SOFC SYSTEM AND METHOD WHICH MAINTAIN A REDUCING ANODE ENVIRONMENT

• US 20180131018A1
• Filed: 11/08/2016
• Published: 05/10/2018
• Est. Priority Date: 11/08/2016
• Status: Active Grant

• Current Assignee: Bloom Energy Corporation
• Original Assignee: Bloom Energy Corporation
• Inventors: PERRY, Martin, BALLANTINE, Arne, GASDA, Michael, KARUPPAIAH, Chockkalingam
• Granted Patent: US 10,361,442 B2
• Time in Patent Office: Days
• CPC Class Codes: H01M 2008/1293 Fuel cells with solid oxide electrolytes
• CPC Class Codes: H01M 8/04074 Heat exchange unit structures specially adapted for fuel cell
• CPC Class Codes: H01M 8/04097 with recycling of the reactants H01M8/04119, H01M8/04104 take precedence
• CPC Class Codes: H01M 8/04201 Reactant storage and supply, e.g. means for feeding, pipes
• CPC Class Codes: H01M 8/04228 during shut-down
• CPC Class Codes: H01M 8/04303 applied during shut-down
• CPC Class Codes: H01M 8/04708 of fuel cell reactants
• CPC Class Codes: H01M 8/04955 Shut-off or shut-down of fuel cells
• CPC Class Codes: H01M 8/0656 by electrochemical means H01M8/065 takes precedence
• CPC Class Codes: Y02E 60/50 Fuel cells

Abstract

A solid oxide fuel cell system and method including a hotbox containing a fuel cell stack, a fuel supply configured to provide a fuel to the fuel cell stack, and a hydrogen supply thermally integrated with the hotbox. The hydrogen supply is configured to produce hydrogen during or shortly after the SOFC system is shutdown using residual heat of the hot box, and to provide the hydrogen to the SOFC stack such that an anode reducing environment is maintained in the stack.

Claims

1. A solid oxide fuel cell (SOFC) system, comprising:

a hotbox containing a SOFC stack;

a fuel supply configured to provide a fuel to the fuel cell stack; and

a hydrogen supply thermally integrated with the hotbox,

wherein the hydrogen supply is configured to produce hydrogen during or shortly after the SOFC system shutdown using residual heat of the hot box, and to provide the hydrogen to the SOFC stack, such that an anode reducing environment is maintained in the SOFC stack.

2. The SOFC system of claim 1, further comprising:

a hydrogen conduit fluidly connecting the hydrogen supply to the fuel cell stack; and

a first valve configured to control hydrogen flow through the hydrogen supply conduit, the first valve is powered by the SOFC stack and the first valve is a normally open valve configured to automatically open when the SOFC system is shut down.

3. The SOFC system of claim 1, wherein the hydrogen supply is embedded between walls of the hotbox or disposed inside of the hotbox.

4. The SOFC system of claim 3, wherein the hydrogen supply is embedded between upper parts of the walls of the hotbox.

5. The SOFC system of claim 1, wherein the hydrogen supply comprises a solid metal hydride hydrogen storage material.

6. The SOFC system of claim 5, further comprising:

a hydrogen separator configured to separate hydrogen from an anode exhaust conduit of the SOFC stack; and

a recharge conduit configured to provide separated hydrogen from the hydrogen separator to the hydrogen supply.

7. The SOFC system of claim 6, wherein:

the recharge conduit is configured to provide the separated hydrogen to the hydrogen supply during steady-state operation of the SOFC system;

the hydrogen supply is configured to store the hydrogen provided by the separator during steady-state operation of the SOFC system; and

the hydrogen supply is configured to release the stored hydrogen during or shortly after the SOFC system shutdown using the residual heat of the hot box, and to provide the released hydrogen to the anode electrodes of the SOFC stack before the SOFC stack temperature reaches 750°

C.

8. The SOFC system of claim 1, wherein the hydrogen supply comprises a thermochemical hydrogen generation source which produces the hydrogen from a hydrogen and oxygen containing source using the residual heat of the hot box.

9. The SOFC system of claim 8, wherein:

the thermochemical hydrogen generation source comprises a material selected from zinc, ceria (CeO₂), ceria doped with a transition metal or a rare earth, lanthanum-strontium manganite (LSM) and a combination of sodium carbonate and Mn₃O₄; and

the hydrogen and oxygen containing source comprises a water or potassium hydride tank or conduit.

10. The SOFC system of claim 9, further comprising a water separator configured to separate water from an exhaust output from the hotbox and a water tank configured to store the separated water,

wherein the water tank configured to provide the stored water to the hydrogen supply during or shortly after the shutdown of the SOFC system.

11. A method of operating a solid oxide fuel cell (SOFC) system, comprising:

operating the SOFC system which includes a hotbox containing a SOFC stack, a fuel supply and a hydrogen supply in steady state to generate electricity using fuel provided from the fuel supply;

performing a shut down the SOFC system; and

providing hydrogen from the hydrogen supply during or shortly after the SOFC system shutdown using residual heat of the hot box to the SOFC stack, such that an anode reducing environment is maintained in the SOFC stack.

12. The method of claim 11, further comprising automatically opening a normally open first valve during the SOFC system shutdown to provide the hydrogen from the hydrogen supply to the SOFC stack.

13. The method of claim 11, wherein the hydrogen supply is embedded between walls of the hotbox or disposed inside of the hotbox.

14. The method of claim 13, wherein the hydrogen supply is embedded between upper parts of the walls of the hotbox.

15. The method of claim 11, wherein the hydrogen supply comprises a solid metal hydride hydrogen storage material.

16. The method of claim 15, further comprising:

separating hydrogen from an anode exhaust of the SOFC stack; and

providing the separated hydrogen to the hydrogen supply.

17. The method of claim 16, wherein:

the separated hydrogen is provided to the hydrogen supply and stored in the hydrogen supply during steady-state operation of the SOFC system at a temperature above 750°

C.; and

the stored hydrogen is released during or shortly after the SOFC system shutdown using the residual heat of the hot box, and provided to the anode electrodes of the SOFC stack before the SOFC stack temperature reaches 750°

C.

18. The method of claim 11, wherein the hydrogen supply comprises a thermochemical hydrogen generation source which produces the hydrogen from a hydrogen and oxygen containing source using the residual heat of the hot box.

19. The method of claim 18, wherein:

the thermochemical hydrogen generation source comprises a material selected from zinc, ceria (CeO₂), ceria doped with a transition metal or a rare earth, lanthanum-strontium manganite (LSM) and a combination of sodium carbonate and Mn₃O₄; and

the hydrogen and oxygen containing source comprises water or potassium hydride which is provided to the thermochemical hydrogen generation source during or shortly after the shutdown of the SOFC system.

20. The method of claim 19, further comprising:

separating water from an exhaust output from the hotbox;

storing the separated water; and

providing the stored water to the hydrogen supply during or shortly after the shutdown of the SOFC system.

21. The method of claim 11, wherein:

during the steady-state operation, the hydrogen supply is cooled by an air inlet stream supplied to the SOFC stack; and

during or shortly after shut down of the SOFC system, the air inlet stream is turned off.

22. The method of claim 21, wherein:

during the steady-state operation, the hydrogen supply has a temperature above hydrogen filling temperature and below hydrogen release or desorption temperature due to cooling by the air inlet stream; and

during or shortly after the SOFC system shutdown, the hydrogen supply temperature is increased to or above hydrogen release or desorption temperature after the air inlet stream is turned off.

23. The method of claim 22, wherein:

the hydrogen supply comprises a solid metal hydride hydrogen storage material;

during the steady-state operation, the hydrogen supply has a temperature ranging from about 150°

C. to about 300°

C.; and

during the shutdown operation, the hydrogen supply reaches a temperature ranging from about 400°

C. to about 650°

C.

24. A solid oxide fuel cell (SOFC) system, comprising:

a hotbox containing a SOFC stack;

a fuel supply configured to provide a fuel to the fuel cell stack;

an electrolyzer fluidly connected to the fuel inlet conduit of the hotbox;

a water source; and

a power source electrically connected to the hydrogen supply,

wherein the electrolyzer is configured to use power provided by the power source during or shortly after system shutdown to electrolyze water from the water source to produce hydrogen and to provide the hydrogen to the SOFC stack such that an anode reducing environment is maintained in the SOFC stack.

25. The SOFC system of claim 24, wherein the power source is configured to store power generated by the stack and comprises a battery or an ultra capacitor.