Short Path Distillation 101

Short-path distillation is very suitable for the extraction and concentration of heat-sensitive and high-boiling substances. The equipment consist of a cylinder with a heating jacket, a rotor and a built-in condenser. The rotor mount is equipped with a scraping device and a splash-proof device.

The built-in short-path distillation condenser is located in the center of the evaporator and the rotor rotates between the cylinder and the condenser. The short path distillation consists of an externally heated vertical cylinder, a central central condenser, and a wiper that rotates between the distiller and the condenser.

At the beginning of the distillation, the material is fed from the top of the evaporator and evenly distributed over the heating surface through the material liquid distributor on the rotor. The scraper scrapes the material into a thin, turbulent liquid film that is propelled downwards. During this process, the light molecules that escape from the heated surface hardly collide through a short path, condense in the built-in condenser to form a liquid. Then light molecules flow down the condensing duct and pass through a discharge pipe located at the bottom of the evaporator. Heavy molecules are collected in a circular channel under the heating channel, then pass through the side of the tube and flow out.

short path distillation
short path distillation

Why use a Short Path Distillation System

For meeting the need of concentrating and extracting substances from mixtures in many fields, people invented several distillation devices for achieving their destinations. Among the distillation devices invented, short path distillation is one of the most popular in the marketing. Short-path distillation is a high-vacuum distillation process in which the feedstock is heated in a short-path evaporator. The material was scraped into a film and the light components were evaporated under high vacuum and condensed on a built-in condenser. The separated light and heavy components are continuously discharged under high vacuum. Molecular distillation or vacuum short-path distillation is an more effective method when conventional distillation does not achieve the desired effect. In the distillation operation, short path distillation can achieve higher yields and more stable production control.

Short path distillation process
Short path distillation process

Short path distillation process

1. Molecules diffuse from the liquid body to the evaporation surface.

Generally, the diffusion rate in the liquid phase is the main factor controlling the rate of molecular distillation, 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 economical and reasonable distillation temperature should be selected on the premise of the thermal stability of the material to be processed.

3. Molecules fly from the evaporation surface to the condensation surface.During the evaporation of vapor molecules from the evaporation surface toward the condensation surface, they may collide with each other or with air molecules remaining between the two sides.

4. Molecule condensation on the condensation surface. As long as there is enough temperature difference between the hot and cold sides (generally 70~100 °C), 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 form.

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