FLOTATION LINE

Abstract

A flotation line for treating mineral ore particles suspended in slurry is disclosed. The flotation line includes a scavenger part and a scavenger cleaner part. The flotation line is characterized in that the scavenger part or the scavenger cleaner part includes a flotation cell with blast tubes for introducing slurry infeed into the flotation cell; or in that the scavenger part or the scavenger cleaner part is followed by a flotation cell with blast tubes for introducing slurry infeed into the flotation cell. Further, a use of the flotation line is presented, as well as a flotation plant including a flotation line according to the invention.

Claims

1. A flotation line for treating mineral ore particles suspended in slurry, comprising a scavenger part with a scavenger flotation cell for the separation of slurry into underflow and overflow; and a scavenger cleaner part comprising a scavenger cleaner flotation cell for the separation of slurry into overflow and underflow wherein overflow from a scavenger flotation cell is arranged to flow into a regrinding step and then into the scavenger cleaner flotation part; underflow from a last scavenger flotation cell of the flotation line and a last scavenger cleaner flotation cell of the flotation line is arranged to be removed from the flotation line as tailings; at least 30% of the flotation volume in the flotation line comprises a mechanical agitator comprising a system for introducing flotation gas into the flotation cell; the flotation cells of the flotation line are connected in series and arranged in fluid communication so that a subsequent flotation cell is arranged to receive underflow from a previous flotation cell as slurry infeed; wherein the scavenger part or the scavenger cleaner part comprises a flotation cell with blast tubes for introducing slurry infeed into the flotation cell; or in that the scavenger part or the scavenger cleaner part is followed by a flotation cell with blast tubes for introducing slurry infeed into the flotation cell; a flotation cell with blast tubes configured to receive underflow from a scavenger flotation cell or a scavenger cleaner flotation cell as slurry infeed; and a blast tube configured to restrict flow of slurry infeed from an outlet nozzle, and to maintain slurry infeed under pressure in the blast tube.

2. The flotation line according to claim 1, wherein it further comprises a rougher part with a rougher flotation cell for the separation of slurry into underflow and overflow, the overflow arranged to flow directly into a cleaner flotation line, and the underflow from a last rougher flotation cell arranged to flow into the scavenger part as slurry infeed.

3. The flotation line according to claim 2, wherein the rougher part comprises at least two flotation cells, or 2-7 flotation cells, or 2-5 flotation cells.

4. The flotation line according to claim 1, wherein at least 60% of the flotation volume in the flotation line comprises a mechanical agitator comprising a system for introducing flotation gas into the flotation cell.

5. The flotation line according to claim 1, wherein the scavenger part comprises a flotation cell with blast tubes.

6. The flotation line according to claim 5, wherein the flotation cell with blast tubes is preceded by a scavenger flotation cell.

7. The flotation line according to claim 5, wherein the flotation cell with blast tubes is preceded by a scavenger flotation cell comprising a mechanical agitator.

8. The flotation line according to claim 5, wherein the flotation cell with blast tubes is preceded by a further flotation cell with blast tubes.

9. The flotation line according to claim 5, wherein a flotation cell with blast tubes is the last flotation cell of the scavenger part.

10. The flotation line according to claim 1, wherein the scavenger cleaner part comprises a flotation cell with blast tubes.

11. The flotation line according to claim 10, wherein the flotation cell with blast tubes is preceded by a scavenger cleaner flotation cell.

12. The flotation line according to claim 10, wherein the flotation cell with blast tubes is preceded by a scavenger cleaner flotation cell comprising a mechanical agitator.

13. The flotation line according to claim 11, wherein the scavenger cleaner flotation cell is preceded by a Jameson cell in which the size range of the flotation gas bubbles is 0.4 to 1.2 mm; or a further flotation cell with blast tubes, in which the size range of the flotation gas bubbles is 0.05 to 0.7 mm.

14. The flotation line according to claim 11, wherein the scavenger cleaner flotation cell is preceded by a further flotation cell with blast tubes configured to restrict flow of slurry infeed from an outlet nozzle, to maintain slurry infeed under pressure in the blast tube, and to induce a supersonic shockwave into the slurry infeed as it exits the blast tube.

15. The flotation line according to claim 10, wherein the flotation cell with blast tubes is the last flotation cell of the scavenger cleaner part.

16. The flotation line according to claim 10, wherein the scavenger part comprises a flotation cell with blast tubes.

17. The flotation line according to claim 16, wherein the flotation cell with blast tubes is preceded by a scavenger flotation cell.

18. The flotation line according to claim 16, wherein the flotation cell with blast tubes is preceded by a scavenger flotation cell comprising a mechanical agitator.

19. The flotation line according to claim 16, wherein the flotation cell with blast tubes is preceded by a further flotation cell with blast tubes.

20. The flotation line according to claim 16, wherein a flotation cell with blast tubes is the last flotation cell of the scavenger part.

21. The flotation line according to claim 1, wherein overflows of the flotation cells comprise a concentrate, and underflows of the flotation cells are arranged to flow into the tailings.

22. The flotation line according to claim 1, wherein underflow from a previous flotation cell is arranged to be led into the subsequent flotation cell by gravity.

23. The flotation line according to claim 1, wherein the flotation line comprises at least three flotation cells, or 3-10 flotation cells, or 4-7 flotation cells.

24. The flotation line according to claim 1, wherein the scavenger part comprises at least two flotation cells, or 2-7 flotation cells, or 2-5 flotation cells.

25. The flotation line according to claim 1, wherein the scavenger cleaner part comprises at least two flotation cells, or 2-6 flotation cells, or 2-4 flotation cells.

26. The flotation line according to claim 1, wherein the ratio of height (H) of a flotation cell with blast tubes, the height measured as the distance from the bottom of a flotation tank of the flotation cell to a launder lip of the flotation tank, to diameter (D) of the flotation cell with blast tubes, the diameter measured at a distance of an outlet nozzle of a blast tube from the bottom of the flotation tank, (H/D) is 0.5 to 1.5.

27. The flotation line according to claim 1, wherein the volume of a flotation cell with blast tubes is at least 10 m.sup.3.

28. The flotation line according to claim 1, wherein a flotation cell with blast tubes comprises 2-40 blast tubes, preferably 4-24 blast tubes.

29. Use of a flotation line according to claim 1 in recovering particles comprising a valuable material suspended in slurry.

30. The use according to claim 29 in recovering particles comprising nonpolar minerals such as graphite, sulphur, molybdenite, coal, and talc.

31. The use according to claim 29 in recovering particles comprising polar minerals.

32. The use according to claim 31 in recovering particles from minerals having a Mohs hardness of 2 to 3, such as galena, sulfide minerals, PGMs, and/or REO minerals.

33. The use according to claim 32 in recovering particles comprising Pt.

34. The use according to claim 31 in recovering particles comprising Cu from minerals having a Mohs hardness from 3 to 4.

35. The use according to claim 34 in recovering particles comprising Cu from low grade ore.

36. A flotation plant comprising a flotation line according to claim 1.

37. The flotation plant according to claim 36, wherein the plant comprises at least two, or at least three flotation lines according to claim 1.

38. The flotation plant according to claim 36, wherein a flotation line is arranged to recover particles from minerals having a Mohs hardness of 2 to 3, such as galena, sulfide minerals, PGMs, and/or REO minerals.

39. The flotation plant according to claim 38, wherein a flotation line is arranged to recover particles comprising Pt.

40. The flotation plant according to claim 36, wherein a flotation line is arranged to recover particles comprising Cu from minerals having a Mohs hardness from 3 to 4.

41. The flotation plant according to claim 40, wherein a flotation line is arranged to recover particles comprising Cu from low grade ore.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0118] The accompanying drawings, which are included to provide a further understanding of the current disclosure and which constitute a part of this specification, illustrate embodiments of the disclosure and together with the description help to explain the principles of the current disclosure. In the drawings:

[0119] FIG. 1 is a vertical cross-section of a flotation cell with blast tubes,

[0120] FIG. 2 is a schematic drawing of a flotation line according to an embodiment of the invention,

[0121] FIG. 3 is a schematic drawing of a flotation line according to a different embodiment of the invention, and

[0122] FIG. 4 a schematic drawing of a flotation line according to yet another embodiment of the invention.

DETAILED DESCRIPTION

[0123] Reference will now be made in detail to the embodiments of the present disclosure, an example of which is illustrated in the accompanying drawings.

[0124] The description below discloses some embodiments in such a detail that a person skilled in the art is able to utilize the flotation cell, flotation line and its use based on the disclosure. Not all steps of the embodiments are discussed in detail, as many of the steps will be obvious for the person skilled in the art based on this disclosure.

[0125] For reasons of simplicity, item numbers will be maintained in the following exemplary embodiments in the case of repeating components.

[0126] The enclosed FIG. 1 illustrates a flotation cell 200 with blast tubes 4 in some detail. The figure is not drawn to proportion, and many of the components of the flotation cell 200 with blast tubes 4 are omitted for clarity. FIGS. 2-4 illustrate in a schematic manner embodiments of a flotation line 10. The direction of flows of slurry is shown in the figures by arrows.

[0127] A flotation cell 200 with blast tubes 4, as well as a rougher flotation cell 110, a scavenger flotation cell 120, and a scavenger cleaner flotation cell 130, are intended for treating mineral ore particles suspended in slurry and for separating the slurry into an underflow 400 and an overflow 500, the overflow 500 comprising a concentrate of a desired mineral. The flotation cell 200 with blast tubes 4 comprises a flotation tank 210 that has a centre 211, a perimeter 212, a bottom 213 and a side wall 214. The flotation cell 200 further comprises a launder 202 and a launder lip 221 surrounding the perimeter 212 of the flotation tank 210. A rougher flotation cell 110, a scavenger flotation cell 120, and a scavenger cleaner flotation cell 130 may be of any suitable flotation cell type known in the art. They may for example, comprise a mechanical agitator 70 comprising a system for introducing flotation gas into the flotation cell. In an embodiment, a scavenger flotation cell 120, and a scavenger cleaner flotation cell 130 may comprise a Jameson cell, in which a size range of flotation gas bubbles is 0.4 to 1.2 mm.

[0128] In the accompanying figures, launder 202 is a perimeter launder. It is to be understood that a launder 202 may comprise, alternatively or additionally, a central launder arranged at the centre 211 of the flotation tank 210, as is known in the technical field. A launder lip of a central launder may face towards the perimeter 212 of the flotation tank 210, or towards the centre 211 of the flotation tank 210, or both. The overflow 500 is collected into the launder 202 or launders as it passes over a launder lip 221, from a froth layer formed in the upper part of the flotation tank 210. The froth layer comprises an open froth surface A.sub.f at the top of the flotation tank 210.

[0129] Underflow 400 is removed from or led out of the flotation tank via a tailings outlet. According to an embodiment, the tailings outlet 240 may be arranged at the side wall 214 of the flotation tank 210. The tailings outlet 240 may be arranged at the side wall 214 of the flotation tank 210 at a distance from the bottom 213 of the flotation tank 210. The distance is to be understood as the distance of the lowest point of the tailings outlet 240 or outlet opening in the side wall 214 of the flotation tank 210 from the tank bottom 213. The distance may be 1 to 15% of the height H of the flotation tank 210. For example, the distance may be 2%, or 5% or 7.5%, or 12% of the height H. Alternatively, the tailings outlet 240 may be arranged at the bottom 213 of the flotation tank 210. The tailings outlet 240 may be controlled by a dart valve, or by any other suitable manner known in the field, to control the flow rate of underflow from the flotation tank 210. Even if the tailings outlet 240 is controlled by internal or external structures such as up-flow or down-flow, respectively, dart boxes, the tailings outlet 240 is ideally located at the lower part of the flotation tank 210, i.e. near or adjacent to the bottom 213 of the flotation tank, or even at the bottom 213 of the flotation tank 210. More specifically, underflow 400 or tailings are removed from the lower part of the flotation tank 210, and at or near the side wall 214 of the flotation tank 210, at a settling zone B.

[0130] The flotation tank 210 may further comprise a froth crowder shaped to direct froth in an open froth surface A.sub.f, towards the launder lip 221. The froth crowder may be a central froth crowder 261, or an internal perimeter froth crowder 262 arranged within the flotation tank 210 at a desired depth, at the side wall 214 of the flotation tank 210.

[0131] A central froth crowder 261 is arranged concentric to the centre 211 of the flotation tank 210. The central froth crowder 61 may have a shape of a cone or a truncated cone. The central froth crowder 261 may have a shape of a pyramid or a truncated pyramid. In other words, a vertical cross-section of a central froth crowder 261 may be an inverted triangle with a vertex pointing towards the bottom 213 of the flotation tank. In case the central froth crowder 261 is has a truncated structure or shape, the vertex is only functional, i.e. it is to be visualised as the lowest point of the structure or shape as continued to a complete untruncated form, whereby a included angle may be identified irrespective of the actual shape or form of the central froth crowder. The included angle may be 20 to 80°. For example, the included angle may be 22°, or 37.5° or 45°, or 55°, or 63.75°, or 74°. In an embodiment, the central froth crowder 261 is arranged to block 25 to 40% of the open froth surface A.sub.f.

[0132] Alternatively or additionally to the central froth crowder 261, the flotation tank may comprise an internal perimeter crowder 262, arranged in the side wall 214 of the flotation tank 210 so that a lowest point of the internal perimeter crowder is located at a distance from the bottom 213 of the flotation tank 10. The distance may be ½ to ⅔ of the height H of the flotation cell 200. The internal perimeter crowder 262 may be formed to comprise a diagonal intake starting from the lowest point, and angled towards the centre 211 of the flotation tank 210, and extending between a first part of the side wall 214 of the flotation tank 210 and a second part of the side wall 214 so that an angle of inclination of the diagonal intake in relation to the first part of the side wall 214 is 20 to 80°. The angle of inclination may be for example 22°, or 37.5° or 45°, or 55°, or 63.75°, or 74°. The internal perimeter crowder 262 may be arranged to block ⅕ to ¼ of a pulp area A.sub.p, which is measured at a distance h.sub.1 of an outlet nozzle 43 of a blast tube 4 from the bottom 213 of the flotation tank 210, at a mixing area A. The mixing area A, i.e. the part or zone of the flotation tank in vertical direction where the slurry is agitated or otherwise induced to mix the ore particles suspended in the slurry with the flotation gas bubbles, is formed roughly at a vertical section of the flotation tank 210 around the lower parts of the blast tubes 4 and the impingers 44.

[0133] Additionally or alternatively, the flotation tank 210 may further comprise a bottom structure 207, arranged on the bottom 213 of the flotation tank 210, and having a shape that allows particles suspended in slurry to be mixed in a mixing zone A created over the bottom structure 207, and to settle down in a settling zone B surrounding the bottom structure 207.

[0134] The shape of the bottom structure 207 may be defined as follows: the vertical cross-section of the bottom structure 207 may be understood to display a form of a functional triangle that comprises a first (top) vertex, pointing away from the bottom 213 of the flotation tank 210; a second vertex; and a third vertex, the two latter disposed at the bottom 213 of the flotation tank 210. A first side is formed between the first vertex and the second vertex. A second side is formed between the first vertex and the third vertex. A base is formed between the second vertex and the third vertex, the base being thus parallel to and on the bottom 213 of the flotation tank 210. A central axis of the functional triangle is substantially concentric with the centre 211 of the flotation tank 210. “Substantially” in this context is to be understood so that during manufacturing and/or installation of the bottom structure 207, it is possible that slight deviations from the centre 211 of the flotation tank 210 may naturally occur. The intention is, nevertheless, that the two axes, central axis of the functional triangle (which is also the central axis of the bottom structure 207) and the centre of the flotation tank 210 are coaxial.

[0135] A base angle between the first side and the base (and/or between the second side and the base), in relation to the bottom 213 of the flotation tank 210 is 20 to 60°. For example, the angle may be 22°, or 27.5° or 35°, or 45°, or 53.75°. Further, an included angle between the first side and the second side is 20 to 100°. Preferably, the included angle is 20 to 80°. For example, the included angle may be 22°, or 33.5°, or 45°, or 57.75°, or 64°, or 85.5°. The functional triangle may therefore be an isosceles triangle or an equilateral triangle.

[0136] The functional triangle is in essence a form which may be identified though the abovementioned features, regardless of the actual form of the bottom structure 207, which may be, depending on the cross-section and other structural details of the flotation tank 210, for example a cone, a truncated cone, a pyramid, or a truncated pyramid. A cone or a truncated cone may be suitable from for a flotation tank with a circular cross-section. A pyramid or a truncated pyramid may be a suitable form for a flotation tank 210 with a rectangular cross-section.

[0137] The bottom structure 207 comprises a base, corresponding to the base of the functional triangle (i.e. the base c of the functional triangle defines the base of the bottom structure 207), and arranged on the bottom 213 of the flotation tank 210. Further, the bottom structure comprises a mantle. The mantle is defined at least by the first vertex, the second vertex and the third vertex of the functional triangle. Therefore, irrespective of the actual form of the bottom structure 207, the functional triangle defines the extreme physical dimensions of the bottom structure 207. For example, in case the bottom structure 207 has an irregular form yet being rotationally symmetrical, it would fit into the functional triangle in its entirety. In an embodiment, the mantle is at least partly defined by the first side and the second side of the functional triangle. An example of such an embodiment is a bottom structure 207 having the form of a truncated cone. In an embodiment, the mantle is defined essentially entirely by the first side and the second side of the functional triangle, i.e. the bottom structure 207 has the form of a cone.

[0138] The bottom structure 207 has a height, measured from the topmost part of the bottom structure 207 to the bottom 213 of the flotation tank 210. In case the form of the bottom structure is a cone or a pyramid, the topmost part is also the first vertex of the functional triangle. In case the bottom structure 207 has some sort of truncated form, the height is measured from the level top of the truncated form to the bottom 213 of the flotation tank 210. The height is greater than ⅕ and less than ¾ of the height H of the flotation cell 200. Further, a diameter of the base of the bottom structure 207 may be ¼ to ¾ of a diameter D of the flotation cell 200. In case a flotation tank 210 and/or the bottom structure 207 has a non-circular cross-section, the diameters are measured as the maximal diagonals of the respective parts (bottom structure 207 base and tank bottom 213). In an embodiment, the surface area of a base of the bottom structure 207 is less than 80% of the surface area of the bottom 213 of the flotation tank 210. The surface area of the base may be 25 to 80% of the surface area of the bottom 213 of the flotation tank 210.

[0139] Further, the volume of the flotation tank 210 taken by the bottom structure 207 may be 30 to 70% of the volume of the flotation tank 210 taken by the mixing zone A.

[0140] The bottom structure 207 may additionally comprise any suitable support structures and/or connecting structures for installing the bottom structure 207 into the flotation tank 210, on the bottom 213 of the flotation tank 210. The bottom structure 207 may be made of any suitable material such as metal, for example stainless steel.

[0141] The flotation cell 200 with blast tubes 4 has a height H, measured as the distance from the bottom 213 of the flotation tank 210 to the launder lip 221. At the perimeter 212 of the flotation tank 210, the height H is at most 20% lower than the height H at the centre 211 of the flotation tank 210. In other words, the flotation tank 10 may have different vertical cross-sections—for example, the side wall 14 of the flotation tank 10 may include at its lower part a section that is inclined towards the centre 11 of the flotation tank 10.

[0142] Further, the flotation cell 200 with blast tubes 4 has a diameter D, measured at a distance h.sub.1 of an outlet nozzle 43 of a blast tube 4 from the bottom 213 of the flotation tank 210. In an embodiment, the height H to diameter D ratio H/D of the flotation cell 200 with blast tubes 4 is 0.5 to 1.5.

[0143] The flotation cell 200 with blast tubes 4 may have a volume of at least 10 m.sup.3. The flotation cell 200 with blast tubes 4 may have a volume ranging from 20 to 1000 m.sup.3. For example, the volume of the flotation cell 200 with blast tubes 4 may be 100 m.sup.3, or 200 m.sup.3, or 450 m.sup.3, or 630 m.sup.3.

[0144] The flotation cell 200 with blast tubes 4 may comprise 2-40 blast tubes 4, or 4-24 blast tubes 4 for introducing slurry infeed 100 into the flotation cell 200 or into the flotation tank 210. In an embodiment, there are 16 blast tubes 4. In another embodiment, there are 24 blast tubes 4. In yet another embodiment, there are 8 blast tubes 4. The exact number of blast tubes 4 may be chosen according to the specific operation, for example the type of slurry being treated within the flotation cell 200, the volumetric feed flow rate to the flotation cell 200, the mass throughput feed to the flotation cell 200, or the volume or dimensions of the flotation cell 200. In order to properly disperse flotation gas within the flotation tank 210, 4 to 6 blast tubes 4 may be employed.

[0145] A blast tube 4 is configured to restrict flow of slurry infeed from an outlet nozzle 43, and to maintain slurry infeed under pressure in the blast tube 4. A blast tube 4 comprises an inlet nozzle 41 for feeding slurry infeed 100 into the blast tube 4; an inlet 42 for pressurized air or other gas, so that the slurry infeed 100 may be subjected to pressurized air or other gas as it is discharged from the inlet nozzle 41; an elongated chamber 40 arranged to receive under pressure the slurry infeed 100; and the outlet nozzle 43. The outlet nozzle 43 may further be configured to produce a supersonic shockwave into the slurry infeed, the supersonic shockwave inducing formation of flotation gas bubble-particle agglomerates. For example, and to the outlet nozzle 43 may induce a supersonic shockwave into the slurry infeed 100 as it exits the blast tube 40. In addition, the supersonic shockwave may extend to the slurry adjacent or surrounding the outlet nozzle so that even outside the blast tube, the creation of small size flotation gas bubble-particle agglomerates is thus possible.

[0146] Flotation gas is entrained through a turbulent mixing action brought about by the jet, and is dispersed into small bubbles in the slurry infeed 100 as it travels downwards through the elongated chamber 40 to an outlet nozzle 43 configured to restrict the flow of slurry infeed 100 from the outlet nozzle 43, and further configured to maintain slurry infeed 100 under pressure in the elongated chamber 40.

[0147] For restricting the flow, an outlet nozzle 43 may comprise a throttle such as a throat-like restricting structure. From the outlet nozzle 43, more specifically from the throttle, slurry infeed 100 issues under pressure into the flotation cell 200. As the slurry infeed 100 passes through the outlet nozzle 43, or through the throttle of the outlet nozzle 43, flotation gas bubbles are reduced in size by the pressure changes, and by the high-shear environment downstream of the outlet nozzle 43. The velocity of the gas-liquid mixture in outlet nozzle 43, or in the throttle, may exceed the speed of sound when the flow of infeed slurry 100 becomes a choked flow and flow downstream of the throttle becomes supersonic, and a shockwave forms in the diverging section of the outlet nozzle 43. In other words, the outlet nozzle 43 may be configured to induce a supersonic shockwave into slurry infeed 100. The flow of slurry infeed 100 becomes choked when the ratio of the absolute pressure upstream the outlet nozzle 43 to the absolute pressure downstream of a restricting structure of the outlet nozzle 43 exceeds a critical value. When the pressure ratio is above the critical value, flow of slurry infeed 100 downstream of the restricting structure of the outlet nozzle 43 becomes supersonic and a shockwave is formed. Small flotation gas bubbles in slurry infeed 100 mixture are split into even smaller by being forced through the shockwave, and forced into contact with hydrophobic ore particles in slurry infeed 100, thus creating flotation gas bubble-ore particle agglomerates.

[0148] An outlet nozzle 43 may be disposed inside the flotation tank 210 at a desired depth. An outlet nozzle 43 may be positioned at a vertical distance from the launder lip 221, the distance being at least 1.5 m. In other words, the length of the portion of a blast tube 4 disposed inside the flotation tank 210 below the launder lip 221 level is at least 1.5 m. In an embodiment, the distance of the outlet nozzle 43 from the launder lip 221 is at least 1.7 m, and the distance h.sub.1 of the outlet nozzle 43 from the bottom 213 of the flotation tank 210 is at least 0.4 m. For example, the distance of the outlet nozzle 43 from the launder lip 221 may be 1.55 m, or 1.75 m, or 1.8 m, or 2.2 m, or 2.45 m, or 5.25 m; and the distance h.sub.1, irrespective of the distance of the outlet nozzle 43 from the launder lip 221, may be 0.45 m, 0.55 m, 0.68 m, 0.9 m, or 1.2 m. Further, the ratio of the distance of the outlet nozzle 43 from the launder lip 221 to the height H of the flotation cell 210 may be 0.9 or lower. The depth at which the blast tubes 4 are disposed inside the flotation tank 210 may depend on a number of factors, for example on the characteristics of the slurry and/or valuable mineral to be treated in the flotation cell 200, or on the configuration of a flotation line 1 in which the flotation cell 200 is arranged. The ratio of a distance h.sub.1 of an outlet nozzle 43 from the bottom 213 of the flotation tank 210 to height H of the flotation tank 210, h.sub.1/H may be 0.1 to 0.75.

[0149] A diameter of an outlet nozzle 43 may be 10 to 30% of the diameter of an elongated chamber 40 of a blast tube 4. The diameter of an outlet nozzle 43 may be 40 to 100 mm. For example, the diameter of an outlet nozzle 43 may be 55 mm, or 62 mm, or 70 mm.

[0150] By arranging an outlet nozzle to have a certain diameter, the velocity of the slurry infeed may be maintained at a level favourable for the creation of small size flotation gas bubbles, and for the probability of these bubbles to contact the ore particles in the slurry. Especially, to maintain a shockwave after the outlet nozzle, a slurry velocity of 10 m/s or higher needs to be maintained. By designing the outlet nozzle in relation to the blast tube size, the effect of slurry infeed flow rate in different types of flotation cells may be accounted for.

[0151] A blast tube 4 may further comprise an impinger 44 configured to contact a flow of slurry infeed 100 from the outlet nozzle 43 and to direct the flow of slurry infeed 100 radially outwards and upwards of the impinger 44. Slurry infeed 100 exiting from the outlet nozzle 43 is therefore directed to contact the impinger 44. A distance from a bottom of the impinger 44 to the outlet nozzle 43 may be 2 to 20 times the diameter of the outlet nozzle 43. For example, the distance from the bottom of the impinger 44 to the outlet nozzle 43 may be 5 times, 7 times, or 12 times, or 15 times the diameter of the outlet nozzle 43. The ratio of the distance from the bottom of the impinger 44 to the outlet nozzle 43, to the distance h.sub.1 of an outlet nozzle 43 from the bottom of the flotation tank 10, may be lower than 1.0. Further, a distance of the bottom of the impinger 44 from the bottom 213 of the flotation tank 210 may be at least 0.3 m. For example the distance of the bottom of the impinger 44 from the bottom 213 of the flotation tank 210 may be 0.4 m, or 0.55 m, or 0.75 m, or 1.0 m. The impinger 44 may comprise an impingement surface intended for contacting the flow of slurry infeed 100 exiting the outlet nozzle 43. The impingement surface may be made of wear-resistant material to reduce the need for replacements or maintenance.

[0152] The slurry, which in essence is a three-phase gas-liquid-solid mixture, rising out of the impinger 44 enters the upper part of the flotation tank 210, and the flotation gas bubbles rise upwards and separate from the liquid to form a froth layer. The froth rises upwards and discharges over the launder lip 221 into the launder 202 and out of the flotation cell 1 as overflow 500. The tailings or underflow 400, from which the desired material has substantially been removed, pass out from the flotation tank 210 through an outlet arranged at or near the bottom 213 of the flotation tank 210.

[0153] Some of the coarse hydrophobic particles that are carried into the froth may subsequently disengage from flotation gas bubbles and drop back into the flotation tank 210, as a result of bubble coalescence in the froth. However, the majority of such particles fall back into the flotation tank 210 in such a way and position that they may be captured by bubbles newly entering the flotation tank 210 from the blast tubes 4, and carried once more into the froth layer.

[0154] The blast tubes 4 may be arranged concentric to the perimeter 212 of the flotation tank 210 at a distance from the centre 211 of the flotation tank 210, the distance being preferably equal for each blast tube 4. This may be the case when the flotation tank 210 is circular in cross-section. The blast tubes 4 may be further arranged so that each blast tube 4 is located at a distance of an outlet nozzle 43 from the centre 211 of the flotation tank 210, the distance being preferably equal for each blast tube 4. For example, the distance of an outlet nozzle 43 from the centre 211 of the flotation tank 210 may be 10 to 40% of the diameter D of the flotation tank 210. According to different embodiments of the flotation cell 200, the distance of an outlet nozzle 43 from the centre 211 of the flotation tank 210 may be 12.5%, or 15%, or 25% or 32.5% of the diameter D of the flotation tank 210.

[0155] Alternatively, the blast tubes 4 may be arranged parallel to the side wall 214 of the flotation tank 210, at a distance from the side wall 14. This may be the case when the flotation tank 210 is rectangular in cross-section. Additionally, the parallel arranged blast tubes 4 may be further arranged at a straight line within the flotation tank 210. The distance of the outlet nozzle 43 of a blast tube 4 from the side wall 214 of the flotation tank 210 may be 10 to 40% of the diameter D of the flotation tank 210. In an embodiment, the distance of the outlet nozzle 43 of a blast tube 4 from the side wall 214 of the flotation tank 210 is 25% of the diameter D of the flotation tank 210. According to different embodiments of the flotation cell 10, the distance of the outlet nozzle 43 of a blast tube 4 from the side wall 214 of the flotation tank 210 may be 12.5%, or 15%, or 27% or 32.5% of the diameter D of the flotation tank 210. Additionally, the parallel arranged blast tubes 4 may be further arranged at a straight line within the flotation tank 210.

[0156] Further, in all the above mentioned embodiments, the blast tubes 4 may be arranged at equal distance from each other so that a distance between any two adjacent outlet nozzle 43 is the same.

[0157] A slurry fraction 300 may be taken out from the flotation tank 210 via an outlet 31 arranged at the side wall 214 of the flotation tank 210. This slurry fraction 300 is recirculated into blast tubes 4 as infeed slurry. In an embodiment the slurry infeed 100 comprises 40% or less of slurry fraction 300. In an embodiment, the slurry infeed 100 comprises 50% or less slurry fraction 300. For example, the slurry infeed may comprise 5%, or 12.5%, or 20%, or 30%, or 37.5%, or 45% of the slurry fraction 300. Alternatively, the slurry infeed 100 may comprise 0% of slurry fraction 300, i.e. no recirculation of slurry taken from the flotation tank 210 back to the flotation cell 200 takes place, but the slurry infeed 100 comprises 100% of fresh slurry 200, for example from a previous flotation cell 110, 120, 130, 200 (that is, underflow 400 from a previous flotation cell), or from a previous process step.

[0158] The slurry fraction 300 may be recirculated to all of the blast tubes 4 of the flotation tank 210, or, alternatively, to some of the blast tubes 4, while other blast tubes 4 receive fresh slurry 200, comprising either the underflow 400 of a previous flotation cell 110, 120, 130, 200, or a slurry flow from some preceding process step, depending on the location of the flotation cell 200 within a flotation line 8. The outlet 31 may be arranged at a distance from the bottom 213 of the flotation tank 210. The distance of the outlet 31 from the bottom 213 of the flotation tank 210 is to be understood as the distance of the lowest point of the outlet or outlet opening in the side wall 214 of the flotation tank 210 from the tank bottom 213. The distance of the outlet 31 from the bottom 213 of the flotation tank 210 is 0 to 50% of the height H of the flotation cell 200. The outlet 31 may advantageously be positioned at a settling zone where the particles suspended in slurry and not captured by the flotation gas bubbles and/or the upwards flow of slurry descend towards the bottom 213 of the flotation tank 210. In an embodiment, the outlet 31 is arranged at the lower part of the flotation tank 210. For example, the distance of the outlet 31 from the bottom 213 of the flotation tank 210 may be 2%, or 8%, or 12.5%, or 17, or 25% of the height H of the flotation cell 200. Even if the outlet 31 is controlled by internal or external structures such as up-flow or down-flow dart boxes, respectively, the outlet 31 is ideally located at the lower part of the flotation tank 210, i.e. near or adjacent to the bottom 213 of the flotation tank. More specifically, slurry fraction 300 is removed from the lower part of the flotation tank 210.

[0159] The flotation cell 200 may also comprise a conditioning circuit 3. The conditioning circuit 3 may comprise a pump tank 30, or other such additional vessel, in fluid communication with the flotation tank 210. In the pump tank 30 infeed of fresh slurry 2 and a slurry fraction 300 taken from the flotation tank 210 via an outlet 31 are arranged to be combined into slurry infeed 100, which is then led into blast tubes 4 of the flotation tank 210. The fresh slurry 2 may be for example underflow 400 from a preceding flotation cell 110, 120, 130, 200, or in case the flotation cell 200 is the first flotation cell of a flotation line 1, an infeed of slurry coming from a grinding unit/step or a classification unit/step. It is also possible that slurry fraction 300 and fresh slurry 2 are distributed into the blast tubes 4 without being first combined in a pump tank 30.

[0160] The combined slurry may be recirculated to all of the blast tubes 4 of the flotation tank 210, or, alternatively, to some of the blast tubes 4, while other blast tubes 4 receive fresh slurry 200, comprising either the underflow 400 of a previous flotation cell 110, 120, 130, 200, or a slurry flow from some preceding process step, depending on the location of the flotation cell 200 within a flotation line 1.

[0161] The outlet 31 may be arranged at the side wall 214 of the flotation tank 210, at a distance from the bottom 213 of the flotation tank 210. The distance of the outlet 31 from the bottom 213 of the flotation tank 210 may be 0 to 50% of the height H of the flotation cell 200 with blast tubes 4. For example, the distance of the outlet 31 from the bottom 213 of the flotation tank 210 may be 2%, or 8%, or 12.5%, or 20%, or 33% of the height H of the flotation cell 200.

[0162] Additionally, the conditioning circuit may comprise a pump 32 arranged to intake the slurry fraction 300 from the flotation tank 10, and to forward slurry infeed 100 from the pump tank 30 to the blast tubes 4. The slurry fraction 300 may comprise low settling velocity particles such as fine, slow-floating particles. The slurry fraction may be taken from or near the bottom of the flotation tank 210. Additionally or alternatively, the conditioning circuit 3 may further comprise a distribution unit (not shown in FIG. 1), arranged to distribute slurry infeed 100 into the blast tubes 4. The pump 32 may also be used to forward the slurry infeed 100 into the blast tubes 4. In order to distribute the slurry infeed 100 evenly into the blast tubes 4, a distribution unit may be utilized. The distribution unit may, for example, comprise a feed pipe inside the flotation tank 210, configured to distribute slurry fraction 300 directly into the blast tubes 4. For example, the distribution unit may comprise conduits arranged outside the flotation tank 210, leading to a separate feed distributor configured to distribute slurry fraction 300, or a combination of slurry fraction 300 and fresh slurry 200 into the blast tubes 4.

[0163] The flotation line 10 for treating mineral ore particles suspended in slurry comprises a scavenger part 12 with one or more scavenger flotation cells 120 for the separation of slurry into underflow 400 and overflow 500. The scavenger part 12 may comprise at least two scavenger flotation cells 120. The scavenger part 12 may comprise 2 to 7 scavenger flotation cells 120. The scavenger part 12 may comprise 2 to 5 scavenger flotation cells 120. The scavenger part 12 comprises also one or more flotation cells 200 with blast tubes 4. Alternatively, the scavenger part 12 may be followed by one or more flotation cell 200 with blast tubes 4.

[0164] A flotation cell 200 with blast tubes 4 is configured to receive underflow 400 from a preceding scavenger flotation cell 120 as slurry infeed 100, or as part of a slurry infeed 100, to be combined with the slurry fraction 300 from the flotation cell 200 with blast tubes 4 prior to feeding it into a flotation cell 200 with blast tubes 4 as infeed slurry 100.

[0165] In the scavenger part 12, the flotation cell 200 with blast tubes 4 may be preceded by one or more scavenger flotation cell 120. Alternatively or additionally, the flotation cell 200 with blast tubes 4 may be preceded by a scavenger flotation cell 120 comprising a mechanical agitator 70. Further, alternatively or additionally, the flotation cell 200 with blast tubes 4 may be preceded by a further flotation cell 200 with blast tubes 4. According to an embodiment, the flotation cell 200 with blast tubes 4, or the flotation cells 200 with blast tubes 4, is/are the last flotation cell/s of the scavenger part 12.

[0166] The flotation line 10 further comprises a scavenger cleaner part 13 with one or more scavenger cleaner flotation cells 130 for the separation of slurry into underflow 400 and overflow 500. The scavenger cleaner part 13 may comprise at least two scavenger cleaner flotation cells 130. The scavenger cleaner part 13 may comprise 2 to 6 scavenger cleaner flotation cells 130. The scavenger cleaner part 13 may comprise 2 to 5 scavenger cleaner flotation cells 130. The scavenger cleaner part 13 comprises also one or more flotation cells 200 with blast tubes 4. Alternatively, the scavenger cleaner part 13 may be followed by one or more flotation cell 200 with blast tubes 4.

[0167] A flotation cell 200 with blast tubes 4 is configured to receive underflow 400 from a preceding scavenger cleaner flotation cell 130 as slurry infeed 100, or as part of a slurry infeed 100, to be combined with the slurry fraction 300 from the flotation cell 200 with blast tubes 4 prior to feeding it into a flotation cell 200 with blast tubes 4 as infeed slurry 100.

[0168] In the scavenger cleaner part 13, the flotation cell 200 with blast tubes 4 may be preceded by one or more scavenger cleaner flotation cells 130. Alternatively or additionally, the flotation cell 200 with blast tubes 4 may be preceded by a scavenger cleaner flotation cell 130 comprising a mechanical agitator 70. Further, alternatively or additionally, the flotation cell 200 with blast tubes 4 may be preceded by a further flotation cell 200 with blast tubes 4. In an embodiment, a scavenger cleaner flotation cell 130 is preceded by a Jameson cell. In the Jameson cell, the flotation gas bubbles display a size range of 0.4 to 1.2 mm. In an embodiment, a scavenger cleaner flotation cell 130 is preceded by further flotation cell 200 with blast tubes 4. In that flotation cell, the flotation gas bubbles display a size range of 0.05 to 0.7 mm. In a yet another embodiment, the scavenger cleaner flotation cell 130 may be preceded by a further flotation cell with blast tubes 4, configured to restrict flow of slurry infeed 100 from an outlet nozzle 43, to maintain slurry infeed 100 under pressure in the blast tube 4, and to induce a supersonic shockwave into the slurry infeed 100 as it exists the blast tube. According to an embodiment, the flotation cell 200 with blast tubes 4, or the flotation cells 200 with blast tubes 4, is/are the last flotation cell/s of the scavenger cleaner part 13.

[0169] The configuration of the scavenger part 12, as described above, is variable independently of the configuration of the scavenger cleaner part 13, as described above. In other words, the scavenger part 12 may comprise one or more flotation cells 200 with blast tubes 4, the scavenger cleaner part 13 may comprise one or more flotation cells 200 with blast tubes 4, or both may comprise one or more flotation cells 200 with blast tubes 4, as well as any number and type of scavenger flotation cells 120 or scavenger cleaner flotation cells 130, respectively, in the scope defined by the embodiments described herein.

[0170] The flotation line 10 may also comprise a rougher part 11 with one or more rougher flotation cells 110 for the separation of slurry into underflow 400 and overflow 500. The rougher part 11 may comprise at least two rougher flotation cells 110, or 2-7 rougher flotation cells 110, or 2-5 rougher flotation cells 110. The overflow 500 is arranged to flow directly into a cleaner flotation line (not shown in the figures). In case there are more than one rougher flotation cells 110, overflows of a number of rougher flotation cells 110 may be combined and then arranged to flow into the cleaner flotation line. The underflow 400 from a last rougher flotation cell 110 is arranged to flow into the scavenger part 12 as slurry infeed. The slurry infeed may comprise fresh slurry 2 to be combined with the slurry fraction 300 from a flotation cell 200 with blast tubes 4 prior to feeding it into a flotation cell 200 with blast tubes 4 as infeed slurry 100. Alternatively, the slurry infeed may be fed directly to a preceding flotation cell 120, 200.

[0171] All in all, the flotation line 10 may comprise at least three flotation cells 110, 120, 130, 200. The flotation line 10 may comprise 3 to 10 flotation cells 110, 120, 130, 200. The flotation line 10 may comprise 4 to 7 flotation cells 110, 120, 130, 200.

[0172] The flotation cells 110, 120, 130, 200 of the flotation line 10 are connected in series and arranged in fluid communication so that a subsequent flotation cell is arranged to receive underflow 400 from a previous flotation cell as slurry infeed, or, in the case of a flotation cell 200 with blast tubes 4, alternatively, as a part of a slurry infeed 100 comprising a slurry fraction 300 from the flotation cell 200 with blast tubes 4 and fresh slurry 2, which is the underflow 400 of the previous flotation cell.

[0173] Overflow 500 for a scavenger flotation cell is arranged to flow into a regrinding step 91 and then into the scavenger cleaner flotation part 13. In case there are more than one scavenger flotation cells 120, overflows 500 of a number of scavenger flotation cells 120 may be combined and then arranged to flow into the regrinding step 91 (see FIG. 2). Overflow 500 from a flotation cell 200 with blast tubes 4 (in a scavenger line 12 or in a scavenger cleaner line 13) may be arranged to flow into a cleaner flotation line (not shown in the figures). In case there are more than one flotation cells 200 with blast tubes, their overflows 500 may be combined and arranged to flow into the cleaner flotation line (see FIG. 2). Alternatively, overflow(s) 500 of a flotation cell 200 or flotation cells 200 in the scavenger line 12 may be combined with the overflow(s) of the scavenger flotation cell(s) 120 and arranged to flow into the regrinding step 91. Yet alternatively, overflow 500 of one flotation cell 200 with blast tubes 4 may be combined thus, while overflow 500 of another flotation cell 200 with blast tubes 4 may be led to a cleaner line (see FIG. 3). Further, overflows 500 or some overflows 500 of flotation cells 200 with blast tubes 4 may be arranged to flow into a separate regrinding step 91, and from there, into further processing (see FIG. 4).

[0174] Overflow 500 for a scavenger cleaner flotation cell is arranged to flow into further processing according to state of the art. Overflow 500 from a flotation cell 200 with blast tubes 4 in a scavenger cleaner line 13 may be arranged to flow into a cleaner flotation line (not shown in the figures). Alternatively, overflow(s) 500 of a flotation cell 200 or flotation cells 200 in the scavenger line 13 may be combined with the overflow(s) of the scavenger cleaner flotation cell(s) 130 and arranged to flow into further processing (see FIG. 3). Further, overflows 500 or some overflows 500 of flotation cells 200 with blast tubes 4 in the scavenger cleaner part 13 may be arranged to flow into a separate regrinding step 91, and from there, into further processing (see FIG. 4).

[0175] Underflow 400 from a last scavenger flotation cell 120 of the flotation line 10, as well as underflow 400 from a last scavenger cleaner flotation cell of the flotation line 10 is arranged to be removed from the flotation line 10 as tailings 800. Overflows 500 of the flotation cells 110, 120, 130, 200 may comprise a concentrate, and underflows 400 of the flotation cells 110, 120, 130, 200 may be arranged to flow into the tailings 800 (either directly or indirectly through treatment in a number of subsequent flotation cells). The flows of slurry, for example underflow 400 from a previous flotation cell 110, 120, 130, 200 may be arranged to be led into a subsequent flotation cell by gravity. Alternatively or additionally, a low-head pump may be utilized in transferring the flows of slurry.

[0176] At least 30% of the flotation volume in the flotation line 10 comprises a mechanical agitator 70 comprising a system for introducing flotation gas into the flotation cell. In an embodiment, at least 60% of the flotation volume in the flotation line 10 comprises a mechanical agitator 70. For example, depending on the aggregate volume of the flotation cells in the flotation line 10, and the volume of individual flotation cells 110, 120, 130, 200 within the flotation line 10, 33% of the flotation cells, 40% of the flotation cells, 50% of the flotation cells, or 67% of the flotation cells, or 75% of the flotation cells, may comprise a mechanical agitator 70.

[0177] The flotation line 10 may be preceded by other processes such as grinding, classification, screening, heavy-medium process, coarse particle recovery process, spirals, and other separation processes; and other flotation processes. A number of processes may follow the flotation line 10, such as regrinding, cleaner or other flotation processes, centrifuging, filtering, screening or dewatering.

[0178] According to another aspect of the invention, the flotation line 10 may be used in recovering particles comprising a valuable material suspended in slurry. In an embodiment, the use may be directed to recovering particles comprising nonpolar minerals such as graphite, sulphur, molybdenite, coal, talc.

[0179] According to another embodiment, the use may be directed to recovering particles comprising polar minerals.

[0180] In a further embodiment, the use is directed to recovering particles from minerals having a Mohs hardness of 2 to 3, such as galena, sulfide minerals, PGMs, REO minerals. In a yet further embodiment, the use is specifically directed to recovering particles comprising platinum.

[0181] In a further embodiment, the use is directed to recovering particles comprising copper from mineral particles having a Mohs hardness of 3 to 4. In a yet further embodiment, the use is specifically directed to recovering particles comprising copper from low grade ore.

[0182] The flotation line 10 described herein is particularly suitable for, but not limited to, use in recovering valuable mineral containing ores, where the mineral ore particles comprise copper (Cu), zinc (Zn), iron (Fe), pyrite, or a metal sulfide such as gold sulfide. Mineral ore particles comprising other valuable mineral such as Pb, Pt, PGMs (platinum group metals Ru, Rh, Pd, Os, Ir, Pt), oxide mineral, industrial minerals such as Li (i.e. spodumene), petalite, and rare earth minerals may also be recovered according to the different aspects of this invention.

[0183] The flotation line 10 is suitable for use in recovering mineral ore particles comprising a valuable mineral, particularly from low grade ore. The flotation line 10 is particularly suitable for recovering mineral ore particles comprising Cu from low grade ore. The flotation line 10 is also suitable for recovering mineral ore particles comprising Fe by reverse flotation.

[0184] According to a further aspect of the invention, a flotation plant comprises a flotation line 10 according to this specification. In an embodiment, the flotation plant may comprise at least two flotation line 10. In an embodiment, the flotation plant may comprise at least three flotation lines 10. In an embodiment, the flotation plant may comprise at least one first flotation line 10 for the recovery of a first concentrate, and at least one second flotation line 10 for the recovery of a second concentrate.

[0185] The flotation plant may comprise a flotation line 10 arranged to recover particles comprising Cu from minerals having a Mohs hardness from 3 to 4. In particular, such a flotation line 10 may be arranged to recover particles comprising Cu from low grade ore. Alternatively or additionally, the flotation plant may comprise a flotation line 10 arranged to recover particles from minerals having a Mohs hardness of 2 to 3, such as galena, sulfide minerals, PGMs and/or REO minerals. In particular, such a flotation line 10 may be arranged to recover particles comprising Pt.

[0186] The flotation plant may further comprise an arrangement for further treating the mineral ore particles suspended in slurry so that the second concentrate is different from the first concentrate. In an embodiment, the arrangement for further treating the mineral ore particles may be a grinding step disposed between a first flotation line 10 and a second flotation line 10. In an embodiment, the arrangement for further treating the mineral ore particles may be an arrangement for the addition of flotation chemicals, disposed between a first flotation line 10 and a second flotation line 10.

[0187] The embodiments described hereinbefore may be used in any combination with each other. Several of the embodiments may be combined together to form a further embodiment. An arrangement, a method, a plant or a use, to which the disclosure is related, may comprise at least one of the embodiments described hereinbefore. 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 invention and its embodiments are thus not limited to the examples described above; instead they may vary within the scope of the claims.