Laboratory-scale Study of Nickel-catalyst Pellets Performance for Tar Steam Reforming Obtained from Biomass Gasification

Abstract

Biomass steam gasification is a promising solution to obtain an H2-rich syngas to be exploited in high temperature SOFC to produce electricity with high efficiency and a reduced environmental impact. The aim of the H2020 BLAZE project is to integrate a dual fluidized bed biomass gasifier with a 25 kWe SOFC. Tars, in any case, have been identified as one of the major impurities in biomass gasification fuel gas, causing degradation of the anodes of the SOFC due to carbon deposition. Hot gas cleaning and conditioning using ceramic filter candles, filled with an annular packed-bed of commercial nickel-based catalyst, has been identified as the best solution to convert tars and reduce them to few hundreds of mg Nm-3. This work reports the results obtained in one task of the BLAZE project, in which two different commercial catalysts supplied by Johnson Matthey (catalyst A and catalyst B) have been tested at micro-reactor scale to evaluate their activity for the steam reforming of tar with the presence of sulfur compounds, which act as catalyst deactivators, and at temperatures comparable with those obtainable in biomass steam gasification. The main objective of this work was to evaluate which catalyst could be used inside the filter candles in the BLAZE power plant and which are the best operating conditions to have a conversion of tar as required for the SOFC. Twelve tests were conducted, six for each catalyst, varying both the temperature (750, 800 and 850 °C) and the concentration of thiophene in the pseudo-tar solution fed, a compound used to simulate the sulfur compounds deactivators of the catalyst (one with 50 ppm of thiophene, the other with 100 ppm). The results show that the hydrocarbons conversion increases (reaching 100%) with increasing temperature and decreasing thiophene concentration. Furthermore, catalyst A showed better performance than B.