The present invention relates to a solvent extraction settler arrangement adapted for hydrometallurgical liquid-liquid extraction processes.

BACKGROUND OF THE INVENTION

As disclosed in e.g. publications WO 97/40899, WO 97/40900 and WO 97/41938 a solvent extraction settler arrangement is known which is adapted for hydrometal ^¬ lurgical liquid-liquid extraction processes and which typically comprises a mixing unit for preparing a dis ^¬ persion from mutually immiscible solutions. A settler is arranged to separate solution phases from a disper ^¬ sion fed from the feed end while the dispersion flows towards the discharge end of the settler. A feeding device is located at the feed end for feeding the dis ^¬ persion prepared by the mixing unit to the settler.

In the known technology the dispersion is fed into the settler at a single feed point located at the center of the feed end or in the vicinity thereof via an up ^¬ take channel. The problem is that the single feed point feeding dispersion requires a distribution fence to be arranged near the feed end of the settler to distribute the flow of the dispersion to the whole width of the settler. OBJECT OF THE INVENTION

The object of the invention is to eliminate the disad ^¬ vantages mentioned above.

In particular, it is the object of the invention to provide a feeding device which eliminates the need for the distribution fence and the uptake channel and still is able to provide a uniform mass flow distribu ^¬ tion of the dispersion to the settler.

SUMMARY OF THE INVENTION

According to an aspect of the invention, the present invention provides a solvent extraction settler arrangement adapted for hydrometallurgical liquid-liquid extraction processes. The settler arrangement compris ^¬ es a mixing unit for preparing a dispersion from mutu- ally immiscible solutions, a settler having a feed end and a discharge end, said settler being arranged to separate solution phases from a dispersion fed from the feed end while the dispersion flows towards the discharge end, and a feeding device located at the feed end for feeding the dispersion prepared by the mixing unit to the settler.

In accordance with the invention, the feeding device comprises an elongated feed launder having a first end for receiving the dispersion from the mixing unit, and a second end. The feed launder extends alongside the feed end of the settler. The feed launder has a form of a conical tube with a cross-section converging towards the second end and an inclined bottom ascending towards the second end. A plurality of feed pipes are arranged along the length of the feed launder at a distance from each other, each feed pipe having a third end opening to the inner space of the feed laun ^¬ der at the bottom to receive the dispersion from the feed launder and a fourth end opening to the settler to conduct the dispersion to the settler.

The advantage of the invention is that, when used in connection with a large settler tank, the multiple point feed of the dispersion provided by a plurality of feed pipes ensures a uniform mass flow distribution of the dispersion to multiple feed points. When used in connection with a settler consisting of mutually separate settler sections, the advantage is that dis ^¬ persion can be fed uniformly via a feed pipe to each settler section. The dispersion flow distributes uni- formly to the whole width of the tank so that a single uptake channel and distribution fence are no more needed. The shape of the feed launder also allows min ^¬ imizing the generation of small droplets. The conical shape of the feed launder also ensures that the flow rate of the dispersion in the feed launder is constant so that the residence time distribution in the launder is as uniform as possible, so that no standing zones where the separation of the phases could occur are formed. The conical shape and the inclined bottom of the feed launder ensure that the heavier solution phase, which may separate from the dispersion already in the feed launder, flows back to the first end of the feed launder and further to the mixing unit. The feed launder being a tube has an advantage that it can be made air-tight. The air-tight construction elimi ^¬ nates oxidation of the reagent, thus lowering make-up costs. The air-tight construction also decreases evap ^¬ oration of the reagent, thus also lowering make-up costs .

In one embodiment of the settler arrangement, the feed launder is a hollow body made of a fibre-reinforced plastic composite and manufactured by filament winding technology. Manufacturing of the feed launder made of a fibre-reinforced plastic composite by filament wind ^¬ ing gives the lauder a required strength. Automated filament winding of the launder enables lower fabrica ^¬ tion costs compared to any other manufacturing method, such as hand laminating.

In one embodiment of the settler arrangement, the feed launder is a hollow body made of steel. In one embodiment of the settler arrangement, the ar ^¬ rangement comprises a level control valve connected to the third end of each feed pipe inside the feed laun ^¬ der .

In one embodiment of the settler arrangement, the lev ^¬ el control valve comprises an extendable and collapsi- ble tube member, such as a bellows tube, having a low ^¬ er end connected to the third end of the feed pipe, and an upper end. An overflow lip is attached at the upper end of the tube member. An actuator is connected to the overflow lip for vertical adjustment of the height position of the overflow lip.

In one embodiment of the settler arrangement, the set ^¬ tler consists of one tank having a single uniform flow space. All feed pipes open to said single flow space.

In one embodiment of the settler arrangement, the set ^¬ tler consists of a plurality of mutually separated elongated parallel settler sections each extending from the feed end to the discharge end and forming a plurality of parallel flow spaces. At least one feed pipe is connected to each settler section. Parallel settler sections allow a plug flow of the dispersion and solutions through the settler section. An advantage with the parallel settler section design is that, if needed for maintenance, an individual settler section can be shut off from the process simply by interrupting the dispersion flow to the settler section by lifting the overflow lip in connection with the respective feed pipe above the level of the dispersion in the feed launder. BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are included to pro ^¬ vide a further understanding of the invention and constitute a part of this specification, illustrate em- bodiments of the invention and together with the de ^¬ scription help to explain the principles of the inven ^¬ tion. In the drawings:

Figure 1 shows a plan view of a settler arrangement according to a first embodiment of the invention,

Figure 2 shows a section II-II from Figure 1,

Figure 3 shows a plan view of a settler arrangement according to a second embodiment of the invention,

Figure 4 shows a section IV-IV from Figure 1,

Figure 5 shows an enlarged detail A from Figure 2,

Figures 6 and 7 show a level control valve in two po ^¬ sitions .

DETAILED DESCRIPTION OF THE INVENTION

Figures 1 and 3 show solvent extraction settler arrangements which are adapted for hydrometallurgical liquid-liquid extraction processes.

The settler arrangement comprises a mixing unit 1 for preparing a dispersion from mutually immiscible solu ^¬ tions. The mixing unit 1 includes, in this case, a pumping unit 19 and two mixers 20. A settler 2 is ar ^¬ ranged to separate solution phases from a dispersion which is fed from the feed end 3 while the dispersion flows towards the discharge end 4. A feeding device 5 is arranged at the feed end 3 for feeding the disper- sion prepared by the mixing unit 1 to the settler 2. Discharge launders 21 and 22 are arranged at the dis ^¬ charge end 4 to receive and discharge the separated solutions .

The feeding device 5 comprises an elongated feed laun ^¬ der 6. From the mixing unit 1 the dispersion is conducted to a first end 7 of the feed launder 6. The feed launder 6 extends alongside the feed end 3 of the settler 2. The feed launder 5 has a form of a conical tube with a cross-section converging towards the second end 8 of the feed launder 6. The feed launder 6 has a form of a conical tube which has substantially a form of a square pyramid with cambered edges. The feed launder 6 may be made of steel or fibre- reinforced plastic composite. Preferably the feed launder 6 is a hollow body made of a fibre-reinforced plastic composite and manufactured by filament winding technology. As can be seen in Figure 5, the cross- section of the feed launder is substantially rectangu ^¬ lar with cambered corners. Such a form allows it to be easily detached from the mandrel on which it is wound. Further, referring to Figures 4 and 5, the feed launder also has an inclined bottom 9 which linearly as- cends from the first end 7 to the second end 8 of the feed launder 6.

A plurality of feed pipes 10 are arranged along the length of the feed launder 6 at a distance from each other. Each feed pipe 10 has a third end 11 which opens to the inner space of the feed launder 6 at the bottom 9 to receive the dispersion from the feed launder 6. Each feed pipe 10 has a fourth end 12 which opens to the settler 2 to conduct the dispersion to the settler 2. In the embodiment shown in Figure 1 the settler 2 con ^¬ sists of one large tank which has a single uniform flow space which extends widthwise to the whole area of the tank and lengthwise from the feed end 3 to the discharge end 4. In this case, all the feed pipes 10 open to said single uniform flow space.

In the embodiment shown in Figure 3 the settler 2 con ^¬ sists of a plurality of widthwise mutually separated elongated parallel settler sections 2 ' each extending from the feed end 3 to the discharge end 4 and forming a plurality of parallel flow spaces. At least one feed pipe 10 is arranged between the feed launder 6 and each settler section 2 ' to feed dispersion from the feed launder 6 to said settler section.

As can be seen in Figures 5 to 7, a level control valve 13 is connected to the third end 11 of each feed pipe 10 inside the feed launder 6. The level control valve 13 comprises an extendable and collapsible tube member 14, such as a bellows tube. The tube member 14 has its lower end 15 connected to the third end 11 of the feed pipe 10. An overflow lip 17 is attached at the upper end of the tube member 14. An actuator 18 is connected to the overflow lip 17 for vertical adjust ^¬ ment of the height position of the overflow lip.

Figure 6 shows the level control valve 13 in a posi ^¬ tion in which the overflow lip 17 is at a level below the surface level of the dispersion in the feed laun ^¬ der 6 whereby the dispersion is allowed to flow to the feed pipe 10.

Figure 7 shows that the level control valve 13 is lifted to a position in which the overflow lip 17 is above the surface level of the dispersion in the feed launder 6 whereby the flow of the dispersion from the feed launder 6 to the feed pipe 10 is interrupted and no dispersion flows to the settler 2 or settler section 2. Safety can be ensured by attaching also a shut-off cap 23 tightly to the fourth end 12 of the feed pipe 10 to prevent any leakage of dispersion from the feed pipe 10.

It is obvious to a person skilled in the art that with the advancement of technology, the basic idea of the invention may be implemented in various ways. The in ^¬ vention and its embodiments are thus not limited to the examples described above; instead, they may vary within the scope of the claims.