Effects of operating conditions and reactor structure on biomass entrained-flow gasification

Abstract

A Eulerian-Lagrangian CFD model is utilized to investigate the effects of three different factors on biomass entrained-flow gasification, including the gasifying medium, reactor structure, and feedstock properties. For gasifying medium, O2, CO2, steam, and a blend of steam and CO2 are used. Results show that the introduction of O2 improves the CO production and carbon conversion but an excessive use leads to a decline in combustible gas yield, steam decomposition and cold gas efficiency. Introducing CO2 raises the CO yield, carbon conversion and cold gas efficiency but reduces the steam decomposition. Moreover, the H2 production, carbon conversion and lower heating value rise while the steam decomposition declines with steam addition. Besides, steam-CO2 composite gasification is better than both pure CO2 gasification and steam gasification in syngas yield, carbon conversion and lower heating value but worse in steam decomposition. Regarding reactor structure, enlarging the biomass inlet has little effect on the product gas yield but accelerates the pyrolysis process. Keeping the biomass inlet away from the gasifier axis improves the combustible gas yield and conversion efficiencies. Finally, for feedstock properties, the biomasses with a higher volatile or fixed carbon content and a lower moisture content generate a high combustible gas yield.