A Diesel-Fuelled Solid Oxide Fuel Cell (SOFC) 1 kW Generator: System and Component Studies
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A steady-state simulation of a diesel-fuelled SOFC system was developed using a process simulation software package (VMGSim). The system was studied by conducting a sensitivity analysis of six independent variables (steam to carbon ratio, oxygen to carbon ratio, fuel utilization, air utilization, reformer pre-heater approach temperature and cathode temperature to the SOFC) and their effect on three response variables (net system efficiency, stack efficiency, system exhaust temperature). The steam to carbon ratio, fuel utilization and air utilization were the most influential independent variables and thus affected the greatest change in the performance metrics. Secondly, a multi-variable study was carried out on the most influential variables and constrained optima for the efficiencies (45% net system, 47% stack) and system exhaust temperature (78 degrees Celsius) were obtained. For the second part of this work, a steam reforming heat-exchange reactor was modeled using COMSOL. The reactor performance was assessed on the basis of selectivity and residence time for a given conversion. Both the kinetic models of Parmar et al. (2010) and Shi et al. (2009) for catalytic diesel steam reforming were applied and compared. Differences in performance were attributed to differences in the catalyst support and the reaction mechanisms used for deriving the reforming rate expressions. Finally, a proof of concept multi-scale modeling and design tool was developed by integrating the CFD model with the process simulation. Two-way communication between four different software components; COMSOL, VMGSim, Matlab and Microsoft Excel was achieved.