Drying equipment is the use of thermal energy to reduce the moisture content of the mechanical equipment, used to dry the object. The drying equipment heats the moisture in the material (generally refers to moisture or other volatile liquid components) to escape to obtain a solid content of the specified moisture content. The purpose of drying is for the purpose of material use or further processing. Such as wood in the production of wood mold, wood drying can prevent the deformation of the product, ceramic billet in the calcination before drying can prevent the finished product cracking. Another dry material is also easy to transport and storage, such as the harvest of food to a certain moisture content below, to prevent mildew. As the natural drying can not meet the needs of the development of production, a variety of mechanized drying equipment more and more widely applied.
 
Drying equipment drying process requires the consumption of a lot of heat, in order to save energy, some high moisture content of materials, containing solid substances in the suspension or solution generally first mechanical dehydration or heating evaporation, and then dry in the dryer to get dry solid.
 
Drying equipment in the drying process requires the completion of both heat and mass (moisture) transfer, to ensure that the wet surface of the material vapor partial pressure (concentration) is higher than the external space of the moisture partial pressure, to ensure that the heat source temperature is higher than the material temperature.
 
The heat is transferred from the high temperature heat source to the wet material in various ways, so that the surface of the material is wetted and vaporized and escaped into the external space, resulting in a difference in moisture content between the surface and the inside of the material. The internal wet to the surface diffusion and vaporization, so that the material wet content continues to decrease, and gradually complete the drying of the material as a whole.
 
The drying rate of the material depends on the rate of surface vaporization and the rate of diffusion of internal moisture. The drying rate and the surface temperature of the material are kept stable as long as the dry external conditions are constant, and this stage is called constant speed drying stage; when the wet content of the material is reduced to a certain The drying rate is determined mainly by the internal diffusion rate and decreases with the decrease of the wet content. This stage is called the deceleration drying stage, and the drying rate is lower than the surface evaporation rate.