GB801102A - Improvements in or relating to process of separating components of oleaginous mixtures by fractional crystallization - Google Patents

Abstract

A process for separating the components of oleaginous matter by fractional crystallization, for example to obtain winterized salad oil from cottonseed oil, comprises dissolving the matter in a selective solvent, most suitably n-hexane, to form a miscella which is rapidly cooled to a <PICT:0801102/III/1> first critical temperature Ts above the highest freezing temperature Tc of the components of the miscella, then further cooled at a rate not exceeding 0.5 DEG F. per minute to an ultimate temperature Tu intermediate between Tc and the gelling temperature Tj of the miscella, and finally separating the solute crystals formed from the miscella. The fatty raw material for the process preferably contains small amounts of moisture which freezes to minute ice crystals in the course of the process and so provide nuclei on which crystals may form. The miscella is preferably kept at the ultimate temperature Tu for 90-120 minutes and is gently stirred throughout the process. A suitable apparatus as shown in the Figure, in which the process may be carried out, comprises a source of miscella 11, which passes through heat exchanger 12 into refrigerated heat exchanger 13 where the temperature is reduced to temperature Ts. The miscella is then passed to winterizing tank 14 which is divided into several vertically aligned compartments 20, any of which may be by-passed if desired, and which assists in flow control, the contents of each compartment being stirred by paddles attached to rotating shaft 38. The time of passage of the miscella from entry until it reaches the floor 19 of the bottom of the tank is adjusted to 90-120 minutes at the end of which time its temperature is suitably 0-5 DEG F. After leaving the winterizing tank, the miscella passes to settling tank 50, the contents of which are also stirred gently, the crystals which settle out being drawn off through hollow rotating arm 54 and conduit 60 to preheater 70, where the crystals are melted. The melt passes thence to evaporator 71 and flash chamber 72 for the separation of the solvent which is condensed in 73, the stearine passing to storage by way of stripping column 74. The liquid winterized fraction from settling tank 50 is passed back through line 64 to heat exchanger 12, where it cools incoming miscella, before being taken off for removal of solvent and recovery of winterized oil. By appropriate temperature control, waxes, gums, and other impurities having distinctive freezing points may also be removed from oleaginous matter. U.S.A. Specification 2,619,421 is referred to.