OPERATION OF FUEL CELL SYSTEMS WITH REDUCED CARBON FORMATION AND ANODE LEADING EDGE DAMAGE

• US 20100047637A1
• Filed: 07/22/2009
• Published: 02/25/2010
• Est. Priority Date: 07/23/2008
• Status: Active Grant

• Current Assignee: Bloom Energy Corporation
• Original Assignee: Bloom Energy Corporation
• Inventors: McELROY, James F., Venkataraman, Swaminathan, Weingaertner, David, Couse, Stephen
• Granted Patent: US 9,287,571 B2
• Time in Patent Office: Days
• US Class Current: 429/440
• CPC Class Codes: H01M 2008/1293 Fuel cells with solid oxide electrolytes
• CPC Class Codes: H01M 8/0618 Reforming processes, e.g. autothermal, partial oxidation or steam reforming
• CPC Class Codes: H01M 8/0637 Direct internal reforming at the anode of the fuel cell
• CPC Class Codes: Y02E 60/50 Fuel cells

Abstract

A method of operating a fuel cell system includes introducing a fuel mixture comprising hydrogen, fuel, and steam at a fuel inlet of the fuel cell system, and operating the fuel cell system to generate electricity. A ratio of hydrogen to carbon from fuel (H₂:C_fuel) in the fuel mixture is within a range of 0.25:1 to 3:1, inclusive; and a ratio of steam to carbon (S:C) in the fuel mixture is less than 2:1.

Claims

1. A method of operating a fuel cell system, comprising:

introducing a fuel mixture comprising hydrogen, fuel, and steam at a fuel inlet of the fuel cell system; and

operating the fuel cell system to generate electricity;

wherein a ratio of hydrogen to carbon from fuel (H₂;

C_fuel) in said fuel mixture is within a range of 0.25;

1 to 3;

1, inclusive; and

a ratio of steam to carbon (S;

C) in said fuel mixture is less than 2;

1.

2. The method of claim 1, wherein said fuel comprises a fuel comprising carbon and hydrogen.

3. The method of claim 2, wherein said fuel is selected from the group consisting of methane, natural gas, propane, alcohol, or syngas derived from coal or natural gas reformation.

4. The method of claim 1, wherein said fuel cell system is a solid oxide fuel cell system.

5. The method of claim 4, wherein said fuel cell system comprises a solid oxide fuel cell system with an external reformer.

6. The method of claim 4, wherein said fuel cell system comprises a solid oxide fuel cell system with an internal reformer.

7. The method of claim 1, wherein said S:

C ratio is less than or equal to 1.2;

1.

8. The method of claim 1, wherein said H₂:

C_fuel ratio is within the range of 0.5;

1 to 1.5;

1.

9. The method of claim 1, wherein source of said hydrogen is recycled anode exhaust gas.

10. The method of claim 8, wherein the recycled anode exhaust gas is up to 70% of the total anode exhaust gas.

11. The method of claim 10, wherein the recycled anode exhaust gas is 50% to 70% of the total anode exhaust gas.

12. The method of claim 8, further comprising converting steam to hydrogen in all or a portion of anode exhaust gas using a water-gas shift reactor prior to reintroduction of all or a portion of the reformed anode exhaust gas into the fuel cell system.

13. A method of operating a fuel cell system, comprising:

introducing a fuel mixture at a fuel inlet of the fuel cell system; and

operating the fuel cell system to generate electricity;

wherein said fuel mixture comprises a partially reformed hydrocarbon fuel and recycled anode exhaust gas; and

the steam to carbon ratio (S;

C) in said fuel mixture is less than 2;

1.

14. The method of claim 13, wherein a portion of hydrocarbon fuel reformed prior to introduction at the fuel inlet is 5% to 15%.

15. The method of claim 14, wherein said reforming a portion of said fuel is conducted with a catalytic reactor.

16. The method of claim 13, wherein the recycled anode exhaust gas is up to 70% of the total anode exhaust gas.

17. The method of claim 13, wherein an average cell voltage of the fuel cell system is increased as compared to operation of the fuel cell system operating at S:

C greater than or equal to 2;

1.

18. The method of claim 13, further comprising converting steam to hydrogen in anode exhaust gas using a water-gas shift reactor prior to reintroduction of the anode exhaust gas into the fuel cell system.

19. The method of claim 13, wherein the mixture comprises carbon monoxide, carbon dioxide, water vapor, hydrogen and fuel, and a percentage of said fuel in the mixture is less than or equal to 20%.

20. The method of claim 13, wherein the fuel comprises methane or natural gas and the percentage of said fuel in said mixture is within a range of about 13% to about 19%.

21. A solid oxide fuel cell stack, comprising:

a plurality of solid oxide fuel cells and a plurality of interconnects, each of the plurality of fuel cells comprising;

a solid oxide electrolyte;

an anode electrode adapted for internal fuel reformation; and

a cathode electrode;

wherein the anode electrode and the cathode electrode are symmetrical in a region where fuel enters the fuel cell.

22. The stack of claim 21, wherein the anode and cathode are symmetrical around their entire area.

23. The stack of claim 21, wherein the region where fuel enters the fuel cell comprises a region near the fuel inlet riser opening in the electrolyte and the anode electrode is offset from the fuel inlet riser opening by at least 4 mm.

24. The stack of claim 23, wherein the anode electrode is located over a fuel distribution plenum in an adjacent interconnect.

25. The stack of claim 23, wherein the anode electrode is not located over a fuel distribution plenum in an adjacent interconnect.