CFD modeling of the flow dynamics and gasification in the combustor and gasifier of a dual fluidized bed pilot plant

Abstract

Numerical simulation of the dense gas-solid reactive flow in a pilot-scale dual fluidized bed for biomass gasification is conducted with large eddy simulation coupled with multiphase particle-in-cell approach. After validating the numerical results with the experimental data, the hydrodynamics of different components operating under different flow regimes are explored. The results show that dense bottom and dilute upper exist in the combustor, while the elutriation of fine particles appears in the freeboard of gasifier. Strong swirling flow together with the fishtailing phenomenon of gas phase appear in the cyclone. Gas density is large in the lower part of combustor, and decreases along the horizontal direction. Large thermal conductivity and specific heat capacity of gas phase exist in the gasifier due to the large mass fraction of low-temperature steam. Biomass inlet results in a large mass fraction of gaseous species in the right part of gasifier. The size distribution of heat carrier negligibly affects the gas thermal property in the lower part of both the combustor and gasifier.