FUEL CELL AND APPARATUS FOR WATER REMOVAL BY EVAPORATING THE WATER FROM THE ELECTROLYTE OF FUEL ELEMENTS

1324264 Treating electrolyte of fuel cells SIEMENS AG 11 Nov 1970 [12 Nov 1969] 53744/70 Heading H1B A method of removing water from the electrolyte of a fuel cell by evaporation utilizes, in the evaporation, heat which has been liberated externally of the fuel cell in the production of a reactant for the cell. Hydrogen peroxide entering a decomposer 1 via orifice 2 is exothermically decomposed by contact with a silver catalyst 3, and the oxygen this formed passes through a ceramic filter 4, which forms a catalyst support, and a porous filter 5. The purified oxygen then passes through heat-exchanger tubes 7 and leaves the decomposer by pipe 6 which leads directly to the cathodes of the cell. Water in the oxygen is condensed in the tubes 7 and removed via pipe 9 after passing through a porous disc 12 which has a capillary pressure for water higher than the oxygen pressure in the decomposer. Electrolyte from a fuel cell battery 13, Fig. 2, enters the decomposer by pipe 10 and is heated by contact with the tubes 7 before leaving via pipe 11 which leads to an evaporator unit in which the water content of the electrolyte is reduced. The evaporator unit may be of various forms but is specifically described as comprising a concentrator 21 in which the heated electrolyte is brought into contact with an inert gas which is circulated by a fan 23. The gas passes through a cooler 24 in which water taken up from the electrolyte is condensed for removal. The electrolyte is taken from the concentrator 21 via a cooler 27 before being returned to the battery 13. The latter is supplied with hydrazine and with oxygen from the decomposer 1 and the electrolyte is KOH. Other arrangements are envisaged in which the heat is derived from the catalytic decomposition of hydrazine, or from the dissolution of metals, e.g. aluminium, or from a hydride of boron or of an alkali or alkaline-earth metal, e.g. LiBH 4 , NaBH 4 , LiH, or CaH 2 .