Note: Descriptions are shown in the official language in which they were submitted.
126556~
COAL SLURRY SYSTEM
3ACKGROUND OF THE INVENTION
The present invention is in the field of coal transportatlon
and power plant utilization thereof and is specifically directed
to unique methods and apparatus for conveying and feeding coal by
a liquified gas/coal slurry pipeline to a power plant including
unique power plant efficiency increasing methods and apparatus.
The vast majority of coal consumed at power plants in the
United States is tranqported from the mine head to the power
plants by rail or barge. Unfortunately, the cost of transporta-
tion by rail is quite substantial as a consequence of the inher-
ent expense of rail transportation and the fact that individuaL
railroads are frequently the only means by which coal can be
transported from a particular mine. While barge transportation
is generally more economical where available, many power plants
and mines do not have access to waterways capable of enabling
water transport~tion.
The foregoing and other problems have consequently resulted
j in a number of proposals for transporting coal in an lLquid
slurry pumped through a pipellnY. A number oi coal-water ~lurry
plpelines have been built and commercially explo$ted in the
United State~ with the longest pipeline of this type being in
excess of 270 miles in length. However, coal-water slurry pipe-
lines require both an adequate source of water conveniently
located with respect to the mine and me~ns ~or disposing of the
transport water at the downstream end of the pipeline. Unfortu-
A nately, the foregoing circumstances are not always present,
~.~.
::
126ss~l
particularly in the West, and such pipelines are becoming less
feasible with the passage of time.
, The prior art has consequently come forth with a variety of
I proposals aimed at overcoming or reducing the shortcomings of
present known coal transportation methods. For example, U.S.
Patents Nos. 4,173,530; 4,178,231: 4,178,233; and 4,265,737 dis-
close the concept of using fluorochlorocarbons as coal carriers
in a slurry system. ~ates United States patent No. 1,390,230
discloses the concept of a coal slurry in which the liquid carri-
er is oil or some other liquid hydrocarbon. Gruber, et al.
United States patent No. 4,027,688 discloses a coal slurry in
which pulverized coal is tran~ported by a liquid hydrocarbon and
methanol carrier mixture. Hamilton United States patent No.
1,385,447 discloses conveying coal through a pipeline by the use
of a gas or fluid in which producer gas is a con~tituent of the
carrier employed in the slurry. Keller U.S. Patent No. 3,968,999
discloses the use of methanol or LPG as the slurry media.
Wunsch, et al. United States patent No. 3,1~0,691 discloses the
concept of providing a coal slurry in which the carrier media
comprises a liquified gas maintained at a sufficient pressure to
I remain in liquified condition until released at the end of the
pipeline for expansion to permit the carrier gas to separate from
! the solid materials. 3ritish patent No. 2,027,446 diseloses the
conveyance of pulvorized coal with a liqu~d fuel constituent.
Other prior United States patentg have disclosed the use of
liquified carbon dioxide as the carrier media of a coal slurry
system. For example, Paull United States patent No. 3,976,443
discloseq a slurry tank 17 in which pulverized coal is mixed ~lith
! li~uid carbon dioxide and pumped through a pipeline by a feed
, pump 24 through a heater 26 for discharge in a burner 30.
!
126~5~
Similarly, Santhanam United States patent Nos.
4,206,610 and 4,377,356 also disclose the concept o~
conveying coal by the use of a liquid carbon dioxide
slurry.
However, none of the prior art patents suggesting
the use of liquified carbon dioxide as the carrier media
for a coal slurry has been commercially exploited in so
far as Applicants are aware. One possible reason for
the non-exploitation o~ the Santhanam patents is the
fact that the specification and claims of at least the
,610 patent conflictingly indicate that the coal/liquid
carbon dioxide slurry is adiabatically expanded and that
prior to the adiabatic expansion, heat is introduced
into the slurry to make up for the heat lost in the
expanding to avoid solidification of the carbon dioxide.
Since adiabatic expansion by definition does not involve
heat loss, the aforementioned patent presents a basic
inconsistency on its face.
Thus, while a variety of coal slurry pipeline
systems have been suggested, they have not effectively
presented facts resulting in widespread acceptance.
SUMMARY OF THE INVENTION
According to an aspect of the invention, a method
of operating a power plant of the type including a steam
boiler and condenser comprising:
(a) providing a predetermined weight of
pulverized coal into a closed chamber;
(b) providing liqui~ied gas in the closed
chamber so as to substantially fill the closed chamber
with a slurry at a predetermined pressure and
temperature; and
(c) discharging slurry from the lower end of
said closed chamber while simultaneously injecting a
pressure maintaining gas at a pressure and temperature
slightly above said predetermined pressure and
A
~2~556~
temperature into the upper extent of said chamber so as
to maintain said slurry at a sufficiently high pressure
as to prevent flashing of the liquid to vapor during the
slurry discharge.
Achievement of the foregoing aspect in the preferred
embodiments of the invention is through the provision of
accurate means for providing a liquified carbon dioxide or
other liquified gas carrier media for pulverized coal in
which the ratio of the coal to the carrier media and the
consequent density of the slurry is carefully controlled
for optimum flow
1265561
efficiency. More specifically, a ~easured quantity of pulverizea
coal is mixed with a measured quantity of liquified carbon
dioxide in a batch type operatlon providing a slurry of the
required density. It should be understood that while the in~en-
tion is described in connection with the use of liquified carbon
dioxide as the carrier media, other liquified gases could be used
instead of carbon dioxide. The slurry is provided in a pres-
surized chamber and is discharged from the lower end of the cham-
ber at a predetermined pressure in excess of the pressure and
temperature at which flashing of the liquified carbon dioxide
would occur. Pressuri2ed gaseous carbon dioxide at a higher
temperature than that of the slurry is automatically introduced
into the closed chamber above the slurry surface for maintaining
pressure in the chamber at a required level above the critical
pressure at which flashing could occur during the entire dis-
charge of the batch of slurry from the chamber. Thus, during the
discharge operation, there i5 no drop in pressure in the slurry
which is fed into a pipeline connected to the suction inlet of a
pump. The pres~ure is maintained at a sufficiently high level as
to preclude fla~hing of the carbon dioxide at the inlet of the
pump.
The pulverized coal/liquified carbon dioxide slurry is then
pumped through a pipeline to a power plant in which it i9 dis-
charged through pressure reduclng nozzle means into a primary
separator to reduce its pressure non-adiabatically and to flash
most of the carbon dioxide into gaseous form. The carbon dioxide
i9 separated from the solid materials by passage through a series
of separator units comprising a primary separator, a secondary
separator, a tertiary separator and a bag dust collector. The
separated coal i9 metered and fed by a blower into burner units
of a boiler of the power plant. The gaseous carbon dioxide
A
~2655~
resultant from the decompression of the liquified carbon dioxide
is at a low temperature and may tempoL^arily include some soLld
frozen particles.
The lower temperature gaseous carbon dioxide from the sepa-
rators and bag dust collector is passed through a heat exchanger
in which it absorbs heat from glycol being pumped in a closed
loop through the heat exchanger and through the basin of the
cooling tower of the power plant. The water in the cooling tower
basin is consequently cooled by the gaseous carbon dioxide so as
to consequently provide a resultant increase in the power plant
efficiency. Alternatively, the low temperature carbon dioxide
gas can be placed in heat exchange relation with the chilled
water from the cooling tower flowing through a conduit to the
steam condenser of the power plant. As a third alternative, a
portion of the low temperature qaseous carbon dioxide can be
injected directly into the cooling tower water to lower its
temperature, decrease the pH to a desired level so as to prevent
scaling and promote recarbonation following lime softening of
cooling tower makeup water.
Additionally, the gaseous carbon dioxide from the heat ex-
changer (or remaining non-injected carbon dioxide in the case of
the thlrd option) can then be compressed and stored for sale or
for further usago. One such typo of further usage comprises
injecting the gaseouq carbon dioxlde into an oil well for enhanc-
ing the recovery o petroleum products from the well. ~he gas-
eous carbon dioxide can optionally be returned to the mine source
for re-liquification and subsequent use in the slurry pipeline if
desired.
One particularly effective combination involves usage of
carbon dioxide received from a well head near the coal mine, liq-
uification and usage of the carbon dioxide as the slurry carrier
A
126~
medla in a "one-way" pipeline to the power plant, usage of the
gasified carbon dioxide in the power plant a5 discussed previouS
ly and reinjection of the gaseous carbon dioxide into an ~11
well. A system of the aforementioned type would be particularly
efficient ln terms of the powe. requirements of the "one-way"
pipeline. Moreover, such a system would result in enhanced oil
recovery from the particular well or wells into which the carbon
dioxide is injected.
A better understanding of the various embodiments of the
invention will be achieved when the following detailed descrip-
tion is considered in conjunction with the appended drawings in
which the same reference numerals are used for the same parts as
illustrated in the different drawing figures.
~RIEF DESCRIPTION OF THE DRAWINGS
_. _ .. ..
Figure lA is a process schematic of a slurry preparation
portion of a first embodiment for practice of the invention;
Figure lB is a proces~ schematic of the remaining power
plant portion of the Figure lA embodiment of the invention;
Figure 2A i5 a process schematic of a portion of a second
embodiment for practice of the invention;
Figure 2B i9 a proces~ schematic o~ the remaining portion of
the second embodlment7
Figure 3 is an enlarged flow schematic of a coal and carbon
dioxide mixing ~ystem employed in the second embodiment; and
Figure 4 is a flow schematic of alternative heat exchange
means employable with either the first or ~econd embodiment;
Figure 5 is a flow schematic o~ a further alternative heat
exchange means employable with either the first or second embodf-
ments; and
~265~
Figure 6 is a flow schematic of yet another alternative hea-
exchange means employable with either the first or second embodi-
ment of the invention.
DESCRIPTION OF THE PREF~RR~D EMBODIMENTS
-
Attention is initially invited to Figures lA and 1~ for ref-
erence with respect to the rollowing discussion of the first
embodiment of the invention. The first embodiment includes three
primary elements comprising a coal source such as a pile of coal
10, a gaseous carbon dioxide source such as a well 12 and a con-
ventional coal burning boiler 14 of a steam turbine power plant~
The primary elements are interconnected by various handling,
storing and conveying devices for achieving a controlled input of
pulverized coal into the boiler 14. In addition to boiler 14,
the power plant includes a turbine 17 connected ~o boiler 14 by
high pressure stream line 9 and to a condenser 19 by an exhaust
steam line 21. A cooling tower 106 provides cooling water to
condenser 19 by a chilled water line 23 including pump 23' and
receives heated water from the condenser by warm water return
line 25. Condensate from condenser 19 i9 returned to boiler 14
by feedwater pump 27 in feedwater line 29. The aforementioned
relationship of ~he power plant components is completely conven-
tional.
Gas such as carbon dioxide from well 12 ~lows through a well
head valve 16 to a field transmission line 18 whlch conveys the
well head gas to conventional gas separation, purification and
compression means 20 which removes water and/or other undesirable
contaminates from the gas. The major constituent of the gas is
carbon dioxide however, it should be understood that the well
head gas can also include other gases Quch as methane, ethane,
propane, nitrogen and hydrogen sulfide. The purified gas is
A
1265561
compressed to a dense phase or liquid form and injected into a
pipeline 22 whlch conveys it to liquified gas storage means 53.
The liquified gas in storage means 53 is removed therefrom by
supply pump 42 as required for conveyance to a slurry preparation
plant for mixing with pulverized coal as illustra~ed in Figure
~A.
The slurry preparation plant includes a main feed hopper 24
which receives coal from the main coal source lO by means of
front end loaders 26 or other conventional conveying and/or
handling equipment. Coal from the hopper 24 is moved by conven-
tional conveyor means 28 into crushing, grinding and pulverizing
mill means 30 which provides pulverized coal which is moved by
conveying means 32 into a pulverized coal storage hopper 34 of
conventional design and which includes discharge control means 36
for discharging the pulverized coal into conveyor means 38 for
selective delivery to either a first weigh hopper 40 or a second
weigh hopper 140 or alternatively, simultaneous delivery to both
hoppers. It should be understood that the pulverized coal con-
veyor 38 is of conventional construction and includes convention-
al control mean~ 39 for directing the pulverized coal to either
one or the other or both of hoppers 40 and 140. ~he pulverized
coal conveyor means 38 will normally feed coal into one of the
hoppers until a predetermined amount of coal is Ln the hopper at
which time flow lnto that particular hopper will be terminated.
The pulverized coal will then be conveyed into the other hopper
to charge same while the pulverized coal in the first hopper is
being mixed with liquid carbon dioxide to form a slurry and dis-
charged in a manner to be discussed.
A first mix tank 44 has an upper inlet connected to an in-
feed conduit 46 which receives pulverized coal at atmospheric
pressure flowing through a solids control valve 4~ provided on
12655~i.
the lower end of the flrst wei~h hopper 40. A pressure isolatlen
valve 50 is pOSltioned in conduit 46 between the sollds controL
valve 48 and the inlet to the mix tan~ 44. Additionally, a gas
line 52 is connected through a gas flow control valve 54 to in-
feed conduit 46 at a point between valve 50 and the inlet to
first mix tank 44. Gas line 52 receives gas from a heater 55
whlch in turn receives liquified gas supplied from a booster pump
57 in heater feed line 58 connected to pipeline 22. The li~-
uified gas is converted into its gaseous phase by heater 56 as it
passes through the heater from which it flows into a gas accumu-
lator 55.
Pipeline 22 also connects to a first filiing line 60 con-
nected to the mix tank 44 and including a shut off valve 62. In
like manner a second filling line 160 connectC the pipeline 22 to
the lower portion of a second mix tank 144 through a shut off
valve 162. An agitator pump 64 has a suction line 66 connected
to the upper portion of mix tank 44 and a discharge line 68 con-
nected to the lower portion of mix tank 44 so that operation of
pump 64 serves to stir the contents of mix tank 44 in an obvious
manner. Alternate means of stirring (i.e., paddle mixer) could
be ussd in mix tank 44 if desired.
Weigh hopper 140 has a solids control valve 148 for dis-
charging pulverized coal into an infeed conduit 146 connected at
its lower end to an inlet in the second mix tank 144. A pressure
containing valve 150 is provided in the infeed conduit in the
same manner as valve 50 is provided in the infeed conduit 46. A
gas line 152 includes a gas accumulator 155 analogous to accumu-
lator 55, a heater 156 analogous to heater 56, a booster pump
157, and a gas flow control valve 15~ analogous to gas flow
control valve 54. Agitation pump 164 has suction and discharge
lines 166 and 168 connected to mix tank 144 for agitating the
A
12~5~;61
contents thereof here again, mechanical mixing means could also
be employed if desired. Thou~h gas accumulators, booster pumFs
and heaters are shown dedicated to a single mix tank, they could
be combined to serve both mix tanks.
~ ischarge valves 45 and 145 are provided at the lower ends
o~ mix tanks 44 and 144 respectfully for discharge of slurry by
slurry discharge lines 47 and 147 respectively which discharge
into a slurry pipeline 80 operatinq at pressures ranging between
850 and 1200 psig. Slurry pipeline 80 is connected to the inlet
of a pipeline pump 82 having an outlet connected through a valve
86 to a transmission pipeline 84 which may be hundreds of miles
in length (and include additional pumps).
In operation, the slurry preparation system illustrated in
Figure lA discharges slurry first from mix tank 44 and then from
mix tank 144 while the first mix tank 44 is being recharged. The
slurry in mix tanks 44 and 144 will normally be at a pressure in
the range of 900 to 1200 psig; however, pressures up to 1500 psig
may be used if desired, such as when viscous slurry is involved.
A cycle of operation will be discussed with it being assumed
that slurry i~ initially being discharged from the second mix
tank 144 through line 147. Valves 150 and 162 are in a closed
condition and valve 145 is an open condition. While the slurry
is being discharged through valve 145 ga~eous carbon dioxide is
provided from heater 1S6 through gas accumulator 155, line 152
and gas flow control valve 154 to the upper portion of the inte-
rior of mix tank 144 in the space above the liquid in the mix
tank. The gaseous carbon dioxide is supplied at a temperature
exceeding 90F and at a pressure of at least 950 psig. The gas
pressure should exceed the pressure in line 80 by at least 50
psig and the maximum gas pressure would be 1550 psig. The gas-
eous carbon dioxide introduced into the mix tank 14~ by line 1;2
~2~556~
11
maintains pressure in the tank and in the slurry being dischar~ec
therefrom at a sufficiently high level in line 147 and slurry
pipeline 80 up to the inlet of pump 82 to preclude flashir.g of
any of the liquid carbon dioxide and subsequent undesirable
thickening of the slurry. Gas flow control valves 54 and 154 are
constant pressure type valves and automatically maintain the
deslred pressure downstream of themselves and in the upper extent
of the mix tanks 44 and 144.
Valve 145 is closed prior to exhau~ting of the slurry from
the mix tank 144 so as to preclude the entry of gas into the
slurry discharge line 147. Termination of feed from the second
mix tank 144 is also accompanied by closure of gas flow control
valve 154 and the opening of valves 45 and 54 to initiate the
feed of slurry to lines 47 and 80. Valves 45 and 54 are opened
gradually prior to the closing of valves 154 and 145 to insure
continuous flow of slurry to pipeline 80.
; The manner in which the mix tankc 44 and 144 are charged
with coal and liquid carbon dioxide will now be discussed with
specific reference to mix tank 44 however, it should be under-
stood that the charging of the second mix tank 144 i9 effected in
il an identical manner. The coal is crushed, ground, pulverized,
; dried and classified in conventional mean~ 30 and i~ ~upplied to
the pulverized coal storage hopper 34 from which it i9 fed by
pulverized coal conveyor means 38 into the upper end of the first
weigh hopper 40. After a predetermined charge of coal has been
provided in the fir~t weigh hopper 40, feed to hopper 40 is ter-
minated and the coal is then directed by means 39 to the second
weigh hopper 140 assuming the second weigh hopper is not full at
j that time. Valves 54, 62 and 45 are in a closed condition prior
to the charging of the mix ~ank 44. Valves 48 and 50 are opened
A ; to permit a predetermined weight of pulverized coal from wei~;~
1265561
12
hopper 40 to consequentlY flow ln~o the mix tank 44. Valves 48
and 50 are then closed and liquid valve 62 is opened to permlt
liquid carbon dioxide to flow into the mix tank 44 to achieve a
slurry having a specific desired density. The density of the
slurry can be varied by varyinq the weight of coal which is
provided in the mix tank while always substantially filling the
remaining volume of the mix tank wlth li~uid carbon dioxide. It
will therefore be apparent that chanqing the amount of coal will
automatically effec~ a change in the slurry density.
Circulating pump 64 is actuated so as to achieve and main-
tain a uniform slurry density throughout the tank. The slurry in
the mix tank 44 is consequently in condition for ready discharqe
into line 47 and the slurry pipeline 80. Discharge of slurry
into the pipeline is effected by opening of valve 45 and a simi-
lar simultaneous opening of valve 54 which permits the injection
of gaseous carbon dioxide at a temperature greater than 90F and
a pressure of approximately 950 psi above the liquid level in the
mix tank 44. The injection of the gaseout carbon dioxide is con-
trolled by the constant pressure of valve 54 so that the pressure
in the tank does not decrease as the slurry is discharged out-
wardly through the valve means 45. Sufficient pressure is conse-
quently maintained in the tank and in the slurry pipeline 80 to
prevent any flashing of tho liquid carbon dioxlde at the suction
inlet of pipeline pump 82.
It will be appreciated that the weigh hopper 40 can be re-
ceiving pulverized coal at the same time that the mix tank 44 is
discharging liquid carbon dioxide/coal slurry into the slurry
pipeline 80. Since the valves 4~ and 50 are closed, there is no
possibility of the pulverized coal flowing into the mix tank 44
; during the same time that the slurry is being discharged from the
Alower end of the mix tank. Valva 45 is closed shortly prior to
126556~
13
the time that the slurry would exhaust form the mix tank 44 so as
to preclude the injection of gas into the slurry discharge line
47. Simllarly, valve 54 is also closed to terminate the supply
of gaseous carbon dioxide to mix tank 44.
In case of a malfunction of either or both of the mix tanks,
valve 79 can be opened to maintaln suction pressure at the pump
inlet of pump 82 to protect the pump from cavitation. Similarly,
valve 79 can also be opened to bypass the mixing vesse~s 44 and
144 when it is desired to clear the pipelines 80, 84 of slurry by
the flushing of same with the liquified carbon dioxide.
Figure 1~ illustrates the downstream end of the slurry
transmission pipeline 84 which discharges into a power plant
facility in which the pulverized coa' from the slurry is burned
in boiler 14. It should be understood that the slurry transmis-
sion pipeline can be of any desired length and can include plural
pumps along its length as needed for maintaining pressure and
flow. In any event, the slurry transmission pipeline 84 normally
operates at a minimum pressure of 900 to 950 psig and at ambient
earth temperature of approximately 70F. Pipeline 84 discharges
into a pressure reduction restriction, or series of restrictions
or nozzle~ 88 discharging into cyclone separator 90 in which the
temperature will be in the range of 0 through 25F with the
pressure being in the range of 300 to 450 psig. The slurry up-
stream of the pressure reduction mean~ 88 ia at a pressure above
the liquid-gas saturation point and the pressure is reduced in a
non-adiabatic manner below the liquid-gaq saturation point as the
slurry moves through the pressure reduction means 88. Conse-
quently, a sub~tantial portion of the liquified gas is trans-
formed from the liquid state to the gaseous state and a portion
may be in solid state for a a short time duration. Moreover, any
residual liquified gas that is not transformed into gas by the
.. ~ .
~265S61
14
pressure reduction or solidified gas that is formed during the
pressure reduction will absor~ latent heat from the coal and be
converted to gas in a relatively i-apid manner. Also, any carbon
dioxide that is solidified as a consequence of the pressure
reduction will quickly be converted to gaseous form by the
absorption of heat from the coal.
Separation of the gas from the coal is effected by cyclone
separator 90 from which the pulverized coal is discharged down-
wardly for further handling in a manner to be discussed later.
The gas and any entrapped fine coal particles therein from the
cyclone separator 90 flow through a gas line 94 into a bag dust
collector 92 which separates the remaining coal particles from
the cold gas ~0 to 25F) which is then conveyed by a line 96 to
conventional filter dehydrator means 98 from which dehydrated the
gas then flows in line 99 through a heat exchanger 100 where the
gas is placed in heat exchange relationship with a glycol loop
102 in which glycol i9 circulated by a pump 104. Glycol loop 102
also communicates in a heat exchange relationship with the circu-
lating water in a cooling tower 106. Sincé the temperature of
the gas passing through the heat exchanger 100 is substantially
less than the temperature in the cooling tower, the gas cools the
glycol in glycol loop 102 which in turn cools the water in the
cooling tower 106. Liquids other than glycol having a freezing
temperature lower than 0F can alJo be employ-d if desired.
The chilled cooling tower water from cooling tower 106 is
circulated through condenser 19 by circulating pump 23' and lines
23 and 25 and i9 used for condensing the steam in condenser 19.
The reduction in temperature effected by the additional cooling
of the cooling tower water by glycol loop 102 consequently per-
mits the pumping of a reduced amount of water to the condenser or
''~' `
`" . '
126556
the same amount at a lower temperature so as to provide a.~.
increase in overall efficiency of the power plant.
The gas from heat exchanger 100 is at a temperature in the
range of 60 to 90F and is discharged inte a line 108 communi-
cating with the inlet of a compressor 110 which compresses the
gas and discharges it lnto a l1ne 112 communicating with gas
storage means 114 from which the gas can eventually be discharged
for use in a variety of ways. For example, if the gas is carbon
dioxide, i~ could be used for reinjection into an oil field to
enhance the oil recovery~ On the other hand, if the gac is com-
bustible, it could be sold or used as a fuel.
The pulverized coal particles separated from the ga in the
cyclone separator 90 and the bag dust collector 92 pass through
valve means 116, 118 into dense phase conveyor transporter hous-
ing members 120, 122 respectively which basically comprise closed
hoppers. Residual gas from the transporter housing members 120
and 122 flows into a line 124 communicating with the inlet of a
compressor 126 which compreQses the gas and inject3 it into line
97 connected to line 96. operation of compressor 126 also lowers
the pressure in members 120 and 122 to the range of 35 to 70 psig
before valve means 128, 130 are operated to dump the pulverized
coal into pneumatic conveyor 132.
The pulverized coal from the den~e pha~e conv~yor transport-
er housing members 120 and 122 passes through flow control valve
mean~ 128 and 130 respectively into a pneumatic conveyor 132
which communicate~ on its downstream end with flow control valve
means 134 which is operable for directing the coal to either a
long term pulverized ~torage facility 136 or a feed line 137
which communicates with means for directing the coal to boiler
14.
A
`:
~L2655~
~,
Firs~ and second short term coal storage bunkers 154 and 16~
are provided for receiving the pulv~rized coal fro~ feed line 137
th~ough valve 168 and bunker select valve 170. The long term
storage facllity 136 discharges through a valve flow control 172
into a pneumatic conveyor 174 which communicates through a valve
176 to a line 180 connected to bunker select control valve 170.
All coal storage facilities and bunkers have a nitrogen or other
inert gas blanketing system (not shownt for protection against
spontaneous combustion of the pulverized coal. The pulverized
coal is fed to one or the other of the bunkers 164, 165 at any
given time and coal flowing from the first bunker 164 will enter
, scale means 182 from which it flows into a mill 184 which grinds
, the coal to a desired size for injection into the boiler. Fan
185 is connected to mill 184 for conveying the coal therefrom
pneumatically to line 155 for flow to boiler 14.
Alternatively, the pulverized coal can be fed from bunker
165 into a scale 186 from which it flows directly (without fur-
, ther pulverization) into a pneumatic fuel conveyor 188 driven bya blower 190. In any event, the pulverized coal in pneumatic
fuel conveyor laa i9 conveyed directly to fuel iniectors 15 for
combustion in boiler 14.
I It should be understood that the simplified arrangement
illustrated in Figure~ 1~ and lA can be modifled 3ubstantially
for different size in~tallations. For example, additional
cyclone separators 90 and bag dust collectors 92 and mixing ves-
sels could be employed for larger installations. Also, plural
storage facilities 136, coal bunkers 164 and 165 could also be
employed if needed.
Figure 4 illustrates an alternative heat exchange embodiment
in which the chilled gas from filter dehydrator 98 flows directly
I through a coil 72 ln a heat exchanger housing 73 mounted in the
.~
126~S~l
chilled water pipeline 23 so that the water is directly cooled in
the pipeline. The gas then flows into line 108 in the same ma~-
ner as in the first embodiment.
Figure S illustrates a second heat exchange embodiment i.
which the chilled gas from the filter dehydrator 98 flows through
a heat exchange coil 75 provided in the cooling tower basin 106'
below the water level so that the water in the basin is direct~y
cooled by the chilled gas which is then conveyed to line 108
which is connected to the downstream equipment as illustrated in
the first embodiment.
Figure 6 illustrates a third heat exchange embodiment in
which lines 99 and 108 are directly connected and a branch line
76 including a control valve 77 extends therefrom. Line 76 has a
nozzle means 177 at its outer end for directly injecting the
chilled carbon dioxide gas into the basin 106' of the cooling
tower 106 to consequently cool the water therein, Moreover, the
injection of the gaseous carbon dioxide serves to decrease the p~
of the water to reduce the possibility of scaling in the tower ln
a highly desirable manner and to promote recarbonation following
lime softening of cooling tower makeup water. The amount of car-
bon dioxide lnjected directly into the basin is controlled by
valve means ~7 in an obvious manner. The remaining gaseous
carbon dioxide flows through line 108 to compressor 110 etc. o~
the fir~t embodiment.
The embodiment illustrated in Figures 2A and 2B is a more
complex variation such as could be used for testing purposes.
This embodiment will now be discussed in detail with initial re~-
erence being made to Figure 2A which illustrates first and second
relatively large pulverized coal storage hoppers 200 and 202
which selec~ively receive pulverized coal from a screw conveyor
A 204. Pressurized gas lines 209 and 211 are periodicall~
l~SS~
r~
activated to inject pressurlzed gas at approximately S0 psig 1nto
the coal storage hoppers 200 and 202 for the purpose of stirrir.g
the pulverized coal and preventing settllng and to also maintair.
an inert gas blanket over the pulverized coal as a safety fea-
ture. Pulveri~ed coal is selectively fed from the coal storage
hoppers 200 and 202 by outfeed conveyor 206 from which it is
deposited in a hopper feed conveyor 208 which discharges into a
reversible screw conveyor 210 which discharges into either a
first feed hopper 2i2 or a second feed hopper 21q (Fig. 2~) in
accordance with the direction in which the screw of conveyor 210
is driven.
Weigh hopper 212 discharges into a coal feed line 216 which
includes a solids flow control valves 218 and 234 as best illus-
trated in Figure 3. Valve 234 and a corresponding valve 239 on
hopper 214 are not illustrated in Figure 23 due to space limita-
tions. The lower end of coal feed line 216 communicates with the
interior of a first mix tank 220. A second coal feed line 230
communicates the second weigh hopper 214 with a second mix tank
232. Lines 216 and 230 are connected to source 264 line of rela-
tively low pressure carbon dioxide gas and a source 265 of rela-
tively high pressure carbon d~ox~de gaY through line 262 and
¦ pneumatic control valves 267 and 269 respQctively. A pressure
I regulator 264' l~ig. 2B) malntaln4 a pres~ure of approximately
300 psia in lLne 264 whereas a pressure regulator 265' maintains
a pressure of approximately 900 psia in line 265. Regulator 264'
is initially operated to pressurize either mixing tank 220 or 232
up to 300 psig following which regulator 265' is operated to
bring the mixing tank up to 900 psig. The two stage pressuriza-
tion prevents the formation of solid carbon dioxide in the tanks
by avoiding exces~ive pressure drops.
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Control valves 234 and 218 are provided in coal feed li~.e
216 along with and on opposite sides of an expansion jolnt 238.
Similar control valves 239 and 240 are provided on opposite sides
of an expansion joint 242 in the second coal feed line 230.
A gas line 244 having a pressure relief valve at its upper
end extends upwardly from the upper end of mix tank 220 and is
connected to a second gas line 246 connected through a valve 248
to the lower end of welgh hopper 212. Filter means 250 is
provided in gas line 246 and has a pressure differential sensor
252 is connected across the filter means. Gas line 246 is con-
nected to gas line 209 extending from the coal storage hopper 202
by means of a through connection to line 213. Pressure regulator
260 is provided in line 209 and i5 set to open when the upstream
pressure falls below 50 psig.
Gas line 254 similarly extends upwardly from mix tank 232
and is cor,nected to a gas line 268 anaiogous to line 246 and hav-
ing filter means 270 and associated pressure differential means
272 mounted therein. A valve 274 is mounted in the upper end of
gas line 268 adjacent a connection to the lower end of weigh
hopper 214. Lino 211 extending from hopper 200 is connected
through pressu~o regulator 194 to line 213' which is connected to
gas line 26~. Pressure regulator 194 opens when its upstream
pressure falls below 50 psig. Llne~ 213 and 213' are connected
to suction line 215 extending from the inlet of a compressor 524
~Fig. 2B).
A circulating pump 280 is aqsociated with the first mix tank
220 and has its inlet connected to a line 282 through valve 284
to the upper end of mix tank 220. Additionally, a further line
286 connects the inlet of circulating pump 280 to the coal feed
line 216 through a valve 288. The outlet of circulating pump 280
i5 connected to a line 300 which is in turn connected to a line
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302 which communicateS with the lower portion of mix tank 220
through a valve 304. A source line 305 of liquified gas is con-
nected to line 302 by line 307. Additionally, line 300 communi-
cates through valve 310 with a slurry discharge line 306 extend-
ing from the lower end of mix tank 220 and having a valve 308
beneath its junction with line 300.
Similarly, a circulating pump 330 is provided wlth the
second mix tank 232 and has its inlet connected to lines 332, 334
whlch respectively include valves 336 and 338. The outlet of
circulating pump 330 is connected to a line 340 which i5 in turn
connected through valve 344 to a slurry discharge line 342 ex-
tending from the bottom of mix tank 232. Line 342 is connected
through line 306 to a liquified gas source line 303.
First and second slurry pumps 352 and 353 have their inlets
connected to the main infeed line 350 (which receives slurry from
lines 306 and 342) through valves 354 and 356 and have their out-
lets connected to a high pressure slurry feed line 358 with the
outlet of pump 352 comprising a line 360 in which valves 362 and
364 are provided. Similarly, the outlet of pump 353 comprises a
line 366 in which valves 368 and 3tO are provided. High pressure
slurry feed line 35B flowq through a series of valves 374, 382,
334, and 386 to the inlet of heater 390. Orifice plate pressure
drop means 394 is provided immediately downstream of heater 390
to receive denso phase slurry at approxlmately 140F and acts to
drop the pressure thereof to approximately 900 psia.
The main slurry feed line 358 is connected to motor operator
control valveq 400 and 402 ~Figure 2A) which respectively control
flow to first and second banks of gas/solids separator units to
be discussed. Flow through the valve 402 is directed through a
restricting nozzle 404 which effects a non-adiabatic pressure
drop to approximately 300 psig and from which the discharge lS
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direc~ed into a primary separator 406 which separates a substar.-
tial portion of the coal from the carrler gas with the coal beir.g
directed downwardly through an isolation valve 408 to a dense
phase con~eyor feed 410 from which it enters pneumatic conveyor
llne 412. A line 414 connects the upper portion of the primary
separator 406 to the inlet of a secondary separator 416 having an
isolation valve 418 and a dense phase con~eyor feed 420 connected
to its lower end. Coal particles separated from the gas flow
into dense phase conveyor feed 420 and pneumatic conveyor line
412 in the same manner as occurs with the primary separator 406.
A line 422 includes an atmospheric vent line 424 and pressure
relief valve 426 and is joined to a tertLary separator 428 having
isolation valve 429 connected to a den~e phase conveyor feed 430
which is connected to the pneumatic conveyor feed line 412 in the
same manner as previously discussed separators 406 and 416. An
; outlet line 440 from the tertiary separator 428 is conn~cted to
the inlet of a bag dust collector 442 which has an isolation
valve 444 and dense phase conveyor feed 446 at its lower end con-
nected to the pneumatic conveyor 412. A pressure differential
¦ sensor 448 i9 provided across the inlet and outlet of the bag
dust collector 442. Gas from the bag dust collector 442 flows
¦ through a control valve 450 in gas line 452 into the inlet o~ a
i filter/ dehydrator unit 454 across which a pressure differential
sensor 456 is provlded. Gas from the filter/dehydrator unit 454
j goes into line 520 to be stored, recycled, sold or otherwise
disposed of such as through oil field well injection. The gas in
line 520 is chilled and can be used for cooling the condenser
~ cooling water of the power plant in the manner illustrated in an~
! f Figures lB, 4 or 5. Following such use, the gas can be
¦ recycled or used as needed for other purposes.
~L26~i~61
~ he second bank of separator units receives slurry from a
restricting nozzle 404' identical to nozzle 404 and cons1sts of a
primary separator 460, a 5econd separator 462, a tertiary separa-
tor 464 and a bag dust collector 466 in which the arrangement is
exactly identical to the arrangement of the separator 406, etc.
of the first bank of units. A gas outlet line 468 flows through
a control valve 470 into the gas infeed line 452 of the
filter/dehydrator 454. Similarly, a pneumatic conveyor line 470
receives coal particles from the separator units 460, 462, 464
and the bag dust collector 466 and joins with the pneumatic line
412 to form a coal feed line 472 connected to the upper end of a
scale feed bunker 474. The structure and operation of the second
bank of separator units is identical to the first bank of separa-
tor units.
Scale feed bunker 474 feeds the pulverized coal into a con-
ventional belt scale 476 which is modified for handling pulver-
ized material. The belt scale monitors the coal flow and which
in turn feeds the coal into a mill 478 for reducing the particle
size. The reduced coal particles from mill 478 and carrier gas
therefore are fed by a blower 480 to boiler feed lines 482, 484,
486, and 488 to provide combustion coal for the boiler throuqh
flow control valves 506, 508 and 509 respectively.
Coal for u8e ln the system is prepared as best illustrated
in Fig. 2-A by the use of feed hopper means 630 connected by a
conduit 635 to crushing, grinding, pulverizing and drying means
640 analogous to elements 24, 30 of the first embodiment. A dis-
charge line 645 extends from the outlet of the crushing, grlnd-
ing, pulverizing and drying means to the inlet of cyclone separa-
tor 490.
Gas from the upper end of the cyclone separator 490 flows
through a line 512 into a bag house 514 which provides further
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coal/gas separation with the coal being discharged into the auger
conveyor 510 and the gas bein~ discharged outwardly by blower
means 516.
The gas dlscharge from compressor 524 is at a pressure of
approximately 1200 psig and flows through a valve 526 into a heat
exchanger 528 which reduces the temperature of the gas from 260~
to 70O Fahrenheit and which discharges the now liquified gas i~to
line 530 ~hich is connected to liquid gas so-lrce line 305 extend-
ing to line 307 and mix tank 220 as previously descri~ed. Line
530 is also connected to gas accumulator 534 which stores liqui-
fied gas at 1200 psig and 70F. Similarly, line 303 provides
simil~r communication to mix tank 232 and further line 536 ex-
tends from line 305 to a juncture with line 350 downstream of
valve 351 as shown in Figure 2B. A pipeline pressure booster
pump 537 is provided in association with line 536 for maintaining
~adequate pressure therein during a pumping operation through line
536.
A line 540 is also connected to the output from compressor
524 to provide gaseous flow through valve 542 into an inlet line
544 of comprQssor 546 which discharges into gas accumulator 548
¦ which stores gas at a pressure in the range of 1300 to 1500 pslg
¦ and temperatures in the ranqe of 320 to 350F. A liquified gas
storage tank 549 has an upper outlet connected to line 544 and a
lower outlet connected to line 550 which is in turn connected
through a valve 551 to the inlet of a liquid pump 552 which dis-
charges into a heat exchanger 554 which discharges into liquid
accumulator 534. A main liquid carbon dioxide storage tank ,00
is connected to line 550 by line 702 flowing through valve 704.
Line 556 provides communication between line 530 and line 544
through valves 557 and 558 a further line 560 provides bypass
A communication between line 265 and line 544.
