Method of foam aeration and flotation of pulp of finely disseminated minerals and device for its implementation

Abstract

FIELD: enrichment of minerals.SUBSTANCE: methods of foam aeration and flotation for the separation of minerals, in particular copper, zinc, lead and other finely disseminated sulfide and oxygen-mineral ores. The method of foam aeration and flotation of finely disseminated minerals involves feeding conditioned pulp into a flotation chamber, creating air bubbles, bringing them into contact with mineral particles, and removing the foam product in the form of flotation concentrate. In the working volume of the flotation chamber, a screw and an impeller are used together, installed with the possibility of creating a low-turbulent flow of pulp and adjustable mixing. Air is supplied through an annular multi-layer porous plate located in the aeration zone and having layers with different pore sizes, ensuring the formation of microbubbles. The operating parameters of the screw, impeller and porous plate are selected so that the average volumetric size of the formed air bubbles is 30-50 mcm. The method is implemented using a device for froth aeration and flotation of finely disseminated minerals, comprising a flotation chamber with pulp feed and discharge pipes, a screw and an impeller installed in the flotation chamber, an air supply means and an annular multilayer porous plate located in the interaction zone of the screw and the impeller.EFFECT: increase of efficiency of flotation of finely disseminated minerals.13 cl, 3 dwg, 1 ex

Description

[0001] The invention relates to the enrichment of minerals by flotation methods, in particular to methods and devices for separating minerals, and can be used for finely dispersed minerals for the purpose of extracting useful components.

[0002] Flotation typically utilizes the differences in hydrophobicity between the components. The components are introduced into a flotation cell, where air is bubbled, creating bubbles. Hydrophobic particles preferentially attach to the bubbles, lifting them to the top of the cell. The floated particles (the concentrate) are separated, dewatered, and stored. Less hydrophobic particles (the tailings) tend to migrate to the bottom of the cell, where they can be removed. Two common forms of flotation separation processes are direct flotation and reverse flotation. In direct flotation, the concentrate is the concentrate product, and the tailings are the waste rock. In reverse flotation, the waste rock component is floated into the concentrate, while the waste rock remains in the pulp.The objective of flotation is to separate and recover as much of the valuable constituent(s) of the fine material as possible in the highest possible concentration, which then becomes available for additional downstream processing steps.

[0003] Traditional methods of aeration are known, carried out in mechanical flotation machines, where various types of mixers are used as aerating and mixing devices (Meshcheryakov N.F. Conditioning and flotation devices and machines, M., Nedra, 1990, p. 337).

[0004] Pneumatic flotation machines are known, in which pneumatic, hydropneumatic and hydraulic aerators are used, however, when using them it is impossible to achieve such a high dispersion of bubbles as in mechanical machines (Glembotsky V.A., Klassen V.I. Flotation methods of enrichment, M., Nedra, 1981, 303 p.).

[0005] A pneumatic flotation machine is also known, which uses the method of flotation separation of finely dispersed minerals (Theory and technology of ore flotation, edited by O.S. Bogdanov, M., Nedra, 1990, pp. 283-284).

[0006] The disadvantage is the impossibility of extracting finely disseminated minerals due to the fact that the bubble size is too large - 100-300 microns.

[0007] A technical solution is known under Russian Patent No. 2284222, "Method for Aerating Flotation Pulp." The aeration method involves pumping air into the pulp through perforated rubber tubes, creating three layers in the container: bromoform, liquid glass, and water, with air pumped into the pulp through these layers.

[0008] The disadvantage of this technical solution is the impossibility of flotation of finely dispersed ores in this way, since it is impossible to obtain a small bubble size.

[0009] Russian Federation patent No. 2111064 is known – “Pneumatic flotation machine”. The pneumatic flotation machine comprises a flotation chamber made in the form of an upwardly expanding cone-shaped vessel with a bell in the upper part, a slit-shaped screening surface located at the level of the upper edge of the flotation chamber with a cross-section of the slits increasing from the axis of the flotation chamber, a device for feeding coarse-grained feed to the froth layer, a device for loading fine-grained pulp, a tubular mixer installed along the axis of the flotation chamber, a branch pipe for unloading the chamber product, a froth collecting trough, a pneumohydraulic aerator, a parabolic reflector, the tubular mixer is made in the form of an ejector, the pneumohydraulic aerator is coaxially placed directly above the device for loading fine-grained pulp, the parabolic reflector is coaxially fixed under the tubular mixer with an annular gap relative to its lower end,wherein the diameter of the end part of the parabolic reflector exceeds the end diameter of the tubular mixer,

[0010] In this device, due to the placement of the pulp supply pipes in diametrically opposite directions, the pulp acquires a rotational movement.

[0011] However, this device does not provide flotation of finely disseminated minerals due to the inability to produce small air bubbles necessary for flotation of finely disseminated materials.

[0012] A "Method for the flotation separation of finely dispersed minerals and a flotation machine for implementing the same" is known, Russian Federation Patent No. 2254170. The method includes saturating a mineral suspension with gas bubbles by mixing it with a gas-water emulsion previously prepared by mechanical dispersion, mineralizing the gas bubbles and separating the mineralized bubbles in the form of a flotation concentrate, wherein the mineral suspension is mixed with a gas-water emulsion containing from 66 to 70% gas in the form of bubbles with a size of less than 50 μm, and the process of mineralization of the gas bubbles is carried out with simultaneous mixing and movement of the suspension in ascending and descending flows.

[0013] A flotation machine for separating finely dispersed minerals includes an aeration reactor having an input for the processed mineral suspension and connected to a chamber for separating mineralized bubbles, wherein the machine additionally contains a gas-water emulsion generator connected to the aeration reactor, and the aeration reactor contains an input for introducing a gas-water emulsion and is made of at least two vertically arranged pipes, one of which realizes an ascending and the other a descending flow of a mineral suspension mixed with a gas-water emulsion.

[0014] However, this device does not provide flotation of finely disseminated minerals due to inefficient distribution of air bubbles by the aeration unit.

[0015] The closest to the claimed solution is Kyrgyz patent No. 2281 “Method for aerating flotation pulp of finely disseminated non-ferrous metal ores.”

[0016] In flotation machine 1, air enters the inner cavity of the housing through air ducts in hollow shaft 2. Pulp is mixed with air in the tank of flotation machine 4 by an impeller and strikes the stator plates 3, which are necessary for air diffusion and bubble formation. Ceramic plates 5 are located at the bottom of the flotation machine, to which high-pressure hoses are connected. The plates are held in place by a ceramic plate fixing system 6. Compressed air is supplied from a compressor with an operating pressure of 8 bar to provide the plates with compressed air. Air, together with pulp, is distributed both in the center and throughout the lower part of the tank of the flotation machine, forming a mixture of minerals and air microbubbles, Fig. 4. Air microbubbles, generated due to small pores of 3-5 μm in size in the ceramic plates, rise to the surface of the machine chamber together with minerals.In addition, part of the pulp, due to its circulation, again falls into the lower part of the vat and is mixed, thereby repeating the process of forming a mineral mixture.

[0017] The formation of microbubbles in flotation machines increases the recovery of metals and minerals due to the collision and fixation of finely disseminated ores.

[0018] As a result of applying the proposed method, the yield of finely dispersed minerals of the 20-45 µm class increased by an average of 0.7%, and of the 20 µm class by an average of 1.5%. Metal recovery using microbubbles is higher compared to recovery using equipment without microbubble generation: gold by 1%, silver by 2.5%, copper by 0.8%.

[0019] It is necessary to reduce local velocity gradients and shear stresses, minimize turbulence zones, while ensuring uniform distribution of pulp and air. Reduce the pulp flow velocity at the chamber entrance and in the bubble contact zone; ensure a long contact zone between the pulp and air bubbles. The greater the distance and contact time at low turbulence, the higher the chance of fine particle capture. Avoid high-speed aeration pulses to ensure effective flotation of finely disseminated minerals.

[0020] The technical problem of the invention is to create a method and device in which the movement of pulp and air bubbles is ensured in an ascending flow, minimizing flow turbulence, while ensuring efficient flotation of finely disseminated minerals.

[0021] The technical result in the proposed patent is achieved by increasing the degree of dispersion of air bubbles during their generation through the use of an annular multilayer porous plate with a pore diameter of 1.0 to 1.5 microns. This allows for the production of small-diameter microbubbles ranging from 30 to 50 microns, thereby increasing the yield of finely disseminated slurries in the froth flotation product. Furthermore, the technical result is achieved by feeding the microbubbles in an ascending flow, in which the pulp acquires a rotational motion. This is achieved through the design of the device, namely the use of a screw with an impeller, which minimizes bubble collapse and accelerates the flotation process.

[0022] The stated problem is solved due to the fact that in the method of froth aeration and flotation of finely disseminated minerals, including the supply of conditioned pulp to the flotation chamber, the creation of air bubbles, their contact with mineral particles, the removal of the froth product in the form of a flotation concentrate, in the working volume of the flotation chamber, a screw and an impeller are used together, installed with the possibility of creating a low-turbulent flow of pulp and adjustable mixing, while air is supplied through an annular multi-layer porous plate located in the aeration zone and having layers with different pore sizes, ensuring the formation of microbubbles, and the operating parameters of the screw, impeller and ceramic plate are selected so that the average volumetric size of the formed air bubbles is 20-50 μm.The annular multilayer porous plate comprises at least two ceramic layers with decreasing pore size toward the pulp contact zone of the outlet surface, and the layer of the annular multilayer porous plate on the pulp contact zone side has a pore size of 1.0-2.0 μm. Each subsequent layer after the open layer on the pulp contact zone side has larger pores for air distribution and pressure equalization, and the overall porosity of the annular multilayer porous plate is 30-60%, with air supplied under pressure from 2.2 to 2.7 atmospheres. The screw is designed with a variable pitch along its length, ensuring a gradual reduction in the shear rate of the pulp as it moves from the pulp feed zone to the foam layer. The distance from the surface of the annular multilayer porous plate to the closest point of the impeller blades is maintained within 5-50 mm to ensure a stable zone of formation of a uniform bubble dispersion.Additionally, chemical treatment of the pulp with flotation reagents is used. The flotation process modes are selected by an automated control system (ACS).

[0023] A device for froth aeration and flotation of finely disseminated minerals comprises a flotation cell with pulp inlet and outlet ports, a screw and impeller installed within the flotation cell, an air supply, and an annular multilayer porous plate located in the interface zone of the screw and impeller. The device is designed to implement the method. Furthermore, the screw is equipped with a speed control device, variable blade pitch, and a speed control device. The impeller is equipped with guide vanes to create a predetermined velocity field. The annular multilayer porous plate is replaceable and modular, allowing for the exchange of layers with different porosity.

[0024] The method is used for flotation of copper, zinc, lead and other finely disseminated sulfide and oxygen-mineral ores in order to increase recovery and selectivity by obtaining a finely dispersed and homogeneous bubble phase with a size of 30-50 μm.

[0025] Fig. 1 schematically shows a general side view of the flotation cell.

[0026] Fig. 2 schematically shows a top view of the aeration unit.

[0027] Fig. 3 schematically shows a ring-shaped multilayer porous plate.

[0028] The device is a flotation machine 1, consisting of a flotation cell 2, provided with an inlet pipe 3 for feeding pulp, a froth collecting trough with a pipe 4, a pipe for discharging tailings 5. The flotation cell 2 also has a hollow shaft 6 for feeding compressed air, located along the central axis of the flotation cell 2, a screw 7 for moving the pulp, designed according to the principle of a pipe in a pipe, with clockwise rotation, which ensures that during rotational movement the pulp is fed to the top, ensuring maximum adhesion of air microbubbles and minimizing turbulence of the ascending flow with finely disseminated minerals of the pulp. At the bottom, the screw 7 is equipped with an impeller 8, the blades of which ensure that the pulp raised upwards is distributed evenly throughout the entire volume of the flotation chamber 2. The screw fastening unit 9 provides support and free rotation of the screw 7 and impeller 8 for moving the pulp of the flotation chamber 2.The screw 7 and the impeller 8 have additional supports 10. The annular multilayer porous plate 11, located in the aeration zone, is made porous, it has inlet air ducts 12 in the form of hoses communicating with the hollow shaft 6 for air supply. The annular multilayer porous plate 11 has radial ribs 13 for stability in the body of the flotation cell 2. The device has a drive system 14 and a compressor 15. The froth layer 16. The inlet pipe 3 for feeding the pulp is equipped with a flow equalizer 17 for the incoming pulp into the flotation cell 2, it is made in the form of, for example, a deflector or a pocket at the pulp inlet to the flotation cell 2.

[0029] The annular multilayer porous plate 11 consists of the following layers: the first layer is a perforator 18 (active layer) - a highly porous plate, preferably made of silicon carbide (SiC) or mullite (Al2O3-SiO2) with open pores of 1-3 μm and a height of 0.5-2 mm with a porosity of 30-40%. It is located on a strong support plate 19 (coarsely porous), preferably made of silicon carbide (SiC) or a corundum porous plate (Al2O3) with open pores of 50-100 μm and a height of 5-10 mm, this design rests on a perforated leveling plate 20, with holes of 2-3 mm and a height of 1.5-2 mm, for example, made of stainless steel or aluminum. The entire sandwich structure is rigidly secured to a frame 21, for example, made of stainless steel. A system of air ducts 12 is installed beneath the annular multilayer porous slab 11. The annular multilayer porous slab 11 is designed as a disk with a central hole.The annular multilayer porous plate is replaceable and modular, allowing for the interchangeability of layers with different porosity. The perforator 18, as well as the support plate 19, can be assembled from sections (not shown in the figure).

[0030] The outer diameter of the annular multilayer porous plate 11 is smaller than the inner diameter of the flotation cell 2, and the inner diameter is designed to ensure free rotation of the impeller 8.

[0031] For finely disseminated minerals, it is especially important to obtain small bubbles and ensure the aerator system operates in a manner that prevents bubble agglomeration. If this process is not prevented, the bubbles may collide with each other and coalesce into larger bubbles, which reduces flotation efficiency and is unacceptable for the flotation of finely disseminated minerals.

[0032] The device allows to minimize pulp turbulence in flotation cell 2 while maintaining effective particle-bubble contact.

[0033] Example of the method of froth aeration and flotation of finely disseminated minerals

[0034] The reagents selected included collectors to increase particle hydrophobicity; depressants to suppress gangue; foaming agents to stabilize fine bubbles; and activators to improve flotation activity. The mixing stage for finely disseminated minerals lasted for 3-10 minutes to ensure uniform adsorption of the reagents.

[0035] Then the pulp was fed into the flotation chamber 2 through the inlet pipe 3 and the device for equalizing the flow of incoming pulp 17 in the form of a deflector or pocket at the entrance of the pulp into the flotation chamber 2.

[0036] Flotation cell 2 was initially filled with water to 80-90% to stabilize the pulp level, prevent dry starts of the air supply system, and create the correct hydrodynamic regime, as well as ensure proper air supply. Drive system 14 rotated screw 7 to move the pulp and impeller 8. After flotation cell 2 was filled with water, compressor 15 was turned on and air was supplied through hollow shaft 7 at pressure, starting at 0.5 atmospheres, into the aeration system via air ducts 12. Pulp was then added. The pulp gradually displaced the water, and flotation cell 2 entered operating mode.

[0037] At the same time, the auger 7 for moving the pulp and the impeller 8 with blades, rotating clockwise, working at low speeds, moved the pulp upward, distributing it throughout the entire volume of the flotation chamber 2. Air was supplied at a pressure of 2.2 to 2.7 atmospheres into the aeration system, namely from the hollow shaft 6 through the air ducts 12 in the form of hoses into the annular multilayer porous plate 11 with open pores of 1.0-2.0 μm in diameter with the formation of bubbles of 30-50 μm.

[0038] The working pressure depends on the size of the holes, the type and thickness of the annular multilayer porous plate 11, the power, the hydrostatic head - the height of the pulp above the annular multilayer porous plate, the solid component of the pulp in%.

[0039] The characteristics were selected experimentally. The uniformity of foaming was then verified. The optimal pulp hardness was up to 30% solids, which ensured slow settling and better contact between the mineral particles and the air bubbles.

[0040] The longer the distance and contact time of mineral-air bubbles under low turbulence, the higher the chance of capturing small particles.

[0041] Next, the bubbles came into contact with the particles. Finely disseminated minerals require prolonged stirring.

[0042] Then the bubbles containing the particles rose to the top of the flotation chamber, forming foam.

[0043] Foam overflowed the threshold or was removed by mechanical scrapers (not shown in the figure).

[0044] Foam concentrate with increased content of useful minerals and tailings were obtained, which were discharged through tailings discharge pipe 5.

[0045] The operating settings and modes were controlled by the automated control system. It controlled the air supply, smooth start and stop of the rotating impeller 8 and screw 7. The automated control system also optimized the solids content of the pulp to 30%.

[0046] Using sensors, the control system monitored the flotation process, creating gentle upward pulp flows that facilitated the rise of particles into the froth, and controlled the flotation concentrate yield. The control system also ensured the presence of a gentle, stable, but not particularly thick froth layer, and gentle froth removal, minimizing the loss of particles from the froth into the pulp. There were virtually no inertial forces within the froth, causing separation.

[0047] The automated control system also monitored the pulp flow at the entrance to flotation cell 2 and in the bubble-pulp contact zone.

[0048] Turbulent fluctuations were measured using acoustic-hydrodynamic sensors.

[0049] Turbulence was also monitored, preventing it, using other indicator indicators, namely changes in recovery, an increase in the fine fraction in the tails, floating foam cavities, which are indirect signs of high turbulence.

[0050] The auger and impeller ran at low speed, multi-point aeration reduced turbulence.

[0051] The presented task, namely the creation of a method and device in which the movement of pulp and air bubbles is ensured in an ascending flow, minimizing flow turbulence, while ensuring efficient flotation of finely disseminated minerals, has been accomplished, as confirmed by the description and example.

[0052] For finely disseminated minerals, turbulence must be minimal. This is achieved by the proposed design, which uses a screw 7 to move the pulp, along with an impeller 8.

[0053] It was necessary to obtain small air bubbles with a diameter of 30-50 microns.

[0054] This is achieved in the claimed invention by using an annular, multilayer, porous plate 11 in the form of a disk with open pores of 1.0-2.0 μm as diffusers. Air was forced into the annular, multilayer, porous plate 11 at a pressure of 2.2 to 2.7 atmospheres and a pH of 8-10, which reduced the effective bubble diameter to 30-50 μm, all other conditions being equal. The process was carried out with the correct selection of collector agents, which increased the yield of finely dispersed slurries in the froth flotation product. Furthermore, the microbubbles were fed in an upward flow, minimizing their collapse and accelerating the flotation process.

[0055] Industrial applicability is also confirmed by the example and description of the invention.

[0056] The claimed method and device can be used for flotation of copper, zinc, lead and other finely disseminated sulfide and oxygen-mineral ores in order to increase recovery and selectivity by obtaining a finely dispersed and homogeneous bubble phase with a size of 30-50 microns.

[0057] List of items

[0058] 1. flotation machine

[0059] 2. Flotation chamber

[0060] 3. Inlet pipe

[0061] 4. Foam collecting chute with branch pipe

[0062] 5. Tail discharge pipe

[0063] 6. hollow shaft

[0064] 7. Auger

[0065] 8. Impeller

[0066] 9. Auger mounting unit

[0067] 10. screw and impeller support

[0068] 11. Ring-shaped multilayer porous plate

[0069] 12. Air ducts

[0070] 13. Radial ribs

[0071] 14. Drive system

[0072] 15. compressor

[0073] 16. Foam layer

[0074] 17. Incoming pulp flow equalizer

[0075] 18. Punch

[0076] 19. Support plate

[0077] 20. Perforated leveling plate

[0078] 21. frame.

Claims

1. A method for froth aeration and flotation of finely disseminated minerals, including feeding conditioned pulp into a flotation chamber with a hollow shaft for feeding compressed air, an impeller, an air supply means and a porous plate located along the central axis of the flotation chamber, creating air microbubbles, their contact with mineral particles, removing the froth product in the form of a flotation concentrate, characterized in that the flotation chamber is equipped with a screw for mixing the pulp, mounted with the possibility of rotation, while the impeller is located in the lower part of the screw to create a low-turbulent flow of pulp and controlled mixing, and the porous plate is located in the interaction zone of the screw and the impeller, wherein the porous plate is made annular multilayer, having layers with different pore sizes, and the operating parameters of the screw, impeller and annular multilayer porous plate are selected so that the average volumetric size of the formed air bubbles is 30-50 microns.

2. The method according to claim 1, characterized in that the annular multilayer porous plate includes at least two layers of ceramic with a pore size decreasing towards the contact zone with the pulp of the outlet surface.

3. The method according to paragraph 1 or 2, characterized in that the layer of the annular multilayer porous plate on the side of the contact zone with the pulp is made with a pore size of 1.0-2.0 μm.

4. The method according to any of paragraphs 1-3, characterized in that each subsequent layer after the open layer on the side of the contact zone with the pulp has larger pores for distributing air of the multilayer porous plate and makes up 30-40%.

5. The method according to any of paragraphs 1-4, characterized in that air is supplied to the annular multilayer porous plate under pressure from 2.2 to 2.7 atmospheres and the flotation process is carried out at a pulp density of up to 30% solids.

6. The method according to any one of paragraphs 1-5, characterized in that the screw is made with a variable pitch of the turns along the length, ensuring a gradual decrease in the shear rate of the pulp when moving from the pulp feed zone to the foam layer.

7. The method according to any one of paragraphs 1-6, characterized in that the distance from the surface of the annular multilayer porous plate to the closest point of the impeller blades is maintained within the range of 5-50 mm to ensure a stable zone of formation of a homogeneous bubble dispersion.

8. The method according to any of paragraphs 1-7, characterized in that additional chemical treatment of the pulp with flotation reagents is used.

9. The method according to any of paragraphs 1-8, characterized in that the selection of flotation process modes is carried out by an automatic control system (ACS).

10. A device for froth aeration and flotation of finely disseminated minerals, comprising a flotation chamber with pulp feed and discharge pipes located along the central axis of the flotation chamber with a hollow shaft for supplying compressed air, an impeller, an air supply means and a porous plate, characterized in that the flotation chamber is equipped with a screw for mixing the pulp, mounted with the possibility of rotation, wherein the impeller is located in the lower part of the screw, and the porous plate is in the interaction zone of the screw and the impeller, wherein the porous plate is made annular multilayer, having layers with different pore sizes.

11. The device according to item 10, characterized in that the auger is equipped with a speed control device, variable blade pitch, a rotation device, and the impeller is equipped with guide blades for creating a given speed field.

12. The device according to paragraph 10 or 11, characterized in that the annular multilayer porous plate is made replaceable and modular with the possibility of replacing layers with different porosity.

13. The device according to paragraph 10 or 12, characterized in that the annular multilayer porous plate is made of the following layers: the first layer is a perforator - a highly porous plate, which is located on the second layer - a strong support plate, and it, in turn, rests on the third layer - a perforated leveling plate.

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