JP7848511B2 - Chromite ore separation and recovery equipment, and chromite ore recovery method - Google Patents

Description

This invention relates to a chromite ore separation and recovery apparatus and a chromite ore recovery method. More specifically, this invention relates to a chromite ore separation and recovery apparatus and a chromite ore recovery method for separating and recovering chromium-containing iron ore from an ore slurry subjected to leaching treatment in a wet smelting method for recovering nickel and cobalt from nickel oxide ore by high-pressure acid leaching.

In recent years, the monopolization of mining rights for mineral resources such as coal, iron, copper, nickel, cobalt, chromium, and manganese has progressed, leading to a significant increase in raw material costs. Therefore, as a measure to reduce costs in the metal smelting sector, technological development is underway to utilize lower-grade raw materials that were previously not used due to their cost disadvantages.

In nickel smelting plants, chromite ore is separated and recovered from the ore slurry, a mixture of nickel oxide ore and water, within the wet smelting plant using the High Pressure Acid Leach method, which involves acid leaching nickel oxide ore with sulfuric acid under pressure. This separation and recovery of chromite ore is carried out in a separation and recovery facility that connects a classification device, which separates the slurry based on the particle size differences contained in the ore slurry, with a specific gravity separation device, which further concentrates the chromium content from the slurry classified to the coarser-grained side through specific gravity separation, thereby separating and recovering a high-chromium concentration slurry (see Patent Documents 1 and 2).

In a separation and recovery facility consisting of multiple types of separation devices connected together as described above, the method chosen to increase the processing capacity of ore slurry is often to add identical devices in parallel for each processing stage, rather than increasing the size of individual devices. This is because adding existing devices in parallel, where processing conditions are already stably established, makes it easier to predict changes in slurry concentration and particle size distribution due to changes in the equipment configuration, and thus allows for relatively easy and appropriate management of the overall operating conditions of the facility, compared to replacing existing devices with new, larger ones.

For example, in the above-mentioned separation and recovery facility, which consists of multiple types of separation devices connected together, if multiple specific gravity separation devices are installed in parallel downstream, it is necessary to stably supply the desired amount of slurry from the upstream classification device to each of the multiple specific gravity separation devices downstream. While it is conceivable to distribute the slurry to the downstream devices using a liquid supply piping system with branched pipes, this method makes it difficult to stably and evenly distribute the slurry because the slurry flow rate tends to fluctuate locally due to uneven flow of solids within the liquid supply piping.

Japanese Patent Publication No. 2012-107289 Japanese Patent Publication No. 2017-52992

The present invention aims to stably and evenly distribute slurry to multiple devices arranged in parallel downstream from an upstream device, in a chromite ore separation and recovery facility comprising a configuration in which identical separation devices are installed in parallel.

The inventors of the present invention have found that the above problems can be solved by installing a slurry relay tank having multiple overflow weirs as slurry discharge ports upstream of the multiple parallel-arranged separation devices in a chromite ore separation and recovery facility comprising a configuration in which multiple separation devices of the same type are installed in parallel, and by further installing a dilution water supply device that injects an appropriate amount of dilution water to adjust the slurry concentration into the piping that transports the slurry to the slurry relay tank, and have completed the present invention. Specifically, the present invention provides the following:

(1) A chromite ore separation and recovery facility comprising: a classification device for separating and recovering a chromium-containing slurry from an ore slurry based on the particle size difference of the particles constituting the ore slurry; and a plurality of specific gravity separation devices located downstream of the classification device for separating and recovering a high-chromium-concentration slurry from the slurry separated and recovered by the classification device through specific gravity separation treatment; wherein the facility further comprises a slurry relay tank and a dilution water supply device, the slurry relay tank being installed between the classification device and the specific gravity separation devices, and having an agitator and a plurality of overflow weirs for evenly distributing and discharging the agitated slurry downstream; and a dilution water supply pipe extending from the dilution water supply device being connected to a slurry flow pipe connecting the classification device and the slurry relay tank.

According to the chromite ore separation and recovery equipment described in (1), the slurry can be stably and evenly distributed from the upstream classification device to multiple specific gravity separation devices arranged in parallel downstream. Furthermore, by directly injecting dilution water into the slurry transport pipe, blockage of the slurry transport pipe due to slurry stagnation can be prevented.

(2) The chromite ore separation and recovery facility according to (1), wherein the overflow weir is equipped with an overflow weir closing mechanism that can stop the discharge of slurry as needed, and the number of overflow weirs is greater than the number of specific gravity separation devices connected to the downstream side of the slurry relay tank.

According to the chromite ore separation and recovery equipment in (2), the overflow weirs exceeding the number of downstream specific gravity separation devices currently in operation can be closed, and when additional specific gravity separation devices are installed in the future, they can be opened and made functional. This allows the chromite ore separation and recovery equipment to have the flexibility to adapt to changes in the number of specific gravity separation devices.

(3) The chromite ore separation and recovery apparatus described in (1) or (2), wherein the liquid phase flow channel overflowing the overflow weir is a channel with a substantially rectangular vertical cross-sectional shape and a flat bottom.

In the chromite ore separation and recovery facility described in (3), the relationship between the flow rate of the liquid phase overflowing the overflow weir and the head (height of the overflow liquid level) h maintains a linear correlation. Therefore, compared to triangular overflow weirs with uneven bottoms, fluctuations in slurry discharge volume when the liquid level of the slurry in the tank fluctuates locally can be suppressed to a smaller range, further enhancing the stability of the uniform distribution of slurry to the downstream equipment in the chromite ore separation and recovery facility described in (1) or (2).

(4) A chromite ore separation and recovery apparatus according to any one of (1) to (3), wherein the classification apparatus is a hydrocyclone and the specific gravity separation apparatus is a density separator and/or spiral concentrator.

According to the chromite ore separation and recovery equipment of (4), in the process of separating and recovering chromite ore from nickel oxide ore slurry through multiple stages, the supply amount of slurry introduced into the downstream specific gravity separation stage can be stably maintained within an appropriate range. This allows for a stable improvement in the chromium separation and recovery rate.

(5) A method for recovering chromite ore by separating and recovering chromite ore from nickel oxide ore slurry, comprising: a classification step of separating the slurry according to the particle size difference of the contained particles; a slurry concentration adjustment step of adjusting the slurry concentration by injecting diluent water into the slurry classified to the coarser particle side in the classification step; a slurry distribution step of distributing the slurry whose slurry concentration has been adjusted in the slurry concentration adjustment step evenly into multiple slurry channels by passing it through a slurry relay tank having a stirrer and multiple overflow weirs as slurry discharge ports; and a specific gravity separation step of separating and recovering a high-chromium concentration slurry, in which the chromium content has been further concentrated, from each of the slurries distributed in the slurry distribution step using a specific gravity separation device, wherein in the slurry concentration adjustment step, the amount of diluent water injected is adjusted so that the slurry concentration introduced into the slurry distribution step is 35% or more and 40% or less.

According to the chromite ore recovery method of (5), the slurry can be stably and evenly distributed from the upstream classification device to multiple gravity separation devices arranged in parallel downstream. Furthermore, by maintaining the slurry concentration supplied from the upstream classification device to the multiple gravity separation devices arranged in parallel downstream within a predetermined range, the disintegration due to particle collisions in the slurry transfer tank during the slurry distribution process is promoted, thereby improving the separation and recovery rate of chromium in the gravity separation process.

(6) The method for recovering chromite ore according to (5), wherein the cross-sectional shape of the overflow liquid channel in the overflow weir of the slurry relay tank in which the slurry distribution step is performed is rectangular with a flat bottom, and the slurry distribution step is performed while maintaining the relationship between the channel width d and the height h of the overflow liquid in the range of 0.5d ≤ h ≤ 2d.

According to the chromite ore recovery method of (6), it is possible to prevent wear of the flow path due to excessive flow velocity of the discharged slurry, and furthermore, the influence of local fluctuations in the liquid level of the slurry in the tank on the flow velocity of the discharged slurry can be minimized, thereby improving the stability of uniform distribution of the slurry.

According to the present invention, in a chromite ore separation and recovery facility comprising a configuration in which separation devices of the same type are installed in parallel, the slurry can be stably and evenly distributed from the upstream device to multiple devices arranged in parallel downstream.

This diagram schematically shows the overall configuration of the chromite ore separation and recovery equipment of the present invention. This is a schematic diagram showing the basic configuration of a hydrocyclone suitable as a classification and processing device for the chromite ore separation and recovery equipment of the present invention. This is a plan view of the slurry relay tank that constitutes the chromite ore separation and recovery equipment of the present invention. Figure 3 is a magnified view of a portion of the slurry relay tank, illustrating the structure around the overflow weir. This is a process diagram showing the overall flow of a wet smelting process for recovering nickel and cobalt from nickel oxide ore. This is a process diagram showing the general flow of the chromite ore recovery method, which is carried out as a sub-process of the overall process shown in Figure 5.

The following describes in detail specific embodiments of the "chromite ore separation and recovery equipment" and the "chromite ore recovery method" of the present invention. However, the present invention is not limited to the following embodiments, and various modifications are possible without altering the essence of the invention.

<Chromite ore separation and recovery facility>
The "chromite ore separation and recovery equipment" of the present invention is equipment that performs a process of recovering chromite ore from the ore slurry (chromite ore recovery process S2) in parallel with the pretreatment of the ore slurry when carrying out the ore slurry treatment process S2 (see Figure 5), which is a partial process of the "wet smelting method for nickel oxide ore" described later.

[Overall structure]
Figure 1 is a schematic diagram showing the overall configuration of a chromite ore separation and recovery facility 10, which is an example of an embodiment of the "chromite ore separation and recovery facility" of the present invention. As shown in the figure, the chromite ore separation and recovery facility 10 is composed of at least a classification processing device 1, a slurry relay tank 2, a plurality of specific gravity separation devices 3 (3A, 3B, 3C, 3D), and a dilution water supply device 4.

In the chromite ore separation and recovery facility 10, multiple specific gravity separation devices 3 (3A, 3B, 3C, 3D) are arranged in parallel downstream of the classification and processing device 1, with a slurry relay tank 2 in between that distributes the slurry to each of the specific gravity separation devices 3A, 3B, 3C, and 3D. While the number of these specific gravity separation devices 3 is shown as four in the diagram, as an example, it is not limited to this, and any number of devices (two or more) can be installed as needed.

Furthermore, a slurry transfer pipe 15 is installed between the coarse-grain discharge port (underflow discharge port 14 in Figure 2) of the classification device 1 and the slurry transfer tank 2. This pipe transfers the slurry, which has been classified by the classification device 1 into the relatively larger particle size (coarse-grain) side, to the slurry transfer tank 2.

Furthermore, a dilution water supply pipe 41 is connected to the dilution water supply device 4, which injects the dilution water supplied from the device into the slurry flow pipe 15. The dilution water supply pipe 41 extends from the dilution water supply device 4 and is connected to the slurry flow pipe 15, which is installed connecting the classification processing device 1 and the slurry relay tank 2, in a manner that allows for the injection of dilution water into the slurry flow pipe 15.

[Classification Processing Equipment]
The classification apparatus 1 is a device that classifies an ore slurry, such as nickel oxide ore, based on the difference in particle size of the particles contained in the ore slurry. Specifically, a hydrocyclone can be preferably used as the classification apparatus. A "hydrocyclone" is a known device that uses centrifugal force to classify solid particles dispersed in a slurry, mainly based on differences in particle size (see, for example, Japanese Patent Publication No. 55-1047666).

The hydrocyclone 1 shown in Figure 3 is an example of a hydrocyclone that can be preferably used in the present invention. According to the hydrocyclone 1, by supplying nickel oxide ore slurry at a predetermined pressure from the supply pipe 12, a downward flow that swirls down near the wall surface inside the tapered cylindrical section 11 and an upward flow that rises near the center are generated, allowing the nickel oxide ore slurry to be separated into coarse and fine particles.

Here, generally, the specific gravity of chromite is equivalent to that of iron hydroxide such as goethite, but because the particle sizes are different, coarse chromite and fine goethite can be efficiently separated by a "hydrocyclone." From the overflow outlet 13 of the hydrocyclone 1, a mixture containing relatively small-grained goethite (fine particles) is discharged as overflow (O/F) and sent to the leaching process S3 as a raw material for nickel recovery. Then, from the spigot (underflow outlet) 14 of the hydrocyclone 1, a mixture containing relatively large-grained chromite ore (coarse particles) is discharged as underflow (U/F), and this underflow (U/F) is sent to the slurry relay tank 2 via the slurry flow pipe 15.

[Slurry relay tank]
As shown in Figure 3, the slurry relay tank 2 is a cylindrical storage tank equipped with multiple overflow weirs 22 (22A, 22B, 22C, 22D) and an agitator 24. In the slurry relay tank 2, the slurry that has been transported from the classification treatment device 1 through the slurry transport pipe 15 in the chromite ore separation and recovery equipment 10 is temporarily stored, agitated in the tank, and then discharged evenly from each of the overflow weirs 22A, 22B, 22C, 22D. It is preferable that the slurry relay tank 2 has a capacity that allows for a residence time of 1 minute or more.

The multiple overflow weirs 22 (22A, 22B, 22C, 22D) are preferably provided at equal intervals in the circumferential direction of the storage area within the tank, at the upper end of the side wall of the tank body 23, as shown in Figure 3. In this specification, "overflow weir" refers to a type of outlet structure for controlling the amount of liquid phase discharged in a tank capable of storing a liquid phase. By appropriately setting the height of the weir relative to the liquid level of the liquid phase, it is an outlet structure that allows overflow liquid within a certain range to flow out uniformly over the weir at a predetermined discharge rate. As an example, the overflow weirs 22 (22A, 22B, 22C, 22D) can be constructed by forming rectangular notches at the upper end of the side wall of the tank body 23, as shown in Figure 4.

Each overflow weir 22 (22A, 22B, 22C, 22D) is preferably equipped with an overflow weir closing mechanism that can, as needed, close the outflow path of the overflow liquid formed above the upper edge of the weir. The overflow weir closing mechanism can be provided, for example, by installing a closing plate that can cover the entire opening portion of the rectangular cutout constituting the overflow weir from the inside of the tank, and which can be moved up and down as needed to open and close the opening portion.

Furthermore, if the overflow weir 22 is equipped with an overflow weir closing mechanism, the slurry relay tank 2 can be provided with more overflow weirs 22 than the number of specific gravity separation devices 3 connected to the downstream side. This provides the chromite ore separation and recovery facility 10 with the flexibility to easily accommodate changes in the number of specific gravity separation devices 3.

Furthermore, as shown in Figure 4, it is preferable that the overflow weir 22 is configured such that the vertical cross-sectional shape of the flow path of the liquid phase overflowing the weir and flowing out of the tank is approximately rectangular. Because the flow path of the liquid phase overflowing the weir and flowing out of the tank is formed by a flat bottom surface and a pair of sides erected perpendicular to it, the relationship between the flow rate of the liquid phase overflowing the weir and the head (the height of the overflow liquid's surface) h maintains a linear correlation. Therefore, compared to a triangular overflow weir with an uneven bottom surface, fluctuations in the slurry discharge rate when the liquid level of the slurry in the tank fluctuates locally can be suppressed to a smaller fluctuation range.

Furthermore, as shown in Figure 4, it is preferable to design the overflow weir 22 such that the relationship between the flow path width d of the overflow liquid channel and the head h is within the range of 0.5d ≤ h ≤ 2d. When the cross-sectional shape of the overflow liquid channel in the overflow weir 22 is a rectangle with a flat bottom, if h exceeds 2d, the flow velocity of the discharged slurry increases, necessitating measures to prevent wear of the channel. On the other hand, if h is less than 0.5, local fluctuations in the liquid level of the slurry in the tank have a large effect on the flow velocity of the discharged slurry, making uniform distribution of the slurry difficult.

The slurry discharged from each overflow weir 22A, 22B, 22C, and 22D is transported through the downstream slurry transport pipes 21 (21A, 21B, 21C, 21D) to the multiple specific gravity separators 3 (3A, 3B, 3C, 3D) on the downstream side.

[Specific gravity separation device]
A specific gravity separation device is a device that separates ore in a slurry using a specific gravity separation process that separates the ore based on the difference in gravity (specific gravity of the particles). This process concentrates the portion containing particles with a higher specific gravity, further promoting the concentration of chromium components, and then separates and recovers the high-chromium grade slurry.

Specifically, a "density separator" and/or a "spiral concentrator" can be preferably used as the specific gravity separation device. A "density separator" is a known device in which slurry is supplied from the top of the device, and the specific gravity separation of the slurry is performed by the upward flow of injected water (teeter water (TW)) injected from the bottom of the device (see, for example, Japanese Patent Application Publication No. 2017-600930).

Furthermore, a "spiral concentrator" is a separation device equipped with a slurry channel that acts as a spiral-shaped, inclined slide. Mineral particles with different specific gravities mixed in the slurry introduced into the spiral concentrator are separated by gravity as they flow through the spiral channel. The coarse, heavy chromite ore (Conc) is recovered from the innermost concentrate (Conc) basin.

[Dilution water supply device]
The dilution water supply device 4 is a device that supplies dilution water to adjust the slurry concentration to an appropriate range for the slurry that is separated and recovered in the classification processing device 1 and sent to the slurry relay tank 2. Various known water supply devices with the required water supply capacity can be used as the dilution water supply device 4. However, a unique feature of the separation and recovery equipment 10 is that the dilution water supply device 4 is configured to be able to directly inject an appropriate amount of dilution water into the slurry flow pipe 15, which is the flow pipe for the slurry that is separated and recovered in the classification processing device 1 and sent to the slurry relay tank 2. Specifically, the dilution water supply device 4 and the slurry flow pipe 15 are connected by a dilution water supply pipe 41, and the dilution water passes through the dilution water supply pipe 41 to the slurry flow pipe 15 and is injected directly into the pipe.

<Method for recovering chromite ore>
The method for recovering chromite ore according to the present invention (hereinafter also simply referred to as the "chromite ore recovery method") is performed as a step to recover chromite ore in parallel with the execution of the ore slurry processing step S2, which is a part of the flow of the "wet smelting method for nickel oxide ore" shown in Figure 5. The recovery of chromite ore performed in the ore slurry processing step S2 is usually carried out in a procedure that performs processing with multiple types of physical separation devices, but the "chromite ore recovery method" is a recovery method that is suitable when the specific gravity separation step, which is one of the physical separation device processing performed in the process, is carried out by multiple specific gravity separation devices installed in parallel. Furthermore, it is preferable to perform the "chromite ore recovery method" using the "chromite ore separation and recovery equipment" of the present invention, which has been described in detail above.

In the "Wet Smelting Method for Nickel Oxide Ore," the process of recovering chromite ore in parallel with the ore slurry processing step S2 typically involves sequentially performing only the classification step S21, the specific gravity separation step S25, and the magnetic separation step S26 from the steps shown in Figure 6. In contrast, the "Chromite Ore Recovery Method" is characterized by performing the specific gravity separation step S25 using multiple parallel-installed specific gravity separation devices, as shown in Figure 1. Furthermore, as shown in Figure 6, two additional intermediate processing steps—slurry concentration adjustment step S22 and slurry distribution step S23—are added between the classification step S21 and the specific gravity separation step S25.

[Classification process]
Classification step S21 is a step in which the nickel oxide ore slurry is classified according to the difference in particle size of the particles contained in the ore slurry. In this step, the mixture containing goethite is separated as overflow (O/F) and the mixture containing chromite ore is separated as underflow (U/F). As described above, a hydrocyclone can be preferably used as the classification apparatus for performing classification step S21 in the "Method for recovering chromite ore".

[Slurry concentration adjustment process]
The slurry concentration adjustment step S22 is a step in which an appropriate amount of diluent water is injected into the slurry that has been classified to the coarse-grain side in the classification step S21 and is being fed into the downstream slurry distribution step S23 to adjust the slurry concentration. The amount of diluent water injected into the slurry is the amount necessary and sufficient to maintain the slurry concentration (concentration of solids in the slurry) in the range of 35% to 40%. If the slurry concentration is higher than the above concentration range, a high-load type agitator is required, which is undesirable from an economic standpoint. On the other hand, if the slurry concentration is lower than the above concentration range, the load on the agitator is reduced, but the tank capacity becomes larger, which is a drawback. Furthermore, if the slurry concentration is within the above range, due to the viscosity of the slurry, sedimentation separation in the tank is unlikely to occur as long as stirring continues, and the uniformity of the slurry is easier to maintain.

[Slurry distribution process]
The slurry distribution step S23 is a step in which the slurry, whose slurry concentration has been appropriately adjusted in the slurry concentration adjustment step S22, is distributed to multiple slurry channels via a slurry relay tank having multiple overflow weirs as slurry outlets. It is preferable to use the slurry relay tank 2, which constitutes the chromite ore separation and recovery equipment of the present invention, as described in detail above, as the slurry relay tank.

Furthermore, in the "Chromite Ore Recovery Method," when using a slurry relay tank 2 as the slurry relay tank for the slurry distribution step S23, where the cross-sectional shape of the overflow liquid flow path in the overflow weir 22 can be a rectangle with a flat bottom, it is preferable to perform the "Chromite Ore Recovery Method" within the range of operating conditions that can maintain the relationship between the flow path width d and the head h of the overflow liquid flow path within the range of 0.5d ≤ h ≤ 2d.

[Specific gravity separation process]
The specific gravity separation step S25 is a step in which a high-chromium concentration slurry, which has had its chromium content further concentrated, is separated and recovered by specific gravity separation treatment from the slurry distributed to each slurry flow path in the slurry distribution step S23, using a plurality of specific gravity separation devices installed in parallel. As described above, a "density separator" and/or a "spiral concentrater" can preferably be used as the specific gravity separation device for the specific gravity separation step S25 in the "method for recovering chromite ore".

[Magnetic beneficiation process]
The magnetic separation process S26 is a process in which magnetite ore is removed from chromite ore, in which the chromium component has been concentrated by the specific gravity separation process S25, by magnetic separation treatment, thereby reducing the iron content. Since magnetite ore (Mag) is removed, the product becomes non-magnetized material (Non-Mag).

<Wet smelting method for nickel oxide ore>
The "chromite ore separation and recovery equipment" and "chromite ore recovery method" of the present invention, as described in detail above, are suitable separation and recovery equipment and recovery method as technical means for carrying out a partial process to recover chromite ore within the flow of a wet smelting process using nickel oxide ore as a raw material (hereinafter referred to as the "wet smelting method for nickel oxide ore"). Below, the "wet smelting method for nickel oxide ore," which is the overall process in which the present invention can be carried out as a partial process, will be described.

[Ore processing process]
The ore processing step S1 is a step in which nickel oxide ore is mixed with water to form a nickel oxide ore slurry. In this specification, the ore slurry which is a mixture of nickel oxide ore and water is referred to as "nickel oxide ore slurry".

[Ore slurry processing process]
The ore slurry processing step S2 is a pretreatment step for the ore slurry to be subjected to the leaching step S3, in which foreign matter is removed from the nickel oxide ore slurry and the ore particle size is adjusted. The "chromite ore recovery method" of the present invention can be performed as a process to separate and recover chromium from the ore slurry, which is the target of processing (chromite ore recovery step S2 (see Figure 6)) in the ore slurry processing step S2, which is performed as a partial step of the "wet smelting method for nickel oxide ore," as shown in Figure 5.

[Leaching process]
The leaching process S3 is a process in which valuable components such as nickel and cobalt are leached from the ore slurry with sulfuric acid using an autoclave or the like to obtain a leached slurry.

[Solid-liquid separation process]
The solid-liquid separation step S4 is a step in which the above-mentioned leaching slurry is separated into a leaching liquid containing nickel and cobalt and a leaching residue slurry using a multi-stage thickener or the like.

[Neutralization process]
The neutralization step S5 is a step in which the above-mentioned leachate is separated into a mother liquor containing nickel and a neutralized precipitate slurry.

[Zinc removal process]
The zinc removal step S6 is a step in which a sulfidating agent is added to the mother liquor to separate it into a mother liquor for nickel recovery and a zinc sulfide precipitate containing zinc sulfide.

[Sulfurization process]
The sulfidation step S7 is a step in which a sulfidating agent is added to the mother liquor for nickel recovery to separate it into a mixed sulfide containing nickel and cobalt (Ni, Co mixed sulfide) and a poor liquid. This poor liquid is ultimately sent to the final neutralization step S8, which is a downstream step, but as shown in Figure 5, part or all of it can also be used as washing water for the leaching residue in the solid-liquid separation step S4.

[Final neutralization step]
The final neutralization step S8 is a process in which the leachate residue slurry separated in the solid-liquid separation step S4 is neutralized to a pH of approximately 8 to 9 to obtain the final neutralized residue. This final neutralized residue is stored in the tailing dam.

As explained above, the "Wet Smelting Method for Nickel Oxide Ore" is an overall process comprising the ore processing step S1, the ore slurry processing step S2, the leaching step S3, the solid-liquid separation step S4, the neutralization step S5, the zinc removal step S6, the sulfidation step S7, and the final neutralization step S8. The "Chromite Ore Recovery Method" of the present invention is a partial process that can be implemented as the ore slurry processing step S2 within this overall process, and the "Chromite Ore Separation and Recovery Equipment" of the present invention is suitable industrial equipment for implementing such a "Chromite Ore Recovery Method."

The present invention will be further described below with reference to examples, but the present invention is not limited in any way by these examples.

<Example 1>
In the chromite ore separation and recovery facility 10, which has the configuration shown in Figure 1, nickel oxide ore slurry was supplied to a classification treatment device (hydrocyclone) 1, and underflow (coarse grain; solid content concentration 60%, flow rate 55 ^m³ /h) and overflow (fine grain) were obtained.
The underflow was allowed to flow naturally through the slurry transfer pipe 15 to the slurry transfer tank 2 installed in the lower section. Then, dilution water (47 ^m³ /h) was added to the slurry transfer pipe 15 by injecting it into the pipe through a dilution water supply pipe 41 connected to the middle of the slurry transfer pipe 15, thereby adjusting the slurry concentration in the slurry transfer tank 2 to 40%.
The slurry relay tank 2 has a capacity of 2 ^m³ , and the overflow weir consists of four overflow weirs 22 (22A, 22B, 22C, 22D) spaced at 90-degree intervals. Each weir has a roughly rectangular vertical cross-sectional shape and a flat bottom, with a channel width (d) of 75 mm and a channel height (H) of 75 mm. The slurry in the tank was then stirred at a rotation speed of 180 RPM using an agitator with a stirring power of 1.5 kW/ ^m³ .
Four specific gravity separation devices 3 were installed, and slurry was distributed from the slurry relay tank 2 to all four specific gravity separation devices 3 (3A, 3B, 3C, 3D).
During the implementation described above, the flow rate and concentration of the slurry discharged from each overflow weir were measured. The difference between the maximum and minimum slurry flow rates was 5.8%, indicating that the expected uniform distribution of slurry was achieved. Similarly, the difference between the maximum and minimum slurry concentrations was 3.0%, indicating that a slurry with uniform concentration was distributed.

(Example 2)
The amount of liquid supplied to the classification processing device (hydrocyclone) 1 was set to half the amount supplied in Example 1, and the slurry was distributed to only two specific gravity separators (3A, 3D) from only two diagonally located overflow weirs (22A, 22D) using the same procedure. A closing plate was attached to the unused overflow weirs (22B, 22D) to form an overflow weir closing mechanism, and the slurry was distributed with the discharge of slurry stopped.
During the implementation described above, the flow rate and concentration of the slurry discharged from each overflow weir were measured. The difference between the maximum and minimum slurry flow rates was 6.6%, indicating that the expected uniform distribution of slurry was achieved. Furthermore, the difference between the maximum and minimum slurry concentrations was 3.6%, indicating that a slurry with uniform concentration was distributed.

(Example 3)
In the same procedure as in Example 2, slurry was distributed from only two adjacent overflow weirs (22A, 22C) to only two specific gravity separators (3A, 3C). The overflow weirs not in use (22B, 22D) were closed off by installing closure plates as described above to stop the discharge of slurry.
During the implementation described above, the flow rate and concentration of the slurry discharged from each overflow weir were measured. The difference between the maximum and minimum slurry flow rates was 7.4%, indicating that the expected uniform distribution of slurry was achieved. Furthermore, the difference between the maximum and minimum slurry concentrations was 5.2%, indicating that a slurry with uniform concentration was distributed.

(Comparative Example 1)
We attempted to distribute the slurry using the same procedure as in Example 1, except that instead of injecting the same amount of diluting water used to adjust the slurry concentration into the slurry transport pipe 15, we added the same amount of diluting water as in Example 1 directly to the slurry relay tank. However, the hydrocyclone underflow became clogged in the slurry transport pipe 15, forcing us to interrupt operations.

From the above results, it can be seen that, according to the present invention, in a chromite ore separation and recovery facility comprising a configuration in which separation devices of the same type are installed in parallel, the slurry can be stably and evenly distributed from the upstream device to multiple devices arranged in parallel downstream.

1. Classification and Processing Equipment (Hydrocyclone)
11 Tapered pipe section 12 Supply piping 13 Overflow outlet 14 Underflow outlet (spigot)
15. Slurry flow pipe (U/F)
16. Slurry flow pipe (O/F)
2 Slurry relay tank 21 (21A, 21B, 21C, 21D) Slurry flow pipe 22 (22A, 22B, 22C, 22D) Overflow weir 23 Tank body 24 Agitator 3 (3A, 3B, 3C, 3D) Specific gravity separation device 4 Dilution water supply device 41 Dilution water supply pipe 10 Chromite ore separation and recovery equipment S1 Ore processing process S2 Ore slurry processing process (Chromite ore recovery process)
S3 Leaching process S4 Solid-liquid separation process S5 Neutralization process S6 Zinc removal process S7 Sulfurization process S8 Final neutralization process S21 Classification process S22 Slurry concentration adjustment process S23 Slurry distribution process S24 Specific gravity separation process S25 Magnetic beneficiation process

Claims (6)

A classification apparatus for separating and recovering a chromium-containing slurry from an ore slurry based on the particle size difference of the particles constituting the ore slurry, and a plurality of specific gravity separation apparatuses arranged downstream of the classification apparatus for separating and recovering a high-chromium concentration slurry from the slurry separated and recovered by the classification apparatus, in which the chromium content has been further concentrated by specific gravity separation.
A chromite ore separation and recovery facility equipped with,
It further includes a slurry relay tank and a dilution water supply device.
The slurry relay tank is installed between the classification apparatus and the specific gravity separation apparatus, and has an agitator and a plurality of overflow weirs that distribute and discharge the agitated slurry toward the specific gravity separation apparatus , and the difference between the maximum and minimum flow rates of the slurry discharged from the plurality of overflow weirs is 7.4% or less.
A dilution water supply pipe extending from the dilution water supply device is connected to a slurry flow pipe connecting the classification processing device and the slurry relay tank.
A facility for separating and recovering chromite ore. The overflow weir is equipped with an overflow weir closing mechanism that can stop the discharge of slurry as needed.
The number of the overflow weirs is greater than the number of gravity separation devices connected to the downstream side of the slurry relay tank.
The chromite ore separation and recovery apparatus according to claim 1. The cross-sectional shape of the channel through which the overflow liquid overflowing the overflow weir flows is substantially rectangular, and the bottom surface of the channel is flat .
A chromite ore separation and recovery apparatus according to claim 1 or 2. The classification apparatus is a hydrocyclone, and the specific gravity separation apparatus is a density separator and/or spiral concentrator.
A chromite ore separation and recovery apparatus according to any one of claims 1 to 3. A method for recovering chromite ore by separating and recovering chromite ore from nickel oxide ore slurry,
A classification process that separates the slurry based on the difference in particle size of the contained particles,
In the classification process, a slurry concentration adjustment step is performed in which dilution water is injected into the slurry that has been classified to the coarse particle side to adjust the slurry concentration.
In the slurry concentration adjustment step, the slurry whose slurry concentration has been adjusted is distributed to a plurality of specific gravity separation devices and discharged via a slurry relay tank having a stirrer and a plurality of overflow weirs as slurry discharge ports, and the difference between the maximum and minimum flow rates of the slurry discharged from the plurality of overflow weirs is 7.4% or less in the slurry distribution step.
A specific gravity separation step is performed to separate and recover a high-chromium concentration slurry, which has a further concentrated chromium content, from each of the slurries distributed in the slurry distribution step, using the specific gravity separation device.
It includes,
A method for recovering chromite ore, wherein in the slurry concentration adjustment step, the amount of dilution water injected is adjusted so that the slurry concentration introduced into the slurry distribution step is 35% or more and 40% or less. The cross-sectional shape of the channel of the overflow weir through which the overflow liquid flows is substantially rectangular, and the bottom surface of the channel is flat .
The slurry distribution process is performed while maintaining the relationship between the channel width d of the channel and the height h of the overflow liquid in the channel within the range of 0.5d ≤ h ≤ 2d.
The method for recovering chromite ore according to claim 5.