WO2024180640A1 - Flotation ore-dressing system and flotation ore-dressing method using same - Google Patents

Abstract

This flotation ore-dressing system separates and recovers useful minerals included in ore of an ore slurry by carrying out a flotation ore-dressing treatment on said ore slurry, the flotation ore-dressing system comprising: a slurification tank 1 that receives ore containing useful minerals and preparation water for slurifying said ore, to prepare an ore slurry; a flotation ore-dressing facility 5 composed of one or a plurality of continuous flotation ore-dressing tanks 10, to carry out a flotation ore-dressing treatment on said ore slurry extracted from the slurry tank 1; and a microbubble-containing water generation device 6 that generates microbubble-containing water including microbubbles having a diameter of 100 μm or less, said microbubble-containing water being supplied to at least one of the flotation ore-dressing tanks 10.

Description

Flotation system and flotation method using same

The present invention relates to a flotation system and a flotation method using the same.

The minerals contained in the ores extracted from mines can be broadly divided into useful minerals (minerals that contain a large amount of the target metal) and gangue minerals (minerals that contain almost no target metal), and in metal smelting, the first step in the process is to separate and recover the target metal from the ore, called beneficiation. There are various beneficiation methods that utilize the differences in the physical properties of the mineral species in the ore, such as flotation, gravity separation, and magnetic separation, but in the beneficiation of sulfide ores, which are mainly made up of chalcopyrite, flotation is a physical separation method that utilizes the difference between hydrophobicity and hydrophilicity, which is expressed as the difference in wettability of the mineral surface, and is widely used.

For example, Patent Document 1 discloses a technology in which ore containing copper minerals and arsenic minerals is first subjected to pretreatment such as crushing and grinding, and then a liquid such as water is added to prepare an ore slurry containing ore of a specified particle size, and a first flotation process is carried out under conditions in which no collector or only a small amount of collector is added to this ore slurry to remove the arsenic minerals as float, and then a second flotation process is carried out under conditions in which a collector is added to the resulting sinking ore (tailings) slurry containing copper minerals to recover the copper minerals as float.

JP 2022-35750 A

The flotation method of Patent Document 1 above involves processing the sinking ore recovered in the first flotation step in the second flotation step, but in copper smelting, as shown in Figure 1, a process is generally adopted in which the ore slurry refined in the crushing and grinding step is processed in a rough sorting step as the first flotation step, and the resulting float side is processed in a refinery step as the second flotation step, and the float side is treated as a concentrate containing useful minerals in a downstream smelter. In this case, both the tailings separated as the sinking ore side in the first and second flotation steps are transported to a tailings dam.

In the separation of floating ore and sinking ore using the above-mentioned flotation method, air bubbles are introduced into the ore slurry in the flotation tank. As a result, mineral particles with hydrophobic surfaces adhere to the air bubbles that rise through the ore slurry, and then rise through the ore slurry, forming what is known as "froth" that floats on the surface of the ore slurry while still attached to the air bubbles. This froth floating on the liquid surface is collected by overflowing the top end of the flotation tank or by being scraped off with a scraper such as a spatula.

On the other hand, mineral particles with hydrophilic surfaces do not adhere to air bubbles and so sink as they are in the ore slurry. In the case of copper smelting, the slurry containing this sink is extracted as tailings from the bottom of the flotation tank and introduced into a solid-liquid separation means such as a thickener, where it is concentrated by solid-liquid separation and then transported as final tailings to, for example, a tailings dam. When useful minerals are recovered as floats, as in the flotation process described above, the surfaces of the useful minerals may be adjusted to be hydrophobic in order to increase the recovery rate.

The efficiency of separation of the floating ore and the sinking ore by the above-mentioned flotation method is affected by the size of the air bubbles introduced into the ore slurry, so it is preferable to introduce air bubbles with an appropriate diameter. In the case of a commercially available flotation machine, the general diameter of the air bubbles that can be generated in the flotation tank is at least several mm, and the mineral particles that are likely to adhere to air bubbles of this diameter and are likely to be separated as floating ore are particles with a diameter of about one-tenth to one-fifth of the general air bubble diameter described above, specifically, particles with a diameter of about several tens of μm to 200 μm. However, in recent years, the amount of high-quality ore mined has tended to decrease, and the amount of ore that can be efficiently separated into useful minerals by flotation processing by crushing to a diameter of about 100 μm to about 1 mm as in the past has decreased. For this reason, an increasing number of ores require crushing to a diameter of finer than about 100 μm, for example, to a diameter of about 20 μm or less.

As described above, in order to efficiently process finer ores by flotation than ever before, it has been considered to introduce fine bubbles with a volume equivalent diameter of less than 100 μm into the ore slurry. For example, a technique has been proposed in which high-pressure air is passed through a porous body immersed in the ore slurry to release air in the form of fine bubbles into the ore slurry, and the porous body is rotated to cause the released fine bubbles to detach from the surface of the porous body so that the released multiple fine bubbles do not gather near the surface of the porous body and become coarse. This allows the fine bubbles to be effectively introduced into the ore slurry, making it possible to attach the ore consisting of fine particles with a particle size of about 20 μm or less to the fine bubbles detached from the porous body and efficiently recover it as float ore.

However, when a porous body is immersed in an ore slurry as described above, fine ore particles in the ore slurry tend to gradually penetrate the porous body and clog it, which can cause a problem that it becomes difficult to steadily introduce fine bubbles into the ore slurry. When this problem occurs, it can be dealt with by replacing the clogged porous body with a new one, but in actual operation, frequently replacing the porous body is too time-consuming and costly, and is therefore not practical. The present invention was made in consideration of the problems inherent in such conventional flotation methods, and aims to provide a flotation system that can steadily introduce fine bubbles into the ore slurry to be flotation processed over a long period of time.

In order to achieve the above object, the flotation system of the present invention is a flotation system that separates and recovers useful minerals contained in the ore in an ore slurry by flotation processing the ore slurry, and is characterized in that it has a flotation equipment consisting of a slurrying tank that receives ore containing the useful minerals and preparation water for slurrying the ore to prepare an ore slurry, one or more continuous flotation tanks that perform flotation processing on the ore slurry extracted from the slurrying tank, and a fine bubble-containing water generating device that generates fine bubble-containing water containing fine bubbles with a bubble diameter of 100 μm or less, and the fine bubble-containing water is supplied to at least one of the one or more flotation tanks.

The flotation method according to the present invention includes a preparation step in which ore containing useful minerals is mixed with preparation water to prepare an ore slurry, and a flotation step in which the ore slurry prepared in the preparation step is introduced into one or a series of multiple flotation tanks to perform flotation, and is characterized in that fine bubble-containing water containing fine bubbles with a bubble diameter of 100 μm or less is supplied to at least one of the one or a series of multiple flotation tanks.

The present invention has great industrial value because it is possible to stably introduce fine bubbles into the ore slurry to be subjected to flotation treatment for a long period of time.

FIG. 1 is a block flow diagram of a method for treating ore by flotation to which the flotation system of the present invention is suitably applied. FIG. 1 is a process flow diagram of a flotation system according to a first embodiment of the present invention. FIG. 2 is a partially cutaway perspective view of a Denver-type flotation machine preferably used in the flotation system of the present invention. FIG. 4 is a perspective view showing a tip portion of an agitator provided in the Denver type flotation machine shown in FIG. 3 . FIG. 2 is a process flow diagram of a flotation system according to a second embodiment of the present invention. FIG. 11 is a process flow diagram of a flotation system according to a third embodiment of the present invention.

1. Method for treating ore by flotation First, a method for treating ore by flotation to which the flotation system of the present invention is suitably applied will be described with reference to Fig. 1, and then an embodiment of the flotation system of the present invention will be described in detail. The method for treating ore by flotation shown in Fig. 1 includes a crushing and grinding process in which the mined ore raw material is crushed and ground, a rough sorting process in which water is added to the ore finely crushed by the crushing and grinding process to prepare an ore slurry, which is introduced into a flotation facility to separate the ore into hydrophobic float and hydrophilic sink, a regrinding process in which the float separated in the rough sorting process is ground again to make it finer, and a refinement process in which the slurry containing the ore finer crushed in the regrinding process is introduced into a flotation facility to separate the ore into hydrophobic float and hydrophilic sink. Each of these processes will be described in detail below.

[Crushing and grinding process]
The crushing and grinding process is a process in which the ore to be subjected to flotation treatment, which has been extracted from a mine, is crushed and ground finely to such an extent that useful minerals and gangue minerals become separate particles. In the flotation process, which is the next process after the crushing and grinding process, separation is performed by a physical method that does not cause chemical changes inside the particles, so in this crushing and grinding process, it is ideal to crush and grind the ore so that each particle constituting the powder ore consists of only either useful minerals or gangue minerals, as is called "liberation". For this reason, the extent to which the ore is crushed and ground is determined appropriately depending on the size of the minerals contained in the ore.

In crushing ores, multiple types of crushing equipment such as cone crushers, SAG mills, HPGRs, and ball mills are generally used to crush the ores in stages, but in this case, the economically feasible lower limit for the particle size of the crushed powder is about 100 μm. In contrast, in recent years, the size of minerals contained in ores has been reduced to about 25 μm or less, and it is becoming difficult to separate the minerals by crushing them to a particle size of about 100 μm using the above-mentioned general crushing equipment. Therefore, as necessary, ultra-fine crushers such as bead mills are used in the final stage of crushing, which makes it possible to refine the particle size of the crushed powder to about 25 μm or less.

In the grinding process, which is carried out immediately before the "coarse selection process" and "refining process," the ore that has been finely divided by the crushing process is further refined, and deposits and oxide films on the particle surface are removed to make the ore clean. This reduces the variation in the surface treatment effect of additives (floatation agents) such as collectors, inhibitors, and coagulants that are added during the flotation process. This grinding is carried out by processing the ore slurry containing powdery ore in a circulation system equipped with, for example, a cyclone and a ball mill.

[Rough selection process, fine selection process]
In both the rough sorting (rough ore sorting) process and the refinement (refined ore sorting) process, the powder particles that have been refined in the previous process are subjected to a flotation treatment to separate the useful mineral particles that are mixed in the powder particles. Specifically, the powder particles are brought into contact with air bubbles in water, and the hydrophobic particles are attached to the air bubbles as float. The particles float in the water with the bubbles, while the hydrophilic particles that do not adhere to the bubbles sink in the water as ore. Generally, metals are hydrophobic, while the surfaces of rocks such as silica are hydrophilic. Therefore, the above principle can be used to separate useful minerals from gangue minerals.

In this flotation process, the above powder and granules are first mixed with a liquid such as water or seawater to prepare a suspended ore slurry. In preparing this ore slurry, the solids concentration of the ore slurry is determined so as not to place an excessive load on the equipment in the subsequent process, and so as to maximize the amount of concentrate recovered as float relative to the amount of ore slurry introduced into the flotation equipment under this constraint; this solids concentration is generally 25 to 45 mass%. A flotation agent is generally added to the ore slurry prepared in this way so that the difference in wettability between the particle surfaces of the useful minerals and the particle surfaces of the gangue minerals becomes more pronounced. This allows the surface properties of the particles contained in the ore slurry to be flotation-processed and the properties of the liquid phase to be modified to the desired properties suitable for flotation. This modification operation of the ore slurry is sometimes called "conditioning".

The flotation agents added for the above-mentioned "conditioning" include agents that adsorb to the surface of mineral particles to change the surface properties, and agents that change the properties of the liquid phase of the ore slurry. Examples of the former agents that change the surface properties of mineral particles include collectors such as sodium, xanthate, and ethyl xanthate that impart hydrophobicity to the surface of mineral particles, and inhibitors such as gelatin, lactic acid, and starch that do not impart hydrophobicity. On the other hand, examples of the latter agents that change the properties of the liquid phase of the ore slurry include pH adjusters such as hydrochloric acid, hydrogen peroxide, caustic soda, and lime that adjust the pH, and foaming agents such as MIBC, pine oil, and cresylic acid that dissolve in the ore slurry to generate stable bubbles. The flotation agents for the above-mentioned "conditioning" may be added to the ore slurry before it is introduced into the flotation equipment in a storage tank installed in the upstream of the flotation equipment, or may be added to the ore slurry inside the flotation equipment. Alternatively, it may be added in two separate portions to both the ore slurry in the storage tank and the ore slurry in the flotation equipment.

The flotation equipment is composed of one or several flotation tanks connected in series, and in each flotation tank, air bubbles are blown into the charged ore slurry while stirring it with an agitator, causing the air bubbles to come into contact with the particles in the ore slurry. As a result, as mentioned above, particles with hydrophobic surfaces adhere to the air bubbles, so they rise with the air bubbles and float in the form of froth on the liquid surface. On the other hand, particles with hydrophilic surfaces sink without adhering to the air bubbles. The stirring conditions in each flotation tank are appropriately adjusted to perform an optimal flotation process, taking into account the tank capacity, the amount of ore slurry charged per unit time, the rising speed of air bubbles, which generally have a bubble diameter of about several mm, the amount of air bubbles introduced, etc.

2. Flotation system The flotation system of the first embodiment of the present invention supplies water containing fine bubbles having a diameter of 100 μm or less to at least one of one or a plurality of consecutive flotation tanks constituting the flotation facility. The flotation system of the first embodiment of the present invention can be applied to both the rough sorting (rough sorting) process and the cleaning (cleaning) process, but the following description will be specifically given of the case where the system is applied to the rough sorting (rough sorting) process.

As shown in FIG. 2, the flotation system of the first embodiment of the present invention comprises a slurry tank 1 that receives ore that has been crushed by a crushing device such as a ball mill (not shown) and preparation water such as industrial water for slurrying the ore, prepares an ore slurry having a predetermined solid content concentration, and temporarily stores the ore slurry, a slurry pump 2 that pressurizes the ore slurry extracted from the slurry tank 1, a classification device 3 such as a cyclone that wet classifies the ore slurry pressurized by the slurry pump 2, and a coarse-grained slurry that mainly contains coarse ores exceeding a predetermined size classified by the classification device 3. The system includes a grinding mill 4 that introduces ore into the system to refine it and grind it, a flotation system 5 consisting of one or more consecutive flotation tanks into which fine-grained slurry containing fine ores classified by the classifier 3 is introduced to perform flotation processing, a microbubble-containing water generator 6 that generates water containing microbubbles with a bubble diameter of 100 μm or less to be supplied to at least one of the one or more flotation tanks, and a solid-liquid separation means 7 such as a thickener that separates the ore slurry extracted from the flotation system 5 into final tailings and clear water by concentrating it through gravitational settling.

Among the devices constituting the above-mentioned flotation system, the slurry tank 1, slurry pump 2, classifier 3, and grinding mill 4 are connected in this order via piping to form a circulation system. With this configuration, the fine-grained slurry containing only fine ores, for example those with a particle size of 25 μm or less, classified by the classifier 3 among the ores contained in the ore slurry extracted from the slurry tank 1, can be supplied to the flotation equipment 5, making it possible to carry out the flotation treatment efficiently. On the other hand, the coarse-grained slurry containing coarse ores, for example those with a particle size of more than 25 μm, classified by the classifier 3 can be introduced into the grinding mill 4 for fine particle size and then returned to the slurry tank 1, so that all the ores charged to the slurry tank 1 can be treated by the flotation equipment 5.

Each of the single or multiple consecutive flotation tanks constituting the flotation equipment 5 is preferably equipped with a gas suction type agitator 20 in the approximate center of the tank 10, which is a cylindrical container, as shown in FIG. 3. A flotation tank equipped with such a gas suction type agitator 20 is also called a Denver-type flotation machine, and as shown in FIG. 4, the rotating shaft 21 of the agitator 20 is formed of a hollow round bar with an open tip, and an impeller 22 with multiple stirring blades that radiate out is attached to the tip side.

A cage-shaped stator 23 is fixed to the bottom surface of the tank 10 so as to surround the impeller 22 all around. The stator 23 is composed of an annular partition plate 23a that surrounds the impeller 22 all around at a position that corresponds to approximately the center of the height of the impeller 22, a number of plate-like bodies 23b that are erected on the upper surface of the partition plate 23a at equal intervals all around, and annular reinforcing members 23c attached to the upper ends of the plate-like bodies 23b. The stator 23 is supported by a number of legs 25 that erect from a disk-shaped base 24 provided on the bottom surface of the tank 10.

With this configuration, when the agitator 20 consisting of the rotating shaft 21 and the impeller 22 at its tip is rotated by the motor 26 installed at the top of the tank 10, the ore slurry inside the stator 23 is discharged radially by the centrifugal force generated by the rotating multiple agitating blades, forming a flow of ore slurry that flows in from below the stator 23 as shown by the white arrows and is discharged radially from the impeller 22 as shown by the black arrows. On the other hand, the tip of the hollow rotating shaft 21 opens inside the impeller 22, which becomes negative pressure due to the rotation of the impeller 22, so that the air sucked in from the upper end of the rotating shaft 21 flows downward inside the shaft and is discharged as air bubbles from the opening at the tip of the rotating shaft 21. For this reason, the flow of ore slurry indicated by the black arrows that is discharged radially from the impeller 22 entrains air bubbles discharged from the opening at the tip of the rotating shaft 21.

The ore slurry containing air bubbles discharged radially from the impeller 22 as described above passes through the gaps between adjacent plates 23b provided on the upper surface of the partition plate 23a, and collides with the surfaces of the plates 23b in the process. As a result, the air bubbles contained in the ore slurry are generally finely divided to a bubble diameter of about 100 μm to several mm. However, as mentioned above, in recent years, there has been a demand for flotation treatment of ore slurries containing ores that have been finely crushed to a particle diameter of 25 μm or less, preferably 20 μm or less, and therefore there is a demand for technology that can introduce fine air bubbles with a bubble diameter of 100 μm or less into the flotation tank 10.

The flotation system of the first embodiment of the present invention has a microbubble-containing water generating device 6 that generates microbubble-containing water containing microbubbles with a bubble diameter of 100 μm or less, and the microbubble-containing water generated by this microbubble-containing water generating device 6 is used as at least a part of the preparation water for preparing the above-mentioned ore slurry. This allows the microbubble-containing water to be indirectly introduced into at least one of the above-mentioned one or multiple consecutive flotation tanks 10, eliminating the problem of clogging that occurs when a rotating porous body is immersed in an ore slurry to generate conventional microbubbles.

In other words, in the conventional method of immersing a rotating porous body in an ore slurry, the porous body would become clogged within a few hours at most, causing a problem of blocking the gas flow path. However, by adopting the flotation system of the first embodiment of the present invention, it is possible to stably introduce fine air bubbles into the ore slurry in the flotation tank over a long period of time, such as several months or more. Therefore, even when the ore slurry to be flotated contains particles with a particle size of 25 μm or less, it is possible to perform the flotation process with an extremely high operating rate.

In addition, bubbles are gas surrounded by a gas-liquid interface in a medium such as an ore slurry, and among them, bubbles with a volume-equivalent diameter of less than 100 μm are called fine bubbles. In TC281 (fine bubble technology) of the International Organization for Standardization (ISO), fine bubbles are defined as microbubbles (MB) with a volume-equivalent diameter of 1 μm or more and less than 100 μm, and ultrafine bubbles (UFB) with a volume-equivalent diameter of less than 1 μm. In the present invention, fine bubbles with a bubble diameter of 100 μm or less may include only the former type of microbubbles, or only the latter type of ultrafine bubbles. Alternatively, the fine bubbles may be composed of microbubbles and ultrafine bubbles. In addition, the volume-equivalent diameter is the diameter calculated from the volume of the bubbles assuming that they are spherical in shape.

The fine bubble-containing water generating device 6 is not particularly limited as long as it can stably generate fine bubbles having a diameter of 100 μm or less in water. For example, it may be capable of stably generating microbubbles in water, or may be capable of stably generating ultrafine bubbles in water. Alternatively, the fine bubble-containing water generating device 6 may be composed of a microbubble-containing water generating device capable of stably generating microbubbles in water and an ultrafine bubble-containing water generating device capable of stably generating ultrafine bubbles in water, so that both microbubbles and ultrafine bubbles are contained in the water.

The principles of generating microbubbles industrially can be broadly divided into four categories: (1) those using turbulent flow or shear flow, (2) those using cavitation, collapse, crushing, or shock waves, (3) those using the pressurized dissolution method, and (4) those using a fine hole method. The microbubble-containing water generating device 6 can use one or a combination of these principles.

For example, a generator of water containing fine bubbles that uses the principle of shear flow is a swirling flow type generator. This generator generates a swirling flow in a cylindrical container by introducing a high-speed water flow from the tangential direction into the container, and the gas sucked in by the negative pressure generated at the central axis of the container is subjected to shear by the swirling flow, thereby micronizing the bubbles. An ejector type generator is an apparatus that generates water containing fine bubbles that uses the principles of turbulence, shear flow, collapse, and cavitation by ejecting a pressurized fluid from a liquid ejection nozzle in a negative pressure chamber, drawing gas into the negative pressure chamber and generating cavitation to cause the gas to flow into a mixing chamber in a gas-liquid mixed state, where the shear and turbulent effects create micronized bubbles.

In addition, a device for generating water containing microbubbles using the pressurized dissolution method circulates water in a container through a circulation piping system equipped with a pump installed outside the container, sucking in gas from the suction side piping of the pump, and pressurizing the water containing the sucked gas in a dissolution tank installed on the discharge side of the pump to dissolve the gas in the water in a supersaturated state, and then discharging the water with the dissolved gas from the outlet nozzle of the circulation piping system that opens in the water in the container, thereby generating microbubbles. A device for generating water containing microbubbles using the fine pore method generates microbubbles by passing gas through countless pores in ceramic or metal porous bodies, filters, etc., and some devices also generate even finer bubbles by cutting the bubbles by forming a liquid flow that becomes a so-called cross flow at the outlet side of the pores.

In any of the above microbubble-containing water generating devices, the flotation system of the first embodiment of the present invention uses clear water containing almost no solids, such as industrial water, well water, seawater, or clear water described below, as the raw water used for the microbubble-containing water. This eliminates the need to consider the problem of clogging caused by clogging that occurs when a conventional rotating porous body is immersed in an ore slurry to directly generate microbubbles, allowing for a high degree of freedom in the selection of the model of the microbubble-containing water generating device 6, and allows the optimum device to be selected from a wide range of manufacturers and models.

Furthermore, there are no particular limitations on the method for measuring the bubble size distribution of the microbubbles contained in the water, and it may be appropriately selected according to the diameter of the microbubbles. For example, there are particle trajectory analysis methods in which the movement of bubbles is visualized by the scattered light when the bubbles are irradiated with laser light, and the bubble size is measured by the Stokes-Einstein equation from the speed of the Brownian motion; dynamic light scattering methods (fiber optics method) in which the bubble size is determined by calculating the autocorrelation function from the information on the intensity fluctuation of the scattered light when the bubbles are irradiated with laser light; dynamic light scattering methods (cross correlation method) in which the bubble size is measured by the cross correlation method, which removes signals due to multiple scattering from the signals obtained by two detectors when two laser beams are irradiated on the same measurement area; Examples of such methods include the laser diffraction and scattering method, which determines the bubble size distribution from the intensity distribution pattern of the diffracted and scattered light emitted when laser light is irradiated; the resonance mass measurement method, which determines the bubble size from the change in the resonance frequency of the cantilever caused by bubbles passing through the flow path inside the cantilever; the electrical detection zone method, which measures the volume and number of bubbles by measuring the change in electrical resistance between electrodes inside and outside the passage according to the Coulter principle caused by bubbles passing through a narrow passage; and the image analysis method, which uses a highly sensitive CCD camera to capture the projected image of bubbles passing through a flow cell and analyze the data to measure the bubble size.

As described above, in the flotation system of the first embodiment of the present invention, the microbubble-containing water generated in the microbubble-containing water generator 6 is used as at least a portion of the preparation water supplied to the slurry tank 1. Therefore, when the above-mentioned "conditioning" is performed in the slurry tank 1 or, if necessary, in a stirring tank provided downstream, the effect of promoting mixing of the flotation agent added for "conditioning" with the microbubbles is also obtained. In this way, when "conditioning" is performed before the flotation process, the various flotation agents and microbubbles can be dispersed homogeneously in the ore slurry, so that the flotation process in the downstream flotation equipment 5 can be performed even more efficiently.

In the flotation system of the first embodiment of the present invention, as shown by the dotted line in FIG. 2, the clear water recovered in the solid-liquid separation equipment 7, which is typified by a thickener, may be reused as at least a portion of the raw water for the microbubble-containing water generating device 6. This reduces the consumption of industrial water, well water, seawater, etc. introduced from outside the system, so that if the site where the flotation system is installed has few water resources, it becomes possible to prepare the ore slurry while minimizing water consumption under the constraints of limited water resources.

Furthermore, since the microbubbles have an extremely slow floating speed and tend to remain in the liquid for a long time, it is possible to repeatedly use the microbubbles remaining in the clear water after solid-liquid separation of the ore slurry for the flotation process. This allows the microbubbles generated by the microbubble-containing water generating device 6 to be further added to the clear water containing a large amount of microbubbles, so that microbubble-containing water containing an extremely high concentration of microbubbles can be generated and introduced into the flotation equipment 5. Furthermore, when the clear water recovered by the solid-liquid separation means 7 is used as raw water to generate the microbubble-containing water, the flotation agents remaining in the clear water, such as the above-mentioned collector, inhibitor, pH adjuster, and foaming agent, can be reused, so that the consumption of these flotation agents added to the ore slurry can be reduced.

Next, a flotation system according to a second embodiment of the present invention will be described with reference to FIG. 5. In the flotation system according to the second embodiment of the present invention, the supply pipe 8 for the microbubble-containing water generated in the microbubble-containing water generating device 6 is branched just before joining the supply pipe 9 for the preparation water, and the end of the branched branch pipe 8a opens in each flotation tank 10 of the flotation equipment 5. The rest of the flotation system is almost the same as the flotation system according to the first embodiment. This makes it possible to directly introduce the microbubble-containing water not only into the ore slurry in the slurry tank 1, but also into each of the flotation tanks 10 constituting the flotation equipment 5, so that the effect obtained by introducing the microbubbles into the ore slurry can be exerted over a wider range. The flotation tanks 10 to which the microbubble-containing water is introduced are not limited to all tanks as shown in FIG. 5, and may be introduced only into the most upstream tank of a series of multiple flotation tanks.

Next, a flotation system according to a third embodiment of the present invention will be described with reference to FIG. 6. In the flotation system according to the third embodiment of the present invention, the microbubble-containing water generated in the microbubble-containing water generating device 6 is not introduced into the slurry tank 1, but is directly introduced only into the flotation equipment 5, and is otherwise substantially the same as the flotation system according to the first embodiment. In this case, as shown by the dotted line, the clear water recovered in the solid-liquid separation means 7 may be used as at least a part of the raw water for the microbubble-containing water generating device 6, or may be used as at least a part of the preparation water introduced into the slurry tank 1, or may be used for both. In addition, the flotation tank 10 into which the microbubble-containing water is introduced is not limited to only the most upstream tank among the multiple consecutive flotation tanks as shown in FIG. 6, and may be introduced into multiple tanks.

Furthermore, in the flotation system of the third embodiment of the present invention, the microbubble-containing water generating device 6 can be disposed immediately before the flotation tank 10 to which the microbubble-containing water is introduced. In this case, the liquid transport distance for introducing the microbubble-containing water generated by the microbubble-containing water generating device 6 into the flotation equipment 5 through piping can be made shorter than that of the second embodiment described above, so that the inconvenience of the microbubbles disappearing due to the long liquid transport distance can be effectively avoided. This allows microbubble-containing water containing a larger amount of microbubbles to be introduced into the flotation equipment 5. That is, microbubbles tend to disappear faster when they are present in less turbid microbubble-containing water than when they are present in a turbid ore slurry, and they tend to disappear faster in water with little turbidity, such as industrial water, well water, seawater, or clear water.

　The above describes the flotation system of the present invention using the first to third embodiments, but the present invention is not limited to the above embodiments and can include various modifications and variations within the scope of the present invention. In other words, the technical scope of the present invention extends to the scope of the claims and their equivalents. Note that the recovery rate of useful minerals by flotation is not necessarily improved by increasing the amount of fine bubbles introduced into the flotation tank. Therefore, it is preferable to determine which of the first to third embodiments to adopt for the ore to be beneficiated based on the correlation between the amount of fine bubbles contained in the ore slurry and the recovery rate of useful minerals, which is determined by performing a flotation process on a trial basis under various conditions before actual operation.

[Example 1]
875 g of ore with a Cu content of 0.49% by mass to be dressed was pulverized using a bead mill, and then sieved to obtain fine powder of 20 μm or less consisting of useful mineral particles and gangue mineral particles. This powder was subjected to flotation treatment using a flotation system having the requirements of the present invention as shown in FIG. 2. Specifically, the powder was first charged into a slurrying tank 1, and fine bubble-containing water produced in a fine bubble-containing water producing device 6 was supplied as preparation water for slurrying the powder to prepare an ore slurry. A rotary microbubble generator made of a carbon ceramic porous body manufactured by Anzai Kantetsu Co., Ltd. was used as the fine bubble-containing water producing device 6, and fine bubble-containing water was produced under the conditions of a supply air pressure of 0.4 MPaG and a supply air amount of 2.7 L/min. In addition, as the raw water for the fine bubble-containing water, clarified water (filtrate) obtained by suction filtration was used, assuming that the ore slurry discharged from the flotation equipment 5 would be separated into solid and liquid using a thickener as the solid-liquid separation means 7.

Calcium hydroxide was added to the ore slurry in the slurry tank 1 prepared by the above method to adjust the pH to 9.0. In addition, conditioning was performed by adding 15 g/t of methyl isobutyl carbinol (MIBC) as a foaming agent, 5 g/t of Flottec's F4244 (model number 4244) as a collector, and 15 g/t of diesel oil per ton of ore in the ore slurry. The solids concentration (slurry concentration) of the ore slurry at the end of this conditioning was 30 mass%.

The ore slurry prepared as described above was extracted from the slurry tank 1, pressurized by the slurry pump 2, and introduced into the flotation means 5 via a wet cyclone as the classification device 3. In the classification device 3, a circulation system was configured so that the coarse ore slurry, which mainly contains mineral particles larger than 200 μm in diameter, returns to the slurry tank 1 via the grinding mill 4 so that the fine-grained slurry, which mainly contains mineral particles larger than 200 μm in diameter, can be introduced into the flotation equipment 5. The flotation equipment 5 used was a facility consisting of four consecutive flotation tanks 10.

The above-mentioned flotation system was used to carry out flotation processing for a total of 30 minutes. A Denver-type flotation device as shown in FIG. 3 was used for each of the four flotation tanks 10, and the bubble diameter in the ore slurry was measured in each flotation tank 10 using the bubble diameter measuring device disclosed in the specification of International Publication No. 2022/097477. That is, this bubble diameter measuring device is a device consisting of a measurement chamber in which bubbles in a liquid containing solids are introduced from below and a transparent inclined surface is provided at a position where the introduced bubbles rise, a photographing device for photographing bubbles passing through the transparent inclined surface, an introduction pipe for introducing bubbles into the measurement chamber, and a bubble introduction valve for introducing and blocking bubbles into the introduction pipe. Using this bubble diameter measuring device, bubble diameter measurements were carried out twice, 30 seconds after the start of the flotation processing and 30 minutes after (at the end).

As a result, it was confirmed that in both of the above two bubble diameter measurements, there were similar amounts of fine bubbles with diameters in the range of 1 μm to 100 μm. In other words, it was found that by using a flotation system that meets the requirements of the present invention, fine bubbles can be stably introduced into the ore slurry even after a period of time has passed since the start of the flotation process.

[Example 2]
Instead of supplying the fine bubble-containing water to the slurry tank 1, the water was directly supplied to the ore slurry in the most upstream tank of the four flotation tanks 10 of the flotation equipment 5 as shown in FIG. 6, and seawater was used as preparation water for the slurry tank 1. Except for this, the flotation treatment was carried out in the same manner as in Example 1.

As a result, it was confirmed that in both of the above two bubble diameter measurements, there were a similar number of fine bubbles with diameters in the range of 1 μm to 100 μm. In addition, in both of these bubble diameter measurements, it was confirmed that the amount of fine bubbles contained in the ore slurry was greater than in Example 1. In other words, it was found that by directly supplying the fine bubble-containing water generated in the fine bubble-containing water generating device 6 to the flotation tank, a greater amount of fine bubbles can be contained in the ore slurry.

[Comparative Example]
The flotation treatment was carried out in the same manner as in Example 2, except that instead of directly supplying the fine bubble-containing water to the ore slurry in the most upstream tank of the four flotation tanks 10 in the flotation equipment 5, the fine bubble-containing water generating device 6 was immersed in the ore slurry in the most upstream tank, thereby generating fine bubbles directly in the ore slurry in the tank.

As a result, it was confirmed that 30 seconds after the start of the flotation process, the same amount of fine bubbles with diameters between 1 μm and 100 μm were present as in Example 2 above, but by the end of the 30 minutes, the amount of air supplied had decreased to 1.2 L/min due to blockages caused by clogging in the porous body. In addition, the amount of fine bubbles with diameters between 1 μm and 100 μm contained in the ore slurry had clearly decreased 30 minutes after the start compared to 30 seconds after the start.

REFERENCE SIGNS LIST 1 Slurry tank 2 Slurry pump 3 Classifier 4 Grinding mill 5 Flotation equipment 6 Microbubble-containing water generator 7 Solid-liquid separation means 8 Supply pipe for microbubble-containing water 8a Branch pipe 9 Supply pipe for preparation water 10 Flotation tank 20 Agitator 21 Rotating shaft 22 Impeller 23 Stator 23a Partition plate 23b Plate-shaped body 24 Base 25 Leg 26 Motor

Claims (5)

A flotation system for separating and recovering useful minerals contained in ore in an ore slurry by flotation treatment of the ore slurry, comprising:
The flotation system includes a flotation facility consisting of a slurrying tank that receives ore containing the useful minerals and preparation water for slurrying the ore to prepare an ore slurry, one or a plurality of continuous flotation tanks that perform flotation processing on the ore slurry extracted from the slurrying tank, and a micro-bubble-containing water generator that generates micro-bubble-containing water containing micro-bubbles having a bubble diameter of 100 μm or less, and the micro-bubble-containing water is supplied to at least one of the one or a plurality of flotation tanks. The flotation system according to claim 1, characterized in that the fine bubble-containing water generating device is a microbubble-containing water generating device that generates water containing microbubbles with a bubble diameter of 1 μm to 100 μm, and/or an ultrafine bubble-containing water generating device that generates water containing ultrafine bubbles with a bubble diameter of less than 1 μm. The flotation system according to claim 1, further comprising a solid-liquid separation means for performing solid-liquid separation of the tailings slurry discharged from the flotation equipment, and using the clear water separated by the solid-liquid separation as the water for the microbubble-containing water. The flotation system according to any one of claims 1 to 3, in which the microbubble-containing water is used as at least a portion of the preparation water. A flotation method comprising a preparation step of mixing ore containing useful minerals with preparation water to prepare an ore slurry, and a flotation step of introducing the ore slurry prepared in the preparation step into one or a series of multiple flotation tanks to perform flotation, and supplying fine bubble-containing water containing fine bubbles with a bubble diameter of 100 μm or less to at least one of the one or a series of multiple flotation tanks.

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