Blast tube, flotation cell, flotation line, diffuser device, and method for installing diffuser device into blast tube

Abstract

A blast tube (4) for introducing slurry infeed (100) into a flotation tank (10), wherein the blast tube (4) comprises an inlet nozzle (41) for feeding slurry infeed (100) into the blast tube (4); and at least one gas inlet (42) for gas (23); a gas chamber (5) for receiving the gas (23) from the at least one gas inlet (42), wherein the gas chamber (5) is located around the at least one inlet nozzle (41). The blast (4) further comprises a diffuser (6) for evenly distributing the gas (23) from the gas chamber (5) into the slurry infeed (100), and an elongated chamber (40) arranged to receive the slurry infeed (100). The diffuser (6) is arranged in connection with the gas chamber (5) and the diffuser (6) comprises at least one aperture (7) configured to distribute the gas (23) from the gas chamber (5) into the slurry infeed (100) as it is discharged from the inlet nozzle (41).

Description

[0001] BLAST TUBE , FLOTATION CELL, FLOTATION LINE , DIFFUSER DEVICE , AND METHOD FOR INSTALLING DIFFUSER DEVICE INTO BLAST TUBE

[0002] FIELD OF THE INVENTION

[0003] The current disclosure relates to a blast tube, a flotation line, a method for treating particles suspended in slurry, a diffuser device, and a method for installing or retrofitting a diffuser device into a blast tube .

[0004] BACKGROUND

[0005] Blast tubes are used for introducing slurry infeed into a flotation tank. However, blast tubes may further be developed to improve recover of floating minerals .

[0006] SUMMARY

[0007] This summary is provided to introduce a selection of concepts in a simplified form that are further described below in the detailed description. This summary is not intended to identify key features or essential features of the claimed subj ect matter, nor is it intended to be used to limit the scope of the claimed subj ect matter. The scope of protection sought for various embodiments of the present disclosure is set out by the independent claims .

[0008] According to a first aspect, a blast tube for introducing slurry infeed into a flotation tank is disclosed, wherein the blast tube comprises an inlet nozzle for feeding slurry infeed into the blast tube; at least one gas inlet for gas; a gas chamber for receiving the gas from the at least one gas inlet, wherein the gas chamber is located in close proximity to the at least one inlet nozzle; a diffuser for evenly distributing the gas from the gas chamber into the slurry infeed; and an elongated chamber arranged to receive the slurry infeed, wherein the diffuser is arranged in connection with the gas chamber; and the diffuser comprises at least one aperture configured to distribute the gas from the gas chamber into the slurry infeed as it is discharged from the at least one inlet nozzle . Uneven gas distribution around the blast tube top inlet nozzle may cause unsteady flow patterns inside the blast tube and hinder small bubble creation. Large changes in void fraction, for example big bubbles or portions of slurry infeed with entrained gas, may cause rapid changes in the flow velocity when they pass through the bottom outlet nozzle . Ideally the flow should be as homogeneous as possible . The diffuser may ensure that the gas is distributed evenly around the flowing j et . The diffuser may allow distribution of gas, such as air, more effi¬ ciently. It may also allow better control of the size of the gas bubbles in the infeed slurry.

[0009] According to an example embodiment of the first aspect, at least one aperture is arranged to point downwards parallel to the slurry infeed, to point vertically upwards against the slurry infeed, and / or to point sideways perpendicular to the slurry infeed. Small bubbles are formed when the infeed slurry travels fast through the compressed gas . The sideways or upwards located ap¬ ertures or holes, which point perpendicular to or against the slurry infeed may promote uneven flows in¬ side the blast tube . When the apertures are pointing downwards, gas flow may increase the relative speed of the slurry infeed.

[0010] According to an example embodiment of the first aspect, the at least one blast tube comprises a nozzle holder for holding the at least one inlet nozzle, wherein the gas chamber is arranged inside the nozzle holder, inside the elongated chamber, or outside the elongated chamber . The gas chamber may be located different places around or in close proximity to the inlet nozzle (s ) . Size of the gas chamber may depend on the place where it is located. For example, it is possible to create bigger gas chambers inside the elongated chamber or outside the elongated chamber than inside the nozzle holder . However, it may be easy to form the gas chamber inside the nozzle holder . The gas chamber located outside the elongated chamber is made of plastic, for example .

[0011] According to an example embodiment of the first aspect, when the gas chamber is arranged inside the nozzle holder, the gas chamber is configured to be formed between a nozzle holder inner wall, a nozzle holder outer wall, and a gas chamber bottom; when the gas chamber is arranged inside the elongated chamber, the gas chamber is configured to be formed between an upper part of an elongated chamber outer wall, the nozzle holder outer wall, a gas chamber top, and the gas chamber bottom; or when the gas chamber is arranged outside the elongated chamber, the gas chamber is configured to be formed by the upper part of the elongated chamber outer wall, the gas chamber bottom, the gas chamber top, and a gas chamber outer wall . The gas chamber may be placed where it is structurally easiest to build. Needed size of the gas chamber may also affect where it should be placed.

[0012] According to an example embodiment of the first aspect, when the gas chamber is arranged inside the nozzle holder, at least part of the gas chamber bottom and / or at least part of the nozzle holder inner wall comprises the diffuser; when the gas chamber is arranged inside the elongated chamber, at least part of the gas chamber bottom and / or at least part of the nozzle holder outer wall comprises the diffuser; or when the gas chamber is located outside the upper part of the elongated chamber, at least part of the elongated chamber outer wall comprises the diffuser. The diffuser may be placed in different parts of the gas chamber depending on what kind of gas flows are needed.

[0013] According to an example embodiment of the first aspect, the diffuser is configured to form a vertical cylinder in close proximity to or around the at least one inlet nozzle or below nozzle holder; and / or a horizontal disc inside the nozzle holder or around the nozzle holder . The cylindrical diffuser may enable the horizontally supplied gas to be evenly distributed around the inlet slurry. When the apertures are arranged at different heights of the cylindrical diffuser, air may also be distributed vertically from different heights . The disc like diffuser may enable downward gas flow to be evenly distributed. The apertures may be arranged at different distance of the center of the cylindrical diffuser to promote even gas flow.

[0014] According to an example embodiment of the first aspect, two or more apertures of the diffuser are arranged evenly around the diffuser for evenly distributing the gas . Arranging apertures evenly around the diffuser may allow the gas to be evenly distributed into the slurry infeed.

[0015] According to an example embodiment of the first aspect, a diameter of the at least one aperture is from 1 cm to 5 cm, or from 5 cm to 10. The openings or apertures must be large enough so that the slurry infeed does not block them, but small enough so that the gas bubbles can be kept at the desired size . Openings below 1 cm may allow the slurry infeed to block the openings and openings much bigger than 10 cm may create too large gas bubbles or unwanted uneven gas distribution.

[0016] According to an example embodiment of the first aspect, gas velocity through the at least one aperture is from 1 to 100 m / s . The gas velocity through the at least one aperture or hole may have effect to gas distribution and gas bubble formation. According to an example embodiment of the first aspect, the at least one blast tube further comprises an outlet nozzle configured to restrict flow of slurry infeed from the outlet nozzle .

[0017] According to an example embodiment of the first aspect, the at least one gas inlet is for pressurized gas .

[0018] According to a second aspect, a flotation cell for treating particles suspended in slurry and for separating the slurry into an and an overflow is disclosed, wherein the flotation cell comprises a flotation tank; a launder and a launder lip; and at least one blast tube according to any of the first aspects above for introducing slurry infeed into the flotation tank.

[0019] According to a third aspect, a flotation line comprising a number of fluidly connected flotation cells, wherein at least one of the flotation cells is a flotation cell according to the second aspect .

[0020] According to a fourth aspect, a method for introducing slurry infeed into a flotation tank with at least one blast tube is disclosed, wherein the at least one blast tube comprises at least one inlet nozzle; at least one gas inlet for gas; a gas chamber located at least partly in close proximity to the at least one inlet nozzle; a diffuser comprising at least one aperture, wherein the diffuser is arranged in connection with the gas chamber; and an elongated chamber arranged to receive the slurry infeed, wherein in the method at least one inlet nozzle feeds slurry infeed into the blast tube; the gas chamber receives the gas from the at least one gas inlet; the at least one aperture of the diffuser distributes the gas from the gas chamber into the slurry infeed as it is discharged from the at least one inlet nozzle .

[0021] According to a fifth aspect, a diffuser device for a blast tube is disclosed, wherein the diffuser device comprises a diffuser device bottom comprising an opening in the middle of the diffuser device bottom; a circular wall part around a perimeter of the diffuser device bottom; and a cylindrical diffuser comprising at least one aperture, wherein the diffuser is arranged vertically on top of the diffuser device bottom around the opening, wherein the diffuser device is configured to distribute gas through the at least one aperture of the diffuser into slurry infeed. The diffuser device may be used when building a new blast tube of a flotation cell or when retrofitting the diffuser device into an old blast tube .

[0022] According to an example embodiment of the fifth aspect, the diffuser device is configured to form a gas chamber with a nozzle holder of the blast tube, when the diffuser device is configured to be inserted or retrofitted into the blast tube; the diffuser device is configured to be inserted or retrofitted into the blast tube below a nozzle holder of the bast tube; and the diffuser device is configured to distribute the gas through the at least one aperture from the gas chamber into slurry infeed as it is discharged from an inlet nozzle of the flotation cell .

[0023] According to a sixth aspect, a method for installing or retrofitting a diffuser device according to any of the fifth aspects above into at least one blast tube of a flotation cell, wherein the diffuser device comprises a bottom having an opening in the middle of the bottom; a circular wall part around a perimeter of the bottom; and a cylindrical diffuser arranged vertically on top of the bottom around the opening, wherein the diffuser comprises at least one aperture, and wherein the at least one blast tube comprises at least one inlet nozzle for feeding slurry infeed into the blast tube; a nozzle holder for holding the at least one inlet nozzle; at least one gas inlet in the nozzle holder for gas; and an elongated chamber arranged to receive the slurry infeed; wherein the method comprises forming a blast tube by installing the diffuser device below the nozzle holder, wherein the diffuser device and the nozzle holder form a gas chamber; receiving the gas from the at least one gas inlet of the formed gas chamber; and distributing the gas from the gas chamber through the at least one aperture of the diffuser into the slurry infeed as it is discharged from the at least one inlet nozzle . Providing the diffuser device to the retrofitted blast tube means that existing blast tube may be used. Instead of exchanging the entire blast tube, flotation cell, or flotation line, the equipment is only partly renewed. Thereby, the described solutions may provide more sustainable technology with considerable environmental benefits compared to prior art solutions . One advantage of the described solutions is that the retrofitting may not be limited to a specific kind of blast tube, flotation cell, tank or line . The disclosed retrofitting method may be used in any existing blast tube, flotation cell, tank or line . The solution provides a way to reuse existing structure of the blast tube, flotation cell or line . Different adjustments may need to be made depending on the blast tube that is retrofitted. In some example solutions a larger part of the blast tube structure may need to be exchanged than in others . In any case, the solution may enable large capex savings since a considerable part of any apparatus may be reused .

[0024] BRIEF DESCRIPTION OF THE DRAWINGS

[0025] The present disclosure will be better understood from the following detailed description read in light of the accompanying drawings, wherein:

[0026] Fig. 1 shows an example of a flotation cell in a side view according to an example embodiment,

[0027] Fig. 2 shows an example of a blast tube comprising a gas chamber inside a nozzle holder according to an example embodiment, Figs . 3a to 3c show examples of blast tubes comprising a gas chamber inside an elongated chamber according to example embodiments,

[0028] Fig. 4 shows an example of a blast tube comprising a gas chamber outside an elongated chamber according to example embodiment,

[0029] Fig. 5a shows an example of a diffuser device seen above according to an example embodiment,

[0030] Fig. 5b shows an example of the diffuser device of figure 5a in a side view according to an example embodiment,

[0031] Fig. 5c shows an example of a blast tube comprising a diffuser device according to an example embodiment,

[0032] Figs . 6a and 6b show examples of a flotation line according to example embodiments,

[0033] Fig. 7 shows an example method for introducing slurry infeed into a flotation tank with at least one blast tube according to an example embodiment, and Fig. 8 shows an example method for installing or retrofitting a diffuser device into at least one blast tube according to an example embodiment .

[0034] DETAILED DESCRIPTION

[0035] Reference will now be made in detail to the embodiments of the present disclosure, an example of which is illustrated in the accompanying drawings .

[0036] The description below discloses some embodiments in such a detail that a person skilled in the art is able to utilize a blast tube, a flotation cell, a flotation line and methods 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 .

[0037] For reasons of simplicity, item numbers will be maintained in the following exemplary embodiments in the case of repeating components . According to an example embodiment, a blast tube for introducing slurry infeed into a flotation tank is disclosed. The blast tube may comprise an inlet nozzle for feeding slurry infeed into the blast tube, at least one gas inlet for gas, and a gas chamber for receiving gas from the at least one gas inlet . The fed gas may be pressurized gas . The blast tube may comprise the at least one gas inlet for pressurized gas . The gas chamber may be located at least partly in close proximity to the at least one inlet nozzle . The gas chamber may also be located at least partly around the at least one inlet nozzle . The blast tube may further comprise a diffuser for evenly distributing gas from the gas chamber into the slurry infeed, and an elongated chamber arranged to receive the slurry infeed. The blast tube may also comprise an outlet nozzle configured to restrict flow of slurry infeed from the outlet nozzle . The diffuser may be arranged in connection with the gas chamber . This means that at least one wall of the gas chamber comprises a diffuser . Thus, the diffuser forms one or two walls of the gas chamber . The diffuser may comprise at least one aperture configured to distribute the gas from the gas chamber into the slurry infeed as it is discharged from the inlet nozzle . The diffuser may comprise a body part and at least one aperture or hole . The body part may have a disc-like or cylindrical shape .

[0038] The diffuser may evenly distribute flotation gas, such as air, to a slurry j et or slurry infeed to maximize bubble creation efficiency and improve steady state conditions in a blast tube or downcomer . The diffuser may be a ring-like or disk-like perforated plate . The perforated plate may be located horizontally in close proximity to or around at least one inlet nozzle . The diffuser may also be a circular tube or cylinder comprising perforations . The circular cylinder may be located vertically in close proximity to or around at least one inlet nozzle . The diffuser may be located in close proximity to or around the slurry feed means such as at least one inlet nozzle . The diffuser may allow gas, for example air, to aerate slurry evenly through at least one hole or perforation of the perforated plate or circular cylinder . The diffuser may distribute evenly gas to slurry infeed to maximize bubble creation efficiency and improve steady state conditions in the blast tube . The diffuser comprising evenly located aperture (s) may ensure that the gas is distributed evenly around the flowing slurry infeed.

[0039] By a blast tube is meant a device in which flotation gas is introduced into slurry infeed, thereby creating finer flotation gas bubbles that are able to entrap also finer particles already during the bubble formation in the blast tube . The blast tube may be a dual high-shear device . In particular, a blast tube in a flotation cell according to the invention may operate under pressure, and no vacuum is needed.

[0040] A flotation cell is meant for treating mineral ore particles suspended in slurry by flotation. Thus, valuable metal-containing ore particles are recovered from ore particles suspended in slurry. By flotation line herein is meant a flotation arrangement where a number of flotation cells are arranged in fluid connection with each other so that the underflow of each preceding flotation cell is directed to the following or subsequent flotation cell as an infeed until the last flotation cell of the flotation line, from which the underflow is directed out of the line as tailings or rej ect flow. Slurry is fed through a feed inlet to the first flotation cell of the flotation line for initiating the flotation process . A flotation line may be a part of a larger flotation plant or arrangement containing one or more flotation lines . Therefore, a number of different pre-treatment and post-treatment devices or stages may be in operational connection with the components of the flotation arrangement, as is known to the person skilled in the art .

[0041] By a flotation cell is herein meant a tank or vessel in which a step of a flotation process is performed. A flotation cell is typically cylindrical in shape, the shape defined by an outer wall or outer walls . The flotation cells regularly have a circular crosssection. The flotation cells may have a polygonal, such as rectangular, square, triangular, hexagonal or pentagonal, or otherwise radially symmetrical cross-section, as well . The number of flotation cells may vary according to a specific flotation line and / or operation for treating a specific type and / or grade of ore, as is known to a person skilled in the art .

[0042] The flotation cell may be a froth flotation cell, such as a mechanically agitated cell, a column flotation cell, a self-aspirated pneumatic flotation cell, or a dual flotation cell . The flotation cell may also be a fluidized bed flotation cell, or an overflow flotation cell operated with constant slurry overflow.

[0043] All the flotation cells of a flotation line according to the invention may be of a single type, that is, rougher flotation cells in the rougher part, scavenger flotation cells in the scavenger part, and scavenger cleaner flotation cells of the scavenger cleaner flotation line may be of one single flotation cell type so that the flotation arrangement comprises only one type of flotation cells as listed above . Alternatively, a number of flotation cells may be of one type while other cells are of one or more type so that the flotation line comprises two or more types of flotation cells as listed above .

[0044] Depending on its type, the flotation cell may comprise a mixer for agitating the slurry to keep it in suspension. By a mixer is herein meant any suitable means for agitating slurry within the flotation cell . The mixer may be a mechanical agitator . The mechanical agitator may comprise a rotor-stator with a motor and a drive shaft . The cell may have agitators arranged higher up in the vertical direction of the cell, to ensure a sufficiently strong and continuous upwards flow of the slurry .

[0045] A flotation cell may comprise a bottom structure arranged on the bottom of the flotation tank, and having a shape that allows particles suspended in slurry to be mixed in a mixing zone created by the flow of slurry infeed from the outlet nozzles of the blast tubes over the bottom structure; and to settle down in a settling zone surrounding the bottom structure . Optionally, the bottom structure may have a shape that prevents buildup of solid materials, such as particles suspended in a slurry at the bottom of the flotation tank. The bottom structure may be for example a cone, a truncated cone, a pyramid, or a truncated pyramid.

[0046] By overflow herein is meant the part of the slurry collected into the launder of the flotation cell and thus leaving the flotation cell . Overflow may comprise froth, froth and slurry, or in certain cases, only or for the largest part slurry. In some embodiments, overflow may be a retain flow containing the valuable material particles collected from the slurry. In other embodiments, the overflow may be a rej ect flow. This is the case when the flotation arrangement, plant and / or method is utilized in reverse flotation.

[0047] By underflow herein is meant the fraction or part of the slurry which is not floated into the surface of the slurry in the flotation process . Eventually the underflow from the final flotation cell of a flotation line or a flotation arrangement may leave the entire arrangement as a tailings flow or final residue of a flotation plant .

[0048] By downstream herein is meant the direction concurrent with the flow of slurry towards the tailings ( forward current, denoted in the figures with arrows) , and by upstream herein is meant the direction counter current with or against the flow of slurry towards the tailings .

[0049] By concentrate herein is meant the floated part or fraction of slurry of ore particles comprising a valuable mineral . In normal flotation, concentrate is the part of the slurry that is floated into the froth layer and thereby collected into the launders as overflow .

[0050] By pre-treatment and / or post-treatment and / or further processing is meant for example comminution, grinding, separation, screening, classification, fractioning, conditioning or cleaning, all of which are conventional processes as known to a person skilled in the art . A further processing may include also at least one of the following: a further flotation cell, which may be a conventional cleaner flotation cell, a recovery cell, a rougher cell, or a scavenger cell .

[0051] The flotation line may comprise any combinations of a regrind circuit, cleaner, rougher, and / or scavenger flotation cells . The amount of the cells may depend on the hydraulic gradient or step heights available down the flotation line . The flotation line may be a flotation circuit, flotation bank, or flotation train. The person skilled in the art is familiar with these various terms .

[0052] In froth flotation for mineral ore, upgrading the concentrate is directed to an intermediate particle size range between 40 pm to 150 pm. Fine particles are thus particles with a diameter of 1 to 40 pm, and ultrafine particles may be identified as falling in the lower end of the fine particle size range of 1 to 10 pm. Coarse particles have a diameter greater than 150 pm.

[0053] By a mixing zone B is meant herein a vertical part or section of the flotation tank in which active mixing of particles suspended in slurry with flotation gas bubbles takes place . In addition to this mixing zone B created into an entire vertical section of the flotation tank, separate and regional individual mixing subzones may be created at areas where slurry flow is directed radially outwards by individual impingers to meet and become intermingled. This may further promote contacts between flotation gas bubbles and particles, thereby increasing the recovery of valuable particles . Further, this additional mixing may eliminate the need for a mechanical mixer for suspending solids in the slurry .

[0054] By a settling zone A is meant a vertical part of a section of the flotation tank in which particles may not associated with flotation gas bubbles or otherwise may not be able to rise towards the froth zone C on the top part of the flotation tank descend and settle towards the tank bottom to be removed in the tailings as underflow. The settling zone A is below the mixing zone B . The froth zone C is above the mixing zone B .

[0055] By disposing a tailings outlet at the side wall of the flotation tank, underflow may be removed at a zone where the slurry by most parts comprises particles descending or settling towards the tank bottom. In the flotation cell according to the invention, the settling zone is deeper near the side wall of the flotation tank. At this area, mixing action and turbulence created by the blast tubes does not affect the settling particles, which, for the most part, do not comprise any valuable material, or comprise only a very small amount of valuable material . At this part, the settling action is also most pronounced due to the lack of turbulence interfering the descent by gravity of the particles . In addition, friction forces created by the tank side wall further decrease the turbulence and / or flows . Thus, taking underflow out of the flotation tank at a position arranged on this relatively calm settling zone, it may be ensured that as little as possible of the valuable material comprising particles are removed from the flotation tank - these particles should, rather, be floated, or, if for some reason having ended up in the settling zone, recirculated back into the flotation tank as slurry infeed through the blast tubes .

[0056] At least one blast tube may comprise an impinger configured to contact a flow of slurry infeed from the outlet nozzle and to direct the flow of slurry infeed radially outwards and upwards of the impinger . By arranging the outlet nozzle and the impinger at an optimum distance from each other, the impinger may be configured to deflect and direct the flow of slurry infeed radially outwards and upwards of the impinger to create the earlier mentioned mixing zones within the flotation tank, and to promote the ascent of particles towards the froth layer . At the same time, it may be necessary to minimize the wear caused by high-velocity flows of slurry on the impinger . By positioning the outlet nozzle and the impinger at a certain relation to each other, it may be possible to optimize the flotation process within a flotation cell equipped with blast tubes, as well as minimise wear to the impinger parts . The blast tubes may be arranged concentric to the perimeter of the flotation tank at a distance from a froth crowder .

[0057] The valuable mineral may be for example Cu, or Zn, or Fe, or pyrite, or 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 the present invention.

[0058] The enclosed figure 1 illustrates 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. Figures 2 to 4b illustrate in a schematic manner embodiments of blast tubes 4 comprising a diffuser 6. Figures 5a and 5b show a diffuser device 30 and figure 5c show a blast tube 4 comprising a diffuser device 30. Figures 6a and 6b illustrate an example of a flotation line . The direction of flow of slurry is shown in the figures by arrows .

[0059] An example of figure 1 shows a flotation cell 1. The flotation cell may comprise a flotation tank 10 comprising a center 11, a perimeter 12, a substantially horizontal bottom 13, and a side wall 14. The flotation cell may further comprise a launder 2 and a launder lip 21 surrounding the perimeter 12 of the tank 10 , and at least one blast tube 4 for introducing slurry infeed 100 into the tank 10.

[0060] The device for combining gas stream, such as an air stream, and a slurry infeed stream to obtain particle-bubble aggregates and then introducing the combined air stream and slurry infeed into the tank may be any sparger unit, such as a downcomer, blast tube, reflux sparger, cell sparger, or a mechanical sparging system, or any other obvious sparger solution for the person skilled in the art, such as a self-aspiring sparger unit .

[0061] The flotation cell 1 may be 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 .

[0062] The underflow 400 may be removed from or led out of the flotation tank 10 via a tailings outlet 140. According to an embodiment, the tailings outlet 140 may be arranged at the side wall 14 of the flotation tank 10. The tailings outlet 140 may be arranged at the side wall 14 of the flotation tank 10 at a distance from the bottom 13 of the flotation tank 10. The distance is to be understood as the distance of the lowest point of the tailings outlet 140 or outlet opening in the side wall 14 of the flotation tank 10 from the tank bottom 13. The distance may be 1 to 15 % of the height of the flotation tank 10. Alternatively, the tailings outlet 140 may be arranged at the bottom 13 of the flotation tank 10. The tailings outlet 140 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 10. Even if the tailings outlet 140 is controlled by internal or external structures such as up-flow or down-flow, respectively, dart boxes, the tailings outlet 140 is ideally located at the lower part of the flotation tank 10, i . e . near or adj acent to the bottom 13 of the flotation tank, or even at the bottom 13 of the flotation tank 10. More specifically, at least part of the underflow 400 or tailings are removed from the lower part of the flotation tank 10, and at or near the side wall 14 of the flotation tank 10.

[0063] The flotation tank 10 has a height, measured as the distance from the bottom 13 of the flotation tank 10 to the launder lip 21. At the perimeter 12 of the flotation tank 10, the height may be substantially equal to, greater, or smaller than the height at the center 11 of the flotation tank 10. In other words, the flotation tank 10 may have different vertical cross-sections, the side wall 14 of the flotation tank 10 may include at its lower part a section that may be inclined towards the center 11 of the flotation tank 10.

[0064] The flotation tank 10 may have a volume of at least 5 m3. The flotation tank 10 may have a volume ranging from 20 to 1500 m3. For example, the volume of the flotation tank 10 may be 100 m3, or 200 m3, or 450 m3, or 630 m3.

[0065] The blast tubes 4 may introduce slurry infeed 100 into the flotation tank 10. A blast tube 4 may comprise an inlet nozzle 41 for feeding slurry infeed 100 into the blast tube 4, an inlet 42 for air or other gas 23, so that the slurry infeed 100 may be subj ected to air or other gas as it is discharged from the inlet nozzle 41, and an elongated chamber 40 arranged to receive under pressure the slurry infeed 100. The blast tube 4 may further comprise an outlet nozzle 43 configured to restrict flow of slurry infeed 100 from the outlet nozzle 43 and to maintain slurry infeed in the elongated chamber 40. The air or other gas may be pressurized. The bast tube 4 may further comprise a diffuser 6 and a gas chamber 5. The diffuser 6 may distribute gas 23 evenly from the gas chamber 5 into the slurry infeed 100. The diffuser 6 may be arranged in connection with the gas chamber 5 and it may comprise at least one aperture 7 configured to distribute the gas 23 from the gas chamber 5 into the slurry infeed 100 as it is discharged from the at least one inlet nozzle 41. The diffuser 6 may be located in a gas chamber bottom 15, a gas chamber inner wall 18, and / or a gas chamber outer wall 17 .

[0066] Flotation gas 23 may be entrained through a turbulent mixing action brought about by the j et, and may be 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 may be configured to maintain slurry infeed 100 under pressure in the elongated chamber 40.

[0067] According to an embodiment, the outlet nozzle 43 may further be configured to produce a supersonic shockwave into the slurry infeed 100, the supersonic shockwave may induce formation of flotation gas bubble - particle agglomerates .

[0068] 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 tank 10.

[0069] As the slurry infeed 100 passes through the outlet nozzle 43, or through the throttle of the outlet nozzle 43, flotation gas bubbles may be 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 becomes a choked flow and flow downstream of the throttle becomes supersonic, and a shockwave forms in the outlet nozzle 43. In other words, the outlet nozzle 43 may be configured to induce a supersonic shockwave into slurry infeed 100.

[0070] An outlet nozzle 43 may be disposed inside the flotation tank 10 at a desired depth . An outlet nozzle 43 may be positioned at a vertical distance from the launder lip 21 . The outlet nozzle 43 may be positioned below the launder lip 21 and the froth zone . The outlet nozzle 43 may be in the mixing zone .

[0071] At least one 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 440 of the impinger 44 to the outlet nozzle 43 may be 2 to 20 times the diameter of the outlet nozzle 43.

[0072] The slurry, which in essence may be a two-phase gas-liquid mixture, may rise out of the impinger 44 and may enter the upper part of the flotation tank 10, and the flotation gas bubbles may rise upwards and separate from the liquid to form a froth layer . The froth may rise upwards and discharge over the launder lip 21 into the launder 2 and out of the retrofitted flotation cell 1 as overflow 500. The tailings or underflow 400, from which the desired material has substantially been removed, may pass out from the flotation tank 10 through an outlet arranged at or near the bottom 13 of the flotation tank 10. There may be 2-40 blast tubes 4, or 4-24 blast tubes 4 arranged in a flotation cell 1. In an embodiment, there are 8 or 16 blast tubes 4. The blast tubes 4 may be arranged concentric to the perimeter 12 of the flotation tank 10 at a distance from the center 11 of the flotation tank 10. This may be the case when the flotation tank 10 is circular in cross-section. The blast tubes 4 may be arranged parallel to the side wall 14 of the flotation tank 10, at a distance from the side wall 14 . This may be the case when the flotation tank 10 is rectangular in cross-section. 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 adj acent outlet nozzle 43 is the same .

[0073] A slurry fraction 300 may be taken out from the flotation tank 10 via an outlet 31 arranged at the side wall 14 of the flotation tank 10. This slurry fraction 300 is recirculated into blast tubes 4 as infeed slurry 100. In an embodiment, the slurry infeed 100 comprises 100 % or less of slurry fraction 300. In an embodiment, fresh slurry 200 may be introduced from a feed box 30 into the flotation tank 10 through a slurry inlet near or adj acent to the bottom 13 of the flotation tank. Alternatively, the fresh slurry feed 200 from the feed box 30 may be fed directly to the pumping system of the slurry recycling circuit 3. The pumping system may comprise a pump 32. Alternatively, the fresh slurry feed 200 may be optionally diverted into the flotation tank 10 through the slurry inlet and / or to the pumping system.

[0074] The outlet 31 may be arranged at a distance from the bottom 13 of the flotation tank 10. The distance is to be understood as the distance of the lowest point of the outlet or outlet opening in the side wall 14 of the flotation tank 10 from the tank bottom 13. The distance is 0 to 50 % of the height of the flotation tank 10. 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 10, i . e . near or adj acent to the bottom 13 of the flotation tank. More specifically, slurry fraction 300 is removed from the lower part of the flotation tank 10. Lowest part of the outlet 31 may be located at the same level as the bottom 13. The outlet 31 may be located at the settling zone A.

[0075] According to an example embodiment, the flotation cell further comprises a feed box 30 for feeding the fresh slurry 200 into the flotation cell 1 and / or to the pumping system. If the feed box 30 is connected to the flotation tank 10 and the pumping system the feed of the fresh slurry 200 may be configured to be diverted into the flotation tank and / or to the pumping system.

[0076] According to an example embodiment, a blast tube 4 introduces slurry infeed 100 into a flotation tank 10. The blast tube 4 may comprise an inlet nozzle for feeding slurry infeed 100 into the blast tube 4, at least one gas inlet 42 for gas, and a gas chamber 5 for receiving gas 23 from the at least one gas inlet 42. The gas chamber 5 may be located in close proximity to or around the at least one inlet nozzle 41. The blast tube 4 may further comprise a diffuser 6 for evenly distributing gas 23 from the gas chamber 5 into the slurry infeed 100, and an elongated chamber 40 arranged to receive the slurry infeed 100. The blast tube 4 may also comprise an outlet nozzle 43 configured to restrict flow of slurry infeed 100 from the outlet nozzle 43. The diffuser 6 may be arranged in connection with the gas chamber 5 and it may comprise at least one aperture 7 configured to distribute the gas 23 from the gas chamber 5 into the slurry infeed 100 as it is discharged from the inlet nozzle 41.

[0077] According to an example embodiment, at least one aperture 7 is arranged to point vertically downwards parallel to the slurry infeed 100, to point vertically upwards against the slurry infeed 100, and / or to point sideways perpendicular to the slurry infeed 100.

[0078] According to an example embodiment, gas velocity through the at least one aperture is from 1 to 100 m / s .

[0079] According to an example embodiment, two or more apertures 7 of the diffuser 6 are arranged evenly around the diffuser 6 for evenly distributing the gas 23.

[0080] According to an example embodiment, a cross section of the at least one aperture 7 is circular, oval, square, polygon, elongated hole, or any combination of them. In an embodiment one elongated hole may go around or partly around the diffuser .

[0081] According to an example embodiment, the gas chamber 5 comprises a gas chamber inner wall 18, gas chamber outer wall 17, the gas chamber bottom 15, and the gas chamber top 16. The gas chamber inner wall 18 and / or the gas chamber bottom 15 may comprise the diffuser 6 or may be made of diffuser 6. The gas chamber may be a closed space comprising at least one gas inlet 42 for the gas 23 inflow and at least one aperture for the gas outflow 23. The gas chamber 5 may be a tubular chamber located outside the elongated chamber 40, or inside or around the nozzle holder 9.

[0082] According to an example embodiment, a diameter of the at least one aperture 7 is from 1 cm to 5 cm, or from 5 cm to 10 cm.

[0083] According to an example embodiment, the diffuser 6 is a disc-like diffuser or a cylindrical diffuser . The apertures 7 may be located evenly at the canter, outer, and / or inner circle of the disc-like diffuser . The apertures 7 may be located evenly at the upper, center, and / or lower part of the cylindrical diffuser 6. The apertures 7 may also be located evenly around the diffuser 6. According to an example embodiment, the at least one blast tube 4 comprises a nozzle holder 9 for holding the at least one inlet nozzle 41. The gas chamber 5 may be arranged inside the nozzle holder 9, inside the elongated chamber 40, or outside the elongated chamber 40. The horizontal disc-like diffuser 6 arranged inside the nozzle holder 9 or around the nozzle holder 9 may be arranged at the bottom part of the nozzle holder 9. Locating the horizontal disc-like diffuser 6 at the lowest part of the nozzle holder 9 may allow the most effective gas distribution towards the slurry infeed 100. The horizontal disc diffuser 6 arranged inside the nozzle holder 9 may be arranged between the nozzle holder inner wall 22 and the nozzle holder outer wall 20. It may be easy to form the gas chamber 5 by installing the horizontal disc diffuser 6 between the nozzle holder inner wall 22 and the nozzle holder outer wall 20.

[0084] According to an example embodiment, the at least one blast tube 4 comprises one or more inlet nozzles 41. The diffuser may be located in close proximity to or around all the plurality of inlet nozzles 41. The gas chamber 5 may form a donut-like gas chamber 5 in close proximity to or around all the inlet nozzles 41. This means that when there is plurality of inlet nozzles 41, only one gas chamber 5 may surround all the plurality of the inlet nozzles 41.

[0085] An example of figure 2 shows a blast tube 4 comprising an inlet nozzle 41 located inside the nozzle holder 9. The nozzle holder 9 may comprise a nozzle holder inner wall 22 and a nozzle holder outer wall 20. The inlet nozzle 41 may be located inside the nozzle holder inner wall 22 . The inner and outer walls 22, 20 may form an open chamber . The blast tube 4 may comprise a diffuser 6 located inside the nozzle holder 9. The diffuser 6 may be located inside the nozzle holder 9 between the nozzle holder inner wall 18 and the nozzle holder outer wall 20. When the diffuser 6 is located between the nozzle holder inner wall 22 and outer wall 20, the diffuser 6 may close the open chamber and form a closed gas chamber 5. The gas chamber 5 may be formed between a nozzle holder inner wall 22, a nozzle holder outer wall 20, and a gas chamber bottom 15. This means that the nozzle holder inner wall 22 may form a gas chamber inner wall 18 and the nozzle holder outer wall 20 may form a gas chamber outer wall 17. Thus, the gas chamber 5 may form a circular, tubular, or donut-like chamber in close proximity to or around the at least one inlet nozzle 41. The gas chamber may be closed comprising the at least one gas inlet 42 and at least one aperture 7 . The at least one gas inlet may be located at the nozzle holder outer wall 20. The nozzle holder outer wall 20 may form the gas chamber outer wall 17.

[0086] At least part of the gas chamber bottom 15 and / or at least part of the nozzle holder inner wall 22 may comprises the diffuser 6. The example of figure 2 shows that the diffuser 6 is located at the gas chamber bottom 15 or the diffuser 6 forms the gas chamber bottom 15. The diffuser 6 may comprise body part 25 and at least one aperture 7 or hole . The body part 25 may be a circular plate comprising apertures 7. The diffuser 6 may be configured to form a horizontal disc inside the nozzle holder 9. Two or more apertures 7 of the diffuser 6 may be arranged evenly around the diffuser 6 for evenly distributing the gas 23. The apertures 7 may be located evenly at the center, outer, and / or inner circle of the disc like diffuser 6. In the example of figure 2 the blast tube 4 comprises only one inlet nozzle 41. However, there may be one or more inlet nozzles 41.

[0087] Examples of figures 3a to 3c show blast tubes 4 comprising a gas chamber 5 located inside an elongated chamber 40 of the blast tube 4 or between the elongated chamber outer wall 19 and a nozzle holder outer wall 20. An example of figure 3a shows the blast tube 4 comprising a gas chamber 6 located inside an elongated tube 40 and / or outside a nozzle holder 9. A gas chamber 5 may be configured to be formed by an upper part of an elongated chamber outer wall 19, a nozzle holder outer wall 20, a gas chamber top 16, and a gas chamber bottom 15. This means that the nozzle holder outer wall 20 may form a gas chamber inner wall 18. The upper part of the elongated chamber outer wall 19 may form a gas chamber outer wall 17. An elongated chamber top wall 24 may form the gas chamber top 16. Thus, the gas chamber 5 may form a circular, tubular, or donut-like chamber in close proximity to or around the at least one inlet nozzle 41 and / or around the nozzle holder . The gas chamber may be a closed chamber comprising the at least one gas inlet 42 and at least one aperture 7. The at least one gas inlet 42 may be located at the elongated chamber outer wall 19, which is forming the gas chamber outer wall 17.

[0088] At least part of the gas chamber bottom 15 and / or at least part of the nozzle holder outer wall 20 may comprise the diffuser 6. The example of figure 3a shows that the diffuser 6 is located at the gas chamber bottom 15 or the diffuser 6 forms the gas chamber bottom 15. The diffuser 6 may be a circular plate comprising apertures 7. The diffuser 6 may be configured to form a horizontal disc around the nozzle holder 9. The diffuser 6 may be configured to form a horizontal disc between the elongated chamber outer wall 19 and the nozzle holder outer wall 20. The diffuser may be located around the lowest part of the nozzle holder outer wall 20. Two or more apertures 7 of the diffuser 6 may be arranged evenly around the diffuser 6 for evenly distributing the gas 23. In the example of figure 3a the blast tube 4 comprises only one inlet nozzle 41 and the apertures are arranged evenly in the diffuser on the central circumference of the circular diffuser 6. Even though only one inlet nozzle is disclosed, there may be plurality of inlet nozzles 41.

[0089] An example of figure 3b shows a blast tube 4 comprising a gas chamber 5 located inside an elongated tube 40 and / or outside a nozzle holder 9. The arrangement is similar to what is shown in figure 3a but the diffuser 6 is cylindrical and located at the nozzle holder outer wall 20. The nozzle holder outer wall 20 may comprise the diffuser 6. The diffuser may comprise a base part 25 and at least one aperture 7 . The nozzle holder outer wall 20 may form a gas chamber inner wall 18. The upper part of the elongated chamber outer wall 19 may form a gas chamber outer wall 17.

[0090] The example of figure 3b shows that the diffuser 6 is located in the gas chamber inner wall 18 or the diffuser 6 forms the gas chamber inner wall 18. The diffuser 6 may be configured to form a vertical tube or cylinder in the gas chamber inner wall 18 or the at least one inlet nozzle 41. Two or more apertures 7 of the diffuser 6 may be arranged evenly around the diffuser 6 for evenly distributing the gas 23. In the example of figure 3b the blast tube 4 comprises a plurality of inlet nozzles 41. The apertures 7 may be located evenly at the upper, center, and / or lower part of the cylindrical diffuser 6.

[0091] An example of figure 3c shows a blast tube 4 comprising a gas chamber 5 located inside an elongated tube 40 and / or outside a nozzle holder 9 or the at least one inlet nozzle 41. The arrangement is similar to what is shown in figure 3b but the blast tube 4 comprises a plurality of inlet nozzles 41.

[0092] Figure 4 shows an example of a blast tube 4 comprising diffusers 6, wherein the gas chamber 5 is located outside the elongated chamber 40.

[0093] An example of figure 4 shows a blast tube 4, wherein the gas chamber 5 is configured to be formed by an upper part of an elongated chamber outer wall 19, a gas chamber bottom 15, a gas chamber top 16, and a gas chamber outer wall 17. This means that the elongated chamber outer wall 19 may form a gas chamber inner wall 18. Thus, the gas chamber 5 may form a circular, tubular, or donut like chamber in close proximity to or around the at least one inlet nozzle 41, the elongated chamber outer wall 19, and / or around the nozzle holder . The gas chamber 5 may be a closed chamber comprising the at least one gas inlet 42 and the at least one aperture 7. The at least one gas inlet may be located at the gas chamber outer wall 17. At least part of the elongated chamber outer wall 19 may comprise the diffuser 6.

[0094] The example of figure 4 shows that the diffuser 6 is located at the gas chamber inner wall 18 or the diffuser 6 forms the gas chamber inner wall 18. The diffuser 6 may be configured to form a vertical tube or cylinder around at least part of the nozzle holder 9 or the at least one inlet nozzle 41. Two or more apertures 7 of the diffuser 6 may be arranged evenly around the diffuser 6 for evenly distributing the gas 23. In the example of figure 4 the blast tube 4 comprise plurality of inlet nozzles 41. The apertures 7 may be located evenly at the upper, center, and / or lower part of the tubular diffuser 6.

[0095] An example of figure 5a shows a diffuser device 30 seen from above obliquely and figure 5b shows the diffuser device 30 of figure 5a in a side view.

[0096] According to an example embodiment, the diffuser device 30 for a blast tube 4 is disclosed. The diffuser device 30 may comprise a diffuser device bottom 31 comprising an opening 32 in the middle of the diffuser device bottom 31. The diffuser device bottom 31 may have a disc-like form. The diffuser device 30 may further comprise a circular wall part 33 around a perimeter of the diffuser device bottom 33. The wall part 33 may be a vertical wall part . Further, the diffuser device may comprise a cylindrical diffuser 6 comprising at least one aperture 7. The diffuser may be a vertical and cylindrical diffuser . The diffuser device 30 may also comprise a flange part 34 at the top of the circular wall part 33. It may form a horizonal and circular protrusion outside the circular wall part 33. The flange part 34 may be used for attaching the flange part 34 to the blast tube 4. The diffuser 6 may be arranged vertically on top of the diffuser device bottom 31 around the opening 32. The diffuser device 30 may be configured to distribute gas 23 through the at least one aperture 7 of the diffuser 6 into slurry infeed 100 when the diffuser device 30 is installed or retrofitted into the blast tube 4. The diffuser device 30 may be used when building a new blast tube 4 of the flotation cell 1 or when retrofitting the diffuser device 30 into an old blast tube 4 .

[0097] According to an example embodiment, the wall part 33, which is an outer wall, and the diffuser device bottom 31 are configured to form a gas chamber 5 with a nozzle holder 9 of the blast tube 4, when the diffuser device 30 is configured to be installed or retrofitted into the blast tube 4 .

[0098] An example of figure 5c shows an example of a blast tube 4 comprising a diffuser device 30. In the example the diffuser device 30 is retrofitted or installed into the blast tube 4 of a flotation cell 1. The blast tube 4 may be formed by installing the diffuser device 30 below the nozzle holder 9. The diffuser 6 may be located below the nozzle holder inner wall 22. The diffuser device 30 may be arranged between the nozzle holder 9 and an elongated chamber 40. The diffuser device 30 may be arranged between a lower part of the nozzle holder 9 and an upper part of the elongated chamber 40. The diffuser device 30 and the nozzle holder 9 may form a gas chamber 5. The diffuser device 30 may receive gas 23 from the at least one gas inlet 42 of the formed gas chamber 5 and may distribute the gas 23 from the gas chamber 5 through the at least one aperture 7 of the diffuser 6 into the slurry infeed 100 as it is discharged from the inlet nozzle 41.

[0099] The gas chamber 5 may be formed of a nozzle holder inner wall 22, an elongated chamber top 24, a nozzle holder outer wall 20, and the diffuser device 30. This means that the nozzle holder inner wall 22 and the diffuser 6 may form a gas chamber inner wall 18. The gas chamber 5 may form a circular, tubular, or donut like chamber at least partly in close proximity to or around the at least one inlet nozzle 41. The gas chamber 5 may be a closed chamber comprising the at least one gas inlet 42 and the at least one aperture 7. The at least one gas inlet 42 may be located at the nozzle holder outer wall 20, which may form the gas chamber outer wall 17 . The example of figure 5c shows that the diffuser 6 is located below the nozzle holder 9. The diffuser 6 may be configured to form a tubular and circular cylinder below the nozzle holder 9. Two or more apertures 7 of the diffuser 6 may be arranged evenly around the diffuser 6 for evenly distributing the gas 23. The apertures 7 may be located evenly at the upper, center, and / or lower circle of the cylinder diffuser 6. In the example of figure 5c the blast tube 4 comprises only one inlet nozzle 41 but plurality of inlet nozzles 41 may be used.

[0100] Examples of figure 6a and 6b show flotation lines 8. A flotation line 8 may comprise a number of fluidly connected flotation cells 1, la, and at least one of the flotation cells is a flotation cell 1 according to the above described embodiments of the flotation cell 1. In an embodiment of the flotation line 8, the flotation cell 1 according to the invention is preceded by a flotation cell la . A flotation cell la may be of any type known in the field. Alternatively or additionally, the flotation cell 1 may be preceded by a mechanical flotation cell . An example of figure 6b shows a flotation line 8 comprising a rougher part 81 with a flotation cell la; a scavenger part 82 with a flotation cell la arranged to receive underflow 400 for the rougher part 81 ; and a scavenger cleaner part 820 with a flotation cell la arranged to receive overflow 500 from the scavenger part 82. In the flotation line 8, the last one flotation cell 1 of the scavenger part 82 , and alternatively or additionally, the last flotation cell 1 of the scavenger cleaner part 820 is a flotation cell 1 according to the invention, with blast tubes 4 . The blast tubes 4 may comprise a diffuser 6 or a diffuser device 30.

[0101] The flotation line 8 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 8, such as regrinding, cleaner or other flotation processes, centrifuging, filtering, screening or dewatering.

[0102] Figure 7 illustrates an example of a method for introducing slurry infeed 100 into a flotation tank 10 with at least one blast tube 4. The at least one blast tube 4 may comprise at least one inlet nozzle 41, at least one gas inlet 42 for gas 23, a gas chamber 5 located in close proximity to or around the at least one inlet nozzle 41, and a diffuser 6 comprising at least one aperture 7, wherein the diffuser may be arranged in connection with the gas chamber 5. The at least one blast tube 4 may further comprise an elongated chamber 40 arranged to receive the slurry infeed 100 and an outlet nozzle 43 configured to restrict flow of slurry infeed 100 from the outlet nozzle 43.

[0103] At operation 700, the method may comprise that at least one inlet nozzle 41 may feed slurry infeed 100 into the blast tube 4 . At operation 710, the method may comprise that the gas chamber 5 may receive the gas 23 from the at least one gas inlet 42.

[0104] At operation 720, the method may comprise that the at least one aperture 7 of the diffuser 6 may distribute the gas 23 from the gas chamber 5 into the slurry infeed 100 as it is discharged from the at least one inlet nozzle 41 .

[0105] Figure 8 illustrates an example of a method for installing or retrofitting a diffuser device 30 according to example embodiment above into at least one blast tube 4 of a flotation cell 1. The diffuser device may comprise a bottom 31 having an opening 32 in the middle of the bottom 31, a circular wall part 33 around a perimeter of the bottom 31, a diffuser 6 arranged vertically on top of the bottom 31 around the opening 32, wherein the diffuser may comprise at least one aperture 7. The diffuser 6 may comprise a cylindrical diffuser . The at least one blast tube 4 may comprise at least one inlet nozzle 41 for feeding slurry infeed 100 into the blast tube 4, nozzle holder 9 for holding the at least one inlet nozzle 41, at least one gas inlet 42 in the nozzle holder 9 for gas 23, and an elongated chamber 40 arranged to receive the slurry infeed 100. The at least one blast tube 4 may or may not further comprise an outlet nozzle 43 configured to restrict flow of slurry infeed 100 from the outlet nozzle .

[0106] At operation 800, the method may comprise forming a blast tube 4 by installing the diffuser device 30 below the nozzle holder 9, wherein the diffuser device 30 and the nozzle holder 9 may form a gas chamber 5.

[0107] At operation 810, the method may comprise receiving the gas 23 from the at least one gas inlet 42 of the formed gas chamber 5.

[0108] At operation 820, the method may comprise distributing the gas 23 from the gas chamber 5 through the at least one aperture 7 of the diffuser 6 into the slurry infeed 100 as it is discharged from the at least one inlet nozzle 41 .

[0109] 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 .

[0110] It will be understood that any benefits and advantages described above may relate to one embodiment or may relate to several embodiments . The embodiments are not limited to those that solve any or all of the stated problems or those that have any or all of the stated benefits and advantages .

[0111] The term "comprising" is used in this specification to mean including the feature ( s) or act (s) followed thereafter, without excluding the presence of one or more additional features or acts . It will further be understood that reference to ' an' item refers to one or more of those items .

Claims

33CLAIMS1 . A blast tube ( 4 ) for introducing slurry in-feed ( 100 ) into a flotation tank ( 10 ) , wherein the blast tube ( 4 ) comprisesan inlet noz zle ( 41 ) for feeding slurry infeed ( 100 ) into the blast tube ( 4 ) ;at least one gas inlet ( 42 ) for gas ( 23 ) ; a gas chamber ( 5 ) for receiving the gas ( 23 ) from the at least one gas inlet ( 42 ) , wherein the gas chamber ( 5 ) is located in close proximity to the at least one inlet noz zle ( 41 ) ;a di ffuser ( 6 ) for evenly distributing the gas ( 23 ) from the gas chamber ( 5 ) into the slurry infeed ( 100 ) ; andan elongated chamber ( 40 ) arranged to receive the slurry infeed ( 100 ) , whereinthe di f fuser ( 6 ) is arranged in connection with the gas chamber ( 5 ) ; andthe di f fuser ( 6 ) comprises at least one aperture ( 7 ) configured to distribute the gas ( 23 ) from the gas chamber ( 5 ) into the slurry infeed ( 100 ) as it is discharged from the at least one inlet noz zle ( 41 ) .2 . The blast tube ( 4 ) according to claim 1 , wherein at least one aperture ( 7 ) is arranged to point vertically downwards parallel to the slurry infeed ( 100 ) , to point vertically upwards against the slurry infeed ( 100 ) , and / or to point sideways perpendicular to the slurry infeed ( 100 ) .3 . The blast tube ( 4 ) according to claim 1 or claim 2 , wherein the at least one blast tube ( 4 ) comprises a noz zle holder ( 9 ) for holding the at least one inlet noz zle ( 41 ) , wherein the gas chamber ( 5 ) is arranged inside the noz zle holder ( 9 ) , inside the elongated chamber ( 40 ) , or outside the elongated chamber344 . The blast tube ( 4 ) according to claim 3 , wherein when the gas chamber ( 5 ) is arrangedinside the noz zle holder ( 9 ) , the gas chamber ( 5 ) i s configured to be formed between a noz z le holder inner wall ( 22 ) , a noz zle holder outer wall ( 20 ) , and a gas chamber bottom ( 15 ) ;inside the elongated chamber ( 40 ) , the gas chamber ( 5 ) is configured to be formed between an upper part of an elongated chamber outer wall ( 19 ) , the noz z le holder outer wall ( 20 ) , a gas chamber top ( 16 ) , and the gas chamber bottom ( 15 ) ; oroutside the elongated chamber ( 40 ) , the gas chamber ( 5 ) is configured to be formed by the upper part of the elongated chamber outer wall ( 19 ) , the gas chamber bottom ( 15 ) , the gas chamber top ( 16 ) , and a gas chamber outer wall ( 17 ) .5 . The blast tube ( 4 ) according to any of claims 2 to 4 , whereinwhen the gas chamber ( 5 ) is arranged inside the noz zle holder ( 9 ) , at least part of the gas chamber bottom ( 15 ) and / or at least part of the noz zle holder inner wall ( 22 ) comprises the di f fuser ( 6 ) ;when the gas chamber ( 5 ) is arranged inside the elongated chamber ( 40 ) , at least part of the gas chamber bottom ( 15 ) and / or at least part o f the noz zle holder outer wall ( 20 ) comprises the di f fuser ( 6 ) ; or when the gas chamber ( 5 ) is located outside the upper part o f the elongated chamber ( 40 ) , at least part of the elongated chamber outer wall ( 19 ) comprises the di f fuser ( 6 ) .6 . The blast tube ( 4 ) according to any one of the preceding claims , wherein the di f fuser ( 6 ) is configured to forma vertical cylinder in close proximity to or around the at least one inlet nozzle (41 ) or below nozzle holder ( 9) ; and / ora horizontal disc inside the nozzle holder (9) or around the nozzle holder ( 9) .

7. The blast tube (4 ) according to any one of the preceding claims, wherein two or more apertures (7) of the diffuser ( 6) are arranged evenly around the diffuser ( 6) for evenly distributing the gas (23) .

8. The blast tube (4 ) according to any one of the preceding claims, wherein a diameter of the at least one aperture ( 7 ) is from 1 cm to 5 cm, or from 5 cm to 10 .

9. The blast tube (4 ) according to any one of the preceding claims, wherein gas velocity through the at least one aperture is from 1 to 100 m / s .

10. The blast tube (4 ) according to any one of the preceding claims, wherein the at least one blast tube (4 ) further comprises an outlet nozzle (43) configured to restrict flow of slurry infeed ( 100) from the outlet nozzle (43) .

11. The blast tube (4 ) according to any one of the preceding claims, wherein the at least one gas inlet (42 ) is for pressurized gas (23) .

12. A flotation cell ( 1 ) for treating particles suspended in slurry and for separating the slurry into an underflow (400) and an overflow (500) , wherein the flotation cell ( 1 ) comprisesa flotation tank ( 10) ;a launder (2 ) and a launder lip (21 ) ; andat least one blast tube ( 4 ) according to any of claims 1 to 11 for introducing slurry infeed ( 100 ) into the flotation tank ( 10 ) .13 . A flotation line ( 8 ) comprising a number of fluidly connected flotation cells ( la ) , wherein at least one of the f lotation cells is a flotation cell ( 1 ) according to claim 12 .14 . A method for introducing slurry infeed ( 100 ) into a flotation tank ( 10 ) with at least one blast tube ( 1 ) , wherein the at least one blast tube ( 4 ) comprisesat least one inlet noz zle ( 41 ) ; at least one gas inlet ( 42 ) for gas ( 23 ) ;a gas chamber ( 5 ) located at least partly in close proximity to the at least one inlet noz zle ( 41 ) ;a di f fuser ( 6 ) comprising at least one aperture ( 7 ) , wherein the di f fuser ( 6 ) is arranged in connection with the gas chamber ( 5 ) ; andan elongated chamber ( 40 ) arranged to receive the slurry infeed ( 100 ) , wherein in the methodat least one inlet noz zle ( 41 ) feeds slurry infeed ( 100 ) into the blast tube ( 4 ) ;the gas chamber ( 5 ) receives the gas ( 23 ) from the at least one gas inlet ( 42 ) ;the at least one aperture ( 7 ) of the di f fuser ( 6 ) distributes the gas ( 23 ) from the gas chamber ( 5 ) into the slurry infeed ( 100 ) as it is discharged from the at least one inlet noz zle ( 41 ) .15 . A di f fuser device ( 30 ) for a blast tube ( 4 ) , wherein the di f fuser device ( 30 ) comprises37a di f fuser device bottom ( 31 ) comprising an opening ( 32 ) in the middle of the di f fuser device bottom ( 31 ) ;a circular wall part ( 33 ) around a perimeter of the di f fuser device bottom ( 31 ) ; anda cylindrical di f fuser ( 6 ) comprising at least one aperture ( 7 ) , whereinthe di f fuser ( 6 ) is arranged vertically on top of the di f fuser device bottom ( 31 ) around the opening ( 32 ) , whereinthe di f fuser device ( 30 ) is configured to distribute gas ( 23 ) through the at least one aperture ( 7 ) of the di f fuser ( 6 ) into slurry infeed ( 100 ) .16 . The di f fuser device ( 30 ) according to claim 15 , whereinthe di f fuser device ( 30 ) is configured to form a gas chamber with a noz zle holder ( 9 ) of the blast tube ( 4 ) , when the di f fuser device ( 30 ) is configured to be inserted or retrofitted into the blast tube ( 4 ) ;the di f fuser device ( 30 ) is configured to be inserted or retrofitted into the blast tube ( 4 ) below a noz zle holder ( 9 ) of the bast tube ( 4 ) ; andthe di f fuser device ( 30 ) is configured to distribute the gas ( 23 ) through the at least one aperture ( 7 ) from the gas chamber ( 5 ) into slurry infeed ( 100 ) as it is discharged from an inlet noz zle ( 41 ) of the flotation cell ( 1 ) .17 . A method for instal ling or retrofitting a di f fuser device ( 30 ) according to claim 15 or claim 16 into at least one blast tube ( 4 ) of a flotation cell ( 1 ) , whereinthe di f fuser device comprisesa bottom ( 31 ) having an opening ( 32 ) in the middle of the bottom ( 31 ) ;38a circular wall part ( 33 ) around a perimeter of the bottom ( 31 ) ; anda cylindrical di f fuser ( 6 ) arranged vertically on top of the bottom ( 31 ) around the opening ( 32 ) , wherein the di f fuser comprises at least one aperture ( 7 ) , and wherein the at least one blast tube ( 4 ) comprises at least one inlet noz zle ( 41 ) for feeding slurry infeed ( 100 ) into the blast tube ( 4 ) ;a noz zle holder ( 9 ) for holding the at least one inlet noz zle ( 41 ) ;at least one gas inlet ( 42 ) in the noz zle holder ( 9 ) for gas ( 23 ) ; andan elongated chamber ( 40 ) arranged to receive the slurry infeed ( 100 ) , wherein the method comprisesforming a blast tube ( 4 ) by instal ling the di ffuser device ( 30 ) below the noz zle holder ( 9 ) , wherein the di f fuser device ( 30 ) and the nozzle holder ( 9 ) form a gas chamber ( 5 ) ;receiving the gas ( 23 ) from the at least one gas inlet ( 42 ) of the formed gas chamber ( 5 ) ; and distributing the gas ( 23 ) from the gas chamber ( 5 ) through the at least one aperture ( 7 ) of the di f fuser ( 6 ) into the slurry infeed ( 100 ) as it is discharged from the at least one inlet noz zle ( 41 ) .

Images