US2660590A

US2660590A - Fractionation of fatty materials

Info

Publication number: US2660590A
Application number: US748573A
Authority: US
Inventors: John T Dickinson
Original assignee: MW Kellogg Co
Current assignee: MW Kellogg Co
Priority date: 1947-05-16
Filing date: 1947-05-16
Publication date: 1953-11-24
Anticipated expiration: 1970-11-24

Description

Nov. 24, 1953 .1. T.- DlcKlNsoN 2,560,590

FRACTIONATION oF FATTY MATERIALS Trams Nov. Z4, 1953 .1. T. nlcKnNsoN 2,650,590

FRACTIONATION OF' FTTY MATERIALS ATTURAZEQSE Patented Nov. 24, 1953 UNITED STATES John T. Dickinson, Basking Ridge,

RATENT OFFICE N. J., assigner' to The M. W. Kellogg Company, Jersey City, N. J., a corporation of Delaware Application May 16, 1947, Serial No. 748,573

5 Claims. l

This invention relates to improvements in the fractionation of fats and related high molecular weight materials of animal, vegetable and marine origin. These materials, designated hereinafter as fatty materials, include the fatty oils and fatty solids which comprise glycerides, fatty acids, and unsaponii'lable compounds, and other high molecular weight mixtures of similar origin, such as cashew nut shell liquid.

The fatty materials may be treated by means of a selective solvent at temperatures in a range from about 110 F. below the critical temperature of the solvent to a few degrees above the critical temperature of the solvent to fractionate them into a plurality of fractions at least one of which is superior in some respect to the original fatty material. For example, a fatty oil, such as a fish oil, may be treated to separate a fraction concentrated in fatty acids, to separate a fraction in which the color bodies are concentrated, or to separate a fraction in which desirable ingredients such as sterols and oil-soluble vitamins are obtained in high concentration. Also a soybean oil may be treated to separate a small fraction containing the color bodies, phosphatides and mucilaginous materials as Well as a fraction rich in unsaturated glycerides and therefore suitable as a paint oil. Another fraction containing more saturated glycerides suitable for salad oils and a small fraction containing sterols and tofj,

pane, the butanes, the pentanes and the corre- .Y

sponding olefins as well as mixtures thereof, such as a mixture of methane and normal butane. Other solvents include other organic compounds such as halogenated hydrocarbons including dichlordiuormethane and methyl fluoride. other solvents which may be used are carbon dioxide, ammonia and dimethyl ether. In general, it may be said that inert and nonreactive compounds having critical temperatures not sub-,- stantially higher than 450 F. and in which at least one component of the crude oil to be treated is soluble at temperatures above about 100o F. below the critical temperature, may be employed satisfactorily and are to be included within the term low-boiling solvent. The preferred solvents are those having a critical temperature less than 325O F. such as normally gaseous compounds which have the desired solvent power when maintained in the liquefied state, for example, propane.

The fractionation of fatty materials by means of solvents requires separation of the solvent from the products in order to reuse the solvent in the treatment of further quantities of fatty materials. The recovery of a solvent of relatively low critical temperature ordinarily involves evaporation of the solvent from the extract and raffinate phases formed in the fractionation process. This may be accomplished by heating such solventcontaining mixtures at the same pressure as employed in the fractionation zone to vaporize the solvent. However, it is preferred to reduce the pressure on Such mixtures to a substantially lower pressure level to effect substantial evaporation of solvent by that means alone. Since this has the effect of cooling the mixture to a relatively low temperature, it is necessary ordinarily to heat the mixture to assist evaporation. The evaporated solvent must then be returned to the L form in which it is to be employed in the process,

and this is accomplished ordinarily by condensing the vapors by means of cooling and pumping the condensate thus obtained up to the operating pressure employed in the fractionation zone.

It is an object of the present invention to provide an improved process for recovering and recirculating the solvent contained in the extract phase, according to which the relatively expensive steps of vaporizing and condensing the vapors and pumping the condensate up to the operating pressure are eliminated.

The present process involves the treatment of the extract phase obtained from a fractionation step to obtain a solvent-rich liquid phase containing a higher proportion of the solvent than said extract phase and separate liquid phase containing a lower proportion of the solvent than said extract phase, and hereinafter referred to as an oil-rich phase. This is accomplished by heating the nal extract phase to a temperature above -that employed in said extraction step, while at the same time maintaining pressure at such a level that the solvent is not vaporized. Even though the extract phase and its constituents are maintained in the liquid phase when the temperature is increased to a point near or above the critical temperature, the solvent power of the solvent is decreased to such an extent that many or all of the oil components of the extract phase are separated as a separate phase. The solvent-rich phase may contain small quantities of those components which are most soluble in the solvent but normally these components form only a very minor proportion of this phase. The solvent-rich phase is then withdrawn for reuse as solvent and the oil-rich phase, which may contain minor amounts of the solvent, is separately withdrawn. Phase separation of the extract phase also is accomplished by reducing pressure, while maintaining the temperature substantially the same. or while simultaneously raising temperatures. The pressure will not be reduced below the point at which the solvent will be Vaporized but only suiciently to lower its solvent power for some cf the components of the dissolved oil.

Having separated the extract phase into a solvent-rich phase and an oil-rich phase in the manner described above, these components may be further utilized in the system without further treatment. The solvent-rich phase may be returned to the fractionation tower for contact with fresh fatty oil to be treated. The solvent-rich phase is cooled to a temperature below that at which it emerges from the phase separator previously mentioned to bring it to the desired extraction temperature. By virtue of the lower temperature, the solvent portion of the solventrich phase will have its solvent power increased so that it will function in a manner similar to a pure solvent when it comes in contact with the fresh fatty oil feed.

The solvent-rich phase withdrawn from the phase separator may be returned for reuse in the fractionating zone without any further treatment other than cooling. However, in the treatment of many fatty mixtures there may be concentrated in this solvent-rich phase highly soluble fatty acids which are difficult to precipitate in the phase separator and thus tend to accumulate in the system. To prevent such accumulation the recirculated solvent-rich phase may be treated in accordance with this invention with a suitable neutralizing agent to convert such fatty acids to soaps which are then separated from the solvent solution by gravity.

The improved method of this invention is applicable to a single stage fractionation, in which only two fractions are produced, or t-o multistage treatments in which either the extract or the raffinate, or both, from a preliminary fractionation are subjected to further fractionation treatment in a separate zone. According to this modification, the fatty mixture is treated in a plurality of fractionating towers in which the operating conditions are varied to effect in each tower the desired fractionation of the fatty mixture introduced therein.

The fractionation treatment of the improved process preferably is carried out in a vertically elongated fractionation tower provided with trays, baies, packing, or other suitable means for promoting the intimate contact of counterflowing liquid phases. The fatty material to be treated, hereinafter referred to as oil, is introduced into such a tower preferably at an intermediate point. If it is desired to operate the tower to effect mere stripping of one portion of the oil from another portion by means of the solvent, the oil may be introduced to the tower at a point near the top. If it is desired to effect closer fractionation of the oil, it is introduced into the tower at a point substantially below the top in order to provide in that portion of the tower above the oil charge point a rectification zone, as distinguished from the stripping zone below the oil charge point. The solvent, which is composed of recirculated solvent-rich phase from the phase separator and any makeup solvent required, is introduced at the desired temperature into the tower at a point slightly above the bottom thereof. The temperature and pressure maintained in the tower are selected to effect separation of the oil into fractions of the desired relative size. The tower is maintained under a pressure effective to prevent vaporization of solvent in the tower and the fractionation is carried out in a temperature range above approximately 100 F. below the critical temperature of the solvent. The critical temperature of propane is 206.3o F. and the critical pressure is 617.4 p. s. i. Thus when using propane as the solvent the maximum operating pressure will be in the range of 60G-'700 p. s. i.

The invention will be further described in more detail by reference to the accompanying drawings, in which Fig. 1 is a diagrammatic view in elevation of an arrangement of apparatus for carrying out various preferred modifications of the invention and in which Fig. 2 illustrates further modifications of the invention.

According to Fig. i, fresh oil feed is introduced through line iI to fractionating tower I2. The solvent material for tower I2 is introduced through line i3 to a point near the bottom of the tower I2. As the solvent material ascends through the fractionating tower I2, it dissolves the more soluble portions of the oil forming an extract phase which is withdrawn from the top of fractionating tower I2 through line I4. Line I 4 is provided with a heater I5 for raising the temperature of the extract phase to a point higher than the nal temperature of the extract phase as it leaves the fractionation tower. The heated material is then introduced into a phase separator I6 where it is permitted to stratify. The lighter or upper phase consists of a solventri-ch phase which contains a far higher proportion of solvent than said extract phase. This solvent-rich liquid phase is withdrawn from the phase separator I6 through line II which is provided with a cooler I8 to lower the temperature to that point at which it is desired to introduce the solvent material into the bottom of fractionating tower I2 via line I3. The heavier or lower phase which accumulates in the bottom of the phase separator I6, is withdrawn through line I9. This phase is an oil-rich liquid phase containing a small proportion of the solvent. Due to the fact that a small portion of the solvent is generally included in the oil-ri-ch liquid phase, it is necessary and desirable to supply make-up solvent through line E into line I 3.

The temperature in the top of tower I2 is maintained at the level necessary, in view of the solvent:oi1 ratio employed, the pressure of tower I2, and other factors, to dissolve in the solvent phase at that point only those ingredients of the oil charge which are desired in the overhead product of tower I2. In general it may be said that relatively high `temperatures in the top of tower I2 are associated with relatively high solventzoil ratios. When employing propane as the solvent the temperatures necessary in the top of tower I2 ordinarily are in the range of 17o-200 F.

The temperature in the bottom of tower I2, which is controlled by the temperature of the incoming stream of solvent, may be maintained at the same level as the top temperature. However, it is preferred to maintain a substantial temperature gradient in tower I2 between a maximum temperature in the top of the tower and a minimum temperature in the bottom of the tower. Therefore, the range of temperatures employed in the bottom of tower I2 when using propane as the solvent is approximately 14C-200 F. The bottom temperature is selected with the object of excluding from the lower phase material withdrawn from the bottom of tower I2 those constituents of the oil charge which it is desired to include in `the overhead product. However, the temperature in the bottom of tower I2 must be maintained above any temperature at which there occurs complete miscibility of the oil with the solvent. A relatively high bottom temperature is maintained in tower I2 when it is desired to withdraw as bottoms product only a small i proportion of the oil charged to the tower, as is the case when operating tower I2 to decolorize a vegetable oil. In general, relatively high bottom temperatures are associated with relatively high solvent:oil ratios, and vice versa.

To provide intensive rectication oi the oil in the upper part of tower I2 above the oil charge point a substantial temperature gradient may be maintained between the temperature of the tower at the oil charge point and a higher temperature at the top. In this manner a substantial proportion of the oil in solution in the solvent phase at the oil charge point is precipitated as a lower phase in the upper part of the tower. Alternatively, or in addition, to this method of rectification, tower I2 may be reiluxed externally by returning a portion of the oil-rich liquid phase in line I9 to tower I 2 at a point near the top thereof, through line 2 I.

The lower phase raiiinate produced in tower I2 is withdrawn from the bottom thereof through line 3|. This material may be treated to recover the oil component thereof as a product of the process, or may be subjected to further treatment as described below.

Prior to the return of solvent through line I3 for reuse in tower I2 this material may be subjected to neutralization treatment to remove highly soluble fatty acids which might otherwise tend to accumulate in the solvent. For this purpose all or a portion of the solvent phase flowing through line I 3 is diverted through line 86. Caustic solution is introduced into line 86 through line d8, and the resulting mixture is passed into a separator il?, unused caustic solution are settled out of the solvent by gravity and are withdrawn from the bottom of separator S'I through line 89. The treated solvent is withdrawn from the top of separator 8l through line 9i), which connects with line i3. Additional cooling means are provided at 9i if it is desired to conduct neutralization at a higher temperature than that desired in the bottom of tower I2.

The invention is applicable to a multi-tower operation in which the oil feed is separated into more than two fractions. According to one method, further fractionation of the oil treated in tower I2 is effected by subjecting to further fractionation treatment the oil-rich liquid phase material separated in phase separator I6. This method is illustrated generally by the remainder of Fig. 1. According to another method, the oil feed to tower I2 may be further fractionated by further treatment of the lower phase material' In separator 8'! the soaps and withdrawn from the tower through line 3i. This method is illustrated in Fig. 2. It will be understood, however, that any desirable combination of these methods may be employed.

Referring again to Fig. l, the remainder of the oil-rich liquid phase in line I9 is carried forward through line 22 and is introduced into a second fractionating tower 23 at a mid-point thereof. The operation of this tower corresponds with the operation of the rst fractionating tower except as to operating conditions. A solvent material is introduced into the bottom of the tower through line 24 and ascends through the tower dissolving additional quantities of the oil which is introduced through line 22. An extract phase is withdrawn from the top of tower 23 through line 25 which is provided with a heater 26 and is then introduced into a phase separator 2l. A second solvent-rich liquid phase is formed in separator 2! and is withdrawn through line 28 provided with a cooler Z9, rThis phase is then passed into the bottom of fractionating tower 23 via line 2li where it functions as the solvent for the fractionation of the oil-rich liquid phase recovered from the first phase separator I6. If desired, additional solvent, such as propane, may be introduced through line 3@ to line 24 for admixture with said solvent-rich liquid phase.

Certain components of the original oil introduced through line II to tower I2 are, at the conditions employed in the operation of this tower, insoluble or immiscible with the solvent material and these components, due to their greater specic gravity, flow to the bottom of said fractionation tower and are withdrawn through line 3I. This constitutes a rst fraction. A similar phenomenon occurs in said second fractionation tower and those components of the oil introduced through line 22, which are not soluble in the solvent material at the conditions employed in this tower, descend through said tower and are withdrawn from the bottom thereof through line 32. This material constitutes a second fraction.

The oil-rich liquid phase which accumulates in the bottom of separator 2l may be passed through line 33 to a third fractionation tower 34. A solvent material is introduced into the bottom of said tower through line 35 and an extract phase is withdrawn through line 3E provided with a heater 3? and thence into phase separator 38. The solvent-rich liquid phase which separates in separator 38 is returned through line 39 provided with a cooler i0 and line 35 to the bottom of fractionating tower 34, as is the case with the previous towers. The insoluble components of the oil in tower 3d accumulate in the bottom of said tower and are withdrawn through line di a third fraction. The oil-rich liquid phase which accumulates in the bottom of separator 38 is withdrawn through line 42 as a fourth fraction. A portion of this material may be returned to the top of fractionating tower 34, through line t3 for refiuxing. If it is desired to .Fractionate the original oil into more than four fractions, it is possible to further treat the oilrich liquid phase obtained from separator 38 by passing it to one or more additional fractonating towers.

l'i additional solvent is needed to make up for extraneous losses, this may be added to the solvent-rich liquid phase in line 35 through line 43. A source oi make-up solvent may be maintained in a storage tank eilt.

As the fractions recovered through lines 3I,

7 32, 4| and 42 contain solvent, it is desirable to subject these fractions to evaporation for the complete recovery of any solvent present. The recovered solvent may be returned to the pro pane storage tank 44.

Instead of treating the solvent in line I3 to remove fatty acids, it may be desirable to apply this treatment to the solvent in line 39.

According to Fig. 2, an oil to be fractionated is introduced through line 5l to a fractionating tower 52 at a mid-point thereof. A solvent material is introduced at a point near the bottom of said tower through line 53. The ascending solvent material dissolves the more soluble components of the oil to be fractionated and forms an extract phase which is withdrawn through line 54 provided with a heater 55 and is thence introduced into a phase separator 56, The solventrich liquid phase is withdrawn from the top of said separator through line 51 which is provided with a cooler 58 and is then passed into fractionating tower 52 through line 53. The oil-rich liquid phase which accumulates in the bottom of separator is withdrawn through line 59. A

portion of this phase may be returned to the top of fractionating tower 52 through line 56 for refluxing said tower. The remainder of the oilrich phase may be withdrawn from the system through line 6l as a first fraction. Certain components of the fatty material to be fractionated are insoluble in the solvent material under the conditions employed in tower 52. These insoluble or undissolved components flow downwardly through said tower and are withdrawn through line 62, They are then passed through line 53 to a second fractionating tower 54.

A solvent material is introduced through line to a point near the bottom of tower 55 for further fractionating the oil. The solvent and the more soluble components of the oil form an extract phase which is withdrawn from the top of said tower 54 through line 56 provided with a heater 61 and thence into a phase separator 68. The solvent-rich liquid phase is withdrawn from the top of separator 5S through line 69 which is provided with a cooler 16 and thence to line 65 for introduction into tower 64. The oil-rich liquid phase which accumulates in the bottom of separator 5S is withdrawn through line 1l. may be returned to the top of fractionating tower 54 through line 12 for refiuxing said tower. The remainder of the oil-rich phase may be withdrawn from the system as a second fraction. Those components of the fatty material being fractionated in tower 54 which are insoluble in the solvent material introduced through line G5 under the conditions employed in said fractionation tower will descend to the bottom of said tower and may be withdrawn through line 13. These insoluble components are then passed through line 13 to a third fractionating tower 14. A solvent material is introduced to a point near the bottom of said tower through line 15, and the fatty material is fractionated in a manner similar to that which occurs in towers 52 and 64. The conditions of temperature and pressure existing in tower 14 differ from the preceding towers as will be described further herein. The soluble components will dissolve in the solvent material and may 'oe withdrawn from the top of fractionating tower if through line 15 which is provided with a heater 11 and thence to a phase separator 18. The solvent-rich liquid phase which forms in A portion of this phase separator 18 may be withdrawn through line 19 provided with a cooler 80 and thence to line 15 for introduction into tower 14. The oil-rich liquid phase may be withdrawn from the bottom of separator 1B through line 8|. A portion of this phase may be returned to the top of tower 14 through line 82 for reiiuxing said tower. The remainder of said oil-rich liquid phase may be withdrawn from the system as a third fraction through line Bi. Those components of the oil which are insoluble in the solvent material under the conditions employed in tower 14 will descend to the bottom of said tower and may be withdrawn through line 83 as a fourth fraction. If desired, to further fractionate the fourth fraction, it is possible to pass this material to another one or more fractionating towers.

.Since a small portion of the solvent material is carried forward from tower to tower in admixture with the insoluble components from each tower, it is necessary to add make-up solvent to the solvent material being introduced to the bottom of each of said towers. For this purpose a propane storage tank 84 is provided to supply fresh solvent through line 85 to lines 53, 55 or 15 as desired. Small losses of the solvent make-up occur by the withdrawal of the first, second and third fractions from the system since in each case the fraction being withdrawn may contain small amounts of the solvent which remain with the oily material after the phase separation occurs in

separators

56, 68 and 18.

Since the oil fractions recovered from phase separators 56, G8, and 18 may contain small quantities of the solvent, it is generally desirable to recover this solvent from the oil component of the oil-rich liquid phase by means of evaporation. The recovered solvent may then be returned directly to the propane storage tank 84.

it has been stated hereinbefore, that the operating conditions of the towers shown in Fig. l and the towers shown in Fig. 2 will vary. Those operating conditions which may be varied are the temperature, pressure, and refiux ratio. For example, in Fig. 1 the temperature employed in tower 34 may be higher than that employed in tower 23, which in turn may be higher than that employed in tower l2. Under these conditions the feed to tower I2 will be fractionated at low temperatures within the temperature range previously mentioned. Under these conditions a comparatively large portion of the oil will be taken overhead in line E4 as the extract and a comparatively small fraction will be withdrawn through line 3i. in the succeeding tower, which may be operated at a higher temperature, the solvent power of the solvent will be reduced so that some components of the oil introduced through line 22 to tower 23 will be insoluble in the solvent at this higher temperature even though the same components were soluble in the solvent in the preceding tower.

With regard to Fig. 2, the temperature employed in each tower may be lower than that employed in the preceding tower since in this modification of the present invention it is the undissolved components of the oil of the preceding tower which is to be fractionated in the succeeding tower. For example, the temperature employed in tower 54 should be lower than that employed in tower 52 so that the desired components of the oil in line 63 will be dissolved in the solvent at the temperature employed even though the same components were insoluble with the solvent in tower 52.

` Another variable operating condition may be the pressure if it is desired to maintain a constant temperature throughout the series of towers. In this instance the pressure in the succeeding towers in Fig. 1 may be decreased so that components of the oil which are soluble in the solvent in tower l2 will berejected by the solvent when they are fractionated in tower Z3. Conversely, in the system shown in Fig. 2 the pressure will be increased in succeeding towers since in this modification it is desired that the solubility of the solvent be increased in successive towers. For example, some of those cornponents of the oil which are insoluble under the conditions employed in tower 52 and which are transferred through line 53 to tower` Sil will be soluble in the solvent material at the conditions employed in this tower.

A third alternative for varying the conditions in the various fractionating towers is the ratio of material returned to fractionating tower through lines t0, l2, or 82 compared with the quantity of material being withdrawn through lines G., et or l5, respectively. Generally speaking, the greater this ratio, generally referred to as the reflux ratio, the smaller the quantity of material withdrawn since this extract material will consist of a higher proportion of the more soluble components of the oil. Thus in Fig. l additional bottoms fractions can be produced in towers 23 and Srl by progressively increasing the reflux ratio. Likewise in Fig. 2 additional overhead fractions are produced by progressively lowering the reux ratio in towers and lli.

Having now described my invention and the method of practicing the same, what I claim is:

1. A process for obtaining a desired extract fraction from a fatty material by extraction with a solvent having a critical temperature not substantially higher than 450 F., which includes the steps of: contacting said fatty material with an extracting liquid comprised of a solvent-oil inixture at a temperature within the range near the critical temperature in which solubility decreases as temperature increases, and under liquefying pressure, to fractionate said fatty material into a raffinate phase and an extract phase containing the desired extract; withdrawing said extract phase and reducing the ratio of pressure to temperature thereof, while substantially preventing vaporization of said solvent, to reduce the solvent power of said solvent and fractionate said extract phase into a solvent-rich liquid phase and an oil-rich liquid phase containing the desired extract; increasing the ratio of pressure to temperature of said solvent-rich phase to increase the solvent power thereof, while maintaining said phase in liquid condition; and returning said solvent-rich phase to said contacting step to serve as said extracting liquid therein.

2. A process for obtaining a desired extract fraction from a fatty material with a solvent having a critical temperature not substantially higher than 450" F., which includes the steps of: contacting said fatty material with an extracting liquid comprised of a solvent-oil mixture at a temperature within the range near the critical temperature in which solubility decreases as temperature increases, and under liquefying pressure, to fractionate said fatty material and an extract phase containing the desired extract; Withdrawing said extract phase and reducing the pressure thereon, While substantially preventing vaporization of said solvent to precipitate all the desired extract into an oil-rich liquid phase, leaving a solvent-rich liquid phase; pumping said solventrich phase to said contacting step to serve as said extracting liquid therein. l

3. A method for separating an extract fraction from a fatty material by extraction with a solvent having a critical temperature not substantially higher than 450 F., which includes the steps of: contacting said fatty material with an extracting liquid comprised of a mixture of said solvent and previously extracted components of said fatty material, said contacting being carried out at a temperature within the range near the critical temperature in which solubility decreases as temperature increases, and under liquefying pressure, to fractionate said fatty material into a raffinate phase and an extract phase; withdrawing said extract phase and increasing the temperature thereof while preventing any substantial vaporization, to a temperature suinciently near the critical temperature to precipitate most of the oil content of said extract fraction into an oil-rich liquid phase, leaving a solvent-rich liquid phase; cooling said solventrich liquid phase to approximately the temperature of said contacting step; and returning said cooled solvent-rich phase to said contacting step to serve as said extracting liquid therein.

4. A method for separating an extract oil from a fatty material by fractionation with a solvent having a critical temperature not substantially higher than 450 F., in a vertically extended fractionation zone having a solvent inlet and raffinate phase outlet in the lower region of said zone, an extract phase outlet in the upper region of said zone, and a charging inlet intermediate said regions, which method includes the steps of: introducing said fatty material into said charging inlet and introducing a solvent mixture of said solvent and a minor proportion of previously extracted components of said fatty material into said solvent inlet; counterrlowing said fatty material and said solvent-oil mixture within said vertically extended fractionation zone at temperatures within the range near the critical temperature in which solubility decreases as temperature increases, and under liquefying pressure, to fractionate said fatty material into a raffinate phase and a relatively lighter extract phase containing most of the solvent; withdrawing said extract phase from said fractionation zone through said extract phase outlet and increasing the temperature of said extract phase to a substantially higher temperature sufficiently near the critical temperature to separate said extract phase into two liquid phases without vaporization, a relatively heavy product phase and a light phase comprised of solvent and a minor proportion of oil remaining in solution from said extract phase; separating said light phase from said product phase by gravity and cooling said light phase to approximately the temperature within the lower region of said fractionation zone; and introducing said cooled solvent-oil phase into said fractionation zone through said solvent inlet to serve as said solvent mixture.

5. A method for separating an extract oil from a fatty material containing fatty acids by fractionation with a solvent having a critical temperature not substantially higher than 450 F. in a vertically extended fractionation zone having a solvent inlet and a railinate phase outlet in the lower region of said zone, an extract phase outlet in the upper region of said zone, and a charging l inlet intermediate said regions, which method includes the steps of: introducing said fatty 1 1 material into said charging inlet and introducing into said solvent inlet a solvent mixture comprised of said solventl and a minor proportion of previously extracted components of said fatty material; counterflowing said fatty material and said solvent-oil mixture within said vertically extendedfractionation zone at temperatures within the range near the critical temperature in which solubility decreases as temperature increases, and under liquefying pressure, to fractionate said fatty material into a rafiinate phase and a rela` tively'lighter extract phase containing most of the solvent; withdrawing said extract phase from said fractionation zone' through said extract phase outlet and increasing the temperature of said extract phase to a substantially higher temperature suillciently near4 the critical temperature to separate said extract phase into two liquid phases without. vaporization, a relatively heavy product phase and a light phase comprised of 20 solvent and a minor proportion of oil including light fatty acids remaining in solution from said 12 extract phase; separating said lighter phase and cooling it; contacting part of said cooled light phase with alkali to precipitate said light fatty acids as soaps and prevent their accumulation in said fractionation zone; recombining said pai-'t with said light phase and a minor amount of fresh solvent added to make up losses; and introducing said light phase into said fractionation zone through said solvent inlet to serve as said solvent mixtures'.

JOHN 'I'. DICKINSON.

References Cited in the fil of this patr-it UNITED STATES PATENTS Number Name Date 2,118,454 Schaafsma May 24. 1938 2,219,652 Hixson et al. .v v r Oct. 29, 1940 2,247,496 Hixson et al. July 1, 1941 2,281,865 Van Dijck .v r May 5, 1942 2,329,889 Ewing .Y Sept. 21V, 1943 2,346,491 Kirsted e Apr. 11, 1944

Claims

1. A PROCESS FOR OBTAINING A DESIRED EXTRACT FRACTION FROM A FATTY MATERIAL BY EXTRACTION WITH A SOLVENT HAVING A CRITICAL TEMPERATURE NOT SUBSTANTIALLY HIGHER THAN 450* F., WHICH INCLUDES THE STEPS OF: CONTACTING SAID FATTY MATERIAL WITH AN EXTRACTING LIQUID COMPRISED OF A SOLVENT-OIL MIXTURE AT A TEMPERATURE WITHIN THE RANGE NEAR THE CRITICAL TEMPERATURE IN WHICH SOLUBILITY DECREASES AS TEMPERATURE INCREASES, AND UNDER LIQUEFYING PRESSURE, TO FRACTIONATE SAID FATTY MATERIAL INTO A RAFFINATE PHASE AND AN EXTRACT PHASE CONTAINING THE DESIRED EXTRACT; WITHDRAWING SAID EXTRACT PHASE AND REDUCING THE RATIO OF PRESSURE TO TEMPERATURE THEREOF, WHILE SUBSTANTIALLY PREVENTING VAPORIZATION OF SAID SOLVENT, TO REDUCE THE SOLVENT POWER OF SAID SOLVENT AND FRACTIONATE SAID EXTRACT PHASE INTO A SOLVENT-RICH LIQUID PHASE AND AN OIL-RICH LIQUID PHASE CONTAINING THE DESIRED EXTRACT; INCREASING THE RATIO OF PRESSURE TO TEMPERATURE OF SAID SOLVENT-RICH PHASE TO INCREASE THE SOLVENT POWER THEREOF, WHILE MAINTAINING SAID PHASE IN LIQUID CONDITION; AND RETURNING SAID SOLVENT-RICH PHASE TO SAID CONTACTING STEP TO SERVE AS SAIS EXTRACTING LIQUID THEREIN.