The drying in a rotary vacuum dryer is a batch operation under vacuum. It is possible to dry heat sensitive materials at well below boiling points of water and solvents. Drying time depends on material being dried, amount of solvent or water to be removed, desired final moisture content, permissible jacket temperature etc. The dryer is available in sizes ranging from 100 liters to 20,000 liters gross volume. The volume of wet material loaded into the dryer is usually restricted to 40-45% of gross volume.