How to choose a suitable drying machine?-- 1

Material drying generally means to remove water in material with high moisture content by heat energy, further to obtain solid product with low moisture content. Usually, there are two existence states of water in material: one is bound water, which is the water existing in material in the form of loose chemistry or liquid solution, or in the fine structure of the solid. Another is unbound water, free on material surface.

Drying material by heating is a process of dewatering while transferring heat and mass. The following two processes happen in succession, and control drying speed successively.

Process one: external conditions control process, also called speed-constant drying process. Heat is conveyed from surrounding environment to material surface as as to evaporate surface moisture, which is removed as vapor. The drying speed of this process depends on air temperature, material temperature and moisture content, air speed, material exposed surface area, pressure and other external conditions.

Process two: internal conditions control process, also called speed-reducing drying process. Internal moisture is transferred to material surface, then being evaporated. The migration of moisture in material is an interaction process of material property, temperature and moisture content.

Both two processes affect the drying speed. By the means of convection, conduction, or radiation, heat is conveyed from surrounding environment to material. In some cases, these heat transfer methods make function jointly. The main heat transfer method can make industrial dryer different in form and design. In most cases, heat is conveyed to material surface firstly, then into inner. Heat acts inside the material, where the water content is. At last the water removed as vapor, to produce dry product with low moisture content, meeting a certain requirement. Specially, air is the most commonly-used as well the most cost-saving drying medium in drying process. It is the heat carrier, also can carry volatilized water out of the dryer.

There are three goals for the drying technology is recognized by scholars: First, the drying operation to ensure product quality; Second, dry operation does not pollute the environment; Third, to save energy.