Electrical efficiency of ethanol fuelled solid oxide fuel cell system : comparison between distillation and pervaporation for bioethanol purification

Abstract

The overall electrical efficiencies of the solid oxide fuel cell (SOFC) systemintegrated with two different bio-ethanol purification processes, i.e. distillation and pervaporation were investigated and compared. It was found that the purification by pervaporation consumed less heat energy than that by distillation but the additional electrical power is required for the vacuum pump operation. In addition, two different levels of the permeate pressure for pervaporation were studied. The results show that the lowering pressure at the permeate side from 0.1 atm to 0.05 atm required less heat consumption but more electrical power consumption. For the SOFC system integrated with the purification process, the simulation studies were based on the condition that the net useful heat (Qnet) is equal to zero. It was found that the most suitable operating voltage is between 0.65 and 0.8 V and the operating temperature is in the range between 973 and 1173 K. For the effect of the ethanol recovery, the optimal ethanol recovery of the SOFC system integrated with distillation and pervaporation process are 95% and 99% respectively. The results indicate that the SOFC system integrated with pervaporation process with the permeate pressure of 0.1 atm offers the maximum overall electrical efficiency that is 41.6% (voltage = 0.7 V, temperature = 1073 K, separation factor = 923 and ethanol recovery = 99%)