Atomizing device, method for producing metal powder, and method for producing valuable metal

Abstract

The present invention provides a technology for stabilizing the supply amount of molten metal when manufacturing metal powder by atomization processing, thereby obtaining metal powder with small deviation in particle size. The present invention is an atomizing device (1) for manufacturing metal powder by spraying fluid into molten metal (M), comprising: a tundish (11) into which the molten metal (M) is injected and discharged from a liquid discharge nozzle (11N) installed at a bottom (11b); a fluid injection nozzle (12) arranged below the tundish (11) and injecting fluid into the molten metal (M) falling from the tundish (11); a mechanism for measuring the liquid level (Mh) in the tundish (11) by taking an image obtained by photographing the inside of the tundish (11); and a mechanism for calculating the amount of molten metal (M) injected into the tundish (11) based on the liquid level (Mh) and injecting the molten metal (M) in such a manner as to keep the liquid level substantially constant. The interior of the tundish (11) is formed into a shape in which the liquid surface area of ​​the injected molten metal (M) increases upward in the vertical direction.

Description

Technical Field

[0001] The present invention relates to an atomizing device, a method for producing metal powder using the atomizing device, and a method for producing valuable metal. Background Art

[0002] In recent years, lithium-ion batteries have become increasingly popular as lightweight, high-output secondary batteries. A lithium-ion battery consists of a negative electrode material, a positive electrode material, a separator, and an electrolyte solution containing an electrolyte such as lithium hexafluorophosphate (LiPF6), enclosed within a metal outer can made of aluminum or iron. The negative electrode material is composed of a negative electrode active material such as graphite fixed to a negative electrode current collector made of copper foil. The positive electrode material is composed of a positive electrode active material such as lithium nickelate or lithium cobaltate fixed to a positive electrode current collector made of aluminum foil. The separator is composed of a porous organic resin film such as polypropylene.

[0003] One of the main applications of lithium-ion batteries is in hybrid and electric vehicles. When the vehicle or the battery itself reaches the end of its life, the lithium-ion batteries used in them become waste. Given the lifecycle of vehicles, it is expected that the lithium-ion batteries used in vehicles will be discarded in large quantities in the future.

[0004] Many proposals have been made to recycle such used batteries or defective products generated during manufacturing (hereinafter collectively referred to as "spent lithium-ion batteries") as resources. For example, Patent Document 1 proposes a method in which spent lithium-ion batteries with aluminum outer cans are placed on a mesh, heated at a temperature above approximately 660°C (the melting point of aluminum), causing the aluminum material to melt and fall through the mesh of the mesh. The molten aluminum material is then separated from the non-molten material that constitutes the battery body by leaving it on the mesh.

[0005] Furthermore, by adding a flux such as calcium oxide to waste lithium-ion batteries to lower the melting point of their mixture with aluminum oxide and then melting them in air at temperatures above 1400°C, they can be separated into alloys containing metals such as copper, nickel, cobalt, and iron, whose so-called standard free energy of formation of oxides is higher than that of carbon, and oxides containing metals such as aluminum, calcium, and lithium, whose oxide free energy of formation is lower than that of carbon. If copper can be separated from an alloy primarily containing copper, nickel, cobalt, and iron, it can be recycled as copper metal using existing copper smelting processes, while nickel and cobalt can be recycled as nickel and cobalt metal using existing nickel or cobalt smelting processes. This allows for the low-cost recovery of valuable metals.

[0006] However, when copper-nickel-cobalt-iron alloys are put into existing copper smelting processes, although copper and nickel are separated and recovered, cobalt is distributed to oxides along with iron, making it difficult to recover cobalt as a single substance. Therefore, research is underway to acid-leach the copper-nickel-cobalt alloy, dissolving the nickel and cobalt in a solvent, separating the copper as a dissolved residue, and reusing existing smelting processes to recover copper, nickel, and cobalt. While copper-nickel-cobalt alloys typically have high corrosion resistance, depending on their particle morphology, such as particle size, shape, surface roughness, and composition distribution, they may not dissolve at all in sulfuric acid for more than 24 hours. Therefore, a copper-nickel-cobalt alloy that stably dissolves in acid is desired.

[0007] Regarding this copper-nickel-cobalt alloy, for example, it has been proposed to improve its acid leachability by powdering it by a gas atomization method.

[0008] Prior art literature

[0009] Patent Literature

[0010] Patent Document 1: Japanese Patent Application Laid-Open No. 04-276006. Summary of the Invention

[0011] Problems to be solved by the invention

[0012] Regarding copper-nickel-cobalt alloy powder, the alloy powder was classified and its acid leaching properties in sulfuric acid solutions with a pH of 0.5 to 3 were investigated. The results showed that fine powder with a particle size of less than 10 μm reacted violently with concentrated sulfuric acid, making it difficult to control the pH concentration. On the other hand, coarse powder with a particle size of more than 300 μm was difficult to dissolve.

[0013] When molten metals such as copper-nickel-cobalt alloys are powdered using atomization, it has been confirmed that the particle size distribution of the resulting metal powder exhibits a so-called bimodal distribution, with a peak appearing on the coarser side of the target particle size. The generation of coarse particles associated with this bimodal distribution reduces the dissolution rate during acid leaching. Consequently, the generated coarse particles must be classified and removed, resulting in reduced productivity.

[0014] One of the reasons for the bimodal distribution caused by powderization based on the atomization method is known to be the time period when the liquid level of the ladle is maintained at the target height during the atomization process, and the time period when the alloy melt is over-injected from the melting furnace, causing the liquid level to rise. When the liquid level is high, the supply of the alloy melt to the atomization and crushing part temporarily increases, and the particle size after crushing increases.

[0015] It should be noted that, for example, Patent Document 1 discloses a method for maintaining a constant ratio between the injection flow rate and the molten metal flow rate by varying the injection pressure and / or flow rate while measuring the liquid level (liquid level height) within the tundish with a detector (liquid level gauge). By performing this operation during the atomization process, the molten metal stream flowing from the tundish can be easily atomized to a predetermined particle size distribution and predetermined particle size.

[0016] The present invention has been completed in view of the above-mentioned facts, and its purpose is to provide a technology for stabilizing the supply amount of molten metal when manufacturing metal powder by atomization processing, for example, when recovering valuable substances such as copper, nickel, and cobalt contained in waste lithium-ion batteries, thereby obtaining metal powder (atomized powder) with small particle size deviation.

[0017] Technical solutions to problems

[0018] (1) The first invention of the present invention is an atomizing device, which is an atomizing device for producing metal powder by spraying a fluid into a molten metal, and comprises: a tundish, into which the molten metal is injected and from which the molten metal is discharged from a liquid discharge nozzle installed at the bottom; and a fluid injection nozzle, which is arranged below the tundish and sprays the fluid onto the molten metal falling from the tundish, wherein the tundish is formed at least inside thereof in a shape in which the liquid surface area of ​​the injected molten metal increases as it goes upward in the vertical direction, and the atomizing device comprises: a mechanism for measuring the liquid level of the molten metal in the tundish based on an image taken by photographing the inside of the tundish; and a mechanism for calculating the amount of the molten metal injected into the tundish based on the measured liquid level, and injecting the molten metal in a manner so as to keep the liquid level approximately constant.

[0019] (2) The second invention of the present invention is an atomizing device. In the first invention, the mechanism for measuring the liquid level of the molten metal in the tundish utilizes a thermal image, and the thermal image is obtained based on infrared rays radiated from the tundish.

[0020] (3) A third invention of the present invention is an atomizing device, wherein in the first invention or the second invention, the fluid jetting nozzle jets high-pressure water as the fluid.

[0021] (4) The fourth invention of the present invention is an atomizing device, wherein in any one of the first to third inventions, the molten metal contains copper, nickel and cobalt, and the metal powder includes alloy powder containing copper, nickel and cobalt as constituent components.

[0022] (5) The fifth invention of the present invention is an atomizing device, which is used in the fourth invention to produce alloy powder for acid leaching in the process of recovering valuable metals from waste lithium-ion batteries.

[0023] (6) The sixth invention of the present invention is a method for manufacturing metal powder, which is a method for manufacturing metal powder using an atomizing device that sprays fluid into molten metal to manufacture metal powder, the atomizing device comprising: a tundish, into which the molten metal is injected and from which the molten metal is discharged from a liquid discharge nozzle installed at the bottom; and a fluid injection nozzle, which is arranged below the tundish and sprays the fluid onto the molten metal falling from the tundish; the tundish is formed at least inside thereof in a shape in which the liquid surface area of ​​the injected molten metal increases as it goes upward in the vertical direction, the atomizing device also comprising: a mechanism for measuring the liquid level of the molten metal in the tundish based on an image taken by photographing the inside of the tundish; and a mechanism for calculating the amount of molten metal injected into the tundish based on the measured liquid level, and injecting the molten metal in a manner that keeps the liquid level approximately constant.

[0024] (7) The seventh invention of the present invention is a method for producing metal powder, wherein in the sixth invention, the molten metal contains copper, nickel and cobalt, and the method produces alloy powder containing copper, nickel and cobalt as constituent components.

[0025] (8) The eighth invention of the present invention is a method for producing valuable metals, which is a method for producing valuable metals from waste lithium-ion batteries, comprising: a step of producing an alloy powder containing copper, nickel and cobalt as constituent components from an alloy melt from the waste lithium-ion batteries; and a step of leaching the alloy powder with an acid; in the step of producing the alloy powder, an atomizing device is used to produce the alloy powder by spraying a fluid into the alloy melt, the atomizing device comprising: a tundish into which the molten metal is injected and from which the molten metal is discharged from a liquid discharge nozzle installed at the bottom; and A fluid injection nozzle is arranged below the tundish and injects the fluid toward the molten metal falling from the tundish. The tundish is formed at least inside thereof in a shape in which the liquid surface area of ​​the injected molten metal increases as it goes upward in the vertical direction. The atomizing device also has: a mechanism for measuring the liquid level of the molten metal in the tundish based on an image taken by photographing the inside of the tundish; and a mechanism for calculating the amount of molten metal injected into the tundish based on the measured liquid level, and injecting the molten metal in a manner so that the liquid level remains approximately constant.

[0026] Effects of the Invention

[0027] According to the present invention, the supply rate of molten metal from a tundish in an atomizing device can be stabilized, and metal powder with small variations in particle size can be produced.

[0028] Thus, for example, in a method for recovering valuable metals from waste lithium-ion batteries, even when copper-nickel-cobalt alloy powder is produced by atomization processing, the particle size deviation of the obtained alloy powder is suppressed, and alloy particles that are easy to control acid leaching can be effectively obtained as alloy powder for acid leaching treatment. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 This is a diagram showing an example of the configuration of an atomizing device.

[0030] Figure 2 It is a vertical cross-sectional view of the interior of the tundish, and is a diagram showing an example of the internal shape.

[0031] Figure 3 It is a vertical cross-sectional view of the interior of the tundish, and is a diagram showing an example of the internal shape.

[0032] Figure 4 FIG. 1 is a diagram showing a conventional tundish having a cylindrical inner shape.

[0033] Figure 5 This is a vertical cross-sectional view of the interior of a tundish, used to illustrate the function by comparing the shape with a conventional tundish. DETAILED DESCRIPTION

[0034] Hereinafter, a specific embodiment of the present invention (hereinafter referred to as "the present embodiment") will be described in detail. It should be noted that the present invention is not limited to the following embodiment, and various modifications can be made without changing the gist of the present invention. In addition, in this specification, the expression "X to Y" (X and Y are arbitrary numerical values) means "X or more and Y or less".

[0035] 1. Atomization device

[0036] <1-1. Summary>

[0037] An atomizer produces metal powder by spraying a fluid such as high-pressure water or gas onto molten metal, breaking it into droplets and solidifying the shattered and scattered droplets. The term "droplet-like" refers to the molten metal in the form of liquid droplets (molten droplets). The resulting metal powder is also called atomized powder.

[0038] Figure 1 This figure shows an example of the configuration of an atomizing device according to this embodiment. The atomizing device 1 includes a tundish 11 for discharging molten metal M injected from a melting furnace (crucible furnace) 3; a fluid injection nozzle 12 for injecting fluid onto the molten metal M falling from the tundish 11; and a chamber 13. The fluid injection nozzle 12 is disposed above the chamber 13, which serves as a location for forming droplets by injecting fluid to generate metal powder.

[0039] In the atomizing device 1 , at least the inner shape of the tundish 11 is formed in such a shape that the liquid surface area of ​​the poured molten metal M increases upward in the vertical direction.

[0040] In addition, the atomizing device 1 includes: a measuring unit 31 for measuring the height of the liquid level Ms (liquid level height Mh) of the molten metal M in the tundish 11; and a control unit 32 for controlling the amount of molten metal M injected into the tundish 11 based on the liquid level height Mh measured by the measuring unit 31.

[0041] The measuring unit 31 obtains an image of the liquid surface Ms of the molten metal M in the tundish 11 by photographing the inside of the tundish 11, and measures the liquid level Mh based on the image. For example, it is preferable to photograph a thermal image obtained by infrared rays radiated from the tundish 11. The measuring unit 31 can calculate the area of ​​the liquid surface Ms by photographing the image of the liquid surface Ms in the tundish 11. As described above, in the atomizing device 1, the internal shape of the tundish 11 is formed in a shape in which the area of ​​the liquid surface Ms of the injected molten metal M increases as it moves upward in the vertical direction. Therefore, when the liquid level Mh fluctuates up and down, it can be detected based on the difference in the area of ​​the liquid surface Ms, so that the liquid level Mh can be accurately measured.

[0042] Methods utilizing sound waves or light reflection are also conceivable as methods for measuring the liquid level Mh within the tundish 11. However, since the liquid level Ms of the molten metal M may fluctuate due to pouring or be affected by, for example, hot air currents generated above the liquid level Ms due to the high temperature of the molten metal M, accurate measurement of the liquid level Mh may be impossible. In this regard, the measuring unit 31 captures an image of the liquid level Ms of the molten metal M within the tundish 11 and calculates the area from the image to measure the liquid level. This allows accurate and efficient measurement of the liquid level Mh without being affected by various factors.

[0043] exist Figure 2 and Figure 3 11A and 11B are shown with different ratios of opening diameter R1 to bottom diameter R2. While the ratio of opening diameter R1 to bottom diameter R2 is not particularly limited, the ratio represented by R2 / R1 is preferably between approximately 0.25 and 0.65, and more preferably between approximately 0.30 and 0.55. By preferably maintaining such a ratio in the tundish 11, fluctuations in the liquid level Mh can be more easily and accurately detected.

[0044] According to this atomizing device 1, the liquid level of the molten metal M in the tundish 11 can be maintained substantially constant, thereby stabilizing the supply rate of the molten metal M from the tundish 11. As a result, the molten metal M supplied at a stable supply rate can suppress variations in the particle size of the metal powder produced by injecting a fluid into the molten metal M.

[0045] Furthermore, the atomizing device 1 is preferably used, for example, as a device for producing alloy powder (copper-nickel-cobalt alloy) for use in an acid leaching process (acid leaching) from a molten metal (alloy melt) M containing copper (Cu), nickel (Ni), and cobalt (Co) in a process for recovering valuable metals from waste lithium-ion batteries. Specifically, the atomizing device 1 stabilizes the supply of the alloy melt M from the tundish 11 and efficiently produces alloy powder with reduced particle size variation. Therefore, by using such alloy powder for acid leaching, the leaching efficiency of valuable metals such as Ni and Co can be effectively improved.

[0046] It should be noted that in Figure 1 1 shows a water atomizing device 1, which uses high-pressure water as the fluid ejected from the fluid ejecting nozzle 12. In the following, the water atomizing device is used as an example to continue the description, but even a gas atomizing device that uses gas as the fluid can be well applied. Figure 1 In FIG. 1 , although the atomizing device 1 is not included, the melting furnace 5 for injecting the molten metal M into the tundish 11 is also shown.

[0047] 1-2. Components of the Atomizer

[0048] [Tundish]

[0049] The tundish 11 stores molten metal M poured from the melting furnace 5 and discharges the molten metal M from a discharge nozzle 11N mounted on the bottom 11b into the chamber 13. The molten metal M discharged from the tundish 11 freely falls from the discharge nozzle 11N and is supplied into the chamber 13.

[0050] It should be noted that discharging the molten metal M from the liquid discharge nozzle 11N into the chamber 13 is also referred to as "supplying" the molten metal M. As will be described in detail later, the molten metal M freely falling from the liquid discharge nozzle 11N collides with the high-pressure water ejected from the fluid injection nozzle 12 provided at an upper position of the chamber 13 and forms droplets, which are then supplied into the chamber 13 in a scattered state.

[0051] The tundish 11 is formed at least inside such a shape that the liquid surface area of ​​the molten metal M poured from the melting furnace 5 and accumulated increases as it goes upward in the vertical direction. Figure 1 The up and down directions in the composition drawings shown are Figure 1The vertical direction of the tundish 11 shown in the vertical section. In other words, it is the direction in which the molten metal M is gradually stored from the bottom 11b to the upper opening 11a in the tundish 11. In addition, the liquid level of the molten metal M is Figure 1 The portion indicated by "Ms" in the figure refers to the upper surface of the molten metal M poured into and accumulated in the tundish 11. For example, if the interior of the tundish 11 has an inverted truncated cone shape, the liquid surface of the molten metal M is a substantially circular surface. The area of ​​the liquid surface Ms refers to the area of ​​the upper surface of the molten metal M. The opening 11a is provided near the upper portion of the tundish 11 and is used to pour the molten metal M from the melting furnace 5.

[0052] Figure 2 、 Figure 3 Each of the figures is a vertical cross-sectional view of the interior of the tundish 11, illustrating an example of the internal shape. As shown in each figure, the interior of the tundish 11 has an inverted truncated cone or an inverted cone, for example. The interior of the tundish 11 is formed such that the area of ​​the liquid level Ms gradually increases from the bottom 11b toward the upper opening 11a, that is, as the height of the liquid level Ms (liquid level height Mh) of the poured molten metal M rises.

[0053] In the tundish 11 having such an internal shape, for example, the molten metal M can be maintained almost constantly at a predetermined target liquid level Mh. That is, while the molten metal M is supplied from the liquid discharge nozzle 11N of the tundish 11, new molten metal M is continuously injected into the tundish 11 from the melting furnace 5 at a constant speed. By making the internal shape of the tundish 11 such that the area of ​​the liquid surface Ms increases as the liquid level Mh increases, the change in the liquid level Mh of the injected molten metal M becomes slow. Therefore, for example, the liquid level Mh of the molten metal M can be maintained almost constantly at a target height. It should be noted that the injection speed of the molten metal M from the melting furnace 5 to the tundish 11 is maintained at an almost constant speed. In addition, the injection of the molten metal M into the tundish 11 can be performed, for example, by tilting the melting furnace 5 (see Figure 1 ).

[0054] Furthermore, in the atomizing device 1, the measurement unit 31 measures the liquid level Mh of the molten metal M in the tundish 11. Based on this liquid level Ms, the control unit 32 automatically adjusts the inclination angle of the melting furnace 5 to adjust the amount of molten metal M poured into the tundish 11, so that the liquid level Mh remains substantially constant at a predetermined height. This allows the liquid level Mh of the molten metal M to be maintained constant with greater accuracy.

[0055] Since the supply amount (supply rate) of the molten metal M supplied from the liquid discharge nozzle 11N is caused by the pressure based on the liquid level of the molten metal M in the ladle 11, as long as the liquid level can be kept almost constant, the supply amount of the molten metal M supplied from the liquid discharge nozzle 11N per unit time can be stabilized to be almost constant according to the nozzle diameter.

[0056] It should be noted that the supply rate of the molten metal M can be appropriately set according to conditions such as the particle size of the metal powder to be produced and the injection rate of high-pressure water from the fluid injection nozzle 12 described later. For example, the supply rate of the molten metal M is set within a range of approximately 10 kg / min to 75 kg / min.

[0057] Here, the molten metal M supplied from the discharge nozzle 11N into the chamber 13 collides with the high-pressure water ejected from the fluid injection nozzle 12 above the chamber 13, forming droplets that then scatter. At this point, as the supply rate of the molten metal M from the tundish 11 changes, the size of the resulting droplets also changes, causing variations in the particle size distribution of the metal powder (atomized powder) produced within a specified timeframe. For example, if the liquid level of the molten metal M injected from the melting furnace 5 increases, the supply rate of the molten metal M from the discharge nozzle N increases based on the increased liquid level. Consequently, the size of the droplets formed by colliding with the high-pressure water ejected at a constant velocity increases, producing metal powder with relatively large particle sizes. This particle size distribution may exhibit, for example, a bimodal distribution, resulting in variations in particle size.

[0058] In this regard, the internal shape of the tundish 11 described above stabilizes the supply rate of the molten metal M as long as the liquid level of the injected molten metal M can be maintained substantially constant. This suppresses variations in the size of the molten droplets formed by the impact of the high-pressure water, and the resulting metal powder has a sharp, unimodal particle size distribution.

[0059] In addition, at the stage where the molten metal M is poured from the melting furnace 5 into the tundish 11 and the molten metal M in the tundish 11 is reduced and the liquid level is gradually lowered, for example, Figure 4 In the conventional tundish 100 having a cylindrical interior, as the liquid level decreases, the amount of molten metal supplied from the discharge nozzle 100N gradually decreases. As a result, the droplets formed by colliding with the high-pressure water jet at a constant velocity decrease in size, producing metal powder with a relatively small particle size. This particle size distribution, for example, exhibits a bimodal distribution, resulting in particle size deviations. It should be noted that Figure 4 The cylindrical shape of the interior of the tundish 100 shown is not a shape in which the liquid surface area increases as the liquid level rises, but a shape in which the liquid surface area remains constant regardless of the liquid level.

[0060] In this regard, Figure 5 As shown, the internal shape of the tundish 11 described above eliminates the portion indicated by the dashed circle in the figure, which would otherwise reduce the supply rate of the molten metal M, compared to a tundish with a cylindrical interior (the portion indicated by the phantom line). Therefore, even as the liquid level gradually decreases, the pressure fluctuations based on the liquid level are reduced, thereby maintaining a stable supply rate of the molten metal M. Furthermore, since the supply rate of the molten metal M is stabilized, variations in the size of the droplets formed by the impact of the high-pressure water can be suppressed, resulting in a sharp, unimodal particle size distribution of the resulting metal powder.

[0061] In this way, through the tundish 11, the supply amount of the molten metal M supplied from the liquid discharge nozzle 11N can be stabilized both in the stage where the molten metal M is continuously poured into the interior from the melting furnace 5, which accounts for the majority, and in the final stage where the injection of the molten metal M is completed and the liquid level gradually decreases.

[0062] Furthermore, as described above, in the atomizing device 1, the liquid level Mh of the molten metal M in the tundish 11 is measured by the measuring unit 31. Based on this liquid level Ms, the control unit 32 automatically adjusts the inclination angle of the melting furnace 5 to adjust the amount of molten metal M poured into the tundish 11 so that the liquid level Mh remains substantially constant at a predetermined height. This allows the liquid level Mh of the molten metal M to be maintained at a constant level with greater accuracy, and the supply rate of the molten metal M from the tundish 11 can be more effectively stabilized.

[0063] Back to Figure 2 、 Figure 3 As shown in these figures, the inner shape of the tundish 11 (11A, 11B) is, for example, an inverted truncated cone or an inverted cone. The inner shape of the tundish 11 is such that the diameter of the upper opening 11a (opening diameter) R 1 Larger than the diameter of the bottom 11b (bottom diameter) R 2 The shape of the tundish 11 is formed in such a way that the liquid surface area gradually increases as the liquid level of the molten metal M increases. Figure 2 、 Figure 3 ), the wall surface at a position corresponding to the liquid level position (not shown) of the molten metal M is inclined, for example, forming an inverted truncated cone or an inverted cone.

[0064] exist Figure 2 The tundish 11A and Figure 3 In the tundish 11B shown, the opening diameter R 1 With bottom diameter R 2 The ratio of different schemes. As R 1 With R2 The ratio is not particularly limited, but is determined by R 2 / R 1 The ratio relationship represented by is preferably about 0.25 or more and about 0.65 or less, and more preferably about 0.30 or more and about 0.55 or less. 2 / R 1 When R is smaller than 0.25, the liquid level can be kept almost constant at the target height, but the internal volume is reduced and the atomization processing efficiency is reduced. 2 / R 1 When it becomes greater than 0.65, due to the approach Figure 4 Because of the cylindrical shape shown, it may be difficult to stabilize the liquid level.

[0065] In addition, if Figure 3 The illustrated tundish 11B has a bottom 11b formed into an inverted truncated cone shape. This bottom 11b can be provided with an inclined portion 21 that slopes downward toward the discharge nozzle 11N mounted on the bottom 11b. It should be noted that the inclined portion 21 is provided within the tundish 11B. By providing the inclined portion 21, which slopes downward toward the discharge nozzle 11N, it is possible to more effectively suppress a decrease in the amount of molten metal M supplied through the discharge nozzle 11N, particularly after the injection of the molten metal M has been completed and the liquid level has gradually decreased. This further stabilizes the supply amount and reduces variations in the particle size of the resulting metal powder.

[0066] It should be noted that the material of the tundish 11 is not particularly limited and can be made of alumina, for example. Furthermore, the material of the liquid discharge nozzle 11N, which is attached to the bottom 11b of the tundish 11, is also not particularly limited and can be made of zirconia, for example. The nozzle diameter of the liquid discharge nozzle 11N can be appropriately determined based on the type (composition) of the molten metal and the amount of molten metal discharged, and can be, for example, approximately 3 mm to 10 mm.

[0067] In addition, Figures 1 to 3 , the opening 11a of the tundish 11 is shown as being entirely open, but this is not limited to being entirely open. As described above, the opening 11a refers to a pouring port located near the top of the tundish 11 and used to pour the molten metal M from the melting furnace 5. It suffices to have an opening near the ceiling of the tundish 11 for pouring the molten metal M from the melting furnace 5. Note that, even in this case, the opening 11a refers to the portion of the top surface of the tundish 11 that includes the opening.

[0068] [Fluid Jet Nozzle]

[0069] The fluid injection nozzle 12 is located at the upper portion (ceiling) of the chamber 13, described later, and is a nozzle that injects high-pressure water as a fluid onto the molten metal M that is supplied from the liquid discharge nozzle 11N of the tundish 11 and freely falls. It should be noted that since the location where the fluid injection nozzle 12 is installed and the high-pressure water is injected into the molten metal M is where the molten metal M is pulverized into droplets, this portion is referred to as the atomization and pulverization section.

[0070] High-pressure water, acting as a fluid, is the medium used to pulverize the molten metal M. While this embodiment illustrates the use of high-pressure water as the fluid, an inert gas such as nitrogen or argon, or a gas such as air, may also be used. In this case, a gas atomizer utilizes high-pressure gas as the fluid to produce metal powder. The aforementioned shape of the tundish 11 is readily applicable to both water and gas atomizers.

[0071] The structure and shape of the fluid jet nozzles 12 are not particularly limited as long as they can spray high-pressure water at the desired spray rate toward the molten metal M. Preferably, an even number (e.g., two, four, or six) of fluid jet nozzles 12 are disposed relative to each other, with the falling molten metal M as the central axis. Furthermore, the angle (injection angle) of the high-pressure water sprayed toward the molten metal M in the fluid jet nozzles 12 can be adjusted to maximize the yield of produced metal powder. For example, the relative angle (vertical angle) of the high-pressure water can be adjusted to, for example, 30° to 50°, and the spray angle (vertical angle) of the water relative to the falling molten metal M can be adjusted to 15° to 25°.

[0072] Furthermore, it is preferable that the injection conditions of the high-pressure water injected from the fluid injection nozzle 12 be appropriately set according to the particle size of the metal powder to be produced.

[0073] Specifically, regarding the injection conditions, the pressure of the high-pressure water sprayed is preferably set to, for example, 6 MPa or higher and 20 MPa or lower. If the pressure is less than 6 MPa, the particle size of the resulting metal powder may become too large, while if the pressure exceeds 20 MPa, the metal powder may become excessively fine, reducing separation and recovery efficiency. Furthermore, increasing the pressure requires the use of an expensive pump, which increases the production cost of the metal powder.

[0074] The mass ratio (water ratio) of the high-pressure water injection rate to the supply rate (falling rate) of the molten metal M is preferably set to approximately 5.0 times or more and 7.0 times or less, for example. The supply rate of the molten metal M is the average supply rate per unit time, while the high-pressure water injection rate is the average injection rate per unit time. If the supply rate of the molten metal M or the high-pressure water injection rate varies over time, the average value is used. If the water ratio is less than 5.0 times, the particle size of the resulting metal powder may be too large. If the water ratio exceeds 7.0 times, the metal powder may be excessively fine.

[0075] The temperature of the high-pressure water sprayed is preferably set to, for example, approximately 2°C to 35°C. If the water temperature is too low, there is a risk of water freezing in the piping during equipment shutdown, causing leaks and other problems. If the water temperature is too high, the particle size of the resulting metal powder tends to increase. The temperature of the high-pressure water can be controlled by adjusting the set temperature of a cooler 19, for example.

[0076] [Chamber]

[0077] The chamber 13 is connected to the tundish 11 at the position of the liquid discharge nozzle 11N, and the molten metal M is supplied from the tundish 11 through the liquid discharge nozzle 11N. In addition, the above-mentioned fluid injection nozzle 12 is provided at the top of the chamber 13. By injecting high-pressure water onto the molten metal M supplied from the liquid discharge nozzle 11N and freely falling, it forms droplets and generates metal powder.

[0078] Specifically, within chamber 13, when high-pressure water is sprayed onto molten metal M falling through liquid discharge nozzle 11N, the molten metal M is pulverized into droplets. The resulting droplets scatter within chamber 13 and fall toward the bottom. Furthermore, the resulting droplets are cooled by the high-pressure water and further cooled as they scatter and fall within chamber 13, rapidly solidifying into a metal powder form. In atomizing device 1 employing a water atomization method, the water sprayed from fluid injection nozzle 12 accumulates in the lower portion of chamber 13, forming an aqueous phase. The solidifying metal powder also flows into this aqueous phase and is cooled.

[0079] It should be noted that in the chamber 13, the angle (injection angle) of the high-pressure water injected into the molten metal M is adjusted to maximize the yield of the produced metal powder. Furthermore, as described above, the amount of molten metal falling per unit time, the amount of high-pressure water injected per unit time, the pressure of the injected high-pressure water, the temperature of the high-pressure water, and the like can be appropriately set based on the yield of the metal powder or the desired particle size of the metal powder.

[0080] Furthermore, the chamber 13 is configured to maintain its internal pressure above atmospheric pressure by flowing an inert gas such as nitrogen to prevent air from entering the chamber 13. Furthermore, the chamber 13 is connected to a gas exhaust structure 18 that allows gases such as hydrogen that fill the chamber 13 to be exhausted to the outside without the inflow of air.

[0081] A discharge port 13 e for discharging the slurry containing the metal powder is provided at the bottom of the chamber 13 , and the metal powder is recovered through a recovery pipe 14 connected to the discharge port 13 e .

[0082] [Measurement Department]

[0083] The measuring unit 31 is, for example, located above the tundish 11 and measures the liquid level Mh of the molten metal within the tundish 11. The measuring unit 31 captures an image of the liquid surface Ms of the molten metal M within the tundish 11 by imaging the interior of the tundish 11. As described above, the internal shape of the tundish 11 is such that the area of ​​the liquid surface Ms of the poured molten metal M increases upward in the vertical direction. As a result, the liquid level Mh can be accurately measured based on the difference in the area of ​​the liquid surface Ms as it fluctuates.

[0084] The measuring unit 31 is composed of a device such as a camera or a thermal imager. A thermal imager that can capture thermal images of infrared radiation emitted from the tundish 11 is preferred. It should be noted that while there are methods for measuring the liquid level Ms using the reflection of sound waves or light, these methods are sometimes difficult to use because the liquid level fluctuates due to pouring or is affected by hot air currents generated by the high temperature of the molten metal M.

[0085] More specifically, in the atomizing device 1, a measuring unit 31 can be provided above the tundish 11. For example, a thermal imager is provided as the measuring unit 31 above the tundish 11 to clearly observe the upper surface contour of the molten metal M in the tundish 11, detect infrared rays radiated from the tundish 11, and obtain the temperature distribution in the form of a thermal image. Since the tundish 11 is formed in a shape such as an inverted cone, in which the area of ​​the molten metal M increases as it moves upward in the vertical direction, the upper surface of the molten alloy M is observed as a circle. Therefore, by setting the relationship between the diameter of the circle and the liquid level (Mh) in advance as an arithmetic expression, the liquid level Mh of the molten alloy M in the tundish 11 can be calculated from the diameter of the circle. In this way, in the measuring unit 31, the liquid level Mh can be accurately calculated by a simple method of photographing the upper surface contour of the molten metal M in the tundish 11.

[0086] In the measurement unit 31, for example, to clarify the top surface contour of the molten metal M within the tundish 11, image processing can be used to convert the image into a binary or multi-valued image. This allows the area of ​​the circle to be digitized and the previously calculated relationship between the circle's area and the liquid level Mh to be expressed as an equation. Furthermore, if the tundish 11 is in the shape of an inverted quadrangular pyramid, the liquid level Mh can also be calculated from the area of ​​the quadrilateral. Alternatively, for example, the top surface of the molten metal M can be divided into a grid and the number of grids can be measured, or the distance between parallel lines tangent to the contour can be measured as the length. In any case, the liquid level Mh can be calculated simply by approximating the relationship between the measured value and the liquid level Mh to an equation.

[0087] Since the measurement unit 31, comprised of a device such as a camera or thermal imager, is located above the tundish 11, for example, it is susceptible to radiant heat and hot air currents from the tundish 11. In this regard, the effects of radiant heat can be mitigated by inserting light-shielding glass or heat-shielding glass that is less permeable to infrared rays between the camera or thermal imager and the tundish 11. Furthermore, to avoid hot air currents from within the tundish 11, observation is performed from an obliquely upward position rather than directly above the tundish. This allows the top surface profile of the molten metal M to be observed as an ellipse rather than a circle if the tundish 11 is in the shape of an inverted cone. If the tundish 11 is in the shape of an inverted quadrangular pyramid, the area can be approximated to a square, rectangle, trapezoid, or the like. This prevents the camera or thermal imager from overheating and preventing measurement.

[0088] It should be noted that even if the falling molten metal M is captured in the image when the molten metal M is poured, as long as an area of, for example, more than half of the upper surface of the liquid surface in the tundish 11 can be observed, the liquid level height Mh can be appropriately calculated based on this area.

[0089] Information on the value of the liquid level Mh of the molten metal M measured by the measuring unit 31 is transmitted to the control unit 32, described later, and the amount of molten metal M poured from the melting furnace 5 into the tundish 11 is adjusted so that the liquid level Ms of the molten metal M in the tundish 11 remains substantially constant at a predetermined height. By determining the liquid level Mh of the molten metal M in the tundish 11 by the measuring unit 31, it is possible to calculate how much the liquid level Mh is below or above the target height, and to appropriately control the amount of molten metal M poured from the melting furnace 5 to reduce this difference.

[0090] [Control Department]

[0091] The control unit 32 obtains information on the liquid level Mh of the molten metal M in the tundish 11 measured by the measuring unit 31 and adjusts the injection amount of the molten metal M into the tundish 11 so that the liquid level Mh remains substantially constant.

[0092] Here, the molten metal M is poured from the melting furnace 5 into the tundish 11, for example, by tilting the melting furnace 5 (see Figure 1 In the atomizing device 1, after the information on the liquid level Mh of the molten metal M in the tundish 11 measured by the measuring unit 31 is transmitted to the control unit 32, the control unit 32 automatically adjusts the inclination angle of the melting furnace 5 to adjust the amount of molten metal M poured into the tundish 11 so that the liquid level Mh is substantially constant at a predetermined height. This allows the liquid level Mh of the molten metal M to be maintained constant with high precision.

[0093] More specifically, for example, the control unit 32 controls the tilting device that adjusts the inclination of the melting furnace 5 based on the information on the liquid level Mh of the molten metal M in the tundish 11 sent from the measuring unit 31. The control unit 32 is configured to adjust the inclination of the melting furnace 5 by, for example, supplying oil to a hydraulic cylinder that drives the tilting device or releasing the oil pressure.

[0094] For example, if the control unit 32 determines that the measured liquid level Mh is below the target lower limit, it operates the hydraulic pump of the tilting device to increase the tilt angle of the melting furnace 5, thereby increasing the amount of molten metal M poured in. As a result, the liquid level Mh automatically rises to the target height. Alternatively, if the control unit 32 determines that the liquid level has reached the target upper limit, the oil in the hydraulic cylinder of the tilting device is released to release the oil pressure, restoring the tilt of the melting furnace 5 and reducing the amount of molten metal M poured in. By repeating this operation, the liquid level Mh can be adjusted between the upper and lower limits, and the amount of molten alloy dropped from the tundish 11 per unit time can be kept constant.

[0095] [Other components]

[0096] In the atomizing device 1, the other end of the recovery pipe 14 is connected to a filter 15. In the filter 15, the slurry containing the metal powder discharged through the recovery pipe 14 is subjected to a solid-liquid separation process, separating and recovering the metal powder as a solid component from the slurry. The water from which the metal powder has been separated in the filter 15 is stored in a tank 16 connected via a pipe. After its temperature is regulated by a cooler 19 and other means, it is circulated by a high-pressure pump 17 and supplied to the fluid injection nozzle 12. In the fluid injection nozzle 12, pressure is applied to the circulated water and it is reused as high-pressure water for pulverizing the molten metal M.

[0097] 2. Methods for recovering valuable metals

[0098] Next, a method for recovering valuable metals will be described. The method includes a step of producing an alloy powder containing Cu, Ni, and Co as constituent components using the atomizing device 1 having the above-described configuration.

[0099] The method for recovering valuable metals according to this embodiment is a method for recovering valuable metals from waste lithium-ion batteries. Specifically, the method comprises: a step of pre-treating the waste lithium-ion batteries (waste battery pre-treatment step S1); a step of melting the pre-treated waste lithium-ion batteries to prepare an alloy melt (containing Cu, Ni, and Co) M (alloy melt preparation step S2); a step of spraying a fluid into the alloy melt M to produce alloy powder (alloy powder production step S3); and a step of leaching the produced alloy powder with acid (acid leaching step S4).

[0100] Furthermore, the alloy powder production step S3 is characterized by using the atomizing device 1 having the above-described configuration. In the alloy powder production step S3, by using the atomizing device 1 and producing the alloy powder by the atomization method, the liquid level of the molten alloy M in the tundish 11 can be maintained substantially constant, and the supply rate of the molten alloy M from the tundish 11 can be stabilized. As a result, the molten alloy M supplied at a stable supply rate can suppress variations in the particle size of the alloy powder produced by jetting a fluid into the molten alloy M.

[0101] In a method for recovering valuable metals from waste lithium-ion batteries, when acid leaching is performed on alloy powder (copper-nickel-cobalt alloy) containing Cu, Ni, and Co as constituents to selectively leach Ni or Co into a solution, it has been confirmed that variations in the alloy powder particle size affect the acid leaching efficiency. Depending on the particle morphology, including the particle size distribution, some particles may be virtually insoluble in acid. In this regard, by producing the alloy powder using an atomization method using the atomizing device 1 in the alloy powder production step S3, variations in particle size are suppressed, enabling the production of alloy powder with a sharp particle size distribution. This effectively improves the leaching efficiency during acid leaching.

[0102] [Waste battery pre-treatment process]

[0103] The waste battery pretreatment step S1 is a process for pre-treating waste lithium-ion batteries, which serve as raw materials for valuable metal recovery. This pre-treatment occurs before the raw materials are melted to produce a molten alloy in the alloy preparation step S2, described later. Here, waste lithium-ion batteries include not only used batteries but also defective batteries generated during the battery manufacturing process.

[0104] Specifically, the waste battery pre-treatment step S1 includes a detoxification step S11 for detoxifying the waste lithium ion batteries and a pulverization step S12 for pulverizing the waste lithium ion batteries.

[0105] The harmless treatment process S11 is a process for carrying out a treatment (also referred to as "harmless treatment") for the purpose of explosion-proofing and harmless treatment of waste lithium-ion batteries and removal of outer cans. Since lithium-ion batteries are closed systems with electrolytes and the like inside, there is a risk of explosion when waste lithium-ion batteries are directly used for crushing treatment, etc., which is dangerous. Therefore, it is preferred to implement a discharge treatment or electrolyte removal treatment by some method. In addition, the outer cans that constitute waste lithium-ion batteries are mostly made of aluminum (Al) or iron (Fe) as metals, and such metal outer cans are relatively easy to recycle directly. Therefore, by removing the electrolyte and outer cans in the harmless treatment process S11, it is possible to improve the recovery rate of valuable metals (Cu, Ni, Co) while improving safety.

[0106] The specific method for harmless treatment is not particularly limited. For example, a method of physically opening a hole in the waste lithium-ion battery with a needle-like knife tip to remove the electrolyte can be used. Another method of harmless treatment is heating the waste lithium-ion battery to burn the electrolyte.

[0107] The crushing step S12 is a process for crushing the contents of the detoxified spent lithium-ion batteries to obtain crushed materials. The crushed materials are used as raw materials for melting (liquification). The crushing step S12 is a process aimed at improving the reaction efficiency in the dry smelting process. By improving the reaction efficiency, the recovery rate of valuable metals (Cu, Ni, Co) can be increased.

[0108] The specific method of the pulverization treatment is not particularly limited, and the pulverization can be performed using a conventionally known pulverizer such as a cutter mixer.

[0109] It should be noted that when recovering Al or Fe contained in the outer cans of spent lithium-ion batteries, the crushed material can be screened using a vibrating screen after pulverization. Since Al easily becomes powdered through light pulverization, it can be effectively recovered. Furthermore, Fe contained in the outer cans can be recovered through magnetic screening.

[0110] [Preheating process]

[0111] If necessary, before the alloy melt preparation step S2 including the melting step S21 described later, a step (preheating step) of preheating (oxidatively calcining) the crushed waste lithium ion batteries (crushed material) to form a preheated material may be provided.

[0112] In the preheating step (oxidation roasting step), a treatment is performed to reduce the amount of carbon contained in the waste lithium-ion batteries. By providing this step, even if the waste lithium-ion batteries contain excessive carbon, the carbon can be effectively oxidized and removed, which can promote the alloying of valuable metals in the subsequent melting step S21.

[0113] That is, in the melting process, the valuable metals are reduced and locally converted into molten particles, but carbon sometimes becomes a physical obstacle when the molten particles (valuable metals) agglomerate. If carbon hinders the agglomeration and integration of the molten particles and the separation of the resulting alloy (metal) and slag, the recovery rate of the valuable metals will decrease. In contrast, by providing a preheating process to oxidize and remove carbon, the agglomeration and integration of the molten particles in the melting process can be promoted, and the recovery rate of the valuable metals can be improved. In addition, since the phosphorus (P) contained in the waste lithium-ion battery is an impurity that is relatively easy to be reduced, when carbon is present in excess, there is a possibility that phosphorus is reduced and incorporated into the alloy together with the valuable metals. In this regard, by removing excess carbon in advance in the preheating process, phosphorus can be prevented from mixing into the alloy. It should be noted that the amount of carbon contained in the preheated product (crushed product after preheating treatment) is preferably less than 1% by mass.

[0114] Furthermore, by providing a preheating step, oxidation variations can be suppressed. In the preheating step, treatment (oxidative roasting) is preferably performed at an oxidation level sufficient to oxidize relatively low-value-added metals (such as aluminum) contained in spent lithium-ion batteries. The degree of oxidation can be easily controlled by adjusting the temperature, duration, and / or environment of the preheating treatment.

[0115] For example, the degree of oxidation is adjusted as follows. Specifically, aluminum (Al), lithium (Li), carbon (C), manganese (Mn), phosphorus (P), iron (Fe), cobalt (Co), nickel (Ni), and copper (Cu) are generally oxidized in the order of Al > Li > C > Mn > P > Fe > Co > Ni > Cu. During the preheating process, oxidation is performed until all of the Al is oxidized. While oxidation can be continued until a portion of the Fe is oxidized, it is preferable to maintain the degree of oxidation at a level where the Co is not oxidized and distributed into the slag.

[0116] The preheating treatment is preferably carried out in the presence of an oxidizing agent. This allows for efficient oxidation and removal of carbon (C) as an impurity and oxidation of Al. The oxidizing agent is not particularly limited, but is preferably an oxygen-containing gas (air, pure oxygen, oxygen-enriched gas, etc.) for ease of handling. Furthermore, the amount of oxidizing agent introduced is preferably, for example, approximately 1.2 times the chemical equivalent required for oxidation of the respective substances to be oxidized.

[0117] The preheating temperature (heating temperature) is preferably 600°C or higher, more preferably 700°C or higher. This heating temperature further improves carbon oxidation efficiency and shortens heating time. Furthermore, the heating temperature is preferably 900°C or lower, thereby reducing thermal energy costs and improving preheating efficiency.

[0118] The preheating treatment can be performed using a known roasting furnace. Furthermore, it is preferable to use a furnace (preparatory furnace) different from the melting furnace used in the subsequent melting step S21, and perform the preheating treatment in this preparatory furnace. As a preheating furnace, any type of furnace can be used as long as it can supply an oxidant (oxygen, etc.) while roasting the charged material and perform the oxidation treatment therein. Examples include conventionally known rotary kilns and tunnel kilns (hearth furnaces).

[0119] [Alloy melt preparation process]

[0120] The alloy melt preparation step S2 is a step for melting waste lithium-ion batteries to prepare an alloy melt (an alloy melt containing Cu, Ni, and Co) M. The alloy melt preparation step S2 comprises a melting step S21 for melting crushed waste lithium-ion batteries; a recovery step S22 for separating slag from the melt and recovering an alloy containing valuable metals; and a melting step S23 for converting the recovered alloy into the alloy melt M.

[0121] In the melting step S21, raw materials (crushed or preheated waste lithium-ion batteries) are placed in a melting furnace and heated to melt the raw materials to produce an alloy (metal) containing Cu, Ni, and Co as constituent components, and slag located above the alloy. Specifically, the raw materials are first heated and melted to form a melt. The melt contains the molten alloy and slag. Next, the obtained melt is made into a molten material. The molten material contains the alloy and slag in a separately agglomerated state.

[0122] The alloy mainly contains valuable metals. Therefore, the valuable metals and other components can be separated into alloys and slag respectively. This is because metals with relatively low added value (such as Al) have high oxygen affinity, while valuable metals have low oxygen affinity. For example, aluminum (Al), lithium (Li), carbon (C), manganese (Mn), phosphorus (P), iron (Fe), cobalt (Co), nickel (Ni) and copper (Cu) are usually oxidized in the order of Al>Li>C>Mn>P>Fe>Co>Ni>Cu. That is, Al is most easily oxidized and Cu is least easily oxidized. Therefore, metals with relatively low added value (such as Al) are easily oxidized into slag, while valuable metals (Cu, Ni, Co) are reduced to alloys. In this way, metals with relatively low added value and valuable metals can be separated into slag and alloys.

[0123] When melting the raw materials, the oxygen partial pressure can be controlled. The control of the oxygen partial pressure can be carried out by a known method. For example, a method of introducing a reducing agent or an oxidizing agent into the raw material or the melt obtained by melting the raw material can be cited. As the reducing agent, a material with a high carbon grade (graphite powder, graphite particles, coal, coke, etc.) or carbon monoxide can be used. Alternatively, a component with a high carbon grade in the raw material can be used as a reducing agent. In addition, as the oxidizing agent, an oxidizing gas (air, oxygen, etc.) or a material with a low carbon grade can be used. Alternatively, a component with a low carbon grade in the raw material can be used as an oxidizing agent.

[0124] The reducing agent or oxidizing agent can be introduced by known methods. For example, if the reducing agent or oxidizing agent is a solid substance, it can be added to the raw materials or melt. Alternatively, if the reducing agent or oxidizing agent is a gaseous substance, it can be introduced through an inlet such as a spray gun provided in the melting furnace. The timing of introducing the reducing agent or oxidizing agent is not particularly limited and can be introduced simultaneously with the addition of the raw materials into the melting furnace or at the stage where the raw materials are melted into the melt.

[0125] In addition, a flux may also be introduced (added) during the melt treatment in the melting step S21. By adding a flux, the melt treatment temperature can be lowered, which can reduce energy costs. In addition, phosphorus (P) can be further removed. The flux preferably contains an element that forms an alkaline oxide, which can contain impurity elements and has a low melting point. For example, since phosphorus is oxidized to form an acidic oxide, the stronger the alkalinity of the slag formed by the melt treatment, the easier it is to incorporate phosphorus into the slag and remove it. Among them, as a flux, it is more preferred to contain a calcium compound that is low in price and stable under normal temperature conditions. As a calcium compound, for example, calcium oxide (CaO) or calcium carbonate (CaCO3) can be mentioned.

[0126] In the melting process, the heating temperature when the raw materials are melted is not particularly limited, but is preferably above 1400°C and below 1600°C, more preferably above 1450°C and below 1550°C. By making the heating temperature above 1400°C, the valuable metals (Cu, Co, Ni) are fully melted, and an alloy is formed in a state in which the fluidity is improved. Therefore, the efficiency of separating the alloy and the slag in the recovery step S22 described later can be improved. In addition, it is more preferable to make the heating temperature above 1450°C, which can further improve the fluidity of the alloy and the separation efficiency of the impurity components and the valuable metals. On the other hand, when the heating temperature exceeds 1600°C, while the heat energy is wasted, the consumption of refractory materials such as crucibles or furnace walls also becomes intense, and there is a possibility of reduced productivity.

[0127] In the recovery step S22, slag is separated from the melt obtained in the melting step S21, and the alloy containing the valuable metals is recovered as the alloy raw material. The slag and the alloy have different specific gravities. Since the slag, which has a lower specific gravity than the alloy, accumulates above the alloy, it can be easily separated and recovered through specific gravity separation. Through the processing in the recovery step S22, an alloy raw material containing Cu, Ni, and Co as constituent components can be obtained.

[0128] In the melting step S23, the recovered alloy raw material is heated and melted to form an alloy melt M. Specifically, the prepared alloy raw material is placed in a melting furnace (crucible furnace) and heated to melt the alloy raw material to form a fluid melt (alloy melt M). The heating and melting temperature is preferably 1450°C or higher and 1550°C or lower from the perspective of producing the desired alloy powder in the alloy powder production step S3 described later. Through the treatment in the melting step S23, an alloy melt M containing Cu, Ni, and Co as constituent components can be obtained.

[0129] [Alloy powder production process]

[0130] The alloy powder production step S3 is a step for producing alloy powder (atomized powder) by an atomization method using the atomizing device 1. Specifically, the alloy melt M obtained in the melting furnace 5 is poured into the tundish 11 constituting the atomizing device 1. The alloy melt M is supplied from the tundish 11 to the chamber 13 in a free-fall manner at a predetermined supply rate. The falling alloy melt M is then sprayed with a fluid such as high-pressure water or high-pressure gas to pulverize it into droplets. Within the chamber 13, the pulverized and scattered droplets are rapidly cooled and solidified, thereby producing alloy powder.

[0131] The valuable metal recovery method of this embodiment is characterized in that, in the alloy powder production step S3, an atomizing device 1 having the configuration described in detail above is used to produce alloy powder. Specifically, the atomizing device 1 includes: a tundish 11 into which molten alloy M is poured and discharged from a liquid discharge nozzle 11N mounted on a bottom 11b; and a fluid injection nozzle 12 disposed below the tundish 11 to inject fluid toward the molten alloy M falling from the tundish 11. The tundish 11 is shaped so that, at least within its interior, the liquid surface area of ​​the molten alloy M injected from the melting furnace 5 increases upward in a vertical direction.

[0132] In addition, the atomizing device 1 also includes: a measuring unit 31 for measuring the height of the liquid level Ms of the molten metal M in the tundish 11 (liquid level height Mh), and a control unit 32 for controlling the amount of molten metal M injected into the tundish 11 based on the liquid level height Mh measured by the measuring unit 31, and automatically adjusting the inclination angle of the melting furnace 5 to adjust the amount of molten metal M injected into the tundish 11 so that the liquid level height Mh is approximately constant at a specified height.

[0133] The specific structure of the atomizing device 1 has been described in detail above, so the description is omitted here.

[0134] In the alloy powder production step S3, by using the atomizing device 1 to produce the alloy powder, the liquid level of the molten metal M in the tundish 11 can be maintained substantially constant, thereby stabilizing the supply rate of the molten metal M from the tundish 11. Furthermore, as a result, the molten metal M supplied at a stable supply rate can suppress particle size variation in the alloy powder produced by spraying a fluid into the molten metal M. The alloy powder thus produced, which has a small particle size variation, can be subjected to acid leaching in the acid leaching step S4 described later, effectively improving the leaching efficiency of valuable metals such as Ni and Co.

[0135] Here, as described above, the alloy melt provided for the production of alloy powder using the atomizing device 1 is derived from waste lithium-ion batteries and contains Cu, Ni, and Co, which are components of the batteries, and at least manganese (Mn) and iron (Fe), which are impurity components. The mass ratio of these metal elements in the alloy melt is not particularly limited, but for example, the five metal elements of Cu, Ni, Co, Mn, and Fe are each contained at a ratio of 0.1% by mass or more, and the total of these five metal elements is 98% by mass or more. In addition, the mass ratio of Cu in the alloy melt is, for example, about 24% by mass or more and about 80% by mass or less.

[0136] The temperature of the alloy melt is not particularly limited, but for example, when the total mass % of Ni, Co, Mn, and Fe is "T", it is preferably adjusted to a range of (1383 + 1.9 × T) ° C or higher and (1483 + 1.9 × T) ° C or lower, and the temperature-adjusted alloy melt is injected into the atomizing device 1. By adjusting to this temperature, the molten state of the alloy melt is appropriately maintained, and when the alloy powder is injected into the atomizing device 1 to produce the alloy powder, an alloy powder with smaller deviation in particle size can be obtained.

[0137] The temperature of the alloy melt can be adjusted in the melting furnace ( Figure 1The temperature can be adjusted in the melting furnace 5 shown in the figure, and can also be used as the temperature condition during the melting step S23. Alternatively, after the alloy melt is obtained by melting, a separate temperature adjustment step can be provided, such as by applying heat from a heat source. It should be noted that, for example, by configuring the melting furnace 4 as an induction furnace, it is possible to efficiently apply heat energy at a predetermined frequency output.

[0138] Furthermore, before the molten alloy M is poured from the melting furnace 5 into the tundish 11 of the atomizing device 1, the interior of the empty tundish 11 may be preheated to a temperature of 1000°C or higher using, for example, an LPG burner. This eliminates the temperature difference between the molten alloy M stored in the tundish 11 and the molten alloy M in the melting furnace, thereby suppressing a decrease in the temperature of the molten alloy M poured into the tundish 11 and maintaining an appropriate temperature.

[0139] In addition, by controlling the ratio of the average weight per unit time of the high-pressure water sprayed into the alloy melt M to the average mass per unit time of the falling alloy melt M, the average mass per unit time of the falling alloy melt M, and the water supply pressure of the high-pressure pump 17 used to spray water into the alloy melt M within a specified range, the particle size deviation of the alloy powder can be suppressed. For example, the average weight per unit time of the high-pressure water sprayed into the alloy melt M is set to, for example, about 5.0 to 7.0 times the average mass per unit time of the falling alloy melt M. In addition, the average mass per unit time of the falling alloy melt M is set to about 10 kg / min. to 75 kg / min. In addition, the water supply pressure of the high-pressure pump 17 used to spray water into the alloy melt M is set to about 8 MPa to 20 MPa. It should be noted that the sprayed water is cooled by the cooler 19 to keep its temperature constant.

[0140] [Acid leaching process]

[0141] In the acid leaching step S4 (valuable metal recovery step), the produced alloy powder is leached with an acid solvent, selectively dissolving Ni and Co from the alloy powder in the acid solvent. This separates copper (Cu) from Ni and Co. In this way, the valuable metals Ni and Co can be recovered in a form separated from Cu.

[0142] As an acid solvent, a known acid solution used in the recovery of valuable metals can be used. Specifically, as an acid solution, sulfuric acid, hydrochloric acid, nitric acid, etc. can be enumerated. For example, as an acid solution, sulfuric acid is used, and by immersing the alloy powder in the sulfuric acid, the Ni and Co in the alloy powder are dissolved in the sulfuric acid solution and become nickel sulfate and cobalt sulfate in the solution. On the other hand, the Cu in the alloy powder becomes copper sulfate with low solubility and precipitates as a residue. Therefore, the Cu component (copper sulfate) that can become a precipitate can be separated from the solution containing Ni and Co.

[0143] As described above, the alloy powder produced in the alloy powder production step S3 has a small deviation in particle size. Therefore, it has excellent leaching and separation recovery properties during acid leaching. Therefore, the valuable metal recovery method of this embodiment using such alloy powder, i.e., alloy powder produced using the atomizing device 1, can leach Ni and Co as valuable metals at a high leaching rate, and can separate and recover Ni and Co from Cu with high separation properties.

[0144] Example

[0145] Hereinafter, the present invention will be described in more detail with reference to examples, but the present invention is not limited to the following examples at all.

[0146] 《Examples, Comparative Examples》

[0147] [Example]

[0148] In the Examples and Comparative Examples, intermediate waste from lithium-ion battery factories or decontaminated used batteries circulating in the waste battery market were used (waste battery pretreatment step S1). A molten alloy was obtained from the waste battery samples in the alloy melt preparation step S2. Then, in the alloy powder production step S3, alloy powder containing copper (Cu), nickel (Ni), and cobalt (Co) as constituent components was produced from the obtained alloy melt.

[0149] In the alloy powder production step S3, the Figure 1 The atomizing device (1) of the construction example is shown in FIG. That is, a water atomizing device (1) having an inverted truncated cone shape is used, wherein the surface area of ​​the alloy melt (M) injected into the tundish (11) increases as it goes upward in the vertical direction. More specifically, in Examples 1 to 4, a tundish (11) having an internal cross-sectional shape as shown in FIG. Figure 2 The diameter R of the bottom (11b) is shown 2 The diameter R of the opening (11a) 1 The ratio (R 2 / R 1 ) is 0.5 (referred to as "inverted truncated cone [1]" in Table 2 below). In addition, in Example 5, a water atomizing device (1) having an internal cross-sectional shape such as Figure 3 The diameter R of the bottom (11b) is shown 2 The diameter R of the opening (11a) 1 The ratio (R 2 / R 1 ) is a water atomizing device (1) of a tundish (11) with a thickness of 0.3 (represented as "inverted frustum [2]" in Table 2 below).

[0150] It should be noted that in the water atomizing device (1), the tundish (11) is made of alumina, and a zirconia liquid discharge nozzle (11N) with a nozzle diameter of 4mm to 8mm is installed on the bottom (11b) of the tundish 11.

[0151] In addition, the water atomization device (1) further comprises: a measuring unit (31) for measuring the liquid level (Mh) of the alloy melt (M) in the tundish (11); and a control unit (32) for controlling the amount of the alloy melt (M) injected into the tundish (11) based on the measured liquid level Mh, and automatically adjusting the inclination angle of the melting furnace (3) to adjust the amount of the alloy melt (M) injected into the tundish (11) so that the liquid level (Mh) is approximately constant at a specified height.

[0152] In addition, in the water atomizing device (1), a mechanism (measuring unit 31) for measuring the liquid level (Mh) of the alloy melt (M) installed in the tundish (11) is provided above the tundish. More specifically, in Examples 1, 2, and 5, a camera is used as the mechanism for measuring the liquid level (Mh), and a light-shielding glass is inserted between the camera and the tundish (11) to adjust the exposure, so that the upper surface contour of the alloy melt in the tundish (11) can be clearly observed. Since the tundish (11) is in the shape of an inverted cone, the upper surface of the alloy melt is observed as a circle. By setting the relationship between the diameter of the circle and the liquid level (Mh) in advance as an arithmetic expression, the liquid level (Mh) of the alloy melt (M) in the tundish (11) can be calculated from the diameter of the circle. It should be noted that in order to make the upper surface contour of the alloy melt (M) in the intermediate ladle (11) clear, it is converted into a binary or multi-valued image through image processing, the area of ​​the circle rather than the diameter is quantified, and the relationship between the area of ​​the circle and the liquid level height calculated in advance is used as an arithmetic formula.

[0153] The information of the liquid level (Mh) calculated by the measuring unit (31) is sent to the control unit 32. The control unit 32 adjusts the tilt angle of the melting furnace (3) to automatically adjust the amount of alloy melt (M) poured from the melting furnace (3) to the tundish 11, so that the liquid level Mh in the tundish (11) is kept substantially constant. As a result, the amount of alloy melt supplied from the tundish (11) to the water atomization process is also kept constant.

[0154] In addition, in Examples 3 and 4, a thermal imager is used as a means for measuring the liquid level (Mh), and a thermal image is directly captured in a manner that clearly defines the upper surface contour of the alloy melt (M) in the tundish (11). By using a thermal imager, the thermal imager can detect infrared rays radiated from the tundish (11) and obtain the temperature distribution in the form of a thermal image. Thus, the liquid level (Mh) is calculated from the upper surface contour of the alloy melt (M) in the tundish (11). Since the tundish (11) is in the shape of an inverted cone, the liquid level (Mh) can be easily calculated from the upper surface contour of the alloy melt (M) in the tundish (11) by preparing a relationship expression with the actual liquid level (Mh) in advance.

[0155] In the alloy powder production step S3, the temperature of the alloy melt is adjusted by the output of an induction furnace (melting furnace 5) with a frequency of 400 Hz, the induction furnace (5) is tilted, and the alloy melt (M) is flowed into a tundish (11) having an internal shape of an inverted truncated cone. The liquid level of the alloy melt (M) in the tundish (11) is kept almost constant, and the amount of liquid discharged per unit time from the liquid discharge nozzle (11N) is kept constant. The alloy melt (M) is supplied to the chamber (13) of the water atomizing device (1). At this time, information on the liquid level (Mh) of the alloy melt (M) in the tundish (11) measured by the measuring unit (31) is sent to the control unit (32), and the induction furnace (5) is tilted while adjusting the inclination of the tilting device for injecting the alloy melt (M) into the tundish (11).

[0156] The control unit (32) adjusts the inclination of the tilting device by supplying oil to the hydraulic cylinder or releasing the oil pressure. More specifically, in the control unit (32), when it is determined that the measured liquid level (Mh) is lower than the target lower limit, the hydraulic pump is operated to increase the inclination of the tilting device to tilt the induction furnace (5), thereby increasing the injection amount of the alloy melt (M), thereby automatically raising the liquid level (Mh) to the target height. In addition, when it is determined that the liquid level (Mh) has reached the target upper limit, the oil in the hydraulic cylinder is released to release the oil pressure, and the inclination of the induction furnace (5) is restored to reduce the injection amount. By repeating these steps, the liquid level (Mh) is adjusted to between the upper limit and the lower limit, and the amount of molten alloy supplied per unit time from the tundish (11) is kept constant.

[0157] It should be noted that when discharging the alloy melt (M) from the induction furnace (5) to the tundish (11), in order to maintain the temperature of the alloy melt (M) in the induction furnace (5) at the same level as the temperature of the alloy melt (M) discharged from the liquid discharge nozzle (11N) of the tundish (11), the empty tundish (11) is heated to above 1000°C in advance using an LPG burner.

[0158] In a water atomizing device (1), a molten alloy is supplied from a tundish (11) via a liquid discharge nozzle (11N) into a chamber (13) at a substantially constant discharge rate. A fluid injection nozzle (12) disposed above the chamber (13) sprays high-pressure water onto the molten alloy falling from the liquid discharge nozzle (11N), thereby crushing the molten alloy into droplets to produce alloy powder. The alloy powder obtained in the chamber (13) is transferred to a filter (15) via a recovery pipe (14), where solid-liquid separation is performed and the powder is recovered.

[0159] [Comparative Example]

[0160] In Comparative Example 1, a water atomizing device having an internal cross-sectional shape as shown in FIG. Figure 4 The alloy powder was manufactured in the same manner as in the example except that the device for measuring the liquid level of the alloy melt in the tundish (100) was not provided.

[0161] In Comparative Examples 2 and 3, alloy powders were produced in the same manner as in the example except that the device for measuring the level of the molten alloy installed in the tundish was replaced with the following device as the water atomizing device.

[0162] Specifically, in Comparative Example 2, the alloy melt level was measured using sound waves. However, sound wave measurement of the liquid level is significantly affected by the air temperature within the measurement range. The higher the temperature, the faster the speed of sound. Consequently, the measurement results differ at high and low temperatures, making this method unusable. Furthermore, if air is flowing within the factory, the calculated liquid level will be skewed by the direction or intensity of the flow. Furthermore, it is not possible to install a heat shield between the measuring instrument and the tundish to mitigate the effects of radiant heat or hot air flow from the tundish, making this method unusable.

[0163] In addition, in Comparative Example 3, the weight of the molten alloy in the tundish is obtained based on the weight change of the tundish, and the liquid level is calculated from this. However, in the water atomization method, in order to prevent hydrogen explosion, the tundish and the water atomization processing chamber must be sealed to prevent air from flowing in. Since the tundish and the chamber are integrated, a weight measuring mechanism cannot be configured and measurement cannot be performed. It should be noted that even if the weight including the chamber is to be measured, the weight of water or powder will also be included. Compared with the overall weight, the weight of the molten alloy in the tundish is too small, and the change in liquid level cannot be detected with high precision based on the weight change.

[0164] Results and Evaluation

[0165] Table 1 below shows the composition of the alloy melts in each test example of Examples 1 to 5 and Comparative Examples 1 to 3. Table 1 shows the composition of the chemical quantitative analysis results excluding gas components (carbon, nitrogen, and oxygen).

[0166] Table 1

[0167]

[0168] Table 2 below shows the production conditions of the alloy powders in each test example of Examples 1 to 5 and Comparative Example 1 and the test results thereof.

[0169] In each test, the presence or absence of abnormalities during processing when producing and processing alloy powder (atomized powder) under various conditions, the particle size distribution of the produced alloy powder, and the acid leaching efficiency when the alloy powder was acid leached were evaluated.

[0170] Regarding abnormalities during atomization processing, it is confirmed whether liquid clogging occurs in the liquid discharge nozzle (11N) during processing. The case where liquid clogging occurs is evaluated as abnormality (recorded as "yes" in the table), and the case where liquid clogging does not occur is evaluated as no abnormality (recorded as "no" in the table).

[0171] Regarding the particle size distribution of the alloy powder, the case where no coarse-grained powder with a particle size of 300 μm or more and no fine powder with a particle size of less than 5 μm are produced is judged and evaluated as good (denoted as "○" in the table), and the case where either or both coarse-grained powder and fine powder are produced is judged and evaluated as poor (denoted as "×" in the table).

[0172] Regarding the acid leaching efficiency, the alloy powder containing Cu, Ni, and Co as constituent components produced in each test example was immersed in a sulfuric acid solution and subjected to acid leaching treatment. The case where Ni and Co dissolved at a dissolution rate (leaching rate) of 98% or more within 6 hours from the start of the treatment was judged and evaluated as having good acid leaching efficiency (denoted by "○" in the table), and the case where the dissolution rate was less than 98% was judged and evaluated as having insufficient acid leaching efficiency (denoted by "×" in the table). It should be noted that the sulfuric acid solution was prepared in an amount of 2.0 to 3.0 equivalents of sulfuric acid required to dissolve Ni and Co as sulfates.

[0173] Table 2

[0174]

[0175] In Examples 1 to 4, alloy powders were produced using an apparatus in which the interior of the tundish (11) was formed into an inverted truncated cone. The produced alloy powders did not produce coarse particles with a particle size of 300 μm or more or fine particles with a particle size of less than 5 μm. Furthermore, during acid leaching of the alloy powders, more than 98% of Ni and Co dissolved within 6 hours, which was considered satisfactory. Furthermore, during the atomization process, no abnormalities such as liquid clogging occurred, and satisfactory operation was achieved.

[0176] In addition, in Example 5, the alloy powder was produced by using an apparatus in which the shape of the tundish (11) was formed into an inverted truncated cone. In the produced alloy powder, not only did no coarse powder with a particle size of 300 μm or more or fine powder less than 5 μm be produced, but also the proportion of fine powder in the range of 5 μm or more was small, showing a sharper particle size distribution. This is believed to be because in Example 5, by using an apparatus in which the shape of the tundish (11) was formed into an inverted truncated cone, the alloy powder was not produced. 2 / R 1 The alloy powder was produced using a substantially inverted conical device having a smaller ratio than that used in Examples 1 to 4. Even when the alloy melt in the tundish (11) became less, the supply rate from the liquid discharge nozzle (11N) varied little. Furthermore, during acid leaching of the alloy powder, more than 98% of Ni and Co dissolved within 6 hours, which was satisfactory. Furthermore, no abnormalities such as liquid clogging occurred during the atomization process, allowing for satisfactory operation.

[0177] On the other hand, in Comparative Example 1, alloy powder was produced by using an apparatus in which the shape of the tundish (100) was formed into a conventional cylindrical shape and without measuring the liquid level. Although abnormalities such as liquid clogging did not occur during the atomization process, coarse particles with a particle size of 300 μm or more and fine powder with a particle size of less than 5 μm were produced. In addition, in acid leaching of the alloy powder, the dissolution rate of Ni and Co within 6 hours was less than 98%.

[0178] Description of Reference Signs

[0179] 1. Atomization device (water atomization device)

[0180] 11, 11A, 11B Tundish

[0181] 11a Opening

[0182] 11b bottom

[0183] 11N liquid nozzle

[0184] 12 Fluid Jet Nozzles

[0185] 13 Chamber

[0186] 13e Exhaust

[0187] 14 Recovery piping

[0188] 15 filters

[0189] 16 cans

[0190] 17 High-pressure pump

[0191] 18 Gas exhaust structure

[0192] 21 inclined portion

[0193] 31 Measurement Department

[0194] 32 Control Unit

[0195] 5. Melting furnace (induction furnace).

Claims

1. An atomizing device, wherein: It is an atomizing device that sprays fluid into molten metal to produce metal powder. The atomizing device comprises: a tundish, into which the molten metal is injected and from which the molten metal is discharged through a liquid discharge nozzle installed at the bottom; as well as a fluid injection nozzle, arranged below the tundish, for injecting the fluid toward the molten metal falling from the tundish, The tundish is shaped like an inverted truncated cone or an inverted cone at least inside the tundish, wherein the surface area of ​​the metal melt injected therein increases upward in the vertical direction, and the diameter of the upper opening inside the tundish, i.e., the opening diameter R 1 The bottom diameter R 2 By R 2 / R 1 The ratio relationship represented is 0.25 or more and 0.65 or less, The atomizing device includes a mechanism for capturing an image of the interior of the tundish to capture the contour of the upper surface of the molten metal in the tundish, and measuring the liquid level of the molten metal in the tundish based on the diameter of a circle having the contour of the upper surface and a previously determined relationship between the liquid level of the tundish and the diameter of a circle at the contour, or based on the area of ​​a circle having the contour of the upper surface and a previously determined relationship between the liquid level of the tundish and the area of ​​a circle at the contour; and A mechanism for calculating the amount of molten metal to be injected into the tundish based on the measured liquid level and injecting the molten metal so as to keep the liquid level constant.

2. The atomizing device according to claim 1, wherein: The mechanism for measuring the liquid level of the molten metal in the tundish utilizes a thermal image obtained based on infrared rays radiated from the tundish.

3. The atomizing device according to claim 1 or 2, wherein: The fluid jetting nozzle jets high-pressure water as the fluid.

4. The atomizing device according to claim 1 or 2, wherein: The molten metal contains copper, nickel and cobalt, The metal powder includes alloy powder containing copper, nickel, and cobalt as constituent components.

5. The atomizing device according to claim 4, wherein: In the process of recovering valuable metals from waste lithium-ion batteries, the atomizing device is used to produce alloy powder for acid leaching.

6. A method for producing metal powder, wherein: It is a method for producing metal powder using an atomizing device that sprays fluid onto molten metal to produce metal powder. The atomizing device comprises: a tundish, into which the molten metal is injected and from which the molten metal is discharged through a liquid discharge nozzle installed at the bottom; as well as a fluid injection nozzle, arranged below the tundish, for injecting the fluid toward the molten metal falling from the tundish, The tundish is shaped like an inverted truncated cone or an inverted cone at least inside the tundish, wherein the surface area of ​​the metal melt injected therein increases upward in the vertical direction, and the diameter of the upper opening inside the tundish, i.e., the opening diameter R 1 The bottom diameter R 2 By R 2 / R 1 The ratio relationship represented is 0.25 or more and 0.65 or less, The atomizing device further includes: a mechanism for capturing an image of the contour of the upper surface of the molten metal in the tundish by capturing the interior of the tundish, and measuring the liquid level of the molten metal in the tundish based on a diameter of a circle having the contour of the upper surface and a previously determined relationship between the liquid level of the tundish and the diameter of a circle at the contour, or based on an area of ​​a circle having the contour of the upper surface and a previously determined relationship between the liquid level of the tundish and the area of ​​a circle at the contour; and A mechanism for calculating the amount of molten metal to be injected into the tundish based on the measured liquid level and injecting the molten metal so as to keep the liquid level constant.

7. The method for producing metal powder according to claim 6, wherein: The molten metal contains copper, nickel and cobalt, The production method produces alloy powder containing copper, nickel, and cobalt as constituent components and having a unimodal particle size distribution.

8. A method for producing valuable metals, wherein: The invention relates to a method for producing valuable metals from waste lithium-ion batteries. The method includes the steps of: producing an alloy powder containing copper, nickel, and cobalt as constituent components from a molten metal from the waste lithium-ion battery; and The process of leaching the alloy powder with acid, In the step of producing the alloy powder, an atomizing device is used to spray a fluid onto the molten metal to produce the alloy powder. The atomizing device comprises: a tundish into which the molten metal is injected and from which the molten metal is discharged through a liquid discharge nozzle installed at the bottom; and a fluid injection nozzle, arranged below the tundish, for injecting the fluid toward the molten metal falling from the tundish, The tundish is shaped like an inverted truncated cone or an inverted cone at least inside the tundish, wherein the surface area of ​​the metal melt injected therein increases upward in the vertical direction, and the diameter of the upper opening inside the tundish, i.e., the opening diameter R 1 The bottom diameter R 2 By R 2 / R 1 The ratio relationship represented is 0.25 or more and 0.65 or less, The atomizing device further includes: a mechanism for capturing an image of the contour of the upper surface of the molten metal in the tundish by capturing the interior of the tundish, and measuring the liquid level of the molten metal in the tundish based on a diameter of a circle having the contour of the upper surface and a previously determined relationship between the liquid level of the tundish and the diameter of a circle at the contour, or based on an area of ​​a circle having the contour of the upper surface and a previously determined relationship between the liquid level of the tundish and the area of ​​a circle at the contour; and A mechanism for calculating the amount of molten metal to be injected into the tundish based on the measured liquid level and injecting the molten metal so as to keep the liquid level constant.

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