Thermodynamic Analysis of Diesel Reforming Options for SOFC Systems

Development of a diesel reformer for solid oxide fuel cells widens the application of the SOFC system by making it more fuel-flexible. While technologies for conversion of fuels containing these hydrocarbons are commercially available, the industrial scale processes and the composition of the reformed gas are not ideally suited to SOFC systems. The work is extremely challenging and will require some novel approaches to solving some of the technical problems. A key step in fuel processing is reforming of the fuel to a mixture containing hydrogen and methane. There are three routes for this conversion: steam reforming, autothermal reforming and partial oxidation. In this work we carried out a thermodynamic analysis of the three reforming routes. Minimum steam-to-carbon ratios for steam reforming and for autothermal reforming and minimum oxygen-to-carbon ratios for autothermal reforming and partial oxidation and their corresponding temperatures required for carbon-free operation were identified. Fuel processor efficiencies and reformer heat requirements were computed to identify practical operating conditions. SOFC stack efficiencies for 85% fuel utilisation were computed to identify the commercially viable options for the system.