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| | Difference between Short-path Distillation and Mol (6th Feb 23 at 1:38am UTC) | | | Original Title: Difference between Short-path Distillation and Molecular Distillation-Shanghai DEA Short-path distillation, "short path" refers to a shorter distance, in a broad sense, the evaporator adopts the design scheme that the distance from the evaporation surface to the condensation surface is less than 300 MM, which can be called a short-path distiller. In terms of design structure, it can be divided into scraper short-path distiller, centrifugal short-path distiller and short-path distillers evolved from the condenser installation position of film evaporator improved by some manufacturers in recent years. At present, the most mature technology widely used is the scraper short-distance distiller, which is designed to consist of a vertical evaporation cylinder heated externally, a central condenser and a rotating film scraper between the distiller and the condenser. The distillation process is as follows: the material is added from the top of the evaporator, and is continuously and uniformly distributed on the heating surface by the feed liquid distributor on the rotor, and then the film scraper scrapes the feed liquid into a very thin layer of turbulent liquid film, which is pushed downward in a spiral shape. In this process, the light components escaping from the heating surface are condensed into liquid on the built-in condenser through a very short route and almost without collision, and flow down the condenser tubes and discharged through the discharge tube at the bottom of the evaporator; the residual liquid, namely the heavy components, is collected in the circular channel under the heating area and then flows out through the discharge tube at the side. Molecular distillation, more precisely, the principle of molecular distillation, wiped film distillation ,molecular distillation systems, is different from the traditional distillation which relies on the principle of boiling point difference separation, but relies on the difference of mean free path of molecular motion of different substances to achieve separation. In the distillation process, when a liquid mixture flows along a heating plate and is heated under a certain specific pressure condition, light and heavy molecules can escape from the liquid surface and enter a gas phase, and because the free paths of the light and heavy molecules are different, the molecules of different substances have different moving distances after escaping from the liquid surface, If a condensation plate can be properly set (the distance between the evaporation area and the condensation surface is generally less than 100mm), the light molecules will be condensed and discharged when they reach the condensation plate, while the heavy molecules will be discharged along the mixed liquid when they do not reach the condensation plate. In this way, the purpose of material separation is achieved. Expand the full text Attention should be paid to "specific pressure conditions" and "evaporation surface and condensation surface distance" from the description of the distillation process. That is to say, not all raw materials can realize molecular distillation; the molecular distillation process can only be realized in a scraper type short-path distiller or a centrifugal type short-path distiller; the molecular distillation is not simply distillation in the short-distance distiller, but molecular distillation, and molecular distillation must be realized by realizing molecular-level motion and realizing a separation process at a specific pressure and a specific temperature. Therefore, it is wrong to simply confuse molecular distillation with short-path distillation, and their essence is different. Features of Shanghai DEA's scraper short-path distiller: Extremely high vacuum: The special structural design of the scraper short-path distiller allows the operating pressure to reach an extremely low operating vacuum. The vacuum of the experimental scale equipment can reach 0.001 mbar, and even the industrial scale equipment can reach 0.01-0.05 mbar. The operating temperature is much lower than the boiling point of the material: because the scraped path distillation adopts the central condensation mode, the distance between the evaporation area and the condensation surface is generally less than 50mm (the distance between the experimental device is less than 10mm), so there is only a slight pressure drop between the evaporator and the condenser, that is to say, the vacuum degree at the end of the vacuum system is almost close to the vacuum of the evaporator. The design of DEA fully meets the requirements of molecular distillation process. The heating time is short: by adopting the film forming design of the vertically rotating scraper, the residence time of the material on the heating wall is only more than ten seconds. Due to the strict distance requirement between the heating wall of short-path distillation and the condenser, the light molecules escaping from the liquid surface reach the condensing surface almost instantaneously, and the heating time of the light molecules in the vapor phase can be ignored in this process. The potential for thermal decomposition is minimized. Superior efficiency of mass transfer and heat transfer: DEA short-path distillation uses a mechanical film wiping system,winterization filtration, which is different from the uneven film formation defects of other falling film evaporators. In the short-path evaporator, the material film thickness is uniform and the flow characteristics are excellent. Because the area of the liquid level and the heating surface is almost equal, the efficiency of mass transfer and heat transfer is superior. Return to Sohu to see more Responsible Editor:. toptiontech.com | |
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