Cross-influence of toluene as tar model compound and HCl on Solid Oxide Fuel Cell anodes in Integrated Biomass Gasifier SOFC Systems

Abstract

Integrated Biomass Gasifier Solid Oxide Fuel Cell Systems represent an alternative to fossil fuel based power plants, and direct internal tar reforming allows achieving high efficiency and decreasing system complexity. However, at present, tar is removed or reformed externally since there is not yet general agreement on the fate of these compounds in the anode chamber, and no information is available on the combined effects of tar and other biosyngas contaminants. In this paper, we present the results of short-term experiments on the cross-influence of HCl and tar on Ni-GDC Solid Oxide Fuel Cell anode and on direct internal tar reforming. Initially, the cell was fed with humidified hydrogen and an increasing concentration of HCl (8, 42 and 82 ppmv) and toluene (2.5, 4.2 and 8.4 g/Nm3) separately. Successively, 8.4 g/Nm3 of toluene and an increasing concentration of HCl were fed to the cell. We used polarisation and power density curves, and outlet gas composition analysis to evaluate the contaminants effects. The presence of HCl and toluene caused only a marginal increase in the cell Area Specific Resistance (around 1.5% when the cell was operated at Open Circuit), and the Area Specific Resistance remained then constant during the exposure time. However, HCl affects tar reforming decreasing the concentration of CO2 and CO at the cell outlet. The results indicate the feasibility of direct internal toluene reforming and suggest the revision of currently used tolerance limits based on contaminants cross-influence effects. Extensive research on this topic is still required.