The vacuum rake dryer operates on the principle of heat transfer by conduction and vacuum drying under low temperature conditions. The machine consists of a jacketed vessel with a rotating central shaft fitted with specially designed rake blades. The blades continuously move the material within the vessel, ensuring uniform mixing and heating of the product.
The dryer works by creating a vacuum in the vessel, which lowers the boiling point of water and other solvents present in the material. Heat is then applied to the jacket, which conducts through the walls of the vessel and into the material. The moisture in the material evaporates due to the vacuum, and the vapor is removed by a condenser and vacuum pump.
As the material dries, it forms a thin film on the surface of the vessel. The rake blades scrape and break up the film, exposing more of the material to the heating surface and facilitating further drying. The process continues until the desired level of dryness is achieved.
The vacuum rake dryer is an efficient and effective way to dry heat-sensitive, viscous, and pasty materials that cannot be dried easily using traditional methods. It is widely used in the pharmaceutical, chemical, food, and other industries.