Extraction Of Diglycerides By Short Path Distillation

Short path distillation apparatus is a special technique for liquid-liquid separation. The mean free path of vapor molecules is greater than the distance between the evaporation surface and the condensation surface under high vacuum conditions, so the difference in the evaporation rate of the components in the feed liquid can be used to separate the liquid mixture.

 

Short path distillation application:

1. Fine chemicals: such as extraction of diglycerides, purification of polymer intermediates, extraction of lanolin, etc.;

2. Pharmaceutical field: such as extracting natural vitamin AE to synthesize amino acids and glucose derivatives;

3. Food industry: such as refining fish oil, deacidification, refining higher alcohol, separation of mixed oil;

4. Other fields: petroleum industry, chemical industry, environmental protection.

There are many experiments using the short path distillation working principle, and the Short path distillation application is also very broad. This article mainly introduces the extraction of diglycerides by short path distillation.

 

Operation process:

Cdu 1000 distillation consists of a cylinder with jacket heating, laboratory water circulation pump, short path distillation vacuum pressure and other components. The inner condenser is located in the center of the evaporator, and the rotor with wiped film system rotates between the evaporator and the condenser.

The distillation process is: the material is added from the top of the evaporator, and is continuously and evenly distributed on the heating surface by the material-liquid distributor on the rotor, and the film scraper scrapes the product into an extremely thin, turbulent liquid film. During this process, the light molecules escaping from the heating surface are condensed into liquid on the condenser almost without collision, and flow down the condenser tube and discharged through the discharge tube at the bottom of the evaporator; the residual liquid is heavy Molecules are collected in a circular channel under the heating zone and flow out through a lateral discharge tube.

 

Short path distillation working principle:

Distillation is a method of separating mixed liquids in chemical unit operations. It is divided into atmospheric distillation and vacuum distillation. It mainly uses the different volatility of each component in the mixed liquid to achieve the purpose of separation. That is to say, the separated When the saturated vapor pressure of the light component liquid is greater than the pressure of the system, the material can be separated, so the lower the pressure in the system (the higher the vacuum degree), the easier it is to be separated. Molecular distillation is the introduction of saturated steam on the basis of ordinary distillation. The concept of pressure and molecular mean free path captures and accumulates the light component molecules separated from the liquid phase main body at the fastest speed, that is, the distance from the heating surface to the condensation surface is equal to or less than the escape free path of the light component molecules, but It must be larger than the molecular mean free path of the heavy components. In order to obtain a good capture effect, the condensation area should be larger than the evaporation area to achieve the purpose of molecular distillation. However, due to the influence of the equipment structure, the actual equipment cannot achieve the ideal molecular distillation conditions. , can only approach or simulate molecular distillation, so we call it a short-path still.

 

Factors affecting the separation capacity of short-path stills:

1. The diffusion rate of light components in the mixed liquid from the liquid phase body to the heating surface.

2. The saturated vapor pressure of the light components and the vacuum degree of the system.

3. The speed of light component molecules escaping to capture and condensation accumulation (that is, the distance from the heating surface to the condensation surface).

 

In view of the above short path distillation working principle, in order to improve the diffusion speed of light components from the liquid phase body to the evaporation surface, a scraping film type is used to scrape the material evenly on the heating surface into a thin film, so that the mixed liquid is formed into a thin film. The diffusion speed of light components from the liquid phase body to the evaporation surface reaches the maximum, and the diffusion time is very short. A built-in condenser is placed inside the equipment, so that the distance between the heating surface and the condensation surface is less than or equal to the molecular mean free path of the light components , the molecules escaping from the evaporating surface will fly and condense to the condensing surface without hindrance, so that the collection and accumulation of light components will reach the fastest limit speed. The instantaneous condensation of light components will have almost no resistance drop. It can ensure a high vacuum inside the equipment.