Evaluation of a 3 kWel Reformer-operated High Temperature PEM System – Experiment and Simulation

Kurzfassung

High temperature polymer electrolyte membrane fuel cells (HT-PEMFC) can be operated with reformate containing carbon monoxide levels up to several vol.-%. This enables the design of a coupled reformer fuel cell system with reduced complexity and enhanced robustness. An experimental study and an Aspen Plus system model is presented. The experimental results were obtained with a methane reforming unit (WS Reformer) and a fuel cell module with three stacks and 76 cells each (SerEnergy). The characterization of the components was focused on the effect of different process parameters on system behaviour and total system efficiency. Mainly the variation of CO concentration, operation temperature, load and water content of the anode feed gas were investigated. Both subsystems were modelled using Aspen Plus flowsheeting software. The reforming and the water gas shift reactors were realized by a Gibbs reactor model. Kinetic limitations have been taken into consideration by applying a temperature approach in Aspen Plus, which allows for non-equilibrium conditions in the product gas. The reformate gas composition from the model shows good agreement with the experimental results. The hydrogen conversion efficiency reaches 72 to 75 %. Based on the experimental results the fuel cell module was modelled taking into account the dependence of performance on the operation parameters of the module. This was realized by the implementation of a performance map. The Aspen model of the coupled process including hydrogen generation and fuel cell system was then used for process optimization. Thermal integration was realized by applying the Pinch Method. As a result, an optimized system configuration could be identified. For the coupled reformer-HTPEM-system an overall electric efficiency of 30 - 40 % can be achieved.