Comparison of Novel and Commercial Catalysts for the Steam Reforming of Tar Obtained from Biomass Gasification

Abstract

The hot gas cleaning and conditioning unit represents a crucial step in the biomass gasification process to achieve the quality of the syngas required for downstream processes. Catalyst-filled filter candles can be used to convert tar and remove particulate matter. In this work, a laboratory-scale packed bed reactor was used to evaluate the performance of a novel patented Ni-based tar reforming catalyst (C&CS #1050 B). To simulate the impurities of the syngas, a solution of naphthalene, toluene and thiophene (as equivalent H2S) was selected. The steam reforming tests were carried out with a tar content of 13 g/Nm3, two gas hourly space velocities (6000 and 13000 h-1), two thiophene contents (equivalent to 50 and 100 ppmv of H2S) and temperatures ranging between 650 and 800 °C. Superior catalytic performance was observed at 50 ppmv (from 700 to 800 °C) compared to a commercial catalyst at GHSV of 6000 h-1. Furthermore, a conversion rate of 100 % was achieved at each temperature even with an H2S content of 100 ppmv. Although tests at higher GHSV (13000 h-1) have shown worst conversion results, the tar conversion rate was higher than shown by the previously tested commercial catalyst (close to 100% at 800°C and above 95 % at 750 °C). Finally, based on the results, a relative low temperature (650 °C) is sufficient to achieve complete tar conversion even at 100 ppmv of thiophene. These results open up the exploitation of the new catalyst in the sorption enhanced gasification processes where low temperatures are required.