The process of molecular distillation

Distillation is a method of separating liquid compositions and extracting volatile metals or metal compounds from ore by using the characteristics of different volatility of each substance at a certain temperature.
Distillation is widely used in the chemical industry and metallurgical industry. The former is used to purify a series of pure products, such as rectified alcohol and fractionated petroleum. In the metallurgical industry, distillation is used to extract volatile metals, especially in the production of rare metals, to separate chlorides of certain metals (such as titanium and silicon), as one of the methods to purify rare metals, and to recover metallurgical processes Some volatile substances used in, such as ether and other organic solutions.
The process of molecular distillation:
Short path stills are also suitable for molecular distillation. The molecular flow goes directly from the heating surface to the condenser surface. The molecular distillation process can be divided into the following four steps:
1. Molecules diffuse from the main body of the liquid phase to the evaporation surface: Generally, the diffusion speed in the liquid phase is the main factor controlling the molecular distillation speed, so the thickness of the liquid layer should be reduced as much as possible and the flow of the liquid layer should be strengthened.
2. Free evaporation of molecules on the surface of the liquid layer: The evaporation rate increases with the increase of temperature, but the separation factor sometimes decreases with the increase of temperature. Therefore, the thermal stability of the processed material should be the premise , Choose an economical and reasonable distillation temperature.
3. Molecules fly from the evaporation surface to the condensation surface: When the vapor molecules fly from the evaporation surface to the condensation surface, they may collide with each other or the air molecules remaining between the two surfaces. Since evaporation molecules are much heavier than air molecules, and most of them have the same direction of motion, their collisions have little effect on the direction of flight and the speed of evaporation. The residual gas molecules are in chaotic thermal motion between the two sides, so the number of residual gas molecules is the main factor that affects the direction of flight and the evaporation speed.
4. Molecules condense on the condensing surface: As long as there is a sufficient temperature difference between the hot and cold sides, and the form of the condensing surface is reasonable and smooth, it is considered that the condensation step can be completed in an instant, so it is very important to choose a reasonable condenser