Numerical simulation of particulate flows in CFB riser with drag corrections based on particle distribution characterization

Abstract

A heterogeneous drag force model was developed using a Eulerian-Lagrangian scheme for multiphase flow modeling. The model is based on an idea called particle distribution characterization (PDC), in which transient distribution of particle position is analyzed with an intuitive method to quantify the local heterogeneity of gas-solid flow for drag force correction. The model was implemented into the multiphase particle-in-cell (MP-PIC) method and applied to particulate flow simulation in circulating fluidized bed (CFB) risers. Whereas traditional homogeneous drag models tend to over-estimate gas-particle interactions and present homogeneous flow fields, the developed PDC model successfully predicts the heterogeneous gas-solid flow structures. The PDC predictions on time-averaged distributions and solid fluxes also correspond better with experimental measurements. Effects of the statistical parcel weight, an important parameter in computational parcel assumption in MP-PIC method (wherein parcels are employed to represent real particles), were investigated with both traditional and the PDC drag models. Results show defects of the assumption that agree with literature. It is proved that the PDC drag model is applicable to particulate flow modeling in CFB riser, and considerable for simulation of other industrial processes.