U.S. patent application number 12/136664 was filed with the patent office on 2009-05-28 for fuel cell system and method for generating electrical energy using a fuel cell system.
Invention is credited to Peter Alin, Olaf DUEBEL, Per Ekdunge, Axel Koenig, Ronald Mallant, Jessica Grace Reinkingh.
Application Number | 20090136799 12/136664 |
Document ID | / |
Family ID | 7868449 |
Filed Date | 2009-05-28 |
United States Patent
Application |
20090136799 |
Kind Code |
A1 |
DUEBEL; Olaf ; et
al. |
May 28, 2009 |
FUEL CELL SYSTEM AND METHOD FOR GENERATING ELECTRICAL ENERGY USING
A FUEL CELL SYSTEM
Abstract
A fuel-cell system, particularly a fuel-cell system for a drive
system of a motor vehicle, includes an autothermic reformer unit
configured to generate hydrogen from a raw material. The hydrogen
is used to operate a fuel-cell unit disposed downstream of the
reformer unit. An oxidation device configured to convert carbon
monoxide into carbon dioxide is disposed between the reformer unit
and the fuel cell unit. A water injection device is disposed in the
oxidation device and is configured to inject water into the
oxidation device.
Inventors: |
DUEBEL; Olaf; (Isenbuettel,
DE) ; Koenig; Axel; (Wolfsburg, DE) ; Ekdunge;
Per; (Guteborg, SE) ; Alin; Peter;
(Landskrona, SE) ; Reinkingh; Jessica Grace;
(Malvern, PA) ; Mallant; Ronald; (Alkmaar,
NL) |
Correspondence
Address: |
KENYON & KENYON LLP
ONE BROADWAY
NEW YORK
NY
10004
US
|
Family ID: |
7868449 |
Appl. No.: |
12/136664 |
Filed: |
June 10, 2008 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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11621392 |
Jan 9, 2007 |
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12136664 |
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09700833 |
Jun 7, 2001 |
7160638 |
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PCT/EP99/03378 |
May 17, 1999 |
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11621392 |
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Current U.S.
Class: |
429/420 |
Current CPC
Class: |
Y02E 60/50 20130101;
H01M 8/1007 20160201 |
Class at
Publication: |
429/17 ;
429/19 |
International
Class: |
H01M 8/06 20060101
H01M008/06 |
Foreign Application Data
Date |
Code |
Application Number |
May 20, 1998 |
DE |
198 22 691.8 |
Claims
1-24. (canceled)
25. A fuel-cell system, comprising: a reformer unit configured to
produce hydrogen from a raw material; a fuel-cell unit disposed
downstream of the reformer unit and operable in accordance with the
hydrogen produced by the reformer unit; an oxidation device
configured to convert carbon monoxide into carbon dioxide and
disposed between the reformer unit and the fuel-cell unit; an
oxygen source configured to supply a first oxygen-containing
substance to the oxidation device; and a water-injection device
disposed at the oxidation device; wherein the fuel-cell system is
arranged such that, during operation of the fuel-cell system, the
water-injection device injects water into the oxidation device
during each operation of the oxidation device for the
conversion.
26. The fuel-cell system according to claim 25, wherein the
fuel-cell system includes a drive system of a motor vehicle.
27. The fuel-cell system according to claim 25, wherein the raw
material includes a liquid raw material.
28. The fuel-cell system according to claim 25, wherein the
reformer unit includes a mixer configured to mix the raw material
and a second oxygen-containing substance.
29. The fuel-cell system according to claim 28, wherein the second
oxygen-containing substance includes at least one of water and
air.
30. The fuel-cell system according to claim 25, further comprising
a two-stage compressor configured to supply compressed air to at
least one of a process gas between the oxidation device and the
fuel-cell unit and a cathode of the fuel-cell unit.
31. The fuel-cell system according to claim 25, further comprising
a water separation device disposed in at least one of an
exhaust-gas stream from a cathode of the fuel-cell unit, an
exhaust-gas stream from an anode of the fuel-cell unit and a
cleaned-gas stream from the oxidation unit, the water separating
device being configured to separate the water contained in the
corresponding gas and to supply the water to a water-storage device
disposed upstream from the reformer unit.
32. The fuel-cell system according to claim 31, wherein the water
separation device includes a condenser.
33. The fuel-cell system according to claim 31, further comprising
a water circulation loop configured to cool at least one of the
water separation device, the fuel-cell unit, air supplied to a
cathode of the fuel-cell unit and air supplied to the reformer
unit.
34. The fuel-cell system according to claim 25, further comprising
a catalytic burner configured to combust exhaust gas from an anode
of the fuel-cell unit and to direct corresponding waste heat
through a heat exchanger to the reformer unit.
35. The fuel-cell system according to claim 34, wherein the
catalytic burner is connected to a supply tank supplying the raw
material.
36. The fuel-cell system according to claim 25, further comprising:
an expander disposed in an exhaust-gas stream of a cathode of the
fuel-cell unit; and a compressor disposed in a supply-air stream of
the fuel-cell unit; wherein the expander and the compressor are
arranged on a common shaft.
37. The fuel-cell unit according to claim 36, wherein the
compressor includes a two-stage compressor.
38. The fuel-cell unit according to claim 25, wherein the raw
material includes a hydrogen-containing substance.
39. The fuel-cell unit according to claim 38, wherein the
hydrogen-containing substance includes at least one of methanol and
gasoline.
40. The fuel-cell system according to claim 25, further comprising:
a two-stage compressor including: a first stage via which
compressed air at a first pressure is supplied to a cathode of the
fuel-cell unit; and a second stage via which compressed air at a
second pressure higher than the first pressure is supplied to the
reformer unit.
41. The fuel-cell system according to claim 25, further comprising
a water separation device disposed in a cleaned-gas stream from the
oxidation unit, the water separation device being configured to
separate the water contained in the corresponding gas and to supply
the water to a water-storage device that supplies the water
injected by the water-injection device into the oxidation
device.
42. The fuel-cell system according to claim 25, further comprising:
a first water-storage device disposed in a first water circulation
loop, the water-injection device obtaining the water injected into
the oxidation device from the first water-storage device via
circulation of the water of the first water-storage device through
the first water circulation loop; and at least one second
water-storage device disposed in a second water circulation loop
arranged for circulating the water of the at least one second
water-storage device in proximity to elements of the fuel-cell
system for cooling the elements; wherein the circulation of the
water of the first water-storage device through the first water
circulation loop and the circulation of the water of the at least
one second water-storage device through the second water
circulation loop are separately controlled.
43. The fuel-cell system according to claim 25, wherein, for each
supply of the first-oxygen containing substance to the oxidation
unit, a corresponding amount of water is injected by the
water-injection device into the oxidation device.
44. A method for generating electrical energy using a fuel-cell
system, comprising: producing hydrogen from a raw material in a
reforming process, a fuel-cell unit of the fuel-cell system being
operable in accordance with the produced hydrogen; oxidizing carbon
monoxide into carbon dioxide after the reforming process and
upstream of the fuel-cell unit; and for the oxidizing, during the
oxidizing: supplying a first oxygen containing substance; and
injecting water.
45. The method according to claim 44, wherein the fuel-cell system
includes a drive system of a motor vehicle.
46. The method according to claim 44, wherein the water is injected
as one of a vapor and an aerosol.
47. The method according to claim 44, further comprising supplying
compressed air to at least one of a process gas between a carbon
monoxide oxidizing unit and the fuel-cell unit and a cathode of the
fuel-cell unit.
48. The method according to claim 44, further comprising:
separating water from at least one of a cathode-exhaust stream of
the fuel-cell unit and an anode-exhaust stream of the fuel-cell
unit; and supplying the separated water to the reforming
process.
49. The method according to claim 44, further comprising: burning
an exhaust gas from an anode of the fuel-cell unit; and supplying
waste heat generated by the burning step to the reforming
process.
50. The method according to claim 44, further comprising: burning
the raw material; and supplying heat energy generated by the raw
material burning to the reforming process.
51. The method according to claim 44, wherein the raw material
includes a hydrogen-containing substance.
52. The method according to claim 51, wherein the
hydrogen-containing substance includes at least one of methanol and
gasoline.
53. The method according to claim 44, further comprising: supplying
compressed air at a first pressure to a cathode of the fuel-cell
unit; and supplying compressed air at a second pressure higher than
the first pressure to a reformer unit that performs the reforming
process.
54. The method according to claim 44, further comprising:
separating water from a cleaned-gas of a stream from an oxidation
unit that performs the oxidizing step; and supplying the separated
water to a water-storage device that supplies the water that is
injected during the oxidizing step.
55. The method according to claim 44, further comprising separately
controlling a first water circulation loop for providing the water
that is injected during the oxidizing step from a first
water-storage device and a second water circulation loop for
circulating water from at least one second water-storage device for
cooling elements of the fuel-cell system.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] The present application is a continuation of U.S. patent
application Ser. No. 11/621,392, filed on Jan. 9, 2007, which is a
continuation of Ser. No. 09/700,833, now U.S. Pat. No. 7,160,638,
which was the national stage of PCT International Patent
Application No. PCT/EP99/03378, having an international filing date
of May 17, 1999, each of which is expressly incorporated herein in
its entirety by reference thereto.
FIELD OF THE INVENTION
[0002] The present invention relates to a fuel-cell system
particularly a drive system of a motor vehicle, having a reformer
unit for producing hydrogen from a raw material, such as, for
example, a liquid raw material, while feeding in air, in order to
operate a downstream fuel-cell unit; An oxidation device for
converting carbon monoxide into carbon dioxide is located between
the reformer unit and the fuel-cell unit. In addition, the present
invention relates to a method for generating electrical energy,
using a fuel-cell system, particularly for a drive system of a
motor vehicle; Hydrogen is produced from a raw material, in a
reforming process, as air is fed in, in order to operate a
fuel-cell unit; Carbon monoxide is oxidized to carbon dioxide after
the reforming process and in front of the fuel-cell unit.
BACKGROUND INFORMATION
[0003] A catalytic hydrogen generator is described in European
Published Patent Application No. 0 217 532, which produces hydrogen
from a methanol-air mixture in an autothermal reformer unit.
Located in the reformer unit is a thermocouple, which controls the
supply of air to the methanol-air mixture so that the air supply is
reduced as the temperature increases at the location of the
thermocouple in the reformer.
[0004] International Published Patent Application No. WO 96/00186
describes a hydrogen generator, the catalyst being positioned
around an inlet pipe for the methanol-air mixture, so that the
methanol-air mixture flows radially through the catalyst.
[0005] German Published Patent Application Nos. 43 45 319 and 43 29
323 each describe a fuel-cell current-generating system, in which
hydrogen is produced from a methanol-water mixture in a reformer
unit. The hydrogen is supplied to a downstream fuel cell for
generating electrical energy. To generate a sufficient amount of
heat for the reaction in the reformer, a portion of the methanol is
not added to the methanol-water mixture but is rather combusted in
an additional burner.
[0006] An electric vehicle having a driving battery made of fuel
cells is described in German Published Patent Application No. 196
29 084, the fuel cells being arranged in such that they are cooled
by the wind from driving.
[0007] In the article "Heureka?" in DE-Z Autotechnik No. 5/1997, on
pages 20 to 21, a motor vehicle having a fuel-cell drive is
described, where the hydrogen necessary for operating the fuel
cells in the vehicle is obtained from gasoline. In this
arrangement, the gasoline is converted into hydrogen in a
multi-step process. Prior to conversion, the gasoline is converted
into the gaseous state by heating it in an evaporator. Hydrogen and
carbon monoxide are formed in a partial-combustion reactor, under
oxygen-deficient conditions. Copper-oxide and zinc-oxide catalysts
are provided for oxidizing the carbon monoxide, and steam is used
to supply oxygen for the reaction. In a further step, a final
carbon monoxide fraction of approximately 1% is subsequently burned
in a conventional platinum oxidation catalyst. The mixture of
hydrogen, carbon monoxide, and carbon dioxide obtained in this
manner still contains 10 ppm carbon monoxide, which is not harmful
to a downstream fuel cell. After being cooled down to approximately
80 degrees Celsius in a heat exchanger, the gas is supplied into
the fuel cell.
[0008] A similar fuel-cell system for motor vehicles is described
in the article "Alternative Fuel" appearing in the Japanese
periodical, Asia-Pacific Automotive Report, Jan. 20, 1998, Vol.
272, page 34 to 39, where a methanol reformer unit is provided to
produce hydrogen for a fuel cell. In this arrangement, water
produced in the electrochemical reaction of hydrogen and oxygen is
reused for the reforming process. For the reforming process,
deionized water and methanol are mixed, evaporated, and converted
into hydrogen and carbon dioxide at a temperature of 250 degrees
Celsius. The hydrogen is supplied to a fuel cell, which, in a
catalytic process, converts the hydrogen, together with atmospheric
oxygen, into electrical energy and water. The heat energy necessary
for the evaporation and for the reforming process is produced in a
catalytic burner, which is located downstream from the fuel cell
and is run by residual gas from the fuel cell. This gas contains
hydrogen, since the fuel-cell system only utilizes approximately
75% of the supplied hydrogen. If an insufficient quantity of
residual hydrogen is available for the catalytic burner, methanol
from the fuel tank is used to generate heat for the reformer.
Before introducing the gas produced in the reformer, of which a
portion is hydrogen, this gas is purified by a catalytic reaction,
in which carbon monoxide is converted into carbon dioxide. In one
embodiment of a fuel-cell system for a motor vehicle, the methanol
reformer includes an evaporator, a reformer, and an oxidation unit
for carbon monoxide.
[0009] German Published Patent Application No. 43 22 765 describes
a method and a device for dynamically controlling the power output
for a vehicle having a fuel cell, which supplies electrical energy
to an electrical drive unit. Starting from a power requirement
corresponding to the position of an accelerator pedal, a mass
flowrate of air is calculated, which is needed by the fuel cell to
provide a corresponding, desired power output. The speed of a
compressor positioned in an intake line of the fuel cell is
controlled as a function of the required air flow rate.
[0010] A method and a device for supplying air to a fuel-cell
system is described in European Published Application No. 0 629
013. In this arrangement, process air is compressed by a
compressor, before it enters a corresponding fuel cell. After
process air flows through the fuel cell, the removed exhaust air is
expanded over a turbine, in order to recover energy. The turbine,
the compressor, and an additional driving motor are arranged on a
common shaft. The compressor is designed to have a variable speed,
and is arranged, along with an expander in the form of a turbine,
on a common shaft, in order to expand the exhaust air. The air flow
rate for the fuel cell is controlled by using an expander having a
variable absorption capacity.
[0011] A screw-type compressor for a refrigerator is described in
International Published Patent Application No. WO 97/16648. The
screw-type compressor includes two pump chambers, an outlet of a
first pump chamber being connected to a secondary inlet of a second
pump chamber.
SUMMARY
[0012] The present invention is based on the object of providing a
fuel-cell system that can be used more economically and in an
environmentally friendlier manner, to generate electrical energy,
particularly for a drive system of a motor vehicle, while operating
at high efficiency and occupying a small space.
[0013] The above and other beneficial objects of the present
invention are achieved by providing a fuel-cell system and method
as described and claimed herein.
[0014] The present invention provides for a fuel-cell system having
a water-injection device at the oxidation device, the
water-injection device injecting water into the oxidation
device.
[0015] This arrangement has the advantage that, simultaneously to
removing carbon monoxide from a process gas, which is from the
reformer unit and has a high concentration of hydrogen for the
fuel-cell unit, the process gas is sufficiently cooled or
precooled, so that it can be directed to the fuel-cell unit without
an expensive cooling device or by using a correspondingly less
expensive cooling device. In addition, the injected water supplies
oxygen necessary to oxidize carbon monoxide, this oxidation
reaction simultaneously releasing hydrogen, so that the amount of
oxygen having to be separately supplied to the oxidation device can
be reduced, and at the same time, the concentration of hydrogen in
the process gas can be increased. At the same power output, the
additional hydrogen enrichment in the oxidation device allows the
fuel-cell system to be dimensioned smaller thereby correspondingly
reducing the required space and the cost of equipment for the
fuel-cell system.
[0016] In one embodiment, the reformer unit includes a mixer for
the raw material and an oxygen-containing substance, such as, for
example, water and/or air.
[0017] A closed water cycle may be attained without having to
transport large amounts of water for the reforming process, in that
a water-separation device, such as, for example, a condenser, is
provided in an exhaust-gas stream from a cathode of the fuel-cell
unit, and/or in an exhaust-gas stream from an anode of the
fuel-cell unit. The condenser removes the water contained in the
corresponding exhaust gas and supplies it to a water storage device
connected upstream from the autothermal reformer unit.
[0018] An embodiment of the present invention provides a separate
water cycle, which cools the water-separation devices, the
fuel-cell unit, the air supplied to a cathode of the fuel-cell
unit, and/or the air supplied to the reformer unit. To generate the
appropriate heat energy necessary for the reaction in the reformer
unit, a catalytic burner is provided, which combusts exhaust gas
from an anode of the fuel-cell unit and directs the corresponding
waste heat through a heat exchanger to the reformer unit.
[0019] Alternatively, heat may be generated for the reformer unit
by connecting the catalytic burner to a storage tank for the raw
material.
[0020] Energy may be recovered by providing an expander in a
cathode-exhaust stream of the fuel-cell unit and by providing a
compressor, such as, for example a two-stage compressor, in a
supply-air stream of the fuel-cell unit, the expander and
compressor being arranged on a common shaft.
[0021] Such a two-stage compressor further increases the
environmental compatibility and the efficiency of the fuel-cell
system, in that two tappable pressure stages provide the rest of
the system with different levels of air pressure. The cathode of
the fuel-cell unit is subjected to a relatively low pressure by a
first stage, while a second stage initially feeds air at a higher
pressure to the reformer unit. Because of its higher relative
pressure level, the second stage compensates for the pressure
losses occurring along the longer path to the extent that
approximately the same pressure is applied to the anode and cathode
sides of the fuel-cell unit.
[0022] The raw material may include a substance containing
hydrogen, such as, for example, methanol or gasoline.
[0023] In the method according to the present invention, water is
injected during the oxidation of carbon monoxide to carbon
dioxide.
[0024] This has the advantage that, simultaneously to removing
carbon monoxide from a process gas, which is from the reforming
process and has a high concentration of hydrogen for the fuel-cell
unit, the process gas is sufficiently cooled or precooled, so that
it can be directed to the fuel-cell unit without an expensive
cooling device or by using a correspondingly less expensive cooling
device. In addition, the injected water also supplies the oxygen
necessary to oxidize carbon monoxide, this oxidation reaction
simultaneously releasing hydrogen, so that the amount of oxygen
having to be supplied separately to the oxidation device can be
reduced, and at the same time, the concentration of hydrogen in the
process gas is increased. At the same power output, the additional
hydrogen enrichment in the oxidation device allows the fuel-cell
system to be dimensioned smaller, thereby correspondingly reducing
the required space as well as the cost of equipment for the
fuel-cell system.
[0025] In order for the supply water to achieve a high efficiency,
it may be injected in the form of a vapor or aerosol.
[0026] An additional increase in the efficiency of the fuel-cell
unit may be attained by supplying compressed air to a process gas
between the carbon monoxide oxidation and the fuel-cell unit and/or
to a cathode of the fuel-cell unit.
[0027] A closed water cycle may be attained without having to
transport large amounts of water for the reforming process by
removing water from a cathode exhaust stream of the fuel-cell unit
and/or from an anode exhaust stream of the fuel-cell unit and
supplying it to the reforming process.
[0028] To generate the appropriate heat energy necessary for the
reaction of the reforming process, an exhaust gas from an anode of
the fuel-cell unit is burned, and the corresponding waste heat is
supplied to the reforming process.
[0029] Alternatively, heat may be generated for the reformer unit
by burning a raw material and supplying the corresponding heat
energy to the reforming process.
[0030] A hydrogen-containing substance, such as, for example,
methanol or gasoline, may be used as a raw material.
BRIEF DESCRIPTION OF THE DRAWING
[0031] FIG. 1 is a schematic block diagram of an embodiment of a
fuel-cell system according to the present invention.
DETAILED DESCRIPTION
[0032] In the fuel-cell system, illustrated schematically in FIG. 1
hydrogen for a fuel-cell unit 10 having an anode 12, a cathode 14,
and a cooling element 16 is produced by an autothermal reformer
unit 18, which includes a mixer 20, a heat exchanger 22, an
evaporator 24, and a catalytic reformer 26. To produce hydrogen, a
raw material, such as, for example methanol from a methanol tank
28, and water from a water tank 30 are supplied to mixer 20. The
mixture of methanol and water is evaporated in evaporator 24, and a
process gas in the form of a crude gas 32, which has a high
fraction of hydrogen, is generated in a catalytic reaction in
catalytic reformer 26.
[0033] The crude gas contains, inter alia, carbon monoxide (CO),
which must be removed before supplying it into fuel-cell unit 10.
Crude gas 32 is directed into an oxidation unit 34, in which carbon
monoxide is oxidized to carbon dioxide (CO.sub.2) in the presence
of air supplied by line 36, so that a CO concentration of less than
20 ppm results. At the same time, water from water tank 30 is
supplied via a line 44, the supplied water being injected into
oxidation unit 34 by an injection device 46. This simultaneously
cools the process gas in oxidation unit 34. In an anode-gas
condenser 40, the cleaned gas 38 produced and cooled in this manner
has water removed from it, which is supplied back to water tank 30
via line 42. Cleaned gas 38 having a high concentration of hydrogen
is then directed into anode 12 of fuel-cell unit 10. For example,
cleaned gas 38 contains 50% H.sub.2, 25% N.sub.2, and 25% CO.sub.2
at a temperature of approximately 180 to 200 degrees Celsius.
[0034] Before being directed into anode 12, cleaned gas 38 is
cooled down, for example to approximately 85 degrees Celsius in
anode-gas condenser 40.
[0035] On cathode side 14, compressed air from a two-stage,
screw-type compressor 50 is supplied via line 48 to fuel-cell unit
10. All of the air lines are indicated by dotted lines in FIG. 1.
Thus, the fuel-cell unit generates electrical energy in a
conventional manner by the reaction
H.sub.2+1/2O.sub.2.fwdarw.H.sub.2O+el. energy.
[0036] The electrical energy can be tapped off at electrodes 12, 14
and supplied to an electric motor 52. Two-stage, screw-type
compressor 50 includes a first stage 54 having a pressure of for
example, approximately 3 bar for cathode 14; and a second stage 56
having a pressure of, for example, 3.7 bar for the fuel gas, i.e.,
dehydrated, cleaned gas 38, to be supplied to anode 12. Using
another tap on screw-type compressor 50, compressed air is supplied
via line 58 to cleaned gas 38, downstream from anode-gas condenser
40.
[0037] A water separator 62, separates water from anode gas 60 and
supplies it via line 64 to water tank 30. Disposed in cathode
exhaust stream 66 is a condenser 68, which removes water from
cathode gas 66 and supplies it via line 70 to water tank 30. A
closed water circulation loop for the process gas is thus formed,
so that large amounts of water do not have to be transported for
the production of hydrogen in reformer unit 18.
[0038] A separate water circulation loop 72 indicated by a wavy
line in FIG. 1 is provided to cool the air supplied to mixer 20, to
cool anode gas condenser 40, water separator 62, and condenser 68,
and to cool the air 48 supplied to cathode 14. This separate water
circulation loop 72 includes a cooling-water tank 74, a deionized
water tank 76, and corresponding heat exchangers 78 and 80 at
cathode 14 air supply 48 and mixer 20 air supply, respectively.
[0039] Anode exhaust stream 60 flows into catalytic burner 82, in
which anode gas 60 is further combusted to form heat energy. This
heat energy is transferred by heat exchanger 22 to evaporator 24
and catalytic reformer 26, where it sustains the catalytic reaction
for producing hydrogen. Air is supplied to catalytic burner 82 by
line 84. Downstream from catalytic burner 82, water from water tank
30 may optionally be supplied to anode gas 60 by line 86.
Alternatively, methanol from methanol tank 28 may be supplied by
line 88 to catalytic burner 82 so that even in the case of an
insufficient anode exhaust stream 60, for example, during start-up
of the fuel-cell system, it is ensured that a sufficient amount of
heat energy is generated the reformer unit 18.
[0040] Cathode exhaust stream 66 is cooled in a heat exchanger 90
of separate water circulation loop 72 and is then thermally
coupled, via heat exchanger 92, to anode exhaust stream 60 before
both exhaust streams 60 and 66 exit the system.
[0041] In this arrangement, cathode exhaust stream 66 is directed
through an expansion turbine 94 that is positioned, together with a
compressor 96 for drawing in air 98, on a common shaft 100. The
compressor is provided as an input stage, in front of two-stage
compressor 50. Thus, energy contained in cathode exhaust stream 66
is recovered in order to compress air 98 in compressor 96.
[0042] A particular advantage of this embodiment, which is
characterized by a high efficiency, a small space requirement, and
a low equipment cost, is achieved by combining two-stage compressor
50 and autothermal reformer unit 18 with the additional injection
46 of cooling water during the selective oxidation of carbon
monoxide (CO) in oxidation unit 34 and by combining this with an
autonomous water circulation loop 30, 40, 42, 62, 64, 68, 70.
* * * * *