Evaluation of monolith catalyst in catalytic combustion of anode off-gas for solid oxide fuel cell system

Solid oxide fuel cells (SOFC) can operate at high temperatures (> 650 °C) and have attracted attention because of their high efficiency. However, the CH4, CO, and H2 contained in the anode off-gas that are not reformed or does not participate in the SOFC power generation process must be treated. A catalytic combustion process, which can improve the efficiency by treating the target substances and heat recovery, is essential for this purpose. This study examined the CH4 combustion performance of Pd- and Pt-supported catalysts in the presence or absence of H2O in the feed, at O2/2CH4 ratios of 15 and 20, at a gas hourly space velocity (GHSV) of 5000, 10,000, and 20,000 h−1, and at inlet temperatures of 100–580 °C. The Pd-rich catalyst with a cell per square inch of 400 exhibited the best CH4 combustion performance, as CH4 combustion was possible even at an inlet temperature of 200–300 °C. The performance of this catalyst was evaluated by applying it to a 5-kW scale catalytic combustor. CH4, CO, and H2 combustion experiments of the catalyst in this apparatus were performed at a O2/C of 12–15, GHSV of 8400–16,800 h−1, and inlet temperatures of 100–580 °C, and CO and H2 conversions exceeding 98 % and a CH4 conversion exceeding 75 % were obtained. We expect that the results of this study can be used for the scale-up design of high-efficiency SOFC systems capable of reducing the concentrations of emitted CO and CH4 and utilize the heat generated in the power generation process through the AOG catalytic combustor.