A detailed process model of biomass gasification in bubbling fluidized bed: integration of hydrodynamics into reaction modeling

A detailed process model is proposed to simulate the air-gasification of biomass (wood chips) in a bubbling fluidized bed gasification system at different temperatures (650-800 degrees C) and equivalence ratios, ERs (0.08-16), using ASPEN Plus simulator. The process was assumed fully steady-state, and gasification section was modeled by implementing FORTRAN user-subroutines for reaction kinetics and hydrodynamic parameters. Experimental results from air-gasification of wood chips in a bubbling fluidized bed gasifier were used to validate the model. The model predictions were in good agreement with experimental results. The validation results also showed that ASPEN Plus can describe the gasification process in fluidized bed gasifiers well. Specifically, ER initially decreased the carbon conversion efficiency (CCE), with a minimum followed by an increase. An optimal ER was crucial for minimizing tar yield (TY). Higher temperatures yielded higher H2 contents and lower tar yields. Smaller particles decreased TY and increased gas lower heating value (LHV). Under optimal conditions (ER = 0.13, T = 750 degrees C, and D = 0.2 mm), the product gas generated during air-gasification of wood chips achieved a low tar yield of 4.61 g/Nm3. These results confirmed the significant potential of biomass gasification in high-quality syngas production with low tar content. This article also provides valuable information for selecting operation conditions to achieve high-quality syngas for engineering applications and lays a foundation for the design of industrial-scale fluidized bed gasifiers in the future.