Experimental investigation of droplet deposition on a single particle

Abstract

Spray coating or granulation is used to produce coarse granular solid particles by spraying solutions or suspensions in the form of fine droplets on fluidized particles followed by drying in a stream of fluidizing air. The quality and thickness of granulation or coating on the particle should be uniform. A part of the liquid-droplets from the spray-nozzle collide with the particle, of which, a part bounces back and the remaining part adheres on the surface of the particle giving layered-growth. In this work, the granulation process is carried out on a single spherical particle. Experiments are conducted to study the influence of process parameters, drying conditions, impact velocities and physical properties of sprayed solutions on the kinetics of granulation and on the morphology of the end product. A change in the drying condition changes the viscosity and surface tension of the sprayed solution. With increase in droplet velocity, the growth rate decreases. The results are useful to model the droplet deposition behaviour in fluidized bed granulation.