Investigation of Liquid Distribution in Fluidised Bed Granulation Using a Single Particle Surface Coverage Fraction

Fluidised bed granulation is used in many process industries. In these systems, liquid binder is generally added to the fluidised bed through the use of atomising sprays. Typical spray nozzles produce droplets much smaller than the particle size of the powder, however, most research in wetting and nucleation has been for cases where the droplets are much larger than the particles, and there is very little research for systems where the droplets are smaller than the particles. This paper presents a series of discrete element method (DEM) simulations investigating wetting, liquid distribution and mixing in a fluidised bed granulator. A novel method for incorporating the liquid spray is implemented in the model, and a new parameter for the single particle surface coverage, Фp, is used to predict the fractional liquid coverage of particles. The objective of these simulations is to investigate mixing and liquid distribution in a fluidised bed granulator, with the future aim to develop an advanced model for agglomeration based on liquid coverage. The effect of superficial air velocity, liquid spray rate and spray size are investigated. The addition of these innovations to fluidised bed granulation modelling represent a significant improvement over existing models for fluidised bed granulation which assume uniform liquid coverage or use an increase in surface energy to simulate the effect of particle wetting.