Hydrogen-rich gas production from catalytic steam gasification of biomass in a decoupled dual loop gasification system

In order to strengthen tar destruction and hydrogen-rich gas production in the biomass gasification, a novel decoupled dual loop gasification (DDLG) system was proposed. The system decouples gasification process into fuel gasification, tar reforming and residual char combustion, which occur in three independent reactors, i.e. gasifier, reformer and combustor. Both the gasifier and the reformer are separately interconnected with the combustor, forming two circulation loops in parallel. With pine sawdust as feedstock, and calcined olivine as both solid heat carriers and in-situ tar destruction catalyst, the performance of biomass gasification was investigated. The results indicate that the reforming after the gasifier and the presence of olivine catalyst greatly improve the tar destruction. Specifically, at the gasifier temperature of 700 ℃, the reformer temperature of 850 ℃ and the steam to carbon mass ratio (S/C) of 1.2, the tar content in product gas decreases to 13.9 g/m³, and the dry gas yield and H₂ concentration reach 1.0 m³/kg, and 38.8%, respectively.