US2627500A - Distillation of fatty acids, tall oil, and the like - Google Patents

Description

Feb. 3, 1953 R. H. POTTS ET AL 2,627,500

DISTILLATION OF FATTY ACIDS, TALL OIL, AND THE LIKE Filed Dec. 15, 1947 Ill w" N ,La

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Patented Feb. 3, 1953 DISTILLATION F FATTY ACIDS, TALL OIL, AND THE LIKE Ralph H. Potts, La Grange, and Roy N. Olson,

Chicago, 111., assignors to Armour and Company, Chicago, 111., a corporation of Illinois Application December 15, 1947, Serial No. 791,857

9 Claims. (Cl. 202-46) This invention relates to the distillation of fatty acids, tall oil, and the like.

In the distillation of fatty acids, tall oil and similar materials in which the product is adversely affected by decomposition at high temperatures, it has heretofore been felt desirable to limit the amount of steam employed in the distillation of such products. The use of steam in somewhat larger amounts is desirable from the standpoint of reducing the temperature differentials existing in the top and bottom portions of the fractionating or distillation tower and particularly for reducing the temperature in the lower portion of the tower. However, the use of such large amounts of steam has a disadvantage in that a substantial entrainment occurs. This entrainment in addition to the actual loss incurred, passes into the vacuum equipment, solidifies in the condensers, resulting in costly shutdowns. For this reason, the quantity of steam has been restricted and in some cases dispensed with altogether.

The following example illustrates the advantage in using larger amounts of injected steam and emphasizes the unfortunate limitation of steam required to avoid entrainment losses. Consider a system operating with a feed composed of 50% palmitic acid and 50% stearic acid, a pressure of mm. at the top of the tower and 45 mm. at the base of the tower. The vapor temperature at the top of the tower would then be the temperature at which the vapor pressure of palmitic acid is 5 mm. or 385 F. The temperature at the base of the tower would be the temperature corresponding to a vapor pressure of stearic acid of 44 mm. or 514 F.

If we now consider a system in which the partial pressure of the palmitic acid at the top of the tower is again 5 mm. but the total pressure is 30 mm. the remaining 25 mm. being the result of the admission of 5 mols of steam per mol of fatty acid then we will find a considerable difference in the conditions existing at the base of the tower even though the top tower temperature remains the same, i. e., 386 F. The 20 fractionating trays can again be designed for a pressure drop of 2 mm. per tray and the total pressure existing at the base of the tower will be 70 mm. The partial pressure of the fatty acid vapor will be /6 of 70 mm. or 11.6 mm., and the corresponding vapor temperature at the base of the tower will be the temperature at which stearic acid exhibits a vapor pressure of 11.6 mm. or 450 F.

From the above it will be noted that the use of steam considerably reduces the temperature required in the base of the tower and such reduced temperature sharply reduces the thermal decomposition of the product and results in a much improved product.

It will be obvious from the foregoing that if some simple means can be provided which will take care of the entrainment and prevent serious entrainment losses while at the same time permitting the use of large amounts of steam, a decided advance will have taken place. In the first place, a temperature difference existing between the top and bottom of the tower will be reduced, as in the example above, from F. to 64 F. This difference more nearly represents the difference that exists between the respective boiling points of palmitic and stearic acid and is not so dependent upon tower pressure as in the first instance. This should provide for better fractionating conditions, as pressure changes due to fractionating vacuum will not cause as much change in still conditions. In the second place, the temperature existing in the base of the tower is 64 F. lower when usin steam, and consequently, decomposition is greatly reduced. v

An object of the present invention is to provide a process utilizing to the full the use of steam in distillation while at the same time overcoming entrainment losses. A further object is to provide a process in which thermo-compressor steam which is employed in reducing the pressure upon a tower is utilized for carrying any entrainment resulting from the use of steam in a distillation tower to a second tower in which such entrainment is recovered. A still further object is to provide for a steam distillation tower a supply of steam employed in a steam ejector pump for reducing the pressure in another tower, such steam being utilized for the additional important purpose of carrying any entrainment from the preceding tower to the tower into which the steam from such steam ejector pump is introduced. A still further object is to provide a process employing the thermo-compression steam usedin one tower for steam distilling in another tower whereby entrainment losses are reduced and hot-well losses of any entrainment past the condensers will be eliminated. Other specific objects and advantages will appear as the specification proceeds.

The invention is illustrated in connection with apparatus in which it may be eifectively employed, in the accompanying drawing in which is set out a diagrammatic layout of such apparatus.

In the illustration given, itwill be noted that there are three towers. Tower I receives the incoming feed in line Ii] and the residue from tower I passes from pipe II to tower 2 where fractional distillation is carried out. Residue from tower 2 passes through line I2 into tower 3. It will be noted that a single casing provides towers 2 and 3 and that the two towers are separated by an imperforate wall It.

Tower I is employed for steam distillation and in the preferred process is employed mainly for stripping a relatively light vapor fractionfrom the feed material. Such a fraction is condensed in condenser I l and the liquid product is recovered through line I5.

cating with the condenser H5 is a vapor pipe I6 leading to a catch-all IT. A reflux line pipe I8. leads from the bottom of the catch-all I1 and returns to an intermediate portion of tower I. A vapor pipe I9. leadsfrom the catch-all I'I to a barometric condenser 28; Communicating with the top of the barometric condenser is an ejector pump BI. Since. such apparatusfor maintaining. reduced pressure iswell known, a further detailed description is believed unnecessary.

The feed material consisting of fatty. acids, tall oil or similar types of material enters the stripping tower I through. line It and the unvaporized residue. passes downwardly and. flows through line H into tower 2 where it isfurther fractionated. The line II is provided with. an electrically"controlled valve 22 which in turn is controlled by a level controlling electric mecha-. nism 23; Since suchlevel maintaining mechanism is wellknown in the. art, a detailed description-here is believed unnecessary.

In tower-2; vapors are condensed in the condenser Zlt and a secondliquid fraction drawn off through the. pipe 25. It will be understood that a number of liquid fractions may be recovered from difierent portions of the tower. Leading from the condenser 2 is a vapor pipe 26 which communicates with a steam ejector pump 27!. Steam is introduced into the pump 25. throughthe valve controlled line 28. Such a pump iseffective in reducing. the pressure within condenser 2d and tower 2. The steam discharged through the pump. 2'I- is conducted by pipe to a heater til in which the temperature of the steam may be raised. The steam is heated by steam coils SI or by any other suitable. means. The reheated steam enters the bottom of tower I and is effective in the steam distilling of the product in that tower.

We have already referred to the withdrawal of residue from tower 2 and the passing. of the same through pipe I2 into the lower tower 3, The pipe I2 is provided with an electrically controlled valve 32 which in turn is controlled by an electrically operated level control device 33 similar to the structure 23 employed in tower I. Heating coils for steam or other material. 35 may be employedin connection with tower 3. If desired, the tower 3 may be left unheated and employed solely as an unheated flash drum. If desired, entrainment eliminators 35 may be supported in the upper portion of tower 3. A withdrawal pipe 35 for residue is controlled by the electrically operated valve 51 which is in turn controlled by the electrical level maintaining device 38.

Communicating with the top of tower 3 is a vapor withdrawal pipe 39' leading to a condenser A reduced pressure. is. maintained by a structure whichis wellzknown. and which will be briefly described. Communis.

40. A liquid fraction is recovered from the condenser through the pipe 4L Communicating with the condenser 40 is a Vapor pipe 42 to which is connected a two-stage steam ejector pump. Steam is introduced through the valve controlledpipe, 43 into the pump 434 and steam is also introduced through the valve controlled pipe 45 into the pump 46. The steam outlet from pump id communicates with pump $5 and the combined output of steam passes through pipedl'into the reheater 53 where a steam coil 99' may be used for raising the temperature of the steam. It will be understood that any type of heating meansmay be employed for this purpose.- Thesteam passes from the heater 48 into the lowerportion of tower 2.

As an example of the process, the following may be set out. A fatty acid compounded mainly of palmitic and oleic acids was passed through feed line It into tower I; The top of tower I was maintained at a temperature of 315 F. while the tower bottom was maintained at about 400 F. Tower 2 had a toptemperature of 382 F. and a bottom temperature of 456 F. Tower 3 hada top temperature of about 375 F. with the temperature of the liquid in the bottom being about 425 F.

The fraction recovered from tower I through pipe I5 consisting mainly of an odoriferous materialwas withdrawn mainly for the purpose of removing this constituent from the remaining material. The fraction, 2 recovered from tower 2 through pipe 25 oonsistedlmainly of palmitic acid whilefraction 3 from pipe 4| leading from tower 3, consisted mainly ofoleic acid. The residue through pipett was a heavy tarry material. The proportions in the specific example were 5% in fraction I (odoriferous material), 20%. in fraca tion 2 (palmitic), 55% in fraction 3 (oleic) and 20% in residue.

In the above specific example, lbs. of steam was introduced through pipe l3, 600.1bs. through pipe d5 and 400 lbs. through pipeZB. Tower I had a top pressure of 40mm. of mercury. Tower 2 had a top pressure-of 30 mm. and abottom pressure of '70 mm. while tower 3 had a. pressure of 2 mm. Hg.

The heaters Btand it were efiectivelyemployed not only as steam reheaters but also as reboilers. They were effective in introducing additional heat into the material being vaporized as well as in raising the temperatureof the incoming steam.

In the operation of the process as described above, it was found that entrainment losses were nullified by carrying the entrainment through the medium of the thermo-ccmpressor steam back into the next tower so that such entrainment materials were wholly recovered. Whether entrainment was large or small was of little consequence because the materialentrained was immediately subjected to a steam distillation in the next tower. The processresultsin a saving of steam but more important is the fact that the steam is employed, as a vehiclefor the return of entrained material so that it can be recovered. With the new process any desired large amount of steam may be employed with all the attendant advantages. which havev been described as flowing from such use while. at the same time the disadvantages heretofore following theuse of such large amounts of steam are eliminated.

The foregoing process involving fractional distillation or straight distillation has been described in connection with fatty acids, tal-l acids, etc., for

the purpose of specifically illustrating the invention. It will be understood. that the invention is applicable for the treatment of fatty acid derivatives, such as their esters, alcohols, nitriles, amines, etc. The invention is particularly effective with fatty acids and such derivatives having from 8 to 24 carbon atoms in their hydrocarbon radical. Broadly, the invention applies to all organic materials whose distillation temperature is such that decomposition occurs or is likely to occur in the range of the distillation temperatures. The invention is particularly useful in the treating of such an organic material having from 8 to 24 carbon atoms in its hydrocarbon radical.

While in the foregoing spec fication we have set out the process in great detail and in connection with apparatus which is described in detail, it will be understood that such details of steps and structure may be varied widely by those skilled in the art without departing from the spirit of our invention.

We claim:

1. In a process for distilling an or anic material having from 8 to 24 atoms in its hydrocarbon radical, the steps of maintaining at least two distillation zones, passing material to be distilled into the first of said zones, withdrawing vapors therefrom, passing material from said first zone to the second zone, condensing vapors from said second zone, withdrawing a portion of the condensate, passing steam pa t said second zone and in open communication with the condensing area thereof, and passing said steam and material entrained therewith from said second zone into said first zone.

2. In a process for the distillation of an organic material having from 8 to 24 atoms in its hydrocarbon radical, the steps of maintaining at least two distillation zones, passing material to be distilled into the first of said zones, withdrawing vapors therefrom, passing material from said first zone to the second zone, condensing vapors from said second zone, passing steam past said second zone and in open communication with the condensing zone thereof, and introducing said steam with material entrained therewith from said second zone into said first zone.

3. In a process for distilling an organic material having from 8 to 24 carbon atoms in its hydrocarbon radical, the steps of steam distilling the material to be distilled, withdrawing vapors therefrom, passing material therefrom to a second distillation zone, condensing vapors from said second zone, withdrawing a portion of the condensate, discharging steam past said zone and in open communication with the condensing portion of said second zone, and directing said discharged steam together with material entrained therewith into said first distillation zone.

4. In a process for distilling an organic material having from 8 to 24 carbon atoms in its hydrocarbon radical, the steps of steam distilling the material to be distilled, withdrawing vapors therefrom, passing unvaporized material therefrom to a second distillation zone, condensing vapors evolved from said second zone, discharging steam past said second zone and in open communication with the condensing portion of said second zone, reheating the discharged steam and introducing it into said first distillation zone.

5. In a process for treating fatty acids and tall oil, the steps of subjecting the material to be distilled to a plurality of separate fractional distillation operations, condensing vapors from said separate distillation operations, withdrawing a portion of the condensate, passing steam past one of said zones in open communication with the condensing zone thereof, and introducing said steam and material entrained thereby into a preceding distillation zone.

6. In a process for treating fatty acids and tall oil, the steps of subjecting the material to be distilled to a plurality of separate distillation operations, condensing vapors from a plurality of said distillation operations, withdrawing a portion of the condensate, passing steam in a plurality of streams past said zones and in open communication with the condensing zone thereof, and passing each of said steam streams into preceding distillation zones.

7. In a process of the character set forth, the steps of steam distilling the material to be distilled to strip the same of light vapors, distilling the stripped material under reduced pressure, condensing vapors from said second zone, withdrawing condensate, passing steam in a stream past the condensing zone of said second distilling zone and in open communication therewith, introducing said stream of steam into said first distillation zone, passing material from said second zone into a third distillation zone of reduced pressure, passing steam past the third distillation zone in open communication therewith, and introducing said second stream of steam into said second distillation zone.

8. In a process for treating an organic material having from 8 to 24 carbon atoms in its hydrocarbon radical, the steps of subjecting said material to steam distillation, withdrawing and condensing vapors therefrom, withdrawing condensate, passing unvaporized heated residue therefrom to a second zone, condensing vapors from said second zone, passing steam in a stream past said second zone and in open communication with the condensing zone of said second distillation zone, and passing said steam together with material entrained therewith into said first mentioned zone.

9. In a process for treating a material stock selected from the group consisting of fatty acids and tall oil, the steps of subjecting said stock to steam distillation, withdrawing and condensing vapors therefrom, passing unvaporized heated residue therefrom to a second zone, condensing vapors from said second zone, passing steam in a stream past said second distillation zone and in open communication with the condensing zone of said second distillation zone, heating said stream of steam and passing the same into said first mentioned distillation zone.

RALPH I-I. PO'I'TS. ROY N. OLSON.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date Re. 22,775 Potts July 30', 1946 2,161,798 Carter June 13 1939 2,164,593 Rector July 4, 1939 2,224,984 Potts et a1. Dec. 17, 1940 2,361,411 Murphy Oct. 31, 1944 2,368,669 Lee et a1. Feb. 6, 1945 2,461,694 McCubbin et a1. Feb. 15, 1949

Claims (1)

1. 6. IN A PROCESS FOR TREATING FATTY ACIDS AND TALL OIL, THE STEPS OF SUBJECTING THE MATERIAL TO BE DISTILLED TO A PLURALITY OF SEPARATE DISTILLATION OPERATIONS, CONDENSING VAPORS FROM A PLURALITY OF SAID DISTILLATION OPERATIONS, WITHDRAWING A PORTION OF THE CONDENSATE, PASSING STEAM IN A PLURALITY OF STREAMS PAST SAID ZONES AND IN OPEN COMMUNICATION WITH THE CONDENSING ZONE THEREOF, AND PASSING EACH OF SAID STEAM STREAMS INTO PRECEDING DISTILLATION ZONES.

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