On the capacity of continuous powder classification in a gas-fluidized bed with horizontal sieve-like baffles

Abstract

Using horizontal sieve-like baffles in fluidized beds increases the tendency of particle mixtures to segregate. This may be utilized to devise a new process for dry classification of particles according to size or density. To predict the capacity of a continuous classification process based on this principle, the segregation rate must be known in addition to the final concentration profile. This paper describes an experimental investigation of this, using a fluidized bed with horizontal sieve-like baffles and an equal density mixture. The experiments confirmed that the baffles increase the particle segregation in the bed, and hence, the purity of the flotsam in the top layer. The capacity of a continuous fluidized bed particle classifier and the effect of particle size on the obtainable segregation are discussed. A first modelling attempt to describe the rate of growth of the lower segregation layer is presented. The mechanistic model for axial particle transport proposed in the literature is only partially successful in explaining the experimental results.