Use of gasification syngas in SOFC: Impact of real tar on anode materials

The integration of gasification systems and solid oxide fuel cells (SOFCs) is a promising technology for reaching economic feasibility of combined heat and power production. However, the impurities present in gasification syngas have the potential to interact with the SOFC anode. In particular, tars have been identified as one of the major impurities in biomass and coal gasification fuel gas, causing degradation of the anodes due to carbon deposition. Model tar compounds (toluene, benzene, naphthalene) are commonly used to represent those arising from biomass/coal gasification. However, model tars may fail to simulate the degradation effects of real tars on SOFC anodes. This paper presents the results of an experimental study on the impact of a real gasification tar on two commercially available anode materials, Ni/YSZ (yttria stabilised zirconia) and NiO/CGO (gadolinium doped ceria). Less degradation of the anode powders by carbon formation occurred when the anodes were exposed to humidified hydrogen gas containing the real tar, as compared with toluene, used as model tar. The presence of increasing steam contents reduced the amounts of carbon deposited. The properties of the recovered tars were similar, irrespective of the percentages of steam.