US2225557A - Process of refining vegetable oils - Google Patents

Description

Dec. 17, 1940. H. M. DUVALL JR PROCESS OF REFINING VEGETABLE OILS Filed June 25, 1938 Patented Dec. 11, 1949 UNITED muss,

PATENT OFFICE 2,225,557 I PROCESS or Rename VEGETABLE OILS Howard -M, Duvall, Jr Jackson Heights, N. Y.,

assignor to Refining, Inc., Reno, Nev., a corporation of Nevada Y, Application June 23, 1 938,'ScrialNo.215,463 Y 9 qlaims. r01; 260-425) This invention relates to a process ofr efining vegetable and animal oils-and more particularly to a process in which at least a portion of .the gums are removed prior to neutralization.

An object of the invention is to provide a process of refining vegetable oils in which effective separation of soap stock from the oil is accomplished after at least a portion of the minor constituents or gums has been removed from thejoil;

In the alkali refining of so-called degummed oils," it has been found extremely difiicult, if not impossible, to consistently secure an effective separation of the soap-stock from the oil. If the conventional batch method of alkali refining oils is employed, the soap stock fractionates, that is, when the soap stock settles, a liquor which is predominantly water separates from the soap thereof as the lower or nigre layer, the soap in'admixture with a large proportion'of the neutral oil forms an intermediate layer, and the remainderor the neutral oil forms the upper layer. A clean separation of soap from neutral oil is therefore not possible. This has prevented the successful refining of degummed crude oil by the batch method. Substantially the same thing many times happens in continuous refining. The nigre along with some of the soap discharges from the of the soap stockabove referred toisxprevented,

and a clean separation can be effected; Apparently the gums or minor constituents, contained in the original crude act as'emulsifying agents to prevent the fractionating, of the soap stock and all ofthe soap stock 'is discharged as the heavy efliuent, providing a clean separation between the soap stock and the oil." Furthermore, an excessive amount of minor constituents in the oil being refined causes an excessive entrainment of neutral oil in the soap stock. By the present invention the amount of minor constituents, in the mixture subjected to alkali refining, may. be adjusted to the optimum amount which will cause effective separation with a minimum amount of oil entrained in the soap stock.

It is, therefore, an object of the present invention to provide a process of refining degummed oils in which a sufiicient amount of undegummed oil is added to, the degummed oil to prevent stratification of the soap stock.

Another object .of the invention is to provide a'process of refining vegetable oils in which oil is first degummed to recover phosphatides and other minor constituents and then mixed with a portion of undegummed oil and subjected to alkali refining to remove the free fatty acids thereof. I I

A further object of the invention is to provide a process of refining degummed oils in which the oil is refined in admixture with a portion of undegummed oils in order to effect continuous centrifugal separation of the soap stock from the oil. A still further object of the invention is to provide a process in which the amount of gums in the oil subjected to alkali refining is adjusted to provide an effective separation of soap stock from the oil with a minimum of oilentrained in the soap stock.

Other objects and advantages of the invention will appear in the following description of the .preferred process given in conjunction with the attached drawing, which is a diagrammatic view of an apparatus suitablefor carrying out a continuous process in which the oil is first degummed andlthen admixed with a portion of undegummed oil and subjected to alkali refining.

Referring to the drawing, a source of supply of crude vegetable oil is shown as a tank It); a source of supply of a gum precipitating reagent is shown as a tank II; and a source of supply of an alkali refining reagent is shown as a tank l2. Oil. may be withdrawn from the tank ill by a pump I3 and delivered through a meter l4 in the "pipedii and thence through one or more heat ex- .4 change. devices 16 to'a mixing device H. The heatjexchange' devices l6 preferably include coils I 8 through-which the oil is passed and casings lflthr'ough which any desired heating medium maybe circulated by the pipes 20 and 2|. The

heat exchange devices iii are employed to bring theoil to a mixing temperature suitable for the particular oil being treated.

The tank II for the precipitating reagent may include "a heating coil 22 in: order to bring the precipitating reagent to a temperature suitable for mixing the same with the oil. The precipitating reagent may be withdrawn from the tank I i by means of a pump 23 and delivered through a meter 24 to'the mixing device H. The mixing device I! may comprise any suitable type of flow mixer which is capable of producing an intense mixing action between the oil and reagent, for example a closed mechanical agitator.

The mixture .of oil, reagent and precipitated gums is then preferably passed through one or more heat exchange devices 25, which may be entirely similar to the heating devices IE, to a continuous centrifugal separator 26. Precipitated gums including valuable phosphatides and other minor constituents are continuously discharged from centrifugal 26 through a spout 21 into a receiver 28. These materials, particularly from vegetable oils, form a valuable byproduct and may be further purified to recover substantially pure phosphatides or may beemployed as such in their crude state as phosphatidic materials.

The degummed oil is discharged from centrifugal 26 through a spout 29 into a tank 30 which is preferably closed except for a vent 3| The tank 30 may be relatively small and merely serves as a reservoir to compensate for any slight differences in flow between different portions of the process. The degummed oil may be withdrawn from the tank 30 by means of a pump 32 and delivered through. a meter 33 and a heat exchange device 34, similar to the heat exchange device l6, and a pipe 35 to any suitable type of flow miser 35' at the junction of the pipe 35 with a pipe 36 which delivers a portion of undegummed oil into the pipe 35. The pipe 36 may receive undegummed oil from the pump l3 Val ter 4| to the mixer 39. The refining reagent in the tank l2 may be brought to any desired predetermined temperature suitable for mixing the same with the oil to be treated by means of a heating coil 43 positioned in the tank l2. The

mixer 39 may also be any suitable type of flow mixer. Since the alkali refining reagent readily mixes with the oil, the intensity of mixing in the mixer 39 may not be as great as that in the mixer i1. Soap stockis formed substantially as soon as the refining reagent contacts the, oil in the mixer 39 and a mixture of soap stock and oil is passed through a heat exchange device 44, similar to the heat exchange device I6, and thence to a continuous centrifugal separator 45. Soap stock is discharged from the centrifugal 45 as the heavy effluent through a spout 41 into a receiver 48, and refined oil substantially free of soap stock is discharged through the spout 48 into a receiver 49.

In the apparatus illustrated, proportioning has been shown as being effected by pumps and meters, but it is understood that any suitable type of proportioning apparatus may be employed. The centrifugal separators 26 and 45 are preferably of the heated type disclosed in the patent to Benjamin Clayton, No. 2,100,277, issued November 23, 1937, since by the use of such heated centrifugals continuous discharge of the heavy effluent can be secured over extended lengths of time without cleaning of the centrifugal.

The temperature at which the oil and degumming reagent are delivered to the mixer I! will depend upon the nature of the oil being treated. Certain oils respond to treatment with mixing at relatively high temperatures, in which case the heating devices l9 may be employed to bring The mixture of degummed the oil to a predetermined temperature suitable for the particular oil being treated. with other amount of gums, also depending upon the na-' ture of the 011 being treated. In the case of either preheating, i. e., before mixing, or subse quent heating, any required number of heat exchange devices 25. may be employed to secure .the correct time of treatment between mixing and separation. This time usually is found to lie between 5 and 15 minutes, but with exceptional oils may be less than 5 minutes or, in some cases, as long as 30 minutes. In general, the higher the temperature of treatment and the smaller the amount of precipitating reagent employed, the shorter will be the time between mixing and separation to effect maximum separation of gums from a particular oil. Centrifugal separation of the gums from the oil is usually most efficient at temperatures between and F. Thus the heat exchange devices may be employed to either heat or cool the mixture in order to secure the optimum temperature of separation.

The degumming reagent'may be water alone. but is preferably a relatively concentrated solution of anelectrolyte. Such concentrated solutions may be neutral or slightly acid or slightly alkaline, but strongly acid or alkaline solutions should be avoided, since they will attack both neutral oiland the'valuable constituents of the gums. lutions may be concentrated solutions of neutral salts, such as sodium chlorlde,'with very slight Such slightly acid or alkaline soamounts of strong acids or alkalies added therei to, in which case the pH of the solution should not vary widely from neutrality. Preferably a concentrated solution of a very weak acid is employed and the preferred reagent is approximately a l0% solution of boric acid. This solution. has a pH of approximately 3 and not only precipitates more minor constituents than water or neutral concentrated solutions, but in addition preserves the discharged gums from fermentation or putrefactlon even after the boric acid has been substantially removed therefrom. The degumming reagent should be employed in sufficientamount to precipitate the minor constituents and wet the oil, but excessive amounts will cause excessive entrainment of oil with the gums. In most cases 2% is sufflcient but the amount will vary between 1 and 10% with different oils.

The heat exchange device 34 may be employed to either heat or cool the degummed oil prior to alkali refining in order to bring the oil to a pre determined temperature for mixing, found most. suitable for the particular oil being treated; Ash

in the case of the degumming step, the best temperature for mixing with the alkali refining reagent will vary with the nature of the oil being treated, but will usually lie between 70 and 160 F. The lower temperatures in this range are employed if the heat exchange device 44 is emdevice 44 may be employed to provide time of treatment for color removal as well as for increasing or decreasing the temperature of the mixture of oil and soap stock to bring it to the temperature found most suitable for separation in the centrifugal separator 45; This temperature must be sufliciently high that the emulsion which tends to form between the oil and soap stock is broken and will also vary with the particular nature of the oil being treated, but will ordinarily lie between 120 and 160 F.

The refining reagent may be employed in concentrations and amounts conforming to the recognized practices in the art of alkali refining vegetable oils. amounts and concentration of the refining solution, which is ordinarily a caustic soda solution; will depend upon the freefatty acid content of the oil as well as the type of oil being refined.

The amount of crude or undegummed oil added to the degummed oil in order to secure effective separation of the soap stock during the refining operation will also vary with the nature of the oil being treated. The amount of gums necessarily present in the mixture of oils to cause effective separation of soap stock will usually increase with the free fatty acid content of the oils. The higher the free fatty acid content, the. more soap which is produced in the alkallrefining operation, and, in general, the greater amount of soap produced, the greater the amount of gums which are necessary to prevent stratification.

But other factors, such as the type of free fatty high free fatty acid content usually has a high gum content, but this is not invariable. Thus no definite proportions of crude oil to be added or gum contents in the mixture of oil which are applicable to all oils can be given, but the correct amount of crude or undegummed oil to be added to a particular oil can easily be determined in running .the process. With oils that are extremelyv high in gums or minor constituents, only a small portion of the undegummed oil usually need be added to the degummed oil for the effectiveseparation. As the amount of minor constituents in the crude oil becomes less, a greater amount. of the crude oil should usually be added to the degummed 011. For example, for cottonseed oils running extremely high in minor constituents, say3% to 4%, only approximately 10% of crude oil usually need be mixed with the degummed oil. For oils running from 1% to il /2% of minor constituents, it may be necessary to add suflicient crude oil to form a mixture of two-thirds degummed oil and one-third crude oil. n the other hand, for exceptional oils which run considerably less than 1% of minor constituents, it may at times be necessary to form a mixture containing as high as 90% of the untreated or crude oil.

The present process is particularly adapted to the refining of vegetable oils such as, for example, cottonseed, soya bean, corn, sesame, cocoanut, and peanut oils, but in certain cases is found to be applicable to animal oils. Thus the presentinvention provides a process of refining degummed oil'in which the soap stock may be separated cleanly from the neutral oil. As was stated above, the alkali refining of degummed oil has heretofore been impractical by the batch method and extremely difficult even with improved continuous processes. In addition, the present process not only provides for the recovery of valuable byproducts which would be damaged or destroyed if the crude undegummed oil were directly alkali refined, but also markedly reduces the refining losses over even improved continuous processes of directly refining the crude oil and over the total refining losses occasioned by first degumming the oil and then attempting to alkali refine the. degummed oil. For example, a crude oil containing 1% or more of minor constituents and refined directly with alkali, without degumming-frequently results in the production of soap stock containing from to of neutral oil. This same crude cottonseed oil, when two-thirds of it is degummed with water or boric acid and then the remaining one-third of the crude mixed. with the degummed twothirds and the mixture alkali refined by the continuous method, the free oil in the soap stock from the alkali refining will run as low as 3% to 5% of free oil. Since usually not more than 1% of free 011 is lost in the degumming operation, it will be seen that a substantial saving in refining losses is accomplished by the present process. It will further be seen that the present process allows the percentage of minor constitdetails thereof 'maybe varied within the scope of the following claims.

I claim as my invention:

1 uents in the oil to be adjusted to that which will 1. The process of refining animal and vege table oils containing gums, which, comprises treating said oil to remove the major portion of the gums therefrom to, form adegummed oil, adding an amount of the original undegummed oil to said degummed oil sufficient to bring the amount of gums in the resultant oil to a predetermined minimum amount which will cause effectlve separation of soap stock from neutral oil cluding phosphatides, which comprises, mixing agum-precipitating reagent with said oil, separating the precipitated gums from said oil, thereafter m ng said oilwith suflicient undegummed oil to cause effective separation of soap stock from the oil during subsequent alkali refining, thereafter mixing an alkali refining reagent with said oil. to form a mixture of oil and soap stock and separating the said soap stock from said oil.

4. The process of refining vegetable oils from which minor constituents including phosphatides have been separated and recovered, which comprises, mixing said oil with a similar oil containing gums, thereafter adding an alkali refining reagent to said oil to form, a mixture of oil and soap stock including said gums, and separating said soap stockfrom said oil. f

5. In the process of alkali refining degummed oil, in which an alkali refining reagent is added to said oil and the resulting soap stock sepa- I rated from said oil, the improvement which comprises adding sufiicient oil containing gums to said degummed oil during said process to cause said soap stock to" contain sufllcient gums to prevent stratiflcation thereof, whereby said soap' stock can be cleanly separated from said oil.

6. In a process of alkali refining degummed vegetable oils containing free fatty acids, said process including adding an alkali refining reagent to said oil to neutralize said free fatty acids to thus form a mixture of oil and soap stock and separating the said soap stock from said oil, the improvement which comprises adding to said oil during said process suflicient oil containing gums to cause said soap stock to separate cleanly from the refined oil.

7. A process of alkali refining animal and vegetable oils containing gums and free fatty acids. which comprises, adding a similar oil having a different gum content to adjust the gum content of said oil to an amount which will cause the soap stock produced in said process to'separate cleanly from the refined oil with a minimum entrainment of neutral oil in said soap stock, adding an alkaline refining reagent to said oil in which the gum content has been adjusted in order to form a mixture of soap stock and refined oil, and thereafter separating said refined oil from said soap stock.

8. In the process of refining animal and vegetable oils which includes the steps of adding an alkali refining reagent to said oil and separating the resulting soap stock from said 011, the improvement which comprises adding a similar oil having a difierent gum content to adjust the gum content of said oil during said process to an amount which will cause clean separation of the,

soap stock from said oil at a minimum entrainment of oil in the said soap stock.

9. A continuous process of refining animal and vegetable oils, which comprises, continuously mixin a degumming reagent with said oil in an amo t sufilcient to cause precipitation of said gums and wet said oil, thereafter continuously centrifugally separating precipitated gums from said oil at a temperature which facilitates such separation, continuously mixing sufiicient undegummed oil with the separated oil to adjust the gum content of the resulting mixture to a predetermined percentage which will cause efiective separation of soap stock from refined oil with a minimum oil entrainment in said soap stock when the mixture of oil is subjected to alkali refining, continuously mixing an alkali refining reagent with said mixture of oils, and thereafter continuously centrifugally separating the resulting soap stock from refined oil at an emulsion breaking temperature.

HOWARD M. DUvALL, James.

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