Method for retrofitting process equipment into flotation cell

Abstract

A method for retrofitting process equipment into a flotation cell, wherein the flotation cell comprises a flotation tank (10) comprising a centre (11), a perimeter (12), a bottom (13), and a side wall (14); a launder (2) and a launder lip (21); wherein the method comprises forming a retrofitted flotation cell (1) by installing the process equipment to the flotation cell, wherein the process equipment comprises at least one device for combining an air stream and a slurry infeed (100) to obtain particle-bubble aggregates and then introducing the combined air stream and slurry infeed (100) into the tank (10), and providing a slurry recycling circuit (3) to the retrofitted flotation cell (1) wherein the slurry recycling circuit (3) comprises a pumping system.

Description

FIELD OF THE INVENTION

[0001] The current disclosure relates to a method of retrofitting process equipment into a flotation cell and to a flotation line, and a flotation line.BACKGROUND

[0002] A flotation cell is used to separate valuable material containing particles from particles suspended in slurry. However, flotation cells may further be developed to recover floating minerals.SUMMARY

[0003] 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 subject matter, nor is it intended to be used to limit the scope of the claimed subject matter. The scope of protection sought for various embodiments of the present disclosure is set out by the independent claims.

[0004] According to a first aspect, a method for retrofitting process equipment into a flotation cell is disclosed. The retrofitted flotation cell may be used for treating particles suspended in slurry and for separating the slurry into an underflow and an overflow. The flotation cell may comprise a flotation tank comprising a centre, a perimeter, a bottom, and a side wall; a launder and a launder lip; wherein the method may comprise forming a retrofitted flotation cell by installing the process equipment to the flotation cell, wherein the process equipment may comprise at least one device for combining an air stream and a slurry infeed to obtain particle-bubble aggregates and then introducing the combined air stream and slurry infeed into the tank, and providing a slurry recycling circuit to the retrofitted flotation cell wherein the slurry recycling circuit comprises a pumping system. The pumping system may comprise a pump and pump motor. The tank may have a substantially horizontal bottom. The launder and a launder lip may surround the perimeter of the tank. According to an example embodiment, the at least one device is any sparger unit. The sparger unit may be for example a downcomer, blast tube, reflux sparger, or cell sparger. Combination of the air stream and the slurry infeed may create air bubbles and resultant particle-bubble aggregates that may then be introduced into the tank.

[0005] According to an example embodiment, providing a slurry recycling circuit to the retrofitted flotation cell means that existing devices or at least part of the existing devices of the cell may be used, or new devices may be used. At least one of an existing equipment a such as a drive motor, electrical equipment, and / or superstructure may be reused.

[0006] The disclosed solutions provide several advantages. Since the solutions include providing a retrofitting process equipment into an existing flotation cell, this means that a significant part of the flotation cell equipment and existing units may be reused. Instead of exchanging the entire 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.

[0007] One advantage of the described solutions is that the retrofitting may not be limited to a specific kind of flotation cell, tank or line. The disclosed retrofitting method may be used in any existing flotation cell, tank or line. The solution provides a way to reuse the "superstructure" of the flotation cell or line. Different adjustments may need to be made depending on the flotation apparatus that is retrofitted. In some example solutions a larger part of the flotation equipment 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.

[0008] The retrofitting may include at least providing a sparger unit, such as a downcomer, blast tube or the like. In addition, a pumping system may be provided. Preferably, the pumping system may be installed and connected directly to the flotation tank.

[0009] One benefit of this invention may relate to how the pumping system of the recirculation line is utilized. According to embodiments of the solution according to this disclosure, the pumping system may be connected directly to flotation cell or at least two flotation cells. No external hopper may thus be required. The total dynamic head on the pumping system may be reduced compared to conventional flotation cells with recirculation lines. Typically, pumping systems may need to be able to pump up to 20 or 30 m, but in the disclosed solution the pumping height may be significantly reduced. The pumping system may thus be used in a way that may provide a significant reduction of energy needed. This may reduce the carbon footprint and thus may provide important environmental benefits.

[0010] According to one embodiment, the flotation line includes at least two, or at least three retrofitted flotation cells. The flotation line may include at least one retrofitted flotation cell. Using the retrofitting method in several adjacent flotation cells enhances the benefits and total recovery of valuable minerals from the flotation line.

[0011] According to an example embodiment, an existing mechanically or pneumatically agitated flotation cell is retrofitted to a retrofitted flotation cell with at least one device for combining 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, such as a blast tube, and a slurry recycling circuit. The mechanical flotation cell may comprise a mixer for agitating the slurry to keep it in suspension. The mixer may be a mechanical agitator. The mechanical agitator may comprise a rotor-stator with a motor and a drive shaft, and the rotor-stator construction arranged at the bottom part of the flotation cell.

[0012] According to an example embodiment, an existing tank may also be replaced if it is substantially corroded or worn.

[0013] When retrofitting the existing flotation cell, a drive mechanism and motor with the rotor and stator of the existing mechanical flotation cell may be removed. An existing tank of the original mechanical flotation cell may be equipped with at least one blast tube. Fresh slurry may be fed directly into the tank, or via the original and existing feed box of the mechanical flotation cell, or the fresh slurry may be directly from an upstream cell or tank, or any combination of these slurry streams. A drive motor of the original mechanical flotation cell may be reused as a pump motor in the slurry recycling circuit. Also, existing air supply of the original mechanical flotation cell may be reused.

[0014] According to an example embodiment, the retrofitted flotation cell may be used to recover only fast floating minerals. Thus, it may not be necessary to produce supersonic shockwave in an outlet nozzle of the at least one blast tube and therefore the slurry velocity in at least one retrofitted blast tube may be lower than in the conventional blast tubes. Retrofitted blast tube design may be simplified because two expensive compressors and feed hopper, which are normally used with flotation cells comprising blast tubes may be eliminated.

[0015] According to an example embodiment, the retrofitted flotation cell with at least one blast tube may be positioned as the first cell or as the first and second cell in a flotation line. The flotation line may comprise any combinations of a regrind circuit, cleaner, rougher, and / or scavenger flotation cells instead of the current method where the flotation cell with blast tubes may be a completely separate installation operating on its own. The first or both the first and the second flotation cells may be changed to the retrofitted flotation cells in the rougher flotation line. 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 blank, or flotation train. The person skilled in the art is familiar with these various terms.

[0016] According to an example embodiment, when flotation feed will be around 180 µm - 300 µm there may be no need for the retrofitted flotation cell to operate with the sonic choke producing a shockwave. The slurry velocity may be lower, for example in the range of 2 - 3 m / s. At very high velocities the wear rates on Feed spigot and Sonic Choke spigot as well as an impingement bowl may be very high and may make the retrofit uneconomic. Hence, the retrofitted flotation cell may recover the fast floating minerals. The addition of froth washing may ensure that the concentrate produced may be of higher grade than may have been possible using the original not retrofitted flotation cell arrangement. Also, any contaminants, for example Fluorine, may be much lower than was previously possible.

[0017] According to an example embodiment, when the sonic choke slurry velocity is lower, for example 2 - 3 m / s, it may be possible to eliminate the need for two or more new compressors and reuse the existing air supply to the retrofitted flotation cells as back pressure may be significantly lower. This may cause savings.

[0018] According to an example embodiment, it may be possible to use sonic choke slurry velocity. To maintain a shockwave after the outlet nozzle, a slurry velocity of 10 m / s or higher may need to be maintained. The slurry velocity is for example 10-30 m / s, or15-25 m / s, such as 20m / s.

[0019] It may also be possible to utilize the existing slurry head inside the original flotation cell. The pumping system may be located below the tank if needed without increasing the overall static head on the pumping system. This may be a significant advantage for carrying out planned maintenance on the pump and pump motor. In this disclosure, the following definitions are used regarding flotation.

[0020] 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 reject 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.

[0021] 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 cross-section. 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.

[0022] The flotation cell may be a froth flotation cell, such as a mechanically agitated cell or tank cell, a column flotation cell, a Jameson cell, or a dual flotation cell. In a dual flotation cell, the cell comprises at least two separate vessels, a first mechanically agitated pressure vessel with a mixer and a flotation gas input, and a second vessel with a tailings output and an overflow froth discharge, arranged to receive the agitated slurry from the first vessel. The flotation cell may also be a fluidized bed flotation cell (such as a HydroFloatTM cell), wherein air or other flotation gas bubbles which are dispersed by the fluidization system percolate through the hindered-setting zone and attach to the hydrophobic component altering its density and rendering it sufficiently buoyant to float and be recovered. In a fluidized bed flotation cell axial mixing is not needed. The flotation cell may also be an overflow flotation cell operated with constant slurry overflow. In an overflow flotation cell, the slurry is treated by introducing flotation gas bubbles into the slurry and by creating a continuous upwards flow of slurry in the vertical direction of the first flotation cell. At least part of the valuable metal containing ore particles are adhered to the gas bubbles and rise upwards by buoyancy, at least part of the valuable metal containing ore particles are adhered to the gas bubbles and rise upwards with the continuous upwards flow of slurry, and at least part of the valuable metal containing ore particles rise upwards with the continuous upwards flow of slurry. The valuable metal containing ore particles are recovered by conducting the continuous upwards flow of slurry out of the at least one overflow flotation cell as slurry overflow. As the overflow cell is operated with virtually no froth depth or froth layer, effectively no froth zone is formed on the surface of the pulp at the top part of the flotation cell. The froth may be non-continuous over the cell. The outcome of this is that more valuable mineral containing ore particles may be entrained into the concentrate stream, and the overall recovery of valuable material may be increased.

[0023] 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.

[0024] 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.

[0025] 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.

[0026] By arranging a bottom structure at the bottom of a flotation tank, the bottom structure extending upwards in the flotation tank, it may be possible to obtain better distribution of fine and / or small particles suspended in slurry. At the centre of the flotation tank, particles cannot descend and settle, as the flow of slurry infeed from the blast tubes may reach the raised centre part of the flotation tank, which ensures good mixing at that part. Particles that may have already detached from flotation gas bubbles and began their descent may be recaptured by the bubbles on account of the turbulent conditions in the mixing zone. On the other hand, the flotation tank bottom nearer the tank perimeter has a zone of a sufficient depth that allows for unfloated, most likely valueless particles to settle down and descend to be efficiently removed from the flotation tank. This settling zone is not affected by the slurry infeed flow from the blast tubes. Further, such a relatively calm zone may inhibit formation of short circuiting of the slurry flows within the flotation tank, where the same slurry material bypasses the separation zone and goes directly from feed inlet to the tailings outlet. The above features may promote increased recovery of fine particles.

[0027] By arranging the bottom structure to have a certain size, especially in respect to the mixing zone, the mixing zone and the settling zone may be designed to have desired characteristics (size, depth, turbulence, residence time of particles in the mixing zone, settling speed and probability of valueless fraction in the settling zone etc.). In a conventional flotation cell, a majority of this area (without any mechanical mixing at the bottom of the flotation tank) would be subjected to sanding, as there is little or no mixing. If the area fills up with solids, there is a risk of this solid matter slumping in and at the same time blocking a tailings outlet and / or a recirculate outlet located at the settling zone.

[0028] 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 entrap also finer particles already during the bubble formation in the blast tube. The blast tube may be dual high-shear device. In particular, a blast tube in a flotation cell according to the invention operates under pressure, and no vacuum is needed.

[0029] 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 reject flow. This is the case when the flotation arrangement, plant and / or method is utilized in reverse flotation.

[0030] 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.

[0031] 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.

[0032] 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.

[0033] By a rougher flotation, rougher part of the flotation line, rougher stage and / or rougher cells herein is meant a flotation stage that produces a rougher concentrate. The objective is to remove a maximum amount of the valuable mineral at as coarse a particle size as practical. Complete liberation is not required for rougher flotation, only sufficient liberation to release enough gangue from the valuable mineral to get a high recovery. The primary objective of a rougher stage is to recover as much of the valuable minerals as possible, with less emphasis on the quality of the concentrate produced.

[0034] The rougher concentrate is normally subjected to further stages of cleaner flotation in a rougher cleaner flotation line to reject more of the undesirable minerals that have also risen to the froth, in a process known as cleaning. The product of cleaning is known as cleaner concentrate or final concentrate.

[0035] Rougher flotation is often followed by scavenger flotation that is applied to the rougher tailings. By a scavenger flotation, a scavenger part of the flotation line, scavenger stage and / or a scavenger cell is meant a flotation stage wherein the objective is to recover any of the valuable mineral material that was not recovered during the initial rougher stage. This might be achieved by changing the flotation conditions to make them more rigorous than the initial roughing, or, in some embodiments of the invention, by the introduction of microbubble into the slurry. The concentrate from a scavenger cell or stage could be returned to the rougher feed for re-floating or directed to a regrinding step and thereafter to a scavenger cleaner flotation line.

[0036] By cleaner flotation, a rougher / scavenger cleaner line, cleaner / cleaning stage and / or a cleaner cell is meant a flotation stage wherein the objective of cleaning is to produce as high a concentrate grade as possible.

[0037] 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.

[0038] By slurry surface level herein is meant the height of the slurry surface within the flotation cell as measured from the bottom of the flotation cell to the launder lip of the flotation cell. In effect, the height of the slurry is equal to the height of a launder lip of a flotation cell as measured from the bottom of the flotation cell to the launder lip of the flotation cell. For example, any two subsequent flotation cells may be arranged in a stepwise fashion in a flotation line so that the slurry surface level of such flotation cells is different (i.e. the slurry surface level of the first of such flotation cells is higher than the slurry surface level of the second of such flotation cells). This difference in the slurry surface levels is defined herein as "step" between any two subsequent flotation cells. The step or the difference in slurry surface levels is a difference allowing the flow of slurry to be driven by gravity or gravitation force, by creating a hydraulic head between the two subsequent flotation cells.

[0039] By a flotation line herein is meant an assembly or arrangement comprising a number of flotation units or flotation cells in which a flotation stage is performed, and which are arranged in fluid connection with each other for allowing either gravity-driven or pumped slurry flow between flotation cells, to form a flotation line. In a flotation line, 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 reject flow. It is also conceivable that a flotation line may comprise only one flotation stage performed either in one flotation cell or for example in two or more parallel flotation cells.

[0040] Slurry is fed through a feed inlet to the first flotation cell of the flotation line for initiating the flotation process. Flotation line may be a part of a larger treatment plant containing one or more flotation lines, and a number of other process stages for the liberation, cleaning and other treatment of a desired material. Therefore, a number of different pre-treatment and post-treatment devices or arrangements may be in operational connection with the components of the flotation line, as is known to the person skilled in the art.

[0041] By ultra-fine bubbles herein is meant flotation gas bubbles falling into a size range of 0,05 mm to 0,7 mm, introduced into the slurry in a blast tube. In contrast, "normal" flotation gas bubbles utilized in froth flotation display a size range of approximately 0,8 to 2 mm. Larger flotation gas bubbles may have a tendency to coalesce into even larger bubbles during their residence in the mixing zone where collisions between particles and flotation gas bubbles, as well as only between flotation gas bubbles take place. As ultra-fine bubbles are introduced into slurry infeed prior to its feeding into a flotation tank, such coalescence is not likely to happen with ultra-fine bubbles, and their size may remain smaller throughout their residence in the flotation cell, thereby affecting the ability of the ultra-fine bubbles to catch fine particles.

[0042] By providing herein is meant using existing parts or devices of the cell or installing new parts or devices to the cell.

[0043] By superstructure herein is meant the superstructure of a flotation cell or flotation line, wherein the superstructure comprises at least one of the following parts of the flotation cell or flotation line: a foundation, steel support base, piping, electrical wiring, instrumentation, instrumentation wiring, supporting structure, channels, troughs, and / or the flotation tank.

[0044] According to an example embodiment of the first aspect, the method may comprise connecting the pumping system or the pump directly to the flotation tank.

[0045] According to an example embodiment of the first aspect, the method may comprise forming a retrofitted flotation cell by removing and / or reusing at least one flotation cell part or device; and installing process equipment to the flotation cell, wherein the process equipment may comprise at least one device for combining an air stream and a slurry infeed to obtain particle-bubble aggregates and then introducing the combined air stream and slurry infeed into the tank, and providing a slurry recycling circuit to the retrofitted flotation cell wherein the slurry recycling circuit may comprise the pumping system.

[0046] According to an example embodiment of the first aspect, the device for combining an air stream and a slurry infeed to obtain particle-bubble aggregates and then introducing the combined air stream and slurry infeed into the tank may comprise at least one blast tube. The at least one device may be a blast tube.

[0047] According to an example embodiment of the first aspect, the slurry recycling circuit may comprise an outlet, a first slurry pipe, a pumping system, and a second slurry pipe. In the pumping system the pump may be connected to a pump motor.

[0048] According to an example embodiment of the first aspect, fresh slurry may be fed into the flotation tank and / or to the pumping system.

[0049] According to an example embodiment of the first aspect, the slurry recycling circuit may circulate a slurry from the flotation tank to slurry infeed and distribute the slurry infeed to the at least one blast tube.

[0050] According to an example embodiment of the first aspect, the flotation cell further comprises a feed box for feeding fresh slurry into the flotation cell and / or to the pumping system. The feed box may be an existing feed box or a retrofitted feed box.

[0051] According to an example embodiment of the first aspect, the feed box may be connected to the flotation tank and / or to the pumping system, wherein if the feed box is connected to the flotation tank and the pumping system the feed of fresh slurry may be diverted into the flotation tank and / or to the pumping system.

[0052] According to an example embodiment of the first aspect, the recycling circuit may comprise at least one distribution unit or feed manifold, and a pumping system, wherein the pumping system may intake the slurry fraction from the flotation tank and may forward the slurry fraction to the at least one distribution unit or feed manifold.

[0053] According to an example embodiment of the first aspect, the pumping system may combine the fresh slurry from the feed box and the slurry fraction from the tank to slurry infeed and may distribute the slurry infeed to the at least one blast tube, distribution unit, and / or feed manifold.

[0054] According to an example embodiment of the first aspect, the at least one removed and / or reused flotation cell part or device may comprise at least one of the following: a pump, a motor, a drive motor, a drive mechanism, a rotor, a stator, and / or an air blower.

[0055] According to an example embodiment of the first aspect, the removed and / or reused drive motor may be reused as a pump motor for the pumping system in the slurry recycling circuit.

[0056] According to an example embodiment of the first aspect, the the pumping system may be located below or on the same level as the retrofitted flotation cell.

[0057] According to an example embodiment of the first aspect, the removed and / or reused air blower may be used as an air supply for the at least one sparger unit, such as a blast tube. The air blower may be a low air pressure blower. The pressure of the air blower is for example < 0,9 Bar.

[0058] According to an example embodiment of the first aspect, the flotation cell may comprise a superstructure, wherein the superstructure of the flotation cell to be retrofitted with the process equipment, is utilized in the construction of the retrofitted flotation cell, wherein the superstructure may comprise at least one of the following: a foundation, steel support base, piping, electrical wiring, instrumentation, instrumentation wiring, supporting structure, channels, troughs, and / or the flotation tank.

[0059] According to an example embodiment of the first aspect, the method may further comprise installing a bottom structure on a bottom of the flotation tank, wherein the bottom structure may have a shape that may limit particle buildup in the centre of the tank. The bottom structure may have a shape that may prevent buildup of solid materials, such as particles suspended in a slurry at the bottom of the flotation tank. The bottom structure may be used to minimize / reduce settling of particles radially from the centre of the tank. It may limit particle buildup from settling in the centre of the tank.

[0060] According to an example embodiment of the first aspect, the method may further comprise reusing or installing a mechanical mixer at the bottom of the flotation tank, wherein the said mechanical mixer may be operated to prevent buildup of solid materials at the bottom of the flotation tank.

[0061] According to an example embodiment of the first aspect, the retrofitted flotation cell may recover the fraction of floating minerals from the slurry.

[0062] According to an example embodiment of the first aspect, the retrofitted flotation cell may recover the fraction of fast floating minerals from the slurry. According to an example embodiment of the first aspect, the retrofitted flotation cell may process slurry containing solid particles suspended in a slurry having an average particle size of about 1 to 2000 µm. According to an example embodiment average particle size is about 5 to 400 pm, or about 10 to 380 pm, or about 15 to 370 pm, or about 20 to 360 pm, or about 25 to 350 pm, or about 50 to 340 pm, or about 100 to 330 pm, or about 120 to 320 pm, or about 150 to 310 pm, or about 180 to 300 µm.

[0063] According to an example embodiment of the first aspect, the process equipment may comprise 2-40 blast tubes or 4-24 blast tubes.

[0064] According to an example embodiment of the first aspect, the at least one blast tube may comprise an outlet nozzle, wherein the outlet nozzle may produce a supersonic shockwave into the slurry infeed, wherein the supersonic shockwave may induce formation of flotation gas bubble-particle agglomerates.

[0065] According to an example embodiment of the first aspect, the at least one device for combining the air stream and the slurry infeed to obtain particle-bubble aggregates and then introducing the combined air stream and slurry infeed into the tank may be self-aspirating.

[0066] According to an example embodiment of the first aspect, the at least one device for combining the air stream and the slurry infeed to obtain particle-bubble aggregates and then introducing the combined air stream and slurry infeed into the tank may comprise at least one blast tube, which at least one blast tube may be pressurized. The at least one pressurized blast tube may produce velocities needed for a shockwave. However, the at least one blast tube may not need to produce a shockwave.

[0067] According to an example embodiment of the first aspect, an internal deflector may be provided inside the flotation tank to guide the fresh slurry entering the flotation tank towards the outlet.

[0068] According to an example embodiment of the first aspect, the at least one blast tube further comprises 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.

[0069] According to an example embodiment, the at least one blast tube may comprise an inlet nozzle for feeding slurry infeed into the blast tube; an inlet for pressurized gas, the slurry infeed subjected to the pressurized gas as it is discharged from the inlet nozzle; an elongated chamber arranged to receive under pressure the slurry infeed; and an outlet nozzle configured to restrict flow of slurry infeed from the outlet nozzle, and to maintain slurry infeed in the elongated chamber under pressure.

[0070] According to an example embodiment of the first aspect, an internal deflector may be provided inside the flotation tank to guide the fresh slurry entering the flotation tank towards outlet.

[0071] According to an example embodiment, a flotation line is provided. The flotation line comprises a number of fluidly connected flotation cells, and it is characterized in that at least one of the flotation cells is a retrofitted flotation cell.

[0072] According to an example embodiment, use of the flotation line according to the invention is intended for recovering particles comprising a valuable material suspended in slurry.

[0073] According to a second aspect, a method for retrofitting process equipment into a flotation line is disclosed. The flotation line may comprise a number of fluidly connected flotation cells, wherein at least one flotation cell may comprise a flotation tank comprising a centre, a perimeter, a bottom, and a side wall; a launder and a launder lip; and at least one flotation cell part or device, wherein the method may comprise forming at least one retrofitted flotation cell by installing the process equipment to the at least one flotation cell, wherein the process equipment may comprise at least one device for combining 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; and providing a slurry recycling circuit to the at least one retrofitted flotation cell, wherein the slurry recycling circuit may comprise a pumping system.

[0074] According to a third aspect, a flotation line comprising a number of fluidly connected flotation cells, wherein process equipment is configured to be retrofitted into at least one flotation cell is disclosed. The at least one flotation cell may comprise a flotation tank comprising a centre, a perimeter, a bottom, and a side wall; a launder and a launder lip; wherein the process equipment may be configured to be installed to the flotation cell; and a slurry recycling circuit may be configured to be provided to the at least one retrofitted flotation cell, wherein the slurry recycling circuit may comprise a pumping system. The process equipment may be configured to be installed to the existing flotation cell. The existing flotation cell may have been used for another purpose.

[0075] According to an example embodiment of the third aspect, the flotation line may comprise at least one superstructure, wherein the at least one superstructure of the at least one flotation cell to be retrofitted with the process equipment may be configured to be utilized in the construction of the retrofitted flotation cell, wherein the superstructure may comprise at least one of the following: a foundation, steel support base, piping, electrical wiring, instrumentation, instrumentation wiring and / or supporting structure, channels, troughs, and / or the flotation tank.

[0076] According to an example embodiment of the third aspect, the flotation line may comprise a rougher part; a scavenger part arranged to receive underflow from the rougher part; and a scavenger cleaner part arranged to receive overflow from the scavenger part, wherein the first or first and the second flotation cell of at least one of the following: the rougher part, scavenger part, and / or the scavenger cleaner part may be the retrofitted flotation cells.

[0077] According to an example embodiment of the third aspect, the flotation line may comprise 2-8 fluidly connected flotation cells, or 2-6 fluidly connected flotation cells, or 2-5 fluidly connected flotation cells, or 2-4 fluidly connected flotation cells, or 2-3 fluidly connected flotation cells, wherein the first flotation cell, or the first and the second flotation cell, or flotation cells 1-3, or flotation cells 1-4, or flotation cells 1-5, or flotation cells 1-6, or flotation cells 1-7, or flotation cells 1-8 in the flotation line may be retrofitted with process equipment according to the methods of the first or second example embodiments above.

[0078] According to an example embodiment of the third aspect, the first and the second flotation cell in the flotation line may be located on the same relative level and may be configured to be retrofitted with process equipment according to the methods of the first or second example embodiments above, wherein the feed of fresh slurry may be configured to be directed to the first flotation cell and / or the second flotation cell in the flotation line, wherein the first flotation cell may be fluidly connected to the second flotation cell and the first flotation cell may be optionally fluidly connected to the third flotation cell, wherein the fluid connection between the first and the second flotation cell in the flotation line may be configured to be suspended by a valve or a barrier, and wherein if the fluid connection between the first and the second flotation cell in the flotation line may be configured to be suspended, the feed of fresh slurry may be configured to be independently directed to the first flotation cell and / or the second flotation cell in the flotation line, and wherein the underflow from the first flotation cell and / or the second flotation cell in the flotation line may be configured to be directed to the third flotation cell in the flotation line. According to an example embodiment, the recovery of coarse particles in a flotation process may be improved. The particles may, for example, comprise mineral ore particles such as particles comprising a metal.

[0079] In froth flotation for mineral ore, upgrading the concentrate is directed to an intermediate particle size range between 40 µm to 150 µm. 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 µm. Coarse particles have a diameter greater than 150 µm. In froth flotation of coal, upgrading the concentrate is directed to a particle size range between 40 µm to 500 µm. Fine particles in coal treatment are particles with a diameter of 1 to 500 pm, and ultrafine particles those that fall into the lower end of the fine particle size range. Coarse coal particles have a diameter greater than 500 µm.

[0080] Recovering very coarse or very fine particles is challenging, as in a traditional mechanical flotation cell, fine particles are not easily entrapped by flotation gas bubbles and may therefore become lost in the tailings. Typically, in froth flotation, flotation gas is introduced into a flotation cell or tank via a mechanical agitator. The thus generated flotation gas bubbles have a relatively large size range, typically from 0,8 to 2,0 mm, or even larger, and are not particularly suitable for collecting particles having a finer particle size.

[0081] Coarse particle recovery may be improved by increasing the number of flotation cells within a flotation line, or by recirculating the once-floated material (overflow) or the tailings flow (underflow) back into the beginning of the flotation line, or to preceding flotation cells. A cleaner flotation line may be used in order to improve the grade of concentrate. In addition, a number of flotation arrangements employing fine flotation gas bubbles or even so-called microbubbles have been devised. Introduction of these smaller bubbles or microbubbles may be done prior to feeding the slurry into the flotation cell, i.e. the ore particles are subjected to fine bubbles in a feed connection or the like to promote formation of ore particle-fine bubble agglomerates, which may then be floated in flotation cells such as flash flotation cells or column cells. Alternatively, fine bubbles or microbubbles may be introduced directly into the flotation cell, for example by spargers utilizing cavitation. These kinds of solutions are not necessarily feasible in connection with mechanical flotation cells, as the turbulence caused by mechanical agitation may cause the ore particle-fine bubble agglomerates to disintegrate before they are able to rise into the froth layer to be collected into overflow and thus recovered.

[0082] The flotation cells may be used in all flotation suitable mineral liberation operations, where there typically is a flotation line comprising one or two such flotation cells at the end of the liberation circuit for the recovery of especially fine coal particles. The flotation suitable minerals are for example coal, base metals such as copper, lead, zinc, precious metals (PEMs), gold, silver, graphite, talc, rare earth minerals, lithium, and any other valuable mineral which may be removed by using the flotation process. In the liberation circuit, a process water recirculation system circulates water from the end part of the circuit (i.e. from the flotation line and a dewatering circuit) back to the front circuit (beginning of the liberation circuit).

[0083] By using a retrofitted flotation cell according to the present invention, the amount of frother required to optimize the flotation process may be significantly reduced without significantly compromising bubble formation, bubble to particle engagement, stable froth layer formation or the recovery of desired material. At the same time, problems associated with recirculating process water from downstream circuit to front circuit may be alleviated. A blast tube operating under pressure may be completely independent of the flotation tank. A better flotation gas flowrate may be reached, and finer bubbles created, and frother usage optimized, as the blast tube operation is not dependent on frother dosage.

[0084] In a retrofitted flotation cell according to an example embodiment, sufficiently small flotation gas bubbles, so-called ultra-fine bubbles, may be created to ensure efficient entrapment of fine ore particles. Typically, ultra-fine bubbles may have a bubble size distribution of 0,05 mm to 0,7 mm. For example, decreasing "Sauter mean" flotation gas bubble size to a diameter of 0,3 to 0,4 mm means that the number of bubbles in 1 m 3< of slurry may be as high as 30 to 70 million, and the total mean surface area of the bubbles 15 to 20 m 2< . In contrast, if the mean bubble size is around 1 mm, the number of bubbles in 1 m 2< of slurry is around 2 million, and the total mean surface area 6 m 2< . In the retrofitted flotation cell may thus be possible to reach 2,5 to 3 times higher bubble surface area than in flotation cells according to prior art solutions. It goes without saying that the effect of such an increase in bubble surface area in recovery of valuable material comprising particles is significant.

[0085] One of the effects that may be gained with the present invention is the increased depth or thickness of a froth layer may be obtained with the retrofit cells compared to original mechanical cells. A thicker froth layer contributes to higher grade and also to increased recovery of smaller particles.

[0086] By disposing a number of blast tubes into a flotation cell, the probability of collisions between flotation gas bubbles, as well as between gas bubbles and particles may be increased. Having a number of blast tubes may ensure an improved distribution of flotation gas bubbles within a flotation tank, and the bubbles exiting the blast tubes are distributed evenly throughout the flotation tank, the distribution areas of individual blast tubes have the possibility of intersecting each other and converging, thus promoting an extensively even flotation gas bubble distribution into the flotation tank, which in turn may affect the recovery of especially smaller particles beneficially, and also contribute to the aforementioned even and thick froth layer. When there are several blast tubes, collisions between flotation gas bubbles and / or particles in the slurry infeed from different blast tubes 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.

[0087] By disposing the outlet nozzles of the blast tubes at a suitable depth, i.e. disposing them at a specific vertical distance from the launder lip, the distribution of flotation gas bubble may be optimized in an even and constant manner. As the residence time of bubbles within a mixing zone may be kept high enough by a suitable depth of the blast tube outlet nozzles, the bubbles may be able to contact and adhere to the fine particles in the slurry efficiently, thus improving the recovery of smaller particles, and also promoting froth depth, stability and evenness at the top of the flotation tank.

[0088] By a mixing zone 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 created into an entire vertical section of the flotation tank, separate and regional individual mixing subzones may be created at areas where slurry flows directed radially outwards by individual impingers 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.

[0089] By a settling zone is meant a vertical part of section of the flotation tank in which particles not associated with flotation gas bubbles or otherwise not able to rise towards the froth zone 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 is below the mixing zone.

[0090] 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. Further, by removing underflow from the settling zone near the side wall of the flotation tank, the entire volume of the flotation tank may be efficiently utilized - there is no need to configure a separate lower settling zone below the blast tubes, as is the case in for example a Jameson cell. In some embodiments, it is even foreseeable that the volume of the flotation tank may be decreased at the centre of then tank, thereby decreasing the volume of the settling zone where the turbulence caused by slurry infeed from the blast tubes may influence the probability of particles settling towards the bottom of the tank and allowing full use of the flotation tank volume. The volume of the flotation tank may be decreased at the centre of the tank for example by arranging a bottom structure at the flotation tank bottom, at the centre of the tank. In addition, it may be possible to dispose the blast tubes (the outlet nozzles) relatively deep into the flotation tank, and still ensure a sufficient calm settling zone at the side wall of the flotation tank. Also, this further promotes the efficient use of the entire volume of the flotation tank.

[0091] The flotation cell, and the flotation line and its use according to the invention have the technical effect of allowing the flexible recovery of various particle sizes, as well as efficient recovery of valuable mineral containing ore particles from poor ore raw material with relatively low amounts of valuable mineral initially. The advantages provided by the structure of the flotation line allows the accurate adjustment of the flotation line structural parameters according to the target valuable material at each installation.

[0092] By treating the slurry according to the present invention as defined by this disclosure, recovery of valuable material containing particles may be increased. The initial grade of recovered material may be lower, but the material (i.e. slurry) is also thus readily prepared for further processing, which may include for example regrinding and / or cleaning.

[0093] In an embodiment of the method for retrofitting process equipment into a flotation cell according to the invention, the flotation cell prior to the retrofitting is a mechanically or pneumatically agitated flotation cell.

[0094] In a further embodiment of the method for retrofitting process equipment into a flotation cell according to the invention, other flotation cells may follow the retrofitted flotation cell in the flotation line. Preferably, the first or the first and the second flotation cells in a flotation line may be retrofitted with the new process equipment.

[0095] In an embodiment, the flotation cell prior to the retrofitting may comprise process equipment, the process equipment comprising motor(s), driver motor(s), rotor(s), stator(s), agitator(s), and / or air blower(s), the process equipment being optionally removed and / or reused in the retrofitted installation. The reuse of the existing process equipment may greatly lower the costs of the method for retrofitting process equipment into a flotation cell.

[0096] In a further embodiment, the retrofitted flotation cell may utilize the motor(s) and / or drive motor(s) from the flotation cell as a pump motor(s).

[0097] In a further embodiment, the flotation cell may be configured to recover fast floating fractions of particles suspended in a slurry. The fast floating fraction may comprise particles suspended in a slurry that may be considered liberated particles of valuable mineral, which fast floating particles may readily separate preferably into the froth. In this configuration, the velocity of the infeed slurry may be reduced, having an additional benefit of reducing the wear rates of the flotation cell parts and equipment, and reducing the time required for servicing and maintenance.

[0098] In an embodiment of the flotation cell, a blast tube further comprises 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.

[0099] An impinger deflects the flow of slurry infeed radially outwards to the flotation tank sidewall and upwards towards the flotation tank upper surface (i.e. to the froth layer) so the fine flotation gas bubble - ore particle agglomerates do not short circuit into the tailings. All of the slurry infeed from the blast tubes are forced to rise up towards the froth layer at the top region of the flotation tank before gravity has the chance to influence the particles not adhered to flotation gas bubbles, forcing them to descend and eventually report to tailings flow or underflow. Thereby the probability of valuable material containing particles short-circuiting may be diminished. Slurry is highly agitated by the energy of the deflected flow, and forms mixing vortexes in which the size of the bubbles may be further reduced by the shear forces acting upon them. The high-shear conditions favorably also induce high number of contacts between flotation gas bubbles and particles in the slurry within the flotation tank. As the flow of slurry is forced upwards towards the froth layer, turbulence reduces and the flow becomes relatively uniform, which may contribute to the stability of the already formed bubbles, and flotation gas bubble- particle agglomerates, especially those comprising coarser particles.

[0100] 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 minimise 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 optimise the flotation process within a flotation cell equipped with blast tubes, as well as minimise wear to the impinger parts.

[0101] In an embodiment of the flotation cell, the volume of the flotation tank is at least 5 m 3< , preferably 20 to 1500 m 3< .

[0102] In an embodiment of the flotation cell, the blast tubes are arranged concentric to the perimeter of the flotation tank at a distance from a froth crowder.

[0103] In yet another embodiment of the flotation cell, the outlet is arranged at the sidewall of the flotation tank, at a distance from the bottom of the flotation tank.

[0104] In yet another embodiment of the flotation cell, the distance of the outlet from the bottom of the flotation tank is 0 to 50 % of the height of the flotation tank.

[0105] By taking slurry from the bottom of a flotation cell it may be ensured that the finer particles settled to the bottom of the flotation tank may be efficiently reintroduced into the part of the flotation tank where active flotation process takes place, before the finer particles are reported to tailings. Thus, the recovery rate of valuable material may be improved as the particles comprising even minimal amounts of valuable material may be collected into the concentrate.

[0106] The flotation process may be made more efficient when only a part of the slurry within the flotation tank is recirculated back into the same flotation tank as slurry infeed via the blast tubes. Especially as the impingers, designed to direct the flow of slurry radially outwards and upwards to form turbulent conditions to the mixing zone and to the additional mixing subzones, as explained earlier, are highly efficient in creating favorable conditions to flotation gas bubble - particle agglomerate creation and thus ensuring effective recovery of particles comprising valuable material, it may not be necessary to recirculated substantial amounts of the slurry to be treated again in the same flotation cell.

[0107] An embodiment of the use of the flotation line according to the invention is particularly intended for recovering mineral ore particles comprising nonpolar minerals such as graphite, sulphur, molybdenite, coal, and talc.

[0108] 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.

[0109] By using the flotation arrangement according to the present invention, the recovery of such low amounts of valuable mineral, for example copper, may be efficiently increased, and even poor deposits cost-effectively utilized. As the known rich deposits have increasingly already been used, there is a tangible need for processing the less favorable deposits as well, which previously may have been left unmined due to lack of suitable technology and processes for recovery of the valuable material in very low amounts in the ore.BRIEF DESCRIPTION OF THE DRAWINGS

[0110] The accompanying drawings, which are included to provide a further understanding of the invention and constitute a part of this specification, illustrate embodiments of the invention and together with the description help to explain the principles of the invention. In the drawings: Fig. 1 depicts a flotation cell according to an embodiment of the invention in side view, Fig. 1b depicts a flotation cell according to an embodiment of the invention seen from above, Fig. 2 depicts a flotation cell according to another embodiment of the invention in side view, detailing the dimensions of the system, Fig. 3a, 3b, and 3c are schematic drawings of flotation lines according to embodiments of the invention, Fig. 4 is a schematic presentation of forms of the bottom structure according to embodiments of the invention, Fig. 5 shows an example method for retrofitting process equipment into a flotation cell; and Fig. 6 shows an example method for retrofitting process equipment into a flotation line. DETAILED DESCRIPTION

[0111] Reference will now be made in detail to the embodiments of the present disclosure, an example of which is illustrated in the accompanying drawings.

[0112] The description below discloses some embodiments in such a detail that a person skilled in the art is able to utilize the flotation cell, flotation line and its use based on the disclosure. Not all steps of the embodiments are discussed in detail, as many of the steps will be obvious for the person skilled in the art based on this disclosure.

[0113] For reasons of simplicity, item numbers will be maintained in the following exemplary embodiments in the case of repeating components.

[0114] The enclosed figures 1 and 2 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. Figures 3a-c illustrate in a schematic manner embodiments of the flotation line. The direction of flows of slurry is shown in the figures by arrows. Figure 1 example shows a retrofitted flotation cell 1. The flotation cell may comprise a flotation tank 10 comprising a centre 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 flotation cell part or device. When a retrofitted flotation cell 1 is formed the at least one flotation cell part or device may be removed, and the process equipment may be installed to the flotation cell. The process equipment may comprise at least one device for combining an air stream and a slurry infeed stream to obtain particle-bubble aggregates and then introducing the combined air stream and slurry infeed 100 into the tank, such as at least one blast tube 4 for introducing slurry infeed 100 into the tank 10.

[0115] The device for combining 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.

[0116] 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.

[0117] 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 L 6 from the bottom 13 of the flotation tank 10. The distance L 6 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 H of the flotation tank 10. For example, the distance L 6 may be 2 %, or 5 % or 7,5 %, or 12 % of the height H. 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 adjacent 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.

[0118] Referring in particular to figures 1-2, the flotation cell 1 may comprise a flotation tank 10 that has a centre 11, a perimeter 12, a bottom 13 and a side wall 14. The flotation cell 1 further comprises a launder 2 and a launder lip 21 surrounding the perimeter 12 of the flotation tank 10.

[0119] In the accompanying figures, launder 2 is a perimeter launder. It is to be understood that a launder 2 may comprise, alternatively or additionally, a central launder arranged at the centre 11 of the flotation tank 10, as is known in the technical field. A launder lip of a central launder may face towards the perimeter 12 of the flotation tank 10, or towards the centre 11 of the flotation tank 10, or both. The overflow 500 may be collected into the launder 2 or launders as it passes over a launder lip 21, from a froth layer formed in the upper part of the flotation tank 10. The froth layer may comprise an open froth surface at the top of the flotation tank 10.

[0120] The flotation tank 10 has a height H, 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 H may be substantially equal to or greater than the height at the centre 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 centre 11 of the flotation tank 10.

[0121] The flotation tank 10 may have a volume of at least 5 m 3< . The flotation tank 10 may have a volume ranging from 20 to 1500 m 3< . For example, the volume of the flotation tank 10 may be 100 m 3< , or 200 m 3< , or 450 m 3< , or 630 m 3< .

[0122] The retrofitted 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 pressurized air or other gas, so that the slurry infeed 100 may be subjected to pressurized air or other gas as it is discharged from the inlet nozzle 41; an elongated chamber 40 arranged to receive under pressure the slurry infeed 100; 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 under pressure.

[0123] Flotation gas may be entrained through a turbulent mixing action brought about by the jet, and may be dispersed into small bubbles in the slurry infeed 100 as it may 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.

[0124] 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. For example, and to the outlet nozzle 43 may induce a supersonic shockwave into the slurry infeed 100 as it exits the blast tube 40. In addition, the supersonic shockwave may extend to the slurry adjacent to or surrounding the outlet nozzle so that even outside the blast tube, the creation of small size flotation gas bubble - particle agglomerates may thus be possible.

[0125] 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.

[0126] As the slurry infeed 100 passes through the outlet nozzle 43, or through the throttle of the outlet nozzle 43, flotation gas bubbles are reduced in size by the pressure changes, and by the high-shear environment downstream of the outlet nozzle 43. The velocity of the gas-liquid mixture in outlet nozzle 43, or in the throttle, may exceed the speed of sound when the flow 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.

[0127] The flow of slurry infeed 100 may become choked when the ratio of the absolute pressure upstream the outlet nozzle 43 to the absolute pressure downstream of a restricting structure of the outlet nozzle 43 may exceed a critical value. When the pressure ratio is above the critical value, flow of slurry infeed 100 downstream of the restricting structure of the outlet nozzle 43 may become supersonic and a shockwave may be formed. Small flotation gas bubbles in slurry infeed 100 mixture are split into even smaller by being forced through the shockwave and forced into contact with hydrophobic ore particles in slurry infeed 100, thus creating flotation gas bubble-ore particle agglomerates.

[0128] As seen from the example of FIG. 1 the tank 10 may be divided to a froth zone C, a mixing zone B, and a settling zone A. By the froth zone C is meant herein a vertical part or section of the flotation tank 10. The froth zone C may be about 1-25 % from the height of the settling zone A. In the froth zone C desirable minerals may be adhered to bubbles and may be transported to a launder lip. The froth zone C may comprise froth and slurry.

[0129] By a mixing zone B is meant herein a vertical part or section of the flotation tank 10 in which active mixing of particles suspended in slurry with gasified fluid bubbles may takes place. The mixing B zone may comprise gas bubbles, slurry, and fluid. The mixing zone B may be below the froth zone C.

[0130] By a settling zone A is meant a vertical part of section of the flotation tank 10 in which particles not associated with gasified fluid bubbles or otherwise not able to rise towards the froth zone C or may not be able to stay in the froth zone C on the top part of the flotation tank 10 may 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 settling zone A may comprise slurry. In the settling zone A gangue minerals may be settled and transported to tailings outlet 140 and / or outlet 31.

[0131] 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 C. The outlet nozzle 43 may be in the mixing zone B.

[0132] According to an example embodiment, when flotation feed will be around 180 µm - 300 µm there may be no need for the retrofitted flotation cell 1 to operate with the sonic choke producing a shockwave. The slurry infeed velocity exiting from the outlet nozzle 43 may be lower, for example in the range of 2 - 3 m / s.

[0133] 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 L 3 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. For example, the distance L 3 may be 5 times, 7 times, or 12 times, or 15 times the diameter of the outlet nozzle 43.

[0134] 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.

[0135] Some of the coarse hydrophobic particles that are carried into the froth may subsequently disengage from flotation gas bubbles and drop back into the flotation tank 10, as a result of bubble coalescence in the froth. However, the majority of such particles may fall back into the flotation tank 10 in such a way and position that they may be captured by bubbles newly entering the flotation tank 10 from the blast tubes 4, and carried once more into the froth layer.

[0136] 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 16 blast tubes 4. In another embodiment, there are 24 blast tubes 4. In yet another embodiment, there are 8 blast tubes 4. The exact number of blast tubes 4 may be chosen according to the specific operation, for example the type of slurry being treated within the flotation cell 1, the volumetric feed flowrate to the flotation cell 1, the mass throughput feed to the flotation cell 1, or the volume or dimensions of the flotation tank 10. In order to properly disperse flotation gas within the flotation tank 10, 4 to 6 blast tubes 4 may be employed.

[0137] The blast tubes 4 may be arranged concentric to the perimeter 12 of the flotation tank 10 at a distance from the centre 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 further arranged so that each blast tube 4 is located at a distance of an outlet nozzle 43 from the centre 11 of the flotation tank 10, the distance being preferably equal for each blast tube 4.

[0138] 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.

[0139] Further, in all the above mentioned embodiments, the blast tubes 4 may be arranged at equal distance from each other so that a distance between any two adjacent outlet nozzle 43 is the same.

[0140] 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. 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 90 into the flotation tank 10 through a slurry inlet 33 near or adjacent to the bottom 13 of the flotation tank. Alternatively, the fresh slurry feed 200 from the feed box 90 may be fed directly to the pumping system of the slurry recycling circuit 3. The pumping system may comprise a pump 32 and a pump motor 53. Alternatively, the fresh slurry feed 200 may be optionally diverted into the flotation tank 10 through the slurry inlet 33 and / or to the pumping system. The flow of the fresh slurry 200 into the flotation tank 10 and / or to the pumping system may be adjusted with a valve 34 and valve 35. If the flow of fresh slurry is into the flotation tank 10, the fresh slurry may mix with the slurry in the flotation tank, which mixed slurry may form the slurry fraction 300, which may be recirculated into the at least one blast tube 4 through the recirculation circuit 3.

[0141] In an embodiment, the flow of slurry in the slurry recycling circuit 3 comprises at least the slurry fraction 300 from the flotation tank 10, wherein the volumetric flow of the recirculated slurry from the flotation tank 10 to the slurry infeed 100 is at least 100 % of the volume of the feed of fresh slurry 200. The recirculated slurry from the flotation tank 10 to the slurry infeed 100 is for example, 150 % of fresh slurry 200 by volume, or 200 % of fresh slurry 200 by volume, or 250 % of fresh slurry 200 by volume, or 300 % of fresh slurry 200 by volume, or 350 % of fresh slurry 200 by volume. The recirculation of slurry has the advantage of reintroducing the particles suspended in a slurry into the slurry infeed 100 and possibly increasing the probability of capturing valuable substances into the froth.

[0142] In an embodiment of the invention, the flow of fresh slurry 200 arriving into the flotation tank 10 through the slurry inlet 33 is deflected downwards towards the bottom 13 of the flotation tank 10 by an internal deflector. The internal deflector may be arranged so that the feed of fresh slurry 200 is guided towards the slurry outlet 31. Feeding the fresh slurry 200 into the flotation tank 10 has the added benefit of mixing the fresh slurry with the slurry in the flotation tank. The internal deflector may help the flow of fresh slurry 200 mixed with the slurry in the flotation tank 10 to preferably flow towards the slurry outlet 31.

[0143] The outlet 31 may be arranged at a distance L 4 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 L 4 is 0 to 50 % of the height H 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 adjacent 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.

[0144] According to an example of figure 1b the tank 10 is divided to four quadrants Q1-Q4 seen from above of the tank 10. The outlet 31 may be located withing a same quadrant Q1 as the inlet 33. The quadrant is a sector equal to one-quarter of a cross section of the tank. The quadrant is a quarter of a circle or a quarter of the circumference of a circle. The circumference of a circle may be the circumference of the tank side wall 14 seen from above. The outlet 31 and the inlet 33 may be located at an angle from 0° to 90°, or from 0° to 45° from each other seen from above of the tank 10.

[0145] The inlet 33 may be arranged at a distance L 8 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 L 8 is 0 to 50 % of the height H of the flotation tank 10. Preferably the distance L 8 is higher than the distance L 4 so that the inlet 33 is positioned above outlet 31. The inlet 33 may be located at the mixing zone B. The inlet 33 may be located at the same height with the impinger 44.

[0146] Additionally, the flotation tank 10 may further comprise a bottom structure 7 (see Figs.4), arranged on the bottom (13), and may have a shape that may allow particles suspended in slurry to be mixed in the mixing zone B created over the bottom structure 7, and to settle down in a settling zone A surrounding the bottom structure 7. Optionally, the bottom structure 7 may have a shape that prevents buildup of solid materials, such as particles suspended in a slurry at the bottom of the flotation tank.

[0147] The bottom structure 7 may be for example a cone, a truncated cone, a pyramid, or a truncated pyramid. A cone or a truncated cone may be suitable for a flotation tank with a circular cross-section. A pyramid or a truncated pyramid may be a suitable form for a flotation tank with a rectangular cross-section.

[0148] The bottom structure 7 has a height h 4 , measured from the topmost part of the bottom structure 7 to the bottom 13 of the flotation tank 10. In case the form of the bottom structure is a cone or a pyramid, the topmost part is also the first vertex 71 of the functional triangle 700. In case the bottom structure 7 has some sort of truncated form, the height h 4 is measured from the level top of the truncated form (see middle image of Fig. 4) to the bottom 13 of the flotation tank 10. The height h 4 is greater than 1 / 5 and less than 3 / 4 of the height H of the flotation tank 10. Further, the diameter d 3 of the base 73 of the bottom structure 7 may be 1 / 4 to 3 / 4 of a diameter D of the bottom 13 of the flotation tank 10. In case a flotation tank 10 and / or the bottom structure 7 has a non-circular cross-section, the diameters are measured as the maximal diagonals of the respective parts (base 73 and bottom 13). In an embodiment, the surface area of a base 73 of the bottom structure 7 is less than 80 % of the surface area of the bottom 13 of the flotation tank 10. The surface area of the base 73 may be 25 to 80 % of the surface area of the bottom 13 of the flotation tank 10.

[0149] The bottom structure 7 may additionally comprise any suitable support structures and / or connecting structures for installing the bottom structure 7 into the flotation tank 10, on the bottom 13 of the flotation tank 10. The bottom structure 7 may be made of any suitable material such as metal, for example stainless steel.

[0150] According to the example embodiment, the method further comprises installing a slurry recycling circuit 3 to the retrofitted flotation cell 1

[0151] The slurry recycling circuit 3 may comprise a first slurry pipe 50 feeding the slurry fraction 300 from the outlet 31 to the pumping system and a second slurry pipe 51 feeding the slurry fraction 300 from the pumping system to the slurry infeed 100.

[0152] According to the example embodiment, the flotation cell further comprises a feed box 90 for feeding fresh slurry 200 to the slurry recycling circuit 3 or into the flotation tank 10.

[0153] According to the example embodiment, the pumping system combines the fresh slurry 200 and the slurry fraction 300 to slurry infeed 100 and distributes the slurry infeed 100 to the at least one blast tube 4.

[0154] The outlet 31 may be arranged at the side wall 14 of the flotation tank 10, at a distance L 4 from the bottom 13 of the flotation tank 10. The distance L 4 may be 0 to 50 % of the height H of the flotation tank 10. For example, the distance L 4 may be 2 %, or 8 %, or 12,5 %, or 20 %, or 33 % of the height H of the flotation tank 10.

[0155] Additionally, the slurry recycling circuit 3 may comprise a pumping system arranged to intake the slurry fraction 300 from the flotation tank 10, and to forward slurry infeed 100 to the at least one blast tube 4. The slurry fraction 300 may comprise low settling velocity particles such as fine, slow-floating particles. The slurry fraction may be taken from or near the bottom of the flotation tank 10, for example from the settling zone A. The pumping system may also be used to forward the slurry infeed 100 into the blast tubes 4.

[0156] According to the example embodiment, the total dynamic head h 3 on the pumping system may be measured as the distance from the surface of the slurry at the perimeter 12 of the tank 10 to the level of slurry at the highest most point of the second slurry pipe 51 in the slurry recycling circuit 3. The total dynamic head on the pumping system may be reduced compared to conventional flotation cells with recirculation lines. Typically, pumps 32 may need to be able to pump up to 20 or 30 m, but in the disclosed solution the pumping height may be significantly reduced due to the slurry within the tank 10 being in constant communication with the pumping system thereby reducing the total head on the pumping system.

[0157] According to the example embodiment, the at least one removed flotation cell part or device comprises at least one of the following: a motor, a drive motor, a drive mechanism, a rotor, a stator, and / or an air blower.

[0158] According to the example embodiment, the removed drive motor is reused as a pump motor 53 in the slurry recycling circuit 3.

[0159] According to the example embodiment, the pumping system is located below the retrofitted flotation cell 1.

[0160] According to the example embodiment, the removed air blower is used as an air supply for the at least one blast tube 4.

[0161] According to an example embodiment, the pumping system is directly connected to the flotation tank 10.

[0162] According to an example embodiment, a retrofitted flotation cell 1 is configured to be formed by removing and / or reusing at least one flotation cell part or device. Then the process equipment may be installed to the flotation cell. The process equipment may comprise at least one device for combining an air stream and a slurry infeed 100 to obtain particle-bubble aggregates. After that the combined air stream and slurry infeed 100 may be configured to be introduced into the tank 10 and a slurry recycling circuit 3 is configured to be provided to the retrofitted flotation cell 1, wherein the slurry recycling circuit may comprise the pumping system.

[0163] According to an example embodiment, wherein the device for combining an air stream and a slurry infeed 100 to obtain particle-bubble aggregates and then introducing the combined air stream and slurry infeed 100 into the tank 10 comprises at least one blast tube 4.

[0164] According to an example embodiment, the slurry recycling circuit 3 comprises an outlet 31, a first slurry pipe 50, a pumping system, and a second slurry pipe 51. The pumping system may comprise a pump 31 and a pump motor 53, wherein the pump 31 is connected to a pump motor 53.

[0165] According to an example embodiment, fresh slurry 200 is fed into the flotation tank 10 and / or to the pumping system.

[0166] According to an example embodiment, the slurry recycling circuit 3 is configured to circulate a slurry fraction 300 from the flotation tank 10 to slurry infeed 100 and distribute the slurry infeed 100 to the at least one blast tube 4.

[0167] According to an example embodiment, the flotation cell further comprises a feed box 90 for feeding the fresh slurry 200 into the flotation cell 1 and / or to the pumping system.

[0168] According to an example embodiment, the feed box 90 is connected to the flotation tank 10 and / or to the pumping system, wherein if the feed box 90 is connected to the flotation tank 10 and the pumping system the feed of the fresh slurry 200 is configured to be diverted into the flotation tank and / or to the pumping system. If the feed box 90 may be connected to the flotation tank 10 and the pump 32 the feed of the fresh slurry 200 is configured to be diverted into the flotation tank and / or to the pump 31.

[0169] According to an example embodiment, the at least one removed and / or reused flotation cell part or device comprises at least one of the following: a motor, a drive mechanism, a rotor, a stator, and / or an air blower.

[0170] According to an example embodiment, the removed and / or reused motor is configured to be reused as a pump motor 53 for the pumping system in the slurry recycling circuit 3.

[0171] According to an example embodiment, the pump 32 and pump motor 53 are located below or on the same level as the retrofitted flotation cell 1.

[0172] According to an example embodiment, the removed and / or reused air blower is configured to be used as an air supply for the at least one blast tube 4.

[0173] According to an example embodiment, the flotation cell 1 comprises a superstructure, wherein the superstructure of the flotation cell 1 to be retrofitted with the process equipment, is configured to be utilized in the construction of the retrofitted flotation cell 1. The superstructure may comprise at least one of the following: a foundation, steel support base, piping, electrical wiring, instrumentation, instrumentation wiring, supporting structure, channels, troughs, and / or the flotation tank 10.

[0174] According to an example embodiment, a bottom structure 7 is configured to be installed on a bottom 13of the flotation tank 10. The bottom structure 7 has a shape that may allow particles suspended in a slurry to limit particle buildup in the centre of the tank 10.

[0175] According to an example embodiment, a mechanical mixer is configured to be reused or installed at the bottom 13 of the flotation tank 10. The said mechanical mixer may be configured to be operated to prevent buildup of solid materials at the bottom 13 of the flotation tank 10.

[0176] According to an example embodiment, the retrofitted flotation cell 1 is configured to recover the fraction of floating minerals from the slurry.

[0177] According to an example embodiment, the retrofitted flotation cell 1 is configured to process slurry containing solid particles suspended in a slurry having an average particle size of about 1 to 2,000 µm.

[0178] According to an example embodiment, the process equipment comprises 2-40 blast tubes 4 or 4-24 blast tubes 4.

[0179] According to an example embodiment, the at least one device for combining the air stream and the slurry infeed 100 to obtain particle-bubble aggregates and then introducing the combined air stream and slurry infeed 100 into the tank 10 is self-aspirating.

[0180] According to an example embodiment, the at least one device for combining the air stream and the slurry infeed 100 to obtain particle-bubble aggregates and then introducing the combined air stream and the slurry infeed 100 into the tank 10 comprises at least one blast tube 4, which blast tube 4 is pressurized.

[0181] According to an example embodiment, the at least one blast tube comprises an impinger 44 configured to contact a flow of slurry infeed 100 from an outlet nozzle 43 and to direct the flow of the slurry infeed 100 radially outwards and upwards of the impinger 44.

[0182] The method according to any preceding claim, wherein an internal deflector is provided inside the flotation tank 10 to guide the fresh slurry 200 entering the flotation tank 10 towards the outlet 31.

[0183] According to another aspect of the invention, flotation lines 8 are presented in figures 3a, 3b, and 3c. A flotation line 8 comprises a number of fluidly connected flotation cells 1a, and at least one of the flotation cells is a retrofitted flotation cell 1 according to the above described embodiments. In an embodiment of the flotation line 8, at least one flotation cell 1a follows the retrofitted flotation cell 1. A flotation cell 1a may be of any type known in the field. Alternatively, or additionally, the flotation cell 1a may be preceded by mechanical flotation cell.

[0184] In an embodiment of the flotation line 8, it comprises a rougher part 81 with retrofitted flotation cells 1; a scavenger part 82 with a flotation cell 1 arranged to receive underflow 400 for the rougher part 81; and a scavenger cleaner part 820 with a flotation cell 1 arranged to receive overflow 500 from the scavenger part 82 (see Fig. 3b). In the flotation line 8, the first and second flotation cell 1 of the rougher part 81, the first and second flotation cell 1 of the scavenger part 82, and alternatively or additionally, the first flotation cell 1 of the scavenger cleaner part 820 may be a retrofitted flotation cell 1 according to the invention, with at least one blast tube 4. Additionally, in the flotation line 8, as described above, the retrofitted flotation cell 1 according to the invention, with the at least one blast tube 4, may be followed by a mechanical flotation cell 1a.

[0185] According to an example embodiment, in the flotation line 8, at least one flotation cell 1 of the scavenger part 82, at least first flotation cell 1 of the scavenger cleaner part 820, and / or at least first flotation cell 1 of the rougher part 81 is a retrofitted flotation cell 1 according to the invention.

[0186] 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.

[0187] According to a further aspect of the invention, the flotation line 8 may be used in recovering particles comprising a valuable material suspended in slurry. In an embodiment, the use may be directed to recovering particles comprising nonpolar minerals such as graphite, sulphur, molybdenite, coal, talc.

[0188] According to the example embodiment, a flotation line 8 comprising a number of fluidly connected flotation cells is disclosed. The process equipment may be configured to be retrofitted into at least one flotation cell. At least one flotation cell may comprise a flotation tank 10 comprising a centre 11, a perimeter 12, a substantially horizontal bottom 13, and a side wall. At least one flotation cell may further comprise a launder 2 and a launder lip 21 surrounding the perimeter 12 of the tank 10, The process equipment may be configured to be installed to the at least one flotation cell 1. The process equipment may comprise at least one device for combining an air stream and a slurry infeed 100 to obtain particle-bubble aggregates and then introducing the combined air stream and slurry infeed into the tank 10. A slurry recycling circuit 3 may be configured to be provided to the at least one retrofitted flotation cell 1, wherein the slurry recycling circuit 3 may comprise a pumping system.

[0189] According to the example embodiment, the flotation line 8 may comprise at least one superstructure. The at least one superstructure of the at least one flotation cell 1 to be retrofitted with the process equipment may be configured to be utilized in the construction of the retrofitted flotation cell 1. The superstructure may comprise at least one of the following: a foundation, steel support base, piping, electrical wiring, instrumentation, instrumentation wiring, supporting structure, channels, troughs, and / or the flotation tank 10.

[0190] According to the example embodiment, the flotation line 8 may comprise 2-8 fluidly connected flotation cells 1, 1a, or 2-6 fluidly connected flotation cells 1, 1a, or 2-5 fluidly connected flotation cells 1, 1a, or 2-4 fluidly connected flotation cells 1, 1a, or 2-3 fluidly connected flotation cells 1, 1a. The first flotation cell 1, or the first and the second flotation cell 1, or flotation cells 1-3, or flotation cells 1-4, or flotation cells 1-5, or flotation cells 1-6, or flotation cells 1-7, or flotation cells 1-8 in the flotation line 8 may be configured to be retrofitted with process equipment according to any of the preceding claims.

[0191] According to the example embodiment, the first and the second flotation cell 1 in the flotation line 8 may be located on the same relative level and may be configured to be retrofitted with process equipment according to any of the embodiments above. The feed of fresh slurry 200 may be configured to be directed to the first flotation cell 1 and / or the second flotation cell 1 in the flotation line 8, wherein the first flotation cell 1 may be fluidly connected to the second flotation cell 1 and the first flotation cell may be optionally fluidly connected to the third flotation cell 1a. The fluid connection between the first and the second flotation cell 1 in the flotation line 8 may be configured to be suspended by a valve or a barrier. If the fluid connection between the first and the second flotation cell 1 in the flotation line 8 is configured to be suspended, the feed of fresh slurry 200 may be configured to be independently directed to the first flotation cell 1 and / or the second flotation cell 1 in the flotation line 8. The underflow 400 from the first flotation cell 1 and / or the second flotation cell 1 in the flotation line 8 may be configured to be directed to the third flotation cell 1a in the flotation line 8.

[0192] Fig. 5 illustrates an example of a method for retrofitting process equipment into a flotation cell. The method may comprise forming a retrofitted flotation cell 1 by removing the at least one flotation cell part or device, or keeping all parts of the flotation cell by verifying that there is no interference with any process equipment to be installed. The flotation cell may comprise a flotation tank 10 comprising a centre 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.

[0193] At operation 500, the method may comprise forming a retrofitted flotation cell 1 by installing process equipment to the flotation cell, wherein the process equipment may comprise at least one device for combining an air stream and a slurry infeed 100 to obtain particle-bubble aggregates and then introducing the combined air stream and slurry infeed 100 into the tank 10.

[0194] At operation 510, the method may comprise further providing a slurry recycling circuit 3 to the retrofitted flotation cell 1, wherein the slurry recycling circuit 3 may comprise a pumping system.

[0195] Fig. 6 illustrates an example of a method for retrofitting process equipment into a flotation line 8. The method may comprise forming a retrofitted flotation line 8 by removing the at least one flotation cell part or device, or keeping all parts of the flotation cell by verifying that there is no interference with any process equipment to be installed. Aat least one flotation cell may comprise a flotation tank 10 comprising a centre 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.

[0196] At operation 600, the method may comprise forming at least one retrofitted flotation cell 1 by installing the process equipment to the at least one flotation cell, wherein the process equipment may comprise at least one device for combining an air stream and a slurry infeed 100 to obtain particle-bubble aggregates and then introducing the combined air stream and slurry infeed 100 into the tank 10.

[0197] At operation 610, the method may comprise providing a slurry recycling circuit 3 to the at least one retrofitted flotation cell 1, wherein the slurry recycling circuit 3 may comprise a pumping system.

[0198] 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 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.

Examples

Embodiment Construction

[0111]Reference will now be made in detail to the embodiments of the present disclosure, an example of which is illustrated in the accompanying drawings.

[0112]The description below discloses some embodiments in such a detail that a person skilled in the art is able to utilize the flotation cell, flotation line and its use based on the disclosure. Not all steps of the embodiments are discussed in detail, as many of the steps will be obvious for the person skilled in the art based on this disclosure.

[0113]For reasons of simplicity, item numbers will be maintained in the following exemplary embodiments in the case of repeating components.

[0114]The enclosed figures 1 and 2 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. Figures 3a-c illustrate in a schematic manner embodiments of the flotation line. The direction of flows of slurry is shown in the figures by arrows. Figure ...

FIELD OF THE INVENTION

[0001] The current disclosure relates to a method of retrofitting process equipment into a flotation cell and to a flotation line, and a flotation line.BACKGROUND

[0002] A flotation cell is used to separate valuable material containing particles from particles suspended in slurry. However, flotation cells may further be developed to recover floating minerals.SUMMARY

[0003] 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 subject matter, nor is it intended to be used to limit the scope of the claimed subject matter. The scope of protection sought for various embodiments of the present disclosure is set out by the independent claims.

[0004] According to a first aspect, a method for retrofitting process equipment into a flotation cell is disclosed. The retrofitted flotation cell may be used for treating particles suspended in slurry and for separating the slurry into an underflow and an overflow. The flotation cell may comprise a flotation tank comprising a centre, a perimeter, a bottom, and a side wall; a launder and a launder lip; wherein the method may comprise forming a retrofitted flotation cell by installing the process equipment to the flotation cell, wherein the process equipment may comprise at least one device for combining an air stream and a slurry infeed to obtain particle-bubble aggregates and then introducing the combined air stream and slurry infeed into the tank, and providing a slurry recycling circuit to the retrofitted flotation cell wherein the slurry recycling circuit comprises a pumping system. The pumping system may comprise a pump and pump motor. The tank may have a substantially horizontal bottom. The launder and a launder lip may surround the perimeter of the tank. According to an example embodiment, the at least one device is any sparger unit. The sparger unit may be for example a downcomer, blast tube, reflux sparger, or cell sparger. Combination of the air stream and the slurry infeed may create air bubbles and resultant particle-bubble aggregates that may then be introduced into the tank.

[0005] According to an example embodiment, providing a slurry recycling circuit to the retrofitted flotation cell means that existing devices or at least part of the existing devices of the cell may be used, or new devices may be used. At least one of an existing equipment a such as a drive motor, electrical equipment, and / or superstructure may be reused.

[0006] The disclosed solutions provide several advantages. Since the solutions include providing a retrofitting process equipment into an existing flotation cell, this means that a significant part of the flotation cell equipment and existing units may be reused. Instead of exchanging the entire 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.

[0007] One advantage of the described solutions is that the retrofitting may not be limited to a specific kind of flotation cell, tank or line. The disclosed retrofitting method may be used in any existing flotation cell, tank or line. The solution provides a way to reuse the "superstructure" of the flotation cell or line. Different adjustments may need to be made depending on the flotation apparatus that is retrofitted. In some example solutions a larger part of the flotation equipment 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.

[0008] The retrofitting may include at least providing a sparger unit, such as a downcomer, blast tube or the like. In addition, a pumping system may be provided. Preferably, the pumping system may be installed and connected directly to the flotation tank.

[0009] One benefit of this invention may relate to how the pumping system of the recirculation line is utilized. According to embodiments of the solution according to this disclosure, the pumping system may be connected directly to flotation cell or at least two flotation cells. No external hopper may thus be required. The total dynamic head on the pumping system may be reduced compared to conventional flotation cells with recirculation lines. Typically, pumping systems may need to be able to pump up to 20 or 30 m, but in the disclosed solution the pumping height may be significantly reduced. The pumping system may thus be used in a way that may provide a significant reduction of energy needed. This may reduce the carbon footprint and thus may provide important environmental benefits.

[0010] According to one embodiment, the flotation line includes at least two, or at least three retrofitted flotation cells. The flotation line may include at least one retrofitted flotation cell. Using the retrofitting method in several adjacent flotation cells enhances the benefits and total recovery of valuable minerals from the flotation line.

[0011] According to an example embodiment, an existing mechanically or pneumatically agitated flotation cell is retrofitted to a retrofitted flotation cell with at least one device for combining 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, such as a blast tube, and a slurry recycling circuit. The mechanical flotation cell may comprise a mixer for agitating the slurry to keep it in suspension. The mixer may be a mechanical agitator. The mechanical agitator may comprise a rotor-stator with a motor and a drive shaft, and the rotor-stator construction arranged at the bottom part of the flotation cell.

[0012] According to an example embodiment, an existing tank may also be replaced if it is substantially corroded or worn.

[0013] When retrofitting the existing flotation cell, a drive mechanism and motor with the rotor and stator of the existing mechanical flotation cell may be removed. An existing tank of the original mechanical flotation cell may be equipped with at least one blast tube. Fresh slurry may be fed directly into the tank, or via the original and existing feed box of the mechanical flotation cell, or the fresh slurry may be directly from an upstream cell or tank, or any combination of these slurry streams. A drive motor of the original mechanical flotation cell may be reused as a pump motor in the slurry recycling circuit. Also, existing air supply of the original mechanical flotation cell may be reused.

[0014] According to an example embodiment, the retrofitted flotation cell may be used to recover only fast floating minerals. Thus, it may not be necessary to produce supersonic shockwave in an outlet nozzle of the at least one blast tube and therefore the slurry velocity in at least one retrofitted blast tube may be lower than in the conventional blast tubes. Retrofitted blast tube design may be simplified because two expensive compressors and feed hopper, which are normally used with flotation cells comprising blast tubes may be eliminated.

[0015] According to an example embodiment, the retrofitted flotation cell with at least one blast tube may be positioned as the first cell or as the first and second cell in a flotation line. The flotation line may comprise any combinations of a regrind circuit, cleaner, rougher, and / or scavenger flotation cells instead of the current method where the flotation cell with blast tubes may be a completely separate installation operating on its own. The first or both the first and the second flotation cells may be changed to the retrofitted flotation cells in the rougher flotation line. 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 blank, or flotation train. The person skilled in the art is familiar with these various terms.

[0016] According to an example embodiment, when flotation feed will be around 180 µm - 300 µm there may be no need for the retrofitted flotation cell to operate with the sonic choke producing a shockwave. The slurry velocity may be lower, for example in the range of 2 - 3 m / s. At very high velocities the wear rates on Feed spigot and Sonic Choke spigot as well as an impingement bowl may be very high and may make the retrofit uneconomic. Hence, the retrofitted flotation cell may recover the fast floating minerals. The addition of froth washing may ensure that the concentrate produced may be of higher grade than may have been possible using the original not retrofitted flotation cell arrangement. Also, any contaminants, for example Fluorine, may be much lower than was previously possible.

[0017] According to an example embodiment, when the sonic choke slurry velocity is lower, for example 2 - 3 m / s, it may be possible to eliminate the need for two or more new compressors and reuse the existing air supply to the retrofitted flotation cells as back pressure may be significantly lower. This may cause savings.

[0018] According to an example embodiment, it may be possible to use sonic choke slurry velocity. To maintain a shockwave after the outlet nozzle, a slurry velocity of 10 m / s or higher may need to be maintained. The slurry velocity is for example 10-30 m / s, or15-25 m / s, such as 20m / s.

[0019] It may also be possible to utilize the existing slurry head inside the original flotation cell. The pumping system may be located below the tank if needed without increasing the overall static head on the pumping system. This may be a significant advantage for carrying out planned maintenance on the pump and pump motor. In this disclosure, the following definitions are used regarding flotation.

[0020] 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 reject 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.

[0021] 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 cross-section. 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.

[0022] The flotation cell may be a froth flotation cell, such as a mechanically agitated cell or tank cell, a column flotation cell, a Jameson cell, or a dual flotation cell. In a dual flotation cell, the cell comprises at least two separate vessels, a first mechanically agitated pressure vessel with a mixer and a flotation gas input, and a second vessel with a tailings output and an overflow froth discharge, arranged to receive the agitated slurry from the first vessel. The flotation cell may also be a fluidized bed flotation cell (such as a HydroFloatTM cell), wherein air or other flotation gas bubbles which are dispersed by the fluidization system percolate through the hindered-setting zone and attach to the hydrophobic component altering its density and rendering it sufficiently buoyant to float and be recovered. In a fluidized bed flotation cell axial mixing is not needed. The flotation cell may also be an overflow flotation cell operated with constant slurry overflow. In an overflow flotation cell, the slurry is treated by introducing flotation gas bubbles into the slurry and by creating a continuous upwards flow of slurry in the vertical direction of the first flotation cell. At least part of the valuable metal containing ore particles are adhered to the gas bubbles and rise upwards by buoyancy, at least part of the valuable metal containing ore particles are adhered to the gas bubbles and rise upwards with the continuous upwards flow of slurry, and at least part of the valuable metal containing ore particles rise upwards with the continuous upwards flow of slurry. The valuable metal containing ore particles are recovered by conducting the continuous upwards flow of slurry out of the at least one overflow flotation cell as slurry overflow. As the overflow cell is operated with virtually no froth depth or froth layer, effectively no froth zone is formed on the surface of the pulp at the top part of the flotation cell. The froth may be non-continuous over the cell. The outcome of this is that more valuable mineral containing ore particles may be entrained into the concentrate stream, and the overall recovery of valuable material may be increased.

[0023] 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.

[0024] 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.

[0025] 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.

[0026] By arranging a bottom structure at the bottom of a flotation tank, the bottom structure extending upwards in the flotation tank, it may be possible to obtain better distribution of fine and / or small particles suspended in slurry. At the centre of the flotation tank, particles cannot descend and settle, as the flow of slurry infeed from the blast tubes may reach the raised centre part of the flotation tank, which ensures good mixing at that part. Particles that may have already detached from flotation gas bubbles and began their descent may be recaptured by the bubbles on account of the turbulent conditions in the mixing zone. On the other hand, the flotation tank bottom nearer the tank perimeter has a zone of a sufficient depth that allows for unfloated, most likely valueless particles to settle down and descend to be efficiently removed from the flotation tank. This settling zone is not affected by the slurry infeed flow from the blast tubes. Further, such a relatively calm zone may inhibit formation of short circuiting of the slurry flows within the flotation tank, where the same slurry material bypasses the separation zone and goes directly from feed inlet to the tailings outlet. The above features may promote increased recovery of fine particles.

[0027] By arranging the bottom structure to have a certain size, especially in respect to the mixing zone, the mixing zone and the settling zone may be designed to have desired characteristics (size, depth, turbulence, residence time of particles in the mixing zone, settling speed and probability of valueless fraction in the settling zone etc.). In a conventional flotation cell, a majority of this area (without any mechanical mixing at the bottom of the flotation tank) would be subjected to sanding, as there is little or no mixing. If the area fills up with solids, there is a risk of this solid matter slumping in and at the same time blocking a tailings outlet and / or a recirculate outlet located at the settling zone.

[0028] 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 entrap also finer particles already during the bubble formation in the blast tube. The blast tube may be dual high-shear device. In particular, a blast tube in a flotation cell according to the invention operates under pressure, and no vacuum is needed.

[0029] 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 reject flow. This is the case when the flotation arrangement, plant and / or method is utilized in reverse flotation.

[0030] 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.

[0031] 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.

[0032] 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.

[0033] By a rougher flotation, rougher part of the flotation line, rougher stage and / or rougher cells herein is meant a flotation stage that produces a rougher concentrate. The objective is to remove a maximum amount of the valuable mineral at as coarse a particle size as practical. Complete liberation is not required for rougher flotation, only sufficient liberation to release enough gangue from the valuable mineral to get a high recovery. The primary objective of a rougher stage is to recover as much of the valuable minerals as possible, with less emphasis on the quality of the concentrate produced.

[0034] The rougher concentrate is normally subjected to further stages of cleaner flotation in a rougher cleaner flotation line to reject more of the undesirable minerals that have also risen to the froth, in a process known as cleaning. The product of cleaning is known as cleaner concentrate or final concentrate.

[0035] Rougher flotation is often followed by scavenger flotation that is applied to the rougher tailings. By a scavenger flotation, a scavenger part of the flotation line, scavenger stage and / or a scavenger cell is meant a flotation stage wherein the objective is to recover any of the valuable mineral material that was not recovered during the initial rougher stage. This might be achieved by changing the flotation conditions to make them more rigorous than the initial roughing, or, in some embodiments of the invention, by the introduction of microbubble into the slurry. The concentrate from a scavenger cell or stage could be returned to the rougher feed for re-floating or directed to a regrinding step and thereafter to a scavenger cleaner flotation line.

[0036] By cleaner flotation, a rougher / scavenger cleaner line, cleaner / cleaning stage and / or a cleaner cell is meant a flotation stage wherein the objective of cleaning is to produce as high a concentrate grade as possible.

[0037] 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.

[0038] By slurry surface level herein is meant the height of the slurry surface within the flotation cell as measured from the bottom of the flotation cell to the launder lip of the flotation cell. In effect, the height of the slurry is equal to the height of a launder lip of a flotation cell as measured from the bottom of the flotation cell to the launder lip of the flotation cell. For example, any two subsequent flotation cells may be arranged in a stepwise fashion in a flotation line so that the slurry surface level of such flotation cells is different (i.e. the slurry surface level of the first of such flotation cells is higher than the slurry surface level of the second of such flotation cells). This difference in the slurry surface levels is defined herein as "step" between any two subsequent flotation cells. The step or the difference in slurry surface levels is a difference allowing the flow of slurry to be driven by gravity or gravitation force, by creating a hydraulic head between the two subsequent flotation cells.

[0039] By a flotation line herein is meant an assembly or arrangement comprising a number of flotation units or flotation cells in which a flotation stage is performed, and which are arranged in fluid connection with each other for allowing either gravity-driven or pumped slurry flow between flotation cells, to form a flotation line. In a flotation line, 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 reject flow. It is also conceivable that a flotation line may comprise only one flotation stage performed either in one flotation cell or for example in two or more parallel flotation cells.

[0040] Slurry is fed through a feed inlet to the first flotation cell of the flotation line for initiating the flotation process. Flotation line may be a part of a larger treatment plant containing one or more flotation lines, and a number of other process stages for the liberation, cleaning and other treatment of a desired material. Therefore, a number of different pre-treatment and post-treatment devices or arrangements may be in operational connection with the components of the flotation line, as is known to the person skilled in the art.

[0041] By ultra-fine bubbles herein is meant flotation gas bubbles falling into a size range of 0,05 mm to 0,7 mm, introduced into the slurry in a blast tube. In contrast, "normal" flotation gas bubbles utilized in froth flotation display a size range of approximately 0,8 to 2 mm. Larger flotation gas bubbles may have a tendency to coalesce into even larger bubbles during their residence in the mixing zone where collisions between particles and flotation gas bubbles, as well as only between flotation gas bubbles take place. As ultra-fine bubbles are introduced into slurry infeed prior to its feeding into a flotation tank, such coalescence is not likely to happen with ultra-fine bubbles, and their size may remain smaller throughout their residence in the flotation cell, thereby affecting the ability of the ultra-fine bubbles to catch fine particles.

[0042] By providing herein is meant using existing parts or devices of the cell or installing new parts or devices to the cell.

[0043] By superstructure herein is meant the superstructure of a flotation cell or flotation line, wherein the superstructure comprises at least one of the following parts of the flotation cell or flotation line: a foundation, steel support base, piping, electrical wiring, instrumentation, instrumentation wiring, supporting structure, channels, troughs, and / or the flotation tank.

[0044] According to an example embodiment of the first aspect, the method may comprise connecting the pumping system or the pump directly to the flotation tank.

[0045] According to an example embodiment of the first aspect, the method may comprise forming a retrofitted flotation cell by removing and / or reusing at least one flotation cell part or device; and installing process equipment to the flotation cell, wherein the process equipment may comprise at least one device for combining an air stream and a slurry infeed to obtain particle-bubble aggregates and then introducing the combined air stream and slurry infeed into the tank, and providing a slurry recycling circuit to the retrofitted flotation cell wherein the slurry recycling circuit may comprise the pumping system.

[0046] According to an example embodiment of the first aspect, the device for combining an air stream and a slurry infeed to obtain particle-bubble aggregates and then introducing the combined air stream and slurry infeed into the tank may comprise at least one blast tube. The at least one device may be a blast tube.

[0047] According to an example embodiment of the first aspect, the slurry recycling circuit may comprise an outlet, a first slurry pipe, a pumping system, and a second slurry pipe. In the pumping system the pump may be connected to a pump motor.

[0048] According to an example embodiment of the first aspect, fresh slurry may be fed into the flotation tank and / or to the pumping system.

[0049] According to an example embodiment of the first aspect, the slurry recycling circuit may circulate a slurry from the flotation tank to slurry infeed and distribute the slurry infeed to the at least one blast tube.

[0050] According to an example embodiment of the first aspect, the flotation cell further comprises a feed box for feeding fresh slurry into the flotation cell and / or to the pumping system. The feed box may be an existing feed box or a retrofitted feed box.

[0051] According to an example embodiment of the first aspect, the feed box may be connected to the flotation tank and / or to the pumping system, wherein if the feed box is connected to the flotation tank and the pumping system the feed of fresh slurry may be diverted into the flotation tank and / or to the pumping system.

[0052] According to an example embodiment of the first aspect, the recycling circuit may comprise at least one distribution unit or feed manifold, and a pumping system, wherein the pumping system may intake the slurry fraction from the flotation tank and may forward the slurry fraction to the at least one distribution unit or feed manifold.

[0053] According to an example embodiment of the first aspect, the pumping system may combine the fresh slurry from the feed box and the slurry fraction from the tank to slurry infeed and may distribute the slurry infeed to the at least one blast tube, distribution unit, and / or feed manifold.

[0054] According to an example embodiment of the first aspect, the at least one removed and / or reused flotation cell part or device may comprise at least one of the following: a pump, a motor, a drive motor, a drive mechanism, a rotor, a stator, and / or an air blower.

[0055] According to an example embodiment of the first aspect, the removed and / or reused drive motor may be reused as a pump motor for the pumping system in the slurry recycling circuit.

[0056] According to an example embodiment of the first aspect, the the pumping system may be located below or on the same level as the retrofitted flotation cell.

[0057] According to an example embodiment of the first aspect, the removed and / or reused air blower may be used as an air supply for the at least one sparger unit, such as a blast tube. The air blower may be a low air pressure blower. The pressure of the air blower is for example < 0,9 Bar.

[0058] According to an example embodiment of the first aspect, the flotation cell may comprise a superstructure, wherein the superstructure of the flotation cell to be retrofitted with the process equipment, is utilized in the construction of the retrofitted flotation cell, wherein the superstructure may comprise at least one of the following: a foundation, steel support base, piping, electrical wiring, instrumentation, instrumentation wiring, supporting structure, channels, troughs, and / or the flotation tank.

[0059] According to an example embodiment of the first aspect, the method may further comprise installing a bottom structure on a bottom of the flotation tank, wherein the bottom structure may have a shape that may limit particle buildup in the centre of the tank. The bottom structure may have a shape that may prevent buildup of solid materials, such as particles suspended in a slurry at the bottom of the flotation tank. The bottom structure may be used to minimize / reduce settling of particles radially from the centre of the tank. It may limit particle buildup from settling in the centre of the tank.

[0060] According to an example embodiment of the first aspect, the method may further comprise reusing or installing a mechanical mixer at the bottom of the flotation tank, wherein the said mechanical mixer may be operated to prevent buildup of solid materials at the bottom of the flotation tank.

[0061] According to an example embodiment of the first aspect, the retrofitted flotation cell may recover the fraction of floating minerals from the slurry.

[0062] According to an example embodiment of the first aspect, the retrofitted flotation cell may recover the fraction of fast floating minerals from the slurry. According to an example embodiment of the first aspect, the retrofitted flotation cell may process slurry containing solid particles suspended in a slurry having an average particle size of about 1 to 2000 µm. According to an example embodiment average particle size is about 5 to 400 pm, or about 10 to 380 pm, or about 15 to 370 pm, or about 20 to 360 pm, or about 25 to 350 pm, or about 50 to 340 pm, or about 100 to 330 pm, or about 120 to 320 pm, or about 150 to 310 pm, or about 180 to 300 µm.

[0063] According to an example embodiment of the first aspect, the process equipment may comprise 2-40 blast tubes or 4-24 blast tubes.

[0064] According to an example embodiment of the first aspect, the at least one blast tube may comprise an outlet nozzle, wherein the outlet nozzle may produce a supersonic shockwave into the slurry infeed, wherein the supersonic shockwave may induce formation of flotation gas bubble-particle agglomerates.

[0065] According to an example embodiment of the first aspect, the at least one device for combining the air stream and the slurry infeed to obtain particle-bubble aggregates and then introducing the combined air stream and slurry infeed into the tank may be self-aspirating.

[0066] According to an example embodiment of the first aspect, the at least one device for combining the air stream and the slurry infeed to obtain particle-bubble aggregates and then introducing the combined air stream and slurry infeed into the tank may comprise at least one blast tube, which at least one blast tube may be pressurized. The at least one pressurized blast tube may produce velocities needed for a shockwave. However, the at least one blast tube may not need to produce a shockwave.

[0067] According to an example embodiment of the first aspect, an internal deflector may be provided inside the flotation tank to guide the fresh slurry entering the flotation tank towards the outlet.

[0068] According to an example embodiment of the first aspect, the at least one blast tube further comprises 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.

[0069] According to an example embodiment, the at least one blast tube may comprise an inlet nozzle for feeding slurry infeed into the blast tube; an inlet for pressurized gas, the slurry infeed subjected to the pressurized gas as it is discharged from the inlet nozzle; an elongated chamber arranged to receive under pressure the slurry infeed; and an outlet nozzle configured to restrict flow of slurry infeed from the outlet nozzle, and to maintain slurry infeed in the elongated chamber under pressure.

[0070] According to an example embodiment of the first aspect, an internal deflector may be provided inside the flotation tank to guide the fresh slurry entering the flotation tank towards outlet.

[0071] According to an example embodiment, a flotation line is provided. The flotation line comprises a number of fluidly connected flotation cells, and it is characterized in that at least one of the flotation cells is a retrofitted flotation cell.

[0072] According to an example embodiment, use of the flotation line according to the invention is intended for recovering particles comprising a valuable material suspended in slurry.

[0073] According to a second aspect, a method for retrofitting process equipment into a flotation line is disclosed. The flotation line may comprise a number of fluidly connected flotation cells, wherein at least one flotation cell may comprise a flotation tank comprising a centre, a perimeter, a bottom, and a side wall; a launder and a launder lip; and at least one flotation cell part or device, wherein the method may comprise forming at least one retrofitted flotation cell by installing the process equipment to the at least one flotation cell, wherein the process equipment may comprise at least one device for combining 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; and providing a slurry recycling circuit to the at least one retrofitted flotation cell, wherein the slurry recycling circuit may comprise a pumping system.

[0074] According to a third aspect, a flotation line comprising a number of fluidly connected flotation cells, wherein process equipment is configured to be retrofitted into at least one flotation cell is disclosed. The at least one flotation cell may comprise a flotation tank comprising a centre, a perimeter, a bottom, and a side wall; a launder and a launder lip; wherein the process equipment may be configured to be installed to the flotation cell; and a slurry recycling circuit may be configured to be provided to the at least one retrofitted flotation cell, wherein the slurry recycling circuit may comprise a pumping system. The process equipment may be configured to be installed to the existing flotation cell. The existing flotation cell may have been used for another purpose.

[0075] According to an example embodiment of the third aspect, the flotation line may comprise at least one superstructure, wherein the at least one superstructure of the at least one flotation cell to be retrofitted with the process equipment may be configured to be utilized in the construction of the retrofitted flotation cell, wherein the superstructure may comprise at least one of the following: a foundation, steel support base, piping, electrical wiring, instrumentation, instrumentation wiring and / or supporting structure, channels, troughs, and / or the flotation tank.

[0076] According to an example embodiment of the third aspect, the flotation line may comprise a rougher part; a scavenger part arranged to receive underflow from the rougher part; and a scavenger cleaner part arranged to receive overflow from the scavenger part, wherein the first or first and the second flotation cell of at least one of the following: the rougher part, scavenger part, and / or the scavenger cleaner part may be the retrofitted flotation cells.

[0077] According to an example embodiment of the third aspect, the flotation line may comprise 2-8 fluidly connected flotation cells, or 2-6 fluidly connected flotation cells, or 2-5 fluidly connected flotation cells, or 2-4 fluidly connected flotation cells, or 2-3 fluidly connected flotation cells, wherein the first flotation cell, or the first and the second flotation cell, or flotation cells 1-3, or flotation cells 1-4, or flotation cells 1-5, or flotation cells 1-6, or flotation cells 1-7, or flotation cells 1-8 in the flotation line may be retrofitted with process equipment according to the methods of the first or second example embodiments above.

[0078] According to an example embodiment of the third aspect, the first and the second flotation cell in the flotation line may be located on the same relative level and may be configured to be retrofitted with process equipment according to the methods of the first or second example embodiments above, wherein the feed of fresh slurry may be configured to be directed to the first flotation cell and / or the second flotation cell in the flotation line, wherein the first flotation cell may be fluidly connected to the second flotation cell and the first flotation cell may be optionally fluidly connected to the third flotation cell, wherein the fluid connection between the first and the second flotation cell in the flotation line may be configured to be suspended by a valve or a barrier, and wherein if the fluid connection between the first and the second flotation cell in the flotation line may be configured to be suspended, the feed of fresh slurry may be configured to be independently directed to the first flotation cell and / or the second flotation cell in the flotation line, and wherein the underflow from the first flotation cell and / or the second flotation cell in the flotation line may be configured to be directed to the third flotation cell in the flotation line. According to an example embodiment, the recovery of coarse particles in a flotation process may be improved. The particles may, for example, comprise mineral ore particles such as particles comprising a metal.

[0079] In froth flotation for mineral ore, upgrading the concentrate is directed to an intermediate particle size range between 40 µm to 150 µm. 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 µm. Coarse particles have a diameter greater than 150 µm. In froth flotation of coal, upgrading the concentrate is directed to a particle size range between 40 µm to 500 µm. Fine particles in coal treatment are particles with a diameter of 1 to 500 pm, and ultrafine particles those that fall into the lower end of the fine particle size range. Coarse coal particles have a diameter greater than 500 µm.

[0080] Recovering very coarse or very fine particles is challenging, as in a traditional mechanical flotation cell, fine particles are not easily entrapped by flotation gas bubbles and may therefore become lost in the tailings. Typically, in froth flotation, flotation gas is introduced into a flotation cell or tank via a mechanical agitator. The thus generated flotation gas bubbles have a relatively large size range, typically from 0,8 to 2,0 mm, or even larger, and are not particularly suitable for collecting particles having a finer particle size.

[0081] Coarse particle recovery may be improved by increasing the number of flotation cells within a flotation line, or by recirculating the once-floated material (overflow) or the tailings flow (underflow) back into the beginning of the flotation line, or to preceding flotation cells. A cleaner flotation line may be used in order to improve the grade of concentrate. In addition, a number of flotation arrangements employing fine flotation gas bubbles or even so-called microbubbles have been devised. Introduction of these smaller bubbles or microbubbles may be done prior to feeding the slurry into the flotation cell, i.e. the ore particles are subjected to fine bubbles in a feed connection or the like to promote formation of ore particle-fine bubble agglomerates, which may then be floated in flotation cells such as flash flotation cells or column cells. Alternatively, fine bubbles or microbubbles may be introduced directly into the flotation cell, for example by spargers utilizing cavitation. These kinds of solutions are not necessarily feasible in connection with mechanical flotation cells, as the turbulence caused by mechanical agitation may cause the ore particle-fine bubble agglomerates to disintegrate before they are able to rise into the froth layer to be collected into overflow and thus recovered.

[0082] The flotation cells may be used in all flotation suitable mineral liberation operations, where there typically is a flotation line comprising one or two such flotation cells at the end of the liberation circuit for the recovery of especially fine coal particles. The flotation suitable minerals are for example coal, base metals such as copper, lead, zinc, precious metals (PEMs), gold, silver, graphite, talc, rare earth minerals, lithium, and any other valuable mineral which may be removed by using the flotation process. In the liberation circuit, a process water recirculation system circulates water from the end part of the circuit (i.e. from the flotation line and a dewatering circuit) back to the front circuit (beginning of the liberation circuit).

[0083] By using a retrofitted flotation cell according to the present invention, the amount of frother required to optimize the flotation process may be significantly reduced without significantly compromising bubble formation, bubble to particle engagement, stable froth layer formation or the recovery of desired material. At the same time, problems associated with recirculating process water from downstream circuit to front circuit may be alleviated. A blast tube operating under pressure may be completely independent of the flotation tank. A better flotation gas flowrate may be reached, and finer bubbles created, and frother usage optimized, as the blast tube operation is not dependent on frother dosage.

[0084] In a retrofitted flotation cell according to an example embodiment, sufficiently small flotation gas bubbles, so-called ultra-fine bubbles, may be created to ensure efficient entrapment of fine ore particles. Typically, ultra-fine bubbles may have a bubble size distribution of 0,05 mm to 0,7 mm. For example, decreasing "Sauter mean" flotation gas bubble size to a diameter of 0,3 to 0,4 mm means that the number of bubbles in 1 m 3< of slurry may be as high as 30 to 70 million, and the total mean surface area of the bubbles 15 to 20 m 2< . In contrast, if the mean bubble size is around 1 mm, the number of bubbles in 1 m 2< of slurry is around 2 million, and the total mean surface area 6 m 2< . In the retrofitted flotation cell may thus be possible to reach 2,5 to 3 times higher bubble surface area than in flotation cells according to prior art solutions. It goes without saying that the effect of such an increase in bubble surface area in recovery of valuable material comprising particles is significant.

[0085] One of the effects that may be gained with the present invention is the increased depth or thickness of a froth layer may be obtained with the retrofit cells compared to original mechanical cells. A thicker froth layer contributes to higher grade and also to increased recovery of smaller particles.

[0086] By disposing a number of blast tubes into a flotation cell, the probability of collisions between flotation gas bubbles, as well as between gas bubbles and particles may be increased. Having a number of blast tubes may ensure an improved distribution of flotation gas bubbles within a flotation tank, and the bubbles exiting the blast tubes are distributed evenly throughout the flotation tank, the distribution areas of individual blast tubes have the possibility of intersecting each other and converging, thus promoting an extensively even flotation gas bubble distribution into the flotation tank, which in turn may affect the recovery of especially smaller particles beneficially, and also contribute to the aforementioned even and thick froth layer. When there are several blast tubes, collisions between flotation gas bubbles and / or particles in the slurry infeed from different blast tubes 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.

[0087] By disposing the outlet nozzles of the blast tubes at a suitable depth, i.e. disposing them at a specific vertical distance from the launder lip, the distribution of flotation gas bubble may be optimized in an even and constant manner. As the residence time of bubbles within a mixing zone may be kept high enough by a suitable depth of the blast tube outlet nozzles, the bubbles may be able to contact and adhere to the fine particles in the slurry efficiently, thus improving the recovery of smaller particles, and also promoting froth depth, stability and evenness at the top of the flotation tank.

[0088] By a mixing zone 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 created into an entire vertical section of the flotation tank, separate and regional individual mixing subzones may be created at areas where slurry flows directed radially outwards by individual impingers 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.

[0089] By a settling zone is meant a vertical part of section of the flotation tank in which particles not associated with flotation gas bubbles or otherwise not able to rise towards the froth zone 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 is below the mixing zone.

[0090] 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. Further, by removing underflow from the settling zone near the side wall of the flotation tank, the entire volume of the flotation tank may be efficiently utilized - there is no need to configure a separate lower settling zone below the blast tubes, as is the case in for example a Jameson cell. In some embodiments, it is even foreseeable that the volume of the flotation tank may be decreased at the centre of then tank, thereby decreasing the volume of the settling zone where the turbulence caused by slurry infeed from the blast tubes may influence the probability of particles settling towards the bottom of the tank and allowing full use of the flotation tank volume. The volume of the flotation tank may be decreased at the centre of the tank for example by arranging a bottom structure at the flotation tank bottom, at the centre of the tank. In addition, it may be possible to dispose the blast tubes (the outlet nozzles) relatively deep into the flotation tank, and still ensure a sufficient calm settling zone at the side wall of the flotation tank. Also, this further promotes the efficient use of the entire volume of the flotation tank.

[0091] The flotation cell, and the flotation line and its use according to the invention have the technical effect of allowing the flexible recovery of various particle sizes, as well as efficient recovery of valuable mineral containing ore particles from poor ore raw material with relatively low amounts of valuable mineral initially. The advantages provided by the structure of the flotation line allows the accurate adjustment of the flotation line structural parameters according to the target valuable material at each installation.

[0092] By treating the slurry according to the present invention as defined by this disclosure, recovery of valuable material containing particles may be increased. The initial grade of recovered material may be lower, but the material (i.e. slurry) is also thus readily prepared for further processing, which may include for example regrinding and / or cleaning.

[0093] In an embodiment of the method for retrofitting process equipment into a flotation cell according to the invention, the flotation cell prior to the retrofitting is a mechanically or pneumatically agitated flotation cell.

[0094] In a further embodiment of the method for retrofitting process equipment into a flotation cell according to the invention, other flotation cells may follow the retrofitted flotation cell in the flotation line. Preferably, the first or the first and the second flotation cells in a flotation line may be retrofitted with the new process equipment.

[0095] In an embodiment, the flotation cell prior to the retrofitting may comprise process equipment, the process equipment comprising motor(s), driver motor(s), rotor(s), stator(s), agitator(s), and / or air blower(s), the process equipment being optionally removed and / or reused in the retrofitted installation. The reuse of the existing process equipment may greatly lower the costs of the method for retrofitting process equipment into a flotation cell.

[0096] In a further embodiment, the retrofitted flotation cell may utilize the motor(s) and / or drive motor(s) from the flotation cell as a pump motor(s).

[0097] In a further embodiment, the flotation cell may be configured to recover fast floating fractions of particles suspended in a slurry. The fast floating fraction may comprise particles suspended in a slurry that may be considered liberated particles of valuable mineral, which fast floating particles may readily separate preferably into the froth. In this configuration, the velocity of the infeed slurry may be reduced, having an additional benefit of reducing the wear rates of the flotation cell parts and equipment, and reducing the time required for servicing and maintenance.

[0098] In an embodiment of the flotation cell, a blast tube further comprises 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.

[0099] An impinger deflects the flow of slurry infeed radially outwards to the flotation tank sidewall and upwards towards the flotation tank upper surface (i.e. to the froth layer) so the fine flotation gas bubble - ore particle agglomerates do not short circuit into the tailings. All of the slurry infeed from the blast tubes are forced to rise up towards the froth layer at the top region of the flotation tank before gravity has the chance to influence the particles not adhered to flotation gas bubbles, forcing them to descend and eventually report to tailings flow or underflow. Thereby the probability of valuable material containing particles short-circuiting may be diminished. Slurry is highly agitated by the energy of the deflected flow, and forms mixing vortexes in which the size of the bubbles may be further reduced by the shear forces acting upon them. The high-shear conditions favorably also induce high number of contacts between flotation gas bubbles and particles in the slurry within the flotation tank. As the flow of slurry is forced upwards towards the froth layer, turbulence reduces and the flow becomes relatively uniform, which may contribute to the stability of the already formed bubbles, and flotation gas bubble- particle agglomerates, especially those comprising coarser particles.

[0100] 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 minimise 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 optimise the flotation process within a flotation cell equipped with blast tubes, as well as minimise wear to the impinger parts.

[0101] In an embodiment of the flotation cell, the volume of the flotation tank is at least 5 m 3< , preferably 20 to 1500 m 3< .

[0102] In an embodiment of the flotation cell, the blast tubes are arranged concentric to the perimeter of the flotation tank at a distance from a froth crowder.

[0103] In yet another embodiment of the flotation cell, the outlet is arranged at the sidewall of the flotation tank, at a distance from the bottom of the flotation tank.

[0104] In yet another embodiment of the flotation cell, the distance of the outlet from the bottom of the flotation tank is 0 to 50 % of the height of the flotation tank.

[0105] By taking slurry from the bottom of a flotation cell it may be ensured that the finer particles settled to the bottom of the flotation tank may be efficiently reintroduced into the part of the flotation tank where active flotation process takes place, before the finer particles are reported to tailings. Thus, the recovery rate of valuable material may be improved as the particles comprising even minimal amounts of valuable material may be collected into the concentrate.

[0106] The flotation process may be made more efficient when only a part of the slurry within the flotation tank is recirculated back into the same flotation tank as slurry infeed via the blast tubes. Especially as the impingers, designed to direct the flow of slurry radially outwards and upwards to form turbulent conditions to the mixing zone and to the additional mixing subzones, as explained earlier, are highly efficient in creating favorable conditions to flotation gas bubble - particle agglomerate creation and thus ensuring effective recovery of particles comprising valuable material, it may not be necessary to recirculated substantial amounts of the slurry to be treated again in the same flotation cell.

[0107] An embodiment of the use of the flotation line according to the invention is particularly intended for recovering mineral ore particles comprising nonpolar minerals such as graphite, sulphur, molybdenite, coal, and talc.

[0108] 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.

[0109] By using the flotation arrangement according to the present invention, the recovery of such low amounts of valuable mineral, for example copper, may be efficiently increased, and even poor deposits cost-effectively utilized. As the known rich deposits have increasingly already been used, there is a tangible need for processing the less favorable deposits as well, which previously may have been left unmined due to lack of suitable technology and processes for recovery of the valuable material in very low amounts in the ore.BRIEF DESCRIPTION OF THE DRAWINGS

[0110] The accompanying drawings, which are included to provide a further understanding of the invention and constitute a part of this specification, illustrate embodiments of the invention and together with the description help to explain the principles of the invention. In the drawings: Fig. 1 depicts a flotation cell according to an embodiment of the invention in side view, Fig. 1b depicts a flotation cell according to an embodiment of the invention seen from above, Fig. 2 depicts a flotation cell according to another embodiment of the invention in side view, detailing the dimensions of the system, Fig. 3a, 3b, and 3c are schematic drawings of flotation lines according to embodiments of the invention, Fig. 4 is a schematic presentation of forms of the bottom structure according to embodiments of the invention, Fig. 5 shows an example method for retrofitting process equipment into a flotation cell; and Fig. 6 shows an example method for retrofitting process equipment into a flotation line. DETAILED DESCRIPTION

[0111] Reference will now be made in detail to the embodiments of the present disclosure, an example of which is illustrated in the accompanying drawings.

[0112] The description below discloses some embodiments in such a detail that a person skilled in the art is able to utilize the flotation cell, flotation line and its use based on the disclosure. Not all steps of the embodiments are discussed in detail, as many of the steps will be obvious for the person skilled in the art based on this disclosure.

[0113] For reasons of simplicity, item numbers will be maintained in the following exemplary embodiments in the case of repeating components.

[0114] The enclosed figures 1 and 2 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. Figures 3a-c illustrate in a schematic manner embodiments of the flotation line. The direction of flows of slurry is shown in the figures by arrows. Figure 1 example shows a retrofitted flotation cell 1. The flotation cell may comprise a flotation tank 10 comprising a centre 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 flotation cell part or device. When a retrofitted flotation cell 1 is formed the at least one flotation cell part or device may be removed, and the process equipment may be installed to the flotation cell. The process equipment may comprise at least one device for combining an air stream and a slurry infeed stream to obtain particle-bubble aggregates and then introducing the combined air stream and slurry infeed 100 into the tank, such as at least one blast tube 4 for introducing slurry infeed 100 into the tank 10.

[0115] The device for combining 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.

[0116] 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.

[0117] 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 L 6 from the bottom 13 of the flotation tank 10. The distance L 6 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 H of the flotation tank 10. For example, the distance L 6 may be 2 %, or 5 % or 7,5 %, or 12 % of the height H. 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 adjacent 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.

[0118] Referring in particular to figures 1-2, the flotation cell 1 may comprise a flotation tank 10 that has a centre 11, a perimeter 12, a bottom 13 and a side wall 14. The flotation cell 1 further comprises a launder 2 and a launder lip 21 surrounding the perimeter 12 of the flotation tank 10.

[0119] In the accompanying figures, launder 2 is a perimeter launder. It is to be understood that a launder 2 may comprise, alternatively or additionally, a central launder arranged at the centre 11 of the flotation tank 10, as is known in the technical field. A launder lip of a central launder may face towards the perimeter 12 of the flotation tank 10, or towards the centre 11 of the flotation tank 10, or both. The overflow 500 may be collected into the launder 2 or launders as it passes over a launder lip 21, from a froth layer formed in the upper part of the flotation tank 10. The froth layer may comprise an open froth surface at the top of the flotation tank 10.

[0120] The flotation tank 10 has a height H, 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 H may be substantially equal to or greater than the height at the centre 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 centre 11 of the flotation tank 10.

[0121] The flotation tank 10 may have a volume of at least 5 m 3< . The flotation tank 10 may have a volume ranging from 20 to 1500 m 3< . For example, the volume of the flotation tank 10 may be 100 m 3< , or 200 m 3< , or 450 m 3< , or 630 m 3< .

[0122] The retrofitted 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 pressurized air or other gas, so that the slurry infeed 100 may be subjected to pressurized air or other gas as it is discharged from the inlet nozzle 41; an elongated chamber 40 arranged to receive under pressure the slurry infeed 100; 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 under pressure.

[0123] Flotation gas may be entrained through a turbulent mixing action brought about by the jet, and may be dispersed into small bubbles in the slurry infeed 100 as it may 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.

[0124] 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. For example, and to the outlet nozzle 43 may induce a supersonic shockwave into the slurry infeed 100 as it exits the blast tube 40. In addition, the supersonic shockwave may extend to the slurry adjacent to or surrounding the outlet nozzle so that even outside the blast tube, the creation of small size flotation gas bubble - particle agglomerates may thus be possible.

[0125] 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.

[0126] As the slurry infeed 100 passes through the outlet nozzle 43, or through the throttle of the outlet nozzle 43, flotation gas bubbles are reduced in size by the pressure changes, and by the high-shear environment downstream of the outlet nozzle 43. The velocity of the gas-liquid mixture in outlet nozzle 43, or in the throttle, may exceed the speed of sound when the flow 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.

[0127] The flow of slurry infeed 100 may become choked when the ratio of the absolute pressure upstream the outlet nozzle 43 to the absolute pressure downstream of a restricting structure of the outlet nozzle 43 may exceed a critical value. When the pressure ratio is above the critical value, flow of slurry infeed 100 downstream of the restricting structure of the outlet nozzle 43 may become supersonic and a shockwave may be formed. Small flotation gas bubbles in slurry infeed 100 mixture are split into even smaller by being forced through the shockwave and forced into contact with hydrophobic ore particles in slurry infeed 100, thus creating flotation gas bubble-ore particle agglomerates.

[0128] As seen from the example of FIG. 1 the tank 10 may be divided to a froth zone C, a mixing zone B, and a settling zone A. By the froth zone C is meant herein a vertical part or section of the flotation tank 10. The froth zone C may be about 1-25 % from the height of the settling zone A. In the froth zone C desirable minerals may be adhered to bubbles and may be transported to a launder lip. The froth zone C may comprise froth and slurry.

[0129] By a mixing zone B is meant herein a vertical part or section of the flotation tank 10 in which active mixing of particles suspended in slurry with gasified fluid bubbles may takes place. The mixing B zone may comprise gas bubbles, slurry, and fluid. The mixing zone B may be below the froth zone C.

[0130] By a settling zone A is meant a vertical part of section of the flotation tank 10 in which particles not associated with gasified fluid bubbles or otherwise not able to rise towards the froth zone C or may not be able to stay in the froth zone C on the top part of the flotation tank 10 may 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 settling zone A may comprise slurry. In the settling zone A gangue minerals may be settled and transported to tailings outlet 140 and / or outlet 31.

[0131] 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 C. The outlet nozzle 43 may be in the mixing zone B.

[0132] According to an example embodiment, when flotation feed will be around 180 µm - 300 µm there may be no need for the retrofitted flotation cell 1 to operate with the sonic choke producing a shockwave. The slurry infeed velocity exiting from the outlet nozzle 43 may be lower, for example in the range of 2 - 3 m / s.

[0133] 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 L 3 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. For example, the distance L 3 may be 5 times, 7 times, or 12 times, or 15 times the diameter of the outlet nozzle 43.

[0134] 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.

[0135] Some of the coarse hydrophobic particles that are carried into the froth may subsequently disengage from flotation gas bubbles and drop back into the flotation tank 10, as a result of bubble coalescence in the froth. However, the majority of such particles may fall back into the flotation tank 10 in such a way and position that they may be captured by bubbles newly entering the flotation tank 10 from the blast tubes 4, and carried once more into the froth layer.

[0136] 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 16 blast tubes 4. In another embodiment, there are 24 blast tubes 4. In yet another embodiment, there are 8 blast tubes 4. The exact number of blast tubes 4 may be chosen according to the specific operation, for example the type of slurry being treated within the flotation cell 1, the volumetric feed flowrate to the flotation cell 1, the mass throughput feed to the flotation cell 1, or the volume or dimensions of the flotation tank 10. In order to properly disperse flotation gas within the flotation tank 10, 4 to 6 blast tubes 4 may be employed.

[0137] The blast tubes 4 may be arranged concentric to the perimeter 12 of the flotation tank 10 at a distance from the centre 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 further arranged so that each blast tube 4 is located at a distance of an outlet nozzle 43 from the centre 11 of the flotation tank 10, the distance being preferably equal for each blast tube 4.

[0138] 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.

[0139] Further, in all the above mentioned embodiments, the blast tubes 4 may be arranged at equal distance from each other so that a distance between any two adjacent outlet nozzle 43 is the same.

[0140] 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. 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 90 into the flotation tank 10 through a slurry inlet 33 near or adjacent to the bottom 13 of the flotation tank. Alternatively, the fresh slurry feed 200 from the feed box 90 may be fed directly to the pumping system of the slurry recycling circuit 3. The pumping system may comprise a pump 32 and a pump motor 53. Alternatively, the fresh slurry feed 200 may be optionally diverted into the flotation tank 10 through the slurry inlet 33 and / or to the pumping system. The flow of the fresh slurry 200 into the flotation tank 10 and / or to the pumping system may be adjusted with a valve 34 and valve 35. If the flow of fresh slurry is into the flotation tank 10, the fresh slurry may mix with the slurry in the flotation tank, which mixed slurry may form the slurry fraction 300, which may be recirculated into the at least one blast tube 4 through the recirculation circuit 3.

[0141] In an embodiment, the flow of slurry in the slurry recycling circuit 3 comprises at least the slurry fraction 300 from the flotation tank 10, wherein the volumetric flow of the recirculated slurry from the flotation tank 10 to the slurry infeed 100 is at least 100 % of the volume of the feed of fresh slurry 200. The recirculated slurry from the flotation tank 10 to the slurry infeed 100 is for example, 150 % of fresh slurry 200 by volume, or 200 % of fresh slurry 200 by volume, or 250 % of fresh slurry 200 by volume, or 300 % of fresh slurry 200 by volume, or 350 % of fresh slurry 200 by volume. The recirculation of slurry has the advantage of reintroducing the particles suspended in a slurry into the slurry infeed 100 and possibly increasing the probability of capturing valuable substances into the froth.

[0142] In an embodiment of the invention, the flow of fresh slurry 200 arriving into the flotation tank 10 through the slurry inlet 33 is deflected downwards towards the bottom 13 of the flotation tank 10 by an internal deflector. The internal deflector may be arranged so that the feed of fresh slurry 200 is guided towards the slurry outlet 31. Feeding the fresh slurry 200 into the flotation tank 10 has the added benefit of mixing the fresh slurry with the slurry in the flotation tank. The internal deflector may help the flow of fresh slurry 200 mixed with the slurry in the flotation tank 10 to preferably flow towards the slurry outlet 31.

[0143] The outlet 31 may be arranged at a distance L 4 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 L 4 is 0 to 50 % of the height H 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 adjacent 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.

[0144] According to an example of figure 1b the tank 10 is divided to four quadrants Q1-Q4 seen from above of the tank 10. The outlet 31 may be located withing a same quadrant Q1 as the inlet 33. The quadrant is a sector equal to one-quarter of a cross section of the tank. The quadrant is a quarter of a circle or a quarter of the circumference of a circle. The circumference of a circle may be the circumference of the tank side wall 14 seen from above. The outlet 31 and the inlet 33 may be located at an angle from 0° to 90°, or from 0° to 45° from each other seen from above of the tank 10.

[0145] The inlet 33 may be arranged at a distance L 8 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 L 8 is 0 to 50 % of the height H of the flotation tank 10. Preferably the distance L 8 is higher than the distance L 4 so that the inlet 33 is positioned above outlet 31. The inlet 33 may be located at the mixing zone B. The inlet 33 may be located at the same height with the impinger 44.

[0146] Additionally, the flotation tank 10 may further comprise a bottom structure 7 (see Figs.4), arranged on the bottom (13), and may have a shape that may allow particles suspended in slurry to be mixed in the mixing zone B created over the bottom structure 7, and to settle down in a settling zone A surrounding the bottom structure 7. Optionally, the bottom structure 7 may have a shape that prevents buildup of solid materials, such as particles suspended in a slurry at the bottom of the flotation tank.

[0147] The bottom structure 7 may be for example a cone, a truncated cone, a pyramid, or a truncated pyramid. A cone or a truncated cone may be suitable for a flotation tank with a circular cross-section. A pyramid or a truncated pyramid may be a suitable form for a flotation tank with a rectangular cross-section.

[0148] The bottom structure 7 has a height h 4 , measured from the topmost part of the bottom structure 7 to the bottom 13 of the flotation tank 10. In case the form of the bottom structure is a cone or a pyramid, the topmost part is also the first vertex 71 of the functional triangle 700. In case the bottom structure 7 has some sort of truncated form, the height h 4 is measured from the level top of the truncated form (see middle image of Fig. 4) to the bottom 13 of the flotation tank 10. The height h 4 is greater than 1 / 5 and less than 3 / 4 of the height H of the flotation tank 10. Further, the diameter d 3 of the base 73 of the bottom structure 7 may be 1 / 4 to 3 / 4 of a diameter D of the bottom 13 of the flotation tank 10. In case a flotation tank 10 and / or the bottom structure 7 has a non-circular cross-section, the diameters are measured as the maximal diagonals of the respective parts (base 73 and bottom 13). In an embodiment, the surface area of a base 73 of the bottom structure 7 is less than 80 % of the surface area of the bottom 13 of the flotation tank 10. The surface area of the base 73 may be 25 to 80 % of the surface area of the bottom 13 of the flotation tank 10.

[0149] The bottom structure 7 may additionally comprise any suitable support structures and / or connecting structures for installing the bottom structure 7 into the flotation tank 10, on the bottom 13 of the flotation tank 10. The bottom structure 7 may be made of any suitable material such as metal, for example stainless steel.

[0150] According to the example embodiment, the method further comprises installing a slurry recycling circuit 3 to the retrofitted flotation cell 1

[0151] The slurry recycling circuit 3 may comprise a first slurry pipe 50 feeding the slurry fraction 300 from the outlet 31 to the pumping system and a second slurry pipe 51 feeding the slurry fraction 300 from the pumping system to the slurry infeed 100.

[0152] According to the example embodiment, the flotation cell further comprises a feed box 90 for feeding fresh slurry 200 to the slurry recycling circuit 3 or into the flotation tank 10.

[0153] According to the example embodiment, the pumping system combines the fresh slurry 200 and the slurry fraction 300 to slurry infeed 100 and distributes the slurry infeed 100 to the at least one blast tube 4.

[0154] The outlet 31 may be arranged at the side wall 14 of the flotation tank 10, at a distance L 4 from the bottom 13 of the flotation tank 10. The distance L 4 may be 0 to 50 % of the height H of the flotation tank 10. For example, the distance L 4 may be 2 %, or 8 %, or 12,5 %, or 20 %, or 33 % of the height H of the flotation tank 10.

[0155] Additionally, the slurry recycling circuit 3 may comprise a pumping system arranged to intake the slurry fraction 300 from the flotation tank 10, and to forward slurry infeed 100 to the at least one blast tube 4. The slurry fraction 300 may comprise low settling velocity particles such as fine, slow-floating particles. The slurry fraction may be taken from or near the bottom of the flotation tank 10, for example from the settling zone A. The pumping system may also be used to forward the slurry infeed 100 into the blast tubes 4.

[0156] According to the example embodiment, the total dynamic head h 3 on the pumping system may be measured as the distance from the surface of the slurry at the perimeter 12 of the tank 10 to the level of slurry at the highest most point of the second slurry pipe 51 in the slurry recycling circuit 3. The total dynamic head on the pumping system may be reduced compared to conventional flotation cells with recirculation lines. Typically, pumps 32 may need to be able to pump up to 20 or 30 m, but in the disclosed solution the pumping height may be significantly reduced due to the slurry within the tank 10 being in constant communication with the pumping system thereby reducing the total head on the pumping system.

[0157] According to the example embodiment, the at least one removed flotation cell part or device comprises at least one of the following: a motor, a drive motor, a drive mechanism, a rotor, a stator, and / or an air blower.

[0158] According to the example embodiment, the removed drive motor is reused as a pump motor 53 in the slurry recycling circuit 3.

[0159] According to the example embodiment, the pumping system is located below the retrofitted flotation cell 1.

[0160] According to the example embodiment, the removed air blower is used as an air supply for the at least one blast tube 4.

[0161] According to an example embodiment, the pumping system is directly connected to the flotation tank 10.

[0162] According to an example embodiment, a retrofitted flotation cell 1 is configured to be formed by removing and / or reusing at least one flotation cell part or device. Then the process equipment may be installed to the flotation cell. The process equipment may comprise at least one device for combining an air stream and a slurry infeed 100 to obtain particle-bubble aggregates. After that the combined air stream and slurry infeed 100 may be configured to be introduced into the tank 10 and a slurry recycling circuit 3 is configured to be provided to the retrofitted flotation cell 1, wherein the slurry recycling circuit may comprise the pumping system.

[0163] According to an example embodiment, wherein the device for combining an air stream and a slurry infeed 100 to obtain particle-bubble aggregates and then introducing the combined air stream and slurry infeed 100 into the tank 10 comprises at least one blast tube 4.

[0164] According to an example embodiment, the slurry recycling circuit 3 comprises an outlet 31, a first slurry pipe 50, a pumping system, and a second slurry pipe 51. The pumping system may comprise a pump 31 and a pump motor 53, wherein the pump 31 is connected to a pump motor 53.

[0165] According to an example embodiment, fresh slurry 200 is fed into the flotation tank 10 and / or to the pumping system.

[0166] According to an example embodiment, the slurry recycling circuit 3 is configured to circulate a slurry fraction 300 from the flotation tank 10 to slurry infeed 100 and distribute the slurry infeed 100 to the at least one blast tube 4.

[0167] According to an example embodiment, the flotation cell further comprises a feed box 90 for feeding the fresh slurry 200 into the flotation cell 1 and / or to the pumping system.

[0168] According to an example embodiment, the feed box 90 is connected to the flotation tank 10 and / or to the pumping system, wherein if the feed box 90 is connected to the flotation tank 10 and the pumping system the feed of the fresh slurry 200 is configured to be diverted into the flotation tank and / or to the pumping system. If the feed box 90 may be connected to the flotation tank 10 and the pump 32 the feed of the fresh slurry 200 is configured to be diverted into the flotation tank and / or to the pump 31.

[0169] According to an example embodiment, the at least one removed and / or reused flotation cell part or device comprises at least one of the following: a motor, a drive mechanism, a rotor, a stator, and / or an air blower.

[0170] According to an example embodiment, the removed and / or reused motor is configured to be reused as a pump motor 53 for the pumping system in the slurry recycling circuit 3.

[0171] According to an example embodiment, the pump 32 and pump motor 53 are located below or on the same level as the retrofitted flotation cell 1.

[0172] According to an example embodiment, the removed and / or reused air blower is configured to be used as an air supply for the at least one blast tube 4.

[0173] According to an example embodiment, the flotation cell 1 comprises a superstructure, wherein the superstructure of the flotation cell 1 to be retrofitted with the process equipment, is configured to be utilized in the construction of the retrofitted flotation cell 1. The superstructure may comprise at least one of the following: a foundation, steel support base, piping, electrical wiring, instrumentation, instrumentation wiring, supporting structure, channels, troughs, and / or the flotation tank 10.

[0174] According to an example embodiment, a bottom structure 7 is configured to be installed on a bottom 13of the flotation tank 10. The bottom structure 7 has a shape that may allow particles suspended in a slurry to limit particle buildup in the centre of the tank 10.

[0175] According to an example embodiment, a mechanical mixer is configured to be reused or installed at the bottom 13 of the flotation tank 10. The said mechanical mixer may be configured to be operated to prevent buildup of solid materials at the bottom 13 of the flotation tank 10.

[0176] According to an example embodiment, the retrofitted flotation cell 1 is configured to recover the fraction of floating minerals from the slurry.

[0177] According to an example embodiment, the retrofitted flotation cell 1 is configured to process slurry containing solid particles suspended in a slurry having an average particle size of about 1 to 2,000 µm.

[0178] According to an example embodiment, the process equipment comprises 2-40 blast tubes 4 or 4-24 blast tubes 4.

[0179] According to an example embodiment, the at least one device for combining the air stream and the slurry infeed 100 to obtain particle-bubble aggregates and then introducing the combined air stream and slurry infeed 100 into the tank 10 is self-aspirating.

[0180] According to an example embodiment, the at least one device for combining the air stream and the slurry infeed 100 to obtain particle-bubble aggregates and then introducing the combined air stream and the slurry infeed 100 into the tank 10 comprises at least one blast tube 4, which blast tube 4 is pressurized.

[0181] According to an example embodiment, the at least one blast tube comprises an impinger 44 configured to contact a flow of slurry infeed 100 from an outlet nozzle 43 and to direct the flow of the slurry infeed 100 radially outwards and upwards of the impinger 44.

[0182] The method according to any preceding claim, wherein an internal deflector is provided inside the flotation tank 10 to guide the fresh slurry 200 entering the flotation tank 10 towards the outlet 31.

[0183] According to another aspect of the invention, flotation lines 8 are presented in figures 3a, 3b, and 3c. A flotation line 8 comprises a number of fluidly connected flotation cells 1a, and at least one of the flotation cells is a retrofitted flotation cell 1 according to the above described embodiments. In an embodiment of the flotation line 8, at least one flotation cell 1a follows the retrofitted flotation cell 1. A flotation cell 1a may be of any type known in the field. Alternatively, or additionally, the flotation cell 1a may be preceded by mechanical flotation cell.

[0184] In an embodiment of the flotation line 8, it comprises a rougher part 81 with retrofitted flotation cells 1; a scavenger part 82 with a flotation cell 1 arranged to receive underflow 400 for the rougher part 81; and a scavenger cleaner part 820 with a flotation cell 1 arranged to receive overflow 500 from the scavenger part 82 (see Fig. 3b). In the flotation line 8, the first and second flotation cell 1 of the rougher part 81, the first and second flotation cell 1 of the scavenger part 82, and alternatively or additionally, the first flotation cell 1 of the scavenger cleaner part 820 may be a retrofitted flotation cell 1 according to the invention, with at least one blast tube 4. Additionally, in the flotation line 8, as described above, the retrofitted flotation cell 1 according to the invention, with the at least one blast tube 4, may be followed by a mechanical flotation cell 1a.

[0185] According to an example embodiment, in the flotation line 8, at least one flotation cell 1 of the scavenger part 82, at least first flotation cell 1 of the scavenger cleaner part 820, and / or at least first flotation cell 1 of the rougher part 81 is a retrofitted flotation cell 1 according to the invention.

[0186] 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.

[0187] According to a further aspect of the invention, the flotation line 8 may be used in recovering particles comprising a valuable material suspended in slurry. In an embodiment, the use may be directed to recovering particles comprising nonpolar minerals such as graphite, sulphur, molybdenite, coal, talc.

[0188] According to the example embodiment, a flotation line 8 comprising a number of fluidly connected flotation cells is disclosed. The process equipment may be configured to be retrofitted into at least one flotation cell. At least one flotation cell may comprise a flotation tank 10 comprising a centre 11, a perimeter 12, a substantially horizontal bottom 13, and a side wall. At least one flotation cell may further comprise a launder 2 and a launder lip 21 surrounding the perimeter 12 of the tank 10, The process equipment may be configured to be installed to the at least one flotation cell 1. The process equipment may comprise at least one device for combining an air stream and a slurry infeed 100 to obtain particle-bubble aggregates and then introducing the combined air stream and slurry infeed into the tank 10. A slurry recycling circuit 3 may be configured to be provided to the at least one retrofitted flotation cell 1, wherein the slurry recycling circuit 3 may comprise a pumping system.

[0189] According to the example embodiment, the flotation line 8 may comprise at least one superstructure. The at least one superstructure of the at least one flotation cell 1 to be retrofitted with the process equipment may be configured to be utilized in the construction of the retrofitted flotation cell 1. The superstructure may comprise at least one of the following: a foundation, steel support base, piping, electrical wiring, instrumentation, instrumentation wiring, supporting structure, channels, troughs, and / or the flotation tank 10.

[0190] According to the example embodiment, the flotation line 8 may comprise 2-8 fluidly connected flotation cells 1, 1a, or 2-6 fluidly connected flotation cells 1, 1a, or 2-5 fluidly connected flotation cells 1, 1a, or 2-4 fluidly connected flotation cells 1, 1a, or 2-3 fluidly connected flotation cells 1, 1a. The first flotation cell 1, or the first and the second flotation cell 1, or flotation cells 1-3, or flotation cells 1-4, or flotation cells 1-5, or flotation cells 1-6, or flotation cells 1-7, or flotation cells 1-8 in the flotation line 8 may be configured to be retrofitted with process equipment according to any of the preceding claims.

[0191] According to the example embodiment, the first and the second flotation cell 1 in the flotation line 8 may be located on the same relative level and may be configured to be retrofitted with process equipment according to any of the embodiments above. The feed of fresh slurry 200 may be configured to be directed to the first flotation cell 1 and / or the second flotation cell 1 in the flotation line 8, wherein the first flotation cell 1 may be fluidly connected to the second flotation cell 1 and the first flotation cell may be optionally fluidly connected to the third flotation cell 1a. The fluid connection between the first and the second flotation cell 1 in the flotation line 8 may be configured to be suspended by a valve or a barrier. If the fluid connection between the first and the second flotation cell 1 in the flotation line 8 is configured to be suspended, the feed of fresh slurry 200 may be configured to be independently directed to the first flotation cell 1 and / or the second flotation cell 1 in the flotation line 8. The underflow 400 from the first flotation cell 1 and / or the second flotation cell 1 in the flotation line 8 may be configured to be directed to the third flotation cell 1a in the flotation line 8.

[0192] Fig. 5 illustrates an example of a method for retrofitting process equipment into a flotation cell. The method may comprise forming a retrofitted flotation cell 1 by removing the at least one flotation cell part or device, or keeping all parts of the flotation cell by verifying that there is no interference with any process equipment to be installed. The flotation cell may comprise a flotation tank 10 comprising a centre 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.

[0193] At operation 500, the method may comprise forming a retrofitted flotation cell 1 by installing process equipment to the flotation cell, wherein the process equipment may comprise at least one device for combining an air stream and a slurry infeed 100 to obtain particle-bubble aggregates and then introducing the combined air stream and slurry infeed 100 into the tank 10.

[0194] At operation 510, the method may comprise further providing a slurry recycling circuit 3 to the retrofitted flotation cell 1, wherein the slurry recycling circuit 3 may comprise a pumping system.

[0195] Fig. 6 illustrates an example of a method for retrofitting process equipment into a flotation line 8. The method may comprise forming a retrofitted flotation line 8 by removing the at least one flotation cell part or device, or keeping all parts of the flotation cell by verifying that there is no interference with any process equipment to be installed. Aat least one flotation cell may comprise a flotation tank 10 comprising a centre 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.

[0196] At operation 600, the method may comprise forming at least one retrofitted flotation cell 1 by installing the process equipment to the at least one flotation cell, wherein the process equipment may comprise at least one device for combining an air stream and a slurry infeed 100 to obtain particle-bubble aggregates and then introducing the combined air stream and slurry infeed 100 into the tank 10.

[0197] At operation 610, the method may comprise providing a slurry recycling circuit 3 to the at least one retrofitted flotation cell 1, wherein the slurry recycling circuit 3 may comprise a pumping system.

[0198] 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 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.

Examples

Embodiment Construction

[0111]Reference will now be made in detail to the embodiments of the present disclosure, an example of which is illustrated in the accompanying drawings.

[0112]The description below discloses some embodiments in such a detail that a person skilled in the art is able to utilize the flotation cell, flotation line and its use based on the disclosure. Not all steps of the embodiments are discussed in detail, as many of the steps will be obvious for the person skilled in the art based on this disclosure.

[0113]For reasons of simplicity, item numbers will be maintained in the following exemplary embodiments in the case of repeating components.

[0114]The enclosed figures 1 and 2 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. Figures 3a-c illustrate in a schematic manner embodiments of the flotation line. The direction of flows of slurry is shown in the figures by arrows. Figure ...

Claims

1. A method for retrofitting process equipment into a flotation cell, wherein the flotation cell comprises a flotation tank (10) comprising a centre (11), a perimeter (12), a bottom (13), and a side wall (14); a launder (2) and a launder lip (21); wherein the method comprises forming a retrofitted flotation cell (1) by installing process equipment to the flotation cell, wherein the process equipment comprises at least one device for combining an air stream and a slurry infeed (100) to obtain particle-bubble aggregates and then introducing the combined air stream and slurry infeed (100) into the tank (10); and providing a slurry recycling circuit (3) to the retrofitted flotation cell (1), wherein the slurry recycling circuit (3) comprises a pumping system.

2. The method according to claim 1, wherein the method comprises connecting the pumping system directly to the flotation tank (10).

3. The method according to claim 1 or 2, wherein the method comprises forming a retrofitted flotation cell (1) by removing and / or reusing at least one flotation cell part or device; installing process equipment to the flotation cell, wherein the process equipment comprises at least one device for combining an air stream and a slurry infeed (100) to obtain particle-bubble aggregates and then introducing the combined air stream and slurry infeed (100) into the tank (10), and providing a slurry recycling circuit (3) to the retrofitted flotation cell (1) wherein the slurry recycling circuit (3) comprises the pumping system.

4. The method according to any one of the preceding claims, wherein the device for combining an air stream and a slurry infeed (100) to obtain particle-bubble aggregates and then introducing the combined air stream and slurry infeed (100) into the tank (10) comprises at least one blast tube (4).

5. The method according to any one of the preceding claims, wherein the slurry recycling circuit (3) comprises an outlet (31), a first slurry pipe (50), a pumping system, and a second slurry pipe (51).

6. The method according to any preceding claim, wherein fresh slurry (200) is fed into the flotation tank (10) and / or to the pumping system.

7. The method according to any preceding claim 4-6, wherein the slurry recycling circuit (3) circulates a slurry fraction (300) from the flotation tank (10) to slurry infeed (100) and distributes the slurry infeed (100) to the at least one blast tube (4).

8. The method according to any preceding claim, wherein the flotation cell further comprises a feed box (90) for feeding the fresh slurry (200) into the flotation cell (1) and / or to the pumping system.

9. The method according to claim 8, wherein the feed box (90) is connected to the flotation tank (10) and / or to the pumping system, wherein if the feed box (90) is connected to the flotation tank (10) and the pumping system the feed of the fresh slurry (200) is diverted into the flotation tank and / or to the pumping system.

10. The method according to any of claims 3 to 9, wherein the at least one removed and / or reused flotation cell part or device comprises at least one of the following: a motor, a drive mechanism, a rotor, a stator, and / or an air blower.

11. The method according to claim 10, wherein the removed and / or reused motor is reused as a pump motor (53) for the pumping system in the slurry recycling circuit (3).

12. The method according to claim 11, wherein the pump (32) and pump motor (53) are located below or on the same level as the retrofitted flotation cell (1).

13. The method according to any of claims 10 to 12, wherein the removed and / or reused air blower is used as an air supply for the at least one blast tube (4) .

14. The method according to any preceding claim, wherein the flotation cell (1) comprises a superstructure, wherein the superstructure of the flotation cell (1) to be retrofitted with the process equipment, is utilized in the construction of the retrofitted flotation cell (1), wherein the superstructure comprises at least one of the following: a foundation, steel support base, piping, electrical wiring, instrumentation, instrumentation wiring, supporting structure, channels, troughs, and / or the flotation tank (10).

15. The method according to any preceding claim, wherein the method further comprises installing a bottom structure (7) on a bottom (13) of the flotation tank (10), wherein the bottom structure (7) has a shape that allows particles suspended in a slurry to limit particle buildup in the centre of the tank (10).

16. The method according to any preceding claim, wherein the method further comprises reusing or installing a mechanical mixer at the bottom (13) of the flotation tank (10), wherein the said mechanical mixer is be operated to prevent buildup of solid materials at the bottom (13) of the flotation tank (10).

17. The method according to any preceding claim, wherein the retrofitted flotation cell (1) recovers the fraction of floating minerals from the slurry.

18. The method according to any preceding claim, wherein the retrofitted flotation cell (1) processes slurry containing solid particles suspended in a slurry having an average particle size of about 1 to 2,000 µm.

19. The method according to any preceding claim, wherein the process equipment comprises 2-40 blast tubes (4) or 4-24 blast tubes (4).

20. The method according to any preceding claim, wherein the at least one device for combining the air stream and the slurry infeed (100) to obtain particle-bubble aggregates and then introducing the combined air stream and slurry infeed (100) into the tank (10) is self-aspirating.

21. The method according to any preceding claim 4-20, wherein the at least one device for combining the air stream and the slurry infeed (100) to obtain particle-bubble aggregates and then introducing the combined air stream and the slurry infeed (100) into the tank (10) comprises at least one blast tube (4), which at least one blast tube (4) is pressurized.

22. The method according to any preceding claim 4-21, wherein the at least one blast tube comprises an impinger (44) configured to contact a flow of slurry infeed (100) from an outlet nozzle (43) and to direct the flow of the slurry infeed (100) radially outwards and upwards of the impinger (44).

23. The method according to any preceding claim, wherein an internal deflector is provided inside the flotation tank (10) to guide the fresh slurry (200) entering the flotation tank (10) towards the outlet (31) .

24. A method for retrofitting process equipment into a flotation line (8), wherein the flotation line (8) comprises a number of fluidly connected flotation cells (1), wherein at least one flotation cell (1) comprises a flotation tank (10) comprising a centre (11), a perimeter (12), a bottom (13), and a side wall (14); a launder (2) and a launder lip (21); wherein the method comprises forming at least one retrofitted flotation cell (1) by installing the process equipment to the at least one flotation cell, wherein the process equipment comprises at least one device for combining an air stream and a slurry infeed (100) to obtain particle-bubble aggregates and then introducing the combined air stream and slurry infeed (100) into the tank (10); and providing a slurry recycling circuit (3) to the at least one retrofitted flotation cell (1), wherein the slurry recycling circuit (3) comprises a pumping system.

25. A flotation line (8) comprising a number of fluidly connected flotation cells, wherein process equipment is configured to be retrofitted into at least one flotation cell, wherein at least one flotation cell comprises a flotation tank (10) comprising a centre (11), a perimeter (12), a bottom (13), and a side wall (14); and a launder (2) and a launder lip (21); wherein the process equipment is configured to be installed to the at least one flotation cell (1), wherein the process equipment comprises at least one device for combining an air stream and a slurry infeed (100) to obtain particle-bubble aggregates and then introducing the combined air stream and slurry infeed (100) into the tank (10); and a slurry recycling circuit (3) is configured to be provided to the at least one retrofitted flotation cell (1), wherein the slurry recycling circuit (3) comprises a pumping system.

26. A flotation line (8) according to claim 25, wherein the flotation line (8) comprises at least one superstructure, wherein the at least one superstructure of the at least one flotation cell (1) to be retrofitted with the process equipment is configured to be utilized in the construction of the retrofitted flotation cell (1), wherein the superstructure comprises at least one of the following: a foundation, steel support base, piping, electrical wiring, instrumentation, instrumentation wiring, supporting structure, channels, troughs, and / or the flotation tank (10).

27. The flotation line (8) according to claim 25 or claim 26, wherein the flotation line (8) comprises 2-8 fluidly connected flotation cells (1), or 2-6 fluidly connected flotation cells, or 2-5 fluidly connected flotation cells, or 2-4 fluidly connected flotation cells, or 2-3 fluidly connected flotation cells, wherein the first flotation cell (1), or the first and the second flotation cell (1), or flotation cells 1-3, or flotation cells 1-4, or flotation cells 1-5, or flotation cells 1-6, or flotation cells 1-7, or flotation cells 1-8 in the flotation line (8) is (are) configured to be retrofitted with process equipment according to any of the preceding claims.

28. The flotation line (8) according to any of the preceding claims 25 to 27, wherein the first and the second flotation cell (1) in the flotation line (8) are located on the same relative level and are configured to be retrofitted with process equipment according to any of the preceding claims, wherein the feed of fresh slurry (200) is configured to be directed to the first flotation cell (1) and / or the second flotation cell (1) in the flotation line (8), wherein the first flotation cell (1) is fluidly connected to the second flotation cell (1) and the first flotation cell (1) is optionally fluidly connected to the third flotation cell (1a), wherein the fluid connection between the first and the second flotation cell (1) in the flotation line (8) is configured to be suspended by a valve or a barrier, and wherein if the fluid connection between the first and the second flotation cell (1) in the flotation line (8) is configured to be suspended, the feed of fresh slurry (200) is configured to be independently directed to the first flotation cell (1) and / or the second flotation cell (1) in the flotation line (8), and wherein the underflow (400) from the first flotation cell (1) and / or the second flotation cell (1) in the flotation line (8) is configured to be directed to the third flotation cell (1a) in the flotation line (8).

Images