Rotary dryers are mainly used in the chemical and miner […]
Rotary dryers are mainly used in the chemical and mineral industries. In the area of food, their most common applications are for dehydrating waste materials (citrus peels, vegetable trimmings) and animal feedstuffs (alfalfa).
Rotary dryers consist of a metal cylinder with internal flights or louvers. The cylinder is slightly inclined, and the material is fed in at the high end and discharged at the low end. Hot air is blown in a co-current or countercurrent direction.
As the cylinder rotates, the material climbs in the direction of rotation. When it reaches a position where its angle of repose has been exceeded, the material falls back to the bottom of the cylinder.
Most of the drying takes place while the material falls through the air blast. Using very hot air or combustion gases, rotary dryers can also function as roasters for nuts, sesame seeds and cocoa beans.