United States
Environmental Protection
Agency
National Risk Management
Research Laboratory
Research Triangle Park, NC 27711
Research and Development
EPA/600/SR-95/106
August 1995
Project Summary
Effects of Changing
Coals on the Emissions of
Metal Hazardous Air
Pollutants from the
Combustion of Pulverized
Coal
C. Andrew Miller
Tests were conducted at the U.S. En-
vironmental Protection Agency's Air
Pollution Prevention and Control Divi-
sion (APPCD) in Research Triangle
Park, NC, to evaluate the effects of
changing coals on the emissions of
metal hazardous air pollutants from
coal-fired boilers. The objectives of the
tests were to determine how the emis-
sions of metal hazardous air pollutants
would change if low sulfur coals were
substituted for higher sulfur coals and
to measure the correlation between
emissions from a small scale combus-
tor and emissions from a full scale util-
ity boiler burning the same coal. The
tests were funded by the Illinois Clean
Coal Institute.
This Project Summary was developed
by EPA's National Risk Management
Research Laboratory's Air Pollution
Prevention and Control Division, Re-
search Triangle Park, NC, to announce
key findings of the research project
that is fully documented in a separate
report of the same title (see Project
Report ordering information at back).
Overview
The small scale tests were conducted
on APPCD's 29 kW (100,000 Btu/hr) In-
novative Furnace Reactor (IFR), and
samples were taken prior to any pollution
control equipment to allow application of
different control efficiencies to the uncon-
trolled emissions. Six coals were burned
in the IFR under similar combustion con-
ditions, and each coal was sampled for 10
metals: antimony, arsenic, beryllium, cad-
mium, chromium, lead, manganese, mer-
cury, nickel, and selenium. Each of these
metals is on the list of 189 compounds
and compound classes listed as hazard-
ous air pollutants under Title III of the
1990 Clean Air Act Amendments. The six
coals included two Illinois bituminous coals
with an average sulfur content of 2.23%
(the high sulfur coals in this test program),
two western subbituminous coals with an
average sulfur content of 0.57%, and two
other coals used in full scale test pro-
grams. The final two coals were chosen
to allow a direct comparison of the small
scale results to full scale emissions tests.
No general correlation was found be-
tween sulfur content and metals emissions
for the six coals tested. This result is in
agreement with previous results that have
noted no general correlation between sul-
fur content and metal content in coals.
The small scale IFR emissions correlated
well with emissions from a full scale utility
boiler burning the same coal, although the
IFR results tended to be consistently lower.
The difference is likely due to physical
differences in the two systems, such as
the volume to surface area ratio, and the
sharpness of turns in the gas path.
The results of the IFR tests showed
that changes in the uncontrolled emis-
sions tended to correlate well with the
corresponding changes in the as-fed metal
content of the coals for arsenic, mercury,
and selenium. For beryllium, chromium,
manganese, and nickel, changes in the
uncontrolled emissions with different coals
Printed on Recycled Paper
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did not correlate well with the changes in
the as-fed trace metal contents. The re-
maining three metals, antimony, cadmium,
and lead, did not show conclusive results
when comparing emissions to as-fed trace
metal contents. The factor that determines
the degree of correlation between the as-
fed trace metal concentration and the un-
controlled stack emissions appears to be
the vapor pressure of the metal. Metals
that have high vapor pressures tend to
exhibit strong correlations between the as-
fed metal concentration in the coal and
the uncontrolled emissions, while metals
with low vapor pressures tend to show a
much weaker correlation. In summary, the
study illustrates that predictions of metal
emissions based only on the trace metal
content of the coal are not accurate in all
cases. Such predictions cannot be used
with any confidence for refractory metals,
but do have some degree of validity for
the more volatile metals of interest.
The EPA author, C. Andrew Miller (also the EPA Project Officer, see below) is with
the National Risk Management Research Laboratory's Air Pollution Prevention
and Control Division, Research Triangle Park, NC 27711.
The complete report, entitled "Effects of Changing Coals on the Emissions of Metal
Hazardous Air Pollutants from the Combustion of Pulverized Coal," (Order No.
PB95-246385; Cost: $19.50, subject to change) will be available only from:
National Technical Information Service
5285 Port Royal Road
Springfield, VA 22161
Telephone: 703-487-4650
The EPA Project Officer can be contacted at:
Air Pollution Prevention and Control Division
National Risk Management Research Laboratory
U.S. Environmental Protection Agency
Research Triangle Park, NC 27711
United States
Environmental Protection Agency
National Risk Management Research Laboratory (G-72)
Cincinnati, OH 45268
Official Business
Penalty for Private Use $300
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EPA
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EPA/600/SR-95/106
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