Claims
- 1. A method of operating a fuel cell system on an impure fuel, said system including at least one fuel cell, a stream of said impure fuel supplied to said fuel cell, and a mechanism for introducing oxygen into said fuel stream for reaction with an impurity in said fuel stream within said fuel cell, said method comprising introducing a variable concentration of oxygen into said fuel stream periodically.
- 2. The method of claim 19 wherein said oxygen is introduced into said impure fuel stream in a series of periodic pulses.
- 3. The method of claim 19 wherein said impurity comprises carbon monoxide.
- 4. The method of claim 21 wherein said fuel stream comprises up to about 1000 ppm carbon monoxide.
- 5. The method of claim 19 wherein said impurity comprises carbon dioxide.
- 6. The method of claim 20 wherein the period of the pulses is in the range from about 1 to 50 seconds.
- 7. The method of claim 20 wherein said oxygen is introduced into said impure fuel stream in a series of periodic pulses of air.
- 8. The method of claim 25 wherein the concentration of air introduced into said fuel stream during said periodic pulses is less than about 4% by volume of said fuel stream.
- 9. The method of claim 25 wherein a substantially continuous baseline concentration of air is introduced into said fuel stream between said periodic pulses of air.
- 10. The method of claim 27 wherein said baseline concentration of air is less than about 0.8% by volume of said fuel stream.
- 11. The method of claim 20 wherein the duration of said periodic pulses is less than about half the period.
- 12. The method of claim 19 wherein said at least one fuel cell is a solid polymer fuel cell.
- 13. The method of claim 19 further comprising maintaining the fuel stoichiometry in said fuel cell at greater than or equal to 1.
- 14. A fuel cell system comprising:
at least one fuel cell; a source of an impure fuel stream for supply to said fuel cell; a mechanism for introducing a variable concentration of oxygen into said impure fuel stream for reaction with an impurity in said fuel stream within said fuel cell; and a monitoring device for monitoring a fuel cell operating characteristic indicative of the concentration of said impurity in said fuel stream; and a flow controller responsive to the monitoring device for adjusting said oxygen concentration in response to said monitored operating characteristic.
- 15. The fuel cell system of claim 32 wherein said monitoring device comprises a sensor fuel cell.
- 16. The fuel cell system of claim 32 further comprising a mechanism for maintaining a sufficient amount of fuel in said impure fuel stream such that the fuel stoichiometry is greater than or equal to 1.
- 17. A fuel cell system comprising:
at least one fuel cell; a source of an impure fuel stream for supply to said fuel cell; and a mechanism for introducing a variable concentration of oxygen into said impure fuel stream for reaction with an impurity in said fuel stream within said fuel cell wherein said oxygen introducing mechanism comprises a flow controller for periodically introducing oxygen into said fuel stream.
CROSS-REFERENCE TO RELATED APPLICATION(S)
[0001] This application is a division of U.S. patent application Ser. No. 09/221,206 filed Dec. 23, 1998, which is, in turn, related to and claims priority from U.S. Provisional Patent Application Ser. No. 60/091,531 filed Jul. 2, 1998, entitled “Sensor Cell For An Electrochemical Fuel Cell Stack”. The '206 non-provisional and '531 provisional applications are each incorporated herein by reference in their entirety.
Provisional Applications (1)
|
Number |
Date |
Country |
|
60091531 |
Jul 1998 |
US |
Divisions (1)
|
Number |
Date |
Country |
Parent |
09221206 |
Dec 1998 |
US |
Child |
09772036 |
Jan 2001 |
US |