Importance

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Abstract

A fuel cell system having a fuel cell with a first reactant inlet, a first reactant outlet, a second reactant inlet, a second reactant outlet, a coolant inlet and coolant outlet. A first reactant supply subsystem supplies a first reactant incoming stream to the first reactant inlet of the fuel cell, and a second reactant supply subsystem supplies a second reactant incoming stream to the second reactant inlet of the fuel cell. A first reactant recirculation subsystem recirculates at least a portion of a first reactant exhaust stream from the first reactant outlet to the first reactant inlet. A second reactant recirculation subsystem can be provided for recirculating at least a portion of a second reactant exhaust stream from the second reactant outlet to the second reactant inlet. The first reactant is an oxidant gas and preferably an oxygen enriched gas. The oxygen enriched gas is preferably a mixture of oxygen and a gas which is inert to the fuel cell stack. The inert gas is preferably selected from the group consisting of nitrogen, carbon dioxide, helium, neon, argon, krypton, xenon, and radon. The oxygen concentration of the first reactant is advantageously between 20 to 50 percent by volume. The second reactant is preferably a fuel gas selected from the group consisting of purified hydrogen and reformate gas.

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First Claim