Using a manganese ore as catalyst for upgrading biomass derived gas

Secondary catalytic tar cleaning has been evidenced as a promising technology for upgrading gas derived from biomass gasification. When applying this technology downstream a biomass gasifier, the tar fraction in the raw gas can potentially be reduced and the content of hydrogen be increased. In this work, experiments have been conducted in a chemical-looping reforming (CLR) reactor. The present reactor system features a circulating fluidized bed as the reformer section, which offers a higher gas-solid contact time than a bubbling bed configuration previously tested. All experiments were performed using raw gas from the Chalmers 2–4 MW_th biomass gasifier as feedstock to the reactor system. The catalyst inventory consisted of a natural manganese ore, and its activity was evaluated at three different temperature levels—800, 850, and 880 °C—and with an oxygen content of 2.2 %, corresponding to a theoretical air-to-fuel ratio of 0.06. Experimental results showed that the manganese ore exhibits catalytic activity with respect to tar conversion, and a tar reduction of as much as 72 % was achieved at 880 °C. Moreover, this material showed high activity towards hydrogen production and overall, an interesting upgrading capacity toward this producer gas. An H₂/CO ratio of nearly 3 in the produced gas can make this material potentially interesting for application in an SNG system. Regarding the analysis of the physicochemical characteristics, the material showed signs of agglomeration with traces of sand most likely resulting from previous sieving during particle preparation. Though, a positive aspect is that this occurred without impacting the catalyst activity.