Moisture exists in a loose chemically bound form or in a liquid solution in the solid phase, or is collected in the capillary structure of a solid. The vapor pressure of this liquid is lower than the vapor pressure of pure liquid, which is called bound moisture; The moisture content of the surface is called unbound water. Chlorinated polyvinyl chloride

Due to the existence of polar genes in the macromolecular structure of chlorinated polyethylene (CPE), and the structure of its powder is very loose, so that not only "unbound water" but also "bound water" will be present in its wet powder. It is difficult to dry it to a moisture content of not more than 0.3% (wet basis) (at this time, it is considered to be qualified for drying).

For this purpose, we choose hot air as the heat transfer medium for drying (fluidized). The granular material containing moisture is in contact with the hot airflow. Since the water vapor pressure on the surface is greater than the partial pressure of water vapor in the hot air, the water vapor is supplied by the material The particle surface diffuses into the hot air and is carried away by the hot air that is constantly flowing and renewed.

With the continuous evaporation of the moisture on the surface of the material, the humidity inside the material particles is greater than the surface humidity, forming a humidity gradient, the moisture inside the particles continues to diffuse to the surface until the equilibrium moisture of the material is reached.