Valuable element recovery method and metal production method

Abstract

In the present invention, a reducing agent and a slag-forming agent containing CaO and SiO2 are added to an oxide containing manganese (Mn) and at least one element selected from the group consisting of nickel (Ni) and cobalt (Co), and the resultant mixture is heated to reduce the oxide. The reducing agent contains an aluminum-containing material and an iron-containing material. The iron-containing material is at least one selected from the group consisting of metallic iron and iron oxide. The total added amount of the aluminum-containing material and the iron-containing material is 0.8 to 1.5 equivalents inclusive. As a result, Ni and Co can be recovered in large amounts and preferentially over Mn.

Description

Methods for recovering valuable elements and methods for producing metals

[0001] This invention relates to a method for recovering valuable elements and a method for producing metals.

[0002] In recent years, the demand for lithium-ion batteries has been rapidly increasing due to the spread of electric vehicles. In particular, the CO2 emissions of recent years ２ From the perspective of reducing emissions, the demand for electric vehicles that do not use fossil fuels is expected to expand further in the future, and consequently, the demand for lithium-ion batteries is also expected to increase further.

[0003] The positive electrode material of a lithium-ion battery consists 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 These are some examples. Metal elements such as Ni, Co, and Mn are not abundant globally. Therefore, recovering these metal elements (valuable elements) from the cathode material of lithium-ion batteries is extremely beneficial from the standpoint of efficient resource utilization.

[0004] One method for recovering valuable elements is a dry process in which the cathode material is heated together with a reducing agent and a slag-forming agent to reduce and generate the valuable elements (Patent Document 1).

[0005] Japanese Patent Publication No. 2021-95628

[0006] In dry processing, composite oxide (LiNiO ２ LiCoO ２ LiMnO ２ By reducing ), a metal containing valuable elements (Ni, Co, Mn) (product metal) and slag (product slag) are produced. At this time, it is desirable to reduce and recover as many valuable elements as possible, but at the same time, it is sometimes required to minimize the reduction of Mn (to prevent Mn from transferring to the product metal and to leave it in the product slag).

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

[0008] As a result of intensive studies, the present inventors have found that the above object can be achieved by adopting the following configuration, and have completed the present invention. That is, the present invention provides the following [1] to [8]. [1] A reducing agent and CaO and SiO are added to an oxide containing at least one element selected from the group consisting of nickel and cobalt and manganese, and heated to reduce the oxide. The reducing agent contains an aluminum-containing substance and an iron-containing substance, the iron-containing substance is at least one selected from the group consisting of metallic iron and iron oxide, and the total amount of the aluminum-containing substance and the iron-containing substance added is 0.8 equivalent or more and 1.5 equivalents or less. A method for recovering valuable elements. ２ A slag-forming agent containing is added, and the oxide is reduced by heating. The reducing agent contains an aluminum-containing substance and an iron-containing substance, the iron-containing substance is at least one selected from the group consisting of metallic iron and iron oxide, and the total amount of the aluminum-containing substance and the iron-containing substance added is 0.8 equivalent or more and 1.5 equivalents or less. A method for recovering valuable elements. ２ The mass ratio (CaO / SiO) between CaO and SiO contained in the slag-forming agent ２ is 0.60 or more. The method for recovering valuable elements according to [1] above.

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

[0010] [Method for recovering valuable elements] In general terms, the method for recovering valuable elements in this embodiment involves reducing the oxide, which will be described later, by heating it with the addition of a reducing agent and a slag-forming agent, which will also be described later. This embodiment will be described in more detail below. Note that the following description also serves as a description of the method for producing the metal (the resulting metal).

[0011] <Reduction Target (Oxide)> 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 also contain lithium (Li). Examples of such oxides include the positive electrode material of lithium-ion batteries (waste lithium-ion batteries). The positive electrode material of lithium-ion batteries is generally LiNiO ２ LiCoO ２ LiMnO ２ It consists of oxides (composite oxides) such as those mentioned above. By subjecting lithium-ion batteries to pretreatment such as the removal of the electrolyte, the positive electrode material (oxide) can be obtained.

[0012] <Reducing Agents> When recovering valuable elements as generated metals from the oxides mentioned above by dry processing, Mn is generally inevitably reduced and transferred to the generated metal. However, Mn that has transferred to the metal is difficult to separate (for example, when wet processing is carried out, the process is complicated due to the large number of steps). For this reason, it is sometimes required to minimize the reduction of Mn (to prevent Mn from transferring to the generated metal and to leave it in the generated slag). In addition, depending on the reducing agent, the reduction of Ni and Co may be insufficient.

[0013] Therefore, in this embodiment, reducing agents containing aluminum-containing substances and iron-containing substances are used in amounts described later. As a result, as shown in the [Examples] below, the reduction of Mn is suppressed while a high reduction rate for Ni and Co is obtained. That is, a metal product containing little Mn and a large amount of Ni and Co is obtained.

[0014] Examples of aluminum-containing materials include metallic aluminum (Al). The form of metallic aluminum (Al) is not particularly limited and can be in powder or shot form. If it is in shot form, the particle size may be, for example, 1 to 15 mm, or 3 to 10 mm. The metallic aluminum (Al) may also be scrap aluminum cans.

[0015] The iron-containing substance is at least one selected from the group consisting of metallic iron (Fe) and iron oxide. The iron-containing substance as a reducing agent is described below.

[0016] For metallic iron (Fe), for example, scrap or granular iron used in steel mills may be used.

[0017] Iron oxides are generally ferrous oxide (FeO), also called wustite, and triiron tetroxide (FeO), also called magnetite. ３ O ４ ) and ferric oxide (Fe), also known as hematite ２ O ３ Iron oxides are classified into three types. Of these, ferrous oxide (wustite) is preferred as iron oxide because it readily triggers reduction reactions. Iron oxide may also be at least one of the dust, scale, and sludge (hereinafter referred to as "dust" for convenience) that are produced as by-products in the steelmaking process. Using dust as iron oxide is preferable from the viewpoint of effectively utilizing by-products of the steelmaking process and utilizing an inexpensive iron source.

[0018] Referring to the Ellingham diagram (not shown), the Mn / MnO equilibrium is the same as the Fe / FeO equilibrium and the FeO / Fe ３ O ４ It is less virtuous than equilibrium. Therefore, it is thought that using an iron-containing substance as a reducing agent can suppress the inclusion of Mn in the resulting metal product.

[0019] The content (total content) of aluminum-containing substances and iron-containing substances in the reducing agent is preferably 50% by mass or more, more preferably 75% by mass or more, even more preferably 90% by mass or more, and particularly preferably 100% by mass.

[0020] By the way, conventionally, carbon-containing substances are known as reducing agents. Examples of carbon-containing substances include solid carbon-containing substances such as graphite, coke, and solid hydrocarbons; gaseous carbon-containing substances such as carbon monoxide (CO) and hydrocarbon gases (e.g., propane gas); and the like. When using such carbon-containing substances as reducing agents, gases such as CO are generated when reducing oxides. Therefore, from the perspective of suppressing the generation amount of CO, it is preferable that the content of the carbon-containing substance in the reducing agent is low. Specifically, 5% by mass or less is preferable, 3% by mass or less is more preferable, 1% by mass or less is still more preferable, and 0% by mass may also be acceptable. ２ When using such carbon-containing substances as reducing agents, gases such as CO are generated when reducing oxides. Therefore, from the perspective of suppressing the generation amount of CO, it is preferable that the content of the carbon-containing substance in the reducing agent is low. ２ Specifically, 5% by mass or less is preferable, 3% by mass or less is more preferable, 1% by mass or less is still more preferable, and 0% by mass may also be acceptable.

[0021] 《Addition amount of reducing agent》 The total addition amount of the aluminum-containing substance and the iron-containing substance is 0.8 equivalent or more and 1.5 equivalents or less. From the perspective of obtaining a higher reducing power, the total addition amount of the aluminum-containing substance and the iron-containing substance is preferably 0.9 equivalent or more, more preferably 1.0 equivalent or more, and still more preferably 1.2 equivalents or more. However, if the reducing power becomes too high, Mn is also easily reduced. Therefore, from the perspective of suppressing the reduction of Mn, this total addition amount is preferably 1.3 equivalents or less, more preferably 1.1 equivalents or less, and still more preferably 0.9 equivalents or less.

[0022] Among the aluminum-containing substance and the iron-containing substance, from the perspective of obtaining a higher reducing power, the addition amount of the aluminum-containing substance is preferably 0.5 equivalent or more, more preferably 0.7 equivalent or more, still more preferably 0.9 equivalent or more, and particularly preferably 1.1 equivalents or more. However, if the reducing power becomes too high, Mn is also easily reduced. Therefore, from the perspective of suppressing the reduction of Mn, the addition amount of the aluminum-containing substance is preferably 1.2 equivalents or less, more preferably 1.0 equivalents or less, and still more preferably 0.7 equivalents or less.

[0023] The amount of reducing agent required to reduce NiO and CoO of the oxide to be reduced is referred to as 1.0 equivalent. For example, when the reducing agent is metallic iron (Fe), ferrous oxide (FeO), and metallic aluminum (Al), the reduction using 1 equivalent of the reducing agent is shown as follows respectively. Fe + (NiO, CoO) → (Ni, Co) + FeO 3FeO + (NiO, CoO) → (Ni, Co) + Fe ３ O ４ 2Al + 3(NiO, CoO) → 3(Ni, Co) + Al ２ O ３

[0024] When determining the addition amount of the reducing agent, first, the contents of NiO and CoO in the oxide to be reduced are determined. Specifically, the contents of Ni and Co in the object to be reduced (oxide) are measured and regarded as the contents of NiO and CoO in the object to be reduced (oxide) respectively. The contents of Ni and Co are measured using an energy dispersive X-ray analyzer (EDX).

[0025] 〈Flux〉 When reducing the oxide, a flux containing calcium oxide (CaO) and silicon dioxide (SiO ２ ) is used together with the reducing agent described above. The content (total content) of CaO and SiO ２ in the flux is preferably 90% by mass or more, more preferably 95% by mass or more, still more preferably 98% by mass or more, and particularly preferably 100% by mass.

[0026] 《Mass ratio (CaO / SiO ２ )》 The mass ratio (CaO / SiO ２ ) between CaO and SiO ２ is also called the basicity. From the viewpoint of maintaining a high reduction rate for Ni and Co, it is preferable that the flux does not have an excessively low basicity. Specifically, the mass ratio (CaO / SiO ２ ) of the flux is, for example, 0.50 or more, preferably 0.60 or more, more preferably 0.80 or more, still more preferably 1.00 or more, even more preferably 1.20 or more, particularly preferably 1.25 or more, and most preferably 1.30 or more.

[0027] There is no particular upper limit to the basicity of the slag-forming agent, but if it is too high, Mn tends to be more easily reduced thermodynamically. For this reason, the mass ratio of the slag-forming agent (CaO / SiO ２ For example, the value is 2.00 or less, preferably 1.80 or less, and more preferably 1.60 or less.

[0028] 《Amount of Debris-Building Agent Added》 The amount of debris-building agent added is not particularly limited, but the mass ratio of the debris-building agent to the oxide to be reduced (debris-building agent / oxide) is preferably 0.40 to 1.00, more preferably 0.45 to 0.85, and even more preferably 0.50 to 0.80.

[0029] <Heating> The oxide to be reduced is heated with a reducing agent and a slag-forming agent added. This reduces the oxide.

[0030] The heating temperature when heating oxides is preferably 1300°C or higher, more preferably 1350°C or higher, even more preferably 1400°C or higher, and particularly preferably 1450°C or higher, because it helps to suppress insufficient reduction. The upper limit of the heating temperature is not particularly limited and is set appropriately according to the performance of the equipment (furnace) used for heating, but if the heating temperature is too high, it may incur unnecessary costs. For this reason, the heating temperature is preferably 1800°C or lower, and more preferably 1700°C or lower.

[0031] Examples of the atmosphere used when heating oxides (heating atmosphere) include nitrogen gas (N ２ Suitable atmospheres include inert atmospheres such as argon gas (Ar) atmospheres and reducing atmospheres such as aluminum monoxide gas (CO) atmospheres.

[0032] The heating time for the oxide (heating time) is preferably one hour or longer, more preferably two hours or longer, and even more preferably three hours or longer, because it helps to suppress insufficient reduction. There is no particular upper limit to the heating time. However, if the heating time is too long, it may incur additional costs. For this reason, the heating time is preferably six hours or less, and more preferably five hours or less.

[0033] The equipment used for heating oxides is not particularly limited and includes conventionally known equipment such as electric furnaces, resistance furnaces, high-frequency melting furnaces, low-frequency melting furnaces, rotary kilns, vertical furnaces, and steelmaking furnaces.

[0034] <Derived Metal> As described above, the metal obtained by the reduction of the oxide (derived metal) contains little Mn and a large amount of Ni and Co. In other words, according to this embodiment, Ni and Co can be recovered in large amounts and preferentially over Mn from the oxide to be reduced. The derived metal may contain only one of Ni and Co (or one in greater amounts than the other). Furthermore, since an iron-containing substance is used as a reducing agent, the derived metal may also contain iron (Fe).

[0035] <Slag produced> As mentioned above, slag (slag produced) is also obtained by the reduction of oxides. The slag produced contains oxides of valuable elements not included in the metal produced (for example, MnO). In addition, since an iron-containing substance is used as a reducing agent, the slag produced also contains FeO and other elements.

[0036] The present invention will be specifically described below with reference to examples. However, the present invention is not limited to the examples described below.

[0037] <Positive Electrode Material> First, as the oxide to be reduced, the positive electrode material from a lithium-ion battery (waste lithium-ion battery) was prepared. Specifically, the lithium-ion battery was subjected to pretreatment such as decomposition, discharge, and removal of the electrolyte, and the positive electrode material was separated. The component composition of the positive electrode material was Ni:Mn:Co = 6:2:2 in molar ratio.

[0038] <Reducing Agents> Shot-shaped metallic aluminum (Al) (particle size: 10 mm) was prepared as a reducing agent. In addition, powdered metallic iron (Fe) obtained by atomization and powdered ferrous oxide (FeO) were prepared as reducing agents. Furthermore, powdered coke (C) was prepared as a reducing agent.

[0039] <Slag-forming agent> CaO and SiO ２ A slag-forming agent consisting of CaO and SiO was prepared. ２The mass ratio of (CaO / SiO ２ Several types of slag-forming agents with different properties were prepared.

[0040] <Reduction of Cathode Material> The prepared cathode material was placed in an electric furnace with a heat size of 150 kg, a reducing agent and a slag-forming agent were added, and the furnace was heated. In this way, the cathode material was reduced to obtain the generated metal and generated slag. The heating temperature was 1600°C, the heating time was 3 hours, and the heating atmosphere was an Ar atmosphere. 30 kg of slag-forming agent was added for every 45 kg of cathode material. That is, the mass ratio of slag-forming agent to cathode material (slag-forming agent / cathode material) was approximately 0.67. The type and amount of reducing agent used (unit: equivalent), and the mass ratio of slag-forming agent used (CaO / SiO) are as follows. ２ The results are shown in Table 1 below.

[0041] <Reduction Rate> For each of the metal elements Ni, Co, and Mn, the reduction rate was calculated based on the following formula, and the unit was converted from "mass%" to "mol%". The results are shown in Table 1 below. Reduction Rate = 100 × (Amount of metal element contained in the generated metal [g]) / (Amount of metal element contained in the oxide to be reduced [g])

[0042] <Residual Rate (Li) in the Generated Slag> The residual rate of Li in the generated slag was calculated based on the following formula, and the unit was converted from "mass%" to "mol%". The results are shown in Table 1 below. Residual rate in generated slag = 100 × (Amount of metal element contained in the generated slag [g]) / (Amount of metal element contained in the oxide to be reduced [g])

[0043] <CO ２ Amount generated: CO generated during the reduction of the cathode material. ２ Measure the amount, CO ２ Amount generated (unit: Nm) ３ The results were calculated as follows. The results are shown in Table 1 below.

[0044]

[0045] <Summary of Evaluation Results> As shown in Table 1 above, Invention Examples 1 to 14, which used aluminum-containing substances and iron-containing substances as reducing agents in a total amount of 0.8 equivalents to 1.5 equivalents, suppressed the reduction of Mn while achieving high reduction rates for Ni and Co. In other words, Ni and Co could be recovered in large quantities from the cathode material, and preferentially over Mn.

[0046] Comparing Invention Example 1 and Invention Example 2, it was found that Invention Example 2, which used Fe and FeO as the iron-containing material, yielded results equivalent to those of Invention Example 1, which used Fe alone as the iron-containing material.

[0047] Comparing Invention Example 1 and Invention Example 3, it was found that Invention Example 3, which had a larger amount of aluminum-containing substance (Al) added, showed a higher reduction rate of Ni and Co, while Invention Example 1, which had a larger amount of iron-containing substance (Fe) added, was able to further suppress the reduction of Mn.

[0048] Mass ratio of slag-forming agent (CaO / SiO ２ Comparing Invention Examples 3-5 and 14, which differ only in the mass ratio of the slag-forming agent (CaO / SiO), ２ As the mass ratio of the slag-forming agent (CaO / SiO) increased, there was a tendency for the reduction rate of each element to increase. ２ Even when the mass ratio (CaO / SiO) was as low as 0.50, Invention Example 14 showed a higher reduction rate of Ni and Co and suppressed the reduction of Mn compared to Comparative Examples 4 and 5, which used only an iron-containing substance (Fe or FeO) as a reducing agent. This is because the mass ratio of the slag-forming agent (CaO / SiO) ２ This is thought to be because the effect of ) on the reduction of Ni and Co was relatively small, and the slag produced by the oxidation of the reducing agent had good fluidity.

[0049] When comparing Invention Examples 6 to 8, which differ only in the amount of aluminum-containing substance (Al) added, a tendency was observed for the reduction rate of each element to increase as the amount of Al added increased. A similar trend was observed in the comparison results of Invention Examples 6 and 9-10, which differ only in the amount of iron-containing substance (Fe) added, and in the comparison results of Invention Examples 11-13, which differ only in the amount of iron-containing substance (FeO) added.

[0050] Comparative Examples 1-2 and 7, which used only aluminum-containing material (Al) as a reducing agent, showed a higher reduction rate of Mn compared to Invention Examples 1-14, which used both aluminum-containing material (Al) and iron-containing material (Fe or FeO) as reducing agents, and were unable to sufficiently suppress the reduction of Mn. Specifically, for example, Comparative Example 7, in which 0.8 equivalents of aluminum-containing material (Al) were added, showed a higher reduction rate of Mn compared to Invention Examples 6 and 11, in which a total of 0.8 equivalents of aluminum-containing material (Al) and iron-containing material (Fe or FeO) were added. Furthermore, Comparative Example 7, with 0.8 equivalents of the reducing agent added, showed a lower reduction rate of Ni and Co than Comparative Example 2, with 1.4 equivalents of the reducing agent added. This is presumed to be because the viscosity of the slag produced by the oxidation of the reducing agent was higher, making the reduction less likely to proceed.

[0051] Comparative Examples 3 to 5, which used only an iron-containing substance (Fe or FeO) as a reducing agent, showed lower reduction rates for Ni and Co and insufficient reduction of Ni and Co compared to the respective inventive examples.

[0052] Comparative Example 6, which used a carbon-containing substance (C) as a reducing agent, showed a higher reduction rate of Mn compared to the examples of the invention, and the reduction of Mn could not be sufficiently suppressed. ２ The number of occurrences was large.

Claims

1. An oxide containing at least one element selected from the group consisting of nickel and cobalt, and manganese, with a reducing agent, CaO and SiO ２ A method for recovering valuable elements, comprising adding a slag-forming agent containing and heating to reduce the oxide, wherein the reducing agent contains an aluminum-containing substance and an iron-containing substance, the iron-containing substance is at least one selected from the group consisting of metallic iron and iron oxide, and the total amount of the aluminum-containing substance and the iron-containing substance added is 0.8 equivalents or more and 1.5 equivalents or less.

2. CaO and SiO contained in the slag-forming agent ２ The mass ratio of (CaO / SiO ２ The method for recovering a valuable element according to claim 1, wherein the ratio is 0.60 or higher.

3. The method for recovering a valuable element according to claim 1 or 2, wherein the temperature at which the oxide is heated is 1450°C or higher.

4. The method for recovering a valuable element according to any one of claims 1 to 3, wherein the iron oxide is ferrous oxide.

5. The method for recovering a valuable element according to any one of claims 1 to 4, wherein the iron-containing substance is at least one selected from the group consisting of dust, scale, sludge, and scrap.

6. A method for recovering a valuable element according to any one of claims 1 to 5, wherein a metal containing iron and at least one element selected from the group consisting of nickel and cobalt is obtained by reducing the oxide.

7. A method for recovering a valuable element according to any one of claims 1 to 6, wherein the oxide is obtained from a lithium-ion battery.

8. A method for producing a metal containing iron and at least one element selected from the group consisting of nickel and cobalt, using a method for recovering valuable elements according to any one of claims 1 to 7.

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