FLOTATION CELL

Abstract

A flotation cell for treating particles suspended in slurry. The flotation cell includes a fluidized bed; a recovery zone at an upper part of the flotation cell; a launder lip and a recovery launder; a tailings outlet arranged below the recovery launder; and a first feed inlet arranged to supply a primary slurry feed comprising fresh slurry into the fluidized bed at a first position. The flotation cell has a height measured from the bottom of the flotation cell to the launder lip. The flotation cell includes an agitator arranged adjacent to the bottom of the fluidized bed.

Claims

1. A flotation cell (1) for treating particles suspended in slurry and for separating the slurry into underflow (400) and overflow (500), the flotation cell comprising a fluidized bed (10) formed by a fluid feed (11) configured to supply a fluid to the flotation cell, and by a flotation gas feed configured to supply flotation gas, in which fluidized bed flotation gas bubbles adsorb to hydrophobic particles to form gas bubble-particle agglomerates that rise toward the top of the flotation cell; a recovery zone (20) at an upper part (13) of the flotation cell, configured to collect the gas bubble-particle agglomerates rising in the fluidized bed; a launder lip (26) and a recovery launder (24) arranged at the top of the flotation cell, and arranged to remove particles collected in the recovery zone from the flotation cell as overflow; a tailings outlet (12) arranged below the recovery launder, and arranged to remove non-collected particles descending from the recovery zone as underflow; and a first feed inlet (14) arranged to supply a primary slurry feed (100) comprising fresh slurry into the fluidized bed at a first position (P); wherein the flotation cell has a height (H) measured from the bottom (110) of the flotation cell to the launder lip, characterized in that the flotation cell comprises an agitator (18) arranged adjacent to the bottom of the flotation cell.

2. The flotation cell according to claim 1, characterized in that the agitator (18) is arranged to create a flow of slurry directed towards a perimeter (16) of the flotation cell (1) and substantially perpendicular to the supply of fluid from the fluid feed (11).

3. The flotation cell according to claim 1 or 2, characterized in that the agitator (18) is a non-aspirating agitator.

4. The flotation cell according to any one of the preceding claims, characterized in that the agitator (18) is a mechanical agitator comprising an impeller.

5. The flotation cell according to any one of the preceding claims, characterized in that the recovery zone (20) is arranged above the fluidized bed (10).

6. The flotation cell according to any one of the preceding claims, characterized in that the recovery zone (20) is arranged at an upper part (19) of the fluidized bed (10).

7. The flotation cell according to any one of the preceding claims, characterized in that the recovery zone (20) comprises a froth layer (25) at the top of the flotation cell (1).

8. The flotation cell according to any one of claims 1 to 6, characterized in that the recovery zone (20) comprises no froth layer (25) at the top of the flotation cell, and the flotation cell is arranged to be operated with constant slurry overflow.

9. The flotation cell according to any one of the preceding claims, characterized in that the primary slurry feed (100) is arranged to be fed into the fluidized bed (10) at a first position (P) within an upper 50% (½ H) of the flotation cell height and higher than the tailings outlet (12).

10. The flotation cell according to any one of the preceding claims, characterized in that the primary slurry feed (100) is arranged to be fed into the flotation cell at a first position (P) within an upper 30% of the flotation cell height (H).

11. The flotation cell according to any one of the preceding claims, characterized in that the primary slurry feed (100) is arranged to be fed into the recovery zone (20).

12. The flotation cell according to any one of the preceding claims, characterized in that the primary slurry feed (100) is arranged to be fed into the fluidized bed (10) so that the primary slurry feed has a flow direction counter-current to the rising bubble-particle agglomerates.

13. The flotation cell according to any one of claims 1 to 11, characterized in that the primary slurry feed (100) is arranged to be fed into the fluidized bed (10) from a perimeter (16) of the flotation cell (1) so that the primary slurry feed has a flow direction substantially perpendicular to the rising bubble-particle agglomerates.

14. The flotation cell according to any one of the preceding claims, characterized in that the flotation gas feed comprises gas infeed spargers.

15. The flotation cell according to claim 14, characterized in that the gas infeed spargers are arranged radially around a perimeter (16) of the flotation cell (1) below the fluidized bed (10).

16. The flotation cell according to claim 14, characterized in that the gas infeed spargers are arranged radially around a perimeter (16) of the flotation cell (1) at a height within the fluidized bed (10).

17. The flotation cell according to any one of the preceding claims, characterized in that it further comprises a second feed inlet (15) arranged to supply a secondary slurry feed (200), comprising at least slurry recirculated from a flotation cell (1, 2), into the fluidized bed (10) at a second position (S) below the first position (P), so as to contribute to the formation of the fluidized bed.

18. The flotation cell according to claim 17, characterized in that the secondary slurry feed (200) is arranged to be fed into the fluidized bed (10) so that the secondary slurry feed has a flow direction counter-current to the rising bubble-particle agglomerates.

19. The flotation cell according to claim 17, characterized in that the secondary slurry feed (200) is arranged to be fed into the fluidized bed (10) from the perimeter (16) of the flotation cell (1) so that the secondary slurry feed has a flow direction substantially perpendicular to the rising bubble-particle agglomerates.

20. The flotation cell according to claim 17, characterized in that the secondary slurry feed (200) is arranged to be fed into the fluidized bed (10) so that the secondary slurry feed has a flow direction concurrent to the rising bubble-particle agglomerates.

21. The flotation cell according to any one of the claims 17 to 20, characterized in that the second feed inlet (15) comprises the fluid feed (11).

22. The flotation cell according to any one of claims 17 to 21, characterized in that the secondary slurry feed (200) comprises slurry recirculated from the flotation cell (1) via a recirculation circuit (3), and obtained at a third position (R) which is arranged lower than the launder lip (26) and higher than the first position (P).

23. The flotation cell according to any one of claims 17 to 21, characterized in that the secondary slurry feed (200) comprises slurry recirculated from the flotation cell (1) via a recirculation circuit (3), and obtained at a third position (R) which is arranged lower than the first position (P).

24. The flotation cell according to claim 22 or 23, characterized in that the recirculation circuit (3) comprises a pump (30) arranged to intake a slurry fraction from the third position (R) and to forward the slurry fraction into the second feed inlet (15) as secondary slurry feed (200).

25. The flotation cell according to any one of claims 22 to 24, characterized in that the recirculation circuit (3) comprises a third feed inlet (31) for introducing a feed of slurry (300) into the secondary slurry feed (200) prior to the secondary slurry feed being fed into the fluidized bed (10) via the second feed inlet (15).

26. The flotation cell according to any one of the claims 22 to 25, characterized in that the secondary slurry feed (200) comprises slurry recirculated from a further flotation cell (2) separate to the flotation cell (1).

27. The flotation cell according to any one of the preceding claims, characterized in that the tailings outlet (12) is arranged below a second feed inlet (15), arranged to supply a secondary slurry feed (200) comprising at least slurry recirculated from a flotation cell (1, 2) into the fluidized bed (10), at a second position (S) below the first position (P).

28. Use of the flotation cell according to any one of claims 1 to 27 in recovering a valuable material suspended in slurry.

29. The use according to claim 28, in recovering particles comprising Cu from low grade ore.

30. A method for treating particles suspended in slurry and for separating the slurry into underflow (400) and overflow (500) in a flotation cell (1) according to any one of claims 1 to 27, characterized in that the slurry below a fluidized bed (10) is agitated.

31. The method according to claim 30, characterized in that by agitating, a flow of slurry directed towards a perimeter (16) of the flotation cell (1) and substantially perpendicular to the supply of fluid from a fluid feed (11) is created.

32. The method according to claim 30 or 31, characterized in that no flotation gas is supplied into the fluidization bed (10) by the agitating.

33. The method according to any one of claims 30 to 32, characterized by feeding flotation gas into the flotation cell (1) below the fluidized bed (10).

34. The method according to any one of claims 30 to 32, characterized by feeding flotation gas into the flotation cell (1) at a height within the fluidized bed (10).

35. The method according to any one of claims 30 to 34, characterized by feeding the primary slurry feed (100) into the fluidized bed (10) so that it has a flow direction divergent from the rising bubble-particle agglomerates.

36. The method according to any one of claims 30 to 35, characterized by the primary feed (100) comprising at least 20 w-% particles having a size of at least 300 μm.

37. The method according to any one of claims 30 to 37, characterized by feeding a secondary slurry feed (200), comprising at least slurry recirculated from a flotation cell (1, 2), into the fluidized bed (10), so as to contribute to the formation of the fluidized bed.

38. The method according to claim 37, characterized by the secondary slurry feed (200) comprising fine particles having a P80 50% or less of the P80 of the primary slurry feed (100).

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0090] 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:

[0091] FIGS. 1-3 present vertical cross-sectional views of embodiments of the flotation cell according to the invention, and

[0092] FIG. 4 shows two flotation cells of which at least one, flotation cell 1, is a flotation cell according to the invention.

DETAILED DESCRIPTION

[0093] Reference will now be made in detail to the embodiments of the present disclosure, an example of which is illustrated in the accompanying drawing.

[0094] The description below discloses some embodiments in such a detail that a person skilled in the art is able to utilize the flotation cell, its use and the method 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.

[0095] For reasons of simplicity, item numbers will be maintained in the following exemplary embodiments in the case of repeating components. Directions of flow are indicated with arrows.

[0096] The enclosed FIGS. 1-4 illustrate a flotation cell 1 in some detail. The figures are not drawn to proportion, and many of the components of the flotation cell 1 are omitted for clarity.

[0097] The flotation cell 1 according to the invention is 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 (valuable) mineral.

[0098] The flotation cell 1 comprises a fluidized bed 10 with a fluid feed 11 for supplying a fluid into the flotation cell to form and maintain a fluidized bed 10. In the fluidized bed 10, flotation gas bubbles adsorb to hydrophobic particles comprising valuable material to form bubble-particle agglomerates. The bubble-particle agglomerates rise toward an upper part 13 of the flotation cell 1 in the fluidized bed 10. The flotation cell 1 has a height H, measured from a bottom 110 of the flotation cell 1 to a launder lip 26.

[0099] The flotation cell 1 comprises a flotation gas feed for supplying flotation gas. In an embodiment, the flotation gas feed comprises gas infeed spargers. The gas infeed spargers may be arranged radially around a perimeter 16 of the flotation cell 1, below the fluidized bed 10. In an alternative embodiment, the gas infeed spargers are arranged radially around the perimeter 16 of the flotation cell 1 at a height within the fluidized bed 10. The gas infeed spargers are in both instances thus arranged to supply flotation gas through a sidewall 17 of the flotation cell 1.

[0100] The flotation gas feed may also, alternatively or additionally, be incorporated into the fluid feed 11. Alternatively or additionally, the flotation gas feed may be incorporated into a first feed inlet 14 which supplies a primary slurry feed 100 into the flotation cell 1. Alternatively or additionally, the flotation gas feed may be incorporated into a second feed inlet 15 which supplies a secondary slurry feed 200 into the fluidized bed 10.

[0101] The flotation cell 1 further comprises a recovery zone 20 arranged at the upper part 13 of the flotation cell, and configured to collect the bubble-particle agglomerates rising in the fluidized bed 10. The recovery zone 20 may be arranged above the fluidized bed. Alternatively, the recovery zone 20 may be arranged at an upper part 19 of the fluidized bed 10.

[0102] The bubble-particle agglomerates ascending in the fluidized bed 10 become transported to the recovery zone 20. The recovery zone 20 may comprise a froth layer 25 at the top of the flotation cell 1. The recovery zone 20 floats the bubble-particle agglomerates rising from the fluidized bed 10 to the froth layer 25. Alternatively, the recovery zone 20 may comprise no discernible froth layer, in which case the flotation cell is arranged to be operated with constant, and intentional, slurry overflow, i.e. as an overflow flotation cell.

[0103] A recovery launder 24 and the launder lip 26 are disposed at the top of the flotation cell 1, and arranged to remove particles collected in the recovery zone 20 as overflow 500 comprising a concentrate of desired (valuable) material. The recovery launder 24 may be a perimeter launder, with a launder lip 26 surrounding the perimeter 16 of the flotation cell 1, at the top of the flotation cell 1, over which launder lip 26 the collected particles flow into the recovery launder 24, as is known in the art.

[0104] A tailings outlet 12 is arranged below the recovery launder 24, and arranged to remove non-collected particles descending from the recovery zone 20 as underflow 400. The tailings outlet 12 may arranged in the form of a perimeter tailings launder continuously surrounding the entire perimeter 16 of the flotation cell (FIGS. 1, 2). Alternatively, the tailings outlet 12 may be sectional, i.e. not continuous around the perimeter 16. In yet an alternative embodiment, the tailings outlet 12 may comprise a simple outlet or opening at the perimeter of the flotation cell 1 (FIG. 3). The tailings outlet 12 may be located below the second feed inlet 15.

[0105] An agitator 18 is arranged disposed adjacent to the bottom 110 of the flotation cell, that is, at or near a bottom 110 of the flotation cell 1. The agitator may be arranged so that it is disposed within the fluidized bed 10 in the flotation cell 1. For example, in case of very low-intensity agitation and relatively strong flow of fluid from the fluid feed 11, it may be possible to create and maintain a fluidized bed 10 already at very near the bottom 110 of the flotation cell 1, so that the mixing action of the agitator 18 does not disrupt the fluidized bed. Alternatively, the agitator may be arranged below the fluidized bed 10.

[0106] The agitator 18 is arranged to create a flow of slurry directed towards the perimeter 16 of the flotation cell 1 so that the flow is substantially perpendicular to the supply of fluid from the fluid feed 11. The agitator 18 is further arranged to create a sufficiently slow or inert flow of slurry so as to not disturb the fluidized bed 10. The sideways directed, relatively calm flow ensures that the stability of the fluidized bed 10 can be maintained, and thus the probability of collisions between flotation gas bubbles and particles comprising valuable material kept at a high level.

[0107] In an embodiment, the agitator 18 is a non-aspirating agitator, i.e. the agitator 18 comprises no flotation gas supply or a flotation gas generator, and the agitating/mixing is done without gas generation or gas supply. The agitator 18 may comprise an impeller. The agitator 18 may, for example, be a mechanical agitator or mixer comprising a stator and a rotor, and operational equipment and system as is known in the art.

[0108] The primary slurry feed 100 comprises fresh slurry, which may originate from a grinding step or grinding arrangement, from underflow or tailings of another flotation cell or another part of a flotation arrangement or flotation line of which the flotation cell 1 is a part. In an embodiment, the primary slurry feed 100 comprises fresh slurry that has not been classified or fractioned after grinding. In an embodiment, the primary slurry feed 100 comprises coarse particles, for example ore particles having a P80 of 500-600 μm. In an embodiment, at least 20 w-% of the particles in the primary slurry feed 100 have a size of at least 300 μm.

[0109] The primary slurry feed 100 is fed into the flotation cell 1 by the first feed inlet 14. The primary slurry feed 100 is arranged to be fed into the flotation cell 1 at a first position P. The first position P may, in an embodiment, be located within an upper 50% ½H of the flotation cell height H, and higher than the tailings outlet 12 (FIG. 1). In an embodiment, the primary slurry feed 100 is arranged to be fed into the flotation cell 1 at a position P within an upper 30% of the flotation cell height H (FIG. 2). In an embodiment, the primary slurry feed 100 is arranged to be fed into the recovery zone 20. In an embodiment, the primary slurry feed 100 is arranged to be fed into the froth layer 25 of the flotation cell 1 (FIG. 3).

[0110] In an embodiment, the first feed inlet 14 is arranged at the centre C of the flotation cell 1, which is also the centre of the fluidized bed 10 and the recovery zone 20 (see FIG. 4). In an embodiment, the first feed inlet 14 comprises a circular section through which the primary slurry feed 100 is fed into the flotation cell 1. The circular section encompasses the centre C of the flotation cell 1 and is arranged to distribute the primary slurry feed 100 evenly around the centre C of the flotation cell 1. The circular section may for example comprise a circular trough or pipe/tube, which may have an open upper side, or comprise openings, so that the primary slurry feed 100 led into the circular section may flow through the open upper side or the openings in a controlled manner.

[0111] In an embodiment, the primary slurry feed 100 is arranged to be fed into the flotation cell 1/fluidized bed 10 so that it has a flow direction counter-current to the rising bubble-particle agglomerates, as well as the direction of flow of the fluid fed into the fluidized bed 10 by the fluid feed 11 (see FIG. 1). The first feed inlet 14 may comprise a sparger or a number of spargers. Any other suitable feed inlet such as a downcomer or a pipe or conduit may be used as the first feed inlet 14.

[0112] Alternatively, the primary slurry feed 100 may be arranged to be fed into the flotation cell 1/fluidized bed 10 from the perimeter 16 of the flotation cell 1 so that the primary slurry feed 100 has a flow direction substantially perpendicular to the rising bubble-particle agglomerates (see FIG. 2). Accordingly, the first feed inlet 14 may comprise a sparger assembly 140 arranged into a sidewall 17 of the flotation cell 1, the sparger assembly 140 arranged to create flotation gas bubbles, to cause attachment of flotation gas bubbles onto particles in the primary slurry feed 100, and to introduce the primary slurry feed 100 into the flotation cell 1/fluidized bed 10. The sparger assembly 140 may comprise a number of spargers arranged radially around the perimeter 16 of the flotation cell 1, so that each sparger is evenly spaced from each other.

[0113] The spargers may be cavitation spargers, jetting spargers or Venturi spargers, and thus the sparger assembly 140 and the first feed inlet 14 may comprise flotation gas feed as explained above.

[0114] The sparger assembly 140, i.e. the spargers, may also serve in generating flotation gas bubbles with an appropriate size distribution by injecting flotation gas into the primary slurry feed 100. For example, a jetting sparger (such as SonicSparger™ Jet), based on ultrasonic injection of air or air and water, may be utilized. Another example of a sparger is a cavitation or Venturi sparger (such as SonicSparger™ Vent), the operation of which is based on the Venturi principle which is highly efficient in generating large amount bubbles with relatively small size (0.3-0.9 mm). In a cavitation sparger, a recirculate of slurry from the flotation cell is forced through the sparger to generate bubbles through cavitation.

[0115] Also any other suitable type of feed inlets known in the art may be used as the first feed inlet 14.

[0116] A secondary slurry feed 200 may be arranged to be fed into the fluidized bed 10 at a second position S below the first position P, via the second feed inlet 15.

[0117] The secondary slurry comprises at least slurry recirculated from a flotation cell 1, 2. The secondary slurry feed 200 contributes to the formation of the fluidized bed 10. The slurry recirculated from the flotation cell 1 may be obtained at a third position R, which is located between the recovery launder 24 and the tailings outlet 12. In an embodiment, the third position R is arranged lower than the launder lip 26 and higher than the first position P at which the primary slurry feed 100 is arranged to be fed into the flotation cell 1. Alternatively, the secondary slurry feed 200 may be obtained at the third position R arranged lower than the first position P.

[0118] In an embodiment, alternatively or additionally, the secondary slurry feed 200 comprises slurry 300 recirculated from a further flotation cell 2, separate to the flotation cell 1 (FIG. 4). This recirculated slurry 300 may for example comprise a slurry fraction taken similarly from a position S of the further flotation cell 2, or it can comprise overflow or underflow from a further flotation cell, or a combination of overflow or underflows from several further flotation cells, and having a similar particle size distribution as the slurry in the fluidized bed 10 of the flotation cell 1.

[0119] In yet another embodiment, alternatively or additionally, the secondary slurry feed 200 may comprise a feed of slurry 300 from another part of the flotation line or flotation arrangement, for example from classification, fractionation or grinding. The feed of slurry 300 may, for example, be fresh slurry similar to the fresh slurry comprised by the primary slurry feed 100. In an embodiment, the secondary slurry feed 200 comprises fine particles having a P80 50% or less of the P80 of the primary slurry feed 100. For example, the secondary slurry feed 200 may comprise fine particles having a P80 of approximately 200 μm.

[0120] In general, recirculating slurry in the manner as described in connection with the secondary feed 200, it may be possible to control the mass balance of the flotation cell 1 in an efficient manner.

[0121] The secondary slurry feed 200 is fed into the flotation cell 1, into the fluidized bed 10 by the second feed inlet 15. The secondary slurry feed 200 contributes to the formation of the fluidized bed 10, and may thus decrease the need of fresh water in the fluid via the fluid feed 11. The secondary slurry feed 200 may have a flow direction divergent from the rising bubble-particle agglomerates in the flotation cell 1. Alternatively, the secondary slurry feed 200 may have a flow direction concurrent with the rising bubble-particle agglomerates.

[0122] In an embodiment, the secondary slurry feed 200 is arranged to be fed into the flotation cell 1/fluidized bed 10 so that the secondary slurry feed 200 has a flow direction counter-current to the rising bubble-particle agglomerates (see FIG. 3), as well as the direction of flow of the fluid fed into the flotation cell 1 by the fluid feed 11. In this case the second feed inlet 15 may comprise a sparger or a number of spargers. Any other suitable feed inlet such as a downcomer or a pipe or conduit may be used as the second feed inlet 15.

[0123] In an alternative embodiment, the secondary slurry feed 200 is arranged to be fed into the flotation cell 1/fluidized bed 10 from the perimeter 16 of the flotation cell 1 so that the flow direction of the secondary slurry feed 200 is substantially perpendicular to the rising bubble-particle agglomerates (see FIGS. 1, 2). In this case, the second feed inlet 15 may comprise a number of feed openings 150 arranged into a sidewall 17 of the flotation cell 1. The feed openings 150 may be arranged into the sidewall 17 evenly distributed along the perimeter 16 of the flotation cell 1 so as to form a circle or gird of evenly-spaced apart feed openings 150.

[0124] In a yet another alternative embodiment, the secondary slurry feed 200 is arranged to be fed into the flotation cell 1/fluidized bed 10 so that the secondary slurry feed 200 has a flow direction concurrent to the rising bubble-particle agglomerates. For example, the second feed inlet 15 may be incorporated with the fluid feed 11, i.e. the second feed inlet 15 comprises the fluid feed 11, and the secondary slurry feed 200 fed into the flotation cell 1/fluidized bed 10 from the bottom 110 of the flotation cell 1. It is also possible that the second feed inlet 15 comprises the fluid feed 11 also in the embodiments where the flow direction of the secondary slurry feed 200 is divergent from the rising bubble-particle agglomerates, i.e. also when the second feed inlet 15 is arranged at or via the perimeter 16 and/or sidewall 17 of the flotation cell 1. In some cases, it may be possible to significantly reduce the amount of fluid needed to maintain the fluidized bed 10 due to the employment of secondary slurry feed 200 in this purpose, in the manner described above. In all of the above embodiments, the second feed inlet 15 and/or the feed openings 150 may comprise for example spargers, such as cavitation spargers, jetting spargers or Venturi spargers, and thus the feed openings 150 (and the second feed inlet 15) may comprise flotation gas feed as explained above.

[0125] The feed openings 150, such as spargers, may also serve in generating flotation gas bubbles with an appropriate size distribution by injecting flotation gas into the secondary slurry feed 200. For example, a jetting sparger (such as SonicSparger™ Jet), based on ultrasonic injection of air or air and water, may be utilized. Another example of a sparger is a cavitation or Venturi sparger (such as SonicSparger™ Vent), the operation of which is based on the Venturi principle which is highly efficient in generating large amount bubbles with relatively small size (0.3-0.9 mm). In a cavitation sparger, a recirculate of slurry from the flotation cell is forced through the sparger to generate bubbles through cavitation.

[0126] Also any other suitable type of feed inlets known in the art may be used as the second feed inlet 15 and/or feed openings 150.

[0127] In all cases where spargers may be used to feed primary slurry feed, secondary slurry feed, and/or flotation gas into the flotation cell, there are many benefits that may improve the flotation performance:

[0128] By disposing a sparger or a number of spargers into a flotation cell according to the invention, the probability of collisions between flotation gas bubbles, as well as between gas bubbles and particles may be increased. Having a number of spargers may ensure an improved distribution of flotation gas bubbles within a flotation cell, and the bubbles exiting the blast tubes are distributed evenly throughout the flotation cell, the distribution areas of individual spargers have the possibility of intersecting each other and converging, thus promoting an extensively even flotation gas bubble distribution into the flotation cell, which in turn may affect the recovery of particles comprising valuable material beneficially, and also contribute to the aforementioned even and thick froth layer. When there are several spargers, collisions between flotation gas bubbles and/or particles in the slurry infeed from spargers are promoted as the different flows intermingle and create local mixing subzones. As the collisions are increased, more bubble-particle agglomerates are created and captured into the froth layer, and therefore recovery of valuable material may be improved.

[0129] By generation of fine flotation gas bubbles, by bringing them into contact with the particles, and by controlling the flotation gas bubble-particle agglomerates-liquid mixture of slurry, it may be possible to maximize the recovery of hydrophobic particles into the recovery zone and into the flotation cell overflow or concentrate, thus increasing the recovery of desired material irrespective of its particle size distribution within the slurry.

[0130] The number of spargers directly influences the amount of flotation gas that can be dispersed in the slurry. In conventional froth flotation, dispersing an increasing amount of flotation gas would lead to increased flotation gas bubble size. For example, in a Jameson cell, an air-to-bubble ratio of 0.50 to 0.60 is utilized. Increasing the average bubble size will affect the bubble surface area flux (S.sub.b) detrimentally, which means that recovery may be decreased. In a flotation cell according to the invention, with spargers, significantly more flotation gas may be introduced into the process without increasing the bubble size or decreasing Sb, as the flotation gas bubbles created into the slurry infeed remain relatively small in comparison to the conventional processes. On the other hand, by keeping the number of spargers as small as possible, costs of refitting existing flotation cells, or capital expenditure of setting up such flotation cells, may be kept in check without causing any loss of flotation performance of the flotation cells.

[0131] By arranging a sparger assembly evenly and radially around the perimeter of the flotation cell, the introduction of primary slurry feed may be achieved evenly throughout the flotation cell, which improves the flotation efficiency further. Spargers may, at the same time as acting as a feed inlet, serve in providing flotation gas feed into the flotation cell, for example by introducing flotation gas bubbles, e.g. fine bubbles or microbubbles directly into the slurry as it is delivered into the flotation cell via the spargers of the sparger assembly.

[0132] By microbubbles herein is meant flotation gas bubbles falling into a size range of 1 μm to 1.2 mm, introduced into the slurry by a specific microbubble generator. More specifically, depending on the manner in which the microbubble generator is arranged, the majority of the microbubbles fall within a specific size range.

[0133] Jetting spargers may be utilized around the perimeter of the flotation cell for the infeed of primary slurry feed as well as direct introduction of microbubbles with a size range of 0.5 to 1.2 mm into the slurry. Especially if microbubbles are introduced in to the fluidized bed, they may have higher probability of colliding with finer particles in the mixing zone, thus improving the reporting of also those particles into the froth zone. Cavitation spargers or Venturi spargers may be utilized to introduce primary slurry feed, additional fluid, e.g. water, and air or other flotation gas into the flotation cell by arranging cavitation spargers around the perimeter of the flotation cell. Cavitation spargers may be used to introduce microbubbles with a size range of 0.3 to 0.9 mm. Flotation air/gas, or flotation air/gas and water, respectively, can be introduced into the spargers to create microbubbles with a size range of 0.3 to 1.2 mm, injected directly into the flotation cell. The microbubbles may especially attach to the finer mineral ore particles, while the “normal” flotation gas bubbles present in the fluidized bed adhere to coarser particles. Thereby, an increase the overall recovery of valuable mineral may be achieved.

[0134] In contrast, “normal” flotation gas bubbles utilized in froth flotation display a size range of approximately 0.8 to 2 mm, and are introduced into the slurry by or via a mechanical agitator or by/via flotation gas inlet(s). Furthermore, these flotation gas bubbles may have a tendency to coalesce into even larger bubbles during their residence in the mixing zone where collisions between mineral ore particles and flotation gas bubbles, as well as only between flotation gas bubbles take place. As microbubbles are introduced into a flotation cell outside the turbulent mixing zone, such coalescence is not likely to happen with microbubbles, and their size may remain smaller throughout their residence in the flotation cell, thereby affecting the ability of the microbubble to catch fine ore particles.

[0135] The secondary slurry feed 200 comprising slurry recirculated from the flotation cell 1 may be recirculated via a recirculation circuit 3. The recirculation circuit 3 may comprise a pump 30 arranged to intake a slurry fraction from the third position R, and to forward the slurry fraction into the second feed inlet 15 as secondary slurry feed 200, or as a part of the secondary slurry feed 200. In an embodiment, the recirculation circuit 3 comprises a third feed inlet 31 for introducing a feed of slurry 300 into the secondary slurry feed 200 prior to the secondary slurry feed 200 being fed into the flotation cell 1 via the second feed inlet 15. As described above, the feed of slurry 300 may comprise any suitable additional fraction of slurry taken from another part of a flotation line or arrangement of which the flotation cell 1 is a part.

[0136] In an embodiment, the primary slurry feed 100 is arranged to be fed into the froth layer 25 of the flotation cell 1, i.e. the first position P at which the primary slurry feed 100 is introduced into the flotation cell 1 is arranged at the upper part 13 of the flotation cell, right at the height of the forth layer 25 (see FIG. 3). The first feed inlet 15 may, for example be arranged at one point at the perimeter 16 of the flotation cell 1. The recovery launder 24, in this case, may be an outlet arranged at another point at the perimeter 16, for example substantially opposite the first feed inlet 15. The secondary slurry 200 comprises slurry recirculated from the flotation cell 1 via a recirculation circuit 3, and obtained at the third position R which is arranged lower than the first position P. The secondary slurry feed 200 may have a flow direction divergent (counter-current, perpendicular) from the rising bubble-particle agglomerates, as is shown in FIG. 3, or a flow direction concurrent with the rising bubble-particle agglomerates.

[0137] The flotation cell 1 may have circular cross-section. The flotation cell 1 may have a diameter of at least 1.0 m, measured at the height of the second position S. The flotation cell 1 may have a diameter of over 2 m. The flotation cell may have a diameter between 2 to 8 m, for example 2.25 m; 3.5 m; 5 m; 6.75 m; or 7.8 m. The flotation 1 may also have a cross-section that is divergent from circular, e.g. rectangular or square. In case the cross-section is not circular, the diameter is measured as the maximum diagonal of the cross-sectional form.

[0138] The flotation cell 1 may have a substantially level bottom. The manner of feeding the primary slurry feed 100 and the secondary slurry feed 200 into the flotation cell 1 may help in minimizing the build-up of sediment at the bottom 110 of the flotation cell 1. Therefore no special solutions, such as conical, slanting or funnel-like bottom structures may be required, as is the case in conventional fluidized bed flotation cells. Further, it may be possible to avoid arranging a cleaning hatch or other maintenance constructions at the bottom 110 of the flotation cell 1, thereby making its constructions easier and more cost-effective. Naturally also the need of performing maintenance operations may be decreased, thereby reducing operational costs.

[0139] The flotation cell 1 as defined above may be used in recovering a valuable material suspended in slurry. In a further embodiment, the use is specifically directed to recovering particles comprising copper from low grade ore.

[0140] According to another aspect of the invention, the method for treating particles suspended in slurry and for separating the slurry into underflow 400 and overflow 500 in a flotation cell 1 as described above comprises agitating the slurry below the fluidized bed F. In an embodiment, the agitation or by agitating, a flow of slurry is created, which is directed towards the perimeter 16 of the flotation cell 1, substantially perpendicular to the supply of fluid from the fluid feed 11. In an embodiment, the no flotation gas is generated or supplied by the agitating/agitation, i.e. it is a non-aspirating manner of agitating.

[0141] Flotation gas may be fed or provided into the flotation cell 1 below the fluidized bed 10, in the manner and by the features described above. Alternatively, flotation gas may be fed or provided into the flotation cell 1 at a height within the fluidized bed 10, that is via the sidewall 17 of flotation cell 1 at a height in which the fluidized bed 10 resides.

[0142] The primary slurry feed 100 may be fed into the flotation cell at a first position P on top of the fluidized bed 10—in the recovery zone 20, or in the froth layer 25—or into the fluidized bed F, via a first feed inlet 14, so that the primary slurry feed has a flow direction divergent from the rising bubble-particle agglomerates. The primary slurry feed 100 may be fed into the flotation cell 1/fluidized bed 10 so that is has a flow direction counter-current to the rising bubble-particle agglomerates, as explained above. Alternatively, the primary slurry feed 100 may be fed into the flotation cell 1/fluidized bed 10 from the perimeter 16 of the flotation cell 1 so that it has a flow direction substantially perpendicular to the rising bubble-particle agglomerates.

[0143] A secondary slurry feed 200 comprising at least slurry recirculated from a flotation cell may be fed into the fluidized bed 10 via a second feed inlet 15 so as to contribute to the formation of the fluidized bed 10.

[0144] In an embodiment, the secondary slurry feed 200 may fed into the fluidized bed 10 so that it has a flow direction counter-current to the rising bubble-particle agglomerates. In an alternative embodiment, the secondary slurry feed 200 may be fed into the fluidized bed 10 from the perimeter 16 of the flotation cell 1 so that it has a flow direction substantially perpendicular to the rising bubble-particle agglomerates. In an alternative embodiment, the secondary slurry feed 200 may be fed into the fluidized bed 10 so that it has a flow direction concurrent with the rising bubble-particle agglomerates.

[0145] 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. A flotation cell, a use, or a method, 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.