US2471942A - Method of recovering volatile materials - Google Patents

Description

May 31, 19494. E, F, DREW 2,471,942

METHOD OF RECOVERING VOLATILE MATERIALS Filed Aug. 25, 1945 UAI/f 25 CPM/snc' IN VEN TOR. [QA/fsf F DREW ABY Patented May 31,1949

METHOD F RECDVERING VOLATILE MATERIALS Ernest F. Drew, New York, N. Y. Application August 23, 1945, Serial No. 612,275

Claims. 1

The present invention is directed to oils and fats and more particularly to a method and an apparatus for the treatment of waste and objectionable vapors emanating from the splitting of such oils and fats for the production of free fatty acids.

It has been common practice to treat vegetable and other oils and fats which are glycerides of mixed higher fatty acids in order to hydrolyze the same and to split the fatty acids from the glycerine. This has been accomplished by the use of such splitting agents as mineral acids, Twitchell reagent and the like, under the application of heat and sometimes of pressure. Such processes give rise to vapors having undesirable and often disagreeable odors which in many cases presented a great nuisance to the surrounding community if such vapors were allowed to escape during the process. Such vapors include in most cases, in addition to the disagreeable odors, vapors of water, mineral acid, fatty acid and glycerine. Some of the vapors may be derived from the sulphonating or splitting agent used in the process.

Attempts have been made to prevent the diffusion of such vapors into the outside air both to abate the nuisance caused by such vapors in a community and to prevent the unnecessary loss of valuable ingredients in said vapors. However, efforts to economically recover such vapors have heretofore not met with success.

The present invention is intended to overcome such diflculties and has among its objects the provision of a method and an `apparatus for the treatment of such vapors whereby they may be absorbed and the objectionable odors eliminated.

It is also among the objects of the present invention to provide a treatment of vapors given off in the hydrolysis of fats and oils whereby the fatty acids contained in such vapors may be economically recovered.

It is still further among the objects of the present invention to provide a means for fractionating the fatty acids of certain oils and fats whereby a mixture of lower `fatty, acids contained in such oils may be recovered.

In practicing the present invention, there is provided an absorption tower into which the waste vapors are led and allowed to pass upwardly through the same.,` In the center of the tower is an absorption unit having a solution of caustic soda passing downwardly counter-current to the upwardly traveling vapors. A body of caustic alkali solution is maintained in the bottom of the tower with a pump or the like for circulating thesame over the absorption unit.` The cycle `oi treatment is maintained until a certain concentration of fatty acid has been absorbed in the caustic alkali in the form ci soap. Usually from 4 to 5% of fatty acid in the solution is considered sufficient to enable economical recovery of the fatty acid from the solution. It is desirable to have a minimum concentration of ycaustic alkali in the solution of about 2% in order to avoid interference by foaming of the soap in the solution. It is also important that the solution being circulated be kept at a relatively high temperature, usually in the neighborhood of the boiling point of water in order that there shall be a minimum of absorption of water vapor from the mixed vapors being treated. This contributes greatly to the eiectiveness of the operation.

Such a process enables the recovery 0f sub` stantially all of the fatty acids which may be present in the vapors and the absorption is in such a form that the fatty acids may be readily recovered therefrom. Simultaneously therewith, the objectionable odors present in the vapors are also absorbed and are eliminated from the atmosphere. When such oils as the coconut type of oil is treated, the vapors thereof contain the lower fraction of the fatty acids present in the original oil and the absorption of such fatty acids from the vapors is capable of providing the mixed lower fatty acids, which as a unit are eminently suitable for adaptation in commerce, as for example, in the form of the polyalkylene glycols for use as plasticizers.

In the accompanying drawing constituting a part hereof and in which like reference characters indicate like parts, the single gure is a vertical cross-sectional view taken through an apparatus made in accordance with the present application, some parts being shown in elevation and other parts being shown diagrammatically.

In the treating vessel l, there is performed the operation of splitting the oil or fat by any of the usual reagents. The vapors produced in the process pass through duct or pipe 2 which extends vertically upward through the central part of the bottom 3 of a vertical tower s. The upper end 5 of duct 2 is provided with a series of openings to allow the vapors to escape into the tower. A cap 6 is provided at the top of pipe 2 to prevent accidental entrance of solution into the same.

In the bottom of the tower is a body 1 of caustic soda solution. The amount of caustic soda present is usually not less than 2% and may be as much as 35%. A coil 8 surrounds pipe 2 and is provided with. valves 9 whereby the :dow of steam orcther heating agent may be controlled .to maint tain the desired temperature in the solution.. Usually a temperature of 210 to 215 F. is so maintained. A pipe I extending from tower Il is at a level just below openings 5. When the solution in the tank becomes too high, the liquid passes through pipe I0 into overflow chamber II and out through I2 for re-use.

In the bottom 3 of the tower which slopes slightlytand iat the lowest point thereof, there is an exit vopening I3 and a pipe |54 leading fIto pump I5. A pipe I6 from the pump has a check valve I'I therein, said pipe extending upwardly and then horizontally as shown at 4,8, .passing into thev tower at an intermediate point 'thereof into space I9. A spray head is adapted to disseminate liquid into the tower. Between horizontal perforated plates 2| and 22 is an absorption-unit 23 of any suitable type, such as the welll-known Raschig rings, suitably packed in order to cau-se liquid to pass downwardly over the surfaces in contact with vthe vapors passing upward-ly -in the unit.

`Above the-spray 21)` are a pair of :similar horizontalyperfforated platesi'li and .25 having between the same-a packing =or :filling `26 which may also be of Rasohig rings. rIhe spentgases-and vapors after passage through `the Aunit `i5 -enter upper end 2.1of the vtower and pass out therefrom through opening-or stack 28.

-Inthe-operation of Athe 'apparatus rf'or the treatment of =thefwaste vapors, the caustic soda solutionis maintained 'at yabout .the boi-ling .poi-nt .of

water and is-continuously circulated fby .pump H.

Vapors-areallowed to pass through the dusty-'2 :out o'fiopenings 5 and upwardly through .absorption unit 23. rIhe vapors lcome -into -intimatefcontact with the hot caustic soda ysolution whereby :.all acid yvapors'are absorbed and recovered from fthe vapors. VBecause of fthe high temperature of the solution, very little, if any, rwater vapor -is Tabsorbed -therein and -itpasses up .i out fof `#the absorption unit withfother `unabsorbed substances. The circulation of theliquid is continued, vcausingra gradual -building up inthe solution 'of fatty acid soaps. When -the -fattyacid vcontent reaches A to 5% orhigherand lthe caustic sod'acontentis -down to about l 21% `the :solution .may be :removed for the recoveryfof the fatty acids. fA fresh -caustic soda solution .is introduced and the -cycle .is continued.

Due -to the fine Asubdivision Lof the-solution as -it is-sprayedfrozn -thespray head intozthe-tower,-and the upwardly owing current of,-g.ases.and vapors, someof the .solution maybe Icarried yalong with the lsame. Therefore, .the spray `.removal unit 2.5 is provided, which catches .the-spray on ythe .packing material and the solution lflows downwardly and eventually yreaches the absorption unit. The temperature of the spray removal unit is falso preferably. maintainedat about the'bo'iling `point ofi-water so as not to dilute .the solution. .'Ihereforejthe 4gases .passing out .through stack Iacontain .substantially all ofthe water vapor which hadbe'enpresent in lth'e vapors induct 32.

"-The solutioncontaining the-soaps may ithen be a'c'idulated as bythe use 'of sulphuric acid. in the usual manner to split the soap stock. Theresulting product contains 'atleast '99% of vfatty :acids andthey may beused as such or 'be re'distilled or otherwise treated for further purification.

The present Ainvention is adapted'for 'use in tall cases where 'fats and oils 'of 'a glyceri'de fatty 'acid typeare splitto reco'Ve 'fatty acids. The 'invention iszparticularl-y adapted for use where "the coconut type :of oil-is split. Such loils lcontain ."a substantial famountof lower fatty' a'ci'ds having 6,8, 10, -'12 and 1'4c`arbon atoms'in'addition tothefattyacids of 16 and 18 carbon atoms which are present in practically all vegetable and animal oils. It has been found that the vapors produced in the splitting of, say, coconut oil, contain only the lower fatty acids present in such oil having from 6 to 12 carbon atoms. When such a mixture of fatty acids is recovered first in the form of soap and then in the form of the mixture of free fatty acids, the approximate composition vitlrzereof is as fol- :lows:

Per cent Caproic (C6) 15.9 "CapryIic'(Cs) 56.8 ifCaprio (C10) 19.4 1121.111104- etc. (C12+) 7.9

Therefore, the present invention provides a simple and inexpensive means for fractionating the fatty acids of coconut oil to recover a mixture of lower fatty acids. These have been found eminently suitable for use .as the. mixed polyethylene glycol esters,as..plasticizers l'for various resinous materials, `synthetic `rubber and the like.

Although the invention has been described lby use o`f a certain vspecific example, 4the invention is not 'limited 'thereto as various modifications rin theprocessand the apparatusmay bemade within theiscope of 'the invention. =For instance, the caustic-soda solution may be .used until ltheconcentration df Ithe lfa't'ty acid ,is 'greater than that speciedLherein, or-Ithe 'caustic soda content thereo`f .may lbe replenished continuously .or intermittently. Also, the process vmay be operated so .that a part of the caustic `soda .is withdrawn for 'the recovery 'of fatty acids. and .the volume replenished byfrfesh caustic soda solution. Other alkalis ythan sodium hydroxide may, o'f `course, Joe used inthe process. The minimum concentration of alkali may beless 'than I2,% in somecases. 'Ihe absorption .units may be `of diiferentoharacter and under suitable conditions 'the `-un'i'ts -may be 4entirely omitted where the tower is .sufficiently 4high and the absorption of lthejia'tty acids and objectionable odors is sufciently complete without the necessity 0`f r.packing 'in the tower. In place of steam, other means maybe used for maintaining the desired te'mperatureo'f the circulating soluti'on.

`The'inve'ntion. is applicable not `only to vapors resultingfr'om the splittingofo'ils and .'fats, but also `to vaporsarising from various `.other operations `on .glyceri'de `oils, fats, fatty acids, soap stock, rand others, wherein 'the vapors contain acid constituents, water kvaporand objectionable odors.

'These .andother .changes in the details -of theprac'tice of `thejinvention may lbemade without 'departing from the spirit thereof andthe invention is to belbroadly construed and inotto be'limited except by vthe spirit of .the-.claims appended hereto.

'I lclaim:

"1. .Ameth'od o'i treating waste vapors L'from the hydrolysis of oilsandffats which, comprises passing said vapors 'into lContact .with an aqueous solution of caustic alkaliofover .21% .-.to absorb constituents thereof, `continuing said contact until substantial amount .of 'fatty acid has lbeen absorbed, arresting 'the absorption .when the. conceritration of said caustic alkali lhas decreased tofa point no'tbelow 'about '2% 'and then recovering said 'acidfromsaid-solution.

"2. ,Amethod of treating Waste vapors from the hydrolysis 'of oils and fats 'which 'comprises passing said zvaporsirito contact l'with an aqueous sdlu'tion o'frausuc alkali aorabmn `2-"35% to aibsorb constituents thereof, continuing said contact until a substantial amount of fatty acid has been absorbed to permit recovery of said acid from said solution, arresting the absorption when the concentration of said caustic alkali has decreased to a point not below about 2% 3. A method of treating waste vapors from the hydrolysis of oils and fats which comprises passing said vapors into contact with an aqueous solution of caustic alkali of over 2% to absorb constituents thereof, maintaining said solution near the boiling point of water to minimize dilution thereof by condensed steam, continuing said contact until a substantial amount of fatty acid has been absorbed to permit recovery of said acid from said solution, arresting the absorption when the concentration of` said caustic alkali has decreased to a point not below about 2%.

4. A method of treating waste vapors from the hydrolysis of oils and fats which comprises passing said vapors into contact with an aqueous solution of caustic alkali of over 2% to absorb constituents thereof, continuing said contact until a substantial amount of fatty acid has been absorbed to permit recovery of said acid from said solution, arresting the absorption when the concentration of said caustic alkali has decreased to a point not below about 2%, acidulating the soap so formed and recovering the fatty acid therefrom.

5. A method of treating waste vapors from the hydrolysis of coconut type oil which comprises passing said vapors into contact with an aqueous solution of caustic alkali of over 2% to absorb constituents thereof, continuing said contact until a substantial amount of fatty acid has been absorbed to permit recovery of said acid from said solution, arresting the absorption when the concentration of said caustic alkali has decreased to a point not below about 2%, said recovered acids being a mixture of the lower fatty acids present in said oil.

6. A method of treating waste vapors from the hydrolysis of oils and fats which comprises passing said vapors upwardly in contact with a countercurrent of an aqueous solution of caustic alkali of over 2%, recycling said solution until a substantial amount of fatty acid has been absorbed to permit recovery of said acid from said solution, arresting the absorption when the concentration of said caustic alkali has decreased to a point not below about 2%.

'7. A method of treating waste vapors from the hydrolysis of oils and fats which comprises passing said vapors upwardly in contact with a countercurrent of an aqueous solution of caustic alkali of over 2%, maintaining said solution near the boiling point of water to minimize dilution thereof by condensed steam, recycling said solution until a substantial amount of fatty acid has been absorbed to permit recovery of said acid from said solution, arresting the absorption when the concentration of said caustic alkali has decreased to a point not below about 2 8. A method of treating waste vapors from the hydrolysis of oils and fats which comprises passing said vapors upwardly in contact with a countercurrent of an aqueous solution of caustic alkali of at least 2%, said vapors first passing in heat-exchange contact with said solution, recycling said solution until said solution contains about 4-5% of fatty acid, arresting the absorption when the concentration of said caustic alkali has decreased to a point not below about 2%, hydrolyzing said solution and recovering fatty acid therefrom.

9. A method of treating waste vapors from the hydrolysis of oils and fats which comprises passing said vapors upwardly in contact with a countercurrent of an aqueous solution of caustic alkali of over 2%, maintaining the temperature of said solution at about the boiling point of water, continuing said contact until the free Caustic alkali in said solution has dropped to about 2%, and then recovering the absorbed fatty acid from said solution.

10. A method of treating waste vapors from the hydrolysis of oils and fats which comprises passing said vapors upwardly in contact with a countercurrent of an aqueous solution of caustic alkali of over 2%, maintaining the temperature of said solution at about the boiling point of water, continuing said contact until the fatty acid content of said solution has reached at least 4 to 5%, and then recovering the absorbed fatty acid from said solution.

ERNEST F. DREW.

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

UNITED STATES PATENTS Number Name Date 944,533 Allen Dec. 28, 1909 1,027,022 Whiteley May 21, 1912 1,141,266 Raschig June 1, 1915 1,314,765 Stone Sept. 2, 1919 1,726,401 Lw Aug. 27, 1929 1,826,349 Harding et al. Oct. 6, 1931 1,889,652 Gensecke Nov. 29, 1932 2,193,321 Leithe Mar. 12, 1940 2,422,794 McCorquodale et al. June 24. 1947

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