IL26322A - Method for fluid extraction and apparatus therefor - Google Patents

Description

A METHOD FOR FLUID EXTRACTION AND APPARATUS THEREFOR This invention relates generally to a method for extracting fluids and more particularly pertains to the extraction of fluids in a fluid extraction device whereby the droplet dispersal and mixing energy characteristics of the fluids are varied progressively throughout the device. The invention further relates to one type of fluid extraction device for practicing the method and more particularly to improvements in that type of device often referred to as a Centrifugal Countercurrent Exchange or Contacting device.

The ef iciency of any extraction device is dependent upon the degree of intimate mixing of the fluids and this in turn is achieved by the dispersion of the fluids into droplets. Control of the character and extent of the droplet dispersion affords a means for varying the mixing energy within the device. Hence, the smaller the droplets the more intimate is the contact between the fluids.

Recently* it was discovered that when processing two liquids in a countercurrent exchange device which have the tendency to emulsify, the emulsification could be averted if the droplets dispersal characteristics of the liquids are varied progressively or gradiently throughout the radial length of the countercurrent exchange device. For example, in penicillin extraction when an extractive solvent such as amyl acetate is used, the extractive solvent is fed into the outer or peripheral portion of the rotor, whereas the high potency broth or "beer" containing the penicillin solute and having a greater specific gravity than the extractive solvent is fed into the rotor adjacent the periphery of the rotor.

When the broth is at maximum potency, there is the greatest tendency or the liquids to emulsify upon contacting each other. Hence, to prevent the emulsion in this example, the droplet dispersion of the liquids should be at the maximum adjacent the axis of the rotor. As the broth flovs outwardly toward the periphery of the rotor and contacts the extractive solvent, the potency of the broth decreases progressively.

When the high gravity broth finally reaches the input position of the low gravity extractive solvent, the potency of the broth is substantially reduced from what it was when the broth was initially introduced. At this radial level within the rotor, the fresh extractive solvent extracts the remaining penicillin solute from the broth. With the potency of the broth at a minimum strength adjacent the periphery of the rotor, there is no longer the tendency of the liquid to emulsify.

Hence, the droplet dispersion at this level may be made minima^ to a ford toaxiiaum liquid contact* Therefore, since the extraction of the solute f om the broth takes place progressively through the rotor, the tendency of the liquid to emulsify decreases as the broth travels toward the periphery. Consequently, the droplet dispersion could be safely decreased on a graduated or progressive basis from the axis to the periphery of the rotor which corresponds to the progressive decrease in the potency of the broth.

In the case where chloroform is used as an extractive solvent, the droplet dispersion characteristics of the exchange device should he lite converse. Since the chloroform is a higher gravity liquid than the high potency broth or beer, it would be introduced near the axis of the rotor, whereas the high potency broth would be introduced near the periphery of the rotor. As in the other example, the tendency to emulsify would be greater at the area or radial level where the high potency broth is initially introduced, which now is adjacent the periphery of the rotor. Accordingly, to prevent the occurrence of liquid emulsion and to have optimum system ef iciency, the droplet dispersion pattern should vay progressively from a maximum droplet dispersion adjacent the periphery of the rotor to a minimum droplet dispersion adjacent the axis of the rotor.

Similarly in other types of liquid extraction devices; i.e., gravity columns, mixers and settlers, rotating disc columns, centrifuges, etc,, the same conditions would prevail.

It is therefore a primary object of this invention to provide a method of efficient fluid extraction. It is a related object to efficiently extract a substance from contacting liquids without causing the emulsification of liquids when extracting the desired substance therefrom.

It is another object to provide a m t&od for varying the contacting surface area between two mixed liquids in order to efficiently extract a particular substance therefrom and to optimize the amount of liquids which could be processed during a given unit of time.

It is another object to provide a method for efficiently extracting a substance from contacting liquids within a centrifugal countercurrent exchange device* It is still another object to optimize the ef iciency of operation of solvent extraction devices, including countercurrent devices, by decreasing progressively the size of the droplet dispersion to correspond to the decrease is the potency of the fluid from which the solute is being extracted* It is therefore a primary feature of this invention to provide spaced apart partition walls having apertures therein* The combined areas of the apertures within each wall are made to vary progressively from the point of introduction of one fluid to the point of introduction of a second fluid* The relative aperture areas determine the relative contacting surface areas between fluids at various positions between said points of fluid introduction. j In some of our prior countercurrent exchange devices, removable disc columns were used to vary the droplet dispersion characteristic of the device by varying the perforation pattern of the disc columns. These exchange devices comprised a rotor having spaced concentric separator bands therein with a facte plurality of series of aligned holes arranged to afford cavities extending radially from the innermost to the outermost of the separator bands. The disc columns were removably positioned in each of said cavities. The droplet dispersion pattern was varied by the interchanging of the disc columns, or by providing disc columns having pairs of rotatale discs mounted on elongated tie-rods. The discs could he indexed or iotated with respect to each other to thereby change the size of the openings or the droplet dispersion pattern therethrough* Although these disc columns were an improvement, they nevertheless had many objectionable features, For example, if a variation in the perforation pattern of the disc column was necessary, it was necessary to remove the individual disc assemblies from the tie-rod and reposition the discs of the disc assembly around the tie-rod. Moreover, the adjustability of the discs was limited by the number of sides of the polygonal con iguration of the tie—rod cross-section. Furthermore, these disc columns did not have the capability to vary the perforation pattern throughout the radial length of the rotor on a precise graduated basis and hence these exchange devices operated at less than optimum efficiency.

An improved disc column is disclosed in this application which overcomes the aforementioned problems and is capable of providing in a simple and precise manner, the desired graduated droplet dispersal pattern throughout the counter-current exchange device. Said improved disc column generally comprises a plurality of disc assemblies and each of these disc assemblies comprises a stationary disc and a movable disc selectively rotatable with relation to each other without necessitating the removal of the discs from the disc column. An indexing rod is associated with each of the movable discs. which permits the rotation of all of the discs simultaneously to achieve a uniform perforation pattern or a graduated perforation pattern. In another embodiment, the disc assemblies each have a movable disc with a plurality of indexing perforations that cooperate with an indexing projection on a fixed disc to accomplish graduated indexing of the disc perforations.

It is therefore another primary object of this invention to provide an improved disc column for countercurrent exchange devices wherein the disc column is completely adjustable to different perforation patterns without requiring r the removal of any discs therefom and with but a Banimum number of operations to adjust the disc column* Still another important object of this invention is to provide an improved disc column for countercurrent exchange devices of the character described wherein the movable ί discs thereof can be adjusted simultaneously with one operation to achieve either a uniform or a graduated perforation pattern throughout the disc column.

She invention will be described with reference to the accompanying drawings, in which: Fig. 1, is a fragmentary, vertical sectional view of a centrifugal countercurrent exchange device with interchangeable disc columns embodying the principles of our invention; Fig. 2, is an enlarged vertical view of an improved disc column embodying the principles of our invention; Fig.3, is a top view of Pig. 2i Fig.4, is a bottom view of Fig.2; Fig.5, is a crose-eectional view taken on the plane of line 5-5 in Fig.2 and viewed in the direction indicated; Fig.6, is a cross-eectional view taken on the plane of line 6-6 in Fig.2 and vewed in the direction indicated; Fig.7» is a fragmentary view similar to Fig.2, but with only one indexing rod and the inner and outer disc assemblies shown with one other disc assembly, said indexing rod being shown in its "open position"; Fig. 8, is a cross-sectional view taken on the plane of line 8-8 in Fig.7» viewed in the direction indicated and illustrating the relationship of the discs of a disc assembly in its "open position"; Fig.9» is a fragmentary elevational view similar to Fig.7» wherein the disc assemblies are shown with the indexing red in its "closed position"; Fig.10, is a sectional view taken on the plane of line 10-10 in Fig.9» viewed in the direction indicated, and illustrating the relationship of the discs of a disc assembly in its "closed position"» Fig.11, is a fragmentary, elevational view similar to Figs.7 and 9, wherein the indexing rod thereof is torsion-ally positioned to afford a "graduated" peroration pattern in the disc assemblies; Fig.12, is a sectional view taken on the plane of line 12—12 in Fig.11 and viewed in the direction indicated; Fig.13, is a view similar to ^g.- 11» wherein toe indexing rod is torsionally disposed to afford a graduated perforation pattern in the disc assembly opposite from that shorn in Fig.11; Fig* 14» is a sectional view taken on the plane of line 14-14 in Fig. 3 and viewed in the direction Radicated; Fig* 15» is a plane view of a modified stationary disc to be used in a disc column without an indexing rod; Fig.16» is a modified movable disc to be used in superimposed relationship with the dise of the embodiment shown in Fig.15» and Fig.17» is a sectional view taken on the plane of line 17-17 in Fig.15.

Referring to the drawings, a preferred embodiment is illustrated which may he used when performing the method of our invention* However, as will be more apparent as the description proceeds, other structural arrangements may he used and are within the contemplation of the invention. Turning now to Fijg.l, the reference numeral 10 indicates generally a centrifugal countercurrent exchange device. Since the basic countercurrent exchange device 10 is generally well known, only so much thereof as is necessary for an understanding of tiie subject invention will be described. The device thus comprises a shaft 12 suitably journalled for rotation in a supporting structure 14. A rotor 16 is rigidly connected to the shaft 12 for rotation therewith and the entire device is enclosed in a removable protective cover 17.

Suitable passageways such as 18 and 20 are provided s in the shaft 12 for respectively supplying -tee heavier liquid to the central area of the rotor 16 and removing the lighter liquid therefrom. Similarly* suitable passages such as 22 and 24 are provided for respectively supplying the lighter liquid under pressure to the peripheral area of the rotor 16 and removing the heavier liquid therefrom. Communicating with the passageway 24 for removing the heavier liquid are passageways 26, provided between the spill-over discs 28 as indicated. The separator bands 32 are lightly perforated or preferably completely imperforate over their entire areas save for a plurality of holes arranged in aligned relationship to afford a series of disc column cavities such as 94, |§, 38 and 40.

Removably positioned within each of the cavities 34» 6» 38 and 40» is one of our novel disc columns 42· The disc column 42 (see Fig, 2) comprises a central tie rod 41» which is hexagonal in cross-section throughout its length except for the end positions 43» 44. The end portion 43 includes a shoulder portion 43a and a washer portion 43b interposed between the shoulder portion 43a and the disc assemblies 3 45. As seen in Fig. =g, the end portion 43 terminates in a polygonal shape 43 c that is dimensioned-to be received in openings suitably drilled and positioned in the drive sha t 12 at the inner portion of the rotor 16. The end portion 44 of each of the disc columns is associated with the outer wall of the rotor 16 as will be store fully explained hereafter. Although the cross-section of the tie rod 41 is shown as being hexagonal* other noncircular constructions of the tie rod 41 are contemplated.

Removably mounted on the tie rod 41 1B a plurality of disc assemblies 45 (Fig. 2). Each of the disc assemblies 45 includes a movable disc 46 and a stationary disc 43 in contiguously superimposed relationship. The movable discs (Fig . ) 46 have central circular openings 50 /Circumscribing the hexagonal tie rod 41 and being sized to afford rotation there-around for the purpose of indexing the disc assemblies 45· (Fig .6 ) The stationary discs 49^ ave hexagonal central openings 52 having tiie identical conf guration of the cross-section of the tie rod 41· Thus* once the stationary discs 46 are assembled with the tie rod protruding through their central openings, they cannot b8 rotated.

Each of the discs 6» 48 axe preferably formed with a plurality of perforations of varying size such as 57» 58 (Fig.4}· The size and shape of said perforations are substantially identical In each disc assembly. The perforations 57» 50 of each disc are radially spaced fom the center of each disc assembly 45 and are arcuately spaced equally one from the other around the center of each of said disc assemblies. Thus, when the disc assemblies 45 are positioned with the sets of perforations 57» 53 of the movable discs46 thereof in alignment with the sets of perforations 57, 58 of the stationary discs* the disc assemblies are in their "open position" as shown in Fig.8. Conversely* when the movable discs 46 are positioned so that the perforations in both discs of the disc assembly are completely obstructed, the disc assemblies are in their "closed position", as illustrated in Fig.10.

Vertical spacers 54 are interposed between each pair of disc assemblies 45 and they are reminrably mounted on the tie rod 41» to provide spacing of the disc assemblies in accordance with the separator bands 32» The disc assemblies 45 are retained by the shoulder portion 43a at end portion 43; and the other end portion 44 is provided with a means or releasably locking the discs for the purpose of indexing. As will be seen from Fig.2» a lock nut 44a cooperates with the tie rod 41 by threadedly engaging a cap screw 44b which in turn threadedly engages the end of the tie rod. The lock nut 44a is separated from the disc assemblies 45 by a lock washer 44c. Thuse when the movable discs 46 are positioned in their desired places, the tightening of the lock nut 44a releasably locks the disc assemblies 45 n the positions desired. The cap screw 44b also serves as a means for adjusting the length of the tie rod so that it can be extended within the rotor casing.

Once the disc columns 42 are indexed and locked into position, they are operationally retained in the rotor 16 by means of their end portions 43 being positioned in the shaft 12 as seen in Pig.1. A plurality of circular portholes 68 are provided in the cylindrical outer wall of the rotor in alignment with each of the cavities 34, 36, 38 and 40. Huge 60 ar threadedl associated with each of the poryholes 68 and the same preferably abut the heads of the cap screws 44b after the length of the cap screws 44b have been adjusted to operationally retain each of the disc columns 42 within the rotor. Por purposes of explanation, the disc assemblies 45 closest to the shaft will be referred to as the inner disc assembly; and the disc assemblies 45 closest to the outer end of the rotor will be called the outer disc assembly.

As seen in Fig.5» each movable disc 46 includes openings 46a, 46b which open to the periphery and are diametrically opposed. A pair of indexing rods 56, 56 are associated with the movable discs 46 by extending through the aligned openings 46a, 46b in all of said movable discs of the disc column 42. la the preferred construction, the indexing rods 56, 56 are shown fixedly attached at 56a to the movable disc of the inner disc asseiably and hence is adjacent to the shaft of the device 10 when the disc columns 42 are assembled in the device, fhe indexing rods 56, 56 are removably associated with all the other openings of the movable dies 46 of the disc assemblies 45· The indexing rods 56* 5 correspond in length to the distance between the top and the bottom movable discs of the diso column 42; and they each have an extending portion overlapping the movable disc 46 of the outer disc assembly.

As seen in Fig, 6r each of the stationary discs 48 is =B3?& formed with a pair of diametrically-opposed, peripherally-opening, elongated, arcuate indexing grooves 48a, 48b. The indexing rods are positionable and are movable within said grooves. These indexing grooves 48a, 48b have opposite end walls 48c, 48d which limit the path of movement of the indexing rods 36» It has been ound that in the case of equally spaced sets of perforations, the movement of the movable disc with relation to the stationary disc an angular distance of one-half (■£) of the number of degrees of spacing between the perforations, accomplishes complete indexing of the disc assemblies from an "open position" as illustrated in Fig.8, to a"closed position" as illustrated in Fig. 10, Accordingly, in. the illustrated disc assembly where there is equal spacing of two sets of six perforations 57, 58 the angular length of the arcuate grooves 48a, 48b is thirty (30°) degrees. This provides complete indexing adjustability between the movable discs 46 and the stationary discs 48.

From Fig.4 it will be seen that we have shown the stationary disc in the outer disc assembly as not having any indexing grooves because we have found that this construction enables us to more rmly lock the indexing rods into position when the lock nut 44a is tightened. However, for description purposes, we will refer to all stationary discs as having the same configuration* There are many different indexing positions that our novel disc column 42 offers. Turning now specifically to Figs.7 and 8 it will be seen that when the indexing rods are totated to their "open position" at one end of the elongated arcuate indexing grooves 48a, 48b, the movable discs 6 are caused to rotate with respect to the stationary discs 48 and be positionedaiwith their sets of perforations 57, 58 in a fully aligned or MopenM iHx±ifi_s relationship, When the indexing rods 56 have been rotated to their "closed position" at the other extreme end of the elongated arcuate indexing grooves 48a, 48b, as illustrated in Fig, 9, the sets of perforations 57, 58 are 6 fully obstructed. As seen in Fig, 3, the indexing rods 56 are shown positioned midway between the ends of the elongated arcuate indexing grooves 48a, 48b, Accordingly, the movable discs 6 have been partially rotated with the stationary discs 48, so that the perorations are partially obstructed as illustrated in Fig.6.

Still another type of indexing can be achieved when the indexing rods 6 are "torsionally or spirall M moved to the positions illustrated in Figs.11 and 13. As shown, one extreme disc assembly 45 is in its "open position" and the opposite extreme disc assembly 45 is in its "closed position". In these positions, the movable discs 46 of the disc column are moved with relation to the stationary discs 48 on a graduated basis so that the sets of perforations 57* 58 in. the discs are gradually obstructed* ¾ius, in the case where the indexing rods have been torsionally moved to the position llustrated in Fig.11, the inner disc assembly 45 is in its "closed position" with its perforations fully onstructed as seen from Fig.10. However, the outer disc assembly, which is closest to the periphery of the rotor 16 has its perforations unobstructed. Thus, this disc assembly is in its "open position" as illustrated in Fig.8. Of course, the disc assemblies that acre positioned between the inner disc assembly and outer disc assembly are partially obstructed on a graduated basis. Accordingly, Fig. 12 shows a disc assembly which is disposed near the outer disc assembly as being partially obstructed and almost completely open. On the other hand, where the indexing rods 6 have been moved to an equal distance from the opposite end wall of indexing groove 48 position, as shown in Fig. 14, the same disc assembly of Fig. 12 is substantially more obstructed and nearly closed. If the inner disc assembly of Fig.13 were shown, it would be fully open, whereas the outer disc assembly would be fully closed, because the indexing rods are 1 the exact opposite position to that of Fig. 11· 3a addition to torsional positioning of the indexing rods 56 with their ends either in the open or closed positions for the extreme opposite disc assemblies as illustrated in Figs. 11 and 13» the ndexing rods could be tor-sionally positioned at different angles between the two extremes shown. Accordingly, different increments of perforation graduation through the disc column 42 between these two extremes of fully "open" and fully "closed", may likewise be achieved.

As aforementioned, we have also provided a modified disc assembly for a dise column which is indexable without indexing rods. This modified disc assembly also can be indexed without being removed om a disc column and with a minimum number of operations. Accordingly, Fig. 15 illustrates a modified stationary disc 60 having two sets of multiple perforations such as 62, 63 therein. These perforations are preferably disposed with relation to the discs in the same positions as the aforementioned perforations 57, 53. The modified stationary discs 60 have an hexagonal central opening 64, which can be assembled with relation to a tie rod in the same manner as the discs hereinbefore men- (Fig. 17) tioned. An indexing projection 60a As formed in the modified stationary disc 60} and it is preferably located near the periphery thereof on the same diameter as one of the equally spaced sets of perforations, 62, 63» A modified (Fig. 16) movable disc 65 /having a plurality of arcuately spaced indexing perforations 65a is provided in the modified disc assembly. As in the case of the ether disc assemblies 45, it is superimposed in a contiguous relationship with the modified mov- 65 able disc=61 so that its projecting indexing portion 60a can register with each one of the arcuately spaced indexing perforations 65a. The modified movable disc^ also has two sets of perforations 62, 63» equally spaced thereround. As in the case of the aforementioned movable discs 46» it also is provided with a central circular opening 66, which is sized to circumscribe in freely rotatable relationship, the tie rod 41 in order to affoSd preselected rotational position— ing of the modified movable discs 6i=with relation to the modified stationary discs 60 for indexing purposes. The arcuately spaced indexing perforations 65a are disposed along the length of a thirty (30°) degree arc which extends from the center diameter of one of the equally spaced sets of perforations 62, 63· The thirty (30°) degree arc is therefore substantially the same length as the elongated arcuate indexing grooves 48a, 48b so that indexing from the "open" to the "closed** positions can be realized.

Thus, it will be seen that when it is desired to index a disc column embodying our modified disc assemblies, each of the modifed movable discs is rotated with respect to the modified stationary discs, and the arcuate indexing perforations cooperate with the projecting indexing portions to obtain different degrees of obstruction in the disc assemblies in accordance with the different possible indexing positions, When the modified movable discs are properly set, a locking means such as the locking nut 44a can then be used to hold the modified discs in position.

In the foregoing, an improved disc column was disclosed which is particularly adaptable for accomplishing the method ©f this invention. Te a©v*l method herein enables fluids to be processed efficiently whereby the amount of fluid extraction per unit of time is optimized. Moreover, the method is particularly suitable for efficiently extracting solute from a mixture and at the same time preventing liquids which have the tendency to emulsify from doing the same.

The novel method comprises generally, the introduction a region of a first quantity of a fluid into =ss=*sree and the introduction region of a seconi fluid from the eraa where the first fluid is introduced. The first fluid may be a aiarture of fluids which Sncludes substance or solute which is to be extracted therefrom. The second fluid then would be an extractive fluid for extrac-ting the substance from the frst fluid* he fluids are caused to nix together. ¾he extraction takes place within the space between the areas of fluid introduction. However, the quantities of the fluids are caused to be dispersed into streams or into droplets of progressively varying size between the areas of introduction of the fluids. The largest size streams or the minimum dispersion of the quantities of fluid are caused to occur in the area of the extract-rich fluids, and hence adjacent to the area of introuction of the fluid having the extract substance therein, -¾i the area of the extract-rich fluids, extremely intimate contact between the fluid is not essential. Conversely, the smallest size streams or the maximum dispersion of the fluids are caused to occur in the area where the fluids have the least amount of th$ extract substance therein* and hence should be adjacent the area where the extractive fluid is introduced. In this area, extremely intimate contact between the fluid is necessary in order to extract the remaining substance within the first fluid. By progressively varying the dispersion of the fluids, tiie effect of the extractive solvent and the available mixing force in extracting the desired substance is optimized.

Ibis method of progressively varying the droplet dispersion of fluids may also be used in any of the known types of solvent extractors, viz., rotating disc columns, mixers and settlers, centrifuges and gravity columns. In these types of systems, intimate contact between fluids for extracting a particular substance is achieved by the downward movement of a lover specific gravity fluid. The fluids mix and a substance is extracted therefrom as they pass through spaced apart aper-tured partition nails which define successive mixing chambers. The progressive variation of the size of the apertures in the partition walls correspondingly varies the contacting surface area of the fluids within the contacting chambers.

She aforementioned method is particularly suited to the centrifugal countercurrent exchange device 10. When the device 10 is used, a first fluid is introduced adjacent the periphery of the rotor and a second fluid having a greater specific gravty than the first fluid is introduced adjacent the axis 12 of the rotor. One of the fluids is an extractive fluid and the other fluid includes a substance or solute to be extracted therefrom. Partitions such as the bands 32 are spaced apart between the axis 12 and the periphery of the rotor to define a plurality of fluid contacting chambers.

Perforations are provided within each band to permit communication between chambers, She perforation patterns within the bands are varried progressively between the axis and the periphery of the rotor* She largest perforation pattern which causes a minimum dispersion of the fluids is positioned adjacent the areas of the extract-rich fluids. As the counter-current exchange device operates, the fluids travel between the axis and the periphery of the rotor and the solute is extracted progressively within the radial length of the rotor.

In the example given earlier relating to the processing of penicillin, the broth was dispersed to the greatest degree adjacent the rotor periphery, and therefore the relative size of the droplet pattern of the broth and solvent extraction at the rotor periphery was smaller than at any other area within the rotor. ¾ this manner, the broth which at this radial level containes a very small amount of solute therein, makes extremely intimate contact with the resh extractive solvent (amyl acetate), and the remaining amount of solute is thereby easily extracted. Furthermore, at the periphery the fluids are able to utilize the increased energy due to the circumferential rotor velocity. This further insures adequate contact between the low potency broth and the solvent, for extracting the remaining penicillin* The improved disc column 42 affords a precise and convenient means for providing the desired progressive perforation patterns within the rotor. ISae perforation patterns of the disc assemblies 45 are varied progressively when an upper portion of the indexing rod 56 is positioned adjacent one end wall of the indexing groove 48 in the stationary disc of the outer disc assembly and a lower portion of the indexing rod 56 is positioned adjacent the opposite end wall but of the indexing groove 48 in the stationary disc of the inner disc assembly. In his manner, the maximum relative perforation pattern occurs at one extreme end of the disc column which may be either adjacent the axis or the periphery of the rotor, and the minimum relative perforation pattern occurs at the opposite extreme of the disc column which also may be either adjacent the axis or the periphery of the rotor. Thus, the perforation patterns between the extreme and assemblies vary progressively, therefore, as is obviously seen, the simple manipulation of the indexing rod provides the desired perforation pattern for the entire disc column 42.

From the foregoing description and drawings, it should be apparent that we have provided both a novel method and a novel and improved disc column which fulfills the stated objects of our invention i a remarkably unobvious and unexpected fashion. As aforedescribed, the disc assemblies have pairs of discs that are readily indexed to afford variously sized perforation patterns with a minimum number of operations and without the necessity for removing the discs from the disc columns. Also, the new and novel indexing means employs indexing rods which enable the disc assemblies to be selectively adjusted in one operation either when it is desired to have a uniform perforation pattern in each of the disc assemblies, or a progressively graduated perforation pattern* Moreover* our method disclosed herein optimizes the amount of a substance which may be extracted from a fluid mixture in a unit of time by progressively varying the intimate contacting area between fluids, A means of accomplishing this is by progressively or gradiently varying the perforation patterns in the spaced apart partitioned walls which are positioned between the areas of introduction of the two fluids whose specific gravities vary one om the other* The disc column 42 disclosed herein is particularly suitable to precisely controlling the desired progressive perforation pattern throughout the disc assemblies of the disc column* foration pattern sufficiently large within the areas where the fluids are rich la their content of solute.

It should be realized that while we have illustrated and described ou invention with relation to a pa of straight indexing rods, other indexing rods of different shapes can be embodied in this Invention wften it is desired to vary the patterns on a different basis other than linearly; Also; it is not necessary to have a pair of indexing rods and indexing grooves to accommodate said indexing rods, as our disc columns could operate with merely one indexing rod and with indexing grooves to accommodate merely one indexing rod.

Claims (2)

1. C L A I M S : 1 · A disc column for use in aligned cavities in a centrifugal countercurrent exchange device of spaced concentric bands, said disc column comprising a plurality of disc assemblies mounted in spaced relationship on a tie rod, each of said disc assemblies including a movable perforated disc and a stationary perforated disc, the perforation pattern through each of said disc assemblies being determined by the indexing of the movable disc with relation to the corresponding stationary disc, an indexing rod extending through arcuate indexing grooves formed in the stationary discs and extending through accommodating openings within the movable discs to link said disc assemblies together, said arcuate indexing grooves having end walls to limit the movement of said indexing rod, said disc assembly having a maximum open position when the indexing rod is positioned at one end of the groove and a fully closed position when said indexing rod is positioned at the other end of the groove, the perforation patterns being of said disc assemblies R3Fe varied progressively when an upper portion of the indexing rod is positioned adjacent one end of the indexing groove in the stationary disc of the extreme end disc assembly of the disc column and a lower portion of the indexing rod is positioned adjacent the opposite end vail of the indexing groove in the stationary disc of the opposite extreme end disc assembly of the disc column, means for introducing one fluid into said column adjacent one end thereof and means for introducing a different fluid into said column adjacent the other end thereof, said progressive variation of said perforation patterns causing the intimate contacting area of said fluids to be varied correspondingly in a progressive manner* 2. A centrifugal countercurrent exchange device including a rotor, a shaft, a plurality of spaced concentric bands having ho 4s formed therein to af ord a radially extending cavity, a disc column positioned in said cavity, said disc column comprising: an elongated tie rod; a plurality of disc assemblies mounted in spaced relationship on said tie rod, and respectively being radially aligned with said bands, each of said disc assemblies including a movable perforated disc and a stationary perforated disc, said discs being contiguously superposed on each other; and indexing means to enable the movable discs of said disc assemblies to be rotated around said tie rod and thereby vary the indexing of the perforations of said movable disc in relation with the perforations of said stationary disc for the corresponding disc assembly. 3. A centrifugal countercurrent exchange device as claimed in Claim 2, wherein: said tie rod has a non-circular cross-sectional area; said stationary disc includes a central opening complementary to the non-circular cross-sectional area of said tie rod and accommodates said tie rod therethrough; and said indexing means comprises a circular central opening formed in said movable discs, said circular opening being dimensioned to accommodate said tie rod and to permit the rotation of said movable dise around said 4. In a centrifugal countercurrent exchange device as claimed in Claim 2 or Claim 3, wherein said indexing means comprises x an elongated arcuate indexing groove formed in the stationary discs of said disc assemblies; at least one indexing rod extending through said indexing grooves and through accommodating openings within said movable discs to link said plurality of disc assemblies together, said indexing grooves having end walls to limit the movement of said indexing rod, the movement of said indexing rod within said indexing grooves causing only the movable discs to rotate around said tie rod to thereby index simultaneously the discs for each of said disc assemblies* JjT A eountercurrent exchange device as claimed in 4 Claim=-7, wherein the movable disc and stationary disc for each assembly have identical sets of perforations therein, the perforations of each of said sets are radially spaced from the center of the disc assembly, said sets of perforations are separated from each other by an equal number of degrees, the arcuate length of said arcuate indexing grooves corresponding to one half (i) of said degree separation between said sets of perforations, said arcuate length of said grooves permitting said indexing rod to vary the openings through said disc assembly between a maximum open position when the indexing rod is positioned at one end of the groove to a fully closed position when the indexing rod is positioned at the other end of said arcuate groove. A eountercurrent exchange device as claimed in 4 5 Clams? or Claim 3, wherein at least one indexing groove of each stationary disc is in alignment with an indexing groove of each of the other stationary discs, the positioning of said indexing rod through said aligned indexing grooves whereby an upper portion of the indexing rod is adjacent one end wall of the arcuate indexing groove of the stationary disc of one of said end assemblies and a lower portion of the indexing rod is adjacent the opposite end wall of the arcuate indexing groove of the opposite end disc assembly provides a pro* gressiveljr varying perforation pattern through said disc column from one of said end disc assemblies to the other of said end disc assemblies, said progressively varying perforation pattern causing the intiiaate fluid contacting area to correspondingly vary in a progressive manner. A countercurrent exchange device as claimed in 3 6 any of Claims=6 to=9, wherein: the upper end of said indexing rod is ixedly attached to the movable disc of the outer upper end disc assembly; the stationary disc of said lower end disc assembly does not have an indexing groove to receive said indexing rod and thereby serves to protect the lower end of the indexing rod from being moved out of place and a closure means threade&ly associated with said tie rod to maintain said disc assemblies securely in place when tightly abutting against said lower stationary disc. 8. ϋ. A courttercurrent exchange device, as claimed 2 7 in any of Claims §= to M¼ wherein each of said movable discs is formed vith a plurality of indexing perforations disposed at an equal distance radially around the center thereof, each of said stationary discs having a projecting index portion protruding outwardly theref om and being sized and disposed to be received by any of said indexing perforations in said movable discs, whereby said movable disc of each disc assembly can be rotatably indexed with relation to each of said stationary discs in a plurality of ixed positions by moving said indexing projecting portion to alignment with a different perforation of said stationary discs. A countercurrent exchange device, as claifflsd 2 8 in any of Claims =5 to wherein said discs of each disc assembly are of the same size and have identical sets of perforations therein, and each set of said perforations are radially spaced from the center of said disc assemblies and are arcuately spaced apart equally one from the other about the cente of said disc assemblies, 10. ¾5¾ A countercurrent exchange device, as claimed 2 9 in any of Claims =§ to wherein said indexing perforations and projections are disposed near the peripheries of said discs, and said indexing perforations are disposed within an arc equal in length to half of the degree spacing between said sets of perforations, ©aid indexing perforations being located with respect to each of said indexing projections within said arc between an open perforation position and a closed perforation position* 1 1 . A method of liquid extraction between relatively immiscible liquids of varying densities in which said liquids are gradiently dispersed, substantially as described in the specification. 1

2. 4§. A centrifugal countercurrent exchange device for effecting intimate contact between relatively immiscible liquids of varying densities, substantially as shown in the accompanying drawings and described in the specification. Tel-Aviv, this fo day of August, 1966 AGSSNT OR APPLICANTS