United States
Environmentaf Protection
Agency
Air and Energy Engineering
Research Laboratory
Research Triangle Park, NC 27711
Research and Development
EPA/600/S7-88/001 Apr. 1988
&ERA Project Summary
Fundamental Combustion
Research Applied to Pollution
Formation: Volume II.
Physics and Chemistry of
Two-Phase Systems
W.R. Seeker and M.P Heap
As a part of EPA's Fundamental
Combustion Research (FOR)
Program, eight studies were
conducted by various investigators
to better understand the physics and
chemistry of two-phase combustion
with respect to pollution formation.
Reports from these studies are
grouped into three sections, bound
separately, which comprise Volume II
of the FCR report series. Volume Ha
describes mechanisms of fuel
nitrogen processing in large-cale
utility flames burning pulverized coal
and heavy fuel oils, in three parts: (1)
The High Temperature De-
composition and Combustion of
Pulverized Coal (EERC); (2) Detailed
Measurement of Long Pulverized
Coal Flames for the Characterization
of Pollutant Formation (International
Flame Research Foundation; and (3)
Heavy Oil Combustion in Shear
Layers (United Technologies
Research Center). Volume lib gives
information on the influence of
various combustion parameters (i.e.,
fuel type, stoichiometry, residence
time, temperature and mixing) on the
fate of volatile fuel nitrogen, in four
parts: (1) Method for Characteriza-
tion of Coal During Thermal
Decomposition (United Technologies
Research Center); (2) The Volatility of
Fuel Nitrogen Species (Rockwell); (3)
Stirred Reactor Study of Pollutant
Formation from Combusting
Pulverized Coal Clouds (Acurex) and
(4) Pollutant Formation from Com-
bustion of Fuel Oils in a Well-Mixed
Combustor (Battelle). Volume lie
gives information on the kinetic rates
and mechanisms of nitrogen oxide
(NO) reduction on solid particles, in
three parts: (1) Trials on NO and NH3,
Alumina, Quartz, Graphite, and Soot;
(2) Comparative Study of Coal and
Char; and (3) Trials on Fly Ashes and
Study of Reactions Involving
Hydrogen Cyanide (Institut Francais
du Petrole).
This Project Summary was
developed by EPA's Air and Energy
Engineering Research Laboratory,
Research Triangle Park, NC, to
announce key findings of the research
project that is fully documented in
three separate volumes of the same
title (see Project Report ordering
Information at back).
Introduction
The EPA has conducted a wide range
of research projects under its
Fundamental Combustion Research
Applied to Pollution Formation (FCR)
program. The principal goal of the FCR
program was to generate the
understanding of combustion behavior
necessary to help develop control
strategies to minimize nitrogen oxide
(NOX) emissions from stationary sources.
Because of the increased use of coal and
residual fuel oils, the dominant stationary
-------
source of NOX for the foreseeable future
is the conversion of nitrogen in the fuel.
This observation implies a need to
understand the various phenomena
associated with burning fuels containing
high levels of nitrogen.
The FCR program involved program
planning, management, and synthesis of
the overall program, and subcontracting
to various organizations separate projects
included within program elements.
Subcontracts accounted for 70% of the
program and were used to ensure that
FCR had the benefit of the best scientific
talent available. Every effort was made to
use subcontractors who had the
necessary experience and, in many
cases, equipment to produce quality
results in a short time frame.
A wide variety of combustion
phenomena can have a direct impact on
the NOX emission rate from pulverized
coal and residual oil fired boilers. The
FCR program structure, described in
Figure 1, was established to allow for
investigation into phenomena believed to
be critical to meeting the program goals.
Three major program areas were
augmented by two program support
areas. The major program area.Transport
Process in Reacting Systems allowed for
studies into the ballistics and fluid
mechanics of bringing fuel and air into
contact with each other and into the
transport of the reacting mixture under
boiler conditions. The major program
area, Physics and Chemistry of Two-
Phase Systems, is devoted to
understanding the decomposition and
processing of solid and liquid fuels as a
function of the reactive environment and
local thermal conditions. The Gas Phase
Chemistry major program area was
provided to better understand the gas
phase reactions leading to NO formation,
particularly reactions involving
nitrogenous species from fuel
devolatilization. The two program support
areas, Analytical Tool Development and
Measurement Systems were provided to
assist in performing experiments and
analyzing data. This program structure is
designed to permit studies into a wide
variety of areas influencing NOX
formation and control. It also permits
focusing individual studies leading to two
major program outputs:
- A description of the chemical limits
on NO production in order to
ascertain the lower bounds of both
fuel and thermal NO production
under a series of process constraints
which were not limited in any way by
fuel/ air contacting.
- A description of fuel NO formation in
turbulent diffusion flames for gas,
liquid.and pulverized coal systems.
Documentation of research performed
under the FCR program is contained in
four basic volumes and a special report.
Each volume (or volume series reports
on the work accomplished in a major
program area or program support area.
Volume I (EPA-600/7-85-048) covers
work in the Gas-Phase Chemistry
program area. Volume II addresses
Physics and Chemistry of Two-Phase
Systems, Volume III is devoted to the
FCR effort in Measurement Systems.and
Volume IV is concerned with Analytical
Tool Development and Transport
Processes. In addition, a special report
(EPA-600/7-85-048) has been issued
to document the proceedings of a
workshop held by FCR contractors.
Most of the FCR effort was devoted to
the Physics and Chemistry of Two-
Phase Systems program area which
consisted of eight individual research
projects. Accordingly, Volume II has
been subdivided into three separately
bound components denoted as Volumes
Ha, lib, and He.
Physics and Chemistry of
Two-Phase Systems
The critical processes which must be
addressed to understand the interplay
between two-phase combustion and
pollution formation are listed in Figure 2.
The processes are displayed in relative
position against a photograph of an
actual turbulent pulverized-coal
diffusion flame. The ability to address
these processes represents the
benchmark of the accomplishments of
the FCR program in this major program
area. The processes, and, therefore, the
important areas of research, are:
Ignition. The ignition of flames influences
not only stability, which is an
extremely important operating
parameter, but also premixing which
can strongly impact fuel nitrogen
conversion.
Physical Processes During Devola-
tilization. The mechanism by which
volatiles are released from the coal
matrix can dramatically influence a
wide variety of phenomena including
temperature response, ignition, the
environment in which volatile
nitrogen will react, and soot
formation. Very little is known about
how pulverized coal or fuel oil
actually decomposes in flames.
Nitrogen Devolatilized. Bench-scale
tests indicate that the conversion 4
volatile nitrogen is the largest
contributor to total fuel nitrogen
conversion to NO. Also, the volatility
of fuel nitrogen is strongly tied to the
fuel type and the time/temperature
history of the particular application
therefore, it is imperative that the
volatility of fuel nitrogen be
understood if the conditions fo
minimum fuel nitrogen conversior
are to be generalized.
Species Evolved and Fraction of Mas;
Devolatilized. The amount o
hydrocarbon species evolved from
the fuel is expected to impact th<
local stoichiometry, soot formation
and the local temperature; also, th<
impact of fuel type am
time/temperature history is not we
understood. Of particular interest i
the form the nitrogenous compound
and the light and heavy hydrocarbo
yield.
Temperature Response. The temperatur
response of the fuel particles c
droplets influences almost a
aspects of the pollution forme
sequence. Little is known about wh;
factors influence the particl
temperature and how that paramete
in turn, affects other parameters.
Soot Formation. Soot formation i
important because it is a primai
pollutant itself, it can act as a smoli
limit to how rich the primary stac
can be taken, and it can act as
source of carbonaceous material c
which fuel nitrogen species can t
reduced to molecular nitrogen. Tt
mechanisms of soot formation fro
pulverized coal and fuel c
combustion have as yet not be<
explored. Little is even known abo
the amounts of soot formed in sui
flames.
Char NO Reduction. NO can react wi
heterogeneous particulate to I
reduced to molecular nitrogen. T
degree to which this occurs f
flame-formed particulate, and unc
what conditions, is not known.
Char Nitrogen Conversion to NOX. T
traditional staging Iow-N0x conc<
addresses only the volatile nitrog
species. The conversion of t
nitrogen that remains in the char
NO thus represents the ultimate lii
that can be achieved using stag
combustion. The conversion of i
remaining char nitrogen needs to
explored if this limit is to be lower
Further, questions remain concern
how the first-stage processi
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Major Program Areas
Transport Process in
Reacting Systems
Physics and Chemistry
of Two Phase
Systems
Gas Phase Chemistry
Reactor Flame
Experiments
Program Elements
Program Support Areas
Kinetic
Mechanism
Development
Analytical Tool '•'•
Development
Measurement
Systems
Heterogeneous
NO Reduction
Description of Fuel
NO Formation
in Turbulent
Diffusion Flames
Chemical Limits of
NO Production
/VO» Control
Strategy
Figure 1. FCR-I program structure.
-------
Ignition
Physical
Processes
During
Devolatilization
Char Burnout
Time
Char Nitrogen
Conversion
to NO,
Char NO
Reduction
Fraction of Mass
Devolatilized
Soot
Formation
• Fuel Effects
• Influence of Time/Temperature/Stoichiometry History
Figure 2. Critical processes influencing the fate of fuel nitrogen in pulverized coal flames.
influences the subsequent character
and reactivity of the char. This can
be an important aspect of whether
the char will burn out within the
combustor volume.
A program plan was developed to
both determine what questions were
necessary for the development of
multimedia control technologies for
stationary sources and to address those
questions. It was not possible to address
every issue, but a focused program
evolved which was directed toward the
important issues of relevance to the
Combustion Research Branch (CRB) of
EPA in order for the results to be
applied. This major program element
(i.e., the physics and chemistry of two-
phase combustion) consisted of eight
well-defined priority target areas,and
the ensuing research effort was guided
toward the specific problem of the area.
The target areas and the individual
projects which made up these areas are:
Flame Combustion Processes (Volume
Ha)
The High Temperature Decomposition
and Combustion of Pulverized
Coal - EER
Detailed Measurement of Long
Pulverized-Coal Flames for the
Characterization of Pollutant
Formation - International Flame
Research Foundation
Heavy Oil Combustion in Shear Layers
- United Technologies Research
Center
Devolatilization and Volatile Reactions
(Volume Mb)
Method for Characterization of Coal
During Thermal Decomposition -
United Technologies Research
Center
The Volatility of Fuel Nitrogen Species -
Rockwell
Stirred Reactor Study of Pollutant
Formation from Combusting
Pulverized Coal Clouds - Acurex
Pollutant Formation from Combustion of
Fuel Oils in a Well- Mixed
Combustor - Battelle
Heterogeneous NO Reduction (Volume
lie)
Mechanisms of Nitric Oxide Reduction on
Solid Particles - Institut Francais
du Petrole
The first program area (Volume I la)
consists of programs to define the
physical and chemical processes
-------
occurring in large scale utility flames
lurning pulverized coal or heavy fuel
oils. The major emphasis is on
understanding the mechanisms of fuel
nitrogen processing in flames of this
type, developing a data base for model
development,and exploring scale effects.
The second area (Volume Mb) considers
only the devolatilization and early
combustion processes. The programs in
this area were designed to yield
information on the influence of
combustion parameters such as fuel
type, stoichiometry, residence time,
temperature, and degree of mixing on
the fate of volatile fuel nitrogen. The final
area (Volume lie) provides information on
the kinetic rates and mechanisms of
heterogeneous NO reduction for typi-
cal combustion-generated particulate,
which are necessary to assess the
relative importance of heterogeneous
reduction processes.
Volume Ha - Flame
Combustion Processes
This volume consists of final
documentation on three individual efforts
dealing with flame combustion
processes.
High Temperature
Decomposition and Combustion
of Pulverized Coal (EER)
Despite the fact that coal has been
burned for decades and has been the
subject of study for nearly as long, little
is actually known about the physical
processes occurring to the individual coal
particles and their close environment.
The purpose of this study was to fill this
data gap by directly observing the
microscale phenomena that occur around
individual coal particles as they burn in
an environment simulating large-scale,
turbulent diffusion flames.
The experimental facility employed
was a downfired flat-flame burner with a
centerline port for injection of pulverized
coal particles. The methane/air fired
flat-flame burner produced a
background of hot reaction products. As
the pulverized coal particles entered this
environment, they were ignited and
produced a long flame which was
remarkably similar to many practical
boiler flames.
A variety of optical and intrusive
measurement techniques were em-
ployed to examine the microscale
phenomena associated with the burning
coal particles. Both holography and high
speed shadowgraph photography were
used to visualize the burning particles.
Two color optical pyrometry was used to
measure the particle temperature,and
sodium D line reversal was used to
measure gas temperature. Extractive
sampling was employed to determine the
local gas chemical composition and to
examine the morphology of the
particulate.
Figure 3 presents a mosaic of flame
observations and indicates spatial
variation of surface morphology and the
local environment of the burning coal
particles. Photographs from re-
constructed holograms (on the righthand
side of Figure 3) indicate that the
devolatilizing coal particles can produce
a cloud of soot particles which are seen
to collapse into long fiberous shapes.
These results were the first experiments
to indicate the formation of either the
soot cloud or the long structures. The
experimental program includes trial
series examining coal type, initial particle
size, particle injection velocity and
background gas temperature and
stoichiometry.
Detailed Measurements of
Long-Pulverized Coal Flames
for the Characterization of
Pollutant Formation (IFRF)
This study utilized state-of-the-art
measuring techniques to characterize in
detail a number of long pulverized coal
flames under well-defined input and
boundary conditions. These experiments
were relatively large scale, having been
conducted in a 1.9 x 1.9 m cross section
furnace fired at the 2 MWt level.
Measurements in these flames
included the determination of local gas
and solids compositions and concentra-
tions, temperatures, and radiative and
aerodynamic characteristics. The mea-
surements were of sufficient detail for
use in validation of predictive procedures
both for global combustion processes
and for specific phenomena relating to
coal particle combustion.
The flames for all six trials were
produced with a very simple double
concentric, parallel-flow burner system.
This burner system generates long
flames which are far-field dominated
and where the heat release is protracted.
Such flame shapes exhibit the real
characteristics of certain classes of
furnaces flames such as cement kilns
and possibly tangentially fired boilers.
Further, the far-field domination
significantly simplifies the problem of
mathematically simulating the process.
Thus, the experimental results reported
represent an initial data base for
developing a verified model of pulverized
coal combustion in a practical furnace
environment.
The six long coal flames investigated
represent variations due to air and fuel
input velocities and temperatures. These
variations have a direct impact on the
flame mixing characteristics and on the
coal particle heating rate. Complete flow
field mapping data are presented in both
graphic and tabular form. Despite many
difficulties encountered in measuring in
such flames, particularly for sampling in
regions of nigh temperature and solids
concentrations, the consistency between
the various measurements is generally
good. Indications are that globally the
combustion is controlled by mixing and
that the influence of fuel kinetics is
basically the same in all cases. In
particular, NHa concentrations are always
very low, while HCN was found to form
very rapidly and in large amounts More
detailed evaluation of these data is still
required for a quantitative interpretation
of fuel nitrogen conversion to HCN and to
NO.
Heavy Oil Spray Combustion in
Shear Layers (UTRC)
This program consisted of two phases:
(1) design and fabrication of an
apparatus, and (2) preliminary
combustion experiments A unique shear
layer mixing and composition apparatus
was developed which simulates high
shear, diffusive combustion with heavy oil
droplet injection as found in the near-
field combustion zone of boilers and
furnaces. The apparatus, shown in Figure
4, provides:
(l)Two-dimensional mixing and
combustion of uniform streams of air
and rich combustion products fed
from either side of a splitter plate.
(2) Uniform injection of a monodisperse
heavy oil spray into the shear layer
by means of 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.
(5)Three-dimensional probing of the
flow field.
The design phase of the program
consisted 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 initially. The design
-------
CH'4/'Air Main
Burner Flow I
Coal and
''Transport Air
CHt/Air
Dilution Flow
~a25J"^Water Cooled
Sintered
Copper Disk
Holograms
A/ote; / in. = 2.54 cm
Figure 3. Coal flame visualization.
-------
• Perforated Plates
60% Open
Honeycomb Flow
Straighteners
Air Inlet
Movable Injector Box
Fuel Manifold
Splitter Plate
Vibrator
Droplet Injector
Figure 4. Heavy oil spray combustor.
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
trajectories 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 locations were selected to
accommodate the required droplet
trajectories, provide complete vapori-
zation if desired, and provide sufficient
hot soak time for substantial conversion
of volatile fuel nitrogen compounds to
molecular nitrogen. The design of a low
turbulence wind tunnel, combustion
chamber, and phase sensitive probe
completed this task.
Due to program time constraints, only
initial system verification tests were
performed during this effort. The testing
which was performed consisted of (1)
verification of uniform properties of the
hot and cold streams at the splitter plate
trailing edge, (2) demonstration of high
injection velocities and uniform droplet
size and penetration with No. 2, 5, and 6
oils in vibrating multicapillary injectors,
(3) determination of stable flow regimes
as a function of primary and secondary
stream velocities, (4) flame stability and
flashback studies, (5) high speed
cinematography of the shear layer with
injection of No. 2 and 6 fuel oil, and (6)
preliminary flame probing.
Volume 11 b - Devolatilization
and Volatile Reactions
This volume consists of final
documentation of four efforts dealing with
devolatilization and reaction of volatile
components. As such, the studies
concentrate on the early flame zone
processing of high nitrogen fuels.
Method for Characterization of
Coal During Thermal
Decomposition (UTRC)
This study is a continuation of an
earlier effort to develop a model of the
coal devolatilization process. Basically,
the model assumes that a coal particle
can be represented as a series of
functional chemical groups which are
-------
split into tar-forming and non-tar-
forming fractions. The functional groups
include carboxyl, hydroxyl, two ether,
non-volatile, aliphatic, aromatic
hydrogen, and carbon as shown in
Figure 5.
The evolution of each component into
a gas phase (carboxyl into COg, aromatic
hydrogen into H2, etc.) is represented by
a first order function of the form Y(i) =
Y°(i)exp(-Kjt). There are two ether
components since CO is typically
evolved in two distinct steps. Values for
the initial coal composition representation
are derived from quantitative infrared
measurements, ultimate analysis,and
pyrolysis data for the particular fuel.
When coal particles thermally
decompose, a substantial portion of the
initial mass is evolved as a tar. Infrared
analysis of these tars shows that their
spectra are very similar to those of the
parent coal, except that the tar has
enhanced aliphatic content. The
evolution of the tar is represented by a
first-order diminishing of the tar forming
fraction according to X = X°exp(-Kxt).
The kinetic rate constants KC and Kx
are represented by Arrhenius
expressions derived from experimental
data. The thrust of the current program
was to expand the model to include
nitrogen evolution and to examine,
theoretically and experimentally, a series
of coals being used in other EPA NOX
control development programs. The ex-
perimental studies included vacuum and
1-atmosphere thermal decomposition
studies. The vacuum experiments were
performed in a heated grid facility which
allowed the coal sample to be heated at
a controlled rate to a specific final
temperature. Fourier transform infrared
analysis was used to monitor the volatile
yield and speciation as a function of
time. The 1-atmosphere experiments
were performed in an isothermal furnace
and allowed for particle heating rates one
to two orders of magnitude greater than
in the heated grid trials. These latter
tests included examinations of the
various coals as well as studies of the
high temperature thermal decomposition
of the tars.
The various results obtained in this
study provide insight into the thermal
decomposition process but also indicate
the need for significant modification to
the basic hypotheses of the model.
Specifically, it was observed that the
volatile product distribution and evolution
rates are sensitive functions of physical
parameters such as thermal drive, final
temperature, and initial particle size.
Thus, variations in product distributions
are not simply the result of variations in
the functional group mix of the parent
coal. An initial attempt to modify the
model is presented as part of this report.
The basic result, however, is that
additional theoretical and experimental
studies are required to produce a
generally acceptable model of coal
decomposition.
The Volatility of Fuel Nitrogen
Species (Rocketdyne/Rockwell)
This FCR program task is a
continuation of an earlier EPA sponsored
program where a two-stage inert
pyrolysis reactor was developed to study
the evolution of fuel nitrogen species.
That earlier study showed that reactive
volatile nitrogen evolved from the fuel in
the first-stage pyrolysis process is
converted to HCN in the second stage
when the second stage is held at about
1400 K. This two-stage reactor tech-
nique, therefore, permits a simple
measurement of the reactive nitrogen
yield from fuel thermal decomposition.
The thrust of this task was to
examine samples of various fuels being
used in other CRB-sponsored NOX
control development programs. A total of
19 fuels (including residual oils, coal
derived liquids and coals) were subjected
to the two stage pyrolysis process,and
the HCN yield was compared to NO
production from controlled combustion
tests.For the seven coals tested, an
encouraging correlation was developed
relating the HCN yield from pyrolysis to
the percent conversion of fuel bound
nitrogen to NOX in the combustion tests.
This correlation, shown in Figure 6,
generates several concerns about its
generality and fundamental basis, but the
results do indicate a possible approach
for relating NOX production potential to
the chemical characteristics of the fuel.
Pollutant Formation from
Pulverized Coal Clouds and Fuel
Oils
The third and the fourth tasks were
to develop coal- and oil-fired well-
stirred reactors to simulate the early
processing of fuels in commercial
boilers. The coal-fired reactor
development program report is entitled,
Stirred Reactor Study of Pollutant
Formation from Combusting Pulverized
Coal Clouds (Acurex). The oil-fired
reactor development program report is
entitled, Pollutant Formation from
Combustion of Fuel Oils in a Well-
Mixed Combustor (Battelle). |
The major portion of both tasks was"
devoted to developing and characterizing
the facilities. In each case, cold flow
models were first constructed to evaluate
the basic design concepts and to
demonstrate the ability to produce a high
degree of stirring in the two-phase
environment. Next, reacting versions of
the facilities were constructed, and ex-
tensive characterization experimentation
performed. These tests revealed
problems with each facility which casts
uncertainty on the interpretation of
experimental data. For the coal-fired
reactor, the gas phase appeared to be
well stirred, but the solid phase had
much more of a plug flow character.
Further, a strong hysteresis effect was
associated with the fuel injectors. For the
oil-fired facility, a significant fraction of
the fuel spray impacted the furnace walls,
thereby distorting the early fuel reaction
process. Limited combustion testing was
performed in both programs, but the
above noted experimental difficulties cast
doubt on data interpretation.
Volume lie • Heterogeneous
NO Reduction
This report documents a study
performed at the Institut Francais di
Petrol into the heterogeneous reaction o
NO (and other nitrogenous species) or
solid-phase material typically found ir
industrial flames. This extensive
systematic study was performed in <
packed-bed reactor maintained a
controlled temperatures. Meterei
quantities of gaseous reactants flowe<
through the bed, and the outle
composition was monitored as a functioi
of time and reactor conditions.
The program involved systematicall
varying the complexity of the be
material, beginning with alumina, an
building to soot and coal char. The ink
composition of the reacting gases wa
also systematically varied, beginning wit
CO/argon mixtures. Hydrogen and the
hydrocarbons were added. As regard
nitrogenous species, the study include
NO, Na, NHa, and HCN as input reactai
gases. The experimental approac
included experiments with each mixtui
(gas- and solid-phase) of sufficiei
detail to extract global, intrinsic reactic
rates and overall reaction order.
This experimental program, thouc
massive in scope, should be considere
an initial screening exercise to identi
what heterogeneous reaction paths are
potential importance to defining the N
-------
Gas
Char
a) Functional Group Composition of Coal
bj Initial Stage of Decomposition
Non-Tar Forming
Fraction (1-X°)
Tar Forming
Fraction X°
c) Later Stage of Decomposition
W//////,
X
•H2O~
•CO-
Etc
xiaeoeooeaeoeoQeofleoflooaaaeflt
d) Completion of Decomposition
ft
\
Figure 5. Basic coal devolatilization model.
emission level from pulverized- coal-
fired experiments. Of particular
significance is the sequence of reactions
involving HCN and NHa on soot. As
noted in the earlier discussion the study
of coal thermal decomposition (Volume
lla),the early devolatilization process is
often accompanied by the formation of a
cloud of soot particles. This environment
(see Figure 3) closely resembles a
packed-bed reactor and represents a
field of solid material through which the
coal volatiles must pass. The intrinsic
rate data developed indicate that
heterogeneous reactions of HCN and
NHa with soot may lead to formation of
molecular nitrogen.
-------
50
40
in
3
•Q
O
o
o
30
20
10
BC19
% to NO= -0,013 + 1.99 (% to HCN)
I
5 10 15 20 25
Percent Fuel-N to HCN in Pyrolysis at 1100°C
Figure 6. Percent NO in combustion vs. percent HCN in pyrolysis at 1100°C.
*U.S.Government Printing Office: 1988 — 548-158/67113
10
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