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Short path distiller

First. Overview

   Many such as petroleum heavy residues, chemicals, pharmaceuticals and natural foods, health products, fatty acids, etc., are often heat sensitive, viscous and / or have high boiling point materials. The separation of these materials from their other components while maintaining the quality of the product can only be rectified at low boiling temperatures or even below boiling temperatures, and can only be thermally decomposed in a short period of time. Or the polymerization is reduced to a small extent to eliminate damage to the product.

   When the operating vacuum is about 500 Pa, it can be carried out in a thin film evaporator and a falling film evaporator. However, if the distillation must be operated under medium to high vacuum (e.g., pressure between 0.001 and 100 Pa), there is a problem. It is necessary to use an evaporator in which the vapor pressure of the product does not exceed the pressure drop between the heated surface and the condensing surface, so that the evaporator with the external condenser is excluded from the distillation process in the medium and high vacuum range.

   In contrast, SPE short-range evaporators are well suited for this application, and the condenser is built into the evaporator directly opposite the heating evaporation. Therefore, the short-range evaporator is a relatively new one that has not been widely used in industrial production, and can solve the new separation technology that cannot be solved by a large number of conventional distillation techniques.

Second, the operation process

   The SPE short-range evaporator consists of a jacketed cylinder, internal condenser and rotor. The inner condenser is located in the center of the evaporator, and the rotor with the wiper system rotates between the evaporator and the condenser.

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

Third, the basic principles

   Distillation is a method for separating mixed liquids in chemical unit operations. It is divided into atmospheric distillation and vacuum distillation. It mainly uses the volatility of each component in the mixed liquid to achieve separation. That is, separated. Light component

When the saturated vapor pressure of the 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 degree of vacuum), the easier it is to separate. The molecular distillation is based on the introduction of saturated vapor pressure and molecules on the basis of ordinary distillation. The concept of the mean free path captures the accumulation of light component molecules from the liquid phase at a fast rate, 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 must be greater than the recombination The average free path of the molecule, in order to obtain a good capture effect, the condensation area is larger than the evaporation area to achieve the purpose of molecular distillation, but due to the influence of the structure of the equipment, the actual equipment can not reach the ideal molecular distillation conditions, can only be close Or simulating molecular distillation, so we call it a short-range distiller. The factors that determine the separation capacity of the short-range distiller are as follows: 

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

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

   3.The saturated vapor pressure of the light component and the vacuum of the system. 

   In view of the above working principle, in order to increase the speed of light component diffusion from the liquid phase body to the evaporation surface, the scraping film type is used to uniformly scrape the material into a thin film on the heating surface to make the light component in the mixed liquid. The diffusion speed from the liquid body to the evaporation surface is reached, and the diffusion time is very short. A built-in condenser is placed inside the device 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 component, and the evaporation surface The escaping molecules fly unobstructed and agglomerate on the condensation surface, allowing the collection of light components to reach a fast limit speed. The instantaneous condensation of the light components has almost no resistance drop, thus ensuring the internal maintenance of the device. High vacuum. 

   Molecular mean free path λ=8.589  n/p  (T/M)1/2

   n        Material viscosity

   p        pressure 

   T        temperature

   M        Molecular weight

   Therefore, the factors determining the mean free path of the molecule are vacuum, heating temperature, viscosity and molecular weight. The higher the degree of vacuum (the lower the pressure), the larger the mean free path of the molecule, the higher the temperature, the larger the mean free path of the molecule, and the lower the average molecular weight. Cheng Yuexiao. Therefore, adjusting the degree of vacuum is an effective parameter for changing the mean free path of the molecule, which can be determined according to the specific situation, ie the operating cost. Increasing the temperature can also increase the mean free path of the molecule, and also increase the saturated vapor pressure of the light component. It will greatly improve the separation ability, but it will have a negative impact on product quality.

Fourth, the characteristics:

Short-range distiller (molecular distillation) has the following characteristics compared with ordinary distillation:

   1: The separation operation can be achieved at a temperature at the boiling temperature of the material, as long as the pressure of the system is lower than the saturated vapor pressure of the light component of the material and the distance between the heating surface and the condensation surface is less than or equal to the molecular mean free path of the light component, It can achieve the purpose of separation.

   2: Ordinary distillation is operated above the boiling point of the material, so evaporation and condensation are a reversible process. The short-range distillation (molecular distillation) separation operation can be achieved below the boiling temperature, so the evaporation of the short-range distillation (molecular distillation) Condensation is an irreversible process.

   3: Ordinary distillation has bubbling, boiling phenomenon, short-range distillation (molecular distillation). The separation operation is realized below the boiling point temperature, so there is no bubbling or boiling phenomenon, which is beneficial to maintain a high vacuum in the whole system.

Fifth, the internal structure: 

   Wuxi Haiyuan Biochemical Equipment Co., Ltd. is a professional manufacturer of short-range distiller (molecular distillation). While digesting and absorbing foreign technology, combined with the knowledge of molecular distillation of our professional technicians, we have designed and manufactured precise and accurate short-path distillation. (Molecular distillation), different scraping film forms are selected for different materials to adapt to different process requirements, and different types of built-in condensers are available for selection to meet the average free path material of different molecules, reasonable configuration And precise and accurate processing to ensure the distance between the evaporation surface and the condensation surface, the evaporation surface of the processing and polishing through the crucible makes the material flow more smoothly.

Sixth, system equipment configuration:

   Reasonable system configuration not only ensures the normal operation of the short-range distiller (molecular distillation), but also avoids unreasonable investment. In general, the short-range distiller (molecular distillation) requires a higher operating vacuum, so before entering the short-range distiller (molecular distillation), the material should be subjected to short-range distillation (molecular distillation (the degree of vacuum affects the light component ( The non-condensable gas, the low-boiling residual part) is first removed. It has been proved that the scraper-type thin film evaporator is an ideal pre-discharge device, and the selective scraper-type thin film evaporator can ensure the short-range distillation (molecular distillation) in a high vacuum state. normal operation.

Seven, application areas

Petrochemical industry: amides, amines, quinoline derivatives, epoxy resins, resin acids, isocyanates, isobutyl ketones, peroxides, liquid crystals, polyethylene glycols, silicone oils, softeners, etc.;

Pharmaceutical industry: amino acid esters, polymer intermediates, vitamin E, vitamins, etc.;

Oil industry: diglycerides, dimerized fatty acids, fatty acids, fatty acid derivatives, polyglycerides, acids, lanolin alcohols, etc.;

Food industry: monoglyceride, lauric acid, propylene glycol fat, L-lactic acid, cod liver oil, rice bran oil, small three wheat germ oil, cinnamon oil, rose oil, etc.; 

Eight, product specifications

   Choosing a reasonable size is very important for short-range evaporators. The table below lists the standard dimensions and the dimensions of the equipment.

Model Heating area m2 Condensation area m2 Evaporation inner diameter mm Total equipment height mm WeightKG
SPE6 0.06
0.06 80 1000 35
SPE10 0.1 0.12 125 1100 50
0.3 0.5 210 1750 110
SPE80 0.5 0.8 300 2100 160
SPE100 1.0 1.5 350 2730 240
SPE150 1.5 2.5 400 3200 520
SPE200 2 3.0 500 3500 680
SPE300 3.0 5.0 600 4800 1100
SPE400 4 7.5 700 5500 1380
SPE600 6 10 800 5800 1750
SPE800 8 16 1000 6800 3500

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