Unsteady-state motion of a polydisperse gas suspension in a cocurrent-flow reactor

This article presents a system of equations for determining the velocity field of polydisperse gas and of the individual fractions of the polydisperse material as a function of channel height and radius, with allowance for changes in the regime of flow around the particles. The proposed method is based on a procedure developed previously for the calculation of the unsteady-state motion of a two-phase system with a polydisperse solid phase and with a nonuniform velocity profile of the carrier medium. The initial distribution of disperse-phase concentrations across the section of the channel is assumed to be uniform and equal to the concentration of particles in the fluidized bed. It is determined that the velocity profile of the single-phase flow differs from the steady-state profile, the actual profile being determined in particular by the design of the gas distributor. The velocity profile of the carrier medium depends on the distribution of disperse-phase concentration with respect to cross section and height of the channel. In the process of motion, there is a redistribution of particles of different sizes relative to the cross section of the channel, and this determines a change in structure of the flow of the polydisperse gas suspension.