United States
Environmental Protection
Agency
Industrial Environmental Research
Laboratory
Research Triangle Park NC 27711
Research and Development
EPA-600/S7-83-056 Feb. 1984
Project Summary
Analysis of Low NOX
Operation of Two Pulverized-
Coal-Fired Utility Boilers
S.S. Cherry
The operation of two pulverized-coal-
fired utility boilers subject to the 1971
New Source Performance Standard
was reviewed to determine if other
boilers could adopt a similar mode of
operation to reduce nitrogen oxide
(NOx) emissions. These two boilers had
been identified, during a previous
study, as low NOx emission sources.
It was determined that reburnering,
burner modification, or optimizing the
overt ire air system of existing Foster
Wheeler boilers offered the potential to
reduce NOX significantly. It was also
determined that existing Babcock &
Wilcox boilers would probably not
respond to further combustion modifica-
tions.
This Project Summary was developed
by EPA's Industrial Environmental
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
information at back).
Introduction and Summary
It was determined that the N0xemissions
from two boilers (Unit 1 of Public Service
Co. of New Mexico's San Juan Station,
and Unit 3 of Iowa Power and Light's
Council Bluffs Station) were lower than
other pulverized coal-fired utility boilers
analyzed during a previous study. The
purpose of the program was to determine
if other boilers manufactured by Foster
Wheeler (San Juan Unit 1) and Babcock &
Wilcox (Council Bluffs Unit 3) could
achieve a lower NO emission rate.
It was determined that Foster Wheeler
boilers with the single-register Intervane
burner and operating with overfire air
(OFA) could, potentially, reduce emissions
by one of the following:
1. Burner modification: including coal
splitters in the annular coal nozzle.
2. Burner replacement: substituting
the newer dual-register controlled-
flow/split-flame variable-velocity
(CF/SV) burner for the Intervane
burner.
3. Overfire air: increasing the amount
of OFA or optimizing the OFA
damper settings.
The approach selected must be unit-
specific.
It was determined that the newer
Babcock & Wilcox boilers would probably
not be able to achieve a significantly
lower NOx emission rate using these
techniques. All new boilers have dual-
register burners and compartmented
windboxes (for closer control of burner
air flow).
Discussion
The NOx measured during the perfor-
mance test conducted on Foster Wheeler
boilers subject to the 1971 New Source
Performance Standard (NSPS) is summa-
rized in Table 1 .* Note that most of these
units have the single-register, high-
turbulence Intervance (IV) burner and are
operating with OFA.
*San Juan Unit 1 was designed to comply with the
State of New Mexico NO, limitation of 0.45 lb/108
Btu (194 ng/J) and not the 1971 NSPS. However, it is
included in this study of other Foster Wheeler units
subject to the 1971 NSPS
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Table 1. Summary of Foster Wheeler Pulverized-Coal-Fired NSPS Utility Boilers
Test
1A.
IB.
1C.
2.
3.
4.
5.
6.
7.
8.
9.
10.
11.
12.
13.
14.
Utility
Public Service Co. New Mexico
Omaha Public Power District
Proprietary
Portland Genera/ Electric
Nebraska Public Power District
Proprietary
Proprietary
Northern Indiana Public Service
Iowa Public Service
Allegheny Power Service
Allegheny Power Service
Proprietary
Proprietary
Proprietary
Station
San Juan
Nebraska City
-
Boardman
Gentlemen
-
-
Schahfer
Neal
Pleasants
Pleasants
-
-
Unit
1
1
-
1
7
-
--
15
4
1
2
-
—
--
Gross
MWe
360
575
114
530
650
500
534
511
630
660
660
770
860
736'
Firing
Mode"
1
2
1
2
2
2
2
2
2
2
2
2
2
2
No. of
Burners
16
28
8
32
32
24
24
24
28
24
24
48
32
40
Burner
Type"
IV
IV
CF/SV
IV
IV
CF/SV
IV
IV
CF
IV
IV
IV
IV
IV
IV
IV
Overfrre
Air
No
Yes
No
Yes"
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Coal Performance
Type* lb/10eBtu
Sub.
Sub.
Sub.
Sub.
Sub.
Sub.
Sub.
Sub.
Sub.
Bit.
Bit.
Bit.
Bit.
Bit.
1.O5
0.63
0.35
0.479
0.699
0.5T
0.354
0.518
0.465"
0.45
0.345
0.61
0.61
0.63
0.66
0.43
NO,
ng/J
452
271
151
206
301
245
152
223
200
194
148
262
262
271
284
185
" 7 = Front-wall
2 = Opposed-wall
" IV , Intervane
CF/SV = Controlled-flow/'split-flame variable velocity
CF = Controlled flow
" Sub. = Subbituminous
Bit. = Bituminous
d Interstage air
e Overfire air closed
1 Two boilers supplying one steam turbine.
Figure 1 is a plot of these data in terms
of the gross MWe per firing wall.* Also
shown in this figure is a linear regression
of these data (except Tests 3,5, and 9)
which shows a high degree of correlation
(r2 = 0.80) of NO, in terms of MWe/wall.
Linear regressions of data obtained on
pre-NSPS boilers are also highly cor-
related in terms of this parameter (r2 —
0.81 for baseline, r2 = 0.85 for staged
combustion).
Results from San Juan Unit 1 with the
dual-register controlled-flow/split-flame
variable-velocity burner (Figure 2) indicate
a NOX reduction of 32 to 44 percent with
respect to the IV burner operating with
OFA. However, results from Boardman
Unit 1 (Test 4, Table 1) are not consistent
with San Juan Unit 1; i.e., it was
anticipated that the emissions for the
CF/SV burner-equipped Boardman Unit
1 should have been lower.
Adding coal splitters to the IV burner
(operating without OFA has been demon-
strated to significantly reduce NO*
emissions from pre-NSPS units. However,
these results have also been shown to be
highly unit-specific.
It was determined that the low emissions
for Tests 5 and 9 (Table 1) were due to a
modification of the OFA system to
increase OFA flow. These modifications
'The performance NO, is that measured during the
performance test required by the 1971 NSPS using
EPA Method 7
700
600
•^500
el
O
*300
i
I
§200
700
Pre-1971 NSPS Units
Baseline
Staged Combustion
400
300
(13)
2OO
c
i
(1C)
O Front-Wall, Subbituminous
CD Opposed-Wall. Subbituminous
• Opposed-Wall, Bituminous
O CF/SV Burner, without OFA
100
0.
O
100 200 300 400
System Load/Firing Wall, Gross MWe
500
Figure 1. Foster Wheeler NSPS units, Intervane burners with OFA.
were apparently responsible for achieving
a NOx level lower than the correlation
based on other Foster Wheeler boilers
(Figure 1).
An analysis of Babcock & Wilcox NSPS
boilers operating with Subbituminous
coal (Figure 3) indicated that Council
Bluffs Unit 3 was not a particularly low
NOx emission source when compared
with other B&W 1971 NSPS units. These
data demonstrate that the performance
test NOx for Council Bluffs Unit 3 is no
different than the sample mean.
This result implies that B&W NSPS
units operating with Subbituminous coal
would probably not be able to achieve
-------
1.2
1.0
0.8
0.6
=8
O
0.4
0.2
IV
IV = Intervene Burner
CF/SV = Controlled-Flow/
Split-Flame
Variable- Velocity
Burner
IV
CF/SV
500
400
300
1
i
200
100
Figure 2.
Closed Open
Overfire Air Ports
Low NO* burner comparison.
Closed Open
(Not Yet Tested)
flame variable velocity configuration)
offers the potential to reduce NOX
emission on Foster Wheeler 1971 NSPS
boilers. Quantification of the effectiveness
of these approaches is uncertain due to
an apparent unit specific nature of the
results. The effectiveness of burner
replacement should become more firmly
established as new units with the CF/SV
burner are performance tested. Optimizing
the OFA system would probably be most
applicable to units with a low windbox-to-
furnace pressure differential.
significantly lower NOx. (All such units
have dual-register burners and compart-
mented windboxes.)
Conclusions
(Note: The objective of this effort was to
assess the potential NO* reduction for
1971 NSPS boilers manufactured by
Babcock & Wilcox and Foster Wheeler,
based on the operation of Council Bluffs
Unit 3 (B&W) and San Juan Unit 1 (F.W.).)
It was concluded that:
1. B&W 1971 NSPS units would not
significantly benefit from the adop-
tion of Council Bluffs Unit 3's mode
of operation.
2. Foster Wheeler 1971 NSPS units
would benefit from a burner modifi-
cation, burner replacement, or
optimization of the overfire air
system. The degree of potential NO*
reduction is uncertain.
The first conclusion is based on a
comparison between Council Bluffs Unit
3 and other subbituminous-coal-fired
B&W boilers, which showed no statistical
difference in NOx emission levels mea-
sured during the performance test. Thus,
the initial perception that Council Bluffs
Unit 3 was a significantly low NOX source
is not warranted when compared to other
B&W 1971 NSPS units.
Burner modification (adding primary
air/coal stream splitters to single register
burners) or burner replacement (replacing
Intervane burner with controlled flow/split
-------
auu
400
£
d
3? 300
<*>
^200
O
100
0
I
I I I I I I
Subbituminous Coal
Dual-Register Burners f~\ _
Compartmented Windbox
9 Council Bluffs Unit 3
+ Mean
_
-
I
_
o o o
o+°o o* -
o °
o
-
I I 1 1 1 1
250
200
-J
150 %
i
100
50
O
700 200 300
System Load/Firing Wall, Gross MWe
400
Figure 3. Babcock & Wilcox 1971 NSPS boilers.
S. S. Cherry is with KVB. Inc., Irvine. CA 92714.
Michael C. Osborne is the EPA Project Officer (see below).
The complete report, entitled "Analysis of Low NO* Operation of Two Pulverized-
Coal-Fired Utility Boilers," (Order No. PB84-118918; Cost: $8.50, subject to
change) will be available only from:
National Technical Information Service
5285 Port Royal Road
Springfield. VA 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
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