Relationship between flow structure and mass transfer in fast fluidized bed

Abstract

This paper analyzes the relationship between flow structure and mass transfer in fast fluidized beds for Geldart A and B particles. It does this by employing the eight heterogeneous local bed structural parameters ( U fd , U fc , U pd , U pc , d c , f, ɛ d and ɛ c ) solved by Wang et al. [W. Wang, J. Li, Simulation of gas–solid two-phase flow by a multi-scale CFD approach of the EMMS model to the sub-grid level, Chemical Engineering Science, 62 (2007) 208–231] using the energy-minimization multi-scale (EMMS) model, in conjunction with a proposed theory on multi-scale mass transfer (MSMT) in a fast fluidized bed using the user defined scalars function in the commercial software Fluent 6.2.16 to solve the related mass conversion equations. The influence of the size and behavior of clusters on mass transfer in fast fluidized beds is discussed. The reaction in a fast fluidized bed is considered to comprise inside diffusion and outside diffusion of the particles as well as intrinsic reaction kinetics. Based on this theory and method, the decomposition of ozone at ambient temperature is calculated in a fast fluidized bed with average and local bed structure parameters and the axial and radial dimensionless concentrations of ozone and averaged mass transfer coefficients are compared to experimental data from the literature. The agreement between calculation and experimental data is good.