1. The condition of the material to be dried (such as material shape, size, stacking method), the moisture content, density, viscosity and other properties of the material itself. Generally, if the material particles are fine and uniform, the pile is loose, and the thickness is thin, the internal moisture is easy to diffuse. If the initial temperature of the material is increased, the pre-treatment by vacuum filtration, and the moisture content of the material is reduced, the vacuum drying speed can be increased.
2. The higher the degree of vacuum, the more conducive to the vaporization of moisture at a lower temperature, but too high a vacuum is harmful to heat conduction and will affect the heating effect of the material.
In order to increase the drying speed of the material, the vacuum degree should be considered comprehensively according to the characteristics of the material. Generally, the vacuum degree should not be lower than 1×104Pa.
Factors Affecting the Drying Speed of Double Cone Rotary Vacuum Dryer
The drying process of the double-cone rotary vacuum dryer is tested. The vacuum degree, drying temperature, steam pressure and drying time are used as parameters. The curve of the test shows that the drying process of the double-cone rotary vacuum dryer can be divided into the first heating and the second There are five levels: one constant temperature, second heating, second constant temperature and cooling. in:
(1) The first heating is the preheating stage of heating the material to make it rise. In this stage, the amount of water vaporization in the material is very small;
(2) The first constant temperature is the constant-rate drying stage, during which a large amount of free water, surface water and capillary water of the material vaporize. Therefore, the temperature and vacuum are in a constant state, and the degree of vacuum is approximately equal to the saturated vapor pressure of water at the drying temperature;
(3) The second temperature increase is the process of heating the material to migrate the internal moisture to the surface of the material. Because the vaporized water is very small, the temperature of the material and the real degree also increase;
(4) The second constant temperature is the stage where the vaporized material is wrapped in water and part of the crystal water. The dry water mobility is determined by the vaporization rate, so the temperature and vacuum are in a stable state;
(5) At the beginning of the cooling stage, turn off the heating steam, and pass cooling water to the jacket of the cylinder to cool the cylinder to lower the temperature of the internal materials in order to discharge the dried products.
The properties of the different stages of the drying process of the double cone rotary vacuum dryer are also different, so different operating parameters should be set according to its different stages, so that the functions of the equipment can be used more effectively.
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