Spray drying technology can realize the conversion of material from fluid state to dry granular form by spraying feed into the hot drying medium. This is a continuous particle treatment drying operation. The material can be a solution, suspension, dispersion or emulsion. Dry products can be in the form of powders, granules or agglomerates depending on the physical and chemical properties of the feed, spray dryer design and final powder characteristics.
There are five main steps involved in the spray drying process:
(1) Concentration: The raw material is usually concentrated before being introduced into the spray dryer.
(2) Atomization: The optimal conditions of evaporation to dry product caused by the atomization stage have the desired characteristics.
(3) Droplet contact: In the chamber, the atomized liquid is brought into contact with the hot gas, causing more than 95% of the moisture contained in the droplets to evaporate within seconds.
(4) Droplet drying: Water evaporation occurs in two stages: In the first stage, there is enough moisture in the water droplets to replace the evaporated liquid on the surface and evaporation occurs. At the beginning of the second stage, there is no longer enough humidity to maintain saturated conditions on the droplet surface, causing the surface to form on a dry shell. Evaporation then depends on the diffusion of moisture through the shell, which increases in thickness. ^Later separation stage. Wet scrubbers are often used to clean and cool the air so it can release the atmosphere.
(5) Separation: Cyclone, bag filter and electrostatic precipitator can be used in short communication spray drying process which has the advantage that it can be designed into almost any required capacity.
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