Investigation on gas–solid flow behavior in a multistage fluidized bed by using numerical simulation

Abstract

Poor gas–solid flow structure is one of the primary factors restricting desulfurization efficiency in dry process. A multistage fluidized bed was developed to improve dynamic characterizations. A 3D numerical simulation based on two-fluid model was applied to systematically study the gas–solid flow behavior in the multistage fluidized bed. The model was first verified by comparison with experimental data, and good agreement was achieved between the experiment and simulation. Results showed that the axial flow uniformity decreased in the multistage fluidized bed. Solid holdup and turbulent intensity increased significantly in enlarged sections, together with reducing solid velocity. The radial profiles of gas–solid two phases became uniform along the height of enlarged section. Moreover, superficial gas velocity and solid mass flux exerted different effects on radial distributions. Hydrodynamic profiles maintained similar tendencies between two enlarged sections. Though gas–solid flow exhibited weak behavior in the upper enlarged section, the total flow development was fast in comparison with the lower enlarged section. The comparison results of hydrodynamic characteristics between the enlarged and traditional beds showed that a gas–solid flow structure contributed to the improvement of reaction performance for desulfurization was obtained in the multistage fluidized bed.