Method for recovering valuable element

Abstract

Provided is a method for recovering a valuable element in which an oxide containing manganese and at least one element selected from the group consisting of nickel and cobalt is reduced using a reducing gas under heating, the reducing gas containing a hydrogen-containing gas containing a hydrogen element. This allows Ni and Co to be recovered preferentially over Mn. The hydrogen-containing gas is preferably at least one selected from the group consisting of a hydrocarbon gas, an ammonia gas, and a hydrogen gas, and more preferably a hydrogen gas.

Description

Method for recovering valuable elements

[0001] The present invention relates to a method for recovering valuable elements.

[0002] In recent years, the demand for lithium-ion batteries has increased sharply due to the spread of electric vehicles. ２ From the perspective of reducing emissions, demand for electric vehicles that do not use fossil fuels is expected to continue to expand in the future, and the demand for lithium-ion batteries is also expected to increase further in the future.

[0003] The cathode material of a lithium-ion battery is made of an oxide (composite oxide) containing nickel (Ni), cobalt (Co), manganese (Mn), etc. A specific example of this composite oxide is LiNiO ２ , LiCoO ２ , LiMnO ２ Metal elements such as Ni, Co, and Mn are not abundant worldwide. Therefore, recovering these metal elements (valuable elements) from the positive electrode material of lithium-ion batteries is extremely beneficial from the viewpoint of effective resource utilization.

[0004] As a treatment for recovering valuable elements, for example, a dry treatment in which a positive electrode material is heated together with a reducing agent to reduce and generate valuable elements can be mentioned (Patent Document 1).

[0005] Japanese Patent Application Laid-Open No. 2021-95628

[0006] In the dry process, a composite oxide (LiNiO ２ , LiCoO ２ , LiMnO ２ By reducing the iron ore, metals containing valuable elements (Ni, Co, Mn) (product metals) and slag (product slag) are produced. In this process, it is sometimes required to minimize the reduction of Mn (to prevent Mn from transferring to the product metals and to allow it to remain in the product slag).

[0007] The present invention has been made in view of the above points, and an object of the present invention is to provide a method for recovering valuable elements that can recover Ni and Co preferentially over Mn.

[0008] As a result of extensive research, the present inventors have found that the above object can be achieved by employing the following configuration, and have thus completed the present invention. Specifically, the present invention provides the following [1] to [9]. [1] A method for recovering a valuable element, comprising heating and reducing an oxide containing manganese and at least one element selected from the group consisting of nickel and cobalt with a reducing gas, wherein the reducing gas comprises a hydrogen-containing gas containing elemental hydrogen. [2] The method for recovering a valuable element according to [1] above, wherein the hydrogen-containing gas is at least one selected from the group consisting of hydrocarbon gas, ammonia gas, and hydrogen gas. [3] The method for recovering a valuable element according to [1] above, wherein the hydrogen-containing gas is hydrogen gas. [4] The method for recovering a valuable element according to any of [1] to [3] above, wherein the content of the hydrogen-containing gas in the reducing gas is 50% by volume or more. [5] The method for recovering a valuable element according to any of [1] to [4] above, wherein the temperature when heating the oxide is 800°C or more. [6] The method for recovering a valuable element according to any one of [1] to [5] above, wherein the heated reducing gas is supplied to the oxide, thereby reducing the oxide while heating it. [7] The method for recovering a valuable element according to any one of [1] to [6] above, wherein the reducing gas is introduced into a furnace while the oxide is being charged, and the furnace is a vertical furnace. [8] The method for recovering a valuable element according to any one of [1] to [7] above, wherein the product obtained by reducing the oxide is subjected to magnetic separation or reheating as a post-treatment. [9] The method for recovering a valuable element according to any one of [1] to [8] above, wherein the oxide is obtained from a lithium-ion battery.

[0009] According to the present invention, Ni and Co can be recovered preferentially over Mn.

[0010] FIG. 1 is a schematic diagram showing a vertical furnace.

[0011] [Method for recovering valuable elements] In the method for recovering valuable elements of this embodiment, an oxide described below is reduced by heating it and using a reducing gas described below. Hereinafter, this embodiment will be described in more detail.

[0012] <Oxide to be reduced> The oxide to be reduced contains at least one element selected from the group consisting of nickel (Ni) and cobalt (Co) and manganese (Mn), and may further contain lithium (Li). An example of such an oxide is a cathode material for a lithium ion battery (waste lithium ion battery). Generally, a lithium ion battery is composed of a combination of components such as a cathode material, an anode material, and a separator, and further includes an electrolyte solution. The cathode material for a lithium ion battery is generally LiNiO ２ , LiCoO ２ , LiMnO ２ The cathode material (oxide) is made of oxides (composite oxides) such as ZnO, ZnS, and ZnO. A cathode material (oxide) can be obtained by subjecting a lithium-ion battery to a pretreatment, such as removal of the electrolyte. The oxide to be reduced may contain a component other than the cathode material of the lithium-ion battery, but preferably does not contain an anode material. The content of the cathode material in the oxide to be reduced is preferably 51% by mass or more, more preferably 75% by mass or more, even more preferably 85% by mass or more, particularly preferably 95% by mass or more, and may even be 100% by mass.

[0013] <Reducing Gas> When valuable elements are recovered as product metals from the oxides described above by dry treatment, Mn is generally also inevitably reduced and transferred to the product metals. In this case, if, for example, Si or Al is used alone as a reducing agent, Mn is also likely to be metallized. However, since Mn that has transferred to the product metals is difficult to separate, there are cases where it is required to minimize the reduction of Mn (prevent Mn from transferring to the product metals).

[0014] Therefore, in this embodiment, a reducing gas containing a hydrogen-containing gas is used as the reducing agent. As a result, as shown in the Examples below, reduction of Mn can be suppressed, resulting in a metal product containing less Mn and more Ni and Co. In other words, Mn can be prevented from transferring to the metal product as much as possible and can be left in the slag product. In this way, Ni and Co can be recovered preferentially over Mn.

[0015] In addition, in dry processing, in addition to the reducing agent, a slag-forming agent (CaO, SiO２ However, in this embodiment, since no slag forming agent is required, the amount of slag generated can be reduced.

[0016] The hydrogen-containing gas is a gas containing hydrogen (H), and examples thereof include hydrocarbon gas and ammonia gas (NH ３ ) and hydrogen gas (H ２ ) is preferably at least one selected from the group consisting of: As the hydrocarbon gas, for example, a hydrocarbon gas having 1 to 4 carbon atoms is exemplified, and a specific example thereof is methane (CH ４ ), ethane (C ２ H ６ ), propane (C ３ H ８ ), butane (C ４ H １０ ) and alkanes such as ethylene (C ２ H ４ ) and alkenes; acetylene (C ２ H ２ ) and the like; and the like.

[0017] Hydrogen gas is preferred as the hydrogen-containing gas because it has a superior effect of reducing Ni and Co while suppressing the reduction of Mn, and also because it allows the reduction reaction to proceed easily even at a relatively low temperature.

[0018] When a carbon-containing substance such as carbon is used as a reducing agent, carbon dioxide (CO ２ However, by using a hydrogen-containing gas (particularly hydrogen gas) as a reducing agent, the generation of carbon dioxide can also be suppressed.

[0019] The reducing gas may be, in addition to a hydrogen-containing gas, for example, helium gas (He), argon gas (Ar), or nitrogen gas (N ２ The gas may contain an inert gas such as toluene.

[0020] The content of the hydrogen-containing gas in the reducing gas is, for example, 40% by volume or more, but from the viewpoint of obtaining a high reducing power, it is preferably 50% by volume or more, more preferably 75% by volume or more, even more preferably 90% by volume or more, and particularly preferably 100% by volume. However, if the reducing power becomes too high, Mn is also easily reduced. Therefore, from the viewpoint of suppressing the reduction of Mn, the content of the hydrogen-containing gas in the reducing gas is preferably 90% by volume or less, more preferably 75% by volume or less, even more preferably 60% by volume or less, and particularly preferably 45% by volume or less.

[0021] The reducing gas preferably does not substantially contain other reducing gases different from the hydrogen-containing gas. Examples of other reducing gases include hydrogen-free gases that do not contain hydrogen elements, such as carbon monoxide (CO). The content of other reducing gases different from the hydrogen-containing gas in the reducing gas is preferably 5% by volume or less, more preferably 3% by volume or less, even more preferably 1% by volume or less, and particularly preferably 0% by volume.

[0022] The pressure of the reducing gas supplied to the oxide is not particularly limited, and may be, for example, 0.5 to 1.5 atm (50.6625 to 151.988 kPa), or may be 1.0 atm (101.325 kPa).

[0023] The flow rate of the reducing gas supplied to the oxide is not particularly limited, and may be, for example, 0.5 to 5.0 NL / min, or may be 1.0 NL / min.

[0024] <Heating> In this embodiment, the oxide to be reduced is heated during reduction. The temperature (heating temperature) when heating the oxide is, for example, 600°C or higher. From the viewpoint of obtaining high reducing power, it is preferably 800°C or higher, more preferably above 900°C, even more preferably above 950°C, even more preferably above 1000°C, particularly preferably above 1000°C, more particularly preferably above 1050°C, very preferably above 1100°C, and most preferably above 1300°C. On the other hand, if the heating temperature is too high, costs tend to increase. For this reason, the heating temperature is preferably 1500°C or lower, more preferably 1400°C or lower. Furthermore, if the reducing power becomes too high, Mn is also likely to be reduced. For this reason, from the viewpoint of suppressing the reduction of Mn, the heating temperature is preferably 1100°C or lower, more preferably 900°C or lower, and even more preferably 700°C or lower.

[0025] The time for heating the oxide (heating time) is preferably 1 hour or more, more preferably 2 hours or more, and even more preferably 3 hours or more, because this makes it easier to suppress insufficient reduction. On the other hand, if the heating time is too long, extra costs may be incurred. For this reason, the heating time is preferably 6 hours or less, and more preferably 5 hours or less.

[0026] The method for heating the oxide is not particularly limited, but for example, a method of supplying a heated reducing gas to the oxide can be used. This allows the oxide to be reduced while being heated. In this case, the temperature of the heated reducing gas can be considered as the heating temperature.

[0027] Furnace Examples of equipment used for heating and reducing oxides include furnaces, specific examples of which include electric furnaces, resistance furnaces, high-frequency melting furnaces, low-frequency melting furnaces, rotary kilns, vertical furnaces (shaft furnaces), steelmaking furnaces, etc. Of these, vertical furnaces are preferred because the flow of charged raw materials (from top to bottom) and the flow of heated reducing gas (from bottom to top) are in opposite directions (so-called countercurrent flow), making it easier to ensure that the reducing gas comes into contact with the raw materials.

[0028] 1 is a schematic diagram showing a shaft furnace 1. When using the shaft furnace 1, for example, pellet-shaped oxide 3 is charged into the shaft furnace 1 from the furnace top 2 of the shaft furnace 1, and heated reducing gas is introduced into the shaft furnace 1 from a gas inlet 5 provided on the furnace wall 4 (approximately at the center in the vertical direction) of the shaft furnace 1. As a result, the oxide 3 is reduced while being heated by the reducing gas as it descends inside the shaft furnace 1. A product 7 obtained by the reduction of the oxide 3 is discharged from an outlet 6 provided at the bottom of the shaft furnace 1. The product 7 contains produced metal and produced slag.

[0029] <Post-treatment> To separate the product metal and the product slag, the product (containing the product metal and the product slag) obtained by the reduction of the oxides may be subjected to magnetic separation or reheating as a post-treatment. The reheating treatment is, for example, a process in which the product is heated and melted in an electric furnace. As a result, the molten product slag is placed on top of the molten product metal in the electric furnace, and only the molten product metal can be removed from the electric furnace.

[0030] <Product Metal> As described above, the product metal contains little Mn and much Ni and Co. The product metal may contain only one of Ni and Co (or one of them in greater amounts than the other).

[0031] The present invention will be specifically described below with reference to examples, but the present invention is not limited to the examples described below.

[0032] First, cathode material from used lithium-ion batteries was prepared. Specifically, the lithium-ion batteries were subjected to pre-treatments such as disassembly, discharge, and removal of the electrolyte, and the cathode material was separated. The molar composition of the cathode material was Ni:Mn:Co = 6:2:2.

[0033] Next, the cathode material was reduced using the vertical furnace described with reference to FIG. 1 . More specifically, pelletized oxide was charged into the top of the vertical furnace. In addition, a reducing gas containing the gas species shown in Table 1 below (the remainder being nitrogen gas) was heated and introduced into the furnace through the gas inlet of the vertical furnace at a flow rate of 1.0 NL / min. The content (unit: vol %) of the gas species in the reducing gas and the temperature (unit: °C) of the heated reducing gas are shown in Table 1 below. The heating time was 3 hours. The cathode material was reduced while being heated, and a product (product metal and product slag) was obtained. Next, a reheating treatment was performed as a post-treatment. That is, the obtained product was heated and melted at 1600 °C in an electric furnace, and the product metal and product slag were separated.

[0034] The reduction rates (unit: mol %) of the metal elements Ni, Co, and Mn were determined for the resulting metals. The results are shown in Table 1 below. The reduction rate is the ratio of the amount of metal actually obtained to the theoretical amount of metal produced by the reduction reaction. For example, if the reduction rate of Ni is 85 mol %, this means that 80 mol % of the Ni contained in the positive electrode material was reduced and transferred to the resulting metal, and the remaining 20 mol % remained in the resulting slag.

[0035]

[0036] <Summary of Evaluation Results> As shown in Table 1 above, Examples 1 to 17, in which a reducing gas containing a hydrogen-containing gas was used, had a lower reduction rate of Mn compared to Comparative Example 1, in which a reducing gas containing a hydrogen-containing gas was not used. This shows that Ni and Co were reduced while suppressing the reduction of Mn.

[0037] In addition, when Examples 1 to 5 are compared, in which only the type of hydrogen-containing gas (gas species) is different, hydrogen gas (H ２ In Example 5, a hydrocarbon gas or ammonia gas (NH ３ It can be seen that, compared with Examples 1 to 4 in which the gas used was oxidized, Ni and Co were reduced to a greater extent while suppressing the reduction of Mn. This was also the case in Examples 11 to 15 in which only the type of gas was different.

[0038] Furthermore, when Examples 5 to 8, which differ only in the content of the hydrogen-containing gas (hydrogen gas), are compared, it can be seen that the greater the content of the hydrogen-containing gas, the greater the reduction of Ni and Co, and the smaller the content of the hydrogen-containing gas, the greater the suppression of reduction of Mn. This was also true for Examples 15 and 16, which differ only in the content of the hydrogen-containing gas.

[0039] Furthermore, comparing Examples 5, 9, 10, 15, and 17, which differ only in the temperature of the heated reducing gas, it can be seen that the higher the temperature, the more Ni and Co can be reduced, and the lower the temperature, the more Mn reduction can be suppressed. This was also true for Examples 1 and 11, Examples 2 and 12, Examples 3 and 13, Examples 4 and 14, and Examples 7 and 16, which differ only in the temperature of the heated reducing gas.

[0040] 1: Vertical furnace 2: Furnace top 3: Oxide 4: Furnace wall 5: Gas inlet 6: Outlet 7: Products (produced metal and produced slag)

Claims

1. A method for recovering valuable elements, comprising heating and reducing an oxide containing manganese and at least one element selected from the group consisting of nickel and cobalt using a reducing gas, wherein the reducing gas includes a hydrogen-containing gas containing hydrogen element.

2. The method for recovering valuable elements according to claim 1, wherein the hydrogen-containing gas is at least one selected from the group consisting of hydrocarbon gas, ammonia gas, and hydrogen gas.

3. The method for recovering valuable elements according to claim 1, wherein the hydrogen-containing gas is hydrogen gas.

4. A method for recovering valuable elements according to any one of claims 1 to 3, wherein the content of the hydrogen-containing gas in the reducing gas is 50% by volume or more.

5. A method for recovering valuable elements according to any one of claims 1 to 4, wherein the temperature at which the oxide is heated is 800°C or higher.

6. A method for recovering valuable elements according to any one of claims 1 to 5, wherein the heated reducing gas is supplied to the oxides, thereby reducing the oxides while heating them.

7. A method for recovering valuable elements according to any one of claims 1 to 6, wherein the reducing gas is introduced into a furnace while the oxide is being charged into the furnace, and the furnace is a vertical furnace.

8. A method for recovering valuable elements according to any one of claims 1 to 7, wherein the product obtained by reducing the oxide is subjected to a post-treatment such as magnetic separation or reheating.

9. The method for recovering valuable elements according to any one of claims 1 to 8, wherein the oxide is obtained from a lithium ion battery.

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