US2239747A - Process of refining oil - Google Patents

Description

April 29,1941.

RocEss oF REFINING on.

Filed Feb. 25, 1938 2 Sheets-Sheet 1 Patented .Apr. 29, 1941 PROCESS F REFINING OIL .Benjamin B. Thurman, Bronxville, N. Y.. assigner to Refining, Inc., Nevada Reno, Nev., a corporation of vApplication Februsryzs, 193s, seal No. 192,654

11 claim.v (ci. zoo-425) This invention relates to a process of refining oil, and more particularly to a process for alkali refining animal and vegetable oils. Y

Animal and vegetable oils have been conventionally rened 'by mixing therewith a caustic alkali -solution of a concentration and in an' amount determined from long experience in reflning such oils in order to form soap stock which was allowed to settle from the oil. This process was carried on in large open kettles often holding as much as sixty thousand pounds of oil. The oil was first placed in the kettle and the alkali then added in sufficient amounts to neutralize the free fatty acids of the oil and provide a large excess for reaction with colorimpurities and for forming a soap stock which would effectively settle from the oil. The addition ofV the alkali to the oil was performed at relatively low temperatures, i. e., 70 to 80 F., as the renner had learned from experience that preheating a large body of the oil tended to set the colors therein,

' rendering them difficult or impossible to be removed in the refining process or subsequently. 'I'he oil and caustic mixture was vigorously agitated until a so-called "pin brea was obtained, indicating neutralization of the free fatty acids. The entire mixture was then heated by any suitable means, such as steam coils positioned in the kettle, and the rate of agitation reduced. Heating and slow agitation was continued until a break was produced, at which time agitation and heating were discontinued and the resulting soap stock allowed to settle from the oil. The oil refining operations, but if agitation were continued inl order to keepthelsoap stock from stratifying into large masses which could not be handled by the centrifuge, a major portion of the soap stock was broken up and beaten back into 4the oil until centrifugal devices were ineffective to separate the soap stock from the oil.

In accordance with the present invention, it has been found that, by employing a much smaller excess, a soap stock is formed which is not f broken up or beaten back into the oil by conwas then drawn off, and further processed, for

example by washing and vacuum drying, or clay treatment, to remove residual soap stock, alkali and water, and then, if desired, was subjected to bleaching and deodorization.

In order to obtain good color reduction and form a soap stock which would readily settle `from the oil without excessive entrainment of oil, the rener found it necessary to use a large excess of alkali. This large excess invariably caused saponification of substantial amounts of neutral oil, but was considered necessary, .as

y above stated, for color reduction and the formation of a readily settlea'ble soap stock. Because of the large excess and the resulting type of soap stock formed, it was necessary to discontinue agitationl as soon as the break.had occurred in order to prevent breaking up the particles of soap stock and beating them back into the oil, such that an inseparable emulsion would be formed. Attempts had been made to centrifugally separate the oil from the soap stock formed in such tinued agitation after the break and yet color reduction can be accomplished by maintaining the mixture in a heated condition and agitating the same after the break. 'I'his can be accomplished without excessive saponiiication of the neutral oil because of the small excess. The resulting soap stock may be maintained in substantial even distribution bythe continued agitation, and the resulting mixture of oil and soap stock can be centrifugally separated to produce a relatively clean oil. Such centrifugal separation markedly reduces the amount of oil en- Vtrained in the soap stock over the conventional batch settling step', such that the losses incurred in the process of the present invention are much less than those of the conventional "batch rening process. It is, therefore, an object of the invention to provide a process of refining vegetable and animal oils in which the soap stock is centrifugally separated from the oil and a smaller excess than that conventionally employed is utilized.

Another object of the invention is to provide a process of refining vegetable and animal oils in which the Aoil and refining reagent may be mixed in existing apparatus and the resulting soap stock centrifugally separated from the oil. A further object of the invention is to provide a process of refining animal and vegetable oils in which thealkali employed in conventional processes is .markedly reduced in order to prevent reemul'sification of the soap stock under continued agitation.

A still further object of the invention is to provide a pr'o'cess of refining animal and vegetable oils in which the oil'and alkali may be mixed in relatively large quantities and the resulting soap stock centrifugally separated from the oil.

Other objects and advantages of the` inventionl will appear in the following description thereof made in connection with the attached drawings, of which:

Figure 1 is a diagrammatic view of an apparatus suitable for carrying out the invention; and

Figure 2 is a similar view of an apparatus suitl able for carrying out a modified process.

Referring to the drawings, and more particularly to Figure l, 8 and 9 indicate supply tanks for oil and refining reagent respectively; I and II indicate mixing and separation conditioning devices; I2 indicates a pump for delivering a. mixlture of oil and soap stock to-a centrifugal separating system indicated generally at I3,

The mixing and conditioning devices I0 and il may be similar to the kettles employed in the conventional batch refining of oil and may each include a casing il, an agitator I5 rotated from any suitable source of power by a pulley I6, and

a heating coil II. Provision is madefor introducing oil and alkali into the mixers il and II, for example by pipes I8` and I9 respectively. The oil can be heated to a owable condition in the tank 8 by a heating coil I8' anda similar coil i9 can be provided in the tank 9 for bringing the rening reagent to a desired temperature. One

of the mixers I0 and Il can be employed for forming a'mixture of oil and alkali while a similar mixture is being Withdrawn from the other mixer and delivered by rthe pump I2 to the centrifugal separating system I3. The oil can be withdrawn from the mixer III through a pipe provided with a valve 2I and from the mixer II through a pipe 22 provided with a valve 23. The pipes 20 and 22 join with a common pipe 24 at 25 so that, by opening one of .the valves 2I and 23 and closing the other, the pump I2 will deliver the mixture'through a pipe 26 for distribution to the centrifugal separators 2T, 2l and 29, all of which can be employed simultaneously to increase the capacity of the refining system. Each of the centrifugals is provided with a. spout through which the oil is discharged as the lighter emuent into funnels 3l, all connected to a common pipe 32, through which the oil may be delivered to conventional steps, such as washing and vacuum drying or clay treatment for removing residual alkali, soap stock and water. Each of the centrifugals may also be provided with a spout 33 through which the soap stock is discharged as the heavy eiiluent into any suitable receptacles 3|.

The centrifugal separators may be of any type capable of separating soap stock from oil and are preferably of the heated type disclosed :in my Patent No. 2,100,276.

In carrying out the process of the present invention, a quantity of oil to be refined may be introduced'intoone of the mixing devices, such as the device I0. The devices Id and II may be ofextremely large capacity, if desired, such as the sixty thousand pound kettles above referred to, but are preferably of smaller capacity, for

example, from a few hundred pounds up toeight or ten thousand pounds capacity. When introduced, the oil is preferably at approximately ordinary room temperature, that is, between '10 and 80 F., but this temperature, with various oils, may range between and 90 F.. Also, the

refining reagent is preferably within suchrange of temperatures so that mixing is accomplished within such range. If the oil is not at the desired temperature, the heating coil I1 may be employed to raise the temperature. of the oil to that desired. As stated before, it is imdesirable to bring a large body of oil to an elevated tempera.-

ture much above those above mentioned before adding alkali, as colors are thereby set in the cil, particularly in the case of cottonseed oil.

After the oil is introduced into the mixer Ill',4 vigorous agitation is started by rotating the agitator I5 and the correct amount of alkali solution, lpreferably caustic soda, is run in through the pipe I9. While the agitation should be vigorous in order to promptly mix the alkali solution with the oil, and at all times maintain a substantially uniform mix-ture thereof, it should not be sufiicient to cause any substantial amount of air to be beaten into the mixture. It is also possible to simultaneously add the oil and reagent while running' the agitator I5 in order to mix the materials as they are added.

The amount of alkali and the concentration of the alkali solution will depend upon the type of oil being treated, particularly its free fatty acid content. 'Ihe amount of alkali necessaryto neutralize the free fatty acids may be determined by known means by measuring the freefatty acid content of a. sample of the oil. `In conventional batch refining the amount excess over that necessary to neutralize the free fatty acids has been'determined from rules and tables prepared for the use of reners, and by the experience of the renner performing the operation. As stated before, in conventional batch operations extremely large excesses are ordinarily employed,

in many cas being two or three times the- "iining, and also in order to produce a soap stock which would readily settlel from the oil without entraining excessive amounts of oil. However, even by employing such large excesses, the

amount of oil entrained was greatly in excess of that present in the soap stock separated from the oil in the present invention. Also, the large excess caused much greater saponification of neutral oil than takes place in the present process, as one part of caustic soda will saponify more than seven pants of oil. Since the present process does not contemplate settling the soap stock from the oil, the large excess above referred to is not required, and, in fact,- generally cannot be I employed. An exact excess applicable to every oil cannot be given, as the necessary excess will vary with the type and quality of oil being treated. In general, it can-be stated that the excess em'- ployed in accordance with the present invention is materially less than that necessary in conventional batch operatlons. The concentrations of the refining solutions, however, will ordinarily be similarV to those conventionally employed in batch operations. The necessary concentration again depends upon the type and quality of oil being treated, and its free fatty acid content, and the reiiner depends upon published rules and tables as well as his own experience in determining what concentrations should be employed.

When .the correct amount of alkali has been added to the oil in the mixer I0, vigorous agitation is continued until the pin break is obtained, shown by the presence of small flocks of sion, heat is applied, for example by passing any desired heating medium, such as steam, through the heating coil I1. `Heating and agitation is v continued until the emulsion is broken, as shown bythe condition of a sample of the mixture in which condition the soap stock is readily separabie from the oil. The temperature at which the break occurs will also vary with different 0118.

, occurs between 100 and 160 F. and

batch operations in which agitation is stopped as soon as the break isreached. As stated before, continued agitation after the break has been reached, in conventional batch processes employing a. large excess would cause the soap stock particles to'be broken up and nely dispersed in the form of an emulsion in the oil, rendering the same inseparable by settling or centrifugal separation. However, by employing Vthe small excess of the present invention, the agitation can be continued to maintain the mixture substantially uniform without forming a difficultly separable emulsion. The amount of excess employed must be balanced against the time the mixture is maintained in the mixing device under agitation after the break. If the mixing device has an extremely'large capacity as compared to the amount of mixture which may be separated in a short time by the centrifugals employed, a smaller excess must'be employed in vorder to prevent beating soap stock back into the oil. In other words, even with a small excess, the agitation cannot be continuedindefinitely without rendering the mixture ineiciently separable. y On the other hand, sufficient excess must be employed to produce the necessary colorreduction. The longer the time of agitation after breaking, the less the excess which can be employed. Thus it is seen that the precise amount of excess employed with any given oil depends upon the nature of the oil and the relative capacities voi? the mixing devices and centrifugal separating devices. 'I'he relative capacities -of the mixer and centrifugal should be such that in no case is continued agitation after the break necessary for more than two or three hours unless the excess contemplated by the present invention is much smaller than that necessary to form the easily settleable soap stock required in conventional batch rening. When employing thev conventional batch excess, the separation must be performed in a Vmuch shorter time after the break than with the small excesses disclosed herein.

The nature of the agitation after the break has occurred is also of importance. -Too violent agitation will form aninseparable mixture,l more especially in an open kettle, even if small excesses are employed. Mechanical agitators of the general type disclosed in the drawing and provided with one or more impellers for causing relaatively slow uniform agitation of the oil have been found effective, while other types of agitation such as those involving rapid'recirculation of the mixture invariably produce inseparable emulsions. The agitation should be only that necessary to maintain the mixture of oil and soap stock in substantially uniform condition, that is in the substantially uniformly agglomerated condition resulting from slow agitation after the break and providing most eective separation, such that no stratification and formation of large masses of soap stock takes place. Such large masses of soap stock unbalance the fluid columns in the centrifugal separators, such that separation is not uniform 'and soap stock is discharged with thel oil and oil with the soap stock.

Itis evident that one mixer only maybe einployed in the present invention, but-'by employing two or more mixers in parallel continuous separation may be Vaccomplished in the cen- -trifugal separating system I3.

Since the mixture leaving the mixers Il or Il is in broken condition and at a suitable temperature for centrifugal separation, it may be delivered directly to oneor more centrifugal separators. An exceptionally clean 'Y sepa-ration of the oil from the soap stock can be accomplished therein, such that entrainment of `oil in the soap stock is markedly reduced over that accomplished in conventional batch operation. Also. the small excess employed during mixing markedly .reduces the saponifcation of neutral oil. Thus the over'all losses of the present process vare much lower than vthose resulting from -the conventional batch operation. An oil of good color is obtained despite the small excess' employed and an efficient economical process obtain'ed with substantially all vegetable and animal oils encountered.

Also, as shown in Figure 2, continuous mixing followed by a period of treatment similar to that in mixers I0 or Il can be employed. 'I'hus in Figure 2 oil may be pumped from a supply tank therefor through a pipe 36 by a proportioning pump 31 to a mixer 38. The refining reagent may be pumped from a supply tank 39 through a pipe 40 bya proportioning pump 4I to the mixer 38.. A

n heating coil 42 through which any desired heating f medium, such as steam or hot water, can be circulated may be positioned in the oil supply tank 38 so as to keep the oil therein in a flowable condition, but in general it is not desirable to heat a large body of oil in the tank 35 to temperatures much above thosel necessary to render the..

oil readily pumpable. A similar coil 43 may also be positioned in the supply tank 39 for the reflning reagent in order to bring this reagent to .any desired predetermined temperature.

The proportioning pumps 3l and 4i maybe driven, for example, by a variable speed electric motor 84 and have a variable speed device 45 positioned between the pumps so that any desired amounts and proportions of oil and refining reagent can be delivered to the mixer 38. The particular proportioning apparatus disclosed is by way of example only, and any other apparatus capable of -pumping accurate predetermined proportions and amounts of oil and refining reagent can be substituted therefor.A

If it is desired to preheat the oil prior to mixing, the oil may bepassed through a flow heating device which may include a coil 46 positioned in a casing 41 through which any desired heating Vmedium, such as steam or hot water, can be circulated by the pipes 48 and 49.. Similarly, the refining reagent can be preheated prior to mixing by passing the same through a heating device including a coill 50 positioned in a casing 5i similar to the casing 41 surrounding the coil 45. The mixing device 38 may be any effective flow mixing device such as a mechanical agitator or a device in which a streamvof one of the materials is injected at right angles into a stream of the other. The flow mixing device disclosed in'my copending application Serial No. 190,673

filed February l5, 1938, now Patent No. 2,142,062,

.steam, may be circulated through the heating jacket by pipes 60 and 6|. The agitator 56 may be of any suitable type which' will maintain the mixture in .the treating chamber in substantially uniform condition without beating the soap stock back into the oil to form a difiicultly separable mixture, and is preferably provided with scrapers 62 contacting the walls of the casing 54 'so as to remove therefrom any soap stock which may deposit upon the walls.

The mixture may be discharged through a pipe 53 and a pipe 54 connected to pipe 25, which may be the same as the pipe of Figure 1, 1ead-` ing to one or more centrifugal separators 21 sim- 20 ilar to those shown in Figure 1. If it is desired to further heat the mixture in order to bring it to. that desired for optimum separating conditions, instead of passing the oil through the pipe- B4 it may be passed through a heating device which 25 may include a heating coil 55 positioned in a oasing 6@ through which any desired heating medium, such as hot water, may be circulated by means of the pipes 51 and 68. Thus, by closing the valve 69 in pipe 64 and opening the valve 10 30 in the pipe leading to thecoil 65, themixture may be passed through the heating coil, while it may be bypassed around the heating coil by opening the valve 10 and closing the valve 59.

In many cases, it has been found advantageous to introduce a heated diluting medium such as water or salt solution into the pipe 25 immediately before the mixture is delivered to the centrifugal separators. Thus, a pipe 1l provided with a valve 'I2 may be employed for introducing such a medium into the mixture. If desired, ad-

introducing water or salt solution at a higher temperature than the mixture in the pipe 25 so as to promote separation in the centrifugal separa- 45 tors, but in anyevent the water or salt solution. is separated with the soap stock and acts as a diluting agent therefore in order to render the same easily discharged from the separators. Any

Also, it is advantageous to add such a salt to the mixing and conditioning devices of Figure 1 or have the same present in the treating chamber of Figure 2, to harden the 55 soap stock and make it more difilcult to beat back into the oil.

In the modification of the invention disclosedl with reference to Figure 2. the mixture formed in the mixer 38 may be introduced into the treating chamber 53 at relatively lowtemperatures. for example temperatures between 60 and 90 F.,

.and heated in the treating chamber'upto an emulsion breaking temperature during-agitation therein. The treatment inthe agitating chamvber 53 is for the purpose of enabling the low excess discussed with reference to Figure 1 to be l"employed and still give suillcient time for color vremoval. Thus, the chamber 53 may 4,be sufilperature such that no emulsion is formed in the ditional heat can be supplied to the mixture by.

, salt, such as a salt of an alkali metal, which has no deleterious reaction with the oil or soap stock, .may be employed.

mixer 38 or, if formed, is broken substantially immediately after mixing. In this case, the mixture enters the treating chamber in an already broken condition and agitation is continued therein until desired color reduction has been produced with the low excess contemplated and the mixture then delivered to the centrifugal separators. As stated above, additional heat may be imparted to the mixture, if found desirable, in the coil 65. In many cases such additional heating is found desirable, as separation may be found more effective for a particular oil at a somewhat higher temperature than that found optimum for treatment in the treating chamber 53. Such a heating coil may, in some instances, also be employed prior to centrifugal separation and for the same purpose in the process practiced in the .apparatus disclosed in Figure 1. As a still further modification of the process, the mixture may be maintained at a relatively low temperature below the emulsion breaking temperature, i. e. not substantially above F. for most oils, inthe treating chamber 53 and then the oil brought to an emulsion breaking temperature in the heating coil 55 and then delivered to the centrifugal separators for separation.

Although a closed treating chamber 53 has been disclosed and is preferable, it is possible te employ an open agitator tank as the treatment chamber, since the agitation in the treating chamber is only suiilcient to maintain the mixture in relatively uniform condition and is insufilcient to cause air to be beaten into the mixture. The process practiced in the apparatus of Figure 2 is essentially similar to that practiced in the apparatus of Figure 1, since a low excess, as compared to conventional refining, is employed and agitation may be continued after the break has been produced. In :this process also, the refining losses are minimized` because oi the low excess and low entrainment of 'neutral oii in the soap stock. Effective color removal is likewise produced, even though a low excess is employed, as sumcient time is provided for color reaction.

Thus, the process of the present-invention may be practiced with such oils as cottonseed, soya bean, corn, rape seed, as well as certain animal oils, in which is intended to be included iish oils such as herring., menhaden oil or sperm oil.y It will be appreciated that this process will be found more particularly adapted for certain types of oils, for example the oils which may be classified as slow breaking oils, or as cold pressed oils."v The present process is suiilciently exibie that any necessary time of treatment can be employed.

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

I claim as my invention:

1. The method of refining animal/and vege- A and reagent to mix the same: heating the mixture to break said emulsion whilecontinuing sufilcient agitation to cause the remaining color imsoap stock is separated from said oil.

refining solution wit puriti'es to, combine with the resultant soap stock -continuing agitation of the heated mixture in a relatively large vessel lat a rate sulcient to prevent stratilcation of the mixture; withdrawing a the stratification of said mixture While providing for reaction of said excess with said coloring mastream of said mixture from said vessel during 5 said continued agitation; delivering the same to a centrifugal separator; and separating said soap stock from said oil.

2. The process of refining animal and vegetable oils containing free .fatty acids, which com-` prises: mixing an alkali refining reagent with a bodyI of said oil in an amount which will neutralize the free fatty acids and provide an excess sufficient to reduce the color of the oil during prolonged agitation under heated conditions but sub- 15 tatlng the heated mixture in a relatively large vessel at a rate sucient to prevent stratification but insufficient to form an inseparable emulsion; and delivering a stream of said mixture to a centrifugal lseparator wherein the resulting 3. The process of rening animal and vegetable oils containing freefatty acids and coloring impurities, which omprises: mixing an alkali a body of said oil at a temperature between approximately and 90 F. in 30 order to form an emulsion, said refining reagent being added in amount sufficient to neutralize the free fatty acids and provide an excess for color reduction which is materially less than that necessary for forming a soap stock which can be'35 settled from the oil; agitating said mixture and heating the same to anemulsion breaking temperature to break said emulsion; continuing said agitation in a relatively large vessel after the emulsion has been broken at a rate sufiicient to 40 maintain the mixture substantially uniform without beating said soap stock back into said oil; and withdrawing a stream of said mixture and subjecting the same to centrifugal separation to 4 separate said soap stock from said oil.

4. The process of refining animal and vegetable oilscontaining free fatty acids and color impurlties, which comprises: mixing an alkali rening reagent with said oil in sufncient amounts terials and conditioning the mixture for centrifugal separation, and thereafter continuing the motion of said body of mixture sulcient to prevent stratiflcation but insuiilcient to beat the soap stock back into the oil while withdrawing a stream of said mixture and centrifugally separating the resulting soap stock from refined oil.

6. 'I-'he process of refining animal and vegetable oils containing free fatty acids, which comprises:

mixing with said oil an alkaline refining reagent in suilicient amounts to neutralize said free fatty acids and provide an excess which is substantially less than that required to forma settleable soap stock and sufllciently small that the resulting mixture of oil and soap stock may be agitated foi" a prolonged period of time when in a condition for centrifugal separation without forming an inseparable mixture; maintaining a body of said mixture at a temperature sufficiently high to condition the same for centrifugal separation; agitating said mixture for a relatively long period of time at said temperature at a rate suflicient to maintain the mixture relatively uniform but insuflicient to produce an inseparable emulsion; withdrawing a stream of said mixture from said body; and continuously centrifugally separating the soap stock from the oil in said stream.

7. 'I'he process of refining animal and vegetable oils containing free fatty acidsI which comprises: bringing a metered streamof said oil into contact with a metered streani of an alkali rening reagent in sufficient amount, to neutralize said free fatty acids and provide an excess which is substantially less than that required to form a settleable soap stock; delivering the resulting stream into a relatively large body of oil; agitating said relatively large body of oil at a rate suicient to prevent stratification of soap stock resulting from the neutralization of lsaid free fatty acids but insuiiicient to cause an inseparable 5 for centrifugal separation; withdrawing a stream to neutralize the free fatty acids and provide an '50 excess suiiicient to reduce the color of the oil during agitation under heated vconditions but which is substantially less than that required to form a readily settleable soap stock and insumcient to.

substantially attack the neutra1 ou; agitaung a 55 body of the'resulting mixture in a relatively large vessel at an emulsion breaking temperature at the rate providing eifective agglomeration but insumcient -to produce an inseparable emulsion for suillcient time to cause reaction of said excessio with a substantial portion of said color impurities; and ldelivering a stream of said mixture at a substantially uniform and regulated rate to a .centrifugal separator wherein the resulting soap Astock is separated from said oil.

5. The process of refining animal and vegetable oils, containing free fatty acids and coloring material. which comprises: mixing an alkali renning reagent with said oil in sulcient amounts to neutralize said free fatty acids 'and provide an 70 excess for colorremoval which is insufficient to form a readily settleable soap stock; maintaining a relatively large body of said mixture at a temperature above the emulsion breaking temperature thereof in suilicient motion to prevent 75 of said mixture from said body of oil during agitation thereof; delivering the stream of mixture to a centrifugal separator; and continuously centrifugally separating said soap stock from said oil.

6. 'I'he process of refining animal and Vege- I table oils containing free fatty acids, which comprises: Ibringing a metered stream of said oil into contact with a meteredV stream of an alkali refining reagent in suflicient amount to neutralize said free fatty acids and provide an'excess which is substantially less than that required to form a -settleable soap stock; delivening the resulting stream into a relatively vlarge body of oil; heating said body of oil to a temperature which will facilitate centrifugal separation While agitating the same at a rate sumcient to prevent stratification of soap stock resulting from the neutralization of said free fatty acids but insuficientl to cause an inseparable emulsion; withdrawing a stream of said mixture from said body during said agitation; delivering the stream of mixture to a centrifugal separator;f and continuously centrifugally separating said soap stock from said. oil. i

v9. A process of refining animal and vegetable oils containing free fatty acids, which comprises: bringing' a metered stream of said oil at a temperature which willfacilitate subsequent centrifugal separation ,of soap stock from the oil arable emulsion to be formed while at a 'temperature which will facilitate centrifugal separation; withdrawing a stream of said mixture from said body of oil during said agitation; delivering the stream of said mixtureto a centrifugal separator; and continuously centrifugally separating the said soap stock from said 10. The process of refining animal and vegetable oils containing free fatty acids and coloring matter, which cox'nprises: bringing a metered stream of said oil into contact with a metered stream of an alkali rening reagent in sumcient amount to neutralize said free fatty acids and provide an excess for reaction with said coloring matter which is substantially less than that required to form a settleable soap stock and insufcient in amount to cause an inseparable emulsion to be formed during prolonged agitation of the resulting mixture; delivering the resulting streaminto. a relatively large body of oil; agitating said relatively large body f oil at a rate suilicient to prevent stratication of soap stock V2,239,746? l Y resulting from the neutralization of said free fatty acids and at a temperature which will condition the mixture for centrifugal separation while providing time for reaction with said coloring matter; withdrawing a stream of said mixture from said body of bi1 during said agitation; delivering a stream of mixture to a centrifugal separator; and continuously centrifugally separating said soap stock from said oil.

11. The process of refining animal and vegetable oils containing free fatty acids and color impurities, which comprises: mixing an alkali refining reagent with a relatively large body of oil in an amount sufilcient to neutralize said free fatty acids and provide a low excess for reaction with said color impurities, the excess or said reiining reagent being substantially less than that required toform a settleable soap stock and insufficient to saponi'fy substantial quantities of said oil; agitating the resulting Ibody of mixture at a rate sumclent to prevent stratification of soap stock resulting from the neutralization of said free fatty acids but insufiicient to cause an inseparable emulsion to be formed and at a temperature sumciently high to condition the mixture for centrifugal separation; withdrawing a stream o1' said mixture from said body of oil during said agitation: delivering the stream of mixture to a centrifugal separator; and continuously centrifugally separating said soap stock from said oil.

BENJAMIN H. THURMAN.

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