RU2836106C2 - Liquid-liquid extractor and battery containing such extractors - Google Patents

Abstract

FIELD: performing operations.

SUBSTANCE: group of inventions relates to a liquid-liquid extractor and a battery for liquid-liquid extraction, comprising at least one liquid-liquid extractor. Liquid-liquid extractors are adapted to very low flow rates of liquid passing through them. Outlet passages contain downstream of the settling chamber, where heavy and light phases are separated, phase overflows, the edge of which has an irregular in height shape, for example, toothed. Circulation channels of the phases are preferably open in order to also reduce the risk of blocking the liquid with air bubbles.

EFFECT: group of inventions reduces the effect of capillarity and air effects, which can make the liquid flow irregular.

20 cl, 13 dwg

Description

Field of technology to which the invention relates

The present invention relates to the field of chemical engineering and, more specifically, to liquid-liquid extractors, as well as to a battery containing such extractors.

State of the art

These extractors are designed to transfer dissolved substances between two immiscible phases, usually called the aqueous phase and the solvent or the organic phase, or the heavy phase and the light phase. They belong to the family of mixer-settlers. The two liquid phases are mixed to form an emulsion, then separated by sedimentation, which allows the solute originally contained in one of the liquids to be transferred to the second liquid. It often happens that a battery of many cascades is used, each containing such an extractor, in order to obtain the best extraction in a process where the phases pass successively through each of the cascades. Extractors usually contain a mixing section in which the emulsion is formed by the movement of the moving body, and a settling section in which the liquid phases are separated. The circulation of the phases in these batteries is usually countercurrent.

Liquid-liquid extractors of various sizes are proposed, from large industrial devices capable of containing several tens of cubic meters per cascade, to small-volume devices whose extractors can contain several hundred millimeters per cascade.

Extractors with very low throughput and very low extraction flow rates have been developed for nuclear fuel applications. Very low flow rates can be in the range of a few tens to a few hundred millimetres per hour. An example of such an extractor is described in FR 1580163 A. A battery of extractors which is adapted for such applications and which allows easy assembly and modification by remote manipulation is described in FR 2831075 A.

Other extractors are described in detail in documents EP 0531213 A1 and FR 2459064 A1.

A particular problem associated with low flow rates is that capillary forces can make the liquid phase flows uneven, with variations that may be unacceptable in phase levels or mixing in compartments. Another frequently encountered problem is the difficulty of modifying a battery of extractors in a hostile environment such as a nuclear one, or of dismantling and adjusting individual extractors, which are often small for low flow rates, by remote manipulation or with a glove box.

The invention relates firstly to an improved liquid-liquid extractor which can be of a smaller size and is made with various improvements ensuring particularly good flow uniformity even at very low flow rates, facilitated sedimentation and various elements of equipment which can be easily installed on a fixed structure of the extractor by remote manipulation, if necessary. Another aspect of the invention is a battery containing such extractors and designed in such a way that it can be easily used in a nuclear environment, i.e. in a glove box or in a shielded chain mechanism, due to the great simplicity of installation and assembly by remote manipulation.

The essence of the invention

In general, the invention relates to a liquid-liquid extractor containing a hollow block with mixing and settling chambers communicating via a fluid medium, inlet passages of two liquid phases leading to the mixing chamber, and outlet passages of two liquid phases connected to the settling chamber, which is characterized in that the outlet passages are provided with overflows near the settling chamber, and each of them is made with an edge of the overflow of liquid phases having an uneven height in the form of a broken line limiting a plurality of reliefs.

Weirs or drains are obstacles to the flows of liquid phases, which are limited by the height above which the flow begins to flow. The weirs discussed in this document are placed at the outlets of the settling chamber at different heights so that the height of each of the phases at this point can be adjusted. A broken line in this document will refer to a line, as a rule, delimiting a plurality of reliefs, alternately protruding and deepening, with a slope whose evolution is irregular, with many inversions of directions along the line. In the case of very low flow velocity, the flow passes through the lower parts of the deepened reliefs due to their narrowness, which avoids significant action of capillary forces and retention of liquid in front of the weir. This effect does not exist on a straight weir, or on the horizontal side of the flow, or on sides with a slight slope, or even on the bottom of a trough of circular cross-section, the radius of curvature of which would be much greater than that of the reliefs provided in this document.

According to a preferred form, the edge of the overflow of at least one of the overflows consists of a plurality of recesses tapering downwards to zero width and formed by two inclined edges.

According to another form, compatible in this respect with the previous one, the edge of the overflow of at least one of the overflows has teeth consisting of alternating identical and evenly distributed reliefs.

In a particular embodiment of the invention, one of the weirs is located at the junction between the settling chamber and the outlet passage of one of the said liquid phases, known as the light phase; whereby it limits the total height of the phases in the settling chamber.

According to another embodiment compatible with the previous embodiment, the other of the overflows can be placed in the inlet well of the outlet passage of the other liquid phase, known as the heavy phase, at a height that can be adjusted in the inlet well in order to adjust the relative retention time of the two liquid phases in the extractor.

According to an optional but important improvement, the outlet passages consist mainly or essentially of channels open on the upper side of the block, forming an extractor structure. However, the effect of this open outlet channel design is similar to that of the overflow reliefs: the effects of capillary action, flow delays at low flow rates, and also the entrapment of air bubbles are reduced, and thus a better uniformity of flow is also achieved.

These open channels, which are the focus of the gravity flows of the liquid phases, can preferably run in a straight line, for example parallel to the sides of the block, where the outlet passages open; they can be quite long without drawbacks and continue, for example, at least half the length of the block measured parallel to the sides. The flow of the flows remains easy and uniform, and the extractor block remains compact. Such an arrangement is useful in order to obtain an extractor in which the inlet and outlet openings of each of the liquid phases are aligned along two lines perpendicular to the sides. The interest in such an arrangement is shown in batteries containing multiple cascades assembled on the sides: all the extractors in this case have the same orientation and their similar equipment is aligned in parallel lines, which facilitates the manipulation of the battery, improves its appearance and makes possible general checks of the sediments for all the cascades of the battery, if all the settling chambers are turned towards the observer and are open for viewing, for example through an inspection hole or other transparent wall.

The outlet channels are also preferably quite wide, optionally each with a width equal to at least one third of the width, measured perpendicular to the sides, of the settling chamber, also in order to be able to regulate the gravity flow in these places.

The extractor may comprise a third overflow located between the mixing chamber and the settling chamber and made in the same manner as the previous ones and with the same effect, with the edge of the overflow of liquid phases having an uneven height in the form of a broken line limiting a plurality of reliefs.

According to other possible additional improvements:

- the extractor contains a lowering plate, immersed in the settling chamber and continuing to a protective distance from the bottom of the settling chamber;

- the extractor contains settling equipment that can be inserted into the settling chamber by moving and that contains a coalescence mesh with a previously formed emulsion, immersed in the settling chamber and facilitating the coalescence of one of the liquid phases;

- this settling equipment contains a second coalescence mesh that promotes coalescence of the other liquid phase;

- the block includes a console, on the upper side of which a recirculation pump can be installed, wherein the recirculation pump is provided with vertical suction and discharge pipes, respectively, immersed in the outlet passage of one of the liquid phases and in the suction chamber provided in the block and communicating via a fluid medium with the mixing chamber.

Another aspect of the invention is a battery for liquid-liquid extraction, comprising at least one extractor in accordance with the above; the extractor or extractors and end modules are aligned and secured on a rail, wherein the end modules contain connections to counter-current circuits of the liquid phase in the battery, the inlet openings and outlet openings of each of the phases are located on the continuation between the extractors.

The battery may preferably comprise separator plates that are tightly pressed against the extractors and carry seals surrounding the inlet and outlet openings of the liquid phases, so as to also facilitate the installation of the device.

Liquid-liquid extractors, end modules and, if necessary, separator plates can be mutually connected on a rail with the possibility of sliding along it in order to also facilitate installation.

Another improvement that can be envisaged is to provide the battery with a heating means. This means can be installed inside or under the rail and consist of a heating mat, for example, by means of electrical resistance. Another device can comprise a device for circulating a coolant passing through the block of each of the battery extractors.

Brief description of the drawings

Various aspects, features and advantages of the invention will now be described in more detail with the aid of the following figures, which thus illustrate some purely illustrative embodiments:

Fig. 1 - top view of the extractor;

Fig. 2 - longitudinal section of the outlet passage of the heavy phase;

Fig.3 - adjustable overflow of heavy phase;

Fig.4 - phase mixing chamber;

Fig.5 - equipment for emulsifying the mixture;

Fig.6 - equipment facilitating settling;

Fig.7 - recirculation equipment;

Fig.8 - overflow of light phase;

Fig.9 - battery with multiple extractor cascades;

Fig.10 - rail for mounting and supporting the battery;

Fig.11 - sealing plate between extractors;

Fig.12 - embodiment of a refrigerant extractor;

Fig. 13 - an embodiment of a rail for supporting a battery with a built-in heating means.

Detailed description of the invention

First, a separate liquid-liquid extractor 60 shown in Fig. 1 will be described. It consists of a block 1, generally a parallelepiped, almost regular and limited by two long vertical sides, which are the first side 2 and the second side 3, parallel to the previous side, two short vertical sides, of which the front side 4 and the back side 5 are perpendicular to the previous sides, and a lower side 6 and an upper side 7, which are perpendicular to all previous sides. The block 1 is hollow with chambers that include a mixing chamber 8, a settling chamber 9, as well as an inlet passage 10 of the heavy phase, an inlet passage 11 of the light phase, an outlet passage 12 of the heavy phase and an outlet passage 13 of the light phase. The inlet passages 10 and 11 of the heavy phase and the light phase end in the mixing chamber 8, respectively, starting from the second side 3 and the first side 2, and the outlet passages 12 and 13 of the heavy phase and the light phase start from the settling chamber 9 and end, respectively, on the first side 2 and on the second side 3. The openings of the inlet and outlet passages 10 and 12 of the heavy phase on the sides 2 and 3 are aligned in a direction perpendicular to these sides 2 and 3, and the openings of the inlet and outlet passages 11 and 13 of the light phase are also aligned in this direction.

In this way, it is possible to obtain batteries consisting of a plurality of series-connected cascades, each of which contains one of these extractors 60, where single passages of the heavy phase and the light phase are formed, successively passing through all the mixing chambers 8 and settling chambers 9 and following counter-current paths through the extractors 60. Such a battery will be described below. Passage through a plurality of extractors 60 is used to improve the extraction of the dissolved substance.

The outlet passages 12 and 13 of the heavy phase and the light phase mainly comprise sections parallel to the sides 2 and 3, respectively, called the outlet channel 14 of the heavy phase and the inlet channel 15 of the light phase; The outlet channel 14 of the heavy phase is adjacent to the first side 2 and continues from the inlet well 16 to the outlet well 17, the former of which is adjacent to the settling chamber 9 and to the front side 4 at a distance slightly greater than half the length of the extractor between the front side 4 and the rear side 5. The outlet channel 15 of the light phase is in fluid communication with the settling chamber 9 by means of the overflow 18 of the light phase and continues to the outlet well 19, adjacent to the second side 3 at approximately half the mentioned length of the extractor 60. The mixing chamber 8, the settling chamber 9 and the largest section of the outlet channels 12 and 13, of which, in particular, the outlet channels 14 and 15, open from the extractor 60, passing to their upper side 7. Such an arrangement makes it possible to reduce the influence of the capillary phenomenon and the capture of air bubbles, which can block the outlet flow even at very low flow rates.

The front side 4 is partially transparent and is provided with an inspection hole 20 (shown in Fig. 2, 6 and 9) which allows observing, in each extractor 60 of the battery, the sequence of sedimentation and pumping of the phases: indeed, the inspection hole 20 partially delimits the settling chamber 9 and the inlet of the inlet passage 13 of the light phase. Alternatively, the entire block 1 can be transparent.

The outlet channels of the heavy phase and the light phase 14 and 15 are provided with intermediate wells 21 and 22, which can receive spectrophotometric probes for the operational analysis of the phase composition. The movement of the light phase flow is shown by arrows 53.

In Fig. 2 and 3, the outlet passage 12 of the heavy phase is additionally shown. The inlet well 16 includes a lower opening 23, which communicates via a fluid medium with the bottom of the settling chamber 9: the heavy phase accumulates in the inlet well 16 during the execution of the method and ends by reaching the overflow 24 of the heavy phase, which is a separate part, shown in detail in Fig. 3. The overflow 24 of the heavy phase, as a rule, has a cylindrical shape and contains from top to bottom a gripping holder 25, a thread 26 and a socket 27. The holder 25 projects on the extractor above the upper side 7, the thread 26 enters the threaded part corresponding to the upper part of the inlet well 16, and the socket 27 continues in the latter with a gap, with the exception of its lower section, which is provided with a sealing ring 28, contacting the inlet well 16 above the lower opening 23 and under the connection with the outlet channel 14 of the heavy phase.

The upper portion of the seat 27, above the seal 28, is provided with triangular cutouts 29 distributed along its periphery and limited by the lower saw-toothed edge 30 in such a way that each of the triangular cutouts 29 has a lower end 31 forming an acute angle. The lower ends 31 continue in front of the connection with the outlet channel 14 of the heavy phase, and the heavy phase is discharged into this channel when it reaches the level of the triangular cutouts 29. It can then flow into the outlet channel 14 of the heavy phase before reaching the outlet opening 17 and exiting the extractor 60. The movement of the flow of the heavy phase is shown by arrows 32.

The design of the extractor 60 with a single hollow block 1 allows adding various equipment to it by installing it through the upper side 7, by screwing, for example, with an overflow 24 of the heavy phase, or by simple insertion by vertical movement, for example, equipment that will be described below. Adjustments and manipulations with extractors 60, as well as their assembly into batteries are significantly simplified and can be performed using remote control devices or through glove boxes.

In Fig. 4 a mixing chamber 33 is shown, which is immersed in the mixing chamber 8 with a narrow gap. This is a hollow part of approximately cylindrical shape, open upwards and provided on one side with an upper recess 34, the lower edge of which is a mixing weir 35, with a lower opening 36 at the bottom and a vertical pin 37 rising vertically at the top on its upper side. When the mixing chamber 33 is installed, the upper groove 34 and the mixing weir 35 continue in front of the upper section of the settling chamber 9 and form a level above which the mixture present in the chamber 33 can flow into the settling chamber 9. The mixing weir 35 has a sawtooth or toothed shape, and its upper edge, through which the mixture flows to the settling chamber, has the shape of a broken line, forming alternately small protruding and deepening reliefs. Thus, the height of this upper edge can vary. In addition, the recessed reliefs preferably taper downwards, which is verified if the reliefs are separated by sloping sides. In extreme cases, it can be provided that the sloping sides are connected together at right angles to give the lower part of the recessed reliefs a zero width. These arrangements have the effect of regulating the flow even at very low flow rates, despite the capillary forces that can cause a delay in the liquid, temporarily accumulating in the form of drops, or due to a slight hang-up on the weir and splashing of the flow; the design of the mixing weir proposed here, limited by a broken line forming a plurality of reliefs, provides a small or minimum flow width for a liquid with a low flow rate, if it is barely at the level of the weir, which reduces the effect of capillary forces and tends to maintain a constant flow.

A similar arrangement with an overflow edge in the form of a broken line characterizes the overflow 24 of the heavy phase for the same purpose, and also characterizes the overflow 18 of the light phase, which will be described in detail below. In addition, the open design of the outlet channels 14 and 15 also pursues the same purpose of reducing the influence of capillary forces and regulating flows.

In Fig. 5 there is shown a support bearing block 38 supporting a stirring device 39 with vertical blades, which can be placed on the upper edge 40 of the mixing chamber 33 in a fixed angular position thanks to a vertical pin 37; and a motor 41, which can be placed on the upper edge of the support bearing block 38 so as to rotate the stirring device 39 when it is turned on, whereby the stirring device 39 penetrates into the mixing chamber 33 at this moment to mix the liquid phases and create an emulsion.

Two other pieces of equipment can also be installed in the extractor by insertion from the upper side 7. The first enters the settling chamber 9, is designated by the general pos. 42 (Fig. 6), and can comprise a lowering plate 43, as well as two coalescent screens 44 and 45, each of which is connected to the upper plate 46. In the state shown, the lowering plate 43 is located vertically and adjoins the mixing chamber 8; its function is to force the mixture to enter the settling chamber 9 through the middle. The coalescent meshes 44 and 45, as their name indicates, are intended to promote the fusion of the phase that is in the emulsion into the other phase, thus ensuring a clear separation of the heavy phase and the light phase and their superposition in the settling chamber 9. One of the coalescent meshes 44 can be hydrophobic and the other hydrophilic, in order to promote the coalescence of the organic phase (in general, the light phase) as well as the aqueous phase (in general, the heavy phase) according to the category of the emulsion. Alternatively, two coalescent meshes can be used for coalescence of the phases in the emulsions that are difficult to recover. The coalescent meshes 44 and 45 are also arranged vertically, parallel to the lowering plate 43 and continue towards the middle of the settling chamber 9 in any order. An exhaust tab 47, rising upward and attached to the upper plate 46, is added to allow handling of the equipment.

Another removable piece of equipment is shown in Fig. 7 and consists of a recirculation pump 48, which is used in some processes and is used to partially return one of the phases, in this case the heavy phase, to the mixing chamber 8. The recirculation pump 48 is mounted on a horizontal console 49, attached to the rear side 5 of the block 1 and projecting backwards (however, for clarity, the recirculation pump 48 is shown raised above the console 49). It is provided with a vertical suction pipe 50 and a vertical discharge pipe 51, capable of penetrating, respectively, into the discharge well 17 of the heavy phase for sucking in the flow therein and into the vertical recirculation well 52, made in the block 1 next to the mixing chamber 8. The recirculation well 52, like the channels 10 and 11 for introducing the heavy phase and the light phase, leads into the mixing chamber 8, and the liquids that follow them then enter the mixing chamber 34 through the lower opening 36.

Fig. 8 shows that the outlet channel of the light phase 15 is at a different level compared to the overflow 18 of the light phase. The overflow of the light phase in this case is carried out by means of the edge of the overflow, crossed by the flow of liquid and formed by a broken line, forming horizontal lower sections and inclined sections and, thus, protruding flat upper reliefs alternating with triangular depressions narrowing downwards.

Another aspect of the invention will now be described using the last figures 9-13 of the present description, which show the assembly of extractors 60 described so far to form an extraction battery.

Such a battery is shown in Fig. 9. The extractors 60 are arranged side by side on a flat support rail 61, the ends of which are mounted on supports 62. It should be noted that the inspection openings 20 are aligned on one side of the battery in order to ensure a quick general study of the processes carried out in the battery. Such an arrangement is due, in particular, to the arrangement of mutually aligned mixing chambers 8 and mutually aligned settling chambers 9, parallel to the support rail, and the channels of the heavy phase 14 and the light phase 15, rather long and parallel to the sides 2 and 3, through which the assembly of the extractors 60 takes place, so that the inlet and outlet channels of each of the phases exit the block 1 in positions aligned in a direction perpendicular to the sides 2 and 3, and parallel to the support rail 61; while the usual arrangement of battery extractors is transverse, with mixing and settling chambers alternating in two parallel lines, which makes it possible to use outlet channels for the liquid phase that are shorter and almost perpendicular to the sides (like the inlet channels 10 and 11 in this document), but therefore with the disadvantage that complete control of the settling of the cascades is no longer possible.

In Fig. 10 it is shown that the support rail 61 can consist of any number of individual plates 63 assembled together by screwing and fixing the shape at the place of their connection 64. The ends of the support rail have opposite stops 65 and 66, one (66) of which can at least contain a pin for tightening the battery, in order to avoid separation of its elements and to ensure sealing of the channels 10-13. In addition to the extractors 60, the battery contains at its ends and, therefore, in contact with the stoppers 65 and 66, two end modules 67 and 68, which also have the shape of a parallelepiped and contain input and output connections, generally designated pos. 69, of the phases leading to the rest of their circulation circuits. The end modules 67 and 68 communicate via a fluid medium with the inlet and outlet channels of the adjacent extractor 60. The battery coupling is also provided by sections of sliders and reliefs 70 (shown in Fig. 2) for moving the extractors 60 on the support rail 61, but without the possibility of lifting them. A similar system is provided on the end modules 67 and 68. In addition to this, the battery is equipped (Fig. 11) with separating plates 71 between the extractors 60, which are provided with two support seals 74 and 75 with holes 72 and 73. The separating plates 71 are provided with a lower groove 76, which is adjusted on the support guide 61 and allows them to be held in the desired position on it. When tightening, the inlet and outlet passages 10-13 of the extractors 60 continue with each other with openings 72 and 73 between them and seals 74 and 75 around them, which ensures the tightness of the fluid circuits.

Finally, we will turn our attention to the possibility of regulating the temperature of the liquid phases. This can be achieved by circulating the coolant through the extractors 60. One embodiment, shown in Fig. 12, can comprise, in a block 77 slightly larger in volume than block 1 described above, channels for feeding coolant comprising an inlet passage 78 for coolant located near the rear side 5, an outlet passage 79 for coolant, also located near the rear side 5 and connecting the inlet and outlet passages 78 and 79, an internal channel successively comprising a first descending section 80, a longitudinal section 81 located near the lower side 6 and directed towards the front side 4, a second longitudinal section 82 which directs the liquid back towards the rear side 5, parallel to and in the opposite direction to the first longitudinal section 81, and an ascending section 83. The longitudinal sections 81 and 82 are separated by a partition 84. They pass the coolant below the mixing chambers 8 and settling chambers 9.

Another possibility is mentioned with respect to Fig. 13. The temperature regulation can be carried out by each plate 63 of the support rail 61, which is provided with a cavity 85, opening, for example, on its lower side, and which is filled with a flat heating mat 86, provided with connections to the outer side 87. A cover 88 is screwed on in order to close the cavity 85 and hold the heating mat 86 in it.

Claims (20)

1. A liquid-liquid extractor (60) comprising a hollow block (1) with a mixing chamber (8) and a settling chamber (9) which communicate, inlet passages (10, 11) of two liquid phases leading into the mixing chamber, and outlet passages (12, 13) of two liquid phases leading into the settling chamber, characterised in that the outlet passages are provided with overflows (18, 24) near the settling chamber (9) and each of them is made with an edge of the overflow of liquid phases which has an uneven height in the form of a broken line limiting a plurality of reliefs. 2. A liquid-liquid extractor according to claim 1, characterized in that the edge (30) of the overflow of at least one of the overflows (24) consists of a plurality of depressions tapering downwards to zero width and formed by two inclined edges. 3. A liquid-liquid extractor according to claim 1, characterized in that the edge of the overflow of at least one of the overflows has a zigzag shape and consists of identical and evenly distributed reliefs. 4. A liquid-liquid extractor according to any one of claims 1 to 3, characterized in that one of the overflows (18) is located at the junction between the settling chamber and the outlet passage of one of the said liquid phases, known as the light phase. 5. A liquid-liquid extractor according to any one of claims 1 to 4, characterized in that the other of the overflows (24) is located in the inlet well (16) of the outlet passage (14) of the other liquid phase, known as the heavy phase, at an adjustable height in the inlet well. 6. A liquid-liquid extractor according to any one of claims 1 to 5, characterized in that the outlet passages essentially consist of channels (14, 15) open on the upper side (1) of the block. 7. A liquid-liquid extractor according to claim 6, characterized in that the channels (14, 15) extend parallel to the side walls (2, 3) of the block (1), where the outlet passages are open along at least half the length of the block, measured parallel to the side walls (2, 3), the inlet and outlet passages of the heavy phase exit the block (1) at locations aligned along a first line perpendicular to the side walls, and the inlet and outlet passages of the light phase exit the block at locations aligned along a second line perpendicular to the side walls. 8. A liquid-liquid extractor according to claim 7, characterized in that each channel (14, 15) has a width equal to at least one third of the width, measured perpendicular to the sides (2, 3), of the settling chamber (9). 9. A liquid-liquid extractor according to any of the preceding claims, characterized in that it comprises a third overflow (38) between the mixing chamber (8) and the settling chamber (9), provided with an overflow edge for liquid phases having an uneven height in the form of a broken line limiting many reliefs. 10. A liquid-liquid extractor according to any of the preceding claims, characterized in that it comprises a settling equipment (42) that can be immersed in the settling chamber by moving and comprising a descending plate (43) immersed in the settling chamber (9) and continuous up to a protective distance from the bottom of the settling chamber. 11. A liquid-liquid extractor according to claim 10, characterized in that the settling equipment (42) contains a coalescent mesh (44, 45) immersed in a settling chamber (9). 12. A liquid-liquid extractor according to claim 11, characterized in that the equipment contains a second coalescent mesh (45), wherein the coalescent meshes have opposite wettability properties with respect to one of the liquid phases. 13. A liquid-liquid extractor according to any one of claims 1 to 12, characterized in that the unit includes a console (49), on the upper side of which a recirculation pump (48) can be installed, wherein the recirculation pump is equipped with vertical suction and discharge tubes (50, 51) immersed respectively in the outlet passage (12) of one of the liquid phases and in a recirculation well (52) recessed into the unit (1) and communicating with the mixing chamber (8). 14. A battery for liquid-liquid extraction, comprising at least one liquid-liquid extractor according to any one of claims 1 to 13, characterized in that at least one extractor (60) and end modules (67, 68) are aligned and secured to a support, wherein the end modules contain connections to the circuits of counter-current liquid phases in the battery, wherein the inlets and outlets of each of the phases are located on the continuation between the extractors. 15. A battery for liquid-liquid extraction according to claim 14, characterized in that it contains separator plates (71) pressed against the extractors, and support seals (74, 75) surrounding the inlet and outlet openings for the liquid phases. 16. A battery for liquid-liquid extraction according to any one of claims 14 or 15, characterized in that the liquid-liquid extractors, end modules and, if necessary, separator plates are connected to each other on a rail, forming a support with the possibility of sliding along the rail. 17. A battery for liquid-liquid extraction according to any of paragraphs 14-16, characterized in that the support contains a heating mat. 18. A battery for liquid-liquid extraction according to any one of paragraphs 14-16, characterized in that it contains a device for circulating a coolant passing through the block of at least one liquid-liquid extractor. 19. A battery for liquid-liquid extraction according to any one of claims 14-18, in which the extractors are made according to claim 7, characterized in that all extractors are placed in such a way that their homologous components are aligned along lines parallel to the rail. 20. A battery for liquid-liquid extraction according to claim 19, characterized in that the extractors (60) are transparent in at least one section (20) that opens into the settling chambers (9).