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Molecular Distillation
with Short Path Evaporators

Molecular distillation is mostly carried out in short path evaporators. While performing the evaporation the molecules are streaming directly from the heating surface to the internal condenser and there is no flow in the opposite direction.

Essential conditions are:

  1. The partial pressure of the residual gas must be so low that the mean free path of the residual gas molecules is a multiple value of the distance between the heating surface and the condenser.
  2. At saturation pressure, the mean free path of the vapour molecules must have the same range as the the distance between the heating surface and the condenser.

Under these ideal conditions molecular distillation takes place without any obstruction from residual gas molecules. All vapour molecules reach the surface of the condenser without colliding with other molecules and thus returning to the liquid.

The operation pressure of 0.001 mbar (a) and the distance between heating surface and condenser in Buss-SMS-Canzler short path evaporators provide ideal conditions to allow the molecular distillation.