A model for the interparticle surface separation in concentrated mono- and polydisperse suspensions.

A.C. Hoffmann, Department of Chemical Engineering, Stratingh Institute, University of Groningen, Nijenborgh 4, 9747 AG Groningen, The Netherlands.
J. Kevelam, Department of Organic and Molecular Inorganic Chemistry, Stratingh Institute, University of Groningen, Nijenborgh 4, 9747 AG Groningen, The Netherlands

Abstract
In this article the interparticle surface separation in mono- and polydisperse concentrated suspensions of spherical particles is considered. For monosized particles it is shown that the 'expansion' argument of Frankel and Acrivos (1967) can be extended from cubic to arbitrary packing geometries. This argument is then further extended to polydisperse suspensions resulting in an equation of the same form, but incorporating the surface mean particle diameter, for the interparticle surface separation in terms of the packing fraction of the equivalent packed bed (a packed bed with the same packing geometry as the suspension) and that of the suspension. Toward the end of the paper another approach to interparticle surface separation in suspensions (the 'volume of free liquid' argument) is explored, and is shown to confirm the use of the surface mean particle diameter for polydisperse suspensions. A relation potentially useful also for suspensions of non-spherical particles is given.