Axial holdup distributions of gas and solid particles in three-phase fluidized bed for gas-liquid(slurry)-solid systems.

Abstract

The behavior of gas and solid particles was studied in a so-called three-phase fluidized bed of 12-cm diameter. The mean gas holdups in the dense and lean regions and the mean solid holdup in the dense region were correlated by experimental equations. The axial distribution of solid holdup in the lean region was analyzed by the sedimentation diffusion model. The mean settling velocity, vp, and the longitudinal dispersion coefficient of solid particles, Ep, were correlated with previous data for bubble columns with suspended solid particles, respectively, as follows.For Ug/v1<30: vp=vt{1+1.5(Ug/vt}0.3ψ2.5lFor (dpvt/vl)=0.3-2.5: UgDT/Ep={13Fr/(1+8Fr0.85)}{1+0.009(dpvt/vl)Fr-0.8}For (dpvt/vl)=2.5-640: UgDT/Ep={13Fr/(1+8Fr0.85)}(1+0.023Fr-0.8)where DT = column diameter; dp = particle diameter; Fr=Ug/√dGT; g = acceleration of gravity; Ug = superficial gas velocity; vt = terminal velocity of solid particle; vl = kinematic viscosity of liquid or slurry; ψl = (volume fraction of liquid or slurry)/(l-volume fraction of gas).