US2219088A - Process of refining vegetable oils - Google Patents

Description

Oct. 22, 1940. B. CLAYTON PROCESS OF REFINING VEGETABLE OILS Filed Jan. 4, 1959 www Patented'ct. 4' n. l

. y UNITED STATES PROCESS oF alFlNmG VEGETABLE oILs 1 y Benjamin' Clayton, Houston, Tex. Application .muuuy 4,isssgserial'uauazsi f amaims. (o1. 26o- 4 25)v This invention relates to the rening of vegeup an equilibrium vvliich preventsV completey neu- `table oils, andmoreparticularlyto a' process `in tralization of the free fatty "`acids. Also, this which an alkaline reagent, which decreases the gas becomes occludedinthe soap stock, renderemulsifying properties of gummy materials con-v ing the samevlighter-inweight,and extremely 5 tained in the oils, is added thereto prior'to the diiicult to'y cleanly separate from theoilrf v I addition of a caustic alkali so Ias to decrease A the In accordanceilwith the present inventiomit refining losses of the processin refining of vegehas been found that sodiumA carbonate'may beE table oils. V` l employed in combinationwithcaustic alkalies not Vegetable oils in theform received by thereonly to reduce the Aneutral oil entrainedinthe lo 'liners usually contain relatively large amounts jof Asoap stock butto decrease the loss due Vtolat-y l. V

phatides, proteins, resins, carbohydrates, etc. An gums may be present during rening, any. losses 1 y alkaline refining reagent, when added to the oil, due to prior degumming of the oilsareavoided. neutralizes the free fatty acids thereof and pre- The sodium carbonate, preferably'. in aqueous cipitates the Vgums to form soap stock which solution, is added tothe oil prior to adding'the l5 can be continuously,centrifugally separated from )caustic alkali, Aand ilxes the' gums-so that their the oil. In, order to substantially .completely emulsifying properties are, diminishedy andthe neutralize the free fatty acids and decolori'ze the amount of neutraloil entrained inthe vsoap stock oil, caustic alkalies are ordinarily employed as reis lessened. AIt is added to the oil under temperazo ilning reagents. j An'excess thereof is used to reture conditions or in suflicient excess to prevent 20 act with colorv impurities.v This excess also atthe formation of any substantial'amountA of Vcartacks neutraloil to produce less valuable soap, bon dioxide. the-sodium carbonate doesnot resulting in arening loss.` Alsothe attack neutral oil, the. mixing with-the sodium terials present in the soap stock ca"1v1rse"i. I large Vcarbonate can be done either in iiowor as abatch amount of neutral oil to be entrainedj therein. operation. At least a part of the free fatty acids Th'eentrained neutral oil also constitutes anex are neutralizedto formsoap, .and theresulting gummy materials, such'as, for example, v phostack on theoil byfthe caustic alkali. Since the Gil tremely important refining los s.j n s mixture of oil and soapvstock is then admixed The removal of the gums by a degummin'g step with-tv caustic alkali, for example, caustic'` soda. prior to alkali refining has been suggested; but The caustic soda completesthe neutralization oi.'

in conventionaljdegumming steps considerable y the free fattyvacids, and reduces the color'of the y30 l oil is entrained in the gums separated'from` the `oil. :The resulting soap stock.. can be separated oil prior to alkali refining, A lso,l the soap stock fromithe oil with very littlecontained neutral resulting from alkali refining;A being relatively oil.y They presence of relatively large amounts' of free of gums, is diicult to separte cleanly from sodium carbonate also1appears to inhibit the atthe oil. It has been found that the employment tack of the caustic,alkaliuponneutral oil, so that 35 of an alkali which will not saponify neutraloils, refining losses Vdue tosaponiflcation -ofl neutral for example, sodium carbonate, 'not only reduces oil are also reduced. v: I y refining losses resulting from the saponiiication It is, therefore, an objectfof the present invenof neutral oil but causes less neutral oil to been tion to provide Ya process of T'rening vegetable 40 trained in the soap stock. Such alkaliesA as oils'in which a non-saponifying alkaline' reagent 40.

sodium carbonate apparently reduce or destroy is employed to iix the gums contained inthe oil in t the'emulsifying properties ofthe gums, that is to non-emulsifying form prior to the addition 'of `a'. say, the gums are fixed in non-emulsii'ying form; caustic alkalireningreagenti A" l y Such non-saponifying alkaline reagents; how- -Another-objectof thejinventi'on is to provide a ever,Y` do not completely neutralize 'the free fatty process of refining rvegetable oils in which oil en' 45 acids nor do they appreciably reduce the color trained in the soap stock resulting therefrom, due of oils requiring decolorizing even if an 'excessis to the presence of 'gums vini-the oil, isfreduced.v employed. This is particularly true with sodium A further object of ,the invention isto provide carbonate, which has been found' to jbe the most a process yfor thealkaline refningof vegetable eflcient gum fixing reagent. Carbon dioxide gas oils, in which a non-saponifying''alkaliis' em-l 50 tends to form unlessextremely large excesses are "ployed in combination with va caustic alkalidn employed or the temperaturey in the process is orderto-reduce'rening lossesdue to vsapo a.;

kept below that which produces satisfactory -retion of 'neutral oil Vand entrain'mentof a neu ral 4 flning. The carbon dioxide becomes dissolved in oil in the soap stock separated from the oil. f

the oil and water present in the process. setting other objects' and advantages of Athe inven'- 55' the coil being surrounded by a casing I5 through which any desiredheatingvor `cooling medium maybe circulated. i

An aqueous solution of a non-saponifying alkali, for example, soda ashis withdrawn from a source of supply shown. as a tank I6 by a proportioning pump II and delivered to the mixer I3. The mixer I3 is preferably of the type in which the alkaline reagent is injected at right anglesinto allowing stream of the oil and is pref,-

erably ofthe type disclosed in my copending ia'p- 'pucauon Serial Nc. l190,673,flied'February 15,

1938, although any type of closed flow mixer, vsuch as a mechanical agitator, may be employed. The nonsaponifying alkali reacts with at least v'a' portion of thefree fatty acids in the oil and plie'- cipitates gums to formjsoap stock.v` More important, it fixes the gums contained in the soap stock 1n non-emulsifying form by inhibitingtheir emulsifyi'ng' properties. 't

'I'he mixture of oil and soap stock is then passed through a second heat exchange devicel including acoil I9 and a casing 20 through which a heat exchange medium may be passed.' The oil leaving the heatA exchange' device I8 is delivered to a second mixing device 2| which may be similar to themixing deviceI I3.l An aqueous solution of a causticalkali such` as caustic Vsoda is withdrawnfrom'fa source oifsupply shown as a tank 22 byla proportioning pump23 and delivered to the mixer 2I. 'Ihe proportioning pumps II, I1 and 23 are shown as being driven by a variable vspeed electric motor 24 with variable speed devices 2l and 26 positioned between the pumps II and 23, respectively, although any othertype of suitahleiproportioning mechanism capable of` accurately-,'proportioning streams of the various materials and delivering themv under pressure to the. mixing devices may be substitutedl therefor. The caustic soda solution delivered the mixer^2I completes'the neutralization of the free fatty acids, and reacts with coloringmaterials present in the oil to decolorize the oil. The resulting mixture of oil and soapstock is then preferably passed through a third heat exchange device 21 including a coil 28' and a casing 29 -through whicha heat exchange medium may be passed. The resulting mixture is then delivered to a continuous centrifugal yseparator 3l in which the soap stock is separated from the oil and delivered as the heavy emuentthrough a spout 3l into a receiver 32. The oil' is delivered as the light eiiiuent through a spout33 finto a receiver 3|. 'l'.he centrifugal separator 30 is preferably of the heated type disclosed .in lPatent No. 2,100,277, granted November 23, y1937. l v

In the aboveprocess, the heat exchanger I2 is employed to bringy the oiltola mixing temperature found most effective ,for the particular oil being treated.y This temperature is ordinarily relltively low, for example, between 'I0 and 100 ananas tion will appear in the following description of preferred embodiments made in connection with F., in order to preventthe formation of carbon dioxide when soda ash is employed, although with increased amounts of soda ash this temperature.

may be somewhat higher. 1n general, better mixing and more complete neutralization of the free fatty acids is accomplished at the higherV temperature, although this willvary with the nature of the oil such as its viscosity and amount of gums contained therein. The amount of soda ash employed is usually that necessary to bel 'chemically equivalent to the free `fatty acids in theoil, although lesser amounts may be employed lif the temperature of.. mixing is relatively low,

and, on the other handf'excesses of soda ash as great as or slightly greater than twice the amount chemically equivalent to the' free fatty acids may be employed to insure that no carbon dioxide is formed.

The heat'exchanger I3 is employed to bring the mixture of ,oil and soap stock from the mixer I3 to the temperature of mixing with caustic alkali found most effective for the particular cil being treated. This temperature will v arywith different oilsbeingtreated, depending uponthe amount ofgums contained therein, the amount lof free fatty` acids am! thefviscosityof the oil. `That is to say, the temperature ofv mixing willyary from 70 F. or lower to ashigh as 160 F. Thus, the most effective temperature for mixing in the vmixer 2| rn'ay be lower or higher than theftem'- perature found effective for mixing inthe mixer I3, ',or, ,in some instances, may be the jsalme'.l rIn the latter` case the heat exchangerr I8 4rnayfbe eliminated or alternatively employed to provideva vtreating time, for example, 2 to 5. minutes, so as to insure fixing of the gums innon-emulsifying form aswell as better neutralization of free fatty acids. 'I'he time of treating in the coil I9 fjthe heat exchanger I 8 may be as long as necessary, depending upon vthe oil lbeing. treated, as the alkaline reagentv present thereinfdoes not attack neutral oil.V However, this'tirne of treatment is mation of any substantial quantities of carbon dioxide. Itis preferred to 'employ a relatively concentratedy aqueous solution of the sodium carbonatelin orderto cut down the 'amount of water correlated with the temperature "to prevent for-l eno with kkhighly colored oils, provide an .excess suillcient to react with the color impurities toy decolorize the oil. Since all of the sodiumA carbonate employed is `ordinarily n ot effective to neutralize freey fatty acids, usually considerably greater amounts of combined soda ash and caustic soda must vbe employed than the amount chemically equivalent to the lfree Vi'atty acids.

The caustic soda solution is also-preferably relatively concentrated i norder tocut down-the amount of water in the process, but the concentration of this solution will againsdependupon the amount o'fnwater necessary to` provide for continuous and clean separation ofthe soap stock from the oil. .With certain oils itis found that agitation by the agitator 3B is then continued to a relatively low temperature of mixing with the caustic soda is preferable, as color reactions apparently proceed with greater rapidity under low temperature conditions, although with other` oils y. relatively high temperaturesin the mixer 2l secured by the heat exchanger I3 have been found to provide for better separation inthe centrifugal separator. ,y y i The heat exchanger 21 may be employed `to adjust thetemperature ofthe mixture leaving the mixer 2|,to that found to give mosteffective separation for the particular .oil being treated.

VThis separation temperaturey is usually found to lie between and 160 F..and will vary with different oils. If the temperature ofmixing in the mixer `2l happens to be that found most effective forl separation in the centrifugal separator 30, the heat exchanger 21 may be omitted or employed to give a treating period without change of temperature. 'I'his procedure has been found desirable with certain oils in order to provide time for color reaction andalso condition the mixture for centrifugal separation, but in general should be made as short nas possible, for example, 2 to 5 minutes, as the caustic soda present in the mixture will also attack neutral oil. The prior addition of the sodium carbonate appears to inhibit this reaction, but the saponication of neutral oil does take place to some extent and increases with length of time of treatment and with increased temperature in the heat exchanger 2l. By employing the lheated centrifuge referred to, at least a portion of the heat required for Aseparation with a particular oil may sometimes be imparted to the oil Within the separator itself, thus cutting down the length of time the oil is in contact with the caustic soda at elevated temperatures. lIn'any event, the heating of the soap stock layer adjacent the Wall of the centrifugal .bowl in the heated centrifugal separater referred to provides for the uniform 'discharge of the soap stock from the separator.

The apparatus disclosed in FigureZ is similar to that in Figure 1, except that provision is made for mixing the soda ash with a batch of vthe crude oil. This apparatus mayinclude Va vessel 35 which may be similar'to neutralizing kettles 'commonly employedin the batch refining of vegetable oils. The vessel 35 is Apreferably provided with a mechanical agitator driven from any suitable source of power 3T and maybe further provided with a heating jacket 38 through which any desired heating medium maybe circulated. Crude vegetable oil may be delivered intol the vessel 35 through a pipe 39 and the non-saponifying neutralizing reagent delivered through. a

pipe 40. In usual operations, a body of oil is first delivered into the kettle and then .an aqueous solution of soda ash .run in through the pipe 40 during agitation by means of the agitator 38 neutralized, and the gums precipitated and xed in non-emulsifying form, thereby forming soap stock in the vessel 35. The temperatures of mixing are preferably substantially the same as those discussed with respect to the mixer I3 in Figure 1, and the amount of soda. ash added may be also substantially the same as that discussed with reference to the process of Figure 1. Conditions of mixing in the vessel 35 are carried on so as to avoid the formation of any substantial amounts of carbon dioxide when soda ash is employed, and mixing is continued until substantially all of the gums are precipitated. Suicient prevent `stratification of the soap stock in the i kettle35, and the resulting mixture is withdrawn from'the vesselv 35 by the proportioning pump 4| and delivered through a heat exchange device'42 to,v a mixer 43. Caustic-soda solution is Vwithdrawn from a source of supply shown as a tank 44 by means of a proportioning pump 45 anddelivered to the mixer 43. As shown'lin Figure '1, the proportioning pumps 4| and 45 may be driven able speed device 41 positioned betweenthe pump 4I and the motory 46. -'1'he mixture produced in the mixer 43 is then preferablyv passed through a l.heat exchange device 48 and delivered to a continuous 4centrifugal separator 43 in whichthe `soap stock is separated from theoil and delivered as the heavy eiiiuent through a spout 50 into' a receiver 5i. The rening oil isdelivered asthe light efiiuent through a spout 52; into thereceiver 53. i.

The process carried vout in the apparatus of yFigure Zafter the non-saponifying alkaline reagent has been mixed with -the oil may be entirelysimilar to that carried out in Figure 1.

That is to say, the heat exchangers-42 and,

the mixingof the non-saponifying alkaliwith the oil prior to adding the caustic alkali precipitates the'gums and inhibits theiremulsifying `properties and also inhibits theattack on the neutral oil by the caustic alkali subsequently adby a variable speedelectric motor 46with a varimixed therewith. The preferred non-saponifying alkali is the .soda ash above referred to,.as this material is available in large quantities at small costA and also appears. to be a better inhibitor of the emulsifyingproperties of the gums f and saponifying power of thevcaustic alkali upon the oil. However,other non-saponifying alkalis such as sodium silicate, trisodium phosphate and Vequivalent potassium salts as .well as other alkali metal salts of weak acids maybe employed withlsatisfactory results. 'I'he preferredcaustic alkali is caustic soda, `although it is possible to jemploy otherk caustic alkalies. such as` causticV Vpotash. In anyl case, the refining; losses due to entrainment of `neutral oil in the soapstock and also due to attackonneutral oil by the caustic alkali are reduced over prior processes. u

While the addition ofthe' caustic alkali` subsequent to mixing with the non-saponifying alkali more effectively inhibits the emulsifying properties of the gums, vit is recognized that improved results over conventional refining processes can be produced by adding the non-saponifying alkali with or after the addition of the caustic. Thus a' mixture of non-saponifying alkali such as sodium carbonate and a caustic alkali such as caustic soda may be added in ow, such as at 2| in Figure 1, or mixed with theoil in the tank 35 offFigure 2 and the caustic soda tank 44 and mixer 43 of this figure eliminated. 'I'he emulsifying properties of the gums in the mixture are inhibited so `as to provide more effective separation, and by tive separation of the soap stock is accomplished -without substantial entrainmentof neutral oil in ment of my invention, it is understood that the details therof. may b'e-varied within the Ascope of the followixig'claims;

"Iclaim: f y y 1. A continuous process of refining vegetable oils, which comprises, adding to a vegetable oil saponifying alkali in an amount suilicient to partlysneutralize .the free fatty acids and inhibit the emulsifying properties of the gums and' to produce soap stock incapable of satisfactoryA centrifugalv separation, thereafter continuously, as a stream, adding sufficient 'caustic alkali to the resulting mixture tosubstantially completely neutralize the free fatty acids and to produce soap stock ofiinc ased centrifugal separability and continuously` entrifugally-separating the resulting soap stock from said oil.

, 2. A continuous process of refining vegetable oils containing gums and free fatty acids, which comprises, lmixing suilicient sodium carbonate with said o ilfto at least partly neutralize the free fatty acidsand fix said gums in non-emulsifying form, thereafter mixing a flowing stream of the resulting -4mixture with a flowing stream of -an Y aqueous solution of caustic alkali in an `amount suilicient"to substantially completely neutralize the `free fattyY acids and to continuously condition the so stock for centrifugal separation, and continuously centrifugally separating the ing soapstock from neutralioil.

3. AQontinuous process of refining vegetable oils containing free fatty acids, gummy materials, and. coloring impurities, which comprises, mixing an aqueoussoluticn of sodium carbonate with said oil in sufficient amount and concentration to neutralize at least a kportion of the free fatty acids .and inhibit the emulsifying propertiesA of said gummy material, thereafter admixing a iiowihg stream. of' the resulting mixture with lan aqueous solution ofcausticY soda in sufficient amount and concentration .to substantiallycompletely neutralize the free fatty acids and react Withfl/ said coloring impurities to reduce the' color of the oil and to continuously condition the soap stock forcentrifugal separation, and continuously centrifugally separating vthe resulting conditioned soap stock from said neutral oil whereby the amount of neutral oil entrained in said soap stock is minimized.

"1. A continuous process of refining vegetable oils,"which comprises,.adding to a vegetable oil containing gums and free fatty acids a nonsaponifying alkali in an amount sufficient t6 partly neutralize the free fatty acids and inhibit the emulsifying properties of the gums, thereafter adding, as a stream, suflicient caustic alkali tothe resulting mixture to substantially comcontaining gums and free fatty acids a -nonesultn' 3,219,088 j amount of carbon dioxide is evolved, so that effecpletely neutralize the free fatty acids and to continuously condition the soap stock for'centrifugal separation and `continuously centrifugally separatingthe resulting soap stock from said oil at a 'temperature' facilitating such separation.'

' V5; A continuous process of retlning vegetable oils, which comprises, adding tp a vegetable oil containing gums and free fatty acids a nonthereafter adding a stream of an aqueous soluugally separating the' resultant soap stock from said oil.y

sapopirying .Ankauin an amountsumcient to at 'least partly neutralize the vfree fatty acids and y inhibit the emulsifying properties of 'the gums.

6. A continuous process of refining vegetable oils, which comprises, adding to a vegetable oil containing gums and free fatty acids a nonsaponifying alkali in an amount sumient' to at least partly neutralize ythe free fatty acids and inhibit the emulsifying properties of the gums, thereafter adding sulcient caustic alkali to the resulting mixture to substantially completely neutralize the free fatty lacid, heating a stream of said mixture to la temperature facilitating centrifugal separation, and continuously' centrifugally separating the resultant soap stock from saidoil. *l n 7.` A continuous process of rening vegetable v oils containing gums and free fatty acids, which comprises, mixing suiiicient sodium carbonate with said oil to at least partly neutralize the free fatty acids and fix said gums in non-emulsifying form, thereafter continuouslyadmixing a stream containing suflicient caustic alkali with said oil and sodium carbonate to substantially completely neutralize the free fatty acids and separating the resulting soap stock from neutral oil.

` 8. A continuous process of renning vegetable oils containing gums and free fatty acids, which comprises. Amixing sumcient aqueous solution o f sodium carbonate with said 'oil'to at least partly neutralize the free fatty acids and fix said gums in Ynon-emulsifying form, thereafter mixing a flowing stream of the `resulting mixture with a flowing stream of an aqueous solution of lcaustic alkaliin an amount sufficient to substantially \9.- A continuous process of refining vegetable voils containing free fatty acids, which'comprises,

mixing sufficient sodium carbonate with said' oil to neutralize a major portion of the free fatty acids, thereafter adding sufficient caustic alkali to substantially completely neutralize the vfree fatty acids, and' separating the resulting soapstock from the oil. f

v BENJAMIN CLAYTON.

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