United States
Environmental Protection
Agency
Industrial Environmental Research
Laboratory
Research Triangle Park NC 27711
Research and Development
EPA-600/S9-83-001 May 1983
&EB\ Project Summary
Proceedings of the Fifth
Fundamental Combustion
Research Contractors Workshop
M. P. Heap
These proceedings are for The Fifth
EPA Fundamental Combustion Re-
search Contractors Workshop, held
January 23, 24. and 25, 1980, in
Newport Beach. CA. The purpose of
the workshop was to exchange infor-
mation between the various contrac-
tors engaged in fundamental combus-
tion research for EPA and to coordinate
their activities. In addition, the work-
shop provided for a review of EPA's
Fundamental Combustion Research
(FCR) Program by EPA's Science Ad-
visory Board. The five conference ses-
sions dealt with gas-phase chemistry
and heterogeneous NO reduction,
chemical and physical effects of ther-
mal decomposition, bench-scale reac-
tor studies, two-phase turbulent flames,
and model development
The main thrust of the FCR program
is elucidating the mechanism of NO
formation from fuel bound nitrogen.
Several papers addressed the gas-phase
conversion of fuel nitrogen species to
NO, N2, HCN. or NH3. Advanced diag-
nostic techniques were used to inves-
tigate the physical changes taking
place during the thermal decomposi-
tion of pulverized coal particles. Bench-
scale reactor data were presented on
the conversion of fuel bound nitrogen
to NO in liquid- and solid-fuel flames.
Studies on turbulent diffusion flames
included detailed characterization of
nonswirling coal flames and methods
of measuring droplet size from fuel oil
atomizers. Engineering analysis is a
strong component of EPA's FCR pro-
gram, and papers were presented on
the analysis of turbulent diffusion
flames.
This Project Summary was developed
by EPA's Industrial Environmental Re-
search Laboratory, Research triangle
Park. NC, to announce presentations
at the workshop that are fully docu-
mented in a separate report of the
same title (see Project Report ordering
information at back).
Introduction
This report summarizes the proceed-
ings of the Fifth EPA Fundamental Com-
bustion Research (FCR) Contractors Work-
shop, held January 23,24, and 25,1980,
in Newport Beach, CA. The workshop
brought together current EPA contractors
engaged in combustion research activities,
to ensure efficient technology transfer
between the various groups working in
related areas Members of EPA's Science
Advisory Board also attended the work-
shop to review the activities for EPA
management
The workshop was opened by W. &
Lanier of IERL-RTP, Project Officer for the
FCR program He welcomed the partici-
pants, expressing the hope that the work-
shop would be a forum for discussion and
interchange which would benefit all of the
projects. He informed the participants of
EPA/I ERL-RTFs Combustion Research
Branch activities in the area of NOx control
and how the research programs were
planned to provide input for the tech-
nology development programs. It was
stated that many of the research projects
had relatively short-term goals because
low-NOx systems were currently being
developed and installed However, in
keeping with the fundamental nature of
the program, several programs had been
included which were expected to pay off in
the long term.
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The FCR program focuses on the control
of NOX and primary related pollutants
generated by large, confined, one-atmos-
phere, turbulent diffusion flames from
pulverized coal, synfuels, or residual oils
which radiate to cold walls. The various
projects funded by FCR were selected to
provide a deeper insight into the spectrum
of processes characterizing these flames.
W. S. Lanier, EPA/IERL-RTP, chaired
Session I, Gas-Phase Chemistry and Heter-
ogeneous NO Reduction, which included
the following papers:
"Modeling of Fuel-Nitrogen Chemistry
in Combustion: The Influence of Hydro-
carbons," J. M. Levy, MIT Energy
Laboratory.
"Development of a Kinetic Mechanism
to Describe the Fate of Fuel Nitrogen in
Gaseous Systems," T. L Corley, Energy
and Environmental Research Corpora-
tion.
"NOX Formation in Flat, Laminar, Op-
posed-Jet Methane Diffusion Flames,"
W. A. Hahn and J. 0. L Wendt, University
of Arizona.
"The Formation and Destruction of
Nitrogenous Species During Hydrocar-
bon/Air Combustion," D. W. Blair,
Exxon Research and Engineering Com-
pany.
"Laboratory Scale Coal Studies," J. M.
Beer, A. F. Sarofim, J. M. Levy, D.
Altrichter, and L Timothy, Massachu-
setts Institute of Technology.
" Mechanisms of Nitric Oxide Reduction
on Solid Particles," G. G. de Soete,
Institut Francais du Petrole.
Papers in Session II, Thermal Decompo-
sition-Chemical and Physical Effects,
chaired by A. F. Sarofim, MIT, were:
"Volatility of Fuel Nitrogen," R Gay, A.
E. Axworthy, V. H. Dayan, and H. L.
Recht Rockwell International.
"High Temperature Pyrolysis of Oil
Droplet and Coal Particle Streams," J.
M. Beer, A. F. Sarofim, S. P. Hanson, and
A. K. Gupta, Massachusetts Institute of
Technology.
"The Characterization of Coals During
Thermal Decomposition," P. R Solomon,
United Technologies Research Center.
"The Physical and Chemical Effects
Occurring During the Thermal Decompo-
sition of Coal Particles and Oil Droplets,"
W. R Seeker, G. S. Samuelsen, and M.
P. Heap, Energy and Environmental
Research Corporation.
Session III, Bench-Scale Reactor Studies,
was chaired by J. P. Longwell, MIT. The
papers presented included:
"Pollutant Formation During the Com-
bustion of Residual Fuel Oils in a Well-
Stirred Reactor," M. Murphy, Battelle
Columbus Laboratories.
"Pollutant Formation from Combusting
Pulverized Coal Clouds," P. M. Goldberg,
H. Tong, and R. Kendall, Acurex Corpo-
ration.
"Reactor Studies to Assess the Impact
of Fuel Characteristics on Fuel NOX
Formation," M. P. Heap, D. W. Pershing,
G. C. England, S. L. Chen, R. Nihart, and
D. P. Rees, Energy and Environmental
Research Corporation.
"Pollutant Formation During Fixed-Bed
and Suspension Coal Burning," D. W.
Pershing, University of Utah.
The papers in Session IV, Two-Phase
Turbulent Diffusion Flames, chaired by W.
S. Lanier, were:
"An Experimental Approach to the Study
of Heavy Oil Spray Combustion in Shear
Layers," A. Vranos, United Technologies
Research Center.
"Spray Characterization," W. R. Seeker,
and G. S. Samuelsen, Energy and Envi-
ronmental Research Corporation.
"The Application of Droplet Sizing Inter-
ferometry and Holography to the Mea-
surement of Spray Droplet Size and
Velocity," C. F. Hess and W. D. Bachalo,
Spectron Development Laboratories.
"Characterization of Long Turbulent
Pulverized Coal Diffusion Flames," R.
Payne, The International Flame Research
Foundation.
The chairman of Session V, Model Devel-
opment was T. J. Tyson, Energy and
Environmental Research Corporation. He
introduced the following papers:
"Development of a Coherent Flame
Model for Turbulent Chemically React-
ing Flows," F. E. Marble and J. E.
Broadwell, California Institute of Tech-
nology.
"General Kinetic Analysis Codes," C. J.
Kau and T. J. Tyson, Energy and Environ-
mental Research Corporation.
Abstracts of Papers
Introduction to the Fifth EPA
Fundamental Combustion
Research Contractors
Workshop
W. S. Lanier
Organizationally, the Fundamental Con
bustion Research (FCR) Program is fun(
ed through the Combustion Researc
Branch (CRB) of EPA's Industrial Enviror
mental Research Laboratory at Researc
Triangle Park(IERL-RTP). The CRB chart)
calls for the development of emissic
control technology for pollutants gene
ated by stationary combustion source
through modification of the basic combu,
tion process. Consequently, the primai
focus of the FCR program is the formatic
and destruction of NOX in flames. Boile
firing pulverized coal and high-nitrog<
liquid fuels produce most of the N(
emitted by stationary sources. Thus, tl
projects funded as part of the FCR pr
gram concentrated on the mechanism
fuel nitrogen conversion in large tw
phase turbulent diffusion flames.
As regards the mechanics of the FC
program, when a particular research top
is selected for investigation, a number
options are open. If the prime contract
Energy and Environmental Research (EE
Corporation, has an existing expertise, o
no expertise is known to exist there is t
option to pursue the research topic at EE
This has been the dominant choice 1
numerical modeling activities. Other c
tions open include sole-source, limit
source, or full competitive procurement
general, the sole-source or limited co
petitive route has been selected. Anotf
option allows the CRB to fund the activ
directly through either a contract or gra
Consequently, a variety of contracting (
tions are available, and many have be
used.
Modeling of Fuel Nitrogen
Chemistry in Combustion: Tl
Influence of Hydrocarbons
J. M. Levy
Despite uncertainties in the currer
available mechanistic and kinetic d
base, it is possible to model (althoi
imperfectly) fuel nitrogen conversion
the presence of simple fuels. Unfortun<
ly, there is a strong coupling between 1
nitrogen and hydrocarbon chemistry.
the heat release mechanism for real fi
is complex, it is necessary to develo
methodology to treat the hydrocarl
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Tiechanism in some global manner which
:an be linked with the fuel nitrogen mech-
jnism. Consequently, the conversion of
:uel bound nitrogen in a hydrocarbon
combustion environment requires a reac-
ion mechanism which can be viewed as a
synthesis of three subsets: fuel nitrogen,
hydrocarbon oxidation, and hydrocarbon/
nitrogen interactions. The outstanding
phenomenological question raised in con-
nection with the modeling of hydrocarbon
chemistry pertains to the fate of the free-
radical pool. Hydrocarbon fragments ef-
fectively catalyze radical recombinations,
and free radical overshoots are much less
in hydrocarbon systems than in hydro-
carbon-free systems.
Development of a Kinetic
Mechanism to Describe the
Fate of Fuel Nitrogen in
Gaseous Systems
T. C. Corley
This paper concerns the development of
a kinetic mechanism which can predict
adequately the conversion of fuel nitrogen
compounds to NO in gaseous systems. A
four-step approach was used to develop
the mechanism: ( 1 ) assemble elements of
the reaction model, (2) select data sets for
malysis to resolve critical questions under
well-defined reaction conditions, (3) iden-
tify and correct deficiencies by comparing
with data generated in shock tubes and
flames, and (4) use the completed sub-
element of the reaction mechanism as a
known element of more complex systems.
Application of the procedure to elements
of the reaction model indicates:
• CH2O - CO - H2 - Oa system is
complete.
— HCO is important for chain-
branching in rich, wet CO flames.
— Decomposition and oxidation of
CHaO is slower than previous
predictions.
a mechanism requires addi-
tional analysis.
— Chain-branching path required:
NH2 + NO = N2 + H+OH.
— Ignition delay controlled by:
NH2 + 02 = HNO + OH.
— N2 HI species may be important
for rich processing of NHa.
— Overall oxidation of NHs too
slow with present mechanism.
• HCN-02 reaction model must be
compared with other data.
• Hydrocarbon mechanisms require
further study.
— Ignition delays for CH4-02 pre-
dicted
NOx Formation in Flat, Laminar,
Opposed-Jet Methane Diffusion
Flames
W. A. Hahn and J. 0. L Wendt
The detailed structure of a flat, laminar,
opposed-jet diffusion flame can be mod-
eled. By properly coupling the momentum
and energy conservation equations and by
using detailed finite rate combustion kine-
tics, it is possible to model the detailed
structure of a flat laminar, opposed-jet
diffusion flame.
Such a flame is one-dimensional, if the
proper velocity boundary conditions are
used. Measurements with a laboratory
CH4/N2/02 opposed-jet diffusion flame
gave good agreement with predictions
with respect to one-dimensionality, tem-
perature, and species profiles within the
reaction zone. However, the actual loca-
tion of the reaction zone was displaced
slightly. The theoretical/experimental
tool developed was used to test kinetic
mechanisms of NO formation from fuel
nitrogen. In this case, anhydrous ammonia
was introduced first with the fuel, and then
with the oxidizer. The formation of NO
was predicted reasonably well by using a
detailed kinetic mechanism developed by
others, when ammonia was introduced
with the fuel; but agreement was poor
when ammonia was injected in the air
side. This indicates that there are some
deficiencies in the ammonia pyrolysis
kinetic mechanism when it is used in the
absence of hydrocarbon fragments. The
qualitative dependence of the NO profile
on flame stretching was correctly pre-
dicted by the model.
The Formation and Destruction
of Nitrogenous Species During
Hydrocarbon/Air Combustion
D. W. Blair
An experimental investigation was car-
ried out of the critical aspects of the
formation and destruction of nitrogenous
chemical species during hydrocarbon/air
combustion. The primary purpose of the
work was to provide reliable experimental
information to aid in developing detailed
kinetic models. The experiments were run
in two significantly different laboratory
combustors over a wide range of indepen-
dent thermochemical variables (equiva-
lence ratio, temperature, fuel species, fuel
nitrogen species, and characteristic resi-
dence times). Two reactors, the jet-stirred
combustor and the multiburner, both de-
veloped with EPA funds, were used. Con-
clusions drawn from this work include:
• With both equivalence ratio and
flame temperature held constant,
specific hydrocarbon chemistry in-
fluences both thermal nitrogen fixa-
tion and fuel nitrogen conversion.
• Fuel chemistry is more important in
the multiburner than it is in the jet-
stirred combustor. Contributions
of combustion environment to this
difference appear to exceed those
of reaction time.
• While the conversion of fuel nitro-
gen depends on fuel nitrogen spe-
cies, the dependency in the multi-
burner considerably exceeds that in
the jet-stirred combustor. This ar-
gues that differences in combus-
tion environment between the two
combustors are important.
• Because: production of'fixed nitrogen
products differs significantly be-
tween the multiburner and the jet-
stirred combustor, choosing be-
tween these combustors, as mod-
els of given practical combustors,
should be based on which one best
approaches conditions that will exist
in the given combustor.
Laboratory Scale Coal Studies
J. M. Beer, A. F. Sarofim, J. M.
Levy, D. Altrichter, and L. Timothy
There is a possibility that, in pulverized
coal flames, NO produced early in the
combustion process is later reduced by
char generated by the partial combustion
of coal. Indirect evidence for the impor-
tance of NO reduction reactions in coal
combustors is provided by the observation
in pilot-scale combustors that the NO
concentration passes through a maximum
and undergoes substantial reduction in
later stages of combustion, particularly
under fuel-rich conditions. To assess the
role of char in reducing NO, a three-part
research program has been undertaken
involving: (1) determining kinetics of the
NO/char reaction under conditions of in-
terest to pulverized coal combustion, (2)
measuring temperature/time histories and
burning times of coal particles to provide a
basis for testing models for coal com-
bustors, and (3) using the kinetic informa-
tion to develop a model to predict (first)
char loading and temperature profiles, and
(then) the reduction of NO by char under
different simulated coal combustion con-
ditions. Preliminary data is presented on
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NO/char reactions and on the burning
temperatures and times of coal particles
for conditions encompassing the range of
interest in pulverized coal flames.
Mechanisms of Nitric Oxide
Reduction on Solid Particles
G. G. de Soete
In the last few years, attention has been
focused on the role played by flame-born
solid particles (e.g. soots, coal and char
particles, fly ash) in the process of in situ
(i.e., within the flame or in the hot combus-
tion products) heterogeneous reduction of
NOX. Three main problems must be
solved: (1) elucidating the kinetic mech-
anisms of heterogeneous NO reduction
under typical flame and flue gas condi-
tions, (2) determining the reaction rates
which control the disappearance of NO,
the formation of intermediate species, and
the rate of their transformation of N2, and
(3) checking the relevance of heterogen-
eous reduction paths compared to homo-
geneous reduction mechanisms. This
paper describes a study which will provide
information on the first two problems
using packed-bed reactors which will then
lead into a general investigation of the
heterogeneous NO reducing mechanisms.
Data are presented which indicate that
both IMH3 and HCN can be formed during
the reduction process, depending on the
type of solid and the gas-phase composi-
tion.
Volatility of Fuel Nitrogen
R L. Gay, A E. Axworthy, V. H.
Dayan, and H. L. Hecht
An experimental program has been
completed for the measurement of fuel
nitrogen volatility using a quartz two-stage
pyrolysis reactor. Solid and liquid fossil
fuels were heated in helium in the first
stage of the reactor at temperatures up to
1100°C The volatile nitrogen compounds
released were measured by converting
them to HCN in the second stage of the
reactor at 1100°C. The HCN was collected
in dilute sodium carbonate solution and
measured colorimetrically.
Twenty fossil fuel samples were stud-
ied, consisting of petroleum-based fuel
oils, synthetic oils from coal and shale, and
coals. All of the samples tested produced
the greatest yield of volatile nitrogen
compounds at a first-stage temperature of
1100°C. The maximum yields of volatile
nitrogen from petroleum fuel oils were 35-
48 percent of the nitrogen in the sample.
The yield curves increased continuously
from 300°C with a slight dip at 600-
750°C The maximum volatile nitrogen
yields from shale oils were 70-79 percent,
while the coal liquids yielded 50 percent
The nitrogen species in shale oils were
very volatile at low temperatures, giving
HCN yields of about 65 percent at a
pyrolysis temperature of only 200°C.
A variety of bituminous and lignite coals
were tested In general, the coals ex-
hibited much lower fuel nitrogen evolution
than did the fuel oils. Maximum coal
volatile nitrogen yields obtained at a pyrol-
ysis temperature of 1100°C were about
15-25 percent. A plot of the percentage of
fuel nitrogen converted to NO during
combustion (measured elsewhere) vs the
percentage of fuel nitrogen volatilized at
1100°C was found to give a strong linear
correlation with a variety of coals. This
correlation may provide an excellent means
of predicting NO formation for any given
coal, simply by measuring its nitrogen
volatility at 1100°C.
High-Temperature Pyrolysis of
Oil Droplet and Coal Particle
Streams
J. M. Beer, A. F. Sarofim, S. P.
Hanson, and A. K. Gupta
A series of high-temperature flow reac-
tor experiments were carried out with coal
particles under pyrolysis and combustion
conditions. Techniques are described to
study the pyrolysis of heavy liquid fuel
droplets. The purpose of these investiga-
tions was to provide kinetic data on fuel
nitrogen evolution and general volatile
release In addition, experimental evidence
was sought to determine if the ignition of
volatiles in the vicinity of coal particles
influences the further evolution of nitro-
genous compounds from the pyrolyzing
particle. Preliminary results indicate during
droplet pyrolysis the evolution rates of
fuel-nitrogen compounds are affected
strongly by rapid heating to high-tempera-
ture conditions similar to those encount-
ered in practical flames. The development
and application of a technique to obtain
time-resolved particle temperatures are
reported The nature of the data acqui-
sition, storage, and analysis permits statis-
tical studies to be made of coal particle
time/temperature histories. Information
of this type would perhaps explain the
observations which indicate different yields
of NOX from fuel of seemingly similar fuel
characteristics.
The Characterization of Coals
During Thermal Decompositioi
P. R. Soloman
A relation between coal organic struc
ture and the products of thermal decorr
position has been developed by measui
ing the modeling vacuum devolatilizatio
of 12 bituminous coals and a lignite. Th
relation allows the prediction of the tim
and temperature dependent evolution c
the major products of pyrolysis from
knowledge of the coal's functional grou
distribution using a general kinetic modi
with rate constants independent of co
rank. The model assumes that larc
molecular fragments (monomers) are n
leased from the coal "polymer" with on
minor alteration to form tar, while simi
taneous cracking of the chemical structu
forms the light molecules of the gas. At
chemical component of the coal can, ther
fore, evolve as part of the tar or as •<
independent species. The model may I
used to predict the amount of volatile fi
nitrogen evolved in pyrolysis, which
essential in estimating the conversion
fuel nitrogen to NOX.
The Physical and Chemical
Effects Occurring During the
Thermal Decomposition of Co
Particles and Oil Droplets
W. R Seeker, G. S. Samuelsen, f
P. Heap, J. 0. Trolezer, and
C. F. Hess
Events occurring during the them
decomposition of liquid droplets and c
particles in the initial stages of heat relez
in turbulent diffusion flames are of a
siderable significance to the designers
low pollutant emission combustors.
pulverized coal flames the partition off
nitrogen between the volatile and c
fractions, for example, will impact
production of fuel NO. Earlier studies hi
demonstrated that holography could
used to observe the behavior of coal \.
tides during combustion. The appro;
taken in the present study was to obse
particles/droplets under well-contro
conditions which simulated those encoi
ered in real systems. This was accc
plished by the construction of a reai
which allowed the particle/droplets tc
injected into high temperature ga
whose temperature and composition
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and high-speed photography. Two-color
particle pyrometry was used to measure
particle temperatures, and solid and gas-
eous samples were extracted to investi-
gate the variation of composition with
time. Initial evaluations of the results ob-
tained to date, on the physical phenomena
which occur during the thermal decom-
position of pulverized coal particles, in-
dicate that:
• Volatile coal fractions are ejected
from coal particles in jets; for large
bituminous coal particles, these jets
produce a trail of small particles.
• Coal composition and volatile evo-
lution rate influence particle tem-
perature.
• Large soot structures can be formed
from the bulk gases produced when
bituminous coal particles decom-
pose.
Pollutant Formation From
Combusting Pulverized Coal
Clouds
P. M. Goldberg, H. long, and
R Kendall
The objective of this experimental study
was to provide information on the mech-
anisms of coal combustion and subse-
quent NOX formation under conditions
similar to those found in the near-burner
region of a high-intensity pulverized coal
flame. A jet-stirred reactor system is used
in this study to simulate this type of
combustion environment The stirred com-
bustor can roughly simulate a flame region
where a high degree of recirculation is
present The first goal of the program was
to design a well-mixed coal reactor cap-
able of operating at residence times of 20-
200 ms. After completing the design and
fabrication, noncombusting mixing studies
were conducted to verify that a high level
of gas-phase mixing exists in the reactor.
Once gas-phase mixing performance was
verified, subsequent experiments were
directed at quantifying particle mixing
behavior. Combustion experiments began
after completion of this task
Combustion results show that devolatil-
ization may be essentially completed in
the 50-100 ms time range. The exhaust
concentrations and temperature depen-
dence on equivalence ratio are similar to
those expected in larger time scale sys-
tems. This might lead to the conclusion
that enhanced volatile yields play a major
role in combustion. It has been observed
that fuel nitrogen conversion is correlat-
able with equivalence ratio, reaction effici-
ency, and temperature. It was also found
that the nitrogen depletion of the char
corresponds roughly to the weight loss
exhibited by the char, although a limited
range of weight loss (75-95 percent) was
examined.
Reactor Studies to Assess the
Impact of Fuel Characteristics
on Fuel NO* Formation
M. P. Heap, D. W. Pershing, and
Q C. England
This paper describes results obtained to
date in two ongoing investigations to
assess the impact of fuel properties on
pollutant formation. The approach taken in
both investigations was experimental,
wherein both solid and liquid fuels were
burned in the absence of molecular nitro-
gen. The oxidant consisted of a mixture of
Oa, Ar, and C02 (21 percent by volume
Oa). The COa was added to maintain the
same adiabatic flame temperature for both
the artificial oxidant and air. NO formed
during combustion with this artificial N2-
free oxidant is called fuel NO.
Data are presented showing the impact
of fuel properties on NOX formation from
liquid fuels under both excess air and
staged conditions. These data indicate
that:
• The formation of fuel NO from
petroleum and alternative liquid
fuels mainly depends on their total
fuel nitrogen content.
• NOX control techniques for high
nitrogen fuels, which rely on the
generation of a high-temperature
primary fuel-rich zone, appear to
give the maximum opportunity for
NOX reduction.
Twenty-six coals have been tested under
fuel-lean conditions: it appears that al-
though fuel nitrogen content is important
it is not the only fuel characteristic dic-
tating fuel NO formation. It appears that
the volatility of the fuel nitrogen has an
important impact on fuel NO formation,
particularly under well-mixed conditions.
Under fuel-rich conditons, the coal com-
position impacts the gas-phase nitrogen
species distribution. With bituminous
coals, ammonia represents a substantially
smaller fraction of the total fixed nitrogen
than with subbituminous or lignite coals.
Of the nine coals tested in detail, only one--
a Utah bituminous-formed substantial
amounts of HCN under well-mixed condi-
tions. Contrary to liquid fuel, increasing
the temperature of a fuel-rich primary zone
does not appear to reduce stack emissions
from a coal-fired staged combustor.
Pollutant Formation During
Fixed-Bed and Suspension Coal
Combustion
G. P. Starley, S. L Manis, S. P.
Pearcell, D. M. Slaughter, and
D. W. Pershing
Recent large-scale pilot and field tests
have (at least partially) demonstrated the
potential of combustion modifications for
NOX control in stoker-fired boilers. The
overall objective of this program is to study
the formation of NOX and SOX under
carefully controlled experimental condi-
tions typical of stoker-fired boilers. In
particular, the following major research
areas are being considered: (1) the evolu-
tion and oxidation of fuel nitrogen and
sulfur, (2) the retention of SOX by ash
and/or solid-chemical sorbents in both
suspension- and fixed-bed burning, and
(3) the effectiveness of distributed air
addition for NOx control in stoker-fired
coal systems.
Results with the suspension furnace do
not support the hypothesis that a large
fraction of the NOX is formed in the over-
throw phase; however, many additional
heating rates must be studied before any
firm conclusions can be reached. The
following tentative conclusions have been
reached regarding the formation of NOX in
a fixed-bed combustion system:
1. NO formation is not uniform through-
out the burning time of the bed. The
formation maximizes early in the
process, prior to the peak combus-
tion rate, and then gradually de-
creases.
2. Staged air addition is a potentially
effective means of NO control.
Exhaust concentrations decrease
approximately linearly with decreas-
ing bed stoichiometry.
An Experimental Approach to
the Study of Heavy Oil Spray
Combustion in Shear Layers
A Vranos and B. A. Knight
This paper describes a two-phase pro-
gram: (1) design and fabrication of an
apparatus, and (2) preliminary combus-
tion experiments. A unique shear layer
mixing and combustion apparatus was
developed which simulates high-shear
diffusive combustion with heavy oil drop-
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let injection as found in the near-field
combustion zone of boilers and furnaces.
The apparatus provides: (1) two-dimen-
sional mixing and combustion of uniform
streams of air and rich combustion pro-
ducts fed from opposite sides of a splitter
plate, (2) uniform injection of a mono-
disperse heavy oil spray into the shear
layer by a linear array of fuel injectors
beneath the combustor wall, (3) control of
droplet path, residence time, and extent of
vaporization, (4) control of hot and cold
stream inlet properties, and (5) three-
dimensional probing of the flow field.
The design phase of the program con-
sisted of two tasks: aerodynamic and
thermodynamic design and mechanical
design. A wind tunnel, hot gas generator,
combustion chamber, droplet injection
system, and phase-sensitive sampling
probe were designed in the first task. The
design of the apparatus was influenced
most strongly by the diverse requirements
of the fuel injection system. The injector
was designed so that the angle of droplet
penetration into the shear layer could be
varied over a wide range. Droplet trajec-
tories were computed for vaporizing No. 6
oil droplets injected from the floor of the
combustor into a hot rich environment
provided by a hot gas generator. Hot gas
generator dimensions and injector loca-
tions were selected to accommodate the
required droplet trajectories, provide com-
plete vaporization if desired, and provide
sufficient hot soak time for substantial
conversion of fuel nitrogen compounds to
molecular nitrogen.
Spray Characterization
W. R Seeker and G. S. Samuelsen
A program has been established to
explain the dependence of NOX emissions
from fuel-oil fired combustors on atomiz-
ing nozzle type, and nozzle operating con-
ditions. Toward this end, a cold chamber
spray rig, patterned after the firetube sim-
ulator at EER, was built to characterize
nozzle spray behavior. As the initial step in
the program, nonintrusive optical tech-
niques are being applied and evaluated for
(1) consistency of data, and (2) applicabil-
ity to the study of spray behavior which
impacts NOX emission. The optical tech-
niques include diffraction, visibility, and
holography. At this juncture in the pro-
gram, visibility measurements are con-
cluded. Significant differences exist be-
tween these data and data acquired in an
independent program conducted at the
IFRF. The resolution of these differences
is not in progress.
The Application of Droplet
Sizing and Interferometry and
Holography to the Measurement
of Spray Droplet Size and
Velocity
C. F. Hess and W. P. Bachalo
Droplet sizing interferometry (DSI) and
laser holography are used in a fuel spray
study. The size and velocity distributions
of the fuel droplets produced by a Sonicore
nozzle in a cylindrical rig are obtained. The
two techniques are evaluated and com-
pared. The power and flexibility of the
interferometer in the study of the fuel
droplet size and velocity are demonstrated.
The data obtained by the two techniques
are compared and are shown to agree very
well. Although holography is adequate for
sizing droplets, the analysis of the holo-
grams is time-consuming. The DSI mea-
sures size and velocity of the individual
droplets, provides an immediate data dis-
play, and is therefore a very powerful
diagnostic tool for liquid sprays.
Development of a Coherent
Flame Model for Turbulent
Chemically Reacting Flows
F. E. Marble and J. E. Broadwell
The coherent flame model is applied to
the methane/air turbulent diffusion flame
with the objective of describing the pro-
duction of NO. The example of a circular jet
of methane discharging into a stationary
air atmosphere is used to illustrate appli-
cation of the model. In the model, the
chemical reactions take place in laminar
flame elements which are lengthened by
the turbulent fluid motion and shortened
when adjacent flame segments consume
intervening reactant The rates with which
methane and air are consumed and NO
generated in the strained laminar flame are
computed numerically in an independent
calculation. The model predicts NO levels
of about 80 ppm at the end of the flame
generated by a 30.5 cm (1 ft) diameter jet
of methane issuing at 3.05 x 103 cm/sec
(100 ft/sec). The model also predicts that
this level varies directly with the fuel jet
diameter and inversely with the jet velocity.
General Kinetic Analysis Codes
C. J. Kau and T. J. Tyson
A computer code, capable of predicting
or analyzing premixed or diffusion flames,
is reported The generality of the code
allows the computation of various con-
figurations; e.g. one-dimensional time-
dependent planar/spherical, steady two-
dimensional planar, and steady axisym-
metric nonrecirculating reacting flow sys-
tems. Physical phenomena such as laminar
unequal species diffusivities, radiation,
flame holder recombination effect and
heat loss are treated Several phenomeno-
logical turbulent eddy viscosity models,
based on mixing length theory, are also
incorporated into the coda Kinetically the
code can treat up to 200 two- or three-
body basic reactions and up to 52 species.
A linearized implicit finite difference
network is used. Thus, all the dependent
variables, except cross-stream velocity, of
all the grid points at the same coordinate
line (or at the same integration step) are
solved simultaneously in coupled fashion.
The inversion of a block tridiagonal matrix
is required at each integration step.
For illustrative purposes, detailed cal-
culation of four types of laminar flames are
presented: a flat flame, an opposed-jet
diffusion flame, a coflowing diffusion
flame, and a nonrecirculating confined
flame.
•&U. S. GOVERNMENT PRINTING OFFICE: 1983/659-095/1941
-------
M. P. Heap, compiler, is with Energy and Environmental Research Corp., Irvine,
CA 92714.
W. Steven Lanier is the EPA Project Officer (see below).
The complete report, entitled "Proceedings of the Fifth Fundamental Combustion
Research Contractors Workshop," (Order No. PB 83-164 483; Cost: $44.50,
subject to change} will be available only from:
National Technical Information Service
5285 Port Royal Road
Springfield, v'A 22161
Telephone: 703-487-4650
The EPA Project Officer can be contacted at:
Industrial Environmental Research Laboratory
U.S. Environmental Protection Agency
Research Triangle Park, NC 27711
United States
Environmental Protection
Agency
Center for Environmental Research
Information
Cincinnati OH 45268
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Fees Paid
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