Performance of SOFCs using model waste gases: A case study

Abstract

Municipal solid waste landfills and steelmaking industry produce large amounts of high-calorific waste gases which can be utilized for energy generation. The possibility of SOFC operation using model landfill and coke-oven gases without external steam reforming of methane was experimentally demonstrated employing a SOFC short-stack comprising two electrolyte-supported membrane-electrode assemblies of planar geometry. The current-voltage dependencies, polarization resistances and composition of the effluent fuel oxidation products were tested as function of time during approximately 600 h. In all cases, complete conversion of methane occurs at the anodes even under open-circuit conditions. The maximum power density of 183 mW/cm2 was achieved for the humidified landfill gas at 850 °C and current density of 320 mA/cm2; the fuel utilization was 67% at current density of 222 mA/cm2. Neither microstructural changes nor carbon deposition were revealed by microscopic analyses after the SOFC tests. However, thermodynamic estimations showed that local anode coking may occur in a narrow zone near the fuel inlet where the fuel utilization only starts. This process correlating with local cooling detected in the vicinity of fuel inlet, may be responsible for degradation in the SOFC performance observed in the waste gas utilization regime.