ADVANCED ALKALINE WATER ELECTROLYSIS AT ENHANCED PRESSURES (30 TO 60 BARS) AND ENHANCED TEMPERATURES (100 DEGREES TO 200 DEGREES C)
Component development for medium pressure, medium temperature water electrolysis comprises different techniques for cathode and anode activation and small scale (4 cm**2) pretesting and bench scale (36 cm**2) long-term testing. For the latter purpose a 1 kW pilot plant was constructed and ambient pressure and enhanced pressure experiments were performed from 1000 to 3000 hours and above this limit. Most important newly developed component is a nickel net backed porous oxide ceramic diaphragm. NiTiO-3, BaZrO-3, BaTiO-3 and CaTiO-3 were tested as oxide ceramic material and BaTiO-3 and CaTiO-3 selected eventually as the most appropriate materials with respect to raw material and processing costs and chemical and mechanical long-term stability. Both materials are optimally used in the form of Ni cermets. Diaphragms are prepared of large scale (60 x 60 cm**2), of high mechanical strength and by procedures which may be easily turned into industrial practice which exhibit under operation conditions surface specific resistances not exceeding 0.25 ohms x cm**2. Own data are supported by data obtained by Sodeteg and Gaz de France. Electrode activation is performed at cathodes by electrodeposition of Zn/Ni and Zn/Ni/Co alloys. These alloys can be leached in KOH and are further activated and stabilized by in-situ addition of molybdenum. Most effective anode activation is performed by in-situ deposition of Co-xO-yOH-z. Cathodic activation yields in 150 mV improvement and anodic activation in 80 mV improvement at 1 A/cm**2 at 90 degrees C and at 1 A/cm**2. Assembly technique of bench scale electrolyser cells assuring zero-gap geometry can be put into large-scale practice easily because of its intrinsic flexibility. Economic evaluation which takes into account wear and corrosion of constructive materials reveals, that operation temperature should not exceed 160 degrees C and that under optimal conditions hydrogen production may be performed with 20 to 25 % gain in energy efficiency resulting in hydrogen costs from electrolysis which are lower by approximately 20 % than for conventional electrolysis.
Bibliographic Reference: EUR 9406 EN (1984) MF, 81 P., BFR 120, BLOW-UP COPY BFR 405, EUROFFICE, LUXEMBOURG, POB 1003
Availability: Can be ordered online
Record Number: 1989122099100 / Last updated on: 1987-01-01
Available languages: en