THE FEDERAL
R&D PLAN FOR AIR-POLLUTION CONTROL
*
BY COMBUSTION-PROCESS MODIFICATION
Final Report
prepared under Contract CPA 22-69-147
January 11, 1971
for
Air Pollution Control Office
ENVIRONMENTAL PROTECTION AGENCY
BATTELLE MEMORIAL INSTITUTE
Columbus Laboratories
505 King Avenue ' \
Columbus, Ohio .432&1
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THE FEDERAL
R&D PLAN FOR AIR-POLLUTION CONTROL
BY COMBUSTION-PROCESS MODIFICATION
Final Report
Contract CPA 22-69-147
to
Air Pollution Control Office
ENVIRONMENTAL PROTECTION AGENCY
January 11, 1971
Coordinating Editors
David W. Locklin
Albert E. Weller
Richard E. Barrett
Contributing Authors
Edgar S. Cheaney
Frederick A. Creswick
Richard B. Engdahl
Herbert R. Hazard
Joseph A. Hoess
Arthur Levy
Abbott A. Putnam
William T. Reid
Philip R. Sticksel
Joseph F. Walling
BATTELLE MEMORIAL INSTITUTE
Columbus Laboratories
505 King Avenue
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ACKNOWLEDGMENTS
The Battelle study team acknowledges the helpful comments and sugges-
tions of Dr. Kay H. Jones, Project Officer, representing the APCO Office of
Science and Technology. Additional information was furnished during the course
of the study by other staff within APCO and by personnel of other government
agencies, the Center for Air Environment Studies, various universities, research
organizations, trade associations, and industrial companies.
Members of the Battelle study team are identified as authors of individual
chapters; however, contributions of other staff are acknowledged, especially the
editorial guidance of Dolores M. Landreman.
ii
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ABSTRACT
This report presents the results of a study conducted by a team at
Battelle-Columbus for the Air Pollution Control Office to (1) identify gaps in
combustion technology, particularly in the understanding of how combustion
processes may be modified to reduce pollutant emissions, and (2) recommend a
comprehensive 5- Year Plan with priorities for effectively allocating resources for
APCO-supported combustion R&D directed toward meeting projected needs for
air-pollution control of energy-conversion systems by combustion modification.
The resulting Plan includes only R&D for modification of the combustion process,
and does not include downstream control systems, as they are covered in other
APCO plans.
Combustion applications considered as elements of the Plan include:
central-station power generation; industrial processing; industrial steam generation,
commercial and residential heating; gas turbines and external-combustion engines;
and reciprocating internal-combustion engines. Also considered are needs for
supporting fundamental research.
A 5-Year Plan of combustion R&D is presented, with "R&D opportuni-
ties" identified and ranked in five priority levels. The Plan includes the descrip-
tion of 49 applied R&D opportunities in specific combustion application areas
and 27 research opportunities of a more fundamental and broadly applicable
nature. Applied-R&D opportunities were ranked by a priority rationale which
includes the following factors as criteria: (1) pollutants affected, (2) likely per-
centage reduction of nationwide combustion emissions by completing and imple-
menting the specific R&D, (3) time to implementation of R&D results, (4)
likelihood of emission reduction by some noncombustion or downstream control
method, and (5) relative implementation cost. Fundamental research opportunities
were ranked by a different priority rationale based on their relevance to applied-
R&D needs.
The methodology for priority ranking, both within and across different
application areas, can be used to update the Plan periodically as new technology
and criteria emerge.
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THE FEDERAL
R&D PLAN FOR AIR-POLLUTION CONTROL
BY COMBUSTION-PROCESS MODI FICA TION
Final Report
Contract CPA 22.69.147
TABLE OF CONTENTS
Chapter
I. EXECUTIVE SUMMARY
. . . . . . . .. .. .. .. ..
.. .. .. .. ..
Background. . . . . . . . . . . . . . . . . . . .
Scope of R&D Plan. . . . . . . . . . . . . . . . . . . .
Organization of the 5-Year R&D Plan. . . . . . . . . . . . . .
Philosophy of R&D Planning. . . . . . . . . . . . . .
Summary of the 5-Year R&D Plan. . . . . . . . . . . . . . .
II.
APPROACH TO THE COMBUSTION R&D PLAN. . . . . . . . .
Planning Rationale. . . .
Emission Data and Projections
Structure of Report. . . .
.. .. .. ..
.. .. .. .. ..
.. .. .. ..
.. .. .. .. ..
.. .. .. .. .. .. .. .. .. .. ..
.. .. .. .. .. .. .. .. .. ..
III.
CENTRAL.STATION POWER PLANTS. .
.. .. .. .. .. .. .. ..
.. .. .. .. ..
IV.
INDUSTRIAL PROCESSING
.. .. .. .. .. .. .. .. .. .. .. .. .. ..
.. .. .. ..
V.
INDUSTRIAL STEAM GENERATION AND
COMMERCIAL AND RESIDENTIAL HEATING
.. . . . . .. . . . . . .
VI.
CONTINUOUS.COMBUSTION ENGINES-
GAS TURBINES AND EXTERNAL.COMBUSTION ENGINES
. . . . .
1- 1
- 2
- 2
- 3
- 6
- 9
11- 1
- 1
- 9
-18
. 111- 1
. IV- 1
V- 1
. . VI- 1
VII. RECIPROCATING INTERNAL-COMBUSTION ENGINES. . . . . . . . . . VII- 1
VIII. FUNDAMENTAL AND BROADLY APPLICABLE COMBUSTION RESEARCH. . VIII- 1
Combustion Physics. . . . . . . . . . . . . . . . . . .. - 2
Combustion Chemistry. . . . . . . . . . . . . . . . . .. -12
Priority Ranking Procedure for Research Opportunities
in the Fundamental and Broadly Applicable Area. . . . . . . . .
IX.
SUMMARY OF THE 5-YEAR COMBUSTION R&D PLAN. .
. . . . .
Appendix
A. Priority Rating Methodology for Applied-R&D Opportunities.
. .. . . .
B.
Derivation of the Emissions Data and Projections Used in Planning. .
. . . . .
(More detailed tables of contents are shown
on the divider page for each chapter)
-26
. . IX- 1
A- 1
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THE FEDERAL
R&D PLAN FOR AIR-POLLUTION CONTROL
BY COMBUSTION-PROCESS MODIFICATION
Chapter I
EXECUTIVE SUMMARY
David W. Locklin
Albert E. Weller
Richard E. Barrett
TABLE OF CONTENTS
EXECUTIVE SUMMARY.
. . . .
. . . . . . . . . . . . . .
. . . 1- 1
BACKGROUND. . . . . . .
. . . . . . . .
. . . . .
. . - 2
SCOPE OF R&D PLAN
. . . .
. . . . . . . . . . .
. . . . .
. . - 2
ORGANIZATION OF THE 5-YEAR R&D PLAN.
. . . . .
. . . . . .
. . - 3
Organization Matri)(. . . . . . . . . . . . . . . . . . . . . - 3
Applied R&D for Combustion Sources. . . . . . . . . . . . - 4
Supporting Fundamental Research. . . . . . . . . . . . . . - 5
Classification of Pollutants. . . . . . . . . . . . . . . . - 5
PHILOSOPHY OF R&D PLANNING. . . . . .
. . . .
. . . . .
. . . - 6
Priority Ranking Rationale. . . . . . . . . . . . . - 6
Emission Projections. . . . . . . . . . . . . . . . . . - 7
Implications of the Planning Methodology and Scope. . . . . . . - 7
SUMMARY OF THE 5-YEAR R&D PLAN.
. . . .
. . . . . .
. . - 9
Technical Content of the Plan. . . . . . . . . . .
Central-Station Power Plants. . . . . . . .
Industrial Processing . . . . . . . . . .
Industrial Steam Generation and
Commercial and Residential Heating. . . . . . . . . . .
Continuous-Combustion Engines -
Gas Turbines and External-Combustion Engines. . . . . . .
Reciprocating Internal-Combustion Engines. . . . . . . . . .
Fundamental and Broadly Applicable Combustion Research.
Recommendations Relating to Supporting Activity . . . .
Summary of Funding Requirements for the Plan. . . . . . .
. . . . . . - 9
. . . . . -10
. . . . . -10
. -10
. -11
. -11
. -12
. -12
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1-1
THE FEDERAL
R&D PLAN FOR AI R-POLLUTION CONTROL
BY COMBUSTION-PROCESS MODIFICATION
to
Air Pollution Control Office
ENVIRONMENTAL PROTECTION AGENCY
CHAPTER I
EXECUTIVE SUMMARY
Combustion processes for energy-conversion purposes constitute the major source of air
pollution in the United States. Thus, effective planning of R&D in this area is of key importance
for the long-range success of the nation's air-pollution-control program. Recognizing this need,
the Air Pollution Control Office initiated this in-depth study to (1) identify gaps in combustion
technology, particularly in the understanding of how combustion processes may be modified to
reduce pollutant emissions, and (2) develop a comprehensive 5-Year Plan for effectively allocating
resources available for APCO-supported combustion R&D directed to meeting projected needs for
air-pollution control.
Figure 1-1 illustrates the relative magnitude of the problem to which this Plan is directed
by showing the percentage contribution of energy-conversion combustion processes to the
nationwide problem arising from emissions of various pollutants from all sources. (These emission
data are further discussed in Chapter II.)
Particulate SO. NO.
100-
CO
HC
PNA
Lead
'0
D Noncombustion
sources
80 -
II)
a>
~
:0
o
(/) 60 -
u
L-
a>
Cl.
20 -
II Combustion for
energy conversion
Figure 1-1. Percentage Contribution of Combustion-Source Emissions to the Total Nationwide
Inventory of Pollutant Emissions
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1-2
BACKGROUND
.
Historically, the thrust of most R&D in the combustion field has been to optimize
equipment performance characteristics rather than to reduce pollutant emissions. For example,
burner or engine development has usually been conducted with the objective of enhancing
operating range, response, efficiency, reliability, manufacturing economy, or compactness. While
the limitation of smoke emission has traditionally provided one performance constraint for the
designer, only comparatively recently has R&D attention been given to the relation of combus-
tion processes and system design to emissions of other pollutants.
Thus, only a small portion of past combustion research is directly applicable to air-
pollution considerations, but much more is indirectly relevant because of its potential contribu-
tion to the overall understanding of the combustion process. This study has utilized generally
pertinent combustion technology, as background, in addition to specific results of R&D aimed
directly at air-pollution control.
SCOPE OF R&D PLAN
The s- Year Combustion R&D Plan recommended in this report is directed to the control
of pollutant emissions from stationary and vehicular combustion sources through modification of
combustion processes, rather than emission control by add-on or downstream devices. The Plan is
confined to combustion R&D, both fundamental and applied, for energy-conversion systems
utilizing prime fuels and air.
The limitations imposed by this scope can be emphasized by the following tabulation:
Within Scope of Plan Outside Scope of Plan
. Combustion carried out for the . Combustion for other purposes, such as
purpose of energy conversion, incineration, chemical processing, etc.
including the production of heat,
as the prime objective.
. Pollutant control gained by . Downstream controls, even though
modification of the combustion combustion may be involved; limestone
process. reactions in furnaces or fluidized beds.
. Combustion processes using prime . Combustion processes using waste fuels,
fuels (i.e., those normally sold by-product fuels, specialty fuels, etc.,
commercially). even though carried out for energy
conversion purposes.
. Fundamental research needed for . Associated research in other technical
understanding of combustion areas, even though necessary to apply
processes and their effects on the results of combustion research,
pollutant emissions. such as alloy development, heat trans-
fer equipment, etc.
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1-3
ORGANIZATION OF THE 5-YEAR R&D PLAN
The recommended R&D Plan is organized by program elements, identified by application
areas or categories of major pollutant sources rather than by pollutants. Consequently, combus-
tion R&D opportunities for like applications are grouped together in separate program elements
(e.g., power plants, IC engines, etc.); all relevant pollutants are considered within each element.
Supporting fundamental research constitutes an additional program element.
ORGANIZATION MATRIX
The matrix chart shown in Table 1-1 illustrates the manner in which the Plan is organized
in terms of the program elements and the pollutants considered. The numbers in the chart give
the percentage contribution of each source category to the total emission of a particular
pollutant from all combustion sources within the scope of the Plan. Thus, these numbers serve to
identify those sources that are major emitters of a specific pollutant and define the importance
of controlling a specific source.
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Pollutants
1. Products of Incomplete
Combustion
Combustible particulate
co
Gaseous HC
Polynuclear aromatics
Odor
2. Oxides of Nitrogen, NOx
3. Emissions Resulting From
Combustion-Improving Additives
Lead and other trace metals
4. Emissions Resulting From Fuel
Contaminants
Sulfur, sax
Ash
Other noncombustible
additives
Table 1.1. Organization Matrix for Combustion R&D Plan
APPLIED R&D FOR COMBUSTION SOURCES
SUPPORTING
FUNDAMENTAL
RESEARCH
Continuous-Combustion Sources
Cyclic Comb.
Industrial Fundamental
Central- Industrial Steam Gen. 8< Gas Turbine$ 8< Reciprocating & Broadly
Station Commercial 8< External Comb.
Power Plants Procening RMidential EnginM IC Engilll!$ Applicable
Heating Comb. A_ell
Ch. III Ch. IV Ch. V Ch. VI Ch. VII Ch. VIII
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- - - -
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Potential Impact of Combustion R&D
Nun-,bers In table refer to percentage contribution from each class of source to the total emission of the IdentIfIed pollutant from all combustion for energy
converSion 11966 data). n md Icates negligible.
-------
1-4
The shaded boxes in Table 1-1 indicate the degree to which combustion R&D within the
particular program element is expected to contribute to the overall control of the specific
pollutant emission from energy conversion combustion sources. Factors considered in setting the
degree of potential impact of combustion R&D are:
1. The extent to which a specific pollutant may be amenable to control by
modification of the combustion process
2. The contribution of the source to the total combustion-derived emission
of a specific pollutant, as indicated by the percentages shown
3. The judgment of the project team as to the importance of the specific
source and pollutant, either at the present time or in the future.
Thus, while SOx is high on the list of pollutants under attack by control authorities, it is not
readily controllable by combustion modification only. Gas turbines and external-combustion
engines are not presently strong contributors to the nationwide NOx level; however, the new
interest anticipated in unconventional automotive engines places this area in a high-potential-
impact category. Where no box is shown, the combination of pollutant and source was
considered outside the scope of the R&D Plan or of minor significance.
The program elements of the Plan and the pollutants considered are categorized in the
following manner.
Applied R&D for Combustion Sources
For convenience in treating the applied technology and pertinent R&D needs, combustion
sources were divided into two main classifications: continuous-combustion systems and cyclic-
combustion systems. These classifications include the following combustion applications, or
pollutant sources:
Continuous-Combustion Systems
. Central-Station Power Plants
. Industrial Processing
(combustion for thermal processing, excluding steam generation)
. Industrial Steam Generation and Commercial and Residential Heating
(including boilers not covered under central stations)
. Continuous-Combustion Engines -
Gas Turbines and External-Combustion Engines
Cyclic-Combustion Systems
. Reciprocating Internal-Combustion Engines.
These individual source categories are considered as program elements within the Plan.
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1-5
Supporting Fundamental Research
A sixth program element is comprised of fundamental and broadly applicable research
that will support applied-R&D needs. This element covers fundamental physical and chemical
aspects of combustion processes having relevance to applied-R&D opportunities in one or more
of the source categories. It is anticipated that funding of fundamental research in this program
element will be through the grants mechanism, while the applied R&D is more likely to be
funded through the contracts mechanism or to be conducted as in-house programs.
Classification of Pollutants
Pollutants of primary interest were classified according to the manner in which, or the
degree to which, combustion modification offers a means of control and, thus, where combus-
tion R&D can be effective. Four main categories were defined:
1. Products of Incomplete Combustion
When considering emissions from the combustion process itself, it was convenient to
group pollutants that are products of incomplete combustion and, thus, can be strongly
influenced by conditions that are amenable to control through combustion-system design. These
pollutants are: combustible particulate, CO, gaseous hydrocarbons, polynuclear aromatics, and
odor. R&D directed to modification of the combustion process can be particularly effective in
the control of pollutants in this category.
2. Oxides of Nitrogen
The formation of NOx is strongly influenced by the time-temperature pattern in the
combustion process. The relations of time, temperature, and concentrations which are important
to NOx formation can be controlled to some extent in combustion-system design and, thus,
modification of the combustion process offers promise as a means for NOx control.
3. Emissions Resulting from Combustion-Improving Additives
Another category of combustion pollutants includes those resulting from combustion-
improving additives, principally lead as an antiknock agent in gasoline. Here the principal R&D
interest is in engines, fuels, or combustion conditions that eliminate the need for combustion-
improving additives. Combustion-improving additives have not had widespread application for
continuous-combustion systems. Additives used for other, noncombustion purposes are con-
sidered in the fourth category.
4. Emissions Resulting from Fuel Contaminants
Contaminants that are present naturally in fuels and noncombustible additives are the
origin of still another category of pollutants. These contaminants include sulfur compounds, ash,
and additives for stability or corrosion protection. Emissions of such contaminants generally
cannot be controlled by modification of the combustion process itself. However, modification of
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1-6
the combustion process may influence the form of the contaminates in such a way as to aid
control by other, noncpmbustion means. Such contaminants were not a primary focus of this
R&D planning study, but where combustion modifications could contribute to their control,
appropriate research was identified. The fluidized-bed combustor using limestone for control of
SOx is a new combustion process or "combustion modification". One objective with such com-
bustors is the integration of the combustion process with post-combustion or downstream control
systems, rather than control through the combustion process itself. The fluidized-bed combustor
was considered in this study insofar as R&D needs are related to the combustion process.
PHILOSOPHY OF R&D PLANNING
The 5- Year Combustion R&D Plan presented in this report is based on a philosophy of
(1) matching technology gaps and needs with definable R&D tasks and (2) establishing priorities
to provide effective allocation of available resources for supporting R&D projects. The early part
of the study was devoted to identification of technology gaps and opportunities that could be
exploited to contribute needed technology. After needed prejects - called R&D opportunities
later in this report - had been specifically defined, they were evaluated and ranked as to
priority. *
Priority Ranking Rationale
The priority ranking rationale for applied-R&D opportunities included the following
criteria:
. Pollutants affected
. Potential effectiveness in controlling the affected pollutants, consider-
ing nationwide emissions from energy-conversion combustion sources
projected over a 20-year period
. Time to implementation of R&D results
. Likelihood of alternative noncombustion or competing downstream
control systems.
. Costs of implementation.
Five priority levels, A through E, were established for applied R&D opportunities. A different
priority scale, I through 5, was established for fundamental-research opportunities b.ased on
their relevance to applied R&D needs~ through this method, fundamental-research o~portunities
that would support high-ranking applied-R&D opportunities were ranked highest.
Applying this priority rating methodology, the R&D opportunities were classified in
priority categories and are presented in such a manner that the R&D Plan can be utilized in
programming for various levels of resource allocations for the next 5 years.
*The priority ranking rationale is summarized in Chapter II and is covered in more detail in Appendix A.
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1-7
Emission Projections
To determine the potential effectiveness of a given R&D opportunity, or the benefit
associated with a specified degree of pollutant control, projections of annual emissions over the
next 20 years were used. These projections, shown in Figure 1-2, are indicative of trends
expected to occur if the present policy of emission control remained unchanged.
Implications of the
Planning Methodology and Scope
A number of features of the planning methodology should be emphasized as they affect
utilization of the Plan; these are briefly discussed as follows.
Type of Plan
The planning approach used results in a plan of the resource-allocation type falling in the
"fixed-resources/variable goal" class. That is, the Plan is intended to maximize the achievement
for any given research funding allocation. The plan is not of the "variable-resources/fixed goal"
type designed to achieve, for example, a fixed reduction in pollutant emissions.
Relative Significance of Pollutants
The benefit associated with R&D opportunities for priority ranking in the applied-R&D
areas is based on the fraction of the total pollutants emitted in the period 1970-1990 from
energy-conversion combustion sources which could likely be controlled by undertaking the
specified R&D. Nationwide projections of emission levels were used, as these emission data were
the best available on a consistent base and are believed to be representative of the relative levels
of combustion pollutants in typical industrialized urban areas. Should there be interest in
considering the effect of more localized data where special health effects are clearly at stake, the
planning rationale described could be modified to consider R&D priorities on this basis.
The priority ranking procedure applied equal weight to all pollutants. Should criteria be
established at some future time regarding the relative significance of the pollutants, appropriate
weighting factors can be incorporated into the priority ranking methodology in updating the
Plan.
Parallel R&D Approaches
In some areas, the Plan includes parallel R&D approaches applying to the same general
source and pollutant combination, even within the same priority category. In view of the overall
needs in combustion R&D and the comparatively low level of current R&D effort, parallel
approaches are considered justified at this time. As research progresses and as the Plan is updated
with more fully defined factors entering the ranking process, one or more alternatives may be
dropped.
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1-8
100
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The following emissions are considered negligible in comparison with the emissions from other sources:
802 - gas-fueled power plants; gasoline, diesel, and gas stationary engines
CO - gas-fueled and oil-fueled power plants
HC - gas-fueled power plants
Particulate - gas stationary engines
Figure 1-2.
Projected Annual Emissions From Energy-Conversion Combustion Sources
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1-9
Scope Limitation of Plan
It should be reemphasized that the scope of this R&D Plan is limited to modification of
the combustion process for energy-conversion processes using prime fuels. The Plan does not
include R&D for downstream control systems which may be applied to combustion sources,
although the rationale for priority ranking of R&D for combustion modification includes an
adjustment where there is a likelihood that downstream controls may be preferable in particular
applications. Further, the Plan does not include R&D in other technical areas which may be
needed to implement the results of the combustion R&D.
Thus the Plan represents only a part of the total R&D activities which can be directed
toward a reduction of air pollution from combustion sources. Plans in other areas must obviously
be considered together with this Combustion Plan in developing an overall R&D program for
air-pollution control from combustion sources.
SUMMARY OF THE 5-YEAR R&D PLAN
The following pages provide a brief summary of the 5-Year R&D Plan - including
technical content in areas of both applied R&D and fundamental research, recommendations
relating to supporting activity, and a summary of estimated funding requirements by priority
level for each program element.
TECHNICAL CONTENT OF THE PLAN
Technical background for R&D recommendations is covered in Chapters III through VIII
for each of the areas constituting program elements of the Plan. Discussion in each of those
chapters includes an appraisal of the status of combustion technology and identification of R&D
needed to fill technology gaps for pollution control by combustion modification. Current R&D
relevant to these areas is also taJulated, including both APCO projects and other R&D efforts.
In each of the program elements of the Plan, R&D opportunities or needed projects are
defined as to technical objective, rationale and incentive, estimated R&D cost, and time to
implementation. An evaluation of potential benefit and priority ranking is included with each
R&D opportunity. R&D opportunities in each program element are grouped in priority categories
according to the ranking evaluation and summarized in Chapter IX for all program elements by
priority category.
Areas encompassed by R&D opportunities recommended within the various program
elements are briefly outlined in the following section. Further details are found in the chapters.
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1-10
Central-Station Power Plants
(16 R&D opportupities)
. Laboratory and field investigations of means to suppress NOx by:
- low-excess-air combustion
- flue-gas recirculation
- two-stage combustion
- fuel properties.
. Development of new power-plant combustion concepts such as:
- high-turbulence combustion
- fluidized bed
- gasification
- electrochemical oxidation.
. Analytical and experimental investigations to promote means of retain-
ing ash and slag within the furnace, or of altering the ash so as to
promote its collection by downstream equipment.
. Development of research instrumentation and measuring conditions
existing in central-station-power-plant furnaces.
Industrial Processing
(5 R&D opportunities)
. Programs aimed at NOx reduction in:
- rotary kilns for cement and lime production
- glass-melting furnaces
- open-hearth furnaces
- regenerative melting furnaces
- iron-sintering and iron-pelletizing processes.
Industrial Steam Generation and
Commercial and Residential Heating
(13 R&D opportunities)
. Development of Design Criteria
- mathematical modeling of the combustion process
- mixing, turbulence, combustion intensity, and temperature
- internal and external recirculation
- two-stage combustion
- fluidized-bed combustion
- PNA formation in fixed coal beds.
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1-11
. Development of New and Improved Equipment Approaches
- application of new design criteria
- development of low-peak-temperature units.
. Investigation of Other Factors
- transient conditions
- additives and emulsions (residual fuel oil)
- maintenance
- more comprehensive emissions factors.
Continuous-Combustion Engines -
Gas Turbines and External-Combustion Engines
(5 R&D opportunities)
. Aircraft and Industrial Gas Turbines
- design of primary-combustion zone to reduce NOx emissions
- design of secondary-combustion and dilution zone to reduce NOx
- development of criteria for reduction of CO, HC, and odor at idle
and low power.
. Automotive Gas Turbines
- development of a low-emission automotive-size gas-turbine com-
bustor prototype.
. Automotive Rankine-Cycle Engine
- development of low-emission
motive engines.
combustors for Rankine-cycle auto-
Reciprocating Internal-Combustion Engines
(10 R&D opportunities)
. Gasoline Engines
- stratified-charge engines
- lean-mixture operation and mixture preparation
- generally applicable studies: wall quench, effect
ticulate and PNA formation.
of lube oil, par-
. Diesel Engines
- better understanding of combustion process for ultimate modifying
of the diesel fuel-injection and combustion process so as to mini-
mize emissions.
. General
- kinetics of NOx formation in IC engines
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1-12
Fundamental and Broadly
Applicable Combl!stion Research
(27 research opportunities)
. Physical Orientation
- path-history relations in combustion
- combustion of single and small number of droplets and particulates
- combustion in fluidized beds
- preparation of monographs on turbulence and droplet combustion.
. Chemical Orientation
- chemistry of the formation and destruction of PNA, soot, and
odorants
- kinetics of HC - 02 reactions
- kinetics of NOx - HC reactions
- miscellaneous.
. Combined Physical and Chemical
- global kinetic descriptions of combustion processes.
Recommendations Relating
to Supporting Activity
. Coordination and Communication
- monitoring of potentially useful combustion R&D by all sectors
- preparation of bibliographies, organization of conferences, and
broadening of report distribution to stimulate interchange of ideas
- provision for interpretation of fundamental-research results for use
in application.
. Program Planning
- provision for periodic updating
technology and criteria.
of the R&D Plan to reflect new
SUMMARY OF FUNDING REQUIREMENTS
FOR THE PLAN
Table 1-2 summarizes estimated annual and 5-year funding levels for the various program
elements of the Plan, breaking out the funding associated with each priority category. This
funding includes provision for introducing R&D for new concepts or accelerating on-going R&D
as a contingency for needs not now identified (designated as unranked priority N). Table 1-3
summarizes 5-year funding levels by accumulating highest priority categories for each program
element.
Funding levels estimated for each of the R&D opportunities in all program elements are
listed by priority category in Chapter IX.
-------
TABLE 1-2. SUMMARY OF 5-YEAR COMBUSTION R&D PLAN BY PROGRAM ELEMENTS AND PRIORITIES WITHIN ELEMENTS
Number Estimated R&D Costs, $1000
R&D Program Element
Descri bed Priority of By Fiscal Years
in Chapter or Source Category Level R&D 5-Year
Opportunities '71 '72 '73 '74 '75 Total
III Central-Station Power Plants A 3 275 325 525 550 325 2,000
B 4 700 1,450 1,850 3,900 4,000 11 ,900
C 4 325 475 575 550 400 2,325
D 3 300 350 400 250 300 1,600
E 2 225 250 300 100 100 975
N 1 - 250 350 400 500 1,500
- - - - - - -
Total 17 1,825 3,100 4,000 5,750 5,625 20,300
IV Industrial Processing A 0 - - - - - -
B 0 - - - - - -
C 0 - - - - - -
D 0 - - - - - -
E 5 650 1,150 1,100 1,300 - 4,200
N 1 - 50 50 50 50 2UO
- - - - - - -
Total 6 650 1,200 1,150 1,350 50 4,400
V Industrial Steam Generation and A 0 - - - - - -
Commercial and Residential B 3 375 425 475 475 350 2,100
Heating C 4 625 600 560 360 60 2,205
D 4 700 600 525 150 150 2,125
E 2 400 475 450 425 125 1,875
N 1 - 150 200 250 250 850
- -- - - - - -
Total 14 2,100 2,250 2,210 1,660 935 9,155
-
I
-
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TABLE 1-2. (Continued)
Number Estimated R&D Costs, $1000
R&D Program Element
Described Priority of By Fiscal Years
in Chapter or Source Category Level R&D 5- Year
Opportunities '11 '12 '73 '74 '75 Total
VI Continuous Combustion Engines - A 2 700 500 400 400 - 2,000
Gas Turbines and Extemal- B 1 250 200 200 - - 650
Combustion Engines C 1 200 200 - - - 400
D 1 100 200 200 - - 500
E 0 - - - - - . -
N I - 100 150 150 200 600
-- - - -- - - -
Total 6 1,250 1,200 950 550 200 4,150
VII Reciprocating Intemal-Combustion A 3 700 760 700 - - 2,160
Engines B 3 370 370 370 370 370 1.850
C 1 100 100 100 - - 300
D 3 370 370 270 200 200 1,410
E 0 - - - - - -
N 1 - 250 300 300 350 1,200
- - - - - - -
Total 11 1,540 1,850 1,740 870 920 6,920
VIII Fundamental and Broadly 1 4 800 675 575 575 575 3,200
Applicable Combustion Research 2 4 670 570 545 470 470 2,725
3 6 625 600 600 600 425 2,850
4 5 535 575 525 350 350 2,335
5 8 740 635 410 160 100 2,045
N 1 - 150 200 250 300 900
- - - - - - -
Total 28 3,370 3,205 2,855 2,405 2,220 14,055
Communications and Planning 300 300 300 300 300 1,500
Overall Totals 11,035 13,105 13 ,205 12,885 10,250 60,480
....
I
-
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1-15
TABLE 1-3. SUMMARY OF 5-YEAR FUNDING ESTIMATES BY CUMULATIVE PRIORITIES FOR
PROGRAM ELEMENTS OF THE 5-YEAR COMBUSTION R&D PLAN
Estimated 5-Year R&D Costs, $1,000*
(Number of R&D opportunities is shown in parentheses)
Priority or Cumulative Priorities
All
Applied R&D A A-B A-C A-D A-E N Priorities
Chapter
III Central-S tation 2,000 13,900 16,225 17,825 18,800 1,500 20,300
Power Plants (3) (1) (11) (14) (16) (1) (17)
IV Industrial Processing - - - - 4,200 200 4,400
(5) (1) (6)
V Ind. Steam Generation & - 2,100 4,305 6,430 8,305 850 9,155
Comm. & Res. Heating (3) (7) (11) (13) (1) (14)
VI Continuous Combustion 2,000 2,650 3,050 3,550 3,550 600 4,150
Engines (2) (3) (4) (5) (5) (1) (6)
VII Reciprocating 2,160 4,010 4,310 5,720 5,720 1,200 6,920
IC Engines (3) (6) (1) (10) (10) (1) (11)
- -- - - - - -
Totals, Applied R&D 6,160 22 ,660 27 ,890 33,525 40,575 4,350 44,925
(8) (19) (29) (40) (49) (5) (54)
, '-2 '-3 '-4 '-5 N
VlII Fundamental Research 3,200 5,925 8,775 11,110 13,155 900 14,055
(4) (8) (14) (19) (27) (1) (28)
-
A A-B A-C A-D A-E
and and and and and
, '-2 '-3 '-4 '-5 N
Totals by 10,860 30,085 38,165 46,135 55,230 5,250 60,480
Funding Levels(a)
N
Indicates unranked general provision for new concepts and opportunities.
(a) Totals of applied R&D and fundamental research in priorities shown, including supporting activities of
communications and planning.
*Breakdowns of recommended funding by years (FY '71-'75) are shown in individual chapters and summarized
-------
Chapter II
APPROACH TO THE COMBUSTION R&D PLAN
Edgar S. Cheaney
Richard E. Barrett David W. Locklin
Richard B. Engdahl Philip R. Sticksel
Joseph A. Hoess Albert E. Weller
TABLE OF CONTENTS
PLANNING RATIONALE
. . . . . .
. . . .
. . . . . .
Primary Goal of the R&D Plan
Structure of the R&D Plan. . . .
. . . .
. . . . .
. . . . . .
. . . . . . .
Derivation of Content for the R&D Plan
Methodology of Priority Ranking. . .
. . . . .
. . . .
. . . . . . .
. . . . .
EMISSION DATA AND PROJECTIONS. . .
. . . . .
. . . . . . .
Pollutant Emission Inventory. . .
. . . . . .
. . . . . . .
Forecasts of Pollutant Emissions. . .
STRUCTURE OF REPORT. . . . .
. . . . .
. . . . .
. . . .
Chapters Covering Program Elements of the R&D Plan
. . . .
Organization of Material Within Elements of the R&D Plan.
. . . . .
Survey of Current R&D Relevant to the Plan
Explanation of Format for Displaying
Evaluations of Applied R&D Opportunities .
. . . . . .
. . . .
. . . . . . . . . .
11- 1
- 2
- 3
- 4
- 5
- 9
- 9
-11
-18
-18
-19
-19
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I
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II-I
CHAPTER II
APPROACH TO THE COMBUSTION R&D PLAN
In a planning study that is concerned with the identification and selection of research
investments, the resulting R&D plan is intimately related to the valuation and decision-making
process used in developing the plan. Thus, the approach to this study is best discussed in terms
of the planning rationale, as presented in the following section.
An additional factor important to the development of the 5- Year Combustion R&D Plan
is the projection of pollutant emissions that serves to define the problem which the R&D Plan is
designed to attack. As this factor becomes an integral part of the priority ranking methodology,
it is also discussed within this chapter.
The overall structure of the report is outlined at the end of this chapter to facilitate the
understanding of the arrangement of material and the terminology used in presenting the R&D
Plan.
PLANNING RATIONALE
The rationale underlying a plan of this type should make it capable of being changed in a
logical and internally consistent manner in. response to changes in external factors. That is, the
rationale makes the plan dynamic. Long-range plans for R&D programs must be designed for
updating because the future cannot be fully predicted. The only aspect of the future to which a
high probability can be attached is that criteria and technology will change; and changed
conditions will inevitably alter the basis upon which any long-range plan is founded.
It is also true that an explicit planning methodology can incorporate only a limited
number of factors entering into R&D investment decisions. The effects of these factors must
always be supplemented by judgments made by the decision maker using the plan as a tool. It is
essential that APCa staff who will be using the Plan presented in this report be critically aware
of the factors underlying the planning rationale, so their supplementary judgments can be added
in a knowledgeable and consistent way.
The planning rationale used in this study will be discussed in terms of four main subjects:
1. Primary goal of the Plan
2. Structure of the Plan
3. Derivation of content for the Plan
4. Methodology by which priority rankings were assigned to the R&D
opportunities recommended in the Plan.
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11-2
1. PRIMARY GOAL OF THE R&D PLAN
The primary goal for the R&D Plan is to achieve the greatest possible net reduction of
pollutant emissions from energy-conversion comb.ustio? s~urces through. support of a program of
combustion R&D projects as constrained by certam gmdelmes as follows.
. Priorities must be given to program components to facilitate project
selection with limited resources.
. Priorities must be based on combined considerations of potential
benefits (emission reduction) and implementation costs.
. Time-urgency of emission reductions must be recognized.
. The assumed forecasting horizon for estimating benefits is 20 years.
. The established planning horizon for R&D funding is 5 years.
Although the goal statement is not complex, it implies a number of logical constraints which
substantially affected the scope and thrust of the Plan. These implications are discussed below.
Implications of Program Goal
The Plan is to be of the resource-allocation type, falling in the "fixed-resources/variable-
goals" class. That is, the Plan is to provide for the greatest possible pollutant emission reduction
subject to the guidelines above (variable goal) for any given total funding allocation (fixed
resource). Alternatively, the Plan might have been of the "variable-resource/fixed-goal" type with
a specified amount of reduction to be achieved at a minimum (but unknown) funding level. *
The Combustion R&D Plan is so designed because the state of scientific knowledge
concerning pollutant effects from combustion sources in general is still too imprecise to logically
support or rationalize quantitative statements of requirements for reduction of specific
pollutants. However, this situation is changing as air-pollution effects come under more intensive
study. It may be desirable, as the advancing state of knowledge permits, to change the planning
basis to the fixed-benefit type to achieve specific reductions of certain pollutants.
A complexity is introduced by the fact that cost-benefit planning techniques are called
for in deriving project priorities, although the overall planning process is of the resource-
allocation type. The costs considered in establishing priorities are implementation costs, whereas
the resources to be allocated are the costs of supporting R&D for a 5-year period. It is important
for correct understanding of the planning rationale to distinguish between these two types of
costs and their entirely separate roles in the planning methodology.
*In a general way, APCO's automotive-emissions control program falls in this latter category since it is based on
achieving specified emission levels at definite times. However, the Plan developed during this study is
confined to combustion R&D only. It is not believed, for example, that the 75/76 standards set for automotive
emissions can be met through combustion modifications only. Thus, the 75/76 standards represent an unrealistic
goal or "fixed benefit" for the combustion R&D activities being evaluated in this study. For this reason, and
because a fixed-resource/variable-goal approach is more appropriate for pollutant sources for which specific
emission standards have not yet been established, a fixed-resource/variable-goal approach was selected for this
Combustion R&D Plan.
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11-3
The only basis for crediting benefits to a suggested item of R&D is the ability to show
that the results of the work are likely to bring about an actual reduction in the emission of
pollutants. * For highly applied-development projects, it is possible to construct direct-relevance
paths showing the plausibility of a pollution reduction being associated with the suggested R&D.
In the case of fundamental research, there is no similar direct relationship for crediting benefits
to the research; however, benefits can be credited to fundamental-research projects on the basis
of their relevance to applied-R&D projects.
The planning guidelines included in the goal statement establish two "horizons". One is
related to the design of the Plan itself; the other is concerned with the forecasting period used in
assessing benefits. The planning horizon of 5 years was established by APCO. The forecasting
horizon of 20 years (1970-1990) was chosen during the study as the best compromise that could
be obtained between confidence limits of forecasting and the need to provide adequate time for
R&D projects to be conducted and completed, to be implemented, and to accrue benefits.
The effect on the planning process of the definition of benefits as actual reductions in
pollutant emissions is significant. A severe burden was placed on the forecasting part of the
study by the requirement that the results of planned research be visualized in quantitative terms
well beyond the period of initial implementation. Nonetheless, this is the only satisfying basis
upon which to assess such benefits, and the principle was adhered to in the development of the
Plan.
2. STRUCTURE OF THE R&D PLAN
The basic structure of the 5- Year Combustion R&D Plan was determined by APCO
through the original specification that the Plan be established in terms of programs, elements,
and projects. This specification defined the Plan as a 3-level structure and prescribed the
nomenclature to be applied to each level. However, it was necessary during the planning study to
give this structure specific meaning by deciding what was to be included in each level of the Plan
and what the scope of each level was to be.
The program is defined here to include combustion R&D activities within the scope of
this study recommended for support by Government agencies at the Federal level to fill gaps in
the technology or to pursue promising R&D opportunities. Thus, the program is a complex of
related activities and budgets. Each subunit of the program finds its place in the whole because it
contributes in some definite way to the accomplishment of the goal that has been defined.
Program elements are the major subdivisions of the program. The program elements are
established as pollution-source categories or application areas. Thus, one of the elements of the
program is "central-station power plants"; another element is "reciprocating internal-combustion
engines". Supporting fundamental research is treated as a separate element.
*In considering such reductions, localized concentrations of pollutants (e.g., in a specific industrial city) were not
taken into account; only the net reduction in the nationwide emission inventory was considered. Some emission
sources (e.g., industrial processing), which make relatively small emission contributions on a nationwide-
emission-tonnage basis, might have a much more significant local impact. However, including localized emission
levels was beyond the scope of this study.
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II-4
All items of R&D in the program that relate to a source category are g~ouped ~nd
budgeted as part of this element. Elements are defined in this way to make possIble logIcal
grouping of research .subjects from an administrative and funding standpoint. There ~ere
relatively few cases in which applied R&D opportunities crossed element boundary hnes.
Elements might also have been defined as pollutants (e.g., S02, NOx, etc.), but this would not
have taken into consideration the interrelation of different pollutants affected by combustion
modification. Elements might also have been defined by project type (Le., all engineering te~t
work might have been c1-ustered together, all exploratory development, and so on), but this
would not have taken full advantage of relevant technology.
Six elements were defined. Five are applied R&D elements, covering the source cate-
gories: (1) central-station power plants, (2) industrial processing, (3) industrial steam generation
and commercial and residential heating, (4) continuous-combustion engines, and (5) reciprocating
internal-combustion engines. The sixth element covers fundamental research or research that is
broadly applicable to two or more application areas.
In the structure of the Plan, elements are subdivided into projects. The project is the
basic unit of which the Plan is composed. At this level most of the R&D needs and opportunities
were identified. Projects are referred to elsewhere in this report as R&D opportunities and the
two terms are synonymous.
A project is considered to be a single stream of R&D activity aimed at producing a
reduction in air pollution by virtue of some improvement or innovation through combustion
R&D. Projects or R&D opportunities may consist of more than one definable task. These tasks
may be conducted in parallel or in series, depending on the nature of the project. Multiple-task
projects could be carried out under more than one contract, in-house program, or grant.
3. DERIVATION OF CONTENT FOR
THE R&D PLAN
The content of the R&D Plan, consisting of R&D opportunities and their costs, was
assem bled as a result of conceptual and analytical study of a 13-man team. The staff was
composed of technologists qualified in either the chemistry and physics of combustion or in the
specialized technology of the source categories involved. The team developed the Plan's content
in two steps:
. Identification of R&D opportunities on a provisional basis
. Screening and selection of R&D opportunities to be included in the
Plan.
First, members of the team were assigned various aspects of combustion to study in
detail. This was done to enable them to identify areas in which R&D is needed or where
additional R&D is justified because of the new requirement to examine the combustion process
from the standpoint of air pollution. The work was characterized as identification of "gaps" in
the present knowledge of the field. In effect, the team members defined R&D opportunities that
should be carried out from engineering and scientific viewpoints and then reviewed current R&D
to determine whether the field was adequately covered. '
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11-5
The experience of the individual members of the team was heavily relied upon in this
phase of the project. In addition to a review of available information, contacts were made with
pertinent sources in the technical community through correspondence and a number of field
interviews.
Second, the suggested R&D opportunities were subjected to a judgmental screening
process, and suggestions with insufficient merit to be included in the R&D Plan were eliminated.
The screening criteria were:
. The research must give promise of filling a knowledge gap in a
pollutant-problem area
. There must be plausible reason to anticipate that the results of the
research will have potential for pollutant reduction
The screening process was carried out by committee action, with project team members
participating as appropriate. The process was essentially one of committee questioning of the
persons suggesting specific research ideas. Some ideas were rejected as violating one or more of
the screening criteria. However, in most of the cases, the questioning procedure produced
amplifications and refinements of the original suggestions. Therefore, the content of the R&D
Plan can properly be regarded as the product of coordinated group effort, rather than the result
of individual effort in compartmentalized fields of investigation.
All the R&D opportunities that survived this screening process are included in the 5-Year
R&D Plan presented in this report. The committee activities described here were limited to
selection of items for inclusion. No effort was made in committee to establish priority ranking at
that point. However, the numerical values of planning factors which later entered into the
priority rankings were reviewed and challenged through a similar committee approach.
4. METHODOLOGY OF PRIORITY RANKING
To make possible "fixed-resource" planning in advance of knowing the magnitude of
resources actually available, it was necessary to arrange the content of the R&D Plan in a
priority ordering. This makes it feasible, in applying the Plan, to consider any given funding
level.
Applied R&D Priorities
In the case of the applied areas, priorities were assigned on the basis of:
. Relative potential for pollution reduction
. Relative cost to implement the results of the research
. Expert judgment.
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II-6
Fundamental Research Priorities
For the fundam~ntal research opportunities, priority ranking was han~led somewha~ dif-
ferently than for the applied R&D opportunities. Fundamental research projects were assIgned
priorities based on:
. Relationship to applied-R&D opportunities, as expressed by relevance
numbers.
. Expert judgment.
The methodology used to establish priority ranking of fundamental projects is discussed in
Chapter VIII.
Methodology of Priority Ranking
for Applied R&D
A detailed discussion of the methodology used to set priorities for applied R&D is
presented in Appendix A. A brief summary of that methodology is given in the ~ollowi~g
paragraphs. The process is discussed in terms of the first two components of the evaluation basIs:
(1) relative potential for reducing pollution and (2) relative implementation costs. This is fol-
lowed by a discussion of how these two components were combined to produce a single index of
priority.
Potential for Pollution Reduction
Potential for pollution reduction is the measure of benefit associated with each identified
R&D opportunity. Potential was estimated using a quasiquantitative procedure resulting in the
calculation of a dimensionless Relative Potential Benefit Factor, Bk, which is the measure of
benefit for a specific research opportunity, k. The numerical value of Bk was calculated by
applying a group of four factors associated with pollutant sources and R&D opportunities to a
Pollutant-Significance Factor, Pi, associated with each specific pollutant, i, and summing the
resul ts.
The numerical value assigned to Pi for a specific pollutant is defined as the relative
benefit that would be associated with a 100 percent reduction in the projected uncontrolled
emission of that pollutant from all energy-conversion combustion sources during the period 1970
to 1990 as compared with the same percentage reduction for other pollutants for the same
period. Thus, Pi is a proxy for the "total problem" over the next 20 years presented by anyone
pollutant to which a given R&D opportunity might be related. In effect, then, Pi also represents
the maximum possible benefit with respect to a specific pollutant related to an R&D oppor-
tunity if the outcome of the work enabled the elimination of all of that pollutant during the
specified time period. As a result of discussions with APCa personnel, Pi was assumed to be
unity for all pollutants. While the present state of knowledge concerning the relative significance
of emission of each pollutant does not fully support any assumption as to values for Pi, the
above assumption is considered reasonable for purposes of this planning study. When the state of
knowledge permits a set of priorities to be established among the pollutants, new Pi's can be
assigned reflecting these, and the R&D Plan can be adjusted accordingly.
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11-7
The four source-category- and research-opportunity-associated factors are numerical
measures of the limitations imposed by the following considerations on the reduction of
pollutant emissions that could be achieved:
. Sources affected by the R&D opportunity and quantity of pollutant
emissions from these sources
. Time to first implementation of the project's results
. Percent of pollutant reduction to be achieved
. Alternative controls not in the scope of combustion R&D, such as
application of downstream controls.
Details concerning the emissions from the various sources are given in Appendix B.
Implementation Cost
Implementation cost for an R&D opportunity is defined as the total cost to society for
implementing the results of the R&D by application to all installations within the source
categories affected. In general, the magnitude of the implementation cost for an R&D oppor-
tunity would far exceed the cost of performing the R&D. Consequently, implementation cost
was the only cost factor considered significant in establishing priority rankings.
Estimates of implementation costs were made by the project team on the basis of
experience and judgment. These estimates were made in terms of increase or decrease in annual
cost, i.e., dollars per year, and included consideration of:
. Changes in capital equipment costs
. Changes in fuel, additive, and power costs
. Changes in maintenance and operating labor costs.
However, because detailed cost studies were not made and because of the uncertainty necessarily
involved in estimating costs far in the future and for items not yet developed, the estimates of
implementation cost were translated into a "verbal portrayal" of the values (high, medium, low,
and very low). These verbal portrayals represent the following approximate cost ranges:
. high:
greater than $1 billion per year
$1 00 million to $1 billion per year
(>$109)
($108 to 109)
($107 to 108)
«$107)
. medium:
. low:
. very low:
$10 million to $100 million per year
less than $10 million per year.
Combination of Benefits and Costs
for Priority Rankings
Ideally, it would be desirable to assign a unique priority index to each individual project
in the total Plan (independent of program element). While such a numerical rating was utilized in
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II-8
the planning process, the individual ratings have been categorized for p~rposes of t~is report. The
estimates and forecasts involved in the calculations of benefits and ImplementatIon costs were
considered too uncertain to permit fine numerical discrimination in presenting the final results of
the priority ranking. Instead, projects were clustered into five priority groupings - A, B: C, D,
and E. The groupings have common significance for all the applied program elements SInce all
applied R&D opportunities in these elements were evaluated on the same basis.
In assigning each R&D opportunity to one of the five priority groupings, both potential
for pollution reduction, as measured by Bk, and the general magnitude of possible implementa-
tion cost, as indicated by the verbal portrayal of cost, were considered. However, greater
emphasis was placed on potential for air-pollution reduction than on possible implementation
costs because at this time benefit estimates are considered more important (and more reliable)
than implem:ntation-cost ~stimates. Furthermore, the need for actually funding the implementa-
tion of a given project cannot possibly arise until the research is nearing completion. At that
time a far better appraisal of both costs and benefits can be made. Therefore, although
implementation cost should be accounted for in establishing priority, it is logical to reduce its
significance compared with the significance of expected benefits.
The procedure used to accomplish the combined priority ranking was to assign a
numerical value on a logarithmic scale, i.e., 1, 2, 4, and 8, to each of the four implementation
cost categories, i.e., very low, low, medium, and high, respectively. The Bk for a given R&D
opportunity was then divided by either 1, 2, 4, or 8, depending on the implementation cost
category into which the opportunity was estimated to fall. The resulting modified Bk values were
then rank ordered from highest to lowest, and cutoff points judgmentally selected to define
priority groupings A, B, C, D, and E.
While this procedure for including consideration of implementation cost does not permit
the R&D opportunities rated lowest with respect to potential for pollution reduction to be
placed in the A-priority group, it does permit some modest variations in priority ranking. For
example, some R&D opportunities with medium values for Bk are ranked in either B, C, or D
priority groups, depending on whether they are estimated to have very low, low, or medium
implementation costs.
It should be noted that the above procedure makes no specific recognition of the
combustion R&D opportunities that are competing, or even mutually exclusive in the sense that
they represent alternative approaches to combustion modification for controlling the same
pollutants from the same sources. Although this feature necessitates some care on the part of the
decision maker employing the Plan, such conflicting R&D opportunities were retained because
they represent alternative schemes whose relative merits cannot be distinguished at this time,
other than as accounted for in the priority rankings. Preliminary or exploratory work on the
alternative schemes would make possible further discrimination at some future time, permitting a
change in priorities or the elimination of distinctly unpromising R&D opportunities from the
Plan.
-------
11-9
EMISSION DATA AND PROJECTIONS
Essential needs of the R&D planning methodology are: (1) knowledge of the present
levels of pollutant emissions and (2) reasonable predictions of what emission levels may be
expected in the future if present trends continue. In response to these needs, a compilation was
made of the latest available information on emissions from combustion sources (1966), and
available projections of emissions between 1970 and 1990 were obtained. Most of the emissions
data and projections were obtained from APCO sources; when no projections were available,
needed data were derived by Battelle staff members. These projections were used to determine
the quantity of pollutant emissions affected by each R&D opportunity.
A summary of the data compilation and of the emission projections follows. Additional
data are presented in Appendix B and the projected pollutant values used in the priority ranking
derivations are tabulated in Tables B-1 through B-S.
POllUTANT EMISSION INVENTORY
Table II-I, an inventory of U.S. pollutant emissions for 1966, is presented to illustrate
the present level of emissions for various combustion sources. The table is based primarily on
data developed and collected by the APCO Division of Air Quality and Emission Data
(DAQED). These DAQED data have been published in the Nationwide Inventory of Air Pollutant
Emissions, 1968. *
In this study, only portions of the detailed APCO breakdowns that apply to
energy-conversion combustion sources were used. For instance, the "Industrial Processing"
category in Table II-I does not include emissions from the manufacture of coke, nor does it
include pollutants arising from materials being processed; for example, data are not included for
iron oxide particles emitted during steel processing. Also, piston-aircraft emissions have been
included in the "Mobile Gasoline" category with automobile emissions as part of IC-engine
emissions; jet-aircraft emissions appear in the "Gas Turbine" category.
The method generally used to determine nationwide pollutant emissions employs tables
of fuel usage (or vehicle miles) broken down by type of fuel user. The amount of fuel consumed
(or the number of vehicle miles) is multiplied by an emission factor appropriate for the
combustor, engine, or boiler. Fuel-usage and vehicle-miles data can be obtained from the U.S.
Census Department's annual Statistical Abstract of the United States. In general, the emission
factors used to generate data contained in Table II-I were taken from the Compilation of Air
Pollution Emission Factors (2nd Printing, 1969). * * DAQED has used factors different from these
in cases where more recent or detailed information within APCO has indicated" that the
published values are in error. For instance, DAQED has made allowances for the variation of
emissions with automobile age.
*Nationwide Inventory of Air Pollutant Emissions, 1968, USDHEW Public Health Service Publication No. AP-73,
Raleigh, North Carolina (1970), 36 pp.
**Duprey, R. L., Compilation of Air Pollutant Emission Factors, Second Printing, USDHEW Public Health Service
Publication No. AP-42, Raleigh, North Carolina (1968), 67 pp.
-------
Table 11-1 - Nationwide Inventory of Pollutant Emissions by Class of Source(a) 1966, 106 Tons/Year
Pollutants
1. Products of incomplete Combustion
Combustible Particulate{C)
CO
Gaseous HC
PNA(b)
2. NOx
3. Combustion-Improving Additives
Lead(d)
4. Fuel Contaminants
SO (d)
x
Ash (Noncombustible ParticulateHc)
5. Total Particulate
102.1
31.51. 27.9
12. 11.2
18.9
30.9
-
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65.8
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0.21
23.5
22.9
6.8
-
10.1
(a) Sources of data: APCD/DAQED and DPCE plus APCD (NAPCA) Reports.
(b) PNA shown in 103 tons/year.
(c) Combustible particulate apportioned from total data by Battelle judgment.
-, not available.
n, emission considered negligible.
Continuous Combustion for Energy Conversion
<0.1
13.5
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pow"r PI~nt<
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(d) Emission values for Lead are for 1967.
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-------
11-11
FORECASTS OF POLLUTANT EMISSIONS
Figures II-I through 11-5 depict the trends of pollutant emissions from energy-conversion
com bustion sources that can be expected between 1970 and 1990. The curves are illustrative of
the pollutant projections used in evaluating the R&D opportunities identified in this report. Data
upon which these figures are based are presented in Tables B-1 through B-4.
Sources of Data for Forecasts
Emission projections presented in Figures II-I through 11-5 are based primarily on APCO
sources. When the APCO emission forecasts were obtained, they had not yet been collected in
one document. APCO's Division of Process Control Engineering (DPCE) is engaged in developing
projections for emissions of SOx, particulates, and NOx from stationary sources. When com-
pleted, these DPCE projections are to be combined with those already developed by DAQED.
Other forecasts included in Figures II-I through 11-5 are from reports completed for NAPCA by
Northern Research and Engineering Corporation * and Esso Research and Engineering
Company * *. In cases when APCO forecasts did not cover all of the categories of interest,
predictions were developed from the same fuel-usage (or vehicle-mileage) sources used for the
projections by APCO.
In Table 11-1, "total particulate" is split into "combustible particulate" and "ash (non-
combustible particulate)" in accordance with published data or by the judgment of the Battelle
team. These particulate data follow the definition of particulate matter assumed by Duprey in
Compilation of Air Pollutant Emission Factors. ***
Some Factors Influencing Emission Trends
In Figures II-I through 11-5, the curves showing rising trends reflect forecasts of increased
demands for energy and transportation. The curves showing projected decreases in emissions with
time are based on predicted switching to fuels emitting lesser amounts of pollutants or on
anticipated emission controls.
The changes in curve slope are the result of various conflicting influences - e.g., more
stringent regulations and better control devices on the one hand and increased number of
pollutant-producing units on the other. In Figures 11-2 and 11-3 the implementation of the 1970
regulations concerning automobile emissions of HC and CO is reflected in downward trends for
these emissions until the projected increase in the automobile and small-truck population causes
emissions to increase. Decreased emissions of particulates from coal-fired power plants due to the
increased use of control devices such as electrostatic precipitators on both new and existing
plants have been predicted by DPCE. However, Figure 11-1 shows that it will probably be several
years before implementation will be sufficient to cause a downward trend in the overall national
emission curve for this source.
*Final Report to National Air Pollution Control Administration, Nature and Control of Aircraft Engine Ex-
haust Emissions, from Northern Research and Engineering Corporation (November, 1968), 388 pp, Contract
No. PH 22-68-27.
**Final Report, Volume II, to National Air Pollution Control Administration, Systems Study of Nitrogen Oxide
Control Methods for Stationary Sources, from Esso Research and Engineering Company, Government Research
Laboratory (November, 1969), Contract No. PH-22-68-55.
***Op. cit.
-------
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Continuous-Combustion Sources
~~~r'!"!.lC~~i~9- - --
Comm;-Res. Heafing
---
---
0.1
1970
1980
1990
11-12
I.C. Engines
I I
oso\if\.:--
,""obi\e t ~
::;.:-- --'-
--- .- diesel
--' --1J;Obi\e.
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0,0"".......""
o~"\ ...
'0(\ ...
S \0";, ...."" I
...
...
...
1970
1980
1990
Year
Particulate from stationary gas engines considered negligible
Figure 11-1. Projected Annual Emissions of Total Particulate from
-------
100.0
10.0
~
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>-
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-
IDa
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11-13
Continuous-Combustion Sources
I.C. Engines
~ qoso\i"~
qoso\i":. ---
5'0' iOl'laf~ 1 - - -
-_.....----
. ",\c" ".'
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II-14
Continuous-Combustion Sources
LC. Engines
10.0
~/i~
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r" ,.'
. ,,\ "
~~. '
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. ' . 'COf1lf1l R
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. e
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. 0('\ -d', ese\
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-- S~""od'
.... '0('\
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1970
1980
1990
1970
1980
1990
Year
HC from gas-fueled power plants considered negligible
Figure 11-3. Projected Annual Emissions of HC from Continuous- and
-------
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~
0
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>.
.........
(/)
c:
0
......
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11-15
Continuous-Combustion Sources
I.C. Engines
\\~e
o~o
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~
gas
./'
diese\. . . . . . .'
., ~~~~~~~~.f.~... ......,
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. oaf':!,
5\0\\0 ",""
---""
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0.1
1970
1980
1990
1990
1970
1980
Year
Figure 11-4. Projected Annual Emissions of NOx from Continuous- and
-------
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10.0
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11-16
Continuous-Combustion Sources
I.C. Engines
,
\IfIob\\e, qaso\i~
~
---~
o\e~''''''-
\IfIob\\,!J .,;:;.'
~'
~'
I I
Industrial Processing
----
----
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-
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t? "
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'?I' \~~~,.."
,/ c,\' , "
" c."'"
.. ....~~<. .
1970
1980
1990
1970
1980
1990
Year
SOx from gas-fuel power plants and gasoline, diesel, and
gas stationary engines considered negligible
Figure 11-5. Projected Annual Emissions of SOx from Continuous- and
-------
II-I 7
In the case of aircraft emissions, the NAPCA report by Northern Research and Engi-
neering Corporation * forecasts a reduction of particulate emissions and an increase in NOx
emissions, reflecting the installation of smokeless jet engines. The reduction in particulate
emissions from jet aircraft will only temporarily retard the rise of the national pollution emission
curve for this source. If the increase in air travel continues at the rate of growth experienced in
recent years, even a reduction of 50 percent in individual aircraft pollutant emissions will be
overcome by the overall increase in jet engine population and the greater mileage flown.
Confidence Level of Forecasts
As mentioned previously, all the emission projections - whether derived by APCO or
Battelle - were calculated by multiplying appropriate emission factors for various pollutant
sources by projections of fuel usage (or mileage). There must always be some hesitancy in
claiming that the emission factors used are undeniably correct, as they can vary with the type,
age, and operating mode of the equipment population assumed. They may also vary in future
years as a result of developments in processes, fuels, equipment, or operating patterns.
Even more uncertain are the projections of fuel usage. They are generally developed by
extrapolating past trends in usage, population growth, or demand, all of which are known to
change. For instance, in the case of the Bureau of Mines forecast of energy demand, ** the
derivation was based on trends prevailing up to 1963; by the time the projections were published
in 1968, some of the predictions were already known to be inaccurate. DPCE, to make its
current predictions of emissions from stationary sources as nearly accurate as possible, has
obtained and employed more recent published and unpublished fuel-usage data from the Atomic
Energy Commission and the Federal Power Commission.
Because of the uncertainties in these inputs to the development of emission projections,
the projections must be considered as having only limited accuracy. Most suspect of all are the
absolute magnitudes of levels projected. However, the trends shown in Figures II-I through 11-5
are probably indicative of what will occur if the present policy of emission control remains
unchanged.
For this planning study, the aim in developing these breakdowns of emissions and in
deriving the projections has been to define the problem of combustion emissions in relation to
the overall air-pollution problem and the relation of the emissions from various combustion
sources to each other. Even in View of the uncertainties of the projections, this aim has probably
been achieved.
The projections in Figures II-I through 11-5 afford the opportunity to develop a semi-
quantitative method of placing priorities on possible combustion R&D opportunities. Using these
projections, estimates can be made of the reductions in emissions that would result if selected
R&D opportunities were funded to fruition.
*Op. cit.
**Morrison, W. E., and Readling, C. L., An Energy Model for the United States Featuring Energy Balances for
the Years 1947 to 1965 and Projections and Forecasts to the Years 1980 and 2000, Bureau of Mines Informa-
tion Circular IC 8384 (July, 1968).
-------
11-18
STRUCTURE OF REPORT
Chapters Covering Program Elements of the R&D Plan
Major combustion-source categories or application areas are discussed in separate chapters
within this report as they pertain to the development of the Combustion R&D Plan. Funda-
mental research is covered separately, but the relevance of fundamental research opportunities to
the application areas is indicated. Chapter designations are as follows:
Applied R&D for Major Source Categories
Continuous-Combustion Sources:
. Chapter III.
. Chapter IV.
. Chapter V.
. Chapter VI:
Central-Station Power Plants
Industrial Processing
Industrial Steam Generation and
Commercial and Residential Heating
Continuous-Combustion Engines -
Gas Turbines and External-Combustion
Engines
. Chapter VII.
Cyclic-Combustion Sources:
Reciprocating Internal-Combustion Engines
Fundamental Research
. Chapter VIII. Fundamental and Broadly Applicable Combustion Research
5-Year R&D Plan
. Chapter IX.
Summary of the 5- Y ear Combustion R&D Plan
Thus, Chapters III through VIII cover separate program elements within the S-Year Plan, and
Chapter IX provides a summary.
The Appendixes cover additional details of the planning rationale and priority ranking
procedure, plus emission data and projections utilized in the ranking evaluation.
-------
11-19
Organization of Material Within
Elements of the R&D Plan
Applied Program Elements. Each of the chapters on combustion processes for the major
source categories mcludes material which provides the following coverage:
. Definition of chapter scope, and general background
. Pollutants of principal concern within the source category
. Emission levels from combustion processes with present practice
. Emission levels attainable with latest technology or potentially attain-
able with promising approaches to combustion modification
. R&D needed to fill technology gaps
. Identification of current R&D relevant to emission control by com-
bustion modification (including tabulation of projects)
. Description of R&D opportunities recommended for the 5- Year Plan,
with funding by fiscal year
. Evaluation and priority ranking of R&D opportunities
. Summary of R&D opportunities by priorities.
Fundamentally Oriented Program Element. Chapter VIII, covering fundamental and
broadly applicable combustion research, is organized in a similar manner, except research needs in
areas of combustion physics and in combustion chemistry are discussed in separate sections.
Current research is identified as pertinent to both areas, and descriptions of research oppor-
tunities recommended for the Plan cover both areas.
Also covered in Chapter VIII is the methodology used for priority ranking of research
opportunities considered to be fundamental and broadly applicable; in this procedure the priority
ranking is based on relevance of a given "fundamental" research opportunity to specific needs
identified under the applied program elements.
Survey of Current R&D Relevant to the Plan
The study provides an overview of current R&D effort by both the private and govern-
mental sectors of the research community. A tabulation of current R&D appears in each of the
chapters covering a program element. It must be recognized that availability of information on
R&D conducted by private industry is limited by proprietary considerations. In the governmental
sector, R&D funded by APCO (NAPCA) and other agencies in fiscal years 1968 through 1970*
has been considered as current R&D; the tabulations include in-house programs, contracts, and
grants.
*FY '71 information is included, where available.
-------
11-20
Tabulations of current R&D. These tabluations include:
.
. Contract or project title
. Sponsoring organization and contract number
. Research organization conducting the work
. Principal investigator(s)
. Objective or scope
. Funding (where known).
Sources of Information. Current R&D was identified and information was obtained from
a variety of sources, including:
. APCO contracts lists and information provided by the APCO staff
. Information provided by searches of DOD projects through the
Defense Documentation Center (literature searches and DOD work
unit summaries), searches of NASA reports, searches of other govern-
ment research projects compiled by the Interagency Advance Power
Group, and data sheets on recent and current research by the
Smithsonian Institution's Science Information Exchange
. Information assembled by the Center for Air Environment Studies, at
Pennsylvania State University, as part of an extensive NAPCA survey
of current research in air pollution *
. Information on foreign R&D activities from the NAPCA Profile
Study on Air Pollution Control in Foreign Countries, being con-
ducted by Esso Research and Engineering Company**
. Discussions and correspondence with personnel of government
agencies, trade associations, industrial companies, research organi-
zations; and universities
. Follow-up discussions with investigators known to the Battelle staff,
or identified through the above sources, or identified by authorship
of papers in the literature.
The tabulations of current R&D projects in the chapters should be viewed within the limits of
the Jibove sources and, thus, cannot be considered a complete listing, particularly of R&D
undertaken by private industry. However, the survey is considered adequate for the purpose of
this planning study, as information which is obscure or proprietary at this time may never be
published, or publication may be delayed beyond its usefulness for the 5-Year R&D Plan.
*Through cooperation of the Center, information sheets as supplied by survey respondents were reviewed and
scre<::ned by Battelle staff to identify combustion-oriented projects. The completed survey was later published
1'>:, PHS as Guide to Research in Air Pollution, 1969. under Contract CPA 22-69-37.
**Through cooperation of Esso R&E, indexed information cards from their survey being compiled at Esso's
laboratories at Abingdon, England, were screened by personnel of Battelle's London office for relevant
combustion R&D. The completed study will be published soon under NAPCA Contract CA 22-69-88.
-------
11-21
Explanation of Format for Displaying Evaluations
of Applied-R&D Opportunities
The R&D opportunities identified and recommended for the 5-Year Plan are described at
the end of each of the applied R&D chapters covering major source categories (Chapters III
through VII). These descriptions include:
. Technical objective and approach
. Rationale and incentive.
The description of each applied R&D opportunity is followed by tabulated information concern-
ing the R&D opportunity.
Figure 11-3 is a sample format intended to illustrate the tabulated material and permit
explanation of its features.
Figure 11.3. Sample Format for Evaluation Summaries of Applied R&D Opportunities
Estimated R&D Cost & Time
R&D Cost Range, 1000's: $
R&D Time Range: Years
- $
Recommended 5-year Funding, 1000's: FY '71.'75
Funding by Fiscal Year, $1oo0's
'69.70 I '71
x**
'72
'73
'74
'75
'76+
Recommended
Provision for funding
on-going R&D
Evaluation
Sources Affected: Categories: e.g., Central.Station Power Plants or Diesel Engines
Relative Potential Benefit (overall rating) : Very Low --+ Very High
Pollutants Affected
cpt CO
HC
PNA
Odor
NOx
Lead
SOx
Ash
~
--
--
% Reduction, Range
Expected
Fraction of ECC Emissions Affected
Noncombustion Controls Factor
Relative Potential Benefit Factor
Implementation Time, years: Range most likely: Est.
Bk Summation
Relative Implementation Cost: Very Low, Low,
Medium, or High
Relative Priority Rating: A, B, C, D or E
Notes:
* shown on $ level of Recommended 5-Year Funding or '76+ funding indicates that R&D may include
one or more field demonstrations to apply results of the R&D.
X indicates that one or more APCO current projects (defined as active in 1969 or 1970) are relevant to
the combustion R&D opportunity described.
tcp = combustible particulate.
-------
11-22
Items incorporated in the format illustrated in Figure II-3 are as follows:
. Estimates of R&D time and cost
- Ranges likely in time and cost, due to imprecision in forecasting
these factors
- Recommended funding by fiscal year and 5-year total.
. Relevance of one or more current APCO projects to this R&D
- Shown by "X" in FY'69-'70 Column*
(Funding levels for current APCO R&D are not shown due to
difficulty in apportioning fractions of current projects which
are relevant to several identified R&D opportunities).
. Sources Affected
- Categories of pollutant sources to which this R&D is applicable.
. Relative Potential Benefit (overall rating)
- A verbal descriptor of the potential value of the R&D in
reducing pollutant emissions - expressed as Very Low, Low,
Medium Low, Medium, Medium High, High, or Very High. This is
a verbal description of the numerical Relative Potential-Benefit
Factor, Bk-
. Pollutants Affected
- Entries in the table within a specific pollutant column indicate
that the R&D affects emissions of that pollutant
- "CP" refers to combustible particulate.
. Percentage Reduction, Range
- The percentage reduction in pollutant emission from the speci-
fied sources resulting from application of the R&D - expressed
numerically as a range from low to high.
. Percentage Reduction, Expected
- The expected reduction in pollutant emission from the specified
sources resulting from this R&D.
*In cases where a given R&D opportunity is relevant to other opportunities or to current R&D projects, the key
designations of the relevant projects are shown above the title of the given opportunity.
-------
II- 23
. Fraction of ECC Emissions Affected
The fraction of the total pollutant emission from all energy-
conversion-combustion sources summed over the period
1970-1990 which can be affected by this R&D.
- This fraction is determined by both the sources affected (based
on data presented in Table B-S) and the time required to
complete and implement the results of this R&D.
. Noncombustion-Controls Factor
- A factor which allows for the likelihood that competing con-
trols (e.g., downstream controls) may be applied to the sources,
thus reducing the benefit that could be accomplished if this
R&D opportunity were successfully completed.
. Relative Potential-Benefit Factor
- The product of: (Percentage Reduction, Expected), (Fraction of
ECC Emissions Affected), and (1.0 minus Noncombustion
Controls Factor). This value presents a relative-numerical mea-
sure of the reduction in total ECC emissions of that pollutant
over the 1970-1990 period which might be ascribed to this
R&D.
- The column headed "l; " is the summation of the Relative
Potential-Benefit Factors for each pollutant. This sum is the
single overall numerical measure of the benefit expected from
this R&D and is identified elsewhere as Bk'
. Implementation Time, years
- The total elapsed time between beginning the described R&D
and making the first field implementation of the results -
expressed both as a d!lge and a most-likely value.
- This factor is used in establishing the Fraction of ECC Emis-
sions Affected.
. Relative Implementation Cost
- The estimated cost of implementing the R&D results expressed
by the verbal descriptors Very Low, Low, Medium, or High.
. Relative Priority Rating
- The priority class, ranging from A (high) to E (low), in which
the R&D opportunity is placed by the ranking procedure.
- The priority ranking of the R&D opportunities is based on a
combination of the Relative Potential-Benefit Factor, Bk, and a
measure of the Relative Implementation Cost.
-------
11-24
Details concerning t~ individual items and the procedures used to derive the Relative Potential-
Benefit and the Relative Priority Ranking are discussed in Appendix A.
SUMMARY OF PRIORITIES FOR THE 5-YEAR PLAN
At the end of each chapter, the R&D opportunities and funding requirements within the
particular source category or program element are summarized by priority class. A consolidated
summary of R&D opportunities and funding requirements for all applied program elements (and
fundamentally oriented research opportunities as a group) is presented by priority class in
Chapter IX. Summary tables in Chapter IX present estimated funding levels by year, by 5-year
total, by priority class, and by program element.
-------
Chapter III
CENTRAL-STATION POWER PLANTS
William T. Reid
Albert E. Weller
TABLE OF CONTENTS
SCOPE OF CHAPTER AND BACKGROUND.
. . . . . . . .
. . . .
. . . .
Historical Background of Development . . . . . . . . . .
Future Criteria for Design. . . . , . . . . . . . . . . . . . . .
POLLUTANTS OF PRINCIPAL CONCERN
. . . . . . .
. . . . . . . . . .
Products of Incomplete Combustion. . . . . . . . . . .
Nitrogen Oxides. . . . . . . . . . . . . . . . . . . . .
Sulfur Oxides. . . . . . . . . . . . . . . . . . . . . .
Fly Ash and Other Noncombustible Particulates. . . . . . . . . .
EMISSION LEVELS FROM COMBUSTION PROCESSES IN POWER PLANTS. .
. . . .
Emission Levels with Present Power-Plant Practice
Emission Levels for Power Plants Probably
Attainable with Latest Technology. .
. . . . . . . .
. . . .
. . . .
. . . . . . . .
PROMISING NEW COMBUSTION SYSTEMS. . . . . . . . .
. . . . . . . .
Control of Emissions with Fluidized-Bed Combustion. . . . . . . .
Status of Fluidized-Bed Combustion. . . . . . . . . . .
Burning Rates in Fluidized-Bed Combustion. . . . . . . . . . .
Emission Data from Fluidized-Bed Experiments . . . . . . .
Appraisal of Fluidized-Bed Combustion for Power Plants. . . .
Advanced Power Cycles. . . . . . . . . . . . . . . . . . . . .
GAPS IN NEEDED COMBUSTION R&D TO REDUCE POWER-PLANT EMISSIONS. . .
Two-Stage Combustion. . . . . . . . . . . . . . . . . .
Recirculation. . . . . . . . . . . . . . . . . . . . . . . . .
Improved Combustion and Heat Extraction. . . . . . . . . . . . . . .
Gasification. . . . . . . . . . . . . . . . . . . . . .
Fluidized-Bed Combustion. . . . . . . . . . . . . . . . . . . .
Ash Capture. . . . . . . . . . . . . . . . . . . . . . . . .
Fly-Ash Agglomeration. . . . . . . . . . . . . . . . . . . . . .
Ash Fluxing. . . . . . . . . . . . . . . . . . . . . .
Modification of Fly-Ash Resistivity. . . . . . . . . . . . . .
SUMMARY OF CURRENT AND RELEVANT COMBUSTION R&D .
R&D OPPORTUNITIES RECOMMENDED FOR THE 5-YEAR PLAN
Summary by Priorities. . . . . . . . . . . . . .
. . . . .
. . . . . . . .
. . . .
. . . .
REFERENCES FOR CHAPTER III
. . . . . . . . .
. . . . . . . .
111- 1
- 2
- 3
- 4
- 4
- 4
- 5
- 5
- 6
- 6
-12
-14
-14
-14
-17
-18
-20
-21
-21
-22
-22
-23
-23
-23
-23
-23
-24
-24
-24
-27
-45
-------
.
!
-------
111-1
CHAPTER III
CENTRAL-STATION POWER PLANTS
SCOPE OF CHAPTER AND BACKGROUND
This chapter is concerned with potentially valuable combustion research to reduce the
principal air pollutants emitted by large central-station power plants (100 MW and larger) having
fossil-fuel-fired steam generators. These pollutants are: (1) products of incomplete combustion -
i.e., partially oxidized fuel emitted as combustible particulate matter, carbon monoxide, and
polynuclear aromatics (PNA); (2) nitrogen oxides; (3) sulfur oxides; and (4) fly ash and
particulates formed from fuel contaminants and noncombustible additives. Thus far only par-
ticulate emissions have been controlled to any appreciable extent and this, in great part, has been
by use of mechanical collectors and electrostatic precipitators downstream of the combustion
process.
Table 111-1 shows the emission of various pollutants from central-station power plants in
terms of the total emission from all energy-conversion combustion sources burning prime fuels.
Table 111-1. Pollutant Emissions From Central-Station Power Plants*
Contribution to Nation-
wide ECC Emissions,
percent
Pollutant Coal Oil Gas Total
Products of Incomplete Combustion
Combustible Particulate 18 <1 <1 18
CO <1 nil nil <1
Gaseous HC <1 <1 nil <1
PNA nil nil nil <1
NOx 16 2 3 21
Combustion-Improving Additives
Lead nil nil nil nil
Fuel Contaminants
SOx 59 4 nil 63
Ash (Noncombustible Particulate) 72 <1 nil 72
*Data derived from Table 11-1.
-------
III - 2
Clearly, central-station power plants are important emitters of combustible part~culates,
nitrogen oxides, sulfur oxides, and noncombustible particulates (ash), and they are likely to
remain so unless appropriate steps are taken.
The generation of electric power by public utilities is expected to increase from about
1.57 x 1012 kWh in 1970 to 2.4 x 1012 kWh in 1975, a growth of 53 percent in the 5-year
period. Historically, the generation of electric power has about doubled every 10 years. For the
future, many estimates call for doubling in 8 years. Most of this power is and will be generated
by the combustion of prime fuels. The following tabulation shows the sources of energy for the
current pattern of electric-power generation.
Energy Sources for the Generation of
Electric Power by Public Utilities (1969)
Fuel
Percentage
Fossil-Fuel-Fired Plants
Coal
Oil
Gas
49
9
22
Noncombustion Plants
(Nuclear, Hydro, Etc.)
20
Little combustion research is now being conducted by boiler manufacturers, public
utilities, fuel suppliers, or research laboratories to minimize air pollution resulting from the
combustion process itself in large central-station power plants. Central-station power plants
traditionally have sought to produce electricity at the lowest possible cost, achieved mainly by
engineering advances and by empirically derived developments.
Historical Background 01 Development
Fuel economy in the best plants has not changed radically since 1950, approximating
8600 Btu per kWh, or an overall thermal efficiency of 40 percent. Conditions in boiler furnaces
are about the same as they have been for the past few decades.
Figure 111-1 illustrates a typical time~temperature profile in a modern boiler.
The one significant change in generating electricity has been in the increasing size of the
boilers. Over the past 25 years, the largest boilers have increased from less than 100 MW
capability to more than 1000 MW; units rated at 1300 MV are now on order. Steam pressure has
increased from 2400 psi to 3500 psi in 25 years, but steam temperature has not changed
appreciably over this time, increasing only from 950 F to 1000 F. Units have been built with
pressures up to 5000 psi and temperatures up to 1200 F, but these are exceptions, not the rule.
Thus, while the physical size of boiler furnaces has increased tremendously, the temperature of
the heat-receiving surfaces, and hence the heat-absorption rate, has not changed significantly.
-------
111-3
Although combustion research has aided broadly in the design of large boiler furnaces,
generally these units have been improved by small incremental design changes, largely on an
empirical basis. There has been little variance in the basic design of boiler furnaces over the last
25 years, and little change is foreseen in the immediate future except for the possible introduc-
tion of fluidized-bed combustors.
2800
2400
2000
IJ...- 1600 -
~
~
~
CI)
a.
E 1200
~
Future Criteria 10r Design
800
/PreciPitator
400 350 F
I Superheoter/ Reheoter/ I
Economizer/Air Heater
Furnace Slack
o
~IIO 2 see+-- 2 to 5 see .1.. 510 6 see
Time
300 F
~I
Figure Itl-'. Time-Temperature Profile in a Typical Large Boiler Furnace
The economics of power generation may have to be revised radically in light of the
present demands for clean air. Minimum costs per kWh of output - the goal of central-station
power-plant operators since the industry began - may now have to be replaced by a new
criterion of minimum contamination of the atmosphere per kWh generated. In the future, the
costs of clean operation may have to be accepted in the same way as the costs of fuel, of
maintenance, or of money. With this viewpoint, predictions of the lower limits of emissions from
future large boiler furnaces should be based on what will be technically feasibility rather than on
cost. At the same time, when a choice is available between alternative schemes, the lower cost
one will naturally be selected. The estimates in this chapter of probably attainable levels of
pollutants reflect emphasis on feasibility rather than on cost, but without ignoring economics
entirely.
The burning of fuels in fluidized beds is discussed in a separate section because of the
wide interest in this unique combustion process.
-------
IlIA
POLLUTANTS OF PRINCIPAL CONCERN
Four classes of pollutants generated by central-station power plants are of most concern:
. Products of incomplete combustion, including fuel emitted as
combustible particulate matter, CO, gaseous He, and PNA
. NOx
. SOx
. Fly ash and particulates formed from fuel contaminants and
from noncombustible additives.
Products of I ncomplete Combustion
Small amounts of unburned fuel are emitted from modern coal-fired boiler furnaces. In
most cases, such unburned coal particles are coked, often forming cenospheres_* with low bulk
density. This devolatilized, unburned coal seldom exceeds 25 percent of the weight of the fly
ash. On an efficiency basis, the carbon loss usually will not exceed 0.5 percent of the coal fired.
Droplets of fuel oil will not survive the flame in a boiler furnace, although, if atomization
is poor, "sparklers" of larger-than-average oil droplets can be seen beyond the normal flame
envelope. When burning residual fuel oil with very low excess air to prevent formation of S03
(typically as little as 0.2 percent oxygen in the flue gas), small amounts of CO may be present in
the flue gas. Very-low-ex cess-air operation, although practiced widely in Europe, has not been
popular in the United States because of associated control problems.
CO levels in flue gas are usually under 1000 ppm and sometimes as low as 100 ppm.
Other substances that may be emitted as partial oxidation products of the fuel are aldehydes and
organic acids, and PNA. The organic acids usually are not characterized, although formic acid
probably predominates. Polynuclear aromatics, including pyrene, perylene, benzopyrene,
anathrene, and coronene have been identified in flue gas from coal-fired units.
Nitrogen Oxides
To attain high combustion efficiency and to use boiler-furnace volume effectively,
combustion temperatures frequently reach 3100 F in large central-station units. Such high
temperatures are maintained for a short time, perhaps as little as 50 milliseconds in the flame
region. The flue gas is then cooled to about 350 F over a period usually ranging up to 5 seconds,
as shown in Figure III-I.
Nitrogen in combustion air reacts with oxygen at the peak temperatures to form NO,
the amount so produced depending largely on the peak temperature. Nitrogen compounds in the
fuel also may contribute to NOx formation.
*Cenospheres are microscopic, porous spheres of carbon remaining after partial combustion of a hydrocarbon.
-------
III-5
Sulfur Oxides
Natural gas is the only fossil fuel used in power plants that is substantially free of sulfur.
Coal contains varying amounts of sulfur as organic sulfur which is part of the coal substance
itself, and as pyritic sulfur which exists as discrete particles of FeS2. On the average, these two
forms of sulfur are about equally prevalent in American coals. Some of the pyritic sulfur can be
removed by coal preparation, but none of the organic sulfur can be removed without destroying
the complex coal substance. Hence, most of the sulfur originally in coal, ranging typically up to
5 percent, enters the furnace and is converted by combustion into sulfur oxides, mostly S02.
Insignificant amounts of sulfur are captured by slag, bottom ash, and fly ash.
In oil, sulfur occurs as part of the complex mixture of compounds making up petroleum
fuels. Residual fuel oil occasionally contains up to 5 percent sulfur. No physical methods will
remove such sulfur compounds, but hydrodesulfurization can remove varying amounts of sulfur
during refining. Costs of desulfurization are high but are decreasing.
It is axiomatic that, at usual furnace temperatures, changes in combustion have no effect
on SOx emission other, possibly, than shifting the ratio of S02 to S03, which is usually 100: 1.
Only under highly reducing conditions, not currently used in steam-power-plant practice, is the
sulfur present as H2S,
Fly Ash and Other Noncombustible Particulates
Coal-fired dry-bottom furnaces capture only a small amount of the ash present, perhaps
20 percent. With slag-tap furnaces, about half the ash forms slag on the furnace walls and on the
hearth, and with cyclone furnaces, about 90 percent of the ash forms slag. The remaining ash in
each case either is caught as deposits on superheater and reheater elements or in ash hoppers, or
is carried out of the boiler as fly ash. A combination of mechanical and electrostatic collectors
can usually remove at least 95 percent of this particulate matter from the flue gas, and
occasionally as much as 99 percent.
Coal contains 100 to 200 times more ash than fuel oil. Hence, the fly-ash problem is
more serious for solid fuels than for liquid fuels. Changes in the combustion system of coal-fired
units have little effect on the emission of ash except that slag-tap and cyclone furnaces are more
effective than dry-bottom furnaces in converting ash into slag, and therefore in decreasing the
dust burden in the flue gas. Generally, the quantity of ash emitted from oil-fired boiler furnaces
is insignificant. Nevertheless, even this small amount of ash can cause a problem by forming a
visible stack plume.
Two forms of noncombustible additives that contribute to particulate emissions are used
in oil-fired boiler furnaces: (1) MgO as a means of controlling external corrosion and (2)
metal-based proprietary compounds added as "combustion improvers". Neither type of additive
is used in large quantities and their contribution to power-plant emissions is negligible.
-------
III-6
EMISSION LEVELS FROM COMBUSTION PROCESSES
Following are discussions of levels of emission with present practice and levels probably
attainable with the latest technology.
EMISSION LEVELS WITH PRESENT POWER-PLANT PRACTICE
Products 01 Incomplete Combustion
Combustible loss when burning pulverized coal depends upon many factors, such as the
heat-liberation rate in the furnace, the proximate analysis of the coal (in particular the volatile
matter), the particle size of the pulverized coal, and the excess air. In short, the parameters of
time, temperature, and turbulence - plus the reactivity of the coal - all influence the fraction
of unburned fuel escaping from a large central-station boiler furnace.
Unburned Carbon
At typical operating conditions* the carbon loss can be expected not to exceed 0.1
percent with dry ash removal and about half this for a slag-tap furnace,( 1) Table III-2 shows the
carbon loss that can be expected when burning coals of different volatile content under various
Table 111-2. Unburned Carbon Loss From Pulverized-Coal-Fired Boiler Furnaces(1)
Heat Volatile(a) Unburned Carbon,
Release Matter Coal Smaller Ib/106 Btu Input(b)
Rate, in Coal, Than 200 Mesh, Excess Air, Dry-Bottom Slag-Tap
1000 Btu/ft3-hr percent percent percent Furnaces Furnaces
20 20 65 10 3 3
20 48 65 10 0.3 0.2
20 48 80 10 0.06 0.03
20 48 80 40 0.03 0.02
40 20 65 10 5 3
40 48 65 10 0.6 0.5
40 48 80 10 0.2 0.2
40 48 80 40 0.06 0.05
(at Dry, ash-free basis.
(b) Based on 13,100 Btu/lb for coal.
*For example, a furnace liberation rate of 20,000 Btu per cu ft-hr with 48 percent volatile matter on a dry,
ash-free basis, with 80 percent of the coal pulverized to a particle size smaller than 74 microns, and with
10 percent excess air.
-------
111-7
conditions. It is evident that the rank of the coal is highly important, with furnace heat-
liberation rate and excess air having a significant effect. Both heat-liberation rate and excess air
are controllable, and their effects might be enhanced by the results of appropriate combustion
R&D. However, the small quantity of unburned carbon leaving the furnace provides little
incentive for improvement.
When burning oil, the same general conditions apply except that droplet size is significant
rather than particle size, and excess air is less important. One problem encountered with oil-fired
furnaces that does not occur with coal-fired units is the emission of "acid smuts", agglomerates
of unburned carbon saturated with condensed sulfuric acid. Control measures are available,(2)
and acid smuts presently pose no real problem in central-station power plants.
Carbon Monoxide
The level of CO in the flue gas of large boiler furnaces is low. Because CO repre-
sents a loss in fuel, it is kept to levels below the detection limits of conventional Orsat gas
analyzers, or less than 0.1 percent (1000 ppm). With low-excess-air burners, CO levels, measured
by an infrared analyzer, can be used to control the combustion air. The first significant
measurable increase in CO is taken as a signal that the oxygen available is inadequate.
Bureau of Mines measurements(3) in a pulverized-coal-fired boiler furnace showed
momentary CO peaks of as much as 1000 ppm, but with the usual levels well below 100 ppm.
Hangebrauck( 4) reported CO levels equivalent to 0.004 to 0.10 Ib per 106 Btu input for
pulverized-coal-fired furnaces. At the 100-ppm level, 0.084 Ib of CO is present in flue gas for
106 Btu input.
Polynuclear Aromatics
Information on the presence of PNA in the flue gas of central-station power plants has
been obtained by the Public Health Service,(5,6) the Bureau of Mines,(3) and Bituminous Coal
Research, Inc.(7) No consistent pattern has emerged relating emission levels of PNA and
operating conditions in central-station power plants.
The one major factor apparently affecting the output of a typical polynuclear aromatic
[benzo(a)pyrene (BaP)] is gross heat input to the furnace. Table 111-3 compares the effect of
heat input on the amount of benzo(a)pyrene (BaP) emitted for systems ranging from hand-fired
to central-station power-plant furnaces burning coal, oil, and gas.
Nitrogen Oxides
The amount of NOx in flue gases depends largely on the peak temperature reached
during combustion, since the cooling rate is high and the rate of decomposition is low. The
primary reaction product is NO, with N02 formed after the flue gases are cooled.
Figure 111-2 illustrates the NO level in eight different central-station boiler plants burning
gas and oil in horizontal or tangentially fired furnaces.(8) In these examples, higher NO
concentrations occurred with oil firing than with gas by a factor of about 2. Figure 111-2 also
illustrates that there can be large differences between different units. No firm explanation is
available concerning the pronounced influence of the firing method. Obvious possibilities are that
the peak temperatures must vary and that the residence times can be appreciably different.
-------
111-8
Table 111-3. Effect of Gross Heat Input on Emission of Benzo(a)Pyrene(S.6)
Gross Heat Input BaP in Flue Gas,
to Furnace, micrograms/106 Btu input
Fuel Btu/hr Maximum Minimum
Coal 5 x 104 1 x 107 4 x 103
Oil 5 x 1 04 100 <40
Gas 5 x 104 <20
Coal 1 x 107 4 x 1 03 50
Oil 1 x 107 50 20
Gas 1 x 107 <20
Coal 1 x 1 09 5 x 102 15
Oil 1 x 109
Gas 1 x 109
.--- - ---- -_.,-----~-----_._-,---~----- ---~------------ --------
E 600
a.
a.
ai
"U
)(
o 400-
-------- ------ --
c
Q)
0'
o
L..
+-
Z 200
o
Plant;
Firing:
Fuel:
EIS ABC E F GElS A B D E F
I-Horiz.----II-Tang.~ I--Horiz.-------I j.Tan~
1- Oil --- -11--- Gas ~I
Figure 111-2. Comparison of Horizontal and Tangential Firing,
-------
111-9
Without making major changes, but by varying auxiliary air dampers, NOx levels have been
lowered in some of the units of Figure 111-2 by up to 32 percent for oil firing and up to 31
percent for gas firing.(8) By partially delaying air admission, and thus the final complete
oxidation of the fuel, peak temperatures and the NOx concentration are decreased. Despite this
success, "two-stage" combustion is not used commonly in everyday practice.
Figure 111-3 illustrates experimental work in a small-scale test tunnel and the actual NO
levels in the El Segundo Station of the Southern California Edison Company.(9) With 85 percent
of the air supplied through the burner in the test tunnel, NO levels were less than a third of
those with the total air supplied through the burner. It was found that essentially all formation
of NO occurred within a comparatively small zone within a few feet of the burner. Limited
recirculation in the test tunnel had little effect on NO formation and humidifying the com-
bustion air did not lower the NO appreciably. The reason for this is not clear, since the flame
temperature should have been decreased significantly both by recirculation and by increasing the
humidity.
Emission of NOx from coal-fired boiler furnaces depends at least in part on the way the
coal is fired, and on the boiler load. Under full-load conditions, for example, firing pulverized
coal through either vertical, corner, or wall burners showed about a 2 to 1 difference in NOx
emission, the NOx levels after the fly ash collector ranging between 310 and 606 ppm, or 0.55
to 0.95 lb NOx per 106 Btu.(10) With a cyclone furnace, where the temperatures are higher,
1160 ppm or 2.2 lb NOx per 106 Btu was emitted. At part load, the amount of NOx was
o Oil firing
100 0 Gas firing
Qj
>
~
0 I
E
0 ! I
c:
'0
C 60 2H
QJ
~
QJ eH-
a. ~I
01
QJ 01
>
QJ 40 E
-I ~I
QJ ~I
:2 I
6 1
u 1
:E I
z 20
I
I
1
1
I
080 90 100 110 120
Tola I Ai r Through Burner, percent
Figure 111-3. Comparison of EI Segundo and Alliance Test-Tunnel Results
During Two-Stage Combustion(9)
-------
III -10
appreciably less, ranging between 171 and 453 ppm, or 0.31 to 0.74 Ib per 106 Btu for
pulverized coal, and 784 ppm, or 1.8 Ib per 106 Btu for cyclone firing. There is an
appreciable differenc6 possible between individual units, and there is the further complication of
the influence of nitrogenous compounds in the coal. The coals fired here contained from 1.3 to
1.6 percent nitrogen as shown by an ultimate analysis; the exact nitrogen compounds in the coal
were not investigated.
According to the extensive NAPCA/Esso study,o 1) electric generating plants can be
expected to emit 0.76 Ib of NOx per 106 Btu input for coal, 0.69 Ib for residual fuel oil, and
0.38 Ib for natural gas.
Sulfur Oxides
Emission of S02 depends almost entirely on the amount of sulfur in the fuel. A possible
exception is with coals containing appreciable amounts of CaO in the ash, as do some Illinois
coals and a few of the lower-rank coals. In such cases, as much as a fourth of the sulfur may be
retained in the ash as CaS04. It can be assumed generally that 95 percent or more of the sulfur
in the fuel will be evolved as SOx if the fuel is burned in conventional furnaces.
With the coals commonly burned today, the S02 in flue gas ranges from about 800 ppm
to 4000 ppm. Table 111-4 lists S02 emissions for typical sulfur levels in American coals. It also
shows the S03 emissions, assuming that S03 is one percent of the S02. S03 in flue gas, which
even in very low concentrations can produce a visible plume from the stack, results from
reactions in the flame where oxygen atoms oxidize S02 to S03. Figure 111-4 shows the change in
flame-produced S03 under noncatalytic conditions as excess air is varied. (12)
The oxidation of S02 to S03 by catalytically active surfaces contributes little or nothing
to the S03 in flue gas; such S03 commonly reacts with the surface or is adsorbed on fly ash.
The amount of S03 formed this way can vary widely; generally it amounts to less than 5
percent of the total sulfur in the flue gas.
Table 111-4. Sulfur Oxides in Flue Gas From Coal Firing(a)
Sulfur in Coal, S02 in Flue S02, Ib/106 S03 in Flue S03,lb/106
percent Gas, ppm(b) Btu Inputlc) Gas, ppm(d) Btu Input(d)
1 800 1.53 8 0.019
2 1600 3.06 16 0.038
3 2400 4.59 24 0.057
4 3200 6.11 32 0.076
5 4000 7.64 40 0.095
(a) Assuming no capture of 802 by coal ash.
(b) Based on 140 ft3 wet flue gas/lb coal at 32 F and 1 atm.
(c) Based on 13,100 Btu/lb coal.
(d) Based on 803 in flue gas being 1 percent of the 802.
-------
III -11
40
E
a.
a.
rt')
o
(f)
30
20
10
Fuel: Natural gas contain-
ing 5~ percent S by weight
Sampling position: 24 in.
from burner plate
o
Figure 111-4. Effect of Excess Air on Formation of 803(12)
Table 111-5. Fly Ash in Flue Gas
Coal: 10 percent ash; 13,100 Btu/lb
Dusting Loading as
Percentage of
Ash in Coal Fired
Ash Suspended in Flue Gas
Ib/kWh Output(a) Ib/106 Btu Input
10 (typical cyclone burner)
25
0.0065
0.016
0.033
0.052
0.065
0.76
1.90
3.80
6.08
7.60
50 (typical slag-tap furnace)
80 (typical dry-bottom furnace)
100
-------
111-12
Fly Ash and Other Noncombustible Particulates
The quantity .of fly ash emitted by modem boiler furnaces depends on the fusion
characteristics of the ash, the furnace design, and the time-temperature-turbulence conditions in
the furnace during combustion.
Table 111-5 lists calculated quantities of solid particulates suspended in the flue gas for
varying levels of dust loading. Part of the fly ash settles and is caught in ash hoppers and
mechanical collectors as the flue gas moves through the boiler. This fraction varies widely, and
only the larger particles of ash are removed in this way. Electrostatic precipitators are commonly
used to capture smaller particles, and there has been some experimental use of bag filters to
remove the smallest ash fragments.
EMISSION LEVELS FOR POWER PLANTS
PROBABLY ATTAINABLE WITH LATEST TECHNOLOGY
Products 01 Incomplete Combustion
There appears to be no inherent technical reason why the amount of carbon, CO, and
PNA from conventional large boiler furnaces should not be held at the lowest 'levels that have
been observed in such furnaces. As an example, for pulverized-coal-fired boilers these levels are:
Combustible particulate
CO
PNA
0.05 lb per 106 Btu input
0.0004 lb per 106 Btu (5 ppm)
5.5 lb per 1012 Btu.
The high-temperature and long-residence-time requirements to reach these levels do not appear to
be so great as to conflict with the requirements for low NOx' Smaller furnaces, to match the
emission levels of larger units, might require such changes as higher rates of heat release and the
use of fuels that react more rapidly. However, the trend of the public utilities is to larger and
larger furnaces.
Making further improvements in performance will require a more detailed understanding
of the effect of time, temperature, and turbulence on the burnout of the products of incomplete
combustion, plus a translation of this understanding to changes in design and operation.
Nitrogen Oxides
The concentration of NO formed during combustion is controlled by the peak tempera-
ture, the availability of nitrogen, and - according to the usually accepted reaction mechanism -
the concentration of oxygen atoms.
As all practical central-station combustion devices must use air as the oxidant there is
,
little possibility of reducing the availability of nitrogen. Most attempts at reducing the
concentration of NO have centered on reducing the peak combustion temperature. Such attempts
include the use of two-stage combustion, with heat extraction, and cooled-flue-gas recirculation.
-------
111-13
The possibility of reducing the a-atom concentration has not been widely considered.
Operation near stoichiometric fuel-air ratio, which would be expected to reduce the 02 and a
levels, can result in high NO levels if the temperature is increased. However, it should be noted
that a reduction in a-atom levels would be expected in the first stage of a two-stage burning
process and that this may contribute to the observed reduction in NO.
Experiments on two-stage combustion in boiler furnaces(9) have demonstrated a reduction
in NOx levels of about 50 percent, and in an experimental combustor, a reduction of about 70
percent. Extrapolation of these results suggests that a well-engineered two-stage combustion
system might reduce the NOx levels to about 10 percent of the current levels, or 0.04 - 0.07 Ib
per 106 Btu for gas- and oil-fired boilers.
For coal-fired units, the best performance demonstrated in an actual central-station plant
appears to be an emission of about 0.5 - 0.6 Ib NOx per 106 Btu from a conventional
pulverized-coal-fired unit. However, in experiments in a small furnace simulating a central-station
boiler furnace, changes in excess air level and control of air admission locations made possible
NOx reductions of perhaps 60 percent (from 550 ppm to 210 ppm in the experimental
furnace).03) If these results could be duplicated in a full-scale boiler furnace, emission levels of
0.2 - 0.41b 106 Btu would result.
Sulfur Oxides
If downstream control measures and fuel selection are excluded, there is no current or
near-future technology available to control sax emissions from central-station power plants, with
the exception of fluidized-bed combustors using limestone or dolomite as the inert bed material.
Emissions are thus dependent on the sulfur content of the fuel and are as previously described in
Table 111-4.
Fly Ash and Other Noncombustible Particulates
Emissions of fly ash and other noncombustible particulates are currently controlled by
downstream methods, and no control measures are known which could eliminate the need for
such downstream controls, although, as pointed out previously, changes in the firing method can
reduce the dust burden on the collectors.
An important aspect of fly-ash control is that when the S03 level in the flue gas is
reduced, conventional electrostatic collectors become less efficient.
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111-14
PROMISING NEW COMBUSTION SYSTEMS
Two unconventional approaches to combustion for central-station power plants are
receiving new attention, namely fluidized-bed combustion and gasification of fuels for ad-
vanced power cycles. These concepts are discussed in this section.
CONTROL OF EMISSIONS WITH FLUIDlZEO.BED COMBUSTION
Burning crushed coal in a fluidized bed of limestone could have considerable merit for
reducing air pollution. The residence time can be made long, and the fuel-bed temperature
limited to perhaps 1800 F. Calcined limestone should be effective in capturing S02 and S03
since CaS04 is stable at this temperature. Further, since one of the features of a fluidized bed is
temperature uniformity, there should be no localized high-temperature zones, and the formation
of NOx would be largely avoided. Particulate emission might be high, requiring an electrostatic
precipitator to prevent excessive emission of fly ash from the stack.(14)
Status of Fluidized-Bed Combustion
Most investigations of fluidized-bed combustors have been done on a laboratory scale,
and most of the projections for large-scale systems for central-station power plants must be based
on these limited data, including burning rates, carryover, heat transfer, S02 capture, and the like.
However, sophisticated engineering analyses are being done now to lead to concepts for eventual
trial on a large scale.
United States
In the United States, Pope, Evans and Robbins(15) have investigated fluidized-bed
com bustion experimentally most extens~vely but their efforts have been directed toward indus-
trial boilers with an output up to about 350,000 Ib per hr of steam. Such preassembled boiler
furnaces with maximum shipping dimensions of 12 ft wide, 16 ft high, and 60 ft long would
provide this rating. Ten or more of these "modules" might be assembled further into a large
boiler furnace with an output of 3 to 5 106 Ib per hr of steam.
The modular fluidized-bed boiler concept of Pope, Evans and Robbins is based on
BCURA's projection of a heat release of a 106 Btu per sq ft-hr for the fuel bed, equivalent to
burning 76 Ib per hr of a typical bituminous coal. On establishing the design parameters of the
Fluidized Bed Module (FBM)05) at this burning rate, it was found by these investigators that
imbedded heat-transfer surfaces were undesirable. Excessive cooling of the bed could lead to
excessive carbon losses through carryover, even with a secondary, lower-velocity carbon-recovery
fluidized bed operating at 2000 F. Nevertheless, Pope, Evans and Robbins are enthusiastic about
the modular concept as the proper approach to large utility-type boilers. Their projected heat
balance for a 50-MW fluidized-bed utility boiler shows a net thermal absorption of 91.8 percent
and a carbon loss of 2 percent.
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III-IS
The U. S. Bureau of Mines( 15) has investigated the burning of coal in a fluidized-bed
combustor as a means of reducing the emission of pollutants. Their goals are to evaluate the
suitability of different coals; to study erosion, corrosion, and deposition on heat-transfer
surfaces; and to determine heat-transfer characteristics in fluidized beds. Preliminary burning tests
have been made using alumina as the inert bed material. Boiler-tube investigations, to be made in
an l8-inch-diameter combustor, using eight types of alloys (ranging from mild steel to TP 316
alloy containing l8Cr, l4Ni, and 3Mo) were planned for late in 1970. Based on tests of only
lOG-hr duration, there is some question that enough damage will occur under non-accelerated
conditions to permit meaningful extrapolations of metal wastage for different alloys over the
nominal life of a fluidized-bed combustor.
A wide variety of concepts are being evaluated by Westinghouse,(l5) mostly stressing a
pressurized system at 10 atmospheres to operate in conjunction with a gas-turbine expander. In
their preliminary design calculations for a unit with a rating of 600 MW, regenerated lime would
be used to capture 95 percent of the S02 in the flue gas. This would require large amounts of
lime in the bed - about 8 times stoichiometric based on S02 - which mainly would affect the
costs of handling and regeneration. Details of the final system are still being developed. For the
present, a modular design based on a unit 12 ft by 16 ft by 40 ft is being considered to permit
shop fabrication. This unit would have a fluidized bed area of 50 to 60 sq ft. The number of
these units required, the configuration in which they are stacked, and details of the handling of
solids and gases have not been established as yet. Projected cost for the pressurized power plant
is $156 per kW, based on a boiler efficiency of 89 percent and allowing $40 per kW for the
fluidized-bed system. The major design details yet to be established concern the arrangement of
heat-transfer surfaces; the location and physical layout of evaporator, superheater, reheater, and
economizer sections; and the provision of baffles and gas deflectors to minimize carryover.
Preliminary layouts proposed by Foster Wheeler(l5) for Westinghouse call for tall cylin-
drical boiler furnaces with annular or rectangular beds to make maximum use of the space within
the pressurized shell. Annular beds are preferred; coal would be introduced tangentially at a
number of points on the outer periphery of the beds. Such a concept permits stacking
evaporator, superheat, and reheat sections of the boiler in one continuous shell, simplifying gas
handling. Comparison between pulverized-co aI-fired boiler furnaces and the proposed fluidized-
bed system with a gas turbine show a markedly smaller combustor for the fluidized system, with
material costs only 18 to 19 percent that of conventional units. Final concepts are still being
developed.
Consideration is being given( 15) to the Ignifluid process for two 300 MW units at the
proposed Nanticoke Station of UGI (The United Gas Improvement Co.) to burn Pennsylvania
anthracite culm. Tests in France burning this Pennsylvania anthracite in an Ignifluid unit suggest
that a burning rate of 130 Ib per sq ft-hr can be achieved, but carbon in the resulting ash from the
anthracite culm in these tests was 17 to 20 percent. Hence the proposed boiler furnaces will re-
quire post-combustion units to decrease the carbon loss to 10 percent of the ash. The exact status
of these two proposed units is not clear.
France
The "Ignifluid" process developed in France has been intended for industrial rather than
for utility applications. Proposals have been made to build 250-MW power plants in Europe with
twin Ignifluid boilers, but the present status of those proposals is unknown. Interest in the
United States by UGI may lead to large-scale -units here before they are available in Europe.
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III-l 6
Germany
Lurgi(24) has tleveloped a fluidized-bed combustion system to dispose of refinery wastes
in Germany, but the fuels are sufficiently different and the scale of the combustor is small
enough that the design may not be easily adaptable to large central-station power plants. Data
from that development, nevertheless, should be helpful.
Czechoslovakia
A large effort on fluidized beds has been going on in Czechoslovakia, mainly as a way of
burning coals containing more than 50 percent ash. The fluidized combustor is to act as a gas
producer, not a steam generator, by burning the coal with about one-third stoichiometric air.
This gas then is to pass to a conventional boiler where the remaining air will be provided. Plans
were being made in 1969 to build a 33-MW demonstration unit with a 10-ft diameter combustor.
England
The National Coal Board (NCB) in England has been particularly active in fluidized-bed
com bustion, both at their laboratories in Stoke Orchard and at the BCURA Industrial Labora-
tories in Leatherhead. Their work stresses economics. Because a fluidized bed can maintain a
heat-transfer coefficient of 50 to 100 Btu per sq ft-hr- F at a bed temperature of 1500 F, at least
a four-fold reduction is expected in the capital costs of a boiler, superheater, and reheater.
Further, at this low combustion temperature, plant availability should be improved because of
freedom from external corrosion and deposits. Taking into account increased costs for com-
pressing the fluidizing air and distributing it to the combustion zone should still lead to an
expected net savings of 10 percent in the overall costs of a 500-MW unit, according to early
estimates by NCB.
In recent tests(24) of British coals by the NCB at a fluidizing velocity of 3 fps, it was
found on the average that a Ca/S ratio of 1 would remove 48 percent of the S02 from flue gas;
a Ca/S ratio of 2 would remove 75 percent; and a Ca/S ratio of 3 would remove 94 percent.
Conceptual designs were begun by NCB in 1968 of a 600-MW and a l20-MW power
plant, based on a fluidizing velocity of 3 fps and a bed area of 38 sq ft per MW. For the
66Q-MW station, 25,000 sq ft of bed would be required, distributed as 15 beds, each 80 ft by 20
ft in area, with a bed depth of 2 ft. Tubular heat-receiving surfaces would be in two or three
horizontal layers immersed in the fluidized bed. The total depth of the unit is not described, nor
is the arrangement of gas-offtake flues, economizers, air heaters, and the like. Other details have
not been established, such as control and distribution of coal to the beds and wi thin each 1600-
sq ft bed; the type of wall and roof construction, whether water-wall or refractory; the method
of start-up; or the means of accommodating rapid large swings in load.
The work at the BCURA Industrial Laboratories has been along two main lines:
atmospheric-pressure units for large utility boilers as well as industrial steam generators, and a
5-atmosphere pressurized combustor for an advanced cycle involving a gas turbine. Experimental
rigs for both concepts have been built at Leatherhead.
The combined cycle being considered at BCURA would use a fluid-bed combustor
operating at 87 psi to generate steam, with the hot flue gas expanding through a gas turbine.(6)
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111-17
Their pilot-scale rig, built inside the pressure shell used earlier at BCURA in studying gasification,
provides a rectangular fluidized bed with an area of 8 sq ft, in which it is expected that 1000 Ib
per hr of coal can be burned at temperatures up to 1500 F. At this moderate level, the coal ash
will not sinter and the formation of NO should be low.
The earliest significant experimental results at BCURA show that coal crushed to -1/16
in. can be burned in a fluidized bed of coal ash at air velocities ranging from about 2 to 14 fps,
and at bed temperatures of 1500 F without sintering the coal ash. Heat-transfer coefficients
attained have been between 40 and 100 Btu per sq ft-hr-F. CO in the flue gas was high at a
stoichiometric air/fuel ratio, sometimes reaching 1 percent. In this early work at BCURA, 20
percent excess air lowered CO to 0.5 percent, and 50 percent excess air was required to decrease
the CO to less than 0.2 percent. Major fuel losses, however have been in elutriation of unburned
coal from the bed, as was also the case for the Pope, Evans and Robbins fluidized combustor.
Without recycling cyclone-captured particles, this loss has been as high as 25 percent. With
recycling, carbon loss has been decreased, but it may reach 10 percent at high fluidizing
velocities.
Australia
In Australia, the Commonwealth Scientific and Industrial Research Organization (CSIRO)
is investigating combustion in fluidized beds with considerable emphasis on heat transfer.(7)
Early tests were made in a 9-in.-diameter bed of fluidized sand at temperatures in the range 750
F to 1850 F. The maximum rate of heat release was 124,000 Btu p~r cu ft-hr of combustion
chamber, with virtually complete combustion at only 2 percent excess air. Maximum heat~
transfer coefficient was 50 Btu per sq ft-hr-F, about half the maximum reported by others. This
coefficient decreased as the temperature in the bed increased, explained by CSIRO as the result
of increased voids in the bed at higher gas-flow rates. Although operating a fluidized combustor
at increased pressure should increase output as far as heat release is concerned, as well as
improve the quality of fluidization and offset the effect on gas density of expansion of gas in a
hot fuel bed, any possible benefits of pressure may be lessened because the overriding factor
influencing the capacity of the system is heat transfer and not heat release.(8)
Present plans by CSIRO include studying the behavior of inorganic matter in Australian
coals in a 3-stage experimental combustor 1 ft square and 12 ft high. The main bed will have a
depth variable between 6 and 36 in., and the two successive beds each will be up to 12 in. deep.
Burning Rates in Fluidized-Bed Combustion
There is no general agreement as yet on the burning rate most desirable in a fluidized-bed
combustor. This rate depends on many factors, involving highest permissible fuel-bed tempera-
ture, fuel reactivity, and carryover. In the interests of low initial capital investment, high burning
rates are wanted, but if this in turn leads to excessive carryover, or to sintering of ash, then
lower burning rates may have to be accepted.
In the Czechoslovakian combustor burning a coal with a calorific value probably not
higher than 7000 Btu per Ib, the firing rate necessary to generate 33 MW at 40 percent overall
thermal efficiency will be 40,000 Ib per hr of coal. For the proposed 10-ft-diameter fluidized
combustor, the burning rate of coal would have to be 510 Ib per sq ft-hr.
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111-18
For the NCB estimate of 38 sq ft per MW, assuming a coal with 12,000 Btu per lb, the
burning rate will be 700 lb per sq ft-hr. With the BCURA pressurized combustor at roughly 6
atmospheres, the burning rate will be 125 lb per sq ft-hr. As noted earlier, the Ignifluid tests
burning anthracite culm were at 130 lb per sq ft-hr. The burning rate in the proposed Westing-
house lD-atmosphere combustor might be estimated from the stated volumes of the fuel beds for
the evaporator, superheat, and reheat sections, but other factors related to the depth of the beds
have not been established as yet.
Fluidizing velocity affects performance in that high air velocity requires larger fuel
particles to limit carryover losses, but these larger particles lead to a lower heat-transfer
coe ffici end 1 5) Hence there is a tendency to use moderate air velocities, both from the
standpoint of heat transfer and carryover, but this means that the rating of the unit may be less
than if higher velocities were chosen. It is apparent, then, that the choice of fluidizing velocity is
an engineering compromise to achieve high throughput, a reasonable overall cycle efficiency, and
low capital costs and operating charges.
Experimental combustors have operated at much lower rates. A 2-sq ft combustor
operated by BCURA(19) is reported to burn coal at 500 lb per hr or 160 lb per sq ft-hr. The
small BCURA combustor(14) had a maximum heat input of 3.15 MW per sq m, equivalent to
106 Btu per sq ft-hr, or to 83 lb per hr of coal. The much larger beds operated by Pope, Evans
and Robbins also were based on a heat input of 106 Btu per sq ft-hr(14), again equivalent to
83 lb per hr of coal. Tests by the Bureau of Mines(14) in a 2-ft-diameter bed burning anthracite
showed a burning rate of only 9 to 17 lb per sq ft-hr in a 3-ft-deep bed.
In the Australian work, the three-stage experimental combustor has been designed and is
being constructed for heat-release rates varying between 20,000 and 200,000 Btu per cu ft-hr, or
200,000 to 2,000,000 Btu per sq ft-hr. For a 1O,00D-Btu coal, this is equivalent to 20 to 200 lb
per sq ft-hr.
The large discrepancy between experimental results and expected performance can be
based in part on the scale of the systems. It may indicate, too, that problems can be expected in
operating central-station combustors at heat input rates three to five times greater than have
been achieved in small combustors. For the present, it appears that burning rates approaching
150 lb per sq ft-hr of coal may be practical in large combustors.
Emission Data from Fluidized-Bed Experiments
Only a few data are available as yet on the emission of various pollutants from fluidized
beds. Brief tests made in England at the BCURA Industrial Laboratories of the National Coal
Board showed that chlorine was not retained in conventional beds of fluidized coal ash and that
,
with coals containing 20 and 35 percent ash of unspecified composition, only 5 to 10 percent of
the sulfur was retained in the solids - about the same as would be expected with a chain-grate
stoker. At 1600 F, the NOx output was 400 to 450 ppm, somewhat higher than should be
obtained at this temperature, suggesting that nitrogenous compounds in the coal might have been
res ponsi bl e.
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III-l 9
In an unpublished report on work at BCURA on the reaction between limestones and
S02 in fluidized beds(l5), which also effectively summarized the state of the art in the United
States, similar conclusions were reached as have been drawn from studies of limestone for the
dry-injection processes. These conclusions are:
1. Internal surface area of limestones is increased greatly by calcination
2. An impermeable shell of CaS04 slows down further reaction with
SOx
3. The CaS04 shell has little effect in some dolomites
4. Fine grinding minimizes the shell effect, with a particle size of a few
microns being optimal
5. Reaction rate increases with temperature for limestones but for
dolomites is temperature independent between 1300 F and 1650 F
6. C02 in the tlue gas suppresses the calcination of limestones under
pressure but has little effect on dolomite.
These experimental runs were made in a fluidized bed 1.6 in. in diameter, but the report
also describes other tests in a fluidized bed 2 ft in diameter and 2 ft deep, where 40 percent of
the S02 was captured with limestone and 60 percent with another.
Tests in England by the National Coal Board (NCB) in a 6-in.-diameter fluidized bed
burning two English coals and one American coal are summarized in Figure III-5. (20) The
limestone used contained 99 percent CaC03. The fluidized fuel bed in each test was 2 it deep
and the gas velocity was 2 ft per second, for an average gas residence time of 1 second. Excess
air was 10 to 20 percent, and the fuel-bed temperature was 1470 F.
c
Limestone Size
-12.0 -10 S.
a.s.s. 8.S.S Cool %
@ G Goldthorpe 2.05
F Farmington 2.25
"G
GG""-G
;>0 '- FF'
I I I @~~G& I I
'1:>.0 Q5 1.0 1.5 2.0 2.5
CalS Stoichiometric Ratio in Feed
"0
II>
If 100
~ 80
o
C
~ 60
II>
0..
II>
o 40
II>
o
C)
.=
(/)
Figure 111-5. Retention 01 Sulfur in Fluidized-Bed
Tests by National Coal Board(20)
-------
111-20
Capture of S02 was affected appreciably by the size of the limestone, the smaller stone
being more effective, .based on a single test with Coal G. There was an unexplained difference in
sulfur retention between Coal F and Coals G and B. However, under these test conditions, it is
evident that a stoichiometric ratio of CaO to S resulted in the capture of one-half to two-thirds
of the sulfur originally present in the fuel for limestone crushed to -10 B.S.S. Based on the
observed effect of particle size, it was concluded by NCB that excess lime was present in the
interior of the particles.
A computer program has been written at Argonne(21) to calculate the extent of S02
removal in a fluidized bed by a limestone and a dolomite as a function of bed height, superficial
gas velocity, particle size, and stoichiometry. A recent paper reported on experimental work at
Argonne(22) involving studies in a small laboratory fluidized bed with limestone present to
capture S02. Factors investigated include gas velocity, the size of the limestone particles, the
influence of temperature, and the stoichiometric ratio of Ca to S. These experimental measure-
ments, still in progress, show that about 40 percent of the S02 is captured when the Ca/S ratio
is one, and that the amount of S02 removed increases as the surplus of lime increases. At a
stoichiometric ratio of 2, from 60 to 70 percent of the S02 is removed; a ratio of 3 is necessary
to capture 90 percent of the S02. The influence of temperature in the range of 1550 F to 1650 F
is negligible. Smaller particles of limestone favor the capture of S02, but the minimum size is
established by carry-over in the air stream. Gas velocity has an appreciable influence, with about
a sixth more S02 being removed at 3 ft per second than at 9 ft per second, undoubtedly because
of the longer residence time.
Appraisal of Fluidized-Bed Combustion for Power Plants
Translation of all these data in terms of large-scale performance is difficult. The only
possible conclusion is that a surplus of limestone above the stoichiometric ratio will have to be
added with coal to obtain nearly complete removal of S02. This unreacted lime will remain with
the ash from the coal and the converted CaS04 removed from the fluidized bed. Fluidized
combustors appear superior in capturing S02 to the dry injection of limestone into pulverized-
coal-fired boiler furnaces, but the extent of the improvement is not clear as yet. Removal of 80
percent or more of the S02 from a flue-gas stream will require large amounts of limestone,
probably up to 3 times stoichiometric in some cases, leading to consideration of regenerating the
lime as noted by Westinghouse. (15)
Experimental work is continuing by many investigators, largely with APCO support.
Important programs are being conducted by Consolidation Coal Company,(23,24) by
Westinghouse,(25) and by Pope, Evans and Robbins.(26) Engineering studies now being con-
ducted are bringing experienced power-plant designers into the field to contribute their experi-
ence and practical viewpoint.
Fluidized-bed combustors in large central-station power plants will be quite different
from today's huge boiler furnaces. Modular design almost certainly will be stressed, but the size
and the geometry of fluidized-bed combustors are still unsettled. It is fairly certain that such
combustors will be appreciably more effective than other limestone-injection systems in utilizing
limestone for SOx capture when 80 to 90 percent of the SOx must be removed. They should
lead to lower NOx levels because of the controlled low temperature in the combustor, although
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111-21
this has not been confirmed as yet experimentally. Fluidized-bed combustors will pose problems
in particulate emission, probably requiring elaborate reinjection systems to handle carry-over of
unburned combustibles. Finally, they may be best adaptable to base-load operation.
It is too soon to compare the overall effectiveness of fluidized-bed combustors with the
limestone-slurry scrubbing systems of so much interest presently to the utilities. Both schemes
have merit, but both also have disadvantages that will affect their final wide-scale acceptance.
ADVANCED POWER CYCLES
Concepts other than those used presently in central-station power plants undoubtedly will
be developed over the next 30 years to convert the energy in fuels into electricity. Magneto-
hydrodynamics and fuel cells offer most promise of the so-called direct-energy-conversion
processes, but both have serious shortcomings. More attractive at present are advanced power
cycles wherein two or more energy-extraction systems are combined in a single power plant.
Typical of such systems is the burning of a gaseous fuel in a pressurized boiler furnace
followed by expansion of the hot products of combustion through a gas turbine. The gaseous
fuel could be natural gas, but a more likely fuel is a hot sulfur-free producer gas made from
coal, or a fuel gas produced from residual fuel oil. A suitable gasification scheme including a hot
gas-de sulfurizing step is required. In addition to a higher overall thermal efficiency, which can be
expected to exceed 50 percent, such cycles have the great advantage of essentially complete
removal of sulfur and particulates from the exhaust gas. Formation of NOx might also be less
since all the nitrogen compounds in the original coal would have been destroyed during
gasification and peak combustion temperatures might be lowered.
Many types of advanced power cycles can be devised, including those in which volatile
matter in the coal is distilled off and only the residual char is burned in the power plant. Such
systems have been investigated for many years, but without the present-day incentive of emission
control. The need for "clean" power is renewing that interest.(27)
Advanced power cycles need to be investigated intensively, not only for their increased
thermal efficiency, but because power plants based on such cycles can potentially emit sub-
stantially less pollutants than current plants.
GAPS IN NEEDED COMBUSTION R&D
TO REDUCE POWER-PLANT EMISSIONS
Operation of large central-station boiler furnaces has become relatively routine, despite
the great complexity of today's installations. Similarly, furnace design has settled into a few
recognizable patterns, with the three major boiler manufacturers each favoring design concepts
that they originated. Such concepts as the cyclone furnace and the comer-fired furnace were
developed through long and diligent engineering studies. Combustion "research" was involved
only to the extent that it provided a general understanding of the combustion process.
-------
111-22
This can be illustrated by the continuous reference to "time, temperature, and
turbulence" in comments concerning conditions needed in boiler furnaces. But these terms are
used in the qualitative rather than the quantitative sense. The designer provides as much time as
possible for combustion within the limits of furnace volume established by construction costs
and heat-transfer rates. Temperatures during combustion are established by slagging, external
corrosion, and heat-transfer problems. Turbulence is made as great as possible commensurate
with reasonable expenditures for fan horsepower. The furnace is more than a combustor; it also
absorbs about half of the total heat released, and so its configuration is as much determined by
heat absorption as it is by combustion.
So far as the furnace designer is concerned, there have been no gaps in combustion
research. He has succeeded admirably with the information available to him in the sense that the
market has accepted his product. But he is now being forced to recognize that there are serious
gaps when air-pollution-control problems are considered. For example, because the time-
temperature history of particles in boiler furnaces is not known, it is not possible to define
the environment around a particle of injected limestone. Similarly, little is known about
temperature patterns, and even less is known about the influence of such variables as heat
transfer, burner design and location, fuel residence time, and reaction kinetics.
The understanding of combustion needed to build a large boiler furnace that meets with
market success is not sufficient for control of air pollution. Far more detailed knowledge in
many areas will be necessary. In the following discussions a number of major gaps in knowledge
about the combustion process in central-station power plants are described and some possibilities
for filling these gaps are pointed out.
Two-Stage Combustion
As discussed previously, two-stage combustion has been investigated as a method of
controlling NOx emissions, and has even been demonstrated in a crude way in gas- and oil-fired
central-station plants. Further work to achieve an engineering optimization of the process is still
required.
Two-stage combustion is not generally regarded as applicable to coal firing, although the
earliest downfired furnaces for pulverized coal operated somewhat in this fashion. Also, the work
reported by Bienstock( 13) can be considered as an approach to two-stage combustion of coal.
Thus, the possibility of applying two-stage combustion in coal-fired plants should not be ignored.
Recirculation
The peak temperature in a combustor can be controlled by recirculating cooled flue gas
to the combustor inlet, and this offers a means of controlling NO emissions. Demonstrations
of flue-gas recirculation in central-station power plants and engineering studies to optimize the
quantity, temperature, and point of injection of the recirculated gases are needed.
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111- 23
Improved Combustion and Heat Extraction
Emissions of NOx and products of incomplete combustion might both be better con-
trolled if current understandings of combustion and heat transfer were applied to the design of
large boiler furnaces. The concept of a well-mixed zone followed by a plug-flow zone has been
shown to be the optimum combustion process in terms of combustion efficiency, and hence
would promise to minimize emissions of products of incomplete combustion. A combustion
system based on this concept may also be adaptable to good control of heat extraction and thus
of the peak flame temperature. Emissions of NOx might thereby be controlled.
Gasification
Gasification of coal or residual fuel oil can be considered as a type of multistage com-
bustion, where the first stage, the gasifier, is operated fuel rich. Under such conditions, the
sulfur in the fuel is released as H2S which can le removed from the hot gas. Such schemes have
been proposed in the past, and Babcock & Wilcox is . currently studying one variation where the
ash-and-sulfur-free gas is burned in a combined boiler-and-gas-turbine cycle.
Development of the gasifier is an important feature of this process, in addition to the
several noncombustion problems. In addition to controlling the emission of SOx' the multistage
feature may contribute to the reduction of NOx emissions.
Fluidized-Bed Combustion
The combustion of coal in a fluidized bed of limestone has been shown to be a promising
method of controlling SOx emissions. Several combustion problems are involved in this not-well-
understood process. These problems include achieving efficient combustion at low levels of
excess air, control, and the minimization of fuel carry-over. Satisfactory solutions of these
problems are needed. (As in all application areas, only R&D concerned with combustion
problems per se is included in the 5- Y ear Plan.)
Ash Capture
Cyclone furnaces presently capture 90 percent of the ash in coal as molten slag, and
slap-tap furnaces capture about 50 percent of the ash. It is not unreasonable to expect that
higher captures could be achieved if that were the objective of a comprehensive R&D program. If
99 percent capture were achieved, the emission of particulate matter would be lowered to about
0.08 lb per 106 Btu.
Fly-Ash Agglomeration
Ash particles could be much more easily removed from the combustion gases if
agglomeration of the fly ash particles could be promoted. In order to adhere, the particles must
be "sticky", which implies some lower temperature limit at which agglomeration can occur. High
turbulence or pulsating flows may promote agglomeration of the sticky particles.
-------
111-24
Ash Fluxing
Slag-tap furnaces are restricted by ash fusibility with respect to the coals they can burn.
Fluxing with limestone and mill scale or iron ore can reduce the viscosity of coal-ash slags to
almost any desired range. In addition to the possibility of extending the use of slagging furnaces
and possibly increasing their ash capture, fluxing would permit the use of low-sulfur coals (which
typically have high ash-fusion temperatures) in existing slagging furnaces.
Modification of Fly-Ash Resistivity
Electrostatic precipitators fall in efficiency when the electrical resistivity of the ash
particles exceeds about 2 x 1010 ohm-centimeters. Normally S03 present in the flue gas from
high-sulfur coals condenses on fly-ash particles, forming an adsorbed layer of sulfates that lowers
the electrical resistivity. With low-sulfur coals, this layer does not form, and ash resistivity can be
too high for effective precipitator action. The only known corrective actions are to operate the
precipitator at higher temperatures, say 800 F, where the electrical resistivity of the ash is lower,
or to make the precipitator much larger.
To achieve satisfactory ash resistivity, it may be possible to induce changes in the surface
of the ash particles by modifying the combustion process or by using some as-yet-undisclosed
additive compatible with other requirements.
SUMMARY OF CURRENT AND RELEVANT COMBUSTION R&D
Large central-station boiler furnaces have been developed to their present status mainly
by gradual engineering improvements; comparatively little of what is generally termed
"combustion research" has been involved in these advances.
The current R&D activities identified during the course of this study are listed in Table
111-6.
-------
Table 111-6. Current Combustion R&D - Central-Station Power Plants
Sponsoring
Project Organization Principal
Key Project or Contract Title and Contract No. Research Organization Investigator Objective or Scope Funding, $
III-a Systems study of nitrogen oxides control NAPCA-DPCE Esso Res. & Engr. Co. Dr. W. Bartok Define the nature and extent of NOx 3B9,307 (Total)
methods CPA 22-68-55 Linden, New Jersey emissions in U.s. and recommend
5-year R&D program for control
III-b Selected R&D of nitrogen oxides control NAPCA-DPCE Esso Res. & Engr. Co. Collect additional data on NOx emis- 363,025 (FY 70)
methods for stationary sources CPA 70-90 Linden, New Jersey sions and investigate the application
of control methods on selected
sources
111-<: Model for NOx formation in stationary NAPCA-DPCE Mass. Inst. Tech. H. C. Hottel Develop models for the formation of 28,000 (FY '69)
combustion processes CP A 22-69-44 Cambridge, Mass. G. C. Williams NOx in furnaces, determine param~
Task No.3 A. F. Sarofin eters which influence emission levels,
and recommend control methods
III-d Reducing emission of sulfur and nitrogen NAPCA National Coal Board Investigate the potential of fluidized-bed 300,000 (FY '70)
oxides by using fluidized combustion CPA 70-97 Great Britain combustion of coal for reducing SOx
of coal and NOx emissions
III-e Fluidized-bed combustion studies of NAPCA-DPCE Bureau of Mines Assess feasibility and commercial -
various coals I nteragency transfer Coal Res. Center potential of various coals for firing -
'i"'
Morgantown, Pa. in fluidized-bed combustors N
VI
III-f Reduction of atmospheric pollution by NAPCA-DPCE Argonne Nat'l Lab. A. A. Jonke Examine feasibility and prospects of 190,000 (FY '69)
application of fluidized-bed combustion Interagency transfer Argonne, III. fluidized-bed combustion for steam 267,000 (FY 70)
generation
IIliJ Characterization and control of air NAPCA-DPCE Pope, Evans, & Robbins J. W. Bishop Evaluate potential of fluidized-bed 246.498 (FY '70)
pollutants from a fluidized-bed CPA 70-10 S. Ehrlich combustion for controlling air
combustion unit E. B. Robison pollution
III-h Conceptual design - fluid-bed com- NAPCA-DPCE Westinghouse Electric Dr. B. W. Lancaster Develop conceptual designs of three 344.487 (FY '70)
bustion systems CPA 70-9 Corp. Dr. D. L. Keairns fluidized-bed boilers (60, 300 and
Res. & Devel. Ctr. 600 mw)
Pittsburgh, Pa.
III-i Solvent refined coal cost study NAPCA-DPCE General Tech. Corp. Dr. R. G. Shaver 38,272 (FY '69)
CPA 22-69-82
III-j Conduct studies on sulfur control by NAPCA Scientific Res. Study kinetics of coal gasification 241,884 (Total)
means of coal gasification PH 86-68-65 I nstruments Corp. techniques on a laboratory scale
III-k Technological and economic feasibility NAPCA-DPCE United Aircraft Res. A. A. LeShane Define and evaluate advanced techni- 292,654 (FY '69)
study of advanced power cycles and CPA 22-69-114 Lab. ques for thermal-<:ycle electrical
methods of producing nonpolluting East Hartford, Conn. power generation to reduce pollutant
-------
Table 111-6.
(Continued)
Project
Key
Project or Contract Title
Sponsoring
Organization
and Contract No.
Research Organization
Principal
Investigator
Objective or Scope
Funding, $
111-1
231,728 (Total)
III-m
III-n
111-0
III-p
II'-q
High-sulfur combustor study
NOx from coal combustion
Development of two-stage coal
combustion process
Study of resistivity and conditioning
of fly ash
Effect of two-stage combustion and
low-02 firing in reducing nitrogen
oxide emissions from fossil-fuel-fired
steam generators
Study combustion phenomena of
utility boilers to minimize forma-
tion of oxides of nitrogen
NAPCA-DPCE
CPA 22-69-151
NAPCA-DPCE
I nteragency transfer
NAPCA-DPCE
CPA 70 - 146
NAPCA
CPA 70 - 149
City of Los Angeles
Dept. Water & Power
Southern Calif.
Edison Co.
Chemical Const. Co.
New York, N.Y.
Bureau of Mines
Black, Sivalls, &
Bryson
Southern Res. Inst.
City of Los Angeles
Dept. Water & Power
Los Angeles. Calif.
Southern Calif.
Edison Co.
Los Angeles. Calif.
J. Belding
G. McClellan
I. Shah
D. Bienstock
R. L. Amsler
E. R. Bauer, Jr.
Select, design, and evaluate a high-sulfur
combustor and sulfur-recovery
processes
Evaluate the factors involved in NOx
formation during coal combustion
Determine the feasibility of a new coal
combustion-process wherein primary com-
bustion occurs in a molten iron bath and
secondary combustion occurs in a normal
boiler
Assess electrostatic precipitator performance
improvement and capital and operating
costs of flue gas conditioning systems
Evaluate effort of two-stage combustion
and low excess air firing on reducing
NOx emissions
Determine parameters which influence
NOx emission from gas- and oil-fired
utility boilers
225,000 (FY '70)
667,561 (FY '71)
-
-
-
I
N
0'\
-------
111-27
R&D OPPORTUNITI ES RECOMMENDED FOR THE 5-YEAR PLAN
Sixteen R&D opportunities related to control of pollution from central-station power
plants by combustion modification are recommended in the following areas:
. Laborawry and field investigations of means to suppress NOx by:
- low-excess-air combustion
- flue-gas recirculation
- two-stage combustion
- fuel selection
. Development of new power-plant combustion concepts permitting
control of SOx, NOx, or ash emissions, such as:
- high-turbulence combustion
- fluidized bed
- gasification
- electrochemical oxidation.
. Analytical and experimental investigations to promote means of
retaining ash and slag within the furnace, or of altering the ash so as
to promote its collection by downstream equipment.
. Development of research instrumentation for measuring conditions
existing in central-station power-plant furnaces and carrying out a
program of obtaining such measurements.
Descriptions and evaluations of these R&D opportunities are presented in the following
pages. The priority ranking of these opportunities is summarized in the table at the end of this
chapter.
-------
111-28
R&D Opportunity: III-I
Related to: III-p
Experimental Investigation of Feasibility of Burning Pulverized Coal With Low Excess Air
Technical Objective and Approach
The objective is to determine changes from conventional practice necessary to burn coal in suspension with
essentially stoichiometric quantities of air with the intent of improving downstream control of ash, reducing the
formation of S03 from S02, and possibly gaining some control of NOx formation. Accomplishing this objective
may require improved burners, finer-sized coal, and higher turbulence levels in the furnace.
The approach should include laboratory-scale combustion studies to provide the basic information and
development studies on larger prototype systems.
Rationale and Incentive
Fuel technologists have been successful in burning residual fuel oil with no more than 1.0 percent excess air in
the flue gas, with many advantages demonstrated for such low excess air. If pulverized coal could also be burned
with low excess air rather than with 15 percent excess air, as is common today in large boiler furnaces, the problem
with emissions would be eased. Advantages are that the volume of flue gas would be reduced appreciably and more
effective control of particulates would be possible, higher efficiency would be achieved (meaning less thermal
pollution of the atmosphere), no S03 would be present in the stack, and low excess air would limit NOx formation.
Estimated R&D Cost & Time
R&D Cost Range, 1000's: $450-$1,000
R&D Time Range: 3-5 years
Recommended 5-year Funding, 1000's: $500
Funding by Fiscal Year, $1oo0's
'69-70 I ~
125
'72
'73
'74
'75
76+
125 250
Evaluation
Sources Affected: Coal Power Stations
Relative Potential Benefit (overall rating): Medium
Pollutants Affected
CP
CO
HC
PNA
Odor NOx Lead SOx Ash
- -
10-25 5-20
16 11
0.15 0.50
o 0.7
2.40 1.65
~
--
% Reduction, Range
Expected
Fraction of ECC Emissions Affected
Noncombustion Controls Factor
Relative Potential Benefit Factor
4.05
I mplementation Time, years: 5-10
most likely: 7
Relative Implementation Cost: Medium
Relative Priority Rating: D
-------
111-29
R&D Opportunity: III-2
Related to: III-3, 4; VIII-27; III-a, b, c, q
Analytical and Experimental Research to Develop Criteria for the Application of Flue-Gas Recircu-
lation to Minimize NOx Emission from Central-Station Power Plants
Technical Objective and Approach
The objective is to develop criteria for the application of flue-gas recirculation to large boiler furnaces.
The approach should include studies of the quantity of flue gas required, the point of injection, and methods
of mixing the flue gas with either the combustion air or burning gases. The influence of flue-gas temperature and
composition (as determined by the fuel and fuel-air ratio) on the effectiveness of recirculation and method of
recirculation should also be studied. Experimental work with laboratory and pilot-scale equipment should be
supported by analytical studies. Flue-gas recirculation in an existing central-station plant should be demonstrated.
Rationale and Incentive
Recirculation of flue gas to decrease the formation of NOx has been demonstrated on a small scale and in a
limited way on a large scale, but little factual information is available on the volume of flue gas to be recirculated,
its composition, its temperature, and the point at which it is injected into the furnace. Probably related principally
to lowering flame temperature, recirculation should be investigated extensively on both a laboratory and a plant
scale to learn whether this process is adaptable to large boiler furnaces. Identifying optimum values for each of
these parameters is necessary to assure maximum effectiveness of this method of controlling NOx emission.
Estimated R&D Cost & Time
R&D Cost Range, 1000's: $6,OOG-$1O,OOO
R&D Time Range: 4-6 years
Recommended 5-year Funding, 1000's: $7,600*
Funding by Fiscal Year, $1oo0's
'69-70 [ 2!
X 200
'72
'73
'74
'75
'76+
850 1050 2500 3000 10,000*
Evaluation
Sources Affected: Coal, Oil, and Gas Power Stations
Relative Potential Benefit (overall rating): Medium High
Pollutants Affected
CP
co
HC
PNA
Odor
NOx
Lead
SOx
Ash
~
---
--
% Reduction, Range
Expected
Fraction of ECC Emissions Affected
Noncombustion Controls Factor
Relative Potential Benefit Factor
Implementation Time, years: 4-6
75-90
81
0.22
o
17.82
17.82
most likely: 5
Relative Implementation Cost: Medium
-------
III-3D
R&D Opportunity: 111-3
Related to: III-2, 4, 5; VIII-27, III-a, b, c, m, p, q
Experimental Investigation to Develop Design Criteria for the Application of Two-Stage Com-
bustion for NOx Control, With Demonstration in a Coal-Fired Central-Station Power Plant
Technical Objective and Approach
The objective is to develop design criteria for application of two-stage combustion for NOx control to
pulverized-coal-fired boiler furnaces.
The approach should be: (1) to determine the feasibility of such application, (2) to develop design criteria if
warranted, and (3) to demonstrate the process on a large scale. The program should involve work with laboratory
and pilot-scale furnaces. The investigation should aim at determining the extent to which temperatures in the final
stage could be reduced, and the effect of the amount of heat extracted between stages on the rate of burning of the
coal particles and the behavior of the ash. Optimized conditions should be sought for each stage and the reduction
in NOx emission should be determined. Finally, a full-scale two-stage combustion furnace should be designed, built,
and demonstrated in an operating power plant.
Rationa Ie and Incentive
Two-stage combustion has been demonstrated at power plant scale as a successful method of reducing the
emission of NOx from gas-fired boilers. However, as yet, no studies of this process as applied to the much more
common coal-fired plants appear to have been made. The earliest downfired furnaces for firing pulverized coal
employed essentially a two-stage combustion process, and this suggests that two-stage combustion with pulverized
coal may be feasible.
Estimated R&D Cost & Time
R&D Cost Range, 1000's: $11,000-$15,000
R&D Time Range: 5-8 years
Recommended 5-year Funding, 1000's: $2,200*
Funding by Fiscal Year, $1oo0's
'69-70 12!
X 200
'72
200
'73
400
'74
'75
'76+
400 1000 10,000*
Evaluation
Sources Affected: Coal Power Stations
Relative Potential Benefit (overall rating): Medium
Pollutants Affected
CP
CO
HC
PNA
Odor
NOx
Lead
SOx
Ash
~
--
--
% Reduction, Range
Expected
Fraction of ECC Emissions Affected
Noncombustion Controls Factor
Relative Potential Benefit Factor
20-80
50
0.125
o
6.25
6.25
I mplementation Time, years: 8-12
most likely: 10
Relative Implementation Cost: Low
-------
1II-31
R&D Opportunity: III-4
Related to: III-2, 3, 5; VIII-27; III-a, b, c, p, q
Experimental Investigation to Develop Design Criteria for Application of Two-Stage Combustion for
NOx Control, With Demonstration in an Oil-Fired Central-Station Power Plant
Technical Objective and Approach
The objective is to develop design criteria for optimizing the application of two-stage combustion to gas- and
oil-fired power plants.
The approach should involve determination of optimum geometries, heat release for each stage, and amount of
heat extraction between stages. Both laboratory and pilot-scale equipment should be used. The results should be
demonstrated in a full-scale oil-fIred power plant boiler because such a plant presents difficulties not presented by
gas-fIred plants.
Rationale and Incentive
Two-stage combustion, applied in a relatively crude way, has been demonstrated to reduce NOx emissions from
a gas-fIred power plant. Optimization of the process has promise of making substantially greater reductions of NOx'
Additionally, the application of two-stage combustion to oil-fIred power plants should be investigated. It is expected
that, while the problem with oil firing will be more difficult, essentially the same optimization criteria will apply to
both gas- and oil-fired boilers.
Estimated R&D Cost & Time
R&D Cost Range, 1000's: $1,500-$3,000
R&D Time Range: 3-5 years
Recommended 5-year Funding, 1000's: $1,800*
Funding by Fiscal Year, $1oo0's
'69-70 12!
X 200
'72
'73
'74
75
'76+
300
300 1000
Evaluation
Sources Affected: Oil and Gas Power Stations
Relative Potential Benefit (overall rating): Medium
Pollutants Affected
CP
CO
HC
PNA
Odor
NOx
Lead
sax
Ash
k
---
--
% Reduction, Range
Expected
Fraction of ECC Emissions Affected
Noncombustion Controls Factor
Relative Potential Benefit Factor
Implementation Time, years: 3-8
50-80
72
0.047
o
3.38
3.38
most likely: 5
Relative Implementation Cost: Very Low
-------
111-32
R&D Opportunity: III-S
Related to: III-3, 4; VIII-2S; III-c
Exploratory Research and Experimental Feasibility Evaluation of a Low-Emission Combustion
System for Central-Station Power Plants Using the Concept of a High-Turbulence Primary Com-
bustion Zone Plus a Plug-Flow Zone
Technical Objective and Approach
The objective is to investigate the feasibility of applying modern combustion knowledge to the design of large
boiler furnaces, with the intent of ultimately reducing the production of pollutants.
The approach should include analytical and design studies of the feasibility of designing a boiler furnace
consisting of a well-stirred region followed by a plug-flow region. If feasibility is indicated, laboratory and pilot-scale
studies of the burning of residual oils and pulverized coal in such furnaces should be conducted. The results will
provide assurance of feasibility and establish the major design parameter needed for ultimate full-scale applications.
Rationale and Incentive
Current understanding of the combustion process indicates that the "optimum" combustion process (from the
viewpoint of efficient use of furnace volume) consists of a well-stirred region followed by a plug-flow region. This
type of combustion process might lead to emission reduction as all air and fuel elements theoretically would have
the same time-temperature history and no inhomogeneities would exist.
Current boiler furnaces are not believed to approach this ideal sequence. Research to demonstrate the
feasibility of such a process and to investigate how the variables influence the emission of pollutants is needed. A
major part of the development of such a process is not directly associated with pollutant control, however.
Estimated R&D Cost & Time
R&D Cost Range, 1000's: $1,600-$2,500
R&D Time Range: 5-8 years
Recommended 5-year Funding, 1000's: $950
Funding by Fiscal Year, $1oo0's
'69-70 12!
100
'72
150
'73
'74
250
75
300
'76+
150
1000
Evaluation
Sources Affected: Coal, Oil, and Gas Power Stations
Relative Potential Benefit (overall rating): Medium
Poll utants Affected
CP
co
HC
PNA
Odor NOx Lead SOx Ash
- -
0-50 0-90
12 22
0.16 0.36
o 0.7
1.92 2.38
~
--
% Reduction, Range
Expected
Fraction of ECC Emissions Affected
Noncombustion Controls Factor
Relative Potential Benefit Factor
0-90
22
0.10
0.65
0.77
0-90
22
0.0017
o
0.04
5.11
I mplementation Time, years: 5-15
most likely: 10
Relative Implementation Cost: High
-------
111-33
R&D Opportunity: III-6
Related to: III-7; VIII-20; III-e
Experimental Investigation of the Combustion Mechanism of Coal in a Fluidized Bed of Noncom-
bustible Particles
Technical Objective and Approach
The objective is to develop needed data on the complicated situation existing when particles of coal are burned
in close contact with inert particles to which they are transferring thermal energy. A further complication that
should be studied is the interaction between burning and inert particles as it affects the diffusion inward of oxygen
and outward of CO and C02 around each particle of coal.
The approach should consist of experimental investigation of the many variables involved under controlled
conditions. Burning tests of single particles of various coals in simulated fluidized beds should be undertaken to
provide a better understanding of this phenomenon.
Rationale and Incentive
Much information has been developed over the past 50 years on the burning of single particles of coal
suspended in a stream of air. Similarly, devolatilization of a coal particle and combustion of the residual coke need
to be investigated under the special conditions of closely surrounding inert particles to determine their influence on
the combustion process. Such a study should result in a sufficiently detailed understanding of the mechanism of
combustion in fluidized beds to permit establishing optimum conditions in large fluidized-bed combustors.
Estimated R&D Cost & Time
R&D Cost Range, 1000's: $300-$600
R&D Time Range: 2-4 years
Recommended 5-year Funding, 1000's: $500
Funding by Fiscal Year, $1OO0's
'69-70 12!
X 125
'72
125
'73
'74
'75
'76+
250
Evaluation
Sources Affected: Coal Power Stations
Relative Potential Benefit (overall rating): High
Pollutants Affected
CP
CO
HC
PNA
Odor NOx Lead SOx Ash
- -
25-75 50-99 0-50
40 71 15
0.12 0.46 0.34
o 0.3 0.7
4.80 22.86 1.53
Relative Implementation Cost: Medium
~
---
% Reduction, Range
Expected
Fraction of ECC Emissions Affected
Noncombustion Controls Factor
Relative Potential Benefit Factor
I mplementation Time, years: 8-15
29.19
most likely: 10
-------
111-34
R&D Opportunity: III-? .
Related to: III-6; VIII-20; III-e
Experimental Investigation of Factors Influencing Completeness of Coal Combustion in Fluidized
Beds With Low Excess Air
Technical Objective and Approach
The objective is to determine the amount of excess air needed in fluidized-bed combustors to keep CO and
unburned fuel at a reasonably low level. The aim should be to provide more adequate information on the optimum
conditions in the fuel bed for the best possible utilization of the fluidizing air, the effect of reactivity of the fuel,
and the influence of heat-extracting surfaces.
The approach should include an experimental program, conducted on a small laboratory scale, to define the
factors influencing the minimum amount of air needed to burn different coals in fluidized beds. This research
should permit identification of conditions under which CO can be kept to levels not exceeding 0.1 percent and
carryover of unburned fuel can be lowered to the equivalent of carryover in existing combustion systems.
Rationale and Incentive
The type of fluidized-bed combustor receiving most attention today operates with a fIxed air supply, to
provide fluidization, and controlled small amounts of coal in the combustor. Idealized conditions to ensure full
utilization of the coal are not yet defInable, and reports of unburned fuel carryover and CO in the flue gas with
nominal amounts of excess air vary greatly between different experimenters.
Estimated R&D Cost & Time
R&D Cost Range, 1000's: $300-$600
R&D Time Range: 2-4 years
Recommended 5-year Funding, 1000's: $500
Funding by Fiscal Year, $1OO0's
'69-70 12!
X 50
'72
75
'73
125
'74
250
'75
'76+
Evaluation
Sources Affected: Coal Power Stations
Relative Potential Benefit (overall ratingl: High
Pollutants Affected
CP
co
HC
PNA
Odor NOx Lead SOx Ash
- -
25-75 50-99 0-50
40 71 15
0.12 0.46 0.34
o 0.3 0.7
4.80 22.86 1.53
Relative Implementation Cost: Medium
~
--
% Reduction, Range
Expected
Fraction of ECC Emissions Affected
Noncombustion Controls Factor
Relative Potential Benefit Factor
29.19
I mplementation Time, years: 8-15
most likely: 10
-------
111-35
R&D Opportunity: III-8
Related to: III-j, k
Development of Improved Coal-Gasification Systems to Produce Sulfur- and Ash-Free Gas Suitable
for Advanced Power Cycles
Technical Objective and Approach
The objective is to devise a gasifier to deliver hot clean gas to a combustion system with particular attention
paid to removal of H2S from the hot fuel gas before it is burned.
The approach should include an investigation of such possibilities as cyclone, fluid-bed, and pulverized-
coal-suspension gasification. Development of a preferred system should be carried through pilot scale to a stage
where a full-scale demonstration is feasible.
Rationale and Incentive
Advanced power cycles (e.g., burning fuel gas in a pressurized furnace with heat extraction followed by
expansion through a gas turbine) could well provide entirely new ways of generating electricity at efficiencies as
high as 60 percent with minimum emission of air pollutants. To implement such schemes, a coal-gasification process
that will yield a hot gas efficiency at reasonable cost is needed. Sulfur removal from the hot gas is a necessary
feature if the process is to be practical from an air pollution viewpoint. With a successful method of removing sulfur
from the hot fuel gas, S02 emission could be essentially eliminated and NOx could be more easily controlled. The
higher efficiency attainable would also ease the overall emission problem.
It should be noted that while the sulfur-removal process and development of the power cycle are not included
within this combustion-oriented development, they are necessary accompaniments and their influence on the
gasification process is considerable.
Estimated R&D Cost & Time
R&D Cost Range, 1000's: $850-$2,000
R&D Time Range: 4-6 years
Recommended 5-year Funding, 1000's: $1,000
Funding by Fiscal Year, $1oo0's
'69-70 I '71
X 100
'72
'73
150
'74
300
75
325
'76+
125
Evaluation
Sources Affected: Coal Power Stations
Relative Potential Benefit (overall rating) : Very High
Pollutants Affected
CP
co
HC
PNA
Odor
NOx
Lead
SOx
Ash
~
--
--
% Reduction, Range
Expected
Fraction of ECC Emissions Affected
Noncombustion Controls Factor
Relative Potential Benefit Factor
Implementation Time, years: 5-15
45-90
69
0.095
0.7
1.97
most likely: 10
30-90
60
0.13
o
7.80
50-100
75
0.48
0.3
25.20
50-100
75
0.36
0.7
8.10
43.07
Relative Implementation Cost: High
-------
111-36
R&D Opportunity: III-9
.
Exploration of the Feasibility of Electrochemical Oxidation of Coal for Direct Energy Conversion
Technical Objective and Approach
The ultimate objective is to determine the feasibility of coal fuel cells as sources of central-station (or the
equivalent) power.
Because of the difficulty of the problem and the expected remoteness of a successful coal fuel cell, no detailed
approach can be given. However, a limited program to keep abreast of fuel cell work by others and to investigate
problems peculiar to coal fuel cells is most appropriate until the state of the art has advanced to the point where a
useful definite approach can be identified.
Rationale and Incentive
Fuel cells using coal as the fuel may offer a long-range solution to the need for supplying large quantities of
electrical energy without excessive emissions. Electrochemical oxidation of coal will probably be carried out at
relatively low temperatures thus avoiding formation of large quantities of NOx' The generation of other pollutants is
uncertain and would depend on details of the as-yet-unknown process.
Estimated R&D Cost & Time
R&D Cost Range, 1000's: $250-open
R&D Time Range: 5 years-open
Recommended 5-year Funding, 1000's: $500
Funding by Fiscal Year, $1oo0's
'69.70 I '71
100
'72
100
'73
100
'74
100
'75
'76+
100 100/year
Evaluation
Sources Affected: Coal Power Stations
Relative Potential Benefit (overall rating): Low
Poll utants A ftected
CP
CO
HC
PNA
Odor NOx Lead SOx Ash
- -
0-100 0-100
17 17
0.030 0.059
o 0.7
0.51 0.30
L
--
% Reduction, Range
Expected
Fraction of ECC Emissions Affected
Noncombustion Controls Factor
Relative Potential Benefit Factor
0-100 0-100 0-100 0-100
17 17 17 17
0.017 .0004 .0007 0
0.7 0 0 0
0.09 0.01 0.01 0
0.92
Implementation Time, years: 15-20
most likely: 18
Relative Implementation Cost: High
-------
111-37
R&D Opportunity: III-W
Related to: VIII-2; III-b, m
Laboratory-Scale and Field Investigation of the Effect of Rank of Coal on Emission of NOx
Technical Objective and Approach
The objective is to determine the influence of coal rank on the formation of NOx.
The approach should involve experimentally burning coals of various ranks in a laboratory or pilot-scale
furnace simulating a central-station boiler furnace. The effect of combined nitrogen in the various coals should be
determined. Finally, trials should be conducted in power-plant boilers with coals of several ranks.
Rationale and Incentive
Bituminous coal is burned most commonly today for generating electricity, but most of our reserves are of
lower rank coals. Generally these are also low in sulfur. There is a gradual trend toward using these coals, but little
is known about their tendency to form NOx during combustion. Because of the fuel's high moisture content, flame
temperatures may be low and NOx formation minimal. In general, the rank of coal needs to be assessed as affecting
NOx formation, not only for the sub-bituminous coals but for other coal ranks as well.
Estimated R&D Cost & Time
R&D Cost Range, 1000's: $100-$300
R&D Time Range: 1-3 years
Recommended 5-year Funding, 1000's: $150
Funding by Fiscal Year, $1OO0's
'69-70 12!
75
'72
75
'73
'74
'75
76+
Evaluation
Sources Affected: 15 Percent of Coal Power Stations
Relative Potential Benefit (overall rating): Low
Pollutants Affected
CP
co
HC
PNA
Odor
NOx
Lead
SOx
Ash
L
---
--
% Reduction, Range
Expected
Fraction of ECC Emissions Affected
Noncombustion Controls Factor
Relative Potential Benefit Factor
I mplementation Time, years: 2-5
0-50
42
0.028
o
1.18
1.18
most likely: 3
Relative Implementation Cost: Very Low
-------
111-38
R&D Opportunity: III-11
Related to: VIII-2
Laboratory-Scale Investigation of the Effect of Residual Fuel-Oil Properties and Composition on
Emissions, and Development of Convenient Methods to Characterize Oils in Terms of Emission
Tendency, Including NOX and Particulates
Technical Objective and Approach
The objective of this research program is to investigate the relative pollutant-forming tendencies of different
residual fuel oils and to develop convenient analytical methods for classifying such oils as to their pollutant-forming
tendencies.
The approach should involve burning residual oil samples in a laboratory furnace to classify them as to their
tendency to form particulates and NOX and possibly other pollutants such as PNA. Should significant differences be
found with different oils, a search should be made for convenient analytical methods for classifying the oils.
Combinations of physical properties and easily measured chemical properties should be investigated as potential
measures of the pollutant-forming tendencies of the oils.
Rationale and Incentive
A number of simple physical tests and other indices have been developed for distillate fuels to characterize
their combustion performance (i.e., smoke tendency). Such combustion indices are limited in the residual oil area,
and their application as measures of pollutant-forming tendencies has not been explored even in the case of distillate
fuels. Simple procedures, either empirically derived indices or analytical tests of properties, to classify residual oils
on the basis of their pollutant-forming tendency would be useful in the specification of these fuels for critical
areas. Indices could also be useful in establishing fuel-oil standards.
One specific question that needs to be answered is the contribution of nitrogen compounds in the fuel oil to
NOX emissions.
Estimated R&D Cost & Time
R&D Cost Range, 1000's: $350-$550
R&D Time Range: 3-4 years
Funding by Fiscal Year, $1000's
Evaluation
Recommended 5-year Funding, 1000's: $475
69-70
71 72 '73 '74 75
125 150 200
76+
Sources Affected: 10 Percent of Oil Power Stations and Industrial Steam
Relative Potential Benefit (overall rating): Very Low
Pollutants Affected
CP CO HC PNA Odor NO*
Lead
SOX
Ash
% Reduction, Range
Expected
Fraction of ECC Emissions Affected
Noncombustion Controls Factor
Relative Potential Benefit Factor
0-50
42
0.003
0
0.13
0.13
Implementation Time, years: 2-5 most likely: 4
Relative Priority Rating: E
-------
111-39
R&D Opportunity: III-12
Related to: 111-13; III-o
Experimental Investigation of the Effect of Mineral Composition of Coal on Fly-Ash Resistivity and
Other Characteristics
Technical Objective and Approach
The objective is to identify the characteristics of the coal most important in predicting precipitator efficiency
and to provide a useful means of selecting coals when high fly-ash collection efficiency is important.
The approach should be to identify the minerals in coal by a petrographic examination, burn the coal under
closely controlled laboratory conditions, and determine the electrical resistivity of the ash. By examining a large
number of coals of markedly different mineral composition, it should be possible to decide which minerals or
combinations of minerals have the greatest influence on electrical properties of the fly ash.
Rationale and Incentive
Factors related to the composition of the coal being burned in large central-station power plants have never
been correlated with the ability of electrostatic precipitators to capture fly ash from that coal
A factor undoubtedly influencing the electrical resistivity of fly ash is the forms of the minerals providing the
inorganic matter in coals. Of the hundred or so minerals eventually forming fly ash, probably less than a dozen have
any significant influence on the surface properties of fly ash establishing electrical resistivity.
Estimated R&D Cost & Time
R&D Cost Range, 1000's: $150-$350
R&D Time Range: 1-3 years
'69-70
Funding by Fiscal Year, $ 1000's X
Evaluation
Sources Affected: Coal Power Stations
Relative Potential Benefit (overall rating): Medium
Recommended 5-year Funding, 1000's: $275
71
75
72
75
73
125
74 75
76+
Pollutants Affected
% Reduction, Range
Expected
Fraction of ECC Emissions Affected
Noncombustion Controls Factor
Relative Potential Benefit Factor
CP CO HC PNA Odor NOX Lead SOX Ash
0-50
18
0.59
0.7
3.19
I
__
3.19
Implementation Time, years: 3-6 most likely: 5
Relative Priority Rating: C
-------
II 1-40
R&D Opportunity: III-13
Related to: III-12; III-o
Analytical and Exper~ental Investigation of the Effect of Combustion Conditions on Fly-Ash
Resistivity and Other Characteristics
Technical Objective and Approach
The objective is to identify means of improving the efficiency of electrostatic precipitators by controlling
resistivity of fly ash by modifying the combustion process.
The approach should be to determine how combustion conditions affect the electrical properties of fly ash by
burning selected coals in the laboratory under conditions approaching those in a large boiler furnace. Rate of
burning, particle size, amount of excess air, and rank of coal should be varied so that the factors that affect the
resistivity of fly ash can be determined.
Rationale and Incentive
The ability of an electrostatic precipitator to capture particles of fly ash depends largely on the electrical
resistivity of the fly ash. When the electrical resistivity exceeds 2 x 1010 ohm-centimeters, the normal voltage
gradients in a precipitator are upset and the collection efficiency drops abruptly.
Formation of sulfates condensed on the outer surface of fly-ash particles is generally considered to control the
resistivity of fly ash. Conditions under which these electrically conductive films form are not known. In fact, it is
not certain that sulfates are even responsible, although there seems to be a relationship between sulfur content of
the fuel and the resistivity of the fly ash. The state of oxidation, the degree of sintering, and the high-temperature-
induced reactions between fly-ash particles also may be involved.
Estimated R&D Cost & Time
R&D Cost Range, 1000's: $300-$600
R&D Time Range: 3-5 years
Recommended 5-year Funding, 1000's: $450
Funding by Fiscal Year, $1000's
'69-70 I ~
X 50
'72
100
'73
'74
'75
'76+
150 150
Evaluation
Sources Affected: Coal Power Stations
Relative Potential Benefit (overall rating): Medium
Pollutants Affected
CP
co
HC
PNA
Odor
NOx
Lead
SOx
Ash
L
--
--
% Reduction, Range
Expected
Fraction of ECC Emissions Affected
Noncombustion Controls Factor
Relative Potential Benefit Factor
0-90
28
0.68
0.7
5.71
5.71
Implementation Time, years: 2-5
most likely: 3
Relative Implementation Cost: Low
-------
111-41
R&D Opportunity: III-14
Related to: III -15
Analytical and Experimental Investigation of the Feasibility of Fluxing Coal Ash for Minimizing
Emission of Particulates From Central-Station Power Plants
Technical Objective and Approach
The objective is to determine the feasibility of adding fluxes to coal-fired boiler furnaces to encourage capture
of ash as slag. A secondary objective is to determine whether the use of fluxes will permit burning of low sulfur
coals in existing slag-tap and cyclone furnaces.
Feasibility and economics of fluxing in cyclone furnaces, and in ordinary slag-tap furnaces, should be evaluated
initially by analytical studies based on available information and then by tests in full-scale boiler furnaces.
Rationale and Incentive
Slag-tap and cyclone furnaces convert much more of the ash in coal into molten
common dry-bottom pulverized-coal-fired boiler furnaces. This lower dust loading in
requirements for downstream mechanical and electrostatic collectors.
slag than do the more
the flue gas eases the
Decreasing the viscosity of coal-ash slags will tend to increase the amount of ash converted to slag, thereby
decreasing the dust loading in the flue gas. Fusibility of coal ash varies widely, but addition of inexpensive fluxes
such as limestone (CaO) and mill scale or iron ore (Fe203) can lower slag viscosity appreciably.
Also, low sulfur coals normally have high ash fusion temperatures and cannot be burned in existing slag-tap
and cyclone furnaces. The use of fluxes may permit such furnaces to burn low sulfur coals, thus decreasing the
emission of sulfur oxides.
Estimated R&D Cost & Time
R&D Cost Range, 1000's: $200-$600
R&D Time Range: 2-5 years
Recommended 5-year Funding, 1000's: $300
Funding by Fiscal Year, $1OO0's
'69-70 I ~
100
'72
100
73
100
'74
75
76+
Evaluation
Sources Affected: 100 Percent Coal Power Stations for Ash; 20 Percent Coal Power Stations for SOx
Relative Potential Benefit (overall rating): Medium High
Pollutants Affected
CP
co
HC
PNA
Odor
NOx
Lead
SOx
Ash
L
---
--
% Reduction, Range
Expected
Fraction of ECC Emissions Affected
Noncombustion Controls Factor
Relative Potential Benefit Factor
Implementation Time, years: 4-5
50-90
73
0.13
0.3
6.64
25-90
52
0.59
0.7
920
15.84
most likely: 5
Relative Implementation Cost: Medium
-------
III -42
R&D Opportunity: III-IS
Related to: III-14
Analytical and Experimental Investigation of a Super-Slagging Furnace to Achieve High Capture of
Coal Ash for Central-Station Power Plants
Technical Objective and Approach
The objective is to demonstrate the feasibility of capturing perhaps 99 percent of coal ash as molten slag in
large boiler furnaces.
One approach is through improved cyclone burners. The investigation should cover increased swirl, geometry
changes, and optimized operating temperatures. Additionally, this study should determine whether it would be
possible by specific design to increase substantially the ash capture of a conventional slag-tap furnace. Studies of
ash-particle agglomeration and deposition should be carried out. Subscale and analytical work will be needed.
Rationale and Incentive
Coal-fired cyclone furnaces capture about 90 percent of the coal ash as slag, but the dust loading is still high.
If 99 percent conversion of ash to slag could be achieved, the dust loading would be nearly equivalent to that with
residual fuel oil, making practical the use of bag filters for ultimate clean-up of the flue gas. Such a super-slagging
furnace could be a more economical way of decreasing dust loading than using electrostatic precipitators ahead of a
bag filter. Except where complete removal of fly ash is necessary, the super-slagging furnace alone would lead to a
nearly clean stack.
Estimated R&D Cost & Time
R&D Cost Range, 1000's: $800-$1,500
R&D Time Range: 4-8 years
Recommended 5-year Funding, 1000's:
$1 ,100
Funding by Fiscal Year, $1000's
'69-70 12!
100
'72
150
'73
150
'74
'75
'76+
300 400
Evaluation
Sources Affected: Coal Power Stations
Relative Potential Benefit (overall rating): Medium
Pollutants Affected
CP
CO
HC
PNA
Odor
NOx
Lead
SOx
Ash
~
--
--
% Reduction, Range
Expected
Fraction of ECC Emissions Affected
Noncombustion Controls Factor
Relative Potential Benefit Factor
45-90
55
0.36
0.7
5.94
5.94
I mplementation Time, years: 8-12
most likely: 10
Relative Implementation Cost: Low
-------
111-43
R&D Opportunity: III-16
Related to: III-2, 3, 4
Development of Improved Research Instrumentation and Sampling for Measurement of Local Con-
ditions Within Combustion Systems
Technical Objective and Approach
The objective is to develop new instrumentation for determining more exactly the conditions existing in local
regions within boiler furnaces.
The approach should be to develop methods for measuring instantaneous temperatures, gas velocity, and
direction of gas flow in large central-station boilers, plus flame volume and position, localized heat transfer, and
dust loading. A special case is measurement of spot temperature fluctuation in fluidized beds.
Utilizing this equipment, measurements should be made in several sizes and designs of boiler furnaces to
provide data on conditions existing in these units. These data, which are lacking at the present time, may suggest ideas
for modifying the combustion process in boiler furnaces to reduce emissions.
Rationale and Incentive
A major problem in relating fundamental studies of combustion to the improvement of large combustors such
as boiler furnaces, as well as the empirical improvement of such furnaces, has been the inability to define conditions
in these systems adequately. Dust-laden, high-temperature gases moving in nearly random fashion in extraordinarily
large enclosures pose as-yet-unsolved problems in measurement. If conditions within the furnace cavity can be
measured, a huge step will have been made in defming better how the combustion process can be modified or
controlled to minimize furnace emissions.
As an example, better agglomeration of ash particles to form large particles of fly ash would permit their
capture by mechanical systems and ease the load on electrostatic precipitators. This agglomeration can be achieved
most readily if temperature patterns, residence time, and collision rate during and immediately following com-
bustion are known and controlled.
Estimated R&D Cost & Time
R&D Cost Range, 1000's: $350-$1,000
R&D Time Range: 3-5 years
Recommended 5-year Funding, 1000's: $500
Funding by Fiscal Year, $1oo0's
'69-70 [ '71
100
'72
150
'73
150
'74
100
'75
'76+
Evaluation
Although funding the R&D Opportunity described above will not contribute directly to reducing emissions, it will provide
data useful to other R&D. A judgmental evaluation was used to assign the Relative Priority Rating to this R&D
Opportunity .
-------
111-44
R&D Opportunity: III-New Concepts
Provision for Exploring New Concepts and New R&D Opportunities that Evolve from the Program,
Accelerating Promising R&D, or Conducting Demonstrations of Promising Concepts for Reducing
Emissions from Central-Station Power Plants by Combustion Modification
Technical Objective and Approach
The objective is to provide for long-range flexibility in the R&D program to enable APCO to take advantage of
opportunities that are not presently evident, but which can arise during the course of this program.
The approach should be to make specific provisions in the R&D program to explore the feasibility of new and
novel concepts and to accelerate research, development, and demonstration of promising concepts for reducing
emissions by combustion-process modification. Worthwhile ideas for combustion-process modification to reduce
emissions from central-station power plants might originate as the result of novel design concepts or through
in-depth understanding derived from well-planned R&D. The merits of specific R&D opportunities should be
decided by evaluating the particular concepts as they evolve.
Rationale and Incentive
No radical changes in large power plants have occurred over the past 30 years, but the necessity of
constructing as much generating capability in the next 8 years as exists today and the pollution problem suggest
that new ways of converting fuels into electricity will be sought by many scientists and engineers.
One example of a novel concept is the proposed application of the fluidized bed to central-station power
plants. Other concepts for combustion modification might result from the development of a radically new heat
engine or from combining presently known cycles in a unique fashion.
Recommended Funding Allocation
'71
'72
250
'73
'74
'75
500
5-year Funding, 1000's: $1,500
- -
Funding by Fiscal Year, $1000's
350
400
Evaluation
This R&D Opportunity is unranked. Potential benefit, implementation time, implementation cost, and funding level for
each specific opportunity must be evaluated when the opportunity is identified. The suggested funding level anticipates
effort on several R&D opportunities.
-------
TABLE 111-7. SUMMARY BY PRIORITIES
CENTRAL-STATION POWER PLANTS
Relative Current Estimated R&D Costs, $1000
Priority R&D Opportunity APCO By Fiscal Years
Rating R&D 5- Y ear On-Going
Effort '71 '72 '73 '74 '75 Total '76+
A III -6 Experimental Investigation of the Combustion Mech- X 125 125 250 - - 500 -
anism of Coal in a Fluidized Bed of Noncombustible
Particles
A III-7 Experimental Investigation of Factors Influencing Com- X 50 75 125 250 - 500 -
pleteness of Coal Combustion in Fluidized Beds with
Low Excess Air
A III -8 Development of Improved Coal Gasification Systems to X 100 125 150 300 325 1,000 -
Produce Sulfur- and Ash-Free Gas Suitable for Advanced
Power Cycles - - - - - -
Totals, Priority A 275 325 525 550 325 2,000
B III-2 Analytical and Experimental Research to Develop Criteria X 200 850 1,050 2,500 3,000 7,600* 10,000*
for the Application of Flue-Gas Recirculation to Minimize
NOx Emission from Central-Station Power Plants
B III -3 Experimental Investigation to Develop Design Criteria for X 200 200 400 400 1,000 2,200* 10,000*
the Application of Two-Stage Combustion for NOx
Control, with Demonstration in a Coal-Fired Central-
Station Power Plant
B IlIA Experimental Investigation to Develop Design Criteria for X 200 300 300 1,000 - 1 ,800* -
the Application of Two-Stage Combustion for NOx
Control, with Demonstration in an Oil-Fired Central-
Station Power Plant
B III-14 Analytical and Experimental Investigation of the Feasibility - 100 100 100 - - 300 -
of Fluxing Coal Ash for Minimizing Emission of Particu-
lates from Central-Station Power Plants
- - - - - -
Totals, Priority B 700 1,450 1,850 3,900 4,000 11 ,900
.....
.....
.....
I
~
-------
TABLE 111-7. (Continued)
Relative Current Estimated R&D Costs, $1000
Priority R&D Opportunity APCO By Fiscal Years
Rating R&D 5- Year On-Going
Effort '71 '72 '73 '74 '75 Total '76+
C III-12 Experimental Investigation of the Effect of Mineral Composi- X 75 75 125 - - 275 . -
tion of Coal on Fly-Ash Resistivity and Other Characteristics
C III-13 Analytical and Experimental Investigation of the Effect of X 50 100 150 150 - 450 -
Combustion Conditions on Fly-Ash Resistivity and Other
Characteristics
C III-IS Analytical and Experimental Investigation of a Super-Slagging - 100 150 150 300 400 1,100 -
Furnace to Achieve High Capture of Coal Ash for Central-
Station Power Plants
C III-I 6 Development of Improved Research Instrumentation and - 100 150 150 100 - 500 -
Sampling for Measurement of Local Conditions Within
Combustion Systems - - - - - -
Totals, Priority C 325 475 575 550 400 2,325
D III-I Experimental Investigation of Feasibility of Burning - 125 125 250 - - 500 -
Pulverized Coal with Low Excess Air
D III-5 Exploratory Research and Experimental Feasibility - 100 150 150 250 300 950 1,000
Evaluation of a Low-Emission Combustion System for
Central-Station Power Plants using the Concept of a
High-Turbulence Primary Combustion Zone Plus a
Plug-Flow Zone
D III-I 0 Laboratory-Scale and Field Investigation of the Effect - 75 75 - - - 150 -
of Rank of Coal on Emission of NOx - - - - - -
Totals, Priority D 300 350 400 250 300 1,600
-
-
-
~
-------
TABLE 111-7. (Continued)
Relative Current Estimated R&D Costs, $1000
Priority R&D Opportunity APCO By Fiscal Years
R&D 5- Y ear On-Going
Rating Effort '71 '72 '73 '74 '75 Total '76+
E III-9 Exploration of the Feasibility of Electrochemical Oxidation - 100 100 100 100 100 500 100/yr
of Coal for Direct-Energy Conversion
E III-II Laboratory-Scale Investigation of the Effect of Residual - 125 150 200 - - 475 -
Fuel-Oil Properties and Composition on Emissions, and
Development of Convenient Methods to Characterize
Oils in Terms of Emission Tendency, Including NOx
and Particulates -
- - - - -
Totals, Priority E 225 250 300 100 100 975
N III -N Provision for Exploring New Concepts and New R&D Oppor- - - 250 350 400 500 1,500 -
tunities that Evolve from the Program, Accelerating
Promising R&D, or Conducting Demonstrations of
Promising Concepts for Reducing Emissions from
Central-Station Power Plants by Combustion Modification
Totals, All Priorities 1,825 3,100 4,000 5,750 5,625 20,300
-
-
-
I
~
-------
111-48
REFERENCES FOR CHAPTER III
1. Steam, Its Generation and Use, Babcock & Wilcox, New York (1963), pp 17-21.
2. Reese, J. R., Jonakin, J., and Caracristi, V. S., "Prevention of Residual Oil Combustion
Problems by Use of Low Excess Air and Magnesium Additive", Combustion, 36 (5)
(November, 1964), pp 29-37.
3. Orning, A. A., Smith, John F., and Schwartz, C. H., "Minor Products of Combustion in
Large Coal-Fired Steam Generators", ASME Paper 64-WUjFU-2 (1964), 12 pp.
4. Hangebrauck, R. P., von Lehmden, D. J., and Meeker, J. E., "Emissions of Polynuclear
Hydrocarbons and Other Pollutants from Heat-Generation and Incineration Processes", Jour.
Air Poll. Control Assoc., 14 (7) (July, 1964), pp 267-278.
5. Hangebrauck, R. P., von Lehmden, D. J., and Meeker, J. E., Sources of Polynuclear
Hydrocarbons in the Atmosphere, PHS Publication No. 999-AP-33 (1967),44 pp.
6. Cuffe, S. T., Gerstle, R. W., Orning, A. A., and Schwartz, C. H.,
from Coal-Fired Power Plants", Report No.1, Jour. Air Poll.
(September 1964), pp 353-362; Rept. No.2, Jour. Air Poll.
(February, 1965), pp 59-64.
"Air Pollutant Emissions
Control Assoc., 14 (8)
Control Assoc., 15 (2)
7. Diehl, E. K., du Breuil, F., and Glenn, R. A., "Polynuclear Hydrocarbon Emission from
Coal-Fired Installation", Trans. ASME, J. Eng. Power, 89, Series A (2) (April, 1967), pp
276-282.
8. Sensenbaugh, J. D., and Jonakin, James, "Effect of Combustion Conditions on Nitrogen
Oxide Formation in Boiler Furnaces", ASME Paper 6Q-WA-334 (1960), 6 pp.
9. Barnhardt, Donald H., and Diehl, ErIe K., "Control of Nitrogen Oxides in Boiler Flue Gases
by Two-Stage Combustion", Jour. Air Poll. Control Assoc., 10 (5) (October, 1960), pp
397-408.
10. Cuffe, Stanley, T., and Gerstle, Richard W., Emissions From Coal-Fired Power Plants: A
Comprehensive Summary, PHS Publication No. 999-AP-35 (1967), 26 pp.
11. Bartok, W., Crawford, A. R., Cunningham, A. R., Hall, H. J., Manny, E. K., and Skopp, A.,
Systems Study of Nitrogen Oxide Control Methods for Stationary Sources, Final Report,
Esso Res. & Engrg. Co. (November 20, 1969), NAPCA Contract PH-22-68-55.
12. Barrett, Richard E., Hummell, John D., and Reid, William T., "Formation of S03 in a
Noncata1ytic Combustor", Trans. ASME, J. Eng. Power, 88, Series A (2) (April, 1966), pp
165-172.
13. Bienstock, D., Amsler, R. L., and Bauer, E. R., Jr., "Formation of Oxides of Nitrogen in
Pulverized Coal Combustion", Jour. Air Poll. Control Assoc., 16 (8) (August, 1966), pp
442-445.
-------
111-49
14. First International Conference on Fluidized-Bed Combustion, Hueston Woods, NAPCA,
November 18-22, 1968.
15. Second International Conference on Fluidized Bed Combustion, Hueston Woods, NAPCA,
October 4-7, 1970.
16. "Fluidized-Bed Combustion", J. Fuel & Heat Tech., 16 (2) (March, 1969) pp 2-5.
17. "A Coal-Burning Fluidized-Bed Combustion System", J. Fuel & Heat Tech., 15 (5)
(September, 1968), pp 11-13.
18. Waters, P. L., and Watts, A., "The Application of Fluidization to Coal Combustion",
Preprint, Inst. Fuel Conf., Canberra (November, 1968).
19. Review of British Program on Fluidized-Bed Combustion: Report of u.s. Team, 17-28
February, 1969, ANLjES-CEN-1000, Argonne Nat'l Labs. (August, 1969),48 pp.
20. McLaren, J., and Williams, D. F., "Combustion Efficiency, Sulfur Retention and Heat
Transfer in Pilot-Plant Fluidized-Bed Combustor", Combustion, 41 (11) (May, 1970), pp
21-26.
21. Jonke, A. A., et al., Reduction of Atmospheric Pollution by the Application of Fluidized-
Bed Combustion, ANLjES-CEN-1001, Argonne National Labs., Annual Report (July, 1968 -
June, 1969), 62 pp.
22. Jonke, A. A., Carls, E. L., Jarry, R. L., and Anastasia, L. J., "Reduction of Atmospheric
Pollution by the Application of Fluidized-Bed Combustion", Preprint, Am. Power Conf.,
Chicago (April 22, 1970).
23. Curran, C. P., and Gorin, Everett, Phase II. Bench-Scale Research on CSG Process. Studies
on Mechanics of Fluo-Solids Systems, Consolidation Coal Co., R&D Rept. No 15, Off. Coal
Res., Contract 14-01-0001-415 (June, 1964 - June, 1968),101 pp.
24. Zielke, Clyde W., Lebowitz, Howard E., Struck, Robert T., and Gorin, Everett, "Sulfur
Removal During Combustion of Solid Fuels in a Fluidized Bed of Dolomite", Jour. Air Poll.
Control Assoc., 20 (3) (March, 1970), pp 164-169.
25. NAPCA Contract No. CPA 7(}9, Evaluation of Fluidized-Bed Combustion Process.
26. NAPCA Contract No. CPA 7(}10, Study of Characterization and Control of Air Pollutants
from a Fluidized Bed.
27. Squires, Arthur M., "Clean Power From Coal", Science, 169 (3948) (August 28, 1970), pp
821-828.
-------
Chapter I V
INDUSTRIAL PROCESSING
Herbert R. Hazard
TABLE OF CONTENTS
SCOPE OF CHAPTER AND BACKGROUND. . . . .
. . . . .
EMISSION LEVELS FROM THERMAL PROCESSING IN INDUSTRY
. . . .
Sources of NOx from Thermal Processing.
Prospects for Reduction of Emission Levels
. . . . .
. . . . . .
. . . . . .
. . . . .
R&D APPROACHES TOWARD REDUCTION OF NOx
THROUGH COMBUSTION MODIFICATION. . . . . . . . .
Rotary Kilns
. . . .
. . . . . . . .
. . . . . .
Glass-Melting Furnaces. . . . . . . . . . . .
Open-Hearth Furnaces. . . . . . . . . . . .
. . . . . .
. . . . . .
Iron-Ore Pelletizing Machines. . . . . . . . . . . . . . . .
Iron-Sintering Machines. . . . . . . . . . . . . . .
Steel Rolling, Forging, and Heat-Treating Furnaces. . . . . . . . .
Fuel-Rich Afterburning for Regenerative Furnaces. . . . . . . . .
SUMMARY OF CURRENT AND RELEVANT COMBUSTION R&D
. . . . .
R&D OPPORTUNITIES RECOMMENDED FOR THE 5-YEAR PLAN. .
Summary by Priorities. .
. . . . . .
. . . .
. . . . . .
REFERENCES FOR CHAPTER IV
. . . .
. . . .
. . . . .
IV- 1
- 1
- 2
6
7
- 7
- 8
- 8
- 9
- 9
-10
-10
-12
-14
-20
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IV-I
CHAPTER IV
INDUSTRIAL PROCESSING
SCOPE OF CHAPTER AND BACKGROUND
This chapter discusses combustion for thermal processing in industry, which includes all
uses of heat for processing, but does not include steam generation, power generation, or space
heating. The principal sources of pollutant emissions in thermal processing are:
. Iron production
. Steel production
. Cement and lime production
. Glass melting
. Aluminum production
. Brick, tile, and ceramic production
Several important fuel uses were excluded because they were considered to be conversion
processes rather than combustion applications. These include the blast furnace, the foundry
cupola, the coke oven, and ore-roasting plants. The effluents from these plants are not
combustion products in the usual sense, because they contain extremely high quantities of
process effluents such as CO, S02, and particulates.
EMISSION LEVELS FROM THERMAL PROCESSING IN INDUSTRY
Table IV-I summarizes the contribution of the thermal processing industries to total U.S.
pollutant emission levels as a percentage of the total. These percentages are based on the
tonnages listed in Table IV-2, obtained by apportioning about 30 percent of industrial combus-
tion fuels to the thermal processing area.
Emissions in Table IV-I that are large enough to warrant attention are combustible par-
ticulate, PNA, NOx, and sax. Emissions of CO and gaseous HC are relatively low.
Most pollutants from industrial processing sources are not subject to reduction by
modification of the combustion process. For example, the particulates include those from
thermal processing in which the finest fractions of the processed materials or ash escape with the
combustion gases; such particulate emission would normally be reduced by means of dust
collectors rather than by combustion modifications. Likewise, the sax emissions reflect use
of thermal processing to remove sulfur from ores and metals, and sax cannot be reduced
by combustion modifications. PNA is probably largely unburned volatile matter from coal
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IV-2
combustion; most of it may originate from steel-industry coke ovens, and it can be reduced only
by improved contain!TIent during the coking process.
Table IV-'. Emissions From Thermal Processing in Industry*
Pollutant
Contribution to
Nationwide ECC
Emissions,
percent
Products of Incomplete Combustion
Combustible particulate
CO
Gaseous HC
PNA
6
1
1
4
NOx
SOx
3
5
Ash (noncombustible particulate)
3
*Derived from data in Table 11-1.
However, NOx, formed in the combustion process under conditions of high flame
temperature and available oxygen, can be significantly reduced by modification of combustion
conditions to reduce either temperature or oxygen availability. Accordingly, the combustion
R&D opportunities discussed in this chapter are concerned entirely with reduction of NOx from
industrial combustion processes.
Sources of NOx from Thermal Processing
Table IV-2 lists large thermal processing industries, the fuel thermal input to each, and
estimates of NOx concentrations and emission levels for each. The values of thermal input were
taken from a series of American Gas Association reports, A Study of Process Energy
Requirements for U.S. Industries (2). Values are based on data from the 1962 Census of
ManufacturesO) with much of it updated to 1966.
The values of NOx concentration in the exhaust gas include Battelle estimates, data
from the Esso NOx study(3), and values based on recommended emission factors for industrial
applications from Reference 3. These values are based on ppm N02 by volume in exhaust gas
corrected to stoichiometric conditions.
The values of tons NOx per 1012 Btu are based upon the fact that the volume of
exhaust gas per Btu is nearly independent of fuel type, so that the weight of NOx per unit of
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IV-3
Table IV-2. Estimate 01 NOx Emissions From Various Thermal Processes in Industry
NOx
Concen-
tration, NOx Emission
Fuel Usage, ppm NOx Tons NOx Tons NOx
1012 Btu/yr in Flue Gas per 1012 Btu per Year
Iron Production
Blast furnace (840)
Blast furnace air preheating 200 10 7 1 ,400
I ran are pelletizing 27 500 348 9,400
Iron sintering 80 500 348 27,000
Steel Production
Open-hearth furnaces 425 270 200 85,000
Steel soaking pits 198 200 140 27,800
Reheat furnaces 300 200 140 42,000
Heat treating 79 200 140 11 ,000
Iron and Steel Foundries
Air preheat for gray-iron cupolas 8 50 35 300
Malleable-iron melting and heat treating 12 200 140 1,700
Steel melting and heat treating 14 200 140 1,900
Aluminum Production
Alumina calcining 96 300 224 21,500
Scrap smelting 12 200 140 1,700
Foundry melting 6 200 140 800
Heat treating 9 200 140 1,300
Copper Production, All Uses 52 200 140 7,300
Zinc Production 41 200 140 5,800
Cement and Lime Production 518 360 250 129,000
Rotary cement kilns 423 360 250 (105,000)
Lime kilns 95 360 250 (24,000)
Glass Melting and Processing 132 625 435 87,000
Ceramic Kilns 145 300 224 32,600
Baking - Bread, Biscuits, Etc. 54 40 27 1,500
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IV-4
heat value depends almost entirely upon the NOx concentration, in ppm. The tabulated values
are based upon exhaust-gas weight of 927 Ib per 106 Btu, and NOx calculated as N02, so that
each ppm of NOx accounts for 0.7 ton N02 per 1012 Btu.
The total NOx emission level from the sources listed in Table IV-2 is 496,000 tons per
year, which is approximately 5 percent of total U.S. emission of NOx. This is less than the value
of 11 percent in Table 1-2, obtained by apportioning total emission from industrial sources
among the three major categories: industrial boilers, gas engines, and thermal processing. The
source of the discrepancy is not evident, but the difference may be attributable to either error in
the apportioning process or lack of accuracy of emission factors used in making various NOx
emission inventories.
Table IV-3 summarizes emission levels from important industrial sources of NOx, as
estimated in the Esso systems study of NOx(3). The method of calculating these values was
entirely different from the method used for calculating values in Table IV-2, being based upon
emission per ton of product, and total product output in the base period (1968). However, the
values in the two tables are in relatively good agreement and satisfactory for purposes of
identifying significant NOx sources.
Table IV-3. Esso Estimates of NOx Emission levels
for Thermal Processing(3) (1968)
Source
NOx Emission,
tons per year
NOx Concentration,
ppm
Cement and lime kilns
Glass melting
Open-hearth furnaces
I ran sintering
Ceramic kilns
Blast-furnace stoves
Coke ovens
Cupolas
Soaking pits
Total
129,000
110,000
85,000
27,000
21 ,000
20,000
6,000
805
550
399,000
200-400
137 -1320
500-800
3-70
1.7-6.6
45
13
21-25
Of the sources in Tables IV-2 and IV-3, those large enough to warrant R&D toward
reduction of NOx emissions appear to be cement, lime, and alumina kilns; glass melting and
processing furnaces; open-hearth furnaces; and, possibly, soaking pits, reheat furnaces, and
heat-treating furnaces used in the steel industry. The results of research on glass-melting furnaces
and open-hearth furnaces could be applied to other reverbratory furnaces used for melting
aluminum, copper, brass, and malleable iron, although these are relatively small emitters of NOx.
In the case of blast-furnace stoves, R&D for control of NOx by combustion modification
does not appear warranted. The Battelle and Esso estimates are 1,400 and 20,000 tons per
year, respectively; both estimates are relatively small, and the difference is the result of different
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IV-5
estimating approaches. It is important to note that the Esso data indicate that the concentration
of NOx in the exhaust from these stoves is only 1.7 to 6.6 ppm, which is so low that it appears
impractical to reduce it further by combustion modifications. The NOx concentration is low be-
cause of the low heating value of blast-furnace gas (90 Btu per ft3); flame characteristics are
similar to those obtained with very large ratios of flue-gas recirculation.
The open-hearth furnace is a somewhat special case because it is being replaced rapidly
by the basic oxygen furnace. Although a large percentage of the present open-hearth capacity
will have been replaced by 1990, the projected 1990 emission of 30,000 tons NOx per year from
this source will still be significant, and some research toward its reduction appears justified.
Table IV-4 summarizes the projected growth rates and NOx emissions for significant NOx
sources, based on Reference 4 for growth rates, Reference 5 for open-hearth furnace production
rates, and Reference 3 for NOx emission factors. It can be seen that NOx emission from cement
and lime kilns and from glass-melting furnaces should double by 1990; emission from iron-
ore pelletizing machines should increase by a factor of 1.8; and emission from open-hearth
furnaces should decline significantly. Total emissions should increase by 57 percent by 1990 if no
control measures are implemented.
Table IV-4. Projected NOx Emissions From Selected Industrial Sources
Growth Projected Emissions, tons/year
Rate(a), % '68 70 '75 '80 '90
Rotary Kilns
Cement and Lime Kilns 3.2 129 138 161 188 258
Alumina Calcining Kilns 2.3 21 22 25 28 35
Glass-Melting Furnaces 3.2 110 118 138 160 220
Clay Tile, Brick, and Ceramic Kiln 3.2 21 23 26 31 42
Open-Hearth Furnaces(b) 85 72 54 44 30
lron-Sintering Machines 27 27 27 27 27
Iron-Ore Pelletizing Machines 2.3 9 10 11 13 16
Steel Forming and Heat Treating 2.3 81 85 95 106 134
Totals 483 762
(a) From Reference 4.
(b) Projected production rates from Reference 5, emission factors from Reference 3.
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IV-6
Prospects for Reduct!on of Emission Levels
As has been discussed, NOx emissions are the only significant emissions that can be
effectively reduced through modification of the combustion processes involved in thermal
processing. All of the thermal processing industries are mature industries in which combustion
equipment has undergone continuing development over many years. This development has made
possible optimum process quality control and economics, but it has not been greatly concerned
with pollutant emissions except for visible smoke and particulate emissions, which have been
regulated. Moreover, there is incentive for industry to operate large furnaces as efficiently as is
practical, so that emissions of products of incomplete burning are minimized.
NOx is formed by oxidation of the nitrogen in the fuel and in the combustion air, under
conditions of high temperature in the presence of oxygen. Thus, formation of NOx can be
minimized by:
. Minimizing flame temperature
. Burning under reducing conditions
. Two-stage burning which achieves low flame temperatures and reduc-
ing conditions.
Flame temperature can be minimized by recirculating flue gas through the flame as a
diluent to limit peak temperature, by using a large amount of excess combustion air as a diluent,
or by two-stage burning with heat removal from the flame before addition of air to complete the
com bustion.
Burning under reducing conditions, with less than stoichiometric air, limits the availability
of oxygen and, thus, reduces formation of NOx. However, this results in combustion products
containing a high proportion of unburned fuel components which must be burned later in the
process by addition of air.
Two-stage combustion is a combined process in which fuel is burned under reducing
conditions, following which heat is removed from the combustion products and the remaining
fuel is burned under oxidizing conditions, but at a temperature low enough to limit the
oxidation ot' nitrogen. A variant of two-stage combustion is carried out without heat removal
between stages in the gas turbine, where the short residence time for the second stage of
combustion kinetically limits NOx emission.
The possibility of applying flue-gas recirculation, burning under reducing conditions, or
two-stage burning to the thermal processing industries varies with each type of equipment.
Accordingly, these are considered separately in the following discussion of possible R&D
approaches.
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IV-7
R&D APPROACHES TOWARD REDUCTION OF NOx
THROUGH COMBUSTION MODI FICATION
There appears to be a good probability that the NOx emissions projected in Table IV-4
can be reduced significantly through modification of the combustion process and that, with
moderate success, the total emission levels through 1990 can be held at or near present levels.
Combustion modifications that appear most suitable for all processes are: (1) recirculation of
exhaust gas into the burners to reduce peak flame temperatures and (2) modification of burners
to delay mixing and produce effects similar to those in two-stage burning. The means for
carrying out these modifications, the problems that will be encountered, and the probable level
of success will vary from process to process. Some of the processes for which R&D benefits are
foreseen are discussed below.
Rotary Kilns
Rotary kilns are used for production of Portland cement, the calcining of lime, and the
calcining of alumina. In all of these, the kiln is a slightly inclined rotating tube fired at the lower
end and fed with raw material at the higher end. Kiln lengths vary from 150 to 500 feet and
diameters from 12 to 25 feet. Many kilns are fitted with dust collectors and with air heaters to
regenerate exhaust heat.
Cement Kilns. In 1967, there were 188 cement plants in operation in the U.S. Portland
cement is made in large kilns fed with a mixture of clay and limestone (or similar materials) plus
minor ingredients to provide a carefully proportioned mixture of calcium, silicon, aluminum, and
iron. The ground ingredients are slowly heated to 2200 F, at which temperature they react
exothermally and quickly reach 2700 F. A long flame, with slow mixing of air and fuel, is used
to control the temperature distribution in the kiln and the position of the hot reaction zone.
Recuperative air heaters are usually used to recover exhaust heat and to preheat combustion air
to about 500 F.
In view of the critical nature of the heat distribution within the kiln, it is not obvious
whether modifications of the fuel and air admission at the burner end of the kiln could
accomplish the effect of two-stage combustion; in fact, the conventional system may approach
this condition. However, it does appear possible to apply exhaust-gas recirculation to cement
kilns by ducting exhaust gas to the burner with preheated inlet air and, thus, reducing peak
flame temperature. It is not clear how much recirculation could be maintained without reducing
kiln temperature or capacity, or what level of NOx reduction could be achieved. However, it
appears possible that NOx could be reduced by as much as 50 percent.
Lime Kilns. In 1967, 33 of 209 plants accounted for 63 percent of U.S. lime produced(2).
Eighty-five percent of the commercial U.S. lime is produced in rotary kilns(2). Lime kilns, for
calcining of limestone, normally operate much like a cement kiln, except that the limestone is
heated to only 2200 F. During dead-burning of dolomitic limestone to make refractories, however,
the lime is heated to 2500 F or more. Because of the moderate temperature level and the
absence of a specific reaction zone, modification of lime kilns to reduce NOx by either burner
changes or exhaust-gas recirculation appears to offer a high probability for success.
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IV-8
Alumina Kilns. In 1967, all U.S. production of alumina was concentrated in eight plants.
Alumina-calcining kilps, like lime kilns, operate at a moderate temperature of 2200 F, so that
the possibility of successful application of flue-gas recirculation or burner modifications to
reduce NOx emissions appears good. The annual thermal input to alumina calcining kilns is about
equal to the input to lime kilns, and the reaction temperatures are the same, so that it is
probable that the same type of combustion modifications would be applicable to both. It
appears possible to reduce NOx emissions by 50 percent or more by combustion modifications.
Glass-Melting Furnaces
Most glass is melted in large continuous-melting tanks that are regenerative furnaces
operating at high temperatures. Incoming air is heated to a high temperature in brick checkers,
and exit gas is cooled in a second set of checkers. The flow direction is reversed periodically to
maintain both sets of checkers at similar temperatures and thus maintain constant firing
conditions. Flame temperature is near 3500 F, and the process temperature is maintained at the
highest level possible consistent with satisfactory refractory life. The combination of high air
preheat and hot refractory temperature results in high flame temperature and high NOx
concentrations, reported to be in the range from 435 to 1320 ppm(3). However, the actual glass
temperature during the refining period is only about 2700 F, so that it appears possible to
reduce peak flame temperature significantly and, thus, reduce NOx emission, without greatly
reducing production rate.
The chemistry of the glass being melted determines whether an oxidizing or reducing
flame is required, so that two-stage burning does not appear generally compatible with produc-
tion requirements. However, it appears desirable to alter burner mixing patterns to provide slow
mixing and long flames and, thus, avoid high local temperatures. In addition, it may prove
feasible to utilize an effective level of flue-gas recirculation to further reduce maximum local
flame temperature without greatly reducing mean furnace radiating temperature. In view of the
long residence time and high temperature level in the glass-melting furnace, it is unlikely that
NOx can be reduced to a low level, but a reduction of as much as 50 percent of current
emission levels appears attainable if optimum conditions can be determined and maintained.
Open-Hearth Furnaces
Open-hearth furnaces, like glass tanks, are large reversible regenerative reverbratory
furnaces in which chemical reactions and heating take place. In processing a batch of iron to
make steel, scrap is melted, molten iron is added, and the metal is slowly heated and refined
under a layer of slag. The making of steel is an oxidation process, with oxygen provided from
iron ore added to the bath, by use of oxygen lances through the roof, by reduction of carbon
dioxide evolved from limestone, and by oxidation from the combustion atmosphere above the
bath. Combustion takes place under oxidizing conditions at high temperature, limited only by
the temperature limits of the furnace refractories. The NOx levels vary between 500 and 800 ppm.
The use of oxygen injection through lances directed into the bath, and under the burners to in-
crease flame temperatures near the bath, but not near the roof, provides local regions of high
flame temperature conducive to high NOx emissions.
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IV-9
It is probable that measures to control or reduce NOx may also reduce furnace produc-
tivity, but some significant NOx reduction may be possible with acceptable productivity levels.
As with glass tanks, the most attractive solutions appear to be flue-gas recirculation to minimize
high peak temperatures without greatly reducing mean radiating temperature, and modification
or adjustment of burners to provide more gradual mixing and combustion.
The number of open-hearth furnaces in service is scheduled to decline from 467 units in
1968 to 257 units in 1973, with a further gradual decline through 1990 because the newer basic
oxygen furnace operates at significantly lower cost when the cost of particulate emission controls
is included. However, the projected emission of NOx from open-hearth furnaces in 1990 is
30,000 tons per year, which is still significant.
Iron-Ore Pelletizing Machines
In 1968, nine iron-ore pelletizing machines in the U.S. produced 45,000,000 tons of
pelletized ore, with estimated NOx emission of 9,400 tons. These machines are located at, or
close to, the iron mines producing the ore, and burn heavy oil or natural gas. It is anticipated
that the production of iron pellets will grow at a rate proportional to that of steel production, at
about 2.3 percent per year.
In one type of pelletizing machine, pellets formed from a wet slurry of fmely divided ore
are carried upon a moving belt about 300 feet long while being heated to about 2200 F by
combustion products passing through the moving pellet bed. Mter the pellets have sintered,
incoming combustion air is passed upward through the hot pellet bed to cool the pellets and
recover the heat by preheating the combustion air. Heavy oil or natural gas is burned in a
refractory chamber above the pellet bed, many burners being used to control temperature distri-
bution. Flame radiation to the bed is avoided to minimize excessive heating of the surface of the
pellet bed.
The highest gas temperature utilized in the pellet bed is about 2500 F, and all fuel is
burned in conventional burners. Thus, it appears possible to reduce present NOx emission levels
by as much as 50 percent through application of combustion modifications such as flu~s
recirculation or burner modifications.
lron-Sintering Machines
Iron sintering is carried out within steel mills as a means of recovering and utilizing fme
kon oxide dust from plant sources and from dusty ores. The fme oxide is mixed with flue dust,
coke breeze, and limestone in a slurry which is fed to the sintering machine. In the sintering
machine the sinter is slowly heated to about 2200 F as it passes over a moving belt 60 to 100 feet
long. A gas or oil flame in the entrance region brings the sinter to its ignition temperature, after
which combustion of carbon within the sinter provides the remaining heat required to sinter the
kon. The ignition fuel provides only 1/5 of the total heat.
The Esso estimate(3) for NOx emission from sintering machines is 27,000 tons per year.
In view of the fact that most of the combustion in sintering takes place within the sinter, in
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IV -10
which the combustible material is in the form of mixed carbon, the opportunities for reduction
of NOx emission through combustion modifications appear limited. However, it appears possible
to minimize the NOx emission from the ignition flame by burner modifications or flue-gas
recirculation. Flue-gas recirculation may also reduce the NOx emitted from combustion within
the sinter.
Because of changes in steel-mill practices, it is anticipated that no new sintering machines
will be built, but that those in operation will remain active. Thus, NOx emission from sintering
operations should not grow in the future.
Steel Rolling, Forging, and
Heat-Treating Furnaces
Steel rolling, forging, and heat treating accounts for consumption of about 615 x 1012
Btu per year of fuel, which is consumed entirely within steel mills. About half of this is
coke-oven gas and blast-furnace gas, and the balance is natural gas and fuel oil. The soaking pits,
reheat furnaces, and heat-treating furnaces in which this fuel is burned are large and each has
many burners, all adjusted to provide the desired temperature distribution and heating conditions
within the furnace. Metal temperatures are fairly moderate, less than 2300 F, and combustion
conditions are adjusted for highest efficiency without smoke, at near-stoichiometric, but
oxidizing, conditions. Actual emission factors for these furnaces are not available, but it seems
reasonable to use factors recommended for industrial combustion of natural gas and fuel oi1(3),
which are equivalent to about 200 ppm NOx in the exhaust, or 140 tons per 1012 Btu.
There appears to be some opportunity to reduce NOx emissions through combustion
modifications. Flue-gas recirculation could reduce peak flame temperatures without greatly
reducing mean radiating temperatures, but would require considerable ducting and a revision of
combustion controls. Likewise, two-stage burning, with reducing conditions within the furnace
and an afterburner at the furnace outlet, would seem possible with some types of furnaces,
although means must be found to insert and remove steel from the furnaces without loss of
combustible and toxic combustion products. This area appears to require considerable investiga-
tion, both to ascertain present NOx emission levels and to devise acceptable control methods,
but R&D appears justifiable as this is a potentially large source with a moderate growth rate.
Fuel-Rich Afterburning for Regenerative Furnaces
Regenerative furnaces are those utilizing exhaust-heated checkers for heating incoming
air, such as open-hearth furnaces and glass-melting furnaces. Because of the high temperature
levels at which they operate, and the necessity for oxidizing atmospheres for the processes in
which they are used, it may prove impractical to reduce NOx emission to a satisfactory level
through combustion modifications within the furnace. An alternative approach would be to use a
fuel-rich afterburner to destroy the NOx in the flue gas, followed by recovery of the heat
produced by combustion, and a second afterburner operating at lower temperature to remove
unburned fuel remaining from the first afterburner.
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IV-II
Figure IV-I is a schematic diagram of a fuel-rich afterburner system for one of the two
reversible regenerator banks. In this system, fuel such as natural gas is added to the hot
combustion products from the furnace to burn out remaining oxygen by partial combustion of
the methane to CO and H2, which takes place readily at elevated temperature. At this
temperature, and within the time available, it appears possible that NO can be reduced by the CO
and H2 to an acceptably low level, but kinetic studies are needed to verify this. The hot
reducing gas would then pass through the first checker for cooling to about 2000 F. On leaving
the fIrst checker, it would pass through a second afterburner where sufficient air would be added
to burn the CO and H2 generated in the fIrst afterburner. The gas, now slightly oxidizing, would
pass into the second checker for final cooling. The heat value of the fuel burned in the first
afterburner would be recovered in the two checker banks and then added to the incoming air
upon reversal of the flow pattern.
It is conceivable that this process could be used for both glass-melting tanks and
open-hearth furnaces should it prove practical and economical.
First Afterburner
Add CH4 to burn 'JII
Or.idizing gas Oz ond generate
at 3200 F er.cess CO and Hz to
700 ppm NO reduce NO
d.,V CD -q~ I /
.
o/$lua - @ .J Er.haus~
-
~- I - -;:\1 -
.-. I - _5~1- Second
First checker: - :'f - - checker:
Reduce gos temp '- - '1- Cool gas
to 2000 F I @ to 500 F
II I
I I
I
I. Furnace hearth I
2. Fuel-rich afterburner Second Afterburner
3. First checker stage Add air, burn off
4. Second afterburner CO. Hz from 0
5. Second checker stage at low temperature
Figure IV.1. Schematic Diagram of Fuel-Rich Afterburner System for Regenerative Furnaces
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IV-I 2
SUMMARY OF CURRENT AND RELEVANT COMBUSTION R&D
Table IV-5 summarizes current combustion R&D programs related to reduction of
pollutant emissions from thermal processing industries.
The two Esso programs are industry-wide studies of control methods suitable for reduc-
tion of NOx by all means, but with emphasis on combustion modifications. The second program
listed has the objective of identifying and evaluating emissions from combustion sources in the
iron, steel, and aluminum industries. The APeO program of demonstration of new sintering-
process technology is just beginning.
The research program of the International Flame Research Foundation, at IJmuiden,
Holland, merits special comment. This group effort, over a period of many years, has involved
studies of detailed effects of flame aerodynamics and mixing, fuel type, and heat-removal rates on
the radiation from large flames. Much has been learned about the details of soot formation and
decomposition, temperature profiles within flames, and concentration of CO, 02, and C02
throughout flames as combustion proceeds. The facilities and skills which have been developed at
this large experimental facility are applicable to detailed study of pollutant generation and
decomposition within large flames.
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Project
Key
Project or Contract Title
Table IV-5.
Sponsoring
Organization
and Contract No.
Current Combustion R&D - I ndustrial Processing
Research Organization
Principal
Investigator
Funding, $
Objective or Scope
IV-a
W. Bartok
IV-b
IV-<:
IV-d
IV.e
Systems study of nitrogen oxides control
methods for stationary sources
Selected R&D of nitrogen oXides control
methods for stationary sources
Evaluation of conventional combustion
sources In the iron and steel mdustry
and aluminum industry
Demonstration of new technology for
controlltng all emissions from the
smtenng process
Various studies related to combustion
for industrial processing
NAPCA.DPCE
PH 22-68-55
NAPCA-DPCE
CPA 70.90
NAPCA-DPCE
EHSD 71-21
NAPCA.DPCE
CPA 70-Neg. 185
Various industrial
organ izations
contribute
Esso Res. & Eng. Co.
Linden, New Jersey
Consider methods for reducing NOx
emissions from stationary sources
including industrial processing
389,307 (Totall
Esso Res. & Eng. Co.
Linden, New Jersey
Obtain improved data on NOx emis-
sions and determine effect of some
control techniques on a limited
number of applications
363,025 (FY '70)
=<
I
-
W
Walden Res. Corp.
Cambridge, Mass.
Evaluate cost effectiveness of current
emissions-<:ontrol technology, and
define needed control for these units
64,268 (FY '71)
International Flame
Research Foundation
IJmuiden, Holland
W. Leuckel
Studies to determine combustion condi.
tlOns within flames typical industrial
furnaces Including heat transfer and
velocity, temperature, and concentra-
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IV-l4
R&D QPPORTUNITIES RECOMMENDED FOR THE 5-YEAR PLAN
Five R&D opportunities in the area of thermal processing in industry were identified.
These cover R&D for NOx reduction in:
. Rotary kilns for cement and lime production
. Glass-melting furnaces
. Open-hearth furnaces
. Regenerative melting furnaces
. Iron-sintering and iron-pelletizing processes.
Descriptions and evaluations of the R&D opportunities are presented on the following pages.
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IV-IS
R&D Opportunity: IV-I
Related to: VIII-27, 28; IV-a, b, e
Analytical and Experimental Research on the Reduction by Combustion Modifications of NOx
Emission From Rotary Kilns for Production of Cement and Lime, Including Full-Scale Demonstra-
tion Application
Technical Objective and Approach
The objective is to develop information necessary for the modification of firing practice to reduce emission of
NOx from large rotary kilns used in cement and lime production.
The approach should involve examination of possible modifications that might prove applicable such as
techniques for minimizing peak combustion temperatures by the use of long-flame burners with delayed mixing of
fuel and combustion air and the use of flue-gas recirculation. An analytical model should be used to explore the
probable effects of these changes, following which experiments should be carried out in a laboratory-sized,
non-rotating kiln model. If significant success is achieved with the laboratory model, the most suitable modifications
should be applied to a full-scale lime kiln or a full-scale cement kiln.
Rationale and Incentive
Cement kilns are among the largest stationary emitters of NOx' Each kiln is large enough to be a significant
local emission source. The cement-burning process takes place over a short section of the kiln at 2700 F; extremely
high flame and refractory temperatures are not required for satisfactory processing. It is probable that the local high
temperatures responsible for high NOx levels can be reduced significantly without loss of output. Delayed mixing of
fuel and air is now used for process control but has not been investigated in relation to NOx emission; when
optimized for NOx, the mixing patterns may be different. Also, flue-gas recirculation appears applicable to such
systems.
This emission source is expected to grow at a rate of 3.2 percent per year, with NOx emissions increasing from
129,000 tons in 1968 to 258,000 tons in 1990. A reduction of NO x emissions of about 45 percent appears probable
by combustion modifications.
Estimated R&D Cost & Time
R&D Cost Range, 1 COO's: $500-$800
R&D Time Range: 3-5 years
Recommended 5-year Funding, 1000's: $700*
Funding by Fiscal Year, $1 COO's
'69-70 12!
100
'72
200
73
200
74
200
75
'76+
Evaluation
Sources Affected: Rotary Kilns for Production of Cement and Lime
Relative Potential Benefit (overall rating): Very Low
Pollutants Affected
CP
CO
HC
PNA
Odor
NOx
Lead
SOx
Ash
~
---
--
% Reduction, Range
Expected
Fraction of ECC Emissions Affected
Noncombustion Controls Factor
Relative Potential Benefit Factor
Implementation Time, years: 4-6
0-60
43
.0053
o
0.23
0.23
most likely:5
Relative Implementation Cost: Very Low
Relative Priority Rating: E
-------
IV-16
R&D Opportunity: IV-2
Related to: VIII-27, 28; IV-a, b, e
Analytical and Experimental Research on the Reduction of NOx From Glass-Melting Furnaces by
Combustion Modifications
Technical Objective and Approach
The objective is to develop information necessary for the modification of firing practice for glass-melting tanks
to reduce the emission of NOx'
This approach should consist of investigating several combustion modifications, for example: (1) use of
long-flame burners in combination with considerable internal recirculation, (2) use of flue-gas recirculation, and (3)
use of two-stage combustion, where glass chemistry is suitable. The effects of these modifications upon predicted
local flame temperatures and NOx levels should be investigated analytically as a basis for experimental work.
Experiments should then be carried out in a day tank (a small batch-type tank). If significant success is achieved at
this level, the most suitable modifications should then be made ready for application to a large continuous-melting
tank.
Rationale and Incentive
Most glass is melted in large reverberatory furnaces having regenerative brick checkers for heat recovery and air
preheating. Flame and furnace temperatures are very high, leading to high emission of NOx, in the range of 750
ppm. The actual glass melting and refining temperature is about 2700 F; therefore, extremely high overall furnace
temperature is not required. Thus it appears possible to modify the combustion practice to minimize peak flame
temperature without a significant reduction of rQof temperature and mean gas radiating temperature.
This emission source is expected to grow at a rate of 3.2 percent per year, with NOx emissions increasing from
110,000 tons in 1968 to 220,000 tons in 1990. With a moderate level of success, a reduction of NOx emissions of
about 50 percent appears probable by combustion modifications.
Estimated R&D Cost & Time
R&D Cost Range, 1000's: $300-$500
R&D Time Range: 2-4 years
Recommended 5-year Funding, 1000's: $400
Funding by Fiscal Year, $1oo0's
'69-70 12!
100
'72
200
'73
'74
'75
'76+
100
Evaluation
Sources Affected: Glass-Melting Furnaces
Relative Potential Benefit (overall rating): Very Low
Poll utants Affected
CP
CO
HC
PNA
Odor
NOx
Lead
SOx
Ash
~
--
--
% Reduction, Range
Expected
Fraction of ECC Emissions Affected
Noncombustion Controls Factor
Relative Potential Benefit Factor
20-80
50
.0046
o
0.23
0.23
Implementation Time, years: 4-6
most likely: 5
Relative Implementation Cost: Very Low
-------
IV-I7
R&D Opportunity: IV-3
Related to: VIII-28; IV-a, b, c, e
Analytical and Experimental Research on Reduction of NOx Emissions From Open-Hearth
Furnaces by Modification of Firing Techniques, Including Demonstration
Technical Objective and Approach
The objective is to reduce NOx emissions from open-hearth furnaces.
The approach should include an analytical examination of the conditions within the open-hearth furnace to
determine the effects of local variations in combustion conditions and flame temperatures upon production rates
and NOx emissions. If encouraging results are obtained, a laboratory model should be constructed for experimental
investigation of the parameters involved. If laboratory results are promising, experimentation should be followed by
application to a full-scale furnace.
Rationale and Incentive
Although a great many open-hearth furnaces have been retired, and more are to be retired in the near future,
those remaining will continue to be significant emitters of NOx. It is estimated that the NOx emissions from this
source will decrease from 88,000 tons in 1968 to 44,000 tons in 1980 and30,000 tons in 1990. A reduction of NOx
emissions of about 50 percent appears possible by combustion modifications.
Estimated R&D Cost & Time
R&D Cost Range, 1000's: $500-$2,000
R&D Time Range: 2-5 years
Recommended 5-year Funding, 1000's:
$2,000*
Funding by Fiscal Year, $1OO0's
'69-70 12!. '72
250 250
'73
'74
'75
'76+
500 1000
Evaluation
Sources Affected: Open-Hearth Furnaces
Relative Potential Benefit (overall rating) : Very Low
Pollutants Affected
CP
co
HC
PNA
Odor
NOx
Lead
SOx
Ash
~
---
--
% Reduction, Range
Expected
Fraction of ECC Emissions Affected
Noncombustion Controls Factor
Relative Potential Benefit Factor
20-60
47
.0009
o
0.04
0.04
Implementation Time, years: 6-8
most likely: 7
Relative Implementation Cost: Very Low
-------
IV-18
R&D Opportunity: IV-4
Related to: VIII-28; IV-a, b, c, e
Analytical and Experimental Research on Fuel-Rich Afterburning to Reduce NOx Emission From
Regenerative Melting Furnaces
Technical Objective and Approach
The objective is to reduce NOx emissions from regenerative furnaces by the use of a fuel-rich afterburner and a
second fuel-lean afterburner with heat removal following each afterburner. (See Figure IV-I.)
The approach should be to investigate analytically and then in actual furnaces the effect of adding fuel to the
high-temperature gas stream leaving a regenerative furnace, such as an open-hearth or glass-melting furnace, thus
providing time for the NOx to react with the fuel under reducing conditions to decompose the NOx' The gas should
then be cooled by passing it through part of the regenerator, after which air should be added to burn out the CO
formed in the fuel-rich afterburner. This would reheat the gas stream somewhat, after which it should be passed
through the second regenerator section for final cooling.
Rationale and Incentive
Because of process chemistry limitations, it may not be feasible to reduce NOx emitted from open-hearth
furnaces and from glass tanks by modifications of the combustion process. However, both of these processes operate
with regenerators for heat recovery which makes it feasible to add fuel to the exhaust stream and recover the heat
of combustion in the regenerator that follows. The fuel-rich afterburning would provide a reducing atmosphere to
promote reactions resulting in destruction of NOx.
The sum of NOx emissions from glass-melting furnaces and open-hearth furnaces will grow from 195,000 tons
in 1968 to 250,000 tons in 1990. A reduction of NOx emissions of about 50 percent appears possible by combus-
tion modifications.
Estimated R&D Cost & Time
R&D Cost Range, 1000's: $200-$1,000
R&D Time Range: 2-4 years
Recommended 5-year Funding, 1000's: $800*
Funding by Fiscal Year, $1oo0's
'69-70 12.!. '72
X 100 300
'73
300
'74
100
'75
'76+
Evaluation
Sources Affected: ~Glass-Melting Furnaces and Open-Hearth Furnaces
Relative Potential Benefit (overall rating) : Very Low
Poll utants Affected
CP
co
HC
PNA
Odor
NOx
Lead
SOx
Ash
~
---
--
% Reduction, Range
Expected
Fraction of ECC Emissions Affected
Noncombustion Controls Factor
Relative Potential Benefit Factor
20-90
52
.0056
o
0.29
0.29
Implementation Time, years: 4-6
most likely: 5
Relative Implementation Cost: Low
-------
IV -19
R&D Opportunity: IV-5
Related to: VlII-27, 28; IV-a, b, c, d, e
Analytical and Experimental Investigation of Combustion Modifications to Reduce NOx Emission
From Iron-Sintering and Iron-Pelletizing Processes
Technical Objective and Approach
The objective is the modification of the combustion process to reduce NOx emissions from iron-pelletizing and
sintering machines used in processing iron ore and/or steel-plant iron oxides.
The approach should include analytical investigation of the effect of combustion modifications on the process.
The technique that seems best for NOx reduction should be investigated experimentally in a full-size unit. It is
expected that combustion modifications such as two-stage combustion or flue-gas recirculation will greatly reduce
NOx emissions without affecting the processing variables adversely.
Rationale and Incentive
Iron pelletizers are large machines, generally located at the iron mine, used to make hard, often partially
reduced, pellets of the finely ground ore. Sintering machines are similar in operation, but are used within steel
plants to recover in usable form the finely divided iron oxide collected from plant sources. These machines are
fairly large users of fuel, and process requirements are such that high flame temperatures are not essential.
Therefore, it appears feasible to apply combustion modifications for reduction of NOx'
NOx emissions from these sources are expected to grow at a rate of 6 percent per year, from 27,000 tons in
1968 to 98,000 tons in 1990. A reduction of NOx emissions of about 50 percent appears possible by combustion
modifications.
Estimated R&D Cost & Time
R&D Cost Range, 1000's: $100-$ 5 00
R&D Time Range: 1-3 years
Recommended 5-year Funding, 1000's: $300
Funding by Fiscal Year, $1000's
'69-70 12.! '72
100 200
'73
'74
'75
'76+
Evaluation
Sources Affected: lron-Sintering and Pelletizing Plants
Relative Potential Benefit (overall rating): Very Low
Pollutants Affected
CP
co
HC
PNA
Odor
NOx
Lead
SOx
Ash
~
---
--
% Reduction, Range
Expected
Fraction of ECC Emissions Affected
Noncombustion Controls Factor
Relative Potential Benefit Factor
Implementation Time, years: 3-5
30-60
48
.0018
o
0.09
0.09
most likely: 4
Relative Implementation Cost: Very Low
-------
IV-20
R&D Opportunity: IV -New Concepts
Provision for Exploring New Concepts and New R&D Opportunities that Evolve from the Program,
Accelerating Promising R&D, or Conducting Demonstrations of Promising Concepts for Reducing
Emissions from Combustion Equipment used for Industrial Processing by Combustion Modification
Technical Objective and Approach
The objective is to provide for long-range flexibility in the R&D program to enable APCO to take advantage of
opportunities that are not presently evident, but which can arise during the course of this program.
The approach should be to make specific provisions in the R&D program to explore the feasibility of new and
novel concepts and to accelerate research, development, and demonstration of promising concepts for reducing
emissions by combustion-process modification. Worthwhile ideas for combustion-process modification to reduce
emissions from combustion equipment used for industrial processing might originate as the result of novel design
concepts or through in-depth understanding derived from well-planned R&D. The merits of specific R&D oppor-
tunities should be decided by evaluating the particular concepts as they evolve.
Rationale and Incentive
Industry utilizes a variety of thermal processes, each having different problems and combustion restraints.
Although these restraints somewhat limit the extent of combustion modification, it appears possible that new
concepts for reduction of emissions from specific processes may arise.
Recommended Funding Allocation
'71
'72
50
'73
Funding by Fiscal Year, $1OO0's
50
'74
50
'75
50
5-year Funding, 1000's: $200
Evaluation
This R&D Opportunity is unranked. Potential benefit, implementation time, implementation cost, and funding level for
each specific opportunity must be evaluated when the opportunity is identified. The suggested funding level anticipates
effort on several R&D opportunities.
-------
TABLE IV-G. SUMMARY BY PRIORITIES
INDUSTRIAL PROCESSING
(Combustion for Thermal Processing, not including Steam Generation)
Relative Current Estimated R&D Costs, $1000
Priority R&D Opportunity APCO By Fiscal Years
R&D 5- Year On-Going
Rating Effort '71 '72 '73 '74 '75 Total '76+
E IV-1 Analytical and Experimental Research on the Reduction by - 100 200 200 200 - 700* -
Combustion Modifications of NOx from Rotary Kilns for
Production of Cement and Lime, Including Full-Scale
Demonstration Application
E IV-2 Analytical and Experimental Research on the Reduction of - 100 200 100 - - 400 -
NOx from Glass Melting Furnaces by Combustion
Modifications
E IV-3 Analytical and Experimental Research on Reduction of - 250 250 500 1,000 - 2,000* -
NOx Emissions from Open-Hearth Furnaces by
Modifications of Firing Techniques, Including
Demonstra tion
E IV-4 Analytical and Experimental Investigation of Fuel-Rich X 100 300 300 100 - 800* -
Afterburning to Reduce NOx Emission from
Regenerative Melting Furnace
E IV-5 Analytical and Experimental Investigation of Combustion - 100 200 - - - 300 -
Modifications to Reduce NOx Emission from Iron-Sintering
and Iron-Pelletizing Processes - - - - -
Totals, Priority E 650 1,150 1,100 1,300 4,200
N IV-N Provision for Exploring New Concepts and New R&D - - 50 50 50 50 200 -
Opportunities that Evolve from the Program, Aeee!-
erating Promising R&D, or Conducting Demonstrations
of Promising Concepts for Reducing Emissions from
Combustion Equipment used for Industrial Processing
by Combustion Modification
Totals, All Priorities 650 1,200 1,150 1,350 50 4,400
-
~
-------
IV-22
REFERENCES FOR CHAPTER IV
1.
1963 Census of Manufactures, Fuels and Electrical Energy Consumed in Manufacturing
Industries: 1962, U.S. Dept. of Commerce, Bureau of the Census, MC63(1 )-7.
2.
A Study of Process Energy Requirements for U.S. Industries, American Gas Association
Report No. C-20000 (Complete series), American Gas Association, Inc., New York, New
York.
3.
Bartok, W., et al., Systems Study of Nitrogen Oxide Control Methods for Stationary
Sources, Esso Research and Engineering Company Report GR-2-NOS-69, Prepared under
NAPCA Contract No. PH-22-68-55 (November 20, 1969).
4.
An Energy Model for the United States Featuring Energy Balances for the Years 1947 to
1965 and Projections and Forecasts to the Years 1980 and 2000, Bureau of Mines Informa-
tion Circular IC-8384 (July, 1968).
5.
Varga, J., and Lownie, H. W., A Systems Analysis Study of the Integrated Iron and Steel
Industry, Battelle Memorial Institute, Final Technical Report, CST! No. PB 184577,
prepared under NAPCA Contract No. PH 22-68-65.
-------
Chapter V
INDUSTRIAL STEAM GENERATION
AND COMMERCIAL AND RESIDENTIAL HEATING
R. E. Barrett
D. W. Locklin
TABLE OF CONTENTS
SCOPE OF CHAPTER AND BACKGROUND. .
. . . . . . . . . . .
POllUTANT EMISSION LEVELS. . . . .
. . . . . . . . . . .
Emission levels with Present Practice
. . . . . . . . . . . .
Emission levels Attainable with latest Technology
and Prospects for Further Reduction. . . . . . . . . . . .
TECHNOLOGY GAPS FOR EMISSION CONTROL BY
COMBUSTION-PROCESS MODIFICATION. . . .
. . . . .
. . . .
Gas, Oil, and Pulverized-Coal Combustion. . . . . . . . . . .
Basic Understanding of the Combustion Process. . . . . .
Combustion Equipment Development. . . . . . . . .
Other Investigations. . . . . . . . . . . . . . .
Coal Combustion in Fixed- and Fluidized-Beds. . . . . . . . .
PNA Formation and Destruction. . . . . . . . . . .
Fluidized-Bed Combustion. . . . . . . . . . . . .
Flue-Gas Recirculation. . . . . . . . . . . . . . .
SUMMARY OF CURRENT AND RELEVANT COMBUSTION R&D .
. . . .
R&D OPPORTUNITIES RECOMMENDED FOR THE 5-YEAR PLAN
. . . .
Summary by Priorities. .
. . . . . .
. . . .
. . . . . .
REFERENCES FOR CHAPTER V
. . . . . . . . . . .
. . . . .
v- 1
7
7
-11
-12
-12
-12
-14
-17
-20
-20
-21
-21
-22
-26
-41
-------
-------
V-I
CHAPTER V
INDUSTRIAL STEAM GENERATION AND
COMMERCIAL AND RESIDENTIAL HEATING
SCOPE OF CHAPTER AND BACKGROUND
Energy-I,;onversion devices within the source category of Industrial Stearn Generation and
Commercial and Residential Heating are used primarily for converting chemical energy in fuel to
thermal energy in the form of stearn, hot water, or warm air. In this chapter, possibilities for
pollutant emission reduction by combustion modification are discussed as they pertain to the
following applications:
. Industrial
- stearn generation
- space heating
- service water heating
. Commercial
- space heating
- service water heating
. Residential
- space heating
- service water heating
Principal fuels utilized for these applications include:
. Solid fuels
- bituminous coal
- small quantities of anthracite coal and lignite
. Liquid fuels
- residual fuel oil
- distillate fuel oil
- liquid-petroleum products (propane and butane)
. Gaseous fuels
- natural gas
Table V-I shows the contribution of industrial stearn-generation and commercial- and
residential-heating sources to nationwide pollutant emissions from energy-conversion combustion
processes. (These percentages are based on data in Table II-I). It should be noted that the
percentage contributions reported in Table V-I are for annual emissions. Considerable seasonal
variations occur with commercial and residential heating, contributing a significantly higher per-
centage of emissions for colder localities during the winter.
-------
V-2
Table V-1. Emissions From Industrial Steam Generation & Commercial
. & Residential Heating
Pollutant
Contribution to Nationwide ECC Emissions, percent
Industrial Steam Commercial &
Generation Residential Heating
Total
Products of Incomplete Combustion
Combustible Particulate 36 9 45
CO nil 1 1
Gaseous HC <1 1 1
PNA nil 90 90
NOx 12 5 17
Combustion-I mproving Additives
Lead, etc. nil nil nil
Fuel Contaminants
SOx 19 12 31
Ash (Noncombustible Particulate) 21 4 25
Ranges of fuel-input rates typical of the different applications included within the scope
of this chapter are listed in Table V-2. Although these fuel-input rates range up to 600 x 106
Btu per hr, emission inventory data for the "industrial" category are generally limited to firing
rates below 100 x 106 Btu per hr (or about 80,000 Ib steam per hr). However, the discussion
Table V-2. Typical Fuel Input Rates(3)
Building Type and/or Use
Range of Fuel Input, 106 Btu/hr
Residential:
Houses and small apartments (1-4 family)
Large, multiple-dwelling, apartments
0-1.0
0.5-5.0
Commercial and institutional:
Office buildings, hotels, theaters, stores, churches, small
colleges, small hospitals, libraries, public buildings,
warehousing, and manufacturing (without large process-
steam requirements)
1-50
Large commercial and institutional:
Housing projects, colleges, hospitals, and manufacturing
(without large process-steam requirements)
10-200
Small industrial (with large process-steam requirements)
1-100
Large industrial (with large process-steam requirements)
10-600
-------
V-3
and R&D opportunities described in this chapter apply to all units smaller than about 500 x 106
Btu per hr. Larger boilers are covered in Chapter III on Central-Station Power Plants; some R&D
opportunities described in that Chapter also apply to smaller boilers.
Fuel Consumption for Various Applications*
Figure V-I shows the quantities of energy used, by fuels, for industrial steam generation
for recent years and projections through 1980. These plots were obtained by estimating the
percentage of fuel used for steam generation by each industry (based on data in Reference 2) and
assuming for each fuel that the ratio of fuel used for steam generation to total fuel consumed by
the industrial sector( 1) is constant. Oil and gas consumption for industrial steam generation are
increasing rapidly, while coal consumption is remaining at a nearly constant rate.
Figure V-2 shows the relative quantities of each fuel used for commercial and residential
space heating for recent years and projections through 1980. The use of solid fuels for space
heating has been steadily declining, and will continue to decline, with possible exceptions in
some localized rural areas. Liquid and gaseous fuels have assumed an increasing share of the
space-heating load, and their use will continue to increase in terms of quantity, although the
growth of electric heating may cause the percentage of the space-heating market utilizing liquid
and gaseous fuels to decline.
Fuel-use data in Figure V-2 represent "retail dealer deliveries to other consumers" (as per
Reference 2). This includes primarily household and commercial users; however, some unknown
portion of small industrial users likely is included. Although this definition does not match
exactly with the energy-use categories in this chapter, it is sufficiently close to represent the
general fuel-use pattern for purposes of this study.
Combustion Equipment
Figure V-3 lists the different types of combustion equipment used for industrial steam
generation and commercial and residential heating, including typical ranges of the firing rates
covered by each type of equipment.
Table V-3 shows the total number of automatic heating units, by major classes, in resi-
dential use as of the end of 1969. Figure V-4 shows past and predicted future trends in residential
heating units by fuel.
* A problem of definition is encountered in surveying the literature on fuel usage and pollutant emissions for
narrowly defined source categories. Available data are based on subjective definitions of "commercial and
residential" "industrial" and "industrial process". For example, some references use the term "industrial
process" without specifying whether it includes or excludes industrial steam raising and industrial space heating.
Likewise the Bureau of Mines energy-model report(l) defines "commercial and residential" fuel as "retail dealer
deliverie~ to other consumers"; practically, this limits fuel consumption to about 1000 gallons fuel oil per month
or a firing-rate capacity of about 500,000 Btu/hr. Obviously, this definition of "commercial and residential"
fuel usage does not correspond with how the fuel is actually utilized (compare with Table V-2). To make use of
available information the Bureau of Mines definition of commercial and residential fuel usage was accepted.
Fuel usage for indust;ial steam raising was obtained by estimating that portion of each fuel likely to be used for
steam generation for each industry. Additional detail regarding these estimates is given in Chapter IV, Industrial
Processing.
-------
V-4
100
80
60
40
20
::>
CD 10
!! 8 Gas - --
Q --
6 --
-
C
.2 4
Ci Coal
E
::> -- ---
10
CD
,., 8
0 6
C
0 4
a.
E
::>
I
LL
0.8
0.6
04
0.2
1962 1965
Gas -
-----:t:=-
- - Petroleum
--
Coal
--
--
1970
Year
1975
1980
-------
Fuel and Equipment
Gaseous fuel
Premixing burner(s)-
Nozzle mixing burner{s)-
Liqu id fuel
Pot-type vaporizing burner
Rotary cup burner
Low-pressure air-atomizing burner
Pressure atomiz ing burner-
Steam or high - pressure - air atomizing burner-
Solid fuel
Hand - fired
Underfeed stoker, single retort, refractory hearth
Underfeed stoker, single retort, dumping grates
Underfeed stoker, multiple retort
Vibrating or shaking - grate stoker
Traveling or chain- grate stoker
Spread stoker
Pulverized coal
- 0.01
More than one gas or oil burner may be installed in a
single furnace to obtain high firing rates.
~
Vt
0.1
1.0
100
10
1000
Burner or Furnace Firing Rate, 106 Btu/hr
Figure V-3. Types and Firing Rates of Combustion Equipment Used for Industrial Steam Generation and Commercial and Residential Heating
-------
V-6
. Table V-3. Automatic Heating Units in
Residential Use in 1969(9)
Gas-fired un~ts 19,985,250 (58.8%)
Oil-fired units 11,186,650 (32.9%)
Oil furnaces 5,800,564
Oil-fired boilers 5,386,086
Coal stokers 340,000* «1%)
Electric-heating units 2,818,745 (8.3%)
Total 33,990,645
*Not included in total.
100
Coal and others,includina- '. '." .:.........:::.:::.:.:::.:.:::.:
en
0>
c:
OJ
3
o
a
+-
o
I-
+-
c:
OJ
U
L...
OJ
0..
Oil
'+-
o
Figure V-4.
-------
V-7
Pollutants of Principal Concern
Pollutants of principal concern from industrial steam-generation and commercial and
residential space-heating combustion processes include:
. Products of incomplete combustion - combustible particulate, CO,
gaseous HC, and PNA (odor-producing compounds generally fall in
this category)
. NOx
. ~Ox
. Fly ash and other noncombustible particulate.
Emissions of combustible particulate, CO, HC, and PNA are usually associated with
incomplete combustion, PNA coming primarily from coal-fired sources. NOx is formed during
combustion either from nitrogen in the fuel or by fixation of atmospheric-nitrogen in the
high-temperature flame environment. sax and fly ash are generally associated with fuel im-
purities and are little affected by the combustion process. Noncombustible particulate from coal
and residual-fuel-oil combustion include, in addition to fly ash, fuel additives used for various
purposes. The ash or additives may contain such trace pollutants as manganese, lead, barium,
chlorides, and fluorides.
For applications within the scope of this chapter, pollutants that may be controlled by
modification of the combustion process received principal emphasis. These include combustible
particulates, CO, HC, PNA, and NOx.
POLLUTANT EMISSION LEVELS
Although the weight of pollutants emitted by individual units considered in this chapter
is low when compared with emissions from combustion units burning large volumes of fuel
(power stations), the additive effect of a large number of units operating in densely populated
areas can be serious. Also, the low stacks and the low heat content of the exhaust gas from these
smaller pollutant sources may cause the pollutants to remain relatively close to ground level
where they contribute to the local pollution problem. Therefore, although many of these
pollutant sources are small individually, they are worthy of attention because of their concen-
tration in urban areas.
Emission Levels with Present Practice
Table V-4 presents a summary of the pollutant emission factors for major fuels and for
several sizes of equipment. Average or "best values"* and ranges are shown where data permit.
These data represent uncontrolled pollutant emissions and generally represent average values rec-
ommended for use in community air-pollution surveys. Emissions from individual units may vary
widely from the average values.
*"Best values" is defined as the best estimate of average emission levels.
-------
Table V-4. Pollutant Emission Factors From Small- and Intermediate-Size Combustion Sources, Lb/106 Btu(a)
Natural Gas Fuel Oil Coal
0-10 x 106 10-100 x 106 0-10 x 106 10-100 x 106 0-10 x 106 10-100 x 106
Pollutant Btu/hrlbl Btu/hrlcl Btu/hrlbl Btu/hrlcl Btu/hrlbl Btu/hrlcl
Products of I ncomplete Combustion
Combustible particulate 0.025 0.024 0.043 0.066 0.45 1.2
CO 0.0004 10.000-1.3) 0.0004 (0.OOO-Q.13) 0.013 (0.000-Q.13) 0.013 1O.000-Q.02) 2.3 (0.14-3.5) 0.10 10.029-Q.12)
Gaseous HC 0.004 (nil-Q.068) 0.005 Inil-Q.00451 0.013 0.017 (0.013-Q.26) 0.55 (0.036-0.77) 0.054 (0.006-Q.077)
PNA 0.33 0.22 0.18 0.11 44.0 0.44
NOx 0.13 (0.07-Q.18) 0.20 10.03-Q.35) 0.48 (0.06-Q.9) 0.58 (0.47-Q.9) 0.18 10.015-Q.31) 0.79 (0.65-Q.8) <:
I
00
Fuel Contaminants
Total particulate 0.025 (nil-Q.03) 0.024 (nil-Q.03) 0.071 10.053-Q.08) 0.11 (0.053-Q.20) 1.0 (0.3-4.5) 2.6 10.6-17.3)
sax 0.008 1O.0004-Q.0013) 0.0008 (0.0004-Q.0013) 0.27 1.87 10.3-3.7) 3.15 (0.75-8.3) 3.15 (0.75-8.3)
Noncombustible particulate nil nil 0.028 0.044 0.55 1.4
(a)
Shown as "best value (range)" based on References 3 and 11-17.
Natural Gas - 1,000 Btu/cu ft
19,000 Btu/lb
- 150,000 Btu/gal
19,000 Btu/lb
Coal - 13,000 Btu/lb.
APCO defines as domestic and commercialJ 15)
APCO defines as industrial.(15)
Conversion factors used when data in references were given in other units are:
Fuel Oil
Ib)
-------
V-9
Table V-5 is a summary of PNA emissions from various types of coal-burning equipment.
This table presents a detailed breakdown of the aromatics into specific compounds. Figure V-5
shows the range of benzo(a)pyrene emissions from various sizes of coal-burning units; some data
on emissions from oil- and gas-fired units are also included.
Generally, the following observations can be made regarding emissions from sources
discussed in this chapter:
Products of Incomplete Combustion
. Combustible particulate, CO, and HC emissions increase with increas-
ing difficulty in air-fuel mixing (natural gas < oil < coal).
. CO and PNA emissions from coal-fired units decrease as unit size
increases and better air-fuel mixing and higher temperatures are
achieved (hand-fired> nonspreader stoker> spreader stoker). See
Figure V-5 for benzo(a)pyrene emissions.
. HC emissions decrease as unit size increases; longer residence times
probably permit burning to be more nearly complete.
Nitrogen Oxides
. NOx emissions increase as unit size increases and are probably related
to the higher temperatures achieved in larger units; however,
residence time may also be a factor.
. NOx emissions increase with increasing difficulty in air-fuel mixing
(natural gas < oil < coal).
Sulfur Oxides
. SOx emissions are almost entirely dependent on the sulfur content of
the fuel and, except for sulfur pickup by coal ash, are largely
independent of firing method.
Fly Ash and Other Noncombustible Particulates
. Noncombustible particulate emissions increase as the ash content of
the fuel increases (natural gas < distillate oil < residual oil < coal).
-------
v-tO
Table "-5.
Polynuclear Aromatics Emitted by Bituminous Coal With Various
Firing Methods(a)(3,16)
Type of Unit
Pulverized Spreader Chain-grate
Firing Cyclone Stokers Stoker Underfeed Stokers
Benzo(a)pyrene 0.04.Q.31 0.49 0.04 0.057 0.082 22 0.26 8.4
Pyrene 0.20.Q.40 2.25 0.23 1.30 0.860 35 3.70 17
Benzo(e)pyrene 0.05.Q.58 0.87 0.13 0.770 0.290 17 0.510 11.9
Perylene 0.15 0.04 3.5
Benzo(ghiJperylene 0.02-1.42 0.44 9.9 1.28
Anthanthrene 0.64
Coronene 0.02.Q.12 0.01 0.02 0.057 0.73 2.64
Anthracene 1.9
Phenanthrene 22 2.2 64
Fluoranthene 0.18.Q.85 0.17 0.11 0.790 1.50 83.9 7.1 103
Benz(a)anthracene 8.6 1.23
(a) From Smith and Gruber(69). Figures are pounds per 1012 Btu input.
Hand.
fired
880
1,320
220
132
660
198
66
880
2,200
2,200
107
Legend
o - Coal
@-Oil
~ - Gas
Emission less than
value plotted
<
+-
:J
a.
c:
+- 106
o
Q)
.c.
Cf)
Cf)
e
0\ 105
:J
iD
ID
o
}
......
0\
::t
Q)
+-
o
cr:
c:
o
"(j)
Cf)
E
w
Cl.
o
CD
104
106 107 108 109
Gross Heat Input to Furnace, Btu/hr
1010
Figure V-5.
-------
V-II
To date, there has been only limited control of pollutant emissions from residential and
commercial space-heating sources, although smoke control has been enforced locally on larger
units to reduce visible particulate emissions, and increasingly strict standards on smoke emissions
from oil-fired units have been adopted. (19) The widespread conversion of residential heating
from coal to oil and natural gas, which has occurred in the past three decades, has significantly
reduced pollutant emissions associated with incomplete combustion and emissions of noncom-
bustible particulate. Additionally, recent regulations for several of the larger cities and federal
facilities(20) have limited the sulfur content of coal and fuel oils to reduce SOx emissions.
With two exceptions, the pollutant-control methods already applied do not represent
emission contrcl by modification of the combustion process. Rather, they involve application of
simple mechanical devices for removal of particulate from the flue gas of larger coal-fired units,
equipment replacement (either with or without fuel substitution), or regulation of the properties
of allowable fuels.
The exceptions, where the combustion process itself is affected, are: (1) improved design
of oil-fired units to reduce smoke (generally by better atomization and mixing) and (2)
application of overfire air to ensure more complete combustion in larger coal-fired units.
Emission Levels Attainable With Latest Technology
and Prospects for Future Reduction
With the exceptions already noted (primarily smoke control), there generally has been
little incentive to control emissions from industrial steam-generation and commercial and resi-
dential heating sources. Thus, historically, little effort has gone into advancing the technology of
emission control for these applications, so the emission levels attainable with latest technology
probably would not be significantly different from current emission levels as listed in Table V-4.
Average data on emissions from general modern oil burners confirms this assumption(21).
Recently there has been increased interest in the development of techniques for
controlling emissions from such equipment. Current research in this area will be discussed in a
subsequent section of this report.
There appears to be no reason why emission levels cannot be reduced to levels char-
acteristic of the best units by utilizing current technology, upgrading installation and servicing,
etc. Reducing emissions to levels below those currently attainable is not an unrealizable goal.
-------
V-12
TECHNOLOGY GAPS FOR EMISSION CONTROL
BY COMBUSTION.PROCESS MODIFICATION
The first step necessary in determining what combustion R&D is needed to reduce
emissions is to identify what is known and what is unknown about how the combustion process
affects emissions and how the results of current R&D are likely to contribute. These subjects are
covered in the following discussion. A tabulation of current combustion R&D is presented at the
end of this section.
GAS, OIL AND PULVERIZED.CDAL COMBUSTION
In contrast to coal combustion for industrial steam generation and commercial and
residential heating, where a declining market limits potentially attractive R&D opportunities, gas
and oil usage for these purposes is increasing at a significant rate and, therefore, longer-term
R&D opportunities of a more basic nature can be attractive. Hence, gaps in the basic under-
standing of the combustion process in gas- and oil-rued small and intermediate-size combustion
equipment are discussed, as well as gaps in knowledge pertaining to the application of specific
techniques that show promise for reducing emissions. Potential contributions of current R&D in
this area are also cited.
Although pulverized-coal combustion is not treated extensively in the following discus.
sion, much of the basic combustion technology would also apply to this fuel.
Basic Understanding of the Combustion Process
Although basic combustion research will probably result in an improved understanding of
the relationships between combustion phenomena and burner variables, it will not necessarily
have an immediate effect on burner design. Burner design is not a well developed scientific
discipline but has been, and still is, partly an art. Most burner designs are arrived at by trial and
error and hardwar~oriented development, not by direct application of a body of knowledge on
the subject of combustion. This is not too surprising, considering the complexity of the
combustion process. There are large gaps in the basic knowledge of combustion and its
application to burner units, and empirical design equations are limited to simple combustion
systems.
However, as more is learned about the combustion process, there is greater hope that
more use will be made of general guidelines and relationships between combustion phenomena
and burner-design variables. Also, there will be improved understanding of the relationship
between pollutant emissions and combustion conditions, so that burners and furnaces can be
designed to provide conditions for minimum pollutant generation.
Therefore, although basic combustion research is necessary for future advancement of
burner and furnace design from the art stage to a more scientific stage, and for eventual
reduction in pollutant formation, the more basic research in this area must be viewed with only
cautious optimism with respect to quickly realized reductions in emissions from the classes of
combustion equipment covered in this chapter.
-------
V-13
Examination of the gaps in the basic understanding of the combustion process might be
simplified by considering two different levels of understanding. Ultimately, a comprehensive
understanding of the combustion process, as it occurs in small- and intermediate-size combustion
equipment, will be needed to construct complete mathematical models describing both the
physical and the chemical aspects of the process. Complete models are certainly many years in
the future. In the meantime, a better empirical knowledge of relationships between combustion
variables, equipment performance, and emissions would be a useful tool for designing equipment.
Mathematical Model of the Combustion Process
A complete physical and chemical description of a generalized combustor design together
with the ability to quantify the description to fit the requirements of a specific usage, including
minimization of pollutant production, would provide an ultimate tool for the designer.
Consideration might be given to how nearly realizable such a tool is, without regard for the
economics of its use as compartd with other possible design procedures.
In a pure sense, the mathematical model of a combustor would be based on the most
fundamental fluid dynamics, chemical, and heat-transfer relations. But in a more practical sense,
the designer would be willing to be less basic and use coefficients obtainable from the literature
for various parameters, just as he uses pipe size, surface characteristics, and Reynolds number to
determine pressure drops in pipes. On this basis, the only questions are whether available
computers are capable of handling the number of variables involved, and whether the knowledge
of the needed coefficients is adequate.
At the present time, a completely general description of combustion systems is beyond
reach, so a specific system consisting of an oil-fired heating unit can be used to illustrate
present capabilities. Processes that are involved in the operation that can be described adequately
for simple systems on the basis of presently available experimental results are atomization;
mixing of the fuel, air, and recirculated flue gas; vaporization; ignition of the fuel; droplet
combustion; and flow patterns. Because the combustion rate in practical combustors operating at
atmospheric pressure is generally mixing controlled, rather than chemically controlled, it then is
possible to describe the gross aspects of the combustion process for simple combustion systems.
The next stage is to computationally allow for the heat transfer from the combustion
gases to surfaces, which is the aim of most combustors. This heat transfer is both convective and
radiative. The latter becomes increasingly important as the size of the combustor increases, as the
carbon-to-hydrogen ratio of the fuel increases, and as the flame temperatures increase. Because
radiative transfer from the gas is a volume and not a surface phenomenon, the equations rapidly
increase in complexity as finer detail in the combustor structure is included. And, obviously, if
the combustion gases lose heat, the factor must be iterated back into the computations. At the
present time, considerable effort is being spent in developing routine and practical ways to
calculate the convective-radiative heat-transfer portion of the combustion process in practical
systems.
For air-pollution problems, one more stage must be involved in the mathematical
modeling. The gross flow patterns, composition profiles, and temperature profiles must be used
as a basis for defining the various path environments in which pollutants such as NOx are
produced. In general, nei ther the knowledge of kinetics nor the knowledge of the physical fine
structure is adequate to proceed with this stage.
-------
V-14
Finally, it should be noted that a combination of mathematical modeling, physical
modeling, and prototype experiment!) can often be used more effectively than any single
approach, such as mathematical modeling, to solve the combustion problem at hand.
Empirical Knowledge
Relating Combustion Variables to Emissions
Emissions from combustion equipment could be reduced if equipment designers had an
empirical knowledge (not necessarily a full understanding) of how important combustion system
variables affect pollutant emissions. Historically, such relationships have been defined only for
emission of smoke. These relationships were derived from investigations to determine how
emission of smoke might be reduced. For instance, it has been known that smoke emission is
reduced by increasing turbulence or mixing, flame temperature(22), residence time in the hot
zone, and excess air and by improving fuel atomization. Likewise, such approaches can be
expected to reduce the other products of incomplete combustion including CO, HC, and odor.
Hence, the three T's of combustion (time, temperature, and turbulence) have been the
significant variables at the disposal of designers in their attempts to control the overall combus-
tion process. Temperature may not be freely selected in all cases, as heat-transfer I criteria must be
considered. Likewise, the efficient use of space may impose limits on time. Power requirements
for combustion-air blowers place limits on turbulence. Therefore, combustion-unit designers must
make compromises between the requirements for efficient, clean combustion and other
considerations such as cost, noise level, and compactness.
In addition, the increasing concern for reducing air pollution is forcing designers to
consider pollutant emissions as a major factor in equipment performance. However, despite
recent efforts(2I,23,24) many of the needed empirical relationships between controllable com-
bustion variables and emission levels have not been developed. To provide designers with the
input needed to produce low-emission combustion units, relationships will need to be developed
between pollutant emissions and combustion variables such as mixing, turbulence, combustion
intensity, flame temperature, residence time, internal recirculation, time-temperature profiles, etc.
Combustion- Equipment Development
Basic combustion-process studies will not be useful unless they result in: (1) the
development of new or improved low-emission burners or (2) determination of operating
conditions by which present burner emissions can be reduced. However, burner development can
proceed without awaiting completion of either of the above-mentioned studies. In fact, a number
of efforts have been and are under way to develop low-pollution combustion units.
Because combustion must occur in a limited time (for space efficiency) and at high
temperature (for space efficiency and for high heat-transfer rates), conditions favorable to
pollutant formation seem difficult to eliminate. Although some reduction in pollutant formation
can be expected from burner development efforts, without a background of understanding of
the formation of pollutants as part of the basic combustion process, it is difficult to forecast the
chances of major successes or breakthroughs that would significantly reduce emissions.
-------
V-IS
Techniques for Lowering Peak Gas Temperatures
It has been generally accepted that NOx is formed during the combustion process by the
reaction of nitrogen and oxygen atomg,{2S,26) Hence, NOx emissions are associated with
high-temperature combustion with excess air. (Some studies sgugest that fuel-bound nitrogen may
be the primary source of nitrogen in the formation of NOx from firing oil and coal' however
further study in this area appears needed.) , ,
Obviously, if NOx forms in the presence of excess air at high temperatures, two possible
approaches to lowering NOx emissions are to:
. Reduce gas temperatures
. Reduce excessive air, especially in high-temperature regions.
Techniques that have been suggested to accomplish one or both of the above include:
. Flue-gas recirculation
. Two-stage combustion
. Designing combustion devices to achieve low peak temperatures by
other means such as catalytic or surface burners, radiant burners, and
burners that operate with large quantities of excess air.
While each of these techniques for reducing NOx appears to have merit, none have been
developed to the point where they have proved practical.
Flue-Gas Recirculation. Flue-gas recirculation involves diluting the fuel-air mixture in the
combustion zone with cooled flue gases and, thereby, reducing flame temperature rise and peak
gas temperature. Utilizing cooled flue gas as the diluent does not adversely affect combustion
efficiency as neither the mass nor the temperature of exhaust products need increase.
Several studies(27-31) have shown that recirculated flue gas can also contribute to lower
emission of smoke when firing fuel oil. One of these studies(27) reported that CO, HC, and NOx
emissions were held at low levels by recirculation when firing No.2 fuel oil into a boiler at I
gph.
Application of flue-gas recirculation to small and intermediate size combustion equipment
is limited by knowledge gaps in the following areas:
. Effect on emission levels of variables such as temperature of the
recirculated gas, point at which the gas is injected, and quantity of
recirculated gas
. Corrosion and deposits associated with recirculation
. Control of recirculated flue gas quantity in equipment operating at
variable firing rates
. Start-up problems.
-------
V-16
Two-Stage Combustion. Two-stage combustion involves burning fuel in a fuel-rich primary
zone, partially copling the combustion products, and, finally, supplying additional air and
completing combustion in a secondary zone. Thus, two-stage combustion makes possible low
peak gas temperatures, because the combustion products are cooled before combustion is
completed and oxygen levels are low in the highest temperature region - the primary combus-
tion zone. Barnhart and Diehl have demonstrated that conversion to two-stage combustion
reduced NOx emissions from a gas- and oil-fired utility boiler by 30 to 50 percent.(32)
Bienstock, Amsler, and Bauer found that, when pulverized coal was burned in a power plant with
5 percent excess air in the primary zone and 17 percent excess air added at the proper location
downstream, NOx emissions did not increase above levels obtained when burning with 5 percent
excess air and no downstream air addition. (33) Two-stage combustion has not been demonstrated
as practical on smaller combustion units.
Application of two-stage combustion to small- and intermediate-size combustion equip-
ment is limited because of gaps in knowledge of:
. Effect on emissions of important combustion variables such as primary-
zone fuel-air ratio, temperature drop between the primary and the
secondary zones, and secondary zone fuel-air ratio.
. Possible corrosion associated with reducing conditions in the primary zone.
. How to design combustion equipment to achieve effective two-stage com-
bustion (Le., how to achieve necessary mixing in the secondary zone, how
to achieve burnout of incompletely burned products formed in the pri-
mary zone, what the residence-time requirements are for primary and
secondary zones, and how to incorporate sufficient cooling between zones
without increasing equipment size and emissions of smoke, CO, and HC.)
Other Techniques for Achieving Low-Temperature Combustion. Several other techniques
available for achieving combustion at low-peak-gas temperatures include:
. Catalytic- or surface-combustion burners
. Radiant-heating devices
. Combustors that operate at high excess air.
These techniques have not been developed to the point of practical application to heating boilers
or furnaces.
Surface combustion has been used successfully on a number of gas-fired infrared or
surface heating units. These units operate with combustion zone temperatures of about 1800 F
to ?~OO F and, although no specific data are available, these units are likely to have low NOx
emIs,slOn l~vels.. Sur~ace combustion of gaseous fuels could be incorporated into residential
heatmg umts wIth httle difficulty, although practical combustion of fuel oil has not been
demonstrated for long-term operation. Potential problems with fuel oil include achieving com-
plete combustion, achieving uniform fuel feed across the burner face, and preventing deposits on
the burner surface.
-------
V-17
Radiant heating devices have potential for operating with low NOx emissions because the
high rate of heat transfer from the combustion zone reduces peak temperature. Incorporating
this concept into residential heating units should reduce NOx emissions from these sources.
Development of residential furnaces utilizing radiant burners would require conversion from a
convection to a radiant heat exchanger; there is no reason why this is not technically feasible,
although equipment might be larger.
Combustion at extremely high air-fuel ratios would obviously reduce peak gas tempera-
tures by dilution. Consequently, NOx emissions would be reduced below levels for present
equipment. However, efficiency would also suffer as the greater mass of flue gas would increase
losses. It is diffIcult to envision how units operating at high air-fuel ratios could be both efficient
and have low NOx emissions. Therefore, this concept appears to have limited value.
Other Investigations
Gaps exist with respect to knowledge of several other phases of the combustion process
and combustion-system design, and these gaps may also limit emission control by combustion
modification. More information is needed concerning the effect on emissions of transients,
of additives and emulsions, and of burner servicing and maintenance.
Transients
Few data relating emissions to transient conditions appear in the literature(2l). However,
observation of the operation of on-off combustion devices reveals that emission levels of
pollutants - like particulates, HC, and odor - are relatively high during transient conditions.
Investigations are needed to determine emission levels during transient conditions and the
contribution of these emissions to total emissions. If emissions during transient periods are
significant on a weight basis, techniques for their reduction should be investigated.
Servicing and Maintenance
Although only scattered data on burner servicing and maintenance are available(34,35), it
is known that lack of proper burner adjustment and/or maintenance can result in poor com-
bustion(36) and higher levels of pollutant emissions. This is especially true with regard to
pollutants associated with incomplete combustion of the fuel (combustible particulate, CO, and
HC). For example, Table V-6 shows smoke measurements before and after burner adjustment on
a total of 310 oil-fired units. Burner adjustment, as detailed in Table V-7, produced significantly
lower smoke levels, especially from residential burners.
Medium- to large-size combustion units are most likely to receive proper maintenance
under service contracts or by onsite operators. Therefore, reasonably good combustion perform-
ance of these units should be realized. However, emissions that service personnel and/or
operators cannot easily detect (NOx PNA, etc.) still may not receive proper attention. Education
and proper instrumentation will assist in this area.
Conversely, small units such as found in single- to 4-family residences and in small
commercial buildings are likely to receive no attention until a forced shutdown occurs. This lack
-------
V-i8
Table V-G. Smoke Ratings on Tested Oil Burners(35)
Percent of Burners Before and After Adjustment
Commercial Commercial
Domestic Distillate Distillate Residual
Smoke No. Before After Before After Before After
o 13 24 17 24 10 14
1 27 50 25 22 15 15
2 16 22 15 32 14 20
3 17 2 13 3 15 21
4 8 0 10 8 15 10
5 8 1 9 7 7 10
6 2 1 3 2 7 3
7 4 0 6 2 4 3
8 3 0 0 0 5 3
9 2 0 2 0 8 1
Table V-7. Oil-Burner Adjustments Related to Reduction in Smoke(35)
Single Adjustment
Reduction No Reduction
Multiple Adjustment
Reduction No Reduction
Cleaned nozzle 24 9
Replaced nozzle 12 5 81 33
Replaced parts or cleaned air intake system 1 5 68 27
Adjusted air intake 23 9 153 93
Adjusted draft 4 5 44 25
Adjusted oil pressure 3 11 51 22
Adjusted oil temp. 13 15
Changed firing rate 2 7 29 12
Improved* boiler condition 4 5 61 18
-------
V-19
of servicing is more likely with natural-gas-fired units than with liquid-fired units as natural gas is
received by pipeline and technically trained representatives of the burner or fuel supplier rarely
visit the installations. Fortunately, the gaseous fuels are more easily burned and, therefore, gas
combustion equipment is simpler so that burner maladjustment is less likely.
Limited efforts that are under way in this area will contribute to the knowledge of
relationships between burner maintenance and pollutant formation and will serve as guides for
future R&D. If maintenance is a significant factor in pollutant emissions, there will not
necessarily be any reduction in emissions unless accompanied either by design of burners
requiring less maintenance or education and/or legislation ensuring that the needed maintenance
is performed.
Additives and Emulsions
The use of additives appears to offer little promise for reduction of pollutant emissions.
However, because no additional equipment is required to fire fuels containing additives, the
concept of using additives to reduce emissions continues to hold appeal from the economic
viewpoint. Also, the successful use of antiknock additives in automotive engines serves as
encouragement for hope in this area.
APCO has examined some 300 'additives for distillate fuels in small combustion rigs and
has found only a few that appear to cause reduction in emission of smoke.(37,38) Even those
additives that cause reduction in emissions have a rather minimal effect on emission levels.
Considering that the group of 300 additives tested by APCO probably represents a good cross
section of the available additive compounds, it appears unlikely that much further work can be
justified for distillate fuels. Additives that have some promise of reducing emissions from com-
bustion of residual fuel oil should be investigated.
Fuel modification as a technique for reducing emissions has not been extensively investi-
gated. However, APCO has sponsored investigations(39-41) aimed at testing water-in-fuel-oil
emulsions. The concept is based on earlier work with large individual drops of emulsion that
showed that the water inside an oil drop flashed to steam and caused an explosion of the oil
drop, or "secondary atomization".(42) The smaller oil droplets resulting from the secondary atomi-
zation mix with air and burn more quickly and completely than larger droplets. To date, it has
not been proven that atomization is improved when firing water-in-distillate-oil emulsions in
practical combustors. However, a one-third reduction of NOx emission was measured when firing
water-in-distillate fuel emulsions(43), possibly because the water caused a reduction of the flame
temperature. Emulsions may prove more beneficial when firing residual fuel oil because of the
increased difficulty of atomization.
More Comprehensive Emission Data
Currently available emission data on small- and intermediate-size combustion equipment
are of marginal value for many purposes including R&D planning and as a measure of current
technology. However, the potential usefulness of additional emission measurements and
characterization is difficult to evaluate. Measurements should be correlated with design variables,
fuels, operating conditions, and service conditions. Data correlated with well-defined operating
conditions or design variables will be useful as the basis for design criteria and for relating
basic-combustion-process studies to performance of real equipment.
-------
V-20
COAL COMBUSTION IN FIXED. AND FLUIDIZED BEDS
Study of trends in fuel use for the "household and commercial sector" of the economy
(Figure V-2) readily leads to the conclusion that the use of coal as a fuel by this sector will
continue to decrease rapidly. In fact, coal supplies an insignificant portion of the energy utilized
for commercial and residential heating. Figure V-I shows that coal continues to be a significant
fuel for industrial steam generation. However, with the increasingly widespread application of
limits on the sulfur content of coal used as fuel (and the limited availability of low-sulfur coal),
it is likely much of the industrial steam generation currently utilizing coal will shift to gas and/or
low-sulfur oil, if available. Therefore, only limited R&D aimed at reducing emissions from small-
and intermediate-size coal-fired combustion units appears justified, and this R&D should be
directed toward filling specific knowledge gaps.
Three specific areas have been identified where the lack of understanding of the coal-
combustion process handicaps emission control by combustion-process modifications.
PNA Formation and Destruction
The total mass of nationwide emissions of PNA is relatively small (CO, HC, and NOx
emissions are over 1000 times greater); however, PNA compounds are considered to be signif-
icant pollutants as some of them are carcinogenic.
Over 90 percent of all PNA emissions from energy-conversion combustion processes
is attributed to commercial and residential coal-fired sources utilizing fixed-bed combustion.
Although small coal-fired units are disappearing from use, their contribution with regard to PNA
emissions is so significant that they cannot be ignored.
PNA compounds may be present in the coal itself or may form during the combustion
process.(44,4S) However, there appears to be no data in the literature which identify PNA as
being present in coal. Diehl, DuBruel, and Glenn( 46) observed variations in PNA emissions when
firing different coals on a pulsating-grate stoker. However, they also observed such variations
when operating a pulverized-coal-fired boiler with one fuel and under essentially constant
conditions. Consequently, they were not able to relate PNA emissions to coal, and the source of
PNA remains uncertain.
The destruction of PNA, as for any other hydrocarbons, should be by oxidation during
the combustion process. The literature appears to contain no data which would identify any
unique conditions required for oxidation of PNA.(4S) However, the fact that PNA compounds
are emitted suggests incomplete combustion of these compounds.
Data in both Figure V-S and Reference 46 indicate that PNA emissions decrease as unit
size increases. Larger units provide longer residence times in the flame and, generally, higher
average gas temperatures - so that conditions contributing to more nearly complete combustion
prevail. Also, fixed-bed combustion units (with poorer mixing) tend to emit larger quantities of
PNA than do spreader stokers or pulverized-coal-fired units.
It is possible that, with a better knowledge of how PNA occurs or forms and of the
conditions promoting its oxidation, possibilities for modification of the combustion process to
reduce PNA emissions could be identified.
-------
V-2l
Fluidized-Bed Combustion
Fluidized-bed combustion of coal has been proposed as a technique for reducing SOx
emissions from the combustion of high-sulfur coal for steam generation. To accomplish this,
limestone is added to the fluidized bed to react with S02 and S03 as they are liberated from
the coal. (3 7,47)
However, fluidized-bed combustion also has the potential for reducing NOx emissions
from coal combustion because of the reported low temperatures of the fluidized bed. Theo-
retically, with bed temperatures of about 1800 F, little NOx would form as the nitrogen-fixation
reaction does ..ot proceed rapidly at this temperature. However, Argonne National Labora-
tories(48) reported relatively high NOx emission levels for a laboratory fluidized-bed combustor,
even with the nitrogen in the air replaced with argon. They attributed these emissions to
nitrogen bound in the fuel. However, it is possible that local, high-temperature regions exist
within fluidized-bed combustors and that NOx can form by the nitrogen-fixation reaction in
these regions. Additional investigations are needed to answer the question of the source of NOx
in fluidized-bed combustion of coal.
It is likely that most R&D on coal-fired fluidized beds will be directed at central-station
power plant application. However, the technology developed in these studies will generally apply
to industrial-stearn-generation applications as well. One objective of a APCO-sponsored project
underway at Westinghouse is to develop a conceptual design for a fluidized bed for this
application.
Additional discussion of fluidized-bed technology is contained in Chapter III on Central-
Station Power Plants.
Flue-Gas Recirculation
Flue-gas recirculation has been suggested by a number of investigators as a technique for
reducing peak temperatures and NOx formation. Application of flue-gas recirculation to fixed
coal beds presents special problems of increasing emissions of particulate due to higher total gas
flow and gas velocities through the bed. Also, lower bed temperatures may result in increased
emissions of CO and HC due to incomplete combustion.
Experimental studies are needed to determine whether flue-gas recirculation is a practical
technique for reducing NOx emissions from fixed-bed coal combustion units.
-------
V-22
SUMMARY OF CURRENT AND RELEVANT COMBUSTION R&D
Table V-8 is a list of R&D projects currently under way which may develop data and/or
techniques useful for reducing pollutant emissions from combustion systems for industrial steam
generation and commercial and residential heating. NAPCA-sponsored and NAPCA-in-house
projects are listed first, followed by projects sponsored by other Federal Government agencies,
industrial-sponsored projects, and foreign projects.
Not included in this listing are projects that have proprietary implications and projects
from which results will not be generally available. Development projects by burner manufacturers
would generally fall into this category and not be listed.
Also not included are projects directed at removing contaminants from fuel by refining
processes, projects directed at developing post-combustion control processes, and projects to
develop improved instrumentation for measuring air-pollutant emissions. Although R&D in
these areas is important relative to the overall pollution-control problem, it is not specifically
aimed at reducing emissions by combustion-process or combustion-equipment modification.
Current R&D related to the equipment of concern in this chapter may be classified as
follows:
. Understanding the Basic Combustion Process - research aimed at obtain-
ing a better understanding of the physical combustion process including
kinetics, mixing, ignition, and other phenomena affecting combustion,
either in laboratory rigs or in practical combustors.
. Hardware Development - developmental work aimed at modifying existing
combustion equipment or developing new combustion equipment to burn
fuels with minimum pollutant emissions.
. Use of Additives and Emulsions - measurements aimed at determining the
usefulness of fuel additives or emulsions for emission reduction.
. Determining the Role of Burner Servicing and Maintenance - studies
aimed at determining the operating conditions and servicing necessary to
minimize emissions.
. Collection of Emission Data - measurements aimed at a more precise
determination of the extent and nature of pollutants emitted from various
types of combustion equipment, including both additional emission
measurements and analytical treatment of available data.
-------
Table V-So Current Combustion R&D - Industrial Steam Generation and Commercial and Residential Heating
Sponsoring
Project Organization Principal
Key Project or Contract Title and Contract No. Research Organization Investigator Objective or Scope Funding, $
V-a Systems study of nitrogen oxides con. NAPCA-DPCE Esso Aes. & Eng. Co. Dr. W. Bartok Define the nature and extent of NOx 389,307 (Total)
trol methods for stationary sources CPA 22-6B-55 Li nden, New Jersey emissions in U.S. and recommend 5-year
R&D program for control
V-b Selected A&D of nitrogen oxides NAPCA-DPCE Esso Aes. & Eng. Co. Collect additional data on NOx emissions 363,025 (Total)
,control for stationary sources' CPA 70-90 Linden, New Jersey and investigate the application of control
methods on selected sources
V< Fossil-fuel combustion equipment NAPCA-DPCE Waldon Aes. Corp. Dr. J. A. Ehrenfeld Correlation of pollutant emissions for 241,902 (FY '69)
CPA 22-69-B5 Cambridge, Mass. A. W. Doyle various types of combustion equipment
V-d Low emission oil burner NAPCA.DPCE Not selected Design and develop a low emission oil-
E HSD 71-Neg 28 fired residual or small commercial
heating unit
V.., Guide to good practice for federal NAPCA-DA Amer. Boiler Manu; W. Axtman Recommendations on proper operation 31,522 (FY '69)
facilities oil burnnrs CPA 22-69-133 facturers Asso. for minimum emissions
V-f Studies of preparation and firing of NAPCA-DPCE Battelle Memorial I nst. A. E. Barrett Develop techniques for preparing emul. ~
emulsified distillate and residential PH 86-68.84 Columbus Lab. sions and demonstrate how they can N
fuel oils Tasks No.8, 16, 22 Columbus, Ohio be fired W
V-g Conceptual design - fluid-bed NAPCA-DPCE Westinghouse Electric Dr. B. W. Lancaster Conceptual design of an large industrial 344.487 IFY 701
combustion - systems CP A 70-9 Corp. Res. & Dev. Dr. D. L. Kearns coal-fired fluidized-bed combustor
Ctr. (500,000 Ib/hr steam)
Pittsburgh, Penn.
V-h Models for NOx formation in NAPCA-DPCE Mass. Inst. Tech. H. C. Hottel Develop quantitative models for the 28,000 (FY '69)
stationary combustion processes CPA 22-69-44 Fuels Aes. Lab. G. C. Williams formation of NOx in furnaces, influence
Task No.3 A. F. Sarofin of varying parameters, and methods to
reduce by combustion process
modification
V.j Low emission continuous flow NAPCA-DMVRD Marquardt Co. C. V. Burkland Correlation of finite.kinetic-chemical 97,000 IFY '691
combustion for vehicle propulsion CP A 22-69-128 Van Nuys, Calif. combustion-analysis model with
actual combustor tests
V-j Incinerator oyerfire-alr mixing study NAPCA-DPCE Arthur D. Little Improve understanding of overfire air 69,738 (FY 711
EHSD 71-6 Cambridge, Mass. and emissions, data may be useful
for flxed.bed coal-combustion units
V-k Charactenstics of flames causing NAPCA-DPCE Buresu of Mines J. Grumer Correlate emission from small gas 303,000 ITotal)
pollutIOn Interagency transfer Pittsburgh, Penn. M. E. Harns burners with design variables
V.A.Rowe
-------
Table V-B. (Continued)
Project
Key
Project or Contract Title
Sponsoring
Organization
and Contract No.
Research Organization
Principal
Investigator
Objective or Scope
Funding, $
V.u
V-v
VOW
V-I
Residential heating project
NAPCA-DPCE
NAPCA.DPCE
u. S. Navy
u. S. Navy
Navy Ship Systems
Command
u. S. Navy
Naval Material Command
NASA
NASA
State of California
American Gas Asso.
Amencan Gas Assa.
American Petroleum
Inst.
American Telephone
and Telegraph
NAPCA.DPCE
Cincinnati, Ohio
NAPCA.DPCE
Cincinnati, Ohio
u. S. Navy
Civil E n9. Lab.
Port H ueneme, Calif.
u. S. Navy
Naval Ship Eng. Ctr.
PhiladelphIa, Penn.
u. S. Navy
Naval Weapons Ctr.
China Lake, Calif.
NASA
LewIs Res. Crr.
Cleveland, Ohio
NASA
Jet Prop. Lab.
Pasadena. Calif.
UCLA
Los Angeles, Calif.
Institute"of Gas
Technology
Chicago. III.
Battelle Memorial I nst.
Columbus Lab.
Columbus, OhIo
Battelle Memorial Inst.
Columbus Lab.
Columbus, Ohio
American Telephone
and Telegraph
Bell Telephone Lab.
V.m
Fuel additive project
V-n
Distillate fuels research
V-o
Problems resulting from burning
residual fuel in naval boilers
V.p
Secondary combustion in air-
augmented rockets
V-q
High.turbulence burner research
V.r
Combustion-kinetics in an opposed
jet burner
V.s
Applied chemical kinetics
V-t
Fundamental study of the combus-
tion of natural gas
Basic studIes of momentum flux,
combustlon.intensity, and noise
in gas-fIred combustors
Emissions from oil-fired
residential and commercial
burners
Air pollution reduction in heating
plants and diesel engines
J. H. Wasser
D. P. Howecamp
G. B. Martin
J H. Wasser
J. E. Johnson
W. A. Fntz, Jr.
J. E. Crump
W. Roudebush
J. H. Rupe
C. Chu
Dr. R. B. Rosenberg
Dr. R. Perfel
Dr. R. V. Serauskas
A. A. Putnam
D. W. Locklin
A. Levy
R. B. Engdahl
Identify burner variables and burner
designs that minimize emissions
Identify additives that reduce emissions
Improve understanding of heterogeneous
combustion
Eliminate problems of combustion
fouling of burner equipment
Understanding of the two.stage-
combustion process
Improve understanding of the relation-
ships between turbulence and
combustion
Improve understanding of the kinetics
of combustion systems
I mprove understanding of kinetics
of combustion process for opposed-
jet diffusion flames
Improve understanding of the
combustion process for gaseous fuels
Improve understanding of the
combustion process in gas-fi red
units
Field study to measure gaseous and
particulate emissions from a range of
oil-fired combustion units
Effects of additives on reductIon of
emissIOns from oil-fired units
60,000 (F Y '69'
75,000 (FY '69)
~
tV
-------
Table V-B. (Continued)
Project
Key
Project or Contract Title
Sponsoring
Organization
and Contract No.
Research Organization
Principal
Investigator
Objective or Scope
Funding, $
9.500
V-x
V-y
V-z
V~aa
V-bb
V-cc
V-dd
V..,e
V-If
V-gg
Emissions from dO'mestic and
commercial space heating units
burning gas and oil
Temperature and air distribution in large
rectangular incinerator furnaces
Blue flame combustion with No.2
fuel oil
Control of pollutant emissions from
oil-fired boilers by an additive
Effects of additives on combustion of
fuel 0115 and reduction of 502 in
flue gases
Development and testing of domestIc
heating appl iances with reference to
the emission of smoke, unburned
hydrocarbons, and other pollutants
I nvestigation of soot
Studies of steam boilers and burner
control measures to minimize air
pollution
Studies of the use of additives for the
reduction of emissions from vehicles
and 011 firing
Investigations of emissions of otl
furnaces in regard to offensive
odors
American Society of
Heating, Refrigerating,
and Air Conditioning
Engineers
Morse Boulger, Inc.
Canadian Government
Canadian Government
Swedish Waters and
Air Pollution
Res. Lab.
Oslo, Norway
Landesamt fur forschung
des Landes Nordrhein
West falen
A. D. Little
Cambridge, Mass.
Morse Boulger, Inc.
Ansonia, Conn.
Canadian Combustion
Res. Lab.
Ottawa, Ontario,
Canada
Canadian Combustion
Res. Lab.
Ottawa, Ontario,
Canada
Royal Tech. H. Sch.
Inst. of Inorganic
Chemistry
Stockholm, Sweden
The Heating and
Ventilating Res.
Ass'n.
Brocknell, England
Swedish Waters and
Air Pollution
Res. Lab.
Stockholm, Sweden
Norwegian Steam Boilers
Owners Ass'n.
Oslo, Norway
Instttute for Metallurgy
Wullnerstrasse, Germany
Lehrstuhl fur Metal-
lurgle der Kern-
brennstoffe und
Theoreflsch Hutten.
kunde der Tech.
nlschen Hochschule
Aachen
Aachen, Germany
John Swanton, Jr.
M. Dvirka
H. Whaley
G. K. Lee
F. D. Friedrich
c. Brasset
B. Steen
A. Steineger
Dr. Ottmar Knacke
Survey of literature pertaining to burner
adjustment and maintenance and their
effect on emission levels
Data on effect of overfire air jets on
smoke and 10 emissions may apply
to fi xed~bed coal combustion
Develop low-emission blue-flame oil
burner
Develop and test an additive for control
of emissions from oil.fired boilers
~
IV
VI
Data on microstructure of soot
Identification of odoriferous compounds
-------
V-26
R&D OPPORTUNITIES RECOMMENDED FOR THE 5-YEAR PLAN
Thirteen R&D opportunities have been identified that will fill gaps in technology as
applied emission control by combustion modification to industrial steam generation and
commercial and residential heating. The R&D opportunities recommended for the 5- Year Plan
include work in the following areas:
Combustion Process R&D to Evolve Design Criteria
. Mathematical modeling of the combustion process
. Mixing, turbulence, combustion intensity, and temperature
. Internal recirculation
. External recirculation
. Two-stage combustion
. Fluidized-bed combustion
. PNA formation in fixed coal beds.
Development of New and Improved Equipment Approaches
. Apply design criteria
. Develop low-peak-temperature units.
Investigation of Other Factors
. Transient conditions
. Additives and emulsions (residual fuel oil)
. Maintenance
. More comprehensive emissions factors.
These R&D opportunities range from short tasks (e.g., evaluation of additives and emulsions for
reducing emissions from residential fuel oil combustion) to initiating work on long-term tasks
(e.g., development of a complete mathematical model of the combustion process in equipment
covered in this chapter).
Each of the R&D opportunities suggested involves work that is not likely to be
adequately supported by industry or other governmental agencies. APCO has already supported
work related to 8 of the 13 proposed R&D opportunities.
In addition to benefiting from the work suggested in these R&D opportunities, combus-
tion technology relating to industrial steam generation and commercial and residential heating is
likely to benefit from certain work in other areas. Specifically, these include studies of ash
properties from combustion of coal, studies of fluidized-bed combustion, investigations of the
effect of fuel-bound nitrogen on NOx emissions and, indirectly, a number of the fundamental
and broadly applicable research opportunities.
The R&D opportunities are described in detail on the following pages and their priorities
summarized at the end of this chapter.
-------
V-27
R&D Opportunity: V-I
Related to: V-2,3; VIll-13, 18, 19,22,25; V-d, k, I, n, q, t, u, z
Experimental Investigation to Develop Design Criteria for Minimum Pollutant Emissions from
Small- and Intermediate-Size Combustion Equipment, Considering Mixing, Turbulence, Combustion
Intensity, and Furnace Temperature
Technical Objective and Approach
The objective is to define the effect of important combustion variables on pollutant formation in small- and
intermediate-size combustion equipment and to develop design criteria for minimizing emissions from these units.
The approach should be to: (1) measure levels of mixing, turbulence, combustion intensity, furnace tempera-
ture, and other variables in current designs of combustion equipment, (2) determine optimum levels of each variable
using laboratory combustion rigs, and (3) develop criteria for design of low-emission combustion units.
Rationale and Incentive
Although the overall air-fuel ratio of combustion devices may be sufficient to avoid pollutant formation,
pollutants do form. A substantial part of the pollutant formation may occur in local pockets that are either fuel
rich or too lean to provide satisfactory combustion. These local pockets are the result of incomplete mixing (or
unmixedness) of fuel, air, and recirculated combustion products.
Combustion intensity and furnace temperature are major factors in the formation of NOx and, also, are related
to completeness of combustion.
The development of design criteria relating emission formation to important combustor variables, such as:
mixing, turbulence, combustion intensity, and furnace temperature, would contribute to the design of low-emission
combustion equipment.
Estimated R&D Cost & Time
R&D Cost Range, 1000's: $500-$1,700
R&D Time Range: 3-10 years
Recommended 5-year Funding, 1000's: $850
Funding by Fiscal Year, $1OO0's
'69-70 12!
X 200
'72
'73
'74
'75
'76+
200
150
150
150
Evaluation
Sources Affected: Oil, Gas, and Yz Coal Industrial Steam Plus Oil and Gas Commercial and Residential
Relative Potential Benefit (overall rating): Medium
,
Poll utants Affected
CP
co
HC
PNA
Odor
NOx
Lead
SOx
Ash
~
---
--
% Reduction, Range
Expected
Fraction of ECC Emissions Affected
Noncombustion Controls Factor
Relative Potential Benefit Factor
0-30 0-30 0-30
18 18 18
.14 .0014 .010
.2 0 0
2.02 0.02 0.18
0-30
18
.044
o
0.79
0-40
20
.071
o
1.42
4.43
Implementation Time, years: 5-12
most likely: 7
Relative Implementation Cost: Very Low
Relative Priority Rating: B
-------
V-28
R&D Opportunity: V-2
Related to: V-I, 3; VIII-13, 22, 25; V-d
Experimental Laboratory Investigation of the Effect of Internal Recirculation on Emissions,
Demonstration of Optimum Internal Recirculation on Several Small- and Intermediate-Size Com-
bustion Units, and Development of Design Criteria
Technical Objective and Approach
The objective is to define optimum internal recirculation for combustion with low emissions and to determine
how it might be achieved in various types of equipment.
The approach initially should involve simple laboratory rigs with configurations not too different from those of
practical combustion units. Factors studies for their influence on internal recirculation should include: air
momentum (and distribution between primary, secondary, and tertiary air), combustion chamber shape (including
edges and abrupt enlargements), and firing intensity. Relations developed in the laboratory studies should be verified
through application to several commercial combustion devices. Design criteria should be developed for incorporating
optimum internal recirculation into the design of low-emission combustion equipment.
Rationale and Incentive
Internal gas recirculation is known to occur in essentially all combustion devices included within the scope of
this study. However, relatively little information is available for quantifying the internal recirculation necessary to
achieve combustion with low emissions. A better understanding of internal recirculation would permit the design of
combustion units with recirculation levels appropriate for minimum emissions.
Estimated R&D Cost & Time
R&D Cost Range, 1000's: $300-$1,200
R&D Time Range: 2-10 years
Recommended 5-year Funding, 1000's: $750
Funding by Fiscal Year, $1oo0's
'69-70 12!
100
'72
150
'13
200
'74
200
'75
100
76+
Evaluation
Sources Affected: Oil, Gas, and Yz Coal Industrial Steam Plus Oil and Gas Commercial and Residential
Relative Potential Benefit (overall rating): Medium
Pollutants Affected CP CO HC PNA Odor NOx Lead SOx Ash ~
- - - -
% Reduction, Range 0-30 0-30 0-30 0-30 0-40
Expected 15 15 15 15 20
Fraction of ECC Emissions Affected .14 .0014 .010 .044 .071
Noncombustion Controls Factor .2 0 0 0 0
Relative Potential Benefit Factor 1.68 0.02 0.15 0.66 1.42 3.93
Implementation Time, years: 5-12 most likely: 7 Relative Implementation Cost: Very Low
-------
V-29
R&D Opportunity: V-3
Related to: V-I, 2; VIII-I, 4, 6, 8, 9,13,17,19,22,25; V-h
Development of Analytical Models to Provide Design Guidance for Small- and Intermediate-Size
Combustion Equipment
Technical Objective and Approach
The objective is to develop and improve chemical and physical models of the complete combustion process in
small- and intermediate-size combustion equipment. The ultimate objective is to develop a complete chemical and
physical model of the combustion process so that emissions can be predicted for proposed combustor designs
without the need for experimental data.
The approach should be initiated with careful examination of the literature to include what is known relating
to significant phenomena such as atomization, mixing, turbulence, internal and external recirculation, reaction
kinetics, heat transfer, and profiles of velocity, temperature, and composition. Models will of necessity be crude at
the start because of gaps in knowledge, but as additional information becomes available from laboratory investiga-
tions and field measurements, the models should be refined. Where it is recognized that needed information will not
be forthcoming from planned research, laboratory investigations should be conducted to generate the needed data.
Rationale and Incentive
There are gaps in the understanding of the basic chemical and physical phenomena associated with combustion
in small and intermediate-size combustion equipment. In fact, burner and/or furnace design is largely an art
involving cut-and-try development techniques and usually not venturing far from successful past designs.
To minimize the pollutant emissions from combustion equipment, it would be desirable to base new designs on
a sound understanding of the combustion phenomena. The development of models of the combustion process and
combustion devices would contribute to this understanding. Using these models, pollutant emissions from proposed
equipment designs could be evaluated and design alterations made to reduce emissions.
Although the complete physical and chemical models are far in the future, the process of developing the model
should be started soon, as it may guide future research by identifying specific gaps in data relating to the
combustion process.
Estimated R&D Cost & Time
R&D Cost Range, 1000's: $30o-0pen
R&D Time Range: 5 years-Open
Recommended 5-year Funding, 1000's: $500
Funding by Fiscal Year, $1oo0's
'69-70 [ 2!
75
'72
75
'73
125
'74
'75
100
'76+
125
100/year
Evaluation
Sources Affected: Oil, Gas, and Vz Coal Industrial Steam, Plus Oil and Gas Commercial and Residential
Relative Potential Benefit (overall rating): Medium
Poll utants Affected
CP
co
HC
PNA
Odor
NOx
Lead
SOx
Ash
~
---
--
% Reduction, Range
Expected
Fraction of ECC Emissions Affected
Noncombustion Controls Factor
Relative Potential Benefit Factor
Implementation Time, years; 5-12
0-30
15
.12
.2
1.44
0-30 0-30
15 15
.0014 .0091
o 0
0.02 0.14
0-30
15
.038
o
0.57
0-40
20
.060
o
1.20
3.37
most likely: 10
Relative Implementation Cost: Very Low
-------
V-30
R&D Opportunity: VA
Related to: V-I, v
Experimental Investigation of the Contribution of Transient Conditions To Emissions from Resi-
dential and Small Commercial Combustion Equipment, and Development of Means of Minimizing
Emissions During Transient Conditions
Technical Objective and Approach
The objective is to determine the effect on emissions of transient conditions and to devise means to reduce it.
The approach should be to measure emission levels during transient conditions with several types of combus-
tion equipment. Typical operating cycles should be investigated and the portion of pollutant emissions occurring
during transient conditions should be established. Subsequently, ways of reducing emissions during transient
conditions should be devised. This might involve reducing the severity of the transient phenomena (operating a
modulating device in place of an on-off device) or reducing the changes occurring in the combustion chamber during
the transient condition (e.g., use a cold-wall combustion chamber for oil furnaces).
Rationale and Incentive
Considerably higher than average pollutant emissions frequently accompany transient conditions (such as the
start and end of a firing cycle) for small- and intermediate-size combustion equipment. This is particularly true for
startup of units that operate with hot firebox walls (such as domestic oil furnaces), as the walls must heat to
operating temperature before emissions are stabilized. Also, a few seconds may be required to establish gas-
movement patterns in fireboxes and mixing may be poor during this period.
It would be desirable to determine what portion of total emissions occurs during transient conditions and, if
this portion is significant, to determine ways of avoiding high emissions during these periods.
Estimated R&D Cost & Time
R&D Cost Range, 1,000's: $550-$1,300
R&D Time Range: 3-8 years
Recommended 5-year Funding, 1000's: $775
Funding by Fiscal Year, $1000's
'69-70 I ~
X 200
'72
175
'73
150
'74
125
'75
125
'76+
Evaluation
Sources Affected: Oil and Gas Commercial and Residential
Relative Potential Benefit (overall rating): Very Low
Pollutants Affected
CP
CO
HC
PNA
Odor
NOx
Lead
SOx
Ash
~
--
--
% Reduction, Range
Expected
Fraction of ECC Emissions Affected
Noncombustion Controls Factor
Relative Potential Benefit Factor
0-10 0-10 0-10
5 5 5
.055 .0005 .003
o 0 0
0.28 0 0.02
0-5
3
.032
o
0.10
0.40
I mplementation Time, years: 4-10
most likely: 7
Relative Implementation Cost: Medium
-------
V-31
R&D Opportunity: V-5
Related to: VIII-6, 10, 11,12
Experimental Investigation of the Mechanisms by which PNA is Formed and Destroyed during the
Combustion of Coal on Fixed Beds and Development of Design Criteria to Minimize PNA
Emissions with Demonstration on Boiler Units
Technical Objective and Approach
The objective is to determine and control the mechanism of PNA formation and destruction in coal-burning
combustion equipment.
The approach should include investigation of both the pyrolysis-phase and the gas-phase combustion of
fuel-bed burning. Effects of bed temperature profile, local air-fuel ratio, bed characteristics, fuel characteristics, and
other factors should be experimentally determined using laboratory combustors and making measurements on
operating equipment.
After the mechanism of PNA emission is established, the results should be incorporated into guidelines for the
design of practical units with low PNA output.
Rationale and Incentive
The single major source of the total national PNA emissions is the burning of coal in small- to intermediate-size
combustion devices. Although the number of small- and intermediate-size coal-fired combustion sources is decreas-
ing, this source will continue to account for the largest portion of PNA emissions. Therefore, it is important to
determine how these emissions can be reduced.
Estimated R&D Cost & Time
R&D Cost Range, 1000's: $400-$1,000
R&D Time Range: 2-8 years
Recommended 5-year Funding, 1000's:
$600*
Funding by Fiscal Year, $1000's
'69-70 [ 2! '72
X 150 150
'73
150
'74
150
'75
'76+
Evaluation
Sources Affected: 1!z Coal Industrial Steam Plus Coal Commercial and Residential
Relative Potential Benefit (overall rating): Medium High
Poll utants Affected
CP
CO
HC
PNA
Odor
NOx
Lead
SOx
Ash
~
---
--
% Reduction, Range
Expected
Fraction of ECC Emissions Affected
Noncombustion Controls Factor
Relative Potential Benefit Factor
Implementation Time, years: 4-10
0-90
48
0.36
o
17.28
17.28
most likely: 6
Relative Implementation Cost: Very Low
Relative Priority Rating: C
Although the ranking procedure would assign this R&D opportunity a Relative Priority Rating in the A category, it has
judgementally been reduced to Rating C, as it is believed that the major sources of PNA emissions are not ECC sources and,
-------
V-32
R&D Opportunity: V-6
Related to: V-7; VIII-27; V-a, b, h, p
Experimental Investigation of the Application of Flue-Gas Recirculation and Two-Stage Combustion
(and in combination) to Residential and Small Commercial Oil and Gas Burners with Demonstra-
tion Prototypes
Technical Objective and Approach
The objective is to solve problems associated with the applications of flue-gas recirculation and two-stage
combustion to residential and small commercial combustion equipment.
The approach should include laboratory investigations of recirculation to determine: (1) the necessary level of
recirculation for various sizes and types of burners, for various firing rates, and for various fuels; (2) the optimum
temperature of recirculated flue gas and the optimum point of injection; (3) means for supplying the energy
necessary to accomplish the flue-gas movement associated with recirculation; and (4) methods for avoiding corrosion
of the recirculation loop. For units operated over a range of firing rates, it will be necessary to consider controls to
vary the quanity of recirculated gas as a function of firing rates. Above all, recirculation for emission reduction
should not reduce performance of the unit in such areas as flame stability and ignitability.
Laboratory investigations of two-stage combustion should determine: (1) methods to avoid impractically long
residence times, (2) methods to avoid the formation of smoke or intermediates difficult to oxidize, (3) the effect of
local reducing conditions on corrosion, and (4) means to ensure complete mixing of the secondary air with the
products of the primary combustion to complete combustion.
Mter laboratory work has been completed, demonstration prototypes should be constructed.
Rationale and Incentive
Recirculation of flue gas and two-stage combustion are promising techniques for reducing peak
combustion-zone temperatures and, therefore, reducing NOx emissions without sacrificing unit efficiency. Several
studies have shown that recirculation and two-stage combustion can reduce NOx emissions. In fact, for small-size
combustion equipment, flue-gas recirculation and/or two-stage combustion may be the only practical techniques,
from an economic standpoint, for reducing NOx emissions.
Estimated R&D Cost & Time
R&D Cost Range, 1000's: $300-$1,000
R&D Time Range: 2-6 years
Recommended 5-year Funding, 1000's: $600*
Funding by Fiscal Year, $1OO0's
'69-70 12!.
200
72
200
'73
200
'74
'75
76+
Evaluation
Sources Affected: Oil and Gas Commercial and Residential
Relative Potential Benefit (overall rating): Medium
Pollutants Affected
CP
co
HC
PNA
Odor
NOx
Lead
SOx
Ash
I:
--
--
% Reduction, Range
Expected
Fraction of ECC Emissions Affected
Noncombustion Controls Factor
Relative Potential Benefit Factor
0-50
28
.060
o
1.68
20-50
35
.040
o
1.40
3.08
Implementation Time, years: 4-8
most likely: 5
Relative Implementation Cost: Medium
-------
V-33
R&D Opportunity: V-7
Related to: III-2, 3, 4; V-6; VIII-27; V-a, b, h, p
Experimental Investigation of the Application of Flue-Gas Recirculation and Two-Stage Combustion
(and in combination) to Typical Oil- and Gas-Fired Industrial Package Boilers With One Demonstra-
tion Prototype
Technical Objective and Approach
The objective is to solve problems associated with the application of flue-gas recirculation and two-stage
combustion to oil- and gas-fired industrial package boilers.
The approach should include laboratory investigations of recirculation to determine: (1) the necessary level of
recirculation for various sizes and types of burners, for various firing rates, and for various fuels; (2) the optimum
temperature of recirculated flue gas and the optimum point of injection; (3) means for supplying the energy
necessary to accomplish the flue-gas movement associated with recirculation; and (4) methods for avoiding corrosion
of the recirculation loop. For units operated over a range of firing rates, it will be necessary to consider controls to
vary the quantity of recirculated gas as a function of firing rates. Above all, recirculation for emission reduction
should not reduce performance of the unit in such areas as flame stability and ignitability.
Laboratory investigations of two-stage combustion should determine: (1) methods to avoid impractically long
residence times, (2) methods to avoid the formation of smoke or intermediates difficult to oxidize, (3) the effect of
local reducing conditions on corrosion, and (4) means to ensure complete mixing of the secondary air with the
products of the primary combustion to complete combustion.
After laboratory work has been completed, a demonstration prototype should be constructed.
Rationale and Incentive
Recirculation of flue gas and two-stage combustion are promising techniques for reducing peak
combustion-zone temperatures and, ,therefore, reducing NOx emissions without sacrificing unit efficiency. Several
studies have shown that recirculation and two-stage combustion can reduce NOx emissions. In fact, for oil- and
gas-fired industrial package boilers, flue-gas recirculation and/or two-stage combustion may be the only practical
techniques, from an economic standpoint, for reducing NOx emissions.
Estimated R&D Cost & Time
R&D Cost Range, 1000's: $400-$1,300
R&D Time Range: 2-5 years
Recommended 5-year Funding, 1000's: $650*
Funding by Fiscal Year, $1000's
'69-70 [ ~
250
72
200
73
200
'74
75
76+
Evaluation
Sources Affected: Oil and Gas Industrial Steam
Relative Potential Benefit (overall rating): Medium Low
Pollutants Affected
CP
CO
HC
PNA
Odor
NOx
Lead
SOx
Ash
~
---
--
% Reduction, Range
Expected
Fraction of ECC Emissions Affected
Noncombustion Controls Factor
Relative Potential Benefit Factor
Implementation Time, years: 4-8
0-50
28
.038
o
1.06
20-70
48
.034
o
1.63
2.69
most likely: 5
Relative Implementation Cost: Low
-------
V-34
R&D Opportunity: V-8
Related to: V-6, 7; VlII-20, 27; V-a, b, h
.
Experimental Laboratory Investigation of the Application of Flue-Gas Recirculation to Fixed-Bed
Coal Combustion with Laboratory Demonstration
Technical Objective and Approach
The objective is to solve problems associated with the applications of flue-gas recirculation to fIXed-bed coal.
combustion equipment.
The approach should include laboratory investigations to determine: (1) the necessary level of recirculation for
various sizes and types of beds for various firing rates, and for various fuels; (2) the optimum temperature of
recirculated flue gas and the optimum point of injection to maintain good combustion and reduce NOx formation;
(3) the energy necessary to accomplish the flue-gas movement associated with recirculation; and (4) means for
preventing corrosion of the recirculation loop. For units operated over a range of firing rates, it will be necessary to
consider controls to vary the quantity of recirculated gas as a function of firing rates. Above all, recirculation for
emission reduction should not reduce performance of the unit in such areas as flame stability and ignitability.
Laboatory equipment should be developed for demonstration purposes.
Rationale and Incentive
Recirculation of flue gas is a promising technique for reducing peak combustion-zone temperatures and,
therefore, reducing NOx emissions without sacrificing unit efficiency. In fact, for small- and intermediate-sized
fixed-bed combustion equipment, flue-gas recirculation may be the only practical technique, from an economic
standpoint, for reducing NOx emissions.
Estimated R&D Cost & Time
R&D Cost Range, 1000's; $500-$1,500
R&D Time Range: 2-6 years
Recommended 5-year Funding, 1000's: $1,100*
Funding by Fiscal Year, $1OO0's
'69-70 I ~ '72 '73
- 200 300 300
'74
300
'75
'76+
Evaluation
Sources Affected: % Coal Industrial Steam
Relative Potential Benefit (overall rating): Very Low
Pollutants Affected
CP
co
HC
PNA
Odor
NOx
Lead
SOx
Ash
~
--
--
% Reduction, Range
Expected
Fraction of ECC Emissions Affected
Noncombustion Controls Factor
Relative Potential Benefit Factor
20-70
35
.011
o
0.38
0.38
Implementation Time, years: 4-9
most likely: 6
Relative Implementation Cost: Low
-------
V-35
R&D Opportunity: V-9
Related to: III-6, 7; V-g
Conceptual Design and Supporting Experimental Investigations to Guide the Application of
Fluidized-Bed Combustion of Coal to Industrial Steam Generation
Technical Objective and Approach
The objective is to develop fluidized-bed combustion units for industrial steam generation.
The approach should include conceptual studies to establish equipment configurations and economical feasibil-
ity and experimental studies are needed to resolve technical questions and develop design criteria. Particularly
needed are further studies of the emission of NOx from such combustion systems, including the possible
contribution of chemically-bound nitrogen in the coal, and studies to determine how emissions of HC, CO, and PNA
can be avoided.
Rationale and Incentive
Fluidized-bed combustion of coal offers the prospect of reduction of NOx emissions due to lower combustion
temperatures as well as the removal of sulfur oxides by reaction with limestone in the bed. Although fluidized-bed
demonstrations to date have been with units many times smaller than those necessary for industrial steam
generation, the scale-up to industrial steam generation is much less than for the proposed central-station power plant
applications.
Studies by the Argonne National Laboratory have indicated that NOx emissions from fluidized-bed combustion
of coal are not low. Based on experiments with argon substituted for the nitrogen in air, they concluded that the
NOx formed from the nitrogen in the fuel. However, these tests were not conclusive as local high-temperature
regions in the fuel bed might have produced the same NOx levels. Therefore, it will be necessary to determine
experimentally whether or not fluidized-bed combustion produces low NOx emissions and, if it does not, how the
process might be controlled to produce low emissions.
NAPCA is currently sponsoring a conceptual study of an industrial-size fluidized bed and several experimental
studies.
Estimated R&D Cost & Time
R&D Cost Range, 1000's: $600-$2,000
R&D Time Range: 3-10 years
Recommended 5-year Funding, 1000's:
$1,050
Funding by Fiscal Year, $1oo0's
'69-70 I ~
X 250
'72
250
'73
250
'74
150
'75
150
'76+
Evaluation
Sources Affected: Coal Industrial Steam
Relative Potential Benefit (overall rating): Medium
Pollutants Affected
CP
CO
HC
PNA
Odor
NOx
Lead
SOx
Ash
~
---
--
% Reduction, Range
Expected
Fraction of ECC Emissions Affected
Noncombustion Controls Factor
Relative Potential Benefit Factor
30-75
44
.018
o
0.79
50-95
74
.042
o
3.11
0-50
15
.062
.5
0.46
4.36
I mplementation Time, years: 6-12
most likely: 8
Relative Implementation Cost: Medium
-------
V-36
R&D Opportunity: V-lO
Experimental Investigation to Develop Low-Peak-Temperature Residential Heating Units to Reduce
NOx Emissions
Technical Objective and Approach
The objective is to develop low-peak-temperature gas- and oil-flred heating units to reduce NOx emissions from
residential space heating equipment.
The approach should include
which achieve acceptable thermal
incompletely burned fuel or CO.
investigations aimed at developing low-peak-temperature domestic heating units
efficiencies with low-temperature flue gas and do not increase emissions of
One type of unit that should be studied is the catalytic gas burner with peak temperatures of 1800 F to 2000
F. Other approaches include radiant burners and burners that operate at high air/fuel ratios.
Rationale and Incentive
Flue-gas cleanup processes and extensive modifications of combustion equipment (such as two-stage com-
bustion) will quite likely be uneconomical for small space-heating units. Furthermore, current combustion
technology indicates that low NOx emissions can be achieved only by burning at low temperatures. Therefore, it is
desirable to investigate the development of low-temperature heating units.
Estimated R&D Cost & Time
R&D Cost Range, 1000's: $250-$900
R&D Time Range: 2-8 years
Recommended 5-year Funding, 1000's: $475
Funding by Fiscal Year, $1oo0's
'69-70 12!
75
'72
100
'73
150
'74
150
'75
76+
Evaluation
Sources Affected: Oil and Gas Commercial and Residential
Relative Potential Benefit (overall rating): Medium Low
Poll utants Affected
CP
co
HC
PNA
Odor
NOx
Lead
SOx
Ash
~
--
--
% Reduction, Range
Expected
Fraction of ECC Emissions Affected
Noncombustion Controls Factor
Relative Potential Benefit Factor
40-90
75
.034
o
2.55
2.55
I mplementation Time, years: 3-10
most likely: 6
Relative Implementation Cost: Low
-------
V-37
R&D Opportunity: V-ll
Related to: VlII-18; V-f, m, aa, bb, ff
Experimental Investigation of Additives and Emulsions for Reducing Emissions from Residual
Fuel-Oil Combustion
Technical Objective and Approach
The objective is to determine whether either atomization, combustion, or emissions are favorably affected by:
(1) additives in the oil or (2) firing water-in-oil emulsions.
The approach should include investigation of the few additives that have shown promise for reducing emissions
from distillate oil combustion and of additives for which some sound evidence of emission reduction is available.
The emulsion concept should be developed to the point where it can be determined whether emulsification of fuel
oil improves atomization and combustion and, thereby, lowers emission levels (beyond the effect of the water on
lowering flame temperature).
Studies should be carried out with laboratory rigs that provide combustion conditions not too different from
those characteristic of practical equipment. Atomization studies could be conducted in a freeze-out chamber or by
holographic techniques.
Rationale and Incentive
The use of fuel additives to improve combustion and, therefore, to reduce emissions at low cost is appealing.
However, extensive tests by NAPCA using additives in distillate fuel oil have not shown substantial reductions in
emissions. Because residual fuel oil is more difficult to atomize and burn than distillate fuel oil, additives might be
expected to show a greater effect on residual oil combustion than on distillate combustion.
It might even be feasible to alter the physical properties affecting atomization characteristics of fuel oils by
incorporating additives in the fuel oil. Better atomization will produce improved combustion and, consequently,
lower emissions.
The emulsion concept for obtaining improved atomization appears interesting. NAPCA investigation of firing
water-in-distillate fuel-oil emulsions indicated there was a 1/3 reduction in NOx emissions. The use of emulsions in
units firing residual fuel oil may prove more beneficial because of the inherent difficulty in buring residual oil.
One or both of these techniques may be useful in reducing emissions from small and intermediate-size
combustion equipment.
Estimated R&D Cost & Time
R&D Cost Range, 1000's: $100-$300
R&D Time Range: 1-3 years
Recommended 5-year Funding, 1000's: $175
Funding by Fiscal Year, $1oo0's
'69-70 I 71
X 100
'72
'73
74
75
76+
75
Evaluation
Sources Affected: Oil Power Plants, Industrial Steam, and Commercial and Residential
Relative Potential Benefit (overall rating): Medium Low
Pollutants Affected
CP
co
HC
PNA
Odor
NOx
Lead
SOx
Ash
L
---
--
% Reduction, Range
Expected
Fraction of ECC Emissions Affected
Noncombustion Controls Factor
Relative Potential Benefit Factor
0-40 0-20 0-20
20 10 10
.059 .0008 .0056
000
1.18 0.01 0.06
0-50
22
.054
o
1.19
2.44
Implementation Time, years: 2-4
most likely: 3
Relative Implementation Cost:
Medium
-------
V-38
R&D Opportunity: V-12
Related to: V-e, 0, v, x
Experimental Inves4tigation of the Effect of Burner Maintenance on Emissions from Commercial
and Residential Oil Burners, and Development of Design Criteria to Minimize Performance
Deterioration
Technical Objective and Approach
The objective is to (1) determine the minimum maintenance required to keep various types of oil burners
operating at the lowest possible emission levels, and (2) determine which components tend to require maintenance
to prevent pollutant emissions from increasing.
The approach should include field measurements of emissions from a large number of oil burners, adjusting or
servicing these units to return them to good operating condition, and annual or semiannual emission measurements
to determine deterioration of performance with time. Results of this study should include: (1) development of
recommendations for maintenance work and intervals, and (2) guidelines for the design of burners that require
minimum maintenance to operate at low emission levels for long time periods.
Rationale and Incentive
Lack of maintenance and/or servicing is known to result in increased smoke levels, even with well-designed
oil-burning equipment. A similar relation might be found for other pollutants.
Estimated R&D Cost & Time
R&D Cost Range, 1000's: $200-$400
R&D Time Range: 2-4 years
Recommended 5-year Funding, 1000's: $300
Funding by Fiscal Year, $1oo0's
'69-70 12!
150
'72
75
'73
75
'74
75
'76+
Evaluation
Sources Affected: Oil Commercial and Residential
Relative Potential Benefit (overall rating): Low
Pollutants Affected
CP
co
HC
PNA
Odor
NOx
Lead
SOx
Ash
~
--
--
% Reduction, Range
Expected
Fraction of ECC Emissions Affected
Noncombustion Controls Factor
Relative Potential Benefit Factor
0-30 0-30 0-30
15 15 15
.031 .0005 .0032
o 0 0
0.47 0.01 0.05
0.53
Implementation Time, years: 4-8
most likely: 6
Relative Implementation Cost: Low
-------
V-39
R&D Opportunity: Vo13
Related to: V-4; V-b, 1, v
Measurement of Emissions from Various Types of Industrial, Commercial, and Residential Combus-
tion Equipment to Develop More Comprehensive Emission Factors and to Provide Design Guidance
Technical Objective and Approach.
The objective is to upgrade the knowledge of emissions from various types of combustion equipment firing
various fuels under different conditions.
The approach should consist of field measurements of emissions from various combustion units. A sufficiently
large number of units should be included so as to enable both average emission levels and ranges to be established.
As there are likely quite large differences in emission levels from different designs of equipment for similar
applications, data should be obtained for different types of units and not general categories such as "domestic oil
burners" .
Rationale and Incentive
Reliable emission data are lacking for some kinds of equipment, fuels, and operating conditions; also, there are
serious questions as to the accuracy of older data. Accurate data would be useful for emission inventories, future
planning, identifying types of combustion equipment that emit particularly large quantities of pollutants, and
providing guidelines for other research efforts.
Estimated R&D Cost & Time
R&D Cost Range, 1000's: $300-$600
R&D Time Range: 3-6 years
Recommended 5-year Funding, 1000's: $480
Funding by Fiscal Year, $1oo0's
'69-70 12! '72
X 1 50 150
'73
'74
'75
'76+
60
60
60
Evaluation
Although funding this R&D Opportunity will not contribute directly to reducing emissions, it will provide data useful to
other R&D. A judgmental evaluation was used to assign the Relative Priority Rating to this R&D Opportunity.
-------
V-40
R&D Opportunity: V-New Concepts
Provision for Explorirtg New Concepts and New R&D Opportunities that Evolve from the Program,
Accelerating Promising R&D, or Conducting Demonstrations of Promising Concepts for Reducing
Emissions from Combustion Equipment used for Industrial Steam Generation and for Space and
Water Heating by Combustion Modification
Technical Objective and Approach
The objective is to provide for long-range flexibility in the R&D program to enable APCO to take advantage of
opportunities that are not presently evident, but which can arise during the course of this program.
The approach should be to make specific provisions in the R&D program to explore the feasibility of new and
novel concepts and to accelerate research, development, and demonstration of promising concepts for reducing
emissions by combustion-process modification. Worthwhile ideas for combustion-process modification to reduce
emissions from combustion equipment used for space and water heating and industrial steam generation might
originate as the result of novel design concepts or through in-depth understanding derived from well-planned R&D.
The merits of specific R&D opportunities should be decided by evaluating the particular concepts as they evolve.
Rationale and Incentive
The design of combustion equipment for industrial steam generation will probably benefit from combustion
developments for central-station power plants. Refinements and new ideas relating to combustion processes for
generating steam will likely see initial application in power plants because of their much greater share of total
emissions. However, techniques that prove beneficial for reducing power-plant emissions may also have application
to industrial steam generation.
The design of future residential and commercial heat equipment will be influenced by such objectives as low
noise level, high combustion intensity (affecting equipment size), and demands for modulation rather than on-off
controls. It is possible that the design of equipment to achieve these objectives may provide opportunities for
emission reduction by incorporating features such as improved atomization and mixing, variable-area air inlets,
recirculation, and control of flame luminosity.
Recommended Funding Allocation
'71
'72
150
'73
200
'74
250
'75
250
5-year Funding, 1000's: $ 850
Funding by Fiscal Year, $1000's
Evaluation
This R&D Opportunity is unranked. Potential benefit, implementation time, implementation cost, and funding level for
each specific opportunity must be evaluated when the opportunity is identified. The suggested funding level anticipates
effort on several R&D opportunities.
-------
TABLE V-9. SUMMARY BY PRIORITIES
INDUSTRIAL STEAM GENERATION AND COMMERCIAL AND RESIDENTIAL HEATING
Current Estimated R&D Costs, $1000
Relative
Priority R&D Opportunity APCO By Fiscal Years
R&D 5- Y ear On-Going
Rating Effort '71 '72 '73 '74 '75 Total '76+
B V-I Experimental Investigation to Develop Design Criteria for X 200 200 150 150 150 850 -
Minimum Pollutant Emissions from Small- and Intermediate-
Size Combustion Equipment, Considering Mixing, Turbu-
lence, Combustion Intensity, and Furnace Temperature
B V-2 Experimental Laboratory Investigation of the Effect of - 100 150 200 200 100 750 -
Internal Recirculation on Emissions, Demonstration of
Optimum Internal Recirculation on Several Small- and
Intermediate-Size Combustion Units, and Development
of Design Criteria
B V-3 Development of Analytical Models to Provide Design - 75 75 125 125 100 500 100jyr
Guidance for small- and Intermediate-Size Combustion
Equipment
- - - - - - -
Totals, Priority B 375 425 475 475 350 2,100
C V-5 Experimental Investigation of the Mechanisms by which PNA X 150 150 150 150 - 600* -
is Formed and Destroyed during the Combustion of Coal on
Fixed Beds and Development of Design Criteria to Minimize
PNA Emissions with Demonstrations on Boiler Units
C V-7 Experimental Investigation of the Application of Flue-Gas X 250 200 200 - - 650* -
Recirculation and 2-Stage Combustion (and in combination)
to Typical Oi1- and Gas-Fired Industrial Package Boilers
with one Demonstration Prototype
~
oj:::.
-------
TABLE V-g. (Continued)
Current Estimated R&D Costs, $1000
Relative NAPCA
Priority R&D Opportunity R&D By Fiscal Vears 5-Vear On-Going
Rating Effort '71 '72 '73 '74 '75 Total '76+
.
C V-lO Experimental Investigation to Develop Low-Peak-Temperature - 75 100 150 150 - 475 -
Residential Heating Units to Reduce NOx Emissions
C V-I3 Measurement of Emissions from Various Types of Industrial, X 150 150 60 60 60 480 -
Commercial, and Residential Combustion Equipment to
Develop More Comprehensive Emission Factors and to
Provide Design Guidance - - - - - -
Totals, Priority C 625 600 560 360 60 2,205
D V-6 Experimental Investigation of the Application of Flue-Gas X 200 200 200 - - 600* -
Recirculation and 2-Stage Combustion (and in combination)
to Residential and Small-Commercial Oil & Gas Burners
with Demonstration Prototypes
D V-9 Conceptual Design and Supporting Experimental Investiga- X 250 250 250 150 150 1,050 -
tions to Guide the Application of Fluidized-Bed Combus-
tion of Coal to Industrial Steam Generation
D V-ll Experimental Investigation of Additives and Emulsions for X 100 75 - - - 175 -
Reducing Emissions from Residual Fuel-Oil Combustion
D V-12 Experimental Investigation of the Effect of Burner - 150 75 75 - - 300 -
Maintenance on Emissions from Commercial and
Residential Oil Burners and Development of Design
Criteria to Minimize Performance Deterioration - -
- - - -
Totals, Priority D 700 600 525 150 150 2,125
<:
,
~
-------
TABLE V-9. (Continued)
Relative Current Estimated R&D Costs, $1000
Priority R&D Opportunity APCO By Fiscal Years
Rating R&D 5- Y ear On-Going
Effort '71 '72 '73 '74 '75 Total '76+
E V-4 Experimental Investigation of the Contribution of Transient X 200 175 150 125 125 775 -
Conditions to Emissions from Residential and Small
Commercial Combustion Equipment, and Development of
Means of Minimizing Emissions during Transient Conditions
E V-8 Experimental Laboratory Investigation of the Application of - 200 300 300 300 - 1,100* -
Flue-Gas Recirculation to Fixed-Bed Coal Combustion
with Laboratory Demonstration - - - - - -
Totals, Priority E 400 475 450 425 125 1,875
N V-N Provision for Exploring New Concepts and New R&D Oppor- - - 150 200 250 250 850 -
tunities that Evolve from the Program, Accelerating
Promising R&D, or Conducting Demonstrations of
Promising Concepts for Reducing Emissions from Com-
bustion Equipment used for Industrial Steam Generation
and for Space and Water Heating by Combustion
Modification
Totals, All Priorities 2,100 2,250 2,210 1,660 935 9,155
<:
~
-------
V-44
REFERENCES FOR CHAPTER V
1. Morrison, W. E., and Readling, C. L., An Energy Model for the United States Featuring
Energy Balances for the Years 1947 and 1965 and Projections and Forecasts to the Years
1980 and 2000, Bureau of Mines Information Circular, IC 8384 (July, 1968), 127 pp.
2.
1963 Census of Manufacturers, Fuels and Electric-Energy Consumed in Manufacturing
Industries: 1962, U.S. Department of Commerce (July, 1964), 75 pp.
3. Smith, W. F., and Gruber, C. W., Atmospheric-Emissions from Coal Combustion - An
Inventory Guide, HEW Publication No. 999-AP-24 (April, 1966), p 39.
4. Johnson, A. J., and Auth, G. H., Fuels and Combustion Handbook, Chapters 22-24,
McGraw Hill Book Company, Inc., New York (1951).
5. Smith, M. L., and Stinson, K. W., Fuels and Combustion, Chapters 6 and 7, McGraw Hill
Book Company, Inc., New York (1952).
6. Griswold, J., Fuels, Combustion, and Furnaces, Chapters 9-11, McGraw Hill Book
Company, Inc., New York (1946).
7. Faust, F. H., and Kaufman, G. T., Handbook of Oil Burning, Section 4, Oil-Heat Institute
of America, Inc. (1951).
8. Industrial Combustion Data, A Handbook, Hauck Manufacturing Company, Brooklyn, New
York (1953).
9. "Oilheating Users Total 11,186,650", Fueloil and Oil Heat, 29 (1) (January, 1970), pp
44-50.
10. Control Techniques for Sulfur Oxide Air Pollutants, NAPCA Publication No. AP-52
(January, 1969), p 8.
11. Williams, J. D., and Edmisten, N. G., An Air Resource Management Plan for the Nashville
Metropolitan Area, PHS Publication No. 999-AP-18 (September, 1965), pp 23-44.
12. The Louisville Air Pollution Study, Robert A. Taft Sanitary Engineering Center Technical
Report A61-4, Appendix B (1961).
13. Smith, W. S. Atmospheric Emissions from Fuel Oil Combustion - An Inventory Guide,
PHS Publication No. 999-AP-2 (November, 1962), 955 pp.
14. Control Techniques for Particulate Air Pollutants, NAPCA Publication No. AP-51 (January,
1969), pp 8-12.
15. Duprey, R. L., Compilation of Air-Pollutant Emission Factors, PHS Publication No.
999-AP-42 (1968), pp 3-7.
-------
V-45
16. Engdahl, R. B., Stationary Combustion Sources, Air Pollution, Vol. III, Chapter 32,
Academic Press, Inc., New York (1968).
17. Chass, R. L., and George, R. E., "Contaminant Emission from the Combustion of Fuels"
,
Jour. Air Pollution Control Association, 10 (1) (February, 1960), pp 34-43.
18. Hangebrauck, R. P., Von Lahmden, D. J., and Meeker, J. E., Sources of Polynuclear
Hydrocarbons in the Atmosphere, PHS Publication No. 999-AP-33 (1967),44 pp.
19. Peoples, G., "Upgrading Oil-Burner Performance Standards", Paper No. SP65-H presented at
Fifth API Conference on Distillate Fuel Combustion, Chicago, Illinois (June 1-3, 1965) 8
pp.
20. Impact of Air-Pollution Regulations on Fuel Selection for Federal Facilities, National
Research Council Technical Report No. 57 (1970), 52 pp.
21. Howekamp, D. P., and Hooper, M. H., "Effects of Combustion-Improving Devices on Air
Pollutant Emissions from Residential Oil-Fired Furnaces", presented at NOFI New and
Improved Oil Burner Workshop, Tarrytown, New York (September 24-25, 1969), 24 pp.
22. Belyea, H. A., and Holland, W. J., "Flame Temperature in Oil-Fired Fuel-Burning Equip-
ment and Its Relationship to Carbonaceous Particulate Emissions", Jour. Air Pollution
Control Association, 17 (5) (May, 1967), pp 320-323.
23. Wasser, J. H., Hangebrauck, R. P., and Schwartz, A. J., "Effects of Air-Fuel Stoichiometry
on Air Pollutant Emissions from an Oil-Fired Test Furnace", Jour. Air Pollution Control
Association, 18 (5) (May, 1968), pp 332-337.
24. Wasser, J. H., Martin, G. B., and Hangebrauck, R. P., "Effect of Combustion Gas Residence
Time on Air Pollutant Emissions from an Oil-Fired Test Furnace", presented at NOFI
Workshop, Linden, New Jersey (September 17-18, 1968), 18 pp.
25. Sawyer, R. F., Caretto, L. S., and Starkman, E. S., "The Formation of Nitric Oxide in
Combustion Processes", presented to Central States Section, Combustion Institute,
Columbus, Ohio (March 26-27, 1968).
26. Hardison, L. c., "Techniques for Control of Oxides of Nitrogen", Paper No. 69-164,
presented at 62nd Annual Meeting Air Pollution Control Association, New York (June
22-26, 1969), 27 pp.
27. Andrews, R. L., Siegmund, C. W., and Levine, D. G., "Effect of Flue Gas Recirculation on
Emissions from Heating Oil Combustion", presented at 61st Annual Meeting, Air Pollution
Control Association, St. Paul (June 23-27, 1968),41 pp.
28. Dunn, F. R., Jr., "Improved Oil-Burner Performance with Recirculation of Combustion
Gases", Paper No. CP61-8 presented at API Research Conference on Distillate Fuel Com-
bustion, Chicago, Illinois (March 14-15, 1961), 13 pp.
-------
V-46
29. Cooper, P. W., Komo, R., Marek, C. J., and Solbrig, C. W., Recirculation and Fuel-Air
Mixing as Rel~ted to Oil-Burner Design, API Publication No. 1723, American Petroleum
Institute, New York (May, 1964), 72 pages.
30. Koizumi, M., Mizutani, H., Takamura, Y., and Nogata, K., "High Space Heat Release and
Low Excess Air Combustion of Heavy Fuel Oil Using Exhaust Gas Recirculation Method",
Bulletin of JSME, 12 (51) (1969), pp 530-538.
31. Reba, I., Combustion of Residual Fuel with Massive Recirculation, Report on U.S. Dept. of
Commerce, Maritime Administration Contract No. MA-38l7, PB-177747 (August, 1967), 86
pp.
32. Barnhart, D. H., and Diehl, E. K., "Control of Nitrogen Oxides in Boiler Flue Gases by
Two-Stage Combustion", presented at Annual Meeting, Air Pollution Control Association,
Los Angeles (June, 1959), 24 pp.
33. Bienstock, D., Amsler, R. L., and Bauer, E. R., Jr., "Formation of Oxides of Nitrogen in
Pulverized Coal Combustion", Jour. Air Pollution Control Association, 16 (8) (August,
1966), pp 442-445.
34. Burroughs, L. c., "Air Pollution by Oilburners Measurable but Insignificant", Fueloil and
Oil Heat, 22 (6) (June, 1963), pp 43-46.
35. "HEW Issues Guidelines to Control Pollution; Tests Show Distillate Within Limits", Fueloil
and Oil Heat, 28 (3) (March, 1969), p 57.
36. Kroshel, C. F., "Improving Performance of Domestic Heating Oil Equipment Through
Installation and Servicing Procedures", presented at 40th Annual Convention, NOFI,
Chicago (April 12, 1962), 26 pp.
37. Hangebrauck, R. P., and Kittredge, G. D., "The Role of Combustion Research in Air
Pollution Control", presented to Eastern Section, Combustion Institute, Morgantown, West
Virginia (September 29 - October 1, 1969), 17 pp.
38. Martin, G. B., Wasser, J. H., and Hangebrauck, R. P., "Status Report on Study of Effects
of Fuel Oil Additives on Emissions from an Oil-Fired Test Furnace", presented at 63rd
Annual Meeting of the Air Pollution Control Association, St. Louis (June 14-18, 1970), 20
pp.
39. Barrett, R. E., Moody, J. W., and Locklin, D. W. Preparation and Firing of Emulsions of
No.2 Fuel Oil and Water, Summary Report on NAPCA Contract PH-86-68-84, Task Order
No.8, PB-189075 (November 1, 1968), 36 pp.
40. Barrett, R. E., Moody, J. W., Hazard, H. R., Putnam, A. A., and Locklin, D. W., Residual
Fuel Oil- Water Emulsions Summary Report on NAPCA Contract PH-86-68-84, Task Order
No. 16, PB-189076 (January 12, 1968),82 pp.
-------
V-47
41. Barrett, R. E., Hazard, H. R., McComis, C., and Locklin, D. W., Design, Construction, and
Preliminary Combustion Trials of a Rig to Evaluate Residual Fuel-Oil/Water Emulsions,
Summary Report on NAPCA Contract PH 86-68-84, Task Order No. 22 (July 15, 1970),
46 pp.
42. Ivanov, V. M., and Nefedov, P. I., Experimental Investigation of the Combustion Process on
Natural and Emulsified Fuels, NASA Technical Translation No. TT F-258 (January, 1965),
23 pp.
43. Private communication from G. B. Martin, DPCE, NAPCA.
44. Ornig, A. A., Schwartz, C. H., and Smith, J. F., "A Study of the Minor Products of Coal
Combustion", Paper No. 64-PWR-4, presented at National Power Conference, Tulsa,
Oklahoma (September 27 October 1, 1964), 8 pp.
45. Ornig, A. A., Smith, J. F., and Schwartz, C. H., "Minor Products of Combustion in Large
Coal-Fired Steam Generators", Paper No. 64-W AjFU-2, presented at Winter Annual Meet-
ing, ASME, New Yark (November 29 - December 4, 1964), 12 pp.
46. Diehl, E. K., Du Breil, F., and Glenn, R. A., "Polynuclear Hydrocarbon Emission from
Coal-Fired Installations", Transactions ASME, Series A, Jour. Engineering for Power, 89 (2)
(April, 1967), pp 276-282.
47. Pope, M., and Bishop, J. W., "Progress in Fluidized Bed Boilers", Power Engineering, 74 (5)
(May, 1970), pp 46-49.
48. Jonke, A. A., Carls, E. L.,Jarry, R. L., and Anastasia, L. J., Reduction of Atmospheric
Pollution by the Application of Fluidized-Bed Combustion, Annual Report, Argonne
National Laboratories, ANLjES-CEN-lOOI (June, 1969),62 pp.
-------
Chapter VI
CONTINUOUS-COMBUSTION ENGINES -
GAS TURBINES AND EXTERNAL-COMBUSTION ENGINES
Herbert R. Hazard
TABLE OF CONTENTS
SCOPE OF CHAPTER AND BACKGROUND. . . . . . . . . . . . . VI- 1
Pollutants of Principal Concern. . . . . . . . . . . . . .. - 2
GAS TURBINES
. . . . . .
. . . . .
. . . . . . . .
Gas-Turbine Applications. . . . . . . . . . . . . . . . .
Aircraft Gas Turbines. . . . . . . . . . . . .
Industrial Gas Turbines. . . . . . . . . . . . . . . .
Automotive Gas Turbines. . . . . . . . . . . .
Emission Characteristics of Present Gas Turbines. . . . . . . . .
Aircraft Gas Turbines. . . . . . . . .
Industrial Gas Turbines. . . . . . . . . . . . . . . .
Automotive Gas Turbines. . . . . . . . . . . . . . .
. . . .
Prospects for Emission Reduction from Gas Turbines
by Combustion Modification. . . . . . . . . . . . . . . .
Typical Gas-Turbine Combustor Design. . . . . . . . . .
Reduction of Smoke and NOx . . . . . . . . . .
Reduction of CO, HC, and Odor. . . . . . . . . . . .
EXTERNAL-COMBUSTION ENGINES. . . .
. . . . . .
. . . . .
Rankine-Cycle Engines. . . . . . . . . . .
Combustion-System Requirements. . . . .
Emission Levels of Reported Rankine-Cycle
Combustion Systems. . . . . . . .
. . . .
. . . . . . .
. . . . .
Stirling-Cycle Engines. . . . . . . .
. . . . . . . .
SUMMARY OF CURRENT AND RELEVANT
COMBUSTION R&D ...... . . . . .
. . . .
. . . . .
R&D NEEDED TO FILL GAPS IN TECHNOLOGY.
. . . . . .
. . . .
R&D OPPORTUNITIES RECOMMENDED FOR THE 5-YEAR PLAN
. . . .
Summary by Priorities. .
. . . . . . . . . . . .
. . . .
REFERENCES FOR CHAPTER VI
. . . . . . . . . . . . . . . .
- 3
- 3
- 3
- 3
- 3
- 4
- 4
- 6
- 7
- 7
- 7
- 8
-11
-12
-14
-14
-15
-16
-17
-17
-20
-27
-------
-------
VI-I
CHAPTER VI
CONTINUOUS-COMBUSTION ENGINES -
GAS TURBINES AND EXTERNAL-COMBUSTION ENGINES
SCOPE OF CHAPTER AND BACKGROUND
This chapter is concerned with combustion in continuous-combustion engines, including
gas turbines and external-combustion engines. External-combustion engines of principal interest
are the automotive Rankine-cycle engine and the automotive Stirling-cycle engine.
At the present time, gas-turbine engines are a small source of pollutants because of their
relatively clean exhaust and their relatively limited total installed power level. However, as the
application of gas turbines expands in the future, and the emissions of pollutants from other
sources are reduced by future controls, it is expected that emissions from gas turbines will grow
in importance.
The Rankine-cycle automotive engine, the Stirling-cycle automotive engine, and the
automotive gas turbine are of great interest because of their potential capability of replacing the
present automotive gasoline engine and reducing significantly the emissions from automobiles.
Table VI-I shows the percentages of total national emissions from energy-conversion
combustion (ECC) processes contributed by aircraft gas turbines and industrial gas turbines.
Total emission levels are below two percent for all pollutants.
Table VI-'. Emissions From Aircraft and Industrial Gas Turbines*
Pollutant
Contribution to Nationwide ECC Emissions, percent
Aircraft Stationary Total, All
Gas Turbines Gas Turbines Gas Turbines
Products of Incomplete Combustion
Combustible Particulate
PNA
nil
<1
nil
nil
nil
nil
CO
Gaseous HC
<1
1
1
NOx
<1
<1
Combustion-Improving Additives
Lead
nil
nil
nil
Fuel Contaminants
SOx
Ash (Noncombustible Particulate)
nil
nil
nil
nil
nil
<1
'Derived from data in Table 11-1 and References 1 and 3.
-------
VI-2
POLLUTANTS OF PRINCIPAL CONCERN
Aircraft Gas Turbines
The pollutants of greatest interest for aircraft in terminals are CO, HC, and odor, which
are emitted in substantial quantities during idle and taxi operations. During approach and
takeoff, smoke is of principal interest because of its visibility, although its emission on a weight
basis is negligible. During high-altitude cruise, the principal pollutants are combustible partic-
ulates (invisible smoke) and NOx. Sulfur is present in small quantities in the fuel (0.1 to 0.3
percent), and S02 is emitted in relatively small quantities.
Stationary Gas Turbines
The emissions from stationary gas turbines when operating at high power levels are
combustible particulate and NOx, and emission levels are similar to those from aircraft gas
turbines at high power levels. However, industrial turbines are not usually operated for extended
periods at low power levels and, thus, do not contribute significant quantities of CO, HC, and
odor. Although most industrial units bum natural gas as fuel, many are suitable for burning
high-sulfur distillates or residual fuel oils should the need arise.
Automotive Gas Turbines
At the present time, automotive gas turbines can meet proposed 1980 automotive
emission standards, except for NOx. Emission levels of NOx from these gas turbines are about 4
times the proposed standards.
Rankine-Cycle Automotive Engines
For continuous, full-load firing conditions, experimental Rankine-cycle burners have
demonstrated the ability to meet proposed 1980 emission standards. However, a very large
turndown ratio is required for such burners, and part-load operation with acceptable emission
levels has not been demonstrated.
Stirling-Cycle Automotive Engines
The combustors utilized in Stirling-cycle engines are quite similar to those used in gas
turbines, and emissions are similarly low. However, the turn-down problem is more critical, since
the entire turn-down range of the burner occurs at fixed (ambient) pressure. Critical pollutants
have not yet been delineated for automotive Stirling-cycle engines, but it is expected that NOx
will be of greatest concern at high power levels and that CO and HC will be of greatest concern
at idle and low power levels.
-------
VI-3
GAS TURBINES
GAS-TURBINE APPLICATIONS
Covered in this section are applications of gas turbines for aircraft propulsion, industrial
uses, and automotive power plants.
Aircraft Gas Turbines
Historically, the gas turbine was first developed for propulsion of military ahCIaft. In
1959 the first turbojet transport, the Boeing 707, was introduced. Within the short span of 10
years the turbojet, the turboprop and, later, the turbofan engine replaced all piston engines in
U.S. airline service, with greatly reduced operating cost and improved passenger acceptance.
At the present time about 2000 first-line transport aircraft are in service, and they emit
about 0.25 percent of nationwide emissions from ECC sources. The average utilization of a
commercial transport is about 10 hours per day.
About half of all jet aircraft fuel is consumed by military aircraftJ 1) Although
they outnumber commercial aircraft, their utilization factor is lower. It is estimated that the
pollutant emissions from military aircraft are equal to those for civil aircraft, in proportion to
fuel consumption for each.
Industrial Gas Turbines
The success of aircraft gas turbines led to the development of industrial gas turbines
based on aircraft technology. In general, the heavy-duty industrial unit is designed for longer life
and has larger combustors suitable for heavier fuels than an aircraft unit, often including selected
grades of No.6 fuel oil. A more recent development is the direct application of aircraft turbojet
engines as gas generators to drive heavy-duty power turbines for pipe-line pumping and for
generation of peaking power for utilities. These aircraft engines are highly developed and very
efficient, and they can be started and brought to full power within 5 minutes. Furthermore, a
complete gas generator can be replaced in as little as 4 hours and the old unit moved to an
overhaul shop, minimizing maintenance costs.
At the present time, about 50,000,000 hp of gas-turbine capacity is installed in the U.S.
in industrial and utilities service(3), of which half of the total power is generated by units of
20,000 hp or larger. The fuel consumption of these industrial units is estimated to be about
equal to that of aircraft units.
Automotive Gas Turbines
Automotive gas turbines have been under continuous development for more than 20
years, but none is yet in production as a commercial engine. Present efforts of Ford and
General Motors are directed toward production of a heavy-duty engine for trucks and buses. In
-------
VI-4
this application, the gas turbine is competitive with the diesel engine. It has the potential
advantages over die diesel of longer life, less maintenance, lighter weight, and smaller size.
Emission levels of pollutants should be considerably lower than those of either diesel engines or
gasoline engines, and cost should be similar to that of diesel engines.
The greatest potential application for the gas turbine in the reduction of pollution levels,
however, is as a passenger-car engine. The Chrysler Corporation undertook such a development in
the years between 1950 and 1968, and solved many technical and production problems in
preparing for introduction of such an engine. However, costs were not competitive with those of
current gasoline engines, and the development effort was reduced to a low level following a
nationwide field trial utilizing 50 automobiles.
The principal obstacle to application of the gas turbine to passenger automobiles is the
mismatch of passenger-car power requirements and gas-turbine power characteristics. The
passenger car operates most of the time at very low power levels, with occasional operation at
high power levels. Thus, it requires an engine that is efficient at low power levels and at idle, as
is the gasoline engine. The gas turbine is most efficient at maximum power, and loses efficiency
rapidly at power levels below 1/4 power. The idling fuel consumption of a typical automotive gas
turbine is 13 Ib per hr(4) compared with only 2 Ib per hr for a gasoline engine. While it is
technically possible to apply gas turbines to automobiles today, with much reduced emission of
pollutants, the fuel consumed by automobiles would increase somewhat. (The Chrysler field trials
indicated that average driving cost, using a cheaper fuel, was about the same as for a standard
auto, although fuel consumption for the gas turbine car was slightly higher.)
EMISSION CHARACTERISTICS OF PRESENT GAS TURBINES
Aircraft Gas Turbines
The aircraft gas-turbine combustor operates over a wide range of combustion conditions
with different emissions over different parts of the operating range. Fuel-air ratio in the
combustor can vary over a 4: 1 range, between full power and idle; the combustor pressure can
vary over a 10: 1 range; and fuel flow can vary over a 100: 1 range.
Figure VI-l illustrates the relation between combustor fuel-air ratio, pressure, engine
speed, and altitude for a typical engine having a pressure ratio of 5.(5) Combustors must operate
satisfactorily at all conditions within such a performance envelope, and must relight satisfactorily
under altitude windmilling conditions. Most of the recent engines have higher combustor
pressures, but operating characteristics are similar.
Table VI- 2 summarizes the emission characteristics of a typical turbofan engine used
widely in transport aircrafd6) This particular engine is fitted with the most recent design of
combustor and emits no visible smoke. The values for carbon emission for a smoking engine
would be about twice those shown in Table VI-2, and NOx emissions would be somewhat lower.
Combustors that emit no visible smoke have been developed by the three major manufacturers of
large aircraft turbine engines. (7,8,9)
-------
.Q
-------
VI-6
Figure VI-2 illustrates the relation between combustion efficiency and engine power
setting for typical turbojet engines. The inefficiency, or loss, is in the form of CO and unburned
HC and this accounts for the odor associated with ground operation of jet aircraft.
,
100
Range of efficiency for
different engines
-
c::
Q)
~
Q)
a.
- 90
>.
u
c
Q)
u
-
-
w
c::
o
i5 80
:J
..c
E
o
u
70
100%
Idle
Power Level
Cruise
Figure VI-2. Relation of Combustion Efficiency to Power level for Turbojet and
Turbofan Aircraft Engines
Industrial Gas Turbines
Industrial gas turbines have emission characteristics similar to those of aircraft gas
turbines. In fact, many are aircraft-engine adaptations. However, heavy-duty gas turbines often
utilize air atomization for improved low-load operation with No.2 fuel oil or heavier fuel, and
they seldom operate at low loads. Accordingly, the principal emissions of interest are NOx and
smoke. Manufacturers of large gas turbines have recently developed heavy-duty combustors that
produce no visible smoke, following practice pioneered for aircraft gas turbines.O 0, 11)
The most widely burned fuel for industrial gas turbines is natural gas, followed by
distillate fuel oil. Only minor amounts of other fuels are burned, including blast-furnace gas,
coke-oven gas, naptha, and residual fuel oil. Except for residual fuel oil, these fuels are very low
in sulfur, and emissions of S02 are very small.
-------
VI-7
Automotive Gas Turbines
Automotive gas turbines are highly regenerated machines having combustor-inlet tempera-
tures of about 1000 F. This leads to primary-zone temperatures approaching 4000 F, with
complete combustion and low emission levels for CO, HC, odor, and smoke. (4) NOx emission
levels are extremely low compared with those of gasoline and diesel engines, but they exceed the
proposed 1976 emission standards by a factor of about five.
Table VI-3 shows emissions from four different gas turbines, and compares them with
Federal 1976 standards for automobile emissions.< 12, 16) The General Motors data for 200 hp
and 130 hp engines were computed from test data for the 280 hp engine.
Table VI-3. Emissions From Automotive Gas Turbines, g/mi, 7-Mode Driving Cycle
GMT-309(16)
Pollutant 280 h p * 200 hp** 130 hp**
CO 7.0 4.7 2.3
HC 0.35 0.25 0.13
NO 2.3 2.0 1.8
Chrys. * (12)
130 hp
Fed. Std.
1976
(New driving cycle)
3.5
0.32
1.9
4.7
0.46
(0.40)***
*Test data.
UComputer simulation based on larger engine.
u*Not established yet but expected to be 0.4 to 0.5 g per mi.
PROSPECTS FOR EMISSION REDUCTION FROM GAS
TURBINES BY COMBUSTION MODIFICATION
When current aircraft and industrial gas turbines were developed, the principal criteria for
combustor evaluation were size, weight, durability, and performance. Emission of smoke or odors
was not considered significant unless it represented a performance loss. Now, however, with the
current emphasis on reduction of air pollution, much consideration is being given to pollutants
emitted from gas turbines and the means by which they can be reduced. As a first step, visible
smoke has been eliminated by development of new combustors. It appears fairly certain that
other pollutants will also be reduced significantly in the next decade. The factors involved in
such reductions, and some of the means by which reductions might be accomplished, are
discussed below. These are, in general, equally applicable to aircraft, industrial, and automotive
gas turbines, although each turbine cycle has somewhat different conditions of combustor
temperature and pressure.
Typical Gas-Turbine Combustor Design
Figure VI-3 shows a cross section of a modern annular combustor for a large aircraft gas
turbine.(8) Although gas turbine combustors vary in size and shape, all incorporate the important
features shown in this figure. Air from the compressor outlet, at the left, is slowed in the
diffuser; air near the axis enters the shroud and is directed to the primary zone. The remaining
air passes between the shell and the combustor liner and is admitted through the liner through
-------
VI-8
various holes and slots. Fuel is admitted through a ring of 64 fuel nozzles, of which one is
shown. A substantial part of the primary combustion air enters the primary zone through swirl
vanes around the fuel nozzle; the rest enters through rings of holes in the liner. The arrangement
of swirl vanes and holes is carefully developed to provide nearly uniform fuel-and-air mixtures
throughout the primary zone. Combustion is carried to about 80 percent completion or more in
the primary zone, following which the mixture enters the dilution zone, where more air is
admitted in high-velocity jets, and combustion is completed rapidly. In some combustors, a
distinct secondary-combustion zone is used for completion of combustion before admission of
the bulk of dilution air.
i
Sw'" ,"oJ J
Inner liner
Figure VI-3. Schematic Section of General Electric Annular Combustor for Low Smoke Emission(S)
The combustor liner is constructed of thin sheet metal. It is cooled by a film of air over
the inside surface and by external convection and radiation.
Combustor heat-release rates for aircraft combustors at full power are usually about
5,000,000 Btu per ft3-hr-atm. The combustor of Figure VI-3 operates at a pressure of 25 atm
(375 psi) and a heat-release rate of 125,000,000 Btu per ft3-hr. The corresponding residence
time in the primary zone is 2 or 3 milliseconds, with an additional 5 or 6 milliseconds in the
dilution zone. The combustor inlet temperature is about 1000 F, and the outlet temperature is
about 2300 F. Primary-zone combustion temperatures range from 3600 to 4000 F.
The relation of combustor design to formation of pollutants in combustors of this type is
discussed below.
Reduction of Smoke and NOx
Smoke, or visible concentrations of soot, and NO are formed concurrently in the primary
zone during combustion. In general, fuel-rich combustion conditions favor high soot concentra-
tions and low NO concentrations, and fuel-lean combustion conditions favor low soot concentra-
tions and high NO concentrations. The kinetics of smoke formation in rich mixtures have been
studied(l3), but little is known at the present time about the kinetics of NO formation in rich
-------
VI-9
mixtures. In practice, with perfect mixing, mixtures with fuel-equivalence ratios* up to about 2.0
can bum without formation of visible smoke, but soot forms rapidly in richer mixtures. It is
known that the concentration of NO in homogeneous mixtures drops sharply at fuel equivalence
ratios above 1.2 or so, but this is hard to confirm in practical combustion chambers because of
incomplete mixing and stratification. When both visible smoke and high NO concentrations are
emitted by gas turbine combustors, it appears probable that the high NO levels are generated in
local lean zones and the high soot levels are generated in local rich zones. It appears possible
that, with perfect mixing and with an equivalence ratio somewhat greater than 1.2, combustion
should take place without visible smoke and with relatively low NOx emission.
During the past 5 years, considerable effort has been expended in reducing visible smoke
from aircraft gas turbines, and combustors that operate without visible smoke are now available
for most engines used in airline and military service.(7,8,9) The means of smoke reduction has
been rather extensive redevelopment of the combustor primary zone. Past practice was to
operate with full-power equivalence ratios of up to 3.0 in the primary zone, followed by gradual
dilution in the secondary zone, where combustion was completed. The new design practice is to
limit overall primary-zone equivalence ratio to about 1.5, with a peak value below 2.0. This is
achieved by improved air admission through swirl vanes in the dome, injection of air through the
fuel-nozzle retaining nuts, and use of small air nozzles to direct jets of air directly into the small
rich regions downstream of the fuel nozzles. These changes have eliminated visible smoke, but
actual soot concentration in the exhaust is still about half that previously measured with heavy
black smoke. With the reduction in visible smoke, the concentration of NOx in the exhaust has
increased significantly.
Figure VI-4 shows two laboratory combustors, one that produces heavy black smoke and
one that produces no visible smoke(8). The variation of fuel equivalence ratio across a diameter
of the ~rimary zone is shown for both combustors, with an average for each. Combustor A, of
Combustor A
1
Average I
I
I
Fuel nozzle
Dilution ports./
4
10 1 Z, 3 ,
Radial position Fuel equivalence ratio
\-
Air~-
Fuel
nozzle 0'1 t' ./
I U Ion
ports
High
primary
combustion
zone air floW4
o
Figure VI.4. Combined Effects of Primary Combustion Zone Air Quantity and Mixing
Effectiveness on Smoke Emission(S)
*Equivalence ratio as used here is defined as: (fuel-air ratio)/(stoichiometric fuel-air ratio).
-------
VI-IO
conventional design, has an average equivalence ratio of 2.8 (very rich), and fuel is concentrated
near the wall. Combustor B has an average equivalence ratio of 1.0, with a peak value of 1.9.
Combustor A emits' heavy black smoke at simulated full load conditions, and Combustor B emits
no visible smoke. The concentration of rich fuel-and-air mixture near the outside of Combustor
A makes it easy to light at high altitude, and the large concentration gradient results in stable
operation over a very wide range of fuel-air ratios. Combustor B is much more difficult to light
and has much narrower stability limits, but does meet engine requirements.
At the present time, design criteria and developed combustors are available for replace-
ment of smoking combustors for almost all air transports, and almost complete refitting of the
airline fleet is planned by the end of 1972.(15) Smokeless combustors have also been developed
for large industrial gas turbines. However, attention has not, until now, been given to reduction
of NOx emissions from gas turbines.
The reduction of NOx emissions from gas turbines appears difficult at this time because
little success has been achieved and little is known, in quantitative terms, about the design
conditions that will best resolve the NOx and smoke emissions problem. In general, the new
"smokeless" combustors generate more NOx than those they replace. Furthermore, the develop-
ment trend for new gas turbine engines is toward higher pressure ratios (up to 40: I in advanced
development engines), which lead to higher combustor temperatures and higher NOx emissions.
Thus, considerable progress toward the reduction of NOx will be required to avoid increasing
emissions in coming years.
In considering the theoretical means of reducing NO formation in combustor primary
zones, only two approaches appear practical. One is the use of much leaner primary zones to
reduce flame temperature; the other is the use of rich primary zones with operation at fuel
equivalence ratios above 1.2, to reduce availability of oxygen for NO formation, followed by
secondary combustion in an intermediate combustion region with rapid combustion and dilution.
Soot formed in the rich primary zone would burn out in the secondary zone if the concentration
were not excessive(14). However, neither of these approaches can be carried very far unless
consideration is given to the fact that the fuel-air ratio in the primary zone varies by 3 to 1 or
more over the engine load range, and the new primary-zone conditions must be compatible with
this situation. As an extreme measure, it may be necessary to provide a variable-area stator ring
to control air admission to the primary zone, with controls such that primary-zone fuel-air ratio
can be held nearly constant over the engine operating range. This would be an expensive change
and, probably, would not be acceptable at present low levels of gas turbine pollutant emissions.
However, it may prove more acceptable for a ru.gh-production application such as automobiles.
General Motors has carried out extensive research on the combustor for the GT-309
automotive gas turbine in attempting to meet proposed 1976 emission standards for NOx. In
carrying out a large number of changes in fuel-air ratio, residence time, and fuel spray
distribution they succeeded in reducing NOx emissions by only 40 percent, and this was
accompanied by a significant increase in CO emissions.( 15) Their lowest NOx emissions were
obtained using a very lean primary zone, in combination wit16 early quenching of the flame with
dilution air. Full-load NOx emissions were reduced from about 125 ppm to about 75 ppm by
these changes.
-------
VI-II
The prospects for reducing flame temperature by recirculation of exhaust gas appear
poor. Cooled combustion products are not available at combustor pressure, and turbine exit gas
at high temperature cannot easily be cooled for introduction into the compressor inlet.
Reduction of CO, HC, and Odor
CO, HC, and odor are products of incomplete combustion emitted from aircraft gas
turbines at the low power settings used for idle and taxi operation; emission of these pollutants
is minor at cruise and take-off power levels. At low power settings, fuel flow rates are very low
and fuel atomization is marginal, which leads to deterioration of combustion. Furthermore, the
primary zone is very fuel lean, with excess air of 200 to 500 percent. This results in the
quenching of partially burned combustion products by dilution with excess air. Finally, tempera-
tures and pressures are low. As shown in Figure VI-2, the combustion efficiency at idle for
various engines ranges from 85 to 96 percent, indicating that from 4 to 15 percent of the fuel
fired is emitted as products of incomplete combustion.
With combustors in present engines, combustion efficiency is near 100 percent over the
important upper part of the operating range where nearly all of the fuel is burned. Any changes
to improve combustion at idle must be such that efficiency at higher loads is not compromised.
The means by which combustion efficiency might be improved at idle are not obvious,
and no research toward such improvement has been carried out. However, it appears desirable to
change the mode of combustor operation in some way to improve the conditions described
abeve. Several ways by which this could be done are:
1. Use variable geometry to reduce air flow into the primary zone at
reduced power settings, maintaining nearly stoichiometric fuel-air
ratios over the load range.
2. Change the fuel system to permit fuel admission through a limited
number of fuel nozzles at idle, so that each fuel nozzle would admit
sufficient fuel for good atomization, and the combustion region at
each fuel nozzle would be large enough for good combustion
efficiency. The fuel system could operate on alternate fuel nozzles at
low loads, for example, and all fuel nozzles would open at a higher
power setting. A change of this type is most suitable for annular
combustors; it would require alteration of the fuel control and fuel
manifolds.
3. Utilize air atomization at low loads to improve fuel atomization.
It would be difficult to justify the cost and complexity of a variable-geometry primary-
zone air control for aircraft gas turbines, but fuel-system modifications, if effective, could
probably be justified. Industrial gas turbines, in general, operate very little at idle and low power
settings, and emissions at these conditions are not significant. Finally, automotive gas turbines,
being highly regenerated and utilizing air atomization of fuel, have achieved acceptable levels of
CO, HC, and odor emissions. Although they use only one fuel nozzle, the concept of variable-
air-admission geometry could be used to improve both idle emissions of CO and HC and
high-power-Ievel emissions of NOx'
-------
VI-12
EXTERNAL-COMBUSTION ENGINES
Two types of external combustion engines are of interest for possible future application
to passenger automobiles: the Rankine-cycle engine and the Stirling-cycle engine. The Rankine
cycle is a vapor cycle with an organic liquid or water as the working fluid. The Stirling cycle is a
gas cycle with compressed gas as the working fluid. Both have the potential characteristic of very
low pollutant emissions.
The incentive for development of external-combustion engines and the automotive gas
turbine is the potential low emission of air pollutants by such engines. At the present time the
automobile is the source of about 60 percent by weight of all pollutant emissions, so that any
change that significantly reduces the emissions from automobiles will have a major impact on
air pollution.
Table VI-4 summarizes the incentives for continuous-combustion automotive engine R&D.
The emission levels that appear probable for an improved automotive gas turbine represent a
reduction of 90 percent below emissions of 1970 vehicles. The possible emission levels from an
ultimate external-combustion engine may represent a 95 to 98 percent reduction.
Table VI-5 summarizes the present status of emissions from continuous-combustion
automotive engines, and compares them with emissions for 1970 vehicles and 1976 standards for
automotive engines. Those emissions that exceed the 1976 standards are underlined for easy iden-
tification. The table shows that NOx levels are generally higher than the 1976 standards, although
HC and CO emission standards are met by most engines.
Table VI-4. Incentives for Development of Continuous-Combustion Automotive Engines
1970 Vehicle, Federal 1976 Improved Ultimate External
Pollutant 1972 Procedure Standard Gas Turbine* Combustion Engine*
HC, g/mi 4.6 0.46 0.22 0.1
% reduction 90 91 95
CO, g/mi 47 4.7 2.4 0.4
% reduction 90 90 98
NOx, g/m 6.0** (0.4)*** 1.0 0.3
% reduction 93 83 95
*Battelle estimate.
** Representative value; no Federal standards are applicable.
***Not established yet but expected to be 0.4 to 0.5 9 per mi.
-------
VI-13
Table VI-5. Emissions from Present Conventional and Unconventional Automotive Engines
ppm g/mi
HC CO NOx HC CO NOx
Uncontrolled I C engine 900 3.5% 1500 11.5 80 5-6
1970 IC engine, 1972 procedure 4.6 47 6-7*
FEDERAL 19761C ENGINE STANDARDS 0.46 4.7 (0.40)**
Automotive Gas Turbines
General Motor GT-309 Technology( 16)
280 hp test data - standard burner - - - 0.29 2.5 3.75
-
lean burner - - - 0.34 7.4 2.25
130 hp simulation - standard burner - - - 0.12 1.0 2.80
lean burner - - - 0.15 2.9 1.75
Chrysler field-trial model A-831 (12) - - - 0.32 23.5 1.9
- -
Automotive Rankine-Cycle Engines
General Motors SE-101 vehicle(17) - - - 1.0 8.0 2.2
- - -
General Motors SE-124 vehicle(17) - - - 0.3 1.0 1.7
-
Marquardt laboratory combustor(18) 10 120 120 - - -
TECD auto design study(19) 15 60 40 0.05 0.35 0.25
1923 Doble(17) - - - 1.4 3.9 2.0
-
Automotive Stirling-Cycle Engines
Philips 80-hp Stirling-cycle engine(20)
Without exhaust gas recirculation I - 79 107 - - -
With 33 percent exhaust gas recirculation - 122 40 - - -
General Motors Stir-Lee I Hybrid Cart20) 1-2 100-200 550-1100 0.1 1.0 2.6
-
General Motors 10-hp Stirling engine(20)
Full load: Air-fuel ratio 25 2.0 30 500 - - -
Air-fuel ratio 20 1.0 40 1050 - - -
Half load: Air-fuel ratio 40 0.6 40 130 - - -
Air-fuel ratio 20 2.0 130 750 - - -
*Battelle estimate.
-------
VI-14
RANKINE-CYCLE ENGINES
The RankiI;e-cycle engine is considered to have great promise as a potential replacement
for the automotive gasoline engine because it can bum fuel continuously at atmospheric pressure
under carefully controlled conditions. It is reasoned that these combustion conditions are
conducive to the lowest practical1evel of emissions of NOx, CO, and HC.
However, development of Rankine-cycle engines suitable for future automotive applica-
tion has just begun, and the desired low emission levels have not been demonstrated over the
range of conditions encountered in an automotive application. Accordingly, APCO is proceed-
ing with an extensive R&D program to develop the technology needed for advanced Rankine-
cycle engines and, eventually, to develop complete automotive propulsion systems. The combus-
tion system for the Rankine-cycle engine must meet particularly demanding requirements.
Combustion-System Requirements
The important design criteria that must be met by a Rankine-cycle combustion system
include the following:
. Wide turn-down range
. Compact design
. Low noise level
. Moderate pressure drop
. Very low emissions of NOx, CO, HC, smoke, and odor
. Simple and practical control systems
. Suitability for widely available fuels.
Wide turn-down range is a particularly important aspect of any automotive engine. It is
estimated that the idle fuel-consumption rate for an automotive Rankine-cycle engine will be
only 1 to 3 Ib fuel per hr, and the full-load rate will be about 100 Ib per hr, for a turn-down ratio of
30: 1 to 100: 1. At the present time, no known burner will operate over a 100: 1 turn-down ratio,
and it is expected that development of a low-emission burner for such a turn-down range will
require a considerable extension of technology. Although many continuous-combustion systems
operate with very low emission levels at one firing rate, the development of a wide-range burner
having low emission levels at all firing rates will be a difficult task.
Alternatively, an on-off burner control system might be used, or a burner might be
modulated through a part of the operating range, with on-off control for the lowest power levels.
The important criteria for on-off control are the frequency of cycling, which depends upon
boiler heat-storage capacity, and the effects of on-off transients upon emissions. It is now
popular to propose boilers of minimum size, weight, and cost, having virtually no internal water
storage. These boilers have low heat-storage capacity and are, thus, suitable only for use with a
highly responsive modulating burner and controls. The addition of boiler water-storage capacity
can increase the heat storage and lengthen the cycling periods for on-off burner operation at the
expense of added size and weight, and of slower start-up.
-------
VI-IS
Compact design is required to minimize overall engine size. A heat-release rate of
1,500,000 Btu per ft3-hr, requiring a volume of 1.3 ft3, has been specified by APCO as being
desirable for automotive power plants. This heat-release rate appears reasonable with moderate
pressure drop.
Pressure drop for the Rankine-cycle burner must be moderate, at about 12 in. wg or less,
to limit fan power consumption to a reasonable value of about 1.5 hp. With this pressure level at
full load and a minimum pressure drop of about 0.5 in. wg, a turn-down ratio of 5 can be
obtained with a conventional burner. Additional turn-down would require either variable
geometry, variable fuel-air ratio, on-off operation, or other unconventional features.
Noise level is higWy dependent upon burner pressure drop and should be acceptable with
the above limit on pressure drop.
The emission levels of NOx, CO, HC, smoke, and odor will depend greatly upon details
of design and operation. It appears necessary that: (1) a hot, intense flame be developed at all
firing rates from 1 lb per hr to 100 lb per hr, (2) that fuel-air ratio be controlled closely, and (3)
that excessive flame temperature at high firing rates be avoided - either by use of boiler cooling
surface to limit flame temperature, by control of fuel-air ratio for lean operation, or by
two-stage combustion. Exhaust-gas recirculation is another technique that can be used to reduce
NOx emission. Fuel atomization and distribution within the combustion space have a significant
influence upon emission levels.
A practical detail of great importance is the means of control of fuel and air flow rates.
It will be necessary for a control system to regulate the fuel flow and the air flow to the burner
in exactly the right quantities to meet driver demands.
Finally, the fuel to be burned must be one that can be made available in great quantities
to the motoring public. Fortunately, a continuous-combustion system does not require high-
octane fuels, and simple wide-boiling-range distillate mixtures can be burned.
Emission levels of Reported Rankine-Cycle
Combustion Systems
Emission levels for four Rankine-cycle combustion systems are known to have been
published. Three Rankine-cycle automobiles have been operated over the 7-mode cycle by General
Motors(17), and an experimental low-emission combustion system has been tested by Marquardt
under a NAPCA contract(18). Emission levels for these combustion systems are included in Table
VI-5.
The two General Motors vehicles were considerably different in design and operation. The
S£-lOl engine, built by the GM Research Laboratory and tested in a 5500-1b vehicle, utilized very
high combustion intensity, at 3.75 x 106 Btu perft3-hr. It employed a fixed-geometry burner and a
modulating control system. The combustion control was based upon driving the fuel pump,
combustion-air fan, and feed water pump by the expander through a two-speed drive. The low
drive speed was about adequate for steady-state operation, and high drive speed provided for
acceleration. A two-step fuel-nozzle bypass control regulated the outlet steam temperature. The
-------
VI-16
air-fuel ratio at the burner was 25: 1 at high fuel flow and 35: 1 at low fuel flow. On-off control
was used as neede£. The pollutant emissions from this burner, shown in Table VI-5, were
considerably higher than the 1976 standards.
The General Motors SE-124 vehicle incorporated a boiler built by Besler Developments, for
which the combustor heat-release rate was 0.95 x 106 Btu per ft3-hr. As used in a 3500-lb vehicle,
emission levels were lower than for the SE-10l, as shown in Table VI-5. However, NOx emissions
exceeded the 1976 standards by a factor of 4.
The Marquardt combustion system was operated only at high firing rates with no attempt
to obtain the turn-down range required by an operating engine. Under the test conditions the
emission levels were extremely low. Thermo Electron Corporation (TECO) has used the
Marquardt results in a design study of a Rankine-cycle passenger car(19) and results are shown in
Table VI-5. Emission levels calculated for all pollutants were far below the 1976 standards. How-
ever, these results make no allowance for on-off operation or for a wide turn-down range, either of
which would increase emission levels.
The excellent low-emission performance of the Marquardt experimental burner demon-
strates that extremely low emission levels are possible under ideal conditions. It appears probable
that, with sufficient R&D, a fully modulated combustion system meeting Federal 1976
emission standards can be developed.
STIRLING-CYCLE ENGINES
In the Stirling-cycle engine, a gaseous working fluid is heated in a heat exchanger fired by
an external combustor. The exhaust from this heat exchanger is very hot at about 1400 F, and a
regenerator is used to recover part of the exhaust heat and improve thermal efficiency. In this
regenerator, the combustion air is heated to 1000 F or more.
The combustion-system requirements for the Stirling-cycle engine are similar to those for
the Rankine-cycle engine as discussed above. However, the use of highly preheated combustion
air increases adiabatic flame temperature and the potential for NOx emissions.
Stirling-cycle engines have been under development for more than 30 years by the N. V.
Philips Research Laboratories of The Netherlands, and more recently, by General Motors under
license to Philips. A recent paper(2l) discusses emission levels from a 10-hp General Motors engine
and an 80-hp automotive engine developed by Philips. Results, including interpretation in terms of
automotive application, are summarized at the bottom of Table VI-5. The Philips unit emitted
79 ppm of CO and 107 ppm of NOx with normal firing. When exhaust-gas recirculation, at 33
percent, was introduced, emission concentrations changed to 122 ppm CO and 40 ppm NOx.
The General Motors Stir-Lec I was a hybrid car utilizing the 10-hp GM Stirling engine in
combination with a battery and electric drive system. The Stirling engine drove an alternator to
charge the battery and power the electric drive motor. Emission characteristics of the car are
shown in Table VI-5.(20) The emission levels for HC and CO were below Federal 1976 standards,
but NOx was high by a factor of 6.
-------
VI-17
The 10-hp General Motors unit was shown to be sensitive to fuel-air ratio and to air
preheat temperature. As shown in Table VI-5, HC concentration was very low, at 0.6 to 2 ppm;
CO concentration varied from 30 to 130 ppm under different conditions, and NOx was high, at
130 to 1050 ppm.
It appears probable that an automotive Stirling-cycle engine could meet the Federal 1976
emission standards, based upon the low emission of NOx shown for the Philips engine with
exhaust-gas recirculation, although the General Motors results without this feature show excessive
NOx emissions.
SUMMARY OF CURRENT AND RELEVANT
COMBUSTION R&D
Table VI-6 summarizes current combustion R&D for continuous-combustion engines. All
of the projects listed are related to either gas turbines or Rankine-cycle engines.
Most of the gas-turbine research is related to reduction of emission of smoke or of NOx
and to development of techniques and instrumentation for emission measurements; this work is
supported or planned by APCO, FAA, and the USAF Aero Propulsion Laboratory. As a
continuing effort, emission data are to be taken for all future combustor tests at the NASA
Lewis Research Center, and it is expected that this will eventually provide sufficient data to
permit parametric analyses of design variables in terms of pollutant emissions.
The R&D related to low-emission combustion systems for Rankine-cycle engines are those
projects supported by NAPCA.
R&D NEEDED TO FILL GAPS IN TECHNOLOGY
The R&D needed to fill technological gaps related to continuous-combustion engines is of
two types:
. Long-range fundamental research that will provide guidance regarding
physics and kinetics of combustion, and the factors influencing
fonnation and decomposition of various pollutants. (Such studies are
discussed in Chapter VIII.)
. Short-range applied research to develop low-emission combustion
systems to meet immediate needs.
It appears that fundamental research will require many years, and that results will not assist
greatly in immediate short-range applied research. However, it is to be expected that the
fundamental information and understanding of combustion pollutant fonnation developed will
eventually guide future applied research.
-------
Table VI-G. Current Combustion R&D - Continuous-Combustion Engines
Sponsoring
Project Organization Principal
Key Project or Contract Title and Contract No. Research Organization Investigator Objective or Scope Funding, $
VI-a Study of continuous flow combustion NAPCA-DMVR&D Marquardt Co. C. V. Burkland Develop low-emission burner for external- 96,683 (FY '69)
systems for external combustion vehicle CPA 22-69-128 Van N uys, Cal if. combustion vehicle power plants
power plants
.
VI-b Development of low-emission burner for NAPCA-DMVR&D Solar Div. W. Compton Develop low-emission burner for Rankine 151,254 (FY 70)
rankine cycle automobile engine EHS 70-106 I nternat. Harvester cycle engines
San Diego, Calif.
VI-c Development of low-emission burner for NAPCA-DMVR&D Battelle Mem. Inst. H. R. Hazard Develop low-emission burner to Rankine 93,300 (FY '70)
rankine cycle automobile engine EHS 70-117 Columbus Lab. cycle engines
Columbus, Ohio
VI-d Evaluation of low-emission burner for NAPCA-DMVR&D Paxve, Inc. Mr. Zwick Develop low-emission burner to Rankine 73,000 (FY '70)
ran kine cycle automobile engine EHS 70-125 Newport Beach, Calif. cycle engines
VI-e Develop sampling system and measure NAPCA Williams Res. Corp. H. B. Moore 45,000 (FY '69)
exhaust emissions from contractor's CPA 22-69-84 Walled Lake, Mich.
gas turbine engines
VI-f Design criteria for reduction of NOx NAPCA-DMVR&D Northern Res. & E ngr. R. Fletcher Develop design parameters for control of 97,800 (FY '70) <:
emissions from aircraft turbojet & FAA Corp. C. Bastress NOx emission from high-pressure-ratio 'i'"
-
engines Cambridge, Mass. gas turbine-combustors 00
VI-g Study of emissions from high inlet NAPCA Not selected
temperature gas turbines E-HSD 71-Neg. 50
Vi-h Low NOx emission combustor for NAPCA Not selected Develop design data and criteria for auto-
automobile gas turbine-engines E-HSD 71-Neg. 104 motive gas turbine combustors to meet
1980 emission goals
VI-i Design criteria for reduction of CO and FAA
UHC emissions from aircraft turbojet
engines
VI-j Study of the visibility of exhaust smoke NAPCA-DMVR&D liT Res. Inst. M. Jackson 91,000 (FY '69)
from aircraft engines & FAA Chicago, Illinois J. Stoc kham
VI-k Parametric study of combustor design NASA NASA H. Childs 15,000 (FY '70)
variables and their relation to pollutant Lewis Res. Ctr.
emissions from aircraft gas turbines Cleveland, Ohio
VI-I Reduction of CO and UHC emissions U.S. Air Force Study mechanisms and develop new
from aircraft turbojet engines Aero Propulsion Lab. designs to reduce CO and UHC
emissions at low power
VI-m Fuel additives to reduce NOx emissions U.S. Air Force - (FY 71)
-------
Table VI-G.
(Continued)
Project
Key
Project or Contract Title
Sponsoring
Organization
and Contract No.
Funding, $
Principal
Investigator
Research Organization
Objective or Scope
VI-n
Develop procedures and equipment, con-
struct mobile measurement system
VI-o
VI-p
VI-q
VI-r
VI-s
VI-5
Turbine engine exhaust emission
measurement
U.S. Air Force
Aero Propulsion Lab.
Turbo propulsion augmenter exhaust
emissions
U.S. Air Force
Aero Propulsion Lab.
Develop 3500 F sampling system and
measure emissions from afterburner
- (FY 71)
J79 engine low-smoke combustor
development
U.S. Air Force
Aero Propulsion Lab.
General Electric Co.
Flight Propulsion Div.
Cincinnati, Ohio
D. W. Bahr
1,000,000'
Development of instruments and pro-
cedures for measuring gaseous pollutants
from aircraft turbine engines
Soc. Auto. Engr.
Soc. Auto. Engr.
Committee E-31
Phillip Sallee, Ch.
American Airlines
;$
I
-
\0
Development of low-smoke combustors
for JT8D. JT3 and J54 engines
Pratt & Whitney Aircraft
East Hartford, Conn.
J. J. Faitani
6,000,000'
Research into the reduction of noise
and smoke from gas turbine engines
National Gas Turbine
Establishment
Pyestock. Farnborough
Hampshire, England
Studies of the reduction of smoke and
nitrogen oxides and unburned fuel
emissions from jet engi nes by means
of mechanical modifications and fuel
additives
Rolls-Royce, Ltd.
Scientific Development
Labs.
Derby, England
P. Walker
-------
VI-20
The immediate short-range problems that require attention include the following:
. Dev~lopment of gas-turbine combustors that emit less NOx than
current combustors.
. Development of new combustor concepts to greatly reduce the emis-
sion of HC, CO, and odor at idle and low-power settings
. Development of low-emission combustors for the special conditions
encountered in automotive gas turbines.
. Development of special low-emission combustors for automotive
Rankine-cycle engines having the wide turn-down range needed for
such application.
R&D OPPORTUNITIES RECOMMENDED FOR THE 5-YEAR PLAN
Five R&D opportunities related to continuous-combustion engines are recommended for
the 5-Year Plan. All of these are short-range applied R&D projects to develop low-emissions
combustion systems. Three of these are aimed at reduction of emission from aircraft and
industrial gas turbines, one is for development of a low-emission combustor for automotive gas
turbines, and one is for development of low-emission combustors with wide turn-down range for
automotive Rankine-cycle engines. Recommended R&D opportunities are as follows:
Aircraft and Industrial Gas Turbines
VI-I. Primary-zone design to reduce NOx emission
VI-2. Secondary-combustion and dilution zone design to reduce NOx
VI-3. Criteria for reduction of CO, HC, and odor at idle and low power
Automotive Gas Turbines
VI-4. Development of a low-emission automotive-size gas-turbine com-
bustor prototype
Automotive Rankine-Cycle Engine
VI-5. Development of low-emission combustors for Rankine-cycle auto-
motive engines.
The R&D opportunities designated VI-I, VI-3, and VI-5 have been identified by APCO as future
areas of research and some projects along these lines are being initiated. It will be noted from
Table VI-6 that both FAA and USAF Aero Propulsion Laboratory are planning research to
reduce emissions from aircraft gas turbines, and coordination of these efforts with APCO efforts
is recommended.
-------
VI-2!
R&D Opportunity: VIol
Related to: V4; VI-2; VIII-I, 25, 26; VI-f, k, h, t
Analytical and Experimental Research on Relation of Gas-Turbine Combustor Primary-Zone Design
to Emission of NOx
Technical Objective and Approach
The objective is the reduction of NOx emission from aircraft and stationary gas turbines.
The approach should consist of analytical modeling of the primary zone to study kinetics and physics of the
flame, followed by experimental confirmation of the model and determination of experimental coefficients. The
principles and general design guidelines developed should be investigated using an existing engine. However, this
experimental combustor need not meet all usual operational requirements, but simply provide realistic primary-zone
mixing, turbulence, pressure, and temperature conditions. Specific design criteria should be formulated on the basis
of analytical and experimental results.
Rationale and Incentive
Some turbojet engines emit rather low levels of NOx while others emit very high levels. It is believed that the
NOx level is dependent upon the primary-zone equivalence ratio and upon the completeness of mixing, but the
optimum equivalence ratio for different operating pressures and inlet-air temperatures is not known. It is anticipated
that mathematical modeling of primary-zone physical conditions and kinetics will permit study of these factors and
guidance toward development of future combustors.
Work in this area is already in progress under an FAA contract with joint APCO funding.
Estimated R&D Cost & Time
R&D Cost Range, 1000's: $200-$400
R&D Time Range: 2-3 years
Recommended 5-year Funding, 1000's: $400
Funding by Fiscal Year, $1oo0's
'69-70 I ~
X 200
'72
200
'73
'74
'75
'76+
Evaluation
Sources Affected: Stationary and Aircraft Gas Turbines
Relative Potential Benefit (overall rating): Medium Low
Pollutants Affected
CP
CO
HC
PNA
Odor
NOx
Lead
SOx
Ash
~
---
--
% Reduction, Range
Expected
Fraction of ECC Emissions Affected
Noncombustion Controls Factor
Relative Potential Benefit Factor
30-50
47
0.034
o
1.60
1.60
Implementation Time, years: 3-5
most likely: 4
Relative Implementation Cost: Very Low
Relative Priority Rating: C
-------
VI-22
R&D Opportunity: VI-2
Related to: VI-I; VIII-I, 25, 27; VI-f, k, h, t
Analytical and Experimental Research to Explore Relation of Gas-Turbine Secondary-Combustion-
and Dilution-Zone Design to NOx Emission
'Technical Objective and Approach
The objective is to explore the relation of secondary-combustion and dilution-zone design to emission of NOx'
The approach should include using an analytical model relating local temperatures, oxygen concentrations, and
mixing conditions to residence time for various geometric assumptions together with suitable kinetic equations for
study of the formation and decomposition of NOx' This should be followed by an experimental study to confirm
results of the analytical study and to develop design criteria and experimental coefficients for future application in
the analytical design of combustors.
Rationale and Incentive
In the gas turbine combustor, combustion can be carried out with a deficiency of air in the primary zone and
addition of secondary air to complete the combustion in a secondary zone, with subsequent addition of dilution air
to reduce gas temperature to the range of 1500 to 2500 F. It is believed that the emission of NOx, CO, and smoke
can be influenced by the dilution ratios, residence time, and mixing characteristics of the secondary and dilution
zones, in which combined residence time is less than 10 milliseconds. Optimum design should minimize emission of
NOx' CO, and smoke.
Estimated R&D Cost & Time
R&D Cost Range, 1000's: $300-$500
R&D Time Range: 2-3 years
Recommended 5-year Funding, 1000's: $500
Funding by Fiscal Year, $1OO0's
'69-70 12! '72
100 200
'73
'74
'75
'76+
200
Evaluation
Sources Affected:. Stationary and Aircraft Gas Turbines
Relative Potential Benefit (overall rating): Low
Pollutants Affected
CP
co
HC
PNA
Odor
NOx
Lead
SOx
Ash
~
--
--
% Reduction, Range
Expected
Fraction of ECC Emissions Affected
Noncombustion Controls Factor
Relative Potential Benefit Factor
0-30
15
0.034
o
0.51
0.51
Implementation Time, years: 3-5
most likely: 4
Relative Implementation Cost: Very Low
-------
VI-23
R&D Opportunity: VI-3
Related to: VI4; VIII4, 6, 9,17,25,26; VI-i, k, 1
Analytical and Experimental Research to Develop Criteria for Reduction of CO, HC, and Odor
EmissioJ1s From Aircraft Gas Turbines at Idle and Low Power
Technical Objective and Approach
The objective is to devise means of improving combustion efficiency and reducing emission of unburned
hydrocarbons at idle and low power without compromising performance at higher power levels.
The approach should include analytical consideration of physical changes to alter distribution of fuel in the
primary zone at low loads to provide greater concentration of combustion in locally rich zones (including one or
more fuel nozzles) or by utilizing variable-geometry concepts to reduce air flow into the primary zone at low loads
and thus avoid excessively lean combustion conditions. Satisfactory concepts must be suitable for practical
application to aircraft combustors, considering weight, simplicity, and reliability. An experimental program is also
recommended.
Rationale and Incentive
The design of the primary zone for an aircraft gas turbine is such that fuel-air ratios vary over a range of about
5:1 between idle and full-load operation. This results in very lean combustion conditions at low loads, with
relatively poor combustion efficiency and high emission levels of partly burned fuel. The low efficiency is believed
to result from quenching of the flame with cold air before combustion is completed, due to the lean conditions.
This problem is most important with aircraft gas turbines, which are of large size and spend considerable ground
time at idle and taxi conditions. This creates odor problems in aircraft areas. A successful program should result in
elimination of most of the exhaust odors, unburned hydrocarbons, and CO associated with airport operations.
Demonstration of successful combustion modifications under laboratory conditions should lead to their application
in future engines and, possibly, development of retrofit fuel system modifications for current engines.
Work in this area is planned for FY '71 by the FAA and by the USAF Aero Propulsion Laboratory.
Estimated R&D Cost & Time
R&D Cost Range, 1000's: $450-$650
R&D Time Range: 2-3 years
Recommended 5-year Funding, 1000's: $650
Funding by Fiscal Year, $1 COO's
'69-70 I ~
250
'72
200
'73
200
'74
'75
'76+
Evaluation
Sources Affected: 90 Percent of Aircraft Gas Turbine Emissions of CO, He, and Odor
Relative Potential Benefit (overall rating): Medium
Pollutants Affected
CP
co
HC
PNA
Odor
NOx
Lead
SOx
Ash
L
---
--
% Reduction, Range
Expected
Fraction of ECC Emissions Affected
Noncombustion Controls Factor
Relative Potential Benefit Factor
Implementation Time, years: 3-5
50-80 50-80
68 68
.0086 .019
o 0
0.58 1 29
50-80
68
.076
o
5.17
7.04
most likely: 5
Relative Implementation Cost: Low
-------
VI-24
R&D Opportunity: VI.4
Related to: VI-I, 2, 3,; VlII-25, 26; VI-f, h, i, k, 1, t
Development of a Lo~-Emission Automotive-Size Gas-Turbine Combustor Prototype
Technical Objective and Approach
The objective is the development of a prototype combustor for an automotive gas turbine that meets Federal
1976 emission standards.
The approach should include utilizing the best currently available knowledge regarding the influence of
combustor design upon emissions to develop a low-emission automotive gas turbine combustor. This may necessitate
the introduction of new hardware concepts such as variable geometry.
The combustor must meet all performance and operational requirements of a production model automotive gas
turbine and should be installed in a suitable turbine for demonstration purposes. Heavy-duty automotive gas
turbines, suitable for buses and trucks, are now near introduction, and production models should be available at the
end of the program for experimental investigation of the applicability of these design criteria.
Rationale and Incentive
In the development of past automotive gas-turbine combustors, minimum emissions of NOx and unburned
hydrocarbons have not been primary performance requirements. Nevertheless, emission levels of current gas turbines
approach the proposed 1976 emission standards, and it appears probable that considerably lower emission levels can
be achieved. The present automotive gas-turbine designs include effective regenerators, leading to very high
combustor flame temperature and high (by 1976 standards) NOx emission levels. Thus, it may be necessary to
introduce rather different design concepts to meet NOx emission standards.
Estimated R&D Cost & Time
R&D Cost Range. 1000's: $400-$800
R&D Time Range: 2-4 years
Recommended 5-year Funding, 1000's: $800*
Funding by Fiscal Year, $1oo0's
'69-70 12!
200
'72
200
73
200
'74
200
'75
76+
Evaluation
Sources Affected: Mobile Gasoline Engines
Relative Potential Benefit (overall rating): Very High
Pollutants Affected
CP
CO
HC
PNA
Odor
NOx
Lead
SOx
Ash
~
--
--
% Reduction, Range
Expected
Fraction of ECC Emissions Affected
Noncombustion Controls Factor
Relative Potential Benefit Factor
90-95 85-91 85-91
94 89 89
.096 .48 .34
.5 .8 .8
4.51 8.54 6.05
60-90 100
78 100
25 .59
2 .8
15.60 - 11.80
Ralativa Implementation Cost: High
46.50
I mplementation Time, years: 8-12
most likely: 10
-------
VI-25
R&D Opportunity: VI-S
Related to: VlII-2S, 26; VI-a, b, c, d
Development of Low-Emission Combustors for Rankine-Cycle Automotive Engines
Technical Objective and Approach
The objective is the development of one or more demonstration models of combustion systems suitable for
application to automotive Rankine-cycle engines.
The approach should include both analytical and experimental work and should be heavily hardware oriented.
It is anticipated that, in the near future, various new concepts for such combustion systems will be suggested. The
most promising of these should be evaluated and, if warranted, work should be carried through an exploratory
development phase. The technology developed during this program should provide the technical base for future
development and application of Rankine-cycle automotive engines.
Rationale and Incentive
The low-emission Rankine-cycle combustor must operate over a turndown range much wider than that of any
currently available burner: a turn-down ratio of 100: I to 30: 1, depending upon engine application details. No
burner meeting this turndown requirement with low emissions has yet been demonstrated, and this appears to be a
key element in the success of any future Rankine-cycle automotive application. This requirement, plus the added
requirements of compactness, low noise level, and moderate power demand for the combustion-air fan and fuel
pump, add up to a difficult and challenging development opportunity that will require a considerable extension of
the current state of art of burner technology. With satisfactory development, it should be possible to meet or exceed
the Federal 1976 automotive emission standards.
Work in this area has been started under several AFCO contracts.
Estimated R&D Cost & Time
R&D Cost Range, 1000's: $600-$1,200
R&D Time Range: 2-4 years
Recommended 5-year Funding, 1000's:
$1,200
Funding by Fiscal Year, $1OO0's
'69-70 12! '72 '73
X 500 300 200
'74
200
'75
'76+
Evaluation
Sources Affected: Mobile Gasoline Engines
Relative Potential Benefit (overall rating): Very High
% Reduction, Range
Expected
Fraction of ECC Emissions Affected
Noncombustion Controls Factor
Relative Potential Benefit Factor
90-95 90-98 90-95
94 94 93
0.79 .35 .26
.5 .8 .8
3.71 6.58 4.84
CP CO HC PNA Odor NOx Lead SOx Ash ~
- -
90-95 100
93 100
.20 .49
.2 .8
14.88 9.80 39.81
Relative Implementation Cost: High
Pollutants Affected
---
Implementation Time, years:
10-15 most likely: 12%
-------
VI-26
R&D Opportunity: VI-New Concepts
Provision for Exploripg New Concepts and New R&D Opportunities that Evolve from the Program,
Accelerating Promising R&D, or Conducting Demonstrations of Promising Concepts for Reducing
Emissions from Gas Turbines and External-Combustion Engines by Combustion Modification
Technical Objective and Approach
The objective is to provide for long-range flexibility in the R&D program to enable APCO to take advantage
of opportunities that are not presently evident, but which can arise during the course of this program.
The approach should be to make specific provisions in the R&D program to explore the feasibility of new and
novel concepts and to accelerate research, development, and demonstration of promising concepts for reducing
emissions by combustion-process modification. Worthwhile ideas for combustion-process modification to reduce
emissions from gas turbines and external-combustion engines might originate as the result of novel design concepts
or through in-depth understanding derived from well-planned R&D. The merits of specific R&D opportunities
should be decided by evaluating the particular concepts as they evolve.
Rationale and Incentive
Reduction of emission levels from gas turbines and external-combustion engines will be a continuing goal,
especially if such engines are applied to passenger automobiles. It is probable that, as presently foreseeable
improvements are implemented, other opportunities for combustion modification to reduce emissions will become
evident.
Recommended Funding Allocation
71
'72
100
'73
150
'74
150
'15
200
5-year Funding, 1000's: $600
Funding by Fiscal Year, $1000's
Evaluation
This R&D Opportunity is unranked. Potential benefit, implementation time, implementation cost, and funding level for
each specific opportunity must be evaluated when the opportunity is identified. The suggested funding level anticipates
effort on several R&D opportunities.
-------
TABLE VI-7. SUMMARY BY PRIORITIES
CONTINUOUS-COMBUSTION ENGINES - GAS TURBINES AND EXTERNAL-COMBUSTION ENGINES
Relative Current Estimated R&D Costs, $1000
Priority R&D Opportunity APCO By Fiscal Years
Rating R&D 5- Year On-Going
Effort '71 '72 '73 '74 '75 Total '76+
-
A VIA Development of a Low-Emission Automotive-Size Gas-Turbine - 200 200 200 200 - 800 -
Combustor Prototype
A VI-5 Development of Low-Emission Combustors for Rankine-Cycle X 500 300 200 200 - 1,200 -
Automotive Engines - - - - -
Totals, Priority A 700 500 400 400 2,000
B VI-3 Analytical and Experimental Research to Develop Criteria for - 250 200 200 - - 650 -
Reduction of CO, HC, and Odor Emissions From Aircraft
Gas Turbines at Idle and Low Power
C VI-I Analytical and Experimental Research on Relation of Gas- X 200 200 - - - 400 -
Turbine Combustor Primary-Zone Design to Emission of NOx
D VI-2 Analytical and Experimental Research to Explore Relation of - 100 200 200 - - 500 -
Gas-Turbine Secondary-Combustion- and Dilution-Zone
Design to NOx Emission
N VI-N Provision for Exploring New Concepts and New R&D Oppor- - - 100 150 150 200 - 600 -
tunities that Evolve From the Program, Accelerating
Promising R&D, or Conducting Demonstrations of Promising
Concepts for Reducing Emissions From Gas Turbines and
External Combustion Engines by Combustion Modification
Totals, AU Priorities 1,250 1,200 950 550 200 4,150
:$
I
N
-------
VI-28
REFERENCES FOR CHAPTER VI
1.
Nature and Control of Aircraft Engine Exhaust Emissions, Northern Research and Engi-
neering Corporation, Report No. 1134-1, prepared for NAPCA under Contract No. PH
22-68-27 (November, 1968).
2.
Bastress, E. Karl, "Nature and Control of Aircraft Exhaust Emissions", presented at 62nd
Annual Meeting, Air Pollution Control Association (June, 1969).
3.
Sawyer's Gas Turbine Catalog, 1968 Edition, Gas Turbine Publications, Stamford,
Connecticut.
4.
Cornelius, W., Stivender, D. L., and Sullivan, R. E., "A Combustion System for a Vehicular
Regenerative Gas Turbine Featuring Low Air Pollutant Emissions", SAE Paper No. 670936,
presented October 30, 1967.
5.
Hazard, H. R., "Combustors", Chapter 5 in Gas Turbine Engineering Handbook, Gas Turbine
Publications, Inc., Stamford, Connecticut, 1966. Second Edition, 1970.
6.
Courtesy Pratt & Whitney Aircraft.
7.
Faitani, J. J., "Smoke Reduction in Jet Engines Through Burner Design", SAE Paper No.
680348 (May 2, 1968).
8.
Bahr, D. W., Smith, J. R., and Kenworthy, M. J., "Development of Low Smoke Emission
Combustors for Large Aircraft Turbine Engines", AIAA Paper No. 69-493, presented at
AIAA 5th Propulsion Joint Conference (June 9-13, 1969).
9.
Gradon, K., and Miller, S. C., "Spey Combustion Development for Military Applications",
ASME Paper No. 68-GT-21, presented at ASME Gas Turbine Conf. (March 17-21, 1968).
10.
Hilt, M. B., Fenimore, C. P., and Johnson, R. H., "Hydrocarbon Combustion Smoke and
Its Elimination from Heavy Duty Gas Turbines", presented at the 1970 Joint Power
Generation Conference, ASME (September, 1970).
11.
Taylor, W. G., Davis, F. F., DeCorso, S. M., Hussey, C. E., and Ambrose, M. J., "Reducing
Smoke from Gas Turbines", Mechanical Engineering (July, 1968), pp 29-35.
12.
Korth, M. W., and Rose, A. H., "Emissions from a Gas Turbine Automobile", SAE Paper
No. 680402 (May, 1968).
13.
"Soot Formation Rates in Premixed C5 and C6 Hydrogen Flames at Pressures Up to 20
Atmospheres", Combustion and Flarrze, 8 (3) (September, 1964).
14.
Starkman, E. S., Mizutani, Y., Sawyer, R. F., and Teixeira, D. P., "The Role of Chemistry
in Gas Turbine Emissions", presented at 1970 ASME Gas Turbine Conference, Brussels (May,
1970).
-------
VI - 29
15.
Time Requirements for Retrofitting Jet Aircraft with Improved Combustor Designs,
Northern Research and Engineering Corp. Report No. 1148-1, prepared for NAPCA under
Contract No. CPA 22-69-90 (July, 1969).
16.
Cornelius, Walter, and Wade, Wallace R., "The Formation and Control of Nitric Oxide in a
Regenerative Gas Turbine Burner", SAE Paper No. 700708, presented September 14-17,
1970.
17.
Vickers, P. T., Haverdink, W. H., Mondt, and Wade, W. R., "General Motors' Steam
Powered Passenger Cars - Emissions, Fuel Economy, and Performance", SAE Paper No.
700670 (August 27, 1970).
18.
Study of Continuous Flow Combustion Systems for External Combustion Vehicle Power-
plants, Marquardt Corporation Report, prepared under NAPCA Contract No. CPA
22-69-128 (June, 1970).
19.
Conceptual Design - Rankine-Cycle Power System With Organic Working Fluid and
Reciprocating Engine for Passenger Vehicles, Thermo Electron Corp. Report No. TE4121-
133-70, prepared under NAPCA Contract No. CPA 22-69-132 (June, 1970).
20.
Lienisch, John H., and Wade, W. R., "Stirling Engine Progress Report - Smoke, Odor,
Noise, and Exhaust Emissions", SAE Paper No. 680081 (January, 1968).
-------
Chapter VII
RECIPROCATING INTERNAL-COMBUSTION ENGINES
Frederick A. Creswick
TABLE OF CONTENTS
SCOPE OF CHAPTER AND BACKGROUND.
. . . .
. . . .
Engine Types
. . . . . .
. . . .
. . . .
Pollutants of Principal Concern. .
. . . . .
. . . . .
EMISSION LEVELS FROM IC-ENGINE COMBUSTION PROCESSES. . . . .
Gasoline Engines. . . . . . . . . . . . . .
Emission Levels for Present-Production Engines .
Emission Levels Attainable With Latest Technology
Emission Goals. . . . . . . . . . . .
. . . . . .
. . . . . .
. . . . . .
Diesel Engines. . . . . . . . . . . . . . .
Emission Levels for Present-Production Engines.
Emission Levels Attainable With Latest Technology. . . . . .
Emission Goals. . . . . . . . . . . . . . . . . .
GAPS IN NEEDED R&D TO REDUCE ENGINE EMISSIONS BY
COMBUSTION-PROCESS MODI FICA TION .
. . . . . .
Gasoline-Engine R&D Gaps.
. . . . . . . .
. . . .
Diesel-Engine R&D Gaps. . . .
. . . . . .
. . . . . . .
SUMMARY OF CURRENT AND RELEVANT COMBUSTION R&D . .
Gasoline Engines
Diesel Engines. .
. . . . . . . .
. . . . .
. . . . . . .
. . . . . . .
. . . . .
Summary of Current R&D
. . . . . .
. . . .
R&D OPPORTUNITIES RECOMMENDED FOR THE 5-YEAR PLAN
. . . .
Summary by Priorities. . .
. . . . . . .
. . . . .
REFERENCES FOR CHAPTER VII
. . . . .
. . . .
. . . . . . .
. VII- 1
- 2
- 4
- 4
4
- 4
- 6
- 7
- 8
- 8
- 8
- 9
- 9
- 9
-12
-12
-12
-13
-13
-21
-33
-------
-------
VII-l
CHAPTER VII
RECIPROCATING INTERNAL-COMBUSTION ENGINES
SCOPE OF CHAPTER AND BACKGROUND
This chapter deals with possibilities for emission reduction by modification of combus-
tion in reciprocating, or piston-type, internal-combustion (lC) engines for both vehicular and
stationary applications. Certain types of rotary IC engines are also included because their
combustion processes are essentially the same.
IC engines are important sources of air pollutants. This is particularly true of the
automotive gasoline engine, both because of the large number of such engines and because they
are, compared with many other combustion sources, heavy emitters of many of the pollutants of
current concern. Table VII-I shows the percentage contribution of gasoline, diesel, and gas
engines to the nationwide total emission of pollutants from all energy-conversion combustion
(ECC) sources.
Table VII-1. Emissions From Reciprocating IC Engines*
Pollutant
Contribution to Nationwide EGG
Emissions, percent
Gasoline Diesel and
Engines Gas Engines
Total
Products of Incomplete Combustion
Combustile Particulate
GO
12 18 30
97 1 98
93 5 98
6 nil 6
39 19 58
Gaseous HC
PNA
NOx
Combustion-Improving Additives
Lead
99
nil
99
Fuel Contaminants
SOx
Ash (Noncombustible Particulate)
<1
nil
nil
1
<1
*Derived from data in Table 11-1.
-------
VII-2
ENGINE TYPES
Two basic "types of IC engines must be considered: spark-ignited gasoline engines and
diesel or compression-ignition engines. Although it is assumed that readers are acquainted with
the basic operation of both engine types, attention is called to some of the more important
characteristics of each.
Gasoline Engines
Three descriptors are often used synonymously to refer to the same type of engine:
gasoline, spark ignited (SI), and Otto cycle. These engines generally use gasoline as fuel, the
fuel-air charge is generally homogeneous, and combustion is spark ignited. There are various
types of these engines that differ in construction, application, and exhaust-emission character-
istics; six types are described below.
The 4-stroke-cycle, multicylinder engine is the most widely used type of gasoline engine
and is available in automotive, industrial, and aircraft versions. Automotive engines are designed
for use in motor vehicles; therefore, light weight, compactness, responsiveness, and capability of
operation over a wide range of speeds and loads are required. Industrial-type engines include
both those with basic automotive configurations and those designed specifically for industrial use
- usually smaller than the automotive types. Applications of industrial-type engines include light
marine propulsion; light farm, construction, and industrial uses; and standby or emergency
stationary power generation. Aircraft reciprocating engines are designed specifically for light
weight, reliability, and operability at various attitudes and altitudes; they are seldom used for
other applications. The combustion process and the emission characteristics of all these engines
are similar.
Single-cylinder 4-cycle gasoline engines are usually built with more rudimentary induction
and ignition systems than the multicylinder engines. Therefore, while the combustion process is
basically the same, the emission characteristics are probably somewhat different because less
control is exerted over air-fuel ratio and ignition timing. These engines are used for garden,
recreational, and very light industrial applications.
Small 2-stroke-cycle gasoline engines have markedly different emission characteristics for
two basic reasons. First, the products of combustion are scavenged out of the cylinder by
unburned air-fuel mixture; because this process is inherently inefficient, some raw fuel finds its
way into the exhaust. Second, lubricating oil is generally mixed with the gasoline, which creates
a characteristic "haze" in the exhaust. In some 2-cycle engines, the lubricating oil is force fed
from a separate reservoir. In either case, the oil or its products of combustion are present in the
exhaust gases. Two-cycle engines are used as outboard motors and for motorcycles, light hand
tools, and garden and very light industrial applications.
Rotary engines such as the Wankel differ somewhat from piston engines in emission
characteristics because of the substantially different shape of their combustion chambers. In
addition, there is a blow-by path past the apex seals directly into the exhaust which is not
present in reciprocating engines (except those with a leaking exhaust valve).
-------
VII-3
Stratified-charge engines are spark ignited, but do not operate with a homogeneous
fuel-air charge. Instead, the fuel is injected in-cylinder in some manner so as to achieve a
localized combustion region in part of the combustion chamber. Such engines are operated
unthrottled over at least part of their load range, and overall fuel-air mixtures are very fuel-lean
at light loads. Some of these engines have a multifuel capability. First-cost considerations have so
far inhibited any general use of this type of engine.
Gaseous-fueled SI engines of various types are in use in small numbers, operating on
natural gas or LPG fuel. Operating characteristics are similar to those of gasoline-fueled engines.
It is possible to run natural-gas-fueled engines exceptionally lean; under these conditions, the
exhaust can be substantially cleaner (and less reactive) than that of gasoline-fueled engines.
In general, the points which will be made in the discussion of gasoline-engine combustion
phenomena are applicable to all types of gasoline engines; however, with 2-cycle and stratified-
charge engines additional factors are significant.
Diesel Engines
Diesels operate on heavier distillate fuels or on residual fuels. Fuel is injected in-cylinder
and the combustion process is heterogeneous and initiated by compression ignition; more
specifically, compression ignition takes place as a result of the high temperature of the air charge
that is produced by the compression process.
Diesel engines are manufactured in a number of varieties; the following paragraphs
describe some of the principal features that characterize them.
Both 2-cyc1e- and 4-cyc1e-type diesels are available; the differences in the combustion
process and the emission characteristics are distinguishable but not markedly different.
Turbocharged diesels use an exhaust-gas-driven dynamic compressor-turbine unit
(turbocharger) to increase the rate of air flow through the reciprocating unit. As a result,
combustion occurs at a higher pressure and generally with a leaner fuel-air ratio than in naturally
aspirated engines. However, mismatches of speed between the reciprocating engine and the
turbocharger during speed/load transients can cause momentary over-rich operating conditions.
Direct-injection diesels have an injector that sprays fuel directly into the cylinder. Usually
the injector is centrally located; the fuel spray pattern is symmetrical; and the piston crown is
contoured to give the desired combustion-chamber shape. Precombustion-chamber diesels have an
ancillary chamber closely connected to the main cylinder. Fuel injected into the precombustion
chamber is expelled at high velocity into the main combustion chamber.
Discussions of diesel-engine combustion that follow in this chapter are generally
applicable to all types of diesel engines.
-------
VII-4
POLLUTANTS OF PRINCIPAL CONCERN
Gasoline-Engine Emissions
The gasoline-engine pollutant emissions of principal concern are CO, HC, NOx, PNA,
lead, and other particulates. Unmodified fuel molecules are a minor constituent of the gaseous
hydrocarbon emissions, which are primarily light paraffins and olefins, along with traces of
aromatics, aldehydes, and other oxygenates. Smoke emissions are not presently of major concern.
Some odor is characteristic of gasoline-engine exhaust; however, this odor is not generally
considered a pollutant of great concern.
Diesel-Engine Emissions
The diesel-engine pollutant emissions of principal concern are smoke, CO, HC, PNA,
odor, and NOx' A large portion of the diesel-engine hydrocarbon emissions are unmodified fuel
molecules. Emissions of CO from diesels are very low compared with the emissions from gasoline
engines. Smoke and odor are highly noticeable and consequently cause public complaint. Since
specifications for sulfur content of diesel fuels are not as stringent as for gasoline, diesels may
emit small amounts of sax; however, these emissions are not presently of great concern.
EMISSION lEVELS FROM IC-ENGINE COMBUSTION PROCESSES
The following discussion summarizes the current state of the art regarding emissions from
IC-engine combustion processes, covering gasoline engines and diesel engines separately.
GASOLINE ENGINES
Emission levels for Present-Production
Gasoline Engines
Gasoline-engine emission levels vary substantially with the mode of operation. It is now
common practice to use composite emission levels averaged over a driving cycle to represent
output of automotive engines. No such practices have been established for the rest of the
gasoline-engine po pula tion.
Emission levels from new automotive engines have been subject to Federal regulation
since 1968; consequently, Federal standards can be used to characterize present emission levels.
These are presented in Table VII-2.
-------
VII-5
Table VII-2. Federal Standards for New Light-Duty Vehicle Emissions*
(g/mj)
Pollutant Pre-1968 1968
Uncontrolled Stds**
HC 11.5 3.3
(900 ppm) (275 ppm)
CO 80 35
(3.5%) (1.5%)
NOx 5.9
(1500 ppm)
Particulate 0.3
1970
Stds
2.2
(180 ppm) ***
23
(1.0%) ** *
*Composite levels for a Federal 7-mode driving cycle.
**Converted to mass emission levels for a 4000-lb vehicle.
***Converted to concentration levels for a 4000-lb vehicle.
Power levels during the Federal 7-mode cycle are below 20 hp; consequently, the values
in Table VII-2 do not represent the emission levels from highly loaded heavy-duty industrial
engines.
Multicylinder industrial engines operating at higher loads generally emit higher concentra-
tions of NOx and somewhat lower He. CO emissions are affected more by fuel-air ratio than by
load; consequently, CO levels are strongly influenced by carburetion. The following tabulation
gives emission levels that are assumed to be characteristic of highly loaded constant-speed
engines.
Emission Levels for Highly Loaded
Constant-Speed Gasoline Engines
Pollutant Concentration Mass, g/hp-hr
HC 100-200 ppm 1.7 - 3.4
CO 1-2% 30 - 60
NOx 2000-4000 ppm 10 20
Emissions of NOx vary with manifold vacuum, compression ratio, ignition timing, and fuel-air
ratio, and they can range as high as 5000 ppm.
No data were found for large industrial types of spark-ignited engines using natural-gas
fuel; however, on the basis of laboratory single-cylinder engine tests( 1), it can be assumed that
NOx emissions may be as high as 10 to 15 g per hp-hr. He and CO emission levels will be
strongly influenced by carburetion.
-------
VII -6
Small crankcase-scavenged 2-cycle engines tend to emit very high concentrations of HC.
In one study of l-cycle motorcycle engines(2), the following composite emission levels were
observed in driving-cycle tests.
Emission Levels for 2-Cycle Engines
in a 7-Mode Driving Cycle
Pollutant Concentration
HC
CO
NOx
2000 . 6000 ppm
1.5 7.5%
100 - 500 ppm
Emission levels Attainable With latest
Technology for Gasoline Engines
Gasoline-engine emission levels attainable with the latest technology are difficult to
estimate for two reasons: (1) the technology has been moving fairly rapidly and (2) engine
manufacturers are hesitant to reveal data or forecasts regarding attainable levels. Further, in
many instances, emission levels can be reduced by compromising performance; in these cases,
attainable levels are set by deciding how large a performance degradation is acceptable.
Hydrocarbons. Emissions of HC can be reduced by combustion-chamber design to
minimize crevices and quench spaces. Moderately lean fuel-air mixtures, retarded ignition timing,
and lower compression ratio also tend to reduce HC emissions, but these involve making some
performance compromises. There are no established minimum levels of HC emission attainable
with present technology; however, concentration levels below 50 ppm are probably attainable
under ideal conditions.
Carbon Monoxide. With respect to CO, single-cylinder studies(3) have demonstrated that
concentration levels on the order of 0.1 percent can be achieved at constant speed with
moderately lean mixtures. There are no established minimum levels of CO emission attainable in
a driving cycle with present technology.
Oxides of Nitrogen. Reductions in NOx emissions of up to 75 percent have been
demonstrated during a driving cycle with the use of exhaust-gas recirculation (EGR), the
resulting composition NOx concentration level being about 400 ppm.( 4) There is, however, some
question as to whether this amount of recycle (about 15 percent) permits satisfactory drive-
ability. Further, EGR can be used only at part-load; therefore, it is less suitable for use with
engines in nonautomotive applications that operate continuously at high load. Emissions of NOx
from highly loaded engines can be reduced to some extent by retarded ignition timing(5), with
some sacrifice in performance.
In general, NOx levels from gasoline engines can be reduced, particularly at part load, but
such reductions involve a trade-off with performance. The optimum trade-off has not been
established.
-------
VII -7
Emission Goals for Gasoline Engines
Goals have been established for composite driving-cycle exhaust emissions from future
automotive-type vehicles. Alternative controls, such as catalytic or thermal reactors, may be more
significant than combustion modifications in meeting these goals.
Several sets of research goals have been used by NAPCA in the past, and Federal
Standards for 1972, 1975, and 1980 light-duty vehicles have been established previously.
However, new Federal Standards for HC, CO, and NOx, established by the 1970 Amendment to
the Clean Air Act, now supersede both research goals and proposed standards previously set by
NAPCA for 1975 and later.
The 1972 standards, as described in the November 10, 1970, Federal Register, are based
on a new driving schedule, a new exhaust sampling procedure, and different instrumentation
from that specified for the 1970 Federal Standards. As a result of these changes, a direct
comparison between standards for 1970 and 1972 is not possible, although conversion factors
have been established.
Federal Standards for 1972 and later are given below, along with a comparison with 1970
standards using DHEW's conversion factors.
Present and Future Federal Standards for Composite Emissions from
Light-Duty Vehicle Engines on a Driving Cycle, g/mi
1970 Vehicle,
Pollutant 1970 Stds 1972 Procedure 1972 Stds 1975 Stds 1976 Stds
HC 2.2 4.6 3.4 0.46 0.46
CO 23 47 39 4.7 4.7
NOx (0.4)
The value shown above for the 1976 NOx standard is in parentheses to indicate that this
standard has not been established as of this writing, but it is expected to be about 0.4 or 0.5 g
per mi. A value of 0.03 g per mi for particulate emissions has been used previously as a 1980
NAPCA goal.
There are no similar standards or goals for gasoline
Combustion modifications or use of control devices developed
may not be feasible for nonautomotive applications.
engines in other applications.
for automotive engines mayor
It would be unrealistic to expect that gasoline-engine emission levels, even with major
combustion-process modifications, could be made as low as those for external combustion units.
However such levels should be considered as a theoretically possible limit.
,
-------
VII-8
DIESEL ENGINES
Emission Levels for Present-Production
Diesel Engines
As with gasoline engines, diesel-engine emissions vary substantially with the mode of
operation. A range of emission levels characteristic of present diesels is given in the following
tabulation.
Characteristic Emission Levels for Diesel
Engines at Constant Speed*(6-9)
Pollutant Idle Full Load
HC. ppm 20 to 300 150 to 1000
CO. percent 0.01 to 0.1 0.03 to 0.3
NOx. ppm 200 to 400 750 to 2500
*Not corrected for C02.
Since the diesel operates typically with fuel-air ratios in the range of 0.01 to 0.05, correction
factors for C02 (Le., for equivalent concentrations at stoichiometric fuel-air ratios) range from
about 1.3 at full power to nearly 10 at idle.
The broad range of emission levels given above reflects the difference in emissions from
different types of diesels: 2-cycle vs. 4-cycle, turbocharged vs. naturally aspirated, and direct-
injection vs. precombustion-chamber injection. An outstanding characteristic of diesel emissions is
the low CO level.
Other highly noticeable characteristics of diesel engines are odor and smoke. Presently,
there are no absolute scales for the measurement of diesel exhaust odor; however, there are a
number of smoke-level ratings available. Diesel engines for motor vehicles are now subject to
Federal regulations which allow:
. 40 percent opacity during the engine acceleration mode
. 20 percent opacity during the engine lugging mode.
Opacity in this instance is measured with the U.S. Public Health Service Smokemeted 1 0)
Emission Levels Attainable With
Latest Technology for Diesel Engines
Recent reductions in diesel engine emission levels have been brought about through
fuel-injector improvements - elimination of fuel dripping from the injector after the main
injection period has been an important factor in direct-injection engines. The effect of such
modifications has been to shift emission levels toward the lower end of the range shown above.
-------
VII-9
. Furt~er reductions in certain emissions, particularly NOx and smoke, are possible by
deratmg engInes. However, manufacturers and users both have had strong incentives not to use
this approach.
Emission Goals for Diesel Engines
Appropriate goals for diesel-engine emissions appear to be the following:
. Elimination of detectable odor and visible smoke
. Reduction of NOx to levels approaching that which would be
obtained by combustion of very lean homogeneous fuel-air mixtures
. No increase in CO levels.
Although there is no firm technical basis on which to demonstrate that these goals are
attainable, there is a rationale for expecting that major improvements are possible: the diesel
operates with moderate to large amounts of excess air with which low smoke and NOx are
achievable in other combustion configurations; also, with a nonpremixed fuel-air charge, wall-
quench effects can ideally be avoided.
Inhomogeneity in the fuel-air charge makes the compression-ignition process feasible but
also results in high smoke, odor, and NOx. A general goal should be to modify the injection-
combustion process as far as possible to minimize the contribution of inhomogeneity to high
emissions.
GAPS IN NEEDED R&D TO REDUCE ENGINE EMISSIONS BY
COMBUSTION-PROCESS MODIFICATION
Gasoline-Engine R&D Gaps
Gasoline-engine combustion is well understood as compared with many other types of
combustion. This is mainly because of the possibility of assuming a homogeneous premixed
fuel-air charge in analytical investigations. The actual mechanism of hydrocarbon-02 oxidation in
gasoline engines is only partly understood; fortunately, however, an understanding of this
mechanism is not presently essential as far as emission reduction problems are concerned. (The
hydrocarbon-02 system has been studied primarily in relation to its influence on preignition,
autoignition, and related phenomena in gasoline engines.)
CO and NO
Satisfactory predictions of the observed levels of CO and NOx in engine exhaust have been
derived on the basis of analytical investigations of the kinetics of the expanding products of
combustion in an engine cylinder by Newhall(ll) and Keck(l2). These investigations covered
-------
VII-I 0
stoichiometric or lean fuel-air ratios. Analytical predictions for fuel-rich mixtures have been less
successful; however,. the CO and NO emissions can be predicted with reasonable accuracy using
the extensive experimental data available. Lack of knowledge about the kinetics of the
HC-02-N 2 system represents a gap in our understanding of gasoline combustion, but such
knowledge does not appear at present to be essential for reduction of emissions.
HC
Unburned HC in the exhaust has been shown to be largely the result of wall quenching
or because of crevices in the combustion chamber where combustion does not take place.(l3-lS)
Investigations of the wall-quench phenomenon( 16-18) have not been completely successful,
although empirical expressions for the appearance of wall-quenched HC as a function of cylinder
temperature and pressure have been derived(lS). Further work on wall quenching appears to be
needed to gain more complete information concerning the effects of engineering and operating
variables on the appearance of unburned HC; however, great reductions in emission levels are not
expected to result from such work.
The potential effect of lubricating oil on cylinder walls on HC emission has been largely
ignored. This has been justified on the basis that oil consumption in modern engines is generally
too low to contribute significantly to HC emissions. However, in light of proposed 1980 auto
standards, emissions derived from lubricating oil could be more significant, particularly if the
response of these emissions to thermal or catalytic reactors is different from that of fuel-derived
exhaust HC.
Particulates and PNA
The characteristics of particulate and PNA emissions and their sources and formation
have been under investigation for some time(l9-21); however, this work is not complete, and
further work is needed.
Fuel Effects
It has long been recognized that substitute or modified fuels can substantially affect
engine emissions. For example, hydrogen used as a fuel does not produce any HC or CO
emissions. However, cost, supply, handling, storage, and engine-derating factors are all against the
use of H2. Other fuels, such as methane, can produce moderate benefits and have fewer
disadvantages. No alternative fuel appears practical for use at present as a nationwide substitute
for gasoline. However, there does not appear to be any basis for concluding that a practical,
low-emission substitute for gasoline can never be found. Consequently, it appears reasonable to
continue to consider the use of an alternative fuel as an R&D opportunity that could be
significant in reducing emissions. However, the probability of economic and practical success for
this approach is considered low.
Possible modifications of gasoline fuel to reduce emissions have been investigated exten-
sively(22). The effect of fuel composition on the amount and reactivity of HC emissions is
currently being studied by a number of organizations. While such investigations are justifiable,
particularly as conducted by fuel suppliers, the expected gains are not large, at least in terms of
-------
VII -11
effective HC emission reductions. The effect of fuel variables on particulate and PNA emissions is
more direct, but appears to have received less study; thus, this is considered an R&D gap at
present.
Effects of Engineering Variables
The effects of most engineering variables on emission levels have been investigated
extensively(23). One exception to this is lean-mixture operation. There is sufficient information
available to indicate that major reductions in NOx emissions are possible with the use of
ultralean fuel-air mixtures; however, the limits of the potential reduction have not been
established, and there is also a question as to how ultralean mixtures affect HC emissions(24).
Consequently, further investigations of lean-mixture operation of gasoline engines are needed.
A necessary adjunct to the investigation of lean-mixture operation, and a current R&D
gap, is information on the effect of mixture preparation (degree of homogeneity and fuel
atomization, and the amount of fuel vaporization) on combustion and emissions. There is reason
to expect that mixture preparation may have a significant effect on lean-mixture combustion and
combustion limits.
A related area of work, although not combustion research in itself, is the development of
fuel-induction systems capable of providing uniform distribution of fuel to the individual
cylinders of multicylinder engines. Improved induction systems will be needed if practical
lean-mixture engines are to be developed.
Combustion-Process Modifications
Certain modifications to the conventional gasoline-engine combustion process can result
in reduced emissions. Two principal examples are exhaust-gas recirculation (EGR) and stratified-
charge engines. The potential benefits of EGR have been demonstrated, and device development
associated with EGR has established practical recycle levels and has proved out the durability of
the system. ( 4)
Stratified-charge engines have been under investigation for at least 25 years, but only
recently have they been looked at as a possible low-emission engine.(25,26) This work has been
generally encouraging, and further study of the potential of stratified-charge engines appears
justified.
Other combustion-process modifications could lead to similar or greater reductions in
gasoline-engine emissions(27). Promising novel concepts in this area should be considered poten-
tially deserving of R&D support.
Characterization of Exhaust Emissions
Studies to characterize various emissions from engine sources are conducted for two
reasons: (1) to aid in understanding the combustion process and (2) to evaluate the significance
of the engine as a source of air pollution. For purposes of this study, only those emission-
characterization studies having the former objective are considered to be combustion R&D.
Examples of needed R&D of this kind include the further study of particulate and PNA
emissions, as has been mentioned previously.
-------
VII -12
Most NAPCA programs to characterize emissions appear to have the second objective.
This work is neede.d, but not considered part of combustion R&D as covered in this report.
Diesel-Engine R&D Gaps
The diesel-engine combustion process is not well understood, compared with the knowl-
edge of gasoline-engine combustion. This is because of the heterogeneous nature of the combustion
process. The fuel-injection, mixing, vaporization, ignition, and combustion processes that take
place are extremely complex and difficult to describe mathematically.
Ignition delay and rate of heat release have been of principal interest in the past, and
empirical models for these phenomena have been formulated(28). Vaporization, ignition, and
combustion of fuel droplets have also been studied, but with less success(28). Some under-
standing of smoke formation has been gained(29), and research on odor formation has tended to
support the theory that odorous exhaust emissions are produced by partial oxidation in regions
too lean to burn at the start of combustion(30). However, efforts to identify the actual
compounds that cause the characteristic diesel-exhaust odor have been only partly successful to
date.(31)
The development of a realistic fuel-mixing and vaporization model for diesel combustion
appears to be a significant R&D step that is fundamental to further diesel research. The result of
this work, if successful, would be the ability to predict fuel-concentration, temperature, and
pressure levels within the cylinder as a function of time and position. Related R&D gaps are: the
identification of the odor-producing constituents of diesel exhaust, and further understanding of
pyrolysis in fuel-rich regions and nonflame reactions in fuel-lean regions.
The principal objective of work in the diesel R&D gaps mentioned above is to gain
insight as to possible modifications to the diesel combustion process that will result in reduced
emissions. While the heterogeneous nature of this process makes it difficult to investigate, it also
allows great latitude for innovation in the way the fuel is introduced and burned.
It is recognized that the desired combustion-process modifications need not spring from a
detailed understanding of the combustion phenomena, but may also be the result of intuitively
derived concepts. Both approaches are considered to be part of the needed combustion R&D in
the diesel-engine field.
SUMMARY OF CURRENT AND RELEVANT COMBUSTION R&D
Gasoline Engines
Most of the combustion research relating to gasoline-engine exhaust emissions is being
conducted by private industry, and is aimed principally at multicylinder, 4-stroke-cycIe auto-
motive type engines. This research is generally applicable to the entire population of gasoline
engines.
-------
VII -13
The automobile manufacturers, oil companies, and additive-chemical companies are the
principals in this research, and the scope of their programs is considered proprietary. Combustion
research in this area is also conducted by cooperative industrial groups and trade associations,
principally the Inter-Industry Emission Control Program(32) (initially the Ford-Mobil program),
the Chrysler-Esso Program, the American Petroleum Institute, and the Coordinating Research
Council(33). Limited information on the scopes of these programs has been made public, but
many technical details have been considered proprietary; publication of some of these results is
expected eventually.
A substantial amount of the literature and information available on gasoline-engine
combustion has been contributed by the private sector, but such publications do not generally
cover programs currently under way.
Funding for the entire private-sector gasoline-engine emission-control program is esti-
mated to be on the order of several hundred million dollars annually. There is no breakdown
available on the amount of this work that can be considered gasoline-engine combustion R&D,
but it is expected that it would not exceed one-third or one-quarter of the entire program.
Gasoline-engine combustion R&D is being conducted by the Government through
agencies such as the Bureau of Mines and Department of Defense as well as APCO. Reference 34
describes both combustion R&D and alternative-control research under way through Federal
agencIes.
Diesel Engines
Combustion research related to diesel-engine emissions is conducted by engine manu-
facturers, oil companies, and the Government; this work has not reached the proportions of the
gasoline-engine research work. It can be assumed that most of the research being conducted by
private industry is being done by manufacturers of engines for over-the-highway application.
Summary of Current R&D
Tables VII-3 and VII-4 present a summary of gasoline-engine and diesel-engine
combustion-research projects under way, on which some information is available.
-------
Table VII-3. Current Combustion R&D - Gasoline Engines
Sponsoring
Project Organization Principal
Key Project or Contract Title and Contract No. Research Organization Investigator Objective or Scope Funding, $
VII-a Gasoline composition & vehicle exhaust NAPCA-DCP Esso Res. & Eng. Co. G. P. Haas Effect of fuel comp., engine operating 50,603 (FY '70)
gas PNA content CPA 70.104 Linden, N. J. variables, and emission control svs~~ 32,879 (FY '69)
CPA 22-69-56 tern on PNA emission rate
CRC CAPE-6-68 .
VII.b Emission reduction using gaseous fuels NAPCA-DCP Inst. of Gas Technology Determine pollutant emissions for 68,994 (FY '70)
for vehicular propulsion CP A 70-69 Chicago, III. engines fired with gaseous fuels
VII-c Selected R&D of nitrogen oxides NAPCA-DCPE Esso Res. & Epg. W. 8artok Characterization & control of NOx from 363,025 (FY '701
control methods for stationary CPA 70-90 Linden, N. J. stationary I C engines
sources PH 22-68-55
VII-d Effects of fuel and engine variables NAPCA-DCP Dow Chemical Co. J. B. Moran Relationship of fuel additive to 230,886 (FY '701
on the characteristics of particulate CPA 22-69.145 Midland, Mich. particulate emission composition 104,000 (FY '69)
emissions in automotive exhaust & nature
VII-e Studv of emissions from two-cycle NAPCA-DMVR&D Olson Labs. H. J. Wimette Characterize motorcycle engine 961 (FY '701
engines CPA 22-69-91 Dearborn, Mich. emissions 10,941 (FY '691
;:$
VII-f Study of influence of fuel atomization, NAPCA-DMVR&D Battelle Memorial Inst. F. A. Creswick Develop induction system for lean- 89,150 (FY '70) -
I
vaporization, and mixing processes CPA 70-20 Columbus, Ohio mixture operation -
on pollutant emissions from motor .t::-
vehicle power plants
VII-g Study of exhaust emissions from NAPCA-DMVR&D Scott Res. Labs. W. Zegel Measurement of CO, HC, and NOx 1,075 (FY '70)
reciprocating aircraft power CPA 22-69-129 Plumsteadville, Pa. under various flight modes 89,650 (FY '69)
plants
VII-h Design criteria for hydrogen burn- NAPCA-DMVR&D Oklahoma State Univ. R. Schoeppel Develop a hydrogen burning engine 55,815 (FY '70)
iog engines EHS 70-103 Stillwater, Okla. and determine emissions
VII-i Decomposed methanol as a low NAPCA-DMVR&D Univ. of Santa Clara R. Pefley Study emissions from CFR engine 27,486 (FY '701
emission fuel EHS 70-118 (FY '70) M. Saad running on CO :2H2 42,269 (FY '691
CPA 22-69-70 Consolidated Eng.
Tech., Inc.
Mountain View, Calif.
(FY '691
VII-j Gentrol of NOx emissions from NAPCA-DMVR&D - Bendix Res. Labs. D. Bernard Fuel injection with lean mixtures 105,102 (FY '70)
mobile SOurCes EHS 70.122 Southfield, Mich.
VII-k Exhaust emissions from uncontrolled NAPCA-DMVR&D Southwest Res. I nst. C. T. Hare Determine emissions from selected 88,452 (FY '701
vehicles and related equipment EHS 70-108 San Antonio, Texas K. Springer uncontrolled mobile sources
using internal combustion
engines
VII.I Studv of relationship of engine NAPCA-DMVPC Automotive Res. 48,868 (FY '69)
deterioration to exhaust emissions CPA 22-69-140 Assoc., Inc.
-------
Table VII-3. (Continued)
Sponsoring
Project Organization Principal
Key Project or Contract Title and Contract No. Research Organization Investigator Objective or Scope Funding, $
VII-m A feasIbility study on the control of NAPCA-DMVPC Esso. Res. & Eng. D. Wade Exhaust-gas recirculation 98.180 (FY '69)
nitrogen oxides in automotive engine CPA 22-69-89 Lmden, N. J. D. G. Levine
exhaust PH 86-67-25 W. Glass
VII.n Study of the interactions of fuel NAPCA-DMVR&D Ethyl Corp. R. Kerley Determine interactions of fuel 62,348 (FY '691
volatility and automotive design CPA 22-69-66 Ferndale, Mich. volatility and automotive
as they relate to driveability CRC CAPE-4-68 Also 8ureau of Mmes design on driveabil ity
8artlesville, Okla.
VII-o Heavy duty vehicle emissions NAPCA-DMVPC Southwest Res. I nst. Measurement of emissions from 10- (FY '701
PH 86-67-72 San Antonio, Texas 24,000 Ib G VW 90501 ine-englne- 57,814 (FY '691
powered trucks (FY '68)
174,634 (FY '671
VII-p Aromatic by-products of combustion NAPCA-ORG Unlv. of California 8. D. Tebbens Study formation of PNA compounds 52,561 (FY '70)
AP 00275 8erkeley, Cal if. J. F. Thomas and fate once airborne 50,297 (FY '69)
M. Muki 45,066 (FY '68)
7,675 (FY '70) <::
VII-q Reduction of polycyclic aromatic NAPCA-ORG Univ. of Birmingham R. Long -
-
hydrocarbons AP 00323 England 4,290 (FY '691 I
-
7,600 (FY '68) VI
VII-r Carburetors, reduction of engine NAPCA-ORG Univ. of Michigan J. A. Bolt Reduction of carburetor metering 55,629 (FY '70)
exhaust emissions AP 00365 Ann Arbor, Mich. D. L. Harrington errors 50.492 (FY '691
S. Derezinski 103,968 (FY '68)
(FY '67)
VII-s Combustion gas composition NAPCA-ORG Unlv. of California E. S. Starkman Mechanisms of formation of combustion- 140,229 (FY '69)
AP 00385 Berkeley, Calif. generated air pOllution precursors 103,968 (FY '68)
50,157 (FY '67)
34,999 (FY '661
VII-t Engine emission reduction by com- NAPCA-ORG Penn. State Umv. W. E. Meyer Inv. the effect of heterogeneous flame 50,238 (FY '70)
bustion control AP 00560 University Park, Pa. propagation on HC & CO emissions 52,262 (FY '69)
40,107 (FY '68)
50,686 (FY '67)
VII-u Combustion process analysis NAPCA-ORG Univ. of WIsconsin H. K. Newhall Kinetics of CO & NO formation 36,816 (FY '70)
AP 00582 Madison, Wis. 18,888 (FY '691
14,713 (FY '68)
27,865 (FY '67)
VII-v Kinetics of nitrogen-oxide auto- NAPCA-ORG Univ. of Washington A. Hertzberg Shock-tube simulation of engine 47,877 (FY '701
motive pollution AP 00763 Seattle, Wash. R. C. Corlett processes 58,169 (FY '69)
A. T. Rossano 63,019 (FY '68)
-------
Table VII-3.
(Continued)
Project
Key
Project or Contract Title
Sponsoring
Organization
and Contract No.
Research Organization
Principal
Investigator
Objective or Scope
Funding, $
VII-w
VII-x
VII-y
VII-z
VII-aa
VII-bb
VII-cc
VII-dd
Kinetics 01 nitric oxide at high
temperatures
Non-equilibrium effects in internal
combustion engine
Characteristics and photochemical
reactivity of fuel components and
combustion products
Interactions between fuel composi-
tions and engine factors influencing
exhaust emissions
Products of combustion of distillate
fuels for motive power
Ford combustion process (hybrid)
Fuels combustion research
Effect of fuel volatility on automo.
tive emissions
NAPCA-ORG
AP 00858
NAPCA-ORG
AP 00871
NAPCA-DCP
Interagency
transfer
NAPCA-DMVR&D
Interagency
transfer
NAPCA-DMVR&D
Interagency
transfer
NAPCA-DMVPC
U. S. Army
Tank Auto. Command
DAAE 07-68-C-0880
Bureau of Mines
Bureau of Mines
Drexel Inst. Tech.
Philadelphia, Pa.
Cooper Union
New York, N. Y.
Bureau of Mines
Bartlesville, Okla.
Bureau of Mines
Bartlesville, Okla.
8ureau of Mines
Bartlesville, Okla.
Ford Motor Co.
Dearborn, Mich.
Bureau of Mines
Bartlesville, Okla.
Bureau of Mines
Bartlesville, Okla.
R. A. Matula
W. Chinitz
B. Dimitriades
H. B. Carroll
T. C. Wesson
J. E. Payne
J. M. Clingenpeel
J. R. Allsup
B. Dimitriades
T. C. Wesson
R. W. Hurn
H. B. Carroll
W. F. Marshall
R. W. Hurn
A. Simko
R. W. Hurn
J. A. Tipton
B. H. E celeston
B. H. Noble
J. E. Payne
H. 8. Carroll
J. M. Clingenpeel
B. Dimitriades
D. L. French
T. C. Wesson
Photochemical reactivity of auto-engine
exhaust compounds
Relationship of combustion products
to fuel composition and combustion~
process variables
Low-i!mission stratfield-charge
engine
Effect of fuel and engine variables
on nature 01 exhaust emissions
(both gasoline and diesel engines)
Effect of light-i!nd volatility
changes on exhaust emissions
35,916 (FY '70)
46,526 (FY '69)
9,825 (FY '70)
180,000 (FY '70)
145,000 (FY '70)
;S
-
I
-
0\
185,000 (FY '70)
-------
Table VII-3. (Continued)
Project
Key
Project or Contract Title
Sponsoring
Organization
and Contract No.
Research Organization
Principal
Investigator
Objective or Scope
Funding, $
Stratified-<:harge engine
VII...e
VII-ff
VII-gg
VII-hh
VII-i;
VII-jj
VII-kk
VII.II
VI'-mm
VII-nn
V 11-00
VII-pp
T exaCQ combustion process
Effects of gasoline properties on
exhaust emissions caused by
combustion-<:hamber deposits
Nature of the physical-chemical character-
istics of the particles associated with
PAH present in automobile exhaust
Combustion process analysis
Combustion process control
Emission reduction for spark.ignited
outboard engines
lNG vehicle
Combustion and exhaust emission of
automobile gasoline engine during
acceleration
The influence of mixture condition on
nitrogen oxide emissions from auto-
motive gasoline engines
Effect of mixture Quality and com-
custion chamber configuration on
exhaust emission
U. S. Army
Tank Auto. Command
Coordinating Res.
Council
CAPE-3-68
Coordinating Res.
Council
CAPE-12-68
State of California
State of California
Outboard Marine
Corp.
San Diego Gas &
Electric Co.
Japan Automobile
Res. Inst.
Nissan Motor Co.,
ltd.
Motor Ind. Res.
Assoc. (U. K.)
Texaco Res. labs.
Beacor. N. Y.
Industry labs.
Battelle Memorial I nst.
Columbus, Ohio
Univ. of California
los Angeles
Univ. of California
los Angeles
Univ. of Michigan
Ann Arbor, Mich.
San Diego Gas &
Electric Co.
San Diego, Calif.
Waseda Univ.
Japan
Eng. labs, Nisson
Motor Co.
YOkosuka, Japan
Motor Ind. Res. Assoc.
Warwickisfire,
England
Mobil Oil Co. ltd.
Res. & Tech. Servo lab.
Stanford-Ie-Hope,
Essex, England
Univ. of Strathclyde
Dept. of Pure & Applied
Chern.
Glasgow, Scotland
E. Mitchell
C. Melton
W. M. Henry
l. B. Robinson
J. O. Pinkerton
R. D. Kopa
D. Cole
T. Saitoh
H. Kuroda
Y. Nakajima
A. E. Dodd
Z. Holubecki
L D. lytollis
J. H. Boddy
Effect of gasoline props. and additives
Collection & characterization of exhaust
particulates
Study formation of exhaust-gas pollutants
Effect of water injection; effect of wall
deposits; molecular beam sampling
Characterization 111 n~Ju(;tion of emissions
<
-
-
I
-
-...J
Influence of inlet air condition, mixture
condition, and exhaust-gas
recirculation
S;ngle-cylinder engine
Studies on exhaust gas recirculation
and the related effects on fuel Quality
on vehicle exhaust emissions
Studies on formation of nitrogen oxides
-------
Table VII-3. (Continued)
Project
Key
Project or Contract Title
Sponsoring
Organization
and Contract No.
Research Organization
Principal
Investigator
Objective or Scope
Funding. $
VII-qq
VII-rr
VII-ss
VII-tt
VII-uu
Analysis of vehicle emissions with
emphasis on aromatic polycyclic
hydrocarbons
National Res.
Council, Italy
Zenith Carburetor Co.
Ltd.
Dunstable, Beds,
England
Institute for Piston
Engines
Langer Kamp,
Germany
Institut Francais de
Petrole
France
Stazione Speri-
mentale Per I
Combustibili,
Milano
Univ. of Perugia
Italy
Dr. H. Muller
M.Sale
A. Galtieri
F. Casellato
A. Candeli
V. Mastrondrea
G. Morozzi
Studies in the reduction of emissions
from automotive engines by modifica~
ticns to carburetor and induction~
manifold design
Effects of mixture preparation and
operating conditions on vehicle
exhaust gas composition and
air injection
:s
'i'"
......
00
Determination of polycyclic aromatic
hydrocarbons in engine exhaust
Automotive emission reduction through
development of stratified mixtures,
exhaust gas recirculation, fuel injection..
and fundementals of NDx formation
Chromatographic and spectrophotometric
analysis of PNA emissions
Effect of fuel and engine variables on
-------
Table VII-4. Current Combustion R&D - Diesel Engines
oject Sponsoring Organization Principal Funding, $
Key Project or Contract Title and Contract No. Research Organization Investigator Objective or Scope
VII-vv Diesel exhaust composition and odor NAPCA-DMVR&D A. D. Little. Inc. P. Levens Analysis for odor-producing constituents 66,500 (FY '70)
CPA 22-69-63 Cambridge, Mass. of diesel exhaust using condensation, 33,263 (FY '69)
(CRC CAPE 7-681 solvent, extraction, and liquid column
chromatography
VII-ww Single cylinder research engine oper- NAPCA-DMVR&D Univ. of Michigan J. A. Bolt Effect of very high supercharge on 44,450 (FY '70)
ating in a diesel cycle U. S. Army Ann Arbor, Mich. N. Henein emissions -~
Tank Auto. Command
DAA E07-69-C-1289
VII-xx Study of chemical species in diesel NAPCA-DMVR&D Illinois Institute of A. Gaynor Compound identification using GC and 33,000 (FY '69)
exhaust and their contributions to CPA 22-69-98 Technology mass spec.
exhaust odors (CRC CAPE 7-68) Chicago, III.
VII-yy I nvestigation of diesel powered vehicle NAPCA-DMVPC Southwest Res. Inst. K. J. Springer InvestigatIon of odor, smoke, HC, CO, 237,578 (FY '69)
odor and smoke PH 22-68-23 San Antonio, Texas and NOx emissions and controls on
diesel buses and truck tractors
VII-zz A field study of diesel engine exhaust NAPCA-DMVR&D Southwest Res. I nst. 117,954 (FY '69) -<
PH 22-68-36 San Antonio, Texas -
...
VII-aea Control of NOx, fuel injection- NAPCA-DMVR&D K. Bastress Develop design parameters for control 37,475 (FY '70) ..-
Northern Res. & \C
diesel engines EHS 70-116 Engr. Corp. of NOx in diesel engines
Cambridge, Mass.
VII-bbb Liquid fuel ignition and combustion NAPCA-ORG Rutgers Univ. R. L. Peskin Basic mechanisms of ignition and com- 36,385 (FY '68)
AP 00906 New Brunswick, N. J. bustion of droplets 28,068 (FY '70)
VII-ccc Fuel injection system analysis: diesel NAPCA-ORG Univ. of Michigan J. A. Bolt Computer simulation and expo work to 49,614 (FY '69)
smoke reduction AP 00835 Ann Arbor, Mich. N. Henein eliminate undesirable spray char 29,319 (FY '70)
VII-ddd D.esel fuel combustion chemistry as NAPCA-ORG Drexel Inst. of Technology R. A. Matula 29,863 (FY '70)
related to odor AP 00576 Philadelphia, Pa. 53,589 (FY '69)
25,912 (FY '681
VII-eee Composition, smoke, and odor of diesel Bureau of Mines Bureau of Mi nes W. F. Marshall Effect of fuel comp, engine design, and
combustion products Bartlesville, Okla. R. W. Hum operating parameters on smoke, odor,
J. W. Vough and other emissions
D. J. Veal
VI'-fff Correlation of trace diesel exhaust Bureau of Mines Bureau of Mines R. W. Freedman Evaluate toxic components in diesel
products with engine operation Pittsburgh, Pa. H. A. Watson exhaust in addition to major
constituents
VII-ggg Internal combustion engine simulation U. S. Army Univ. of Wisconsin P. S. Myers Computer simulation and correlation of
-------
Table VII-4.
(Continued)
Project
Key
VII-hhh
VII-iii
VII-jjj
VII-kkk
Project or Contract Title
Compression-ignition engine combustion
phenomene
Investigation of transient diffusion fleme
phenomena in a diesel engine combus-
tion chamber
Search for analytical procedures cover-
ing diesel exhaust fumes and a method
for measuring the oxygenated
hydrocarbons in the fumes
Control of exhaust smoke by fuel
additives in automobile diesel
engines
Sponsoring Organization
and Contract No.
U. S. Army
Aberdeen Proving Gd.
Caterpillar Tractor Co.
Ontario Dept. of Energy
Resources Management
Japan Automobile Res.
Inst., Inc.
Research Organization
Southwest Res. Inst.
Army Coating Chem. Lab.
San Antonio. Texas
Univ. of Illinois
Urbana. III.
Univ. of Waterloo
Waterloo. Ontario
Canada
Waseda Univ.
Japan
Principal
Investigator
R. D. Quillian
W. L. Hull
E. K. Buxholz
F. W. Karasek
M. Nabetani
T. Saitoh
Objective or Scope
Basic studies of CI process; effect of
fuel properties
Funding, $
I nvestigation of precombustion chamber
phenomena under high supercharge
Chem. analysis of oxygenated organic
components in diesel exhaust
Mechanism of smoke formation and its
control
::;
7"
IV
-------
VII - 21
R&D OPPORTUNITIES RECOMMENDED FOR THE 5-YEAR PLAN
Eleven R&D opportunities directed toward reduction of emissions from reciprocating IC
engines are recommended. Six of these are related to gasoline-engine combustion three to diesel
, ,
and two generally applicable to both gasoline and diesel engines. These opportunities cover the
following areas:
Gasoline Engines
. Stratified-charge engines
. Lean-mixture operation and mixture preparation
. Alternative fuels
. Generally applicable
- wall quench
- effect of lube oil
- particulate and PNA formation
Diesel Engines
. Combustion-process modifications through better understanding of
com bustion processes
General
. Kinetics of NOx formation in IC engines
. Novel concepts for combustion-process modification
In the case of exhaust-gas recirculation, no funding for FY 1971 through 1975 is
recommended because it is believed that current APCO projects will have demonstrated the
effectiveness of EGR systems and that any further work on EGR should be conducted with
industrial funds. The remaining gasoline-engine combustion R&D opportunities are aimed either
at the development of modified or unconventional combustion processes, or at gaining more
basic information believed to be generally applicable to reducing gasoline-engine emissions.
The diesel-engine combustion R&D opportunities are all aimed at ultimately modifying
the diesel fuel-injection and combustion process so as to minimize emissions. Two approaches to
this are recommended: one using a more thorough understanding of the diesel combustion
process to shed light on modifications that can be made to reduce emissions, the other stemming
directly from ideas for combustion-process modifications for which there is some reason to
expect that reduced emissions will be achieved.
These R&D opportunities are described on the following pages and their priorities
summarized at the end of this chapter.
-------
VII-22
R&D Opportunity: VII-I
Related to: VII.bb, ee, ss
Support of Development and Evaluation of Stratified-Charge Gasoline Engines
Technical Objective and Approach
The objective is to investigate further the potential of producing low-cost stratified-charge engines for operation
at low emission levels.
The approach should consist of supporting stratified-charge engine development programs with the additional
funds needed for work on reducing emission levels.
Rationale and Incentive
Stratified-charge engines have been under development for at least 25 years, but only recently have their low
emission possibilities become of interest.
These engines typically operate with in-cylinder fuel injection and with lean overall fuel-air ratios. Therefore, it
is theoretically possible to lower substantially the effect of wall quenching on hydrocarbon emissions and, also, to
achieve combustion at relatively low temperatures, thus achieving low NOx emissions. However, the heterogeneous
nature of the combustion process can lead to locally high-temperature zones and locally fuel-rich zones as well as to
incomplete combustion in very lean regions. Thus, emission reduction possibilities may not be fully achieved.
Present development efforts are showing promising results; therefore, support of these efforts appears justified.
Certain types of stratified-charge engines have a limited multifuel capability. Such engines, if practical for
general automotive use, could eliminate the high-octane requirement of automotive gasoline and the use of lead
additives.
Estimated R&D Cost & Time
R&D Cost Range, 1000's: $600-$1,500
R&D Time Range: 3 years
Recommended 5-year Funding, 1000's: $1,200.
Funding by Fiscal Year, $1oo0's
'69-70 171 72 73
X 400 400 400
'74
75
76+
Evaluation
Sources Affected: Mobile and Stationary Gasoline Engines Plus Gas Engines
Relative Potential Benefit (overall rating): Very High
Pollutants Affected
CP
co
HC
PNA
Odor
NOx
Lead
SOx
Ash
~
--
--
% Reduction, Range
Expected
Fraction of ECC Emissions Affected
Noncombustion Controls Fector
Relative Potential Benefit Factor
I mplementation Time, years: 3-8
50-80 25-75
68 50
0.69 0.60
.8 .8
9.38 6.00
60-80 0- , 00
70 30
0.41 0.82
.2 .8
22.96 4.92
43.26
most likely: 5
Relative Implementation Cost: Very Low
Relative Priority Rating: A
-------
VII-23
R&D Opportunity: VII-2
Related to: VII-f, j
Development of Implementation Criteria for Lean-Mixture Operation of Gasoline Engines
Technical Objective and Approach
The objective is to further explore the incentive for developing engines that will operate on ultralean fuel-air
mixtures and to develop basic information that will be useful in a hardware engine-development program.
The approach should include investigation of certain aspects of lean-mixture operation that require further
study:
1. Establishing lean limits for good combustion. This limit will be affected by combustion-product residuals
(and, therefore, manifold vacuum), mixture preparation, mixture motion, and possibly by ignition-system
energy and timing. Possible effects of lean-mixture on octane-number requirements might also be
investigated.
2. Establishing the effect on emission levels. Once the requirements for good combustion have been estab-
lished, the real potential for emission reduction can be explored. If some increase in HC emissions is
observed, it may be pertinent to determine whether wall quench, and the effect of lean mixtures on wall
quench, is significant.
3. Definition of induction-system and ignition-system requirements for production engines. This work should
establish a basis for follow-on hardware development.
Most of this work should be done with engines, perhaps initially with single-cylinder laboratory engines and
eventually with multicylinder automotive engines, both using special induction systems to control closely the fuel-air
ratio and the mixture state. Supporting work, such as bomb studies, might also be helpful for investigating some of
the more fundamental aspects of this area and for separating the effects of different variables. As the results of any
such study will be to some extent dependent upon the configuration of the equipment used, two parallel projects
might be justified.
Rationale and Incentive
It is anticipated at present that reductions in NOx levels to 80 to 95 percent of 1970 standards can be
achieved by operating at fuel-air ratios of 0.05 (air-fuel ratio of 20: 1) or leaner. Lean-mixture operation is not
expected to increase CO emissions. HC emission concentrations with present engines increase slightly with ultralean
operation; however, there is some question as to whether this is a necessary result.
Estimated R&D Cost & Time
R&D Cost Range, 1000's: $300-$660
R&D Time Range: 3 years
Recommended 5-year Funding, 1000's: $660*
Funding by Fiscal Year, $1oo0's
'69-70 I ~
X 200
'72
260
'73
200
'74
'75
'76+
Evaluation
Sources Affected: Mobile and Stationary Gasoline Engines Plus Gas Engines
Relative Potential Benefit (overall rating): High
Pollutants Affected
CP
CO
HC
PNA
Odor
NOx
Lead
SOx
Ash
~
---
--
% Reduction, Range
Expected
Fraction of ECC Emissions Affected
Noncombustion Controls Factor
Relative Potential Benefit Factor
0-50
25
0.57
.8
2.85
0-50
25
0.46
.8
2.30
50-95
78
0.36
.2
22.46
27.61
I mplementation Time, years: 4-10
most likely: 8
Relative Implementation Cost: Medium
-------
VII- 24
R&D Opportunity: VlI-3
.
Related to: VlII-17, 18; VlI-f, r, dd, mm, nn, qq, rr
Experimental Research on the Effect of Fuel-Air Mixture Preparation on Gasoline-Engine Emissions
Technical Objective and Approach
The objective is to determine the effect of fuel-air mixture preparation on the combustion process, on emission
levels, and on the lean operating limit.
The approach should be to investigate various mixture-preparation variables including: degree of fuel atomiza-
tion, degree of mixture homogeneity, relative amounts of fuel in liquid and vapor form, and time variations in these
variables. The study should be conducted primarily with heavily instrumented single-cylinder engines.
Rationale and Incentive
This work is related to the recommended study of lean-mixture operation as more uniform mixing and
distribution will be necessary for lean operation. However, it is listed separately because the results could be more
generally applicable in that improved mixing and distribution will minimize local inhomogeneities that can
contribute significantly to high emission levels.
Estimated R&D Cost & Time
R&D Cost Range, 1000's: $200-$500
R&D Time Range: 3-5 years
Recommended 5-year Funding, 1000's: $300
Funding by Fiscal Year, $1000's
'69-70 171 72
X 100 100
73
100
74
75
76+
Evaluation
Sources Affected: Mobile and Stationary Gasoline Engines
Relative Potential Benefit (overall rating): High
Pollutants Affected CP CO HC PNA Odor NOx Leed SOx Ash ~
-- - -
% Reduction, Ranga 10-50 10-50 50-95 0-20
Expected 27 27 78 10
Fraction of ECC Emissions Affected 0.62 0.49 0.33 0.78
Noncombustion Controls Factor .8 .8 .2 .8
Relative Potential Benefit Factor 3.35 2.65 20.59 1.56 28.15
Implementation Time, years: 4-8 most likely: 6 Reletive Implementation Cost: Medium
-------
VII-25
R&D Opportunity: VII-4
Related to: VIII-4, 5; VII-nn
Analytical and Experimental Research on Gasoline-Engine Wall-Quench Phenomena
Technical Objective and Approach
The objective is to gain a better basic understanding of wall-quench phenomena and of the effect on emissions
of important variables.
The approach should include single-cylinder engine studies, bomb studies, and steady-flow premixed flame
studies of variables such as mixture ratio, mixture preparation, mixture motion, fuel composition, temperature and
pressure, wall surface condition, and combustion-chamber shape.
Rationale and Incentive
Although this R&D opportunity represents a current knowledge gap, it is anticipated that most of the potential
benefits have already been realized as the result of empirical studies of the effect of engineering variables on
hydrocarbon emissions. Consequently, short-term gains, if any, would be moderate. Ultimately, however, such work
will improve understanding of the mechanism of pollutant formation in IC engines, and the results could be more
significant as further gains become more difficult to achieve.
Estimated R&D Cost & Time
R&D Cost Range, 1000's: $200-$500
R&D Time Range: 3-5 years
Recommended 5-year Funding, 1000's: $300
Funding by Fiscal Year, $1OO0's
'69-70 12!
100
72
100
'73
100
'74
'75
76+
Evaluation
Sources Affected: Mobile and Stationary Gasoline Engines Plus Gas Engines
Relative Potential Benefit (overall rating): Medium Low
Pollutants Affected
CP
co
HC
PNA
Odor
NOx
Lead
SOx
Ash
~
---
--
% Reduction, Range
Expected
Fraction of ECC Emissions Affected
Noncombustion Controls Factor
Relative Potential Benefit Factor
0-50
22
0.54
.8
2.38
2.38
I mplementation Time, years: 2-10
most likely: 5
Relative Implementation Cost: Low
-------
VII- 26
R&D Opportunity: VII-.5
Experimental Research on the Effect of Lubricating Oil on Gasoline-Engine Emissions
Technical Objective and Approach
The objective is to determine: (1) the form in which consumed oil appears in engine exhaust (i.e., how much is
oxidized?) and (2) the effect of exhaust clean-up devices, such as thermal reactors or catalytic reactors, on
lubricating oil or lubricating-oil combustion products in the exhaust.
The approach should include basic investigations as well as studies using single-cylinder and multicylinder
engines.
Rationale and Incentive
The effect of lubricating oil on gasoline-engine emissions has been largely ignored in the past, probably
because, even if all the oil normally consumed appeared as HC in the exhaust, the resulting contribution to emission
levels would be minimal. A consumption rate of one quart per 4000 miles is equivalent to only 0.20 g per rill of
hydrocarbons if no combustion takes place, less than one tenth of 1970 standards. However, in view of 1980
standards of 0.25 g per mi for hydrocarbons, oil could be far more important in the future.
While only minor HC reductions from 1970 levels could be anticipated to result from this study, this study
would evaluate the importance of lubricating-oil control on emissions from the projected low-emission engines of
the future.
Estimated R&D Cost & Time
R&D Cost Range, 1000's: $140-$300
R&D Time Range: 2-5 years
Recommended 5-year Funding, 1000's: $210
Funding by Fiscal Year, $1ooo's
'69-70 171
- 70
72
70
73
70
74
75
76+
Evaluation
Sources Affected: Mobile and Stationary Gasoline Engines Plus Gas Engines
Relative Potential Benefit (overall rating): Low
Pollutants Affected
CP
co
HC
PNA
Odor
NOx
Lead
50x
Ash
~
---
--
% Reduction, Range
Expected
Fraction of ECC Emissions Affected
Noncombustion Controls Fector
Relative Potential Benefit Fector
0-10
5
0.12
.5
0.30
0-10
5
0.46
.8
0.46
0-20
10
.097
.4
0.58
1.34
Implementation Time, years: 4-10
most likely: 8
Relative Implementation Cost: Low
-------
VII-27
R&D Opportunity: VII-6
Related to: VlI-4; VIII-6, 10, 11, 12; VII-a, p, q, tt
Experimental Research on the Formation of Particulate and PNA Emissions From Gasoline Engines
Technical Objective and Approach
The objectives are to further characterize particulate and PNA emissions from gasoline engines, to gain an
understanding of the mechanism by which they form during the combustion process, and to determine the
relationship of these emissions to fuel composition and oil consumption and composition.
The approach should include basic studies and both single-cylinder- and multicylinder-engine studies.
Rationale and Incentive
The effect of the combustion process on PNA and particulate matter formation is only partly understood.
Further study might result in the reduction of these pollutants through combustion-process modifications, fuel and
lubricant changes, or oil-control improvements.
Estimated R&D Cost & Time
R&D Cost Range, 1000's: $200-$1,000
R&D Time Range: 3-5 years
Recommended 5-year Funding, 1oo0's: $1,000
Funding by Fiscal Year, $1oo0's
'69-70 12! 72
X 200 200
'73
200
'74
200
75
200
76+
Evaluation
Sources Affected: Mobile and Stationary Gasoline Engines
Relative Potential Benefit (overall rating): Medium
Pollutants Affected CP CO HC PNA Odor NOx Lead SOx Ash ~
--- - -
% Reduction, Range 0-50 0-60 0-10
Expected 22 23 5
Fraction of ECC Emissions Affected 0.12 .097 0.70
Noncombustion Controls Factor 0.5 0.4 0.8
Relative Potential Benefit Factor 1.32 1.34 0.70 3.36
Implementation Time, years: 4-10 most likely: 8 Relative Implementation Cost: Medium
-------
VII- 28
R&D Opportunity: VII-7
.
Related to: VIII-17, 18; VII-bbb, ccc
Initiate Development of a Model of the Diesel-Engine Combustion Process by Analytical and
Experimental Development of a Fuel-Air Mixing-and-Vaporization Model
Technical Objective and Approach
The short-range objective is to develop an analytically based understanding of the fuel-air mixing and
vaporization phenomena that precede combustion in the diesel-engine cylinder. This would enable prediction of
temperature-pressure-fuel concentration histories as a function of location in the combustion chamber up to the
point at which combustion is initiated.
The approach should be a theoretical investigation supplemented by extensive experimental studies both in
engines and in other types of laboratory combustion apparatus.
Rationale and Incentive
80 far, investigators generally have been unable to qualitatively describe the diesel-engine combustion process in
terms of local temperatures, fuel concentrations, reaction rates, etc. (although a good empirical understanding of
ignition delay and overall rate of heat release exists). Development of a good model of the combustion process
(including both physical and chemical factors) will provide knowledge of the mechanisms whereby pollutants are
formed with current diesel combustion systems and may give significant insights into combustion process modifica.
tions that will reduce the pollutants. A first step toward formulating a good model of the combustion process is to
develop a good mixing and vaporization model.
Estimated R&D Cost & Time
R&D Cost Range, 1000's: $300-$1,000
R&D Time Range: 5 years
Recommended 5-year Funding, 1000's:
$1,000
Funding by Fiscal Year, $1OOO's
'69-70 171
X 200
72
200
73
200
74
200
75
200
76+
Evaluation
Sources Affected: Mobile and Stationary Diesel Engines
Relative Potential Benefit (overall ratingl: Medium High
Pollutants Affected CP CO HC PNA Odor NOx Lead SOx Ash
-- - -
% Reduction, Range 0-90 0-50 0-90 0-60 0-90 0-75
Expected 48 25 48 23 48 39
Fraction of ECC Emissions Affected 0.11 .0074 .066 0 0.46 .042
Noncombustion Controls Factor .5 .5 .5 .4 .5 .1
Relative Potential Benefit Factor 2.64 0.09 1.58 0 11.04 1.47
Implementation Time, years: 4-10 most likely: 6 Relative Implementation Cost: Medium
Relative Priority Rating: B
1:
-------
VII- 29
R&D Opportunity: VII-8
Related to: VII-9; VIII-6, 7; VII-w, xx, ddd, eee, jjj
Experimental Investigation to Identify Odor-Producing Constituents in Diesel-Engine Exhaust, the
Mechanism of their Formation, and Combustion Modifications to Reduce Emissions of these
Constituents
Technical Objective and Approach
The objective of this research is to identify the chemical
contribute to its characteristic odor, to determine the mechanism
these species by combustion modification.
species present in diesel-engine exhaust that
of their formation, and to reduce emission of
Several approaches exist for relating the chemical composition of diesel-engine exhaust samples to the odor of
the exhaust. The chemical aspect can involve either analytical identification of compounds existing in diesel exhaust
or preparation of synthetic exhaust gases for comparison on the basis of odor with diesel exhaust. All approaches
should involve human panels for odor evaluation.
Following identification of the odor-producing compounds, the mechanism by which these compounds form
should be investigated, primarily in laboratory combustion rigs.
Specific approaches to combustion modification cannot be determined until the odor-producing constituents
and their mechanism of formation are identified.
Rationale and Incentive
One route to the reduction of odor-producing exhaust from diesel engines is to begin with the identification of
the odorous compounds. If the odor-producing compounds can be identified, the mechanism of their formation can
be identified using existing basic knowledge of the combustion process, provided a good mixing and vaporization
model exists. Finally, a precise knowledge of the mechanism by which the odor-producing compounds form can
lead to defining a combustion-process modification that will reduce odor emission.
Estimated R&D Cost & Time
R&D Cost Range, 1000's: $200-$1,000
R&D Time Range: 3-5 years
Recommended 5-year Funding, 1000's: $500
Funding by Fiscal Year, $1OO0's
'69-70 I ~
X 100
'72
100
'73
'74
'75
100
'76+
100 100
Evaluation
Sources Affected: Mobile and Stationary Diesel Engines
Relative Potential Benefit (overall rating): Medium High
Pollutants Affected
CP
co
HC
PNA
Odor
NOx
Lead
SOx
Ash
~
--
--
% Reduction, Range
Expected
Fraction of ECC Emissions Affected
Noncombustion Controls Factor
Relative Potential Benefit Factor
0-90
48
.066
.5
1.58
0-90
48
0.46
.5
11.04
12.62
I mplementation Time, years: 4-10
most likely: 6
Relative Implementation Cost: Medium
-------
VII-3D
R&D Opportunity: VII-9
.
Related to: VlII4, 6, 8, 9, 10; VlI-hhh, iii
Experimental Laboratory Research on
Combustion
Preflame and N on flame Reactions in
Diesel-Engine
Technical Objective and Approach
The objective is to obtain basic information on formation of smoke and odor-producing compounds in
preflame and nonflame zones during diesel-engine combustion.
The approach should include basic chemistry studies of carbon formation during pyrolysis and subsequent
flame combustion in fuel-rich regions, and of the production of odor-producing compounds by non.flame reactions
in very lean regions. These studies should be conducted as laboratory research - not in an engine. In addition to
establishing fuel-air distribution requirements, this research might suggest other modifications to the combustion
process for reducing emissions.
Rationale and Incentive
Laboratory (nonengine) research on the preflame and nonflame reactions characteristic of diesel-engine
combustion can help establish limits on the range of fuel-air ratios that can be permitted in local regions without
producing odor and smoke. This research will assist in establishing goals for the degree of uniform fuel-air
distribution that must be achieved to avoid excess emissions from diesel engines.
Estimated R&D Cost & Time
R&D Cost Range, 1000's: $200-$350
R&D Time Range: 3-5 years
Recommended 5-year Funding, 1000's: $350
Funding by Fiscal Year, $1ooo's
'69-70 171
- 70
72
70
73
70
74
70
75
70
76+
Evaluation
Sources Affected: Mobile and Stationary Diesel Engines
Relative Potential Benefit (overall rating): Medium High
Pollutants Affected CP CO HC PNA Odor NOx Lead SOx Ash ~
-- - -
% Reduction, Range 0-90 0-90 0-90
Expected 48 48 48
Fraction of ECC Emissions Affected 0.11 .066 0.46
Noncombustion Controls Factor .5 .5 .5
Relative Potential Benefit Fector 2.64 1.58 11.04 15.26
Implementation Time, years: 4-10 most likely: 6 Relative Implementation Cost: Medium
-------
VII-3l
R&D Opportunity: VII -10
Related to: VIII-3; VII-u, v, w, pp, aaa
Investigation of Kinetics of NOx Formation in IC Engines With Fuel-Rich Mixtures
Technical Objective and Approach
The objective of this research is to investigate the possibility of reducing NOx emission from IC engines by
combustion-process or engine-hardware modifications which take advantage of new information to be generated in a
study of the nitrogen-oxygen kinetics coupled with the hydrocarbon-oxygen combustion process. (This does not
include implementation of existing knowledge of nitrogen-oxygen kinetics.)
The approach is to determine, by sampling or other procedures, the NOx concentrations existing at discrete
times and places within an engine operating at other than very fuel-lean conditions. The resulting data should be
examined and correlated with engine operating variables to identify conditions which could be exploited to
minimize the formation or to maximize the destruction of NOx. The possibility of exploiting these conditions in a
practical commercial engine would be examined.
Rationale and Incentive
The general behavior of the nitrogen.oxygen system is understood and this understanding can be applied to
combustion processes which are sufficiently fuel-lean. However, the behavior is not understood when significant
competition for 0 atoms occurs, for example, under fuel-rich conditions. Hence, the possibility exists that engine
operating conditions could be found which exploit the (largely unknown) behavior of the nitrogen-oxygen system
under these non-lean combustion conditions to reduce NOx emissions. As NOx from IC engines may be difficult to
control otherwise, an increase in HC and CO emissions, which could be controlled downstream, might be acceptable.
Estimated R&D Cost & Time
R&D Cost Range, 1000's: $0-$400
R&D Time Range: 0-4 years
Recommended 5.year Funding, 1000's: $200
Funding by Fiscal Year, $1ooo's
'69-70 171 72
X 100 100
73
'74
'75
'76+
Evaluation
Sources Affected: All IC Engines
Relative Potential Benefit (overall rating): Medium
Pollutants Affected
CP
CO
HC
PNA
Odor
NOx
Lead
SOx
Ash
I:
---
--
% Reduction, Range
Expected
Fraction of ECC Emissions Affected
Noncombustion Controls Factor
Relative Potential Benefit Factor
I mplementation Time, years: 4-10
0-30
12
0.42
.2
4.03
4.03
most likely: 6
Relative Implementation Cost: Medium
-------
VII-32
R&D Opportunity: VII-New Concepts
Provision for Exploring New Concepts and New R&D Opportunities that Evolve from the Program,
Accelerating Promising R&D, or Conducting Demonstrations of Promising Concepts for Reducing
Emissions from Reciprocating Internal-Combustion Engines by Combustion Modification
Technical Objective and Approach
The objective is to provide for long-range flexibility in the R&D program to enable APCO to take advantage of
opportunities that are not presently evident, but which can arise during the course of this program.
The approach should be to make specific provisions in the R&D program to explore the feasibility of new and
novel concepts and to accelerate research, development, and demonstration of promising concepts for reducing
emissions by combustion-process modification. Worthwhile ideas for combustion-process modification to reduce
emissions from reciprocating IC engines might originate as the result of novel design concepts or through in-depth
understanding derived from well-planned R&D. The merits of specific R&D opportunities should be decided by
evaluating the particular concepts as they evolve.
Rationale and Incentive
Appropriate R&D support can be expected to encourage conception of IC-engine combustion-process modi-
fications that might result in substantial emission reductions.
Gasoline Engines. Combustion-process modification appears to be the only engine modification route to
achieving ultimate emission goals. Investigations of this kind are being conducted presently on exhaust-gas recircula-
tion (EGR) and on stratified-charge engines. EGR modifies the combustion process by the introduction of an
additional dilutent to the reactants. In a stratified-charge engine, the modification of the combustion process is
more drastic and can iesult in the elimination of wall-quench effects.
Diesel Engines. The combustion process in diesel engines is characterized by compression ignition, operation
with lean fuel-air ratios, the use of heavy hydrocarbon fuels with short ignition-delay properties, and some means of
injecting the fuel into the cylinder at a controlled time and rate. Variations in these factors, particularly the way in
which fuel is injected, strongly affect the combustion process and the resulting emissions. For example, there are
several approaches to the fuel-injection process (e.g., direct-injection engines vs. precombustion engines) and their
emission characteristics are substantially different in some respects.
Fuels. While there are candidate fuels, such as hydrogen, that could give low emissions, none are presently
practical for various reasons including high cost, inadequate supply, engine derating, and problems in handling and
on-vehicle storage. Although it appears at this time that there is no readily available suitable alternative fuel, there is
no proof that such a fuel could never be found.
Recommended Funding Allocation
'71
'72
250
'73
300
'74
'75
350
5-year Funding, 1000's: $1,200
Funding by Fiscal Year, $1000's
300
Evaluation
This R&D Opportunity is unranked. Potential benefit, implementation time, implementation cost, and funding level for
each specific opportunity must be evaluated when the opportunity is identified. The suggested funding level anticipates
effort on several R&D opportunities.
-------
TABLE VII-5. SUMMARY BY PRIORITIES
RECIPROCATING INTERNAL-COMBUSTION ENGINES
Relative Current Estimated R&D Costs, $1000
Priority R&D Opportunity APCO By Fiscal Yea"
R&D 5- Y ear On-Going
Rating Effort '71 '72 '73 '74 '75 Total '76+
A VII-l Support of Development and Evaluation of Stratified- X 400 400 400 - - 1,200 -
Charge Gasoline Engines
A VII-2 Development of Implementation Criteria for Lean- X 200 260 200 - - 660 -
Mixture Operation of Gasoline Engines
A VII-3 Experimental Research on the Effect of Fuel-Air X 100 100 100 - - 300
Mixture Preparation on Gasoline-Engine Emissions - - - -
Totals, Priority A 700 760 700 2,160
B VII-7 Initiate Development of a Model of the Diesel-Engine Com- X 200 200 200 200 200 1,000 -
bustion Process by Analytical and Experimental Develop-
ment of a Fuel-Air Mixing-and-Vaporization Model
B VII -8 Experimental Investigation to Identify Odor-Producing X 100 100 100 100 100 500 -
Constituents in Diesel-Engine Exhaust, the Mechanism
of their Formation and Combustion Modifications to
Reduce Emissions of the Constituents
B VII-9 Experimental Laboratory Research on Pre-Flame and Non- - 70 70 70 70 70 350 -
Flame Reactions in Diesel-Engine Combustion - - - - - -
Totals, Priority B 370 370 370 370 370 1,850
C VIlA Analytical and Experimental Research on Gasoline-Engine - 100 100 100 - - 300 -
Wall-Quench Phenomena
<::
-
-
I
W
-------
TABLE VII-5. (Continued)
Relative Current Estimated R&D Costs, $1000
Priority R&D Opportunity APCO By Fiscal Yean
Rating R&D 5- Y ear On-Going
Effort 71 '72 '73 '74 '75 Total . '76+
D VII-5 Experimental Research on the Effect of Lubricating Oil - 70 70 70 - - 210 -
on Gasoline-Engines Emissions
D VII -6 Experimental Research on the Formation of Particulate X 200 200 200 200 200 1,000 -
and PNA Emissions from Gasoline Engines
D VII -10 Investigation of Kinetics of Nitrogen-Oxide Formation X 100 100 - - - 200 -
in IC engines with Fuel-Rich Mixtures - - - - - -
Totals, Priority D 370 370 270 200 200 1,410
N VII-N Provision for Exploring New Concepts and New R&D Oppor- - - 250 300 300 350 1,200 -
tunities that Evolve from the Program, Accelerating
Promising R&D, or Conducting Demonstrations of
Promising Concepts for Reducing Emissions from
Reciprocating Internal-Combustion Engines by
Combustion Modification
Totals, All Priorities 1,540 1,850 1,740 870 920 6,920
:5
>;<
(N
-------
VII-35
REFERENCES FOR CHAPTER VII
1.
Lee, R. C., and Wimmer, D. B., "Exhaust Emission Abatement by Fuel Variations to
Produce Lean Combustion", SAE Preprint No. 680769 (1968).
2.
Wimette, H. J., and VanDerveer, R. T., "Report on the Determination of Mass Emissions
from Two-Cyc1e Engine Operated Vehic1es" , prepared for NAPCA/DHEW by Olson
Laboratories, Incorporated (January 23, 1970), Contract No. CPA 22-69-91.
3.
Huls, T. A., Myers, P. S., and Vyehara, O. A., "Spark Ignition Engine Operation and
Design for Minimum Exhaust Emission", SAE Transactions, Paper No. 660405, 75, Sect.
2 (1967), p 699.
4.
Evaluation of Exhaust Recirculation for NOx Control, Volume 1, prepared for
NAPCA/DHEW by Esso Research & Engineering Co. (July 1, 1969), Contract No. PH
86-67-25.
5.
Huls, T. A., and Nickol, H. A., "Influence of Engine Variables on Exhaust Oxides of
Nitrogen Concentrations from a Multicylinder Engine", SAE Preprint No. 670482 (1967).
6.
Yumlu, V. S., and Carey, A. W., Jr., "Exhaust Emission Characteristics of Four-Stroke,
Direct Injection, Compression Ignition Engines", SAE Preprint No. 680420 (1968).
7.
Perez, J. M., and Landon, E. W., "Exhaust Emission Characteristics of Precombustion
Chamber Engines", Paper No. 680421, SAE Transactions, 77, Sect. 2 (1968), P 1516.
8.
Merrion, David F., "Effect of Design Revisions on Two Stroke Cycle Diesel Engine
Exhaust", Paper No. 680422, SAE Transactions, 77, Sect. 2 (1968), p 1534.
9.
Marshall, W. F., and Hum, R. W., "Factors Influencing Diesel Emissions", Paper No.
680528, SAE Transactions, 77, Sect. 3 (1968), p 2139.
10.
"Standards for Exhaust Emissions, Fuel Evaporative Emissions, and Smoke Emissions
Applicable to 1970 and Later Vehicles and Engines", Federal Register, 33 (108)
(Tuesday, June 4, 1968), p 8304.
11.
Newhall, Henry K., "Kinetics of Engine-Generated Nitrogen Oxides and Carbon Mon-
oxide", Twelfth Symposium (International) on Combustion, The Combustion Institute,
Pittsburgh (1969), p 603.
12.
Lavoie, George A., Heywood, John B., and Keck, James C., "Experimental and Theo-
retical Study of Nitric Oxide Formation in Internal Combustion Engines", Combustion
Science and Technology, 1 (1970), P 313.
13.
Scheffler, Charles E., "Combustion Chamber Surface Area, A Key to Exhaust Hydro-
carbons", Paper No. 660111, SAE Transactions, 75, Sect. 1 (1967), p 571.
-------
22.
23.
25.
26.
27.
28.
VII-36
14.
Daniel, W. A., "Engine Variable Effects on Exhaust Hydrocarbon Composition (A
Single-Cylinder Engine Study with Propane as the Fuel)", Paper No. 670124, SAE
Transactions, 76, Sect. 1 (1968), p 774.
15.
Daniel, Wayne A., "Why Engine Variables Affect Exhaust Hydrocarbon Emission", SAE
Preprint No. 700108 (1970).
16.
El-Mawla, Ahmed Gad, and Misrky, William, "Hydrocarbons in the Partial-Quench Zone
of Flames: An Approach to the Study of the Flame Quenching Process", SAE Preprint
No. 660112 (1966).
17.
Kurkov, Anatole P., and Mirsky, William, "An Analysis of the Mechanism of Flame
Extinction by a Cold Wall:, Twelfth Symposium (International) on Combustion, The
Combustion Institute, Pittsburgh (1969), p 615.
18.
Agnew, John T., "Unburned Hydrocarbons in Closed Vessel Explosions, Theory Versus
Experiment Applications to Spark Ignition Engine Exhaust", Paper No. 670125, SAE
Transactions, 76, Sect. 1 (1968), p 796.
19.
McKee, H. C., and McMahon, W. A., Polynuclear Aromatic Content of Vehicle Emis-
sions, Technical Report No.1 to Committee for Air and Water Conservation, American
Petroleum Institute from Southwest Research Institute (August 28, 1967).
20.
Habibi, Karam, "Characterization of Particulate Lead in Vehicle Exhaust - Experimental
Techniques", Environmental Science and Technology, 4 (March, 1970), p 239.
21.
Begeman, C. R., and Colucci, J. M., "Polynuclear Aromatic Hydrocarbon Emissions from
Automobiles and Engines", SAE Preprint No. 700469 (1970).
Hum, R. W., "Fuel: A Factor in Internal Combustion Engine Emissions", ASME Paper
No. 69-WAjAPC-8 (1969).
Hittler, D. L., and Hamkins, L. R., "Emission Control by Engine Design and Develop-
ment", SAE Preprint No. 680110 (1968).
24.
Trayser, D. A., and Creswick, F. A., "Effect of Induction-System Design on Automotive-
Engine Emissions", ASME Paper No. 69-WAjAPC-7 (1969).
Thomson, John C., Exhaust Emissions from a Turbocharged Texaco Combustion Process
(TCP) Stratified Charge Engine, Internal Report, NAPCAjDHEW, DMVPC (April 1970).
Dunne, Jim, "Ford's New Smog-Free Engine", Popular Science Monthly, May 1970, p 55.
Newhall, H. K., and El Messiri, I. A., "A Combustion Chamber Designed for Minimum
Engine Exhaust Emissions", SAE Preprint No. 700469 (1970).
Lyn, W. T., "The Spectrum of Diesel Combustion Research", Keynote Lecture, Diesel
Combustion Symposium, London, April 7-9, 1970.
-------
29.
30.
31.
VII-37
Wulfhorst, D. E., and Carey, A. W., Jr., "A Photographic Study of the Influence of
Barium Based Additives on Diesel Engine Combustion", Presented at the Spring Meeting
of the Central States Section of the Combustion Institute, Columbus (March 26, 1968).
Barnes, Gerald J., "Relation of Lean Combustion Limits in Diesel Engines to Exhaust
Odor Inensity", Paper No. 680445, SAE Transactions, 77, Sect. 3 (1968), p 1706.
Chemical Identification of Odor Components in Diesel Exhaust, Reports to Coor-
dinating Research Council Inc., and NAPCA/DREW, from A. D. Little, Inc., CRC Project
No. CAPE-7-68; NAPCA Contract No. CPA 22-69-63 (Second Quarterly Report,
September 12, 1969; Third Quarterly Report, December 15, 1969).
32.
Taylor, R. E., and Campau, R. M., "The IIEC - A Cooperative Research Program for
Automotive Emission Control", API Preprint No. 17-69 (1969).
33.
APRAC Status Report, Coordinating Research Council, Inc., New York (January, 1970).
34.
Federal Research and Development Plan for Mobile Sources Emission Control, FY
1970-1975 (Third Draft), prepared by NAPCA/DREW and Ernst & Ernst (1969).
-------
Chapter VIII
FUNDAMENTAL AND BROADL Y APPLICABLE
COMBUSTION RESEARCH
Albert E. Weller
Arthur Levy
Abbott A. Putnam
Joseph F. Walling
TABLE OF CONTENTS
SCOPE OF CHAPTER AND BACKGROU~D. . . . . .
. . -- .. ..
. . VIII- 1
COMBUSTION PHYSICS. . . . . . - . . . . . . . . . . . . .
Qassification of Combustion Processes . . . .
.. .. .. .. .. .. .. ..
Suggested Research in Combustion Physics. . . . . . . . . . -
Premixed Ftames. . . . . . . . . . . - . . . . .
uaseous DUfusion Flames. . . . . . . . . . . . . .
Droplet Combustion. . . . . . . . . . . . . . . .
Pulveriied-Coal Combustion. . . . . . . . . . . . .
Burning in Fixed and- Fluidized Beds. . . . . . . . . .
COMBUSTION CHEMISTRY
.. .. ... .. .. .. ..
.. .. .. ..
.. 8-- ... .. .. .. ..
RipOUs. Kinetics- . . . . .
.. .. .. .. ..
.. 8--" ." .. .. .. .. ...
Alternatives to Rigorous Kinetics.
.. .. .. .. .. ..
.. .. .. ... .. .. .. ..
Suggested Research: in .Combustion Chemistry .
.. .. .. ..
.. -.. .. .. ..
SUMMARY OF CURRENT AND RELEVANT fUNDAMENTAL
COMBUSTION RESEARCft . . . . . . . . . . . .
.. .. .. .. .. ...
RESEARCH OPPORTUNITIES RECOMMENDED' EORTHE
S.~AR PLAN.. . . . . . . . . . . . . .. - .
.. .. .. .. .. ...-..
PRIORrPf RANKING PROCEDURE FOR RESEARCH OPPORTUNITIES
IN THE FUNDAMENTAL AN~ BROADLY. APPLICABLE AREA. . . . .
Philosophy of "riority Rankilig for Fundamenta' Research . . . . .
RankeinQ:by Relevance to. Applied-RaD o-pportunities . - . . . . .
Disptayof Associated.. Priority Numbers. . . " . . . . . . . -
DESCRIPTIONS OF FUNnAM£NT AL AND BROAD" V
APPLICABLE RESEARCH OPPORTUNITIES. . . . . .
.. .. .. .. .. -
REfERENCES. FOR eHAPTER~ VIII. . . .
.- .. .. .. ..
.. ... .. .. .. .. ..
- 2
- 4
-10
- 'm
-11
-11-
-t1
-12
-IZ
-12
-16
-17-
-18
-18.
-26
-26
-2&
-21
-28
-------
-------
VIII-I
CHAPTER VIII
FUNDAMENTAL AND BROADLY APPLICABLE
COMBUSTION RESEARCH
SCOPE OF CHAPTER AND BACKGROUND
This chapter is concerned with combustion research that is fundamentally oriented and/or
broadly applicable to the applied areas discussed in previous chapters. The term "fundamentally
oriented" is used to indicate that the research is oriented towards gaining an understanding of, or
gathering data about, combustion processes, rather than oriented primarily to solving specific
problems in the applied areas. However, emphasis is placed not on obtaining scientific knowledge
for its own sake, but rather on obtaining pertinent information that is potentially useful for
reducing pollutant emissions from energy-conversion-combustion sources. * Further, the depth of
the understanding being sought is generally restricted to that needed for engineering applications.
Therefore, much of the research discussed in this chapter is empirical or phenomenological in
character.
When the combustion process is viewed on an input-output basis, it is clearly a chemical
process. Certain chemical species enter the process, and different chemical species emerge.
However, any detailed examination of the combustion process reveals that the chemical process
involved differs from many others in that by far the larger part of the chemical reactions occur,
at least in homogeneous-gas reactions, in a very narrow zone - the combustion wave.
This characteristic of the combustion reaction, that it occurs in a narrow region essentially
as a discontinuity, results from the highly exothermic character of the overall chemical reaction
coupled with the moderately high activation energy of the overall reaction. Studies of the
combustion process show that the process by which the discontinuity (or combustion wave, or
flame front) propagates itself is dependent on heat and mass diffusion. Consequently, many of
the easily observable characteristics of a flame are dependent on physical rather than chemical
processes. Combustion in the commercially important heterogeneous systems (Le., not premixed
on a molecular scale) is even more dependent on physical factors, as mixing phenomena appear
invariably to control the observed reaction rate.
Because of the observed importance of physical, largely aerodynamic, phenomena in
practical combustion systems, combustion research has historically been in large part a branch of
aerodynamics, particularly when the research has been related to engineering design problems.
* A continuing problem encountered in discussing combustion research in the context of this study is that of
separating combustion research, in the general sense, from combustion research directed towards the reduction
of air-pollutant emissions. This separation proves to be difficult, as the areas overlap to a large extent with
varying degrees of emphasis. Insofar as possible, a separation has been made. However, large areas remain in
which the primary emphasis would ordinarily be assigned to "combustion research" rather than "pollution
research"; yet these areas appear to require study if the objective of understanding the formation and fate of
pollutant emissions from combustion processes is to be reached.
-------
VIII - 2
In this view, the details of the mechanism by which the fuel is oxidized and the heat of
combustion is released are considered unimportant and largely ignored. However, as the concern
of the equipment designer, and consequently of the combustion research investigator, has
broadened to include air-pollution aspects, this situation seems to be changing. It may still be
acceptable in this view to ignore the part chemistry plays in the main heat-releasing reaction.
However, the role of chemistry, as contrasted to physics, in determining the emission of very low
concentrations (in terms of the heat balance) of species other than C02, H20 and N2, probably
cannot be ignored.
Figure VIII-I illustrates one way in which the physical and chemical phenomena involved
in combustion can be organized. The organization there shown can be regarded as a hierarchy
ranging from very basic science at the bottom to applied engineering at the top.
Also illustrated in Figure VIII-I are the approximate boundaries of research considered
appropriate to the scope of this study. These boundaries were chosen on the assumption that the
ultimate level of understanding required is roughly that sufficient to predict the emissions of
pollutants from combustion processes. It is not intended that these predictions necessarHy be
made from "first principles". Predictions based on empirical and phenomenological models are
perfectly acceptable as long as the predictions have useful accuracy and their limitations are
known.
The following discussion is divided between combustion physics and combustion
chemistry. This separation reflects the history of combustion research. However, a more unified
approach would be desirable and will probably be developed in the future.
COMBUSTION PHYSICS
It is clear that fundamental studies of combustion physics cut across the classifications of
combustion-equipment applications or source categories used in the Plan and discussed
previously. The fundamental studies considered here are concerned more with equipment that
simulates, or can be used to simulate, various flow paths through combustion devices than with
actual practical devices. This type of approach can be especially important in the case of
pollution-related combustion research, because in many combustion devices the significant pollu-
tion problems result from a small number of specific "bad" paths of flow through the devices.
Recent progress in eliminating smoke emission from aircraft gas turbines emphasizes this point.
To approach the presentation of this type of path study in systematic manner, the
phenomena involved in various combustion devices are classified into four different flame
types and three time-history cases. This makes possible systematic consideration of pollution
resulting from paths with various histories of temperature, composition, and so forth, as a
function of time. First a brief description of the flame type is presented, then the manner in
which it is related to air pollution is outlined, and finally various specific types of research
programs which could give information necessary to fill in gaps in knowledge related to the
prediction or suppression of air pollution are discussed. At the conclusion of this chapter the
suggestions for experimental projects are presented as research opportunities.
-------
VIII-3
Design a Development O~
Specific Combustors
---
-- .........
-- ~
Design a Development of Mathematical Models of ,
Combustion Systems Combustion Processes
",.-r:. - - - ~ /
/ /' Globa~ K~netic \ I
I - Descnpttons y
/ Experimental a Analytical S-tudies / /
COMBUSTION of a Single Combustion Proc,ass /' /
PHYSICS /'
/ /' I
,// /
COMBUSTION
CHEMISTRY
/
/
I
I
I
,
I
//
-1' Global Chemical
(Kinetics
ReactiOr1l
\ Mechon~
-------
VIII -4
CLASSIFICATION OF COMBUSTION PROCESSES
In general,. the physical factors that influence the combustion process need to be
understood to permit the prediction of pollutant output by a given combustor system under a
given set of operating conditions. These factors include fuel properties and fuel preparation,
mixing and turbulence, temperature, residence time, and dilution and recirculation. However, the
degree to which each of these factors is important to any particular combustor is influenced by
the general type of flame present and the general method in which the combustor operates.
Therefore, in identifying specific items of research that should be carried out, it is helpful to
classify the types of flame and combustion processes as shown in Table VIII-I. The importance
of the various influences can then be judged as they bear on each type of flame and combustion
process.
Table VIII-1. Classification Matrix of Combustion-Process Applications
Flame Type
and Fuel Continuous Cases Transient Cases Cyclic Cases
Premixed I ndustrial Processing I ndustrial Processing SI Engines
Gas Comm. & Residential Heating Comm. & Residential Heating Pulse Combustors
External-Comb. Engines External-Comb. Engines -
Diffusion Central Stations - SI Engines
Gas I ndustrial Steam Generation I ndustrial Steam Generation CI Engines
I ndustrial Processing Industrial Processing Pulse Combustors
Comm. & Residential Heating Comm. & Residential Heating -
Gas Turbines Gas Turbines -
External-Comb. Engines External-Comb. Engines -
Droplet Central Stations - SI Engines
I ndustrial Steam Generation industrial Steam' Generation CI Engines
Industrial Processing I ndustrial Processing Pulse Combustors
Comm. & Residential Heating Comm. & Residential Heating -
Gas Turbines Gas Turbines -
External-Comb. Engines External-Comb. Engines -
Solid fuel Central Stations - Pulse Combustors
Industrial Steam Generation - -
I ndustrial Processing I ndustrial Processing -
Comm. & Residential Heating Comm. & Residential Heating -
-------
VIII-5
In this matrix, the various combustion devices considered specifically in the preceding
chapters are identified. While these two methods of classification (namely, by flame type and by
application) are related, they are not identical. The purpose in using the flame classification here
is to simplify' the identification of fundamental work that can apply to one or more of the
classifications used elsewhere in this report.
In using Table VIII-I, it should be noted that continuous combustion processes include
steady-state operation at both maximum-load conditions, or design-load conditions, and part-load
conditions. '
Transient conditions include the changes from one load to another that cannot be treated
as a' series of quasi-steady-state conditions. Transient cases may be important when the changes
are rapid oompared with flow' time through the system. or with the time needed to achieve
near~equilibrium ; environmental conditions. Start-up and shutdown' are particularly severe cases,
and they have received little attention as far as air pollution is concerned.
The cyclic process includes both the internal-combustion engine and potential pulse-
combustor systems; part-load ,and transient cases in these .systemsare considered as included
therein]
Four different flame types have been called out as of practical interest, namely, (1)
premixed gaseous flames, (2) gaseous diffusion flames, (3) droplet flames" and (4) solid-fuel
flames. The following sections cover, for each flame type, the information that' is presently
available or can be deduced, what is still required, whether it is reasonable to expect it to be
obtained in the required time period, and' the research that must be initiated to obtain the
necessary information. Premixed flames are disctissed first because many of'the results obtainable
from studies of premixed flames should be broadly applicable to the other three flame types.
" ,
Premixed-Gas-flame Combustion
" ,
The' ,premixed gas flame is the 'simplest of the fouT'flatne types shown' in Table VIII-I.
The atomic composition throughout the combustor is close to uniform, although' preferential
diffusion effects may cause deviations from uniformity.
, Continuous Case/ For, the' continuous-flow' process, the major problem is predicting
velocity and temperature' patterns. Detailed methods for predicting th~ flame shape:and the
temperatare ,patterns in' combustion.. systems are not, well developed-;' although a. variety' of
semiempirical formulations are 'available. However, flow patterns in cold-flow systems ar~ usually
quite similar to' those in combustion systems, so that modeling procedures and simple computa-
tional techniques can often be used to predict gross flow patterns." '
From the, viewpoint. of air-pollution research, values' of the pertinent flow and tem-
perature parameters' in a given combustor could be measured rather than' computed. The
measured, parameters 'could then be related to the measured, pollution concentrations. For
tW
-------
VIII -6
means is sufficient( I), providing reasonable assumptions can be made relative to the fl~me
interface.
Transient Case. The remarks made previously concerning the continuous-flame case
generally hold in the case of the premixed transient flame as well. Even the computational
procedure mentioned can be extended to the transient case (at a greatly increased, computational
cost, however).
Cyclic Case. In the case of cyclic combustors, such as some SI engines and pulse
combustors, the ability to determine temperatures, compositions, and velocities is not adequate.
hi the case of the SI engine, one wall of the combustion chamber is moving, the pressure and
temperature are going through large ranges during a cycle, and the flame expansien rate is
complicated by the fact that even the fundamental burning velocity of the (uel;.air mixture can
be varying throughout the cycle. The flow pattern is not expected to be symmetric, and the
development of simple computational procedures to handle this cyclic problem canno,t be
expected in the- near future.
In- general, it is. probable that the most profitable research relative to the pollution
aspects of cyclic combustion physics will be hardware-oriented applied R&D. However, tliere'is
one area in which basic research on the production of pollutants should be carried out, and that
is in regard to wall quenching~ This can be investigated by bomb methods, although a ctose tie..ilt
of available results with data on critical flash-back distance antt reTated parmneters indicates. the
possibiIit}t of profitably using continuous flow rigs in such a study.
The chance that a premixed pulse combustor will be of commerciaf signifICance in the
near future is not large enough to warrant consideration here.
Gaseoas. Diffusion-Flame Combustion
The second flame type showl) in Table VIII-I, the gaseous diffusion. flarne~ is of interest
not only in itself but hecause it forms a- model for certain aspe<:ts of droplet combusfion and
solid-fuel combustion as well. . .
TIre mixing of fuel and' ail'. in the combustion region. is an. essential part of the
diffusiOn-flame phenomenon and it' fs associated with ponutant production. As- compared-- with
the pr.emixed-flame type, this mixing process introduce! new experimental and theoretical
compliCations. On the other hantf~ the mixing process-- is usually the gross rate-contl'oUing. faCtor-
in a. t\u'-bulent diffusion flame. Consequentfy, the condftions of mixing are often of far more-
imf)9rtance than chemical kinetic considerations for an understanding of such. flames (possibly
excluding some pollution aspects). . . .
. Continuous case~ Foul' different types of. continuous diffusion flames can be di8'
tinguished:. (1) the confmed nonturbulent flame, (2) tfie unconfined non turbulent flame, (3) the
confinect. turbulent flame, and {4) the unconfmed turbulent flame. In the confined flame,..
both fuel and air are in limited supply; in tfie unconfined flame, only the fiter is limited~. Also,An
the unconfined flame, buoyancy effects may pray an important rote in the observed phenomena.
by controlling the rate of air mfxing into the flame. Generally speaKing,. simple theory will
-------
VIII-?
predict many of the gross details of steady-state gaseous diffusion flames, although some
diffusion flames burn with a certain periodicity that is not fully understood. However, in the
detail needed for pollution studies, the state of knowledge is not as advanced.
In discussions of turbulent diffusion flames, turbulent mixing is usually viewed as the
rate-controlling factor; the reaction rate is not considered to be controlling, or even important,
other than through its effect on flame stability. However, turbulence itself is not well understood
in complex systems, and additional complications arise from the presence of a flame that adds a
random set of volume sources as the gases expand by heat from random pockets of combustion.
Nonturbulent and turbulent diffusion flames do have a feature in common: the flames
must be held af some point)- fine, or area. In a nonturbulent flame, the adjacent fuel and air
interdiffuse over the edge of the burner. At some distance less than the quenching distance, a
combustible mixture of varying composition is reached over a region greater than the nonnal
flame thickness. In this region, at the quenching distance, a premixed flame aevelops and holds
(or "seats") the diffusion flame. In fact, the diffusion flame may be pictured as a stepwise series
of premixed flames,- each with hotter but mOTe dilute initial compositions. *
In a-- turbulent flame, this seating of the flame often does: not occur. On the contrary,
there are onry local regions where- the maximum turbulent flame speed can exceed the velocity
of the on-com:ing Iuel-air mixture. Therefore, the flame-holding points shift about in space as
the loeaI,low-velocity regions shift about-in the turbulent stream. Furthermore, all of the leading
edges of the flame must move at maximum premixed flame speed through the- turbulent mixture,
stretching and. spreading the flame. When the flame no longer contacts enough loeal regions
where- it can "buck" tIte oncoming stream and not be extinguished, it will blow off unless held
by- some fndependent energy- source. It is rathey surprising that little quantitative information on
this phenomenon in industrial-size confined burners- is available in the literature.
It is clear that- various racal cells of tlie fuel and- air will- be- of different compositions and
ternperatures~ and that they will have different molecular and thermal dilutions as tliey approach
the reaction zone. ThiS variation from the average- o! local time and space. concentrations is
known as the:unmixedness ot: the ITuid;-(2) Conditionsc will be. extremely conducive to the
production of various pollutants in some cells)- while in others they win not. ThUSt it might btt
expected that fluid-supply pattem)- intensity and- 8-cale . af turbulence, and toeal heat-sink
conditions will have substantial effects- on the production of pol1utanb.- .
In the above discussion, it has- Deen- shown that many features. of diffusionfTames are
similar to those of premixed. flames and. that the character of the turbuIenGe. IS- a controlling
factor iIi the performance of diffusion flames of high gI:OSS volumetric mtensity. It is difficult to
see ho-w more than ~ gross understanding of the production of a pol1utant- in a- tmbulent
diffusion flame would: be possible without a fundamental uJidersf-anding of the flame vropagation
in sueh a combustion- s-ystemi
"In many combustors;. a premixed flame with insufficient. primary air forc-omplete combustion is fonowed-by--a
diffusion flame.- to comptete c<:ombustion; thU8-.- there is an interrelationship between. the two-types of flames.
-------
VIII -8
Transient and Cyclic Cases. Many of the cyclic and transient aspects of turbulent:
diffusion flames can be considered as large~scale turbulence effects similar to those discuSsed:
above.
Droplet and Particle Combustion
Droplet combustion in liquid-fuel-fired systems adds the additional complications offuer
injection (involving atomization), fuel trajectory, and fuel vaporization to the factors discussed
thus far.
Atomization. Liquid fuel may be atomized for injection into the burner by a variety:of
methods. By far. the most common methods are pre'Ssure-jet .atomizatiQn and two-fluid atomiza.,
tion, ordinarily using' either steam or air. As' might be' expected, there is a greater range of Cases.
possible.with two-fluid atomization with respect to type of fuel, size of droplet produced, and'
spray pattern. Literature is fairly extensive on the subject .of atomization.(3) However, available
information needs to be organized. . from the viewpoint of combustion applications to determine
the extent of the practical gaps in knowledge.
. Trajectory: For droplet combustion; the atomized. fuel (and :atoJ}1izingair or steam, if
any) . interacts in the combustion chamber with the surrounding . atmosphere, : aspirating" the
atrriosphere into the spray. In turn, the incoming atmosphere causes separation, of the fueHntQ
finer or coarser droplets. Thus, droplet trajectories jn the chamber 'are affected ,by the droplet
direction~ and momenta' at the' time ,of breakup from the spray . sheet, by the flow of" th..e
surrounding gas, and by their size and density.'Effective atomizer .and burnet'designcan direct
the large droplets to fuel-defiCient tegions~ On the other hand, if the droplets are too large, th~y
can impact on walls or go through the combustor without burning completely. The trajectQry 'of
a single droplet in a quiescent environment can be predicted; for the usual initial size and
velocity of droplet, the droplet Reynold's, number is sufficiently low to permit use of ' a simple
viscous-drag law. In the event of evaporation and/or cO'mbustion, the 'Reynold's' number effect
seems to shift som'ewhat, ,but more important effects result from initial turbulence in the stream
and dropl-ets in close proximity acting as a coherent mass. However, these problems are being
resolved' through various research efforts. . . '. ,
'. . .
Vaporization and Burning. As the droplets move, into a ho;t. gas environment, they begip.
to vaporize before they ignite'c 4) In fact, a collection of sufficiently small droplets, uniformly
distributed, can act as a premixed gaseous fuel. Larger droplets, on the'9ther hand, will ignite and
burn, as individual droplets. The flame' might bum as. asb.e~th . completely. surrounding' the
droplet, or, if there is sufficien.t relative velocity, it might open at the leading edge and evenpuU
away completely to the wake region. Again, close' proximity of. the droplets cauSeS .large
interaction effects.
. . . . )
There can be other complications for commercial liquid fuels, as contrasted with the pure
liquids on which vaporization and combustion tests are often made. While the lighter fractions
are vaporized and burned, the heavier fractions can be pyrolyzing and polymerizing. Particulate
matter. (including cenospheres) can be formed and carried through the combustion' system
without burning. Such performance is undesirable from the standpoint of heat-exchanger fouling
as well as from the air-pollution standpoint and attempts are usuallY. made to avoid this
-------
VIII-9
condition. Less severe conditions might still lead to air-pollution problems while not producing
the gross effects indicated.
Solid-Fuel Combustion. Fundamental studies of the burning of solid fuels can be
restricted from the air-pollution standpoint, in the context of Table VIII-l, to include only the
continuous-flow case. Only in the case of pulse combustors is there a problem with respect to
cyclic combustion, and such solid-fuel combustors are of insignificant commercial importance at
present. Transients in solid-fuel combustion are likely to be slow enough to be considered as a
series of continuous-flow cases. Continuous-flow-combustion considerations can be divided
between those relating to pulverized coal and those relating to the burning of considerably larger
sizes of coal, either in a fixed bed or a fluidized bed.
Even with narrowing of the range of interest to continuous-flow combustion, the process
seems to be considerably more complex than in the case of gaseous or liquid fuels. For instance,
it is known that the rate of combustion, the fraction of early carbon burnout, and the nature of
the solid residue depend strongly on the caking properties, volatility, and size distribution of the
coal, and the inlet-air and furnace-wall temperatures - as well as the usual variables, including
turbulence, that characterize the air stream.
Combustion of Pulverized-Coal. Despite the above-mentioned complicating factors, in
many respects the combustion of pulverized coal resembles that of gaseous and liquid fuels.
Since air is used to carry the pulverized coal into the combustion chamber, the injection process
resembles some types of two-fluid liquid atomization, although the necessary "preatomization"
of the coal precludes certain types of injection systems and makes some other possibilities more
difficult. In the case of bituminous coal, after the pulverized fuel enters the combustion chamber
there may be considerable gaseous fuel evolved as the particles are heated.
Combustion of a particle of pulverized coal usually occurs in two steps: (1) devolatiliza-
tion and burning of the evolved gaseous matter and (2) burning of the remaining solid nucleus.
Consequently, some results of studies of gaseous fuel flames from an air-pollution standpoint
may be applicable here. The trajectories of solid particles follow laws similar to those governing
liquid-fuel droplet trajectories. However, combustion is not in the gas phase as in the case of
liquid fuel; it occurs on the solid surface.
The rate of combustion may be limited by diffusion rate at high temperatures or by
chemical-reaction rate at lower temperatures. Furthermore, while most liquid-fuel droplets tend
to become smaller with time (in a rather simple size-time relationship), solid-fuel particles may
initially swell. Solid-fuel particles will also leave an ash residue.
Combustion in Fixed and Fluidized Beds. The problems of burning in fixed and fluidized
beds of coal are of a specialized nature, and are quite different from the burning of pulverized
coal; they are even less related to the liquid and gaseous-fuel combustion phenomena discussed
previously. The comments made in Chapters III and V are considered sufficient for the purposes
of this study.
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VIII-I 0
SUGGESTED RESEARCH IN COMBUSTION PHYSICS
Discussed below are suggested types of research in combustion physics which could
generate the information necessary to fill gaps in knowledge related to the prediction of, or
suppression of, pollutant emissions from combustion processes. The organization follows the
classification of combustion processes by flame type.
Premixed Flames
A series of fundamental studies on premixed flames can be identified that will yield
immediate and practical results, although a complete explanation of the results will require a
concomitant increased understanding of the chemical kinetics of the processes involved.
In these studies, a one-dimensional or plug-flow-type experimental combustor would be
used. Temperature-rise time could be controlled by burner orifice size (in an array of orifices)
and firing rate. Temperature-decay time could be controlled by surface-to-volume ratio, firing
rate, and wall temperature.
With such a combustor, it would be possible to investigate recirculation (while varying gas
temperatures* and point of admission of the recirculated gases), two-stage and multi-stage
combustion, and air dilution ** and leakage. In some cases, slight equipment modification might
be required such as the installation of additional banks of injectors. Even the turbulence level
could be controlled by insertion of turbulence-generating devices, although the possibility of
catalytic surface reaction should not be overlooked.
With this idealized one-dimensional experimental condition, the effects of varying the
temperature-time relation on various pollutants of interest can be studied for various fuel-air
premix compositions. Specific studies should be made at the pertinent pressures and maximum
temperatures of interest for methane, natural gas, ethane, ethylene, propane, butane, vaporized
gasoline, and vaporized kerosene. Measurements should be made to determine emissions of
particulates, HC, PNA, odor, and NOx. In all cases, the N2, 02, C02, CO, temperature, and flow
velocity should be measured.
Data obtained from these studies could form a basis for predicting emissions from more
complex practical combustion devices. Possibly sufficient data would become available to enable
testing of various hypotheses for handling kinetic data to obtain reasonably accurate predictions
of pollutant levels.
To summarize the recommendations in regard to basic studies of the combustion physics
of premixed flames, as they apply to air-pollution problems, the recommended work should be
carried out principally with a plug-flow laboratory-type combustor. Some bomb studies or similar
studies should also be made relative to quenching problems in IC engines. If there should be a
* A separate combustor might be used to supply the "recirculated" gases.
**This approach might also be used at the proper pressure to study air-pollution effects of quenching of combus-
tion in internal-combustion engines, as one example, and in gas-turbine combustors, as another example.
-------
VIII-ll
large reduction or termination of func~ing by other Government and private sources that are
currently supporting studies of laminar and turbulent flame speed and the flame stability of
pertinent fuels at the conditions of interest (pressures, temperatures, and compositions), NAPCA
support in these areas would also be important.
Gaseous Diffusion Flames
Basic studies of the combustion physics of gaseous diffusion flames, as they apply to
air-pollution problems, should concentrate largely on combined experimental-analytical-
theoretical investigations of the details of turbulent diffusion flames in the range of turbulence
intensity and scale encountered in industrially significant combustors. In studies of the effects of
various concentration gradients on pollution production, confined nonturbulent diffusion flames
might also be used.
Droplet Combustion
Much of the necessary fundamental work on droplet combustion can be expected to
proceed without any particular support from NAPCA. However, there are some areas in which
additional support could accelerate significant programs and some areas which relate strictly to
air pollution.
While there appears to be a considerable amount of information available on droplet
production, trajectory, evaporation, and burning, there is a decided lack of up-to-date, unbiased,
in-depth analysis. Adequate critical review of this information and publication of monographs
not only would aid fundamental investigations in the field, by emphasizing the items needing
clarification, but would aid development efforts in more applied areas of liquid-fuel combustion.
It would also appear worthwhile to make a fundamental study of the generation of
pollutants by various fuels and various-size droplets moving through an environment comparable
to that expected in practical combustors. It would be interesting for the design engineer to
know, for instance, whether NOx generation is promoted or discouraged by the burning of a fuel
in a droplet sheath, as contrasted with the burning of completely vaporized droplets. Appropriate
experiments should be carried out with the usual fuels and with droplets of the size range
normally expected in a combustor.
Pulverized-Coal Combustion
It would appear that some research should be conducted on the combustion of the
complex mixture of gases evolved when coal is heated rapidly. These are mostly complex
hydrocarbons but they also include such simple gases as hydrogen and methane. The residual
"coked" carbon particle, which will retain varying amounts of hydrocarbons (depending upon
the original composition of the coal and the speed with which the particle is heated) should also
be evaluated as a combustible particle.
-------
VIII-l 2
In the case of pulverized coal itself, consideration should be given to the possibility that
certain types of ash could have specific effects on the' types of pollutants produced. Because
both pyrolysis of tlie coal constituents and chemical reactions of chemically bonded nitrogen can
take place during the coal-particle heating period, there is the possibility that particle-size
distribution can affect pollutant production. The effect of such distributions on the various
pollutants should be investigated. These investigations could be carried out in a plug-flow furnace
such as described above for gaseous fuels.
Burning in Fixed and Fluidized Beds
The problems associated with burning in fixed and fluidized beds of coal are quite
different from those associated with the burning of pulverized coal in conventional furnaces.
However, fluidized-bed combustion occurs at a relatively low flow rate and with large sizes of
coal elements; this means that a relatively simple type of fundamental experiment might be of
value.
It is possible to visualize a simulated fluidized bed in which individual particles could be
suspended in a hot gaseous medium of controlled composition and temperature. Their size, mass,
and temperature history could then be studied. For the most part, however, efforts concerned
with fundamentally oriented research in this particular area could be confined to abstracting
pertinent information from the large amount of general literature on fixed and fluidized beds.
COMBUSTION CHEMISTRY
Combustion chemistry as related to pollutant emissions can be examined from two
viewpoints: (1) the viewpoint of rigorous chemical kinetics and (2) the more-pragmatic alterna-
tive viewpoint in which any model, procedure, etc., which produces useful answers is acceptable.
RIGOROUS KINETICS
With respect to the first viewpoint, it might seem that the objectives of this section of
the report should be to identify the information on chemical kinetics that is needed to
understand the emission of pollutants from the combustion process and to recommend a
program of research to fill such information gaps. While such an approach seems quite logical, it
is not currently feasible. This is due largely to the fact that the probably relevant body of
chemical information is staggering, and perhaps unmanageable, in size. Further, this body of
information is largely undeveloped, and criteria for selecting the more technologically important
parts of this body of information are largely unknown.
This does not mean that chemical kinetics can make no contribution to the under-
~tandin~ ?f pollutant emissions. In fact, such contributions have already been made, for example
In provIding understanding of the thermal fixation of nitrogen in fuel-lean combustion systems,
-------
VIII-13
understanding of the oxidation states in which sulfur appears in combustion gases, and under-
standing of the oxidation of CO in the CO - H2 - 02 system.
From the standpoint of chemical kinetics, a chemical reaction is "understood" if rate
constants are available for all the elementary reactions involved in the process leading from
reactants to products. An elementary reaction, for example
o + N2 .
. NO + N
is a reaction that occurs as shown' by the' equation without intermediate steps. For the
high-temperature N2 - 02 reaction, three elementary reactions involving six chemical species
appear to provide an adequate description of the system, although' additional species and
elementary reactions may be involved to some extent. In the case of the H2 - 02 system,
perhaps nine chemical species are observed, and for the CH4 - 02 system, perhaps thirteen -
without considering those species containing more than one carbon atom. The complexity of the
situation where multicomponent comtnercial fuels, such as hiavy oils, are involved can perhaps
be imagined.
The possible elementary reactioTI'sbetween these species are not easy to study: in general,
an individual elementary reaction cannot be isolated from the overall process and' exaIniiled!
independently. The species involved are often highly reactive and fleeting.
....-"
The chemically reaCting' 'systems that' should be considered in ordinary combustiolI
studies, and in studies of the emission of pollutants, can probably be classified as follows:
. Nitrogen - Oxygen
. . Hydrocarbon, - OKygen
. Hydrocarbon - Nitrogen
. Organically Bound N, P, S, Metals, etc. -" Oxygen.
Some aspects of these systems and the present state ,of, knowledge, c.oncerning them ~re ,discussed
in the following sections.
The Nitrogen-Oxygen System
The nitrogen-oxygen system, cOq1pared with hydrocarbon-oxygen ,systems, is, not com~
plex. Y~t a sizable .number Qfelementary reactions can be written just; for thy. species uS\lal~y
considered in flames. ,This system holds practic!ll iQterest Jor ,some aerospace and indu.strial
applications and it has some characteristics which make it attractive to the pure scientist as we,ll.
Consequently, it has been the subject of much study, and estimates of the rate constants for a
great many of the possible reactions are available.(5,6) .'
If the equilibria of the N2 - 02 system are examined at the temperature levels found in
flames, it appears that NO is the majqr product, the amouI).t of N02 being much smaller. N20
may be involved as an intermediate in the decomposition of NO. ..It is. w9rth noting that, other
-------
VIII-l 4
factors being fixed, the NO + N02 concentration does not increase monotonically with tempera-
ture. A maximum appears in the region of 3500 K, after which the equilibrium amounts of NO
+ N02 diminish. (7)
Once formed, NO and N02 may react with 0, H, OR, hydrocarbon radicals, etc., just as
do many other species to be found in flames. Even in systems where these reactive substances
are present, however, reasonable success has sometimes been achieved in describing the kinetic
behavior of NO by using models which exclude many such reactions.(S) Thus, even in
hydrocarbon-air systems, a reasonably satisfactory treatment of the NO problem has sometimes
been achieved. Usually two relatively simple mechanisms are invoked. Above 1700 K or so,
02+M- - 20+M
O+N2 - NO+N
N+02 - NO+O
The fll'S-t reaction is often assumed to be equilibrated-, although the assumption is not essential
and is sometimes quite wrong. Thel'e seems little reason to doubt the importance or essential
correctness of this mechanism.
At intermediate temperatures (below about 1700 K) where few N atoms can exist (and:
therefore the previous mechanism becomes very slowt the elementary reaction,
N2:+ 02 - 2NO- ,
bas been used~ Uhtil fairly recently this was thought to be a simpfe homogeneous bimolecular
reaction ,roceeding through a- four-center-activated complex. However, -recent evidence suggestS,
that thee-intermediate temperature- decomposition {th~ reverse reaction} proceeos with
2ND -N20+ 0:
38: a rate..determining step, probably foUowed-_by
N-20 ow- --N2+0
20+M --- 02-+M
If~ this- is true, then a mechaniSllF of formation of NO in the NT - 02 system in this temperature
range is not necessariry simply the "reverse,t- of the fatter three: eqJ1ations. Therefore, the
mechanism and rate of formation-of NO In the nitrogen-oxygen system below about t7GG:K are--
wWertain. (9t
At still lower temperatures - below perliaps nOG K - Jie:teroge-neous reactions- begin ta-
predominate. This region is of little interest in Gambustion processes- .
The two sets of high'-temperature reactions pr-OVitte a commonly used basis fGr reaction-
modeling. However, other eteine-ntary reaetion rates are- knewn for this system- and they coul&-be
included in a model if desired.. . . . .
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VIII-IS
It is perhaps possible to assert that NO formation rates can be kept small by keeping the
temperature low and by keeping the amounts of 02 and N2 small. Further generalities are not
warranted because multiple roles may be played by N2 and 02. Perhaps this can be better
appreciated if it is noted that, beyond some point, N2 or 02 can function as a temperature-
moderating diluent as well as a reactant. There is yet another possible role. Nitrogen may alter
the thermal conductivity sufficiently in some situations to overcome the diluent role and make a
flame hotter, not cooler.< 1 0) Obviously these roles must be established in each instance.
The Hydrocarbon-Oxygen System
Complete combustion of a hydrocarbon is defined as a process in which the only reaction
products are C02 and H20. Practical instances of hydrocarbon combustion yield a considerably
more varied product list. These other carbon-containing species are attributed to incomplete
combustion.
Hydrocarbon-oxygen systems are impressively complex. Below about 500 K, hydrocarbons
may react slowly with oxygen. Between about 500 and 700 K is a region of complex ignition
behavior often called the cool-flame region. These flames may be extinguished, stabilized, made
periodic, or caused to ignite a second, hotter flame, depending on other variables. Products of
such cool flames are various oxygen-containing species that are destroyed at higher temperatures.
Cool flames may be related to preignition phenomena in internal-combustion engines. At present,
it is considered likely that such reactions proceed by a chain process, and suggestions have been
made for such mechanisms. ( 11) .
High-temperature oxidation reactions of hydrocarbons are also enormously complex. It is
usually thought that pyrolysis (cracking) must be considered in addition to reactions of oxygen
and oxygenated species. Pyrolysis reactions are usually described in terms of Rice-Herzfeld
mechanisms(12). [Considerable discussion has recently ensued about the importance of molecular
mechanisms. The issue still seems undecided(13).] Rice-Herzfeld mechanisms involve the creation
of free radicals (usually by fission of a reactant), chain propagation by hydrogen abstraction from
the parent compound and/or radical stabilization by splitting off olefins, and termination by
radical destruction. In the case of combustion, free radicals could be created by 0, OH, or H
attack on the hydrocarbon. Hydrocarbon radicals might then react in a number of ways. If the
radical is massive, it might undergo fission to form an olefin and another less-massive radical.
In oxygen-deficient regions of a combustion process, radical concentrations may become
sufficiently high for radical recombination and polymerization reactions to become significant.
Sizable polymers may undergo molecular rearrangements, plus hydrogenation and dehydro-
genation reactions, depending on local conditions. In this way it is possible to rationalize the
persistence of hydrocarbons in quenched combustion gas from fuel-rich regions as due to radical
recombination; polynuclear aromatics as due to polymerization plus hydrogenation favored at
lower temperatures; and combustible particulates as due to polymerization, ring-forming
rearrangements, and dehydrogenation favored at higher temperatures.
This, of course, does not begin to account quantitatively, or even completely
qualitatively, for such processes. No attention has been paid here, for example, to nucleation, to
different classes of combustible particulates that have been recognized, or to the effect of
electric fields.
-------
VIII-l6
In fuel-lean regions it is usually considered that hydrocarbons will be fragmented by OH
and 0 attack with the formation of CH3, H20, and lower-molecular-weight hydrocarbons. CH3.
may react with 0 or 02 ultimately to form CO. The CO is thought to be converted to C02
largely by reaction with OH.(4) The specific reaction rates for the reaction of hydrocarbons with
OH are probably somewhat higher than for the reaction of CO with OH. Thus, until the
hydrocarbon concentration is reduced, most OH will react with hydrocarbons rather than with
CO, and the elimination of CO in combustion is ultimately tied to the completeness of
hydrocarbon oxidation.
The Hydrocarbon-Nitrogen System
The hydrocarbon-nitrogen system includes all of the hydrocarbon pyrolysis reactions, and
what has been stated about them previously applies here as well. There are two other relevant
classes of reactions that belong in this system: the nitrogen-hydrogen and the nitrogen-atom-
hydrocarbon reactions. Many of the rate constants in the nitrogen-hydrogen system have been
estimated.(S) There is at least a basis for including the system in a model if this is desired.
Nitrogen-atom-hydrocarbon reactions have been observed, although extensive detailed informa-
tion does not seem to be available. However, at present more detailed knowledge of this reaction
system is probably unimportant.
Organics (Containing Chemically Combined
N, P, S, Metals, Etc.)-Oxygen System
It is probably necessary to consider such organics individually when quantitative results
are of interest. However, two rather general statements might be made. First, if molecules
containing P, S, metals, etc., are to be considered pollutants, no type of combustion modifica-
tion alone can contribute to the solution of the emission problem. This is merely because the
element will survive any chemical process. If it is considered objectionable, it will have to be
removed from the input or the exhaust. Second, it is likely that the mechanisms and rates of the
reactions of nitrogen contained in a fuel will depend on the details of its chemical environment
in the fuel. It is not clear that mechanistic knowledge of such reactions will have an important
bearing on near-term engineering design to control NOx.
ALTERNATIVES TO RIGOROUS KINETICS
The approach of rigorous chemical kinetics would seem to be the preferred approach to
problems in combustion chemistry in that such an approach promises the greatest generality of
results. However, this approach does not appear to be currently feasible, at least for the totality
of problems considered here. Thus some alternative approach is needed.
As in all cases where engineering demands exceed the capabilities of basic science, the
alternatives have been empirical and phenomenological descriptions of the processes of interest.
The major difficulty with such approaches is that there is no assurance that the description will
have the generality required for practical application. This difficulty has been extensively
discussed in terms of modeling and scale-up of chemical processes. However, useful results are
-------
VIII-] 7
possible, even though limited. Examples include global* reaction-rate models for heat release in
hydrocarbon-air systems, empirical models correlating certain emissions from gasoline engines,
and mixed models of the combustion process in rocket engines. Although phenomenological
descriptions may be limited in generality, it can always be hoped that further study and
refinements will extend their usefulness.
SUGGESTED RESEARCH IN COMBUSTION CHEMISTRY
Much of the research suggested in the preceding section on combustion physics could
equally as well have been regarded as related to combustion chemistry, specifically the develop-
ment of an empirical global-kinetic scheme relating the emission of pollutants to the (mainly)
physical-process variables. The remaining research to be considered here is essentially of a finer
cut: attempted isolation of specific features or parts of the combustion process which have a
distinctly chemical nature.
Within the realm of combustion chemistry, the pollutants of greatest concern are those
involving products of incomplete combustion, that is, products that are not fully oxidized, and
nitrogen oxides.
The research activities suggested by the above considerations are:
. Information should be obtained on chemical kinetics of simplified
systems and isolated parts of the combustion process where possible.
Specifically, studies of the interactions of the N2 - 02 system and
the CO - 02 - H2 system with some simplified HC - 02 system seem
indicated.
. Long-range basic chemical kinetic studies of the HC - 02 - N2 system
and the development of schemes for dealing with complex reacting
systems are needed.
. Empirical descriptions should be developed of the reaction kinetics
involved in the formation and destruction of products of incomplete
combustion and NOx.
*The term "global" is used here both in the sense of overall and in the sense that internal details are excluded.
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VIII-l 8
SUI\DMARY OF CURRENT AND RELEVANT FUNDAMENTAL
COMBUSTION RESEARCH
Before listing the ongoing fundamental research on air pollution as related to the
combustion process, general sources of published information in this area should be noted. A
significant portion of such work in the U.S. and abroad is eventually reported or referred to in
the volumes containing the papers presented at the biannual International Symposia on
Combustion, sponsored by The Combustion Institute. A second important collection of funda-
mental combustion papers is Combustion and Flame, the journal of The Combustion Institute.
Centers of fundamental research in this area can easily be identified from these sources. Other
papers are scattered through the technical literature.
As discussed elsewhere, a systematic search was made of the literature to identify
currently active programs related to the combustion aspects of air pollution. The projects
identified in this search were screened from the point of view of fundamental research. The
projects of interest are listed in Table VIII-2 (Combustion Physics) and VIII-3 (Combustion
Chemistry). In these projects, either the spirit of the study appears to be fundamental or the
procedure and/or expected results will apparently fall in this area. Information on time, cost, and
rate of effort was almost completely lacking; therefore, these items are not included in the
tabulation.
RESEARCH OPPORTUNITIES RECOMMENDED FOR THE
5-YEAR PLAN
Opportunities for fundamentally oriented research activities in combustion were recom-
mended in the following categories:
. Physical Orientation
- Path-history relations
- Single and small number of droplets and particulates
- Combustion in fluidized beds
- Turbulence and droplet monographs
. Chemical Orientation
- PNA, soot
- HC - 02 kinetics
- NOx - HC kinetics
- (Miscellaneous)
. Combined
- Global kinetic descriptions
The 31 fundamental and broadly applicable research opportunities that were identified are
described in more detail at the end of this chapter, following the description of the procedure
used for priority ranking. Of the 31 research opportunities., 27 of these have been evaluated and
priority ranked, one is unranked, and 3 are discussed but not recommended. A summary by
priorities is provided at the end of this chapter.
-------
Table VIII-2. Current Research in Combustion Physics
Project
Key
Sponsoring
Organization
and Contract No.
Research Organization
Principal
Investigator
96,683 (FY '691
Project or Contract Title
VIlI-a
Low emission continuous flow combustion
for vehicle propulsion systems
NAPCA-DMVRD
CPA 22-69-128
Marquardt Co.
Van Nuys, Cal.
C. V. Burkland
VIlI-b
Research and development engineering
services
NAPCA-DPCE
CPA 22-69-144
Task No.4
Mass. I nst. of Tech.
Cambridge, Mass.
E. R. Gilliland
K. Smith
VII 1-<: Liquid fuel injection and combustion NAPCA-ORG Rutgers Univ. R. L. Peskin
AP 00906 New Brunswick, N.J. C. E. Polymeropoulos
VIlI-d Engine emission reduction by combustion NAPCA-ORG Penn. State Univ. W. E. Meyer
control AP 00560 Univ. Park, Pa. S. S. Lestz
VIlI-e Reduction of atmospheric pollution by NAPCA-DPCE Argonne Nat. Lab. A. A. Jonke
application of fluidized-bed combustion Argonne, III.
VIlI-f Characteristics of flames causing NAPCA-DPCE Bureau of Mi nes J. Grumer
pollution Explosives Res. Ctr. M. E. Harris
Pittsburgh, Pa. V. R. Rowe
E. B. Cook
VIII-g NOx from coal combustion NAPCA-DPCE Bureau of Mines D. Bienstock
Pittsburgh, Pa. R. L. Amsler
E. R, Lauer, Jr.
VIlI-h Ignition of heterogeneous and condensed Bureau of Mines Bureau of Mines I. Liebman
phase systems by intense laser radiation Explosives Res. Ctr. H. E. Perlee
-Pittsburgh, Pa.
VIlI-i Yield of nitric oxide from constant NASA UCLA R. D. Kopa
volume combustion Los Angeles, Calif,
Objective or Scope
Develop all technical information neces-
sary to optimize continuous-flow com-
bustion systerns in mobile equipment
for lowest possible emissions
Collect and organize current theories,
data, and empirical expressions regarding
heat transfer in fluidized beds. Interpret,
evaluate, and rework this information in
an effort to develop an improved physical
model, and/or a more effective empirical
expression
Make experimental and analytical study of
the basic mechanisms of ignition and com-
bustion of single- and multi-drop
configurations
Determine effect on HC and CO emissions
of homogeneous charge engines by hetero-
geneous flame propagation due to local
variations in air motion
Evaluate potential of fluidized-bed combus-
tion for pollution control
Study the factors that lead to or limit emis-
sions of NOx, CO, and light hydrocarbons
in gas appliances and develop a burner de-
sign that utilizes these findings
Evaluate the factors involved in NOx forma-
tion during coal combustion
Determine if there is a minimum particle
size below which a radiantly heated parti-
cle will not self-ignite or ignite a flammable
atmosphere
Determine the effect of wall properties on
the yield of nitric oxide formed during
combustion in a constant-volume reaction
vessel
Funding, $
14,786 (FY '691
28,068 (FY '701
37,385 (FY '69)
50,238 (FY '70)
52,262 (FY '69)
<:
-
-
-
I
-
\0
190,000 (FY '69)
267,000 (FY '701
201,000 (FY '64-67)
77,000 (FY '631
-------
Table VII 1-2.
(Continued)
Project
Key
Sponsoring
Organization
and Contract No.
Research Organization
Principal
Investigator
Project or Contract Title
VIlI-j
Complex mixing models for chemical
reaction
U.S. Air Force Off. of
Scientific Res.
City College Res. Found. R. Shinnar
New York, N.Y.
VIII-k Nucleating agent injection mechanisms U.s. Air Force U.S. Air Force S. J. Birstein
Cambridge Res. Labs
Cambridge, Mass.
VIII-I I nvestigation of conditions leading to U.s. Air Force Ohio State Univ. R. Edse
spontaneous ignition Res. Foundation
Columbus, Ohio
VIII-m Wave dynamic studies U.S. Air Force Univ. of Calif. A. K. Oppenheim
Off. Scientific Res. Berkeley, Calif.
VIII-n Compression-ignition engine combustion U.S. Army Southwest Res. Inst. R. D. Quillian, Jr.
phenomena Coating Chem. Lab. San Antonio, Tex.
VII 1-0 Analytical studies in burning initially U.S. Army TRW, Inc. F. E. Fendell
unmixed reactions Redondo Beach, Calif.
VIlI-p Internal combustion engine simulation U.S. Army Univ. of Wis. P. Myers
Tank Auto. Command Madison, Wis. O. Uyhara
VIlI-q The study of flame propagation in clouds Nat'l Sci. Found. Worcester Poly tech. C. W. Shipman
of sol id fuel particles in air Inst.
Worcester, Mass.
VIII-r
Chemically reacting flows
State of California
UCLA
Los Angeles. Calif.
V. E. Denny
A. F. Mills
Objective or Scope
Funding, $
Evaluate the effect of the stochastic and
nonuniform nature of the transport
processes on non-isothermal nonlinear
reactions. Special attention will be paid
to the unsteady behavior of exothermic
reactions in premixed and non-premixed
flow systems
Study experimentally the break-up of
droplets injected into high-velocity gas
streams
Analytically and experimentally investigate
the conditions leading to spontaneous
ignition in flowing explosive gas mixtures
Investigate gas-wave-dynamic phenomena
during transition from combustion initia-
tion to establishment of stable detonation
in reactive gaseous media
~
-
-
I
IV
o
Obtain a more basic insight into compression.
ignition process and to investigate effects of
fuel properties on engine performance and
exhaust emissions
Make a theoretical study of the effect of free
convection on thin flame shape, droplet
drag, and surface mass transfer rates of a
burning spherical droplet
Make computer simulations of diesel and Otto
cycle engines with correlation of exhaust
smoke to various parameters
Study the propagation of flame in clouds of
solid fuel dispersed in air by mapping the
composition, density, and velocity through-
out the burning zone, to deduce reaction
rates from the appropriate material balance
equations.
Analyze (using numerical methods) turbulent
reacting flows in ducts including effects of
intra~particle heat and mass transfer in the
-------
Table VIII-2.
(Continued)
Project
Key
Project or Contract Title
Sponsoring
Organization
and Contract No.
Research Organization
Principal
Investigator
Objective or Scope
Funding, $
VIII-s
VIlI-t
VIII-u
VI II-v
VIII-w
VIII-x
XIII-y
XIII-z
Investigation of transient diffusion flame
phenomena in a diesel engine combus-
tion chamber
Air pollution problems relating to
combustion
Desulphurizing combustion in a chemi-
cally active fluidized bed
Short term work on pollution from
petrol engines
Long term work on pollution from
petrol engines
Combustion of monosized droplet
streams in stationary self-supporting
flames
Research into flames and combustion
with emphasis on the domestic and
commercial utilization_of gas
Studies on flame aerodynamics and
operating variables to reduce emissions
Caterpillar Tractor Co.
Esso Petroleum Co.,
Ltd.
MI RA Research
Programme
MI RA Research
Programme
Shell (Fellowship)
Univ. of III.
Urbana, III.
Purdue Univ.
Lafayette, Ind.
Esso Petroleum Co.,
Ltd.
England
Motor Industry Res.
Asso.
Warwickshire, England
Motor Industry Res.
Asso.
Warwickshire, England
Sheffield Univ.
England
The Gas Council
Watson House Res. Div.
Fulham, London,
England
Res. Center of the
French (National)
Coal Industries
France
W. L. Hull
E. K. Buchholz
L. F. Albright
G. Moss
J.W.T. Craig
C. D. Haynes
M. Southall
A. E. Dedd
Z. Holubecki
I. D. Lytollis
A.S.M. Nuruzzaman
E.A.K. Patrick
M. Delanney
M.Busso
Determine what happens in the combustion gf
chamber of a diesel engine under very
highly supercharged conditions
Determine surface and heat transfer effects
on nitric oxide production in combustion
gases
Develop a fluidized bed to effect the reduc-
tion of sulfur oxides emissions from oil
fuel combustion
-<
.....
.....
.....
,
IV
-
Assess use of exhaust recirculation as a
means of controlling nitric oxide, to assess
variable dilution sampling method
Assess the effect of mixture quality and
combustion chamber configuration on
exhaust emission of a single cylinder engine
Determine the effect of fuel characteristics,
drop size, and droplet spacing on the com-
-------
Table VII 1-3. Current Research in Combustion Chemistry
Sponsoring
Project Organization Principal
Key Project or Contract Title and Contract No. Research Organization Investigator Objective or Scope Funding, $
VIlI-aa Infrared spectroscopic study of gas-solid NAPCA-DPCE General Technologies J. S. Burton Develop a rapid technique for providing 51.879 (FY '691
interactions CPA 22-69-59 Corp. quantitative information about the 39,643 (FY '701
CPA 70-03 mechanism of a heterogeneous reaction
VIII-bb Structures of some oxides of nitrogen NAPCA-QRG Penn. State Univ. I. C. Hisatsune I nvestigate the structures and reactions of 19,016 (FY '701
AP 00018 Univ. Park, Pa. some oxy-nitrogen compounds 21,7391FY '691
VIII-cc Microkinetics studies in reactions of NAPCA-QRG Calif. Inst. of Tech. W. H. Corcoran Study reactions of oxides of nitrogen at None IFY '701
nitric oxide AP 00265 Pasadena, Calif. room temperatures and in plasma jets of 575 IFY '69)
argon, to study the partial oxidation of
hydrocarbons, particularly at very low
concentrations of oxygen
VIII.dd Kinetics and thermochemistry NAPCA.ORG Stanford Res. Inst. S. W. Benson 97,759 IFY '70)
AP 00353 Menlo Park, Cal if. 95,584 (FY '69)
VIlI-ee Kinetic behavior of inorganic radicals NAPCA-QRG Kansas State Univ. D. W. Setser Find ways of producing inorganic free 41,502 (FY '701
AP 00391 Manhattan, Kan. radicals in clean sources so that rate 32,292 fFY '691 <:
constant can be measured in a direct way -
-
-
I
Reactions of S02 with hydrocarbon NAPCA-QRG Cornell Univ. S. H. Bauer 54,716 (I'Y '701 N
VIlI-ff N
CO and H2 AP 00633 Ithaca, N.Y. 64,705 IFY '69)
VIII-gg Matrix isolation of nitrogen oxides NAPCA-QRG Howard Univ. W. A. Guillory 3,500 (FY '70)
AP 00638 Washington, D.C. 32,918 IFY '681
VIII-hh Activation energies for radical and NAPCA-ORG Stanford Res. Inst. S. W. Benson 29,861 IFY '701
molecular reactions AP 00698 Menlo Park, Calif. 30,501 (FY '69)
VIlI-ii Kinetics of sulfur-oxide formation in NAPCA-ORG Battelle Mem. Inst. A. Levy Determine kinetics and mechanism of 43,697 (FY '70)
flames AP 00464 Columbus Lab. sulfur oxidation using a mass-spectrometer 49,876 (FY '69)
Columbus, Ohio
VIlI-jj Use of electric fields in combustion NAI'CA-QRG Penn. State Univ. R. J. Heinsohn Study the production of carbon and nitrogen 17,462 (FY '70)
AP 00643 Univ. Park, Pa. oxides in flames subjected to electrostatic 32,804 (FY '691
fields
VIlI-kk Reduction of polycyclic aromatic NAPCA-QRG Univ. of Birmingham R. Long Study pyrolysis in diffusion and formation of 7,675 (FY '701
hydrocarbons AP 00323 Birmingham, England R. Perry polycyclic aromatic hydrocarbons during 4,290 (FY '69)
M. D. Crittenden incomplete combustion
VII 1.11 Kinetics of NO at high temperatures NAPCA-ORG Drexel Inst. of Tech. R. A. Matula 35,916 (FY '70)
AP 00858 Philadelphia, Pa. 46,526 (FY '69/
VIlI-mm Kinetics of particle growth NAPCA-QRG Clarkson College of Tech. F. C. Goodrich Determine the rate of growth of aerosol 17,772 (FY '70)
-------
Table VIII-3. (Continued)
Project
Key
Project or Contract Title
Sponsoring
Organization
and Contract No.
Research Organization
Principal
Investigator
Objective or Scope
Funding, $
None (FY '70)
24,416 (FY '69)
VIlI-nn
VI 11-00
VIII-pp
VIII-qq
VIlI-rr
VIlI-ss
VIII-tt
VIII-uu
VIlI-vv
VIlI-ww
Photolysis and fluorescence of oxides of
nitrogen
Chemistry of sulfur in hot combustion
gases
Kinetics of NO and CO formation in
combustion gases
Diesel fuel combustion chemistry as
related to odor
Physical chemistry of high temperature
gases
Gas reaction kinetics
lon-molecule reactions in flames
Kinetic spectroscopy of chemically
active systems
Pyrolysis of metal and metal hydride
particles
Sychroton photo ionization with mass
spectrometric detection
NAPCA-ORG
AP 00595
NAPCA-ORG
AP 00639
NAPCA-ORG
AP 01228
NAPCA-ORG
AP 00576
NASA
U.S. Navy
ONR
U.S. Air Force
SREP
U.S. Air Force
Off. Scientific Res.
u.s. Air Force
Off. Scientific Res.
u.S. Air Force
Off. Scientific Res.
III. Inst. of Tech.
Chicago, III.
Univ. of Washington
Seattle, Washington
Mass. Inst. of Tech.
Cambridge, Mass.
Drexel Univ.
Philadelphia, Pa.
NASA
Lewis Res. Ctr.
Cleveland, Ohio
Harvard Un iv.
Cambridge, Mass.
liT Res. Inst.
Chicago, III.
Indiana Univ.
Bloomington, Ind.
Univ. Denver
Denver. Colo.
Univ. of Wisc.
Madison, Wisc.
H. Von Weyssenhoff
C. B. Meyer
J. C. Keck
R. A. Matula
R. S. Brokaw
G. Kistiakowsky
P. Feng
E. J. Bair
W. H. McLain
J. W. Taylor
Measure fluorescence spectra and life-
times of nitrogen dioxide with spectral
resolution of both exciting and emitted
light
Obtain knowledge of the reaction rates
and mechanisms in high temperature
gases
Identify first formed fragments and their
electrical state by analysis of chemilu-
minescent spectrum from reactions of
oxygen with simple hydrocarbons
Study ion-molecule (including negative ions)
reactions in flames using a mass
spectrometer
Elucidate detailed quantitative mechanisms
and rates of the individual chemical pro-
cesses which contribute to overall results
of complex reactions and to determine the
distribution of energy in reaction systems
and its rate of change
Provide detailed experimental information
concerning important chemical and physical
processes associated with the pyrolysis and
combustion of metal and metal hydride
particles
Study the ionization and decomposition of
molecules and free radical species using
radiation from a synchrotron
56,007 (FY '70)
46,694 (FY '70)
29,863 (FY '70)
<:
-
-
-
I
tV
-------
Table VIII-3. (Continued)
Sponsoring
Project Organization Principal
Key Project or Contract Title and Contract No. Research Organization Investigation Objective or Scope Funding. $
VIII-xx Turbulence in gaseous detonations U.s. Air Force General Elec. D. R. White Determine by spectroscopic techniques the
Schenectady. N. Y. concentration of selected species of light
hydrocarbons and oxygen in shock waves
and examine the effect of selected
additives as reaction promotars and
inhibitors
VIII-yy Kinetics of reactions in flames and U.S. Air Force U.S. Air Force K. Scheller Gain information on the mechanism and
detonations Aerospace Res. Lab. kinetics of reactions in flames, shock
Dayton, Ohio waves, and detonations
VIII-zz Infrared chemiluminescence from gas U.S. Air Force U.S. Air Force A. T. Stair Conduct controlled laboratory studies to
reactions Cambridge Res. Labs. determine the partition of energy into
Cambridge, Mass, the internal modes, to perform theo-
retical studies to describe the tempera-
tures and populations of equilibrium
and nonequilibrium gases
VIlI-aaa Quantitative high temperature infrared U.S. Air Force Technion Res. & Dev. U. P. Oppenheim Determine the laws which govern the emission :::;
spectroscopy Off. Scientific Res. Found, and absorption of C02, H20, NO, CO, -
-
Haifa, Israel N02, and CH2 in the near infrared region I
N
of the spectrum (1-1DI-n. under controlled ~
conditions of pressure, composition and
temperature
VIII-bbb Kinetics of hydrogen-oxygen and U.S. Air Force Univ. of Hull R. R. Baldwin Supply definite answers to several of the
hydrocarbon-oxygen reactions Off. Scientific Res- Hull, England controversial questions concerning the
kinetics of oxidation and combustion of
hydrogen and hydrocarbons
VIII-ccc Basic combustion research - diesel U.S. Army Tank Univ. of Mich. J. A- Bolt Learn more about ignition delay, rates of 3D,ODD/yr
engines Auto. Command Ann Arbor, Mich. N. Henein pressure rise and other combustion phe-
nomena for highly supercharged diesel
cylinders
VIII-ddd Thermal decomposition of hydrocarbons Nat'l Bureau Standards Nat" Bureau Standards W. Tsang
in a single pulse shock tube
VIlI-eee High-temperature chemical information Nat" Bureau Standards Nat" Bureau Standards J. J. Diamond
VIII-fff Atomic reaction kinetics Nat" Bureau Standards Nat'l Bureau Standards J. T. Herron Make a systematic survey of the rates of
R. E. Huie reaction of ground state atomic oxygen
with organic compounds
VIII-ggg Effect of electric field on kinetics of Nat'l Sci- Found. Penn State Univ. P. M. Becker Identify the specific-chemical reactions that
an opposed jet diffusion flame Univ. Park, Pa. R. J. Heisohn are important in a flame under the in-
-------
Table VIII-3. (Continued)
Project
Key
Sponsoring
Organization
and Contract No.
Project or Contract Title
Research Organization
Principal
Investigator
Funding, $
Objective or Scope
VIII-hhh
State of Calif.
Chieh Chu
Applied chemical kinetics
VIII-iii
Fundamental study of the combustion
of natural gas
American Gas Association
VIII-jjj
Gas-sol id dispense system
Aerofall Mills & Nat'l
Res. Council
VIlI-kkk
Formation of oxides of nitrogen in
oscillating combustion
Sheffield City Corp.
Clean Air Group
VIII-III
Studies on the formation of oxides
of nitrogen in combustion systems
VIII-mmm
Bond dissociatIon energies in pOlyatomic
molecules by kinetic methods
U.K. Science Res.
Council
UCLA
Los Angeles, Calif.
Study in an opposed jet diffusion flame the
kinetics of combustion processes of interest
to pollution cC'ntrol
Inst. of Gas Tech.
Chicago, III.
I nvestigate new principles and develop funda-
mental data to improve our understanding of
the role of ions in flames, the formation of
trace constituents in flames, and the effect of
solids on combustion
<:
......
......
......
I
tV
VI
Aerofall Mills Ltd.
Canada
R. R. Turner
H. D. Goodfellow
Carry out fundamental examination of the d
physical and chemical forces which in-
fluence the behavior of solid particles in
gas streams
Dept. of Fuel Technology
and Chem. Eng.
Univ. of Sheffield
Sheffield, England
T. D. Brown
D. Thompson
Predict and measure oxides of nitrogen in
oscillating combustion systems in the
frequency range 600-1600 Hz
Dept. of Fuel Technology
and Chem. Eng.
Univ. of Sheffield
Sheffield, England
Univ. of Birmingham
Birmingham, England
J. A. Kerr
Determine bond energies in hydrocarbons
-------
VIII-26
PRIORJTY RANKING PROCEDURE fOR RESEARCH OPPORTUNITIES
IN THE FUNDAMENTAL AND BROADLY APPLICABLE AREA
Philosophy of Priority Ranking
for Fundamental Research
The rationale employed to priority rank R&D opportunities in the applied areas has been
described previously in Chapter II. The significant point here is that applied-R&D opportunities
accrued value, or priority, only by promising a direct and foreseeable route to a (roughly)
predictable reduction in pollutant emissions. On this basis, research opportunities in the funda-
mental and broadly applicable area have no similar value: they are directed not so much towards
achieving an immediate predictable reduction in pollutant emissions, but rather towards achieving
an understanding of the problems or towards the accumulation of basic data pertinent to
pollutant emissions from combustion sources.
It can be, and has been, argued that this is entirely appropriate: that the research
opportunities in the fundamental and broadly applicable area should have no value in the
context of this study. Such arguments are strongly supported by the historical fact that
fundamental research in combustion has been at best loosely coupled to the design and
development of combustion devices. At least on the surface, it appears that fundamental
combustion research has been either unconnected with practical problems, or has served to
explain, after the fact, the success of the equipment designer. It is also true that fundamentally
oriented research undertaken at the present time is highly unlikely to influence the outcome of
applied R&D within the 5-year research period considered in this study.
However, it can be argued that such a viewpoint is entirely short ranged, and, in the long
rang~, is apt t6 greatly limit the ability to solve combustion-associated emission problems. While
the combustion-equipment designer may draw on the "art" for support, rather than on the
results of fundamental research, this art is strongly supported by previous fundamental research.
Furthermore, examples, even though possibly isolated ones, can be found where the results of
fundamentally oriented combustion research have directly contributed to the solution of engi-
neering problems. Perhaps the strongest example in the pollution-oriented field is the funda-
mental work on the chemistry of the nitrogen-oxygen system.
Accepting the argument that fundamentally oriented combustion research is deserving of
support within the context of this study, the problem remains as to how such research should be
priority ranked. Clearly, any such ranking should reflect the major applications orientation of the
Plan. The procedure adopted does reflect the applications orientation and has certain features
which parallel the ranking of applied- R&D opportunities.
Ranking by Relevance to
Applied-R&D Opportunities
The approach taken in assigning priority rank to the fundamental and broadly applicable
research opportunities is based on their relevance to the set of applied-R&D opportunities. A
quasiquantitative measure of the relevance was obtained by assigning a set of relevance numbers,
-------
VIU-27
ranging between 0 and 1, to eacn fundamental-research opportunity. Non-zero values were
assigned when the fundamental-research opportunity had some bearing on an applied R&D
opportunity. If the connection visualized was vague or remote (for example, the connection
between basic chemical research on hydrocarbon-oxidation mechanisms and the emission of
hydrocarbons from IC engines), a low value was assigned. Higher values were assigned where the
fundamentally oriented research could make a direct contribution to the applied R&D. A
relevance number of 1.0 was chosen to indicate that the results of the fundamentally oriented
research were required for successful completion of the applied R&D.
Relevance numbers were assigned on the basis of expert judgment through consensus of
three members of the study team with extensive background in both fundamental and applied
combustion research. The values of the assigned relevance numbers ranged from 0 to 0.8.
Several schemes were investigated for assigning priority rank to the fundamentally oriented
research opportunities by using the relevance numbers to "borrow" benefit or priority from the
applied-R&D opportunities. The method finally chosen, on the basis that it yielded the most
satisfying priority ranking and most closely paralleled the procedure used to rank the applied-
R&D opportunities, was to "borrow" priority from the applied-R&D opportunities in proportion
to the relevance numbers, and then sum the borrowed priority to give an associated priority.
Numerical Priority Scale of Associated Priority. The five priority ranks, A to E, of the
applied-R&D opportunities were assigned numerical values of 16, 8, 4, 2, and 1, respectively.
This logarithmic scale was chosen to avoid the elevation of a fundamental-research opportunity
to a high priority rank by association with a large number of low-ranked applied-R&D
opportunities. The products of the numerical values assigned to priority ranks for applied-R&D
opportunities and the appropriate relevance numbers were then summed for each fundamentally
oriented research opportunity by program elements (e.g., Central-Station Power Plants) to yield
an associated-priority number. The 27 fundamental-research opportunities were then ranked in
order of their associated-priority number, and grouped into five priority classes for each applied
program element by assigning the 6 highest-ranked opportunities to the first priority, the next
three groups of 5 to the second, third, anq fourth priorities, and the final 6 to the fifth priority.
The fundamental-research opportunities were then given overall priority rankings based on their
total relevance to each applied R&D priority. A cummulative procedure was used in which, for
-example, relevance not used in assigning a research opportunity to the first priority class was
applied to the second priority class. The cuts between priority classes were then made
judgmentally.
Display of Associated Priority Numbers
Each fundamental and broadly applicable research opportunity described at the end of
this chapter thus has 6 priority rankings: one for each of the five applied program elements and
one for the overall program. This multiple ranking is used because a specific research opportunity
may rank very high when viewed in terms of a single program element, and yet be ranked
relatively low in terms of the overall program. Thus, the multiple ranking may be used to
provide some additional insight into balancing the fundamental and applied programs.
BATTEI..l.E MEMORIAL INSTITUTE - COLUMBUS LABORATORIES
~,~.:,
.
-------
VIII-28
Comparison With Applied-R&D Priorities. It should be noted that the procedures applied
to priority rank the applied and fundamentally oriented research opportunities are not fully
equivalent. To emphasize this difference, the five priority groups for the fundamentally oriented
research opportunities have been identified by the numbers 1 (highest priority) through 5 (lowest
priority) in contrast to the letters A through E used to designate the priority groups of the
applied- R&D opportunities.
A feature of the procedure outlined above is that specific research opportunities may
accumulate no associated priority from some program elements. Rather than being included in
the last priority group, which would be misleading, they have been designated by a dash,
indicating that they have no relevance to that applied element. Also, certain relevant funda-
mentally oriented research opportunities that have been evaluated as not capable of making
further significant contributions to the applied research have been carried through the evaluation
process. (An example is research on the chemistry of the nitrogen-oxygen system where only
species derived from N2, 02 or their combination are considered; further refinement of the
chemistry of this system is considered highly unlikely to contribute to a reduction in pollutant
emissions.) Such research areas have been identified in their overall rating by the description nr
(not recommended) rather than being assigned to the last priority group.
DESCRIPTIONS OF FUNDAMENTAL AND BROADLY
APPLICABLE RESEARCH OPPORTUNITIES
The following pages contain descriptions and priority ranking of 31 research
opportunities in the fundamental and broadly applicable area.
-------
VIII-29
R&D Opportunity: VIII-l
Related to: VI-I, 2; VIII-3, 28; VIII-g, i, cc, pp, kkk, 11l
Experimental and Theoretical Investigations of the Interactions and Coupling of the N2 - 02 System
with Other Reactions and Species in Combustion Systems
Technical Objective and Approach
The objective is to achieve the ability to model NOx in a combustor operating in the stoichiometric to
fuel-rich region.
The approach should consist initially of attempting to integrate the known N2 - 02 system with some kind of a
global model of the HC - 02 system. This might be done by finding a measure of the reducing or oxidizing "power"
of the overall fuel-air mixture and empirically relating this to observed NOx concentrations. The experimental
combustion equipment should be designed to yield a simple and well characterized flow. A flat-flame burner
followed by a plug-flow zone is suggested.
Rationale and Incentive
NOx models for fuel-lean systems are reasonably successful. That is not the case for fuel-rich systems, and it is
suspected that the influence of the HC - 02 reaction in the availability of 0 atoms may be responsible. A method of
modeling the NOx formation process in other than fuel-lean combustion systems is needed if analysis-design
procedures are ever to be used in optimizing combustion for NOx emissions.
Estimated R&D Cost & Time
R&D Cost Range, 1000's: $200-$2,000
R&D Time Range: 1-5 years
Recommended 5-year Funding, 1000's: $1,000
Funding by Fiscal Year, $1OOO's
'69.70 1'71 72
X 200 200
73
74
75
76+
100/yr
200
200 200
Evaluation
Associated Priority Ranking:
III
Power
Plants
IV
Industrial
Processing
V VI VII
Industrial, Continuous- I nternal-
Commercial, Combustion Combustion
Residential Engines Engines
3 2 3
-------
VIII-3D
R&D Opportunity: VIII-2
Related to: III-lO, 11; VIII-g
Experimental Studies of the Contribution of Combined Nitrogen in Fuels to the Emission of NOx
Technical Objective and Approach
The objective is to determine the contribution of chemically bound nitrogen in the fuel on NOx profIles in a
combustor, particularly whether the chemically bound nitrogen contributes to the formation of NOx levels above
that attributable to thermal fIxation.
The approach should involve the burning of nitrogen-free fuels doped with various organic nitrogen compounds
in a flat-flame burner and sampling for NOx. Combustion air should be replaced by argon-oxygen mixtures for many
of the experiments.
Rationale and Incentive
Nitrogen in the fuel may be thermally equilibrated during the combustion process, or such chemically bound
nitrogen might be directly oxidized to NOx at levels substantially in excess of the thermal equilibrium, particularly
in low-temperature combustion processes. When nitrogen-containing coal or heavy oil is the fuel, the contribution of
the chemically bound nitrogen in the fuel to NOx emissions may be highly signifIcant and may interfere with
schemes for reducing NOx levels by reducing the peak system temperature to low values.
Estimated R&D Cost & Time
R&D Cost Range, 1000's: $100-$500
R&D Time Range: 1-5 years
Recommended 5-year Funding, 1000's: $375
Funding by Fiscal Year, $1ooo's
'69-70 1'71
100
72
100
'73
75
'74
50
75
50
'76+
Evaluation
Associated Priority Ranking:
III
Power
Plants
IV
Industrial
Processing
V
Industrial,
Commercial,
Residential
VI
Continuous-
Combustion
Engines
VII
Internal-
Combustion
Engines
5
-------
VIII-31
R&D Opportunity: VIII-3
Related to: VIII-bb, gg, 11, nn
Investigation of the Kinetics of the N2 - 02 (only) System
Technical Objective and Approach
It is not recommended that any effort be devoted to the study of NOx kinetics in systems restricted to species
derivable from N2 and 02, as such systems are sufficiently well understood for pollution-related purposes.
Rationale and Incentive
Adequate elementary rate constants are available for important elementary reactions in the N2 - 02 system.
Models for NOx emissions seem adequate for systems that approximate the N2 - 02 systems (Le., fuel-lean systems).
For fuel-rich systems, models are not so good, but this is because of the inadequate treatments of the hydrocarbon-
oxygen systems and their coupling with the N2 - 02 system. That situation will not be remedied by further study of
the N2 - 02 system.
Estimated R&D Cost & Time
R&D Cost Range, 1000's: None
R&D Time Range: None
Recommended 5-year Funding, 1000's: $0
Funding by Fiscal Year, $1OOO's
'69:0 1'~1
72
'73
'74
75
76+
Evaluation
Associated Priority Ranking:
III
Power
Plants
IV
Industrial
Processing
V VI VII
Industrial, Continuous- Internal-
Commercial, Combustion Combustion
Residential Engines Engines
nr nr nr
nr
nr
-------
VIII-32
R&D Opportunity: VIII-4
Related to: VIII-9; VIII-bbb, ddd, fff
.
Experimental Determinations of the Global Kinetics of Dilute HC - 02 Systems and Kinetics in
Quenched Systems
Technical Objective and Approach
The objective is the measurement of gross rates of removal of hydrocarbons and other carbon-containing
species in dilute and quenched systems.
The approach should include measurements of rates of disappearance as a function of temperature, pressure,
concentrations, and perhaps concentrations of a few other controllable species (CO, C02, H20, 02) and wall
effects. Interpretation of results in terms of a mechanism is not intended. The results need not be expressed in a
conventional rate expression to be useful.
The research should involve measurements in a variety of systems, such as the tail gases from ordinary flames,
a heated plug-flow system, packed reactors, and well-stirred reactors. Sampling and analysis should be the major
measurement techniques. Considerable attention should be devoted to the problem of defining the limitations of the
results, primarily by exploring a wide range of variables.
Rationale and Incentive
Global kinetic data may be useful in the design of combustion equipment to minimize the emission of HC, CO,
and related reducing species.
Estimated R&D Cost & Time
R&D Cost Range, 1000's: $200-$500
R&D Time Range: 2-5 years
Recommended 5-year Funding, 1000's: $400
Funding by Fiscal Year, $1OO0's
'69.70 171
- 100
72
100
'73
100
'74
100
75
'76+
Evaluation
Associated Priority Ranking:
III
Power
Plants
IV
Industrial
Processing
V
Industrial,
Commercial,
Residential
VI
Continuous-
Combustion
Engines
VII
Internal-
Combustion
Engines
3
3
3
3
-------
VIII-33
R&D Opportunity: VIII-S
Related to: VII4; VIII4, 9; VIII-i, t, w. aa
Experimental Investigation of Wall-Quenching Phenomena as Related to the Formation of Pollutants
Technical Objective and Approach
The objective is to determine the relation of wall quenching in various turbulent environments to the
production of pollutants by a burning mixture.
Two approaches are suggested. In the ftrst approach, the combustible mixture should be ignited at one end of
a duct, and~he production of various species DY the resulting combustion should be determined. The area-to-volume
ratio should be varied by inserting axial rods. At the igniting end, a thin burst diaphragm could be used to isolate
temporarily the flash tube from a large pressure-stabilizing volume ftlled with inert gas.
In the second approach, a combustion bomb should be used to study wall-quenching effects, using vaporized
gasoline, vaporized kerosene, and propane. The bomb should be of a type in which turbulence of controlled scale
and intensity can be generated. Provision should be made for preheating the bomb and starting the explosion at
other than atmospheric pressure. Provision should also be made for changing the surface-to-volume ratio. In addition
to data on initial and ftnal composition of all species of interest, data should be obtained on turbulent flame speed,
final temperature, and pressure.
Rationale and Incentive
Data relating wall-quenching phenomena to formation of pollutants would permit specifying the conditions
under which pollution production (incomplete combustion) by wall quenching can be minimiz~d. '
Estimated R&D Cost & Time
R&D Cost Range, 1000's: $100-$800
R&D Time Range: 3-6 years
Recommended 5-year Funding, 1000's: $735
Funding by Fiscal Year, $1ooo's
'69-70 1'71
85
72
200
73
150
'74
150
75
150
76+
Evaluation
Associated Priority Ranking:
III
Power
Plants
IV
Industrial
Processing
V
Industrial,
Commercial,
Residential
VI
Continuous-
Combustion
Engines
VII
Internal-
Combustion
Engines
3
4
4
-------
VIII-34
R&D Opportunity: VIII-6
Related to: VIII-?, 9; VIII.bbb
Experimental Investigation of the Kinetics of Oxygenated Intermediates and Their Destruction by
Oxidation
Technical Objective and Approach
The objective is to characterize the formation and destruction of oxygenates in combustion processes.
One approach should be studies of the oxidative destruction of such materials in moderately hot, low-oxygen
environments. The influence of other species, such as H20, CO, and C02, should be investigated.
Rationale and Incentive
It is suspected that oxygenates are contributors to diesel exhaust odors and odors from other combustion
sources. Better knowledge of their behavior will be useful in alleviating the problem.
Estimated R&D Cost & Time
R&D Cost Range, 1000's: $100-$300
R&D Time Range: 2-4 years
Recommended 5-year Funding, 1000's: $150
Funding by Fiscal Year, $1000'$
'69-70 171
- 50
72
50
73
50
74
~ 17~
Evaluation
Associated Priority Ranking:
III
Power
Plants
IV
Industrial
Processing
V VI VU
Industrial, Continuous- Internal-
Commercial, Combustion Combustion
Residential Engines Engines
4 3 1
5
-------
VIII-35
R&D Opportunity: VIII-7
Related to: VII-8; VIII-6, 9; VIII-gg
Experimental Investigation of the Contribution of Specific Fuel Constituents to Odor Production in
the Combustion Process
Technical Objective and Approach
The objective is to determine what, if any, chemical species in diesel fuels contribute in a major way to the
formation of odorants in diesel exhaust.
The approach should be to operate a diesel engine with well-dermed fuels, possibly with a "synthetic" fuel
selected for low odor production and doped with specific chemical species to be investigated.
Rationale and Incentive
It is suspected that specific chemical species in diesel fuels contribute as such to the characteristic diesel
exhaust odor. It is possible that specific ehemical species in the fuels may also contribute in a major way to the
formation of partial-oxidation products which are strong odorants. If such fuel components are found to exist,
refining processes might be altered to eliminate them from the fuel.
Estimated R&D Cost & Time
R&D Cost Range, 1000's: $100-$400
R&D Time Range: 1-4 years
Recommended 5-year Funding, 1000's: $150
Funding by fiscal Veer, $1000'5
~17'
X Iso
72
SO
73
SO
74
75
76+
Evaluation
Associated Priority Ranking:
III
Power
Pfants
IV
Industrial
PFocessin~
V
Industrial,
CommerciaF,
Residential
VI
Continuous-
Combustion
Engines
VJI
Internal-
Combustion
Engines
s
1-
-------
VIII-36
R&D Opportunity: VIII-8
Related to: VIII-bb
Investigations of the 'Kinetics of the CO - 02 - H2 (only) System
Technical Objective and Approach
No work is recommended, as the current understanding of this system is adequate for the purposes here
considered.
Rationale and Incentive
Reasonably adequate iriforrilation about important reactions of CO in combustion systems is available. The
major problem lies in integrating this information with information relative to other processes also occurring.
Therefore, no study is recommended of CO combustion reactions as such. .
Estimated R&DCost & Time
R&D Cost Range, 1000's: None
R&D Time Range: None
Recommended 5-year Funding, 1000's: $0
Funding by Fiscal Year, $1oo0's
'69-70 I ':1
'72
73
'74
75
76+
Eval~ation
Associated Priority Ranking:
III
Power
Plants
IV
Industrial
Processing
V VI VII
Industrial, Continuous- Internal.
Commercial, Combustion Combustion
Residential Engines Engines
nr. nr nr
nr
.nr
-------
VIII-37
R&D Opportunity: VIII-9
Related to: VIII-4, 6, 8, 10; VIII-ss, bbb, iii
Fundamental Experimental Studies of HC Oxidation Kinetics
Technical Objective and Approach
The objective is to develop a better understanding of the kinetics and mechanisms of hydrocarbon oxidation.
The approach should be broad in scope because the HC - 02 system is so little understood. Relevant approaches
range from conventional batch-reactor studies to studies with shock tubes. This research will of necessity include
some study of pyrolysis reactions.
Rationale and Incentive
A better understanding of the HC - 02 system is basic to a scientific understanding of the combustion process,
including the emission of many of the pollutants of current concern. Because of the complexity of the subject area,
practical results cannot be expected at an early date; in fact, it is not feasible even to suggest specific techniques or
subareas at this time. The field of study extends to considerations well beyond pollution, and activity in this field
derives support from other interests.
Estimated R&D Cost & Time
R&D Cost Range, 1000's: $100-$1,000
R&D Time Range: 1-5 years
Recommended 5-year Funding, 1000's: $250
Funding by Fiscal Year, $1 COO's
'69-70 12!
- 50
72
50
73
50
'74
50
75
50
76+
50/yr
Evaluation
Associated Priority Ranking:
III
Power
Plants
IV
Industrial
Processing
V VI VII
Industrial, Continuous- I nternal-
Commercial, Combustion Combustion
Residential Engines Engines
4 4 4
4
3.
-------
VIII-38
R&D Opportunity: VIII-lO
Experimental and Theoretical Studies of the Kinetics and Mechanism of HC Pyrolysis Reactions
Related to: VIII-9; VIII.kk
Technical Objective and Approach
The objective is a better, broader knowledge of pyrolysis reactions.
Because the area is broad and largely unexplored, no specific goals or approaches can be suggested. All things
considered, a low level of support seems advisable until specific pollution-related goals and approaches can be
specified.
Rationale and Incentive
Pyrolyses are poorly understood and yet basic to any scientific understanding of the combustion process. These
reactions are important in many processes, and support for research also comes from other interests not oriented to
pollution abatement.
Estimated R&D Cost & Time
R&D Cost Range, 1000's: $100-$500
R&D Time Range: 1-5 years
Recommended 5-year Funding, 1000's: $250
Funding by Fiscal Year, $1000's
'69-70 I '71
X 50
72
50
73
50
'74
50
'15
50
76+
50tyr
Evaluation
Associated Priority Ranking:
III
Power
Plants
IV
Industrial
Processing
V VI VII
Industrial, Continuous- Internal-
Commercial, Combustion Combustion
Residential Engines Engines
4 4 2
2
2
-------
VIII-39
R&D Opportunity: VIII-II
Related to: V-5; VII.6; VIII-12
Experimental Investigation of the Contribution of PNA Contained in Solid and Liquid Fuels to the
Emission of PNA
Technical Objective and Approach
The objective is to measure PNA and other important specie profiles in PNA-doped or PNA.fueled flames and,
thus, follow the destruction of PNA in the combustion process. Conditions leading to the most rapid or complete
destruction of PNA should be sought, and the influence of the main combustion process on the destruction should
be determined.
The approach should be to conduct investigations using a flat-flame burner followed by a plug-flow zone, with
the entire region between the burner face and some far-downstream position being sampled for PNA and any other
species which are identified to be important in the destruction of PNA. Such conventional variables as fuel type and
fuel-air ratio should be examined, as well as residence time, flame temperature, temperature decay, and the nature
of the PNA molecule.
Rationale and Incentive
Coal and some liquid fuels may contain PNA. It will be useful to have information about the behavior of
fuel-supplied PNA and to learn how it may differ from the behavior of other fuel species in the flame. Ultimately,
such understanding should lead to capability for designing combustion devices for minimum PNA emission.
Estimated R&D Cost & Time
R&D Cost Range, 1000's: $100-$200
R&D Time Range: 1-3 years
Recommended 5-year Funding, 1000's: $100
Funding by Fiscal Year, $1ooo's
'69-70 12!
50
72
50
'73
'74
75
76+
Evaluation
Associated Priority Ranking:
III
Power
Plants
IV
Industrial
Processing
V
Industrial,
Commercial,
Residential
VI
Continuous-
Combustion
Engines
VII
Internal-
Combustion
Engines
2
3
-------
VIII -40
R&D Opportunity: VIII -12
Related to: V-S; VII-6; VIII-9, 11; VIII-kk
Experimental Studies of the Formation and Destruction of PNA in Flames
Technical Objective and Approach
The objective is to obtain information about PNA profiles in flames. Conditions favorable and unfavorable to
their formation and destruction should be sought, and global reaction rates obtained. lITtimately, kinetic
mechanisms may be identified.
The approach suggested is sampling from various regions in the flame of a flat-flame burner. The fuel employed
would be a variable, as would the fuel-air ratio and possibly the presence of diluents and the initial reactant
temperature.
Rationale and Incentive
Little information is available on the way in which PNA is formed in combustion, or on its subsequent
destruction. It is possible that better knowledge of these processes could permit the design of combustion devices
optimized with respect to PNA emissions.
Estimated R&D Cost & Time
R&D Cost Range, 1000's: $200-$750
R&D Time Range: 2-5 years
Recommended 5-year Funding, 1000's: $500
Funding by Fiscal Year, $1OOO's
'69-70 171 72
X 100 100
'73
'74
75
100
76+
100 100
Evaluation
Associated Priority Ranking:
III
Power
Plants
IV
Industrial
Processing
V
Industrial,
Commercial,
Residential
VI
Continuous-
Combustion
Engines
VII
I nternal-
Combustion
Engines
3
3
-------
VIII -41
R&D Opportunity: VIII-13
Related to: V-I; VIII-14; VIII-mm
Experimental and Theoretical Investigations of the Formation of Soot in Flames
Technical Objective and Approach
The objective is to gain knowledge of the conditions and processes leading to the formation of soot in flames
and combustion reactions, with the expectations that ultimately such knowledge will lead to an ability to design
combustion systems which do not emit soot. -
In view of the primitive state of knowledge concerning soot formation, a highly specific approach cannot be
suggested. However, examination of simple, well-characterized flames using modern sampling and analytical
techniques is the obvious beginning. Searches for the precursors of visible soot, studies of the nucleation and growth
process, and examinations of the relationships of soot to other flame species, particularly PNA, seem to be
indicated.
Rationale and Incentive
Some features of the soot-formation process, or factors that influence it, are known, but the understanding is
not adequate to permit predictions. For example, the ability of various diluents, including flue gas, to suppress soot
formation has been known for many years, but no satisfactory mechanism or even empirical correlation has been
suggested. As the most likely chemical structure for soot is a very large PNA molecule, the relationship between
soot and the lower molecular weight PNA's emitted by combustion systems deserves study.
Estimated R&D Cost & Time
R&D Cost Range, 1000's: $300-$1,000
R&D Time Range: 2-8 years
Recommended 5-year Funding, 1000's: $375
Funding by Fiscal Year, $1oo0's
'69-70 12!.
X 75
72
75
73
75
74
75
75
75
76+
150
Evaluation
Associated Priority Ranking:
III
Power
Plants
IV
Industrial
Processing
V VI VII
Industrial, Continuous- Internal-
Commercial, Combustion Combustion
Residential Engines Engines
2 3 2
4
3
-------
VIII-42
R&D Opportunity: VIII-l4
Related to: VIII-13
Investigations of the Kinetics and Mechanism of Soot Combustion in Flames and Post-Combustion
Gas Streams
Technical Objective and Approach
The objective is to learn something of the kinetics of combustion of soot, including, if possible, precursors to
visible soot, with the ultimate intent of being able to specify the conditions needed to consume such flame species
if their formation cannot be prevented.
In view of the fine particulate nature of soot, most experimental work will of necessity approach the problem
through flame studies. Because of the primitive state of knowledge in this area, highly specific approaches and
research goals cannot be stated.
Rationale and Incentive
Combustion of comparatively pille carbon has been studied in the past but soot has received little attention.
Some empirical data have been obtained on soot burnout (e.g., from the work at Sheffield University) but no
correlation other than the most general influence of oxygen and temperature seems to have been advanced.
Estimated B&D Cost & Time
R&D Cost Range, 1000's: $250-$1,000
R&D Time Range: 2-5 years
Recommended 5-year Funding, 1000's: $500
Ftmding by Fiscal Year, $1000'5-
'69:.70 [ 71 7,2
X ~100 100
73
1QO
74 75'. 76+
100 100 -
Evaluation
Associated PrioriW Ranking:
trI
Power-
Plants
IV
Industrial
Processing
V VI V/t
Industrial, Continuous- tnternal-
Commercial, Combustion Combustion
Residential Eng.ines Eng.ines
3 3. 2
4
3'
-------
VIII-43
R&D Opportunity: VIII -15
Related to: VIII.ff, ii, 00
Analytical and Experimental Studies of the Kinetics of Sulfur Oxidation in the Combustion Process
Technical Objective and Approach
The objective is to clarify existing information on sulfur oxidation and to determine the interactions with
other species in the flame and post-flame region.
Approaches should include studies of reactions in flames and continuous-flow nonflame systems.
Rationale and Incentive
Sulfur oxidation level may have some influence on the effectiveness of downstream controls. Kinetics may be
important in that relation. It must be emphasized that combustion modifications cannot change the fact that the
combustion of sulfur-containing fuels will lead to the emission of sulfur species in the combustion gases.
Estimated R&D Cost & Time
R&D Cost Range, 1000's: $100-$300
R&D Time Range: 1-2 years.
Recommended 5-year Funding, 1000's: $150
Fundtng by Fiscal Year, $1000'5
'69-70 171
X 75
72
75
'13
'74
75
76+
Evaluation
Associated Pfiority Ranking:
III
Power
Plants
~V
Industrial
Processing
V
Industrial,
COmmercial,
Residential
VI
Continuous-
Combustion
Engines
VII
Internal-
Combustion
Engines
2
-------
VIII -44
R&D Application: VIII-16
Investigations of the Chemistry of Lead in Combustion Processes
Technical Objective and Approach
No study is recommended, as no useful result can be foreseen.
Rationale and Incentive
Lead is emitted from IC engines burning leaded gasoline, and this fact cannot be altered by any foreseen
possibility for appropriate modification of the combustion process. It must be emphasized, however, that combus-
tion research aimed at eliminating the need for lead, or at replacing lead by a less obnoxious additive, might provide
valuable results.
Estimated R&D Cost & Time
R&D Cost Range, 1000's: None
R&D Time Range: None
Recommended 5-year Funding, 1000's: $0
Funding by Fiscal Year, $1oo0's
'69-70 1'~1
72
73
74
75
76+
Evaluation
Associated Priority Ranking:
III
Power
Plants
IV
I ndustr ial
Processing
V VI VII
Industrial, Continuous- I nternal-
Commercial, Combustion Combustion
Residential Engines Engines
nr nr nr
nr
nr
-------
VIII-45
R&D Opportunity: VIII-I7
Related to: VIII-I 8, 19; VIII-c, q, x
Analytical and Experimental Investigation of the Influence of Inhomogeneities on Pollutant For-
mation in Droplet Flames and Pulverized-Coal Flames
Technical Objective and Approach
The objective is to determine the effect of scale of inhomogeneity (e.g., premixed fuel and air versus the same
fuel in droplets) on chemical behavior and local temperatures and thus on the formation of pollutants.
The approach should be to conduct research with various laboratory rigs. Experimental design and
instrumentation would be a major problem in this research.
Rationale and Incentive
Practical combustion systems burning solid and liquid fuels have obvious inhomogeneities. These inhomoge-
neities may cause substantial deviations between, for example, the overall fuel-air ratio and the fuel-air ratio in those
regions where combustion is occurring. Macroinhomogeneities of this character, due for example to imperfect
mixing of gaseous fuels and air, are suspected as being the cause of certain pollutants being emitted in concentra-
tions greater than expected. Knowledge of the effects of inhomogeneity at the scale of oil droplets or pulverized
coal particles on the behavior of a system would be useful in applying data from homogeneous systems to
heterogeneous ones, or in showing that such applications are not feasible.
Estimated R&D Cost & Time
R&D Cost Range, 1000's: $100-$400
R&D Time Range: 1-4 years
Recommended 5-year Funding, 1000's: $150
Funding by Fiscal Year, $1OOO's
'69.70 "71
75
72
75
73
74
75
76+
Evaluation
Associated Priority Ranking:
III
Power
Plants
IV
Industrial
Processing
V
Industrial,
Commercial,
Residential
VI
Continuous-
Combustion
Engines
VII
Internal-
Combustion
Engines
2
4
-------
VIII-46
R&D Opportunity: VIII-18
Related to: V-I,ll; VII-3-?, VIII-17, 19; VIII-c, q, x
.
Experimental Investigation of the Relation of Size Distribution and Relative Velocity of Burning
Droplets and Particulates to the Formation of Pollutants
Technical Objective and Approach
The objective is to determine the relation of droplet (and particle) size distribution and relative velocity of
liquid fuel droplets (and pulverized-coal particles) to the formation of pollutants.
The approach should include experimental measurements in a plug-flow furnace with fuel droplets (gasoline,
No.2 heating oil, heavy fuel oil) and pulverized-coal particles (P.C. and devolatilized P.C.) uniformly distributed
over the cross section. Alternatively, more conventional types of combustors might have to be used with close
delineation and study of a specific flow path with a controllable path history. Provision must be made for varying
droplet or particle size and distribution and the relative velocity of droplets or particles and the air.
Rationale and Incentive
With respect to studies of liquid fuels, the results of this program may permit specification of the optimum
droplet size distribution to minimize pollution. It might also suggest new types of spray formation. The work may
establish the effect on the formation of pollutants of having fuel in droplet form rather than vapor form.
In the case of pulverized coal, this program should establish the effect of particle size distribution on pollutant
emissions. In combination with the results of other studies, this program should lead to an understanding of the
interaction of particulate-matter burning and volatile-matter burning on pollutant formation.
Estimated R&D Cost & Time
R&D Cost Range, 1000's: $800-$1,150
R&D Time Range: 4-6 years
Recommended 5-year Funding, 1000's: $1,000
Funding by Fiscal Year, $1OOO's
'69.70 I '71
X 200
72
200
'73
'74
'75
200
'76+
200
200
Evaluation
Associated Priority Ranking:
III
Power
Plants
IV
Industrial
Processing
V
Industrial,
Commercial,
Residential
VI
Continuous-
Combustion
Engines
VII
Internal-
Combustion
Engines
4
-------
VIII-47
R&D Opportunity: VIII-19
Related to: V-I; VIII-I?, 18; VIII-c, 0, x
Experimental Studies of Single or Small Number of Burning Droplets and Particles to Determine
the Relation of Size and Other Factors to Pollutant Formation
Technical Objective and Approach
The objective is to gain an understanding of pollution-related aspects of droplet and particle burning by
observing the burning, in a hot environment, of single droplets and particles, or small numbers of them; in the size
range common to fuel sprays.
The approach should be based on the projection of droplets and particles through various hot environments.
Measurement and analysis are expected to be difficult, and development of suitable techniques will be an important
part of the program. It is essential that the size, size distribution, and relative velocity of droplets (or particles) and
the environment be in the range characteristic of prototype combustors.
Rationale and Incentive
Research to improve the understanding of the relation of the life history of a droplet or particle, or an array
of them, to pollutant formation, and of the characteristics of the life history that lead to particulate formation
should lead to reducing these emissions. For liquid fuels, the results could suggest changes in spray nozzles to alter
droplet size distribution in a beneficial manner. For pulverized coal, an understanding of the relation of the life
history of particles to pollutant formation should aid in formulating the proper burning conditions and size
distribution of the fuel.
Estimated R&D Cost & Time
R&D Cost Range, 1000's: $175-$350
R&D Time Range: 2-4 years
Recommended 5-year Funding, 1000's: $325
Funding by Fiscal Year, $1ooo's
'69-70 171
X 100
72
73
'74
75
76+
75
75
75
Evaluation
Associated Priority Ranking:
III
Power
Plants
IV
Industrial
Processing
V VI VII
Industrial, Continuous- I nternal-
Commercial, Combustion Combustion
Residential Engines Engines
2 2 2
3
2
-------
VIII -48
R&D Opportunity: VIII-20
.
Experimental Investigation of the Burning Process of a Solid-Fuel Particle in Simulated Fluidized or
Fixed Beds
Technical Objective and Approach
The objective is to gain understanding of fluidized-bed combustion and associated reactions by determining the
life history of burning fuel particles in simulated fluidized beds.
The approach should involve use of a rig in which the particles are fixed and the gases move through the array.
The particle of interest should be studied in detail as time progresses. Input gases should be varied with respect to
temperature, composition, and flow rate. Off-gases from the array could be analyzed. With proper insulation and
refractory walls (possibly preheated before a test array is inserted), it should be possible to keep the equipment
relatively small.
Rationale and Incentive
Research to provide insight into the reaction processes in a fluidized bed and to permit identifying the stages
of the process in which pollutants are formed, destroyed, or captured, in combination with classical information on
fluidized beds, should help to specify optimum operating conditions for low emissions. This, of course, is directed
primarily toward the elimination of 802 and 803 from the burning of coal, and possibly the reduction of NOx'
Estimated R&D Cost & Time
R&D Cost Range, 1000's: $225-$350
R&D Time Range: 2-3 years
Recommended 5-year Funding, 1000's: $225
Funding by Fiscal Year, $1OO0's
'69-70 I '71
X 125
'72
100
'73
'74
'75
'76+
Evaluation
Associated Priority Ranking:
III
Power
Plants
IV
Industrial
Processing
V
Industrial,
Commercial,
Residential
VI
Continuous-
Combustion
Engines
VII
Internal-
Combustion
Engines
3
-------
VIII-49
R&D Opportunity: VIII-21
Related to: VIII-j, iii
Experimental Determination of the Effect of Composition Gradients and Gaseous Fuel Type on the
Production of Pollutants in Laminar Diffusion Flames
Technical Objective and Approach
.
The objective is to determine the effect of composition gradients and fuel type on the formation of pollutants,
especially particulates, in laminar diffusion flames with gaseous fuels.
The approach should involve building a relatively simple enclosed nonturbulent-diffusion-flame rig. Initially
attention should be focused on the effect of fuel-air gradient and temperature on the formation of various
pollutants. Then the effect of fuel type (considering several pure hydrocarbons from methane through butane) on
the production of pollutants should be investigated. After preliminary tests have been conducted with NOx, CO,
etc., concentration should be on production of particulate manner.
Rationale and Incentive
A better understanding of the factors involved in particulate growth and decay as related to fuel composition,
as well as composition gradients, would be of particular value for the design of residential heating units. The most
obvious effect of fuel type is that on smoke production. Reformulation of some fuels might be indicated. The
information should also help to clarify the structure of turbulent diffusion flames.
Estimated R&D Cost & Time
R&D Cost Range, 1000's: $200-$550
R&D Time Range: 3-4 years
Recommended 5-year Funding, 1000's: $270
Funding by Fiscal Year, $1000's
'69-70 171
X 90
72
60
'73
60
74
60
75
76+
Evaluation
Associated Priority Ranking:
III
Power
Plants
IV
Industrial
Processing
V
Industrial,
Commercial,
Residential
VI
Continuous-
Combustion
Engines
VII
I nternal-
Combustion
Engines
5
2
3
2
-------
VIII-50
R&D Opportunity: VIII-22
Related to: V-I, 2, 3; VIII-21; VIII-y, ill
Experimental Investigation of the Effect of Turbulence and Gaseous Fuel Type on Pollutant
Formation in Turbulent Diffusion Flames
Technical Objective and Approach
The objective is to determine the effect of turbulence and fuel type on the production of pollutants in
turbulent diffusion flames with gaseous fuels.
Probably a large rig should be used for this study, especially if the rate of effort is minimum. Turbulence scale
and intensity should be the major variables considered. The effect of fuel type should also be investigated. Special
instrumentation might have to be developed for solving problems related to the effect of "unmixedness" on the
production of pollutants. Attention should be given to the part that flame stability plays in the production of
pollutants.
Rationale and Incentive
Many industrial flames are of the turbulent-diffusion-flame type. This research should provide guidelines for the
optimization of turbulent conditions in gaseous-fuel combustion systems to minimize pollutant emission and form a
basis for studies of other fuels burned in like manner.
Estimated R&D Cost & Time
R&D Cost Range, 1000's: $800-$1,550
R&D Time Range: 4-5 years
Recommended 5-year Funding, 1000's: $1,025
Funding by Fiscal Year, $1oo0's
'69.70 171 72
X 275 225
'73
'74
150
75 , '76+
150 -
225
Evaluation
Associated Priority Ranking:
III
Power
Plants
IV
Industrial
Processing
V
Industrial,
Commercial,
Residential
VI
Continuous-
Combustion
Engines
VII
Internal-
Combustion
Engines
2
3
-------
VIII-S 1
R&D Opportunity: VIII-23
Related to: VIII-21, 24
Experimental Determination of the Effect of Pressure on Pollutant Formation in Laminar Diffusion
Flames
Technical Objective and Approach
The objective is to determine the effect of pressure on the formation of pollutants in laminar diffusion flames
of vaporized liquid fuels.
The approach should be to use a modified type of nonturbulent-diffusion-flame rig. Because fuels of interest
include vaporized gasoline and kerosene, a provision for heating must be made. In addition, the system must be
capable of being pressurized. It is known that pressure has an effect on soot formation, and probably on the
formation of other pollutants as well.
Rationale and Incentive
A fundamental understanding of pollutant formation from higher hydrocarbons under various pressure
conditions would be helpful in understanding, and ultimately in reducing, the formation of pollutants in diesel and
gas-turbine engines.
Estimated R&D Cost & Time
R&D Cost Range, 1000's: $175-$300
R&D Time Range: 2-4 years
Recommended 5-year Funding, 1000's: $250
Funding by Fiscal Year, $1OOO's
'69-70 1'71
100
72
75
'73
'74
75
76+
75
Evaluation
Associated Priority Ranking:
III
Power
Plants
IV
Industrial
Processing
V
Industrial,
Commercial,
Residential
VI
Continuous-
Combustion
Engines
VII
I nternal-
Combustion
Engines
5
4
4
-------
VIII-52
R&D Opportunity: VIII-24
Related to: VIII.23
Experimental Investigation of the Effect of Pressure on Pollutant Formation in Turbulent Diffusion
Flames
Technical Objective and Approach
The objective is to determine the effect of combustion-chamber pressure on the formation of pollutants by
turbulent diffusion flames of vaporized liquid fuels.
The approach should be to examine, in an appropriate rig, the effects of pressure on a turbulent diffusion
flame. Gasoline, kerosene, and propane should be included in this study. Turbulence scale and intensity should be
varied over a range comparable to that typical for industrial units and the extent of "unmixedness" and its
influence determined. The problems of studying the details of "unmixedness" and its effects will be complicated by
the pressure (if only because the size scale for measurement decreases with increasing pressure).
Rationale and Incentive
Results should aid directly in the reduction of pollutants from gas-turbine-type combustors and indirectly in
the reduction of pollutants from IC engines.
Estimated R&D Cost & Time
R&D Cost Range, 1000's: $400-$500
R&D Time Range: 3-4 years
Recommended 5-year Funding, 1000's: $500
Funding by Fiscal Year, $1oo0's
'69-70 I '71 '72
200 150
'73
150
'74
'75
76+
Evaluation
Associated Priority Ranking:
III
Power
Plants
IV
Industrial
Processing
V
Industrial,
Commercial,
Residential
VI
Continuous-
Combustion
Engines
VII
I nternal-
Combustion
Engines
2
-------
VIII-53
R&D Opportunity: VIII-25
Related to: III-5; V-I, 2, 3; VI-I, 2, 3,4,5; VIII-26; V-iii
Experimental Determination of the Relation of Pollutant Output to Path History Along Flow Paths
Typical of Combustion Systems Burning Premixed Gaseous Fuels
Technical Objective and Approach
The objective is to determine the relation of pollutant output to the flow path history typical for combustion
systems burning premixed gaseous fuels.
The approach should include measurements to determine the production of pollutants as a function of flow
path history in plug-flow combustors simulating path conditions in actual furnaces burning premixed gaseous
hydrocarbon fuels. Specifically, natural gas, methane, ethane, propane, butane, and ethylene should be studied as
fuels. The volatile gases driven off by rapid heating of coal should also be investigated. The primary variables
considered should be mixture ratio, fuel type, and intensity and scale of turbulence. The effects of change in
cooling rate and firing rate should also be examined. Primary measurements should be temperature, velocity, and
composition (02, C02, CO, N2, input fuel, NOx, CnHm, particulates). At least one rig should be of a size
commensurate with prototype practice.
Rationale and Incentive
Considerable reduction in pollutant emissions might be achieved if it were possible to specify conditions along
flow paths for minimizing pollutant formation. The results from the burning of coal volatiles might lead to new
concepts for pulverized-coal-burner design to minimize pollution. Results should also be applicable in a more basic
manner to diffusion-flame combustion systems and be of value in studies of global kinetics.
Estimated R&D Cost & Time
R&D Cost Range, 1000's: $500-$1,500
R&D Time Range: 4-6 years
Recommended 5.year Funding, 1oo0's: $1,325
Funding by Fiscal Year, $1OO0's
'69-70 171
275
72
'73
'74
75
76+
225 225 300 300
Evaluation
Associated Priority Ranking:
III
Power
Plants
IV
Industrial
Processing
V
Industrial,
Commercial,
Residential
VI
Continuous-
Combustion
Engines
VII
Internal-
Combustion
Engines
2
2
4
-------
VIII-54
R&D Opportunity: VIII-26
Related to: VI-l, 2, 3,4
Experimental Determination of the Relation of Pollutant Output to Path History Along Flow Paths
Typical of Combustion Systems Burning Vaporized Hydrocarbons at Pressures Other Than
Atmospheric
Technical Objective and Approach
The objective is to determine the effect of pressure on the relation of pollutant output to flow path history
typical for vaporized fuel in hydrocarbon combustors operating at pressures other than atmospheric.
The approach should include operation of plug-flow combustors over a range of pressures sufficient to give
data pertinent to both gas-turbine operation and IC-engine operation. The main variables should be fuel type
(vaporized gasoline, vaporized kerosene, propane), mixture ratio, and pressure. The effects of turbulence and cooling
rate should also be examined. Primary measurements should be temperature, velocity, and composition.
Rationale and Incentive
Pressure is known to have an influence on the combustion process. For example, the color of propane-air
flames changes from blue to yellow as the pressure is increased from 1/4 to 4 atm. In view of the importance of
combustion at elevated pressures in the gas turbine and IC engine, some understanding of the influence of pressure
on pollutant emissions is desirable. The data obtained 'by this research, in combination with data from other
programs giving more details on effect of turbulence, etc., would permit specifying the path conditions which
minimize pollutant production in pressurized combustion systems.
Estimated R&D Cost & Time
R&D Cost Range, 1000's: $350-$950
R&D Time Range: 3-5 years
Recommended 5-year Funding, 1000's: $800
Funding by Fiscal Year, $1OO0's
'69-70 "71 '72
X 250 175
'73
'74
100
75
100
76+
175
Evaluation
Associated Priority Ranking:
III
Power
Plants
IV
Industrial
Processing
V
Industrial,
Commercial,
Residential
VI
Continuous-
Combustion
Engines
VII
Internal-
Combustion
Engines
2
-------
VIII-55
R&D Opportunity: VIII-27
Related to: III-2, 3, 4; IY-I, 2,5; Y-6, 7,8; YI-2
Experimental Determination of the Effects of Addition of Recirculated Combustion Products,
Secondary Air, and/or Supplemental Fuel on Pollutant Formation
Technical Objective and Approach
The objective is to determine the effect on pollutant production of the addition of recirculated combustion
products, secondary air, and/or supplemental fuel at various stages of combustion of premixed gaseous fuels.
The approach should be to employ a plug-flow combustor rig with special provision for injecting the various
test gases uniformly across various sections. Natural gas and propane are suggested as fuels. Primary measurements
should be of temperature, velocities, and composition. Provision should be made for generating products of
combustion and cooling them in varying amounts. For the air injection, provision should be made for heating. The
injection of supplemental fuel at various stages of combustion should also be examined. Finally, the effect of
interstage cooling of the products is also of great importance and should be examined.
Rationale and Incentive
There is considerable evidence that the optimum amount of recirculation of combustion products will minimize
pollution. The suggested research should help define this optimum for premixed gaseous flames and provide
guidelines for using recirculation for other types of combustors. The results probably will also furnish a guide to the
potential benefits and the optimum use of two-stage and multi-stage combustion to minimize air pollution.
Information would also be obtained on the beneficial or deleterious effects of rapid air quenching. Finally, the
results of the fuel-injection tests might reveal two-stage combustion possibilities. However, this information may be
more valuable in highlighting the deleterious effect of supplying fuel in the wrong stage of the combustion process.
Estimated R&D Cost & Time
R&D Cost Range, 1000's: $400-$800
R&D Time Range: 3-6 years
Recommended 5-year Funding, 1000's: $650
Funding by Fiscal Year, $1ooo's
'69-70 171
X 200
72
'73
'74
75
75
75
76+
150 150
Evaluation
Associated Priority Ranking:
III
Power
Plants
IV
Industrial
Processing
V
Industrial,
Commercial,
Residential
VI
Continuous-
Combustion
Engines
VII
Internal-
Combustion
Engines
3
-------
VIII-56
R&D Opportunity: VIII-28
Related to: IV-I, 2, 3, 4, 5; VIII-I; VIII-y
Experimental Investigation
Industrial-Size Flames
of
Nitrogen
Oxide
and
Other
Pollutant
Formation in
Large
Technical Objective and Approach
The objective is to determine the influence of design and operating variables pertinent to natural-gas-,
heavy-fuel-oil-, and pulverized-coal-fired diffusion-flame burners and furnaces of industrial or commercial size on the
concentration of nitrogen oxides and other pollutants in the exhaust gases.
The approach should be to determine the production of NOx, CO, particulates, and other pollutants in the
exhaust gases and at other critical regions in combustion systems of industrial or commercial size. Pertinent data on
flow velocities, temperature, and gas composition should also be obtained. Burners resembling commercially
available units, but with more precisely known and controllable characteristics, should be used. Reasonable levels of
thermal loads should be applied to the furnaces. Phenomenological explanation of the experimental results, leading
to improvements in designs directed toward minimizing pollution, should be sought. The results should be compared
with existing mathematical models of pollution production in furnaces.
Rationale and Incentive
The results of this program should reveal possibilities for relatively straightforward and simple design changes in
present commercial and small industrial combustors and in firing practice to minimize pollutant production.
Furthermore, the results should reveal the proper direction for development of new designs of this equipment.
Because optimum performance is related to such concepts as recirculation and two-stage combustion, direction
should also be given to fundamental and applied programs related specifically to these concepts.
Estimated R&D Cost & Time
R&D Cost Range, 1000's: $425-$800
R&D Time Range: 3-5 years '
Recommended 5-year Funding, 1000's: $675
Funding by Fiscal Year, $1OO0's
'69-70 12!
175
'72
'73
'74
125
75
125
76+
125 125
Evaluation
Associated Priority Ranking:
III
Power
Plants
IV
Industrial
Processing
V
Industrial,
Commercial,
Residential
VI
Continuous-
Combustion
Engines
VII
I nternal-
Combustion
Engines
4
-------
VIII-57
R&D Opportunity: VIII-29
Related to: VIII-I?, 18,21,22
Preparation of a Monograph and Operation of an Information Center on Turbulence Aspects of
Typical Combustor Flow Systems
Technical Objective and Approach
The objective is to produce a monograph on the turbulence aspects of typical practical combustion systems
and to promote the interchange of information in this area among various NAPCA-sponsored research teams and
others.
The approach should be to establish a team with responsibility for coordinating the turbulence aspects of all
NAPCA-sponsored fundamental research programs. The team should serve as a source of information on the
turbulence characteristics of practical combustors, supply information on the various ways to model or scale
turbulence characteristics for various design approaches being considered, and produce a monograph covering the
subject. Some small amount of experimental work will probably be required, including field measurements of
turbulence in various combustion systems.
Rationale and Incentive
One factor common to all industrial combustion systems is the presence of turbulence. A rather extensive
waste of effort would result if each research team were required to investigate the turbulence conditions typical to
their areas of interest. Coordination and exchange of research results on turbulence aspects of combustion would
reduce the overall cost and loss of time associated with duplicate efforts.
In addition to the coordinating effort, the overview provided by the program should produce some empirical
conclusions relating turbulence characteristics to pollutant production that could be put into use rather rapidly in
reducing pollutant emissions of combustion systems.
Estimated R&D Cost & Time
R&D Cost Range, 1000's: $325-$600
R&D Time Range: 5 years
Recommended 5-year Funding, 1oo0's: $600
Funding by Fiscal Year, $1000's
'69-70 I '71
120
72
120
73
120
74
120
75
120
76+
Evaluation
Associated Priority Ranking:
III
Power
Plants
IV
Industrial
Processing
V VI VII
Industrial, Continuous- Internal-
Commercial, Combustion Combustion
Residential Engines Engines
2 2 3
4
2
-------
VIII-58
R&D Opportunity: VIII-3D
Related to: VIII-I?, 18, 19
Preparation of a Monograph and Support of an Information Center on Atomization, Droplet
Trajectories, and Droplet Burning
Technical Objective and Approach
The objective is to provide a source for current information on droplet production, trajectory, evaporation, and
burning.
The approach should involve compiling information available in the literature, analyzing the data found, and
making necessary calculations for the writing of an up-to-date monograph on the subject. The writer of the
monograph could also provide consultation during the program, and update the monograph at the end of a specified
five-year period.
No experimental work is contemplated.
Rationale and Incentive
Preparation of a monograph on droplet production, trajectory, evaporation, and burning would eliminate the
necessity for multiple independent reviews of the literature by the various researchers working in this area.
Establishing an information center would provide for updating the information and for interpretation.
Estimated R&D Cost & Time
R&D Cost Range, 1000's: $250-$500
R&D Time Range: 3-5 years
Recommended 5-year Funding, 1000's: $425
Funding by Fiscal Year, $1OO0's
'69.70 I '71
X 100
'72
100
'73
75
'74
75
'75
75
'76+
Evaluation
Associated Priority Ranking:
III
Power
Plants
IV
Industrial
Processing
V
Industrial,
Commercial,
Residential
VI
Continuous-
Combustion
Engines
VII
Internal.
Combustion
Engines
4
2
2
2
-------
VIII-59
R&D Opportunity: VIII-New Concepts
Provision for Exploring New Concepts and New Research Opportunities that Evolve from the
Program and Accelerating Fundamental and Broadly Applicable Combustion Research that Promises
to Yield Insight or to Solve Problems Associated with Applied Research
Technical Objective and Approach
The objective is to provide for long-range flexibility in the research program to enable APCO to take
advantage of opportunities in the fundamental and broadly applicable areas that are not presently evident, but
which can arise during the course of this program.
The approach should be to make specific provisions in the research program to explore new research concepts
and to accelerate research in areas which promise to improve the understanding or to solve problems associated with
the reduction of pollutant emissions. The merits of specific research opportunities should be evaluated as they
evolve.
Rationale and Incentive
As the research and development activities directed towards control of pollutant emissions from energy-
conversion-combustion sources progress, opportunities for research work in the fundamental and broadly applicable
areas will arise. Such new opportunities may be associated with problems encountered in applied R&D activities,
with new ideas for research, with the uncovering of gaps in knowledge and understanding by continuing research
efforts, or by the addition of new pollutants to those of current major concern.
Support of fundamental and broadly applicable research in such newly uncovered areas has the potential of
speeding the development of controls, preventing wasted effort in unpromising fields, and reducing the duplication of
effort which otherwise might take place.
Recommended Funding Allocation
'71
'72
150
'73
'74
250
'75
Funding by Fiscal Year, $1OO0's
200
300
5-year Funding, 1000's: $900
Evaluation
This R&D Opportunity is unranked. The evaluation and funding level for each specific research opportunity must be
determined when the opportunity is identified. The suggested funding level anticipates effort on several research
opportu n ities.
-------
TABLE VIII-4. SUMMARY Of PRIORITIES
FUNDAMENTAL AND BROADLY APPLICABLE COMBUSTION fiESi:ARCH
Relative Current Estimated R&D Costs, $1000
Priority R&D Opportunity APCO By Fiscal Years
Rating R&D 5- Y ear On-Going
Effort '71 '72 '73 '74 '75 Total '76+
I VIII-I8 Experimental Investigation of the Relation of Size Dis- X 200 200 200 200 200 1,000 -
tribution and Relative Velocity of Burning Droplets and
Particulates to the Formation of Pollutants
1 VIII-20 Experimental Investigation of the Burning Process of a X 125 100 - - - 225 -
Solid-Fuel Part~cIe in Simulated Fluidized or Fixed Beds
1 VIII-25 Experimental Determination of the Relation of Pollutant - 275 225 225 300 300 1,325 -
Output to Path History along Flow Paths Typical of
Combustion Systems Burning Premixed Gaseous Fuels
1 VIII- 27 Experimental Determination of the Effects of Addition of X 200 150 150 75 75 650 -
Recirculated Combustion Products, Secondary Air, and/or
Supplemental Fuel on Pollutant Formation
- - - - - -
Totals, Priority 1 800 675 575 575 575 3,200
<:
......
......
.......
I
0\
-------
TABLE VIII-4. (Continued)
Relative Current Estimated R&D Costs, $1000
Priority R&D Opportunity APCO By Fiscal Vears
R&D 5- V ear On-Going
Rating Effort '71 '72 '73 '74 '75 Total '76+
2 VIII-22 Experimental Investigation of the Effect of Turbulence X 275 225 225 150 150 1,025 -
and Gaseous Fuel Type on Pollutant Formation in
Turbulent Diffusion Flames
2 VIII-28 Experimental Investigation of Nitrogen Oxide and Other - 175 125 125 125 125 675 -
Pollutant Formation in Large Industrial-Size Flames
2 VIII-29 Preparation of a Monograph and Operation of an Infor- - 120 120 120 120 120 600 -
mation Center on Turbulence Aspects of Typical
Combustor Flow Systems
2 VIII-30 Preparation of a Monograph and Support of an Infor- X 100 100 75 75 75 425 -
mation Center on Atomization, Droplet Trajectories,
and Droplet Burning
- - - - - -
Totals, Priority 2 670 570 545 470 470 2,725
<:
.....
.....
.....
I
-------
TABLE VIII-4. (Continued)
Relative Current Estimated R&D Costs, $1000
.
Priority R&D Opportunity APCO By Fiscal Vears
R&D 5- V ear On-Going
Rating Effort '71 '72 '73 '74 '75 Total 76+
3 VlII-l Experimental and Theoretical Investigations of the Inter- X 200 200 200 200 200 1,000 100/yr
actions and Coupling of the N2-02 System with Other
Reactions and Species in Combustion Systems
3 VIII-4 Experimental Determination of the Global Kinetics of Dilute - 100 100 100 100 - 400 -
HC-02 Systems and Kinetics in Quenched Systems
3 VlII-1O Experimental and Theoretical Studies of the Kinetics and X 50 50 50 50 50 250 50/yr
Mechanism of HC Pyrolysis Reactions
3 VlII-12 Experimental Studies of the Formation and Destruction X 100 100 100 100 100 500 -
of PNA in flames
3 VIII -13 Experimental and Theoretical Investigations of the X 75 75 75 75 75 375 150
Formation of Soot in Flames
3 VlII-19 Experimental Studies of Single or Small Number of Burning X 100 75 75 75 - 325 -
Droplets and Particles to Determine the Relation of Size
and Other Factors to Pollutant Formation
- - - - - -
Totals, Priority 3 625 600 600 600 425 2,850
<:
.....
.....
.....
I
0\
-------
TABLE VIII-4. (Continued)
Current Estimated R&D Costs, $1000
Relative APCO
Priority R&D Opportunity R&D By Fiscal Years 5-Year On-Going
Rating Effort '71 '72 '73 '74 '75 Total 76+
4 VIII -5 Experimental Investigation of Wall-Quenching Phenomena - 85 200 150 150 150 735 -
as Related to the Formation of Pollutants
4 VIII -6 Experimental Investigation of the Kinetics of Oxygenated - 50 50 50 - - 150 -
Intermediates and Their Destruction by Oxidation
4 VIII-7 Experimental Investigation of the Contribution of Specific X 50 50 50 - - 150 -
Fuel Constituents to Odor Production in the Combustion
Process
4 VIII-14 Investigations of the Kinetics and Mechanism of Soot Com- X 100 100 100 100 100 500 -
bustion in Flames and Post-Combustion Gas Streams
4 VIII-26 Experimental Determination of the Relation of Pollutant X 250 175 175 100 100 800 -
Output to Path History Along Flow Paths Typical of
Combustion Systems Burning Vaporized Hydrocarbons
at Pressures Other Than A ~mospheric
- - - - - -
Totals, Priority 4 535 575 525 350 350 2,335
-<
-
-
-
I
0\
-------
TABLE VIII-4. (Continued)
Relative Current Estimated R&D Costs, $1000
Priority R&D Opportunity APCO By Fiscal Years
Rating R&D 5- Y ear On-C}oing
Effort '71 '72 '73 '74 '75 Total '76+
5 VIII-2 Experimental Studies of the Contribution of Combined - 100 100 75 50 50 375 -
Nitrogen in Fuels to the Emission of NOx
5 VIII -9 Fundamental Experimental Studies of HC Oxidation Kinetics - 50 50 50 50 50 250 50/yr
5 VIII-ll Experimental Investigation of the Contribution of PNA - 50 50 - - - 100 -
Contained in Solid and Liquid Fuels to the Emission of PNA
5 VIII-IS Analytical and Experimental Studies of the Kinetics of X 75 75 - - - 150 -
Sulfur Oxidation in the Combustiol1 Process
5 VIII-17 Analytical and Experimental Investigation of the Influence - 75 75 - - - 150 -
ofInhomogenieties on Pollutant Formation in Droplet
Flames and Pulverized-Coal Flames
5 VIII-21 Experimental Determination of the Effect of Composition X 90 60 60 60 - 270 -
Gradients and Gaseous Fuel Type on the Production of
Pollutants in Laminar Diffusion Flames
5 VIII-23 Experimental Determination of the Effect of Pressure on - 100 75 75 - - 250 -
Pollutant Formation in Laminar Diffusion Flames
5 VIII-24 Experimental Investigation of the Effect of Pressure on - 200 150 150 - - 500 -
Pollutant Formation in Turbulent Diffusion Flames
- - - - - -
Totals, Priority 5 740 635 410 160 100 2,045
<:
-
-
-
I
0\
-------
TABLE VIII-4. (Continued)
Relative Current Estimated R&D Costs, $1000
Priority R&D Opportunity NAPCA By Fiscal Vears
Rating R&D 5- V ear On-Going
Effort '71 '72 73 '74 75 Total 76+
N VIII-N Provision for Exploring New Concepts and New Research - - 150 200 250 300 900 -
Opportunities that Evolve from the Program and
Accelerating Promising Fundamental and Broadly
Applicable Combustion Research that Promises to Yield
Insight or to Solve Problems Associated with Applied
Research
Total, All Priorities 3,370 3,205 2,855 2,405 2,220 14,055
-<
-
-
-
I
0\
-------
VIII-66
REFERENCES FOR CHAPTER VIII
1. "High-Speed Computing in Fluid Dynamics", The Physics of Fluids, Supplement II (1969).
2. Hawthorne, W. R., Weddell, P. S., Hottell, H. C., "Mixing and Combustion in Turbulent
Gas Jets", lrd Symposium (International) on Combustion, p 266, The Combustion Institute,
Pittsburgh (1949).
3. Dombrowski, N., and Munday, G., "Spray Drying", Biochemical and Biological Engineering
Science, Vol 2, p 209, Edited by N. Blakebrough, Academic Press (1968).
4. Wood, B. J., and Rosser, W. A., Jr., "An Experimental Study of Fuel Droplet Ignition",
AIAA Journal, 7 (1969), p 2288.
5. Bahn, Gilbert S., Reaction Rate Compilation for the H-O-N System, Gordon and Breach,
New York (1968).
6. Schofield, K., "An Evaluation of Kinetic Rate Data for Reactions of Neutrals of Atmo-
spheric Interest", Planetary and Space Science, 15 (1967), pp 643-670.
7. Van Beck-Visser, E., "Composition of Nitrogen Oxide Equilibria", Journal of Chemical
Physics, 29 (1958), pp 1358-1360.
8. Fenimore, C. P., Chemistry in Premixed Flames, Macmillan, New York (1964).
9. Camac, M., and Feinberg, R. M., "Formation of NO in Shock Heated Air", Eleventh
Symposium (International) on Combustion, The Combustion Institute, Pittsburgh (1967),
p 137.
10. Atalla, R. H., and Wohl, K., "The Role of Inerts ih Hydrocarbon Flames", Tenth Sympo-
sium (International) on Combustion, The Combustion Institute, Pittsburgh (1965), p 259.
11. Yang, C. H., and Gray, B. F., "The Slow Oxidation of Hydrocarbon and Cool Flames",
Journal of Physical Chemistry, 73 (1969), pp 3395-3406.
12. Benson, S. W., The Foundations of Chemical Kinetics, McGraw Hill, New York (1960).
13. Homer, J. B., and Kistiakowsky, G. B., "Oxidation and Pyrolysis of Ethylene in Shock
Waves", Journal of Chemical Physics, 47 (1967)1 pp 5290-5295.
14. Fristrom, R. M., and Westenberg, A. A., Flame Structure, McGraw Hill, New York (1965).
-------
Chapter IX
SUMMARY OF THE 5-YEAR COMBUSTION R&D PLAN
TABLE OF CONTENTS
SCOPE OF CHAPTER. . . . . . . . . . . . .
. . . . . . .
COMMENTS ON FEATURES AFFECTING UTILIZATION
OF THE PLAN. . . . . . . . . . . . . . .
. . . . . . .
Scope Limitation of the Plan. . . . . . . . . . . . . . .
Organization of the Plan and Allocations Between Fundamental
and Applied Areas. . . . . . . . . . . . . . . . . .
Competing Research Opportunities. . . . . . . . . .
Provisions for Exploring New Opportunities and Accelerating
Promising Research. . . . . . . . . . . . . . . . .
SUPPORTING ACTIVITIES. . .
. . . . . .
. . . . . .
Coordination and Communication. . . . . .
Future Program Planning. . . . . . . . .
. . . .
. . . .
SUMMARY TABLES OF R&D AND FUNDING LEVELS FOR THE
5-YEAR PLAN. . . . . . . . . . . . . . . . . . .
IX-1
-1
-1
-1
-2
-2
-3
-3
-4
-------
-------
IX-l
CHAPTER IX
SUMMARY OF THE 5-YEAR COMBUSTION R&D PLAN
SCOPE OF CHAPTER
This summary chapter includes discussion of several features of the Plan which should be
recognized to provide a proper perspective for its utilization. In addition, recommendations are
presented for supporting activities needed to enhance implementation of the R&D results
growing out of the program. Finally, summary tables are provided showing funding levels for the
Plan - by year, by 5-year total, by priorities, and by program elements.
COMMENTS ON FEATURES AFFECTING
UTILIZATION OF THE PLAN
Several aspects of the Plan which should be recognized in its utilization relate to (1) the
limitations of scope of the Plan, (2) the organization of the Plan, including the historic problem
of allocating resources between application-oriented R&D and fundamentally oriented research,
(3) presentation of competing research opportunities, and (4) provision for adding new R&D on
new concepts not now identified or for accelerating on-going R&D.
1. Scope Limitation 01 the Plan
It should be reemphasized that the plan considers only research concerned with combus-
tion modification in energy-conversion combustion processes which use prime fuels. Other
combustion processes, and combustion processes not using prime fuels, are not considered, nor
are the research needs of other approaches to emission control considered. Also, the scope of the
plan does not include research activities which are not directly concerned with the combustion
process, even though such activities may be necessary for the successful implementation of some
included combustion research.
Thus, the Plan represents only a part of the total R&D activities which can be directed
towards a reduction of air pollution from combustion sources. Plans in these other areas must
obviously be considered together with this Combustion Plan in developing a coordinated research
and development program.
2. Organization 01 the Plan and Allocations
Between Fundamental and Applied Areas
Program elements of the Combustion R&D Plan correspond to the scope outlined in each
of the previous chapters, generally organized by applications or source categories, namely:
-------
IX-2
. Central-Station Power Plants
. Industrial Processing
. Industrial Steam Generation and Commercial and Residential Heating
. Continuous-Combustion Engines -
Gas Turbines and External-Combustion Engines
. Reciprocating IC Engines
. Fundamental and Broadly Applicable Combustion Research.
Although these program elements do not correspond directly to the organization of APCO, it is
believed that this selection of program elements, by grouping like applications and considering all
pertinent pollutants within these applications, is best suited to the development and presentation
of this Plan.
R&D opportunities have been recommended and priorities ranked within each of these
elements. The lack of short-range benefit that could be attributed to fundamental research
precluded development of a common ranking scale based on benefit for the fundamental and
applied-R&D areas. Therefore, the research opportunities in the fundamental and broadly appli-
cable area have been priority ranked according to their relevance to applied-R&D needs. Thus,
although the ranking procedure is different from that used to rank the applied-R&D oppor-
tunities, the two sets of priority rankings do provide a device for allocating research resources
between the two areas. Judgmental criteria may still be applied to include other factors.
3. Competing Research Opportunities
Another aspect which may require consideration is that this Plan does not distinguish
between parallel or competing research opportunities in the same area, other than through the
priority ranking procedure. This is not a limitation if adequate funding is available and allows for
parallel approaches where desirable, particularly early in the program. As research progresses and
the factors entering the ranking process become better defined, application of the planning
methodology will select the more favorable line. However, in the event of restrictive funding
levels, it may be necessary to make additional judgmental decisions between competing research
opportunities.
4. Provisions for Exploring New Opportunities
and Accelerating Promising Research
In planning for future R&D, it is not possible to anticipate every need or include every
possible research opportunity of merit. To provide for the funding of promising new research
opportunities, as well as to possibly accelerate other work along promising lines, an unranked
"research opportunity" has been added to each of the program elements and coded New
Concepts (N) for the tabulations.
The funding level associated with each of these unranked new-concept provisions was
established judgment ally by considering the importance of the respective program elements, the
-------
IX-3
likelihood that new, high priority, research opportunities might be conceived within that
element, and the likely relative funding level of that element. The resulting total unranked
funding level is approximately 20 percent of the total A + B priority funding in the application-
oriented areas, and 15 percent of the 1 + 2 priority funding in the fundamentally oriented area.
It should be noted that the funding explicitly associated with these unranked R&D
opportunities represents only a part of the funds that would be anticipated to be available for
such purposes. As a result of the dynamic characteristics of the Plan, some lines of investigation
undertaken will undoubtedly be abandoned as research results refine the basis for the benefit
calculation. It is assumed here that unexpended funds originally committed to such investigations
become a part of the unranked funding and, thus, become available for contingency purposes.
SUPPORTING ACTIVITIES
In addition to the specific R&D in technical areas, supporting activity is recommended to
(1) coordinate related R&D and communicate the results of the combustion-R&D program to
engineering designers as a means of expediting control implementation by combustion modifica-
tion, and (2) provide for periodic updating of the Combustion R&D Plan. Provision for these
activities is included in the summary tables of program funding.
1. Coordination and Communication
The following activities are needed to obtain maximum effectiveness of the resources
allocated for the Combustion R&D Plan:
. To monitor air-pollution-related
R&D by all sectors:
- APCO R&D
- Other government R&D
- Trade associations
- Private industry (when reported).
and potentially useful combustion
. To collect, update, and distribute bibliographies on pertinent subjects
(with significant abstracts) to stimulate interchange of ideas.
. To provide for interpretation of fundamental research results for use
by designers in engineering application. (The preparation of compre-
hensive monographs in specific areas could serve as a vehicle to speed
utilization of fundamental research results in other R&D programs
and in control implementation.)
. To sponsor or organize technical conferences of specific scope, with
prompt and broad publication of proceedings or notes:
- Small conferences of R&D personnel
- Open conferences.
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IX-4
. To speed and broaden report distribution of APCO-supported R&D
- Contracts
- In-house R&D
- Grants.
The current practice for handling APCO contract reports is through the National Techni-
cal Information Service, with announcement of availability and distribution of xerocopies to
requesters, usually a number of months after the report is issued. (No similar procedure appears
standardized as yet for reporting results of in-house or grants research.) An additional procedure
is recommended whereby R&D organizations having a special interest in a given area could be
placed on a distribution list to automatically receive copies of reports in that area as soon as
issued.
2. Future Program Planning
The supporting activity for the R&D program should provide for periodic updating of the
opportunities and priorities. The overall planning rationale and the methodology of priority
ranking of R&D opportunities, as described in Appendix A, permits iteration of the technique to
reflect new technology and new criteria.
SUMMARY TABLES OF R&D AND FUNDING
LEVELS FOR THE 5-YEAR PLAN
The following tables summarize the R&D opportunities and funding requirements of
5-Year Combustion R&D Plan:
Table IX-I. Summary of R&D Opportunities and Funding Levels by
Priorities
Listing all applied R&D opportunities, grouped by
mated annual funding. (Funding for each priority
category is also shown.)*
priorities, with esti-
in the fundamental
Table IX-2. Summary of Funding Levels by Program Elements**
Listing of estimated annual funding by program element and by priorities
within each element.
Table IX-3. Summary of 5- Year Funding by Cumulative Priorities**
Listing of estimated 5- Year funding by accumulating highest priority
categories for each program element.
*Tot~l funding levels f?r opportunities in each of the five priority categories of fundamental and broadly
applicable research are mcluded at the end of each of the corresponding applied R&D . .t t .
**. pnon y ca egones.
Tables IX-2 and IX-3 are also mcluded at the end of the Executive Summary as Tables 1-2 and 1-3 respectively.
-------
TABLE IX-1. SUMMARY OF R&D OPPORTUNITIES AND FUNDING LEVELS BY PRIORITIES FOR 5-YEAR COMBUSTION R&D PL.AN
Current Estimated R&D Costs, $1000
Relative APCO
Priority R&D Opportunity R&D By Fiscal Years 5- Y ear
Rating Effort '71 '72 '73 '74 '75 Total
A III -6 Experimental Investigation of the Combustion Mech. X 125 125 250 - - 500
anism of Coal in a Fluidized Bed of Noncombustible
Particles
A III-7 Experimental Investigation of Factors Influencing X 50 75 125 250 - 500
Completeness of Coal Combustion in Fluidized Beds
with Low Excess Air
A III-8 Development of Improved Coal Gasification Systems to X 100 125 150 300 325 1,000
Produce Sulfur- and Ash-Free Gas Suitable for Advanced
Power Cycles
A VI-4 Development of a Low-Emission Automotive-Size Gas. - 200 200 200 200 - 800
Turbine Combustor Prototype
A VI-5 Development of Low-Emission Combustors for Rankine. X 500 300 200 200 - 1,200
Cycle Automotive Engines
A VII -1 Support of Development and Evaluation of Stratified- X 400 400 400 - - 1,200
Charge Gasoline Engines
A VII - 2 Development of Implementation Criteria for Lean.Mixture X 200 260 200 - - 660
Operation of Gasoline Engines
A VII-3 Experimental Research on the Effect of Fuel-Air Mixture X 100 100 100 - - 300
Preparation on Gasoline-Engine Emissions - - - - - -
Totals, Priority A 1,675 1,585 1,625 950 325 6,160
-
>.<
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TABLE IX-1. (Continued)
Relative Current Estimated R&D Costs, $1000
Priority R&D Opportunity APCO By Fiscal Years
Rating R&D 5- Year
Effort '71 '72 '73 '74 '75 Total
1 VIII All Priority 1 Fundamental and Broadly Applicable - 800 675 575 575 575 3,200
Combustion Research
B III-2 Analytical and Experimental Research to Develop Criteria X 200 850 1,050 2,500 3,000 7 ,600~
for the Application of Flue-Gas Recirculation to Mini-
mize NOx Emission from Central-Station Power Plants
B III-3 Experimental Investigation to Develop Design Criteria for X 200 200 400 400 1,000 2,200*
the Application of Two-Stage Combustion for NOx
Control, with Demonstration in a Coal-Fired Central-
Station Power Plant
B III-4 Experimental Investigation to Develop Design Criteria for X 200 300 300 1,000 - 1 ,800*
the Application of Two-Stage Combustion for NOx
Control, with Demonstration in an Oil-Fired Central-
Station Power Plant
B III-14 Analytical and Experimental Investigation of the Feasibility - 100 100 100 - - 300
of Fluxing Coal Ash for Minimizing Emission of Particu-
lates from Central-Station Power Plants
B V-I Experimental Investigation to Develop Design Criteria X 200 200 150 150 150 850
for Minimum Pollutant Emissions from Small- and
Intermediate-Size Combustion Equipment, Considering
Mixing, Turbulence, Combustion Intensity, and Furnace
Temperature
B V-2 Experimental Laboratory Investigation of the Effect of - 100 150 200 200 100 750
Internal Recirculation on Emissions, Demonstration of
Optimum Internal Recirculation on Several Small- and
Intermediate-Size Combustion Units, and Development
of Design Criteria
B V-3 Development of Analytical Models to Provide Design - 75 75 125 125 100 500
Guidance for Small- and Intermediate-Size Combustion
Equipment
-
>.<
-------
TABLE IX-1. (Continued)
Relative Current Estimated R&D Costs, $1000
Priority R&D Opportunity APCO By Fiscal Years
R&D 5- Y ear
Rating Effort '71 '72 '73 '74 '75 Total
B VI-3 Analytical and Experimental Research to Develop Criteria - 250 200 200 - - 650
for Reduction of CO, HC, and Odor Emissions From
Aircraft Gas Turbines at Idle and Low Power
B VII-7 Initiate Development of a Model of the Diesel-Engine Com- X 200 200 200 200 200 1,000
bustion Process by Analytical and Experimental Develop-
ment of a Fuel-Air Mixing-and-Vaporization Model
B VII-8 Experimental Investigation to Identify Odor-Producing X 100 100 100 100 100 500
Constituents in Diesel-Engine Exhaust, the Mechanism
of their Formation and Combustion Modifications to
Reduce Emissions of the Constituents
B VII -9 Experimental Laboratory Research on Pre-Flame and Non- - 70 70 70 70 70 350
Flame Reactions in Diesel-Engine Combustion - - - - - -
Totals, Priority B 1,695 2,445 2,895 4,745 4,720 16,500
2 VIII All Priority 2 Fundamental and Broadly Applicable - 670 570 545 470 470 2,725
Fundamental Combustion Research
C III-12 Experimental Investigation of the Effect of Mineral Com- X 75 75 125 - - 275
position of Coal on Fly-Ash Resistivity and Other
Characteristics
C III-B Analytical and Experimental Investigation of the Effect of X 50 100 150 150 - 450
Combustion Conditions on Fly-Ash Resistivity and Other
Characteristics
C III-IS Analytical and Experimental Investigation of a Super-Slagging - 100 150 150 300 400 1 ,1 00
Furnace to Achieve High Capture of Coal Ash for Central-
Station Power Plants
-
>.<
-------
TABL~ IX-1. (Continued)
Relative Current Estimated R&D Costs, $1000
Priority R&D Opportunity APCO By Fiscal Years
Rating R&D 5- Y ear
Effort '71 '72 '73 '74 '75 Total
C 1II-16 Development of Improved Research Instrumentation and - 100 150 150 100 - ~OO
Sampling for Measurement of Local Conditions Within
Combustion Systems
C V-5 Experimental Investigation of the Mechanisms by which PNA X ISO 150 150 150 - 600
is Formed and Destroyed during the Combustion of Coal on
Fixed Beds and Development of Design Criteria to Minimize
PNA Emissions with Demonstrations on Boiler Units
C V-7 Experimental Investigation of the Application of Flue-Gas X 250 200 200 - - 650
Recirculation and 2-Stage Combustion (and in combination)
to Typical Oil- and Gas-Fired Industrial Package Boilers
with One Demonstration Prototype
C V-lO Experimental Investigation to Develop Low-Peak-Temperature - 75 100 150 150 - 475
Residential Heating Units to Reduce NOx Emissions
,
C V-13 Measurement of Emissions from Various Types of Industrial, X 150 150 60 60 60 480
Commercial, and Residential Combustion Equipment to
Develop More Comprehensive Emission Factors and to
Provide Design Guidance
C VI-I Analytical and Experimental Research on Relation of Gas- X 200 200 - - - 400
Turbine Combustor Primary-Zone Design to Emission of NOx
C VII -4 Analytical and Experimental Research on Gasoline-Engine - 100 100 100 - - 300
Wall-Quench Phenomena - - - -
- -
Totals, Priority C 1,250 1,375 1,235 910 460 5,230
3 VIII All Priority 3 Fundamental and Broadly Applicable - 625 600 600 600 425 2,850
Combustion Research
-
>.<
-------
TABLE IX-1. (Continued)
Current Estimated R&D Costs, $1000
Relative APCD
Priority R&D Opportunity R&D By Fiscal Vears 5- V ear
Rating Effort '71 '72 '73 '74 '75 Total
D III-I Experimental Investigation of Feasibility of Burning - 125 125 250 - - 500
Pulverized Coal with Low Excess Air
D III-5 Exploratory Research and Experimental Feasibility - 100 150 150 250 300 950
Evaluation of a Low-Emission Combustion System
for Central-Station Power Plants using the Concept of
a High-Turbulence Primary Combustion Zone Plus a
Plug-Flow Zone
D III-lO Laboratory-Scale and Field Investigation of the Effect - 75 75 - - - 150
of Rank of Coal on Emission of NOx
D V-6 Experimental Investigation of the Application of Flue- X 200 200 200 - - 600
Gas Recirculation and 2-Stage Combustion (and in com-
bination) to Residential and Small-Commercial Oil & Gas
Burners with Demonstration Prototypes
D V-9 Conceptual Design and Supporting Experimental Investiga- X 250 250 250 150 150 1,050
tions to Guide the Application of Fluidized-Bed Combus-
tion of Coal to Industrial Steam Generation
D V-II Experimental Investigation of Additives and Emulsions for X 100 75 - - - 175
Reducing Emissions from Residual Fuel-Oil Combustion
D V-12 Experimental Investigation of the Effect of Burner - 150 75 75 - - 300
Maintenance on Emissions from Commercial and
Residential Oil Burners and Development of Design
Criteria to Minimize Performance Deterioration
-
>.<
-------
TABLE IX-1. (Continued)
Relative Current Estimated R&D Costs, $1000
Priority R&D Opportunity APCO By Fiscal Years
Rating R&D 5-Year
Effort '71 '72 '73 '74 '75 Total
D VI-2 Analytical and Experimental Research to Explore Relation - 100 200 200 - - 500.
of Gas-Turbine Secondary -Combustion- and Dilution-
Zone Design to NOx Emission
D VII-5 Experimental Research on the Effect of Lubricating Oil - 70 70 70 - - 210
on Gasoline-Engines Emissions
D VII-6 Experimental Research on the Formation of Particulate X 200 200 200 200 200 1,000
and PNA Emissions from Gasoline Engines
D VII -10 Investigation of Kinetics of Nitrogen-Oxide Formation X 100 100 - - - 200
in IC engines with Fuel-Rich Mixtures - - - - - -
Totals, Priority D 1,470 1,520 1,395 600 650 5,635
4 VIII All Priority 4 Fundamental and Broadly Applicable - 535 575 525 350 350 2,335
Combustion Research
E III-9 Exploration of the Feasibility of Electrochemical Oxidation - 100 100 100 100 100 500
of Coal for Direct-Energy Conversion
E III -11 Laboratory-Scale Investigation of the Effect of Residual - 125 150 200 - - 475
Fuel-Oil Properties and Composition on Emissions, and
Development of Convenient Methods to Characterize
Oils in Tenus of Emission Tendency, Including NOx
and Particulates
E IV-1 Analytical and Experimental Research on the Reduction - 100 200 200 200 - 700*
by Combustion Modifications of NOx from Rotary Kilns
for Production of Cement and Lime, Including Full-Scale
Demonstration Application
-
~
-
-------
TABLE IX-'. (Continued)
Relative Current Estimated R&D Costs, $1000
Priority R&D Opportunity APCO By Fiscal Years
R&D 5- Year
Rating Effort '71 '72 '73 74 '75 Total
E IV-2 Analytical and Experimental Research on the Reduction of - 100 200 100 - - 400
NOx from Glass Melting Furnaces by Combustion
Modifications
E IV-3 Analytical and Experimental Research on Reduction of - 250 250 500 1,000 - 2,000*
NOx Emissions from Open-Hearth Furnaces by Modifi-
cations of Firing Techniques, Including Demonstration
E IV-4 Analytical and Experimental Investigation of Fuel-Rich X 100 300 300 100 - 800*
Afterburning to Reduce NOx Emission from Regen-
erative Melting Furnace
E IV-5 Analytical and Experimental Investigation of Combustion - 100 200 - - - 300
Modifications to Reduce NOx Emission from Iron-
Sintering and Iron-Pelletizing Processes
E V-4 Experimental Investigation of the Contribution of Transient X 200 175 150 125 125 775
Conditions to Emissions from Residential and Small Com-
mercial Combustion Equipment, and Development of Means
of Minimizing Emissions During Transient Conditions
E V-8 Experimental Laboratory Investigation of the Application of - 200 300 300 300 - 1,100
Flue-Gas Recirculation to Fixed-Bed Coal Combustion with
Laboratory Demonstration - - - - -
-
Totals, Priority E 1,275 1,875 1,850 1,825 225 7,050
5 VIII All Priority 5 Fundamental and Broadly Applicable - 740 635 410 160 100 2,045
Combustion Research
-
>.<
-
-------
TABLE IX-1. (Continued)
Relative Current Estimated R&D Costs, $1000
Priority R&D Opportunity APCO By Fiscal V ears
Rating R&D 5- V ear
Effort '71 '72 '73 '74 '75 Total
N III oN Provision for Exploring New Concepts and New R&D - - 250 350 400 500 1,500
.
Opportunities that Evolve from the Program, Accel-
erating Promising R&D, or Conducting Demonstrations
of Promising Concepts for Reducing Emissions from
Central-Station Power Plants by Combustion Modification
N IV-N Provision for Exploring New Concepts and New R&D - - 50 50 50 50 200
Opportunities that Evolve from the Program,
Accelerating Promising R&D, or Conducting
Demonstrations of Promising Concepts for Reducing
Emissions from Combustion Equipment used for
Industrial Processing by Combustion Modification
N V-N Provision for Exploring New Concepts and New R&D - - 150 200 250 250 850
Opportunities that Evolve from the Program,
Accelerating Promising R&D, or Conducting
Demonstrations of Promising Concepts for Reducing
Emissions from Combustion Equipment used for
Industrial Steam Generation and for Space and
Water Heating by Combustion Modification
N VI-N Provision for Exploring New Concepts and New R&D - - 100 150 150 200 600
Opportunities that Evolve from the Program,
Accelerating Promising R&D, or Conducting
Demonstrations of Promising Concepts for Reducing -
Emissions from Gas Turbines and External Com-
bustion Engines by Combustion Modification
......
>,<:
-
-------
TABLE IX-1. (Continued)
Relative Current Estimated R&D Costs, $1000
Priority R&D Opportunity APCO By Fiscal Vears
R&D 5- V ear
Rating Effort '71 '72 '73 '74 '75 Total
N VII -N Provision for Exploring New Concepts and New R&D - - 250 300 300 350 1,200
Opportunities that Evolve from the Program,
Accelerating Promising R&D, or Conducting
Demonstrations of Promising Concepts for Reducing
Emissions from Reciprocating Internal-Combustion
Modification
N VIII-N Provision for Exploring New Concepts and New R&D - - 150 200 250 300 900
Opportunities that Evolve from the Program
and Accelerating Fundamental and Broadly Applicable
Combustion Research that Promises to Yield Insight
or to Solve Problems Associated with Applied Research - - - - -
Totals, Priority N 0 950 1,250 1,400 1,650 5,250
- - Communications and Planning - 300 300 300 300 300 1,500
Totals, All Applied R&D 7,365 9,600 10,050 10,180 7,730 44,925
Totals, All Fundamental Research 3,370 3,205 2,855 2,405 2,220 14,055
Totals, All R&D 11,035 13,105 13,205 12,885 10,250 60,480
-
>,<
-
-------
TABLE IX-2. SUMMARY OF FUNDING lEVELS BY PROGRAM ELEMENTS AND PRIORITIES FOR 5-YEAR COMBUSTION R&D PLAN
Number Estimated R&D Costs, $1000
R&D Program Element
Descri bed Priority of By Fiscal Years
in Chapter or Source Category level R&D 5-Year
Opportunities '71 '72 '73 '74 '75 Total
.
III Central-Station Power Plants A 3 275 325 525 550 325 2,000
B 4 700 1,450 1,850 3,900 4,000 11 ,900
C 4 325 475 575 550 400 2,325
D 3 300 350 400 250 300 1,600
E 2 225 250 300 100 100 975
N 1 - 250 350 400 500 1,500
- - - - - - -
Total 17 1,825 3,100 4,000 5,750 5,625 20,300
IV Industrial Processing A 0 - - - - - -
B 0 - - - - - -
C 0 - - - - - -
D 0 - - - - - -
E 5 650 1,150 1,100 1,300 - 4,200
N 1 - 50 50 50 50 200
- - - - - - -
Total 6 650 1,200 1,150 1,350 50 4,400
V Industrial Steam Generation and A -
o - - - - - -
Commercial and Residential B 3 375 425 475 475 350 2,100
Heating C 4 625 600 560 360 60 2,205
D 4 700 600 525 150 150 2,125
E 2 400 475 450 425 125 1,875
N 1 - 150 200 250 250 850
- - - - - - -
Total 14 2,100 2,250 2,210 1,660 935 9,155
.....
~
-
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TABLE IX-2. (Continued)
Number Estimated R&D Costs, $'1000
R&D Program Element of
Described Priority By Fiscal Years
in Chapter or Source Category Level R&D 5-Year
Opportunities '71 '72 '73 '74 '75 Total
VI Continuous Combustion Engines - A 2 700 500 400 400 - 2,000
Gas Turbines and External- B 1 250 200 200 - - 650
Combustion Engines C 1 200 200 - - - 400
D 1 100 200 200 - - 500
E 0 - - - - - -
N 1 - 100 150 150 200 600
- - - - - - -
Total 6 1,250 1,200 950 550 200 4,150
VII Reciprocating Intemal-Combustion A 3 700 760 700 - - 2,160
Engines B 3 370 370 370 370 370 1.850
C 1 100 100 100 - - 300
D 3 370 370 270 200 200 1,410
E 0 - - - - - -
N 1 - 250 300 300 350 1,200
- - - - - - -
Total 11 1,540 1,850 1,740 870 920 6,920
VIII Fundamental and Broadly 1 4 800 675 575 575 575 3,200
Applicable Combustion Research 2 4 670 570 545 470 470 2,725
3 6 625 600 600 600 425 2,850
4 5 535 575 525 350 350 2,335
5 8 740 635 410 160 100 2,045
N 1 - 150 200 250 300 900
- - - - - - -
Total 28 3,370 3,205 2,855 2,405 2,220 14,055
Communications and Planning 300 300 300 300 300 1,500
Overall Totals 11 ,035 13,105 13,205 12,885 10,250 60,480
-
~
..-
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IX-16
TABLE IX-3. SUMMARY OF 5-YEAR FUNDING ESTIMATES BY CUMULATIVE PRIORITIES FOR
PROGRAM ELEMENTS OF THE 5-YEAR COMBUSTION R&D PLAN
Estimated 5-Year R&D Costs, $1,000*
(Number of R&D opportunities is shown in parentheses)
Priority or Cumulative Priorities
All
Applied R&D A A-B A-C A-D A-E N Priorities
Chapter
III Central-S tation 2,000 13,900 16,225 17,825 18,800 1,500 20,300
Power Plants (3) (7) (11) (14) (16) (1) (17)
IV Industrial Processing - - - - 4,200 200 4,400
(5) (1) (6)
V Ind. Steam Generation & - 2,100 4,305 6,430 8,305 850 9,155
Comm. & Res. Heating (3) (7) (11) (13) (1) (14)
VI Continuous Combustion 2,000 2,650 3,050 3,550 3,550 600 4,150
Engines (2) (3) (4) (5) (5) (1) (6)
VII Reciprocating 2,160 4,010 4,310 5,720 5,720 1,200 6,920
IC Engines (3) (6) (7) (10) (10) (1) (11)
- - - - - - -
Totals, Applied R&D 6,160 22,660 27,890 33,525 40,575 4,350 44,925
(8) (19) (29) (40) (49) (5) (54)
1 '-2 '-3 '-4 1-5 N
VIII Fundamental Research 3,200 5,925 8,775 11,110 13,155 900 14,055
(4) (8) (14) (19) (27) (1) (28)
A A-B A-C A-D A-E
and and and and and
1 '-2 '-3 '-4 1-5 N
Totals by 10,860 30,085 38,165 46,135 55,230 5,250 60,480
Funding Levels(a)
N Indicates unranked general provision for new concepts and opportunities.
(a) Totals of applied R&D and fundamental research in priorities shown, including supporting activities of
communications and planning.
*Breakdowns of recommended funding by years (FY '71-'75) are shown in individual chapters and summarized
-------
Appendix A
PRIORITY RATING METHODOLOGY
FOR APPLIED-R&D OPPORTUNITIES
Joseph A. Hoess
Edgar S. Cheaney
TABLE OF CONTENTS
PRIORITY RATING METHODOLOGY FOR APPLIED-R&D OPPORTUNITIES. . . . .
Pollutant-Significance Factor.
. . . . . . . . . . . . .
Pollutant-Source Factor. .
. . . . . . . .
. . . .
. . . . . . . .
Pollutant-Source Factor Corrected for Implementation Time
. . . . . . . . .
Pollutant-Reduction Factor. . .
Alternative-Control Factor.
. . . . . . . .
. . . . . .
. . . .
. . . . . .
. . . . . . .
. . . . . . .
Potential-Benefit Factor. .
. . . . . . . .
. . . . . . . . . . . .
Implementation Cost. .
. . . .
. . . . . . .
. . . . . . . . . .
Combination of Benefits and Costs for Priority Rankings
. . . . . . . . . .
A- 1
- 2
- 2
- 3
- 5
- 6
- 8
- 9
-------
-------
A-I
APPENDIX A
PRIORITY RATING METHODOLOGY FOR
APPLI ED-R&D OPPORTUNITI ES
This appendix outlines the methodology used to establish priorities for the applied-R&D
opportunities in the 5- Year R&D Plan for reduction of emissions from energy-conversion com-
bustion (ECC) sources by combustion-process modification. Priorities were assigned on the basis
of:
. Relative potential for air-pollution reduction
. Relative cost to implement the results of the research
. Expert judgment.
Specific influences or factors considered in setting priorities are discussed in the following
paragraphs. These are: *
1. Pollutant-Significance Factor, Pi
2. Pollutant-Source Factor, Sij
Percent of pollutant i emission from all ECC sources from 1970 to
1990 contributed by ECC source j
3. Pollutant-Source Factor Corrected for
Implementation Time, (ST)ijk
4. Pollutant-Reduction Factor, Rijk
S. Alternative-Control Factor, Aij
6. Relative Potential-Benefit Factor, Bk
Factors 1-5 are combined to give Bk:
Bk = 100 ~ Pi x (ST)ijk x Rijk x (l-Aij)
ij ,
7. Estimated increase or decrease in annual cost associated with
implementation
8. Relative priority (considering Factors 6 and 7).
*Subscripts:
i refers to a specific pollutant
j refers to a specific pollutant source
k refers to a specific R&D opportunity.
-------
A-2
1. Pollutant-Significance Factor, Pi
The numericaf value assigned to Pi for pollutant i is defin~d as the relative benefit
associated with a 100 percent reduction in the projectedunconfrolledemission* of pollutant i
from all ECC sources during the peri'Od 1970 to 19'90 as compared with the same percentage
reduction for other pollutants for the same period. Thus, Pi is a proxy for the "total problem"
over the next 20 years presented by anyone pollutant that a given R&D opportunity might attack.
Nine specific pollutants were considered: combustible particulate, CO, gaseous HC,
polynuclear aromatics, odor,. NOx,.lead, sax, and fly ash (noncombustible particulate). As a
result of discussions with NAPCA personnel, Pi was assumed to be unity for each of these
pollutants. While the present state of knowledge concerning the relative significance of pollutant
emissions does not fully support any assumption as to values for Pi, the above assumption is
considered reasonable for the purposes of this. planning study. When the state of knowledge
permits a set of priorities to be established among the pollutants, new values for Pi can be
assigned reflecting these, and the R&D Plan can be adjusted accordingly. ..
2. Pollutant-Source Factor, Sij
Sij is the projected percent emission of pollutant i from all ECC sources from 1970 to
1990 contributed by ECC source j. This factor is depicted in Figure A-I.
L.. \ ECC
0 \ \ot" 0\
Q) 10'0
>-
"
-
c 0
0
-
::J
-
0 C sout"ce \
a..
II) EC .
c
~
Time ---+-
tons uncontrolled pollutant i from
Area B ECC source j (1970 to 1990)
Sij= =
Area (A+B) tons uncontrolled pollutant i from
all ECC sources (1970 to 1990)
Figure A-1. Definition of Pollutant-Source Factor S"
, 1/
*"Pro~ect~d uncontrolled emissi.o~s" are defined as the magnitude of nationwide emissions expected, without
consIdenng controls beyond eXIstmg technology. These projections are presented in Appendix B.
-------
A-3
Table A-I lists the values estimated
considered. Values for Sij vary from 0 to
pollutant for all ECC sources is equal to 1.0.
for Sij for each pollutant and for each source
1.0, and the sum of these values for a specific
The values listed in Table A-I were developed from the emission data and projections of
emissions by sources from 1970 to 1990 which are given in Appendix B. Specifically, the values
in Table A-I can be derived from the values in Table B-5. Because there are no applicable
quantitative measures or emission projections available for odor, values for Sij were judgmentally
assigned to this pollutant by the study team. A factor of 0.6 was assigned to diesel engines
(distributed between mobile and stationary engines in the same proportion as unburned
hydrocarbons) and 0.1 was assigned to aircraft gas turbines. The remaining 0.3 was distributed
nonspecifically among all other ECC sources.
3. Pollutant-Source Factor Corrected for
Implementation Time, (ST)ijk
(ST)ijk represents the maximum percent of pollutant i projected between 1970 and 1990
from all ECC sources that is susceptible to reduction by the successful implementation of R&D
opportunity k as applied to source j. This is depicted in Figure A-2.
L-
o
Q)
>-
........
EGG soufces
\ 'Of 0\\
10'0
-
c:
o
-
:J
o
a..
@
oufce \
EGG s
III
c:
o
I-
@
1970 .l ,
r First Field Implementation
of R 8 D Opportunity k
Time~
Area B2
(ST) Uk =
IJ Area (A + Bl + B2)
=
tons uncontrolled pollutant i from ECC source j
from time of first 9perational device utilizing
results of R&D opportunity k to 1990
tons uncontrolled pollutant i from all ECC
combustion sources (1970 to 1990)
Figure A-2. Definition of Pollutant-Source Factor Corrected for Implementation Time, (ST)ijk
-------
Cyclic Combustion for
Continuous Combustion for Energy Conversion Energy Convenion
ao Commercill &
c:
Central-5tation .~ Industrial Stelm Residential Mobile Stationary
Power Pllnts g Generation Space Heating GIS Turbines IC Engines IC Engines
Pollutants It .
ftj ~ .E .
.;: .. i
1;; C: .5
0 t! j "I 1 1
~ .. ;:, ftj 11 "3 II " I
5 III ~ 0 5 5 £ :< i5 i5
CJ u CJ u CJ CJ CJ CJ
1. Products of
Incomplete Combustion
Combustible Particullte 19.0 0.7 0.7 8.9 18.1 1.7 3.3 2.0 4.3 3.4 2.2 1.6 17.7 9.5 0.7 6.4 n
CO 0.3 n n 0.1 0.2 <.1 <'1 0.6 0.1 <.1 0.3 1.3 90.0 0.6 4.6 0.3 1.2
HC 0.5 0.1 n - 0.6 0.1 0.2 0.6 0.4 n 0.5 2.5 80.8 6.8 2.0 2.0 3.0
PNA n n n 6.8 n n n 73.1 2.1 3.9 n n 14.0 n n n n
Odor . I I I I I I 8 I I I 8 10 8 46 8 14 8
2. NOx 20.9 2.1 3.7 2.3 3.1 1.5 2.9 0.1 2.5 2.0 2.2 1.5 41.6 3.5 0.6 1.1 8.3
3. Combustion-Improving Additives
Lead n n n n n n n n n n n n 99.6 n 0.3 n n
4. Fuel Contaminants
SOx 77.1 5.7 n 2.9 7.3 1.9 n 1.0 2.1 n 0.5 0.3 0.8 0.3 n n n
Ash 81.1 0.2 n 15.0 10.7 0.5 n 1.2 1.5 n n n n n n n n
TABLE A.1. ESTIMATED VALUES FOR POLLUTANT.SOURCE FACTOR. Sij. x ,02
(Percent of '97~'990 Pollutant Emissions From All ECC Sources Contributed by Specific Sources)
~
~
n. emission considered negligible.
.Odor source fectors judgmentellv usigned bV B8ttellelt8ff.
-------
A-5
When a timing factor is applied in the above manner, an R&D opportunity estimated to
require a long period before field implementation will be penalized relative to an R&D oppor-
tunity for which only a short period is required. Further, the penalty will be greater when the
emission of pollutant i is decreasing over time than when it is increasing, For example, if the
emission per year of pollutant i from source j is remaining constant over time, a maximum of 50
percent of the 1970-1990 emission of pollutant i from source j would be susceptible to
reduction by an R&D opportunity to be implemented in 1980. However, if the emission of
pollutant i were doubling every 10 years, a maximum of 67 percent of the emission would be
susceptible to reduction.
In evaluating an R&D opportunity, the sum of (ST)ijk for each source is calculated for
each pollutant affected. The results of these calculations are listed in the evaluation summaries at
the end of each applied R&D opportunity description under the title, "Fraction of ECC
Emissions Affected",
4. Pollutant-Reduction Factor, Rijk
Rijk is defmed as the percent reduction of pollutant i from. source j that i~ ex?ected to
result from completing the work recommended for R&D opportumty k, plus applicatIOn to all
systems of the sources affected. Rijk is depicted in Figure A-3.
~
c
Q)
>-
......
ECC sources
\ ~or 0\\
1'0'0
-
c:
c
-
:J
o
-
o
a..
tJ)
c:
o
I-
@
1970
Time --+-
Area B22
Rijk = Area (B21 + B22)
Area B22
(ST). x Rook =
iJk IJ Area (A + Bl + B21 + B2V
Figure A-3. Definition of Pollutant-Reduction Factor, Rijk
-------
A-6
In establishing an average or expected value for Rijk, the study team estimated both
minimum (pessimistic) and maximum (optimistic) reductions that might result from the research
and the implementation of results. They also estimated the reduction that in their opinion is
most likely to result, taking into account the technical feasibility of the particular R&D
opportunity in question. On the basis of the assumption that the underlying probability
distribution for the reduction factors follows a Beta distribution, the expected value (at this
point in time) of the reduction factor can be estimated by:
expected reduction = 1/6 [pessimistic estimate + 4 (most likely estimate)
+ optimistic estimate] .
Both the estimated range of values and calculated expected values for Rijk are listed in the
evaluation summaries. The expected value is used in the calculation of Bk'
5. Alternative-Control Factor, Aij
Aij is a judgmental factor which allows for the likelihood that competing noncombustion
controls (e.g., downstream controls) may be applied to remove a specific pollutant from a given
source. Aij is applied to reduce the relative benefit associated with R&D opportunities which are
applicable to the particular pollutants and sources in question. Aij is applied by multiplying the
product of the Pollutant-Source Factor Corrected for Implementation Time and Pollutant-
Reduction Factor by (l-Aij).
Table A-2 is a listing of the values assigned to Aij for various combinations of sources
and pollutants. (Except for coal-fired boilers and reciprocating internal-combustion engines, non-
combustion controls were not considered likely to significantly reduce emissions and, therefore,
Aij was assigned a value of zero for all pollutants.)
Values for Aij are listed in the evaluation summaries for the R&D opportunities under
the title "Noncombustion-Controls Factor". Where an R&D opportunity is applicable to more
than one source, a composite value is listed. The composite value is the weighted average of the
value of Aij for each of the sources affected. The weighting is proportional to the amount of the
pollutant in question contributed by each source.
Coal-Fired Power Plants and Industrial Steam Generation
Combustible particulate and ash were assigned values of 0.7 and 0.5 for coal-fired power
plants and industrial steam generation, respectively, to allow for wider application and higher
efficiencies from mechanical separators and electrostatic precipitators in those applications. SOx
was assigned a value of 0.3 for coal-fired power plant; to allow for the possible use of the
various downstream controls currently under development or in the advanced engineering stage.
Gasoline Engines
Hydrocarbons and CO can be controlled effectively by both manifold reactors and
catalytic reactors. Although neither of these devices is presently available in a practical, low-cost
form, no other controls appear more feasible at present. Therefore, Aij for HC and CO was
estimated at 0.8.
-------
TABLE A.2. ASSIGNED VALUES FOR ALTERNATIVE-CONTROL FACTOR, Alj
Cyclic Combustion for
Continuous Combustion for Energy Convenion Energy Convenlon
DI Commercial &
I:
Central Station .~ Industrial Steam Residential Mobile Stationary
Power Plants u Generation Space Heating Gas Turbines IC Engines IC Engines
Pollutants E
II..
m ~ .. ..
.~ 1\1 ii
I: .5 .5
1;; 0 .. a ! i !
m VI :] m :II m VI "j u I
o 0 '" '0 0 0 '" .. '"
(.) ~ .!: (.) 0 ~ (.) 0 ~ en :.[ ~ i5 ~ i5 ~
1. Products of
Incomplete Combustion
Combustible Particulate .7 0 0 - .5 0 0 - 0 0 - - .5 .5 .5 .5 0
CO 0 0 0 - 0 0 0 - 0 0 - 0 .8 .5 .8 .5 0
HC 0 0 - - 0 0 0 - 0 0 - 0 .8 .5 .8 .5 0
PNA 0 - - - 0 0 0 0 0 0 - - .4 .4 .4 .4 0
Odor - - - - - - - - - - - 0 - .5 - .5 -
2. NOx 0 0 0 0 0 0 0 - 0 0 0 0 .2 .1 .2 .1 .2
3. Combustion-Improving Additives
Lead -
- - - - - - - - - - - - .8 - .8 - 0
4. Fuel Contaminants
SOx .3 - - - 0 - - - - - - - - - - - -
Ash .7 0 0 - .5 - - - - - - - - - - - -
.
-. An assumed value for Aij was not required for these combinations of pollutant_urce classifications end pollutent categories.
~
-------
A-8
Removal of NOx presently appears more difficult than removal of CO and HC. Some
experimental devices for catalytic reduction are claimed to be effective, but there have been no
convincing public demonstrations. On the other hand, exhaust-gas recirculation is in the advanced
experimental-development stage and promises to suppress 50 to 75 percent of the NOx.
Lean-mixture operation is another promising approach, though not as far advanced.
There is no firm basis at present for estimating Aij for NOx emissions from gasoline
engines. However, since noncatalytic controls presently are preferable and somewhat more fea-
sible, a value of 0.2 was assumed.
Lead particulates will probably be eliminated through the removal of lead additives from
the fuel. Therefore, Aij for lead was assumed to be 0.8. Other particulates will probably be
removed by downstream cleanup devices. However, the nature of the required cleanup device will
be affected by the amount, size, and composition of the particulates. Consequently, possible
combustion modification to make the particulates easier to control would be worthwhile.
Therefore, Aij was assumed to be 0.5 for combustible particulates.
PNA emissions have been observed to be affected by fuel, lube-oil, and engine variables.
PNA compounds such as benzo(a)pyrene can be present in the fuel and can be formed during
the combustion process. They would probably be vaporized at exhaust temperature, but would
be a liquid or solid particulate at normal ambient temperature. For the present, it appears that
Aij for PNA should be somewhat lower than for particulates in general. A value of 0.4 was
assumed.
No noncombustion controls for gasoline-engine emissions of odor, SOx, or ash are
anticipated.
Diesel Engines
Because there is far greater latitude for modifying the diesel-engine combustion process
without changing the basic nature of the engine than there is for the gasoline engine, and
because diesels are not facing stringent emission controls in the very near future, generally lower
values for Aij were assumed for the diesels than for gasoline engines. The assumed values are
listed in Table A-2.
Natural-Gas Engines
Except for NOx, the pollutant emissions from natural-gas engines are generally quite low.
Thus, no noncombustion control was assumed for these pollutants. Aij for NOx was assumed to
be 0.2 to allow for the possible use of catalytic contrgls.
6. Potential-Benefit Factor, Bk
Bk is a single overall numerical measure of the relative benefit (i.e., percentage reduction
in total ECC pollutant emissions over the 1970-1990 period) ascribed to each R&D opportunity.
It is defined as the product of each of the factors discussed up to this point, summed for each
pollutant and source affected:
-------
A-9
Bk = 100 ~ Pi x (ST)ijk x Rijk x (I-Aij),
'I
where (ST)ijk ~d Rijk are expressed as fractions. Values calculated for Bk for a11 the applied
R&D opportunItIes range from 0.04 to 46.50.
1. Implementation Cost
Implementation cost for an R&D opportunity is defined as the total cost to society for
implementing the results of the R&D by application to all installations within the source
category affected-. In general, the magnitude of the implementation cost for an R&D opportunity
would f-ar exceed the cost of performing the R&D. Consequently, implementation cost was the
only cost factor considered significant in establishing priority rankings.
Estimates of implementation cost were made by the project staff on the basis of
experience and analogy. These estimates were made in terms of the increase or decrease in
annual (Le., 1980) cost that might result from application of the resuIts of the R&D opportunity
to all systems of the sources affected. Considered in the estimates were:
. Changes in capital equipment depreciation and other capital charges per year.
This item was estimated to be equal to 0.15 times the change in capital
equipment cost.
. Changes in fuel, additive, and power costs per year.
. Changes in operating labor and maintenance costs per year.
In estimating these changes in yearly cost, no attempt was made to follow an implementation
model in which yearly costs would be dependent on the timing of introduction of new systems
and retrofitting of existing systems. Rather, an artificial condition was assumed where the results
of the R&D were assumed to have been applied to all systems of the sources affected. Further,
changes in capital-equipment cost were estimated as though the results of the R&D had been
incorporated into all systems when they were new.
Because detailed cost studies were not made, and because of the uncertainty necessarily
involved in making estimates for so far in the future and for items not yet developed, the
estimates- of implementation cost were translated into a "verbal portrayal" of the values (high,
medium, low, and very low). These verbal portrayals represent the following approximate cost
ranges:
Low
- greater than $1 billion per year
- $100 million to $1 billion per year
- $16 million to $100 million per year
(>$109)
($108 to 109)
($107 to 108)
«$107)
High
Medium
Very low - less than $1 0 million per year
-------
A-lQ
8. Combination of Benefits and Costs
for Priority Rankings
Ideally, it would be desirable to assign a unique priority index. to each individual project
in the total Plan (independent of program element). While such a numerical :rating was utilized iri
the planning process, the individual ratings have been categorized for purposes of this report. The
estimates and forecasts involved in the calculations of benefits and implementation costs were
considered too uncertain to permit such fine discrimination -in presenting the final results 'of the
priority ranking. Instead, projects were clustered into five priority groupings: A, B, C, D, and E.
The groupings have common significance for all the applied program elements since all applied-
R&D opportunities in these elements were evaluated on the same basis. .
In assigning' R&D opportunities to 'one of the five priority groupings, both' potential for
pollution reduction (as measured by Bk) and the general magnitude of possible implementation
cost (as measured by the verbal portrayals of cost) were considered. However, greater emphasis
was placed on potential for air-pollution reduction than on possible implementation costs. This
reasoning is based on the fact that the benefit estimates are considered more important (.and
more reliable) at this time than the implementation-cost estimates. Furthermore, the need for
actually funding the implementation of a given project cannot possibly arise until the research is
nearing completion. At that time, a far better appraisal of both costs and benefits can be made.
Therefore, although implementation cost should be accounted for in establishing priority, it is
logical to reduce its significance at this time compared with the significance of expected benefits.
The procedure used to accomplish the combined priority ranking was to assign a
numerical value on a logarithmic scale, i.e., 1, 2, 4, and 8, to each of the four implementation
cost categories, i.e., very low; low, medium,' and high, respectively. The Bk 'for a given R&D
opportunity was then divided by either 1, 2, 4, or 8, depending on the implementation cost
category into which the R&D opportunity was estimated to fall. The resulting modified Bk values
were then rank ordered from highest to lowest, and cutoff points were judgmentally selected to
define priority groupings A, B, C, D, and E. .
Whiie the procedure does not permit the R&D opportunities rated lowest with respect to
potential for pollution reduction to be ranked in the A-priority group, it does permit some
modest variations in priority ranking due to consideration of implementation costs. For example,
some R&D opportunities with medium values for Bk were ranked in either B~, C-, or D-priority
groups, depending on whether they were estimated to have very low, low, or medium imple-
mentation costs.
-------
Appendix B
DERIVATION OF THE EMISSION DATA
AND PROJECTIONS USED IN PLANNING
Philip R. Sticksel
Richard B. Engdahl
TABLE OF CONTENTS
DEVELOPMENT OF EMISSION INVENTORY DATA IN TABLE 11-1 . . . .
SOURCES OF PROJECTIONS FOR COM6USTION EMISSIONS. . . . . .
Projections for Continuous-Combustion Applications
Projections for Cyclic-Combustion Applications. .
. . . . . . .
. . . . . . .
REFERENCES FOR APPENDIX B . . . . . . .
. . . .
. . . . .
B- 1
- 3
-10
-17
-------
-------
B-1
APPENDIX B
DERIVATION OF THE EMISSIONS DATA
AND PROJECTIONS USED IN PLANNING
Most of the nationwide emissions data presented in Table II-I and the projections in
Figures II-I through II-S were supplied by the APCO Division of Air Quality and Emission Data
(DAQED). DAQED is responsible for collecting and compiling the results of past and current
nationwide emission inventories as well as projections of future emissions. Data are generated
through efforts of DAQED, other APCO Divisions, and under APCO-sponsored contracts.
A basic tool for deriving emissions data is the list of emission factors in Compilation of
Air Pollution Emission Factors. (1) These emission factors have been altered slightly by APCO in
cases where additional information became available, such as emission-factor dependence on the
age of an automobile. To derive emissions for past years, the emission factors can be applied to
tabulations of fuel usage, vehicle miles, aircraft takeoffs and landings, etc., as published annually
in the Statistical Abstract of the United States. (2) To forecast future emissions, these emission
factors can be applied to projections of energy demand, fuel usage, and transportation activity.
Projections are being developed continually by various Federal agencies such as the Federal
Power Commission, the Bureau of Mines, and the Department of Transportation.
DEVELOPMENT OF EMISSION INVENTORY DATA IN TABLE 11-1
The principal source of information for Table II-I is Nationwide Inventory of Air
Pollutant Emissions, 1968. (3) This book was prepared by DAQED as a tool for continuing
improvement of the accuracy of nationwide emission inventories. It includes data for emissions
for the year 1966 as well as 1968.
Many of the entries in Table II-I were taken directly from the extensive unpublished
source data of the DAQED compilations. In some cases in this study, emission source classes had
to be subdivided. These subdivisions were made using references such as the Census of Manu-
factures(4) for guidance in calculating the amount of fuel used for combustion in various
industries. Following is a discussion pointing out the differences between the breakdown of
Table II-I and the breakdown in Reference 3.
Combustible and Noncombustible Particulates
It was assumed that coal-fIred power plants have boilers fired with pulverized coal and
that 10 percent of the particulate emissions would be combustible particulate'
-------
B-2
from internal-combustion engines and gas turbines were considered to consist almost entirely of
combustible particulate, except for the lead portion. For other particulate-emissions sources, the
combustible particulate- was assumed to be 40 to 50 percent of the total, in agreement with
various published data.
Industrial Combustion Sources
In Reference 3, the category "Industrial Processing" includes processing not involving
combustion as well as processing involving combustion. The noncombustible emissions from the
coke-production industry, the metals industry, and the chemical industry make up most of the
difference between the "All Sources" and "All Combustion Sources" totals. In Table II-I
emissions from steam-generation equipment, process combustion equipment, and stationary gas
engines are broken out specifically from the total for "Industrial Processing".
After reviewing published data(4) of fuel usage by industry.classes, the Battelle team
evolved a set of approximate percentages for the relationship of industrial steam-generation
emissions to total industrial-combustion emissions.
The NAPCA research report by the Esso Research and Engineering Company( 6) points
out that the natural-gas engines used for pumping natural gas are an important source of NOx.
DAQED and DPCE have used the data in the Esso report for their nationwide emission
inventories and emission projections.
To determine the emissions of other pollutants (chiefly CO and HC) from these natural-
gas engines, the NOx emissions reported by Esso and a set of emission factors suggested by
Cooper-Bessemer(7) for two- and four-cycle engines were used. These factors are:
0.084 lb of NOx/lb of fuel
0.01 lb of HC/lb of fuel-,
0.02 lb of CO/lb of fuel.
These emissions were placed in the "Stationary Gas Engines;' category, and the remaining
emissions from industrial combustion processing were placed under "Industrial Processing".
Thus the total industrial emissions for 1966 is equal to the !!um of four emission sources
as listed in Table II-I: (l)"lndustrial Processing", (2) "Industrial Steam Generation '- Coal, Oil,
and Gas", (3) "Stationary Gas Engines", and (4) the difference between "Total, All Sources"
and "Total, All Combustion Sources".
Aircraft
Aircraft emissions for 1967 have been inventoried by the Northern Research and Engi-
neering Corporation.(8) This inventory was used to estimate the emissions for 1966 from both
civilian and military aircraft during both cruise and terminal operations. The emissions were
divided into those from jet aircraft and those from piston aircraft. The piston-aircraft emissions
-------
B-3
were. added. to, the automobile and light-truck emissions. The sum appears in the "Mobile
GasolIne EngIne' column. Jet aircraft emissions are shown under "Gas Turbines".
Source Totals
The "All Sources" total figures, except those for CO and NOx were taken directly from
Reference 3. The CO and NOx totals were modified because of some changes in data for
industrial and mobile gasoline-engine emissions. The totals of emissions under "All Energy-
Conversion Combustion" are the summation of all the entries in the table under the headings
"Continuous Combustion" and "Cyclic Combustion". When the totals in the last two categories,
"Solid Waste Incineration" and "Miscellaneous Combustion", are added to the totals under "All
Energy Conversion Combustion", the "Total, All Combustion Sources" entries are obtained.
"Miscellaneous Combustion" includes emissions from forest fires, structural fires in buildings,
agricultural burning, coal-refuse burning, and wood burning. The differences between the "Total,
All Sources" and "Total, All Combustion-Sources" are the emissions from non-combustion
industrial processing and emissions attributed to vessels operating outside the United States.
SOURCES OF PROJECTIONS FOR COMBUSTION EMISSIONS
The curves in Figur.es II-I through II-5 are a synopsis of the projections developed as an
input for the rating scheme of research opportunities. In some cases, the curves represent a
smoothing of the original data.
Tables B-1 through B-5 provide a tabulation of the data used in plotting the curves of
Figures II-I through 11-5. These data were used to develop the values of the Projected Pollutant-
Source Factors (Sij).
In preparing these emission projections, a number .of contributions were used: the
energy-demand projections from Morrison and Readling(9), aircraft fuel usage and terminal-
emission projections from the Northern Research report(8), NOx-emission forecasts from the Esso
report(6), automotive emission projections prepared by DAQED in 1969 and published in the
Nationwide Inventory of Air Pollutant Emissions, 1968, and stationary-source emission projec-
tions prepared by DPCE in 1969-1970 based on projections of energy demand made by the
Federal Power Commission and the Atomic Energy Commission.
The principal set of emission factors used has been those published by Duprey(l). Each
of the emission-projection sources listed above involves a different variation of Duprey's factors.
For industrial steam-generation emissions, the Battelle team used a set of factors based on other
literature.
Because of the variety of data sources utilized for projecting future pollutant-emission
levels a few inconsistencies occurred between calculated projections and data reported in
DAQED inventories, such as Reference 3, and tabulated in Table II-I. When these discrepancies
occurred the calculated projections were used in Tables B-1 through B-5. However, the discrep-
ancies w~re not sufficiently large to effect the ranking of any R&D opportunities.
-------
Table 8.1 - Fore~S1 of U.S. Poltutant Emissions From Combustion of Prim, Fuels for Energy Conversion 1970, 106 tons/year
Con-1inuQus Combustion for Energy Conversion Cyclic Combustion- for
I;nergy Conversion
CI Commerc;ial &
c:
Central.StilfiQn 'in Ind\Jstrial Steam Residential Mobile Stationary
"'
Power Plants f! Generation Space Heating Gas Turbines IC Engines IC Engines
Pollu~flts 0
Pi-
iii ~ .~ G>
.;: '" ~ .
.... c: .S
"' 0 ~ a i a i
iii "' :;] iii I:: iii :II ';; u :g
o ", ,, 8 0 ~ ... '" G> '" G>
U 0 c.? 1; 0 c.? U 0 c.? In :.i c.? 0 c.? 0 c.?
-
1. Products ~d
Incomplete Combustion
Combustible Particulate 0.60 0.012 0.02 0.26 0.57 0.04 0.08 0.10 0.11 0.07 0.04 0.03 0.38 0.30 0.01 0.15 n
CO 0.08 11 n 0.02 0.12 0.01 <.01 0.43 0.03 <.01 0.04 0.29 65.0 0.20 1.7 0.10 0.50
HC 0.03 0.01 n - 0.06 0,01 0.0;2 p.09 0.04 n 0.01 0.12 13.6 0.40 0.15 0.15 0.25
PNA(a) n n n 0.30 n n n 6.3 0,10 0.1q n n 0.48 n n n n
.
2. NOx 3.8 0.40 O.:W 0.41 0.93 Q.33 0.65 p.07 0.64 0.38 Q.15 0.12 7,6 0.60 0.13 0.27 2.1
3. Combustion-Improving
Additives
Lead n n n n n n n n 11 n " n 0.23 n <.01 n n
4. Fuel Contaminants
SOx 18.7 1.3 n 1.39 3.71 1.07 <,01 0.85 1.2 n 0.09 0.06 0.28 0.11 n n n
Ash 5.0 0.01 n 0.26 0.66 0.03 n 0.12 0.08 n n n n A n n n
=
,J:.
(a) PNA shown in 103 tORs/year.
-. not available.
-------
:' '
Table 8-2 .,... Fprecast of U.S. Pollutant EmissiOl1s From COllflbustion of Prime Fuels for Energy C;pnversio" 1975, 106 tons/year
CQntinuous Com~u~~io" for ~ner9Y Conver.ion Cyclic Combustion for
Energy Conversion
c:n Commercial &
c:
Central-Station 'iij I ndustrial Steam Residential Mobile Stationary
III
Power Plants QI Generation Space Heating Gas Turbines IC Engines IC Engines
u
Pollutants 0
...
"" >
iii ... QI QI
-------
Table B-3 - Forecast of U.S. Pollutant Emissions From Combustion of Prime Fuels for Energy Conversion 1980, 106 tons/year
Continuous Combustion for Energy Conversion Cyclic Combustion for
Energy Conversion
'" Commercial &
c
Central-Station 'iij I ndustrial Steam Residential Mobile Stationary
-------
Table 8-4 - Forecast of U.S. Pollutant Emissions From Combustion of Prime Fuels for Energy Conversion 1990, 106 tons/year
Continuous Combustion for Energy Conversion Cyclic Combustion for
Energy Conversion
en Commercial &
c:
Central-Station 'iij Industrial Steam Residential Mobile Stationary
II>
Power Plants Q) Generation IC Engines IC Engines
.Q "0 Qj "0 Qj
co II> :J co II> co ... ~ II> II> II>
"0 - II> II> .,!! II> .'!!
o co 0 .- co 0 co co co co co
U 0 C) c: U 0 C) u 0 C) ... ~ C) a C) a C)
- en
1. Products of
Incomplete Combustion
Combustible Particulate 0.50 0.03 0.03 0.26 0.55 0.06 0.12 0.03 0.15 0.15 0.14 0.09 0.62 0.48 0.03 0.25 n
CO 0.19 n n 0.03 0.11 0.01 <.01 0.16 0.04 <'01 0.27 1.19 45.5 0.40 2.3 0.20 0.60
HC 0.07 0.01 n - 0.06 0.01 0.03 0.03 0.05 n 0.10 0.52 7.3 1.0 0.25 0.25 0.30
PNA(a} n n n 0.40 n n n 1.6 0.10 0.30 n n 0.91 n n n n
2. NOx 9.0 1.0 1.6 1.07 0.91 0.50 1.03 0.02 0.83 0.85 1.5 0.83 17.1 1.5 0.20 0.40 2.5
3. Combustion-I mproving
Additives
Lead n n n n n n n n n n n n 0.46 n <.01 n n
4. Fuel Contaminants
SOx 57.6 4.4 n 1.33 3.63 0.95 <.01 0.30 1.0 n 0.63 0.27 0.46 0.21 n n n
Ash 3.3 0.01 n 0.31 0.64 0.04 n 0.04 0.10 n n n n n n n n
tC
I
-...J
(a) PNA shown in 103 tons/vear.
-, not available.
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Table 8-5 - Forecast of Total 1970-1990 U.S. Pollutant Emissions From Combustion of Prime Fuels for Energy Conversion, 106 tons
I Continuous Combustion for Energy Conversion Cyclic Combustion for
I Energy Conversion
I c:
0
.~ C> Commercial &
. ::J c:
Central-Station .;;; Industrial Steam Residential Mobile Stationary
I >.J:J en
c> E II> Generation IC Engines
~8 Power Plants <.> Space Heating Gas Turbines IC Engines
Pollutants 0
w c: ct
0 ~ ~
~.~ III ... II> 11> .
c: - .!: .!:
. II> ti 0 ~ Si 5i Si Q;
- > 0; ::J 0; .;::;
~ c: en '" 0; en ~ en en
0 0 0 III " 0 III 0 III III III .!!! III II> III
6 c: 6 '" ~ Ci
I-U U C1 - U 0 C1 U C1 en C1 0 C1 C1
1. Products of
Incomplete Combustion
Combustible Particulate 60.7 11.5 0.5 0.5 5.4 10.9 1.0 2.0 1.2 2.6 2.1 1.3 0.9 10.7 5.8 0.4 3.9 n
CO 921.0 2.7 n n 0.5 2.2 0.2 <.1 5.4 0.7 <.1 2.5 10.6 833.0 5.8 42.8 3.0 11.5
HC 192.5 1.0 0.2 n - 1.2 0.2 0.5 1.1 0.9 n 0.9 4.9 155.3 13.0 3.8 3.8 5.7
PNA(a) I 95.0 n n n 6.5 n n n 69.5 2.0 3.7 n n 13.3 n n n n
2. NOx 580.7 121.3 12.6 21.5 13.2 18.1 8.5 16.9 0.8 14.6 11.7 12.8 8.5 242.0 20.5 3.3 6.5 48.0
3. Combustion-I mproving
Additives I
Lead 6.8 n n n n n n n n n n n I) 6.8 n <.1 n n
4. Fuel Contaminants
SOx 992.3 764.8 56.5 n 28.5 72.1 18.7 <.1 10.6 21.9 n 5.5 2.9 7.6 3.1 n n n
Ash 119.3 96.5 0.2 n 5.9 12.7 0.7 n 1.5 1.8 n n n n n n n n
b:I
I
00
(a) PNA shown in 103 tons/vear.
-. not available.
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B-9
The differences between the data presented in Figures II-I through 11-5 and the data in
Tables B-1 through B-4 are as follows:
1. "Industrial Process" curves in the figures represent the summation of both
"Industrial Steam Generation" and "Industrial Process" in the tables. This
includes industrial steam generation by coal, oil, and gas.
2. "Commercial and Residential" curves in the figures represent the sum of
commercial and residential space heating as listed under coal, oil, and gas in
the tables.
3. No curves are presented in the figures for piston-engine aircraft.
4. in the figures the three curves for "Power-Total" labeled "No Controls",
"Low Level of Controls", and "High Level of Controls" were obtained from
Figure 6 of a paper by Hangebrauck and Spaite.(10) These data are not
reported in the tables.
In both the tables and figures, nationwide emissions were considered; thus, aircraft
emissions both at airports and during cruise were included in the totals for jet and piston
aircraft. The basic data for aircraft emissions came from the Northern Research report(8). In that
report, predictions of jet aircraft emissions included the expectation that smokeless engines
would be installed between 1967 and 1979 which would reduce the quantities of particulate,
CO, and HC emitted but increase the emission of NOx. The Battelle forecasts do not include
decreases in CO and HC emissions, as the technology for achieving these reductions has not yet
been developed.
The following detailed discussion* of the development of the projections for combustion
emissions is divided into two major parts: (1) Projections for Continuous-Combustion Applica-
tions and (2) Projections for Cyclic-Combustion Applications.
*The following abbreviations are used in the explanatory notes.
M&R = Morrison and Readling( 9)
Esso = Esso Research and Engineering Company( 6)
C-B = Cooper-Bessemer< 7)
NR = Northern Research and Engineering(8)
HLM = Hangebrauck, von Lehmden, Meeker< 11)
DOT = Department of Transportation.
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B-lO
PROJECTIONS FOR CONTINUOUS-COMBUSTION APPLICATIONS
Total Particulates*
. Power Plants; Coal
These are unpublished DPCE projections based on the Federal Power
Commission's unpublished estimates of power requirements and the
assumption of an increased percentage of both existing and new coal-fired
power plants being equipped with particulate controls.
. Power Plants; Oil and Gas
Battelle made this projection on the basis of the M&R fuel-usage projec-
tions. No increase in controls was assumed and the same emission factors as
used by NAPCA for establishing 1966 emissions were used.
. Industrial Steam Generation
The M&R forecast of energy requirements** to 1980 was used and extended
to 1990 at the same rate of growth. The following emission factors
representing information in several publications were used:
Total Particulate
. Emissions, Ib/106 Btu
Coal QlL Gas
0.26
0.11
0.024
It was further assumed that 60 percent of the particulate emissions from
coal combustion were removed by control devices.
. Industrial Processing
This value is the difference between the total emissions from industrial
combustion and the steam-generation portion of those emissions. The fore-
casts of total industrial emissions of particulates from coal combustion were
obtained from DPCE for 1970 (a value of 1.72 x 106 tons). The gas
contribution was considered as negligible and the fuel-oil contribution was
*The projection of total particulate emission from all sources was made prior to breaking down the particulates
into combustibles and noncombustibles (or ash). Only total particulates are considered.
**There seems to be a contradiction between the M&R forecast for industrial energy requirements and their
forecast for the coal, oil, and gas requirements through 1980. All of these curves are relatively constant except
the curve for the coal tonnage requirements which drops sharply. The M&R projection for energy demand was
used instead of their coal tonnage forecast to develop industrial emissions.
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B-ll
taken as 10 percent of the coal sum. It was assumed that the coal usage
would remain constant through 1990, while the fuel-oil emissions would
increase at the rate of fuel-oil-usage increase predicted by M&R.
. Commercial and Residential
Th~ ~ 966 value of emissions was broken down into coal, oil, and gas
emISSIOns following ratios developed by Battelle. The M&R rates of growth
of commercial and residential fuel usage from 1965 to 1980 were plotted
and extrapolated to 1990.' Particulate emissions from coal, oil, and gas
combustion were ptojected from 1966 to 1990 following the fuel
projections.
. Aircraft Gas Turbines
The NR report gives a 1967 value for fuel consumption by civilian and
military jets and emission indices for cruise with the note that 80 percent
of the fuel is consumed during cruise. From this, 1967 emissions during
cruise were determined. After 1979, the civilian-aircraft emissions in
terminals were predicted to increase at a 1 0 perc~nt growth rate. It was
predicted that civilian, traffic will increase at a 10 percent growth rate
through 1990, a growth rate similar to the growth rate -shown in the civil
aviati9nportion of NR's Figure 10.
The military-aircraft cruise activity was held constant at the 1967 level. The
1967 military-aircraft emissions in terminals were taken to be in the same
ratio to civilian-aircraft emissions in terminals as the military- ~nd civilian-
aircraft emissions during cruise. Military-aircraft emissions in terminals were
taken as constant from 1967 to 1990.
The NR report takes into account a drop of 50 percent in particulate
emissions in terminals between 1967 and 1979, owing to the installation of
smokeless engines. Projections for military aircraft emissions in terminals
were reduced by the Battelle team by this same ,factor over the same time
period. For emissio'ns of particulate during cruise, a 50 percent drop
starting in 1975 was assumed.
The sum of all military- and civilian-aircraft emissions during cruise and in
terminals is given in Tables B-1 through B-4. "
. Stationary Gas Turbines
Estimates were made of the 1969 emissions of pollutants from stationary
gas turbines on the basis of the fact that the fuel consumption of stationary
turbines in 1969 was equal to the 1967 fuel consumption by aircraft
turbines. Emissions of the different pollutants were derived from judgments
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B-12
of the relation between aircraft cruise emissions and the emissions fTom
stationary' turbines which would generally be running in the same mode.
The ratios of the nationwide emissions from aircraft gas turbines (total of
military and civilian aircraft, terminal, and cruise) to industrial and utilities
gas turbines, if both aircraft and stationary gas turbines used the same
amount of fuel, were estimated as foHows:
Pollutant
Combustible
particu{ate
Ratio of Aircraft Gas Turbine
Emissions to Stationary Gas
Turbine Emissions
CO
HC
1 to 1
10 to 1
NOx
SOx
10 to t
1 to 1
0.5 to 1
A growth rate of 16 percent for stationary gas turbine purchases in recent
years was reduced to to percent by Battelle in predicting 1970-1990
emissions. The emission forecasts were projected from the 1969 figures and-,
as was done for aircraft, the particulate emissions were cut in half after
1975.
Carbon Monoxide
. Power Plants.
Using M&R fuel-usage forecasts, DAQED projected emissions for 1970 and
1975. These data were developed by DAQED in early 1969 using
Duprey's emission factors '(to. the Battelle team's knowledge, the projec-
tions are unpublished). The forecasts were extended to 1980 using M&R
fuel-usage forecasts and to 1990 using an extrapolation of the M&R
forecasts.
. Industrial Steam Generation
See procedure for particulates, page B-I0, except:
- no control of emissions assumed
- emission factors used are as follows:
CO Emissions, Ib/106 Btu
Coal Oil Gas
0.10
0.013
0.0004
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B-13
. Industrial Processing
These CO emissions were taken to be the difference between total industrial
emissions and total industrial steam-generation emissions. DAQED made
forecasts of 1970 industrial-processing emissions from the combustion of
coal, oil, and gas. These were projected to 1980 by the Battelle team
following the M&R projection of energy demands by industry for the three
fuels and to 1990 by extrapolating the M&R curves.
. Commercial and Residential
See procedure for projecting particulates, page B-ll.
. Aircraft Gas Turbines
The same procedure was followed as for particulates from this source
except that no reduction in emissions during cruise was assumed in 1975
after the completion of smokeless engine installations, and the emissions in
terminals were assumed to increase from 1967 to 1990 at a IO-percent
growth rate, instead of using the 1979 value given in Table 55 of the NR
report.
. Stationary Gas Turbines
See procedure for projecting particulates, page B-II, except:
- no reduction assumed after 1975 engine changeovers.
Hydrocarbons
. Power Plants
See procedure for CO, page B-12.
. Industrial Steam Generation
See procedure for CO, page B-12.
- emission factors used are as follows:
HC Emissions, Ib/106 Btu
Coal Oil Gas
0.054
0.017
0.005
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B-14
. Industrial Processing
See procedur.e for CO, page B-13.
. Commercial and Residential
See procedure for particulates, page B-1!.
. Gas Turbines, Aircraft and Stationary
See procedure for CO, page B-13.
Polynuclear Aromatics (PNA)
. Power Plants
Using the 1965 PNA emissions calCulated by DAQED and the fuel usage in
1966 interpolated from the M&R report, a base emission factor was estab-
lished. The emissions were projected to 1990. following the M&R' fuel
projections and the Battelle extrapolation of them.DAQED had broken
down emissions from coal and fuel-oil stationary combustion into power
plant, industry, and residential. The Battelle team apportioned the 1966
total of emissions from natural-gas combustion (234 tons) into the follow-
ing distribution:
PNA Emissions From Stationary Sources
Fired by Natural Gas
Tons/year
Industrial Combustion
o
134
Power Plants
Residential & Commercial
100
These divisions were made after consulting HLM (pp 11 and 14), assuming
that emission factors would be about the same from both industrial and
residential sources if the combustion air/fuel ratios were correctly adjusted.
The emissions of 134 tons and 100 tons then reflect the ratio of natural gas
used by these sources.
. Industrial Steam Generation and Processing
Using the DAQED and the Battelle apportioning of 1966 PNA emissions
(see previous paragraph), future emissions were projected following the
M&R forecasts of industrial energy demand. It was assumed that 90 percent
of the total industrial combustion emissions of PNA were from processing
and 10 percent were from steam generation.
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B-15
. Commercial and Residential Heating
As described in the previous two paragraphs, future PNA emissions were
projected to follow the 1980 M&R fuel-usage forecasts and the Battelle
extensions of these fuel forecasts to 1990.
. Gas Turbines
In the absence of any data, emissions from these sources were considered to
be negligible.
Nitrogen Oxides
The best reference for projections of NOx is the Esso report (Table 3-34). Before this
was available, earlier data were provided to Battelle by. DAQED, but these are in substantial
agreement with Esso forecasts.
. Power Plants
See procedure for CO, page B-12.
. Industrial Steam Generation and Processing
See procedure for CO, page B-12, B-13.
- emission factors used are as follows:
NOx Emissions, Ib/106 Btu
Coal Oil Gas
- -
0.79 0.58
0.20
. Commercial and Residential Heating and Gas Turbines
See procedure for particulates, page B-ll.
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B-16
Sulfur Oxides
. Power Plants
DPCE has projected emissions from power plants on the basis of a forecast
(unpublished) of power demands made by the Federal Power Commission.
These total utility emissions were divided between coal, fuel oil, and gas in
the same ratio as the 1966. SOx emissions listed in Table 11-1. No SOx
controls were assumed in these projections.
. Industrial Steam Generation
See procedure for CO, page B-12.
- emission factors used are as follows:
SOx Emissions, Ib/106 Btu
Coal Oil Gas
3.15
1.87
0.0008
The SOx emissions from oil-fIred steam generation were altered to cor-
respond to a drop in the sulfur content of the oil from 1.7 percent to 1
percent between 1970 and 1980.
. Industrial Processing
This is the difference between total emissions from industrial combustion
and emissions from industrial steam generation. The total emissions from
industrial combustion are the sum of a DPCE forecast of SOx emissions
from the burning of distillate and residual oil by industry, a Battelle
forecast of coal emissions, and an estimate of emissions from burning
natural gas which were considered to be less than 0.01 x 106 tons per year.
The projection of total industrial coal-combustion emissions of SOx was
made by estimating 1965 emissions using the M&R values of coal burned
by industry, 9.87 x 107 tons, and the emission factor of 38 S from Table 3
of the Duprey report; S is assumed to be 2.6 percent sulfur. This
estimate of 1965 emission was projected to 1990 following the M&R
projections of 1980 industrial energy demands from coal and was extrapo-
lated to 1990.
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B-17
. Aircraft Gas Turbines
On page 3 of the NR report, a value of S02 emissions at FAA-controlled
terminals is given for 1967. Military-aircraft emissions in terminals were
approximated as being equal to the civilian-aircraft emissions following the
almost equal amounts of fuel consumed by these jets in 1967 (Table 49 of
the NR report). Since 80 percent of the fuel is consumed in the cruise
mode, the cruise emissions of S02 were determined by multiplying the
terminal emissions by 4.
Starting with these 1967 base emissions, civilian-aircraft emissions in ter-
minals and during cruise were projected to increase to 1990 at a 10-percent
growth rate, while military-aircraft emissions were projected to remain at
their 1967 level. The sums of civilian- and military-aircraft emissions are
entered in Tables B-1 through B-4.
. Stationary Gas Turbines
A 1969 value of SOx emissions was determined as described in the preced-
ing write-up on particulate emissions from stationary gas turbines. This
emission was then projected to grow at a 10 percent rate until 1990.
PROJECTIONS FOR CYCLIC-COMBUSTION APPLICATIONS - IC ENGINES
All Pollutants
. Mobile Gasoline Engines
These emissions are the sum of the emissions from gasoline-powered motor
vehicles and from piston-engine aircraft. DAQED furnished Battelle a DOT
projection to 1990 of motor-vehicle-miles per year. This projection is
divided into automobiles, light-duty trucks, and several classes of heavy-
duty trucks. It is assumed that the automobiles and light-duty trucks use
gasoline, while the heavy-duty trucks use diesel fuel.
Using the DOT projections, DAQED made forecasts of the emissions of CO,
HC, and NOx with the assumption of the implementation of 1970
standards for the control of automobile emissions (CO and HC). This
forecast was made in 1969 with the additional assumption that the test-
cycle procedures would not be changed. The projections have been pub-
lished in Nationwide Inventory of Air Pollutant Emissions, 1968(3).
For the projections of motor-vehicle emissions of total particulate (consist-
ing almost entirely of combustible particulate) and of SOx, the DOT
vehicle-mile forecasts and the Duprey emission factors were used. The DOT
projections were also used in making the forecasts of PNA and lead
emissions. These two pollutants were predicted to increase from their base
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B-18
values at the same growth rate as vehicle miles. These base values were
given by VAQED as 215,000 tons of lead emitted from automobiles in
1967, 304 tons of PNA emitted from automobiles in 1966, and 136 tons of
PNA emitted from trucks in 1966.
The piston-engine-aircraft emission projections were obtained from the NR
report using the table on page 3 of that report as a base for calculating
1967 civilian-aircraft emissions at terminals. Then 1967 military- and
civilian-aircraft emissions during cruise were obtained using 80 percent of
the fuel listed in NR Table 49 and using the emission factors in that table.
The military-aircraft emissions in terminals for 1967 were assumed to have
the same ratio to civilian-aircraft emissions in terminals as the ratio of
military- to civilian-aircraft fuel used in 1967.
The emissions were projected to follow the curves in NR Figure 10 which
gives the piston-engine fuel consumption to 1979 for civil aviation and total
aviation. Military-aircraft consumption was taken as the difference between
total and civil aviation. Beyond 1979, civilian-aircraft emissions were fore-
cast to increase at a growth rate of 3 percent, while military-aircraft
emissions would remain constant at the 1979 level.
. Mobile Diesel Engihes
Emissions of PNA and lead from piston-engine aircraft were considered to
be negligible. The emissions of all pollutants from diesel-powered vehicles
were projected to increase from the 1966 values at the rate of growth
predicted by DOT for the total of all classes of heavy-duty trucks. Data on
emissions from railroad diesel engines were not available at the time the
projections were made and were not included in this category. Inclusion of
these data would increase mobile diesel engine emission totals but would
not have affected ranking of R&D opportunities.
. Stationary Gasoline and Diesel Engines
In 1969 DAQED made projections of CO, HC, and NOx to 1990 for
nonhighway use of motor fuels. The predicted emissions of each of these
pollutants were divided between diesel and gasoline in the same ratios as
were true in 1966.
The combustible particulate emissions from stationary diesel and gasoline
engines were predicted to increase at the same rate as DAQED had pre-
dicted for HC emissions from these sources. sax emissions were considered
to be negligible.
. Stationary Natural-Gas Engines
The Esso report points out the importance of NOx emissions from the
natural-gas-powered pumps used for pipelines and gas plants. This report
-------
B-19
gives forecasts to 2000 for the NOx emissions from these gas engines. Using
the C-B set of emission factors for two- and four-cylinder engines, estimates
were made of the emissions of HC and CO. These emissions were predicted
to increase at the same rate as the Esso forecast for NOx emission from
these engines.
Emissions of pollutants other than NOx, CO, and HC from stationary gas
engines were considered to be negligible.
REFERENCES FOR APPENDIX B
(1) Duprey, R. L., Compilation of Air Pollutant Emission Factors, Second Printing, USDHEW
Public Health Service Publication No. AP-42, Raleigh, North Carolina (1968), 67 pp.
(2) U.S. Bureau of the Census, Statistical Abstract of the United States, U.S. Government
Printing Office, Washington, D.C. (1967).
(3) Nationwide Inventory of Air Pollutant Emissions, 1968, USDHEW Public Health Service
Publication No. AP-73, Raleigh, North Carolina (1970), 36 pp.
(4) U.S. Bureau of the Census, Census of Manufacturers: 1963, Fuels and Electric Energy
Consumed in Manufacturing Industries: 1962, Series M63(1)-6, U.S. Government Printing
Office, Washington, D.C. (1964).
(5) Smith, W. S., and Gruber, C. W., Atmospheric Emissions From Coal Combustion - An
Inventory Guide, USDHEW Public Health Service Publication No. AP-24, Cincinnati, Ohio
(1966), pp 63-65.
(6) Final Report, Volume II, to National Air Pollution Control Administration, "Systems Study
of Nitrogen Oxide Control Methods for Stationary Sources", from Esso Research and
Engineering Company, Government Research Laboratory (November, 1969), Contract No.
PH 22-68-55.
(7) Personal communication in July, 1970, between F. Creswick of Battelle Memorial Institute,
Columbus Laboratories, and M. Helmick of The Cooper-Bessemer Division of Cooper
Industries.
(8) Final Report to National Air Pollution Control Administration, "Nature and Control of
Aircraft Engine Exhaust Emissions", from Northern Research and Engineering Corporation
(November, 1968), 388 pp, Contract No. PH 22-68-27.
(9) Morrison, W. E., and Readling, C. L., An Energy Model for the United States Featuring
Energy Balances for the Years 1947 to 1965 and Projections and Forecasts to the Years
1980 and 2000, Bureau of Mines Information Circular IC 8384 (July, 1968).
(10) Hangebrauck, R. P., and Spaite, P. W., "Pollution From Power Production", paper presented
at 25th Annual Convention of the National Limestone Institute, Washington, D.C. (January,
1970).
(11) Hangebrauck, R. P., von Lehmden, D. J., and Meeker, J. W., Sources of Polynuclear
Hydrocarbons in the A tmosphere, Public Health Service Publication No. AP-33, Cincinnati,
Ohio (1967), pp 5-14.
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.
II
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II
II
CONTENTS
I. EXECUTIVE SUMMARY
II. APPROACH TO R&D PLAN
III. POWER PLANTS
IV. INDUSTRIAL PROCESSING
V. IND. STEAM GENERATION &
COMM. & RES. HEATING
VI. CONTINUOS-COMB. ENGINES
VII. RECIPROCATING IC ENGINES
EPA Library
111111111111111111111111111111111111111111111
T 11395
VIII. FUNDAMENTAL COMBUSTION RESEARCH
IX. SUMMARY OF R&D PLAN
A. PRIORITY RATING METHODOLOGY
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