US2274802A

US2274802A - Fatty acid distillation

Info

Publication number: US2274802A
Application number: US320825A
Authority: US
Inventors: Mills Victor
Original assignee: Procter and Gamble Co
Current assignee: Procter and Gamble Co
Priority date: 1940-02-26
Filing date: 1940-02-26
Publication date: 1942-03-03
Anticipated expiration: 1959-03-03

Description

March 3, 1942. v. MILLS 2274802.

FATTY ACID DISTILLATION 4Filed Feb. 26, 1940 'o Condenser-.s L

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5 Setondafylfea'r la I 22 l' (rga v 2l j I 25 `Vlr-f .l prima? Heaer nfi- 8 I'IGJ. l ,ze

fece/wr ed 7zm l 5 7b (ndensers Q. 4 n f3) A 28 5 Secondary #enfer 'A y 9 Primary Heater P lnqvEm-on BY l//cTo/f MILLS.

ATTORNEYS.

` Patented Mar. 3, 1942 FAT-Traci msTrLLA'rIoN Victor Mills, Cincinnati, Ohio, assignor to The Procter & Gamble Company,

a corporation of Ohio Application February 2c, 1940, serial Np. 320,825

s claims.

This invention relates to a continuous -process for distilling higherfatty acids from materials 4containing the same, and more particularly concerns a process for the dry distillation of such materials, that is, distillation without the use of steam or other added gaseous medium. This application is related to my pending application, Serial No. 321,306, liled 'February 28,

1940, which is a continuation-impart of application ,Serial No. 245,440, filed December 13, 1938, in which I have described a method for the distillation of free fatty acids from fatty acid containing materials involving heating the stock to a Ytemperature sulciently high that 'the latent heat required 'for vaporization of most of the fatty acids is contained therein, introducing the heated materialinto a hot liquid body of undistilled residue contained within a zone maintained at low absolute pressure whereupon most of the fre'e fatty acids vaporize substantially instantaneously, employing the vapors thus formed to eiect continuous circulation of undistilled residue. in accordance with the air-lift principle and/or the ejector principle, continuously withdrawing the vapors .from the low pressure zone and condensing same, and continuously withdrawing excess undistilled residue from said zone. To eiect vaporization under these conditions of subs'tantially'all of the vapo'rizable fatty acids in a hydrolyzed materialsuch as tallow or grease, for example, would require preheating the stock to a temperature in the neighborhood of 650 F. Under such drastic heat treatment the odor of the distillate is very often impaired even though the preheating and subsequent flashing steps are promptly carried out. Under preferred operating conditions as described in my related pending application above referred to, the stockis preheated to. a temperature in the range of about 550-575 F. whereby 'l5-80% of the distillable fatty acids are vaporized. The unvaporized residue is normally collected and stored until a suiiicient quantity has been accumulated and then re-run through the apparatus in a manner similar to that used on the original material. The

Cincinnati, Ohio,

terial takes place. Furthermore subsequent separate distillation of the undistilled residue results in a distillate fraction having different characteristics than the original distillate obtained and therefore there existsa certain amount of fractionation which may be undesirable.. Also when the cooled residue is subsequently subjected to distillation a A material amount, of heat must again be added to bring the stock todistillation temperature.

The vpresent invention is directed toward obtaining the higher percentage of fatty acid distillate without allowing the undistilled residue from the first operation to cool down appreciabl or to come in contact with the atmosphere.

In accordance with my invention the hot residue from the first distillation step is pumped under vacuum from the first distillation device, through a reheater, and then conducted into a secondary still which may be constructed, for example, either separately from the primary still or within the primary still.

My invention will be more fully understood from the following description taken in conjunction with the appended drawing in which Figure 1 illustrates diagrammatically one form of distillation apparatus which may be used in A control valve 6 to the primary heating' unit 'I such as a heat exchanger, thence through pipe 8 into the still 9. The still 9 is provided with a prifatty acid additionally removed by this secondary mary undistilled residue basin I0, a primary .circulating tube II, open at its' ends I2'and I3, and a primary y baille I4. The undistilled residue which collects in basin I0 is continuously drawn off through pipe I5 by means of -pump I6 and delivered through pipe I1 and control valve I8, secondary heater I9, and pipe 20 into bottom end 2l ofthe secondary circulating tube 22 within the secondary basin 23. Secondary baille 24 is employed to accomplish the same purpose as primary baille I4, which purpose is described in detail below. Secondary undistilled residue from the secondary basin 23 is conducted by pipe 25 'to receiver 26 which may. be continuously or inter- 2'I. Vapor pipe 28 conducts the combined fatty acid vapors of the primary and secondary distillation steps to suitable condensing equipment' not shown. j

The apparatus shown in Figure 2 is essentially the same as that shown in Figure 1 except that the secondary basin 23 is an integral part of a secondary still 29 which is connected to still 9,. by means of a secondary vapor pipe 30.

The apparatus shown in Figure 1, for example, may be operated as follows: The material to be distilled, containing a substantial -amount of higher free fatty acids,-is drawn from tank 3 and pumped by/ means of pump 4 through pipe 5 and feed control valve 6 to the primary heater I wherein" the material is heated to a sui'ciently high temperature so that the necessary latent heat of vaporization of most of the fatty acids is contained therein. The heated fatty acid ccntaining material is then conducted through pipe 8 to still 9 which is maintained at an absolute pressure of about 0.5 inch of mercury orless, such as 0.05 to 0.1 inch of mercury, and wherein substantially instantaneous vaporization of most of the fatty acids taires place. As above described, the still comprises a primary residue basin i in which is substantially centrally located a primary circulation tube II. The relative vertical position of this tube is so adjusted that its bottom end l2 is submerged in the undistilled residue in the still basin I0 and that its top or outlet end I3 is above the s urface of the undistilled residue. Suitably` located .above the primary circulating tube II is a circular, umbrella-shaped, primarydeection baille I4. As will be noted from the drawing, the heated fatty acid material as introduced into the still is directed upward within the tube Il. Since the fatty acid material is heated sufiiciently to effect substantially instantaneous vaporization of unvaporized fatty acids at the pressure within the still, fatty acid vapors will immediately form and by the air-lift principle and/or the ejector principle will cause flow of undistilled residue and' fatty acid vaporsup the tube I I and against baille I4. Further expansion of that portion of the fatty acids vaporized in the heat exchanger l also takes place due to the reduced pressure in the still. The velocity of the mixture of vapor and undistilled residue is such that as the undistilled residue strikes the baille I4 a curtain of liquid is formed, which curtain may be directionally controlled by the shape of the baffle. I have found that this curtain is very effective in removing entrainment ordinarily accompanying ash distillation, probablybecause of the intimate contact of the vapor with the liquid residue.

Theundistilled residue continues to collect in the basin I0 as distillation progresses, any excess above the predetermined amount to be kept in the basin for circulation being removed by pump I6 through pipe I and delivered through pipe l1, control valve I8 to the secondary heater I9 wherein the undistilled residue is reheated so as to incorporate therein suilicient heat for vaporization of fatty acids contained in said undistilled residue. The heated residue passes throughpipe 20 and is introduced into the bottom end 2| of the secondary circulating tube 22 contained in secondary residue basin 23.A As in` the case of the rst step of the distillation, fatty acids contained in the heated material volatilize and thereby projectan admixture of same with secondary undistilled residue against the secundistilled residue is formed. The undistilled residue over and above that required for circulation in the secondary basin 23 is continuously drawn off through pipe 25 to receiver 26 from which the residue may be pumpedcontinuously or intermittently as desired. The fatty acid vapors from the primary and secondary distillation steps combine within the vaporization zone of the still 9 and pass through vapor pipe 28 to suitable condensing equipment.

As above described in the case of Figure 2, a complete secondary still 29 may be constructed in a manner similar to the construction of still 9 except, of course, preferably on a smaller scale. The fatty acids volatilized in still 29 in this case pass through vapor pipe 30 and either may be condensed separately from the vapors of the primary distillation or may be combined therewith and passed-through the vapor pipe 28 to suitable condensing equipment. The undistilled residue from the secondary distillation step is, of course, removed in a manner similar to that above described or if desired may again be reheated and subjected to distillation conditions.

While the above description gives in detail the general aspects of my invention, improvements such as the following may be incorporated, the essential features of said improvements being diagrammatically shown bydotted lines in the drawing. It is obvious that vaporization of the fatty acids in the fatty-acid-containing mate-l rial requires a certain amount of latent heat which must be available at or above the fatty acid vaporization temperature corresponding to the operating pressure. An increase in volume of material being heated without a corresponding increase in weight of fatty acid to be vaporized makes possible a reduction in temperature to which the stock must be heated in order that it contain sufficient sensible heat to vaporize that fatty acid. Therefore by recirculating a portion of the undistilled residue and thereby diluting the incoming fatty-acid-containing material the advantages of lower temperatures may be realized. If, however, temperature is not an item of concern and pressure is, then of course, the diluted material may be heated to the same temperature that is used in operations not employing recirculation, thereby incorporating a larger amount of available heat for-vaporization ofthe free fatty acids in the mixture and making possible operation at a higher pressure within the still.

If it is desired to recirculate a portion of the primary undistilled residue and thereby realize advantages as above pointed out, then valve 40 in pipe 4I returning to the inlet side of the' heater and valve 42 in pipe II leading to the secondary heater may be adjusted to give the desired amount of recirculation, the4 temperature.

- my invention I do not take the precaution to ally light in color and may be used to resistance to passage of the stock through the heater, for example, from about 20 pounds to about zero pounds gage pressure whereby a mixture of superheated liquid and fatty acid vapors are formed before introduction into the still proper. This arrangement differs over prior practice of ash distillation and has presented at least two advantages. First, the control valve is subjected to throttling relatively cool fatty acid containing material rather than hot material, thereby greatly 'reducing the' corrosive action of the fatty acids on the valve, and, second, some of the fatty acids are permitted to volatilize on passage through the heat exchanger and thus the temperature of the material need not be carrie'd as high as would be necessary. if

pressure were applied to prevent any fatty acidv .3 contained in the basin za and th-admixture is projected upward against the secondary baille 24, the fatty-acid vapors thus formed combining with .the .fatty acid vapors evolved in the primary dis,-

tillation step and passing off to suitable condensing lequipment through the vapor pipe'28. The

fatty acidsv actually vaporized and condensed' amount to approximately95 per cent of the stock glycerin to as high degree as possible andthe tion in order to remove substantially all of the free fatty acid containedv therein. The undistilled residue resulting from this application of my process on oils such as palm oil is exceptiondirectly for any suitable purpose.

4As a specific example of my procedure carried out in accordance with the method illustrated diagrammatically. in Figure 1, no recirculation being employed, impurefatty acids resulting from the hydrolysis of tallow are heated continuously in primary heater I to a temperature of S-575 F. and are introduced into the lower end I2 of the primarycirculating tube II.of still 9 which is maintained at a pressure of about 0.08 inch of mercury absolute pressure. Approximately -80 per cent of the stock volatilizes immediately and causes circulation of the primary undistilled residue contained in the basin I0 whereby said undistilled residue is projected upwardly against the primary baille I4 and deflected so as to form a curtain. of undistilled residue outward, downward, and away from the vapor outlet. 'I'he temperature immediately drops` due to volatilization of fatty acids and the fatty. acid vapors at a temperature of about 450 F. pass through the vapor pipe 28 to suitable condensing equipment. The undistilled residue, which confed to the still, theA remaining five per cent being undistilled and/or undistillable residue which is continuously drawn off through pipe 25 to recated within the. primary still, since by this ar-l rangement there is less heat loss and the secondary stillneed not be air tight.

'I'he advantages of recirculation as above described may be -exemplified as follows. By recirculating primary undistilled residue in amount equal to about thirty-four per cent of the feed of the original fatty-acid-containing material to the primary circulating tube and by recirculating about sixty-nine per cent of the feed of primary residue to the secondary circulation tube, the' temperature to which the respectivev feeds should be heated may be reduced to about 515 F. with simultaneous increase in pressure in thelstill to about 0.16 inch of mercury. The higher fatty acids with which I am prini cipally concerned are the saturated and unsaturated carboxylic acids occurring in vegetable,

animal, or marine fats and oils-and containing mostly from about-ten to about twenty .c :aibon4 atoms per molecule, such as oleic', linolic, stearic,

palmitic, myristic, lauric, etc. The principal use .of such acids is in the manufacture of soap and candles. Other impure higher fatty acids-Which are of less common occurrence such as the higher acids resulting from the oxidation vof parailin may'also be purified by distillation in accordance with the present invention.

Having thus described my invention, what I claim` and desire to secure by Letters Patent is:

1. A process of continuously distilling at reduced pressure without'the use -of an added gaseous medium higher fatty acids from a material rated. in said material to effect substantiallyl instantaneous vaporization of most of the free fatty acids contained therein when subsequently subjected to said reduced pressure, continuouslyintroducing the thus heated material into a hot sists of about 20-25 per cent of the stock fed and which likewise has dropped in temperature to approximately 450 F., is removed by means of pump I6, reheated in the secondary heater I9 to 575-590 F., and introduced into the bottom end 2i of the secondary circulation tube 22 contained within the secondary basin 23. Fatty 'acids contained in the heated residue are volatilized, be-j come admixed with secondary undistilled residue liquid body of primary undistilled residue contained within a zone maintained at a pressure less than the average pressure in said heating zone and not substantially exceeding 0.5 inch of mercury whereupon most of the free fatty acids I vaporize substantially instantaneously,y employing the vapors thus formed Without the aid of an added gaseous medium to project said residue upwardly against a baiiie to form a directionally controlled curtain of undistilled residue, continuously withdrawing excess undistilled residue Y from said zone, reheating the said excess residue to incorporate sufficient heat in same tosubstantially completely vaporize the fatty acids contained thereink at the pressure within said zone and thereby leave a secondary undistilled residue. continuously introducing the said heated 1 excess residue into a hot liquid body of said secondary undistilled residue and employing the vapors thus formed to project a stream of said secondary undistilled residue, intimately admixed with said vapors; upwardly against a baffle in a zone at said low pressure so as to form a directionally controlled curtain of secondary undistilled residue, continuously withdrawing the fatty acid vapors and condensing same and continuously withdrawing said secondary undistilled residue',

2. In a process of dry flash distillation of fatty acids including :the step ofprojecting undistilled residue intimately admixediwith vaporized fatty acids without the-'aid of an added gaseous medium against a baille in a low pressure distillation zone so as to create a curtain of undistilled residue, the steps of removing excess residue over and above the predetermined amount necessary for the admixture projected. reheating -the removed residue to incorporate suilicient heat in same to vaporize most of the free fatty acids contained therein at low pressure and thereby leave a secondary undistilled residue, continuously introducing said heated residue into ahot liquid.

body of said secondary undistilled residue and employing the vapors thus formed without the aid of an added gaseous medium to project a stream of said secondary undistilled residue intimately admixed with said vapors upwardly against a ballle in a zone at said low pressure so as to create a curtain of said secondary undistilled residue.

3. The process in accordance with claim 2 in which the vapors from the first and second vaporization are combined before being condensed.

4. I'he process in accordance with claim 2, in which the vapors are separately. condensed.

i 5. The process of claim 2, in which the secondary and primary vaporizations are conducted within the same distillation zone.

6. The process of claim 2, in which. the secondary and primary vaporizations are conducted in separate, interconnected zones.

7. A process of subjecting to redistillation an undistilled residue from a primary distillation of a fatty-acid-containing material comprising heating the undistilled residue to incorporate sucient heat in same to vaporize most of the free fatty acids contained therein at low pressure and thereby leave a secondary undistilled residue, continuously introducing said heated residue into a hot liquid body of said secondary undistilled residue and employing the vapors thus formed without the aid of an added gaseous medium to project a stream of said secondary undistilled residue intimately admixed with said vapors upwardly against a baille in a zone at said low pressure so as to create a curtain of said secondary undistilled residue.

8. A processv of subjecting to redistillation an undistilled residue from a primary distillation of a fatty-acid-containing material comprising heating the undistilled residue while subjecting same to progressively decreasing pressure to incorporate sufficient heat in same to vaporize