SOFC running on steam reforming of biogas: External and internal reforming

Abstract

In this work, two approaches of SOFC operation fuelled by biogas are considered: one where the endothermic steam reforming and electrochemical reaction are operated in different units (external reforming SOFC) and another where biogas is introduced to the SOFC stack and directing reformed on the anode side (internal reforming SOFC). The model of SOFC system is designed and developed using Aspen Plus simulator software. Equilibrium gas composition obtained from steam reforming reaction can be calculated based on Gibbs free energy minimization method. Electrochemical equations taking into account all voltage losses (activation, ohmic and concentration lo sses) are written in a calculator block by Fortran code. Effect of operating conditions, i.e. temperature, pressure and steam to carbon molar ratio on SOFC performances is examined. From the simulation results, it was found that under the same operation conditions (steam to carbon molar ratio of 0.5, SOFC temperature of 1,173 K and SOFC pressure of 3 atm), the internal reforming SOFC has higher electrical efficiency (24 %) than external reforming SOFC (85.67 %). However, when the carbon dixide emission is considered, the simulation result reveals that the anode exhuast gas of the internal reforming SOFC has higher amount of carbon dioxide (7.4 %) compared with that of the external reforming SOFC (1.4 %(. Copyright © 2016, AIDIC Servizi S.r.l.