U.S. patent application number 11/609109 was filed with the patent office on 2008-06-12 for systems and methods using an unmixed fuel processor.
Invention is credited to Parag Prakash Kulkarni, Rizeq George Rizeq, Raul Fernando Subia.
Application Number | 20080134666 11/609109 |
Document ID | / |
Family ID | 39135126 |
Filed Date | 2008-06-12 |
United States Patent
Application |
20080134666 |
Kind Code |
A1 |
Kulkarni; Parag Prakash ; et
al. |
June 12, 2008 |
Systems and Methods Using an Unmixed Fuel Processor
Abstract
Disclosed herein are systems and method for using unmixed fuel
processors. In one embodiment, a system for using an unmixed fuel
processor comprises: an unmixed fuel processor and a power
generating unit. The unmixed fuel processor comprises: a
gasification reactor, an oxidation reactor and a regeneration
reactor. The gasification reactor comprises a CO.sub.2 sorbent
material. The oxidation reactor comprises an oxygen transfer
material. The regeneration reactor is configured to receive spent
CO.sub.2 sorbent material from the gasification reactor and to
return regenerated CO.sub.2 sorbent material to the gasification
reactor, and configured to receive oxidized oxygen transfer
material from the oxidation reactor and to return reduced oxygen
transfer material to the oxidation reactor. The power generating
unit configured to receive an oxygen depleted stream from the
oxidation reactor and to produce electricity.
Inventors: |
Kulkarni; Parag Prakash;
(Tustin, CA) ; Rizeq; Rizeq George; (Mission
Viejo, CA) ; Subia; Raul Fernando; (Anaheim,
CA) |
Correspondence
Address: |
GENERAL ELECTRIC COMPANY;GLOBAL RESEARCH
PATENT DOCKET RM. BLDG. K1-4A59
NISKAYUNA
NY
12309
US
|
Family ID: |
39135126 |
Appl. No.: |
11/609109 |
Filed: |
December 11, 2006 |
Current U.S.
Class: |
60/227 |
Current CPC
Class: |
C01B 2210/0046 20130101;
C01B 2203/0283 20130101; C01B 3/50 20130101; C01B 2203/0485
20130101; F23C 99/00 20130101; F23C 2900/99008 20130101; C10J
2300/0973 20130101; Y02E 20/18 20130101; Y02E 20/346 20130101; C01B
2203/84 20130101; C10J 2300/1606 20130101; C10J 2300/1678 20130101;
Y02P 20/129 20151101; C10J 2300/1675 20130101; C01B 2203/147
20130101; C10J 2300/093 20130101; C10J 2300/0956 20130101; C10J
2300/1637 20130101; C10J 2300/1807 20130101; Y02E 20/34 20130101;
C01B 3/12 20130101; C10J 2300/165 20130101; F23C 10/00 20130101;
C10J 3/482 20130101; Y02E 20/16 20130101; C01B 13/0229 20130101;
C01B 2203/0415 20130101; C01B 2203/0475 20130101; C01B 3/52
20130101; Y02P 20/13 20151101; C01B 3/56 20130101; C01B 2203/043
20130101; C10J 2300/1853 20130101; C10J 3/725 20130101 |
Class at
Publication: |
60/227 |
International
Class: |
F01B 23/00 20060101
F01B023/00 |
Goverment Interests
[0001] This invention was made with Government support under
contract number DOE NETL DE-FC26-05NT40974 awarded by the U.S.
Department of Energy. The Government may have certain rights in the
invention.
Claims
1. A system for using an unmixed fuel processor, comprising: an
unmixed fuel processor comprising a gasification reactor with a
solid hydrocarbon fuel inlet, water inlet, and hydrogen outlet, and
comprising a CO.sub.2 sorbent material; an oxidation reactor with
an air inlet and effluent outlet, and comprising an oxygen transfer
material; and a regeneration reactor with a water inlet and a
CO.sub.2 stream outlet, wherein the regeneration reactor is
configured to receive spent CO.sub.2 sorbent material from the
gasification reactor and to return regenerated CO.sub.2 sorbent
material to the gasification reactor, and configured to receive
oxidized oxygen transfer material from the oxidation reactor and to
return reduced oxygen transfer material to the oxidation reactor;
and a power generating unit configured to receive an oxygen
depleted stream from the oxidation reactor and to produce
electricity.
2. The system of claim 1, wherein the power generating unit
comprises an expander configured to reduce the pressure of the
oxygen depleted stream to produce a reduced pressure stream; a
first heat recovery steam generator configured to transfer heat
from the reduced pressure stream to a water stream to produce
steam; and a steam turbine configured to generate electricity from
the steam.
3. The system of claim 2, further comprising a plant configured to
receive hydrogen from the gasification reactor and nitrogen from
the first heat recovery steam generator, and to produce
ammonia.
4. The system of claim 2, further comprising a plant configured to
receive hydrogen from the gasification reactor, nitrogen from the
first heat recovery steam generator, and CO.sub.2 from the
regeneration reactor, and configured to produce urea.
5. The system of claim 1, further comprising a plant configured to
receive hydrogen from the gasification reactor and to produce a
material selected from the group consisting of urea, ammonia, and
combinations comprising at least one of the foregoing
materials.
6. The system of claim 1, further comprising a second heat recovery
steam generator configured to receive a hydrogen stream from the
gasification reactor; a shift reactor configured to receive the
hydrogen stream from the second heat recovery steam generator and
to convert CO in the hydrogen stream to CO.sub.2; a gas clean-up
unit configured to receive the hydrogen stream from the shift
reactor and to reduce a concentration of an impurity in the
hydrogen stream; and a pressure swing absorption unit configured to
receive the hydrogen stream from the gas clean-up unit, to separate
hydrogen in the hydrogen stream from other stream components, and
to produce a purified hydrogen stream and a PSA off-gas; and a
compressor configured to receive and compress the PSA off-gas to
form a compressed PSA-off gas; wherein the oxidation reactor and/or
a combustor are configured to receive the compressed PSA
off-gas.
7. The system of claim 6, wherein the combustor is configured to
receive all of the compressed PSA off-gas stream and to produce a
combustion stream, the power generating unit is configured to
receive the combustion stream, and the oxidation reactor is
configured to receive no compressed PSA off-gas.
8. The system of claim 1, further comprising a second heat recovery
steam generator configured to receive a hydrogen stream from the
gasification reactor; a shift reactor configured to receive the
hydrogen stream from the second heat recovery steam generator and
to convert CO in the stream to CO.sub.2; a gas clean-up unit
configured to receive the hydrogen stream from the shift reactor
and to remove from the hydrogen stream; and a fuel cell configured
to receive the hydrogen stream from the gas clean-up unit and to
produce electricity and a by-product stream; wherein the compressor
is configured to receive the by-product stream from the fuel
cell.
9. The system of claim 8, wherein the power generating unit
comprises a first heat recovery steam generator configured to
transfer heat from the oxygen depleted stream to a water stream to
produce steam; and a steam turbine configured to generate
electricity from the steam.
10. The system of claim 9, wherein the first heat recovery steam
generator is in direct fluid communication with the oxidation
reactor and the oxidation reactor is in direct fluid communication
with the compressor.
11. The system of claim 1, further comprising a second compressor
configured to compress air prior to the air entering the oxidation
reactor.
12. The system of claim 1, further comprising a third heat recovery
steam generator configured to receive a CO.sub.2 stream from the
regeneration reactor.
13. The system of claim 12, wherein the regeneration reactor is
configured to receive a portion of the CO.sub.2 stream.
14. A system for producing electricity, comprising: an unmixed fuel
processor comprising a gasification reactor with a solid
hydrocarbon fuel inlet, steam inlet, and hydrogen outlet, and
comprising a CO.sub.2 sorbent material; an oxidation reactor with
an air inlet and effluent outlet, and comprising an oxygen transfer
material; and a regeneration reactor with a steam inlet and a
CO.sub.2 stream outlet, wherein the regeneration reactor is
configured to receive spent CO.sub.2 sorbent material from the
gasification reactor and to return regenerated CO.sub.2 sorbent
material to the gasification reactor, and configured to receive
oxidized oxygen transfer material from the oxidation reactor and to
return reduced oxygen transfer material to the oxidation reactor; a
shift reactor configured to receive the hydrogen-rich syngas stream
from the gasification reactor and to convert CO in the hydrogen
stream to CO.sub.2; a gas clean-up unit configured to receive the
hydrogen-rich syngas stream from the shift reactor and to reduce a
concentration of an impurity in the hydrogen stream; a pressure
swing absorption unit configured to receive the hydrogen stream
from the gas clean-up unit, to separate hydrogen in the hydrogen
stream from other stream components, and to produce a purified
hydrogen stream and a PSA off-gas; and a compressor configured to
receive and compress the PSA off-gas to form a compressed PSA-off
gas; and a power generating unit configured to receive an oxygen
depleted stream from the oxidation reactor and to produce
electricity; wherein the oxidation reactor and/or a combustor are
configured to receive the compressed PSA off-gas.
15. A method for producing electricity, comprising: gasifying solid
hydrocarbon fuel with water; adsorbing CO.sub.2 with a CO.sub.2
adsorbing material to produce a spent CO.sub.2 sorbent material and
a hydrogen stream comprising hydrogen; oxidizing an oxygen transfer
material and producing an oxygen depleted stream in an oxidation
reactor; regenerating the spent CO.sub.2 adsorbing material and the
oxidized oxygen transfer material and producing a CO.sub.2 stream;
and generating electricity in a power generating unit with the
oxygen depleted stream.
16. The method of claim 15, wherein generating the electricity
further comprises reducing a pressure of the oxygen depleted
stream; producing steam by transferring heat from the oxygen
depleted steam to form a cooled stream; and passing the steam
through a steam turbine.
17. The system of claim 16, further comprising reacting the
hydrogen with nitrogen in the cooled stream to produce ammonia.
18. The system of claim 16, further comprising reacting the
hydrogen, nitrogen in the cooled stream, and the CO.sub.2 in the
CO.sub.2 stream, to produce urea.
19. The method of claim 15, wherein generating the electricity
further comprises using the hydrogen in a fuel cell to produce
electricity; producing steam by transferring heat from the oxygen
depleted steam; and passing the steam through a steam turbine to
produce additional electricity.
20. The method of claim 15, further comprising reacting hydrogen to
produce a material selected from the group consisting of urea,
ammonia, and combinations comprising at least one of the foregoing
materials.
21. The method of claim 15, further comprising recovering heat from
the hydrogen stream; converting CO in the hydrogen stream to
CO.sub.2; reducing a concentration of an impurity in the hydrogen
stream; and separating hydrogen in the hydrogen-rich syngas stream
from other stream components to form a purified hydrogen stream and
a PSA off-gas; compressing the PSA off-gas.
22. The method of claim 21, further comprising combusting the
compressed PSA off-gas to produce a combustion stream and producing
electricity with the combustion stream.
23. The method of claim 21, further comprising introducing the
compressed PSA off-gas to the oxidation reactor.
Description
BACKGROUND
[0002] This application relates generally to unmixed fuel
processors, and more particularly, to systems and methods for
producing electricity and/or hydrogen using unmixed fuel
processors.
[0003] With its abundant domestic supply, coal is one of the most
secure, reliable, and affordable energy supplies for the U.S.
today, gasification of coal to produce electricity is being
commercially introduced as Integrated Gasification Combined Cycle
(IGCC) power plants. However, one of the major problems in modern
industrial society is the air pollution by conventional combustion
systems based on fossil fuels. The oldest recognized air pollution
problem is the emission of smoke. In modern boilers and furnaces,
smoke emissions could be eliminated or at least greatly reduced by
the use of Over Fire Air ("OFA") technology. Other types of air
pollution produced by combustion include particulate emissions such
as fine particles of ash from pulverized coal firing, oxides of
sulfur (SO.sub.2 and SO.sub.3), carbon monoxide emissions, volatile
hydrocarbon emissions and the release of two oxides of nitrogen, NO
and NO.sub.2. More recently, the problem of global warming due to
greenhouse gas emissions of CO.sub.2 from power plants and other
combustion systems has become a matter of serious environmental
concern.
[0004] Another major technological problem concerns the use of coal
as a fuel for powering gas turbines. Gas turbines are the lowest
capital cost systems available for generating electrical power.
Since the thermodynamic efficiency of gas turbines increases with
increasing turbine inlet temperature, efforts to improve turbine
efficiency generally involve increasing the turbine inlet
temperature to higher levels. As a result, turbine blades and other
components have been engineered to tolerate increasing high inlet
temperatures. It is well known that the hot gases produced by coal
firing contain fly ash (which is erosive to turbine blades). In the
presence of this erosive fly ash, the maximum service temperature
at which turbine blades can operate is less than it would be
otherwise. This limitation significantly decreases the overall
process efficiency and lowers the competitiveness of coal as a gas
turbine fuel. These and other disadvantages have also prevented
lower cost (and abundant) coal from being considered an attractive
gas turbine fuel. If a process were developed whereby coal could be
burned in a manner that produced hot gases that were not erosive or
corrosive, the need for temperature reduction would be eliminated
and coal would become a much more economically viable gas turbine
fuel.
[0005] U.S. Pat. Nos. 5,339,754, 5,509,362, and 5,827,496, disclose
a method of burning fuels using a catalyst that is readily reduced
when in an oxidized state and readily oxidized when in a reduced
state, with the fuel and air being alternatively contacted with the
catalyst. The fuel reduces the catalyst and is oxidized to carbon
dioxide (CO.sub.2) and water vapor. In turn, the air oxidizes the
catalyst and becomes depleted of oxygen. Combustion can thereby be
effected without the need of mixing the fuel and air prior to or
during the combustion process. If means are provided whereby the
CO.sub.2 and water vapor and the oxygen depleted air can be
directed in different directions as they leave the combustion
process, the mixing of fuel and air can be completely avoided. This
particular method of combustion has become known in the art as
"unmixed combustion".
[0006] Hence, there continues to be a need for more efficient,
environmentally friendly, reliable power generation process.
BRIEF DESCRIPTION
[0007] Disclosed herein are embodiments of systems and method for
using unmixed fuel processors. In one embodiment, a system for
using an unmixed fuel processor comprises: an unmixed fuel
processor and a power generating unit. The unmixed fuel processor
comprises: a gasification reactor, an oxidation reactor and a
regeneration reactor. The gasification reactor has a solid
hydrocarbon fuel inlet, water inlet, and hydrogen outlet, and
comprises a CO.sub.2 sorbent material. The oxidation reactor has an
air inlet and effluent outlet, and comprises an oxygen transfer
material. The regeneration reactor has a CO.sub.2 stream outlet and
is configured to receive spent CO.sub.2 sorbent material from the
gasification reactor and to return regenerated CO.sub.2 sorbent
material to the gasification reactor, and configured to receive
oxidized oxygen transfer material from the oxidation reactor and to
return reduced oxygen transfer material to the oxidation reactor.
The power generating unit configured to receive an oxygen depleted
stream from the oxidation reactor and to produce electricity.
[0008] In one embodiment, a method for using an unmixed fuel
processor comprises: gasifying a solid hydrocarbon fuel with water,
capturing CO.sub.2 with a CO.sub.2 sorbent material to produce a
spent CO.sub.2 sorbent material and a hydrogen stream comprising
hydrogen, oxidizing an oxygen transfer material and producing an
oxygen depleted stream in an oxidation reactor, regenerating the
spent CO.sub.2 sorbent material and the oxidized oxygen transfer
material and producing a CO.sub.2 stream, and generating
electricity in a power generating unit with the oxygen depleted
stream.
[0009] The above described and other features are exemplified by
the following figures and detailed description.
BRIEF DESCRIPTION OF THE DRAWINGS
[0010] Refer now to the figures, which are exemplary, not limiting,
and wherein like numbers are numbered alike.
[0011] FIG. 1 is a schematic illustration of an exemplary
embodiment of an unmixed fuel processor (UFP) system.
[0012] FIG. 2 is a schematic diagram of an exemplary embodiment of
an integrated gasification combined cycle (IGCC) polygeneration
plant including CO.sub.2 capture.
[0013] FIG. 3 is a schematic diagram of an exemplary embodiment of
an unmixed fuel processor polygen system with CO.sub.2
separation.
[0014] FIG. 4 is a schematic diagram of an exemplary embodiment of
unmixed fuel processor polygen system with combustion of the PSA
off-gas.
[0015] FIG. 5 is a schematic diagram of an exemplary embodiment of
unmixed fuel processor polygen system with use of the H.sub.2 and
the CO.sub.2 and/or N.sub.2
[0016] FIG. 6 is a schematic diagram of an exemplary embodiment of
unmixed fuel processor polygen system with CO.sub.2 separation for
electricity generation at low pressure.
DETAILED DESCRIPTION
[0017] Integrated gasification combined cycle (IGCC) technology is
well suited to better meet the needs for power generation from coal
more cleanly than other technologies. It is also compatible with
carbon sequestration and production of hydrogen fuel. Also, since
unmixed fuel processor (UFP) technology offers the potential for
reduced cost, increased process efficiency, and/or lower emissions
relative to other gasification and combustion systems, a
combination of the combined cycle (CC) and UFP technologies could
be improve efficiency in an environmentally friendly fashion. This
combined technology could be employed in conjunction with fuel
cells and/or with additional plants (e.g., urea and/or ammonia
generating plants) to produce electricity, urea, and/or ammonia,
while also producing a stream that is ripe for CO.sub.2
sequestration.
[0018] Referring now to the figures, wherein like elements in the
several figures are numbered alike for convenience and clarity of
the figures, but are not discussed in relation to each figure. FIG.
1 schematically illustrates an unmixed fuel processor 80 and the
flows therein. In unmixed fuel processer technology, solid
hydrocarbon fuel (e.g., coal, biomass, etc.), water (e.g., steam),
and air are converted into separate streams of hydrogen-rich gas in
a gasification reactor 28, CO.sub.2-rich gas that can be sent for
sequestration in a regeneration reactor 30, and oxygen-depleted
(vitiated) air in the oxidation reactor 32 (at high temperature
(e.g., about 1,100.degree. C. to about 1,300.degree. C.) and
pressure (e.g., about 1 atmospheres (atm) to about 60 atm)) that
can be used to generate electricity, e.g., in a gas turbine
expander. The UFP technology captures CO.sub.2 at a high
temperature (about 600.degree. C. to about 1,200.degree. C., or,
more specifically, about 750.degree. C. to about 1,100.degree. C.)
and high pressure (about 1 atmospheres (atm) to about 60 atm, or,
more specifically, about 20 atm) using CO.sub.2 sorbent material.
Further, as fuel and air are not mixed together and also because of
the lower gas turbine inlet temperature (e.g., temperatures of less
than or equal to about 1,300.degree. C. compared to about
1,400.degree. C. for other gas turbine systems), the UFP process
can produce lower amounts of pollutants such as NOx as compared to
a non-UFP process.
[0019] The UFP technology concept generally uses three circulating
fluidized bed reactors containing CO.sub.2 sorbent material and
oxygen transfer material (OTM). CO.sub.2 sorbent material (e.g.,
metal oxide and/or metal carbonate systems based on elements such
as calcium (Ca), magnesium (Mg), sodium (Na), lithium (Li), silicon
(Si), as well as combinations comprising at least one of the
foregoing) absorbs and/or adsorbs CO.sub.2 to form carbonates
(sorbent-CO.sub.2). The OTM is a metal oxide (e.g., an oxide of
iron, nickel, copper, manganese, and so forth, as well as
combinations comprising at least one of the foregoing), which can
be oxidized to form metal oxides (OTM-O). A mixture of the bed
materials is present in each reactor, and the bed materials undergo
a variety of transformations and reactions as they move from one
reactor to another. Each reactor serves a different key purpose:
gasification, CO.sub.2 release, or oxidation.
[0020] The gasification reactor 28 initially gasifies solid
hydrocarbon fuel (e.g., coal and/or other fossil fuels containing
elements C, H, O, as well as combinations comprising at least one
of the foregoing); coal (e.g., pulverized coal) fed to this is
partially gasified with water (e.g., superheated steam) to produce
H.sub.2, CO, and CO.sub.2. Conditions in the gasification reactor
(e.g., a temperature of about 600.degree. C. to about 900.degree.
C., or, more particularly, about 750.degree. C. to about
850.degree. C.; and a pressure of about 1 atm to about 60 atm, or,
more particularly, about 15 atm to about 20 atm) facilitate
CO.sub.2 absorption by the CO.sub.2 sorbent material. The reduction
in gas-phase CO.sub.2 concentration shifts the equilibrium of the
water-gas shift reaction to deplete CO from the gas phase
(CO+H.sub.2O.fwdarw.H.sub.2+CO.sub.2). The removal of both CO and
CO.sub.2 in the gasification reactor 28 results in a H.sub.2-rich
product stream. The circulation of bed materials provides a
continuous supply of fresh CO.sub.2 sorbent material from and
transfers spent CO.sub.2 sorbent material to the regeneration
reactor 30.
[0021] The regeneration reactor 30 is the location of CO.sub.2
release from spent CO.sub.2 sorbent material
(sorbent-CO.sub.2+heat.fwdarw.sorbent+CO.sub.2), thereby
regenerating the CO.sub.2 sorbent. Regeneration occurs as the hot
bed material (oxygen transfer material, e.g., at a temperature of
about 1,100 to about 1,300.degree. C.) transferred from the
oxidation reactor 32 heats regeneration reactor 30, increasing the
bed temperature to a sufficient level for CO.sub.2 release; e.g.,
to a temperature of about 900.degree. C. to about 1,100.degree. C.
(e.g., at a pressure of about 1 atm to about 20 atm). The CO.sub.2
release generates a CO.sub.2-rich product stream suitable for
sequestration. In addition, the oxidized oxygen transfer material
from oxidation reactor 32 is reduced by the sygnas generated from
gasification of char as it provides the oxygen needed to oxidize CO
to CO.sub.2 and H.sub.2 to H.sub.2O.
OTM-O+CO.fwdarw.OTM+CO.sub.2
OTM-O+H.sub.2.fwdarw.OTM+H.sub.2O
[0022] The reduced oxygen transfer material is oxidized in
oxidation reactor 32:
OTM+1/2O.sub.2.fwdarw.OTM-O+heat
Hence, air fed to the oxidation reactor 32 re-oxidizes the oxygen
transfer material via a highly exothermic reaction that consumes
most of the oxygen in the air feed. Thus, the oxidation reactor 32
produces high-temperature (temperature of about 1,100.degree. C. to
about 1,300.degree. C.), high-pressure (e.g., a pressure of greater
than or equal to about 15 atm, or, more particularly, about 15 atm
to about 20 atm) oxygen-depleted (vitiated) air for use in a gas
turbine expander, as well as generating heat that is transferred to
gasification reactor 28 and regeneration reactor 30, via solid
transfer. Essentially, the regeneration reactor 30 exchanges bed
materials with both gasification reactor 28 and oxidation reactor
32 with no direct gasification reactor-to-oxidation reactor
transfer, thereby allowing for the regeneration and recirculation
of both the CO.sub.2 sorbent material and the oxygen transfer
material. CO.sub.2 sorbent material captures CO.sub.2 in the
gasification reactor 28 and releases it in regeneration reactor 30,
while the oxygen transfer material is oxidized in oxidation reactor
32 and reduced in regeneration reactor 30. Other exemplary UTP
units that can be used in the systems disclosed herein is disclosed
in U.S. patent application Ser. No. ______ to Kulkarni et al.,
Attorney Docket No. 217323-1 (GE3-0180), filed concurrently
herewith.
[0023] Referring now to FIG. 2 that is a schematic view of an
exemplary integrated gasification combined cycle (IGCC)
polygeneration plant for electricity production from a solid
hydrocarbon fuel (e.g., coal). The plant includes an air separation
unit 2 that receives air and separates the oxygen and nitrogen. The
oxygen enters a syngas generator 4 along with coal. From the
generator 4, the syngas is cooled in a heat exchanger 6 prior to
entering a water gas shift reactor (shift reactor) 8 where carbon
monoxide in the stream is converted to carbon dioxide. From the
shift reactor, the stream then passes through a gas clean-up unit
(e.g., a syngas clean-up unit, an acid gas recovery (AGR) unit, and
the like) 10 to remove sulfur, carbon dioxide scrubber 12 to remove
carbon dioxide (CO.sub.2), and pressure swing absorption (PSA) unit
14 to separate impurities from the hydrogen (H.sub.2) stream. The
impurities are burned in a combustor 16 along with the nitrogen
stream from the air separation unit and compressed air from
compressor 18. The combustion stream enters the power generating
unit 100 comprising optional expander(s) 20 (e.g., turbines), heat
recovery steam generator(s) (HRSG) 22, steam turbine(s) 24 and
generator(s) 26.
[0024] FIG. 3 shows the UFP process, described in FIG. 1,
integrated in a polygen plant that can produce hydrogen and/or
electricity along with CO.sub.2 capture. In FIG. 3, the air
separation unit is not required (not shown) as with many polygen
plants, CO.sub.2 separation is inherent in the unmixed fuel
processor (UFP) 80 comprising reactors 1 (R1), 2 (R2), and 3 (R3),
and heat exchange losses are reduced or eliminated due to the use
of oxygen depleted air (vitiated stream) in the expander 20. In
this arrangement, air is introduced directly to a compressor 40
prior to entering the UFP 80. The compressor can compress the air
to a pressure of about 2 atm to about 60 atm, or, more
specifically, about 15 atm to about 20 atm. In the UFP 80, air and
the compressed PSA off-gas from the PSA unit 14 enter the oxidation
reactor 32 where oxygen transfer material is oxidized prior to
entering the CO.sub.2 release reactor 30 (regeneration
reactor).
[0025] From the CO.sub.2 release reactor 30, reduced oxygen
transfer material returns to the oxidation reactor 32, and
regenerated CO.sub.2 sorbent material passes to the gasification
reactor 28, while a CO.sub.2 rich stream,r can pass through heat
recovery steam generator and condenser 36 and/or through compressor
38 prior to sequestration. The CO.sub.2 stream can then be
sequestered. Part of the high pressure CO.sub.2 stream can be
recycled to the CO.sub.2 release reactor 30. Recycle of CO.sub.2
decreases the steam requirement for fluidization and thus increases
the overall efficiency of the process (e.g., an increase in
efficiency of greater than or equal to 0.5%, or, even greater than
or equal to about 2%).
[0026] In the gasification reactor 28, coal is gasified and the
CO.sub.2 sorbent material captures CO.sub.2, facilitating the water
gas shift reaction that converts additional CO to CO.sub.2 for
adsorption and produces a H.sub.2 rich stream containing greater
than or equal to about 60 volume percent (vol %) H.sub.2 in the
syngas stream, or, more specifically about 60 vol % to about 90 vol
% H.sub.2 in the syngas. The CO.sub.2 sorbent material returns to
the CO.sub.2 release reactor 30, while the gasification reactor
effluent (a CO.sub.2 reduced stream) can pass from the gasification
reactor 28, and through a heat recovery steam generator 34, a shift
reactor 8, a gas clean-up (e.g., an acid gas recovery (AGR)) unit
10, and pressure swing absorption unit 14. The shift reactor 8 can
reduce the concentration of CO in the CO.sub.2 reduced stream from
about 10 vol % to about 30 vol % down to less than or equal to
about 1 vol %, while producing more H.sub.2. The acid gas recovery
unit 10 removes impurities such as chlorine, sulfur, and ammonia,
from the stream (e.g., from the coal-derived syngas). The pressure
swing absorption unit 14 further purifies the stream from shift
reactor to produce a pure H.sub.2 stream (e.g., 99.99% pure) that
can be employed, for example, for fuel cell based applications.
[0027] The hydrogen stream exiting the PSA unit 14 can be used as
desired (e.g., liquefaction, fuel cells, turbines, and so forth),
while the PSA off-gas can be compressed in compressor 18 and
returned to the oxidation reactor 32 and/or combusted. In other
words, all of the PSA off-gas can be recycled to the oxidation
reactor 32, or all of the PSA off-gas can be combusted, or, a
portion of the PSA off-gas can be recycled to the oxidation reactor
32 while another portion of the PSA off-gas can be combusted. With
the recycle of CO.sub.2 to the regeneration reactor 30, steam flow
to the reactor can be reduced and hence operating costs can be
reduced. An effluent stream from the oxidation reactor 32 and/or
combustor (see FIG. 4), can then be used in the power generating
unit 100.
[0028] As noted above and as illustrated in FIG. 4, the PSA off-gas
can be directed to the oxidation reactor 32 and/or a combustor 16.
When all or a portion of the PSA off-gas is combusted, the
combustion stream can be directed to the expander 20 of the power
generating unit 100. Combustion of the PSA off-gas enhances system
efficiency due to the introduction of higher temperature gas (about
1,300.degree. C. to about 1,400.degree. C.) to the expander 20. In
addition, or alternative, to using PSA off-gas in a combustor 16,
all or a portion of the hydrogen stream from the PSA unit 14 can be
used in various plant(s) 42. (See FIG. 5) Possible plant(s) 42
include urea, ammonia, and so forth, as well as combinations
comprising at least one of these plants.
[0029] In FIG. 6, the PSA unit has been replaced with a fuel cell
44. In this embodiment, the compressor 40 and expander 20 have been
removed, allowing direct fluid communication between the compressor
18 and the oxidation reactor 32, and between the oxidation reactor
32 and the heat recovery steam generator 22. The optional removal
of the compressor 40 and expander 20 (see FIG. 3), enables the low
pressure electricity generation. As a result, capital expenditures
can be minimized with the low pressure, low temperature production
of electricity.
[0030] These systems employing power generation with the unmixed
fuel processor (UFP) as disclosed herein enable multiple advantages
over systems that do not employ the UFP. For example, (i) a fuel
cell can be added to the system to further enable electricity
generation and/or back-up power generation, an air separation unit
is not required as in many power generation systems; (ii) CO.sub.2
separation is inherent in the UFP system disclosed; (iii) the
hydrogen from the UFP is substantially rich (e.g., greater than or
equal to about 80 vol %), thereby reducing the load on the pressure
swing absorber; (iv) since a hot oxygen depleted stream can be sent
directly to the power generating unit, heat exchange losses are
eliminated; (v) the recirculation of the CO.sub.2 to the
regeneration reactor reduces the amount of steam needed in that
reactor, thereby enhancing system efficiency; (vi) the use of the
combustor to combust some or all of the PSA off-gas increases inlet
temperatures to the expander, again improving system efficiency;
and (vii) the hydrogen and nitrogen produced in the system are in a
condition that can be used to produce urea and/or ammonia.
[0031] Ranges disclosed herein are inclusive and combinable (e.g.,
ranges of "up to about 25 wt %, or, more specifically, about 5 wt %
to about 20 wt %", is inclusive of the endpoints and all
intermediate values of the ranges of "about 5 wt % to about 25 wt
%," etc.). "Combination" is inclusive of blends, mixtures, alloys,
reaction products, and the like. Furthermore, the terms "first,"
"second," and the like, herein do not denote any order, quantity,
or importance, but rather are used to distinguish one element from
another, and the terms "a" and "an" herein do not denote a
limitation of quantity, but rather denote the presence of at least
one of the referenced item. The modifier "about" used in connection
with a quantity is inclusive of the state value and has the meaning
dictated by context, (e.g., includes the degree of error associated
with measurement of the particular quantity). The suffix "(s)" as
used herein is intended to include both the singular and the plural
of the term that it modifies, thereby including one or more of that
term (e.g., the colorant(s) includes one or more colorants).
Reference throughout the specification to "one embodiment",
"another embodiment", "an embodiment", and so forth, means that a
particular element (e.g., feature, structure, and/or
characteristic) described in connection with the embodiment is
included in at least one embodiment described herein, and may or
may not be present in other embodiments. In addition, it is to be
understood that the described elements may be combined in any
suitable manner in the various embodiments.
[0032] All cited patents, patent applications, and other references
are incorporated herein by reference in their entirety. However, if
a term in the present application contradicts or conflicts with a
term in the incorporated reference, the term from the present
application takes precedence over the conflicting term from the
incorporated reference.
[0033] While the invention has been described with reference to a
preferred embodiment, it will be understood by those skilled in the
art that various changes may be made and equivalents may be
substituted for elements thereof without departing from the scope
of the invention. In addition, many modifications may be made to
adapt a particular situation or material to the teachings of the
invention without departing from essential scope thereof.
Therefore, it is intended that the invention not be limited to the
particular embodiment disclosed as the best mode contemplated for
carrying out this invention, but that the invention will include
all embodiments falling within the scope of the appended
claims.
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