Hydrodynamics and gas-liquid mass transfer in liquid-solid and gas-liquid-solid fluidized beds

An operating regime map is constructed based on the minimum fluidization and terminal velocities of solid particles in cocurrent upward gas-liquid-solid systems with liquid as the continuous phase. Common operating ranges for three phase fluidized bed systems and slurry bubble column systems are thus clearly defined. A mechanistic model is also developed to describe the terminal velocity of spherical particles in gas-liquid mediums. The model parameter, the bubble-wake and particle interaction coefficient, is shown to be a function of particle properties only.; In the second topic of this work, a fluid-mechanic model is proposed to account for the bed voidage-liquid velocity or sedimentation velocity relationship for both liquid-solid fluidization and sedimentation under low Reynolds number conditions. The model is established based on the cell model concept with consideration of drag reduction due to particle alignment and nonuniformity of the local flow field due to distributor effects. It is shown that the model can explain the experimental discrepancy of the bed expansion and sedimentation data reported in the literature.; Regarding the final topic of this work, theoretical models for the rising velocity and gas-liquid mass transfer coefficient of a single bubble in liquids and liquid-solid mediums are presented. The model for the bubble rising velocity is based on a force balance on a single bubble taking into account the impaction force due to solid particles. The mass transfer model, on the other hand, considers two different mechanisms, i.e., transfer through both the bubble roof and the bubble base. Mass transfer through the bubble base can be further divided into two cases depending on the operating conditions. The predictions for the rising velocity and gas-liquid mass transfer coefficient of the single bubble in liquids as well as in liquid-solid fluidized beds are reasonably good.