ES3008951T3 - Flotation cell - Google Patents

Abstract

A flotation cell (1) is described for treating suspended particles in sludge and separating it in an overflow (400) and an overflow (500). The flotation cell comprises a flotation tank (10) with a center (11), a perimeter (12), a substantially horizontal bottom (13), and a side wall (14); a trough (2) and a trough lip (21) surrounding the perimeter (12) of the tank (11); and a bottom structure (7) arranged above the bottom (13), the shape of which allows the suspended particles in sludge to mix in a mixing zone (A) above the bottom structure and to settle in a sedimentation zone (B) surrounding said structure. The flotation tank further comprises blow tubes (4) for introducing the sludge feed (100) into the tank. In addition, a flotation line and its use are described. (Automatic translation with Google Translate, without legal value)

Description

DESCRIPTION

Flotation cell

FIELD OF TECHNIQUE

The present disclosure relates to a flotation cell for separating particles containing valuable material from particles suspended in slurry and to a flotation line and its use.

BACKGROUND OF THE INVENTION

Document CN 107 362 911 A discloses a flotation cell comprising a flotation tank comprising a pan and a pan flange surrounding the perimeter of the tank, an open foam surface at the top of the flotation tank, jet tubes for introducing slurry into the flotation tank and a lower structure arranged on the bottom of the flotation tank.

Document WO 2015/108044 A1 discloses a flotation tank comprising a sparging unit with an inlet nozzle for introducing slurry into the sparging unit and an inlet for pressurized gas. The sparging mechanism of the sparging unit sprays the gas into the bubble dispersion and the attachment of the particles to the bubbles occurs in the sparging unit before the mixture of slurry and bubbles is discharged into the flotation tank. The sparging unit further comprises an outlet nozzle that restricts the flow of the slurry out of the sparging unit. SUMMARY OF THE INVENTION

The flotation cell according to the present disclosure is characterized by what is presented in claim 1.

The waterline according to the present disclosure is characterized by what is presented in claim 17.

The use of the flotation line according to the present disclosure is characterized by that presented in claim 20. A flotation cell is provided for the treatment of suspended particles in slurry and for separating the slurry into an underflow flow and an overflow flow. The flotation cell comprises a flotation tank comprising a center, a perimeter, a flat, essentially horizontal bottom, and a side wall; a pan and a pan flange surrounding the perimeter of the tank; and a lower structure disposed above the bottom and shaped to allow particles suspended in slurry to mix in a mixing zone above the lower structure, and to settle in a settling zone surrounding the lower structure. The flotation cell is characterized in that the flotation tank further comprises jet tubes for introducing the slurry charge into the flotation tank. A jet tube comprises an inlet nozzle for introducing the slurry charge into the jet tube; an inlet for pressurized gas, the slurry charge being subjected to the pressurized gas as it is discharged from the inlet nozzle; an elongated chamber arranged to pressurize the slurry charge; and an outlet nozzle configured to restrict the flow of the slurry charge from the outlet nozzle and to maintain the slurry charge in the elongated chamber under pressure; and wherein the jet tubes are arranged in a position relative to the lower structure such that mixing is induced in the mixing zone.

According to one aspect of the invention, a flotation line is provided. The flotation line comprises a plurality of fluidly connected flotation cells, and is characterized in that at least one of the flotation cells is a flotation cell according to the invention.

According to another aspect of the invention, the use of the flotation line according to the invention is intended for the recovery of particles comprising a valuable material suspended in slurry.

With the invention described herein, the recovery of fine particles in a flotation process can be improved. The particles can, for example, comprise mineral ore particles, such as particles comprising a metal.

In froth flotation for mineral ore, the concentrate is concentrated to an intermediate particle size range of between 40 pm and 150 pm. Fine particles are therefore particles with a diameter between 0 and 40 pm, and ultrafine particles can be identified as falling at the lower end of the fine particle size range. Coarse particles have a diameter greater than 150 pm. In froth flotation of coal, the concentrate is concentrated to an intermediate particle size range of between 40 pm and 300 pm. In coal processing, fine particles are particles with a diameter between 0 and 40 pm, and ultrafine particles are those at the lower end of the fine particle size range. Coarse coal particles have a diameter greater than 300 pm.

Recovering very coarse or very fine particles is challenging because, in a traditional mechanical flotation cell, fine particles cannot be easily trapped by flotation gas bubbles and can therefore be lost in the tailings. Typically, in froth flotation, flotation gas is introduced into a flotation cell or tank through a mechanical agitator. The flotation gas bubbles thus generated have a relatively large size range, typically between 0.8 and 2.0 mm, or even larger, and are not particularly suitable for collecting finer particles.

Fine particle recovery can be improved by increasing the number of flotation cells within a flotation line, or by recirculating the floated material (overflow overflow) or tailings flow (underflow overflow) back to the beginning of the flotation line or to previous flotation cells. A finishing flotation line can be used to improve fine particle recovery. In addition, various flotation arrangements have been devised that employ fine flotation gas bubbles or even so-called microbubbles. The introduction of these smaller bubbles or microbubbles can be carried out before the slurry is introduced into the flotation cell; that is, the ore particles are subjected to fine bubbles at a feed connection or similar to promote the formation of agglomerates of ore particles and fine bubbles, which can then be floated in flotation cells such as flash flotation cells or column cells. Alternatively, fine bubbles or microbubbles can be introduced directly into the flotation cell, for example, by spargers utilizing cavitation. These types of solutions are not necessarily viable for mechanical flotation cells, as the turbulence caused by mechanical agitation can cause agglomerates of ore particles and fine bubbles to disintegrate before they can rise to the froth layer to be collected in the upper overflow and thus recovered.

Column flotation cells act as three-phase settlers in which particles move downward in a hindered settling environment against a flow of rising flotation gas bubbles generated by spargers located near the bottom of the cell. Although column flotation cells can improve the recovery of finer particles, particle residence time depends on the settling velocity, which can impact the flotation of large particles. In other words, while the flotation solutions mentioned above can have a beneficial effect on the recovery of fine particles, overall flotation performance (recovery of all valuable material, quality of recovered material) can be undermined by the negative effect on the recovery of larger particles.

To overcome the above problems, so-called pneumatic flotation cells are used. In this way, the flotation gas is introduced into a high-shear device such as a slurry-laden downcomer, thereby creating finer flotation gas bubbles that can trap even finer particles during bubble formation in the jet tube. However, these high-performance flotation cells may require the creation of a vacuum in the downcomer to effectively achieve the bubble formation rate necessary to trap the desired particles in the short time the slurry load remains in the jet tube.

Once they exit the downcomer, the particle agglomerates and flotation gas bubbles immediately rise to the froth layer above the flotation cell, and no more particles are trapped in the section of the flotation cell downstream from the jet tube outlet. This can cause a significant portion of the particles comprising a desired material (mineral) to simply fall to the bottom of the flotation tank and end up in the tailings, reducing the flotation cell's recovery rate.

However, so-called high-performance flotation cells or pneumatic flotation cells of the Jameson cell type typically do not include any flow restrictions to control the pressure within the downcomer tube after the formation of particle agglomerates and flotation air bubbles. Such pressure control is advantageous not only in view of the pressure at which the flotation gas bubbles form (effect on bubble size), but also for adjusting the relative pressure to that at which they will be used in the flotation tank. In this way, bubble coalescence after formation can be minimized. This is particularly advantageous since the particle capture rate by the flotation gas bubbles decreases as bubble size increases (provided the air-to-liquid ratio remains the same).

Furthermore, so-called high-performance flotation cells can be used in coal liberation operations, where there is typically a flotation line comprising one or two such flotation cells at the end of the liberation circuit for the recovery of particularly fine coal particles. In the liberation circuit, a process water recirculation system circulates water from the final part of the circuit (i.e., from the flotation line and a dewatering circuit) back to the front circuit (start of the liberation circuit). Flotation chemicals, especially frothers, often cause problems in processes upstream of the flotation line. The problems can be mitigated somewhat by minimizing the use of frothers in the waterline, but if insufficient frother is added to the flotation process, froth formation in prior-art jet tubes can be impaired, leading to unstable process conditions and particularly unstable operation of the downcomer and froth layer in a flotation cell, which in turn adversely affects the recovery of the desired particles. Particle recovery within the entire particle size distribution of a slurry is impaired as bubble size increases with lower frother dosage, particularly for coarse particles.

In prior art downcomers, the flotation gas is introduced in a self-priming manner due to the formation of a vacuum within the downcomer. The residence time of the flotation air that must be entrained within the slurry is very short, making the system very sensitive to process variations. It is necessary to constantly add frothers to overcome the restriction effect of the air flow rate required to maintain or even increase the vacuum inside the downcomer in order to keep conditions as constant as possible for bubble-particle coupling, since frothers prevent bubbles from coalescing and rising back into the air space not filled by the slurry inside the downcomer. However, the addition of a quantity of frothers required by the constant use of a prior art downcomer creates problems in other parts of the process, particularly in coal operations, as described above. Therefore, the solution has been to decrease the froth dosage, which negatively affects the vacuum in the downcomer, bubble formation, as well as bubble size and surface area, and significantly decreases the recovery of the desired particles, making the high-performance flotation cells known in the prior art inefficient in that application.

By using a flotation cell according to the present invention, the amount of froth agent required to optimize the flotation process can be significantly reduced without significantly compromising bubble formation, bubble attachment to particles, the formation of a stable froth layer, or the recovery of the desired material. Simultaneously, problems associated with recirculating process water from the downstream to the front-end circuit can be mitigated. A pressurized jet tube is completely independent of the flotation tank. Improved flotation gas flow rates can be achieved, finer bubbles can be created, and froth agent usage can be optimized, since the jet tube's operation is independent of froth agent dosage.

In known prior art solutions, problems are primarily related to limitations in the amount of flotation gas that can be supplied relative to the amount of liquid flowing through the downcomer, and to the requirement for relatively high concentrations of expensive frothers or other surfactants to produce small bubbles. With the invention presented herein, the flotation of fine and ultrafine particles comprising, for example, mineral ore or coal can be improved by reducing the size of the flotation gas bubbles introduced into the slurry charge in a jet tube, by increasing the flotation gas supply rate relative to the flow rate of particles suspended in the slurry, and by increasing the shear intensity or energy dissipation rate in or adjacent to the jet tube. This increases the probability that finer particles will adhere to or be trapped by smaller flotation gas bubbles, and improves the recovery rate of the desired material such as mineral or coal. In a flotation cell according to the invention, sufficiently small flotation gas bubbles, so-called ultrafine bubbles, can be created to ensure that the fine ore particles are effectively trapped. Typically, ultrafine bubbles can have a bubble size distribution between 0.05 mm and 0.7 mm. For example, decreasing the average size of the flotation gas bubbles to a diameter of between 0.3 and 0.4 mm means that the number of bubbles in 1 m of slurry can reach between 30 and 70 million, and the total average surface area of the bubbles between 15 and 20 m. In contrast, if the average bubble size is approximately 1 mm, the number of bubbles in 1 m of slurry is approximately 2 million, and the total average surface area is 6 m. In the flotation cell according to the invention, it may therefore be possible to achieve a bubble surface area between 2.5 and 3 times greater than in flotation cells according to prior art solutions. Needless to say, the effect of such an increase in bubble surface area is significant for the recovery of particles comprising valuable material.

At the same time, the recovery of coarser particles can be kept at an acceptable level by achieving a high flotation gas fraction in the slurry and by avoiding highly turbulent zones below the froth layer. This means that the well-known advantages of mechanical flotation cells can be utilized, even though mechanical agitation may not necessarily be present in the flotation cell. Furthermore, the upward movement of the slurry or pulp within the flotation tank increases the likelihood that coarser particles will also rise toward the froth layer with the slurry flow.

One of the effects that can be achieved with the present invention is the increase in the depth or thickness of a froth layer. A thicker froth layer contributes to increased recovery of smaller particles, and a separate froth washing step common in column flotation cells can be eliminated.

By arranging a number of jet tubes in a flotation cell according to the invention, the probability of collisions between flotation gas bubbles, as well as between gas bubbles and particles, can be increased. Having several jet tubes can ensure a better distribution of the flotation gas bubbles within a flotation tank, and the bubbles exiting the jet tubes are distributed evenly throughout the flotation tank. The distribution areas of the individual jet tubes have the possibility of intersecting each other and converging, thus promoting a largely uniform distribution of the flotation gas bubbles in the flotation tank, which in turn can beneficially affect the recovery of especially small particles and also contribute to the aforementioned uniform and thick froth layer. When there are several jet tubes, collisions between flotation gas bubbles and/or particles in the slurry feed from different jet tubes are promoted, since the different flows intermingle and create local mixing sub-zones. As collisions increase, more bubble-particle agglomerates are created and captured in the foam layer, so the recovery of valuable material can be improved.

By generating fine flotation gas bubbles or ultrafine bubbles, bringing them into contact with the particles, and controlling the mixing of the liquid slurry, particle agglomerates, and flotation gas bubbles, it may be possible to maximize the recovery of hydrophobic particles in the froth layer and in the overflow or concentrate from the flotation cell, thereby increasing the recovery of the desired material regardless of its particle size distribution within the slurry. It may be possible to achieve high quality for a portion of the slurry stream, while simultaneously achieving high recovery for the entire slurry stream passing through a flotation line.

By arranging the jet tubes in a position relative to the lower structure, mixing of the slurry can be induced and improved in a mixing zone surrounding the lower structure. For example, by arranging the jet tube outlet nozzles at a suitable depth, i.e., arranging them at a specific vertical distance from the pan flange, the distribution of the flotation gas bubbles can be optimized in a uniform and consistent manner. Since the bubble residence time within a mixing zone can be kept sufficiently long by a suitable depth of the jet tube outlet nozzles, the bubbles can be able to contact and adhere to the fine slurry particles effectively, thereby improving the recovery of smaller particles and also promoting froth depth, stability, and uniformity in the upper portion of the flotation tank.

A mixing zone is understood here as a vertical portion or region of the flotation tank in which active mixing of suspended particles in the slurry with flotation gas bubbles takes place. In addition to this mixing zone created over an entire vertical section of the flotation tank, individual, separate, regional mixing subzones can be created in areas where the radially outwardly directed slurry flows from individual strikers meet and intermingle. This can further promote contact between the flotation gas bubbles and the particles, thereby increasing the recovery of valuable particles. Furthermore, this additional mixing can eliminate the need for a mechanical mixer for the suspended solids in the slurry.

The settling zone refers to a vertical portion of the flotation tank region where particles not associated with buoyant gas bubbles or otherwise unable to rise to the froth zone above the flotation tank descend and settle to the bottom of the tank to be eliminated in the tailings as an underflow. The settling zone is below the mixing zone.

The flotation cell, the flotation line, and their use according to the invention have the technical effect of enabling the flexible recovery of various particle sizes, as well as the efficient recovery of ore particles containing valuable minerals from low-grade ore feedstock with relatively low amounts of valuable minerals initially. The advantages provided by the flotation line structure allow the structural parameters of the flotation line to be precisely adjusted according to the target valuable material of each installation.

By treating the slurry according to the present invention as defined in the present disclosure, the recovery of particles containing valuable material can be increased. The initial quality of the recovered material may be lower, but the material (i.e., the slurry) is also therefore easily prepared for further processing, which may include, for example, regrind and/or cleaning.

In this disclosure, the following definitions relating to flotation are used.

Fundamentally, the purpose of flotation is to recover a concentrate of ore particles containing a valuable mineral. Concentrate here refers to the portion of the slurry recovered in the overflow or underflow conveyed outside a flotation cell. Valuable mineral refers to any mineral, metal, or other material of commercial value.

Flotation involves phenomena related to the relative buoyancy of objects. The term flotation includes all flotation techniques. Flotation can be, for example, froth flotation, dissolved air flotation (DAF), or induced gas flotation. Froth flotation is a process for separating hydrophobic materials from hydrophilic materials by adding gas, for example, air or nitrogen, or any other suitable medium, to the process. Froth flotation can be based on a natural hydrophilic/hydrophobic difference or on hydrophilic/hydrophobic differences produced by the addition of a surfactant or a collecting chemical. Gas can be added to the raw material to be flotated (slurry or pulp) in several different ways.

A flotation cell is intended for the flotation treatment of mineral ore particles suspended in slurry. In this way, ore particles containing valuable metals are recovered from the ore particles suspended in the slurry. A flotation line is understood here as a flotation arrangement in which several flotation cells are arranged in fluid connection with one another, such that the underflow from each preceding flotation cell is directed to the next or subsequent flotation cell as inlet charge up to the last flotation cell in the flotation line, from which the underflow is directed out of the line as tailings or reject flow. The slurry is introduced through a feed inlet to the first flotation cell in the flotation line to initiate the flotation process. A flotation line may be part of a larger flotation plant or arrangement containing one or more flotation lines. Therefore, several different pre-treatment and post-treatment devices or stages may be in operative connection with the components of the flotation arrangement, as is known to those skilled in the art.

The flotation cells of a flotation line are fluidly connected to one another. The fluid connection can be achieved through conduits of varying lengths, such as pipes or tubes, the length of which depends on the overall physical construction of the flotation arrangement. Alternatively, the flotation cells can be arranged with one another in a direct cell connection. A direct cell connection refers to an arrangement whereby the outer walls of any two successive flotation cells are connected to one another so that an outlet of a first flotation cell can be connected to the inlet of the next flotation cell without any separate conduit. Direct contact reduces the need for piping between two adjacent flotation cells. This reduces the need for components during waterline construction, speeding up the process. It could also reduce sanding and simplify waterline maintenance. The fluid connections between the flotation cells can comprise various regulating mechanisms.

By "contiguous", "adjacent" or "abutting" flotation cell is meant here the flotation cell immediately after or before any flotation cell, downstream or upstream, or whether on a roughing waterline, on a swept waterline or the relationship between a flotation cell on a roughing waterline and a flotation cell on a swept waterline to which the bottom overflow flow from the flotation cell on the roughing waterline is directed.

A flotation cell is understood here as a tank or vessel in which a flotation process step is performed. A flotation cell is typically cylindrical in shape, defined by one or more outer walls. Flotation cells typically have a circular cross-section. Flotation cells may also have a polygonal cross-section, such as rectangular, square, triangular, hexagonal, or pentagonal, or may be otherwise radially symmetrical. The number of flotation cells may vary according to a specific flotation line and/or operation for processing a specific type and/or quality of ore, as is known to those skilled in the art.

The flotation cell may be a froth flotation cell such as a mechanically agitated cell, for example, a TankCell, a column flotation cell, a Jameson cell, or a double flotation cell. In a double flotation cell, the cell comprises at least two separate vessels, a first mechanically agitated pressure vessel with a mixer and a flotation gas inlet, and a second vessel with a tailings outlet 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 HydroFloat™ cell), where air or other flotation gas bubbles dispersed by the fluidization system percolate through the hindered settling zone and adhere to the hydrophobic component, altering its density and rendering it sufficiently buoyant for it to float and be recovered. In a fluidized bed flotation cell, axial mixing is not required. The flotation cell may also be a top overflow flotation cell operating with a constant top overflow flow of slurry. In a top overflow flotation cell, the slurry is treated by introducing flotation gas bubbles into the slurry and creating a continuous upward flow of slurry in the vertical direction of the first flotation cell. At least some of the ore particles containing valuable metals adhere to the gas bubbles and rise upward by buoyancy, at least some of the ore particles containing valuable metals adhere to the gas bubbles and rise upward with the continuous upward flow of slurry, and at least some of the ore particles containing valuable metals rise upward with the continuous upward flow of slurry. The ore particles containing valuable metals are recovered by conducting the continuous upward flow of slurry out of the at least one top overflow flotation cell as an overflow flow of slurry. Since the top overflow cell operates with virtually no froth depth or froth layer, in practice, no froth zone forms on the pulp surface at the top of the flotation cell. The froth may not be continuous throughout the cell. This results in more ore particles containing valuable mineral being entrained into the concentrate stream, and the total recovery of valuable material may increase.

All of the flotation cells of a waterline according to the invention may be of a single type, i.e., the roughing flotation cells in the roughing portion, the sweeping flotation cells in the sweeping portion, and the sweep finishing flotation cells of the sweep finishing waterline may be of a single flotation cell type such that the flotation arrangement comprises only one type of flotation cells as recited above. Alternatively, a number of the flotation cells may be of one type, while other cells are of one or more types, such that the waterline comprises two or more types of flotation cells as recited above.

Depending on its type, the flotation cell may comprise a mixer for agitating the slurry and keeping it in suspension. A mixer here refers to any means suitable for agitating the 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 rotor-stator structure arranged at the bottom of the flotation cell. The cell may have auxiliary agitators arranged at a higher height in the vertical direction of the cell to ensure a continuous and sufficiently intensive upward flow of the slurry.

A flotation cell may comprise one or more froth agglomerators. A froth agglomerator is understood here to mean a froth blocker, a froth deflector, an agglomeration board or an agglomeration board device, or any other such structure or side structure, for example, a side wall, inclined or vertical, having an agglomerating effect, i.e., an agglomeration side wall, which may also be an agglomeration side wall internal to the flotation tank, i.e., an internal perimeter agglomerator.

By using a froth agglomerator, it may be possible to direct so-called "friable froth," i.e., a loose-textured froth layer typically comprising larger flotation gas bubbles agglomerated with the mineral ore particles intended for recovery, more efficiently and reliably toward the froth overflow flange and the froth collection pan. A friable froth can break easily, since agglomerates of gas bubbles and ore particles are less stable and have reduced toughness. Such a froth or froth layer cannot readily sustain the transport of ore particles, and especially coarser particles, toward the froth overflow flange for collection in the pan, thereby resulting in retrogression of the particles into the pulp or slurry within the flotation cell or tank, and reduced recovery of the desired material. Brittle froth is typically associated with low mineralization, i.e., agglomerates of gas bubbles and ore particles with a limited amount of ore particles comprising a desired mineral that have been able to adhere to the gas bubbles during the flotation process within a flotation cell or tank. The problem is particularly acute in large flotation cells or in large-volume and/or large-diameter tanks. With the present invention, it may be possible to agglomerate and direct the froth toward the upper overflow froth flange, thereby reducing the froth transport distance (thus reducing the risk of backflow) while maintaining or even reducing the length of the upper overflow froth flange. In other words, the handling and direction of the froth layer in a froth flotation cell or tank can be more efficient and simpler.

It may also be possible to improve froth recovery and thus the recovery of valuable mineral particles in large flotation cells or tanks from brittle froth specifically in the later stages of a flotation line, for example, in the roughing and/or sweeping stages of a flotation process.

Furthermore, with the invention described herein, the froth area on the slurry surface within a flotation tank can be reduced in a mechanically robust and simple manner. Simultaneously, the overall length of the top overflow flange in a froth flotation unit can be reduced. Robustness in this case is to be understood as meaning structural simplicity and durability. By reducing the froth surface area of a flotation unit by using a froth agglomerator instead of adding additional froth collection pans, the froth flotation unit as a whole can be a simpler construction, for example, because there is no need to channel the collected froth and/or the top overflow flow away from the added agglomerator. Conversely, from an additional pan, the collected top overflow flow would have to be channeled to the outside, which would increase the construction of the flotation unit.

Particularly at the downstream end of a flotation line, the amount of desired material that can be entrapped in the froth within the slurry can be very small. To collect this material from the froth bed to the froth collection pans, the froth surface area must be reduced. By providing a froth agglomerator in the flotation tank, the open froth surface between the froth overflow ribs can be controlled. The agglomerator can be used to direct or guide the upwardly flowing slurry within the flotation tank toward a froth overflow rib of a froth collection pan, thereby allowing or facilitating froth formation very close to the froth overflow rib, which can enhance the collection of valuable ore particles. The froth agglomerator can also influence the overall convergence of flotation gas bubbles and/or agglomerates of ore particles and gas bubbles in the froth bed. For example, if the gas bubbles and/or the agglomerate flow of ore particles and gas bubbles is directed toward the center of a flotation tank, a froth agglomerator can be used to increase the froth area at the perimeter of the tank, and/or closer to any desired froth overflow ridge. Furthermore, it may be possible to reduce the open froth surface area relative to the ridge length, thereby improving recovery efficiency in the froth flotation cell.

A jet tube is understood to mean a high-shear double device in which flotation gas is introduced into the slurry feed, thereby creating finer flotation gas bubbles that can also trap finer particles during bubble formation in the jet tube. In particular, a jet tube in a flotation cell according to the invention operates under pressure, and no vacuum is required.

The term "overflow" refers here to the portion of the slurry collected in the flotation cell pan and thus exiting the flotation cell. The overflow may comprise froth, froth and slurry, or in some cases, only or mostly slurry. In some embodiments, the overflow may be an accepted flow containing the valuable material particles collected from the slurry. In other embodiments, the overflow may be a rejected flow. This is the case when the flotation arrangement, plant, and/or method are used in reverse flotation.

The term "bottom overflow" refers to the fraction or portion of the slurry that does not float to the surface of the slurry during the flotation process. In some embodiments, the bottom overflow may be a rejected flow exiting a flotation cell through an outlet, typically arranged at the bottom of the flotation cell. Finally, the bottom overflow from the final flotation cell of a flotation line or flotation arrangement may exit the entire arrangement as tailings or final residue from a flotation plant. In some embodiments, the bottom overflow may be an accepted flow containing valuable mineral particles. This is the case where the flotation cell or flotation line is used in reverse flotation.

Reverse flotation refers here to a reverse flotation process typically used in iron recovery. In this case, the flotation process is directed to collect the non-valuable portion of the slurry flow in the upper overflow. In the reverse flotation process for iron, the upper overflow typically contains silicates, while valuable iron-containing mineral particles are collected in the lower overflow. Reverse flotation can also be used for industrial minerals, i.e., geological minerals mined for their commercial value other than fuels or sources of metals, such as bentonite, silica, gypsum, and talc.

Downstream here refers to the direction coinciding with the flow of slurry towards the tailings (forward flow, indicated in the figures by arrows), and upstream here refers to the direction countercurrent to or against the flow of slurry.

The term "concentrate" refers here to the floated portion or slurry fraction of ore particles comprising a valuable mineral. In normal flotation, the concentrate is the portion of the slurry that floats to the froth layer and is therefore collected in the pans as an overflow. A first concentration concentrate may include ore particles comprising a valuable mineral, while a second concentration concentrate may comprise ore particles comprising another valuable mineral. Alternatively, the distinctive definitions first and second may refer to two concentration concentrates of ore particles comprising the same valuable mineral but with two distinctly different particle size distributions.

The term rough flotation, rough flotation part of the waterline, rough stage, and/or roughing cells refers to a flotation stage that produces a concentrate. The objective is to extract the maximum amount of valuable mineral with as coarse a particle size as possible. The primary objective of a rough stage is to recover as much valuable mineral as possible, with less emphasis on the quality of the concentrate produced.

The rough concentrate typically undergoes additional finishing flotation stages in a rough finishing flotation line to reject more of the undesirable minerals that have also migrated to the froth, in a process known as finishing. The finished product is known as the finishing concentrate or final concentrate.

Rough flotation is often followed by sweep flotation, which is applied to the rough tailings. A sweep flotation, part-waterline sweep, sweep stage, and/or sweep cell refers to a flotation stage in which the objective is to recover any valuable mineral material not recovered during the initial roughing stage. This could be achieved by changing the flotation conditions to make them more stringent than the initial roughing or, in some embodiments of the invention, by introducing microbubbles into the slurry. The concentrate from a sweep cell or stage could be returned to the rough feed for refloating or directed to a regrind stage and, thereafter, to a sweep finishing flotation line.

Finishing flotation, a roughing/sweeping finishing line, finishing/finishing stage and/or a finishing cell means a flotation stage in which the finishing objective is to produce as high a quality of concentrate as possible.

Pretreatment and/or post-treatment and/or further processing means, for example, crushing, grinding, separation, screening, classification, fractionation, conditioning, or cleaning, all of which are conventional processes known to those skilled in the art. Further processing may also include at least one of the following: an additional flotation cell, which may be a conventional finishing flotation cell, a recovery cell, a roughing cell, or a sweeping cell.

The slurry surface level here refers to the height of the slurry surface within the flotation cell, measured from the bottom of the flotation cell to the pan flange of the flotation cell. The slurry height is, in fact, equal to the height of a pan flange of a flotation cell, measured from the bottom of the flotation cell to the pan flange of the flotation cell. For example, any two successive flotation cells may be arranged in a staggered manner on a waterline, such that the slurry surface level of such flotation cells is different (i.e., the slurry surface level of the first such flotation cell is higher than the slurry surface level of the second such flotation cell). This difference in slurry surface levels is defined here as the "step" between any two successive flotation cells. The step or difference in slurry surface levels is a difference that allows the slurry flow to be driven by the force of gravity, by creating a hydraulic head between the two successive flotation cells.

A waterline is understood here as an assembly or arrangement comprising several flotation units or flotation cells in which a flotation stage is carried out, and which are arranged in fluid connection with one another to allow the flow of slurry driven by gravity or pumped between flotation cells, to form a waterline. In a waterline, several flotation cells are arranged in fluid connection with one another, such that the underflow from each preceding flotation cell is directed to the next or subsequent flotation cell as inflow charge up to the last flotation cell of the waterline, from which the underflow is directed out of the line as tailings or reject flow. It is also conceivable that a waterline may comprise only one flotation stage carried out in one flotation cell or, for example, in two or more parallel flotation cells.

The slurry is introduced through a feed inlet into the first flotation cell of the waterline to initiate the flotation process. The waterline may be part of a larger treatment plant containing one or more waterlines and a series of other process steps for the liberation, cleaning, and other treatment of a desired material. Thus, several different pretreatment and posttreatment devices or arrangements may be in operative connection with the components of the waterline, as is known to those skilled in the art.

Ultrafine bubbles are understood here to mean flotation gas bubbles in the size range of 0.05 mm to 0.7 mm, introduced into the slurry in a jet tube. In contrast, "normal" flotation gas bubbles used in froth flotation have a size range of approximately 0.8 to 2 mm. Larger flotation gas bubbles may tend to coalesce into even larger bubbles during their residence in the mixing zone, where collisions occur between particles and flotation gas bubbles, as well as between flotation gas bubbles alone. Since ultrafine bubbles are introduced into the slurry batch before it is introduced into a flotation tank, such coalescence with ultrafine bubbles is unlikely to occur, and their size may remain smaller throughout their residence in the flotation cell, thereby affecting the ability of ultrafine bubbles to entrap fine particles.

In the flotation cell according to the invention, the outlet nozzle is configured to produce a supersonic shock wave in the slurry charge, the supersonic shock wave inducing the formation of particle agglomerates and flotation gas bubbles.

A supersonic shock wave is created when the velocity of the slurry charge passing through the outlet nozzle exceeds the speed of sound, i.e., the slurry charge flow is throttled when the ratio of the absolute pressure upstream of the outlet nozzle to the absolute pressure downstream of the outlet nozzle throttle exceeds a critical value. When the pressure ratio exceeds the critical value, the slurry charge flow downstream of the throttling portion of the outlet nozzle becomes supersonic, and a shock wave is formed. The small buoyancy gas bubbles in the slurry charge mixture are broken up into even smaller ones as they are forced through the shock wave, and are forced into contact with the hydrophobic ore particles in the slurry charge, thereby creating agglomerates of buoyancy gas bubbles and ore particles. The supersonic shock wave produced in the slurry charge at the outlet nozzle discharge transfers to the slurry within the flotation tank immediately adjacent to an outlet nozzle, thereby promoting the formation of flotation gas bubbles also in the slurry outside the outlet nozzles. After exiting the outlet nozzle, the fine ore particles may come into contact with the small flotation gas bubbles for a second time, since there are several such jet tubes/outlet nozzles discharging into a common mixing zone in which the probability of secondary bubble-particle contacts increases due to the intermixing slurry flows exiting the jet tubes.

In one embodiment of the flotation cell, a height of the flotation tank, measured as the distance from the bottom to the rim of the pan, is at most 20% lower at the perimeter of the flotation tank than at the center of the flotation tank.

In one embodiment of the flotation cell, the vertical cross-section of the lower structure is a functional triangle comprising a first vertex pointing away from the bottom of the flotation tank, a second vertex, and a third vertex; a first side between the first vertex and the second vertex; a second side between the first vertex and the third vertex; and a base between the second and third vertices on the bottom of the flotation tank; and a central axis substantially concentric with the center of the flotation tank.

In another embodiment of the flotation cell, the base angle between the first side and the base, or the second side and the base with respect to the bottom of the flotation tank is between 20 and 60°.

In another embodiment of the flotation cell, the included angle between the first side and the second side is between 20 and 100°, preferably between 20 and 80°.

In another embodiment of the flotation cell, the lower structure comprises a base on the bottom of the flotation tank and defined by the base of the functional triangle, and a lining defined at least by the first, second and third vertices of the functional triangle.

In yet another embodiment of the flotation cell, the liner is at least partially defined by the first and second sides of the functional triangle.

In one embodiment of the flotation cell, a height of the lower structure is greater than 1/5 and less than 3/4 of a height of the flotation tank (10), measured as the distance from the bottom to the pan rim.

By providing a substructure at the bottom of a flotation tank, extending the substructure upward into the flotation tank, it may be possible to achieve a better distribution of fine and/or small particles suspended in the slurry. In the center of the flotation tank, the particles cannot descend and settle, since the slurry charge flow from the jet tubes can reach the elevated central part of the flotation tank, ensuring good mixing in that part. Particles that have already been able to detach from the flotation gas bubbles and begin their descent can be captured again by the bubbles due to the turbulent conditions of the mixing zone. Furthermore, the bottom of the flotation tank closest to the tank perimeter has a zone of sufficient depth to allow unfloated particles, most likely worthless, to settle and descend to be efficiently removed from the flotation tank. This settling zone is not affected by the slurry charge flow from the jet tubes. Furthermore, such a relatively calm zone can prevent the formation of short-circuits in slurry flows within the flotation tank, where the same slurry material continues to recirculate within the tank without being adequately separated or settled. The above characteristics can favor greater recovery of fine particles.

In one embodiment of the flotation cell, the flotation tank further comprises a central froth agglomerator arranged at a distance from the bottom of the flotation tank.

In another embodiment of the flotation cell, a height of the lower structure is between 1/3 and 3/4 of the distance of the central froth agglomerator from the bottom of the flotation tank.

In one embodiment of the flotation cell, the flotation tank further comprises an internal perimeter foam agglomerator, a lowest point of the internal perimeter foam agglomerator arranged at a distance from the bottom of the flotation tank.

In another embodiment of the flotation cell, the ratio of a height of the lower structure to the distance of the lowest point of the inner perimeter foam agglomerator relative to the bottom of the flotation tank is 1.0 or less.

In one embodiment of the flotation cell, a diameter of a base of the lower structure is between 1/4 and 3/4 of a diameter of the bottom of the flotation tank.

In one embodiment of the flotation cell, the surface area of a base of the lower structure is between 25 and 80% of the surface area of the bottom of the flotation tank.

In one embodiment of the flotation cell, the ratio of the height of the flotation tank, measured as the distance from the bottom to the rim of the pan, to the diameter of the flotation tank, measured at a height of the outlet nozzle from the bottom, is between 0.5 and 1.5; that is, the ratio of the height of the tank to the diameter of the tank is between 0.5 and 1.5.

In one embodiment of the flotation cell, the volume of the flotation tank is at least 20 m3, preferably between 20 and 1,000 m3.

By arranging a flotation tank with sufficient volume, the flotation process can be better controlled. The rise distance to the froth layer above the top of the flotation tank does not become too great, which can help ensure that the agglomerates of ore particles and flotation gas bubbles remain together until the froth layer and particle setback can be reduced. Likewise, an adequate bubble rise velocity can be achieved to maintain good concentrate quality. Using flotation cells with a sufficient volumetric size increases the probability of collisions between gas bubbles created in the flotation cells, for example, by a rotor, and particles comprising valuable mineral, thereby improving the recovery rate of the valuable mineral as well as the overall efficiency of the flotation arrangement. Larger flotation cells have greater selectivity, as more collisions can occur between gas bubbles and ore particles due to the longer time the slurry remains in the flotation cell. Therefore, most of the ore particles containing valuable minerals can float. Furthermore, the setback of floating ore particles can be greater, meaning that ore particles containing very little valuable mineral fall back to the bottom of the flotation cell. Therefore, the quality of the overflow and/or concentrate from larger flotation cells can be higher.

These types of flotation cells can guarantee high quality. Furthermore, the overall efficiency of the flotation cell and/or the entire flotation line can be improved. Furthermore, if the first flotation cells in a flotation line have a relatively high volume, there may be no need for large subsequent flotation cells; instead, the flotation cells downstream of the first flotation cell(s) can be smaller and therefore more efficient. In the flotation processes of certain minerals, it may be easy to float a significant portion of the ore particles comprising high-grade valuable mineral. In that case, it may be possible to have smaller volume flotation cells downstream of the flotation line and still achieve a high recovery rate.

In one embodiment of the flotation cell according to the invention, the flotation cell comprises between 2 and 40 jet tubes, preferably between 4 and 24 jet tubes.

The number of jet tubes directly influences the amount of flotation gas that can be dispersed in the slurry. In conventional froth flotation, dispersing an increasing amount of flotation gas would lead to an increase in the size of the flotation gas bubbles. For example, in a Jameson cell, an air-to-bubble ratio of between 0.50 and 0.60 is used. Increasing the average bubble size will negatively affect the bubble surface area (Sb) flux, meaning that recovery may decrease. In a flotation cell according to the invention, with pressurized jet tubes, significantly more flotation gas can be introduced into the process without increasing bubble size or decreasing Sb, since the flotation gas bubbles created in the slurry charge remain relatively small compared to conventional processes. On the other hand, by keeping the number of jet tubes as small as possible, the costs of reconditioning existing flotation cells, or the investments in commissioning such flotation cells, can be kept under control without causing any loss of flotation performance of the flotation cells.

In one embodiment of the flotation cell, the jet tubes are arranged concentrically to the perimeter of the flotation tank at a distance from the center of the flotation tank.

In one embodiment of the flotation cell, the jet tubes are arranged parallel to the side wall of the flotation tank, at a distance from the side wall.

The exact number of jet tubes within a flotation cell can depend on the size or volume of the flotation tank, the type of material to be collected, and other process parameters. By arranging a sufficient number of jet tubes in a flotation cell, and by arranging them in a specific manner relative to the center of the flotation tank and the perimeter and/or sidewall, an even distribution of ultrafine bubbles can be ensured, as well as a uniform mixing effect caused by the shear forces within the secured tank.

In one embodiment of the flotation cell, a jet tube further comprises a striker configured to contact a slurry charge flow from the outlet nozzle and to direct the slurry charge flow radially outward and upward from the striker.

A striker deflects the slurry charge flow radially outward toward the sidewall of the flotation tank and upward toward the upper surface of the flotation tank (i.e., toward the froth layer), so that agglomerates of ore particles and fine flotation gas bubbles do not short-circuit in the tailings. The entire slurry charge from the jet tubes is forced upward toward the froth layer in the upper region of the flotation tank before gravity has a chance to influence particles not adhering to the flotation gas bubbles, forcing them down and eventually into the tailings flow or the overflow below. In this way, the probability of short-circuiting of particles containing valuable material can be reduced. The slurry is intensely agitated by the energy of the diverted flow, forming mixing vortices in which the bubble size can be further reduced by the shear forces acting on them. High shear conditions also favorably induce a high number of contacts between flotation gas bubbles and slurry particles within the flotation tank. As the slurry flow is forced upward toward the froth layer, turbulence is reduced and the flow becomes relatively uniform, which can contribute to the stability of already formed bubbles and of particle agglomerates and flotation gas bubbles, especially those comprising coarser particles.

By arranging the outlet nozzle and the striker at an optimal distance from each other, the striker can be configured to deflect and direct the slurry charge flow radially outward and upward from the striker to create the aforementioned mixing zones within the flotation tank and to promote particle ascent toward the froth layer. At the same time, it may be necessary to minimize the wear caused by high-velocity slurry flows on the striker. By positioning the outlet nozzle and the striker in a certain relationship to each other, it may be possible to optimize the flotation process within a flotation cell equipped with jet tubes, as well as minimize wear on the striker parts.

In another embodiment of the flotation cell, the volume of the flotation tank taken by the lower structure is between 30 and 70% of the volume of the flotation tank taken by the mixing zone.

By arranging the lower structure to a specific size, especially with respect to the mixing zone, the mixing zone and the settling zone can be designed to have the desired characteristics (size, depth, turbulence, particle residence time in the mixing zone, settling velocity, and probability of a worthless fraction in the settling zone, etc.). In a conventional flotation cell, most of this zone (without mechanical mixing at the bottom of the flotation tank) would be subject to sanding, as there is little or no mixing. If the zone fills with solids, there is a risk that this solid matter will collapse and, in turn, block a tailings outlet and/or a recirculation outlet located in the settling zone.

In one embodiment of the flotation cell, it further comprises a conditioning circuit.

In another embodiment of the flotation cell, the conditioning circuit comprises a pump tank in fluid communication with the flotation tank, wherein the pump tank charge of fresh slurry and a slurry fraction taken from the flotation tank through an outlet are arranged to combine into the slurry charge.

In yet another embodiment of the flotation cell, the outlet is arranged on the side wall of the flotation tank, at a distance from the bottom of the flotation tank.

In yet another embodiment of the flotation cell, the distance of the outlet from the bottom of the flotation tank is between 0 and 50% of the height of the flotation tank.

In another embodiment of the flotation cell, the conditioning circuit further comprises a pump arranged to receive the slurry fraction from the flotation tank and to drive the slurry charge from the pump tank.

In another embodiment of the flotation cell, the conditioning circuit further comprises a distribution unit arranged to distribute the slurry load.

By removing slurry from the bottom of a flotation cell, it is possible to ensure that the finest particles settled at the bottom of the flotation tank can be efficiently reintroduced into the part of the flotation tank where the active flotation process takes place, before the finest particles move to the tailings. This improves the recovery rate of valuable material, as particles comprising even minimal amounts of valuable material can be collected in the concentrate.

By recirculating a slurry fraction from the bottom of the flotation tank into the jet tubes through an outlet arranged in the side wall of the flotation tank, the recirculated fraction is thus obtained in a zone where the slurry largely comprises particles that sink or settle to the bottom of the tank. Due to the probabilistic nature of a flotation process, it may happen that the particles nevertheless still comprise valuable material. Particularly in the settling zone closest to the side wall of the flotation tank, the slurry may comprise particles comprising such valuable material that they have not been captured by the flotation gas bubbles and/or by the upwardly directed slurry flow near the strikers in the mixing zone. In this position, the slurry is also affected by the slurry feed flow from a single jet tube, which creates turbulence. Therefore, there is a greater likelihood that particles comprising valuable material will not be captured by the flotation gas bubbles or/and the upwardly directed slurry flow. To also recover valuable material from these particles, it may be advantageous to reprocess this slurry fraction in the same flotation cell, for example, as part of the slurry charge. Overall recovery can therefore be further improved.

In one embodiment of the flotation cell, the flotation tank further comprises a tailings outlet for removing the bottom overflow flow.

In another embodiment of the flotation cell, the tailings outlet is arranged on the side wall of the flotation tank, at a distance from the bottom of the flotation tank.

In yet another embodiment of the flotation cell, the distance of the tailings outlet from the bottom of the flotation tank is between 1 and 15% of a height of the flotation tank, measured as the distance from the bottom to the pan rim.

The tailings outlet may be located at the bottom of the flotation tank, or on the side wall of the flotation tank, in the sedimentation zone.

By providing a tailings outlet in the side wall of the flotation tank, the lower overflow flow can be extracted in a zone where the slurry mostly comprises particles that descend or settle to the bottom of the tank. In the flotation cell according to the invention, the settling zone is located at a greater depth near the side wall of the flotation tank. In this zone, the mixing action and turbulence created by the jet tubes do 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. It is in this part where the settling action is most pronounced due to the absence of turbulence that would interfere with the gravity descent of the particles. Furthermore, the frictional forces created by the side wall of the tank further reduce the turbulence and/or flows. In this way, by withdrawing the bottom overflow from the flotation tank at a position arranged above this relatively calm settling zone, it can be ensured that as little valuable particles as possible are removed from the flotation tank (these particles should instead float or, if for some reason they have ended up in the settling zone, be recirculated back to the flotation tank as slurry feed via the jet tubes). Furthermore, by withdrawing the bottom overflow from the settling zone near the side wall of the flotation tank, the entire volume of the flotation tank can be utilized efficiently (there is no need to set up a separate bottom settling zone below the jet tubes, as is the case, for example, in a Jameson cell). In some embodiments, it is even envisaged that the volume of the flotation tank may be reduced in the center of the tank, thereby decreasing the volume of the settling zone, where turbulence caused by the slurry loading of the jet tubes may influence the likelihood of particles settling to the bottom of the tank, and allowing full use of the flotation tank volume. The volume of the flotation tank may be reduced in the center of the tank, for example, by arranging a bottom structure at the bottom of the flotation tank, in the center of the tank. Furthermore, it may be possible to arrange the jet tubes (the outlet nozzles) at a relative depth in the flotation tank, while still ensuring a sufficiently calm settling zone on the side wall of the flotation tank. Furthermore, this also promotes efficient use of the entire volume of the flotation tank.

In one embodiment of the inventive flotation line, the inventive flotation cell is preceded by a flotation cell. The flotation cell may be of any suitable type.

In one embodiment of the flotation line, the flotation cell according to the invention is preceded by a mechanical flotation cell.

In another embodiment of the waterline, the waterline comprises a roughing portion with a flotation cell; a sweeping portion with a flotation cell arranged to receive the lower overflow flow from the roughing portion; and a sweeping finishing portion with a flotation cell arranged to receive the upper overflow flow from the sweeping portion, where the last flotation cell of the sweeping portion and/or the sweeping finishing portion is a flotation cell according to the invention.

In yet another embodiment of the waterline, the flotation cell according to the invention is preceded by a mechanical flotation cell.

An embodiment of the use of the flotation line according to the invention is intended in particular to recover mineral ore particles comprising non-polar minerals such as graphite, sulfur, molybdenite, coal and talc.

The treatment of slurries for the recovery of such industrial minerals as bentonite, silica, gypsum, or talc can be enhanced by utilizing reverse flotation. In the recovery of industrial minerals, the objective of flotation may be, for example, the removal of dark particles to the rejected overflow stream and the recovery of white particles to the accepted underflow stream. In such a process, some of the lighter, finer white particles may end up in the overflow stream. Such particles could be effectively recovered by the invention according to the present disclosure. In reverse flotation, particles comprising undesirable material are removed from the slurry by arranging gas bubbles to adhere to those particles and removing them from the flotation cell in the overflow stream, while particles comprising valuable material are recovered in the underflow stream, thereby reversing the conventional flotation flows of being accepted in the overflow stream and rejected in the underflow stream. Typically, in reverse flotation, the large mass entrainment of valuable material can cause significant problems in the control of the flotation process.

An embodiment of the use of the flotation line according to the invention is intended in particular for the recovery of particles comprising polar minerals.

An embodiment of the use of the flotation line is intended in particular for the recovery of mineral particles having a Mohs hardness of between 2 and 3, such as galena, sulfide minerals, PGM minerals, and/or REO minerals.

Another embodiment of the use of the flotation line is intended in particular for the recovery of particles comprising Pt.

An embodiment of the use of the flotation line is intended in particular for the recovery of particles comprising Cu from minerals with a Mohs hardness of between 3 and 4.

Another embodiment of the use of the flotation line is intended in particular for the recovery of particles comprising Cu from low-grade ore.

The valuable mineral may be, for example, Cu, Zn, Fe, pyrite, or metal sulfide such as gold sulfide. Ore particles containing other valuable minerals such as Pb, Pt, PGM (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 in accordance with the different aspects of the present invention.

For example, in the recovery of copper from low-grade ores obtained from poor ore deposits, the amounts of copper can be as low as 0.1% by weight of the feed, i.e., of the slurry charge entering the flotation line. The flotation line according to the invention can be very practical for recovering copper, since copper is a mineral that is considered easily floatable. In the liberation of ore particles comprising copper, it may be possible to obtain a relatively high quality of the first flotation cells of the flotation line. Recovery can be further increased by a flotation cell according to the invention.

By using the flotation arrangement according to the present invention, the recovery of such small quantities of valuable mineral, e.g., copper, can be efficiently increased, and even poor deposits can be profitably utilized. Since the known rich deposits have already been increasingly exploited, there is a tangible need to also process less favorable deposits, which previously may have been left unexploited due to a lack of suitable technology and processes for recovering valuable material in very small quantities from the ore.

BRIEF DESCRIPTION OF THE DRAWINGS

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

Figure 1 is a 3D projection of a flotation cell according to an embodiment of the invention, Figure 2 represents a flotation cell according to an embodiment of the invention, seen from above, Figure 3 represents a flotation cell according to an embodiment of the invention in side view, Figure 4a is a vertical cross-section of the flotation cell of Figure 3 along a section A-A,

Figure 4b shows a vertical cross-section of another embodiment of the flotation cell of Figure 3 along section A-A,

Figure 5 is a schematic illustration of a flotation cell according to the invention, detailing the dimensions of the flotation cell,

Figures 6a and 6b are schematic drawings of waterlines according to embodiments of the invention, Figure 7 shows schematic vertical cross-sections of embodiments of flotation tanks according to the invention, and

Figure 8 is a schematic presentation of the shapes of the lower structure according to the embodiments of the flotation cell.

DETAILED DESCRIPTION

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

The description that follows discloses some embodiments in such detail that a person skilled in the art will be able to use the flotation cell, the waterline, and their use based on the disclosure. Not all steps of the embodiments are set forth in detail, as many of the steps will be obvious to a person skilled in the art based on this disclosure.

For the sake of simplicity, the reference numbers will be retained in the following exemplary embodiments in the case of repeated components.

The accompanying Figures 1-5 and 7-8 illustrate a flotation cell 1 in some detail. The figures are not drawn proportionally, and many of the components of the flotation cell 1 are omitted for clarity. Figures 6a and 6b schematically illustrate embodiments of the waterline. The direction of the slurry flows is shown in the figures by arrows.

The flotation cell 1 according to the invention is intended for treating mineral ore particles suspended in slurry and for separating the slurry into a lower overflow flow 400 and an upper overflow flow 500, the upper overflow flow 500 comprising a concentrate of a desired mineral.

Referring in particular to Figures 1-5, the flotation cell 1 comprises a flotation tank 10 having a center 11, a perimeter 12, a bottom 13 and a side wall 14. The flotation cell 1 further comprises a pan 2 and a pan rim 21 surrounding the perimeter 12 of the flotation tank 10.

In the accompanying figures, the pan 2 is a perimeter pan. It is to be understood that a pan 2 may alternatively or additionally comprise a central pan arranged in the center 11 of the flotation tank 10, as is known in the art. A pan flange of a central pan may be directed toward the perimeter 12 of the flotation tank 10, or toward the center 11 of the flotation tank 10, or toward both. The upper overflow flow 500 is collected in the pan 2 or pans by passing over a pan flange 21, from a foam layer formed on top of the flotation tank 10. The foam layer comprises an open foam surface Af on the top of the flotation tank 10.

The bottom overflow flow 400 is removed or led out of the flotation tank through a tailings outlet 140. According to one embodiment, the tailings outlet 140 may be arranged in the side wall 14 of the flotation tank 10 (see Figure 5). The tailings outlet 140 may be arranged in the side wall 14 of the flotation tank 10 at a distance L6 from the bottom 13 of the flotation tank 10. The distance is to be understood as the distance of the lowest point of the tailings outlet 140 or outlet opening in the side wall 14 of the flotation tank 10 from the bottom of the tank 13. The distance L6 may be 1 to 15% of the height H of the flotation tank 10. For example, the distance L6 may be 2%, 5%, 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 (see FIG. 1). In any case, the tailings outlet 140 is arranged in a settling zone B, at the bottom of the flotation tank 10. The tailings outlet 140 may be controlled by a dart valve, or in any other suitable manner known in the field, to control the flow rate of the underflow flow from the flotation tank 10. Even if the tailings outlet 140 is controlled by internal or external structures such as upflow or downflow dart boxes, respectively, the tailings outlet 140 is ideally located at the bottom 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, the underflow flow 400 or tailings are withdrawn from the bottom of the flotation tank 10, and at or near the side wall 14 of the flotation tank 10.

The flotation tank 10 has a height H, measured as the distance from the bottom 13 of the flotation tank 10 to the pan rim 21. At the perimeter 12 of the flotation tank 10, the height H is essentially equal to or greater than the height H at the center 11 of the flotation tank 10. Expressed another way, the flotation tank 10 may have different vertical cross sections (see figure 7), for example, the side wall 14 of the flotation tank 10 may include at its bottom a section that is inclined towards the center 11 of the flotation tank 10.

Furthermore, the flotation tank 10 has a diameter D, measured at a distance h1 from an outlet nozzle 43 with respect to the bottom 13 of the flotation tank 10. In one embodiment, the ratio H/D height H to diameter D of the flotation tank 10 is between 0.5 and 1.5.

The flotation tank 10 may have a volume of at least 20 m3. The flotation tank 10 may have a volume between 20 and 1,000 m3. For example, the volume of the flotation tank 10 may be 100 m3, 200 m3, 450 m3, or 630 m3.

The flotation tank 10 comprises jet tubes 4 for introducing the slurry charge 100 into the flotation tank 10. A jet tube 4 comprises an inlet nozzle 41 for introducing the slurry charge 100 into the jet tube 4; an inlet 42 for air or other pressurized gas, such that the slurry charge 100 can be subjected to air or other pressurized gas as it is discharged from the inlet nozzle 41; an elongated chamber 40 arranged to pressurizedly receive the slurry charge 100; an outlet nozzle 43 configured to restrict the flow of the slurry charge 100 from the outlet nozzle 43, and to maintain the slurry charge in the elongated chamber 40 under pressure.

The flotation gas is entrained through a turbulent mixing action caused by the jet, and is dispersed into small bubbles in the slurry charge 100 as it travels downwardly through the elongated chamber 40 to an outlet nozzle 43 configured to restrict the flow of the slurry charge 100 from the outlet nozzle 43, and further configured to maintain the slurry charge 100 under pressure in the elongated chamber 40.

The outlet nozzle 43 may further be configured to produce a supersonic shock wave in the slurry charge, the supersonic shock wave inducing the formation of particle agglomerates and buoyant gas bubbles. For example, the outlet nozzle 43 may induce a supersonic shock wave in the slurry charge 100 as it exits the jet tube 40. In addition, the supersonic shock wave may extend into the slurry adjacent to or surrounding the outlet nozzle, such that the formation of particle agglomerates and small buoyant gas bubbles is therefore possible even outside the jet tube.

To restrict the flow, an outlet nozzle 43 may comprise a throttle such as a throat-shaped restriction structure. From the outlet nozzle 43, more specifically the choke, the slurry charge 100 is forced out under pressure into the flotation tank 10. As the slurry charge 100 passes through the outlet nozzle 43, or through the choke in the outlet nozzle 43, the flotation gas bubbles are reduced in size by pressure changes and the high shear environment downstream of the outlet nozzle 43. The velocity of the gas-liquid mixture in the outlet nozzle 43, or in the choke, may exceed the speed of sound when the flow becomes choked and the flow downstream of the choke becomes supersonic, and a shock wave is formed at the diverging section of the outlet nozzle 43. Stated another way, the outlet nozzle 43 is configured to induce a supersonic shock wave in the slurry charge 100. The slurry charge flow 100 is throttled when the ratio of the absolute pressure upstream of the outlet nozzle 43 to the absolute pressure downstream of a choke or other restricting structure of the outlet nozzle 43 exceeds a critical value. When the pressure ratio exceeds the critical value, the slurry charge flow 100 downstream of the choke of the outlet nozzle 43 becomes supersonic, and a shock wave is formed. Small buoyancy gas bubbles in the slurry charge mixture 100 break up into even smaller ones as they are forced through the shock wave, and are forced into contact with hydrophobic ore particles in the slurry charge 100, thereby creating agglomerates of buoyancy gas bubbles and ore particles.

An outlet nozzle 43 may be arranged within the flotation tank 10 at a desired depth. An outlet nozzle 43 may be positioned at a vertical distance L5 from the pan rim 21, the distance L5 being at least 1.5 m. In other words, the length of the portion of a jet tube 4 arranged within the flotation tank 10 below the level of the pan rim 21 is at least 1.5 m. In one embodiment, the distance L5 is at least 1.7 m, and the distance h1 of the outlet nozzle 43 relative to the bottom 13 of the flotation tank 10 is at least 0.4 m. For example, the distance L5 may be 1.55 m, 1.75 m, 1.8 m, 2.2 m, 2.45 m, or 5.25 m; and the distance h-i, independently of the distance L5, may be 0.45 m, 0.55 m, 0.68 m, 0.9 m, or 1.2 m. Likewise, the ratio of the distance L5 to the height H of the flotation tank 10 may be 0.9 or less. The depth at which the jet tubes 4 are arranged within the flotation tank 10 may depend on various factors, for example, on the characteristics of the slurry and/or the valuable mineral to be treated in the flotation cell 1, or on the configuration of a flotation line on which the flotation cell 1 is arranged. The ratio of a distance h1 of an outlet nozzle 43 relative to the bottom 13 of the flotation tank 10 to the height H of the flotation tank 10, h-i/H, may be between 0.1 and 0.75.

A diameter of an outlet nozzle 43 may be between 10 and 30% of the diameter of an elongated chamber 40 of a jet tube 4. The diameter of an outlet nozzle 43 may be between 40 and 100 mm. By way of example, the diameter of the outlet nozzle 43 may be 55 mm, 62 mm or 70 mm.

By arranging an outlet nozzle with a specific diameter, the velocity of the slurry charge can be maintained at a level favorable for the creation of small flotation gas bubbles, and for these bubbles to be more likely to come into contact with the ore particles in the slurry. In particular, to maintain a shock wave after the outlet nozzle, a slurry velocity of 10 m/s or higher is required. The design of the outlet nozzle in relation to the size of the jet tube allows the effect of the slurry charge flow rate to be taken into account in different types of flotation cells.

A jet tube 4 may further comprise a striker 44 configured to contact a slurry charge flow 100 from the outlet nozzle 43 and to direct the slurry charge flow 100 radially outward and upward of the striker 44. Thus, the slurry charge 100 exiting the outlet nozzle 43 is directed to contact the striker 44. A distance L3 from a bottom 440 of the striker 44 to the outlet nozzle 43 may be between 2 and 20 times a diameter of the outlet nozzle 43. For example, the distance L3 may be 5 times, 7 times, 12 times, or 15 times a diameter of the outlet nozzle 43.

The ratio of the distance L3 to the distance h1 of an outlet nozzle 43 relative to the bottom 13 of the flotation tank 10, L3/h-i, may be less than 1.0. Also, a distance h3 of a bottom 440 of the striker 44 relative to the bottom 13 of the flotation tank 10 may be at least 0.3 m. For example, the distance h3 may be 0.4 m, 0.55 m, 0.75 m, or 1.0 m.

The striker 44 may comprise an impact surface adapted to come into contact with the grout charge flow 100 exiting the outlet nozzle 43. The impact surface may be made of wear-resistant material to reduce the need for replacements or maintenance.

The slurry, which is essentially a three-phase gas-liquid-solids mixture, exiting the striker 44 enters the top of the flotation tank 10, and the flotation gas bubbles rise upward and separate from the liquid to form a froth layer. The froth rises upward and is discharged over the pan flange 21 into the pan 2 and out of the flotation cell 1 as the top overflow 500. The tailings or the bottom overflow 400, from which substantially all the desired material has been removed, exits the flotation tank 10 through an outlet disposed at or near the bottom 13 of the flotation tank 10.

Some of the coarse hydrophobic particles carried into the froth may subsequently detach from the buoyancy gas bubbles and fall back into the flotation tank 10 as a result of bubble coalescence in the froth. However, the majority of such particles fall back into the flotation tank 10 in such a manner and position that they can be captured by the bubbles that have just entered the flotation tank 10 from the jet tubes 4 and transported back into the froth layer.

There may be 2-40 jet tubes 4, or 4-24 jet tubes 4 arranged in a flotation cell 1. In one embodiment, there are 16 jet tubes 4. In another embodiment, there are 24 jet tubes 4. In another embodiment, there are 8 jet tubes 4. The exact number of jet tubes 4 may be chosen based on the specific operation, for example, the type of slurry being treated in the flotation cell 1, the volumetric feed rate to the flotation cell 1, the mass feed rate to the flotation cell 1, or the volume or dimensions of the flotation tank 10. To properly disperse the flotation gas within the flotation tank 10, between 4 and 6 jet tubes 4 may be employed.

The jet tubes 4 may be arranged concentrically to the perimeter 12 of the flotation tank 10 at a distance from the center 11 of the flotation tank 10. This may be the case when the flotation tank 10 has a circular cross-section. The jet tubes 4 may further be arranged such that each jet tube 4 is located at a distance L1 from an outlet nozzle 43 with respect to the center 11 of the flotation tank 10, the distance preferably being the same for each jet tube 4. For example, the distance L1 may be between 10 and 40% of the diameter D of the flotation tank 10. According to different embodiments of the flotation cell 1, the distance L1 may be 12.5%, 15%, 25% or 32.5% of the diameter D of the flotation tank 10.

The jet 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 has a rectangular cross-section. A distance L2 of the outlet nozzle 43 of a jet tube 4 with respect to the side wall 14 of the flotation tank 10 may be between 10 and 40% of the diameter D of the flotation tank 10. In one embodiment, the distance L2 is 25% of the diameter D of the flotation tank 10. According to different embodiments of the flotation cell 10, the distance L2 may be 12.5%, 15%, 27% or 32.5% of the diameter D of the flotation cell 10. Additionally, the jet tubes 4 arranged in parallel may also be arranged in a straight line within the flotation tank 10.

Furthermore, in all the aforementioned embodiments, the jet tubes 4 can be arranged at the same distance from each other so that a distance between any two adjacent outlet nozzles 43 is the same.

The flotation tank 10 comprises a lower structure 7 (see especially figures 2, 4a, 4b, 5 and 8), arranged on the bottom (13), and with a shape that allows the particles suspended in slurry to mix in a mixing zone A created by the flow of slurry charge 100 coming from the outlet nozzles 43 of the jet tubes 4 on the lower structure 7, and to settle in a sedimentation zone B surrounding the lower structure 7.

The shape of the lower structure 7 can be defined as follows (see Figure 8): it can be understood that the vertical cross-section of the lower structure has the shape of a functional triangle 700 comprising a first (upper) vertex 71, pointing away from the bottom 13 of the flotation tank 10; a second vertex 71a; and a third vertex 71b, the latter two being arranged on the bottom 13 of the flotation tank 10. Between the first vertex 71 and the second vertex 71a, a first side a is formed. Between the first vertex 71 and the third vertex 71b, a second side b is formed. Between the second vertex 71a and the third vertex 71b a base c is formed, whereby the base c is parallel to and lies on the bottom 13 of the flotation tank 10. A central axis 70 of the functional triangle 700 is essentially concentric with the center 11 of the flotation tank 10. "Essentially" is to be understood in this context as meaning that during manufacture and/or installation of the lower structure 7 slight deviations from the center 11 of the flotation tank 10 may naturally occur. The intention is, however, that the two axes, the central axis 70 of the functional triangle (which is also the central axis of the lower structure 7) and the center of the flotation tank 10, are coaxial.

A base angle a between the first side a and the base c (and/or between the second side b and the base c), with respect to the bottom 13 of the flotation tank 10, is between 20 and 60°. For example, the angle a may be 22°, 27.5°, 35°, 45°, or 53.75°. Likewise, an included angle p between the first side a and the second side b is between 20 and 100°. Preferably, the included angle p is between 20 and 80°. By way of example, the included angle p may be 22°, 33.5°, 45°, 57.75°, 64°, or 85.5°. Therefore, the functional triangle may be an isosceles triangle or an equilateral triangle.

The functional triangle is essentially a shape that can be identified by the aforementioned characteristics, regardless of the actual shape of the lower structure 7, which may be, depending on the cross-section and other structural details of the flotation tank 10, for example a cone, a truncated cone, a pyramid, or a truncated pyramid. A cone or a truncated cone may be a suitable shape for a flotation tank with a circular cross-section. A pyramid or a truncated pyramid may be a suitable shape for a flotation tank with a rectangular cross-section.

The lower structure 7 comprises a base 73, corresponding to the base c of the functional triangle 700 (i.e., the base c of the functional triangle 700 defines the base 73 of the lower structure 7), and arranged on the bottom 13 of the flotation tank 10. Furthermore, the lower structure comprises a liner 72. The liner 72 is defined at least by the first vertex 71, the second vertex 71a and the third vertex 71b of the functional triangle 700. Therefore, regardless of the actual shape of the lower structure 7, the functional triangle 700 defines the extreme physical dimensions of the lower structure 7. For example, if the lower structure 7 has an irregular shape but is rotationally symmetrical, it would fit into the functional triangle 700 in its entirety (see the last image of Figure 8). In one embodiment, the liner 72 is at least partially defined by the first side a and the second side b of the functional triangle. An example of such an embodiment is a lower structure 7 having the shape of a truncated cone (see the middle image of Figure 8). In one embodiment, the covering 72 is essentially entirely defined by the first side a and the second side b of the functional triangle 700, i.e. the lower structure 7 has the shape of a cone (see the first image of Figure 8).

The lower structure 7 has a height h4, measured from the highest part of the lower structure 7 to the bottom 13 of the flotation tank 10. In the case where the shape of the lower structure is a cone or a pyramid, the highest part is also the first vertex 71 of the functional triangle 700. In the case where the lower structure 7 has some kind of truncated shape, the height h4 is measured from the flat top of the truncated shape (see the middle image of figure 8) to the bottom 13 of the flotation tank 10. The height tu is greater than 1/5 and less than 3/4 of the height H of the flotation tank 10. Likewise, the diameter d3 of the base 73 of the lower structure 7 can be between 1/4 and 3/4 of a diameter d1 of the bottom 13 of the flotation tank 10. In the case where a flotation tank 10 and/or the lower structure 7 have a non-circular cross-section, the diameters being measured as the maximum diagonals of the respective parts (base 73 and bottom 13). In one embodiment, the surface area of a base 73 of the lower 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 between 25 and 80% of the surface area of the bottom 13 of the flotation tank 10.

Likewise, the volume of the flotation tank 10 taken by the lower structure 7 may be between 30 and 70% of the volume of the flotation tank 10 taken by the mixing zone A.

The lower structure 7 may further comprise any support structure and/or connection structure suitable for installing the lower structure 7 in the flotation tank 10, on the bottom 13 of the flotation tank 10. The lower structure 7 may be made of any suitable material such as metal, for example, stainless steel.

The flotation tank 10 may further comprise a froth agglomerator 6 shaped to direct froth at the open froth surface Af toward the pan flange 21, as shown in Figures 4b and 5. The froth agglomerator 6 may be a central froth agglomerator 61, and/or an internal perimeter froth agglomerator disposed within the flotation tank 10 at a desired depth adjacent the side wall of the flotation tank 10.

A central froth agglomerator 61 is arranged concentrically with the center 11 of the flotation tank 10. The central froth agglomerator 61 may be in the shape of a cone or a truncated cone. The central froth agglomerator 61 may be in the shape of a pyramid or a truncated pyramid. Expressed another way, a vertical cross-section of a central froth agglomerator 61 may be an inverted triangle with an apex pointing toward the bottom 13 of the flotation tank. In the case where the central froth agglomerator 61 has a truncated structure or shape, the apex is only functional, i.e., it should be visualized as the lowest point of the continuous structure or shape up to a complete non-truncated shape, so that an included angle α can be identified independently of the actual shape or conformation of the central froth agglomerator. The included angle α may be between 20 and 80°. For example, the included angle a may be 22°, 37.5°, 45°, 55°, 63.75°, or 74°. In one embodiment, the central foam agglomerator 61 is arranged to block between 25 and 40% of the open foam surface Af.

Alternatively or in addition to the central froth agglomerator 61, the flotation tank may comprise an inner perimeter agglomerator 62, arranged in the side wall 14 of the flotation tank 10 such that a lowest point 620 of the inner perimeter agglomerator is located at a distance fu from the bottom 13 of the flotation tank 10. The distance h2 may be between 1/2 and 2/3 of the height H of the flotation tank 10. The inner perimeter agglomerator 62 may be formed to comprise a diagonal inlet 14c starting from the lowest point 620, and angled towards the center 11 of the flotation tank 10, and extending between a first part 14a of the side wall 14 of the flotation tank 10 and a second part 14b of the side wall 14 such that an angle of inclination p of the diagonal inlet 14c with respect to the first part 14a of the wall lateral 14 is between 20 and 80°. The angle of inclination p can be, for example, 22°, 37.5°, 45°, 55°, 63.75° or 74°. The inner perimeter agglomerator 62 may be arranged to block between 1/5 and % of a pulp area Ap, which is measured at a distance h1 from an outlet nozzle 43 of a jet tube 4 with respect to the bottom 13 of the flotation tank 10, in a mixing zone A. The mixing zone A, i.e. that part or zone of the flotation tank in the vertical direction in which the slurry is agitated or otherwise induced so that the ore particles suspended in the slurry are mixed with the flotation gas bubbles, is formed approximately adjacent to a vertical section of the flotation tank 10 around the lower parts of the jet tubes 4 and the impaction troughs 44 (see figure 5).

A slurry fraction 300 can be withdrawn from the flotation tank 10 through an outlet 31 arranged in the side wall 14 of the flotation tank 10. This slurry fraction 300 is recirculated to the jet tubes 4 as inlet slurry. In one embodiment, the slurry charge 100 comprises 40% or less of slurry fraction 300. In one embodiment, the slurry charge 100 comprises 50% or less of slurry fraction 300. By way of example, the slurry charge may comprise 5%, 12.5%, 20%, 30%, or 45% of slurry fraction 300. Alternatively, the slurry charge 100 may comprise 0% of slurry fraction 300, i.e., there is no recirculation of slurry taken from the flotation tank 10 back to the flotation cell, but rather the slurry charge 100 comprises 100% of newly arrived slurry 200, for example, from a previous flotation cell (i.e., underflow 400 of a flotation cell). previous), or from a previous step in the process.

The slurry fraction 300 may be recirculated to all of the jet tubes 4 of the flotation tank 10 or alternatively to some of the jet tubes 4, while other jet tubes 4 receive newly arrived slurry 200, comprising the underflow flow 400 from a previous flotation cell or a slurry flow from some previous process step, depending on the location of the flotation cell 1 within a waterline 8. The outlet 31 may be arranged at a distance L4 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 relative to the bottom 13 of the tank. The distance L4 is between 0 and 50% of the height H of the flotation tank 10. The outlet 31 may advantageously be positioned in a settling zone where particles suspended in slurry and not captured by the flotation gas bubbles and/or the upward flow of slurry descend towards the bottom 13 of the flotation tank 10. In one embodiment, the outlet 31 is arranged at the bottom of the flotation tank 10. For example, the distance L4 may be 2%, 8%, 12.5%, 17% or 25% of the height H of the flotation tank 10. Even if the outlet 31 is controlled by internal or external structures, such as upflow or downflow dart boxes, respectively, the outlet 31 is ideally located at the bottom of the flotation tank 10, i.e., close to or adjacent to the bottom 13 of the flotation tank. More specifically, slurry fraction 300 is removed from the bottom of flotation tank 10.

The flotation cell 1 may also comprise a conditioning circuit 3. The conditioning circuit 3 may comprise a pump tank 30, or another such additional vessel, in fluid communication with the flotation tank 10. In the pump tank 30, the newly arrived slurry charge 200 and a slurry fraction 300 taken from the flotation tank 10 through an outlet 31 are arranged to combine into the slurry charge 100, which is then conducted to the jet tubes 4 of the flotation tank 10. The newly arrived slurry 200 may be, for example, the underflow 400 from a previous flotation cell or, in the case where the flotation cell 1 is the first flotation cell in a flotation line, a slurry charge from a grinding unit/step or a classification unit/step. It is also possible for the slurry fraction 300 and the newly arrived slurry 200 to be distributed between the jet tubes 4 without first being combined in a pump tank 30.

The combined slurry may be recirculated to all jet tubes 4 of the flotation tank 10 or alternatively to some of the jet tubes 4, while other jet tubes 4 receive newly arrived slurry 200, comprising the underflow flow 400 from a previous flotation cell or a slurry flow from some previous process step, depending on the location of the flotation cell 1 within a waterline 8.

The outlet 31 may be arranged in the side wall 14 of the flotation tank 10, at a distance L4 from the bottom 13 of the flotation tank 10. The distance L4 may be 0 to 50% of the height H of the flotation tank 10. For example, the distance L4 may be 2%, 8%, 12.5%, 20% or 33% of the height H of the flotation tank 10.

Additionally, the conditioning circuit may comprise a pump 32 arranged to receive the slurry fraction 300 from the flotation tank 10, and to drive the slurry charge 100 from the pump tank 30 to the jet tubes 4. The slurry fraction 300 may comprise low settling velocity particles such as slow floating fines. The slurry fraction may be taken from or near the bottom of the flotation tank 10. Additionally or alternatively, the conditioning circuit 3 may further comprise a distribution unit (not shown in the figures), arranged to distribute the slurry charge 100 between the jet tubes 4. The pump 32 may also be used to drive the slurry charge 100 into the jet tubes 4. In order to evenly distribute the slurry charge 100 between the jet tubes 4, a distribution unit may be used. The distribution unit may, for example, comprise a feed pipe within the flotation tank 10, configured to distribute the slurry fraction 300 directly between the jet tubes 4. By way of example, the distribution unit may comprise conduits arranged outside the flotation tank 10, leading to a separate feed distributor configured to distribute the slurry fraction 300, or a combination of slurry fraction 300 and newly arrived slurry 200, between the jet tubes 4.

According to another aspect of the invention, the flotation lines 8 are shown in Figures 6a and 6b. A flotation line 8 comprises a plurality of fluidly connected flotation cells 1a, and at least one of the flotation cells is a flotation cell 1 according to the above-described embodiments of the flotation cell 1 according to the invention. In one embodiment of the flotation line 8, the flotation cell 1 according to the invention is preceded by a flotation cell 1a. A flotation cell 1a may be of any type known in the art. Alternatively or additionally, the flotation cell 1 may be preceded by a mechanical flotation cell 1b (see Figure 6a).

In one embodiment of the waterline 8, it comprises a roughing portion 81 with a flotation cell 1a; a sweeping portion 82 with a flotation cell 1a arranged to receive the lower overflow flow 400 for the roughing portion 81; and a sweeping finishing portion 820 with a flotation cell 1a arranged to receive the upper overflow flow 500 from the sweeping portion 82 (see Figure 6b). At the waterline 8, the last flotation cell 1 of the sweeping part 82 and, alternatively or additionally, the last flotation cell 1 of the sweep finishing part 820 is a flotation cell 1 according to the invention, with jet tubes 4. Additionally, at the waterline 8, as described above, the flotation cell 1 according to the invention, with the jet tubes 4, may be preceded by a mechanical flotation cell 1b.

Flotation line 8 may be preceded by other processes such as grinding, classification, screening, levigation, coarse particle recovery, spirals, and other separation processes; and other flotation processes. Flotation line 8 may be followed by various processes such as regrind, finishing, or other flotation processes, centrifugation, filtering, screening, or dewatering.

According to another aspect of the invention, the flotation line 8 can be used for the recovery of particles comprising a valuable material suspended in slurry. In one embodiment, the use can be directed toward the recovery of particles comprising non-polar minerals such as graphite, sulfur, molybdenite, coal, or talc.

According to another embodiment, the use may be directed to the recovery of particles comprising polar minerals.

In another embodiment, the method is directed toward the recovery of mineral particles with a Mohs hardness of between 2 and 3, such as galena, sulfide minerals, PGMs, and REO minerals. In yet another embodiment, the method is specifically directed toward the recovery of particles comprising platinum.

In another embodiment, the use is directed to the recovery of particles comprising copper from mineral particles having a Mohs hardness of between 3 and 4. In yet another embodiment, the use is specifically directed to the recovery of particles comprising copper from low-grade ore.

The embodiments described herein can be used in any combination with one another. Several of the embodiments can be combined with one another to form another embodiment. A flotation cell to which the disclosure relates may comprise at least one of the embodiments described above. It is obvious to one skilled in the art that, with the advancement of technology, the basic idea of the invention can be implemented in various ways. Thus, the invention and its embodiments are not limited to the examples described above, but may vary within the scope of the claims.

Claims (20)

1. Flotation cell (1) for the treatment of suspended particles in slurry and for the separation of the slurry into a lower overflow flow (400) and an upper overflow flow (500), the flotation cell comprising a flotation tank (10) comprising a center (11), a perimeter (12), an essentially horizontal flat bottom (13) and a side wall (14); a pan (2) and a pan flange (21) surrounding the perimeter (12) of the tank (11); and a lower structure (7) arranged on the bottom (13), and with a shape that allows the particles suspended in slurry to mix in a mixing zone (A) on the lower structure, and to settle in a sedimentation zone (B) surrounding the lower structure, where the flotation tank further comprises jet tubes (4) for introducing the slurry charge (100) into the tank, comprising a jet tube an inlet nozzle (41) for introducing the slurry charge (100) into the jet tube; an elongated chamber (40) arranged to receive the grout charge under pressure; characterized in that the jet tube (4) further comprises an inlet (42) for pressurized gas, the slurry charge being subjected to the pressurized gas as it is discharged from the inlet nozzle; an outlet nozzle (43) configured to restrict the flow of slurry charge from the outlet nozzle, and to maintain the slurry charge in the elongated chamber under pressure; and whereby the jet tubes are arranged in a position relative to the lower structure such that mixing is induced in the mixing zone, and where the outlet nozzle (43) is configured to produce a supersonic shock wave in the slurry charge (100), the supersonic shock wave inducing the formation of particle agglomerates and flotation gas bubbles. 2. Flotation cell according to claim 1, characterized in that a height (H) of the flotation tank (10), measured as the distance from the bottom (13) of the flotation tank to the pan rim (21), at the perimeter (12) of the flotation tank is at most 20 % lower than in the center (11) of the flotation tank. 3. Flotation cell according to claim 1 or 2, characterized in that the vertical cross-section of the lower structure (7) is a functional triangle (700) comprising a first vertex (71) pointing away from the bottom (13) of the flotation tank (10), a second vertex (71a) and a third vertex (71b); a first side (a) between the first vertex and the second vertex; a second side (b) between the first vertex and the third vertex; and a base (c) between the second and third vertices on the bottom (13) of the flotation tank; and a central axis (70) essentially concentric with the center (11) of the flotation tank. 4. Flotation cell according to claim 3, characterized in that the base angle (a) between the first side (a) and the base (c), or the second side (b) and the base with respect to the bottom (13) of the flotation tank (10) is between 20 and 60°. 5. Flotation cell according to claim 3 or 4, characterized in that the included angle (p) between the first side (a) and the second side (b) is between 20 and 100°, preferably between 20 and 80°. 6. Flotation cell according to any of claims 3 to 5, characterized in that the lower structure comprises a base (73) on the bottom of the flotation tank (10) and defined by the base (c) of the functional triangle (700), and a lining (72) defined at least by the first, second and third vertices (71, 71a, 71b) of the functional triangle. 7. Flotation cell according to claim 6, characterized in that the lining (72) is defined at least partially by the first and second sides (a, b) of the functional triangle (700). 8. Flotation cell according to any one of claims 1 to 7, characterized in that a height (tu) of the lower structure (7) is greater than 1/5 and less than 3/4 of a height (H) of the flotation tank (10), measured as the distance from the bottom (13) to the rim of the pan (21). 9. Flotation cell according to any one of claims 1 to 8, characterized in that the flotation tank (10) further comprises a central foam agglomerator (61) arranged at a distance (hs) from the bottom (13) of the flotation tank. 10. Flotation cell according to claim 9, characterized in that a height (tu) of the lower structure (7) is between 1/3 and 3/4 of the distance (hs). 11. Flotation cell according to any of claims 1 to 10, characterized in that the flotation tank (10) further comprises an internal perimeter foam agglomerator (62), a lowest point (620) of the internal perimeter foam agglomerator arranged at a distance (h2) from the bottom (13) of the flotation tank. 12. Flotation cell according to claim 11, characterized in that the ratio of a height (fu) of the lower structure (7) to the distance (h2) is 1.0 or less. 13. Flotation cell according to any one of claims 1 to 12, characterized in that a diameter (d3) of a base (73) of the lower structure (7) is between 1/4 and 3/4 of a diameter (d-i) of the bottom (13) of the flotation tank (10). 14. Flotation cell according to any one of claims 1 to 13, characterized in that the surface area of a base (73) of the lower structure (7) is between 25 and 80% of the surface area of the bottom (13) of the flotation tank (13). 15. Flotation cell according to any one of claims 1 to 14, characterized in that a ratio (H/D) of a height (H) of the flotation tank (10), measured as the distance from the bottom (13) to the rim of the pan (21), with respect to the diameter (D) of the flotation tank, measured at a height (h-i) of the outlet nozzle (43) from the bottom (13), is between 0.5 and 1.5. 16. A flotation cell according to any one of claims 1 to 15, characterized in that a jet tube further comprises a striker (44) configured to come into contact with a slurry charge flow from the outlet nozzle (43) and to direct the slurry charge flow (100) radially outward and upward from the striker. 17. A flotation line (8) comprising several flotation cells (1a) connected fluid-wise, characterized in that at least one of the flotation cells is a flotation cell (1) according to any one of claims 1 to 16. 18. Waterline according to claim 17, characterized in that the flotation cell (1) is preceded by a flotation cell (1a). 19. Waterline according to claim 18, characterized in that the waterline comprises a roughing part (81) with a flotation cell (1a); a sweep portion (82) with a flotation cell (1a) arranged to receive the lower overflow flow (400) from the roughing portion; and a sweep finishing part (820) with a flotation cell (1a) arranged to receive the upper overflow flow (500) from the sweep part, wherein the last flotation cell of the sweep part and/or the sweep finishing part is a flotation cell (1) according to any one of claims 1-16. 20. Use of a flotation line (8) according to claims 17 to 19 in the recovery of particles comprising a valuable material suspended in slurry.