Carbon dioxide removal from air for alkaline fuel cells operating with liquid-hydrogen - A synergistic advantage

This paper reports the outcome of a project undertaken to explore the synergistic use of alkaline fuel cells and liquid hydrogen. An experimental program was conducted to develop and test a system to address simultaneously: thermomechanical exergy recovery from liquid hydrogen; the need to remove CO2 from air so that the purified air can be used in hydrogen-air alkaline Fuel cells. An earlier paper by Ahuja and Green (Ahuja, V. and Green, R., International Journal of Hydrogen Energy, 1996, 21(5), 415-421) discussed the use of thermomechanical exergy recovery in CO2, removal from air for alkaline Fuel cells operating with hydrogen stored as liquid. An energy balance for refrigeration purification for the CO2 removal, a schematic description of the process, and an overview of the thermal analysis of matrix heat exchangers were presented. These were used to show that the proposed process of CO2 removal by refrigeration purification using thermomechanical exergy recovery from liquid hydrogen depended on very high effectiveness heat exchangers. Results of heat exchanger effectiveness tests were given to show that heat exchangers of the requisite effectiveness could be built. This paper presents results from the experimental program used to evaluate this CO2 removal process. Results of rests on CO2 removal, the use of a reversing heat exchanger to process natural humidity, regeneration of the heat exchanger where CO2 is removed, pressure drop, single heat exchanger and overall system effectiveness, are shown. The results establish that a re enerable process for CO2 removal from alkaline fuel cell feed air by refrigeration purification, using the cooling available from thermomechanical exergy recovery from liquid hydrogen, is achievable. (C) 1997 International Association for Hydrogen Energy.