US2182755A - Process of refining animal and vegetable oils - Google Patents

Description

therein, no precise concentration and amount of reagent can be stated. In general, suilicient alkaline reagent should be employed to neutralize the free fatty acids inthe oil and to provide a considerable excess for reaction with other impurities such as gums and coloring matter in the' oil. For example, 5.7% by weight of a 14 B. caustic soda solution is suitable for refining cottonseedoil containing 1.4% of free4 fatty acid.

The process herein described is also applicable to the refining of animal and vegetable oils, particularly the drying oils such as linseed and soya bean oil. with acid reagents. Such acid reagents react with gums and coloring impurities in the oil, probably by dehydration or carbonization reaction, to precipitate the same and render them separable from the oil. The acid reagent generally used is relatively concentrated sulphuric acid, for example, B. sulphuric acid in amounts ranging from 1 to 10% although other acids, such as relatively concentrated hydrochloric acid can also be employed.

'dilute solutions of acids, alkalies or salts are employed in amounts ranging from 1 to 10% of the oil to precipitate the gums contained in the oils probably by hydration thereof. Such degumming operations are not to be confused with the alkali and acid refining operations above described. In alkali refining, Suflicient alkali is employed to neutralize all of the free fatty acids and provide an excess for other reactions, and in acid refining the gums, etc., are. subjected to drastic treatment with acids, whereas in partial refining with a very dilute solution, sufficient alkali is not employed to react with any substantial portions of the free fatty acids and the acid reagents which may be alternatively employed are of insufficient strength to perform any substantial carbonization or dehydration reaction. Alkali refining, acid refining, and partial refining or degumming are independent operations but present certain common problems as discussed hereinafter. Degumming may be employed before refining and even as a part of the same continuous process.` By degumming before refining, less reagent is necessary in therefining operation and refining losses are reduced,

particularly with alkalirefining.

In all of the types of refining above described, an emulsion between the oil and the aqueous reagent which is apparently of the water in oil type tends to be produced during admixture. If the oil -ano reagent are mixed cold, i. e., at temperatures in the neighborhood of 'I5 to 90 F., or lower, an emulsion is usually formed which cannot be eiectively separated by centrifugal separation. By preheating either the oil or reagent or both so that the temperature'of the resulting mixtureis relatively high, the formation of such an emulsion is opposed suclrthat it does not form, or if the emulsion is formed, it is transitory only and is immediately broken to render the mixture separable. The emulsion opposing orbreaking temperature which is necesfary L.o provide effective centrifugal separation varies vith the particular oil being treated and the natureof the reagent employed. The most stable emulsions are generally produced in alkali refinfore, vno precise temperaturev can be given for every condition but such temperatures will ordi -narily range between F. for pure oils up to 200 F for very impure oils. For most oils temperature: from to 140 F. can be satisfactorily employed as emulsion breaking or oppasing temperatures.

It is ordinarily sufficient to preheat only the oil as the amount of refining reagent is usually small in comparison with the amount of oil beills mixed therewith. In such case, the oil must be preheated to a temperature suiliciently high to produce an emulsion breaking or opposing temperature of the mixture. The preheated oil rapidly heats the reagent in the mixing zone so that a resultant uniform temperature is produced. Although, as indicated, it is generally preferable to preheat the oil, it is within the contemplation of the present invention to preheat only the reagent to a temperature sufciently high to produce an emulsion breaking or opposing temperature of the mixture.

Since the mixture is produced at a temperature sufficiently high to break or oppose the formation of any emulsion which may tend to form during mixing, the mixture of oil and foots is immediately in condition-for centrifugal separation. Thus the mixing can be performed just before the materials enter the centrifugal and in many cases the mixing can be performed directly in the entrance 4of the centrifugal by deliverlng separate streams of 'oil and reagent to the centrifugal as many centrifugals produce considerable agitation of the entering materials.

As indicated above, any desired form of centrifugal which is capable of continuously separating foots from vegetable and animal oils may be employed. It is, however, preferred to employ the heated centrifugal disclosed in the co-pending application of Benjamin Clayton, Serial No. 34,258, filed August 1, 1935, now Patent No. 2,100,277, granted November 23, 1937. Such a centrifugal can be employed to maintain the temperature of the materials in the centrifugal and also promotes the delivery of the heavy efuent as a continuous stream from the centrifugal.

In accordance with the present invention, the entire process may be performed within a relatively few minutes, for example, a stream of oil has been preheated by flowing the same through a heating coil constructed of three-quarter inch pipe approximately 250 feet long at the rate of approximately 16 pounds per minute and the temperature raised from substantially room temperature to F. in approximately 11/2 minutes. It is, of course, understood that other types of flow heating devices can be substituted for the coils disclosed. It is desirable to heat the oil as rapidly as practicable and maintain in heated condition for as short a time as practical and in general it is desirable to bring the oil to the de sired temperature in a period of .less than-five minutes. The oil is mixed with the reagent immediately after heating and immediately centrif- I ugally separated. One of the advantages of the present' process is that the mixing may be performed in a. closed mixing zone so that no substantial amount of air is present in the mixture. In the centrifugal above referred to the oil remains in the centrifuge not more than three minutes such that the oil is in contact with the relining reagent -for a period somewhat less. The

in less than ten minutes.

By the term animal and vegetable oilsl we mean oils derived from animal. and vegetable sources. such as glyceride oils, and intend to ern- 10 Having described our invention, We claim:

1. A process for the quick and continuousreflning of animal and vegetable oils containing free fatty acids which comprises the steps ofi mixing with said oil a refining reagent capable 5' of acting upon the impurities in said oil to form foots, separating the foots 'substantially as quickly as they are formed by subjecting the mixture to immediate centrifugal separation with the aid of heat su'icient to facilitate said separation, said 20 heat'being supplied by preheating at least one of the admixed materials before admixture with the other, the process being characterized by the avoidance of any substantial period of contact of the refining reagent with the oil after 25 the adrnixing thereof. v

2. The process as defined in claim 1 in which the heat is supplied by preheating the oil prior to its admixture with the refining reagent,

-3; The process' as defined in claim 1 in which 30 properly proportioned streams of the oil and reagent are contacted substantially as theyfenter the centrifugal.

4. A process forV the substantially simultaneous forming and separation of foots from rened oilsy which comprises the. steps of collidingV streams of a refining reagent capable of acting upon impurities in the eil to form foots and the oils, under super-atmospheric pressure, to effect substantially instantaneous formation of said foots and immediately separating said foots substantially as quickly as the same are formed by immediately subjecting the mixture to centrifu gal separation for continuously separating said foots from the oil, conditioning the mixture for said separation by' preheating one of said admixed materials before admixture with the other, the process thereby being characterized by the avoidance of any substantial period of contact of the refining reagent with the oil after the admixing thereof. l

5. The process as defined in claim 4 in which the oil is preheated to an emulsion breaking temperature.

6. The process as deflned'in claim 4 in which the oil is preheated to a temperature not sub-

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