Spray drying is a one-step continuous unit operation that employs liquid atomization to produce droplets that are dried to individual particles when moved in a hot gaseous drying medium. A spray dryer consists of a feed pump, atomizer, air heater, air dispenser, drying chamber and systems for exhaust air cleaning and powder recovery/separator. The three stages that occur in a spray dryer before drying is accomplished include:Atomization
Spray-air mixing and moisture evaporation.
Dry product separation from the exit air.
The nature of the final product obtained after drying in a spray dryer depends on;The design and operation of the spray dryer.
The physicochemical properties of the feed.
Spray dryer process layoutThe different process layouts of spray dryer include;
Open cycle layout.
Closed cycle layout.
Semi-closed (standard) layout.
Semi-closed (self-inertizing) layout.
Two stages layout.
Read Also: Rotary Dryer
Spray dryer is used in drying pharmaceuticals like penicillin, blood products, enzymes, vaccines etc.
Chemical industries e.g. phenol-formaldehyde resin, catalysts, PVC emulsion type, amino acids etc.
Ceramic industries e.g. aluminium oxide, carbides, iron oxides, kaoline etc.
Dye stuffs and pigments e.g. chrome yellow, food colour, titanium dioxide, paint pigments etc.
Fertilizer production e.g. nitrates, ammonium salts, phosphates etc.
Detergent and surface-active agents e.g. detergent enzymes, bleach powders, emulsifying agents etc.
Food industries e.g. milk, whey, egg, soya protein etc.
Fruits and vegetables e.g. banana, tomatoes, coconut milk etc.
Beverage e.g. coffee, tea etc.
Biochemical industries e.g. algea, fodder antibiotics, yeast extracts, enzymes etc.
Environmental pollution control e.g. flue gas desulfurization, black liquor from paper-making etc.