US2658907A - Refining fatty oils - Google Patents

Description

NOV. 10, 1953 G, H, PALMER 2,658,907

REFINING FATTY OILS ATTORNEYS G. H. PALMER REFINING FATTY OILS Nov. 10, 1953 5 'sheets-sheet 2 Filed April 12, 195o ATTORNEYS Nov. l0, 1953 Filed April 12, 1950 G. H. PALMER REFINING FATTY orLs 3 Sheets-Sheet 3 ATTORNEYS Patented Nov. l0, 1953 REFINING FATTY OILS George H. Palmer, Fanwood, N. J., assgnor to The M. W. Kellogg Company, Jersey City, N. J., a corporation of Delaware Application April 12, 1950, Serial N0. 155,489

Claims. (Cl. E60-428.5)

This invention relates to improvements in the rening and fractionation of fatty oils, i.e. oils consisting principally of glycerol esters of fatty acids, such as cottonseed oil, cocoanut oil, linseed oil, soybean oil, palm oil, peanut oil, sardine body oil, cod liver oil, menhaden oil, and whale oil.

This application is a continuation-in-part of my copending application Serial No. 6,459, led February 5, 1948, and issued as Patent No. 2,505,- 338, on April 25, 1950.

It has been suggested previously to fractionate fatty oils by contacting the oil with a low-boiling solvent at temperatures in a temperature range, near the critical temperature of the solvent, in which the solubility of the oil and solvent decreases with rising temperature. Thistemperature range lies above the temperature of maximum solubility which is ordinarily not more than about 100 F. below the critical temperature of the solvent, and extends to a few degrees above the critical temperature of the solvent.

In this temperature range solubility is greatly affected by conditions which affect the density of the solvent. The condition of the solvent in this temperature range, in which its solvent power is greatly affected by slight changes in temperature and/or pressure, has been designated arbitrarily as the paracritical state. In this condition the pressure is always maintained sufficiently high to keep the solvent substantially entirely in liquid condition, and the degree of solubility Aof the oil and the solvent is affected by the temperature, the relative quantities of solvent and oil employed, the pressure, and the nature of the solvent.

This invention relates to an improved method of fractionating fatty oils by means of a relatively volatile, i. e. relatively low-boiling, solvent while the solvent is in the paracritical state.

Relatively volatile solvents are employed for the reason that the solvents which are partially miscible with the oil while in the paracritical state ordinarily are those having critical temperatures no higher than 450 F., and it is desirable to avoid operating temperatures which might produce some thermal effect on the oil being treated.

In carrying out the improved fractionation process any fluid may be employed which is partially miscible, while in its paracritcal state,

with the oil to be treated, and does not react chemically with the oil. Such solvents include low-boiling hydrocarbons, such as methane, ethane, propane, the butanes, the pentanes, and

the corresponding olefns, as Well as mixtures lil thereof, such as a mixture of methane and normal butane, or a mixture of ethane and propane. Other agents include organic compounds such as halogenated hydrocarbons, including dichlordifluor methane and methyl uoride. Still other solvents which may be used are dimethyl ether, methyl ethyl ether, carbon dioxide, and ammonia,

The low-boiling normally gaseous paraflin hydrocarbons are preferred solvents because of their lower cost and relative inertness, and because they are miscible with most fatty oils to the desired degree. Propane is ordinarily preferred in carrying out the process but the other low-boiling hydrocarbons may be preferred in the treatment of certain oils. It may be advantageous to modify the propane, or other hydrocarbon solvent employed, by the incorporation of a small amount of a different solvent. Furthermore, the employment of relatively impure materials, such as commercial propane containing small quantities of other hydrocarbons, principally ethane, is Within the scope of the invention.

In accordance with the improved process of this invention the fatty oil is rened by fractionation treatment which separates the oil into three or more separate fractions having distinctly different properties. This treatment is carried out in at least two separate contacting zones.

It is a principal object of the invention to provide a process for 'continuously fractionating a, fatty oil into three or more fractions in at least two separate contacting zones by means of circulating solvent While evaporating and condensing a smaller quantity of solvent thanin previous processes for effecting the same fractionation. It is a further object to provide a continuous process for fractionating ya fatty oil into three or more fractions in two or more separate contacting zones without evaporation of the solvent except for the purpose of separating the solvent from product fractions. Other objects of the invention Will be apparent from the following more detailed description of the invention.

The process of this invention comprises rening fatty oils by solvent fractionation with a low boiling solvent under paracritical conditions in a series of at least two separate fractionations, in which all or a part of the solvent for the first of said fractionations is obtained from the extract phase of the second fractionation zone (i. e., the secondary extract phase) without resorting to evaporation and recompression of the solvent. In accordance with one modification of the improved process of this application, which is a continuation-in-part of prior copending application aesaco? 3 Serial No. 6,459, filed February 5, 1948, at least a portion of said secondary extract phase is heated to separate it into an upper solvent phase and a lower oil phase, the former constituting an improved solvent for the first fractionation, and the latter serving as reflux material in the second fractionation, or the rst fractionation, or both.

The inventionV will bedescribed-in detail with reference to the accompanying drawings, in which:

Figure 1 is a diagrammatic representation in elevation of an arrangement of apparatus for carrying out one embodiment of the `improved process, with certain modifications,

Figure 2 is a diagrammatic representation. ini elevation of an arrangement of apparatus forl carrying out an embodiment of? the .inventionin which the oil is fractionated intofour product fractions, and

Figure 3 is a diagrammatic representation in elevation ofan arrangement ofl apparatus forl effecting fractionation; ofV a fatty oil `into fourfractions by a flowv arrangementdifferent )from that-'of Figure 2.

Fig. 1 illustrates anarrangementof apparatus for Vfractionating a fatty oil into three product fractions,l in accordance with the improved process off-this invention. This operation produces a relatively large intermediate fraction which is light in color and vsubstantially neutral, a relatively Ismallzffirst, rainate lfraction comprising a concentration-of Athe color bodies of the fatty oil, anda final extract fraction whichis a concentration of 'fatty'acids and other highly soluble componentsgoflthe' fatty oil. Thev relativelylargezintermediate.fraction-isaJ substantially rened Oil and requires-little, any; further treatment prior to use as a refined oil. 'Ihe relatively 'small'rst rafiinate fractionl may be a wasteproduct fraction butV ordinarily this small' fraction' contains a: concentration of "components which itis ldesirable to recover. The relatively small final extract fraction also may be awaste product fractionibut this fractionlalso may' conta'irr valuable components which it isdesirable Ato recover. For exampleyinzthe. refining -of soybean oilby the process represented'. by Fig. 1, the: rst raffinate fraction kcontainsa relativelyxhigh. concentration of lecithin4 and other phosphatides, :and the nal extract fraction contains, inadditionto the fatty acids,.a relativelylhigh concentration'of tocopherols and sterols. :'LEach of. the relatively,` small fractions represents a concentration of valuable componentstand may be converted-into lh-ighly desii-able products-byfurther treatment.

In the process of Fig.' 1, the first raffinate fractionand-the nal-extracti fraction are cachordinarily limitedto a .quantity equivalent toless than lOY'per cent (by weight) of :the fatty oil beingvtreated. Preferably the yfirst raffinate fractionl constitutes no more than 5v percentfof the fatty oil, `while the final-extract fra'ctionfislimited to 2 perrrcent'orl less of thewfatty oil. -For example, in therening offsoybean oil the `first rainatefraction preferably is limitedto 2 per cent or lessof the -fatty.oi1, while the -final ex-A tractff-ra'ction isabout 1 or 2 per cent of the 4fatty oil. t

In the process illustratedinFig.` l,-a fatty-oil is treated inY an extraction' zoneiprovidedby fractions-ting tower -10- to separate theflrst raffinate fraction, which is withdrawn from vthe-bottom of tower. I0. Extract. oil; whosemost. solublecomponents` compriseA the. most; soluble components of Atheliatty oil,"i si withdrawn fromthe-.top -of 4 tower l as a part of the extract phase and further treated in a separate fractionating zone in tower Il to separate such extract oil into a final extract fraction and the relatively large interme- 5 diate fraction of the fatty oil.

Tower H is arranged and equipped to provide intimate contact of the extract oil and solvent under conditions. whichl eiect'f close" fractionation 'f- Athe oil, i. e. 'concentration int the extract of l0 components undesired in the intermediate prodnuct, or desired to be concentrated in the final eX- tract product. To this end, fractionating tower l I iss'ubstantially elongated vertically and is pro- .vided with'contact means, such as trays, baffles or l51pa'cking,toeffectintimate contact of counter- *'owing liquidphases. Tower Ii also is provided with means for effecting extensive refluxing of the tower with extract oil. Such reiluxing is y .ieffect'edrfbymeans of at least one heating coil 12, which heat the extract phase as it iiows up the tower to precipitate oilv from the extract phase, or it may be provided by separating a porticnof theV extract oil from the extract phase and. returning it to the upper part of tower Il, i. e. external reuxing. While one heating coil I2 is shown, a plurality of such coils may. be provided between the coil l2 and the top of tower Il.

The initial extraction treatment of the fatty oil to separate a rst raffinate, containing a conf centration of the color bodies, may be carried out under any suitable conditions, but it is preferred to effect substantially complete removal of color bodies and .a high concentration ofothercomponents of lesser solubility in the first raiiinrte product by subjecting the fatty oil initially to fractionation treatment under conditions. substantially equivalent. to-those-provided by tower ll. Consequently, tower lis generallyn similar to tower H in the provision of the various means for achieving close fractionation, i. e. substantial segregation of thefless soluble components of the fatty oil in the raffinate, and vice versa.

In the normal operation of fractionating tower IB a solvent stream consisting essentially of propane or other suitable solvent is introducedY into the tower at a point nearthe bottom thereof, through line l5. The solvent stream is heated or cooled to the temperature desired in the bottom of the tower, by means indicated at i6, and line |5is provided with a pump l1 to overcome the pressure maintained on tower i0. A stream of the fatty-oil to betreated, such asi-soybean oil, is introduced into tower I0 at. one or more intermediatepoints, as through line- I8. The operating conditions imposed on tower l0 are such that,-at equilibrium conditions, the fatty oil Ais only partly soluble in the upilowing; solvent stream. Asa result of the difference in gravity between the undissolved oil-phase and the solvent phase, the

undissolved oil phase fiows downwardly in counter-current contact with the upowing solvent phase. VThe solvent phase flows upwardly toward an overheaddrawoif linegat I9 while the-oil,-or lower, or raffinate, phase iiows downwardlytoward a bottoms drawoff line at 29. The upiiowing solventphase contains all but afsmall proportion of the solvent introduced from line I5 and a portion of the fatty oil. This phase alsomay be designated as the: propane phase, or upper phase,

or extract phase. The lower. or oil phase contains only a small proportion-of the solvent and a portion of the oilin ajsolvent: oil ratio much lower than that existingfin the solvent phase.

The volumetric'4 ratio of solventY and oil introduced into tower vHl should benotlower than about 6:1 and preferably should be at least 10:1, for example, :1 to 30:1, or higher. Tower I0 is maintained under suilicient pressure to maintain the solvent substantially entirely in liquid condition. The operation essentially requires contact of the liquid solvent phase with the liquid oil phase, but the formation of a small quantity of solvent vapor is not objectionable so long as it does not interfere with the flowr of the liquid phases in counter-current contact through and out of the tower. Since the operation of tower I0 essentiallyV involves withdrawing the major portion of the fatty oil in the extract phase, the maximum temperature in the tower ordinarily is substantially lower than the critical temperature of the solvent. The critical temperature of propane is 206.3 F., whereas the critical pressure is 617.4 p. s. i. Consequently, when using propane as the solvent a maximum operating pressure of 40G-700 p. s. i. is satisfactory.

Tower Iii is divided into two zones by the introduction of the fatty oil from line i8 at an intermediate point. The upper zone, lying above this point, is the rectification zone in which the operation of the tower is directed substantially entirely to achieving the desired degree of fractionation of the constituents of the fatty oil which are absorbed in the solvent phase at lower points in the tower. The lower zone, lying below the oil charge point, is primarily a stripping zone in which the undissolved fatty oil and oil precipitated in the rectication zone are sub-l jected to the stripping action of the upowing stream of solvent, to dissolve in the solvent phase all constituents of the fatty oil except those which it is desired to include in the first rannate fraction, to be withdrawn through line Eil.

Rectification may be effected by heating the solvent phase, as it flows upwardly past the cil charge point to the top of the tower, to a temperature above the temperature in the bottom of the tower. Since the lowest temperature in the solvent phase is substantially higher than the temperature of maximum solubility of the oil and solvent, and since the solvent phase is saturated with oil at the lower temperature, the heating of the solvent phase to a higher temperature as it flows up the tower results in a decrease in density of the solvent and a corresponding precipitation of a part of the oil previously dissolved. This precipitated oil forms a new raiiinate phase which flows down the tower in counter-current contact with the solvent phase, to eifect further rectification of the oil.

Any suitable means may be employed for heating the solvent phase as it iiows up the tower. but ordinarily this is effected by heating coils M which are located at suitable intervals in that portion of the tower in which it is desired to maintain a temperature gradient. The temperature differential between the top and bottom of tower IB may vary from 1 F. to 60 F. The temperature gradient employed may be concentrated entirely between the oil charge point and the top of the tower or it may extend from top to bottom of the tower. Conveniently, al relatively small temperature gradient may be imposed on the stripping zone, while a larger temperature gradient is imposed on the rectification zone.

Alternative to the maintenance of a temperature gradient in tower lil, or in combination with that method, the tower may be refluxed by the return to the top of the tower of a portion of the extract oil, According to this method all, or a portion, of the extract phase withdrawn through line I9 is diverted through line 2l which connects with a separator 22. The pressure on the extract phase flowing through line 2| is substantially reduced by means of valve 23 to eifect vaporization of the greater part of the solvent contained in the extract phase. To assist in this operation heating means 2e! may be provided in line 2l. In vessel 22 the liquids and vapors are separated and the solvent vapors pass overhead through line25, which connects with solvent storage vessel 26. A cooler 21 is provided in line 25 to condense the solvent vapors.

The removal of solvent from the extract phase in vessel 22 may not be complete, and it is preferable not to remove the solvent completely since this requires excessive reduction in pressure at 23 or excessive heating, and since the return of a small part of the solvent in the reflux liquid does not interfere with the operation of towerA lll. For example, if tower lll is operated with a propane solvent at about 600 p. s. i., the pressure may be reduced at 23 to about 209 p. s. i., heat being supplied at 24 to replace heat of evaporation. This effects a sufficient removal of solvent and simplifies condensation of the solvent vapors at 21.

The reilux liquid, comprising extract oil and a small amount of the solvent, is collected in the bottom of vessel 22 and withdrawn therefrom through line 23 by means of pump 2S. All, or a portion, of this oil is diverted from line 28 through line 30 for return to the top of tower I.

The refluxing of tower i0 by the return of extract oil through line 3G is not essential to the operation of tower Ill as reiux oil from other sources may be introduced into the top of tower il). For example, a suitable portion of rafnate phase produced in tower I l may be collected and returned to the top of tower I6, by means not shown. Moreover it may be desirable to avoid all external refluxing, relying only on the reiiuxing provided by the temperature gradient to effect the desired rectification of the extract.

Conditions of temperature and pressure Vin tower l0 are regulated to distribute to the railinate phase which collects in the bottom of tower IU, only a minor proportion of the fatty oil. In the two-zone system of operation illustrated by Fig. 1 it is desirable ordinarily to limit the proportion of the oil in the railinate phase withdrawn through line 2i! to the maximum proportion which is necessary to remove the color bodies and other relatively insoluble constituents from the extract. This will require ordinarily a ralnate containing not more than about 5 per cent of the fatty oil and, in the treatment of certain oils, such as soybean oil, this proportion may be 2 per cent or less. However, it may be desirable to operate tower I0 to produce a ralinate containing a substantially larger, although minor, proportion of the fatty oil. For example, it may be desirable to operate tower I6 to produce a raffinate oil representing a concentration of the more unsaturated glyceride components of the fatty oil for use as a drying oil. For this purpose it may be desirable to produce a raffinate oil in tower I0 representing 15 per cent, or more, of the fatty oil charged to tower I il. Ordinarily, however, the production of such a drying oil fraction is effected in a three-zone arrangement, to be described below. v

The exact operating conditions selected for tower l0 depend upon the character of the oil being treated and the proportions of the oil and solvent employed, as, well; as the desired tributon of the oil between the raftinate and exe. tract. oil desired in the` rainate, the lower will be. the temperature desired in the bottom of tower. On the other h and, a relatively-high ra-v tio, ofy solvent, to oil charged to tower I0, requires a` higher bottom temperature inthe tower to counteract the greater solvent power in the 'relafv tively largeproportion of solvent. rEil-ie tempera-v ture in the top of tower tV is suliiciently higher thanV the bottom temperature to, prov-ide thez de sirecl temperature gradient, and the. introduction of reflux liquid from line 311 requires. a somewhat lower top temperature than would be required in the absence of' external reflux-` ing. If no temperature gradient is imposed on tower I0, and the tower is refluxecl externally to. effect rectification, the tower tempera:- ture necessarily must besubstantially lower than in the absence of such external rectilcation, in order to incorporate the desired proportion of the fatty oil in the raiinate. In general, the bottom temperature controls the amount of oil rejected to the rainate phase forwithdrawal as bottoms, while the` top. tempera-A ture controls the amount of oil withdraw-n overhead to produce the extract oil to. be withdrawn and refluxed oil to be returnedto the. tower. In the treatment of soybean oil to. removeA a small rafiinate as a concentration of color bodies the temperature in the bottom of tower It will fall within the range of 14o-.190 E, while the temperature at the top of the tower will be in the range of 15o-200 F.

The extract oil from tower I0 is further fractionated in tower I I to separate it into a rafnate comprising a major portion of the` oil charged to tower Il, and an extract containing a portion of the oil charged to tower I I. In accordance with a preferred modication of the process of Fig. l the portion of the extract phase withdrawn through line i9, and not diverted through line 2i for production of reflux liquid, is passed on through control valve 3| to an intermediate pol-nt of tower II. Tower Il is similar to tower I0 in construction and in the provision of means for effecting contact of counter-flowing liquid phases, heating the extract phase, and external reluxing. A solvent stream is drawn from reservoir by means of line 32 and introduced into tower II at a low point. Line 32 is provided with pump 33 and temperature control means 34. Tower H is operated at somewhat higher temperatures than is tower I0, as it is desired to include in the final extract phase a substantially smaller proportion ofthe fatty oil than has previously been dissolved in tower ID. Tower II preferably is operated with a temperature gradient, and under these conditions the bottom temperature will be in the range 16o-195 F., while the top temperature lis in the range 165-210" F., although in certain cases an even higher top temperature may be imposed on tower II.

Heating means 35 are provided in line It)` to regulate the temperature of the solvent phase from tower IU introduced into tower Il through line I9. The temperature of this liquid maybe brought to the temperature desired to be maintained vin tower II at the point of introduction, or the liquid from line I9 may be heated to an even higher temperature to assist inV heating the solvent phase flowing upwardly in tower II toward the outlet of line I9.

Tower Il conveniently is maintained under a The smaller the proportion or thev fattyv Snmcien-,tly lower pressure than tower I0. in order to permit flowing the solyent, phase, from tower I0. directly through line. i9. into tower II.. Preterably tower I I; isy maintamed substantiallyatA the pressure required to prevent. substantial vaporization or the4 solvent; in the. tower. This requires maintaining tower IIL under a pressure` subst an, tiallyhigher than the minimum required; to maintain liquid conditions, since. tower I0, is. at a, lower temperature than tower Ile. However, this. does not, adversely anect the operation of tower t0, since the maximum temperature of towerV t0. does not extend ordinarily to a. level at which the density of the solvent. is greatly affected by` variations, of pressure.

However, in tower tI it is desired to. maintain the pressure as.` low as possible. In the. operation of tower Il it. is advantageous to provide rectili-` cation by imposing atemperature gradient on the tower, while limiting external reflux-ing to the minimum. In the improved process of this application some latitude in the percentage of oil in the final extract phase is permissible; but in many cases, it will be found desirable to keep the oil content of the nal extract solution to the lowest percentage justified by the economics of the process. It may be necessary to impose a relatively high temperature at the top of the tower. Consequently, the temperatures in tower II may extend into the region in which the dens-ity of the solvent is greatly affected by variations in pres-` sure, and in which the change in density of the` solvent produced by a change in the temperature is at a maximum at the lowest pressure neces-A i. sary to prevent substantial vaporization of the solvent.

Operating conditions in tower Il are adjusted to form a secondary raiinate phase, in the bottom of the tower, which contains oil equivalent to a major proportion of the oil charged to the tower through line I9. For example, in the treatment of soybean oil by the two-zone system of operation of Fig. l, the oil charged to tower Il may be distributed to the secondary rainate in the bottom of the tower in an amount equivalent to approximately 90 per cent of the oil charged to tower Il and equivalent to a major proportion of the oil charged to the system through line I8. For example, when tower II is operated to produce a rst rainate product, to be withdrawn through line 20, equivalent to less than 10 per cent of the fatty oil introduced through line I8, the second rainate product accumulated in the bottom of tower I I may contain oil equivalent to at least per cent of the fatty oil from line I8. Ordinarily in the rening of soybean oil this two-zone process will involve distributing not more than 5 per cent of the fatty oil to the first raiinate product and at least 93 per cent to the second raffinate product. In accordance with one speciic embodiment of the invention as applied to treatment of soybean oil, the first rainate product withdrawn through line 20 may be limited to 2 per cent or less, while the second raiiinate product, collected in the bottom of tower II, may comprise 96 per cent or more of the fatty oil introduced into the system through line I8.

The solvent introduced into the bottom of tower I I from line 32 functions principally in that tower to strip from the lower phase flowing down the tower such components of the oil as are undesired in the second rafnate product, and in clude these undesired components in the final extract product, along with other relatively 9 soluble components of the oil which may be desired in the nal extract product. Ordinarily solvent should be introduced into tower II from line 32 in a volumetric ratio of solvent from line 32 to oil introduced from line I9 of at least 6:1, and preferably at least 10:1.

The final extract phase iiows out of the top of tower II through line 35 to a separating vessel 31. The pressure is reduced substantially at valve 38 in line 36 to permit evaporation of at least the greater part of the solvent. To assist this operation heat is applied at 39. Solvent vaporized in this way is separated from the remaining liquid in vessel 31 and is withdrawn overhead for recirculation in the system through line 40, which connects with line 25. The liquid collected in the bottom of vessel 31 is withdrawn through line 4I for recovery and further treatment of the oil product fraction contained therein. If necessary, a portion of this liquid may be returned as reflux liquid to the top of tower II through line 42, which is provided with a pump 43.

The second rainate product fraction is withdrawn from the bottom of tower I I through line 44, which connects with a separating vessel 45. Pressure on this material is released by valve 46 suiiiciently to effect evaporation of at least the greater part of the solvent, heat being applied at 41 to assist evaporation. Solvent separated in vessel 45 is withdrawn overhead and recirculated in the system through line 48, which connects with line 40. The liquid separated in the bottom of vessel 45 is withdrawn through line 49 for further treatment and recovery of the oil product fraction contained therein.

According to the preferred modication of the process of Fig. l, as described above, the extract phase from the top of tower I Il is passed to tower II through line I9 without the separation of 'any of the solvent contained therein except for the production of reflux liquid in tower I0. Preferably it is desired to avoid evaporation of solvent from the extract phase of tower I even to this extent, since it is possible to provide reiluxing of tower I9 by means of a temperature gradient in the tower or Iby means of reflux liquid obtained from some other external source, as mentioned above. It is advantageous to introduce into tower I I as much as possible of the solvent contained in the extract phase from tower I0. One advantage is that fractionation of the oil in tower II appears to be assisted by the presence of the propane accompanying the oil charged from line I9. Another advantage will be described in more detail below.

Nevertheless, the process includes, as one modication, the substantial separation of solvent at 22 from all or a substantial portion of the extract oil transferred from tower III to tower II. For this purpose line 28 connects with line I9, as shown, whereby oil containing a. relatively small amount of solvent in admixture therewith may be transferred from vessel 22 to tower II for further fractionating treatment.

In accordance with a further modication of the process of Fig. 1 the extract phase liquid flowing through line I9 may be treated to effect a preliminary separation thereof into separate liquid phases which are separately introduced into tower I I at different points. In this modification extract solution flowing through line I9 is diverted therefrom through line 50, which connects with vessel I. Heating means 52 are 'introduced into tower II.

'interposed in une so to heat the extract ,solution Viiowing through line 50 to a substantially higher The upper phase, which now contains a smaller amount of oil, is withdrawnthrough line 53 and introduced intoy tower I I at a point which may be somewhat below the connection of line I9 with tower II. The lower phase liquid in vessel 5I contains much less solvent than was present in the extract solution in line I9. This liquid is withdrawn through line 54, which connects with line I9, whereby this liquid is introduced into tower II at a point which may Vbe substantially above the point of introduction o1' the upper phase material from vessel 5I. Cooling means 55 and 56 are provided in lines 54 and 53 to adjust the temperatures of these liquids to those lat which they are desired to be In thismodication all, orV substantiallyall, of the extract solution from line I9 is thus -diverted through line 5I) by suitable manipulation of valve 51 in line 50 and valve 58 in line I9. The phases separated in vessel 5I are thus introduced into tower II when the extract phase is heated,v at 52, to a ternperature suiiiciently high to precipitate all but a small proportion of the oil. Alternatively, a smaller proportion of the oil may be precipitated and the lower phase liquid from the bottom of vessel 5I may then be introduced into tower II at a lower point than the point of in-I troduction of the upper phase material from vessel 5I.

In accordance with the improved process of this invention the stream of solvent for use in tower I0 is provided by continuously diverting a portion of the upflowing extract phase from the rectification zone of tower II (i. e. from some point between the charge oil inlet of pipe I9 into tower II and the final extract phase outlet to line 36 at the top of the tower) and heating this diverted extract phase to fractionate it into an upper solvent recycle fraction, which is introduced into the tower I Il through line I5, anda lower oil reflux fraction which is employed Iasreflux oil in either tower I0 or tower II or both. Upiiowing extract phase in tower II may be -collected by any suitable means for withdrawing extract phase substantially free of downilowing raiiinate phase. For example, an inverted collecting trough II Il may be employed within the tower II.

Extract phase is withdrawn from trough I I 0 through line III and introduced into a vertically extended heating tower II2 at a point near the lower end thereof. Heating tower II2 is heated by a series of heating coils I I3, preferably operated to provide a temperature gradient increasing with elevation. The maximum temperature in heating tower II2 is independent of the maximum temperature in tower II and may be somewhat higher, to promote maximum precipitation of oil in tower II2. Temperatures within tower I I2 may be adjusted to produce an overhead phase which has a substantially lower oil ycontent than the extract phase withdrawn from tower II through line 35. Heating tower II 2 may be provided with packing or trays which encourage the separation of the two counterowing phases which form because of the rise in temperature within the paracritioal range. The upper phase, which is referred to herein as a solvent recycle fraction,

.is withdrawn from the upper end of heating Ytower llvthrough line I5 which,.as previously described, connects with the lower part of tower I0. `Since the temperature desired in the'bot- .tom of tower I ordinarily is substantially lower .than the temperature at which. thenal. extract rphase emerges from heating tower' H2, cooling means are provided at I6in line I5 to cool the solvent recycle fraction flowing therethroughto the temperature desired. in the bottomof tower (Il. Preferably pump I'Lisplaced downstream :and containing, asa result of -theclose fractionation therein, a-` concentration of only the most soluble components fof the fatty oil vbeing treatedis substantially as effective as lsolvent treating agent in tower I0 asa stream opfan equivalent volume of 'pure solvent. .The oil components contained -in the nal extract-phase liq- .fuidflowing through line -I are presentin such small concentration and arev so. highly soluble, partcularlyafter the cooling step at t6, that they Vhave' no appreciable effect on the ac- 'tion of the solvent portion of this liquid in treating the`.fresh fatty oil-charged from line` `Il! in tower I0. Y

` This method of operation has the advantage that it permits limiting the vaporization of the solvent to" the 'minimum` quantity necessary for recirculation in relatively pure form vto the bottomiof'tower Il through line 32,01' to the quan- 'tity necessary to be recovered' from liquid "prod- .ucts withdrawn through lines 2l), 28, v4I andJlS. In this method-of operation two essentially separate sol-vent treatments areeffected --by means of .a single circulating stream of propane, represented by'- the vpropane introduced into reservoir 2 8' from line 25 -and passed from reservoir v26 -to tower Il through line` 32. This is van important advantage, vsince recovering the solvent by evaporation and condensation represents a substantial proportion of the operatingcost of the refining process. A This method of operation has the further advantage that it permits employing inttower- I0 substantially any. desired. solventroil ratio: -Substantially all the solvent introduced into tower l0 from line I5 flows back-again toltower'll through line I9: If valve`3 -in line-36 isl-controlled to provide for removal offafdesiredquan tity of iinal extract phase for recovery of the final extract product fraction thequantity of -nal--extract solution returned-through line- I5f for reuse intower l0 maybe varied at--wilLf-by control of pump I1, without unduly disturbing the operation ofthesystem. U y fr The 'heavier of the two phases formed in heating tower II2, ris referred-.tovv herein as fa reflux oil fraction, .althoughit does-contain solvent, verylcommonly more than-50 percent solvent; but its `solvent content-is--small in comparison with-the solvent content -of the solvent-recycle' fraction. The reflux oil fraction-is withdrawn from the bottom of-heating--tower I I2 through line IM and valve H5 and introduced through line H6 by means of pump I'Il -into theupper part of tower II to flowy downwardly and Serve as reflux therein (being of higher-density than the extract phase in tower-Hf) --In the alternative or. .simultaneouslvreflux oil'fraction from heating tower ll2'may be Adiverted*through line Hato .the upper portion of primary tower I0, by

means of pump II 9. If temperature adjustments are required, cooling means (not shown)maybe provided in lines I IG or lI I8 to cool the rellux oil. It is an important advantage of the method described-above in Aconnection lwith Figfl that the temperatures of fractionation for obtaining the final extract phase at the top of 'tower II are independent of the temperatures employed in heating-tower II2 for obtaining recycle solvent land reflux oil fractions.y Temperature' conditions above collector IIIl may loe-adjusted and kept constant over along period of time, if necessary, Ain ordery to-obtain a final product of high quality and consistent composition, while -atlthe same time temperature conditions in heating tower H2 may be varedfrom time `to time if process conditions require it.

According to--an illustrative embodiment of the vprocess of Fig-1,100 volumes of fatty oil introduced into towergID from yline I8 'in a unit of time-are treated with 1860 volumes of liquefied propane introduced into tower I `irom-line l5. Tower ID is operated to distribute 2 parts, 'by weight, of the oil to the rst'raflinate product fraction withdrawn throughline I2t. The remainder of the fatty eiland substantiallyall of the propane pass overhead through liney IS--and are transferred directly -to tower II for further treatment. Into tower Il, 1000 v volumes ofipropanaf-rom reservoir 26,- are introduced through vline 32 to complete the strpping'operation-in that tower, as-described abovea ApproximatelylOO volumes` of propane are withdrawn from'tower Il inthe-secondary rafnate phase through line A4; VThe remaining 2700 volumes of propane pass upwardly in tower II at H0. One-third of this propane-is 'included in-the'nal extract phase withdrawn through' line 36 and passedto vessel .3l-for recovery of solvent andthe nal extract product fractionfof theoilsTwo-thirds of the extractl solution, containing-1800'volumes of propane, arecwithdrawn from tower H through-line Hi and returned to -towerfillthroug-h line I5. rIhe operation'of'tower I'i-is controlled to include in theY iinal extract' fraction a proportion 'of' the oil such that the amount-recovered at r:il for withdrawal from theprocessA through lined I and for-refluxing through-lineM-isequivalent t'of partsby weight# of the '100 ypartsv -of` oil charged tothe process` throughfline UI8.` Consequently, the 1800 volumes "ofA propane 'withdrawn from tower il throughline VIII contain-about parts offoil. -This'extract isheated in tower H2'to a final temperature eiective to'reduce the oil content thereof'tonofmore :than 1 parto'f oil per parts-charged to tower I 'I'his o'ilis combined with the oil extracted in towerl l5 wherebythe extract phase `passing out'ofto'wer l0 through line ISfconta-ins 99partst offoiland approximately'lSOO volumes of propane. In this example1 tower ID" isoperated ata propanefoi-I ratiol of approximately lzl'whereas towell is maintained-at a' propanetoil ratio of 4'approximately 10:1. The`100'0 volumes of propane charged intothebottom-of tower" II are recovered byl vaporization at-31` an'dd. The volumes of propane' indicated Ain this examplev merely illustrate an approximate distribution of propane in the vsystem-andfdofnottake into account the relatively smalll quantities of' propane' which are recovered in secondary' recovery operations' on theproduct fractionsandsmall quantities of make-up propane 'which l'are introduced into ileservor 26 Vfrom line 59 to replace `inevitable osses'.`

Since the oil contained in the solution flowing through line I represents a highly soluble small proportion of the fatty oil, and since the solubility of this small proportion of oil is greatly increased by the cooling step at I6, the proportion of oil in the solvent stream introduced into the bottom of tower I5 from line I5 may be substantially increased over that indicated in the foregoing illustrative embodiments. However, best operation of the process involves controlling the operation of tower II2 to restrict the amount of oil included in the recycle solvent fraction. For

this reason also it is desirable to operate towerv II substantially without the return of external reflux oil through line 42, or with the smallest amount of external reuxing necessary to produce Suitable rectication of the product oil fraction. Any product oil desired for rectification through line 52 must be carried overhead insolution through line 36. Increasing the quantity of oil in line 3S to provide reflux oil at 31 also in- Volves a corresponding increase in the concentration of oil in the solution diverted from tower I I through line III.

In a further modication of the process of Fig. l, the solvent stream flowingv through line I5 to the bottom of tower I0 may be supplemented by a small quantity of relatively pure solvent diverted from line 32 through line ci). In this operation it may be desirable to introduce the solution from line I5 into tower Iii at a somewhat higher point, as through line SI.

For a specic example of the application of the improved process reference may be made to a rening treatment of a crude soybean oil having a fatty acid content of about 0.25 per cent. The oil is charged continuously to tower I0 of Fig. l and subjected in that tower to operating conditions designed to produce a rst ralinate fraction containing 2.5 weight per cent of the charge oil. This tower is held under a 'pressure of 585 p. s. i., and temperatures of 168 F., 164 F., and 158 F. are maintained at the top, oil charge point, and bottom, respectively. The final extract phase produced in this tower is passed continuously to tower II. In this tower the extract phase is subjected to treatment at substantially higher temperatures, and the tower is reiluxed with a temperature gradient and by the return of external reflux oil. Fresh liquefied propane is introduced into the bottom of this tower from line 32. Tower II is regulated as to operating conditions to produce a second rafnate product in the bottom of the tower containing about 955 weight per cent of the oil charged to the rst fractionating tower. Tower II is held under a pressure of 590 p. s. i., and

temperatures of 195 F., 181 F., and 169 F. are maintained at the top, oil charge point, and bottom, respectively. The fresh propane is charged to the bottom of the tower Il at a rate of 3280 volumes per 100 volumes of oil charged to the first tower. The extract solution from the top of the tower I0 contains 2780 volumes of propane per 100 volumes of oil charged to tower I6. Ap-

proximately 100 volumes of propane per 100 volumes of charge oil are included in the second extract phase withdrawn from the bottom of the second tower. The extract solution flowing upwardly at IIB in tower I I contains about 5960 volumes of propane per 100 volumes of oil charged to the ilrsttower. A portion of the final extract solution containing 3180 volumes of propane is withdrawn through line 38' and treated to Vaporize the propane and separate liquid oil for rwithdrawal as the final extract product and for return as reflux liquid to the top of the second tower. The remaining portion of the extract phase, containing about 2780 volumes of propane per volumes of fresh charge oil, is withdrawn at IIB through line II. Tower II is reluxed externally by the return of approximately 4 parts of oil per 100 parts of fatty oil charged to tower I0 and the extract oil is withdrawn as product at the rate of 2 parts by weight per 100 parts of oil charged to tower I0. The extract phase withdrawn from tower II through line III contains about 10 parts by weight of oil per 100 parts of oil charged to tower I0. This extract is heated in tower II2 to a final temperature of about 205 F., to reduce the oil content through to no more than 1 part of oil per 100- parts of oil charged to tower` IIS.' The lower phase precipitated in tower II2 is passed through line Il to tower Il as reflux liquid. Thus, the solvent stream introduced into the bottom of tower Ill contains approximately l part of the final extract oil per 100 parts ofA oil charged to the tower. This operation produces a substantially rened soybean oil equivalent to 95.5 weight per cent of the crude oil, of light color and containing less than 0.1 per cent fatty acids. The nal extract product oil withdrawn from the top of the second tower contains about 5.o weight per cent fatty acids and is a concentration of sterols, tocopherols, and other similar constituents of the soybean oil. The first raiiinate product withdrawn from the bottom of the tower Ill is a concentration of the color bodies of the crude soybean oil and also contains phosphatides, such as lecithin, in high concentration. This operation thus produces, through the operation of essentially a single ,circulating stream of solvent, a separation of the crude soybean oil into three fractions representing a lecithinconcentrate, a sterol and tocopherol concentrate, and a substantially rened oil of good color.

In the modification illustrated in Fig. 1 the means shown for heating the extract phase diverted from tower II through lineIII are desirable'but not essential. This heating step may be accomplished in a single stage, with a single phase separation.

The improved process also is applicable to the separation of a fatty oil into four fractions, as

by the use of three fractionating towers. One

embodiment of this modication is illustrated in Fig. 2, in which fractionating tower lila is `ar ranged to function substantially in the ysame manner as tower Iii of Fig. 1. In this modification the oil content of the final extractfphase' withdrawn through line 36a is Very low because refluxing is accomplished independently by a separate piece of apparatus communicating with the final processing tower at points substantially below the top of the tower. The rst fractionating tower Ica preferably is operated to separate as the first raninate in the bottom of the tower a relatively small fraction, i. e. not more than about 10 per cent, and preferably 5 per cent or less, of the cil charged to the process through line I ila. This small fraction represents a concentration of the color bodies and other relatively insoluble components of the oil, and is withdrawn-from the process through line 20a. The modication of Fig. 2 differs from that of Fig. l in that the extract oil withdrawn overhead from tower lila through line lea is sub- Jected to a preliminary fractionation to produce an' intermediate rannate product, prior `to being passed to tower IIa .for lthe production of the small .iinal extract fraction.

' Thisintermediate `fractionation of the extract oilirom tower Illa is provided in towerr62, which is similar in construction and operation to towers `Illa and I Ia, being provided with means for promoting intimate contact of counter-flowingliquid phases and being provided with vheating coils 63 for control of temperature and. the maintenance of a .temperature gradient. In Fig. 2 apparatus for supplying external reflux' oil to towers Illa, SZ'and .I Ia has not been shown, for simplicity of presentation. It will be understood, however,

that any or all fractionating towers of Fig. `2

maybe subjected to external renuxing in the manner described in connection with towers IB and II of Fig. 1.

.In'Fign 2 the parts whose function and operatin are generally similar to corresponding parts of Fig. 1 are indicated by similar reference numerals, with subscript er The description of such parts in Fig. 1 applies also to the corresponding parts oi Fig. `2, except as modified in the description of Fig. 2.

In accordance with the modification of Fig. 2 the extract solution withdrawn from the top of tower I a through line 19a is passed to an intermediate point of tower 62. Alternatively, all or a portion of the solution owing through line Ba may be diverted through line 50a, and heated to a substantially higher temperature by heating means 52a to eiect the formation of separate liquid phases. The phases are separated in vessel 5m and separate phases are withdrawn through lines' 53a and 54a`for separate introduction into tower 62 in the manner described in connection with the separate phases withdrawn from vessel 5I Aof Fig. l.

Tower B2 is operated to separate the oil introduced therein into a relatively small intermediate raiinate fraction representing a concentration of the more unsaturated components of the oil. For example, in the refining of soybean oil by the modification of Fig. 2, tower 62 may be operated to separate an intermediate raninate fraction representing to 35 per cent of the oil charged to the process through line I 3a. The intermediate railinate fraction thus produced has an increased value as a drying oil and is of good color by reasonv of the removal of color' bodies from the oil in tower Illa.. Such a drying oil fraction separated from a crude soybean oil in the method of Fig. 2 has an iodine number of 145 to 155, while the remaining oil carried overhead in solution in tower 62 has a substantially lower iodine number of 125 to 135.

Tower 62 is operated at temperatures intermediate to those imposed on tower Illa and tower I'I, and the tower maybe subjected to external refluxing if desired. The intermediate raiinate product is withdrawn from the bottom of tower 62 through line 64, which discharges into a separator 65. vPressure is released at valve 66 sufriciently to evaporate the solvent which separates from the remaining liquid in vessel 65. The solvent vapors pass overhead through line B'Lwhich connects with solvent reservoir 26a. A cooler 21a is provided to condense the solvent vapors prior to introduction of the solvent into vessel 26a. The intermediate extract fraction is withdrawn from the bottom of vessel 65 through line 68 for further treatment for the recovery of the oil contained therein.

The extract solution. is withdrawn from the top 1 of Atower 62 `through line`69', which connects with atower I Iaatan intermediate point. Tower I Iais operated substantially exactly vin themanner described in connection withto'wer vI I of Fig. 1, to separate the oil introduced into tower YI Ia into a relatively .large nalrainate product and a relatively small final extract product. The operating conditions for tower .I Ia ordinarily differ somewhat from thoseapplied in tower A-I I in the two-Zoneprocess of'Fig. l, since the nal extract fraction to be removed overhead in tower IIa ordinarily represents a `larger proportion Vof the oil charged to tower .Ila than the proportion of oil charged to tower Ii represented by the final ex# tract product produced by that tower. Thus ccntrol of tower `I Ia ordinarily is easier than control of tower II, since the ratio of the extract product to the raffinate product is somewhat larger than in .tower II.

The rainate phaseseparated in the bottom -ol' tower IIa is withdrawn through line 44a which connects with a separating vessel 45a. Pressure is released by valve 46a whereby the solvent contained in this rafnate product is largely evaporated and separated overhead as a vapor in vessel 45a. The solvent vapors are returned for reuse through line 48a, which connects with line B'I. The nal raiiinate product, produced in tower I la, is withdrawn from vessel 45a .through line 49a. for further treatment, such as the removal of residual quantities of solvent, and other desired further refining steps. This product is, however, except for the presence of solvent, a substantially refined oil of good color in which the fatty acid content has been reduced to the amount which is readily removable :by moderate steam stripping.

.The final extract phase is withdrawn from the top of tower IIa through line 36a, which connects with separating vessel 37a, and is provided with a valve 38a and heating means 39a. This equipment is operated in the same manner as similar equipment shown in Fig. 1 whereby the solvent is largely evaporated and withdrawn from vessel 31a through line 40a which, in this arrangement, is connected with line El for recirculation of the solvent. The iinal extract product is withdrawn through line 4Ia for further treatment, such as the removal of residual quantities solvent, and other desired rening steps. This fraction represents a high concentration of the fatty acid content of the fatty oil being treated, and also a high concentration of the sterol and tocopherol content of the fatty oil.

A portion of the iinal extract phase flowing through line 36a is diverted through line ld, which is provided with cooling means Ilia and a pump Ila. Line |50. connects with tower 10a at a low point in order to supply to tower Illa a stream of solvent, in a manner analogous to the operation of line I5 and tower I0 in Fig. 1. A suicient quantity of final extract phase is diverted through line I5a. to provide a solvent stream for tower 62 also. The solvent stream for tower 62 is diverted from line I5a through line 69, which is provided with cooling means 'It and a pump 1I. Line 69 connects with tower 52 at a low point in order to supply the solvent stream to that tower in the manner described in connection with line I5 and tower I0 of Fig. 1. Line 69, cooling means 10, and pump 'II operate in a manner analogous to line I5, cooling means I6, and pump H of Fig. 1.

According to the modicationof Fig. 2 refluxing is provided for tower Ila by means 'ofv` a separate evaporator chamber |25. Upowing extract phase is collected from tower I la by means of an inverted collector trough |26, which is located at some point intermediate between the charge oil inlet and the extract phase outlet. Secondary extract phase entrapped in collector |26 is somewhat richer in oil content than the nal secondary extract phase, because the former is collected at a lower point in tower Id than the latter. The collected secondary extract phase is withdrawn through line |21 and its density increased and its solvent content reduced by vaporizing at least part of its solvent content in evaporating chamber |25 by means of heating coil |28. Propane vapor is returned to vapor line 61 through line |29 and the partially desolventized remainder is pumped back to tower llc. through line |30 by means of pump 3|. Line |30 is shown entering tower ||a at a point higher than collector trough |25 but the point of introduction may also be lower than trough |25. The reflux material thus obtained will ilow downwardly in tower lla by virtue of its increased density and, being of a composition near the extract oil composition, it accomplishes the desirable rectifying eiects.

This operation makes it possible to withdraw a secondary extract phase through line 36a which contains product oil only. Thus, the secondary extract phase material diverted through line Ia to serve as solvent in the other two fractionating towers, Illa and 62, contains a smaller amount of oil than would be the case if tower Ila were reuxed by means of a portion of the product separated at 31a.

According to an illustrative embodiment of the process of Fig. 2, 100 volumes of fatty oil introduced into tower Illa from line Ita in a unit of time are treated with 1800 volumes of liquefied propane introduced into tower Illa from line |a. Tower |0a is operated to distribute 2 parts of the fatty oil to the first rainate product withdrawn through line a. The remainder of the fatty oil and substantially all the propane pass overhead through line |9a and are transferred directly to tower 62 for further treatment. Into tower B2 1800 volumes of propane are introduced through line 69. Tower 62 is operated to separate an intermediate ramnate fraction equivalent to 30 parts of the oil charged to the process. This oil and about 30 volumes of propane are withdrawn from the process through line 65. The remainder of the oil introduced into tower 62, together with all the remainder of the propane, passes overhead and is introduced into tower a for treatment in the manner described. In tower l Ia conditions are controlled to separate a nal rafnate product comprising 66 parts of the oil charged to the process. This oil and approximately 70 volumes of propane are withdrawn from the process through line 44a. Of the 3600 volumes of propane charged to tower |52 per 100 parts of oil charged to the process through line Isa, approximately 30 volumes are withdrawn from the bottom and the remaining 3570 volumes are introduced into tower lla through line 69. Into the bottom of tower Ha approximately 1900 volumes of propane are introduced through line 32a, which connects the bottom of tower ||a with reservoir 26a. Of the total of 5470 volumes of propane thus charged to tower ||a approximately '10 volumes are withdrawn from the bottom with the raflinate. The remaining 5400 volumes pass upwardly in tower Ha and 4500 volumes are withdrawn in the 18 final extract phase through line 36a. A portion of this final extract phase containing 900 volumes of propane passes to vessel 31a for recovery of solvent and the final extract product. The

remaining 3600 volumes of propane are diverted through line |5a, and of this quantity 1800 volumes pass through line 60 to the bottom of tower |52, while 1800 volumes are introduced into the bottom of tower Ita. Since the prop-ane passed to vessel 31a contains approximately 2 parts of the oil as the final extract product the 3600 volumes of propane diverted through line 15a are accompanied by approximately 8 parts of fatty oil per parts of oil charged to tower Illa. `This fatty oil is equally distributed between the streams of solvent passing to towers |0a and 52.

tower Ita through line |9a contains approximately 1800 volumes of propane and approximately 102 parts of the fatty oil per 100 parts of oil charge. After the separation treatment in tower 62 the extract phase passing overhead from that tower through line 69' contains approximately 3570 volumes of propane and 58 parts of oil per 100 parts of the fatty oil charged to the process?" To assist in rectifying the extract phase in tower Ila, a portion of the upflowing extract solution, containing 900 volumes of propane, is withdrawn through line 21.v The oil phase separated at |25 is returned as reiiux through line |30. The oil content of the reux fraction returned through line |30 comprises about 2-4 parts of oil by weight per 100 parts of oil charged to tower |0a, the exact amount in this range depending on the magnitude of the temperature gradient between trough |26 and the top of tower lla.

In a further modification of the process of Fig. 2, the solvent stream flowing through line 69 to the bottom of tower 62 may be supplemented by a small quantity of relatively pure solvent diverted from line 32a through line 12. In this operation it may be desirable to introduce the solution from line 69 into tower S2 at a somewhat higher point.

In a further modification of the process of Fig. 2, the solvent stream flowing through line |5a to the bottom of tower |0a may be treated to remove free fatty acids. In this operation all or a portion of the licuids owing through line ldl are diverted through line 13. is introduced through line 14 and the resulting mixture passes through mixer 15 to a settler 16. [n settler 1S the soaps formed are permitted to settle and are drawn olf through line 11, while the resulting neutral solution is returned to line l5@ through line 1B. This modification has the advantage that the accumulation of fatty acids in the lsystem is reduced and any soaps which are not removed by settling at 16 are subiected to two precipitation treatments in towers ma and 52 prior to the final separation of the railinate fraction of the oil in tower Il r1., which may be intended for use as an edible oil.

A further modification of the application of the t process to the continuous separation of the fatty oil into four fractions by the use of three fractionating towers is illustrated in Fig. 3. In this K modification a part of the iinal extract phase withdrawn from the upper end of the second frac- I ticnation tower indicated in Fig. 3 by the numeral l ib is heated to paracritically fractionate it into a recycle solvent fraction and a reflux cil frac- Consequently in the above opera-k tion the overhead extract phase withdrawn from Alkali tion: The r'irstfractionatingetower mb preferably-1` is operated to' separate astb'e first rainate in portion of the fatty oil. treatmentv of' soybeanV oil charged to tower lilo through line |811 operatingv conditions are controlled to separate a raflinatecomprisine a minor' portionv of the fatty oil charged to the tower andrepresenting a concentration of the unsaturated' components ofthe fatty oil'. as-well as a concentration of color bodies and other relativelyk insolublecomponents ofthe oil. In this modification tower llib is operated under conditions elective to produce a rafna-te comprising oil equivalent to 15 to 45* per cent ofthe fatty oil charged to tower |13. preferably 25 to 35 per cent. Tower lb is constructed and arranged to function substantially in the same manner as tower Ilof Fig. 1. Tower Hb is constructed and arranged to function substantially in the same manner asV tower Il of Fig. 1 and towerY Ha of Alig. 2. The operation of tower Hb closely resembles that ofitowerV Ha, since the extract oil treated in tower lib represents a fraction of lthe' fatty oil' generally similar to the fraction treated in tower Ha. of' Fig. 2. The modification ofFig. 3 differs from that of Fig. l largely in that' the relatively large minor fraction of the fatty oil separated as rafiinate' in tower leb is 'further treated' in tower T9 to extract most -of'this raffinate in intermediate extract'product oil of goed color 'and good' drving' qualities. whileY con-r centratmgthe color' bodies'and other lessl soluble componentsin arelatively small rainateprodu ct separated in the bottom' of tower 19'. Tower 19' is similar in construction and arrangement to the other fractionating'towers. being arranged to effect close fractionation of' the oil into the desired fractions. Tower 13, like the other towers described, is substantially elongated vertically and is provided'with contact means to facilitate-Y contact of` theV counter-flowing' liquid phases. Tower T8' is provided with heating coils 80 for control of temperature and the maintenance of a tempera-ture gradient; and'may also be provided with meansv for effecting external refluxihgof'the tower. In Fig. 3 apparatus for supplying' external reflux oil to towers lilo. Hb and 19 has been omitted', for simplicity of presentation. It is to' be understood, howeverv that any or all of' these towersmay befsubiected to'` external refluxing in thema-nner described in connectio'nwith towers Hl'and Il ofFig.' 1.

In Fig. 3 the parte whose function and operation are generally similar* to corresponding r`parts of Fig; 1 are indicated by similar reference numerals, with the subscript 13. It will be under stood that the description' of such parts given above in connection with'Fig. I applies alsoY to similarly numbered' parts' of 3, except" as modified byfthe descriptiorrof Fig. 3'.

The relatively large raflinate, comprising a minor fraction of theffatty'oil; whichY isf-collected in the-bottom of tower' ib'islwithdrawn therefrom through line 2Gb, which connects with'tower 'I9 at an intermediate point. A solvent stream is introduced into tower'lf from line Yil'l and this solvent stream flows upwardly in tower 1Q in' counter-current contact with the downiiowing oil phase, in the manner described above in connection with the other towers.- Since tower i9" is provided to extract a maior portion of the oil charged to the towerv the operating temperature of tower 19 ordinarily is somewhat lower than that. of tower I b. Ordinarily operating conditionsin4 tower 'le are regulated .to restrictthenal raiinate in' this tower toV lesstl'ian 1i) perlcent, and preferably less than 5 per cent, of. the fatty oil charged to the process through line leb. This; minor fraction, representing a concentration: of color bodies andV other. less soluble components. of the fatty oil, is withdrawnV fromA tower. 'l5 through lineZ.

The extract. phaseformed in tower i3 iswithfj drawn overhead throughline 83, which connects with separating vesselV 34. Pressure on this ex tract phase isy reduced at valve to effect substantial evaporation of the solvent, heat being supplied by heating means Si! to facilitateevaporation. The solventvapors are separated in vesn sel Se and withdrawn overhead through line El, which connects with line atb, whereby the solvent is conveyed bach to solvent reservoir 25h; cooling means 2lb being provided in line ich to'condense the solvent vapors. The liquid separated in vessel is withdrawn through line BB- for fur ther treatment, such as the. removal cfresidual quantitiesv of. solvent, and other desired refining steps; r'his fraction isa drying oil of good color.

The extract phase produced in tower Hl?) is withdrawn overhead through line Ito', which connects with tower Sib at an intermediate point thereof. In tower l lo the extract oil is subjected to further fractionation treatment with relatively pure solvent introduced into'the bottom 0f tower Hb through line 32o from reservoir 26o. Tower lio is operated to separate the extract oil introduced into the tower into a relatively large inter.- mediate fraction as a raffinate product and a relatively small nal extract fraction comprising a concentration of the most soluble components of the fatty oil, The operation of tower lib is generally similar to that of tower il and tower lia, and the details of operation described in connection with those towerszapply also to the operation of tower Hh. The relatively large rafiinate produced in tower lib is withdrawn. from the. bottom thereof through line del), which connects with. a. separating vessel 5b. Pressure. is reduced at valve I-b whereby there is substantial evaporation of solvent which passes overhead in vessel 45o through line 8b to line e817. The liquid separated in vessel 555e is withdrawn through line 9b for further treatment to recover the substantially refined fraction of light color and low fatty acid content.

The final extract phase formed in tower Hb is withdrawn overhead through line 36h, which connects with separating vessel 3117. Pressure is released at Valve 3% and heat is supplied at heating means 39h to eiect substantial evaporation of the solvent which passes overhead in vessel 3111 through line 40o. A relatively small nal extract fraction is withdrawn from the processfrom vessel 31o through line Mb. This fraction represents a concentration of fatty acids of the fatty oil and also a concentration/of the tocopherol and sterol content ofthe oil.

A portion of the solvent phase fiowing through linek 35o is diverted therefrom through line |35' and heater. v|36 to a separating vessel |31; The'l heatingv of the secondary extract fractions already ata temperature well up in the paracritical range, causes it to precipitate most of its oilinto a lower phase-which separates in vessel |31. This lower phase material is pumped' back into the.

upper end of tower Hb by way of line |38 andk pump |39. The oil fraction thus returned to tower l lo serves therein as a reflux. The lighter phase which. has, at most, a Very small remaining oil content, is withdrawn from-the upper part of separating vessel |31 through line |5b and is 1ntroduced into the lower end of tower |b to serve therein as solvent. This recycled solvent fraction may be cooled by cooling means |6b to 1ncrease its solvent power and pumped in at proper pressure by pump |1b in substantially the same manner as in the case of line |5 in Fig. l and line |5a of Fig. 2. Another portion of the solvent recycle fraction from vessel |31 may be diverted through line 8| in order to supply a portion of the final extract phase to the bottom of tower 19 as the solvent stream therefor. Line 8| is provided with cooling means 89 and a pump 90 to effect transfer of the extract phase into tower 19 and to cool the extract phase to the lower temperature desired in the bottom of tower 19.

The solvent recycle fraction leaving vessel |31 may be divided between lines |51) and 8l in any desired proportion by means of valves |40 and |4|. In some cases, all the solvent recycle will be diverted to tower 19 through line 8|, tower ||Jb being supplied with a stream of fresh propane through line |51) in lieu of solvent recycle. Thus pure propane is used in tower Ib to separate original charge oil into a primary extract and a primary rafnate, each of which is then refractionated in towers ||b and 19, respectively; the solvent stream for fractionating the primary rafnate in tower 19 may be comprised in whole or in part of solvent recycle fraction obtained by heating extract phase from the fractionation of primary extract with fresh propane in tower 1lb.

The operation illustrated in Fig. 3 is particularly advantageous when tower ||b is to be reuxecl externally, as by means of product from line 41h, in addition to any reuxing by material from line |38.

While a single heating means, at |36, is provided in Fig. 3 for the treatment of the extract to be recycled followed by a single phase separation, at I 31, it is evident that a heating tower like tower l2 of Fig. 1 may be employed for the same purpose in Fig. 3.

According to an illustrative embodiment of the process of Fig. 3, 100 volumes of fatty oil are charged into the system through line |8b in a unit of time, while 1100 volumes of liquefied propane are introduced into the bottom of tower Hb through line 32h. Extract solution from the top of tower Hb is transferred through line |35 to separating vessel |31 at the rate necessary to separate solvent recycle solution at the rate of 2000 volumes of propane per 100 volumes of charge oil. From vessel |31 solvent recycle solution is transferred through line |513 to the bottom of tower |81; at the rate of 1500 volumes per 100 volumes of oil charged to tower |012. Tower |0b is operated to distributev 31 parts of the oil contained therein to a rst raffinate which separates in the bottom of tower |017. This rainate fraction, containing about 30 volumes of propane, is transferred through line h to tower 19. ySolvent recycle solution from the vessel |31 is introduced, through line 8|, into the bottom of tower 19 at the rate of 500 volumes per 100 volumes of oil charged to the process through line |82). Tower 1S is operated to separate a final raffinate fraction containing- 2 parts of the fatty oil which is withdrawn from the bottom of tower 19 through line 82. Substantially all the pro- -pane introduced into tower 19 passes overhead through line 83, and these 530 volumes of propane are recovered at 84 for recirculation to reservoir 26h. The 1500 volumes of propane introduced into the bottom of tower |0b from line |5b pass entirely to the extract phase withdrawn overhead, except for approximately 30 volumes which are included in the raffinate solution withdrawn through line 20h. The 1470 volumes of propane contained in the extract phase flowing from the top of tower |0b through line |9b are all introduced into tower b. The sum of this volume plus the volu -e of propane introduced into the bottom of tower lb from line 32D is 2570. Tower ||b is controlled to separate a raffinate fraction equivalent to approximately y tower lh through line 44h also contains approximately '70 volumes of propane. The remainder of the propane introduced into tower Hb, 2500 volumes, is included in the extract solution withdrawn from the top of tower ||b through line 36h. As has been described, approximately fourfths of this extract phase is diverted to vessel |31 through line |35. The remaining one-fifth of the extract phase withdrawn from tower ||b is passed to vessel 31h forseparation of the solvent from the product oil. The operating conditions of tower ||b are controlled whereby approximately 2 parts by weight of the fatty oil, per parts of fatty oil charged to the process through line |81), are recovered from solvent at 31h. Consequently, the solvent stream passed to i vessel |31 contains 8 parts of fatty oil. The extract solution is heated at |36 to a temperature effective to precipitate about one-half the oil content thereof as lower phase material for reflux. Consequently, the extract phase flowing through line |9b to tower ||b contains 73 parts by weight of fatty oil per 100 parts of oil charged to the process through line 8b.

In accordance with one modification of the method of Fig. 3, all or a portion of the solvent stream for tower 19 may be provided in an alternative manner. In this modication a portion of the extract phase flowing through line leb from tower Illb to tower I lb is diverted through line 9|, which connects with a phase separating vessel 92. The extract phase material flowing through line 9| is heated by heating means 93 to a temperature sufficiently high to effect precipitation of the maximum possible proportion of the oil content thereof as a separate liquid phase. The precipitated material settles out as a lower liquid phase in vessel 9'2. This material is Withdrawn from the bottom of vessel 92 through line 94 which discharges into line |917 whereby the lower phase material separated in vessel 92 is subjected to fractionating treatment in tower Ib in the manner described. Cooling means 05 may be provided in line 94 to adjust the temperature. The upper phase is withdrawn overhead from vessel 92 through line 86. Line SB connects with line 8| to effect transfer of the overhead phase material from vessel 32 to the bottom of tower 19 as all or a portion of the solvent stream for that tower.

In accordance with a further modification of the process of Fig. 3, the solvent stream flowing to tower 19 through line 8! is treated to remove 23; drapnsthroushilmeli is..t he r.ry returned .tov line-3l through line |02.- thegfattyjacid content of the solvent,v which might otherwise ,be included in. the. drying. oil fraction, is removed prior to contact ofthev solvent with the Qiltreated intower 1.9.

nzany--of the above-described methodsl of opf erating the process-of Figs 3, tower YIIb may be operated primarily to strip the rafnate product of .thetower andvproduce asolventstream atthe top. In this operation no extract solution from tower. 1lb passes to vessel 31h for separation. of oil, andtheiig-htportionof the fatty oil is al1 incorporated n-theextractproduct or tower TIS, exceptior fatty acids removed at |09.

.InY the foregoing detailed description. of the improved process reference has been made` to therefining .of vegetable oils suchassoybean oil, inwhioh the final `extract fraction is a concentration. of. tocopherolssterols, and fatty acids. The process-ofthe invention applicable also to thetrea-tmentot. vitamin-containing fish oils to separate a small. final extract which is a concentration of the vitamin content of theY charge oil. In the treatment. of a vitamin oil in the processing. arrangement of Fig. 1, the oil may be treated in tower I9 to separate a small rafiinate fraction which is a concentration of the color bodies,v and the decolorizedextract oil is then further treatedV in tower. ll to separateV a smallv final extract fraction containing the vitaminsinhigh concentration. The rainate fraction .separated in tower l I is a refined oil of good color which still may have suiiicient vitamin potency for certain uses as a vitamin oil.

The. processing arrangement of Fig. 1 also may .be used. in subjecting a vitamin oil to a twostage concentrating treatment. In thisV arrange.. mentv tower I is operated under conditions eifeotive to separate a rainnate comprising the bulk ofi the oil. A relatively small extract fraction is then passed to tower l I for further concentrationv treatment to produce the final small extract. In thsprocessing arrangement it may be desirable to operate tower l0. to separate anextract fraction containing only a little more of the oil than is desired in the final fraction containing the vitaminconcentrate. For example, tower ill may be operated to separate a raiiinate containing 96 per centof the oil. The .4 per cent extract oil from tower Ill is then fractioned in tower H into approximately equal portions, the raiiinate fraction from tower Il constituting the vitamin concentrate. This method of operation is based on the fact. that the concentration of the highly soluble stearincontent of vitamin oils in the final extract. fraction makes it. difficult to pro.

duce concentrates .of high potency in the nal ex. tract. In this operation, by careful regulation ofthe operation of. tower l! the vitamin content ofthe oil is largely. concentrated in the ralinate withdrawn from the bottom of towerv ll through line` 44. The oil fraction recoveredoverhead from tower l! and withdrawn through line 4I may then be subjected to refrigeration to separate the stearinfrom any oil included in the extract fraction. The stearin separated in this manner may be washed'` by means of relatively cold solvent from reservoir 2B, prior to passage of the solvent totower Il through line 32, in order to recover and return to the system any vitamin-containing oil included in the iinal extract fraction from tower ll.

ory these methods .or treatment ci. fish oilsY This. ,medi lisationv has; the advantage that..

` heIleutralized solvent i 'pyr meansor the processing arrangement of Fig. 1 may-becarried out also in the processing ar.- rangement of Fig. 2, with-certain additional steps provided for by Fig. 2. For example, a fish body oil may be treated in accordance with the arn rangement of Fig. 2 to separate a small color fraction at 2cd, an intermediate drying oil fraction ali-64; an intermediate edible oil fraction at Lillo., and a vitamin fraction at lila. Alternatively, towersv B2 and lio oi Fig. 2 may be employed in a two-stage concentration treatment of decolorized extract oil from tower lee, as described above in connection with Fig. l.

The. operating conditions and the material distributions described above in connection with the various modifications of the process illustrated by the drawings necessarily refer to conditions existing after equilibrium has been reached in the operation of the process. It will be understood tl'rat` any of the available operating expedients may be employed for reaching equilibrium conditions. For example, in starting up the system represented by Fig. 1, tower Il may he operated temporarily at a higher-than-normal top tempera-ture until the oil recovered at 3i is of desired quality. Thereafter the temperature may be lowered gradually to increase the quantity of the oil distributed to the extract phase. Furthermore, all of the oil separated at 3'! may be returnedrto the top of tower ll through line i2 until the quality of the oil separated at 3'! is satisfactory. Similar starting-up procedures may be applied to the other systems of operation illustrated in the drawings.

From the foregoing description it will he seen that the object of the disclosed method in all its species is to reduce the oil content of that portion of the secondary extract phase which is to be employed as solvent in the primary frac tionating tower; and, further, that this object is accomplished by separating reliux oil from said secondary extract phase material.

In the species of Fig. 1, a side stream of secondary extract phase is withdrawn from the secondary fractionating zone at some point intel mediate between the charge oil inlet and the extract phase outlet, iiowed upwardly in a zone of increasing temperature, preferably to a maximum temperature exceeding the maximum temperature of the secondary fractionating zone, to form a recycle solvent phase and a reflux oil phase. The reflux oil so precipitated may be introduced into the secondary fractionating zone as reflux or may be used, in part at least, as reiiux in any preceding fractionating bone i. e. any fractionating which is upstream in the process flow` The recycle solvent phase may have an oil content much less than the content of product oil in the fina-l extract phase.

In the species. of Fig. 2, the final secondary extract phase does not carry reflux oil because theV refluxing is accomplished separately at a lower point in the secondary fractionation zone.

In the species of Fig. 3 no side stream is withdrawn, but a portion of the fina-l extract phase is diverted and separated bv heat into a recycle solvent phase and reux oil phase. The reiiux oilphase should ordinarily loe returned to the top of the tower through which it was obtained regardless of whether this tower is to be reluxed externally or by other means. The quantity oflower phase material thus returned may be sufficient to do all the necessary refluxing; oritlmay be supplemented by external remixing! inthe usual manner, i. e. by returning 25 some' of the product oil which remains aftery the vaporization of solvent.

I claim:

1. In the rening of a fatty oil by a series of at least two paracritical fractionations with a low boiling solvent having a critical temperature not substantially higher than 450 each of said fractionations being carried out in a vertically extended fractionation zone with an extract phase outlet at the upper end, raffinate phase outlet and solvent inlet near the lower end, and a charge oil inlet intermediate said ends, the improvement which includes the steps of charging said fatty oil and a solvent comprised prini cipally of said low boiling solvent to a rst vertically extended fractionation zone and regulating the conditions of temperature and pressure therein to forni a primary extract phase and a primary rainate phase; separately withdrawing said extract and rafnate phases from said extract and raffinate phase outlets respectively and charging to a second vertically extended fractionation zone a charge derived from one of said phases; countercurrently contacting said charge with said low boiling solvent in said second zone and regulating the conditions of temperature and pressure therein to fractionate said charge into a secondary extract phase and a secondary raiiinate phase; collecting a portion of said upflowing extract phase from said second fractionation zone at a point substantially above the charge oil inlet; heating said withdrawn extract phase material to evaporate at least part of the solvent content thereof and to produce a reflux material substantially heavier than said withdrawn extract phase; returning said reflux material to said second fiactionation zone at a point above its charge oil inlet; llowing extract phase upwardly to a region of higher temperature above said sidestream withdrawal and said reux return; withdrawing a iinal secondary extract phase from above said region; recovering a product from a part of said nal secondary extract phase, and diverting another part to the lower portion of said first fractionation zone to serve therein as solvent.

2. In the refining of a fatty oil by a series of at least two paracritical fractionations with a low boiling solvent having a critical temperature not substantially higher than 450 F. each of said fractionations being carried out in a vertically extended fractionation zone with an extract phase outlet at the upper end, raffinate phase outlet and solvent inlet near the lower end, and a charge oil inlet intermediate said ends, the improvement which includes the steps of: charging said fatty oil and a solvent comprised principally of said low boiling solvent to a first vertically extended fractionation zone and regulating the conditions of temperature and pressure therein to form a primary extract phase and a primary raffinate phase; separately withdrawing said extract and raffinate phases from said extract and raffinate phase outlets respectively and charging to a second vertically extended fractionation zone a charge derived from one of said phases; countercurrently contacting said charge with said low boiling solvent in said second zone and regulating the conditions of temperature and pressure therein to fractionate said charge into a secondary extract phase and a secondary raiiinate phase; collecting a portion of said upflowing extract phase from said second fractionation zone at a point between its charge oil inlet and its extract phase outlet; introducing said withdrawn secondary extract phase ma- Y terial into the lower end of a vertically extended heating zone in which a gradient of temperatures increasing with elevation is manitalned to produce a separation of said withdrawn secondary extract phase material into an upper solvent phase and lower oil phase; introducing said lower oil phase into at least one of said fractionation zones at a point above its charge oil inlet to serve as reflux therein; withdrawing said upper solvent phase from the upper end oi' said vertically extended heating zone and introducing it into the lower portion or' said first fractionation zone to serve as solvent therein and withdrawing secondary extract phase containing a rectii'ied secondary extract from said second fractionation zone at a point above the introduction or' said reliux.

lh the refining of a fatty oil by a series or' at least two paracritical Iractionations with a low-boiling solvent having a critical temperature not substantially higher than 450 li., each oi' said fractiohatlohs being carried out in a vertically extended fractionation Zone with an extract phase outlet at the upper end, a rainnate phase outlet and a solvent inlet in the lower end, and a charge oil inlet intermediate said ends, wherein ratty oll and` a solvent comprised primarily or' said low-boiling solvent are charged to the nrst 0I' said Zones, and conditions therein are regulated to ioriii primary extract and rai'- flnate phases, and a charge derived from one ol salti phases is introduced into the second of said zones roi' fractionation into secondary ex- 'tract ano. raliinate phases, and wherein at least` part 0I the solvent for the first or' said Zones is obtained from the secondary extract phase without evaporation and condensation by the expedient or adjusting the temperature and pressure of at least a portion of' said secondary extract phase to a condition or' reduced solubility to separate it into a solvent phase and an oil phase and withdrawing said solvent phase, adjusting its temperature and pressure to a condition oi' greater solubility, and introducing said solvent phase into the lower portion of the rst of said fractionation zones to supply at least a part of the solvent therein, an improved method ol' refluxing which includes the steps of: withdrawing a sidestream of upfiowing secondary extract phase 'lroni the second of' said iractionation zones at a point below the extract phase outlet and above the charging inlet of said zone; separating a relatively heavy reflux fraction from said withdrawn sidestreain; and pumping said reflux fraction back into said second fractionation zone at a point above said sidestream withdrawal, to serve as reflux in said second fractionation zone.

4. In the refining of a fatty oil by a series of at least two paracritical iractionatiohs with a low-boiling solvent having a critical temperature not substantially higher than 59" F., each of said fractionations being carried out in a vertically extended fractionation zone with an extract phase outlet at the upper end, a raffinate phase outlet and a solvent inlet in the lower end, and a charge oil inlet intermediate said ends, wherein fatty oil and a solvent comprised primarily of said low-boiling solvent are charged to the first of said zones, and conditions therein are regulated to form primary extract and raffinate phases, and a charge derived from one of said phases is introduced into the second of said zones for fractionation into secondary ex- Peet of. elle Seltene. ne; of; Sei@ is obtained from the segvdiaigg, entgegen 913%@ Without evaporation and condensatie the expedient. of; eeljuflne; olle.- oeszlpeeeftune. and PleSSlle. off. e? leefoo e. Dorlioll. off; SedQ Seoenelely elolefet Rheee. o9 of, oondlolon. of; ,f edueed; Sole: bility. to oeloereoe le. into @Solvent phase; oll.. Dloeee, epfl Willelxowllg. oevsl. solver;Jo ehee, efllolng; los tememento.. @nel Preeeure to.. o. ooloellion of greet eolllloilllyf. 2.11.51 iobroeluoine Seid.. Solveoololoeee. l me. portionof. the fleet of Sold., freeolon zooe. oo. sunlolyf et leest. o. poele.. of; the., Solyelttllereln, improved meollo@ of Yellooelloga Whloll. looludee. the. Stone. of.: willldrewioe. eisleo m otfu fowlnetoeov ondaryextreotolloe o. tloneorl Zones.. et of. point; loeloyv. elle. elem' o? phaee outlet enel. above.. elleA ehring; o.f. Sedzone.; heetineeeislt-Wioll ewnexereooohose s'umolentlytojeansee eenen .lortinoeewof 1m 5l. fraoolooe. witlloo.. sylooewlel eyerrorellorn rev. turning. heavier. o felellyvollgulol freolllone to. .said seoonelreetlonetion .Zone @te eoloo oloove elle charging mlo'ofloo eryeb @ein @e 1... introducing. ollelihteli of. Se.l l.l.-owo. o heeeo. mile the.. lower part; of; Seid.. met. felllqlleltioll. zel-le. meerve therein.. as, oelyelloi; @nel withdrawing.. a. nalseondary. eyteetlonel V9.1 -e 'd eeeellol. fyationtion. zone.. one a.. nel of. el?

Claims (1)

1. IN THE REFINING OF A FATTY OIL BY A SERIES OF AT LEAST TWO PARACRITICAL FRACTIONATIONS WITH A LOW BOILING SOLVENT HAVING A CRITICAL TEMPERATURE NOT SUBSTANTIALLY HIGHER THAN 450* F., EACH OF. SAID FRACTIONATONS BEING CARRIED OUT IN A VERTICALLY EXTENDED FRACTION ZONE WITHIN AN EXTRACT PHASE OUTLET AND SOLVENT INLET NEAR THE LOWER END, PHASE OUTLET AND SOLVENT INLET NEAR THE LOWER END, AND A CHARGE OIL INLET INTERMEDIATE SAID ENDS, THE IMPROVEMENT WHICH INCLUDES THE STEPS OF: CHARGING SAID FATTY OIL AND A SOLVENT COMPRISED PRINCIPALLY OF SAID LOW BOILING SOLVENT TO A FIRST VERTICALLY EXTENDED FRACTIONATION ZONE AND REGULATING THE CONDITIONS OF TEMPERATURE AND PRESSURE THEREIN TO FORM A PRIMARY EXTRACT PHASE AND A PRIMARY RAFFINATE PHASE; SEPARATELY WITHDRAWING SAID EXTRACT AND RAFFINATE PHASES FROM SAID EXTRACT AND RAFFINATE PHASE OUTLETS RESPECTIVELY AND CHARGING TO A SECOND VERTICALLY EXTENDED FRACTIONATION ZONE A CHARGE-DERIVED FROM ONE OF SAID PHASES; COUNTERCURRENTLY CONTACTING SAID CHARGE WITH SAID LOW BOILING SOLVENT IN SAID SECOND ZONE AND REGULATING THE CONDITIONS OF TEMPERATURE AND PRESSURE THEREIN TO FRACTIONATE SAID CHARGE INTO A SECONDARY EXTRACT PHASE AND A SECONDARY RAFFINATE PHASE; COLLECTING A PORTION OF SAID UPFLOWING EXTRACT PHASE FROM SAID SECOND FRACTIONATION ZONE AT A POINT SUBSTANTIALLY ABOVE THE CHARGE OIL INLET; HEATING SAID WITHDRAWN EXTRACT PHASE MATERIAL TO EVAPORATE AT LEAST PART OF THE SOLVENT CONTENT THEREOF AND TO PRODUCE A REFLUX MATERIAL SUBSTANTIALLY HEAVIER THAN SAID WITHDRAWN EXTRACT PHASE; RETURNING SAID REFLUX MATERIAL SAID SECOND FRACTIONATION ZONE AT A POINT ABOVE ITS CHARGE OIL INLET; FLOWING EXTRACT PHASE UPWARDLY TO A REGION OF HIGHER TEMPERATURE ABOVE SAID SIDESTREAM WITHDRAWAL AND SAID REFLUX RETURN; WITHDRAWING A FINAL SECONDARY EXTRACT PHASE FROM ABOVE SAID REGION; RECOVERING A PRODUCT FROM A PART OF SAID FINAL SECONDARY EXTRACT PHASE, AND DIVERTING ANOTHER PART TO THE LOWER PORTION OF SAID FIRST FRACTIONATION ZONE TO SERVE THEREIN AS SOLVENT.

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