Abstract: The anodes of fuel cells in a fuel cell stack are passivated during no load, hot-hold periods by directing a stream of desulfurized natural gas through the anode side of the cells in the stack. The cell voltage is thus maintained below 800 millivolts, preferably between 300 and 500 millivolts, during such periods.

Abstract: Pressure differential 6 between cathode 2 and anode 3 is controlled by valve 24, 26 of valve complex 20. The complex 20 is located within anode recirculation loop 8, 9, 3, 20 whereby controllability is not lost with no flow through the anode. Control is thereby retained during nitrogen purging of the cathode.An orifice 22 in the valve complex 20 precludes accidental full closure of the complex, and is selected to avoid immediate damage to the fuel cell on such closure.

Abstract: Heat exchanger 4 operates in counterflow relationship to cool reformed gas and to heat raw gas during operation with gaseous raw fuel feed. It also operates in counterflow relationship when preheating the system while recirculating inert gas. This same heat exchanger 4 operates in parallel flow relationship when liquid raw fuel is to be vaporized. Only one heat exchanger is required while avoiding cracking and fouling in the heat exchanger.

Abstract: Fuel cell coolant loop (2) is to be controlled to maintain set point 38 temperature of the return coolant. Waste heat heat exchanger 10 is controlled to maintain set point 22 temperature in the waste heat fluid. Heat rejection heat exchanger removes additional heat as required to maintain the set point (38) temperature.If both set point temperatures cannot be maintained, a control override allows the waste heat fluid temperature to drop.

Abstract: Fuel cell performance is degraded by recycling a portion of the cathode exhaust through the cells and, if necessary, also reducing the total air flow to the cells for the purpose of permitting operation below a power level which would otherwise result in excessive voltage.

Abstract: A product-water management system removes steam produced by the reaction of ydrogen and oxygen in a fuel cell, by circulating a hydrogen stream, containing the steam, from the fuel cell to a condenser where the water is liquified and collected in a sump. A continuously operating pump forces water and/or hydrogen from the sump through a transfer line to a water storage tank. Hydrogen is vented back to the condenser from the storage tank through a vent line concentrically mounted within the transfer line. A tank drain on the storage tank allows hydrogen to be purged between missions.

Abstract: A power plant for producing electricity uses fuel cells run on pressurized air and pressurized fuel. The air is compressed by compressor apparatus which is driven by waste energy in the form of hot pressurized gases produced in the power plant. In one embodiment the compressor apparatus includes a turbine operably connected to a compressor for driving the same. At part power, in order to maintain the pressure of the air being fed to the cells while reducing the amount of air fed to the cells, a portion of the compressed air is bypassed around the fuel cells, is increased in temperature using an auxiliary burner, and is delivered into the turbine to help drive the compressor. By doing this the mass flow of air through the cells may be reduced without reducing the mass flow of gases into the turbine thereby maintaining the speed of the compressor at part power.

Abstract: A fuel cell power plant for producing electricity uses pressurized air and fuel in the cells. The air is compressed by compressor apparatus powered by waste energy in the form of hot pressurized gases including hot pressurized steam produced by the power plant. In one embodiment the compressor apparatus includes a turbine operably connected to a compressor, and hot pressurized gases produced by the power plant flow into the turbine thereby driving the compressor. The steam is generated by heat from the fuel cells, passes through the fuel cells adjacent the cathode electrode thereof, and is delivered into the turbine along with the other gases.