US2181563A - Process of refining vegetable and animal oils - Google Patents

Description

Nov. 28, 1939.\

O. E. FRDING Filed Sept. 2. '1957 iff/744555.'

CE/vr/e/Faaf PROCESS 0F REFINING VEGETABLE AND ANIMAL OILS ozoffzmgffahj Patented Nov. 28, 1939 UNITED sTATEs PATENT OFFICE PROCESS OF REFINING VEGETABLE AND ANIMAL OILS Application september 2, 1937, serial No. 162,100

In Sweden October 8, 1936 '3 Claims.

In the refiningof vegetable oils containing free fatty acids it is known to intimately mix the oil with a saponifying agent, usually an alkali such as caustic soda, to effect a saponification of the fatty acids and to then separate the oil from the soaps by settlement or centrifugation. It is necessary to heat the oil to temperatures which Vary with the duration of the process and the character of theoil being treated. The oil is sometimes heated to thedesired ultimate temperature before mixing with the alkali, sometimes during mixing, sometimes after mixing, and som'etimes during and after mixing, and it is sometimes/heated before mixing to a moderate temperature and during or after mixing to the nal temperature desired. When the heating is wholly or mainly effected in the mixer, it is usual to ldecrease the rate or amount of agitation as the heating of the oil proceeds so that the oil will be in a comparatively quiescent state before separation. proposed or practiced both in batch and continuously. Centrifugal separation of the oil and the soap is of advantage in that the time of heating and mixing may be somewhat shortened and the mixture conveyed to the centrifuge before saponification of the fatty acids is quite completed, the saponication being completed in the separator due to the -intimate admixture therein of the constituents before their separation is completed. In all these processes it is customary, after the separation, whether by centrifugation or settling, to wash with water and separate the soap-containing water from the oil.

It has been. proposed `to heat the oil to various maximum temperatures, ranging from 80 F. to 140 or 150 F. or even higher. The objection to the higher range of temperature is that the soaps are'more soluble in the oil at a higher temperature and soap contained in the oil in solution cannot of course be separated by gravity or centrifugal force. In the subsequent washing part of the soap is hydrolyzed and the fatty acids thereby liberated are dissolved in the oil, so that the ultimate refined oil does not in Vmany cases vmeet the requirement of neutrality. The objections to heating the oil to a relatively high temperature may be, of course, avoided by not heating the oil during the process or by heating it to within a comparatively low temperature range;

`but this method is objectionable in that the neu- 'Ihese various processes have been A bleaching of the` I have found that the advantages of both high and low heating may be securedand the disadvantages of both avoided, by interposing, between the mixing and heating step or steps and the centrifuging step, a cooling step whereby the temperature, prior to separation; is so reduced as to throw out of solution a major proportion of the soaps. In many cases,4by the use of this process, separated oil is of such quality Athat the subsequent Washing operation may be altogether dispensed with, which is obviously an additional advantage.

The process is applicable to any of the known processes, but itis particularly applicable to any of the known processes that is practiced continuously as distinguished from batch processes.

The single figure of the drawing illustrates in diagram an apparatusv adapted to carry out the process in a continuous manner.

'I'he diagrammed apparatus illustrates a known continuous apparatus for practicing the process continuously with the addition thereto of a cooler interposed in the series of devices just before the outlet to the first separator. The crude oil from tank I (which may or may not be preliminarily heated to a comparatively low temperature) flows or may be pumped through the tube 2 into and through the mixer 4. Into tube 2 a solution of caustic soda, sodium or potassium carbonate, or any other suitable alkali or saponifying agent, is introduced from the tank 3. Any suitable proportioning device adapted to insure a uniform ratio between the oil feed and the alkali feed may be utilized, but the use of such devices is Well known and forms no part of the invention and I have merely shown two Valves, Il and l2, on pipe 2 y and on the pipe from tank 3, which may be handregulated to govern the proportioning. The reaction starts in the v`mixer and may be completed in the heater 5; or all the heating may be applied in the tank I; or the relative positions of the mixer and heater may be reversed; or some or all of the heating may be effected in the mixer, which for that purpose may be steam jacketed, as indicated by the reference numeral 13. From the heater 5 the oil passes through a cooler 6 and thence goes tothe centrifugal separator 1. If the separated oil still contains too much soap to meet the requirements in any given case, the oil, by means of pump 8, is conveyed to a water Washer 9 and thence to a centrifugal separator I0, wherein the soap-containingA water is separated from the oil.

In treating .some oils it is advantageous to mix with alkali at a rather low temperature, since lit cluding the cooler.

avoids the formation, in the rst part of the process, of a less readily separable emulsion. With most oils, of which cocoa oil and cottonseed oil are examples, the emulsion is less pronounced and it is 4usually entirely practicable to do all Vthe heating in the tank I, say by means of a steam coil I3; or the positions of the heater 5 and mixer 4 may be reversed so that the oil will be heated in stream before ygoing to the mixer. I n treating practically all oils it is quite feasible to effect the heating simultaneously with the mixing.

When refining a peanut oil containing 3.5% free fatty acids (in the apparatus shown, with the cooler 6 omitted) with a 15% NaOH solution,

` drolysis.

The same oil was treated according to the present invention in the apparatus shown, in-

The mixing was carried out at about 78 F., the .oil was heated to about 122 F. and cooled to about 86 F. prior to separation. The content of NaOH in the separated oil was .01%. The content of fatty acids in the washed oil was .10%.

A soya oil containing 1.8% free fatty acids was mixed with a 10% NaOH solution at about 68 F. and was separated at about 113 F. The NaOH content in the separated oil was .03%, free fatty acids .07%. After washing the content of free fatty acids was .12%.

The same oil was treated according to the present invention in the apparatus shown, including the cooler, but was cooled to about 68 F. before the separation.` The NaOH content in the separated oil was .002%, and since this corresponds to a content of soap of only about .015%, the oil could be treated with bleaching earth without Washing.

A cocoa oil having a content of fatty acids of 5.4% was mixed with a 1% NaOH solution at about 112 F. and was` separated at about 140 F. The NaOH content of the separated oil was .04%, the content of free fatty acids .08%. After wash,-l ing the content of free fatty acids was .16%.

'I'he same oil was treated in accordance with my invention,lthe heating, however, being effected in the tank I instead of in the heater 5. 'I'he temperature of the oil when being mixed with the lye wasv about 122 F. and at the separation was about 90 F. The NaOH content of the separated oil was .009%, after the washing .002%. 'I'he content of fatty acids in the washed oil was .09%.

What I claim and. desire to protect by Lettersl Patent is:

1. In the process of refining vegetable and animal oils wherein the oil is mixed with a saponifying agent to effect sapon'ification of fatty acids contained in the oil and heated through a considerable range of temperature and the oil then separated from undissolved soaps, the improvement which comprises interposing between they mixing and heating procedure and the separation of the oil from the soaps a cooling step in which the mixture is cooled through the major part of the temperature range through which it was heated to thereby increase the proportion' of undissolved soaps before separation and substantially reduce the proportion of soaps inthe subsequently separated oil.

2. In the continuous process of refining vegetable and animal oils, which comprises, as a first procedure, flowing a stream of a saponifying agent into contact with a, owing stream of oil,

subjecting the mixture during its flow to a mixing action so as to eifect saponication of fatty acids in the oil and heating the oil to within a range of temperature customary in the process, and then as a following procedure subjecting the flowing mixture to centrifugal force and thereby separating the oil from the soaps that are not dissolved in the oil, the improvement which comprises eiecting a substantial reduction inthe soap content of the separated oil by reducing the temperature of the oil between the mixing and heating procedure and the centrifugal separation procedure to a temperature substantially nearer to that of the unheated oil than to that to which the oil was previously heated.

3. In the continuous process of refining vegetable and animal oils, which comprises, as a first procedure, flowing a stream of a saponifying agent into contact with a flowing stream of oil, subjecting the mixture during its flow to a mixing action so as to eifect saponiiication of fatty acids in the oil and heating the oil to Within a range of temperature customary in the process, then as a following procedure subjecting the flowing mixture to centrifugal force to thereby separate the oil from the soaps not dissolved therein, and then as a final procedure washing the separated oil with water and separating the soap-containing Water from the oil, the 11nprovement which comprises effecting a substantial reduction in the fatty acid content of the final washed oil by reducing the temperature of the oil between the mixing and heating procedure and the centrifugal separation procedure through the major part of the temperature range through which it was heated.

-oLoF EINAR. FRDINGf

Images