Simulation and Optimization of Biomass Gasification Process in Fluidized Bed Coupled with Entrained-Flow Bed

Biomass gasification serves as a key carbon-neutral technology. To effectively address the challenge of tar treatment during biomass gasification, the National Institute of Clean and low-carbon Energy developed a fluidized bed coupled with an entrained-flow bed. A steady-state Aspen Plus V12 model was designed to assess the compatibility between the two beds and optimize operating parameters. The model divides the process into three main zones: fluidized bed gasification, entrained-flow bed gasification, and bottom slag treatment, employing a reaction-restricted equilibrium assumption. Simulation results indicate that an increase in pressure leads to a reduction in the concentration of syngas components (CO and H2), an insignificant rise in gas low heating value (LHV), and a notable decline in cold gas efficiency (η). A higher equivalence ratio (ER) results in decreased syngas components, along with a significant reduction in both LHV and η. The introduction of carbon dioxide reduces syngas components and lowers LHV. Similarly, the addition of steam reduces the CO content of the syngas and decreases its LHV. When the fluidized bed temperature exceeds 900 °C, changes in LHV and gas yield become negligible, while variations remain minimal when the entrained-flow bed temperature exceeds 1200 °C.