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Abstract

Dry coating of powders, in forming a layer, consists of fine particles of one component onto the surface of coarser particles of another component. In the process, fine particles are transferred among colliding coarse particles (carriers) until a steady-state distribution of fines on the carriers surface is attained. A stochastic model was developed for the kinetics of fines transfer based on a birth-death population balance including theoretically-derived one-step transition probabilities. First, the population balance equation is solved under steady-state conditions leading to the result that, at equilibrium, the number of fines per carrier follows a Bernoulli distribution. Based on the obtained equilibrium distribution, an approximate transient solution proposed agrees fairly well with the numerical solution of the birth-death equation. Model predictions were compared qualitatively with earlier experimental results.