&EPA
United States
Environmental Protection
Agency
Industrial Environmental Research
Laboratory
Research Triangle Park NC 27711
EPA-600/7-79-219
September 1979
IMOx Emission Factors
for Wood-Fired Boilers
Interagency
Energy/Environment
R&D Program Report
-------
RESEARCH REPORTING SERIES
Research reports of the Office of Research and Development, U.S. Environmental
Protection Agency, have been grouped into nine series. These nine broad cate-
gories were established to facilitate further development and application of en-
vironmental technology. Elimination of traditional grouping was consciously
planned to foster technology transfer and a maximum interface in related fields.
The nine series are:
1. Environmental Health Effects Research
2. Environmental Protection Technology
3. Ecological Research
4. Environmental Monitoring
5. Socioeconomic Environmental Studies
6. Scientific and Technical Assessment Reports (STAR)
7. Interagency Energy-Environment Research and Development
8. "Special" Reports
9. Miscellaneous Reports
This report has been assigned to the INTERAGENCY ENERGY-ENVIRONMENT
RESEARCH AND DEVELOPMENT series. Reports in this series result from the
effort funded under the 17-agency Federal Energy/Environment Research and
Development Program. These studies relate to EPA's mission to protect the public
health and welfare from adverse effects of pollutants associated with energy sys-
tems. The goal of the Program is to assure the rapid development of domestic
energy supplies in an environmentally-compatible manner by providing the nec-
essary environmental data and control technology. Investigations include analy-
ses of the transport of energy-related pollutants and their health and ecological
effects; assessments of, and development of, control technologies for energy
systems; and integrated assessments of a wide-range of energy-related environ-
mental issues.
EPA REVIEW NOTICE
This report has been reviewed by the participating Federal Agencies, and approved
for publication. Approval does not signify that the contents necessarily reflect
the views and policies of the Government, nor does mention of trade names or
commercial products constitute endorsement or recommendation for use.
This document is available to the public through the National Technical Informa-
tion Service, Springfield, Virginia 22161.
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EPA-600/7-79-219
September 1979
NOX Emission Factors
for Wood-Fired Boilers
by
Arthur B. Nunn
TRW Environmental Engineering Division
201 N. Roxboro Street, Suite 200
Durham, N. C. 27701
Contract No. 68-02-2613
Task No. 30
Program Element No. 1NE825
EPA Project Officer: John O. Milliken
Industrial Environmental Research Laboratory
Office of Environmental Engineering and Technology
Research Triangle Park, NC 27711
Prepared for
U.S. ENVIRONMENTAL PROTECTION AGENCY
Office of Research and Development
Washington, DC 20460
-------
ABSTRACT
NOX emission data from fourteen (14) wood-fired boilers have been
reviewed. Types of wood fuel being fired included sawdust, chips,
shavings, edgings, bark, and various other processing residues. Boilers
tested ranged in size from 1.5 to 67 MW (4 500 to 200 000 Ib stream/hr).
The major finding was that wood-fired boilers emit considerably less
NO (on an energy basis) than fossil fuel boilers of comparable size.
/\
This is interesting because most wood-fired boilers operate with high
levels of excess air, a practice which normally is associated with
increased NOX emissions. Average emission factors were 0.3g NO per
kg fuel for boilers less than 10 MW, and 1.6g NOX per kg fuel for boilers
greater than 10 MW.
iii
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IV
-------
CONTENTS
Abstract .............................. 1-il-
Figures ........................ '.'.'.'.'.'.'. vi
Tables ............................... vi
Acknowledgement ........................... V1-^
1.0 Introduction ....................... 1
2.0 Methodology ........................ 3
3.0 Results ...........
• ••••••••••••••• i
4.0 Conclusions and Recommendations .............. 13
4.1 Conclusions ..................... 13
4.2 Recommendations ................... 14
5.0 References ........................ 15
Appendix A - Test Data
-------
FIGURES
3-1 Effect of Boiler Size on NO Emission Rate ]]
3-2 Effect of Excess Air on NO Emission Rate 12
X
TABLES
2-1 Test Data Sources 5
3-1 Emissions Summary 9
3-2 NOX Emission Factors 10
A-l Boiler A A_2
A-2 Boiler B A_3
A-3 Boiler C A-4
A-4 Boiler D A_5
A-5 Boiler E A_6
A-6 Boiler F A_7
A-7 Boiler G A_8
A-8 Boiler H A_9
A-9 Boiler I A_10
A-10 Boiler J A_u
A-ll Boiler K A_12
A-12 Boiler L A_13
A-13 Boiler M A_14
A-14 Boiler N A_15
VI
-------
ACKNOWLEDGEMENT
The technical direction and assistance of Mr. John Mil liken of IERL-RTP
are gratefully acknowledged. The assistance of Ms. Gerldine Dorosz and Mr.
Tony Eggleston of the TRW Environmental Engineering Division in the data
collection and report preparation areas of this project is greatly appreciated.
Vll
-------
V111
-------
SECTION 1
INTRODUCTION
During this period of energy shortages and rapidly rising fuel costs,
alternate fuels for all types of boilers are receiving increased interest.
The use of wood processing residues (e.g., bark, sawdust, and shavings)
is being emphasized by the U.S. Department of Energy (DOE) in a Wood Combustion
Commercialization Program. This is, by no means, a new technology. At
present, wood combustion in industrial boilers produces approximately 0.4
Quads of energy per year. Due to the abundance of wood processing residues,
it is the goal of the DOE to expand its use throughout the country.
As with the combustion of any type of fuel, the environmental impact
associated with boiler emissions must be investigated. There is, at present,
however, a paucity of data pertaining to wood-fired boiler emissions. The
purpose of this report is to assist the U.S. Environmental Protection Agency
in ascertaining the magnitude of NOX emissions from such boilers and developing
applicable emission factors.
-------
-------
SECTION 2
METHODOLOGY
Source test data were obtained from eleven (11) industrial boilers
using some type of wood as the sole fuel and three (3) boilers using
wood in conjunction with oil, coal, or natural gas. The types of wood
being used as fuel were primarily wood processing residues and included
sawdust, chips, shavings, edgings, bark, and various other scraps. The
following information was extracted from the source test data:
Size of Boiler
Manufacturer
Type of Fuel
Fuel Feed Rate
Heat Content of Fuel
Temperature of Fire Box
Percent Excess Air
NOx Concentration in Exhaust Gas
Exhaust Flow Rate
Exhaust Temperature
Type of Control Device
Type of Sampling Procedure.
-------
Not all of the information was available for each boiler tested, and
for summary purposes, estimates were made in some cases. Boilers tested
ranged in size from 1.5 to 67 MU (4,450 to 200,000 Ib steam/hour). No
plant larger than 17.0 MW (59,600 Ib steam/hour) which was fired on wood
alone was tested.
On the basis of the collected data, N0x emission rates were calculated
in the units of g/kg fuel, Ib/ton fuel, mg/106 joule, and lb/106 Btu.
The boilers were then separated into the following three categories:
<10.0 MW (29,670 Ib steam/hour)
210.0 .MW
>10.0 MW (wood as supplement to coal).
Emission factors were calculated for these three categories on the basis
of the mean emission rates of those boilers tested in each category.
Of the fourteen (14) boilers tested, six (6) were small industrial
boilers located in Vermont and studied by the EPA Region I.1 Two of the
boilers in which wood was used on a co-firing basis were tested by KVB,
Inc. for EPA's Industrial Environmental Research Laboratory at Research Tri-
2
angle Park. One test was performed on a small power generation plant in
0
Vermont. The remaining five (5) boilers were tested by TRW for the EPA.4
Table 2-1 describes each boiler for which data are presented and the source
from which it came.
The results of all tests and calculations are presented in Section
3 and Appendix A of this report.
-------
TABLE 2-1. TEST DATA SOURCES
Boiler^ Size
A 1.5 MW (4,450 Ib steam/hr)
B 2.5 MW (7,420 Ib stea/hr)
C 2.0 MW (5,930 Ib steam/hr)
D 2.5 MW (7,420 Ib steam/hr)
E 2.9 MW (8,600 Ib steam/hr)
F 1.5 MW (4,450 Ib steam/hr)
6 1.5 MW (4,450 Ib steam/hr)
H 11.6 MW (34,000 Ib stean/hr)
I 16.8 MW (50,000 lb steam/hr)
J 6.6 MW (19,580 lb steam/hr)
K 5.7 MW (17,000 lb steam/hr)
L 33.0 MW (100,000 lb steam/hr)
M 67.0 MW (200,000 lb steam/hr)
N 33.0 MW (100,000 Ib steam/hr)
Fuel Type
Shavings
Shavings/Sawdust
Shavings/Sawdust
Edgings
Scraps
Shavings/Sawdust
Pressed Sawdust
Pine Wastewood
Sawdust
Sawdust
Wastewood
80% Chips/20% Oil
85% Bark/15% Gas
20% Bark/80% Coal
Data Source
Reference 1
Reference 1
Reference 1
Reference 1
Reference 1
Reference 1
Reference 4
Reference 4
Reference 4
Reference 4
Reference 4
Reference 3
Reference 2
Reference 2
-------
-------
SECTION 3
RESULTS
NOx emission rates remained relatively constant within boiler size
categories. As boilers increase in size, however, the emission rates for NO
/\
also increase. There is, unfortunately, a shortage of information avail-
able on wood fired boilers larger than 17 MW (50,600 lb steam/hour).
Presented in Table 3-1 is a summary of the emission rates calculated
for all boilers involved in the study. Expanded information on each
boiler can be found in Appendix A. Sampling was accomplished using either
continuous measurement with a chemiluminescence analyzer or by grab sample
by EPA Measurement Method 7. In each case, exhaust flow measurements were
made in accordance with EPA Method 2. A review of the test and calibration
procedures utilized indicates that the tests were carried out properly
and the data are reliable.
The correlation of emission rates with respect to boiler size is
shown in Figure 3-1. From this, it can be seen that a definite relation-
ship exists and, on that basis, it was decided that two emission factors
would be developed with 10 MW (29,670 Ib steam/hour) serving as the
dividing point. Emission rates for the boilers smaller than 10 MW are
remarkably similar as are their operating parameters. These boilers
operate with an average of more than 300% excess air. In addition, fire
-------
box temperatures are generally in the range of 1000 to 1100°C (1832 to
2012°F). The larger boilers (>10 MW) exhibit less consistency in operating
parameters and emission rates. The excess air usage ranges from 62 to 155%
and the fire box temperatures are unknown.
An interesting phenomenon discovered during this study involves
the relationship between emission rates and excess air consumption.
Figure 3-2 depicts this relationship. For conventional fossil fuel fired
boilers, NO emissions generally increase with an increase in excess air.
/v
This study revealed that for wood-fired boilers, the opposite relationship
exists. This can be explained by the fact that the high levels of excess
air decrease the fire box temperature, thereby decreasing the rate of
formation of thermal NO . Thermal NO refers to NO formed by the oxidation
XXX
of atmospheric nitrogen in the combustion air. It must be noted that the data
presented in Figure 3-2 cover a variety of sizes of boilers. Studies should be
conducted, therefore, which hold the boiler size constant and vary the excess
air usage while monitoring NO emissions.
J\
All emission factors are presented in Table 3-2. These emission factors
are based on the test data from those plants in each size category. Most of
the large wood-fired boilers are co-fired with a conventional fossil fuel.
Although boilers in which wood is the primary fuel are the focus of this
study, emissions data from these co-fired systems were included in the develop-
ment of emission factors. A separate emission factor was developed for
boilers in which wood is used as a minor supplement to coal only.
8
-------
TABLE 3-1. EMISSIONS SUMMARY
Boiler
A
B
C
D
E
F
G
H
I
J
K
L (20%
M (15%
N (80%
Boiler Size (MW)
1.5
2.5
2.0
2.5
2.9
1.5
NA (1.5)*
11.6
16.8
6.6
5.7
Fuel Oil) 33.0
Natural Gas) 67.0
Coal) 33.0
Emission
g NO/ kg Fuel
A
0.10
0.10
0.10
0.75
0.10
0.04
0.04
1.20
1.06
VJ.G!?
0.27
0.80
NA (3.00)*
4.04
Factors
mg NO../106 joule
— a x *
5.0
6.0
5.0
38.0
6.0
2.0
2.0
60.0
55.0
5.0
14.2
50.9
124.0
168.0
* Estimated
-------
TABLE 3-2. N0v EMISSION FACTORS
y\
Boiler Size
<10.0 MW
£10.0 MW
>10.0 MW*
g NO/kq Fuel
A
0.30
1.60
4.00
mg NOX/106 joule
9.0
70.0
170.0
Wood used as supplement to coal only.
10
-------
2rC|
_L
• :
LEGEND
O Vermont Study (Ref. 1)
D TRW Test (Ref. 4)
Figure 3-1
BOILER SIZE (MU)
Effect of boiler size on NOV emission rate.
A
-------
O Vermont Study (Ref. 1)
TRW Test (Ref. 4)
A KVB Test (Ref. 2)
O MRI Test (Ref. 3)
PERCENT EXCESS AIR
Figure 3-2. Effect of excess air on NO
„ emission rate.
-------
SECTION 4
CONCLUSIONS AND RECOMMENDATIONS
4.1 CONCLUSIONS
On the basis of the data reviewed, it is concluded that wood-fired
boilers in the category < 30 MW (approximately 100,000 Ib steam/hr)
emit considerably less NOX (on an energy basis) than fossil fuel
boilers of comparable size. For wood-fired boilers larger than 30 MW,
the differential is probably not as great, but wood boilers in
this size category are still expected to emit somewhat less than comparably
sized fossil fuel boilers. These conclusions are based on comparison
of wood boiler N0x emission factors developed in this study to fossil
fuel boiler emission factors cited in AP-42 (5).
For the range of boiler sizes studied, the NO emission factors
A
were found to decrease as excess air increased. In contrast, higher
levels of excess air in fossil fuel boilers are normally associated
with increased NOX emission rates. In the case of the wood boilers,
it is suspected that the cooling effect of large quantities of excess
air resulted in lower average firebox temperatures. This would decrease
the amount of thermal NO formed. Thermal NO refers to NO resulting
* x x
from the oxidation of molecular nitrogen (N2) that is present as the
primary molecular component of combustion air.
13
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4.2 RECOMMENDATIONS
(1) It is recommended that N0x emission factors for larger
wood-fired boilers be established. Specifically, NO emissions for
J\
wood boilers in the size category > 30 MW (100,000 Ib steam/hr)
should be determined. Because the NO emission factors per unit of
A
fuel or per unit of energy are expected to be greater for this category,
this assessment is important to the NO /wood combustion issue.
A
(2) It is recommended that additional data on NO from bark-fired
A
boilers be obtained. The composition and physical form of this residue
fuel could result in NO emission rates significantly different from
A
other wood based fuels.
(3) It is recommended that the effects of co-firing with various
fossil fuels, particularly oil and gas, be investigated.
(4) It is recommended that for all future wood-boiler assessment
projects, the average firebox temperature be measured. This information
would help to resolve the mechanism by which more or less NO is formed.
A
(5) For the long term, it is recommended that the effects of
(a) combustor design, (b) operating conditions, and (c) fuel parameters
on NO emission rates be studied. This would lead directly to recommenda-
A
tions of combustion modification that would decrease NO emissions, if
A
that action became necessary.
14
-------
SECTION 5
REFERENCES
1. Sanborn, Cedric R., Evaluation of Wood-Fired Boilers and Wide-Bodied
Cyclones in the State of Vermont, U.S. Environmental Protection
Agency, Region I, Boston, Massachusetts, March 1, 1979.
2. Hunter, S. C., Carter, W. A., McElroy, M. W., Cherry, S. S., and
Buening, H. J., Application of Combustion Modifications to Industrial
Combustion Equipment. KVB. Inc.. Tustin. California. January 1Q7Q,
EPA-600/7-79-015a (NTIS No. PB 294 214).
3. Golembiewski, M., Environmental Assessment of a Waste-to-Energy Process
Wood and Oil Fired Power Boiler, Midwest Research Institute, Kansas
City, Missouri, February 1979 (DRAFT)
4. Unpublished data, TRW Environmental Engineering Division, Durham,
North Carolina, 1979.
5. Compilation of Air Pollutant Emission Factors (Third Edition),
AP-42, U.S. Environmental Protection Agency, Office of Air Quality
Planning and Standards, Research Triangle Park, North Carolina,
August 1977.
15
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16
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APPENDIX A
TEST DATA
-------
A-l
-------
TABLE A-l. BOILER A
Size of Boiler
Manufacturer
Type of Fuel
Fuel Feed Rate
Heat Content of Fuel
Temperature of Fire Box
Percent Excess Air
NO Concentration in Exhaust
1 x
Exhaust Flow Rate
Exhaust Temperature
Control Equipment
Sampling Methodology
1.5 m (5.1 MMBtu/hr) (150 HP)(4450 Ib/hr)
D. M. Dillon
Dried and Green Shavings
363 kg/hour
19.6 x 106 0/kg
1038°C
324%
1.8 ppm
160 DSCM/min.
127°C
None
EPA Method 7
(800 Ib/hour)
(8440 Btu/lb)
(1900°F)
(5737 DSCF/min.)
(260°F)
NO Emission Rate
/\
q/kq Fuel
0.10
Ib/ton Fuel
0.19
mq/106J
5.0
lb/106Btu
0.011
A-2
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TABLE A-2. BOILER B
Size of Boiler
Manufacturer
Type of Fuel
Fuel Feed Rate
Heat Content of Fuel
Temperature of Fire Box
Percent Excess Air
N0y Concentration in Exhaust
Exhaust Flow Rate
Exhaust Temperature
Control Equipment
Sampling Methodology
2.5 MW (8.5 MMBtu/hr) (250 HP)(7,420 Ib/hr)
Keeler
Oak, Maple, and Pine Shavings and Sawdust
454 kg/hour
19.1 x 106 J/kg
1038°C
534%
2.6 ppm
163 DSCM/min.
187°C
Ash Collector
EPA Method 7
(1000 Ibs/hour)
(8220 Btu/lb)
(1900°F)
(5825 DSCF/min)
(368°F)
NO Emission Rate
g/kg Fuel
0.10
Ib/ton Fuel
0.20
mg/106J
6.0
lb/106Btu
0.013
A-3
-------
TABLE A-3. BOILER C
Size of Boiler
Manufacturer
Type of Fuel
Fuel Feed Rate
Heat Content of Fuel
Temperature of Fire Box
Percent Excess Air
NO Concentration in Exhaust
/\
Exhaust Flow Rate
Exhaust Temperature
Control Equipment
Sampling Methodology
2.0 MW (6.8 MMBtu/hr) (200 HP)(5,930 Ib/hr)
D. M. Dillon
Maple Shavings and Sawdust
400 kg/hour
19.5 x 106 J/kg
1200°C
432%
1.7 ppm
194 DSCM/min.
118°C
None
EPA Method 7
(880 lb/hour)
(8387 Btu/lb)
(2200°F)
(6911 DSCF/min.)
(245°F)
NO Emission Rate
" x
q/kq Fuel
0.10
Ib/ton Fuel
0.20
mg/106J
5.0
lb/106Btu
0.012
A-4
-------
TABLE A-4. BOILER D
Size of Boiler
Manufacturer
Type of Fuel
Fuel Feed Rate
Heat Content of Fuel
Temperature of Fire Box
Percent Excess Air
NO Concentration in Exhaust
/\
Exhaust Flow Rate
Exhaust Temperature
Control Equipment
Sampling Methodology
2.5 MW (8.5 MMBtu/hr) (257 HP)(7420 Ib/hr)
D. M. Dillon
Hard and Softwood Edgings
562 Kg/hour
19.5 x 106 J/kg
1038°C
134%
3.0 ppm
137 DSCM/min.
231 °C
None
EPA Method 7
1240 Ib/hour)
(8400 Btu/lb)
(1900°F)
(4878 DSCF/min.)
(447°F)
NO Emission Rate
q/kq Fuel
0.75
Ib/ton Fuel
1.50
mg/106J
38.0
lb/106Btu
0.088
A-5
-------
TABLE A-5. BOILER E
Size of Boiler
Manufacturer
Type of Fuel
Fuel Feed Rate
Heat Content of Fuel
Temperature of Fire Box
percent Excess Air
NO Concentration in Exhaust 'ias
J^
Exhaust Flow Rate
Exhaust Temperature
Control Equipment
Sampling Methodology
Emission Rate
g/kq Fuel
0.10
2.9 MU (9.9 MMBtu/hr) (300 HP)(8,600 Ib/hr)
Erie City
Hard and Softwood Scraps
(2580 Ib/hour)
(8056 Btu/lb)
(1900°F)
1170 kg/hr
18.7 x 106 J/kg
1038°C
172%
6.9 ppm
177 DSCM/min.
142°C
None
EPA Method 7
Ib/ton Fuel mg/106J lb/106Btu
0.20 6.0 0.015
(6306 DSCF/min.)
(287°F)
A-6
-------
TABLE A-6. BOILER F
Size of Boiler
Manufacturer
Type of Fuel
Fuel Feed Rate
Heat Content of Fuel
Temperature of Fire Box
Percent Excess Air
NO Concentration in Exhaust rias
A
Exhaust Flow Rate
Exhaust Temperature
Control Equipment
Sampling Methodology
1.5 MM (5.1 MMBtu/hr) (150 HP)(4,450 Ib/hr)
D. M. Dillon
Maple and Pine Shavings and Sawdust
300 kg/hour
20.6 kg/hour
1038°C
360%
9.8 ppm
94 DSCM/min.
206°C
None
EPA Method 7
(660 Ib/hour)
(8856 Btu/lb)
(1900°F)
(3361 DSCF/min.)
(403°F)
NO Emission Rate
q/kg Fuel Ib/ton Fuel mg/106J 1b/106Btu
0.04 0.07 2.0 0.004
A-7
-------
TABLE A-7. BOILER 3
Size of Boiler
Manufacturer
Type of Fuel
Fuel Feed Rate
Heat Content of Fuel
Temperature of Fire Box
Percent Excess Air
NO Concentration in Exhaust Sas
/\
Exhaust Flow Rate
Exhaust Temperature
Control Equipment
Sampling Methodology
NO Emission Rate
1 x
q/kq Fuel
0.04
1.5 MW (5.1 MMBtu/hr)
Will-Burt Company
Pressed Sawdust
93 kg/hour
19.3 x 106 J/kg
NA
NA
7.0 ppm
5 DSCM/min.
84°C
None
Chemiluminescence
Ib/ton Fuel
0.07
(150 HP)(4,450 Ib/hr)
(205 Ib/hour)
(8300 Btu/lb)
(170 DSCF/min.)
(184°F)
mq/106J 1b/106Btu
2.0 0.004
A-8
-------
TABLE A-8. BOILER H
Size of Boiler
Manufacturer
Type of Fuel
Fuel Feed Rate
Heat Content of Fuel
Temperature of Fire Box
Percent Excess Air
N°xConcentration in Exhaust rias
Exhaust Flow Rate
Exhaust Temperature
Control Equipment
Sampling Methodology
5135 kg/hour
19.3 x 106 J/kg
11.6MW (39.5 MMBtu/hr) (1,185 HP)(34,000 Ib/hr)
Puget Sound Machinery
Pine Nastewood From Sawmill
(11,320 Ib/hour)
(8300 Btu/lb)
NA
110%
25 ppm
2514 DSCM/min.
68°C
None
Chemiluminescence
(89,800 DSCF/min.)
(155°F)
NO Emission Rate
g/kg Fuel Ib/ton Fuel mg/T06J 1b/106Btu
1.20 2.40 60.0 0.147
A-9
-------
TABLE A-9. BOILER I
Size of Boiler
Manufacturer
Type of Fuel
Fuel Feed Rate
Heat Content of Fuel
Temperature of Fire Box
Percent Excess Air
16.8 MM (57.3 MMBtu/hr) (1720 HP)(50,000 Ib/hr)
Erie City Iron Uorks
Sawdust
(17,000 Ib/hour)
1711 kg/hour
19.3 x 106 J/kg
NA
109%
NO Concentration in Exhaust rias 47 ppni
X
Exhaust Flow Rate
Exhaust Temperature
Control Equipment
Sampling Methodology
1740 DSCM/min.
68°C
None
Chemiluminescence
(8300 Btu/lb)
(62,111 DSCF/min.)
(155°F)
NO Emission Rate
g/kq Fuel
1.06
Ib/ton Fuel
2.1
mg/106J lb/106Btu
55.0 0.127
A-10
-------
TABLE A-10. BOILER J
Size of Boiler
Manufacturer
Type of Fuel
Fuel Feed Rate
Heat Content of Fuel
Temperature of Fire Box
Percent Excess Air
N0x Concentration in Exhaust rias 1.8 ppm
Exhaust Flow Rate 676 DSCM/min.
Exhaust Temperature 69°C
Control Equipment None
Sampling Methodology Chemiluminescence
6.6 MM (22.5 MMBtu/hr) (675 HP)(19,580 Ib/hr)
Wei Ions, Inc.
Sawdust
1044 kg/hour
19.3 x 106 J/kg
NA
457%
(2300 Ib/hour)
(8300 Btu/lb)
(23,868 DSCF/min.)
(157°F)
NO Emission Rate
A
q/kg Fuel Ib/ton Fuel mg/106J lb/106Btu
0.09 0.18 5.0 0.011
A-ll
-------
TABLE A-ll. BOILER K
Size of Boiler
Manufacturer
Type of Fuel
Fuel Feed Rate
Heat Content of Fuel
Temperature of Fire Box
Percent Excess Air
NO Concentration in Exhaust Sas
A
Exhaust Flow Rate
Exhaust Temperature
Control Equipment
Sampling Methodology
5.7 MM (19.4 MMBtu/hr) (586 HP)(17,000 Ib/hr)
Wei Ions
Sawmill Waste Wood
(1284 kg/hour)
19.3 x 106 J/kg
NA
99%
6.6 ppm
577 DSCM/min.
104°C
None
Chemiluminescence
(2830 Ib/hour)
(8300 Btu/lb)
(20,387 DSCF/min)
(219°F)
NO Emission Rate
x
g/kg Fuel Ib/ton Fuel mg/106J lb/106Btu
°-27 0.53 14.2 0.032
A-12
-------
TABLE A-12. BOILER L
Size of Boiler
Manufacturer
Type of Fuel
Fuel Feed Rate
Heat Content of Fuel
Temperature of Fire Box
Percent Excess Air
NO Concentration in Exhaust 'Sas
3\
Exhaust Flow Rate
Exhaust Temperature
Control Equipment
Sampling Methodology
33 MM (112.6 MMBtu/hr) (3370 HP)(100,000 Ib/hr)
Wickes
80% Wood Chips/20% No. 2 Fuel Oil
8981 kg/hour
24.9 x 106 J/kg
NA
155%
66 ppm
1252 DSCM/inin.
153°C
2 Mechanical Collectors
Chemiluminescence
(19,800 Ib/hour)
(6,766 Btu/lb)
(44,700 DSCF/min.)
(307°F)
NOX Emission Rate
g/kg Fuel Ib/ton Fuel mg/106J lb/106Btu
0.80 1.60 50.9 0.118
A-13
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TABLE A-13. BOILER M
Size of Boiler
Manufacturer
Type of Fuel
Fuel Feed Rate
Heat Content of Fuel
Temperature of Fire Box
Percent Excess Air
NO Concentration in Exhaust
^
Exhaust Flow Rate
Exhaust Temperature
Control Equipment
Sampling Methodology
67 MM (229 MM Btu/hr)
B and W
85% Bark/ 15% Natural
NA
19.4 x 106 J/kg
NA
62%
184 ppm
NA
NA
Electrostatic Precipitator
Chemi 1 umi nescence
(6868 HP) (200, 000 Ib/hr)
(8331 Btu/lb)
NO Emission Rate
A
g/kq Fuel
NA
Ib/ton Fuel
NA
mg/106J 1b/106Btu
124 0.290
A-14
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TABLE A-14. BOILER N
Size of Boiler
Manufacturer
Type of Fuel
Fuel Feed Rate
Heat Content of Fuel
Temperature of Fire Box
Percent Excess Air
33 MW (112.6 MMBtu/hr) (3370 HP)(100,000 Ib/hr)
Wickes Boiler Company
20% Bark/80% Coal
NA
23.8 x 106 J/kg (10,208 Btu/lb)
NA
92%
NO Concentration in Exhaust rias 273 ppm
A
Exhaust Flow Rate
Exhaust Temperature
Control Equipment
Sampling Methodology
NO Emission Rate
/\
q/kq Fuel
4.04
(409°F)
NA
209°C
Multiclone
Chemiluminescence
ID/ton Fuel mg/106J 1b/106Btu
8.16 168 0.39
A-15
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TECHNICAL REPORT DATA
(Please read Instructions on the reverse before completing)
REPORT NO.
EPA-600/7-79-219
3. RECIPIENT'S ACCESSION NO.
4. TITLE AND SUBTITLE
NOx Emission Factors for Wood-Fired Boilers
5. REPORT DATE
September 1979
6. PERFORMING ORGANIZATION CODE
7. AUTHOR(S)
Arthur B. Nunn
!. PERFORMING ORGANIZATION REPORT NO.
. PERFORMING ORGANIZATION NAME AND ADDRESS
TRW Environmental Engineering Division
201 N. Roxboro Street, Suite 200
Durham, NC 27701
10. PROGRAM ELEMENT NO.
1NE825
11. CONTRACT/GRANT NO.
68-02-2613, Task 30
2. SPONSORING AGENCY NAME AND ADDRESS
EPA, Office of Research and Development
Industrial Environmental Research Laboratory
Research Triangle Park, NC 27711
13. TYPE OF REPORT AND PERIOD COVERED
Final: A/7Q to ry/7Q
14. SPONSORING AGENCY CODE
EPA/600/13
5.SUPPLEMENTARY NOTES IERL-RTP project officer is John 0. Milliken, Mail Drop 63, 919/
541-2745.
The report gives results of a review of NOx emission data from 14 wood-
fired boilers. Types of wood used as fuel included sawdust, chips, shavings, edgings,
/T n ?nn on Pressing residues. Boilers tested ranged in size from 1.5 to 67
MW (4,500 to 200,000 Ib steam/hr). The major finding was that wood-fired boilers
emit considerably less NOx (on an energy basis) than fossil fueled boilers of
comparable size, in spite of the fact that most wood-fired boilers operate with
high levels of excess air, a practice normally associated with increased NOx
MW^and ] fiTS emissj°n<:factors w*re 0.3 g NOx per kg fuel for boilers less than
MW, and 1.6 g NOx per kg fuel for boilers greater than 10 MW.
7.
KEY WORDS AND DOCUMENT ANALYSIS
DESCRIPTORS
b.lDENTIFIERS/OPEN ENDED TERMS
c. COSATI Field/Group
Pollution
Boilers
tfood
Fuels
Nitrogen Oxides
Pollution Control
Stationary Sources
13B
13A
11L
21D
07B
Release to Public
EPA Form 2220-1 (9-73)
19. SECURITY CLASS (This Report)
Unclassified
20. SECURITY CLASS (TMipage)
Unclassified
21. NO. OF PAGES
41
22. PRICE
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