Liquid/liquid extraction

where the relative plate spacing, t /_Dthe surface velocity of the distributed phase during flooding, i /_cthe surface velocity of the continuous phase when flooding, Ap the density diflerence and σ the interfacial tension.

2. Extraction column according to claim 1, characterized in that in series at least two perforated plates (12) and at least one Ab- or deflecting plate (14) are included.

3. Extraction column according to claim 1, characterized in that in series a disc, at least two perforated plates (12) and a Ab- or deflecting plate (14) are included.

An extraction column according to any one of claims 1 to 3, characterized by a plurality of peripheral openings in the plates (12, 14) and a plurality of tie bars (54) and star plates (56, 58) in the housing (10), the tie bars (54) extend through the peripheral openings in the plates (12, 14) and terminate in the star plates (56, 68).

5. Extraction column according to claim 4, characterized by a device for fastening the star plates (56, 58) on the vertical connecting rod (56).

6. Extraction column according to one of claims 1 to 5, characterized in that spacers (36) between the plates (12,14) are arranged and that the connections (54) through the peripheral openings in the plates (12,14) and the spacers (36) are guided through.

The invention relates to an extraction column, comprising a housing, with a vertical connecting rod (shaft) arranged in the housing, with a device for carrying out a reciprocating movement of the connecting rod and with a plurality of reciprocating perforated plates which are horizontal on the connecting rod in the Are spaced apart from each other.

Liquid extraction methods and apparatus for carrying them out have long been known. Fixed fills or trays are used to assist in the separation of the components of liquid phases which are passed countercurrently or in the same direction through the device. However, such methods and the devices provided for carrying them out have a very low efficiency. The reason for this is simply that even in liquid phase countercurrent processes, there is insufficient energy available to effect effective mass transfer. Therefore, in general, the extraction columns used to carry out such processes must be very large to reach a level equivalent to a theoretical level known as HETS, thereby yielding extraction columns of useful efficiency, with λE7S values ​​of 1.83 m (6 feet) to 6.1 meters (20 feet) or more.

To overcome the deficiency inherent in the extraction columns used in these processes and in carrying out the same, some time ago an attempt was made to add energy to the extraction columns used by placing in the columns a series of mixers on long vertical shafts, both with and without zones of mesh material to allow unification of the phases between the mixers. While such extraction columns are an improvement over previous columns using fixed fillings or troughs, they lack the insusceptibility of producing very small droplets near the agitators or mixers. In a development of this second generation of extraction columns, a series of mixing and settling chambers are used, which are provided side by side in a horizontal arrangement. But even with the improvements achieved in the second generation of extraction columns, maximum efficiency is still not achieved. The aforementioned horizontal arrangement also requires a costly construction and claimed like many older embodiments of extraction columns a large floor area.

In other constructions, pulsation of liquids in continuous phase to be extracted in a fixed column is used. However, such constructed columns have found little use, mainly because it is difficult to keep the motion uniform in large columns, and further high powers are required to move large volumes of liquid in such columns. Later developments are columns that use a series of perforated plates that can be reciprocated in a suitable manner. However, even such columns, in which the distance between the plates is uniform, have certain shortcomings with respect to the EETS values, the other size and design factors, and the efficiency with respect to the volume of the liquid phases transported through such columns and with respect to the liquid separation to be performed therewith. However, such pillars with perforated plates are superior in their operating values ​​to the earlier columns mentioned above; however, there is still a need for further improvements in reciprocating plate extraction columns as they should be smaller in size and have better overall efficiency.

From DE-OS 17 67 271 a generic device is known in which perforated plates at the same distance from each other over the entire height

the column are arranged. The determination of the plate spacing is done there intuitively or in the estimation method, which, among other things leads to the fact that to achieve a good efficiency very large columns are required.

The invention has for its object to provide a s extraction column of smaller size, the efficiency and operating data are improved compared to the known extraction columns.

This object is achieved in that the relative distance between the plates in different parts of the column corresponds to the following relationship:

(Up + 0.67 Uc)²-⁵

15

where / the relative plate spacing, U₀ the surface velocity of the distributed phase when flooding, Uc the surface velocity of the continuous phase when flooding, Ap the density difference, and σ the interfacial tension.

By means of this relationship it is possible to determine the spacing of the perforated plates in certain parts of a reciprocating plate extraction column. It is possible to predict the optimal plate spacing from the physical properties of each phase in different sections of a given column and from the flow rates of the distributed and continuous phases in the different sections of an extraction column by employing the relationship of the invention. The pitch of the perforated plates is proportional to an expression which can be determined from the surface velocity of the distributed phase during flooding, the surface velocity of the continuous phase during flooding, the density difference and the interfacial tension. The distance between perforated plates is not constant throughout the entire column, but only within different sections, since the quantities included in the relationship depend on the section in which they are detected. For a lower portion of the column therefore result in different sizes than for a middle or upper range.

Preferred embodiments of the extraction column according to the invention are specified in the subclaims.

Further features and advantages of the invention will become apparent from the description of embodiments of the figures. From the figures shows

Fig. 1 is an elevational view of an Extrak Uonssäule invention;

Fig. 2 is an elevational view of a drive means used in the column of the invention;

3 and 3 A are top views in section along lines 3-3 and IA-IA in Fig. 1, respectively, showing a perforated plate and a baffle plate used in the column of the invention;

F i g. Figure 4 is a schematic representation of the arrangement of the baffles and the perforated plates in columns of different diameters formed according to the invention, with the perforated plates arranged at a distance of 50.8 mm;

F i g. Figure 5 is a schematic view of the arrangement of the distances between the baffles and the perforated plates in columns of different diameters according to the invention, the perforated plates being spaced 25.4 mm apart; Figures 6a to 6d are schematic representations of various arrangements of perforated plates, baffles and discs in a column according to the invention;

Figure 7 is a schematic representation of the arrangement of the distances between the baffles and the perforated plates in pillars of various diameters according to the invention, the perforated plates being 76.2 mm apart;

F i g. Figure 8 is a schematic representation of the arrangement of the distances between the baffles and the perforated plates in pillars of various diameters according to the invention, the perforated plates being spaced 101.6 mm apart; and

Fig. 9 is a graph showing the relationship between the diameters of the extraction columns and the distances of the baffles for a separation column according to the invention, wherein the perforated plates have a distance of 25.4 mm and 50.8 mm from each other.

As mentioned, extraction columns with reciprocating plates are well known. However, the exact design of the spacing between the perforated plates and the baffles and / or slices used therein was determined by variable plate distance experiments in a given column. However, such an intuitive solution is cumbersome, tedious and inaccurate. In the test method z. B. the distribution of fluids or Liquids passing through the extraction column are visually observed to determine drop size, residence, and fall rate, with all of these sizes judged qualitatively as to whether plate spacing increases in certain parts of a reciprocating plate extraction column or to be downsized. The invention remedies this deficiency; it is possible to predict the optimal plate spacing from the physical properties of each phase in the different sections of a given column and from the flow rates of the distributed and continuous phases in the different sections of an extraction column by applying the equations already mentioned.

It is already known and already described in a paper by MHI Baird, RG McGinnis and GC Tann in "Proceedings of the International Solvent Extraction Conference," Society of Chemical Industry, The Hague, April 1971, that the following relationship applies:

0.67 U_c) = K₁

3 \0,2

2 \ l / 3

In it are:

U₀ = Surface velocity of the distributed phase during flooding;

U_c = Surface velocity of the continuous phase during flooding;

K₁ = a constant whose value is irrelevant here;

σ - interfacial tension;

ψ = energy intake per unit volume; ρ = average density;

Pc = density of the continuous phase; g = gravitational acceleration;

Ap = density difference;

μ_€ = Viscosity of the continuous phase.

It is also known that ψ is proportional to (Af)¹Zl is in which

A = amplitude of the stroke;

/ = Frequency of the float;

/ = Plate spacing.

10

Therefore, the following relationship applies:

0,6,0.4

l / 3)

15

(2)

It should be noted that in the above-mentioned mathematical relationships smaller quantities such as ρ 0,2 and

J_ \

1/3

V PcV-C /

usually neglected.

Since the physical properties A ρ, ie the density difference, and σ, ie the interfacial tension, and the surface velocities in the different parts of an extraction column change, it is therefore necessary to achieve optimum operating results to ensure that no part of the column mixed too weak which would give poor extraction efficiency and is not overly mixed, which would lead to premature flooding of the column. Since A and / are necessarily constant for all column sections, the following relationship holds:

(i / o + 0.67 U_c) ~ /°·⁴ (Ap)²ⁿ σ⁰⁶ Therefore:

(3)

40

, (U₀ + 0.67 U_c)²·⁵ UpY "σ¹*

(4)

45

From relationship (4), an optimum relative plate spacing in the various parts of a column can be calculated, in that no part of the column represents a significant bottleneck in volume flow per unit time due to excessive movement and no parts of the column with low mass transfer efficiency because of less than to work the optimal movement. Such bottlenecks in terms of throughput and low efficiency in parts of the column occur when the plate spacing is not optimized. Within the scope of relationship (4), the process of the present invention can be varied widely, depending on the liquid phases passed countercurrently through a given column, the flow rate through the column and the respective optimized spacing of the reciprocating plates, and the Hin and the speed of movement and the amplitude of these movements.

Reference is now made to FIG. 1. The embodiment of the reciprocating column of the invention shown therein includes a housing 10 which may be formed of any suitable material, e.g. As metal, glass or other suitable material, depending on the respective liquid phases to pass through the apparatus. It is generally preferred. Door the housing and for all other parts used in connection with the apparatus to use a material that is not attacked by the liquid phases passed through. As can be seen from Fig. 1, the column consists of a series of so-called. Open or perforated plates 12 and baffles 14, which are shown in detail in Figs. 3 and 3 A, where they are 12 'or 14 'are designated; they are also mounted on a central shaft 16, which is driven by any suitable means with a reciprocating motion, for. B. with a in FIG. 2 drive mechanism shown, which includes a Antriebsauibau 18, a variable speed drive motor 20, bearing blocks 22, a clutch 24, a drive shaft 26, a stroke adjustment 28, a connecting rod 30, a yoke 32 and a guide bearing 34, wherein the drive mechanism with the central shaft 16 is connected, so with the plate stack shaft of the column. The mechanism for generating the reciprocating motion of the driving device driven by the motor 20 may be in the amplitude of the reciprocating motion between about 0 and about

50.8 mm can be varied by means of the stroke adjustment 28. The drive means and the reciprocating mechanism may be further constructed so that the speed and amplitude of the reciprocation may be varied as desired, depending on the particular application and diameter of the column used therewith. The series of perforated plates 12 and baffles 14 can be realized at intervals according to the above relationship, can be widely varied in number per unit height, and distributed over such a height in the column, which ensures good performance. The column shown may, for. B. have an overall height of about 6.1 meters, with the row of panels placed at a height of about 3 meters inside the housing 10 and the panels held spaced apart by spacers 36 of suitable size at a variable spacing. Above and below the plates, clearance spaces 38 and 40 are provided in the housing to minimize the entrainment of the fluids. Intake feeders are suitably located in nozzles 42 and 44 to assure the distribution of the heavy and light liquids, respectively. The heavy and light liquids are discharged through a nozzle 46 and 48, respectively.

Reference is now made to FIG. 3. A typical reciprocating perforated plate 12 'is provided with punched out areas or openings 50, the free area generally making up about 50% of the total area of ​​each plate, and the openings being relatively large, on the order of the size of holes in the dimension 6.35 mm up

15.9 mm. The diameter of the plate is slightly less than the inner diameter of the housing 10th

As can be seen from Fig. 3A, in contrast, the typical cover plate 14 'has a single, large, central punched-out area or opening 52, but the diameter of the plate is like that of the perforated plate, that is slightly less than that Inner diameter of the housing 10.

As from the Fi g. 3 and 3A in more detail, the plate stack shaft or central shaft 16 of the column passes through a central opening in a perforated plate 12 'which is large enough to accommodate the diameter while at the same time loosely resting on the shaft Shaft is fitted and the plates of adjacent perforated plates by suitable spacers 36 are spaced. In contrast, the shaft 16 extends through the central axis of the relatively large opening 52 of a typical baffle 14 '. The plate stacks are spaced apart from each other and held relative to the shaft 16 by a plurality of connecting rods 54 and suitable spacers 36, the connecting rods being circumferentially open. in the perforated plates and baffles. The tie rods suitably terminate in star plates 56, 58 having relatively large central apertures (not shown) similar to those in the baffles. The star plates are secured to the middle shaft 16 in any suitable manner, e.g. B. by means of a hub and in the radial direction extending spokes o. The like. (Not shown). The number of connecting rods is not critical and can vary greatly depending on the diameter of the column. In the case of the small diameter columns, that is up to about 61 cm, in general about up to six tie rods are sufficient to provide the required strength and rigidity of the plate stacks. However, the particular construction shown for spacing the plates is not critical as long as the plates are spaced only according to relationship (4). Thus, the plate stacks may be supported by any suitable means instead of tie rods and stone plates, if desired.

According to the invention it is further provided that the extraction column contains not only the reciprocating perforated plates 12, but preferably by deflecting plates 14. Although the column can be operated without baffles, its presence improves the extraction efficiency in columns that are more than 76.2 mm in diameter.

It should also be noted in this regard that with an increase in the diameter of a column, when the number of perforated plates, the z. A distance of 25.4 mm, remains constant, the extraction efficiency achieved by the method in such a column is lower than that of a column of smaller diameter. This loss of efficiency will be a !! by the fact I? causes greater axial mixing to occur in a larger diameter column than in a Heiner diameter column. On the other hand, with relatively large diameter columns, the array of baffles greatly improves the extraction efficiency compared to a column of the same diameter using only perforated plates. However, even if baffles are used in a large diameter column, the extraction efficiency is generally not as high as a small diameter column.

By extrapolation, it was shown that the height of an equivalent theoretical (HETS) sieve changes with the diameter of the extraction column in accordance with the following mathematical relationship:

Ζ)

⁰²⁵

for an extraction system with light extraction and HETSu₁₁₁ ~ Z)⁰"³⁸

for an extraction system with difficult extraction,

wherein HETS_Wed."The minimum value of HETS achieved

ίο and D are the column diameters.

The above relationships reported in the literature relate to extrapolations based on experiments with 76.2 mm diameter columns without baffles and 304.8 mm to 914.4 mm with some baffles

! 5 are based. For the 914.4 mm diameter column, the distance between the plates was 381 mm. The baffles in the large diameter column have been proven to reduce axial mixing and reduce HETS_mln compared to the value for HETS_Mtnachieved without the use of baffles. As already mentioned, baffles are not required for small diameter columns.

Thus, in the case of large diameter columns, an additional improved efficiency can be achieved if additional baffles are used to reduce mixing in the axial direction, resulting in better extraction efficiencies. Some of these improved over the previous solutions embodiments are shown as embodiments in Figs. 4, 5, 6, 7, 8 and 9.

In the context of de.^r A wide variety of plate assemblies are possible as long as the plates are spaced in accordance with the above relationship (4). In Figs. 4 and 5, embodiments for a distance of 25.4 mm and 50.8 mm of the perforated plates and baffles are shown. From these figures, it can be seen that the ratio of the number of baffles to the perforated plates is greater for a column with pitches of 50.8 mm than that at distances of 25.4 mm. In the form shown in Fig. 4, a 304.8 mm diameter column with a pitch of 50.8 mm, a baffle plate is preferably used for every three perforated plates. On the other hand, in a column of the same diameter and 25.4 mm intervals, a baffle plate is used on every six perforated plates, as shown in FIG. These arrangements are repeated for the total number of plates used in a column. As in the embodiment of FIG. 4th one pillar of 304.8 mm diameter and 50.8 mm plate spacing, one baffle plate 14 is followed by three perforated reciprocating plates 12 and another baffle plate 14 followed by three perforated reciprocating plates (not shown), etc ., up to the total number of plates required for the pillar concerned.

According to the invention, further different embodiments of deflection schemes are provided, e.g. B.

the embodiment shown in Fig. 6, whereby a further reduction of the axial mixing is achieved. Various arrangements of perforated plates, baffles and discs are shown in Figs. 6a-6d, e.g. As a disc 60, which is arranged under a baffle plate 14, wherein behind the disc, two or more perforated plates 12 are arranged, which can be used in the invention. The respective arrangement requirements shown

Menus are repeated as often as necessary. In contrast to the embodiment shown in Fig. 6a, an arrangement is shown in Fig. 6b, in which the position of the baffle plate 14 and the disc 60 is reversed. It can therefore each in Fig. 6a or 6b in the implementation of the method according to the invention, depending on whether the light or the heavy phase is the distributed phase in the respective liquid-liquid extractor medium, the arrangement according to FIG. 6a is preferred for a light distributed phase in a given liquid-liquid extraction medium.

In Fig. 6c, an embodiment is shown in which two baffles 14 in a row two or more perforated plates 12 follow. Another arrangement is shown in Fig. 6d where the row of plates is arranged so that one baffle 14 is followed by two perforated plates 12, one disc 60, two additional perforated plates 12 and one final baffle 14, this arrangement as often as required is repeated. Various other combinations of perforated plates, baffles and discs are possible within the scope of the invention.

It should be noted that in the particular arrangements shown in the drawings and discussed above, the distances between the perforated plates and baffles and between the perforated plates and the discs and baffles may be the same as the distances between the perforated plates, or greater distances.

In the various plate assemblies, all perforated plates and discs may be assembled in the form of a plate stack, using tie rods and star plates or any other suitable means to support the plate stack reciprocated in the column at the given rate and amplitude , The arrangements of the perforated plates and baffles as z. B. in Figs. 4 8 to 8 can further be used in an extraction column in which uniform plate spacing is preferred with the same repeat pattern. In most cases, however, plate spacing is not uniform when optimum performance is to be achieved and physical properties and flow rates vary in different parts of the column. The basic plate spacing can therefore be varied in different parts of a given column, and the relative distances between perforated plates as such and between perforated plates and baffles and between baffles as such and baffles and discs can be designed so that the distances remain the same or different and vary in different parts of the column. The respective number of plates used depends on the plate spacing, as z. B. in Figs. 4 and 5 is shown

It is now on Fi g. 9, reference is made. The graph shown there on a logarithmic scale is an aid in the practice of the invention, namely in the general determination of the distance of the baffles for a spacing of the perforated plates of 25.4 mm and 50.8 mm, respectively, for pillars of different diameters in particular in Figs. 4 and 5 are shown. Such as B. from Fig. 4 As can be seen, the baffle spacing for a 50.8 mm plate spacing of the perforated plates is about 203.2 mm for 101.6 mm to 152.4 mm columns. While the graph shown is not absolutely accurate, it can be used as an aid in sizing the baffle plate standoff in any given system as soon as the column diameter, which is a function of throughput, is selected and the final relative distance ratio of the perforated plates by application the relationship (4) is calculated more accurately. For plate spacings greater than 50.8 mm, similar design curves can be made to select appropriate baffle spacing. It should be noted that baffle spacings can be determined equally for the various other plate assemblies as mentioned above.

By "plates" are here perforated plates, baffles or baffles, discs and star plates and the like. To understand how they are used in a column according to the invention.

In relation (4), it does not matter which standard units of values ​​are used therein as long as the same units are used in the different parts of a column. For example, if the interfacial tension in the upper part of the column is measured in dynes per centimeter, it must be measured in the lower units in the same units because the ratio of these values ​​is important to the invention.

The invention will be further explained below by way of examples.

example 1

An extraction column with reciprocating plates is used according to the construction of the device described above, with only the described perforated plates and a diameter of 25.4 mm at a total height of 3048 mm. Thus, a liquid-liquid extraction of phenol from water is carried out using isobutyl acetate as a solvent, the process specification is at most 50 ppm of phenol in the raffinate According to the extraction technique generally used, the plate spacing is initially determined essentially by intuition or Estimation from the top to the bottom of the column determined so that the column used has a plate section of 1981 mm with a plate spacing of 25.4 mm and a plate section of 457 mm with a plate spacing of 50-8 mm, the entire plate section 2438 mm. The used plate distance of 50.8 mm is located in the upper part of the column, whereby this is again determined by intuition or estimation.

The operating conditions are as follows:

Phenol concentration: 5% in water

Phenol solution temperature: 40⁰C

Flow rate of phenol solution: 250 ml / min

Flow rate of isobutyl acetate: 34 ml / min

Temperature of the added isobutyl acetate: Ambient temperature (about 25 ° C)

Temperature of the column:

Ambient temperature (about 25 ° C).

The following results are achieved during operation:

Stroke x Gcschw.

Phenol raffinate concentration (ppm)

2,286 m / min 3,150 m / min 3,556 m / min

2000 200 column flooded

The drop size is much smaller in the top of the column than near the bottom, indicating that much better efficiency is achieved in the top of the column than near the bottom. However, the process specification of at most about 50 ppm of phenol in the raffinate (water) was not achieved. This example illustrates the prior art practice; usually the next step in this technique is to intuitively increase the plate spacing in the top of the column, or by estimating it once or several times until the required process specification is achieved, if possible without flooding the column.

Example 2

915 mm at a distance of 25.4 mm, the distribution of the plate spacing being estimated on the basis of estimated density differences in the various sections of the column. The column is then put into operation under the following conditions:

Phenol concentration:

8% in water (actual feed specification)

Phenol solution temperature: 4O⁰C

Flow rate of phenol solution: 250 ml / min

Flow rate of isobutyl acetate: 34 ml / min

20 temperature of the supplied isobutyl acetate: ambient temperature (about 25⁰C)

Column temperature: 2S ambient temperature (about 25 ⁰C).

The following operating values ​​were achieved:

Stroke x speed

30 phenol raffinate concentration (ppm)

The column used in Example 1 is again used 4.572 m / min door liquid-liquid extraction of phenol 5.639 m / min from water, but the distribution of the 35 plate spacing is calculated using relationship (4) according to the invention and only a total length of 1829 mm of the plate stack is used. Further, since the interfacial tension at this time is unknown and the flow rates in 40 different sections of the column are different, though not greatly different, an approximation of the plate pitch variation is calculated by relation (4), the density difference of the calculation being taken as the most important variable 45 becomes. The density difference measured at the top of the column is 1.0060 minus 0.950, ie 0.056, and in the bottom region of the column 1.000 minus 0.882, ie 0.118. If only these values ​​are used in the relationship and the others neglected to perform a quick approximation, the plate spacing ratio from the top to the bottom of the column is calculated as follows:

Column flooded

/ 0.118V^/3 V 0.056 /

The following observations were made during operation. A much better intensity of movement is achieved with the stack of plates used. This accounts for the better total extraction of the phenol from water and leads to the raffinate specification of 50 ppm at a stack height of only 1829 mm. Furthermore, the droplet size is uniform virtually everywhere, being somewhat smaller near the top of the column.

This example clearly demonstrates the improvements achieved by the invention over the conventional methods and apparatus of Example 1.

Example 3

Example 2 is repeated, except that a more accurate calculation of the pad spacing after measurement is performed as follows:

3,46

55

However, since the flow rates and the interfacial tension are known to exert an influence, the calculated result is rounded up to 4.0, and a 4 to 1 plate pitch change from the top to the bottom of the column is 1829 mm in total Based on disk stack. Beginning in the upper part of the stack, only 305 mm plates with a spacing of 101.6 mm are used, followed by 305 mm plates with a distance of 76.2 mm, followed by 305 mm plates with a distance of 50.8 mm and to this

Upper Lower

Column area Column area

<p><tgroup cols="3"><tbody><row><entry>Relative values</entry><entry>218,6</entry><entry>187,4</entry></row><row><entry> {U_D + 0.67 U_c) </entry><entry></entry><entry></entry></row><row><entry>density difference</entry><entry>0,056</entry><entry>0,118</entry></row><row><entry>Interfacial tension</entry><entry>7,3</entry><entry>9,8</entry></row></tbody></tgroup></p>

Based on the given measurements, a more accurate optimization of the disk pitch ratio is made using the relationship! A \

13

218,6

, 6 ψ, 4 /

187,4/ _ 1,47 _ ₇.

/ 0,056Y ⁷³Z ^ Y⁵ (0.2887) (0.6429) V 0.118 / V9.8 /

A more precise optimization of the plate pitch variation is therefore 8: 1. In a column employing this plate variation variation, a raffinate containing less than 50 ppm of phenol can be obtained

To illustrate the invention, an aqueous phenol solution and isobutyl acetate as a solvent have been cited as an example; Of course, the method and apparatus of the invention can be used to separate a wide variety of liquid mixtures using a wide variety of suitable solvents. Thus, the invention is by no means limited to the separation of phenol from water with isobutyl acetate as a solvent or any other suitable solvent.

The method according to the invention has numerous advantages. For example, it may be carried out by means of the apparatus in such a manner that optimum conditions can be achieved and liquid settling can be performed on a wide variety of liquid mixtures. The invention further minimizes the required volume of a reciprocating plate extraction column for performing the respective liquid-liquid extraction.

The extraction column for carrying out the method according to the invention can be designed so that the requirements of the respective liquid phases to be processed are precisely met. The invention also allows the construction of extraction columns of widely varying sizes, as the relative plate arrangements can be readily determined using the relationship given, rather than the empirical methods heretofore employed.

4 sheets of drawings

45

50

60 65