Fluidization of mixtures of two solids: a unified model of the transition to the fluidized state

Fluidization of binary beds of dissimilar solids has place along a fluidization velocity interval bounded by the“initial” and the “final fluidization velocity” of the mixture, with segregation phenomena that continuoslychange the internal distribution of their components.Varying with the relative importance of size and density differences between components, the fluidizationprocess may follow more than one mechanism, depending on whether the process of fluidization startsfrom bed top or bottom. The paper shows how, irrespective of the fluidization pattern exhibited by thetwo-solid system, the limiting velocities of its fluidization interval are calculated with good accuracy by thesame relationships, derived from the analysis of the fluidization force equilibrium.The model proposed provides a unique theoretical frame for the analysis of the fluidization behaviour ofany two-solid system and encompasses as a particular case the behaviour of simpler mixtures, whosecomponents differ only in density or size.