Thermodynamic assessment of solid oxide fuel cell system integrated with bioethanol purification unit

Abstract

A solid oxide fuel cell system integrated with a distillation column (SOFC–DIS) has been proposed in this article. The integrated SOFC system consists of a distillation column, an EtOH/H 2O heater, an air heater, an anode preheater, a reformer, an SOFC stack and an afterburner. Bioethanol with 5 mol% ethanol was purified in a distillation column to obtain a desired concentration necessary for SOFC operation. The SOFC stack was operated under isothermal conditions. The heat generated from the stack and the afterburner was supplied to the reformer and three heaters. The net remaining heat from the SOFC system ( Q SOFC,Net) was then provided to the reboiler of the distillation column. The effects of fuel utilization and operating voltage on the net energy ( Q Net), which equals Q SOFC,Net minus the distillation energy ( Q D), were examined. It was found that the system could become more energy sufficient when operating at lower fuel utilization or lower voltage but at the expense of less electricity produced. Moreover, it was found that there were some operating conditions, which yielded Q Net of zero. At this point, the integrated system provides the maximum electrical power without requiring an additional heat source. The effects of ethanol concentration and ethanol recovery on the electrical performance at zero Q Net for different fuel utilizations were investigated. With the appropriate operating conditions (e.g. C EtOH = 41%, U f = 80% and EtOH recovery = 80%), the overall electrical efficiency and power density are 33.3% (LHV) and 0.32 W cm −2, respectively.