EPA-650/2-74-091
SEPTEMBER 1974
Environmental Protection Technology Seri
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EPA-650/2-74-091
SYSTEMS ANALYSIS REQUIREMENTS
FOR NITROGEN OXIDE CONTROL
OF STATIONARY SOURCES
by
R. A. Brown, H. B. Mason, and R. J. Schreiber
Aerotherm/Acurex Corporation
485 Clyde Avenue
Mountain View, California 94042
Contract No. 68-02-1318
Task 3
ROAP No. 21ADE-029
Program Element No. LAB013
EPA Project Officer: R.F.Sanders
Control Systems Laboratory
National Environmental Research Center
Research Triangle Park, North Carolina 27711
Prepared for
OFFICE OF RESEARCH AND DEVELOPMENT
U.S. ENVIRONMENTAL PROTECTION AGENCY
WASHINGTON, D. C. 20460
September 1974
-------
This report has been reviewed by the Environmental Protection Agency
and approved for publication. Approval does not signify that the
contents necessarily reflect the views and policies of the Agency,
nor does mention of trade names or commercial products constitute
endorsement or recommendation for use.
ii
-------
FOREWORD
This document presents the results of a brief systems study of nitrogen
oxide control methods for stationary sources. The report provides updated in-
formation on NO emission sources and NO control technology and concludes with
X X
recommendations of R&D requirements.
Aerotherm extends its appreciation for the valuable assistance provided
by the following individuals, organizations, and companies: Dr. J.O.L. Wendt
and D.L. Pershing of the University of Arizona; C.R. McCann of the U.S. Bureau
of Mines; W.H. Barr of the Pacific Gas and Electric Co.; R.N. Levine and K.A.
Krumwiede of the Southern California Edison Co.; W.J. Armento and W.L. Sage of
the Babcock and Wilcox Co.; D.P. Teixeira of the Electric Power Research Insti-
tute; W. Bartok and A. R. Crawford of Esso Research and Engineering. We
would also like to give special thanks for information provided by the follow-
ing members of the Control Systems Lab of EPA: J. S. Bowen, G. B. Martin,
R. E. Hall, D. B. Lachapelle, W. S. Lamer, J. H. Nasser of the Combustion
Research Section; Bruce Henschel of the Advanced Process Section and G.
Haselberger of the Regenerable Processes Section.
This survey was performed for the Engineering Analysis Branch of the
Control Systems Laboratory, U.S. Environmental Protection Agency. R.F. Sanders
was the task officer. The Aerotherm Project Manager was Dr. Larry W. Anderson.
Dr. Carl B. Moyer acted as advisor for all phases of the study. The study was
performed during the months of January and February, 1974.
111
-------
TABLE OF CONTENTS
Section Pa9e
1 SUMMARY 1-1
1.1 Characterization of Emission Sources 1-1
1.1.1 Emission Factors 1-4
1.1.2 Prospects for NO Emission 1-4
1.2 Survey of Options for N8 Control 1-6
1.3 Combustion Modification Technology 1-9
1.3.1 Fundamental Studies 1-9
1.3.2 Application of Combustion Modifications 1-13
1.4 Assessment of R&D Requirements 1-14
2 INTRODUCTION 2-1
3 CHARACTERIZATION OF EMISSION SOURCES 3-1
3.1 Sources of Nitrogen Oxides 3-1
3.2 Emission Factors 3-7
3.3 Prospects of NO Emissions 3-13
3.3.1 Large Utrlity Boilers 3-13
3.3.2 Domestic and Commercial Sources 3-17
3.3.3 Stationary I.C. Engines and Gas Turbines 3-19
3.3.4 Industrial Combustion Sources 3-22
3.3.5 Non-Combustion Sources 3-22
3.4 NO Emission Trends 3-22
3.5 Summary 3-24
4 SURVEY OF OPTIONS FOR NO CONTROL 4-1
4.1 Combustion Sources 4-2
4.1.1 Modification of Existing Units 4-2
4.1.2 Fuel Modification 4-6
4.1.3 Alternate Processes for New Units 4-8
4.1.4 Flue and Exhaust Gas Treatment 4-10
4.2 Non-Combustion Sources 4-12
4.3 Summary 4-13
5 COMBUSTION MODIFICATION TECHNOLOGY FOR N0x CONTROL 5-1
5.1 Combustion Generated NO 5-1
5.1.1 Thermal NO x 5-2
5.1.2 Fuel NO 5-5
5.2 Systems Program for Combustion Modifications 5-6
5.3 Application of Fundamental Studies 5-7
5.3.1 Strategies for Model Development 5-9
5.3.2 Status and Prospects of Modeling 5-11
5.4 Application of Combustion Modifications 5-18
5.4.1 Implementation Strategy of Combustion
Modifications 5-18
5.4.2 Status and Prospects 5-25
5.4.3 Cost - 5-41
5.5 Summary 5-46
-------
Section
TABLE OF CONTENTS (Concluded)
ASSESSMENT OF R&D REQUIREMENTS 6-1
6.1 Combustion Modifications 6-1
6.1.1 Fundamental Studies 6-2
6.1.2 Fuels R&D 6-7
6.1.3 Process R&D 6-10
6.1.4 Field Testing 6-12
6.2 Flue Gas Treatment 6-13
6.3 Alternate Processes 6-13
REFERENCES R-l
ADDITIONAL BIBLIOGRAPHY B-l
TECHNICAL DATA REPORT T-l
VI
-------
LIST OF FIGURES
Figure
Page
1-1 Total NO Emitted in the U.S. from Stationary Sources, 1-3
1971 (Fr8m Data Obtained from References 2 and 4)
1-2 Estimated Annual Electric Utility Generation by Primary 1-5
Energy Sources
1-3 Stationary Source N0x Emission Trends 1-7
2-1 Summary of the Approach to the Present Study 2-3
3-1 Total NO Emitted in the U.S. from Stationary Sources, 3-4
1971 X
3-2 Total NO Emitted in the U.S. from Stationary Sources, 3-5
1971 (Fr&n Data Obtained from References 2 and 4)
3-3 Estimated Annual Electric Utility Generation by Primary 3-14
Energy Sources
3-4 Trends of Sources of U.S. Energy Supply: 1950-1970 3-15
(Actual)/1975-1985 (Projected)
3-5 Stationary Source NO Emission Trends 3-23
X
3-6 Stationary and Mobile N0x Emission Trends 3-24
4-la Effects of Nitric Oxide Control Methods (Natural Gas 4-3
Fuel)
4-lb Effects of Nitric Oxide Control Methods (Oil Fuel) 4-3
4-2 Catalytic Combustion Systems 4-14
4-3 Molecular Sieve System 4-15
5-1 Kinetic Formation of Nitric Oxide 5-3
5-2 The Combustion Control Program for N0x Control 5-8
5-3 Typical Sequence in Model Development 5-12
5-4 Two-Stage Combustion (After Reference 35) 5-20
5-5 Typical Combustion Modification Implementation Program 5-24
5-6 Increasing Excess Air Decreases Smoke but Increases NO 5-28
5-7 Effectiveness of FGR with Fuel Oil Type 5-30
VII
-------
LIST OF FIGURES (Concluded)
Figure Page
5-8 Effect of Excess Air on NO for Gas, Oil, and Coal 5-32
5-9 Effect of Load on NO for Gas, Oil, and Coal 5-32
5-10 Effect of Preheat on N0x for Gas, Oil, and Coal 5-33
5-11 Effect of FGR on NO for Gas, Oil, and Coal 5-33
5-12 Effect of Speed and Power Output on Emissions; Cater- 5-37
piller 4-Cycle Precombustion Chamber; Diesel Engine
5-13 Catalytic Reduction of NO by Ammonia 5-39
5-14 Effect of Cooled Exhaust Gas Recirculation on NO 5-42
Emission (Using Oil as Fuel)
5-15 Effect of Cooled Exhaust Gas Recirculation on NO 5-42
Emission (Using Natural Gas as Fuel)
5-16 Equipment Costs of NO Control Methods for Existing 5-44
Coal-Fired Units (Hea£ Transfer Surface Changes Not
Included)
5-17 Equipment Costs of NO Control Methods for Existing 5-45
Coal-Fired Units (Hea£ Transfer Surface Changes Not
Included)
Vlll
-------
LIST OF TABLES
Table
1-1 Total NO Emissions from Stationary Sources (x 10 6 tons/ 1-2
year) x
1-2 Summary of NO Control Options 1-8
X
l-3a Modification Techniques for Utility and Industrial 1-10
Boilers
l-3b Modification or Control Techniques for Stationary I.C. 1-11
Engines and Gas Turbines
1-4 Recommended R&D 1-14
3-1 Total NO Emissions from Stationary Sources (x 10 5 tons/ 3-2
year) x
3-2 1971 Estimates of NO Emissions from Fossil-Fuel 3-6
Stationary Sources x
3-3 NO Emissions from Fossil-Fuel Electrical Utility Units 3-6
3-4 Emission Factors for NO from Stationary Sources 3-8
X
3-5 Comparison Between Coal, Oil and Gas on Equivalent Btu 3-13
Basis; Electric Power Generation (Ibs NO /109 Btu)
X
3-5 NO Emission Factors for Residential and Commercial Oil- 3-18
Fired Heaters and Boilers (lbs/103 gal)
3-7 Total Installed Horsepower and Emission from Reciprocating 3-20
I.C. Engines
3-8 NO Emission Factors for Reciprocating I.C. Engines 3-21
(gift NO /Bhp-Hr)
X
3-9 Total Estimated Horsepower & Emissions from Gas Turbines 3-21
4-1 Cost for NO Abatement Facilities for the No. 3 Nitric 4-16
Acid Unit a£ TVA
4-2 Summary of NO Control Options 4-17
X
5-1 Factors Controlling the Formation of Thermal N0x 5-4
5-2 Typical Strategies for Model Development 5-10
5-3 Status of Model Development 5-13
-------
LIST OF TABLES (Concluded)
Table Page
5-4 Emission Control Methods for Reciprocating Engines 5-35
5-5 1973 Operating Costs of W>x Control Methods for 5-46
New Coal-Fired Units (Tangential); Single Furnace
5-6a Modification Techniques for Utility and Industrial Boilers 5-48
5-6b Modification or Control Techniques for Stationary I.C. 5-49
Engines and Gas Turbines
6-1 Summary of Combustion Research Section Program 6-3
6-2 Recommended R&D 6-4
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SECTION 1
SUMMARY
This report presents the results of a two-month study by the Aerotherm
Division of Acurex Corporation to identify systems requirements for the
control of nitrogen oxide emissions from stationary sources. The study
focused on the evaluation of developments, since the 1969 Esso Research and
Engineering Systems study , in the character of NO emission sources and in
X
NO control technology. It is concluded that planning priority should be for
coal fired utility and industrial boilers followed by stationary internal
combustion engines. The most attractive short- and long-term option for
control of NO emissions is combustion modification technology. The priority
items are development of techniques for control of the conversion of fuel-
bound nitrogen to NO, and development of combustion modifications for the
major area sources such as pipeline I.C. engines, and commercial and domestic
combustion units.
1.1 CHARACTERIZATION OF EMISSION SOURCES
Currently available inventories of NO emission were compared with the
X
data presented in the 1969 Esso study. No new major sources of NO were dis-
X
covered. Table 1-1 shows a comparison of the Esso projected inventory for 1970
with two recent EPA inventories (References 2 and 3). Figure 1-1 presents the
Reference 2, AP-115, data as a pie chart. As can be seen from the data the
greatest difference is in the utility-size boilers category which increased to
4.7 x 106 tons/year from the earlier estimate of 3.84 x 106 tons/year. This
difference is due to more refined analysis of boiler types and their individual
emission factors as well as an updated emission factor for gas-fired boilers.
Reference 3 indicates a further increase in utility boiler emissions; however,
these data are rather preliminary.
A further breakdown of the emission sources reveals that, since the Esso
study, coal combustion has remained as the largest contributor to the total
stationary source NO emissions at 42 percent. In electrical utility generation.
coal contributes 63 percent of the NO emissions. It is anticipated that the
fractional contribution and total levels from coal will increase substantially
during the next decade.
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TABLE 1-1
TOTAL NOX EMISSIONS FROM STATIONARY SOURCES (X 106 tons/year)
Source
Utility Size Boilers
Recip. I. C. Engines
Industrial Size Boilers
Forest Fires (controlled)
Domestic And Commercial
Space Heaters
Gas Turbines
Solid Waste
Disposal
Process Heaters
Nitric Acid Plants
Other Sources
Total
EPA (1974)(3)
5.88
0.918
3.91
d
0.945
d
0.179
2.876
d
d
14.7
AP-115, 1971(2)
4.71
.2 75
0.79
a
0.395
a
a
0.338
11.038
Esso, est. 1970, (1)
3.841
2.097b
2.81
a
1.001
a
a
a
> '0 235
-*^'
9.986
Other, 1970(3,4,5)
3.3-6.0C
1.95-2.3
Notes:
a. Included In Industrial-size Boilers
b. Pipeline And Gas Plants Only
c. Depending on Load Factor (High Number For Full Load)
d. Not included in NEDS data
-------
NON COMB,
3%
INDUSTRIAL
COMBUSTION
(-ZS.8%)
UTILITY
BOILER
(42, -7%)
TORSI NE-S
(7.1,3%)
RESlP. c COMMEI20AL
(~7."2%)
4,110,000
2,350,000
•£,050,000
340, OOP
II ,040,OOO
•SOURCE.
UTILITY
t
E£SIG>ENTIAL ^ ^OMMEBCIAL
NON- COMBUSTION SOURCES
Figure 1-1. Total N0¥ Emitted in the U.S. from Stationary Sources, 1971
A
(From Data Obtained from References 2 and 4)
1-3
-------
Figure 1-1 reveals that stationary I.C. engines and gas turbines con-
tribute 21 percent to the total NO emissions. There is a considerable range
of estimates of NO emissions from I.C. engines starting from a low of 0.95 x
A
106 tons/year to a high of 2.3 x 10s tons. The effect of these emissions on
overall air quality is unknown.
1.1.1 Emission Factors
Emission factors have been updated and more explicitly defined for each
source category. A few sources which appear in the Esso report are absent from
the latest EPA emission factor data book, AP-42. These include diesel I.C. en-
gines installed in petroleum refineries, boilers and natural gas engines in nat-
ural gas plants, natural gas engines in pipelines, sintering and other furnaces
in steel-making, lime kilns and glass manufacture. Many of these undelineated
topics may be imbedded in other categories. Recent data show emission factors
for oil fired residential heaters 67 percent higher than reported by Esso.
These latest emission factors for residential units have not been incorporated
in the reported emission inventories shown in Table 1-1.
1.1.2 Prospects for NOX Emission
Trends for the future include the impact of the following factors:
• Changes in energy demand
• Fuel switching
• Adaptation of controls.
Figure 1-2 shows a long term projection of fuel utilization for electrical
Q
utility generation . This curve assumes that fuels will be readily available
and that generating plants will be built to meet the demand. Environmental
laws and international political developments have hindered these sources
in the recent past. Thus we see a much greater utilization of direct coal
combustion in the next decade. From 1980 to 2000 there will be greater
emphasis on "clean fuels" derived from coal, i.e., synthetic gas and oil.
For residential and commercial sources we see the following trends:
• Reduced emissions due to reduced load (cooler homes)
• Some switching back to coal-fired home heating systems
• In the longer term, switching to electrical heat (provided
the power plants can meet the demand)
• Increases in efficiency of the home heater system and greater
housing insulation to reduce the total load and thus emissions
1-4
-------
1965 70
85 1990
Figure 1-2. Estimated Annual Electric Utility Generation
by Primary Energy Sources
1-5
-------
• By the year 2000, the possible widespread use of solar heating for
homes.
Total estimated NO emissions from industrial combustion has not changed
• X
much since 1969. Little field testing has been done in this area and, except
for large industrial boilers, control techniques have not been well defined.
Emission control efforts will continue to expand, along with fuel substitution
trends.
Control schemes for the primary non-combustion source, nitric acid
plants, have been developed to meet 1980 EPA standards.
s
Total stationary source NO trends have exceeded the predicted trends
as shown in Figure 1-3. However, there is a slight downward trend due to
revised emission estimates and controls on West Coast utilities.
1.2 SURVEY OF OPTIONS FOR NO CONTROL
A
Since the Esso study the effectiveness of numerous NO control options
X
has been evaluated. Present or potential options are categorized as follows:
• Modification of the existing process
• Modification of the fuel
• Treatment of the flue gas
• Use of an alternate process.
These options were evaluated in this report on the basis of the following criteria:
• Cost effectiveness
• Availability (short-term options)
• Low risk development (long-term options)
• Impact on unit efficiency
• Impact on operational difficulty
• Overall environmental impact due to process control
• Compatibility with projected fuel allocations.
The results are summarized in Table 1-2. For the control of existing
combustion sources, combustion modification has remained the most expedient,
most reliable and cost effective technique. For noncombustion sources, flue
gas treatment is preferred.
For long term NO control, the incorporation of combustion modifications
X
into new unit design appears to be the single most effective strategy for
1-6
-------
KEPORT
-2000
Figure 1-3. Stationary Source NOX Emission Trends
1-7
-------
TABLE 1-2
SUMMARY OF NOX CONTROL OPTIONS
Option
Combustion
Modification
Synthetic
Fuels
Fuel
Additives
Fluidized
Bed
Boiler
Flue or
Exhaust Gas
Treatment
Approach to NOX Control
Suppress formation of
thermal, fuel Nox by
modifying operating
conditions
Reduced flame
temperatures from
low Btu gas yields
reduced NOX
Reduce or decompose
NO to No by
catalytic addition
Low bed temperature
suppresses thermal
N0x
Reduce NO to N?
by catalytic
treatment
Effectiveness
Short Term
Present
applicability;
preferred
option
Negligible
application
Not
effective
N.A.
Preferred for
nitric acid
plants
Long Term
Incorporate into
optimized low
NOX design
Promising low
risk concept for
post-1980
High risk
development
Medium risk
concept for
post-1980
Possible for
control of
I.C. Engines
Overall Evaluation
Priority option for short
and long term control of
boilers, furnaces, turbines
Attractive long term option;
May require combustion modifications
Not promising
Promising long term option;
May require combustion modifications
Potential long-term option for backup
of combustion modification for
boilers, furnaces. Possible long-
term option for I.C. Engines. Priority
option for nitric add plants.
CO
-------
stationary sources. Large electric power generation units will undoubtedly
benefit from developments in the use of synthetic fuels and fluidized bed com-
bustion in conjunction with combined power cycles. Even these advanced con-
cepts, however, may require combustion modification for NO control. The bulk
of stationary sources — area sources such as pipeline I.C. engines, industrial
combustion, and domestic heaters •— will increasingly utilize combustion modi-
fications for NO control in new equipment design.
We conclude that combustion modifications are clearly the priority item
in program planning for NO control of stationary sources.
X
1.3 COMBUSTION MODIFICATION TECHNOLOGY
Since the Esso study, there have been fundamental advances in identifying
the formative mechanisms for thermal and fuel NO . The capability for relating
NO formation mechanisms to specific combustion modifications has not yet been
X
established, however. Accordingly, the EPA program to devise and test modi-
fication techniques is broadly based with simultaneous focus on fundamental
studies, pilot scale testing on laboratory scale equipment, and full scale
testing on commercial equipment. The overall short term objective of the
program is to develop verified, cost effective techniques for retrofit modi-
fication of existing units. Most of the significant reductions in NO emis-
X
sions have resulted or directly benefited from the efforts of this program.
The overall long term objective of the program is to develop optimized
control concepts for new units and to define minimum attainable emission levels.
For both the short and long term studies, the priority development area is
combustion modification techniques for control of fuel nitrogen conversion to
NO.
1.3.1 Fundamental Studies
The fundamental studies area of the combustion control program is
primarily a long term effort to develop a basic understanding of NO formation.
X
Since the Esso study, the emphasis has been on modeling the individual key
phenomena involved in NO formation. Significant advances have been made in
the areas of fluid flow solution, thermal NO kinetics, gaseous hydrocarbon
X
oxidation, and thermal radiation. These results have had the short term yield
of aiding in evaluating data from pilot and full scale tests, and in suggesting
ideas for combustion modification techniques. Only preliminary advances have
been made in the modeling of fuel NO and of the effects of turbulent mixing
X
on hydrocarbon and NO reaction rates. These are both considered priority R&D
areas. In the long term, the individual models for the key phenomena will be
1-9
-------
TABLE l-3a
MODIFICATION TECHNIQUES FOR UTILITY AND INDUSTRIAL BOILERS
Modification Techniques
Major Effect
Major Potential Problems
Utility and Industrial Boilers
Low Excess Air Operation
Off-Stoichiometric
Combustion
Flue Gas Recirculation
Reduced Air Preheat
Operation
Load Reduction
Water, Steam Injection
Equipment Modifications:
O'low NOX" Burner
• Boiler Wash
OUiden Burner Spacing
«Tangential firing
(as opposed to wall-
firing)
Oxygen concentration
reduction
Fuel-rich burner operation
Reduced residence time of
fuel at peak temperature
Peak temperature reduction
Peak temperature reduction
Peak temperature reduction
Peak temperature reduction
Peak temperature reduction
Provides off-stoichiometric
combustion at burner
Readily fuel/air adjustable
Fuel-flexible
Maintains rated heat
transfer rate
Reduce peak temperature
Reduce interference
between burner flames
Peak temperature reduction
Slower, more controlled,
combustion
Increased furnace slagging
Nearer smoke threshold
Flame instability, smoking
Higher convective section
temperatures
Flame instability
Boiler efficiency reduction
Boiler efficiency reduction
Boiler efficiency reduction
Boiler efficiency reduction
Increased corrosion
Retrofit problems:
Compatibility with existing
furnace
Conversion investment costs
Boiler downtime
Boiler downtime
Maintenance expense
New unit design only;
retrofit cost prohibitive
1-10
-------
TABLE l-3b
MODIFICATION OR CONTROL TECHNIQUES FOR STATIONARY I.C. ENGINES AND GAS TURBINES
Modification or
Control Techniques
Major Effect
Major Potential Problems
Reciprocating I.C. Engines
Speed vs. Stoichiometry
Decreased Torque Load
(at constant speed)
Decreased Air Manifold
Temperature
Increased Valve Overlap
Exhaust Gas Recirculation
Catalytic Converter,
Anmonia as Reducing Agent
(Post Combustion Control
Method)
Water Injection
Precombustion chamber
With speed, NO increases
under fuel-rich and
decreases under fuel-lean
conditions
Peak temperature reduction
Peak temperature reduction
Peak temperature reduction
Peak temperature reduction
Reduction of NO, NO- to
N and 0
Peak temperature reduction
Peak temperature reduct-
tion; 0- starvation
Retrofit difficulties;
inability to meet load
demand
Retrofit difficulties;
inability to meet load
demand
Efficiency reduction
Fuel economy reduction
Applicable only to
4-cycle engines
Intake manifold fouling
Additional control system
Operational difficulties
Efficiency reduction
Expensive
Current catalysts sensitive
to impurities in fuel
Increased maintenance;
additional equipment for
water handling
Costly for retrofit
1-11
-------
TABLE l-3b (Concluded)
Modification or
Control Techniques
Major Effect
Major Potential Problems
Gas Turbines
Lean-Out Primary Zone by
Modifying Combustion
Chamber Design
Water injection
Exhaust Gas Recirculation
Peak temperature reduction
Reduced residence time of
fuel at peak temperature
Peak temperature reduction
Peak temperature reduction
Less control over flame
stabilization
Less control over lower
lean extinction performance
Reduced efficiency
Increased maintenance
Additional equipment for
water handling
Reduced efficiency
Additional control system
Operational difficulties
1-12
-------
coupled, refined, and verified by correlation with test data to ultimately
yield predictions of NO formation.
1.3.2 Application of Combustion Modifications
The present study concludes that combustion modification, including both
operation and equipment variation, is the most viable means of reducing NO
X
formation from stationary sources. Tables l-3a and l-3b list the most common
modification techniques applicable to utility and industrial boilers, station-
ary gas turbines and reciprocating I.C. engines.
The effectiveness of these combustion modifications has been demonstrated
more completely during the past several years. The record of achievement on
steam electric power plants is particularly impressive, with response to these
modifications dependent mainly on fuel type. NO from gas-fired installations
showed the greatest reductions since thermal NO is the only formation
mechanism involved. Diminished degrees of success have been attained for
oil and coal firing due to the influence of fuel NO .
X
For all three fuels, off-stoichiometric combustion techniques have prov-
en to be the most effective in suppressing both thermal and fuel NO . Firing
under low (5-10 percent) excess air conditions has become standard operating
procedure for most utility and industrial boilers. The other modification
methods, such as flue gas recirculation and reduced air preheat, are increasing-
ly costly to implement in terms of investment, operating costs, and loss of
plant efficiency.
Reports have shown that serious operating problems theoretically
associated with combustion modifications can largely be avoided. However,
a certain amount of additional vigilance, as well as willingness to tolerate
a decrease in flexibility, is required of the plant operator.
Since 1969, a lesser amount of practial N0_ modification work has been
X
performed on stationary reciprocating I.C. engines and gas turbines. This is
due in part to a general lack of appreciation of the importance of these
sources. The contribution of this type of source has since been estimated to
be quite significant. The most promising NO reduction methods include hard-
X
ware modification for I.C. engines (i.e., precombustion chamber) and water
injection for gas turbines.
The combustion modification cost picture is blurred. In most cases,
such information has gone unreported or is of a proprietary nature. It has
been concluded, however, that generalized cost data would be difficult to
compile due to the disparity between the responses of essentially identical
1-13
-------
combustion systems to a given modification. These disparities are due to
plant condition, operating modes, fuel differences, etc.
The current clean fuels shortage has significantly influenced the
course of NO control programs for utility and industrial boilers. The en-
X
couraging results obtained from natural gas and oil firing have become some-
what academic due to the probable widespread substitution of coal for these
fuels. It is therefore mandatory that all aspects of combustion modification
techniques for coal firing be thoroughly researched in both sub- and full-scale
tests. Achieving maximum NO suppression and thermal efficiency concurrently
X
are the ultimate goals.
As emissions from utility and industrial boilers are controlled, the
contributions from area sources, such as stationary reciprocating I.C. engines
and gas turbines, will become more significant. NO control systems R&D and
their application to on-line systems is currently accelerating.
1.4 ASSESSMENT OF R&D REQUIREMENTS
Table 1-4 summarizes the items identified in this study as requiring
further development. The recommendations are categorized as follows:
• Combustion Modification Technology
Fundamental Studies
Fuels R&D
Process R&D
Field Testing and Survey
• Flue Gas Treatment
• Alternate Processes
The overall priority item is development of control techniques for coal-fired
units. Individual items regarded as high priority are summarized below.
• Fuel NOX - The continuing Rocketdyne study is leading to an under-
standing of mechanisms by which fuel bound nitrogen is converted
to NO. As preliminary results are obtained, independent studies,
at a similar level of funding, should be initiated for key aspects
of the study such as volatilization and pyrolysis models, and
carbon burnout models.
• Mixing Effects on Reaction Rates - An understanding of N0x formation
in practical combustors must account for the effects of distortion
of the flame zone due to turbulent mixing. A new program with
1-14
-------
TABLE 1-4
RECOMMENDED R&D
R&D Area
Fundamental
Studies
1
Fuels R&D
I
Subheading
Fluid Flow
Solutions
Thermal NOX
Fuel NOX
Turbulent
Viscosity
Mixing Effect
On Reaction
Rates
Thermal
Radiation
Off-Stoich-
iometric
Combustion
Burner
Optimization
for Fuel NOX
Program
f
Continue 2-0 code development
Apply 2-D jet flame boundary layer
codes
Pressure- velocity codes for 2-D re-
circulating flow
Pressure velocity method for 3-D
HCN emission in fuel-rich flames
Esso-Ultrasystem codes with diffu-
sional effects
Volatilization + pyrolysls models
Post-pyrolysis heterogeneous carbon
burnout models
Couple participate combustion with
luminous radiation
Synergism of NOX and SO?
HCN
2 Equation turbulence models 1n re-
circulating 2-D flow code
Nonisotropic turbulence models for
swirling 2-0 boundary layer jet flames
Experimental and analytical study of
turbulent premixed and diffusion
flames - simple geometry
Coordinate existing radiation models
with fuel nitrogen study
Determine optimum design parameters
for staged firing with coal
Determine optimum design parameters
for low NO burner
: Priority
Medium
Medium
Low
Low
Medium
Medium
High
High
High
High
High
Medium
Medium
High
Medium
High
High
New Program/
Continuation
Continuation
New
New
New
Continuation
Continuation
Continuation
Continuation
Continuation
Continuation
Continuation
New
New
New
Continuation
New
New
Reasoning
Incorporate current auxiliary models •
Test turbulence model, mixing effects on '
kinetics, 2$ flow models, luminous radi-
ation effects
Utilize current technology
Obtain flow patterns and scaling laws
Determine potential as a pollutant
Extend findings to practical flow
situations
Extend Rocketdyne findings Into Inde-
pendent studies
ii ii ii
H ii n
n n n
Determine potential as a pollutant
Utilize current technology
Verify models in simple flow geometries
Develop models for effect of mixing on
reaction rates
Utilize findings of Rocketdyne study
Present research indicates this to be
most viable NOx control technique for
coal combustion
Effective option for fuel nitrogen
control
-------
TABLE 1-4. Continued
R&D Area
Fuels R&D
continued
Process R&D
Field
Testing
Subheading
Burner •'
Optimization
for Thermal NO
Radiation
Measurement
Corrosion &
Fouling
Coal Type
Synthetic
Fuels
Oil Atomiza-
tion
Optimization
Modification
Corrosion
Studies
Off-Stoichio-
metrlc
Combustion
Intermediate
Bound
Compounds
Optimized
Modification
and Areas
Sources
Catalytic
Combination
Pulverized
Coal -Fired
Equipment
Corrosion &
Slagging
Area
Sources
Program
Determine optimum design parameters
for low NOX burner using low nitrogen
fuels
Determine realistic radiation heat
fluxes for coal, oil and gas
Determine ability to do subscale
corrosion and fouling studies of NOX
control schemes
Systematically test different types of
coal - effect of properties on NOX
emissions
NOX emissions from fuels and equipment
conversion problems
Determine effects of fuel atomizatlon
technique on NOX
Determine optimized modification
schemes for each fuel and process
Perform full scale studies of NOX
control techniques on corrosion and
fouling
Expand full scale testing for staging
on coal combustion
Determine fate of chemically bound
nitrogen in full scale equipment
Continue to expand ongoing programs
to determine optimized schemes;
especially area sources
Exploratory work to determine full
potential
Determine current stationary source
control technology (CSST)
Determine effects of CSST on corro-
sion and fouling
Determine CSST for area sources
Priority
•' High
Low
High
Medium
Medium
Medium
Medium
High
High
Low
High
Low
High
High
High
New Program/
Continuation
New
New
New
New
Continuation
Continuation
Continuation
Continuation
Continuation
New
Continuation
Continuation
Continuation
Continuation
Continuation
Reasoning
May be effective option for thermal NOX
as well
Input to radiation models
Very important factor to determine appli-
cability, of controls
Determine applicability of control tech-
niques over spectrum of coal types
rlecessary to identify problems of future
fuels
Potential control technique; coordinate
i.'ith optimum burner design
liecessary for immediate retrofit
Full scale testing will yield the ultimate
data
ii ii n
Determine if there really is a problem
in full scale equipment
Determine applicability on full scale
equipment
Potential long range option
Coal-fired equipment has highest
priority
Additional data very Important
Field data lacking
-------
TABLE 1-4. Concluded
R4D Area
' Field
Testing
continued
Flue Gas
Treatment
Alternate
Processes
Subheading
Alternate
Fuels '
™~
Synthetic
Fuels
Advanced
Power
Generation
Cycles
Program
Exploratory work to determine nature
and extent of problem
Review state of the art
Determine NOX problems
Determine NO problems
Priority
,- Low
Low
Low
Low
New Program/
Continuation
New
New
New
New
Reasoning
Extent of use and NO problems are
unknown ,
May be required for secondary cleanup
Fuels may be extensively used in 1980-
2000
ii 'ii n
-------
coordinated experimentation and analysis for a simple flow geometry
would contribute to the basic understanding of this effect and sup-
plement the coupled modeling effort being done by UARL.
Off-Stoichiometric Combustion - This is regarded as the most effec-
tive retrofit method for simultaneous suppression of thermal and
fuel NO formation. A new program in fuels R&D and a continuing
X
program in process R&D is required to fully exploit the potential
of this technique.
Burner Optimization - Burner configuration and injection pattern
should be optimized, particularly for new unit design, to suppress
the formation of thermal and fuel NO. A generalized Fuels R&D
program to investigate types of firing for gas, oil and coal would
provide the data needed for design optimization.
Corrosion and Fouling - The effectiveness of combustion modification
schemes can be limited by the increased propensity for corrosion
resulting from the modified combustion conditions. This problem
requires study on both subscale and full-scale units.
Area Source Testing - A field testing program is needed to extend
the technology developed for control of utility boilers to the con-
trol of the major area sources.
1-18
-------
SECTION 2
INTRODUCTION
In 1969, Esso Research and Engineering published results of a system
study of NO control from stationary sources with the following objectives:
• Characterize stationary source NOX emissions
• Assess NO control technology
X
• Explore utility of modeling for NOX predictions
• Analyze cost effectiveness of control techniques
• Recommend R&D plan for NO control technology
X
Esso estimated that stationary sources comprised 60 percent of total NOX emis-
sions and of that percentage, 98 percent was due to combustion sources ranked
as follows: (1) electric power plants (37.5 percent), (2) industrial combus-
tion (29.2 percent), (3) pipelines and gas plants (20.8 percent), (4) domestic
and commercial heaters, (10.4 percent). Based on the limited data and experi-
ence at that time, Esso concluded that the most promising short term option
for NO control was combustion modification.
A
The Esso study was done when the concerted government program for N0x
control was in the preliminary stages. Since that time, there have been numer-
ous developments both in the character of present or projected emission sources
and in techniques for NOV control. Recently, obstacles encountered in achiev-
X
ing effective control of mobile sources have led to a stronger emphasis on
control of stationary sources. The supply shortage of petroleum fuels is
leading; in the short term, to conversion to coal firing, and, in the long term,
to a re-evaluation of alternate combustion processes for replacement of existing
units. The effectiveness of the combustion modification strategy for control of
large boilers has been validated, since the Esso study, for gas and oil firing,
and preliminarily for coal firing. With coal, the strategy is complicated by
the conversion to NOV of the nitrogen compounds in the fuel. Control of the
X (
major area sources - industrial, commercial, and domestic combustion units -
is being initiated, using where possible, experience derived from control of
utility boilers.
2-1
-------
In view of the changing pattern of NOV control for stationary sources,
X
Aerotherm Division of Acurex Corporation has been conducting a study for the
Control Systems Laboratory of the Environmental Protection Agency in order to
assess the current status of NOX control technology. Particular emphasis is
on identifying changes, since 1969, which would reorient the focus of systems
planning. Individual objectives are:
• Characterize current and projected stationary NO emission sources
X
• Evaluate present and potential options for NO control
X
• Characterize the status and prospects of combustion modification
technology
• Determine requirements for R&D
The Esso report gave a comprehensive treatment of virtually all aspects
of the stationary NO emission problem including detailed descriptions of em-
mission sources and control techniques. For the present study, it was there-
fore possible to focus, at the outset, on the most significant changes impact-
ing systems planning. Figure 2-1 summarizes the approach used for this study,
and, also, provides a schematic outline of this report. The conclusions and
recommendations of this study were based on a review of recent literature and
discussions with industrial users and manufacturers. Based on the survey of
emission sources, given in Section 3, and on the evaluation of control options,
given in Section 4, it is concluded that the focus of short-term systems plan-
ning remains on combustion modifications for large boilers and the major areas
sources. Section 5 is the main section of the report and is devoted to giving
an overview of combustion modification technology. Potential R&D areas iden-
tified in Section 5 are summarized in Section 6.
2-2
-------
SHOfrr
FOCUS ON
tOMBUSTIOM
MODIFICATIONS
1
1
SEC 5
FLUE £»tff TIZeAT-
MENT ALTERNATE
PUEL ANP PROCESSES
sec. «
SECTIOM 4: IDENTIFY PRIORITY OPTIONS
STOPY INITIATION
PROBLEM OF
NO, FORMA-
TION; THEISM AL,
PlIPl MO.
MOPeUNCi:
SINCE nt*
EESULTS
£
STATUS
MODIFICATION TECHNOLOGY
SECTION 5- CHAEACTEElZe STATUS OF COMBUSTION
Figure 2-1 Sunr.iary of the Approach to the Present Study
-------
SECTION 3
CHARACTERIZATION OF EMISSION SOURCES
This section reviews briefly the NOV emission inventory presented in
i
the 1969 Esso study with emphasis on recent data, significant changes, and
areas of questionable data. The present study has emphasized current stationary
source emissions, but includes some reflections on the projections for 1980
and 2000.
3.1 SOURCES OF NITROGEN OXIDES
No new major sources of NO have been discovered during the past five
A
years. The primary sources of nitrogen oxides are many combustion processes
and some noncombustion processes such as nitric acid plants. The Esso report
pointed out that the NO formed in combustion comes from two distinct sources:
-------
TABLE 3-1
TOTAL NOX EMISSIONS FROM STATIONARY SOURCES (X 10s tons/year)
Source
Utility Size Boilers
Recip. I. C. Engines
Industrial Size Boilers
Forest Fires (controlled)
Domestic And Commercial
Space Heaters
Gas Turbines
Solid Waste
Disposal
Process Heaters
Nitric Acid Plants
Other Sources
Total
EPA(3) 1974
5.88
0.918
3.91
d
0.945
d
0.179
2.876
d
d
14.7
AP-115, 1971(2)
4.71
L /i c->
7 t.DJ
.2 75
0.79
a
0.395
a
a
0.338
11.038
Esso, est. 1970, (1)
3.841
2.097b
2.81
a
1.001
a
a
a
> 0 235
•ta^
9.986
Other, 1970(3,4,5)
3.3-6.0C
1.95-2.3
10
10
Notes:
a. Included In Industrial-size Boilers
b. Pipeline And Gas Plants Only
c. Depending on Load Factor (High Number For Full Load)
d. Not included in NEDS data
-------
and 4, a revised pie chart was constructed as shown in Figure 3-1. This chart
corresponds to the Esso pie chart (Figure 3-1 in Reference 1) but employs the
AP-115 data in Table 3-1. The I.C. engine data and industrial boiler data were
divided into industrial combustion and pipeline-gas plant categories on the ba-
4
sis of the estimated I.C. engine data from the McGowin (Shell) study . Figure
3-1 indicates that the order of importance of each category has not changed.
The greatest change is in the estimate of the electrical utility category, which
increased from the 1970 Esso estimate of 3.84 x 10s tons of N0v per year to 4.77
X
x 106 tons/year. The reason for this will be discussed under the section on
large utility boilers. However, Figure 3-1 does not give a representative pic-
ture of the importance of internal combustion engines, because they are distri-
buted between pipelines and gas plants, electrical utilities and industrial com-
bustion. Using the figure 2.22 x 10s tons/year, the contribution of I.C. engines
is 20.1 percent of the total stationary source emissions. This will be further
discussed in Section 3.1.3 on I.C. engine emissions. A more representative pie
chart can then be made which divides the sources into the following categories:
• Large utility bdilers
• I.C. engines and gas turbines
• Industrial Combustion
• Residential and commercial heating
• Noncombustion sources.
This revised pie chart is shown in Figure 3-2.
It must be remembered that data presented in total amounts does not
necessarily reflect the importance of the source. Other factors such as
altitude, climatology, geographical location and population density should
be considered.
For the year 1971, the distribution for coal, oil and gas contributions
to total NO production for stationary sources is shown in Table 3-2. This
A
table shows the importance of coal to the total NOV emissions. This importance
A
is further amplified by considering the percentage contribution by the electric
utility industry: 63.4 percent as shown in Table 3-3. This percentage will
certainly increase during the next decade as some utilities convert to coal.
There is also a trend to oil and away from gas. For example, according to
management at two West Coast utilities their boilers were typically 70-75 percent
gas-fired last year, are 40 percent gas-fired this year and will only be five
percent gas-fired next year. There will also be a move in the industrial sector
towards greater utilization of coal.
3-3
-------
ELECTRICAL
UTILITY
(4-3.
INDUSTRIAL
COMBUSTION
PIPELINES
PLANTS
TONS i«ni
1^0,000
34Q, QQO
I ,O40,OOO
TYPE OF INSTALLATION
UTILITY
e ^AS PLANTS
NOKJ
US, TOTA.L.
Figure 3-1. Total NOX Emitted In The U.S. From Stationary Sources. 1971.
3-4
-------
NOK1 COMB,
UTILITY
BOILER
TOMS,
4,110,000
2,350,000
•2.,050,OOO
340,QQO
II,O40,OOO
UTILITY
6 AS
K6SIPENTIAL ^ COMMERCIAL
' 60URCSS
Figure 3-2. Total NOX Emitted In The U.S. From Stationary Sources, 1971,
(From Data Obtained From References 2 and 4)
3-5
-------
TABLE 3-2
1971 ESTIMATES OF NOX EMISSIONS FROM
FOSSIL-FUEL STATIONARY SOURCES
Fuel
Gas
Oil
Coal
Emissions
10 6 tons/year
4.6
1.4
3.9
Percent of*
Total Stationary
Sources
41.6
12.7
35.3
Does not add to 100 percent; remainder is other combustion and non-combustible
sources.
TABLE 3-3
N0x EMISSIONS FROM FOSSIL-FUEL ELECTRICAL UTILITY UNITS
Fuel
Percent of Total NO Emissions
A
From Electrical Utilities
Gas
Oil
Coal
21.6
15.0
63.4
3-6
-------
3.2 EMISSION FACTORS
The estimates outlined above for NOV emissions from stationary sources
A
depend on three factors:
1. The total number of sources
2. The emission factor for each source
3. The use factor for each source
The Esso report used emission factors derived principally from the 1968
Edition of "Air Pollution Emission Factors," AP-42, with their own revision for
CO boilers and catalytic cracking regenerators. The data reported in Table 3-1
from AP-115 are based on emission factors from the February, 1972 edition of
AP-42, and include most of the emission factors reported in the April 1973
edition of AP-426.
Table 3-4 compares the emission factors from the Esso report to the
1
7
latest edition of AP-42 and a paper by Jenkins and of McCutchen for all
sources which emit NOV. Only a few sources are mentioned in the Jenkins
A
paper and these generally agree with AP-42, except for the average figure given
for pulverized coal-firing of steam power plants which seems rather high. As
As can be seen from the table, the AP-42 document goes into much greater detail
than did the Esso report. When this greater detail is listed, the average Esso
value is given for the category. Note also that the factors are presented
next to each major heading in the units given by AP-42. (These units are not
on an equivalent BTU basis.) However, most of the fuel combustion sources
are grouped under the fuel type in External Combustion Sources rather than the
particular industry. For example, the Esso report estimates emission from
heaters, boilers, gas engines and gas turbines under gas plants, petroleum
production and pipelines. Strangely, a few emission sources are missing from
AP-42 . These sources include diesel I.e. engines in petroleum refineries,
heaters, boilers and gas engines in gas plants, gas engines in pipelines,
sintering and other furnaces in steel making, lime kilns and glass manufacture.
Many of these may be accounted for under external combustion sources. Alternative-
ly, sources included in AP-42 but not mentioned in the Esso report are LPG
combustion, wood and bark combustion, tunnel kilns in brick manufacture and
fiber glass manufacture. Most of these are relatively minor sources and may
have been included under other headings.
3-7
-------
TABLE 3-4
EMISSION FACTORS FOR NOX FROM STATIONARY SOURCES
Source Category
External Combustion Sources
Bituminous Coal Comb. (Ibs/ton)
Pulverized
General
Met bottom
Dry bottom
Cyclone
Stoker (Large)
Stoker (Small)
Hand Fired
Anthracite Coal Comb. (Ibs/ton)
Pulverized
Overfeed Stokers
Hand Fired Units
Fuel Oil (N0x lb/103gal)
Power Plant
Tangential Fired
Residual
Distillate
Domestic
Nat. Gas (N0x lb/106ft3)
Power Plant
Tangential ly Fired Power Plant
Ind. Process
Domestic and Com. Heating
LPG Comb. (lbs/103gal)
Ind. Proc. Furn-Propane
Ind. Proc. Furn-Propane
Domes, and Com. Furn. Butane
Domes, and Com. Furn. Propane
Mood and Bark Comb. (Ib/ton)
AP-42 Rev.
(Ref. 6)
18
30
18
55
15
6
3
18
6-15
3
105
50
40-80
40-80
12
600
300
120-230
80-120
12.1
11.2
8-12
7-11
10
Esso
(Ref. 1)
19.98
19.98
8.0
19.98
19.98
8.0
103.9
71.9
12.0-71.9
12
390
214
116
ND
ND
EPA Paper
(Ref. 7)
33
105
418
3-8
-------
TABLE 3-4 CONTINUED
Source Category
Refuse Incineration (Ib/ton)
Municipal
Industrial/Commercial
Multiple Chamber
Single Chamber
Trench
Controlled Air
Flue Fed Single Chamber
Flue Fed Modified
Domestic Single Chamber
w/o Primary Burner
w/ Primary Burner
Pathological
Auto Body Incineration (Ib/car)
Conical Burner (Ib/ton)
Municipal Refuse
Wood Refuse
Open Burning (Ib/ton)
Municipal Refuse
Automobile Comp.
Agric. Field Burn.
Landscape Refuse
Wood Refuse
Stationary Gas Turbines
(Oil, lb/106Btu)
(Gas, lb/106Btu)
Adipic Acid (Ibs/ton)
High Explosive Mfg. (Ibs/ton)
Nitration Reactors.
Nitric Acid Cone.
Red Water Incin.
AP-42 Rev
(Ref. 6)
3
3
2
4
10
3
10
1
2
3
.1
5
1
6
4
2
2
2
.84
.57
12
160
1
6
Esso
(Ref. 1)
2.0
2.4
2.4
2.4
2.4
2.4
2.4
2.4
2.4
2.4
.67
.67
10.9
10.9
2.0
.11-0.32
0.2
11.6-13
2.5-6
2.5-6
2.5-6
EPA Paper1
(Ref. 7)
3-9
-------
TABLE 3-4 CONTINUED
Source Category
Low Explosive Mfg. (Ibs/ton)
Nitrocellulose Reactor Pot.
Nitrocellulose Sulfuric Acid Cone.
Nitric Acid Mfg. (Ib/ton acid)
Weak Acid Uncontrolled
Catalytic Comb. N.G. fired
Catalytic Comb. H2 fired
Catalytic Comb. Mixture
High Strength Acid
Coffee Roasting (Ibs/ton)
Nitrate Fertilizers (Ibs/ton)
w/Granulator
Dryers & Coolers
Sugar Cane Processing
Field Burning (Ib/acre burned)
Blast Furnace (Ibs/ton of pig iron)
Coke Manufacture (Ib/ton)
Charging
Coking Cycle
Cupola Furnace
Steel Foundries (Ib/ton)
Electric Arc
Open Hearth
Other Furnaces in Steel Making
Sintering
Brick Manufacture (Ibs/ton)
Tunnel Kilns (Ib/ton)
Gas Fired
Oil Fired
Coal Fired
AP-42 Rev.
(Ref. 6)
12
29
50-55
2-7
0-1.5
.8-1.1
.2-5.0
0.1
0.9
3.0
30
ND
.03
.01
ND
.2
.01
ND
ND
.15
1.1
0.9
Esso
(Ref. 1)
2.5-6
2.5-6
57
Neg.
Neg.
.397
.065
.065
.11
ND
2.45
.086
1.04
ND
ND
ND
EPA Paper1
(Ref. 7)
43
3-10
-------
TABLE 3-4 CONTINUED
Source Category
Periodic Kilns
Gas Fired
Oil Fired
Coal Fired
Cement Mfg. Kilns (Ibs/ton)
Lime Kilns
Fiber Glass Mfg. (Ib/ton)
Textile Products
Glass Furnace
Regenerative
Recuperative
Curing Oven
Wool Products (Ibs/ton)
Glass Furnace
Regenerative
Recuperative
Electric
Curing Oven
Cooling
Petroleum Refineries
Boilers & Process Heaters
Oil Fired (lb/103bbl)
Gas Fired (lb/103ft3)
Fluid Cat-Cracking Units
(lb/103bbl fresh feed)
Moving Bed Cat Cracking
(lb/103bbl fresh feed)
Compressor I.C. Engines
(Ib/103ft3gas burned)
I.C. Engines-Diesel (lbs/103bbl)
Gas Turbines (Ib/103ft3gas burned)
AP-42 Rev.
(Ref. 6)
0.42
1.7
1.4
2.6
ND
9.2
29.2
2.6
5.0
1.7
0.27
1.1
0.2
2900.
.023
71
(37.1-145.0)
5
0.9
ND
ND
Esso
(Ref. 1)
1.68
3.84
4.128
1.53-3.69
1.152-2.74
ND
ND
ND
ND
ND
ND
ND
ND
2800
.21
4.2
4.2
4.2
.77-4.35
.0093
.2
EPA Paper1
(Ref. 7)
3-11
-------
TABLE 3-4 CONCLUDED
Source Category
Gas Plants (Ibs/103ft3gas burned)
Heaters & Boilers
Gas Engines
Gas Turbines
Pipelines (Ibs/103ft3gas burned)
Gas Engines
Gas Turbines
Glass Mfg. (lb/106Btu)
AP-42 Rev.
(Ref. 6)
ND
ND
ND
ND
ND
ND*
Esso
(Ref. 1)
.19
4.3
.2
7.3
0.2
.87
EPA Paper1
(Ref. 7)
Included most likely as external combustion sources
3-12
-------
3.3 PROSPECTS OF NOV EMISSIONS
A
The data presented in the previous sections are continuously being
refined and updated as more detailed studies of each source and data from
field tests become available. This section discusses these changes for each
major stationary source as well as the factors which will influence the
emissions in the future. These factors include
• Changes in energy demand
• Fuel switching
• Impact of NOV controls.
A
3.3.1 Large Utility Boilers
3.3.1.1 Emissions Factor Adjustments and Refinements
The greatest change in the emission factors for large utility boilers
has been for gas-fired plants. Esso reported 390 Ibs N0x/106ft2 of gas and
AP-42 reported 600 Ibs N0v/106ft3 of gas. Between the gas emission factor
A
change and more detailed factors for each type of coal-fired unit, the overall
emissions have increased from the 1970 Esso estimate of 3.84 x 10s tons/year
to 4.71 x 10s tons per year.
It should be noted that these estimates do not include the effect of
emission controls. However, other than in West Coast utilities and new
plants across the U.S., there has been very little application of NOX con-
trols to date, especially on oil- and coal-fired plants. The gas- or oil-
fired utilities on the West Coast have seen reductions in NOX by a factor of 2.
3.3.1.2 Relative Significance of Different Fuels
Converting the revised emission factors in Table 3-4 to an equivalent
BTU basis gives a better indication of the relative importance of each fuel,
as shown in Table 3-5.
TABLE 3-5
COMPARISON BETWEEN COAL, OIL AND GAS ON EQUIVALENT BTU BASIS;
ELECTRIC POWER GENERATION (Ibs NOx/109 Btu)
Natural Gas
(1046 BTU/ft3)
Fuel Oil
(149,966 BTU/gal)
Coal (avg)
(11,867 BTU/lb)
3-13
574
700
758
-------
Thus, for any given plant there should be an 8 percent increase in NO when
converting from oil to coal and a 30 percent increase when going from gas to
oil provided the load remains constant. If the unit was designed to operate
on dual fuels the load will most likely not be lowered. However, if the boiler
was not initially designed to operate on a different fuel, converting from gas to
oil to coal will generally reduce load.
3.3.1.3 Projections for the Future
Projections for the future are speculative at best. In the very short
term we see many utilities decreasing their load from 5 to 15 percent to meet
the "energy crisis" in fuel supply. This reduction in load will yield a
corresponding reduction in NOV. The duration of this situation is even more
8
speculative. However, longer term projection as shown in Figure 3-3 indicate
continuing increase in coal, oil, and gas generating capacity with a substantial
increase in nuclear capacity*
I
s 2
t -.HYDROi
1965
Figure 3-3.
70
85 1990
Estimated Annual Electric
Utility Generation By Primary
Energy Sources
Projections such as this assume that the fuel will be available and that the
generating stations will be built to meet the demand. In fact, the future use
of fossil fuels is difficult to project. Figure 3-4 shows an estimated break-
down of the total U.S. energy demand by each domestic energy source and the
required imports to meet the demand. This particular estimate shows that by
1975, 15.3 percent of the energy could be imported, chiefly as petroleum for
3-14
-------
(Numerical entries are percent
of annual demand)
DEMAND
1950 1955 1800 1835
1970
1975 1980
1605
Figure 3-4. Trends Of Sources Of
U.S. Energy Supply;
1950-1970(Actual)/1975-1985(Projected)
3-15
-------
which the availability and price depend on the international political
situation. Even with adequate domestic and imported oil and gas we have
seen shortfalls in getting the energy to the public due to delays in increasing
refinery capacity because of the relative attractiveness of investment abroad
and because of environmental considerations.
With the recent emphasis toward becoming energy independent there is
certainly going to be an effort made to utilize the 3.2 trillion tons of
potential coal supplies in the U.S. In order to meet the short term energy gap
the sulfur regulations on coal may have to be relaxed and there will prob-
ably be a greater utilization of coal than indicated on Figures 3-3 or 3-4.
In the longer term, however, there also may be a number of problems in meeting
the demand for coal for direct combustion and, eventually, for coal gasification
and liguifaction. These problems include:
• Mining capacity
Trained miners
Availability of mining equipment
Process water
• Large investment requirements
• Transportation of the coal to the utility
• Environmental Considerations
Use of low sulfur coal
Strip mining overburden
Scarred landscape
Water pollution from acid mine drainage
Underground mining resulting in land subsidence with time
Coal preparation waste; slag heaps
Thus to what extent and how fast the coal actually gets utilized is also
very speculative, and, as listed above, similar uncertainties make it difficult
to project oil usage.
We see the following non-quantified trends in the electric utility
industry:
• In the short term 1974 - 1980, increased use of direct combustion
of coal
• Switching from gas to oil where feasible
3-16
-------
• Accelerated use of nuclear energy
• Emphasis on "clean fuels" for the 1980 - 2000 period
Synthetic gas from coal
Synthetic oil from coal
Shale oil
Fluid!zed bed combustion of coal
Combined cycle schemes using low BTU synthetic gas,
synthetic oil, or fluidized bed combustion of coal.
It is not presently possible to project the potential impact of these
fuels switching trends on total NOV emissions except to observe that at least
A
in the short term the NO problem should intensify. The trends cannot be
A
quantified with any certainty, and in any case there is presently no informa-
tion with regards to NOV emissions from combustion of synthetic gas or oil,
X
shale oil or the use of low BTU gas in combined cycle schemes. Some pre-
liminary information is available on fluidized beds combustion of coal. This
will be discussed in Section 4.1.3.1.
3.3.2 Domestic and Commercial Sources
Additional data on emissions factors for home heaters and commercial
boilers are shown in Table 3-6 from a report by Barrett . This data was
developed under EPA and American Petroleum Institute sponsorship and updates
the AP-42 document . The recommended emission factors are 67 percent higher
for oil-fired residential units and approximately the same for commercial
boilers. Further studies by Rocketdyne under EPA contract will help to define
the level of controllable emissions by optimizing the combustor.
The trends predicted in the Esso study are still valid, although the
levels may be higher due to recent emission factors. However, if the energy
shortfall continues the following events may occur:
• Reduced emissions due to reduced load (cooler homes)
• Some switching back to coal-fired home heating systems
• In the longer term switching to electrical heat (provided the
power plants can meet the demand)
• Increases in efficiency of the home heater system and greater
housing insulation to reduce the total load and thus emissions
• By the year 2000, some homes using solar heating.
3-17
-------
TABLE 3-6
NOX EMISSION FACTORS FOR RESIDENTIAL AND COMMERCIAL
OIL-FIRED HEATERS AND BOILERS {lbs/103 gal)»,10
Residential Heaters
Battelle-Suggested Emission Factor
AF-42 Emission Factor
20.0
12.0
Commercial Boilers
Battelle-Suggested Emission Factors
No. 2 Oil
No. 4
No. 5
No. 6
LSR (Low Sulfur Resid.)
AP-42 Emission Factors
Distillate
Residual
20 +
20 +
20 +
20 +
20 +
78No.s
85N°'6
87N
89N
84N
O.E
0.6
0.6
20 - 40
20 - 40
where: N = multiplication factor equal to percent nitrogen
in fuel oil. Typical values are:
GRADE
2
4
5
6
LSR
N
.01
.2
.3
.4
.2
3-18
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3.3.3 Stationary I.C. Engines and Gas Turbines
Total emissions from stationary I.C. engines and gas turbines are
probably the least-well documented and are now believed to represent from 20
to 30 percent of the stationary source emissions (Table 3-1). Table 3-7 gives
an indication of the problem by showing the total estimated horsepower and
emissions of I.C. engines in the U.S. by several authors including Esso. As
can be seen in the table, estimates of installed horsepower and of the total
emissions vary by a factor of two and do not always correspond. It should be
noted, however, that the Esso emissions only include the gas pipeline and oil
and gas production sources. Preliminary data generated by Aerospace under
4
EPA contract agree fairly closely with the Shell estimate done under an
earlier EPA contract. Table 3-8 summarizes the emission factors used for each
engine type by Esso and Shell. In general, the emission factors do not differ
greatly, although the Shell data are usually higher. It should be remembered,
however, that a significant percentage of these engines (gas pipeline and oil
and gas production engines) are located in non-urban areas and that the resi-
dence time of NO or NO, in the atmosphere is only a few days .
Installed horsepower and estimated emissions from stationary gas tur-
bine engines are presented in Table 3-9. There is considerable discrepancy
between the Esso numbers and the Shell report; however, the total emissions
amount to only 1 percent of the total stationary source emissions. The elec-
tric power generating turbines chiefly represent standby and peaking units
(although an increasing number are coming on as base load units) but are im-
portant since they occur in urban areas. When on line they can represent a
sizeable point source of emisssions. The Aerospace study will also be taking
a better look at these emission sources.
We see the following trends with regard to I.C. engines and gas turbines.
• Significant increase in the use of gas turbines for gas pipelines,
oil field application and peaking and standby units for electrical
power generation
• Continued increase in I.C. engine applications but many applications
going to gas turbines for greater reliability (unless fuel costs
becomes prohibitive)
• Increased use of gas turbines for combined cycle plants.
3-19
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TABLE 3-7
TOTAL INSTALLED HORSEPOWER AND EMISSION FROM RECIPROCATING I.C. ENGINES
Engine Type
Gas Engines
Oil & Gas Transmission Lines
Utility Electric Power Generators
Agricultural Wells
Oil & Gas Production
Cornier ical/ Institutional /Industrial
Municipal Water & Sewer Treatment
Oil Fueled Engine
Diesel - Precombustion Supercharged
Diesel - Precombustion Nonsupercharged
Diesel - Direct Injection Supercharged
Diesel - Direct Injection Nonsuper-
charged
Total Horsepower
Engine Application
Peaking Power
Gas Pipeline
Oil & Gas Production
Agricultural Wells
Standby
Other
Total Emissions
Installed Horsepower
Esso1
10s hp
53.0
(total )
0.7
0.1
14.0
2.0
69.8
Shell4'3
106 hp
11.28
3.80
0.00
7.00
0.23
0.46
11.86
37.74
Aerospace
106 hp
NOX Generation by I.C. Engines
(tons/year)
10s ton/yr
7
1.596
0.730
?
?
?
(2.326)
10s ton/yr
0.062
0.930
0.832
0.319
0.0
0.093
2.236
106 ton/yr
0.065-5b
?
?
7
7
?
1.95
Includes dual fuel engines.
blncludes peaking power and standby from normal load to full load capacity.
3-20
-------
TABLE 3-8
N0¥ EMISSION FACTORS FOR RECIPROCATING
x I.C. ENGINES (gm.NOx/Bhp-Hr)
Engine
Diesel, Precombustion
Chamber
Diesel, Precombustion
Chamber
Diesel, Direct Injection
Diesel, Direct Injection
Natural Gas (Otto)
Natural Gas (Otto)
Supercharged?
Yes
Yes
Yes
Esso1
3.36
1.37-1.95
11.75
4.29-9.17
25.4
12.7
Shell4
5.3
5.9
13.8
11.2
12.5
11.8
AP-426
3.8-22.7
TABLE 3-9
TOTAL ESTIMATED HORSEPOWER & EMISSIONS
FROM GAS TURBINES
Esso
Turbojet - Oil
Turbojet - Gas
Esso Total
Shell
Electric Power Gen.
Oil and Gas Pipelines
Natural Gas Processing
Plants
Shell Total
Horsepower (106hp)
5
46
51
30.44
3.52
1.53
35.49
Emissions (tons/yr)
?
?
21,000a
62,920
39,800
28,130
130,200
Includes only oil and gas piplines (19,000 tons/year) and natural gas
processing plants (2,000 tons/year)
3-21
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An EPA grant (No. R80227D with Aerospace Corporation) will provide fur-
ther data on I.C. engines and will recommend an R&D program for I.C. engines
as a source of NOX .
3.3.4 Industrial Combustion Sources
Industrial combustion sources include industrial boilers and process
heaters, total energy systems, incineration and other burning, metallurgical
processes, kilns for cement, limestone, and ceramics, and glass manufacture.
As can be seen by studying Table 3-4, many of the emission factors have been
further updated and more finely divided but the overall effect on total emis-
sion from industrial processes has not changed much from the Esso prediction.
Except for industrial package boilers, which contribute a significant percent-
age of NOV to this area source, very little testing has been done to date.
5
Again, the Aerospace study will provide additional estimates on NOX emissions
from these industrial area sources. Further testing of these area sources is
planned by the Combustion Research Section, Control System Laboratory of EPA.
Trends for the future include:
• Steady growth in the number of plants
• Perhaps some fuel switching to oil or coal depending on
- Environmental laws
- Price availability of fuel
• Higher preheat and O_ enrichment for energy efficiency.
3.3.5 Non-Combustion Sources
As has been mentioned in numerous references the primary noncombustion
source of NOV emissions is in the manufacture of nitric acid. Emission factors
A,
are now more detailed but the total emissions are approximately as predicted by
Esso.
Discussions with EPA personnel indicate that commercial and economical
control schemes have been developed (e.g., Union Carbide-Molecular Sieve scheme)
and could soon reduce the emission to 10 - 25 ppm from an uncontrolled value of
around 200 ppm.
3.4 NOX EMISSION TRENDS
The trend of NOY emission from stationary sources from 1950 to 1971 from
?
from AP-115 is illustrated in Figure 3-5. Also shown in Figure 3-5 is the
Esso predicted curve from 1950 to the year 2000. As can be seen on the curve
NOV levels have already reached the 1975 level predicted by Esso. The slight
A
downward trend in 1971 is due to revised emission factors and implementation
3-22
-------
AP-U5
mo i°ieo
YEAR
-2000
Figure 3-5. Stationary Source N(L Emission Trends
3-23
-------
of NO^ controls on the West Coast. If further controls are implemented both
on stationary and mobile sources the potential trend may be as illustrated
12
in Figure 3-6 . This figure shows the contribution for controlled and
uncontrolled emission of each fuel type for total NOV emissions. However,
A
Figure 3-6 does not reflect the impact of fuel switching. Additional studies
to predict trends which incorporate recent developments are necessary.
2000
Figure 3-6. Stationary And Mobile NOV Emission Trends
A
3.5 SUMMARY
Recent data have not substantially altered the NO contributions
X
reported by the Esso study. However, it must be remembered that a straight
ranking of amounts of emissions does not consider the importance of factors
such as altitudes, dispersion, climate, geographical location, etc. These
other factors are particularly important when considering I.C. engines. New
data brought out in this section include the following:
• NO., emissions from steam electric generating are higher than
predicted by the Esso report for 1970 - 1971.
• NOX emission quantities from I.C. engines and gas turbines is not well
defined, but may contribute 20-30 percent of the total.
• The effects of NO emission from I.C. engines on the overall
A
air quality is unknown.
3-24
-------
• Emission factors have been updated with recent data and are
now more detailed in all categories.
• Emission factors for oil fired residential heaters are 67
percent higher than reported by Esso.
• There is very little field data on industrial combustion sources.
• NOV controls have been incorporated on West Coast electrical
A
power plants.
Trends for the future include the following:
• There will be a significant increase in the utilization of coal
and oil in power generation, leading to an intensified NOX
problem which is impossible to quantify at this time.
• Industrial area sources may be switching to oil or coal if the
energy shortage continues, leading to an intensified NOX problem
which is impossible to quantify at this time.
• Home heating systems will become more efficient if the cost of
fuel rises and we may see a smaller increase in NOX emission as
a result.
• The degree to which NOV controls will be implemented in other areas
A
depends on local and federal regulations, such as the New Source
Performance Standards (NSPS), amount of fuel switching and further
developments for oil and coal.
Recommendations for future work to more clearly define the status of emissions
include:
• Those sources which seem to be missing from AP-42 should be in-
vestigated to determine if they appear in some other category.
• A better assessment of the relative importance of each source should
be made.
• Additional field data is necessary for industrial combustion sources,
I.C. engines and gas turbines.
• A study is necessary to determine a reasonable implementation plan
for NOV controls on stationary sources and to determine the impact
A
on NO., emissions.
3-25
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SECTION 4
SURVEY OF OPTIONS FOR N0x CONTROL
The preceding section surveyed NO emission sources with a view toward
X
identifying changes since the publication of the Esso report which would alter
the focus of control program planning. This section gives a corresponding sur-
vey of candidate NO control techniques as applicable to the sources character-
X
ized in Section 3. The objective here is to identify the attractive short and
long-term options for NO control through evaluation of developments and user
X
experiences subsequent to the Esso study.
Short term options for NO control necessarily involve retrofit modifi-
X
cations of existing units. Following the Esso study, there has been extensive
testing and application of retrofit concepts. Long-range options include in-
corporation of unit modifications into optimized design for new units as well
as use of alternate processes. The selection of alternate processes is usually
motivated by process economics for which pollution control devices are an im-
portant tradeoff. Increasing recognition of projected gas and oil fuel short-
ages, subsequent to the Esso study, has given impetus to the design and evalu-
ation of alternate processes, particularly for power generation.
The criteria for evaluation of short and long-range options include:
• Cost effectiveness
• Availability (short term options)
• Low-risk development (long-range options)
• Impact on unit efficiency
• Impact on operational difficulties
• Overall environmental impact due to process control
• Compatibility with projected fuel allocations
Options for NO control from combustion sources are evaluated in Section 4.1;
non-combustion sources are treated in Section 4.2.
4-1
-------
4.1 COMBUSTION SOURCES
Combustion generated NO results from the thermal fixation of atmospheric
X
nitrogen in the combustion air, or from conversion of bound nitrogen in the fuel.
Thermal N0x can be formed in the oxidation of virtually any fuel in the presence
of air, while fuel NO results primarily with firing of coal and the heavier
residual and crude oils. From a systems standpoint, the control of NO emissions
X
can be approached by four strategies:
• Modification of operating conditions in existing units to alleviate
conditions favorable to NO formation;
• Modification of fuel by denitrification, use of additives, or sub-
stitution with a low NO forming fuel;
• Treatment of flue or exhaust gas for NO removal;
• Use of alternate low NO processes in new units.
Control techniques in these categories are reviewed below.
4.1.1 Modification of Existing Units
The Esso report concluded, on the basis of the limited data available,
that retrofit modification of existing units was the most promising approach
to the reduction of NO emissions. In the intervening period, the feasibility
X
and some limitations of this strategy have been demonstrated, particularly for
utility boilers. Evaluations of the combustion modification strategy are given
below for boilers, stationary engines, and other combustion sources.
4.1.1.1 Utility and Industrial Boilers
Utility boilers are the largest single stationary source of NO emissions
and are also "point sources" in the sense of having a very high ratio of total
emissions to the number of units. These units have accordingly been the most
extensively modified as part of the N0x control program. Industrial boilers
are usually regarded as an "area source," with a low ratio of emissions to num-
ber of units, and have been accorded a lower priority in the NO control program.
X
The technology for modification of these units is currently under development
utilizing, where possible, experience derived from the modification of utility
boilers.
The most significant achievement in NO control has been with gas fired
units. Typically, reductions from uncontrolled levels of 400-1000 ppm to a con-
trolled level on the order of 200 ppm have been attained through reduction of
the peak flame temperature and through creation of fuel-rich conditions in the
4-2
-------
primary flame zone. The cost-effective techniques favored to produce these
changes in operational conditions are off-stoichiometric combustion by biased
burner firing, reduction of excess air, and, less frequently, recirculation of
flue gas into the primary combustion air. Figure 4-1 shows results from the
modification of a 750 MW horizontally-opposed, face-fired unit .
two 1000
V"
700 *l»
Since the Esso
study, the validity of combustion modifications for N0x reduction in oil-fired
units has been demonstrated. Operational guidelines for coal-fired units are
currently being formulated through field testing. In general, tests indicate
that emission reductions for oil and coal-fired units are less than for gas-
fired units with comparable combustion modification. The most effective
scheme is a combination of low excess air and off-stoichiometric firing. In-
dications are that the effectiveness of flue gas recirculation decreases as
the quantity of bound nitrogen in the fuel increases.
Figure 4-lb shows typical reductions from modification with oil firing
for the same unit as the gas fired results in Figure 4-la. Although the modi-
fications yielded significant emission reduction, the percent reduction with
each modification is less with oil than with gas. The minimum emission level
4-3
-------
achieved through the combined modifications was higher for oil than for gas.
For the firing of coal, the minimum emission level demonstrated through combus-
tion modification is higher than for either oil or gas. This pattern has signi-
ficant impact in view of the increasing conversion of utility boilers to coal
firing.
Although combustion modifications remain as the most attractive option
for reduction of uncontrolled emissions, there are limitations to the effec-
tiveness of this strategy for attaining very low emission levels. Limitations
arise through operational difficulties such as burner instability or corrosion,
emission of other pollutants such as smoke or CO, or a reduction in thermal
efficiency. For this situation, the diminishing returns from further applica-
tion of combustion modification would eventually justify, on a cost effective-
ness basis, use of alternate techniques, such as flue gas treatment, for a
backup control technique. Most modifications to date have been done without
optimizing burners for combustion modifications. Improved burner designs com-
bined with other modification techniques should show significant effects. Fur-
ther results and evaluations for the combustion modification strategy are given
in Section 5.
4.1.1.2 Gas Turbine and Reciprocating Engines
The NO control technology for stationary I.e. engines and gas turbines
X
has developed from the automotive industry and aircraft industry respectively.
Each of these sources will be discussed separately.
Reciprocating I.e. Engines
Equipment modification control techniques for existing units include the
following:
• Modification of operating conditions
Speed
Torque/Load
Ignition timing
Fuel injection timing
Air temperature
Air pressure
Exhaust back pressure
• Exhaust gas recirculation
• Water injection
4-4
-------
• Valve timing
• Compression ratio
All of the operating conditions can be changed in a direction to decrease
NO emission. The modifications mechanism in reducing NO is in general to
X X
lower the flame temperature, decrease the availability of oxygen or to shorten
the equivalent residence time. The general effect of these changes when moving
to lower NO is to increase fuel consumption, increase emission of CO,H/C or
X
smoke or to reduce performance. The relationship between each of these opera-
ting parameters will be discussed in Section 5. Exhaust gas recirculation and
water injection have also been shown to be an effective method of NO reduction
X
in I.C. engines. Side effects include increased fuel consumption and possibly
less engine reliability and life. Increased valve overlap has similar effects
as E.G.R. and could be implemented by simply changing the camshaft. Consider-
able data has been developed in each of these areas since the Esso study and
will be reported in Section 5. At this time the most viable technique in the
short term for both diesel and spark ignition gas engines is water injection.
Gas Turbines
Potential equipment modification control schemes include the following:
• Minor combustor can modification
• Reduced turbine inlet temperature by reducing power
• Exhaust gas recirculation
• Water injection
Although considerable data has been developed in the last few years for
each of these schemes no single method has been ruled out or achieved the de-
sired reduction. All are still undergoing investigation. In the short term
some electric utilities are trying water injection but feel the ultimate solu-
tion will be through new combustor can development which will provide a replace-
ment can. Recent developments will be discussed in Section 5.
4.1.1.3 Other Combustion Sources
Other combustor sources for NO include the following industrial sources.
• Metallurgical furnaces
• Cement, lime and ceramic kiln
• Glass manufacture
• Incineration and waste disposal
• Residential and commercial space heating
4-5
-------
No specific NO control technology was found in the recent literature
x 10
for any of these areas. The Battelle study surveyed emission from space
heaters and showed the effect of excess air on NO emissions and other pollu-
Jk
tants for 33 existing oil-fired units (decreasing excess air lowers NO emis-
14
sions). Data reported in a paper by Howekamp showed similar results for
five "combustion improving" oil-fired burner heads for use in residential heat-
ers. The Howekamp data showed a peak NO emission at a stoichiometric air-fuel
X
ratio around 1.6 and decreasing on either side of this point. None of these
devices substantially changed N0x emissions. Rocketdyne , currently under
contract with EPA to develop an "optimum" home heater size burner, have devel-
oped a low excess air burner with 30 percent to 50 percent reduction in NOX .
This design is currently undergoing long term cyclic testing. Aerospace Cor-
poration15 under EPA contract is currently working on technology assessment of
the other combustion sources but no data have been reported. This will be
followed by a field study to better determine the emission factors and current
range of control. Thus, the general discussion presented in the Esso report
for NO control for each of these sources is still valid.
4.1.2 Fuel Modification
Fuel Switching
For a NO control strategy, natural gas firing is attractive because, as
X
discussed in Section 4.1.1.1, the effectiveness of combustion modification is
better than for oil or coal firing, particularly with high levels of fuel
nitrogen, and the optimum emission level is thought to be lowest for gas. De-
spite the superior cost effectiveness of NO control in gas-firing, the econo-
mic considerations in fuel selection are currently dominated by the petroleum
supply deficiency, and the trend, as stated in Section 3, is toward coal-fired
units. On a short-term basis, fuel switching to natural gas or low nitrogen
oil is not a promising option.
A promising long range option is the use of clean synthetic fuels derived
from coal16'17. Candidate fuels include low Btu gas (100-300 Btu/scf), interme-
diate Btu gas (300-500 Btu/scf) and synthetic oil. Process and economic evalu-
ations for the use of these fuels in power generation are being made by the EPA,
The Office of Coal Research, The Bureau of Mines, and the Electric Power Research
Institute. Two options considered likely are firing of low-Btu gas in a conven-
tional boiler, and the use of low Btu gas in a combined gas and steam turbine
power generation cycle. For both systems, economics favor placement of both the
gasifier and power generation cycle at the minehead, so the most extensive use of
these options would be for new units to replace fossil fuel units starting around
1980.
4-6
-------
The NO emissions from low Btu gas-fired units are expected to be low
X
due to reduced flame temperatures characteristic of the lower heating value
fuels. The effects on NO emission of the molecular nitrogen and the inter-
X
mediate fuel nitrogen compounds, such as ammonia, in the low Btu gas have not
been determined and require study.
As a NO control strategy, the use of synthetic fuels is promising in
X
the long term but will not remove the burden from combustion modifications in
the short term.
Fuel Additives
In principle, use of fuel additives could reduce NO emissions through
X
one or a
1 R 1 Q 7(1
combination of the following effects '':
• Reduction of flame temperature through increased thermal radiation
or dilution
• Catalytic reduction or decomposition of NO to N-
• Reduction of local concentrations of atomic oxygen
Martin et al. tested 206 fuel additives in an oil-fired experimental
18 19
furnace , and four additives in an oil-fired package boiler . None of
the additives tested reduced NO emissions but some additives containing
nitrogen increased NO formation.
Shaw tested seventy additives in a gas turbine combustor and found
that only metallic compounds promoting the catalytic decompostion of NO to
N_ had a significant effect on NO emissions. From 15 percent - 30 percent
reductions in NO were achieved with addition of 0.5 percent by weight of
X
iron, cobalt, manganese, and copper compounds. The use of this technique
for NO control is not attractive, however, due to increased cost, serious
operational difficulties, and the presence of the additives, as a pollutant,
in the exhaust gas.
An indirect reduction of NOX could result from use of additive metals
21 22
intended to prevent boiler tube fouling ' . The excess air level in oil-
fired boilers is frequently set sufficiently high to prevent tube fouling.
Use of additives could allow use of a lower level of excess air which in turn
would reduce NO emissions. The emission reduction from this strategy is quite
X
limited and the cost effectiveness is likely to be poor.
Fuel Denitrification
For firing of heavy oils and coal, N0x emission reduction could be
achieved through removal of the chemically bound nitrogen from the fuel. No
4-7
-------
effective denitrification process has been demonstrated and progress is hindered
somewhat by uncertainty as to the types of compounds comprising the fuel nitro-
gen. There is some speculation that the desulfurization treatment has a side
benefit of reducing fuel nitrogen, but this has not been verified.
In view of the attractive cost effectiveness of combustion modification,
and the projected conversion to clean synthetic fuels, denitrification does not
appear to be a promising long range options for N0x control.
4.1.3 Alternate Processes for New Units
For new units, the combustion control technology derived from retrofit
of existing units can be incorporated, together with new concepts not applica-
ble for retrofit, into designs optimized for N0x control. The flexibility of
this approach yields potentially lower costs and higher effectiveness relative
to the retrofit of existing units. Alternatively, the economic factors involved
in projected fuel conversions and emission control for use of high sulfur fuels
may dictate selection of an alternate combustion process.
4.1.3.1 Utility and Industrial Boilers
Optimized Design
Retrofit concepts applicable to new design include: optimized burner
placement and biasing for off-stoichiometric combustion, flue gas recirculation,
and overfire air ports for two-stage combustion. New design concepts include
optimized burner design, particularly for suppression of fuel N0x, and larger
furnace volume. Ideally, the combustion chamber design should be tailored to
the flame shape found from burner optimization studies to yield the lowest N0x
emission. One design which approaches this concept is the tangentially fired
boiler. The low heat release rate and slow mixing of oxygen with the fuel in
tangential firing yields relatively low rates of formation of both thermal NOX
and fuel NOX-
With implementation of the above techniques, boiler manufacturers have
been able to meet the EPA New Source Performance Standards (NSPS):
Coal 0.7 Ib N02/106Btu
Oil 0.3 Ib N02/106Btu
Gas 0.2 Ib N02/106Btu
For units going into service beyond 1980, this approach to N0x control may be
replaced by use of alternate processes, discussed below.
4-8
-------
Alternate Processes
In the period beyond the year 2000 it is projected that the U. S. energy
requirements will largely be met by a combination of fission and fusion reactors
and solar energy conversion supplemented by fossil fuels, MHD, and geothermal
power . In the interim, fossil fuels will remain the major energy source
with increasing use being made of low-grade high-sulfur coals. Two promising
concepts for the use of these coals in the clean and efficient production
of energy are use of synthetic fuels derived from coal, discussed in Section
4.1.2, and fluidized bed combustion.
Suggested advantages of fluidized bed combustion compared to conventional
, ., 24,25,26
boilers are :
• Compact size yielding low capital cost, modular construction, fac-
tory assembly, and low heat transfer area
• Higher thermal efficiency yielding lower thermal pollution
• Lower combustion temperature (1400°F-1800°F) yielding less fouling
and corrosion
• Applicable to a wide range of low-grade fuels including char from
synthetic fuels processes
• Adaptable to a high efficiency gas-steam turbine combined power
generation cycle
The feasibility of the FBC for power generation depends in part on the follow-
ing: development of efficient methods for regeneration and recycle of the
dolomite/limestone materials used for sulfur absorption and removal; obtaining
complete combustion through flyash recycle or an effective carbon burnup cell;
development of a hot-gas particulate removal process to permit use of the com-
bustion products in a combined-cycle gas turbine without excessive blade erosion.
The potential for reduced NO emissions with fluidized bed combustion is
currently under investigation in several EPA funded projects. Preliminary tests
04 25
with pilot scale units ' indicated that emission levels well within the EPA
standard of 0.7 Ib N02/106Btu for a new coal-fired units can be achieved. At
the operational temperatures of the fluidized bed, the rate of formation of
thermal NO is very low and nearly all NO emitted results from conversion of
fuel nitrogen. The fuel nitrogen content in the coals used in the pilot tests
was not given, so these results cannot be generalized.
Several of the pilot scale units have been tested for the effects of
26
operational variables on NO emissions. BCURA has reported preliminary
evidence that their pressurized fluidized bed yields lower emissions
4-9
-------
than their atmospheric unit. The bed temperature has little effect on NO
emissions in the range from 1400°F-1800°F, but operation with excess air in-
25 27
creases NO significantly. Argonne , and Esso , have suggested that opera-
tion with two-stage combustion may be effective for NO control in the firing
of high nitrogen content coals. Esso suggests that two-stage combustion
could have the additional advantage of increasing the efficiency of the sulfur
removal process.
From a NO control standpoint fluidized bed combustion is regarded as
X
medium risk concept because the economic feasibility of the basic process as
well as NO control techniques has not been fully estal
X
ventional boilers or low Btu gas combined-cycle units.
well as NO control techniques has not been fully established relative to con-
X
4.1.3.2 Gas Turbines and Reciprocating Engines
Control methods for new reciprocating I.C. engines and gas turbines in-
clude all of those techniques mentioned for retrofit (Section 4.1.1.2) plus
those listed below.
I.C. Reciprocating Turbines
Precombustion Chamber Reduce Turbine Inlet Temperature
Prevaporize Fuel
Major Combustor Can Modification
There has been work in each of these areas which will be discussed in Section
5.4.2.2.
4.1.3.3 Other Combustion Sources
Other than the development of an optimum burner by Rocketdyne for home
heating application, no new information was available on alternate processes
for these other combustion sources for NO control.
4.1.4 Flue and Exhaust Gas Treatment
Esso reported in the 1969 report that of the various flue gas treatment
schemes the aqueous scrubbing systems using alkaline solutions held the most
28
promise. In a subsequent study by Chappel at Esso under EPA sponsorship
a number of aqueous solutions were investigated. The following conclusions
are quoted from the Chappel report:
• The addition of N02 to flue gas to improve N0x (mostly NO) absorption
does not appear promising.
4-10
-------
• Sulfite solutions and slurries are efficient N0--S02 absorbents.
Soluble sulfites (Na-SO-) are better NO absorbers than insoluble
slurries (CaSOJ .
• Calcium, magnesium and zinc hydroxide slurries are effective NO--SO-
absorbers.
• Limestone (CaCO,) is also a good N0--S02 absorbent.
• Sulfide solution are excellent N02-S02 absorbers but do generate
a small amount of NO.
• Part of the absorbed SO- is oxidized to sulfate.
• Combined NO -SO. scrubbing seems feasible using any of several
hydroxide or carbonate systems provided NO (NO) can be effectively
X
oxidized by NO- upstream from the scrubbing unit.
The following recommendations were made for areas of future work.
"Pilot plant studies are needed to scale up the bench scale work devel-
oped in this study. The following critical factors need to be defined under
process conditions:
• Rates of NO- absorbtion by different aqueous solutions under pro-
cess conditions.
• Effect of scrubber design on absorbtion.
• Requirements for anti-oxidants must be assessed.
• The product distribution for the absorbed NO must be measured.
• Study of spent solution regeneration.
• Methods of optimizing NO to NO- oxidation by catalyst or ozone."
Although an exhaustive study was not made due to time limitations, to
our knowledge there is still currently no established gas treating processes
for NO control, especially for control of NO emissions from power plants.
X X
Reference is made to a new process developed by the Krebs Company in Section
4.2, Non-Combustion Sources, which is reported to be applicable to combustion
sources in a combined SO--NO scrubbing scheme. However, to date it has not
ft X
been applied to a full scale power plant. It is the general belief by most
researchers that the primary control of NO emission will be through combustion
modification and at some future time flue gas treatment schemes may be utilized
to perform
ppm level.
to perform a secondary control, say to achieve 10-20 ppm of NO from a 60-100
4-11
-------
4.2 NON-COMBUSTION SOURCES
Non-combustion sources include the following:
• Nitric Acid Plants
» Amonium Nitrate Manufacture
• Organic Oxidations
• Organic Nitrations
• Explosives
• Phosphate Rock Acidulation
• Metals treatment and etching
Nitric acid plants are the largest source of NO from these industries,
X
although the other sources often produce intense local concentrations of NO ,
X
typically as a brown NO- plume. However, due to the relatively small contri-
bution of these sources and the limited scope of this study, the control meth-
ods for these sources were not thoroughly investigated. It is our opinion
that either scrubbing for NO- or process changes have been made on many of the
sources to meet local ordinances for visible plumes. The reader is referred
to References 29-32 for details on a number of processes. Reference 19 pro-
vides descriptive information on hundreds of U.S. patents since 1950 for flue
gas treatment. The following areas are covered:
• Catalytic conversion of industrial stack gases
• Absorptive techniques for removing nitrogen oxides from gases
• Liquid scrub processes for removal of nitrogen oxides
• Combustion techniques for eliminating oxides in gas stream
In addition, a recent development by the Krebs Company is reported to
achieve flyash, SO- scrubbing and NO scrubbing in a single apparatus. The
system utilizes an aqueous solution of NaOH in conjunction with high efficiency,
high surface area scrubbers, and a proprietary catalyst for NO, N02 conversion
to N-. It is reported applicable to any size source from metal etching plants
to utility boiler and has achieved efficiencies of 99.5 percent for flyash, 93
percent SO- and 35-70 percent for NO . NO and NO, are converted to N- and N-O
& OO A £ & &
in the process
For existing nitric acid plants there are basically two methods that are
being utilized as retrofit schemes, catalytic combustion and molecular sieve
adsorption :
4-12
-------
Catalytic Combustion
This process involves the reaction of methane or hydrogen-rich fuel by
N02 or NO and 02 over a catalyst to produce C02, H20 and N2. The oxygen content
of the tail gas is an important factor in determining the flow scheme of the
catalytic combustion system, since the maximum oxygen removal per stage is
approximately 3 percent. Therefore; above 3 percent oxygen either a two stage
system is used or one stage with recycle. Most plants use a single stage
unit and achieve only decoloration of the NO- to NO. By using additional
stages, fuel, and catalyst all the NO can be abated but it is usually con-
34
sidered too costly. Several catalytic schemes are shown in Figure 4-2 .
Molecular Sieve Adsorption
Union Carbide is currently working on a commercial molecular sieve ad-
sorption scheme for NO removal from nitric acid plant tail gases. Concentra-
X
tion of less than 10 ppm are achievable. Figure 4-3 shows a typical schematic
of the system. Two parallel streams are run to enable continuous operation
while one stream is being regenerated. During- the adsorption cycle the nitric
oxide is catalytically converted to nitrogen dioxide, the tail gas water vapor
is adsorbed and the total NO is adsorbed as NO-. During regeneration the
nitrogen dioxide is recycled to the nitric acid absorption equipment. Proponents
for the molecular sieve scheme claim compliance with projected EPA regula-
tions. It may also be more attractive due to less fuel consumption.
Table 4-1 presents some typical costs for the two schemes based on a TVA
34
nitric acid plant . Union Carbide reports costs for their scheme of approxi-
mately $1.50/ton of HNO- for a 300 ton/day plant. These costs are changing
rapidly due to increased cost of stainless steel.
4.3 SUMMARY
A summary evaluation of NO control options is given in Table 4-2. For
the control of existing combustion sources, combustion modification has remained,
since the Esso study, as the quickest, most reliable and cost effective technique.
For non-combustion sources, flue gas treatment is preferred.
For long term NO control, the incorporation of combustion modifications
X
into new unit design appears to be the single most effective strategy for
stationary sources. Large electric power generation units will undoubtedly
benefit from developments in the use of synthetic fuels and fluidized bed com-
bustion in conjunction with combined power cycles. Even these advanced concepts,
however, may require combustion modification for NO control. The bulk of sta-
X
tionary sources — area sources such as pipeline I.C. engines, industrial
4-13
-------
FUEL
STEAM
HEAT HEAT
ABSORPTION EXCHANGE EXCHANGE COMBUSTION
(EXISTING) (EXISTING)
ONE-STAGE (02<3%)
STEAM
GENERATION
POWER
RECOVERY
(EXISTING)
STEAM FUEL
STEAM
STEAM
COMBUSTION GENERATION
HEAT STEAM
ABSORPTION EXCHANGE GENERATION
(EXISTING) (EXISTING)
ONE-STAGE RECYCLE (Og >3%)
POWER
RECOVERY
(EXISTING)
STEAM
FUEL STEAM
HEAT STEAM
ABSORPTION EXCHANGE GENERATION
(EXISTING)
STEAM
COMBUSTION GENERATION COMBUSTION
TWO-STAGE (02 >3%)
STEAM
GENERATION
POWER
Figure 4-2. Catalytic Combustion Systems
-------
i
M
Ul
TAIL GAS
CONTAINING NOX
r
HOT GAS
CONTAINING
OESORBED N02 *
CLEAN DRY
TAIL GAS'
NO OXIDATION TO N02
a
N02AND H20 ADSORPTION
HEAT
EXCHANGE
(EXISTING)
POWER
RECOVERY
(EXISTING)
_J
HOT GAS
ABSORPTION
(EXISTING)
REGENERATION
Figure 4-3. Molecular Sieve System
-------
TABLE 4-1
COST FOR NOX ABATEMENT FACILITIES
FOR THE NO. 3 NITRIC ACID UNIT AT TVA
Approximate Investment Cost, $
Depreciation Cost (10 yr.),
$/Ton HN03
Approximate Operating Costs,
$/Ton HN03
Natural Gas
Electricity
Steam
Cooling Water
Reduction Catalyst
Molecular Sieve
Operation, Overhead, and
Maintenance
Byproduct Credits
Steam
Nitric Acid
Total Operating Cost
Total Estimated Cost for NOU
h
Abatement, $/Ton HN03
Catalytic
Combustion
Using Natural Gas
290,000
0.53
1.48
--
—
~
0.10
—
1.00
-2.04
__
0.54
1.07
Molecular
Sieve
Adsorption
675,000
1.24
0.07
0.11
0.06
0.04
--
0.26
1.00
—
-0.25
1.29
2.53
aData are for two-stage or partial recycle-type combustion process.
bTotal cost for NOX abatement is the sum of the project cost with 10 year
depreciation and the operating costs.
4-16
-------
TABLE 4-2
SUMMARY OF NOX CONTROL OPTIONS
Option
Combustion
Modification
Synthetic
Fuels
Fuel
Additives
Fluidized
Bed
Boiler
Flue or
Exhaust Gas
Treatment
Approach to NO Control
Suppress formation of
thermal, fuel Nox by
modifying operating
conditions
Reduced flame
temperatures from
low Btu gas yields
reduced NOX
Reduce or decompose
NO to Ng by
catalytic addition
Low bed temperature
suppresses thermal
NOX
Reduce NO to N?
by catalytic
treatment, or absorp-
tion of MO or N02.
Effectiveness
Short Term
Present
applicability;
preferred
option
Negligible
application
Not
effective
N.A.
Preferred for
nitric acid
plants
Long Term
Incorporate into
optimized low
NOX design
Promising low
risk concept for
post-1980
High risk
development
Medium risk
concept for
post-1980
Possible for
control of
I.C. Engines
Overall Evaluation
Priority option for short
and long term control of
boilers, furnaces, turbines
Attractive long term option;
May require combustion modifications
Not promising
Promising long term option;
May require combustion modifications
Potential long-term option for backup
of combustion modification for
boilers, furnaces. Possible long-
term option for I.C. Engines. Priority
option for nitric acid plants.
-------
combustion, and domestic heaters — will increasingly utilize combustion modifi-
cations for NO control in new equipment design.
A
Combustion modifications are clearly the priority item in program plan-
ing for NO control of stationary sources. In order to indicate requirements
X
for effective utilization of combustion modifications, the next section char-
acterizes the current status of combustion control in the light of developments
since the Esso study.
4-18
-------
SECTION 5
COMBUSTION MODIFICATION TECHNOLOGY FOR NOX CONTROL
The Esso systems survey detailed an R&D plan for which the priority
category was the development of combustion modification technology. The
recommendations focused on pilot scale and full scale testing of combustion
modification techniques with support from fundamental studies on the combustion
process and NOV formation mechanism. Subsequently the EPA has organized a
A.
Combustion Control Program to develop and coordinate R&D for NOX control; the
Esso recommendations have largely been treated as part of the operation of
this program. In this chapter, a review is made of the achievements, current
status, and prospects for combustion control technology. The objective is to
specify areas of development required for program planning. Specific R&D
recommendations follow in Section 6.
The basic objective of combustion modification technology is to discover
and apply techniques which alleviate NOX formation. A review of known factors
involved in the problem of thermal and fuel NOX formation is given in Section
5.1. A combustion control program directed at confronting the problem is
described in Section 5.2. The status and limitations are given in 5.3 for
fundamental studies, and in 5.4 for pilot and full scale testing. Representative
cost data for combustion modifications are given at the end of 5.4.
5.1 COMBUSTION GENERATED NOV
A
Oxides of nitrogen formed in combustion processes are usually due either
to thermal fixation of atmospheric nitrogen in the combustion air, leading to
thermal NOV, or to the conversion of chemically bound nitrogen in the fuel,
A
leading to fuel NOV. Any coupling between these two mechanisms is thought to
A
be minor so that total NOV emissions are essentially the sum of thermal and
A
fuel NO... For natural gas and light distillate oil firing, all NOX is formed
via atmospheric fixation. With residual, or crude oil, and coal, the
contribution from fuel bound nitrogen can be significant and, under certain
operating conditions, predominant.
5-1
-------
A third potential mechanism of NO., formation arises in processes such
as glass manufacturing, where the raw materials in contact with the combustion
products contain nitrogen compounds. Little is known about the extent of
conversion to NOV of the nitrogen compounds, or of the effects of combustion
A
modifications on this mechanism.
5.1.1 Thermal NOX
The detailed chemical mechanism by which molecular nitrogen in the
combustion air is converted to nitric oxide is not fully understood. In
practical combustion equipment, particularly for liquid or solid fuels, the
kinetics of the N2~°2 system are coupled to the kinetics of hydrocarbon
oxidation and both are influenced, if not dominated, by effects of turbulent
mixing in the flame zone. It is, however, generally accepted that the most
significant reactions in the formation of thermal NOV are those of the Zeldovich
A
chain mechanism:
02 + M ^0 + 0 + M , (5-1)
N2 + 0 £?NO + N , (5-2)
02 + N^?NO + 0 , (5-3)
for which reaction (5-2) is the rate controlling mechanism. "M" is a third
body, normally taken as N2- Additional mechanisms are reviewed in Section
5.3.2.
Due principally to the high energy required to break the N- bond in
(5-2), the activation energy for NO formation via the Zeldovich mechanism
is considerably larger than for typical rate-controlling reactions in hydro-
carbon oxidation. This entails that NO formation is initiated well after
initiation of fuel combustion and is extremely temperature sensitive with
virtually all NO being formed in the high temperature regions of the flame.
For the time scales involved in the flow through commercial combustors, the
high temperature dependence of the NO system means that total NO emissions are
far below equilibrium levels. NO formation is thus kinetically controlled with
the emission level dependent on time of exposure to the high temperature.
Figure 5-1 illustrates the temperature and time dependencies of NO
formation for an idealized one-dimensional premixed system of methane and
air . The results at 0.01 sec for three values of stoichiometric ratio (S.R.)
5-2
-------
KINETIC FORMATION
OF NITRIC OXIDE
6000
1000
i
a.
100
SR-OSO
STOICHIOUCTRIG
10
2800 300O 320O 3400 3600 3800 4000
TEMPERATURE «F
Figure 5-1. Kinetic Formation Of Nitric Oxide
5-3
-------
show, as expected, that NO formation is suppressed by reduced availability of
oxygen. In a practical combustor, departure from S.R. = 1 would result in
reduced temperatures which would further suppress NO formation. It is pre-
cisely these factors of high sensitivity to temperature, concentration level,
and time of exposure which makes the formation of thermal NO., susceptible to
the combustion modification strategy.
Ideally, the formation of thermal NO could be reduced by four tactics:
A
• Reduce nitrogen level at peak temperature
• Reduce oxygen level at peak temperature
• Reduce peak temperature
• Reduce time of exposure at peak temperature.
Esso showed that reduced nitrogen level is impractical so the strategy has
focused on the fundamental parameters of oxygen level, peak temperature, and
time of exposure. These parameters are in turn dependent on secondary com-
bustion variables such as combustion intensity and internal mixing in the
flame zone - effects which are ultimately determined by primary equipment and
fuel parameters over which the combustion engineer has some control. A
hierarchy of effects leading to thermal NO., formation is depicted on Table 5-1.
TABLE 5-1
FACTORS CONTROLLING THE FORMATION OF THERMAL NOV
Primary Equipment
and Fuel Parameters
Inlet temperature,
velocity
Firebox design
Fuel composition
Injection pattern
of fuel & air
Size of droplets
or particles
Burner swirl
External mass
addition
Secondary
Combustion Parameters
Combustion intensity
Heat removal rate
Mixing of combustion
products into
flame
Local fuel-air ratio
Turbulent distortion
of flame zone
Fundamental
Parameters
Oxygen level
Peak temp.
Exposure time
at peak
temp.
Thermal
NO,,
Although causal relationships between the four categories shown in Table 5-1
are not firmly established, combustion modification technology is, nevertheless,
confronted with the task of reducing thermal NOX through modification of equip-
ment and fuel parameters. This task has been approached with efforts ranging
from the short-term testing of equipment modifications on commercial units, in
5-4
-------
order to determine the effects on NOX emission, to long-term fundamental
studies and pilot testing directed at achieving a basic understanding of NOX
formation. The Combustion Control Program devised to coordinate these efforts
is described in Section 5.2.
5.1.2 Fuel NOX
Since the Esso study, there has been increasing recognition of the
role of fuel bound nitrogen in NO., emissions. With increasing utilization of
coal, particularly high nitrogen coal, fuel NOX control has become a priority
item in combustion modification technology.
When a droplet or particle of fuel is injected through a flame, some,
and possibly most, of the fuel nitrogen compounds go towards the formation of
intermediate nitrogen compounds, such as HCN or NH3, in the gas phase volatil-
ization products. The remainder of the nitrogen stays in the char or soot
and may be converted during carbon burnout. A number of fuel bound nitrogen
compounds have been identified, '37 but the degree of conversion to NO does
36 37 38
not appear to be strongly dependent on the type of compound ' ' . The
percent of fuel nitrogen which gets converted to NO is strongly dependent on
the combustion conditions, but generally decreases as the percentage of nit-
rogen in the fuel is increased.
In contrast to thermal NOX, fuel nitrogen conversion is generally
regarded as being relatively insensitive to temperature. This may be due to
the relatively low energies involved in the formation of the intermediate
compounds from the fuel bound compounds. The most critical factor in fuel
NOV conversion appears to be the local conditions in which volatilization and
A
formation of intermediate compounds occurs. In a reducing atmosphere, it is
suspected that the intermediate compounds go to form N_ or other compounds
with little subsequent conversion to NO. In an oxidizing atmosphere, conver-
sion of the intermediates to NO is thermodynamically favored over conversion
to N_. Although basic understanding of these phenomena is only in the pre-
liminary stage, a promising strategy for fuel NO., reduction appears to be
modification of the burner or combustion conditions to allow volatilization
to occur prior to massive entrainment of oxygen in the flame zone.
The fate of fuel-bound nitrogen which does not go to NO is uncertain.
There are indications that other pollutants, such as HCN, may result when NO
formation is suppressed '. This possibility may, indeed, constitute a
limitation to fuel NOV reduction strategies and requires investigation.
A
5-5
-------
5.2 SYSTEMS PROGRAM FOR COMBUSTION MODIFICATIONS
A combustion modification program to attack the problem of NOX
formation must satisfy both the short term requirement for immediate
application of combustion modification to existing units, and the long term
requirement for generation of optimized low NOX design concepts for new units.
These requirements must be met in the face of difficulties such as: uncer-
tainties in NOV formation mechanisms; lack of causal relation between equip-
A
ment parameters and the formative mechanisms; lack of reliable laws for scaling
pilot scale data to full scale units; prohibitive time and cost of exhaustive
full scale testing. In view of these factors, the EPA, based partly on the
Esso recommendations, has formulated an R&D program involving fundamental
studies, pilot scale testing and full scale testing. The program is
organized into four component areas:
Fundamental Studies
Fuels R&D
Process R&D
Field Testing and Survey
Fundamental Studies involves bench scale experimentation as well as
analytical modeling to attain a better understanding of the physical and
chemical phenomena in combustion and NOX formation. This understanding
provides a rational basis on which to evaluate data and trends from pilot and
full scale testing. Fundamental studies also contribute to the generation of
basic ideas for potential combustion modifications and aid in the application
and optimization of combined modifications. Finally, the basic understanding
of the combustion process can be useful in combating operational difficulties
resulting from modifications and hence extends the effectiveness of the
modification strategy.
Fuels R&D involves the generalized testing of combustion modifications
on non-commercial, versatile, laboratory test equipment. Its presence in the
R&D program is necessitated by the prohibitive cost of diversified testing of
full scale units. Fuels R&D functions as a screening of candidate modification
techniques in order to evaluate and optimize generalized procedures and detect
limitations or operational difficulties. Fuels R&D occupies a middle position
between the basic chemical and physical focus of fundamental studies and the
hardware focus of process R&D and field testing.
5-6
-------
Process R&D involves demonstration testing of modification techniques
on units with hardware which is characteristic of commercial systems. It
functions in the development of operational guidelines for implementation
of combustion modifications in commercial equipment/ and serves to detect and
solve operational difficulties.
Field Testing and Survey involves the continuing definition and
application of state-of-the-art technology for full-scale commercial equipment.
The results from this effort go directly to industrial application for control-
led emissions.
The functioning and interrelationships of the component areas of the
modification program are depicted schematically in Figure 5-2. Field testing
and survey is the central short-term focus of the program and operates
parallel to the supporting areas of fundamental studies, fuels R&D, and pro-
cess R&D. Field testing benefits from information generated in the supporting
areas and provides input to these areas in the form of test data and infor-
mation on operational difficulties, limitations, and cost effectiveness.
Thus, the directional requirements of R&D in the four component areas are
continually redefined in view of results from the other areas. This yields
a flexible base on which to respond to changing requirements in short and long
term objectives.
5.3 APPLICATION OF FUNDAMENTAL STUDIES
Since the Esso study, the most significant developments impacting the
fundamental studies area are the increasing importance of the fuel NOY prob-
A
lent, and the increasing use of computerized analysis of basic physical and
chemical phenomena. These developments have broadened the scope of funda-
mental studies and have somewhat reoriented the strategy used for support of
short- and long-term requirements. This section characterizes the application
to combustion modification technology of fundamental studies in order to give
directional requirements for R&D planning.
Fundamental studies involves experimentation and analysis aimed at
understanding the NO formation process. The incorporation of these elements
A
into a simulation of the actual combustion process is termed modeling. The
scope of modeling extends from simple scaling relations for extrapolating
pilot scale tests, to a mathematical simulation of complex phenomena such as
hydrocarbon oxidation or fuel nitrogen conversion. Models are the long-term
end product of fundamental studies in the sense that they represent the best
available rationalization derived from analysis and experimentation.
5-7
-------
_J
r
i
(BA-SlC \
MODIFICATION)
IDEAS /
i
.
FUEL.S
E<
1
jo
(OPTIMUM \
MODIFICATION!
'
,
peocess
B<
^
1
^
^
(c5eMOM€>TE*kreD\
MOC5IFltA,TlON J
T6C.HNQ LO6-Y /
STATE OF
THE AET
CONTROL
eM.-S-S.OKJS
DESl^iNJ FOR
SJEW UNITS
FUBTHER.
Xl-Vens
Figure 5-2 The Combustion umtrol Program for N0x Control
-------
5.3.1 Strategies for Model Development
On a short-term basis, the principle functions of modeling are to
generate basic ideas for combustion modifications, guide in the experimental
planning of pilot tests, and to provide a rational basis for data evaluation.
The long-term function includes definition of the minimum attainable emission
levels, optimization of combustion modifications, and ultimately, predictions
for use in low NOV designs. Since the exploratory modeling study of Esso ,
X
there have been extensive experimental and analytical efforts directed at
fulfilling both the short- and long-term function of modeling. As would be
expected for an inherently long term program, much work remains for the full
utilization of the potential of fundamental studies. The experience to date,
however, does offer valuable guidelines for facilitating further development.
From a systems perspective, strategies for coordinating model development
include:
• Simultaneous focus on experimentation and analysis,
• Integration of short and long term requirements,
• Simultaneous development of auxiliary relations,
• Consistent level of sophistication in models,
• Use of complex models to calibrate simple models,
• Coupling of combustion and NO., modeling.
Some uses and implications of these strategies are summarized on Table 5-2.
At the time of the Esso study, the emphasis in fundamental studies was
on physical modeling which, typically, avoids consideration of basic phenomena,
such as turbulent mixing, thermal radiation, etc., through use of restrictive
physical assumptions. As delineated in Table 5-2, the recent emphasis in
fundamental studies is on formulation of auxiliary models for each of the key
phenomena contributing to NOX formulation. These are:
• Fluid flow phenomena
• Hydrocarbon combustion
• Thermal NO..
• Fuel NOX
• Turbulent viscosity
• Turbulent mixing effects on kinetics
• Thermal radiation
• Droplet or particulate flow and combustion.
5-9
-------
TABLE 5-2
TYPICAL STRATEGIES FOR MODEL DEVELOPMENT
Strategy
Description
Examples
Possible Future Applications
Coordinated
Experimentation
and Analysis
Computerized analysis has
refocused priority on experimen-
tation. Data inititiates, refines
and verifies models, so experimental
planning requires coordination
with modeling needs (Fig. 5-3).
Modeling of swirl effects in gas
turbine combustors (UARL);
identification of key species in
hydrocarbon flames (Esso, Ultra-
systems)
Turbulent mixing effects on
combustion and NOX formation
in jet diffusion flames.
Modeling of pulverized coal
flames
tn
M
o
Integration of
Short and Long
Term Requirements
Short term requirements
are a natural fallout
of long term program
(Fig. 5-3)
UARL flame modeling yields useful
flow pattern predictions
Fuel nitrogen modeling to
generate new ideas for
combustion modifications
Simultaneous
Development of
Auxiliary Models
Focus modeling at a basic
level to identify effects
on NOX formation
Current programs on H/C kinetics,
NOX kinetics, radiation, etc.
Expansion of fuel nitrogen
modeling efforts; modeling of
turbulent mixing effects on
H/C and NO kinetics
Use of Complex
Models to
Calibrate Simple
Models
Develop approximate
techniques from results of
single or coupled auxiliary
models
Global H/C kinetics from detailed
kinetic calculations; simple flow
models from recirculating flow code;
correlations for luminous radiation
Simple eddy mixing models for
effects of turbulent mixing
on reactions
Coupling of NOX
Modeling and
Combustion
Modeling
H/C and NOX kinetics are
coupled in many combustors;
turbulent mixing dominates
reaction rates in practical
systems, so NOX predictions
must be coupled to combustion
predictions
Modeling of flame-zone NOX
formation (Ultrasystems, Esso)
Coupling of combustion
aerodynamics and NOX
modeling (UARL)
-------
In the short term, these auxiliary models are used to generate ideas for
combustion modification concepts, and to develop understanding of specific
aspects of the NO., formation process. In the long term, two more auxiliary
models can be coupled to relate fuel or equipment parameters to NOX formation.
The evolutionary development of NO., modeling through the above approach
is depicted on Figure 5-3. The current emphasis is on formulation of first
generation models for the key items such as fuel NOX and hydrocarbon combustion.
The ultimate utility of this approach is contingent upon development of the
auxiliary models to a consistent level of sophistication. The status and
prospects of auxiliary model development is reviewed in the following section.
5.3.2 Status and Prospects of Modeling
The priority area in fundamental studies is the investigation of the
basic phenomena such as NOX kinetics, fuel NOX, and thermal radiation
involved in NO., formation. This information is necessary to relate NOV
A «
formation to actual combustion modifications and, effectively, fill in the
gaps in Table 5-1.
Table 5-3 gives a summary of status and prospects of auxiliary models
related to NOV formation. The final column contains a speculation on the
X
probable optimum level of development for use in data correlations and pre-
dictions. The status of these individual areas is reviewed below. This is
not intended to be an exhaustive treatment of current research, but only an
indication of requirements for R&D planning.
Fluid Flow Solutions
This is the most advanced area of combustion modeling primarily because
the problems in code development are mathematical rather than physical and thus
do not require experimentation. Early fluid flow solutions, used for example,
by Esso and IFKF , employed plug flow or well stirred reactor concepts.
It was found necessary to place several of these elements in a series or
parallel arrangement in order to approach a realistic simulation of practical
flows. This added complexity required ever increasing empirical specification
to link the various elements. Esso38 and IFRF reported unsatisfactory results
with this approach. The use of well-stirred or plug-flow elements to model gas
43
turbine combustors has been more promising
The numerical flow solution is a natural extension of the use of series
and parallel well-stirred reactors or plug flow elements. With the numerical
appraoch, the flow field is divided into a large number of computation cells,
5-11
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/PBEIJMINARY
(MODIFICATION
\ CONCEPTS
\ /PILOT \
) (SCAL& J
J \ PATA. /
/BKOONALIZeX / OTHER \ / FULL AND \
1 ISOLATED J lAuxiLiABr) 1 PI LOT •SCALE)
\PHENCM EMA/ V MODELS / \ OATA* /
SHORT-TFRAA EFFORT: DEVELCI'MfMT tf INDIVIDUAL
AUXILIARY
LONG-TERM EFFOffT : COUPLED MODELS FOR PkecxCTioUS
Figure 5-3 Typical Sequence in Model Development
-------
TABLE 5-3
STATUS OF MODEL DEVELOPMENT
Area
Fluid
Flow
Solution
Gas-phase
Hydrocarbon
Combustion
Thermal
NO
Kinetics
Turbulent
Viscosity
Mixing
Effects on
Kinetics
Thermal
Radiation
Fuel
Nitrogen
24> Droplet,
Particulate
Combustion
Current
Capability
Plug flow;
stirred reactor;
2-0 Boundary
Layer
Equilibrium diffusion
flames; prefixed
flames with global
kinetics
Zeldovich
Mechanism
Algebraic mixing
length
Neglect mixing; time-
averaged temperature,
concentration used in
kinetic calculation
Gas phase radiation
simple geometries
Advanced Stage of
Development
2-D Recirculating flow
with swirl ;
3-D Boundary Layer
Multi-step reaction for
methane
Extended Zeldovich
Super Equilibrium prompt NO
One- and two-equation
models for boundary layers
Simple eddy mixing
models for flame zone
Simple correlations for
luminous radiation; gas
radiation in complex geometries
Non-reacting 2-D droplet/
parti culate flow;
single droplet combustion
Preliminary Stage of
Development
3-D Recirculating
flow
Multi-step reaction
for complex
hydrocarbons
Coupled NO and
hydrocarbon kinetics
Two equation models for
recirculating flow; multi-
equation Reynolds stress
models
Statistical treatment
of temperature, concentration
fluctuation effects on
reaction rates
Models for luminous
radiation
Modeling of volatilization
and heterogeneous fuel
NOX conversion, single
particles
Models for multi-
droplet/parti culate flames
Estimated Best Use in
Practical Predictions
2-D Recirculating flow
Multi-step reactions
for complex hydrocarbons
Coupled NO and hydrocarbon
kinetics
Two equation models for
swirling flows
Eddy mixing models for
rates of coirfcustion and
NO formation
Combined gaseous, luminous
radiation models for
complex geometries
Fuel NOX models for
pulverized coal flames
Droplet/ parti culate density
and size distribution for
use in fuel NOX and luminous
radiation models
-------
each of which can be considered as a well-stirred reactor. The advantage of
this approach is that the mass and energy transport between cells satisfies
the governing mass, momentum, and energy balances.
Two dimensional boundary layer codes have achieved a near-optimum state
of development and are in routine use for a variety of flows including axi-
44
symmetric flames with small swirl . These codes can be exploited in the EPA
fundamental studies through use in predicting jet flames, with or without
swirl, to test models for turbulent viscosity, radiation, two phase flow, and
effects of turbulent mixing on flame propagation.
Two-dimensional recirculating flow codes in present use are mostly based
45
on the Imperial College vorticity-stream function {) code . Differing
versions of this type of code are possessed by Aerotherm, Battelle, KVB Engi-
neering, UARL, and Ultrasystems. UARL is currently doing an important study, in-
cluding experimentation, to model swirling reacting flows in combustors. Further
development of the basic (i^-oj) code will be mainly in the areas of numerical
stability and computing time reduction. There has also recently been developed
a pressure-velocity (p-v) code for 2-D recirculating flows . This code has
considerable advantage over the (<|>-u>) code, particularly in boundary condition
specification and computational efficiency, because the solution is made with
the physical variables. The (p-v) method is also readily extended to 3-D
flow , whereas the (i|i-a>) method is not. The 3-D codes are useful for ob-
taining crude predictions of furnace flow patterns, but accurate flame zone
predictions are precluded by uncertainties in turbulence and other parameters.
Hydrocarbon Oxidation
For prediction of combustion in hydrocarbon premixed flames, it is
necessary to reduce the numerous elementary reactions involved to a manage-
able set of controlling reactions which simulate the actual process. EPA is
currently funding three related studies which will lead to a better definition
of the important reactions and the kinetic constants for both hydrocarbon
oxidation and NO formation. Esso R&E is measuring concentrations in premixed
flames in order to identify important species and mechanisms in the flame zone.
Ultrasystems is doing a corresponding modeling study to reduce the detailed
methane kinetics to a small number of controlling reactions. Part of this
effort involves correlation of the Esso data. SRI is conducting a supporting
study to develop prediction methods for the kinetic constants for elementary
reactions. These results are useful in determining rate controlling or
global reactions. These three studies are contributing to the basic under-
standing of combustion and NOX formation which is required for modeling of
complex hydrocarbon combustion and the coupling with NOX formation.
5-14
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For many practical combustors, the flames are of diffusion type for
which the mixing rate of fuel and oxidizer controls the heat release rate.
Nitric oxide emission patterns for diffusion flames can be quite different,
especially in the dependency of fuel-air ratio, than for premixed flames '
This factor, coupled with the importance of diffusion flame phenomena in fuel
nitrogen conversion, gives diffustion flame studies a level of importance
comparable to premixed flame studies.
Thermal NO Mechanisms
There has been extensive testing of the degree of coupling between NO
kinetics and combustion kinetics under various combustion conditions. The
precise conditions under which alternate mechanisms apply is not fully under-
stood. Proposed mechanisms are reviewed below in order of increasing
complexity.
i) Zeldovich with Equilibrium Concentration of Oxygen Atoms, [0]:
This is the classical mechanism by which NO formation proceeds
according to:
02 + M s± 20 + M , [0] = Keg [02] /z , (5-4)
N2 + 0 ^ NO + N , (5-5)
02 + N e=? NO + O , (5-6)
and for which reaction (5-4) is in equilibrium. This mechanism
has been applied extensively especially for I.e. engines, and
the best success has been obtained in the post-flame region of
fuel-lean high pressure flames.
ii) Zeldovich with Non-equilibrium [OJ: Fenimore noted that
reactions (5-4) - (5-6), with equilibrium [0], failed to predict
NO formations near the flame zone. The "prompt NO" phenomenon
51 — 54
has since been observed by several other investigators
Bowman and others ~ have suggested that prompt NO is due
to non-equilibrium [0] concentrations in the near-flame region.
Use of (5-5) and (5-6) with super-equilibrium levels of [0] has
given reasonable correlations of prompt NO in many cases. It has
yet to be determined when this approach is sufficient to explain
prompt NO, and, also, what constitute satisfactory approximations
for the non-equilibrium concentration of [0].
5-15
-------
iii) Extended Zeldovich: For fuel rich flames, the concentration of
the JOB] radical in the near flame region is sufficiently high to
give importance to an additional reaction:
N t OH5*NO + H. (5-7)
This reaction has been used both with the equilibrium oxygen atom
assumption as well as the super-equilibrium 10] correction. The
contribution of (5-7) to NO formation is far less than from the
Zeldovich reactions, but its inclusion for fuel-rich flames seems
necessary.
iv) Fully Coupled NOV/HC Kinetics: Fenimore and Iverach have
A
proposed that IN] atoms participating in the Zeldovich reactions
may, in part, be due to reactions with flame radicals such as:
CH + N2 -> HCN + N ,
C2 + N2 ^2CN '
C + N2^CN + N .
The validity or conditions of applicability of these reactions
has not been fully established, but it is generally agreed that
in fuel rich, low pressure flames, NOV kinetics are coupled to
A
the combustion kinetics. The Esso and Ultrasystems studies
mentioned above are looking at the coupling mechanisms which
exist in the flame zone. An additional coupling, that between
NOV and sulphur dioxide, is being studied by the University of
A
Arizona.
Turbulent Viscosity
Flow predictions in swirling flame zone requires modeling of the
turbulent viscosity. Following the development of flow prediction codes, it
became possible to test and refine turbulence models in complex flow situa-
tions. Routine use is now being made of algebraic mixing length models ' ,
and one- or two-equation models '' in which differential equations are
solved for turbulence parameters such as turbulent kinetic energy or the
length scale. For recirculating flows, these models are normally used with
the assumption that the turbulence is locally isotropic. For high rates of
5-16
-------
swirl, it has been shown that the viscosity in the swirl direction differs
radically from the main flow direction, and the locally isotropic assumption
is not adequate for predictions. Testing of viscosity models for low and
high rates of swirl would be useful.
Multi-equation Reynolds stress models are being developed by the Los
Alamos group and the Imperial College group. These are costly to compute and
this level of complexity is usually not required. Their chief contribution
to combustion modeling will probably be to calibrate simple one- or two-
equation models.
Turbulent Mixing Effects on Reaction
The distortion of the flame zone due to turbulence has been identified
as a high priority study area by several investigators. In turbulent flames,
the local temperature and concentration exhibit large fluctuations due to the
mixing of turbulent eddies. The rate of combustion and NOX formation are
highly non-linear functions of temperatures and concentration; use of time
average values yields erroneous flame propagation and NO^ formation predictions.
Predictions of the effects of turbulent mixing is still in a preliminary
stage of development. Several eddy-mixing models have been used, either for
combustion reaction rates ' , or for NOV formation , with some success.
65
MIT has proposed a statistical approach for the specification of the compo-
sition of eddies for use in prediction of combustion and NO formation.
A
Thermal Radiation
Thermal radiation is of particular importance in NO^ formation from
utility and industrial boilers, but less so for I.e. engines and domestic
heaters. Modeling activities are focused both on methods for calculating
radiative transport and on eraissivity predictions for gases and luminous
flames.
For furnace heat transfer predictions, the zone method and the two
or four flux models ' have both been applied, with the flux models usually
preferred for use in numerical flow codes. Radiative properties for the gas
6 8
phase combustion products are known to an adequate degree for most cases ;
for luminous flames, the radiation is dominated by scattering and particulate
69
density, and the properties are less developed . The IFRF has been extensively
involved in measuring flame radiation and modeling luminous emissivities.
Battelle has developed a radiation computation scheme for use in the Spalding
type of recirculating flow code. These efforts are useful for providing in-
sight into the effects of radiation on NO., formation.
5-17
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Fuel Nitrogen
Fundamental studies of fuel NOV conversion are in a preliminary state;
A
most useful results in relating fuel NOX to equipment parameters have derived
from fuels R&D36'39.
40
Shell , in an exploratory review of the fate of fuel bound nitrogen,
concluded that most of the nitrogen goes to the char residue and may be con-
verted to NO during heterogeneous carbon burnout. IFRF has suggested, however,
that nearly all fuel NOV is formed from the gaseous pyrolysis products.
37
Rocketdyne is doing a comprehensive study of several aspects of fuel NOV
A
conversion which is helping to clarify the mechanisms involved.
Both Shell and Rocketdyne have suggested that significant quantities
of HCN may be formed as an intermediate compound of the fuel nitrogen.
Concentrations of CN-type molecules, possibly HCN, in excess of 30 ppm have
41
been measured in an experimental burner by Appleton and Heywood . This
aspect of fuel nitrogen conversion requires attention, as it could be a
limitation on the extent to which conversion of fuel nitrogen to NO is
suppressed.
Droplet or Particle Combustion and NO Formation
This is a supporting area for fuel nitrogen and luminous radiation
studies and has benefited from non-EPA programs in chemical process engineering.
There are numerous models for the combustion of single oil droplets or coal
particles; recently several groups have presented models for NO forma-
tion around oil droplets. The Rocketdyne study on fuel nitrogen will include
two-phase flow modeling as part of their program.
5.4 APPLICATION OF COMBUSTION MODIFICATIONS
As discussed in the Esso report and in the NO^ control technology
literature subsequent to it, combustion modification is the most viable means
of reducing NO generation. This section presents a review of the implementa-
A
tion strategy, the present status and prospects, and the costs of implementing
the various modifications.
5.4.1 Implementation Strategy of Combustion Modifications
As discussed in Section 5.1, NO formation in flames depends on com-
bustion physics and chemistry; specifically, time, temperature, and
stoichiometry. Understanding and then altering these fundamental processes
is the basis for the effectiveness of combustion modification techniques.
5-18
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This subsection briefly discusses the theory and implementation strategy of
these modifications. Both operating condition and equipment modifications
are covered. The bulk of this discussion applies to utility and industrial
boilers.
5.4.1.1 Low Excess Air Operation (LEA)
Low excess air firing in boilers reduces the concentration of oxygen
available for combination with nitrogen (atmospheric or fuel-bound), thus
reducing NOY formation. Since a certain amount of excess air is always re-
A
quired in practical combustion systems, LEA operation is capable of causing
poor combustion with resultant production of unburned fuel and smoke. On oil
and coal firing, furnace slagging is also increased with decrease in excess
air causing increased maintenance and possible operating problems. Implement-
ation of LEA requires minimal additonal operating expense, no equipment al-
terations or redesign, and usually results in a slight increase in thermal
efficiency.
At the present time, most utility boilers operate at what is considered
minimum excess air, and LEA is not considered a combustion modification in the
true sense of the word. The minimum level is set by CO levels for gas and smoke
levels for oil. Oil requires 1/2 - 1 percent more excess air or 02 than gas.
The Esso report presented some early results on the effectiveness of
LEA operation on gas- and oil-fired boilers. At the time, little or no infor-
mation was available on the application of LEA operation to coal-fired units.
Progress since then is presented in later sections.
5.4.1.2 Off-Stoichiometric (O/S) Combustion
This NO reduction technique is usually implemented on large boilers
with multiple burners arranged in rectangular matrices mounted either on one
boiler wall (front-fired) or on opposite walls (horizontally-opposed-fired).
This method can also be used on corner-fired boilers (tangentially-fired), but
in most cases the normally low NOV emissions from boilers of this type can be
A
adequately reduced by simpler techniques, such as lowering excess air.
In general, this method has the effect of fuel-rich burner operation,
already identified as an effective NO reducing process, with combustion of the
rising bulk gases in lower temperature post-flame regimes where the remainder
of the required air is introduced. The time duration for which most of the
fuel is exposed to peak temperatures is, therefore, reduced. Depending on the
stoichiometry, fuel-rich primary zone combustion may have the secondary effect
of lowering the peak flame temperature.
5-19
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In off-stoichiometric firing, the flame is long, yellow, and smoky, as
opposed to the short and intense flame observed on normal firing. The flame
also extends farther up in the furnace, sometimes causing excessive reheat
(convective section) temperatures. On some units, increased operator vigilance
is required due to decreased effectiveness of the flame detector system.
In practice, off-stoichiometric combustion consists of operating some
burners (usually the ones located in the lower part of the pattern) fuel-rich
while the burners in the upper part of the pattern operate on pure air. Off-
stoichiometric combustion is a generic term and several modes of operation are
associated with it.
So-called "simulated overfire air" operation results when the top row
of burners operate on pure air. "Two-stage" combustion works on the principles
of off-stoichiometric combustion except that the fuel-rich burner operation is
achieved by diverting a portion of the total required air through separate
ports located above the burner pattern. This is also known as "overfire air/NOx
port" operation. In certain boilers, NO reduction optimization requires that
the burners operate either fuel- or air-rich in a staggered configuration.
This is sometimes called "biased" fired.
The "two-stage" combustion technique is shown in Figure 5-4 below.
Secondary
Oxidizing Zone
C+02-»-C02
"NOX Port"
I CH4+202-»-C02+2H20
I CH4+02-C+2H20
^ C+0,-»-CO+0
^ Furnace
*r wan
Ml
Nozzle
\ N+Og+NO+O
Primary
Reducing Zone
Air
Register
Figure 5-4. Two-Stage Combustion (After Reference 35)
5-20
-------
A vertical cross-section of a utility boiler burner is shown schematically.
Two-stage combustion of natural gas (methane) is depicted, and a few of the
global reaction mechanisms associated with the primary and secondary combus-
tion zones are identified.
As of 1969, the date of publication of the Esso report, only a limited
quantity of information was available on the actual effectiveness of off-
stoichiometric techniques for NO reduction in boilers. Fairly significant
results had been obtained for gas-fired utility boilers by Pacific Gas and
Electric Company and Southern California Edison Company, and from coal-fired,
sub-scale combustion in tests performed by the U.S. Bureau of Mines (1966).
This modification technique has been more thoroughly investigated during the
last several years, and subsequent sections of the present study review the
recent developments.
5.4.1.3 Flue Gas Recirculation (FGR)
A portion of the flue gas recycled back to the primary combustion zone
reduces NO formation by acting as a thermal ballast to dilute the reactants,
thereby reducing both the peak flame temperature and partial pressure of
available oxygen at the burner inlet. Possible flame instability, loss of
heat exchanger efficiency, and, for packaged boilers, condensation on internal
heat transfer surfaces, limits the utility of FGR on some units.
Although it has been concluded that FGR reduces thermal NO, recent data
has cast doubts on its capability to reduce fuel NO. More investigation is
required, as the present uncertainty will have significant impact on the
applicability of FGR to oil and coal firing.
At the time of the Esso report there existed a paucity of information
concerning the effectiveness of this method on NO reduction, the only re-
74
ported work being performed by Andrews, et. al. . New data has come to
light since then, and is included in Section 5.4.2.
5.4.1.4 Reduced Air Preheat Operation
Reducing the amount of combustion air preheat lowers the primary com-
bustion zone peak temperature, generally lowering NO production as a result.
It is seldom considered practical, however, due to the associated loss in
thermal efficiency.
There have been recent indications that increasing air preheat actually
fuel NOV formation on
J\
ranted to explain this result.
92
reduces fuel NOV formation on coal firing . Further investigations are war-
5-21
-------
This modification technique was not mentioned in the Esso report due to
a lack of empirical data concerning its effectiveness. It may have some merit,
however, and will be discussed further in Section 5.4.2.
5.4.1.5 Load Reduction
The term "load" is defined as the percentage of its rated capacity at
which the furnace or boiler is being operated. Increasing boiler load causes
an increase in primary combustion zone volumetric heat release rate which
generally increases the rate of NO formation. Reducing boiler load is accom-
plished by reducing the reactant flow rate (fuel and oxidizer) into the
furnace, thereby lowering the heat release rate (also known as combustion
intensity) and peak flame temperature.
Although there are no capital costs involved in implementing load
reduction, it is usually undesirable to reduce boiler capacity. Load reduction
increases boiler efficiency due to longer residence times and more complete
combustion, but the lower flow rates result in a decrease in overall
efficiency due to decreased turbine efficiency.
This modification technique was not mentioned in the Esso report due
to a lack of empirical data concerning its effectiveness. It has some merit,
however, and is briefly discussed in Section 5.4.2.
5.4.1.6 Water or Steam Injection
Injecting water or steam into boilers is yet another means of reducing
peak combustion temperatures to reduce NO formation. Its use may entail some
undesirable operating conditions, such as decreased thermal efficiency due to
the high heat capacity of water compared with that of flue gas or other inert
diluents, and increased equipment corrosion.
The Esso report noted from one study that water injection was effective
in reducing NOV emissions from an internal combustion engine. No other
A
investigation had been carried out up to that time. It has since been shown
to be a viable means of NO suppression for stationary gas turbines.
X
5.4.1.7 Combinations of Techniques
Since 1969, it has been demonstrated that several of the previously
discussed modification techniques can be effectively utilized in combination
since they reduce NO by different mechanisms. Most often, off-stoichiometric
combustion is used in conjunction with flue gas recirculation, low excess air,
5-22
-------
reduced air preheat, or reduced load. The latter three methods lower peak
combustion temperatures, while off-stoichiometric operation reduces the amount
of fuel burned at peak temperature. For the most part, combining techniques
has been shown to be complementary but not additive for NO reduction.
5.4.1.8 Equipment Design Modification
From what is known of the theory of NO formation in continuous
2\
combustion processes, the ideal equipment design would provide for lower
peak temperature flames and more controlled rates of combustion. Research
and testing has shown that much can be done to accomplish these goals.
According to Krippene a low NOV emission burner should be designed as
A
fuel-flexible as possible, be able to operate at minimum excess air levels,
and not cause an emissions tradeoff problem. In most new utility boiler
designs, burner spacing has widened to provide more cooling of the burner
zone area. In addition, the furnace enclosure should be built to allow
sufficient time for complete fuel combustion from slower and more controlled
heat release rates, such as that associated with the off-stoichiometric
operating mode.
As mentioned in the Esso report, the tangential firing method for
large utility boilers is in itself a viable low NOX emission technique.
Notable results have been obtained from tests of tangentially-fired units, by
7fi — 78
Combustion Engineering . It has been observed, however, that from many
such boilers the response to operating modifications has been less impressive
than from boilers of other designs,, even though the magnitude of the initial,
uncontrolled emission was lower.
5.4.1.9 Typical Utility Boiler Combustion Modification Implementation
Program
As a vehicle for emphasizing the importance of cost-benefit factors,
the Esso report1 contained an extensive analysis of minimum cost paths for
NOV control by combustion modification. An updated study of this kind is
X
required, since the original is based on estimated costs and the fuel NOX
problem was not fully appreciated at the time. An approach for beginning
such an analysis is presented in Figure 5-5.
5-23
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IMPLEMENT 0/S
INSTALL WATER
STEAM INJCCTlON
IM-STA.LL MODIFIES
LOW NOX) 30EN6B5
TRY ALT5RNATe
Ops^e/s.FL
TEE/CTMEWT')
Figure 5-5 Typical Combustion Modification Implementation Program
5-24
-------
Figure 5-5 shows, in flow-chart form, a typical decision process for
implementation of the appropriate combustion modification techniques. The
simplest, least expensive, and most expedient techniques are initially
utilized, followed by those requiring capital investment, operating expense,
boiler down-time, and decreased thermal efficiency. This simplistic model
reflects the possible ineffectiveness of temperature-reduction schemes (i.e.,
FGR, water injection) on emissions from coal combustion, and has as its
ultimate goal the reduction of NO concentration (shown as [NOX]) to regulation
levels. In practice, obviously, the decision process is more complex.
Impracticalities of certain of the techniques for a given boiler may require
an extensive re-ordering of the control steps as given in the figure.
5.4.2 Status and Prospects
Methods of controlling NO., emissions from combustion systems by
combustion modification techniques were treated at some length in the Esso
report. Since 1969, however, much more experience in testing and applying
these operating modes has been gained.
This section discusses the present status and prospects for reducing
NOV emissions from stationary sources by combustion modifications. The scope
A
of this section focuses on those combustion systems usually categorized as
"point" sources: utility and large industrial boilers. "Area" or "complex"
sources, comprised partly of stationary I.e. engines and gas turbines, are also
discussed. Other area sources, such as commercial and domestic heating
equipment, are discussed when similarities exist with point sources.
5.4.2.1 Utility and Industrial Boilers
The net decrease in NOV emissions from conventional fossil-fueled
A
boilers through changes in operating mode or equipment design depends on
many factors. Among them are boiler geometry and cleanliness, burner design,
spacing and state of repair, load, and most importantly, the fuel itself. In
this section, the relative effectiveness of the various combustion modification
techniques for reducing NO from gas-, oil-, and coal-fired boilers or combus-
tors will be discussed. This information was obtained from the open literature
and a number of confirmatory personal contacts.
When attempting to draw general conclusions from N0x reduction figures
obtained from separate boilers, it must be kept in mind that even identical
boilers give widely differing test results for the same modification. This is
due to varying boiler cleanliness, uneven burner loading, equipment condition,
5-25
-------
and a myriad of other factors, most of them not easily identifiable. Unless the
sample size is large, extrapolations based on boiler size are probably invalid.
As implied in Figure 5-5 in the preceding section, the practical limit
on the modifications are based initially on three subjective criteria: stack
plume appearance (i.e., smoke production, its opaqueness and/or Ringlemann
number), flame appearance (i.e., color and dimensions) and incipience of
flame instability at the burner. When problems are encountered, imple-
mentation is halted and the situation re-evaluated. Stack gas sampling for
NO.., CO, and 0, is usually carried out concurrently. In the long term, the
effects of the modification on such factors as burner condition, furnace
slagging and corrosion, ability to change fuels, and boiler load are
monitored to varying degrees.
5.4.2.1.1 Gas
The highest degree of success in reducing NO by the application of
combustion modifications has been obtained on gas firing for both full and
pilot scale furnaces. The reason for this effectiveness lies in the fact
that all of these techniques reduce thermal NO , which is the only NO formation
A X
mechanism in gas combustion.
Low excess air operation has been shown to be extremely effective in
lowering NOV emission from gas-fired boilers. An extensive study of NOV re-
A A
duction techniques applied to six wall-fired utility boilers done by Bartok,
79
e_t al. showed reductions of 25 to 60 percent at full load. NOV reduction
L ~ A
magnitude depended not only on lowering excess air, but also on furnace de-
sign and firing method.
80
In other reports, Barr obtained a 23 percent NO reduction on a 750
MW front-fired unit as a result of lowering excess air. Off-stoichiometric
firing was subsequently implemented on this unit to achieve further reductions.
Blakeslee reported a 33 percent NO., reduction on a 250 MW tangentially-fired
utility boiler when the flue gas oxygen content was decreased from 3.9 percent
to 0.6 percent.
In most cases, LEA was implemented without serious flame stability
problems, and an increase in thermal efficiency was noted.
5-26
-------
From both full and pilot scale results, flue gas recirculation has been
proven effective for lowering NOX formation from gas combustion. In general,
NOV reduction figures range from 20 to 60 percent on various boiler designs
A
and load conditions. Subscale testing has shown that the magnitude of NOX
reduction is mainly dependent on the amount of gas recirculated up to the
point of incipient flame instability and other undesirable operating conditions.
Some references which may be scanned for further details are References 79,
82, 83, and 78.
On gas firing, off-stoichiometric combustion has been shown to be one
of the most effective means of NO., control and also one of the easiest to
implement. Biased firing is the most frequently used and most effective method,
while overfire air/NO port operation achieves less reduction, particularly where
79
biasing has already been implemented. Bartok published NO reduction figures
X
of 25 to 58 percent from wall-fired utility boilers ranging from 80 to 480 MW
when two-stage combustion was applied. Similar results are reported on
go 04 pc
Southern California Edison units by Bagwell , Breen , and Teixeira . The
effectiveness of off-stoichiometric combustion on gas-firing has been well
researched and documented.
Water injection into utility boilers has been tested to a limited
extent. Blakeslee reports a 50 percent maximum NO reduction at full load
for a 250 MW tangentially-fired unit when water was injected at a rate of 45
pounds per million Btu fired. Boiler convective section temperature increased
by 250"F and boiler efficiency dropped 5 percent. The economic penalties
resulting from this method, as well as from reduced load or air preheat, make
such techniques unattractive.
A significant amount of work has been done on optimizing gas burner
design for low NOV. Of the three types of burners, spuds, radial spud, and
A
ring, the latter forms the least NOX while the spud type maximize NOX
formation. In addition, burners which produce low turbulence flames have
been found to release lower quantities of NOX-
In all, the effectiveness of NOV reduction from most gas-fired equip-
A
ment has been adequately explored. Further investigation may not be war-
ranted because the number of large gas-fired utility and industrial boilers
(the largest point NO., sources), small to begin with, is now declining
rapidly due to the present natural gas supply shortage. For example, several
West Coast utilities estimate reductions from about 70 percent gas-firing in
1972, to less than 10 percent in 1974. Low sulfur residual oil will be the
predominant fuel utilized on the West Coast.
5-27
-------
5.4.2.1.2 Oil
In general, a poorer record of NOX reduction has been compiled for
oil-fired units, largely because of reduced operating flexibility. Fuel NOX
becomes an important contribution to the total NO., emission from a given unit,
and the individual modifications are less effective and more complicated to
implement. Nevertheless, substantial reductions have been achieved, in some
instances as high as 50 percent on utility boilers.
As for gas, operating at minimum excess air conditions is a valid
reduction scheme. From tests on six wall-, oil-fired utility boilers, Bartok,
79
et al. reported a NOV reduction range of 23 - 56 percent at full load.
A
LEA operation seemed most effective on front wall-fired units, although this
sample size was rather small.
gg
On other utility boiler tests, Campbell reported a 17 percent NOX
decrease by lowering excess 0, from 3.8 percent to 1.5 percent on a 290 MM
front-fired unit.
No reliable correlations between furnace design and effectiveness of
LEA operation on utility boilers have been or can be made at this time.
The importance of avoiding smoke production when approaching reducing
conditions at the burner has been well documented. A typical example was
Q 7
generated from sub-scale testing by Muzio and Wilson on a 3.7 x 106 Btu/hr
research furnace. Figure 5-6 depicts the NO and smoke trends as a function
of excess air.
300
too
8
K
s
I 100
£
Fuel: No. 6 oil
Load: 92 %
10
20
40
50
Exam Air. X
Figure 5-6. Increasing Excess Air Decreases Smoke but Increases NO
5-28
-------
The thrust of other recent subscale testing has been to segregate the
relative importances of thermal and fuel NO under low excess air conditions.
Firing "blank" fuels (i.e., no nitrogen) doped with varying amounts of nitrogen-
88
bearing compounds, Turner found that at any given level of excess air, the
NOV concentration increases with fuel nitrogen content, although not proper-
A
tionately. As excess air was increased, the fraction of fuel nitrogen
converted to NO increased, but the fraction decreased with increasing nitrogen
content at a given excess air level. Total NO concentration in the flue gas,
however, increased with fuel nitrogen concentration. These conclusions have
89 90
been substantiated by Pershing . In a more recent study, Martin found that
although fuel NO decreased as excess air was lowered, thermal NO actually in-
creased. This behavior was attributed to specific characteristics of the fur-
nace used in the investigation. It was concluded, however, that limiting ex-
cess air may not, a priori, be a valid control technique for all small oil-fired
boilers.
81
According to Jain , commercial and industrial boilers generally
operate at an average excess air level of 15 to 25 percent, with some smaller
and older units operating at as high as 35 to 40 percent excess air. Early
tests have shown that these levels can be safely reduced to about 10 percent,
causing substantially lower NO., emissions. As for gas-fired boilers of this
size range, a number of field testing and survey programs are currently
being performed to more fully characterize the NOV contributions from small
A
oil-fired boilers.
Off-stoichiometric combustion has also been demonstrated to be effective
79
in reducing NO., from oil-fired power plants. Bartok, et al. , reported
net NOY reductions of 19 to 35 percent for five wall-fired boilers ranging in
77 78
size from 80 to 320 MW. Blakeslee ' , obtained reductions of 20 to 55
percent for several 78 to 400 MW tangentially-fired units when two-stage
combustion was implemented. Similar impressive results were reported by
85
Teixeira from the NOV reduction program being carried out at Southern
A
California Edison. Some research has shown that off-stoichiometric techniques
reduce both fuel and thermal NOV formation. Such conclusions were arrived
88
at by Turner in doped fuel tests.
Although more work, especially full-scale field testing, is required
to investigate the effectiveness of off-stoichiometric methods on reducing
fuel NO.,, the effectiveness of these techniques on net NOV emissions from
A A
large boilers has been solidly demonstrated. Smaller industrial and commercial
boilers, however, do not lend themselves to such methods. For packaged boilers,
furnace volume and the number of burners are usually too small, and implemen-
tation of such modifications is usually uneconomical '
5-29
-------
For flue gas recirculation on full size utility boilers, reduction
78 79
figures in the range of 20 to 40 percent are most common . Bartok, et al.
reported a 50 percent reduction in NOX emissions from a 250 MW front-fired
twin furnace when FGR was combined with low excess air and staged firing
operating conditions. Similar results from combining techniques have been
obtained by Barr and James from a 750 MW unit at full load.
The importance of introducing the flue gas directly into the combustion
air as opposed to injection into the furnace volume is described in a paper
86
by Campbell . On a 342 MW oil-fired unit, recirculating gas from the
economizer outlet to the upper furnace area caused no change in NOX , while
on a 250 MW oil-fired utility boiler, routing the gas through the windbox
produced a 15 percent NOX reduction at 80 percent load.
39 88 — 90
Sub-scale research ' has shown that flue gas recirculation with
liquid fuel combustion reduces NOX formation by the thermal fixation mechanism
but does not affect fuel nitrogen conversion. Consequently, less significant
total NOX reductions would be expected when FGR is applied to units firing
fuels bearing nitrogen compounds. Typical results in this regard are shown
Q *]
in Figure 5-7, from work done by Muzio and Wilson on a 3.7 x 106 Btu/hr
research furnace. The role of fuel nitrogen conversion is clearly stated when
comparing the curves for natural gas and nitrogen-containing No. 2 and No. 6
fuel oils.
Mo. 60ll|N00-271ppm)
20IIIN00°«4ppm)
Natural Gas (NO,, - M ppm)
EXCESS AIR: 1TX
LOAD.
10 20
X RECIRCULATION
Figure 5-7. Effectiveness of FGR with Fuel Oil Type
5-30
-------
Although it is estimated that substantial reductions may be obtained by
FGR on commercial and industrial boilers, essentially no published data exists
to back up this claim. The Esso report discussed the early work done by
74
Andrews, et al. , and this seems to be the state of the art. In any case,
installation of FGR on existing package boilers would require capital invest-
ment in ducts, fans, and control systems, as well as additional operating costs
due to the power needed for a forced draft system. Generally applicable to
typical package boiler emission control methods is the research reported in
Reference 87.
Water injection is currently being tested on one unit in Southern
California. Due to the loss in plant efficiency usually assoicated with this
method, it may be used to a limited extent in combinations with other tech-
niques to supplement their NOX reduction capabilities.
In the area of burner modifications for oil-fired utilities, one of
the most straightforward is installing new atomizing orifices for biased firing.
For those burners operating fuel-rich, the orifices are enlarged to accomodate
the increased fuel flow caused by the burners out of service.
Krippene states the criteria for a low NO., burner. The design should
afford a limited turbulence, controlled diffusion flame, with a combustion
process reminiscent of off-stoichiometric techniques. The quantities of
fuel and air mixed at the burners should be minimized to that required to
sustain combustion, while the remainder of the fuel is combusted slowly and
efficiently further downstream. Burner flexibility is crucial for maintaining
efficient combustion of a wide range of fuel oils under varying load
conditions.
In the near future, oil will become an increasingly important fuel
for stationary sources. Fortunately, many of the installations that will
soon be converted from gas- to oil-firing were originally designed for dual
fuels. Many more, however, will require some degree of modification before
compatibility with oil is attained. Furthermore, such units must retain the
highest degree of flexibility possible to assure efficient combustion of a
wide variety of fuel oils at consistently high load levels.
5.4.2.1.3 Coal
Just as the response to combustion modifications for oil-firing was
less impressive than for gas, so their effectiveness for coal fuel is dimin-
ished further. The contribution from fuel N conversion is very important
and the number of cost-effective modifications is commensurately reduced.
Since the possible number of operating problems on coal-firing are more
numerous and the propensity to produce smoke or participates is greater,
-------
the modifications which are effective are less flexible and must, in all cases,
be applied with great care. Most of the existing data on this topic has been
generated from pilot-scale tests, with a limited amount from large utility
boilers. KVB Engineering of Tustin, California, is currently conducting an EPA-
sponsored industrial boiler NOX control study. Due to the negligible amount of
presently available information on coal-fired commercial and industrial boilers,
the following discussion focuses on utility boilers.
In tests on eight utility boilers ranging in size from 125 to 800 MW,
91
Crawford reported average NO reduction figures of 40 to 50 percent under
low excess air and biased firing conditions. Tangentially-fired units pro-
duced the lowest NOV under both baseline and modified operation, and load was
A.
not effected during burner pattern firing changes for wall-fired units.
Increased slagging was a problem, and it was recommended that long term cor-
rosion investigations be made on future coal testing.
The dependence of net NOX reduction on fuel type for given modification
variables was shown in sub-scale tests (5.6 x 106 Btu/hr, 500 Ib/hr coal-fired
furnace) by Armento and Sage . Figures 5-8, 5-9 and 5-10 show NO emission
A.
as a function of excess air, firing rate (load), and preheat, respectively.
Figure 5-8. Effect of Excess Air on NOV for Gas, Oil, and Coal
.A
Figure 5-9. Effect of Load on NO for Gas, Oil, and Coal
X
5-32
-------
Figure 5-10. Effect of Preheat on NOX for Gas, Oil, and Coal
It was concluded that coal produced more NO for all modifications due to fuel
N conversion. For this particular experimental system the excess air and load
load tests showed that oil produced less NO than gas. These results were
J\
due to the more luminous and larger oil flame envelope, leading to greater
radiation and a lower bulk gas temperature. Except for this phenomenon, the
authors concluded that the observed trends shown in Figures 5-8 and 5-9
would be valid and useful scale-up information.
As was stated earlier in this report, there is some conflict over
whether or not temperature reduction schemes, such as flue gas recirculation
and water injection, are effective for reducing NOX on coal- or heavy oil-
firing. The sub-scale testing by Armento and Sage produced a 10 to 15 percent
maximum reduction in NOV for the application of 10 to 15 percent flue gas
A
recirculation, as shown in Figure 5-11. The oil fired in the tests contained
0.23 percent fuel-bound nitrogen and the coal 1.1 percent. Again, it was pro-
posed that the more luminous oil flame caused FGR to be less effective on oil
than on coal, just the opposite of what is normally expected.
FLUE GAS RECYCLED. *
Figure 5-11. Effect of FGR on NO., for Gas, Oil, and Coal
5-33
-------
A wide variety of results have been published by other investigators.
McCann, et at. , reported a 39 percent NOX reduction at 25 percent flue gas
recirculated to secondary air for a 500 Ib/hr pulverized coal-fired unit. These
results may be questionable, since the concurrent carbon loss increase data
showed that incomplete combustion was taking place. From tests by Pershing,
00
et al. on a 4 Ib/hr pulverized coal-fired furnace, it was concluded that FGR
was ineffective as a NOV reduction technique.
A
Most researchers have agreed that decreases in NOX on coal firing by
FGR were relatively minor and were probably associated with the elimination
of thermal NO... The larger portion of the total NOX results from conversion
of fuel-bound nitrogen. FGR would perhaps be used to supplement the reduc-
tions obtained by other techniques, such as off-stoichiometric combustion,
that are postulated to be effective for fuel NOX reduction.
According to Krippene , much can be done to alleviate operational
problems through combustion equipment modification. To provide closer control
over fuel and air flow through the burners, some coal-fired utility boilers
have installed individual windboxes for groups of burners supplied by a given
pulverizer. This is an important modification for biased firing since continu-
ous air purge through the burners out of service is a requirement.
The "low NO " furner described in the preceding section on oil firing
is also effective on coal firing. Defined as a "triple concentric" burner
due to its unique design, it produced a combustion process similar to the
two-stage technique used on a boiler as a whole.
As discussed in Sections 5.1 and 5.2, research has shown that there
are possibly two different fates in store for fuel-bound nitrogen during and
after combustion. It will either be converted to N_, or NO, along with other
intermediate products (several of which have been identified as cyanide
compounds). These reactions depend more on stoichiometry than on temperature.
Under oxidizing conditions more NO is produced, while nitrogen is the favored
product from a reducing atmosphere, such as that afforded by off-stoichiometric
combustion. In full- and sub-scale tests so far, these techniques have been
shown to be quite effective for reducing NOX on coal-firing, and will probably
be implemented on new and existing coal-fired utility boilers and on boilers
being converted from scarcer fuels to coal.
As discussed in Section 3.4 of this report, the current clean fuels
shortage and slower-than-anticipated construction of nuclear generating
plants has vaulted coal, the use of which had been steadily declining over
the past 30 years, into prominence as a major short-term energy resource.
To avoid any further degradation in ambient air quality, emissions from the
burgeoning number of coal-fired stationary sources must be controlled.
5-34
-------
Specifically for NO., abatement, this will require further pilot- and full-
scale research and development on the NOX reduction effectiveness of combustion
equipment and operation modifications with minimum economic penalties.
5.4.2.2 Turbines and Reciprocating Internal Combustion Engines
This section updates the status of the control technology for NO..
emissions from stationary reciprocating I.C. engines and gas turbines.
5.4.2.2.1 Reciprocating I.C. Engines
Most of the control technology for stationary I.C. engines has been
developed by the automotive industry. Table 5-4 lists the control techniques
for all exhaust pollutants.
TABLE 5-4
EMISSION CONTROL METHODS FOR RECIPROCATING ENGINES
I. Engine Modifications
A. Operating Conditions:
B. Engine Hardware:
II. Exhaust Treatment
1. Speed
2. Torque/Load
3. Air/Fuel Ratio
4. Ignition Timing
5. Fuel Injection Timing
6. Air Temperature
7. Air Pressure
8. Exhaust Back Pressure
1. Exhaust Recirculation
2. Water Injection
3. Valve Timing
4. Combustion Chamber -
Stratified Charge
5. Compression Ratio
Discussed
in
Esso Study
A. Exhaust Thermal Reactor (CO/HC)
B. Catalytic Converter: 1. Oxidation (CO/HC)
2. Reduction of NOX by CO, H2,
NH
3, or natural gas
X
X
x
X
X
5-35
-------
In general, changes that reduce NOV emissions have the reverse effect on CO
A
and hydrocarbon emissions and fuel consumption.
The optimum choice for any particular engine will depend on the effect
4
of the controls, reliability, durability and engine life. A study by McGowin
recommended the following NOV control techniques for stationary diesel and
J\
natural gas engines:
SHORT & IMMEDIATE TERM LONG TERM
Water Injection Catalytic
Precombustion Chamber NOX Reduction
Natural Water Injection Catalytic
Increased valve overlap
for 4 cycle N.A. engines
Gas , , , , NOV Reduction
Increased valve overlap X
The precombustion chamber or stratified charge engine has the potential
of reducing diesel NO., emissions by a factor of two. NO., emissions can also
be reduced by 70 percent or more by injection of water into the combustion
chamber at the rate of 1 Ib of water for each pound of fuel. However, fuel
consumption is likely to increase and the long term effects of this practice
are not known. The parameters or control techniques that were omitted in the
Esso study or schemes where significant new data have been developed will now
be discussed.
Engine Speed
For a 4-cycle gasoline engine, NOV emission increases with speed under
A
fuel-rich conditions, decrease with speed under fuel-lean conditions and
4
remain nearly constant at the optimum air/fuel ratio. The Shell study
showed a 58 percent decrease in NOX emissions with a 10 percent increase in
speed for a two cycle, naturally-aspirated gas engine. The decrease may be
partly attributable to simultaneous change in the apparent air/fuel ratio in
the cylinder.
Torque Load
4
The Shell study also showed a dramatic increase in NO., emission with
increasing torque. Emissions increased from 15 gms/Bhp-hr to 23 gms/Bhp-hr
when increasing the torque from 83 Bmep to 90 Bmep on a two stroke, atmospheric
spark-gas engine. This effect is further illustrated by data developed at
Caterpiller Tractor Company for a precombustion chamber diesel engine as shown
in Figure 5-12. However, with this type of engine, NOX emission increase with
speed at constant power output.
5-36
-------
ISO
240
200
L
SI60
120
80
40
800 1200 1600 2000 2400
ENClNi SPiED-RPM
K0.miuto.4w/'"
Figure 5-12. Effect of Speed and Power Output on Emissions;
Caterpillar 4-Cycle Precombustion Chamber;
Diesel Engine
Air Manifold Temperature and Exhaust Back Pressure
As might be expected, NOX emissions increase with increasing air
manifold temperature. For a spark ignition gasoline engine under lean condi-
tions increasing manifold air pressure increased emission. Conversely,
increasing exhaust back pressure on a 2-stroke, naturally-aspirated engine
decreases NOV .
A
Valve Overlap
For a four cycle naturally-aspirated engine, increasing valve overlap
produces the same effect as exhaust gas recirculation. As the valve overlap
increases, the percentage of exhaust present in the fresh charge increases
which results in an EGR effect. Fuel economy may suffer, however. Increasing
valve overlap can only be applied to four cycle engines.
Exhaust Gas Recirculation
Although this technique was mentioned in the 1969 Esso study, considerable
work has been performed since that time. In a recent paper by Komiyama and
94
Heywood a model was developed to predict NOV emission, given the design and
A
operating conditions for spark ignition engines and percent of exhaust gas
recirculation. Good agreement was shown between the model and experimental
data over a wide range of fuel/air ratios and engine speeds. Typical
reductions of 38 percent have been achieved under lean conditions. The paper
shows that in lean mixtures nitric oxide concentration freezes early in the
5-37
-------
expansion stroke. Under rich conditions considerable nitric oxide decomposi-
tion occurs during combustion before the concentrations are fixed. Caterpillar
has published EGR data for a precombustion chamber diesel which showed a
possible 73 percent NO^ reduction. However, a number of problems exist for
EGR applied to stationary I.C. engines, which include the following:
• Requirement to accurately meter the amount recirculated
• Must cool the exhaust products prior to injection
• Fouling of intake manifolds, and aftercoolers by particulates
• Long term effects on lubricating oil and engine life.
Catalytic Converter
Numerous post-combustion control methods have been developed by the
automotive industry to treat the exhaust products from an I.C. engine. These
techniques include exhaust manifold thermal reactors, catalytic converters,
exhaust gas scrubbers and solid sorbents. The exhaust thermal reactor requires
a rich mixture operation and reduces only HC and CO. Exhaust gas scrubbing
and solid sorbents create secondary pollution problems, are too costly for
single engine application, and there is no known NO scrubbing technique. Thus,
X
only the catalytic converter seems to be practical for stationary I.C. engines.
Catalytic converters can be designed for the oxidation of CO and hydrocarbons,
or reduction of NO., by CO, H_, NH_ or natural gas. Only the latter scheme
will be discussed.
NO..J can be removed by catalytic reduction using CO and hydrogen, or by
adding a reducing agent such as ammonia or natural gas. Only under rich
operating conditions will sufficient hydrogen and CO be present to achieve
the required reactions. Since most stationary engines operate under fuel-lean
conditions only the addition of natural gas or ammonia seem practical. Injec-
tion of natural gas requires that there be sufficient gas to react with the
remaining O~ before NOy can be reduced. This technique may require several
stages of reactors. Of these catalytic reduction methods, the ammonia
scheme holds the most promise.
The ammonia reduction technique is shown schematically in Figure 5-13,
together with typical conversion curves for two different catalysts. Several
advantages of this scheme are:
• Reduction of NOX takes place in the presence of 02-
• CO and H/C oxidation occurs simultaneously on the same catalyst.
5-38
-------
ENGINE
A/F • 15
r.CO S;TI NO
UO ps- HC
O 2 V. v CO
,
.
,
3NO • 2NH3— i~-|N2 + 3HjO
KC * 02 — *-C02* H:0
CO * -502 — - *- CO,
CATALYTIC CONVERTER
AIR AQUEOUS NH,
100 r
60
O
60
8
O 40
20
01% Pd. 6V. Cu on Si-alumina
6V. Cu on Si-alumina
J
6CO 700 600 900 1000 liOO
CATALYST 7EM?t»ATU8S *f .
ISEFERSNCE'. U S. PATENT
9. C63)
Figure 5-13. Catalytic Reduction of NO by Ammonia
5-39
-------
• Allows operation of the engine at maximum fuel economy or
power.
Areas of additional R&D work required for system optimization are
as follows:
• Determine optimum catalyst composition.
• Determine catalyst durability.
• Determine resistance to catalyst poison present in the fuel
(Sulfur and metal impurities).
5.4.2.2.2 Gas Turbines
As with reciprocating engines, the most viable control techniques are
engine modifications and exhaust treatment. The comments made for exhaust
gas treatment also apply to turbines but it must be remembered that more than
twice as much air must be handled for an equivalent output. Thus, the exhaust
gas treatment schemes do not seem too practical.
The approaches that are usually taken include combustor chamber design
modification, water injection, modification of fuel properties, and exhaust
gas recirculation. It is generally known that emissions of nitrogen oxides
increase with power level and that power is directly related to maximum local
combustion temperatures. NOV emission can also be directly related to
J\
combustor inlet temperature and, in turn, to compressor pressure ratio.
A frequently-used technique has been to lower the peak flame temperature
by leaning out the primary zone through combustion chamber design. An alter-
9 5
nate method presented by Parikh, Sawyer and London was to increase the
homogeneity of the primary zone composition by using gaseous or vaporized
liquid fuels. Both schemes can create problems in the ability to maintain
flame stabilization and lower lean extinction performance. Reducing the
residence time of the hot gases will also lead to lower concentrations of NO.
Residence time may be decreased by moving the dilution holes upstream or
increasing the flow velocity through the primary zone. Typical reduction of
15 percent are not uncommon for lean primary zone combustors.
Injection of water into the combustor primary zone or injection of steam
94
into the combustion air can typically reduce NOX emission by up to 85 percent
However, large quantities of demineralized water must be handled and engine
maintenance is increased.
5-40
-------
Exhaust gas recirculation has an affect similar to lean primary zone
combustion. Typical results for EGR are shown in Figures 5-14 and 5-15 for
96
oil and gas fired systems respectively .
NASA has been working on the development of low pollutant-generation
combustors ("Clean Combustor Program") for aircraft engines. A great number
of concepts are being tested which include lean primary zone combustors, a
short residence time combustor, combustion which increases the homogeneity
of the primary zone composition through the use of multiple arrays of "swirl-
can" modules or a premix package, and two stage combustors which use a "pilot
combustion zone" (similar to the precombustion chamber diesel engine).
Variable geometry combustors are also being explored to achieve the most
favorable configuration for any load. However, a variable geometry scheme
will not be necessary for stationary gas turbine installations. Details of
97
these configurations are reported in a paper by R. E. Jones . To data none
of the combustor designs have achieved the desired goal for the proposed
1979 EPA limits for aircraft engines but it is felt that some of the designs
will have the potential for further NOV reduction.
A
5.4.3 Cost
There is an overall paucity of reliable data on the costs involved in
implementing combustion modifications on either conventional utility and
industrial boilers or stationary gas turbines and reciprocating I.e. engines.
Much of the cost information is proprietary, and the overall state of definitive
cost analyses is still quite primitive. The data exhibit a wide range of costs
for a given modification on the same type of combustion system. In any case,
available information will be presented in this section, but without extensive
critique or evaluation. The bulk of the discussion will center on utility
and industrial boilers. Limited cost data for stationary I.C. engine and gas
4
turbine modifications were published by McGowin .
The costs of implementing the combustion modification techniques
described in preceding sections is basically the sum of the initial capital
cost, annual capital cost, and annual operating cost (which includes any
cost savings). Based on estimates for these costs, the Esso report presented
the results of a cost effectiveness study performed for NO., control on utility
boilers by means of combustion modification. Since 1969, however, it has
been revealed that a wide variation in the effectiveness of the control
techniques among boilers exists. This problem will require that future
cost-effectiveness evaluations be done on an individual boiler basis.
5-41
-------
100
so
Combustor 6" (SM)
fuel No 20)1
Air Flow 2 Msec
AirlnleUomp «JO°F
Combustor Pressure 70 psu
NO RocirculJlion
(02=210W
• Recircutation
(02=18.7W
/.
°/
°/
x°
800 1000 1200 1400 1(00
Combustor Exit Temperature "F
1800
! DryVolumelric Basis
Figure 5-14.
Effect of Cooled Exhaust Gas Recirculation
on NO Emission (Using Oil as Fuel)
Conditions
Combustor &' Sid
Fuel Natural Gas
~ Air Flow 2 Ibs/si-c
An Inlet Temp 5?5°F
Combustor Pressure 60 psia
Curve I Mo Recirculation
~ Curve II Recirculotion
1209 1410 1600
Combustor Exit Temperature "F
' Dry Volumetric Basis
Figure 5-15.
Effect of Cooled Exhaust Gas Recirculation
on NO Emission (Using Natural Gas as Fuel)
5-42
-------
The most recent data of this sort was published by Blakeslee and
Selker for new and existing tangential, coal-fired utility boilers. This
data is summarized in Figures 5-16 and 5-17. It is felt that these
costs should approximate those for units of other designs, firing different
fuels. The bands of area explicitly show the ranges of the data, and that
retrofitting existing units is always more expensive than if the modification
was included in the original design.
Further data exists on retrofitting a 15 percent flue gas recirculation
98
system on existing wall-fired units operating on gas and oil. Teixeira
states that a probable upper cost limit would be $4.2/KW for a 480 MW retrofit,
occasioned by extensive hardware changes and increased operating costs. Barr
and James13, for the same modification but on a 750 MW gas-fired unit, reported
a cost of $1/KW. It involved a far less complex conversion program, and is
considered the probable lower cost limit.
Most investigators agree that low excess air operation decreases
operating costs by increasing boiler efficiency slightly. This technique
has become standard operating procedure on most existing utility and
industrial boilers. Cost savings afforded by LEA operation are usually
supplanted by additional, concurrent modifications.
As mentioned in Section 5.4.2.2, a commonly-used burner modification
for biased firing is enlargement of the atomizing orifices to accomodate the
higher fuel flow rate caused by out-of-service burners. Southern California
Edison Company experienced a cost of approximately $5000 per unit for this
modification. This technique is generally limited to new and existing gas-
and oil-fired plants. Implementation on existing coal units would necessitate
more elaborate and expensive changes in fuel handling equipment if they are
not currently capable of firing dual fuels. Additional cost estimates were
81
given by Berkau and Lachapelle
Increased operating costs are normally associated with combustion
modifications, but published data is scarce. One set of data, published by
Blakeslee and Selker is shown in Table 5-5. It should be noted that although
the total annual cost increases with boiler size, the operating cost on a KWHR
basis decreases.
5-43
-------
:RFIRE AIR
INDBOX GAS RECIRCULATION
OVEJRFIRE AIR AND WINDBOX
RECIRCULATION
RECIRCULATICN THRU MILLS
ER INJECTION INCLUDING FAN
$DUCT CHANGES
-R INJECTION V.'ITHOUT KAN
1DUCT CHANGES
100 200 300 400 500 600 700 800
UNIT SIZE
(MW)
Figure 5-16. Equipment Costs of NOX Control Methods for Existing
Coal-Fired Units (Heat Transfer Surface Changes not
Included)
5-44
-------
DBOX GAS RECIRCULATION
(30%)
.rOVERFIRE AIR
COMBINED
OVERFIRE AIR AND WINDBOX
_GAS RECIRCULATION
I" RECIRCULATION THRU
MILLS
WATER INJECTION
200
300 400 500
UNIT SIZE
(MW)
600
700
800
Figure 5-17.
Equipment Costs of NOX Control Methods for
Existing Coal-Fired Units (Heat Transfer
Surface Changes not Included)
5-45
-------
TABLE 5-5
1973 OPERATING COSTS OF NOX CONTROL METHODS FOR
NEW COAL-FIRED UNITS (TANGENTIAL); SINGLE FURNACE
CONTROL METHOD
W RATING
EQUIPMENT COSTS 103)
ANNUAL FIIIO CHARGE 1o'$
ADDITIONAL ANNUAL FUEL
OvmriRC
AIR (a*)
100
31
5
450
63
10
750
90
14
WlNDBOX
FLUC GAI
RECIRC. (30!f)
100
350
56
450
1185
190
750
1650
264
COMBINATION
8F 1 AND 2
100
375
60
450
1248
200
750
1800
288
COAL MILL
FLUI GAI
RCCIRC. (17*)
100
300
48
450
1015
162
750
1425
228
WATER
INJECTION
100
160
26
450
560
90
750
B2S
132
C«s' 10 » ......... ......... ......... ......... 147 660 IOS9
ADDITIONAL ANNUAL FAN
Powell COST 103$ ......... 21 95 158 21 95 158 22 100 166 13 58 57
TOTAL ANNUAL COST 103« S 10 14 77 285 422 81 2S3 446 70 262 394 186 8C8 1323
OPERATING COST MILLS/KVM) 0.009 0.004 0.003 0.143 0.117 0.104 0.150 0.121 0.110 0.130 0.108 O.OS7 0.344 0.332 0.327
BASED ON: A. DELIVERED AND ERECTED EQUIPMENT COSTS (+ 10£ ACCURACY). CXCLUOING CONTINGENCY AND INTEREST DURING CONSTRUCTION.
6. 5400 ffl/YR AT RATED Hit AND NET PLANT »t7i RATE OF 9400 BTU/KW-R.
C. 50#/106BTU COAL COST.
D. «50/HP TAN POWER COST, OR J40/HP PCR TEAR.
E. ANNUAL FIXED CHARCE BATE or 16jf.
F. OPERATING COSTS ARE + lOi.
G. DOCS NOT INCLUDE COS~ OF WATER PIPING IN PLANT OR COST OF MAKEUP WATER.
BASE UNIT OPERATING COSTS* FOR COAL FIRED POVCR PLANTS EXCLUDING SOg REMOVAL SYSTEMS.
Jim SHE »W 100 450 750
OPERATING COST MILLS/MM) 16.2 13.5 12.6
•INCLUDES 1S73 CAPITAL COSTS, LABOR, MAINTENANCE, FUEL COSTS +20$ CONTINGENCY +17? INTEREST DURING CONSTRUCTION
Essentially no data were readily available on the costs of implementation
of combustion modifications on industrial boilers. It is anticipated, however,
that such information will be diffuse and generally difficult to interpret
and correlate, directly reflecting the wide spectrum of equipment design and
normal operating conditions .
5.5 SUMMARY
From a systems perspective, the most significant developments in com-
bustion modification technology since the Esso study are the increasing
dependence on coal with the concomitant problem of fuel NOX/ and the formation
of the combustion control program to develop the technology for NOX control.
In this section we have reviewed the problem of NOX formation and the status
of the component areas of the program directed at attacking the problem in
order to identify developmental requirements for systems planning.
Although preliminary identification of chemical and physical mechanisms
in thermal and fuel NOX formation has been made, there is still an inadequate
understanding of the relationship between fuel and equipment parameters and
NOV formation. Accordingly, the program to devise and test modification
A
techniques is broadly based with simultaneous focus on fundamental studies,
pilot scale testing on laboratory scale equipment, and full scale testing on
commercial equipment. The overall short term objective of the program is to
5-46
'°
-------
develop verified, cost effective techniques for retrofit modification of
existing units. Most of the significant reductions in NOX emissions have
resulted or directly benefited from the efforts of this program. The overall
long term objective of the program is to develop optimized control concepts
for new units and to define minimum attainable emission levels. For both the
short and long term studies, the priority development area is combustion
modification techniques for control of fuel nitrogen conversion to NO.
The fundamental studies area of the combustion control program is
primarily a long term effort to develop a basic understanding of NOX formation.
Since the Esso study, the emphasis has been on modeling the individual key
phenomena involved in NOV formation. Significant advances have been made in
A
the areas of fluid flow solution, thermal NO., kinetics, gaseous hydrocarbon
oxidation, and thermal radiation. These results have had the short term yield
of aiding in evaluating data from pilot and full scale tests, and in suggesting
ideas for combustion modification techniques. Only preliminary advances have
been made in the modeling of fuel NOV and of the effects of turbulent mixing
A
on hydrocarbon and NO reaction rates. These are both considered priority R&D
areas. In the long term, the individual models for the key phenomena will be
coupled, refined, and verified by correlation with test data to ultimately
yield predictions of NOX formation.
Combustion modification testing is conducted within the fuels R&D,
process R&D, and field testing component areas of the combustion control
program. These efforts have resulted in operational guidelines for use by
industry in NOV control through combustion modifications. Stationary source
A
combustion or other operating modification techniques, their major NOX reducing
effects, and problems usually associated with them are summarized in Tables
5-6a. and b.
For utility and industrial boilers, the effectiveness of these
modifications on NOV reduction depend on a large number of factors. These
A
include boiler geometry and cleanliness, burner design, spacing, and state
of repair, load, and, most importantly, the fuel itself. All of the techniques
discussed are effective to varying degrees on gas firing due to suppression of
thermal NO., production. The contribution of fuel NOX reduces both the number
of cost-effective techniques and net NOX reduction figures attained by them
for oil and coal fuel. To date, published data have cast doubt on the NOX-
reduction effectiveness of temperature-reduction schemes, such as flue gas
recirculation, for combustion systems firing coal and heavy fuel oils, both
of which contain nitrogen-bearing compounds. By the same token, off-
stoichiometric combustion has been shown to reduce both thermal and fuel NOX,
but more data is required, especially for coal combustion.
5-47
-------
TABLE 5-6a
MODIFICATION TECHNIQUES FOR UTILITY AND INDUSTRIAL BOILERS
Modification Techniques
Major Effect
Major Potential Problems
Low Excess Air Operation
Off-Stoichiometric
Combustion
Flue Gas Recirculation
Reduced Air Preheat
Operation
Load Reduction
Water, Steam Injection
Equipment Modifications:
• "Low NOX" Burner
• Boiler Wash
• widen Burner Spacing
• Tangential firing
(as opposed to wall-
firing)
Oxygen concentration
reduction (Fuel-rich
burner operation)
Fuel-rich burner operation
Reduced residence time of
fuel at peak temperature
Peak temperature reduction
Peak temperature reduction
Peak temperature reduction
Peak temperature reduction
Peak temperature reduction
Provides off-stoichiometric
combustion at burner
Readily fuel/air adjustable
Fuel-flexible
Maintains rated heat
transfer rate
Reduce peak temperature
Reduce interference
between burner flames
Peak temperature reduction
Slower, more controlled,
combustion
Increased furnace slagging
Nearer smoke threshold
Flame instability, smoking
Higher convective section
temperatures
Flame instability
Boiler efficiency reduction
Boiler efficiency reduction
Boiler efficiency reduction
Boiler efficiency reduction
Increased corrosion
Retrofit problems:
Compatibility with existing
furnace
Conversion investment costs
Boiler downtime
Boiler downtime
Maintenance expense
New unit design only;
retrofit cost prohibitive
New unit design only
5-48
-------
TABLE 5-6b
MODIFICATION OR CONTROL TECHNIQUES FOR STATIONARY I.C. ENGINES AND GAS TURBINES
Modification or
Control Techniques
Major Effect
Major Potential Problems
Reciprocating I.C. Engines
Speed vs. Stoichiometry
Decreased Torque Load
(at constant speed)
Decreased Air Manifold
Temperature
Increased Valve Overlap
Exhaust Gas Recirculation
Catalytic Converter,
Armenia as Reducing Agent
(Post Combustion Control
Method)
Water Injection
Precombustion chamber
With speed, NO increases
under fuel-rich and
decreases under fuel-lean
conditions
Peak temperature reduction
Peak temperature reduction
Peak temperature reduction
Peak temperature reduction
Reduction of NO, N02 to
No and 00
Peak temperature reduction
Peak temperature reduct-
tion; Op starvation
Retrofit difficulties;
inability to meet load
demand
Retrofit difficulties;
inability to meet load
demand
Efficiency reduction
Fuel economy reduction
Applicable only to
4-cycle engines
Intake manifold fouling
Additional control system
Operational difficulties
Efficiency reduction
Expensive
Current catalysts sensitive
to impurities in fuel
Increased maintenance;
additional equipment for
water handling
Costly for retrofit
5-49
-------
TABLE 5-6b (Concluded)
Modification or
Control Techniques
Major Effect
Major Potential Problems
Gas Turbines
Lean-Out Primary Zone by
Modifying Combustion
Chamber Design
Water injection
Exhaust Gas Recirculation
Peak temperature reduction
Reduced residence time of
fuel at peak temperature
Peak temperature reduction
Peak temperature reduction
Less control over flame
stabilization
Less control over lower
lean extinction performance
Reduced efficiency
Increased maintenance
Additional equipment for
water handling
Reduced efficiency
Additional control system
Operational difficulties
5-50
-------
SECTION 6
ASSESSMENT OF R&D REQUIREMENTS
Esso concluded the systems study of stationary source NO emissions with
X
a detailed R&D plan in four categories:
• Combustion process studies
• Combustion flue gas treatment
• Noncombustion process studies
• Supporting studies
The priority R&D recommendations were in the combustion process studies area,
which was further subdivided into Basic and Supporting Research, and Applied
R&D. As described earlier, the EPA subsequently formulated an R&D program
which incorporated and expanded upon the Esso R&D plan. The results of these
and related efforts were reviewed in Chapters 4 and 5, and the purpose of this
chapter is to suggest R&D topics for areas identified in that review as requir-
ing further study.
Due to the limited scope of the present study, no attempt has been made
to specify R&D schedules or level of funding. That approach would require a
more comprehensive review of ongoing programs as related to future requirements.
A qualitative ranking of priorities into high, medium, and low categories is
given based on probable impact on emissions for short-term programs, or, low-
risk development for long-term programs.
6.1 COMBUSTION MODIFICATIONS
The overall trend in combustion modification R&D is to establish the re-
lationships between fuel or equipment parameters and the operating conditions
promoting NOX formation. Within this context, the emerging emphasis is on N0x
formation in coal fired units, and on control technology for area sources such
as industrial combustion equipment, 1C engines, and commercial or domestic
heaters.
Table 6-1 summarizes ongoing EPA research (for stationary sources) by
relating R&D study areas to specific contracts in the four areas of fundamental
studies, fuels R&D, process R&D, and field testing and survey. There are
6-1
-------
additional relevant programs which are funded outside the EPA. These are
primarily in the areas of fundamental studies and field testing. Also, be-
tween the EPA stationary source and mobile source programs, there are mutually
beneficial areas that could be exploited.
The following four sections give suggested additions or extensions to
the ongoing programs listed on Table 6-1. These R&D recommendations are
further summarized in Table 6-2.
6.1.1 Fundamental Studies
Several of the more pressing problems in the fundamental studies area
are the development of a basic understanding of fuel NO conversion, the need
X
to relate fundamental studies to measured performance, and, more broadly, the
development of scaling laws for generalizing pilot-scale test results. R&D
suggestions relating to these areas, as well as the ongoing long-term programs,
are given below in the context of the fundamental studies framework presented
in Section 5.
Fluid Flow Solutions; There exists an extensive library of computer
codes for flow prediction in a variety of geometries. The priority items in
this area are, therefore, not with basic code development, but with testing
of auxiliary relations for use in existing codes.
Medium priority:
• Continue use of 2-D recirculating code to test models for swirl,
radiation, kinetics, etc., and to increase numerical stability and
reduce running time.
• Apply 2-D jet flame boundary layer codes to test turbulence models,
mixing effects on kinetics, 2 flow models, luminous radiation ef-
fects, etc. Supplement with experimentation on these effects.
Low priority:
• Initiate use of pressure-velocity method for 2-D recirculating flow
to gradually replace -the stream function-vorticity method.
• Assess use of pressure-velocity method for 3-D flow for obtaining
flow patterns and scaling relations.
Thermal NOxs The high priority items in this area are covered by exist-
ing programs. Supplementary interest areas of medium priority are:
• Determine HCN emissions from fuel-rich flames.
• Utilize results of Esso/Ultrasystems study in a realistic flow situa-
tion, such as 2-D jet flames, with full diffusional effects.
Fuel NOX and 2
-------
TABLE 6-1
SUMMARY OF COMBUSTION RESEARCH SECTION PROGRAM
FUTURE
R & D
AREAS
-S
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FUNDAMENTAL STUDIES
Fluid Flow Solutions
Thermal NOX
Fuel NO,
Turb. Vise.
Turb Mixing/Kinetic Coupling
Radiation
It Droplet, Part Comb.
Hydrocarbon Combustion
FU L R a 0
ffi
cnnnaccnHa
Staged Comb
Burner Opt. for Fuel N,
Radiation Measurement
Corrosion 4 Fouling
Coal Types
Synthetic Fuels
Oil Atom zat ion
Optimized Modification
Optimized Burner Design
PR CESS R S D
Corrosion Studies
Catalytic Comb.
Staging, Overfire Air
Interned. CBN Compounds
Optimized Modification
S Area Sources
FIELD TESTING
• Corrosion for Var. Coals
• Modification for Pulv. Coal
• Emission from I C Engines
• Capability of Gas & Oil
Fired Equipment
• Modifications for Other Coal
Comb.
t Other Fuels
• Instrumentation
4fl*
IS
6-3
-------
TABLE 6-2
RECOMMENDED R&D
R&D Area
Fundamental
Studies
Fuels R&D
Subheading
Fluid Flow
Solutions
Thermal NOX
Fuel NOX
Turbulent
Viscosity
Mixing Effect
On Reaction
Rates
Thermal
Radiation
Off-Stoich-
lometric
Combustion
Burner
Optimization
for Fuel NOX
Program
Continue 2-D code development
Apply 2-D jet flame boundary layer
codes
Pressure-velocity codes for 2-D re-
circulating flow
Pressure velocity method for 3-D
HCN emission in fuel-rich flames
Esso-Ultrasystem codes with diffu-
sional effects
Volatilization + pyrolysis models
Post-pyrolysis heterogeneous carbon
burnout models
Couple particulate combustion with
luminous radiation
Synergism of NOX and S02
HCN
2 Equation turbulence models in re-
circulating 2-D flow code
Nonisotropic turbulence models for
swirling 2-D boundary layer jet flames
Experimental and analytical study of
turbulent premixed and diffusion
flames - simple geometry
Coordinate existing radiation models
with fuel nitrogen study
Determine optimum design parameters
for staged firing with coal
Determine optimum design parameters
for low HO burner
Priority
Medium
Medium
Low
Low
Medium
Medium
High
High
High
High
High
Medium
Medium
High
Med i urn
High
High
New Program/
Continuation
Continuation
New
New
New
Continuation
Continuation
Continuation
Continuation
Continuation
Continuation
Continuation
New
New
New
Continuation
New
New
Reasoning
Incorporate current auxiliary models
Test turbulence model, mixing effects on
kinetics, 2$ flow models, luminous radi-
ation effects
Utilize current technology
Obtain flow patterns and scaling laws
Determine potential as a pollutant
Extend findings to practical flow
situations
Extend Rocketdyne findings into inde-
pendent studies
ii ii H
n ii H
H ii n
Determine potential as a pollutant
Utilize current technology
Verify models in simple flow geometries
Develop models for effect of mixing on
reaction rates
Utilize findings of Rocketdyne study
Present research indicates this to be
most viable NOx control technique for
coal combustion
Effective option for fuel nitrogen
control
-------
Table 6-2. Continued
R&D Area
Fuels R&D
continued
Process R&D
Field
Testing
Subheading
Burner
Optimization
for Thermal NO
Radiation
Measurement
Corrosion &
Fouling
Coal Type
Synthetic
Fuels
Oil Atomiza-
tion
Optimization
Modification
Corrosion
Studies
Off-Stoichio-
metric
Combustion
Intermediate
Bound
Compounds
Optimized
Modification
and Areas
Sources
Catalytic
Combination
Pulverized
Coal -Fired
Equipment
Corrosion &
Slagging
Area
Sources
Program
Determine optimum design parameters
for low NOX burner using low nitrogen
fuels
Determine realistic radiation heat
fluxes for coal, oil and gas
Determine ability to do subscale
corrosion and fouling studies of NOX
control schemes
Systematically test different types of
coal - effect of properties on NOX
emissions
NOX emissions from fuels and equipment
conversion problems
Determine effects of fuel atomization
technique on NOX
Determine optimized modification
schemes for each fuel and process
Perform full scale studies of NOX
control techniques on corrosion and
fouling
Expand full scale testing for staging
on coal combustion
Determine fate of chemically bound
nitrogen in full scale equipment
Continue to expand ongoing programs
to determine optimized schemes;
especially area sources
Exploratory work to determine full
potential
Determine current stationary source
control technology {CSST)
Determine effects of CSST on corro-
sion and fouling
Determine CSST for area sources
Priority
High
Low
High
Medium
Medium
Medium
Medium
High
High
Low
High
Low
High
High
High
New Program/
Continuation
New
New
New
New
Continuation
Continuation
Continuation
Continuation
Continuation
New
Continuation
Continuation
Continuation
Continuation
Continuation
Reasoning
tlay be effective option for thermal NO
as well x
Input to radiation models
Very important factor to determine appli-
cability of controls
jetermine applicability of control tech-
niques over spectrum of coal types
necessary to identify problems of future
fuels
Potential control technique; coordinate
\'ith optimum burner design
necessary for immediate retrofit
Full scale testing will yield the ultimate
data
H n n
Determine if there really is a problem
in full scale equipment
Determine applicability on full scale
equipment
Potential long range option
Coal-fired equipment has highest
priority
Additional data very important
Field data lacking
-------
Table 6-2. Concluded
R&D Area
Field
Testing
continued
Flue Gas
Treatment
Al ternate
Processes
Subheading
Alternate
Fuels
--
Synthetic
Fuels
Advanced
Power
Generation
Cycl es
Program
Exploratory work to determine nature
and extent of problem
Review state of the art
Determine NO problems
Determine NOX problems
Priority
Low
Low
Low
Low
New Program/
Continuation
New
New
New
New
Reasoning
Extent of use and NOX problems are
unknown
May be required for secondary cleanup
Fuels may be extensively used in 1980-
2000
II II M
-------
nitrogen conversion and droplet/particulate combustion. As preliminary results
become available, these could be used as the basis for further, independent, high
priority studies*.
• Volatilization and pyrolysis models of single droplet or particulate
flow. Extend to one or 2-D combustion of a cloud of particles.
• Post-pyrolysis heterogeneous carbon burnout models.
• Coupling of particulate combustion results with luminous radiation
modeling.
• Incorporate Rocketdyne findings in University of Arizona study on
synergism of NO and S0~.
X b
• Establish level of HCN emission due to fuel nitrogen intermediaries.
Turbulent Viscosity; A medium priority effort in turbulence modeling
would benefit the use of computer codes to predict combustion flow fields,
• Test the two-equation turbulence models in a recirculating 2-D flow
code.
• Test nonisotropic turbulence models for swirling 2-D boundary layer
jet flames.
Effects of Mixing on Reaction Rates: This is a high priority area as
flame zone mixing can dominate the reaction rates for combustion and NO,, forma-
X
tion. For developing fundamental understanding, a closely coordinated experi-
mental and analytical study of turbulent premixed and diffusion flames in simple
geometries would be most beneficial.
Thermal Radiation; A continuing effort should be made to incorporate
into existing radiation models results obtained from the fuels nitrogen study
and efforts in other auxiliary areas.
6.1.2 Fuels R&D
This research area derives its nomenclature from the historical inves-
tigations on pilot scale versatile combustion equipment for each "fuel" type,
coal, oil and gas. Basically, it is concerned with subscale experimental stud-
ies on equipment with the flexibility to vary burner parameters or to study in
staging, overfire air, flue gas recirculation, air preheat, etc. Based on the
results of the present study, the following areas of pilot scale activity are
identified as needing further definition.
6-7
-------
Priority
• Off-stoichiometric combustion High
• Burner optimization for fuel nitrogen High
• Burner optimization of thermal nitrogen High
• Radiation measurements Low
• Corrosion, fouling tests High
• Systematic testing of coal types for effects of Medium
chemically bound nitrogen and S/N ratio
• Synthetic fuels Medium
• Oil atomization studies Medium
• Optimum modification scheme for each fuel and process Medium
An indication of priorities, high, medium or low is given for each of
the study areas. High priority areas include those associated with N0x emis-
sions from coal combustion, fuel nitrogen problems, problems associated with
area sources, or where vital information on any important subject is lacking.
Medium priority attention is given to those areas where some information is
available but additional data would be very helpful, or areas that need work
but are not quite as essential for controlling the major NOX sources. Low
priority items generally include long range problems and those areas that
would contribute additional understanding if funds were available.
Each of these fuel R&D areas will be briefly described in the following
paragraphs. Further work is necessary to define exactly what should be done in
each of these areas. As was noted on Table 6-1, the current R&D program covers
most of these areas to some extent but is limited by available funds.
Off-Stoichiometric Combustion (High Priority)
The emphasis in this area should be on the application of off-stoichio-
metric firing techniques to coal combustion. Tests are needed to determine the
effects of the following parameters on staged combustion:
• First stage air/fuel ratio
• Residence time to point of injection of secondary air
• Direction and method of injection of secondary air
• Heat absorption between stages
• Burner variables (swirl, velocities, etc.)
Studies with oil and gas firing would also be of interest.
6-8
-------
Burner Optimization for Fuel Nitrogen (High Priority)
Burner design principles need to be identified to achieve low N0x emis-
sions for fuels with chemically bound nitrogen. The optimum burner design
would achieve the same effect as staging through local combustion aerodynamics.
It is realized that a universal burner for all applications (boilers/ furnaces,
etc.) is not practical, but development would benefit from identification of
general design principles. A burner design for utility boilers may be the best
focal point for this project.
Burner Optimization for Thermal Nitrogen (High Priority)
A different approach to burner design may be desirable when fuel nitro-
gen conversion is not of concern. Although the use of natural gas as a fuel
for utility boilers seems to be on the decline, its combustion will remain a
significant factor for emissions from area sources. Therefore, burner design
principles should be developed for low NOX distillate oil and gas burners. De-
vising an optimized burner design for typical home-heater size combustion sys-
tems would be on approach.
Radiation Measurements (Low Priority)
In order to provide a realistic heat transfer model of the combustion
process, data on radiation heat fluxes from gas, oil and coal flames is essen-
tial. Tests could be performed in a versatile subscale piece of equipment.
However, care must be taken to ensure that wall heat fluxes resemble those in
full scale equipment.
Corrosion and Fouling Test (High Priority)
Since corrosion and slagging problems are of vital concern to utility
boiler operators, it is essential that the detrimental effects of the various
NO control schemes be determined. The possibility of doing accelerated sub-
X
scale corrosion and fouling tests should be investigated as it would, no doubt,
be much cheaper than full scale testing. Many investigators, however, contend
that subscale corrosion tests are not reliably scaled to full scale equipment.
Exploratory tests would be helpful in this regard.
Systematic Testing of Coal Types (Medium Priority)
There are many varieties of coal, due to differing proportions of nitro-
gen, sulfur, carbon-hydrogen ratio, ash, heat capacity and other properties.
It is very likely that a wide range of NO emission magnitudes can result from
6-9
-------
use of these coals. Thus, a systematic study in subscale apparatus is recom-
mended to determine the relative effects of percentage fuel nitrogen, sulfur
nitrogen ratio and other coal properties on NO emission.
X
Synthetic Fuels (Medium Priority)
As was noted in Section 3, considerable research activity will take
place in the next decade aimed at developing synthetic gaseous and liguid fuels
from coal, and oil from oil shale and tar sand. Studies should be initiated
to evaluate the possible NOV emissions from the combustion of such exotic fuels,
X
as well as the concomitant problems (i.e., load derating) of converting exist-
ing plants to these fuels.
Oil Atomization Studies (Medium Priority)
An integral part of an oil-fired combustor design is the manner in which
the oil is atomized. The atomization technique and the mixing patterns will
greatly influence the formation of NO . It is recommended that the current
studies at Rocketdyne be continued and possibly expanded.
Optimized Modification Scheme for Each Fuel Type and Application (Medium Priority)
As was noted in Table 6-1 there are several ongoing studies to determine
the optimum NO control scheme for each fuel and application. It is felt that
X
these types of studies, including periodic evaluation of the status of the
schemes, are valuable and should be contined. Perhaps greater emphasis should
be placed on determining optimized NO reduction schemes for area sources, such
as industrial boilers, furnaces and domestic and commercial heating systems,
using versatile, although not necessarily subscale, equipment.
6.1.3 Process R&D
Process R&D is concerned with the full scale implementation of one or
more control schemes. Recommended R&D study areas and priorities are as follows:
Priority
• Corrosion studies High
• Off-stoichiometric combustion (staging) High
• Intermediate chemically bound nitrogen compounds Low
• Optimized modifications and area sources High
• Catalytic combustion L°w
Each of these areas will be briefly discussed.
6-10
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Corrosion and Fouling Studies (High Priority)
Two full scale corrosion and fouling studies will soon be implemented
(conducted by Combustion Engineering and the TVA). It is recommended this
area of research be greatly expanded. A short study should be undertaken to
determine the most effective means of averting the corrosion and slagging prob-
lems associated with NO control schemes. It would be highly desirable to be
capable of performing subscale corrosion tests as was suggested in Section 6.1.2.
An accelerated corrosion and slagging program in full-scale units should in any
case, be promoted.
Off-Stoichiometric Combustion (Staging) (High Priority)
The findings from the fuels R&D staging studies should be applied to
full-scale equipment to verify the results. The Combustion Engineering and TVA
demonstrations will contribute valuable data, but will not provide much informa-
tion regarding the optimum injection point. Although it is realized that full-
scale testing is rather costly, it is recommended that additional studies be
made.
Intermediate Chemically Bound Nitrogen Compounds (Low Priority)
As was discussed in Section 5, there remains some question as to the fate
of chemically bound nitrogen. That is, whether it is converted to NO, N2 or
even HCN. It is proposed that the fate of these compounds in full-scale equip-
ment be studied to determine how the conversion, especially conversion to HCN
occurs. Results obtained should be coordinated with data from pilot-scale and
bench-scale tests.
Optimized Modification and Area Sources (High Priority)
There are a number of ongoing programs in the process R&D area to deter-
mine or evaluate the optimum NOX control scheme. These programs are of great
value and should be continued. Although programs concerned with controls for
coal combustion in utility boilers should not be de-emphasized, more effort
should be placed on controls for area sources, such as industrial boilers and
furnaces, commercial and home heating systems as well as 1C engines and gas
turbines. These studies may require more funds than are now available. A
number of programs are in the planning stage at EPA .
Catalytic Combustion (Low Priority)
Catalytic combustion has been shown to be a potential low NO emission
combustion mechanism. Some additional exploratory work to determine the full
potential of catalytic combustion should be performed.
-------
6.1.4 Field Testing
Field tests have been used in the past to determine current emission
levels as well as the capability of existing equipment to produce lesser quan-
tities of NO . Much of this work is currently underway or has been completed.
However, the following areas require continuing or additional work.
Priority
• Field testing of pulverized coal-fired equipment High
• Corrosion and slagging for various types of coals High
• Field testing of area sources High
• Alternate fuels Low
Field Testing of Pulverized Coal-Fired Equipment (High Priority)
This test work is an ongoing program at EPA, through Esso Research and
Engineering, to determine levels of NOX emissions and control capability of
existing equipment. This work is providing significant background material
and, in light of many utilities switching to coal in the near future, it is
recommended that studies of this type be accelerated and expanded.
Corrosion and Slagging (High Priority)
The above field tests offer an excellent opportunity to determine the
effect of selected control methods (i.e., low excess air, flue gas recircula-
tion, and off-stoichiometric combustion) on slagging and corrosion for many
types of boilers. This is being done through the Esso field test work on
utility boilers and should be continued and expanded in light of fuel conver-
sion activity.
Field Testing of Area Sources (High Priority)
There has been considerable emission survey work on industrial boilers
and commercial and home heating systems. Additional statistically representa-
tive data for these sources would be worthwhile. Applying N0x reduction tech-
niques to them is the next logical step. In addition to this ongoing work,
emissions and controls for other area sources such as industrial furnaces, sta-
tionary reciprocating 1C engines, and gas turbines need to be defined. In
particular, as was indicated in Section 3, there is a considerable range of NOX
emission estimates for 1C engines. The importance of this source of emissions
requires clarification.
6-12
-------
Alternate Fuels (Low Priority)
Combustion of alternate fuels, particularly waste materials, may have
an associated NO emission problem. Fuels such as pitch and waste products
X
from chemical plants are used in process heaters or are directly incinerated.
Some exploratory work should be performed to determine the nature and extent
of the problem.
6.2 FLUE GAS TREATMENT
Since this area was not extensively explored in the present study, it
is rather difficult to make valid R&D recommendations. Perhaps as a first step
a study should be undertaken to thoroughly review the state of the art and
recommend areas of future research. Some NO researchers interviewed during
X
the course of this survey recommended additional flue gas treatment studies
because this option may be needed as a secondary cleanup scheme to meet more
stringent laws (especially as the population of sources increases). Flue gas
treatment may be the most cost-effective technique for some of the smaller
sources comprising area sources. At this time, however, combustion modification
still seems to be the most promising alternative. •
6.3 ALTERNATE PROCESSES
Some funds should be allocated for monitoring the status of and the
developments in the longer range alternate power generation schemes. These
may include the following:
• Synthetic fuels:
Methanol
Hydrogen
Garbage and waste
Low Btu and High Btu gas
Sewer gas
• Advanced power generation cycles
Fluidized bed boiler
Combined cycle
If, at some future time, one or more of these processes show promise,
additional programs should be initiated to characterize any NO emission prob-
lems associated with such systems.
6-13
-------
REFERENCES
1.* 3ARTOK,W, ET,AL,» 'SYSTEMS STUDY OP NITROGEN OXIDE CONTROL.
METHODS FOR STATIONARY 33URCE8-V3LUME II, I PREPARED FOR NATIONAL AIR
P3LLJTION CONTROL ADMINISTRATION, NTI3 REPORT MO, PB 192-789, E8SO, |969,
2.* ENVIRONMENTAL PROTECTION AGENCY, 'NATIONAL AIR POLLUTANT EMISSION
TREN3S, I9((0»1970,i BY J,H, CAVEMDER, D,S, KIRCMER, A,J, HOFFMAN,
JAN, 1973,
3.* EMISSION DATA PROM NATIONAL EMISSION DATA SYSTEM, NATIONAL AIR DATA
BRANCH, MONITORING AND DATA ANALYSIS DIVISION, OFFICE OF AIR QUALITY,
PLANNING AND STANDARDS, EPA, MARCH 14, 1974.
4.* MCGOWIN,C,R,, 'STATIONARY INTERNAL COMBUSTION ENGINES IN THE UNITED
STATES,1 EPA CONTRACT NO, EHSD 71«
-------
1.4A HOWE«A«1P,D.P,, AND M,H, HOOPER, 'EFFECTS OF COMBUSTION IMPROVING
DEVICES ON AIR POLLUTANT EMISSIONS FROM RESIDENTIAL OIL-FIRED
FURNACES,' PAPER 70*45 AT TMEi 63RD ANNUAL MEETING OF THE AIR POLLUTION
CONTROL ASSOCIATION* ST, LOUIS, MISSOURI, JUNE 14*18, 1970,
15.* PRIVATE DISCUSSION WITH 5,8 MARTIN, COMBUSTION RESEARCH SECTION,
CONTROL SYSTEMS LAB, EPA, FEB, 15, 1974,
16.* HOTTEL, H.C., J.B, HOWARD, 'NEW ENERGY TECHNOLOGY,* MIT PRESS, 1971,
17.* 1FFICE OF COAL RESEARCH, (COAL TECHNOLOGY-KEY TO CLEAN ENERGY,*
1973M974 ANNUAL REPORT, U.S, DEPT, OF INTERIOR, 1974,
18.* 1ARTIN, G.'B,, D.'H, PERSHING, E,E, BERKAU, 'EFFECTS OF FUEL ADDITIVES
ON AIR POLLUTANT EMISSIONS FROM DISTILLATE OIL'FIRED FURNACES,* EPA,
3FFICE OF AIR PROGRAMS, AP-B7, JUNE 1971,
19.* ?ER3HlNG,D,W(, G,B, MARTIN, E'.E, BERKAU, R,E. HALL, 'EFFECTIVENESS
DF SELECTED FUEL ADDITIVES IM CONTROLLING POLLUTION EMISSIONS FROM
RESIDUAL-OIL-FIRED BOILERS,' EAP»650/2«73-031, OCTOBER, 1973.
20.* SNAW,H(, 'REDUCTION OF NITROGEN OXIDE EMISSIDNS FROM A GAS
TURBINE COlBUSTOR BY FUEL' MODIFICATIONS,' ASHC TRANS, JOURNAL-OF
ENGINEERING FOR POWER, 95, 4, P8 301, OCT. J975,
21.*
-------
27 * HAMMONS, G,AM M,S, sums, A, SKOPP, 'STUDIES OF NOX AND sox
'CONTROL TECHNIQUES IN A DEGENERATIVE LIMESTONE FtUIDIZED BED COAL
COMBJSTION PROCESS,' ESS3 R » E COMPANY, PREPARED UNDER CONTRACT
CPA 70*19 pOR DIVISION OP PROCESS CONTROL ENGINEERING OFFICE OF AIR
PR3G*AMS, NAPCA, INTERIM REP3RT, JANUARY 1, l«7l«JUNE I, 1971,
28 » CHAPPELL* G,A., 'DEVELOPMENT OF THE AQUEOUS PROCESSES FOR REMOVING
'NOX FROM FLUE GASESf' PREPARED FDR EPA BY tSSO Rt t E, CO,, EPA
R272051, SEPT., 1972, IF,
29.* FIRST, M.'W.'i AND F.J, VIL2S JR, 'CLEANING OF STACK GASES CONTAINING
HIGH CONCENTRATIONS OF NITROSEN OXIDES,' JOURNAL' OF THE AIR POLLUTION
CONTROL ASSOCIATION, 21, 3, P, 122, MARCH, 1971,
30 » HARDlSON,L.Ct, 'TECHMIOUES FOR CONTROLLING THE OXIDES OF NITROGEN,'
'jJURNAL OF THE AIR POLLUTION CONTROL ASSOCIATION, 20, 6, P377, JUNE, 1970,
31.* LAWRENCt, A.'A.', 'NITROGEN OXIDE EMISSION CDVTROL,1 POLLUTION CONTROL
REVIEW NO, 9, NOYES DATA CORP,, 1972,
32.* PROCESSES RESEARCH, INC., CINCINNATI, OHIO, (AIR POLLUTION FROM
NITRATION PROCESSES,' NTIS-P3217016, MARCH 1972,
33.* PRIVATE DISCUSSION WITH DR, R, NEVILLE, KRE3S ENGINEERING,
MARCH IB, (974.
34.* BARBER, J.C., H,L. FAUCETT, 'CONTROL OF NITR3GEN OXIDE EMISSIONS FROM
MITHIC ACID PLANTS,' PRESENTED AT THE PROCEEDIMG3 OF THE THIRD ANNUAL
INDUSTRIAL AIR POLLUTION CONTROL CONFERENCE, KN3XVILLE, TfNN,,
, 1975,'
35.* SArtDON, A,'H., R.S. SADOW3KI, 'AN EXPERIMENTAL: CORRELATION OF OXIDES
OF NITROGEN EMISSIONS FR3M P3WER BOILERS BASED 31 FIELD DATA,' TRANS,
ASME. JOURNAL OF ENGINEERING FOR POWER, 95, 3, P, Ib5, JULY 1973,
36 * MARTIN, G.B,, E.E. BERKAJ, 'AN INVESTIGATE OF THE CONVERSION OF
VARI1US FUEL NITROGEN' COMPOUNDS TO NITROGEN OXIDES IN OIL COMBUSTION,'
AJCHE NATIONAL MEFTING, THE CQHBUSTION PROCESS t MR POLLUTION, ATLANTIC
CITY, 'JEW JERSEY, AUGUST, 1971,
}7 * AXWORTHY, A.E.', M. SCHUMAN, I INVESTIGATION 3F THE MECHANISM AND
'CHEMISTRY OF FUEL NITROGEN INVERSION TO NITROSEN OXIDES IN COMBUSTION,'
PULVERIZED COAL COMBUSTION SEMINAR, ENVIRONMENTAL, PROTECTION AGENCY,
RESEARCH TRIANGLE PARK, N,C., JUNE, 1973,
33* 3ARTQK,W., V,8, ENGLEMAN, B.G, DEL VALLE, 'LABORATORY STUDIES
'AND MATHEMATICAL MODELING OF NOX FORMATION IN COMBUSTION PROCESSES,'
REPORT GRU.36 N03,71, ESSO RESEARCH AND ENGINEERING COMPANY, LINDEN,
NEW JERSEY, 1971,
R-3
-------
39.* TURNER, D.W., EJ &L., 'INFLUENCE OP COMBUSTION MODIFICATION AND
FUEL NITROGEN CONTENT ON NITROGEN OXIDES EMISSIONS
FROM FUEL OIL COMBUSTION*' ESSO RESEARCH AND ENGINEERING CO,,
40.« STERNLING,C.V.*, J.3.L, WENDT, 'KINETIC MECHANISMS GOVERNING THE KATE
3F CHEMICALLY BOUND SULFUR AMD NITROGEN IN COMBUSTION,* SHELL
DEVELOPMENT COMPANY FINAL' REPORT, EPA CONTRACT EHS»D 7l?45, AUGUST,
1972.'
41.* ApPLETaN,J.P,, J,B, HEYW300, 'THE EFFECTS 3F IMPERFECT FUEL'MR MIXING
IN A BURNER ON NO FORMATION FROM NITROGEN IN TIE AIR AND THE FUEL*1
FOURTEENTH SYMPOSIUM (INTERNATIONAL) ON COMBUSTION, P777 THE COMBUSTION
INSTITUTE* PITTSBURG, 1973,
42.* HEAP,M,P., T,M, LOWES, A^D R. WALMSLEY* 'EMISSION OF NITRIC OXIDE
FROM LARGE TURBULENT DIFFUSI3N FLAMES,i FOURTEENTH SYMPOSIUM
(INTERNATIONAL) ON CDMBUSTICH,P883, THE COMBUSTIDN INSTITUTE, PITTSBURG,
1973.'
43.* CORNELIUS* K,, W.G, AGNErf, (EMISSIONS FROM CDNTINUOS COMBUSTION
SYSTEMS*' PLENUM PRESS, NEW YORK* NtY,, 197?.
44.* LULEY, D.'G.f 'TURBULENT SKIRLING FLAME PREDICTION,' AIAA PAPER
73-631, 1973.
45. * SOSMAN, A.D,* ET AJ,,f 'HEAT AND MASS TRANSFER IN RECIRCULATING
FL3MS,' ACADEMIC PRESS, 1969,
46.* OATANKAR, s.v., o.a. SPALDING*' NUMERICAL PREDICTION OF THREE-
DIMENSIONAL FLOHS,' IMPERIAL COLLEGE REPORT EF/TH/A/46, JUNE,1972,
47. * »ATANKAR* s,v.', AND 3,8, SPALDING* 'A COMPUTER MODEL FOR THREE-
DIMENSIONAL FLOW IN FURNACES*' FOURTEENTH SYMP3SIUM (INTERNATIONAL) ON
COMBJSTION, PbOS THE COM3U3TION INSTITUTE, PITTSBURG* 1973,
48.* WILLIAMS, GCC.', A.F, SAROFIM, 'MODELS FOR NO FORMATION IN COMBUSTION
PROCESSES,! FINAL'REPORT UNDER HEM CONTRACT CPA 22«69»
-------
51.* n SOTErG.'G., 'FORMATION AND DECOMPOSITION DP: NITRIC UXIDt IN
COMBJSTION PRODUCTS OF HYDROCARBON FLAMES,' PRESENTED AT 'AMERICAN FLAME
DAYS'/AMERICAN FLAME RESEARCH COMMITTEE, SEPT 6 AND 1, 1972,
52.* LANCE, H.B,, »NOX FORMATION IN PREMIXED COHSJSTIONi A KINETIC MODEL
AND EXPERIMENTAL DATA,' PAPER SAB AT AICHE SIXTY-FOURTH ANNUAL MEETING
SAM FRANCISCO, CALIFORNIA, NOVEMBER 2B-DECEMBER 2, 1971,
53.* THOMPSON, o,, T.D.' BIQWN, AND J,M, BEER, 'NDX FORMATION IN
COMBJSTION,! COMBUSTION AND FLAME, 19, P69, 1972,
54.* IVERBACH,0(, K,S, BASDEN, AND N,Y, KIROV, 'FORMATION UF NITRIC OXIDL
IN FJEL"LEAN AND FUEL-HIGH FLAMES," FOURTEENTH SYMPOSIUM (INTERNATIONAL)
ON COMBUSTION, P767 THE CQMBJSTI3N INSTITUTE, PITTSBURG, 1973,
55.* 1UWHAN,C,T., 'KINETICS OF' NJTRIC OXIDE FURCATION IN COMBUSTI3N
PROCESSES,! FOURTEENTH SYMPOSIUM (INTERNATIONAL!) ON COMBUSTION, P729,
THE COHUSTlON INSTITUTE, PITTSBURG, 1973,
56.* 34, N3V, 1970,
61- * L'lLLEY, D.G.', N.A. CHIGIER. INON-ISOTROPIC TURBULENT STRESS
DIST1I3UTJ3N IN SNIRLING FL04S FROM MEAN VALUE DISTRIBUTIONS,'
INTERNATIONAL JOURNAL OF HEAT AND MASS TRANSFER, 1«,P,573, 1971,
62. * HOWE, N,'M., c.'w, SHIPMAN,IA TENTATIVE MODELI FOR RATES OF
CQMBJSTION IN CONFINED TURBULENT FLAMES,' TENTH SYMPOSIUM (INTERNATIONAL)
3N C3MBUSTION, PITTSBURGH, PENN,, 1965,
63- « HASON, H,B,, D.B, SPALDING, (PREDICTION OF REACTION RATES IN
TURBJLENT BOUNDARY«LAYER FLOrfS,' PROCEEDINGS OF. THE COMBUSTION
INSTITUTE EUROPEAN SYMPOSIUM, ACADEMIC PRESS, 1973.
R-5
-------
64-» 9UAN, F',, E, MARBLE* AND J,R, KLIEGEL, (NITRIC OXIDE FORMATION IN
TURBULENT DIFFUSION FLAMES,' FOURTEENTH SYMPOSIUM (INTERNATIONAL) ON
C01BJ3TION, P851, THE COMBUSTION INSTITUTE, PITTSBURG, 1973.
65.* FLAGAM,R.C.I J.P, APPLETDN, INITRIC OXIDE FJRMATION FROM FUEL BOUND
NITR1GEN IN AN OIL FIRED BURNER,' 66TH ANNUAL AICHE MEETING,
PHILADELPHIA, PENN,, NOVEMBER, 1973,
66.* JOHNSON, T.R., J,M, BEER7, 'THE ZONE METHOD ANALYSIS OF RADIANT
HEAT TRANSFER- A MODEL FDR LUMINOUS RADIATION, I J, INST, FUEL, P,301,
SEPT, \973.
67 * GIBSON, M.M., B.B. MORGAN, 'MATHEMATICAL MODEL OF COMBUSTION OF SOLID
PARTICLES JN A TURBULENT STREAM WITH RECIRCULATION,' J, INST, FUEL
P.S17. DEC. 1970,
68- * HOTTEL, H.C., A,F SA"»OFH, 'THE STATUS OF CALCULATIONS
OF RADIATION FROM NON-LUMINOUS FLAMES, J, INST. PUEL, P.295, SEPT, 1973.
69- * SEER', J.'M., R.'G. SID3AL, 'RADIATIVE HEAT TRANSFER IN FURNACES AND
COMB'JSTQRS,' ASME PAPER 7Z*MA/HT»29, NOV., 1972,
7°- * ALTENKIRCH,K.A., S,M, SHAHED, R,F, SAHVER, 'NITRIC OXIDE FORMATION
ARDLHD DROPLETS BURNING AT ELEVATED PRESSURES,' COMBUSTION SCIENCE AND
TECHNOLOGY,5,4,P147, JUNE, 1972,
71- * SANDERS, C,F,, EJ AJ.,» 'THE EFFECT OF DROPLET COMBUSTION ON
NITRIC OXIDE EMISSIONS B* DILI FLAMES,' PRESENTED AT WESTERN STATES
SECTION, THf COMBUSTION INSTITUTE, SEATTLE, APRIU 2a, 1972,
72. * ORHATION IN
FUEL DROPLET COMBU3TIUN,' 1ST AMERICAN FLAME DAYS, SPONSORED BY THE
AMERICAN FLAME RESEARCH COMMITTEE, CHICAGO, SEPT. e>-7, 1972,
73. * 3fJACCO,F,V., 'NITRIC DXI3E FORMATION IN DRDPLET DIFFUSION FLAMES,'
FOURTEENTH SYMPOSIUM (INTERNATIONAL) ON COMBUSTTJN, P,831, THE COMBUSTION
INSTITUTE, PITT3BURG, J973,
74. * ANDREWS,R.'L., c,w. SIEGMUND, D,G, LEVINE, 'EFFECT OF FLUE GAS
RECHCULATION ON EMISSIONS FROM HEATING OIL COMBUSTION, ' AIR
POLLUTION CONTROL ASSOCIATION, PREPRINT NO. 68«21,
75. * '
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76-* 3LAKE8LEE, C.E,, A,P, SELKER, 'PILOT FIELD TEST PROGRAM TO STUDY
METHODS FOR REDUCTION OF NOX FORMATION IN TANGENTIALLY COAL FIRED
STEAM GFNERATING UNITS,' PULVERIZED COAL COMBUSTION SEMINAR,
ENVIRONMENTAL PROTECTION AGEMCV, RESEARCH TRIANGLE PARK, N,C,, JUNE,
1973,
77.* 3LAKE3LEE,CgE,', 'RED'JCTIiJN OF NOX EMISSIONS 9Y COMBUSTION
MODIFICATIONS TO A GAS-FINED 250-MW TANGENTIAL-FIRED BOILER,* CONFERENCE
DM NATURAL GAS RESEARCH AND TECHNOLOGY, ATLANTA, GEORGIA, JUNE 5-7, 1972
78-* JLAKESLEE,C,'E.*, H,E,3URBACH, (CONTROLLING NOX EMISSIONS FROM
STEAM GENERATORS,' JOURNAL OF' THE AIR POLLUTION CONTROL ASSOCIATION, 23,
1,1973,
79.* 3ARTOK.W, EJ ALi 'SYSTEMATIC FIELD STUDY OF MOX EMISSION CONTROL
METH303 FOR UTILITY BUILERS, • PREPARED FOR THE OFFICE OF AIR PROGRAMS
ENVIRONMENTAL PROTECTION AGENCY RESEARCH TRIAN3LE PARK, N,C,,
Tl, NTIS NO. PB210-739, ESSO, 1971.
80.* 3ARR,W.H,', 'CONTROL 3F N3 IN POWER PLANT OPERATIONS,1 AIM POLLUTION
CONTROL ASSOCIATION, WEST COAST SECTION, FIFTH TECHNICAL MEETING, OCT.
1970.
81-* 3ERKAU,E.'E., AND 0,6, LACHAPELLE, 'STATUS 3F EPA'S COMBUSTION
PROGRAM FOR CONTROL OF NITROGEN OXIDE EMISSIONS FROM STATIONARY
SOURCES— SEPTEMBER 1972*' SOUTHEASTERN APCA MFETING, RALEIGH, N,C,,
SEPT,' 1972,
82.* 3AGrtELL»F.A, EJ AJ,,, 'UTILITY BOILER OPERATING MODES FOR REDUCED
NITRIC OXIDE EMISSIONS,' JOURNAL OF THE AIR POLLUTION CONTROL
ASSOCIATION, 21, 11, P702, NDV, 1971,
83.* HALSTEAD,C.J., EJ Ai,, 'NITROGEN OXIDES COMTR3L IN G*S FIRED
SYSTEMS USING FLUE GAS RECIRCULATION AND WATER INJECTION,' I .G.T./A, G, A,
CONFERENCE ON NATURAL GAS RESEARCH AND TECHNOLOGY, ATLANTA, GEORGIA,
JJME, 1972,
84.* 3REEN,B.'P.'f 'CONTROL OF THE NITRIC OXIDE MISSIONS FROM FOSSIL FUELED
BOILERS,' THE FOURTH MESTINGHOUSE INTERNATIONAL. SCHOOL FOR ENVIRONMENTAL
HAMA3EMENT, JULY 15*18, 1973,
85.* TEIXEIRA, DfP., R.'E, THOMPSON, 'UTILITY BOILER OPERATING MOOES FOR
REOUEt!) MITRIC OXIDL EMISSIONS WITH OIL FUEL FIRING,! PAPtR 73^310 AT
THE S6TH ANNUAL MEETING IF AIR POLLUTION CONTROL ASSOCIATION, CHICAGO,
JUNE 21-2B, 1973,
86.* C»1PBELL,D,, 'CONTROL OF MOX AND S02 IN CENTRAL POWER GENERATING
STATIONS,' IN PROCEEDINGS, AI* POLLUTION CONTROL ASSOCIATION, MID>*ATLANTIC
STATES SECTION, SEMI-ANNUAL TECHNICAL CONFERENCE ON RECENT DEVELOPMENTS IN
AIR POLLUTION FRDM STATIONARY SOURCES, MAY, 1972,
R-7
-------
87. * MUZIO, L,J,» ET AJj,, 'EMISSIONS FROM SMALL B'JILERS,' PRESENTED AT
WESTERN STATES SECTION, THE COMBUSTION INSTITUTE, LOS ANGELES* OCT.,
1973,'
88. * TURNER, D>., C.W. SIEGMJND, 'STAGED COMBUSTION AND FLUE GAS
RECYCLEI POTENTIAL FOR MINIMIZING NOX FROM FUEL, m COMBUSTION,'
1ST AMERICAN FLAME DAYS, SPONSORED BY THE AMERICAN FLAME RESEARCH
COMMITTEE, CHICAGO, SEPT, 6-7, 1972,
89. * PERSHlNG, D.W., J.H, BROWN, 6,8, MARTIN, F,E, BERKAU, 'INFLUENCb OF
DESISN VARIABLES ON THE PRODJCTION OF THERMAL AND FUEL N(]X FRUM RESIDUAL
311 AND COAL COMBUSTION,' 66TH ANNUAL AICHE MEETING, PHILADELPHIA,
PENNSYLVANIA, NOVEMBER, 1973,
90. * MARTIN, G,, E,E. BF.RKAU, 'EVALUATION OF VARITJS COMBUSTION
MODIFICATION TECHNIQUES FOR CONTROL OF THERMAL A
-------
97 * JONES, R.E., 'ADVANCED TECHNOLOGY FOR REDUCIMG AIRCRAFT ENGINE
' SOLUTION, I ASHE PAPER 7S«HA/AER>2, 1973,
98.* TEIXEIRA, O.P., ' COMBUSTION MODIFICATION FO* POWER PLANT CONTROL,'
IN (COMBUSTION SOURCES Qf. AP POLLUTION AND THEH CONTROL,'CONTINUING
EOUC^TTDN IN ENGINEFRlMGt UNIVERSITY EXTENSION, A.MD THE COLLEGE OF
ENGINICRING, UNIVERSITY 3F CALIFORNIA, BERKELEY, AUG., 1973,
R-9
-------
ADDITIONAL BIBLIOGRAPHY
* AIMAN,W,'R.'/ 'A CRITICAL TEST FOR MODELS OF THE NITRIC OXIDE FORMATION
PROCESS IN SPARK«IGNITION ENGINES*' 14TH SYMPOSIUM INTERNATIONAL) ON
COMBUSTION, P, 8&1, THE COMBUSTION INSTITUTE, PITTSBURGH, 1973,
* AIR POLLUTION CONTROL! ASSOCIATION, (STATE OF THE ART OF AIR
POLLUTION CONTROL TECHNIQUES FOR INDUSTRIAL PROCESSES AND POWER
GENERATION,' SOUTHERN SECTION THIRD ANNUAL INDUSTRIAL AIR POLLUTION
CONTROL CONFERENCE, MARCH, 1973,
* AIR POLLUTION CONTROL ASSOCIATION, 'RECENT DEVELOPMENTS IN
CONTROLLING AIR POLLUTION FROM STATIONARY COMBUSTION SOURCES,' MAY,
1972,
* &IR POLLUTION CONTROL ASSOCIATION, 'FUTURE APPROACHES TO THE CONTROL
OF AIR POLLUTION,I WEST COAST SECTION, FIFTH TECHNICAL MEETING, OCTOBER,
1970,
i
« ALLEN,J,D., 'A REVIEW OF METHODS OF ANALYSIS 'OR OXIDES OF NITROGEN,
JOURMAL OF THE INSTITUTE OF FUEL, XLVI, 38F.'A., EJL *Lt» 'OXIDES OF NITROGEN EMISSION REDUCTION PROGRAM
FOR OIL AND GAS FIRED UTILITY BOILERS' 32ND ANNUAL MEETING OF THE
AMERICAN PDWFR CONFERENCE, ILLINOIS INSTITUTE OF TECHNOLOGY,
APRIL 21*23, 1970.'
* 3ARRETT,L.B., AND T,E, WADDELl, 'COST OF AIR POLLUTION DAMAGE! A
STATUS REPORT,''NTIS AP-85, ENVIRONMENTAL PROTECTION AGENCY RESEARCH
TRIANGLE PARK, NORTH CAROLINA, FEB., 1973,
* 3ARRETT, R.E,, EJ Aii' 'RESIDUAL FUEL OIL-WATER EMULSIONS,'
BATTELLE MEMORIAL INSTITUTE, COLUMBUS, OHIO, P48b666a, JAN,, 1970, MF,
* BARRETT,R.E, H,R, HAZARD, D,W, LOCKLIN, 'DESIGN AND PRELIMINARY
COMBJ8TION TRIALS OF A BURNER FOR FIRING NO, 6 FUEL OIL AT LOW RATES,'
NATIONAL OIL FUEL INSTITUTE, INC,, THIRD NEK AND IMPROVED OIL BURNER
EQUIPMENT WORKSHOP, HARTPORD, CONN,, SEPTEMBER 23-24, 1970,
B-l
-------
* 3ARTOK,W., A,R, CRAWFORD, A, 3KOPP, 'CONTROL OF NOX EMISSIONS
FROM STATIONARY COMBUSTION SOURCES,' AICHE 3RD JOINT MEETING, 'CONTROL
3F NITROGEN OXIDE POLLUTION) SYMPOSIUM, DENVER, COLORADO, AUG. 1970,
* 3ARTOK,W,, A,R, CRAWFORD, A, SKUPP, 'CONTROL' OF NOX EMISSIONS FROM
STATIONARY SOURCES,* CHEMICALI ENGINEERING PROGRESS, 67, 2, P6«, FEB 1971,
* *EER,J,M,, "RECENT ADVANCES IN THE TECHNOLOGY OF FURNACE FLAMES,'
JOURNAL OF THE INSTITUTE OF FUEL, XLV, P.370, JULY, 1972,
* 3ELLf ET'A^., 'NITRIC OXIDE REDUCTION BY CONTROLLED COMBUSTION
PROCESSES,! WESTERN STATES SECTION/COMBUSTION INSTITUTE SPRING
MEETING, APRIL 20-21, 1970,
* BELL, EJ AJ,*> 'COMBUSTIOM CONTROL FOR ELIMINATION OF NITRIC OXIDE
EMISSIONS FROM FOSSIL FUEL PDMER PLANTS,' THIRTEENTH SYMPOSIUM (INTER*
NATIONAL) ON COMBUSTION, P,755, THE COMBUSTION INSTITUTE, PITTSBURGH,
1973,
* 3ERtER,AtWf, J,N, DRISCOLL, AND P, MORGENSTE^N, 'REVIEW AND
STATISTICAL ANL.YS1S OF STACK SAMPLING PROCEDURES FOR THE SULFUR AND
NITROGEN OXIDES IN FOSSIL. FUEL.: COMBUSTION, ' PAPER 70*33 AT THE 63RD
ANNIJ&L MEETING OF THE AIR POLLUTION CONTROL ASSOCIATION, 3T, LOUIS,
MISSOURI JUNE i«-ia, 1970,
* :>ERKELEV,U.C,, 'COHBUSTI3N SOURCES OF AIR POLLUTION AND THE IK
CONTROL,' CONTINUING EDUCATION IN ENGINEERING, U,C,B, EXTENSION, AUG.
1973.
* 3ERNSTEIN,R(H., J.R, EHRENFELD, AND T,R, PARKS, 'COST EFFECTIVENESS
MEASJREMENTS OF EMISSION CONTROL EQUIPMENT FOR INTERMEDIATE«SIZE
BOILFR3,' PAPER 72-74 AT THE 65TH ANNUAL MEETING OP THE AIR POLLUTION
CON-noL ASSOCIATION, MIAMI BEACH, FLORIDA, JUNE 18-22, 1972,
« 5IENST3CK, D(, R,L, AMSLER, E(R, BAUER, 'FORMATION OF OXIDES OF
NITR1GEN IN PULVERIZED COAL COMBUSTION,' JOURNAL OF THE AIR POLLUTION
CONTROL ASSOCIATION, 16, 8, P, 442, AUG, 1966,
3ISHOP, J.W," LI'AJ,.,, 'STATUS OF THE DIRECT CONTACT HEAT TRANSFERRING
BCD BOILER,' ABME 'APLR 6B««IA/FU««, 9EC, 1968,
30BQ,D.L,, LT'Al,, 'A SURVEY OF FUEL AND ENERGY INFORMATION SOURCES,
I,' NTIS DOCUMENT NO, PB1973B6,
B-2
-------
» 30CCIQ,J,, C. WEILERSTEIN, R, EDEkMAN, 'ON HE RELATIONSHIP BETWEE
MODELING AND BASIC EXPERIMENTS IN DEFINING FLAHE.GENERATED POLLUTANTS
FROM REAL SYSTEMS,' 1ST AMERICAN FLAME DAYS, SPONSORED BY THE AMERICAN
RESEARCH COMMITTEE* CHICAGO* SEPT, 6*7* 1972,
* 30WMAN,B.R,, D.T, PRATT, AND C,T, CROWE, 'EFFECTS OF TURBULENT
FIXING AND CHEMICAL KINETICS ON NITRIC OXIDE PRODUCTION IN A JET*
STIRRED REACTOR,' FOURTEENTH SYMPOSIUM (INTERNATIONAL) ON COMBUSTION,
P819 THE COMBUSTION INSTITUTE, PJTTSBURG, 1973,
* 30WMAN, C.'T,', D.J. 3EERY, 'INVESTIGATION OF NO FORMATION KINETIC
IN COMBUSTION PROCESSESI THE METHANE-OXYGENi-NITROGEN REACTION,' IN
EMISSIONS FROM CONTINUOUS COMBUSTION SYSTEMS, W, CORNELIUS AND w,G.
ACNE* EDITORS, PLENUM PRESS, NEK YORK, 1972,
» -»OWMAN,C.T., EJ AJ,,, 'NITRIC OXIDE FORMATION IN COMBUSTION PROCESSES
«ITH STRONG REClRCULATION, ' UNITED AIRCRAFT RfSEARCH LABS, CONN,,
NTIS-PB223003, JUNE 1973,
* 30WMAN,C.T., UN EXPERIMENTAL AND ANALYTICAL INVESTIGATION OF THE
HIGH-TEMPERATURE OXIDATION MECHANISMS OF HYDROCARBON FUELS,'
COMBUSTION SCIENCE AND TECHNOLOGY, 2, 2 AND 3, P, 161, NOV. 1970,
A 30MM*N,C.T., 'INVESTIGATION OP NITRIC OXIDE- FORMATION KINETICS IN
COMBJSTION PROCESSESI THE HY5ROGEN»OXYGEN»NITR3GE.M REACTION, » COMBUSTION
SCIENCE AND TECHNOLOGY, 3, 1, P, 37, APRIL 1971,
* 3RANCH,M.C,, 'THE ENERGY CRISIS AND ALTERNATE FUELS,'
IN 'COMBUSTION SOURCES OF AIR POLLUTION AND THEIR CONTROL* 'CONTINUING
EDUCATION IN ENGINEERING. UNIVERSITY EXTENSION, AND THE COLLEGE OF
ENGINEERING, UNIVERSITY OF CALIFDRNIA, BERKLEY, AUG., 1973,
* 3REEN, B.P., 'OPERATIONAL; CONTROL OF THE NITRIC OXIDE EMISSIONS
FROM STATIONARY BOILERS,' IN EMISSIONS FROM CONTINUOUS COMBUSTION
SYSTEMS, H, CORNELIUS AND H.'B-, AGNEW EDITORS, PLENUM PRESS, NEW YORK,
1972;
* 9REEN,B.P.', T.C. K3SVIC, 'A SURVEY OF NITRIC OXIDE CONTROL FOR
OIL FIRED BOILERS,' ASME AIR POLLUTION CONTROL DIVISION, NATIONAL
SYMPOSIUM, PHILADELPHIA, APRIL 25, 1973.
A 3RElSACHER,Pf, R,J, NICHOLS, AND ri,A, HICKS, 'EXHAUST EMISSION
REDUCTION THROUGH TMO*STAGE COMBUSTION,! COMBUSTION SCIENCE AND
TECHNOLOGY 6,4,P191, DEC,, 1972,
* 3ROWN,T.D., AND V.I, HANBY, 'HIGH INTENSITY COMBUSTION,' PAPER NO,
INST, F-NAFTC»2 AT NORTH AMERICAN FUEL TECHNOLOGY CONFERENCE, INSTITUTE
OF F.JEL, OTTAWA, CANADA, MAY, 1970,
B-3
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* 3R3WN,T.D., 'THE PERFORMANCE OP' VANE SN1RLER3 IN DOMESTIC OIL
BURNERS,1 DIVISIONAL REPORT PRC 72/59«CCRLi FUELS RESEARCH CENTER,
CANADA, DEPARTMENT OF ENERGY, MINES AND RESOURCES, MINES BRANCH, OTTAHA,
JULY 1972,
* 3UETERS,K.A,, EJ AL.,, 'NDX EMISSIONS FROM TAN5ENTIALLY FIRED
UTILITY BOlLERS-A TWO PART PAPER,' 66TH ANNUAL AICHE MEETING,
PHILADELPHIA, PENN,, N3VEMBE*, 1973,
* CALVERT,S.', 'AIR P3LI.UTXW RESEARCH PROBLMS,' JOURNAL OF THE AIR
POLLUTION CONTROL ASSOCIATION, 21, 11, P.694, N3V8 1971,
* GALVERT, S,, ET At,, 'NET SCRUBBER SYSTEM STUDY, VOL, I,
SCRUBBER HANDBOOK,! PREPARED BY A,P,T, INC,, RIVERSIDE, CA, FOR EPA,
EPA 3272118A, JULY, 1972, MF,
• rALVERT, St, ET A^|f 'WET SCRUBBER SYSTEM STJDY, VOL, 2,
FHAL REPORT AND BIBLMG^APHY, ' PREPARED BY A.'P.T,, RIVERSIDE, CA,
FUR FPA, EPA R2<-72118B, JULY, 1972, MF,
* CARETT1,L.S,, 'MODELING POLLUTANT FORMATION IN COMBUSTION
PROCESSES, i FOURTEENTH SYMPOSIUM (INTERNATIONAL) 3N COMBUSTION, PB03,
THE COMBUSTION INSTITUTE, PITTSBJRG, 1973,
* CHAIKIVSKY,M,, C.H. SIEGMUND, 'LOW^EXCESS AIR COMBUSTION OF HEAVY •
FUEL— HIGH- TEMPERATURE DEPOSITS AND CORROSION,' ASME TRANSACTIONS,
JOURNAL OF ENGINEERING F3R P3WER, 87, P.379, OCTt, 1965,
CHAKRABARTI,G.'« C. CSU, 'REDUCTION OF NITRIC OXIDE WITH AMMONIA UN
CHRQMITE AND NICKEL-C3PPER OXIDE CATALYSTS,' ATMOSPHERIC
ENVIRONMENT, 6, 5, P, 297, MAY 1972,
* COSBY, W.'T., 'AN ENGINEERING APPROACH TO THE REDUCTION OF ATMOSPHERIC
POLLUTION FROM COMBUSTION PROCESSES,' JOURNAL IF THE INSTITUTE OF FUEL,
XLVI. 385, P.165, APRIL, 1973,
* CRAIG, R. A.*, H.'O, PRITCHARD, (NITRIC OXIDE 'REDUCTION IN THE PRESENCE
3F FLOWING AND COMBUSTINF H2-AIR MIXTURES,' PRESENTED AT THE CENTRAL
STATES SECTION, THE CQMBJSTnN INSTITUTE, BAR1LESVILLE, OKLAHOMA, MAR,,
1972.
* CRANDAuliri.A., 'THE IMPLICATIONS OF CHANGE! ELECTRIC POWER GENERATION,'
1IT SUMMER STUDY ON CRITICAL ENVIRONMENTAL PROBLEMS, WILLIAMS COLLEGE,
JULY. 1970,
* CRAWFORD, A,R.', E,H, MANNY, W, BARTOK, R,E, HALL, 'NHX EMISSION
CONTROL FOR COAL-FIRED UTILITY BOILERS,' PAPER «232,
AICHF SIXTY-SIXTH ANNUYAL.I MEETING, NOVEMBER, 1973, PHILADELPHIA,
PENNSYLVANIA,
B-4
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* CUFFE, 3.T., R,*f GERSTLE;, 'EMISSIONS FROM C3AL-FIRED POUER PLANTS*
A COMPREHENSIVE SUMMARY,' U,S, OEPT, OP H,E(H;, NTI3 PB171708, 1967,
* DEPARTMENT OF THE INTERIOR, 'UNITED STATES ENERGY, A SUMMARY REVIE*,'
JAN., 1972,
* DEPARTMENT OF THE INTERI3R,IENERGY FOR LIVIN5,' CONSERVATION YEARBOOK
SERIES, NUMBER 6, FEB. i?72,
* 3EPT, 3F THE INTERIOR* (ENERGY FACT SHEETS, 1971,' FEB., 1972
* SERWENTfR.'G.', H.'N.'M, STEWART, 'AIR POLLUTION FROM THE OXIDES OF
MITR3GEN IN THE UNITED KINGD3M,! ATMOSPHERIC ENVIRONMENT, 7,
-------
* P.NGLEMAN, FT AJ^, 'EXPERIMENTAL AND THEORETICAL STUDIES 3F NOX
FORMATION IN A JET-STIRRED CDMBUSTOR,' FOURTEENTH SYMPOSIUM
(INTERNATIONAL) ON COMBUSTION, P755 THE COMBU3TI3N INSTITUTE,
PITTSB'JRG, J973,
* ENVIRONMENTAL PROTECTION AGENCY, 'AIR POLLUTION ASPECTS OF EMISSION
SOURCES* CEMENT MANUFACTURING, A BIBLIOGRAPHY HITH ABSTRACTS,' NTI3-AP9
-------
* ENVIRONMENTAL PROTECTION AGENCY* 'AIR POLLUTION ASPECTS OF EMISSION
SOURCES! NITRIC ACID MANUFACTURINGS BIBLIOGRAPHY WITH ABSTRACTS*I
NTISi AP-93* RESEARCH TRIANGLE PARK* NORTH CAROLINA. MAY 1971,
• ERMENC,E,D,, 'CONTROLLING NITRIC OXIDE EMISSION,' CHEMICAL
ENGINEERING, 77, 12* P19S, JUNE 1970,
* PABUSS,B,M(, AND I,
-------
* SHEEN, p, p., cj AJ,;, 'COMBUSTION CONTROL FOR ELIMINATION OF NITRIC
OXIDE EMISSIONS FROM FOSSIL-FUEL POWER PLANTS,* THIRTEENTH SYMPOSIUM
(INTERNATIONAL) ON COMBUSTION P391, THE COMBUSTION INSTITUTE,
PITT3BURG, 1971.
^LL»H.J., N, BARTOK, "NDX CONTROL FROM STATIONARY SOURCES,* ENVIRON*
SCIENCE AND TECHNOLOGY, 5,
-------
* ^EAPfM.P,, T,M, LOWES, AND R, WALMSLEY, 'THE EFFECT OF BURNER
PARAMETERS ON NITRIC QXI3E FORMATION IN NATURAL* 5AS AND PULVERISED
FUEL FLAMES* ' UST AMERICAN FLAKE DAYS, SPONSORED BY THE AMERICAN FLAME
RESEARCH COMMITTEE, CHICAGO, SEPT, 6-7, 1972,
* HENZfO.J,, (EMISSION REGULATIONS FOR FUEL-BUYING INSTALLATIONS •
EFFECT OF THE CLEAN AIR ACT, I AS*E PAPER 7l-NA/APC«2, MOV, 1971,
* HERRICK,R;L«» (CONSIDERATIONS OF EMISSION CONTROL METHODS AND
DEVICES FOR STATIONARY 83URCES, ' ASME PAPER 71»4A/FU»5, NOV. 1971,
* HEYWDOD, J.B., ET AL,, 'PREDICTIONS OF NITRIC OXIDE CONCENTRATIONS
IN A SPARK-IGNlTlON ENGINE COMPARED NlTH EXHAUST MEASUREMENTS,* SAE
PAPER 710011, AUTOMOTIVE ENGINEERING CONGRESS, DETROIT, MICH,, JANUARY
11-15,
* HEYMOODrJ.'B., T, MJKUS, IPARAMETER8 CONTROLLING NITRIC OXIDE
EMISSIONS FROM GAS TURBINE C3MBU8TDR3,' PAPER 21, ATMOSPHERIC POLLUTION
BY AIRCRAFT ENGINES, AGARD CP125, APRIL, 1973.
* HOLLINDEN, G,A., S,S, RAV, (CONTROL OF NOX FORMATION IN WALL, COAL-
FIRED UTILITY BOlLERSl TVArEPA INTERAGENCY AGREEMENT,1 PULVERIZED
COAL COMBUSTION SEMINAR, ENVIRONMENTAL PROTECTION AGENCY, RESEARCH
TRIANGLE PARK, N,C., JUNE, 1975,
* HOMER, J.B.', AND M,M, BUTTON, 'NITRIC OXIDE FORMATION AND RADICAL
OVERSHOOT IN PREMIXEO HYDROGEN FLAMES,' COMBUSTION AND FLAME, 20, 1 ,P7l ,
PEB; 1973,
* HOWEKAMP,D,P(, 'FLAME RETENTION-EFFECTS ON AIR POLLUTION,* NINTH
ANNUAL CONVENTION, NATIONAL OIL FUEL INSTITUTE, ATLANTIC CITY, N.J.,
JUNE 9-10-11, 1970,
* JAlNrL.K,, E.L. CALVIN, AND R,L, LOQPER, 'STATE OF THE ART FOR
CONTROLLING NOX EMI8SIDNS-PART !., UTILITY BOILERS,' OFFICE OF RESEARCH
AND HONITQRING U,3, ENVIRONMENTAL- PROTECTION AGENCY WASHINGTON, 0. C,,
EPA-R2*72«07ZA, SEPTEMBER 1972,
* JAMES, D.'N.', 'COPING KITH NOXl A GROWING PRHuEM,' ELECTRICAL WORLD,
P.lfl, PEB, ), 1971,
* JAMES, D*E;, 'A BOILER MANUFACTURER'S VIEW 3* NITRIC OXIDE FORMATION,
1 AI* POLLUTION CONTROL ASSOCIATION, WEST COAST SECTION, FIFTH TECHNICAL
MEETING, QCT,, 1970,
« JC1NKE, A,A,, Ej'Aiu, 'REDUCTION OF ATMOSPHERIC POLLUTION BY THE
APPLICATION OF FlUIDIZED-BEO COMBUSTION,' ANNUAL' REPORT PREPARED BY
ARGONNE NATIONAL LABORATORY FOR EPA, JULY 1970«JUNE 1971,
B-9
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* KEAIRNSi D,L,, LI Alt, 'EVALUATION OF THE PLUIDIZED BED COMBUSTION
PROCESS, ' wESTINGHOUSt RESEARCH LABS, PITTSBURGH, PENN,,
EPA.fcOS/2-73i»0 1ST AMERICAN FLAME
DAYS, SPONSORED BY THE AMERICAN FLAME RESEARCH COMMITTEE, CHICAGO, SEPT,
6-7, 1972,
* LAVOIE,A,, B.HEYWODD, J.C,KECK, 'EXPERIMENTAL' AND THEORETICAL STUDY
OF NITRIC QXIDE FORMATION IN INTERNAL COMBUSTION ENGINES,' COMBUSTION
SCIENCE AND TECHNOLOGY, 1, 4, P. 313, FEB, 1970,
* LESOURD,D.'A.', gj AL,,, C3MPKEHENSIVE STUDY JF SPECIFIED A{R POLLUTION
SOURCES TO ASSESS THE ECONOMIC EFFECTS OF AIR 3J&LITY STANDARDS, RESEARCH
TRIANGLE INSTITUTE, DURHAM, N,C,, PB197647, DEC, 1970,
B-10
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* LEVY,.:,, EJ AL.i 'A FIELD INVESTIGATION OPi EMISSIONS FROM FUEL OIL
COMBUSTION FOR SPACE HEATING, * BATTELLE REPORT, API PROJECT SS*S, TO
AMERICAN PETROLEUM INSTITUTE, COMMITTEE ON AIR AID MATER CONSERVATION,
NOVEMBER 1, l«7l,
* LlVESEVtJ.'B,, A.\. ROBERTS, A.KILLIAM8, 'THE FORMATION OF OXIDES OF
NITROGEN IN SOME OXY»PRO"ANE FLAMES,1 COMBUSTION SCIENCE AND TECHNOLOGY*
0, 1, P.* 9, SEPT, 1971,
* LOCKLIN, D,W., A,E, KELLER, R,E, BARRETT, 'THE FEDERAL R+D PLAN FOR
UR-BOLLUTION CONTROL BY COMBUSTION-PROCESS MODIFICATION,' BATTELLE
FINAL' REPORT, CONTRACT CPA 22-69.J47, TO ENVIRONMENTAL PROTECTION AGENCY
, JANUARY 11, 1971,
* LOWES, T.M., £1 Ai,, 'THE. PREDICTION OF FURNACE PERFORMANCE,' 1ST
AMERICAN FLAME DAYS, SPONSORED BY THE AMERICAN FLIA"E RESEARCH
COMMITTEE, CHICAGO, SEPT, 6«7, 1972,
* MACKINNON, D,J,, AND INGRAHAM, T,R,, IMINIMIZJNG NOX POLLUTANTS FROM
STEAM BOILERS,' JOURNAL' OF THE AIR POLLUTION CONTROL ASSOCIATION, II, 6,
P471, JUNE, 1972,
» MARTENEY, P.J.', 'ANALYTICAL STUDY OF THE KINETICS OF FORMATION OF
NITROGEN OXIDE IN HYDROCARBON-AIR COMBUSTION,* COMBUSTION SCIENCE AND
TECHNOLOGY, 1, b, P,
-------
ft MELLOR, A.M., 'CURRENT KINETIC MODELING TECHNIQUES FOR
CONTINUOUS FLOW COMBUSTORSf' IN EMISSIONS FROM CONTINUOUS COMBUSTION
SYSTEMS, W. CORNELIUS AN3 M.'S, AGNEW EDITORS, 'LENUM PRESS, NEW YORK,
1972.'
* MELLOR, A.M., R.O. ANDERSON, R(A( ALTENKIRCH, AND J,H. TUTTLE,
•EMISSIONS FROM AND WITHIN AM ALLISON j«33 COMSUSTOR,' COMBUSTION
SCIENCE AND TECHNOLOGY, 6, 3, P. 169, NOV., 1972,
* HIKUS, T., AND HEV4D1D, J,B,, (THE AUTOMOTIVE GAS TURBINE AND NITRIC
OXIDE EMISSIONS,' REPORT 71-11, FLUID MECHANICS LABORATORY, DEPARTMENT
OF MECHANICAL ENGINEERING, MASSACHUSETTS INSTITUTE OP TECHNOLOGY, JUNE,
1971,
* MITCHELL, R,E,, 'MATHEMATICAL MODEL FOR THE RATE OF NO PRODUCED IN
COAL FIRED UTILITY BOILERS,! FUELS RESEARCH LABORATORY, DEPARTMENT OF
CHEMICAL ENGINEERING, MASSACHUSETTS INSTITUTE OF TECHNOLOGY, JAN. 1971,
* -inORE, J., 'THE EFFECTS OF ATMOSPHERIC MOISTURE ON NITRIC OXIDE
!»ROOJCTION, I 'COMBUSTION AND FLAME, 17, P265, 1971,
* MOVER, C,B., R.A, BROrtN, R,J. SCHREIBER ' A SURVEY OF THE EFFECTS OF
COMBJSTION MODIFICATIONS ON PARTICULATE EMISSIONS,* AEROTHERM FINAL REPORT
7«»91, FOR EPA CONTROL SYSTEMS LAB, RESEARCH TRUNGLE PARK, NORTH
DEC.' 1973.
* MULLAN, J.'W,, 'PROJECTED COAL SUPPLIES UNDER ENVIRONMENTAL
CONSIDERATIONS,' PAPER NT. 73-60, APCA 66TH ANNUAL MEETING, JUNE 1973,
* HUZIO, L.'J., R.P, WILSON, EXPERIMENTAL COM3JSTOR FOR DEVELOPMENT OF
PACKAGE BOILER EMISSION CONTROL TECHNIQUES » PHASE I OF III
ULTRASYSTEM5 INC,, REPORT, CONTRACT NO, 68"02'0222 FOR API AND EPA,
JULY, 1973.
* MYERS, P.S,, ICOMBUSTION PROBLEMS IN AUTOMOTIVE AIR POLLUTION,*
FOURTEENTH SYMPOSIUM, (INTERNATIONAL) ON COMBUSTION, P871, THE
COMBUSTION INSTITUTE, 1973',
* MYERS, P.S,, 'NATION'S COST/BENEFIT RATION WEIGHS HEAVILY ON AUTO
EMIS3inNS,i SAE JOURNAL, 76, 3, P20, MARCH 1970,
* NATIONAL COAL BOARD, LONDON, ENGLAND, FLUI3ISED COMBUSTION CONTROL
GROU1*, 'REDUCTION OP ATMOSPHERIC POLLUTION, MAIN REPQRTI PREPARED FOR
EPA, SEPTEMBER, 1971g
B-12
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• NATIONAL. COAL BOARD, LONDON, ENGLAND, PLUIOISED COMBUSTION CONTROL
GROUP, 'REDUCTION OF ATM3SPHERIC POLLUTION APPENDIX 1, EXPERIMENTS
WITH THE 36 IN, COMBUSTO*, (TASK I),' PREPARED FOR CPA, SEPTEMBER 1971,
« NATIONAL REFERRAL CENTER FOR SCIENCE AND TECHNOLOGY, ' A DIRECTORY OF
INFORMATION RESOURCES IN THE UNITED STATES,! LIBRARY OF CONGRESS, WASH,,
JUNE J967,
* 4EMHALL* H.K,, 'KINETICS OF ENGINE. GENERATED NITROGEN OXIDES
AND CARBON MONOXIDE,* TWELFTH SYMPOSIUM (INTERNATIONAL) ON COMBUSTION,
P603, THE COMBUSTION INSTITUTE, PITTSBURG, 1969,
* MEWHALLV H,K(, AND 8,M, SHAHED, 'KINETICS OF, NITRIC OXIDE FORMATION
IN HIGH-PRESSURE: FLAMES,* THIRTEENTH SYMPOSIUM (INTERNATIONAL) ON
COMB'JSTION, P381 THE COMBUSTION INSTITUTE, PITTSBURG, 1971,
* NOR3TEK, E.R., AND A,H, LEFEBVRE, (EFFECTS 3F' FUEL INJECTION METHOD
ON GAS TURBINE"CQMBUST3R EMISSIONS,' IN EMISSIONS FROM CONTINUOUS
CQMBJSTION SYSTEMS, Wt C3RNELHU3 AND WtG, AGNEW EDITORS, PLENUM PRESS,
NEM YORK, 1972.
* 10FERS,j;,C, CARRIER, 'MODELLING OF GAS TUR3INE COMBUSTORSl
CONSIDERATIONS OF COMBUSTION EFFICIENCY AND STABILITY," TRANS, ASME,
JOURNAL OF ENGINEERING FDR PDWER, 95, 2, P, 105, APRIL 1973,
* DP3AHL, A.H., AND R,C. SEAGRAVE, * THE EFFECT 3F OSCILLATORY
COMBISTION ON THE FORMATION OF ATMOSPHERIC POLLUTANTS,* COMBUSTION AND
FLAMF, 1«, 3, P325, JUNE. 1970,
* 1«CONNOR,J.R., J(F. CITAREIIA, 'AN AIR POLLUTION CONTROL COST STUDY
OF THE STEAM-ELECTRIC PQ'IER GENERATING INDUSTRY,! JOURNAL OF THE AIR
POLLUTION CONTROL ASSOCIATION, 20, 5, MAY 1970,
R,E.f CfS. SAMliELSCN, 'VEI.UCI1Y MEASUHfcMEMTS IN A PREMIXED
FLAML by L»SER ANEMOMETRY,I PHEstmtD AT THE 1973 FALL MEETING UK THE
WESTERN STATES SECTION OF THE CHMBUSTION INSTITUTE, LOS ANGEI.LS,
CALIF., OCT,
* 3ERSHING, D.H;, J.«l, BROMN, E,E, BERKAU. 'RELATIONSHIP OF BURNER
DESISN TO THE CONTROL OF NOX EMISSIONS THROUGH COMBUSTION MODIFICATION,'
PULVERIZED COAL COMBUSTION SEMINAR, ENVIRONMENTAL1 PROTECTION AGENCY,
RESEARCH TRIANGLE PARK, N.CF, JUNE, 1973,
* PERSHING, o,w;, E.'E, BERKAU, 'THE CHEMISTRY IF NOX FORMATION AND
CONTROL THROUGH COMBUSTION M3DIFICATIONS, * ENVIR1NMENTAL PROTECTION
AGENCY, RESEARCH TRIANGLE' PARK, NORTH CAROLINA, AUGUST, 1972,
* ȣR8HING, DX, E.E, BER
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* PGMPEI, p., AND HEYWOOD, J,B,, 'THE ROLE OF HIKING IN BURNER-
GENERATED CARBON MONOXIDE AND NITRIC OXIOE»' COMBUSTION AND FLAME,
* PRATT, D.T,, n AU, ICOIPARISON OF FOUR SIMH.E MODELS OF STEADY
FISH COMBUSTION OF F'YROLYZED METHANE AND AIR,* COMBUSTION SCIENCE AND
TECHNOLOGY, 6, 3, P187, NOV., 1972.
* °RATT,D.T., P.C. MALTE, 'FORMATION OF THERMAL! »ND PROMPT NDX IN A
JET-STIRRED COMBUSTOR,' "RESENTED AT ?STH NATIONAL AICHL MEETING,
DETROIT, MICHIGAN, JUNE, 1973.
* 9ROCE3sr.S RESEARCH, INC., 'AIR POLLUTION H31 FUEL COMBUSTION IN
STATIONARY SOURCES,1 EPA R273241, NTIS PB*2223«l, OCT., 1972. (MF)
* auAN, v., J.R. KLIEGEL, N. BAYARD DE VOLO, D,P, TEIXEIRA,
I ANALYTICAL' SCALING OF FL.OWFIELD AND NITRIC OXIDE IN COMBUSTOKS, '
PULVERIZED COAL COMBUSTION SEMINAR, ENVIRONMENTAL' PROTECTION AGENCY,
RESEARCH TRIANGLE PARK, N,C., JUNE, 1973,
* 3UAN, V., C.A.' BODEEN, AND D.P, TEIXEIRA, 'NITRIC OXIDE FORMATION
IN RFCIRCUL'ATING FLOWS,* COM3USTION SCIENCE AN) TECHNOLOGY, 7, 1, P65,
1973.
* 9ISSER, H.E.,* POWER AND THE ENVIRONMENT* A BJTENTIAL CRISIS IN ENERGY
SUPPLY,' ILLINOIS STATE GEOLOGICAL SURVEY, ENVIRONMENTAL GEOLOGY NOTES,
NUMBER 40, DEC,, 1970f
RITCHIMGS, FtA. 'TRENDS IN ENERGY NEEDS,' A31E PAPER 71f-«A/ENER»3,
f 1971,
* 10BISON, E.Bf, ET A!,, ISTUDY OF CHARACTERIZATION AND CONTROL OF AIR
POLLJTANTS FRDM A FLUIOIZED-3ED COMBUSTION UNIT) THE CARBON-BURNUP
CELL.' PREPARED BY POPE, EVANS, AND ROBBINS Ftl* EPA, FEBRUARY, 1972.
» SAHJE1.3EN, G.3., R.E. f'CC<, 'POLLUTANT FCJ^MftTUN JN KEACflNU
Wllri Rt:iRCULAlTCjM, ' PREStNTfO 4T THE 1«»72 FALL MEETI\G UF THE
-itrnrjN :IF THE coM3usH;i^ iN&UTijTt, M-JNTC^LV, CALIF., OCT.
* 3AHUELSEN, G,0., E.S, STARKMAN, 'ANALYTICAL' AND EXPERIMENTAL
INVESTIGATION OF AN AMMONIA/AIR OPPOSED REACTING JET,1 COMBUSTION
SCIENCE AND TECHNOLOGY, 5, 1, P31, MARCH, 1972,
* 3ANTOLERI, J.J., R.D, ROSS, FAST REACTION 3J«NER DESIGNS
MINIMIZE NOX EMISSIONS,' PAPER 73»-303 AT THE 66TH ANNUAL MEETING
OF THE AIR POLLUTION CONTROL ASSOCIATION, CHICAGO, JUNE 24"28, 1973,
* SARUFIM, A.F., AND J.H. POHU, 'KINETICS OF NITRIC OXIDE FORMATION
IN P9EMIXED LAMINAR FLAMES,' FOURTEENTH SYMPOSIUM (INTERNATIONAL) ON
COMBJSTION, P739, THE COMBUSTION INSTITUTE, PITT3BURG, 1974,
B-14
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* SAWYER,R.F,, N.P, CERNANSKY, A.K, OPPENHEIM, 'FACTORS CONTROLLING
POLLUTANT EMISSIONS FROM GAS TURBINE ENGINES,' PAPER 22, ATMOSPHERIC
POLLUTION BY AIRCRAFT ENGINES, A&ARD CP 125, APRIL, 1973,
* SAWYER,R,P., DfPtTEIXEIRA, E,S(STARKHAKI, 'AIR POLLUTION
CHARACTERISTICS OF GAS TURBINE: ENGINES,' TRANS, ASME, JOUNRAL OF
ENGINEERING. FOR POWER, 91, 4, P, 290, OCT. 1969,'
* SAWYER, R.F,, 'EXPERIMENTAL STUDIES OF CHEMICAL PROCESSES IN A
MODEL) GAS TURBINE COMBUSTQR,' IN EMISSIONS FROM CONTINUOUS COMBUSTION
SYSTEMS, N, CORNELIUS AND H.5, AGNEW EDITORS, PLENUM PRESS, NEW
YORK, 1972,
* 3AWYER, R.F,, E.S. STARKMAN, 'GAS TURGINE EXHAUST EMISSIONS,' SAE
PAPE3 680462, MID-YEAR MEETING, DETROIT, MICH., MAY 20«24, 1968,
* SCHAUB,F.S,,K;V,8EIGHTOL» 'N3X EMISSION REDUCTION METHODS FOR LARGE
BORE DIESEL1 AND NATURAL 5AS ENGINES,I ASME PAPER 71-WA/OGP-2, MOV, 1971.
* SCHIRMER, R.M,', 'EFFECT 3F FUEL COMPOSITION 3N PARTICIPATE
EMISSIONS FROM CASE TURBINE ENGINES,' IN EMISSIONS FROM CONTINUOUS
CCHB.JSTI3N SYSTEMS, w. CORNELIUS AND W,G, SAGNEH EDITORS, PLENUM
PRESS, NEW YORK, 1972.'
* SCHRETER, R,E.'» L.'G, POE, AND E,M, KUSKA, 'INDUSTRIAL BURNERS •
TODAY AND TOMORROW,' MECHANICAL ENGINEERING, 92, 6, P,28, JUNE 1970,
* 3EABROOK, H,'H.', B.P, BREEN, 'A PRACTICAL APPROACH TO NOX REDUCTION
IN UTILITY BOILERS,' AMERICAN POWER CONFERENCE, CHICAGO, APRIL 18*20,
I972,i
* 3EERY,D.J.'» C.'T,BOWMAN, 'AN EXPERIMENTAL AND ANALYTICAL STUDY OF
METHANE OXIDATION BEHIND SHOCK WAVES,' COMBUSTI3N AND FLAME, 1U, 1,
P, 37, 1970,
* SHAMED, S.M.", AND H,K, NEWHALU 'KINETICS DF NITRIC OXIDE FORMATION
IN PROPANE.AIR AND HYDROBEN*AIR»DILUENT FLAMES,' COMBUSTION AND
FLAME, 17, P131, 1971,
ft SHAW, H, 'NOX REDUCTION IN GAS TURBINES BY FUEL MODIFICATION,'
1ST AMERICAN FLAME (JAYS, SPONSORED BY THE AMERICAN FLAME RESEARCH
COMMITTEE, CHICAGO, SEPT, 6-7, 1972,
* SHAW, Mt, 'THE EFFECTS OF, HATER, PRESSURE, AND EQUIVALENCE RATIO ON
NITRIC OXIDE PRODUCTION IN GAS TURBINES,' ASME PAPER NO, 7J««A/G7-1,
, 1973,
B-15
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* 3HAW, J.'T., "A COMMENTARY DN THE FORMATION, INCIDENCE, MEASUREMENT
AN3 CONTROL OF NITROGEN OXIDES IM FLUE CAS, i JDU'NAL OF THE INSTITUTE
3F FJEL, XLVI, 385, P170, APRIL, 1973,
* 3HOFF3TALL, D.'R,, D.H, LARSON, 'AERODYNAMIC CONTROL OF NITROGEN
3XIDES AND OTHER POLLUTAMTS FROM FOSSIL FUEL CDM3USTIQN VOLUME 1, DATA
ANALYSIS AMD SUMMARY OF CONCLUSIONS, VOLUME 2, RArf DATA AND EXPERIMENTAL
EQUIPMENT,! PREPARED BY IGT FOR £PA, OCTOBER* 1973,
* SHlFFSTALLfO.R., D,H, LARSON, (AERODYNAMIC C3NTROL OF NITROGEN
3XIOES AND OTHER POLLUTANTS FROM FOSSIL FUEL CJM3U3TION VOLUME I, DATA
ANALYSIS AMD SUMMARY OF CONCLUSIONS, I I,GfT. FINAL REPORT, EPA CONTRACT
68-02-0216, OCTOBER, 1973,
* 9IRIGNANO, W.Af, '3NE-OI1ENSIUNAL ANALYSIS DP: COMBUSTION IN A
ION ENGINE,' COMBUSTION SCIENCE AND TECHNOLOGY, 7, P99, 1973,
SMITH, M.S., C.N. GH'JBER, 'ATMOSPHERIC EMISSIONS FROM COAL
. AN INVENTORY GUIDE,1 U,S. DEPT, OF HEW, NTIS PB170851, APRIL
* SPAI.DIMG, n.B.', 'MATHEMATICAL MODELS OF CONTINUOUS COMBUSTION,'
IN MISSIONS FROM CONTINUOUS COMBUSTION SYSTEMS, «l, CORNELIUS AND
rf.Gj AC.NEH EDITORS, PLENUM PRESS, NEM YORK, 1972,
* STANFORD RESEARCH INSTITUTED 'PATTERNS OF ENERGY CONSUMPTION IN THE
UNITED STATES,' PREPERED FOR THE OFFICE OF SCIENCE AND TECHNOLOGY,
rfASH., D,C., JAM,, 1972,
* STARKMAN, E.3.', EJ AJ,^ 'THE ROLE OF CHEMISTRY IN GAS TURBINE
EMISSIONS,' TRANS^ ASME JOURNAL OF ENGINEERING FOR POWER, 93 SERIES A,
3, P333, JULY, 1971,
* STERNLlNr.,C.'V.', J.3.L, WENDT, 'ON THE OXIDATION OF FUEL NITROGEN
IN A DIFFUSION FLAME,* IN-HOUSE, SHELL DEVELOPMENT CO,, HOUSTON, TEXAS,
AMD JNTVERSITY OF ARIZONA, TUCSON, ARIZONA, 1972,
A STERNLING,C,V;, J.'D.L, WENDT, K(C, YOUN, 'MATHEMATICAL MODELS FOR
THE FORMATION UP POLLUTANTS IN FURNACES SURVEY OF CURRENTLY AVAILABLE
MODELS,' SHELL DEVELOPMENT CDMPA.NY FINAL REPORT, EPA CONTRACT EHS-O-TI-
«5,AUG., 1971.
* THOMPSON, D,', T.D, BROWN, AND J,M( BEER, (FORMATION OF NO IN A
METHANE»AIR FLAME,' FOURTEENTH SYMPOSIUM (INTERNATIONAL) ON COMBUSTION
P787 THE COMBUSTION INSTITUTE* PITTSBURG, 1973,
* THOMPSON, o. P., EJ iLe» ' 'SURVEY OF DOMESTIC* COMMERCIAL AND
COMT^ACT NO, 68«02-02«1 AUGUST, 1972,
INDUSTRIAL HEATING EQUIPMENT AND FUEL USAGE,' CATALYTIC, INC,, EPA
B-16
-------
* THOMPSON, R.E.', D,P, TEIXEIRA, 'THE EFFECTIVENESS OF COMBUSTION
CONTROL IN REDUCING NOX PQR 31 L FIRED POWER PLANT BOILERS,' PAPER
P-115 AT CENTRAL 3TATt3 SECTION, THE COMBUSTION INSTITUTE, MARCH 27«2B,
1973,
* TOMANY, J.'P;, R.R. KOPPANG, AND H,L, SURGE, u SURVEY OF NITROGEN.
OXIDES CONTROL TECHNOLOGY AND THE' DEVELOPMENT 3Fi A LOW NOX EMISSIONS
COMBJSTOR,! TRANS, ASMS JOURNAL 3F ENGINEERING FIR POWER, 93 SERIES A,
!, P293, JjLY, 1971,
LiINDEN, NEW JERSEY, SEPT,,
* TUTTLE, J.'H,, R,A. ALTENKIRCH, AND A,M, HELLO*, 'EMISSIONS FROM AND
MITHIN AN ALLISON J»33 COMBUSTOR III THE EFFECT OF INLET AIR TEMPERATURE
,l COMBUSTION SCIENCE AN9 TECHNOLOGY, 7, P125, 1973,
* VINSON,C.B,, R,I,KERMODE, u MATHEMATICAL MODEL FOR SIMULATION OF
THE 3YNAMIC BEHAVIOR OF THE TYCO PROCESS FOR 832 AND NQX REMOVAL,'
ATMOSPHERIC ENVIRONMENT, 7, 7, P, 723, JULY 1973,
* VQLLMEIM, G,, 'CATALYTIC AFTER-BURNING, A METHOD OF PURIFYING FLUE
GASES, I FOURTEENTH SYMPOSIUM (INTERNATIONAL) ON COMBUSTION, P6S1, THE
COMBUSTION INSTITUTE, PITTSBURG, 1973,
* rfAtTHER, E.G., U RATING OF THE MAJOR AIR POLLUTANTS AND THEIR
SOURCES BY EFFECT,' JOURNAL OF THE AIR POLLUTION CONTROL ASSOCIATION,
22, 5, P352, MAY, 1972,
* *AS3ER,J,H., E,E, 9ERKAU, D(W, PERSHING, 'COMBUSTION INTENSITY
RELATIONSHIP TO AIR POLLUTION EMISSIONS FROM A
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* 4ILLIAMS, G.C.", A.F, 3AR3PIM, AND N, LAMBFRT, (NITRIC OXIDE
FORMATION AND CARBON M3N3XIDE. BURNOUT IN A COMPACT STEAM GENERATOR,!
IN EMISSIONS FROM CONTINUOUS COMBUSTION SYSTEMS, 4, CORNELIUS AND
W,G.' AGNErf EDITORS, PUCNJM PRESS, NEW YORK, 1972,
* rfjTHERSPOON, Rf, ET.Al., I60VERNMENTAL APP«DACHE3 TO AIR POLLUTION
CONTROL,- A COMPENDIUM AND ANNOTATED BIBLIOGRAPHY,! NTIS PB203M1, JULY
1971.
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TECHNICAL REPORT DATA
(Please read luaruetions on the reverse before completing)
i REPORT NO.
EPA-650/2-74-091
3 RECIPIENT'S ACCESSION-NO.
4 TITLE AND SUBTITLE
Systems Analysis Requirements for Nitrogen Oxide
Control of Stationary Sources
5. REPORT DATE
September 1974
6 PERFORMING ORGANIZATION CODE
7 AUTHOR(S)
R.A. Brown, H.B. Mason, andR.J. Schreiber
8. PERFORMING ORGANIZATION REPORT NO
74-98
9 PERFORMING ORG 'VNIZATION NAME AND ADDRESS
Aerotherm/Acurex Corporation
485 Clyde Avenue
Mountain View, California 94042
10 PROGRAM ELEMENT NO.
1AB013; ROAP 21ADE-029
11 CONTRACT/GRANT NO
68-02-1318 (Task 3)
12 SPONSORING AGENCY NAME AND ADDRESS
EPA, Office of Research and Development
NERC-RTP, Control Systems Laboratory
Research Triangle Park, NC 27711
13. TYPE OF REPORT AND PERIOD COVERED
Final: 12/73-2/74
14 SPONSORING AGENCY CODE
15. SUPPLEMENTARY NOTES
16 ABSTRACT^ report gives results of a study to identify systems requirements for the
control of nitrogen oxide (NOx) emissions from stationary sources. It evaluates
developments in the character of NOx emission sources and in NOx control tech-
nology. It is concluded that planning priority should be for coal-fired utility and
industrial boilers, followed by stationary internal combustion (I. C.) engines. The
most attractive short- and long-term option for control of NOx emissions is com-
bustion modification technology. The priority items are development of techniques
for control of the conversion of fuel-bound nitrogen to NO, and development of com-
bustion modifications for the major area sources such as pipeline I.C. engines, and
commercial and domestic combustion units.
KEY WORDS AND DOCUMENT ANALYSIS
DESCRIPTORS
b IDENTIFIERS/OPEN ENDED TERMS
c. COSATi Field/Croup
Air Pollution
Nitrogen Oxides
Combustion
Coal
Boilers
Internal Combustion
Encines
\ir Pollution Control
stationary Sources
Combustion Modification
Fuel Conversion
Utility Boilers
Industrial Boilers
13B
07B
21B
21D
13A
21G
8 DISTRIBUTION STATEMENT
Unlimited
19 SECURITY CLASS /Tnu Report)
Unclassified
21 NO. Or PAGES
165
Unclassified
(Thapagel
EPA Form 2220-1 (9-73)
T-l
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