Numerical simulation of flow behavior of topped gas-particles jet in a bubbling fluidized bed

Abstract

Flow behavior of topped gas-particles jet is simulated by means of gas–solids multi-fluid model in a bubbling fluidized bed. The finer particles from the topped gas-particles jet are ejected into a fluidizing coarse particles bed. The interactions of finer particles and coarse particles are simulated by means of the kinetic theory of binary particles with unequal component granular temperatures. The two-equation k-ε model is used to model gas turbulence of the topped gas-particles jet. The effects of the top gas-particles jet velocity and fluidizing gas velocity on the distributions of volume fraction, velocity and component granular temperatures are analyzed along radial and axial directions of the bed. Simulated volume fractions and axial velocities of finer particles show that the fluidized bed is divided into three regions as (a) the diffusion region near the bottom, (b) the concentrating region and (c) the transport region along bed height. The circulation of particles is formed with the down-flow at the center and the up-flow between the center and the walls. Numerical simulations show that the coarse particles volume fractions decrease and the finer particles volume fractions increase with the increase of topped gas-particles jet velocity and fluidizing gas velocity in the bottom of the bed. The component granular temperatures are larger in the concentrating region than that in the diffusion and transport regions. The penetration length of the topped gas-particles jet with the change of topped gas-particles jet velocity and fluidizing gas velocity is discussed.