US2352160A - Method of distillation - Google Patents

Description

June 27, 1944. A. c. BROWN METHOD OF DISTILLATION Filed NOV. 22, 1941 BY a? i aientefi dune 27, 19 34 METHOD OF DISTILLATION Alexander 0. Brown, Cincinnati, Ohio, assignor to Emery Industries, Inc., Cincinnati, Ohio, a corporation of Ohio Application November 22, 1941, Serial No. 420,128

3 Claims.

This invention relates to an improved process for removing a non-volatile liquid such as an oil from a solvent or volatile liquid comprising one portion which is soluble in the oil and another portion which is insoluble in the oil. The invention also relates to apparatus suitable for carrying out this type of process.

The invention has been made in respect to the problem of separating fatty acids, such as stearic or oleic acid, from a solvent such as methanol in the presence of an appreciable quantity of water. Such separation is required in order that the fatty acids may be obtained free of solvent and in order that the solvent may be recovered a process and apparatus in which separation can be conducted with the formation of a minimum amount of ester.

A further objective has been to provide means for causing removal of the solvent quickly at low temperature so thatthe time of contact of the hot solvent with the hot oil is held in a minimum to prevent any undesirable chemical reactions to take place between the solvent and the oil. A further objective has been to reduce the concentration of the solvent rapidly during the period in which it is at elevated temperature for the same reason.

A still further objective has been to provide a process for recovering the volatile solvent in an .without substantial dilution. For purposes of ilundiluted condition or, more specifically, in conlustration, therefore, the invention is disclosed dition for reuse. It has been appreciated in the in relation to the environment in which such past that exposure of a solution containing solfatty acids and solvent are separated from one vent to direct steam in a bubble tower, packed another. However, it will readily be understood stripping column, or simple still is capable of efthat the process and the apparatus disclosed in fecting rapid reduction of the solvent concenthe specification which follows have general tration and in some instances is capable also of utility in other instances wherein a relatively holding undesirable chemical reactions to a. mininon-volatile oil is to be separated from a volatile mum. However, the solvent vapors produced in solvent and a solvent miscible, oil immiscible liqsuch a process are contaminated with steam and uid such as water. the distillate is therefore diluted. Rectification Heretofore conventional distillation apparatus or additional processing is then necessary to rehas been employed for efiecting separation of store the solvent to its original concentration or liquid components of the types described. Howits original purity, and this type of equipment is ever, in manycases the oil is damaged by the therefore unsuitable for the present purpose behigh temperatures which are involved. More cause of the additional cost involved for rectifiover, in certain instances the oil and solvent, cation or reworking of the distillate. A feature though not reactive with respect to one another of the present invention resides in the fact that at low temperatures, tend to unite chemically at the solvent here is discharged in approximately elevated temperature and thereby produce reits original concentration or, if desirable, may be action products which are undesirable. Thus, discharged in an even more concentrated conin a process such as described in the Myersdition. Muckerheide United States patent application Briefly, in accordance with the invention, the Serial No. 348,246, mixed fatty acids are disliquid mixture of components to be separated is solved in a suitable solvent and the temperature passed in one direction through a chamber over of the solvent is decreased a predetermined a series of trays and a condensible vapor, of amount once or a number of times, whereupon which steam is a part, is passed through the selective fatty acid fractions are caused to cryschamber in the opposite direction for contact tallize from the solvent solution and are removed with the material exposed upon the trays. At therefrom by filtration. Following such selective each tray mass and heat interchange occur becrystallization, it is requisite that the fatty acids tw en the qu d an ap r wh r y h vapo remaining in the filtrate and the solvent thereof becomes enriched as to the more volatile solvent be separated from one another. Solvent such as component and the liquid becomes enriched as methanol readily esterifles the fatty acids at eleto the less volatile, oil immiscible component-in vated temperature forming methyl esters which this case water. Thus, as the mixture underare far less desirable or valuable than the fatty going treatment passes through a series of such acids in the solvent or the uncontaminated solstages, one for example corresponding to each vent itself. In relation therefore to a process in tray, the v t c mponent is depleted and the which fatty acids are to be removed from alcooil immiscible component is enriched so that by 1101 the objective specifically has been to provide the time the solvent is' elevated to the highest temperature its concentration is so low and its dilutionsogreatthatanytendencywhichitmay havetoreactwiththeoil isheldataminimum.

The mixture which is substantially depleted of the more volatile solvent component and enriched as to water content is led from the zone of contact betwen vapor and liquid and is then boiled, and the vapors resulting from the boiling operation are recycled to the liquid vapor contact zone where they go through the cycle just described. However, a portion of the liquid at the boiling zone is withdrawn continuously and permitted to become quiescent, thereby enabling. the oil component of the liquid mixture to separate from the water component. The oil is; decanted substantially free of solvent and the water is returned to the boiling zone.

The vapors in the vapor liquid contact zone differ frompoint to point within the zone, the solvent content being highest adjacent the point of introduction of the liquid being treated and the steam content being highest at the point of discharge. It is to be understood therefore that the term "vapors is used generically to designate a mixture, the consistency of which varies as that vapor passes through the liquid contact zone. It is also to be noted that water is employed as a. means for providing steam as a portion of the vapor. A liquid other than water and diiferent from the volatile solvent of the mixture being treated may be employed in place of water provided however that such llquid be immiscible with the oil component of the mixture being treated. g

In the preferred apparatus to which the invention is directed the countercurrent exchange of heat from .vapor is conducted in a stripping column having an inlet at one end and a conjoint boiler and decanting apparatus at the other. A given supply of water is maintained in the boiler and this apparatus is preferably heated by a suitable steam calandria. The boiler also preferably is equipped with an inlet into which steam may be bled for starting or control purposes. A vapor outlet is provided at the upper part of the stripping column and a series of trays is placed along its length at suitably spaced intervals so that a solvent mixture to be separated may trickle downwardly over the trays toward the boiler while the vapor from the boiler passes upwardly in countercurrent direction. The temperatures are so controlled that in the solvent vapors passing to the solvent vapor outlet the ratio of volatile solvent to water is the same or slightly higher than in the feed mixture.

The boiler itself is preferably divided by a diaphragm or baille which delineates a zone within which the oil may be decanted from the aqueous phase. A return passageway from the decanting zone to the boiler is provided in order that the aqueous phase may be recycled and reevaporated, and an outlet having a suitable vapor lock is provided at such a level that oil collecting above the body of aqueous phase in the decanter section may be removed continuously from the apparatus.

A preferred embodiment of the apparatus of the present invention is shown in the drawing in which the figure is a cross sectional view illustrating somewhat diagrammatically the relationship of the various elements.

In the drawing, the stripping column is designated at I and comprises a vertical chamber having a plurality of trays 2 located therein in spaced relationship, with suitable outlets 3 being provided in staggered relationship so that liquid .introducedononetraymayflowacrossthetray.

{81' exposure of it to heat, then to the tray below A vapor outlet is provided in the dome at the top of the column and an inlet for the solution to be separated also is provided at a point adjacent the topof the column above the uppermost tray thereof.

At the bottom of the stripping column the boiling and decanting apparatus is located and this comprises a suitable tank having means, such as th baille l therein, delineating a boiling section I and decanting section 6. A steam calandria I, a plurality of U tubes or the like, or other suitable heating means, is provided in the boiling section I, while an outlet 8 is provided at a predetermined level in the decanting section so as to permit oil therein to flow through the outlet 8, the vapor lock '0 being provided in the discharge line.

The boiler also is equipped with a supplemental steam line I 0 to enable adjustments to be made in temperature or to supply booster steam to the apparatus if desirable. The decanting portion of the apparatus also may be and preferably is equipped with a sight glass II to show the level of the interface between the oil and water.

The baille 4 contains a series of apertures l2 in a portion above the normal interface level so as to permit the mixture to be decanted to pass therethrough; a passageway II also is provided to permit water to flow back to the boiler section for recycling.

The operation of the apparatus shown in the drawing is as follows:

The mixture of solvent and oil is introduced into the stripping column through the inlet. It is not necessary but it is sometimes desirable to preheat the solution introduced into the stripping column.

The solution introduced into the stripping column trickles over the trays or plates thereof and flows downwardly toward the boiler. Meanwhile vapor is passed upwardly from the boiler and comes into contact with the solution on the trays in the stripping column. At each tray some of the heat of the vapor is imparted to the solution, vaporizing the solvent component thereof, whence the solvent vapors pass upwardly through the stripping column and out the vapor outlet. The vapor giving up its heat to the solvent is thereby condensed.

As the solution flows downwardly through the stripping column over the trays its solvent concentration gradually is depleted on the one hand because of solvent vapor removal and diluted on the other because of the introduction of steam condensate. The number of stages in the chamber to which the liquid being treated is subjected to vapor is such that the solvent content of the liquid is substantially depleted and the water content of the liquid enriched to a point wherethe mixture in the boiler consists of two separable liquid phases substantially devoid of solvent.

By the time the mixture reaches the boiler, at which the highest temperature of the apparatus is maintained, a substantial portion of the solvent is removed and whatever little remains is in such diluted concentration that it is substantially prevented from reacting with the oil.

Thus, when the concentration of solvent with respect to the oil is greatest, the temperature is lowest so that reaction is restrained; when the temperature is highest the concentration of solvent is lowest so that reaction likewise is restrained.

Some of the mixture in the boiler chamber passes through the openings in the baiiie plate into the decanting zone wherein the mixture is allowed to reach a relatively quiescent state, whereupon the aqueous phase separates from the oil. The oil is removed preferably continuously from the oil outlet line 8 and th aqueous phase passes through the return opening to the boiler to be reevaporated.

When the apparatus is first started it may be desirable but not usually necessary that a given amount of water or steam be introduced into the boiler as through the bleeder 10. This steam bleeder also may be used to make up for any loss of water entrained with the oil removed from the decanter.

In practice it has been found that the heating of the apparatus may be controlled conveniently by means of a thermostatically operated steam valve controlled by the temperature of the liquid in the boiler, adjusted to maintain the liquid temperature a few degrees above the boiling point of water.

The following example illustrates the performance of the apparatus in relation to the separation of commercial distilled animal fatty acid from methanol solvent. The apparatus in this case had a bubble plate column with eight plates, with vapor passages, spacing, etc. proportioned according to good engineering practice, The feed consisted of 49% fatty acid and 51% of 90% methanol by weight. The boiler was run at 104 0.; very little supplementary steam was used. The fatty acids removed from the apparatus contained 2.0% of residual solvent consisting of 1.8% methanol or 0.036% anhydrous methanol. Tests of the product showed that appreciable esterification had not occurred. The solvent was recovered as 90.6% methanol. The example illustrates substantial removal of the methanol and recovery of the solvent in slightly more concentrated form than in the feed.

In all previous processes in the apparatus for removal of volatile from non-volatile liquids of this sort, separation has been accomplished by evaporation or distillation, with or without steam or other carrier or by stripping with steam or other carrier. Distillation or evaporation without a carrier requires a high temperature or use of a vacuum to remove substantially all of the solvent, while the usual processes in which steam or other carrier is employed require that another step be performed to eifect removal of the carried from the solvent. In the present process and apparatus the solvent is recovered with the concentration initially used without dilution with additional steam or other carrier.

Having described my invention, I claim:

1. A method for separating the components of a liquid solution comprised of alcohol, water and an oil such as fatty acid in such manner that the alcohol does not esterify the fatty acid, which method comprises establishing countercurrent flow of said solution to steam vapors in a contact zone and at such temperature that the heat of the steam vaporizes the alcohol component of the solution, and the steam is condensed by said solution into water, conducting said alcohol vapors to a condenser, removing the liquid comprised of fatty acid and water after the alcohol is evaporated, reheating the solution of alcohol and water for vaporization of the water content thereof, passing the steam so generated into contact with additional mixture of water, fatty acid and alcohol and simultaneously settling a portion of the mixture of fatty acid and water, decanting the fatty acid so separated and readmixing the water so separated with the mixture of oil and fatty acid being heated.

2. A method for separatingthe components of a liquid solution comprised of alcohol, water and an oil such as a fatty acid, in such manner that the alcohol does not react with the oil, which method comprises contacting said solution with steam vapors in a contact zone wherein said solution passes in countercurrent flow to said steam vapors, at a temperature such that the steam vaporizes at least a portion of the alcohol and is itself condensed to dilute the remainder of said solution, conducting the alcohol vapors to a condenser, withdrawing the remainder of the solution from said contact zone and boiling it, returning the vapors from such boiling to said contact zone, simultaneously conducting a portion of the material being boiled to a quiescent zone and allowing the oil and water components of it to separate from one another, decanting the oil and returning the water to the material being boiled.

3. A process for separating the components of a liquid system, consisting of water, oil and an organic liquid which is more volatile than water, which method comprises passing such liquid into a contact zone in countercurrent flow to steam vapors, maintaining the temperature conditions in said contact zone such that the organic liquid component of said system is vaporized by said steam and the steam in turn is condensed to dilute the remainder of said liquid system, withdrawing the vapors of said organic liquid component and condensing them, passing the remainder to a boiling zone and boiling the remainder therein, conducting steam vapors from the boiling zone into said contact zone, simultaneously conducting a, portion of the material being boiled to a quiescent zone and thereby effecting separation of the oil and water components insaid zone portion from one another, and withdrawing the oil component of said liquid system from said quiescent zone.

ALEXANDER C. BROWN.

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