Foam flotation tank

Abstract

The invention relates to a froth flotation cell which is particularly suitable for roughing and scavenging cells, but can also be used as a cleaner cell. The froth flotation cell includes a flotation tank, a pulp feed line for feeding mineral-containing pulp into the tank, a variable speed pump including feed and discharge lines, a first lower tailing discharge line connected to a first tailing outlet at the bottom of the tank, and a second lower tailing discharge line connected to a second tailing outlet at the bottom of the tank. The pump is configured to pump a combination of fresh and recovered feed into the tank through an external ejector assembly and an internal ejector assembly connected in series in the pump discharge line. An outer injector assembly is located outside the canister and includes an air injector, and an inner injector is located within the canister.

Description

Technical Field

[0001] The present invention relates to mineral processing by froth flotation and more particularly to a froth flotation cell which is particularly suitable for use as a rougher or scavenger cell and may also be used in cleaner, re-cleaner and re-re-cleaner applications. Background Art

[0002] Froth flotation has been around for more than a century as a process for separating and concentrating minerals.

[0003] In froth flotation, ground ore particles are physically separated based on their hydrophobicity. Minerals present in the ore and water slurry become hydrophobic due to the addition of collector chemicals to the slurry. Air is introduced into the slurry and the hydrophobic particles become attached to the air bubbles. The air bubbles with the hydrophobic particles attached rise to the surface and collect in a froth layer which is collected as a mineral-rich concentrate.

[0004] In the past, the mining industry has mainly used mechanical flotation cells, which consist of square or cylindrical tanks or cans with a mechanically driven rotor and stator agitator mechanism through which air is introduced into the bottom of the tank. Typically, a number of such cells are combined in series to form a bank of cells. The main limitation of mechanical cells is their inefficiency when dealing with fine particles that tend to be entrained in the froth. This has led to the use of mechanical cells as the main rougher cells, with column cells often being used as cleaners in certain applications.

[0005] As an alternative to the agitator mechanism of a mechanical tank, a columnar tank uses (internal or external) ejectors to generate bubbles that are introduced into the columnar tank. The slurry feed port is located relatively high in the column, and as the slurry moves down the column, the descending slurry contacts the rising bubbles generated at the bottom of the column. Hydrophobic particles attached to the bubbles form bubble / particle aggregates that rise to the surface. Non-floating material is discharged from the bottom of the column as tailings. Froth washing can also be introduced into the columnar tank, where water is injected into the froth layer to improve the grade of the concentrate by removing gangue particles that accumulate in the froth due to mechanical entrainment.

[0006] Attempts to use the operating principle of columnar cells in roughing and scavenging applications have been unsuccessful and it is an object of the present invention to provide a froth flotation cell which solves this problem. Summary of the invention

[0007] According to the present invention, a froth flotation cell comprises:

[0008] Flotation tanks;

[0009] a slurry feed line for feeding a slurry containing minerals to a tank, the slurry containing minerals being separated into separate froth and tailings fractions by froth flotation;

[0010] variable speed pump, including feed and discharge lines;

[0011] a first low-level tailings discharge outlet line connected to a first tailings outlet at the bottom of the tank, the first low-level discharge line being configured to supply a slurry tailings feed to the pump during operation, the slurry tailings feed being drawn from the bottom of the tank through the first tailings outlet;

[0012] A pump having at least two feed line suction points, the at least two feed line suction points including a slurry feed line and a first low-level discharge line;

[0013] a pump configured to pump a combination of fresh and recycled feed into the tank through an external ejector assembly and an internal ejector assembly connected in-line in a discharge line of the pump, the combination of fresh and recycled feed being a combination of slurry feed and slurry tailings feed;

[0014] an external injector assembly located external to the tank and including an air injector configured to introduce air into the combination of fresh and recycled feeds;

[0015] an internal ejector assembly located within the tank and terminating in a combined fresh and recycled feed outlet through which the combination of fresh and recycled feed is discharged into the tank; and

[0016] A second low-level tailings discharge outlet line is connected to a second tailings outlet at the bottom of the tank. The second low-level discharge line is configured to supply slurry tailings feed to an external process during operation. The slurry tailings feed is drawn from the bottom of the tank through the second tailings outlet.

[0017] The external process may be a further mineral recovery process in which additional quantities of valuable minerals may be separated from the ore pulp by froth flotation with or without regrinding.

[0018] In a preferred form of embodiment of the invention, the external process preferably consists of one or more froth flotation cells similar to those described above.

[0019] Additionally or alternatively, the external process in this embodiment of the invention may consist of one or more scan slots.

[0020] As another alternative, the external process may be a waste disposal process where the flotation tailings are disposed of as mine backfill or as tailings waste.

[0021] In a preferred embodiment of the present invention, the external process consists of one or more additional froth flotation cells similar to the aforementioned froth flotation cells, which are preferably connected to each other so that the froth flotation of the slurry tailings fed from the second low-level tailings discharge outlet of the upstream froth flotation cell is supplied as slurry feed to the slurry feed inlet of the froth flotation cell immediately downstream.

[0022] In such an apparatus, the tank receiving the slurry tailings feed at its slurry feed inlet is the downstream tank, and the tank supplying the slurry tailings feed from its second lower tailings discharge outlet is the upstream tank.

[0023] In this embodiment of the invention, several similar froth flotation cells are preferably installed in the circuit, one downstream of the other, and the second low-level tailings discharge outlet of each upstream cell is connected to feed the slurry tailings from its second low-level tailings discharge outlet to the slurry feed inlet of its immediately downstream cell.

[0024] In another embodiment of the present invention, an internal injector assembly includes at least one internal injector terminating in an outlet that is partially blocked by a diffuser that extends through and partially blocks the injector outlet.

[0025] The injector may include ceramic injector elements connected in series.

[0026] In a preferred form of embodiment of the invention, the internal injector assembly includes a plurality of internal injectors mounted and connected to feed tubes extending radially from a central feed tube connected to a pump discharge line.

[0027] The froth flotation cell preferably includes one or more of an internal launder assembly, a froth scraper assembly, and a froth wash water assembly.

[0028] The external process may consist of at least one scavenger tank or a waste disposal process in which the final pulp tailings are treated as waste.

[0029] The present invention comprises a froth flotation cell group, comprising at least two froth flotation cells according to any one of the preceding claims, wherein the froth flotation cells are installed in a slurry fluid flow circuit, the circuit comprising a first froth flotation cell and at least one other froth flotation cell installed downstream of the first froth flotation cell in the slurry fluid flow circuit, so that the second low-level tailings discharge outlet of each upstream cell is connected to feed the slurry tailings from its second low-level tailings discharge outlet to the slurry feed inlet of its immediately adjacent downstream cell. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] The present invention will be further described with reference to the accompanying drawings, in which:

[0031] Figure 1 is a schematic isometric view of two froth flotation cells according to the present invention;

[0032] Figure 2 yes Figure 1 A front view of a froth flotation cell;

[0033] Figure 3 is a plan view of a froth flotation cell having a tailings discharge to the next flotation cell;

[0034] Figure 4 is a side view of a froth flotation cell;

[0035] Figure 5 is a similar side view showing the recovery piping and ejector assembly mounted at the bottom of the flotation cell (dashed outline);

[0036] Figure 6 yes Figure 5 a schematic isometric view of a recovery pipe and ejector assembly;

[0037] Figures 7 to 12 are a plan view and an isometric view, respectively, of an internal launder arrangement of a froth flotation cell suitable for use in the present invention; and

[0038] Fig.13 and 14 are an isometric view and a plan view, respectively, of a froth wash water system suitable for froth flotation of the present invention;

[0039] Fig.15 is a side view of a froth flotation cell according to the present invention, further showing Fig.13 and 14 Wash water system;

[0040] Fig.16 yes Fig.15 The cross-section view on line AA in ;

[0041] Fig.17 and 18 are an isometric view and a plan view, respectively, of a froth scraper assembly suitable for use in a froth flotation cell of the present invention; and

[0042] Fig.19 is a side view of a froth flotation cell of the present invention including a froth scraper assembly. DETAILED DESCRIPTION

[0043] Mineral processing is a multi-stage operation that generally follows a similar separation process. First, the mineral-bearing ore is mined, crushed, and ground, and then the valuable mineral particles are separated from the waste rock or gangue. The present invention relates to froth flotation in a froth flotation cell as a means of separating minerals from gangue.

[0044] In general, froth flotation involves adding a liquid, usually water, to the ground ore to form a slurry. Typically, this is done in a conditioning tank before the slurry is introduced into one or more froth flotation cells. In the conditioning tank, the ore and water slurry is conditioned with conditioning chemicals, which include collector and frother chemicals, and typically also include inhibitor and activator chemicals. The collector preferably attaches to the desired mineral, making the mineral particles hydrophobic and making the gangue particles non-attached or hydrophilic. The conditioned slurry of water, conditioning chemicals, hydrophobic mineral particles, and hydrophilic gangue particles is called a pulp or slurry.

[0045] The slurry is fed to a froth flotation tank or cell where it is agitated and aerated to create bubbles in the slurry. Hydrophobic mineral particles attach to the bubbles, which rise to the surface forming mineral-rich froth, which is then removed from the cell. The froth eventually collapses to form a concentrate of the target mineral slurry.

[0046] Froth flotation is usually carried out in stages. The first stage is the roughing stage, which produces two slurry flows, the first slurry flow is the coarser concentrate, and the second slurry flow is the gangue minerals that failed to float (called flotation tailings or tailings).

[0047] In the rougher stage, the focus is on mineral recovery, with the main goal being to remove and recover the maximum amount of mineral into a frothy slurry as concentrate.

[0048] The coarser concentrate stream is directed to the cleaning stage where the coarser concentrate is subjected to further flotation, usually in specialized cleaner tanks. The cleaning stage is designed to separate and exclude the maximum amount of unwanted gangue that may be entrained in the froth, and the goal of the cleaning stage is to increase the mineral yield or grade and produce a concentrate of the desired grade of mineral. Multiple cleaning stages may be required.

[0049] The coarser tailings slurry stream is directed to the cleaner stage (sometimes after regrinding). In the cleaner stage, the coarser tailings require further flotation. The goal is to recover any target minerals not recovered in the initial rougher stage. The flotation concentrate from the cleaner stage is usually returned to the coarser feed for refloatation, or is subsequently subjected to further washing stages.

[0050] The final tailings from the scavenger stage are discharged to waste. The final tailings are typically disposed of as mine backfill or sent to a tailings disposal facility for long-term storage. It should be understood that this discharge to waste makes the scavenger loop an open loop. This makes optimization of the rougher and scavenger stages particularly important, as performance losses in these stages cannot be recovered elsewhere in the process.

[0051] The roughing and scavenging cells currently used in the mining industry are mainly mechanically agitated froth flotation cells with a relatively low height-to-diameter ratio (less than 2). In these cells, the volume occupied by the bubbles in the slurry is relatively low, usually between 5% and 10% of the slurry volume. Therefore, several cells are used to increase the overall combined particle flotation cell residence time, thereby increasing the probability of particle / bubble contact. In a typical installation, the flotation cells are arranged in series in one or more cell groups. The slurry transport through the cells is achieved by gravity feeding, which is achieved by arranging the cells in a vertical stepped configuration, in which the tailings discharge from the higher level cell serves as the slurry feed flow to each cell in the next lower level cell. The stepped configuration leads to large-scale and very high-level equipment installations.

[0052] The cleaning tanks currently used in the mining industry are mainly mechanically agitated tanks and column tanks. Unlike mechanically agitated flotation cells, which tend to use relatively short tanks, column tanks have relatively tall tanks with a large height-to-diameter ratio (from 2 to 10, depending on the application). Flotation columns rarely use mechanical slurry agitation and usually use air injection systems (internal and external) that inject air into the column from a relatively low point near the bottom of the column. The slurry is fed into the column at a relatively high position in the column and falls against the bubbles generated by the air injection system. In fact, the air injection system produces a group of fine bubbles that rise to the top of the column, where they form a bubble foam. Hydrophobic particles collide with and attach to the bubbles in the collection zone (the area between the bottom of the column and the interface between the slurry and the foam), and the bubbles form a stable foam in the foam or cleaning zone (the area between the slurry / foam interface and the column overflow). The mineral-rich foam is transported through the cleaning zone by mass action and overflows the column overflow. The overflowing foam is collected in a flow channel extending circumferentially around the upper end of the column. In the launder, the froth collapses into a mineral-rich concentrate that is collected for further processing and refining of the recovered valuable minerals.

[0053] The main advantage of column cells is the high separation grades that can be achieved, which is why column cells are often used as the final concentrate washing step.

[0054] As shown, the froth flotation cell of the present invention incorporates the operating principles of a flotation column in a cell having a relatively low height-to-diameter ratio (less than 2) that is more commonly found in mechanical froth flotation cells.

[0055] The froth flotation cells 10 shown in the drawings are respectively a first cell 10.1 and a second cell 10.2 in a cell group, which may include 2 to 10 cells.

[0056] The cells 10 are substantially identical and similar cell parts are given similar numbers in the drawings. The first cell 10.1 is an upstream cell and the second cell 10.2 is a downstream cell, considering the slurry flowing through the cell group. Each cell 10 comprises a flotation tank (11.1, 11.2, 11.n).

[0057] The froth flotation cell 10 is particularly suitable for use as a rougher cell and a scavenger cell, but may also be used as a cleaner cell.

[0058] The conditioned slurry is fed to the flotation tank 11.1 of the first tank 10.1 through a slurry feed line consisting of a tundish feed 12, which feeds the conditioned slurry to the flotation tank 11.1. Starting from the first tank 10.1, the conditioned slurry is distributed from one tank to another in the tank group 10 (from the flotation tank 11.1 to the flotation tank 11.2, etc.). Only the first downstream tank 10.2 is shown in the figure. Each tank 10 is equipped with a tundish, but in most installations, the tundish 12 of the first tank 10.1 will serve as the main slurry feed.

[0059] Each flotation tank 11 is equipped with a first low tailings discharge outlet pipeline 16 and a second low tailings discharge outlet pipeline 26. In each case, the first low tailings discharge outlet pipeline 16 is a connection pipeline 16 connected to a discharge outlet located at the bottom 24 of the flotation tank 11, and the second low tailings discharge outlet pipeline 26 is a connection pipeline 26 connected to an outlet located at one side of the bottom 24 of the flotation tank.

[0060] Each tank 10 is equipped with a variable speed ejector recovery pump 14. The pump 14 discharges the pump discharge through a discharge line 18 which directs the pump discharge back into the flotation tank 11 of each tank 10.

[0061] Each pump 14 has at least two suction points. The first suction point is a first low-level tailings discharge discharge line 16, which is connected to and extends from a low-level tailings discharge outlet located at the bottom of the flotation tank 11 of the tank 10 connected to the pump 14. The second suction point is a second low-level tailings discharge discharge line 26, which is connected to and extends from the tank (10.1) upstream of the tank (10.2) connected to the pump 14, and the second low-level tailings discharge discharge line 26 extends from the low-level tailings discharge outlet on one side of the flotation tank 11.1 of the upstream tank 10.1 and is located immediately adjacent to its bottom. The third suction point may be a tundish feed device 12 that feeds fresh slurry to the pump feed line 15.

[0062] The discharge from the pump is a combination of fresh slurry feed from the tundish 12 and tailings feed from the first low level discharge outlet line 16 and the second low level tailings discharge outlet line 26 of the upstream froth flotation cell 10, which is recycled back into the flotation tank 11 of each cell 10.

[0063] The discharge of the pump is referred to herein as a "combination of fresh and recovery feed" because the bank of the cell 10 is controlled for recovery tailings feed to constitute the major portion of the discharge of the pump to each flotation tank 11.

[0064] The combination of fresh and recycled feed is recycled back into the flotation tank 11 through an external ejector assembly and an internal ejector assembly consisting of an air ejector system 20 located outside the flotation tank 11 and an ejector system 22 located inside the flotation tank 11 .

[0065] In the combination of fresh and recycled feed, the slurry / air mixing begins outside the flotation tank 11 in the external injection system 20 where pressurized air is injected into the recycled slurry stream upstream of the ceramic elements mounted in series within the air injection system 20. The ceramic elements reduce the size of the pressurized gas bubbles in a shearing action.

[0066] The portion ( 18 . 1 ) of the discharge line 18 downstream of the air injection system 20 conveys the aerated slurry (the slurry / air mixture exiting the air injection system) to the internal injector system 22 .

[0067] In the embodiment of the invention shown in the drawings, the internal ejector system 22 has four internal ejectors 22.1, each having a ceramic element connected in series and terminating in a combined outlet for fresh and recycled feed, which outlet is partially blocked by a disperser 22.2 which disperses the pulp / air mixture laterally transversely to the main axis of the ejector 22.1. As a result, the outflowing pulp / air mixture is radially dispersed into the interior of the flotation tank 11.

[0068] The ejector 22.1 is mounted and connected to a feed pipe 22.3 which extends radially from a central feed pipe 22.4 connected to the aerated slurry discharge line 18.1. The radial mounting of the ejector 22.1 positions the ejector 22.1 midway between the center of the flotation tank 11 and the peripheral wall of the flotation tank 11. As a result, the slurry / air mixture is distributed over the entire cross-sectional area of ​​the flotation tank 11. This creates an evenly distributed group of bubbles that rise through the slurry, covering almost the entire diameter of the flotation tank 11.

[0069] The combination of the inner and outer ejector assemblies 20, 22 provides for more efficient bubble generation and also provides for improved bubble size control.

[0070] The combination of the ejector assemblies 20 and 22 means that gas bubbles are generated both outside and inside the flotation tank 11. Outside the flotation tank 11, the external air ejector system 20 is the first step in gas bubble generation, which occurs before the slurry / air flow is fed to the internal ejector system 22. Inside the flotation tank 11, the internal ejector system 22 is the second step in gas bubble formation before the aerated slurry is distributed into the flotation tank.

[0071] The radial arrangement of the internal ejector system 22 distributes the gas bubbles throughout the cross-sectional area of ​​the flotation tank 11, which is a major factor in the reduced cell height in the flotation tank 10 of the present invention.

[0072] There is no mechanical mixing mechanism in the flotation tank 11. Bubble generation is completely accomplished by the ejector assemblies 20, 22. This makes the flotation cell 10 of the present invention more energy efficient than a mechanical flotation cell, since mechanical agitation in a conventional mechanical flotation cell is one of the main factors in the power consumption of the flotation cell. By eliminating the need for mechanical agitation, the flotation cell of the present invention has much lower power consumption than a mechanical flotation cell, which depends on the speed of the ejector recovery pump and the amount of power consumed.

[0073] In the first (upstream) tank 10.1, the slurry fed through the tundish feed device 12 is recovered in a recovery process, in which the pump 14 replenishes the tundish feed device with tailings extracted from the bottom 24 of the flotation tank 11.1 of the tank 10.1 connected to the pump 14 through the first low-level discharge pipeline 16.

[0074] In the remaining (downstream) tanks 10 (only one such tank 10.2 is shown in the drawing), the slurry is recovered in a recovery process, wherein the pump 14 replenishes the slurry tailings extracted from the flotation tank 11 of the tank 10 connected to the pump 14 to the tundish feeding device 12 through the first low-level discharge discharge pipeline 16, and replenishes the slurry tailings extracted from the tank (10.1 in the drawing) upstream of the tank (10.2 in the drawing) connected to the pump 14 to the tundish feeding device 12 through the second low-level tailings discharge discharge pipeline 26 of the upstream tank 10.1.

[0075] In each case (first and subsequent tanks 10 . 1 , 10 . 2 respectively), a combination of fresh and recycled feed is returned to the flotation tank 11 to which the pump 14 is connected via a pump discharge line 18 and external and internal ejector assemblies 20 , 22 .

[0076] A control valve 28 is installed in series in the second low tailings discharge line 26 of each upstream tank 10. A control valve 28 is installed immediately upstream of the flotation tank 11 of each downstream tank. The control valve 28 controls the amount of slurry fed from the upstream tank (10.1) to the downstream tank (10.2). In most cases, the primary valve control parameter will be to maintain a predetermined slurry level in the flotation tank 11 of the immediately upstream tank 10 of each control valve 28.

[0077] In order to maximize pulp recovery, which is the preferred operation of the flotation cells 10 of the present invention, the pump 14 and control valve 28 are controlled so that each of the cells 10 is fed with more pulp from the bottom of the cell 10 to which the pump 14 is connected, compared to the amount of fresh pulp feed fed from the tundish feed device 12 or from the cell immediately upstream.

[0078] In practice, two or more cells 10 will be connected in series in a cell bank like this, with each upstream cell supplying slurry to its immediately downstream cell, with the final cell discharging into a scavenging process.

[0079] In order to maximize pulp recovery, which is the preferred mode of operation of the flotation cells 10 of the present invention, the control valves 28 in the low tailings discharge outlets 16, 26 of the cells 10 are controlled so that each of the cells 10 draws more of the combination of fresh and recovered feed (from the first low tailings discharge outlet 16) than is drawn from the cell immediately upstream of that cell 10 (from the second low tailings discharge outlet line 26 of the tundish 12 or upstream cell).

[0080] In the example shown in the drawings, in the upstream cell 10.1, the control valve 28 is controlled so that the cell 10.1 is fed with a greater combination of fresh and recycled feed than the amount of fresh slurry feed from the tundish 12. In the downstream cell 10, the control valve 28 is controlled so that the cell 10 is fed with a greater combination of fresh and recycled feed drawn from the flotation tank of the cell 10 than the amount of tailings drawn from the cell immediately upstream thereof.

[0081] In this control arrangement, the primary determinant of the liquid level in the cell 10 is the amount of slurry fed through the slurry feed line formed by the tundish 12. The control valve 28 regulates the liquid level in the cell 10 by balancing the feed with the amount of tailings distributed from the cell 10 to the cell 10 immediately downstream thereof. The primary determinant of the liquid level in the downstream cell 10 is the amount of tailings fed from the upstream cell 10 to the flotation tank of the downstream cell 10 through the second low level tailings discharge outlet line 26.

[0082] The control valve 28 of the downstream tank 10 regulates the liquid level in the downstream tank 10 by balancing the feed from the second low-level tailings discharge outlet line 26 and the amount of tailings distributed from the tank 10 to the next downstream tank 10 .

[0083] The control valves 28 of all the tanks 10 in the tank group are managed and controlled to maximize recovery and maintain a predetermined slurry level in the tank 10 .

[0084] The first low tailings discharge outlet line 16 of each cell 10 is provided with a knife gate 29 which is typically preset to provide a predetermined degree of throttling in the outlet line 16. If finer control of slurry level and slurry recovery is required, the knife gate 29 may be replaced by a secondary control valve which may be controlled synchronously with the control valve 28 so that one or both of the control valve 28 and the secondary control valve (installed in the replacement for the knife gate 29) may be used to control recovery and slurry level in the cell 10.

[0085] In conventional mechanical froth flotation equipment, the liquid level is maintained by gravity feeding through the stepped configuration of flotation cells in the cell bank. In a froth flotation equipment using the froth flotation cells of the present invention, the cells 10 are installed side by side on the same horizontal plane, and instead of the gravity feeding of conventional mechanical froth flotation equipment, the flotation cells 10 of the present invention utilize pumps 14 and process logic controllers (PLC) to maintain the slurry level in the cells 10.

[0086] Since the tanks 10 are at the same level, the pumps 14 create a virtual gravity feed because the net positive suction head (NPSH) of the pumps 14 creates the feed suction that draws the slurry and tailings from one tank to the other, thereby eliminating the necessity for a stepped plant design.

[0087] The froth flotation cell of the present invention preferably comprises one of a plurality of internal launders. Essentially, the internal launder in the froth flotation cell acts as a final separator of the froth containing the valuable mineral from the slurry for recovery of the valuable mineral from the froth and further processing.

[0088] Internal chutes are typically configured as slots or channels within the flotation cell and located near the top of the flotation tank. The internal chutes allow froth to rise and overflow into the chute channel from where it drains by gravity to a peripherally extending chute overflow which drains by gravity to a slurry discharge outlet.

[0089] Variations in internal launder geometry are often made to suit the specific requirements of the flotation process and the properties of the ore being processed. The size, shape, and inclination of the launder will affect froth residence time, froth transport, and froth overflow rate, which in turn can affect the recovery and grade of the flotation process.

[0090] Figures 7 to 12 A variety of different internal flow channel designs are shown.

[0091] Figure 7 and Figure 8 The internal chute 30.1 shown is a simple bi-directional chute having a single transverse channel 32.1 sloping from the centre of the tank towards the periphery to enable froth to be gravity discharged from a discharge outlet 34.1 leading to a peripherally extending chute overflow 36.1.

[0092] Fig. 9 and Fig.10 The internal chute 30.2 shown is a 4-way radial chute having a pair of intersecting transverse channels 32.2 inclined from the centre of the tank to the periphery to enable froth to be gravity discharged from a discharge outlet 34.2 leading to a peripherally extending chute overflow 36.2.

[0093] Fig.11 and Fig.12 The internal chute 30.3 shown in the drawing is an 8-way radial chute having intersecting transverse channels 32.3 sloping from the centre of the tank towards the periphery to enable the froth to be gravity discharged from a discharge outlet 34.3 leading to a peripherally extending chute overflow 36.3.

[0094] The froth flotation cell of the present invention preferably includes a froth wash water system. Examples of such systems are Figures 13 to 19 shown.

[0095] The froth wash water system improves the stability and cleanliness of the froth on the surface of the flotation cell by washing the froth and reducing the amount of worthless gangue material that may be carried from the slurry into the mineral-rich froth. By introducing wash water through the froth wash water system, the gangue material is washed off the froth and drips back into the slurry, and the froth is conditioned to flow more easily into the internal launders, thereby increasing mineral recovery and improving concentrate grade.

[0096] like Figures 13 to 19 As shown, the preferred foam wash water system includes a foam wash water delivery system consisting of a wash water feed tank 37 that distributes water supplied by the wash water feed to a porous plate 38 suspended above the upper edge of the flotation tank 11 by a wash water system superstructure or tank 40. In operation, the porous plate 38 distributes the water fed from the feed tank 37 in the form of a fine droplet spray onto the surface of the froth emerging from the top of the flotation tank 11. The wash water flow rate can be adjusted to optimize wash efficiency and froth stability. The foam wash water system is particularly suitable for use in situations where high levels of gangue or other undesirable minerals are present, which tend to be mixed into the froth. By introducing clean water into the froth, the entrainment of these undesirable materials is reduced, thereby achieving better separation and improving concentrate quality.

[0097] Froth scrapers are commonly used in flotation cells to push (rather than scrape) the froth over the edge of the internal launder. Froth scrapers ensure continuous and controlled removal of froth.

[0098] The froth scraper assembly preferably used with the froth flotation cell of the present invention consists of a curved paddle 42 rotatably mounted in a scraper assembly 44 located at the top of the froth flotation cell structure. The paddle is rotatably driven by a scraper motor and gearbox 46 housed in the scraper assembly 44. The scraper paddle 42 is placed just above the froth layer and its movement is designed to skim or push the froth off the surface of the cell toward a froth collection tank.

[0099] The cells 10 of the present invention are more efficient than mechanical rougher cells and it is suggested that a cell bank of no more than 7 or 8 cells 10 of the present invention replace the large cell banks of conventional rougher equipment (typically consisting of 20 or more mechanical cells).

Claims

1. A froth flotation cell comprising: Flotation tanks; a slurry feed line for feeding a slurry containing minerals into the tank, the slurry containing minerals being separated into separate froth and tailings fractions by froth flotation; variable speed pump, including feed and discharge lines; a first low-level tailings discharge outlet line connected to a first tailings outlet at the bottom of the tank, the first low-level discharge line being configured to supply a slurry tailings feed to the pump in operation, the slurry tailings feed being drawn from the bottom of the tank through the first tailings outlet; The pump has at least two feed pipeline suction points, and the at least two feed pipeline suction points include the slurry feed pipeline and the first low-level discharge pipeline; the pump being configured to pump a combination of fresh and recycled feed into the tank through an external ejector assembly and an internal ejector assembly connected in series in a pump discharge line, the combination of fresh and recycled feed being a combination of slurry feed and slurry tailings feed; The external injector assembly is located external to the tank and includes an air injector configured to introduce air into the combination of fresh and recycled feeds; the internal ejector assembly being located within the tank and terminating in a combined fresh and recycled feed outlet through which the combination of fresh and recycled feed is discharged into the tank; as well as A second low-level tailings discharge outlet pipeline is connected to a second tailings outlet at the bottom of the tank, and the second low-level discharge pipeline is configured to supply slurry tailings feed to an external process during operation, and the slurry tailings feed is extracted from the bottom of the tank through the second tailings outlet.

2. The froth flotation cell according to claim 1, wherein: The external process is a further mineral recovery process in which additional quantities of valuable minerals are separated from the slurry by froth flotation with or without regrinding.

3. The froth flotation cell according to claim 2, wherein: The external process consists of at least one froth flotation cell similar to the froth flotation cell.

4. The froth flotation cell according to claim 3, wherein: The additional froth flotation cells are connected to each other so that the froth flotation of the pulp tailings fed from the second lower tailings discharge outlet of the upstream froth flotation cell is supplied as pulp feed to the pulp feed outlet of the froth flotation cell immediately downstream thereof.

5. The froth flotation cell according to claim 4, wherein: The tank that receives the slurry tailings feed at its slurry feed inlet is the downstream tank, and the tank that supplies the slurry tailings feed from its second low-level tailings discharge outlet is the upstream tank.

6. A froth flotation cell according to any one of the preceding claims, wherein: The internal injector assembly includes at least one internal injector terminating in an outlet that is partially obstructed by a diffuser extending through and partially obstructing the injector outlet.

7. The froth flotation cell according to claim 6, wherein: The internal injector assembly includes a plurality of internal injectors mounted on and connected to a feed pipe extending radially from a central feed pipe connected to the pump discharge line.

8. The froth flotation cell according to any one of claims 6 or 7, wherein: The injector comprises ceramic injector elements connected in series.

9. A froth flotation cell as claimed in any preceding claim including an internal launder assembly.

10. A froth flotation cell according to any one of the preceding claims, comprising a froth scraper assembly.

11. A froth flotation cell as claimed in any preceding claim including a froth wash water assembly.

12. A froth flotation cell according to any one of the preceding claims, wherein: The external process consists of at least one sweep tank.

13. The froth flotation cell according to any one of claims 1 to 11, wherein: The external process is a waste disposal process.

14. A froth flotation cell bank comprising at least two froth flotation cells according to any one of the preceding claims, wherein: The froth flotation cells are installed in a slurry fluid flow circuit, the slurry fluid flow circuit comprising a first froth flotation cell and at least one other froth flotation cell installed downstream of the first froth flotation cell in the slurry fluid flow circuit, so that the second low-level tailings discharge outlet of each upstream cell is connected to feed the slurry tailings from its second low-level tailings discharge outlet to the slurry feed inlet of its immediately downstream cell.

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