关键词: 双流化床, 生物质, 气化, 两相模型, 动力学

Abstract: In order to further study the distribution of synthesis gas concentration in the biomass gasifier of a dual fluidized bed, the two-phase modeling was developed by dividing the bubbling fluidized bed into bubble and emulsion phases, and the mass and heat balance for the two-phases were accounted based on the kinetic rate equations. The simulated values agreed with the experimental data. The effects of ratio of steam to biomass (S/B) and gasification temperature on the composition of synthesis gas were studied. The results showed that the CO content increased with the increase of gasification temperature, and H2 and CO2 contents decreased. The water-gas shift and reforming reactions were promoted to their positive direction with the increase of S/B, leading to more consumption of CO and CH4, and generation of H2 and CO2. When S/B was 0~1.2, the ratio of CO to H2 changed 44%, which indicated that the water-gas shift was the main reaction with the increase of S/B. The profiles of syngas composition along the gasifier height were further analyzed at the gasification temperature 870℃ and S/B 0.75. When the gasifier height was less than 0.5 m, the H2O content decreased sharply, and the molar concentration of H2 increased steeply, and the CO and CO2 contents increased gradually. When the gasifier height was more than 0.5 m, the gasification reactions were inclined to equilibrium.

Key words: dual fluidized bed, biomass, gasification, two-phase model, kinetics