Influence of Operating Conditions on Carbon Deposition in SOFCs Fuelled by Tar-Containing Biosyngas

Abstract

This study presents the influence of operating conditions including steam levels, current density and time on stream on the performance of solid oxide fuel cells (SOFCs) with Nickel/Yttria Stabilized Zirconia (Ni/YSZ) anodes fuelled by tar-containing biosyngas. Changes in impedance spectra and polarization curves of SOFCs after tar exposure were analysed to assess the cell performance. The biosyngas composition and the tar concentration used in these measurements were identical to those measured from a commercial air-blown biomass gasifier that is to be connected to a SOFC system. Operating this type of SOFC under the tar concentrations used in this work could result in severe damage of the cell due to carbon formation on the anodes. Carbon deposition was observed by Scanning Electron Microscopy (SEM) and affected the performance of the SOFC, as shown by the impedance spectra and anode polarization curves of the cells after exposure to tars. However, the risk of carbon deposition can be reduced by increasing steam levels and current loads.