Shift reactor for direct fuel cell hydrogen system

1. A multi-stage shift reactor comprising:

a vessel comprising:

an inner chamber configured to contain a first shift catalyst, the first shift catalyst configured to receive anode exhaust gas from a fuel cell and to output a first shifted gas; and

an outer chamber annularly disposed about the inner chamber and configured to contain a second shift catalyst, the second shift catalyst configured to receive the first shifted gas and output a second shifted gas;

a water injection port downstream from the inner chamber; and

packing between the water injection port and the outer chamber, the packing configured to prevent liquid water from passing therethrough.

2. The shift reactor of claim 1 , wherein the inner chamber and the outer chamber are configured to transfer heat therebetween.

3. The shift reactor of claim 1 , wherein the vessel is configured to contain the first shifted gas.

4. The shift reactor of claim 1 , wherein each of the inner chamber and outer chamber are at substantially the same pressure.

5. The shift reactor of claim 1 , wherein the inner chamber is defined by an inner wall and the outer chamber is defined by an outer wall; and

wherein the outer wall is thicker than the inner wall.

6. The shift reactor of claim 1 , further comprising the first shift catalyst and the second shift catalyst;

wherein each of the first shift catalyst and the second shift catalyst comprises a same material.

7. The shift reactor of claim 1 , further comprising a perforated plate disposed in the inner chamber, the perforated plate configured to support the first shift catalyst;

wherein the perforated plate is configured to allow the first shifted gas to pass therethrough.

8. A fuel cell system comprising:

a fuel cell having an anode and a cathode, the anode configured to output exhaust;

a shift reactor defining a first chamber and a second chamber;

a first shift catalyst disposed in the first chamber and a second shift catalyst disposed in the second chamber;

a water injection port; and

packing configured to prevent liquid water from passing therethrough;

wherein the packing is disposed between the first shift catalyst and the second shift catalyst; and

wherein the water injection port is disposed between the first shift catalyst and the packing.

9. The shift reactor of claim 8 , wherein the first chamber is configured to receive exhaust from the anode, pass the exhaust generally downward in the first shift catalyst, and output a first shifted gas.

10. The shift reactor of claim 9 , wherein the second chamber is configured to receive the first shifted gas from the first chamber, pass the first shifted gas generally upward in the second shift catalyst, and output a second shifted gas.

11. The shift reactor of claim 8 , wherein each of the first shift catalyst and the second shift catalyst comprise the same material.

12. A method of converting exhaust from a fuel cell comprising:

receiving, in a first shift catalyst, anode exhaust gas from a fuel cell;

performing a first water-gas shift reaction in the first shift catalyst;

outputting, from the first shift catalyst, a first shifted gas;

cooling the first shifted gas;

passing the first shifted gas through packing configured to retain liquid water from passing therethrough;

receiving, in a second shift catalyst, the first shifted gas;

performing a second water-gas shift reaction in the second shift catalyst; and

outputting a second shifted gas from the second shift catalyst.

13. The method of claim 12 , wherein the exhaust is output from an anode of the fuel cell.

14. The method of claim 12 , wherein the first shifted gas is cooled by injecting water.

15. The method of claim 14 , wherein the water is injected downstream from the first shift catalyst.

16. The method of claim 12 , wherein the first shifted gas is cooled by a heat exchanger.

17. The method of claim 12 , wherein the method is performed within a single vessel.

18. The method of claim 12 , wherein the anode exhaust gas flow generally downward through the first shift catalyst; and

wherein the first shifted gas flows generally upward through the second shift catalyst.

19. The method of claim 12 , wherein substantially all of the first shifted gas is passed through the packing before being received in the second shift catalyst.

20. The method of claim 12 , wherein the anode exhaust gas received by the first shift catalyst and the first shifted gas received by the second shift catalyst are at substantially similar temperatures.