United States National Risk Management

Environmental Protection Research Laboratory

Agency Research Triangle Park, NC 27711

Research and Development EPA/600/SR-95/106 August 1995

E AP

Effects of Changing

Coals on the Emissions of

Metal Hazardous Air

Pollutants from the

Combustion of Pulverized

Coal

Project Summary

Tests were conducted at the U.S. Environmental Protection Agency’s Air

Pollution Prevention and Control Division (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 emissions 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 combustor and emissions from a full scale utility 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, Research 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) Innovative Furnace Reactor (IFR), and

samples were taken prior to any pollution

control equipment to allow application of

different control efficiencies to the uncontrolled emissions. Six coals were burned

in the IFR under similar combustion conditions, and each coal was sampled for 10

metals: antimony, arsenic, beryllium, cadmium, chromium, lead, manganese, mercury, nickel, and selenium. Each of these

metals is on the list of 189 compounds

and compound classes listed as hazardous 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 programs. 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 between 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 sulfur 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 emissions 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

C. Andrew Miller
2

did not correlate well with the changes in

the as-fed trace metal contents. The remaining 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 asfed trace metal concentration and the uncontrolled stack emissions appears to be

the vapor pressure of the metal. Metals

that have high vapor pressures tend to

exhibit strong correlations between the asfed 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

EPA/600/SR-95/106

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EPA

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