Spraydryer

A spraydryer is an industrial unit that converts liquid feed into a dry powder by atomizing the liquid into a hot drying medium, typically air, which rapidly evaporates the solvent. A typical spray dryer consists of a feed system, an atomizer to create droplets, a drying chamber through which hot gas passes, an air heater, and a particle-collection system such as a cyclone and filter.

In operation, the liquid feed is pumped to the atomizer, which forms fine droplets. The droplets encounter a high velocity jet or spray of hot air, causing rapid evaporation of the solvent. Dry particles are carried out of the chamber with the exhaust and are separated from the drying gas in a cyclone or bag filter, then collected.

Common configurations include co-current and counter-current airflow; atomizers include rotary disk, single-fluid or two-fluid nozzles; some systems are closed-loop for solvent containment.

Applications: widely used to produce powders from liquids: dairy products (milk, whey), coffee, egg and egg products, soups, fruit juices, flavorings and colors, enzymes, probiotics, pharmaceutical excipients, ceramics and polymers.

Advantages include fast drying, ability to produce uniform, fine powders, and good hygienic design. Limitations include high energy use, high capital cost, sensitivity to heat and shear, and potential for the powder to be dusty or to cake; not all liquids are suitable.

Historically, spray drying was developed in the early 20th century and became widespread in food and chemical industries by the mid-20th century.