Concrete as low-cost catalyst to improve gas quality during biomass gasification in a pilot-scale gasifier

Abstract

Abstract Concrete was evaluated as low-cost catalyst for in-situ application in an autothermal 80 kWth pilot-scale bubbling fluidized bed direct (air) biomass gasifier. To improve the understanding of the observed phenomena, the process was also evaluated in smaller-scale reactive system, namely an externally heated 3 kWth bench-scale bubbling fluidized bed. Concrete application showed promising results regarding the relative increase of H2 concentration and H2/CO molar ratio in the producer gas (up to 99.2 and 77.4%, respectively), indicating that this material can promote the water-gas shift reaction. However, this effect was dependent on the gas-solid contact time and catalyst temperature, being that it was only relevant when these parameters were at least 5.2\xa0s and 746\xa0°C, respectively. A maximum lower heating value of 7.5 MJ/Nm3 of the producer gas was found with concrete application (23.8% relative increase), which is higher than commonly found in the literature. Relative increases of up to 25.1, 55.3 and 47.0% for the specific dry gas production, cold gas efficiency and carbon conversion efficiency, respectively, were also found, consequently suggesting that, in addition to the promotion of the water-gas shift reaction, this material has potential to promote tar reforming/cracking and carbon gasification reactions.