A second-order moment model of particles in dense gas-solid flow is proposed based on the kinetic theory of granular flow.The solid phase constitutive model is closed with the approximated third-order moment enclosure equation of particle velocity from the elementary transport theory.The boundary conditions of particles are proposed in considering the energy transfer and dissipations by collisions between the wall and particles.Flow behavior of particles is numerically simulated in a bubble fluidized bed,which indicates the distinct anisotropy behavior of the turbulent particles.Simulated particle velocities are in agreement with the measurements by Muller et al(2008) and Yuu et al(2001).Predicted second-order moment of velocity has the same trend as that of measurements.The calculated Reynolds stresses per unit bulk density agree with the measured data by Muller et al(2008) and with the fluctuating velocity of particles measured by Yuu et al(2001).
Behavior of catalytic cracking reactions of particle cluster in fluid catalytic cracking （FCC） riser reactors was numerically analyzed using a four-lump mathematical model. Effects of the cluster porosity, inlet gas velocity and temperature, and coke deposition on cracking reactions of the cluster were investigated. Distributions of temperature, gases, and gasoline from both catalyst particle cluster and an isolated catalyst particle are presented. The reaction rates from vacuum gas oil （VGO） to gasoline, gas and coke of individual particle in the cluster are higher than those of the isolated particle, but it reverses for the reaction rates from gasoline to gas and coke. Less gasoline is produced by particle clustering. Simulated results show that the produced mass fluxes of gas and gasoline increase with the operating temperature and molar concentration of VGO, and decrease due to the formation of coke.
