Apparatus for distributing a chromite slurry and method for recovering chromite using the same

Abstract

To provide a distribution supply device that can distribute chromite-containing slurry in equal proportions, each of which can be continuously supplied at a fixed flow rate.SOLUTION: A chromite-containing slurry distribution device evenly distributes and supplies chromite-containing slurry to separation devices, which separate chromite from the chromite-containing slurry. The distribution device has: a substantially cylindrical distribution tank 10 in which vertically movable weirs 11 are provided at even intervals in a circumferential direction, the number of weirs being the same as the number of the separation devices; and an agitator 20 in the center of the distribution tank 10. Supply parts of the separation devices lie below the upper ends of the weirs 11 lying at the lowest positions.SELECTED DRAWING: Figure 5

Description

Technical Field

[0001] The present invention relates to a distribution device that distributes and supplies a chromite-containing slurry prepared by adding water to crushed nickel oxide ore to a plurality of separation devices for separating chromite from nickel oxide ore, and a method for recovering chromite using the distribution device.

Background Art

[0002] Nickel oxide ore used as a raw material in the wet smelting method of nickel contains chromite, which is a mineral mainly composed of chromium element. This chromite, which exists in the form of chromite ore in nickel oxide ore, has a higher true specific gravity and larger particle size than other ore components. Therefore, in the ore slurry prepared by adding water to the crushed nickel oxide ore, chromite ore has high sedimentation characteristics.

[0003] In addition, as can be seen from the fact that chromite is industrially used in applications such as abrasives, chromite has a higher hardness than other ore components contained in nickel oxide ore. Therefore, when the ore slurry contains chromite in the wet smelting plant of nickel, there is a concern that the liquid contact parts such as equipment and pipes will be significantly worn. Therefore, in equipment such as liquid delivery pumps, pipes, and valves that handle ore slurries containing chromite, it is necessary to take costly wear countermeasures at the locations where the ore slurry comes into contact with the liquid.

[0004] Therefore, when nickel oxide ore used as a raw material in the wet smelting method of nickel contains chromite, it has been proposed to separate and recover chromite in the upstream process. For example, in Patent Documents 1, 2, and 3, in the high-pressure acid leaching method (High Pressure Acid Leaching) in which sulfuric acid is added to the raw material nickel oxide ore and acid leaching treatment is performed under high temperature and high pressure, before performing the above acid leaching treatment on the ore slurry prepared by adding water after crushing the nickel oxide ore, a technique for separating and recovering chromite by treating the ore slurry in a classification process using centrifugal force or specific gravity difference is disclosed.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Patent Document 2

Patent Document 3

Summary of the Invention

Problems to be Solved by the Invention

[0006] In the classification step using the above specific gravity difference, by introducing the ore slurry into the settling tank, chromite with a high true specific gravity is gravitationally settled in the settling tank and recovered from the bottom of the tank, and the slurry containing particles with a lower true specific gravity than chromite is overflowed as supernatant liquid and can be recovered from the trough at the upper part of the tank. However, such a classification device using the specific gravity difference has a limited processing capacity in commercially available products. When continuously processing a large amount of ore slurry, as in the case of wet smelting of low-grade nickel oxide ore, a single classification device may not be sufficient. In this case, it is necessary to uniformly distribute the above ore slurry to a plurality of classification devices provided in parallel and continuously supply each of them at a constant flow rate.

[0007] As a method of distributing and feeding the ore slurry equally to a plurality of classification devices as described above, a method can be mentioned in which the supply pipe of the ore slurry is branched for each classification device and a valve is provided in each branch pipe, and the opening degree of the valve is adjusted. Alternatively, a method can be mentioned in which a liquid feed pump is provided in each of the above branch pipes and the operation of the liquid feed pump is controlled for the flow rate. However, in any of these methods, wear is likely to occur inside the valve or inside the casing of the liquid feed pump, which is troublesome and costly to repair. Moreover, since it is necessary to stop the operation of the device during the repair, the operation rate of the plant may decrease.

[0008] The present invention has been made in view of the above circumstances, and in order to separate and recover chromite contained in nickel oxide ore used as a raw material for a wet nickel smelting method, for a plurality of separation devices provided in parallel, water is added to the crushed nickel oxide ore. It is an object of the present invention to provide a distribution supply device capable of distributing equal amounts of chromite-containing slurries such as ore slurries prepared and continuously supplying them at a constant flow rate to each.

Means for Solving the Problems

[0009] In order to achieve the above object, a distribution device for a chromite-containing slurry according to the present invention is a distribution device for a chromite-containing slurry that evenly distributes and supplies the chromite-containing slurry to a plurality of separation devices that separate chromite from the chromite-containing slurry. A substantially cylindrical distribution tank provided with a plurality of weirs that can move in the vertical direction at equal intervals in the circumferential direction by the same number as the number of the plurality of Separation devices, and a stirrer provided at the central portion of the distribution tank, and the supply portions of the plurality of separation devices are located below the upper end portions of the plurality of weirs when the plurality of weirs are located at the lowest positions. and a plurality of flow path portions with both upper and lower ends opened are provided on the inner wall surface of the distribution tank to guide the chromite-containing slurry that overflows the plurality of weirs respectively It is characterized by being.

Effects of the Invention

[0010] According to the present invention, for a plurality of separation devices provided in parallel for separating and recovering chromite from nickel oxide ore used as a raw material for a wet nickel smelting method, water is added to the crushed nickel oxide ore. It becomes possible to distribute equal amounts of chromite-containing slurries such as ore slurries prepared and continuously supply them at a constant flow rate to each.

Brief Description of the Drawings

[0011]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

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Figure 7

Figure 8

Embodiments for Carrying Out the Invention

[0012] Hereinafter, an embodiment of a distributor for a slurry containing chromite (hereinafter also referred to as a chromite-containing slurry) according to the present invention will be described by taking as an example the case where the chromite-containing slurry is a coarse-grained side slurry discharged from the bottom side discharge port when an ore slurry prepared by pulverizing nickel oxide ore and adding water is introduced into a hydrocyclone. Note that the distributor of the chromite-containing slurry of the present invention is not limited to the following embodiments, and includes various modification examples, alternative examples, etc. within the scope not departing from the gist of the present invention. That is, the scope of the rights of the present invention extends to the scope of the claims and its equivalent scope.

[0013] 1. Wet nickel smelting method The distributor of chromite-containing slurry according to the embodiment of the present invention is used for separating and recovering chromite in an upstream process from an ore slurry prepared by adding water to crushed nickel oxide ore used as a raw material in a wet nickel smelting method. Therefore, first, the wet nickel smelting method will be described. The wet nickel smelting method is a method of recovering valuable metals such as nickel in the form of sulfides by subjecting a leachate containing valuable metals such as nickel obtained by subjecting an ore slurry to acid leaching treatment under high temperature and high pressure to a sulfidation treatment.

[0014] More specifically, as shown in FIG. 1, the wet nickel smelting method includes a pretreatment step S1 of performing pretreatment such as crushing and sieving on raw nickel oxide ore and adding water to prepare an ore slurry having a predetermined slurry concentration, a chromite recovery step S2 of separating chromite from the above ore slurry and recovering it as a by-product, and an autoclave for the ore slurry after the chromite has been separated and removed. An leaching step S3 of adding sulfuric acid and high-pressure steam inside and performing acid leaching treatment under high temperature and high pressure, and after depressurizing and cooling the leaching slurry containing nickel and cobalt as valuable metals leached by the acid leaching treatment with a flash drum, introducing it to the most upstream side of a plurality of consecutive thickeners, A countercurrent multi-stage washing step S4 of separating and removing leaching residues while washing with washing water introduced to the most downstream side, a neutralization step S5 of adding a neutralizing agent to the leachate after the leaching residues have been separated and removed to separate and remove impurity elements contained in the leachate as neutralization precipitates, and a sulfidation step S6 of adding a sulfiding agent to the neutralized final solution after the neutralization precipitates have been separated and removed to recover nickel and cobalt in the form of mixed sulfides, and a final neutralization step S7 of adding a neutralizing agent to the nickel lean liquid discharged during the recovery of the above mixed sulfides and the leaching residues removed in the above countercurrent multi-stage washing step S4 to perform detoxification treatment.

[0015] In the above nickel hydrometallurgy method, so-called laterite ores such as limonite ore and saprolite ore are mainly used as the nickel oxide ore raw material. The nickel content of laterite ore is generally 0.8 to 2.5% by mass, and nickel is contained as a hydroxide or a hydrous magnesium silicate (magnesium silicate) mineral. Also, the iron content of laterite ore is generally 10 to 50% by mass, and in this case, the iron mainly has the form of trivalent hydroxide (goethite), but a part of divalent iron is contained in hydrous magnesium silicate minerals and the like.

[0016] The above laterite ore further contains chromium, magnesia, and silicon. Among them, most of the chromium is contained in the laterite ore at about 1 to 5% by mass as a chromite mineral containing iron and magnesium. Also, the magnesia content is contained in magnesium silicate minerals other than hydrous magnesium silicate minerals and in magnesium silicate minerals that are unweathered and have a high hardness and contain almost no nickel. The silica content is contained in silica minerals such as quartz and cristobalite (amorphous silica) and hydrous magnesium silicate minerals. These chromite minerals, magnesium silicate minerals, and silica minerals contained in laterite ore contain almost no nickel and are called gangue components.

[0017] 2. Chromite Recovery Step Next, among the above wet nickel smelting methods, the chromite recovery step S2 will be described with reference to FIG. 2. The chromite recovery step S2 includes a centrifugation step S21 in which an ore slurry containing chromite (also referred to as a chromite-containing ore slurry) prepared in the pretreatment step S1 is centrifuged by a hydrocyclone to discharge a coarse-grained side slurry containing coarse chromite from the bottom side discharge port, and discharge a dechromite ore slurry containing fine particles such as goethite from the top side discharge port; a distribution step S22 of distributing the coarse-grained side slurry corresponding to the number of units of the apparatus in the subsequent step; a specific gravity separation step S23 of separating goethite contained in the distributed coarse-grained side slurry using the specific gravity difference; a concentration step S24 of introducing the coarse-grained side slurry after goethite is separated in the specific gravity separation step S23 into a concentrator to further increase the concentration of chromite; and a magnetic separation step S25 of separating the magnetizable material contained in the coarse-grained side slurry with increased chromite concentration in the concentration step S24 using magnetic force.

[0018] As described above, even if the nickel oxide ore used as a raw material in the wet nickel smelting method contains chromite, in the pretreatment step S1, the particle size is preferably made uniform to be 45 μm or more and 1.4 mm or less by pulverization and sieving, and water is added to obtain a predetermined slurry concentration to prepare an ore slurry. Then, by separating chromite in the chromite recovery step S2 for this ore slurry, it is possible to suppress the problem that the liquid contact parts of equipment such as pipes and pumps are significantly worn by chromite in the subsequent leaching step S3 and later steps.

[0019] Thereby, the maintenance cost of the equipment can be suppressed, and the frequency of operation stops due to maintenance can be reduced, so that the operation efficiency of the wet smelting plant can be increased. In this specification, the above particle size of A or more and B or less means that it is on a sieve with an opening of A and under a sieve with an opening of B. Hereinafter, each step constituting such a chromite recovery step S2 will be specifically described.

[0020] 2.1 Centrifugation Step The centrifugal separation step S21 is a step of classifying the chromite ore slurry prepared in the pretreatment step S1 using a hydrocyclone. The hydrocyclone is a classification device composed of a cylindrical part and a reduced-diameter part having an inverted conical shape connected to the lower end thereof. By introducing the chromite ore slurry pressurized by a pump into the cylindrical part from the tangential direction, the chromite ore slurry can be made to descend while swirling at high speed along the inner wall surface. Thus, due to the centrifugal force generated thereby, chromite, which is coarse particles having a high true specific gravity and a large particle size, is discharged from the bottom-side discharge port as a coarse-particle side slurry (also referred to as "underflow "U / F").

[0021] Since only a part of the ore slurry introduced into the hydrocyclone is discharged from this bottom-side discharge port, the remaining ore slurry rises through the central part and is discharged from the top-side discharge port as a fine-particle side slurry (also referred to as "overflow "O / F") containing fine particles such as fine goethite. Fine particles mainly composed of goethite, which are separated in the subsequent specific gravity separation step S23, concentration step S24, and magnetic separation step S25, flow into this fine-particle side slurry, and the dechromitized ore slurry is subjected to acid leaching treatment in the subsequent leaching step S3.

[0022] The classification of the above-mentioned chromite and goethite can be achieved by setting the classification particle size (classification point) of the chromite ore slurry to be classified within an appropriate range, and this classification particle size can be adjusted according to the operating conditions of the hydrocyclone. Specifically, in order to effectively classify the chromite ore slurry, it is preferable that the classification particle size is in the range of 20 to 150 μm, and more preferably in the range of 45 to 75 μm.

[0023] If the classification particle size is less than 20 μm, the proportion of fine particles mixed into the coarse particle side slurry increases, resulting in insufficient quality of the recovered chromite. In addition, the proportion of nickel that should originally be contained in the dechromitized ore slurry treated in the subsequent leaching step S3 and mixed into the coarse particle side slurry increases, leading to an increase in nickel loss. Conversely, when the above classification particle size exceeds 150 μm, the proportion of coarse chromite, magnesia silicate ore, and silica minerals mixed into the fine particle side slurry increases, so there is a risk of abrasion or a decrease in processing capacity in the steps after the leaching step S3. In this centrifugal separation step S21, it is preferable that the chromite concentration of the coarse particle side slurry is concentrated to 41% by mass or more.

[0024] As the operating conditions of the hydrocyclone that are appropriately adjusted to achieve the above classification particle size, for example, the slurry concentration (pulp concentration) of the chromite ore slurry introduced into the hydrocyclone, the operating pressure of the hydrocyclone, the slurry concentration (pulp concentration) of the coarse particle side slurry, the supply amount of the chromite ore slurry to the hydrocyclone, the shape represented by the inner diameter of the hydrocyclone, etc. can be mentioned.

[0025] Among the above operating conditions, the pulp concentration of the chromite ore slurry supplied to the hydrocyclone is not particularly limited, but it is preferably adjusted to about 10 to 30% by mass, and more preferably adjusted to about 15 to 20% by mass. Although the classification by the hydrocyclone can be carried out to some extent even if the pulp concentration is less than 10% by mass, a large amount of water is required for the preparation of the ore slurry in the pretreatment step S1, and it is necessary to remove water by, for example, sedimentation and concentration in the subsequent steps, so the processing cost may increase. Conversely, when the pulp concentration exceeds 30% by mass, the viscosity of the chromite ore slurry becomes too high, and there is a risk that the classification by the hydrocyclone becomes difficult.

[0026] Also, the operating pressure of the hydrocyclone, that is, the pressure of the chromite ore slurry supplied to the hydrocyclone, is not particularly limited, but it is preferably in the range of about 0.1 to 0.3 MPaG in consideration of classification performance, processing speed, etc. Further, the pulp concentration of the coarse particle side slurry as the underflow of the hydrocyclone is preferably 15% by mass or more. The pulp concentration of this underflow can be adjusted, for example, by the opening degree of a valve provided at the bottom side discharge port of the hydrocyclone.

[0027] As described above, among the operating conditions of the hydrocyclone considering classification performance, processing speed, etc., by adjusting the pressure of the ore slurry supplied to the hydrocyclone and the pulp concentration of the ore slurry, the particle size of particles with a particle size of -45 μm (able to pass through a screen with an opening of 45 μm) in the solid content of the coarse particle side slurry is adjusted to be 30% by mass or less. That is, among the particles contained in the coarse particle side slurry, the closer the ratio of particles with a particle size of -45 μm is to 0% by mass, the more desirable it is. However, the closer the ratio of -45 μm particles is to 0% by mass, the easier it is for coarse particles with a low nickel grade to be mixed into the fine particle side slurry, which may cause a factor in nickel recovery loss in the hydrometallurgical process.

[0028] As described above, since chromite has a higher true specific gravity and generally a larger particle diameter than iron hydroxides such as goethite, by using a hydrocyclone as a classification device, coarse particle chromite can be accurately separated from other fine particles such as goethite. That is, it becomes possible to almost eliminate the distribution of chromite to the fine particle side slurry discharged from the top side discharge port as the overflow. Also, since the hydrocyclone has no moving parts, it is suitable for treating a large amount of ore slurry at low cost, and is particularly suitable for treatment when the discharge amount from the top side is larger than the discharge amount from the bottom side. Note that the number of stages of the hydrocyclone is not limited to the above one stage, and two or more stages may be used.

[0029] 2.2 Distribution process The distribution step S22 is a step of distributing the coarse particle side slurry separated in the above centrifugation step S21 using a distribution device. Specifically described, as shown in FIGS. 3 to 5, the distribution device is composed of a bottomed cylindrical distribution tank 10 and a stirrer 20 provided at the central axis portion of the distribution tank 10. The distribution tank 10 is provided at its upper end portion with a plurality of substantially rectangular notch portions 10a (four notch portions 10a are shown in FIG. 3) having the same number as the base number of the subsequent specific gravity separation device at equal intervals in the circumferential direction. A plurality of weirs 11 are provided so as to be movable in the vertical direction so as to block these plurality of notch portions 10a from the inside and to be able to change the liquid level of the overflow. The distribution tank 10 is preferably covered with a disk-shaped lid 12, and a motor 21 of the stirrer 20 is installed at a substantially central portion thereof.

[0030] With such a configuration, the coarse particle side slurry discharged from the bottom side discharge port of the hydrocyclone in the previous step is pressurized by a slurry pump provided as necessary, and then introduced into the distribution tank 10 through a feed pipe (not shown), and is uniformly mixed by the stirring blades 23 provided at the tip of the shaft 22 of the stirrer 20, and is distributed in equal amounts by overflowing these plurality of weirs 11. The coarse particle side slurry that has overflowed these plurality of weirs 11 is temporarily received in a storage portion 13 provided corresponding to each weir 11 outside the distribution tank 10, and then discharged from an opening 13a provided at the bottom thereof and sent to a subsequent specific gravity separation device (not shown) through a discharge pipe 14 connected to the opening 13a.

[0031] The distributor with the above structure is installed such that the supply part of the plurality of specific gravity separation devices is located below the upper ends of the plurality of weirs 11 when the latter are located at the lowest position. Thereby, the coarse-particle side slurry evenly distributed in equal amounts by the distributor can be continuously fed to the plurality of specific gravity separation devices by utilizing only the height difference. Preferably, the above height difference is 3 m or more. If the height difference is less than 3 m, there is a possibility that stable liquid feeding cannot be achieved when fluctuations occur in the pressure loss of the discharge pipe 14, the particle size of the coarse-particle side slurry, or the pulp concentration. Also, the flow rate of the coarse-particle side slurry overflowing each of the plurality of weirs 11 is preferably 3 10 m 3 / hr or more and 200 m 3 / hr or less. If the flow rate overflowing each weir 11 is within the range of 10 m 3 / hr or more and 200 m

[0032] / hr or less, the coarse-particle side slurry can be stably overflowed from the plurality of weirs 11, enabling more even distribution.

[0033] 2.3 Specific gravity separation step The specific gravity separation step S23 is a step of performing a specific gravity separation process on each of the coarse particle side slurries distributed in the above-described distribution step S22 using a specific gravity separation device, thereby separating fine particles such as garnet contained in the coarse particle side slurry, and thereby making it possible to concentrate chromite. That is, in the centrifugal separation step S21 described above, the coarse particle side slurry recovered from the bottom side discharge port of the hydrocyclone as the underflow mainly contains chromite, but also contains some fine particles such as garnet.

[0034] Therefore, in this specific gravity separation step S23, by subjecting the coarse particle side slurry containing fine particles in addition to such chromite to a specific gravity separation process, these fine particles such as garnet can be effectively separated from chromite. In other words, this means further concentrating the chromite in the coarse particle side slurry. The fine particles containing garnet separated in this specific gravity separation step S23 can be mixed with the overflow of the above-described hydrocyclone and used as a dechromitized ore slurry to be treated in the acid leaching treatment of the wet smelting process.

[0035] It is preferable to use at least a spiral concentrator as the specific gravity separation device used in the specific gravity separation step S23. In this case, it is preferable to further provide one or more specific gravity separation devices selected from a density separator, a shaking table, and a spiral concentrator in the subsequent stage of the spiral concentrator. Among these combinations, it is preferable to continuously provide one stage of a spiral concentrator and one stage of a density separator suitable for large-scale processing. Hereinafter, these specific gravity separation devices will be specifically described.

[0036] (Spiral Concentrator) As illustrated in Fig. 6, the spiral concentrator has a structure in which a spiral trough is provided around a central axis extending in the vertical direction. By supplying slurry from the feed section located at the uppermost part and allowing it to flow down while swirling by gravity toward the discharge port located at the lowermost part, the slurry containing fine particles such as goethite with a small specific gravity is pushed to the outer peripheral side by the centrifugal force generated at that time, and the slurry containing chromite with a large specific gravity flows on the inner peripheral side. As a result, by separately collecting the inner peripheral side and the outer peripheral side at the discharge port at the lowermost part, it becomes possible to separate fine particles such as goethite from chromite.

[0037] In the specific gravity separation process using this spiral concentrator, although not particularly limited, it is preferable that the pulp concentration of the slurry supplied to the feed section is more than 15% by mass and less than 35% by mass, and more preferably more than 20% by mass and less than 30% by mass. If this pulp concentration is 15% by mass or less, the separation performance may deteriorate. Conversely, if it is 35% by mass or more, particle flow may stagnate and build-up may easily occur on the inner peripheral side of the spiral concentrator, which becomes the concentration side of chromite during the specific gravity separation process, and the above separation may not be performed well.

[0038] Also, in the specific gravity separation process using a spiral concentrator, the slurry to be processed may be subjected to specific gravity separation in a multi-stage apparatus by continuously connecting a plurality of spiral concentrators. In this case, it is preferable to supply the slurry containing chromite recovered as the slurry on the inner peripheral side of the spiral concentrator to the subsequent-stage spiral concentrator. Thereby, the component of chromite contained in the slurry to be processed can be effectively concentrated to a higher concentration, so that the chromite recovery rate can be further increased.

[0039] (Density Separator) The density separator is also referred to as a Teeter-bed separator. As illustrated in FIG. 7, it is composed of a cylindrical portion and an inclined portion located at the lower part thereof. A plurality of pipes for supplying water called Teeter water are provided at the lower end portion of the cylindrical portion. With such a configuration, fine particles contained in the slurry introduced from the upper part of the cylindrical portion are overflowed at the upper end portion of the cylindrical portion along with the upward flow by Teeter water, and coarse particles contained in the slurry are sedimented against the upward flow by Teeter water, deposited in the inclined portion, and then can be recovered as underflow from the bottom.

[0040] In the specific gravity separation process using this density separator, although not particularly limited, the supply amount of Teeter water is preferably 0.5 to 7.0 m 3 ·h -1 / m 2 If this supply amount is less than 0.5 m 3 ·h -1 / m 2 , the effect of interference sedimentation becomes small, and there is a possibility that the specific gravity separation cannot be performed efficiently. Conversely, if this supply amount exceeds 7.0 m 3 ·h -1 / m 2 , there is a possibility that chromite particles are lifted and transferred to the overflow side. In this case, the recovery rate of chromite decreases, and the chromite content in the ore slurry supplied to the leaching treatment increases, making it difficult to reduce the Cr grade in hematite.

[0041] In the specific gravity separation process using the above density separator, by continuously connecting a plurality of density separators, the slurry to be treated may be subjected to specific gravity separation by a multi-stage apparatus. Thereby, chromite can be separated more effectively, so that the chromite grade (Cr 2 O 3 grade) in the slurry withdrawn as underflow from the density separator at the final stage can be further increased.

[0042] (Shaking Table) As illustrated in FIG. 8, the shaking table consists of a substantially rectangular table that reciprocates horizontally by a driving unit. Slurry is supplied to a corner of the table, and water is supplied from a plurality of openings provided in a pipe extending in the longitudinal direction of the table from the corner. With such a configuration, fine particles such as goethite fall from the other side of the table where the pipe is provided along with the flow of water supplied from the pipe, while the coarse chromite particles are not affected by the flow of water and are conveyed from end to end in the longitudinal direction by the vibration of the table and recovered at the corner opposite to the above-mentioned corner.

[0043] In the specific gravity separation process using the above shaking table, although not particularly limited, it is preferable to adjust the pulp concentration of the slurry supplied from a corner of the above table to exceed 15% by mass and be less than 35% by mass, and more preferably to exceed 20% by mass and be less than 30% by mass.

[0044] 2.4 Concentration Process The concentration process S24 is a process of adjusting the slurry concentration of the pre-concentration slurry treated in the previous specific gravity separation process S23 so as to achieve a preferable slurry concentration as the supply condition of the magnetic separation device employed in the subsequent magnetic separation process S25. There is no particular limitation on the type of the concentrator used in this concentration process S24, but a gravity sedimentation device such as a thickener that can concentrate the slurry at a relatively low cost is preferable.

[0045] 2.5 Magnetic Separation Process The magnetic separation step S25 is a step of removing magnetized substances from the concentrated slurry concentrated in the previous concentration step S24 using a magnetic separation device. The coarse-grained slurry classified and separated to the coarse-grained side in the centrifugal separation step S21 mainly consists of chromite but may contain magnetite and further contains gassite. In the magnetic separation step S25, by subjecting the concentrated slurry containing other mineral components in addition to such chromite to magnetic separation treatment, magnetite as a magnetized substance can be separated from chromite as a non-magnetized substance, which means, in other words, further concentrating chromite.

[0046] The mixture containing magnetite as the magnetized substance separated in this magnetic separation step S25 can be mixed with the overflow of the above-described hydrocyclone to form a dechromitized ore slurry to be treated in the acid leaching treatment of the wet smelting process. Also, when a small amount of gassite is contained in the concentrated slurry to be treated in this magnetic separation treatment, this magnetic separation treatment can include it on the side of the mixture containing the above magnetite, so that it can be used as an ore slurry to be supplied to the acid leaching treatment together with magnetite.

[0047] The above magnetic separation device is not particularly limited, but it is preferable to use a high magnetic field magnetic separation device that generates a relatively high magnetic field strength within the range of 5 to 20 KGauss. Thereby, chromite can be separated and removed extremely efficiently. If the magnetic field strength is less than 5 KGauss, there is a possibility that magnetite as the magnetized substance cannot be effectively separated. Conversely, if the magnetic field strength exceeds 20 kGauss, chromite may be magnetized at the same time.

[0048] By using the high magnetic field magnetic separation device as described above, both magnetite and goethite can be separated and removed. However, since magnetite, which is a magnetized material, can be attracted by a magnet having a relatively low magnetic field strength, it becomes difficult to remove it from the magnet if the magnetic field strength is too high. On the other hand, goethite is not attracted by a magnet having a relatively low magnetic field strength, but is attracted by a magnet having a high magnetic field strength. Therefore, in this magnetic separation step S25, it is preferable to perform magnetic separation using a low magnetic field magnetic separation device that generates a magnetic field strength of about 500 to 2000 Gauss, which is smaller than the magnetic field strength of the high magnetic field magnetic separation device, before performing magnetic separation with the high magnetic field magnetic separation device.

[0049] As described above, the chromite-containing slurry distribution device according to the embodiment of the present invention does not particularly require pumps, valves, etc., so the number of these devices that are prone to wear can be reduced. Therefore, the construction cost and maintenance cost of the equipment can be reduced, and the plant operation rate can be increased because equipment troubles and maintenance frequency due to wear are reduced. In addition, since the number of drive units can be reduced, the operation cost can also be reduced. Furthermore, for the liquid feeding from the slurry distribution device containing chromite, which is prone to wear, a height difference is used, so the flow velocity in the pipe can be made slower than that by liquid feeding with a pump. As a result, the wear of the pipe and the valve provided as necessary can be suppressed.

Example

[0050] [Reference Example] A distribution device was fabricated, which consisted of a distribution tank 10 provided with notches 10a and weirs 11 that can slide up and down to cover them at four locations (A, B, C, D) at the upper end at equal intervals, as shown in FIGS. 3 to 5, and a stirrer 20 provided at the central axis of the distribution tank 10. Then, while rotating the stirrer 20 at a rotational speed of 103 rpm, water at a temperature of 20 to 30 °C was supplied, and it was examined whether water overflowed evenly from the four weirs 11 described above. In addition, the four weirs 11 provided in the distribution tank 10 were adjusted to have the same height. The measurement results are shown in Table 1 below.

[0051]

Table 1

[0052] As can be seen from Table 1 above, the flow rates of the water overflowing from the weirs 11 at the four locations (A, B, C, D) at the upper end of the distribution tank 10 varied within the range of -2.9% to +3.0 from their average value. However, when recovering chromite from the ore slurry prepared as a raw material in the wet smelting method of nickel, usually when distributing to a plurality of separation devices provided in parallel, the allowable range of their variations is 5% or less. Therefore, it was found that the above distribution tank 10 can distribute evenly.

[0053] [Example] In the wet smelting plant of nickel, since chromite was contained in the nickel oxide ore used as a raw material when producing nickel cobalt mixed sulfide by the high-pressure acid leaching method, water was added to the nickel oxide ore composed of particulate matter with a particle size of 45 μm or more and 1.4 mm or less aligned by a crusher and a screen, and an ore slurry prepared to a slurry concentration of 20% by mass was treated in the order of the centrifugal separation step S21, the distribution step S22, and the specific gravity separation step S23 in the process flow diagram as shown in Figure 2, and chromite was separated and recovered from the ore slurry.

[0054] Specifically, in the centrifugal separation step S21, a hydrocyclone manufactured by Salter Cyclones Limited was used, the above ore slurry was pressurized to 0.2 MPaG by a pump and supplied, and a coarse particle side slurry with a pulp concentration of 15% by mass was extracted from the bottom side discharge port of the hydrocyclone. In the distribution step S22, the coarse particle side slurry was distributed while rotating the stirrer 20 at a rotation speed of 103 rpm using a distribution device as shown in Figures 3 to 5, and they were respectively supplied to four spiral concentrators provided in parallel for classification in the specific gravity separation step S23. Incidentally, when the four weirs 11 of the distribution tank 10 of the distribution device were all positioned at the lowest position, their upper ends were 3 m higher than the feed part of the spiral concentrator.

[0055] As a result, the coarse-particle side slurry can be overflowed at each of the four weirs 11 of the distribution tank 10 at a flow rate of about 20 m 3 / hr, and the variation from the average value of these flow rates can be suppressed to 5% or less. In addition, it has become possible to stably operate the four spiral concentrators to recover chromite, and no particularly severe wear has been observed even in the wetted parts of the nickel hydrometallurgy plant.

Explanation of reference numerals

[0056] 10 Distribution tank 10a Notch 11 Weir 12 Lid 13 Storage part 13a Opening 14 Discharge pipe 15 Flow path part 20 Agitator 21 Motor 22 Shaft 23 Agitating blade

Claims

1. A device for distributing a chromite-containing slurry that evenly distributes and supplies the chromite-containing slurry to a plurality of separation devices for separating chromite from the chromite-containing slurry, comprising a substantially cylindrical distribution tank provided with a plurality of weirs movable in the vertical direction at equal intervals in the circumferential direction, the number of which is the same as the number of bases of the plurality of separation devices, and a stirrer provided at the center of the distribution tank. When the plurality of weirs are located at the lowest position, the supply portions of the plurality of separation devices are located below the upper ends of the weirs. On the inner wall surface of the distribution tank, a plurality of flow path portions with both upper and lower ends open are provided to guide the chromite-containing slurry overflowing the plurality of weirs respectively. A device for distributing a chromite-containing slurry, characterized in that.

2. The device for distributing a chromite-containing slurry according to Claim 1, characterized in that the height difference between the upper ends of the plurality of weirs when they are located at the lowest position and the supply portions of the plurality of separation devices is 3 m or more.

3. The flow rate of the chromite-containing slurry overflowing each of the plurality of weirs is 10 m ３ / hr or more and 200 m ３ / hr or less, and the distribution device for the chromite-containing slurry according to claim 1 or 2.

4. A method for recovering chromite contained in an ore slurry prepared by adding water after pulverizing nickel oxide ore used as a raw material in a wet nickel smelting method, comprising a centrifugal separation step of separating the ore slurry into a chromite-containing slurry and a dechromitized ore slurry by introducing the ore slurry into a hydrocyclone, and a separation step of separating fine particles contained in the chromite-containing slurry by distributing and introducing the chromite-containing slurry into a plurality of separation devices respectively. A method for recovering chromite, characterized in that the distribution device according to Claim 1 or 2 is used for distributing the chromite-containing slurry.

5. The method for recovering chromite according to Claim 4, characterized in that the particle size of the ore slurry is 45 μm or more and 1.4 mm or less.

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