Modeling on High-Flux Circulating Fluidized Bed with Geldart Group B Particles by Kinetic Theory of Granular Flow

Abstract

Modeling of the hydrodynamic behaviors of high-flux circulating fluidized beds (HFCFBs) with Geldart group B particles has been performed using a Eulerian multiphase model with the kinetic theory of granular flow (KTGF). The essential models involved are the dispersed k-e turbulence model, the Gidaspow shear viscosity model, and the Syamlal—O'Brien drag model, and the boundary condition is the Johnson and Jackson wall boundary condition. The sensitivities of key model parameters (i.e., particle-particle restitution coefficient (e), particle—wall restitution coefficient (e w ), and specularity coefficient (ϕ)) on the predicted gas velocity, solids velocity, and solids volume fraction were tested. It was found that e has remarkable dependence on the particle diameter. Large-sized particles experience a more sensitive effect of e on predictions. The particle—wall restitution coefficient e w has somewhat of an effect on the simulated values of gas velocity, solids velocity, and solids volume fraction; however, no critical changes in the trends of their radial distributions have been found. The specularity coefficient ϕ has a slight effect on the gas velocity and solids velocity distributions but a pronounced effect on the solids volume fraction distribution. An increase in specularity coefficient results in a reduction in the solids volume fraction near the wall. Based on the comparisons of simulated results with experiments, a group of suitable model parameters for modeling the flow of Geldart group B particles in HFCFB risers by a Eulerian multiphase model with KTGF was determined and verified. Besides, some interesting simulated results that are difficult to measure experimentally were presented under the suggested model parameters.