\ UNITED STATES ENVIRONMENTAL PROTECTION AGENCY
\ YSiZZ S RESEARCH TRIANGLE PARK, NC 27711
%"** OFFICE OF AIR QUALITY PLANNING AND STANDARDS
Technical Note - Estimating Lead (Pb) Emissions from Coal Combustion Sources
BACKGROUND
On November 12, 2008 EPA substantially strengthened the national ambient air quality standards
(NAAQS) for lead (see 73 FR 66964). EPA revised the level of the primary (health-based) standard
from 1.5 micrograms per cubic meter (|ig/m3) to 0.15 (ig/m3, measured as total suspended particles (TSP)
and revised the secondary (welfare-based) standard to be identical in all respects to the primary standard.
In conjunction with strengthening the Pb NAAQS, the EPA promulgated new monitoring requirements
including new design requirements for the Pb NAAQS surveillance network (40 CFR Part 58, Appendix
D, paragraph 4.5). On December 27, 2010, the EPA again revised the Pb monitoring requirements.
Monitoring is now required for Pb sources that may contribute to violations of the Pb NAAQS ["source-
oriented monitoring", paragraph 4.5(a)], and at a minimum of one monitor for any source estimated to
emit 0.50 tpy or more of Pb1. In the 2008 National Emissions Inventory (Version 1), 103 facilities were
identified as emitting greater than 0.50 tpy due to combustion of coal. The purpose of this technical note
is to provide guidance on approaches that may be used to estimated Pb emissions from coal combustion
sources in the absence of site specific lead stack test data.
ESTIMATING LEAD EMISSIONS USING AP-42
AP-42 provides emission factors and process information for more than 200 air pollution source
categories. The emission factors have been developed and compiled from source test data, material
balance studies, and engineering estimates.2 AP-42 provides two approaches for estimating lead
emissions from coal combustion. The first is a straight emission factor for controlled coal combustion
(4.2xlO~4 Ib/ton fired, Table 1.1-18). According to AP-42, this emission factor is applicable to the
combustion of bituminous coal, subbituminous coal, and lignite using a venturi scrubber, spray dryer
absorber, wet limestone scrubber with an electrostatic precipitator (ESP) or Fabric Filter (FF), an ESP, or
aFF.
A second approach is provided in AP-42 that takes into account site specific information including the
concentration of lead in the coal, the ash content of the coal, and PM emission rate. The equation for this
approach, provided in Table 1.1-16, is as follows:
Lead (lb/1012 Btu) = 3.4 * (C/A * PM)080
1 Monitoring agencies may receive a waiver from this requirement where they can "demonstrate the Pb source will not
contribute to a maximum Pb concentration in ambient air in excess of 50 percent of the NAAQS (based on historical
monitoring data, modeling, or other means)." (40 CFR part 58, Appendix D, paragraph 4.5(a)(ii)).
2 http://www.epa.gov/ttnchiel/ap42/
Revised 5/27/2011
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Where:
C = concentration of metal in the coal, parts per million by weight (ppmwt).
A = weight fraction of ash in the coal. For example, 10% ash is 0.1 ash fraction.
PM = Site-specific emission factor for total particulate matter, lb/106 Btu.
EMISSION FACTORS DEVELOPED FOR AIR TOXICS RULE
On March 16, 2001, the EPA proposed a rule that would control air toxic emissions from coal and oil
fired electrical generating units.3 In developing the proposed rule, the EPA collected air toxic emissions
data (including Pb emissions) from over 200 coal fired electrical generating units. These data were used
to develop emission factors for a number of different coal type and emission control combinations. Table
1 contains a summary of the Pb emission factors developed as part of this rule making.
Table 1. Emission Factors Developed for the Utility Boilers MACT Standard
Coal Type
Bituminous
Bituminous
Bituminous
Bituminous
Bituminous
Bituminous
Coal Refuse
Lignite
Lignite
Lignite
Subbituminous
Subbituminous
Subbituminous
Subbituminous
Subbituminous
Boiler Type
Conventional
Conventional
Conventional
Conventional
Fluidized Bed
Fluidized Bed
Fluidized Bed
Conventional
Conventional
Fluidized Bed
Conventional
Conventional
Conventional
Conventional
Conventional
Control Scheme
Fabric Filter + Wet FGD
Fabric Filter
ESP + Wet FGD
ESP
Fabric Filter
ESP
Fabric Filter
Fabric Filter + Wet FGD
Fabric Filter
Fabric Filter
Fabric Filter + Wet FGD
Fabric Filter
ESP + Wet FGD
ESP
Wet FGD/PM Scrubber
Lead Emission
Factor
(Ib/MMBtu)
3.46E-07
1.33E-06
5.26E-06
5.68E-06
3.55E-06
8.68E-07
3.86E-06
4.76E-07
3.80E-06
1.85E-06
5.45E-07
1.24E-06
3.06E-07
1.05E-044
4.77E-06
National Emission Standards for Hazardous Air Pollutants From Coal and Oil-Fired Electric Utility Steam Generating
Units and Standards of Performance for Fossil-Fuel-Fired Electric Utility, Industrial-Commercial-Institutional, and
Small Industrial-Commercial-Institutional Steam Generating Units. A copy of the proposed rule can be found here -
http://www.epa.gov/ttn/arw/utility/fr03my 11 .pdf
4 This emission factor appears to be an outlier. The EPA is currently looking into the emissions data that went into this
emission factor, but at this time has not determined if there is an error associated with this emission factor. Monitoring
agencies are cautioned against the use of this emission factor at this time.
Revised 5/27/2011
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Monitoring agencies may wish to use these emission factors in lieu of the AP-42 approaches discussed
above when determining applicability of the monitoring requirements for these facilities.
FOR FURTHER INFORMATION
This document and other documents intended to assist monitoring agencies implement the Pb monitoring
requirements can be found at - http://www.epa.gov/ttn/amtic/pb-monitoring.html
For additional information, please contact Kevin Cavender of the Air Quality Assessment Division,
Ambient Air Monitoring Group, 919-541-2364, Cavender.kevin@epa.gov.
Revised 5/27/2011
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