Performance study of solid oxide fuel cell with Ni-foam indirect internal reformer: Intrinsic reforming kinetics and temperature uniformity

Abstract

For solid oxide fuel cells, non-uniform temperature distribution has a large effect on the cell’s efficiency over the long-term operation. A methane steam reformer with 10 %Ni/10 %MgO/Ni foam as a catalyst was designed, and the intrinsic kinetic model of the catalyst is developed based on the Langmuir-Hinshelwood theory. An indirect internal reforming (IIR)-SOFC stack is constructed by combing the reformer and the single SOFC stack to improve the uniform temperature distribution and reduce the cell temperature gradient under various operating conditions. The electrical performance and temperature distribution of the IIR-SOFC stack and direct internal reforming (DIR)-SOFC stack are comparatively studied by experiments and numerical simulations. The results show that the two SOFC stacks have almost identical polarization curves under different temperatures, fuel–air flow rates, or steam/methane (S/C). It indicates that the IIR-SOFC stack just changes the position of methane reforming, and the amount of hydrogen and carbon monoxide produced by methane reforming is almost the same. As compared to the DIR-SOFC stack, the IIR-SOFC stack observably lowers the cell temperature uniform index, and the cell global and local temperature gradient, making the cell temperature distribution more uniform. The maximum temperature difference and the maximum temperature gradient on the IIR-SOFC anode are 35.1 % and 307 % less than on the DIR-SOFC anode under the operating condition of 800 °C, S/C = 2.5 and 0.6 V. Overall, the Ni-foam-based IIR-SOFC stack can homogenize the cell temperature distribution, and reduce the cell carbon deposition and mechanical failure.