Combustion Research Program: chapter from Energy and Environment Division annual report 1977 Page: 12 of 28
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172
SECONDARY POLLUTANTS FROM AMMONIA INJECTION
NOx CONTROL PROCESSES
N. J. Brown, R. F. Sawyer, and A. K. GordonINTRODUCTION
Consideration of odd-nitrogen compounds
(essentially all nitrogen containing compounds
other than N2) as air pollutants has been primari-
ly focused upon the nitrogen oxides, NO and NO2,
with occasional interest in ammonia. The oxides
of nitrogen result either directly or indirectly
in atmospheric nitrogen dioxide, photochemical
smog, nitrate compounds, and probably other
compounds whose role in air pollution is less
well defined.
Combustion sources both of the mobile and
stationary types are recognized as the primary
sources of the oxides of nitrogen. The two
principal sources of nitrogen oxides in the
combustion of conventional fuels are oxidation
of atmospheric molecular nitrogen (thermal NOx)
and oxidation of nitrogen containing compounds
in the fuel (fuel nitrogen NOx). Until recently,
the former has been the dominant source of NOx;
however, in combustion processes using crude oil,
coal and shale derived fuels, and some refinery
gases, fuel nitrogen can be a significant and
even dominant source of NOx. The amount of fuel
nitrogen contained in fossil fuel can vary con-
siderably with negligible amounts in natural gas,
significant amounts found in distillate fuels,
and amounts from 0.5 to 3 percent in heavier fuels
(residual oil, coal, coal derived, and shale
derived fuels). The amount of fuel nitrogen NOx
produced in combustion processes increases with
the fuel nitrogen content of the fuel. Fuel
nitrogen nitric oxides may account for more
than half of the nitric oxides emitted from the
combustion of high nitrogen content oil or coal in
power plants.
The mechanism of fuel NOx production,
although not understood, appears favored under
conditions different from those which enhance
thermal NOx production. Consequently, the various
control strategies used in the United States to
meet NOx emission standards, namely the modifi-
cation of the combustion processes to reduce
thermal production, are ineffective in reducing
fuel NOx.
A new NOx control technology has been
patented by Exxon Research and Engineering Company
which selectively removes NO from combustion
effluents through homogeneous reaction with
ammonia and oxygen. This process is distinctly
different from other technologies in that it
removes NOx after its formation rather than
attempting to prevent its formation. Thus, the
process offers the possibility of removing both
thermal and fuel NOx. This process has been
demonstrated commercially in Japan and is likely
to be proposed for use in California for the
control of oxides of nitrogen from stationary
sources. The major question regarding this pro-
cess is its potential for formation of secondary
pollutants, especially at operating conditionsdifferent from those which are optimal for the
reduction of oxides of nitrogen.
In recognition that NOx removal through NH3
addition now appears to be a viable control pro-
cess for stationary combustion sources, a new
research program sponsored by the California Air
Resources Board has been initiated at Lawrence
Berkeley Laboratory which is directed toward
identification and quantification of the nitrogen
containing products formed from the addition of
ammonia. This research will be performed in a
laboratory scale combustion tunnel with a well-
controlled experimental environment. A test
sequence is planned to examine product formation
associated with 1) optimum ammonia addition con-
ditions, 2) off-design ammonia addition conditions,
3) optimum and off-design ammonia addition con-
ditions with an oil fuel rather than the propane
of the first two test series, and 4) the effect
of fuel additives and impurities on the nitrogen-
containing products formed. The overall objec-
tive of this research is to provide a framework
to assist the California Air Resources Board in
assessing potential pollution hazards associated
with application of the ammonia addition control
process to reduce stationary source emissions.
ACCOMPLISHMENTS DURING 1977
A premixed, laminar flat flame is being used
to provide a prototype combustion environment for
developing and testing gas analysis procedures. A
new burner which was designed and fabricated at
Lawrence Berkeley Laboratory has been characterized,
and its ability to support a stable, reproducible
one-dimensional flame has been ascertained. Radial
and axial temperatures and velocity profiles have
been determined for a series of propane/air flames.
An analytical scheme for N2 and NO has been devel-
oped. A laboratory combustion tunnel has been
designed utilizing a propane/air burner followed
by a reaction duct, including a temperature
controller, ammonia injector and sampling ports.
PLANNED ACTIVITIES FOR 1978
A continuing review of developments in the
field of ammonia addition control technology will
be conducted through examination of the open
technical literature and direct contact with in-
dividuals and groups working in this field. This
information is essential to the study of the
secondary pollutant potential of the process. The
combustion tunnel will be constructed and its per-
formance will be characterized. A series of
experiments varying fuel nitrogen additive type
and concentration and equivalence ratio will be
conducted to assess the ammonia addition process.
N2, NO and NH3 concentrations will be measured
as a function of time following the ammonia addi-
tion. Other nitrogen compounds which are products
of the control process will be determined. The
effect of operating at off-design conditions of
temperature and mixture ratio will be determined.
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Budnitz, R. J. Combustion Research Program: chapter from Energy and Environment Division annual report 1977, report, January 1, 1978; Berkeley, California. (https://digital.library.unt.edu/ark:/67531/metadc1188304/m1/12/: accessed April 19, 2024), University of North Texas Libraries, UNT Digital Library, https://digital.library.unt.edu; crediting UNT Libraries Government Documents Department.