Vacuum Drying Rotary Vane Vacuum Pumps & Compressors

Drying is the process of physically manipulating liquid in an absorbent solid to cause it to evaporate and leave the solid that it occupies. Drying can be useful in chemical laboratories, as some anhydrous compounds react in different ways than their hydrous counterparts. This can be used to the advantage of the industry depending on the desired result. Drying is useful in the leather, sugar, paper, tobacco, pharmaceutical, and food industries as well.

Vacuum drying is based on the physical principle that lowering the pressure of the ambient air around a liquid will lower its boiling point. The boiling point of a liquid is dependent on the vapor pressure of the liquid and the pressure of the air surrounding it. When liquid is heated, its temperature increases as the molecules of the liquid begin to gain energy, bumping into each other. The surrounding air exerts a pressure on the liquid that prevents it from evaporating.

At the temperature where the vapor pressure of the liquid is equal to the pressure of the surrounding air, the liquid begins to evaporate. This is because the liquid has gained enough energy to where the molecules are able to overcome their bonds to each other and release their energy by means of converting the excess heat energy into kinetic energy. This can be seen when the liquid begins to boil, and the temperature stagnates. When that pressure is decreased, the energy that is required to evaporate the liquid decreases.

Operation costs to dry batch products in atmospheric pressure can become staggeringly high. The manipulation of pressure to decrease the required heat energy for evaporation cuts operational costs significantly. Another benefit to vacuum drying is that the product can dry in the absence of oxygen, which can cause oxidation and decay to occur in numerous compounds. In addition to this, certain organic compounds are prone to degradation when exposed to excess heat. Water has a relatively high latent heat of vaporization, so the threat of degradation of heat-sensitive hydrated material. By applying negative pressure, the energy applied for evaporation cannot reach such levels of heat.