Biogas Fuel Reforming for Solid Oxide Fuel Cells

In this paper, several strategies for biogas reforming and their ensuing effects on solid oxide fuel cell performance are explored. Synthesized biogas (65% CH4 + 35% CO2) fuel streams are reformed over a rhodium catalyst supported on a porous alumina-foam support. Reforming approaches include steam reforming and catalytic partial oxidation utilizing either air or pure oxygen as the oxidant. A computation model is developed and utilized to guide definition of reforming conditions that maximize both CH4 and CO2 conversion. Model predictions are validated with experimental measurements over a wide range of biogas-reforming conditions. It is shown that higher reforming temperatures activate the CO2 in the biogas through dry-reforming reactions. Such dry-reforming chemistry leads to high CO content in the reformate streams, extensive water-gas shift reactions within the SOFC anode structure, and high SOFC power density. Such high-temperature reforming conditions are prevalent during CPOX with a pure-O-2 oxidant. As this reforming approach is highly exothermic, care must be taken to ensure that catalyst temperatures do not reach levels that can cause catalyst sintering and degradation.