Short Path Distiller
In pharmaceutical and chemical industry there are usually processes where or when a product has to be distilled at a very low pressure, in order to expose it to a temperature that would not affect its properties. Distillation at a very high vacuum level generates a large volume of vapours, which are not practical to condense outside the evaporator, as it is the case with medium vacuum levels. Under these conditions, our short path distiller proves to be the most advisable one. Here, the condenser is placed inside the distiller, close enough to the evaporation surface, so that vapours would not find any obstacle in their way to the condenser, and so avoiding the usual loss of head in traditional distillers.
For most applications, working pressure ranges within 15 mTorr(15 microns) and 1 Torr. But, when working at a very high vacuum, since the distance between the evaporator and the condenser is within the same range or less than the medium free path between molecules, we are talking about a molecular distiller. The liquid to be distilled, comes into a rotating distributor, that spreads it evenly, in such a way, that it produces a thin layer that comes down and covers the evaporation surface, which is being heated by a jacket. A certain number of rollers, which are attached to that plate and powered by a gear motor reducer, rotate at a moderate speed, and the centrifugal force drives them against the layer of the liquid being distilled. Such rotating movement increases the heat transfer coefficient, and it is very appropriate for handling viscose liquids.
Evaporation in layers eliminates boiling point raicing as it is the case with stills having considerable hydraulic heads, at the same time that reduces residence time down to safe levels, a fact that favours product stability. Condensate and exhausted residues are collected at the bottom of the distiller, in separate compartments. Non-condensable exhaust vacuum port is placed at the lower part of the distiller. Vacuum is generated by a 4,5 or 6 stage ejectors and pumps system. Although the products to be separated vapour tension difference increases as vacuum increases, which happen to be an important advantage, it is necessary to place two or three distillers in series, in order to improve separation efficiency when dealing with products that have close boiling points.