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Short-path distillation is a distillation technique that involves the distillate traveling a short distance, often only a few centimeters, and is normally done at reduced pressure. [ 1 ] [ 2 ] Short-path distillation systems often have a variety of names depending on the manufacturer of the system and what compounds are being distilled within them.
The pressure in the system must be maintained from the pump right through the pressure vessel. In smaller systems (up to about 10 mL / min) a simple restrictor can be used. This can be either a capillary tube cut to length, or a needle valve which can be adjusted to maintain pressure at different flow rates.
The method of extractive distillation uses a separation solvent, which is generally non-volatile, has a high boiling point and is miscible with the mixture, but doesn't form an azeotropic mixture. The solvent interacts differently with the components of the mixture thereby causing their relative volatilities to change.
New applications are in inkjet systems where gas in the ink forms bubbles that degrade print quality, a degassing unit is placed prior to the print head to remove gas and prevent the buildup of bubbles keeping good jetting and print quality. The above three methods are used to remove all dissolved gases. Below are methods for more selective ...
Some high-boiling liquids that have an azeotrope with water can be dried by adding toluene or another azeotrope-breaking solvent to allow the extraction of water. The Dean–Stark method is commonly used to measure moisture content of items such as bread in the food industry. This equipment can be used in cases other than simple removal of water.
In azeotropic distillation the volatility of the added component is the same as the mixture, and a new azeotrope is formed with one or more of the components based on differences in polarity. [2] If the material separation agent is selected to form azeotropes with more than one component in the feed then it is referred to as an entrainer.
The other application of the heteroazeotropic distillation is the separation of a binary system (A-B) forming a homogeneous azeotrope. In this case an entrainer or solvent is added to the mixture in order to form an heteroazeotrope with one or both of the components in order to help the separation of the original A-B mixture.
A binary distillation separates a feed mixture stream into two fractions: one distillate and one bottoms fractions. The principle for continuous distillation is the same as for normal distillation: when a liquid mixture is heated so that it boils, the composition of the vapor above the liquid differs from the liquid composition.