(67c) Distribution Nucleation: Quantifying the Liquid Distribution On a Particles Surface Using the Dimensionless Particle Coating Number

Nucleation is a very important first step in wet granulation, as it affects the appearance and function of the final granules.  Over the last decade, researchers have focused on immersion nucleation, where the drops are much larger than the particles.  Far less is known about distribution nucleation, where the drops are much smaller than the particles, as tends to be the case in fluidized beds.

In this paper a newly derived dimensionless parameter, the particle coating number, has been derived with the objective of understanding liquid distribution of small drops over a relatively large particle.  When aided with a simple probabilistic analysis the surface coverage of an individual particle as a function the particle coating number.

Experiments were conducted to validate the parameter by adding drops of PEG1000 (10 μL or 20 μL) randomly over the surface of five different sized particles (20-50 mm diameter). The surface coverage of the particles was measured using image analysis.  The results demonstrated the capability of the particle coating number to predict surface coverage and allow the surface coverage of a particle to be predicted a priori. The effects of drop size, particle size, and particle surface area were investigated and agree qualitatively with independent modeling results.

The results are expected to be valuable in a variety of particle wetting and coating applications where small drops are distributed over larger particles.  The new particle coating number parameter avoids the need for sophisticated modeling and fitted coefficients and will be able to be used in DEM modeling of fluid bed granulation, particularly for predicting the probability of particle collision at a wetted section. It is also expected to form part of a new set of design rules for fluid bed granulation.