Upon entering a fluidized bed gasifier, biomass particles are exposed to very high heating rates that cause rapid increase of particle temperature, evaporation of moisture content and devolatilization (pyrolysis) into volatile matter that constitutes more than 80% of the original particle mass. The rest remains in the form of solid char (almost pure carbon) which is subsequently consumed in heterogeneous gasification reactions in the presence of an oxidizing agent such as air or steam. Predicting the product distribution generated from drying and pyrolysis of biomass particles prior to its integration with the homogeneous and heterogeneous gasification reactions is a key contribution to modeling a biomass gasifier. This modeling study is intended to support the evaluation of the overall performance of UBC Dual Fluidized Bed (DFB) steam gasifier that consists of two interconnected fluidized bed reactors referred to as Bubbling Fluidized Bed (BFB) gasifier and Circulating Fluidized Bed (CFB) riser/combustor. While superheated steam is used to fluidize the gasifier and produce syngas through partial oxidation of solid biomass particles, the unreacted char together with inert silica sand are circulated from the bottom of the gasifier to that of the combustor which operates at higher temperature and fluidized by air at higher superficial gas velocities. The heat requirements of the highly endothermic biomass drying, pyrolysis and gasification reactions are thus provided by continuous circulation of hot sand particles from the top of the combustor to the gasifier.

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