United States
Environmental Protection
Agency
Industrial Environmental
Research Laboratory
Research Triangle Park NC 27711
Research and Development
EPA-600/S7-84-027 Apr. 1984
Project Summary
Distributed Mixing Burner (DMB)
Engineering Design for
Application to Industrial and
Utility Boilers
B.A. Folsom, P. Nelson, J. Vatsky, and E. Campobenedetto
This report summarizes the design of
two prototype distributed mixing burners
(DMBs) for application to industrial and
utility boilers. The DMB is a low-NO,
pulverized-coal-fired burner in which:
(1) mixing of the coal with combustion
air is controlled to minimize NO>
emissions, and (2) an overall oxidizing
environment is maintained to avoid
slagging and corrosion.
Several DMB configurations were
tested in two research furnaces over a
range of operating conditions. The data
were evaluated to develop design
criteria for optimum performance. Two
prototype DMBs were then designed by
integrating the design criteria with
commercial burner components. One
burner was designed for application to
an industrial size (215,000 Ib/hr)
Foster Wheeler boiler. The second
prototype burner was designed for
application to a general class of Babcock
and Wilcox opposed-fired utility size
boilers, because a utility size host boiler
had not been selected.
This report discusses the initial
prototype burner designs. Subsequent
burner testing and burner design changes
are discussed in other reports.
This Project Summary was developed
by EPA's Industrial Environmental
Research Laboratory, Research Triangle
Park, NC, to announce key findings of
the research project that is fully docu-
mented in a separate report of the same
title (see Project Report ordering
information at back).
Introduction
The DMB concept involves staging the
combustion process to minimize NO,
emissions while maintaining an overall
oxidizing atmosphere in the furnace to
minimize slagging and corrosion. NO*
production from fuel nitrogen compounds
is minimized by driving a majority of the
compounds into the gas phase under
fuel-rich conditions and providing a
stoichiometry/temperature history which
maximizes the decay of the evolved
nitrogen compounds to Nz. Thermal NO«
production is also minimized by enthalpy
loss from the fuel-rich zone which
reduces peak temperatures.
Figure 1 shows schematically how the
DMB design sequentially stages the
fuel/air mixing. The combustion process
occurs in three zones. In the first zone,
pulverized coal (transported by the
primary air) combines with the inner
secondary air to form a very fuel-rich (20
to 50 percent theoretical air)recirculation
zone which provides flame stability. The
coal devolatilizes, and fuel nitrogen
compounds are released to the gas
phase. Outer secondary air is added in the
second "burner zone" where the stoichi-
ometry increases up to about 70 percent
theoretical air. This is the optimum range
for reduction of bound nitrogen compounds
to Na. Air to complete combustion process
is supplied through tertiary ports located
outside the burner throat. This allows
substantial residence time in the burner
zone for decay of bound nitrogen com-
pounds to N2 and radiative heat transfer
to reduce peak temperatures. The ter-
tiary ports surround the burner throat pro-
viding an overall oxidizing atmosphere
and minimizing interactions between
adjacent burners.
For the last several years, Energy and
Environmental Research Corporation
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Tertiary Air
Coal and
Primary Air
Very Fuel Rich
Zone (Average
Stoichiometry 40%)
Progressive Air Addition Zone
(Overall Stoichiometry 70%)
Final Air Addition Zone for Burnout
(Overall Stoichiometry 120%)
Figure 1. OMB concept.
(EER) has been working with the EPA to
develop the DMB concept under EPA
Contracts 68-02-1488 and 68-02-2667.
These efforts have focused on experi-
mentally evaluating the performance of
several DMB designs in two research
furnaces. Six DMBs have been tested in
single- and four-burner arrays at firing
rates up to 100 x 106 Btu/hr. The tests
covered wide ranges of DMB design
parameters, adjustments, and operating
conditions. Under optimum conditions,
NOx levels less than 0.15 Ib/106 Btu were
achieved. However, DMB performance
has not been evaluated in commercially
operated steam generators.
The EPA is currently conducting two
programs to provide this field evaluation.
EPA Contract 68-02-3127, with EER as
the prime contractor and Foster Wheeler
as a major subcontractor, involves
evaluation of the DMB concept on two
industrial-size single-wall-fired boilers.
EPA Contract 68-02-3130, with Babcock
and Wilcox as the prime contractor and
EER as the major subcontractor, involves
evaluating the DMB concept on a utility
size opposed-fired boiler. The objectives
of both programs are to achieve NOX
emissions levels less than 0.2 lb/106Btu
without adverse effects on boiler opera-
bility and durability, thermal efficiency.
and the emission of other pollutants.
These field evaluations involve: (1 (transla-
tion of the development burner test data
into practical prototype DMBs, (2) verifi-
cation of the prototype burner perform-
ance through testing in a research
furnace, (3) construction and installation
of these burners in the field boilers, (4)
evaluation of burner/boiler performance
under typical operating conditions, and
(5) documentation of the results.
This report summarizes the first
program element, the prototype DMBs.
These burners were designed by integra-
ting: (1) specific requirements of the host
boilers, (2) DMB design criteria, and (3)
commercial burner components. These
burners will be tested in a research
furnace to fine tune the designs and to
adjust operating variables for an optimum
balance between low NOx emissions and
other performance parameters. Based on
this testing, the final design will be
specified and the necessary burners
fabricated for installation in the host
boilers.
The prototype burner designs discussed
in this report are these initial "flexible"
designs based on the results of previous
DMB development efforts and commercial
burner components. During the testing of
the industrial prototype burner (EPA
Contract 68-02-3127) in the large
watertube simulator (LWS), some design
parameters were changed considerably,
including incorporation of some proprie-
tary Foster Wheeler components and
parameter values. Similarly, although the
utility prototype burners (EPA Contract
68-02-3130) have not yet been tested, it is
expected that the final burner design may
be considerably different from the initial
prototype burner design included in this
report. Results of this LWS testing and
the changes in the burner designs are
documented in annual reports for the
respective programs.
Boiler Characteristics
.The boiler selected as the initial
industrial boiler field evaluation site is
Pearl Station Unit No. 1, owned and
operated by Western Illinois Power
Cooperative (WIPCO), Jacksonville, IL.
This unit has a maximum continuous
rating of 215,000 Ib/hr of steam and is
single-wall-fired with four burners in a 2
x 2 array. Figure 2 is a cross-sectional
view of the unit, and Table 1 lists the
characteristics which impact prototype
burner design.
The utility boiler demonstration site
has not been selected; thus, it is not
possible at this time to precisely define
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Figure 2. Cross section of initial industrial boiler.
the boiler characteristics which influence
prototype burner design. However, the
general characteristics of the family of
boilers from which the field evaluation site
will be selected are listed in Table 2.
These characteristics were the basis for a
preliminary prototype burner design.
DMB Design Criteria
Six DMB configurations ranging from
10 to 100 x 106 Btu/hr were tested to
evaluate their potential for low N0«
emissions and to optimize their design
parameters. The burners were tested in
two research furnaces. A small water-
tube simulator (SWS), with geometry
similar to a 10,000 Ib/hr single-burner
watertube boiler, was used to test the
small burners. The larger burners (50 x
106 Btu/hr and larger) were tested in the
large watertube simulator (LWS). This
furnace has geometry similar to a large
industrial or small utility boiler. It will also
be used to evaluate prototype DMB
performance.
The DMB tests showed that each
configuration could be operated to
produce stable flames and low NOX
emissions in the range of 100 ppm*.The
burner parameters were found to have
significant effects on burner performance.
These parameters can be organized into
four categories: fuel variables, secondary
air variables, tertiary air variables, and
exit geometry.
* All concentrations are corrected to 0% 02, dry.
The fuel system design has significant
influence on flame shape and length.
Nozzles in which the coal and primary air
are injected axially tend to produce slow
fuel/air mixing and long diffusion flames.
Nozzles with impellers cause more rapid
fuel/air mixing which tends to produce
shorter more compact flames. Long
diffusion flames can be used in boilers
with large furnace depths; e.g., opposed
wall-fired units. The NO emissions from
this flame type were generally lower than
those for short flames. However, this may
be valid only for the specific burner
configurations tested and not necessarily
a general result. Smaller furnaces (e.g.,
those in single-wall-fired units) require
shorter flames to avoid flame impingement
on the rear wall. The test results have
shown that the short-flame DMB can be
optimized for low NO emissions, but that
deeper staging (low burner zone stoichio-
metry) is required. A DMB could be
designed to vary flame shape by incorpo-
rating some mechanism for changing the
spreading characteristics of the primary
stream into the secondary airstream. For
burners designed with annulartangential
inlets, this parameter is most easily
varied by burner setback which increases
the residence time in the primary/secon-
dary mixing zone upsteam of the burner
throat. For burners designed with a
central fuel nozzle, impeller blades can be
used to increase the coal spreading rate. In
the short-flame DMBs, optimum results
were obtained with 45° impeller blades.
However, the tests were of limited
duration and did not evaluate erosion
which may limit impeller life in burners
operated for extended periods as in field
boilers. A significant amount of data is
not available to evaluate the effects of
primary velocity. Consequently, DMBs
should be designed to allow primary
velocity to be varied during burner tuning.
This could be achieved by designing for a
low primary velocity and providing
sleeves or other devices to reduce the
nozzle exit diameter. Alternatively, a
conical nozzle exit (e.g., Foster Wheeler's
variable velocity nozzle) could be used.
The air system design has significant
influence on NO and CO emissions. Dual
secondary air channels provide additional
control over fuel/air mixing rates and are
thus preferred over single secondary
burner designs. Burner zone stoichiometry
is the major parameter controlling NO for
the DMB, and the lower limit will be
dictated by CO or flame stability. Flame
stability can be enhanced at lower burner
zone stoichiometries, however, by increas-
ing the secondary swirl without impact on
NO. Since the optimum value of swirl and
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Table 1. Initial Industrial Boiler Demonstration Site Characteristics
Characteristic
Value
Boiler/Furnace
Boiler Capacity, Ib/hr:
Furnace Depth, ft
Furnace Width, ft
Firing Configuration
Burner Capacity, Btu/hr:
Current Burners:
Burner Array, wide x high
Burner Spacing, ft:
Fuel Supply System
Coal Type
Mills:
Primary Stoichiometry at MCft, % T.A."
Primary Temperature, "F
Air Supply System
Air Heater Type
Design Point Excess Air at MCR, %
Windbox Temperature at MCR. °F
Burner Pressure Drop (nominal), in. HiO
Windbox Depth, in.
MCR*
Peak
MCft
Peak
Type
Throat Dia., in.
Horizontal
Vertical
Type
Number
215x10?
245 x 103
20. 6
16.4
Single Wall
69 x JO*
80 x 10e
Intervane
24
2x2
6.0
6.6
Bituminous
Model MB
2
16
155
Regenerative
18
510
3.5
52
8 Maximum continuous rating.
b Theoretical air.
Table 2. Approximate Utility Boiler Demonstration Site Characteristics
Characteristic
Boiler/Furnace
Boiler Capacity at MCR", MW
Furnace Depth, ft
Furnace Width, ft
Firing Configuration
Burner Capacity at MCR, Btu/hr
Current Burners, type
Circular Burner Array, wide x high
Circular Burner Spacing, ft:
Fuel Supply System
Primary Stoichiometry at MCR, % T.A. b
Primary Temperature, °F
Air Supply System
Design Point Excess Air at MCR, %
Windbox Temperature at MCR. °F
Burner Pressure Drop (nominal), in.
Horizontal
Vertical
8 Maximum continuous rating.
" Theoretical air.
burner zone Stoichiometry will depend on
burner characteristics, swirl device, coal
composition, and the overall duty cycle,
DMBs should be designed with sufficient
flexibility to vary this parameter. Flame
stability characteristics are also influenced
by the primary air velocity. The ability to
vary the primary air velocity will also
provide another way to operate at low
burner zone Stoichiometry while main-
taining low CO levels. Tertiary jet velocity
does not appear to be an important design
parameter for NO or CO, although port
Value
32-35
34-48
Opposed Wall
125x J0e
Circular or Cell
3 x 4 or 4 x 3
8-9
8-10
25
150
15
550
4.0
location has a significant impact on CO
burnout. For DMBs designed for field
boilers, the location of tertiary ports will
be determined in part by the burner-to-
burner spacing and other furnace and
windbox design parameters.
The burner exit configuration plays a
key role in flame stability. For most of the
DMB tests, the primary and inner
secondary setbacks (distances from end
of parallel throat—see Figure 3) were
zero, the quarl (refractory throat diver-
gence) half angle was 25 degrees, and its
length was equal to the throat diameter. If
this exit configuration is applied to DMBs
for field boilers, the resulting quarl length
and overall diameter will be considerably
larger than current commercial practice.
Consequently, a shorter quarl length will
probably be required. The test results
discussed above showed that flame
stability decreased with quarl length, and
it may be necessary to increase the coal
nozzle setback or swirl on the primary or
secondary airstreams to achieve satisfac-
tory flame stability in a burner with a
short quarl.
These general burner design require-
ments are summarized in Table 3.
Several of the parameters, listed as site-
dependent (S.D.), will be based on
characteristics of the field boilers. It is
possible that the nominal design point
values may need to be varied for optimum
burner performance. Thus, the prototype
DMBs have been designed to be flexible
so that the design parameters can be
adjusted for optimum performance. Table
3 also lists the range of variables which
will be examined as part of burner
performance optimization tests.
Industrial Prototype Burner
Figure3 is across-sectional view of the
prototype burner (without tertiary air
ports) showing its design details. The
following Foster Wheeler commercial
burner components have been used in
the design: an annular coal nozzle, a
telescoping coal nozzle for primary
velocity control, registers for swirl control
and flow shutoff, air hoods for secondary
flow rate control, and a commercial flame
scanning and ignition system. The coal
and primary air enter through a tangential
inlet to provide swirl. The coal nozzle is a
tapered annulus, and the axial velocity
increases as the coal and air move toward
the burner throat. The exit end of the coal
nozzle is formed from two concentric
cones. The inner cone can be moved
axially to vary the exit area, and hence,
the primary velocity. The outer portion of
the coal nozzle consists of removable
sections so that the overall length of the
coal nozzle may be changed to vary coal
nozzle setback in the burner throat. Each
of two concentric secondary air passages,
supplied from a common windbox, has an
adjustable register for swirl control, an
axialfy movable sleeve for flow rate
control, and a perforated plate (air hood)
for flow rate measurement. Pressure taps
on both sides of each perforated plate
allows the pressure drop to be measured
and correlated with sleeve positions and
flow rates.
4
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Table 3. Distributed Mixing Burner Design Parameters
Parameter
Nominal
Design
Point
Testing
Range
Fuel System
Primary Temperature, °F
Primary Stoichiometry, %
Primary Velocity, ft/sec
Primary Swirl
T.A.'
T.A.
Air System
Secondary
Temperature, °F
Burner Zone Stoichiometry,
Inner Swirl
Outer Swirl
Axial Velocity, ft/sec
Inner/Total Area
Inner/Total Flow Rate
Tertiary
Temperature, "F
Swirl
Axial Velocity, ft/sec
Angle, degrees
Number
Location, radius/throat diameter
Divergence, degrees
Exit
Half Angle, degrees
L ength/Diameter
Setback - Inner Secondary, in.
Setback - Outer Secondary, in.
S.D.'
S.D.
75
45° Vanes
S.D.
50-70
Variable
Variable
60
0.33
0.33
S.D.
None
50
0
4
2.2
0
25
1.0
0
0
130-180
17-30
50-90
Variable
400-650
40-120
Variable
Variable
50-90
Variable
Variable
400-650
40-60
S.D.
Variable
S.D.
Variable
Variable
Operational Variables
Capacity. 10* Btu/hr
Turndown, % capacity
Overall Stoichiometry, % T.A.
S.D.
S.D.
S.D.
~50
100-150
* Site dependent.
b Theoretical air.
The core (that portion of the burner in
the coal nozzle) is supplied with a small
amount of cooling air from the windbox. A
retractable ignition system, including
spark ignition, a 10x10 Btu/hr oil nozzle
and a pilot flame scanner are in the core,
on the burner centerline. The main flame
scanner views the flame through the
inner secondary air passage.
Tertiary air is supplied from the
windbox through outboard tertiary air
ports. The airflow rate through each port
will be controlled and measured by a
control valve not shown in Figure 3. Four
tertiary air ports will be used for the
prototype burner tests. Their locations
(with respect to the burner throat) match
the burner spacing in the host boiler. The
port location to be used in the field will be
selected to uniformly distribute the
tertiary air around and between the
burners. Some compromise may be
required, depending on windbox construc-
tion and furnace structural considerations.
In summary, the industrial prototype
burner has been designed with flexible
parameters to permit the flow rates,
velocities, and swirl in the burner
passages to be varied to optimize burner
performance. The dimensions and ranges
of adjustment are listed in Table 4. All the
dimensions listed match the DMB design
criteria except exit length, which must be
considerably shorter due to windbox
depth limitations. The resulting exit-
length/throat-diameter ratio is 0.40,
compared to 1.0 for the DMB design
point. The effects of this shorter exit
length will be evaluated during the
prototype tests.
Utility Boiler Prototype Burner
Since a utility host site has not been
selected, a preliminary prototype burner
has been designed based on the approxi-
mate utility boiler field evaluation site
characteristics listed in Table 3. This
burner design is preliminary in that it
represents the general burner design; it
does not include the flexibility inherent in
the industrial prototype burner. If the
industrial prototype burner test results
show that additional flexibility is required
in the utility prototype burner, it will be
incorporated in the final design.
Figure 4 is a cross-sectional view of the
preliminary utility prototype burner,
showing its design details. The following
Babcock and Wilcox commercial burner
components were used in the burner: an
axial coal nozzle, registers for flow
shutoff, swirl vanes for inner secondary
swirl, and a commerical flame scanning
and ignition system.
The coal and primary air enter the
nozzle through a 90° elbow. The inlet end
of the nozzle has a venturi, designed to
produce and approximately uniform
distribution of coal at the nozzle exit. The
two concentric secondary air passages
each has a register which allows the
airflow to be shut off when the burner is
out of service. The outer register can be
adjusted to control swirl; however, this
will also vary the flow distribution among
the various burner passages. The inner
secondary has swirl vanes so that the
inner secondary swirl is approximately
independent of register position. The four
tertiary air ports each has a separate
damper. The tertiary ports are rectangular
with the shorter dimension horizontal.
This results in less disturbance to the
tubewall, and hence, greater structural
strength than circular ports of the same
area. The oil ignitor is on the burner
centerline and has a ceramic exterior to
minimize wear. The scanner (not shown)
views the flame through the inner
secondary channel.
The dimensions of this burner are listed
in Table 5. As with the industrial proto-
type burner, the ratios of tertiary-port-
radius/throat-diameter and exit-length/
diameter are less than the DMB design
criteria.
Since the utility host boiler has not
been selected, it is not possible to specify
the furnace firing depth, and hence, the
maximum acceptable flame length. Thus,
is is desirable to provide some way to vary
flame shape and length in the prototype
burner Previous DMB tests have shown
that coal nozzle design is the key
parameter influencing flame shape and
length. Nozzles which channel the coal
into an axial jet produce long narrow
flames, while nozzles which mix the coal
more rapidly with the combustion air
produce shorter flames. The utility
prototype burner nozzle design is expected
to produce a long narrow flame. During
prototype burner testing, alternate nozzle
designs will be evaluated so that the
flame length can be tailored to match the
host boiler furnace depth.
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Note: Unless otherwise
indicated, all dimensions
are in inches.
2-1/2
Firing Face
Ignitor
Coal Inlet
Cast
Refractory
Exit
Sliding
Sleeves
Figure 3. Cross section of industrial prototype burner based on Foster Wheeler design without tertiary air ports.
Prediction of Prototype Burner
Field Operating Characteristics
Since the basis for the prototype design
is the LWS research furnace, not a steam
raising system, then some assurance is
required that the DMB will perform in the
field as predicted. Although indirect, the
approach taken was to evaluate commer-
cial burner operation in the LWS and
compare it against field experience. This
approach provides some assurance that,
if the burner operates satisfactorily in the
LWS, it will also operate satisfactorily in
the field.
In support of the industrial demonstra-
tion program (EPA Contract 68-02-3127),
a Foster Wheeler intervane burner (pre-
N SPS) designed to meet the specifications
of the small capacity host site boiler was
evaluated over a range of excess air and
load. In general, the flames produced by
this burner were short, bright, intense,
and stable. The base of the flame was
within the cylindrical portion of the exit
and filled the divergent portion. In the
furnace, the flame expanded rapidly and
was about 12 ft (five throat diameters)
long. The burner controls (register and
core air control valve) affected the flame
shape: with the controls adjusted similarly
to field settings, the flame shape in the
LWS was somewhat narrower and longer
than those observed with multiburner
arrays in the field. Throughout the tests,
stack opacity was low except for low
excess air conditions, where some black
smoke was observed. The smoke was
generally light gray haze. This similarity
of flame characteristics between the
LWS and field intervane burner test
results suggests that the short-flame
DMB flame characteristcs and stability
observed in the LWS will also be similar
in the field.
CO emissions were about 185 ppm at
20 percent excess air. This is about a
factor of four higher than typical field
boiler CO levels, which are usually less
that 50 ppm. The high CO levels measured
in the LWS are probably due to the
relatively cold furnace design which
quenches CO oxidation above the burner
zone. The CO levels measured during
previous DMB tests in the LWS were
similar to the intervane burner levels.
NO emissions from the intervane
burner, at full load and 25 percent excess
air, were 500 ppm; this is about 100 ppm
lower than that typically measured in
field operating industrial size boilers.
Foster Wheeler has found that, when two
burners are tested in a research facility
such as the LWS, the ratio of NO*
emissions from the same two burners
operating in a commercial steam genera-
tor. Thus, the NOX emissions from the
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ible4. Industrial Prototype Burner Dimensions and Adjustments units. A much more accurate estimate
Adjustment will be made by utilizing prototype DMB
Design Variable
tel Injector
Core Diameter, in.
Core Area, in.2
Nozzle Diameter, in.
Annulus Thickness, in.
Primary Area, in.2
Setback, in.
ner Secondary Channel
Outer Diameter, in.
Annulus Thickness, in.
Area, in.2
Setback, in.
uter Secondary Channel
Outer Diameter, in.
Annulus Thickness, in.
Area, in.2
Setback, in.
irtiary Ducts
Distance from Burner £ , in.
Spacing Around Burner, degrees
Number of Ports
Injection Angle, degrees
Axial Position, in.
Diameter, in.
Total Area, in.2
^iroat and Exit
Throat Diameter, in.
Throat Area, in. 2
Half Angle of Exit, degrees
Length of Exit, in.
Length /Diameter
+
1 n
t-
i
~~— -^ Tertiary
Port
, *•" Scanner
~-^/
Value
9.75
74.7
14.5
2.375
90.5
0
20.75
3.125
173.0
0
30.25
4.75
380.5
0
53
90
4
0
0
13.25
553
30.25
718.7
25
12.0
0.40
|£
M
Observation
„ , , Ports
Splash i J
"i Ignitor >
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Table 5. Preliminary Utility Prototype Burner Dimensions
Design Variable
Nominal Value
Fuel Injector
Nozzle Diameter, in.
Primary Area, in.2
Setback, in.
Inner Secondary Channel
Outer Diameter, in.
Annulus Thickness, in.
Area, in.2
Setback, in.
Outer Secondary Channel
Outer Diameter, in.
Annulus Thickness, in.
Area, in.2
Setback, in.
Tertiary Ducts
Distance from Burner £, in.
Spacing Around Burner, degrees
Number of Ports
Axial Position, in.
Injection Angle, degrees
Length x Width, in.
Total Area, in.2
Throat and Exit
Throat Diameter, in.
Throat Area, in.2
Half Angle of Exit. in.
Length of Exit, in.
Length/Diameter
15.25
182.6
3.0
25.0
4.875
308.0
5.0
32.0
3.5
313.4
5.0
48.0
90
4
0
0
22.0 x 12.0
1065.0
32.0
804.0
25
7
0.219
B. Folsom and P. Nelson are with Energy and Environmental Research Corp.,
Irvine, CA 92714; J. Vatskyis with Foster Wheeler Energy Corp., Livingston, NJ
07039; and E. Campobenedetto is with Babcock and Wilcox Power Generation
Div., Barberton, OH 44203.
G. Blair Martin is the EPA Project Officer (see below).
The complete report, entitled "Distributed Mixing Burner (DMB) Engineering
Design for Application to Industrial and Utility Boilers," (Order No. PB 84-163
260; Cost: $16.00, subject to change) wilt be available only from:
National Technical Information Service
5285 Port Royal Road
Springfield, VA 22161
Telephone: 7O3-487-465O
The EPA Project Officer can be contacted at:
Industrial Environmental Research Laboratory
U.S. Environmental Protection Agency
Research Triangle Park. NC 27711
United States
Environmental Protection
Agency
Center for Environmental Research
Information
Cincinnati OH 45268
Official Business
Penalty for Private Use $300
vf
,10
U.S. GOVERNMENT PRINTING OFFICE: 1964-759-102/926
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