Modelling side-effect spray drying in top-spray fluidised bed coating processes

A model was developed for heat and mass transfer processes in top-spray fluidised bed coating processes. The proposed model combines the use of population balances, describing key particle characteristics during coating, with a 3-phase (namely gas, solids and sprayed liquid) heat and mass transfer model. The model is capable of calculating the dynamic coating mass distributions, the dynamic one-dimensional temperature and humidity distributions for both particles and gas (air) along with the extent to which premature droplet evaporation (spray drying loss) takes place. The model has been experimentally validated using a pilot scale Glatt GPCG-1 fluidised bed unit in which different size fractions of salt (NaCl) crystals were coated with Na-caseinate under varying process conditions.