Distillation takes a SHORT CUT

Vegetable oils, animal fats and fish oils represent a significant part of human food products. World production of oils and fats only for human consumption is over 50million tpa. Oils and fats also form the basic material for a variety of chemical intermediate and final products, including oleo chemicals.

The advantage of a gentle distillation process is to reduce boiling temperatures by decreasing operating pressure, which avoids organic decomposition. This method was first used in the 1930s for the distillation of vitamin E concentrate from seed oils.

Distillation pressures as low as 0.001 mbar are achievable only by using low pressure distillation. Because distillation is now feasible at a very low temperatures, highly sensitive feed materials can now be protected against thermal degradation. Consequently, heat materials such as vitamins and pharmaceuticals can be processed without deterioration of quality.

Typical applications are: physical de-acidification of vegetable oil and animal fat; deodorisation; upgrading of juices, vitamins, and oleoresins; purification of acids like citric acid, lactic acid and omega-3 fatty acids; production of emulsifiers, e.g. monostearates; interesterification for changing the consistency of fats; separation of pesticides; and deglycerination.

Cod liver oil played a crucial part in the discovery of the fat-soluble vitamins A and D. The theraputic properties of cod liver oil were later identified as the essential fatty acids EPA and DHA, belonging to the omega 3-fatty acids group. Vitamin producer Moller ordered a short path distillator (SPD) from the German Alzenau-Horstein-based company UIC to produce capsules with 70 per cent fatty acids. Before SPD, only 28 per cent concentrations had been available.

For gentle distillation, UIC's Thin Film evaporators (TFE) and SPDs have low product residence times between seconds and a few minutes. SPD techniques were developed to break the physical barrier of attaining distillation pressures below 1 mbar. This barrier was caused by the pressure drop of vapours flowing to an external condenser. Using an internal condenser, thereby shortening the path length of vapours, makes low pressure distillation possible.

The primary components of all UIC's plants are the TFEs and SPDs. Each of these components consists of a vertical, cylindrical, double jacketed apparatus which is heated by either thermal oil or steam. A rotating disc inside the top of the evaporator or distillator distributes the feed material by centrifugal force onto the internal surface wall. Gravity causes a downward flow of material, while the roller wipers form a consistently thin film and avoid temperature gradients within the material. The roller wiper system mixes the product film and provides a uniform distribution onto the evaporator surface. Any overheating of the product is avoided, and the residence time of the product at evaporation temperature is drastically reduced. The SPD's condenser is located in the centre of the evaporator so pressure drop is almost completely eliminated. The TFE's vapour is led to an external condenser.

Thin Film evaporators are used in chemical, pharmaceutical, food, and cosmetic industries for the stripping of light volatiles, such as water, alcohols, esters, and similar solvents with high evaporation heat. PE