United States
Environmental Protection
Agency
Air and Energy Engineering
Research Laboratory
Research Triangle Park NC 27711
Research and Development
EPA/600/S7-87/018Sept 1987
&EPA Project Summary
Evaluation of Utility Boiler Radiant
Furnace Residence Time/
Temperature Characteristics: Field
Tests and Heat Transfer Modeling
B. M. Cetegen, W. Richter, J. L Reese, J. LaFond, B. A. Folsom, and R. Payne
This report describes an investigation
of the adequacy of a modeling approach
in predicting the thermal environment
and flow field of pulverized-coal-fired
utility boilers.
Two 420 MW. coal-fired boilers were
evaluated: a single-wall-fired unit and a
tangentially fired unit, representing the
two commonest boilers in the U.S.
Extensive field measurements were
conducted on each unit to determine
detailed temperature, heat flux, gas
species composition, and flow field data
for a range of operating conditions.
Separate modeling approaches were
used to predict boiler thermal per-
formance and flow characteristics. A
three-dimensional zone method of
analysis was used to predict local and
overall heat transfer, temperature pro-
files, and fuel burnout. Such predictive
tools provide a sophisticated treatment
of radiative (Witt transfer, but are de-
coupled from the furnace flow field.
This input to the heat transfer code was
obtained from detailed measurements
in reduced scale isothermal physical
flow models of the two boilers.
Comparisons between model predic-
tions and the detailed field measure-
ment data have demonstrated the
viability of this approach in predicting
furnace performance, and in extrapo-
lating limited available data to alternate
operating conditions. Overall thermal
performance can, in general, be ac-
curately predicted; however, the analy-
sis has shown that the correct quantita-
tive prediction of local temperatures
and other properties requires an ac-
curate specification of inhomogeneities
in boiler input conditions, in the boiler
flow field, and in the local distribution
of wall ash deposits.
This Protect 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 docu-
mented In a separate report of the same
title (see Project Report ordering In-
formation at back).
Introduction
The injection of dry calcium-based
sorbents into the furnace zone of coal-
fired utility boilers (referred to as the
LIMB process) offers the potential for a
cost effective in-situ SO2 control tech-
nology. However, the effectiveness of the
process is very strongly dependent on the
boiler thermal environment, particularly
the temperature/time relationship experi-
enced by the sorbent particles. For
example, the ultimate reactivity of the
sorbent material is very sensitive to the
heating rate and to the peak temperature
levels experienced by the particles. Hence,
optimum sorbent activation requires in-
jection at the appropriate thermal en-
vironment in the boiler. On the other
hand, optimum sorbent reactivity must
be accompanied by mixing and dispersion
of the active sorbent particles in the
furnace gases. Sulfation progresses most
effectively in the temperature window
800-1200°C and requires residence times
on the order of 1 sec. This provides
-------
further constraints on the effectiveness
of the process. Such considerations in-
dicate that a detailed knowledge of boiler
thermal environment and the flow field is
necessary for a given boiler application,
both for predicting S02 removal potential,
and in designing an effective sorbent
injection system.
In order to generate the necessary
boiler information, a purely experimental
approach can be taken, where detailed
in-furnace measurements of gas tem-
peratures and velocities can be made for
each individual coal-fired boiler of interest.
However, such an approach requires
many traverses to fully characterize the
complex three-dimensional temperature
and velocity fields typical of most utility
boilers. Consequently the necessary
measurement programs can be time-
consuming and expensive. An alternative
approach is to use a methodology based
on state-of-the-art analytical or modeling
techniques. Such a methodology, if
authenticated, could offer a faster, less
expensive, and more flexible approach
than that provided by purely experimental
methods.
This report summarizes an EPA-
sponsored research program, the primary
objective of which was to investigate the
adequacy of a modeling approach in pre-
dicting boiler thermal environment and
flow field. The program has included:
• Reviewing available furnace thermal
prediction procedures and flow
models, and selecting a suitable
method to evaluate temperatures
and flow fields in boilers.
• Field tests at two coal-fired utility
boilers (wall-fired and tangentially
fired, representing the two com-
monest boilers in the U.S.) to docu-
ment thermal environment and flow
characteristics.
• Modeling test cases with the selected
heat transfer/flow model.
• Comparing model predictions with
field data.
• Determining the adequacy and ac-
curacy of such an approach for future
predictive evaluations.
Heat Transfer and Flow
Modeling Approach
In this study separate modeling ap-
proaches have been used to predict boiler
thermal performance and flow field. A
three-dimensional general boiler thermal
analysis code was used to simulate test
conditions for which extensive tempera-
ture, heat flux, and gas species composi-
tion data were obtained at two boilers.
This heat transfer code is decoupled from
the furnace flow field, but includes a
sophisticated treatment of the radiative
heat exchange process (mostly respon-
sible for heat exchange in utility boilers)
and a fully coupled solution of heat
balances in a zonal description of the
furnace enclosure. Since the furnace flow
field is an input to the heat transfer code,
it was obtained from isothermal physical
flow modeling for the two boilers. Al-
though there are purely analytical ap-
proaches to flow field prediction, many
uncertainties, assumptions, and difficul-
ties are associated with these approaches,
such that fully mathematical solutions
are available only for simple geometries.
Consequently, reduced scale physical
modeling is now the preferred approach.
The heat transfer model, used to predict
the thermal behavior of the two test
boilers in this program, was EER's three-
dimensional General Boiler Thermal
Analysis Code (GBTAC). This is just one
of several available codes which are based
on the zone method of analysis, and
which are finding increasing application
in the prediction and design of practical
combustion systems. Such heat transfer
codes allow predictions of local and
overall heat transfer, temperature profiles,
and fuel burnout in boiler combustion
chambers and industrial furnaces depen-
dent on actual furnace geometry, oper-
ating conditions, and fuel and wall deposit
characteristics. All major fuel types can
be considered. The EER code can also
handle heat transfer in radiant super-
heater sections simultaneously coupled
with the lower radiant furnace heat
transfer calculations.
The furnace heat transfer model is
decoupled from momentum balances.
Thus, zonal balances of energy, volatile
matter, char particles, and O2 are based
on a prescribed mass flux distribution for
calculating convective transport over the
volume zone boundaries. Such decoupling
is typical of zone models, and allows
concentrating the computational effort
on an accurate simulation of radiative
heat transfer This has been found neces-
sary for reliable thermal performance
predictions of large boiler furnaces.
In this present study the distribution of
mass fluxes through the zone arrange-
ment of the heat transfer model was
obtained through observations and mea-
surements in isothermal physical flow
models.
Test Boilers
In this study, two coal-fired boilers (a
wall-fired boiler, and a tangentially fired
boiler) were evaluated. Each boiler was
subjected to an intensive period of mea-
surement, where detailed in-furnace
probing was conducted to determine
thermal conditions, flow field, and overall
performance data as a function of a range
of operating conditions. Reduced scale
isothermal models were also constructed
of each boiler for the experimental deter-
mination of the flow field, and for the sub-
sequent specification of inputs for heat-
transfer model evaluation.
The wall-fired boiler selected for this
program was Duck Creek Unit 1, owned
and operated by Central Illinois Light
Company (CILCO). This 420 MWB boiler,
near Canton, IL, was built by Riley Stoker
Corporation. The general arrangement of
the boiler is shown in Figure 1. It is front-
wall-fired, with boiler capacity repre-
sentative of medium size wall-fired utility
boilers. The NOX emissions from this unit
were reduced below the limit of 0.7 Ib of
NOX/106 Btu* by retrofitting the original
burners with Iow-N0x burners. The fuel
fired at this unit is a high volatile
bituminous coal which contains approxi-
mately 4% sulfur, and flue gas desul-
furization is achieved by a wet scrubber.
The second boiler was the 420 MWe
tangentially fired Unit 5 of the Conesville
Generating Station near Conesville, OH,
owned and operated by American Electric
Power Corporation. Figure 2 illustrates
the overall arrangement of the boiler.
This unit is considered representative of
medium size tangentially fired boilers.
Heat Transfer Analysis
Detailed flow and heat transfer analyses
have been conducted for a wide range of
furnace operating conditions for both the
Duck Creek and Conesville boilers. In
general, the major test cases were chosen
to correspond with those selected for the
field measurement program in order to
provide a basis for direct comparison of
measured and predicted results. However,
a number of additional cases were also
established to evaluate the sensitivity of
model predictions to certain model inputs
and assumptions. Tables 1 and 2 list the
test cases for the Duck Creek and
Conesville boilers, respectively. For each
of these cases the modeling procedures
were used to make predictions for the
three-dimensional distributions of tem-
perature, velocity, volatile combustion,
unburnt fixed carbon, 02 concentration,
incident and net heat fluxes, and wall
surface temperature. These results, com-
pared to measured values, were used to
lb/10»Btu = 043kfl/GJ
-------
High Temperature
Pendant Superheater
Coal Bunkers
High Temperature
Reheater
Primary Superheater
Primary Reheater
Economizer
Airheater
Mills
Figure 1 General arrangement of Duck Creek Unit 1 boiler
test the accuracy and sensitivity of the
model predictions
Many previous studies for coal-fired
boiler furnaces using EER's furnace heat
transfer and combustion model have
shown that the accuracy of the predictions
obtained from this model depends on a
prescription of mass flux distribution and
on a variety of other model input data.
Since one goal of the project was to
establish the amount and type of input
data necessary to establish reliable time/
temperature predictions, the formulation
of additional input data received consider-
able attention in this study. Certain groups
of key input data are difficult to specify.
One such group relates to the distribution
of ash deposits on the furnace heat
transfer surface, and the specification of
their thermal resistance and emissivity.
A second important subset of inputs
relates to the distribution of air and fuel
flows to individual burners (and hence
local stoichiometries), which is particu-
larly important when overfire or underfire
air is employed for NOX emission control.
An example of the importance of cor-
rect specification of the distribution of
input flows can be found in the compari-
son between analyses for Cases 1 and 3
for the Duck Creek boiler. Case 1 repre-
sents predictions based on minimal in-
formation of actual boiler operation, while
Case 3 represents a more realistic situa-
tion where input flows and stoichio-
metries have been modified based on a
detailed analysis of field data. Predicted
temperature distributions for these cases
are presented in Figure 3. The dramatic
effect on the temperature field is clearly
evident, particularly the strong tempera-
ture stratification caused by the underfire
air jets originating in the lower furnace.
Predicted Case 3 profiles of local gas
temperatures and actual field measure-
ments are compared in Figure 4.
Considering the difficulties inherent to
temperature measurements in full scale
pulvenzed-fuel-fired boiler futnaces and
the many unavoidable model assumptions
and simplifications, the overall agreement
between measured and predicted profiles
of the gas temperatures is satisfactory.
Maximum local differences between cal-
culated and predicted values occur at
elevations in the upper furnace and very
close to the side walls, where steep
temperature gradients are encountered.
Most of the local differences between
predicted and experimental values origi-
nate from asymmetrical effects of actual
furnace operation which are not covered
by the model since symmetry between
west and east furnace half was presumed.
The asymmetrical effects caused by the
non-uniform secondary air damper set-
tings (which were changed almost daily)
are especially noticeable in measured
near-rear-wall temperature profiles at
burner level elevations.
Predicted and measured CVconcentra-
tion profiles are in general directly inverse
to corresponding temperature profiles;
i.e., a low oxygen concentration predicted
or measured locally is associated with a
local high temperature value and vice
versa. This leads to the conclusion that
the temperature profiles in the Duck Creek
furnace are not governed by furnace heat
transfer alone but to a considerable
degree by mixing of underfire air with the
flame zone products, and also by inter-
burner flow mixing due to the inhomo-
geneous firing pattern. Considering that
the furnace model used for the current
anslysis is primarily a (radiative) heat
transfer model, the agreement between
measured and predicted (^-concentration
profiles is again reasonable. It is believed
that a better agreement can only be
achieved by use of a finer computational
grid and by more exact modeling of main
flow development and turbulent exchange
using expensive fluid dynamics models.
Similar comparisons between predicted
and measured results were also obtained
for the Conesville boiler, where a strong
impact of the assumed local distribution
of stoichiometries on flame zone tem-
peratures and 02 profiles was observed.
Figure 5 compares the profiles predicted
without and with the assumption of
mhomogeneous air distribution to the
corners of each burner level. In the case
of non-uniform corner stoichiometries,
the air flow from the rear wall corners
was reduced resulting in an increase of •
near-rear-wall gas temperatures of up to
100 K and more. The effect is particularly
strong for low load at elevation 18.1 m.
Compared to the measured data, the
change to non-homogeneous corner
stoichiometry improved the predictions at
some locations, and at other locations
the discrepancies increased. However,
the corner air distribution assumed in
Cases 3 and 5 was somewhat arbitrary.
Due to such operational uncertainties,
even the most sophisticated computer
model will probably not yield better agree-
ment for local profiles than that obtained
in the current study.
For the Conesville boiler study, dis-
crepancies of the measured and predicted
-------
High
Temperature
Pendant
Superheater
High
Temperature
Reheaters
' U * JJ'Cr i L.
C'^'t'^t •&'^.\ 'I
1 ll.u,U-*t'./IUillU,il llllll, J I
Air Heater
Figure 2.
Mills
General arrangement of Conesville Unit 5 boiler
4
-------
Table 1.
Case
No.
1
2
3
4
5
6
7
8
9
Table 2.
Case
No.
1
2
3
4
5
6
7
Case Description of Duck Creek Heat Transfer Analysis
Test Mills in
Load Condition Operation
% - -
100 N/A A.B.C
100 1.5 A.B.C
100 1.5 A.B.C
100 1.5 A.B.C.
100 N/A A.B.C
60 Preliminary A.B
60 4 A.C
60 4 A.C
60 4 A.C
Excess
Air
%
18.4
18.4
18.4
18.4
18.4
22,8
20.1
20.1
20.1
UFA
%
25
25
25
25
25
0
0
0
25
Burner Level
Stoichiometry
—
Uniform
Non-Uniform
Non-Uniform
Non-Uniform
Non-Uniform
Uniform
Non-Uniform
Non-Uniform,
Increased
Flame Length
Non-Uniform
Increased
Flame Length
Flow Field
Prescription
—
Initial Corrected
for UFA
Corrected
from Case 1
(Flow Field 1)
Corrected
from Case 2
(Flow Field II)
Corrected from
Case 3
Corrected from
Case 2
Corrected
from Initial Flow.
Ash Hopper Flee ire.
Corrected
from Initial Flow,
Ash Hopper Ftecirc.
Corrected from
Case 7
Corrected from
CaseB
Superheater
Deposits
—
Medium
Medium
Medium
Heavy
Medium
Light
Medium
Heavy
Heavy
Water Cooled
Wing Walls
—
No
No
No
No
Yes
No
No
No
No
Case Description of Conesville Heat Transfer Analysis
Load Test Burner Level
% Condition in Operation
100 N/A B.C.D.E
100 1 B.C.D.E
100 1 B.C.D.E
45 5 C.D
45 5 C.D
45 5 C.D
100 3 B.C.D.E
Excess
Air. %
18.8
21.2
21.2
47.3
47.3
47.3
25.0
OFA
8.3
18.9
18.9
59.4
44.2
59.4
18.9
Burner Level
Stoichiometry
Uniform
Non-Uniform
Non-Uniform
Non-Uniform
Non-Uniform
Non-Uniform
Non-Uniform
Corner
Stoichiometry
Uniform
Uniform
Non-Uniform
Uniform
Non-Uniform
Uniform
Non-Uniform
Flow Field
Prescription
Initial
Upgraded;
Corrected for
Burner Level
Stoichiometry
Corrected
from Case 2
for Corner
Burner
Stoichiometry
Corrected
from Case 2
Corrected
from Case 2
Set-up
from Scratch
Corrected
from Case 3
Furnace Wall
Deposit Pattern
Uniform,
Non-Uniform,
Pattern 1
Non-Uniform,
Pattern II
Non-Uniform,
Pattern 1
Non-Uniform.
Pattern II
Non-Uniform.
Pattern 1
Non-Uniform,
Pattern II
-------
1550
= 0.6m
1350
<1350 K'
X = 4.8m
X=72m
(a) Case 1: Gas temperatures (K) 100% load, uniform burner level
load and stoichiometry, 25% UFA.
1500
'/7450
*-
7400
7350
'. <7350 /
'. <7350
0.6m' -•
(b) Case 3: Gas temperatures (Kj 100% load, non-uniform burner
level load and stoichiometry, flow field II, 25% UFA.
Figure 3. Comparison of predicted temperature distributions for Cases 1 and 3 for the Duck
Creek boiler.
temperature profiles in the upper furnace
are believed to be mainly due to differ-
ences in the velocity profiles. The in-
fluence of flow field is demonstrated in
Figure 6. This figure compares tempera-
ture profiles predicted for 45% load at the
radiant superheater inlet plane using two
different flow field prescriptions: the
standard presumed one (Case 4) and an
upgraded one based on field measure-
ments (Case 5). All other model inputs
were kept constant. The upgraded flow
field clearly yields a closer agreement
with measured temperature profiles, and
illustrates the strong influence of this
parameter.
In addition to the flow field, the thick-
ness and conductivity (thermal resistance)
of ash deposits on boiler walls and other
heat transfer surfaces, as input to the
model, can have a large impact on heat
transfer predictions. Usually these are
specified based on observation of the
distribution of deposit thickness and
surface texture in the boiler, with ap-
propriate model parameters assigned
based on experience and standard nu-
merical values. Sensitivity studies based
on such assumptions have been con-
ducted and show clearly that, if local
properties (e.g., temperature and heat
flux) are to be correctly predicted, local
variations in deposit thermal resistance
must also be considered. Figure 7 shows
that an increase of the conductivity to
thickness ratio of the ash deposits at the
superheater surface zone layers k = 14
and 15 from 0.160 to 0.400 kW/m2K
resulted in considerable improvement of
the incident heat flux distribution pre-
dicted in the upper furnace for both load
conditions.
In addition to the prediction of local
properties, averaged properties at various
boiler elevations are also of interest in
the sorbent injection problem. Of particu-
lar interest is the temperature/time profile
through the sulfation temperature win-
dow, since this is a main parameter that
impacts SOj removal. As shown in Figure
8, the optimum model predictions repre-
sent quite well the measured averaged
temperature distributions through the
boilers. Such agreement indicates also
that overall furnace performance (e.g.,
mean exit temperature, furnace heat
absorption) can be predicted accurately if
model inputs are correctly specified. Cor-
responding mean time/temperature pro-
files predicted for Duck Creek full load
Cases 1, 2, and 3 are presented in Figure
9, and show the impact of the various
flow and stoichiometry distribution as-
sumptions. In spite of the different model
-------
K
1600
1500
1400
1300
1200
1100
<
o ^
s~ '^\
•
Y=09m
f ...,',,.,
K
1600
1500
1400
1300
1200
1100
y = 2.7/n
8 10 12 14 16 X.m
K
1600
1500
1400
1300
1200
1100
Y=35m
0
8 10 12 14 16X,m
10 12 14 16
X.m
K
1600 • .'
1500 1
1400 3 /
1300 i
1200
1100
>
0 2
Figure 4.
i 4if • • • • >
r 1 "' Q ^^
j 40m \ •
1 V
1 *
1
\ Y= 46m
\
K
1600
1500
1400
1300
1200
1100
1 i . . r- • , , r-i
0 1
1
'S i \
' ' I
1
Y=6.1m
> |
Profiles at 2= 37 9m
4 6 8 10 l'2 14 /'fi X.m 024 6 3 10 12 14 76 X.m
Comparison of measured and predicted gas temperature profiles at 100% load. ( 0 meas Phase 1. O meas. Phase II,
•— • pred. Case 3)
input conditions utilized in the three cases
and in spite of considerably different pro-
files predicted for furnace hopper and
flame zones, lower furnace exit tempera-
tures (calculated at platen superheater
inlet plane) differ only by 35 K. The most
realistic model predictions are probably
achieved in Case 3. In this case, an
average quench rate of 394 K/s is cal-
culated in the upper furnace The other
quench rates predicted are 331 K/s for
Case 2, and 341 K/s for Case 1.
Conclusion
Detailed heat transfer analyses for a
wall-fired boiler and a tangentially fired
boiler have been conducted for a range of
furnace operating conditions using a
state-of-the-art heat transfer model. Pre-
dictions have been compared with cor-
responding measurement data obtained
in extensive field trials on the two test
boilers. In general, the study has shown
that good agreement between predicted
and measured overall thermal perform-
ance parameters (furnace exit tempera-
ture, peak radiative heat flux, carbon
burnout, etc.) can be achieved if the fuel
and air flows into the furnace, and the
insulating effect of wall deposits are
properly described.
Quantitatively correct predictions of
profiles of local temperatures and other
furnace variables have, however, proven
to be more difficult to achieve. The
analyses have shown that a reasonable
agreement with measured data can be
obtained only if the inhomogeneities in
the input conditions are correctly pre-
scribed, and the flow field incorporated
into the heat transfer model is a good
representation of the flow field in the
actual boiler. This appears to be particu-
larly true when the boiler furnace is
operated under staged combustion con-
ditions, and strong inhomogeneities in
the distribution of stoichiometry result.
The prediction of local properties is also
affected by the ability to correctly describe
the local distribution and properties of
wall ash deposits, although this is less
critical than the flow field specification.
Due to the sensitivity of absolute model
predictions to accurate prescription of
operating conditions and model parame-
ters, some model verifications are always
required especially when the model is
used to support actual design of sorbent
injection systems for existing boilers. The
three methods of model verification are:
• Comparison with design performance
based on manufacturer performance
calculations.
• Comparison with actual overall per-
formance data, which requires a
short field test.
• Detailed performance comparison
including comparison with extensive
temperature, concentration profile,
heat flux, and velocity measure-
ments.
The comparison of model predictions with
design performance is only recommended
if no other boiler performance data are
available. The most desirable and most
efficient approach to model verification is
by using a combination of control room
data and results of an abbreviated field
test. Detailed in-furnace measurements
are only necessary in exceptional cases,
such as boilers with operational problems.
The high expense of the detailed mea-
surements must be weighed against their
value to model verification.
Some of the weaknesses of the current
model can be eliminated, and the ac-
curacy of absolute performance predic-
-------
4/0 x=5?m
O O
'™fj>
1600^''
J*''
<$
O
\
X= 14.5m
8 10 12 Y.m 0 2 4 6 8 10 12 Y.m 0 2 4 6
Gas Tedmperature (K) Profiles at 2 - 26.2m
14
12
10
8
6
4
X= 1.2m
Vo/ % Dry
b S
Ik
//.
--5.1m
K
O
Vol % Dry
8 10 12 Y.m 0 2 4 6 8 10 12 Y.m
Vo/ % Dry
X= 106m
i . n O
X- 14.5m
10 12 Y.m 02 4 6 8 10 12 Y.m 0 2 4 6
02 Concentration (Vol %. Dry) Profiles at Z - 26 2m
8 10 12 Y.m 0 24
8 10 12 X,m
Figure 5.
Impact of non-uniform corner stoichiometry on gas temperature and O2 profiles predicted for 100 and 45% load (100% load.
O meas., O uncertain data pt., a •—• pred Case 2, uniform corner stoichiometry, a1 •—« pred. Case 3, non-uniform corner
stoichiometry; 45% load: 9 meas., b —• pred. Case 4. uniform corner stoichiometry, i1 pred Case 5, mon-uniform corner
stoichiometry.
tions can still be increased. A particular
area where improvement can be obtained
for coal-fired boilers is more accurate
characterization of thermal properties of
fly ash and ash deposits, including
physical structure, optical properties,
wave length, and temperature. This is
also important for the LIMB process since
sorbent injection can affect these pro-
perties. Similarly, the furnace flow pre-
scription could be replaced by advanced
fluid dynamics calculations which include
prediction of turbulent exchange and the
effects of buoyancy (totally neglected in
the current study). An increase in ac-
curacy of local temperature profile pre-
dictions of roughly 20-40 K is expected
from such a modification. A fluid dynamics
model does not make physical flow
modeling unnecessary since physical
models are very useful for validating
numerical flow models under isothermal
conditions.
In spite of the limitations of the current
model, with respect to absolute accurate
performance predictions, the present
model applications carried out for two
boiler furnaces have undoubtedly shown
its usefulness for analysis of furnace
performance and its potential for opti-
mization of the LIMB process. The major
advantage of the model employed is also
its ability to extrapolate limited measure-
ment and performance data from baseline
conditions to a variety of other operating
conditions.
-------
K
1500
1400
1300
X= 1 3m
A
1500
1400
1300
<
1
:~^A^- 1
. *<,''* ^^^C.""*
^ ^*^J
..* 1
-1
X=3.1m \
r' • > > • i
Profiles at Z = 40 6m
8 Y.m
8 Y.m
A
7500
7400
7300
*
• • ' •
•
^*^pq---" '.t~"
' I<^ ***
r*
X= 73/T7
f .
02468
Figure 6. Impact of flow dts
1
^
-H
.%-{
"j
-i
•
j
Y.m
tnbut
ff
1500
1400
1300
4
1
-1
1
_. 1
**s '
•% •*
X=727m , 1
^ 1
r f t • • •
0
8
Y.m
K
7500
7400
7300
*
\
^f^-r-^"^
^ X= 74.5m **%
I * • • f
0
4
8 Y.m
Impact of flow distribution in upper furnace (elevation Z - 40 6m) on temperature proifles predicted for 45% load
f 9 meas . •—• pred Case 4. original flow field
•---• pred Case 6, modified flow field)
Incident Radiative Heat Flux. kW/m2
-« NO Co -k Wi °> ^J
§ 8 § § § § §
1 I I 1 1 1 1
Predictions Conductance/ Thickness
kW/m*/K
7«M/aj», J00% Load 45% Load
K a a' b 6'
70-72 0774 0.057 0.774 0.057
73 0774 0.229 0114 0229
14-16 0.400 0400 0.114 0.400
14-15 SM 0160 0400 0160 0.400 -
Measurements O 9
»^ ^ ,^
i t i i l i l
6 8 10
Furnace Width /X), m
72
74
Figure 7.
Impact of deposits in upper furnace on radiative heat fluxes incident on front
wall at elevation Z = 40 6m
-------
;7oo -
Q Meas Arithmetic Average
O Meas Arithmetic Average of Few Data
a Pred Arithmetic Average, Case 3
b Pred. Mass-Weighted Average, Case 3
10
\ \
20 30
Vertical Distance (Z), m
40
50
(a) Duck Creek. 100% Load and Flow Field II
2000
1800
1700
1600
1500
1400
1200
Burner Levels
UJU
BCDE OF A
Superheater
. Ash
Hopper I
nl
f/
?00% Load. Condition 1
a Pred 3-D Model
a1 Pred 2-D Model
O Meas 2nd Test
\
45% Load, Condition 2
b Pred 3-D Model
Pred 2-D Model
Meas
Uncertain Data Point
• I
10
20 30 40
Vertical Distance /Z/. m
50
60
(b) Conesville
Figure 8.
Mean temperature profiles along the furnace predicted for the Duck Creek and
Conesville boilers and comparison with measurements
10
-------
a. Pred. Case 1, Uniform Burner Level Stoichiometry
b Pred Case 2, Non-uniform Level Stoichiometry Flow Field I
c. Pred. Case 3, Non-uniform Level Stoichiometry Flow Field II
S'H lnlet
Sulfation
Window
§ 7/00
20 15
1 0
2.0
Figure 9.
05 0 0.5 10 1.5
Mean Residence Time IT), S
Dependence of mean time/temperature prof lies predicted for 100% load on burner
level Stoichiometry and flow field assumption (Duck Creek).
B. Cetegen. W. Richter, J. Reese, J. LaFond, B. Folsom, and R. Payne are
with Energy and Environmental Research Corporation, Irvine, CA 92718-
4190.
David G. Lachapelle is the EPA Project Officer fsee below).
The complete report entitled "Evaluation of Utility Boiler Radiant Furnace
Residence Time/Temperature Characteristics: Field Tests and Heat Transfer
Modeling," (Order No. PB 87-213 112/AS; Cost: $36.95, subject to change}
will be available only from:
National Technical Information Service
5285 Port Royal Road
Springfield, VA22161
Telephone: 703-487-4650
The EPA Project Officer can be contacted at:
Air and Energy Engineering Research Laboratory
U S Environmental Protection Agency
Research Triangle Park, NC 27711
11
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