Comparing different single milk droplet drying process with spray drying process

Abstract

Spray drying is currently the main method of industrial milk production because of its high drying speed and high process control accuracy. By controlling the parameters of spray drying process to control the characteristics of the milk powder is well researched. However, the drying mechanism in spray dryer is still not very clear. Methods of measuring single droplet drying kinetics are widely used instead of directly modelling spray drying kinetics. In this study, single droplet drying methods including sessile drying, filament hanging drying, and levitator drying in room temperature are used to compare and simulate the drying kinetics in spray dryer. Experiments show that the droplets in levitator are more spherical, but the final dry particles tend to be more donut-like due to the compression of the upper and bottom sides by the ultrasonic waves. In the filament hanging drying, the droplets are only suspended on the filament by friction. Due to gravity, the shape of the droplets and dried particles is non-sphere droplet shape. In sessile drying, the droplet is half-sphere shape, and the contact area is not changing because of capillary force. By comparison, the final particle morphologies of these are significantly different from those in the spray dryer, therefore, explore the characteristics of spray-dried droplets by monitoring the drying characteristics of single droplets may not suitable on some situation especially on multi-component materials.