The vacuum rotary dryer is a type of conduction dryer. It has a jacketed, cylindrical center tube that can be rotated. A set of hollow arms with paddle, discs, rakes, harrows, or blades are mounted on the center tube.
The solid raw material is loaded into the tube and the chamber will be pumped to vacuum. The heating medium is delivered into the jacket or hollow center tube and doesn't directly contact with the material. By rotating the center tube to stir the material, heat is continuously transferred to the material.
Stirring the material prevents the material from sticking to the heated surface to avoid compromising the heat transfer efficiency and exposes the surface of the material for continuous evaporation. The drying speed is faster than vacuum cabinet dryers.