Distillation

The distillation is a process of separation of Substance S, mixed in form Liquide. It consists in carrying the mixture to boiling and collecting a light Fraction called distillate, and a heavy fraction called residue

History

Distillation was discovered by the Romain S there is more than 2.000 years and range with the state of art by the Moine S of the Moyen-âge.

The simplest distillation, with the most known application (Still), was studied by Rayleigh at the beginning of the 20th century.

The technique of the Alambic had been developed by the alchemist Jabir ibn Hayyan about the year 800. It developed several other apparatuses of which some are still used in chemistry.

Technical details

The process uses the difference in volatility (capacity to be evaporated depend on the temperature) between the components in order to separate them: most volatile a boiling point lower has than the least volatile, etc Ainsi, while heating the liquid, each component will be separate successively (one speaks about cut of distillation). The vapor thus produced can be condensed (Distillat), and the remaining substance is called Résidu. Attention however, the distillate is not always a pure product. It can be a definite mixture of two components (even nonmiscible): one speaks about azeotrope, or mixture azeotropic.

Industrial process

In industrial process and in the case of a discontinuous distillation, the first vapors which pass at the head from column are called “heads of distillation”, then comes the heart (often the heart is the substance which is required in the mixture introduced into the distiller), then at the end of the distillation appear “the tails of distillation”.

There exist also techniques of flash distillation which aim at lowering the boiling points of the various components of the mixture to be distilled, and thus thus make it possible to avoid (or to reduce) the risks of thermal degradation. In the same way distillations can be carried out under pressure in order to allow the separation of made up very volatile (i.e gas)

When the boiling points are very close, one can have interest to use a process of split Distillation, which consists of several stages of successive refinements. It is also possible to introduce part of the distillate at the head of column (in the case of a distillation continues) in order to improve the purity of the vapor phase. nothing included/understood

See too

External bonds

  • Diagram assembly of a distillation
  • Treated reasoned of distillation
  • Manual of Historical distilling
  • of distillation

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