Simulation of solid oxide fuel cell system fuelled by ethanol

Abstract

The research focuses on the simulation of solid oxide fuel cell (SOFC) systems fuelled by ethanol. The study is divided into four parts: theoretical performance analysis of ethanol-fuelled SOFC with different electrolyte, actual performance of ethanol-fuelled SOFC, thermodynamic assessment of SOFC system integrated with bioethanol purification unit and design of thermally integrated bioethanol-fuelled SOFC system with a distillation column. The theoretical performance of SOFC with proton-conducting electrolyte (SOFC-H[superscript +]) is found to be superior to that of oxygen ion conducting electrolyte (SOFC-O[superscript 2-]) although the lower requirement of steam input in the case of SOFC-O[superscript 2-] is taken in to account. However, the actual performance of SOFC-H[superscript +] is inferior to that of SOFC-O[superscript 2-] because the resistance is 45.6 times higher than that of SOFC-O[superscript 2-]. In order to develop the performance of SOFC-H[superscript +] to be comparable to that of SOFC-O[superscript 2-], both electrolyte resistance and other resistances should be simultaneously reduced. A bioethanol-fuelled SOFC system integrated with a distillation column (SOFC-DIS) is proposed to improve the conventional system which was fed by high purity ethanol in order to save distillation energy. The combustion heat from excess fuels is provided to other parts of the system i.e. heaters, a reformer and a reboiler. The SOFC-DIS can operate without demanding heat from an external source when suitable operating voltage and fuel utilizations are selected. To improve the performance of SOFC-DIS, utilization of heat released from a condenser and splitting of some part of cathode outlet stream to be recycled offer the highest efficiency and lowest total cost index. The suitable heat exchanger network for the SOFC-DIS system is that the hot stream from the afterburner is first heat exchanged with the anode-inlet heat exchanger, the reformer, the air heat exchanger, the distillate heat exchanger and a reboiler, respectively. In addition, adjusting SOFC-DIS operating conditions can lower total cost index.