What is the effect of vacuum on short range molecular distillation

Date:2020-3-16 17:14:25  Number:

Short range molecular distillation is composed of a vertical cylinder heated externally, a central condenser and a membrane scraper rotating between the distiller and the condenser.
The distillation process is: the material is added from the top of the evaporator, distributed on the heating surface continuously and evenly by the material liquid distributor on the rotor, and then the scraper scrapes the material liquid into a very thin, turbulent liquid film, and advances downward in a spiral shape. In this process, the light molecules escaping from the heating surface condense into liquid on the built-in condenser after a short route and almost without collision, and flow down the condenser tube, and discharge through the discharge tube at the bottom of the evaporator; the residual liquid is the heavy molecules collected in the circular channel under the heating area, and then flow out through the side discharge tube.
Short range molecular distillation is a high vacuum distillation method. Raw materials are heated in short range molecular distillation equipment, scraped into thin films, and light components are evaporated in high vacuum and condensed on the built-in condenser. The separated light and heavy components are discharged continuously under high vacuum, so how to collect qualified samples or products under high vacuum is the key.
Like other distillation processes, short-range molecular distillation needs to adjust all parameters of the system (such as temperature, pressure, feed volume, etc.) at the beginning of the experiment. The evaporation and condensation of the system have not reached a balance. At this time, the collected light weight and the samples of heavy components cannot accurately represent the parameters of this temperature, pressure and feed volume. Generally, we need to stabilize these parameters The light and heavy fraction samples were collected after 3 to 5 minutes. At the end of the experiment, we need to cool down the equipment, release the vacuum, reduce the amount of feed and other operations. At this time, the collected samples also need to be switched off in time.
How to obtain clear fraction is related to the success or failure of distillation experiment, which is very important for molecular distillation experiment under high vacuum. Therefore, under the condition of not dispersing the vacuum, choosing which kind of sample collection or discharging method has become the concern of the experimenter.

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