Atomizers in spray dryers: a review

Atomization is the most important step in spray drying that defines the properties of liquid droplets after spraying, resulting in various forms of the dry product - from fine powders to granules. It basically refers to the disintegration of the liquid into droplets in the presence of a drying gas circulating in the medium, increasing its surface area until the droplet becomes unstable and disintegrates. The choice of the atomizer's configuration depends on the nature, viscosity of the supply and desired characteristics of the dried product. Atomizers are classified according to the three basic forms of energy commonly employed for the atomization: pressure energy; centrifugal kinetic energy and gaseous energy. This results in the three most common atomizer models: pressure nozzles, rotary disc atomizers and pneumatic nozzles. The sonic and vibrating atomizers are less common. The difference between the atomization enables one to obtain different droplet sizes and, consequently, a different particle size distribution. The selection of the atomizer can be based on some important considerations, such as availability, flexibility, energy consumption or particle size distribution of the dry product.