JP7533027B2 - Method for producing alloy powder and method for recovering valuable metals - Google Patents

Description

The present invention relates to a method for producing alloy powder and a method for recovering valuable metals using the alloy powder production method.

In recent years, lithium ion batteries have become popular as lightweight, high-power secondary batteries. Lithium ion batteries have a structure in which, inside an exterior can made of a metal such as aluminum or iron, a negative electrode material in which a negative electrode active material such as graphite is fixed to a negative electrode current collector made of copper foil, a positive electrode material in which a positive electrode active material such as lithium nickel oxide or lithium cobalt oxide is fixed to a positive electrode current collector made of aluminum foil, a separator made of a porous organic resin film such as polypropylene, and an electrolyte solution containing an electrolyte such as lithium hexafluorophosphate (LiPF ₆ ) are sealed.

One of the main uses of lithium-ion batteries is in hybrid and electric vehicles. Lithium-ion batteries used in these vehicles become waste lithium-ion batteries when the vehicle or the battery itself reaches the end of its life. Along with the life cycle of the vehicle, it is expected that lithium-ion batteries installed in vehicles will also be discarded in large quantities in the future.

Many proposals have been made to reuse such used batteries and defective products generated during manufacturing (hereinafter, these are collectively referred to as "waste lithium-ion batteries") as resources. For example, Patent Document 1 proposes a method in which a waste lithium-ion battery having an aluminum outer can is placed on a mesh body and heated to a temperature of about 660°C or higher, which is the melting point of aluminum, to melt the aluminum material and cause it to drop through the mesh of the mesh body, while leaving the unmelted material that constitutes the battery body on the mesh body, thereby separating the molten aluminum material from the unmelted material.

By the way, when a flux that lowers the melting point of a mixture of calcium oxide and aluminum oxide is added to waste lithium-ion batteries and melted in air at 1400°C or higher, it is possible to separate the alloy containing metals such as copper, nickel, cobalt, and iron whose standard free energy of oxide formation is higher than that of carbon, and oxides containing metals such as aluminum, calcium, and lithium whose standard free energy of oxide formation is lower than that of carbon. If copper can be separated from an alloy that mainly contains copper, nickel, cobalt, and iron, it can be input into an existing copper smelting process and recovered as copper metal, and nickel and cobalt can be recovered as nickel metal and cobalt metal through existing nickel smelting and cobalt smelting processes. This makes it possible to recover valuable metals at low cost.

However, when copper-nickel-cobalt-iron alloys are fed into existing copper smelting processes, although copper and nickel are separated and recovered, cobalt is distributed into oxides together with iron, making it difficult to recover cobalt as a single substance. For this reason, a method is being considered in which copper-nickel-cobalt alloys are acid-leached to dissolve nickel and cobalt in a solvent, and copper is separated as a dissolved residue, and copper, nickel, and cobalt are recovered by utilizing existing smelting processes. Generally, copper-nickel alloys have high corrosion resistance, and depending on the particle form, such as particle size, shape, surface roughness, and composition distribution, they may not dissolve at all in sulfuric acid even after more than 24 hours, so there is a demand for copper-nickel-cobalt alloys that dissolve stably in acid.

For example, it has been proposed that the acid leachability of the copper-nickel-cobalt alloy can be improved by powdering it using a gas atomization method.

International Publication No. 2020/013293

Now, regarding copper-nickel-cobalt alloy powder, the alloy powder was classified and its acid leaching in a sulfuric acid solution with a pH of 0.5 to 3 was investigated. As a result, it was found that fine powder with a particle size of less than 10 μm reacts violently with concentrated sulfuric acid, making it difficult to control the pH concentration, while coarse powder with a particle size of more than 300 μm is difficult to dissolve.

When a molten copper-nickel-cobalt alloy or other alloy (molten alloy) is powderized by atomization, whether by gas atomization or water atomization, the particle size distribution of the resulting alloy powder is a so-called bimodal distribution, and it has been confirmed that a peak occurs on the coarse particle side of the target particle size. The generation of coarse particles that accompanies this bimodal distribution causes a decrease in the dissolution rate during acid leaching. For this reason, the generated coarse particles must be classified and removed, resulting in a decrease in productivity.

It was found that one of the reasons that a bimodal distribution occurs when pulverizing using the atomization method is that the supply amount (supply rate) of the molten alloy is not stabilized when pulverizing the molten alloy by colliding with a fluid. Since the supply amount of the molten alloy is not constant, the particle size of the metal powder obtained by colliding with the fluid varies.

It was also found that the temperature of the molten alloy during atomization also affects the particle size of the resulting alloy powder.

The present invention has been made in consideration of the above-mentioned circumstances, and aims to provide a method for producing alloy powder that can be used to obtain alloy powder (atomized powder) with small particle size variation by atomization when recovering valuable materials such as copper, nickel, and cobalt contained in waste lithium-ion batteries, and a method for recovering valuable metals using the method.

After extensive research, the inventors discovered that during water atomization, there are times when the molten alloy level in the tundish is maintained at a predetermined target height, and times when the molten alloy level rises due to the melting furnace pouring too much. During times when the molten alloy level is high, the amount of molten alloy supplied to the area where the fluid collides and pulverizes the alloy (atomization crushing area) temporarily increases, and as a result, the particle size of the crushed alloy powder increases, resulting in a bimodal particle size distribution.

Then, they discovered that in the water atomizing device used in water atomizing processing, it is important to maintain a constant falling speed (in other words, the amount (supply rate) of the molten alloy from the tundish) until it comes into contact with the fluid (high-pressure water) sprayed at high speed, and that this can be achieved by keeping the height of the molten alloy surface in the tundish constant. Furthermore, they discovered that by adjusting the temperature of the molten alloy poured into the water atomizing device to a specific range depending on the composition of the molten alloy, they can more effectively suppress particle size variation.

Therefore, we devised a method to suppress the variation in the height of the molten metal surface in the tundish and stabilize the supply of the molten alloy by using a tundish with a specific internal shape as a water atomizing device, which stores the molten metal poured from the melting furnace and pours it from a pouring nozzle attached to the bottom. We also considered that by adjusting the temperature of the molten alloy poured into the water atomizing device to a specific range, alloy powder with even smaller particle size variation can be obtained, and thus completed the present invention.

(1) The first invention of the present invention is a method for producing an alloy powder containing copper, nickel, and cobalt as constituents, by using a water atomizing device for producing an alloy powder by injecting high-pressure water into a molten alloy, the molten alloy containing five metal elements, copper, nickel, cobalt, manganese, and iron, at 0.1 mass% or more each, and the total of the five metal elements being 98 mass% or more, the water atomizing device comprising a tundish into which the molten alloy is poured and from which the molten alloy is discharged from a discharge nozzle attached to the bottom of the tundish; and a fluid injection nozzle disposed below the tundish for injecting the high-pressure water into the molten alloy falling from the tundish, at least the inside of the tundish is shaped so that the area of the surface of the molten alloy increases as it moves upward in the vertical direction, and the temperature of the molten alloy is adjusted to a range of (1383 + 1.9 x T) ° C or more and (1483 + 1.9 x T) ° C or less, where "T" is the total mass percent of nickel, cobalt, manganese, and iron.

(2) The second aspect of the present invention is a method for producing an alloy powder according to the first aspect of the present invention, in which the molten alloy contains copper in the range of 24% by mass or more and 80% by mass or less.

(3) The third invention of the present invention is a method for producing alloy powder according to the first or second invention, in which the water atomizing device is configured such that the inside of the tundish is formed in the shape of an inverted truncated cone.

(4) The fourth aspect of the present invention is a method for producing an alloy powder according to any one of the first to third aspects, in which the molten alloy is derived from waste lithium-ion batteries.

(5) The fifth invention of the present invention is a method for recovering valuable metals from waste lithium-ion batteries, which includes a step of using a water atomizer to inject high-pressure water into the molten alloy derived from the waste lithium-ion batteries to produce an alloy powder containing copper, nickel, and cobalt as constituents, and a step of leaching the alloy powder with an acid, in which the step of producing the alloy powder is carried out by carrying out the method for producing the alloy powder according to any one of claims 1 to 4.

According to the present invention, it is possible to effectively produce alloy powder with small particle size variation by producing alloy powder using water atomization.

As a result, even when producing copper-nickel-cobalt alloy powder by atomization in a method for recovering valuable metals from waste lithium-ion batteries, the particle size variation of the resulting alloy powder is reduced, making it possible to effectively obtain alloy particles that are easy to control in acid leaching as alloy powder to be used in acid leaching treatment.

FIG. 2 is a diagram showing an example of the configuration of an atomizing device. FIG. 2 is a vertical cross-sectional view of the inside of a tundish, showing an example of the shape of the inside. FIG. 2 is a vertical cross-sectional view of the inside of a tundish, showing an example of the shape of the inside. FIG. 1 shows a conventional tundish having a cylindrical internal shape. FIG. 2 is a vertical cross-sectional view of the inside of the tundish, illustrating the function based on a comparison of the shape with a conventional tundish.

A specific embodiment of the present invention (hereinafter referred to as "the present embodiment") will be described in detail below. Note that the present invention is not limited to the following embodiment, and various modifications are possible without departing from the gist of the present invention. In addition, in this specification, the expression "X to Y" (X and Y are arbitrary numbers) means "X or more and Y or less."

≪1. Manufacturing method of alloy powder≫
The method for producing alloy powder according to the present embodiment is a method for producing alloy powder containing copper, nickel, and cobalt as constituent components using a water atomizing device that produces alloy powder by injecting high-pressure water into a molten alloy.

Here, the molten alloy supplied to the water atomizing device, i.e., the molten alloy which is the raw material for manufacturing the alloy powder, contains five metal elements: copper (Cu), nickel (Ni), cobalt (Co), manganese (Mn), and iron (Fe). The molten alloy contains each of the five metal elements at a ratio of 0.1% by mass or more, and the total of the five metal elements is 98% by mass or more. Furthermore, the content of Cu in the molten alloy is relatively large compared to the other metal elements, specifically, Cu is contained at a ratio of 24% by mass or more and 80% by mass or less.

Although the details will be described later, the method for producing alloy powder according to the present embodiment is suitable for producing alloy powder (copper-nickel-cobalt alloy powder) containing Cu, Ni, and Co as constituents, which is used as a raw material for acid leaching of the valuable metals Ni and Co in the process of recovering valuable metals from waste lithium-ion batteries. Waste lithium-ion batteries are used waste batteries or defective batteries generated during the battery manufacturing process, and contain at least the above-mentioned metal elements Mn and Fe as well as Cu, Ni, and Co as constituent materials of the battery. Therefore, the molten alloy obtained by heating and melting waste lithium-ion batteries contains Cu, Ni, Co, Mn, and Fe, with a relatively large Cu content.

The method for producing alloy powder according to this embodiment is a method for obtaining alloy powder (atomized powder) by water atomization using molten alloy as described above, and in particular, a water atomization device is used in which at least the inside of a tundish into which the molten alloy is poured and from which the molten alloy is discharged from a discharge nozzle attached to the bottom is formed in a specific shape. Specifically, at least the inside of the tundish in the water atomization device is formed in a shape such that the area of the surface of the poured molten alloy increases as it moves upward in the vertical direction.

In addition, in the method for producing alloy powder, the temperature of the molten alloy poured into the tundish of the water atomizing apparatus configured as described above is adjusted to a range of (1383 + 1.9 x T) °C or more and (1483 + 1.9 x T) °C or less, where "T" is the total mass percentage of Ni, C, Mn, and Fe.

According to this method for producing alloy powder, the level of the molten alloy in the tundish of the water atomizing device can be kept almost constant, thereby stabilizing the amount of molten alloy supplied from the tundish. As a result, the stable supply of molten alloy can reduce the variation in particle size of the alloy powder produced by injecting a fluid into the molten alloy. Furthermore, the temperature of the molten alloy poured into the tundish of the water atomizing device is adjusted to a specific range, and high-pressure water is injected into the molten alloy to produce alloy powder, so that the variation in particle size of the resulting alloy powder can be reduced even more effectively.

As described above, this method for producing alloy powder is suitable for producing alloy powder containing Cu, Ni, and Co as constituent components, for example, in the process of recovering valuable metals from waste lithium-ion batteries. In other words, the alloy powder (copper-nickel-cobalt alloy powder) obtained by this method is an alloy powder with small particle size variation, and by subjecting the alloy powder to acid leaching, the leaching efficiency of valuable metals such as Ni and Co can be effectively improved.

[About the water atomization device]
First, we will explain the water atomizing device used in the method for producing alloy powder. The water atomizing device is a device that produces alloy powder by injecting high-pressure water, which is a fluid, into a molten alloy to break it into droplets, and then solidifying the droplets that have been broken down and scattered. Note that "droplet-like" refers to the molten alloy being in the form of liquid droplets (molten droplets). The resulting metal powder is also called atomized powder.

Figure 1 shows an example of the configuration of an atomizing device used in the method according to this embodiment. The water atomizing device 1 includes a tundish 11 that pours the molten alloy M from a melting furnace (crucible furnace) 3, a fluid injection nozzle 12 that injects a fluid into the molten alloy M that falls from the tundish 11, and a chamber 13 in which the fluid injection nozzle 12 is provided at the top and where droplets are formed by fluid injection to generate alloy powder.

In the water atomizing device 1, at least the internal shape of the tundish 11 is formed in such a way that the surface area of the poured molten alloy M increases as it moves upward in the vertical direction.

With this water atomizing device 1, the surface height of the molten alloy M in the tundish 11 can be kept almost constant, thereby stabilizing the supply amount of the molten alloy M from the tundish 11. As a result, the molten alloy M is supplied at a stable rate, which makes it possible to suppress variation in particle size of the alloy powder produced by injecting a fluid into the molten alloy M.

(Tundish)
The tundish 11 stores therein the molten alloy M poured from the melting furnace 3, and from a pouring nozzle 11N attached to the bottom 11b, the molten alloy M is poured into the chamber 13. The molten alloy M poured from the tundish 11 falls freely from the pouring nozzle 11N and is supplied into the chamber 13.

In addition, discharging the molten alloy M from the discharging nozzle 11N into the chamber 13 is also expressed as "supplying" the molten alloy M. As will be described in detail later, the molten alloy M freely falling from the discharging nozzle 11N collides with the high-pressure water sprayed from the fluid spray nozzle 12 provided at the upper position of the chamber 13, turns into droplets, and is supplied in a scattered state into the chamber 13.

At least the inside of the tundish 11 is formed in such a shape that the area of the surface of the molten alloy M poured from the melting furnace 3 and stored therein increases as it moves upward in the vertical direction. The vertical direction refers to the vertical direction of the diagram of the configuration shown in FIG. 1, and refers to the vertical direction of the tundish 11 shown in the vertical cross section in FIG. 1. In other words, it is the direction in which the molten alloy M gradually accumulates in the tundish 11 from the bottom 11b to the upper opening 11a. The surface of the molten alloy M is the part indicated by "Ms" in FIG. 1, and refers to the upper surface of the molten alloy M poured and stored in the tundish 11. For example, when the internal shape of the tundish 11 is an inverted truncated cone shape, the surface of the molten alloy M is an approximately circular surface. The surface area refers to the area of the upper surface of the molten alloy M. The opening 10a refers to the pouring port for the molten alloy M from the melting furnace 3, which is provided near the top of the tundish 11.

Figures 2 and 3 are vertical cross-sectional views of the inside of the tundish 11, showing examples of the internal shape. As shown in the figures, the inside of the tundish 11 is, for example, in the shape of an inverted truncated cone or an inverted cone. The inside of the tundish 11 is formed in a shape such that the area of the molten alloy surface gradually increases from the bottom 11b to the upper opening 11a, that is, as the height (molten alloy surface level) of the molten alloy M being poured increases.

In the tundish 11 having such an internal shape, the molten alloy M can be maintained at a substantially constant level, for example, at a target specified molten alloy level (molten alloy level height). That is, while the molten alloy M is being supplied from the discharge nozzle 11N of the tundish 11, new molten alloy M is being continuously poured from the melting furnace 3 into the tundish 11 at a constant speed, the internal shape of the tundish 11 is such that the area of the molten alloy M increases as the molten alloy level increases, so that the molten alloy M being poured fluctuates gently, and the molten alloy level can be maintained at a substantially constant level, for example, at a target molten alloy level. The pouring speed of the molten alloy M from the melting furnace 3 to the tundish 11 is kept at a substantially constant speed. The molten alloy M can be poured into the tundish 11 by, for example, tilting the melting furnace 3 (see FIG. 1).

The supply amount (supply rate) of the molten alloy M supplied from the discharge nozzle 11N is due to the pressure based on the height of the molten alloy M surface in the tundish 11. Therefore, if the height of the molten alloy M surface can be maintained approximately constant, the supply amount of the molten alloy M per unit time supplied from the discharge nozzle 11N according to the nozzle diameter can also be stabilized to be approximately constant.

The supply rate of the molten alloy M may be set appropriately depending on conditions such as the particle size of the produced metal powder and the amount of high-pressure water sprayed from the fluid spray nozzle 12 described below. For example, the supply rate of the molten alloy M is set in the range of about 10 kg/min to 75 kg/min.

Here, the molten alloy M supplied into the chamber 13 from the discharge nozzle 11N collides with the high-pressure water sprayed from the fluid spray nozzle 12 at the top of the chamber 13 and disperses in the form of droplets. If the amount of molten alloy M supplied from the tundish 11 changes, the size of the droplets formed also changes, resulting in variation in the particle size distribution of the alloy powder (atomized powder) produced within a given time. For example, if the level of the molten alloy M poured from the melting furnace 3 increases, the amount of molten alloy N supplied from the discharge nozzle N increases based on the increased level of the molten alloy. Then, the size of the droplets formed by the collision of the high-pressure water sprayed at a constant speed increases, and alloy powder with a relatively large particle size is produced, and the particle size distribution is, for example, bimodal, resulting in particle size variation.

In this regard, if the surface height of the poured molten alloy M can be maintained substantially constant due to the internal shape of the tundish 11 described above, the supply amount of the molten alloy M can be stabilized. This makes it possible to suppress the variation in size of the droplets formed by the collision of the high-pressure water, and the particle size distribution of the obtained alloy powder becomes a sharp single-peak distribution.

In addition, when the pouring of the molten alloy M from the melting furnace 3 to the tundish 11 is completed and the amount of the molten alloy M in the tundish 11 decreases and the molten alloy level gradually decreases, for example, in a tundish 100 having a conventional cylindrical internal shape as shown in FIG. 4, the amount of molten metal supplied from the discharge nozzle 100N gradually decreases as the molten alloy level decreases. Then, due to the decrease in the supply amount, the size of the molten metal droplets formed by the collision of the high-pressure water sprayed at a constant speed becomes smaller, and alloy powder with a relatively small particle size is produced, and the particle size distribution becomes, for example, a bimodal distribution, resulting in particle size variation. Note that the cylindrical shape of the inside of the tundish 100 shown in FIG. 4 is not a shape in which the area of the molten alloy surface increases as the molten alloy level increases, but a shape in which the area of the molten alloy surface is constant regardless of the molten alloy level.

In this regard, the internal shape of the tundish 11 described above eliminates the portion shown in the dashed circle in FIG. 5, i.e., the portion that reduces the supply amount of the molten alloy M, compared to a tundish with a cylindrical interior (the shape of the portion represented by the imaginary line) as shown in FIG. 5. Therefore, even if the molten alloy level gradually decreases, the pressure fluctuation based on the molten alloy level becomes small, and the supply amount of the molten alloy M can be stably maintained. Furthermore, since it is possible to stabilize the supply amount of the molten alloy M, the variation in the size of the droplets formed by the collision of the high-pressure water can be suppressed, and the particle size distribution of the obtained alloy powder becomes a sharp single-peak distribution.

In this way, the tundish 11 can stabilize the amount of molten alloy M supplied from the discharge nozzle 11N, both when the molten alloy M is continuously poured into the tundish 11 from the melting furnace 3 and when the pouring of the molten alloy M is completed and the molten alloy level gradually decreases.

Returning to the explanation of Figures 2 and 3, the shape of the inside of the tundish 11 (11A, 11B) is, for example, an inverted truncated cone shape or an inverted cone shape, as shown in these figures. The inside of the tundish 11 is formed so that the diameter (opening diameter) ^R1 of the upper opening 11a is larger than the diameter (bottom diameter) ^R2 of the bottom 11b, and thus the area of the molten alloy M gradually increases as the height of the molten alloy M increases. Naturally, in a vertical cross-sectional view (Figures 2 and 3) of the inside of the tundish 11, the wall surface at a position corresponding to the position of the molten alloy M (not shown) is inclined, forming, for example, an inverted truncated cone shape or an inverted cone shape.

The tundish 11A shown in FIG. 2 and the tundish 11B shown in FIG. 3 each illustrate an embodiment in which the ratio of the opening diameter ^R1 to the bottom diameter ^R2 is different. The ratio of ^R1 to ^R2 is not particularly limited, but the relationship of the ratio represented by ^R2 / ^R1 is preferably about 0.25 to 0.65, more preferably about 0.30 to 0.55. If ^R2 / ^R1 is too small, the molten metal surface height at a predetermined target height can be maintained almost constant, but the internal volume becomes small and the processing efficiency by atomization decreases. On the other hand, if ^R2 / ^R1 is larger than 0.65, the molten metal surface height will be approximated to a cylindrical shape as shown in FIG. 4, so that it may be difficult to stabilize the molten metal surface height.

As shown in FIG. 3, the bottom 11b of the tundish, whose interior is formed in the shape of an inverted truncated cone, can be provided with an inclined portion 21 that slopes downward toward the discharge nozzle 11N attached to the bottom 11b. The inclined portion 21 is provided inside the tundish 11B. By providing the inclined portion 21 that slopes downward toward the discharge nozzle 11N in this way, it is possible to more efficiently suppress the decrease in the supply amount of the molten alloy M supplied through the discharge nozzle 11N, especially at the stage where the pouring of the molten alloy M is completed and the molten alloy surface height gradually decreases. This makes it possible to further stabilize the supply amount and suppress the variation in particle size of the obtained alloy powder.

The material of the tundish 11 is not particularly limited and may be made of alumina, for example. The material of the discharge nozzle 11N attached to the bottom 11b of the tundish 11 is also not particularly limited and may be made of zirconia, for example. The nozzle diameter of the discharge nozzle 11N may be appropriately determined depending on the composition of the molten alloy M and the amount of the molten alloy to be discharged, and may be, for example, about 3 mm to 10 mm in nozzle diameter.

In addition, although Figures 1 to 3 show the opening 11a of the tundish 11 as being open on its entire surface, this is not limited to being open on its entire surface. As described above, the opening 10a refers to the pouring port for the molten alloy M from the melting furnace 3, which is provided near the top of the tundish 11, and it is sufficient that there is an opening in a part near the ceiling of the tundish 11 through which the molten alloy M from the melting furnace 3 is poured. Even in this case, the opening 10a refers to the upper surface of the tundish 11 including the open portion.

(Fluid injection nozzle)
The fluid injection nozzle 12 is provided at the upper part (ceiling) of the chamber 13 described later, and is a nozzle that injects high-pressure water, which is a fluid, onto the freely falling molten alloy M supplied from the outlet nozzle 11N of the tundish 11. Note that the position where the fluid injection nozzle 12 is provided to inject high-pressure water onto the molten alloy M is the position where the molten alloy M is crushed into droplets, and therefore this portion becomes the atomization crushing portion.

The high-pressure water, which is a fluid, is the medium for crushing the molten alloy M.

The structure and shape of the fluid injection nozzle 12 are not particularly limited as long as it can inject the desired amount of high-pressure water into the molten alloy M. In addition, it is preferable that an even number of fluid injection nozzles 12 (e.g., 2, 4, or 6) are provided so as to face the falling molten alloy M as the central axis. In addition, in the fluid injection nozzle 12, the angle (injection angle) of the high-pressure water injected into the molten alloy M can be adjusted so as to maximize the yield of the produced alloy powder. For example, the relative angle (vertex angle) of the high-pressure water can be adjusted to, for example, 30° to 50°, and the injection angle (vertex angle) of the water with respect to the falling molten alloy M can be adjusted to 15° to 25°.

In addition, it is preferable to set the injection conditions of the high-pressure water injected from the fluid injection nozzle 12 appropriately according to the particle size of the alloy powder (copper-nickel-cobalt alloy powder) to be produced.

Specifically, regarding the injection conditions, the pressure of the high-pressure water to be injected is preferably set to, for example, about 6 MPa or more and 20 MPa or less. If the pressure is less than 6 MPa, the particle size of the obtained alloy powder may become excessively large, and if the pressure exceeds 20 MPa, the alloy powder may become excessively fine, reducing the separation and recovery properties. In addition, in order to increase the pressure, it is necessary to use an expensive pump, which increases the production cost of the alloy powder.

The mass ratio (specific water ratio) of the amount of high-pressure water sprayed to the amount of molten alloy M supplied (amount falling) is preferably set to, for example, about 5.0 to 7.0 times. The amount of molten alloy M supplied is the average amount supplied per unit time, and the amount of high-pressure water sprayed is the average amount sprayed per unit time, and if the amount of molten alloy M supplied or the amount of high-pressure water sprayed varies over time, it is the average value. If the specific water ratio is less than 5.0 times, the particle size of the resulting alloy powder may be excessively large, and if the specific water ratio exceeds 7.0 times, the alloy powder may be too fine.

The temperature of the high-pressure water to be sprayed is preferably set to, for example, 2°C or higher and 35°C or lower. If the water temperature is too low, the water may freeze in the piping when the equipment is stopped, causing problems such as water leakage, and if the water temperature is too high, the particle size of the resulting alloy powder tends to become large. The temperature of the high-pressure water can be controlled by providing a chiller (not shown) or the like and adjusting the set temperature.

(Chamber)
The chamber 13 is connected to the tundish 11 at the position of the tapping nozzle 11N, and the molten alloy M is supplied from the tundish 11 through the tapping nozzle 11N. The chamber 13 is also provided with the above-mentioned fluid injection nozzle 12 at its upper part, and by injecting high-pressure water onto the molten alloy M supplied from the tapping nozzle 11N and freely falling, droplets are formed to generate alloy powder.

Specifically, when high-pressure water is sprayed onto the molten alloy M falling through the discharge nozzle 11N in the chamber 13, the molten alloy M is broken down into droplets. The droplets that are generated scatter within the chamber 13 and fall toward the bottom. The droplets that are generated are cooled by the high-pressure water, and are further cooled as they scatter and fall within the chamber 13, rapidly solidifying into alloy powder. In the water atomization device 1 that performs the water atomization method, the water sprayed from the fluid spray nozzle 12 is stored in the lower part of the chamber 13 to form an aqueous phase, and the alloy powder that is heading toward a solidified state also flows into the aqueous phase and is cooled.

In the chamber 13, the angle (spray angle) of the high-pressure water sprayed onto the molten alloy M is adjusted so as to maximize the yield of alloy powder produced. As described above, the amount of molten alloy falling per unit time, the amount of high-pressure water sprayed per unit time, the pressure of the sprayed high-pressure water, the temperature of the high-pressure water, etc. can be set appropriately depending on the yield of alloy powder and the desired particle size of the alloy powder.

The chamber 13 is structured so that its internal pressure can be maintained higher than atmospheric pressure by injecting an inert gas such as nitrogen gas to prevent air from entering the chamber. A gas exhaust structure 18 is also connected to the chamber 13, making it possible to exhaust gases such as hydrogen gas that fill the chamber 13 to the outside without air entering the chamber 13.

An outlet 13e is provided at the bottom of the chamber 13 for discharging the slurry containing the alloy powder, and the alloy powder is collected through a collection pipe 14 connected to the outlet 13e.

(Other configurations)
In the water atomization device 1, a filter 15 is connected to the other end of the recovery pipe 14. In the filter 15, a solid-liquid separation process is performed on the slurry containing the alloy powder discharged through the recovery pipe 2, and the alloy powder, which is a solid content, is separated and recovered from the slurry. The water from which the alloy powder has been separated in the filter 15 is stored in a tank 16 connected through a pipe, and after temperature adjustment is performed by a chiller or the like (not shown), the water is circulated and supplied to the fluid injection nozzle 12 by a high-pressure pump 17. 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 alloy M.

[Regarding temperature control of molten alloy]
In the method for producing alloy powder according to the present embodiment, the temperature of the molten alloy M poured into the water atomizing apparatus 1 having the above-described configuration is adjusted to a specific range. Specifically, when the total mass percent of Ni, C, Mn, and Fe contained in the molten alloy M is "T", the temperature is adjusted to a range of (1383+1.9×T)° C. or more and (1483+1.9×T)° C. or less.

The molten alloy M contains five metal elements, Cu, Ni, Co, Mn, and Fe, each of which is contained in an amount of 0.1% by mass or more, and the total amount of the five metal elements is 98% by mass or more. Furthermore, in the molten alloy M, the content of Cu is relatively large compared to the other metal elements, and specifically, Cu is contained in an amount of 24% by mass or more and 80% by mass or less.

The inventors investigated the melting points of the 10 main compositions of Cu-Ni-Co ternary system recovered from waste lithium-ion batteries, for example, and found that the melting points were inversely proportional to the Cu content, ranging from 1280°C to 1363°C (melting point = 1451°C - 2.86 x Cu content). In reality, depending on the degree of reduction in the reduction melting, a high degree of reduction increases the Fe and Mn in the alloy, while a low degree of reduction decreases the Fe and Mn and also reduces the Co content. However, when the degree of reduction is adjusted so that the Co recovery rate from waste lithium-ion batteries is 95% or more, the melting point of the alloy obtained is 1383°C to 1483°C. Furthermore, from the approximation line when considering the need to ensure the fluidity of the alloy, the temperature of the molten alloy M can be derived to be in the range of "(1383 + 1.9 x T) °C or more and (1483 + 1.9 x T) °C or less," where the total mass of Ni, Co, Mn, and Fe is T mass %.

By adjusting the temperature of the molten alloy M of this composition to the specific range mentioned above (a range of (1383 + 1.9 x T) °C or higher and (1483 + 1.9 x T) °C or lower), the molten state of the molten alloy can be appropriately maintained. Furthermore, it has been found that by pouring the molten alloy M whose temperature has been adjusted in this way into the water atomizing device 1 and atomizing it, the particle size variation of the obtained alloy powder can be further suppressed. This makes it possible to obtain alloy powder with a sharp particle size distribution.

The temperature of the molten alloy M can be adjusted in a melting furnace (melting furnace 3 shown in FIG. 1) that pours the molten alloy M into the tundish 11 of the water atomizing device 1. For example, the melting furnace 3 can be an induction furnace or the like, and the temperature of the molten alloy M (the molten alloy M before being poured into the tundish 11) can be adjusted by outputting a predetermined frequency. The temperature adjustment in the melting furnace 3 can be performed at the stage of molten alloy in the melting furnace 3, or after molten alloy is obtained, a separate temperature adjustment step can be provided to add heat, etc.

The temperature of the molten alloy M may also be adjusted in the tundish 11 of the water atomizing device 1. For example, before supplying the molten alloy M from the tundish 11 to the chamber 13, the molten alloy M is heated by applying heat from inside or outside the tundish 11. This adjusts the temperature of the molten alloy M to a specific range.

In addition, before pouring the molten alloy M from the melting furnace 3 into the tundish 11 of the water atomizing device 1, the inside of the empty tundish 11 may be heated to 1000°C or higher, for example, by 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 3, suppresses the temperature drop of the molten alloy M poured into the tundish 11, and maintains an appropriate temperature.

≪2. How to recover valuable metals≫
Next, a method for recovering valuable metals using the above-mentioned method for producing alloy powder will be described.

The valuable metal recovery method according to the present embodiment is a method for recovering valuable metals from waste lithium-ion batteries. Specifically, this valuable metal recovery method includes a step of pretreating waste lithium-ion batteries (waste battery pretreatment step) S1, a step of melting the pretreated waste lithium-ion batteries to prepare a molten alloy (a molten alloy containing Cu, Ni, and Co) (molten alloy preparation step) S2, a step of injecting a fluid into the molten alloy to produce alloy powder (alloy powder production step) S3, and a step of leaching the produced alloy powder with acid (acid leaching step) S4.

The alloy powder production process S3 is characterized by utilizing the above-mentioned alloy powder production method. That is, a water atomizer 1 is used in which at least the inside of the tundish 11 is shaped so that the area of the surface of the poured molten alloy M increases as it moves upward in the vertical direction, and the temperature of the molten alloy M is adjusted to a range of (1383 + 1.9 x T) °C or more and (1483 + 1.9 x T) °C or less. The total mass percentage of Ni, C, Mn, and Fe contained in the molten alloy M is "T".

By producing alloy powder using this method, the surface height of the molten alloy M in the tundish 11 can be kept almost constant, and the supply amount of the molten alloy M from the tundish 11 can be stabilized. As a result, the molten alloy M is supplied at a stable rate, which makes it possible to suppress the variation in particle size of the alloy powder produced by injecting a fluid into the molten alloy M. Furthermore, by adjusting the temperature of the molten alloy M to a specific range, the variation in particle size of the resulting alloy powder can be suppressed even more effectively.

In a method for recovering valuable metals from waste lithium-ion batteries, when an alloy powder (copper-nickel-cobalt alloy) containing Cu, Ni, and Co as its components is subjected to acid leaching to selectively leach Ni and Co into the solution, it has been confirmed that the particle size variation of the alloy powder affects the acid leaching efficiency. Depending on the particle shape including the particle size distribution, it may hardly dissolve in acid. In this regard, by producing alloy powder (atomized powder) by the above-mentioned method in the alloy powder production process S3, it is possible to obtain alloy powder with a narrow particle size distribution with reduced particle size variation, which makes it possible to improve the leaching efficiency when subjected to acid leaching.

[Waste battery pretreatment process]
The waste battery pretreatment step S1 is a step of pretreating the waste lithium ion batteries, which are the raw material for recovering valuable metals. The pretreatment is a treatment prior to the melting of the raw material to obtain the molten alloy in the molten alloy preparation step S2 described later. Here, the waste lithium ion batteries include not only used batteries but also defective batteries generated during the battery manufacturing process.

Specifically, the waste battery pretreatment process S1 includes a detoxification process S11 for detoxifying the waste lithium-ion batteries, and a crushing process S12 for crushing the waste lithium-ion batteries.

The detoxification process S11 is a process for preventing the waste lithium-ion batteries from exploding, rendering them harmless, and removing the outer cans (also called "detoxification process"). Lithium-ion batteries are sealed systems, and therefore contain electrolytes and the like inside. Therefore, if the waste lithium-ion batteries are used as they are and subjected to crushing or other processes, there is a risk of explosion, which is dangerous. For this reason, it is preferable to perform a discharge process or electrolyte removal process by some method. In addition, the outer cans that constitute the waste lithium-ion batteries are often made of metals such as aluminum (Al) and iron (Fe), and such metal outer cans are relatively easy to collect as they are. Therefore, by removing the electrolyte and outer cans in the detoxification process S11, safety can be improved and the recovery rate of valuable metals (Cu, Ni, Co) can be increased.

The specific method of detoxification is not particularly limited. For example, a method of physically opening holes in the waste lithium-ion batteries with a needle-shaped blade and removing the electrolyte can be used. Another method is to heat the waste lithium-ion batteries and burn the electrolyte to render them harmless.

When recovering Al and Fe contained in the outer cans in the detoxification step S11, the removed outer cans may be crushed and the crushed material may be sieved using a sieve shaker. Since Al is easily turned into powder by light crushing, it can be recovered efficiently. In addition, Fe contained in the outer cans may be recovered by magnetic separation.

The crushing process S12 is a process in which the contents of the waste lithium-ion batteries after the detoxification process are crushed to obtain crushed material. The crushed material obtained becomes the raw material (molten raw material) for melting (molten metal). The crushing process S12 is a process for increasing the reaction efficiency in the dry smelting process, and by increasing the reaction efficiency, the recovery rate of valuable metals (Cu, Ni, Co) can be increased.

The specific method of crushing is not particularly limited. Crushing can be performed using a conventionally known crusher such as a cutter mixer.

[Preheating process]
If necessary, before the molten alloy preparation step S2 including the melting step S21 described later, a step of preheating (oxidizing roasting) the crushed waste lithium ion batteries (crushed material) to prepare a preheated material (preheating step) may be provided.

In the preliminary heating process (oxidation roasting process), a process is carried out to reduce the amount of carbon contained in the waste lithium-ion batteries. By providing such a process, even if the waste lithium-ion batteries contain an excess amount of carbon, the carbon can be effectively oxidized and removed, and the alloying of valuable metals can be promoted in the subsequent melting process S21.

In other words, valuable metals are reduced to localized molten fine particles in the melting process, but carbon can be a physical obstacle when the molten fine particles (valuable metals) aggregate. If carbon prevents the molten fine particles from aggregating and consolidating and the resulting separation of the molten alloy (metal) and slag, the recovery rate of valuable metals may decrease. In response to this, by providing a preheating process to oxidize and remove carbon, the molten fine particles can be aggregated and consolidated in the melting process, and the recovery rate of valuable metals can be increased. In addition, phosphorus (P) contained in waste lithium-ion batteries is an impurity that is relatively easily reduced, so if there is an excess of carbon, there is a possibility that phosphorus will be reduced and incorporated into the molten alloy together with the valuable metal. In this regard, by removing excess carbon in advance in the preheating process, it is possible to prevent phosphorus from being mixed into the molten alloy. It is preferable that the amount of carbon contained in the preheated material (crushed material after preheating treatment) is less than 1% by mass.

In addition, by providing a preheating process, it is possible to suppress the variation in oxidation. In the preheating process, it is preferable to treat (oxidize roast) the waste lithium-ion batteries at a degree of oxidation that can oxidize the relatively low-added-value metals (such as Al) contained in the waste lithium-ion batteries. The degree of oxidation can be easily controlled by adjusting the temperature, time and/or atmosphere of the preheating process.

The degree of oxidation is adjusted, for example, as follows. That is, aluminum (Al), lithium (Li), carbon (C), manganese (Mn), phosphorus (P), iron (Fe), cobalt (Co), nickel (Ni), and copper (Cu) are generally oxidized in the following order: Al>Li>C>Mn>P>Fe>Co>Ni>Cu. In the preheating process, oxidation is allowed to proceed until all of the Al is oxidized. Note that oxidation may be accelerated until part of the Fe is oxidized, but it is preferable to keep the degree of oxidation at a level that prevents Co from being oxidized and distributed to the slag.

The preliminary heating treatment is preferably carried out in the presence of an oxidizing agent. This allows efficient removal of the impurity carbon (C) by oxidation and oxidation of Al. The oxidizing agent is not particularly limited, but oxygen-containing gas (air, quasi-oxygen, oxygen-enriched gas, etc.) is preferred because of its ease of handling. The amount of oxidizing agent introduced is preferably, for example, about 1.2 times the chemical equivalent required for the oxidation of each substance to be the target of the oxidation treatment.

The temperature (heating temperature) of the preheating treatment is preferably 600°C or higher, and more preferably 700°C or higher. By using such a heating temperature, the efficiency of carbon oxidation can be further increased and the heating time can be shortened. In addition, the heating temperature is preferably 900°C or lower, which can reduce thermal energy costs and increase the efficiency of preheating.

The preliminary heating treatment can be carried out using a known roasting furnace. It is also preferable to use a furnace (preliminary furnace) different from the melting furnace used in the subsequent melting step S21, and to carry out the treatment in the preliminary furnace. As the preliminary heating furnace, any type of furnace can be used as long as it is capable of supplying an oxidizing agent (oxygen, etc.) to the charge while roasting it and carrying out the oxidation treatment therein. Examples include the conventionally known rotary kiln and tunnel kiln (hearth furnace).

[Molten alloy preparation process]
The molten alloy preparation step S2 is a step of melting the waste lithium ion batteries to prepare a molten alloy (a molten alloy containing Cu, Ni, and Co) M. A melting step S21 of melting the crushed ion battery material, a recovery step S22 of separating slag from the melt and recovering an alloy containing valuable metals, and a melting step S23 of turning the recovered alloy into a molten alloy M. , has.

In the melting step S21, the molten raw material (crushed or preheated waste lithium-ion batteries) is put into a melting furnace, and the molten raw material is heated and melted to produce an alloy (metal) containing Cu, Ni, and Co as constituents, and slag located above the alloy. Specifically, the molten raw material is first heated and melted to form a molten mass. The molten mass contains the alloy and slag in a molten state. The obtained molten mass is then made into a molten mass. The molten mass contains the alloy and slag in a solidified state.

The alloy mainly contains valuable metals. Therefore, it is possible to separate the valuable metals and other components into alloys and slag. 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 generally oxidized in the order Al>Li>C>Mn>P>Fe>Co>Ni>Cu. In other words, Al is most easily oxidized, and Cu is least easily oxidized. Therefore, metals with relatively low added value (such as Al) are easily oxidized and become slag, and valuable metals (Cu, Ni, Co) are reduced and become alloys. In this way, metals with relatively low added value and valuable metals can be separated into slag and alloys.

When melting the molten raw material, the oxygen partial pressure may be controlled. The oxygen partial pressure can be controlled by a known method. For example, a method of introducing a reducing agent or an oxidizing agent into the molten raw material or the molten mass obtained by melting the molten raw material can be mentioned. As the reducing agent, a material with a high carbon content (graphite powder, graphite grains, coal, coke, etc.) or carbon monoxide can be used. Alternatively, a component of the molten raw material with a high carbon content can be used as the reducing agent. Also, as the oxidizing agent, an oxidizing gas (air, oxygen, etc.) or a material with a low carbon content can be used. Alternatively, a component of the molten raw material with a low carbon content can be used as the oxidizing agent.

The introduction of the reducing agent or oxidizing agent can be carried out by known methods. For example, if the reducing agent or oxidizing agent is a solid substance, it can be introduced by pouring it into the molten raw material or the molten mass. If the reducing agent or oxidizing agent is a gaseous substance, it can be introduced from an inlet such as a lance provided in the melting furnace. There are no particular limitations on the timing of the introduction of the reducing agent or oxidizing agent, and it may be introduced at the same time that the molten raw material is poured into the melting furnace, or it may be introduced when the molten raw material has melted and become a molten mass.

In addition, in the melting process in the melting step S21, a flux may be introduced (added). By adding a flux, the melting process temperature can be lowered, and energy costs can be reduced. Furthermore, the removal of phosphorus (P) can be further promoted. The flux preferably contains an element that incorporates an impurity element to form a basic oxide with a low melting point. For example, phosphorus becomes an acidic oxide when oxidized, so the more basic the slag formed by the melting process, the easier it is to incorporate phosphorus into the slag and remove it. Among them, the flux is more preferably one that contains a calcium compound that is inexpensive and stable at room temperature. Examples of calcium compounds include calcium oxide (CaO) and calcium carbonate (CaCO ₃ ).

In the melting process, the heating temperature for melting the molten raw material is not particularly limited, but is preferably 1400°C or higher and 1600°C or lower, and more preferably 1450°C or higher and 1550°C or lower. By setting the heating temperature at 1400°C or higher, the valuable metals (Cu, Co, Ni) are sufficiently melted and an alloy is formed in a state of enhanced fluidity. Therefore, the efficiency of separating the alloy and the slag in the recovery process S22 described later can be improved. In addition, by setting the heating temperature at 1450°C or higher, the fluidity of the alloy can be further increased, and the efficiency of separating the impurity components and the valuable metals can be further improved. On the other hand, if the heating temperature exceeds 1600°C, thermal energy is wasted and the wear of refractories such as the crucible and furnace wall becomes severe, which may reduce productivity.

In the recovery step S22, slag is separated from the molten material obtained in the melting step S21, and an alloy containing valuable metals is recovered as an alloy raw material. Slag and alloy have different specific gravities. Slag, which has a smaller specific gravity than alloy, collects on top of the alloy, so it can be easily separated and recovered by gravity separation. Through the processing in the recovery step S22, an alloy raw material containing Cu, Ni, and Co as constituents can be obtained.

In the molten metal forming step S23, the recovered alloy raw materials are heated and melted to form a molten alloy M. Specifically, the prepared alloy raw materials are charged into a melting furnace (crucible furnace), and the alloy raw materials are heated and melted to form a fluid molten metal (molten alloy M). The heating and melting temperature is preferably 1450°C or higher and 1550°C or lower, from the viewpoint of producing the desired alloy powder in the alloy powder production step S3 described below. Through the processing in the molten metal forming step S23, a molten alloy M containing Cu, Ni, and Co as constituents can be obtained.

Here, the molten alloy M obtained in the molten metal formation step S23 contains five metal elements: Cu, Ni, Co, Mn, and Fe. The molten alloy contains each of the five metal elements at a ratio of 0.1% by mass or more, and the total of the five metal elements is 98% by mass or more. Furthermore, the content of Cu in the molten alloy is relatively large compared to the other metal elements, and specifically, Cu is contained at a ratio of 24% by mass or more and 80% by mass or less.

Then, in the molten metal process S23, the temperature of the molten alloy M is adjusted to a range of (1383 + 1.9 × T) °C or more and (1483 + 1.9 × T) °C or less, where "T" is the total mass percentage of Ni, C, Mn, and Fe. The temperature of the molten alloy M may be adjusted during the molten metal process, that is, by adjusting the heating temperature of the molten metal process conditions, or after the molten alloy M is obtained by molten metal processing, a separate heating step may be provided to adjust the temperature to a specific temperature range.

[Alloy powder manufacturing process]
The alloy powder production step S3 is a step of producing alloy powder (atomized powder) by an atomization method using the water atomization device 1. Specifically, the molten alloy M having a specific temperature obtained in a melting furnace is poured into the tundish 11 constituting the water atomization device 1, and a predetermined supply amount of the molten alloy M is supplied by free fall from the tundish 11 into the chamber 13, and the falling molten alloy M is crushed into droplets by injecting high-pressure water onto it. In the chamber 13, the crushed and scattered droplets are rapidly cooled and solidified to produce alloy powder.

The valuable metal recovery method according to this embodiment is characterized in that in the alloy powder production step S3, alloy powder is produced using the water atomizing device 1 having the configuration described above in detail. That is, the water atomizing device 1 is equipped with a tundish 11 into which molten alloy M is poured and from which the molten alloy M is poured from a pouring nozzle 11N attached to the bottom 11b, and a fluid injection nozzle 12 disposed below the tundish 11 and injecting a fluid onto the molten alloy M dropping from the tundish 11, and at least the inside of the tundish 11 is shaped so that the area of the molten alloy M poured from the melting furnace 3 increases as it moves upward in the vertical direction.

The specific configuration of the water atomizing device 1 has been described in detail above, so a detailed explanation will be omitted here.

In the alloy powder production process S3, by producing alloy powder using the water atomizer 1, the surface height of the molten alloy M in the tundish 11 can be kept almost constant, and the amount of molten alloy M supplied from the tundish 11 can be stabilized. As a result, the molten alloy M is supplied at a stable rate, and the particle size variation of the alloy powder produced by injecting a fluid into the molten alloy M can be suppressed.

In addition, by adjusting the temperature of the molten alloy M poured into the water atomizing device 1 to the specific range described above, the variation in particle size of the resulting alloy powder can be more effectively suppressed.

The alloy powder produced in this manner, which has a small particle size variation, can be subjected to acid leaching in the acid leaching step S4 described below, thereby effectively improving the leaching efficiency of valuable metals such as Ni and Co.

[Acid leaching process]
In the acid leaching step S4 (valuable metal recovery step), the produced alloy powder is subjected to a leaching treatment with an acid solvent to selectively dissolve Ni and Co from the alloy powder in the acid solvent. This also 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.

As the acid solvent, a known acid solution used for recovering valuable metals can be used. Specific examples of the acid solution include sulfuric acid, hydrochloric acid, and nitric acid. For example, by using sulfuric acid as the acid solution and immersing the alloy powder in the sulfuric acid, the Ni and Co in the alloy powder dissolve in the sulfuric acid solution and become nickel sulfate and cobalt sulfate in the solution. Meanwhile, the Cu in the alloy powder becomes copper sulfate, which has low solubility, and precipitates as a residue. Therefore, the precipitated Cu component (copper sulfate) can be separated from the solution containing Ni and Co.

As described above, the alloy powder produced in the alloy powder production process S3 is an alloy powder with small particle size variation. Therefore, it has the characteristic of excellent leaching properties and separation and recovery properties in acid leaching treatment. Therefore, according to the valuable metal recovery method of this embodiment, which uses such alloy powder, that is, alloy powder produced by pouring molten alloy M adjusted to a specific temperature range into water atomization device 1, the valuable metals Ni and Co can be leached with a high leaching rate, and Ni and Co can be separated and recovered from Cu with high separability.

The present invention will be described in more detail below with reference to examples, but the present invention is not limited to the following examples.

Examples and Comparative Examples
[Example]
In the examples and comparative examples, intermediate scraps from lithium ion battery factories and detoxified used waste batteries circulating in the waste battery market were used (waste battery pretreatment step S1), and a molten alloy was obtained from the waste battery sample through a molten alloy preparation step S2. Then, in an alloy powder production step S3, an alloy powder containing copper (Cu), nickel (Ni), and cobalt (Co) as constituents was produced from the obtained molten alloy.

In the molten alloy preparation step S2, a molten alloy (M) having the composition shown in Table 1 below was obtained through the molten alloy formation step S23. Table 1 shows the composition of the chemical quantitative analysis results excluding gas components (carbon, nitrogen, oxygen). Table 2 below shows the total mass % "T" of Ni, C, Mn, and Fe contained in the molten alloy (M) obtained by molten alloy formation (molten alloy to be provided to the alloy powder production step S3). In addition, in the molten alloy formation step S23, the heating conditions were controlled to obtain the molten alloy M, and the temperature of the obtained molten alloy (M) was adjusted to the "molten alloy temperature" shown in Table 2 below.

In the alloy powder production step S3, an atomizing device (1) whose configuration example is shown in Fig. 1 was used. That is, a water atomizing device (1) was used in which the inside of the tundish (11) had an inverted truncated cone shape such that the area of the surface of the poured molten alloy (M) increases toward the top in the vertical direction. More specifically, in Examples 1 to 4, a water atomizing device (1) was used that had a tundish (11) whose internal cross-sectional shape was as shown in Fig. ² and in which the ratio ( ^R2 / ^R1 ) of the diameter ^R1 of the opening (11a) to the diameter R2 of the bottom (11b) was 0.5 (referred to as "inverted truncated cone shape [1]" in Table 2 below). In Example 5, a water atomizing apparatus ( ¹ ) was used that had a tundish (11) having an internal cross-sectional shape as shown in FIG. 3, in which the ratio ( ^R2 / ^R1 ) of the diameter ^R1 of the opening (11a) to the diameter R2 of the bottom (11b) was 0.3 (referred to as "inverted truncated cone shape [2]" in Table 2 below).

In the water atomizing device (1), the tundish (11) was made of alumina, and a zirconia discharge nozzle (11N) with a nozzle diameter of 4 mm to 8 mm was attached to the bottom (11b) of the tundish 11.

In the alloy powder production process S3, the temperature of the molten alloy was adjusted by the output of the induction furnace (melting furnace 3) with a frequency of 400 Hz, and the induction furnace (5) was tilted to pour the molten alloy (M) into the tundish (111) whose internal shape was an inverted truncated cone. The height of the molten alloy (M) in the tundish (11) was kept almost constant, and the amount of molten alloy (M) discharged per unit time from the discharge nozzle (11N) was kept constant, and the molten alloy (M) was supplied into the chamber (13) of the water atomizer (1).

When pouring the molten alloy (M) from the induction furnace (5) into the tundish (11), the inside of the empty tundish (11) was heated in advance to 1000°C or higher using an LPG burner so that the temperature of the molten alloy (M) in the induction furnace (5) and the temperature of the molten alloy (M) poured from the pouring nozzle (11N) of the tundish (11) were kept at approximately the same temperature.

In the water atomizing device (1), the molten alloy (M) is supplied from the tundish (11) to the chamber (13) through the discharge nozzle (11N) at a nearly constant rate, and high-pressure water is sprayed from the fluid spray nozzle (12) installed at the top of the chamber (13) onto the molten alloy (M) that falls from the discharge nozzle (11N), pulverizing it into droplets to produce alloy powder. The alloy powder obtained in the chamber (13) is transported to the filter (15) through the recovery pipe (14), where it is separated into solid and liquid and recovered.

[Comparative Example]
In the comparative example, a water atomizing apparatus equipped with a cylindrical tundish (100) having an internal cross-sectional shape as shown in FIG. 4 was used, and alloy powder was produced in the same manner as in the examples, except that the temperature of the molten alloy was adjusted to the temperature shown in Table 2 below ("Temperature of molten alloy" in Table 2).

<Results and Evaluation>
Table 2 below shows the production conditions and test results of the alloy powder in each test example of Examples 1 to 5 and Comparative Examples 1 and 2. Table 2 also shows the total mass % "T" of Ni, C, Mn, and Fe contained in the molten alloy (molten alloy provided to alloy powder production step S3) (M) obtained by molten metalization. In addition, the "molten alloy adjustment temperature range" in Table 2 is a temperature range of (1383 + 1.9 x T) °C or more and (1483 + 1.9 x T) °C or less, calculated using the total mass % "T".

In each test, the presence or absence of abnormalities during manufacturing and processing of the alloy powder (atomized powder) under each condition, the particle size distribution of the manufactured alloy powder, and the acid leaching efficiency when the alloy powder was leached with acid were evaluated.

Regarding abnormalities during the atomization process, the occurrence of clogging in the discharge nozzle (11N) during processing was checked, and if clogging abnormalities occurred, it was evaluated as having an abnormality (marked "Yes" in the table), and if no clogging abnormalities occurred, it was evaluated as having no abnormality (marked "No" in the table).

The particle size distribution of the alloy powder was evaluated as good (indicated as "○" in the table) if there was no generation of coarse powder with a particle size of 300 μm or more and no generation of fine powder with a particle size of less than 5 μm, and was evaluated as poor (indicated as "×" in the table) if either coarse powder or fine powder or both were generated.

Regarding the acid leaching efficiency, the alloy powders produced in each test example, containing Cu, Ni, and Co as constituents, were immersed in a sulfuric acid solution to carry out the acid leaching process. If Ni and Co dissolved at a dissolution rate (leaching rate) of 98% or more within 6 hours of the start of the process, the acid leaching efficiency was judged to be good (indicated as "○" in the table), and if the dissolution rate was less than 98%, the acid leaching efficiency was judged to be insufficient (indicated as "×" in the table). Note that the amount of sulfuric acid solution prepared was 2.0 to 3.0 equivalents of the amount of sulfuric acid required to dissolve Ni and Co as sulfates.

In Examples 1 to 4, a water atomizing device (1) was used in which the shape inside the tundish (11) was formed into an inverted truncated cone shape, and the temperature of the molten alloy (M) was adjusted to a temperature within the alloy molten alloy adjustment temperature range to produce alloy powder. As a result, the produced alloy powder did not contain coarse powder with a particle size of 300 μm or more or fine powder with a particle size of less than 5 μm. Furthermore, acid leaching of the alloy powder was also satisfactory, with 98% or more of the Ni and Co dissolving within 6 hours. Furthermore, no abnormalities such as clogging occurred during the atomizing process, and smooth operation was possible.

In Example 5, the water atomizing apparatus (1) was used in which the shape of the inside of the tundish (11) was formed into an inverted truncated cone shape, and the temperature of the molten alloy (M) was adjusted to a temperature (1460°C) included in the alloy molten alloy adjustment temperature range to produce the alloy powder. As a result, the produced alloy powder did not produce coarse powder with a particle size of 300 μm or more or fine powder with a particle size of less than 5 μm, and the proportion of fine powder in the range of 5 μm or more was small, resulting in a sharper particle size distribution. This is considered to be because, in Example 5, the alloy powder was produced using an apparatus formed into an approximately inverted cone shape with a smaller R ² /R ¹ ratio than the apparatuses used in Examples 1 to 4, and therefore the fluctuation in the amount of the molten alloy fed from the discharge nozzle (11N) was small even at the stage where the amount of the molten alloy in the tundish (11) became small. Furthermore, the acid leaching of the alloy powder was also good, with 98% or more of Ni and Co dissolved within 6 hours. Furthermore, no abnormalities such as clogging occurred during the atomization process, and smooth operation was possible.

On the other hand, in Comparative Example 1, the alloy powder was produced using a water atomization device in which the inside of the tundish (100) was formed into a conventional cylindrical shape. Although no abnormalities such as clogging occurred during the atomization process, coarse particles with a particle size of 300 μm or more were produced, and fine powder with a particle size of less than 5 μm was produced. In addition, when the alloy powder was subjected to acid leaching, the dissolution rate of Ni and Co within 6 hours was less than 98%.

In Comparative Example 2, alloy powder was produced using a water atomizer (1) in which the inside shape of the tundish (11) was formed into an inverted truncated cone shape, as in Examples 1 to 5. However, the temperature of the molten alloy was outside the molten alloy adjustment temperature range (1400°C), and coarse particles with a particle size of 300 μm or more were generated. In addition, when the alloy powder was subjected to acid leaching, the dissolution rate of Ni and Co was less than 98% after a treatment time of 9 hours.

REFERENCE SIGNS LIST 1 Water atomizing device 11, 11A, 11B Tundish 11a Opening 11b Bottom 11N Melt outlet nozzle 12 Fluid injection nozzle 13 Chamber 13e Discharge port 14 Recovery pipe 15 Filter 16 Tank 17 High-pressure pump 18 Gas discharge structure 21 Inclined portion 3 Melting furnace (induction furnace)

Claims (4)

A method for producing an alloy powder containing copper, nickel, and cobalt as constituent components, using a water atomizing apparatus for producing an alloy powder by injecting high-pressure water into a molten alloy, comprising the steps of:
The molten alloy contains five metal elements, namely, copper, nickel, cobalt, manganese, and iron, each of which is 0.1 mass% or more, and the total amount of the five metal elements is 98 mass% or more,
The water atomizing device includes:
the molten alloy is poured into a tundish and the molten alloy is discharged from a discharge nozzle attached to a bottom of the tundish; and a fluid injection nozzle is disposed below the tundish and is configured to inject the high-pressure water onto the molten alloy dropping from the tundish,
The water atomizing device is
The inside of the tundish is formed in an inverted truncated cone shape,
At least the inside of the tundish is formed in a shape such that the area of the surface of the molten alloy being poured increases upward in the vertical direction,
The temperature of the molten alloy is adjusted to a range of (1383 + 1.9 × T) ° C. or more and (1483 + 1.9 × T) ° C. or less, where "T" is the total mass% of nickel, cobalt, manganese, and iron.
A method for producing alloy powder. The molten alloy contains copper in an amount of 24% by mass or more and 80% by mass or less.
A method for producing the alloy powder according to claim 1. The molten alloy is derived from a waste lithium ion battery.
The method for producing the alloy powder according to claim 1 or 2 . A method for recovering valuable metals from waste lithium ion batteries, comprising:
A step of producing an alloy powder containing copper, nickel, and cobalt as constituent components by injecting high-pressure water into the molten alloy derived from the waste lithium-ion batteries using a water atomizer;
and leaching the alloy powder with an acid,
In the step of producing the alloy powder, a method for producing an alloy powder according to any one of claims 1 to 3 is carried out.
Methods for recovering valuable metals.

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