The target of this study is to investigate the performance and efficiency of an integrated autothermal reforming and SOFC (solid oxide fuel cell) system fueled by methane. A zero dimensional SOFC stack model

which consists of electrochemical reactions and thermodynamics

is developed by Fortran and validated with experiment results

and links it to Aspen Plus software as a subroutine. Based on mass and energy balances

influences of steam to carbon(S/C) ratio and fuel utilization(Uf) on performance of SOFC power systems are investigated. The simulation results show that increase in the S/C ratio can enhance hydrogen production while reduce CO formation. Oxygen to carbon ratio and system efficiency achieve maximum when S/C ratio is 1.5. Increase of fuel utilization can enhance current density

resulting in increase of excess air ratio and decrease of air utilization. The overall efficiency and electric efficiency of the system all are increase because more chemical energy is converted into electric energy

whose maximum values are 44.5% and 39.2%

respectively. The performance characteristics obtained is of great significance for further optimization of integrated SOFC systems with autothermal reforming of natural gas.