the better burning atmosphere provided by a fluidized bed incinerator is seen in the limited amount
of excess air required for complete combustion of the sludge. Typically, FBCs can achieve complete
combustion with 20 to 50 percent excess air, about half the excess air required by multiple hearth
furnaces. As a consequence, FBC incinerators have generally lower fuel requirements compared to
MHF incinerators.
Fluidized bed incinerators most often have venturi scrubbers or venturi/impingement tray
scrubber combinations for emissions control.
2.2.1.3 Electric Infrared Incinerators -
The first electric infrared furnace was installed in 1975, and their use is not common.
Electric infrared incinerators consist of a horizontally oriented, insulated furnace. A woven wire belt
conveyor extends the length of the furnace and infrared heating elements are located in the roof above
the conveyor belt. Combustion air is preheated by the flue gases and is injected into the discharge
end of the furnace. Electric infrared incinerators consist of a number of prefabricated modules,
which can be linked together to provide the necessary furnace length. A cross section of an electric
furnace is shown in Figure 2.2-3.
2.2-4 EMISSION FACTORS 1/95
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SAND
FEED
THERMOCOUPLE
SLUDGE
INLET
FLUTOIZING
AIR
INLET
REFRACTORY
ARCH
EXHAUST AND ASH
PRESSURE TAP
SIGHT
GLASS
BURNER
TUYERES
FUEL
GUN
PRESSURE TAP
STARTUP
-I PREHEAT
BURNER
FOR HOT
WINDBOX
1/95
Figure 2.2-2. Cross Section of a Fluidized Bed Furnace
Solid Waste Disposal
2.2-5
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o
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The dewatered sludge cake is conveyed into one end of the incinerator. An internal roller
mechanism levels the sludge into a continuous layer approximately one inch thick across the width of
the belt. The sludge is sequentially dried and then burned as it moves beneath the infrared heating
elements. Ash is discharged into a hopper at the opposite end of the furnace. The preheated
combustion air enters the furnace above the ash hopper and is further heated by the outgoing ash.
The direction of air flow is countercurrent to the movement of the sludge along the conveyor.
Exhaust gases leave the furnace at the feed end. Excess air rates vary from 20 to 70 percent.
Compared to MHF and FBC technologies, the electric infrared furnace offers the advantage of
lower capital cost, especially for smaller systems. However, electricity costs in some areas may make
an electric furnace infeasible. One other concern is replacement of various components such as the
woven wire belt and infrared heaters, which have 3- to 5-year lifetimes.
Electric infrared incinerator emissions are usually controlled with a venturi scrubber or some
other wet scrubber.
2.2.1.4 Other Technologies-
A number of other technologies have been used for incineration of sewage sludge, including
cyclonic reactors, rotary kilns, and wet oxidation reactors. These processes are not in widespread use
in the United States and will be discussed only briefly.
The cyclonic reactor is designed for small capacity applications. It is constructed of a vertical
cylindrical chamber that is lined with refractory. Preheated combustion air is introduced into the
chamber tangentially at high velocities. The sludge is sprayed radially toward the hot refractory
walls. Combustion is rapid: The residence time of the sludge in the chamber is on the order of
10 seconds. The ash is removed with the flue gases.
Rotary kilns are also generally used for small capacity applications. The kiln is inclined
slightly from the horizontal plane, with the upper end receiving both the sludge feed and the
combustion air. A burner is located at the lower end of the kiln. The circumference of the kiln
rotates at a speed of about 15 centimeters (cm) per second (6 inches per second). Ash is deposited
into a hopper located below the burner.
The wet oxidation process is not strictly one of incineration; it instead utilizes oxidation at
elevated temperature and pressure in the presence of water (flameless combustion). Thickened
sludge, at about 6 percent solids, is first ground and mixed with a stoichiometric amount of
compressed air. The slurry is then pressurized. The mixture is then circulated through a series of
heat exchangers before entering a pressurized reactor. The temperature of the reactor is held between
175 and 315°C (350 and 600°F). The pressure is normally 7,000 to 12,500 kilopascals (1,000 to
1,800 pounds per square inch grade). Steam is usually used for auxiliary heat. The water and
remaining ash are circulated out the reactor and are finally separated in a tank or lagoon. The liquid
phase is recycled to the treatment plant. Offgases must be treated to eliminate odors: wet scrubbing,
afterburning, or carbon absorption may be used.
2.2.1.5 Co-incineration and Co-firing -
Wastewater treatment plant sludge generally has a high water content and in some cases,
fairly high levels of inert materials. As a result, its net fuel value is often low. If sludge is combined
with other combustible materials in a co-incineration scheme, a furnace feed can be created that has
both a low water concentration and a heat value high enough to sustain combustion with little or no
supplemental fuel.
1/95 Solid Waste Disposal 2.2-7
-------
Virtually any material that can be burned can be combined with sludge in a co-incineration
process. Common materials for co-combustion are coal, municipal solid waste (MSW), wood waste
and agriculture waste. Thus, a municipal or industrial waste can be disposed of while providing an
autogenous (self-sustaining) sludge feed, thereby solving two disposal problems.
There are two basic approaches to combusting sludge with MSW: (1) use of MSW
combustion technology by adding dewatered or dried sludge to the MSW combustion unit, and (2) use
of sludge combustion technology by adding processed MSW as a supplemental fuel to the sludge
furnace. With the latter, MSW is processed by removing noncombustibles, shredding, air classifying,
and screening. Waste that is more finely processed is less likely to cause problems such as severe
erosion of the hearths, poor temperature control, and refractory failures.
2.2.2 Emissions And Controls1"3
Sewage sludge incinerators potentially emit significant quantities of pollutants. The major
pollutants emitted are: (1) paniculate matter, (2) metals, (3) carbon monoxide (CO), (4) nitrogen
oxides (NOX), (5) sulfur dioxide (SO^, and (6) unburned hydrocarbons. Partial combustion of sludge
can result in emissions of intermediate products of incomplete combustion (PIC), including toxic
organic compounds.
Uncontrolled paniculate emission rates vary widely depending on the type of incinerator, the
volatiles and moisture content of the sludge, and the operating practices employed. Generally,
uncontrolled paniculate emissions are highest from fluidized bed incinerators because suspension
burning results in much of the ash being carried out of the incinerator with the flue gas.
Uncontrolled emissions from multiple hearth and fluidized bed incinerators are extremely variable,
however. Electric incinerators appear to have the lowest rates of uncontrolled paniculate release of
the three major furnace types, possibly because the sludge is not disturbed during firing. In general,
higher airflow rates increase the opportunity for paniculate matter to be entrained in the exhaust
gases. Sludge with low volatile content or high moisture content may compound this situation by
requiring more supplemental fuel to burn. As more fuel is consumed, the amount of air flowing
through the incinerator is also increased. However, no direct correlation has been established
between airflow and paniculate emissions.
Metal emissions are affected by metal content of the sludge, fuel bed temperature, and the
level of paniculate matter control. Since metals which are volatilized in the combustion zone
condense in the exhaust gas stream, most metals (except mercury) are associated with fine paniculate
and are removed as the fine particulates are removed.
Carbon monoxide is formed when available oxygen is insufficient for complete combustion or
when excess air levels are too high, resulting in lower combustion temperatures.
Emissions of nitrogen and sulfur oxides are primarily the result of oxidation of nitrogen and
sulfur in the sludge. Therefore, these emissions can vary greatly based on local and seasonal sewage
characteristics.
Emissions of volatile organic compounds (VOC) also vary greatly with incinerator type and
operation. Incinerators with countercurrent airflow such as multiple hearth designs provide the
greatest opportunity for unburned hydrocarbons to be emitted. In the MHF, hot air and wet sludge
feed are contacted at the top of the furnace. Any compounds distilled from the solids are immediately
vented from the furnace at temperatures too low to completely destruct them.
2.2-8 EMISSION FACTORS 1/95
-------
Particulate emissions from sewage sludge incinerators have historically been controlled by wet
scrubbers, since the associated sewage treatment plant provides both a convenient source and a good
disposal option for the scrubber water. The types of existing sewage sludge incinerator controls range
from low pressure drop spray towers and wet cyclones to higher pressure drop venturi scrubbers and
venturi/impingement tray scrubber combinations. Electrostatic precipitators and baghouses are
employed primarily where sludge is co-fired with municipal solid waste. The most widely used
control device applied to a multiple hearth incinerator is the impingement tray scrubber. Older units
use the tray scrubber alone while combination venturi/impingement tray scrubbers are widely applied
to newer multiple hearth incinerators and to fluidized bed incinerators. Most electric incinerators and
many fluidized bed incinerators use venturi scrubbers only.
In a typical combination venturi/impingement tray scrubber, hot gas exits the incinerator and
enters the preceding or quench section of the scrubber. Spray nozzles in the quench section cool the
incoming gas and the quenched gas then enters the venturi section of the control device. Venturi
water is usually pumped into an inlet weir above the quencher. The venturi water enters the scrubber
above the throat and floods the throat completely. This eliminates build-up of solids and reduces
abrasion. Turbulence created by high gas velocity in the converging throat section deflects some of
the water traveling down the throat into the gas stream. Particulate matter carried along with the gas
stream impacts on these water particles and on the water wall. As the scrubber water and flue gas
leave the venturi section, they pass into a flooded elbow where the stream velocity decreases,
allowing the water and gas to separate. Most venturi sections come equipped with variable throats.
By restricting the throat area within the venturi, the linear gas velocity is increased and the pressure
drop is subsequently increased. Up to a certain point, increasing the venturi pressure drop increases
the removal efficiency. Venturi scrubbers typically maintain 60 to 99 percent removal efficiency for
particulate matter, depending on pressure drop and particle size distribution.
At the base of the flooded elbow, the gas stream passes through a connecting duct to the base
of the impingement tray tower. Gas velocity is further reduced upon entry to the tower as the gas
stream passes upward through the perforated impingement trays. Water usually enters the trays from
inlet ports on opposite sides and flows across the tray. As gas passes through each perforation in the
tray, it creates a jet which bubbles up the water and further entrains solid particles. At the top of the
tower is a mist eliminator to reduce the carryover of water droplets in the stack effluent gas. The
impingement section can contain from one to four trays, but most systems for which data are
available have two or three trays.
Emission factors and emission factor ratings for multiple hearth sewage sludge incinerators
are shown hi Tables 2.2-1, 2.2-2, 2.2-3, 2.2-4, and 2.2-5. Tables 2.2-6, 2.2-7, and 2.2-8 present
emission factors for fluidized bed sewage sludge incinerators. Table 2.2-9 presents the available
emission factors for electric infrared incinerators. Tables 2.2-10 and 2.2-11 present the cumulative
particle size distribution and size-specific emission factors for sewage sludge incinerators.
Figure 2.2-4, Figure 2.2-5, and Figure 2.2-6 present cumulative particle size distribution and size-
specific emission factors for multiple-hearth, fluidized-bed, and electric infrared incinerators,
respectively.
1/95 Solid Waste Disposal 2.2-9
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1/95
-------
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1/95
Solid Waste Disposal
2.2-39
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2.2-40
EMISSION FACTORS
1/95
-------
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1/95
Solid Waste Disposal
2.2-41
-------
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2.2-42
EMISSION FACTORS
1/95
-------
Table 2.2-9 (Metric And English Units). SUMMARY OF EMISSION FACTORS FOR
ELECTRIC INFRARED SEWAGE SLUDGE INCINERATORS*
EMISSION FACTOR RATING: E
Source Category''
Uncontrolled
Controlled
Cyclone
Cyclone/impingement
Cyclone/venturi
Cyclone/venturi/impingement
Electrostatic precipitator
Fabric filter
Impingement
Venturi
Venturi/impingement/
afterburner
Venturi/impingement
Venturi/impingement/
Wet ESP
Venturi/Wet ESP
Particulate Matter
kg/Mg Ib/ton
3.7E+00 7.4 E+00
1.9 E+00 3.8 E+00
8.2 E-01 1.6 E+00
9.5 E-01 1.9 E+00
Sulfur Dioxide
kg/Mg Ib/ton
9.2 E+00 1.8 E+01
2.3 E+00 4.6 E+00
Nitrogen Oxides
kg/Mg Ib/ton
4.3 E+00 8.6 E+00
2.9 E+00 5.8 E+00
a Units are pollutants emitted of dry sludge burned.
b Wet ESP = wet electrostatic precipitator.
Source Classification Code 5-01-005-17.
1/95
Solid Waste Disposal
2.2-43
-------
Table 2.2-10 (Metric And English Units). CUMULATIVE PARTICLE SIZE DISTRIBUTION
FOR SEWAGE SLUDGE INCINERATORS3
EMISSION FACTOR RATING: E
Particle Size
(Aim)
15
10
5.0
2.5
1.0
0.625
Cumulative Mass % Stated Size
Uncontrolled
MHb | EIC
15 43
10 30
5.3 17
2.8 10
1.2 6.0
0.75 5.0
Controlled (Scrubber)
MH | FBd
30 7.7
27 7.3
25 6.7
22 6.0
20 5.0
17 2.7
El
60
50
35
25
18
15
a Reference 5.
b MH = multiple hearth incinerator. Source Classification Code (SCC) 5-01-005-15.
c El = electric infrared incinerator. SCC 5-01-005-17.
d FB = fluidized bed incinerator. SCC 5-01-005-16.
2.2-44
EMISSION FACTORS
1/95
-------
>-J 06
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SLUDGE
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tirtlck tlMUr
Figure 2.2-4. Cumulative Particle Size Distribution and
Size-Specific Emission Factors for
Multiple-Health Incinerators
0.24
0.20
60
X
5
VI
o
0.16 2
0.12
(0
a
T-l
0.08 *
•o
41
0.04 2
u
100
Figure 2.2-5. Cumulative Particle Size Distribution and
Size-Specific Emission Factors for Fluidized-Bed Incinerators
2.2-46
EMISSION FACTORS
1/95
-------
3.
I
: j
\
l.SO „„
3
1.25
1.0
u
o
o
0.75 S
|
0.50 ^
0.25
2
torttd*
<»•)
Figure 2.2-6. Cumulative Particle Size Distribution and
Size-Specific Emission Factors for Electric
(infrared) Incinerators
References For Section 2.2
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, EPA-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 SSl-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.
1/95
Solid Waste Disposal
2.2-47
-------
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 Report. 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 Report. 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.
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 Repon For 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 Repon: Rocky Mount Wastewater Treatment Facility, [STAPPA/ALAPCO/
07/28/86-No. 06], Envirotech, Belmont, California, July 1983.
19. Performance Test Repon For The Incineration System At The Honolulu Wastewater Treatment
Plant, Honolulu, Oahu, Hawaii, [STAPPA/ALAPCO/05/22/86-No. 11], Zimpro, Rothschild,
Wisconsin, January 1984.
2.2-48 EMISSION FACTORS 1/95
-------
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 Report, EEI Reference No. 2988, At The Osborne Wastewater
Treatment Plant, Greensboro, North Carolina, [STAPPA/ALAPCO/07/28/86-No. 06],
Paniculate 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.
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 Report-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 Report—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 Report—Northwest 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 Report-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.
1/95 Solid Waste Disposal 2.2-49
-------
32. Stack Sampling Report For Municipal Sewage Sludge Incinerator No. 1, Scrubber Outlet
(Stack), Providence, Rhode Island, Recon Systems, Inc., Three Bridges, New Jersey,
November 1980.
33. Stack Sampling Report, 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 Hearth 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 Hearth Incinerator Burning Sewage Sludge, Contract
No. 68-03-3148, U. S. Environmental Protection Agency, Research Triangle Park, North
Carolina, August 1986.
39. J. B. Farrell and H. Wall, Air Pollution Discharges From Ten Sewage Sludge Incinerators,
U. S. Environmental Protection Agency, Cincinnati, Ohio, August 1985.
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.
2.2-50 EMISSION FACTORS 1/95
-------
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.
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.
1/95 Solid Waste Disposal 2.2-51
-------
60. Particulate 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.
64. D. R. Knisley, et al., Site 3 Draft Emission Test Report And Addendum, Sewage Sludge Test
Program. Volume I: 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 Heanh 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 Heanh 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.
2.2-52 EMISSION FACTORS 1/95
-------
73. Emissions Of Metals, Chromium, And Nickel Species, And Organics From Municipal
Wastewater Sludge Incinerators, Volume I: Summary Report, 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.
76. R. R. Segal, et al., Emissions Of Metals, Chromium And Nickel Species, And Organics From
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 Organics From
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 Organics From
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 Organics From
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 Organics From
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.
1/95 Solid Waste Disposal 2.2-53
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23 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 1 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.
2.3.1 Process Description1"6
Types of incineration described in this section include:
- Controlled air,
- Excess air, and
- Rotary kiln.
2.3.1.1 Controlled-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 2.3-1 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^).. 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
capacities for lower heating value wastes may be higher, since feed capacities are limited by primary
7/93 (Reformatted 1/95) Solid Waste Disposal 2.3-1
-------
Carbon Dioxide,
Water Vapor
Oxygen and Nitrogen
and Excess
to Atmosphere
Air
Main Burner for
Minimum Combustion
Temperature
Air
Volatile Content
is Burned in
Upper Chamber
Excess Air
Condition
Starved-Air
Condition in
Lower Chamber
Controlled
Underfire Air
for Burning
Down Waste
Figure 2.3-1. Controlled Air Incinerator
2.3-2
EMISSION FACTORS
(Reformatted 1/95) 7/93
-------
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.
2.3.1.2 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 2.3-2 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°Fj). 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.
2.3.1.3 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 2.3-3.
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.
7/93 (Reformatted 1/95) Solid Waste Disposal 2.3-3
-------
Flame Port
.Stack
Secondary
^X Air Ports
Second
lary
iX' Burner Port
-Mixing
Chamber
First
Underneath. Port
Hearth
Side View
Secondary
Combustion
Chamber
Mixing
Chamber Hame Port
Cleanout
Doors
Primary
Burner Port
Secondary
Underneath Port
Figure 2.3-2. Excess Air Incinerator
2.3-4
EMISSION FACTORS
(Reformatted 1/95) 7/93
-------
o
2
o
CO
rs
7/93 (Reformatted 1/95)
Solid Waste Disposal
2.3-5
-------
2.3.2 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,
the 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 die waste. Metal 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 (300°F).
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
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 CDDs/CDFs from MWIs may occur as either a vapor or as a fine paniculate.
Many factors are believed to be involved in the formation of CDDs/CDFs and many theories exist
2.3-6 EMISSION FACTORS (Reformatted 1/95) 7/93
-------
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 CDDs/CDFs present in the
refuse feed are carried over, unburned, to the exhaust. The second theory involves formation of
CDDs/CDFs from chlorinated precursors with similar structures. Conversion of precursor material to
CDDs/CDFs 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
CDDs/CDFs 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 (SD) 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 (/xm) 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-laden
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; particulate 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
7/93 (Reformatted 1/95) Solid Waste Disposal 2.3-7
-------
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 paniculate matter, which results
in good control of metals and organics entrained on fine paniculate.
Paniculate collection in an ESP occurs in 3 steps: (1) suspended panicles are given an
electrical charge; (2) the charged panicles 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 a 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
paniculate 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 paniculate 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
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 15 seconds. The
particulates leaving the SD (fly ash, calcium salts, and unreacted hydrated lime) are collected by an
FF or ESP.
2.3-8 EMISSION FACTORS (Reformatted 1/95) 7/93
-------
Emission factors and emission factor ratings for controlled air incinerators are presented in
Tables 2.3-1, 2.3-2, 2.3-3, 2.3-4, 2.3-5, 2.3-6, 2.3-7, 2.3-8, 2.3-9, 2.3-10, 2.3-11, 2.3-12, 2.3-13,
2.13-14, and 2.3-15. 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 2.3-15 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 2.3-16, 2.3-17,
and 2.3-18. 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 (Reformatted 1/95) Solid Waste Disposal 2.3-9
-------
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2.3-10
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(Reformatted 1/95) 7/93
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(Reformatted 1/95) 7/93
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Solid Waste Disposal
2.3-13
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2.3-14
EMISSION FACTORS
(Reformatted 1/95) 7/93
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Solid Waste Disposal
2.3-15
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(Reformatted 1/95) 7/93
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2.3-18
EMISSION FACTORS
(Reformatted 1/95) 7/93
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Solid Waste Disposal
2.3-19
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EMISSION FACTORS
(Reformatted 1/95) 7/93
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(Reformatted 1/95) 7/93
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Hazardous air pc
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Table 2.3-15. PARTICLE SIZE DISTRIBUTION FOR CONTROLLED AIR MEDICAL WASTE
INCINERATOR PARTICIPATE MATTER EMISSIONS3
EMISSION FACTOR RATING: E
Cut Diameter
faro)
0.625
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71.9
References 7-43. Source Classification Codes 5-01-005-05, 5-02-005-05.
2.3-24
EMISSION FACTORS
(Reformatted 1/95) 7/93
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Solid Waste Disposal
2.3-27
-------
References For Section 2.3
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 Suffer General
Hospital, Sacramento, California, California Air Resources Board, April 1988.
16. Test Report For Swedish American Hospital Consumat Incinerator, Bel ing Consultants,
Rockford, Illinois, December 1986.
2.3-28 EMISSION FACTORS (Reformatted 1/95) 7/93
-------
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 HCl From 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, Deny 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 KJamath
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.
31. Stack Emission Testing, Erlanger Medical Center, Chattanooga, Tennessee, Report 1-6299,
Campbell & Associates, April 13, 1988.
7/93 (Reformatted 1/95) Solid Waste Disposal 2.3-29
-------
32. Compliance Emission Testing For Memorial Hospital, Chattanooga, Tennessee, Air Systems
Testing, Inc., July 29, 1988.
33. Source Emission Tests At ERA Tech, North\vood, 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 HO Emission Tests On Therm-Tec Incinerator Stack, Efyra, 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. Repon On Paniculate And HQ Emission Tests On Therm-Tec Incinerator Stack, Cincinnati,
Ohio, Maurice L. Kelsey & Associates, Inc., May 22, 1989.
40. Repon On Compliance Testing, Hamot Medical Center, Erie, Pennsylvania, Hamot Medical
Center, July 19, 1990.
41. Compliance Emission Testing For HCA Nonh 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. Repon Of Emission Tests, Helene Fuld Medical Center, Trenton, New Jersey, New Jersey
State Department of Environmental Protection, December 1, 1989.
2.3-30 EMISSION FACTORS (Reformatted 1/95) 7/53
-------
2.4 Municipal Solid Waste Landfills
2.4.1 General1'4
A municipal solid waste (MSW) landfill unit is a discrete area of land or an excavation that receives
household waste, and that is not a land application unit, surface impoundment, injection well, or waste pile.
An MSW landfill unit may also receive other types of wastes, such as commercial solid waste,
nonhazardous sludge, and industrial solid waste. The municipal solid waste types potentially accepted by
MSW landfills include (most landfills accept only a few of the following categories):
• MSW,
• Household hazardous waste,
• Municipal sludge,
• Municipal waste combustion ash,
• Infectious waste,
• Waste tires,
• Industrial non-hazardous waste,
• Conditionally exempt small quantity generator (CESQG) hazardous waste,
• Construction and demolition waste,
• Agricultural wastes,
• Oil and gas wastes, and
• Mining wastes.
In the United States, approximately 57 percent of solid waste is landfilled, 16 percent is incinerated,
and 27 percent is recycled or composted. There were an estimated 2,500 active MSW landfills in the
United States in 1995. These landfills were estimated to receive 189 million megagrams (Mg) (208 million
tons) of waste annually, with 55 to 60 percent reported as household waste, and 35 to 45 percent reported
as commercial waste.
2.4.2 Process Description2'5
There are three major designs for municipal landfills. These are the area, trench, and ramp methods.
All of these methods utilize a three step process, which includes spreading the waste, compacting the waste,
and covering the waste with soil. The trench and ramp methods are not commonly used, and are not the
preferred methods when liners and leachate collection systems are utilized or required by law. The area fill
method involves placing waste on the ground surface or landfill liner, spreading it in layers, and
compacting with heavy equipment. A daily soil cover is spread over the compacted waste. The trench
method entails excavating trenches designed to receive a day's worth of waste. The soil from the
excavation is often used for cover material and wind breaks. The ramp method is typically employed on
sloping land, where waste is spread and compacted similar to the area method, however, the cover material
obtained is generally from the front of the working face of the filling operation.
Modern landfill design often incorporates liners constructed of soil (i.e., recompacted clay), or
synthetics (i.e., high density polyethylene), or both to provide an impermeable barrier to leachate (i.e.,
water that has passed through the landfill) and gas migration from the landfill.
8/98 Solid Waste Disposal 2.4-1
-------
2.4.3 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.
The New Source Performance Standards (NSPS) and Emission Guidelines for air emissions from
MSW landfills for certain new and existing landfills were published in the Federal Register on
March 1, 1996. The regulation requires that Best Demonstrated Technology (BDT) be used to reduce
MSW landfill emissions from affected new and existing MSW landfills emitting greater than or equal to
50 Mg/yr (55 tons/yr) of non-methane organic compounds (NMOCs). The MSW landfills that are affected
by the NSPS/Emission Guidelines are each new MSW landfill, and each existing MSW landfill that has
accepted waste since November 8, 1987, or that has capacity available for future use. The NSPS/Emission
Guidelines affect landfills with a design capacity of 2.5 million Mg (2.75 million tons) or more. Control
systems require: (1) a well-designed and well-operated gas collection system, and (2) a control device
capable of reducing NMOCs in the collected gas by 98 weight-percent.
Landfill gas (LFG) collection systems are either active or passive systems. Active collection systems
provide a pressure gradient in order to extract LFG by use of mechanical blowers or compressors. Passive
systems allow the natural pressure gradient created by the increase in pressure created by LFG generation
within the landfill to mobilize the gas for collection.
LFG control and treatment options include (1) combustion of the LFG, and (2) purification of the LFG.
Combustion techniques include techniques that do not recover energy (i.e., flares and thermal incinerators),
and techniques that recover energy (i.e., gas turbines and internal combustion engines) and generate
electricity from the combustion of the LFG. Boilers can also be employed to recover energy from LFG in
the form of steam. Flares involve an open combustion process that requires oxygen for combustion, and
can be open or enclosed. Thermal incinerators heat an organic chemical to a high enough temperature in
the presence of sufficient oxygen to oxidize the chemical to carbon dioxide (CO2) and water. Purification
techniques can also be used to process raw landfill gas to pipeline quality natural gas by using adsorption,
absorption, and membranes.
2.4.4 Emissions2'7
Methane (CH4) and CO2 are the primary constituents of landfill gas, and are produced by
microorganisms within the landfill under anaerobic conditions. Transformations of CH4 and CO2 are
mediated by microbial populations that are adapted to the cycling of materials in anaerobic environments.
Landfill gas generation, including rate and composition, proceeds through four phases. The first phase is
aerobic [i.e., with oxygen (O2) available] and the primary gas produced is CO2. The second phase is
characterized by O2 depletion, resulting in an anaerobic environment, where large amounts of CO2 and
some hydrogen (H2) are produced. In the third phase, CH4 production begins, with an accompanying
reduction in the amount of CO2 produced. Nitrogen (N2) content is initially high in landfill gas 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 (i.e., waste composition, design management, and anaerobic
state).
2.4-2 EMISSION FACTORS 8/98
-------
Typically, LFG also contains a small amount of non-methane organic compounds (NMOC). This
NMOC fraction often contains various organic hazardous air pollutants (HAP), greenhouse gases (GHG),
and compounds associated with stratospheric ozone depletion. The NMOC fraction also contains volatile
organic compounds (VOC). The weight fraction of VOC can be determined by subtracting the weight
fractions of individual compounds that are non-photochemically reactive (i.e., negligibly-reactive organic
compounds as defined in 40 CFR 51.100).
Other emissions associated with MSW landfills include combustion products from LFG control and
utilization equipment (i.e., flares, engines, turbines, and boilers). These include carbon monoxide (CO),
oxides of nitrogen (NOX), sulfur dioxide (SO2), hydrogen chloride (HC1), paniculate matter (PM) and other
combustion products (including HAPs). PM emissions can also be generated in the form of fugitive dust
created by mobile sources (i.e., garbage trucks) traveling along paved and unpaved surfaces. The reader
should consult AP-42 Volume I Sections 13.2.1 and 13.2.2 for information on estimating fugitive dust
emissions from paved and unpaved roads.
The rate of emissions from a landfill is governed by gas production and transport mechanisms.
Production mechanisms involve the production of the emission constituent in its vapor phase through
vaporization, biological decomposition, or chemical reaction. Transport mechanisms involve the
transportation of a volatile constituent in its vapor phase to the surface of the landfill, through the air
boundary layer above the landfill, and into the atmosphere. The three major transport mechanisms that
enable transport of a volatile constituent in its vapor phase are diffusion, convection, and displacement.
2.4.4.1 Uncontrolled Emissions — To estimate uncontrolled emissions of the various compounds present
in landfill gas, total landfill gas emissions must first be estimated. Uncontrolled CH4 emissions may be
estimated for individual landfills by using a theoretical first-order kinetic model of methane production
developed by the EPA.8 This model is known as the Landfill Air Emissions Estimation model, and can be
accessed from the Office of Air Quality Planning and Standards Technology Transfer Network Website
(OAQPS TTN Web) in the Clearinghouse for Inventories and Emission Factors (CHIEF) technical area
(URL http://www.epa.gov/ttn/chief). The Landfill Air Emissions Estimation model equation is as follows:
Q™ =LR(e-kc -e-kt) 0)
'4
where:
QCH4 = Methane generation rate at time t, nrVyr;
Lo = Methane generation potential, m3 CH4/Mg refuse;
R = Average annual refuse acceptance rate during active life, Mg/yr;
e = Base log, unitless;
k = Methane generation rate constant, yr"1;
c = Time since landfill closure, yrs (c = 0 for active landfills); and
t = Time since the initial refuse placement, yrs.
It should be noted that the model above was designed to estimate LFG generation and not LFG
emissions to the atmosphere. Other fates may exist for the gas generated in a landfill, including capture
and subsequent microbial degradation within the landfill's surface layer. Currently, there are no data that
adequately address this fate. It is generally accepted that the bulk of the gas generated will be emitted
through cracks or other openings in the landfill surface.
8/98 Solid Waste Disposal 2.4-3
-------
Site-specific landfill information is generally available for variables R, c, and t. When refuse
acceptance rate information is scant or unknown, R can be determined by dividing the refuse in place by the
age of the landfill. If a facility has documentation that a certain segment (cell) of a landfill received only
nondegradable refuse, then the waste from this segment of the landfill can be excluded from the calculation
of R. Nondegradable refuse includes concrete, brick, stone, glass, plaster, wallboard, piping, plastics, and
metal objects. The average annual acceptance rate should only be estimated by this method when there is
inadequate information available on the actual average acceptance rate. The time variable, t, includes the
total number of years that the refuse has been in place (including the number of years that the landfill has
accepted waste and, if applicable, has been closed).
Values for variables L0 and k must be estimated. Estimation of the potential CH4 generation capacity
of refuse (L0) is generally treated as a function of the moisture and organic content of the refuse.
Estimation of the CH4 generation constant (k) is a function of a variety of factors, including moisture, pH,
temperature, and other environmental factors, and landfill operating conditions. Specific CH4 generation
constants can be computed by the use of EPA Method 2E (40 CFR Part 60 Appendix A).
The Landfill Air Emission Estimation model includes both regulatory default values and recommended
AP-42 default values for L0 and k. The regulatory defaults were developed for compliance purposes
(NSPS/Emission Guideline). As a result, the model contains conservative L0 and k default values in order
to protect human health, to encompass a wide range of landfills, and to encourage the use of site-specific
data. Therefore, different L0 and k values may be appropriate in estimating landfill emissions for particular
landfills and for use in an emissions inventory.
Recommended AP-42 defaults include a k value of 0.04/yr for areas recieving 25 inches or more of
rain per year. A default k of 0.02/yr should be used in drier areas (<25 inches/yr). An L0 value of
100 m3/Mg (3,530 ft3/ton) refuse is appropriate for most landfills. Although the recommended default k
and L0 are based upon the best fit to 21 different landfills, the predicted methane emissions ranged from 38
to 492% of actual, and had a relative standard deviation of 0.85. It should be emphasized that in order to
comply with the NSPS/Emission Guideline, the regulatory defaults for k and L0 must be applied as
specified in the final rule.
When gas generation reaches steady state conditions, LFG consists of approximately 40 percent by
volume CO2, 55 percent CH4, 5 percent N2 (and other gases), and trace amounts of NMOCs. Therefore,
the estimate derived for CH4 generation using the Landfill Air Emissions Estimation model can also be used
to represent CO2 generation. Addition of the CH4 and CO2 emissions will yield an estimate of total landfill
gas emissions. If site-specific information is available to suggest that the CH4 content of landfill gas is not
55 percent, then the site-specific information should be used, and the CO2 emission estimate should be
adjusted accordingly.
Most of the NMOC emissions result from the volatilization of organic compounds contained in the
landfilled waste. Small amounts may be created by biological processes and chemical reactions within the
landfill. The current version of the Landfill Air Emissions Estimation model contains a proposed
regulatory default value for total NMOC of 4,000 ppmv, expressed as hexane. However, available data
show that there is a range of over 4,400 ppmv for total NMOC values from landfills. The proposed
regulatory default value for NMOC concentration was developed for regulatory compliance purposes and
to provide the most cost-effective default values on a national basis. For emissions inventory purposes,
site-specific information should be taken into account when determining the total NMOC concentration. In
the absence of site-specific information, a value of 2,420 ppmv as hexane is suggested for landfills known
to have co-disposal of MSW and non-residential waste. If the landfill is known to contain only MSW or
2.4-4 EMISSION FACTORS 8/98
-------
have very little organic commercial/industrial wastes, then a total NMOC value of 595 ppmv as hexane
should be used. In addition, as with the landfill model defaults, the regulatory default value for NMOC
content must be used in order to comply with the NSPS/Emission Guideline.
If a site-specific total pollutant concentration is available (i.e., as measured by EPA Reference Method
25C), it must be corrected for air infiltration which can occur by two different mechanisms: LFG sample
dilution, and air intrusion into the landfill. These corrections require site-specific data for the LFG CH4,
CO2, nitrogen (N2), and oxygen (O2) content. If the ratio of N2 to O2 is less than or equal to 4.0 (as found
in ambient air), then the total pollutant concentration is adjusted for sample dilution by assuming that CO2
and CH4 are the primary (100 percent) constituents of landfill gas, and the following equation is used:
Cp (ppmv) (1 x 106)
Cp (ppmv) (corrected for air infiltration) = (2)
Cco2 (PPmv) + CcH4 (PPmv)
where:
Cp = Concentration of pollutant P in landfill gas (i.e., NMOC as hexane), ppmv;
= CO2 concentration in landfill gas, ppmv.
! = CH4 Concentration in landfill gas, ppmv; and
1 x 106 = Constant used to correct concentration of P to units of ppmv.
If the ratio of N2 to O2 concentrations (i.e., CN , CQ ) is greater than 4.0, then the total pollutant
concentration should be adjusted for air intrusion into the landfill by using equation 2 and adding the
concentration of N2 (i.e., Cj^ ) to the denominator. Values for CCQ > CCH > CN ' ^O > can usualty oe
found in the source test report for the particular landfill along with the total pollutant concentration data.
To estimate emissions of NMOC or other landfill gas constituents, the following equation should be
used:
Q''1M *
where:
Qp = Emission rate of pollutant P (i.e. NMOC), m3/yr;
QCH = CH4 generation rate, m3/yr (from the Landfill Air Emissions Estimation model);
Cp = Concentration of P in landfill gas, ppmv; and
1.82 = Multiplication factor (assumes that approximately 55 percent of landfill gas is
CH4 and 45 percent is CO2, N2, and other constituents).
8/98 Solid Waste Disposal 2.4-5
-------
Uncontrolled mass emissions per year of total NMOC (as hexane), CO2, CH4, and speciated organic and
inorganic compounds can be estimated by the following equation:
*p
MWP * 1 atm
UM = P
(4)
(8.205xl(T5 m3-atm/gmol-°K)(1000g/kg)(273 +T°K)
where:
UMp = Uncontrolled mass emissions of pollutant P (i.e., NMOC), kg/yr;
MWp = Molecular weight of P, g/gmol (i.e., 86.18 for NMOC as hexane);
Qp = NMOC emission rate of P, m3/yr; and
T = Temperature of landfill gas, °C.
This equation assumes that the operating pressure of the system is approximately 1 atmosphere. If the
temperature of the landfill gas is not known, a temperature of 25°C (77°F) is recommended.
Uncontrolled default concentrations of speciated organics along with some inorganic compounds are
presented in Table 2.4-1. These default concentrations have already been corrected for air infiltration and
can be used as input parameters to equation 3 or the Landfill Air Emission Estimation model for estimating
speciated emissions from landfills when site-specific data are not available. An analysis of the data, based
on the co-disposal history (with non-residential wastes) of the individual landfills from which the
concentration data were derived, indicates that for benzene, NMOC, and toluene, there is a difference in the
uncontrolled concentrations. Table 2.4-2 presents the corrected concentrations for benzene, NMOC, and
toluene to use based on the site's co-disposal history.
It is important to note that the compounds listed in Tables 2.4-1 and 2.4-2 are not the only compounds
likely to be present in LFG. The listed compounds are those that were identified through a review of the
available literature. The reader should be aware that additional compounds are likely present, such as
those associated with consumer or industrial products. Given this information, extreme caution should be
exercised in the use of the default VOC weight fractions and concentrations given at the bottom of Table
2.4-2. These default VOC values are heavily influenced by the ethane content of the LFG. Available data
have shown that there is a range of over 1,500 ppmv in LFG ethane content among landfills.
2.4.4.2 Controlled Emissions — Emissions from landfills are typically controlled by installing a gas
collection system, and combusting the collected gas through the use of internal combustion engines, flares,
or turbines. Gas collection systems are not 100 percent efficient in collecting landfill gas, so emissions of
CH4 and NMOC at a landfill with a gas recovery system still occur. To estimate controlled emissions of
CH4, NMOC, and other constituents in landfill gas, the collection efficiency of the system must first be
estimated. Reported collection efficiencies typically range from 60 to 85 percent, with an average of
75 percent most commonly assumed. Higher collection efficiencies may be achieved at some sites (i.e.,
those engineered to control gas emissions). If site-specific collection efficiencies are available (i.e., through
a comprehensive surface sampling program), then they should be used instead of the 75 percent average.
Controlled emission estimates also need to take into account the control efficiency of the control device.
Control efficiencies based on test data for the combustion of CH4, NMOC, and some speciated organics
with differing control devices are presented in Table 2.4-3. Emissions from the control devices need to be
added to the uncollected emissions to estimate total controlled emissions.
2.4-6 EMISSION FACTORS 8/98
-------
Controlled CH4, NMOC, and speciated emissions can be calculated with equation 5. It is assumed that
the landfill gas collection and control system operates 100 percent of the time. Minor durations of system
downtime associated with routine maintenance and repair (i.e., 5 to 7 percent) will not appreciably effect
emission estimates. The first term in equation 5 accounts for emissions from uncollected landfill gas, while
the second term accounts for emissions of the pollutant that were collected but not combusted in the control
or utilization device:
CMp =
UMp *
1 -
100;
UMP *
P
100
1 -
n
cnt
100,
(5)
where:
CMp = Controlled mass emissions of pollutant P, kg/yr;
UMp = Uncontrolled mass emissions of P, kg/yr (from equation 4 or the Landfill Air
Emissions Estimation Model);
r|col = Collection efficiency of the landfill gas collection system, percent; and
r)cnt = Control efficiency of the landfill gas control or utilization device, percent.
Emission factors for the secondary compounds, CO and NOX, exiting the control device are
presented in Tables 2.4-4 and 2.4-5. These emission factors should be used when equipment vendor
guarantees are not available.
Controlled emissions of CO2 and sulfur dioxide (SO2) are best estimated using site-specific landfill gas
constituent concentrations and mass balance methods.68 If site-specific data are not available, the data in
tables 2.4-1 through 2.4-3 can be used with the mass balance methods that follow.
Controlled CO2 emissions include emissions from the CO2 component of landfill gas (equivalent to
uncontrolled emissions) and additional CO2 formed during the combustion of landfill gas. The bulk of the
CO2 formed during landfill gas combustion comes from the combustion of the CH4 fraction. Small
quantities will be formed during the combustion of the NMOC fraction, however, this typically amounts to
less than 1 percent of total C02 emissions by weight. Also, the formation of CO through incomplete
combustion of landfill gas will result in small quantities of CO2 not being formed. This contribution to the
overall mass balance picture is also very small and does not have a significant impact on overall CO2
68
emissions.
The following equation which assumes a 100 percent combustion efficiency for CH4 can be used to
estimate CO2 emissions from controlled landfills:
= UM,
CO,
UM
•at,
100
* 2.75
(6)
where:
C
UMCQ2
UMCH
2.75 =
Controlled mass emissions of CO2, kg/yr;
Uncontrolled mass emissions of CO2, kg/yr (from equation 4 or the Landfill Air
Emission Estimation Model);
Uncontrolled mass emissions of CH4, kg/yr (from equation 4 on the Landfill Air
Emission Estimation Model);
Efficiency of the landfill gas collection system, percent; and
Ratio of the molecular weight of CO2 to the molecular weight of CH4.
8/98
Solid Waste Disposal
2.4-7
-------
To prepare estimates of SO2 emissions, data on the concentration of reduced sulfur compounds within
the landfill gas are needed. The best way to prepare this estimate is with site-specific information on the
total reduced sulfur content of the landfill gas. Often these data are expressed in ppmv as sulfur (S).
Equations 3 and 4 should be used first to determine the uncontrolled mass emission rate of reduced sulfur
compounds as sulfur. Then, the following equation can be used to estimate SO2 emissions:
CMSO = U1VL * — * 2.0 (7)
so2 s
where:
= Controlled mass emissions of SO2, kg/yr;
UMg = Uncontrolled mass emissions of reduced sulfur compounds as sulfur, kg/yr (from
equations 3 and 4);
T)CO| = Efficiency of the landfill gas collection system, percent; and
2.0 = Ratio of the molecular weight of SO2 to the molecular weight of S.
The next best method to estimate SO2 concentrations, if site-specific data for total reduced sulfur
compounds as sulfur are not available, is to use site-specific data for speciated reduced sulfur compound
concentrations. These data can be converted to ppmv as S with equation 8. After the total reduced sulfur
as S has been obtained from equation 8, then equations 3, 4, and 7 can be used to derive SO2 emissions.
= £".! CP * Sp (8)
where:
Cg = Concentration of total reduced sulfur compounds, ppmv as S (for use in equation
3);
Cp = Concentration of each reduced sulfur compound, ppmv;
Sp = Number of moles of S produced from the combustion of each reduced sulfur
compound (i.e., 1 for sulfides, 2 for disulfides); and
n = Number of reduced sulfur compounds available for summation.
If no site-specific data are available, a value of 46.9 ppmv can be assumed for Cs (for use in
equation 3). This value was obtained by using the default concentrations presented in Table 2.4-1 for
reduced sulfur compounds and equation 8.
Hydrochloric acid [Hydrogen Chloride (HC1)] emissions are formed when chlorinated compounds in
LFG are combusted in control equipment. The best methods to estimate emissions are mass balance
methods that are analogous to those presented above for estimating SO2 emissions. Hence, the best source
of data to estimate HC1 emissions is site-specific LFG data on total chloride [expressed in ppmv as the
chloride ion (Cl~)]. If these data are not available, then total chloride can be estimated from data on
individual chlorinated species using equation 9 below. However, emission estimates may be
2.4-8 EMISSION FACTORS 8/98
-------
underestimated, since not every chlorinated compound in the LFG will be represented in the laboratory
report (i.e., only those that the analytical method specifies).
ccl = T.i CP * CIP .
where:
CQ = Concentration of total chloride, ppmv as Cl" (for use in equation 3);
Cp = Concentration of each chlorinated compound, ppmv;
Clp = Number of moles of Cl" produced from the combustion of each chlorinated
compound (i.e., 3 for 1,1,1-trichloroethane); and
n = Number of chlorinated compounds available for summation.
After the total chloride concentration (CC1) has been estimated, equations 3 and 4 should be used to
determine the total uncontrolled mass emission rate of chlorinated compounds as chloride ion (UMC1). This
value is then used in equation 10 below to derive HC1 emission estimates:
= UMr, * -1^21 * 1.03 *
C1 100
1-
100
(10)
where:
= Controlled mass emissions of HC1, kg/yr;
= Uncontrolled mass emissions of chlorinated compounds as chloride, kg/yr (from
equations 3 and 4);
T)CO| = Efficiency of the landfill gas collection system, percent;
1.03 = Ratio of the molecular weight of HC1 to the molecular weight of Cl"; and
T|cn, = Control efficiency of the landfill gas control or utilization device, percent.
In estimating HC1 emissions, it is assumed that all of the chloride ion from the combustion of
chlorinated LFG constituents is converted to HC1. If an estimate of the control efficiency, r|cnt, is not
available, then the high end of the control efficiency range for the equipment listed in Table 9 should be
used. This assumption is recommended to assume that HC1 emissions are not under-estimated.
If site-specific data on total chloride or speciated chlorinated compounds are not available, then a
default value of 42.0 ppmv can be used for CC1. This value was derived from the default LFG constituent
concentrations presented in Table 2.4-1. As mentioned above, use of this default may produce
underestimates of HC1 emissions since it is based only on those compounds for which analyses have been
performed. The constituents listed in Table 2.4-1 are likely not all of the chlorinated compounds present in
LFG.
The reader is referred to Sections 11.2-1 (Unpaved Roads, SCC 50100401), and 11-2.4 (Heavy
Construction Operations) of Volume I, and Section II-7 (Construction Equipment) of Volume II, of the
AP-42 document for determination of associated fugitive dust and exhaust emissions from these emission
sources at MSW landfills.
8/98 Solid Waste Disposal 2.4-9
-------
2.4.5 Updates Since the Fifth Edition
The Fifth Edition was released in January 1995. This is revision includes major revisions of the text
and recommended emission factors conained in the section. The most significant revisions to this section
since publication in the Fifth Edition are summarized below.
• The equations to calculate the CH4, CO2 and other constituents were simplified,
• The default LO and k were revised based upon an expanded base of gas generation data.
• The default ratio of CO2 to CH4 was revised based upon averages observed in available source
test reports.
• The default concentrations of LFG constituents were revised based upon additional data.
• Additional control efficiencies were included and existing efficiencies were revised based upon
additional emission test data.
• Revised and expanded the recommended emission factors for secondary compounds emitted from
typical control devices.
2.4-10 EMISSION FACTORS 8/98
-------
Table 2.4-1. DEFAULT CONCENTRATIONS FOR LFG CONSTITUENTS3
(SCC 50100402, 50300603)
Compound
1,1,1-Trichloroethane (methyl chloroform)"
1 , 1 ,2,2-Tetrachloroethane"
1,1-Dichloroethane (ethylidene dichloride)"
1,1-Dichloroethene (vinylidene chloride)"
1 ,2-Dichloroethane (ethylene dichloride)"
1 ,2-Dichloropropane (propylene dichloride)"
2-Propanol (isopropyl alcohol)
Acetone
Acrylonitrilea
Bromodichloromethane
Butane
Carbon disulfide"
Carbon monoxide6
Carbon tetrachloride"
Carbonyl sulfide"
Chlorobenzene"
Chlorodifluoromethane
Chloroethane (ethyl chloride)"
Chloroform"
Chloromethane
Dichlorobenzene0
Dichlorodifluoromethane
Dichlorofluoromethane
Dichloromethane (methylene chloride)"
Dimethyl sulfide (methyl sulfide)
Ethane
Ethanol
Ethyl mercaptan (ethanethiol)
Ethylbenzene"
Ethylene dibromide
Fluorotrichloromethane
Hexane"
Hydrogen sulfide
Mercury (total)111
Molecular Weight
133.42
167.85
98.95
96.94
98.96
112.98
60.11
58.08
53.06
163.83
58.12
76.13
28.01
153.84
60.07
112.56
86.47
64.52
119.39
50.49
147
120.91
102.92
84.94
62.13
30.07
46.08
62.13
106.16
187.88
137.38
86.18
34.08
200.61
Default
Concentration
(ppmv)
0.48
1.11
2.35
0.20
0.41
0.18
50.1
7.01
6.33
3.13
5.03
0.58
141
0.004
0.49
0.25
1.30
1.25
0.03
1.21
0.21
15.7
2.62
14.3
7.82
889
27.2
2.28
4.61
0.001
0.76
6.57
35.5
2.92X10-4
Emission Factor
Rating
B
C
B
B
B
D
E
B
D
C
C
C
E
B
D
C
C
B
B
B
E
A
D
A
C
C
E
D
B
E
B
B
B
E
8/98
Solid Waste Disposal
2.4-11
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Table 2.4-1. (Concluded)
Compound
Methyl ethyl ketone1
Methyl isobutyl ketone"
Methyl mercaptan
Pentane
Perchloroethylene (tetrachloroethylene)2
Propane
t- 1 ,2-dichloroethene
Trichloroethylene (trichloroethene)3
Vinyl chloride3
Xylenes"
Molecular Weight
72.11
100.16
48.11
72.15
165.83
44.09
96.94
131.38
62.50
106.16
Default
Concentration
(ppmv)
7.09
1.87
2.49
3.29
3.73
11.1
2.84
2.82
7.34
12.1
Emission Factor
Rating
A
B
C
C
B
B
B
B
B
B
NOTE: This is not an all-inclusive list of potential LFG constituents, only those for which test data were
available at multiple sites. References 10-67. Source Classification Codes in parentheses.
a Hazardous Air Pollutants listed in Title in of the 1990 Clean Air Act Amendments.
b Carbon monoxide is not a typical constituent of LFG, but does exist in instances involving landfill
(underground) combustion. Therefore, this default value should be used with caution. Of 18 sites where CO
was measured, only 2 showed detectable levels of CO.
c Source tests did not indicate whether this compound was the para- or ortho- isomer. The para isomer is a
Title Hi-listed HAP.
d No data were available to speciate total Hg into the elemental and organic forms.
2.4-12
EMISSION FACTORS
8/98
-------
Table 2.4-2. DEFAULT CONCENTRATIONS OF BENZENE, NMOC, AND TOLUENE BASED ON
WASTE DISPOSAL HISTORY2
(SCC 50100402, 50300603)
Pollutant
Benzeneb
Co-disposal
No or Unknown co-disposal
NMOC (as hexane)c
Co-disposal
No or Unknown co-disposal
Tolueneb
Co-disposal
No or Unknown co-disposal
Molecular
Weight
78.11
86.18
92.13
Default
Concentration
(ppmv)
11.1
1.91
2420
595
165
39.3
Emission Factor
Rating
D
B
D
B
D
A
a References 10-54. Source Classification Codes in parentheses.
b Hazardous Air Pollutants listed in Title in of the 1990 Clean Air Act Amendments.
c For NSPS/Emission Guideline compliance purposes, the default concentration for NMOC as
specified in the final rule must be used. For purposes not associated with NSPS/Emission
Guideline compliance, the default VOC content at co-disposal sites = 85 percent by weight
(2,060 ppmv as hexane); at No or Unknown sites = 39 percent by weight 235 ppmv as
hexane).
8/98
Solid Waste Disposal
2.4-13
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Table 2.4-3. CONTROL EFFICIENCIES FOR LFG CONSTITUENTS8
Control Device
Boiler/Steam Turbine
(50100423)
Flare0
(50100410)
(50300601)
Gas Turbine
(50100420)
1C Engine
(50100421)
Constituentb
NMOC
Halogenated Species
Non-Halogenated Species
NMOC
Halogenated Species
Non-Halogenated Species
NMOC
Halogenated Species
Non-Halogenated Species
NMOC
Halogenated Species
Non-Halogenated Species
Control Efficiency (%)
Typical Range Rating
98.0
99.6
99.8
99.2
98.0
99.7
94.4
99.7
98.2
97.2
93.0
86.1
96-99+
87-99+
67-99+
90-99+
91-99+
38-99+
90-99+
98-99+
97-99+
94-99+
90-99+
25-99+
D
D
D
B
C
C
E
E
E
E
E
E
* References ^0-67. Source Classification Codes in parentheses.
Halogenated species are those containing atoms of chlorine, bromine, fluorine, or iodine. For any
equipment, the control efficiency for mercury should be assumed to be 0. See section 2.4.4.2 for
methods to estimate emissions of SO2, CO2, and HC1.
c Where information on equipment was given in the reference, test data were taken from enclosed flares.
Control efficiencies are assumed to be equally representative of open flares.
2.4-14
EMISSION FACTORS
8/98
-------
Table 2.4-4. (Metric Units) EMISSION FACTORS FOR SECONDARY COMPOUNDS
EXITING CONTROL DEVICES3
Control Device
Flarec
(50100410)
(50300601)
1C Engine
(50100421)
Boiler/Steam Turbined
(50100423)
Gas Turbine
(50100420)
Pollutant6
Nitrogen dioxide
Carbon monoxide
Particulate matter
Nitrogen dioxide
Carbon monoxide
Particulate matter
Nitrogen dioxide
Carbon monoxide
Particulate matter
Nitrogen dioxide
Carbon monoxide
Particulate matter
Typical Rate,
kg/hr/dscmm
Methane
0.039
0.72
0.016
0.24
0.45
0.046
0.032
5.4 x 10'3
7.9 x ID'3
0.083
0.22
0.021
Emission Factor
Rating
C
C
D
D
C
E
D
E
D
D
E
E
a Source Classification Codes in parentheses.
b No data on PM size distributions were available, however for other gas-fired combustion sources,
most of the particulate matter is less than 2.5 microns in diameter. Hence, this emission factor can be
used to provide estimates of PM-10 or PM-2.5 emissions. See section 2.4.4.2 for methods to estimate
CO2) SO2, and HC1.
c Where information on equipment was given in the reference, test data were taken from enclosed
flares. Control efficiencies are assumed to be equally representative of open flares.
d All source tests were conducted on boilers, however emission factors should also be representative of
steam turbines. Emission factors are representative of boilers equipped with low-NOx burners and
flue gas recirculation. No data were available for uncontrolled NOX emissions.
8/98
Solid Waste Disposal
2.4-15
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Table 2.4-5. (English Units) EMISSION RATES FOR SECONDARY COMPOUNDS
EXITING CONTROL DEVICES3
Control Device
Flarec
(50100410)
(50300601)
1C Engine
(50100421)
Boiler/Steam Turbined
(50100423)
Gas Turbine
(50100420)
Pollutant1"
Nitrogen dioxide
Carbon monoxide
Paniculate matter
Nitrogen dioxide
Carbon monoxide
Particulate matter
Nitrogen dioxide
Carbon monoxide
Particulate matter
Nitrogen dioxide
Carbon monoxide
Particulate matter
Typical Rate,
Ib/hr/dscfm
Methane
2.4 x ID'3
0.045
l.Ox lO'3
0.015
0.028
2.9 x 1C'3
2.0 x 10-3
3.4 x 10-4
4.9 x 10-4
5.2 x 10-3
0.014
1.3xlO-3
Emission
Factor Rating
C
C
D
D
C
E
E
E
E
D
D
E
a Source Classification Codes in parentheses.
b Based on data for other combustion sources, most of the particulate matter will be less than
2.5 microns in diameter. Hence, this emission rate can be used to provide estimates of PM-10
or PM-2.5 emissions. See section 2.4.4.2 for methods to estimate CO2, SO2, and HC1.
c Where information on equipment was given in the reference, test data were taken from
enclosed flares. Control efficiencies are assumed to be equally representative of open flares.
d All source tests were conducted on boilers, however emission factors should also be
representative of steam turbines. Emission factors are representative of boilers equipped with
low-NOx burners and flue gas recirculation. No data were available for uncontrolled NOX
emissions.
References for Section 2.4
1. "Criteria for Municipal Solid Waste Landfills," 40 CFR Part 258, Volume 56, No. 196, October 9,
1991.
2. Air Emissions from Municipal Solid Waste Landfills - Background Information for Proposed
Standards and Guidelines, Office of Air Quality Planning and Standards, EPA-450/3-90-01 la,
Chapters 3 and 4, U. S. Environmental Protection Agency, Research Triangle Park, NC, March 1991.
3. Characterization of Municipal Solid Waste in the United States: 1992 Update, Office of Solid
Waste, EPA-530-R-92-019, U. S. Environmental Protection Agency, Washington, DC, NTTS
No. PB92-207-166, July 1992.
4. Eastern Research Group, Inc., List of Municipal Solid Waste Landfills, Prepared for the
U. S. Environmental Protection Agency, Office of Solid Waste, Municipal and Industrial Solid Waste
Division, Washington, DC, September 1992.
2.4-16 EMISSION FACTORS 8/98
-------
5. Suggested Control Measures for Landfill Gas Emissions, State of California Air Resources Board,
Stationary Source Division, Sacramento, CA, August 1990.
6. "Standards of Performance for New Stationary Sources and Guidelines for Control of Existing
Sources: Municipal Solid Waste Landfills; Proposed Rule, Guideline, and Notice of Public Hearing,"
40 CFR Parts 51, 52, and 60, Vol. 56, No. 104, May 30, 1991.
7. S.W. Zison, Landfill Gas Production Curves: Myth Versus Reality, Pacific Energy, City of
Commerce, CA, [Unpublished]
8. R.L. Peer, et al., Memorandum Methodology Used to Revise the Model Inputs in the Municipal Solid
Waste Landfills Input Data Bases (Revised), to the Municipal Solid Waste Landfills Docket No. A-
88-09, April 28, 1993.
9. A.R. Chowdhury, Emissions from a Landfill Gas-Fired Turbine/Generator Set, Source Test Report
C-84-33, Los Angeles County Sanitation District, South Coast Air Quality Management District,
June 28, 1984.
10. Engineering-Science, Inc., Report of Stack Testing at County Sanitation District Los Angeles Puente
Hills Landfill, Los Angeles County Sanitation District, August 15, 1984.
11. J.R. Manker, Vinyl Chloride (and Other Organic Compounds) Content of Landfill Gas Vented to an
Inoperative Flare, Source Test Report 84-496, David Price Company, South Coast Air Quality
Management District, November 30, 1984.
12. S. Mainoff, Landfill Gas Composition, Source Test Report 85-102, Bradley Pit Landfill, South Coast
Air Quality Management District, May 22, 1985.
13. J. Littman, Vinyl Chloride and Other Selected Compounds Present in A Landfill Gas Collection
System Prior to and after Flaring, Source Test Report 85-369, Los Angeles County Sanitation
District, South Coast Air Quality Management District, October 9, 1985.
14. W.A. Nakagawa, Emissions from a Landfill Exhausting Through a Flare System, Source Test
Report 85-461, Operating Industries, South Coast Air Quality Management District, October 14,
1985.
15. S. Marinoff, Emissions from a Landfill Gas Collection System, Source Test Report 85-511. Sheldon
Street Landfill, South Coast Air Quality Management District, December 9,1985.
16. W.A. Nakagawa, Vinyl Chloride and Other Selected Compounds Present in a Landfill Gas
Collection System Prior to and after Flaring, Source Test Report 85-592, Mission Canyon Landfill,
Los Angeles County Sanitation District, South Coast Air Quality Management District, January 16,
1986.
17. California Air Resources Board, Evaluation Test on a Landfill Gas-Fired Flare at the BKK Landfill
Facility, West Covina, CA, ARB-SS-87-09, July 1986.
18. S. Marinoff, Gaseous Composition from a Landfill Gas Collection System and Flare, Source Test
Report 86-0342, Syufy Enterprises, South Coast Air Quality Management District, August 21, 1986.
19. Analytical Laboratory Report for Source Test, Azusa Land Reclamation, June 30, 1983, South Coast
Air Quality Management District.
20. J.R. Manker, Source Test Report C-84-202, Bradley Pit Landfill, South Coast Air Quality
Management District, May 25, 1984.
8/98 Solid Waste Disposal 2.4-17
-------
21. S. Marinoff, Source Test Report 84-315, Puente Hills Landfill, South Coast Air Quality Management
District, February 6, 1985.
22. P.P. Chavez, Source Test Report 84-596, Bradley Pit Landfill, South Coast Air Quality Management
District, March 11, 1985.
23. S. Marinoff, Source Test Report 84-373, Los Angeles By-Products, South Coast air Quality
Management District, March 27, 1985.
24. J. Littman, Source Test Report 85-403, Palos Verdes Landfill, South Coast Air Quality Management
District, September 25, 1985.
25. S. Marinoff, Source Test Report 86-0234, Pacific Lighting Energy Systems, South Coast Air Quality
Management District, July 16, 1986.
26. South Coast Air Quality Management District, Evaluation Test on a Landfill Gas-Fired Flare at the
Los Angeles County Sanitation District's Puente Hills Landfill Facility, [ARB/SS-87-06],
Sacramento, CA, July 1986.
27. D.L. Campbell, et al., Analysis of Factors Affecting Methane Gas Recovery from Six Landfills, Air
and Energy Engineering Research Laboratory, EPA-600/2-91-055, U. S. Environmental Protection
Agency, Research Triangle Park, NC, September 1991.
28. Browning-Ferris Industries, Source Test Report, Lyon Development Landfill, August 21, 1990.
29. X.V. Via, Source Test Report, Browning-Ferris Industries, Azusa Landfill.
30. M. Nourot, Gaseous Composition from a Landfill Gas Collection System and Flare Outlet. Laidlaw
Gas Recovery Systems, to J.R. Farmer, OAQPS:ESD, December 8, 1987.
31. D.A. Stringham and W.H. Wolfe, Waste Management of North America, Inc., to J.R. Farmer,
OAQPS:ESD, January 29, 1988, Response to Section 114 questionnaire.
32. V. Espinosa, Source Test Report 87-0318, Los Angeles County Sanitation District Calabasas
Landfill, South Coast Air Quality Management District, December 16, 1987.
33. C.S. Bhatt, Source Test Report 87-0329, Los Angeles County Sanitation District, Scholl Canyon
Landfill, South Coast Air Quality Management District, December 4, 1987.
34. V. Espinosa, Source Test Report 87-0391, Puente Hills Landfill, South Coast Air Quality
Management District, February 5, 1988.
35. V. Espinosa, Source Test Report 87-0376, Palos Verdes Landfill, South Coast Air Quality
Management District, February 9, 1987.
36. Bay Area Air Quality Management District, Landfill Gas Characterization, Oakland, CA, 1988.
37. Steiner Environmental, Inc., Emission Testing at BFI's Arbor Hills Landfill, Northville, Michigan,
September 22 through 25, 1992, Bakersfield, CA, December 1992.
38. PEI Associates, Inc., Emission Test Report - Performance Evaluation Landfill-Gas Enclosed Flare,
Browning Ferris Industries, Chicopee, MA, 1990.
39. Kleinfelder Inc., Source Test Report Boiler and Flare Systems, Prepared for Laidlaw Gas Recovery
Systems, Coyote Canyon Landfill, Diamond Bar, CA, 1991.
2.4-18 EMISSION FACTORS 8/98
-------
40. Bay Area Air Quality Management District, McGill Flare Destruction Efficiency Test Report for
Landfill Gas at the Durham Road Landfill, Oakland, CA, 1988.
41. San Diego Air Pollution Control District, Solid Waste Assessment for Otay Valley/Annex Landfill.
San Diego, CA, December 1988.
42. PEI Associates, Inc., Emission Test Report - Performance Evaluation Landfill Gas Enclosed Flare,
Rockingham, VT, September 1990.
43. Browning-Ferris Industries, Gas Flare Emissions Source Test for Sunshine Canyon Landfill.
Sylmar, CA, 1991.
44. Scott Environmental Technology, Methane and Nonmethane Organic Destruction Efficiency Tests of
an Enclosed Landfill Gas Flare, April 1992.
45. BCM Engineers, Planners, Scientists and Laboratory Services, Air Pollution Emission Evaluation
Report for Ground Flare at Browning Ferris Industries Greentree Landfill, Kersey, Pennsylvania.
Pittsburgh, PA, May 1992.
46. EnvironMETeo Services Inc., Stack Emissions Test Report for Ameron Kapaa Quarry, Waipahu, HI,
January 1994.
47. Waukesha Pearce Industries, Inc., Report of Emission Levels and Fuel Economies for Eight
Waukesha 12V-AT25GL Units Located at the Johnston, Rhode Island Central Landfill, Houston
TX, July 19, 1991.
48. Mostardi-Platt Associates, Inc., Gaseous Emission Study Performed for Waste Management of
North America, Inc., CID Environmental Complex Gas Recovery Facility, August 8, 1989. Chicago,
IL, August 1989.
49. Mostardi-Platt Associates, Inc., Gaseous Emission Study Performed for Waste Management of
North America, Inc., at the CID Environmental Complex Gas Recovery Facility, July 12-14, 1989.
Chicago, IL, July 1989.
50. Browning-Ferris Gas Services, Inc., Final Report for Emissions Compliance Testing of One
Waukesha Engine Generator, Chicopee, MA, February 1994.
51. Browning-Ferris Gas Services, Inc., Final Report for Emissions Compliance Testing of Three
Waukesha Engine Generators, Richmond, VA, February 1994.
52. South Coast Environmental Company (SCEC), Emission Factors for Landfill Gas Flares at the
Arizona Street Landfill, Prepared for the San Diego Air Pollution Control District, San Diego, CA,
November 1992.
53. Carnot, Emission Tests on the Puente Hills Energy from Landfill Gas (PERG) Facility - Unit 400,
September 1993, Prepared for County Sanitation Districts of Los Angeles County, Tustin, CA,
November 1993.
54. Pape & Steiner Environmental Services, Compliance Testing for Spadra Landfill Gas-to-Energy
Plant, July 25 and 26, 1990, Bakersfield, CA, November 1990.
55. AB2588 Source Test Report for Oxnard Landfill, July 23-27, 1990, by Petro Chem Environmental
Services, Inc., for Pacific Energy Systems, Commerce, CA, October 1990.
8/98 Solid Waste Disposal 2.4-19
-------
56. AB2588 Source Test Report for Oxnard Landfill, October 16, 1990, by Petro Chem Environmental
Services, Inc., for Pacific Energy Systems, Commerce, CA, November 1990.
57. Engineering Source Test Report for Oxnard Landfill, December 20, 1990, by Petro Chem
Environmental Services, Inc., for Pacific Energy Systems, Commerce, CA, January 1991.
58. AB2588 Emissions Inventory Report for the Salinas Crazy Horse Canyon Landfill, Pacific Energy,
Commerce, CA, October 1990.
59. Newby Island Plant 2 Site 1C Engine's Emission Test, February 7-8, 1990, Laidlaw Gas Recovery
Systems, Newark, CA, February 1990.
60. Landfill Methane Recovery Part II: Gas Characterization, Final Report, Gas Research Institute,
December 1982.
61. Letter from J.D. Thornton, Minnesota Pollution Control Agency, to R. Myers, U.S. EPA, February 1,
1996.
62. Letter and attached documents from M. Sauers, GSF Energy, to S. Thorneloe, U.S. EPA, May 29,
1996.
63. Landfill Gas Particulate and Metals Concentration and Flow Rate, Mountaingate Landfill Gas
Recovery Plant, Horizon Air Measurement Services, prepared for GSF Energy, Inc., May 1992.
64. Landfill Gas Engine Exhaust Emissions Test Report in Support of Modification to Existing 1C Engine
Permit at Bakersfield Landfill Unit #1, Pacific Energy Services, December 4, 1990.
65. Addendum to Source Test Report for Superior Engine #1 at Otay Landfill, Pacific Energy Services,
April 2, 1991.
66. Source Test Report 88-0075 of Emissions from an Internal Combustion Engine Fueled by Landfill
Gas, Penrose Landfill, Pacific Energy Lighting Systems, South Coast Air Quality Management
District, February 24, 1988.
67. Source Test Report 88-0096 of Emissions from an Internal Combustion Engine Fueled by Landfill
Gas, Toyon Canyon Landfill, Pacific Energy Lighting Systems, March 8, 1988.
68. Letter and attached documents from C. Nesbitt, Los Angeles County Sanitation Districts, to K. Brust,
E.H. Pechan and Associates, Inc., December 6, 1996.
69. Determination of Landfill Gas Composition and Pollutant Emission Rates at Fresh Kills Landfill,
revised Final Report, Radian Corporation, prepared for U.S. EPA, November 10, 1995.
70. Advanced Technology Systems, Inc., Report on Determination of Enclosed Landfill Gas Flare
Performance, Prepared for Y & S Maintenance, Inc., February 1995.
71. Chester Environmental, Report on Ground Flare Emissions Test Results, Prepared for Seneca
Landfill, Inc., October 1993.
72. Smith Environmental Technologies Corporation, Compliance Emission Determination of the
Enclosed Landfill Gas Flare and Leachate Treatment Process Vents; Prepared for Clinton County
Solid Waste Authority, April 1996.
73. AirRecon®, Division of RECON Environmental Corp., Compliance Stack Test Report for the
Landfill Gas FLare Met & Outlet at Bethlehem Landfill, Prepared for LFG Specialties Inc.,
Decembers, 1996.
2.4-20 EMISSION FACTORS 8/98
-------
74. ROJAC Environmental Services, Inc., Compliance Test Report, Hartford Landfill Flare Emissions
Test Program, November 19, 1993.
75. Normandeau Associates, Inc., Emissions Testing of a Landfill Gas Flare at Contra Costa Landfill,
Antioch, California, March 22, 1994 and April 22, 1994, May 17, 1994.
76. Roe, S.M., et. al., Methodologies for Quantifying Pollution Prevention Benefits from Landfill Gas
Control and Utilization, Prepared for U.S. EPA, Office of Air and Radiation, Air and Energy
Engineering Laboratory, EPA-600/R-95-089, July 1995.
8/98 Solid Waste Disposal 2.4-21
-------
2.5 Open Burning
2.5.1 General1
Open burning can be done in open drums or baskets, in fields and yards, and in large open
dumps or pits. Materials commonly disposed of in this manner include municipal waste, auto body
components, landscape refuse, agricultural field refuse, wood refuse, bulky industrial refuse, and
leaves.
Current regulations prohibit open burning of hazardous waste. One exception is for open
burning and detonation of explosives, particularly waste explosives that have the potential to detonate,
and bulk military propellants which cannot safely be disposed of through other modes of treatment.
The following Source Classification Codes (SCCs) pertain to open burning:
Government
5-01-002-01 General Refuse
5-01-002-02 Vegetation Only
Commercial/Institutional
5-02-002-01 Wood
5-02-002-02 Refuse
Industrial
5-03-002-01 Wood/Vegetation/Leaves
5-03-002-02 Refuse
5-03-002-03 Auto Body Components
5-03-002-04 Coal Refuse Piles
5-03-002-05 Rocket Propellant
2.5.2 Emissions1"22
Ground-level open burning emissions are affected by many variables, including wind, ambient
temperature, composition and moisture content of the debris burned, and compactness of the pile. In
general, the relatively low temperatures associated with open burning increase emissions of paniculate
matter, carbon monoxide, and hydrocarbons and suppress emissions of nitrogen oxides. Emissions of
sulfur oxides are a direct function of the sulfur content of the refuse.
2.5.2.1 Municipal Refuse -
Emission factors for the open burning of municipal refuse are presented in Table 2.5-1.
2.5.2.2 Automobile Components -
Emission factors for the open burning of automobile components including upholstery, belts,
hoses, and tires are presented in Table 2.5-1.
Emission factors for the burning of scrap tires only are presented in Tables 2.5-2, 2.5-3, and
2.5-4. Although it is illegal in many states to dispose of tires using open burning, fires often occur at
10/92 (Reformatted 1/95) Solid Waste Disposal 2.5-1
-------
Table 2.5-1 (Metric And English Units). EMISSION FACTORS FOR OPEN BURNING
OF MUNICIPAL REFUSE
EMISSION FACTOR RATING: D
Source
Municipal Refuseb
kg/Mg
Ib/ton
Automobile Components0
kg/Mg
Ib/ton
Particulate
8
16
50
100
Sulfur
Oxides
0.5
1.0
Neg
Neg
Carbon
Monoxide
42
85
62
125
TOC"
Methane
6.5
13
5
10
Nonmethane
15
30
16
32
Nitrogen
Oxides
3
6
2
4
a Data indicate that total organic compounds (TOC) emissions are approximately 25% methane, 8%
other saturates, 18% olefins, 42% others (oxygenates, acetylene, aromatics, trace formaldehyde).
b References 2 and 7.
c Reference 2. Upholstery, belts, hoses, and tires burned together.
tire stockpiles and through illegal burning activities. If the emission factors presented here are used
to estimate emissions from an accidental tire fire, it should be kept in mind that emissions from
burning tires are generally dependent on the burn rate of the tire. A greater potential for emissions
exists at lower burn rates, such as when a tire is smoldering, rather than burning out of control. In
addition, the emission factors presented here for tire "chunks" are probably more appropriate than for
"shredded" tires for estimating emissions from an accidental tire fire because there is likely to be
more air-space between the tires in an actual fire. As discussed in Reference 21, it is difficult to
estimate emissions from a large pile of tires based on these results, but emissions can be related to a
mass burn rate. To use the information presented here, it may be helpful to use the following
estimates: tires tested in Reference 21 weighed approximately 7 kilograms (kg) (15.4 pounds [lb])
and the volume of 1 tire is approximately 0.2 cubic meter (m3) (7 cubic feet [ft3]). Table 2.5-2
presents emission factors for particulate metals. Table 2.5-3 presents emission factors for polycyclic
aromatic hydrocarbons (PAH), and Table 2.5-4 presents emissions for other volatile hydrocarbons.
For more detailed information on this subject consult the reference cited at the end of this chapter.
2.5.2.3 Agricultural Waste -
Organic Agricultural Waste -
Organic refuse burning consists of burning field crops, wood, and leaves. Emissions from
organic agricultural refuse burning are dependent mainly on the moisture content of the refuse and, in
the case of the field crops, on whether the refuse is burned in a headfire or a backfire. Headfires are
started at the upwind side of a field and allowed to progress in the direction of the wind, whereas
backfires are started at the downwind edge and forced to progress in a direction opposing the wind.
Other variables such as fuel loading (how much refuse material is burned per unit of land
area) and how the refuse is arranged (in piles, rows, or spread out) are also important in certain
instances. Emission factors for open agricultural burning are presented in Table 2.5-5 as a function
of refuse type and also, in certain instances, as a function of burning techniques and/or moisture
content when these variables are known to significantly affect emissions. Table 2.5-5 also presents
typical fuel loading values associated with each type of refuse. These values can be used, along with
2.5-2
EMISSION FACTORS
(Reformatted 1/95) 10/92
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the corresponding emission factors, to estimate emissions from certain categories of agricultural
burning when the specific fuel loadings for a given area are not known.
Emissions from leaf burning are dependent upon the moisture content, density, and ignition
location of the leaf piles. Increasing the moisture content of the leaves generally increases the amount
of carbon monoxide, hydrocarbon, and particulate emissions. Carbon monoxide emissions decrease if
moisture content is high but increase if moisture content is low. Increasing the density of the piles
increases the amount of hydrocarbon and particulate emissions, but has a variable effect on carbon
monoxide emissions.
The highest emissions from open burning of leaves occur when the base of the leaf pile is
ignited. The lowest emissions generally arise from igniting a single spot on the top of the pile.
Particulate, hydrocarbon, and carbon monoxide emissions from windrow ignition (piling the leaves
into a long row and igniting one end, allowing it to burn toward the other end) are intermediate
between top and bottom ignition. Emission factors for leaf burning are presented in Table 2.5-6. For
more detailed information on this subject, the reader should consult the reference cited at the end of
this section.
2.5.2.4 Agricultural Plastic Film -
Agricultural plastic film that has been used for ground moisture and weed control. Large
quantities of plastic film are commonly disposed of when field crops are burned. The plastic film
may also be gathered into large piles and burned separately or burned in an air curtain. Emissions
from burning agricultural plastic are dependent on whether the film is new or has been exposed to
exposed to vegetation and possibly pesticides. Table 2.5-7 presents emission factors for organic
compounds emitted from burning new and used plastic film in piles or in piles where air has been
forced through them to simulate combustion in an air curtain. Table 2.5-8 presents emission factors
for PAHs emitted from open burning of inorganic plastic film.
10/92 (Reformatted 1/95) Solid Waste Disposal 2.5-13
-------
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2.5-14
EMISSION FACTORS
(Reformatted 1/95) 10/92
-------
Table 2.5-7 (Metric And English Units). EMISSION FACTORS FOR ORGANIC
COMPOUNDS FROM BURNING PLASTIC FILMa
EMISSION FACTOR RATING: C
Pollutant
Benzene
Toluene
Ethyl benzene
1-Hexene
Units
mg/kg plastic
lb/1000 tons plastic
mg/kg plastic
lb/1000 tons plastic
mg/kg plastic
lb/1000 tons plastic
mg/kg plastic
lb/1000 tons plastic
Condition Of Plastic
Unused Plastic
Pileb
0.0478
0.0955
0.0046
0.0092
0.0006
0.0011
0.0010
0.0020
Forced
Airc
0.0288
0.0575
0.0081
0.0161
0.0029
0.0058
0.0148
0.0296
Used
Pileb
0.0123
0.0247
0.0033
0.0066
0.0012
0.0025
0.0043
0.0086
Plastic
Forced
Airc
0.0244
0.0488
0.0124
0.0248
0.0056
0.0111
0.0220
0.0440
a Reference 22.
b Emission factors are for plastic gathered in
0 Emission factors are for plastic burned in a
a pile and burned.
pile with a forced air current.
10/92 (Reformatted 1/95)
Solid Waste Disposal
2.5-15
-------
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2.5-16
EMISSION FACTORS
(Reformatted 1/95) 10/92
-------
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oo
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10/92 (Reformatted 1/95)
Solid Waste Disposal
2.5-17
-------
References For Section 2.5
1. Air Pollutant Emission Factors. Final Report, National Air Pollution Control Administration,
Durham, NC Contract Number CPA A-22-69-119, Resources Research, Inc., Reston, VA,
April 1970.
2. R. W. Gerstle and D. A. Kemnitz, "Atmospheric Emissions From Open Burning", Journal Of
Air Pollution Control Association, 12: 324-327, May 1967.
3. J. O. Burkle, et al., "The Effects Of Operating Variables And Refuse Types On Emissions
From A Pilot-Scale Trench Incinerator1', In: Proceedings Of1968 Incinerator Conference,
American Society Of Mechanical Engineers. New York, p.34-41, May 1968.
4. M. I. Weisburd and S. S. Griswold (eds.), Air Pollution Control Field Operations Guide: A
Guide For Inspection And Control, PHS Publication No. 937, U. S. DHEW, PHS, Division
Of Air Pollution, Washington, D.C., 1962.
5. Unpublished Data On Estimated Major Air Contaminant Emissions, State Of New York
Department Of Health, Albany, NY, April 1, 1968.
6. E. F. Darley, et al., "Contribution Of Burning Of Agricultural Wastes To Photochemical Air
Pollution", Journal Of Air Pollution Control Association, 16: 685-690, December 1966.
7. M. Feldstein, et al., "The Contribution Of The Open Burning Of Land Clearing Debris To
Air Pollution", Journal Of Air Pollution Control Association, 13: 542-545, November 1963.
8. R. W. Boubel, et al., "Emissions From Burning Grass Stubble And Straw", Journal Of Air
Pollution Control Association, 19: 497-500, July 1969.
9. "Waste Problems Of Agriculture And Forestry", Environmental Science And Technology,
2:498, July 1968.
10. G. Yamate, et al., "An Inventory Of Emissions From Forest Wildfires, Forest Managed
Burns, And Agricultural Burns And Development Of Emission Factors For Estimating
Atmospheric Emissions From Forest Fires", Presented At 68th Annual Meeting Air Pollution
Control Association, Boston, MA, June 1975.
11. E. F. Darley, Air Pollution Emissions From Burning Sugar Cane And Pineapple From
Hawaii, University Of California, Riverside, Calif. Prepared For Environmental Protection
Agency, Research Triangle Park, N.C, as amendment of Research Grant No. R800711.
August 1974.
12. E. F. Darley, et al., Air Pollution From Forest And Agricultural Burning. California Air
Resources Board Project 2-017-1, California Air Resources Board Project No. 2-017-1,
University Of California, Davis, CA, April 1974.
13. E. F. Darley, Progress Report On Emissions From Agricultural Burning, California Air
Resources Board Project 4-011, University Of California, Riverside, CA, Private
communication with permission of Air Resources Board, June 1975.
2.5-18 EMISSION FACTORS (Reformatted 1/95) 10/92
-------
14. Private communication on estimated waste production from agricultural burning activities.
California Air Resources Board, Sacramento, CA. September 1975.
15. L. Fritschen, et al., Flash Fire Atmospheric Pollution. U. S. Department of Agriculture,
Washington, D.C., Service Research Paper PNW-97. 1970.
16. D. W. Sandberg, et al., "Emissions From Slash Burning And The Influence Of Flame
Retardant Chemicals". Journal Of Air Pollution Control Association, 25:278, 1975.
17. L. G. Wayne And M. L. McQueary, Calculation Of Emission Factors For Agricultural
Burning Activities, EPA-450-3-75-087, Environmental Protection Agency, Research Triangle
Park, NC, Prepared Under Contract No. 68-02-1004, Task Order No. 4. By Pacific
Environmental Services, Inc., Santa Monica, CA, November 1975.
18. E. F. Darley, Emission Factor Development For Leaf Burning, University of California,
Riverside, CA, Prepared For Environmental Protection Agency, Research Triangle Park, NC,
Under Purchase Order No. 5-02-6876-1, September 1976.
19. E. F. Darley, Evaluation Of The Impact Of Leaf Burning — Phase I: Emission Factors For
Illinois Leaves, University Of California, Riverside, CA, Prepared For State of Illinois,
Institute For Environmental Quality, August 1975.
20. J. H. Southerland and A. McBath. Emission Factors And Field Loading For Sugar Cane
Burning, MDAD, OAQPS, U. S. Environmental Protection Agency, Research Triangle Park,
NC, January 1978.
21. Characterization Of Emissions From The Simulated Open Burning Of Scrap Tires,
EPA-600/2-89-054, U.S. Environmental Protection Agency, Research Triangle Park, NC,
October 1989.
22. W. P. Linak, et al., "Chemical And Biological Characterization Of Products Of Incomplete
Combustion From The Simulated Field Burning Of Agricultural Plastic", Journal Of Air
Pollution Control Association, 39(6), EPA-600/J-89/025, U. S. Environmental Protection
Agency Control Technology Center, June 1989.
10/92 (Reformatted 1/95) Solid Waste Disposal 2.5-19
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2.6 Automobile Body Incineration
The information presented in this section has been reviewed but not updated since it was
originally prepared because no recent data were found and it is rarely practiced today. Auto bodies are
likely to be shredded or crushed and used as scrap metal in secondary metal production operations,
which are discussed in Chapter 12 (Metallurgical Industry).
2.6.1 Process Description
Auto incinerators consist of a single primary combustion chamber in which one or several
partially stripped cars are burned. (Tires are removed.) Approximately 30 to 40 minutes is required to
burn two bodies simultaneously.2 As many as 50 cars per day can be burned in this batch-type
operation, depending on the capacity of the incinerator. Continuous operations hi which cars are
placed on a conveyor belt and passed through a tunnel-type incinerator have capacities of more than
50 cars per 8-hour day.
2.6.2 Emissions And Controls1
Both the degree of combustion as determined by the incinerator design and the amount of
combustible material left on the car greatly affect emissions. Temperatures on the order of 650°C
(1200°F) are reached during auto body incineration.2 This relatively low combustion temperature is a
result of the large incinerator volume needed to contain the bodies as compared with the small quantity
of combustible material. The use of overfire air jets in the primary combustion chamber increases
combustion efficiency by providing air and increased turbulence.
In an attempt to reduce the various air pollutants produced by this method of burning, some
auto incinerators are equipped with emission control devices. Afterburners and low-voltage
electrostatic precipators have been used to reduce paniculate emissions; the former also reduces some
of the gaseous emissions.3'4 When afterburners are used to control emissions, the temperature in the
secondary combustion chamber should be at least 815°C (1500°F). Lower temperatures result in
higher emissions. Emission factors for auto body incinerators are presented in Table 2.6-1. Paniculate
matter is likely to be mostly in the PM-10 range, but no data are available to support this hypothesis.
Although no data are available, emissions of HC1 are expected due to the increased use of chlorinated
plastic materials in automobiles.
10/92 (Reformatted 1/95) Solid Waste Disposal 2.6-1
-------
Table 2.6-1 (English And Metric Units). EMISSION FACTORS FOR AUTO BODY
INCINERATION*
EMISSION FACTOR RATING: D
Pollutants
Particulatesb
Carbon monoxide0
TOC (as CH^0
Nitrogen oxides (N0£d
Aldehydes (HCOH)d
Organic acids (acetic)d
Uncontrolled
Ib/car
2
2.5
0.5
0.1
0.2
0.21
kg/car
0.9
1.1
0.23
0.05
0.09
0.10
With Afterburner
Ib/car
1.5
Neg
Neg
0.02
0.06
0.07
kg/car
0.68
Neg
Neg
0.01
0.03
0.03
a Based on 250 Ib (113 kg) of combustible material on stripped car body.
b References 2 and 4.
c Based on data for open burning and References 2 and 5.
d Reference 3.
References For Section 2.6
1. Air Pollutant Emission Factors Final Report, National Air Pollution Control Administration,
Durham, NC, Contract Number CPA-22-69-119, Resources Research Inc. Reston, VA,
April 1970.
2. E. R. Kaiser and J. Tolcias, "Smokeless Burning Of Automobile Bodies", Journal of the Air
Pollution Control Association, 72:64-73, February 1962.
3. F. M. Alpiser, "Air Pollution From Disposal Of Junked Autos", Air Engineering, 70:18-22,
November 1968.
4. Private communication with D. F. Walters, U. S. DHEW, PHS, Division of Air Pollution,
Cincinnati, OH, July 19, 1963.
5. R. W. Gerstle and D. A. Kemnitz, "Atmospheric Emissions From Open Burning", Journal of
the Air Pollution Control Association, 77:324-327. May 1967.
2.6-2
EMISSION FACTORS
(Reformatted 1/95) 10/92
-------
2.7 Conical Burners
The information presented in this section has not been updated since it was originally prepared
because no recent data were found. The use of conical burners is much less prevalent now than in the
past and they are essentially obsolete.
2.7.1 Process Description1
Conical burners are generally truncated metal cones with screened top vents. The charge is
placed on a raised grate by either conveyor or bulldozer; however, the use of a conveyor results in
more efficient burning. No supplemental fuel is used, but combustion air is often supplemented by
underfire air blown into the chamber below the grate and by overfire air introduced through peripheral
openings in the shell.
2.7.2 Emissions And Controls
The quantities and types of pollutants released from conical burners are dependent on the
composition and moisture content of the charged material, control of combustion air, type of charging
system used, and the condition in which the incinerator is maintained. The most critical of these factors
seems to be the level of maintenance on the incinerators. It is not uncommon for conical burners to
have missing doors and numerous holes in the shell, resulting in excessive combustion air, low
temperatures, and, therefore, high emission rates of combustible pollutants.2
Paniculate control systems have been adapted to conical burners with some success. These
control systems include water curtains (wet caps) and water scrubbers. Emission factors for conical
burners are shown in Table 2.7-1.
10/92 (Reformatted 1/95) Solid Waste Disposal 2.7-1
-------
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2.7-2
EMISSION FACTORS
(Reformatted 1/95) 10/92
-------
References For Section 2.7
1. Air Pollutant Emission Factors, Final Report, CPA-22-69-119, Resources Research Inc.
Reston, VA. Prepared for National Air Pollution Control Administration, Durham, NC
April 1970.
2. T. E. Kreichelt, Air Pollution Aspects Of Teepee Burners, U. S. DHEW, PHS, Division of Air
Pollution. Cincinnati, Ohio. PHS Publication Number 999-AP-28. September 1966.
3. P. L. Magill and R. W. Benoliel, "Air Pollution In Los Angeles County: Contribution Of
Industrial Products", Ind. Eng. Chem, 44:1347-1352. June 1952.
4. Private communication with Public Health Service, Bureau of Solid Waste Management,
Cincinnati, Ohio. October 31, 1969.
5. D. M. Anderson, et al., Pure Air For Pennsylvania, Pennsylvania State Department of Health,
Harrisburg PA, November 1961. p. 98.
6. R. W. Boubel, et al., Wood Waste Disposal And Utilization. Engineering Experiment Station,
Oregon State University, Corvallis, OR, Bulletin Number 39. June 1958. p.57.
7. A. B. Netzley and J. E. Williamson. Multiple Chamber Incinerators For Burning Wood Waste,
In: Air Pollution Engineering Manual, Danielson, J. A. (ed.). U. S. DHEW, PHS, National
Center for Air Pollution Control. Cincinnati, OH. PHS Publication Number 999-AP-40.
1967. p. 436-445.
8. H. Droege and G. Lee, The Use Of Gas Sampling And Analysis For The Evaluation Of
Teepee Burners, Bureau Of Air Sanitation, California Department Of Public Health,
(Presented At The 7th Conference On Methods In Air Pollution Studies, Los Angeles, CA,
January 1965.)
9. R. W. Boubel, "Paniculate Emissions From Sawmill Waste Burners", Engineering
Experiment Station, Oregon State University, Corvallis, OR, Bulletin Number 42, August
1968, p. 7-8.
10/92 (Reformatted 1/95) Solid Waste Disposal 2.7-3
-------
3. STATIONARY INTERNAL COMBUSTION SOURCES
Internal combustion engines often are used in applications similar to those associated with
external combustion sources. The major items within this category are gas turbines and large
heavy-duty general utility reciprocating engines. Most stationary internal combustion engines are used
to generate electric power, to pump gas or other fluids, or to compress air for pneumatic machinery.
The major pollutants of concern are total organic compounds and oxides of nitrogen. There also may
be organic compounds that may be toxic or hazardous.
1/95 Stationary Internal Combustion Sources 3.0-1
-------
3.1 Stationary Gas Turbines For Electricity Generation
3.1.1 General1
A gas turbine is an internal combustion engine that operates with rotary rather than
reciprocating motion. Gas turbines are used in a broad scope of applications including electric power
generators, and in various process industries. Gas turbines are available with power outputs ranging in
size from 300 horsepower (hp) to over 268,000 hp, with an average size of 40,200 hp.2 Gas turbines
greater than 4,021 hp that are used in electrical generation are used for continuous, peaking, or standby
power. The primary fuels used are natural gas and distillate (No. 2) fuel oil.
3.1.2 Process Description
Gas turbines comprise three major components: compressor, combustor, and power turbine.
Ambient air is drawn in and compressed up to 30 times ambient pressure and directed to the
combustor section where fuel is introduced, ignited, and burned. Combustors can either be annular,
can-annular, or silo. An annular combustor is a doughnut-shaped, single, continuous chamber that
rings the turbine in a plane perpendicular to the air flow. Can-annular combustors are similar to the
annular; however, they incorporate can-shaped chambers rather than a single continuous chamber. A
silo combustor has one or more chambers mounted external to the gas turbine body.
Hot combustion gases are diluted with additional air from the compressor section and directed
to the turbine section at temperatures up to 2350°F. Energy from the hot, expanding exhaust gases are
then recovered in the form of shaft horsepower, of which more than 50 percent is needed to drive the
internal compressor and the balance of recovered shaft energy is available to drive the external load
unit2
The heat content of the gases exiting the turbine can either be discarded without heat recovery
(simple cycle); used with a heat exchanger to preheat combustion air entering the combustor can
(regenerative cycle); used with or without supplementary firing, in a heat recovery steam generator to
raise process steam (cogeneration); or used with or without supplementary firing to raise steam for a
steam turbine Rankine cycle (combined cycle or repowering).
Gas turbines may have one, two, or three shafts to transmit power from the inlet air
compression turbine, the power turbine, and the exhaust turbine. Of the four basic turbine operating
cycles (simple, regenerative, cogeneration, and combined cycles), three configurations (1, 2, or
3 shaft), and three types of combustors (annular, can-annular, and silo) for gas turbines, the majority
of gas turbines used in large stationary installations are either peaking simple cycle two-shaft or base
load combined cycle gas turbines.
If the heat recovery steam generator (HRSG) is not supplementary fuel fired, the simple cycle
input-specific emission factors (pounds per million British thermal unit [lb/MMBtu]) will apply to
cogeneration/combined cycle systems. The output-specific emissions (pounds per horsepower-hour
[lb/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.
10/96 Stationary Internal Combustion Sources 3 j.j
-------
Gas turbines firing distillate 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 ash should be used for flue gas
emission factors assuming all metals pass through the turbine.
3.1.3 Emissions
The primary pollutants from gas turbine engines are nitrogen oxides (NOX) and carbon
monoxide (CO). To a lesser extent, hydrocarbons (HC) and other organic compounds, and particulate
matter (PM), which includes both visible (smoke) and nonvisible emissions are also emitted. Nitrogen
oxide formation is strongly dependent on the high temperatures developed in the combustor. Smoke,
CO, and HC, are primarily the result of incomplete combustion. Ash and metallic additives in the fuel
may also contribute to the particulate loading in the exhaust. Oxides of sulfur (SOX) will only appear
in a significant quantity if heavy oils are fired in the turbine. Emissions of sulfur compounds, mainly
sulfur dioxide (S02), are directly related to the sulfur content of the fuel.
3.1.3.1 Nitrogen Oxides -
Nitrogen oxides formation occurs by two fundamentally different mechanisms. The principal
mechanism with turbines firing gas or distillate fuel is thermal NOX, which arises from the thermal
dissociation and subsequent reaction of nitrogen (N2) and oxygen (02) molecules in the combustion
air. Most thermal NOX is formed in high temperature stoichiometric flame pockets downstream of the
fuel injectors where combustion air has mixed sufficiently with the fuel to produce the peak
temperature fuel/air interface. A component of thermal NOX, called prompt NOX, is formed from early
reactions of nitrogen intermediaries and hydrocarbon radicals from the fuel. The prompt NOX forms
within the flame and is usually negligible compared to the amount of thermal NOX formed. The
second mechanism, fuel NOX, stems from the evolution and reaction of fuel-bound nitrogen
compounds with oxygen. Natural gas has negligible chemically-bound fuel nitrogen (although some
molecular nitrogen is present). Essentially all NOX formed is thermal NOX. Distillate oils have low
levels of fuel-bound nitrogen. These levels usually are significant only for high degrees of NOX
controls where thermal NOX has been suppressed to the level where fuel NOX is significant.
The maximum thermal NOX production occurs at a slightly fuel-lean mixture because of excess
oxygen available for reaction. The control of stoichiometry is critical in achieving reductions in
thermal NOX. The thermal NOX generation also decreases rapidly as the temperature drops below the
adiabatic temperature (for a given stoichiometry). Maximum reduction of thermal NOX generation can
thus be achieved by control of both the combustion temperature and the stoichiometry. Gas turbines
operate with high overall levels of excess air, because turbines use combustion air dilution as the
means to maintain the turbine inlet temperature below design limits. In older gas turbine models,
where combustion is in the form of a diffusion flame, most of the dilution takes place in the can
downstream of the primary flame, so that the high excess air levels are not indicative of the NOX
forming potential. The combustion in conventional can designs is by diffusion flames which are
characterized by regions of near-stoichiometric fuel/air mixtures where temperatures are very high and
the majority of NOX is formed. Since the localized NOX forming regions are at much higher
temperatures than the adiabatic flame temperature for the overall mixture, the rate of NOX formation is
dependent on the fuel/air mixing process. The mixing determines the prevalence of the high
temperature regions as well as the peak temperature attained. Also, operation at full loads gives higher
temperatures in the peak NOX forming regions. Newer model gas turbines use lean, pre-mixed
combustion resulting in lower flame (hot spot) temperature and lower NOX.
3.1-2 EMISSION FACTORS 10/96
-------
Ambiert conditions also affect emissions and power output from turbines more than from
external combustion systems. The operation at high excess air levels and at high pressures increases
the influence of inlet humidity, temperature, and pressure. Variations of emissions of 30 percent or
greater have been exhibited with changes in ambient humidity and temperature. Humidity acts to
absorb heat in the primary flame zone through the sensible heat and, if condensation occurs during
compression, the latent heat of vaporization. For a given fuel firing rate, lower ambient temperatures
lower the peak flame temperature, lowering NOX significantly. Lower barometric pressure will also
lower the temperature exiting the compressor turbine which will lower NOX.
3.1.3.2 Carbon Monoxide and Total Organic Compounds (Hydrocarbons) -
Carbon monoxide and HC emissions both result from incomplete combustion. Carbon
monoxide results when there is insufficient residence time at high temperature to complete the final
step in HC oxidation. The oxidation of CO to C02 at gas turbine temperatures is a slow reaction
compared to most HC oxidation reactions. In gas turbines, failure to achieve CO burnout may result
from quenching in the can by the dilution air. With liquid fuels, this can be aggravated by carryover
of larger droplets from the atomizer at the fuel injector. In gas turbines, CO emissions are usually
higher when the unit is run at low loads.
The pollutants commonly classified as HCs can encompass a wide spectrum of volatile and
semi-volatile organic compounds. They are discharged into the atmosphere when some of the fuel
remains unburned or is only partially burned during the combustion process. With natural gas, some
organics are carried over as unreacted, trace constituents of the gas, while others may be pyrolysis
products of the heavier hydrocarbon constituents. With liquid fuels, large droplet carryover to the
quench zone accounts for much of the unreacted and partially pyrolized organic emissions.
3.1.3.3 Paniculate Matter -
Particulate emissions from turbines primarily result from carryover of noncombustible trace
constituents in the fuel. Particulate are typically nondetectable with natural gas firing and marginally
detectable with conventional sampling systems with distillate oil firing because of the low ash content.
Particulate may also be formed from agglomerated soot particles, particularly from liquid fuel firing.
3.1.3.4 Greenhouse Gases - '
Carbon dioxide (CO2), methane (CH4), and nitrous oxide (N2O) emissions are all produced
during natural gas and distillate oil combustion in gas turbines. Nearly all of the fuel carbon is
converted to C02 during the combustion process (typically 99.5 percent for gas and 99 percent for
distillate oil). This conversion is relatively independent of firing configuration. Although the
formation of CO acts to reduce CO2 emissions, the amount of CO produced is insignificant compared
to the amount of CO2 produced. The majority of the fuel carbon not converted to C02 is due to
incomplete combustion.
Formation of N2O during the combustion process is governed by a complex series of reactions
and its formation is dependent upon many factors. Formation of N2O is minimized when combustion
temperatures are kept high (above 1475°F) and excess air is kept to a minimum (less than 1 percent).
Methane emissions vary with the fuel, combustion temperature, and firing configuration, but
are highest during periods of incomplete combustion or low-temperature combustion, such as during
the start-up or shut-down cycle. Typically, conditions that favor formation of N2O also favor
emissions of CH4.
10/96 Stationary Internal Combustion Sources 3.1.3
-------
3.1.4 Control Technologies
There are three generic types of emission controls in use for gas turbines; wet controls using
steam or water injection to reduce combustion temperatures for NOX control; dry controls using
advanced combustor design to suppress NOX formation and/or promote CO burnout; and post-
combustion catalytic control to selectively reduce NOX and/or oxidize CO formed in the turbine.
3.1.4.1 Water Injection -
Water or steam injection is a mature technology that has been demonstrated as very effective
in suppressing NOX emissions from gas turbines. The effect of steam and water injection is to
increase the thermal mass by dilution and thereby reduce the adiabatic flame temperature and the peak
flame temperature in the NOX forming regions. With water injection, there is additional benefit of
absorbing the latent heat of vaporization from the flame zone. Water or steam is typically injected at
a water-to-fuel weight ratio of less than one. Depending on the initial NOX levels, such rates of
injection may reduce NOX by 60 percent or higher. Wet injection is usually accompanied by an
efficiency penalty (typically 2 to 3 percent) but an increase in power output (typically 5 to 6 percent).
The power increase results because fuel flow is increased to maintain turbine inlet temperature at
manufacturer's specifications. Both CO and HC emissions are increased by large rates of water
injection.
3.1.4.2 Dry Controls -
Since thermal NOX is a function of both temperature (exponentially) and time (linearly), the
bases of dry controls are to either lower the combustor temperature using lean mixtures of air and fuel
and/or staging, or decrease the residence time of the combustor. A combination of methods may be
used to reduce NOX emissions such as; lean combustion; reduced combustor residence time; two stage
lean/lean combustion; or two stage rich/lean combustion.
Most gas turbine combustors were originally designed to operate with a stoichiometric mixture
(theoretical amount of air required to react with the fuel). Lean combustion involves increasing the
air-to-fuel ratio of the mixture so that the peak and average temperature within the combustor will be
less than that of the stoichiometric mixture. A lean mixture of air and fuel can be premixed before
ignition, a stoichiometric mixture can be ignited and additional air can be introduced at a later stage
(staging) creating an overall lean mixture in the turbine, or a combination of both can occur.
Introducing excess air at a later stage not only creates a leaner mixture but it also can reduce the
residence time of the combustor, given enough excess air is added at the later stage to create a mixture
so lean that it will no longer combust. The residence time of a combustor can also be decreased by
increasing the turbulence within the combustor.
Two-stage lean/lean combustors are essentially fuel-staged combustors in which each stage
bums lean. The two-stage lean/lean combustor allows the turbine to operate with an extremely lean
mixture and a stable flame that should not "blow off1 or extinguish. A small stoichiometric pilot
flame ignites the premixed gas and provides flame stability. The high NOX emissions associated with
the higher temperature pilot flame is minor side effect compared to the desirable low NOX emissions
generated by the extremely lean mixture.
Two stage rich/lean combustors are essentially air-staged combustors in which the primary
zone is operated fuel rich and the secondary zone is operated fuel lean. The rich mixture will produce
lower temperatures (compared to stoichiometric) and higher concentrations of CO and H2 because of
3.1-4 EMISSION FACTORS 10/96
-------
incomplete combustion. The rich mixture decreases the amount of oxygen available for NOX
generation and the increased CO and H2 concentrations help to reduce some of the NOX formed.
Before entering the secondary zone, the exhaust of the primary zone is quenched (to extinguish the
flame) by large amounts of air and a lean mixture is created. The combustion of the lean mixture is
then completed in the secondary zone.
3.1.4.3 Selective Catalytic Reduction Systems -
Selective catalytic reduction systems selectively reduce NOX emissions by injecting ammonia
(NH3) into the exhaust gas stream upstream of a catalyst. Nitrogen oxides, NH3, and O2 react on the
surface of the catalyst to form N2 and H20. The exhaust gas must contain a minimum amount of 02
and be within a particular temperature range (typically 450 to 850°F) in order for the SCR system to
operate properly. The range is dictated by the catalyst, typically made from noble metals, base metal
oxides such as vanadium and titanium, or zeolite-based material. Exhaust gas temperatures greater
than the upper limit (850°F) will cause NOX and NH3 to pass through the catalyst unreacted.
Ammonia emissions, called NH3 slip, may be a consideration when specifying a SCR system.
Ammonia, either in the form of liquid anhydrous ammonia, or aqueous ammonia hydroxide is
stored on site and injected into the exhaust stream upstream of the catalyst. Although a SCR system
can operate alone, it is typically used in conjunction with water/steam injection systems to reduce NOX
emissions to their lowest levels (less than 10 ppm at 15 percent oxygen for SCR and wet injection
systems).
The catalyst and catalyst housing used in SCR systems tend to be very large and dense (in
terms of surface area to volume ratio) because of the high exhaust flow rates and long residence times
required for NOX, 02, and NH3, to react on the catalyst. Most catalysts are configured in a parallel-
plate, "honeycomb" design to maximize the surface area-to-volume ratio of the catalyst. Some SCR
installations are incorporating CO catalytic oxidation modules along with the NOX reduction catalyst
for simultaneous CO/NOX control.
The average gaseous emission factors for uncontrolled gas turbines (firing natural gas and fuel
oil) are presented in Table 3.1-1. There is some variation in emissions over the population of large
uncontrolled gas turbines because of the diversity of engine designs, sizes, and models. Table 3.1-2
presents emission factors for gas turbines controlled with water injection, steam injection, and selective
catalytic reduction. Emission factors for fuel oil-fired turbines controlled with water injection are
given in Table 3.1-3. Table 3.1-4 presents trace element emission factors for distillate oil-fired
turbines.
10/96 Stationary Internal Combustion Sources 31-5
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3.1.5 Updates Since the Fifth Edition
The Fifth Edition was released in January 1995. Revisions to this section since that date are
summarized below. For further detail, consult the memoranda describing each supplement or the
background report for this section. These and other documents can be found on the CHIEF electronic
bulletin board (919-541-5742), or on the new EFIG home page (http://www.epa.gov/oar/oaqps/efig/).
Supplement A, February 1996
• For the PM factors, a footnote was added to clarify that condensables and all PM from
oil- and gas-fired turbines are considered PM-10.
• In the table for large uncontrolled gas turbines, a sentence was added to footnote "e" to
indicate that when sulfur content is not available, 0.6 lb/106 ft3 (0.0006 Ib/MMBtu)
can be used.
Supplement B, October 1996
• Text was revised and updated for the general section.
• Text was added regarding firing practices and process description.
• Text was revised and updated for emissions and controls.
• All factors for turbines with SCR-water injection control were corrected.
• The C02 factor was revised and a new set of N20 factors were added.
3.1-6 EMISSION FACTORS 10/96
-------
Table 3.1-1. EMISSION FACTORS POR LARGE
UNCONTROLLED GAS TURBINESa
Pollutant
NOX
CO
CO2d
TOC (as methane)
SOX (as S02)e
PM-10
Solids
Condensables
Sizing %
<0.05 um
<0.10 um
<0.15 um
O.20 um
<0.25 um
<1 um
EMISSION
FACTOR
RATINGb
C
D
B
D
B
E
E
D
D
D
D
D
D
Natural Gas
(SCC 2-01-002-01)
Emission
Factor*
(Ib/hp-hr)
(power output)
3.53 E-03
8.60 E-04
0.876
1.92 E-04
7.52 E-03S
1.54 E-04
1.81 E-04
15%
40%
63%
78%
89%
100%
Emission
Factor
(Ib/MMBtu)
(fuel input)
0.44
0.11
109
0.024
0.94S
0.0193
0.0226
15%
40%
63%
78%
89%
100%
Fuel Oil (Distillate)
(SCC 2-01-001-01)
Emission
Factor6
(Ib/hp-hr)
(power output)
5.60 E-03
3.84 E-04
1.32
1.37 E-04
8.09 E-03S
3.04 E-04
1.85 E-04
16%
48%
72%
85%
93%
100%
Emission Factor
(Ib/MMBtu)
(fuel input)
0.698
0.048
165
0.017
1.01S
0.038
0.023
16%
48%
72%
85%
93%
100%
a References 2-3,8-11,13-18. SCC = Source Classification Code. PM-10 = particulate matter less
than or equal to 10 (am aerodynamic diameter; sizing % is expressed in (jm. Condensables are also
PM-10 and all PM from oil and gas-fired turbines is less than lum in size and therefore are
considered PM-10. To convert Ib/hp-hr to g/kw-hr, multiply by 608. To convert from Ib/MMBtu to
ng/J, multiply by 430.
b Ratings reflect limited data and/or a lack of documentation of test results; they may not apply to
specific facilities or populations and should be used with care.
c Calculated from Ib/MMBtu assuming an average heat rate of 8,000 Btu/hp-hr.
d Based on 99.5% conversion of fuel carbon to CO2 for natural gas and 99% conversion for No. 2 oil.
e All sulfur in the fuel is assumed to be converted to S02. S = % sulfur in fuel. For example, if
sulfur content in the fuel is 3.4%, then S = 3.4. When sulfur content is not available,
0.6 lb/106 ft3 (0.0006 Ib/MMBtu) can be used; however, the equation is more accurate.
10/96
Stationary Internal Combustion Sources
3.1-7
-------
Table 3.1-2. EMISSION FACTORS FOR LARGE
CONTROLLED GAS TURBINES"
(SCC 2-01-002-01)
EMISSION FACTOR RATING: C
Pollutant
NOX
CO
N20C
TOC
(as methane)
NH3
NMHC
Formaldehyde
Water Injection
(0.8 water/fuel ratio)
Emission
Factor
(Ib/hp-hr)
(power output)
1.10E-03
2.07 E-03
2.00 E-05
ND
ND
ND
ND
Emission
Factor
(Ib/MMBtu)
(fuel input)
0.14
0.28
0.003
ND
ND
ND
ND
Steam Injection
(1.2 water/fuel ratio)
Emission
Factor
(Ib/hp-hr)
(power output)
9.75 E-04
1.16 E-03
2.00 E-05
ND
ND
ND
ND
Emission
Factor
(Ib/MMBtu)
(fuel input)
0.12
0.16
0.003
ND
ND
ND
ND
Selective
Catalytic
Reduction
(with water
injection)
Emission
Factor
(Ib/MMBtu)
(fuel input)
0.0088b
0.0084
ND
0.014
0.0065
0.0032
0.0027
a References 13,19-24. All data are averages of a limited number of tests and may not be typical of
those reductions that can be achieved at a specific location. To convert from Ib/hp-hr to g/kw-hr,
multiply by 0.608. To convert from Ib/MMBtu to ng/J, multiply by 430. NMHC = nonmethane
hydrocarbons. ND = no data. SCC = Source Classification Code.
b An SCR catalyst reduces NOX by an average of 78%.
c EMISSION FACTOR RATING: E. Based on limited source tests on a single turbine (Reference 5).
Results may not be typical for all locations.
Hazardous air pollutant listed in the Clean Air Act.
3.1-8
EMISSION FACTORS
10/96
-------
Table 3.1-3. EMISSION FACTORS FOR DISTILLATE OIL-FIRED TURB^ES
CONTROLLED WITH WATER INJECTION3
(SCC 2-01-001-01)
EMISSION FACTOR RATING: E
Pollutant
NOX
CO
TOC (as methane)
SOXC
PM-10e
Water Injection
(0.8 water/fuel ratio)
Emission Factor
(Ib/hp-hr) (power output)
2.31 E-03
1.54E-04
3.84 E-05
_d
2.98 E-04
Emission Factor (Ib/MMBtu)
(fuel input)
0.290
0.0192
0.0048
_d
0.0372
a Reference 25. To convert from Ib/hp-hr to g/kw-hr, multiply by 0.608. To convert from Ib/MMBtu
to ng/J, multiply by 430. PM-10 = particulate matter < 10 urn aerometric diameter. SCC - Source
Classification Code.
Calculated from fuel input assuming an average heat rate of 8,000 Btu/hp-hr.
c EMISSION FACTOR RATING: B
All sulfur in the fuel is assumed to be converted to SOX.
e All PM is < 1 (jm in size.
10/96
Stationary Internal Combustion Sources
3.1-9
-------
Table 3.1-4. TRACE ELEMENT EMISSION FACTORS FOR
DISTILLATE OIL-FIRED TURBINESa
(SCC 2-01-001-01)
EMISSION FACTOR RATING. Eb
Trace Element
Aluminum
Antimony0
Arsenic0
Barium
Beiy Ilium0
Boron
Bromine
Cadmium0
Calcium
Chromium0
Cobalt0
Copper
Iron
Lead0
Magnesium
Manganese0
Mercury0
Molybdenum
Nickel0
Phosphorus0
Potassium
Selenium0
Silicon
Sodium
Tin
Vanadium
Zinc
Emission Factor
(Ib/MMBtu)
1.5E-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
1.3E-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
a Reference 2. To convert from Ib/MMBtu to ng/J, multiply by 430.
Code.
Ratings reflect limited data; they may not apply to specific facilities
used with care.
c Hazardous air pollutant listed in the Clean Air Act.
SCC = Source Classification
or populations and should be
3.1-10
EMISSION FACTORS
10/96
-------
References For Section 3.1
1. Alternative Control Techniques Document - NOX Emissions from Stationary Gas Turbines,
EPA 453/R-93-007, January 1993.
2. C. C. Shih, et al., Emissions Assessment Of Conventional Stationary Combustion Systems,
Vol. II: Internal Combustion Sources, EPA-600/7-79-029c, U. S. Environmental Protection
Agency, Cincinnati, OH, February 1979.
3. Final Report - Gas Turbine Emission Measurement Program, GASLTR787, General Applied
Science Laboratories, Westbury, NY, August 1974.
4. Standards Support And Environmental Impact Statement, Volume 1: Proposed Standards Of
Performance For Stationary Gas Turbines, EPA-45 0/2-77-017a, U. S. Environmental
Protection Agency, Research Triangle Park, NC, September 1977.
5. L. P. Nelson, et al., Global Combustion Sources Of Nitrous Oxide Emissions, Research Project
2333-4 Interim Report, Sacramento: Radian Corporation, 1991.
6. R. L. Peer, et al., Characterization Of Nitrous Oxide Emission Sources, U. S. Environmental
Protection Agency, Office of Research and Development, Research Triangle Park, NC, 1995.
7. S. D. Piccot, et al., Emissions And Cost Estimates For Globally Significant Anthropogenic
Combustion Sources OfNOx N2O, CH4, CO, And CO2, U. S. Environmental Protection
Agency, Office of Research and Development, Research Triangle Park, NC, 1990.
8. G. Marland and R. M. Rotty, Carbon Dioxide Emissions From Fossil Fuels: A Procedure For
Estimation And Results For 1951-1981, DOE/NBB-0036 TR-003, Carbon Dioxide Research
Division, Office of Energy Research, U. S. Department of Energy, Oak Ridge, TN, 1983.
9. G. Marland and R. M. Rotty, Carbon Dioxide Emissions From Fossil Fuels: A Procedure For
Estimation And Results For 1950-1982, Tellus 366:232-261, 1984.
10. Inventory OfU. S. Greenhouse Gas Emissions And Sinks: 1990-1991, EPA-230-R-96-006,
U. S. Environmental Protection Agency, Washington, DC, November 1995.
11. IPCC Guidelines For National Greenhouse Gas Inventories Workbook, Intergovernmental
Panel on Climate Change/Organization for Economic Cooperation and Development, Paris,
France, 1995.
12. L. M. Campbell and G. S. Shareef, Sourcebook: NOX Control Technology Data, Radian Corp.,
EPA-600/2-91-029, Air and Energy Engineering Research Laboratory, U. S. Environmental
Protection Agency, Research Triangle Park, July 1991.
13. P. C. Make, et al., NOX Exhaust Emissions For Gas-Fired Turbine Engines,
ASME 90-GT-392, The American Society Of Mechanical Engineers, Bellevue, WA,
June 1990.
10/96 Stationary Internal Combustion Sources 3.1-11
-------
14. C. T. Hare and K. J. Springer, Exhaust Emissions From Uncontrolled Vehicles And Related
Equipment Using Internal Combustion Engines, Part 6: Gas Turbines, Electric Utility Power
Plant, APTD-1495, U. S. Environmental Protection Agency, Research Triangle Park, NC,
February 1974.
15. M. Lieferstein, Summary Of Emissions From Consolidated Edison Gas Turbine, Department
Of Air Resources, City Of New York, NY, November 5, 1975.
16. J. F. Hurley and S. Hersh, Effect Of Smoke And Corrosion Suppressant Additives On
Particulate And Gaseous Emissions From Utility Gas Turbine, EPRI FP-398, Electric Power
Research Institute, Palo Alto, CA, March 1977.
17. A. R. Crawford, et al., "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, EPA-600/2-76-152c,
U. S. Environmental Protection Agency, Cincinnati, OH, June 1976.
18. D. E. Carl, et al., "Exhaust Emissions From A 25-MW Gas Turbine Firing Heavy And Light
Distillate Fuel Oils And Natural Gas", presented at the Gas Turbine Conference And Products
Show, Houston, TX, March 2-6, 1975.
19. G. S. Shareef and D. K. Stone, Evaluation Of SCR NOX Controls For Small Natural Gas-
fueled Prime Movers - Phase I, GRI-90/0138, Gas Research Institute, Chicago, IL, July 1990.
20. R. R. Pease, SCAQMD Engineering Division Report - Status Report On SCR For Gas
Turbines, South Coast Air Quality Management District, Diamond Bar, CA, July 1984.
21. CEMS Certification And Compliance Testing At Chevron USA, Inc. 's Gaviota Gas Plant,
Report PS-89-1837, Chevron USA, Inc., Goleta, CA, June 21, 1989.
22. Emission Testing At The Bonneville Pacific Cogeneration Plant, Report PS-92-2702,
Bonneville Pacific Corporation, Santa Maria, CA, March 1992.
23. Compliance test report on a production gas-fired 1C engine, ESA, 19770-462, Procter And
Gamble, Sacramento, CA, December 1986.
24. Compliance test report on a cogeneration facility, CR 75600-2160, Procter And Gamble,
Sacramento, CA, May 1990.
25. R. Larkin and E. B. Higginbotham, Combustion Modification Controls For Stationary Gas
Turbines, Vol. 11: Utility Unit Field Test, EPA 600/7-81-122, U. S. Environmental Protection
Agency, Cincinnati, OH, July 1981.
3.1-12 EMISSION FACTORS 10/96
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3.2 Heavy-duty Natural Gas-fired Pipeline Compressor Engines And Turbines
3.2.1 General1'3
Natural gas-fired internal combustion engines are used in the natural gas industry at pipeline
compressor and storage stations. The engines and gas turbines are used to provide mechanical shaft
power that drives compressors. At pipeline compressor stations, the engine or turbine is used to help
move natural gas from station to station. At storage facilities, they are used to help inject the natural gas
into high pressure underground cavities (natural gas storage fields), e. g., empty oil fields. Although they
can operate at a fairly constant load, pipeline engines or turbines must be able to operate under varying
pipeline requirements. The size of these engines ranges from 800 brake horsepower (bhp) to 5,000 bhp.
For gas turbines, the capacity ranges from 1,000 to 15,000 bhp.
3.2.2 Process Description1"3
Reciprocating engines are separated into 3 design classes: 2-cycle (stroke) lean burn, 2-stroke
ultra lean (clean) burn, 4-stroke lean burn, 4-stroke clean bum, and 4-stroke rich burn. Each of these have
design differences that affect both baseline emissions as well as the potential for emissions control. Two-
stroke engines complete the power cycle in a single crankshaft revolution as compared to the two
crankshaft revolutions required for 4-stroke engines.
In a 2-stroke engine, the air/fuel charge is injected with the piston near the bottom of the power
stroke. The intake ports are then covered or closed, and the piston moves to the top of the cylinder,
thereby compressing the charge. Following ignition and combustion, the power stroke starts with the
downward movement of the piston. Exhaust ports or valves are then uncovered to exhaust the
combustion products, and a new air/fuel charge is injected. Two-stroke engines may be turbocharged
using an exhaust-powered turbine to pressurize the charge for injection into the cylinder and to increase
cylinder scavenging. 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 cycle and the
power/exhaust cycle. These engines may be either naturally aspirated, using the suction from the piston
to entrain the air charge, or turbocharged, using an exhaust-driven 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 bum engines operate near the
stoichiometric air/fuel ratio 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, 2-stroke designs contribute approximately two-thirds of installed capacity.
Almost all of the gas turbines used by the natural gas industry for pipeline and storage facilities
are simple cycle. A gas turbine is an internal combustion engine that operates with rotary rather than
reciprocating motion. Gas turbines are essentially composed of several major components: compressor,
combustor, and power turbine. Natural gas and compressed air (up to 30 atmospheres pressure) are
injected separately into the combustor can, mixed, and reacted.
The hot expanding exhaust gases are then passed into the power turbine to produce usable shaft
energy. The heat content of the exhaust gases exiting the turbine are not commonly utilized with pipeline
10/96 Stationary Internal Combustion Sources 3.2-1
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applications, although other applications use heat recovery steam generators for cogeneration or
combined cycle application.
Gas turbines may have one, two, or three shafts to transmit power from the inlet air compression
turbine, the power turbine, and the exhaust turbine. The majority of gas turbines used in pipeline
installations are simple cycle two-shaft gas turbines. There are three types of combustor can design in
use: annular, can-annular, and silo. The type of combustor can design depends on the make/model of the
gas turbine. Several stationary engine designs are aircraft-derivative using an annular or can-annular
design.
3.2.3 Emissions
The primary pollutants from natural gas-fueled reciprocating engines and gas turbines are
nitrogen oxide (NOX), carbon monoxide (CO), and total organic compounds (TOC). Nitrogen oxide
formation is strongly dependent on the high temperatures developed in the cylinder or combustor can.
The other pollutants, CO and HC species, are primarily the result of incomplete combustion. Trace
amounts of metals and non-combustible inorganic material may be carried over from the lubricating oil,
from engine wear, or from trace constituents in the gas. Sulfur oxides are very low since sulfur
compounds are removed in the gas treatment plant prior to entry into the pipeline.
3.2.3.1 Nitrogen Oxides -
Nitrogen oxide formation occurs by two fundamentally different mechanisms. The principle
mechanism with gas-fired engines and turbines is thermal NOX, which arises from the thermal
dissociation and subsequent reaction of nitrogen (N2) and oxygen (O2) molecules in the combustion air.
Most thermal NOX is formed in high-temperature regions in the cylinder or combustor can where
combustion air has mixed sufficiently with the fuel to produce the peak temperature fuel/air interface. A
component of thermal NOX, called prompt NOX, is formed from early reactions of nitrogen intermediaries
and hydrocarbon radicals from the fuel. The prompt NOX forms within the flame and is usually negligible
compared to the amount of thermal NOX formed. The second mechanism, fuel NOX, stems from the
evolution and reaction of fuel-bound N2 compounds with oxygen. Natural gas has negligible chemically
bound fuel N2 (although some molecular nitrogen) and essentially all NOX formed is thermal NOX. The
formation of prompt NOX can form a significant part of total NOX only under highly controlled situations
where thermal NOX is suppressed. It is more prevalent with rich burn engines. The rates of these
reactions are highly dependent upon the stoichiometric ratio, combustion temperature, and residence time
at the combustion temperature.
The maximum thermal NOX production occurs at a slightly lean fuel/air mixture ratio because of
the excess availability of oxygen for reaction. The control of stoichiometry is critical in achieving
reductions in thermal NOX. Premixing with lean bum reciprocating engines is effective in suppressing
NOX relative to rich bum engines. The thermal NOX generation decreases rapidly as the temperature
drops below the adiabatic temperature. Thus, maximum reduction of thermal NOX generation can be
achieved by control of both the combustion temperature and the stoichiometry.
Gas turbines operate with high overall levels of excess air because turbines use combustion air
dilution as the means to maintain the turbine inlet temperature below design limits. Most of the dilution
takes place in the can downstream of the primary flame, so that high excess air levels are not indicative of
the N0x-forming potential. The combustion in conventional designs is by diffusion flames that are
characterized by regions of near-stoichiometric fuel/air mixtures where temperatures are very high and
the majority of NOX is formed. Since the localized NOx-forming regions are at much higher temperatures
than the adiabatic flame temperature for the overall mixture, the rate of NOX formation is dependent on
3.2-2 EMISSION FACTORS 10/96
-------
the fuel/air mixing process. The mixing determines the prevalence of the high temperature regions as
well as the peak temperature attained.
3.2.3.2 Carbon Monoxide and Total Organic Compounds (Hydrocarbons) -
Carbon monoxide and hydrocarbon emissions both result from the products of incomplete
combustion. Carbon monoxide results when there is insufficient residence time at high temperature to
complete the final step in hydrocarbon oxidation. In reciprocating engines, CO emissions may indicate
early quenching of combustion gases on cylinder walls or valve surfaces. The oxidation of CO to carbon
dioxide (C02) is a slow reaction compared to most hydrocarbon oxidation reactions. In gas turbines,
failure to achieve CO burnout may result from quenching in the can by the dilution air. CO emissions are
usually higher when the unit is run at low loads.
The pollutants commonly classified as hydrocarbons can encompass a wide spectrum of volatile
and semi-volatile organic compounds. They are discharged into the atmosphere when some of the gas
remains unburned or is only partially burned during the combustion process. With natural gas, some
organics are carryover, unreacted, trace constituents of the gas, while others may be pyrolysis products of
the heavier hydrocarbon constituents. Partially burned hydrocarbons can occur because of poor air/fuel
homogeneity due to incomplete mixing prior to, or during, combustion; incorrect air/fuel ratios in the
cylinder during combustion due to maladjustment of the engine fuel system; or low cylinder temperature
due to excessive cooling through the walls or early cooling of the gases by expansion of the combustion
volume caused by piston motion before combustion is completed.
3.2.3.3 Particulate Matter and PM-104 -
Paniculate emissions with gas-fired turbines and reciprocating engines are non-detectable with
conventional protocols unless the engines are operated in a sooting condition. Otherwise, particulate
could arise from carryover of non-combustible trace constituents in the gas or from lube oil.
3.2.4 Control Technologies
Three generic control techniques have been developed for reciprocating engines and gas turbines:
parametric controls (timing and operating at a leaner air/fuel ratio for reciprocating engines and water
injection for gas turbines); combustion modification such as advanced engine design for new sources or
major modification to existing sources (clean burn reciprocating head designs and dry gas turbine
combustor can designs); and postcombustion catalytic NOX reduction (selective catalytic reduction [SCR]
for gas turbines and lean bum reciprocating engines and nonselective catalytic reduction [NSCR] for rich
bum engines).
3.2.4.1 Control Techniques for Rich Burn Reciprocating Engines5 -
Nonselective Catalytic Reduction -
This technique uses the residual hydrocarbons and CO in the rich burn engine exhaust as a
reducing agent for NOX. In NSCR, hydrocarbons will be oxidized by O2 and NOX, hence the designation
"nonselective". This is in contrast to ammonia injection for SCR where ammonia selectively reacts with
NOX. The excess hydrocarbons and NOX pass over a catalyst, usually a noble metal (platinum, rhodium,
or palladium) which reduces the reactants to N2, CO2, and H20.
The NSCR technique is effectively limited to engines with normal exhaust oxygen levels of
4 percent or less. This includes 4-cycle naturally aspirated engines and some 4-cycle turbocharged
engines. Engines operating with NSCR require tight air/fuel control to maintain high reduction
effectiveness without high hydrocarbon emissions. To achieve optimum NOX reduction performance, the
engine may need to be run in a richer fuel condition than normal.
10/96 Stationary Internal Combustion Sources 32-3
-------
Prestratified Charge -
Prestratified charge combustion is a retrofit system that is limited to 4-cycle carbureted natural
gas engines. In this system, controlled amounts of air are introduced into the intake manifold in a
specified sequence and quantity. This stratification provides both a fuel rich ignition and rapid flame
cooling resulting in reduced formation of NOX.
3.2.4.2 Control Techniques for Lean Burn Reciprocating Engines -
Lean Combustion -
Lean combustion techniques use increased bulk air/fuel ratios to lower peak flame temperature
and reduce NOX formation. Typically, air/fuel ratios are increased from normal levels of 20 to 35 up to
controlled levels of 45 to 50. The upper limit is constrained by the onset of misfiring at the lean limit.
This condition also increases CO and HC emissions.
To maintain acceptable engine performance at lean conditions, high energy ignition systems have
been developed that promote flame stability at very lean conditions. With high energy ignition, a rich
mixture is ignited in a small ignition cell located in the cylinder head. The ignition cell flame passes to
the cylinder where it provides a uniform ignition source. The technique can be retrofit to existing
turbocharged 2- and 4-cycle engines. With new engine designs, NOX reductions of 80 to 90 percent have
been achieved compared to spark ignition designs. In most cases, the NOX reductions have been
accompanied by increases in power output and increased fuel economy.
Selective Catalytic Reduction -
Selective catalytic reduction (SCR) is applicable to lean burn engines. Ammonia (NH3) is
injected upstream of a noble metal, metal oxide or zeolite catalyst to give an NH3: NOX ratio of about 1:1.
The mixture of NH3 and NOX is selectively reduced over the catalyst within a temperature range of 600 to
900°F depending on the catalyst. The major system components are the catalyst and associated housing,
the ammonia storage and delivery system, and the control system. The performance has been less
acceptable than NSCR with rich bum engines, or SCR with gas turbines. The primary difficulty with lean
burn engines has been maintaining air/fuel control, very limited automatic controls, and engine
performance and the inherent variety of engine loading while achieving the necessary exhaust
temperature window for efficient SCR operation.
3.2.4.3 Control Technologies for Gas Turbines -
Water Injection -
Water or steam injection is a technology that has been demonstrated as very effective in
suppressing NOX emissions from gas turbines. The effect of steam and water injection is to increase the
thermal mass by dilution and thereby reduce the adiabatic flame temperature and the peak flame
temperatures in the NOx-forming regions. With water injection, there is the additional benefit of
absorbing the latent heat of vaporization from the flame zone. Water or steam is typically injected at a
water-to-fuel weight ratio of less than 1. Depending on the initial NOX levels, such rates of injection may
reduce NOX by 60 percent or higher. Wet injection is usually accompanied by an efficiency penalty but
an increase in power output. Efficiency penalties of 2 to 3 percent are typical. The power increase results
because fuel flow is increased to maintain turbine inlet temperature at manufacturers' specifications.
Power increases with water or steam injection of 5 to 6 percent are typical. Both CO and HC emissions
are increased by large rates of water injection.
The use of wet injection may be constrained in some applications such as pipeline pumping by
the unavailability of pure water for injection. The choice between water or steam is usually driven by the
availability of steam. Most operators prefer steam because of fewer operational problems, better heat
3.2-4 EMISSION FACTORS 10/96
-------
rate, and increased power augmentation compared to water. The use of water with low mineral content is
a significant cost item with water injection. The reliability of the water treatment system and injection
pumps also can be a major issue in continuous operation under low NOX conditions.
Selective Catalytic Reduction Systems -
Selective catalytic reduction systems are postcombustion technologies that have recently been
applied in limited cases to gas turbines. An SCR system consists of an ammonia storage, feed, and
injection system, and a catalyst and catalyst housing. Selective catalytic reduction systems selectively
reduce NOX emissions by injecting NH3 into the exhaust gas stream upstream of the catalyst. Nitrogen
oxides, NH3, and O2 react on the surface of the catalyst to form N2 and H20. For the SCR system to
operate properly, the exhaust gas must be within a particular temperature range (typically between 450
and 850°F). The temperature range is dictated by the catalyst (typically made from noble metals, base
metal oxides such as vanadium and titanium, and zeolite-based material). Exhaust gas temperatures
greater than the upper limit (850°F) will pass the NOX and ammonia unreacted through the catalyst.
Ammonia emissions, called NH3 slip, are a key consideration when specifying a SCR system. Ammonia,
either in the form of liquid anhydrous ammonia, or aqueous ammonia hydroxide is stored on site and
injected into the exhaust stream upstream of the catalyst. Although an SCR system can operate alone, it
is typically used in conjunction with water/steam injection systems to reduce NOX emissions to their
lowest levels (less than 10 ppm at 15 percent oxygen).
Combustion Modifications -
Several different methods or approaches of reducing NOX emissions from gas turbines are
currently being researched and developed by the manufacturers of gas turbines. Since thermal NOX is a
function of both temperature (exponentially) and time (linearally), the basis of these controls are to either
lower the combustor temperature using lean mixtures air and fuel and/or staging the combustion or
decrease the residence time of the combustor. Some manufacturers use a combination of these methods
to reduce NOX emissions. These methods or approaches are lean combustion; reduced combustor
residence time; two-stage lean/lean combustion; and two-stage rich/lean combustion.
Most gas turbine combustors were originally designed to operate with a stoichiometric mixture
(theoretical amount of air required to react with the fuel). Lean combustion involves increasing the
air/fuel ratio of the mixture so that the peak and average temperature within the combustor will be less
than that of the stoichiometric mixture. A lean mixture of air and fuel can be premixed before ignition, a
stoichiometric mixture can be ignited and additional air can be introduced at a later stage (staging)
creating an overall lean mixture in the turbine, or a combination of both can occur. Introducing excess air
at a later stage not only creates a leaner mixture but can also reduce the residence time of the combustor
(given enough excess air is added at the latter stage to create a mixture so lean that it will no longer
combust). Also, the residence time of a combustor can be decreased by increasing the turbulence within
the combustor.
Two-stage lean/lean combustors are essentially fuel-staged combustors in which each stage burns
lean. The two-stage lean/lean combustor allows the turbine to operate with an extremely lean mixture and
a stable flame that should not "blow off' or extinguish. A small stoichiometric pilot flame ignites the
premixed gas and provides flame stability. The high NOX emissions associated with the higher-
temperature pilot flame is minor compared to the low NOX emissions generated by the extremely lean
mixture.
Two-stage rich/lean combustors are essentially air-staged combustors in which the primary
stage/zone is operated fuel rich and the secondary stage/zone is operated fuel lean. The rich mixture will
produce lower temperatures (compared to stoichiometric) and higher concentrations of CO and H2
because of incomplete combustion. The rich mixture decreases the amount of oxygen available for NO.
x
10/96 Stationary Internal Combustion Sources 32-5
-------
generation and the increased CO and H2 concentrations will help reduce some of the NOX formed. Before
entering the secondary zone, the exhaust of the primary zone is quenched (to extinguish the flame) by
large amounts of air and a lean mixture is now created. The combustion of the lean mixture is then
completed in the second ^.ry zone.
Emission factors for natural gas-fired pipeline compressor engines are presented in Table 3.2-1
for baseline operation and in Tables 3.2-2, 3.2-3, 3.2-4, and 3.2-5 for controlled operation. The factors
for controlled operation are taken from a single source test. Table 3.2-6 lists noncriteria emission factors
for uncontrolled natural gas prime movers.
3.2.5 Updates Since the Fifth Edition
The Fifth Edition was released in January 1995. Revisions to this section since that date are
summarized below. For further detail, consult the memoranda describing each supplement or the
background report for this section. These and other documents can be found on the CHIEF electronic
bulletin board (919-541-5742), or on the new EFIG home page (http://www.epa.gov/oar/oaqps/efig/).
Supplement A, February 1996
• In the table for uncontrolled natural gas prime movers, the SCC for 4-cycle lean burn was
changed from 2-01-002-53 to 2-02-002-54. The SCC for 4-cycle rich bum was changed
from 2-02-002-54 to 2-02-02-002-53.
• An SCC (2-02-002-53) was provided for 4-cycle rich bum engines, and the "less than"
symbol (<) was restored to the appropriate factors.
Supplement B, October 1996
• The introduction section was revised.
• Text was added concerning process description of turbines.
• Text was revised concerning emissions and controls.
• References in various tables were editorially corrected.
• The inconsistency between a C02 factor in the table and an equation in the footnote was
corrected.
3.2-6 EMISSION FACTORS 10/96
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EMISSION FACTORS
10/96
-------
Table 3.2-6. NONCRTTERIA EMISSION FACTORS FOR
UNCONTROLLED NATURAL GAS 2-CYCLE LEAN BURN ENGINES
EMISSION FACTOR RATING: E
Pollutant
Formaldehyde15
Benzene
Tolueneb
Ethylbenzeneb
Xylenesb
Emission Factors
(Ib/hp-hr)
2.93 E-03
3.62 E-06
3.62 E-06
1.81 E-06
5.43 E-06
Reference 20. Source Classification Code 2-02-002-52. Ratings reflect very limited data and may not
apply to specific facilities. To convert from Ib/hp-hr to kg/kw-hr, multiply by 0.608.
b Hazardous air pollutant listed in the Clean Air Act.
References For Section 3.2
1. Standards Support And Environmental Impact Statement, Volume I: Proposed Standards Of
Performance For Stationary Gas Turbines, EPA-450/2-77-017a, September 1977.
2. Engines, Turbines, And Compressors Directory, American Gas Association, Catalog #XF0488.
3. 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.
4. Limiting Net Greenhouse Gas Emissions In The United States, Volume II: Energy Responses,
Report for the Office of Environmental Analysis, Office of Policy, Planning and Analysis,
Department of Energy (DOE), DOE/PE-0101 Volume II, September 1991.
5. C. Castaldini, Evaluation Of Water Injection Impacts For Gas Turbine NOX Control At
Compressor Stations, prepared by Acurex Corp. for the Gas Research Institute, GRI-90/0138,
July 1990.
6. N. L. Martin 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), GRI-89/0041, Gas Research Institute,
Chicago, IL, February 1989.
7. R. E. Fanick, et a/., Emissions Data For Stationary Reciprocating Engines And Gas Turbines In
Use By The Gas Pipeline Transmission Industry — Phases I & II, Project PR-15-613, Pipeline
Research Committee, American Gas Association, Arlington, VA, April 1988.
8. C. Castaldini, NOX Reduction Technologies For Natural Gas Industry Prime Movers,
GRI-90/0215, Gas Research Institute, Chicago, IL, August 1990.
10/96 Stationary Internal Combustion Sources 3.2-13
-------
9. C. Urban, Compilation Of Emissions Data For Stationary Reciprocating Gas Engines And Gas
Turbines In Use By American Gas Association Member Companies, prepared by Southwest
Research Institute Pipeline Research Committee of the American Gas Association, Project
PR-15-86, May 1980.
10. G. Marland and R. M. Rotty, Carbon Dioxide Emissions From Fossil Fuels: A Procedure For
Estimation And Results For 1951-1981, DOE/NBB-0036 TR-003, Carbon Dioxide Research
Division, Office of Energy Research, U. S. Department of Energy, Oak Ridge, TN, 1983.
11. G. Marland and R. M. Rotty, Carbon Dioxide Emissions From Fossil Fuels: A Procedure For
Estimation And Results For 1950-1982, Tellus 366:232-261, 1984.
12. Inventory OfU. S. Greenhouse Gas Emissions And Sinks: 1990-1991, EPA-230-R-96-006,
U. S. Environmental Protection Agency, Washington, DC, November 1995.
13. IPCC Guidelines For National Greenhouse Gas Inventories Workbook, Intergovernmental Panel
on Climate Change/Organization for Economic Cooperation and Development, Paris, France,
1995.
14. C. Castaldini, Environmental Assessment OfNOx Control On A Spark-ignited Large Bore
Reciprocating Internal Combustion Engine, EPA-600/7-86-002A, U. S. Environmental
Protection Agency, Cincinnati, OH, January 6, 1986.
15. C. Castaldini 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, Cincinnati, OH, June 1984.
16. 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.
17. Air Pollution Source Testing For California AB2588 Of Engines At The Chevron USA, Inc.
Carpinteria Facility, Chevron USA, Inc., Ventura, CA, August 30, 1990.
18. Pooled Source Emission Test Report: Gas Fired 1C Engines In Santa Barbara County, ARCO,
Bakersfield, CA, July 1990.
19. C. Castaldini 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.
20. Engines, Turbines, And Compressors Directory, Catalog #XF0488, American Gas Association,
Arlington, VA, 1985.
3.2-14 EMISSION FACTORS 10/96
-------
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 (1C) 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 three primary fuels for reciprocating 1C
engines are gasoline, diesel fuel oil (No.2), and natural gas. Gasoline is used primarily for mobile and
portable engines. Diesel fuel oil is the most versatile fuel and is used in 1C engines of all sizes. The
rated power of these engines covers a rather substantial range, up to 250 horsepower (hp) for gasoline
engines and up to 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 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 2 methods used for stationary reciprocating 1C engines: compression ignition (CI)
and spark ignition (SI). This section deals with both types of reciprocating 1C engines. All diesel-
fueled engines are compression ignited, and all gasoline-fueled engines are spark ignited.
In CI engines, combustion air is first compression heated in the cylinder, and diesel fuel oil is
then injected into the hot air. Ignition is spontaneous because the air temperature is above the
autoignition temperature of the fuel. SI 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.
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 autoignition. 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.1
3.3.3 Emissions
Most of the pollutants from 1C engines are emitted through the exhaust. However, some total
organic compounds (TOC) escape from the crankcase as a result of blowby (gases that 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 TOCs from diesel CI engines enter the
10/96 Stationary Internal Combustion Sources 3 3_1
-------
atmosphere from the exhaust. Evaporative losses are insignificant in diesel engines due to the low
volatility of diesel fuels.
The primary pollutants from internal combustion engines are oxides of nitrogen (NOX), total
organic compounds (TOC), carbon monoxide (CO), and particulates, which include both visible
(smoke) and nonvisible emissions. Nitrogen oxide formation is directly related to high pressures and
temperatures during the combustion process and to the nitrogen content, if any, of the fuel. The other
pollutants, HC, CO, and smoke, are primarily the result of incomplete combustion. Ash and metallic
additives in the fuel also contribute to the paniculate content of the exhaust. Sulfur oxides (SOX) also
appear in the exhaust from 1C engines. The sulfur compounds, mainly sulfur dioxide (SO2), are
directly related to the sulfur content of the fuel
3.3.3.1 Nitrogen Oxides -
Nitrogen oxide formation occurs by two fundamentally different mechanisms. The
predominant mechanism with internal combustion engines is thermal NOX which arises from the
thermal dissociation and subsequent reaction of nitrogen (N2) and oxygen (O2) molecules in the
combustion air. Most thermal NOX is formed in the high-temperature region of the flame from
dissociated molecular nitrogen in the combustion air. Some NOX, called prompt NOX, is formed in the
early part of the flame from reaction of nitrogen intermediary species, and HC radicals in the flame.
The second mechanism, fuel NOX, stems from the evolution and reaction of fuel-bound nitrogen
compounds with oxygen. Gasoline, and most distillate oils have no chemically-bound fuel N2 and
essentially all NOX formed is thermal NOX.
3.3.3.2 Total Organic Compounds -
The pollutants commonly classified as hydrocarbons are composed of a wide variety of organic
compounds and are discharged into the atmosphere when some of the fuel remains unburned or is only
partially burned during the combustion process. Most unburned hydrocarbon emissions result from
fuel droplets that were transported or injected into the quench layer during combustion. This is the
region immediately adjacent to the combustion chamber surfaces, where heat transfer outward through
the cylinder walls causes the mixture temperatures to be too low to support combustion.
Partially burned hydrocarbons can occur because of poor air and fuel homogeneity due to
incomplete mixing, before or during combustion; incorrect air/fuel ratios in the cylinder during
combustion due to maladjustment of the engine fuel system; excessively large fuel droplets (diesel
engines); and low cylinder temperature due to excessive cooling (quenching) through the walls or early
cooling of the gases by expansion of the combustion volume caused by piston motion before
combustion is completed.2
3.3.3.3 Carbon Monoxide -
Carbon monoxide is a colorless, odorless, relatively inert gas formed as an intermediate
combustion product that appears in the exhaust when the reaction of CO to C02 cannot proceed to
completion. This situation occurs if there is a lack of available oxygen near the hydrocarbon (fuel)
molecule during combustion, if the gas temperature is too low, or if the residence time in the cylinder
is too short. The oxidation rate of CO is limited by reaction kinetics and, as a consequence, can be
accelerated only to a certain extent by improvements in air and fuel mixing during the combustion
process.
3.3-2 EMISSION FACTORS 10/96
-------
3.3.3.4 Smoke and Particulate Matter -
White, blue, and black smoke may be emitted from 1C engines. Liquid particulates appear as
white smoke in the exhaust during an engine cold start, idling, or low load operation. These are
formed in the quench layer adjacent to the cylinder walls, where the temperature is not high enough to
ignite the fuel. Blue smoke is emitted when lubricating oil leaks, often past worn piston rings, into the
combustion chamber and is partially burned. Proper maintenance is the most effective method of
preventing blue smoke emissions from all types ef 1C engines. The primary constituent of black
smoke is agglomerated carbon particles (soot) formed in regions of the combustion mixtures that are
oxygen deficient.
3.3.3.5 Sulfur Oxides -
Sulfur oxides emissions are a function of only the sulfur content in the fuel rather than any
combustion variables. In fact, during the combustion process, essentially all the sulfur in the fuel is
oxidized to S02. The oxidation of S02 gives sulfur trioxide (SO3), which reacts with water to give
sulfuric acid (H2S04), a contributor to acid precipitation. Sulfuric acid reacts with basic substances to
give sulfates, which are fine particulates that contribute to PM-10 and visibility reduction. Sulfur
oxide emissions also contribute to corrosion of the engine parts.2"3
3.3.4 Control Technologies
Control measures to date are primarily directed at limiting NOX and CO emissions since they
are the primary pollutants from these engines. From a NOX control viewpoint, the most important
distinction between different engine models and types of reciprocating engines is whether they are
rich-burn or lean-burn. Rich-burn engines have an air-to-fuel ratio operating range that is near
stoichiometric or fuel-rich of stoichiometric and as a result the exhaust gas has little or no excess
oxygen. A lean-bum engine has an air-to-fuel operating range that is fuel-lean of stoichiometric;
therefore, the exhaust from these engines is characterized by medium to high levels of 02. The most
common NOX control technique for diesel and dual-fuel engines focuses on modifying the combustion
process. However, selective catalytic reduction (SCR) and nonselective catalytic reduction (NSCR)
which are post-combustion techniques are becoming available. Controls for CO have been partly
adapted from mobile sources.
Combustion modifications include injection timing retard (ITR), preignition chamber
combustion (PCC), air-to-fuel ratio adjustments, and derating. Injection of fuel into the cylinder of a
CI engine initiates the combustion process. Retarding the timing of the diesel fuel injection causes the
combustion process to occur later in the power stroke when the piston is in the downward motion and
combustion chamber volume is increasing. By increasing the volume, the combustion temperature and
pressure are lowered, thereby lowering NOX formation. ITR reduces NOX from all diesel engines;
however, the effectiveness is specific to each engine model. The amount of NOX reduction with ITR
diminishes with increasing levels of retard.
Improved swirl patterns promote thorough air and fuel mixing and may include a
precombustion chamber (PCC). A PCC is an antechamber that ignites a fuel-rich mixture that
propagates to the main combustion chamber. The high exit velocity from the PCC results in improved
mixing and complete combustion of the lean air/fuel mixture which lowers combustion temperature,
thereby reducing NOX emissions.4
10/96 Stationary Internal Combustion Sources 3.3.3
-------
The air-to-fuel ratio for each cylinder can be adjusted by controlling the amount of fuel that
enters each cylinder. At air-to-fuel ratios less than stoichiometric (fuel-rich), combustion occurs under
conditions of insufficient oxygen which causes NOX to decrease because of lower oxygen and lower
temperatures. Derating involves restricting the engine operation to lower than normal levels of power
production for the given application. Derating reduces cylinder pressures and temperatures, thereby
lowering NOX formation rates.
SCR is an add-on NOX control placed in the exhaust stream following the engine and involves
injecting ammonia (NH3) into the flue gas. The NH3 reacts with NOX in the presence of a catalyst 10
form water and nitrogen. The effectiveness of SCR depends on fuel quality and engine duty cycle
(load fluctuations). Contaminants in the fuel may poison or mask the catalyst surface causing a
reduction or termination in catalyst activity. Load fluctuations can cause variations in exhaust
temperature and NOX concentration which can create problems with the effectiveness of the SCR
system.4
NSCR is often referred to as a Ihree-way conversion catalyst system because the catalyst
reactor simultaneously reduces NOX, CO, and HC and involves placing a catalyst in the exhaust stream
of the engine. The reaction requires that the O2 levels be kept low and that the engine be operated at
fuel-rich air-to-fuel ratios.4
The most accurate method for calculating such emissions is on the basis of "brake-specific"
emission factors (pounds per horsepower-hour [lb/hp-hr]). Emissions are the product of the brake-
specific emission factor, the usage in hours, the rated power available, and the load factor (the power
actually used divided by the power available). However, for emission inventory purposes, it is often
easier to assess this activity on the basis of fuel used.
Once reasonable usage and duty cycles for this category were ascertained, emission values
were aggregated to arrive at the factors for criteria and organic pollutants presented. Factors in
Table 3.3-1 are in pounds per million British thermal unit (Ib/MMBtu). Emission data for a specific
design type were weighted according to estimated material share for industrial engines. The emission
factors in these tables, because of their aggregate nature, are most appropriately applied to a population
of industrial engines rather than to an individual power plant. Table 3.3-2 shows unweighted speciated
organic compound and air toxic emission factors based upon only 2 engines. Their inclusion in this
section is intended for rough order-of-magnitude estimates only.
Table 3.3-3 summarizes whether the various diesel emission reduction technologies (some of
which may be applicable to gasoline engines) will generally increase or decrease the selected
parameter. 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 3.3-3 provides general information on the trends of changes on selected parameters.
3.3-4 EMISSION FACTORS 10/96
-------
3.3.5 Updates Since the Fifth Edition
The Fifth Edition was released in January 1995. Revisions to this section since that date are
summarised below. For further detail, consult the memoranda describing each supplement or the
background report for this section. These and other documents can be found on the CHIEF electronic
bulletin board (919-541-5742), or on the new EFIG home page (http.7/www.epa.gov/oar/oaqps/efig/).
Supplement A, February 1996
No changes.
Supplement B, October 1996
• Text was revised concerning emissions and controls.
• The C02 emission factor was adjusted to reflect 98.5 percent conversion efficiency.
10/96 Stationary Internal Combustion Sources 3 3.5
-------
Table 3.3-1. EMISSION FACTORS FOR UNCONTROLLED GASOLINE
AND DIESEL INDUSTRIAL ENGINES3
Pollutant
NOX
CO
sox
PM-10b
C02C
Aldehydes
TOC
Exhaust
Evaporative
Crankcase
Refueling
Gasoline Fuel
(SCC 2-02-003-01, 2-03-003-01)
Emission Factor
(Ib/hp-hr)
(power output)
0.011
0.439
5.91 E-04
7.21 E-04
1.08
4.85 E-04
0.015
6.61 E-04
4.85 E-03
1.08 E-03
Emission Factor
(Ib/MMBtu)
(fuel input)
1.63
62.7
0.084
0.10
154
0.07
2.10
0.09
0.69
0.15
Diesel Fuel
(SCC 2-02-001-02, 2-03-001-01)
Emission Factor
(Ib/hp-hr)
(power output)
0.031
6.68 E-03
2.05 E-03
2.20 E-03
1.15
4.63 E-04
2.47 E-03
0.00
4.41 E-05
0.00
Emission Factor
(Ib/MMBtu)
(fuel input)
4.41
0.95
0.29
0.31
164
0.07
0.35
0.00
0.01
0.00
EMISSION
FACTOR
RATING
D
D
D
D
B
D
D
E
E
E
a References 2,5-6,9-14. When necessary, an average brake-specific fuel consumption (BSFC) of
7,000 Btu/hp-hr was used to convert from Ib/MMBtu to Ib/hp-hr. To convert from Ib/hp-hr to
kg/kw-hr, multiply by 0.608. To convert from Ib/MMBtu to ng/J, multiply by 430. SCC = Source
Classification Code. TOC = total organic compounds.
b PM-10 = paniculate matter less than or equal to 10 pm aerodynamic diameter. All particulate is
assumed to be < 1 ^m in size.
c Assumes 99% conversion of carbon in fuel to CO2 with 87 weight % carbon in diesel, 86 weight %
carbon in gasoline, average BSFC of 7,000 Btu/hp-hr, diesel heating value of 19,300 Btu/lb, and
gasoline healing value of 20,300 Btu/lb.
3.3-6
EMISSION FACTORS
10/96
-------
Table 3.3-2. SPECIATED ORGANIC COMPOUND EMISSION
FACTORS FOR UNCONTROLLED DIESEL ENGINES3
EMISSION FACTOR RATING: E
Pollutant
Benzeneb
Toluene
Xylenesb
Propyleneb
l,3-Butadieneb'c
Formaldehyde11
Acetaldehyde
Acroleinb
Polycyclic aromatic hydrocarbons (PAH)
Naphthaleneb
Acenaphthylene
Acenaphthene
Fluorene
Phenanthrene
Anthracene
Fluoranthene
Pyrene
Benzo(a)anthracene
Chrysene
Benzo(b)fluoranthene
Benzo(k)fluoranthene
Benzo(a)pyrene
Indeno( 1 ,2,3-cd)pyrene
Dibenz(a,h)anthracene
Benzo(g,h,l)perylene
TOTAL PAH
Emission Factor
(Fuel Input)
(Ib/MMBtu)
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
<1.42E-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
a Based on the uncontrolled levels of 2 diesel engines from References 6-7. Source Classification
Codes 2-02-001-02, 2-03-001-01. To convert from Ib/MMBtu to ng/J, multiply by 430.
b Hazardous air pollutant listed in the Clean Air Act.
c Based on data from 1 engine.
10/96
Stationary Internal Combustion Sources
3.3-7
-------
Table 3.3-3. EFFECT OF VARIOUS EMISSION CONTROL TECHNOLOGIES
ON DIESEL ENGINES'1
Technology
Affected Parameter
Increase
Decrease
Fuel modifications
Sulfur content increase
Aromatic content increase
Cetane number
10% and 90% boiling point
Fuel additives
Water/Fuel emulsions
Engine modifications
Injection timing retard
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
Particulate traps
Selective catalytic reduction
Oxidation catalysts
PM, wear
PM, NOX
PM, BSFC
PM, NOX
PM, power
PM, power, wear
PM, NOX
PM
PM, NOX
NOX
NOX, power
NOY, PM
A.
PM
NOX, PM
PM
NOX, PM
NOX
NOX
NOX
PM, wear
PM
NOX
TOC, CO, PM
a Reference 8. PM = particulate matter. BSFC = brake-specific fuel consumption.
3.3-8
EMISSION FACTORS
10/96
-------
References For Section 3.3
1. H. I. Lips, et al, Environmental Assessment Of Combustion Modification Controls For
Stationary Internal Combustion Engines, EPA-600/7-81-127, U. S. Environmental Protection
Agency, Cincinnati, OH, July 1981.
2. Standards Support And Environmental Impact Statement, Volume 1: Stationary Internal
Combustion Engines, EPA-450/2-78-125a, U. S. Environmental Protection Agency, Research
Triangle Park, NC, July 1979.
3. M. Hoggan, et al., Air Quality Trends In California's South Coast And Southeast Desert Air
Basins, 1976-1990, Air Quality Management Plan, Appendix II-B, South Coast Air Quality
Management District, July 1991.
4. R. B. Snyder, Alternative Control Techniques Document.. NOX Emissions From Stationary
Reciprocating Internal Combustion Engines, EPA-453/R-93-032, U. S. Environmental
Protection Agency, Research Triangle Park, July 1993.
5. C. T. Hare and K. J. Springer, Exhaust Emissions From Uncontrolled Vehicles And Related
Equipment Using Internal Combustion Engines, Part 5: Farm, Construction, And Industrial
Engines, APTD-1494, U. S. Environmental Protection Agency, Research Triangle Park, NC,
October 1973.
6. Pooled Source Emission Test Report: Oil And Gas Production Combustion Sources, Fresno
And Ventura Counties, California, ENSR 7230-007-700, Western States Petroleum
Association, Bakersfield, CA, December 1990.
7. W. E. Osborn and M. D. McDannel, Emissions Of Air Toxic Species: Test Conducted Under
AB2588 For The Western States Petroleum Association, CR 72600-2061, Western States
Petroleum Association, Glendale, CA, May 1990.
8. Technical Feasibility Of Reducing NOX And Particulate Emissions From Heavy-duty Engines,
CARB Contract A132-085, California Air Resources Board, Sacramento, CA, March 1992.
9. G. Marland and R. M. Rotty, Carbon Dioxide Emissions From Fossil Fuels: A Procedure For
Estimation And Results For 1951-1981, DOE/NBB-0036 TR-003, Carbon Dioxide Research
Division, Office of Energy Research, U. S. Department of Energy, Oak Ridge, TN, 1983.
10. A. Rosland, Greenhouse Gas Emissions in Norway: Inventories and Estimation Methods,
Oslo: Ministry of Environment, 1993.
11. Sector-Specific Issues and Reporting Methodologies Supporting the General Guidelines for the
Voluntary Reporting of Greenhouse Gases under Section 1605(b) of the Energy Policy Act of
1992 (1994) DOE/PO-0028, Volume 2 of 3, U.S. Department of Energy.
12. G. Marland and R. M. Rotty, Carbon Dioxide Emissions From Fossil Fuels: A Procedure For
Estimation And Results For 1950-1982, Tellus 366:232-261, 1984.
13. Inventory OfU. S. Greenhouse Gas Emissions And Sinks: 1990-1991, EPA-230-R-96-006,
U. S. Environmental Protection Agency, Washington, DC, November 1995.
14. IPCC Guidelines For National Greenhouse Gas Inventories Workbook, Intergovernmental
Panel on Climate Change/Organization for Economic Cooperation and Development, Paris,
France, 1995.
10/96 Stationary Internal Combustion Sources 3.3-9
-------
3.4 Large Stationary Diesel And AH Stationary Dual-fuel Engines
3.4.1 General
The primary domestic use of large stationary diesel engines (greater than 600 horsepower [hp])
is in oil and gas exploration and production. These engines, in groups of 3 to 5, 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 2 ignition methods used in stationary reciprocating 1C engines, compression ignition
(CI) and spark ignition (SI). In CI engines, combustion air is first compression heated in the cylinder,
and diesel fuel oil is then injected into the hot air. Ignition is spontaneous because the air temperature
is above the autoignition temperature of the fuel. SI 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 CI 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 autoignition. 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.1
3.4.3 Emissions And Controls
Most of the pollutants from 1C engines are emitted through the exhaust. However, some total
organic compounds (TOC) escape from the crankcase as a result of blowby (gases that are vented
from the oil pan after they have escaped from the cylinder past the piston rings) and from the fuel tank
10/96 Stationary Internal Combustion Sources 3.4-1
-------
and carburetor because of evaporation. Nearly all of the TOCs from diesel CI engines enter the
atmosphere from the exhaust. Crankcase blowby is minor because TOCs 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 (NOX),
hydrocarbons and other organic compounds, carbon monoxide (CO), and particulates, which include
both visible (smoke) and nonvisible emissions. Nitrogen oxide formation is directly related to high
pressures and temperatures during the combustion process and to the nitrogen content, if any, of the
fuel. The other pollutants, HC, CO, and smoke, are primarily the result of incomplete combustion.
Ash and metallic additives in the fuel also contribute to the particulate content of the exhaust. Sulfur
oxides also appear in the exhaust from 1C engines. The sulfur compounds, mainly sulfur dioxide
(SO2), are directly related to the sulfur content of the fuel.
3.4.3.1 Nitrogen Oxides -
Nitrogen oxide formation occurs by two fundamentally different mechanisms. The
predominant mechanism with internal combustion engines is thermal NOX which arises from the
thermal dissociation and subsequent reaction of nitrogen (N2) and oxygen (O2) molecules in the
combustion air. Most thermal NOX is formed in the high-temperature region of the flame from
dissociated molecular nitrogen in the combustion air. Some NOX, called prompt NOX, is formed in the
early part of the flame from reaction of nitrogen intermediary species, and HC radicals in the flame.
The second mechanism, fuel NOX, stems from the evolution and reaction of fuel-bound nitrogen
compounds with oxygen. Gasoline, and most distillate oils, have no chemically-bound fuel N2 and
essentially all NOX formed is thermal NOX.
3.4.3.2 Total Organic Compounds -
The pollutants commonly classified as hydrocarbons are composed of a wide variety of organic
compounds and are discharged into the atmosphere when some of the fuel remains unburned or is only
partially burned during the combustion process. Most unburned hydrocarbon emissions result from
fuel droplets that were transported or injected into the quench layer during combustion. This is the
region immediately adjacent to the combustion chamber surfaces, where heat transfer outward through
the cylinder walls causes the mixture temperatures to be too low to support combustion.
Partially burned hydrocarbons can occur because of poor air and fuel homogeneity due to
incomplete mixing, before or during combustion; incorrect air/fuel ratios in the cylinder during
combustion due to maladjustment of the engine fuel system; excessively large fuel droplets (diesel
engines); and low cylinder temperature due to excessive cooling (quenching) through the walls or early
cooling of the gases by expansion of the combustion volume caused by piston motion before
combustion is completed.
3.4.3.3 Carbon Monoxide -
Carbon monoxide is a colorless, odorless, relatively inert gas formed as an intermediate
combustion product that appears in the exhaust when the reaction of CO to C02 cannot proceed to
completion. This situation occurs if there is a lack of available oxygen near the hydrocarbon (fuel)
molecule during combustion, if the gas temperature is too low, or if the residence time in the cylinder
is too short. The oxidation rate of CO is limited by reaction kinetics and, as a consequence, can be
accelerated only to a certain extent by improvements in air and fuel mixing during the combustion
process.
3.4-2 EMISSION FACTORS 10/96
-------
3.4.3.4 Smoke, Particulate Matter, and PM-10 -
White, blue, and black smoke may be emitted from 1C engines. Liquid particulates appear as
white smoke in the exhaust during an engine cold start, idling, or low load operation. These are
formed in the quench layer adjacent to the cylinder walls, where the temperature is not high enough to
ignite the fuel. Blue smoke is emitted when lubricating oil leaks, often past worn piston rings, into the
combustion chamber and is partially burned. Proper maintenance is the most effective method of
preventing blue smoke emissions from all types of 1C engines. The primary constituent of black
smoke is agglomerated carbon particles (soot).
3.4.3.5 Sulfur Oxides -
Sulfur oxide emissions are a function of only the sulfur content in the fuel rather than any
combustion variables. In fact, during the combustion process, essentially all the sulfur in the fuel is
oxidized to SO2. The oxidation of SO2 gives sulfur trioxide (SO3), which reacts with water to give
sulfuric acid (H2S04), a contributor to acid precipitation. Sulfuric acid reacts with basic substances to
give sulfates, which are fine particulates that contribute to PM-10 and visibility reduction. Sulfur
oxide emissions also contribute to corrosion of the engine parts.2'
Table 3.4-1 contains gaseous emission factors for the pollutants discussed above, expressed in
units of pounds per horsepower-hour (Ib/hp-hr), and pounds per million British thermal unit
(Ib/MMBtu). Table 3.4-2 shows the particulate and particle-sizing 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 because they are based only on a single engine test; they are to be
used only for rough order of magnitude comparisons.
Table 3.4-5 shows the NOX reduction and fuel consumption penalties for diesel and dual-fueled
engines based on some of the available control techniques. The emission reductions shown are those
that have been demonstrated. The effectiveness of controls on a 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 3.4-5. These techniques include
internal/external exhaust gas recirculation, combustion chamber modification, manifold air cooling, and
turbocharging.
3.4.4 Control Technologies
Control measures to date are primarily directed at limiting NOX and CO emissions since they
are the primary pollutants from these engines. From a NOX control viewpoint, the most important
distinction between different engine models and types of reciprocating engines is whether they are
rich-burn or lean-bum. Rich-burn engines have an air-to-fuel ratio operating range that is near
stoichiometric or fuel-rich of stoichiometric and as a result the exhaust gas has little or no excess
oxygen. A lean-bum engine has an air-to-fuel operating range that is fuel-lean of stoichiometric;
therefore, the exhaust from these engines is characterized by medium to high levels of 02. The most
common NOX control technique for diesel and dual fuel engines focuses on modifying the combustion
process. However, selective catalytic reduction (SCR) and nonselective catalytic reduction (NSCR)
which are post-combustion techniques are becoming available. Control for CO have been partly
adapted from mobile sources.
Combustion modifications include injection timing retard (ITR), preignition chamber
combustion (PCC), air-to-fuel ratio, and derating. Injection of fuel into the cylinder of a CI engine
initiates the combustion process. Retarding the timing of the diesel fuel injection causes the
combustion process to occur later in the power stroke when the piston is in the downward motion and
10/96 Stationary Internal Combustion Sources 3.4-3
-------
combustion chamber volume is increasing. By increasing the volume, the combustion temperature and
pressure are lowered, thereby lowering NOX formation. ITR reduces NOX from all diesel engines;
however, the effectiveness is specific to each engine model. The amount of NOX reduction with ITR
diminishes with increasing levels of retard.
Improved swirl patterns promote thorough air and fuel mixing and may include a
precombustion chamber (PCC). A PCC is an antechamber that ignites a fuel-rich mixture that
propagates to the main combustion chamber. The high exit velocity from the PCC results in improved
mixing and complete combustion of the lean air/fuel mixture which lowers combustion temperature,
thereby reducing NOX emissions.5
The air-to-fuel ratio for each cylinder can be adjusted by controlling the amount of fuel that
enters each cylinder. At air-to-fuel ratios less than stoichiometric (fuel-rich), combustion occurs under
conditions of insufficient oxygen which causes NOX to decrease because of lower oxygen and lower
temperatures. Derating involves restricting engine operation to lower than normal levels of power
production for the given application. Derating reduces cylinder pressures and temperatures thereby
lowering NOX formation rates.
SCR is an add-on NOX control placed in the exhaust stream following the engine and involves
injecting ammonia (NH3) into the flue gas. The NH3 reacts with the NOX in the presence of a catalyst
to form water and nitrogen. The effectiveness of SCR depends on fuel quality and engine duty cycle
(load fluctuations). Contaminants in the fuel may poison or mask the catalyst surface causing a
reduction or termination in catalyst activity. Load fluctuations can cause variations in exhaust
temperature and NOX concentration which can create problems with the effectiveness of the SCR
system.
NSCR is often referred to as a three-way conversion catalyst system because the catalyst
reactor simultaneously reduces NOX, CO, and HC and involves placing a catalyst in the exhaust stream
of the engine. The reaction requires that the 02 levels be kept low and that the engine be operated at
fuel-rich air-to-fuel ratios.
3.4.5 Updates Since the Fifth Edition
The Fifth Edition was released in January 1995. Revisions to this section since that date are
summarized below. For further detail, consult the memoranda describing each supplement or the
background report for this section. These and other documents can be found on the CFflEF electronic
bulletin board (919-541-5742), or on the new EFIG home page (http://www.epa.gov/oar/oaqps/efig/).
Supplement A, February 1996
No changes.
Supplement B, October 1996
• The general text was updated.
• Controlled NOX factors and PM factors were added for diesel units.
• Math errors were corrected in factors for CO from diesel units and for uncontrolled
NOY from dual fueled units.
A
3.4-4 EMISSION FACTORS 10/96
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10/96
Stationary Internal Combustion Sources
3.4-5
-------
Table 3.4-2. PARTICULATE AND PARTICLE-SIZING
EMISSION FACTORS FOR LARGE UNCONTROLLED STATIONARY DIESEL ENGINESa
EMISSION FACTOR RATING: E
Pollutant
Filterable particulate
< 1 jjm
< 3 \an
< 10 pm
Total filterable particulate
Condensable particulate
Total PM-10C
Total particulate
Emission Factor (Ib/MMBtu)
(fuel input)
0.0478
0.0479
0.0496
0.0620
0.0077
0.0573
0.0697
a Based on 1 uncontrolled diesel engine from Reference 6. Source Classification Code 2-02-004-
01. The data for the particulate emissions were collected using Method 5, and the particle size
distributions were collected using a Source Assessment Sampling System. To convert from
Ib/MMBtu to ng/J, multiply by 430. PM-10 = particulate matter < 10 micrometers (urn)
aerometric diameter.
Particle size is expressed as aerodynamic diameter.
0 Total PM-10 is the sum of filterable particulate less than 10 urn aerodynamic diameter and
condensable particulate.
Total particulate is the sum of the total filterable particulate and condensable particulate.
3.4-6
EMISSION FACTORS
10/96
-------
Table 3.4-3. SPECIATED ORGANIC COMPOUND EMISSION FACTORS FOR LARGE
UNCONTROLLED STATIONARY DIESEL ENGINES3
EMISSION FACTOR RATING: E
Pollutant
Benzene
Tolueneb
Xylenesb
Propylene
Formaldehyde1*
Acetaldehydeb
Acroleinb
Emission Factor
(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
aBased on 1 uncontrolled diesel engine from Reference 7. Source Classification
Code 2-02-004-01. Not enough information to calculate the output-specific emission factors of
Ib/hp-hr. To convert from Ib/MMBtu to ng/J, multiply by 430.
Hazardous air pollutant listed in the Clean Air Act.
10/96
Stationary Internal Combustion Sources
3.4-7
-------
Table 3.4-4. PAH EMISSION FACTORS FOR LARGE
UNCONTROLLED STATIONARY DIESEL ENGINES3
EMISSION FACTOR RATING: E
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
Emission Factor
(Ib/MMBtu)
(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
a Based on 1 uncontrolled diesel engine from Reference 7. Source Classification Code 2-02-004-
01. Not enough information to calculate the output-specific emission factors of Ib/hp-hr. To
convert from Ib/MMBtu to ng/J, multiply by 430.
b Hazardous air pollutant listed in the Clean Air Act.
3.4-8
EMISSION FACTORS
10/96
-------
Table 3.4-5. NOX REDUCTION AND FUEL CONSUMPTION PENALTIES FOR LARGE
STATIONARY DIESEL AND DUAL-FUEL ENGINES3
Control Approach
Derate 10%
20%
25%
Retard 2°
4°
8°
Air-to-fuel 3%
±10%
Water injection (H2O/ruel ratio) 50%
SCR
Diesel
(SCC 2-02-004-01)
NOX
Reduction
(%)
ND
<20
5 -23
<20
<40
28-45
ND
7-8
25 -35
80-95
ABSFCb
(%)
ND
4
1 -5
4
4
2-8
ND
3
2-4
0
Dual Fuel
(SCC 2-02-004-02)
NOX
Reduction
(%)
<20
ND
1 -33
<20
<40
50-73
<20
25 -40
ND
80-95
ABSFC
(%)
4
ND
1 -7
3
1
3-5
0
1 -3
ND
0
a References 1,27-28. The reductions shown are typical and will vary depending on the engine and
duty cycle. SCC = Source Classification Code. ABSFC = change in brake-specific fuel
consumption. ND = no data.
10/96
Stationary Internal Combustion Sources
3.4-9
-------
References For Section 3.4
1. H. I. Lips, et al., Environmental Assessment Of Combustion Modification Controls For
Stationary Internal Combustion Engines, EPA-600/7-81-127, U. S. Environmental Protection
Agency, Cincinnati, OH, July 1981.
2. Standards Support And Environmental Impact Statement, Volume I: Stationary Internal
Combustion Engines, EPA-450/2-78-125a, U. S. Environmental Protection Agency, Research
Triangle Park, NC, July 1979.
3. M. Hoggan, et. al., Air Quality Trends in California's South Coast and Southeast Desert Air
Basins, 1976-1990, "Air Quality Management Plan, Appendix II-B", South Coast Air Quality
Management District, July 1991.
4. Limiting Net Greenhouse Gas Emissions In the United States, Volume II: Energy Responses,
report for the Office of Environmental Analysis, Office of Policy, Planning and Analysis,
Department of Energy (DDE), DOE/PE-0101 Volume II, September 1991.
5. Snyder, R. B., Alternative Control Techniques Document—NOx Emissions from Stationary
Reciprocating Internal Combustion Engines, EPA-453/R-93-032, U. S. Environmental
Protection Agency, Research Triangle Park, July 1993.
6. C. Castaldini, Environmental Assessment OfNOx Control On A Compression Ignition Large
Bore Reciprocating Internal Combustion Engme, Volume I: Technical Results,
EPA-600/7-86/001a, U. S. Environmental Protection Agency, Cincinnati, OH, April 1984.
7. Pooled Source Emission Test Report: Oil And Gas Production Combustion Sources, Fresno
And Ventura Counties, California, ENSR # 7230-007-700, Western States Petroleum
Association, Bakersfield, CA, December 1990.
8. Final Report For An Emission Compliance Test Program On Two Standby Generators Located
At American Car Company, Greenwich, CT, York Services Corp., 1987.
9. Final Report For An Emission Compliance Test Program On A Standby Diesel Generator At
South Central Connecticut Regional Water Authority, West Haven, CT, York Services Corp.,
1988.
10. Air Emission From Stationary Diesel Engines For The Alaska Rural Electric Cooperative
Association, Environmetrics, 1992.
11. Compliance Test Report For Particulate Emissions From A Caterpillar Diesel Generator, St.
Mary's Hospital, Waterburg, CT, TRC Environmental Consultants, 1987.
12. Compliance Measured P articulate Emissions From An Emergency Diesel Generator, Silorsky
Aircraft, United Technologies, Stratford, CT, TRC Environmental Consultants, 1987.
13. Compliance Test Report For P articulate Emissions From A Cummins Diesel Generator,
Colonial Gold Limited Partnership, Hartford, CT, TRC Environmental Consultants, 1988.
14. Compliance Test Report For P articulate Emissions From A Cummins Diesel Generator,
CIGNA Insurance Company, Bloomfield, CT, TRC Environmental Consultants, 1988.
3.4-10 EMISSION FACTORS 10/96
-------
15. Compliance Test Report For Particulate Emission From A Waukesha Diesel Generator, Bristol
Meyers, Wallinsford, CT, TRC Environmental Consultants, 1987.
16. Compliance Test Report For P articulate Emissions From A Cummins Diesel Generator,
Connecticut General Life Insurance, Windsor, CT, TRC Environmental Consultants, 1987.
17. Compliance Measured P articulate Emissions From An Emergency Diesel Generator, Danbury
Hospital, Danbury, CT, TRC Environmental Consultants, 1988.
18. Compliance Test Report For P articulate Emissions From A Caterpillar Diesel Generator,
Colonial Metro Limited Partnership, Hartford, CT, TRC Environmental Consultants, 1988.
19. Compliance Test Report For P articulate Emissions From A Caterpillar Diesel Generator,
Boehringer -Ingelheim Pharmaceuticals, Danbury, CT, TRC Environmental Consultants, 1988.
20. Compliance Test Report For Emissions Of P articulate From An Emergency Diesel Generator,
Meriden - Wallingford Hospital, Meriden, CT, TRC Environmental Consultants, 1987.
21. Compliance Test Report Johnson Memorial Hospital Emergency Generator Exhaust Stack,
Stafford Springs, CT, ROJAC Environmental Services, 1987.
22. Compliance Test Report Union Carbide Corporation Generator Exhaust Stack, Danbury, CT,
ROJAC Environmental Services, 1988.
23. Compliance Test Report Hartford Insurance Company Emergency Generator Exhaust Stack,
Bloomfield, CT, ROJAC Environmental Services, 1987.
24. Compliance Test Report Hartford Insurance Group Emergency Generator Exhaust Stack,
Hartford, CT, ROJAC Environmental Services, 1987.
25. Compliance Test Report Southern New England Telephone Company Emergency Generator
Exhaust Stack, North Haven, CT, ROJAC Environmental Services, 1988.
26. Compliance Test Report Pfizer, Inc. Two Emergency Generator Exhaust Stacks, Groton, CT,
ROJAC Environmental Services, 1987.
27. L. M. Campbell, et al., Sourcebook: NOX Control Technology Data, Control Technology
Center, EPA-600/2-91-029, U. S. Environmental Protection Agency, Cincinnati, OH,
July 1991.
28. Catalysts For Air Pollution Control, Manufacturers Of Emission Controls Association
(MECA), Washington, DC, March 1992.
10/96 Stationary Internal Combustion Sources 3.4-11
-------
4. EVAPORATION LOSS SOURCES
Evaporation losses include the organic solvents emitted from dry cleaning plants, surface
coating operations, and degreasing operations. This chapter presents the volatile organic emissions
from these sources. Where possible, the effect is shown of controls to reduce the emissions of
organic compounds.
1/95 Evaporation Loss Sources 4.0-1
-------
4.1 Dry Cleaning
4.1.1 General1'2
Dry cleaning involves the cleaning of fabrics with nonaqueous organic solvents. The dry
cleaning process requires 3 steps: (1) washing the fabric in solvent, (2) spuming to extract excess
solvent, and (3) drying by tumbling in a hot air stream.
Two general types of cleaning fluids are used in the industry, petroleum solvents and synthetic
solvents. Petroleum solvents, such as Stoddard or 140-F, are inexpensive combustible hydrocarbon
mixtures similar to kerosene. Operations using petroleum solvents are known as petroleum plants.
Synthetic solvents are nonflammable but more expensive halogenated hydrocarbons.
Perchloroethylene and trichlorotrifluoroethane are the 2 synthetic dry cleaning solvents presently in
use. Operations using these synthetic solvents are respectively called "perc" plants and fluorocarbon
plants.
There are 2 basic types of dry cleaning machines, transfer and dry-to-dry. Transfer machines
accomplish washing and drying in separate machines. Usually, the washer extracts excess solvent
from the clothes before they are transferred to the dryer, but some older petroleum plants have
separate extractors for this purpose. Dry-to-dry machines are single units that perform all of the
washing, extraction, and drying operations. All petroleum solvent machines are the transfer type, but
synthetic solvent plants can be either type.
The dry cleaning industry can be divided into 3 sectors: coin-operated facilities, commercial
operations, and industrial cleaners. Coin-operated facilities are usually part of a laundry supplying
"self-service" dry cleaning for consumers. Only synthetic solvents are used hi com operated dry
cleaning machines. Such machines are small, with a capacity of 3.6 to 11.5 kg (8 to 25 Ib) of
clothing.
Commercial operations, such as small neighborhood or franchise dry cleaning shops, clean
soiled apparel for the consumer. Generally, perchloroethylene and petroleum solvents are used hi
commercial operations. A typical "perc" plant operates a 14 to 27 kg (30 to 60 Ib) capacity
washer/extractor and an equivalent size reclaiming dryer.
Industrial cleaners are larger dry cleaning plants which supply rental service of uniforms,
mats, mops, etc., to businesses or industries. Perchloroethylene is used by approximately SO percent
of the industrial dry cleaning establishments. A typical large industrial cleaner has a 230 kg (500 Ib)
capacity washer/extractor and 3 to 6 38-kg (100-lb) capacity dryers.
A typical perc plant is shown in Figure 4.1-1. Although 1 solvent tank may be used, the
typical perc plant uses 2 tanks for washing. One tank contains pure solvent, and the other contains
"charged" solvent (used solvent to which small amounts of detergent have been added to aid in
cleaning). Generally, clothes are cleaned hi charged solvent and rinsed hi pure solvent. A water bath
may also be used.
After the clothes have been washed, the used solvent is filtered, and part of the filtered
solvent is returned to the charged solvent tank for washing the next load. The remaining solvent is
then distilled to remove oils, fats, greases, etc., and is returned to the pure solvent tank. The
4/81 (Reformatted 1/95) Evaporation Loss Sources 4.1-1
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EMISSION FACTORS
(Reformatted 1/95) 4/81
-------
collected solids (muck) are usually removed from the filter once a day. Before disposal, the muck
may be "cooked" to recover additional solvent. Still and muck cooker vapors are vented to a
condenser and separator, where more solvent is reclaimed. In many perc plants, the condenser
offgases are vented to a carbon adsorption unit for additional solvent recovery.
After washing, the clothes are transferred to the dryer to be tumbled in a heated air stream.
Exhaust gases from the dryer, along with a small amount of exhaust gases from the washer/extractor,
are vented to a water-cooled condenser and water separator. Recovered solvent is returned to the
pure solvent storage tank. In 30 to 50 percent of the perc plants, the condenser offgases are vented to
a carbon adsorption unit for additional solvent recovery. To reclaim this solvent, the unit must be
periodically desorbed with steam, usually at the end of each day. Desorbed solvent and water are
condensed and separated, and recovered solvent is returned to the pure solvent tank.
A petroleum plant would differ from Figure 4.1-1 chiefly in that there would be no recovery
of solvent from the washer and dryer and no muck cooker. A fluorocarbon plant would differ in that
an unvented refrigeration system would be used in place of a carbon adsorption unit. Another
difference is that a typical fluorocarbon plant could use a cartridge filter which is drained and
disposed of after several hundred cycles.
4.1.2 Emissions And Controls1"3
The solvent itself is the primary emission from dry cleaning operations. Solvent is given off
by washer, dryer, solvent still, muck cooker, still residue, and filter muck storage areas, as well as by
leaky pipes, flanges, and pumps.
Petroleum plants have not generally employed solvent recovery, because of the low cost of
petroleum solvents and the fire hazards associated with collecting vapors. Some emission control,
however, can be obtained by maintaining all equipment (e. g., preventing lint accumulation, solvent
leakage, etc.) and by using good operating practices (e. g., not overloading machinery). Both carbon
adsorption and incineration appear to be technically feasible controls for petroleum plants, but costs
are high.
Solvent recovery is necessary in perc plants due to the higher cost of perchloroethylene. As
shown hi Figure 4.1-1, recovery is effected on the washer, dryer, still, and muck cooker through the
use of condensers, water/solvent separators and carbon adsorption units. Typically once a day,
solvent in the carbon adsorption unit is desorbed with steam, condensed, separated from the
condensed water, and returned to the pure solvent storage tank. Residual solvent emitted from treated
distillation bottoms and muck is not recovered. As hi petroleum plants, good emission control can be
obtained by good housekeeping (maintaining all equipment and using good operating practices).
All fluorocarbon machines are of the dry-to-dry variety to conserve solvent vapor, and all are
closed systems with built hi solvent recovery. High emissions can occur, however, as a result of
poor maintenance and operation of equipment. Refrigeration systems are installed on newer machines
to recover solvent from the washer/dryer exhaust gases.
Emission factors for dry cleaning operations are presented in Table 4.1-1.
Typical coin-operated and commercial plants emit less than 106 grams (1 ton) per year. Some
applications of emission estimates are too broad to identify every small facility. For estimates over
large areas, the factors in Table 4.1-2 may be applied for coin-operated and commercial dry cleaning
emissions.
4/81 (Reformatted 1/95) Evaporation Loss Sources 4.1-3
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4.1-5
-------
Table 4.1-2 (Metric And English Units). PER CAPITA SOLVENT LOSS EMISSION FACTORS
FOR DRY CLEANING PLANTS*
EMISSION FACTOR RATING: B
Operation
Commercial
Coin-operated
Emission Factors
kg/yr/capita
(Ib/year/cap)
0.6
(1.3)
0.2
(0.4)
g/day/capitab
(Ib/day/cap)
1.9
(0.004)
0.6
(0.001)
a References 2-4. All nonmethane VOC.
b Assumes a 6-day operating week (313 days/yr).
References For Section 4.1
1. Study To Support New Source Performance Standards For The Dry Cleaning Industry,
EPA Contract No. 68-02-1412, TRW, Inc., Vienna, VA, May 1976.
2. Perchloroethylene Dry Cleaners — Background Information For Proposed Standards,
EPA-450/3-79-029a, U. S. Environmental Protection Agency, Research Triangle Park, NC,
August 1980.
3. Control Of Volatile Organic Emissions From Perchloroethylene Dry Cleaning Systems,
EPA-450/2-78-050, U. S. Environmental Protection Agency, Research Triangle Park, NC,
December 1978.
4. Control Of Volatile Organic Emissions From Petroleum Dry Cleaners (Draft), Office Of Air
Quality Planning And Standards, U. S. Environmental Protection Agency, Research Triangle
Park, NC, February 1981.
4.1-6
EMISSION FACTORS
(Reformatted 1/95) 4/81
-------
4.2 Surface Coating
Surface coating operations involve the application of paint, varnish, lacquer, or paint primer,
for decorative or protective purposes. This is accomplished by brushing, rolling, spraying, flow
coating, and dipping operations. Some industrial surface coating operations include automobile
assembly, job enameling, and manufacturing of aircraft, containers, furniture, appliances, and plastic
products. Nonindustrial applications of surface coatings include automobile refinishing and
architectural coating of domestic, industrial, government, and institutional structures, including
building interiors and exteriors and exteriors and signs and highway markings. Nonindustrial Surface
Coating is discussed below in Section 4.2.1, and Industrial Surface Coating in Section 4.2.2.
Emissions of volatile organic compounds (VOC) occur in surface coating operations because
of evaporation of the paint vehicle, thinner, or solvent used to facilitate the application of coatings.
The major factor affecting these emissions is the amount of volatile matter contained in the coating.
The volatile portion of most common surface coatings averages about 50 percent, and most, if not all,
of this is emitted during the application of coatings. The compounds released include aliphatic and
aromatic hydrocarbons, alcohols, ketones, esters, alkyl and aryl hydrocarbon solvents, and mineral
spirits. Table 4.2-1 presents emission factors for general surface coating operations.
Table 4.2-1 (Metric And English Units). EMISSION FACTORS FOR GENERAL SURFACE
COATING APPLICATIONS*
EMISSION FACTOR RATING: B
Coating Type
Paint
Varnish and shellac
Lacquer
Enamel
Primer (zinc chromate)
VOC Emissions
kg/Mg
560
500
770
420
660
Ib/ton
1,120
1,000
1,540
% 840
1,320
a References 1-2.
References For Section 4.2
1. Products Finishing, 47(6A):4-54, March 1977.
2. Air Pollution Engineering Manned, Second Edition, AP-40, U.S. Environmental Protection
Agency, Research Triangle Park, NC, May 1973. Out of Print.
4/81 (Refoimatted 1/95) Evaporation Loss Sources 4.2-1
-------
4.2.1 Nonindustrial Surface Coating1*3'5
Nonindustrial surface coating operations are nonmanufacturing applications of surface coating.
Two major categories are architectural surface coating and automobile refinishing. Architectural
surface coating is considered to involve both industrial and nonindustrial structures. Automobile
refinishing pertains to the painting of damaged or worn highway vehicle finishes and not to the
painting of vehicles during manufacture.
Emissions from coating a single architectural structure or an automobile are calculated by
using total volume and content and specific application. To estimate emissions for a large
geographical area which includes many major and minor applications of nonindustrial surface coatings
requires that area source estimates be developed. Architectural surface coating and auto refinishing
emissions data are often difficult to compile for a large geographical area. In cases where a large
emissions inventory is being developed and/or where resources are unavailable for detailed accounting
of actual coatings volume for these applications, emissions may be assumed proportional to population
or to number of employees in the activity. Table 4.2.1-1 presents factors from national emission data
and gives emissions per population or employee for architectural surface coating and automobile
refinishing.
Table 4.2.1-1 (Metric And English Units). NATIONAL EMISSIONS AND EMISSION FACTORS
FOR VOC FROM ARCHITECTURAL SURFACE COATING
AND AUTOMOBILE REFINISHING3
EMISSION FACTOR RATING: C
Emissions
National
Mg/yr (ton/yr)
Per capita
kg/yr (Ib/yr)
g/day (Ib/day)
Per employee
Mg/yr (ton/yr)
kg/day (Ib/day)
Architectural Surface Coating
446,000 (491,000)
2.09 (4.6)
5.8 (0.013)b
ND
ND
Automobile Refinishing
181,000 (199,000)
0.84(1.9)
2.7 (0.006)c
2.3 (2.6)
7.4 (16.3)c
a References 3,5-8. All nonmethane organics. ND = no data.
b Reference 8. Calculated by dividing kg/yr (Ib/yr) by 365 days and converting to appropriate units.
c Assumes a 6-day operating week (312 days/yr).
Using waterborne architectural coatings reduces VOC emissions. Current consumption trends
indicate increasing substitution of waterborne architectural coatings for those using solvent.
Automobile refinishing often is done in areas only slightly enclosed, which makes emissions control
9/91 (Reformatted 1/95)
Evaporation Loss Sources
4.2.1-1
-------
difficult. Where automobile refinishing takes place in an enclosed area, control of the gaseous
emissions can be accomplished by the use of adsorbers (activated carbon) or afterburners. The
collection efficiency of activated carbon has been reported at 90 percent or greater. Water curtains or
filler pads have little or no effect on escaping solvent vapors, but they are widely used to stop paint
paniculate emissions.
References For Section 4.2.1
1. Air Pollution Engineering Manual, Second Edition, AP-40, U. S. Environmental Protection
Agency, Research Triangle Park, NC, May 1973. Out of Print.
2. Control Techniques For Hydrocarbon And Organic Gases From Stationary Sources, AP-68,
U. S. Environmental Protection Agency, Research Triangle Park, NC, October 1969.
3. Control Techniques Guideline For Architectural Surface Coatings (Draft), Office Of Air
Quality Planning And Standards, U. S. Environmental Protection Agency, Research Triangle
Park, NC, February 1979.
4. Air Pollutant Emission Factors, HEW Contract No. CPA-22-69-119, Resources Research
Inc., Reston, VA, April 1970.
5. Procedures For The Preparation Of Emission Inventories For Volatile Organic Compounds,
Volume I, Second Edition, EPA-450/2-77-028, U. S. Environmental Protection Agency,
Research Triangle Park, NC, September 1980.
6. W. H. Lamason, "Technical Discussion Of Per Capita Emission Factors For Several Area
Sources Of Volatile Organic Compounds", Technical Support Division, U. S. Environmental
Protection Agency, Research Triangle Park, NC, March 15, 1981. Unpublished.
7. End Use Of Solvents Containing Volatile Organic Compounds, EPA-450/3-79-032,
U. S. Environmental Protection Agency, Research Triangle Park, NC, May 1979.
8. Written communications between Bill Lamason and Chuck Mann, Technical Support Division,
U. S. Environmental Protection Agency, Research Triangle Park, NC, October 1980, and
March 1981.
4.2.1-2 EMISSION FACTORS (Reformatted 1/95) 9/91
-------
4.2.2 Industrial Surface Coating
4.2.2.1 General Industrial Surface Coatings
4.2.2.2 Can Coating
4.2.2.3 Magnet Wire Coating
4.2.2.4 Other Metal Coating
4.2.2.5 Flat Wood Interior Panel Coating
4.2.2.6 Paper Coating
4.2.2.7 Polymeric Coating Of Supporting Substrates
4.2.2.8 Automobile And Light Duty Truck Surface Coating Operations
4.2.2.9 Pressure Sensitive Tapes And Labels
4.2.2.10 Metal Coil Surface Coating
4.2.2.11 Large Appliance Surface Coating
4.2.2.12 Metal Furniture Surface Coating
4.2.2.13 Magnetic Tape Manufacturing
4.2.2.14 Surface Coating Of Plastic Parts For Business Machines
9/91 (Reformatted 1/95) Evaporation Loss Sources 4.2.2-1
-------
4.2 J.I General Industrial Surface Coating1"4
4.2.2.1.1 Process Description
Surface coating is the application of decorative or protective materials in liquid or powder
form to substrates. These coatings normally include general solvent type paints, varnishes, lacquers,
and water thinned paints. After application of coating by 1 of a variety of methods such as brushing,
rolling, spraying, dipping and flow coating, the surface is air and/or heat dried to remove the volatile
solvents from the coated surface. Powder type coatings can be applied to a hot surface or can be
melted after application and caused to flow together. Other coatings can be polymerized after
application by thermal curing with infrared or electron beam systems.
Coating Operations -
There are both "toll" ("independent") and "captive" surface coating operations. Toll
operations fill orders to various manufacturer specifications, and thus change coating and solvent
conditions more frequently than do captive companies, which fabricate and coat products within a
single facility and which may operate continuously with the same solvents. Toll and captive
operations differ in emission control systems applicable to coating lines, because not all controls are
technically feasible in toll situations.
Coating Formulations -
Conventional coatings contain at least 30 volume percent solvents to permit easy handling and
application. They typically contain 70 to 85 percent solvents by volume. These solvents may be of
1 component or of a mixture of volatile ethers, acetates, aromatics, cellosolves, aliphatic
hydrocarbons, and/or water. Coatings with 30 volume percent of solvent or less are called low
solvent or "high solids" coatings.
Waterborne coatings, which have recently gained substantial use, are of several types: water
emulsion, water soluble and colloidal dispersion, and electrocoat. Common ratios of water to solvent
organics in emulsion and dispersion coatings are 80:20 and 70:30.
Two-part catalyzed coatings to be dried, powder coatings, hot melts, and radiation cured
(ultraviolet and electron beam) coatings contain essentially no volatile organic compounds (VOC),
although some monomers and other lower molecular weight organics may volatilize.
Depending on the product requirements and the material being coated, a surface may have
1 or more layers of coating applied. The first coat may be applied to cover surface imperfections or
to assure adhesion of the coating. The intermediate coats usually provide the required color, texture
or print, and a clear protective topcoat is often added. General coating types do not differ from those
described, although the intended use and the material to be coated determine the composition and
resins used in the coatings.
Coating Application Procedures -
Conventional spray, which is air atomized and usually hand operated, is 1 of the most
versatile coating methods. Colors can be changed easily, and a variety of sizes and shapes can be
painted under many operating conditions. Conventional, catalyzed, or waterborne coatings can be
applied with little modification. The disadvantages are low efficiency from overspray and high
energy requirements for the air compressor.
4/81 (Reformatted 1/95) Evaporation Loss Sources 4.2.2.1-1
-------
In hot airless spray, the paint is forced through an atomizing nozzle. Since volumetric flow is
less, overspray is reduced. Less solvent is also required, thus reducing VOC emissions. Care must
be taken for proper flow of the coating, to avoid plugging and abrading of the nozzle orifice.
Electrostatic spray is most efficient for low viscosity paints. Charged paint particles are attracted to
an oppositely charged surface. Spray guns, spinning discs, or bell shaped atomizers can be used to
atomize the paint. Application efficiencies of 90 to 95 percent are possible, with good "wraparound"
and edge coating. Interiors and recessed surfaces are difficult to coat, however.
Roller coating is used to apply coatings and inks to flat surfaces. If the cylindrical rollers
move in the same direction as the surface to be coated, the system is called a direct roll coater. If
they rotate in the opposite direction, the system is a reverse roll coater. Coatings can be applied to
any flat surface efficiently and uniformly and at high speeds. Printing and decorative graining are
applied with direct rollers. Reverse rollers are used to apply fillers to porous or imperfect substrates,
including papers and fabrics, to give a smooth uniform surface.
Knife coating is relatively inexpensive, but it is not appropriate for coating unstable materials,
such as some knit goods, or when a high degree of accuracy in the coating thickness is required.
Rotogravure printing is widely used in coating vinyl imitation leathers and wallpaper, and hi
the application of a transparent protective layer over the printed pattern. In rotogravure printing, the
unage area is recessed, or "intaglio", relative to the copper plated cylinder on which the image is
engraved. The ink is picked up on the engraved area, and excess ink is scraped off the nonimage
area with a "doctor blade". The image is transferred directly to the paper or other substrate, which is
web fed, and the product is then dried.
Dip coating requires that the surface of the subject be immersed in a bath of paint. Dipping
is effective for coating irregularly shaped or bulky items and for priming. All surfaces are covered,
but coating thickness varies, edge blistering can occur, and a good appearance is not always achieved.
In flow coating, materials to be coated are conveyed through a flow of paint. Paint flow is
directed, without atomization, toward the surface through multiple nozzles, then is caught in a trough
and recycled. For flat surfaces, close control of film thickness can be maintained by passing the
surface through a constantly flowing curtain of paint at a controlled rate.
4.2.2.1.2 Emissions And Controls
Essentially all of the VOC emitted from the surface coating industry is from the solvents
which are used in the paint formulations, used to thin paints at the coating facility, or used for
cleanup. All unrecovered solvent can be considered potential emissions. Monomers and low
molecular weight organics can be emitted from those coatings that do not include solvents, but such
emissions are essentially negligible.
Emissions from surface coating for an uncontrolled facility can be estimated by assuming that
all VOC hi the coatings is emitted. Usually, coating consumption volume will be known, and some
information about the types of coatings and solvents will be available. The choice of a particular
emission factor will depend on the coating data available. If no specific information is given for the
coating, it may be estimated from the data in Table 4.2.2.1-1.
All solvents separately purchased as solvent that are used hi surface coating operations and are
not recovered subsequently can be considered potential emissions. Such VOC emissions at a facility
can result from onsite dilution of coatings with solvent, from "makeup solvents" required in flow
4.2.2.1-2 EMISSION FACTORS (Reformatted 1/95) 4/81
-------
Table 4.2.2.1-1 (Metric And English Units). VOC EMISSION FACTORS FOR UNCONTROLLED
SURFACE COATING*
EMISSION FACTOR RATING: B
Available Information On Coating
Conventional or waterborne paints:
VOC, wt % (d)
or
VOC, vol % (V)
Waterborne paint:
X = VOC as wt % of total volatiles
including water; and
d = total volatiles as wt % of coating
or
Y =
VOC as vol % of total volatiles
including water; and
V = total volatiles as vol % of coating
Emissions Of VOCb
kg/liter Of Coating Or Ib/gal Of Coating0
d • (coating density)/100
V • (solvent density)/100
d • X • (coating density)/100
V • Y • (solvent density)/100
a Based on material balance, assuming entire VOC content is emitted.
b For special purposes, factors expressed in kg per liter of coating less water may be desired. These
can be computed as follows:
kg per liter of coating = kg per liter of coating less water
1 - (vol % water/100)
c If coating density is not known, typical densities are given in Table 4.2.2.1-2. If solvent density is
not known, the average density of solvent in coatings is 0.88 kg/L (7.36 Ib/gal).
coating and, in some instances, dip coating, and from the solvents used for cleanup. Makeup solvents
are added to coatings to compensate for standing losses, concentration or amount, and thus to bring
the coating back to working specifications. Solvent emissions should be added to VOC emissions
from coatings to get total emissions from a coating facility.
Typical ranges of control efficiencies are given in Table 4.2.2.1-3. Emission controls
normally fall under 1 of 3 categories: modification in paint formula, process changes, or add-on
controls. These are discussed further in the specific subsections that follow.
4/81 (Reformatted 1/95)
Evaporation Loss Sources
4.2.2.1-3
-------
Table 4.2.2.1-2 (Metric And English Units). TYPICAL DENSITIES AND SOLIDS CONTENTS
OF COATINGS*
Reference 1.
Type Of Coating
Enamel, air dry
Enamel, baking
Acrylic enamel
Alkyd enamel
Primer surfacer
Primer, epoxy
Varnish, baking
Lacquer, spraying
Vinyl, roller coat
Polyurethane
Stain
Sealer
Magnet wire enamel
Paper coating
Fabric coating
Density
kg/L
0.91
1.09
1.07
0.96
1.13
1.26
0.79
0.95
0.92
1.10
0.88
0.84
0.94
0.92
0.92
Ib/gal
7.6
9.1
8.9
8.0
9.4
10.5
6.6
7.9
7.7
9.2
7.3
7.0
7.8
7.7
7.7
Solids (Volume %)
39.6
42.8
30.3
47.2
49.0
57.2
35.3
26.1
12.0
31.7
21.6
11.7
25.0
22.0
22.0
Table 4.2.2.1-3. CONTROL EFFICIENCIES FOR SURFACE COATING OPERATIONS8
Control Option
Substitute waterborae coatings
Substitute low solvent coatings
Substitute powder coatings
Add afterburners/incinerators
Reduction15
60-95
40-80
92-98
95
a References 2-4.
b Expressed as % of total uncontrolled emission load.
4.2.2.1-4
EMISSION FACTORS
(Reformatted 1/95) 4/81
-------
References For Section 4.2.2.1
1. Controlling Pollution From the Manufacturing And Coating Of Metal Products: Metal Coating
Air Pollution Control, EPA-625/3-77-009, U. S. Environmental Protection Agency,
Cincinnati, OH, May 1977.
2. H. R. Powers, "Economic And Energy Savings Through Coating Selection", The
Sherwin-Williams Company, Chicago, EL, February 8, 1978.
3. Air Pollution Engineering Manual, Second Edition, AP-40, U. S. Environmental Protection
Agency, Research Triangle Park, NC, May 1973. Out of Print.
4. Products Finishing, 4/(6A):4-54, March 1977.
4/81 (Reformatted 1/95) Evaporation Loss Sources 4.2.2.1-5
-------
4.2.2.2 Can Coating1"4
4.2.2.2.1 Process Description
Cans may be made from a rectangular sheet (body blank) and 2 circular ends (3-piece cans),
or they can be drawn and wall ironed from a shallow cup to which an end is attached after the can is
filled (2-piece cans). There are major differences in coating practices, depending on the type of can
and the product packaged in it. Figure 4.2.2.2-1 depicts a 3-piece can sheet printing operation.
There are both "toll" and "captive" can coating operations. The former fill orders to
customer specifications, and the latter coat the metal for products fabricated within one facility. Some
can coating operations do both toll and captive work, and some plants fabricate just can ends.
Three-piece can manufacturing involves sheet coating and can fabricating. Sheet coating
includes base coating and printing or lithographing, followed by curing at temperatures of up to
220°C (425°F). When the sheets have been formed into cylinders, the seam is sprayed, usually with
a lacquer, to protect the exposed metal. If they are to contain an edible product, the interiors are
spray coated, and the cans baked at up to 220°C (425°F).
Two-piece cans are used largely by beer and other beverage industries. The exteriors may be
reverse roll coated in white and cured at 170 to 200°C (325 to 400°F). Several colors of ink are then
transferred (sometimes by lithographic printing) to the cans as they rotate on a mandrel. A protective
varnish may be roll coated over the inks. The coating is then cured in a single or multipass oven at
temperatures of 180 to 200°C (350 to 400°F). The cans are spray coated on the interior and spray
and/or roll coated on the exterior of the bottom end. A final baking at 110 to 200°C (225 to 400°F)
completes the process.
4.2.2.2.2 Emissions And Controls
Emissions from can coating operations depend on composition of the coating, coated area,
thickness of coat, and efficiency of application. Post-application chemical changes and nonsolvent
contaminants like oven fuel combustion products may also affect the composition of emissions. All
solvent used and not recovered can be considered potential emissions.
Sources of can coating VOC emissions include the coating area and the oven area of the sheet
base and lithographic coating lines, the 3-piece can side seam and interior spray coating processes,
and the 2-piece can coating and end sealing compound lines. Emission rates vary with line speed, can
or sheet size, and coating type. On sheet coating lines, where the coating is applied by rollers, most
solvent evaporates in the oven. For other coating processes, the coating operation itself is the major
source. Emissions can be estimated from the amount of coating applied by using the factors in
Table 4.2.2.1-1 or, if the number and general nature of the coating lines are known, from
Table 4.2.2.2-1.
Incineration and the use of waterborne and low solvent coatings both reduce organic vapor
emissions. Other technically feasible control options, such as electrostatically sprayed powder
coatings, are not presently applicable to the whole industry. Catalytic and thermal incinerators both
can be used. Primers, backers (coatings on the reverse or backside of the coil), and some waterborne
low- to medium-gloss topcoats have been developed that equal the performance of organic
4/81 (Reformatted 1/95) Evaporation Loss Sources 4.2.2.2-1
-------
§
55
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4.2.2.2-2
EMISSION FACTORS
(Reformatted 1/95) 4/81
-------
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4/81 (Reformatted 1/95)
Evaporation Loss Sources
4.2.2.2-3
-------
solventborne coatings for aluminum but have not yet been applied at full line speed in all cases.
Waterborne coatings for other metals are being developed.
Available control technology includes the use of add-on devices like incinerators and carbon
adsorbers and a conversion to low solvent and ultraviolet curable coatings. Thermal and catalytic
incinerators both may be used to control emissions from 3-piece can sheet base coating lines, sheet
lithographic coating lines, and ulterior spray coating. Incineration is applicable to 2-piece can coating
lines. Carbon adsorption is most acceptable to low temperature processes which use a limited number
of solvents. Such processes include 2- and 3-piece can interior spray coating, 2-piece can end sealing
compound lines, and 3-piece can side seam spray coating.
Low solvent coatings are not yet available to replace all the organic solventborne formulations
presently used in the can industry. Waterborne basecoats have been successfully applied to 2-piece
cans. Powder coating technology is used for side seam coating of noncemented 3-piece cans.
Ultraviolet curing technology is available for rapid drying of the first 2 colors of ink on
3-piece can sheet lithographic coating lines.
The efficiencies of various control technologies for can coating lines are presented in
Table 4.2.2.2-2.
4.2.2.2-4 EMISSION FACTORS (Reformatted 1/95) 4/81
-------
Table 4.2.2.2-2. CONTROL EFFICIENCIES FOR CAN COATING LINES*
Affected Facility15
Two-piece Can Lines
Exterior coating
Interior spraying coating
Three-piece Can Lines
Sheet coating lines
Exterior coating
Interior spray coating
Can fabricating lines
Side seam spray coating
Interior spray coating
End Coating Lines
Sealing compound
Sheet coating
Control Option
Thermal and catalytic incineration
Waterborne and high solids coating
Ultraviolet curing
Thermal and catalytic incineration
Waterborne and high solids coating
Powder coating
Carbon adsorption
Thermal and catalytic incineration
Waterborne and high solids coating
Ultraviolet curing
Thermal and catalytic incineration
Waterborne and high solids coating
Waterborne and high solids coating
Powder (only for uncemented seams)
Thermal and catalytic incineration
Waterborne and high solids coating
Powder (only for uncemented seams)
Carbon adsorption
Waterborne and high solids coating
Carbon adsorption
Thermal and catalytic incineration
Waterborne and high solids coating
Reduction (%)c
90
60-90
^100
90
60-90
100
90
90
60-90
<:100
90
60-90
60-90
100
90
60-90
100
90
70-95
90
90
60-90
a Reference 3.
b Coil coating lines consist of coalers, ovens, and quench areas. Sheet, can, and end wire coating
lines consist of coaters and ovens.
c Compared to conventional solvent base coatings used without any added thinners.
4/81 (Reformatted 1/95)
Evaporation Loss Sources
4.2.2.2-5
-------
References For Section 4.2.2.2
1. T. W. Hughes, et al., Source Assessment: Prioritization Of Air Pollution From Industrial
Surface Coating Operations, EPA-650/2-75-019a, U. S. Environmental Protection Agency,
Cincinnati, OH, November 1975.
2. Control Of Volatile Organic Emissions From Existing Stationary Sources, Volume I: Control
Methods For Surface Coating Operations, EPA-450/2-76- 028, U. S. Environmental
Protection Agency, Research Triangle Park, NC, May 1977.
3. Control Of Volatile Organic Emissions From Existing Stationary Sources, Volume II: Surface
Coating Of Cans, Coils, Paper Fabrics, Automobiles, And Light Duty Trucks,
EPA-450/2-77-008, U. S. Environmental Protection Agency^ Research Triangle Park, NC,
May 1977.
4. Air Pollution Control Technology Applicable To 26 Sources Of Volatile Organic Compounds,
Office Of Air Quality Planning And Standards, U. S. Environmental Protection Agency,
Research Triangle Park, NC, May 27, 1977. Unpublished.
4.2.2.2-6 EMISSION FACTORS (Reformatted 1/95) 4/81
-------
4.2.23 Magnet Wire Coating1
4.2.2.3.1 Process Description
Magnet wire coating is applying a coat of electrically insulating varnish or enamel to
aluminum or copper wire used in electrical machinery. The wire is usually coated in large plants that
both draw and insulate it and then sell it to electrical equipment manufacturers. The wire coating
must meet rigid electrical, thermal, and abrasion specifications.
Figure 4.2.2.3-1 shows a typical wire coating operation. The wire is unwound from spools
and passed through an annealing furnace. Annealing softens the wire and cleans it by burning off oil
and dirt. Usually, the wire then passes through a bath hi the coating applicator and is drawn through
an orifice or coating die to scrape off the excess. It is then dried and cured in a 2-zone oven first at
200°C, then 430°C (400 and 806°F). Wire may pass through the coating applicator and the oven as
many as 12 times to acquire the necessary thickness of coating.
4.2.2.3.2 Emissions And Controls
Emissions from wire coating operations depend on composition of the coating, thickness of
coat and efficiency of application. Postapplication chemical changes, and nonsolvent contaminants
such as oven fuel combustion products, may also affect the composition of emissions. All solvent
used and not recovered can be considered potential emissions.
The exhaust from the oven is the most important source of solvent emissions in the wire
coating plant. Emissions from the applicator are comparatively low, because a dip coating technique
is used (see Figure 4.2.2.3-1).
Volatile organic compound (VOC) emissions may be estimated from the factors in
Table 4.2.2.1-1, if the coating usage is known and if the coater has no controls. Most wire coalers
built since 1960 do have controls, so the information in the following paragraph may be applicable.
Table 4.2.2.3-1 gives estimated emissions for a typical wire coating line.
Incineration is the only commonly used technique to control emissions from wire coating
operations. Since about 1960, all major wire coating designers have incorporated catalytic
incinerators into their oven designs because of the economic benefits. The internal catalytic
incinerator burns solvent fumes and circulates heat back into the wire drying zone. Fuel otherwise
needed to operate the oven is eliminated or greatly reduced, as are costs. Essentially all solvent
emissions from the oven can be directed to an incinerator with a combustion efficiency of at least
90 percent.
Ultraviolet cured coatings are available for special systems. Carbon adsorption is not
practical. Use of low solvent coatings is only a potential control, because they have not yet been
developed with properties that meet industry's requirements.
4/81 (Reformatted 1/95) Evaporation Loss Sources 4.2.2.3-1
-------
IS
"S
ex
o
0>
g
cs
oi
rj-'
-------
Table 4.2.2.3-1 (Metric And English Units). ORGANIC SOLVENT EMISSIONS FROM A
TYPICAL WIRE COATING LINEa
Coating Lineb
kg/hr
Ib/hr
12 26
Annual Totals0
Mg/yr
ton/yr
84 93
a Reference 1.
b Organic solvent emissions vary from line to line by size and speed pf wire, number of wires per
oven, and number of passes through oven. A typical line may coat 544Jcg (1,200 Ib) wire/day. A
plant may have many lines.
c Based upon normal operating conditions of 7,000 hr/yr for one line without incinerator.
References For Section 4.2.2.3
1. Control Of Volatile Organic Emissions From Existing Stationary Sources, Volume IV: Surface
Coating For Insulation Of Magnet Wire, EPA-450/2-77-033, U. S. Environmental Protection
Agency, Research Triangle Park, NC, December 1977.
2. Controlled And Uncontrolled Emission Rates And Applicable Limitations For Eighty Processes,
EPA Contract Number 68-02-1382, TRC Of New England, Wethersfield, CT, September
1976.
4/81 (Reformatted 1/95)
Evaporation Loss Sources
4.2.2.3-3
-------
4.2.2.4 Other Metal Coating1"4
4.2.2.4.1 Process Description
Large appliance, metal furniture, and miscellaneous metal part and product coating lines have
many common operations, similar emissions and emission points, and available control technology.
Figure 4.2.2.4-1 shows a typical metal furniture coating line.
Large appliances include doors, cases, lids, panels, and interior support parts of washers,
dryers, ranges, refrigerators, freezers, water heaters, air conditioners, and associated products. Metal
furniture includes both outdoor and indoor pieces manufactured for household, business, or
institutional use. "Miscellaneous parts and products" herein denotes large and small farm machinery,
small appliances, commercial and industrial machinery, fabricated metal products and other industries
that coat metal under Standard Industrial Classification (SIC) codes 33 through 39.
Large Appliances -
The coatings applied to large appliances are usually epoxy, epoxy/acrylic, or polyester
enamels for the primer or single coat, and acrylic enamels for the topcoat. Coatings containing alkyd
resins are also used. Prime and interior single coats are applied at 25 to 36 volume percent solids.
Topcoats and exterior single coats are applied at 30 to 40 volume percent. Lacquers may be used to
touch up any scratches that occur during assembly. Coatings contain 2 to 15 solvents, typical of
which are esters, ketones, aliphatics, alcohols, aromatics, ethers, and terpenes.
Small parts are generally dip coated, and flow or spray coating is used for larger parts. Dip
and flow coating are performed in an enclosed room vented either by a roof fan or by an exhaust
system adjoining the drain board or tunnel. Down or side draft booths remove overspray and organic
vapors from prime coat spraying. Spray booths are also equipped with dry filters or a water wash to
trap overspray.
Parts may be touched up manually with conventional or airless spray equipment. Then they
are sent to a flashoff area (either open or tunneled) for about 7 minutes and are baked in a multipass
oven for about 20 minutes at 180 to 230°C (350 to 450°F). At that point, large appliance exterior
parts go on to the topcoat application area, and single coated interior parts are moved to the assembly
area of the plant.
The topcoat, and sometimes primers, are applied by automated electrostatic disc, bell, or
other types of spray equipment. Topcoats often are more than 1 color, changed by automatically
flushing out the system with solvent. Both the topcoat and touchup spray areas are designed with
side- or down-draft exhaust control. The parts go through about a 10-minute flashoff period,
followed by baking in a multipass oven for 20 to 30 minutes at 140 to 180°C (270 to 350°F).
Metal Furniture -
Most metal furniture coatings are enamels, although some lacquers are used. The most
common coatings are alkyds, epoxies, and acrylics, which contain the same solvents used in large
appliance coatings, applied at about 25 to 35 percent solids.
4/81 (Reformatted 1/95) Evaporation Loss Sources 4.2.2.4-1
-------
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EMISSION FACTORS
(Reformatted 1/95) 4/81
-------
On a typical metal furniture coating line (see Figure 4.2.2.4-1), the prime coat can be applied
with the same methods used for large appliances, but it may be cured at slightly lower temperatures,
150 to 200°C (300 to 400°F). The topcoat, usually the only coat, is applied with electrostatic spray
or with conventional airless or air spray. Most spray coating is manual, in contrast to large appliance
operations. Flow coating or dip coating is done, if the plant generally uses only 1 or 2 colors on a
line.
The coated furniture is usually baked, but in some cases it is air dried. If it is to be baked, it
passes through a flashoff area into a multizone oven at temperatures ranging from 150 to 230 °C
(300 to 450°F).
Miscellaneous Metal Parts And Products -
Both enamels (30 to 40 volume percent solids) and lacquers (10 to 20 volume percent solids)
are used to coat miscellaneous metal parts and products, although enamels are more common.
Coatings often are purchased at higher volume percent solids but are thinned before application
(frequently with aromatic solvent blends). Alkyds are popular with industrial and farm machinery
manufacturers. Most of the coatings contain several (up to 10) different solvents, including ketones,
esters, alcohols, aliphatics, ethers, aromatics, and terpenes.
Single or double coatings are applied in conveyored or batch operations. Spraying is usually
employed for single coats. Flow and dip coating may be used when only 1 or 2 colors are applied.
For 2-coat operations, primers are usually applied by flow or dip coating, and topcoats are almost
always applied by spraying. Electrostatic spraying is common. Spray booths and areas are kept at a
slight negative pressure to capture overspray.
A manual 2-coat operation may be used for large items like industrial and farm machinery.
The coatings on large products are often air dried rather than oven baked, because the machinery,
when completely assembled, includes heat sensitive materials and may be too large to be cured in an
oven. Miscellaneous parts and products can be baked in single or multipass ovens at 150 to 230 °C
(300 to 450°F).
4.2.2.4.2 Emissions And Controls
Volatile organic compounds (VOC) are emitted from application and flashoff areas and the
ovens of metal coating lines (see Figure 4.2.2.4-1). The composition of emissions varies among
coating lines according to physical construction, coating method, and type of coating applied, but
distribution of emissions among individual operations has been assumed to be fairly constant,
regardless of the type of coating line or the specific product coated, as Table 4.2.2.4-1 indicates. All
solvent used can be considered potential emissions. Emissions can be calculated from the factors in
Table 4.2.2.1-1 if coatings use is known, or from the factors in Table 4.2.2.4-1 if only a general
description of the plant is available. For emissions from the cleansing and pretreatment area, see
Section 4.6, Solvent Degreasing.
When powder coatings, which contain almost no VOC, are applied to some metal products as
a coating modification, emissions are greatly reduced. Powder coatings are applied as single coats on
some large appliance interior parts and as topcoat for kitchen ranges. They are also used on metal
bed and chair frames, shelving, and stadium seating, and they have been applied as single coats on
small appliances, small farm machinery, fabricated metal product parts, and industrial machinery
components. The usual application methods are manual or automatic electrostatic spray.
4/81 (Reformatted 1/95) Evaporation Loss Sources 4.2.2.4-3
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EMISSION FACTORS
(Reformatted 1/95) 4/81
-------
Improving transfer efficiency is a method of reducing emissions. One such technique is the
electrostatic application of the coating, and another is dip coating with waterborne paint. For
example, many makers of large appliances are now using electrodeposition to apply prime coats to
exterior parts and single coats to interiors, because this technique increases corrosion protection and
resistance to detergents. Electrodeposition of these waterborne coatings is also being used at several
metal furniture coating plants and at some farm, commercial machinery, and fabricated metal products
facilities.
Automated electrostatic spraying is most efficient, but manual and conventional methods can
be used, also. Roll coating is another option on some miscellaneous parts. Use of higher solids
coatings is a practiced technique for reduction of VOC emissions.
Carbon adsorption is technically feasible for collecting emissions from prime, top, and single-
coat applications and flashoff areas. However, the entrained sticky paint particles are a filtration
problem, and adsorbers are not commonly used.
Incineration is used to reduce organic vapor emissions from baking ovens for large
appliances, metal furniture, and miscellaneous products, and it is an option for control of emissions
from application and flashoff areas.
Table 4.2.2.4-1 gives emission factors for large appliance, metal furniture, and miscellaneous
metal parts coating lines, and Table 4.2.2.4-2 gives their estimated control efficiencies.
4/81 (Reformatted 1/95) Evaporation Loss Sources 4.2.2.4-5
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EMISSION FACTORS
(Reformatted 1/95) 4/81
-------
References For Section 4.2.2.4
1. Control Of Volatile Organic Emissions From Existing Stationary Sources, Volume III: Surface
Coating Of Metal Furniture, EPA-450/2-77-032, U. S. Environmental Protection Agency,
Research Triangle Park, NC, December 1977.
2. Control Of Volatile Organic Emissions From Existing Stationary Sources, Volume V: Surface
Coating Of Large Appliances, EPA-450/2-77-034, U. S. Environmental Protection Agency,
Research Triangle Park, NC, December 1977.
3. Control Of Volatile Organic Emissions From Existing Stationary Sources, Volume V: Surface
Coating Of Miscellaneous Metal Parts And Products, EPA-450/2-78-015,
U. S. Environmental Protection Agency, Research Triangle Park, NC, June 1978.
4. G. T. Helms, "Appropriate Transfer Efficiencies For Metal Furniture And Large Appliance
Coating", Memorandum, Office Of Air Quality Planning And Standards, U. S. Environmental
Protection Agency, Research Triangle Park, NC, November 28, 1980.
4/81 (Reformatted 1/95) Evaporation Loss Sources 4.2.2.4-7
-------
4.2.2.5 Flat Wood Interior Panel Coating
4.2.2.5.1 Process Description1
Finished flat wood construction products are interior panels made of hardwood plywoods
(natural and lauan), particle board, and hardboard.
Fewer than 25 percent of the manufacturers of such fiat wood products coat the products in
their plants, and hi some of the plants that do coat, only a small percentage of total production is
coated. At present, most coating is done by toll coaters who receive panels from manufacturers and
undercoat or finish them according to customer specifications and product requirements.
Some of the layers and coatings that can be factory-applied to flat woods are filler, sealer,
groove coat, primer, stain, basecoat, ink, and topcoat. Solvents used in organic base flat wood
coatings are usually component mixtures, including methyl ethyl ketone, methyl isobutyl ketone,
toluene, xylene, butyl acetates, propanol, ethanol, butanol, naphtha, methanol, amyl acetate, mineral
spirits, SoCal I and II, glycols, and glycol ethers. Those most often used in waterborne coatings are
glycol, glycol ethers, propanol, and butanol.
Various forms of roll coating are the preferred techniques for applying coatings to flat woods.
Coatings used for surface cover can be applied with a direct roller coater, and reverse roll coaters are
generally used to apply fillers, forcing the filler into panel cracks and voids. Precision coating and
printing (usually with offset gravure grain printers) are also forms of roll coating, and several types of
curtain coating may be employed, also (usually for topcoat application). Various spray techniques
and brush coating may be used, too.
Printed ulterior panelings are produced from plywoods with hardwood surfaces (primarily
lauan) and from various wood composition panels, including hardboard and particle board. Finishing
techniques are used to cover the original surface and to produce various decorative effects.
Figure 4.2.2.5-1 is a flow diagram showing some, but not all, typical production line variations for
printed interior paneling.
Groove coatings, applied in different ways and at different points hi the coating procedure,
are usually pigmented low resin solids reduced with water before use, therefore yielding few, if any,
emissions. Fillers, usually applied by reverse roll coating, may be of various formulations:
(1) polyester (which is ultraviolet cured) (2) water base, (3) lacquer base, (4) polyurethane, and
(5) alkyd urea base. Water base fillers are in common use on printed paneling lines.
Sealers may be of water or solvent base, usually applied by airless spray or direct roll
coating, respectively. Basecoats, which are usually direct roll coated, generally are of lacquer,
synthetic, vinyl modified alkyd urea, catalyzed vinyl, or water base.
Inks are applied by an offset gravure printing operation similar to direct roll coating. Most
lauan printing inks are pigments dispersed in alkyd resin, with some nitrocellulose added for better
wipe and printability. Water base inks have a good future for clarity, cost, and environmental
reasons. After printing, a board goes through 1 or 2 direct or precision roll coaters for application of
the clear protective topcoat. Some topcoats are synthetic, prepared from solvent soluble alkyd or
polyester resins, urea formaldehyde cross linkings, resins, and solvents.
4/81 (Reformatted 1/95) Evaporation Loss Sources 4.2.2.5-1
-------
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EMISSION FACTORS
(Reformatted 1/95) 9/91
-------
Natural hardwood plywood panels are coated with transparent or clear finishes to enhance and
protect their face ply of hardwood veneer. Typical production lines are similar to those for printed
interior paneling, except that a primer sealer is applied to the filled panel, usually by direct roll
coating. The panel is then embossed and "valley printed" to give a "distressed" or antique
appearance. No basecoat is required. A sealer is also applied after printing but before application of
the topcoat, which may be curtain coated, although direct roll coating remains the usual technique.
4.2.2.5.2 Emissions And Controls1"2
Emissions of volatile organic compounds (VOC) at flat wood coating plants occur primarily
from reverse roll coating of filler, direct roll coating of sealer and basecoat, printing of wood grain
patterns, direct roll or curtain coating of topcoat(s), and oven drying after 1 or more of those
operations (see Figure 4.2.2.5-1). All solvent used and not recovered can be considered potential
emissions. Emissions can be calculated from the factors hi Table 4.2.2.1-1 if the coating use is
known. Emissions for ulterior printed panels can be estimated from the factors in Table 4.2.2.5-1, if
the area of coated panels is known.
Waterborne coatings are increasingly used to reduce emissions. They can be applied to
almost all flat wood except redwood and, possibly, cedar. The major use of waterborne flat wood
coatings is in the filler and basecoat applied to printed interior paneling. Limited use has been made
of waterborne materials for inks, groove coats, and topcoats with printed paneling, and for inks and
groove coats with natural hardwood panels.
Ultraviolet curing systems are applicable to clear or semitransparent fillers, topcoats on
particle board coating lines, and specialty coating operations. Polyester, acrylic, urethane, and alkyd
coatings can be cured by this method.
Afterburners can be used to control VOC emissions from baking ovens, and there would seem
to be ample recovered heat to use. Extremely few flat wood coating operations have afterburners as
add-on controls, though, despite the fact that they are a viable control option for reducing emissions
where product requirements restrict the use of other control techniques.
Carbon adsorption is technically feasible, especially for specific applications (e. g., redwood
surface treatment), but the use of multicomponent solvents and different coating formulations in
several steps along the coating line has thus far precluded its use to control flat wood coating
emissions and to reclaim solvents. The use of low solvent coatings to fill pores and to seal wood has
been demonstrated.
4/81 (Reformatted 1/95) Evaporation Loss Sources 4.2.2.5-3
-------
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EMISSION FACTORS
(Reformatted 1/95) 9/91
-------
References For Section 4.2.2.5
1. Control Of Volatile Organic Emissions From Existing Stationary Sources, Volume VII:
Factory Surface Coating Of Flat Wood Interior Paneling, EPA-450/2-78-032, U. S.
Environmental Protection Agency, Research Triangle Park, NC, June 1978.
2. Air Pollution Control Technology Applicable To 26 Sources Of Volatile Organic Compounds,
Office Of Air Quality Planning And Standards, U. S. Environmental Protection Agency,
Research Triangle Park, NC, May 27, 1977. Unpublished.
3. Products Finishing, 47(6A):4-54, March 1977.
4/81 (Reformatted 1/95) Evaporation Loss Sources 4.2.2.5-5
-------
4.2.2.6 Paper Coating
4.2.2.6.1 Process Description1"2
Paper is coated for various decorative and functional purposes with waterborne, organic
solventborne, or solvent-free extruded materials. Paper coating is not to be confused with printing
operations, which use contrast coatings that must show a difference in brightness from the paper to be
visible. Coating operations are the application of a uniform layer or coating across a substrate.
Printing results hi an image or design on the substrate.
Waterborne coatings improve printability and gloss but cannot compete with organic
solventborne coatings in resistance to weather, scuff, and chemicals. Solventborne coatings, as an
added advantage, permit a wide range of surface textures. Most solventborne coating is done by
paper converting companies that buy paper from mills and apply coatings to produce a final product.
Among the many products that are coated with solventborne materials are adhesive tapes and labels,
decorated paper, book covers, zinc oxide-coated office copier paper, carbon paper, typewriter
ribbons, and photographic film.
Organic solvent formulations generally used are made up of film-forming materials,
plasticizers, pigments, and solvents. The main classes of film formers used in paper coating are
cellulose derivatives (usually nitrocellulose) and vinyl resins (usually the copolymer of vinyl chloride
and vinyl acetate). Three common plasticizers are dioctyl phthalate, tricresyl phosphate, and castor
oil. The major solvents used are toluene, xylene, methyl ethyl ketone, isopropyl alcohol, methanol,
acetone, and ethanol. Although a single solvent is frequently used, a mixture is often necessary to
obtain the optimum drying rate, flexibility, toughness, and abrasion resistance.
A variety of low solvent coatings, with negligible emissions, have been developed for some
uses to form organic resin films equal to those of conventional solventborne coatings. They can be
applied up to 1/8 inch thick (usually by reverse roller coating) to products like artificial leather goods,
book covers, and carbon paper. Smooth hot melt finishes can be applied over rough textured paper
by heated gravure or roll coaters at temperatures from 65 to 230°C (150 to 450°F).
Plastic extrusion coating is a type of hot melt coating in which a molten thermoplastic sheet
(usually low or medium density polyethylene) is extruded from a slotted die at temperatures of up to
315°C (600°F). The substrate and the molten plastic coat are united by pressure between a rubber
roll and a chill roll which solidifies the plastic. Many products, such as the polyethylene-coated milk
carton, are coated with solvent-free extrusion coatings.
Figure 4.2.2.6-1 shows a typical paper coating line that uses organic solventborne
formulations. The application device is usually a reverse roller, a knife, or a rotogravure printer.
Knife coaters can apply solutions of much higher viscosity than roll coaters can, thus emitting less
solvent per pound of solids applied. The gravure printer can print patterns or can coat a solid sheet
of color on a paper web.
Ovens may be divided into from 2 to 5 temperature zones. The first zone is usually at about
430°C (110°F), and other zones have progressively higher temperatures to cure the coating after most
solvent has evaporated. The typical curing temperature is 120°C (250°F), and ovens are generally
limited to 200°C (400°F) to avoid damage to the paper. Natural gas is the fuel most often used in
4/81 (Reformatted 1/95) Evaporation Loss Sources 4.2.2.6-1
-------
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(Reformatted 1/95) 4/81
-------
direct-fired ovens, but fuel oil is sometimes used. Some of the heavier grades of fuel oil can create
problems, because sulfur oxide (SO) and paniculate may contaminate the paper coating. Distillate
fuel oil usually can be used satisfactorily. Steam produced from burning solvent retrieved from an
adsorber or vented to an incinerator may also be used to heat curing ovens.
4.2.2.6.2 Emissions And Controls2
The main emission points from paper coating lines are the coating applicator and the oven
(see Figure 4.2.2.6-1). In a typical paper-coating plant, about 70 percent of all solvents used are
emitted from the coating lines, with most coming from the first zone of the oven. The other
30 percent are emitted from solvent transfer, storage, and mixing operations and can be reduced
through good housekeeping practices. All solvent used and not recovered or destroyed can be
considered potential emissions.
Volatile organic compound (VOC) emissions from individual paper coating plants vary with
size and number of coating lines, line construction, coating formulation, and substrate composition, so
each must be evaluated individually. VOC emissions can be estimated from the factors in
Table 4.2.2.6-1 if coating use is known and sufficient information on coating composition is
available. Since many paper coating formulas are proprietary, it may be necessary to have
information on the total solvent used and to assume that, unless a control device is used, essentially
all solvent is emitted. Rarely would as much as 5 percent be retained in the product.
Table 4.2.2.6-1. CONTROL EFFICIENCIES FOR PAPER COATING LINES*
Affected Facility
Coating line
Control Method
Incineration
Carbon adsorption
Low solvent coating
Efficiency (%)
95
90+
80 - 99b
a Reference 2.
b Based on comparison with a conventional coating containing 35% solids and 65% organic solvent,
by volume.
Almost all solvent emissions from the coating lines can be collected and sent to a control
device. Thermal incinerators have been retrofitted to a large number of oven exhausts, with primary
and even secondary heat recovery systems heating the ovens. Carbon adsorption is most easily
adaptable to lines which use single solvent coating. If solvent mixtures are collected by adsorbers,
they usually must be distilled for reuse.
Although available for some products, low solvent coatings are not yet available for all
paper-coating operations. The nature of the products, such as some types of photographic film, may
preclude development of a low-solvent option. Furthermore, the more complex the mixture of
organic solvents in the coating, the more difficult and expensive to reclaim them for reuse with a
carbon adsorption system.
4/81 (Reformatted 1/95) Evaporation Loss Sources 4.2.2.6-3
-------
References For Section 4.2.2.6
1. T. W. Hughes, et al., Source Assessment: Prioritization Of Air Pollution From Industrial
Surface Coating Operations, EPA-650/2-75-019a, U. S. Environmental Protection Agency,
Cincinnati, OH, February 1975.
2. Control Of Volatile Organic Emissions From Existing Stationary Sources, Volume II: Surface
Coating Of Cans, Coils, Paper Fabrics, Automobiles, And Light Duty Trucks,
EPA-450/2-77-008, U. S. Environmental Protection Agency, Research Triangle Park, NC,
May 1977.
4.2.2.6-4 EMISSION FACTORS (Reformatted 1/95) 4/81
-------
4.2.2.7 Polymeric Coating Of Supporting Substrates1"8
"Polymeric coating of supporting substrates" is defined as a web coating process other than
paper coating that applies an elastomer or other polymeric material onto a supporting substrate.
Typical substrates include woven, knit, and nonwoven textiles; fiberglass; leather; yarn; and cord.
Examples of polymeric coatings are natural and synthetic rubber, urethane, polyvinyl chloride,
acrylic, epoxy, silicone, phenolic resins, and nitrocellulose. Plants have from 1 to more than
10 coating lines. Most plants are commission coaters where coated substrates are produced according
to customer specifications. Typical products include rainwear, conveyor belts, V-belts, diaphragms,
gaskets, printing blankets, luggage, and aircraft and military products. This industrial source
category has been retitled from "Fabric Coating" to that listed above to reflect the general use of
polymeric coatings on substrate materials including but not limited to conventional textile fabric
substrates.
4.2.2.7.1 Process Description1"3
The process of applying a polymeric coating to a supporting substrate consists of mixing the
coating ingredients (including solvents), conditioning the substrate, applying the coating to the
substrate, drying/curing the coating in a drying oven, and subsequent curing or vulcanizing if
necessary. Figure 4.2.2.7-1 is a schematic of a typical solvent-borne polymeric coating operation
identifying volatile organic compound (VOC) emission locations. Typical plants have 1 or 2 small
(<38 m3 or 10,000 gallons) horizontal or vertical solvent storage tanks that are operated at
atmospheric pressure; however, some plants have as many as 5. Coating preparation equipment
includes the mills, mixers, holding tanks, and pumps used to prepare polymeric coatings for
application. Urethane coatings typically are purchased premixed and require little or no mixing at the
coating plant. The conventional types of equipment for applying organic solvent-borne and
waterborne coatings include knife-over-roll, dip, and reverse-roll coaters Once applied to the
substrate, liquid coatings are solidified by evaporation of the solvent in a steam-heated or direct-fired
oven. Drying ovens usually are of forced-air convection design in order to maximize drying
efficiency and prevent a dangerous localized buildup of vapor concentration or temperature. For safe
operation, the concentration of organic vapors is usually held between 10 and 25 percent of the lower
explosive limit (LEL). Newer ovens may be designed for concentrations of up to 50 percent of the
LEL through the addition of monitors, alarms, and fail-safe shutdown systems. Some coatings
require subsequent curing or vulcanizing in separate ovens.
4.2.2.7.2 Emission Sources1"3
The significant VOC emission sources in a polymeric coating plant include the coating
preparation equipment, the coating application and flashoff area, and the drying ovens. Emissions
from the solvent storage tanks and the cleanup area are normally only a small percentage of the total.
In the mixing or coating preparation area, VOCs are emitted from the individual mixers and
holding tanks during the following operations: filling of mixers, transfer of the coating, intermittent
activities such as changing the filters in the holding tanks, and mixing (if mix equipment is not
equipped with tightly fitting covers). The factors affecting emissions hi the mixing area include tank
size, number of tanks, solvent vapor pressure, throughput, and the design and performance of tank
covers.
9/88 (Reformatted 1/95) Evaporation Loss Sources 4.2.2.7-1
-------
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EMISSION FACTORS
(Reformatted 1/95) 9/88
-------
Emissions from the coating application area result from the evaporation of solvent around the
coating application equipment during the application process and from the exposed substrate as it
travels from the coater to the drying oven entrance (flashoff). The factors affecting emissions are the
solvent content of the coating, line width and speed, coating thickness, volatility of the solvents),
temperature, distance between coater and oven, and air turbulence in the coating area.
Emissions from the drying oven result from the fraction of the remaining solvent that is
driven off in the oven. The factors affecting uncontrolled emissions are the solvent content of the
coating and the amount of solvent retained in the finished product. Fugitive emissions due to the
opening of oven doors also may be significant in some operations. Some plasticizers and reaction
byproducts may be emitted if the coating is subsequently cured or vulcanized. However, emissions
from the curing or vulcanizing of the coating are usually negligible compared to the total emissions
from the operation.
Solvent type and quantity are the common factors affecting emissions from all the operations
in a polymeric coating facility. The rate of evaporation or drying is dependent upon solvent vapor
pressure at a given temperature and concentration. The most commonly used organic solvents are
toluene, dimethyl fonnamide (DHF), acetone, methyl ethyl ketone (MEK), isopropyl alcohol, xylene,
and ethyl acetate. Factors affecting solvent selection are cost, solvency, toxicity, availability, desired
rate of evaporation, ease of use after solvent recovery, and compatibility with solvent recovery
equipment.
4.2.2.7.3 Emissions Control1'2-4'7
A control system for evaporative emissions consists of 2 components: a capture device and a
control device. The efficiency of the control system is determined by the efficiencies of the
2 components.
A capture device is used to contain emissions from a process operation and direct them to a
stack or to a control device. Covers, vents, hoods, and partial and total enclosures are alternative
capture devices used on coating preparation equipment. Hoods and partial and total enclosures are
typical capture devices for use hi the coating application area. A drying oven can be considered a
capture device because it both contains and directs VOC emissions from the process. The efficiency
of capture devices is variable and depends upon the quality of design and the level of operation and
maintenance.
A control device is any equipment that has as its primary function the reduction of emissions.
Control devices typically used in this industry are carbon adsorbers, condensers, and incinerators.
Tightly fitting covers on coating preparation equipment may be considered both capture and control
devices.
Carbon adsorption units use activated carbon to adsorb VOCs from a gas stream; the VOCs
are later recovered from the carbon. Two types of carbon adsorbers are available: fixed-bed and
fluidized bed. Fixed-bed carbon adsorbers are designed with a steam-stripping technique to recover
the VOC material and regenerate the activated carbon. The fluidized-bed units used in this industry
are designed to use nitrogen for VOC vapor recovery and carbon regeneration. Both types achieve
typical VOC control efficiencies of 95 percent when properly designed, operated, and maintained.
Condensation units control VOC emissions by cooling the solvent-laden gas to the dew point
of the solvents) and collecting the droplets. There are 2 condenser designs commercially available:
nitrogen (inert gas) atmosphere, and air atmosphere. These systems differ in the design and operation
9/88 (Reforniatted 1/95) Evaporation Loss Sources 4.2.2.7-3
-------
of the drying oven (i. e., use of nitrogen or air in the oven) and in the method of cooling the solvent
laden air (i. e., liquified nitrogen or refrigeration). Both design types can achieve VOC control
efficiencies of 95 percent.
Incinerators control VOC emissions through oxidation of the organic compounds into carbon
dioxide and water. Incinerators used to control VOC emissions may be of thermal or catalytic design
and may use primary or secondary heat recovery to reduce fuel costs. Thermal incinerators operate
at approximately 890°C (1600°F) to ensure oxidation of the organic compounds. Catalytic
incinerators operate in the rage of 325 to 430°C (600 to 800°F) while using a catalyst to achieve
comparable oxidation of VOCs. Both design types achieve a typical VOC control efficiency of
98 percent.
Tightly fitting covers control VOC emissions from mix vessels by reducing evaporative
losses. Airtight covers can be fitted with conservation vents to avoid excessive internal pressure or
vacuum. The parameters affecting the efficiency of these controls are solvent vapor pressure, cyclic
temperature change, tank size, throughput, and the pressure and vacuum settings on the conservation
vents. A good system of tightly fitting covers on mixing area vessels is estimated to reduce emissions
by approximately 40 percent. Control efficiencies of 95 or 98 percent can be obtained by directing
the captured VOCs to an adsorber, condenser, or incinerator.
When the efficiencies of the capture device and control device are known, the efficiency of
the control system can be computed by the following equation:
(capture efficiency) x (control efficiency) = (control system efficiency)
The terms of this equation are fractional efficiencies rather than percentages. For instance, a system
of hoods delivering 60 percent of VOC emissions to a 90 percent efficient carbon adsorber would
result in a control system efficiency of 54 percent (0.60 x 0.90 = 0.54). Table 4.2.2.7-1 summarizes
the control system efficiencies that may be used in the absence of measured data on mix equipment
and coating operations.
Table 4.2.2.7-1. SUMMARY OF CONTROL EFFICIENCIES*
Control Technology
Coating Preparation Equipment
Uncontrolled
Sealed covers with conservation vents
Sealed covers with carbon adsorber/condenser
Coating Operations'
Local ventilation with carbon adsorber/condenser
Partial enclosure with carbon adsorber/condenser
Total enclosure with carbon adsorber/condenser
Total enclosure with incinerator
.c
Overall Control Efficiency, %l
0
40
95
81
90
93
96
a Reference 1. To be used in the absence of measured data.
b To be applied to uncontrolled emissions from indicated process area, not from entire plant.
c Includes coating application/flashoff area and drying oven.
4.2.2.7-4 EMISSION FACTORS (Reformatted 1/95) 9/88
-------
4.2.2.7.4 Emissions Estimation Techniques1'4"8
In this diverse industry, realistic estimates of emissions require solvent usage data. Due to
the wide variation found in coating formulations, line speeds, and products, no meaningful inferences
can be made based simply on the equipment present.
Plantwide emissions can be estimated by performing a liquid material balance in uncontrolled
plants and in those where VOCs are recovered for reuse or sale. This technique is based on the
assumption that all solvent purchased replaces VOC's which have been emitted. Any identifiable and
quantifiable side-streams should be subtracted from this total. The general formula for this is:
/ solvent \ _ / quantifiable \ = / VOC \
\ purchased/ \solvent output/ \emitted/
The first term encompasses all solvent purchased including thinners, cleaning agents, and the solvent
content of any premixed coatings, as well as any solvent directly used in coating formulation. From
this total, any quantifiable solvent outputs are subtracted. These outputs may include solvent retained
hi the finished product, reclaimed solvent sold for use outside the plant, and solvent contained in
waste streams. Reclaimed solvent which is reused at the plant is not subtracted.
The advantages of this method are that it is based on data that are usually readily available, it
reflects actual operations rather than theoretical steady-state production and control conditions, and it
includes emissions from all sources at the plant. However, care should be taken not to apply this
method over too short a time span. Solvent purchases, production, and waste removal occur hi then-
own cycles, which may not coincide exactly.
Occasionally, a liquid material balance may be possible on a smaller scale than the entire
plant. Such an approach may be feasible for a single coating line or group of lines served by a
dedicated mixing area and a dedicated control and recovery system. In this case, the computation
begins with total solvent metered to the mixing area instead of solvent purchased. Reclaimed solvent
is subtracted from this volume whether or not it is reused onsite. Of course, other solvent input and
output streams must be accounted for as previously indicated. The difference between total solvent
input and total solvent output is then taken to be the quantity of VOCs emitted from the equipment in
question.
The configuration of meters, mixing areas, production equipment, and controls usually will
not make this approach possible. In cases where control devices destroy potential emissions or a
liquid material balance is inappropriate for other reasons, plant-wide emissions can be estimated by
summing the emissions calculated for specific areas of the plant. Techniques for these calculations
are presented below.
Estimating VOC emissions from a coating operation (application/flashoff area and drying
oven) starts with the assumption that the uncontrolled emission level is equal to the quantity of solvent
contained in the coating applied. In other words, all the VOC hi the coating evaporates by the end of
the drying process. This quantity should be adjusted downward to account for solvent retained in the
finished product in cases where it is quantifiable and significant.
Two factors are necessary to calculate the quantity of solvent applied: the solvent content of
the coating and the quantity of coating applied. Coating solvent content can be directly measured
using EPA Reference Method 24. Alternative ways of estimating the VOC content include the use of
9/88 (Reformatted 1/95) Evaporation Loss Sources 4.2.2.7-5
-------
either data on coating formulation that are usually available from the plant owner/operator or
premixed coating manufacturer or, if these cannot be obtained, approximations based on the
information in Table 4.2.2.7-2. The amount of coating applied may be directly metered. If it is not,
it must be determined from production data. These should be available from the plant
owner/operator. Care should be taken in developing these 2 factors to ensure that they are in
compatible units.
Table 4.2.2.7-2. SOLVENT AND SOLIDS CONTENT OF POLYMERIC COATINGS*
Polymer Type
Rubber
Urethanes
Acrylics
Vinylc
Vinyl plastisol
Organisol
Epoxies
Silicone
Nitrocellulose
Typical Percentage, By Weight
% solvent
50-70
50-60
_b
60-80
5
15-40
30-40
50-60
70
% solids
30
40
20
60
60
40
-50
-50
50
-40
95
-85
-70
-50
30
a Reference 1.
b Organic solvents are generally not used in the formulation of acrylic coatings. Therefore, the
solvent content for acrylic coatings represents nonorganic solvent use (i. e., water).
c Solventborne vinyl coating.
When an estimate of uncontrolled emissions is obtained, the controlled emissions level is
computed by applying a control system efficiency factor:
/uncontrolled^
\ VOC /
1 - control system efficiency)
/ VOC \
Remitted/
As previously explained, the control system efficiency is the product of the efficiencies of the capture
device and the control device. If these values are not known, typical efficiencies for some
combinations of capture and control devices are presented in Table 4.2.2.7-1. It is important to note
that these control system efficiencies are applicable only to emissions that occur within the areas
served by the systems. Emissions from such sources as process wastewater or discarded waste
coatings may not be controlled at all.
In cases where emission estimates from the mixing area alone are desired, a slightly different
approach is necessary. Here, uncontrolled emissions will be only that portion of total solvent that
evaporates during the mixing process. A liquid material balance across the mixing area (i. e., solvent
entering minus solvent content of coating applied) would provide a good estimate. In the absence of
4.2.2.7-6
EMISSION FACTORS
(Reformatted 1/95) 9/88
-------
any measured value, it may be assumed that approximately 10 percent of the total solvent entering the
mixing area is emitted during the mixing process, but this can vary widely. When an estimate of
uncontrolled mixing area emissions has been made, the controlled emission rate can be calculated as
discussed previously. Table 4.2.2.7-1 lists typical overall control efficiencies for coating mix
preparation equipment.
Solvent storage tanks of the size typically found in this industry are regulated by only a few
States and localities. Tank emissions are generally small (< 125 kg/yr [275 lb/yr]). If an estimate of
emissions is desired, it can be computed using the equations, tables, and figures provided in
Chapter 7.
References For Section 4.2.2.7
1. Polymeric Coating Of Supporting Substrates, Background Information For Proposed
Standards, EPA-450/3-85-022a, U. S. Environmental Protection Agency, Research Triangle
Park, NC, October 1985.
2. Control Of Volatile Organic Emissions From Existing Stationary Sources — Volume II:
Surface Coating Of Cans, Coils, Paper, Fabrics, Automobiles, and Light Duty Trucks,
EPA-450/2-77-008, U. S. Environmental Protection Agency, Research Triangle Park, NC,
May 1977.
3. E. J. Maurer, "Coating Operation Equipment Design And Operating Parameters",
Memorandum To Polymeric Coating Of Supporting Substrates File, MRS, Raleigh, NC,
April 23, 1984.
4. Control Of Volatile Organic Emissions From Existing Stationary Sources, Volume I: Control
Methods For Surface-Coating Operations, EPA-450/2-76-028, U. S. Environmental Protection
Agency, Research Triangle Park, NC, November 1976.
5. G. Crane, Carbon Adsorption For VOC Control, U. S. Environmental Protection Agency,
Research Triangle Park, NC, January 1982.
6. D. Moscone, "Thermal Incinerator Performance For NSPS", Memorandum, Office Of Air
Quality Planning And Standards, U. S. Environmental Protection Agency, Research Triangle
Park, NC, June 11, 1980.
7. D. Moscone, "Thermal Incinerator Performance For NSPS, Addendum", Memorandum,
Office Of Air Quality Planning And Standards, U. S. Environmental Protection Agency,
Research Triangle Park, NC, July 22, 1980.
8. C. Beall, "Distribution Of Emissions Between Coating Mix: Preparation Area And The
Coating Line", Memorandum To Magnetic Tape Coating Project File, MRS, Raleigh, NC,
June 22, 1984.
9/88 (Reformatted 1/95) Evaporation Loss Sources 4.2.2.7-7
-------
4.2.2.8 Automobile And Light Duty Truck Surface Coating Operations1"4
4.2.2.8.1 General
Surface coating of an automobile body is a multistep operation carried out on an assembly line
conveyor system. Such a line operates at a speed of 3 to 8 meters (9 to 25 feet) per minute and
usually produces 30 to 70 units per hour. An assembly plant may operate up to 2 8-hour production
shifts per day, with a third shift used for cleanup and maintenance. Plants may stop production for a
vacation of one-and-a-half weeks at Christmas through New Year's Day and may stop for several
weeks in summer for model changeover.
Although finishing processes vary from plant to plant, they have some common
characteristics. Major steps of such processes are:
Solvent* wipe Curing of guide coat
Phosphating treatment Application of topcoat(s)
Application of prime coat Curing of topcoat(s)
Curing of prime coat Final repair operations
Application of guide coat
A general diagram of these consecutive steps is presented in Figure 4.2.2.8-1. Application of
a coating takes place in a dip tank or spray booth, and curing occurs in the flashoff area and bake
oven. The typical structures for application and curing are contiguous, to prevent exposure of the wet
body to the ambient environment before the coating is cured.
The automobile body is assembled from a number of welded metal sections. The body and
the parts to be coated all pass through the same metal preparation process.
Fkst, surfaces are wiped with solvent to eliminate traces of oil and grease. Second, a
phosphating process prepares surfaces for the primer application. Since iron and steel rust readily,
phosphate treatment is necessary to retard such. Phosphating also improves the adhesion of the
primer and the metal. The phosphating process occurs in a multistage washer, with detergent
cleaning, rinsing, and coating of the metal surface with zinc phosphate. The parts and bodies pass
through a water spray cooling process. If solventborne primer is to be applied, they are then oven
dried.
A primer is applied to protect the metal surface from corrosion and to ensure good adhesion
of subsequent coatings. Approximately half of all assembly plants use solventborne primers with a
combination of manual and automatic spray application. The rest use waterborne primers. As new
plants are constructed and existing plants modernized, the use of waterborne primers is expected to
increase.
Waterborne primer is most often applied in an electrodeposition (EDP) bath. The
composition of the bath is about 5 to 15 volume percent solids, 2 to 10 percent solvent, and the rest
water. The solvents used are typically organic compounds of higher molecular weight and low
volatility, like ethylene glycol monobutyl ether.
aThe term "solvent" here means organic solvent.
8/82 (Reformatted 1/95) Evaporation Loss Sources 4.2.2.8-1
-------
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When EDP is used, a guide coat (also called a primer surfacer) is applied between the primer
and the topcoat to build film thickness, to fill hi surface imperfections, and to permit sanding between
the primer and topcoat. Guide coats are applied by a combination of manual and automatic spraying
and can be solventborne or waterborne. Powder guide coat is used at one light duty truck plant.
The topcoat provides the variety of colors and surface appearance to meet customer demand.
Topcoats are applied in 1 to 3 steps to ensure sufficient coating thickness. An oven bake may follow
each topcoat application, or the coating may be applied wet on wet. At a minimum, the final topcoat
is baked in a high-temperature oven.
Topcoats hi the automobile industry traditionally have been solventborne lacquers and
enamels. Recent trends have been to higher solids content. Powder topcoats have been tested at
several plants.
The current trend hi the industry is toward base coat/clear coat (BC/CC) topcoating systems,
consisting of a relatively thin application of highly pigmented metallic base coat followed by a thicker
clear coat. These BC/CC topcoats have more appealing appearance than do single coat metallic
topcoats, and competitive pressures are expected to increase then- use by U. S. manufacturers.
The VOC content of most BC/CC coatings hi use today is higher than that of conventional
enamel topcoats. Development and testing of lower VOC content (higher solids) BC/CC coatings are
being done, however, by automobile manufacturers and coating suppliers.
Following the application of the topcoat, the body goes to the trim operation area, where
vehicle assembly is completed. The final step of the surface coating operation is generally the final
repair process, hi which damaged coating is repaired hi a spray booth and is air dried or baked in a
low temperature oven to prevent damage of heat sensitive plastic parts added hi the trim operation
area.
4.2.2.8.2 Emissions And Controls
Volatile organic compounds (VOC) are the major pollutants from surface coating operations.
Potential VOC emitting operations are shown hi Figure 4.2.2.8-1. The application and curing of the
prime coat, guide coat, and topcoat account for 50 to 80 percent of the VOC emitted from assembly
plants. Final topcoat repair, cleanup, and miscellaneous sources such as the coating of small
component parts and application of sealants, account for the remaining 20 percent. Approximately
75 to 90 percent of the VOC emitted during the application and curing process is emitted from the
spray booui and flashoff area, and 10 to 25 percent from the bake oven. This emissions split is
heavily dependent on the types of solvents used and on transfer efficiency. With unproved transfer
efficiencies and the newer coatings, it is expected that the percent of VOC emitted from the spray
booth and the flashoff area will decrease, and the percent of VOC emitted from the bake oven will
remain fairly constant. Higher solids coatings, with then- slower solvents, will tend to have a greater
fraction of emissions from the bake oven.
Several factors affect the mass of VOC emitted per vehicle from surface coating operations in
the automotive industry. Among these are:
VOC content of coatings (pounds of coating, less water)
Volume solids content of coating
Area coated per vehicle
8/82 (Reformatted 1/95) Evaporation Loss Sources 4.2.2.8-3
-------
Film thickness
Transfer efficiency
The greater the quantity of VOC in the coating composition, the greater will be the emissions.
Lacquers having 12 to 18 volume percent solids are higher in VOCs than enamels having 24 to
33 volume percent solids. Emissions are also influenced by the area of the parts being coated, the
coating thickness, the configuration of the part, and the application technique.
The transfer efficiency (fraction of the solids in the total consumed coating that remains on the
part) varies with the type of application technique. Transfer efficiency for typical air atomized
spraying ranges from 30 to 50 percent. The range for electrostatic spraying, an application method
that uses an electrical potential to increase transfer efficiency of the coating solids, is from 60 to
95 percent. Both air atomized and electrostatic spray equipment may be used in the same spray
booth.
Several types of control techniques are available to reduce VOC emissions from automobile
and light duty truck surface coating operations. These methods can be broadly categorized as either
control devices or new coating and application systems. Control devices reduce emissions by either
recovering or destroying VOC before it is discharged into the ambient air. Such techniques include
thermal and catalytic incinerators on bake ovens, and carbon absorbers on spray booths. New
coatings with relatively low VOC levels can be used in place of high-VOC-content coatings. Such
coating systems include electrodeposition of waterborne prune coatings, and for top coats, air spray of
waterborae enamels and air or electrostatic spray of high solids, solventborne enamels and powder
coatings. Improvements in the transfer efficiency decrease the amount of coating which must be used
to achieve a given film thickness, thereby reducing emissions of VOC to the ambient air.
Calculation of VOC emissions for representative conditions provides the emission factors in
Table 4.2.2.8-1. The factors were calculated with the typical value of parameters present in
Tables 4.2.2.8-2 and 4.2.2.8-3. The values for the various parameters for automobiles and light duty
trucks represent average conditions existing in the automobile and light duty truck industry in 1980.
A more accurate estimate of VOC emissions can be calculated with the equation in Table 4.2.2.8-1
and with site-specific values for the various parameters.
Emission factors are not available for final topcoat repair, cleanup, coating of small parts, and
application of sealants.
4.2.2.8-4 EMISSION FACTORS (Reformatted 1/95) 8/82
-------
Table 4.2.2.8-1 (Metric And English Units). EMISSION FACTORS FOR AUTOMOBILE AND
LIGHT DUTY TRUCK SURFACE COATING OPERATIONS11
EMISSION FACTOR RATING: C
Coating
Prime Coat
Solventborne spray
Cathodic electrodeposition
Guide Coat
Solventborne spray
Waterborne spray
Topcoat
Lacquer
Dispersion lacquer
Enamel
Basecoat/clear coat
Waterborne
Automobile
kg(lb)OfVOC
Per Vehicle
6.61
(14.54)
0.21
(0.45)
1.89
(4.16)
0.68
(1.50)
21.96
(48.31)
14.50
(31.90)
7.08
(15.58)
6.05
(13.32)
2.25
(4.95)
Per Hourb
363
(799)
12
(25)
104
(229)
38
(83)
1208
(2657)
798
(1755)
390
(857)
333
(732)
124
(273)
Light Duty Truck
kgOb)OfVOC
Per Vehicle
19.27
(42.39)
0.27
(0.58)
6.38
(14.04)
2.3
(5.06)
NA
NA
17.71
(38.96)
18.91
(41.59)
7.03
(15.47)
Per Hourc
732
(1611)
10
(22)
243
(534)
87
(192)
NA
NA
673
(1480)
719
(1581)
267
(588)
a All nonmethane VOC. Factors are calculated using the following equation and the typical values of
parameters presented in Tables 4.2.2.8-2 and 4.2.2.8-3. NA = not applicable.
Tf Vc
8/82 (Reformatted 1/95)
Evaporation Loss Sources
4.2.2.8-5
-------
Table 4.2.2.8-1 (cont.).
where:
Ey = emission factor for VOC, mass per vehicle Ob/vehicle) (exclusive of any add-on
control devices)
Ay = area coated per vehicle (ft2/vehicle)
GI = conversion factor: 1 ft/12,000 mil
Tf = thickness of the dry coating film (mil)
Vc = VOC (organic solvent) content of coating as applied, less water Ob VOC/gal coating,
less water)
Cj = conversion factor: 7.48 gal/ft3
S0 = solids in coating as applied, volume fraction (gal solids/gal coating)
e-r = transfer efficiency fraction (fraction of total coating solids used that remains on coated
parts)
Example: The VOC emissions per automobile from a cathodic electrodeposited prime coat.
(850 ft2) (1/12000) (0.6 mil) (1.2 lb/gal-H2O) (7.58 gal/ft3)
mass of VOC =
(0.84 gal/gal) (1.00)
= 0.45 Ib VOC/vehicle (0.21 kg VOC/vehicle)
b Based on an average line speed of 55 automobiles/hr.
c Based on an average line speed of 38 light duty trucks/hr.
4.2.2.8-6 EMISSION FACTORS (Reformatted 1/95) 8/82
-------
Table 4.2.2.8-2 (English Units). PARAMETERS FOR THE AUTOMOBILE SURFACE
COATING INDUSTRY1
Application
Prime coat
Solventbome spray
Cathodic electrodeposition
Guide coat
Solventbome spray
Watetborne spray
Topcoat
Solventbome spray
Lacquer
Dispersion lacquer
Enamel
Base coat/clear coatb
Base coat
Clear coat
Waterborne spray
Area Coated
Per Vehicle,
fl?
450
(220-570)
850
(660-1060)
200
(170-280)
200
(170-280)
240
(170-280)
240
(170-280)
240
(170-280)
240
240
(170-280)
240
(170-280)
240
(170-280)
Film
Thickness,
mil
0.8
(0.3-2.5)
0.6
(0.5-0.8)
0.8
(0.5-1.5)
0.8
(0.5-2.0)
2.5
(1.0-3.0)
2.5
(1.0-3.0)
2.5
(1.0-3.0)
2.5
1.0
(0.8-1.0)
1.5
(1.2-1.5)
2.2
(1.0-2.5)
1 VOC Content,
lb/gal-H2O
5.7
(4.2-6.0)
1.2
(1.2-1.5)
5.0
(3.0-5.6)
2.8
(2.6-3.0)
6.2
(5.8-6.6)
5.8
(4.9-5.8)
5.0
(3.0-5.6)
4.7
5.6
(3.-M5.4)
4.0
(3.0-5.1)
2.8
(2.6-3.0)
Volume
Fraction
Solids,
gal/gal-HjO
0.22
(0.20-0.35)
0.84
(0.84-0.87)
0.30
(0.25-0.55)
0.62
(0.60-0.65)
0.12
(0.10-0.13)
0.17
(0.17-0.27)
0.30
(0.25-0.55)
0.33
0.20
(0.13-0.48)
0.42
(0.30-0.54)
0.62
(0.60-0.65)
Transfer
Efficiency,
%
40
(35-50)
100
(85-100)
40
(35-65)
30
(25-40)
40
(30-65)
40
(3(W>5)
40
(30-65)
40
40
(30-50)
40
(30-65)
30
(25-40)
a All values for coatings as applied except for VOC content and volume fraction solids that are for
coatings as applied minus water. Ranges in parentheses. Low VOC content (high solids) base
coat/clear coats are still undergoing testing and development.
b Composite of base coat and clear coat.
8/82 (Reformatted 1/95)
Evaporation Loss Sources
4.2.2.8-7
-------
Table 4.2.2.8-3 (English Units). PARAMETERS FOR THE LIGHT DUTY TRUCK SURFACE
COATING INDUSTRY"
Application
Prime coat
Solventbome spray
Cathodic electrodeposition
Guide coat
Solventbome spray
Waterbome spray
Topcoat
Solventbome spray
Enamel
Base coat/clear coatb
Base coat
Clear coat
Waterbome spray
Area Coated
Per Vehicle,
&
875
(300-1000)
1100
(850-1250)
675
(180-740)
675
(180-740)
750
(300-900)
750
750
(300-900)
750
(300-900)
750
(300-900)
Film
Thickness,
mil
1.2
(0.7-1.7)
0.6
(0.5-0.8)
0.8
(0.7-1.7)
0.8
(0.5-2.0)
2.0
(1.0-2.5)
2.5
1.0
(0.8-1.0)
1.5
(1.2-1.5)
2.2
(1.0-2.5)
VOC Content,
Ib/gal-H2O
5.7
(4.2-3.0)
1.2
(1.2-1.5)
5.0
(3.0-5.6)
2.8
(2.6-3.0)
5.0
(3.0-5.6)
4.7
5.6
(3.4-6.4)
4.0
(3.0-5.1)
2.8
(2.6-3.0)
Volume
Fraction
Solids,
gal/gal-HjO
0.22
(0.20-0.35)
0.84
(0.84-0.87)
0.30
(0.25-0.55)
0.62
(0.60-0.65)
0.30
(0.25-0.55)
0.33
0.20
(0.13-0.48)
0.42
(0.30-0.54)
0.62
(0.60-0.65)
Transfer
Efficiency,
%
40
(35-50)
100
(85-100)
40
(35-€5)
30
(25-40)
40
(30-65)
40
40
(30-50)
40
(30-65)
30
(25-40)
a All values for coatings as applied, except for VOC content and volume fraction solids that are for
coatings as applied minus water. Ranges in parentheses. Low VOC content (high solids) base
coat/clear coats are still undergoing testing and development.
b Composite of typical base coat and clear coat.
References For Section 4.2.2.8
1. Control Of Volatile Organic Emissions From Existing Stationary Sources — Volume II:
Surface Coating Of Cans, Coils, Paper Fabrics, Automobiles, And Ught Duty Trucks,
EPA-450/2-77-008, U. S. Environmental Protection Agency, Research Triangle Park, NC,
May 1977.
2. Study To Determine Capabilities To Meet Federal EPA Guidelines For Volatile Organic
Compound Emissions, General Motors Corporation, Detroit, MI, November 1978.
4.2.2.8-8
EMISSION FACTORS
(Reformatted 1/95) 8/82
-------
3. Automobile And Light Duty Truck Surface Coating Operations — Background Information For
Proposed Standards, EPA-450/3-79-030, U. S. Environmental Protection Agency, Research
Triangle Park, NC, September 1979.
4. Written communication from D. A. Frank, General Motors Corporation, Warren, MI, to
H. J. Modetz, Acurex Corporation, Morrisville, NC, April 14, 1981.
8/82 (Reformatted 1/95) Evaporation Loss Sources 4.2.2.8-9
-------
4.2.2.9 Pressure Sensitive Tapes And Labels
4.2.2.9.1 General1'5
The coating of pressure sensitive tapes and labels (PSTL) is an operation in which some "
backing material (paper, cloth, or film) is coated to create a tape or label product that sticks on
contact. The term "pressure sensitive" indicates that the adhesive bond is formed on contact, without
wetting, heating, or adding a curing agent.
The products manufactured by the PSTL surface coating industry may have several different
types of coatings applied to them. The 2 primary types of coatings are adhesives and releases.
Adhesive coating is a necessary step in the manufacture of almost all PSTL products. It is generally
the heaviest coating (typically 0.051 kg/m2, or 0.011 Ib/ft2 and therefore has the highest level of
solvent emissions (generally 85 to 95 percent of total line emissions).
Release coatings are applied to the backside of tape or to the mounting paper of labels. The
function of release coating is to allow smooth and easy unrolling of a tape or removal of a label from
mounting paper. Release coatings are applied in a very thin coat (typically 0.00081 kg/m2, or
0.00017 Ib/ft2). This thin coating produces less emissions than does a comparable size adhesive
coating line.
Five basic coating processes can be used to apply both adhesive and release coatings:
solvent base coating
waterborne (emulsion) coating
100 percent solids (hot melt) coating
calender coating
prepolymer coating
A solvent base coating process is used to produce 80 to 85 percent of all products in the
PSTL industry, and essentially all of the solvent emissions from the industry result from solvent base
coating. Because of its broad application and significant emissions, solvent base coating of PSTL
products is discussed in greater detail.
4.2.2.9.2 Process Description1'2'5
Solvent base surface coating is conceptually a simple process. A continuous roll of backing
material (called the web) is unrolled, coated, dried, and rolled again. A typical solvent base coating
line is shown in Figure 4.2.2.9-1. Large lines in this industry have typical web widths of
152 centimeters (60 in.), while small lines are generally 48 centimeters (24 in.). Line speeds vary
substantially, from 3 to 305 meters per minute (10 to 1000 ft/min). To initiate the coating process
the continuous web material is unwound from its roll. It travels to a coating head, where the solvent
base coating formulation is applied. These formulations have specified levels of solvent and coating
solids by weight. Solvent base adhesive formulations contain approximately 67 weight percent solvent
and 33 weight percent coating solids. Solvent base releases average about 95 weight percent solvent
and 5 weight percent coating solids. Solvents used include toluene, xylene, heptane, hexane, and
methyl ethyl ketone. The coating solids portion of the formulations consists of elastomers (natural
rubber, styrene-butadiene rubber, polyacrylates), tackifying resins (polyterpenes, rosins, petroleum
8/82 (Reformatted \19S) Evaporation Loss Sources 4.2.2.9-1
-------
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CU ^*i
rv 1
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^•••^^
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D
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-------
hydrocarbon resins, asphalts), plasticizers (phthalate esters, polybutenes, mineral oil), and fillers (zinc
oxide, silica, clay).
The order of application is generally release coat, primer coat (if any), and adhesive coat. A
web must always have a release coat before the adhesive can be applied. Primer coats are not
required on all products, generally being applied to improve the performance of the adhesive.
Three basic categories of coating heads are used in the PSTL industry. The type of coating
head used has a great effect on the quality of the coated product, but only a minor effect on overall
emissions. The first type operates by applying coating to the web and scraping excess off to a desired
thickness. Examples of this type of coater are the knife coater, blade coaler, and metering rod coaler.
The second category of coating head meters on a specific amount of coating. Gravure and reverse
roll coalers are the mosl common examples. The third category of coaling head does nol actually
apply a surface coating, but rather it saturates the web backing. The most common example in mis
category is the dip and squeeze coater.
After solvent base coatings have been applied, the web moves into the drying oven where the
solvents are evaporated from the web. The important characteristics of the drying oven operation are:
source of heat
temperature profile
residence time
allowable hydrocarbon concentration in the dryer
oven air circulation
Two basic types of heating are used in conventional drying ovens, direct and indirect Direcl
heating routes the hot combustion gases (blended with ambient air to the proper temperature) directly
into the drying zone. With indirect heating, the incoming oven air stream is heated in a heat
exchanger with sieam or hot combustion gases but does not physically mix with them. Direct-fired
ovens are more common in the PSTL industry because of their higher thermal efficiency. Indirect
heated ovens are less energy efficient in both the production of steam and the heat transfer in the
exchanger.
Drying oven temperature control is an important consideration in PSTL production. The oven
temperature musl be above Ihe boiling point of the applied solvent. However, the temperature profile
must be controlled by using multizoned ovens. Coating flaws known as "craters" or "fish eyes" will
develop if the initial drying proceeds too quickly. These ovens are physically divided into several
sections, each with its own hot air supply and exhaust. By keeping the temperature of the first zone
low, and then gradually increasing it in subsequent zones, uniform drying can be accomplished
without flaws. After exiting the drying oven, the continuous web is wound on a roll, and the coating
process is complete.
4.2.2.9.3 Emissions1'6-10
The only pollutants emitted in significant quantities from solvent base coating of pressure
sensitive tapes and labels are volatile organic compounds (VOC) from solvent evaporation. In an
uncontrolled facility, essentially all of the solvent used hi the coating formulation is emitted to the
atmosphere. Of these uncontrolled emissions, 80 to 95 percent are emitted with the drying oven
exhaust. Some solvent (from zero to 5 percent) can remain in the final coated product, although this
solvent will eventually evaporate into the atmosphere. The remainder of applied solvent is lost from a
8/82 (Reformatted 1/95) Evaporation Loss Sources 4.2.2.9-3
-------
number of small sources as fugitive emissions. The major VOC emission points in a PSTL surface
coating operation are indicated in Figure 4.2.2.9-1.
There are also VOC losses from solvent storage and handling, equipment cleaning,
miscellaneous spills, and coating formulation mixing tanks. These emissions are not addressed here,
as these sources have a comparatively small quantity of emissions.
Fugitive solvent emissions during the coating process come from the evaporative loss of
solvent around the coating head and from the exposed wet web prior to its entering the drying oven.
The magnitude of these losses is determined by the width of the web, the line speed, the volatility and
temperature of the solvent, and the air turbulence in the coating area.
Two factors that directly determine total line emissions are the weight (thickness) of the
applied coating on the web and the solvent/solids ratio of the coating formulations. For coating
formulations with a constant solvent/solids ratio during coating, any increases hi coating weight would
produce higher levels of VOC emissions. The solvent/solids ratio in coating formulations is not
constant industrywide. This ratio varies widely among products. If a coating weight is constant,
greater emissions will be produced by increasing the weight percent solvent of a particular
formulation.
These 2 operating parameters, combined with line speed, lice width, and solvent volatility,
produce a number of potential mass emission situations. Table 4.2.2.9-1 presents emission factors for
controlled and uncontrolled PSTL surface coating operations. The potential amount of VOC
emissions from the coating process is equal to the total amount of solvent applied at the coating head.
4.2.2.9.4 Controls1'6-18
The complete air pollution control system for a modern pressure sensitive tape or label
surface coating facility consists of 2 sections, the solvent vapor capture system and the emission
control device. The capture system collects VOC vapors from the coating head, the wet web, and the
drying oven. The captured vapors are directed to a control device to be either recovered (as liquid
solvent) or destroyed. As an alternate emission control technique, the PSTL industry is also using
low-VOC content coatings to reduce their VOC emissions. Waterborne and hot melt coatings and
radiation-cured prepolymers are examples of these low-VOC-content coatings. Emissions of VOC
from such coatings are negligible or zero. Low-VOC-content coatings are not universally applicable
to the PSTL industry, but about 25 percent of the production hi this industry is presently using these
innovative coatings.
4.2.2.9.4.1 Capture Systems-
In a typical PSTL surface coating facility, 80 to 95 percent of VOC emissions from the
coating process is captured hi the coating line drying ovens. Fans are used to direct drying oven
emissions to a control device. In some facilities, a portion of the drying oven exhaust is recirculated
into the oven instead of to a control device. Recirculation is used to increase the VOC concentration
of the drying oven exhaust gases going to the control device.
Another important aspect of capture in a PSTL facility involves fugitive VOC emissions.
Three techniques can be used to collect fugitive VOC emissions from PSTL coating lines. The first
involves the use of floor sweeps and/or hooding systems around the coating head and exposed coated
web. Fugitive emissions collected in the hoods can be directed into the drying oven and on to a
control device, or they can be sent directly to the control device. The second capture technique
involves enclosing the entire coating line or the coating application and flashoff areas. By
4.2.2.9-4 EMISSION FACTORS (Reformatted 1/95) 8/82
-------
Table 4.2.2.9-1 (Metric And English Units). EMISSION FACTORS FOR PRESSURE SENSITIVE
TAPE AND LABEL SURFACE COATING OPERATIONS
EMISSION FACTOR RATING: C
Emission Points
Drying oven exhaustb
Fugitives0
Product retentiond
Control device6
Total eraissionsf
Nonmethane VOCa
Uncontrolled,
kg/kg (lb/lb)
0.80 - 0.95
0.01-0.15
0.01 - 0.05
—
1.0
85% Control,
kg/kg (lb/lb)
—
0.01 - 0.095
0.01 - 0.05
0.045
0.15
90% Control,
kg/kg GbAb)
—
0.0025 - 0.0425
0.01 - 0.05
0.0475
0.10
a Expressed as the mass of volatile organic compounds (VOC) emitted per mass of total solvent used.
Solvent is assumed to consist entirely of VOC.
b References 1,6-7,9. Dryer exhaust emissions depend on coating line operating speed, frequency of
line downtime, coating composition, and oven design.
c Determined by difference between total emissions and other point sources. Magnitude is
determined by size of the line equipment, line speed, volatility and temperature of the solvents, and
air turbulence in the coating area.
d References 6-8. Solvent in the product eventually evaporates into the atmosphere.
e References 1,10,17-18. Emissions are residual content in captured solvent-laden air vented after
treatment. Controlled coating line emissions are based on an overall reduction efficiency which is
equal to capture efficiency times control device efficiency. For 85% control, capture efficiency is
90% with a 95% efficient control device. For 90% control, capture efficiency is 95% with a 95%
efficient control device.
f Values assume that uncontrolled coating lines eventually emit 100% of all solvents used.
maintaining a slight negative pressure within the enclosure, a capture efficiency of 100 percent is
theoretically possible. The captured emissions are directed by fans into the oven or to a control
device. The third capture technique is an expanded form of total enclosure. The entire building or
structure which houses the coating line acts as an enclosure. The entire room air is vented to a
control device. The maintenance of a slight negative pressure ensures that very few emissions escape
the room.
The efficiency of any vapor capture system is highly dependent on its design and its degree of
integration with the coating line equipment configuration. The design of any system must allow safe
and adequate access to the coating line equipment for maintenance. The system must also be designed
to protect workers from exposure to unhealthy concentrations of the organic solvents used in the
surface coating processes. The efficiency of a well-designed combined dryer exhaust and fugitive
capture system is 95 percent.
4.2.2.9.4.2 Control Devices -
The control devices and/or techniques that may be used to control captured VOC emissions
can be classified into 2 categories, solvent recovery and solvent destruction. Fixed-bed carbon
8/82 (Reformatted 1/95)
Evaporation Loss Sources
4.2.2.9-5
-------
adsorption is the primary solvent recovery technique used in this industry. In fixed-bed adsorption,
the solvent vapors are adsorbed onto the surface of activated carbon, and the solvent is regenerated by
steam. Solvent recovered in this manner may be reused hi the coating process or sold to a reclaimer.
The efficiency of carbon adsorption systems can reach 98 percent, but a 95 percent efficiency is more
characteristic of continuous long term operation.
The primary solvent destruction technique used in the PSTL industry is thermal incineration,
which can be as high as 99 percent efficient. However, operating experience with incineration
devices has shown that 95 percent efficiency is more characteristic. Catalytic incineration could be
used to control VOC emissions with the same success as thermal incineration, but no catalytic devices
have been found hi the industry.
The efficiencies of carbon adsorption and thermal incineration control techniques on PSTL
coating VOC emissions have been determined to be equal. Control device emission factors presented
hi Table 4.2.2.9-1 represent the residual VOC content in the exhaust air after treatment.
The overall emission reduction efficiency for VOC emission control systems is equal to the
capture efficiency tunes the control device efficiency. Emission factors for 2 control levels are
presented hi Table 4.2.2.9-1. The 85 percent control level represents 90 percent capture with a
95 percent efficient control device. The 90 percent control level represents 95 percent capture with a
95 percent efficient control device.
References For Section 4.2.2.9
1. The Pressure Sensitive Tape And Label Surface Coating Industry—Background Information
Document, EPA-450/3-80-003a, U. S. Environmental Protection Agency, Research Triangle
Park, NC, September 1980.
2. State Of California Tape And Label Coaters Survey, California Air Resources Board,
Sacramento, CA, April 1978. Confidential.
3. M. R. Rifi, "Water Based Pressure Sensitive Adhesives, Structure vs. Performance11,
presented at Technical Meeting On Water Based Systems, Chicago, IL, June 21-22, 1978.
4. Pressure Sensitive Products And Adhesives Market, Frost and Sullivan Inc., Publication
No. 614, New York, NY, November 1978.
5. Silicone Release Questionnaire, Radian Corporation, Research Triangle Park, NC, May 4,
1979. Confidential.
6. Written communication from Frank Phillips, 3M Company, to G. E. Harris, Radian
Corporation, Research Triangle Park, NC, October 5, 1978. Confidential.
7. Written communication from R. F. Baxter, Avery International, to G. E. Harris, Radian
Corporation, Research Triangle Park, NC, October 16, 1978. Confidential.
8. G. E. Harris, "Plant Trip Report, Shuford Mills, Hickory, NC", Radian Corporation,
Research Triangle Park, NC, July 28, 1978.
9. T. P. Nelson, "Plant Trip Report, Avery International, Painesville, OH", Radian Corporation,
Research Triangle Park, NC, July 26, 1979.
4.2.2.9-6 EMISSION FACTORS (Refonnatted 1/95) 8/82
-------
10. Control Of Volatile Organic Emissions From Existing Stationary Sources—Volume II:
Surface Coating Of Cans, Coils, Paper, Fabrics, Automobiles, And Light Duty Trucks,
EPA-450/2-77-008, U. S. Environmental Protection Agency, Research Triangle Park, NC,
May 1977.
11. Ben Milazzo, "Pressure Sensitive Tapes", Adhesives Age, 22:27-28, March 1979.
12. T. P. Nelson, "Trip Report For Pressure Sensitive Adhesives—Adhesives Research, Glen
Rock, PA", Radian Corporation, Research Triangle Park, NC, February 16, 1979.
13. T. P. Nelson, "Trip Report For Pressure Sensitive Adhesives—Precoat Metals, St. Louis,
MO", Radian Corporation, Research Triangle Park, NC, August 28, 1979.
14. G. W. Brooks, "Trip Report For Pressure Sensitive Adhesives—E. J. Gaisser, Incorporated,
Stamford, CT", Radian Corporation, Research Triangle Park, NC, September 12, 1979.
15. Written communication from D. C. Mascone to J. R. Farmer, Office Of Ah- Quality Planning
And Standards, U.S. Environmental Protection Agency, Research Triangle Park, NC,
June 11, 1980.
16. Written communication from R. E. Miller, Adhesives Research, Incorporated, to T. P.
Nelson, Radian Corporation, Research Triangle Park, NC, June 18, 1979.
17. A. F. Sidlow, Source Test Report Conducted At Fasson Products, Division OfAvery
Corporation, Cucamonga, CA, San Bernardino County Air Pollution Control District, San
Bernardino, CA, January 26, 1972.
18. R. Milner, et al., Source Test Report Conducted At Avery Label Company, Monrovia, CA,
Los Angeles Air Pollution Control District, Los Angeles, CA, March 18, 1975.
8/82 (Reformatted 1/95) Evaporation Loss Sources 4.2.2.9-7
-------
4.2.2.10 Metal Coil Surface Coating
4.2.2.10.1 General1'2
Metal coil surface coating (coil coating) is the linear process by which protective or decorative
organic coatings are applied to flat metal sheet or strip packaged in rolls or coils. Although the
physical configurations of coil coating lines differ from one installation to another, the operations
generally follow a set pattern. Metal strip is uncoiled at the entry to a coating line and is passed
through a wet section, where the metal is thoroughly cleaned and is given a chemical treatment to
inhibit rust and to promote coatings adhesion to the metal surface. In some installations, the wet
section contains an electrogalvanizing operation. Then the metal strip is dried and sent through a
coating application station, where rollers coat one or both sides of the metal strip. The strip then
passes through an oven where the coatings are dried and cured. As the strip exits the oven, it is
cooled by a water spray and again dried. If the line is a tandem line, there is first the application of a
prime coat, followed by another of top or finish coat. The second coat is also dried and cured in an
oven, and the strip is again cooled and dried before being rewound into a coil and packaged for
shipment or further processing. Most coil coating lines have accumulators at the entry and exit that
permit continuous metal strip movement through the coating process while a new coil is mounted at
the entry or a full coil removed at the exit. Figure 4.2.2.10-1 is a flow diagram of a coil coating
line.
Coil coating lines process metal in widths ranging from a few centimeters to 183 centimeters
(72 niches), and in thicknesses of from 0.018 to 0.229 centimeters (0.007 to 0.090 inches). The
speed of the metal strip through the line is as high as 3.6 meters per second (700 feet per minute
[ft/min]) on some of the newer lines.
A wide variety of coating formulations is used by the coil coating industry. The more
prevalent coating types include polyesters, acrylics, polyfluorocarbons, alkyds, vinyls and plastisols.
About 85 percent of the coatings used are organic solvent base and have solvent contents ranging
from near 0 to 80 volume percent, with the prevalent range being 40 to 60 volume percent. Most of
the remaining IS percent of coatings are waterborne, but they contain organic solvent in the range of
2 to 15 volume percent. High solids coatings, in the form of plastisols, organosols, and powders, are
also used to some extent by the industry, but the hardware is different for powder applications.
The solvents most often used in the coil coating industry include xylene, toluene, methyl ethyl
ketone (MEK), Cellosolve Acetate™ , butanol, diacetone alcohol, Cellosolve™, Butyl Cellosolve ,
Solvesso 100 and ISO", isophorone, butyl carbinol, mineral spirits, ethanol, nitropropane,
tetrahydrofuran, Panasolve , methyl isobutyl ketone, Hisol 100™, Tenneco T-125 , isopropanol, and
diisoamyl ketone.
Coil coating operations can be classified in 1 of 2 operating categories, toll coalers and
captive coaters. The toll coater is a service coaler who works for many customers according to the
needs and specifications of each. The coaled melal is delivered to the customer, who forms the end
products. Toll coaters use many different coating formulations and normally use mostly organic
solvent-base coatings. Major markets for toll coating operations include the transportation industry,
the construction industry, and appliance, furniture, and container manufacturers. The captive coater
is normally 1 operation in a manufacturing process. Many sleel and aluminum companies have Iheir
own coil coaling operations, where the melal Ihey produce is coaled and Ihen formed into end
8/82 (Reformatted 1/95) Evaporation Loss Sources 4.2.2.10-1
-------
•o
I
oo
o
E
ts
es
D
Ui
4.2.2.10-2
EMISSION FACTORS
(Refoimatted 1/95) 8/82
-------
products. Captive coalers are much more likely to use water-base coatings because the metal coated
is often used for only a few end products. Building products such as aluminum siding are one of the
more important uses of waterborne metal coatings.
4.2.2.10.2 Emissions And Controls1'12
Volatile organic compounds (VOC) are the major pollutants emitted from metal coil surface
coating operations. Specific operations that emit VOC are the coating application station, the curing
oven and the quench area. These are identified in Figure 4.2.2.10-1. VOC emissions result from the
evaporation of organic solvents contained in the coating. The percentage of total VOC emissions
given off at each emission point varies from one installation to another, but, on the average, about
8 percent is given off at the coating application station, 90 percent the oven and 2 percent the quench
area. On most coating lines, the coating application station is enclosed or hooded to capture fugitive
emissions and to direct them into the oven. The quench is an enclosed operation located immediately
adjacent to the exit end of the oven so that a large fraction of the emissions given off at the quench is
captured and directed into the oven by the oven ventilating air. In operations such as these,
approximately 95 percent of the total emissions are exhausted by the oven, and the remaining
5 percent escape as fugitive emissions.
The rate of VOC emissions from individual coil coating lines may vary widely from one
installation to another. Factors that affect the emission rate include VOC content of coatings as
applied, VOC density, area of metal coated, solids content of coatings as applied, thickness of the
applied coating and number of coats applied. Because the coatings are applied by roller coating,
transfer efficiency is generally considered to approach 100 percent and therefore does not affect the
emission rate.
Two emission control techniques are widespread in the coil coating industry, incineration and
use of low-VOC-content coatings. Incinerators may be either thermal or catalytic, both of which have
been demonstrated to achieve consistently a VOC destruction efficiency of 95 percent or greater.
When used with coating rooms or hoods to capture fugitive emissions, incineration systems can
reduce overall emissions by 90 percent or more.
Waterborne coatings are the only low-VOC-content coating technology that is used to a
significant extent hi the coil coating industry. These coatings have substantially lower VOC emissions
than most of the organic solventborne coatings. Waterborne coatings are used as an emission control
technique most often by installations that coat metal for only a few products, such as building
materials. Many such coaters are captive to the firm that produces and sells the products fabricated
from the coated coil. Because waterborne coatings have not been developed for many coated metal
coil uses, most toll coaters use organic solventborne coatings and control their emissions by
incineration. Most newer incinerator installations use heat recovery to reduce the operating cost of an
incineration system.
Emission factors for coil coating operations and the equations used to compute them are
presented hi Table 4.2.2.10-1. The values presented therein represent maximum, minimum, and
average emissions from small, medium, and large coil coating lines. An average film thickness and
an average solvent content are assumed to compute the average emission factor. Values for the VOC
content near the maximum and minimum used by the industry are assumed for the calculations of
maximum and minimum emission factors.
The emission factors in Table 4.2.2.10-1 are useful in estimating VOC emissions for a large
sample of coil coating sources, but they may not be applicable to individual plants. To estimate the
8/82 (Reformatted 1/95) Evaporation Loss Sources 4.2.2.10-3
-------
emissions from a specific plant, operating parameters of the coil coating line should be obtained and
used in the equation given in the footnote to Table 4.2.2.10-1. If different coatings are used for
prime and topcoats, separate calculations must be made for each coat. Operating parameters on
which the emission factors are based are presented in Table 4.2.2.10-2.
Table 4.2.2.10-1 (Metric And English Units). VOC EMISSION FACTORS FOR COIL COATING*
EMISSION FACTOR RATING: C
Coatings
Solventborne
Uncontrolled
Controlled*1
Waterbome
kg/hr (Ib/hr)
Average Normal Range
303 50 - 1,798
(669) (110-3,964)
30 5 - 180
(67) (11 - 396)
50 3 - 337
(111) (7 - 743)
kg/m2 (Ib/ft2)
Average Normal Range
0.060 0.027 - 0.160
(0.012) (0.006 - 0.033)
0.0060 0.0027 - 0.0160
(0.0012) (0.0006 - 0.0033)
0.0108 0.0011-0.0301
(0.0021) (0.0003 - 0.0062)
All nonmethane VOC. Factors are calculated using the following equations and the operating
parameters given in Table 4.2.2.10-2.
(1)
E =
0.623 ATVD
where:
E = Mass of VOC emissions per hour (Ib/hr)
A = Area of metal coated per hour (ft2)
= Line speed (ft/min) x strip width (ft) x 60 min/hr
T = Total dry film thickness of coatings applied (in.).
V = VOC content of coatings (fraction by volume)
D = VOC density (assumed to be 7.36 Ib/gal)
S = Solids content of coatings (fraction by volume)
The constant 0.623 represents conversion factors of 7.48 gal/ft3 divided by the conversion factor of
12 in./ft.
(2)
where:
M = Mass of VOC emissions per unit area coated.
b Computed by assuming a 90% overall control efficiency (95% capture and 95% removal by the
control device).
4.2.2.10-4
EMISSION FACTORS
(Reformatted 1/95) 8/82
-------
Table 4.2.2.10-2 (English Units). OPERATING PARAMETERS FOR SMALL,
MEDIUM, AND LARGE COIL COATING LINES*
Line Size
Solventborne
coatings
Small
Medium
Large
Waterborne
coatings
Small
Medium
Large
Line Speed
(ft/min)
200
300
500
200
300
500
Strip Width
(ft)
1.67
3
4
1.67
3
4
Total Dry
Film
Thicknessb
(in.)
0.0018
0.0018
0.0018
0.0018
0.0018
0.0018
VOC
Content0
(traction)
0.40
0.60
0.80
0.02
0.10
0.15
Solids
Content0
(fraction)
0.60
0.40
0.20
0.50
0.40
0.20
VOC
Densityb
Ob/gal)
7.36
7.36
7.36
7.36
7.36
7.36
a Obtained from Reference 3.
b Average value assumed for emission factor calculations. Actual values should be used to estimate
emissions from individual sources.
0 All three values of VOC content and solids content were used in the calculation of emission factors
for each plant size to give maximum, minimum, and average emission factors.
References For Section 4.2.2.10
1. Metal Coil Surface Coating Industry — Background Information For Proposed Standards,
EPA- 450/3-80-035a, U. S. Environmental Protection Agency, Research Triangle Park, NC,
October 1980.
2. Control Of Volatile Organic Emissions From Existing Stationary Sources Volume II: Surface
Coating Of Cans, Coils, Paper, Fabrics, Automobiles, And Light Duty Trucks,
EPA-450/2-77-008, U. S. Environmental Protection Agency, Research Triangle Park, NC,
May 1977.
3. Unpublished survey of the Coil Coating Industry, Office Of Water And Waste Management,
U.S. Environmental Protection Agency, Washington, DC, 1978.
4. Communication between Milton Wright, Research Triangle Institute, Research Triangle Park,
NC, and Bob Morman, Glidden Paint Company, Strongville, OH, June 27, 1979.
5. Communication between Milton Wright, Research Triangle Institute, Research Triangle Park,
NC, and Jack Bates, DeSoto, Incorporated, Des Plaines, IL, June 25, 1980.
8/82 (Reformatted 1/95)
Evaporation Loss Sources
4.2.2.10-5
-------
6. Communication between Milton Wright, Research Triangle Institute, Research Triangle Park,
NC, and M. W. Miller, DuPont Corporation, Wilmington, DE, June 26, 1980.
7. Communication between Milton Wright, Research Triangle Institute, Research Triangle Park,
NC, and H. B. Kinzley, Cook Paint and Varnish Company, Detroit, MI, June 27, 1980.
8. Written communication from J. D. Pontius, Sherwin Williams, Chicago, IL, to J. Kearney,
Research Triangle Institute, Research Triangle Park, NC, January 8, 1980.
9. Written communication from Dr. Maynard Sherwin, Union Carbide, South Charleston, WV,
to Milton Wright, Research Triangle Institute, Research Triangle Park, NC, January 21,
1980.
10. Written communication from D. 0. Lawson, PPG Industries, Springfield, PA, to Milton
Wright, Research Triangle Institute, Research Triangle Park, NC, February 8, 1980.
11. Written communication from National Coil Coalers Association, Philadelphia, PA, to Office
Of Air Quality Planning And Standards, U.S. Environmental Protection Agency, Research
Triangle Park, NC, May 30, 1980.
12. Written communication from Paul Timmerman, Hanna Chemical Coatings Corporation,
Columbus, OH, to Milton Wright, Research Triangle Institute, Research Triangle Park, NC,
July 1, 1980.
4.2.2.10-6 EMISSION FACTORS (Reformatted 1/95) 8/82
-------
4.2.2.11 Large Appliance Surface Coating
4.2.2.11.1 General1
Large appliance surface coating is the application of protective or decorative organic coatings
to preformed large appliance parts. For this discussion, large appliances are defined as any metal
range, oven, microwave oven, refrigerator, freezer, washing machine, dryer, dishwasher, water
heater, or trash compactor.
Regardless of the appliance, similar manufacturing operations are involved. Coiled or sheet
metal is cut and stamped into the proper shapes, and the major parts are welded together. The
welded parts are cleaned with organic degreasers or a caustic detergent (or both) to remove grease
and mill scale accumulated during handling, and the parts are then rinsed in one or more water rinses.
This is often followed by a process to improve the grain of the metal before treatment in a phosphate
bath. Iron or zinc phosphate is commonly used to deposit a microscopic matrix of crystalline
phosphate on the surface of the metal. This process provides corrosion resistance and increases the
surface area of the part, thereby allowing superior coating adhesion. Often the highly reactive metal
is protected with a rust inhibitor to prevent rusting prior to painting.
Two separate coatings have traditionally been applied to these prepared appliance parts: a
protective prime coating that also covers surface imperfections and contributes to total coating
thickness, and a final, decorative topcoat. Single-coat systems, where only a prune coat or only a
topcoat is applied, are becoming more common. For parts not exposed to customer view, a prune
coat alone may suffice. For exposed parts, a protective coating may be formulated and applied so as
to act as the topcoat. There are many different application techniques in the large appliance industry,
including manual, automatic, and electrostatic spray operations, and several dipping methods.
Selection of a particular method depends largely upon the geometry and use of the part, the
production rate, and the type of coating being used. Typical application of these coating methods is
shown in Figure 4.2.2.11-1.
A wide variety of coating formulations is used by the large appliance industry. The prevalent
coating types include epoxies, epoxy/acrylics, acrylics, and polyester enamels. Liquid coatings may
use either an organic solvent or water as the main carrier for the paint solids.
Waterborne coatings are of 3 major classes: water solutions, water emulsions, and water
dispersions. All of the waterborne coatings, however, contain a small amount (up to 20 volume
percent) of organic solvent that acts as a stabilizing, dispersing or emulsifying agent. Waterborne
systems offer some advantages over organic solvent systems. They do not exhibit as great an increase
in viscosity with increasing molecular weight of solids, they are nonflammable, and they have limited
toxicity. But because of the relatively slow evaporation rate of water, it is difficult to achieve a
smooth finish with waterborne coatings. A bumpy "orange peel" surface often results. For this
reason, their main use in the large appliance industry is as prime coats.
While conventional organic solventborne coatings also are used for prime coats, they
predominate as topcoats. This is due in large part to the controllability of the finish and the
amenability of these materials to application by electrostatic spray techniques. The most common
organic solvents are ketones, esters, ethers, aromatics, and alcohols. To obtain or maintain certain
application characteristics, solvents are often added to coatings at the plant. The use of powder
5/83 (Reformatted 1/95) Evaporation Loss Sources 4.2.2.11-1
-------
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4.2.2.11-2
EMISSION FACTORS
(Reformatted 1/95) 5/83
-------
coatings for topcoats is gaining acceptance in the industry. These coatings, which are applied as a
dry powder and then fused into a continuous coating film through the use of heat, yield negligible
emissions.
4.2.2.11.2 Emissions And Controls1"2
Volatile organic compounds (VOC) are the major pollutants emitted from large appliance
surface coating operations. VOC from evaporation of organic solvents contained hi the coating are
emitted in the application station, the flashoff area and the oven. An estimated 80 percent of total
VOC emissions is given off in the application station and flashoff area. The remaining 20 percent
occurs in the oven. Because the emissions are widely dispersed, the use of capture systems and
control devices is not an economically attractive means of controlling emissions. While both
incinerators and carbon adsorbers are technically feasible, none is known to be used in production,
and none is expected. Improvements in coating formulation and application efficiency are the major
means of reducing emissions.
Factors that affect the emission rate include the volume of coating used, the coating's solids
content, the coating's VOC content, and the VOC density. The volume of coating used is a function
of 3 additional variables: (1) the area coated, (2) the coating thickness, and (3) the application
efficiency.
While a reduction hi coating VOC content will reduce emissions, the transfer efficiency with
which the coating is applied (i. e., the volume required to coat a given surface area) also has a direct
bearing on me emissions. A transfer efficiency of 60 percent means that 60 percent of the coating
solids consumed is deposited usefully onto appliance parts. The other 40 percent is wasted overspray.
With a specified VOC content, an application system with a high transfer efficiency will have lower
emission levels than will a system with a low transfer efficiency, because a smaller volume of coating
will coat the same surface area. Since not every application method can be used with all parts and
types of coating, transfer efficiencies hi this industry range from 40 to over 95 percent.
Although waterborne prune coats are becoming common, the trend for topcoats appears to be
toward use of "high solids" solventborne material, generally 60 volume percent or greater solids. As
different types of coatings are required to meet different performance specifications, a combination of
reduced coating VOC content and unproved transfer efficiency is the most common means of
emission reduction.
In the absence of control systems that remove or destroy a known fraction of the VOC prior
to emission to the atmosphere, a material balance provides the quickest and most accurate emissions
estimate. An equation to calculate emissions is presented below. To the extent that the parameters of
this equation are known or can be determined, its use is encouraged. In the event that both a prune
coat and a topcoat are used, the emissions from each must be calculated separately and added to
estimate total emissions. Because of the diversity of product mix and plant sizes, it is difficult to
provide emission factors for "typical" facilities. Approximate values for several of the variables in
the equation are provided, however.
(6.234xlO'4)P A t V0 D0
E = —- + Ld Dd
VST d d
5/83 (Reformatted 1/95) Evaporation Loss Sources 4.2.2.11-3
-------
where:
E = mass of VOC emissions per unit time (Ib/unit time)
P = units of production per unit time
A = area coated per unit of production (ft2) (see Table 4.2.2.11-2)
t = dry coating thickness (mils) (see Table 4.2.2.11-2)
V0 = proportion of VOC in the coating (volume fraction), as received2
D0 = density of VOC solvent in the coating (Ib/gal), as received
a
Vs = proportion of solids in the coating (volume fraction), as received4
T = transfer efficiency (fraction: the ratio of coating solids deposited onto appliance parts to
the total amount of coating solids used. See Table 4.2.2.11-1.)
Ld = volume of VOC solvent added to the coating per unit time (gal/unit time)
Dd = density of VOC solvent added (Ib/gal)
The constant 6.234 x 10"4 is the product of 2 conversion factors:
8.333 x 10~5 ft . 7.481 gal
and —
mil 3
If all the data are not available to complete the above equation, the following may be used as
approximations:
V0 = 0.38
D0 = 7.36 Ib/gal
Vs = 0.62
Ld = 0 (assumes no solvent added at the plant)
In the absence of all operating data, an emission estimate of 49.9 Mg (55 tons) of VOC per
year may be used for the average appliance plant. Because of the large variation in emissions among
plants (from less than 10 to more than 225 Mg [10 to 250 tons] per year), caution is advised when
this estimate is used for anything except approximations for a large geographical area. Most of the
known large appliance plants are in localities considered nonattainment areas for achieving the
national ambient air quality standard (NAAQS) for ozone. The 49.9-Mg-per-year (55-ton-per-year)
average is based on an emission limit of 2.8 Ib of VOC per gallon of coating (minus water), which is
the limit recommended by the Control Techniques Guideline (CTG) applicable in those areas. For a
plant operating in an area where there are no emission limits, the emissions may be 4 times greater
than from an identical plant subject to the CTG-recommended limit.
a If known, V0, D0, and Vs for the coating as applied (i. e., diluted) may be used in lieu of the values
for the coating as received, and the term Ld Dd deleted.
4.2.2.11-4 EMISSION FACTORS (Reformatted 1/95) 5/83
-------
Table 4.2.2.11-1. TRANSFER EFFICIENCIES
Application Method
Air atomized spray
Airless spray
Manual electrostatic spray
Flow coat
Dip coat
Nonrelational automatic electrostatic spray
Rotating head automatic electrostatic spray
Electrodeposition
Powder
Transfer Efficiency (T)
0.40
0.45
0.60
0.85
0.85
0.85
0.90
0.95
0.95
Table 4.2.2.11-2 (Metric And English Units). AREAS COATED AND COATING THICKNESS8
Appliance
Compactor
Dishwasher
Dryer
Freezer
Microwave oven
Range
Refrigerator
Washing machine
Water heater
Prune Coat
A (ft2)
20
10
90
75
8
20
75
70
20
t (mils)
0.5
0.5
0.6
0.5
0.5
0.5
0.5
0.6
0.5
Topcoat
A (ft2)
20
10
30
75
8
30
75
25
20
t(mils)
0.8
0.8
1.2
0.8
0.8
0.8
0.8
1.2
0.8
a A ^
A = area coated per unit of production, t = dry coating thickness.
References For Section 4.2.2.11
1. Industrial Surface Coating: Appliances—Background Information For Proposed Standards,
EPA-450/3-80-037a, U. S. Environmental Protection Agency, Research Triangle Park, NC,
November 1980.
2. Industrial Surface Coating: Large Appliances—Background Information For Promulgated
Standards, EPA 450/3-80-037b, U. S. Environmental Protection Agency, Research Triangle
Park, NC, 27711, October 1982.
5/83 (Reformatted 1/95)
Evaporation Loss Sources
4.2.2.11-5
-------
4.2 JL.ll Metal Furniture Surface Coating
4.2.2.12.1 General
The metal furniture surface coating process is a multistep operation consisting of surface
cleaning, coatings application, and curing. Items such as desks, chairs, tables, cabinets, bookcases,
and lockers are normally fabricated from raw material to finished product in the same facility. The
industry uses primarily solventborne coatings, applied by spray, dip, or flow coating processes.
Spray coating is the most common application technique used. The components of spray coating lines
vary from plant to plant, but generally consist of the following:
3- to 5-stage washer
Dryoff oven
Spray booth
Flashoff area
Bake oven
Items to be coated are first cleaned in the washer to remove any grease, oil, or dirt from the
surface. The washer generally consists of an alkaline cleaning solution, a phosphate treatment to
improve surface adhesion characteristics, and a hot water rinse. The items are then dried hi an oven
and conveyed to the spray booth, where the surface coating is applied. After this application, the
items are conveyed through the flashoff area to the bake oven, where the surface coating is cured. A
diagram of these consecutive steps is presented in Figure 4.2.2.12-1. Although most metal furniture
products receive only 1 coat of paint, some facilities apply a prime coat before the topcoat to improve
the corrosion resistance of the product. In these cases, a separate spray booth and bake oven for
application of the prime coat are added to the line, following the dryoff oven.
The coatings used in the industry are primarily solventborne resins, including acrylics,
amines, vinyls, and cellulosics. Some metallic coatings are also used on office furniture. The
solvents used are mixtures of aliphatics, xylene, toluene, and other aromatics. Typical coatings that
have been used hi the industry contain 65 volume percent solvent and 35 volume percent solids.
Other types of coatings now being used hi the industry are waterborne, powder, and solventborne
high solids coatings.
4.2.2.12.2 Emissions And Controls
Volatile organic compounds (VOC) from the evaporation of organic solvents in the coatings
are the major pollutants from metal furniture surface coating operations. Specific operations that emit
VOC are the coating application process, the flashoff area and the bake oven. The percentage of total
VOC emissions given off at each emission point varies from one installation to another, but on the
average spray coating line, about 40 percent is given off at the application station, 30 percent hi the
flashoff area, and 30 percent in the bake oven.
Factors affecting the quantity of VOC emitted from metal furniture surface coating operations
are the VOC content of the coatings applied, the solids content of coatings as applied, and the transfer
efficiency. Knowledge of both the VOC content and solids content of coatings is necessary hi cases
where the coating contains other components, such as water.
5/83 (Reformatted 1/95) Evaporation Loss Sources 4.2.2.12-1
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The transfer efficiency (volume fraction of the solids in the total consumed coating that
remains on the part) varies with the application technique. Transfer efficiency for standard (or
ordinary) spraying ranges from 25 to 50 percent. The range for electrostatic spraying, a method that
uses an electrical potential to increase transfer efficiency of the coating solids, is from 50 to
95 percent, depending on part size and shape. Powder coating systems normally capture and
recirculate overspray material and, therefore, are considered in terms of a "utilization rate" rather
than a transfer efficiency. Most facilities achieve a powder utilization rate of 90 to 95 percent.
Typical values for transfer efficiency with various application devices are in Table 4.2.2.12-1.
Table 4.2.2.12-1. COATING METHOD TRANSFER EFFICIENCIES
Application Methods
Air atomized spray
Airless spray
Manual electrostatic spray
Nonrelational automatic electrostatic spray
Rotating head electrostatic spray (manual and automatic)
Dip coat and flow coat
Electrodeposition
Transfer Efficiency (Te)
0.25
0.25
0.60
0.70
0.80
0.90
0.95
Two types of control techniques are available to reduce VOC emissions from metal furniture
surface coating operations. The first technique makes use of control devices such as carbon absorbers
and thermal or catalytic incinerators to recover or destroy VOC before it is discharged into the
ambient air. These control methods are seldom used in the industry, however, because the large
volume of exhaust air and low concentrations of VOC in the exhaust reduce their efficiency. The
more prevalent control technique involves reducing the total amount of VOC likely to be evaporated
and emitted. This is accomplished by use of low VOC content coatings and by improvements in
transfer efficiency. New coatings with relatively low VOC levels can be used instead of the
traditional high VOC content coatings. Examples of these new systems include waterborne coatings,
powder coatings, and higher solids coatings. Improvements in coating transfer efficiency decrease the
amount that must be used to achieve a given film thickness, thereby reducing emissions of VOC to
the ambient air. By using a system with increased transfer efficiency (such as electrostatic spraying)
and lower VOC content coatings, VOC emission reductions can approach those achieved with control
devices.
The data presented in Tables 4.2.2.12-2 and 4.2.2.12-3 are representative of values which
might be obtained from existing plants with similar operating characteristics. Each plant has its own
combination of coating formulations, application equipment, and operating parameters. It is
recommended that, whenever possible, plant-specific values be obtained for all variables when
calculating emission estimates.
5/83 (Reformatted 1/95) Evaporation Loss Sources 4.2.2.12-3
-------
Table 4.2.2.12-2 (Metric Units). OPERATING PARAMETERS FOR COATING OPERATIONS
Plant Size
Small
Medium
Large
Operating
Schedule
(hr/yr)
2,000
2,000
2,000
Number Of
Lines
1
(1 spray booth)
3
(3 booths/line
10
(3 booths/line)
Line Speed"
(m/min)
2.5
2.4
4.6
Surface Area
Coated/yr (m2)
45,000
780,000
4,000,000
Liters Of
Coating Usedb
5,000
87,100
446,600
a Line speed is not used to calculate emissions, only to characterize plant operations.
b Using 35 volume % solids coating, applied by electrostatic spray at 65% transfer efficiency.
Table 4.2.2.12-3 (Metric Units). EMISSION FACTORS FOR VOC FROM SURFACE
COATING OPERATIONSa'b
Plant Size And Control Techniques
Small
Uncontrolled emissions
65 Volume % high solids coating
Waterborne coating
Medium
Uncontrolled emissions
65 Volume % high solids coating
Waterborne coating
Large
Uncontrolled emissions
65 Volume % high solids coating
Waterborne coating
kg/m2 Coated
0.064
0.019
0.012
0.064
0.019
0.012
0.064
0.019
0.012
VOC Emissions
kg/yr
2,875
835
520
49,815
14,445
8,970
255,450
74,080
46,000
kg/hr
1.44
0.42
0.26
24.90
7.22
4.48
127.74
37.04
23.00
a Calculated using the parameters given in Table 4.2.2.12-2 and the following equation. Values have
been rounded off.
E =
0.0254 ATVD
S Te
where:
E = Mass of VOC emitted per hour (kg)
A = Surface area coated per hour (m2)
T = Dry film thickness of coating applied (mils)
4.2.2.12-4
EMISSION FACTORS
(Reformatted 1/95) 5/83
-------
Table 4.2.2.12-3 (cont.).
V = VOC content of coating, including dilution solvents added at the plant (fraction by
volume)
D = VOC density (assumed to be 0.88 kg/L)
S = Solids content of coating (fraction by volume)
Te = Transfer efficiency (fraction)
The constant 0.0254 converts the volume of dry film applied per m2 to liters.
Example: The VOC emission from a medium size plant applying
35 volume % solids coatings and the parameters given in
Table 4.2.2.12-3.
P = (0.0254) (390 m2/hr) (1 mil) (0.65) (0.88 kg/L)
Holograms of VOC/hr CO 35) (0 651
= 24.9 kilograms of VOC/hr
b Nominal values of T, V, S, and Te:
T = 1 mil (for all cases)
V = 0.65 (uncontrolled), 0.35 (65 volume % solids), 0.117 (waterborne)
S = 0.35 (uncontrolled), 0.65 (65 volume % solids), 0.35 (waterborne)
Te = 0.65 (for all cases)
Another method that also may be used to estimate emissions for metal furniture coating
operations involves a material balance approach. By assuming that all VOC hi the coatings applied
are evaporated at the plant site, an estimate of emissions can be calculated using only the coating
formulation and data on the total quantity of coating used in a given time period. The percentage of
VOC solvent in the coating, multiplied by the quantity of coating used yields the total emissions.
This method of emissions estimation avoids the requirement to use variables such as coating thickness
and transfer efficiency, which are often difficult to define precisely.
Reference For Section 4.2.2.12
1. Surface Coating Of Metal Furniture—Background Information For Proposed Standards,
EPA-450/3-80-007a, U. S. Environmental Protection Agency, Research Triangle Park, NC,
September 1980.
5/83 (Reformatted 1/95) Evaporation Loss Sources 4.2.2.12-5
-------
4.2.2.13 Magnetic Tape Manufacturing1"9
Magnetic tape manufacturing is a subcategory of industrial paper coating, which includes
coating of foil and plastic film. In the manufacturing process, a mixture of magnetic particles, resins,
and solvents is coated on a thin plastic film or "web". Magnetic tape is used largely for audio and
video recording and computer information storage. Other uses include magnetic cards, credit cards,
bank transfer ribbons, instrumentation tape, and dictation tape. The magnetic tape coating industry is
included in two Standard Industrial Classification codes, 3573 (Electronic Computing Equipment) and
3679 (Electronic Components Not Elsewhere Classified).
4.2.2.13.1 Process Description1"2
The process of manufacturing magnetic tape consists of:
1. mixing the coating ingredients (including solvents)
2. conditioning the web
3. applying the coating to the web
4. orienting the magnetic particles
5. drying the coating in a drying oven
6. finishing the tape by calendering, rewinding, slitting, testing,and packaging
Figure 4.2.2.13-1 shows a typical magnetic tape coating operation, indicating volatile organic
compound (VOQ emission points. Typical plants have from 5 to 12 horizontal or vertical solvent
storage tanks, ranging in capacity from 3,800 to 75,700 liters (1,000 to 20,000 gallons), that are
operated at or slightly above atmospheric pressure. Coating preparation equipment includes the mills.
mixers, polishing tanks, and holding tanks used to prepare the magnetic coatings before application.
Four types of coaters are used in producing magnetic tapes: extrusion (slot die), gravure, knife, and
reverse roll (3- and 4-roll). The web may carry coating on 1 or both sides. Some products receive a
nonmagnetic coating on the back. After coating, the web is guided through an orientation field, in
which an electromagnet or permanent magnet aligns the individual magnetic particles in the intended
direction. Webs from which flexible disks are to be produced do not go through the orientation
process. The coated web then passes through a drying oven, where the solvents in the coating
evaporate. Typically, air flotation ovens are used, in which the web is supported by jets of drying
air. For safe operation, the concentration of solvent vapors is held between 10 and 40 percent of the
lower explosive limit. The dry coated web may be passed through several calendering rolls to
compact the coating and to smooth the surface finish. Nondestructive testing is performed on up to
100 percent of the final product, depending on the level of precision required of the final product.
The web may then be slit into the desired tape widths. Flexible disks are punched from the finished
web with a die. The final product is then packaged. Some plants ship the coated webs in bulk to
other facilities for slitting and packaging.
High performance tapes require very clean production conditions, especially in the coating
application and drying oven areas. Air supplied to these areas is conditioned to remove dust particles
and to adjust the temperature and humidity. In some cases, "clean room" conditions are rigorously
maintained.
9/90 (Reformatted 1/95) Evaporation Loss Sources 4.2.2.13-1
-------
-------
4.2.2.13.2 Emissions And Controls1'8
The significant VOC emission sources in a magnetic tape manufacturing plant include the
coating preparation equipment, the coating application and flashoff area, and the drying ovens.
Emissions from the solvent storage tanks and the cleanup area are generally only a negligible
percentage of total emissions.
In the mixing or coating preparation area, VOCs are emitted from the individual pieces of
equipment during the following operations: filling of mixers and tanks; transfer of the coating;
intermittent activities, such as changing the filters in the holding tanks; and mixing (if mix equipment
is not equipped with tightly fitting covers). Factors affecting emissions in the mixing areas include
the capacity of the equipment, the number of pieces of equipment, solvent vapor pressure,
throughput, and the design and performance of equipment covers. Emissions will be intermittent or
continuous, depending on whether the preparation method is batch or continuous.
Emissions from the coating application area result from the evaporation of solvent during use
of the coating application equipment and from the exposed web as it travels from the coaler to the
drying oven (flashoff). Factors affecting emissions are the solvent content of the coating, line width
and speed, coating thickness, volatility of the solvent(s), temperature, distance between coater and
oven, and air turbulence in the coating area.
Emissions from the drying oven are of the remaining solvent that is driven off in the oven.
Uncontrolled emissions at this point are determined by the solvent content of the coating when it
reaches the oven. Because the oven evaporates all the remaining solvent from the coating, there are
no process VOC emissions after oven drying.
Solvent type and quantity are the common factors affecting emissions from all operations in a
magnetic tape coating facility. The rate of evaporation or drying depends on solvent vapor pressure
at a given temperature and concentration. The most commonly used organic solvents are toluene,
methyl ethyl ketone (MEK), cyclohexanone, tetrahydrofuran, and methyl isobutyl ketone. Solvents
are selected for their cost, solvency,, availability, desired evaporation rate, ease of use after recovery,
compatibility with solvent recovery equipment, and toxicity.
Of the total uncontrolled VOC emissions from the mixing area and coating operation
(application/flashoff area and drying oven), approximately 10 percent is emitted from the mixing area,
and 90 percent from the coating operation. Within the coating operation, approximately 10 percent
occurs in the application/flashoff area, and 90 percent in the drying oven.
A control system for evaporative emissions consists of 2 components, a capture device and a
control device. The efficiency of the control system is determined by the efficiencies of the
2 components.
A capture device is used to contain emissions from a process operation and direct them to a
stack or to a control device. Room ventilation systems, covers, and hoods are possible capture
devices from coating preparation equipment. Room ventilation systems, hoods, and partial and total
enclosures are typical capture devices used in the coating application area. A drying oven can be
considered a capture device, because it both contains and directs VOC process emissions. The
efficiency of a capture device or a combination of capture devices is variable and depends on the
quality of design and the levels of operation and maintenance.
9/90 (Reformatted 1/95) Evaporation Loss Sources 4.2.2.13-3
-------
A control device is any equipment that has as its primary function the reduction of emissions
to the atmosphere. Control devices typically used in this industry are carbon adsorbers, condensers,
and incinerators. Tightly fitting covers on coating preparation equipment may be considered both
capture and control devices, because they can be used either to direct emissions to a desired point
outside the equipment or to prevent potential emissions from escaping.
Carbon adsorption units use activated carbon to adsorb VOCs from a gas stream, after which
the VOCs are desorbed and recovered from the carbon. Two types of carbon adsorbers are available,
fixed-bed and fluidized-bed. Fixed-bed carbon adsorbers are designed with a steam-stripping
technique to recover the VOCs and to regenerate the activated carbon. The fluidized-bed units used
in this industry are designed to use nitrogen for VOC vapor recovery and carbon regeneration. Both
types achieve typical VOC control efficiencies of 95 percent when properly designed, operated, and
maintained.
Condensers control VOC emissions by cooling the solvent-laden gas to the dew point of the
solvents) and then collecting the droplets. There are 2 condenser designs commercially available,
nitrogen (inert gas) atmosphere and air atmosphere. These systems differ in the design and operation
of the drying oven (i. e., use of nitrogen or air in the oven) and in the method of cooling the
solvent-laden air (i. e., liquified nitrogen or refrigeration). Both design types can achieve VOC
control efficiencies of 95 percent.
Incinerators control VOC emissions by oxidation of the organic compounds into carbon
dioxide and water. Incinerators used to control VOC emissions may be of thermal or catalytic design
and may use primary or secondary heat recovery to reduce fuel costs. Thermal incinerators operate
at approximately 890°C (1600°F) to ensure oxidation of the organic compounds. Catalytic
incinerators operate in the range of 400° to 540°C (750° to 1000°F) while using a catalyst to achieve
comparable oxidation of VOCs. Both design types achieve a typical VOC control efficiency of
98 percent.
Tightly fitting covers control VOC emissions from coating preparation equipment by reducing
evaporative losses. The parameters affecting the efficiency of these controls are solvent vapor
pressure, cyclic temperature change, tank size, and product throughput. A good system of tightly
fitting covers on coating preparation equipment reduces emissions by as much as 40 percent. Control
efficiencies of 95 or 98 percent can be obtained by venting the covered equipment to an adsorber,
condenser, or incinerator.
When the efficiencies of a capture device and control device are known, the efficiency of the
control system can be computed by the following equation:
capture control device _ control system
efficiency x efficiency ~ efficiency
The terms of this equation are fractional efficiencies rather than percentages. For instance, a system
of hoods delivering 60 percent of VOC emissions to a 90 percent efficient carbon adsorber would
have a control system efficiency of 54 percent (0.60 x 0.90 = 0.54). Table 4.2.2.13-1 summarizes
control system efficiencies, which may be used to estimate emissions in the absence of measured data
on equipment and coating operations.
4.2.2.13-4 EMISSION FACTORS (Reformatted 1/95) 9/90
-------
Table 4.2.2.13-1. TYPICAL OF CONTROL EFFICIENCIES*
Control Technology
Coating Preparation Equipment
Uncontrolled
Tightly fitting covers
Sealed covers with carbon adsorber/condenser
c
Coating Operation'
Local ventilation with carbon adsorber/condenser
Partial enclosure with carbon adsorber/condenser
Total enclosure with carbon adsorber/condenser
Total enclosure with incinerator
Control Efficiency %l
0
40
95
83
87
93
95
a Reference 1.
b To be applied to uncontrolled emissions from indicated process area, not from entire plant.
c Includes coating application/flashoff area and drying oven.
4.2.2.13.3 Emission Estimation Techniques1'3"9
In this industry, realistic emission estimates require solvent consumption data. The variations
found in coating formulations, line speeds, and products mean that no reliable inferences can be made
otherwise.
In uncontrolled plants and in those where VOCs are recovered for reuse or sale, plantwide
emissions can be estimated by performing a liquid material balance based on the assumption that all
solvent purchased replaces that which has been emitted. Any identifiable and quantifiable side
streams should be subtracted from this total. The liquid material balance may be performed using the
following general formula:
solvent _ quantifiable _ VOC
purchased solvent output ~ emitted
The first term encompasses all solvent purchased, including thinners, cleaning agents, and any solvent
directly used in coating formulation. From this total, any quantifiable solvent outputs are subtracted.
Outputs may include reclaimed solvent sold for use outside the plant or solvent contained in waste
streams. Reclaimed solvent that is reused at the plant is not subtracted.
The advantages of this method are that it is based on data that are usually readily available, it
reflects actual operations rather than theoretical steady state production and control conditions, and it
includes emissions from all sources at the plant. Care should be taken not to apply this method over
too short a tune span. Solvent purchase, production, and waste removal occur in cycles that may not
coincide exactly.
Occasionally, a liquid material balance may be possible on a scale smaller than the entire
plant. Such an approach may be feasible for a single coating line or group of lines, if served by a
dedicated mixing area and a dedicated control and recovery system. In this case, the computation
begins with total solvent metered to the mixing area, instead of with solvent purchased. Reclaimed
solvent is subtracted from this volume, whether or not it is reused on the site. Of course, other
solvent input and output streams must be accounted for, as previously indicated. The difference
9/90 (Reformatted 1/95) Evaporation Loss Sources 4.2.2.13-5
-------
between total solvent input and total solvent output is then taken to be the quantity of VOCs emitted
from the equipment in question.
Frequently, the configuration of meters, mixing areas, production equipment, and controls
will make the liquid material balance approach impossible. In cases where control devices destroy
potential emissions, or where a liquid material balance is inappropriate for other reasons, plantwide
emissions can be estimated by summing the emissions calculated for specific areas of the plant.
Techniques for these calculations are presented below.
Estimating VOC emissions from a coating operation (application/flashoff area and drying
oven) starts with the assumption that the uncontrolled emission level is equal to the quantity of solvent
contained in the coating applied. In other words, all the VOC in the coating evaporates by the end of
the drying process.
Two factors are necessary to calculate the quantity of solvent applied: solvent content of the
coating and the quantity of coating applied. Coating solvent content can be either directly measured
using EPA Reference Method 24 or estimated using coating formulation data usually available from
the plant owner/operator. The amount of coating applied may be directly metered. If it is not, it
must be determined from production data. These data should be available from the plant
owner/operator. Care should be taken in developing these 2 factors to ensure that they are in
compatible units. In cases where plant-specific data cannot be obtained, the information in
Table 4.2.2.13-2 may be useful in approximating the quantity of solvent applied.
When an estimate of uncontrolled emissions is obtained, the controlled emissions level is
computed by applying a control system efficiency factor:
(uncontrolled VOC) x (1 - control system efficiency) = (VOC emitted)
As previously explained, the control system efficiency is the product of the efficiencies of the capture
device and of the control device. If these values are not known, typical efficiencies for some
combinations of capture and control devices are presented in Table 4.2.2.13-1. It is important to note
that these control system efficiencies apply only to emissions that occur within the areas serviced by
the systems. Emissions from sources such as process wastewater or discarded waste coatings may not
be controlled at all.
In cases where emission estimates from the mixing area alone are desired, a slightly different
approach is necessary. Here, uncontrolled emissions will consist of only that portion of total solvent
that evaporates during the mixing process. A liquid material balance across the mixing area
(i. e., solvent entering minus solvent content of coating applied) would provide a good estimate. In
the absence of any measured value, it may be assumed, very approximately, that 10 percent of the
total solvent entering the mixing area is emitted during the mixing process. When an estimate of
uncontrolled mixing area emissions has been made, the controlled emission rate can be calculated as
discussed previously. Table 4.2.2.13-1 lists typical overall control efficiencies for coating mix
preparation equipment.
Solvent storage tanks of the size typically found in this industry are regulated by only a few
states and localities. Tank emissions are generally small (130 kilograms [285 Ib] per year or less). If
an emissions estimate is desired, it can be computed using the equations, tables, and figures provided
in Chapter 7.
4.2.2.13-6 EMISSION FACTORS (Refoimaaed 1/95) 9/90
-------
Table 4.2.2.13-2 (Metric And English Units). SELECTED COATING MIX PROPERTIES11
Parameter
Solids
VOC
Density of Coating
Density of Coating Solids
Resins /binder
Magnetic particles
Density of magnetic material
Viscosity
Coating thickness
Wet
Dry
Unit
weight %
volume %
weight %
volume %
kg/L
Ib/gal
kg/L
Ib/gal
weight % of solids
weight % of solids
kg/L
Ib/gal
Pa*s
Ibfs/ft2
/im
mil
ftm
mil
Range
15-50
10-26
50 -85s
74-90
1.0 - 1.2
8- 10
2.8 - 4.0
23-33
15-21
66-78
1.2-4.8
10-40
2.7 - 5.0
0.06-0.10
3.8 - 54
0.15-2.1
1.0-11
0.04 - 0.4
Reference 9. To be used when plant-specific data are unavailable.
References For Section 4.2.2.13
1. Magnetic Tape Manufacturing Industry—Background Information For Proposed Standards,
EPA-450/3-85-029a, U. S. Environmental Protection Agency, Research Triangle Park, NC,
December 1985.
2. Control Of Volatile Organic Emissions From Existing Stationary Sources—Volume II: Surface
Coating Of Cans, Coils, Paper, Fabrics, Automobiles, And Light Duty Trucks,
EPA 450/2-77-008, U. S. Environmental Protection Agency, Research Triangle Park, NC,
May 1977.
3. C. Beall, "Distribution Of Emissions Between Coating Mix Preparation Area And The Coating
Line", Memorandum file, Midwest Research Institute, Raleigh, NC, June 22, 1984.
4. C. Beall, "Distribution Of Emissions Between Coating Application/Flashoff Area And Drying
Oven", Memorandum to file, Midwest Research Institute, Raleigh, NC, June 22, 1984.
5. Control Of Volatile Organic Emission From Existing Stationary Sources—Volume I: Control
Methods For Surface-coating Operations, EPA-450/2-76- 028, U. S. Environmental
Protection Agency, Research Triangle Park, NC, November 1976.
9/90 (Reformatted 1/95)
Evaporation Loss Sources
4.2.2.13-7
-------
6. G. Crane, Carbon Adsorption For VOC Control, U. S. Environmental Protection Agency,
Research Triangle Park, NC, January 1982.
7. D. Mascone, "Thermal Incinerator Performance For NSPS", Memorandum, Office Of Air
Quality Planning And Standards, U. S. Environmental Protection Agency, Research Triangle
Park, NC, June 11, 1980.
8. D. Mascone, "Thermal Incinerator Performance For NSPS, Addendum", Memorandum,
Office Of Air Quality Planning And Standards, U. S. Environmental Protection Agency,
Research Triangle Park, NC, June 22, 1980.
9. C. Beall, "Summary Of Nonconfidential Information On U.S. Magnetic Tape Coating
Facilities", Memorandum, with attachment, to file, Midwest Research Institute, Raleigh, NC,
June 22, 1984.
4.2.2.13-8 EMISSION FACTORS (Reformatted 1/95) 9/90
-------
4.2.2.14 Surface Coating Of Plastic Parts For Business Machines
4.2.2.14.1 General1-2
Surface coating of plastic parts for business machines is defined as the process of applying
coatings to plastic business machine parts to improve the appearance of the parts, to protect the parts
from physical or chemical stress, and/or to attenuate electromagnetic interference/radio frequency
interference (EMI/RFI) that would otherwise pass through plastic housings. Plastic parts for business
machines are synthetic polymers formed into panels, housings, bases, covers, or other business
machine components. The business machines category includes items such as typewriters, electronic
computing devices, calculating and accounting machines, telephone and telegraph equipment,
photocopiers, and miscellaneous office machines.
The process of applying an exterior coating to a plastic part can include surface preparation,
spray coating, and curing, with each step possibly being repeated several times. Surface preparation
may involve merely wiping off the surface, or it could involve sanding and puttying to smooth the
surface. The plastic parts are placed on racks or trays, or are hung on racks or hooks from an
overhead conveyor track for transport among spray booths, flashoff areas, and ovens. Coatings are
sprayed onto parts in partially enclosed booths. An induced air flow is maintained through the booths
to remove overspray and to keep solvent concentrations hi the room air at safe levels. Although low-
temperature bake ovens (60°C [140°F] or less) are often used to speed up the curing process,
coatings also may be partially or completely cured at room temperature.
Dry filters or water curtains (in water wash spray booths) are used to remove overspray
particles from the booth exhaust. In waterwash spray booths, most of the insoluble material is
collected as sludge, but some of this material is dispersed in the water along with the soluble
overspray components. Figure 4.2.2.14-1 depicts a typical dry filter spray booth, and
Figure 4.2.2.14-2 depicts a typical water wash spray booth.
Many surface coating plants have only 1 manually operated spray gun per spray booth, and
they interchange spray guns according to what type of coating is to be applied to the plastic parts.
However, some larger surface coating plants operate several spray guns (manual or robotic) per spray
booth, because coating a large volume of similar parts on conveyor coating lines makes production
more efficient.
Spray coating systems commonly used in this industry fall into 3 categories, 3-coat, 2-coat,
and single-coat. The 3-coat system is the most common, applying a prime coat, a color or base coat,
and a texture coat. Typical dry film thickness for the 3-coat system ranges from 1 to 3 mils for the
prune coat, 1 to 2 mils for the color coat, and 1 to 5 mils for the texture coat. Figure 4.2.2.14-3
depicts a typical conveyorized coating line using the 3-coat system. The conveyor line consists of
3 separate spray booths, each followed by a flashoff (or drying) area, all of which is followed by a
curing oven. A 2-coat system applies a color or base coat, then a texture coat. Typical dry film
thickness for the 2-coat system is 2 mils for the color (or base) coat, and 2 to 5 mils for the texture
coat. The rarely used single-coat system applies only a thin color coat, either to protect the plastic
substrate or to improve color matching between parts whose color and texture are molded in. Less
coating solids are applied with the single-coat system than with the other systems. The dry film
thickness applied for the single-coat system depends on the function of the coating. If protective
properties are desired, the dry film thickness must be at least 1 mil (0.001 inches). For purposes of
9/90 (Reformatted 1/95) Evaporation Loss Sources 4.2.2.14-1
-------
o
o
JO
I
ts
CM'
•*'
4.2.2.14-2
EMISSION FACTORS
(Reformatted 1/95) 9/90
-------
&4
I
H
£
N
38
^S
§S£
^%S
I
•a
o
3
ts
s
tu,
9/90 (Reformatted 1/95)
Evaporation Loss Sources
4.2.2.14-3
-------
A
I
I
I
CO
§
M
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CO
M
s
o
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4
a
Cb
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color matching among parts having molded-in color and texture, a dry film thickness of 0.5 mils or
less is needed to avoid masking the molded-in texture. The process of applying 0.5 mils of coating or
less for color matching is commonly known as "fog coating", "mist coating", or "uniforming".
The 3 basic spray methods used in this industry to apply decorative/exterior coatings are air-
atomized spray, air-assisted airless spray, and electrostatic air spray. Air-atomized spray is the most
widely used coating technique for plastic business machine parts. Air-assisted airless spray is
growing in popularity but is still not frequently found. Electrostatic air spray is rarely used, because
plastic parts are not conductive. It has been used to coat parts that have been either treated with a
conductive sensitizer or plated with a thin film of metal.
Air-atomized spray coating uses compressed air, which may be heated and filtered, to atomize
the coating and to direct the spray. Air-atomized spray equipment is compatible with all coatings
commonly found on plastic parts for business machines.
Air-assisted airless spray is a variation of airless spray, a spray technique used in other
industries. In airless spray coating, the coating is atomized without air by forcing the liquid coating
through specially designed nozzles, usually at pressures of 7 to 21 megapascals (MPa) (1,000 to
3,000 pounds per square inch [psi]). Air-assisted airless spray atomizes the coating by the same
mechanism as airless spray, but at lower fluid pressures (under 7 MPa [1,000 psi]). After atomizing,
air is then used to atomize the coating further and to help shape the spray pattern, reducing overspray
to levels lower than those achieved with airless atomization alone. Figure 4.2.2.14-4 depicts a typical
air-assisted airless spray gun. Air-assisted airless spray has been used to apply prime and color coats
but not texture coats, because the larger size of the sprayed coating droplet (relative to that achieved
by conventional air atomized spray) makes it difficult to achieve the desired surface finish quality for
a texture coat. A touch-up coating step with air atomized equipment is sometimes necessary to apply
color to recessed and louvered areas missed by air-assisted airless spray.
Figure 4.2.2.14-4. Typical air-assisted airless spray gun.
In electrostatic air spray, the coating is usually charged electrically, and the parts being coated
are grounded to create an electric potential between the coating and the parts. The atomized coating
is attracted to the part by electrostatic force. Because plastic is an insulator, it is necessary to provide
a conductive surface that can bleed off the electrical charge to maintain the ground potential of the
part as the charged coating particles accumulate on the surfaces. Electrostatic air spray has been
demonstrated for application of prime and color coats and has been used to apply texture coats, but
this technique does not function well with the large-size particles generated for the texture coat, and it
offers no substantial improvement over air-atomized spray for texture coating. A touch-up coating
step with air-atomized spray is sometimes necessary to apply color and texture to recessed and
louvered areas missed by electrostatic spray.
9/90 (Reformatted 1/95)
Evaporation Loss Sources
4.2.2.14-5
-------
The coatings used for decorative/exterior coats are generally solvent-based and waterborne
coatings. Solvents used include toluene, methyl ethyl ketone, methylene chloride, xylene, acetone,
and isopropanol. Typically, organic solvent-based coatings used for decorative/exterior coats are
2 types of 2-component catalyzed urethanes. The solids contents of these coatings are from 30 to
35 volume percent (low solids) and 40 to 54 volume percent (medium solids) at the spray gun
(i. e., at the point of application, or as applied). Waterborne decorative/exterior coatings typically
contain no more than 37 volume percent solids at the gun. Other decorative/exterior coatings being
used by the industry include solvent-based high solids coatings (i. e., equal to or greater than
60 volume percent solids) and 1-component low solids and medium solids coatings.
The application of an EMI/RFI shielding coat is done in a variety of ways. About 45 percent
of EMI/RFI shielding applied to plastic parts is done by zinc-arc spraying, a process that does not
emit volatile organic compounds (VOC). About 45 percent is done using organic solvent-based and
waterborne metal-filled coatings, and the remaining EMI/RFI shielding is achieved by a variety of
techniques involving electroless plating, and vacuum metallizing or sputtering (defined below), and
use of conductive plastics, and metal inserts.
Zinc-arc spraying is a 2-step process hi which the plastic surface (usually the interior of a
housing) is first roughened by sanding or grit blasting and then sprayed with molten zinc. Grit
blasting and zinc-arc spraying are performed in separate booths specifically equipped for those
activities. Both the surface preparation and the zinc-arc spraying steps currently are performed
manually, but robot systems have recently become available. Zinc-arc spraying requires a spray
booth, a special spray gun, pressurized air, and zinc wire. The zinc-arc spray gun mechanically feeds
2 zinc wires into the tip of the spray gun, where they are melted by an electric arc. A high pressure
air nozzle blows the molten zinc particles onto the surface of the plastic part. The coating thickness
usually ranges from 1 to 4 mils, depending on product requirements.
Conductive coatings can be applied with most conventional spray equipment used to apply
exterior coatings. Conductive coatings are usually applied manually with air spray guns, although
air-assisted airless spray guns are sometimes used. Electrostatic spray methods cannot be used
because of the high conductivity of EMI/RFI shielding coatings.
Organic solvent-based conductive coatings contain particles of nickel, silver, copper, or
graphite, in either an acrylic or urethane resin. Nickel-filled acrylic coatings are the most frequently
used, because of their shielding ability and their lower cost. Nickel-filled acrylics and urethanes
contain from 15 to 25 volume percent solids at the gun. Waterborne nickel-filled acrylics with
between 25 and 34 volume percent solids at the gun (approximately 50 to 60 volume percent solids,
minus water) are less frequently used than are organic solvent-based conductive coatings.
The application of a conductive coating usually involves 3 steps: surface preparation, coating
application, and curing. Although the first step can be eliminated if parts are kept free of
mold-release agents and dirt, part surfaces are usually cleaned by wiping with organic solvents or
detergent solutions and then roughened by light sanding. Coatings are usually applied to the ulterior
surface of plastic housings, at a dry film thickness of 1 to 3 mils. Most conductive coatings can be
cured at room temperature, but some must be baked in an oven.
Electroless plating is a dip process in which a film of metal is deposited in aqueous solution
onto all exposed surfaces of the part. In the case of plastic business machine housings, both sides of
a housing are coated. No VOC emissions are associated with the plating process itself. However,
coatings applied before the plating step, so that only selected areas of the parts are plated, may emit
VOCs. Waste water treatment may be necessary to treat the spent plating chemicals.
4.2.2.14-6 EMISSION FACTORS (Reformatted 1/95) 9/90
-------
Vacuum metallizing and sputtering are similar techniques in which a thin film of metal
(usually aluminum) is deposited from the vapor phase onto the plastic part. Although no VOC
emissions occur during the actual metallizing process, prime coats often applied to ensure good
adhesion and top coats to protect the metal film may both emit VOCs.
Conductive plastics are thermoplastic resins that contain conductive flakes or fibers of
materials such as aluminum, steel, metallized glass, or carbon. Resin types currently available with
conductive fillers include acrylonitrile butadiene styrene, acrylonitrile butadiene styrene/polycarbonate
blends, polyphenylene oxide, nylon 6/6, polyvinyl chloride, and polybutyl terephthalate. The
conductivity, and therefore the EMI/RFI shielding effectiveness, of these materials relies on contact
or near-contact between the conductive particles within the resin matrix. Conductive plastic parts
usually are formed by straight injection molding. Structural foam injection molding can reduce the
EMI/RFI shield effectiveness of these materials because air pockets in the foam separate the
conductive particles.
4.2.2.14.2 Emissions And Controls
The major pollutants from surface coating of plastic parts for business machines are VOC
emissions from evaporation of organic solvents in the coatings used, and from reaction byproducts
when the coatings cure. VOC sources include spray booth(s), flashoff area(s), and oven(s) or drying
area(s). The relative contribution of each to total VOC emissions vary from plant to plant, but for an
average coating operation, about 80 percent is emitted from the spray booth(s), 10 percent from the
flashoff area(s), and 10 percent from the oven(s) or drying area(s).
Factors affecting the quantity of VOC emitted are the VOC content of the coatings applied,
the solids content of coatings as applied, film build (thickness of the applied coating), and the transfer
efficiency (TE) of the application equipment. To determine of VOC emissions when waterborne
coatings are used, it is necessary to know the amounts of VOC, water, and solids in the coatings.
The TE is the fraction of the solids sprayed that remains on a part. TE varies with
application technique and with type of coating applied. Table 4.2.2.14-1 presents typical TE values
for various application methods.
Volatile organic compound emissions can be reduced by using low VOC content coatings
(i. e., high solids or waterborne coatings), using surface finishing techniques that do not emit VOC,
improving TE, and/or adding controls. Lower VOC content decorative/exterior coatings include high
solids content (i. e., at least 60 volume percent solids at the spray gun), 2-component catalyzed
urethane coatings, and waterborne coatings (i. e., 37 volume percent solids and 12.6 volume percent
VOC at the spray gun). Both of these types of exterior/decorative coatings contain less VOC than
conventional urethane coatings, which are typically 32 volume percent solids at the gun. Lower VOC
content EMI/RFI shielding coatings include organic solvent-based acrylic or urethane conductive
coatings containing at least 25 volume percent solids at the spray gun and waterborne conductive
coatings containing 30 to 34 volume percent solids at the gun. Use of lower VOC content coatings
reduces emissions of VOCs both by reducing the volume of coating needed to cover the part(s) and
by reducing the amount of VOC in the coatings that are sprayed.
The major technique which provides an attractive exterior/decorative finish on plastic parts for
business machines without emitting VOCs is the use of molded-in color and texture. VOC-free
techniques for EMI/RFI shielding include zinc-arc spraying, electroless plating, the use of conductive
plastics or metal inserts, and in some cases, vacuum metallizing and sputtering.
9/90 (Reformatted 1/95) Evaporation Loss Sources 4.2.2.14-7
-------
Table 4.2.2.14-1. TRANSFER EFFICIENCIES8
Application Methods
Air-atomized spray
Air-assisted airless spray
Electrostatic air spray
Transfer Efficiency
(%)
25
40
40
Type Of Coating
Prime, color, texture, touchup, and fog coats
Prime, color coats
Prime, color coats
a
As noted in the promulgated standards, values are presented solely to aid in determining compliance
with the standards and may not reflect actual TE at a given plant. For this reason, table should be
used with caution for estimating VOC emissions from any new facility. For a more exact estimate
of emissions, the actual TE from specific coating operations at a given plant should be used.
Reference 1.
Transfer efficiency can be improved by using air-assisted airless or electrostatic spray
equipment, which are more efficient than the common application technique (air atomized). More
efficient equipment can reduce VOC emissions by as much as 37 percent over conventional air
atomized spray equipment, through reducing the amount of coating that must be sprayed to achieve a
given film thickness.
Add-on controls applied to VOC emissions in other surface coating industries include thermal
and catalytic incinerators, carbon adsorbers, and condensers. However, these control technologies
have not been used in the surface coating of plastic parts because the large volume of exhaust air and
the low concentrations of VOC in the exhaust reduce their efficiency.
The operating parameters in Tables 4.2.2.14-2 and 4.2.2.14-3 and the emissions factors in
Tables 4.2.2.14-4 and 4.2.2.14-5 are representative of conditions at existing plants with similar
operating characteristics. The 3 general sizes of surface coating plants presented in these tables
(small, medium, and large) are given to assist in making a general estimate of VOC emissions.
However, each plant has its own combination of coating formulations, application equipment, and
operating parameters. Thus, it is recommended that, whenever possible, plant-specific values be
obtained for all variables when calculating emission estimates.
A material balance may be used to provide a more accurate estimate of VOC emissions from
the surface coating of plastic parts for business machines. An emissions estimate can be calculated
using coating composition data (as determined by EPA Reference Method 24), and data on coating
and solvent quantities used in a given time period by a surface coating operation. Using this
approach, emissions are calculated as follows:
where:
MT = total mass of VOC emitted (kg)
Lc = volume of each coating consumed, as sprayed (L)
Dc = density of each coating consumed, as sprayed (kg/L)
W0 = the proportion of VOC in each coating, as sprayed (including dilution solvent added
at plant) (weight fraction)
n = number of coatings applied
4.2.2.14-8 EMISSION FACTORS (Reformatted 1/95) 9/90
-------
Table 4.2.2.14-2 (Metric Units). REPRESENTATIVE PARAMETERS FOR SURFACE COATING
OPERATIONS TO APPLY DECORATIVE/EXTERIOR COATINGS*
Plant
Size
Small
Medium
Large
Operating
Schedule
(hr/yr)
4,000
4,000
4,000
Number Of
Spray Booths
Dry Water
Filter Wash
2 0
5* 0
& 3k
Surface Area
Coated/yr
(nr^Of
Plastic)
9,711
77,743
194,370
Coating Option/Control
Techniques
Baseline coating mixb
Low solids SB coating*1
Medium solids SB
coating6
High solids SB coatingf
WB coating11
Baseline coating mixb
Low solids SB coatingd
Medium solids SB
coating6
High solids SB coatingf
WB coatingh
Baseline coating mixb
Low solids SB coating*1
Medium solids SB
coating*
High solids SB coatingf
WB coatingh
Coating Sprayed
(L/yr)
16,077C
18,500°
11,840°
9,867C/6,167«
16,000°
128,704°
148,100°
94,784°
78,987°/49,3678
128,086°
321,760°
370,275°
236,976°
197,480°/123,425«
320,238°
a Does not address EMI/RFI shielding coatings. SB = solventborne. WB = waterborne.
b Assumes baseline decorative/exterior coating consumption consists of a mix of coatings as follows:
64.8% = Solvent base 2-component catalyzed urethane containing
32 volume % solids at the gun.
23.5% = Solvent base two-component catalyzed urethane containing
50 volume % solids at the gun.
11.7% = Waterborne acrylic containing 37 volume % solids and
12.6 volume % organic solvent at the gun.
c Assumes 25% transfer efficiency (IE) based on the use of air-atomized spray equipment.
d Assumes use of a solvent base coating containing 32 volume % solids at the gun.
e Assumes use of a solvent base coating containing 50 volume % solids at the gun.
f Assumes the use of solvent base 2-component catalyzed urethane coating containing 60 volume %
solids at the gun.
g Assumes 40% TE based on the use of air-assisted airless spray equipment, as required by new
source performance standards.
h Assumes the use of a waterborne coating containing 37 volume % solids and 12.6 volume %
organic solvent at the gun.
1 Assumes 2 spray booths are for batch surface coating operations and remaining 3 booths are on a
conveyor line.
J Assumes 2 spray booths are for batch surface coating operations and remaining 4 booths are on a
conveyor line.
k Assumes that 3 spray booths are on a conveyor line.
9/90 (Reformatted 1/95)
Evaporation Loss Sources
4.2.2.14-9
-------
Table 4.2.2.14-3 (Metric Units). REPRESENTATIVE PARAMETERS FOR SURFACE COATING
OPERATIONS TO APPLY EMI/RFI SHIELDING COATINGS3
Plant
Size
Small
Medium
Large
Operating
Schedule
(hr/yr)
4,000
4,000
4,000
Number Of Spray
Booths
Grit Zinc Arc
Blasting* Spray8
0 0
2 2
4 4
Surface
Area
Coated/yr
(nr^Of
Plastic)
4,921
109,862
239,239
Coating Option/Control
Technique
Low solids SB EMI/RFI
shielding coatingc'd
Higher solids SB EMI/RFI
shielding coatingd>e
WB EMI/RFI shielding
coatingd>f
Zinc arc spray8"'
Low solids SB EMI/RFI
shielding coatingc>d
Higher solids SB EMI/RFI
shielding coatingd'e
WB EMI/RFI shielding
coating >*
Zinc arc sprayg"'
Low solids SB EMI/RFI
shielding coatingc>d
Higher solids SB EMI/RFI
shielding coatingd'e
WB EMI/RFI shielding
coatingd>f
Zinc arc spray8"'
Coating
Sprayed
(L/yr)b
3,334
2,000
1,515
750
74,414
44,648
33,824
16,744
162,040
97,224
73,654
34,460
a Includes sprayed conductive coatings using the dry filter and water wash spray booths listed in
Table 4.2.2.14-2. SB = solventborne. WB = waterborne.
b Assumes 50% transfer efficiency (TE).
c Assumes use of solvent base EMI/RFI shielding coating containing 15 volume % solids at the gun.
d Applied at a 2 mil thickness (standard industry practice).
e Assumes use of a solvent base EMI/RFI shielding coating containing 25 volume % solids at the
gun.
f Assumes use of a waterborne EMI/RFI shielding coating containing 33 volume % solids and
18.8 volume % organic solvent at the gun.
g Assumes use of zinc-arc spray shielding.
h Applied at a 3 mil thickness (standard industry practice).
' Based on amount of zinc wire sprayed per year (kg/yr) and zinc density of 6.32 g/mL.
4.2.2.14-10
EMISSION FACTORS
(Reformatted 1/95) 9/90
-------
Table 4.2.2.14-4 (Metric Units). EMISSION FACTORS FOR VOC FROM SURFACE
COATING OPERATIONS TO APPLY DECORATIVE/EXTERIOR COATINGS8'6
Plant Configuration And
Control Technique
Small
Baseline coating mixc
Low solids SB coatingd
Medium solids SB coating6
High solids SB coatingf
WB coating1
Medium
Baseline coating mix0
Low solids SB coatingd
Medium solids SB coating6
High solids SB coatingf
WB coating8
Large
Baseline coating mixc
Low solids SB coatingd
Medium solids SB coating6
High solids SB coatingf
WB coating8
kg/m2 Coated
0.84
1.14
0.54
0.36 - 0.22
0.18
0.84
1.14
0.54
0.36 - 0.22
0.18
0.84
1.14
0.54
0.36 - 0.22
0.18
Volatile
kg/yr
8,122
11,096
5,221
3,481-2,176
1,778
64,986
88,825
41,800
27,867 - 17,417
14,234
162,463
222,076
104,506
69,671 - 43,544
35,589
Organics
kg/hr
2.0
2.8
1.3
0.87 - 0.54
0.44
16.2
22.2
10.4
7.0 - 4.4
3.6
40.6
55.5
26.1
17.4 - 10.9
8.9
a Assumes values given in Table 4.2.2.14-2, using the following equation: E = LDV
where:
E = VOC emission factors from surface coating operations (kg/yr)
L = Volume of coating sprayed (L)
D = Density coating sprayed (kg/L)
V = Volatile content of coating, including dilution solvents added at plant (weight
fraction)
b Assumes all VOC present is emitted. Values have been rounded off. Does not address EMI/RFI
shielding coatings. Assumes annual operating schedule of 4,000 hours. SB = solventborne.
WB = waterborne.
c Based on use of the baseline coating mix in Table 4.2.2.14-2.
d Based on use of a solvent base coating containing 32 volume % solids at the gun.
e Based on use of a solvent base coating containing 50 volume % solids at the gun.
f Based on use of a solvent base coating containing 60 volume % solids at the gun.
g Based on use of a waterborne coating containing 37 volume % solids and 12.6 volume % organic
solvent at the gun.
9/90 (Reformatted 1/95)
Evaporation Loss Sources
4.2.2.14-11
-------
Table 4.2.2.14-5 (Metric Units). EMISSION FACTORS FOR VOC FROM SURFACE COATING
OPERATIONS TO APPLY EMI/RFI SHIELDING COATINGSa'b
Plant Configuration And Control Technique
Small
Low solids SB EMI/RFI shielding coating0
Higher solids SB EMI/RFI shielding coatingd
WB EMI/RFI shielding coating*
Zinc-arc sprayf
Medium
Low solids SB EMI/RFI shielding coating0
Higher solids SB EMI/RFI shielding coating'1
WB EMI/RFI shielding coatinge
Zinc-arc sprayf
Large
Low solids SB EMI/RFI shielding coating0
Higher solids SB EMI/RFI shielding coatingd
WB EMI/RFI shielding coating6
Zinc-arc sprayf
kg/m2
Coated
0.51
0.27
0.05
0
0.51
0.27
0.05
0
0.51
0.27
0.05
0
Volatile Organics
kg/yr
2,500
1,323
251
0
55,787
29,535
5,609
0
121,484
64,314
12,214
0
kg/hr
0.62
0.33
0.063
0
13.9
7.4
1.4
0
30.4
16.1
3.1
0
a Assumes values given in Table 4.2.2.14-3, using the following equation: E = LDV
where:
E = VOC emission factors from surface coating operations (kg/yr)
L = Volume of coating sprayed (L)
D = Density coating sprayed (kg/L)
V = Volatile content of coating, including dilution solvents added at plant (fraction by
weight)
b Assumes all VOC present is emitted. Values have been rounded off. Does not address EMI/RFI
shielding coatings. Assumes annual operating schedule of 4,000 hours. SB = solventborne.
WB = waterborne.
c Assumes use of solvent base EMI/RFI shielding coating containing 15 volume % solids at the gun.
d Assumes use of a solvent base EMI/RFI shielding coating containing 25 volume % solids at the
gun.
e Assumes use of a waterborne EMI/RFI shielding coating containing 33 volume % solids and
18.8 volume % organic solvent at the gun.
f Assumes use of a zinc-arc spray shielding.
4.2.2.14-12
EMISSION FACTORS
(Refoimatted 1/95) 9/90
-------
References For Section 4.2.2.14
1. Surface Coating Of Plastic Parts For Business Machines—Background Information For
Proposed Standards, EPA-450/3-85-019a, U. S. Environmental Protection Agency, Research
Triangle Park, NC, December 1985.
2. Written communication from Midwest Research Institute, Raleigh, NC, to David Salman,
U. S. Environmental Protection Agency, Research Triangle Park, NC, June 19, 1985.
3. Protectaire® Spray Booths, Protectaire Systems Company, Elgin, IL, 1982.
4. Bmks9 Spray Booths And Related Equipment, Catalog SB-7, Binks Manufacturing Company,
Franklin Park, IL, 1982.
5. Product Literature On Wagner* Air Coat* Spray Gun, Wagner Spray Technology,
Minneapolis, MN, 1982.
9/90 (Reformatted 1/95) Evaporation Loss Sources 4.2.2.14-13
-------
4.3 Waste Water Collection, Treatment And Storage
4.3.1 General
Many different industries generate waste water streams that contain organic compounds.
Nearly all of these streams undergo collection, contaminant treatment, and/or storage operations before
they are finally discharged into either a receiving body of water or a municipal treatment plant for
further treatment. During some of these operations, the waste water is open to the atmosphere, and
volatile organic compounds (VOC) may be emitted from the waste water into the air.
Industrial waste water operations can range from pretreatment to full-scale treatment processes.
In a typical pretreatment facility, process and/or sanitary waste water and/or storm water runoff is
collected, equalized, and/or neutralized and then discharged to a municipal waste water plant, also
known as a publicly owned treatment works (POTWs), where it is then typically treated further by
biodegradation.
In a full-scale treatment operation, the waste water must meet Federal and/or state quality
standards before it is finally discharged into a receiving body of water. Figure 4.3-1 shows a generic
example of collection, equalization, neutralization, and biotreatment of process waste water in a full-
scale industrial treatment facility. If required, chlorine is added as a disinfectant. A storage basin
contains the treated water until the winter months (usually January to May), when the facility is
allowed to discharge to the receiving body of water. In the illustration, the receiving body of water is
a slow-flowing stream. The facility is allowed to discharge in the rainy season when the facility waste
water is diluted.
Figure 4.3-1 also presents a typical treatment system at a POTW waste water facility.
Industrial waste water sent to POTWs may be treated or untreated. POTWs may also treat waste
water from residential, institutional, and commercial facilities; from infiltration (water that enters the
sewer system from the ground); and/or storm water runoff. These types of waste water generally do
not contain VOCs. A POTW usually consists of a collection system, primary settling, biotreatment,
secondary settling, and disinfection.
Collection, treatment, and storage systems are facility-specific. All facilities have some type of
collection system, but the complexity will depend on the number and volume of waste water streams
generated. As mentioned above, treatment and/or storage operations also vary in size and degree of
treatment. The size and degree of treatment of waste water streams will depend on the volume and
degree of contamination of the waste water and on the extent of contaminant removal desired.
4.3.1.1 Collection Systems -
There are many types of waste water collection systems. In general, a collection system is
located at or near the point of waste water generation and is designed to receive 1 or more waste water
streams and then to direct these streams to treatment and/or storage systems.
A typical industrial collection system may include drains, manholes, trenches, junction boxes,
sumps, lift stations, and/or weirs. Waste water streams from different points throughout the industrial
facility normally enter the collection system through individual drains or trenches connected to a main
sewer line. The drains and trenches are usually open to the atmosphere. Junction boxes, sumps,
9/91 (Reformatted 1/95) Evaporation Loss Sources 4.3-1
-------
03
&1
'o
'£
•o
3
•a
c
e
D
i
H
oo
E
4.3-2
EMISSION FACTORS
(Reformatted 1/95) 9/91
-------
trenches, lift stations, and weirs will be located at points requiring waste water transport from 1 area or
treatment process to another.
A typical POTW facility collection system will contain a lift station, trenches, junction boxes,
and manholes. Waste water is received into the POTW collection system through open sewer lines
from all sources of influent waste water. As mentioned previously, these sources may convey sanitary,
pretreated or untreated industrial, and/or storm water runoff waste water.
The following paragraphs briefly describe some of the most common types of waste water
collection system components found in industrial and POTW facilities. Because the arrangement of
collection system components is facility-specific, the order in which the collection system descriptions
are presented is somewhat arbitrary.
Waste water streams normally are introduced into the collection system through individual or
area drains, which can be open to the atmosphere or sealed to prevent waste water contact with the
atmosphere. In industry, individual drains may be dedicated to a single source or piece of equipment.
Area drains will serve several sources and are located centrally among the sources or pieces of
equipment that they serve.
Manholes into sewer lines permit service, inspection, and cleaning of a line. They may be
located where sewer lines intersect or where there is a significant change in direction, grade, or sewer
line diameter.
Trenches can be used to transport industrial waste water from point of generation to collection
units such as junction boxes and lift station, from 1 process area of an industrial facility to another, or
from 1 treatment unit to another. POTWs also use trenches to transport waste water from 1 treatment
unit to another. Trenches are likely to be either open or covered with a safety grating.
Junction boxes typically serve several process sewer lines, which meet at the junction box to
combine multiple waste water streams into 1. Junction boxes normally are sized to suit the total flow
rate of the entering streams.
Sumps are used typically for collection and equalization of waste water flow from trenches or
sewer lines before treatment or storage. They are usually quiescent and open to the atmosphere.
Lift stations are usually the last collection unit before the treatment system, accepting waste
water from 1 or several sewer lines. Their main function is to lift the collected waste water to a
treatment and/or storage system, usually by pumping or by use of a hydraulic lift, such as a screw.
Weirs can act as open channel dams, or they can be used to discharge cleaner effluent from a
settling basin, such as a clarifier. When used as a dam, the weir's face is normally aligned
perpendicular to the bed and walls of the channel. Water from the channel usually flows over the weir
and falls to the receiving body of water. In some cases, the water may pass through a notch or
opening in the weir face. With this type of weir, flow rate through the channel can be measured.
Weir height, generally the distance the water falls, is usually no more than 2 meters (6 feet). A
typical clarifier weir is designed to allow settled waste water to overflow to the next treatment process.
The weir is generally placed around the perimeter of the settling basin, but it can also be towards the
middle. Clarifier weir height is usually only about 0.1 meters (4 inches).
9/91 (Reformatted 1/95) Evaporation Loss Sources 4.3-3
-------
4.3.1.2 Treatment And/Or Storage Systems -
These systems are designed to hold liquid wastes or waste water for treatment, storage, or
disposal. They are usually composed of various types of earthen and/or concrete-lined basins, known
as surface impoundments. Storage systems are used typically for accumulating waste water before its
ultimate disposal, or for temporarily holding batch (intermittent) streams before treatment.
Treatment systems are divided into 3 categories: primary, secondary, or tertiary, depending on
their design, operation, and application. In primary treatment systems, physical operations remove
floatable and settleable solids. In secondary treatment systems, biological and chemical processes
remove most of the organic matter in the waste water. In tertiary treatment systems, additional
processes remove constituents not taken out by secondary treatment.
Examples of primary treatment include oil/water separators, primary clarification, equalization
basins, and primary treatment tanks. The first process in an industrial waste water treatment plant is
often the removal of heavier solids and lighter oils by means of oil/water separators. Oils are usually
removed continuously with a skimming device, while solids can be removed with a sludge removal
system.
In primary treatment, clarifiers are usually located near the beginning of the treatment process
and are used to settle and remove settleable or suspended solids contained in the influent waste water.
Figure 4.3-2 presents an example design of a clarifier. Clarifiers are generally cylindrical and are
sized according to both the settling rate of the suspended solids and the thickening characteristics of
the sludge. Floating scum is generally skimmed continuously from the top of the clarifier, while
sludge is typically removed continuously from the bottom of the clarifier.
Equalization basins are used to reduce fluctuations in the waste water flow rate and organic
content before the waste is sent to downstream treatment processes. Flow rate equalization results in a
more uniform effluent quality in downstream settling units such as clarifiers. Biological treatment
performance can also benefit from the damping of concentration and flow fluctuations, protecting
biological processes from upset or failure from shock loadings of toxic or treatment-inhibiting
compounds.
In primary treatment, tanks are generally used to alter the chemical or physical properties of
the waste water by, for example, neutralization and the addition and dispersion of chemical nutrients.
Neutralization can control the pH of the waste water by adding an acid or a base. It usually precedes
biotreatment, so that the system is not upset by high or low pH values. Similarly, chemical nutrient
addition/dispersion precedes biotreatment, to ensure that the biological organisms have sufficient
nutrients.
An example of a secondary treatment process is biodegradation. Biological waste treatment
usually is accomplished by aeration in basins with mechanical surface aerators or with a diffused air
system. Mechanical surface aerators float on the water surface and rapidly mix the water. Aeration of
the water is accomplished through splashing. Diffused air systems, on the other hand, aerate the water
by bubbling oxygen through the water from the bottom of the tank or device. Figure 4.3-3 presents an
example design of a mechanically aerated biological treatment basin. This type of basin is usually an
earthen or concrete-lined pond and is used to treat large flow rates of waste water. Waste waters with
high pollutant concentrations, and in particular high-flow sanitary waste waters, are
typically treated using an activated sludge system where biotreatment is followed by secondary
clarification. In this system, settled solids containing biomass are recycled from clarifier sludge to the
biotreatment system. This creates a high biomass concentration and therefore allows biodegradation to
occur over a shorter residence time. An example of a tertiary treatment process is nutrient
4.3-4 EMISSION FACTORS (Reformatted 1/95) 9/91
-------
Drive Unit
Effluent Weir
Scraper Blades
Sludge Drawoff Pipe
Figure 4.3-2. Example clarifier configuration.
Cable Ties
Surface
Mechanical
Aerators
Overflow
Weir
Agitated
Surface
Wastewater
Inlet Manifold
Figure 4.3-3. Example aerated biological treatment basin.
9/91 (Reformatted 1/95)
Evaporation Loss Sources
4.3-5
-------
removal. Nitrogen and phosphorus are removed after biodegradation as a final treatment step before
waste water is discharged to a receiving body of water.
4.3.1.3 Applications -
As previously mentioned, waste water collection, treatment, and storage are common in many
industrial categories and in POTW. Most industrial facilities and POTW collect, contain, and treat
waste water. However, some industries do not treat their waste water, but use storage systems for
temporary waste water storage or for accumulation of waste water for ultimate disposal. For example,
the Agricultural Industry does little waste water treatment but needs waste water storage systems,
while the Oil and Gas Industry also has a need for waste water disposal systems.
The following are waste water treatment and storage applications identified by type of
industry:
1. Mining And Milling Operations - Storage of various waste waters such as acid mine
water, solvent wastes from solution mining, and leachate from disposed mining wastes.
Treatment operations include settling, separation, washing, sorting of mineral products
from tailings, and recovery of valuable minerals by precipitation.
2. Oil And Gas Industry - One of the largest sources of waste water. Operations treat
brine produced during oil extraction and deep-well pressurizing operations, oil-water
mixtures, gaseous fluids to be separated or stored during emergency conditions, and
drill cuttings and drilling muds.
3. Textile And Leather Industry - Treatment and sludge disposal. Organic species treated
or disposed of include dye carriers such as halogenated hydrocarbons and phenols.
Heavy metals treated or disposed of include chromium, zinc, and copper. Tanning and
finishing wastes may contain sulfides and nitrogenous compounds.
4. Chemical And Allied Products Industry - Process waste water treatment and storage,
and sludge disposal. Waste constituents are process-specific and include organics and
organic phosphates, fluoride, nitrogen compounds, and assorted trace metals.
5. Other Industries - Treatment and storage operations are found at petroleum refining,
primary metals production, wood treating, and metal finishing facilities. Various
industries store and/or treat air pollution scrubber sludge and dredging spoils sludge (i.
e., settled solids removed from the floor of a surface impoundment).
4.3.2 Emissions
VOCs are emitted from waste water collection, treatment, and storage systems through
volatilization of organic compounds at the liquid surface. Emissions can occur by diffusive or
convective mechanisms, or both. Diffusion occurs when organic concentrations at the water surface
are much higher than ambient concentrations. The organics volatilize, or diffuse into the air, in an
attempt to reach equilibrium between aqueous and vapor phases. Convection occurs when air flows
over the water surface, sweeping organic vapors from the water surface into the air. The rate of
volatilization relates directly to the speed of the air flow over the water surface.
Other factors that can affect the rate of volatilization include waste water surface area,
temperature, and turbulence; waste water retention time in the system(s); the depth of the waste water
in the system(s); the concentration of organic compounds in the waste water and their physical
4.3-6 EMISSION FACTORS (Reformatted 1/95) 9/91
-------
properties, such as volatility and diffusivity in water; the presence of a mechanism that inhibits
volatilization, such as an oil film; or a competing mechanism, such as biodegradation.
The rate of volatilization can be determined by using mass transfer theory. Individual gas
phase and liquid phase mass transfer coefficients (k and k», respectively) are used to estimate overall
mass transfer coefficients (K, Kojl, and KD) for each VOC. Figure 4.3-4 presents a flow diagram to
assist in determining the appropriate emissions model for estimating VOC emissions from various
types of waste water treatment, storage, and collection systems. Tables 4.3-1 and 4.3-2, respectively,
present the emission model equations and definitions.
VOCs vary in their degree of volatility. The emission models presented in this section can be
used for high-, medium-, and low-volatility organic compounds. The Henry's law constant (HLC) is
often used as a measure of a compound's volatility, or the diffusion of organics into the air relative to
diffusion through liquids. High-volatility VOCs are HLC > 10"3 atm-m3/gmol; medium-volatility
VOCs are 10'3 < HLC < 10'^atm-m3/gmol; and low-volatility VOCs are HLC < 10'5 atm-m3/ gmol.1
The design and arrangement of collection, treatment, and storage systems are facility-specific;
therefore the most accurate waste water emissions estimate will come from actual tests of a facility
(i. e., tracer studies or direct measurement of emissions from openings). If actual data are unavailable,
the emission models provided in this section can be used.
Emission models should be given site-specific information whenever it is available. The most
extensive characterization of an actual system will produce the most accurate estimates from an
emissions model. In addition, when addressing systems involving biodegradation, the accuracy of the
predicted rate of biodegradation is improved when site-specific compound biorates are input.
Reference 3 contains information on a test method for measuring site-specific biorates, and
Table 4.3-4 presents estimated biorates for approximately 150 compounds.
To estimate an emissions rate (N), the first step is to calculate individual gas phase and liquid
phase mass transfer coefficients k and k{. These individual coefficients are then used to calculate the
overall mass transfer coefficient, K. Exceptions to this procedure are the calculation of overall mass
transfer coefficients in the oil phase, Koil, and the overall mass transfer coefficient for a weir, KD.
KOJJ requires only k , and KD does not require any individual mass transfer coefficients. The overall
mass transfer coefficient is then used to calculate the emissions rates. The following discussion
describes how to use Figure 4.3-4 to determine an emission rate. An example calculation is presented
in Part 4.3.2.1 below.
Figure 4.3-4 is divided into 2 sections: waste water treatment and storage systems, and waste
water collection systems. Waste water treatment and storage systems are further segmented into
aerated/nonaerated systems, biologically active systems, oil film layer systems, and surface
impoundment flowthrough or disposal. In flowthrough systems, waste water is treated and discharged
to a POTW or a receiving body of water, such as a river or stream. All waste water collection
systems are by definition flowthrough. Disposal systems, on the other hand, do not discharge any
waste water.
Figure 4.3-4 includes information needed to estimate air emissions from junction boxes, lift
stations, sumps, weirs, and clarifier weirs. Sumps are considered quiescent, but junction boxes, lift
stations, and weirs are turbulent in nature. Junction boxes and lift stations are turbulent because
incoming flow is normally above the water level in the component, which creates some splashing.
9/91 (Reformatted 1/95) Evaporation Loss Sources 4.3-7
-------
Treatment and
Storage
aNumbered equations are presented in Table 4.3-1
K{ - Individual liquid phase mass transfer coefficient, m/s
Kg - Individual gas phase mass transfer coefficient, m/s
Kjji - Overall mass transfer coefficient In the oil phase, m/s
KQ - Volatilization - reaeratlon theory mass transfer coefficient
K^ - Overall mass transfer coefficient m/s
N - Emissions, g/s
Wastewater Collection
2 9
2 9
Yes
3 2
1 2
7 16
7 15
7 12
Equations Used to Obtain:
JV Kg_ Kail Kp K N
Flowthrough 1 2
— Disposal 1 2
Biologically
Active?
Flow/through 1 2
Disposal 1 2
—T Flowthrough 1,3 2,4
— Disposal 1,3 2,4
Biologically
Active?
Flowthrough 1,3 2,4
Disposal 1,3 2,4
Flowthrough 1 2
Biologically
Active?
Disposal 1 2
Flowthrough
7 11
7 16
7 15
7 12
7 11
18
17
22
23
7 12
7 12
7 12
10 21
8 24
Figure 4.3.4. Flow diagram for estimating VOC emissions from waste water collection,
treatment, and storage systems.
4.3-8
EMISSION FACTORS
(Reformatted 1/95) 9/91
-------
Table 4.3-1. MASS TRANSFER CORRELATIONS AND EMISSIONS EQUATIONS3
Equation
No. Equation
Individual liquid (kg) and gas (k ) phase mass transfer coefficients
o
1 k, (m/s) = (2.78 x m-6vn /n ^2/3
For: 0 < U10 < 3.25 m/s and all F/D ratios
kf (m/s) = [(2.605 x 10'9)(F/D) + (1.277 x 10-7)](U10)2(Dw^>ether)2/:
For: U10 > 3.25 m/s and 14 < F/D < 51.2
kf (m/s) = (2.61 x 10-7)(U10)2(Dw/Dether)2/3
For: U10 > 3.25 m/s and F/D > 51.2
kc (m/s) = 1.0 x 10'6 + 144 x 10'4 (U*)2'2 (Sc, r°'5; U* < 0.3
kc (m/s) = 1.0 x 10'6 + 34.1 x 10'4 U* (ScL)-°^; U* > 0.3
For: U10 > 3.25 m/s and F/D < 14
where:
U* (m/s) = (0.01)(U10)(6.1 + 0.63(U10))°'5
ScL - jiL/(pLD J
F/D = 2 (A/7t)0'5
kg (m/s) = (4.82 x 10-3)(U10)°-78 (ScG)-°-67 (de)-°-u
where:
ScG = Ma^(Pa^a)
de(m) = 2(A/7r)°^
kj (m/s) = [(8.22 x 10-9)(J)(POWR)(1.024)(T-20)(Ot)(106) *
(MWL)/(VavpL)](Dw/D02iW)a5
where:
POWR (hp) = (total power to aerators)(V)
Vav(ft ) = (fraction of area agitated) (A)
kg (m/s) = (1.35 x l(r7)(Re)U2 (P)0'4 (ScG)°-5 (Fr)-°'21(Da MWa/d)
where:
Re = d2 w pa/(ia
P = [(0.85)(POWR)(550 i
ScG = u /(p D )
Fr = (d*)w2/gc
k, (m/s) = (fair t)(Q)/[3600 s/min (hc)(7tdc)]
where:
aif r = exp [0.77(hc)a623(Q/7rdc)°-66(Dw/D02?w)a66]
kg (m/s) = 0.001 + (0.0462(U**)(ScG)'0-67)
where:
U** (m/s) = [6.1 + (0.63)(U10)]a5(U10/100)
C,^, .i Ifr\ T*\ \
\J\~>s~* — UQ/1U LJ i
9/91 (Reformatted 1/95) Evaporation Loss Sources 4.3-9
-------
Table 4.3-1 (cont.).
Equation
No. Equation
Overall mass transfer coefficients for water (K) and oil (Kp-y) phases and for weirs
7 K= (kt Keq kg)/(Keq kg + kj)
where:
Keq = H/(RT)
8 K (m/s) = [[MWL/(kj L*(100 cm/m)] + [MWa/(k paH*
55,555(100 cm/m))]]4 MWL/[(100 cm/m)pL]
9 Koil = kgKeqoil
where:
Keqoil = P*paMWoil/(poil MWa P0)
10 Kn = 0.16h(n/DmJ°-75
Air emissions (N)
11 N(g/s) = (1 - Ct/Co) V Co/t
where:
Ct/Co =exp[-KAt/V]
12 N(g/s) = K CL A
where:
CL(g/m3) = Q Co/(KA + Q)
13 N(g/s) = (1 - Ct/Co) V Co/t
where:
Ct/Co = exp[-(KA + KeqQa)t/V]
14 N(g/s) = (KA + QaKeq)CL
where:
CL(g/m3) = QCo/(KA + Q + QaKeq)
15 N(g/s) = (1 - Ct/Co) KA/(KA + Kmax b; V/KS) V Co/t
where:
Ct/Co = exp[-Kmax bt t/Ks - K A t/V]
16 N(g/s) = K CL A
where:
CL(g/m3) = [-b + (b2 - 4ac)°'5]/(2a)
and:
a = KA/Q + 1
b = KS(KA/Q + 1) + Kmax b; V/Q - Co
c = -KsCo
4.3-10 EMISSION FACTORS (Reformatted 1/95) 9/91
-------
Table 4.3-1 (cont.).
Equation
No. Equation
17 N(g/s) = (1 - Ctoil/Cooil)VoilCooil/t
where:
CWC°oil =
and:
Cooil = Kow Co/[l - FO + FO(Kow)]
Voil = (FO)(V)
Doi, = (FO)(V)/A
18 N(g/s) = KoilCL)0ilA
where:
CL.oil^™3) = QoilCOoil/^oilA + Qoil)
and:
Coojl = Kow Co/[l - FO + FO(Kow)]
Qoil = (FO)(Q)
19 N(g/s) = (1 - Ct/Co)(KA + QaKeq)/(KA + QaKeq + Kmax b; V/KS) V Co/t
where:
Ct/Co = exp[-(KA + KeqQa)t/V - Kmax b; t/Ks]
20 N(g/s) = (KA + QaKeq)CL
where:
CL(g/m3) = [-b +(b2 - 4ac)°'5]/(2a)
and:
a = (KA + QaKeq)/Q + 1
b = KS[(KA + QaKeq)/Q + 1] + Kmax bj V/Q - Co
c =-KsCo
21 N (g/s) = (1 - exp[-KD])Q Co
/m3) = Qoil(Cooil*)/(KoilA + Qoil)
22 N(g/s) = Koi,CLi0ilA
where:
and:
Cooil* = Co/FO
Qoil =(FO)(Q)
23 N(g/s) = (1 - Ctoil/Cooil*)(Voil)(Cooll*)/t
where:
CWC°oiI* = ^p[-Koi, t/Doil]
and:
Cooil* = Co/FO
Voii = (FO)(V)
Doil = (FO)(V)/A
24 -N (g/s) = (1 - exp[-K n dc hc/Q])Q Co
All parameters in numbered equations are defined in Table 4.3-2.
9/91 (Reformatted 1/95) Evaporation Loss Sources 4.3-11
-------
Table 4.3-2. PARAMETER DEFINITIONS FOR MASS TRANSFER CORRELATIONS AND
EMISSIONS EQUATIONS
Parameter
A
bj
CL
CL,oil
Co
C°oil
Coon*
Ct
ctoil
d
D
d*
Da
dc
de
Dether
DO2,w
Doil
Dw
fair,C
F/D
FO
Fr
gc
Definition
Waste water surface area
Biomass concentration (total biological solids)
Concentration of constituent in the liquid phase
Concentration of constituent in the oil phase
Initial concentration of constituent in the liquid
phase
Initial concentration of constituent in the oil phase
considering mass transfer resistance between
water and oil phases
Initial concentration of constituent in the oil phase
considering no mass transfer resistance between
water and oil phases
Concentration of constituent in the liquid phase at
time = t
Concentration of constituent in the oil phase at
time = t
Impeller diameter
Waste water depth
Impeller diameter
Diffusivity of constituent in air
Clarifier diameter
Effective diameter
Diffusivity of ether in water
Diffusivity of oxygen in water
Oil film thickness
Diffusivity of constituent in water
Fraction of constituent emitted to the air,
considering zero gas resistance
Fetch to depth ratio, de/D
Fraction of volume which is oil
Froude number
Gravitation constant (a conversion factor)
Units
m2 or ft2
g/m3
g/m3
g/m3
g/m3
g/m3
g/m3
g/m3
g/m3
cm
m or ft
ft
cm2/s
m
m
cm2/s
o
cm /s
m
cm2/s
dimensionless
dimensionless
dimensionless
dimensionless
Ibm-ft/s2-lbf
Code3
A
B
D
D
A
D
D
D
D
B
A,B
B
C
B
D
(8.5xlO-6)b
(2.4xl(T5)b
B
C
D
D
B
D
32.17
4.3-12
EMISSION FACTORS
(Reformatted 1/95) 9/91
-------
Table 4.3-2 (cont.).
Parameter
h
hc
H
J
K
KD
Keq
Ke(loil
k8
kc
Kmax
Koil
Kow
MWa
MWoil
MWL
N
NI
°t
P
P*
Po
POWR
Q
Definition
Weir height (distance from the waste water
overflow to the receiving body of water)
Clarifier weir height
Henry's law constant of constituent
Oxygen transfer rating of surface aerator
Overall mass transfer coefficient for transfer of
constituent from liquid phase to gas phase
Volatilization-reaeration theory mass transfer
coefficient
Equilibrium constant or partition coefficient
(concentration in gas phase/concentration in
liquid phase)
Equilibrium constant or partition coefficient
(concentration in gas phase/concentration in oil
phase)
Gas phase mass transfer coefficient
Liquid phase mass transfer coefficient
Maximum biorate constant
Overall mass transfer coefficient for transfer of
constituent from oil phase to gas phase
Octanol-water partition coefficient
Half saturation biorate constant
Molecular weight of air
Molecular weight of oil
Molecular weight of water
Emissions
Number of aerators
Oxygen transfer correction factor
Power number
Vapor pressure of the constituent
Total pressure
Total power to aerators
Volumetric flow rate
Units
ft
m
0
atm-m /gmol
Ib 02/(hr-hp)
m/s
dimensionless
dimensionless
dimensionless
m/s
m/s
g/s-g biomass
m/s
dimensionless
g/m3
g/gmol
g/gmol
g/gmol
g/s
dimensionless
dimensionless
dimensionless
atm
atm
hp
m3/s
Code3
B
B
C
B
D
D
D
D
D
D
A,C
D
C
A,C
29
B
18
D
A,B
B
D
C
A
B
A
9/91 (Reformatted 1/95)
Evaporation Loss Sources
4.3-13
-------
Table 4.3-2 (cont.).
Parameter
Qa
Qoil
r
R
Re
ScG
ScL
T
t
U*
U**
U10
V
Vav
V0il
w
Pa
PL
Poll
ua
UL
Definition
Diffused air flow rate
Volumetric flow rate of oil
Deficit ratio (ratio of the difference between the
constituent concentration at solubility and actual
constituent concentration in the upstream and the
downstream)
Universal gas constant
Reynolds number
Schmidt number on gas side
Schmidt number on liquid side
Temperature of water
Residence time of disposal
Friction velocity
Friction velocity
Wind speed at 10 m above the liquid surface
Waste water volume
Turbulent surface area
Volume of oil
Rotational speed of impeller
Density of air
Density of water
Density of oil
Viscosity of air
Viscosity of water
Units
m3/s
m3/s
dimensionless
atm-m /gmol-K
dimensionless
dimensionless
dimensionless
°C or Kelvin
(K)
s
m/s
m/s
m/s
m3 or ft3
ft2
m3
rad/s
g/cm3
g/cm3 or lb/ft3
g/m3
g/cm-s
g/cm-s
Code3
B
B
D
8.21xlO'5
D
D
D
A
A
D
D
B
A
B
B
B
(1.2xlO'3)b
lb or 62.4b
B
(i.sixio-y
(8.93xlQ-3)b
a Code:
A = Site-specific parameter.
B = Site-specific parameter. For default values, see Table 4.3-3.
C = Parameter can be obtained from literature. See Attachment 1
chemical properties at T = 25°C (298°K).
D = Calculated value.
b Reported values at 25°C (298°K).
for a list of -150 compound
4.3-14
EMISSION FACTORS
(Reformatted 1/95) 9/91
-------
Table 4.3-3. SITE-SPECIFIC DEFAULT PARAMETERS3
Default Parameter15
General
T
U10
Biotreatment Systems
bi
POWR
W
d(d*)
Vav
J
ot
Nl
Diffused Air Systems
Qa
Oil Film Layers
MWoil
Doil
V0il
Qou
Poil
Definition
Temperature of water
Windspeed
Biomass concentration (for biologically active
systems)
Quiescent treatment systems
Aerated treatment systems
Activated sludge units
Total power to aerators
(for aerated treatment systems)
(for activated sludge)
Rotational speed of impeller
(for aerated treatment systems)
Impeller diameter
(for aerated treatment systems)
Turbulent surface area
(for aerated treatment systems)
(for activated sludge)
Oxygen transfer rating to surface aerator
(for aerated treatment systems)
Oxygen transfer correction factor
(for aerated treatment systems)
Number of aerators
Diffused air volumetric flow rate
Molecular weight of oil
Depth of oil layer
Volume of oil
Volumetric flow rate of oil
Density of oil
Default Value
298°K
4.47 m/s
50 g/m3
300 g/m3
4000 g/m3
0.75 hp/1000 ft3 (V)
2 hp/1000 ft3 (V)
126 rad/s (1200 rpm)
61 cm (2 ft)
0.24 (A)
0.52 (A)
3 Ib O2/hp«hr
0.83
POWR/75
0.0004(V) m3/s
282 g/gmol
0.001 (V/A) m
0.001 (V) m3
0.001 (Q) m3/s
0.92 g/cm3
9/91 (Reformatted 1/95)
Evaporation Loss Sources
4.3-15
-------
Table 4.3-3 (cont.).
Default Parameter1*
FO
Junction Boxes
D
NI
Lift Station
D
NI
Sump
D
Weirs
dc
h
hc
Definition
Fraction of volume which is oilc
Depth of Junction Box
Number of aerators
Depth of Lift Station
Number of aerators
Depth of sump
Clarifier weir diameterd
Weir height
Clarifier weir height6
Default Value
0.001
0.9 m
1
1.5 m
1
5.9 m
28.5 m
1.8 m
0.1 m
a Reference 1.
b As defined in Table 4.3-2.
c Reference 4.
d Reference 2.
e Reference 5.
Waste water falls or overflows from weirs and creates splashing in the receiving body of water (both
weir and clarifier weir models). Waste water from weirs can be aerated by directing it to fall over
steps, usually only the weir model.
Assessing VOC emissions from drains, manholes, and trenches is also important in
determining the total waste water facility emissions. As these sources can be open to the atmosphere
and closest to the point of waste water generation (i. e., where water temperatures and pollutant
concentrations are greatest), emissions can be significant. Currently, there are no well-established
emission models for these collection system types. However, work is being performed to address this
need.
Preliminary models of VOC emissions from waste collection system units have been
developed. The emission equations presented in Reference 4 are used with standard collection system
parameters to estimate the fraction of the constituents released as the waste water flows through each
unit. The fractions released from several units are estimated for high-, medium-, and low-volatility
compounds. The units used in the estimated fractions included open drains, manhole covers, open
trench drains, and covered sumps.
4.3-16
EMISSION FACTORS
(Reformatted 1/95) 9/91
-------
The numbers in Figure 4.3-4 under the columns for k{, k , KQil, KD, K, and N refer to the
appropriate equations in Table 4.3-1.a Definitions for all parameters in these equations are given in
Table 4.3-2. Table 4.3-2 also supplies the units that must be used for each parameter, with codes to
help locate input values. If the parameter is coded with the letter A, a site-specific value is required.
Code B also requires a site-specific parameter, but defaults are available. These defaults are typical or
average values and are presented by specific system in Table 4.3-3.
Code C means the parameter can be obtained from literature data. Table 4.3-4 contains a list
of approximately 150 chemicals and their physical properties needed to calculate emissions from waste
water, using the correlations presented in Table 4.3-1. All properties are at 25°C (77°F).
A more extensive chemical properties data base is contained in Appendix C of Reference 1.)
Parameters coded D are calculated values.
Calculating air emissions from waste water collection, treatment, and storage systems is a
complex procedure, especially if several systems are present. Performing the calculations by hand may
result in errors and will be time consuming. A personal computer program called the Surface
Impoundment Modeling System (SIMS) is now available for estimating air emissions. The program is
menu driven and can estimate air emissions from all surface impoundment models presented in
Figure 4.3-4, individually or in series. The program requires for each collection, treatment, or storage
system component, at a minimum, the waste water flow rate and component surface area. All other
inputs are provided as default values. Any available site-specific information should be entered in
place of these defaults, as the most fully characterized system will provide the most accurate emissions
estimate.
The SIMS program with user's manual and background technical document can be obtained
through state air pollution control agencies and through the U. S. Environmental Protection Agency's
Control Technology Center in Research Triangle Park, NC, telephone (919) 541-0800. The user's
manual and background technical document should be followed to produce meaningful results.
The SIMS program and user's manual also can be downloaded from EPA's Clearinghouse For
Inventories and Emission Factors (CHIEF) electronic bulletin board (BE). The CHIEF BB is open to
all persons involved in air emission inventories. To access this BB, one needs a computer, modem, and
communication package capable of communicating at up to 14,400 baud, 8 data bits, 1 stop bit, and no
parity (8-N-l). This BB is part of EPA's OAQPS Technology Transfer Network system and its
telephone number is (919) 541-5742. First-time users must register before access is allowed.
Emissions estimates from SIMS are based on mass transfer models developed by Emissions
Standards Division (ESD) during evaluations of TSDFs and VOC emissions from industrial waste
water. As a part of the TSDF project, a Lotus® spreadsheet program called CHEMDAT7 was
developed for estimating VOC emissions from waste water land treatment systems, open landfills,
closed landfills, and waste storage piles, as well as from various types of surface impoundments. For
more information about CHEMDAT7, contact the ESD's Chemicals And Petroleum Branch (MD 13),
US EPA, Research Triangle Park, NC 27711.
aAll emission model systems presented in Figure 4.3-4 imply a completely mixed or uniform waste
water concentration system. Emission models for a plug flow system, or system in which there is no
axial, or horizontal mixing, are too extensive to be covered in this document. (An example of plug
flow might be a high waste water flow in a narrow channel.) For information on emission models of
this type, see Reference 1.
9/91 (Reformatted 1/95) Evaporation Loss Sources 4.3-17
-------
4.3.2.1 Example Calculation -
An example industrial facility operates a flowthrough, mechanically aerated biological
treatment impoundment that receives waste water contaminated with benzene at a concentration of
10.29 g/m3.
The following format is used for calculating benzene emissions from the treatment process:
I. Determine which emission model to use
II. User-supplied information
III. Defaults
IV. Pollutant physical property data and water, air, and other properties
V. Calculate individual mass transfer coefficient
VI. Calculate the overall mass transfer coefficients
VII. Calculate VOC emissions
I. Determine Which Emission Model To Use — Following the flow diagram in Figure 4.3-4, the
emission model for a treatment system that is aerated, but not by diffused air, is biologically
active, and is a flowthrough system, contains the following equations:
Equation Nos.
Parameter Definition from Table 4.3-1
K Overall mass transfer coefficient, m/s 7
kf Individual liquid phase mass transfer coefficient, m/s 1,3
k Individual gas phase mass transfer coefficient, m/s 2,4
&
N VOC emissions, g/s 16
II. User-supplied Information — Once the correct emission model is determined, some site-specific
parameters are required. As a minimum for this model, site-specific flow rate, waste water
surface area and depth, and pollutant concentration should be provided. For this example, these
parameters have the following values:
Q = Volumetric flow rate = 0.0623 m3/s
D = Waste water depth = 1.97 m
A = Waste water surface area = 17,652 m2
Co = Initial benzene concentration in the liquid phase = 10.29 g/m
III. Defaults — Defaults for some emission model parameters are presented in Table 4.3-3.
Generally, site-specific values should be used when available. For this facility, all available
general and biotreatment system defaults from Table 4.3-3 were used:
U10 = Wind speed at 10 m above the liquid surface = e = 4.47 m/s
T = Temperature of water = 25°C (298°K)
bj = Biomass concentration for aerated treatment systems = 300 g/m
J = Oxygen transfer rating to surface aerator = 3 Ib O2/hp-hr
POWR = Total power to aerators = 0.75 hp/1,000 ft3 (V)
Ot = Oxygen transfer correction factor = 0.83
Vay = Turbulent surface area = 0.24 (A)
d = Impeller diameter = 61 cm
4.3-18 EMISSION FACTORS (Reformatted 1/95) 9/91
-------
.*
d = Impeller diameter = 2 ft
w = Rotational speed of impeller =126 rad/s
Nr = Number of aerators = POWR/75 hp
IV. Pollutant Physical Property Data, And Water, Air and Other Properties — For each pollutant, the
specific physical properties needed by this model are listed in Table 4.3-4. Water, air, and other
property values are given in Table 4.3-2.
A. Benzene (from Table 4.3-4)
f\ O
^w benzene = Diffusivity of benzene in water - 9.8 x 10 cm /s
Da t,enzene = Diffusivity of benzene in air = 0.088 cm /s
^benzene = Henry's law constant for benzene = 0.0055 atm- m3/gmol
Kmaxbenzene = Maximum biorate constant for benzene = 5.28 x 10" g/g-s
Ks benzene = ^a^ saturati°n biorate constant for benzene = 13.6 g/m3
B. Water, Air, and Other Properties (from Table 4.3-3)
pa = Density of air = 1.2 x 103 g/cm3
pL = Density of water = 1 g/cm^(62.4 lbm/ft3)
ua = Viscosity of air = 1.81 x 10"4 g/cm-s
DQ2 w = Diffusivity of oxygen in water = 2.4 x 10"5 cm2/s
Aether = Diffusivity of ether in water = 8.5 x 10 cm /s
MWL = Molecular weight of water =18 g/gmol
MWa = Molecular weight of air = 29 g/gmol
g- = Gravitation constant = 32.17 lbm-ft/lbrs2
*-*C 111 f- I o
R = Universal gas constant = 8.21 x 10 atm-m /gmol
V. Calculate Individual Mass Transfer Coefficients — Because part of the impoundment is turbulent
and part is quiescent, individual mass transfer coefficients are determined for both turbulent and
quiescent areas of the surface impoundment.
Turbulent area of impoundment — Equations 3 and 4 from Table 4.3-1.
A. Calculate the individual liquid mass transfer coefficient, kf:
k((m/s) = [(8.22 x 10-9)(J)(POWR)(1.024)(T-20) *
(Ot)(106)MWL/(VavpL)](Dw^02iW)°-5
The total power to the aerators, POWR, and the turbulent surface area, Va^,, are calculated
separately [Note: some conversions are necessary.]:
1. Calculate total power to aerators, POWR (Default presented in III):
POWR (hp) = 0.75 hp/1,000 ft3 (V)
V = waste water volume, m
V (m3) = (A)(D) = (17,652 m2)(1.97 m)
V = 34,774 m3
POWR = (0.75 hp/1,000 ft3)(ft3/0.028317 m3)(34,774 m3)
= 921 hp
2. Calculate turbulent surface area, Vav (default presented in III):
Vav (ft2) = 0.24 (A)
= 0.24(17,652 m2)(10.758 ft2/m2)
= 45,576 ft2
9/91 (Reformatted 1/95) Evaporation Loss Sources 4.3-19
-------
Now, calculate k{, using the above calculations and information from II, III, and IV:
kt (m/s) = [(8.22 x 10'9)(3 Ib O2/hp-hr)(921 hp) *
(1.024)(25-20)(0.83)( 106)( 18 g/gmol)/
((45,576 ft2)(l g/cm3))] *
[(9.8 x 10'6 cm2/s)/(2.4 x 10'5 cm2/s)]0'5
= (0.00838)(0.639)
kp = 5.35 x ID'3 m/s
B. Calculate the individual gas phase mass transfer coefficient, k :
kg (m/s) = (1.35 x 10-7)(Re)1-42(P)a4(ScG)0-5(Fr)-°-21(Da MWa/d)
The Reynolds number, Re, power number, P, Schmidt number on the gas side, ScG, and
Froude's number Fr, are calculated separately:
1. Calculate Reynolds number, Re:
Re = d2 w pa/ua
= (61 cm)2(126 rad/s)(1.2 x lO'3 g/cm3)/(1.81 x 10'4 g/cm-s)
= 3.1 x 106
2. Calculate power number, P:
P = [(0.85)(POWR)(550 ft-lb/s-hp)/^] gc/(pL(d*)5 w3)
Nj = POWR/75 hp (default presented in III)
P = (0.85)(75 hp)(POWR/POWR)(550 ft-lb/s-hp) *
(32.17 lbm-ft/lbrs2)/[(62.4 Ibm/ft3)(2 ft)5(126 rad/s)3]
= 2.8 x 10'4
3. Calculate Schmidt number on the gas side, ScG:
ScG = ua/(paDa)
= (1.81 x 10"4 g/cm-s)/[(1.2 x 10'3 g/cm3)(0.088 cm2/s)]
= 1.71
4. Calculate Froude number, Fr:
Fr = (d*)w2/gc
= (2 ft)(126 rad/s)2/(32.17 lbm-ft/lbrs2)
= 990
Now, calculate k using the above calculations and information from II, III, and IV:
o
kg (m/s) = (1.35 x 10'7)(3.1 x 106)L42(2.8 x 10-4)°-4(1.71)a5 *
(990)-°-21 (0.088 cm2/s)(29 g/gmol)/(61 cm)
= 0.109 m/s
Quiescent surface area of impoundment — Equations 1 and 2 from Table 4.3-1
A. Calculate the individual liquid phase mass transfer coefficient, k{:
F/D = 2(A/7i)°'5/D
= 2(17,652 m2/7t)°-5/(1.97 m)
= 76.1
U10 = 4.47 m/s
4.3-20 EMISSION FACTORS (Reformatted 1/95) 9/91
-------
For U10 > 3.25 m/s and F/D > 51.2 use the following:
k, (m/s) = (2.61 x 10-7)(U10)2(Dw^>ether)2/3
= (2.61 x 10'7)(4.47 m/s)2[(9.8 x 1(T6 cm2/s)/
(8.5 x 1CT6 cm2/s)!2/3
= 5.74 x 1CT6 m/s
B. Calculate the individual gas phase mass transfer coefficient, k :
o
kg = (4.82 x 10-3)(U10)°-78(ScG)-a67(de)-ai1
The Schmidt number on the gas side, ScQ, and the effective diameter, de, are calculated
separately:
1. Calculate the Schmidt number on the gas side, ScG:
ScG = ua/(paDa) = 1.71 (same as for turbulent impoundments)
2. Calculate the effective diameter, de:
de (m) = 2(A/7t)0-5
= 2(17,652 m2/K)°-5
= 149.9 m
k (m/s) = (4.82 x 10"3)(4.47 m/s)a78 (1.71)-°-67 (149.9 m)'0'11
= 6.24 x 10'3 m/s
VI. Calculate The Overall Mass Transfer Coefficient — Because part of the impoundment is
turbulent and part is quiescent, the overall mass transfer coefficient is determined as an area-
weighted average of the turbulent and quiescent overall mass transfer coefficients. (Equation 7
from Table 4.3-1).
Overall mass transfer coefficient for the turbulent surface area of impoundment,KT
KT (m/s) = (kjKeqk )/(Keqk + k,)
Keq = H/RT
= (0.0055 atm-m3/gmol)/[(8.21 x 10'5 atm-m3/ gmol-°K)(298°K)]
= 0.225
KT (m/s) = (5.35 x 10'3 m/s)(0.225)(0.109)/[(0.109 m/s)(0.225) +
(5.35 x 10'6 m/s)]
KT = 4.39 x 10'3 m/s
Overall mass transfer coefficient for the quiescent surface area of impoundment, KQ
KQ (m/s) = (kcKeqk )/(Keqk + k,)
= (5.74 x TO'6 m/s)(0.225)(6.24 x 10'3 m/s)/
[(6.24 X ID'3 m/s)(0.225) + (5.74 x 10'6 m/s)]
= 5.72 x 10'6 m/s
Overall mass transfer coefficient, K, weighted by turbulent and quiescent surface areas,
AT and AQ
K (m/s) = (KTAT + KqAQ)/A
AT = 0.24(A) (Default value presented in III: AT = Vay)
AQ = (1 - 0.24)A
K (m/s) = [(4.39 x 10'3 m/s)(0.24 A) + (5.72 x 10'6 m/s)(l - 0.24)A]/A
= 1.06 x 10'3 m/s
9/91 (Reformatted 1/95) Evaporation Loss Sources 4.3-21
-------
VII, Calculate VOC Emissions For An Aerated Biological Flowthrough Impoundment — Equation 16
from Table 4.3-1:
N (g/s) = K CL A
where:
CL (g/m3) - [-b + (b2 - 4ac)a5]/(2a)
and:
a-f KA/Q+ 1
b = KS(KA/Q + 1) + Kmax b{ V/Q - Co
c = -KsCo
Calculate a, b, c, and the concentration of benzene in the liquid phase, CL, separately:
1. Calculate a:
a = (KA/Q + 1) = [(1.06 x 10'3 m/s)(17,652 m2)/(0.0623 m3/s)] + 1
= 301.3
2. Calculate b (V = 34,774 m3 from IV):
b = Ks (KA/Q + 1) + Kmax bj V/Q - Co
= (13.6 g/m3)[(1.06 x 10'3 m/s)(17,652 m2)/(0.0623 m3/s)] +
[(5.28 x 10'6 g/g-s)(300 g/m3)(34,774 m3)/(0.0623 m3/s)] - 10.29 g/m3
= 4,084.6 + 884.1 - 10.29
= 4,958.46 g/m3
3. Calculate c:
c = -KsCo
= -(13.6 g/m3)(10.29 g/m3)
= -139.94
4. Calculate the concentration of benzene in the liquid phase, CL, from a, b, and c above:
CL (g/m3) = [-b + (b2 - 4ac)a5]/(2a)
= [(4,958.46 g/m3) + [(4,958.46 g/m3)2 -
[4(301.3)(-139.94)]r5]/(2(301.3))
= 0.0282 g/m3
Now calculate N with the above calculations and information from II and V:
N (g/s) = K A CL
= (1.06 x 10'3 m/s)( 17,652 m2)(0.0282 g/m3)
= 0.52 g/s
4.3.3 Controls
The types of control technology generally used in reducing VOC emissions from waste water
include: steam stripping or air stripping, carbon adsorption (liquid phase), chemical oxidation,
membrane separation, liquid-liquid extraction, and biotreatment (aerobic or anaerobic). For efficient
control, all control elements should be placed as close as possible to the point of waste water
generation, with all collection, treatment, and storage systems ahead of the control technology being
covered to suppress emissions. Tightly covered, well-maintained collection systems can suppress
4.3-22 EMISSION FACTORS (Reformatted 1/95) 9/91
-------
emissions by 95 to 99 percent. However, if there is explosion potential, the components should be
vented to a control device such as an incinerator or carbon adsorber.
The following are brief descriptions of the control technology listed above and of any
secondary controls that may need to be considered for fugitive air emissions.
Steam stripping is the fractional distillation of waste water to remove volatile organic
constituents, with the basic operating principle being the direct contact of steam with waste water.
The steam provides the heat of vaporization for the more volatile organic constituents. Removal
efficiencies vary with volatility and solubility of the organic impurities. For highly volatile
compounds (HLC greater than 10~3 atm-m /gmol), average VOC removal ranges from 95 to
99 percent. For medium-volatility compounds (HLC between 10 and 10 atm-m /gmol), average
removal ranges from 90 to 95 percent. For low-volatility compounds (HLC <10"5 atm-m3/gmol),
average removal ranges from less than 50 to 90 percent.
Air stripping involves the contact of waste water and air to strip out volatile organic
constituents. By forcing large volumes of air through contaminated water, the surface area of water in
contact with air is greatly increased, resulting in an increase in the transfer rate of the organic
compounds into the vapor phase. Removal efficiencies vary with volatility and solubility of organic
impurities. For highly volatile compounds, average removal ranges from 90 to 99 percent; for
medium- to low-volatility compounds, removal ranges from less than 50 to 90 percent.
Steam stripping and air stripping controls most often are vented to a secondary control, such as
a combustion device or gas phase carbon adsorber. Combustion devices may include incinerators,
boilers, and flares. Vent gases of high fuel value can be used as an alternate fuel. Typically, vent gas
is combined with other fuels such as natural gas and fuel oil. If the fuel value is very low, vent gases
can be heated and combined with combustion air. It is important to note that organics such as
chlorinated hydrocarbons can emit toxic pollutants when combusted.
Secondary control by gas phase carbon adsorption processes takes advantage of compound
affinities for activated carbon. The types of gas phase carbon adsorption systems most commonly
used to control VOC are fixed-bed carbon adsorbers and carbon canisters. Fixed-bed carbon adsorbers
are used to control continuous organic gas streams with flow rates ranging from 30 to over
3000 m /min. Canisters are much simpler and smaller than fixed-bed systems and are usually installed
to control gas flows of less than 3 m3/min.4 Removal efficiencies depend highly on the type of
compound being removed. Pollutant-specific activated carbon is usually required. Average removal
efficiency ranges from 90 to 99 percent.
Like gas phase carbon adsorption, liquid phase carbon adsorption takes advantage of
compound affinities for activated carbon. Activated carbon is an excellent adsorbent, because of its
large surface area and because it is usually in granular or powdered form for easy handling. Two
types of liquid phase carbon adsorption are the fixed-bed and moving-bed systems. The fixed-bed
system is used primarily for low-flow waste water streams with contact times around 15 minutes, and
it is a batch operation (i. e., once the carbon is spent, the system is taken off line). Moving-bed
carbon adsorption systems operate continuously with waste water typically being introduced from the
bottom of the column and regenerated carbon from the top (countercurrent flow). Spent carbon is
continuously removed from the bottom of the bed. Liquid phase carbon adsorption is usually used for
low concentrations of nonvolatile components and for high concentrations of nondegradable
compounds.5 Removal efficiencies depend on whether the compound is adsorbed on activated carbon.
Average removal efficiency ranges from 90 to 99 percent.
9/91 (Reformatted 1/95) Evaporation Loss Sources 4.3-23
-------
Chemical oxidation involves a chemical reaction between the organic compound and an
oxidant such as ozone, hydrogen peroxide, permanganate, or chlorine dioxide. Ozone is usually added
to the waste water through an ultraviolet-ozone reactor. Permanganate and chlorine dioxide are added
directly into the waste water. It is important to note that adding chlorine dioxide can form chlorinated
hydrocarbons in a side reaction. The applicability of this technique depends on the reactivity of the
individual organic compound.
Two types of membrane separation processes are ultrafiltration and reverse osmosis.
Ultrafiltration is primarily a physical sieving process driven by a pressure gradient across the
membrane. This process separates organic compounds with molecular weights greater than 2000,
depending on the size of the membrane pore. Reverse osmosis is the process by which a solvent is
forced across a semipermeable membrane because of an osmotic pressure gradient. Selectivity is,
therefore, based on osmotic diffusion properties of the compound and on the molecular diameter of the
compound and membrane pores.
Liquid-liquid extraction as a separation technique involves differences in solubility of
compounds in various solvents. Contacting a solution containing the desired compound with a solvent
in which the compound has a greater solubility may remove the compound from the solution. This
technology is often used for product and process solvent recovery. Through distillation, the target
compound is usually recovered, and the solvent reused.
Biotreatment is the aerobic or anaerobic chemical breakdown of organic chemicals by
microorganisms. Removal of organics by biodegradation is highly dependent on the compound's
biodegradability, its volatility, and its ability to be adsorbed onto solids. Removal efficiencies range
from almost zero to 100 percent. In general, highly volatile compounds such as chlorinated
hydrocarbons and aromatics will biodegrade very little because of their high-volatility, while alcohols
and other compounds soluble in water, as well as low-volatility compounds, can be almost totally
biodegraded in an acclimated system. In the acclimated biotreatment system, the microorganisms
easily convert available organics into biological cells, or biomass. This often requires a mixed culture
of organisms, where each organism utilizes the food source most suitable to its metabolism. The
organisms will starve and the organics will not be biodegraded if a system is not acclimated, i. e., the
organisms cannot metabolize the available food source.
4.3.4 Glossary Of Terms
Basin - an earthen or concrete-lined depression used to hold liquid.
Completely mixed - having the same characteristics and quality throughout or at all times.
Disposal - the act of permanent storage. Flow of liquid into, but not out of a device.
Drain - a device used for the collection of liquid. It may be open to the atmosphere or
be equipped with a seal to prevent emissions of vapors.
Flowthrough - having a continuous flow into and out of a device.
Plug flow - having characteristics and quality not uniform throughout. These will change
in the direction the fluid flows, but not perpendicular to the direction of flow
(i. e., no axial movement)
4.3-24 EMISSION FACTORS (Reformatted 1/95) 9/91
-------
Storage - any device to accept and retain a fluid for the purpose of future discharge.
Discontinuity of flow of liquid into and out of a device.
Treatment - the act of improving fluid properties by physical means. The removal of
undesirable impurities from a fluid.
VOC - volatile organic compounds, referring to all organic compounds except the
following, which have been shown not to be photochemically reactive:
methane, ethane, trichlorotrifluoroethane, methylene chloride,
1,1,1 ,-trichloroethane, trichlorofluoromethane, dichlorodifluoromethane,
chlorodifluoromethane, trifluoromethane, dichlorotetrafluoroethane, and
chloropentafluoroethane.
9/91 (Reformatted 1/95) Evaporation Loss Sources 4.3-25
-------
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9/91 (Reformatted 1/95)
Evaporation Loss Sources
4.3-29
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PROPIONALDEHYDE
4.3-30
EMISSION FACTORS
(Reformatted 1/95) 9/91
-------
c
o
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g-,
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4.3-31
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(Reformatted 1/95) 9/91
-------
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4.3-36
EMISSION FACTORS
(Reformatted 1/95) 9/91
-------
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Evaporation Loss Sources
4.3-37
-------
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4.3-38
EMISSION FACTORS
(Reformatted 1/95) 9/91
-------
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9/91 (Reformatted 1/95)
Evaporation Loss Sources
4.3-39
-------
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4.3.5 Waste Water—Greenhouse Gases
Greenhouse gases are emitted from both domestic and industrial waste water treatment operations.
When biological processes such as suspended-growth and attached-growth units operate in anaerobic
conditions with high biochemical oxygen demand (BOD) loading, the dominant greenhouse gas emitted is
methane (CH4), though lesser quantities of carbon dioxide (CO2) and nitrous oxide (N2O) may also be
emitted. Methane generated from waste water treatment plants may also be collected and utilized as a source
of energy, or flared. An anaerobic process is any treatment process that operates in the absence of oxygen.
The chemical reactions that occur in anaerobic conditions are mitigated by biological activities, such that they
are affected by many different factors (i.e., BOD loading, oxygen concentration, phosphorus and nitrogen
levels, temperature, redox potential, and retention time) which may significantly impact emissions.
4.3.5.1 Domestic Waste Water Treatment Processes -
Publicly owned treatment works (POTWs) are treatment facilities that treat waste water from
residences and businesses of a defined community. Aerobic treatment, which is rapid and relatively low in
odor, is used by a majority of POTWs in the U.S. The most common aerobic treatment process is activated
sludge, where raw waste water is mixed with a sludge of living aerobic microorganisms (the sludge is
activated in a mechanically aerated tank). The microorganisms rapidly adsorb and biologically oxidize the
organic solids suspended in the waste water, producing CO2. POTWs use a wide range of chemical and
biological processes. A POTW usually consists of a number of aerobic, anaerobic, and physical processes.
Those facilities that use biological processes under anaerobic conditions with high BOD loading emit CH4,
and, to a lesser extent, N2O and CO2. None of the data currently available on N2O and CO2 emissions are
useful for developing emission factors for this source. Emissions of CO2 from this source as well as other
biogenic sources are part of the carbon cycle, and as such are typically not included in greenhouse gas
emission inventories. To estimate uncontrolled CH4 emissions from a typical waste water treatment plant,
the following equation can be used:
fib BOD5
\ capita/day
days
yr
0.22 Ib CH4
Ib BOD,
Fraction
Anaerobically
Digested
lbCH
(1)
where:
P is the population of the community served by the POTW.
Note: To convert from Ib CH4/yr to kg CH4/yr, multiply by 0.454.
BOD5 is a standardized measurement for BOD. This 5-day BOD test is a measure of the "strength"
of the waste water; waste water with a high BOD5 is considered "strong." The BOD5-CH4
conversion (0.22 Ib CH4/lb BOD5) is taken from Metcalf & Eddy8 and Orlich.9 The domestic BOD loading
rate (Ib BOD5/capita/day) varies from one population group to the next, usually ranging from 0.10 to 0.17 Ib,
10
with a typical value of 0.13 Ib BOD5/capita/day. To obtain the exact domestic BOD loading rate for a
specific community, contact the local waste water treatment plant operator for that community. It has been
hypothesized that emission factors based on chemical oxygen demand (COD) are more accurate than those
based on BOD.11 Research is currently being conducted by the U. S. EPA relevant to this hypothesis.
02/98
Evaporation Loss Sources
4.3-41
-------
The fraction of the domestic waste water treated anaerobically is calculated by considering which
treatment processes are anaerobic and what percent of the total hydraulic retention time the waste water
spends in these treatment processes. This fraction is dependent on the treatment processes used and the
operating conditions of a specific plant. This information can also be provided by contacting local waste
water treatment plant operators. If treatment activity data are not available from local wastewater treatment
1 0
plant operators, a default value of 15 percent of domestic water treated anaerobically may also be used. A
default value of 15 percent is also recommended in the Intergovernmental Panel on Climate Change (IPCC)
Greenhouse Gas Inventory Reference Manual13
If aBOD5 value of 0.13 lbBOD5 is assumed, the IPCC assumption is used that
15 percent of waste water is anaerobically digested, and none of the gas is recovered for energy or flared, then
equation 1 reduces to the following equation:
Ilb CH. , —*»x x^,,
1.56 1 = Ib 1 (2)
capita/yr/
4.3.5.2 Industrial Waste Water Treatment Processes -
An industrial waste water system uses unit processes similar to those found in POTWs. Such a
treatment system may discharge into a water body or may pretreat the waste water for discharge into a sewer
system leading to a POTW. To estimate uncontrolled CH4 methane emissions from a typical industrial waste
water treatment plant the following equation can be used:
( Ib BOD, ^ ( 0.22 Ib CH,^ Fraction
,, * 2— * 1 * Anaerobically
ft3 wastewater J \ Ib BOD5 J ^ Digested J
fil- days^ _ Ib CH4
yr J yr
where:
Qt = daily waste water flow (ft3/day).
Flow rates for individual industrial waste water treatment facilities (Qj) can be provided by the
operator of the industrial waste water treatment plant or by reviewing a facility's National Pollution Discharge
Elimination System (NPDES) discharge permit.
Industrial BOD loading rates (Ib BOD5/ft3 waste water) vary depending upon the source of the waste
water contamination. Some contaminants have very high BOD5, such as contaminants in food and beverage
manufacturers' waste water. Table 4.3-5 provides a list of typical industrial BOD loading rates for major
industrial sources. To obtain the exact BOD loading rate for a specific facility, contact the facility's waste
water treatment plant operator or review the facility's NPDES discharge permit.
4.3-42 EMISSION FACTORS 02/98
-------
The fraction of the industrial waste water treated anaerobically is dependent on the treatment
processes used in specific plants. The composition of an industrial waste stream is more diverse than
municipal wastewater. The difference makes it very difficult to provide a default fraction of anaerobically
treated wastewater that would be representative of facilities in a specific inventory area. This information can
also be provided by contacting individual waste water treatment plant operators.
4.3.5.3 Controls
Waste water treatment plant operators (domestic as well as industrial) can also provide information
on gas recovery and utilization. If a gas recovery system is in place, uncontrolled CH4 emissions estimates
should be adjusted based on operator estimates of the efficiency of the gas collection system and the
destruction of the collected gas. For more information on control efficiencies, see Section 4.3.3.
4.3.6 Updates Since the Fifth Edition
The Fifth Edition was released in January 1995. In February 1998, this section was revised by the
addition of 4.3.5 which addresses Greenhouse Gas emissions. The revisions made in February 1998 are to be
included in Supplement D.
02/98 Evaporation Loss Sources 4.3-43
-------
Table 4.3-5. BIOCHEMICAL OXYGEN DEMAND (BOD) ESTIMATES FOR VARIOUS
INDUSTRIAL WASTE WATERS
Industry
Fertilizer
Food and
beverages
Beer
Beet sugar
Butter
Cane sugar
Cereals
Cheese
Fruits and
vegetables'1
Meats
Milk
Wine
Iron and steel
Non-ferrous
metals
Petroleum
refining
(Petrochemical)
Pharmaceutical
Pulp and paper
Rubber
Textiles
BOD5 (Ib/ft3)3
0.04
5.31
0.41
0.19
0.08
0.06
1.9
40.27
1.3
7.6
8.43
0.04
0.04
0.25
0.08
0.17
0.04
0.04
Reference
Number
14
15
15,16
17
15
18
17
15
19
15
15
14
14
14
14
14,20
14
14
Range
0.03-0.05b
4.99-5. 62C
0.34-0.47C
0.07-0.09C
Average of BOD values for processing 35 different
fruits an vegetables. The BOD values ranged from
4.370 to 1747.979 lbs/ft3. For the BOD5 value it
was assumed that biodegradation was high such that
the BOD5 value was considered to be 75% of the
BOD value.
--
6.24-8.93c
7.49-9.36c
0.03-0.05b
0.03-0.05b
Average of values reported in Carmichael and
Strzepek (1987).
0.07-0.09°
0.14-0.19
0.03-0.05b
0.03-0.05C
a To convert Ib/fr to kg/m3 multiply by 16.0185.
b A BOD5 value was not provided in the literature. The range of BOD5 values was derived from the ultimate
BOD value from the textile industry, which should have a similar, relatively small value. BOD5 is 55 to 75
percent of ultimate BOD, depending on the biodegradability of the waste stream. The midpoint of the
extrapolated range is presented in the second column as BOD5.
c A range of values is given for BOD5 because a specific BOD5 value was not provided in the literature. The
range of BOD5 values was derived from the ultimate BOD value from the literature. BOD5 is 55 to 75
percent of ultimate BOD, depending on the biodegradability of the waste stream. If the waste stream
contains a large amount of material that does not biodegrade easily, then a value closer to the lower value
should be used. If the waste stream contains a large amount of material that does biodegrade easily, then a
value closer to the higher value should be used. If it is unclear how biodegradable the material is, and
BOD5 data for a specific facility is not available, then a value at the midpoint of the range should be used.
The midpoint of the range is presented in the second column as BOD5.
d For a more complete list of BOD5 values see reference 15.
4.3-44
EMISSION FACTORS
02/98
-------
References For Section 4.3
1. Hazardous Waste Treatment, Storage, And Disposal Facilities (TSDF) — Air Emission Models,
EPA-450/3-87-026, U. S. Environmental Protection Agency, Research Triangle Park, NC,
April 1989.
2. Waste Water Treatment Compound Property Processor Air Emissions Estimator (WATER 7), U. S.
Environmental Protection Agency, Research Triangle Park, NC, available early 1992.
3. Evaluation Of Test Method For Measuring Biodegradation Rates Of Volatile Organics, Draft,
EPA Contract No. 68-D90055, Entropy Environmental, Research Triangle Park, NC,
September 1989.
4. Industrial Waste Water Volatile Organic Compound Emissions — Background Information For
BACT/LAER Determinations, EPA-450/3-90-004, U. S. Environmental Protection Agency,
Research Triangle Park, NC, January 1990.
5. Evan K. Nyer, Ground Water Treatment Technology, Van Nostrand Reinhold Company, New York,
1985.
6. J. Mangino and L. Sutton. Evaluation of Greenhouse Gas Emissions From Wastewater Treatment
Systems. Contract No. 68-D1-0117, Work Assignment 22, U. S. Environmental Protection Agency,
Office of Research and Development, Air and Energy Engineering Research Laboratory, Research
Triangle Park, NC. April 1992.
7. L.C. Huff. Wastewater Methane Emission Estimates-Report to Congress. Contract
No. 68-D1-0117. U. S. Environmental Protection Agency, Office of Research and Development, Air
and Energy Engineering Research Laboratory, Research Triangle Park, NC. July 1992.
8. Metcalf & Eddy, Inc., Waste Water Engineering: Treatment, Disposal, And Reuse, McGraw-Hill
Book Company, p. 621,1979.
9. Dr. J. Orlich, "Methane Emissions From Landfill Sites And Waste Water Lagoons", Presented in
Methane Emissions And Opportunities For Control, 1990.
10. Viessman, Jr. and M.J. Hammer. 1985. Water Supply And Pollution Control. Harper & Row
Publishers, New York, NY.
11. U. S. Environmental Protection Agency, International Anthropogenic Methane Emissions Report
to Congress. Office of Policy Planning and Evaluation, EPA 230-R-93-010. 1994.
12. M.J. Lexmond and G. Zeeman. Potential Of Uncontrolled Anaerobic Wastewater Treatment In
Order To Reduce Global Emissions Of The Greenhouse Gases Methane And Carbon Dioxide.
02/98 Evaporation Loss Sources 4.3-45
-------
Department of Environmental Technology, Agricultural University of Wageningen, the Netherlands.
Report Number 95-1. 1995.
13. Intergovernmental Panel on Climate Control, Greenhouse Gas Inventory Reference Manual, Vol. 3,
IPCC/OECD, p. 6.28, 1994.
14. J. B. Carmichael and K.M. Strzepek, Industrial Water Use And Treatment Practices, United
Nations Industrial Development Organization, Cassell Tycooly, Philadelphia, PA, pp. 33, 36,49, 67
and 85, 1987.
15. D. Barnes, et al, "Surveys In Industrial Waste Water Treatment", Vol. 1, Food And Allied
Industries, Pitman Publishing Inc., Marshfield, Massachusetts, pp. 12, 73, 213 and 316, 1984.
16. Development Document For Effluent Limitations Guidelines And New Source Performance
Standards For The Beet Sugar Processing Subcategory Of The Sugar Processing Point Source
Category, EPA 40/l-74/002b, U. S. Environmental Protection Agency, Effluent Guidelines
Division, Office Of Waste And Hazardous Materials, Washington, DC, January 1974.
17. Development Document For Effluent Limitations Guidelines And New Source Performance
Standards For The Dairy Product Processing Point Source Category, EPA 440/1-74/021 a,
U. S. Environmental Protection Agency, Effluent Guidelines Division, Office Of Waste And
Hazardous Materials, Washington, DC, p. 59, May 1974.
18. Development Document For Effluent Limitations Guidelines And New Source Performance
Standards For The Animal Feed, Breakfast Cereal, And Wheat Starch Segments Of The Grain
Mills Points Source Category, EPA 440/1-74/039a, U. S. Environmental Protection Agency,
Effluent Guidelines Division, Office Of Waste And Hazardous Materials, Washington, DC, pp.
39-40, December 1974.
19. Development Document For Effluent Limitations Guidelines And New Source Performance
Standards For The Rendering Segment Of The Meat Products And Rendering Processing Point
Source Category, EPA 400/l-4/031d, U. S. Environmental Protection Agency, Effluent Guidelines
Division, Office of Waste And Hazardous Materials, Washington, DC, pp. 58, 60, January 1975.
20. E. R. Hall (editor), "Anaerobic Treatment For Pulp And Paper Waste Waters", Anaerobic Treatment
Of Industrial Waste Water, Noyes Data Corporation, Park Ridge, New Jersey
pp. 15-22, 1988.
4.3-46 EMISSION FACTORS 02/98
-------
4.4 Polyester Resin Plastic Products Fabrication
4.4.1 General Description1"2
A growing number of products are fabricated from liquid polyester resin reinforced with glass
fibers and extended with various inorganic filler materials such as calcium carbonate, talc, mica, or
small glass spheres. These composite materials are often referred to as fiberglass-reinforced plastic
(FRP), or simply "fiberglass". The Society Of The Plastics industry designates these materials as
"reinforced plastics/composites" (RP/C). Also, advanced reinforced plastics products are now
formulated with fibers other than glass, such as carbon, aramid, and aramid/carbon hybrids. In some
processes, resin products are fabricated without fibers. One major product using resins with fillers
but no reinforcing fibers is the synthetic marble used in manufacturing bathroom countertops, sinks,
and related items. Other applications of nonreinforced resin plastics include automobile body filler,
bowling balls, and coatings.
Fiber-reinforced plastics products have a wide range of application in industry, transportation,
home, and recreation. Industrial uses include storage tanks, skylights, electrical equipment, ducting,
pipes, machine components, and corrosion resistant structural and process equipment. In
transportation, automobile and aircraft applications are increasing rapidly. Home and recreational
items include bathroom tubs and showers, boats (building and repair), surfboards and skis, helmets,
swimming pools and hot tubs, and a variety of sporting goods.
The thermosetting polyester resins considered here are complex polymers resulting from the
cross-linking reaction of a liquid unsaturated polyester with a vinyl type monomer, list often styrene.
The unsaturated polyester is formed from the condensation reaction of an unsaturated dibasic acid or
anhydride, a saturated dibasic acid or anhydride, and a polyfunctional alcohol. Table 4.4-1 lists the
most common compounds used for each component of the polyester "backbone", as well as the
principal cross-linking monomers. The chemical reactions that form both the unsaturated polyester
and the cross-linked polyester resin are shown in Figure 4.4-1. The emission factors presented here
apply to fabrication processes that use the finished liquid resins (as received by fabricators from
chemical manufacturers), and not to the chemical processes used to produce these resins.
(See Chapter 6, Organic Chemical Process Industry.)
In order to be used in the fabrication of products, the liquid resin must be mixed with a
catalyst to initiate polymerization into a solid thermoset. Catalyst concentrations generally range from
1 to 2 percent by original weight of resin; within certain limits, the higher the catalyst concentration,
the faster the cross-linking reaction proceeds. Common catalysts are organic peroxides, typically
methyl ethyl ketone peroxide or benzoyl peroxide. Resins may contain inhibitors, to avoid self-curing
during resin storage, and promoters, to allow polymerization to occur at lower temperatures.
The polyester resin/fiberglass industry consists of many small facilities (such as boat repair
and small contract firms) and relatively few large firms that consume the major fraction of the total
resin. Resin usage at these operations ranges from less than 5,000 kilograms per year
(11,000 pounds) to over 3 million kilograms (6.6 million pounds) per year.
Reinforced plastics products are fabricated using any of several processes, depending on their
size, shape, and other desired physical characteristics. The principal processes include hand layup,
9/88 (Reformatted 1/95) Evaporation Loss Sources 4.4-1
-------
Table 4.4-1. TYPICAL COMPONENTS OF RESINS
To Form The Unsaturated Polyester
Unsaturated Acids
Maleic anhydride
Fumaric acid
Saturated Acids
Phthalic anhydride
Isophthalic acid
Adipic acid
Polyfunctional Alcohols
Propylene glycol
Ethylene glycol
Diethylene glycol
Dipropylene glycol
Neopentyl glycol
Pentaerythritol
Cross-Linking Agents (Monomers)
Styrene
Methyl methacrylate
Vinyl toluene
Vinyl acetate
Diallyl phthalate
Acrylamide
2-Ethyl hexylacrylate
REACTION 1
0 0
C-O-C Q t
n-HC *= CH + 2n-HOH2C-CH2OH + nV-O-C
Maleic Ethylene Phthalic
anhydride glycol anhydride
00 0
I I «
-C xC-0-CH2-CH2-0-C
i
HC
0
I
C-0-CH2-CH2-0-
i
CH
Unsaturated polyester
REACTION 2
CH2 = CH -
Styrene
Unsaturated
polyester
(_CH2-CH2-0-C-CH-CH-C- 0-CH2-CH2-0-C- <
I
H-C-H
0
n /,
(-0-C-//
0 ~
II ' D
C-0-CH2-CH2-0-C-CH-CH-C-0-CH2-CH2-)n
I
H-C-H
I
H-C-
I
Cross-linked
polyester resin
Figure 4.4-1. Typical reactions for unsaturated polyester and polyester resin formation.
4.4-2
EMISSION FACTORS
(Reformatted 1/95) 9/88
-------
spray layup (sprayup), continuous lamination, pultrusion, filament winding, and various closed
molding operations.
Hand layup, using primarily manual techniques combined with open molds, is the simplest of
the fabrication processes. Here, the reinforcement is manually fitted to a mold wetted with catalyzed
resin mix, after which it is saturated with more resin. The reinforcement is in the form of either a
chopped strand mat, a woven fabric, or often both. Layers of reinforcement and resin are added to
build the desired laminate thickness. Squeegees, brushes, and rollers are used to smooth and compact
each layer as it is applied. A release agent is usually first applied to the mold to facilitate removal of
the composite. This is often a wax, which can be treated with a water soluble barrier coat such as
polyvinyl alcohol to promote paint adhesion on parts that are to be painted. In many operations, the
mold is first sprayed with gel coat, a clear or pigmented resin mix that forms the smooth outer
surface of many products. Gel coat spray systems consist of separate sources of resin and catalyst,
with an airless hand spray gun that mixes them together into an atomized resin/catalyst stream.
Typical products are boat hulls and decks, swimming pools, bathtubs and showers, electrical consoles,
and automobile components.
Spray layup, or "sprayup", is another open mold process, differing from hand layup in that it
uses mechanical spraying and chopping equipment for depositing the resin and glass reinforcement.
This process allows a greater production rate and more uniform parts than does hand layup, and often
uses more complex molds. As in hand layup, gel coat is frequently applied to the mold before
fabrication to produce the desired surface qualities. It is common practice to combine hand layup and
sprayup operations.
For the reinforced layers, a device is attached to the sprayer system to chop glass fiber
"roving" (uncut fiber) into predetermined lengths and project it to merge with the resin mix stream.
The stream precoats the chop, and both are deposited simultaneously to the desired layer thickness on
the mold surface (or on the gel coat that was applied to the mold). Layers are built up and rolled out
on the mold as necessary to form the part. Products manufactured by sprayup are similar to those
made by hand layup, except that more uniform and complex parts can generally be produced more
efficiently with sprayup techniques. However, compared to hand layup, more resin generally is used
to produce similar parts by spray layup because of the inevitable overspray of resin during
application.
Continuous lamination of reinforced plastics materials involves impregnating various
reinforcements with resins on an in-line conveyor. The resulting laminate is cured and trimmed as it
passes through the various conveyor zones. In this process, the resin mix is metered onto a bottom
carrier film, using a blade to control thickness. This film, which defines the panel's surface, is
generally polyester, cellophane, or nylon and may have a smooth, embossed, or matte surface.
Methyl methacrylate is sometimes used as the cross-linking agent, either alone or in combination with
styrene, to increase strength and weather resistance. Chopped glass fibers free-fall into the resin mix
and are allowed to saturate with resin, or "wet out". A second carrier film is applied on top of the
panel before subsequent forming and curing. The cured panel is then stripped of its films, trimmed,
and cut to the desired length. Principal products include translucent industrial skylights and
greenhouse panels, wall and ceiling liners for food areas, garage doors, and cooling tower louvers.
Figure 4.4-2 shows the basic elements of a continuous laminating production line.
Pultrusion, which can be thought of as extrusion by pulling, is used to produce continuous
cross-sectional lineals similar to those made by extruding metals such as aluminum. Reinforcing
fibers are pulled through a liquid resin mix bath and into a long machined steel die, where heat
initiates an exothermic reaction to polymerize the thermosetting resin matrix. The composite profile
9/88 (Reformatted 1/95) Evaporation Loss Sources 4.4-3
-------
Resin netenng device—-
Resn
Top '"Im
/ vV Forming
shoes
Cure area
Heaiefl weioul taote
Bottom film
o
Squeeze -sfe
\
Film
rewinO
9
Cross cut saw or shear
EC*,™ o [|
S |o-0"o-| <-> U |
Cy Pull rolls |
inscection area !
Figure 4.4-2. Typical continuous lamination production process.2
emerges from the die as a hot, constant cross-sectional that cools sufficiently to be fed into a clamping
and pulling mechanism. The product can then be cut to desired lengths. Example products include
electrical insulation materials, ladders, walkway gratings, structural supports, and rods and antennas.
Filament winding is the process of laying a band of resin impregnated fibers onto a rotating
mandrel surface in a precise geometric pattern, and curing them to form the product. This is an
efficient method of producing cylindrical parts with optimum strength characteristics suited to the
specific design and application. Glass fiber is most often used for the filament, but aramid, graphite,
and sometimes boron and various metal wires may be used. The filament can be wetted during
fabrication, or previously impregnated filament ("prepreg") can be used. Figure 4.4-3 shows the
filament winding process, and indicates the 3 most common winding patterns. The process
illustration depicts circumferential winding, while the 2 smaller pictures show helical and polar
winding. The various winding patterns can be used alone or in combination to achieve the desired
strength and shape characteristics. Mandrels are made of a wide variety of materials and, in some
applications, remain inside the finished product as a liner or core. Example products are storage
tanks, fuselages, wind turbine and helicopter blades, and tubing and pipe.
Helical Winding
Polar Winding
Figure 4.4-3. Typical filament winding process/
Closed, such as compression or injection, molding operations involve the use of 2 matched
dies to define the entire outer surface of the part. When closed and filled with a resin mix, the
matched die mold is subjected to heat and pressure to cure the plastic. For the most durable
production configuration, hardened metal dies are used (matched metal molding). Another closed
4.4-4
EMISSION FACTORS
(Reformatted 1/95) 9/88
-------
molding process is vacuum or pressure bag molding. In bag molding, a hand layup or sprayup is
covered with a plastic film, and vacuum or pressure is applied to rigidly define the part and improve
surface quality. The range of closed molded parts includes tool and appliance housings, cookware,
brackets and other small parts, and automobile body and electrical components.
Synthetic marble casting, a large segment of the resin products industry, involves production
of bathroom sinks, vanity tops, bathtubs, and accessories using filled resins that have the look of
natural marble. No reinforcing fibers are used in these products. Pigmented or clear gel coat can
either be applied to the mold itself or sprayed onto the product after casting to simulate the look of
natural polished marble. Marble casting can be an open mold process, or it may be considered a
semiclosed process if cast parts are removed from a closed mold for subsequent gel coat spraying.
4.4.2 Emissions And Controls
Organic vapors consisting of volatile organic compounds (VOC) are emitted from fresh resin
surfaces during the fabrication process, and from the use of solvents (usually acetone) for cleanup of
hands, tools, molds, and spraying equipment. Cleaning solvent emissions can account for over
36 percent of the total plant VOC emissions.4 There also may be some release of paniculate
emissions from automatic fiber chopping equipment, but these emissions have not been quantified.
Organic vapor emissions from polyester resin/fiberglass fabrication processes occur when the
cross-linking agent (anomer) contained in the liquid resin evaporates into the air during resin
application and curing. Styrene, methyl methacrylate, and vinyl toluene are 3 of the principal
monomers used as cross-linking agents. Styrene is by far the most common. Other chemical
components of resins are emitted only at trace levels because they not only have low vapor pressures,
but also are substantially converted to polymers.5'6
Since emissions result from evaporation of monomer from the uncured resin, they depend
upon the amount of resin surface exposed to the air and the time of exposure. Thus, the potential for
emissions varies with the manner in which the resin is mixed, applied, handled, and cured. These
factors vary among the different fabrication processes. For example, the spray layup process has the
highest potential for VOC emissions because the atomization of resin into a spray creates an
extremely large surface area from which volatile monomer can evaporate. By contrast, the emission
potential in synthetic marble casting and closed molding operations is considerably lower because of
the lower anomer content in the casting resins (30 to 38 percent, versus about 43 percent) and the
enclosed nature of these molding operations. It has been found that Styrene evaporation increases
with increasing gel time, wind speed, and ambient temperature, and that increasing the hand rolling
time on a hand layup or sprayup results in significantly higher styrene losses.1 Thus, production
changes that lessen the exposure of fresh resin surfaces to the air should be effective in reducing these
evaporation losses.
In addition to production changes, resin formulation can be varied to affect the VOC emission
potential. In general, a resin with lower monomer content should produce lower emissions.
Evaluation tests with low-styrene emission laminating resins having a 36-percent styrene content
found a 60- to 70-percent decrease in emission levels, compared to conventional resins (43 percent
styrene), with no sacrifice in the physical properties of the laminate.7 Vapor suppressing agents also
are sometimes added to resins to reduce VOC emissions. Most vapor suppressants are paraffin
waxes, stearates, or polymers of proprietary composition, constituting up to several weight percent of
the mix. Limited laboratory and field data indicate that vapor suppressing resins reduce styrene losses
by 30 to 70 percent.7"8
9/88 (Reformatted 1/95) Evaporation Loss Sources 4.4-5
-------
Emission factors for several fabrication processes using styrene content resins have been
developed from the results of facility source tests (B Rating) and laboratory tests (C Rating), and
through technology transfer estimations (D Rating).1 Industry experts also provided additional
information that was used to arrive at the final factors presented hi Table 4.4-2.6 Since the styrene
content varies over a range of approximately 30 to 50 weight percent, these factors are based on the
quantity of styrene monomer used hi the process, rather than on the total amount of resin used. The
factors for vapor-suppressed resins are typically 30 to 70 percent of those for regular resins. The
factors are expressed as ranges because of the observed variability in source and laboratory test
results and of the apparent sensitivity of emissions to process parameters.
Emissions should be calculated using actual resin monomer contents. When specific
information about the percentage of styrene is unavailable, the representative average values hi
Table 4.4-3 should be used. The sample calculation illustrates the application of the emission factors.
Sample Calculation -
A fiberglass boat building facDity consumes an average of 250 kg per day of styrene-
containing resins using a combination of hand layup (75%) and spray layup (25%) techniques. The
laminating resins for hand and spray layup contain 41.0 and 42.5 weight percent, respectively, of
styrene. The resin used for hand layup contains a vapor-suppressing agent.
From Table 4.4-2 the weight percent of monomer emitted for hand layup using a vapor-
suppressed resin is 2 - 7 (0.02 to 0.07 fraction of total styrene emitted); the factor for spray layup is
9-13 (0.09 to 0.13 fraction emitted). Assume the midpoints of these emission factor ranges (0.045
and 0.11, respectively).
Total VOC emissions are:
(250 kg/day) [(0.75)(0.410)(0.045) + (0.25)(0.425)(0.11)] = 6.4 kg/day.
Emissions from use of gel coat would be calculated hi the same manner. If the monomer
content of the resins were unknown, a representative value of 43 percent could be selected from
Table 4.4-3 for this process combination. It should be noted that these emissions represent
evaporation of styrene monomer only, and not of acetone or other solvents used for cleanup.
In addition to process changes and materials substitution, add-on control equipment can be
used to reduce vapor emissions from styrene resins. However, control equipment is infrequently used
at RP/C fabrication facilities, due to low exhaust VOC concentrations and the potential for
contamination of adsorbent materials. Most plants use forced ventilation techniques to reduce worker
exposure to styrene vapors, but vent the vapors directly to the atmosphere with no attempt at
collection. At 1 continuous lamination facility where incineration was applied to vapors vented from
the impregnation table, a 98.6 percent control efficiency was measured.1 Carbon adsorption,
absorption, and condensation have also been considered for recovering styrene and other organic
vapors, but these techniques have not been applied to any significant extent hi this industry.
Emissions from cleanup solvents can be controlled through good housekeeping and use
practices, reclamation of spent solvent, and substitution with water-based solvent substitutes.
4.4-6 EMISSION FACTORS (Reformatted 1/95) 9/88
-------
Table 4.4-2. EMISSION FACTORS FOR UNCONTROLLED POLYESTER RESIN
PRODUCT FABRICATION PROCESSES*
(weight % of starting monomer emitted)
Process
Hand layup
Spray layup
Continuous lamination
Pultrusiond
Filament winding6
Marble casting
Closed molding^
Resin
NVS
5- 10
9-13
4-7
4-7
5- 10
1-3
1 -3
vsb
2-7
3-9
1 -5
1-5
2-7
1-2
1-2
EMISSION
FACTOR
RATING
C
B
B
D
D
B
D
Gel Coat
NVS VSb
26-35 8-25
26-35 8-25
c c
c c
c c
_f _f
_c c
EMISSION
FACTOR
RATING
D
B
—
—
—
—
—
a Reference 9. Ranges represent the variability of processes and sensitivity of emissions to process
parameters. Single value factors should be selected with caution. NVS = nonvapor-suppressed
resin. VS = vapor-suppressed resin.
b Factors are 30-70% of those for nonvapor-suppressed resins.
c Gel coat is not normally used in this process.
d Resin factors for the continuous lamination process are assumed to apply.
e Resin factors for the hand layup process are assumed to apply.
f Factors unavailable. However, when cast parts are subsequently sprayed with gel coat, hand and
spray layup gel coat factors are assumed to apply.
g Resin factors for marble casting, a semiclosed process, are assumed to apply.
Table 4.4-3. TYPICAL RESIN STYRENE PERCENTAGES
Resin Application
Hand layup
Spray layup
Continuous lamination
Filament winding
Marble casting
Closed molding
Gel coat
Resin Styrene Content*
(wt. %)
43
43
40
40
32
35
35
a May vary by at least ±5 percentage points.
9/88 (Reformatted 1/95)
Evaporation Loss Sources
4.4-7
-------
References For Section 4.4
1. M. B. Rogozen, Control Techniques For Organic Gas Emissions From Fiberglass
Impregnation And Fabrication Processes, ARB/R-82/165, California Air Resources Board,
Sacramento, CA, (NTIS PB82-251109), June 1982.
2. Modern Plastics Encyclopedia, 1986-1987, 65(10A), October 1986.
3. C. A. Brighton, et al., Styrene Polymers: Technology And Environmental Aspects, Applied
Science Publishers, Ltd., London, 1979.
4. M. Elsherif, Staff Report, Proposed Rule 1162 — Polyester Resin Operations, South Coast
Air Quality Management District, Rule Development Division, El Monte, CA, January 23,
1987.
5. M. S. Crandall, Extent Of Exposure To Styrene In The Reinforced Plastic Boat Making
Industry, Publication No. 82-110, National Institute For Occupational Safety And Health,
Cincinnati, OH, March 1982.
6. Written communication from R. C. Lepple, Aristech Chemical Corporation, Polyester Unit,
Linden, NJ, to A. A. MacQueen, U. S. Environmental Protection Agency, Research Triangle
Park, NC, September 16, 1987.
7. L. Walewski and S. Stockton, "Low-Styrene-Emission Laminating Resins Prove It In The
Workplace", Modern Plastics, <52(8):78-80, August 1985.
8. M. J. Duffy, "Styrene Emissions — How Effective Are Suppressed Polyester Resins?",
Ashland Chemical Company, Dublin, OH, presented at 34th Annual Technical Conference,
Reinforced Plastics/Composites Institute, The Society Of The Plastics Industry, 1979.
9. G. A. LaFlam, Emission Factor Documentation ForAP-42 Section 4.12: Polyester Resin
Plastics Product Fabrication, Pacific Environmental Services, Inc., Durham, NC, November
1987.
4.4-8 EMISSION FACTORS (Reformatted 1/95) 9/88
-------
4.5 Asphalt Paving Operations
4.5.1 General1'3
Asphalt surfaces and pavements are composed of compacted aggregate and an asphalt binder.
Aggregate materials are produced from rock quarries as manufactured stone or are obtained from
natural gravel or soil deposits. Metal ore refining processes produce artificial aggregates as a
byproduct. In asphalt, the aggregate performs 3 functions: it transmits the load from the surface to
the base course, takes the abrasive wear of traffic, and provides a nonskid surface. The asphalt
binder holds the aggregate together, preventing displacement and loss of aggregate and providing a
waterproof cover for the base.
Asphalt binders take the form of asphalt cement (the residue of the distillation of crude oils),
and liquified asphalts. To be used for pavement, asphalt cement, which is semisolid, must be heated
prior to mixing with aggregate. The resulting hot mix asphalt concrete is generally applied in
thicknesses of from 5 to 15 centimeters (2 to 6 inches). Liquified asphalts are: (1) asphalt cutbacks
(asphalt cement thinned or "cutback" with volatile petroleum distillates such as naptha, kerosene, etc.)
and (2) asphalt emulsions (nonflammable liquids produced by combining asphalt and water with an
emulsifying agent, such as soap). Liquified asphalts are used in tack and seal operations, in priming
roadbeds for hot mix application, and for paving operations up to several inches thick.
Cutback asphalts fall into 3 broad categories: rapid cure (RC), medium cure (MC), and slow
cure (SC) road oils. SC, MC, and RC cutbacks are prepared by blending asphalt cement with heavy
residual oils, kerosene-type solvents, or naptha and gasoline solvents, respectively. Depending on the
viscosity desired, the proportions of solvent added generally range from 25 to 45 percent by volume.
Emulsified asphalts are of 2 basic types: 1 type relies on water evaporation to cure, the other
type (cationic emulsions) relies on ionic bonding of the emulsion and the aggregate surface.
Emulsified asphalt can substitute for cutback in almost any application. Emulsified asphalts are
gaining in popularity because of the energy and environmental problems associated with the use of
cutback asphalts.
4.5.2 Emissions1'2
The primary pollutants of concern from asphalts and asphalt paving operations are volatile
organic compounds (VOC). Of the 3 types of asphalts, the major source of VOC is cutback. Only
minor amounts of VOCs are emitted from emulsified asphalts and asphalt cement.
VOC emissions from cutback asphalts result from the evaporation of the petroleum distillate
solvent, or diluent, used to liquify the asphalt cement. Emissions occur at both the job site and the
mixing plant. At the job site, VOCs are emitted from the equipment used to apply the asphaltic
product and from the road surface. At the mixing plant, VOCs are released during mixing and
stockpiling. The largest source of emissions, however, is the road surface itself.
For any given amount of cutback asphalt, total emissions are believed to be the same,
regardless of stockpiling, mixing, and application times. The 2 major variables affecting both the
quantity of VOCs emitted and the time over which emissions occur are the type and the quantity of
petroleum distillate used as a diluent. As an approximation, long-term emissions from cutback
7/79 (Reformatted 1/95) Evaporation Loss Sources 4.5-1
-------
asphalts can be estimated by assuming that 95 percent of the diluent evaporates from rapid cure (RC)
cutback asphalts, 70 percent from MC cutbacks, and about 25 percent from SC asphalts, by weight
percent. Some of the diluent appears to be retained permanently in the road surface after application.
Limited test data suggest that from RC asphalt, 75 percent of the total diluent loss occurs on the first
day after application, 90 percent occurs within the first month, and 95 percent in 3 to 4 months.
Evaporation takes place more slowly from MC asphalts, with roughly 20 percent of the diluent being
emitted during the first day, 50 percent during the first week, and 70 percent after 3 to 4 months. No
measured data are available for SC asphalts, although the quantity emitted is believed to be
considerably less than with either RC or MC asphalts, and the tune during which emissions take place
is expected to be considerably longer (Figure 4.5-1). An example calculation for determining VOC
emissions from cutback asphalts is given below:
Example: Local records indicate that 10,000 kg of RC cutback asphalt (containing 45 percent
diluent, by volume) was applied in a given area during the year. Calculate the mass
of VOC emitted during the year from this application.
To determine VOC emissions, the volume of diluent present in the cutback asphalt
must first be determined. Because the density of naptha (0.7 kg/L) differs from that
of asphalt cement (1.1 kg/L), the following equations should be solved to determine
the volume of diluent (x) and the volume of asphalt cement (y) in the cutback asphalt:
10,000 kg cutback asphalt = (x liter, diluent) • —-—£ + (y liter, asphalt cement)
and
x liter, diluent = 0.45 (x liter, diluent + y liter, asphalt cement)
From these equations, the volume of diluent present hi the cutback asphalt is
determined to be about 4900 liters, or about 3400 kg. Assuming that 95 percent of
this is evaporative VOC, emissions are then: 3400 kg x 0.95 = 3200 kg (i. e., 32%,
by weight, of the cutback asphalt eventually evaporates).
These equations can be used for medium cure and slow cure asphalts by assuming typical diluent
densities of 0.8 and 0.9 kg/liter, respectively. Of course, if actual density values are known from
local records, they should be used in the above equations rather than typical values. Also, if different
diluent contents are used, they should also be reflected in the above calculations. If actual diluent
contents are not known, a typical value of 35 percent may be assumed for inventory purposes.
In lieu of solving the equations in the above example, Table 4.5-1 may be used to estimate
long-term emissions from cutback asphalts. Table 4.5-1 directly yields long-term emissions as a
function of the volume of diluent added to the cutback and of the density of the diluents and asphalt
cement used hi the cutback asphalt. If short-term emissions are to be estimated, Figure 4.5-1 should
be used hi conjunction with Table 4.5-1.
No control devices are employed to reduce evaporative emissions from cutback asphalts.
Asphalt emulsions are typically used in place of cutback asphalts to eliminate VOC emissions.
4.5-2 EMISSION FACTORS (Reformatted 1/95) 7/79
-------
£ 25-, -|
1WEEK 1 MONTH i MONTHS
Figure 4.5-1. Percent of diluent evaporated from cutback asphalt over time.
Table 4.5-1. EVAPORATIVE VOC EMISSIONS FROM CUTBACK ASPHALTS AS A
FUNCTION OF DILUENT CONTENT AND CUTBACK ASPHALT TYPEa
EMISSION FACTOR RATING: C
Type Of Cutback1*
Rapid cure
Medium cure
Slow cure
Percent, By Volume, Of Diluent In
25%
17
14
5
35%
24
20
8
Cutback0
45%
32
26
10
a These numbers represent the percent, by weight, of cutback asphalt evaporated. Factors are based
on References 1-2.
b Typical densities assumed for diluents used in RC, MC, and SC cutbacks are 0.7, 0.8, and
0.9 kg/liter, respectively.
c Diluent contents typically range between 25 - 45%, by volume. Emissions may be linearly
interpolated for any given type of cutback between these values.
References For Section 4.5
1. R. Keller and R. Bonn, Nonmethane Volatile Organic Emissions From Asphalt Cement And
Liquified Asphalts, EPA-450/3-78-124, U. S. Environmental Protection Agency, Research
Triangle Park, NC, December 1978.
2. F. Kirwan and C. Maday, Air Quality And Energy Conservation Benefits From Using
Emulsions To Replace Asphalt Cutbacks In Certain Paving Operations, EPA-450/2-78-004,
U. S. Environmental Protection Agency, Research Triangle Park, NC, January 1978.
7/79 (Reformatted 1/95)
Evaporation Loss Sources
4.5-3
-------
3. David W. Markwordt, Control Of Volatile Organic Compounds From Use Of Cutback
Asphalt, EPA 450/2-77-037, U. S. Environmental Protection Agency, Research Triangle
Park, NC, December 1977.
4.5-4 EMISSION FACTORS (Reformatted 1/95) 7/79
-------
4.6 Solvent Degreasing
4.6.1 General1'2
Solvent degreasing (or solvent cleaning) is the physical process of using organic solvents to
remove grease, fats, oils, wax or soil from various metal, glass, or plastic items. The types of
equipment used in this method are categorized as cold cleaners, open top vapor degreasers, or
conveyorized degreasers. Nonaqueous solvents such as petroleum distillates, chlorinated
hydrocarbons, ketones, and alcohols are used. Solvent selection is based on the solubility of the
substance to be removed and on the toxicity, flammability, flash point, evaporation rate, boiling
point, cost, and several other properties of the solvent.
The metalworking industries are the major users of solvent degreasing, i. e., automotive,
electronics, plumbing, aircraft, refrigeration, and business machine industries. Solvent cleaning is
also used in industries such as printing, chemicals, plastics, rubber, textiles, glass, paper, and electric
power. Most repair stations for transportation vehicles and electric tools use solvent cleaning at least
part of the time. Many industries use water-based alkaline wash systems for degreasing, and since
these systems emit no solvent vapors to the atmosphere, they are not included in this discussion.
4.6.1.1 Cold Cleaners -
The 2 basic types of cold cleaners are maintenance and manufacturing. Cold cleaners are
batch loaded, nonboiling solvent degreasers, usually providing the simplest and least expensive
method of metal cleaning. Maintenance cold cleaners are smaller, more numerous, and generally use
petroleum solvents as mineral spirits (petroleum distillates and Stoddard solvents). Manufacturing
cold cleaners use a wide variety of solvents, which perform more specialized and higher quality
cleaning with about twice the average emission rate of maintenance cold cleaners. Some cold cleaners
can serve both purposes.
Cold cleaner operations include spraying, brushing, flushing, and immersion. In a typical
maintenance cleaner (Figure 4.6-1), dirty parts are cleaned manually by spraying and then soaking in
the tank. After cleaning, the parts are either suspended over the tank to drain or are placed on an
external rack that routes the drained solvent back into the cleaner. The cover is intended to be closed
whenever parts are not being handled in the cleaner. Typical manufacturing cold cleaners vary
widely hi design, but there are 2 basic tank designs: the simple spray sink and the dip tank. Of
these, the dip tank provides more thorough cleaning through immersion, and often is made to improve
cleaning efficiency by agitation. Small cold cleaning operations may be numerous in urban areas.
However, because of the small quantity of emissions from each operation, the large number of
individual sources within an urban area, and the application of small cold cleaning to industrial uses
not directly associated with degreasing, it is difficult to identify individual small cold cleaning
operations. For these reasons, factors are provided in Table 4.6-1 to estimate emissions from small
cold cleaning operations over large urban geographical areas. Factors in Table 4.6-1 are for
nonmethane VOC and include 25 percent 1,1,1 trichloroethane, methylene chloride, and
trichlorotrifluoroethane.
4.6.1.2 Open-Top Vapor Systems -
Open-top vapor degreasers are batch loaded boiling degreasers that clean with condensation of
hot solvent vapor on colder metal parts. Vapor degreasing uses halogenated solvents (usually
4/81 (Reformatted 1/95) Evaporation Loss Sources 4.6-1
-------
C/9
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4.6-2
EMISSION FACTORS
(Reformatted 1/95) 4/81
-------
Table 4.6-1 (Metric And English Units). NONMETHANE VOC EMISSIONS FROM SMALL
COLD CLEANING DECREASING OPERATIONS*
EMISSION FACTOR RATING: C
Operating Period
Annual
Dailyb
Per Capita Emission Factor
1.8kg
4.0 Ib
5.8 g
0.013 Ib
a
Reference 3.
b Assumes a 6-day operating week (313 days/yr).
perchloroethylene, trichloroethylene, or 1,1,1-trichloroethane), because they are not flammable and
their vapors are much heavier than air.
A typical vapor degreaser (Figure 4.6-1) is a sump containing a heater that boils the solvent to
generate vapors. The height of these pure vapors is controlled by condenser coils and/or a water
jacket encircling the device. Solvent and moisture condensed on the coils are directed to a water
separator, where the heavier solvent is drawn off the bottom and is returned to the vapor degreaser.
A "freeboard1' extends above the top of the vapor zone to minimize vapor escape. Parts to be cleaned
are immersed in the vapor zone, and condensation continues until they are heated to the vapor
temperature. Residual liquid solvent on the parts rapidly evaporates as they are slowly removed from
the vapor zone. Lip mounted exhaust systems carry solvent vapors away from operating personnel.
Cleaning action is often increased by spraying the parts with solvent below the vapor level or by
immersing them in the liquid solvent bath. Nearly all vapor degreasers are equipped with a water
separator which allows the solvent to flow back into the degreaser.
Emission rates are usually estimated from solvent consumption data for the particular
degreasing operation under consideration. Solvents are often purchased specifically for use in
degreasing and are not used in any other plant operations. In these cases, purchase records provide
the necessary information, and an emission factor of 1000 kg of volatile organic emissions per Mg
(2000 Ib/ton) of solvent purchased can be applied, based on the assumption that all solvent purchased
is eventually emitted. When information on solvent consumption is not available, emission rates can
be estimated if the number and type of degreasing units are known. The factors in Table 4.6-2 are
based on the number of degreasers and emissions produced nationwide and may be considerably in
error when applied to a particular unit.
The expected effectiveness of various control devices and procedures is listed in Table 4.6-3.
As a first approximation, this efficiency can be applied without regard for the specific solvent being
used. However, efficiencies are generally higher for more volatile solvents. These solvents also
result in higher emission rates than those computed from the "average" factors listed in Table 4.6-2.
4.6.1.3 Conveyorized Degreasers -
Conveyorized degreasers may operate with either cold or vaporized solvent, but they merit
separate consideration because they are continuously loaded and are almost always hooded or
enclosed. About 85 percent are vapor types, and 15 percent are nonboiling.
4/81 (Refoimatted 1/95) Evaporation Loss Sources 4.6-3
-------
Table 4.6-2 (Metric And English Units). SOLVENT LOSS EMISSION FACTORS FOR
DECREASING OPERATIONS
EMISSION FACTOR RATING: C
Type Of Degreasing
Allb
Cold cleaner
Entire unit0
Waste solvent loss
Solvent carryout
Bath and spray
evaporation
Entire unit
Open top vapor
Entire unit
Entire unit
Conveyorized, vapor
Entire unit
Conveyorized, nonboiling
Entire unit
Activity Measure
Solvent consumed
Units in operation
Surface area and duty
cycled
Units in operation
Surface area and duty
cyclec
Units in operation
Units in operation
Uncontrolled Organic
l,OOOkg/Mg
0.30 Mg/yr/unit
0.165 Mg/yr/unit
0.075 Mg/yr/unit
0.06 Mg/yr/unit
0.4 kg/hr/m2
9.5 Mg/yr/unit
0.7 kg/hr/m2
24 Mg/yr/unit
47 Mg/yr/unit
Emission Factor*
2,000 Ib/ton
0.33 tons/yr/unit
0.18 tons/yr/unit
0.08 tons/yr/unit
0.07 tons/yr/unit
0.08 Ib/hr/ft2
10.5 ton/yr/unit
O.lSlb/hr/ft2
26 tons/yr/unit
52 tons/yr/unit
a 100% Nonmethane VOC.
b Solvent consumption data will provide much more accurate emission estimates than any of the other
factors presented.
c Emissions generally would be higher for manufacturing units and lower for maintenance units.
d Reference 4, Appendix C-6. For trichloroethane degreaser.
e For trichloroethane degreaser. Does not include waste solvent losses.
4.6.2 Emissions And Controls1"3
Emissions from cold cleaners occur through: (1) waste solvent evaporation, (2) solvent
carryout (evaporation from wet parts), (3) solvent bath evaporation, (4) spray evaporation, and
(5) agitation (Figure 4.6-1). Waste solvent loss, cold cleaning's greatest emission source, can be
reduced through distillation and transport of waste solvent to special incineration plants. Draining
cleaned parts for at least 15 seconds reduces carryout emissions. Bath evaporation can be controlled
by using a cover regularly, by allowing an adequate freeboard height, and by avoiding excessive
drafts in the workshop. If the solvent used is insoluble in and heavier than water, a layer of water
5 to 10 centimeters (2 to 4 inches) thick covering the solvent can also reduce bath evaporation. This
is known as a "water cover". Spraying at low pressure also helps to reduce solvent loss from this
part of the process. Agitation emissions can be controlled by using a cover, by agitating no longer
than necessary, and by avoiding the use of agitation with low volatility solvents. Emissions of low
volatility solvents increase significantly with agitation. However, contrary to what one might expect,
agitation causes only a small increase in emissions of high volatility solvents. Solvent type is the
variable that most affects cold cleaner emission rates, particularly the volatility at operating
temperatures.
4.6-4
EMISSION FACTORS
(Reformatted 1/95) 4/81
-------
Table 4.6-3. PROJECTED EMISSION REDUCTION FACTORS FOR SOLVENT DECREASING"
System
Control devices
Cover or enclosed design
Drainage facility
Water cover, refrigerated chiller, carbon
adsorption or high freeboard1*
Solid, fluid spray stream0
Safety switches and thermostats
Emission reduction from control devices (%)
Operating procedures
Proper use of equipment
Waste solvent reclamation
Reduced exhaust ventilation
Reduced conveyor or entry speed
Emission reduction from operating procedures (%)
Total emission reduction (%)
Cold Cleaner
A
X
X
13-38
X
X
15-45
28-83e
B
X
X
X
X
NAd
X
X
NAd
55-69f
Vapor Degreaser
A 1 B
X X
X
X
X
X
20-40 30-60
X X
X X
X X
X X
15-35 20^0
30-60 45-75
Conveyorized
Degreaser
A
X
X
X
X
X
20-30
20-30
B
X
X
X
X
40-60
X
X
X
X
20-30
50-70
a Reference 2. Ranges of emission reduction present poor to excellent compliance. X indicates
devices or procedures that will produce the given reductions. Letters A and B indicate different
control device circumstances. See Appendix B of Reference 2.
b Only one of these major control devices would be used in any degreasing system. Cold cleaner
system B could employ any of them. Vapor degreaser system B could employ any except water
cover. Conveyorized degreaser system B could employ any except water cover and high freeboard.
c If agitation by spraying is used, the spray should not be a shower type.
d Breakout between control equipment and operating procedures is not available.
e A manual or mechanically assisted cover would contribute 6-18% reduction; draining parts
15 seconds within the degreaser, 7 - 20%; and storing waste solvent in containers, an additional
15-45%.
Percentages represent average compliance.
f
As with cold cleaning, open top vapor degreasing emissions relate heavily to proper operating
methods. Most emissions are due to (6) diffusion and convection, which can be reduced by using an
automated cover, by using a manual cover regularly, by spraying below the vapor level, by
optimizing work loads, or by using a refrigerated freeboard chiller (for which a carbon adsorption
unit would be substituted on larger units). Safety switches and thermostats that prevent emissions
during malfunctions and abnormal operation also reduce diffusion and convection of the vaporized
solvent. Additional sources of emissions are solvent carryout, exhaust systems, and waste solvent
evaporation. Carryout is directly affected by the size and shape of the workload, by racking of parts,
and by cleaning and drying time. Exhaust emissions can be nearly eliminated by a carbon adsorber
that collects the solvent vapors for reuse. Waste solvent evaporation is not so much a problem with
vapor degreasers as it is with cold cleaners, because the halogenated solvents used are often distilled
and recycled by solvent recovery systems.
4/81 (Reformatted 1/95)
Evaporation Loss Sources
4.6-5
-------
Because of their large workload capacity and the fact that they are usually enclosed,
conveyorized degreasers emit less solvent per part cleaned than do either of the other 2 types of
degreaser. More so than operating practices, design and adjustment are major factors affecting
emissions, the main source of which is carryout of vapor and liquid solvents.
References For Section 4.6
1. P. J. Mara, et al., Source Assessment: Solvent Evaporation — Degreasing,
EPA Contract No. 68-02-1874, Monsanto Research Corporation, Dayton, OH, January 1977.
2. Jeffrey Shumaker, Control Of Volatile Organic Emissions From Solvent Metal Cleaning,
EPA-450/2-77-022, U. S. Environmental Protection Agency, Research Triangle Park, NC,
November 1977.
3. W. H. Lamason, "Technical Discussion Of Per Capita Emission Factors For Several Area
Sources Of Volatile Organic Compounds", Office Of Air Quality Planning And Standards,
U. S. Environmental Protection Agency, Research Triangle Park, NC, March 15, 1981,
unpublished.
4. K. S. Suprenant and D. W. Richards, Study To Support New Source Performance Standards
For Solvent Metal Cleaning Operations, EPA Contract No. 68-02-1329, Dow Chemical
Company, Midland, MI, June 1976.
4.6-6 EMISSION FACTORS (Reformatted 1/95) 4/81
-------
4.7 Waste Solvent Reclamation
4.7.1 Process Description1"4
Waste solvents are organic dissolving agents that are contaminated with suspended and
dissolved solids, organics, water, other solvents, and/or any substance not added to the solvent during
its manufacture. Reclamation is the process of restoring a waste solvent to a condition that permits its
reuse, either for its original purpose or for other industrial needs. All waste solvent is not reclaimed,
because the cost of reclamation may exceed the value of the recovered solvent.
Industries that produce waste solvents include solvent refining, polymerization processes,
vegetable oil extraction, metallurgical operations, pharmaceutical manufacture, surface coating, and
cleaning operations (dry cleaning and solvent degreasing). The amount of solvent recovered from the
waste varies from about 40 to 99 percent, depending on the extent and characterization of the
contamination and on the recovery process employed.
Design parameters and economic factors determine whether solvent reclamation is
accomplished as a main process by a private contractor, as an integral part of a main process (such as
solvent refining), or as an added process (as hi the surface coating and cleaning industries). Most
contract solvent reprocessing operations recover halogenated hydrocarbons (e. g., methylene chloride,
trichlorotrifluoroethane, and trichloroethylene) from degreasing, and/or aliphatic, aromatic, and
naphthenic solvents such as those used hi the paint and coatings industry. They may also reclaim
small quantities of numerous specialty solvents such as phenols, nitriles, and oils.
The general reclamation scheme for solvent reuse is illustrated in Figure 4.7-1. Industrial
operations may not incorporate all of these steps. For instance, initial treatment is necessary only
when liquid waste solvents contain dissolved contaminants.
STORAGE
TANK VENT
A
o
FUGITIVE
EMISSIONS
FUGITIVE CONDENSER
EMISSIONS VENT »
Oi
FUGITIVE
EMISSION'S
FUGITIVE
EMISSIONS
STORAGE
TANK VENT
FUGITIVE
EMISSIONS
WASTE
SOLVENTS
.
STORAGE
AND
HANDLING
INITIAL
TREATMENT
DISTILLATION
PURIFI-
CATION
STORAGE
AND
HANDLING
RECLAIMED
^SOLVENT
WASTE
DISPOSAL
G
-^INCINERATOR STACK
-^•FUGITIVE EMISSIONS
Figure 4.7-1. General waste solvent reclamation scheme and emission points.1
2/80 (Reformatted 1/95)
Evaporation Loss Sources
4.7-1
-------
4.7.1.1 Solvent Storage And Handling -
Solvents are stored before and after reclamation in containers ranging in size from 0.2-m3
(55-gallon) drums to tanks with capacities of 75 m3 (20,000 gallons) or more. Storage tanks are of
fixed or floating roof design. Venting systems prevent solvent vapors from creating excessive
pressure or vacuum inside fixed roof tanks.
Handling includes loading waste solvent into process equipment and filling drums and tanks
prior to transport and storage. The filling is most often done through submerged or bottom loading.
4.7.1.2 Initial Treatment -
Waste solvents are initially treated by vapor recovery or mechanical separation. Vapor
recovery entails removal of solvent vapors from a gas stream in preparation for further reclaiming
operations. In mechanical separation, undissolved solid contaminants are removed from liquid
solvents.
Vapor recovery or collection methods employed include condensation, adsorption, and
absorption. Technical feasibility of the method chosen depends on the solvent's miscibility, vapor
composition and concentration, boiling point, reactivity, and solubility, as well as several other
factors.
Condensation of solvent vapors is accomplished by water-cooled condensers and refrigeration
units. For adequate recovery, a solvent vapor concentration well above 20 milligrams per cubic
meter (mg/m3) (0.009 grams per cubic foot [gr/ft3]) is required. To avoid explosive mixtures of a
flammable solvent and air in the process gas stream, air is replaced with an inert gas, such as
nitrogen. Solvent vapors that escape condensation are recycled through the main process stream or
recovered by adsorption or absorption.
Activated carbon adsorption is the most common method of capturing solvent emissions.
Adsorption systems are capable of recovering solvent vapors in concentrations below 4 mg/m3
(0.002 gr/ft3) of air. Solvents with boiling points of 200°C (290°F) or more do not desorb
effectively with the low-pressure steam commonly used to regenerate the carbon beds. Figure 4.7-2
shows a flow diagram of a typical fixed-bed activated carbon solvent recovery system. The mixture
of steam and solvent vapor passes to a water-cooled condenser. Water-immiscible solvents are simply
decanted to separate the solvent, but water-miscible solvents must be distilled, and solvent mixtures
must be both decanted and distilled. Fluidized bed operations are also in use.
Absorption of solvent vapors is accomplished by passing the waste gas stream through a liquid
in scrubbing towers or spray chambers. Recovery by condensation and adsorption results in a
mixture of water and liquid solvent, while absorption recovery results hi an oil and solvent mixture.
Further reclaiming procedures are required if solvent vapors are collected by any of these 3 methods.
Initial treatment of liquid waste solvents is accomplished by mechanical separation methods.
This includes both removing water by decanting and removing undissolved solids by filtering,
draining, settling, and/or centrifuging. A combination of initial treatment methods may be necessary
to prepare waste solvents for further processing.
4.7.1.3 Distillation-
After initial treatment, waste solvents are distilled to remove dissolved impurities and to
separate solvent mixtures. Separation of dissolved impurities is accomplished by simple batch, simple
continuous, or steam distillation. Mixed solvents are separated by multiple simple distillation
methods, such as batch or continuous rectification. These processes are shown in Figure 4.7-3.
4.7-2 EMISSION FACTORS (Reformatted 1/95) 2/80
-------
PROCESS BLOWER
DRYING AIR
BLOWER
(OPTIONAL)
CLEAN AIR
EXHAUST
CXI 1 ^ LOW PRESSURE STEAM
I jxjj
-COOLING WATER IN
-WATER CUT
RECOVERED
WASTE SOLVENT
WATER
Figure 4.7-2. Typical fixed-bed activated carbon solvent recovery system/
WASTE SOLVENT
STEAM
EVAPORATION
SOLVENT VAPOR
REFLUX
SOLVENT
VAPOR
I
II I
FRACTIONATION
I
CONDENSATION
T
SLUDGE
DISTILLED SOLVENT
Figure 4.7-3. Distillation process for solvent reclaiming.1
In simple distillation, waste solvent is charged to an evaporator. Vapors are then
continuously removed and condensed, and the resulting sludge or still bottoms are drawn off. In
steam distillation, solvents are vaporized by direct contact with steam which is injected into the
evaporator. Simple batch, continuous, and steam distillations follow Path I in Figure 4.7-3.
2/80 (Refonnatted 1/95)
Evaporation Loss Sources
4.7-3
-------
The separation of mixed solvents requires multiple simple distillation or rectification. Batch
and continuous rectification are represented by Path n in Figure 4.7-3. In batch rectification, solvent
vapors pass through a fractionating column, where they contact condensed solvent (reflux) entering at
the top of the column. Solvent not returned as reflux is drawn off as overhead product. In
continuous rectification, the waste solvent feed enters continuously at an intermediate point in the
column. The more volatile solvents are drawn off at the top, while those with higher boiling points
collect at the bottom.
Design criteria for evaporating vessels depend on waste solvent composition. Scraped surface
stills or agitated thin film evaporators are the most suitable for heat sensitive or viscous materials.
Condensation is accomplished by barometric or shell and tube condensers. Azeotropic solvent
mixtures are separated by the addition of a third solvent component, while solvents with higher
boiling points, e. g., hi the range of high-flash naphthas (155°C, 310°F), are most effectively
distilled under vacuum. Purity requirements for the reclaimed solvent determine the number of
distillations, reflux ratios, and processing time needed.
4.7.1.4 Purification -
After distillation, water is removed from solvent by decanting or salting. Decanting is
accomplished with immiscible solvent and water which, when condensed, form separate liquid layers,
1 or the other of which can be drawn off mechanically. Additional cooling of the solvent/water mix
before decanting increases the separation of the 2 components by reducing their solubility. In salting,
solvent is passed through a calcium chloride bed, and water is removed by absorption.
During purification, reclaimed solvents are stabilized, if necessary. Buffers are added to
virgin solvents to ensure that pH level is kept constant during use. To renew it, special additives are
used during purification. The composition of these additives is considered proprietary.
4.7.1.5 Waste Disposal -
Waste materials separated from solvents during initial treatment and distillation are disposed
of by incineration, landfilling, or deep well injection. The composition of such waste varies,
depending on the original use of the solvent. But up to 50 percent is unreclaimed solvent, which
keeps the waste product viscous yet liquid, thus facilitating pumping and handling procedures. The
remainder consists of components such as oils, greases, waxes, detergents, pigments, metal fines,
dissolved metals, organics, vegetable fibers, and resins.
About 80 percent of the waste from solvent reclaiming by private contractors is disposed of in
liquid waste incinerators. About 14 percent is deposited hi sanitary landfills, usually in 55-gallon
drums. Deep well injection is the pumping of wastes between impermeable geologic strata. Viscous
wastes may have to be diluted for pumping into the desired stratum level.
4.7.2 Emissions And Controls1'3"5
Volatile organic and paniculate emissions result from waste solvent reclamation. Emission
points include storage tank vents [1], condenser vents [2], incinerator stacks [3], and fugitive losses
(numbers refer to Figure 4.7-1 and Figure 4.7-3). Emission factors for these sources are given hi
Table 4.7-1.
Solvent storage results hi volatile organic compound (VOC) emissions from solvent
evaporation (Figure 4.7-1, emission point 1). The condensation of solvent vapors during distillation
(Figure 4.7-3) also involves VOC emissions, and if steam ejectors are used, emission of steam and
noncondensables as well (Figure 4.7-1 and Figure 4.7-3, point 2). Incinerator stack emissions consist
4.7-4 EMISSION FACTORS (Reformatted 1/95) 2/80
-------
Table 4.7-1 (Metric And English Units). EMISSION FACTORS FOR SOLVENT RECLAIMING*
EMISSION FACTOR RATING: D
Source
Storage tank ventb
Condenser vent
Incinerator stack0
Incinerator stack
Fugitive emissions
Spillage0
Loading
Leaks
Open sources
Criteria Pollutant
Volatile organics
Volatile organics
Volatile organics
Particulates
Volatile organics
Volatile organics
Volatile organics
Volatile organics
Emission Factor Average
kg/Mg
0.01
(0.002 - 0.04)
1.65
(0.26-4.17)
0.01
0.72
(0.55 - 1.0)
0.10
0.36
(0.00012 - 0.71)
ND
ND
Ib/ton
0.02
(0.004 - 0.09)
3.30
(0.52 - 8.34)
0.02
1.44
(1.1 -2.0)
0.20
0.72
(0.00024 - 1.42)
ND
ND
a Reference 1. Data obtained from state air pollution control agencies and presurvey sampling. All
emission factors are for uncontrolled process equipment, except those for the incinerator stack.
(Reference 1 does not, however, specify what the control is on this stack.) Average factors are
derived from the range of data points available. Factors for these sources are given hi terms of
kilograms per megagram and pounds per ton of reclaimed solvent. Ranges hi parentheses.
ND = no data.
b Storage tank is of fixed roof design.
c Only 1 value available.
of solid contaminants that are oxidized and released as particulates, unburned organics, and
combustion stack gases (Figure 4.7-1, point 3).
VOC emissions from equipment leaks, open solvent sources (sludge drawoff and storage from
distillation and initial treatment operations), solvent loading, and solvent spills are classified as
fugitive. The former 2 sources are continuously released, and the latter 2, intermittently.
Solvent reclamation is viewed by industry as a form of control in itself. Carbon adsorption
systems can remove up to 95 percent of the solvent vapors from an air stream. It is estimated that
less than 50 percent of reclamation plants run by private contractors use any control technology.
Volatile organic emissions from the storage of solvents can be reduced by as much as
98 percent by converting from fixed to floating roof tanks, although the exact percent reduction also
2/80 (Reformatted 1/95)
Evaporation Loss Sources
4.7-5
-------
depends on solvent evaporation rate, ambient temperature, loading rate, and tank capacity. Tanks
may also be refrigerated or equipped with conservation vents which prevent air inflow and vapor
escape until some preset vacuum or pressure develops.
Solvent vapors vented during distillation are controlled by scrubbers and condensers. Direct
flame and catalytic afterburners can also be used to control noncondensables and solvent vapors not
condensed during distillation. The time required for complete combustion depends on the
flammability of the solvent. Carbon or oil adsorption may be employed also, as hi the case of vent
gases from the manufacture of vegetable oils.
Wet scrubbers are used to remove particulates from sludge incinerator exhaust gases, although
they do not effectively control submicron particles.
Submerged rather than splash filling of storage tanks and tank cars can reduce solvent
emissions from this source by more than 50 percent. Proper plant maintenance and loading
procedures reduce emissions from leaks and spills. Open solvent sources can be covered to reduce
these fugitive emissions.
References For Section 4.7
1. D. R. Tierney and T. W. Hughes, Source Assessment: Reclaiming Of Waste Solvents — State
Oflhe Art, EPA-600/2-78/004f, U. S. Environmental Protection Agency, Cincinnati, OH,
April 1978.
2. J. E. Levin and F. Scofield, "An Assessment Of The Solvent Reclaiming Industry",
Proceedings of the 170th Meeting of the American Chemical Society, Chicago, IL,
35(2):416-418, August 25-29, 1975.
3. H. M. Rowson, "Design Considerations In Solvent Recovery", Proceedings of the
Metropolitan Engineers' Council On Air Resources (MECAR) Symposium On New
Developments In Air Pollutant Control, New York, NY, October 23, 1961, pp. 110-128.
4. J. C. Cooper and F. T. Cuniff, "Control Of Solvent Emissions", Proceedings of the
Metropolitan Engineers' Council On Air Resources (MECAR) Symposium On New
Developments In Air Pollution Control, New York, NY, October 23, 1961, pp. 30-41.
5. W. R. Meyer, "Solvent Broke", Proceedings of TAPPI Testing Paper Synthetics Conference,
Boston, MA, October 7-9, 1974, pp. 109-115.
6. Nathan R. Shaw, "Vapor Adsorption Technology For Recovery Of Chlorinated Hydrocarbons
And Other Solvents", Presented at the 80th Annual Meeting of the Air Pollution Control
Association, Boston, MA, June 15-20, 1975.
4.7-6 EMISSION FACTORS (Reformatted 1/95) 2/80
-------
4.8 Tank And Drum Cleaning
4.8.1 General
Rail tank cars, tank trucks, and drums are used to transport about 700 different commodities.
Rail tank cars and most tank trucks and drums are in dedicated service (carrying one commodity only)
and, unless contaminated, are cleaned only prior to repair or testing. Nondedicated tank trucks (about
20,000, or 22 percent of the total in service) and drums (approximately 5.6 million, or 12.5 percent
of the total) are cleaned after every trip.
4.8.1.1 Rail Tank Cars -
Most rail tank cars are privately owned. Some cars, like those owned by the railroads, are
operated for hire. The commodities hauled are 35 percent petroleum products, 20 percent organic
chemicals, 25 percent inorganic chemicals, 15 percent compressed gases, and 5 percent food
products. Petroleum products considered in this study are glycols, vinyls, acetones, benzenes,
creosote, etc. Not included in these figures are gasoline, diesel oil, fuel oils, jet fuels, and motor
oils, the greatest portion of these being transported in dedicated service.
Much tank car cleaning is conducted at shipping and receiving terminals, where the wastes go
to the manufacturers' treatment systems. However, 30 to 40 percent is done at service stations
operated by tank car owners/lessors. These installations clean waste of a wide variety of
commodities, many of which require special cleaning methods.
A typical tank car cleaning facility cleans 4 to 10 cars per day. Car capacity varies from
40 to 130 cubic meters (m3) (10,000 to 34,000 gallons [gal]). Cleaning agents include steam, water,
detergents, and solvents, which are applied using steam hoses, pressure wands, or rotating spray
heads placed through the opening in the top of the car. Scraping of hardened or crystallized products
is often necessary. Cars carrying gases and volatile materials, and those needing to be pressure
tested, must be filled or flushed with water. The average amount of residual material cleaned from
each car is estimated to be 250 kilograms (kg) (550 pounds [lb]). Vapors from car cleaning not
flared or dissolved in water are dissipated to the atmosphere.
4.8.1.2 Tank Trucks -
Two-thirds of the tank trucks in service in the United States are operated for hire. Of these,
80 percent are used to haul bulk liquids. Most companies operate fleets of 5 trucks or less, and
whenever possible, these trucks are assigned to dedicated service. Commodities hauled and cleaned
are 15 percent petroleum products (except as noted in Part 4.8.1.1), 35 percent organic chemicals,
5 percent food products, and 10 percent other products.
Interior washing is carried out at many tank truck dispatch terminals. Cleaning agents include
water, steam, detergents, bases, acids, and solvents, which are applied with hand-held pressure wands
or by Turco or Butterworth rotating spray nozzles. Detergent, acidic, or basic solutions are usually
used until spent and then sent to treatment facilities. Solvents are recycled hi a closed system, with
sludges either incinerated or landfilled. The average amount of material cleaned from each trailer is
100 kg (220 lb). Vapors from volatile material are flared at a few terminals, but most commonly are
dissipated to the atmosphere. Approximately 0.23 m3 (60 gal) of liquid are used per tank truck steam
cleaning and 20.9 m3 (5500 gal) for full flushing.
2/80 (Reformatted 1/95) Evaporation Loss Sources 4.8-1
-------
4.8.1.3 Drums -
Both 0.2- and 0.11-m3 (30- and 55-gal) drums are used to ship a vast variety of commodities,
with organic chemicals (including solvents) accounting for 50 percent. The remaining 50 percent
includes inorganic chemicals, asphaltic materials, elastomeric materials, printing inks, paints, food
additives, fuel oils, and other products.
Drums made entirely of 18-gauge steel have an average life, with total cleaning, of 8 trips.
Those with 20-gauge bodies and 18-gauge heads have an average life of 3 trips. Not all drums are
cleaned, especially those of thinner construction.
Tighthead drums that have carried materials that are easy to clean are steamed or washed with
base. Steam cleaning is done by inserting a nozzle into the drum, with vapors going to the
atmosphere. Base washing is done by tumbling the drum with a charge of hot caustic solution and
some pieces of chain.
Drums used to carry materials that are difficult to clean are burned out, either in a furnace or
in the open. Those with tightheads have the tops cut out and are reconditioned as open head drums.
Drum burning furnaces may be batch or continuous. Several gas burners bathe the drum in flame,
burning away the contents, lining, and outside paint in a nominal 4-minute period and at a
temperature of at least 480°C (900°F) but not more than 540°C (1000°F) to prevent warping of the
drum. Emissions are vented to an afterburner or secondary combustion chamber, where the gases are
raised to at least 760°C (1400°F) for a minimum of 0.5 seconds. The average amount of material
removed from each drum is 2 kg (4.4 Ib).
4.8.2 Emissions And Controls
4.8.2.1 Rail Tank Cars And Tank Trucks -
Atmospheric emissions from tank car and truck cleaning are predominantly volatile organic
chemical vapors. To achieve a practical but representative picture of these emissions, the organic
chemicals hauled by the carriers must be known by classes of high, medium, and low viscosities and
of high, medium, and low vapor pressures. High-viscosity materials do not dram readily, affecting
the quantity of material remaining in the tank, and high-vapor-pressure materials volatilize more
readily during cleaning and tend to lead to greater emissions.
Practical and economically feasible controls of atmospheric emissions from tank car and truck
cleaning do not exist, except for containers transporting commodities that produce combustible gases
and water soluble vapors (such as ammonia and chlorine). Gases displaced as tanks are filled are sent
to a flare and burned. Water soluble vapors are absorbed in water and are sent to the waste water
system. Any other emissions are vented to the atmosphere.
Tables 4.8-1 and 4.8-2 give emission factors for representative organic chemicals hauled by
tank cars and trucks.
4.8.2.2 Drums -
There is no control for emissions from steaming of drums. Solution or caustic washing yields
negligible air emissions, because the drum is closed during the wash cycle. Atmospheric emissions
from steaming or washing drums are predominantly organic chemical vapors.
Air emissions from drum burning furnaces are controlled by proper operation of the
afterburner or secondary combustion chamber, where gases are raised to at least 760 °C (1400°F) for
a minimum of 0.5 seconds. This normally ensures complete combustion of organic materials and
4.8-2 EMISSION FACTORS (Reformatted 1/95) 2/80
-------
Table 4.8-1 (Metric And English Units). EMISSION FACTORS FOR RAIL TANK CAR
CLEANING"
EMISSION FACTOR RATING: D
Compound
Ethylene glycolb
Chlorobenzeneb
o-Dichlorobenzeneb
Creosote6
Chemical Class
Vapor Pressure
low
medium
low
low
Viscosity
high
medium
medium
high
Total Emissions4
g/car
0.3
15.7
75.4
2350
Ib/car
0.0007
0.0346
0.1662
5.1808
a Reference 1. Emission factors are in terms of average weight of pollutant released per car cleaned.
b Two-hour test duration.
c Eight-hour test duration.
Table 4.8-2 (Metric And English Units). EMISSION FACTORS FOR TANK TRUCK CLEANING4
EMISSION FACTOR RATING: D
Compound
Acetone
Perchloroethylene
Methyl methacrylate
Phenol
Propylene glycol
Chemical Class
Vapor Pressure
high
high
medium
low
low
Viscosity
low
low
medium
low
high
Total Emissions*
g/truck
311
215
32.4
5.5
1.07
Ib/truck
0.686
0.474
0.071
0.012
0.002
* Reference 1. One-hour test duration.
prevents the formation, and subsequent release, of large quantities of NOX, CO, and particulates. In
open burning, however, there is no feasible way of controlling the release of incomplete combustion
products to the atmosphere. The conversion of open cleaning operations to closed-cycle cleaning, and
the elimination of open-air drum burning seem to be the only control alternatives immediately
available.
Table 4.8-3 gives emission factors for representative criteria pollutants emitted from drum
burning and cleaning.
2/80 (Reformatted 1/95)
Evaporation Loss Sources
4.8-3
-------
Table 4.8-3 (Metric And English Units). EMISSION FACTORS FOR DRUM BURNING4
EMISSION FACTOR RATING: E
Pollutant
Particulate
NOX
VOC
Total Emissions
Controlled
g/drum
12b
0.018
Neg
Ib/drum
0.02646
0.00004
Neg
Uncontrolled
g/drum
16
0.89
Neg
Ib/drum
0.035
0.002
Neg
a Reference 1. Emission factors are in terms of weight of pollutant released per drum burned, except
for VOC, which are per drum washed. Neg = negligible.
b Reference 1, Table 17, and Appendix A.
Reference For Section 4.8
1. T. R. Blackwood, et al., Source Assessment: Rail Tank Car, Tank Truck, And Drum
Cleaning, State Of The Art, EPA-600/2-78-004g, U. S. Environmental Protection Agency,
Cincinnati, OH, April 1978.
4.8-4
EMISSION FACTORS
(Reformatted 1/95) 2/80
-------
4.9 Graphic Arts
4.9.1 General Graphic Printing
4.9.2 Publication Gravure Printing
1/95 Evaporation Loss Sources 4.9-1
-------
4.9.1 General Graphic Printing
4.9.1.1 Process Description
The term "graphic arts" as used here means 4 basic processes of the printing industry: web
offset lithography, web letterpress, rotogravure, and flexography. Screen printing and manual and
sheet-fed techniques are not included in this discussion.
Printing may be performed on coated or uncoated paper and on other surfaces, as in metal
decorating and some fabric coating (see Section 4.2, Surface Coating). The material to receive the
printing is called the substrate. The distinction between printing and paper coating, which may
employ rotogravure or lithographic methods, is that printing invariably involves the application of ink
by a printing press. However, printing and paper coating have these elements in common: application
of a relatively high-solvent-content material to the surface of a moving web or film, rapid solvent
evaporation by movement of heated air across the wet surface, and solvent-laden air exhausted from
the system.
Printing inks vary widely hi composition, but all consist of 3 major components: pigments,
which produce the desired colors and are composed of finely divided organic and inorganic materials;
binders, the solid components that lock the pigments to the substrate and are composed of organic
resins and polymers or, hi some inks, oils and rosins; and solvents, which dissolve or disperse the
pigments and binders and are usually composed of organic compounds. The binder and solvent make
up the "vehicle" part of the ink. The solvent evaporates from the ink into the atmosphere during the
drying process.
4.9.1.1.1 Web Offset Lithography -
Lithography, the process used to produce about 75 percent of books and pamphlets and an
increasing number of newspapers, is characterized by a planographic image carrier (i. e., the image
and nonimage areas are on the same plane). The image area is ink wettable and water repellant, and
the nonimage area is chemically repellant to ink. The solution used to dampen the plate may contain
15 to 30 percent isopropanol, if the Dalgren dampening system is used.8 When the image is applied
to a rubber-covered "blanket" cylinder and then transferred onto the substrate, the process is known
as "offset" lithography. When a web (i. e., a continuous roll) of paper is employed with the offset
process, this is known as web offset printing. Figure 4.9.1-1 illustrates a web offset lithography
publication printing line. A web newspaper printing line contains no dryer, because the ink contains
very little solvent, and somewhat porous paper is generally used.
Web offset employs "heatset" (i. e., heat drying offset) inks that dry very quickly. For
publication work the inks contain about 40 percent solvent, and for newspaper work 5 percent solvent
is used. In both cases, the solvents are usually petroleum-derived hydrocarbons. In a publication
web offset process, the web is printed on both sides simultaneously and passed through a tunnel or
floater dryer at about 200 - 290°C (400 - SOOT). The dryer may be hot air or direct flame.
Approximately 40 percent of the incoming solvent remains hi the ink film, and more may be
thermally degraded in a direct flame dryer. The web passes over chill rolls before folding and
cutting. In newspaper work no dryer is used, and most of the solvent is believed to remain in the ink
film on the paper.11
4/81 (Reformatted 1/95) Evaporation Loss Sources 4.9.1-1
-------
GAS-
WASHUP ,*.
SOLVENTS_
WEB
| THERMAL OR
~*1 ^Titn^T^o INK SOLVENT AND
1 INCINERATOR THERMAL DEGRADATION
j | A PRODUCTS
HEAT I
1 EXCHANGER 1
1 #1 I
L_
EXHAUST
1
F
f
\
HEATSET
INK
1
INK
»- FOUNTAINS
1
1
DAMPENINC
SYSTEM
FAN ^"
AN
Tl
WATEF
ISOPRO
VAP
t f ""
WATER ISOPROPANC
1
1
1 .
/) | FILTER || FILTER
FAN MJj
GAS
^ AIR HEATER
FOR DRYER
'
INK SOLVENT AND
HERMAL DEGRADATION
PRODUCTS
1 AND WASHUP
PANOL SOLVENTS
°f It
PLATE AND FLOATER
BLANKET -»- DRYER
CYLINDERS
WATER AND t
ROPANOL VAPOR
AIR
)L
COMBUSTION
PRODUCTS,
f" "" "1 UNBURNED
SHELL AND o DEPLETED
FLAT TUBE 2 A|R
HEAT
EXCHANGER
1 _l
i
f^
AIR AND SMOKE
"J FAN
CHILL
t
AIR
(WITH DALGREN
DAMPENING SYSTEM)
Figure 4.9.1-1. Web offset lithography publication printing line emission points.11
4.9.1-2
EMISSION FACTORS
(Reformatted 1/95) 4/81
-------
4.9.1.1.2 Web Letterpress-
Letterpress is the oldest form of moveable type printing, and it still dominates in periodical
and newspaper publishing, although numerous major newspapers are converting to web offset. In
letterpress printing, the image area is raised, and the ink is transferred to the paper directly from the
image surface. The image carrier may be made of metal or plastic. Only web presses using
solventborne inks are discussed here. Letterpress newspaper and sheet-fed printing use oxidative
drying inks, not a source of volatile organic emissions. Figure 4.9.1-2 shows 1 unit of a web
publication letterpress line.
Publication letterpress printing uses a paper web that is printed on 1 side at a time and dried
after each color is applied. The inks employed are heatset, usually of about 40 volume percent
solvent. The solvent in high-speed operations is generally a selected petroleum fraction akin to
kerosene and fuel oil, with a boiling point of 200 - 370°C (400 - 700°F).13
4.9.1.1.3 Rotogravure-
In gravure printing, the image area is engraved, or "intaglio" relative to the surface of the
unage carrier, which is a copper-plated steel cylinder that is usually also chrome plated to enhance
wear resistance. The gravure cylinder rotates in an ink trough or fountain. The ink is picked up in
the engraved area, and ink is scraped off the nonimage area with a steel "doctor blade". The image is
transferred directly to the web when it is pressed against the cylinder by a rubber covered impression
roll, and the product is then dried. Rotary gravure (web fed) systems are known as "rotogravure"
presses.
Rotogravure can produce illustrations with excellent color control, and it may be used on
coated or uncoated paper, film, foil, and almost every other type of substrate. Its use is concentrated
in publications and advertising such as newspaper supplements, magazines, and mail order catalogues;
folding cartons and other flexible packaging materials; and specialty products such as wall and floor
coverings, decorated household paper products, and vinyl upholstery. Figure 4.9.1-3 illustrates 1 unit
of a publication rotogravure press. Multiple units are required for printing multiple colors.
The inks used in rotogravure publication printing contain from 55 to 95 volume percent low
boiling solvent (average is 75 volume percent), and they must have low viscosities. Typical gravure
solvents include alcohols, aliphatic naphthas, aromatic hydrocarbons, esters, glycol ethers, ketones,
and nitroparaffins. Water-base inks are in regular production use in some packaging and specialty
applications, such as sugar bags.
Rotogravure is similar to letterpress printing in that the web is printed on one side at a time
and must be dried after application of each color. Thus, for 4-color, 2-sided publication printing,
8 presses are employed, each including a pass over a steam drum or through a hot air dryer at
temperatures from ambient up to 120°C (250°F) where nearly all of the solvent is removed.3 For
further information, see Section 4.9.2.
4.9.1.1.4 Flexography -
In flexographic printing, as hi letterpress, the unage area is above the surface of the plate.
The distinction is that flexography uses a rubber image carrier and alcohol-base inks. The process is
usually web fed and is employed for medium or long multicolor runs on a variety of substrates,
including heavy paper, fiberboard, and metal and plastic foil. The major categories of the
flexography market are flexible packaging and laminates, multiwall bags, milk cartons, gift wrap,
folding cartons, corrugated paperboard (which is sheet fed), paper cups and plates, labels, tapes, and
envelopes. Almost all milk cartons and multiwall bags and half of all flexible packaging are printed
by this process.
4/81 (Reformatted 1/95) Evaporation Loss Sources 4.9.1-3
-------
WEB
1
1 THERMAL
1 INCINERATOR P
1
___
"
GAS I HEAT
1 EXCHANGER
#1
!_ _. COMBUSTION
EXHAUST FAN C
i
i
FAN *~*\
t i
'
HEATSET INK
^ PRESS — — ^^^
PRODUCTS.
1 UNBURNED
ROTARY 1 ORGANICS,
#2 1 AIR
•* * bXCHGR r* rRCSII AIR
S . .. — , 1
FILTER | j FILTER J '
i '
Q«" " ™ *0c^LWvH^
I 1 UNIT IS
T t_ USED HERE
1 " ' ""1
^ AIR HEATER j CATALYTIC
FOR DRYER j INCINERATOR!
i !
GAS C*J SUPPLY FAN
V <~» ^
SOLVENT AND THERMAL AIR AND SMOKE
DEGRADATION
PRODUCTS
TUNNEL OR
^WASHUP DRYER
••—SOLVENTS
AIR
1IT
COOL WATER
Figure 4.9.1-2. Web letterpress publication printing line emission points.11
4.9.1-4
EMISSION FACTORS
(Reformatted 1/95) 4/81
-------
TO ATM
OSPHERE
TRACES OF
WATER
AND
SOLVENT
>
•
HOT WATER
_ 1 , ___.
1 i !
{CONDENSER) j DECANTER
SOLVENTi |
-•MIXTURE] h
i » iSTILLl
! . 1 !
* 1 i * , i - i u
I J 1 IWARM 1 ,
1 ' WATER
COOL WATER
STEAM PLUS
SOLVENT
VAPOR 1 |
1 ADSORBER i
* j (ACTIVE MODE)
, ADSORBER '
\f 1 (i-..-/~l-.ir-r-, A-ri»is*l 1 V
• """!' j "
r
STEAM j
l_
- »•
SOLVENTS
>-
+> WATER
COMBUSTION
PRODUCTS
t
1
1
STEAM BOILER |
111"
WATER
SOLVENT LADEN AIR
WEB-
INK
i
INK
FOUNTAIN
; < 1
PRESS
(ONE UNIT)
STEAM DRUM OR
HOT AIR DRYER
CHILL
ROLLS
' 1 T 1 AIR
AIR AIR HEAT COOL WATER
FROM STEAM,
HOT WATER,
OR HOT AIR
PRINTED WEB
Figure 4.9.1-3. Rotogravure and flexography printing line emission points (chill rolls not used in
rotogravure publication printing).11
4/81 (Reformatted 1/95)
Evaporation Loss Sources
4.9.1-5
-------
Steam set inks, employed in the "water flexo" or "steam set flexo" process, are low-viscosity
inks of a paste consistency that are gelled by water or steam. Steam-set inks are used for paper bag
printing, and they produce no significant emissions. Water-base inks, usually pigmented suspensions
in water, are also available for some flexographic operations, such as the printing of multiwall bags.
Solvent-base inks are used primarily in publication printing, as shown in Figure 4.9.1-3. As
with rotogravure, flexography publication printing uses very fluid inks of about 75 volume percent
organic solvent. The solvent, which must be rubber compatible, may be alcohol, or alcohol mixed
with an aliphatic hydrocarbon or ester. Typical solvents also include glycols, ketones, and ethers.
The inks dry by solvent absorption into the web and by evaporation, usually in high velocity steam
drum or hot air dryers, at temperatures below 120°C (250°F).3>13 As in letterpress publishing, the
web is printed on only 1 side at a time. The web passes over chill rolls after drying.
4.9.1.2 Emissions And Controls
Significant emissions from printing operations consist primarily of volatile organic solvents.
Such emissions vary with printing process, ink formulation and coverage, press size and speed, and
operating time. The type of paper (coated or uncoated) has little effect on the quantity of emissions,
although low levels of organic emissions are derived from the paper stock during drying.13 High-
volume web-fed presses such as those discussed above are the principal sources of solvent vapors.
Total annual emissions from the industry in 1977 were estimated to be 380,000 megagrams (Mg)
(418,000 tons). Of this total, lithography emits 28 percent, letterpress 18 percent, gravure
41 percent, and flexography 13 percent.3
Most of the solvent contained in the ink and used for dampening and cleanup eventually finds
its way into the atmosphere, but some solvent remains with the printed product leaving the plant and
is released to die atmosphere later. Overall solvent emissions can be computed from Equation 1 using
a material balance concept, except hi cases where a direct flame dryer is used and some of the solvent
is thermally degraded.
The density of naphtha base solvent at 21 °C (70°F) is 0.742 kilogams per liter (kg/L)
(6.2 pounds per gallon [lb/gal]).
Etotal = T (1)
where:
Etotai = total solvent emissions including those from the printed product, kg (Ib)
T = total solvent use including solvent contained hi ink as used, kg (Ib)
The solvent emissions from the dryer and other printline components can be computed from
Equation 2. The remaining solvent leaves the plant with the printed product and/or is degraded in the
dryer.
= Kd (100-P)
100 100 w
where:
E = solvent emissions from printline, kg (Ib)
I = ink use, liters (gallons)
S and P = factors from Table 4.9.1-1.
d = solvent density, kg/L (lb/gal)
4.9.1-6 EMISSION FACTORS (Refonnatted 1/95) 4/81
-------
Table 4.9.1-1. TYPICAL PARAMETERS FOR COMPUTING SOLVENT EMISSIONS
FROM PRINTING LINESa'b
Process
Web Offset Lithography
Publication
Newspaper
Web Letterpress
Publication
Newspaper
Rotogravure
Flexography
Solvent Content Of Ink
(Volume %) [S]
40
5
40
0
75
75
Solvent Remaining
In Product Plus That
Destroyed In Dryer
(%) [P]c
40 (hot air dryer)
60 (direct flame dryer)
100
40
NA
2-7
2-7
EMISSION
FACTOR
RATING
B
B
B
NA
C
C
a References 1,14. NA = not applicable.
b Values for S and P are typical. Specific values for S and P should be obtained from a source to
estimate its emissions.
c For certain packaging products, amount of solvent retained is regulated by the Food and Drug
Administration (FDA).
4.9.1.2.1 Per Capita Emission Factors -
Although major sources contribute most of the emissions for graphic arts operations,
considerable emissions also originate from minor graphic arts applications, including inhouse printing
services in general industries. Small sources within the graphic arts industry are numerous and
difficult to identify, since many applications are associated with nonprinting industries. Table 4.9.1-2
presents per capita factors for estimating emissions from small graphic arts operations. The factors
are entirely nonmethane VOC and should be used for emission estimates over broad geographical
areas.
Table 4.9.1-2 (Metric And English Units). PER CAPITA NONMETHANE VOC EMISSION
FACTORS FOR SMALL GRAPHIC ARTS APPLICATIONS
EMISSION FACTOR RATING: D
Units
kg/year/capita
Ib/year/capita
g/day/capita
Ib/day/capita
Emission Factor*
0.4
0.8
lb
0.003b
a Reference 15. All nonmethane VOC.
b Assumes a 6-day operating week (313 days/yr).
4/81 (Reformatted 1/95)
Evaporation Loss Sources
4.9.1-7
-------
4.9.1.2.2 Web Offset Lithography -
Emission points on web offset lithography publication printing lines include: (1) the ink
fountains, (2) the dampening system, (3) the plate and blanket cylinders, (4) the dryer, (5) the chill
rolls, and (6) the product (see Figure 4.9.1-1).
Alcohol is emitted from Points 2 and 3. Washup solvents are a small source of emissions
from Points 1 and 3. Drying (Point 4) is the major source, because 40 to 60 percent of the ink
solvent is removed from the web during this process.
The quantity of web offset emissions may be estimated from Equation 1, or from Equation 2
and the appropriate data from Table 4.9.1-1.
4.9.1.2.3 Web Letterpress -
Emission points on web letterpress publication printing lines are: (1) the press (includes the
image carrier and inking mechanism), (2) the dryer, (3) the chill rolls, and (4) the product (see
Figure 4.9.1-2).
Web letterpress publication printing produces significant emissions, primarily from the ink
solvent, about 60 percent of which is lost in the drying process. Washup solvents are a small source
of emissions. The quantity of emissions can be computed as described for web offset.
Letterpress publication printing uses a variety of papers and inks that lead to emission control
problems, but losses can be reduced by a thermal or catalytic incinerator, either of which may be
coupled with a heat exchanger.
4.9.1.2.4 Rotogravure-
Emissions from rotogravure printing occur at: (1) the ink fountain, (2) the press, (3) the
dryer, and (4) the chill rolls (see Figure 4.9.1-3). The dryer is the major emission point, because
most of the VOC hi the low boiling ink is removed during drying. The quantity of emissions can be
computed from Equation 1, or from Equation 2 and the appropriate parameters from Table 4.9.1-1.
Vapor capture systems are necessary to minimize fugitive solvent vapor loss around the ink
fountain and at the chill rolls. Fume incinerators and carbon adsorbers are die only devices that have
a high efficiency in controlling vapors from rotogravure operations.
Solvent recovery by carbon adsorption systems has been quite successful at a number of large
publication rotogravure plants. These presses use a single water-immiscible solvent (toluene) or a
simple mixture that can be recovered in approximately the proportions used in the ink. All new
publication gravure plants are being designed to include solvent recovery.
Some smaller rotogravure operations, such as those that print and coat packaging materials,
use complex solvent mixtures in which many of the solvents are water soluble. Thermal incineration
with heat recovery is usually the most feasible control for such operations. With adequate primary
and secondary heat recovery, the amount of fuel required to operate both the incinerator and the dryer
system can be reduced to less than that normally required to operate the dryer alone.
In addition to thermal and catalytic incinerators, pebble bed incinerators are also available.
Pebble bed incinerators combine the functions of a heat exchanger and a combustion device, and can
achieve a heat recovery efficiency of 85 percent.
4.9.1-8 EMISSION FACTORS (Reformatted 1/95) 4/81
-------
VOC emissions can also be reduced by using low-solvent inks. Waterborne inks, in which
the volatile portion contains up to 20 volume percent water soluble organic compounds, are used
extensively in rotogravure printing of multiwall bags, corrugated paperboard, and other packaging
products, although water absorption into the paper limits the amount of waterborne ink that can be
printed on thin stock before the web is seriously weakened.
4.9.1.2.5 Flexography -
Emission points on flexographic printing lines are: (1) the ink fountain, (2) the press, (3) the
dryer, and (4) the chill rolls (see Figure 4.9.1-3). The dryer is the major emission point, and
emissions can be estimated from Equation 1, or from Equation 2 and the appropriate parameters from
Table 4.9.1-1.
Vapor capture systems are necessary to minimize fugitive solvent vapor loss around the ink
fountain and at the chill rolls. Fume incinerators are the only devices proven highly efficient in
controlling vapors from flexographic operations. VOC emissions can also be reduced by using
waterborne inks, which are used extensively hi flexographic printing of packaging products.
Table 4.9-3 shows estimated control efficiencies for printing operations.
Table 4.9-3. ESTIMATED CONTROL TECHNOLOGY EFFICIENCIES
FOR PRINTING LINES
Method
Carbon adsorption
Incineration1*
Waterborne inkse
Application
Publication rotogravure
operations
Web offset lithography
Web letterpress
Packaging rotogravure
printing operations
Flexography printing
operations
Some packaging rotogravure
printing operations
Some flexography packaging
printing operations
Reduction in Organic Emissions
(*)
75a
95C
95d
65a
60*
65 - 75a
60*
8 Reference 3. Overall emission reduction efficiency (capture efficiency multiplied by control device
efficiency).
b Direct flame (thermal) catalytic and pebble bed. Three or more pebble beds in a system have a heat
recovery efficiency of 85%.
0 Reference 12. Efficiency of volatile organic removal — does not consider capture efficiency.
d Reference 13. Efficiency of volatile organic removal — does not consider capture efficiency.
e Solvent portion consists of 75 volume % water and 25 volume % organic solvent.
f With less demanding quality requirements.
4/81 (Reformatted 1/95)
Evaporation Loss Sources
4.9.1-9
-------
References For Section 4.9.1
1. "Air Pollution Control Technology Applicable To 26 Sources Of Volatile Organic
Compounds", Office Of Air Quality Planning And Standards, U. S. Environmental Protection
Agency, Research Triangle Park, NC, May 27, 1977. Unpublished.
2. Peter N. Formica, Controlled And Uncontrolled Emission Rates And Applicable Limitations
For Eighty Processes, EPA-340/1-78-004, U. S. Environmental Protection Agency, Research
Triangle Park, NC, April 1978.
3. Edwin J. Vincent and William M. Vatavuk, Control Of Volatile Organic Emissions From
Existing Stationary Sources, Volume VIII: Graphic Arts — Rotogravure And Flexography,
EPA-450/2-78-033, U. S. Environmental Protection Agency, Research Triangle Park, NC,
December 1978.
4. Telephone communication with C. M. Higby, Cal/Ink, Berkeley, CA, March 28, 1978.
5. T. W. Hughes, et al., Prioritization Of Air Pollution From Industrial Surface Coating
Operations, EPA-650/2-75-019a, U. S. Environmental Protection Agency, Cincinnati, OH,
February 1975.
6. Harvey F. George, "Gravure Industry's Environmental Program", Environmental Aspects Of
Chemical Use In Printing Operations, EPA-560/1-75-005, U.S. Environmental Protection
Agency, Research Triangle Park, NC, January 1976.
7. K. A. Bownes, "Material Of Flexography", ibid.
8. Ben H. Carpenter and Garland R. Hilliard, "Overview Of Printing Processes And Chemicals
Used", ibid.
9. R. L. Harvin, "Recovery And Reuse of Organic Ink Solvents", ibid.
10. Joseph L. Zborovsky, "Current Status Of Web Heatset Emission Control Technology", ibid.
11. R. R. Gadomski, et al., Evaluations Of Emission And Control Technologies In The Graphic
Arts Industries, Phase I: Final Report, APTD-0597, National Air Pollution Control
Administration, Cincinnati, OH, August 1970.
12. R.R. Gadomski, et al., Evaluations Of Emissions And Control Technologies In The Graphic
Arts Industries, Phase II: Web Offset And Metal Decorating Processes, APTD-1463,
U. S. Environmental Protection Agency, Research Triangle Park, NC, May 1973.
13. Control Techniques For Volatile Organic Emissions From Stationary Sources,
EPA^50/2-78-022, U. S. Environmental Protection Agency, Research Triangle Park, NC,
May 1978.
14. Telephone communication with Edwin J. Vincent, Office Of Air Quality Planning And
Standards, U. S. Environmental Protection Agency, Research Triangle Park, NC, July 1979.
4.9.1-10 EMISSION FACTORS (Reformatted 1/95) 4/81
-------
IS. W. H. Lamason, "Technical Discussion Of Per Capita Emission Factors For Several Area
Sources Of Volatile Organic Compounds", Office Of Air Quality Planning And Standards,
U. S. Environmental Protection Agency, Research Triangle Park, NC, March 15, 1981.
Unpublished.
4/81 (Reformatted 1/95) Evaporation Loss Sources 4.9.1-11
-------
4.9.2 Publication Gravure Printing
4.9.2.1 Process Description1"2
Publication gravure printing is the printing by the rotogravure process of a variety of paper
products such as magazines, catalogs, newspaper supplements and preprinted inserts, and
advertisements. Publication printing is the largest sector involved in gravure printing, representing
over 37 percent of the total gravure product sales value in a 1976 study.
The rotogravure press is designed to operate as a continuous printing facility, and normal
operation may be either continuous or nearly so. Normal press operation experiences numerous
shutdowns caused by web breaks or mechanical problems. Each rotogravure press generally consists
of 8 to 16 individual printing units, with an 8-unit press the most common. In publication printing,
only 4 colors of ink are used: yellow, red, blue, and black. Each unit prints 1 ink color on 1 side of
the web, and colors other than these 4 are produced by printing 1 color over another to yield the
desired product.
In the rotogravure printing process, a web or substrate from a continuous roll is passed over
the image surface of a revolving gravure cylinder. For publication printing, only paper webs are
used. The printing images are formed by many tiny recesses or cells etched or engraved into the
surface of the gravure cylinder. The cylinder is about one-fourth submerged hi a fountain of low-
viscosity mixed ink. Raw ink is solvent-diluted at the press and is sometimes mixed with related
coatings, usually referred to as extenders or varnishes. The ink, as applied, is a mixture of pigments,
binders, varnish, and solvent. The mixed ink is picked up by the cells on the revolving cylinder
surface and is continuously applied to the paper web. After impression is made, the web travels
through an enclosed heated air dryer to evaporate the volatile solvent. The web is then guided along
a series of rollers to the next printing unit. Figure 4.9.2-1 illustrates this printing process by an end
(or side) view of a single printing unit.
At present, only solventborne inks are used on a large scale for publication printing.
Waterborne inks are still hi research and development stages, but some are now being used in a few
limited cases. Pigments, binders, and varnishes are the nonvolatile solid components of the mixed
ink. For publication printing, only aliphatic and aromatic organic liquids are used as solvents.
Presently, 2 basic types of solvents, toluene and a toluene-xylene-naphtha mixture, are used. The
naphtha base solvent is the more common. Benzene is present hi both solvent types as an impurity,
in concentrations up to about 0.3 volume percent. Raw inks, as purchased, have 40 to 60 volume
percent solvent, and the related coatings typically contain about 60 to 80 volume percent solvent. The
applied mixed ink consists of 75 to 80 volume percent solvent, required to achieve the proper fluidity
for rotogravure printing.
4.9.2.2 Emissions And Controls1'3"4
Volatile organic compoi id (VOC) vapors are the only significant air pollutant emissions from
publication rotogravure printing. Emissions from the printing presses depend on the total amount of
solvent used. The sources of these VOC emissions are the solvent components in the raw inks,
related coatings used at the printing presses, and solvent added for dilution and press cleaning. These
solvent organics are photochemically reactive. VOC emissions from both controlled and uncontrolled
publication rotogravure facilities in 1977 were about 57,000 megagrams (Mg) (63,000 tons),
4/81
-------
V)
1
p.
4>
2
I
OS
2
4.9.2-2
EMISSION FACTORS
(Reformatted 1/95) 4/81
-------
15 percent of the total from the graphic arts industry. Emissions from ink and solvent storage and
transfer facilities are not considered here.
Table 4.9.2-1 presents emission factors for publication printing on rotogravure presses with
and without control equipment. The potential amount of VOC emissions from the press is equal to
the total amount of solvent consumed in the printing process (see Footnote f). For uncontrolled
presses, emissions occur from the dryer exhaust vents, printing fugitive vapors, and evaporation of
solvent retained hi the printed product. About 75 to 90 percent of the VOC emissions occur from the
dryer exhausts, depending on press operating speed, press shutdown frequency, ink and solvent
composition, product printed, and dryer designs and efficiencies. The amount of solvent retained by
the various rotogravure printed products is 3 to 4 percent of the total solvent in the ink used. The
retained solvent eventually evaporates after the printed product leaves the press.
There are numerous points around the printing press from which fugitive emissions occur.
Most of the fugitive vapors result from solvent evaporation in the ink fountain, exposed parts of the
gravure cylinder, the paper path at the dryer inlet, and from the paper web after exiting the dryers
between printing units. The quantity of fugitive vapors depends on the solvent volatility, the
temperature of the ink and solvent in the ink fountain, the amount of exposed area around the press,
dryer designs and efficiencies, and the frequency of press shutdowns.
The complete air pollution control system for a modern publication rotogravure printing
facility consists of 2 sections: the solvent vapor capture system and the emission control device. The
capture system collects VOC vapors emitted from the presses and directs them to a control device
where they are either recovered or destroyed. Low-VOC waterborne ink systems to replace a
significant amount of solventborne inks have not been developed as an emission reduction alternative.
4.9.2.2.1 Capture Systems -
Presently, only the concentrated dryer exhausts are captured at most facilities. The dryer
exhausts contain the majority of the VOC vapors emitted. The capture efficiency of dryers is limited
by their operating temperatures and other factors that affect the release of the solvent vapors from the
print and web to the dryer air. Excessively high temperatures impair product quality. The capture
efficiency of older design dryer exhaust systems is about 84 percent, and modern dryer systems can
achieve 85 to 89 percent capture. For a typical press, this type capture system consists of ductwork
from each printing unit's dryer exhaust joined in a large header. One or more large fans are
employed to pull the solvent-laden air from the dryers and to direct it to the control device.
A few facilities have increased capture efficiency by gathering fugitive solvent vapors along
with the dryer exhausts. Fugitive vapors can be captured by a hood above the press, by a partial
enclosure around the press, by a system of multiple spot pickup vents, by multiple floor sweep vents,
by total pressroom ventilation capture, or by various combinations of these. The design of any
fugitive vapor capture system needs to be versatile enough to allow safe and adequate access to the
press in press shutdowns. The efficiencies of these combined dryer exhaust and fugitive capture
systems can be as high as 93 to 97 percent at times, but the demonstrated achievable long term
average when printing several types of products is only about 90 percent.
4.9.2.2.2 Control Devices -
Various control devices and techniques may be employed to control captured VOC vapors
from rotogravure presses. All such controls are of 2 categories: solvent recovery and solvent
destruction.
4/81 (Reformatted 1/95) Evaporation Loss Sources 4.9.2-3
-------
Table 4.9.2-1 (Metric And English Units). EMISSION FACTORS FOR PUBLICATION
ROTOGRAVURE PRINTING PRESSES
EMISSION FACTOR RATING: C
Emission Points
Dryer exhausts1"
Fugitives0
Printed product
Control device6
Total emissionsf
VOC Emissions8
Uncontrolled
Total
Solvent
kg/kg
(Ib/lb)
0.84
0.13
0.03
—
1.0
Raw Ink
kg
L
1.24
0.19
0.05
—
1.48
Ib
gal
10.42
1.61
0.37
—
12.40
75% Control
Total
Solvent
kg/kg
(Ib/lb)
—
0.13
0.03
0.09
0.25
Raw Ink
L
_
0.19
0.05
0.13
0.37
Ib
gal
—
1.61
0.37
1.12
3.10
85% Control
Total
Solvent
kg/kg
(Ib/lb)
—
0.07
0.03
0.05
0.15
Raw
fcg
L
—
0.10
0.05
0.07
0.22
Ink
Jb_
gal
—
0.87
0.37
0.62
1.86
a All nonmethane. Mass of VOC emitted per mass of total solvent used are more accurate factors.
Solvent assumed to consist entirely of VOC. Total solvent used includes all solvent in raw ink and
related coatings, all dilution solvent added and all cleaning solvent used. Mass of VOC emitted per
volume of raw ink (and coatings) used are general factors, based on typical dilution solvent volume
addition. Actual factors based on ink use can vary significantly, as follows:
- Typical total solvent volume/raw ink (and coatings) volume ratio - 2.0 (liter/liter)
(L/L) (gal/gal); range, 1.6 - 2.4. See References 1,5-8.
- Solvent density (Ds) varies with composition and temperature. At 21°C (70°F),
the density of the most common mixed solvent used is 0.742 kg/L (6.2 Ib/gal);
density of toluene solvent used is 0.863 kg/L (7.2 Ib/gal). See Reference 1.
- Mass of VOC emitted/raw ink (and coating) volume ratio determined from the
mass emission factor ratio, the solvent/ink volume ratio, and the solvent density.
kg/L = kg/kg x L/L x Ds
(Ib/gal = Ib/lb x gal/gal x Ds)
b Reference 3 and test data for presses with dryer exhaust control only (Reference 1). Dryer exhaust
emissions depend on press operating speed, press shutdown frequency, ink and solvent composition,
product printed, and dryer design and efficiencies. Emissions can range from 75 - 90% of total
press emissions.
c Determined by difference between total emissions and other point emissions.
d Reference 1. Solvent temporarily retained in product after leaving press depends on dryer
efficiency, type of paper, and type of ink used. Emissions have been reported to range from
1-7% of total press emissions.
e Based on capture and control device efficiencies (see Footnote f). Emissions are residual content in
captured solvent-laden air vented after treatment.
f References 1,3. Uncontrolled presses eventually emit 100% of total solvent used. Controlled press
emissions are based on overall reduction efficiency equal to capture efficiency x control device
efficiency. For 75% control, the capture efficiency is 84% witfi a 90% efficient control device.
For 85% control, the capture efficiency is 90% with a 95% control device.
4.9.2-4
EMISSION FACTORS
(Reformatted 1/95) 4/81
-------
Solvent recovery is the only present technique to control VOC emissions from publication
presses. Fixed-bed carbon adsorption by multiple vessels operating in parallel configuration,
regenerated by steaming, represents the most used control device. A new adsorption technique using
a fluidized bed of carbon might be employed in the future. The recovered solvent can be directly
recycled to the presses.
There are 3 types of solvent destruction devices used to control VOC emissions:
(1) conventional thermal oxidation, (2) catalytic oxidation, and (3) regenerative thermal combustion.
These control devices are employed for other rotogravure printing. At present, none are being used
on publication rotogravure presses.
The efficiency of both solvent destruction and solvent recovery control devices can be as high
as 99 percent. However, the achievable long-term average efficiency for publication printing is about
95 percent. Older carbon adsorber systems were designed to perform at about 90 percent efficiency.
Control device emission factors presented hi Table 4.9.2-1 represent the residual vapor content of the
captured solvent-laden air vented after treatment.
4.9.2.2.3 Overall Control -
The overall emission reduction efficiency for VOC control systems is equal to the capture
efficiency times the control device efficiency. Emission factors for 2 control levels are presented hi
Table 4.9.2-1. The 75 percent control level represents 84 percent capture with a 90 percent efficient
control device. (This is the EPA control techniques guideline recommendation for State regulations
on old existing presses.) The 85 percent control level represents 90 percent capture with a 95 percent
efficient control device. This corresponds to application of best demonstrated control technology for
new publication presses.
References For Section 4.9.2
1. Publication Rotogravure Printing — Background Information For Proposed Standards,
EPA-450/3-80-031a, U. S. Environmental Protection Agency, Research Triangle Park, NC,
October 1980.
2. Publication Rotogravure Printing — Background Information For Promulgated Standards,
EPA-450/3-80-031b, U. S. Environmental Protection Agency, Research Triangle Park, NC.
Expected November 1981.
3. Control Of Volatile Organic Emissions From Existing Stationary Sources, Volume VIII:
Graphic Arts — Rotogravure And Flexography, EPA-450/2-78-033, U. S. Environmental
Protection Agency, Research Triangle Park, NC, December 1978.
4. Standards Of Performance For New Stationary Sources: Graphic Arts — Publication
Rotogravure Printing, 45 FR 71538, October 28, 1980.
5. Written communication from Texas Color Printers, Inc., Dallas, TX, to Radian Corp.,
Research Triangle Park, NC, July 3, 1979.
6. Written communication from Meredith/Burda, Lynchburg, VA, to Edwin Vincent, Office Of
Au: Quality Planning And Standards, U. S. Environmental Protection Agency, Research
Triangle Park, NC, July 6, 1979.
7. W. R. Feairheller, Graphic Arts Emission Test Report, Meredith/Burda, Lynchburg, VA,
EPA Contract No. 68-02-2818, Monsanto Research Corp., Dayton, OH, April 1979.
4/81 (Reformatted 1/95) Evaporation Loss Sources 4.9.2-5
-------
8. W. R. Feairheller, Graphic Arts Emission Test Report, Texas Color Printers, Dallas, TX,
EPA Contract No. 68-02-2818, Monsanto Research Corp., Dayton, OH, October 1979.
4.9.2-6 EMISSION FACTORS (Reformatted 1/95) 4/81
-------
4.10 Commercial/Consumer Solvent Use
4.10.1 General1'2
Commercial and consumer use of various products containing volatile organic compounds
(VOC) contributes to formation of tropospheric ozone. The organics in these products may be
released through immediate evaporation of an aerosol spray, evaporation after application, and direct
release in the gaseous phase. Organics may act either as a carrier for the active product ingredients
or as active ingredients themselves. Commercial and consumer products that release VOCs include
aerosols, household products, toiletries, rubbing compounds, windshield washing fluids, polishes and
waxes, nonindustrial adhesives, space deodorants, moth control applications, and laundry detergents
and treatments.
4.10.2 Emissions
Major volatile organic constituents of these products which are released to the atmosphere
include special naphthas, alcohols, and various chloro- and fluorocarbons. Although methane is not
included in these products, 31 percent of the VOCs released in the use of these products is considered
nonreactive under EPA policy. »4
National emissions and per capita emission factors for commercial and consumer solvent use
are presented in Table 4.10-1. Per capita emission factors can be applied to area source inventories
by multiplying the factors by inventory area population. Note that adjustment to exclude the
nonreactive emission fraction cited above should be applied to total emissions or to the composite
factor. Care is advised in making adjustments, in that substitution of compounds within the
commercial/consumer products market may alter the nonreactive fraction of compounds.
Table 4.10-1 (Metric And English Units). EVAPORATIVE EMISSIONS
FROM COMMERCIAL/CONSUMER SOLVENT USE
EMISSION FACTOR RATING: C
Nonmethane VOCa
Use
Aerosol products
Household products
Toiletries
Rubbing compounds
Windshield washing
Polishes and waxes
National Emissions
103 Mg/yr
342
183
132
62
61
48
103 tons/yr
376
201
145
68
67
53
Per Capita Emission Factors
kg/yr
1.6
0.86
0.64
0.29
0.29
0.22
lb/yr
3.5
1.9
1.4
0.64
0.63
0.49
g/dayb
4.4
2.4
1.8
0.80
0.77
0.59
10-3 Ib/day
9.6
5.2
3.8
1.8
1.7
1.3
4/81 (Reformatted 1/95)
Evaporation Loss Sources
4.10-1
-------
Table 4.10-1 (cont.).
a References 1-2.
b Calculated by dividing kg/yr (Ib/yr) by 365 and converting to appropriate units.
c Totals may not be additive because of rounding.
Nonmethane VOCa
Use
Nonindustrial
adhesives
Space deodorant
Moth control
Laundry detergent
Total0
National Emissions
103 Mg/yr
29
18
16
4
895
103 tons/yr
32
20
18
4
984
Per Capita Emission Factors
kg/yr
0.13
0.09
0.07
0.02
4.2
Ib/yr
0.29
0.19
0.15
0.04
9.2
g/dayb
0.36
0.24
0.19
0.05
11.6
1(T3 Ib/day
0.79
0.52
0.41
0.10
25.2
References For Section 4.10
1. W. H. Lamason, "Technical Discussion Of Per Capita Emission Factors For Several Area
Sources Of Volatile Organic Compounds ", Monitoring And Data Analysis Division,
U. S. Environmental Protection Agency, Research Triangle Park, NC, March 15, 1981.
Unpublished.
2. End Use Of Solvents Containing Volatile Organic Compounds, EPA-450/3-79-032,
U. S. Environmental Protection Agency, Research Triangle Park, NC, May 1979.
3. Final Emission Inventory Requirements For 1982 Ozone State Implementation Plans,
EPA-450/4-80-016, U. S. Environmental Protection Agency, Research Triangle Park, NC,
December 1980.
4. Procedures For The Preparation Of Emission Inventories For Volatile Organic Compounds,
Volume I, Second Edition, EPA-450/2-77-028, U. S. Environmental Protection Agency,
Research Triangle Park, NC, September 1980.
4.10-2
EMISSION FACTORS
(Reformatted 1/95) 4/81
-------
4.11 Textile Fabric Printing
4.11.1 Process Description1"2
Textile fabric printing is part of the textile finishing industry. In fabric printing, a decorative
pattern or design is applied to constructed fabric by roller, flat screen, or rotary screen methods.
Pollutants of interest in fabric printing are volatile organic compounds (VOC) from mineral spirit
solvents in print pastes or inks. Tables 4.11-1, 4.11-2, and 4.11-3 show typical printing run
characteristics and VOC emission sources, respectively, for roller, flat screen, and rotary screen
printing methods.
In the roller printing process, print paste is applied to an engraved roller, and the fabric is
guided between it and a central cylinder. The pressure of the roller and central cylinder forces the
print paste into the fabric. Because of the high quality it can achieve, roller printing is the most
appealing method for printing designer and fashion apparel fabrics.
In flat screen printing, a screen on which print paste has been applied is lowered onto a
section of fabric. A squeegee then moves across the screen, forcing the print paste through the screen
and into the fabric. Flat screen machines are used mostly hi printing terry towels.
In rotary screen printing, tubular screens rotate at the same velocity as the fabric. Print paste
distributed inside the tubular screen is forced into the fabric as it is pressed between the screen and a
printing blanket (a continuous rubber belt). Rotary screen printing machines are used mostly but not
exclusively for bottom weight apparel fabrics or fabric not for apparel use. Host knit fabric is printed
by the rotary screen method, because it does not stress (pull or stretch) the fabric during the process.
Major print paste components include clear and color concentrates, a solvent, and in pigment
printing, a low crock or binder resin. Print paste color concentrates contain either pigments or dyes.
Pigments are insoluble particles physically bound to fabrics. Dyes are in solutions applied to impart
color by becoming chemically or physically incorporated into individual fibers. Organic solvents are
used almost exclusively with pigments. Very little organic solvent is used in nonpigment print pastes.
Clear concentrates extend color concentrates to create light and dark shades. Clear and color
concentrates do contain some VOC but contribute less than 1 percent of total VOC emissions from
textile printing operations. Defoamers and resins are included hi print paste to increase color
fastness. A small amount of thickening agent is also added to each print paste to control print paste
viscosity. Print defoamers, resins, and thickening agents do not contain VOC.
The majority of emissions from print paste are from the solvent, which may be aqueous,
organic (mineral spirits), or both. The organic solvent concentration hi print pastes may vary from
0 to 60 weight percent, with no consistent ratio of organic solvent to water. Mineral spirits used hi
print pastes vary widely in physical and chemical properties (see Table 4.11-4).
Although some mineral spirits evaporate in the early stages of the printing process, the
majority of emissions to the atmosphere is from the printed fabric drying process, which drives off
volatile compounds (see Tables 4.11-2 and 4.11-3 for typical VOC emission splits). For some
specific print paste/fabric combinations, color fixing occurs hi a curing process, which may be
entirely separate or merely a separate segment of the drying process.
8/82 (Reformatted 1/95) Evaporation Loss Sources 4.11-1
-------
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EMISSION FACTORS
(Reformatted 1/95) 8/82
-------
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Evaporation Loss Sources
4.11-3
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4.11-4
EMISSION FACTORS
(Reformatted 1/95) 8/82
-------
Table 4.11-4 (Metric And English Units). TYPICAL INSPECTION VALUES
FOR MINERAL SPIRITS*
Parameter
Range
Specific gravity at 15°C (60°F)
Viscosity at 25°C (77°F)
Flash point (closed cup)
Aniline point
Kauri-Butanol number
Distillation range
Initial boiling points
50 percent value
Final boiling points
Composition (%)
Total saturates
Total aromatics
Cg and higher
0.778 - 0.805
0.83 - 0.95 cP
41 -45°C(105-113°F)
43-62°C(110- 144 °F)
32-45
157 - 166°C (315 - 330°F)
168 - 178°C (334 - 348°F)
199-201°C(390-394°F)
81.5 - 92.3
7.7 - 18.5
7.5 - 18.5
* References 2,4.
Two types of dryers are used for printed fabric, steam coil or natural gas fired dryers,
through which the fabric is conveyed on belts, racks, etc., and steam cans, with which the fabric
makes direct contact. Most screen printed fabrics and practically all printed knit fabrics and terry
towels are dried with the first type of dryer, not to stress the fabric. Roller printed fabrics and
apparel fabrics requiring soft handling are dried on steam cans, which have lower installation and
operating costs and which dry the fabric more quickly than other dryers.
Figure 4.11-1 is a schematic diagram of the rotary screen printing process, with emission
points indicated. The flat screen printing process is virtually identical. The symbols for fugitive
VOC emissions to the atmosphere indicate mineral spirits evaporating from print paste during
application to fabric before drying. The largest VOC emission source is the drying and curing oven
stack, which vents evaporated solvents (mineral spirits and water) to the atmosphere. The symbol for
fugitive VOC emissions to the waste water indicates print paste mineral spirits washed with water
from the printing blanket (continuous belt) and discharged in waste water.
Figure 4.11-2 is a schematic diagram of a roller printing process in which all emissions are
fugitive. Fugitive VOC emissions from the "back grey" (fabric backing material that absorbs excess
print paste) in the illustrated process are emissions to the atmosphere because the back grey is dried
before being washed. In processes where the back grey is washed before drying, most of the fugitive
VOC emissions from the back grey will be discharged into the waste water. In some roller printing
processes, steam cans for drying printed fabric are enclosed, and drying process emissions are vented
directly to the atmosphere.
8/82 (Reformatted 1/95)
Evaporation Loss Sources
4.11-5
-------
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4.11.2 Emissions And Controls1'3'12
Presently there is no add-on emission control technology for organic solvent used in the textile
fabric printing industry. Thermal incineration of oven exhaust has been evaluated in the Draft
Background Information Document for New Source Performance Standard development1 and has been
found unaffordable for some fabric printers. The feasibility of using other types of add-on emission
control equipment has not been fully evaluated. Significant organic solvent emissions reduction has
been accomplished by reducing or eliminating the consumption of mineral spirit solvents. The use of
aqueous or low organic solvent print pastes has increased during the past decade, because of the high
price of organic solvents and higher energy costs associated with the use of higher solvent volumes.
The only fabric printing applications presently requiring the use of large quantities of organic solvents
are pigment printing of fashion or designer apparel fabric, and terry towels.
Table 4.11-5 presents average emission factors and ranges for each type of printing process
and an average annual emission factor per print line, based on estimates submitted by individual
fabric printers. No emission tests were done. VOC emission rates involve 3 parameters: organic
solvent content of print pastes, consumption of print paste (a function of pattern coverage and fabric
weight), and rate of fabric processing. With the quantity of fabric printed held constant, the lowest
emission rate represents minimum organic solvent content print paste and minimum print paste
consumption, and the maximum emission rate represents maximum organic solvent content print paste
and maximum print paste consumption. The average emission rates shown for roller and rotary
screen printing are based on the results of a VOC usage survey conducted by the American Textile
Manufacturers Institute, Inc. (ATMI), in 1979. The average flat screen printing emission factor is
based on information from 2 terry towel printers.
Although the average emission factors for roller and rotary screen printing are representative
of the use of medium organic solvent content print pastes at average rates of print paste consumption,
very little printing is actually done with medium organic solvent content pastes. The distribution of
Table 4.11-5 (Metric And English Units). TEXTILE FABRIC PRINTING ORGANIC
EMISSION FACTORS*
EMISSION FACTOR RATING: C
VOC
kg/Mg fabric or lb/1000 Ib
fabric
Mg (ton)/yr/print linec
Roller
Range
0 - 348°
Average
142d
130°
(139)
Rotary
Range
0 - 945C
Screen
Average
23d
29°
(31)
Flat Screenb
Range
51 - 191C
Average
79e
29C
(31)
a Transfer printing, carpet printing, and printing of vinyl-coated cloth are specifically excluded from
this compilation.
b Flat screen factors apply to terry towel printing. Rotary screen factors should be applied to flat
screen printing of other types of fabric (e. g., sheeting, bottom weight apparel, etc.).
c Reference 13.
d Reference 5.
e Reference 6.
4.11-8
EMISSION FACTORS
(Reformatted 1/95) 8/82
-------
print paste use is bimodal, with the arithmetic average falling between the modes. Most fabric is
printed with aqueous or low organic solvent print pastes. However, in applications where the use of
organic solvents is beneficial, high organic solvent content print pastes are used to derive the full
benefit of using organic solvents. The most accurate emissions data can be generated by obtaining
organic solvent use data for a particular facility. The emission factors presented here should only be
used to estimate actual process emissions.
References For Section 4.11
1. Fabric Printing Industry: Background Information For Proposed Standards (Draft), EPA
Contract No. 68-02-3056, Research Triangle Institute, Research Triangle Park, NC, April 21,
1981.
2. Exxon Petroleum Solvents, Lubetext DG-1P, Exxon Company, Houston, TX, 1979.
3. Memorandum from S. B. York, Research Triangle Institute, to Textile Fabric Printing AP-42
file, Office Of Air Quality Planning And Standards, U. S. Environmental Protection Agency,
Research Triangle Park, NC, March 25, 1981.
4. C. Marsden, Solvents Guide, Interscience Publishers, New York, NY, 1963, p. 548.
5. Letter from W. H. Steenland, American Textile Manufacturers Institute, Inc., to Dennis
Grumpier, U. S. Environmental Protection Agency, Research Triangle Park, NC, April 8,
1980.
6. Memorandum from S. B. York, Research Triangle Institute, to Textile Fabric Printing AP-42
File, Office Of Air Quality Planning And Standards, U.S. Environmental Protection Agency,
Research Triangle Park, NC, March 12, 1981.
7. Letter from A. C. Lohr, Burlington Industries, to James Berry, U.S. Environmental
Protection Agency, Research Triangle Park, NC, April 26, 1979.
8. Trip Report/Plant Visit To Fieldcrest Mills, Foremost Screen Print Plant, memorandum from
S. B. York, Research Triangle Institute, to C. Gasperecz, U. S. Environmental Protection
Agency, Research Triangle Park, NC, January 28, 1980.
9. Letter from T. E. Boyce, Fieldcrest Corporation, to S. B. York, Research Triangle Institute,
Research Triangle Park, NC, January 23, 1980.
10. Telephone conversation, S. B. York, Research Triangle Institute, with Tom Boyce, Foremost
Screen Print Plant, Stokesdale, NC, April 24, 1980.
11. "Average Weight And Width Of Broadwoven Fabrics (Gray)", Current Industrial Report,
Publication No. MC-22T (Supplement), Bureau Of The Census, U. S. Department Of
Commerce, Washington, DC, 1977.
12. "Sheets, Pillowcases, and Towels", Current Industrial Report, Publication No. MZ-23X,
Bureau Of The Census, U. S. Department Of Commerce, Washington, DC, 1977.
8/82 (Reformatted 1/95) Evaporation Loss Sources 4.11-9
-------
13. Memorandum from S. B. York, Research Triangle Institute, to Textile Fabric Printing AP-42
File, Office Of Air Quality Planning And Standards, U. S. Environmental Protection Agency,
Research Triangle Park, NC, April 3, 1981.
14. "Survey of Plant Capacity, 1977", Current Industrial Report, Publication No. DQ-C1(77)-1,
Bureau Of The Census, U. S. Department Of Commerce, Washington, DC, August 1978.
4.11-10 EMISSION FACTORS (Reformatted 1/95) 8/82
-------
5. PETROLEUM INDUSTRY
The petroleum industry involves the refining of crude petroleum and the processing of natural
gas into a multitude of products, as well as the distribution and marketing of petroleum-derived
products. The primary pollutant emitted is volatile organic compounds arising from leakage, venting,
and evaporation of the raw materials and finished products. Significant amounts of sulfur oxides,
hydrogen sulfide, paniculate matter, and a number of toxic species can also be generated from
operations specific to this industry. In addition, a wide variety of fuel combustion devices emits all
of the criteria pollutants and a number of toxic species.
1/95 Petroleum Industry 5.0-1
-------
5.1 Petroleum Refining1
5.1.1 General Description
The petroleum refining industry converts crude oil into more than 2500 refined products,
including liquefied petroleum gas, gasoline, kerosene, aviation fuel, diesel fuel, fuel oils, lubricating
oils, and feedstocks for the petrochemical industry. Petroleum refinery activities start with receipt of
crude for storage at the refinery, include all petroleum handling and refining operations, and they
terminate with storage preparatory to shipping the refined products from the refinery.
The petroleum refining industry employs a wide variety of processes. A refinery's processing
flow scheme is largely determined by the composition of the crude oil feedstock and the chosen slate
of petroleum products. The example refinery flow scheme presented in Figure 5.1-1 shows the
general processing arrangement used by refineries in the United States for major refinery processes.
The arrangement of these processes will vary among refineries, and few, if any, employ all of these
processes. Petroleum refining processes having direct emission sources are presented on the figure in
bold-line boxes.
Listed below are 5 categories of general refinery processes and associated operations:
1. Separation processes
a. Atmospheric distillation
b. Vacuum distillation
c. Light ends recovery (gas processing)
2. Petroleum conversion processes
a. Cracking (thermal and catalytic)
b. Reforming
c. Alkylation
d. Polymerization
e. Isomerization
f. Coking
g. Visbreaking
3. Petroleum treating processes
a. Hydrodesulfurization
b. Hydrotreating
c. Chemical sweetening
d. Acid gas removal
e. Deasphalting
4. Feedstock and product handling
a. Storage
b. Blending
c. Loading
d. Unloading
5. Auxiliary facilities
a. Boilers
b. Waste water treatment
c. Hydrogen production
d. Sulfur recovery plant
1/95 Petroleum Industry 5.1-1
-------
HYDROCARBON SOURCE
HYDROGEN
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5.1-2
EMISSION FACTORS
1/95
-------
e. Cooling towers
f. Blowdown system
g. Compressor engines
These refinery processes are defined below, and their emission characteristics and applicable emission
control technology are discussed.
5.1.1.1 Separation Processes -
The first phase in petroleum refining operations is the separation of crude oil into its major
constituents using 3 petroleum separation processes: atmospheric distillation, vacuum distillation, and
light ends recovery (gas processing). Crude oil consists of a mixture of hydrocarbon compounds
including paraffmic, naphthenic, and aromatic hydrocarbons with small amounts of impurities
including sulfur, nitrogen, oxygen, and metals. Refinery separation processes separate these crude oil
constituents into common boiling-point fractions.
5.1.1.2 Conversion Processes -
To meet the demands for high-octane gasoline, jet fuel, and diesel fuel, components such as
residual oils, fuel oils, and light ends are converted to gasolines and other light fractions. Cracking,
coking, and visbreaking processes are used to break large petroleum molecules into smaller ones.
Polymerization and alkylation processes are used to combine small petroleum molecules into larger
ones. Isomerization and reforming processes are applied to rearrange the structure of petroleum
molecules to produce higher-value molecules of a similar molecular size.
5.1.1.3 Treating Processes -
Petroleum treating processes stabilize and upgrade petroleum products by separating them
from less desirable products and by removing objectionable elements. Undesirable elements such as
sulfur, nitrogen, and oxygen are removed by hydrodesulfurization, hydrotreating, chemical
sweetening, and acid gas removal. Treating processes, employed primarily for the separation of
petroleum products, include such processes as deasphalting. Desalting is used to remove salt,
minerals, grit, and water from crude oil feedstocks before refining. Asphalt blowing is used for
polymerizing and stabilizing asphalt to improve its weathering characteristics.
5.1.1.4 Feedstock And Product Handling -
The refinery feedstock and product handling operations consist of unloading, storage,
blending, and loading activities.
5.1.1.5 Auxiliary Facilities -
A wide assortment of processes and equipment not directly involved in the refining of crude
oil is used in functions vital to the operation of the refinery. Examples are boilers, waste water
treatment facilities, hydrogen plants, cooling towers, and sulfur recovery units. Products from
auxiliary facilities (clean water, steam, and process heat) are required by most process units
throughout the refinery.
5.1.2 Process Emission Sources And Control Technology
This section presents descriptions of those refining processes that are significant air pollutant
contributors. Process flow schemes, emission characteristics, and emission control technology are
discussed for each process. Table 5.1-1 lists the emission factors for direct-process emissions in
1/95 Petroleum Industry 5.1-3
-------
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EMISSION FACTORS
1/95
-------
petroleum refineries. Factors are expressed in units of kilograms per 1000 liters (kg/103 L) or
kilograms per 1000 cubic meters (kg/103 m3) and pounds per 1000 barrels (lb/103 bbl) or pounds per
1000 cubic feet (lb/103 ft3). The following process emission sources are discussed here:
1. Vacuum distillation
2. Catalytic cracking
3. Thermal cracking processes
4. Utility boilers
5. Heaters
6. Compressor engines
7. Slowdown systems
8. Sulfur recovery
5.1.2.1 Vacuum Distillation -
Topped crude withdrawn from the bottom of the atmospheric distillation column is composed
of high boiling-point hydrocarbons. When distilled at atmospheric pressures, the crude oil
decomposes and polymerizes and will foul equipment. To separate topped crude into components, it
must be distilled in a vacuum column at a very low pressure and in a steam atmosphere.
In the vacuum distillation unit, topped crude is heated with a process heater to temperatures
ranging from 370 to 425 °C (700 to 800 °F). The heated topped crude is flashed into a multitray
vacuum distillation column operating at absolute pressures ranging from 350 to 1400 kilograms per
square meter (kg/m2) (0.5 to 2 pounds per square inch absolute [psia]). In the vacuum column, the
topped crude is separated into common boiling-point fractions by vaporization and condensation.
Stripping steam is normally injected into the bottom of the vacuum distillation column to assist the
separation by lowering the effective partial pressures of the components. Standard petroleum
fractions withdrawn from the vacuum distillation column include lube distillates, vacuum oil, asphalt
stocks, and residual oils. The vacuum in the vacuum distillation column is usually maintained by the
use of steam ejectors but may be maintained by the use of vacuum pumps.
The major sources of atmospheric emissions from the vacuum distillation column are
associated with the steam ejectors or vacuum pumps. A major portion of the vapors withdrawn from
the column by the ejectors or pumps is recovered in condensers. Historically, the noncondensable
portion of the vapors has been vented to the atmosphere from the condensers. There are
approximately 0.14 kg of noncondensable hydrocarbons per m3 (50 lb/103 bbl) of topped crude
processed in the vacuum distillation column.2'12"13 A second source of atmospheric emissions from
vacuum distillation columns is combustion products from the process heater. Process heater
requirements for the vacuum distillation column are approximately 245 megajoules per cubic meter
(MJ/m3) (37,000 British thermal units per barrel [Btu/bbl]) of topped crude processed in the vacuum
column. Process heater emissions and their control are discussed below. Fugitive hydrocarbon
emissions from leaking seals and fittings are also associated with the vacuum distillation unit, but
these are minimized by the low operating pressures and low vapor pressures in the unit. Fugitive
emission sources are also discussed later.
Control technology applicable to the noncondensable emissions vented from the vacuum
ejectors or pumps includes venting into blowdown systems or fuel gas systems, and incineration in
furnaces or waste heat boilers.2'12"13 These control techniques are generally greater than 99 percent
efficient in the control of hydrocarbon emissions, but they also contribute to the emission of
combustion products.
1/95 Petroleum Industry 5.1-7
-------
5.1.2.2 Catalytic Cracking -
Catalytic cracking, using heat, pressure, and catalysts, converts heavy oils into lighter
products with product distributions favoring the more valuable gasoline and distillate blending
components. Feedstocks are usually gas oils from atmospheric distillation, vacuum distillation,
coking, and deasphalting processes. These feedstocks typically have a boiling range of 340 to 540°C
(650 to 1000°F). All of the catalytic cracking processes in use today can be classified as either
fluidized-bed or moving-bed units.
5.1.2.2.1 Fluidized-bed Catalytic Cracking (FCC) -
The FCC process uses a catalyst in the form of very fine particles that act as a fluid when
aerated with a vapor. Fresh feed is preheated in a process heater and introduced into the bottom of a
vertical transfer line or riser with hot regenerated catalyst. The hot catalyst vaporizes the feed,
bringing both to the desired reaction temperature, 470 to 525 °C (880 to 980 °F) The high activity of
modern catalysts causes most of the cracking reactions to take place in the riser as the catalyst and oil
mixture flows upward into the reactor. The hydrocarbon vapors are separated from the catalyst
particles by cyclones in the reactor. The reaction products are sent to a fractionator for separation.
The spent catalyst falls to the bottom of the reactor and is steam stripped as it exits the reactor
bottom to remove absorbed hydrocarbons. The spent catalyst is then conveyed to a regenerator. In
the regenerator, coke deposited on the catalyst as a result of the cracking reactions is burned off in a
controlled combustion process with preheated air. Regenerator temperature is usually 590 to 675°C
(1100 to 1250°F). The catalyst is then recycled to be mixed with fresh hydrocarbon feed.
5.1.2.2.2 Moving-bed Catalytic Cracking-
In the moving-bed system, typified by the Thermafor Catalytic Cracking (TCC) units, catalyst
beads (—0.5 centimeters [cm] [0.2 inches (in.)]) flow into the top of the reactor, where they contact a
mixed-phase hydrocarbon feed. Cracking reactions take place as the catalyst and hydrocarbons move
concurrently downward through the reactor to a zone where the catalyst is separated from the vapors.
The gaseous reaction products flow out of the reactor to the fractionation section of the unit. The
catalyst is steam stripped to remove any adsorbed hydrocarbons. It then falls into the regenerator,
where coke is burned from the catalyst with air. The regenerated catalyst is separated from the flue
gases and recycled to be mixed with fresh hydrocarbon feed. The operating temperatures of the
reactor and regenerator in the TCC process are comparable to those in the FCC process.
Air emissions from catalytic cracking processes are (1) combustion products from process
heaters and (2) flue gas from catalyst regeneration. Emissions from process heaters are discussed
below. Emissions from the catalyst regenerator include hydrocarbons, oxides of sulfur, ammonia,
aldehydes, oxides of nitrogen, cyanides, carbon monoxide (CO), and particulates (Table 5.1-1). The
paniculate emissions from FCC units are much greater than those from TCC units because of the
higher catalyst circulation rates used.2*3'5
FCC particulate emissions are controlled by cyclones and/or electrostatic precipitators.
Paniculate control efficiencies are as high as 80 to 85 percent.3'5 Carbon monoxide waste heat
boilers reduce the CO and hydrocarbon emissions from FCC units to negligible levels.3 TCC catalyst
regeneration produces similar pollutants to FCC units, but in much smaller quantities (Table 5.1-1).
The particulate emissions from a TCC unit are normally controlled by high-efficiency cyclones.
Carbon monoxide and hydrocarbon emissions from a TCC unit are incinerated to negligible levels by
passing the flue gases through a process heater firebox or smoke plume burner. In some installations,
sulfur oxides are removed by passing the regenerator flue gases through a water or caustic
scrubber.2"3'5
5.1-g EMISSION FACTORS 1/95
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5.1.2.3 Thermal Cracking -
Thermal cracking processes include visbreaking and coking, which break heavy oil molecules
by exposing them to high temperatures.
5.1.2.3.1 Visbreaking -
Topped crude or vacuum residuals are heated and thermally cracked (455 to 480°C, 3.5 to
17.6 kg/cm2 [850 to 900°F, 50 to 250 pounds per square inch gauge (psig)]) in the visbreaker
furnace to reduce the viscosity, or pour point, of the charge. The cracked products are quenched
with gas oil and flashed into a fractionator. The vapor overhead from the fractionator is separated
into light distillate products. A heavy distillate recovered from the fractionator liquid can be used as
either a fuel oil blending component or catalytic cracking feed.
5.1.2.3.2 Coking-
Coking is a thermal cracking process used to convert low value residual fuel oil to higher-
value gas oil and petroleum coke. Vacuum residuals and thermal tars are cracked in the coking
process at high temperature and low pressure. Products are petroleum coke, gas oils, and lighter
petroleum stocks. Delayed coking is the most widely used process today, but fluid coking is expected
to become an important process in the future.
In the delayed coking process, heated charge stock is fed into the bottom of a fractionator,
where light ends are stripped from the feed. The stripped feed is then combined with recycle
products from the coke drum and rapidly heated in the coking heater to a temperature of 480 to
590°C (900 to 1100°F). Steam injection is used to control the residence time in the heater. The
vapor-liquid feed leaves the heater, passing to a coke drum where, with controlled residence time,
pressure (1.8 to 2.1 kg/cm2 [25 to 30 psig]), and temperature (400°C [750°F]), it is cracked to form
coke and vapors. Vapors from the drum return to the fractionator, where the thermal cracking
products are recovered.
In the fluid coking process, typified by Flexicoking, residual oil feeds are injected into the
reactor, where they are thermally cracked, yielding coke and a wide range of vapor products. Vapors
leave the reactor and are quenched in a scrubber, where entrained coke fines are removed. The
vapors are then fractionated. Coke from the reactor enters a heater and is devolatilized. The
volatiles from the heater are treated for fines and sulfur removal to yield a particulate-free, low-sulfur
fuel gas. The devolatilized coke is circulated from the heater to a gasifier where 95 percent of the
reactor coke is gasified at high temperature with steam and air or oxygen. The gaseous products and
coke from the gasifier are returned to the heater to supply heat for the devolatilization. These gases
exit the heater with the heater volatiles through the same fines and sulfur removal processes.
From available literature, it is unclear what emissions are released and where they are
released. Air emissions from thermal cracking processes include coke dust from decoking operations,
combustion gases from the visbreaking and coking process heaters, and fugitive emissions. Emissions
from the process heaters are discussed below. Fugitive emissions from miscellaneous leaks are
significant because of the high temperatures involved, and are dependent upon equipment type and
configuration, operating conditions, and general maintenance practices. Fugitive emissions are also
discussed below. Particulate emissions from delayed coking operations are potentially very
significant. These emissions are associated with removing the coke from the coke drum and
subsequent handling and storage operations. Hydrocarbon emissions are also associated with cooling
and venting the coke drum before coke removal. However, comprehensive data for delayed coking
emissions have not been included in available literature.4"5
1/95 Petroleum Industry 5.1-9
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Paniculate emission control is accomplished in the decoking operation by wetting down the
coke.5 Generally, there is no control of hydrocarbon emissions from delayed coking. However,
some facilities are now collecting coke drum emissions in an enclosed system and routing them to a
refinery flare.4"5
5.1.2.4 Utilities Plant-
The utilities plant supplies the steam necessary for the refinery. Although the steam can be
used to produce electricity by throttling through a turbine, it is primarily used for heating and
separating hydrocarbon streams. When used for heating, the steam usually heats the petroleum
indirectly in heat exchangers and returns to the boiler. In direct contact operations, the steam can
serve as a stripping medium or a process fluid. Steam may also be used in vacuum ejectors to
produce a vacuum. Boiler emissions and applicable emission control technology are discussed in
much greater detail in Chapter 1.
5.1.2.5 Sulfur Recovery Plant -
Sulfur recovery plants are used in petroleum refineries to convert the hydrogen sulfide (H2S)
separated from refinery gas streams into the more disposable byproduct, elemental sulfur. Emissions
from sulfur recovery plants and their control are discussed in Section 8.13, "Sulfur Recovery".
5.1.2.6 Slowdown System -
The blowdown system provides for the safe disposal of hydrocarbons (vapor and liquid)
discharged from pressure relief devices.
Most refining processing units and equipment subject to planned or unplanned hydrocarbon
discharges are manifolded into a collection unit, called blowdown system. By using a series of flash
drums and condensers arranged in decreasing pressure, blowdown material is separated into vapor and
liquid cuts. The separated liquid is recycled into the refinery. The gaseous cuts can either be
smokelessly flared or recycled.
Uncontrolled blowdown emissions primarily consist of hydrocarbons but can also include any
of the other criteria pollutants. The emission rate in a blowdown system is a function of the amount
of equipment manifolded into the system, the frequency of equipment discharges, and the blowdown
system controls.
Emissions from the blowdown system can be effectively controlled by combustion of the
noncondensables in a flare. To obtain complete combustion or smokeless burning (as required by
most states), steam is injected in the combustion zone of the flare to provide turbulence and air.
Steam injection also reduces emissions of nitrogen oxides by lowering the flame temperature.
Controlled emissions are listed in Table 5.1-1.2-11
5.1.2.7 Process Heaters -
Process heaters (furnaces) are used extensively in refineries to supply the heat necessary to
raise the temperature of feed materials to reaction or distillation level. They are designed to raise
petroleum fluid temperatures to a maximum of about 510°C (950°F). The fuel burned may be
refinery gas, natural gas, residual fuel oils, or combinations, depending on economics, operating
conditions, and emission requirements. Process heaters may also use CO-rich regenerator flue gas as
fuel.
5.1-10 EMISSION FACTORS 1/95
-------
All the criteria pollutants are emitted from process heaters. The quantity of these emissions is
a function of the type of fuel burned, the nature of the contaminants in the fuel, and the heat duty of
the furnace. Sulfur oxides can be controlled by fuel desulfurization or flue gas treatment. Carbon
monoxide and hydrocarbons can be controlled by more combustion efficiency. Currently,
4 general techniques or modifications for the control of nitrogen oxides are being investigated:
combustion modification, fuel modification, furnace design, and flue gas treatment. Several of these
techniques are being applied to large utility boilers, but their applicability to process heaters has not
been established.2'14
5.1.2.8 Compressor Engines-
Many older refineries run high-pressure compressors with reciprocating and gas turbine
engines fired with natural gas. Natural gas has usually been a cheap, abundant source of energy.
Examples of refining units operating at high pressure include hydrodesulfurization, isomerization,
reforming, and hydrocracking. Internal combustion engines are less reliable and harder to maintain
than are steam engines or electric motors. For this reason, and because of increasing natural gas
costs, very few such units have been installed in the last few years.
The major source of emissions from compressor engines is combustion products in the
exhaust gas. These emissions include CO, hydrocarbons, nitrogen oxides, aldehydes, and ammonia.
Sulfur oxides may also be present, depending on the sulfur content of the natural gas. All these
emissions are significantly higher in exhaust from reciprocating engines than from turbine engines.
The major emission control technique applied to compressor engines is carburetion adjustment
similar to that applied on automobiles. Catalyst systems similar to those of automobiles may also be
effective in reducing emissions, but their use has not been reported.
5.1.2.9 Sweetening-
Sweetening of distillates is accomplished by the conversion of mercaptans to alkyl disulfides
in the presence of a catalyst. Conversion may be followed by an extraction step for removal of the
alkyl disulfides. In the conversion process, sulfur is added to the sour distillate with a small amount
of caustic and air. The mixture is then passed upward through a fixed-bed catalyst, counter to a flow
of caustic entering at the top of the vessel. In the conversion and extraction process, the sour
distillate is washed with caustic and then is contacted in the extractor with a solution of catalyst and
caustic. The extracted distillate is then contacted with air to convert mercaptans to disulfides. After
oxidation, the distillate is settled, inhibitors are added, and the distillate is sent to storage.
Regeneration is accomplished by mixing caustic from the bottom of the extractor with air and then
separating the disulfides and excess air.
The major emission problem is hydrocarbons from contact of the distillate product and air in
the "air blowing" step. These emissions are related to equipment type and configuration, as well as
to operating conditions and maintenance practices.4
5.1.2.10 Asphalt Blowing -
The asphalt blowing process polymerizes asphaltic residual oils by oxidation, increasing their
melting temperature and hardness to achieve an increased resistance to weathering. The oils,
containing a large quantity of polycyclic aromatic compounds (asphaltic oils), are oxidized by blowing
heated air through a heated batch mixture or, in a continuous process, by passing hot air
countercurrent to the oil flow. The reaction is exothermic, and quench steam is sometimes needed for
temperature control. In some cases, ferric chloride or phosphorus pentoxide is used as a catalyst to
increase the reaction rate and to impart special characteristics to the asphalt.
1 /95 Petroleum Industry 5.1-11
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Air emissions from asphalt blowing are primarily hydrocarbon vapors vented with the blowing
air. The quantities of emissions are small because of the prior removal of volatile hydrocarbons in
the distillation units, but the emissions may contain hazardous polynuclear organics. Emissions are
30 kg/megagram (Mg) (60 Ib/ton) of asphalt.13 Emissions from asphalt blowing can be controlled to
negligible levels by vapor scrubbing, incineration, or both.4'13
5.1.3 Fugitive Emissions And Controls
Fugitive emission sources include leaks of hydrocarbon vapors from process equipment and
evaporation of hydrocarbons from open areas, rather than through a stack or vent. Fugitive emission
sources include valves of all types, flanges, pump and compressor seals, process drains, cooling
towers, and oil/water separators. Fugitive emissions are attributable to the evaporation of leaked or
spilled petroleum liquids and gases. Normally, control of fugitive emissions involves minimizing
leaks and spills through equipment changes, procedure changes, and improved monitoring,
housekeeping, and maintenance practices. Controlled and uncontrolled fugitive emission factors for
the following sources are listed in Table 5.1-2:
- Oil/water separators (waste water treatment)
- Storage
- Transfer operations
- Cooling towers
Emission factors for fugitive leaks from the following types of process equipment can be found in
Protocol For Equipment Leak Emission Estimates, EPA-453/R-93-026, June 1993, or subsequent
updates:
- Valves (pipeline, open ended, vessel relief)
- Flanges
- Seals (pump, compressor)
- Process drains
5.1.3.1 Valves, Flanges, Seals, And Drains -
For these sources, a very high correlation has been found between mass emission rates and
the type of stream service in which the sources are employed. The four stream service types are
(1) hydrocarbon gas/vapor streams (including gas streams with up to 50 percent hydrogen by
volume), (2) light liquid and gas/liquid streams, (3) kerosene and heavier liquid streams (includes all
crude oils), and (4) gas streams containing more than 50 percent hydrogen by volume. It is found
that sources in gas/vapor stream service have higher emission rates than those in heavier stream
service. This trend is especially pronounced for valves and pump seals. The size of valves, flanges,
pump seals, compressor seals, relief valves, and process drains does not affect their leak rates.17 The
emission factors are independent of process unit or refinery throughput.
Valves, because of their number and relatively high emission factor, are the major emission
source. This conclusion is based on an analysis of a hypothetical refinery coupled with the emission
rates. The total quantity of fugitive VOC emissions in a typical oil refinery with a capacity of
52,500 m3 (330,000 bbl) per day is estimated as 20,500 kg (45,000 Ib) per day (see Table 5.1-3).
This estimate is based on a typical late 1970s refinery without a leak inspection and maintenance
(I/M) program. See the Protocol document for details on how to estimate emissions for a specific
refinery.
5.1-12 EMISSION FACTORS 1/95
-------
Table 5.1-2 (Metric And English Units). FUGITIVE EMISSION FACTORS
FOR PETROLEUM REFINERIES3
EMISSION FACTOR RATING: D
Emission
Source
»
Cooling
towersb
Oil/water
separators0
Storage
Loading
Emission Factor
Units
kg/106 L cooling
water
lb/106 gal cooling
water
kg/103 L
waste water
lb/103 gal
waste water
Emission
Uncontrolled
Emissions
0.7
6
0.6
5
Factors
Controlled
Emissions
0.08
0.7
0.024
0.2
Applicable Control Technology
Minimization of hydrocarbon leaks
into cooling water system;
monitoring of cooling water for
hydrocarbons
Minimization of hydrocarbon leaks
into cooling water system;
monitoring of cooling water for
hydrocarbons
Covered separators and/or vapor
recovery systems
Covered separators and/or vapor
recovery systems
See Chapter 7 - Liquid Storage Tanks
See Section
5.2 - Transportation And M
arketing Of Petroleum Liquids
a References 2,4,12-13.
b If cooling water rate is unknown (in liters or gallons) assume it is 40 times the refinery feed rate (in
liters or gallons). Refinery feed rate is defined as the crude oil feed rate to the atmospheric
distillation column. 1 bbl (oil) = 42 gallons (gal), 1 m3 = 1000 L.
c If waste water flow rate to oil/water separators is unknown (in liters or gallons) assume it is
0.95 times the refinery feed rate (in liters or gallons). Refinery feed rate is defined as the crude oil
feed rate to the atmospheric distillation column. 1 bbl (oil) = 42 gal, 1 m3 = 1000 L.
5.1.3.2 Storage-
All refineries have a feedstock and product storage area, termed a "tank farm", which
provides surge storage capacity to ensure smooth, uninterrupted refinery operations. Individual
storage tank capacities range from less than 160 m3 to more than 79,500 m3 (1,000 to 500,000 bbl).
Storage tank designs, emissions, and emission control technology are discussed in detail in
AP-42 Chapter 7, and the TANKS software program is available to perform the emissions
calculations, if desired.
1/95
Petroleum Industry
5.1-13
-------
Table 5.1-3 (Metric And English Units). FUGITIVE VOC EMISSIONS FROM AN
UNCONTROLLED OIL REFINERY OF 52,500 m3/day (330,000 bbl/day) CAPACITY3
a Reference 17.
b Based on limited data.
Source
Valves
Flanges
Pump seals
Compressor seals
Relief valves
Drains
Cooling towers'5
Oil/water separators (uncovered)15
TOTAL
Number
11,500
46,500
350
70
100
650
1
1
—
VOC Emissions
kg/day
3,100
300
590
500
200
450
730
14,600
20,500
Ib/day
6,800
600
1,300
1,100
500
1,000
1,600
32,100
45,000
5.1.3.3 Transfer Operations-
Although most refinery feedstocks and products are transported by pipeline, some are
transported by trucks, rail cars, and marine vessels. They are transferred to and from these transport
vehicles in the refinery tank farm area by specialized pumps and piping systems. The emissions from
transfer operations and applicable emission control technology are discussed in much greater detail in
Section 5.2, "Transportation And Marketing Of Petroleum Liquids".
5.1.3.4 Waste Water Treatment Plant -
All refineries employ some form of waste water treatment so water effluents can safely be
returned to the environment or reused in the refinery. The design of waste water treatment plants is
complicated by the diversity of refinery pollutants, including oil, phenols, sulfides, dissolved solids,
and toxic chemicals. Although the treatment processes employed by refineries vary greatly, they
generally include neutralizes, oil/water separators, settling chambers, clarifiers, dissolved air
flotation systems, coagulators, aerated lagoons, and activated sludge ponds. Refinery water effluents
are collected from various processing units and are conveyed through sewers and ditches to the
treatment plant. Most of the treatment occurs in open ponds and tanks.
The main components of atmospheric emissions from waste water treatment plants are fugitive
VOCs and dissolved gases that evaporate from the surfaces of waste water residing in open process
drains, separators, and ponds (Table 5.1-2). Treatment processes that involve extensive contact of
waste water and air, such as aeration ponds and dissolved air flotation, have an even greater potential
for atmospheric emissions. Section 4.3, "Waste Water Collection, Treatment And Storage", discusses
estimation techniques for such water treatment operations. WATERS and SIMS software models are
available to perform the calculations.
5.1-14
EMISSION FACTORS
1/95
-------
The control of waste water treatment plant emissions involves covering systems where
emission generation is greatest (such as oil/water separators and settling basins) and removing
dissolved gases from water streams with sour water strippers and phenol recovery units before their
contact with the atmosphere. These control techniques potentially can achieve greater than 90 percent
reduction of waste water system emissions.13
5.1.3.5 Cooling Towers -
Cooling towers are used extensively in refinery cooling water systems to transfer waste heat
from the cooling water to the atmosphere. The only refineries not employing cooling towers are
those with once-through cooling. The increasing scarcity of a large water supply required for
once-through cooling is contributing to the disappearance of that form of refinery cooling. In the
cooling tower, warm cooling water returning from refinery processes is contacted with air by
cascading through packing) Cooling water circulation rates for refineries commonly range from
7 to 70 L/minute per m3/day (0.3 to 3.0 gal/minute per bbl/day) of refinery capacity.2'™
Atmospheric emissions from the cooling tower consist of fugitive VOCs and gases stripped
from the cooling water as the air and water come into contact. These contaminants enter the cooling
water system from leaking heat exchangers and condensers. Although the predominant contaminants
hi cooling water are VOCs, dissolved gases such as H2S and ammonia may also be found
(see Table 5.1-2).2'4-17
Control of cooling tower emissions is accomplished by reducing contamination of cooling
water through the proper maintenance of heat exchangers and condensers. The effectiveness of
cooling tower controls is highly variable, depending on refinery configuration and existing
maintenance practices.4
References For Section 5.1
1. C. E. Burklin, et al., Revision Of Emission Factors For Petroleum Refining,
EPA-450/3-77-030, U. S. Environmental Protection Agency, Research Triangle Park, NC,
October 1977.
2. Atmospheric Emissions From Petroleum Refineries: A Guide For Measurement And Control,
PHS No. 763, Public Health Service, U. S. Department Of Health And Human Services,
Washington, DC, 1960.
3. Background Information For Proposed New Source Standards: Asphalt Concrete Plants,
Petroleum Refineries, Storage Vessels, Secondary Lead Smelters And Refineries, Brass Or
Bronze Ingot Production Plants, Iron And Steel Plants, Sewage Treatment Plants,
APTD-1352a, U. S. Environmental Protection Agency, Research Triangle Park, NC, 1973.
4. Air Pollution Engineering Manual, Second Edition, AP-40, U. S. Environmental Protection
Agency, Research Triangle Park, NC, 1973. Out of Print.
5. Ben G. Jones, "Refinery Improves Paniculate Control", Oil And Gas Journal,
6P(26):60-62, June 28, 1971.
6. "Impurities In Petroleum", Petreco Manual, Petrolite Corp., Long Beach, CA, 1958.
7. Control Techniques For Sulfur Oxide In Air Pollutants, AP-52, U. S. Environmental
Protection Agency, Research Triangle Park, NC, January 1969.
1/95 Petroleum Industry 5.1-15
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8. H. N. Olson and K. E. Hutchinson, "How Feasible Are Giant, One-train Refineries?", Oil
And Gas Journal, 70(l):39-43, January 3, 1972.
9. C. M. Urban and K. J. Springer, Study Of Exhaust Emissions From Natural Gas Pipeline
Compressor Engines, American Gas Association, Arlington, VA, February 1975.
10. H. E. Dietzmann and K. J. Springer, Exhaust Emissions From Piston And Gas Turbine
Engines Used In Natural Gas Transmission, American Gas Association, Arlington, VA,
January 1974.
11. M. G. Klett and J. B. Galeski, Flare Systems Study, EPA-600/2-76-079, U. S. Environmental
Protection Agency, Cincinnati, OH, March 1976.
12. Evaporation Loss In The Petroleum Industry, Causes And Control, API Bulletin 2513,
American Petroleum Institute, Washington, DC, 1959.
13. Hydrocarbon Emissions From Refineries, API Publication No. 928, American Petroleum
Institute, Washington, DC, 1973.
14. R. A. Brown, et al., Systems Analysis Requirements For Nitrogen Oxide Control Of Stationary
Sources, EPA-650/2-74-091, U. S. Environmental Protection Agency, Cincinnati, OH, 1974.
15. R. P. Hangebrauck, et al., Sources Of Polynudear Hydrocarbons In The Atmosphere,
999-AP-33, U. S. Environmental Protection Agency, Research Triangle Park, NC, 1967.
16. W. S. Crumlish, "Review Of Thermal Pollution Problems, Standards, And Controls At The
State Government Level", Presented at the Cooling Tower Institute Symposium, New
Orleans, LA, January 30, 1966.
17. Assessment Of Atmospheric Emissions From Petroleum Refining, EPA-600/2-80-075a through
075d, U. S. Environmental Protection Agency, Cincinnati, OH, 1980.
5.1-16 EMISSION FACTORS 1/95
-------
5.2 Transportation And Marketing Of Petroleum Liquids1"3
5.2.1 General
The transportation and marketing of petroleum liquids involve many distinct operations, each
of which represents a potential source of evaporation loss. Crude oil is transported from production
operations to a refinery by tankers, barges, rail tank cars, tank trucks, and pipelines. Refined
petroleum products are conveyed to fuel marketing terminals and petrochemical industries by these
same modes. From the fuel marketing terminals, the fuels are delivered by tank trucks to service
stations, commercial accounts, and local bulk storage plants. The final destination for gasoline is
usually a motor vehicle gasoline tank. Similar distribution paths exist for fuel oils and other
petroleum products. A general depiction of these activities is shown in Figure 5.2-1.
5.2.2 Emissions And Controls
Evaporative emissions from the transportation and marketing of petroleum liquids may be
considered, by storage equipment and mode of transportation used, in four categories:
1. Rail tank cars, tank trucks, and marine vessels: loading, transit, and ballasting losses.
2. Service stations: bulk fuel drop losses and underground tank breathing losses.
3. Motor vehicle tanks: refueling losses.
4. Large storage tanks: breathing, working, and standing storage losses. (See Chapter 7,
"Liquid Storage Tanks".)
Evaporative and exhaust emissions are also associated with motor vehicle operation, and these
topics are discussed in AP-42 Volume II: Mobile Sources.
5.2.2.1 Rail Tank Cars, Tank Trucks, And Marine Vessels -
Emissions from these sources are from loading losses, ballasting losses, and transit losses.
5.2.2.1.1 Loading Losses -
Loading losses are the primary source of evaporative emissions from rail tank car, tank truck,
and marine vessel operations. Loading losses occur as organic vapors in "empty" cargo tanks are
displaced to the atmosphere by the liquid being loaded into the tanks. These vapors are a composite of
(1) vapors formed in the empty tank by evaporation of residual product from previous loads, (2) vapors
transferred to the tank in vapor balance systems as product is being unloaded, and (3) vapors generated
in the tank as the new product is being loaded. The quantity of evaporative losses from loading
operations is, therefore, a function of the following parameters:
- Physical and chemical characteristics of the previous cargo;
- Method of unloading the previous cargo;
- Operations to transport the empty carrier to a loading terminal;
- Method of loading the new cargo; and
- Physical and chemical characteristics of the new cargo.
The principal methods of cargo carrier loading are illustrated in Figure 5.2-2, Figure 5.2-3, and
Figure 5.2-4. In the splash loading method, the fill pipe dispensing the cargo is lowered only part way
into the cargo tank. Significant turbulence and vapor/liquid contact occur during the splash
1/95 Petroleum Industry 5.2-1
-------
I
tc
O)
il
11
s: rj
O >^4
!3
T3 q>
O ^<
w cd
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a) a>
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5.2-2
EMISSION FACTORS
1/95
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FILL PIPE
VAPOR EMISSIONS
-HATCH COVER
CARGO TANK
Figure 5.2-2. Splash loading method.
VAPOR EMISSIONS ,-<\ /- FILL PIPE
HATCH COVER
CARGO TANK
Figure 5.2-3. Submerged fill pipe.
VAPOR VENT
TO RECOVERY
OR ATMOSPHERE
HATCH CLOSED
VAPORS
'PRODUCT'
CARGO TANK
FILL PIPE
Figure 5.2-4. Bottom loading.
1/95
Petroleum Industry
5.2-3
-------
loading operation, resulting in high levels of vapor generation and loss. If the turbulence is great
enough, liquid droplets will be entrained in the vented vapors.
A second method of loading is submerged loading. Two types are the submerged fill pipe
method and the bottom loading method. In the submerged fill pipe method, the fill pipe extends almost
to the bottom of the cargo tank. In the bottom loading method, a permanent fill pipe is attached to the
cargo tank bottom. During most of submerged loading by both methods, the fill pipe opening is below
the liquid surface level. Liquid turbulence is controlled significantly during submerged loading,
resulting in much lower vapor generation than encountered during splash loading.
The recent loading history of a cargo carrier is just as important a factor in loading losses as
the method of loading. If the carrier has carried a nonvolatile liquid such as fuel oil, or has just been
cleaned, it will contain vapor-free air. If it has just carried gasoline and has not been vented, the air in
the carrier tank will contain volatile organic vapors, which will be expelled during the loading
operation along with newly generated vapors.
Cargo carriers are sometimes designated to transport only one product, and in such cases are
practicing "dedicated service". Dedicated gasoline cargo tanks return to a loading terminal containing
air fully or partially saturated with vapor from the previous load. Cargo tanks may also be "switch
loaded" with various products, so that a nonvolatile product being loaded may expel the vapors
remaining from a previous load of a volatile product such as gasoline. These circumstances vary with
the type of cargo tank and with the ownership of the carrier, the petroleum liquids being transported,
geographic location, and season of the year.
One control measure for vapors displaced during liquid loading is called "vapor balance
service", in which the cargo tank retrieves the vapors displaced during product unloading at bulk plants
or service stations and transports the vapors back to the loading terminal. Figure 5.2-5 shows a tank
truck in vapor balance service filling a service station underground tank and taking on displaced
gasoline vapors for return to the terminal. A cargo tank returning to a bulk terminal in vapor balance
service hormally is saturated with organic vapors, and the presence of these vapors at the start of
submerged loading of the tanker truck results in greater loading losses than encountered during
nonvapor balance, or "normal", service. Vapor balance service is usually not practiced with marine
vessels, although some vessels practice emission control by means of vapor transfer within their own
cargo tanks during ballasting operations, discussed below.
Emissions from loading petroleum liquid can be estimated (with a probable error of
±30 percent)4 using the following expression:
LL = 12.46 (1)
1_1 FT*
where:
LL = loading loss, pounds per 1000 gallons (lb/103 gal) of liquid loaded
S = a saturation factor (see Table 5.2-1)
P = true vapor pressure of liquid loaded, pounds per square inch absolute (psia)
(see Figure 7.1-5, Figure 7.1-6, and Table 7.1-2)
M = molecular weight of vapors, pounds per pound-mole (Ib/lb-mole) (see Table 7.1-2)
T = temperature of bulk liquid loaded, °R (°F + 460)
5.2-4 EMISSION FACTORS 1/95
-------
MANIFOLD FOR RETURNING VAPORS
VAPOR VENT LINE
UNDERGROUND
.STORAGE TANK
Figure 5.2-5. Tank truck unloading into a service station underground storage tank and practicing
"vapor balance" form of emission control.
Table 5.2-1. SATURATION (S) FACTORS FOR CALCULATING PETROLEUM LIQUID
LOADING LOSSES
Cargo Carrier
Tank trucks and rail tank cars
Marine vessels3
Mode Of Operation
Submerged loading of a clean cargo tank
Submerged loading: dedicated normal service
Submerged loading: dedicated vapor balance
service
Splash loading of a clean cargo tank
Splash loading: dedicated normal service
Splash loading: dedicated vapor balance service
Submerged loading: ships
Submerged loading: barges
S Factor
0.50
0.60
1.00
1.45
1.45
1.00
0.2
0.5
a For products other than gasoline and crude oil. For marine loading of gasoline, use factors from
Table 5.2-2. For marine loading of crude oil, use Equations 2 and 3 and Table 5.2-3.
1/95
Petroleum Industry
5.2-5
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The saturation factor, S, represents the expelled vapor's fractional approach to saturation, and it
accounts for the variations observed in emission rates from the different unloading and loading
methods. Table 5.2-1 lists suggested saturation factors.
Emissions from controlled loading operations can be calculated by multiplying the uncontrolled
emission rate calculated in Equation 1 by an overall reduction efficiency term:
1 -
_eff
100
The overall reduction efficiency should account for the capture efficiency of the collection
system as well as both the control efficiency and any downtime of the control device. Measures to
reduce loading emissions include selection of alternate loading methods and application of vapor
recovery equipment. The latter captures organic vapors displaced during loading operations and
recovers the vapors by the use of refrigeration, absorption, adsorption, and/or compression. The
recovered product is piped back to storage. Vapors can also be controlled through combustion in a
thermal oxidation unit, with no product recovery. Figure 5.2-6 demonstrates the recovery of gasoline
vapors from tank trucks during loading operations at bulk terminals. Control efficiencies for the
recovery units range from 90 to over 99 percent, depending on both the nature of the vapors and the
type of control equipment used.5"6 However, only 70 to 90 percent of the displaced vapors reach the
control device, because of leakage from both the tank truck and collection system.6 The collection
efficiency should be assumed to be 90 percent for tanker trucks required to pass an annual leak test.
Otherwise, 70 percent should be assumed.
VAPOR RETURN LINE
V
(TTROCK
TREATED
AIR VENTED
TO
ATMOSPHERE
RECOVERED PRODUCT
TO STORAGE
PRODUCT FROM
LOADING TERMINAL
STORAGE TANK
Figure 5.2-6. Tank truck loading with vapor recovery.
5.2-6
EMISSION FACTORS
1/95
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Sample Calculation -
Loading losses (L^) from a gasoline tank truck in dedicated vapor balance service and
practicing vapor recovery would be calculated as follows, using Equation 1:
Design basis -
Cargo tank volume is 8000 gal
Gasoline Reid vapor pressure (RVP) is 9 psia
Product temperature is 80 °F
Vapor recovery efficiency is 95 percent
Vapor collection efficiency is 90 percent (for vessels passing annual leak test)
Loading loss equation -
where:
S = saturation factor (see Table 5.2-1) - 1.00
P = true vapor pressure of gasoline (see Figure 7.1-6) = 6.6 psia
M = molecular weight of gasoline vapors (see Table 7.1-2) = 66
T = temperature of gasoline = 540 °R
eff = overall reduction efficiency (95 percent control x 90 percent collection) = 85 percent
0^0X6.6X66)
L
540 lOO
= 1.5 lb/103gal
Total loading losses are:
(1.5 lb/103 gal) (8.0 x 103 gal) = 12 pounds (Ib)
Measurements of gasoline loading losses from ships and barges have led to the development of
emission factors for these specific loading operations.7 These factors are presented in Table 5.2-2
and should be used instead of Equation 1 for gasoline loading operations at marine terminals. Factors
are expressed in units of milligrams per liter (mg/L) and pounds per 1000 gallons (lb/103 gal).
1/95 Petroleum Industry 5.2-7
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Table 5.2-2 (Metric And English Units). VOLATILE ORGANIC COMPOUND (VOC) EMISSION
FACTORS FOR GASOLINE LOADING OPERATIONS AT MARINE TERMINALS*
Vessel Tank
Condition
Uncleaned
Ballasted
Cleaned
Gas-freed
Any condition
Gas-freed
Typical overall
situation6
Previous
Cargo
Volatile0
Volatile
Volatile
Volatile
Nonvolatile
Any cargo
Any cargo
Ships/Ocean Bargesb
mg/L
Transferred
315
205
180
85
85
ND
215
lb/103 gal
Transferred
2.6
1.7
1.5
0.7
0.7
ND
1.8
Bargesb
mg/L
Transferred
465
_d
ND
ND
ND
245
410
lb/103 gal
Transferred
3.9
_d
ND
ND
ND
2.0
3.4
a References 2,8. Factors are for both VOC emissions (which excludes methane and ethane) and total
organic emissions, because methane and ethane have been found to constitute a negligible weight
fraction of the evaporative emissions from gasoline. ND = no data.
b Ocean barges (tank compartment depth about 12.2 m [40 ft]) exhibit emission levels similar to tank
ships. Shallow draft barges (compartment depth 3.0 to 3.7 m [10 to 12 ft]) exhibit higher emission
levels.
c Volatile cargoes are those with a true vapor pressure greater than 10 kilopascals (kPa) (1.5 psia).
d Barges are usually not ballasted.
6 Based on observation that 41% of tested ship compartments were uncleaned, 11% ballasted,
24% cleaned, and 24% gas-freed. For barges, 76% were uncleaned.
In addition to Equation 1, which estimates emissions from the loading of petroleum liquids,
Equation 2 has been developed specifically for estimating emissions from the loading of crude oil into
ships and ocean barges:
CG (2)
CL = CA
where:
CL = total loading loss, lb/103 gal of crude oil loaded
CA = arrival emission factor, contributed by vapors in the empty tank compartment before
loading, lb/103 gal loaded (see Note below)
CG = generated emission factor, contributed by evaporation during loading, lb/103 gal loaded
Note: Values of CA for various cargo tank conditions are listed in Table 5.2-3.
5.2-8
EMISSION FACTORS
1/95
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5.2-3 (English Units). AVERAGE ARRIVAL EMISSION FACTORS, CA, FOR CRUDE OIL
LOADING EMISSION EQUATION1
Ship/Ocean Barge Tank Condition
Uncleaned
Ballasted
Cleaned or gas-freed
Any condition
Previous Cargo
Volatile15
Volatile
Volatile
Nonvolatile
Arrival Emission Factor, lb/103 gal
0.86
0.46
0.33
0.33
8 Arrival emission factors (CA) to be added to generated emission factors (CG) calculated in Equation 3
to produce total crude oil loading loss (CjJ. Factors are for total organic compounds; VOC emission
factors average about 15% lower, because VOC does not include methane or ethane.
b Volatile cargoes are those with a true vapor pressure greater than 10 kPa (1.5 psia).
This equation was developed empirically from test measurements of several vessel compartments.7
The quantity CG can be calculated using Equation 3:
CG = 1.84 (0.44 P- 0.42)
MG
(3)
where:
P = true vapor pressure of loaded crude oil, psia (see Figure 7.1-5 and Table 7.1-2)
M = molecular weight of vapors, Ib/lb-mole (see Table 7.1-2)
G = vapor growth factor = 1.02 (dimensionless)
T = temperature of vapors, °R (°F + 460)
Emission factors derived from Equation 3 and Table 5.2-3 represent total organic compounds.
Volatile organic compound (VOC) emission factors (which exclude methane and ethane because they
are exempted from the regulatory definition of "VOC") for crude oil vapors have been found to range
from approximately 55 to 100 weight percent of these total organic factors. When specific vapor
composition information is not available, the VOC emission factor can be estimated by taking
85 percent of the total organic factor.3
5.2.2.1.2 Ballasting Losses -
Ballasting operations are a major source of evaporative emissions associated with the unloading
of petroleum liquids at marine terminals. It is common practice to load several cargo tank
compartments with sea water after the cargo has been unloaded. This water, termed "ballast",
improves the stability of the empty tanker during the subsequent voyage. Although ballasting practices
vary, individual cargo tanks are ballasted typically about 80 percent, and the total vessel 15 to
40 percent, of capacity. Ballasting emissions occur as vapor-laden air in the "empty" cargo tank is
displaced to the atmosphere by ballast water being pumped into the tank. Upon arrival at a loading
port, the ballast water is pumped from the cargo tanks before the new cargo is loaded. The ballasting
of cargo tanks reduces the quantity of vapors returning in the empty tank, thereby reducing the quantity
of vapors emitted during subsequent tanker loading. Regulations administered by the U. S. Coast
Guard require that, at marine terminals located in ozone nonattainment areas, large tankers with crude
oil washing systems contain the organic vapors from ballasting.9 This is accomplished principally by
1/95
Petroleum Industry
5.2-9
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displacing the vapors during ballasting into a cargo tank being simultaneously unloaded. In other
areas, marine vessels emit organic vapors directly to the atmosphere.
Equation 4 has been developed from test data to calculate the ballasting emissions from crude
oil ships and ocean barges7:
where:
P =
LB = 0.31 + 0.20 P + 0.01 PUA
ballasting emission factor, lb/103 gal of ballast water
true vapor pressure of discharged crude oil, psia (see Figure 7.1-5 and Table 7.1-2)
arrival cargo true ullage, before dockside discharge, measured from the deck, feet;
(the term "ullage" here refers to the distance between the cargo surface level and the
deck level)
(4)
Table 5.2-4 lists average total organic emission factors for ballasting into uncleaned crude oil
cargo compartments. The first category applies to "full" compartments wherein the crude oil true
ullage just before cargo discharge is less than 1.5 meters (m) (5 ft). The second category applies to
lightered, or short-loaded, compartments (part of cargo previously discharged, or original load a partial
fill), with an arrival true ullage greater than 1.5 m (5 ft). It should be remembered that these tabulated
emission factors are examples only, based on average conditions, to be used when crude oil vapor
pressure is unknown. Equation 4 should be used when information about crude oil vapor pressure and
cargo compartment condition is available. The following sample calculation illustrates the use of
Equation 4.
5.2-4 (Metric And English Units). TOTAL ORGANIC EMISSION FACTORS
FOR CRUDE OIL BALLASTING3
Compartment Condition
Before Cargo Discharge
Fully loaded0
Lightered or previously
short loadedd
Average Emission Factors
By Category
mg/L Ballast
Water
111
171
lb/103 gal
Ballast Water
0.9 1
1.4 J
Typical Overall
mg/L Ballast
Water
129
lb/103 gal
Ballast Water
1.1
a Assumes crude oil temperature of 16°C (60°F) and RVP of 34 kPa (5 psia). VOC emission factors
average about 85% of these total organic factors, because VOCs do not include methane or ethane.
b Based on observation that 70% of tested compartments had been fully loaded before ballasting. May
not represent average vessel practices.
c Assumed typical arrival ullage of 0.6 m (2 ft).
d Assumed typical arrival ullage of 6.1 m (20 ft).
5.2-10
EMISSION FACTORS
1/95
-------
Sample Calculation -
Ballasting emissions from a crude oil cargo ship would be calculated as follows, using
Equation 4:
Design basis -
Vessel and cargo description: 80,000 dead-weight-ton tanker, crude oil capacity
500,000 barrels (bbl); 20 percent of the cargo capacity is filled
with ballast water after cargo discharge. The crude oil has an
RVP of 6 psia and is discharged at 75°F.
Compartment conditions: 70 percent of the ballast water is loaded into compartments that
had been fully loaded to 2 ft ullage, and 30 percent is loaded
into compartments that had been lightered to 15 ft ullage before
arrival at dockside.
Ballasting emission equation -
LB = 0.31 + 0.20 P + 0.01 PUA
where:
P = true vapor pressure of crude oil (see Figure 7.1-5)
= 4.6 psia
UA = true cargo ullage for the full compartments = 2 ft, and true cargo ullage for the
lightered compartments = 15 ft
LB = 0.70 [0.31 + (0.20) (4.6) + (0.01) (4.6) (2)]
+ 0.30 [0.31 + (0.20) (4.6) + (0.01) (4.6) (15)]
= 1.5 lb/103 gal
Total ballasting emissions are:
(1.5 lb/103 gal) (0.20) (500,000 bbl) (42 gal/bbl) = 6,300 Ib
Since VOC emissions average about 85 percent of these total organic emissions, emissions of VOCs
are about: (0.85)(6,300 Ib) = 5,360 Ib
5.2.2.1.3 Transit Losses-
In addition to loading and ballasting losses, losses occur while the cargo is in transit. Transit
losses are similar in many ways to breathing losses associated with petroleum storage (see Section 7.1,
"Organic Liquid Storage Tanks"). Experimental tests on ships and barges4 have indicated that transit
losses can be calculated using Equation 5:
LT = 0.1 PW (5)
1/95 Petroleum Industry 5.2-11
-------
where:
LT = transit loss from ships and barges, lb/week-103 gal transported
P = true vapor pressure of the transported liquid, psia (see Figure 7.1-5, Figure 7.1-6, and
Table 7.1-2)
W = density of the condensed vapors, Ib/gal (see Table 7.1-2)
Emissions from gasoline truck cargo tanks during transit have been studied by a combination of
theoretical and experimental techniques, and typical emission values are presented in Table 5.2-5.10"11
Emissions depend on the extent of venting from the cargo tank during transit, which in turn depends on
the vapor tightness of the tank, the pressure relief valve settings, the pressure in the tank at the start of
the trip, the vapor pressure of the fuel being transported, and the degree of fuel vapor saturation of the
space in the tank. The emissions are not directly proportional to the time spent in transit. If the vapor
leakage rate of the tank increases, emissions increase up to a point, and then the rate changes as other
determining factors take over. Truck tanks in dedicated vapor balance service usually contain saturated
vapors, and this leads to lower emissions during transit because no additional fuel evaporates to raise
the pressure in the tank to cause venting. Table 5.2-5 lists "typical" values for transit emissions and
"extreme" values that could occur in the unlikely event that all determining factors combined to cause
maximum emissions.
Table 5.2-5 (Metric And English Units). TOTAL UNCONTROLLED ORGANIC EMISSION
FACTORS FOR PETROLEUM LIQUID RAIL TANK CARS AND TANK TRUCKS
Emission Source
Loading operations'1
Submerged loading -
Dedicated normal service1*
mg/L transferred
Ib/103 gal transferred
Submerged loading -
Vapor balance serviced
mg/L transferred
lb/103 gal transferred
Splash loading -
Dedicated normal service
mg/L transferred
lb/103 gal transferred
Splash loading -
Vapor balance service
mg/L transferred
lb/103 gal transferred
Gasoline8
590
5
980
8
1,430
12
980
8
Crude
Oilb
240
2
400
3
580
5
400
3
Jet
Naphtha
(JP-4)
180
1.5
300
2.5
430
4
300
2.5
Jet
Kerosene
1.9
0.016
e
e
5
0.04
e
e
Distillate
Oil No. 2
1.7
0.014
e
e
4
0.03
e
e
Residual
Oil No. 6
0.01
0.0001
e
e
0.03
0.0003
e
e
5.2-12
EMISSION FACTORS
1/95
-------
Table 5.2-5 (cont.).
Emission Source
Transit losses
Loaded with product
mg/L transported
Typical
Extreme
lb/103 gal transported
Typical
Extreme
Return with vapor
mg/L transported
Typical
Extreme
lb/103 gal transported
Typical
Extreme
Gasoline8
0-1.0
0-9.0
0-0.01
0 - 0.08
0-13.0
0-44.0
0-0.11
0-0.37
Crude
Oilb
ND
ND
ND
ND
ND
ND
ND
ND
Jet
Naphtha
(JP-4)
ND
ND
ND
ND
ND
ND
ND
ND
Jet
Kerosene
ND
ND
ND
ND
ND
ND
ND
ND
Distillate
Oil No. 2
ND
ND
ND
ND
ND
ND
ND
ND
Residual
Oil No. 6
ND
ND
ND
ND
ND
ND
ND
ND
a Reference 2. Gasoline factors represent emissions of VOC as well as total organics, because methane
and ethane constitute a negligible weight fraction of the evaporative emissions from gasoline. VOC
factors for crude oil can be assumed to be 15% lower than the total organic factors, to account for the
methane and ethane content of crude oil evaporative emissions. All other products should be
assumed to have VOC factors equal to total organics. The example gasoline has an RVP of 69 kPa
(10 psia). ND = no data.
b The example crude oil has an RVP of 34 kPa (5 psia).
c Loading emission factors are calculated using Equation 1 for a dispensed product temperature of
16°C (60°F).
d Reference 2.
e Not normally used.
In the absence of specific inputs for Equations 1 through 5, the typical evaporative emission
factors presented in Tables 5.2-5 and 5.2-6 should be used. It should be noted that, although the crude
oil used to calculate the emission values presented in these tables has an RVP of 5, the RVP of
crude oils can range from less than 1 up to 10. Similarly, the RVP of gasolines ranges from 7 to 13.
In areas where loading and transportation sources are major factors affecting air quality, it is advisable
to obtain the necessary parameters and to calculate emission estimates using Equations 1 through 5.
5.2.2.2 Service Stations -
Another major source of evaporative emissions is the filling of underground gasoline storage
tanks at service stations. Gasoline is usually delivered to service stations in 30,000-liter (8,000-gal)
tank trucks or smaller account trucks. Emissions are generated when gasoline vapors in the
1/95
Petroleum Industry
5.2-13
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Table 5.2-6 (Metric And English Units). TOTAL ORGANIC EMISSION FACTORS
FOR PETROLEUM MARINE VESSEL SOURCES"
Emission Source
Loading operations
Ships/ocean barges
mg/L transferred
lb/103 gal transferred
Barges
mg/L transferred
lb/103 gal transferred
Tanker ballasting
mg/L ballast water
lb/103 gal ballast
water
Transit
mg/week-L transported
lb/week-103 gal
transported
Gasoline6
_d
_d
_d
_d
100
0.8
320
2.7
Crude
Oilc
73
0.61
120
1.0
c
e
150
1.3
Jet
Naphtha
(JP^t)
60
0.50
150
1.2
ND
ND
84
0.7
Jet Kerosene
0.63
0.005
1.60
0.013
ND
ND
0.60
0.005
Distillate Oil
No. 2
0.55
0.005
1.40
0.012
ND
ND
0.54
0.005
Residual Oil
No. 6
0.004
0.00004
0.011
0.00009
ND
ND
0.003
0.00003
a Factors are for a dispensed product of 16°C (60°F). ND = no data.
b Factors represent VOC as well as total organic emissions, because methane and ethane constitute a
negligible fraction of gasoline evaporative emissions. All products other than crude oil can be
assumed to have VOC factors equal to total organic factors. The example gasoline has an RVP of
69 kPa (10 psia).
c VOC emission factors for a typical crude oil are 15% lower than the total organic factors shown, in
order to account for methane and ethane. The example crude oil has an RVP of 34 kPa (5 psia).
d See Table 5.2-2 for these factors.
e See Table 5.2-4 for these factors.
underground storage tank are displaced to the atmosphere by the gasoline being loaded into the tank.
As with other loading losses, the quantity of loss in service station tank filling depends on several
variables, including the method and rate of filling, the tank configuration, and the gasoline
temperature, vapor pressure and composition. An average emission rate for submerged filling is
880 mg/L (7.3 lb/1000 gal) of transferred gasoline, and the rate for splash filling is 1380 mg/L
(11.5 lb/1000 gal) transferred gasoline (see Table 5.2-7).5
Emissions from underground tank filling operations at service stations can be reduced by the
use of a vapor balance system such as in Figure 5.2-5 (termed Stage I vapor control). The vapor
balance system employs a hose that returns gasoline vapors displaced from the underground tank to the
tank truck cargo compartments being emptied. The control efficiency of the balance system ranges
from 93 to 100 percent. Organic emissions from underground tank filling operations at a service
station employing a vapor balance system and submerged filling are not expected to exceed 40 mg/L
(0.3 lb/1000 gal) of transferred gasoline.
5.2-14
EMISSION FACTORS
1/95
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Table 5.2-7 (Metric And English Units). EVAPORATIVE EMISSIONS FROM GASOLINE
SERVICE STATION OPERATIONS8
Emission Source
Filling underground tank (Stage I)
Submerged filling
Splash filling
Balanced submerged filling
Underground tank breathing and emptying15
Vehicle refueling operations (Stage II)
Displacement losses (uncontrolled)0
Displacement losses (controlled)
Spillage
Emission Rate
mg/L
Throughput
880
1,380
40
120
1,320
132
80
lb/103 gal
Throughput
7.3
11.5
0.3
1.0
11.0
1.1
0.7
a Factors are for VOC as well as total organic emissions, because of the methane and ethane content of
gasoline evaporative emissions is negligible.
b Includes any vapor loss between underground tank and gas pump.
c Based on Equation 6, using average conditions.
A second source of vapor emissions from service stations is underground tank breathing.
Breathing losses occur daily and are attributable to gasoline evaporation and barometric pressure
changes. The frequency with which gasoline is withdrawn from the tank, allowing fresh air to enter
to enhance evaporation, also has a major effect on the quantity of these emissions. An average
breathing emission rate is 120 mg/L (1.0 lb/1000 gal) of throughput.
5.2.2.3 Motor Vehicle Refueling -
Service station vehicle refueling activity also produces evaporative emissions. Vehicle
refueling emissions come from vapors displaced from the automobile tank by dispensed gasoline and
from spillage. The quantity of displaced vapors depends on gasoline temperature, auto tank
temperature, gasoline RVP, and dispensing rate. Equation 6 can be used to estimate uncontrolled
displacement losses from vehicle refueling for a particular set of conditions.13
ER = 264.2 [(-5.909) - 0.0949 (AT) + 0.0884 (TD) + 0.485 (RVP)] (6)
where:
ER = refueling emissions, mg/L
AT = difference between temperature of fuel in vehicle tank and temperature of dispensed fuel,
°F
TD = temperature of dispensed fuel, °F
RVP = Reid vapor pressure, psia
1/95
Petroleum Industry
5.2-15
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Note that this equation and the spillage loss factor are incorporated into the MOBILE model. The
MOBILE model allows for disabling of this calculation if it is desired to include these emissions in the
stationary area source portion of an inventory rather than in the mobile source portion. It is estimated
that the uncontrolled emissions from vapors displaced during vehicle refueling average 1320 mg/L
(11.0 lb/1000 gal) of dispensed gasoline.5'12
Spillage loss is made up of contributions from prefill and postfill nozzle drip and from
spit-back and overflow from the vehicles's fuel tank filler pipe during filling. The amount of spillage
loss can depend on several variables, including service station business characteristics, tank
configuration, and operator techniques. An average spillage loss is 80 mg/L (0.7 lb/1000 gal) of
dispensed gasoline.5"12
Control methods for vehicle refueling emissions are based on conveying the vapors displaced
from the vehicle fuel tank to the underground storage tank vapor space through the use of a special
hose and nozzle, as depicted in Figure 5.2-7 (termed Stage II vapor control). In "balance" vapor
control systems, the vapors are conveyed by natural pressure differentials established during refueling.
In "vacuum assist" systems, the conveyance of vapors from the auto fuel tank to the underground
storage tank is assisted by a vacuum pump. Tests on a few systems have indicated overall systems
control efficiencies in the range of 88 to 92 percent.5'12 When inventorying these emissions as an area
source, rule penetration and rule effectiveness should also be taken into account. Procedures For
Emission Inventory Preparation, Volume IV: Mobile Sources, EPA-450/4-81-026d, provides more
detail on this.
SERVICE
STATION
PUMP
RETURNED VAPORS ^ |^
I" n
DISPENSED GASOLINE
'
Figure 5.2-7. Automobile refueling vapor recovery system.
References For Section 5.2
1. C.E. Burklin and R. L. Honercamp, Revision Of Evaporative Hydrocarbon Emission Factors,
EPA-450/3-76-039, U. S. Environmental Protection Agency, Research Triangle Park, NC,
August 1976.
2. G. A. LaFlam, et al., Revision Of Tank Truck Loading Hydrocarbon Emission Factors, Pacific
Environmental Services, Inc., Durham, NC, May 1982.
5.2-16
EMISSION FACTORS
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3. G. A. LaFlam, Revision Of Marine Vessel Evaporative Emission Factors, Pacific
Environmental Services, Inc., Durham, NC, November 1984.
4. Evaporation Loss From Tank Cars, Tank Trucks And Marine Vessels, Bulletin No. 2514,
American Petroleum Institute, Washington, DC, 1959.
5. C. E. Burklin, et al., A Study Of Vapor Control Methods For Gasoline Marketing Operations,
EPA-450/3-75-046A and -046B, U. S. Environmental Protection Agency, Research Triangle
Park, NC, May 1975.
6. Bulk Gasoline Terminals - Background Information For Proposed Standards,
EPA-450/3-80-038a, U. S. Environmental Protection Agency, Research Triangle Park, NC,
December 1980.
7. Atmospheric Hydrocarbon Emissions From Marine Vessel Transfer Operations,
Publication 2514A, American Petroleum Institute, Washington, DC, 1981.
8. C. E. Burklin, et al., Background Information On Hydrocarbon Emissions From Marine
Terminal Operations, EPA-450/3-76-038a and -038b, U. S. Environmental Protection Agency,
Research Triangle Park, NC, November 1976.
9. Rules For The Protection Of The Marine Environment Relating To Tank Vessels Carrying Oil In
Bulk, 45 FR 43705, June 30, 1980.
10. R. A. Nichols, Analytical Calculation Of Fuel Transit Breathing Loss, Chevron USA, Inc., San
Francisco, CA, March 21, 1977.
11. R. A. Nichols, Tank Truck Leakage Measurements, Chevron USA, Inc., San Francisco, CA,
June 7, 1977.
12. Investigation Of Passenger Car Refueling Losses: Final Report, 2nd Year Program,
APTD-1453, U. S. Environmental Protection Agency, Research Triangle Park, NC, September
1972.
13. Refilling Emissions From Uncontrolled Vehicles, EPA-AA-SDSB-85-6, U. S. Environmental
Protection Agency, Ann Arbor, MI, June 1985.
1/95 Petroleum Industry 5.2-17
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5.3 Natural Gas Processing
5.3.1 General1
Natural gas from high-pressure wells is usually passed through field separators at the well to
remove hydrocarbon condensate and water. Natural gasoline, butane, and propane are usually present
in the gas, and gas processing plants are required for the recovery of these liquefiable constituents
(see Figure 5.3-1). Natural gas is considered "sour" if hydrogen sulfide (H2S) is present in amounts
greater than 5.7 milligrams per normal cubic meters (mg/Nm3) (0.25 grains per 100 standard cubic
feet [gr/100 scf]). The H2S must be removed (called "sweetening" the gas) before the gas can be
utilized. If H2S is present, the gas is usually sweetened by absorption of the H2S in an amine
solution. Amine processes are used for over 95 percent of all gas sweetening in the United States.
Other methods, such as carbonate processes, solid bed absorbents, and physical absorption, are
employed in the other sweetening plants. Emission data for sweetening processes other than amine
types are very meager, but a material balance on sulfur will give accurate estimates for sulfur dioxide
(S02).
The major emission sources in the natural gas processing industry are compressor engines,
acid gas wastes, fugitive emissions from leaking process equipment and if present, glycol dehydrator
vent streams. Compressor engine emissions are discussed in Section 3.3.2. Fugitive leak emissions
are detailed in Protocol For Equipment Leak Emission Estimates, EPA-453/R-95-017, November
1995. Regeneration of the glycol solutions used for dehydrating natural gas can release significant
quantities of benzene, toluene, ethylbenzene, and xylene, as well as a wide range of less toxic
organics. These emissions can be estimated by a thermodynamic software model (GRI-GLYCalc™)
available from the Gas Research Institute. Only the SO2 emissions from gas sweetening operations
are discussed here.
5.3.2 Process Description2"3
Many chemical processes are available for sweetening natural gas. At present, the amine
process (also known as the Girdler process), is the most widely used method for H2S removal. The
process is summarized in reaction 1 and illustrated in Figure 5.3-2.
2 RNH2 + H2S -* (RNH3)2S (1)
where:
R = mono, di, or tri-ethanol
N = nitrogen
H = hydrogen
S = sulfur
The recovered hydrogen sulfide gas stream may be: (1) vented, (2) flared in waste gas flares
or modern smokeless flares, (3) incinerated, or (4) utilized for the production of elemental sulfur or
sulfuric acid. If the recovered H2S gas stream is not to be utilized as a feedstock for commercial
applications, the gas is usually passed to a tail gas incinerator in which the H2S is oxidized to SO2
and is then passed to the atmosphere out a stack. For more details, the reader should consult
Reference 8.
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T3
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13
CO
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5.3-2
EMISSION FACTORS
1/95
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ACID GAS
PURIFIED
GAS
COOLER
<—
C
LEAN AMINE
SOLUTION
u
n STEAM
ylREBOILER
HEAT EXCHANGER
Figure 5.3-2. Flow diagram of the amine process for gas sweetening.
5.3.3 Emissions4'5
Emissions will result from gas sweetening plants only if the acid waste gas from the amine
process is flared or incinerated. Most often, the acid waste gas is used as a feedstock in nearby sulfur
recovery or sulfuric acid plants. See Sections 8.13 "Sulfur Recovery", or 8.10, "Sulfuric Acid",
respectively, for these associated processes.
When flaring or incineration is practiced, the major pollutant of concern is SO2. Most plants
employ elevated smokeless flares or tail gas incinerators for complete combustion of all waste gas
constituents, including virtually 100 percent conversion of H2S to SO2. Little paniculate, smoke, or
hydrocarbons result from these devices, and because gas temperatures do not usually exceed 650°C
(1200°F), significant quantities of nitrogen oxides are not formed. Emission factors for gas
sweetening plants with smokeless flares or incinerators are presented in Table 5.3-1. Factors are
expressed in units of kilograms per 1000 cubic meters (kg/103 m3) and pounds per million standard
cubic feet (lb/106 scf).
Some plants still use older, less-efficient waste gas flares. Because these flares usually burn
at temperatures lower than necessary for complete combustion, larger emissions of hydrocarbons and
paniculate, as well as H2S, can occur. No data are available to estimate the magnitude of these
emissions from waste gas flares.
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Petroleum Industry
5.3-3
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Table 5.3.1 (Metric And English Units). EMISSION FACTORS FOR
GAS SWEETENING PLANTS*
EMISSION FACTOR RATING: SULFUR OXIDES: A
ALL OTHERS: C
Process
Amine
kg/103 m3 gas processed
lb/106 scf gas processed
Paniculate
Neg
Neg
Sulfur Oxides0
(S02)
26.98 Sd
1685 Sd
Carbon
Monoxide
Neg
Neg
Hydrocarbons
e
e
Nitrogen
Oxides
Neg
Neg
a Factors are presented only for smokeless flares and tail gas incinerators on the amine gas
sweetening process with no sulfur recovery or sulfuric acid production present. Too little
information exists to characterize emissions from older, less-efficient waste gas flares on the amine
process or from other, less common gas sweetening processes. Factors for various internal
combustion engines used in a gas processing plant are given in Section 3.3, "Gasoline and Diesel
Industrial Engines". Factors for sulfuric acid plants and sulfur recovery plants are given in
Section 8.10, "Sulfuric Acid", and Section 8.13, "Sulfur Recovery", respectively.
Neg = negligible.
b References 2,4-7. Factors are for emissions after smokeless flares (with fuel gas and steam
injection) or tail gas incinerators.
0 Assumes that 100% of the H2S in the acid gas stream is converted to SO2 during flaring or
incineration and that the sweetening process removes 100% of the H2S in the feedstock.
d S is the H2S content of the sour gas entering the gas sweetening plant, in mole or volume percent.
For example, if the H2S content is 2%, the emission factor would be 26.98 times 2,
or 54.0 kg/1000 m3 (3370 lb/106 scf) of sour gas processed. If the H2S mole % is unknown,
average values from Table 5.3-2 may be substituted. Note: If H2S contents are reported in ppm or
grains (gr) per 100 scf, use the following factors to convert to mole %:
10,000 ppm H2S = 1 mole % H2S
627 gr H2S/100 scf = 1 mole % H2S
The m3 or scf are to be measured at 60°F and 760 mm Hg for this application
(1 Ib-mol = 379.5 scf).
e Flare or incinerator stack gases are expected to have negligible hydrocarbon emissions. To estimate
fugitive hydrocarbon emissions from leaking compressor seals, valves, and flanges, see "Protocol
For Equipment Leak Emission Estimates", EPA-453/R-95-017, November 1995 (or updates).
5.3-4
EMISSION FACTORS
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Table 5.3-2. AVERAGE HYDROGEN SULFIDE CONCENTRATIONS
IN NATURAL GAS BY AIR QUALITY CONTROL REGION*
State
Alabama
Arizona
Arkansas
California
Colorado
Florida
Kansas
Louisiana
Michigan
Mississippi
Montana
New Mexico
North Dakota
AQCR Name
Mobile-Pensacola-Panama City-Southern
Mississippi (FL, MS)
Four Corners (CO, NM, UT)
Monroe-El Dorado (LA)
Shreveport-Texarkana-Tyler (LA, OK, TX)
Metropolitan Los Angeles
San Joaquin Valley
South Central Coast
Southeast Desert
Four Corners (AZ, NM, UT)
Metropolitan Denver
Pawnee
San Isabel
Yampa
Mobile-Pensacola-Panama City-Southern
Mississippi (AL, MS)
Northwest Kansas
Southwest Kansas
Monroe-El Dorado (AR)
Shreveport-Texarkana-Tyler (AR, OK, TX)
Upper Michigan
Mississippi Delta
Mobile-Pensacola-Panama City-Southern
Mississippi (AL, FL)
Great Falls
Miles City
Four Corners (AZ, CO, UT)
Pecos-Permian Basin
North Dakota
AQCR
Number
5
14
19
22
24
31
32
33
14
36
37
38
40
5
97
100
19
22
126
134
5
141
143
14
155
172
Average H2S,
mole %
3.30
0.71
0.15
0.55
2.09
0.89
3.66
1.0
0.71
0.1
0.49
0.3
0.31
3.30
0.005
0.02
0.15
0.55
0.5
0.68
3.30
3.93
0.4
0.71
0.83
1.74b
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Petroleum Industry
5.3-5
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Table 5.3-2 (cont.)-
State
Oklahoma
Texas
Utah
Wyoming
AQCR Name
Northwestern Oklahoma
Shreveport-Texarkana-Tyler (AR, LA, TX)
Southeastern Oklahoma
Abilene- Wichita Falls
Amarillo-Lubbock
Austin-Waco
Corpus Christi-Victoria
Metropolitan Dallas-Fort Worth
Metropolitan San Antonio
Midland-Odessa-San Angelo
Shreveport-Texarkana-Tyler (AR, LA, OK)
Four Corners (AZ, CO, NM)
Casper
Wyoming (except Park, Bighorn, and
Washakie Counties)
AQCR
Number
187
22
188
210
211
212
214
215
217
218
22
14
241
243
Average H2S,
mole %
1.1
0.55
0.3
0.055
0.26
0.57
0.59
2.54
1.41
0.63
0.55
0.71
1.262
2.34C
a Reference 9. AQCR = Air Quality Control Region.
b Sour gas only reported for Burke, Williams, and McKenzie Counties, ND.
c Park, Bighorn, and Washakie Counties, WY, report gas with an average H2S content of 23 mole
References For Section 5.3
1. D. K. Katz, et al., Handbook Of Natural Gas Engineering, McGraw-Hill Book Company,
New York, 1959.
2. R. R. Maddox, Gas And Liquid Sweetening, 2nd Ed. Campbell Petroleum Series, Norman,
OK, 1974.
3. R. E. Kirk and D. F. Othmer (eds.), Encyclopedia Of Chemical Technology. Vol. 7,
Interscience Encyclopedia, Inc., New York, NY, 1951,
4. Sulfur Compound Emissions Of The Petroleum Production Industry, EPA-650/2-75-030.
U. S. Environmental Protection Agency, Cincinnati, OH, 1974.
5. Unpublished stack test data for gas sweetening plants, Ecology Audits, Inc., Dallas, TX,
1974.
5.3-6
EMISSION FACTORS
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6. Control Techniques For Hydrocarbon And Organic Solvent Emissions From Stationary
Sources, AP-68, U. S. Environmental Protection Agency, Research Triangle Park, NC,
March 1970.
7. Control Techniques For Nitrogen Oxides From Stationary Sources, AP-67,
U. S. Environmental Protection Agency, Research Triangle Park, NC, March 1970.
8. B. J. Mullins, et al., Atmospheric Emissions Survey Of The Sour Gas Processing Industry,
EPA-450/3-75-076, U. S. Environmental Protection Agency, Research Triangle Park, NC,
October 1975.
9. Federal Air Quality Control Regions, AP-102, U. S. Environmental Protection Agency,
Research Triangle Park, NC, January 1972.
V"v*'•• r/.•.«•-. ,.,/,»,, „
1/95 Petroleum Industry '(.V*-'' '»'''Vu 'H ?. ^ ' ' 5-3-7
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Region 5, Library (PU2J) h
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