Steam co-gasification of biomass and coal in decoupled reactors

Abstract

Steam co-gasification of pine sawdust and bituminous coal was conducted in a lab-scale external circulating radial-flow moving bed (ECRMB) gasification system. The system is composed of three decoupled reactors, i.e., a gas–solid countercurrent moving bed pyrolyzer, a radial-flow moving bed gasifier and a riser-type combustor. Calcined olivine was used as circulating heat carrier and in-situ tar destruction catalyst as well. The influences of biomass blending ratio (BR), pyrolyzer temperature, gasifier temperature and steam to carbon mass ratio (S/C) on the gasification performance were investigated. The results indicated that the gas and tar yields increased with the increase of BR. Synergetic effect based on gas composition was found during co-gasification. At the S/C range of 0 to 1.3, the gas yield and H2 content in product gas increased but CO2 decreased with the increase of S/C. Higher gasifier temperature promoted the gas yield, H2+CO in product gas, carbon conversion and chemical efficiency of the process. A gas yield of 0.60Nm3/kg daf and a tar yield of 5.8g/Nm3 in the gas were obtained at the gasifier temperature of 850°C, BR of 50% and S/C of 1.3. Pyrolyzer temperature at the range of 500 to 700°C had no remarkable influence on the product gas composition.