One-dimensional modeling of a dual fluidized bed for biomass steam gasification

A one-dimensional model for biomass steam gasification in dual fluidized bed gasifiers is set up with the assistance of Aspen Plus. Both the hydrodynamic and kinetic processes are coupled and simulated. The model predictions agree well with the experimental data reported in the literature. Sensitivity analyses are also performed to investigate the effects of different operating parameters, including the inlet biomass flow rate (Fbio), the steam-to-biomass ratio (Rsb), the sand circulation flux (Scf) and the flow rate of the additional methane burnt in the riser (Fm). Under the benchmark conditions, the mole fractions of H2 and CO2 increase along the height of the bubbling fluidized bed (BFB), while those of CO and CH4 decrease. The gasification temperature decreases slightly against the height in the bed zone, but increases in the freeboard zone. The superficial velocity slightly increases and the bubbles grow against the height in the BFB. Increasing both Fbio and Rsb restricts the gasification process, increasing Scf only slightly affects the gasification results, and increasing Fm promotes the gasification process.