Advantages of Short Path Distillation

1. Advantages of Short Path Distillation Molecular distillation, sometimes called short path distillation, is a separation process for liquids based on the difference in their volatilities, or evaporation rates. It is noted for its high effectiveness in smaller lab-flow applications as well as in high-flow commercial purposes. The molecular distillation equipment works on the same principles as short path distillation. The basic operations and principles of short path distillation are ideal for certain raw materials and finished products which will be discussed below. First, an explanation of the functioning and the components of a short path distiller is necessary in order to grasp the extent of its benefits and functionality. Short Path Distillation Apparatus and Working The liquid raw material is introduced into the “feed tank.” The liquid is then passed on through feed tubes to the central evaporation chamber. This central evaporation chamber is made up of three main components—a wiper blade attached to a rotor on top, an evaporation surface, and internal or external condenser tubes. While conventional wiped film evaporators use external condensers, short path distillation incorporates the condenser within the evaporating chamber. This is an essential point of contrast between the two distillation systems. The vacuum conditions are used to draw out the raw material from the feed tank to the evaporation chamber. The evaporation process takes place under calibrated conditions, following which the distillate particles collect on the condensing tubes and yield to their liquid form. Finally, there are two output nodes—the distillation node and the residue node. The distillate drips down the condensation tubes and is pumped out into a collecting chamber while the residual substances flow down the walls of the evaporator and are collected in the residual chamber. The Principle of Short Path Distillation and the Importance of Vacuum The distillation process inside the evaporation chamber takes place in a vacuum which is monitored by a vacuum gauge. The vacuum is powered by a mechanical roughing pump that in turn primes a diffusion pump. The reduced pressure inside the evaporation chamber is essential for short path distillation, as it reduces the evaporating temperature of the liquid which can be lower than the boiling point of the liquid at standard temperature. These allows for greater

2. purity of the distilled substance as certain substances are temperature sensitive and are unstable at higher temperatures with prolonged exposure. The short path distiller works on the principle of the mean free path of a molecule—generally a few hundredth parts of a centimeter—through which a molecule can travel without collision and modification of its properties, energy or direction. In very low pressures or vacuum, therefore, the short path is generally a few centimeters from the evaporation surface to the condenser tube—assuring the purity of the output in color, fragrance, and viscosity. Considering the Pros and Cons Molecular distillation (short path distillation) has several advantages that deem it highly suited for commercial purposes. For example, it can operate continuously for producing commercial volumes of products. Furthermore, it can function automatically, without requiring manual involvement. However, the molecular distillation equipment also faces certain limitations. The thin/wiped film evaporator is not suited for distilling liquids high in viscosity. Substances high in viscosity can damage the rotor in the evaporation chamber, which in turn can incur high costs to fix or replace. Nevertheless, this drawback can also be overcome in certain cases, by heating the liquid in the feed tank to decrease the viscosity before moving it to the evaporation chamber. One of the leading providers of molecular and short path distillation is InChem Corp. in Rock Hill, S.C. Contact InChem via their website, www.InChemCorp.com, or call 1-800-331-7721.