These three batch type of Vacuum Dryers work on exactly the same principle and belong to the same family.They are, however, suitable for only free flowing materials, which are readily converted from slurry or wet cake to free flowing powder without exhibiting sticking or lump forming properties during the course of drying operations.The rotary action permits gentle folding and mixing of the material thereby enabling it to come in contact with the indirectly heated surfaces resulting in vapourisation of the moisture in the wet particles.