Cf rj A U.S. Environmental Protection Agency Industrial Environmental Research
^1 ť Off ice of Research and Development Laboratory
Research Triangle Park, North Carolina 27711
EPA-600/7-77-027
March 1977
FIRST TRIALS
OF CAFB PILOT PLANT ON COAL
Interagency
Energy-Environment
Research and Development
Program Report
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EPA-600/7-77-027
March 1977
FIRST TRIALS
OF CAFB PILOT PLANT ON COAL
by
D. Lyon
Esso Research Centre
Abingdon, Oxfordshire 0X13 6AE
England
Contract No. 68-02-2159
Program Element No. EHE623A
EPA Project Officer: S.L. Rakes
Industrial Environmental Research Laboratory
Office of Energy, Minerals, and Industry
Research Triangle Park, N. C. 27711
Prepared for
U.S. ENVIRONMENTAL PROTECTION AGENCY
Office of Research and Development
Washington, O.C. 20460
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- ii -
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FIRST TRIALS OF 3/4 MWe
C.A.F.B. PILOT PLANT ON CX>AL
Author:- D. Lyon
Work Done By:- D. Lyon, A.W. Ramsden, A.W. Brimble, O.K. Priestnall,
A. Jennings, D. Storms, (see acknowledgement)
November 1976
- iii -
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CONTENTS M
I SUMMARY !
II INTRODUCTION 2
Considerable background of knowledge of CAFB
operation on heavy fuel oil 2
Only limited information is available on extending
CAFB process to run on coal 2
Recently completed Mini-run represents first trials
of 3/4 MWe continuous unit on coal 2
III EXPERIMENTAL 4
Day-time running as opposed to round-the-clock
operation was successfully demonstrated on the
Mini-run 4
New subsystem equipment incorporated since Run 1O
greatly improved operational reliability 4
New analytical system still has some problems to
be ironed out before Run 11 7
IV COAL QUALITY AND SIZE 11
Lignite quality fed to continuous unit was fairly
accurately defined but Illinois No.6 coal quality
less so , 11
Several different coal feed size ranges have been
tested on Mini-run 12
V RESULTS AND DISCUSSION
Both Texas Lignite and Illinois No.6 coal were
successfully gasified on Continuous Unit 14
Gasifier conditions can be expected to be leaner
and cooler on Lignite compared with fuel oil 15
Desulphurising efficiency on coal can be expected
to match that on fuel oil 15
Satisfactory regeneration while gasifying on Lignite
was demonstrated by slowing bed transfer rate 15
Target of 88% Lignite utilization by CAFB process
was approached under conditions far from optimised 18
New Fines Return System reduced burden of lime into
boiler by factor of ten but did little to reduce
the 'fly-ash' during coal gasification 2O
VI CONCLUSIONS 23
VII FUTURE WORK 24
VIII ACKNOWLEDGEMENTS 25
- iv -
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CONTENTS (Cont.d)
IX FIGURES
X APPENDICES I - V
Appendix I - Tables of Illinois No.6 coal and Texas
Lignite Analysis.
Appendix II - Mass Balances for Carbon, Sulphur and Ash
Appendix III - Experimental Results of Mini-run.
Appendix IV - Stone Analyses.
- v -
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- 1 -
I SUMMARY
The information in this report relates to a mini-run- carried
out on the 3/4 MWe continuous CAFB pilot plant during July-August
1976. These tests represent the first step in a 3 year research
and development programme funded by E.P.A. to extend the CAFB
process to operate on coal. This research effort is seen as a
necessary back-up to a 20 MWe demonstration plant to be constructed
in 1977 at San Benito, Texas.
The entire report is based on about 8$ hours of gasification
on Texas lignite and Illinois No.6 coal. Neverthless the results
do represent the best information available to date on coal gas-
ification using the CAFB process.
No major barriers have yet been identified in conversion of
the process from oil to coal. The quality of the gas produced is
similar and the desulphurising efficiency on coal can be expected
to match or exceed that on oil. The target of 88% lignite utiliz-
ation set by Foster Wheeler Corp Ltd for the Texas demonstration
plant is seen as realistic and was approached in the mini-run under
conditions which can be considered far from optimised. Because of
the need for more air to gasify coal the CAFB converted boiler
dimensioned for fuel oil will probably be downrated by 3O% on coal.
Satisfactory regeneration while gasifying on lignite was
demonstrated by slowing the bed transfer rate compared with oper-
ation on fuel oil. This mode of operation does not in any way
impair gasifier performance but may result in the need to control
regenerator temperature for example by steam injection or flue
gas recycle.
The new fines return system appears to have reduced the burden
of lime into the boiler by a factor of ten but did little to reduce
the 'fly-ash' level in the boiler during coal gasification. Further
work in this area is obviously needed.
Successful operation of the pilot plant on an intermittent
basis as opposed to round-the-clock operation was clearly demon-
strated. This opens up the technical possibility of using a CAFB
converted boiler on a peak shaving rather than a base load basis
but obviously the economics of conversion will largely determine
the extent this is practicable.
An extensive programme of work on lignite gasification is
scheduled to begin in Mid November 1976.
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- 2 -
II INTRODUCTION
Considerable background of knowledge of CAFB operation on
heavy fuel oil
A 3/4 MWe pilot plant was built in 197O to study continuous
operation of the CAFB process using high sulphur fuel oil. Essent-
ially this process gasifies and desulphurises heavy fuel oil
producing a clean, virtually sulphur free gas which can be com-
busted in a conventional gas-fired boiler. Since 197O, nine runs
totalling approximately 2,700 hours of operation on fuel oil have
been carried out. In November 1975, a new gasifier/regenerator
unit was built and a run of approximately 3OO hours duration (Run
1O) was carried out by the end of that year. A report on the
findings of Run 10 is currently being written while reports covering
earlier work are available (EPA-65O/2-74-1O9; EPA-65O/2-75-O27b).
The success of the pilot plant studies has led to the first commer-
ical demonstration of the process being built under licence by
Foster Wheeler Development Corp in Texas. This involves conversion
of a 2O MWe boiler currently fired on natural gas and is scheduled
to be completed by mid 1977.
Only limited information is available on extending CAFB process
to run oh coal '
A prime condition imposed by Central Power and Light owners
of the Texas power plant for conversion of their boiler to CAFB was
that the process should be capable of operating on coal. Prior to
the mini-run, information on the operation of the CAFE process on
coal was limited to batch studies carried out on a 7" diameter
reactor. Experimental work is continuing on this unit.
Recently 'completed' Min-Run represents first trials of
3/4 MWe continuous unit on coal
A mini-test run on the 3/4 MWe continuous unit has recently
been completed in August 1976. This run is the forerunner of a
major study of coal gasification (Run 11) scheduled to start
November 1976.
The main objectives of the mini-test were:-
(1) Test all new subsystem equipment incorporated since Run 10
under actual running conditions.
(2) Gasify and regenerate with Illinois No.6 coal and also
if possible lignite selected by EPA for Run 11.
(3) Identify problem areas associated with coal gasification
which may necessitate major structural changes prior to
Run 11 e.g. need for two cell regenerator.
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- 3 -
(4) Carry out tests specifically requested by Foster Wheeler
Corporation i.e.
Test Commercial SC>2 sample probe
Test silicon carbide coal injection needles."
The generation of quantitative information was not a priire
objective of the mini-run but during the final week the unit was
operating sufficiently trouble free for this to be obtained. While
it is not claimed that the system was in any way optirrised the
results presented in this report represent the best information
to date on coal gasification using the CAFE process.
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COOLING CURVE FOR GASIFIER BED AFTER SHUTDOWN
900
800
o 700
o
111
or
OC
111
600
500
400
300
I
I
I
1
8
16 24 32 40
TIME(HRS)
48 56 64 72 80
FIG.I.
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COAL HANDLING SYSTEM
Level
Detector
Solenoid
Valve
| Vibrator
Recorder
Vacuum
Cleaner
Coal
Oiepeneer
Vent
Coal Injector
FIG.2.
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- 4 -
III EXPERIMENTAL
Day-time running as opposed to round-the-clock operation
was successfully demonstrated on the Mini-run
Previous runs on the continuous pilot plant involved round-
the-clock operation of the unit carried out on a shift basis.
However, during the mini-test the unit was run during the day,
shutdown overnight and cooling of the unit was sufficiently slow
to allow it to be restarted the next day without any problems.
Figure 1 shows an example of the cooling curve obtained. Initially
the unit was restarted on heavy fuel oil and the temperature of
the bed material was not allowed to drop below 65O°C. Later,
however, the unit was successfully restarted at 39O°C on coal and
this meant that the unit could be left shutdown and unattended
at weekends and still be successfully restarted.
The flexibility day-time running of the unit allows should
result in manpower savings and more efficient tackling of any
technical problems which may arise during Run 11. The need for
continuous round-the-clock running of the unit to finally prove
the process on coal will still remain but probably for shorter
periods than in earlier runs.
Perhaps the most important point about the1 method of operating
the unit during the mini-run is its implications for the Texas
demonstration plant. The thermal inertia of the bigger unit in
Texas will undoubtably be greater resulting in a longer time lag
between shutdown and the need to restart. This opens up the poss-
ibility of using a CAFB converted boiler on a peak shaving rather
than base load basis. Further work to explore the flexibility of
the unit in this area is planned for Run 11.
New subsystem equipment incorporated since Run 10 greatly
improved operational reliability
Several new features were incorporated since Run 1O to over-
come problems of equipment reliability during that run. An
important objective of the mini-run was to test these systems
under actual running conditions and identify areas where improve-
ments could be made.
Coal feed system
After Run 10 was completed on fuel oil the limiting factor on
testing the unit on coal was the absence of a coal feed system.
To overcome this the existing limestone handling system was modi-
fied to handle coal. To accommodate the higher feed rates this
entailed, several improvements had to be made and Figure 2 shows
a schematic diagram of the system which was evolved.
The system was fully automatic, the sequence being controlled
by two micro-switches fitted to the weigh-cell recorder. When the
low limit switch was actuated it operated a solenoid valve which
admitted compressed air to the actuators of valves V]_, V2 and
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BROKEN SILICON CARBIDE COAL INJECTOR NEEDLE
FIG.3.
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VIEW OF GASIFIER DISTRIBUTOR SHOWING
PIECES OF SILICON TUBE
FIG. 4.
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Valve Vo opened whilst valves YI and V2 were shut but a flow
restrictor in the line to V$ ensured that Vi and Ľ2 closed before
YS opened. This enabled the pressure in the lock hopper to rise
and prevented a sudden fall in pressure within the coal metering
vessel while it was being filled with coal. Such a surge'was
found during testing to cause blockages in the coal injector
because the pressure differential between the feed system and the
gasifier was momentarily reversed. When enough coal had entered
the weigh hopper to activate the high limit switch on the recorder
this deactivated the solenoid valve and valve V% shut whilst valves
Vi and V2 opened. In this case a flow restrictor was used to
delay the opening of V]_ and V2 until 73 was shut. A third rricro-
switch controlled the power to the vacuum cleaner and was made by
the closing of valve 73. This ensured that at no time was the
vacuum cleaner switched on when valve 73 was open. A level
detector switched off the vacuum cleaner when the lock hopper was
filled with coal. Should the level detector not be actuated with-
in a set time after the actuation of the high limit switch then
an alarm indicated that the coal dispenser was empty and this was
replaced.
During the mini-run the automatic coal handling system worked
well but some problem was experienced with the coal injector. In
response to Foster Wheelers wish to test self-bonded silicon car-
bide as an injector material a sample tube supplied by Carborundurr
Ltd. was used. This tube penetrated the gasifier wall at a posit-
ion 20" above the distributor and was angled downwards so that it
extended into the middle of the gasifier a few inches above the
distributor. Unfortunately, during the course of the mini-run
tests the brittle silicon carbide tube snapped off at the gasifier
wall. Figure 3 shows the remains of the silicon carbide tube
whereas figure 4 shows pieces of the broken tube found in the
distributor pit.
The information on coal gasification found in this report
relates to a period of operation after the coal injector was broken.
Consequently the feeding of the coal at a position 2O" above the
distributor and flush with the wall of the gasifier cannot be
considered optimum conditions and hence the results presented should
be viewed in such a light.
In the forthcoming Run 11 tests a KT-silicon carbide injector
supplied by Foster Wheeler will be tried and also injection of the
coal into the distributor pit via a duct in the distributor. In
order to be able to feed both limestone and coal simultaneously
to the unit a second coal handling system similar to the existing
design but incorporating a screw feeder instead of a vibrator is
to be constructed before Run 11.
Fines Return System
A major source of problems during Run 1O and previous test
runs has been the drainage of fines from the gasifier cyclones and
their subsequent re-injection into the gasifier bed. During Run
1O a lock-hopper arrangement was used, the valves being operated
on a cyclic sequence. Trouble was experienced with these valves,
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FLOW DIAGRAM FOR FINES RETURN SYSTEM
Key to symbols f
(/) Pressure gauges, 0-100" H20
Ľ
Ł><] Pneumatically actuated valves
Metallic flexible hose
N2 purge
Hopper with
fluidised
bed
Level Control
Eductor
\
N2
"purge
Nozzle
Nitrogen supply
through rotameters
and 3-equispaced
nozzles in the
hopper wall
Nz purge
Gasifier
Low
Efficiency
Cyclone
/
Hopper
Pressure
jS Switches
I
High
Efficiency
VCyclone
Water
Jacket
Drain
Keg
Vent
bleed
FIG.5.
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- 6 -
which ran at a high temperature and were consequently poorly lub-
ricated. Also all of the fines were re-injected into the gasifier
and continued use of the system may have led to problems of ash
build-up while operating the unit on coal.
With these points in mind and also the need, due to restricted
height, to positively inject the fines in the Texas unit a valve-
less system was designed with the following attributes
(a) Provision for the removal of large chunks from the system
which may break loose from the cyclone walls during burn-
out .
(b) Provision for fractionating the fines so that a coarse
fraction may be re-injected whilst a finer fraction may
be discarded.
(c) Provision for re-injecting the coarse fraction of fines
at a position remote from the gasifier cyclones and near
the bottom of the gasifier bed.
A schematic layout of the new system is shown in figure 5.
Fines from the two gasifier cyclones enter a Y-shaped duct which
drains into a pot the contents of which may be fluidised by means
of radially disposed gas nozzles. When the pot is not fluidised
the fines accumulate in the Y-shaped duct but when fluidising gas
is provided the contents of the duct drain into the pot and over-
flow a weir into an eductor, being conveyed to two sirall cyclones
in series, by a circulating stream of gas supplied by a small blower
The fluidisation of the drain-pot is intermittent and is cut out
when the height of solids held in the Y-shaped duct falls below a
set level. In this way a seal is maintained and it is possible to
recirculate fines at a chosen pressure.
The new fines return system operated successfully throughout
the mini-run with only a few minor teething problems. Soire improve-
ments to the system were made during the run and a few more are to
be incorporated before Run 11. Essentially this new system repre-
sents a considerable improvement in terms of reliability compared
with previous systems.
Fractionation of the fines is made possible by having the 1st
fines return system cyclone relatively inefficient compared with
the second and thus it allows finer material to pass through and
be collected in the second. No attempt was made during this mini-
run to explore and optimise the partition between the two cyclones
but this is obviously necessary and should be investigated in Run 11
An analysis of the performance of the fines return system in
reducing the dust losses to the boiler can be found in the discuss-
ion section of this report.
Flue Gas Recycle System
The bag filter which was incorporated in the flue gas recycle
system for Run 1O was replaced by a high efficiency cyclone and the
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- 7 -
dust content of the incoming flue gas was reduced by moving the
take-off point downstream of the stack cyclone. The recycled flue
gas was fed directly into the fluidised bed via four 1 11/16"
diameter firebird blue tubes.
This system was tested during the mini-run for several hours
while gasifing on fuel oil and no problems were experienced. No
change in the system is proposed for Run 11.
Bed Transfer System
To avoid problems with poor bed transfer experienced in Run
1O two improvements were carried out:-
(a) The rodding ports were enlarged
(b) A N2 purge was introduced into the regenerator and
gasifier during shutdown with a sulphided bed to avoid
agglomeration of bed material contacted with air.
No problems with the bed transfer system were experienced
during the whole of the mini-run. Any sluggishness experienced
when transferring relatively cold beds was counteracted by increas-
ing the transfer nitrogen pressure. To avoid free-wheeling of
the transfer system the horizontal pulser injectors were progress-
ively moved into the transfer pockets. Good control was obtained
with the injectors protruding approximately 14" into the pockets.
Minor Modifications
Several minor modifications to the unit were made which also
proved successful during the mini-run:-
(a) New main gasifier air blower.
(b) Tapered nozzles were fitted to the gasifier and regen-
erator pressure tappings to increase the bleed velocity
and inhibit blockage.
(c) All manometers were replaced by differential pressure
gauges.
(d) Elimination of kerosene combustion from warm-up procedure
New analytical system still has some problems to be ironed
out before Run 11
With the exception of the Wostoff analyser which was re-
tained as a back-up low SC>2 meter, the entire analytical system
was replaced by new equipment supplied by Hartman and Braun.
In addition a new stack gas sampling line was installed downstrean.
of the point at which the regenerator tail gas is vented to the
stack, at a position where the SC>2 content of the stack gas should
be uniform over the cross sectional area of the stack. This was
incorporated to enable a better sulphur balance to be obtained.
A schematic diagram of the analytical system is shown in Figure 6.
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ANALYTICAL SYSTEM (SCHEMATIC DIAGRAM)
, , From
(Stack
STACK
Thermocouple
^Heated Filter
I _tf-r^
Vent
BOILER
FLUE
GAS
Thermocouple
Moisture
Alarm
<
I
Rotameter
7 y __
Thermocouple
r
I SQ2(0-2000ppm) Oa (0-21%)
Cooler
REGENERATOR
Filter
..X ^^J-
TIT
Drain Water
I
(0-IOOOppm)(0-20%) (0-21%)
Wostoff
COAL
HANDLING _SL
Thermocouple
Filter
Pump
(0-
lOOOppm)
A
S02
High
C0t
o,
a-KD-X
FLUE
GAS
RECYCLE
Trace heated Filter Cooler
T^-f-TDrsCI^
0-15%) (0-20%) (0-21%)
Alarm
Thermocouple
10-^!%}
FIG. 6.
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- 8 -
Both the Wostoff analyser and the Hartman and Braun infrared
analyser simultaneously monitored the S02 emission from the boiler
during the mini-run. Table 1 compares the averaged daily results
obtained from both instruments. This shows the Wostoff consis-
tently read higher than the Hartman and Braun analyser by approx-
imately 1O%. This would give a reasonably small difference in the
measured % SEE of about 3% and therefore is acceptable. Part of
the discrepancy between the two instruments may be due to the slow
response of the Wostoff and for day running when readings were
taken at short intervals of time the fast response infrared instru-
ment is preferred.
TABLE 1
Comparison of Wostoff and Hartman and Braun SO2
Analysers during mini-run
Average Average
Run No. of Hartman & Braun Wostoff A_
Day Readings (ppm) (ppm)
i
1 5 367 392 25
2 10 309 363 54
3 9 287 316 29
MEAN 8 321 357 36
Boiler COo
Table 2 compares the analytical measurements of boiler C02
with the calculated values based on the fuel consumed. During days,
2 and 3 the measured values were consistently lower than the cal-
culated values both with oil and coal. In the case of coal the
calculated values incorporate a correction factor for the percent-
age coal utilised (see page 2O). Boiler C02 is a useful measurement
particularly in the case of coal gasification since it provides a
more direct route to measure utilization in the boiler than the
calculation based on boiler Š2- However, because of the obvious
inaccuracy of the measured values of boiler OC>2 they were not used
in subsequent calculations. However, work is in hand in improve
the reliability of this measurement before Run 11.
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- 9 -
TABLE 2
Comparison of Measured and Calculated Values
for Boiler COg
Average Average
No. of Measured Predicted
Run day Readings Fuel CQ2 (Vol %) CO? (Vol %)
1 2 Oil 11.7 10.2
2 5 Oil 6.6 9.O
2 4 Coal 6.9 1O.3
3 5 Oil 7.3 9.0
3 4 Coal 5.9 8.4
Sulphur Balance (gaseous streams)
At equilibrium conditions with sulphur levels on both gasifier
and regenerator bed material constant then the sulphur added to the
system from the fuel should balance the sulphur found as SO2 gas in
the exit streams i.e. boiler flue and regenerator off-gas. In other
words the sum of these two measurements expressed as a percentage of
the feed sulphur should equal 100%. However, it is possible to
operate the unit for short periods of time under conditions where
sulphur is being stripped from the stone (i.e. giving values greater
than 1OO%) or sulphur is being laid down on the stone (i.e. values
lower than 100%).
During the irini-run this sulphur balance measurement could be
calculated via three independent routes i.e.
(a) Stack S02 analysis (Method A)
(b) Boiler flue and regenerator off-gas analysis (Method B)
(c) Solids analysis for sulphur (Method C).
Table 3 compares the averaged sulphur balances obtained via
all three routes. During days 1 and 2 when the regenerator was
largely inoperative because of high carbon levels on the stone
all three methods appear to give good agreement. However since the
regenerator off-gas was low in S02 all this meant was that the
analyses of the boiler flue and stack SO2 were largely in agreement.
During day 3, however, when the contribution to the sulphur balance
by method B from the regenerator off-gas S02 analysis was high the
agreement was poor particularly during coal gasification. Obviously
the analytical measurement of regenerator SO2 was spurious during
the final day and this should be investigated before Run 11.
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Run day
1
2
2
3
3
- 1O -
TABLE 3
Comparison
of Sulphur
Balances (
in exit gases)
by three Independent Routes
No. of
Readings
3
5
3
4
4
Fuel
Oil
Oil
Coal
Oil
Coal
Sulphur
Method A
45.5
46.0
56.6
146
291.6
Balance (% of Feed)
Method B Method C
42.5
49.8
60.3 66.6
85 . 3 105 . 8
142 15O.4
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- 11 -
IV COAL QUALITY AND SIZE
Lignite quality fed to Continuous Unit was fairly accurately
defined but Illinois No.6 coal quality less so
Two different coals, Illinois No.6 and Texas Lignite were
tested on the continuous unit. The Lignite chosen was that pre-
sently earmarked for use in the Texas Demonstration Plant and will
also be studied exclusively on Run 11.
A major problem with any coal studies is the variability of
coal quality. Consequently, in order to obtain representative coal
analysis and hence realistic mass balances (see Appendix II) periodic
sampling of the coal actually fed to the unit was carried out and
sent for analysis. A complete listing of the sample analyses
obtained is contained in Appendix I, Tables I and II while Table 4
below gives the average values for each coal.
TABLE 4
Analysis of Texas Lignite and Illinois No. 6
fed
to continuous unit
Illinois No. 6
Moisture
Ash
Carbon (corrected)
Hydrogen (corrected)
Sulphur ( tot al )
Nitrogen
Oxygen + errors (by
difference)
Gross calories/GM
Gross BTU/lb
CX>2 %
ACTUAL
4.63
7.36
70.3
4.61
1.78
1.44
9.85
6936
12486
0.16
DRY BASIS
-
7.8
73.64
4.83
1.9
1.5
1O.4
726O
13O68
-
Texas
ACTUAL
14. 02
18.5
51.2
3.6
O.82
l.O
1O.9
5OO4
9OO7
O.51
Lignite
DRY BASIS
-
21.5
59.5
4.2
O.95
1.2
12.6
5817
1O47O
-
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- 12 -
Compared with Illinois No.6, lignite has a higher moisture and
ash content but a lower sulphur content. Actually the moisture
content quoted (14 wt%) relates to the level fed to the unit while
that analysed prior to grinding and some drying was 35%. Seven
lignite samples and three Illinois No.6 coal samples were taken
during the periods of operation and the standard deviation in the
analysis results listed in Table 5 gives a measure of the uniforirity
in quality of the coals.
TABLE 5
Standard Deviation of Analysis Results from Lignite
and Illinois No. 6
Measurement Lignite Illinois No. 6
wt %% Standard Deviation % Standard Deviation
Carbon 3.5 1O.5
Hydrogen 4.1 8.7
Sulphur 15.5 20.O
Ash 5.3 '51
In assessing the validity of any mass balances which are pre-
sented in this report the standard deviations presented in Table 5
are of paramount importance. Obviously in the case of lignite the
quality is fairly accurately defined and reasonably precise mass
balances should be possible. However, the numbers generated for
gasification on Illinois No.6 should be assessed in the light of the
low accuracy in defining the feed quality.
Several different coal feed size ranges have been tested on
Mini-run
The gasification of coal introduces a new variable not relevant
with fuel oil gasification namely feed particle size. Obviously,
the more finely divided the coal the larger the surface area and
hence the more rapid the gasification. On the other hand, small
coal particles are likely to be elutriated more rapidly fronr the
bed and hence the residence time available for gasification should
be shorter. In practice, there may well be an optimum feed size
for good gasification. Foster Wheeler have stated a preference for
feeding coal ground to 4" down and one of the tasks in future coal
runs will be to specify coal sizes acceptable for operation by the
CAFB process. For the mini-run, coal was ground to 1/8" down and
subsequently sieved into various size ranges. Table 6 lists the
feed sizes used for both Lignite and Illinois No.6 coal. In future
references to coal feed sizes in this report the general descript-
ion given in Table 6 will be used.
-------
- 13 -
TABLE 6
Coal Feed Particle Size Distribution (wt %)
Sieve Size in Microns
Coal
Lignite
Lignite
Lignite
Illinois
M/-, R
General 32OO 28OO 14OO 118O
Description 2800 1400 1180 850
8OOy down O O O O
14O5y down 0 0 0.1 2.6
1/8" down 3.9 4.3 4.9 9.8
14O5y down 0.0 0.8 O.8 1.3
85O 6OO 250 15O ,nn
6OO 25O ISO 1OO
5.5 37.7 32.6 4.4 19.7
9.5 46.8 15.6 5.1 2O.3
10.5 25.5 11.3 5.O 25
10.7 31.8 15. O 5.9 33.7
-------
VIEW OF STACK DURING
LIGNITE GASIFICATION
FIG. 7.
-------
- 14 -
V RESULTS AND DISCUSSION
Both Texas Lignite and Illinois No.6 coal were successfully
gasified on Continuous Unit
Two different coals, Illinois No.6 and Texas Lignite were
gasified for the first tiire on the continuous unit during the
mini-run. Initially the unit was gasified on heavy fuel oil and
gradually changed over to coal gasification by slowly increasing
the coal feed rate and backing off fuel oil. Subsequently, however,
startup entirely on coal was found to be equally efficient and
trouble-free and this method was used in later experiments.
Visual inspection of the flame through a viewing port at the
back of the boiler showed a stable, yellowish, smoke-free flame
indistinguishable from that produced from heavy fuel oil gasificat-
ion. Figure 7 shows one of several photographs of the boiler
stack taken during coal gasification which shows a clean flue gas.
Comparison of the gasifier gas quality obtained from heavy
fuel oil and both of the coals tested are shown in Table 7. Apart
from a tendency towards a higher proportion of simple organic
molecules such as methane in the product gas from fuel oil and a
lower quantity of hydrogen gas, the gases are remarkably similar.
TABLE 7
Comparison of Gasifier Gas Quality from
Fuel Oil and Coal
Gasifier Fuel Heavy Fuel Illinois No.6 Texas
Oil Coal Lignite
Nitrogen + inerts 58.4 59.2 59.O
Carbon Monoxide 10.2 12.2 12.2
Carbon Dioxide 10.2 9.9 12.1
Methane 7.7 4.2 2.2
Ethylene 5.0 0.8 O.7
Ethane O.I 0.1 0.1
Hydrogen 8.4 13.6 13.7
In total approximately 8i hours of continuous gasification
were carried out but quantitative information is confined to three
periods of gasification totally slightly under five hours. In
general reading's were taken every 30 minutes and a complete list-
ing of the important measurements is contained in Appendix III,
Table I. In the present discussion the results of all three periods
of gasification will be looked at together and discussed under four
headings, gasification, desulphurisation, regeneration and combust-
ion efficiency.
-------
- 15 -
Gasifier conditions can be expected to be leaner and cooler
on Lignite compared with fuel oil
Table 8 summarises the salient operating conditions for the
three periods of gasification.
No attempt was made to explore different operating conditions
and consequently the conditions for all three periods of gasificat-
ion were relatively similar. The difference in gasifier temperature
between Illinois No.6 and Lignite is due entirely to the cooling
effect of the higher ash and moisture content for the Lignite feed.
No fresh bed material was added during any of the periods of gas-
ification which were carried out on separate days. The drop in
bed depth shown in Table 8 is almost entirely due to bed material
falling back through the gasifier distributor while the bed was
slumped overnight and little or no change in bed depth was noted
when gasifying on oil and a slight increase in bed depth on coal.
The air/fuel ratio in the gasifier for both coals was similar and
compares with typical figures for heavy fuel oil of 20-23% of
stoichiometric combustion. This reflects the need in the case of
coal for more oxidation and less cracking compared with fuel oil.
While the effect of air/fuel ratio has still to be explored it is
unlikely that the gasifier will be operated successfully on coal
at air/fuel ratios significantly richer than 3O% of stoichiometric
combustion. This means that CAFB converted bodler dimensioned for
fuel oil will be derated in the region of 7O% on coal.
Desulphurising efficiency on coal can be expected to match
that on fuel oil
Table 9 summarises the more detailed information on sulphur
removal efficiency (% SRE) found in Appendix III, Table I. This
compares the mean % SRE for the three gasification periods on coal
with the expected result for heavy fuel oil under the same con-
ditions. Since % SRE for fuel oil in the region 8O-9O% can be
attained under specific operating conditions, the conditions the
unit was run with coal were far .from ideal from a desulphurising
point of view. Nevertheless, the results do show that coal can
be desulphurised as efficiently if not more efficiently than fuel
oil under the same conditions.
Also included in'Table 9 are the SC>2 emissions calculated in
terms of Ibs S02 per 106 BTU for each of the gasification periods.
This shows the final period of gasification on 1/8" down Lignite
was better than the New Source Performance Standard of O.6 Ibs S02
per 106 BTU (EPA).
Satisfactory regeneration while gasifying on Lignite was
demonstrated by slowing bed transfer rate
In adapting the CAFB process to operate on coal the part of
the process expected to cause most problems was the regeneration
step. Two problems were anticipated:-
(1) At. high carbon levels on the lime, regeneration does not
take place because the oxygen in the air fed to.the
-------
TABLE 8
Summary of Gasifier Operating Conditions
Duration of
Gasification
( hours )
1.0
2.25
Coal
(type & size)
Illinois No. 6
(1405p down)
Texas Lignite
(8OOy down &
1405 down)
Gasifier Gasifier
Temperature bed depth
O°C (inches).
970 42
896 39
during Mini -run
Gasifier
bed velocity
(ft/sec)
3.7
3.5
on Coal
Air/Fuel
Fresh bed Ratio
feed (Ibs) (% Stoich)
0 30.3
0 32.2
i
M
as
i
1.5
Texas Lignite
(1/8" down)
895
35
3.5
31.6
-------
TABLE 9
Summary of Desulphurising Performance during Mini-run on Coal
Duration of
Gasification
( hours )
1.0
Coal
(type & size)
Illinois No. 6
(1405p down)
Mean
% S.R.E.
on coal
74.8
Expected Result
on -oil (% SHE)
73.8
SOo Emission
(Ib SC-2 per 10^ BTU)
0.73
Texas Lignite
2.25 (800y down & 64.0 68.5 0.76
1405y down) .
l * Texas Lignite R2 4 67 2 o 42
1.5 ,, 82.4 67.2 U.4
-------
- 18 -
regenerator preferentially attacks the carbon to the
exclusion of the sulphur, resulting in an off-gas con-
taining high concentrations of CX)Ł and low SO2-
(2) At the high operating temperatures necessary for Tegen-
eration (>1050°C) some fusion of ash particles from the
coal feed may cause agglomeration to occur in the bed
or alternatively coat the lime particles so as to irake
them inactive to regeneration.
It was expected that both these problems might dictate the
maximum coal feed particle size in the gasifier since carbon and
ash levels in the bed would be expected to be higher with a larger
particle feed.
Table 1O summarises the regenerator operating conditions
during the periods of gasification on coal. During the first two
periods of gasification little attempt was made to bring the
regenerator into action and consequently the high carbon level on
the stone rendered the regenerator virtually inactive. In order
to counteract the high carbon levels on the stone the bed transfer
rates were reduced during the final period of gasification and
effective regeneration was made possible. This result is par-
ticularly encouraging since it was achieved during gasification
with the largest particle size tested. It implies that Lignite
sized at 1/8" down may well be eminently suitable for the CAFE
process and suggests the need to explore larger coal feed sizes
in Run 11 in order to define the upper limit on coal feed size
which still avoids problems in the regenerator.
Two independent techniques were used to measure the bed trans-
fer rate:-
Transfer Rate (Ibs/hr)
(a) From sulphur balance in Gasifier 114.2
(b) From carbon balance in Gasifier 135.6
This should be compared with figures of 400-60O Ibs/hour normally
encountered with oil gasification. One consequence of the lower
transfer rate is the need to operate with high sulphur levels on
the bed material. For example the sulphur level in the gasifier
during the period under discussion was 9.3 wt%. Another result
of the low bed transfer was a high temperature in the regenerator
and the possible need to cool either by flue gas or steam inject-
ion. This aspect of the problem needs to be further explored in
Run 11.
Target of 88% Lignite utilization by CAFB process was
approached under conditions far from optimised
Perhaps the most important question to be answered with coal
gasification is how much coal is actually gasified and burned in
the boiler. This is not such an easy question to answer as it
first appears particularly when dealing with comparatively short
-------
TABLE 1O
Summary of Regenerator Operating Conditions during Mini-run on Coal
Duration of
Run (hours)
1.0
2.25
Coal Type
fed to
gas if ier
Illinois 'No. 6
(14O5y down)
Texas Lignite
(80Oy down &
14O5y down)
Regenerator
Teirperature
C
1O7O
1O75
Regenerator
Bed Depth
(inches)
52
37
Regenerator
Bed Velocity
(ft/sec)
6.1
7.1
Regenerator Output
(% of Feed)
2.7
24.3
1 5 Texas Lignite 1Qfl2 44 6 fi 124 4
1.0 (1/8,, dQWn) 1092 44 6.8 124.4
-------
- 2O -
periods of gasification when full equilibrium conditions have not
been established.
Provided the following information is available the weight of
fuel combusted in the boiler can be calculated:-
(a) Total air fed to the boiler.
(b) Oxygen concentration in flue gas.
(c) Carbon/hydrogen ratio of fuel.
An alternative method involves the measurement of boiler CC>2 but
these readings were shown to be inaccurate (see page 9) during
the mini-run. In order to obtain an accurate measurement of the
boiler air the unit was calibrated on fuel oil for several hours
and the air supply left untouched on transfer to coal gasification.
The carbon/hydrogen ratio of the gasifier product gas was
assumed to be identical to the carbon/hydrogen ratio of the coal
as a first approximation. However, there was some indication from
the product gas analysis shown in Table 7 that some hydrogen enrich-
ment occurs. Nevertheless this should not significantly alter the
conclusions regarding coal utilization and hence for the purposes
of this report was ignored.
Table I in the Appendix III lists the percentage of the coal
combusted in the boiler calculated in this way. Table II sumrr.a-
rises the results for the three periods of gasification. Carbon
balances presented in Appendix II show that some of the coal not
combusted in the boiler can be accounted for by an increase in bed
carbon in the gasifier and fines return system. The final column
in Table II corrects for this and gives the % coal utilised during
each of the periods of gasification. Unfortunately, in the case of
gasification with Illinois No.6 coal the change in bed carbon was
not recorded.
The overall % coal utilised for the two periods of Lignite
gasification achieved under conditions which can be considered far
from optimum was 87% which compares favourably with the 88% coal
utilisation target set by Foster Wheeler for the Texas Demonstrat-
ion plant run on Lignite.
New Fines Return System reduced burden of lime into boiler by
factor of ten but did little to reduce the 'fly-ash' during
coal gasification
Prior to each period of coal,gasification the unit was run for
several hours on fuel oil and Appendix III, Table II gives the
results of these tests. Analysis of solids during oil gasification
was also carried out and this is listed together with the coal data
in Appendix IV.
-------
- 21 -
TABLE 11
Average % Combustion Efficiency in Boiler during
Coal Gasification
Duration of Average % Average
Gasification Coal Combustion % Coaf
(hours) (type & size) Efficiency Utilised
, n Illinois No. 6
i'° (1405y down)
Texas Lignite
2.25 (8OOy & 14O5y 88.8 89.0
down)
Table V, Appendix II gives a solids inventory for the period
of oil gasification on day 3. Throughout this period the material
collected at the various exit streams was high in ash and carbon
despite the fact that no ash was being added to the system. Table
12 gives the proportions of ash, carbon and lime (by difference)
found at the various sources.
The only explanation for this is that these 'fly-ash' particles
were generated during the previous day's gasification on coal and
were being slowly elutriated from the gasifier bed. This implies
that the carbon on these particles was virtually inert to oxidation
in the gasifier. At 3.112O the carbon content of the bed totalled
24 Ibs and this was probably made up of carbon coating the lime
particles together with discrete ash/carbon particles. Since at
the end of the oil period 20 Ibs of carbon was recovered as ' fly-
ash' in the exit streams from the gasifier the implication is that
little of the carbon was present as carbon on lime particles but
that the majority was associated with the ash in the bed. This can
be easily confirmed by analysing the various sieve fractions of the
bed material during this period of operation. Scrutiny of the stone
analysis from the regenerator bed particularly for the period of
coal gasification on day 3 indicates that these 'fly-ash' particles
although virtually inert to oxidation in the gasifier cannot be so
in the regenerator.
Another interesting aspect of this period of oil gasification
is the lime losses from the system. Table V, Appendix II shows
that during this period the lime losses totalled 12.9 Ibs for the
3 1/3 hour period i.e. 4 Ibs/hour. This compares favourably with
a figure of approximately 6 Ibs/hour for a period of 68 hours gas-
ification during Run 10 with no limestone make-up. The significant
difference in this case however is that 9O% of the lime is captured
in the 2nd cyclone of the new fines return system (see Table V,
Appendix II). Neglecting for a moment the 'fly-ash' generated
-------
- 22 -
TABLE 12
Analysis of Solids from Exit Streams of Gasifier
(Period 3.112O-3.144O)
Source
Time
Carbon
(wt %)
Ash
(wt %)
Lime
(wt %)
Stack KO
Stack cyclone
Boiler Back )
& Sides )
Regenerator )
Cyclones )
Fines Return
(2nd cyclone
3.1140
3.134O
3.1140
3.1340
3.1140
3.134O
3.1140
3.134O
3.1120
3.1340
3.1420
48
51
46
38
53
44
52
34
45
28
27
46
44
50
53
38
38
48
52
42
27
28
4.7
3.7
3.3
7.1
7.9
16.1
1.8
11.3
11.2
41.7
41.3
from the coal this means that under purely oil gasification con-
ditions the dust burden into the boiler can be reduced by a factor
of ten by incorporation of the new fines return system.
During the periods of coal gasification few of the 'fly-ash'
particles were recovered in the 2nd cyclone of the fines return
system. This was probably because a large quantity were not in
fact captured by the gasifier cyclones and hence were not avail-
able to the fines return system. Obviously a move towards larger
coal feed particle size will improve this situation but it may
also be necessary to improve the efficiency of the gasifier cyclones
perhaps by operating the unit with one cyclone instead of two as
at present.
-------
-23-
VI CONCLUSIONS
The conclusions which are presented below are entirely based
on about 8% hours of gasification on Texas Lignite and Illinois
No.6 coal carried out on the 3/4 MWe continuous pilot plant and
therefore may well be subject to some modification when more in-
depth studies are carried out. Nevertheless the results do
represent the best information available to date on coal gasificat-
ion during the CAFE process and must be viewed in that light.
No major structural changes in the existing pilot plant
are necessary before Run 11. A new coal feed system
similar to the existing design is considered desirable to
allow both coal and limestone to be fed simultaneously
to the unit if and when this is necessary.
Both Texas Lignite and Illinois No.Scoal can be gas-
ified using the CAFB process to produce a clean, virtually
sulphur-free gas which can be fired in a conventional gas
boiler.
Target of 88% Lignite utilization set by Foster Wheeler
for the Texas Demonstration plant appears to be realistic.
This figure was approached in the mini-run under con-
ditions far from optimised.
The desulphurising efficiency of both coals can be ex-
pected to match or exceed the performance obtained on
fuel oil under similar operating conditions. Flue gas
S02 emission levels better than the New Source Perfor-
mance Standards of 0.6 Ibs SO2 per 1Q6 BTU (E.P.A.) were
achieved with 1/8" down Lignite.
A CAFB conversion boiler dimensioned for heavy fuel oil
may well need to be downrated by approximately 30% on
coal. This arises from the higher air/fuel ratios
necessary in the gasifier when operating on coal.
Satisfactory regeneration of bed material while gasifying
on Lignite can be achieved provided the transfer rate
between gasifier and regenerator is comparatively slow.
This mode of operation does not adversely affect gasifi-
cation or desulphurisation but may result in the need to
cool the regenerator for example by steam or flue gas
injection.
An upper limit on coal feed particle size has not been
determined but gasification and regeneration on 1/8"
down was successfully demonstrated.
' Intermittent operation of the pilot plant as opposed to
round-the-clock operation was successfully demonstrated.
The unit was successfully restarted after a shutdown of
3 days by injecting coal into the bed fluidised at 39O°C.
The new subsystem equipment incorporated since Run 10, in
particular the valve-less fines return system, greatly
improved operational reliability.
-------
- 24 -
The removal of fines from the 2nd. .cyclone of the new fines
return system should reduce the burden of lime fines into
the boiler by a factor of ten but modification either to
the gasifier cyclones to improve their efficiency or the
move to larger coal feed particle sizes may be necessary
to reduce 'fly-ash' in the boiler.
VII FUTURE WORK
The work presented in this report represents only the start
of a major exercise to discover the important features of coal gas-
ification with the CAFB process. Listed below are only a few of
the many avenues which need to be explored before this work can
move into a commercial situation with any degree of confidence.
Explore the effect on gasification, desulphurisation and
regeneration of operating variables such as bed depth,
bed velocity, bed temperature, air/fuel ratio, added
water etc.
Explore the effect of coal feed particle size and if
possible demonstrate the feasibility of operation with
i" down Lignite.
Determine the constraints of intermittent operation of
the unit.
Explore the limitations on regenerator performance of
various carbon and ash levels on the bed material.
Determine optimum conditions for maximum Lignite utiliz-
ation in terms of boiler efficiency.
Compare coal needle injection with injection directly
into the distributor pit. Assess the suitability of
self-bonded silicon carbide as injector material.
Explore distributor nozzle design to prevent bed material
falling back under slumped bed conditions.
Determine contribution of fines return system to com-
bustion efficiency and coal utilization. Explore methods
of improving 'fly-ash' capture by the 2nd cyclone of the
fines return system.
Explore the possibility of coarser gasifier beds and the
need for a fines return system at all with oil gasificat-
ion.
-------
- 25 -
VIII ACKNOWLEDGEMENTS
Work on the CAFB pilot plant is of necessity a teair effort and
without the contribution of each and everyone of the CAFB section
the pages in this report would be blank.
Those not mentioned on the front cover of this report but who
also made their contribution to the team effort were contractors
R. Barbour and F. Rolph. Also the work carried out by Service
Division i.e. workshop, electrical, analytical, site contractors
is also gratefully acknowledged.
-------
- 26 -
APPENDIX
-------
TABLE I
Analysis of Illinois No 6 Coal Feed to Continuous Unit
Moisture
Ash
Carbon (Correc-
ted)
Hydrogen
(Corrected)
Sulphur (Total)
Nitrogen
Oxygen & Errors
($jr Difference^)
Gross Calories/
GM.
Gross BTU/l'b
co2#
A.R.
7.12
10.42
63.56
4.21
2.03
1.20
11.46
6155
11,080
2.4
DRY
-
11.22
68.44
4.53
2.19
1.29
12.33
6625
11,925
-
A.R.
2.14
3.18
78.19
5.02
1.37
1.71
8.39
7780
14,005
0.32
DRY
-
3.25
79.9
5.13
1.40
1.75
8.57
7950
14310
-
A.R.
4.64
8.48
69.21
4.61
1.95
1.40
9.71
'6875
12,375
0.16
DRY
-
8.89
72.58
4.83
2.05
1.47
10.18
7205
12,970
-
NOTE: A.R. = As received
-------
TABLE II
Analysis of Texas Lignite Feed to Continuous Unit
Moisture
Ash
Carbon
(Corrected)
Hydrogen
(Corrected)
Sulphur (Total)
Nitrogen
Oxygen AErrors
(by Difference)
Gross Calories /
GM
Gross BTU/lb
co2#
A.R.
14.15
19.72
49.66
3.53
0*80
0.94
11.18
4980
8965
0.5
DRY
-
22.97
57.87
4.11
0.93
1.10
13.02
5800
10440
-
A.R.
15.78
17.03
50.38
3.59
0.83
1.04
11.35
4865
8755
0.78
, DRY
-
20.22
59.82
4.26
0.99
1.23
13.48
5775
10395
-
A.R.
11.68
17.43
53.57
3.80
0.88
0.91
11.73
5210
9380
0.29
DRY
-
19.73
60.65
4.30
1.00
1.03
13.29
5900
10620
-
A.R.
16.70
19.16
48.64
3.39
0.76
1.15
10.2
4710
8480
0.5
DRY
23.0
58.39
4.07
0.91
1.38
12.25
5650
10170
-
A.R.
11.38
19.13
52.52
3.73
0.81
1.06
11.37
5120
9215
0.41
DRY
-
21.59
59.26
4.21
0.91
1.20
12.83
5775
10395
-
A.R.
14.85
18.75
50.68
3.66
0.84
1.04
10.18
5030
9055
0.55
DRY
22.02
59.51
4.30
0.99
1.22
11.96
5905
10630
-
A.R. -
13.59
18.38
52.6
3.45
0.81
1.08
10.09
5110
9200
0.53
CRY
-
21.27
60.87
3.99
0.94
1.25
11.68
5915
10645
-
NOTE A.R. = As received
-------
- 29 -
APPENDIX II
Maas Balances for Carbon. Sulphur and Ash
Table I lists the carbon and sulphur inventory for a section of the
first period of lignite gasification with 800u down and 1405ji down feed.
The information is presented ,in terms of the weight percent of the feed,identified
VG thf Various sources. Considering the errors involved (see table 2 main
report) the carbon and sulphur balances are satisfactory.
TABLE I
Carbon and Sulphur Inventory for Lignite Gasification
(Period 2.1440 ?Ł
Source
Carbon
(% of Feed")
Sulphur
(% of Feed)
Solids Inventory
Boiler Flue Gas
Regenerator Gas
Total
(1) From Stack SO-
6.8
88.8
3.9
- 99.5
measurement
66.6
36
24.3
126.9
(D
Feed:- Carbon 514.6 Ibs; sulphur 8.33 Ibs
A detailed breakdown of the solids inventory for carbon, sulphur and
ash is presented in table II. Poor recovery of the acid insoluble ash is
evident with the major proportion being recovered at the stack cyclone after
the boiler.
TABLE II
Solids Inventory
Source
IMM^HMMMP^
Stack Knockout
Stack Cyclone
Boiler Back & Side
Regenerator Cyclone
Pines Return System
change
2nd Cyclone (Fines
Return)
Gasifier bed change
Regenerator bed
change
Total
for Lignite Gasification (Period 2.-1440 - 2.164-0)
Carbon
f% of Feed)
1.0
4.2
0.6
0.1
- 0.9
0.9
1.1
- 0.2
6.8
Sulphur
(% of Feed)
1.1
3.0
1.7
0.4
3.6
3.0
68.9
- 15.1
66.6
Acid Insoluble Ash
C% of Feed)
6.1
25.9
1.81
0.6
- 0.1
3.5
7.2
0.3
45.3
Feed:- Carbon 514.6lbs; sulphur 8.331bs; Acid insoluble ash 143.7 Ibs
-------
- 30 -
Table III lists the carton and sulphur inventory for a section of the
second period of lignite gasification with 1/8" down feed.
TABLE III
Carbon and Sulphur Inventory for Lignite Gasification
(Period 3*1540-3.1640)
Source
Carbon
% of Feed)
Sulphur
% of Feed )
Solids inventory
Boiler Flue gas
Regenerator Gas
Total
14.6
78.8
1.8
95.2
- 50.4
15.5
91.6
(D
From Stack SO- measurement
Feed:- carbon 238.1 Ibs
sulphur 3.86 Ibs
Again the balance for carbon and sulphur is acceptable. Table IV gives
a detailed breakdown of the solids inventory for carbon, sulphur and ash. The
larger coal feed size has resulted in a better ash recovery and a higher
proportion found in the gasifier. ~
Table IV
Solids Inventory for Lignite Gasification (Period 3.1540 -3.1640')
Source
Stuck Knockout
iitack Cyclone
Boiler Back & Side
Gasifier Bed change
Regen Bed Change
Fines Return System
Change
Total
0.8
3.4
4.3
5.3
0.5
1.3
14.6
Sulphur
f % of Peed )
1.3
3.9
5.2
-28.2
-25.9
-6.7
-50.4
Acid Insoluble Ash
% of Feed"!
3.5
19.0
11.7
35.3
1.8
5.3
76.6
Feed:- Carbon 238*4 Ibs; sulphur 3.86lbs; acid insoluble ash 66.5
-------
- 31 -
TABLE V
Solids Inventory for Heavy Fuel Oil Gasification (Period
Source
Stack K.O.
Stack Cyclone
Boiler Back &
Side
Regenerator
Cyclone
Pines Return
(2nd cyclone)
Pines Return
System Change
Gasifier "bed
Change
Regenerator
Bed change
Total
Carbon
ilbsl
3.0
0.84
3.4
0.6
12.2
0.-35
-12.0
-0.7
7.7
Sulphur
fibs)
0.08
0.03
0.1
0.03
1.09
0.24
-4.0
1.05
-1.38
- 3.1440)
Ash
fibs)
2.7
1.02
2.7
0.8
11.8
-0.35
-
18.7
3.1120
Lime
fibs)
0.28
0.02
0.84
0.12
11.6
0
-
12.9
Peed;- Carton 784.8 Ibs; sulphur 23.9 Ibs; Ash OlTas, lime 0 Has
-------
- 32 -
Appandii III (Table I)
Enjerimental Results of Mini-Run on Lignite & Illinois No 6 Coal
Time
Coal Type
& Size
Gasifier
Temperature
Gasifier Bed
Depth
(inches)
Gasifier
Bed Velocity
(ft/sec)
Gasifier
Air/Fuel
(% Stolen)
Caps Feed
Mole Ratio
Regen Temp
c
Regen
Velocity
(Ft/sec)
Regen
CO,
(Vol ft
Regen
(Vol$
Regen S
Output
(# of Feed)
Regen Med
Depth
(inches)
% S.R.E.
% SRE
Expected
On Oil
A
Stack '
r^f^eed)
Sulphur
Balance
(% of Feed)
% Combustion
in Boiler
1.1530
1.1630
Illinois
No. 6
-800 p
970
42
3.7
30.3
0
1070
6.1
12.4
0.15
2.7
52
74.8
73.8
+1.0
14.2
27.8
101.3
2.1500
Lignite
-800 )i
890
38
3.5
29.9
0
1065
7.6
17.6
0,4
16.0
36
64.2
68.4
-4.2
62.4
51.8
84.3
2.1600
Lignite
-1405 Ji
885
39
3.5
32.2
0
1075
6.9
17.0
0.9
35.5
36
56.5
69.1
-12.6
78.7
79.0
84,0
2. 1630
Lignite
-1405 Ji
890
' 39
3.5
33.9
0
1080
7.0
16.8
0.3
12.6
38
73.7
68.9
+4.9
39.9
38.9
89.1
2.1655
Lignite
-1405 f.
920
39
3.6
32.7
0
1080
6.9
16.4
0.4
16.0
40
61.5
67.5
- 6.0
39.7
54.5
97.7
3.1530
Lignite
- 1/8"
915
34
3.6
31.3
0
1080
6.7
6.0
7.5
270.8
44
95.6
65.8
+29.8
163.6
275.2
73.6
3.1600
Lignite
-1/8"
900
35
3.5
29.6
0
1090
6.5
5.6
6.8
216.9
44
86.9
66.8
+20.1
124.2
230
72.9
3.1630
Lignite
-1/8"
885
36
3.5
31.7
0
1095
6.7
10.0
7.3
275.4
42
78.5
67.9
+9.4
128.8
296.8
79.1
3.1645
Lignite
-1/8"
880
36
i
3.5
33.7 '
0
1110
7.2
10.0
7.S
341.1
44
76.8
67.9
+8.9
150
364.3
89.7
-------
- 33 -
Appendix III (Table
Experimental Results of Mini-test on Heavy Fuel Oil
Time
Gasifier
Temperature
(°c)
Gasifier
Bed Depth
(inches)
Gasifier
Bed Velocity
(Ft /sec)
Gasifier
Ai r/Fuel
($ Stoich)
Ca/S Feed
Mole Ratio
Regen
Temneraiure
(°C)
Re gen
Velocity
(Ft /sec)
Regen CO
(Vol#) 2
Regen S00
(Volfo) 2
Regen S
Output
(% of Feed)
Regen Bed
Depth
(inches)
% S.R.E.
Predicted
% S.R.E.
A
Stack Sulphur
(% of Feed)
Sulphur
Balance
(% of Feed)
1.1220
930
41
3.6
18.9
0
1040
6.2
18.0
0.8
15
50
59.5
72.4
-12.9
52.9
55.5
1.1330
940
41
3.6
20.2
0
1060
6.3
15.2
0.25
4.8
50
63.8
72.8
-9.1
39.7
41.0
1.1435
950
42
3.7
18.9
0
1055
6.1
12.6
0.2
3.4
52
63.3
70.7
-7.4
35.0
40.0
2.1130
945
39
3.7
22.2
0
1080
5.6
18.0
1.2
23.1
52
56.5
73.5
-16.9
74.0
66.6
2.1200
940
38
3.7
22.2
0
1079
5.5
17.4
0.3
5.6
52
78.9
73.6
+3.7
47.4
26.8
2.1230
975
40
3.8
22.2
0
Yioo
8.2
18.0
0.5
13.6
44
73-3
69.4
+3.5
37.4
40.3
2.1330
970
38
3.8
22.2
0
1070
7.0
14.6
0.5
11.4
44
62.1
69.7
-7.6
49.8
49.2
2.1430
960
38
3.8
22.2
0
1065
7.0
16.2
0.4
9.2
44
62.1
71.2
- 9.0
40.5
47.0
-------
- 34 -
Appendix III (Table II Cont'd)
Experimental Results of Mini-Test on Heavy Fuel Oil
Time
Gasifier
Temperature
(°c)
Gasifier
Bed Depth
(inches)
Gasifier
Bed Velocity
(Ft/sec)
Gasifier
Air/Fuel
(% Stoich)
Ca/S Peed
Mole Ratio
Re gen
Temperature
Regen Velocity
(Ft/ Sec)
Regen CCL
(Vol#) 2
Regen S00
(Vol #) *
Regen S
Output
(% of Feed)
Regen
Bed Depth
(inches)
% S.R.E,
Predicted
% SRE
A
Stack Sulphur
(% Feed)
Sulphur
Balance
(% of Feed
3.1030
955
36
3.7
20.5
0
1020
6.6
18.8
0.8
18.2
48
59.8
69.4
-9.6
44.6
58.4
3.1130
.950
37
3.6
20.5
0
1075
7.0
17.0
3.0
68.3
40
57.6
70.4
-12.8
68.8
110.6
3.1230
930
36
5.2
24.1
0
1085
6.9
14.4
3.8
84.5
44
60.4
75.2
-14.8
75.2
124
3.1330
940
35
5.2
23.9
0
1080
6.9 .
11.8
5.7
125.3
44
53.8
73.8
-19.9
87.9
171.5
3.1430 '
940
34
5.4
24.5
0
1070
6.6
7.6
6.5
132.7
44
55.7
73.8
-18.1
109.1
177.0
-------
- 35 -
Appendix IV (Table
Time
1.1440
1.1540
2.1400
2.1500
2.1600
2.1700
3.1120 '
3.1240
3.1340
3.1440
3.1540
3.1640
Stone
Sulphur
4.22
4.74
6.86
7.67
8.29
8.12
9.1
10.2
9.5
9.24
9.36
9.23
Analyses of Gasifier Bed Material
Carbon Acid insoluble Sulphur
Cwt&) Ash wl
jŁ as SO,
wt^T
5.6 3.2 <0.1
6.7 2.8 0.1
2.6 4.1 0.1
2.6 4.2 ,0.1
2.5 5.6 0.1
3.6 5.1 0.1
2.8 3
3.1 3
2.5 3
.6 < 0.1
.2 < 0.1
.3 0.1
1.4 4.6 < 0.1
1.9 3
.7 <0.1
3.4 6.5 .0.1
Appendix IV (Table
Stone Analyses of Regenerator Bed Material
Time Sulphur Carbon
TwtlT
1.1440 4.28
1.1540 4.6
2.1400 7.8
2.1500 9.05
2.1600 7.36
2.1700 7.42
3.1120 8.2
3.1240 7.9
3.1340 8.5
3.1440 7.31
3.1540 6.22
3.1640 5.45
(wtjt;
1.1
0.8
1.6
1.8
0.9
0.9
no
0.8
1.4
0.4
1.1
0.2
A'cid Insoluble
Ash 'Wt%)
3.4
3.5
3.4
3.9
3.6
4.3
3.3
5.4
3.2
3.9
3.1
4.0
Sulphur
as SO,
0.1
<0.1
0.1
0.1
0.1
0.1
0.1
0.3
0.1
0.3
0.9
0.9
-------
- 36 -
Appendix IV (Table III)
Stone Analyses from 1st Cyclone
Time Sulphur Carbon
W
Ť) Cwt%)
1.1520 3.43 41
1.1540 2.2
54
1.1620 1.32 37
2.1340 3.74 29
2.1420 1.48 56
2.1520 1.57 45
2.1540 1.19 61
2.1620 4.35 23
2.1700 2.06 36
3.1120 1.75 46
3.1340 4.41 26
3.1420 3.12 48
3.1500 3.82 27
3.1540 2.68 28
3.1620 1.19 46
Appendix IV (Table
Fines Return System
Acid Insoluble
Aah Iwt%)
14
22
45
22
35
41
39
28
41
38
19
36
27
28
48
IV)
Sulphur
(as SO.)
wt % *
<0.1
0.1
0.1
0.1
0.1
. 0.1
<0.1
0.1
0.1
<0.1
<0.1
<0.1
0.1
<0. 1
0.1
Stone Analyses from 2nd Cyclone Fines Return System
Time Sulphur Carbon
Wt % wt%
1.1520 2.22 49
1.1540 2.47 57
1.1640 2.18 61
2.1340 3.06 36
2.1420 2.03 45
2.1520 2.36 51
2.1540 1.68 46
2.1620 2.09 32
2.1700 2.2
3.1120 1.8
40
45
3.1340 3.33 28
3.1420 3.72 27
3.1500 3.29 31
3.1520 3.47 36
3.1600 2.77 21
Acid^ Insoluble
Ashlrt^
21
15
25
22
34
34
38
47
44
42
27
28
27
24
24
Sulphur
as SO,
0.1
0.1
0.1
0.1
0.2
0.1
<0.1
0.1
<0.1
<0.1
<0.1
<0.1
<0.1
<0.1
0.2
-------
- 37 -
Appendix IV (Table V)
Stone Analyses
fr.om Stack Knockout. Stack
Cyclone and Boiler Back
& Sides
Source
Stack KO
ti
it
it
ii
it
ii
Stack Cyclone
it
ii
it
ii
ii
ii
Boiler Back
& Sides
ii
ii
ii
it
ii
Time
1.1500
1.1700
2.1330
2.1640
3.1140
3.1340
3.1620
1.1500
1.1700
2.1330
2.1640
3.1140
3.1340
3.1620
1.1500
1.1700
2.1330
2.1640
3.1140
3.1340
3.1620
Sulphur
Wt
-------
- 38 -
Appendix IV (Table VI)
Stone Analyses from Regenerator Cyclone
Time
1.1500
1*1700
2.1330
2.1640
3.1140
3.1340
3.1620
Sulphur
wt %
3.98
2.23
3.51
1.7
1.78
2.68
2.36
Carbon Acid
vrMt Ash
37
63
43
40
52
34
20
Insoluble
'vrtf)
22
31
32
54
48
52
60
Sulphur
as SO,-.
0.6
0*4
0.3
0.1
0.7
1.4
-------
- 39 -
TECHNICAL REPORT DATA
(Please read Instructions on the reverse before completing)
1. REPORT NO.
EPA-600/7-77-027
2.
3. RECIPIENT'S ACCESSION-NO.
4. TITLE AND SUBTITLE
First Trials of CAFB Pilot Plant on Coal
5. REPORT DATE
March 1977
6. PERFORMING ORGANIZATION CODE
. AUTHOR(S)
D. Lyon
8. PERFORMING ORGANIZATION REPORT NO.
9. PERFORMING ORGANIZATION NAME AND ADDRESS
Esso Research Centre
Abingdon, Oxfordshire 0X13 6AE
England
1O. PROGRAM ELEMENT NO.
EHE623A
11. CONTRACT/GRANT NO.
68-02-2159
12. SPONSORING AGENCY NAME AND ADDRESS
EPA, Office of Research and Development
Industrial Environmental Research Laboratory
Research Triangle Park, NC 27711
13. TYPE OF REPORT AND PERIOD COVERED
Task Final: 6-8/76
14. SPONSORING AGENCY CODE
EPA/600/13
15. SUPPLEMENTARY NOTES IERL_RTP project officer for this report is S. L. Rakes, Mail
Drop 61, 919/549-8411 Ext 2825.
is. ABSTRACT Tne report gives results of Si muiirun, carried out on a 0. 75-MWe contin-
uous , chemically active fluidized-bed (CAFB) pilot plant during July-August 1976, as
part of a program to extend the CAFB process to operate on coal. After 8. 5 hours
of gasification on Texas lignite and Illinois No. 6 coal, no major barriers were iden-
tified. The quality of the gas produced was similar to, and the desulfurizing effi-
ciency on coal appeared to match or exceed, that for oil. The target of 88% lignite
utilization was approached in the minirun under conditions which were far from opti-
mum. Because of the need for more air to gasify coal, a CAFB unit dimensioned for
fuel oil will probably have an energy capacity 30% lower when on coal. Satisfactory
regeneration while gasifying on lignite was demonstrated, but control of regenerator
temperature was more difficult. A new fines return system worked well, but did
little to reduce the fly-ash level in the boiler during coal gasification. Operation of
the pilot plant on an intermittent, as opposed to round-the-clock, basis was
successfully demonstrated.
17.
KEY WORDS AND DOCUMENT ANALYSIS
DESCRIPTORS
b.lDENTIFIERS/OPEN ENDED TERMS C. COSATI Field/Group
Air Pollution Regeneration (Engi-
Combustion neering)
Coal Fly Ash
Fluidized Bed Processing
Gasification Fines
Desulfurization
Air Pollution Control
Stationary Sources
CAFB
Particulate
13B
21B
2 ID
13H,07A
07D
13. DISTRIBUTION STATEMENT
Unlimited
19. SECURITY CLASS (ThisReport)
Unclassified
21. NO. OF PAGES
44
20. SECURITY CLASS (Thispage)
Unclassified
22. PRICE
EPA Form 2220-1 (9-73)
------- |