Drying is one of the methods to dehydrate the final product (concentrate) or intermediate product of the concentrator. Its function is to further reduce the moisture content of the product to meet the requirements of users or the next consumption operation. Drying principle of rotary kiln:

The drying of rotary kiln is a kind of operation to remove local moisture (moisture) in materials by using heat energy. The common methods include indirect or direct heat transfer drying method, which takes hot gas as medium, and transfers heat indirectly or directly to the wet material of rotary kiln, so that the moisture on the surface of the material vaporizes, and diffuses to the main body of the air flow through the gas film at the outer surface As a result, there is a moisture difference between the inside and outside of the material, and the moisture inside the material diffuses to the surface in a gaseous or liquid manner, thus drying the material.

The necessary condition for drying materials in rotary kiln is that the pressure of water vapor on the surface of materials (i.e. vaporization intensity) should be greater than the partial pressure of water vapor in drying medium. The greater the pressure difference between the two, the faster the drying speed is, and the drying medium should timely take away the vaporized water vapor. If the pressure difference is zero, the drying operation is stopped. Drying is a process in which heat transfer and vaporization intensity are separated.