Effect of particle shape on liquid-fluidized beds of binary (and ternary) solids mixtures: segregation vs. mixing

Experiments were carried out in water-fluidized binary (and ternary) mixtures of teflon spheres, discs and rods. All particles had the same volume, while the discs and rods had nearly the same sphericity. It is shown that segregation can occur by shape, with similar segregated and mixed zones as when binary mixtures of different size or density are fluidized. The model of Pruden and Epstein (1964; Stratification by size in particulate fluidisation and in hindered settling. Chemical Engineering Science 19, 696), in which the degree of segregation depends on the bulk density difference(s) of the corresponding monocomponent beds at the same liquid velocity, is vindicated qualitatively for each system, but sphericity is not sufficient as a single shape factor to yield a single quantitative correlation of the transitions between segregation patterns for the different systems. Segregation by shape of non-isometric particles appears to require higher reduced density differences than sizing of spheres, probably because of the greater bed instabilities generated by the non-isometric particles. Overall bed voidage is predicted well by the serial model of Epstein et al. (1981; Liquid fluidisation of binary particle mixture– I.Overall bed expansion. Chemical Engineering Science 36, 1803).