Hydrogen passivation shut down system for a fuel cell power plant

A passive hydrogen bleed 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 hydrogen inlet valve (52′) secured in fluid communication with a hydrogen feed line (55′) between a fuel source (54′) and the anode catalyst (14′);
• c. an oxidant inlet valve (56′) secured in fluid communication with an oxidant feed line (62′) extending between an oxidant supply source (58′) and the cathode flow field (42′);
• d. 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′);
• and,
• e. a passive hydrogen bleed line (202) secured in fluid communication between the hydrogen fuel source (54′) and the anode flow path (24′) downstream from the hydrogen inlet valve (52′);
• f. a diffusion media (204) secured in fluid communication with the passive hydrogen bleed line (202) and configured so that hydrogen passing through the hydrogen bleed line (202) must pass through the diffusion media (204), and wherein the diffusion media (204) is configured to permit flow of hydrogen through the bleed line (202) of a lowest flow rate of hydrogen necessary to maintain the fuel cell (12′) in a passive state.

A method of shutting down a fuel cell power plant (200), the power plant (200) including 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′), the method comprising:

• a. disconnecting a primary load (90′) from the fuel cell (12′);
• b. terminating flow of the oxidant into the cathode flow path (24′) from an oxidant source (58′);
• c. connecting an auxiliary load (94′) to the fuel cell (12′);
• d. permitting transfer of the hydrogen fuel from the anode flow path (24′) into the cathode flow path (38′);
• e. closing a hydrogen inlet valve (52′) to terminate flow of the hydrogen fuel into the anode flow path (24′) from a hydrogen fuel source (54′) through a hydrogen feed line (55′) whenever the anode flow path (24′) and cathode flow path (38′) are filled above an acceptable limit of hydrogen to maintain the fuel cell (12′) in a passive state;
• and,
• f. directing flow of hydrogen from the hydrogen fuel source (54′) through a passive hydrogen bleed line (202) into the anode flow path (24′) downstream from the hydrogen inlet valve (52′) at a lowest flow rate of hydrogen necessary to maintain the fuel cell (12′) in a passive state.