SYSTEMS AND METHODS FOR STEAM REFORMING
One embodiment of the present invention is a unique method for operating a fuel cell system. Another embodiment is a unique system for reforming a hydrocarbon fuel. Another embodiment is a unique fuel cell system. Other embodiments include apparatuses, systems, devices, hardware, methods, and combinations for fuel cell systems and steam reforming systems. Further embodiments, forms, features, aspects, benefits, and advantages of the present application will become apparent from the description and figures provided herewith.
1 . A method for operating a fuel cell system, comprising:
providing a catalyst consisting essentially of platinum and ruthenium as catalytically active materials, wherein the platinum content is selected based on a desired level of sulfur resistance; and wherein the catalyst is configured for self cleaning of sulfur compounds when performing steam reforming using a low-sulfur-content hydrocarbon fuel;
providing a catalytic reactor having surfaces having the catalyst disposed thereon and configured to expose the catalyst to at least a hydrocarbon fuel and steam;
reforming a high-sulfur content hydrocarbon fuel with at least steam for a first period of time;
reforming the low-sulfur-content hydrocarbon fuel with at least steam for a second period of time; and
providing reformed hydrocarbon fuel to a fuel cell stack.
2 . The method of claim 1 , wherein the reforming of the low-sulfur-content hydrocarbon fuel is performed after the reforming of the high-sulfur content hydrocarbon fuel.
3 . The method of claim 2 , wherein the reforming of the low-sulfur-content hydrocarbon fuel is performed both before and after the reforming of the high-sulfur content hydrocarbon fuel.
4 . The method of claim 1 , wherein the platinum content is a minimum platinum content consistent with the desired level of sulfur resistance.
5 . The method of claim 4 , wherein the ruthenium content of the catalytically active materials is selected to be approximately 75% to 99.99% by weight; and wherein the platinum content of the catalytically active materials is selected to be approximately 0.01% to 25% by weight.
6 . The method of claim 1 , further comprising providing a carrier for the catalyst.
7 . The method of claim 6 , wherein the carrier includes a refractory oxide, including at least one of silica, alumina, zirconia and tungsten oxides.
8 . The method of claim 7 , wherein the carrier includes mixed refractory oxides having at least two cations.
9 . The method of claim 7 , wherein the alumina oxide is stabilized by at least one of baria, ceria, lanthana and magnesia oxides.
10 . The method of claim 1 , further comprising activating the catalyst by heating the catalyst in hydrogen and/or another reducing gas.
11 . A system for steam reforming a hydrocarbon fuel, comprising:
a catalytic reactor having surfaces configured for exposure to the hydrocarbon fuel and steam; and
a catalyst having catalytically active materials consisting essentially of ruthenium and platinum disposed on the surfaces of the catalytic reactor,
wherein the system is configured to steam reform a hydrocarbon fuel.
12 . The system of claim 11 , wherein the ruthenium content of the catalyst is greater than the platinum content of the catalyst.
13 . The system of claim 11 , wherein the catalyst is configured for self cleaning of sulfur compounds when performing steam reforming using a hydrocarbon fuel having little or no sulfur content.
14 . The system of claim 13 , wherein the little or no sulfur content is less than about 0.05 parts per million by volume.
15 . The system of claim 13 , wherein the catalyst is configured for steam reforming with the hydrocarbon fuel having a sulfur content of greater than 0.1 parts per million by volume for a period of not less than 30 hours; and wherein the catalyst is configured for self cleaning of sulfur compounds when performing steam reforming using a hydrocarbon fuel having little or no sulfur content.
16 . The system of claim 15 , wherein the little or no sulfur content is less than about 0.05 parts per million by volume.
17 . The system of claim 15 , wherein the sulfur content of greater than 0.1 parts per million volume is a sulfur content of greater than 0.5 parts per million by volume.
18 . The system of claim 15 , wherein the catalytic reactor includes a tube having an axis, and having a plurality of channels extending parallel to the axis; and wherein the catalyst is disposed in the surfaces of the channels.
19 . The system of claim 18 , wherein the number of channels is in the range of 200 to 1200 channels per square inch when viewed in a direction along the axis.
20 . The system of claim 18 , wherein the catalyst is supported on a carrier that includes alumina oxide.
21 . The system of claim 20 , wherein the carrier also includes at least one of baria, ceria, lanthana and magnesia oxides.
22 . The system of claim 20 , wherein the catalyst and the carrier do not include alkali metals or oxides thereof.
23 . The method of claim 13 , wherein the catalyst is configured for self cleaning within a period of 50 hours or less to achieve a methane conversion of greater than about 90% of the equilibrium conversion when using natural gas as a hydrocarbon feed stream.
24 . The method of claim 23 , wherein the catalyst is configured for self cleaning within a period of 40 hours or less to achieve a methane conversion of greater than about 90% of the equilibrium conversion.
25 . The method of claim 23 , wherein the catalyst is configured for self cleaning within a period of 25 hours or less to achieve a methane conversion of greater than about 90% of the equilibrium.
26 . The system of claim 13 , further comprising a fuel cell in fluid communication with the catalytic reactor.
27 . The system of claim 13 , wherein the catalytic reactor is configured to steam reform the hydrocarbon fuel with or without an oxidant.
28 . A fuel cell system, comprising:
a fuel cell stack; and
a reformer in fluid communication with the fuel cell stack, wherein the reformer includes a catalytic reactor having surfaces configured for exposure to a hydrocarbon fuel and steam; and a catalyst having catalytically active materials consisting essentially of ruthenium and platinum disposed on the surfaces of the catalytic reactor,
wherein the reformer is configured to steam reform a hydrocarbon fuel and output reformed fuel to the fuel cell stack.
29 . The fuel cell system of claim 28 , wherein the reformer is configured to reform a high-sulfur content hydrocarbon fuel with at least steam for a first period of time; and reform a low-sulfur-content hydrocarbon fuel with at least steam for a second period of time.
30 . The fuel cell system of claim 29 , wherein the catalytic reactor is configured to self-clean sulfur poisoning during the second period of time.
31 . The fuel cell system of claim 30 , wherein the second period of time is less than an amount of time required for a catalyst having a catalytically active material consisting essentially of ruthenium to self-clean.