Reformer and reforming process for production of hydrogen from hydrocarbon fuel
View Patent ↗The invention provides methods and systems for catalytic reforming of a hydrocarbon fuel to produce hydrogen, which may be used as a power source for a fuel cell. In some embodiments, hydrogen is produced by partial oxidation or autothermal reforming of fuel in an oxygen containing gas stream that is rich the majority of the time, with periodic conversion to a lean gas stream for short periods of time to maintain catalytic activity. In one embodiment, hydrogen peroxide is used as the oxidant in an autothermal reforming process. In some embodiments, hydrogen is produced by steam reforming at a low steam to carbon ratio, with a periodic increase in the steam to carbon ratio for short periods of time to maintain catalytic activity.
1. A process for producing H 2 and CO, comprising:
introducing a hydrocarbon fuel and either an aqueous solution of H 2 O 2 or H 2 O and O 2 produced from the aqueous solution, to combine into a gas stream to produce a rich mixture comprising the hydrocarbon fuel;
wherein said rich mixture is produced upstream from a catalytic zone comprising a reforming catalyst and an oxidation catalyst;
wherein said rich mixture flows through said catalytic zone;
wherein a portion of the hydrocarbon fuel in the rich mixture is oxidized on the oxidation catalyst and essentially all of the remaining hydrocarbon fuel is reformed on the reforming catalyst, thereby producing H 2 and CO, and;
at least once every ten minutes the rich mixture is converted to a lean mixture for a short period of time by steps comprising temporarily decreasing or stopping the hydrocarbon fuel introduction, thereby forming lean-rich cycles;
wherein the short periods of lean mixture production are functional to help maintain catalyst activity but are sufficiently short that a temperature of the catalytic zone remains between about 500 and about 850° C. throughout the lean-rich cycles and the lean periods are about 20% or less of the lean-rich cycle time.
2. A process according to claim 1 , further comprising a mixing volume downstream of the catalytic zone, wherein the hydrogen concentration at the outlet of the mixing volume is substantially constant through the lean-rich cycles.
3. A process according to claim 1 , further comprising a mixing volume downstream of the catalytic zone to mix the lower hydrogen concentration produced during a lean cycle with the higher hydrogen concentration produced during rich cycles, wherein the mixing volume provides a volume 1 to 5 times the volume of lean mixture flowing through the catalytic zone over the short lean periods.
4. A process according to claim 1 , wherein the temperature of the catalytic zone remains at or above about 600° C. throughout the lean-rich cycling.
5. A process according to claim 1 , wherein the aqueous solution comprises 20-50% H 2 O 2 by weight.
6. A process according to claim 1 , wherein the transitions from rich to lean raises an H 2 O to carbon ratio for the mixture by a factor of two or more.