US2405158A - Multiple contact countercurrent extractor - Google Patents

Description

1946- c. E. MENSING 2,405,158

MULTIPLE CONTACT COUNTER-CURRENT EXTRACTOR Filed Jan. 16, 1945 fir 35 INVENTOR C'fi/PA 2 Mf/VJ/A/G f 2.

ATTORNEY Patented Aug. 6, 1946 MULTIPLE CONTACT COUNTERCURRENT EXTRAGTOR Carl E. Mensing, Somervillc, N. J., assignor to American Cyanamid Company, New York, N. Y., a corporation of Maine Application January 16, 1945, Serial No. 573,129

2 Claims. (01. 23-2705) The present invention relates to a new and novel multiplecontact, countercurrent mechanical extractor. More particularly, it relates to an improved apparatus for the solvent extraction of one material from a mixture thereof, adapted to require a minimum amount of extracting. solvent and to eliminate the necessity for pumps between stages.

Many different manufacturing operations advantageously make use of solvent extraction procedures. For example, chemical reactions in the production of drugs and dyestuffs are frequently carried out in organic solvents. It is usually necessary to recover and/or purify these solvents. One well-known process of so doing is that of extracting the mixture with an additional solvent which has a selective aflinity for the material to be removed from the mixture but little or no aifinity for the residue.

In the past, various flow schemes have been proposed for carrying out such operations. They cover a wide range. The simplest are those used with small amounts of easily-separable material in which the material to be extracted is simply agitated with the extracting solvent and allowed to separate into layers, the layers decanted and the extracting solvent removed. However, since the solvent ratio is in many cases high, if the volumes to be treated are large, excessively large volumes of selective solvent must be handled. In order to decrease the required volume of solvent, procedures of step-wise, multiple-contact, countercurrent extraction have been developed. It is with these procedures that the apparatus of the present invention is primarily concerned.

In the past, such operations have been customarily carried out by agitating the liquid to be extracted together with the solvent in one vessel, pumping the resultant emulsion into a separating chamber, allowing the emulsion to separate, and separately pumping both layers to the next stage. The solvent flows in one direction and the material to be extracted in the other through a series of such operations. Such a procedure involves n extensive arrangement of tanks and pumps. It involves a considerable power consumption, since each stage requires the operation of an agitator and several pumps. Further, large quantities of both thematerial being extracted and the extracting solvent are being processed which again unduly increases the required apparatus and consequently the fixed overhead. A still further disadvantage lies in the fact that in ordinary agitating operations.

' to these major difficulties.

cannot be utilized since there is a finite time limit in practical operation and equilibrium conditions between solvent and material to be extracted are not attained.

It is the object of the present invention to provide an extracting device which is not subject It is, therefore, a principal object to construct an apparatus in which multiple contacts between solvent and material to be extracted are carried out under conditions such that the maximum extracting power of the solvent is more nearly utilized. Another object is to construct an apparatus in which the agitating and separating operations are carried out in the same chamber. Still another, and not the least important object, is to provide an apparatus in which no pumping between stages is required when a step-wise operation is employed.

The invention will be more fully illustrated in conjunction with the accompanying drawing in which:

Figure 1 represents an elevation, partly in section, of one form of such an apparatus; and

Figure 2 shows a further modification indicating the arrangement of elements for a continuous, countercurrent, step-wise operation.

The basic apparatus, as illustrated in Figure 1, comprises a chamber l, closed. by a cover 2 having mounted thereon a standard 3 which supports a motor which in turn rotates a shaft 5 which extends down into the chamber and terminates in an impellor 6. It is a feature of the present invention that the impeller 6 is arranged to deliver an upward thrust.- Dependent from the cover and surrounding the shaft and impellor is a sleeve 1, shown-in Figure 1 as closed at the bottom and having overflow ports 8 therein near the top. Surrounding sleeve l and also dependent from cover 2, is a battle 9 closed at the top and open at the bottom. Baflie 9 does not extend quite as far down into the chamber as does sleeve 7, although this is not a limiting feature. In the drawing, sleeve 7 and baflie 9 are shown as sections of concentric cylinders. The invention, however, is obviously not so limited since they may be of other cross section.

Fluid to be extracted enters chamber I through a conduit Ill extending down nearly to the bottom of chamber l to a point directly below impellor 6. A second conduit II also enters the chamber, joining with conduit l0 directly under impellor 6 in a T connection l2, the third arm l3 of which extends vertically upward under impellor 6 and into the space enclosed by sleeve the maximum extracting ability of the solvent 1; Above the T connection l2 but below sleeve 3 I, conduit I3 is Joined by an additional conduit I4 which extends vertically upward outside bafile 9 to a point roughly midway the height of chamber I.

Provision is made for the removal of material from chamber at two points; one near the top, and the other near the bottom. At one side of chamber I, near the top thereof, is a small space formed by a baiile I5 having a port I6 therein to open into the main chamber. Any liquid reaching the height of port IE will flow into the small .chamber and then out of the apparatus through a conduit I1.

At another point in the side wall of chamber,

I, near the bottom thereof, a port I8 connects with a conduit I9 which extends vertically upward to approximately the height of chamber I, being provided with a vent 20 at the end thereof. Near the upper end of conduit I9 it is joined through a T connection by a conduit 2| which extends vertically downward, thus forming with conduit I9 a swing U connection which permits control of the height of the interface between fluid layers in chamber I.

The operation of the apparatus is essentially simple. Fluid to be extracted enters through conduit I0 and extracting solvent enters through conduit II. They mix in conduit I3 through which they enter the space enclosed by sleeve 1 and become thoroughly and intimately agitated by the action of the impeller, The latter being designed for upward thrust forces the mixture up through the sleeve, out through openings 8 into the annular space between sleeve I and bafile 9, down through the annular space, under the lower edge of baflle 9 and out into the main space of chamber I. At this point, due to the action of the agitator the mixture is a very highly dispersed emulsion which forms a layer filling the vertical central portion of the chamber. This emulsion breaks and the solvent, containing the desired dissolved constituents, rises into a relatively quiescent supernatant layer which comprises the organic phase and overflows through opening I6 and out of the chamber through conduit I1.

It will be apparent that the flow capacity through the sleeve I and the annular space between the sleeve and baflle is potentially much larger than through the feed conduits Ill and II, Advantage of this fact is taken to provide an important feature of the present invention, namely, the use of conduit I 4 through which, as shown in Figure 1, unseparated or only partially separated emulsion is drawn in by the action of the impellor and recycled. While in Figure 1 the length of conduit is fixed, in practice it is often highly desirable to make the inlet to conduit I4 adjustable in height so that the recycled fluid if so desired may be drawn from either the separated or unseparated layers. By recycling fluid in this manner both fluids or phases are repeatedly broken up and recontacted, thus taking maximum advantage of the solvent power and conversely requiring the use of a minimum of solvent.

As shown in Figure 1, sleeve I is closed at the bottom, fitting tightly around conduit I3. However, this is not necessarily a limitation, In fact, where it is desired to circulate fluid from the lower part of the chamber in excess it is of advantage not to do so.

The extracted material, being the heaviest, eventually settles out of the emulsion, forming the lower layer in the chamber I. The static head of liquid in chamber I forces liquid from this lower layer out through opening I8, up through conduit I9 and down through conduit 2|. By adjusting the height of the inverted U formed by the conduits l9 and 2|, the height above the bottom of the chamber and therefore the volume of the organic phase, i. e. the quiescent solvent layer, may be controlled.

In Figure 2 a modification of the apparatus particularly well adapted for step-wise, continuous, multiple-contact, countercurrent treatment is shown. Although somewhat difierently arranged, it will be noted that each of the elements described in connection with Figure 1 are present in the apparatus arrangement of Figure 2.

In Figure 2 it will be seen that the apparatus comprises a plurality of the extractors shown in Figure 1. For purposes of illustration, three such units are shown although it is obvious that the invention is not limited to any particular number. A large chamber 22 is seen. to be divided into three subsidiary chambers 23, 24 and 25, of approximately equal size, by two dividing walls 26 and 21. Each chamber is provided with a standard 3, motor 4, shaft 5, impellor 6, sleeve 1, openings 8 and bafile 9 supported from the cover as in the case of Figure 1. Each of the chambers is provided with a conduit III for introducing fluid to be extracted as in the case of Figure 1. As to chamber 23, this conduit enters from outsidethe apparatus and in chambers 24 and 25 introduces fluid from the immediately preceding chamber.

Each of the chambers is also provided with a conduit II for introducing solvent thereto in a countercurrent direction to the flow of material to be extracted. It will be noted that instead of conduit I I entering through the top of the chamber as in Figure 1, it is introduced into chamber 25 through a conduit 28 into a pocket 29 formed by a baiiie 30, from which pocket the solvent is carried through a conduit down into the T connection below the impellor as in the case in Figure 1. It will be further noted that each of the chambers has a corresponding pocket 29 and battle 30 but that the solvent flow from one chamber to the next is over the top of the dividing wall 26 and 21, which do not extend the entire height of the chambers.

In each chamber, the mixture of solvent and material to be extracted is carried by conduit I3 up into sleeve I beneath impellor 6 as in Figure 1. However, in order to obtain a more uniform recirculation, conduit I4 has been replaced. In each of the chambers a third concentric baflle 3| is located between sleeve I and bafile 9 and extending about half the height of sleeve I. This baiiie is closed at the top by an annular plate 32. Admission into the annular space between sleeve 1 and baille 3| is by means of a plurality of short conduits 33 spaced approximately equally around the baffle.

The external inverted U formed by conduit I9 and 2| in Figure 1 in each of the chambers 23, 24 and 215 is replaced by a pocket 34 formed at the top of each chamber by a closed cylindrical baifie 35. Extracted liquid from the bottom of each chamber is forced by the action of the impellor up -into pocket 34 through a conduit 39 which extends vertically from a point near the bottom of the chamber up into pocket 34. By adjusting the distance to which conduit 36 extends up into pocket 3| it is possible to control the height of the fluid interface within the chamber as is done by the use of the externally- 5 located, inverted U in Figure 1. Extracted fluid leaves pocket 34 through conduit l0, leading to the next step in the extraction in the case of chambers 23 and 24, or out of the apparatus in the case of chamber 25.

I claim:

1. In an apparatus adapted to carry out countercurrent, stepwise, multiple-contact, solvent extraction: the combination of a closed chamber having a vertically-positioned impellor shaft located therein, said shaft extending downward from the cover of the chamber and terminating in an impellor adapted to produce an upward fluid thrust; a vertical sleeve surrounding said shaft and impellor, said sleeve having at least one overflow port near the top thereof; a baflie surrounding said sleeve and extending at least substantially to the top of the chamber, said baflie' being open at the bottom and providing a passage vertically downward along the major portion of the length of said vertical sleeve; a plurality of converging inlet conduits joining a common conduit, said common conduit terminating within the said sleeve below said impellor; a fluidconducting means having at least one inlet opening in the central space of the chamber outside said baille and arranged to deliver fluid within said sleeve below said imepllor; an overflow means to the exterior of said chamber from the space outside of said baflle and outlet means from the bottom of said space, said outlet means being arranged to permit gravity flow and to retain an effective head of liquid above said impeller.

2. An apparatus according to claim 1 characterized in that the bottom of said sleeve is closed about said means for introducing mixed fluids thereinto.

CARL E. MENSING.

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