High temperature fuel cell system and method of operating same

• US 20050164051A1
• Filed: 12/03/2004
• Published: 07/28/2005
• Est. Priority Date: 01/22/2004
• Status: Active Grant

• Current Assignee: Bloom Energy Corporation
• Original Assignee: Bloom Energy Corporation
• Inventors: Gottmann, Matthias, Finn, John, Venkataraman, Swaminathan
• Granted Patent: US 7,422,810 B2
• Time in Patent Office: Days
• US Class Current: 429/410
• CPC Class Codes: B01J 19/249 Plate-type reactors
• CPC Class Codes: B01J 2208/00309 with two or more reactions in heat exchange with each other, such as an endothermic reaction in heat exchange with an exothermic reaction
• CPC Class Codes: B01J 2208/00716 Means for reactor start-up
• CPC Class Codes: B01J 2219/00006 Large-scale industrial plants
• CPC Class Codes: B01J 2219/2465 Two reactions in indirect heat exchange with each other
• CPC Class Codes: B01J 2219/2479 Catalysts coated on the surface of plates or inserts
• CPC Class Codes: B01J 2219/2481 Catalysts in granular from between plates
• CPC Class Codes: B01J 8/0257 in a cylindrical annular shaped bed
• CPC Class Codes: B01J 8/0285 Heating or cooling the reactor for tubular reactors in furnaces B01J8/062
• CPC Class Codes: C01B 2203/0233 the reforming step being a steam reforming step
• CPC Class Codes: C01B 2203/0283 containing a CO-shift step, i.e. a water gas shift step
• CPC Class Codes: C01B 2203/043 Regenerative adsorption process in two or more beds, one for adsorption, the other for regeneration
• CPC Class Codes: C01B 2203/0475 the impurity being carbon dioxide
• CPC Class Codes: C01B 2203/0495 the impurity being water
• CPC Class Codes: C01B 2203/066 with fuel cells
• CPC Class Codes: C01B 2203/0811 by combustion of fuel
• CPC Class Codes: C01B 2203/0822 the fuel containing hydrogen
• CPC Class Codes: C01B 2203/1035 Catalyst coated on equipment surfaces, e.g. reactor walls
• CPC Class Codes: C01B 2203/1241 Natural gas or methane
• CPC Class Codes: C01B 2203/127 Catalytic desulfurisation
• CPC Class Codes: C01B 2203/1294 : Evaporation by heat exchange with hot process stream
• CPC Class Codes: C01B 3/384 : the catalyst being continuously externally heated
• CPC Class Codes: C01B 3/48 : followed by reaction of water vapour with carbon monoxide
• CPC Class Codes: C01B 3/56 : by contacting with solids; Regeneration of used solids C01B3/508 takes precedence
• CPC Class Codes: H01M 2008/1293 : Fuel cells with solid oxide electrolytes
• CPC Class Codes: H01M 8/04007 : related to heat exchange
• CPC Class Codes: H01M 8/04022 : Heating by combustion
• CPC Class Codes: H01M 8/04097 : with recycling of the reactants H01M8/04119, H01M8/04104 take precedence
• CPC Class Codes: H01M 8/04164 : by condensers, gas-liquid separators or filters
• CPC Class Codes: H01M 8/04268 : Heating of fuel cells during the start-up of the fuel cells
• CPC Class Codes: H01M 8/0612 : from carbon-containing material
• CPC Class Codes: H01M 8/0625 : in a modular combined reactor/fuel cell structure
• CPC Class Codes: H01M 8/0668 : Removal of carbon monoxide or carbon dioxide
• CPC Class Codes: H01M 8/0675 : Removal of sulfur
• CPC Class Codes: H01M 8/12 : operating at high temperature, e.g. with stabilised ZrO2 electrolyte
• CPC Class Codes: H01M 8/18 : Regenerative fuel cells, e.g. redox flow batteries or secondary fuel cells
• CPC Class Codes: H01M 8/2432 : Grouping of unit cells of planar configuration
• CPC Class Codes: H01M 8/249 : comprising two or more groupings of fuel cells, e.g. modular assemblies
• CPC Class Codes: Y02E 60/50 : Fuel cells
• CPC Class Codes: Y02P 20/10 : Process efficiency
• CPC Class Codes: Y02P 20/129 : Energy recovery, e.g. by cogeneration, H2recovery or pressure recovery turbines

Abstract

A high temperature fuel cell stack system, such as a solid oxide fuel cell system, with an improved balance of plant efficiency includes a thermally integrated reformer, combustor and the fuel cell stack.

Claims

1. A solid oxide fuel cell system, comprising:

a solid oxide fuel cell stack; and

a reformer adapted to reform a hydrocarbon fuel to a hydrogen containing reaction product and to provide the reaction product to the stack;

wherein the reformer is adapted to be heated by at least one of a stack cathode exhaust, a combustor which is thermally integrated with the reformer, and at least one of radiative and convective heating from the stack across a gap between the stack and the reformer.

2. The system of claim 1, further comprising a stack cathode exhaust conduit which is thermally integrated with the reformer and which is adapted to heat the reformer using the stack cathode exhaust.

3. The system of claim 2, wherein a first portion the stack cathode exhaust conduit comprises a space located between the stack and the reformer, into which space the stack cathode exhaust is provided from the stack.

4. The system of claim 1, further comprising a combustor which is thermally integrated with the reformer, and which is adapted to heat the reformer.

5. The system of claim 4, wherein a stack cathode exhaust conduit is connected to an inlet of the combustor.

6. The system of claim 4, wherein the combustor shares at least one wall with the reformer.

7. The system of claim 6, wherein the reformer comprises a catalyst containing cylinder and the combustor comprises a catalyst containing tube located in the cylinder core and the combustor tube wall comprises an inner wall of the reformer cylinder.

8. The system of claim 6, wherein the reformer comprises a catalyst containing plate shaped reformer which shares one wall with a catalyst containing plate shaped combustor.

9. The system of claim 6, wherein the reformer is located between the fuel cell stack and the combustor.

10. The system of claim 4, further comprising a catalytic partial oxidation reactor adapted to provide hydrogen into the combustor during system start up.

11. The system of claim 4, further comprising an air heat exchanger, wherein an outlet of the combustor is connected to a first inlet of the air heat exchanger, an air inlet conduit is connected to a second inlet of the air heat exchanger, and a first outlet of the air heat exchanger is connected to a cathode inlet of the stack.

12. The system of claim 1, wherein the reformer is adapted to be heated by at least one of radiative and convective heating from the stack across a gap between the stack and the reformer.

13. The system of claim 12, wherein the gap between the reformer and the fuel cell stack comprises a cathode exhaust conduit of the fuel cell stack.

14. The system of claim 13, wherein an outer reformer wall contains fins which extend into the cathode exhaust conduit and an inner reformer wall contains fins which extend into the combustor.

15. The system of claim 1, wherein the reformer is adapted to be heated by two or more of the stack cathode exhaust, the combustor which is thermally integrated with the reformer, and the at least one of radiative and convective heating from the stack across the gap between the stack and the reformer.

16. The system of claim 15, wherein the reformer is adapted to be heated by the stack cathode exhaust, by the combustor which is thermally integrated with the reformer, and by the at least one of radiative and convective heating from the stack across the gap between the stack and the reformer.

17. The system of claim 1, further comprising:

a condenser adapted to separate water from a stack anode exhaust;

an evaporator adapted to evaporate water to be provided into a stack inlet fuel stream; and

a fuel-steam mixer adapted to mix the evaporated water and the stack inlet fuel stream.

18. The system of claim 1, further comprising:

a desulfurizer fluidly connected to a fuel inlet of the fuel cell stack; and

a water-gas shift reactor fluidly connected to a fuel outlet of the fuel cell stack;

wherein the desulfurizer and the water-gas shift reactor are thermally integrated with each other.

19. The system of claim 1, further comprising:

a connecting conduit connecting a fuel inlet of the fuel cell stack with an outlet of the reformer;

a hydrocarbon fuel inlet conduit connected to an inlet of the reformer; and

a hydrocarbon fuel by-pass line fluidly connected to the fuel inlet of the fuel cell stack, wherein the by-pass line is adapted to provide unreformed hydrocarbon fuel into the fuel inlet of the fuel cell stack.

20. The system of claim 1, further comprising:

a hydrogen separation device fluidly connected to the fuel outlet of the stack;

a carbon monoxide separation device fluidly connected to the fuel outlet of the stack;

a hydrocarbon fuel inlet conduit fluidly connected to a fuel inlet of the stack; and

a carbon monoxide recycle conduit, whose inlet is fluidly connected to an outlet of the carbon monoxide separation device and whose outlet is fluidly connected to the fuel inlet of the stack.

21. The system of claim 1, further comprising:

a PSA separation device fluidly connected to a fuel outlet of the stack; and

a thermal output of the stack in addition to the fuel outlet is thermally integrated with at least a first column of the PSA device.

22. A solid oxide fuel cell system, comprising:

a solid oxide fuel cell stack;

a first means for reforming a hydrocarbon fuel to a hydrogen containing reaction product and for providing the reaction product to the stack; and

a second means for heating the first means using at least one of a stack cathode exhaust, a heat from a combustion reaction, and at least one of radiative and convective heating from the stack.

23. The system of claim 22, wherein the second means for heating the first means uses at least two of the stack cathode exhaust, the heat from a combustion reaction, and the at least one of radiative and convective heating from the stack.

24. The system of claim 22, wherein the second means for heating the first means uses the stack cathode exhaust, the heat from a combustion reaction, and the at least one of radiative and convective heating from the stack.

25. The system of claim 22, further comprising a third means for receiving the stack cathode exhaust and a hydrocarbon fuel and for heating the first means using a combustion reaction of the stack cathode exhaust and the hydrocarbon fuel during steady state operation of the stack.

26. A solid oxide fuel cell system, comprising:

a solid oxide fuel cell stack;

a reformer which is adapted to reform a hydrocarbon fuel to a hydrogen containing reaction product and to provide the reaction product to the stack; and

a combustor which shares at least one wall with the reformer.

27. The system of claim 26, wherein the reformer comprises a catalyst containing cylinder and the combustor comprises a catalyst containing tube located in the cylinder core and the combustor tube wall comprises an inner wall of the reformer cylinder.

28. The system of claim 26, wherein the reformer comprises a catalyst containing plate shaped reformer which shares one wall with a catalyst containing plate shaped combustor.

29. The system of claim 26, wherein the reformer is located between the fuel cell stack and the combustor.

30. The system of claim 29, wherein a space between the reformer and the fuel cell stack comprises a cathode exhaust conduit of the fuel cell stack.

31. The system of claim 30, wherein an outer reformer wall contains fins which extend into the cathode exhaust conduit and an inner reformer wall contains fins which extend into the combustor.

32. A method of operating a solid oxide fuel cell system, comprising:

providing a hydrocarbon fuel and water vapor into a reformer;

reforming the hydrocarbon fuel in the reformer to form a hydrogen containing reaction product;

providing the reaction product into a solid oxide fuel cell stack during steady state operation of the stack; and

heating the reformer during steady state operation of the stack using at least one of a stack cathode exhaust, a combustor which is thermally integrated with the reformer and at least one of radiative and convective heat generated by the stack.

33. The method of claim 32, wherein the step of heating comprises heating the reformer with heat from at least two of the stack cathode exhaust, the combustor and the stack.

34. The method of claim 33, wherein the step of heating comprises heating the reformer with heat from the stack cathode exhaust, the combustor and the stack.

35. The method of claim 32, wherein the step of heating comprises heating the reformer by passing the stack cathode exhaust adjacent to the reformer.

36. The method of claim 35, further comprising providing the cathode exhaust into the combustor after passing the stack cathode exhaust adjacent to the reformer.

37. The method of claim 32, wherein the step of heating comprises heating the reformer by a combustion of a hydrocarbon fuel and air in the combustor.

38. The method of claim 37, further comprising:

determining if the reformer requires additional heat for the reforming reaction; and

controlling the combustor heat output based on the step of determining to provide an desired amount heat from the combustor to the reformer.

39. The method of claim 37, further comprising providing the combustor exhaust into an air heat exchanger to heat air being provided through the air heat exchanger into the stack.

40. The method of claim 32, wherein the step of heating comprises heating the reformer by at least one of radiative and convective heat generated by the stack.

41. The method of claim 40, wherein a space between the reformer and the fuel cell stack comprises a cathode exhaust conduit of the fuel cell stack.

42. The method of claim 32, wherein the combustor heats the reformer by sharing at least one wall with the reformer.

43. The method of claim 42, wherein the reformer comprises a catalyst containing cylinder and the combustor comprises a catalyst containing tube located in the cylinder core and the combustor tube wall comprises an inner wall of the reformer cylinder.

44. The method of claim 42, wherein the reformer comprises a catalyst containing plate shaped reformer which shares one wall with a catalyst containing plate shaped combustor.

45. The method of claim 42, wherein the reformer is located between the fuel cell stack and the combustor.

46. The method of claim 32, further comprising:

providing a hydrocarbon fuel and air into a catalytic partial oxidation reactor;

generating hydrogen in the catalytic partial oxidation reactor;

providing the generated hydrogen into the combustor at system start-up;

heating up the combustor, the reformer and the solid oxide fuel cell stack during system start-up; and

stopping the provision of hydrocarbon fuel and air into the catalytic partial oxidation reactor once the stack reaches a predetermined operating temperature.

47. The method of claim 32, further comprising:

providing an anode exhaust from the fuel cell stack into a condenser;

separating water from the anode exhaust in the condenser;

providing water into an evaporator;

converting water to steam in the evaporator; and

mixing the steam with a fuel being provided to the fuel cell stack.

48. The method of claim 32, further comprising:

providing a hydrocarbon fuel into a desulfurizer;

providing desulfurized hydrocarbon fuel from the desulfurizer into the fuel cell stack;

providing an anode exhaust from the fuel cell stack into a water-gas shift reactor; and

providing heat from the water-gas shift reactor to the desulfurizer.

49. The method of claim 32, further comprising providing unreformed hydrocarbon fuel that does not pass through the reformer into the fuel inlet of the fuel cell stack.

50. The method of claim 32, further comprising starting up the fuel cell system, wherein starting up the fuel cell system comprises:

providing the solid oxide fuel cell stack at room temperature, wherein anode electrodes of the solid oxide fuel cells in the stack are reduced from previous operation;

providing a hydrocarbon fuel and an oxidizer into the combustor; and

raising a temperature of the solid oxide fuel cell stack to an operating temperature using heat from the combustor, such that no separately stored reducing or inert gases are used to flush the anode chamber of the solid oxide fuel cells of the stack during the start-up.

51. The method of claim 32, further comprising:

providing a fuel and an oxidizer into the fuel cell stack;

generating an anode exhaust stream from the fuel cell stack while the fuel and the oxidizer are provided into the fuel cell stack operating in a fuel cell mode;

separating at least a portion of hydrogen from the anode exhaust stream during the fuel cell mode operation in a hydrogen separation device;

separating at least a portion of carbon monoxide from the anode exhaust stream during the fuel cell mode operation in a carbon monoxide separation device; and

recirculating at least a portion of the separated carbon monoxide into a fuel inlet gas stream.

52. The method of claim 32, further comprising:

operating the fuel cell stack in a fuel cell mode;

separating hydrogen from an anode exhaust stream of the stack using a PSA hydrogen separation device; and

heating a first column of the PSA hydrogen separation device under purge using another thermal output of the fuel stack in addition to the anode exhaust stream.