JP7363207B2 - How to recover valuable metals - Google Patents

Description

The present invention relates to a method for recovering valuable metals.

In recent years, lithium ion batteries have become popular as lightweight, high-output batteries. A well-known lithium ion battery has a structure in which a negative electrode material, a positive electrode material, a separator, and an electrolyte are sealed in an outer can. Here, the outer can is made of metal such as iron (Fe) or aluminum (Al). The negative electrode material consists of a negative electrode active material (such as graphite) fixed to a negative electrode current collector (such as copper foil). The positive electrode material consists of a positive electrode active material (lithium nickelate, lithium cobaltate, etc.) fixed to a positive electrode current collector (aluminum foil, etc.). The separator is made of a porous resin film of polypropylene or the like. The electrolytic solution contains an electrolyte such as lithium hexafluorophosphate (LiPF ₆ ).

One of the major uses of lithium-ion batteries is hybrid cars and electric cars. Therefore, it is expected that a large amount of the lithium-ion batteries installed in automobiles will be disposed of in the future as the vehicle reaches its life cycle. There are also lithium-ion batteries that are discarded as defective products during manufacturing. There is a need to reuse such used batteries and defective batteries produced during manufacturing (hereinafter referred to as "waste lithium ion batteries") as resources.

As a reuse method, a pyrometallurgical process has been proposed in which waste lithium-ion batteries are completely melted in a high-temperature furnace. The pyrometallurgy process melts and processes crushed waste lithium-ion batteries to recover valuable metals such as cobalt (Co), nickel (Ni), and copper (Cu), as well as iron (Fe) and aluminum ( This is a method of separating and recovering metals with low added value, such as Al), by utilizing the difference in oxygen affinity between them. In this method, metals with low added value are oxidized as much as possible to form slag, while valuable metals are recovered as alloys with oxidation suppressed as much as possible.

For example, Patent Document 1 discloses a process for recovering enthalpy and metal from a lithium ion battery in a copper smelting furnace, which includes a step of supplying a useful feedstock and a slag forming agent to the smelting furnace, and a heating agent and a reducing agent. and at least a part of the exothermic agent and/or reducing agent is replaced with a lithium ion battery containing one or more of metal iron, metal aluminum, and carbon. , discloses a process (Claim 1 of Patent Document 1). If a copper smelting furnace can be used, valuable metals such as copper and nickel can be efficiently recovered from lithium ion batteries in conjunction with copper smelting. Cobalt is distributed to slag in copper smelting. In order to recover cobalt, for example, a method can be considered in which a waste lithium ion battery is roasted to separate the alloy and slag, and the resulting alloy is wet-processed.

Patent Document 2 is a method for recovering valuable metals containing nickel and cobalt from a waste lithium ion battery containing nickel and cobalt, in which the waste battery is melted to obtain a molten product. a melting step; an oxidation step of oxidizing the waste battery, which is performed on the molten material during the melting step or on the waste battery before the melting step; and removing slag from the molten material. A slag separation step for separating and recovering an alloy containing valuable metals, and a dephosphorization step for separating phosphorus contained in the alloy, and the dephosphorization step includes adding a lime-containing substance to the alloy. , then discloses a method for recovering valuable metals, which is a step of oxidizing the alloy (Claim 1 of Patent Document 2). Patent Document 2 proposes a process for recovering valuable metals by adding silicon dioxide (SiO ₂ ) and calcium oxide (CaO) to lower the melting point of slag when melting waste lithium ion batteries ( [0037] and [0038] of Patent Document 2).

International Publication No. 2015/096945 Patent No. 5853585

However, problems remain even with the methods proposed in Patent Document 1 and Patent Document 2. For example, the method of Patent Document 1 requires high temperature treatment. Another problem is that the oxide in the processing container is easily eroded by the slag and cracks. If such erosion occurs, equipment costs become enormous and valuable metals cannot be recovered at low cost. In the method disclosed in Patent Document 2, since the amount of flux added is large, the amount of waste lithium ion batteries processed becomes small. Furthermore, since the flux contains a large amount of silicon dioxide (SiO ₂ ), which is an acidic oxide, there is a possibility that phosphorus, which becomes an acidic oxide, may be insufficiently removed from the metal. Because of these problems, it is desired to develop a technology for recovering valuable metals from waste lithium ion batteries at low cost.

The present inventors conducted extensive studies in view of such actual circumstances. As a result, the molar ratio of lithium (Li) to aluminum (Al) (Li/Al ratio), the molar ratio of calcium (Ca) to aluminum (Al) (Ca/Al ratio), and the amount of manganese (Mn) in the slag were determined. By focusing on these and limiting these ratios and amounts within predetermined ranges, we have found that the melting temperature of slag can be reduced to a low temperature of 1550° C. or lower, and valuable metals can be recovered at low cost.

The present invention was completed based on such knowledge, and an object of the present invention is to provide a method by which valuable metals can be recovered at low cost.

The present invention includes the following aspects (1) to (7). Note that in this specification, the expression "~" includes the numerical values at both ends thereof. That is, "X to Y" is synonymous with "more than or equal to X and less than or equal to Y."

(1) A method for recovering valuable metals, which includes the following steps:
a preparation step of preparing a charge containing at least lithium (Li) and a valuable metal;
A redox melting step in which the charge is subjected to an oxidation treatment and a reduction melting treatment to obtain a reduced product containing a molten alloy containing valuable metals and slag;
a slag separation step of separating slag from the reduced product and recovering the molten alloy,
The molar ratio of lithium (Li) to aluminum (Al) in the slag (Li/Al ratio) is 0.25 or more, and the molar ratio of calcium (Ca) to aluminum (Al) in the slag (Ca/Al ratio) is 0.30 or more, and the amount of manganese (Mn) in the slag is 5.0% by mass or more.

(2) The method of (1) above, wherein a flux containing calcium (Ca) is added to the charge and/or the treated material in either or both of the preparation step and the redox melting step.

(3) The above-mentioned (1) or Method (2).

(4) The method according to any one of (1) to (3) above, wherein a reducing agent is introduced during the reduction melting process.

(5) The method according to any one of (1) to (4) above, wherein the heating temperature of the reduction melting treatment is 1300° C. or higher and 1550° C. or lower.

(6) The method of (5) above, wherein the heating temperature of the reduction melting treatment is 1350°C or more and 1450°C or less.

(7) The method according to any one of (1) to (6) above, wherein the charge includes a waste lithium ion battery.

According to the present invention, a method is provided in which valuable metals can be recovered at low cost.

An example of a method for recovering valuable metals is shown.

A specific embodiment of the present invention (hereinafter referred to as "this embodiment") will be described. Note that the present invention is not limited to the following embodiments, and various changes can be made without departing from the gist of the present invention.

1. Method for recovering valuable metals The method for recovering valuable metals according to the present embodiment includes the following steps: a preparation step of preparing a charge containing at least lithium (Li) and valuable metals, and an oxidation treatment and reduction process for this charge. The method includes a redox melting process in which a reduced product containing a molten alloy containing valuable metals and slag is obtained by performing a melting process, and a slag separation process in which slag is separated from the reduced product to recover the molten alloy. In addition, the molar ratio of lithium (Li) to aluminum (Al) in the slag (Li/Al ratio) is 0.25 or more, and the molar ratio of calcium (Ca) to aluminum (Al) in the slag (Ca/Al ratio) is 0.25 or more. shall be 0.30 or more. Furthermore, the amount of manganese (Mn) in the slag is 5.0% by mass or more.

This embodiment is a method for recovering valuable metals from a charge containing at least lithium (Li) and valuable metals. Here, the valuable metal is to be recovered, and is at least one metal or alloy selected from the group consisting of copper (Cu), nickel (Ni), cobalt (Co), and combinations thereof. Moreover, this embodiment is mainly a recovery method using a pyrometallurgical process. However, it may be composed of a pyrometallurgical smelting process and a hydrometallurgical smelting process. Details of each step will be explained below.

<Preparation process>
In the preparation process, the charge is prepared. The charge is to be treated to recover valuable metals, and contains lithium (Li), and is further selected from the group consisting of copper (Cu), nickel (Ni), cobalt (Co), and combinations thereof. Contains at least one valuable metal. The charge may contain these components (Li, Cu, Ni, Co) in the form of metals or in the form of compounds such as oxides. The charge may also contain inorganic components and organic components other than these components (Li, Cu, Ni, Co).

The material to be charged is not particularly limited, and examples include waste lithium ion batteries, dielectric materials (capacitors), and magnetic materials. Further, the form is not limited as long as it is suitable for treatment in the subsequent redox melting step. In the preparation step, the charge may be subjected to a treatment such as a crushing treatment to obtain a suitable form. Furthermore, in the preparation process, the charge may be subjected to treatments such as heat treatment and separation treatment to remove unnecessary components such as moisture and organic matter.

<Oxidation-reduction melting process>
In the redox melting step, the prepared charge is subjected to oxidation treatment and reduction melting treatment to obtain a reduced product. This reduced product contains molten alloy and slag separately. The molten alloy contains valuable metals. Therefore, it is possible to separate a component containing a valuable metal (molten alloy) from other components in the reduced product. This is because metals with low added value (such as Al) have a high affinity for oxygen, whereas valuable metals have a low affinity for oxygen. For example, aluminum (Al), lithium (Li), carbon (C), manganese (Mn), phosphorus (P), iron (Fe), cobalt (Co), nickel (Ni) and copper (Cu) are generally It is oxidized in the order of Al>Li>C>Mn>P>Fe>Co>Ni>Cu. That is, aluminum (Al) is the most easily oxidized, and copper (Cu) is the least easily oxidized. Therefore, metals with low added value (Al, etc.) are easily oxidized and become slag, and valuable metals (Cu, Ni, Co) are reduced and become molten metals (alloys). In this way, metals with low added value and valuable metals can be separated into slag and molten alloy.

In this embodiment, the molar ratio of lithium (Li) to aluminum (Al) in the slag (Li/Al ratio) is 0.25 or more, and the molar ratio of calcium (Ca) to aluminum (Al) (Ca/Al ratio) is set to 0.25 or more. shall be 0.30 or more. Lithium (Li) and calcium (Ca) contribute to lowering the melting temperature of slag. Furthermore, if the slag contains a large amount of calcium (Ca), if the charge contains phosphorus, it becomes easier to remove this phosphorus. This is because phosphorus becomes an acidic oxide when oxidized, whereas calcium (Ca) becomes a basic oxide when oxidized. The larger the amount of calcium (Ca) in the slag, the more basic the slag composition becomes, and as a result, it becomes easier to incorporate phosphorus into the slag and remove it.

From the viewpoint of slag melting temperature, the upper limits of the Li/Al ratio and Ca/Al ratio are not particularly limited . For example, lithium oxide (Li ₂ O) alone can be melted at about 1430°C. However, if the Li/Al ratio is too high, the life of the crucible may be shortened depending on the material of the crucible used. Furthermore, if both the Li/Al ratio and the Ca/Al ratio are excessively high, the slag may become difficult to melt. The Li/Al ratio in the slag is more preferably 0.25 or more and 10.00 or less, and even more preferably 0.25 or more and 2.50 or less. The Ca/Al ratio is more preferably 0.30 or more and 3.00 or less, and even more preferably 0.30 or more and 1.00 or less. The amount of slag components (Al, Li, Ca) can be easily controlled by adjusting the composition of the charge and the amount of flux added, which will be described later.

Further, in this embodiment, the amount of manganese (Mn) (Mn quality) in the slag is 5.0% by mass or more. Manganese (Mn) contributes to lowering the melting temperature of slag. Therefore, by adjusting the amount of manganese (Mn) in the slag to be within the above range, even if the Li/Al ratio is as low as less than 0.4, the melting temperature of the slag can be kept below 1550°C. For example, the temperature can be set to 1450°C or less. The upper limit of the amount of manganese (Mn) is not particularly limited. However, if the amount of manganese (Mn) is too large, the slag may become difficult to melt. The amount of manganese (Mn) is preferably 5.0% by mass or more and 10.0% by mass or less, more preferably 5.0% by mass or more and 7.5% by mass or less. Further, the amount of manganese (Mn) in the slag can be easily controlled by adjusting the composition of the charge. For example, by adding a positive electrode material containing manganese (Mn) for a lithium ion battery to the charge, the amount of manganese (Mn) can be controlled.

In order to adjust the amount of calcium (Ca) in the slag, a flux containing calcium (Ca) may be added to the processed material. The flux preferably contains calcium (Ca) as a main component, and examples thereof include calcium oxide (CaO) and calcium carbonate (CaCO ₃ ). Further, the flux may be added at a stage before the reduction melting process. That is, flux may be added to the charge and/or the treated material in either or both of the preparation step and/or the redox melting step (oxidation treatment, reduction melting treatment). However, if the charge itself contains a large amount of calcium (Ca) component, it is not necessary to add flux. Further, it is preferable that the flux does not contain silicon (Si).

During the redox melting step, the oxidation treatment and the reduction melting treatment may be performed simultaneously or separately. An example of a method for performing this simultaneously is a method in which an oxidizing agent is blown into the melt obtained by the reduction melting treatment. Specifically, a metal tube (lance) may be inserted into the melt, and the oxidizing agent may be blown into the melt by bubbling. In this case, an oxygen-containing gas such as air, pure oxygen, or oxygen-enriched gas can be used as the oxidizing agent. However, it is preferred that the redox melting step separately comprises an oxidative roasting step and a reductive melting step. As such a method, during the oxidation treatment, the prepared charge is oxidized and roasted to obtain an oxidized roasted product, and during the reduction melting treatment, the obtained oxidized roasted product is reduced and melted to obtain a reduced product. There are several methods. The details of the oxidation roasting process and the reduction melting process will be explained below.

<Oxidation roasting process>
The oxidative roasting process is a process of oxidizing roasting (oxidation treatment) the charging material to obtain an oxidized roasted product. By providing an oxidation roasting process, even if the charge contains carbon, this carbon can be oxidized and removed, and as a result, the integration of valuable metals into an alloy in the subsequent reduction and melting process can be promoted. . That is, in the reduction melting process, valuable metals are reduced and become locally molten fine particles. Carbon becomes a physical obstacle when molten fine particles (valued metal) aggregate. Therefore, if the oxidation roasting step is not provided, carbon may impede the agglomeration of molten fine particles and the resulting separation of metal (molten alloy) and slag, resulting in a decrease in the recovery rate of valuable metals. On the other hand, by removing carbon in advance in the oxidation roasting process, the agglomeration of molten fine particles (valuable metals) in the reduction melting process progresses, further increasing the recovery rate of valuable metals. becomes possible.

Furthermore, by providing an oxidation roasting step, it is possible to suppress variations in oxidation. In the oxidative roasting step, it is desirable to carry out the treatment (oxidative roasting) at an oxidation degree that is capable of oxidizing metals (such as Al) with low added value contained in the charge. On the other hand, the degree of oxidation can be easily controlled by adjusting the processing temperature, time, and/or atmosphere of oxidative roasting. Therefore, the degree of oxidation can be adjusted more strictly through the oxidation roasting process, and oxidation variations can be suppressed.

The degree of oxidation is adjusted as follows. As mentioned earlier, aluminum (Al), lithium (Li), carbon (C), manganese (Mn), phosphorus (P), iron (Fe), cobalt (Co), nickel (Ni), and copper (Cu) are , generally oxidized in the order of Al>Li>C>Mn>P>Fe>Co>Ni>Cu. In the oxidation roasting step, oxidation is allowed to proceed until the entire amount of aluminum (Al) is oxidized. Although oxidation may be promoted until a part of iron (Fe) is oxidized, the degree of oxidation is kept to such an extent that cobalt (Co) is not oxidized and recovered as slag.

In adjusting the degree of oxidation in the oxidative roasting process, it is preferable to introduce an appropriate amount of oxidizing agent. Particularly if the charge comprises waste lithium ion batteries, the introduction of an oxidizing agent is preferred. Lithium ion batteries contain metals such as aluminum and iron as exterior materials. It also contains aluminum foil and carbon materials as positive and negative electrode materials. Furthermore, in the case of assembled batteries, plastic is used as an external package. All of these are materials that act as reducing agents. By introducing an oxidizing agent, the degree of oxidation in the oxidative roasting process can be adjusted within an appropriate range.

The oxidizing agent is not particularly limited as long as it can oxidize carbon and metals with low added value (such as Al). However, oxygen-containing gases such as air, pure oxygen, oxygen-enriched gases, etc., which are easy to handle, are preferred. The amount of the oxidizing agent to be introduced is approximately 1.2 times (for example, 1.15 to 1.25 times) the amount (chemical equivalent) required for oxidizing each substance to be oxidized.

The heating temperature for oxidative roasting (oxidation treatment) is preferably 700°C or more and 1100°C or less, more preferably 800°C or more and 1000°C or less. At 700° C. or higher, the carbon oxidation efficiency can be further increased and the oxidation time can be shortened. Further, at a temperature of 1100° C. or lower, thermal energy costs can be suppressed and the efficiency of oxidative roasting can be increased.

Oxidative roasting (oxidation treatment) can be performed using a known roasting furnace. Further, it is preferable to use a furnace (preparatory furnace) different from the melting furnace used in the subsequent reduction melting step, and carry out the melting in the preparatory furnace. As the roasting furnace, any type of furnace can be used as long as it is capable of performing oxidation treatment inside the furnace by supplying an oxidizing agent (oxygen, etc.) while roasting the charge. Examples include conventionally known rotary kilns and tunnel kilns (hearth furnaces).

<Reduction melting process>
The reduction melting step is a step in which the obtained oxidized roasted product is heated and reduced and melted to obtain a reduced product. The purpose of this process is to maintain the low value-added metals (Al, etc.) oxidized in the oxidation roasting process as oxides, while reducing and melting the oxidized valuable metals (Cu, Ni, Co) into one. The process is to recover the alloy as a solidified alloy. Note that the material obtained after the reduction treatment is called a "reduced product", and the alloy obtained as a melt is called a "molten alloy".

Preferably, a reducing agent is introduced during the reduction melting process. Further, it is preferable to use carbon and/or carbon monoxide as the reducing agent. Carbon has the ability to easily reduce valuable metals (Cu, Ni, Co) to be recovered. For example, 2 moles of valuable metal oxides (copper oxide, nickel oxide, etc.) can be reduced with 1 mole of carbon. Further, reduction methods using carbon or carbon monoxide are extremely safer than methods using metal reducing agents (eg, thermite reaction method using aluminum). Artificial graphite and/or natural graphite can be used as carbon, and coal or coke can be used as long as there is no fear of impurity contamination.

The heating temperature for the reduction melting treatment is not particularly limited. However, the heating temperature is preferably 1300°C or more and 1550°C or less, more preferably 1350°C or more and 1450°C or less. If the temperature exceeds 1550° C., thermal energy is wasted, and refractories such as crucibles are rapidly consumed, which may reduce productivity. On the other hand, if the temperature is lower than 1300°C, there is a problem that the separability of the slag and the molten alloy deteriorates and the recovery rate decreases. The reduction melting process may be performed by a known method. For example, there is a method in which the oxidized roasted product is charged into an alumina (Al ₂ O ₃ ) crucible and heated by resistance heating or the like. Further, although harmful substances such as dust and exhaust gas may be generated during the reduction melting process, the harmful substances can be rendered harmless by performing treatments such as known exhaust gas treatment.

When an oxidation roasting step is provided, there is no need to perform oxidation treatment in the reduction melting step. However, if the oxidation in the oxidation roasting step is insufficient or if the purpose is to further adjust the degree of oxidation, an additional oxidation treatment may be performed in the reduction and melting step. By performing additional oxidation treatment, it is possible to more precisely adjust the degree of oxidation.

<Slag separation process>
In the slag separation step, slag is separated from the reduced product obtained in the redox melting step, and the molten alloy is recovered. Slag and molten alloy have different specific gravity. Therefore, the slag, which has a lower specific gravity than the molten alloy, collects above the molten alloy and can be separated and recovered by gravity separation.

After the slag separation step, a sulfiding step for sulfurizing the obtained alloy and a pulverizing step for pulverizing the obtained sulfide and alloy mixture may be provided. Furthermore, a hydrometallurgical process may be performed on the valuable metal alloy obtained through such a pyrometallurgical process. By the hydrometallurgical process, impurity components can be removed, valuable metals (Cu, Ni, Co) can be separated and purified, and each can be recovered. Treatments in the hydrometallurgical smelting process include known methods such as neutralization treatment and solvent extraction treatment.

According to the method of this embodiment, the melting temperature of the slag is 1550° C. or lower, for example 1450° C. or lower, and the slag has a low viscosity. Therefore, the slag and the molten alloy can be efficiently separated in the slag separation step, and as a result, valuable metals can be efficiently and inexpensively recovered.

2. Recovery from Waste Lithium Ion Batteries The charge of this embodiment is not limited as long as it contains lithium (Li) and valuable metals. However, it is preferred that the charge comprises waste lithium ion batteries. Waste lithium ion batteries contain lithium (Li) and valuable metals (Cu, Ni, Co), as well as metals with low added value (Al, Fe) and carbon components. Therefore, by using waste lithium ion batteries as a charge, valuable metals can be efficiently separated and recovered. Waste lithium-ion batteries include not only used lithium-ion batteries, but also defective products that occur during the manufacturing process such as positive electrode materials that make up batteries, residue from the manufacturing process, and waste generated during the manufacturing of lithium-ion batteries. This concept includes waste materials in the process. Therefore, waste lithium ion batteries can also be referred to as lithium ion battery waste materials.

A method for recovering valuable metals from waste lithium ion batteries will be explained using FIG. 1. FIG. 1 is a process diagram showing an example of a recovery method. As shown in FIG. 1, this method includes a waste battery pretreatment step (S1) in which the electrolyte and outer can of the waste lithium ion battery are removed, and a first step in which the contents of the waste battery are crushed to obtain a pulverized product. The method includes a pulverization step (S2), an oxidation roasting step (S3) in which the pulverized material is oxidized and roasted, and a reduction and melting step (S4) in which the oxidized and roasted material is reduced and melted to form an alloy. Although not shown, a sulfurization step for sulfurizing the obtained alloy and a second pulverization step for pulverizing the mixture of the obtained sulfide and alloy may be provided after the reduction and melting step (S4). . Details of each step will be explained below.

<Waste battery pre-treatment process>
The waste battery pretreatment step (S1) is performed for the purpose of preventing explosion and rendering harmless the waste lithium ion battery and removing the outer can. Lithium ion batteries are sealed systems, so they contain an electrolyte and the like inside. Therefore, if pulverization is performed in that state, there is a risk of explosion and it is dangerous. It is preferable to perform discharge treatment or electrolyte removal treatment by some method. Further, the outer can is often made of metal such as aluminum (Al) or iron (Fe), and it is relatively easy to collect these metal outer cans as they are. By removing the electrolyte and the outer can in the waste battery pretreatment step (S1) in this way, safety can be improved and the recovery rate of valuable metals (Cu, Ni, Co) can be increased.

The specific method of waste battery pretreatment is not particularly limited. For example, there is a method in which a needle-like cutting edge is used to physically open a hole in a waste battery and remove the electrolyte. Another method is to heat the waste battery and burn the electrolyte to make it harmless.

In the waste battery pre-treatment process (S1), when recovering aluminum (Al) and iron (Fe) contained in the outer can, after crushing the removed outer can, the crushed material is crushed using a sieve shaker. May be sieved. Aluminum (Al) is easily turned into powder by light pulverization, so it can be efficiently recovered. Further, iron (Fe) contained in the outer can may be recovered by magnetic separation.

<First crushing step>
In the first pulverization step (S2), the contents of the waste lithium ion battery are pulverized to obtain a pulverized product. This step aims to increase the reaction efficiency in the pyrometallurgical process. By increasing the reaction efficiency, the recovery rate of valuable metals (Cu, Ni, Co) can be increased. The specific pulverization method is not particularly limited. It can be pulverized using a conventionally known pulverizer such as a cutter mixer. Note that the waste battery pretreatment step and the first pulverization step together correspond to the preparation step described above.

<Oxidation roasting process>
In the oxidative roasting step (S3), the pulverized material obtained in the first pulverizing step (S2) is oxidized and roasted to obtain an oxidized roasted material. The details of this process are as described above.

<Reduction melting process>
In the reduction melting step (S4), the oxidized roasted product obtained in the oxidized roasted step (S3) is reduced to obtain a reduced product. The details of this process are as described above.

<Slag separation process>
In the slag separation step, slag is separated from the reduced product obtained in the reduction and melting step (S4), and the molten alloy is recovered. The details of this process are as described above.

A sulfiding step or a crushing step may be provided after the slag separation step. Furthermore, the obtained valuable metal alloy may be subjected to a hydrometallurgical process. The details of the sulfiding process, the crushing process, and the hydrometallurgical process are as described above.

The present invention will be explained in more detail using the following examples and comparative examples. However, the present invention is not limited to the following examples.

Example 1
(1) Recovery of valuable metals Valuable metals were recovered using waste lithium ion batteries as a charge. Recovery was performed according to the following steps.

<Waste battery pre-treatment process (preparation process)>
As waste lithium ion batteries, 18650 type cylindrical batteries, used prismatic batteries for automobiles, and defective products collected during the battery manufacturing process were prepared. After discharging these waste batteries by immersing them in salt water, water was removed and the batteries were roasted at 260° C. in the atmosphere to decompose and remove the electrolyte and the outer can to obtain battery contents.

<First crushing process (preparation process)>
The obtained battery contents were pulverized using a pulverizer (Good Cutter, Ujiie Seisakusho Co., Ltd.) to obtain a charge.

<Oxidation roasting process>
The obtained pulverized material (charged material) was oxidized and roasted to obtain an oxidized and roasted material. The oxidative roasting was performed in the atmosphere at 900° C. for 180 minutes using a rotary kiln.

<Reduction melting process>
To the obtained oxidized roasted product, graphite was added as a reducing agent in a mole number 0.6 times the total mole number of valuable metals (Cu, Ni, Co), and calcium oxide (CaO) was added as a flux at a Ca/Al ratio. The mixture was added and mixed so that the amount of aluminum was 0.33, and the resulting mixture was placed in an alumina (Al ₂ O ₃ ) crucible. Thereafter, the mixture charged in the crucible was heated and subjected to reduction melting treatment to form an alloy, thereby obtaining a reduced product containing molten alloy and slag. The reduction melting treatment was performed at 1450° C. for 60 minutes by resistance heating.

<Slag separation process>
The slag was separated from the obtained reduced product, and the molten alloy was recovered, which was used as a recovered alloy.

(2) Evaluation <Component analysis of slag>
The component analysis of the slag separated from the reduced product was performed as follows. That is, the obtained slag was cooled, crushed, and analyzed using fluorescent X-rays.

<Valuable metal recovery rate>
The valuable metal (Co) recovery rate was determined as follows. That is, it was determined as (Co weight in recovered alloy) ÷ (Co weight in recovered alloy + Co weight in slag) x 100 (mass%). Note that the component analysis in the recovered alloy was performed using fluorescent X-rays.

Example 2 to Example 5
Same as Example 1 except that the proportions of 18650 type cylindrical batteries, used prismatic batteries, and defective products prepared in the waste battery pretreatment process were changed, and the melting temperature in the reduction melting process was set to the temperature listed in Table 1. Valuable metals were recovered and evaluated.

(3) Results The results obtained for Examples 1 to 5 are shown in Table 1. Note that Examples 1 to 3 are examples, and Examples 4 and 5 are comparative examples.

In Examples 1 to 3, which are examples, the separation of slag and metal (molten alloy) was good. Furthermore, as shown in Table 1, the cobalt (Co) recovery rate was as good as 95% or more. On the other hand, in Examples 4 and 5, which are comparative examples, the cobalt recovery rate was lower than that in the Examples. In Examples 4 and 5, the slag was not completely melted, so it was assumed that the viscosity of the slag became high. In other words, due to the increased viscosity of the slag, a large number of metal particles were present in the recovered slag, which led to a deterioration in the separation of the slag and metal, that is, a deterioration in the cobalt recovery rate. Note that the recovery rates of copper (Cu) and nickel (Ni) exceeded 95% in all cases.

Claims (7)

A method for recovering a valuable metal that is at least one metal or alloy selected from the group consisting of copper (Cu), nickel (Ni), cobalt (Co), and combinations thereof, comprising the following steps:
a preparation step of preparing a charge containing at least lithium (Li) , aluminum (Al), and the valuable metal;
A redox melting step in which the charged material is subjected to an oxidation treatment and a reduction melting treatment to obtain a reduced product containing a molten alloy containing the valuable metal and slag;
a slag separation step of separating slag from the reduced product and recovering the molten alloy,
The molar ratio of lithium (Li) to aluminum (Al) in the slag (Li/Al ratio) is 0.25 or more, and the molar ratio of calcium (Ca) to aluminum (Al) in the slag (Ca/Al ratio) is 0.30 or more, and the amount of manganese (Mn) in the slag is 5.0% by mass or more. The method according to claim 1, wherein a flux containing calcium (Ca) is added to the charge and/or the treated material in one or both of the preparation step and the redox melting step. 3. The method according to claim 1, wherein during the oxidation treatment, the charge is oxidized and roasted to obtain an oxidized roasted product, and during the reduction and melting treatment, the oxidized and roasted product is reduced and melted to obtain a reduced product. Method. The method according to any one of claims 1 to 3, wherein a reducing agent is introduced during the reduction melting process. The method according to any one of claims 1 to 4, wherein the heating temperature of the reduction melting treatment is 1300°C or more and 1550°C or less. The method according to claim 5, wherein the heating temperature of the reduction melting treatment is 1350°C or more and 1450°C or less. A method according to any one of claims 1 to 6, wherein the charge comprises waste lithium ion batteries.

Images