Molecular distillation is mainly used in the process of high molecular weight, temperature resistance and high boiling point distillation. In the process of production, it is mainly composed of an externally heated vertical cylinder, which is located at its center during operation. And a wiper that rotates between the distiller and the condenser. The material is added from the top of the evaporator, and is continuously and evenly distributed on the heating surface through the liquid distributor on the rotor, and then the wiper scrapes the liquid into a very thin, turbulent liquid film and spirals. Push down. To a certain extent, the light molecules that will escape from the heating surface will be condensed into a liquid on the built-in condenser after a short route and hardly collided, and flow down the condenser tube through the evaporator. The discharge pipe at the bottom is discharged; the residual liquid, that is, the heavy molecules, is collected in a circular passage under the heating zone, and then flows out through the discharge pipe on the side.
Basic Principles of Molecular Distillation
According to the principle of thermodynamics shows that, under certain temperature and pressure of the molecular mean free path L=0.707K*T/(πd2P), in D for effective molecular diameter; P for molecular space in which the pressure; T for the molecular environment temperature; K is the Boltzmann constant (Fu and Chen, 1979).
By the molecular mean free path of the movement of the formula, we can see that different kinds of molecules, because of the difference of the effective diameter of the molecule, the mean free path is different, that is, different kinds of escaping from the molecular level not and other molecular collision of flight distance is not the same. Light molecular mean free path, small molecular mean free path, if in away from the liquid surface is smaller than the mean free path of molecular light rather than heavy molecular mean free path set a condensing surface, making molecular light falling on the condensing surface chant condensation, and heavy molecules reach the condensing surface and return to the original level, so as to realize the mixture separation.
Molecular Distillation Features
The typical molecular distillation unit consists of two kinds of centrifugal and rotary film blowing, and the rotating film – type molecular distillation device includes a variable – layer jacket, a condenser and a rotating scraper system.When the material is distilled, the material enters the rotating distributor continuously, and the centrifugal force is swung onto the heating wall, and the film is evenly distributed on the inner wall and downwards flowing.. This unique structure has obvious advantages:
1.The relative volatility of the mixture was explained by the relative volatility of the mixture, and the relative volatility of molecular distillation wasαm=p1/p2(M1/M2)0.5,And conventional distillation of volatile alpha =p1/p2,The p1/p2 is the ratio of the vapor pressure of light recombination in a certain circumstance, the molecular weight of M1 for the light component, and the molecular weight of M2 for the reorganization.
2.Low pressure distillation, condensation and evaporation was very close to the surface and materials by steam must not throttle to the condensing surface, operating pressure can reach 0.01 mbar.
3.Evaporating temperature is low, in the molecular distillation device, the separation of mixtures is due to the different kinds of escaping from the molecular level the mean free path of different nature to achieve, does not need to be boiling, so molecular distillation is operating at a very low boiling point temperature.
4.Heating time is short, the mixed liquid is like a thin film thickness (much less than 1 mm), almost equal to the evaporation surface and the heating surface area, makes the material along the heated surface leave and evaporate quickly, very short residence time, about tens of seconds.
5.Low energy consumption, blows the membrane design almost no products remain in the inner wall of the heating, can avoid the clogging phenomenon; fast steam condensed, compact structure, small vacuum pump can meet the requirements of vacuum, reduce energy consumption; rapid replacement of material, does not produce mixture; therefore, molecular distillation, especially for those with ordinary distillation product loss, poor quality material.
