Improvement of the SOFC System by Anode Recirculation

Abstract

SOFC can utilize a variety of carbon-containing fuels stably and efficiently. Many studies have proved that anode recirculation can effectively improve the system fuel utilization, enhancing the system's electrical efficiency and lowering operating costs. More precisely, anode recirculation takes high power output, high efficiency, and high stability into account at the system level, while these three indexes are contradictory at the SOFC stack level. In this study, multiple SOFC system process models were built with MATLAB, which involved four anode recirculation modes, namely, "conventional low recirculating rate" mode, "conventional high recirculating rate" mode, "recirculation with water gas shift reaction reactor" mode and "recirculation with adiabatic reformer" mode. These modes were compared under different operating conditions. The key parameters that affect the system performance include fuel flow rate, recirculation rate, current per cell, and reformer temperature. Finally, the measured data of industrial-size fuel cells were used to make verification. It is found that the "recirculation with adiabatic reformer" mode can achieve high electrical efficiency while maintaining SOFC stacks working at low fuel utilization conditions. In other words, high power output, high electrical efficiency, and high stability are achieved at the same time. Moreover, it also has considerable feasibility in terms of system thermal balance. This study can provide powerful guidance for SOFC system design and construction.