INDEPENDENT HYBRID POWER PLANT 'PEMFC+MEMS' WITH USE OF MOLECULAR CERAMIC MEMBRANES TO SEPARATE CO and H_2

摘要

As analysis of thermal-technical parameters of the existing polymer exchange membrane fuel cells (PEMFC) indicated, their electrical efficiency is not above 32-37% which is due to relatively high (10-15%) electric power consumption to cover own needs. Its major percentage falls on pump and compressor drive (air, fuel, water supply) using the AC electric engines connected via converter to FC. A real alternative allowing the efficiency increase up to 45% and higher is to apply hybrid plants when an AC turboelectric generator (TEG) is built into the thermodynamic cycle, the latter operating at the expense of utilization of the FC reagent stream power. TEG is a micro turbocompressor with incorporated turbo generator manufactured on the basis of the micro electric-mechanical system (MEMS) technology. The numerical study over the hybrid cycle effectiveness revealed that the optimum efficiency is ensured provided the TEG power does not exceed 12-15% of the total hybrid power plant power. Considering a value of the PEMFC mean power of around 8, a need arises in TEG of 500 to 1500W power to operate as a part of hybrid engine. Among various auxiliaries involved into the PEMFC, there should be devices that ensure getting target values in terms of hydrogen purity, a dominant synthetic gas fraction, at the FC inlet. A need to get and maintain hydrogen purity on the level of 99.99% is related with that if CO content in mixture is higher 0.01%, then a normal operation of FC fails due to "poisoning" effect of the platinum-containing catalysts of the FC electrodes. To forestall this, the palladium molecular membranes are now typically applied which causes the filtered flow temperature limitations within values not exceeding 500-550℃. At the same time, PEMFC in most cases must operate on air and syngas produced by reforming, with their temperature amounting to 800-900℃ . To provide this, we need to have ceramic molecular membranes (CMM) made of a ceramic support in which macropores nano pores are formed (characteristic size of less 0.3nm), the latter achieved through application of a complex of various chemical and physical processes. In the paper presented, findings of numerical studies over a hybrid engine plant are provided, this hybrid plant (PEMFC + MEMS) as compared with alternatives to existing and offered schemes, and, also, test data on the zeolite-based support CMM are demonstrated.