Kinetic models for granule nucleation by the immersion mechanism

Two families of mathematical models for the kinetics of granule nucleation are presented. The first assumes that the driving force is surface tension at the three-phase interface and that this process is retarded by viscous drag. The second model assumes that transport within the nucleus occurs as a consequence of continual small deformations giving rise to a diffusive-type flow. For both of these models planar and spherical geometries are considered. In all cases explicit analytical expressions are deduced, of varying degrees of approximation, enabling their use in a multi-scale description of the granulation process. The models reveal the scaling rules for nucleation and suggest a series of experiments for their verification.

When droplets of liquid are added to dry powder during granulation the two will combine to form the first granules during a process referred to as nucleation. In this paper we present mechanistic models that describe the rate of this process when, as is normally the case, the liquid droplets are larger than the powder particles and so nucleation proceeds by the so-called immersion process.Figure optionsDownload as PowerPoint slide