(Massey University, 2003) Rynhart, P.R.; Jones, J.R.; McKibbin, R.

Show more

Modelling of wet granulation requires the rate of agglomerate coalescence to be estimated.
Coalescence is dependent on the frequency of collisions that occur, and the fraction of collisions
which result in coalescence. The collision rate is a function of granulator kinetics and powder
properties, while the coalescence success rate is dependent on factors including the Stokes
number and particle geometry. This work investigates an aspect of the geometry by examining
the distribution of liquid on the surface of agglomerates in the capillary state. Agglomerates
are created by adding particles, one at a time, about a central tetrahedral arrangement of
four primary particles. For a given agglomerate, the wetted fraction of surface area, defined
as the wetness, is evaluated using an approximate fluid surface. Packing density and binder
saturation parameters are incorporated into the model. Given a number of primary particles
and the volume of binder in a particle, the agglomerate wetness is able to be estimated using
computational geometry.

This paper presents the solution to the liquid bridge profile formed between three equally
sized spherical primary particles. The particles are equally separated, with sphere centres
located on the vertices of an equilateral triangle. Equations for the problem are derived and
solved numerically for given constant mean curvature H0, contact angle , and inter-particle
separation distance S. The binding force between particles is calculated and plotted as a
function of liquid bridge volume for a particular example. Agreement with experiment is
provided.