Modeling of gas-solid flow in a CFB riser based on computational particle fluid dynamics

Abstract

A three-dimensional model for gas-solid flow in a circulating fluidized bed (CFB) riser was developed based on computational particle fluid dynamics (CPFD). The model was used to simulate the gas-solid flow behavior inside a circulating fluidized bed riser operating at various superficial gas velocities and solids mass fluxes in two fluidization regimes, a dilute phase transport (DPT) regime and a fast fluidization (FF) regime. The simulation results were evaluated based on comparison with experimental data of solids velocity and holdup, obtained from non-invasive automated radioactive particle tracking and gamma-ray tomography techniques, respectively. The agreement of the predicted solids velocity and holdup with experimental data validated the CPFD model for the CFB riser. The model predicted the main features of the gas-solid flows in the two regimes; the uniform dilute phase in the DPT regime, and the coexistence of the dilute phase in the upper region and the dense phase in the lower region in the FF regime. The clustering and solids back mixing in the FF regime were stronger than those in the DPT regime.