SIMULATION OF HEAT AND MASS TRANSFER PROCESSES UNDER GRANULES CAPSULATION IN FLUIDIZED BED

The paper studies capsulation of solid particles in a spout fluidized bed. A capsulation is used to protect the particles surface from the negative impact of environmental factors as well as to regulate of active component release rate. In this work, the capsulation is carried out by spraying of polymers dispersions on fluidized bed particles by means of pneumatic nozzles. Drops of polymer dispersion having faced with the particles are spred on their surface, forming a liquid film. Solvent removing by drying causes solidification of the film. Existing calculation methods of capsulation in the apparatuses with fluidized bed have a significant disadvantage. They do not consider the impact of capsule formation on the heat and mass transfer process of the solvent removing from the coating film. Combined modeling these processes allows more accurately predicting the required residence time of the capsulated material in the apparatus. The mathematical model, which allows predicting the change in coverage degree, the moisture content, the temperature of the particles in process time as well as required residence time in the apparatus, was developed. The comparison of the calculated and experimental data shows their good agreement. Taking into account the changes in evaporation surface due to the increasing of particles coverage degree in the capsulation process allows to describe the evolution of the particles parameters more adequately and to select of the process rational parameters.