USRE23680E - Purification of glyceride oils - Google Patents

Description

B. CLAYTON PURIFICATION OF GLYCERIDE OILS July 7, 1953 Re. 23,680

Original Filed April 21. 1943 .54 a J/ J x dz Jnmcwtom flezykzmin C'layiwz lax-2A4, 95,611 4m 3. WOT/P141146 seamed July 7, 1953 PURIFICATION OF GLYCERIDE OILS BenJamin Clayton, Pasadena, Calii'., assignor, by mesne assignments, to Benjamin Clayton, doing business as Refining, Unincorporated Original No. 2,412,251, dated December 10, 1946, Serial No. 483,953, April 21, 1943. Application for reissue October 7, 1952, Serial No. 313,620

23 Claims. (Cl. 260-425) Matter enclosed in heavy brackets II appears in the original patent but forms no part of this reissue specification; matter printed in italics indicates the additions made by reissue.

This invention relates to the purification of oil and more particularly to a process for the re-' moval of small amounts of impurities from glyceride oils, such as animal and vegetable oils, which oils are substantially free of fatty acids and gums.

It is frequently necessary to purify glyceride oils which are low in free fatty acid content, for example, oils having free fatty acid content below 25% and which are also low in materials commonly referred to as gums, namely, phosphatides, proteinaceous materials; resins, etc.v The impurities required to" be removed may be coloring matter or materials which impart to the oil a deleterious taste or odor. Or it may be desired to treat an oil which has naturally occurring impurities in very limited quantities.

-An example of a glyceride oil which requires color removal is a cottonseed oil which has been refined with non-saponifying alkalies such as soda ash or has been refined with insufficient caustic alkali to lower the color of the oil to the required extent. The employment of non-caustic alkali adequately removes the free fatty acid content and also removes substantially all of the shins but the resulting oil is usually of darker color than that desired. The losses resulting from the refining of vegetable oils in a continuous process using soda ash or other non-saponifying alkalies are much less than in processes in which si'iificient caustic alkali is employed in the first instance to not only remove fatty acids and gums from the oil but to produce a low colored. oil. It is. however, necessary to re-refine the oil using a caustic alkali or similar color reducing material to produce a low colored oil.

Cottonseed oils vary widely in their characteristics from year to year and in accordance with production areas. It has been found possible to re-refine certain types of cottonseed oil, after they have been refined by a continuous soda ash process, by using small amounts of relatively dilute caustic alkali in a continuous process to obtain a properly desolorized oil with exceedingly small losses. However, it has also been found that many and perhaps most cottonseed oils, are not capable of being re-refined with small amounts of relatively dilute caustic alkali. Such dilute alkali not only fails to reduce the color of the oil but produces difficultly separable emulsions which are not properly separated in a continuous centrifugal separator.

In accordance with the present invention, it has been found that emulsion difliculties may be obviated and an adequate reduction of the color 2 of the oil can be obtained by employing small amounts of relatively concentrated caustic soda, for example, concentrations between 20 and 50 Baum. The use of, such concentrated solutions, however, has heretofore been found impossible in continuous refining as strong caustic solutions cause the small amount of soap formed during the re-refining operation to be salted out of the caustic solution and to separate with the neutral oil in the centrifugal separator. By employing a strong caustic solution for color removal and then diluting the caustic-immediately before or during separation of the oil from the decolorizing reagent, soap and precipitated impurities, it has been found that the beneficial effects of the strong caustic solution can be obtained while separation difiiculties are obviated. Diificulties similar to those described above are encountered with various other oils which are low in free fatty acid and gum content and the employment of strong caustic solutions to precipitate or remove impurities from the oil, followed by dilution of the caustic solution during or just prior to separation, has also been found applicable in the treatment of such oils. I

It is therefore an object of the present inven tion to provide an improved process for removing impurities from glyceride oils which are low in free fatty acid and gum content.

Another object of the invention is to provide an improved process of removing small amounts of impurities from glyceride oils having low free fatty acid and gum content in which process strong caustic alkali solutions are employed but are diluted prior to the separation operation.

Another object of the invention is to provide a process of re-refining glyceride oils containing only a small amount of impurities in which refining losses are reduced.

A further object of the invention is to provide an improved processof eilectively remov ing impurities from glyceride oils which contain small amounts only of such impurities so as to overcome separation difiiculties.

A still further object of the invention is to provide an improved process of reducing the color of refined glyceride oils by chemical treatmentand with substantially no refining losses.

Other objects and advantages of the invention will appear in the following description of preferred embodiments thereof given with reference to the attached drawing in which:

Fig. l is a schematic diagram of an apparatus suitable for carrying out the present invention, and

i l 'ig. 2 is-a somewhat tic vertical sectional view through a centrifugal separator bowl,

particularly applicable for use in the present invention.

Referring to Fig. l, the process of the present invention is preferably carried out in apparatus in which an oil is treated with a reagent for prep cipitating the impurities and then delivered into a centrifugal separator I. for separation ofthe precipitated material or foots from the oil. The

.miltobetreatedmaybewithdrawnfromasourw 'ofsupplysh'ownasatankil bymeansofaproportioning pump it and delivered through a heatingcoil llofaheat exchange device lltoamixer II. The tank may be provided with a heating coil ll orsimilarheatingmeansformaintaining the oil in the tank ii in'iiuid condition in case oils or fats solid at ordinary temperatures are being treated. The reagent for precipitating impatent to Thurman 2,142,062 granted December .27. 1938. v

A thorough mixtureof the reagent and oil produced in the mixer II is then passed through a heating coil ll of the heat exchanger 24 and delivered into the centrifugal "through the pipe 28. A diluting agent for thereagent in the mixture entering the centrifugal it may be withdrawn from tank 21 by means of a proportioning pump ll and delivered through the coil II of the heat exchanger Ii and a pipe 32 so as to be admixed with the oil reagent mixture at the entrance of the centrifugal separator II. The diluting agent which, in most instances, is water,

dilutes the mixture so that soap formed in the reaction is retained in solution in the aqueous phase or heavy eiiiuent and discharged through the spout it into a receiver it while the purified oil is discharged through a spout it into a receiver 31. The proportioning pumps I2, I! and It may be drivenby a variable speed electric motor is connected directly to the oil pump it and through variable speed devices II and be-- tween the motor 18 and the proportioning pumps is and II, respectively. Other types of proportioning apparatus may, however, be employed, for example, that shown in patent to Thurman above referred.

Instead of delivering the diluting agent into the oil-reagent mixture as the mixture enters the centrifugal separator, it is preferred to admit the diluting agent with the heavy eiiiuent in the centrifugal after separation has been largely accomplished. This avoids substantially all contact between the oil and a dilute reagent so that emulsion. difiiculties are entirely overcome. A suitable type of centrifugal separator for accomplishing this operation is shown in Fig. 2. Such a separator may include a bowl 42 mounted upon a shaft 43 for rotation at high speed and may and outwardly into the lower portionof the bowl. The separation none of the bowl may be provided with a plurality of conical baiiie members II which are apertured at I! adjacent the neutral zone of separation. Material to be separated fiows upwardly through the apertures II, the light eiliuent comprising the oil flowing inwardly in the bowl and being discharged through the outlet port II. The heavier materials comprising to the lower periphery of the bowl. The diluting agent admixes with the heavy eiiluent to dilute the same and cause any soap present in the mixture to be retained in solution or dissolved in the I heavy eiiluent so as to be discharged therewith 1 through the port ll.

In treatment of oils such as those contemplated in the present invention, namely, oils which are low in free fatty acid and gum content, the heavy efiiuent is predominantly an aqueous solution of the reagent even before dilution with the diluting agent. This aqueous solution contains excess reagent and small amounts of soap. Attempts to employ dilute precipitating agents result not only in ineffective removal of impurities from the oil but in the formation 'of tight emulsions which,

heavy effluent through the port ll, resulting in high refininglosses. In many instances also the iilrlipurities are not adequately removed from the o .By employing strong precipitating reagents such as caustic soda solutions ranging between 20to 50 Baum, such emulsions are not encountered and in accordance with the present inven- ,tion refining losses are reduced to avery low also include an outlet port M for the light eiliuent and an outlet 48 for the heavy eifiuent. The oil and reagent mixture containing precipitated impurities, as well as a small amount of soap, is delivered into the centrifugal through a stationary pipe 41 and then delivered into a tubular inner bowl member 48 by means of a distributor II. The inner bowl member I. divides the separation zone of the bowl from the inlet portion thereof and directs the incoming mixture downward y.

- v This difiiculty can be overcome by diluting the I figure. However, small amounts of soap are formed by reaction of thecaustic alkali with residual free fatty acids in the oil or by reaction with the oil itself and this soap is grained out of the heavy eiiluent in the centrifugal. Three layers of strata tend to be built up in the centrifugal bowl: an inner oil layer, an intermediate soap layer, and an outer aqueous layer. These layers are not definitely defined and any attempt to adjust the centrifugal to separate the soap with the aqueous layer causes high refining losses whereas failure to separate the soap with the aqueous layer produces an impure oil requiring extensive further purification treatment.

mixture just prior to centrifugal separation, for example, by'introduc'ing a diluting agent such as water into the mixture entering the centrifugal but a slight amount of difiicultly separable emulsion may be formed due to contact betwee the oil and diluted reagent and it is found that the precipitation of impurities such as coloring matter is not as effective as is the case when separation is substantially complete prior to dilution of the mixture. In the centrifugal separator shown in Fig. 2, diluting of the heavy efliuent after complete or substantially complete separation thereof from the oil causes the soap layer above referred to, to remain in solution or go into solution in the aqueous layer so that it separates cleanly from the oil.

Reaction of color impurities, with a precipitatin'g reagent such as caustic soda usually takes place more rapidly and more completely at low temperatures, for example, temperatures between 70 and 100 F. The oil in the tank ll of Fig. 1 is therefore preferably maintained between these temperatures except in cases where the oil is delivered to the tankfrom a prior refining or similar process at a high temperature or the oil or fat requires heating to a higher temperature to render the same fluid. The heat exchanger I4 is therefore not employed when the oil is at the correct temperature for admixture with the precipitating reagent but may be employed to either cool or heat the oil in In general the temperature of the re-' reagent are thus delivered to the mixer l5 by perature of the mixture to that required for effective centrifugal separation. These temperatures willusually range between 120 and 180 F., depending upon the type of oil being treated, the impurities desired to be removed and. the melting temperature of the oil. The oils being treated will ordinarily contain not more than approximately 25% free fatty acid and only slight amounts or traces of gums. The preferred reagent is a concentrated aqueous solution of caustic soda, for example, solutions rang ing from 20 Baum up to Baum. A conslderable excess of caustic soda over that required to neutralize any free fatty acids present is usually employed. Thus the amounts of caustic solution will usually range between approximately and 4%, the quantity most generally used being in the neighborhood of 2%.

As stated above, the temperature of mixing is preferably between and F. although for removing certain types of impurities this temperature may be as high as to F. The temperature of separation will, however, usually range between 120 and F., although this temperature may at times be as low as 100 F.

Water is the preferred diluting agent and the amount of water will ordinarily range between approximately- 2.5 and ten times the amount of reagent employed. In general, it has been found desirable to reduce the concentration of the excess reagent in the centrifugal to at least 8 Baum although in some instances higher concentrations up to 10 or 12 Baum have been found operable and lower concentrations ranging down to approximately 4" Baum may sometimes be found advantageous in the centrifugal separator. In any event, the amount of. water or other diluting agent employed in the centrifugal separator should be sufficient to cause the soap to separate in solution or in dispersed form in the aqueous phase. Also the temperature of the diluting agent should in general, be at least as high as the temperature of separation and preferably is somewhat higher. Thus the temperature of the diluting agent will range between approximately 100 and 200 F. I

, The material discharged from the centrifuge is in most cases largely water contaihinmexcess caustic soda and a small amount of soap. In general the amount of soap will not exceed 2% and is usually between 2% and 1% of the material discharged. By employing strong'caustic alkali solutions and diluting the same just prior to or during separation, the losses rarely exceed .2% and usually do not exceed .15% whereas the losses when employing equivalent amounts of dilute caustic soda in the first instance may run as'high as 2% or higher. It has been found that even increasing the amount of 'caustic solution does not measurably increase the losses in the process provided suillcient diluting agent is'introduced to carry the concentrationof the reagent in the centrifugal below that at which soap tends to separate with the oil.

While the present process is particularly adaptable to the re-reflning of cottonseed oil: previously refined by a continuous soda ash process, such as oil refined by the processes disclosed in my Patents No. 2,249,701, and No. 2,249,702, granted July 15, 1941, certain vegetable or animal oils in the form they are recovered from the raw material are naturally low in free fatty acids and gums and the present process may be advantageously employed for removal of small amounts of impurities therefrom. Also substantially completely refined oils intended for edible purposes are frequently processed under conditions which somewhat increase their free fatty acid content and impart deleterious tastes or odors thereto. Such oils or fats are advantageously subjected to the process of the present invention Sfor removal of the small amounts of impurities contained therein. Furthermore, certain light colored oils, such as-corn oil, requiring no treatment for color reduction after refining in continuous soda ash processes, are benefited by treatment in accordance with the present invention as in some instances such oils are extremely difiicult to'wash without excessive refining losses. It has been found that treatment in accordance with present invention, it is also possible to employ sodium peroxide which liberates caustic soda while admixed with water and should be used in sufficient amounts to produce the concentration of caustic soda contemplated in the. present invention. The sodium peroxide additionally liberates oxygen which materially assists in removing coloring matter and other impurities from the oil. An advantageous operation is to employ a reagent consisting predominantly of caustic soda-but containing a small amount of -so dium' peroxide or other oxygen liberating material. Other equivalent alkali metal compounds such as potassium compounds are also suitable.

This application is an application for reissue of my Patent No. 2,412,251, granted December 10, 1946 on an application Serial No. 483,953 filed April 21, 1943 which application is a continuation-in-part of my copending application Serial No. 398,480, filed June 17, 1941, which is in turn a division of Serial No. 296,885, filed September 26, 1939, nowvPatent No. 2,249,701, granted July 15, 1941.

While I have disclosed the preferred embodiment of my invention, it is understood that the details thereof may be varied within the scope of the following claims.

I claim:

l. Theprocess of purifying a glyceride oil which is low in free fatty acid and gum content and contains small amounts of other impurities, which process comprises, ixin with said all a caustic soda solution having a concentration between approximately 20 and 50 as, said reagent being added in suflicient amount to precipitate said impurities and prevent the formation of an emulsion in said oil and'said reagent, whereby the resulting mixture will separate into an oil layer, a soap layer, and anaqueous layer containing said impurities when subjected to centrifugal separation, subjecting the resulting mixture to centrifugal separation and diluting said mixture prior to complete separation in the centrifugal to lower of the concentration of the aqueous layer to between appl'oximately i and 86., whereby said soap discharges with said aqueous layer from said centrifugal.

2. The process of purifying a glyceride oil which is low in free fatty acid and gum content and 4. The process of purifyinga glyceride oil which is low in free fatty acid and gum content and contains small amounts of other impurities, which process mixing with said 011 a caustic alkali solution having a concentration between approximately and 50 .se. to precipitate said impurities and form a small amount of soap,

" aqueous phase and said soap have been at least partially separated from said oil. to reduce the concentration of said aqueous phase to at least 8" B6. whereby said soap discharges from said centrifugal with said-aqueous phase.

.' 5. The process of purifyins a glyceride oil which is low in free fatty acids and gumcontent.

- which process comprises mixing with said all a proximately 20 and B., said reagent being added in 'suflicient amount to precipitate said impurities and prevent the formation of an emulsion of said oil and said reagent, whereby the resulting mixture will'separate into an oil layer, a soap layer, and an aqueous layer containing said impurities when subjected to centrifugal separation, subjecting the resulting mixture to centrifugal separation and diluting said reagent prior to complete separation in the centrifugal so as to produce a concentration in said aqueous layer not substantially greater than 8 36., whereby said soap discharges with said aqueous layer from said centrifugal.

3, The process of purifying a glyceride oil which is low in free fatty acid and gum content and contains small amounts of other. impurities; which process'comprises, mixing with said oil a caustic alkali solution having a concentration between approximately 20 and 50 B. to precipitate said approximately 4 and 10 B. whereby said soapdischarges from said centrifugal with said aqueous phase.

caustic alkali solution having a concentration between approximately 20 and 50 as. to precipitate said impurities and to form a small amount of soap, and of suiiicient concentration to stratify the mixture into an oil phase, a soap phase and an aqueous phase when the same is subjected to centrifugal separation, thus interferwith such separation, subjecting the resulting duced to between approximately 4 and 10 36.

-'l. The process of purifying vegetable and ani- -mal oils containing impurities, including free fatty acids, which comprises, mixing therewith an alkaline refining reagent capable of reacting with said impurities to precipitate the same and produce soap, said reagent being added in sufiiciently high concentration to produces. stratifled mixture including an oil phase, a soap phase, and an'a'queous phase when the mixture is subjected to centrifugal separation, thus interfering with said separation, reducing concentration by adding an aqueous diluent to said mixture in sufflcient quantity to overcome such stratiflcation. whereby to permit said soap to be discharged with said aqueous layer, and centrifugally separating the thus conditioned mixture.

8. Theprocess as defined in claim 7 in which the dilution'produces a separation of the heavier efliuent having a Baum between approximately 4 and 10.

9'. The process as defined in claim 7 in which the dilution is effected after the soap has been at least partially separated from the chin the centrifugal apparatus.

-- 10. The process as defined in claim 7 in which the dilution occurs prior tocompleteseparation in the centrifugal.

11. The process as defined in claim 7 in which the impurities separated from the oil in the centrifugal are diluted in the centrifugal after substanthl-separation from the oil.

. 12. A re-reiining process for oils of low impurity content which process comprises the treat-' aqueous phase when the mixture is subjected to centrifugal separation. introducing water to laid mixture "in sumcient quantity to convert the mixture from its thus stratifled condition to a lullciently non-stratifled condition to permit the soapstock to be discharged with the aqueous phase, and cen-triiugally separating the thus conditioned mixture.

13. The process as defined in claim 12 in which the water is introduced at the point of separation in the centrifugal.

14. The process as defined in claim 7 in which the mixture being separated is at a temperature in excess of 100 F.

j 15. The process as defined in claim 7 in which theoil is at a relatively low temperature when mixed with the refining reagent and prior *to separation the temperature of the mixture is raised to that required for eflective centrifugal separation.

16. The process as defined in claim 7 in which the amount of alkali refining reagent is between approximately 55 and 4% of the oil.

17. The process as defined in claim 7 in which gum content of the oil is suihciently low to cause separation d iflculties.

18. The process as defined in claim 7 in which the gum content of the Oil is sufllciently low to cause separation dimculties, the temperature of the mixture being separated is in excess of 100 F, and sufficiently high for eflective centrifugal separation and the quantity of aqueous diluent is sufficient to reduce the concentration of the excess refining reagent in the separated aqueous layer to at least 8' Bawme.

19. The process as defined in claim 7 in which the refining reagent has a concentration between approximately 20"v and 50 Baume.

V10 20. The process as defined in claim 19 in which the quantity of aqueous diluent is suihcient to reduce the concentration of the separated aqueous layer to between approximately 4 and 10 Baume.

21. The P ocess as defined in claim 19 in which the amount of aqueous diluent is sumcient to cause the aqueous lailer discharged from the centrifugal separation to be largely water.

22. The process of purifying vegetable and animal oils, low in gum content and containing im-' purities, including free fatty acids, which comprises, mixing therewith an alkaline refining reagent capable of reacting with said impurities to precipitate the same and produce soap, said reagent being added in sufliciently high concentration to produce a stratified mixture including an oil phase, soap phase, and an aqueous phase when the mixture is subjected to centrifugal separation, thus interfering with said separation, reducing concentration by adding an aqueou diluent to said mixture in sufilcient quantity to overcome such stratification, said quantity of aqueous diluent reducing the concentration of the excess of alkaline reagent to at least 8 Baume, whereby to permit said soap to be discharged with said aqueous layer, and centrifugally separating the thus conditioned mixture.

23. The process as defined in claim 22, in which the temperature of the conditioned mixture during centrifugal separation is in excess of 100 F.

BENJADAIN CLAYTON.

UNITED STATES PATENTS Name Date Thurman Dec. 24, 1940 patent Number

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