THEORETICAL ANALYSIS OF TRANSPORT PHENOMENA OF CERAMIC PARTICLES IN A SPRAY DRYER

초록

Spray drying is an unit process in which liquid fed from other process is converted into dry particles. The liquid feed is atomized in the spray chamber and the resulting droplets are mixed with hot gas. These droplets change into spherically shaped solid particles with evaporiztion of volatile materials. Because of the short drying time resulting from high surface area of the sprayed droplets, spray drying process is very suitable for drying heat-sensitive materials. So spray dryers are widely used in food, chemical and pharmaceutical industries. In the present study numerical simulation of mass, momentum and energy exchange between ceramic particles and hot air were implemented by using commercialized code, Fluent6.0. When airflow pattern in drying chamber is predicted, since hot air entering into the spray chamber has a swirlling effect caused by dispersers' vane angle, a mathematical model containing swirlling or rotation effect was needed. So we chose the RNG k-ε model rather than the standard k-ε model. Particle trajectories in air flow were calculated by using Lagrangian model under assumption of particle being spherical.