Feasibility of direct-biogas SOFC

Abstract

Direct feeding of real biogas generated in a methane fermentation reactor to SOFC was tested by using Ni–ScSZ cermet as an anode material. At the operating temperature of 1000 °C, cell voltage above 0.9 V (at 200 mA cm −2) was stably obtained over 50 h without carbon deposition showing direct-biogas SOFC is feasible. This system is environmental-friendly, compact and cost-effective energy conversion system in which internal dry reforming of CH 4 proceeds on Ni-based anode using CO 2 included in biogas without external reformer and precious metal catalyst. H 2S poisoning test was performed simulating H 2S contamination of biogas. Electrochemical and catalytic properties of Ni–ScSZ anode in feeding simulated biogas mixture (CH 4/CO 2 = 1.5) and their changes by H 2S supply were measured at 1000 °C under 200 mA cm −2. 1 ppm H 2S poisoning caused about 9% voltage drop and about 40% decrease in reaction rate of internal reforming, however, stable operation was achieved and complete recovery of cell voltage and reaction rate after stopping the H 2S supply was confirmed, indicating that direct-biogas SOFC operated at 1000 °C is tolerant to 1 ppm level H 2S contamination.