Biogas fuel reforming for solid oxide fuel cells

In this paper, strategies for biogas reforming and their ensuing effects on solid oxide fuel cell (SOFC) performance are explored. Synthesized biogas (65% CH4 + 35% CO2) fuel streams are reformed over a rhodium catalyst supported on a porous alpha-alumina foam. Reforming approaches include steam reforming and catalytic partial oxidation (CPOX) utilizing either air or pure oxygen as the oxidant. A computational model is developed and utilized to guide the specification of reforming conditions that maximize both CH4 and CO2 conversions. Model predictions are validated with experimental measurements over a wide range of biogas-reforming conditions. Higher reforming temperatures are shown to activate the biogas-borne CO2 to enable significant methane dry-reforming chemistry. Dry reforming minimizes the oxidant-addition needs for effective biogas conversion, potentially decreasing the thermal requirements for reactant heating and improving system efficiency. Such high-temperature reforming conditions are prevalent during CPOX with a pure-O-2 oxidant. While CPOX-with-O-2 reforming is highly exothermic, the endothermicity of dry-reforming chemistry can be exploited to ensure that catalyst temperatures do not reach levels which cause catalyst sintering and degradation. SOFC electrochemical performance under biogas reformate is shown to vary substantially with reforming approach. Cell operation under CPOX-with-O-2 reformate is found to be comparable to that under humidified hydrogen. (C) 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.3697857]