GB1296831A - - Google Patents

Abstract

1296831 Fuel cell system ENERGY CONVERSION Ltd 27 Jan 1970 [28 Feb 1969] 10814/69 Heading H1B Cell reversal is prevented in an electrochemical cell system using hydrogen as fuel and oxygen or air as the reactant, particularly a fuel cell system having electrodes of Pt and Ni, by providing a fluid such as nitrogen helium, argon, distilled water or, aqueous KOH, which is compatible with the electrode and which has no free oxygen, subsequent to shut down and/or prior to start up of the system. In an embodiment prior to start-up the electrolyte pump is switched on and the air compartments are purged with nitrogen before the hydrogen circuits. The nitrogen purge on the anode is then switched to hydrogen and then air is fed to the air electrodes. Anode reversal on shutdown is prevented by purging the cathodes with nitrogen before purging off the oxygen. In another embodiment wherein air is the oxidant the nitrogen atmosphere is provided by not circulating oxygen through the system at shut-down and/or start-up, so that the remaining oxygen is consumed by the leakage currents to produce a nitrogen atmosphere. Where the fluid provided is aqueous KOH which is also the electrolyte the air or oxygen sides of the cells are at least half-flooded and then the hydrogen sides may be flooded. The arrangement may be used for a matrix-type cell or free electrolyte cell and in these cases a small electrical load may be applied during such flooding which remains until start-up.