Patent ID: 8142950

Claim:
A controlled-oxidant flow hydrogen passivation shut-down system for a fuel cell power plant ( 200 ), the system comprising: a. at least one fuel cell ( 12 ′) for generating electrical current from hydrogen containing reducing fluid fuel and oxygen containing oxidant reactant streams, the fuel cell ( 12 ′) including an anode catalyst ( 14 ′) and a cathode catalyst ( 16 ′) on opposed sides of an electrolyte ( 18 ′), an anode flow path ( 24 ′) in fluid communication with the anode catalyst ( 14 ′) for directing the hydrogen fuel to flow through the fuel cell ( 12 ′) and adjacent the anode catalyst ( 14 ′), and a cathode flow path ( 38 ′) in fluid communication with the cathode catalyst ( 16 ′) for directing the oxidant stream to flow through the fuel cell ( 12 ′) and adjacent the cathode catalyst ( 14 ′); b. a non-leaking hydrogen inlet valve ( 202 ) secured in fluid communication with a hydrogen feed line ( 55 ′) between a fuel source ( 54 ′) and the anode catalyst ( 14 ′); c. a combined oxidant and fuel exhaust line ( 206 ) secured in fluid communication with both the cathode flow path ( 38 ′) and the anode flow path ( 24 ′) for directing oxidant and fuel stream exhausts out of the fuel cell ( 12 ′); d. a non-leaking cathode exhaust valve ( 208 ) secured in fluid communication with the combined oxidant and fuel exhaust line ( 206 ); e. a controlled-oxidant flow inlet device ( 209 ) secured in fluid communication with an oxidant feed line ( 62 ′) extending between an oxidant supply source ( 58 ′) and the cathode flow field ( 42 ′); f. hydrogen transfer means secured in communication between the anode flow path ( 24 ′) and the cathode flow path ( 38 ′) for selectively permitting transfer of the hydrogen fuel between the anode flow path ( 24 ′) and the cathode flow path ( 38 ′) g. an oxidant inlet ( 210 ) for directing the oxidant from the controlled-oxidant flow inlet device ( 209 ) to a cathode flow field ( 42 ′), the 5 oxidant inlet ( 210 ) including a portion of the oxidant feed line ( 62 ′) down stream from the controlled-oxidant flow inlet device ( 209 ) and also including an oxidant manifold ( 212 ) adjacent the cathode flow field ( 42 ′), the oxidant inlet ( 210 ) defining an oxidant buffer void ( 214 ) through which the oxidant passes; and, h. wherein the oxidant buffer void ( 214 ) defines an interior volume at least between about thirty percent and about fifty percent of a total volume of both the anode flow path ( 24 ′) and the cathode flow path ( 38 ′).