Research On Characteristics Of Catalytic Partial Oxidation-solid Oxide Fuel Cell Systems

Distributed micro combined heat and power systems based on solid oxide fuel cells?SOFC-m-CHP?could achieve energy-step-utilization with high efficiency and low emission,which have a broad application prospect.Analyses on characteristics of reformer-SOFC subsystem,i.e.core component in a SOFC-m-CHP system which related to fuel pretreatment and energy conversion,are very important for improving system efficiency.Focused on the reformer-SOFC subsystem,this study performed characteristics analyses and operating condition optimization from three aspects,i.e.reformer,SOFC module and system,achieving stable operation of methane catalytic partial oxidation?CPOX?-SOFC systems.From the aspect of reformer,the evaluating reactor was designed and constructed for CPOX reforming of methane,which used for evaluating effects of various operating conditions.The effects of catalysts,temperature,C/O ratio and volume space velocity to methane conversion,selectivity of hydrogen and carbon monoxide,as well as reforming efficiency were obtained through analyzing reforming products.When temperature was 800?and C/O ratio was0.8,peak reforming efficiency of 91.4%was achieved based on 0.5%Rh/Al₂O₃catalyst.From the aspect of SOFC module,two configurations of SOFC were proposed and evaluated,one of which was novel robust flat-chip configuration and another was micro tubular configuration.Electrochemical examination of the two configurations were performed in pure hydrogen.The flat-chip SOFC was planar and electrolyte-supported,which was advantageous for simple manufacture and cold-end sealing.Micro tubular SOFC took an anode-supported tubular configuration with better thermal resistance and electrochemical performance.The reaction temperature of flat-chip SOFC and micro tubular SOFC was about800?and 650?respectively while peak power density of flat-chip SOFC and micro tubular SOFC were 71 m W/cm² and 360 m W/cm² under respective reaction temperatures.From the aspect of system,two integrated systems of SOFC coupled with CPOX reformer were constructed,i.e.CPOX-flat-chip SOFC system and CPOX-micro tubular SOFC system,achieving stable operation of the integrated systems.The characteristics of the two integrated systems under steady state and dynamic state were performed independently.The peak power densities of CPOX-flat-chip SOFC system and CPOX-micro tubular SOFC system were 53 m W/cm² and246m W/cm² respectively while system efficiency was 5.38%and 17.5%.CPOX-flat-chip SOFC system could survive harsh tests of rapid thermal cycling with the temperature change rate well above 200°C·min^-1,and repetitive redox cycling at least 23 times.The response time of CPOX-micro tubular SOFC system towards dynamic voltage or current steps was less than 2s and attenuation rate was less than 1%after a long steady-state operation of 10 hours.