The present invention relates to a method of manufac- turing a launder to be used in co-operation with a solvent extraction settler adapted for hydrometallur- gical liquid-liquid extraction processes. Further, the invention relates to a launder. BACKGROUND OF THE INVENTION

In a typical mixer-settler, in the first step, the aqueous and organic phases are pumped into a mixer or mixers in order to achieve a uniform liquid-liquid dispersion and a small droplet size. In the VSF® tech- nology (stands for Vertical Smooth Flow) developed by the applicant this first step is performed in a pump- mixer called Dispersion Overflow Pump (DOP®) (disclosed e.g. in document US 5,662,871) and in a set of two SPIROK® helical mixers (disclosed in e.g. document US 5,185,081). After mixing, the dispersion is fed into a settler. The settler is typically a large tank which is square in plan and its square area is about several hundred square meters. Dispersion is fed into the settler at the front end of the settler. A dis- tributor fence is arranged at the feed end of the set ^¬ tler to distribute the flow of the dispersion to the whole width of the settler. In the settler, the dis ^¬ persion moves towards the settler back wall and, at the same time, the phases separate by gravity into two layers with a dispersion band remaining between them. Typically, separation fences are arranged in the set ^¬ tler tank to enhance coalescence of the dispersion. In the VSF® technology the separation fences are so- called DDG® fences (Dispersion Depletor Gate) (dis- closed e.g. in document US 7,517,461). At the rear end of the settler, an adjustable weir and launders are used to control the vertical position of the phase interface and. to collect and discharge both phases, respectively. Arrangements of settlers and launders are disclosed also e.g. in documents WO 97/40899, WO 97/40900, WO 97/40901, WO 2009/063128 Al and WO 2010/097516 Al ,

The known launder typically comprises two launders ar- ranged in parallel side-by-side. One of the launders is an overflow launder arranged to receive the lighter solution (e.g. organic phase) as an overflow from the settler and the other launder is an underflow launder arranged to receive the heavier solution (e.g. aqueous solution) as an underflow from the settler. The launder arrangement is made of a fiber-reinforced plastic composite by hand laminating, or by filament winding as described in WO 2010/097516 Al . WO 2009/063128 discloses that the whole launder is in.an.u- factured at a place of manufacture, such as in an en ^¬ gineering workshop, into a self-supporting subassembly which is transferred as a uniform entity to the site of installation where it is installed on the bottom of the settler.

So far, a solvent extraction plant including the launder has been project specified. In each case the lay ^¬ out of the plant and the equipment have been unique. There has not been a possibility for the productiza- tion of launders . The present launders have nonstand ^¬ ard transport dimensions requiring oversize transport which is expensive. Launders known in the prior art also require most of the construction work to be done at the site. This causes problems because of the cru- cial influence of local factors. It may be difficult to get local suppliers. It has been difficult to con ^¬ trol the quality of the site work by local suppliers. Further, the maintenance of the present launders re ^¬ quires a long downtime of the whole solvent extraction settler with which the launder requiring maintenance is connected.

OBJECT OF THE INVENTION

The object of the invention is to eliminate the disad ^¬ vantages mentioned above. In particular, it is an object of the present inven ^¬ tion to provide a method of manufacturing a modular launder and a modular launder in which the individual, in workshop pre-fabricated, - container compatible launder element modules provide shipping container standard compatible transportability, stacking capa ^¬ bility, modularity and scalability of the launder de ^¬ sign .

It is also an object of the present invention to pro- vide a method for manufacturing a modular launder and a modular launder which enable that the construction work at the installation site may be kept at a mini ^¬ mum, resulting in low installation costs and good quality .

Further, it is an object of the present invention to provide a launder which can be easily disassembled and re-located . Further, it is an object of the present invention to provide a launder which can be first delivered as a small-scale test or pilot launder for a pilot solvent extraction plant and later expanded into a launder for a full size solvent extraction plant.

Further, it is an object of the present invention to provide a launder which can be easily maintained. SUMMARY OF THE INVENTION

According to a first aspect, the present invention provides a method of manufacturing a launder to be used in co-operation with a solvent extraction settler adapted for hydrometallurgical liquid-liquid extrac ^¬ tion processes, in which method the launder is in ^¬ stalled at the discharge end of the settler. The meth- od comprises the steps of manufacturing at the site of manufacture, such as in an engineering workshop, a plurality of self-supporting launder element modules each having exterior dimensions, strength and handling and securing means conforming to shipping container standards; transporting the launder element modules to the site of installation as normal freight by transport equipment, such as trucks, trailers and con ^¬ tainer ships, capable of handling and transporting shipping container standard compatible units; and as- sembling at the site of installation the launder element modules into a module group forming a complete launder .

According to a second aspect, the present invention provides a launder to be used in co-operation with a solvent extraction settler adapted for hydrometallurgical liquid-liquid extraction processes. The launder comprises a launder module group consisting of self- supporting launder element modules each having exteri- or dimensions, strength and handling and securing means conforming to shipping container standards to enable shipping container standard compatible trans ^¬ portability. The advantage of the invention is that the launder el ^¬ ement modules can be manufactured in the factory envi ^¬ ronment, which is different from the installation site environment, which provides good quality. The launder modules being shipping container standard compatible units provides all benefits of the normal shipping containers: they can be handled with normal transport equipment and there is no need for oversize transport equipment. The launder element modules having dimen ^¬ sions, strength and handling and securing means conforming to -shipping container standards thus have all the benefits of the transportability of normal ship- ping containers. The launder element modules can be transported on land by trucks and trailers and with container ships by sea. In ports they can be handled with normal container handling equipment. A complete launder, which may comprise a plurality of launder el- ement modules, can be shipped in one delivery. The modular structure enables flexible capacity since more capacity can be built while the solvent extraction plant is running by increasing the number of modules. The launder can easily be re-located and recycled by disassembling the modules at one site and re ^¬ assembling them into a launder located at another site .

In an embodiment of the launder, the launder element module conforms to ISO shipping container standards to enable ISO shipping container standard compatible transportability.

In an embodiment of the launder, the launder is ar- ranged to feed dispersion to a solvent extraction set ^¬ tler. In an embodiment of the launder, the launder is arranged to receive and discharge solution phases sep ^¬ arated in the solvent extraction settler. Preferably both feeding and discharging functions are combined into a common launder element module, discharging functions serving one settler while the feeding func ^¬ tion is serving another settler. In an embodiment of the launder, the launder element module comprises a self-supporting framework structure having a shape of a rectangular parallelepiped with exterior dimensions and corner fittings conforming to shipping container standards, said corner fittings be ^¬ ing attached to each corner of the framework structure. Further, the launder element module comprises a shell, said shell being supported inside the framework structure and forming at least a part of a flow path for the solutions flowing in the launder.

In an embodiment of the launder, the launder element module conforms to standard ISO 668 Series 1 "Freight containers - Classification, dimensions and ratings"; and the corner fittings conform to standard ISO 1161 Series 1 "Freight containers - Corner fittings - spec ^¬ ification". The strength of the modules conforms to standard ISO 1496/1, Annex A. The strength of the cor- ner fittings conforms to standard ISO 1161.

In an embodiment of the launder, the shell is a tubu ^¬ lar hollow body made of a fibre-reinforced plastic composite. Preferably, the shell is manufactured by filament winding technology. The shells connected to each other form a gas-tight tubular flow path for the dispersion and separated solutions. The gas-tight sealed construction eliminates oxidation of the rea ^¬ gent by air, thus lowering make-up costs. The gas- tight construction also decreases evaporation of the reagent, decreasing the release of Volatile Organic Compounds (VOC) to the environment. Manufacturing of the shell made of a fibre-reinforced plastic composite by filament winding gives the shell a required strength. The inner surface of the shell, which in op ^¬ eration comes to contact with the dispersion and sol ^¬ vents, is inherently smooth because it is formed against a mandrel which has a smooth surface. The smooth surface contacting the solvent flow minimizes local turbulences. The smooth surface also minimizes electrostatic charging and thereby reduces the risk for fires due to igniting of volatile organic com ^¬ pounds in the inner atmosphere of the shell caused by electrostatic discharge. Electrostatic charging can also be reduced by adding carbon staple fibers to the plastic composite. Automated filament winding of the shell enables lower fabrication costs compared to any other manufacturing method, such as hand laminating.

In an embodiment of the launder, the module group com ^¬ prises two or more launder element modules arranged in parallel and side-by-side with each other. The side- by-side arrangement of the launder element modules is advantageous because thereby the launder can be made compact and the foundation can be implemented by a plurality of pillars supporting each corner of the launder element modules. One pillar may support one to four corners of the modules.

In an embodiment of the launder, the launder element module comprises a first shell to receive and conduct a light solution phase, and a second shell to receive and conduct a heavy solution phase.

In an embodiment of the launder, the launder element module comprises a third shell adapted to feed disper- sion to a next settler.

In an embodiment of the launder, the launder module group comprises a plurality of launder element mod ^¬ ules. The first shells of the adjacently neighboring launder modules are abutting and connected to each other to form a first flow channel, and the second shells of the adjacently neighboring launder modules are abutting and connected to each other to form a second flow channel.

In an embodiment of the launder, the first shells are conical so that the sequentially connected first shells of the launder element modules in the launder module group together form a conical first flow chan ^¬ nel . In an embodiment of the launder, the second shells are conical so that the sequentially connected second shells of the launder element modules in the launder module group together form a conical second flow chan ^¬ nel .

In an embodiment of the launder, the third shells are conical so that the sequentially connected third shells of the launder element modules in the launder module group together form a conical third flow chan- nel.

The first, second and third flow channels are all tub ^¬ ular closed compartments which have many advantages. As an essentially closed structure the inner atmos- phere of the launders can be sealed from the outer at ^¬ mosphere so that mist emissions cannot escape from the atmosphere in the interior of the launders to the out ^¬ er atmosphere to contaminate the air and worsen the working conditions. Likewise, the surrounding air and e.g. insects and birds cannot enter the launders. In addition, when the lighter solution is an organic phase, the oxidation degree of the organic phase de ^¬ creases whereby solution costs are reduced. Further, in operation, the atmosphere of the launder above the liquid surface is flammable because it contains vola ^¬ tile organic compounds which are released from the hy ^¬ drocarbon based solvents. The gas-tight closed com- partments of the tubular shells provide fire protec ^¬ tion against accidental fires.

The conical first and second flow channels which form discharge channels for the lighter solution (normally organic) and the heavier solution (aqueous solution) have many inlets along their length. The cross section of the conical first and second flow channels increas ^¬ es and the bottom is inclined downwards towards the first and second discharge boxes. After each inlet the flow rate in the first and second flow channels in ^¬ creases. In a conical launder the flow rate remains the same for the whole length of the launder and no return eddies and standing flows are created. Thereby crud accumulation is avoided if the solutions contain solids .

In an embodiment of the launder, the launder element module comprises a first inlet pipe having a first end opening to the inner space of the first shell and a second end opening to the settler, the second end be ^¬ ing adapted to receive the light solution phase as an overflow from the settler. In an embodiment of the launder, the launder element module comprises a second inlet pipe having a third end opening to the inner space of the second shell at a bottom of the second shell, and a fourth end opening to the settler, the fourth end being adapted to re- ceive the heavy solution phase as an underflow from the settler.

In an embodiment of the launder, the overflow height position of the third end of the second inlet pipe inside the second shell is adjustable by a first level control valve to adjust the level of the heavier solu ^¬ tion in the settler. In an embodiment of the launder, the first level con ^¬ trol valve comprises an actuator by which the height position of the third end of the second inlet pipe is adjustable.

In an embodiment of the launder, the launder element module comprises a feed outlet pipe having a fifth end opening to the inner space of the third shell via a second level control valve disposed at a bottom of the third shell, and a sixth end adapted to feed a solu ^¬ tion to a settler.

In an embodiment of the launder, the launder module group comprises a box module comprising a first dis ^¬ charge box supported inside a framework structure for receiving and discharging the lighter solution phase from the first flow channel, and a second discharge box supported inside the framework structure for re- ceiving and discharging the heavier solution phase from the second flow channel.

In an embodiment of the launder, the box module com ^¬ prises a feed box supported inside the framework structure for feeding dispersion to the third flow channel .

The conical third channel which forms a feed launder for the dispersion has a cross section which decreases from the end connected to the feed box towards its other end which is distant from the feed box. This has the advantage that the delay time distribution of the dispersion in the feed launder is uniform so that no standing zones, in which the dispersion would sepa- rate, are formed. The bottom of the third flow channel is inclined downwards towards the feed box, whereby the aqueous solution separated from the dispersion in the feed launder flows back to the mixer via the feed box .

In an embodiment of the launder, the framework struc- ture comprises a first end frame comprising: a hori ^¬ zontal first lower beam; a horizontal first upper beam at a distance from the first lower beam; a vertical first corner post which is fixedly connected to a first end of the first lower beam, defining a first corner, the vertical first corner post being fixedly connected to a first end of the first upper beam, de ^¬ fining a second corner; and a vertical second corner post at a distance from the first corner post, the vertical second corner post being fixedly connected to a second end of the first lower beam, defining a third corner, the vertical second corner post being fixedly connected to a second end of the first upper beam, de ^¬ fining a fourth corner. Further, the framework structure comprises a second end frame comprising a hori- zontal second lower beam; a horizontal second upper beam at a distance from the second lower beam; a vertical third corner post which is fixedly connected to a first end of the second lower beam, defining a fifth corner, the vertical third corner post being fixedly connected to a first end of the second upper beam, de ^¬ fining a sixth corner; and a vertical fourth corner post at a distance from the third corner post, the vertical fourth corner post being fixedly connected to a second end of the second lower beam, defining a sev- enth corner, the vertical fourth corner post being fixedly connected to a second end of the second upper beam, defining an eighth corner. Further, the framework structure comprises a first bottom side rail fix ^¬ edly connected to the first end frame at the first corner and to the second end frame at the fifth cor ^¬ ner; a second bottom side rail fixedly connected to the first end frame at the third corner and to the second end frame at the seventh corner; a first top side rail fixedly connected to the first end frame at the second corner and to the second end frame at the sixth corner; a second top side rail fixedly connected to the first end frame at the fourth corner and to the second end frame at the eighth corner; bottom cross members fixedly connected between and to the first and second bottom side rails; top cross members fixedly connected between and to the first and second top side rails; side cross members fixedly connected between and to the bottom side rails and the top side rails. A corner fitting is attached to each of the first cor ^¬ ner, second corner, third corner, fourth corner, fifth corner, sixth corner, seventh corner and eighth cor- ner.

In an embodiment of the launder, the launder comprises a foundation on which the launder module group is supported at a height above the ground level, thereby providing a space for piping and access below the set ^¬ tler .

In an embodiment of the launder, the foundation comprises a plurality of pillars having ISO shipping standard compatible container lashing fittings to which the corner fittings of the launder element mod ^¬ ules can be connected. The installation of the laun ^¬ der on pillars has the advantage that a minimal amount of excavation work is needed. The installation on pil- lars also makes it possible to speed up the installa ^¬ tion and shortens the project lead time. Pillars also allow easy assembly and disassembly of the modules and launders. When more capacity is needed for the laun ^¬ der, it is easy to increase capacity by simply adding more pillars for the installation of more modules. The increasing of capacity can be done with a short interruption of the process. In an embodiment of the launder, the pillar comprises a lower end which is supported on the ground, an upper end, and one or more container lashing fittings at- tached to the upper end of the pillar.

In an embodiment of the launder, the container lashing fitting comprises a stacking cone. In an embodiment of the launder, the container lashing fitting comprises a twist lock.

In an embodiment of the launder, the pillar comprises one to four container lashing fittings depending on the number of corner fittings to be connected onto the pil ^¬ lar .

In an embodiment of the launder, the pillar comprises a plastic tube, a concrete reinforcement arranged inside the plastic tube, cast concrete cast inside the plastic tube, and a metal base plate attached at the upper end of the pillar, to which base plate one or more contain ^¬ er lashing fittings are fixedly connected. 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 embodiments of the invention and together with the de- scription help to explain the principles of the inven ^¬ tion. In the drawings:

Figure 1 is an axonometric schematic view of a solvent extraction settler equipped with a launder according to an embodiment of the present invention, Figure 2 is an axonometric view of the framework structure of the launder element module of Figure 1,

Figure 3 is an axonometric view of detail A of Figure 2,

Figure 4 is an axonometric view of three interconnect ^¬ ed launder modules of Figure 1, Figure 5 is a side view of the launder module of Fig ^¬ ure 4 ,

Figure 6 is an end view of the three interconnected launder modules of Figure 3,

Figure 7 is a plan view of the three interconnected launder modules of Figure 3, seen from above,

Figure 8 is a view of the layout of the foundation of the settler of Figure 1,

Figures 9 to 12 show an axonometric view of four dif ^¬ ferent types of pillars used in the foundation of Fig ^¬ ure 8, the pillars being equipped with stacking cones as container lashing fittings,

Figures 13 and 14 show another embodiment of the pil ^¬ lar equipped with a twist lock as a container lashing fitting, and

Figure 15 shows a schematic longitudinal section of the pillar.

DETAILED DESCRIPTION OF THE INVENTION

Figure 1 shows one embodiment of a solvent extraction settler which is used in hydrometallurgical liquid- liquid extraction processes for separating solutions mixed in a dispersion into different solution phases. The launder 1 is connected to the settler 2. The dis ^¬ persion pump and mixers which are used to prepare the dispersion are not shown in Figure 1. The settler 2, which is not part of this invention, is shown only schematically. The settler 2 may be of a conventional type comprising a large tank built on the site, or it may be modular and composed of a number of pre ^¬ fabricated, ISO shipping container compatible settler element modules transferred and installed at the site into a complete settler as disclosed in another patent application filed in parallel with this application.

The launder 1 may have two functions. It may be ar- ranged to feed dispersion to the settler 2 (see Figure 4) and it may be arranged to receive and discharge the separated solutions obtained from the settler 2.

The launder 1 comprises a launder module group 5 which consists of three self-supporting launder element mod ^¬ ules 3 and a box module 24 arranged in parallel and side-by-side with each other. Each launder element module 3 has exterior dimensions, strength and han ^¬ dling and securing means 4 conforming to ISO shipping container standards to enable ISO compatible trans ^¬ portability. The launder element module 3 comprises a self-supporting framework structure 6 having a shape of a rectangular parallelepiped with exterior dimensions and corner fittings 4 conforming to ISO shipping container standards. The corner fittings 4 are at ^¬ tached to each corner of the framework structure 6. The launder element module 3 conforms to standard ISO 668 Series 1 "Freight containers - Classification, di ^¬ mensions and ratings"; and the corner fittings 4 con- form to standard ISO 1161 Series 1 "Freight containers - Corner fittings - specification". Shells 7, 8, 9 are supported inside the framework structure 6 and format least a part of a flow path for the solutions flowing in the launder. The shells 7, 8, 9 can be made of steel or a fibre-reinforced plastic composite. The shells 7, 8, 9 are tubular hollow bod ^¬ ies which are preferably made of a fibre-reinforced plastic composite and preferably manufactured by fila ^¬ ment winding technology. As shown in Figure 2, the framework structure 6 encompassing the shells 7, 8, 9 may have the following structure. The framework structure 6 comprises a first end frame 28. The first end frame 28 comprises a hori ^¬ zontal first lower beam 29, a horizontal first upper beam 30 at a distance from the first lower beam, a vertical first corner post 31 which is fixedly con ^¬ nected to a first end of the first lower beam 29, de ^¬ fining a first corner 32, the vertical first corner post 31 being fixedly connected to a first end of the first upper beam 30, defining a second corner 33, a vertical second corner post 34 at a distance from the first corner post 31, the vertical second corner post being fixedly connected to a second end of the first lower beam 29, defining a third corner 35, the verti- cal second corner post 34 being fixedly connected to a second end of the first upper beam 30, defining a fourth corner 36. The framework structure 7 comprises a second end frame 37. The second end frame 37 com ^¬ prises a horizontal second lower beam 38, a horizontal second upper beam 39 at a distance from the second lower beam 38, a vertical third corner post 40 which is fixedly connected to a first end of the second low ^¬ er beam 38, defining a fifth corner 41, the vertical third corner post 40 being fixedly connected to a first end of the second upper beam 39, defining a sixth corner 42, and a vertical fourth corner post 43 at a distance from the third corner post 40, the ver- tical fourth corner post being fixedly connected to a second end of the second lower beam 39, defining a seventh corner 44, the vertical fourth corner post being fixedly connected to a second end of the second upper beam 39, defining an eighth corner 45. A first bottom side rail 46 is fixedly connected to the first end frame 28 at the first corner 32 and to the second end frame 37 at the fifth corner 41. A second bottom side rail 47 is fixedly connected to the first end frame 28 at the third corner 35 and to the second end frame 37 at the seventh corner 44. A first top side rail 48 is fixedly connected to the first end frame 28 at the second corner 33 and to the second end frame 37 at the sixth corner 42. A second top side rail 49 is fixedly connected to the first end frame 28 at the fourth corner 36 and to the second end frame 37 at the eighth corner 45. Bottom cross members 50 are fixedly connected between and to the first and second bottom side rails 46, 47. Top cross members 51 are fixedly connected between and to the first and second top side rails 48, 49. Side cross members 52 are fixedly con ^¬ nected between and to the bottom side rails 46, 47 and the top side rails 48, 49. A corner fitting 4 is at ^¬ tached to each of the first corner 32, second corner 33, third corner 35, fourth corner 36, fifth corner 41, sixth corner 42, seventh corner 44 and eighth corner 45.

The framework structure 6 conforms to standard ISO 668 Series 1 "Freight containers - Classification, dimen ^¬ sions and ratings". The framework structure 6 may preferably have an external length of 6.058 m (20 ft) or 2.991 m (10 ft) and a width of 2.438 m (8 ft). Figure 3 shows a corner fitting 4 fixedly connected to a corner of the framework structure 6. The corner fit ^¬ tings 4 conform to standard ISO 1161 Series 1 "Freight containers - Corner fittings - specification". The corner fitting 4 has a connecting hole at each of its three sides. As can be seen in Figures 4 to 7, each launder element module 3 comprises a first shell 7 to receive and con ^¬ duct a light solution phase. Further, the launder ele ^¬ ment module 3 comprises a second shell 8 to receive and conduct a heavy solution phase. Further, the laun- der element module 3 comprises a third shell 9 adapted to feed dispersion to a next settler 2, as is seen in Figure 4.

With reference to Figures 4 and 7, the launder module group 5 of the shown embodiment comprises three laun ^¬ der element modules 3. The first shells 7 of the adja ^¬ cently neighboring launder modules 3 are abutting and connected to each other to form a first flow channel 10. The second shells 8 of the adjacently neighboring launder modules are abutting and connected to each other to form a second flow channel 11. The third shells 9 of the adjacently neighboring launder modules are abutting and connected to each other to form a third flow channel 12. The first shells 7 are conical so that the sequentially connected first shells 7 of the launder element modules 3 in the launder module group 5 together form a conical first flow channel 10. The second shells 8 are conical so that the sequen ^¬ tially connected second shells 8 of the launder ele- ment modules 3 in the launder module group 5 together form a conical second flow channel 11. The third shells 9 are conical so that the sequentially connect ^¬ ed third shells 9 of the launder element modules 3 in the launder module group 5 together form a conical third flow channel 12. As seen in Figure 1 the module group 5 comprises also a box module 24. The box module 24 comprises a self- supporting framework structure 6 having a shape of a rectangular parallelepiped with exterior dimensions and corner fittings 4 conforming to ISO shipping container standards, the corner fittings 4 being attached to each corner of the framework structure 6. A first discharge box 23 is supported inside the framework structure 6 for receiving and discharging the lighter solution phase from the first flow channel 10. The box module 24 also comprises a second discharge box 26 supported inside the framework structure 6 for receiv ^¬ ing and discharging the heavier solution phase from the second flow channel 11. Further, the box module 5 comprises a feed box 27 supported inside the framework structure 6 for feeding dispersion to the third flow channel 12. The framework structure 6 of the box mod ^¬ ule 24 may be similar to that shown and disclosed in connection with Figure 2.

The conical first and second flow channels 10 and 11 which form discharge channels for the lighter solution (normally organic) and the aqueous solution have many inlets along their length. The cross section of the conical first and second flow channels 10, 11 increas ^¬ es and their bottom is inclined downwards towards the first and second discharge boxes 25, 26. In operation, after each inlet, the flow rate in the first and sec ^¬ ond flow channels 10, 11 increases. In a conical laun- der the flow rate remains the same for the whole length of the launder and no return eddies and stand ^¬ ing flows are created. Thereby crud accumulation is avoided if the solutions contain solids. The conical third channel 12 which forms a feed laun ^¬ der for the dispersion has a cross section which decreases from the end connected to the feed box 27 to- wards its other end which is distant from the feed box 27. This has the advantage that the delay time distri ^¬ bution of the dispersion in the feed launder 12 is uniform so that no standing zones, in which the dis- persion would separate, are formed. The bottom of the third flow channel 12 is inclined downwards towards the feed box 27 whereby the aqueous solution separated from the dispersion in the feed launder 12 flows back to the feed box and further to the mixer.

Due to the conical form of the shells 7, 8, 9 which form the flow channels 10, 11, 12, each launder element module 3 is different from the other due to dif ^¬ ferent sizes of the shells 7, 8, 9. However, the sys- tern may be based on e.g. 14 standard elements which can be configured to a flow rate range of 150 to 8000 m ³ /h. The full length conical flow channel 10, 11, 12 may be manufactured as one piece on a mold or mandrel, and thereafter the flow channel can be cut into sepa- rate parts having lengths which fit inside the frame ^¬ work structure 6, and the parts are then installed in ^¬ side the framework structures 6 of the launder element modules 3. The interconnection of the shells can be made by normal means and methods of connecting plastic tubes, such as by using connecting sleeves and/or by gluing the abutting ends together.

Referring to Figures 4 and 5, the launder element mod ^¬ ule 3 comprises a first inlet pipe 12 having a first end 13 opening to the inner space of the first shell 7 and a second end 14 opening to the settler 2 on the right hand side of Figure 4. The second end 14 is adapted to receive the light solution phase as an overflow from the settler 2 on the right hand side of Figure 4. Further, the launder element module 3 com ^¬ prises a second inlet pipe 15 having a third end 16 opening to the inner space of the second shell 8 at a bottom of the second shell 8, and a fourth end 18 opening to the settler 2. The fourth end 18 is adapted to receive the heavy solution phase as an underflow from the settler. The overflow height position of the third end 16 of the second inlet pipe 15 inside the second shell 8 is adjustable by a first level control valve 17 to adjust the level of the heavier solution in the settler 2. The first level control valve 17 comprises an actuator 19 by which the height position of the third end 16 of the second inlet pipe 15 is ad ^¬ justable. Further, the launder element module 3 com ^¬ prises a feed outlet pipe 20 having a fifth end 21 opening to the inner space of the third shell 9 via a second level control valve 22 disposed at a bottom of the third shell, and a sixth end 23 adapted to feed a solution to a settler 2 on the left hand side of Figure 4.

Figure 8 shows a layout of the foundation designed for the whole settler 2 including the launder module group 5 shown in Figure 1. The launder comprises a founda ^¬ tion 53 on which the module group 5 is supported at a height above the ground level, thereby providing a space for piping and access underneath the launder. The foundation 53 comprises a plurality of pillars 54 having ISO shipping standard compatible container lashing fittings 55, 56 to which the corner fittings 4 of the launder modules 3 and the box module 24 can be connected .

The pillar 54 comprises a lower end 57 which is sup ^¬ ported on the ground, an upper end 58, and one or more container lashing fittings 55, 55 attached to the upper end 58 of the pillar 54.

Figures 9 and 15 show that the pillar 54 comprises a lower end 57 supported on the ground and an upper end 58. One or more container lashing fittings 55, 56 are attached to the upper end 58. As illustrated in Figures 9 to 12, the pillar 54 may comprise one to four con ^¬ tainer lashing fittings 55, 56 depending on the number of corner fittings 4 to be connected onto the pillar. A pillar 54 supporting one corner of the module comprises only one container lashing fitting 55 (Fig. 9) . A pillar 54 supporting two corners of parallel modules com ^¬ prises a pair of container lashing fittings 55 arranged side by side (Fig. 10) . A pillar 54 supporting two corners of sequential modules comprises a pair of contain ^¬ er lashing fittings 55 arranged in a row (Fig. 11) . A pillar 54 supporting four corners of parallel and se ^¬ quential modules comprises two pairs of container lash- ing fittings 55 (Fig. 12) . The container lashing fittings may be stacking cones 55 as shown in Figures 9 to 12, or alternatively, they may be twist locks 56 as shown in Figures 13 and 14. With reference to Figure 15, the pillar 54 comprises a plastic tube 59, a concrete reinforcement of metal 60 arranged inside the plastic tube 59, cast concrete 61 cast inside the plastic tube, and a metal base plate 62 attached at the upper end of the pillar, to which base plate one or more container lashing fittings 55, 56 are fixedly connected.

The launder 1 is manufactured so that that at the site of manufacture, such as in an engineering workshop, a plurality of self-supporting launder element modules 3, 24 are manufactured. Each launder element module 3, 24 has exterior dimensions, strength and handling and securing means 4 conforming to ISO shipping container standards. The launder element modules 3 are trans- ported to the site of installation as normal freight by transport equipment, such as trucks, trailers and container ships, capable of handling and transporting ISO compatible units. At the site of installation the launder element modules 3 are assembled into a module group 5 which forms a complete launder 1. Although the invention has been the described in conjunction with a certain type of launder, it should be understood that the invention is not limited to any certain type of launder. While the present inventions have been described in connection with a number of ex- emplary embodiments and implementations, the present inventions are not so limited, but rather cover vari ^¬ ous modifications and equivalent arrangements, which fall within the purview of the prospective claims.