United States
Environmental Protection
Agency
.Office of Air Quality
Planning and Standards
Research Triangle Park NC 27711
EPA-450/4-79-021
September 1979
&EPA Review of NOx Emission
Factors for Stationary
Fossil Fuel Combustion
Sources
;pi$ffeni
-------
GENERAL DISCLAIMER
This document may be affected by one or more of the following statements
This document has been reproduced from the best copy furnished by
the sponsoring agency. It is being released in the interest of making
available as much information as possible.
This document may contain data which exceeds the sheet
parameters. It was furnished in this condition by the sponsoring
agency and is the best copy available.
This document may contain tone-on-tone or color graphs, charts
and/or pictures which have been reproduced in black and white.
This document is paginated as submitted by the original source.
Portions of this document are not fully legible due to the historical
nature of some of the material. However, it is the best reproduction
available from the original submission.
-------
TECHNICAL REPORT DATA
IPlease readSusimcdom the ,w*ent' bejore completing;
1. REPORT NO, 2.
EPA-450/4-79-021
l3. RECIPIENT'S ACCESSION NO.
PB81 1 4 6 9 8 7
4, TITLE AND SUBTITLE
REVIEW OF NOx EMISSION FACTORS FOR STATIONARY
FOSSIL FUEL COMBUSTION SOURCES
5. REPORT DATE
September 1979
6. PERFORMING ORGANIZATION COOE
7. AUTHORtSJ
R. J. Milligan, et al.
S. PERFORMING ORGANIZATION RSPORT
9. PERFORMING ORGANIZATION NAME ANO ADDRESS
Acurex Corporation
485 Clyde Avenue
Mountain View, CA 94042
10. PROGRAM ELEMENT NO.
11. CONTRACT/GRANT NO.
68-02-2611 and
68=01-4142
12. SPONSORING AGENCY NAME AND ADDRESS
Office of Air Quality Planning and Standards
US Environmental Protection Agency
Research Triangle Park, NC 27711
13. TYPE OF REPORT AND PERIOD COVER
Final Report
14. SPONSORING AGENCY .COOE
15. SUPPLEMENTARY NOTES
EPA Project Officer: Thomas Lahre
16, ABSTRACT
A review of recent NOx test data was performed, and summaries of emission
factors presented for various types of stationary source combustion and for
various fossil fuels. The effects of combustion modifications on NOx emissions
are quantified. Background data are given to help the user determine the
reliability of each factor in particular applications.
1?. . KEY WORDS AND DOCUMENT ANALYSIS
a, DESCRIPTORS
b.IDENTIFIERS/OPEN ENDED TERMS
c. COSAT1 Field; Group
Air Pollution Nitrogen Oxides
Boilers Reciprocating Eugiiv
Combustion Turbines
Emission Factors
Internal Combustion
IS
CL "\SS {TV;/., Kcporti
Unclassified
. ;;v- - ;-r;j7rs^ ~c
, 21 MO. OP PAG fc S
69
57. PRrCE
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EPA-450/4-79-021
ฆ #ฆ ft, I ฆ ฆ
Review of NO* Emission
Factors for Stationary
Fossil Fuel
Combustion Sources
by
R.J. Milligan. W.C. Sailor, J, Wasilewski and W.C. Kuby
Acurex Corporation
485 Clyde Avenue
Mountain View, California 94042
Contract Nos. 68-02-2611 and 68-01-4142
EPA Project Officer: Thomas Lahre
Prepared for
U.S. ENVIRONMENTAL PROTECTION AGENCY
Office of Air, Noise, and Radiation
Office of Air Quality Planning and Standards
Research Triangle Park, North Carolina 27711
September 1 979
I
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This document is issued by the Environmental Protection Agency to
report technical data of interest to a limited number of readers.
Copies are available free of charge to Federal employees, current EPA
contractors and grantees, and nonprofit organizations - in limited
quantities - from the Library Services Office (MD 35), U. S.
Environmental Protection Agency, Research Triangle Park, North Carolina
27711; or, for a fee, from the National Technical Information Service,
5285 Port Royal Road, Springfield, Virginia 22161.
This report was furnished to the Environmental Protection Agency by
Acurex Corporation, 485 Clyde Avenue, Mountain View, California, in
fulfillment of Contract Nos. 68-02-2611 and 68-01-4142. The contents of
this report are reproduced herein as received from Acurex Corporation.
The opinions, findings and conclusions expressed are those of the author
and not necessarily those of the Environmental Protection Agency.
Publication No. EPA-450/4-79-021
-------
TABLE OF CONTENTS
Section Page
1 INTRODUCTION 1
2 UTILITY BOILERS .... ....... 4
2.1 NO Emission Factors for Utility Boilers ...... 4
2.2 Histograms of NO Emissions for Utility Boilers . . 8
2.3 Effect of Controls on NO Emissions
for Utility Boilers .. V 8
2.4 Nitric Oxide as Percent Constituent of
Total N0X Emissions . 15
3 INDUSTRIAL BOILERS 19
3.1 NO Emission Factors for Large Industrial Boilers . . 19
3.2 Histograms of N0X Emissions for Industrial Boilers . 22
3.3 Nitric Oxide as Percent Constituent of
Total NOv Emissions . 22
3.4 Effect of Controls on NO Emissions for
Industrial Boilers 27
3.5 Other Data 27
4 COMMERCIAL AND RESIDENTIAL UNITS . . 30
4.1 N0X Emission Factors for Comnercial Sized Boilers. . 30
4.2 N0X Emission Factors for Residential Furnaces
and Boilers ..... 33
4.3 N0X Emission Factors for Pilot Lights ........ 36
4.4 Histograms of N0X Emissions for Commercial
'and Residential Units ..... 36
4.5 Nitric Oxide as Percent Constituent of Total
N0X Emissions . 36
5 STATIONARY RECIPROCATING ENGINES .... 40
5.1 N0X Emission Factors for Compression
Ignition Engines ..... .... 40
5.2 N0X Emission Factors for Spark Ignition Engines ... 42
5.3 Histograms of N0X Emissions for
Reciprocating Engines 44
5.4 Nitric Oxide as Percent Constituent of Total
N0X Emissions ........ 44
6 GAS TURBINES 52
6.1 N0X Emission Factors for Various Types and Sizes
of Gas Turbine Engines 52
iii
-------
TABLE OF CONTENTS (Concluded)
Section Page
6.2 Histograms of N0X Emissions for Gas
Turbine Engines 52
6.3 State-of-the-Art Control Techniques for N0X
Emissions -- Water Injection 56
6.4 Nitric Oxide as Percent Constituent of
Total NQX Emissions ' . . . 56
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LIST OF ILLUSTRATIONS
Figure Page
2-1 Population Histograms of N0X Emission Factors for
Horizontally Opposed Utility Boilers 9
2-2 Population Histograms of NO* Emission Factors
for Single Wall Utility Boilers . ...... 10
2-3 Population Histograms of N0X Emission Factors
for Cyclone Utility Boilers .............. . 11
2-4 Population Histograms of N0X Emission Factors
for Bituminous Coal Fired Tangential Utility Boilers . . 12
3-1 Population Histograms of N0X Emission Factors
for Industrial Boilers ...... 23
4-1 Population Histograms of NO* Emission Factors
for Natural Gas Fired Commercial Boilers, Residential
Units, and Pilot Lights 37
5-1 Population Histograms of N0X Emission Factors
for Compression Ignition Engines Firing Diesel Fuel ... 45
5-2 Population Histograms of N0X Emission Factors
for Compression Ignition Engines Firing Dual Fuels ... 47
5-3 Population Histograms of N0X Emission Factors
for Stationary Reciprocating, Natural Gas Fired
SI Engines ............... 48
5-4 Population Histograms of N0X Emission Factors
for Stationary Reciprocating Gasoline Fired
Spark Ignition Engines ..... 49
6-1 Population Histograms of N0X Emission Factors
for Gas Turbine Engines ....... 54
6-2 Effectiveness of Water/Steam Injection in Reducing
NGX Emissions 57
6-3 NO and NO2 Concentrations at the Base of No. 3 Stack
for Various Turbine Loads, i.e., Turbine Inlet Temperature
(Reference 6-7) ...... 58
6-4 NO and NQX Concentrations of a Small Turbine at Various
Loads Firing No. 2 Oil ..... . 59
v
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LIST OF TABLES
Table Page
1-1 Conversion Factors 3
2-1 NOx Emission Factors Survey of Utility Boilers
(English Units) 5
2-2 NOx Emission Factors Survey of Utility Boilers
(SI Units) 6
2-3 Average Percent Reduction of N(L Emission Factors
by State-of-the-Art Control Techniques for Utility Boilers
(English Units) 13
2-4 Nitric Oxide as a Constituent of Total N0X Emissions
of Utility Boilers . . . . 15
3-1 N0X Emission Factors Survey of Industrial Boilers
(10 to 100 x 106 Btu/hr) (English Units) ........ 20
3-2 NOx Emission Factors Survey of Industrial Boilers
(2.9 to 29 MW) (ST Units) 21
3-3 Nitric Oxide as a Constituent of Total N0X Emissions
of Industrial Boilers 26
3-4 Comparison of Data from Ferrari et al. with Calculated
Averages for Same Boiler Type and Size 28
4-1 N0X Emission Factors Survey of Commercial Stationary
Steam and Hot Water Generating Units
(0.5 to 10 x 106 Btu/hr) (English Units) 31
4-2 N0X Emission Factors Survey of Commercial Stationary
Steam and Hot Water Generating Units
(0.5 to 10 x 106 Btu/hr) (SI Units). 32
4-3 N0X Emission Factors Survey of Residential Steam
and Hot Water Generating Units (<500,000 Btu/hr)
(English Units) .... . .......... 34
4-4 N0X Emission Factors Survey of Residential Steam
and Hot Water Generating Units (<0.15 MW) (SI Units) . . 35
4-5 Nitric Oxide as a Constituent of Total N0X Emissions
of Coumercial and Residential Boilers and Heating Units
and Pilot Lights 38
vi
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LIST OF TABLES (Concluded)
Table Page
5-1 Baseline NOx Emission Factors Survey of Reciprocating
Compression Ignition (CI) Engines .... 41
5-2 Heat Rates for Compression Ignition Engines 42
5-3 NOv Emission Factors Survey of Reciprocating
Spark Ignition (SI) Engines .............. 43
5-4 Nitric Oxide as a Constituent of Total N0X Emissions
of Reciprocating Engines 50
6-1 N0X Emission Factors Survey of Simple and Regenerative
Cycle Gas Turbines 53
vi 1
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SECTION 1
INTRODUCTION
In order for EPA, states, and local agenices to compile reliable
emission inventories of nitrogen oxides, it is important to have accurate
and precise N0x emission factors. The two major source categories
responsible for the bulk of all manmade N0X emissions are mobile sources
and stationary source combustion. The Monitoring and Data Analysis
Division (MDAD) of The Office of Air Quality Planning and Standards is
responsible for determining the N0x emission factors for the latter
area. Hence, it is periodically necessary that MDAD critically review
the existing emission factors for the major stationary sources of N0x
and update those factors for which newer and more comprehensive data exist.
To assist MDAD in this task, The Energy and Environmental Division
of Acurex has compiled and reviewed the N0x source test data that have
been generated over the last several years on the major stationary
combustion sources. This compilation includes external combustion of
coals, oils and gas in boilers as well as internal combustion in
reciprocating and turbine engines.
Stationary external combustion units are covered in the next three
sections of this report. For the purposes of this report, they are broken
into four categories:
Utility boilers >29 MW (>100 x 10ฎ Btu/hr) input
Industrial boilers -- 2.9 to 29 MW (10 to 100 x 10ฎ Btu/hr)
input
Commercial boilers 150 kW to 2.9 MM (5 x 105 to 10 x
106 Btu/yr) input
Residential furnaces and boilers ~ <150 kw (<5 x 10^ Btu/yr)
input
-------
Within each size category, the boilers are further classified according to
design and fuel. Section 2 is devoted to utility boilers alone.
Section 3 covers industrial boilers and Section 4, commercial and
residential units. In support of the N0x emission factor tables, each
section also contains population-NOx emission histograms, percentage NO
in N0X and, for utility boilers, a section on state-of-the-art control
techniques and their effectiveness.
The last two sections cover stationary reciprocating engines and
turbines, respectively. The breakdown within each section 1s based on
size, number of strokes per combustion cycle and fuel for reciprocating
engines and size, type of cycle and fuel for turbines.
In assessing the data reviewed in this study, it was mandatory that
the following information, in addition to that needed to calculate the
NQX emission factors, be known;
ง The type of boiler or engine e.g., tangential, four stroke
t Boiler operating condition; "baseline"/state-of-the-art NQX
control techniques This was particularly important for .
utility sized boilers and turbines; all other sources had no
N0X control technique applied unless they were specifically
operated under a control evaluation program.
This report is concerned with emissions at the "baseline," or
as-found condition. Thus, baseline emissions are those measured generally
in the absence of any N0X control techniques. For utility and
Industrial boilers, baseline measurements were included if they were made
at 60 to 110 percent load. All data reported without the type of boiler
delineated were rejected; data reported on utility boilers, turbines, etc.
with N0X control techniques specified e.g., BOOS, FGR, water injection,
etc. were included in the section on control effectiveness.
Table 1-1 includes thermal equivalents for fuels discussed in this
report. Since the emission factor tables are expressed both in terms of
lb/fuel unit and ng/J, these factors were used for conversions when the
data was reported in only one set of units.
2
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TABLE 1-1. CONVERSION FACTORS
To Obtain
From
Multiply By
ng/J
ng/J N0X (as NO2)
ng/J N0X (as NOg)
ng/J N0X (as NO2)
N0X ppm @ 3% O2 dry
lb/106 Btu
N0X ppm @ 3% O2 dry
N0X ppm 9 3% 02 dry
N0X ppm @ 3% O2 dry
N0X ppm dry
430
0.510 (natural gas)*
0.561 (oil)*
0.611 (coal)*
( 17-9 \
[20.9 - % 02 dry)
Thermal Equivalents*
Fuel
Heating Value (Gross)
Bituminous coal
10,000 - 14,000 Btu/lb*
(used 12,000 Btu/lb)
Lignite coal
8,000 Btu/lb*
Residual oil
150,000 Btu/gal*
Distillate oil
140,500 Btu/gal*
Natural gas
1,050 Btu/ft3
~These factors used only when data were otherwise insufficient.
Sources:
ป Maloney, K. L., et al., "systems Evaluation of the Use of Low-Sulfur Western
Coal in Existing Small and Intermediate-Sized Boilers," KV8 Inc.,
EPA-600/7-78-153a, July 1978. ,
J
U.S. Environmental Protection Agency, "Compilation of Air Pollutant Emission
Factors," Third Edition, AP-42, August 1977,
3
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SECTION 2
UTILITY BOILERS
For the purposes of this study, utility boilers are defined as
field-erected watertube boilers with a heat input greater than 29 MW
(100 x 10ฎ Btu/hr) used for generation of electricity. This category
Includes the vast majority of field-erected boilers used for utility or
industrial electric power generation via steam production. The major
fuels fired are coal, oil, and natural gas. Within this definition, the
utility boiler population is divided into nine major boiler types and
further subdivided into seven fuel categories. Firing of subbituminous
coal is included in the bituminous category.
2.1 NO. EMISSION FACTORS FOR UTILITY BOILERS
Tables 2-1 and 2-2 contain the N0X emission factors for utility
boilers.* The first table is in English units and the emission factors
are based on the amount of fuel consumed. The second table is in SI units
and the emission factors are given as weight per energy unit released
{ng/J).
A considerable body of data were collected for horizontally opposed
units firing bituminous coal, oil and natural gas. These data were
abstracted from several different sources (References 2-1, 2-2, 2-3, 2-4,
2-5, 2-6 and 2-7). Major differences between the new averages and the
existing AP-42 values occur in the oil- and the bituiiinous coal-fired
units. In the former, the N0x average emission factor was 35 percent
lower and in the latter 50 percent higher. Because of the number of data
~The factors reported in the tables as well as the text are in terms of
HOx emissions as N02 except as noted.
4
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TABLE 2-1. NOx EMISSION FACTORS SURVEY OF UTILITY BOILERS {ENGLISH UNITS)
Type
Boil er
Baseline NO, Emissions as a Function of Fuel*
Coal (lb/ton burned)
Oil (lb/103 Sal ail burned)
Gas (lb/10ฎ SCF gas)
Anthracite
Bituninous
Lignite
Residual
.Distillate
Natural
Process
Tangential
18b
14C (Z7<1)
-22*e
a
7 (2)
-12*
50 ฆ
42 (2)
-16*
300
200 (3)
-33*
Horiiontally
Opposed
ie
27 (8)
+50*
If
105
66 (9)
-35*
700
S70 (10)
-19*
Single Mall
16
20 (11J
. +11*
14 .
13 (IS
-It
1D5
65 (36)
-38*
28(3}
700
340 (39)
-51*
790 (8)
Vertical6
18
18
14 '
105
700
Cye1 one
5S
36 (7)
-35*
17
12 (3)
-29*
105
87 (4)
-17*
700 ฆ
660 (2)
-6*
Met
Bottcm'
30
48 (2)
+60*
14
Spreader
Stoker
15
15 (8}
OS
Overfeed
Stoker
5.4 {2}
aNOx values reported in terms of NO^ .ฃฃ-!-118
bOld AP-42 value
cReconmended replacement number based on new or revised data base
^Number of boilers tested
fPercent change in emissions factor
fIncludes one vertical and one horizontally-opposed unit
5
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TABLE 2-2. N0X EMISSION FACTORS SURVEY OF UTILITY BOILERS (SI UNITS)
Type
Boiler
Baseline NO* Emissions (ng/J) as a Function of Fu*!ฎ
Coal
Oil
Gas
Anthracite
flitunifwus
Lignite
Residual
Oistillate
Natural
Process
Tangential
- ฆ
320b
2S0C (27<1)
-zz*e
215 -
190 (2)
-12*
140
120 (2)
-14*
120 .
80 (3)
-33*
Horizontally
Opposed
320
480 (8)
+50*
380
300
200 (9)
-33*
290
230 (10)
-21*
Single Mall
SO
360 (11)
~12*
380
350 (1)
-8*
300
190 (36)
-37*
86 (3)
290
140 (39)
- -52*
320 (8)
Vertical15
310
320
380
300
290
Cyclone
980
650 (?)
-34*
460
320 (33 .
-30*
300
250 (4)
" -17*
290
270 (2)
-7*
Vet
Bottom'
540
660 (2)
+571!
380
Spreader
Stoker
270
270 (8)
OS
Overfeed
Stoker
100 (2)
*1*0^ values reported in terws of NO^ EE-T-119
b01d AP-42 value
cReeoamended replacement number based on tie* or revised data base
dumber of boilers tested
'Percent change in emissions factor
'includes one vertical and one horizontally-opposed unit
6
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points and the variety of sources, the new numbers appear to be more
justifiable than the old.
Data were also obtained for tangential units firing bituminous coal
(References 2-8, 2-i, 2-2, 2-9, 2-10, 2-11, 2-12, 2-13, and 2-14). The
N0X emission factor obtained from averaging-these baseline test numbers
was 22 percent less than the existing AP-42 value.
A considerable body of data were also obtained for single wall
units firing bituminous coal (References 2-8, 2-2, 2-6, 2-11 through 2-17,
.2-18, 2-19, 2-20, and 2-13), oil (References 2-1, 2-2 and 2-15), natural
gas {References 2-1, 2-3, 2-4, 2-5 and 2-15) and process gas (Reference
2-16). All NO emission factors were less than those given in AP-42
x
except for bituminous coal which showed a slight increase. The decreases
for the oil-fired units (38 percent) and the gas-fired units (51 percent)
give values consistent with expected results when these units are compared
with horizontally opposed units and single wall, large industrial boilers
burning the same fuels. Consistent with the other average values obtained
for single wall and horizontally opposed boilers, it is recommended that
the average value for lignite-fired, single wall boilers be reduced from
14 lb/ton (380 ng/J) to 13 lb/ton (350 ng/J). The eight process gas-fired
ฃ
utility boilers show an average N0x emission factor of 790 lb/10 scf
(330 ng/J).
All of the cyclone boiler data came from a recent compilation of
previous tests (Reference 2-2i). These data show less N0x emission than
the initial AP-42 numbers in all fuel categories. In particular, NO
emissions for bituminous coal-fired cyclone boilers were 34 percent less. .
than the initial AP-42 value. The new data are probably more accurate as
they are based on the average of seven different cyclone boilers. Some
cyclone boilers may have been better classified as large industrial units
but were included in the utility section to provide a better data base.
,:No new data were obtained for vertical units and only two new data
points were obtained for wet bottom units. Both of these were in the
- bituminous coal category (References 2-8 and 2-1). These data suggest
tnat wet bottom, coal-fired boilers should have their NO^ emission
factors increased by some 60 percent. In comparison to cyclone units, the
original wet bottom boiler N0x emission data seem unusually low; the new .
7
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data, especially in light of the recent cyclone boiler data, would seem
more reasonable for such units.
The remaining category for which new information is now available
is for spreader stoker units firing bituminous coal. New data on six
units are included (References 2-15, 2-16, 2-22, 2-23, 2-24, and 2-25).
The average N0X emission value, 15 lb/ton (270 ng/J) is a good
representative value for these units, agreeing well with the industrial
boiler N0X emission factor for the same category. 5 '
Although wet bottom boilers are not mutually exclusive from the
other categories, in this report they are treated separately because of
their very high NO^ emission rates.
2.2 HISTOGRAMS OF N0X EMISSIONS FOR UTILITY BOILERS
Figures 2-1, 2-2, 2-3 and 2-4 are bar graphs of baseline N0x
emission factors versus number of units tested within each boiler ?
type/fuel category.Figure 2-1 covers bituminous coal-, oil- and ;
gas-fired horizontally opposed units; Figure 2-2 covers bituminous coal-,
oil- and gas-fired single wall units. Figure 2-3 covers bituminous coal-
and oil-fired cyclone units and Figure 2-4 covers bituminous coal-fired
tangential units. Since there were Only two data points for natural "
gas-fired cyclone units, no histogram was constructed. With few
exceptions, the data fall quite close together considering the numbers of
variables involved. Two boilers, one a gas-fired, single wall unit and
the other an oil-fired, single wall unit, were too far from the average* ?
based on Chauvenet's criterion and, were excluded from the data presented
in Tables 2-1 and 2-2.
The variation within each boiler and fuel category may be due to ~
load (not all baselines were run at 80 percent load), air preheat, burner
type, furnace dimensions, differences in fuel nitrogen, amount of excess
air, errors in measurement, to name a few. Because of.the number of * s:-.
variables, the data are presented to only two significant figures. -i
2.3 EFFECT OF CONTROLS ON N0x EMISSIONS FOR UTILITY BOILERS r5w
There are several N0X control techniques currently in use with
utility boilers. These include: - "=
t Low Excess Air (LEA) The excess amount of combustion air
supplied is reduced
-------
I
1 _
* ic~
Average
aoo
300
v/zx//j//a
400
soo
r-
600
700
(BO)
1
(160)
(240)
N0X emission factors, lb/10ฐ scf (ng/J)
a. Natural Gas-Fired Horizontally Opposed Boiler
Average
M
Jo
90
I
(140)
I
(200)
(260)
NO^ emission factors, lb/10
qal (ng/J)
Residual Oil-Fired Horizontally Opposed Boilers
800
_E2_p2^.
!320)
900
1150
-V
(480)
EL
Average
1
-T-
35
-T"
40
i
15
~I
20
"J-
?5
30
1
ฃ260)
1
(440)
I
(620)
(600)
N0x emission factors, lb/ton (ng/J)
Bituminous Coal-l"1 red Horizontally Opposed Boilers
Figure 2-1. Population histograms of N0X emission factors for horizontally opposed
utility boilers.
-------
Average
ฆ
uMi
u
10 ,
9 .
8.
7 ,
6
S.
4
3
2
1
emission factors lb/10 scf <ปปg/U}
Hitural Gas-Fired Single Hill Boilers
*ปergge
/y-
m.
25
100
B,
~~i 1
(70) (220)
N0X orission factors, lb/103 gal (ng/J)
b, tesldual 011-Ftred Single Wall Boilers
Mrerage
*
. 125
-T
(370)
L\r
i
10
Wk
II
wk m
25
M.
i
30
35
(2TO!
(450)
(C 30
MS,
K Mission factors, lb/ton (rg/J)
c. BitwiiMus Coal-Fired Single Mall Boilers
fter a statistical analysis these tests were not considered representative of
tfcc boiler population, mvi therefore not Included in the reolaceinent emission
factor.
Figure 2-2. Population histograms of N0X emission factors
for single wall utility boilers.
10
-------
bv
-V
70
(200)
V
Average
80
90
100
(230)
(260)
1
(290)
3
N0X emission factors, lb/10 gal (ng/J)
a. Oi1 -Fired Cyclone Boilers
Average
WL
110
(320)
~T
40
30
35
46
50
!
ฆ (900)
(540) (720)
NQ^ emission factors, lb/ton (ng/J)
b. Bituminous Coal-Fired Cyclone Boilers
Figure 2-3.
Population histograms of N0X emission
factors for cyclone utility boilers.
11
-------
1/1
tf> 5 ~
4-
ฐ 3
u
ซ) o J
JO c
11
v"
(180)
Average
mm
mm
%
III
is
20
(270)
(360)
N0X emission factors, lb/ton (ng/J)
Figure 2-4. Population histograms of N0X emission factors for
bituminous coal-fired tangential utility boilers.
t Off-Stoichiometric Combustion (OSC) Some burners fire a
fuel-rich mixture and combustion is completed by injection of
additional air or lean mixture downstream
Flue Gas Recirculation (FGR) A portion of the flue gas is
recycled to the firebox
Load Reduction (LR) -- The boiler is fired at less than capacity
ง Combinations of two or more of the above
low N0X Burner (LNB)
Much of the data on these controls have previously been analyzed by
Acurex (Reference 2-26). In addition to this review, a section of the
cyclone boiler report (Reference 2-21) considers the applicability of many
N0x control techniques to this boiler type. The Standards Support and
Environmental Impact Statement report on lignite-fired boilers
(Reference 2-27) also dwells on certain of the N0x controls. Table 2-3
indicates the percent reduction one can expect by applying particular
N0X control techniques to each boiler/fuel category.
12
-------
TABLE 2-3. AVERAGE PERCENT REDUCTION OF NOx EMISSION FACTORS BY STATE-OF-THE-ART
CONTROL TECHNIQUES FOR UTILITY BOILERS (ENGLISH UNITS)
hOx Emissions (lb NO^/unlt fuel consumed) as a Function of Fuel
Type Boiler
Coal
Sas
Control
Bituminous
Lignite
Residual 011
Natural
Techniques
N0X (lb/ton)
% Reduction
N0X (lb/ton)
I Reduction
N0X (lb/103 gal)
% Reduction
NQX (lb/106 SCF)
{% Reduction)
Tangential
Baseline
15
--
8
50
300
..
LEA
12
20
6
20
'40'
[20]
210
30
osc
9
40
5
38
'40'
[20]
300
0
FGR
*
'35'
M
120
60
LR
13
15
7
12
45"
M
300
0
OSC + FGR
*
*
"20'
[60
[90]
im
OSC + IR
a
45
4
45
"35'
30
[270,
[101
OSC ~ LR + FGR
*
*
35;
[30]
[60,
bo]
Horizontally
ฆ
Opposed
Baseline
25
14
70
700
LEA
22
10
11
20
56 '
20
600
15
OSC
20
20
11
20.
45
35
' 300
60
FGR
20
20
11
20
60
13
[350]
[60]
LR
ฆ 22
10
13
10
50
30
300
60
OSC + FGR
15
40
[8]
[40]
56
20 .
[175]
[75] .
OSC + LR
19
25
10
25
35
50
. 140
BO
OSC ~ LR ~ FGR
*
*
2B
60
100
B5
lnb
15
40
'Indicates that no data Is available and technique may result In severe corrosion and/or slagging problems
[ ] Indicates engineering estimate
-------
TABLE 2-3. Concluded
(
NQk Emissions (lb NQj/unit fuel consumed} as a Function of Fuel
T/pe Boiler
Coals
Residual Oil
Natural Gas
Control
Bltunlnous
Lignite
Techniques
M>x (lb/ton)
% Reduction
N0X (lb/ton)
I Reduction
H0X (lb/103 gal)
X Reduction
H0X {lb/106 SCF)
(t Reduction)
Single Halt
Baseline
19
--
[11]
I9]
SO
410
LEA
16
15
rzoi
38
25
350
15
0SC
13
30
m
[30]
30
40
210
50
FGR
*
*
[35]
[30]
270
35
LR
14
25
M
[25]
35
30
125
70
osc ~ m
*
*
22
55
105
75
OSC + LR
10
45
[6]
[45]
28
45
BO
80
LR + OSC + FGR
ฆ *
v ซ. . #
22
55
165
60
LNB
11
40
Cyclone
Baseline
36
13
87
660
LEA
*
78
10
[560]
[15]
OSC
*
*
ซ
FGR
161]
[30]
330
50
LR
25 .
30
9
30"
70
20
[330]
[50]
OSC + FGR
*
*
OSC + LR
'
*
OSC ~ IR + FOR
*
'Indicates that no data Is available and technique mjt result In severe corrosion and/or slagging problems
[ ] Indicates engineering estimate
f
-------
It should be noted that off-stoichiometric combustion (OSC), also
known as two-staged combustion, can be accomplished by one of the
following:
Burners-Out-Of-Service (BOOS) -- Lower burners fire a fuel-rich
mixture, while upper burners supply only combustion air
Biased Burner Firing (BBF) Lower burners simply fire a
richer fuel-air mixture than upper burners
Overfire Air (OFA} -- All burners fire a richer mixture, then
additional combustion air is supplied above the firebox
The first two are generally used in a retrofit situation while the last is
principally a new boiler feature.
2.4 NITRIC OXIDE AS PERCENT CONSTITUENT OF TOTAL N0X EMISSIONS
Some data, principally from KVB (Reference 2-10 and 2-11) and the
cyclone boiler report (Reference 2-21) indicate that NO is the principal
constituent of N0x- Of the four boiler categories for which either NO
or N02 were measured along with N0Xป NO constituted at least 95 percent
of the N0X emissions. These data are presented in Table 2-4.
TABLE 2-4. NITRIC OXIDE AS A CONSTITUENT OF TOTAL N0X EMISSIONS
OF UTILITY BOILERS
Type
Boiler
N0/N0x as a Function of Fuel a
Bituminous
Coal
Residual
Oil
Natural
Gas
Single wall
96% (3)b
98% (1)
95% (2)
Cyclone
99% (6)
aWeight percentage, NO reported as NO2
^Numbers in parentheses refers to number of boilers tested.
15
-------
REFERENCES FOR SECTION 2
2-1. Bartok, W., et al"Systematic Study of N0X Emission Control Methods
for Utility Boilers," Exxon Report, GRU-4GN0S-71, December 1971.
2-2. Crawford, A. R., et al., "Field Testing: Application of Combustion
Modifications to Control N0X Emissions from Utility Boilers,"
EPA-650/2-74-066, NTIS-PB 237 344/AS, June 1974.
2-3. Dykema, 0. W.f "Analysis of Test Data for N0X Control in Gas and
Oil-Fired Utility Boilers," EPA-650/2-75-012, NTIS-PB 241 918/AS,
January 1975.
2-4. Dykema, 0. H. and R. E. Hall, "Analysis of Gas-, Oil, and Coal-Fired
Utility Boiler Test Data," in Proceedings of the Stationary Source
Combustion Symposium, Volume III, EPA-600/2-76-152c, NTIS-PB 257
146/AS, June 1976.
2-5. Bartz, D. R., et al., "Control of Oxides of Nitrogen from Stationary
Sources in the South Coast Air Basin," ARB 2-1471 (KVB Report No.
5800-179), September 1974.
2-6. Crawford, A. R., et al., "Field Testing: Application of Combustion
Modification to Power Generating Combustion Sources," Proceedings of
the Second Stationary Source Combustion Symposium, Volume II, UxilTfy
and Large Industrial Boilers, EPA 600/7-77-073b, July 1977.
2-7. Thompson, R. E., et al., "Effectiveness of Gas Recirculation and Staged
Combustion in Reducing N0X on a 560 MW Coal-Fired Boiler," EPRI
Report No. FP-257, NTIS-PB 260 582, September 1976.
2-8. Crawford, A. R., et al., "Control of Utility Boiler and Gas Turbine
Pollutant Emissions by Combustion Modification Phase I,"
EPA-600/7-78-036a, March 1978.
2-9. Blakeslee, C. E., and A. P. Selker, Program for Reduction of N0X from
Tangential Coal-Fired Boilers, EPA-650/2-73-005, 5a and 5b, NTIS-PB 226
547/AS, PB 245 162/AS, PB 246 889/AS, August 1973, June 1975 and August
1975.
2-10. Burrington, R. L., et al., "Overfire Air Technology for
Tangentially-Fired Utility Boilers Burning Western U.S. Coal,"
EPA-600/7-77-117, NTIS-PB 277 012/AS, October 1977.
2-11. Hoi linden, G. H., et al., "N0X Control at TVA Coal-Fired Steam
Plants," ASME Air Pollution Control Division, in Proceedings of the
Third National Symposium, April 1973.
16
-------
2-12. Higginbotham, E, 8. and P. M. Goldberg, "Field Testing of a Tangential
Coal-fired Utility Boiler Effects of Combustion Modification N0X
Control on Multimedia Emissions," Acurex Draft Final Report 79-337,
April 1979. , \
2-13. Crawford, A. R., et al., "N0X Emission Control for Coal-Fired Utility
Boilers," Esso Research and Engineering Company. Paper presented at
the Coal Combustion Seminar, Research Triangle Park, North Carolina,
June 19-20, 1973.
2-14. Crawford, A. R., et al., "The Effects of Combustion Modification on
Pollutants and Equipment Performance of Power Generation Equipment,"
Proceedings of the Stationary Source Combustion Symposium, Volume III,
Field Testing and Surveys, EPA-600/2-76-152c, June 1976.
2-15. Cato, G. A., et al., "Field Testing: Application of Combustion
Modifications to Control Pollution Emissions from Industrial Boilers
Phase I," EPA-650/2-74-078a, NTIS-PB 238 920/AS, October 1974.
2-16. Cato, G. A., et al., "Field Testing: Application of Combustion
Modifications to Control Pollution Emissions from Industrial Boilers
Phase II," EPA-600/2-76-086a, NTIS-PB 253 500/AS, April 1976.
2-17. Hoi linden, G. H., et al., "Control of N0X Formation in Wall
Coal-Fired Boilers, in Proceedings of the Stationary Source Combustion
Symposium, Volume II, EPA-6GQ/2-76-152b,NTIS-PB 256 321/AS, June 1976.
2-18. Hunter, S. C. and H. J. Buening, "Field Testing: Application of
Combustion Modifications to Control Pollutant Emissions from Industrial
Boilers - Phase I and II (Data Supplement)," EPA-600/2-77-122, June
1977.
2-19. U.S. Environmental Protection Agency, "Supplement No. 6 for Compilation
of Air Pollutant Emission Factors," Office of Air Quality Planning and
Standards, AP-42, April 1976.
2-20. Maloney, K. J., "Western Coal Use in Industrial Boilers," Western
States Section/The Combustion Institute, Salt Lake City, Utah,
April 1976.
2-21. Ctvrtnicek, T. E. and S. J. Rusek, "Applicability of N0X Combustion
Modifications to Cyclone Boilers (Furnaces)," EPA-600/7-77-006, January
1977.
* 2-22. Unpublished Data, EPA 68-02-2160, Acurex Corporation, August 1978.
2-23. Maloney, K. L., et al., "Systems Evaluation of the Use of Low-Sulfur
Western Coal in IxisTTng Small and Intermediate-Sized Boilers,"
KVB Inc., EPA-600/7-78-153a, July 1978.
2-24. Gabrielson, J. E., et al., "Field Tests of Industrial Stoker Coal-Fired
Boilers for Emissions Control and Efficiency Improvement - Site A,"
KVB Inc., EPA-600/7-78-136a, July 1978.
17
-------
2-25. Gabriel son, J. E., et al., "Field Tests of Industrial Stoker
Coal-Fired Boilers for Emissions Control and Efficiency Improvement
- Site B," KVB Inc., EPA-600/7-79-Q41a, February 1979.
2-26. Urn, K. J., et al., "Environmental Assessment of Utility Boiler
Combustion Modification N0X Controls," Acurex Draft Report
TR-78-105, April 1978.
2-27. Goodwin, D. R., "Standards Support and Environmental Impact
Statement, Volume I: Proposed Standards of Performance for
Lignite-Fired Steam Generators," EPA-450/2-76-030a, December 1976.
18
-------
SECTION 3
INDUSTRIAL BOILERS
Industrial boilers, for the purposes of this study, are defined as
coal-, oil-, or gas-fired steam generators with rated heat input
capacities ranging from 2.9 to 29 MW (10 to 100 x 106 Btu/hr). These
units are generally packaged boilers, including small, stoker, coal-fired
units as well as oil (residual and distillate) or gas burning firetube and
watertube boilers. As in Section 2, subbituminous coal is included in the
bituminous category.
As with all general definitions, there are exceptions. In fact,
nearly 14 percent of the industrial boiler population have input
capacities greater than 73 MW and nearly 26 percent have input capacities
smaller than 2.9 MW (Reference 3-1). For purposes of this report those
industrial boilers which have rated heat input capacities greater then
29 MW were incorporated with the previous utility boiler review, and those
of less than 2.9 MW were designated as residential-commercial types,
Section 4. 1
3.1 N0X EMISSION FACTORS FOR INDUSTRIAL BOILERS
Industrial boilers burning oil and natural gas have been divided
into two boiler types, watertube and firetube. A considerable quantity of
data much of it from the KVB reports were amassed for each category
(Tables 3-1 and 3-2). As before, Table 3-1 is presented in English units
and Table 3-2 contains the same data presented in SI units. Since
existing AP-42 emission factors for natural gas combustion are expressed
as a range, suggested replacement factors are expressed in the same
manner. Besides these results, the data also include Ultrasystems data
for a watertube and a firetube boiler tested with both natural gas and
residual oil (References 3-2 and 3-3) and Battelle data for a watertube
19
-------
TABLE 3-1. N0X EMISSION FACTORS SURVEY OF INDUSTRIAL BOILERS
(10 to 100 x 106 Btu/hr) (ENGLISH UNITS)
Type
Boiler
Baseline N0X Emissions as a Function of Fuel3
Coal (lb/ton burned)
on (lb/103 gal)
Natural Gas
(lb/10ฎ SCF)
Anthracite
Bituminous
Lignite
Residual
Distillate
iatertube
60 b
60c (14)<1
0X1
22
19 (5)
-1ซ
120-230
150 (13)
70-310e
Flretube
60
37 (6)
-38%
22
21 (7)
120-230
110 (9)
65-150
Spreader
Stoker*
- -
15
14 (3)
7i
i-ซ :
Underfeed
Stoker'
15
9.5 (4)
-37%
6.0
Overfeed
Stoker*"
16
15
7,8 (3)
-50*
6.0
values reported 1n terms of N02 EE-T-120
bQ1d AP-42 value
cReconmended replacement number based on new or revised data base
timber of boilers tested
^ange found for boilers tested
Stokers may be of either watertube or flretube construction
^Percent change In emission factor .
] Engineering estimate
20
-------
TABLE 3-2.
N0X EMISSION FACTORS SURVEY OF INDUSTRIAL BOILERS
(2.9 to 29 MW) (SI UNITS)
Type
Boiler
Baseline NOx Emissions (ng/J) as a Function of Fuel*
Coal
Oil
Natural Gas
Anthracite
Bitwinous
Lignite
Residual
Distillate
Matertube
170b
170c (14)d
-6*9
67
58(5)
-181
49-94
60 (13)
30-130*
Firetube
170
110 (6)
-35*
67
64 (7)
-31
49-94
45 (9)
28-60
Spreader
Stoker^
270
250 ( 3J
71
160
240 h
Underfeed
Stoker^
270
170 (4)
-37*
160
Overfeed
Stoker^
270
270
140 (3)
-50*
160
aNOx values reported in terras of NO? EI-T-121
b01d AP-42 value
cRecoranended replacement number based on new or revised data base
^Number of boilers tested
eRange found for boilers tested
^Stokers may be of either xatertube or firetube construction
^Percent change in emission factor
h[ ] Engineering estimate
21
-------
arid firetube boiler tested with natural gas, distillate oil and residual
oil (Reference 3-4),
Coal-fired industrial boilers are generally of the stoker design.
Pulverized coal units are limited to 29 MW (100 x 1Q6 Btu/hr) as a
minimum size because of efficiency considerations (Reference 3-5). The
KVB data contain two spreader stokers, four underfeed stokers and one
overfeed stoker. A third spreader stoker and two overfeed units were
tested by Rockwell (Reference 3-6). These data for spreader stokers are
consistent with utility boilers of the same category. The averages for
the underfeed and overfeed units appear reasonable. Based on the
bituminous coal NQX emission factors for both spreader and underfeed
stokers, a value of 9 lb/ton (240 ng/J) is suggested rather than the
6 lb/ton (160 ng/J) currently employed. The underfeed stoker lignite
value, however, should be retained. Also there are not enough data for
lignite coal-fired spreader stokers to improve on the existing overfeed
stoker N0x emission value for lignite.
3.2 HISTOGRAMS OF N0x EMISSIONS FOR INDUSTRIAL BOILERS
Figure 3-1 shows bar graphs of baseline emission values versus
class of boiler for those classes in which more than two N0X emission
numbers were gathered. The variation within each boiler and fuel category
may be due to load (not all baselines were run at 80 percent load), air
preheat, burner type, furnace dimensions, differences in fuel nitrogen,
amount of excess air, errors in measurement, to name a few. Because of
the number of variables, the data are presented to only two significant
figures. All baseline data found were included.
3.3 NITRIC OXIDE AS PERCENT CONSTITUENT OF TOTAL N0X EMISSIONS
The total nitrogen oxides (N0x) emissions consist primarily of
two components: Nitrogen dioxide (NO^) and nitric oxide. Thus, if the
concentration of two are known, the third can be determined to some degree *
of accuracy.
KVB determined NO and NO on almost all boilers tested during its >
x
two field investigations. Table 3-3 contains this data reduced to percent
NO in N0X- As can be seen, the average percent NO in N0x is at least
94. The ratio of NO to N0X does not seem to be affected by fuel type or
boiler type or size.
22
-------
4
3
2 H
1
Average
.Y/JMr/y/M Jj
3
5
k
/\r
~~r~
(40)
ซ 2C
1
(80)
NO emission factors. Ib/1Q6 scf (ng/J)
*
2b
4
3
2 H
'\r
-r
50
a. Natural Gas-Fired Front Wall Uatertube Units
Average
m\ m w\ wm fm
75
100
125
I
(20)
(30)
1
(405
(50)
N0x emission factors, 1b/10ฐ scf (ng/J)
b. Natural Gas-Fired Front Wall Fire tube Units
4 -1
3 -
2 -
1 H
Average
LV
-V
15
20
25
(55)
(705
N0X emission factors, lb/10 gal (ng/J)
c. Distillate Qil-FirซJ Front Wall Uatertube Units
300
(120)
150
-f-
(60)
Figure 3-1. Population histograms of N0X emission factors
for industrial boilers.
23
-------
4
3
2
1
wk
Average
m m
20
Vl
ฆ** 4
a
X.'
e
~i
(50)
(80) .
N0X emission factors, lb/10^ gal (ng/J)
d. Distillate Oil-Fired Front Wall Firetube Units
Average
LV
^v
25
50
75
100
[110)
-
l
f/
%
, Wk WK
Z/M
7l
'//<
//t
125
ฃ70)
(2003
I
(330)
N0X emission factors, lb/10 gal (ng/J)
e. Residual Oil-Fired Front Wall Watertube Units
Average
10.
%S2L
40
(90)
(12b)
w\
50
(15b
N0x emission factors, lb/10 gal (ng/J)
f. Residual Oil-Fired Front Wall Firetube Units
Figure 3-1. Continued.
24
-------
4 -i
3 -
2
1
s_
ja
Average
T
10
"T"
15
"V1
(180)
(270)
H
J
H
k
T"
20
T
(360)-
N0 emission factors,
x
lb/ton (ng/J)
Bituminous Coal-Fired Spreader Stokers
'4
3
UVr
f 90)'
Average
M
15
(180)
(270)
N0x emission factors, lb/ton (ng/J)
h. Bituminous Coal-Fired Underfeed Stokers
Figure 3-1. Concluded.
25
-------
TABLE 3-3. NITRIC OXIDE AS A CONSTITUENT OF TOTAL NOx EMISSIONS
OF INDUSTRIAL BOILERS
Type
Boiler -
NO/NOx as a Function of Fuel a
Bi'tumi nous
Coal
Resi dual
Oil
Distil 1 ate
Oil
Natural
Gas
Water tube
99% (12)a
97% (3)
95% (8)
Firetube
98% (4)
95% (5)
94% (9)
Spreader
Stoker
98% (2)
Underfeed
Stoker
98% (4)
'
aWeight percentage, NO reported as NO2
^Numbers in parentheses refers to number of boilers tested
26
-------
3.4 EFFECT OF CONTROLS ON NOฅ EMISSIONS FOR INDUSTRIAL BOILERS
A
No long term testing of state-of-the-art NO emission controls
A
has yet been undertaken for industrial boilers. Because of this, it is
difficult to say whether the NO control techniques developed for
utility boilers will be equally effective for industrial boilers. Short
term tests by KVB and others do indicate, however, that combustion
modification control techniques are effective in reducing NO
X
(References 3-7, 3-8, 3-2 and 3-3). It is not yet recommended that these
limited controlled emissions data be published in AP-42.
3.5 OTHER DATA
One data source for coal-fired boilers which met the requirements
for inclusion in the survey was that of Ferrari (3-9). However, the data
are presented separately for two reasons:
The source of the data is Australia and, although the boilers
may be basically the same, some may be different in design.
Where the data overlaps the data in this study; they are quite
different and generally do not follow the expected trend with
unit size.
Table 3-4 lists Ferrari's values and compares them with averages
for all of the boiler types for which the design is specified. Ferrari
also reported on pulverized coal units but failed to indicate, the type of
units tested. However, his results for pulverized coal are considerably
lower than the averages for tangential, single wall and horizontally
opposed boilers in the utility category.
27
-------
TABLE 3-4. COMPARISON OF DATA FROM FERRARI et al. WITH CALCULATED
AVERAGES FOR SAME BOILER TYPE AND SIZE
-
N0X emission factors (ng/J)
as function of boiler size
Type Unit
Utility
Industrial
Chain Grate Stokers
(overfeed)
141 (4)a
187 (2}b
110C (3)
Spreader Stokers
166
192 (2)
260 (5)
250 (3)
aTop row Ferrari's values.
^Numbers in parentheses refer to number of boilers tested.
cBottom row, NOx emissions update averages.
28
-------
REFERENCES FOR SECTION 3
3-1. "Task 2 Suirmary Report -- Preliminary Summary of Industrial Boiler
Population," prepared by PEDCo in support of OAQPS work on NSPS for
industrial boilers, June 29, 1978.
3-2. Cichanowicz, J. E., et al., "Pollutant Control Techniques for Package
Boilers. Phase I Hardware Modifications and Alternate Fuels,
Ultrasystems Draft Report for EPA 68-02-1498, November 1976.
3-3. Heap, M. P., et al., "Reduction of Nitrogen Oxide Emissions from Field
Operating Package Boilers, Phase III," EPA-600/2-77-025, NTIS-PB 269
277, January 1977.
3-4. Barrett, R. E. and S. E. Miller, "Field Investigation of Emissions from
Combustion Equipment for Space Heating," Battelle-Columbus Laboratories,
EPA-R2-73-084a, API Publication 4180, June 1973.
3-5. "Task 7 Summary Report Technical and Economic Bases for Evaluation of
Emission Reduction Technology," prepared by PEDCo in support of OAQPS
work on NSPS for industrial boilers, June 2, 1978.
3-6. Littman, F. E., et al., "Regional Air Pollution Study. Point Source
Emission Inventory," EPA-600/4-77-014, March 1977.
3-7. Cato, G. A. et al., "Field Testing: Application of Combustion
Modifications to Control Pollutant Emissions from Industrial Boilers
Phase 1," EPA-600/2-74-078a, NTIS-PB 238 920/AS, October 1974.
3-8. Cato, G. A. et al., "Field Testing: Application of Combustion
Modifications to Control Pollutant Emissions from Industrial Boilers --
Phase 2," EPA-600/2-76-086, NTIS-PB 253 920/AS, October 1974.
3-9. Ferrari, L. M., et al., "Nitrogen Oxides Emissions and Emission Factors
for Stationary Sources in New South Wales," International Clean Air
Conference, The Clean Air Society of Australia and New Zealand," May
1967. .
29
-------
SECTION 4
COMMERCIAL AND RESIDENTIAL UNITS
This section not only covers all stationary steam generating
fi
sources whose rated heat input capacity is less than 2.9 MW (<10 x 10
Btu/hr) but also residential hot water, steam and forced air heaters. The
arbitrary dividing line between commercial and residential units is set at
C
150 kW (5 x 10 Btu/hr). As noted previously in the introduction to
industrial boilers, nearly 26 percent of the boilers used in industry have
input capacities less than 2.9 MW. Thus, some commercial boiler data were
obtained from industrial boiler reports.
4.1 N0X EMISSION FACTORS FOR COMMERCIAL SIZED BOILERS
Commercial boilers fall into three categories: stoker fed
coal-fired, hand fed coal-fired, and oil- or gas-fired units generally of
a firetube design. Many are used as a source of hot water rather than a
source of steam or electricity. Tables 4-1 and 4-2 contain information on
those units whose N0x emissions have been measured.
The initial KVB boiler survey (Reference 4-1) contains data on two
firetube boilers with heat input capacities of 2.1 MW (7 x 10ฎ Btu/hr)
and 2.4 MW (8 x 10 Btu/hr). One of these units was run with two grades
of residual oil, distillate oil and natural gas. The other was run with
natural gas only. The oil data have previously been incorporated into
AP-42, supplement 6 (Reference 4-2). The natural gas data are 22 percent
lower than the existing AP-42 number which is composed solely of the
results from seven boilers tested by Battelle (References 4-3 and 4-10).
However, two of these Battel le units were industrial size and the data
have been recalculated to reflect this. Thus, the new value is the
arithmetic average of the remaining five units plus the two KVB results.
30
-------
TABLE 4-1. NQX EMISSION FACTORS SURVEY OF COMMERCIAL STATIONARY STEAM AND HOT WATER
GENERATING UNITS (0.5 to 10 x 10& Btu/hr) (ENGLISH UNITS)
Type
Boiler
Baseline N0X Emissions as a Function of Fuel3
Coal (lb/ton)
Oil (lb/103 gal)
Natural Gas ;
(lb/10ฎ SCF)
Anthracite
Bituminous
Lignite
Residual
Disti Hate
Firetube
60b
6lc (8)d
2e
22
19 (7)
-14%
120
92 (7)
-22%
Commercial
Stokers
2.2-3.2f (1)
6.0
6.0
Commercial
Hand-Fired
Units
3
3.0
aNOx values reported in terms of NOg
b01d AP-42 value
Recommended replacement number based on new or revised data base
^Number of boilers tested
ePercent change in emissions factor
Range as reported in literature, best available information (Reference 4-5)
-------
TABLE 4-2. N0X EMISSION FACTORS SURVEY OF COMMERCIAL STATIONARY STEAM
AND HOT WATER GENERATING UNITS (0.15 to 2.9 MW) (SI UNITS)
Type
Soiler
Basline N0X Emissions (ng/J) as Function of Fuel a
Coal
Oil
Natural Gas
Anthracite
Bituminous
Lignite
Residual
Distillate
Firetube
172b
180c (8)d
2e
67
58 (7)
-15%
49
38 (7)
-22*
Commercial
Stokers
37-55(l)f
110
160
Commercial
Hand-Fired
Units
51
54
aNOx values reported in terms of NC^ EE-T-119
bOTd AP-42 value
cReeonmended replacement number based on new or revised data base
^Number of boilers tested
a
Percent change in emissions factor
Range as reported in literature, best available information (Reference 4-5)
32
-------
Battelle (Reference 4-3) has also tested a 200 kW commercial boiler
fitted with both bituminous and anthracite stokers. This unit was
operated at extremely low loads for most of the test sequences in an
attempt to achieve smokeless results. The N0X emission factors reported
here for anthracite were run at 74 percent load and the bituminous at 49
percent load. Because of the low load and large excess air conditions,
incorporation of the bituminous coal data in AP-42 is not recommended and
have not been included in the reported average.
4.2 N0x EMISSION FACTORS FOR RESIDENTIAL FURNACES AND BOILERS
Residential units fall into the same broad categories as the
commercial boilers, above. N0x emission data for residential units
are contained in Tables 4-3 and 4-4, in English units and SI units,
respectively.
Monsanto (Reference 4-6) has recently published information on a
200,000 Btu/hr furnace and a 200,000 Btu/hr boiler. Both units are
supplied by underfeed stokers and fired, with western subbituminous coal.
Average baseline N0X for the two units is 8.5 lb/ton (152 ng/J). The
N0X emission factors were approximately twice as great for the furnace
as for the boiler using the same coal. This suggests that design features
may play an important part in N0X emission factors for these units.
Several recent sources of data on N0X emissions for natural
gas-fired residential units have been abstracted (References 4-7, 4-8, and
4-9). The most extensive results, conducted by The American Gas
Association (AGA) Laboratories (Reference 4-7) cover 38 gas-fired, forced
air furnaces manufactured by 29 different companies with heat input rates
3 3
ranging from 75 x 10 to 180 x 10 Btu/hr. The average N0X emission
factors for these units are 103 lb NOg/lO^ scf (42.1 ng NO2/J) and
they ranged from 18.8 to 128.1 lb N(yi06 scf (7.7 to 52.5 ng NOj/J).
The lowest number was considered outside of acceptable limits and was
discarded for the final average. The data for the blue flame, high 02
condition, were considered as baseline. A second, low excess air (yellow
flame adjustment) testing sequence showed an average 10 percent decrease
in N0X emissions for this control technique.
Hall (Reference 4-8) reports on the testing of two gas-fired
furnaces and one gas-fired boiler. In these tests NO measurements
averaged 60.5 lb N0/106 scf (24.8 ng NO/J). If one assumes that at
33
-------
TABLE 4-3. N0X EMISSION FACTORS SURVEY OF RESIDENTIAL STEAM AND
HOT WATER GENERATING UNITS {<500,000 Btu/hr)
(ENGLISH UNITS)
Type
Boiler
Baseline N0X Emissions as a Function of Fuel3
Coal (lb/ton)
Oil (lb/103 gal)
Natural Gas
{lb/10ฎ SCF)
Anthracite
Bituminous
Lignite
Residual
Distil late
Residential
Heating
16
80b
1Q2C (44)d
+28*e
Stoker
Units
6.0
8.5 (2)
422
6.0
Hand-F1red
Units
3.0b
aNOx values reported in terms of N02 EE-T-122
bQld AP-42 value
cRecornnended replacement number based on ne* or revised data base
dumber of boilers tfistsd
ePercent change in emissions factor
34
-------
TABLE 4-4. N0X EMISSION FACTORS SURVEY OF RESIDENTIAL (<0.15 MM)
STEAM AND HOT WATER GENERATING UNITS (SI UNITS)
Type
Boiler
Baseline N0X Emissions (ng/J) as a Function of Fuel3 ,
Coal
Oil
Natural Gas
Bituminous
Lignite
Residual
Distillate
Residential
Heating
' ! '
55^
33b
42C (44)d
+28ซe
Stoker
Units
107
152 (2)
42%
: 160
-
Hand-Fired
Units
54b
aNOx values reported in terms of N02
b01d AP-42 value
Recommended replacement number based on new or revised data base
dNumber of boilers tested
ePercent change in emissions factor
-------
least 90 percent of N0x is NO then the NDX concentration (measured in
terms of N02) is 102 lb N02/106 scf (41.8 ng N02/J). The units
tested by Hall were "as is." Those by the A6A were tuned (blue flame).
In both cases, the tests were considered baseline. Similar lack of
effects of boiler tuning on N0x emissions were shown by KVB for
industrial boilers (Reference 4-10).
Finally, Rocketdyne (Reference 4-9), prior to testing various
modifications on the unit, procured and tested a Lennox 011-140 warm air
furnace equipped with a stock Lennox Burner. A baseline run on the unit
gave 98 lb N0/106 scf (40 ng NO/J). This is equivalent to 167 lb
N02/106 scf (68 ng N02/J) of N0X measured as N02 if the NO as
measured previously accounted for 90 percent of the N0x.
Suumation of these 41 individual boilers with the two units
previously averaged in AP-42 Supplement 3 (Reference 4-11) gave 102 lb
6
N02/10 scf (42.0 ng/J) as the overall average.
4.3 N0X EMISSION FACTORS FOR PILOT LIGHTS
Most residential, gas-fired waterheaters and forced air furnaces
contain pilot burners. Fuel input ranged from 828 to 1570 Btu/hr for the
seven pilot lights examined by the AGA (Reference 4-7). The average NO
C A
emission factor for these pilots is 71.3 lb/10 scf (29.2 ng/J), roughly
75 percent of that for the burners.
4.4 HISTOGRAMS OF N0X EMISSIONS FOR COMMERCIAL AND RESIDENTIAL UNITS
Population N0X emission histograms are drawn for gas-fired
commercial boilers, residential heating units and pilot lights. These
histograms are shown in Figure 4-1. All data are within acceptable limits
except the 7.7 ng/J residential unit reported by Thrasher and Dewerth
(Reference 4-7).
4.5 NITRIC OXIDE AS PERCENT CONSTITUTENT OF TOTAL N0X EMISSIONS
Much of the data reviewed was reported in terms of either NO and
N02 or NO and N0x. These data are presented in Table 4-5. A trend in
the data seems to indicate that the smaller the source, the greater the
fraction of NO in the N0X emissions. The pilot light data and 38 data
points for gas-fired residential units were reported by the American Gas
Association Report (Reference 4-7). The remaining N0/N02 data were
taken from two older Battelle documents (Reference 4-3 and 4-4). Data for
commercial units were reported by Battelle (Reference 4-3) and KVB
(Reference 4-1).
36
-------
Lv
T"
10
.Averaae
~r
20
m
30
40
50
T
50
I
100
Emission factor, ng/J (lb x "10 scf)
a. Natural Gas-Fired Commercial Boilers
Average
r
60
i
.150
I
50
1
100
Emission factor, ng/J {lb x 10 scf)
b, Natural Gas-Fired Residential Units
, 150
Average
rnrnM m
T"
40
10
20
~
50
50
I
100
Emission factor, ng/J (16 * 10ฎ scf)
c. Pilot Lights
Figure 4-1. Population histograms of NO* emission factors for
natural gas-fired commercial boilers, residential
units, and pilot lights.
37
-------
TABLE 4-5. NITRIC OXIDE AS A CONSTITUENT OF TOTAL NOx EMISSIONS
OF COMMERCIAL AND RESIDENTIAL BOILERS AND HEATING UNITS
AND PILOT LIGHTS
Type
Bo i 1 er
N0/N0x as a Function of Fuel3
Natural
Gas
Distil late
Oil
Residual
Oil
Cormier ci al
0.5 to 10 x 106
Btu/hr
97 (8)b
99 (7)
99 (7)
Residential
2 to 500 x 103
Btu/hr
As found
79 (2)
Tuned
95 (38)
75 (32)
Pilot Light
<2000 Btu/hr
55 (7)
height percentage, NO reported as NOฃ
^Numbers in parentheses refers to number of boilers tested.
38
-------
REFERENCES FOR SECTION 4
Cato, G. A. et al., "Field Testing: Application of Combustion
Modifications to Control Pollutant Emissions from Industrial
Boilers Phase I," EPA-600/2-74-078a, NTIS-PB 238 920/AS,
October 1974. . , ,
U.S. Environmental Protection Agency, "Supplement No. 6 for Compilation
of Air Pollutant Emission Factors," Second Edition, Office of Air
Quality Planning and Standards, Document AP-42, April 1976.
Barrett, R. E., et al., "Field Investigation of Emissions from
Combustion Equipment for Space Heating," EPA-R2-73-084a (API
Publication 4180), June 1973.
Levy, A., et al., "A Field Investigation of Emissions from Fuel Oil
Combustion for Space Heating," API Publication 4099, November 1971.
Giammar, R. D., et al., "Emissions from Residential and Small
Commercial Stoker-Coal-Fired Boilers Under Smokeless Operation,"
EPA 600/7-76-029, October 1976.
4-6. DeAngelis, 0. G., and R. B. Reznik, "Source Assessment: Coal-Fired
Residential Combustion Equipment Field Tests, June 1977, "EPA
600/2-78-0040, June 1978.
4-7. Thrasher, W. H. and D. W. Dewerth, "Evaluation of the Pollutant
Emissions from Gas-Fired Forced Air Furnaces," American Gas Association
Research Report #1503, Catalog No. U7815, May 1975.
4-8. Hall, R. E., et al., "A Study of Air Pollutant Emissions from
Residential Heating Systems," EPA 650/2-74-003, January 1974.
4-9. Combs, L. P., and A. S. Okuda, "Residential Oil Furnace System
Optimization, Phase II," EPA 600/2-77-028, January 1977.
4-10. Cato, G. A., et al,, "Field Testing: Application of Combustion
Modifications to Control Pollutant Emissions from Industrial Boilers
Phase 2," EPA-600/2-76-086a, NTIS-PB 253 500/AS, April 1976.
4-11. U.S. Environmental Protection Agency, "Supplement No. 3 for Compilation
of Air Pollutant Emission Factors," Second Edition, Office of Air
Quality Planning and Standards, Document AP-42, July 1974.
4-1.
4-2.
4-3.
4-4.
4-5.
39
-------
SECTION 5
STATIONARY RECIPROCATING ENGINES
Reciprocating engines consist of two major subclasses, compression
ignition (CI) and spark ignition (SI). Each subclass is divided into
two-stroke and four-stroke engine cycle categories (Reference 5-1).
Further division by engine use has also been customary (Reference 5-2 and
5-3); however, because engine type and size are constantly changing within
each use category, the substitution of rated power output is recommended.
5.1 . N0X EMISSION FACTORS FOR COMPRESSION IGNITION ENGINES
These engines are divided into three power output categories; large
(>75 kW/cyl), medium (75 kW/cyl to 75 kW/engine), and small (<75 kW/engine).
Further division is by fuel type and by engine cycle. Two fuel types are
characteristic of compression ignition engines; diesel engines, burning
diesel oil fuel, and dual fuel engines, burning a mixture of diesel oil
and gas (natural and synthetic) consisting of anywhere from >95:5 to
<5:95 parts by weight of the two fuels. Some dual fuel engines also have
the capability of burning each fuel separately.
Table 5-1 gives the emission factors in 3 different units. To
convert from output specific units, e.g., gm/hp-hr, to input specific
units, e.g., ng/J and Kg/10 liter or lb/10 gal, heat rates for
compression ignition engines were estimated. These are presented in Table
5-2.
The nitrogen oxides emissions factors for large and medium CI
engines were reported in the Standards Support Document (Reference 5-1)
and Hare and Springer (Reference 5-4). N0X emission factors for small
engines were found in Marshall and Fleming (Reference 5-5) in addition to
Hare and Springer.
40
-------
TABLE 5-1. BASELINE N0X EMISSION FACTORS SURVEY OF RECIPROCATING
COMPRESSION IGNITION (CI) ENGINES "
N0X Emissions as a Function of Stroke and Fuel3
Engine
Size
i
Un i ts
Diesel oil
Dual
Fuel
2 Stroke
4 Stroke
2 Stroke
4 Stroke
arge
75 kW/cyl.
ng/Jb
g/hp-hr
lb/103 galb
No. Engines
1800
13.3
600
(14)
1200
8.8
400
(19)
1520
10.4
c
(3) .
1260
8.6
__c
(6)
edium
75 kW/eng.
75 kW/cyl.
ng/Jb
g/hp-hr
lb/103 galb
No. Engines
1980
16.1
660
(23)
1100
9.0
360
(66)
mall
75 kW/eng.
ng/Jb
g/hp-hr
lb/103 galb
No. Engines
1300
10.5
430
(15)
NOx values reported in terms of NOg
Input Specific
Constituent ratio of dual fuel unknown
41
-------
TABLE 5-2. HEAT RATES FOR COMPRESSION IGNITION ENGINES
Engine Size
Fuel
Heat Rate (Btu/hp-hr)
Large
Medium and Small
Diesel
Dual
Diesel
7000 (Reference 5-1)
6500 (Reference 5-1)
7680 (Reference 5-3)
AP-42, Supplement 4 previously lists Hare and Springer data without
differentiation as to size or number of strokes per firing cycle.
5.2 NO EMISSION FACTORS FOR SPARK IGNITION ENGINES
x
Spark ignition (SI) engines are divided into four categories of
power output; large (>75 kW/cyl), medium (75 kH/cyl to 75 kW/engine),
small (15-75 kW/engine) and very small (<15 kW/engine). Like compression
ignition engines, these engines are further divided by engine cycle and
fuel type. The principal fuels for spark ignition engines are gasoline
and natural gas. Table 5-3 contains the average N0x emissions factors
for these engines.
A substantial body of data was acquired for natural gas-f1red large
and medium sized, stationary, spark ignited (SI) engines (References 5-1,
5-6, 5-7, and 5-8). The current emission factors are 20 percent higher
for two-stroke engines and 40 percent higher for four-stroke engines than
those in AP-42, which are based on Urban and Springer and Dietzman and
Springer alone (Reference 5-6 and 5-7). The best data available were
considered to be that of Dietzman and Springer which were repeated in
Urban and Springer. These were used in the averages in Table 5-3. These
data agreed well with that abstracted from References 5-1 and 5-6.
Data for gasoline fired SI engines were obtained for all categories
except large engines (References 5-4, 5-9, 5-10, and 5-11). Numbers for
the small and very small engine categories are from Hare and Springer
(Reference 5-4). They have previously been abstracted into AP-42 under
"industrial equipment", Section 3.3.3, and "small, general utility
engines", Section 3.2.5. There are no additional data in these
categories, but a minor adjustment was necessary. The values reported
42
-------
TABLE 5-3. BASELINE N0X EMISSION FACTORS SURVEY OF RECIPROCATING
SPARK IGNITION (SI) ENGINES
N0X Emissions as a Function of
Stroke and Fuel3
Engine
Size
Units
Gasoline
Natural Gas
4 Stroke
2 Stroke
4 Stroke
Large
>75 kW/cyl.
ng/jb
g/hp-hr
lb/103 galb
lb/10" SCFb
No. Engines
1560
13.2
4000
55
1960
15.5
4800
24
Med i urn
75 kW/eng.
-75 kW/cyl.
ng/jb
g/hp-hr
lb/103 galb
lb/10b SCFb
No. Engines
740
10.8
260
9
1600
12.7
3900
23
Small
15-75 kW/eng.
ng/jb
g/hp-hr
lb/103 galb
No. Engines
310
5.4
110
3
Very Small
<15 kW/eng.
ng/jb
g/hp-hr
Ib/lO^ galb
No. Engines
198
5.0
69
5
aNO values reported In terms of NO,
L X c>
Input specific values, all others are output specific
43
-------
herein are computed on an evenly weighted average and one engine that was
not tested at baseline was deleted.
5.3 HISTOGRAMS OF NO EMISSIONS FOR RECIPROCATING ENGINES
Population versus N0X emission factor histograms were drawn for
all of the categories of SI and CI engines for which data were obtained.
They appear in Figure 5-1 through 5-4. Two of the histograms contain
blocks with numbers superimposed on them. These blocks represent averages
of a particular number of engines as reported in the literature; values
for the individivual tests were not given. Abscissae of these plots are
marked in both English and SI units where possible.
5.4 NITRIC OXIDE AS PERCENT CONSTITUTENT OF TOTAL NO EMISSIONS
X
Data for percent NO in total NO were taken from Hare and
Springer, Dewerth, and Dietzman and Springer (References 5-4, 5-6, and
5-8). It is presented by engine subclass and category in Table 5-4.
44
-------
Average
~1
(?OCj
(200) (300) . (400) (500) (600) (700) (800)
3
N0X emission factors, ng/J (lb/10 gal)
a. Large 2-Stroke
Average
NO^ emission factors, ng/J (lb/10 gal)
3
2 i
1
Kr
Average
10
EL
Tk
1500
2000
?500
3000
(600)
(800)
K0x emission factors, ng/J (lb/10"' gal)
c. Medium, 2-Stroke
*Nunbers in blocks indicate averages of this nurrber of
engines as reported in the literature. Shaded blocks
indicate individual engines.
Figure 5-1. Population histograms of N0X emission factors for
compression ignition engines firing diesel fuel.
45
-------
Averaoe
2000
200
I
400
N0x enission factors, nq/J {lb/10 gal]
d. Medium, 4-Stroke
600
n
-Q
Average
m
M
Ml
WA
500
1000
1500
200
20uQ
2500
,^
600
I
400
800
NO emission factors, ng/J (lb/10 gal]
e. Small, 4-Stroke
~Numbers 1 n blocks indicate averages of. this number of engines as reported
in the literature. Shaded blocks indicate individual engines.
Figure 5-1. Concluded.
46
-------
us^-
tfi
0)
cn
H-
ฉ
u
0*
XI
1 -
ฆ^r
Average
I
1000
1500
2000
N0x emission factors, ng/J
Large, 2-Stroke
Average
k
2500
%
J
P
<
m ym vn[A
500
1000
1500
2000
N0x emission factors, ng/J
Large, 4-Stroke
Figure 5-2. Population histograms of N0X emission factors for
compression ignition engines firing dual fuels.
47
-------
Average
1000
1500
?000
2500
3000
3c>n
1
(2000)
(4000)
(6000)
NC^ emission factors, ng/J (lb/10 scf)
a. Lame Size, 2-Stroke
Average
(8000)
ซj
jq
WMA
TOCO
1500
2000
2500
3000
3500.
4 -
3 -
2
1 -|
0
1
(COOO)
N0x emission factors, ng/J (lb/10 scf)
b. Large Size, 4-Stroke
Average
V/.\ M El
500
iooo
1500
2000
2500
1
(3000)
(1000)
(5000)
N0x emissions factors, ng/J (lb/10 scf)
c. Medium Size, 4-Stroke
Figure 5-3. Population histograms of N0X emission factors for stationary
reciprocating, natural gas firing SI engines.
48
-------
Average
LV
~~r
200
m wm
VM m m
300
(500)
ซ 'ฆ
3 ฆ
(200)
(600)
(700)
(BOO)
1
(900)
NO emission factors, lb/10 oal (no/J)
x
a. Medium
Average
m
T
100
150
(300)
(400)
(500)
"i0 emission factors, lb/10 gal (ng/J)
b. Small
(1000)
3 "1
2
1
0
Average
m m vfr
50
100
(100)
(ZOO)
(309)
NO e-ssion factors, lb/10 oal (nn/J)
c, Very Sma 11
(41'"'
Figure 5-4. Population histograms of N0X emission factors for stationary
reciprocating gasoline fired Spark Ignition engines.
49
-------
TABLE 5-4. NITRIC OXIDE AS A CONSTITUENT OF TOTAL NOx EMISSIONS
OF RECIPROCATING ENGINES
Engine
Size
N0X Emissions as a Function of Type, Stroke, Fuel and Size3
Compression Ignition
Spark Ignition
Diesel Fuel
Natural Gas
Gasoline
2 Stroke
4 Stroke
2 Stroke
4 Stroke
Large
88 (42)b
83 (9)
Medium
93 (1)
96 {4}
96 (15)
Small
98 (3)
98 (3) : ;;
height percentage, NO reported as NOซ
, ฃ
Number in parentheses refers to number of engines tested
50
-------
REFERENCES FOR SECTION 5
5-1 Youngblood, S. B. et al"Standards Support and Environmental Impact
Statement for Reciprocating Internal Combustion Engines," Acurex Draft
Report TR-78-99, March 1978.
5-2 Anon, "Campi1ation of Air Pollution Emission Factors," U.S.
Environmental Protection Agency, Office of Air Quality Planning and
Standards, Publication AP-42, April 1973 and Supplements.
5-3 Shimizu, A. B., et al., "NQX Combustion Control Methods and Costs for
Stationary Sources Summary Study," EPA 600/2-75-046, September 1975.
5-4 Hare, C. T. and K. J. Springer, "Exhaust Emissions from Uncontrolled
Vehicles and Related Equipment Using Internal Combustion Engines, Final
Report -- Part 5, Heavy-Duty Farm, Construction and Industrial Engines,"
Southwest Research Institute, San Antonio, Texas, AR-898, October 1973.
5-5 Marshall, W. F, and R. D. Fleming, "Diesel Emissions Reinventoried,"
Report of Investigations No. 7530 by the U.S. Department of the
Interior, Bureau of Mines, 1972.
5-6 Dietzmann, H. E., and K. J. Springer, "Exhaust Emissions from Piston and
Gas Turbine Engines Used in Natural Gas Transmission," Southwest
Research Institute, San Antonio, Texas, prepared for American Gas
Association, Arlington, VA, January 1974.
5-7. Urban, C. M. and K. 0. Springer, "Study of Exhaust Emissions from
Natural Gas Pipeline Compressor Engines," Southwest Research Institute,
San Antonio, Texas, prepared for American Gas Association, Arlington,
VA, February 1975.
5-8 Dewerth, D. W., "Air Pollutant Emissions from Spark-Ignition Natural Gas
Engines and Turbines," American Gas Association Laboratories Research
Report No. 1491, September 1973.
5-9 Hare, C. T. and K. J. Springer, "Exhaust Emissions from Uncontrolled
Vehicles and Related Equipment Using Internal Combustion Engines, Final
Report, Part 4, Small Air-Cooled Spark Ignition Utility Engines," U.S.
Environmental Protection Agency, APTD-1493, May 1973.
5-10 Fleming, R. D. and F. R. French, "Durability of Advanced Emission
Controls for Heavy Duty Diesel and Gasoline Fueled Engines,"
EPA 460/3-73-010, September 1973.
5-11 Springer, K. J., "Baseline Characterization and Emissions Control
Technology Assessment of Heavy-Duty Gasoline Engines," Final Report
Southwest Research Institute, San Antonio, Texas, AF-844, November 1972.
51
-------
SECTION 6
GAS TURBINES
6.1 NOx EMISSION FACTORS FOR VARIOUS TYPES AND SIZES OF GAS
TURBINE ENGINES
For the purpose of this study, gas turbines have been divided into
three sizes; large >15 MW (>20,000 hp), medium, 4 to 15 MW (5300 hp to
20,000 hp) and small, <4 MW (<5300 hp). The units were further divided
into simple and regenerative cycle* and subsequently classified as to
fuel. As no distinction could be made between the various types of oil
burned, all of these were combined into liquid fuel. The liquid fuel
category does not contain derived fuels such as methanol but does include
heavy distillates and crudes when reported.
Table 6-1 contains a summation of the data extracted. Much of the
information was obtained from the Standard Support Document (Reference 6-1).
Other sources include Dietzman and Springer (which has already been
incorporated into Supplement 6 of AP-42) (Reference 6-2), Dewerth
(Reference 6-3), Wasser (Reference 6-4), Crawford, et al., (Reference 6-5)
and Acurex (Reference 6-6). Much of the data contained heat rates for the
units tested so that it was possible to determine input specific (lb/MBtu,
ng/J, lb/10ฎ scf or lb/103 gal) as well as output specific (ppm at 15
percent Og, Ib/MWH, g/hp-hr) N0X emission terms.
6.2 HISTOGRAMS OF N0y EMISSIONS FOR GAS TURBINE ENGINES
A
Figure 6-1 shows population N0X emission factor histograms for
the six classes of gas turbine engines in which data on more than two
units were found. The graphs for the small turbine category show numbers
*Regenerative units use exhaust gases to preheat combustion air.
-------
TABLE 6-1. NQX EMISSION FACTORS SURVEY OF SIMPLE AND
REGENERATIVE CYCLE GAS ENGINES
Baseline N0X
Emissions as s Function of Cycle and Fuelฎ
Turbine
Size
Units
Single Cycle
Regenerative Cycle
Natural Gas
Liquid Fuel
Natural ias
Liquid Fuel
Large
No. Engines b
4
16
2
>15 KW
ppm ง 1SS 02
98
188 ,
340
(>20,000 hp)
Ib/fflfflb
4.1
10.2^
_
12.0
g/hp-hrb
1.4
3.5d
4.1
ng/Jc
140
360
650
1b/HBtuc
0.32
0.85
__
1.51
lb/MSCFc
350
lb/103 gal
120
220
Medium
No, Engines h
8
3
4 to 15 MW
ppm @ 151 0?
80
108
(5,300 to
lb/MMHb
3.8
6,1
20,000 hp)
g/hp-hrb
1.3
2.1
ng/Jc
120
210
lb/MBtuc
0.29
0.48
--
lb/MSCFC
300
or
lb/103 gal
70
Small
No. Engines b
30
58
1
1
<4 KW
ppm i 15* 0?
78
93
__
(<5,300 hp)
lb/MMHb
4.9
5.6
6.2
11.4
g/hp-hrb
1.7
1.9
2.1
3.8
ng/jc
120
180
180
360
lb/MBtuc
0.28 '
0.41
0.42
0.84
lb/MSCFC
aw
440
or
lb/lO^ gal
47
120
N0 values reported In terns of NO,
b * c
Output specific values
cInput specific values
^Average of 14 units only
53
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vl
200
1
(0.5)
WM
Average
w
Wm,
300
400
[
(l.o)
I
500
600
700
1.5}
N0X emission factors, ng/J (lb/MBtu)
a. Large, Simple Cycle, Liquid Fuel Fired
OJ
JSt
E
3
100
Average
I
150
(0.2)
(0.3)
m
200
(0.4),
N0x emission factors, ng/J (Ib/NBtu)
b, Large, Simple Cycle, Natural Gas Fired
5
4 _
3 -
2 -
LV
50
Average
100
150
Ep
200
(0.1)
(o.z)
(0.3)
(0.4)
(0.5)
N0X emission factors, ng/J (lb/MBtu)
Medium, Simple Cycle, Natural Gas Fired
Figure 6-1. Population histograms of N0X emission factors
for gas turbine engines.
54
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Average
loo"
Ho"
135"
TOO
1*50
(0.25)
(0.50)
NO^ emission factors, ng/J (lb/ffitu)
d. Medium, Simple Cycle, Liquid Fuel Fired
(0.75)
^V
Average
To"
wwmm
m mm
100
190
ZOO
25*0
(0.2)
(0-2)
(0.4)
(.05)
NO^ emission factors, ng/J (lb/'Stu)
e. Small, Simple Cycle, Natural Gas Fired
4
3-1
2
1
0
Average
MM
(A
_LQQ_
2ML
m
n
vm
JQSL
(0.5)
N0x emission factors, ng/J (Its/MBtu)
f. Small, Simple Cycle, Liquid Fuel Fired
jqT
(1.0)
Figure 6-1. Concluded.
55
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in some of the boxed squares. These numbers represent averages of NO
emission values as they were presented in the literature; individual
values were not presented. The small liquid fuel fired turbine histogram
appears to be bimodal in appearance. This characteristic does not appear
to be related to turbine size or to fuel as all four fuels, Jet A.,
kerosene, and No. 1 and No. 2 fuel oils appear in both modes. It may be
related to the make of turbine or to the method of testing.
6.3 STATE-OF-THE-ART CONTROL TECHNIQUES FOR N0X EMISSIONS - WATER
INJECTION
Water injection into the combustion zone in either as a liquid or
as steam has been used to increase efficiency since 1961 with NO^
control being a fringe benefit. Not until 1971 was, it primarily used to
meet NO regulations (Reference 6-1). A water/fuel ratio of 0.5
a
generally provides a N0x reduction of 50 percent and for a water/fuel
ratio, of 1.0, 80 percent. Steam appears to be less effective as the
energy for vaporization is no longer supplied by the combustion process of
the turbine. Figure 6-2 illustrates the effect of increasing the
water/fuel ratio in reducing the overall N0X concentration. Steam/water
injection appears to work equally well for natural gas and distillate oils.
6.4 NITRIC OXIDE AS PERCENT CONSTITUENT OF TOTAL N0x EMISSIONS
Dietzman and Springer (Reference 6-2) have reported NO as a
percentage of NO for one turbine firing natural gas in the 4 to 15 MW
range. The average of the tests run was 87 percent. Nitric oxide (NO)
was not measured on any of the other turbines examined during this test
program. Dewerth (Reference 6-3) analyzed two 400 hp turbines at 60
percent load for both NO and NO and obtained an 86 percent average of
NO.
Previously, Tuttle, et al., (Reference 6-7) reviewed much of the
data prior,to 1974 and found that it was clearly contradictory as to
whether N0-> (and inversely NO) is a small or large fraction of total
N0x emissions for gas turbine engines. Recently Johnson and Smith
(Reference 6-8) varied a 45 MW gas turbine from idle (15 MW) to full
load. NO as a percentage of N0x increased from 0 to 78 percent as shown
in Figure 6-3. This is roughly collaborated by a second test run by
Wasser (Reference 6-4) on a 0.125 MW turbine at an EPA facility as shown
in Figure 6-4; however, results at low loads indicate a considerable
56
-------
o Natural flis Q
O liquid fuel S u
/ . Or
/ D
fo o0o
' o
'
/Do O s
to /
/ฐ /
/ ฐฐ /
^ O QD ^
/0 /
7ฐ/
/ /
/ /
//
/ /
//
//
_ //
//
J I : 1 L
0.2 0.4 0.6 0.8 1.0 1.2
Mater/Fuel Ratio
Figure 6-2. Effectiveness of water/steam injection In
reducing N0X emissions (Reference 5-1).
57
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120
100
80
a.
n_
c
o
Its
4J
U
o
o
60
40
20
500
Turbine inlet temperature,
15
38
Approximate load, MW
45
Figure 6-3. NO and NO2 concentrations at base of No. 3
stack for various turbine loads, i.e., turbine
inlet temperature (Reference 6-7).
58
-------
i
& 140
c
o
IX}
U 100
c
o
<_>
80 100 120 140
Generator load, kW
160 180
Figure 6-4. NO and N0X concentrations of a small turbine at various
loads firing No. 2 oil (Reference 6-4).
59
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quantity of NO in the EPA turbine exhaust and virtually none reported by
Johnson and Smith. Also indicated is a dropoff of NOg directly from the
low load value for the EPA unit whereas the Johnson and Smith unit shows
an increase prior to dropping off. Much of this difference may be due to
the difference in fuels, type and size of the turbine and operating
parameters.
r
/
60
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REFERENCE FOR SECTION 6
6-1. Anon, "Standards Support and Environmental Impact Statement Volume I
Proposed Standards of Performance for Stationary Gas Turbines,'1
Emission Standards and Engineering Division, U.S. Environmental
Protection Agency, EPA-450/12-77-017a, September 1977.
6-2. Dietzmann, H. E., and K. J. Springer, "Exhaust Emissions from Piston
and Gas Turbine Engines Used 1n Natural Gas Transmission," Southwest
Research Institute, San Antonio, Texas. Prepared for American Gas
Association, Arlington, VA, January 1974.
6-3. Dewerth, D. W., "Air Pollutant Emissions from Spark-Ignition Natural
Gas Engines and Turbines," American Gas Association Laboratories,
Research Report No. 1491, September 1973.
6-4. Wasser, J. H., "Emission Characteristics of Small Gas Turbine
Engines: as reported in The Proceedings of the Stationary Source
Combustion Symposium, Vol. Ill, EPA-600/12-76-152, June 1976.
6-5. Crawford, A. R., et al., "Control of Utility Boiler and Gas Turbine
Pollutant Emissions by Combustion Modification -- Phase 1,"
EPA-600/7-78-036a, March 1978.
6-6. Acurex Corporation, Unpublished data,
6-7. Tuttle, J. H., et al., "Nitrogen Dioxide Formation in Gas Turbine
Engines: Measurements and Measurement Methods," Combustion Science
and Technology 9, 261 (1974) !
6-8. Johnson, G. M. and M. Y. Smith, "Nitrogen Dioxide Emissions from a
Gas Turbine Power Station," International Clean Air Conference, The
Clean Air Society of Australia and New Zealand, Brisbane, Australia,
May 15-19, 1978.
61
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