GB589534A - Improvements in the purification and deodorization of glycerides - Google Patents

Abstract

<PICT:0589534/III/1> <PICT:0589534/III/2> A glyceride oil or fat of animal, vegetable or synthetic origin is purified or deodorized by heating it, bringing it into contact with an inert gas, flowing in the opposite direction to the oil in a primary distilling zone at sub-atmospheric pressure, for a time sufficient for a major part of the odorous and other volatile impurities to be evaporated, continuously passing the treated oil to an independent secondary distilling zone and bringing it into contact with fresh inert gas under a sub-atmospheric pressure much lower than that obtaining at the end of the primary zone and flowing in the opposite direction to the oil, the time of contact being sufficient for the remainder of the volatile impurities to be evaporated, and continuously removing the purified or deodorized glyceride from the secondary distilling zone, while continuously withdrawing volatile impurities separately from each of the distilling zones. As shown in Fig. 1, oil to be purified is fed in a controlled continuous stream from pump 8 to a spray distributor 9 in the vacuum deaerating chamber 10. A stream of water-free inert gas such as nitrogen or carbon dioxide from cylinder 11 is passed up the chamber 10 which is provided with bubble-cap trays 13 for promotion of contact between liquid and gas. The de-aerated oil is drawn through pipe 16 by pump 18 and is passed through heat-exchanger 20 to an atomizing device 22 where it is mixed with a large quantity of inert gas such as dry steam from a header 27. The steam is superheated in the coil 23. The mist of oil and steam is heated in the coil 29 as it passes on to the spray nozzles 33 in the upper portion of the tower 15. The chamber 15s is maintained at a high degree of vacuum. Superheated p steam is admitted to the upper chamber 15s through valve 37. The steam rises through the chamber and bubbles through the liquid on the trays. The liquid is freed from volatile impurities as it flows down the chamber 15s. To minimize the return of condensed impurities or entrained liquid to the main body of liquid from the under surface of the tower top, baffles 39, 40 and 41, and a waste outlet valve 42, are provided. The oil collects as a pool 71 at the bottom of chamber 15s, just above the plate 35 which separates the upper and lower portions of the tower. From pool 71, the oil is continuously withdrawn through valve 52 and is atomized with a large volume of superheated steam in atomizer 56. The mist of oil and steam is heated in coil 58 and is then passed through pipe 60 to the lower chamber 15i of the tower 15. This chamber is maintained under a high degree of vacuum, the absolute pressure being much lower than that obtaining in the lower portion of the chamber 15s. Superheated steam is supplied through valve 65. The nozzle 77 forms a vapour outlet and it is connected to a source of high-vacuum. As an alternative method of operation, the re-heated atomized oil from coil 58 is passed through pipe 68 to the middle part of the upper chamber 15s. Sufficient heat is thus supplied to overcome that lost by evaporation of impurities and by radiation from the tower. Liquid from the pool 71 may, in this case, be transferred directly to the lower chamber, e.g., by an automatically acting overflow loop. The completely deodorized oil accumulates in a pool 80 and is withdrawn continuously through valve 81 and pipeline 82. It passes through heat exchanger 20, a cooler 87, receiving vessel 91, filter 94, and pipeline 95 to a storage vessel. Instead of providing chambers 15s and 15i in a single tower 15, two entirely separate distilling chambers may be provided. As shown in Fig. 2, the superheated steam entering the lower chamber 15i is controlled by a solenoid operated valve 65 and is caused to bubble through the pool of oil. The final deodorizing or purification of the oil is effected alternately in sequence in the finishing vacuum vessels 100a and 100b to which superheated steam is supplied through pipe 102, solenoid-operated valves 103 and distributors 104. The valves 65, 81, 103, 106 and 107 are operated in sequence by means of the time-cycle controller 105. The treated charges of oil are withdrawn in sequence from the vessels 100a , 100b, through the valves 107 so that a substantially constant flow of purified oil is maintained through pipe 85, When the finishing vacuum vessels 100a , 100b, are provided, the apparatus used may be modified by combining chambers 15s, 15i into a single chamber.