Analysis of integrated methane tri-reforming-SOFC system: Effects of operation parameters and reforming strategies

Natural gas-fueled SOFC with a reforming strategy is promising for distributed and portable power generation. In this work, the novel tri-reforming strategy is integrated into the SOFC system. Based on the developed kW-scale system model, the effects of operating parameters on reformer, SOFC and the system performances are investigated comprehensively, along with the spatial properties obtained inside the reformer and the SOFC. Higher inlet O₂ concentration results in higher reformer temperature profile but lower reformer efficiency, while higher H₂O and CO₂ concentrations could lower the temperature profile. The inlet H₂O/CO₂ ratio can regulate the outlet CO/H₂ ratio, thereby offering high fuel flexibility to the system. Increasing excess air ratio and fuel utilization are beneficial for electric efficiency while lowers thermal efficiency due to the extra heat requirement or energy loss. Safe operation favors lower fuel utilization and higher excess air ratio. The tri-reforming strategies exhibit moderate temperature profile inside SOFC, resulting in safer operation. Among the investigated TR strategies, TR_1 (CH₄/H₂O/CO₂/O₂ = 1/2/1/0.5), with a higher proportion of H₂O, proves beneficial for system efficiency and safety; a high system global efficiency of 71 % is obtained with the fuel utilization of 85 % and the excess air ratio of 5. This work not only provides a novel, clean, efficient and fuel-flexible route for portable power source and distributed power generation, but also enables SOFC system design with off-gas recirculation, where CO₂ recycle and the absence of exhaust gas separation offer a practical solution for the reduction of carbon emission in dealing with various fuels.