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RESEARCH REPORTING SERIES
Research reports of the Office of Research and Development, U.S. Environmental
Protection Agency, have been grouped into nine series. These nine broad cate-
gories were established to facilitate further development and application of en-
vironmental technology. Elimination of traditional grouping was consciously
planned to foster technology transfer and a maximum interface in related fields.
The nine series are:
1. Environmental Health Effects Research
2. Environmental Protection Technology
3. Ecological Research
4. Environmental Monitoring
5. Socioeconomic Environmental Studies
6. Scientific and Technical Assessment Reports (STAR)
7. Interagency Energy-Environment Research and Development
8. "Special" Reports
9. Miscellaneous Reports
This report has been assigned to the INTERAGENCY ENERGY-ENVIRONMENT
RESEARCH AND DEVELOPMENT series. Reports in this series result from the
effort funded under the 17-agency Federal Energy/Environment Research and
Development Program. These studies relate to EPA's mission to protect the public
health and welfare from adverse effects of pollutants associated with energy sys-
tems. The goal of the Program is to assure the rapid development of domestic
energy supplies in an environmentally-compatible manner by providing the nec-
essary environmental data and control technology. Investigations include analy-
ses of the transport of energy-related pollutants and their health and ecological
effects; assessments of, and development of, control technologies for energy
systems; and integrated assessments of a wide range of energy-related environ-
mental issues.
EPA REVIEW NOTICE
This report has been reviewed by the participating Federal Agencies, and approved
for publication. Approval does not signify that the contents necessarily reflect
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commercial products constitute endorsement or recommendation for use.
This document is available to the public through the National Technical Informa-
tion Service, Springfield, Virginia 22161.
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DISCLAIMER
This Final Report was furnished to the Environmental Protection Agency by
the GCA Corporation, GCA/Technology Division, Bedford, Massachusetts 01730, in
partial fulfillment of Contract No. 68-02-2693. The opinions, findings, and
conclusions expressed are those of the author and not necessarily those of the
Environmental Protection Agency or of cooperating agencies. Mention of company
or product names is not to be considered as an endorsement by the Environmental
Protection Agency.
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CONTENTS
Figures . iv
Tables vi
1. Introduction and Background 1
2. Commercial and Technical Status 5
Battelle Development Corporation 5
Lurgi Corporation • • 16
Pyropower Corporation 24
Other Efforts 36
Economics 42
3. Summary and Conclusions 50
References 52
111
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FIGURES
Page
Basic fluid bed combustion systems 2
Battelle Multisolid Fluidized-Bed Combustor 6
Schematic of MSFB-0.4 Pilot Plant 10
Battelle Multisolid Fluidized-Bed Steam Generator 11
Sulfur Capture in MSEC - Effect of Entrained Bed Recycle Rate . 12
6 Effect of combustion temperature and calcium to sulfur ratio
on sulfur retention in Battelle's MS-FBC system 13
7 Effect of combustion temperature on limestone requirement
in Battelle's MS-FBC system 14
8 MS-FBC for oil field steam injection 17
9 Two stage combustion in a circulating bed 18
10 Flow diagram of a circulating fluid bed alumina calcining
plant 19
11 Circulating fluid bed boiler scheme 20
12 200 MW(e) CFB utility unit 25
13 Flow diagram of a Circulating Fluidized-Bed Combustion Plant. . 27
14 Commercial system configurations offered by Pyropower
Corporation 28
15 Pyroflow™ combustion chamber retrofitted to a LaMont boiler
at Pihlava board mill, Finland 32
16 PYROFLOW upset transient reponse 33
IV
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FIGURES (continued)
Number
17 100 ton/hr cogeneration plant at Kauttua paper mill, Finland
with specified operating conditions 35
18 Circulating Fluid Bed Pilot Facility at Lurgi, Frankfort,
West Germany 40
19 Schematic Diagram of 2.5 MW CFBC Prototype Module Being
Developed at Studsvik, Sweden 43
20 Deep recirculating fluidized-bed boiler 44
v
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TABLES
Number rage
1 Features and Benefits of the Battelle MS-FBC System 7
2 Comparison of Operating Characteristics of Conventional FBC
and MS-FBC 8
3 Test Parameters for Coal Combustion in the Lurgi Circulating
Fluid Bed Combustion Facility 22
4 Comparison Between the Conventional Fluidized Bed and the Lurgi
Circulating Fluid Bed for the Combustion of Coal 23
5
6
7
8
9
10
Design Parameters for 200 MW(e) CFBC Conceptual Design Study
PYROFLOW™ Circulating Fluidized-Bed Units in Operation or
Preliminary Results of Fuel Tests for North American Market. . .
Circulating Bed Versus Pulverized Coal Boiler Performance. . . .
Results of Cost Comparison Study for Conventional FBC, MS-FBC,
and Conventional Stoker-Fired Boilers
26
30
37
38
46
48
11 Component Operating Costs ($/yr) for 100,000 Ib/hr MS-FBC. ... 49
VI
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SECTION 1
INTRODUCTION AND BACKGROUND
This report summarizes the current technical status of circulating
fluidized-bed combustion (CFBC). Companies that are involved in investigating
this technology and/or developing commercial systems are discussed in Section
2 along with system descriptions and available cost information.
The circulating fluid bed is described as being a second generation FBC
in that the process attempts to remedy some of the potential limitations of
conventional FBCs while still incorporating the inherent process advantages.
The CFBC is also described as being in the transition region between a
classical fluidized-bed and pneumatic transport (see Figure 1). At low gas
velocities, a dense, bubbling classical fluidized-bed results having a
well-defined bed surface. This mode of fluidization is characterized by low
solids entrainment such that recycling is not always necessary. As gas
velocities are increased, the bed surface becomes more and more dispersed and
solids entrainment increases to the point that solids recirculation (usually
with a cyclone) is required to maintain bed inventory. This state has been
referred to as a "circulating" or "fast" fluidization. As shown in Figure 1,
the mean solids velocity increases at a much lower rate than the gas velocity
and thus in the circulating bed mode of operation, a maximum in slip velocity
can be achieved with high heat and mass transfer rates. In conventional FBCs,
superficial gas velocities are limited by bed entrainment velocities. Because
heat release rates per unit base area are limited by the oxygen available for
combustion, the bed entrainment velocity imposes an upper limit on the
attainable heat release. Two techniques for increasing the heat release are
pressurized operation or use of the fast fluidized-bed where fuel and sorbent
are intentionally entrained. Heat release rates for circulating beds are
roughly 2 x 106 Btu/ft2-hr; compared to 0.8 x 106 Btu/ft2-hr for conventional
FBC units.
The major differences between the CFBC and the conventional FBC are that
the CFBC is characterized by its high fluidizing velocity (>10 ft/sec),
continuous recycling or recirculation of bed material, and either separate
beds or zones for heat, exchange. The fluidizing velocity generally ranges
from 2 to 12 ft/sec for conventional FBCs while for the CFBC the range is
about 10 to 30 ft/sec. At the same time, mean bed particle size is much
smaller for the CFBC, 50 to 300 pm compared to 1000 to 1200 ym for the
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INCREASING
SOLIDS
THROUGHPUT
INCREASING EXPANSION
Figure 1. Basic fluid bed combustion systems.
Source: Reference 1.
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conventional FBC. In the circulating bed mode of fluidization, the entire
reactor contains solids of significantly lower density than in conventional
fluidized-beds. In addition, the degree of gas-solids contact over the entire
reactor height leads to longer contact times in the CFB, even at the high gas
velocities employed.
Although dependent upon specific designs, advantages that have been
reported for CFBCs over conventional systems include the following:
• the lower solids concentration (and hence density) and the increased
turbulence resulting from the higher fluidizing velocity in the CFBC
means that the number of feed points can be kept very low because of
the excellent solids mixing.
• the CFBC offers more flexibility in terms of fuel choice (coal,
wood, peat, etc.) than conventional FBCs.
• combustion air is supplied at lower pressures than required for
conventional FBCs.
• the CFBC is capable of two to three times the fuel throughput per
unit base area due to higher combustion air velocities.
• high turbulence and gas-solids mixing, strong solids backmixing, and
continuous solids recirulation all help promote uniform combustor
temperatures and high combustion efficiency (carbon utilization).
• the relatively fine coal and sorbent particle sizes used and long
gas-solids contacting time combine to foster high utilization of
limestone or dolomite sorbents such that calcium to sulfur (Ca/S)
mole ratios of less than 2.25/1 are attainable while achieving
greater than 90 percent SC-2 control.
• heat exchange surfaces need not be as critically designed or costly
since they are usually separated from the combustion zone.
• staged combustion is possible to help minimize NOX emissions.
In addition to these apparent advantages, there are several potential problem
areas (again dependent upon specific designs) as compared to classical FBCs:
• auxiliary power consumption may be increased because of feed
material crushing and fluidizing blower requirements and overall
system pressure drop.
e ancillary equipment requirements (hot cyclones, etc.) may be more
significant in terms of number and severity of design.
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• equipment erosion due to higher velocities is more of a
concern.
• separation of bed material from effluent gas may be more difficult.
These reported advantages and disadvantages are more fully discussed in
the next section as they relate to particular process configurations.
Companies and organizations that are presently involved in circulating bed
development and/or testing and which are discussed in the following section
include the following:
Ahlstrom Company, Helsinki, Finland
Battelle Development Corp., Columbus, Ohio
Combustion Engineering, Inc., Windsor, Connecticut
Conoco Coal Development Co., Library, Pennsylvania
Electric Power Research Institute, Palo Alto, California
Gotaverken, Gb'teborg, Sweden
Lund Institute of Technology, Sweden
Lurgi Corp., River Edge, New Jersey and Frankfort, West Germany
Pyropower Corp., San Diego, California
Stone and Webster Corp., Boston, Massachusetts
Struthers Thermo-Flood Corp., Winfield, Kansas
Studsvik Energiteknik AB, Nykoping, Sweden
Tennessee Valley Authority, Chattanooga, Tennessee
Westinghouse R&D Center, Pittsburgh, Pennsylvania
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SECTION 2
COMMERCIAL AND TECHNICAL STATUS
At the present time, the development and commercialization of circulating
bed technology in the United States is being carried out primarily by the
following groups:
Battelle/Struthers Thermo-Flood (joint venture)
Lurgi Corp./Combustion Engineering (joint venture)
Pyropower Corp.
In addition, Conoco, Stone and Webster, and Combustion Engineering are
involved in a cooperative research program involving development of a slightly
different system configuration. Each of these technical processes is
discussed in this section based upon available literature and personal
communications with each of the companies.
BATTELLE DEVELOPMENT CORPORATION2"8
In 1973, Battelle began work on improving conventional coal-burning
fluidized-bed combustion methods. As a result of these efforts, a new
second-generation FBC process referred to as a Multisolid Fluidized-Bed
Combustion (MS-FBC) system has been developed and patented.
As illustrated in Figure 2, the MS-FBC process features an entrained bed
of small or light particles (typically sand or limestone) and a permanently
fluidized dense bed (typically iron ore or silica)—both in the combustor.
The light, entrained bed penetrates up through the dense bed and is elutriated
from the combustor column. It is then collected in a cyclone and sent to an
external heat exchanger. The cooled entrained bed material is then returned
to the combustor. The entrained bed thus acts as the heat carrier in the
process. The system is capable of burning either high sulfur coal or coke, or
combinations of solid and liquid fuels.
Process features and perceived benefits of the MS-FBC system are
indicated in Table 1. A comparison of a conventional FBC with the Battelle
MS-FBC is provided in Table 2.
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TO
CONVECTIVE
BOILER -^
AND
PARTICULATE
REMOVAL
EXTERNAL
HEAT
EXCHANGER
ENTRAINED
BED
SECONDARY
AIR
DENSE
BED
COAL
Q DENSE BED
o LIMESTONE
ASH
• CARBON
~'.'B ° B at c.jis6 is. »t 4 . o•rjl'a,0o:p.''oo^
?o-0,°go° "o-...°o° QJO°VO.°O, 7^*5 ;o-o°°^n»-^dg:
CRUSHED
LIMESTONE „
PRIMARY
AIR
BATTELLE MULT1SOLID FLUIDI2ED-BED COMBUSTOR
Figure 2. Battelle Multisolid Fluidized-Bed Combustor.
Source: Reference 8.
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TABLE 1. FEATURES AND BENEFITS OF THE BATTELLE MS-FBC SYSTEM
Features
Benefits
1. Combustor and heat exchanger
are decoupled.
2. Low fluidizing velocity (below 2 feet
per second) with clean air in external
heat exchanger/boiler.
3. High fluidizing velocity (^30 feet per
second) in combustor amenable to staged
combustion
4. Operates with crushed (minus
10 mesh) limestone.
5. Simple basic concept.
6. Combustor has no heat-transfer tubes
in dense bed. No cooling during startup
or shutdown.
7. Combustor freeboard has no cooling
tubes, providing additional time at
temperature.
8. Addition of entrained bed in freeboard
region of combustor.
Source: Reference - Report Summary: Battelle's Multisolid Fluidized-Bed Combustion Process.
Excellent response to load changes by changing
entrained bed recirculation. Optimum combustor
shape possible.
May use horizontal heat exchanger tubes if desired,
without concern over erosion of tubes. Extension of
the life of the steam tubes and tube supports.
Optimum heat-transfer coefficients.
Small cross section and violent mixing handles
1.5-inch-size wet lump coal. Staged combustion
significantly reduces NOX emissions. No vulnerability
to coal feed point location.
Limestone structural stability is unimportant. Use of
wider range of limestone possible. Lower consumption
of limestone.
Flexibility in modifications and variations of design.
Maximum fuel flexibility without need for matching
tube surface to fuel. Combustor will start up readily
and remain hot during prolonged shutdown.
Carbon burnup and limestone utilization are
maximized.
Freeboard burning is controlled.
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TABLE 2. COMPARISON OF OPERATING CHARACTERISTICS OF CONVENTIONAL FBC
AND MS-FBC.
FBC
MS-FBC
Superficial gas velocity
Dense bed material
Type
Typical size
Particle density
Entrained bed material
Type
Typical size
Particle density
Sulfur sorbent
Type
Typical size
Method of heat recovery
Steam tubes in dense bed
Steam tubes in freeboard
Steam tubes in entrained bed
Method of controlling dense bed
Temperature
12 ft/sec, max.
Limestone or
dolomite
8 x 30 mesh
2.6 g/cc
Not used
Limestone or
dolomite
8 x 30
Yes
Yes
By immersed
steam tubes
20-30 ft/sec
Iron ore, etc.
6 x 12 mesh
5.2 g/cc
Sand
20-100 mesh
2.6 g/cc
Limestone or
dolomite
Minus 10 mesh
No
Yes
By adjusting
recirculation
rate of en-
trained bed
solid
Source: Reference 2.
-------
Development work on the Battelle system has been conducted in 6-in. by
20-ft high (MSFB-0.4, capacity-0.4 x 10° Btu/hr) and 10-in. by 27-ft high
(MSFB-1, capacity-1.0 x 106 Btu/hr) pilot plant units. The MSFB-0.4 (shown
in Figure 3) has an enlarged freeboard diameter of 8-in. to provide greater
residence time for gas-solids reactions. The configuration of the MSFB-1
pilot plant is similar to that of the MSFB-0.4 except that it has no enlarged
freeboard area. Coarse fuel is fed to each unit by dropping it into the
combustor above the dense bed while fine fuel and limestone are fed by
pneumatic injection near the bottom of the dense bed. The flow of recycled
solids is controlled by non-mechanical "L" valves.
A generalized integration of the advanced MS-FBC design into an
industrial steam generation system is depicted in Figure 4. For a specific
application, the integration and sequence of the various heat transfer steps
would be optimized for the requirements of the particular plant. Steam
superheating can be incorporated either in the flue gas circuit or external
heat exchanger.
Feed systems inject solid fuel up to a nominal 1-1/2-in. size into the
combustor at the top of the dense bed. For staged combustion, 25 to 40
percent of the total combustion air enters through the air distributor at the
bottom of the combustor. The remaining air is added to the combustor in the
freeboard section as secondary air.
Entrained bed material passing through the external boiler is cooled from
1500°-1700°F to 800°-1200°F (dependent upon the application) before being
recycled to the combustor. The recycle stream flow rate is varied to control
the combustor temperature at the desired level.
Thermal efficiency in the MS-FBC system is increased by heat recovery
from the flue gas by a combination of one or more of the following
heat-transfer operations: (1) steam superheater, (2) boiler section, and (3)
feedwater heating. The flue gas is cooled from about 1600°F to approximately
400°F in the economizer zone before passing through final particulate removal
equipment.
Testing in the Battelle pilot plant has been carried out on high-sulfur
coal from Ohio, Illinois, and Pennsylvania. Limestones evaluated were from
Piqua, Ohio and Grove, Virginia. Tan silica pebbles are used as the material
in the dense fluidized bed while fine speculite, limestone, and a rounded sand
were originally tried as the entrained fluidized-bed material. Sand is now
used initially in the entrained bed and is gradually replaced by accumulated
spent limestone.
Sulfur dioxide emission levels of 1.2 Ib S02/10" Btu have been met con-
sistently with Ca/S mole ratios of 1.5 to 2.2 while burning 4 percent sulfur
coal. Figure 5 shows the effect of entrained bed recycle rate on sulfur reduc-
tion while Figures 6 and 7 show the effect of combustion temperature on sulfur
retention and limestone requirement.
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TO
BAGHOUSE
DISTRIBUTOR
START-UP
BURNER
-FLUSDIZING AIR
-NATURAL GAS
Figure 3. Schematic of MSFB-0.4 Pilot Plant.
Source: Battelle Memorial Institute.
10
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ENTRAINED
BED
Figure 4. Battelle Multisolid Fluidized-Bed Steam Generator.
Source: Battelle Memorial Institute.
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3,000
O MSFB-0.4, COAL R = 2,500 LB/HR FT2
A MSFB-1, COAL, R =8,000 LB/HR FT2
0 MSFB-1 DELAYED COKE,
R =8,000 LB/HR FT2
MSFB-1, FLUID COKE
R =9,000 LB/HR FT2
85 PERCENT
CAPTURE
100 PPM
0
1234
Ca/S RATSO, MOLES/MOLE
Figure 5. Sulfur Capture in MSEC - Effect of Entrained
Bed Recycle Rate (R).
Source: Battelle Memorial Institute.
12
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100
90
80
c 70
o>
o
4>
a- 60
c
o
"•£ 50
or
i_
3
H—
"5
40
30
20
10
0
1550-1700 F
Federal S02
Emission
Standard <<
1850 F
Coal. Illinois No. 6
Limestone- Piqua Limestone _
(-325 mesh)
234
Ca/S Molar Ratio
6
Figure 6. Effect of combustion temperature and calcium to sulfur
ratio on sulfur retention in Battelle's MS-FBC system.
Source: Reference 2.
13
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o
o
o
e
O)
53
c
0)
c
0)
e
Q
Note: 851; control to
1.2 Ib S02/106 Btu
CooS- Illinois No. 6
Limestone" Piqua
( -325 mesh)
I400 [500 1600 I700 I800 1900
Combusfor Bed Temperature , F
2000
Figure 7. Effect of combustion temperature on limestone
requirement in Battelle's MS-FBC system.
Source: Reference 2.
14
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The commercialization of Battelle's MS-FBC has been initiated in
conjunction with Struthers Thermo-Flood Corp. (a subsidiary of Struthers Wells
Corp.) of Winfield, Kansas.9"12 Struthers Thermo-Flood has concluded a
license agreement with Battelle Development Corp. covering the MS-FBC system.
The license gives Struthers Thermo-Flood exclusive worldwide rights to the
design for use on secondary oil recovery steam generators.
Prior to the conclusion of the license agreement, Struthers Thermo-Flood
had investigated several solid fuel-firing techniques including pulverized
coal firing, traveling grates, slurry feeds, and fluidized-bed combustors. In
its evaluations, Struthers judged each technique on the basis of the special
design and operating characteristics required for its once-through oil field
steam generators. Such factors as low and uniform heat fluxes, minimum heat
retention, response to load changes, tube corrosion, tube fouling tendency,
etc. were included in the overall evaluation program. Oil field steam
injection projects impose significantly different requirements on steam
generators than conventional steam generation applications; in most cases, the
requirements are even more severe than supercritical electric utility
boilers. Well-designed oil field steam generators must meet the following
minimum criteria:9
• Operate satisfactorily with zero hardness feedwater at temperatures
of 60°F to 220°F containing up to 12,000 ppm total dissolved solids.
• Be capable of responding to rapid and significant changes in load
demand as dictated by injection well requirements with turndown
ratios of greater than 4/1.
• Operate at high thermal efficiencies (88 to 92 percent based upon
the lower heating value of the fuel).
• Operate in a largely unattended mode while providing high operating
reliability coupled with a design incorporating ease in maintenance.
As a result of the evaluation program, Struthers chose the fluidized-bed
combustion system as the solid fuel-firing technique most suitable for oil
field steam generators, specifically the Battelle MS-FBC system.
At present there are two MS-FBC units being installed in the United
States. The first is a 5 x 10^ Btu/hr pilot plant unit with complete
material handling, steam generation, flue gas processing, and control systems
capability being installed at the Struthers Thermo-Flood facility in Winfield,
Kansas. This pilot facility will be utilized for evaluation of enhanced oil
recovery and process heater applications as well as further fuel testing and
development of system improvements.
A second MS-FBC unit rated at 50 x 106 Btu/hr is installed and
undergoing startup at a Conoco facility in Uvalde, Texas. This steam
generator is designed to burn a wide variety of solid fuels including
petroleum coke, coal, and lignite for steam injection being utilized in a tar
sand reservoir. Steam, at an outlet pressure of 2450 psia, will be produced
15
-------
from feedwater ranging in temperature from 70° to 220°F. _A schematic diagram
of the Battelle/Struthers oil field steam production configuration is shown in
Figure 8.
LURGI CORPORATION1'13"17
Lurgi, an engineering company serving the chemical and metallurgical
industries, has over 30 years experience in the design and construction of
high temperature fluidized-bed processes and hardware. In particular, 230
roasters for pyrite or zinc sulfide, 60 sludge incinerators and 60 pickle acid
regeneration units were built using conventional bubbling bed technology.
In order to process fine grained materials at large gas velocities, Lurgi
began developing circulating fluid bed technology around 1960. Their initial
application was for calcination of aluminum trihydrate to cell-grade alumina,
the Lurgi-VAW process, with the first commercial plant going on-line in 1970.
In this type of application, temperature uniformity throughout the
reactor is most important to assure uniform alumina properties. A temperature
deviation in any part of the furnace and cyclone of less than 20°F from a
preset temperature can be achieved at operating temperatures of up to 2650°F
with the large internal and external solids recirculation rate. Heavy fuel
oil or natural gas is burned in two stages with preheated fluidizing air at a
total excess air level of 10 percent and less (see Figure 9).
Fuel and primary air are injected into the lower part of the furnace,
resulting in partially gasifying combustion. Secondary air is introduced
through tuyeres in the upper part of the furnace, providing complete
combustion under low excess oxygen. A typical flow scheme of the process is
shown in Figure 10.
Combustion temperature is controlled by regulating the addition of
aluminum trihydrate and in spite of temperatures as high as 2650°F, NOX
emissions of 40 ppm have been achieved with natural gas firing. Solids
retention time in the circulating fluid bed calciner is controlled
automatically by varying the discharge rate and can be adjusted in wide limits
with bed pressure drops between 28 to 80 in. W.C.* Other applications of the
circulating fluid bed for high temperature, endothermic reactions, such as
calcination of dolomite and limestone and decomposition of sulfates and
hydrated aluminum chloride are in the realization or scale-up phase.
Based on this experience with roasting and combustion in conventional
fluidized-beds and with the operation of circulating fluid bed alumina
calciners, Lurgi began developing CFBC technology as an alternative approach
to coal combustion. This work led to several novel process design
concepts.13-15 One possible design concept is illustrated in Figure 11
showing the flow scheme for a CFBC boiler plant. Fine-sized solids are
fluidized at velocities of 20 to 26 ft/sec. Fine-grained coal (average
*W.C. - Water Column.
16
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SECONDARY
AIR
BLOWER
COAL FEED
LIMESTONE
FEED
CONVECTION
SECTION
(ECONOMIZER)
EXTERNAL
HEAT
EXCHANGER
80% STEAM
PRODUCT TO
INJECTION WELL
Figure 8. MS-FBC for oil field steam injection.
Source: Battelle Memorial Institute.
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SECONDARY AIR
SOLIDS FEED
V
OIL*
ATOMIZING
STEAM
OFFGAS
ALUMINA TO
COOLER
PRIMARY
AIR
Figure 9. Two stage combustion in a circulating
bed.
Source: Reference 1.
18
-------
Al(OH)3 (MOIST
CALCINING
FURNACE
FUEL
t,
ELECTROSTATIC
PREC1PITATOR
STACK
i
Figure 10. Flow diagram of a circulating fluid bed alumina
calcining plant.
Source: Reference 1.
19
-------
SUPERHEATED
**STEAM
COAL LIMESTONE
SUPERHEATER
\
CIRCULATING
FLUID8ED
BOILER
PNEUMATIC
FEEDING
FLUIDIZED BED
ECO*
EVAPORATOR
! t t t t
SECONDARY
AIR BLOWER
ASH DISPOSAL
ASH DISPOSAL
TO STACK
I
ELECTROSTATIC
PRECIPITATOR
AIR PREHEATER
FAN
SECONDARY
AIR.BLOWERII
I PRIMARY
AIR BLOWER
Figure 11. Circulating fluid bed boiler scheme.
Source: Reference 1.
-------
particle size of 200 to 300 urn) is pneumatically fed to the lower part of the
reactor. The number of feed points can be kept low because of the excellent
solids mixing in the low density bed. Lurgi envisions two coal feed points
for a 100 MW(e) boiler. Combustion air is introduced at two levels as shown
in the diagram with combustion able to be sustained at constant conditions
with bed temperatures of 1470° to 1830°F at 10 percent excess air.
In the combustion of high sulfur coal, limestone of roughly the same size
as the coal is added to the bed for S02 removal. S02 removal efficiencies
are enhanced by long gas-solids contacting times due to the presence of bed
material throughout the height of the reactor, usually 50 to 100 ft high.
For the flow scheme shown in Figure 11, the combustion chamber is
refractory-lined in the lower section for protection from the reducing
atmosphere and to facilitate startup. Above the zone of secondary air
injection, the bed is bounded by evaporator tube walls. Heat transfer from
the bed to the tube walls depends on bed density and varies from 20 to 40
Btu/ft -hr-°F for the proposed operating conditions. While most of the
solids collected in the cyclone are returned to the reactor by a fluidized
syphon, a controlled portion flows through a fluidized-bed heat exchanger
where high temperature solids are cooled by heat exchange with immersed
superheater, evaporator or economizer surfaces. In the particular flow scheme
shown, the tube bundles are forced convection evaporator surfaces in the
entrance section and economizer surfaces in the exit section, although other
configurations are possible. The heat transfer in this heat exchanger is high
because the fluidizing velocity can be adjusted to optimal conditions without
affecting combustion air requirements as in classical FBCs.
Combustion tests have been performed in the CFBC unit at the Lurgi
Research Laboratories in Frankfort, West Germany. Two subbituminous coals and
one limestone were tested. Coal properties, parameters varied, and results
are shown in Table 3. These data show the excellent carbon combustion
efficiency and high removals of nitrogen oxides and sulfur dioxide obtained
during the test program. Further development, evaluation and testing in the
Lurgi pilot plant have led to claims that the process is capable of achieving
90+ percent SC^ reduction and 99.5 percent combustion efficiency at a Ca/S
molar ratio of 1.2.
The excellent test results, design studies, and experience with
circulating fluid bed calciners and the published results of combustion in
classical fluidized beds have led Lurgi to develop the tentative comparison
between their CFBC design and conventional FBCs shown in Table 4.
The CFBC process and hardware technology are similar to the
Lurgi-designed alumina trihydrate calcining process of which there are 24 such
units installed or under construction worldwide.* Lurgi Corp. is presently in
the process of commercializing circulating fluidized-bed combustion technology
in the United States although there are currently no such units installed. In
•^Personal Communication between Doug Roeck, GCA, and Phil Mantin, Lurgi
Corp., August 5, 1981.
21
-------
r-o
S3
TABLE 3. TEST PARAMETERS FOR COAL COMBUSTION IN THE LURGI CIRCULATING
FLUID BED COMBUSTION FACILITY
Coal types
Volatiles, %
Ash, %
Sulfur, a %
Nitrogen,3 %
Low heating value, Btu/lb
"A"
20.8
40.8
1.31
1.02
8,100
"B"
21.2
20.7
1.23
1.50
12,000
Mean particle diameter
(feed) , pm
Max. coal feed rate, Ib/hr
Combustion temperature, °F
Excess air, %
SO removal @ Ca/S = 1.5, %
S02 removal @ Ca/S = 2.5, %
NOX without staged combustion, ppm
NOX with primary and secondary air, ppm
Residual carbon in bed material, %
Residual carbon in fly ash, %
237
50 to 60
1560 to 1780
10 to 35
85
No S02 detected
200 to 250
90 to 100
0.1 to 0.5
Max. 3, generally 1
Moisture-free.
Source: Reference 1.
300
-------
TABLE 4. COMPARISON BETWEEN THE CONVENTIONAL FLUIDIZED BED AND THE
LURGI CIRCULATING FLUID BED FOR THE COMBUSTION OF COAL
Criterion
Conventional (bubbling)
fluidized bed
Circulating fluidized bed
Heat exchange
surface
Can/so lids
contacting
Pressure drop
Partial load
Load following
Bed material
Combus tion
e fficiency
Coal crushing
Excess air ratio
Immersed in bed
Erosion problems in close
packing of tubes
Restricted to bed heights
of 1.6 to 6.6 ft
Similar
Down to 70% in one module,
complicated controls
Relatively slow
Relatively coarse
Problems with entrained
fines are encountered
Coarse, coal drying may
be avoided
1.2
1.4
Only tube walls in fluidized
bed combustor, with further
decoupled heat exchange in an
external solids heat exchanger
The whole reactor is filled
with dispersed solids - bed
height 66 to 100 ft
Similar ,
Down to 50% per unit and
lower, simpler control
Faster than conventional FBC
Fine
Virtually complete 99%
Finer particle size, however
coarser than pulverized coal
combustion. Coal drying may
be necessary
1.1
Emission
characterist ics
a. Ca/S rat to for Ca/S = 3 and higher
90% removal
of S02 with
1imestone
addit ion
b. N0x
c. Particulates
Coal feed
Ca/S =1.5-2
(longer contact time, smaller
particles)
Specific thermal
load per unit
cross-section
Temperature
uni formity
100 - 200 ppm
Similar
Simple, 2 feed points per unit
300 400 ppm
Similar
Complicated, large number
of feed points (1 feed
point per 10 to 20 ft2).
Alternatively overbed
feeders have higher carbon
losses in fines
3.2 to 9.5 x 105 Btu/ft2-hr 9.5 -x 105 to 2.5 x 106 Btu/ft2-hr
Freeboard combustion
possible due to fines and
volatiles
Uniform temperature in
reactor and cyclone system
due to high solids re-
circulation rate.
Source: Reference 1.
23
-------
January 1980, the Tennessee Valley Authority awarded a contract for a joint
study by Combustion Engineering and Lurgi to perform preliminary design of a
200 MW(e) and an 800 MW(e) utility boiler using the Lurgi CFBC process.
This work was completed in December 1980. The 200 MW(e) utility boiler
plant is shown in Figure 12. Design parameters are shown in Table 5.
A commercial CFBC unit is being built by Lurgi in Liinen, West Germany at
the Vereinigte Aluminumwerke (VAW). This unit will have a capacity of 84
MW(t) and will both produce high pressure steam (convective section) and
reheat 2.8 x 106 Ib/hr molten salt heat carrier from 650° to 800°F (fluid
bed heater section). On equivalent terms the unit, if designed for steam
production only, would produce 220,000 Ib/hr of steam. (See Figure 13). The
unit will burn high ash coal waste (50 percent by weight, dry basis). The
project began in 1980 and is scheduled for commissioning in mid-1982.*
PYROPOWER CORPORATION18"23
The Pyropower Corporation, formed in September 1980, is equally owned by
General Atomic Company of San Diego, California and Ahlstrom Company of
Helsinki, Finland. Fluidized-bed combustion research has been one of the
major projects at the Hans Ahlstrom Laboratory—the R&D Department of the
Company's Engineering Division in Karhula, Finland—since 1969. Conventional
bubbling fluidized-bed systems have been developed for incineration of such
wastes as sewage sludge, oily sludge, peat and other materials and liquids,
and for heat and steam generation. A total of nine conventional systems have
been sold by Ahlstrom for commercial application in Australia, England,
Finland, France, Sweden, and Syria.
Limitations with conventional fluidized beds (need for many fuel feed
points and limits on the range of fuels to be burned and the fines content to
achieve good combustion efficiencies) led Ahlstrom to develop the PYROFLOW™
circulating fluidized-bed system in 1976. This technology has been developed
in the company's 2.0 MW(j-) pilot plant, which has been in operation since
1977. Two basic system configurations are offered for steam generation as
shown in Figure 14. For the low-to-medium pressure steam applications, a
convective boiler bank is required since all of the evaporative duty cannot be
done in the combustion chamber. A superheater is located at the inlet to the
boiler bank while an economizer for heating incoming feedwater is situated at
the boiler bank outlet. For the medium-to-high pressure steam applications,
all evaporation will be done in the combustion chamber and superheating will
be done in the convection zone of the boiler. An economizer is also installed
in the convection zone. Depending on the fuel to be used, an airheater may
also be included in this second configuration.
The PYROFLOW circulating bed system uses greater air velocities than
conventional FBCs and the entrained particles are separated from the hot gases
in a cyclone collector and reinjected into the bottom of the combustion
^Personal Communication between John Milliken, EPA, and Phil Mantin, Lurgi
Corp., October 29, 1981.
24
-------
Figure 12. 200 MW(e) CFB utility unit.
Source: Reference 16.
25
-------
TABLE 5. DESIGN PARAMETERS FOR 200 MW(e) CFBC
CONCEPTUAL DESIGN STUDY3
Circulating Fluid Bed Combustor—
Combustion temperature:
Excess air ratio:
Fluidizing velocity:
Average carbon content of ash:
Combustion efficiency:
Ca/S mole ratio:
Sulfur removal efficiency:
CFB pressure drop:
Heat transfer coefficient to CFB
tube walls:
Number of coal feed points:
Number of limestone feed points:
Solids entrainment from CFB furnace:
Mean coal feed size:
Mean limestone feed size:
Cyclones—
Axial velocity:
Recycling cyclones efficiency:
Secondary cyclones efficiency:
Fluid Bed Heat Exchanger—
Fluidizing velocity:
Heat transfer coefficient to immersed
tube surface:
FB heat exchanger pressure drop:
1560°F
1.2
19 ft/sec
1 percent
99.4 percent
1.5
90 percent
104 in. W.C.
30 Btu/ft2-hr-°F
1 per 50 MW(e)
1 per 100 MW(e)
0.15 lb/ft3 gas
300-500 ym
250-400 pm
10.5 ft/sec
96 percent
85 percent
3 ft/sec
70 Btu/ft2-hr-°F
36 in. W.C.
aSource: Reference 16.
-------
UMESTONE COAL CIRCULATING
FLUOZED BED
COMBUSTOR
i
V
CONDARY
CYCLONE
WASTE hEAT
:R
FL DOZED BED hEAT EXCHANGER
I
CONVEYING
MR
PRIMARY
AIR
SECONDARY
AIR
Figure 13. Flow diagram of a Circulating Fluidized-
Bed Combustion Plant.
Source: Reference 17.
27
-------
MAIN STF1AM OUTLET
STEAM DHUM
COMBUSTION
CHAMBER
BOILER EXIT GAS
ASH HI:MOVAL
FIRST CONFIGURATION — LOW TO MEDIUM PRESSURE
Evaporation Ibs/hr 20,000-200,000
Steam pressure 200-800 psia
Steam temperature Saturated-600°F
SUPERHEATERS
AMI RCMOVAi
SECOND CONFIGURATION - HIGH PRESSURE
Evaporation Ibs/hr 20,000-200,000
Steam pressure 800-2600 psia
Steam temperature 600-970'T
Figure 14. Commercial system configurations offered by
Pyropower Corporation.
Source: Reference 21,
28
-------
chamber. Turndown ratios of 4:1 can be provided merely by changing flow rates
and fuel feed, and 50 percent load changes within 3 minutes have been
demonstrated. Fuel is fed into the lower combustion chamber and primary air
is introduced through a lower grid. While there is no definite fixed bed
depth, the density of the bed does vary throughout the system with the highest
density at the level where the fuel is introduced. Secondary air is supplied
at various levels to assure gas velocities higher than particle falling
velocity. Combustion takes place at about 1550°F, which is considered optimum
for sulfur retention in a coal/limestone system. A cyclone collector
separates hot gases from the unburned particles and entrained bed material;
the particles are returned to the combustion chamber through a non-mechanical
seal, and ashes are removed through the bottom. Effluent gases from the
cyclone are discharged to the convection section of the boiler. Some of the
heat is absorbed by water walls in the combustion chamber, while the remainder
is recovered in the convection zone.
Major performance features of the PYROFLOW circulating bed system are as
follows:
• It has a high processing capacity (relative to conventional FBC)
because of the high gas velocity throughout the system.
• The operating temperature of 1550°F is reasonably constant
throughout the process due to the high turbulence and circulation of
the solids. This relatively low combustion temperature results in
minimal NOX formation.
• Sulfur present in the fuel is retained in the circulating solids in
the form of calcium sulfate and is thus removed in solid form. The
use of limestone or dolomite sorbents allows a high sulfur retention
rate, and the sorbent requirements are substantially lower than
those for conventional FBCs.
• Combustion air is supplied at 1.5 psig rather than higher pressures
required by conventional FBCs.
• It has a high combustion efficiency.
• It has a better turndown ratio than conventional FBC systems.
• Erosion of heat transfer surfaces is reduced since the surface is
parallel to the gas flow. In conventional FBC systems, the surface
is usually perpendicular to the flow.
A list of Pyropower's commercial circulating bed installations since 1976
is provided in Table 6. Since the first circulating bed system was developed
at Ahlstrom, 11 additional systems in sizes up to 200,000 Ib steam/hr have
been sold for commercial operation. One system has accrued 2 years of
operation with an availability of over 95 percent. Another system represents
the first U.S. installation for Pyropower Corp. and will be used to make steam
for an enhanced oil recovery project near Bakersfield, California. A brief dis-
cussion of some of these industrial applications is provided in the following
paragraphs.
29
-------
TABLE 6. PYROFLOW™ CIRCULATING FLUIDIZED-BED UNITS IN OPERATION
OR UNDER CONSTRUCTION BY PYROPOWER CORP,a
Co
o
i.
9
3.
4.
5.
6.
7.
8.
9.
10.
11.
12.
Customer
Hans Ahlscrom Laboratory
Karhula, Finland
Ahlstrom Company
Pihlava, Finland
Savon Voima Company
Suonenjoki, Finland
Kemira Company
Valkeakoski, Finland
Ahlstrom Company
Kauttua, Finland
Hyvinkaa Lampovoima Company
Hyvinkaa, Finland
Skelleftea Kraft Company
Skelleftea, Sweden
Town of Ruzomberok
Ruzomberok, Czechoslovakia
Hylte Bruk Company
Hylte Bruk, Sweden
Alko Company
Kosken Korva, Finland
Kemira Company
Finland
Gulf Oil Exploration and
Production Co.
Bakersfield, California
Year of
startup
1976
January
1979
September
1979
1980
March 1981
Fall 1981
Fall 1981
Fall 1981
Fall 1982
1982
1983
January
1983
Fuels
Varied
Peat, wood wastes,
and supplementary coal
Peat, wood wastes,
and coal
Zinciferous sludge
Peat, wood wastes,
and coal
Coal primary, alternate
peat or oil
Peat, wood wastes
and coal
Sewage and in-
dustrial sludges
Peat primary,
coal alternate
Peat
Peat, coal, and coal
wastes
Coal
Application
Pilot plant
Cogenerat ion
for board mill
District heating
Incineration
Cogeneration
District heating
District heating
Incinerator
Cogeneration
Process steam
Cogeneration
Process steam for
enhanced oil
recovery
Size
2 MW(t)
5.67 kg/s - 15 MW(t)
(45,000 Ib/hr steam)
7.0 MW ( t )
0.71 kg/s
(5650 Ib/hr)
(21.5% dry)
25 kg/s - 65 MW(t)
(200,000 Ib/hr steam)
25 MW(t)
7.0 MW(t)
1.11 kg/s
(8800 Ib/hr)
(26% dry)
18.27 kg/s - 50 MW(t)
(145,000 Ib/hr steam)
7 kg/s - 16 MW(t)
(56,000 Ib/hr steam)
19.5 kg/s - 52 MW(t)
(155,000 Ib/hr steam)
50 x 106 Btu/hr
input
Source: 1-9: Reference 22.
10-11: Personal Communication between John Milliken, EPA, and Eric Oakes,
Pyropower Corp., October 15, 1981.
12: Chemical Engineering, April 5, 1982, pp. 39-43.
-------
At the end of 1977, Ahlstrom decided to install its first commercial
PYROFLOW system at its own board mill power planf, in Pihlava, Finland.
Construction of this retrofit installation was completed by the end of
December 1978; the commissioning period began in January 1979 and the unit
began commercial operation in April 1979. A schematic diagram of this
installation is shown in Figure 15. The water-tube-cooled combustion chamber
is coupled in parallel to the furnace circuit of the main boiler, delivering a
saturated steam/water mixture to the drum. Over half of the heat generated by
the PYROFLOW combustion process is in the flue gases, which leave the
combustion chamber at 1600°F. The distribution of heat input and steam
absorption during the normal 32 MW(t) plant output at 100 percent load is as
follows:
MW(t)
Heat Input
La Mont boiler 20
PYROFLOW r7
37
Steam Generated
La Mont boiler 25
PYROFLOW water wall _7_
Total 32
Note: Boiler efficiency = 86 percent.
During the last 2 years there were production restrictions that resulted
in periods of low steam demand during which the PYROFLOW unit was shut down,
leaving the reduced steam production to the La Mont boiler. This was done
because the PYROFLOW is easier to start up. Because of many periods of
shutdown and low load operation, it was difficult to assess an availability
figure for the CFBC. A review of plant records from April 1979 to December
1980 revealed that over 10,000 hr of on-line operation were accumulated. This
indicates an availability of 95 percent. The PYROFLOW system did not cause
any forced shutdown throughout 1980, and a thorough inspection at the end of
the year revealed that all areas of the furnace and refractory were in good
condition with no signs of wear.
The Pihlava size unit (45,000 Ib steam/hr) requires only one fuel feed
point, which is fed by a screw feeder. A variable-speed hydraulic motor
drives this screw feeder, which is sized to feed peat, but will also
accommodate bark, wood wastes, and coal. This feed system lends itself to an
effective means of automatic load following.
An example of this system's operating parameters during an abnormal load
swing is shown in Figure 16. These plots show a load reduction because of a
31
-------
STEAM/WATER
STEAM/WATER
COMBUSTOR
Hin I
SECONDARY AIR
I PRIMARY AIR
12 KG/S, 8.62 MPa, 520°C
STEAM OUTLET (97,000 LB/HR,
1250 PSI,970°F)
•— FEEDWATER INLET 190°C (375°F)
TO STACK
I.D. FAN
COMBUSTION
AIR30°C(86°F)
FLY ASH
TM
Figure 15. Pyroflow combustion chamber retrofitted to La Mont
boiler at Pihlava board mill, Finland.
Source: Reference 22.
-------
disturbance in the intermediate steam pressure system of the board mill. At
midnight on April 3, 1980, the boiler was operating at 30 ton/hr output with
most of this output generated by the PYROFLOW combustion unit. At midnight,
the steam output demand decreased from 30 to 20 ton/hr, which was effected by
a 50 percent load reduction in the PYROFLOW combustor. The curves in Figure
16 indicate how the main steam pressure remained fairly constant during the
load swing and the period of low-load operation. The two low-pressure peaks
prior to the load reduction were due to sootblowing. The complete upset and
return to full load were handled fully automatically by the PYROFLOW screw
feeder governed by the boiler control equipment.
D_
GC
UJ
Q_
CO
cc
LLJ
a
UJ
40
30
20
10
0
2i
i-i-
co —
_
sS.
40 h-
30
20
• 10
0
9.0
8.6
8.3
7.9
PYROFLOW
OUTPUT
I
I
1300
1250 s£
-£
1200 £=•
z co
1150 <^
^ Q_
2200 2300 2400 100 200 300
APRILS, 1980 TIME(H) APRIL 4,1980
Figure 16. PYROFLOW upset transient response.
Source: Reference 22.
33
-------
The PYROFLOW unit at the Pihlava plant was installed solely for economic
reasons (to reduce the high operating cost associated with firing fuel oil)
since standards in effect at the time of installation did not require the use
of FBCs for SOX or NOX control. The environmental control aspects and the
capability to fire several fuels have proven to be supplemental advantages of
the Pyropower circulating fluid bed system. Emissions of NOX when burning
peat have been consistently about 250 ppm. The capital costs of this retrofit
installation were about $1 million (1978) and during the first year of
operation this investment was paid back by the operating cost savings realized
by replacing fuel oil with peat, wood waste, and coal. Manpower requirements
were the same as when firing oil.
Also during 1979, a 7 MW(t) district heating circulating bed system
went into service in the city of Suonenjoki, Finland. This plant is a turnkey
installation to provide 248°F water. The design fuels are peat, bark, and
wood wastes, but the plant can also burn coal as a supplementary fuel. No
other information is available on this facility.
In 1978, Ahlstrom evaluated replacing the existing fuel oil-fired boilers
at its pulp and paper mills at Kauttua in Western Finalnd with units capable
of burning wood wastes, peat, and coal. Based on the successful operating
experience of the 22 ton/hr unit at Pihlava and further testing of various
fuels at the Hans Ahlstrom Laboratory, a single 100 ton/hr PYROFLOW boiler was
selected for cogeneration at the Kauttua mills. A schematic diagram of the
plant configuration and the design specifications are indicated in Figure 17.
Plant startup and commissioning began in March 1981. As well as replacing the
two existing oil-fired boilers, an additional 14 MW(e) back-pressure
turbine-generator set was added to the existing 8-MW(e) back-pressure
capacity. Under full-load conditions a total of 22 MW(e) can be generated
along with process steam for the pulp and paper mills. It should be noted
that this installation is the largest cogeneration steam plant in the world
using the circulating bed technique.
Those circulating fluidized-bed combustion systems sold by Pyropower
Corp. and operated thus far have demonstrated the following characteristics:
» multifuel capability
• good boiler efficiency
• good load-following capability
• high availability
• ease of operation
• economical installation to replace oil firing
Pyropower Corp. is now offering PYROFLOW systems to the North American
market and to support this effort a testing program was initiated in 1979 at
34
-------
STEAM/WATER
STEAM OUTLET -*
FUEL •
TO STACK
I.D. FAN
ASH
FLY ASH
Design Specifications:
Steam output
Steam temperature
Steam pressure
Feedwater temperature
Flue gas temperature
Design fuel
Efficiency with design fuel
Other fuels
- 25 kg/s (200,000 Ib/hr)
- 500°C ±7.8°C (932°F ±18°F)
- 8.4 MPa (1218 psig)
- 190°C (374°F)
- 160°C (320°F)
- Peat, 8 MJ/kg (3440 Btu/lb)
- 86%
- wood wastes and coal
Figure 17. 100 ton/hr cogeneration plant at Kauttua
paper mill, Finland with specified operat-
ing conditions.
Source: Reference 22.
35
-------
the 2.0 MW(t) pilot plant at the Hans Ahlstrom Laboratory in Finland.
Testing has been conducted on high sulfur U.S. coals, petroleum coke and U.S.
lignite. The Electric Power Research Institute (EPRl) and the Tennessee
Valley Authority (TVA) are participating in this program and have supplied two
types of Eastern, high sulfur bituminous coal (Ohio No. 6 and Kentucky No. 9)
and a North Dakota lignite (Buelah) for testing. Operating conditions and
initial test results while burning the Ohio No. 6 coal are shown in Table 7,
while overall typical results from further testing of these fuels are shown in
Table 8.
OTHER EFFORTS
Several other groups and organizations have been involved in research
related to circulating fluidized-bed combustion technology.
Combustion Engineering (CE), Conoco, and Stone and Webster are involved
in a joint venture concerning development of a Solids Circulation Boiler for
industrial application (burning of high sulfur coal).* This concept is
basically opposite to that employed in other CFBC configurations in that
combustion of coal takes place in the dense or bubbling bed while heat
exchange occurs in the dilute or entrained bed. Highlights of the concept are
as follows:^
o Combustion is carried out in a highly agitated circulating fluid bed
of inert material. Fuel and limestone are introduced to the
combustion zone where they are rapidly distributed throughout the
bed by the swirling action of the solids.
0 Steam is generated by passing hot solids from the combustion zone
through a water-walled channel in first an upward and then a
downward flow, using secondary air as the solids transfer medium.
Evaporation to steam is maintained at the desired rate by
controlling the quantity of solids circulating through the channel.
• Cooled solids from the downflow channel return to the combustion
zone in a cascade over the bed surface with the accompanying
secondary air. The cascade reduces entrainment from the bed, breaks
up bubbles of gas formed in the bed, assists in the solids
circulating action within the bed, and maintains the combustion zone
in heat balance and thereby constant temperature.
A cold test unit was constructed in April 1980 at the Conoco Coal
Development Company facility in Library, Pennsylvania. A hot test unit
commenced operation in February 1981 at Combustion Engineering's Kreisinger
Development Laboratory in 'Windsor, Connecticut.
^Personal communication between Doug Roeck, GCA and Dr. Melvin Pell, Conoco
Coal Development Company, Library, Pa., August 10, 1981.
36
-------
TABLE 7- INITIAL RESULTS FROM TESTS ON OHIO NO. 6 COAL
Operating Conditions
Combustion temperature 1600°F
Superficial gas velocity ^12 ft/sec
Ca/S ratio 2.25
Excess air ^5
-------
TABLE 8. PRELIMINARY RESULTS OF FUEL TESTS FOR
NORTH AMERICAN MARKET3
Fuel
Parameters
Subbituminous 80 percent Ohio No. 6 Petroleum
coal ash fuel coal coke
Sulfur content,
% by wt. in
dry matter
Nitrogen content,
% by wt. in
dry matter
Ca/S molar ratio
(average)
0.9
1.1
2.3
2.5
0.3
2.3
All tests run at 20 to 30 percent excess air.
Source: Reference 22.
5.1
1.5
1.8
3.5
1.8
2.4
SO retention, %
NO , ppm (v)
X
Combustion
Efficiency, %
84
170
98.0
98
200
98.5
90
280
98.5
90
100
97.0
38
-------
The Tennessee Valley Authority (TVA) and the Electric Power Research
Institute (EPRl) have examined advanced coal combustion technologies for use
in the utility industry and in order to develop performance data for the CFBC
process, TVA contracted Lurgi Chemie to perform a number of test burns with
various U.S. coals and limestones. EPRI has participated in planning the
tests and supplying various fuels.
The coal combustion tests were conducted in one of Lurgi's CFB pilot
plants in Frankfort, West Germany. A simplified flow scheme of this pilot
facility is illustrated in Figure 18. Only a brief summary of the results of
this test program are presented herein; the reader is referred to the original
reference for more detailed information.^
The pilot CFBC has an internal diameter of 14-inches, a height of 13
feet, and is refractory-lined. Effluent gas from the combustor leaves the
recycling cyclone and flows through an empty venturi stage and two further
cyclones before being discharged to a baghouse for final dust collection.
Testing was done with four U.S. coals (Ohio No. 6, Kentucky No. 9,
Freeman, and Beulah-Lignite) and two U.S. limestones (Lowellville and
Vulcan). In addition, a German coal (Ruhr) was burned to show reproducibility
of results previously obtained and a German limestone (Schaefer) was used for
comparative purposes. The following combinations of coals and limestones were
tested over a total of 35 test runs of different parameter combinations:
1. Kentucky No. 9 coal and Vulcan limestone
These are the design coal and limestone selected by TVA for the
200 and 800-MW AFBC and CFBC conceptual design studies being
performed by Combustion Engineering and Lurgi.
2. Ohio No. 6 coal and Lowellville limestone
- This combination has been previously tested at B&W in Alliance,
Ohio under EPRI sponsorship.
3. Freeman coal and Lowellville limestone
This combination has been previously tested by Combustion
Engineering.
4. Beulah lignite
Whereas unfavorable slagging characteristics have been observed
with this coal in previous AFBC tests conducted by DOE (at the
Grand Forks, ND and Morgantown, WV Energy Technology Centers
and at Combustion Power Company in Menlo Park, CA), the
performance of this coal in the CFBC was of interest for
comparison.
39
-------
BAG FILTER
GAS SAMPLING
<*. | "x"
CUD
•-> r-
i i
i i
i i
LJ
\/
CLLL)
RECYCLE VENTURI fT6~")
ASH ^-j '
\ 1 ^ /'
'— V
"te -mr i
-n 0?
^N -STT) \ /CY
-P-
o
T
COMBUSTOR
COAL/
LIMESTONE
ASH TO RECYCLE
AND DISPOSAL
Figure 18. Circulating Fluid Bed Pilot Facility at Lurgi, Frankfort, West Germany.
Source: Reference 25.
-------
5. Ruhr coal and Schaefer limestone
These materials were tested to show reproducibility of earlier
results.
^The coal combustion tests were conducted at temperatures of 1450° to
i750°F and at excess air ratios of between 1.1 and 1.3. Carbon combustion
efficiency for all tests was found to be generally above 99.5 percent. Other
general conclusions of this overall program were as follows:
• the Ca/S molar ratio required for 90 percent S02 removal was found
to be as low as 1.0 for the circulating bed. Past work with
conventional FBC units has indicated that a Ca/S ratio of 2.5 or
more would be required for the same level of S02 reduction.
(Recent work for TVA on a small scale AFBC unit indicates that a
Ca/S ratio of possibly as low as 1.25 is attainable with
recirculation of cyclone and baghouse catch, but the advantage still
appears to be in favor of the CFBC.)
• In conventional bubbling beds, 90 to 94 percent carbon utilization
can be attained without recycle of fly ash while with high recycle,
99 percent utilization has been approached. The results of the TVA
test program showed that generally better than 99.5 percent carbon
utilization was achievable with the CFBC.
• In general, NOX emissions were the same or slightly lower with the
CFBC compared to conventional bubbling beds. It was felt, however,
that better results could be attained for the CFBC in larger scale
equipment.
As a result of the rather encouraging test results from this program, TVA
has initiated construction of a 20-MW(e) pilot plant at its Shawnee generating
facility. This unit will be a hybrid CFB-AFBC, with a design recirculation
rate of five times the coal feed rate.
Several research efforts have also been undertaken in Sweden involving
the CFBC process. At the Lund Institute of Technology, a reactor concept has
been developed that operates with circulating fluidized-beds and segregated
gas phases.2^ The reactor has been demonstrated to work in the gasification
of black shale, utilizing the char as a heat carrier. The reactor principle
can also be applied to physical operations such as activated carbon
adsorption. Other work is being done at Studsvik Energiteknik AB in Nykoping,
Sweden and relates to a 250 kW fast fluidized-bed experimental model designed
for cold flow and combustion experiments.27'28 Following experience with
the 250 kW experimental unit, work on circulating fluidized bed combustors at
Studsvik has aimed at developing a 2.5 MW prototype module. This unit is
intended to be as nearly full scale as possible in order to minimize the
problems normally encountered on scaling up. Thus the height and depth of the
41
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unit (see Figure 19) are in accordance with the design parameters for a 25 MW
bed and the heat generated is transferred to a hot water boiler operating at a
pressure of 16 bar. Scale up is accordingly accomplished by assembling the
requisite number of modules. In order to minimize the effect of changes in
the ratio of surface area/volume with change of size the two side walls of the
2.5 MW prototype are lined with insulating refractory. The rate of flow of
the circulating bed material is governed by non-mechanical valves. The entire
boiler is constructed from water tubes welded together to form membrane
walls. The construction is similar to that used in the manufacture of
conventional oil-fired steam generating plants. As a result there are no
structural components that are subjected to high temperatures and it is
accordingly possible to avoid the use of refractory materials for heat
shielding (with the exception of those used in the prototype to reduce heat
transfer). The particle recirculation and separation units are an integral
part of the main furnace body. At Gotaverken in Goteborg, Sweden,
construction has been nearly completed on an 8 MW(t) demonstration CFBC that
will provide steam for the company's shipyard.* Coal firing is expected to
begin early in 1982 with peat and wood to be used as alternate fuels. A
single screw feeder will be used for each fuel type. The fluidizing velocity
for this system will be 26 to 33 ft/sec. Particulate control will be achieved
with a baghouse and gaseous emissions will be continually monitored.
The Westinghouse R&D Center in Pittsburgh. Pennsylvania has also
investigated circulating bed boiler concepts.^9 A deep recirculating
fluidized-bed combustion boiler (Figure 20) was conceived by Westinghouse as
an alternative to conventional atmospheric and pressurized fluid bed units.
Westinghouse developed a design for this concept operated at elevated
pressure. Westinghouse has estimated that pressure losses for atmospheric
pressure circulating-bed boiler systems would be about 2.7 in. W.C. per foot
of bed height and that overall pressure loss including combustor, air
preheater, particulate control, convection heat transfer, ducting, etc., would
range from 50 to 80 in. W.C.
ECONOMICS
The costs of circulating fluidized-bed combustion systems are not well
defined at this point in time due to a general lack of commercialization of
the process in the U.S. However, a limited amount of cost data comparing
circulating FBC to conventional FBC are available.30~32 These data indicate
that CFBC capital investment costs are similar to those for conventional FBC
systems, and that operating costs for CFBC may be slightly less. The following
paragraphs describe these cost studies which are very much preliminary and
therefore should be considered in that light.
^Personal communication between Bob Hall, GCA, and Dr. Anders Kullendorff,
Gotaverken, November 11, 1981.
42
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Figure 19. Schematic Diagram of 2.5 MW CFBC Prototype Module Being
Developed at Studsvik, Sweden.
Source: Personal communication between John Milliken,
EPA and Allan Brown, Studsvik.
43
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Frwbojrd
P»rticle
S«pjrjtor
Septritlon
Air Primary
Air
Secondary
Air
fuel Infector
Figure 20. Deep recirculating fluidized-bed boiler.
Source: Reference 29.
44
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Pullman Kellog Company has performed conceptual design studies for the
Electric Power Research Institute comparing a circulating bed boiler with a
conventional pulverized coal boiler.30,31 Relative to costs, conclusions of
this study were:
1. A circulating bed boiler should not exceed a conventional
atmospheric fluidized-bed combustor in capital coat, and will
probably be less, due to reduced combustor size. The cost advantage
of a pressurized circulating bed boiler is questionable.
2. The overall efficiency of an electric utility power plant should be
increased by at least 1 percent over a pulverized coal boiler—using
an atmospheric circulating bed boiler, and by at least 3
percent—using a pressurized circulating bed boiler.
3. Actual capital costs for.CFBCs could not be determined due to a lack
of data.
The overall performance of the atmospheric CFBC plant compared to one
using a pulverized coal boiler is summarized in Table 9. Both systems were
designed to meet the following standards:
Particulate matter - 0.05 lb/106 Btu
S02 - 90% removal
NOX - 0.6 lb/106 Btu
The major difference between the two plants is in auxiliary power consumption,
primarily due to a higher system pressure loss in the CFBC. According to the
study, it would be possible to boost the CFBC net plant efficiency from 34.9
percent to 38.8 percent with a high efficiency supercritical steam cycle.
Only one other study was found that provided a direct comparison between
the CFBC and conventional FBCs.^2 in this program, performed under a
Department of Energy contract, a cost comparison study was performed on three
100,000 Ib steam/hr boilers of the following designs: the Battelle MS-FBC
system, a conventional FBC system, and a conventional spreader stoker boiler
equipped with a double-alkali flue gas desulfurization system. The design
conditions for this analysis were as follows:
Steam conditions: 100,000 Ib/hr @ 150 psi
Coal analysis: Illinois No. 6
3.5% sulfur
10.0% ash
10,500 Btu/lb
Boiler utilization: 65% (5,694 hr/yr)
45
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TABLE 9. CIRCULATING BED VERSUS PULVERIZED COAL BOILER PERFORMANCE
Circulating bed
combustor plant
Pulverized coal
plant
Heat input from coal,
Btu/hr
Gross plant output, MW
Auxiliary power consumption, MW
Steam plant
Fans
Scrubber
Others
Total
Net plant output, MW
Net plant efficiency, %
5.18 x 109
580.06
8.49
34.20
7.65
50.34
(33 kW/MW(t))
529.72
34.90
5.32 x 109
570.17
8.49
15.74
11.49
8.62
44.25
(28 kW/MW(t))
525.92
33.74
Source: Reference 31.
46
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Plant location: Chicago, Illinois
Emission standards: Particulate matter - 0.1 lb/10" Btu
S02 - 1.8 lb/106 Btu
NOX - none
The results of this study are shown in Table 10. Although a slight advantage
is shown for the MS-FBC system, given the accuracy of the cost estimates (^25
percent), the costs can be judged to be virtually identical. A detailed
breakdown of the operating costs was available only for the MS-FBC and this is
shown in Table 11. For comparison with the auxiliary power consumption
figures provided earlier in Table 9, electrical consumption for the MS-FBC was
determined to be roughly equivalent to 21 kW/MW(t) with particulate control
and 16 kW/MW(t) without.
47
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TABLE 10. RESULTS OF COST COMPARISON STUDY FOR CONVENTIONAL FBC, MS-FBC,
AND CONVENTIONAL STOKER-FIRED BOILERS3
Type of boiler system
Conventional
f luidized-bed
(FBC)
Component
systems
Coal Receiving
Raw coal storage
Coal preparation
Prepared coal storage
Limestone storage
and receiving
Boiler
Flue gas cleanup
Ash handling and
storage
Totals
Total steam cost
($ per 1000 Ib)
Capital
cost
1060
1170
630
400
490
4100
500
230
8580
7.
Oper.
cost/yr
39
40
36
9
137
1528
79
86
1954
35
Multi-solids
f luidized-bed
(MS-FBC)
Capital
cost
1060
1170
-
350
550
4080
500
230
7940
7.
Oper.
cost/yr
39
40
-
9
151
1598
79
86
2002
20
Stoker-fired
Capital
cost
1060
1170
630
400
-
3600
1560
190
8610
7.
Oper.
cost/yr
39
40
36
9
-
1439
303
74
1940
37
a!979 dollars x 10~3 (±25 percent).
Includes total operating costs plus capital charges.
Source: Reference 32.
48
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TABLE 11. COMPONENT OPERATING COSTS ($/yr) FOR 100,000 Ib/hr MS-FBC'
Component systems
Raw
Coal coal Coal
Items receiving storage prep.
Raw Materials
and Fuel
Coal
Oil
Limestone
Pebbles
Total
All Other
Labor 25,170 25,165
Electricity 255 1,105
Water - - -
R&M 10,000 10,200
Ash disposal - - -
General overhead 3,540 3,645
Total 38,965 40,115
Grand Totals 38,965 40,115
Limestone
storage
Coal and
storage receiving
128,675
128,675
3,430 14,875
1,575 2,820
2,810 2,500
780 2,020
8,595 22,215
8,595 150,890
Flue
gas
Boiler cleanup
1,032,640
3,000
21,300
1,056,940
319,095 10,295
121,625 46,920
20,400
31,220 14,700
49,235 7,190
541,575 79,105
1,598,515 79,105
Ash
storage Totals
1,032,640
3,000
128,675
21,300
1,185,615
13,730 411,760
265 174,565
20,400
4,360 75,790
59,560 59,560
7,790 74,200
85,705 816,275
85,705 2,001,890
Unit costs as follows:
- operating labor - $ll/hr
- coal - $31/ton
- oil - $12.58/bbl
- limestone - $12/ton
- pebble lime - $42/ton
- pebbles - $20/ton
soda ash - $85/ton
- electricity - $0.04/kW-hr
- water - $0.30/1000 gal
- ash disposal - $5/ton
Source: ;Reference 32.
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SECTION 3
SUMMARY AND CONCLUSIONS
This report has presented an update on the technical status of
circulating fluidized-bed combustion. Battelle Development Corp. (Columbus,
Ohio), Lurgi Corp. (River Edge, N.J.), and Pyropower Corp. (San Diego, Calif.)
are undertaking the major efforts in commercializing this process in the
United States.
Battelle has conducted pilot plant tests for several years and now has a
license agreement with Struthers Thermo-Flood Corp. for selling commercial
systems. A 5 x 10^ Btu/hr pilot plant unit is now being installed at the
Struthers facility in Winfield, Kansas for enhanced oil recovery and process
heater evaluations. A 50 x 10" Btu/hr plant has been constructed and is
undergoing startup at a Conoco tar sands reservoir in Uvalde, Texas. This
unit will provide injection steam for enhanced oil recovery operations. Both
of these units are expected to be operational in late 1981/early 1982.
Lurgi Corp. is in the process of commercializing CFBC technology in the
U.S. although at present there are no units installed. Lurgi's CFBC
technology is similar to the Lurgi-designed aluminum trihydrate calcining
process of which there are 24 units installed or under construction worldwide.
Pyropower Corp. is now offering commercial CFBC systems in the U.S. based
upon the European experience of Ahlstrom Co., Pyropower's parent company.
Ahlstrom has sold 10 commercial systems in Finland, Sweden, and Czechoslovakia
and one in the U.S. Of the 11 commercial plants, six are currently operational
aud five are under construction. These units will utilize such fuels as peat,
wood waste, coal, and various sludges.
Costs associated with the CFBC process are very preliminary at this point
in time. Those studies that have been done indicate that capital investment
costs are roughly equivalent to both conventional FBC systems and other
conventional coal boilers. Operating costs for the CFBC are considered to be
less than other systems although a lack of commercial installations indicates
that further cost data would be required before firm conclusions can be drawn.
Much has been reported on the perceived benefits and advantages of the
circulating fluid bed; high combustion efficiency, high sulfur retention at
low Ca/S mole ratios, adaptability to staged combustion for NOX control,
50
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good turndown and load following capabilities, reduced heat exchanger fouling
due to location away from the combustion zone, and capability to fire a wide
range of fuels. In addition, one study has shown that the overall efficiency
of an electric utility power plant could be increased by at least 1 percent
over a pulverized coal boiler equipped with an SC>2 scrubber—using an
atmospheric circulating bed boiler. At the same time the circulating fluid
bed concept contains some technical and economic uncertainties which must be
resolved. For example, those CFBC system designs which employ separate bed
boilers will probably operate at a higher pressure drop than conventional
systems and may require additional equipment such as hot cyclones. Other
potential problems that are specific to the CFBC process are erosion, because
of the high flow velocities, and the separation of bed material from effluent
gas, which is made more difficult than normal because of the high particle
loadings encountered. Additionally, the CFBC would have to demonstrate the
ability to operate under load cycling conditions typical of electric utility
generating plants.
The future development of the process will probably continue at a more
accelerated rate given the current cost of energy and the desire of plant
operators to burn solid fuels—especially those of low quality. Should the
results of TVA's conceptual design program—which includes the circulating
fluid bed—indicate a clear advantage for the CFBC, then EPRI may promote the
construction of a 20 MW(e) pilot plant in the U.S. In the meantime, TVA has
initiated construction of a hybrid CFB-AFBC at its Shawnee facility.
51
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REFERENCES
1. Petersen, V., et al. Combustion in the Circulating Fluid Bed: An
Alternative Approach in Energy Supply and Environmental Protection. In:
Proceedings of the 6th International Conference on Fluidized-Bed
Combustion, Atlanta, Ga. April 9-11, 1980. pp. 212-224.
2. Nack, H. , K. T. Liu, and G. W. Felton. Battelle's Multisolid Fluidized-
Bed Combustion Process. In: Proceedings of the Fifth International
Conference on Fluidized-Bed Combustion. Vol. III. Washington, B.C.
December 12-14, 1977. pp. 223-236.
3. Felton, G. W., et al. Pneumatic Solids Injector and Start-up Burner for
Battelle's Multisolid Fluidized-Bed Combustion (MS-FBC) Process. In:
Proceedings of the Fifth International Conference on Fluidized-Bed
Combustion, Vol. III. Washington, B.C. Becember 12-14, 1977. pp.
241-251.
4. Nack, H. , K. T. Liu, and C. J. Lyons. Control of Sulfur Bioxide and
Nitrogen Oxide Emissions by Battelle's Multisolid Fluidized-Bed
Combustion Process. In: Proceedings of the Sixth International
Conference on Fluidized-Bed Combustion. Atlanta, Ga. April 9-11, 1980.
pp. 979-984.
5. Battelle Memorial Institute, Columbus, Ohio. Fluidized-Bed
Combustion-Industrial Application Bemonstration Projects. Prepared for
U.S. Department of Energy. DOE/FE/2472-42. October 1979.
6. Krause, H. H., et al. Erosion-Corrosion Effects on Boiler Tube Metals in
a Multisolids Fluidized-Bed Coal Combustor. Presented at the Winter
Annual Meeting of the American Society of Mechanical Engineers, Atlanta,
Ga. November 27 - Becember 2, 1977. Paper No. 77-WA/CD-l.
7- Nack, H., D. Anson, and S. T. DiNovo. Status of Battelle's Multisolid
Fluidized-Bed Combustion Process. Presented at: Fluidized-Bed
Combustion: Systems and Applications Conference, London, England.
November 4-5, 1980.
8. Battelle Memorial Institute, Columbus, Ohio. Battelle's Multisolid
Fluidized-Bed Combustion Process, Summary Report on the Status of
Development and Commercialization. September 1981.
52
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9. Fanaritis, J. P., C. J. Lyons, and H. Nack. Application of the Battelle
Multisolid Fluidized-Bed Combustion System to Oil Field Steam
Generators. In: Proceedings of the Sixth International Conference on
Fluidized-Bed Combustion. Atlanta, Ga. April 9-11, 1980. pp. 365-371.
10. Davis, J. S., W. W. Young, and H. Nack. Utilization of Fluidized-Bed
Combustion for Oil Field Steam Generation. Prepared by Struthers Wells
Corp., Struthers Thermo-Flood Corp., and Battelle Columbus Laboratories.
11. Davis, J. S., W. W. Young, and C. J. Lyons. Use of Solid Fuel Possible
for Oil Field Steam Generation. Oil and Gas Journal. June 8, 1981. pp.
129-134.
12. Struthers Thermo-Flood Corporation, Winfield, Kansas. Solid Fuel Fired
Oil Field Steam Generators. January 22, 1981.
13. Reh, L. Fluidized-Bed Processing. Chemical Engineering Progress, Vol.
67, No. 2, February, 1971. pp. 58-63.
14. U.S. Patent No. 4,165,717, Priority 5 September 1975.
15. U.S. Patent No. 4,111,158, Priority 31 May 1976.
16. Matthews, F. T., et al. The Circulating Fluidized-Bed for Utility
Electric Power Generation. Presented at: 1981 Joint Power Generation
Conference, St. Louis, Missouri, October 4-8, 1981.
17. Holighaus, R., and J. Batsch. Overview of the Fluidized-Bed Combustion
Programme of the Federal Republic of Germany. In: Proceedings of the
Sixth International Conference on Fluidized-Bed Combustion, Vol. I.
Atlanta, Ga., April 9-11, 1980. pp. 30-35.
18. Yip, H., W. Rickman, and F. Engstrotn. High-Sulfur Fuel Combustion in a
Circulating Bed. In: Proceedings of the 3rd International Coal
Utilization Exhibition and Conference, Houston, Texas, November 18-20,
1980. pp. 697-714.
19. Engstroin, F. Pyroflow - A Circulating Fluid Bed Reactor for Energy
Production From Biomass. In: Energy From Biomass and Wastes - 4th
Symposium 1980, Ann Arbor Science, Woburn, Mass. pp. 555-566.
20. Engstrom, F. Development and Commercial Operation of a Circulating
Fluidized-Bed Combustion System. In: Proceedings of the 6th
International Conference on Flu-idized-Bed Combustion, Atlanta, Ga. , April
9-11, 1980. pp. 616-621.
21. Pyropower Corporation, San Diego, Calif. Bulletin Nos. PCB-1001 5M
(9/80) and PCB-1001 5M (2/81).
53
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22. Bengtsson, L., et al. Commercial Experience With Circulating
Fluidized-Bed Systems for Cogeneration. Presented at: American Power
Conference, Chicago, 111., April 27-29, 1981. Report PCR-104.
23. Pyropower Corp., San Diego, Calif. Technical Description of Circulating
Fluidized-Bed Combustion Boilers in the Size Range 20,000 Ib/hr to
200,000 Ib/hr Evaporation.
24. Johnson, W. B. Fluidized-Bed Compact Boiler and Method of Operation.
U.S. Patent No. 4,240,377. December 23, 1980.
25. Manaker, A. M., et al. Lurgi Circulating Fluid Bed Pilot Facility Test
Results Using Different U.S. Coals and Limestones. Presented at: 1981
Annual AICHE Meeting, New Orleans, Louisiana, November 8-12, 1981.
26. Berggren, J. C., et al. Application of Chemical and Physical Operations
in a Circulating Fluidized-Bed System. Chemical Engineering Science,
Vol. 35. Pergamon Press Ltd., Great Britain, 1980. pp. 446-455.
27. Stroemberg, L. Combustion in a Fast Fluidized-Bed. Swedish Journal,
April 6, 1979.
28. Harju, R. Description of an Experimental Model for Combustion in a Fast
Fluidized-Bed. Report No. Studsvik/E4—79/72, July 1979.
29. Keairns, D. L., et al. Circulating-Bed Boiler Concepts for Steam and
Power Generation. In: Proceedings of the 13th Inter-Society Energy
Conversion Engineering Conference, San Diego, Calif., August 20-25,
1978. pp. 540-547.
30. Fraley, L. D., L. N. Do, and K. H. Hsiao. Circulating Fluidized-Bed
Boiler. In: Proceedings of the 3rd International Coal Utilization
Exhibition and Conference, Houston, Texas, November 18-20, 1980. pp.
715-722.
31. Pullman Kellog Co. Preliminary Design and Assessment of Circulating-Bed
Boilers. Prepared for Electric Power Research Institute. Report
CS-1426, June 1980.
32. Arthur G. McKee and Company, Cleveland, Ohio. Cost Comparison Study -
100,000 Ib/hr Industrial Boiler. Prepared for the U.S. Department of
Energy under Contract EX-77-C-01-2418, April 16, 1979.
54
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TECHNICAL REPORT DATA
(Pleatr read .'attractions on the reverse before completing)
i REPORT NO.
EPA- 600/7- 82 -051
3.
3. RECIPIENT'S ACCESSION NO,
4 TITLE AND SUSTITLi
Technology Overview: Circulating Fluidized-bed
Combustion
S. REPORT DATE
June 1982
6. PERFORMING ORGANIZATION CODE
1 AUTHO«(S)«
8 PERFORMING ORGANIZATION REPORT NO
Douglas R. Roeck
GCA-TR-81-91-G
10 PROGRAM ELEMENT (*O.
PERFORMING ORGANIZATION NAME AND ADDRESS
rCA/Technology Division
213 Burlington Road
Bedford, Massachusetts 01730
8-02-2693
Task 12
NO.
17. SPONSORING AGENCY NAME AND ADDRESS
EPA, Office of Research and Development
Industrial Environmental Research Laboratory
Research Triangle Park, NC 27711
13. TYPE Of REPO«T AND PERIOD COVE«£D
Task Final; 6/81-2/82
14. SPONSORING AGENCY CODE
EPA/600/13
15 SUPPLEMENTARY NOTES ffiRL-RTP project officer is John O. Milliken, Mail Drop 61,
919/541-7716.
ABSTRACT
rep0rt summarizes the current technical status of circulating fluidized
bed combustion (CFBC). Companies that are involved in investigating this technology
and/or developing commercial systems are discussed, along with system descrip-
tions and available cost information. CFBC is a second-generation FBC system
that is well underway toward commercialization in the U.S. The CFB operates at
higher fluidization velocity, lower mean bed particle size, and higher recirculation
rate than conventional FBC. Probable advantages of CFBC over traditional FBC inc-
lude: more flexibility in fuel selection, reduced number of fuel feed points, higher
combustion efficiency, better calcium utilization, and lower NOx emissions. Poten-
tial process limitations that must still be evaluated, however, include equipment
erosion due to the more severe operating conditions, separation of bed material
from effluent gas, severity of cyclone separation equipment design? and power requ-
irements for process and auxiliary equipment operation. Battelle Development,
Lurgi, and Pyropower are the major companies involved in demonstrating the com-
mercial viability of this process in the U.S. Lurgi and Pyropower are basing their
CFB systems on technology already commercially demonstrated in Europe; after
pilot-proving its process, Battelle is building the first commercial U.S.
KEY WORDS AND DOCUMENT ANALYSIS
DCSCHIPTORS
jj.tDENTIP IEHS/OPSN ENDED T£«MS
c. COSATi i iclil.Croup
Pollution
Combustion
Fluidized Bed Processing
Fluidized Bed Processors
Fluid iz ing
irculation
Pollution Control
Stationary Sources
Circulating Fluidized-
Combustion
2 IB
13H
131
3 DISTRIBUTION STATEMENT
Release to Public
19. SECURITY CLASS
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