The drying process is applied to remove the moisture present on the material. In general, moist solids, are dried with the hot air resulting from the burning of fossil fuel types. The amount of energy required in the drying step, is equal to the energy to evaporate the water on the solid material. High-capacity rotary dryer systems can be designed.

Drying plants are used to reduce the moisture of nuts and fine coal sent for use in coal boiler-operated factories. Plants operating with fully automated system provide an average moisture reduction of 15%.