Integrated fuel cell system
View Patent ↗The invented system includes a fuel-cell system comprising a fuel cell that produces electrical power from air (oxygen) and hydrogen, and a fuel processor that produces hydrogen from a variety of feedstocks. One such fuel processor is a steam reformer which produces purified hydrogen from a carbon-containing feedstock and water. In the invented system, various mechanisms for implementing the cold start-up of the fuel processor are disclosed, as well as mechanisms for optimizing and/or harvesting the heat and water requirements of the system and/or maintaining the purity of the process water used in the system.
1. In a fuel processing system having a hydrogen-production region, in which a mixed gas stream containing hydrogen gas and other gases is produced by steam reforming from a feed stream containing a carbon-containing feedstock and water, and a separation region, in which the mixed gas stream is separated into at least a hydrogen-rich stream from which a product hydrogen stream is formed and a byproduct stream containing at least a substantial portion of the other gases, a method for starting up the fuel processing system comprising:
delivering a stream containing hydrogen gas from a hydrogen storage vessel to a combustion region and combusting the stream to produce a heated fluid stream;
heating the hydrogen-production region with the heated fluid stream until the hydrogen-production region reaches a temperature of at least approximately 250° C.;
delivering a feed stream containing water and a carbon-containing feedstock to the hydrogen-production region to produce by steam reforming the mixed gas stream;
separating the mixed gas stream into the hydrogen-rich stream and the byproduct stream;
delivering at least a portion of the hydrogen-rich stream to the hydrogen storage vessel to at least partially recharge the hydrogen storage vessel and delivering the byproduct stream to the combustion region; and
delivering at least a portion of the hydrogen-rich stream to a fuel cell stack to produce an electric current therefrom.
2. The method of claim 1 , wherein the hydrogen storage vessel includes at least one hydride bed.
3. The method of claim 1 , wherein the hydrogen storage vessel includes a pressurized tank.
4. The method of claim 1 , wherein the method further includes the step of reducing the flow of the stream containing hydrogen gas to the combustion region.
5. The method of claim 4 , wherein the step of reducing the flow includes stopping the flow of the stream containing hydrogen gas to the combustion region.
6. The method of claim 1 , wherein the fuel cell stack includes an anode region and a cathode region and produces an exhaust stream from the cathode region, and further wherein the method includes delivering at least a portion of the cathode exhaust stream to the combustion region.
7. The method of claim 1 , wherein the carbon-containing feedstock includes at least one hydrocarbon, and further wherein the heating step includes heating the hydrogen-production region with the heated fluid stream until the hydrogen-production region reaches a temperature of at least approximately 450° C.
8. The method of claim 1 , wherein the carbon-containing feedstock includes at least one hydrocarbon, and further wherein the heating step includes heating the hydrogen-production region with the heated fluid stream until the hydrogen-production region reaches a temperature of at least approximately 600° C.
9. The method of claim 1 , wherein the carbon-containing feedstock includes methanol.
10. A fuel cell system, comprising:
a hydrogen-producing fuel processor adapted to receive a carbon-containing feedstock and water and to produce a byproduct stream and a product hydrogen stream containing hydrogen gas therefrom, wherein the fuel processor includes a hydrogen-production region, in which the feedstock and water are reacted at an elevated temperature to form a product stream containing hydrogen gas, and a separation region adapted to separate the product stream into at least the product hydrogen stream and a byproduct stream;
a fuel cell stack adapted to receive the product hydrogen stream and produce an electric current therefrom, wherein the fuel cell stack includes a cathode chamber and an anode chamber and is further adapted to produce a water stream that is removed from the cathode chamber of the fuel cell stack; and
a cooling assembly that is adapted to receive and cool the water stream, wherein the cooling assembly includes an ion-exchange bed through which at least a portion of the water stream is passed to remove ions from the water stream.
11. The fuel cell system of claim 10 , wherein only a portion of the water stream is passed through the ion-exchange bed.
12. The fuel cell system of claim 10 , wherein all of the water stream is passed through the ion-exchange bed.
13. The fuel cell system of claim 10 , wherein the ion-exchange bed includes an anion-exchange resin.
14. The fuel cell system of claim 10 , wherein the ion-exchange bed includes a cation-exchange resin.
15. The fuel cell system of claim 14 , wherein the ion-exchange bed includes both anion- and cation-exchange resins.
16. The fuel cell system of claim 10 , further comprising a water storage reservoir adapted to receive the water stream.
17. The fuel cell system of claim 16 , wherein the fuel processor is adapted to receive water from the water storage reservoir.
18. The fuel cell system of claim 16 , further comprising means for recovering water from the product hydrogen stream and for delivering water recovered from the product hydrogen stream to the water storage reservoir.
19. The fuel cell system of claim 16 , further comprising a combustion assembly adapted to combust a combustible stream to produce a heated exhaust stream to heat at least the hydrogen-producing region.
20. The fuel cell system of claim 19 , further comprising means for recovering water from the exhaust stream and for delivering water recovered from the exhaust stream to the water storage reservoir.