Pressure oxidation leaching method and pressure oxidation leaching facility

Abstract

To provide a pressure oxidation leaching method capable of suppressing the deterioration of the electric power consumption unit of an air compressor even if the air compressor of a partial system is stopped.SOLUTION: When the air compressors 21, 22 of a partial series S1 are stopped, the high pressure air produced by the air compressors 21, 22 of the remaining series S2 is distributed and supplied to the autoclaves 10 of all the series S1 and S2. Material slurry containing metallic sulfide is supplied to autoclaves 10 of all series S1 and S2, and the metallic sulfide is subjected to pressure oxidation leaching to produce an aqueous solution of metallic sulphate. Since the autoclaves 10 of all the S1 blocks and S2 blocks are operated, the residence time of the metallic sulfide in the autoclaves 10 becomes long, and the deterioration of the electric power consumption rate of the air compressors 21 and 22 can be suppressed.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a pressure oxidative leaching method and pressure oxidative leaching equipment, and more particularly to a method and equipment for pressure oxidative leaching of metal sulfides. [Background technology]

[0002] A method for obtaining a metal sulfate aqueous solution by pressure oxidative leaching of a metal sulfide is known. For example, a raw material slurry containing nickel sulfide is continuously fed into an autoclave, and pressurized air is blown into the slurry in the autoclave to perform pressure oxidative leaching. This produces a nickel sulfate aqueous solution (for example, Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2021-143391 Summary of the Invention [Problem to be solved by the invention]

[0004] The high-pressure air supplied to the autoclave is produced by a multi-stage air compressor. Air compressors consume a large amount of electricity, and the electricity cost accounts for a large proportion of the facility's operating costs. Therefore, there is a need to reduce the air compressor's power consumption, i.e., the amount of electricity required to produce a unit amount of metal sulfate by pressure oxidative leaching of metal sulfides.

[0005] Pressurized oxidation leaching equipment may be equipped with multiple systems, with each system consisting of an autoclave and an air compressor that supplies high-pressure air to it. To prevent secondary damage in the event of equipment trouble, an interlock is typically installed to automatically shut down the air compressor. For this reason, each system is equipped with a high-pressure air storage tank, and each system is independently controlled. If the air compressor in one system shuts down due to maintenance or a malfunction, the autoclave in that system must also shut down.

[0006] When some autoclaves in a line are shut down, the amount of raw slurry supplied to the autoclaves in the line that are still in operation must be increased to prevent a decrease in production of metal sulfates. However, increasing the amount of raw slurry supplied to the autoclaves shortens the residence time of the raw slurry in the autoclave, lowering the leaching rate of metal sulfides. This results in a decrease in the amount of metal sulfates produced relative to the amount of raw slurry processed. In addition, more high-pressure air is required relative to the amount of raw slurry processed. As a result, the power consumption per unit of the air compressor worsens.

[0007] In view of the above circumstances, an object of the present invention is to provide a pressurized oxidation leaching method and pressurized oxidation leaching equipment that can suppress a deterioration in the power consumption rate of air compressors even when some of the air compressors in the line are stopped. [Means for solving the problem]

[0008] The first aspect of the pressure oxidation leaching method is a pressure oxidation leaching method using multiple systems of pressure oxidation leaching apparatuses, each system having an autoclave and an air compressor. When the air compressor of one system is stopped, high-pressure air produced by the air compressor of the remaining system is distributed and supplied to the autoclaves of all systems, a raw material slurry containing metal sulfide is supplied to the autoclaves of all systems, and the metal sulfide is subjected to pressure oxidative leaching to produce a metal sulfate aqueous solution. The pressurized oxidative leaching method of the second aspect is the method of the first aspect, characterized in that a relationship between the amount of high-pressure air supplied to the autoclave and an appropriate amount of metal sulfide supplied is determined in advance, and the amount of metal sulfide supplied to the autoclave is set to an appropriate amount relative to the actual amount of high-pressure air supplied based on this relationship. A third aspect of the pressurized oxidative leaching method is the second aspect, characterized in that the relationship between the amount of pressurized air supplied to the autoclave and the appropriate amount of metal sulfide supplied is determined so that the leaching rate of the metal sulfide becomes a target value. A fourth aspect of the pressure oxidative leaching method is the third aspect, characterized in that the relationship between the amount of high-pressure air supplied to the autoclave and the appropriate amount of metal sulfide supplied is expressed by the following formula: y=ax+b Here, y is the appropriate supply amount of the metal sulfide, x is the supply amount of the high-pressure air, and coefficients a and b are positive numbers. A fifth aspect of the pressure oxidation leaching facility comprises a plurality of pressure oxidation leaching apparatus lines, each of which has an autoclave that is supplied with a raw material slurry containing metal sulfides and that produces an aqueous metal sulfate solution by pressure oxidative leaching of the metal sulfides, an air compressor that produces high-pressure air, a high-pressure air tank that stores the high-pressure air produced by the air compressor, and a high-pressure air supply pipe that supplies the high-pressure air in the high-pressure air tank to the autoclave, and the high-pressure air tanks in the plurality of systems are connected to each other by tank connecting pipes, and the high-pressure air in the high-pressure air tank can be supplied to the autoclaves in the other systems via the tank connecting pipes. A sixth aspect of the pressurized oxidation leaching equipment is the fifth aspect, characterized in that the storage tank connecting pipe is provided with an on-off valve. A seventh aspect of the pressurized oxidation leaching equipment is the sixth aspect, characterized in that, if an abnormality occurs in any of the multiple lines of pressurized oxidation leaching devices, the on-off valve automatically closes the storage tank connecting pipe connecting to the high-pressure air storage tank of the line in which the abnormality occurs. [Effects of the Invention]

[0009] According to the present invention, even if the air compressors in some lines are stopped, the autoclaves in all lines can be operated using high-pressure air produced by the air compressors in the remaining lines. This extends the residence time of metal sulfides in the autoclaves, and the leaching rate of metal sulfides can be maintained high, thereby suppressing a deterioration in the electricity consumption rate of the air compressors. [Brief explanation of the drawings]

[0010] [Figure 1] FIG. 1 is an illustration of a pressurized oxidation leaching facility according to one embodiment. [Figure 2] Figure (A) is a graph showing the relationship between the amount of high-pressure air supplied to the autoclave and the appropriate flow rate of metal sulfide. Figure (B) is a graph showing the relationship between the amount of metal sulfide supplied to the autoclave and the power consumption rate of the air compressor. [Figure 3] Figure (A) is a graph showing the relationship between the amount of high-pressure air supplied to the first autoclave and the amount of raw slurry supplied, and Figure (B) is a graph showing the relationship between the amount of high-pressure air supplied to the second autoclave and the amount of raw slurry supplied. [Figure 4] Figure (A) is a graph showing the relationship between the total amount of raw slurry supplied and the total amount of power consumed by the air compressor when the first system air compressor is stopped. Figure (B) is a graph showing the relationship between the total amount of raw slurry supplied and the total amount of power consumed by the air compressor when the second system air compressor is stopped. DETAILED DESCRIPTION OF THE INVENTION

[0011] Next, an embodiment of the present invention will be described with reference to the drawings. The pressure oxidative leaching method and pressure oxidative leaching equipment according to one embodiment of the present invention are a method and equipment for obtaining a metal sulfate aqueous solution by pressure oxidative leaching a metal sulfide. Examples of metal sulfides that can be used include nickel sulfide, cobalt sulfide, zinc sulfide, and cadmium sulfide. One or more of these metal sulfides can be used as the raw material. For example, a nickel-cobalt mixed sulfide can be used as the raw material.

[0012] The following steps are taken to obtain a nickel sulfate solution from nickel-cobalt mixed sulfide. First, the raw material, nickel-cobalt mixed sulfide, is repulped to prepare a raw material slurry. Next, the raw material is subjected to pressure oxidation leaching to obtain a leached slurry containing a crude nickel sulfate solution. Next, the iron ions contained in the crude nickel sulfate solution are converted into iron hydroxide precipitates by oxidation neutralization treatment, and this is then subjected to solid-liquid separation together with the leaching residue contained in the leaching slurry. Next, heavy metals such as cobalt contained in the crude nickel sulfate solution are separated by solvent extraction to obtain a high-purity nickel sulfate solution. The obtained high-purity nickel sulfate solution is used for the production of nickel sulfate crystals, etc.

[0013] [Pressurized oxidation leaching facility] Next, the pressurized oxidation leaching equipment AA according to this embodiment will be described. As shown in Figure 1, the pressure oxidation leaching plant AA has multiple pressure oxidation leaching units S1 and S2. In the example shown, the pressure oxidation leaching plant AA has two pressure oxidation leaching units S1 and S2, but it may have three or more units. Hereinafter, one pressure oxidation leaching unit S1 will be referred to as the first system, and the other pressure oxidation leaching unit S2 will be referred to as the second system.

[0014] Each of the pressure oxidation leaching units S1 and S2 consists of multiple units used for pressure oxidation leaching of metal sulfides. Since the first system S1 and the second system S2 are basically the same in configuration, the configuration of the first system S1 will be described below as a representative.

[0015] The pressure oxidative leaching apparatus S1 has an autoclave 10. A raw material slurry containing metal sulfides is supplied to the autoclave 10. The metal sulfides are subjected to pressure oxidative leaching inside the autoclave 10 to produce an aqueous metal sulfate solution. A leaching slurry consisting of the aqueous metal sulfate solution and leaching residue is discharged from the autoclave 10.

[0016] High-pressure air is supplied to the autoclave 10. The supply of high-pressure air maintains the inside of the autoclave 10 at high pressure. The high-pressure air also acts as an oxidizing agent. When the metal sulfide comes into contact with the oxygen in the high-pressure air, the metal sulfide is oxidized, producing an aqueous metal sulfate solution.

[0017] The oxidation leaching reaction of metal sulfides is an exothermic reaction, and if left unchecked, the temperature of the slurry in the autoclave 10 will become too high. To adjust the temperature of the slurry in the autoclave 10 to an appropriate level, cooling is performed by adding cooling water or the like.

[0018] The pressurized oxidation leaching apparatus S1 has one or more air compressors. In the illustrated example, the pressurized oxidation leaching apparatus S1 has two turbo compressors 21 and one reciprocating compressor 22 as air compressors. The two turbo compressors 21 operate in parallel and send air at a gauge pressure of 1.0 to 1.4 MPaG to a medium-pressure air storage tank 31. The reciprocating compressor 22 is connected downstream of the medium-pressure air storage tank 31. The reciprocating compressor 22 further compresses the air in the medium-pressure air storage tank 31, producing high-pressure air at a gauge pressure of 1.8 to 2.2 MPaG, which is sent to the high-pressure air storage tank 32. The high-pressure air produced by the air compressors 21 and 22 is stored in the high-pressure air storage tank 32.

[0019] The high-pressure air storage tank 32 and the autoclave 10 are connected by a high-pressure air supply pipe 41. The high-pressure air in the high-pressure air storage tank 32 is supplied to the autoclave 10 via the high-pressure air supply pipe 41. The amount of high-pressure air supplied to the autoclave 10 is controlled by a flow control valve 42 provided in the high-pressure air supply pipe 41.

[0020] The discharge air volume of each air compressor 21, 22 is controlled so that the pressure in the high-pressure air tank 32 remains constant at a set value. For example, the discharge air volume of the turbo compressor 21 can be adjusted by throttling the inlet valve. The throttling control of the inlet valve is automatically performed so that the pressure in the medium-pressure air tank 31 remains constant at a set value. Because throttling the inlet valve too much can cause surging, there is a lower limit to the throttling control of the inlet valve. If the discharge air volume of the turbo compressor 21 remains excessive even when the flow rate of the inlet valve is set to the lower limit, the discharge air volume can be reduced, for example, by using the following two types of control. The first method is to automatically open a blow-off valve located downstream of the turbo compressor 21 to release high-pressure air. The second method is to adjust the discharge air volume by alternately operating the turbo compressor 21 between no-load and load operation.

[0021] The reciprocating compressor 22 has multiple compressor cylinders, and compresses air by reciprocating pistons within the cylinder tubes that make up the compressor cylinders. The amount of air discharged from the reciprocating compressor 22 can be controlled by adjusting the number of operating compressor cylinders. The number of operating compressor cylinders is automatically adjusted so that the pressure in the high-pressure air storage tank 32 remains constant at the set value.

[0022] The high-pressure air tank 32 of the first system S1 and the high-pressure air tank 32 of the second system S2 are connected to each other by a tank connecting pipe 51. If the pressurized oxidation leaching facility AA has three or more systems of pressurized oxidation leaching devices, the high-pressure air tanks 32 of all the systems are connected to each other by the tank connecting pipes 51.

[0023] It is preferable to provide an on-off valve 52 on the storage tank connecting pipe 51. When the on-off valve 52 is closed, the high-pressure air storage tank 32 of the first system S1 is separated from the high-pressure air storage tank 32 of the second system S2. This allows the first system S1 and the second system S2 to be controlled independently. When the on-off valve 52 is open, the high-pressure air storage tank 32 of the first system S1 and the high-pressure air storage tank 32 of the second system S2 are connected, allowing the exchange of high-pressure air between them. In this state, the high-pressure air in the high-pressure air storage tank 32 of the first system S1 can also be supplied to the autoclave 10 of the second system S2 via the storage tank connecting pipe 51. Conversely, the high-pressure air in the high-pressure air storage tank 32 of the second system S2 can also be supplied to the autoclave 10 of the first system S1.

[0024] It is preferable that, if an abnormality occurs in any of the multiple lines of pressure oxidation leaching apparatus S1, S2 of the pressure oxidation leaching system AA, the on-off valve 52 is automatically closed and the storage tank connecting pipe 51 is blocked. This configuration prevents secondary damage in the event of an equipment malfunction and allows the pressure oxidation leaching system AA to be operated safely. If the pressure oxidation leaching system AA has three or more lines of pressure oxidation leaching apparatus, the high-pressure air storage tanks 32 of each line will be connected by multiple storage tank connecting pipes 51. In this configuration, if an abnormality occurs in any of the multiple lines of pressure oxidation leaching apparatus, it is sufficient to block only the storage tank connecting pipe 51 connected to the high-pressure air storage tank of the line with the abnormality.

[0025] The term "abnormality" used here specifically refers to the interlock conditions in cases where an interlock has been installed to automatically shut down the air compressor to prevent secondary damage in the event of equipment trouble. For example, an abnormality would occur if a high-pressure substance were to burst due to a problem with the equipment, such as a hole caused by wear.

[0026] The pressurized oxidation leaching facility AA has a control device 60. A computer comprising a CPU, memory, etc. can be used as the control device 60. The control device 60 controls the various devices that make up the pressurized oxidation leaching facility AA.

[0027] The present inventors have discovered the following regarding the relationship between the amount of high-pressure air supplied to the autoclave 10 and the amount of metal sulfide supplied. Because high-pressure air is consumed as an oxidizing agent in the oxidative leaching reaction of metal sulfides, an increase in the amount of metal sulfide supplied requires an increase in the amount of high-pressure air supplied. In other words, under conditions that allow the oxidative leaching reaction of metal sulfides to proceed appropriately, the amount of high-pressure air supplied and the amount of metal sulfide supplied are roughly positively correlated.

[0028] However, if the supply rate of metal sulfide is reduced, the residence time of the metal sulfide in the autoclave 10 is increased, accelerating the oxidative leaching reaction. As a result, the oxidative leaching reaction of the metal sulfide proceeds appropriately even with a small amount of air relative to the supply rate of metal sulfide. Therefore, the relationship between the supply rate of high-pressure air and the supply rate of metal sulfide is not a direct proportional relationship but a positive linear relationship.

[0029] Specifically, when the conditions are such that the leaching rate of metal sulfide is the target value, the relationship between the supply amount of high-pressure air and the supply amount of metal sulfide is as shown in the graph in Figure 2(A). Hereinafter, the supply amount of metal sulfide determined relative to the supply amount of high-pressure air so that the leaching rate of metal sulfide is the target value is referred to as the appropriate supply amount of metal sulfide. If the supply amount of high-pressure air to the autoclave 10 is specified and the supply amount of metal sulfide is set to the appropriate supply amount relative to the specified supply amount of high-pressure air, the leaching rate of metal sulfide will be the target value. Note that the leaching rate of metal sulfide refers to the proportion of metal sulfide that is oxidatively leached out of the metal sulfide supplied to the autoclave 10.

[0030] The relationship between the amount of high-pressure air supplied to the autoclave 10 and the appropriate amount of metal sulfide supplied is expressed by a linear function. Specifically, it is expressed by the following formula (1). y=ax+b (1) Here, y is the appropriate supply amount of metal sulfide, and x is the supply amount of high-pressure air.

[0031] The coefficient a is a positive number (greater than 0). This means that the greater the supply amount of compressed air x, the greater the appropriate supply amount of metal sulfide y. The coefficient b is also a positive number. This means that the smaller the supply amount of metal sulfide, the more the oxidation leaching reaction of metal sulfide will proceed even with a smaller amount of air relative to the supply amount of metal sulfide.

[0032] If the relationship between the discharge air volume of the air compressors 21, 22 and the amount of electricity consumed is roughly directly proportional, then the relationship between the supply amount of metal sulfide and the unit electricity consumption of the air compressors 21, 22 is as shown in the graph of Figure 2(B). The smaller the supply amount of metal sulfide, the smaller the unit electricity consumption of the air compressors 21, 22. This is because the smaller the supply amount of metal sulfide, the smaller the amount of air required for oxidative leaching of the metal sulfide relative to the supply amount of metal sulfide, and the power consumption of the air compressors 21, 22 is reduced. Thus, from the perspective of reducing the unit electricity consumption of the air compressors 21, 22, the smaller the supply amount of metal sulfide, the better.

[0033] [Pressure oxidation leaching method] Next, the pressure oxidation leaching method using the pressure oxidation leaching equipment AA will be explained. Below, we will explain in order the normal operation in which all of the lines of the pressurized oxidation leaching equipment AA are operating normally, and the emergency operation in which the air compressors 21, 22 of some of the lines have stopped.

[0034] (1) Normal operation During normal operation, in all systems, high-pressure air produced by air compressors 21 and 22 is supplied to autoclave 10, and pressurized oxidation leaching of metal sulfides is carried out in autoclave 10. High-pressure air is supplied to autoclave 10 in first system S1 from high-pressure air storage tank 32 in first system S1. Also, high-pressure air is supplied to autoclave 10 in second system S2 from high-pressure air storage tank 32 in second system S2.

[0035] Here, the on-off valve 52 of the storage tank connecting pipe 51 may be opened. In this case, the high-pressure air storage tank 32 of the first system S1 and the high-pressure air storage tank 32 of the second system S2 are connected, and the high-pressure air stored therein will be at substantially the same pressure. Furthermore, the high-pressure air produced by the air compressors 21, 22 of the first system S1 and the high-pressure air produced by the air compressors 21, 22 of the second system S2 will be shared by the autoclave 10 of the first system S1 and the autoclave 10 of the second system S2.

[0036] The on-off valve 52 of the storage tank connecting pipe 51 may be closed. In this case, the high-pressure air storage tank 32 of the first system S1 and the high-pressure air storage tank 32 of the second system S2 are separated, and the first system S1 and the second system S2 become independent systems. The high-pressure air produced by the air compressors 21 and 22 of the first system S1 is supplied only to the autoclave 10 of the first system S1. The high-pressure air produced by the air compressors 21 and 22 of the second system S2 is supplied only to the autoclave 10 of the second system S2.

[0037] (2) Emergency operation Due to maintenance, malfunctions, etc., the air compressors 21, 22 of some of the lines may be stopped. In this case, the pressurized oxidation leaching equipment AA is switched from normal operation to emergency operation. If the on-off valve 52 of the storage tank connecting pipe 51 is open during normal operation, it remains open. If the on-off valve 52 of the storage tank connecting pipe 51 is closed during normal operation, it is switched to the open state. In other words, the high-pressure air storage tanks 32 of all lines are brought into communication via the storage tank connecting pipe 51.

[0038] Even when the air compressors 21, 22 of some of the lines are stopped, the air compressors 21, 22 of the remaining lines remain in operation. The high-pressure air produced by the air compressors 21, 22 of the remaining lines that are still in operation is distributed and supplied to the autoclaves 10 of all lines via the storage tank connecting pipes 51. In other words, the operation of the autoclaves 10 of all lines continues, including the line of the stopped air compressors 21, 22. Raw material slurry is supplied to the autoclaves 10 of all lines, and pressure oxidative leaching of metal sulfides is performed.

[0039] For example, suppose that the air compressors 21 and 22 of the first system S1 are stopped. In this case, the high-pressure air produced by the air compressors 21 and 22 of the second system S2 is supplied to the autoclave 10 of the second system S2. The high-pressure air produced by the air compressors 21 and 22 of the second system S2 is also supplied to the autoclave 10 of the first system S1 via the storage tank connecting pipe 51.

[0040] The discharge air volume of the operating air compressors 21, 22 may be the same as during normal operation, or may be increased (up to the maximum discharge air volume) within the limits of the capacity of the air compressors 21, 22. However, since the high-pressure air produced by the operating air compressors 21, 22 is distributed and supplied to the autoclaves 10 in all lines, the amount of high-pressure air supplied to the autoclaves 10 in each line is generally less than during normal operation.

[0041] The amount of metal sulfide supplied to the autoclave 10 of each series is set to an appropriate amount relative to the amount of high-pressure air supplied. Here, the relationship between the amount of high-pressure air supplied to the autoclave 10 of each series and the appropriate amount of metal sulfide supplied is determined in advance. This relationship is preferably determined so that the leaching rate of the metal sulfide becomes a target value. For example, it is determined as a linear function expressed by the above-mentioned formula (1).

[0042] Based on the relationship between the amount of high-pressure air supplied to the autoclave 10 and the appropriate amount of metal sulfide supplied, the amount of metal sulfide supplied to the autoclave 10 in each series is set to an appropriate amount relative to the actual amount of high-pressure air supplied.

[0043] In the past, for example, when the air compressors 21 and 22 of the first system S1 were stopped, the autoclave 10 of the same system, the first system S1, was also stopped. That is, all of the equipment of the first system S1 was stopped, and operation was carried out only with the second system S2. Then, to prevent a decrease in production of metal sulfates, the amount of raw material slurry supplied to the autoclave 10 of the second system S2 was increased. As a result, the electricity consumption rate of the air compressors 21 and 22 increased.

[0044] In contrast, in this embodiment, even if the air compressors 21, 22 of some lines are stopped, the autoclaves 10 of all lines are operated using high-pressure air produced by the air compressors 21, 22 of the remaining lines. Operating all the autoclaves 10 increases the total volume of the autoclaves 10 in the entire pressurized oxidation leaching system AA compared to operating only some of the autoclaves 10. This increases the residence time of metal sulfides in the autoclaves 10, allowing the oxidation leaching reaction to proceed even with a small amount of air. As a result, the metal sulfide leaching rate can be maintained high, and the deterioration of the power consumption rate of the air compressors 21, 22 can be suppressed. Furthermore, the reduction in production of metal sulfate aqueous solution can be minimized.

[0045] As described above, during emergency operation in which the air compressors 21, 22 of some series are stopped due to maintenance or a malfunction, it has been explained that it is possible to suppress a deterioration in the power consumption rate of the air compressors 21, 22. However, it is also possible to intentionally stop the air compressors 21, 22 of some series regardless of maintenance or a malfunction, thereby actively improving the power consumption rate of the air compressors 21, 22.

[0046] For example, if the processing load of the raw slurry is lower (e.g., 80%) than the processing capacity of the pressurized oxidation leaching equipment AA, stopping the air compressors 21, 22 of some of the lines and distributing and supplying the high-pressure air produced by the air compressors 21, 22 of the remaining lines to the autoclaves 10 of all of the lines may improve the power consumption. In this case, it may be necessary to increase the discharge air volume of each of the operating air compressors 21, 22, because this may reduce the amount of power consumed relative to the amount of discharged air. Note that stopping the air compressors 21, 22 also includes, for example, stopping only one of the four air compressors 21 in Figure 1. [Example]

[0047] Next, an example will be described. Pressure oxidation leaching was carried out using the pressure oxidation leaching equipment shown in Figure 1. The operating conditions were as follows: Raw material: Nickel-cobalt mixed sulfide Nickel content of raw material: 57.0-58.5% by weight Cobalt content of raw material: 4.0 to 6.0% by weight Solids concentration of raw slurry: 225-270g / L Gas phase pressure inside the autoclave (gauge pressure): 1.8 to 1.9 MPaG

[0048] The pressurized oxidation leaching facility has two lines of pressurized oxidation leaching equipment. Each line has two turbo compressors, a medium-pressure air storage tank, a reciprocating compressor, and a high-pressure air storage tank. However, the maximum discharge air volumes of the turbo compressor and reciprocating compressor differ between the first and second lines. Maximum air discharge volume of the first turbo compressor: 3,100 Nm 3 / hour x 2 units Maximum air discharge volume of the first reciprocating compressor: 6,200 Nm 3 / time Maximum air discharge volume of the second turbo compressor: 4,000 Nm 3 / hour x 2 units Maximum air discharge volume of the second reciprocating compressor: 8,000 Nm 3 / time

[0049] The first-system turbo compressor adjusts the amount of discharged air by throttling the suction valve when the amount is between 80 and 100% of the maximum amount of discharged air. When the amount is below 80% of the maximum amount of discharged air, the amount of discharged air is adjusted by opening the blow-off valve. The second-system turbo compressor adjusts the amount of discharged air by throttling the suction valve when the amount is between 80 and 100% of the maximum amount of discharged air. When the amount is below 80% of the maximum amount of discharged air, the amount of discharged air is adjusted by repeating no-load and loaded operation.

[0050] The relationship between the amount of compressed air supplied to the autoclave in the first series and the amount of raw slurry supplied when the leaching rate of nickel-cobalt mixed sulfide reached the target value is shown in Table 1 and Figure 3(A). Similarly, the relationship between the amount of compressed air supplied to the autoclave in the second series and the amount of raw slurry supplied when the leaching rate of nickel-cobalt mixed sulfide reached the target value is shown in Table 2 and Figure 3(B).

[0051] [Table 1]

[0052] [Table 2]

[0053] As is clear from Figures 3(A) and 3(B), when the target leaching rate of nickel-cobalt mixed sulfide is required, the relationship between the amount of compressed air supplied to the autoclave and the amount of raw slurry supplied can be expressed as a linear function. The measurement points of the first and second systems were fitted with a linear function to determine the relationship between the amount of compressed air supplied to the autoclave and the appropriate amount of raw slurry supplied.

[0054] The nickel-cobalt mixed sulfide content of the raw slurry is almost constant, so the relationship between the amount of compressed air supplied to the autoclave and the amount of nickel-cobalt mixed sulfide supplied follows the same trend as the relationship between the amount of compressed air supplied to the autoclave and the amount of raw slurry supplied.

[0055] Example 1 The air compressor for System 1 was stopped and the on-off valve on the storage tank connection pipe was left open. The high-pressure air produced by the air compressor for System 2 was distributed and supplied to the autoclaves in Systems 1 and 2, allowing the autoclaves in Systems 1 and 2 to continue operating. The discharge air volume and power consumption of the air compressor for System 2 are shown in Table 3. The amount of high-pressure air supplied to the autoclaves in Systems 1 and 2 is shown in Table 3.

[0056] The feed rate of raw slurry to the autoclave of the first system was set to an appropriate feed rate based on the relationship between the feed rate of high-pressure air to the autoclave of the first system and the appropriate feed rate of raw slurry, obtained by fitting the measurement points shown in Figure 3(A). Similarly, the feed rate of raw slurry to the autoclave of the second system was set to an appropriate feed rate based on the relationship between the feed rate of high-pressure air to the autoclave of the second system and the appropriate feed rate of raw slurry, obtained by fitting the measurement points shown in Figure 3(B). The feed rates of raw slurry to the autoclaves of the first and second systems are shown in Table 3.

[0057] [Table 3]

[0058] Example 2 The air compressor for System 2 was stopped and the on-off valve on the storage tank connecting pipe was left open. The high-pressure air produced by the air compressor for System 1 was distributed and supplied to the autoclaves in Systems 1 and 2, and the autoclaves in Systems 1 and 2 continued to operate. The discharge air volume and power consumption of the air compressor for System 1 are shown in Table 4. The amount of high-pressure air supplied to the autoclaves in Systems 1 and 2 is shown in Table 4. The amount of raw material slurry supplied to the autoclaves in Systems 1 and 2 was set to the appropriate supply amount. The amount of raw material slurry supplied to the autoclaves in Systems 1 and 2 is shown in Table 4.

[0059] [Table 4]

[0060] (Comparative Example 1) The air compressor for System 1 was stopped, and the on-off valve of the storage tank connecting pipe was closed. The autoclave for System 1 was also stopped. In other words, System 1 was stopped, and operation was carried out using only System 2. The discharge air volume and power consumption of the air compressor for System 2 are shown in Table 5. All of the high-pressure air produced by the air compressor for System 2 was supplied to the autoclave for System 2. The supply volume of raw slurry to the autoclave for System 2 was set to the appropriate supply volume. The supply volume of raw slurry to the autoclave for System 2 is shown in Table 5.

[0061] [Table 5]

[0062] (Comparative Example 2) The air compressor for System 2 was stopped, and the on-off valve of the storage tank connecting pipe was closed. The autoclave for System 2 was also stopped. In other words, System 2 was stopped, and operation was carried out using only System 1. The discharge air volume and power consumption of the air compressor for System 1 are shown in Table 6. All of the high-pressure air produced by the air compressor for System 1 was supplied to the autoclave for System 1. The supply volume of raw slurry to the autoclave for System 1 was set to the appropriate supply volume. The supply volume of raw slurry to the autoclave for System 1 is shown in Table 6.

[0063] [Table 6]

[0064] Figure 4(A) shows the relationship between the total feed rate of raw slurry and the total power consumption of the air compressor, which was created based on the results of Example 1 and Comparative Example 1. Figure 4(B) shows the relationship between the total feed rate of raw slurry and the total power consumption of the air compressor, which was created based on the results of Example 2 and Comparative Example 2. Here, the total feed rate of raw slurry is the sum of the feed rate of raw slurry to the autoclave in the first system and the feed rate of raw slurry to the autoclave in the second system. The total power consumption of the air compressors is the sum of the power consumption of all air compressors in the first system and the second system.

[0065] As can be seen from Fig. 4(A), Example 1 has a smaller total amount of power consumed by the air compressor relative to the total amount of raw slurry supplied, compared to Comparative Example 1. This means that Example 1 has a smaller power consumption rate for the air compressor, compared to Comparative Example 1. As can be seen from Fig. 4(B), Example 2 and Comparative Example 2 also have a similar tendency.

[0066] This confirmed that when air compressors in some lines are stopped, the deterioration of the electricity consumption rate of the air compressors can be suppressed by distributing and supplying the high-pressure air produced by the air compressors in the remaining lines to the autoclaves in all lines and continuing to operate the autoclaves in all lines. [Explanation of symbols]

[0067] AA pressurized oxidation leaching equipment S1, S2 Pressure oxidation leaching equipment 10 Autoclave 21 Turbo Compressor 22 Reciprocating compressor 31 Medium pressure air storage tank 32 High-pressure air storage tank 41 High-pressure air supply pipe 42 Flow control valve 51 Storage tank connecting pipe 52 On-off valve 60 Control device

Claims

1. A pressure oxidation leaching method using multiple series of pressure oxidation leaching apparatuses, each having a single series of autoclaves and air compressors, comprising: When the air compressors of some of the lines are stopped, high-pressure air produced by the air compressors of the remaining lines is distributed and supplied to the autoclaves of all the lines; A raw material slurry containing metal sulfides is supplied to all of the autoclaves in the series, and the metal sulfides are subjected to pressure oxidative leaching to produce an aqueous metal sulfate solution. A pressure oxidation leaching method characterized by:

2. a relationship between an amount of the high-pressure air supplied to the autoclave and an appropriate amount of the metal sulfide supplied to the autoclave is determined in advance; Based on the relationship, the amount of metal sulfide supplied to the autoclave is set to an appropriate amount relative to the actual amount of high-pressure air supplied.

2. The pressure oxidative leaching method according to claim 1 .

3. The relationship between the amount of the high-pressure air supplied to the autoclave and the appropriate amount of the metal sulfide supplied is determined so that the leaching rate of the metal sulfide becomes a target value.

3. The pressure oxidative leaching method according to claim 2.

4. The relationship between the amount of high-pressure air supplied to the autoclave and the appropriate amount of metal sulfide supplied is expressed by the following formula:

4. The pressure oxidative leaching method according to claim 3. y = ax + b Here, y is the appropriate supply amount of the metal sulfide, x is the supply amount of the high-pressure air, and coefficients a and b are positive numbers.

5. Equipped with multiple lines of pressure oxidation leaching equipment, Each of the plurality of pressure oxidation leaching apparatuses comprises: an autoclave to which a raw material slurry containing a metal sulfide is supplied and which performs pressure oxidative leaching of the metal sulfide to produce an aqueous metal sulfate solution; an air compressor for producing high-pressure air; a high-pressure air storage tank that stores the high-pressure air produced by the air compressor; a high-pressure air supply pipe that supplies the high-pressure air in the high-pressure air storage tank to the autoclave, the plurality of high-pressure air storage tanks are connected to each other by storage tank connecting pipes, The high-pressure air in the high-pressure air storage tank can be supplied to the autoclaves in other series via the storage tank connecting pipe. A pressurized oxidation leaching facility characterized by:

6. The storage tank connecting pipe is provided with an on-off valve.

6. The pressurized oxidation leaching facility according to claim 5.

7. When an abnormality occurs in any of the pressurized oxidation leaching apparatuses in the plurality of systems, the on-off valve automatically closes the storage tank connecting pipe that connects to the high-pressure air storage tank in the system in which the abnormality occurs.

7. The pressurized oxidation leaching facility according to claim 6.

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