An anisotropic Reynolds mass flux model for the simulation of chemical reaction in gas-particle CFB risers

Abstract

A model is proposed for numerical simulation of the multiphase flow coupled with chemical reaction in gas-particle circulating fluidized bed (CFB) risers. The proposed model is based on the newly developed computational mass transfer (CMT) methodology (Yu and Yuan, 2014) featuring the use of Reynolds mass flux equation to close the turbulent mass transfer equation, so that the anisotropic turbulent mass diffusion in CFB riser can be realized in the simulation. The proposed model consists of the turbulent mass transfer equation for the species with its Reynolds mass flux closure and the relevant formulations of computational fluid dynamics (CFD). With the proposed model, the species concentration and solid volume fraction as well as the velocity distributions along the CFB riser can be predicted. To validate the proposed model, simulation is carried out for the catalytic ozone decomposition in a gas-particle CFB riser. The simulated results are compared with the experimental data and satisfactory agreement is found in both axial/radial distributions of ozone concentration and solid volume fraction. Furthermore, the anisotropic turbulent mass diffusivities are also predicted and validated by the experimental data reported in literature.