Long-Term Operation and Post Analysis of a Stack with Methane Fuel

In the commercialization of the solid oxide fuel cell (SOFC) technology, the long-term stability and the use of hydrocarbon fuels are important. An 18-layer SOFC stack with anode-supported cells was first designed, assembled and operated in Huatsing Power Co., Ltd in China. After the basic performance test with H2, the stack was operated at 750 °C with a 14.53 L/min hydrocarbon fuel for nearly 800 hours. The voltage degradation rate was only 1.42%/kh. Post analysis was performed through SEM and EDS. Microstructures of Ni particles with different degree of carbon deposition at the fuel inlet were observed and discussed. A phenomenon of rainbow-shaped color distributions on the surfaces of anode and nickel mesh in every layer was found. This phenomenon was related to the oxidation of the upper part of the nickel contact layer. Due to the light interference taking place at the nickel-oxide-air interfaces, different thickness of oxide film led to different colors. Carbon deposition and oxide film of nickel contact layer with non-uniform thickness were the possible causes of degradation.