United States
Environmental Protection
Agency
Industrial Environmental Research
Laboratory
Research Triangle Park NC 27711
Research and Development
EPA-600/S7-84-026 Mar. 1984
SERA Project Summary
Pollutant Formation During
Fixed-Bed and Suspension
Coal Combustion
S. C. Manis, J. M. Munro, S. P. Purcell, G. P. Starley, D. M. Slaughter, and
D. W. Pershing
This summarizes a 3-year laboratory
study of factors controlling the forma-
tion of nitrogen and sulfur oxides (NO>
and SOX) in industrial coal-fired boilers,
with emphasis on stoker-fired units.
The study identified the combustion
phenomena governing conversion of
coal constituents to NOK and SO*, and
investigated approaches to controlling
these emissions. The study also consid-
ered possible detrimental effects of
control technology on boiler operation.
Study results indicate that two types
of NO, controls appear to be viable: (1)
the coal feed could be screened to
remove the fines (particles less than 0.1
in.), essentially eliminating the high conver-
sion of nitrogen evolved in the suspen-
sion zone and resulting in an overall
emissions reduction of about 10-40%,
depending on the amount of fines
normally present in the raw coal; or (2)
the primary overfire-air injection port
could be moved to above the spreader
and the suspension zone and bed region
could both be operated substoichi-
ometric, reducing emissions by as much
as 50%. Unfortunately, controlling SO2
formation in either a spreader or mass-
burning stoker unit appears to be diffi-
cult. Coal/limestone pellets can signif-
icantly reduce SOz emissions, and the
effectiveness of the sorbent appears to
increase when the bed-region stoichi-
ometry is reduced below 1.0.
This Project Summary was developed
by EPA's Industrial Environmental Re-
search Laboratory, Research Triangle
Park, NC, to announce key findings of
the research project that is fully docu-
mented in a separate report of the same
title (see Project Report ordering infor-
mation at back).
Purpose and Scope
This report summarizes the results of a
3-year research program to study the
formation and control of nitrogen and
sulfur oxides (NOX and SOX) in industrial
coal-fired boilers with emphasis on
stoker-fired units. In particular, this pro-
gram considered the following major
research areas:
1. the evolution and oxidation of fuel
nitrogen and sulfur;
2. the retention of SOX by ash and/or
solid-chemical sorbents; and
3. the effectiveness of distributed air
addition for NO« control.
In addition, the study attempted to quanti-
fy the combustion process in a stoker
environment and considered possible
detrimental effects of control technology
on boiler operation. The work considered
conditions typical of both spreader-stoker
and mass-burning systems.
The approach was primarily experi-
mental; three types of laboratory furnaces
were utilized to investigate the various
combustion regimes of major importance
in stoker-fired systems:
1. A 200,000 Btu/hr tower furnace
was used to characterize the sus-
pension phase oxidation of fuel
nitrogen and sulfur as a function of
local oxygen concentration, temper-
ature, and particle size.
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2. A 300,000 Btu/hr//xe
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United States
Environmental Protection
Agency
Center for Environmental Research
Information
Cincinnati OH 45268
Official Business
Penalty for Private Use $300
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