Internal reforming characteristics of cermet supported solid oxide fuel cell using yttria stabilized zirconia fed with partially reformed methane

摘要

In order to investigate the internal reforming characteristics in a cermet supported solid oxide fuel cell (SOFC) using YSZ as the electrolyte, the concentration profiles of the gaseous species along the gas flow direction in the anode were measured. Partially reformed methane using a pre-reformer kept at a constant temperature is supplied to the center of the cell which is operated with a seal-less structure at the gas outlet. The anode gas is sucked in via silica capillaries to the initially evacuated gas tanks. The process is simultaneously carried out using five sampling ports. The sampled gas is analyzed by a gas chromatograph. Most of the measurements are made at the cell temperature (T_(cell)) of 750℃ and at various temperatures of the pre-reformer (T_(ref)) with various fuel utilizations (U_f) of the cell. The composition of the fuel at the inlet of the anode was confirmed to be almost the same as that theoretically calculated assuming equilibrium at the temperature of the pre-reformer. The effect of internal reforming in the anode is clearly observed as a steady decrease in the methane concentration along the flow axis. The effect of the water-gas shift reaction is also observed as a decrease in the CO_2 concentration and an increase of CO concentration around the gas inlet region, as the water-gas shift reaction inversely proceeds when T_(cell) is higher than T_(ref). The diffusion of nitrogen from the seal-less outermost edge is observed, and the diffusion is confirmed to be more significant as U_f decreases. The observations are compared with the results obtained by the SOFC supported by lanthanum gallate electrolyte. With respect to the internal reforming performance, the cell investigated here is found to be more effective when compared to the previously reported electrolyte supported cell.