Modeling and experimental analysis of polydispersed particles coating in spouted bed

Polymer film coating has become widely used in pharmaceutical, chemical and food industries today. Such wide acceptance arises from the possibility to routinely use aqueous coating formulations. The technology applied to coat particles depends mainly on the particles characteristics and the desired production, which will also determine the choice for a batch or continuous process. The spouted bed has been applied in coating processes of solid particles to obtain products with modified surface properties. In this work a mathematical model was applied, using the population balance equations, to the batch coating process of polydispersed particles. The generated system of differential equations was solved by the numerical method of Runge–Kutta–Fehlberg using the software Maple 8®. The results were compared with experimental data obtained in a laboratory scale cone-cylindrical spouted bed. Glass beads, with known size distribution, were placed in the bed. Hot air, at a flow rate 20% higher than the minimum spout flow rate, promoted the particles movement. A system composed of magnetic stirrer, peristaltic pump, air compressor and double-fluid atomizer sprayed an aqueous polymeric suspension on the particles. An experimental design, totalizing 11 experiments, was defined to analyze the influences of spouting air temperature, coating suspension flow rate and atomization air pressure on particles growth rate and coating process efficiency. The statistical analysis provided an empirical correlation for the process efficiency and the data obtained were used to compare the experimental results with the simulated ones.