The principle of spray drying method:
Spray drying is a drying method that uses an atomizer to disperse the raw material liquid into droplets, and uses hot gas (air, nitrogen or superheated steam) to dry the droplets to obtain a drying method. The raw material liquid can be a solution, an emulsion, a suspension, or a melt or a paste. The dry product can be made into powder, granule, hollow sphere or pellet as required.
In addition, the atomization of liquid is to disperse the material liquid into mist droplets. The atomizer is a key component of spray drying. At present, there are three commonly used ones.
（1） Airflow atomizer
Compressed air or steam is sprayed from the nozzle at a high speed (≧300m/s), and the material liquid is split into droplets by the friction force generated by the speed difference between the gas and liquid phases.
（2） Pressure atomizer
Use a high-pressure pump to make the liquid obtain high pressure. When the high-pressure liquid passes through the nozzle, the pressure energy is converted into kinetic energy and dispersed into mist droplets when sprayed at high speed.
（3） Rotary atomizer
The feed liquid is thrown from the edge of the disc by the centrifugal force in the high-speed turntable (peripheral speed 90-160m/s) and atomized.
Application of spray drying method:
Spray drying equipment is widely used in the food industry. Many foods, such as milk powder, cream powder, whey powder, egg powder, fruit juice powder, instant coffee, instant tea, chrysanthemum crystal, etc., can be produced by spray drying.