The principle of vacuum dryer operation


The vacuum dryer is a conduction heat transfer dryer. The material is not in direct contact with the heating medium. It is suitable for drying a small amount of muddy and paste-like materials that are not resistant to high temperature and easy to oxidize. The moisture content is 15%~90%. The blades of the capacity rake agitator in the dryer are made of cast iron or steel, installed on a square shaft, 50% of the blades are directed to the left, and the other 50% are directed to the right.

The rotational speed of the shaft is 7~8r/min, which is driven by an electric motor with a gearbox. And the automatic steering device is adopted to make the rotation direction of the shaft change the rotation direction of the agitator every 5~8 minutes. The vacuum dryer has the advantages of simple layout, convenient operation, long service life, stable and reliable performance, small steam consumption, strong practical performance of the vacuum dryer, and good product quality. Drying of pasty materials.

The material to be dried is fed from the top of the shell. Under the agitation of the rake teeth that are constantly rotating forward and backward, the material axis moves back and forth, and the surface in contact with the inner wall of the shell is constantly renewed. It is indirectly heated by steam and uniformly stirred by the rake teeth. The destruction of the destroying rod makes the moisture on the surface of the material more beneficial to be discharged. The vaporized moisture passes through the dry dust collector, the wet dust collector, and the condenser, and is emptied into the vacuum dryer from the outlet of the vacuum pump. When operating, first start the agitator, add the dried material, and close the feeding port. And through steam heating, the pressure of heating steam is usually 0.2~0.4Mpa (gauge pressure).

Use a vacuum pump to extract water vapor and non-condensable gas. Usually, when the material is dry, the vacuum degree is about 700mmHg. The moisture evaporation strength of this kind of dryer varies with the characteristics of the material, humidity, heating steam pressure and vacuum degree. For example, when the vacuum degree is 700mmHg and the heating steam pressure is 0.2Mpa (gauge pressure), the potato starch is dried from the initial water content of 40% to 20%, and the water evaporation strength of the dryer is 5~7kg/m2?h.

The operation of the vacuum dryer is less labor-intensive than the box-type dryer, and it can absorb the effective moisture contained in the material, with good operating conditions and convenient management. Its shortcomings are low production capacity, complicated equipment layout, and easily damaged agitator blades. This kind of dryer is widely used in the dye and pharmaceutical industries.

For example, drying vat dyes, silicone sealant, anthraquinone sulfonic acid, vat olive green R, salicylic acid body, Capron polymer, diaminoanthraquinone and other materials.


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