Method for recovering valuable metals

Abstract

Provided is a method for inexpensively recovering valuable metals, a method for recovering valuable metals, including the following steps: a preparation step of preparing an input material containing at least lithium (Li) and valuable metals; an oxidation-reduction melting step of subjecting the input material to oxidation treatment and reduction melting treatment to obtain a reduction product containing a molten alloy containing valuable metals and a slag; and a slag separation step of separating the slag from the reduction product to recover the molten alloy, the molar ratio of lithium (Li) to aluminum (Al) (Li / Al ratio) in the slag being set to 0.15 or greater and less than 0.40, and the molar ratio of calcium (Ca) to aluminum (Al) (Ca / Al) in the slag being set to 0.15 or greater.

Description

Technical Field

[0001] This invention relates to a method for recycling valuable metals. Background Technology

[0002] In recent years, lithium-ion batteries, as lightweight and high-power rechargeable batteries, have become widely used. A well-known lithium-ion battery has a structure in which negative electrode material, positive electrode material, spacers, and electrolyte are sealed within a package.

[0003] For example, the encapsulation container is made of metals such as aluminum (Al) and iron (Fe). The negative electrode material is composed of a negative electrode active material (such as graphite) fixed to the negative electrode current collector (such as copper foil). The positive electrode material is composed of a positive electrode active material (such as lithium nickel oxide or lithium cobalt oxide) fixed to the positive electrode current collector (such as aluminum foil). The spacer is made of a porous polypropylene resin membrane. The electrolyte contains an electrolyte such as lithium hexafluorophosphate (LiPF6).

[0004] One of the main uses of lithium-ion batteries is in hybrid and electric vehicles. Therefore, based on the lifecycle of a vehicle, a large number of lithium-ion batteries are expected to be discarded in the future. In addition, there are lithium-ion batteries discarded as defective products during the manufacturing process. There is a demand for the reuse of these used batteries or defective batteries generated during manufacturing (hereinafter referred to as "waste lithium-ion batteries") as resources.

[0005] As a method of reuse, a dry smelting process has been proposed, in which waste lithium-ion batteries are completely melted down in a high-temperature furnace. The dry smelting process involves melting down the crushed waste lithium-ion batteries and separating them by utilizing the difference in oxygen affinity between valuable metals (such as cobalt (Co), nickel (Ni), and copper (Cu)) and low-value metals (such as iron (Fe) and aluminum (Al)). In this method, low-value metals are vigorously oxidized to produce slag, while valuable metals are maximally inhibited from oxidation and recycled as alloys.

[0006] Patent Document 1 discloses a process for recovering enthalpy and metals from lithium-ion batteries using a copper smelting furnace. Specifically, it discloses a process characterized by steps including supplying useful feedstocks and slag-forming agents to the smelting furnace, and adding a heating agent and a reducing agent, wherein at least a portion of the heating agent and / or reducing agent is replaced by a lithium-ion battery containing one or more of metallic iron, metallic aluminum, and carbon. If a copper smelting furnace is used, valuable metals such as copper and nickel can be efficiently recovered from lithium-ion batteries in conjunction with copper smelting. Cobalt is distributed into the slag during copper smelting. As a method for recovering cobalt, one consideration is, for example, a method of separating the alloy and slag by roasting spent lithium-ion batteries, followed by wet treatment of the resulting alloy.

[0007] Furthermore, Patent Document 2 discloses a method for recovering valuable metals containing nickel and cobalt from waste lithium-ion batteries containing nickel and cobalt. Specifically, it discloses a method including: a melting step, in which the waste battery is melted to obtain a molten material; an oxidation step, in which the molten material or the waste battery prior to the melting step is oxidized; a slag separation step, in which slag is separated from the molten material and the alloy containing the valuable metal is recovered; and a dephosphorization step, in which phosphorus contained in the alloy is separated, a lime-containing substance is added to the alloy in the dephosphorization step, and then the alloy is oxidized. In Patent Document 2, a process is proposed to recover valuable metals by adding silicon dioxide (SiO2) and calcium oxide (CaO) to lower the melting point of the slag when melting waste lithium-ion batteries.

[0008] Existing technical documents

[0009] Patent documents

[0010] Patent Document 1: International Publication No. 2015 / 096945;

[0011] Patent Document 2: Japanese Patent No. 5853585. Summary of the Invention

[0012] The problem the invention aims to solve

[0013] However, the methods proposed in Patent Documents 1 and 2 also have remaining problems. For example, the method in Patent Document 1 requires high-temperature treatment. Additionally, there is the problem of the oxides in the processing container being corroded by the slag and immediately breaking. If such corrosion occurs, the equipment cost becomes enormous, making it impossible to recover valuable metals cheaply. In the method disclosed in Patent Document 2, the amount of waste lithium-ion batteries processed is reduced due to the large amount of flux added. Furthermore, since the flux contains a large amount of silicon dioxide (SiO2), an acidic oxide, the removal of phosphorus, an acidic oxide, from the metal may be insufficient. Due to these problems, it is desirable to develop a technology for the cheap recovery of valuable metals from waste lithium-ion batteries.

[0014] The present invention is proposed in view of the above-mentioned actual situation, and its purpose is to provide a method for recovering valuable metals at low cost.

[0015] means for solving problems

[0016] The inventors conducted dedicated research to solve the aforementioned problems. The results showed that by focusing on the molar ratio of lithium (Li) to aluminum (Al) in the slag (Li / Al ratio) and the molar ratio of calcium (Ca) to aluminum (Al) (Ca / Al ratio), and specifying these ratios within a defined range, the melting temperature of the slag can be set to a low temperature below 1575°C, enabling the inexpensive recovery of valuable metals, thus completing this invention.

[0017] (1) The first invention of the present invention is a method for recovering valuable metals, comprising the following steps: a preparation step, preparing an ingot containing at least lithium (Li) and a valuable metal; an oxidation-reduction melting step, subjecting the ingot to oxidation treatment and reduction melting treatment to obtain a reduced product containing a molten alloy containing a valuable metal and slag; and a slag separation step, separating slag from the reduced product to recover the molten alloy, wherein the molar ratio of lithium (Li) to aluminum (Al) in the slag (Li / Al ratio) is set to 0.15 or more and less than 0.40, and the molar ratio of calcium (Ca) to aluminum (Al) in the slag (Ca / Al) is set to 0.15 or more.

[0018] (2) The second invention of the present invention is based on the first invention, wherein a method of adding a flux containing calcium (Ca) to the charge and / or the processed material in any one or both of the preparation step and the redox melting step.

[0019] (3) The third invention of the present invention is based on the first or second invention, wherein during the oxidation treatment, the loading material is oxidized and roasted to form an oxidized roasted product, and during the reduction and melting treatment, the oxidized roasted product is reduced and melted to form a reduced product.

[0020] (4) The fourth invention of the present invention is based on any one of the first to third inventions, and is a method of introducing a reducing agent during the reduction melting process.

[0021] (5) The fifth invention of the present invention is based on any one of the first to fourth inventions, wherein the heating temperature of the reduction melting treatment is above 1300°C and below 1575°C.

[0022] (6) The sixth invention of the present invention is based on the fifth invention, wherein the heating temperature of the reduction melting treatment is above 1350°C and below 1450°C.

[0023] (7) The seventh invention of the present invention is based on any one of the first to sixth inventions, wherein the loading includes a waste lithium-ion battery.

[0024] (8) The eighth invention of the present invention is based on any one of the first to seventh inventions, wherein the slag contains less than 15% by mass of manganese oxide (MnO).

[0025] The effects of the invention

[0026] According to the present invention, a method for recovering valuable metals at low cost is provided. Attached Figure Description

[0027] Figure 1This is a process diagram illustrating the method for recovering valuable metals from waste lithium-ion batteries.

[0028] Figure 2 This is a schematic diagram showing the configuration of the apparatus used for the experiment.

[0029] Figure 3 It is a state diagram of the Al2O3-CaO-Li2O system (MnO = 0 wt%) based on the measured melting temperature.

[0030] Figure 4 It is a state diagram of the Al2O3-CaO-Li2O system (MnO = 10 wt%) with the results of melting temperature determination. Detailed Implementation

[0031] Hereinafter, embodiments of the present invention (hereinafter referred to as "this embodiment") will be described. It should be noted that the present invention is not limited to the following embodiments, and various changes can be made without changing the essential points of the present invention.

[0032] 1. Methods for Recycling Valuable Metals

[0033] The method for recovering valuable metals in this embodiment is a method for recovering valuable metals from an incorporation containing at least lithium (Li) and valuable metals.

[0034] The valuable metal consists of copper (Cu), nickel (Ni), cobalt (Co), and combinations thereof, and is at least one metal or alloy selected from the group consisting of copper (Cu), nickel (Ni), cobalt (Co), and combinations thereof. Furthermore, the method of this embodiment is primarily a recovery method based on a dry smelting process. It should be noted that it can also be composed of both dry and wet smelting processes.

[0035] Specifically, the recycling method includes: a preparation step, preparing an ingot containing at least lithium (Li) and a valuable metal; an oxidation-reduction melting step, subjecting the ingot to oxidation and reduction melting to obtain a reduced product containing a molten alloy containing a valuable metal and slag; and a slag separation step, separating the slag from the obtained reduced product to recover the molten alloy.

[0036] Furthermore, the molar ratio of lithium (Li) to aluminum (Al) in the slag (Li / Al ratio) is set to be 0.15 or more and less than 0.40, and the molar ratio of calcium (Ca) to aluminum (Al) in the slag (Ca / Al ratio) is set to be 0.15 or more.

[0037] The following describes in detail each step of the recycling method of this embodiment.

[0038] [Preparation Process]

[0039] In the preparation process, a loading material is prepared. The loading material, intended for the recovery of valuable metals, contains lithium (Li) and at least one valuable metal selected from the group consisting of copper (Cu), nickel (Ni), cobalt (Co), and combinations thereof. The loading material may contain these components (Li, Cu, Ni, Co) in metallic form or in the form of compounds such as oxides. Additionally, the loading material may contain inorganic or organic components other than these components (Li, Cu, Ni, Co).

[0040] There are no particular limitations on the type of material to be used; examples include waste lithium-ion batteries, dielectric materials (capacitors), and magnetic materials. Furthermore, there are no restrictions on the form of the material, as long as it is suitable for subsequent redox melting processes. The material can be pulverized or otherwise processed during the preparation stage to achieve a suitable form. Further, the material can be heat-treated or screened during the preparation stage to remove unwanted components such as moisture and organic matter.

[0041] [Oxidation-reduction melting process]

[0042] In the redox melting process, the prepared charge is subjected to oxidation and reduction melting to obtain a reduced product. This reduced product contains the molten alloy separated from the slag.

[0043] Molten alloys contain valuable metals. Therefore, it is possible to separate the component containing valuable metals (molten alloy) from other components in the reducing agent. This is because low-value metals (such as Al) have a high oxygen affinity, while valuable metals have a 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 typically oxidized in the order Al > Li > C > Mn > P > Fe > Co > Ni > Cu. That is, aluminum (Al) is the easiest to oxidize, while copper (Cu) is the most difficult to oxidize. Therefore, low-value metals (such as Al) are easily oxidized to form slag, while valuable metals (Cu, Ni, Co) are reduced to form molten metals (alloys). As described above, it is possible to separate low-value metals and valuable metals into slag and molten alloy.

[0044] In the recycling method of this embodiment, the molar ratio of lithium (Li) to aluminum (Al) in the slag (Li / Al ratio) is set to 0.15 or more and less than 0.40, and the molar ratio of calcium (Ca) to aluminum (Al) (Ca / Al ratio) is set to 0.15 or more.

[0045] Lithium (Li) and calcium (Ca) help lower the melting temperature of slag. Therefore, by controlling the slag composition within the aforementioned range, the melting temperature of the slag can be set below 1575°C, for example, below 1450°C. Furthermore, a higher calcium (Ca) content in the slag facilitates the removal of phosphorus from the charging materials. This is because phosphorus oxidizes into acidic oxides, while calcium (Ca) oxidizes into basic oxides. Therefore, the higher the calcium (Ca) content in the slag, the more alkaline the slag composition, resulting in easier phosphorus removal from the slag.

[0046] The slag may also be aluminum-free (Al). For example, lithium oxide (Li₂O) alone can melt at around 1430°C. However, when the Li / Al ratio is too high, the crucible life may decrease depending on the material used. Furthermore, when both the Li / Al and Ca / Al ratios are too high, the slag may become difficult to melt. Therefore, the Li / Al ratio in the slag is less than 0.4. There is no particular upper limit to the Ca / Al ratio in the slag, but it is preferably less than 1.0, more preferably less than 0.8, and even more preferably less than 0.3.

[0047] Here, 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 (described later).

[0048] Specifically, a flux containing calcium (Ca) can be added to the processed material to adjust the calcium (Ca) content in the slag. The flux is preferably composed mainly of calcium (Ca), such as calcium oxide (CaO) or calcium carbonate (CaCO3). Furthermore, the flux can be added at a stage prior to the reduction melting process. That is, the flux can be added to the charge and / or processed material in any one or two of the preparation process and / or the redox melting process (oxidation treatment, reduction melting treatment). However, if the charge itself contains a large amount of calcium (Ca), the flux may not need to be added. It should be noted that the flux is preferably silicon-free (Si).

[0049] In a redox melting process, oxidation and reduction melting can be performed simultaneously or separately. One method for simultaneous oxidation is to blow an oxidant into the melt generated during reduction melting. Specifically, a metal tube (spray gun) is inserted into the melt generated during reduction melting, and an oxidant is blown in using bubbling, thus performing oxidation simultaneously with reduction melting. In this case, oxygen-containing gases such as air, pure oxygen, or oxygen-enriched gas can be used as the oxidant.

[0050] Furthermore, it is preferable to perform the oxidation treatment and the reduction melting treatment separately in the oxidation-reduction melting process. As a method of separate treatment, an example is to oxidize and calcine the prepared loading material to form an oxidized and calcined product (oxidation treatment), and then reduce and melt the obtained oxidized and calcined product to form a reduced product (reduction melting treatment).

[0051] This document provides a detailed explanation of the oxidation and reduction melting processes within the oxidation-reduction melting process.

[0052] (Oxidation treatment)

[0053] Oxidation treatment is a process in which the contents are oxidized and roasted to form an oxidized roasted product (hereinafter also referred to as "oxidation roasting treatment"). By performing oxidation roasting treatment, carbon is also oxidized and removed when the contents contain carbon, resulting in the ability to promote the alloying integration of valuable metals in subsequent reduction melting treatment.

[0054] In the reduction melting process described later, the valuable metal is reduced to localized molten particles. At this point, the carbon contained in the charge becomes a physical obstacle to the aggregation of these molten particles (valuable metal). Therefore, without oxidative roasting, carbon can sometimes hinder the agglomeration of the molten particles and consequently impede the separation of the metal (molten alloy) from the slag, reducing the recovery rate of the valuable metal. In contrast, by pre-treating with oxidative roasting to remove carbon and agglomerating the molten particles (valuable metal) generated through the reduction melting process, the recovery rate of the valuable metal can be further improved.

[0055] In the oxidative roasting process, the degree of oxidation can be adjusted as follows. As mentioned above, aluminum (Al), lithium (Li), carbon (C), manganese (Mn), phosphorus (P), iron (Fe), cobalt (Co), nickel (Ni), and copper (Cu) are typically oxidized in the order Al > Li > C > Mn > P > Fe > Co > Ni > Cu. In the oxidation process, treatment continues until all aluminum (Al) is oxidized. Treatment can be accelerated until some iron (Fe) is oxidized; preferably, the degree of oxidation is limited to the point where cobalt (Co) is not oxidized and is recovered as slag.

[0056] When adjusting the degree of oxidation during the oxidative roasting process, it is preferable to introduce an appropriate amount of oxidant. In particular, when the contents include spent lithium-ion batteries, it is preferable to introduce an oxidant. Lithium-ion batteries contain metals such as aluminum and iron as encapsulation materials. They also contain aluminum foil and carbon materials as positive and negative electrode materials. Furthermore, in the case of combined batteries, plastic is used as the outer encapsulation. Since these materials all function as reducing agents, introducing an oxidant allows the degree of oxidation to be adjusted to an appropriate range.

[0057] There are no particular limitations as long as the oxidant can oxidize carbon or low-value metals (such as Al). Oxygen-containing gases such as air, pure oxygen, and oxygen-enriched gases, which are easy to operate, are preferred. The amount of oxidant introduced is approximately 1.2 times (e.g., 1.15 to 1.25 times) the amount (stoichiometric equivalent) required for the oxidation of each substance being oxidized in the oxidative roasting treatment.

[0058] The heating temperature for the oxidative roasting treatment is preferably 700°C or higher and 1100°C or lower, more preferably 800°C or higher and 1000°C or lower. Setting the temperature to 700°C or higher further improves the carbon oxidation efficiency and shortens the oxidation time. In addition, setting the temperature to 1100°C or lower helps to reduce heat energy costs and improve the efficiency of oxidative roasting.

[0059] Oxidative roasting can be carried out using a known roasting furnace. Furthermore, it is preferable to use a furnace different from the melting furnace used in the subsequent reduction melting process (a preparatory furnace), and to perform the roasting within this preparatory furnace. As a roasting furnace, any type of furnace can be used as long as it can roast the pulverized material while simultaneously supplying an oxidant (oxygen, etc.) and processing it within it. Examples include conventionally known rotary kilns and hearth furnaces.

[0060] (Reduction Melting Treatment)

[0061] Reduction melting treatment involves heating the oxidized roasted product obtained through the above-mentioned oxidation roasting treatment to reduce and melt it, forming a reduced product. The purpose of this treatment is to maintain the low-value metals (such as Al) oxidized by oxidation roasting in an oxide state, while reducing and melting the valuable metals (Cu, Ni, Co) and recovering them as an integrated alloy. It should be noted that the alloy obtained after reduction melting treatment is called a "molten alloy".

[0062] In reduction melting processes, a reducing agent is preferably introduced. Furthermore, carbon and / or carbon monoxide are preferred as the reducing agent. Carbon has the ability to readily reduce valuable metals (Cu, Ni, Co) that are being recycled. For example, 1 mole of carbon can reduce 2 moles of valuable metal oxides (copper oxide, nickel oxide, etc.). In addition, reduction methods using carbon or carbon monoxide are far safer than methods using metal reducing agents (e.g., the aluminothermic reaction using aluminum).

[0063] As carbon, artificial graphite and / or natural graphite can be used. Additionally, coal and coke can be used if there is no risk of contamination from impurities.

[0064] There is no particular limitation on the heating temperature for reduction melting, but it is preferably 1300°C or higher and 1575°C or lower, more preferably 1350°C or higher and 1450°C or lower. For example, at temperatures above 1600°C, heat energy is wasted, and the consumption of refractory materials such as crucibles becomes more intense, potentially reducing productivity. On the other hand, at temperatures below 1300°C, the separability between the slag and the molten alloy deteriorates, potentially reducing the recovery rate. Reduction melting can be carried out using known methods. For example, methods such as loading the calcined oxide into an alumina (Al2O3) crucible and heating it by resistance heating can be employed. Furthermore, during reduction melting, harmful substances such as dust and exhaust gases may sometimes be generated; these harmful substances can be neutralized by implementing known exhaust treatment methods.

[0065] If an oxidative roasting treatment is performed before the reduction melt treatment, an oxidation treatment is not required during the reduction melt treatment. However, if the oxidation during the oxidative roasting treatment is insufficient, or if the aim is to further adjust the degree of oxidation, an additional oxidation treatment can be performed during the reduction melt treatment. By performing an additional oxidation treatment, the degree of oxidation can be adjusted more precisely.

[0066] [Slag Separation Process]

[0067] In the slag separation process, slag is separated from the reduced product obtained in the redox melting process, thereby recovering the molten alloy. Since the slag and molten alloy have different specific gravities, the lighter slag concentrates in the upper part of the molten alloy, allowing for separation and recovery through gravity separation.

[0068] Alternatively, after separating and recovering the molten alloy from the slag in the slag separation process, a sulfidation process can be set up to sulfide the obtained alloy, and a pulverization process can be set up to pulverize the mixture of sulfides and alloys obtained in the sulfidation process. Furthermore, the valuable metal alloy obtained through this dry smelting process can also be subjected to a wet smelting process. Through the wet smelting process, impurities can be removed, and valuable metals (Cu, Ni, Co) can be separated, purified, and recovered separately. It should be noted that known methods such as neutralization treatment and solvent extraction treatment can be used as treatments in the wet smelting process.

[0069] As described above, according to the recycling method of this embodiment, the slag is processed to control the Li / Al molar ratio and Ca / Al molar ratio in the slag within the aforementioned specific ranges. As a result, the melting temperature of the slag is below 1575°C, for example below 1450°C, and the slag becomes less viscous. Therefore, the separation of slag and molten alloy in the slag separation process can be performed efficiently, resulting in the efficient and inexpensive recovery of valuable metals.

[0070] 2. Recycling from spent lithium-ion batteries

[0071] In the recycling method of this embodiment, the object to be processed, i.e., the loading material, is not limited as long as it contains lithium (Li) and valuable metals. Among them, waste lithium-ion batteries are preferred as the loading material.

[0072] Waste lithium-ion batteries contain lithium (Li) and valuable metals (Cu, Ni, Co), as well as low-value metals (Al, Fe) and carbon. Therefore, using waste lithium-ion batteries as a loading material allows for the efficient separation and recycling of valuable metals. It should be noted that waste lithium-ion batteries include not only used lithium-ion batteries but also defective products, residues from the manufacturing process, and waste materials generated during the manufacturing of the positive electrode materials and other components. Therefore, waste lithium-ion batteries can also be referred to as lithium-ion battery waste material.

[0073] Figure 1 This is a process diagram illustrating the method for recovering valuable metals from spent lithium-ion batteries. For example... Figure 1 As shown, the method includes: a waste battery pretreatment step (S1) to remove the electrolyte and packaging can of waste lithium-ion batteries; a pulverizing step (S2) to pulverize the contents of the waste batteries to form pulverized material; an oxidative roasting step (S3) to oxidize and roast the pulverized material; a reduction melting step (S4) to reduce and melt the oxidized roasted material to alloy it; and a slag separation step (S5) to separate the slag from the reduced material obtained through the reduction melting treatment to recover the molten alloy. Additionally, although not shown, after the slag separation step (S5), a sulfidation step to sulfidate the obtained alloy and a pulverizing step to pulverize the mixture of sulfide and alloy obtained through the sulfidation step (the pulverizing step S2 can also be called a second pulverizing step) can be provided. The details of each step are explained below.

[0074] [Pre-processing steps for waste batteries]

[0075] The waste battery pretreatment process (S1) is conducted to prevent explosions of waste lithium-ion batteries, ensure their harmless disposal, and remove the packaging canisters. Since lithium-ion batteries are closed systems, they contain electrolytes and other contaminants. If they are crushed in this state, there is a risk of explosion; therefore, it is preferable to perform discharge treatment and electrolyte removal treatment by any method. Furthermore, the packaging canisters are mostly made of metals such as aluminum (Al) and iron (Fe), which are relatively easy to recycle directly. Thus, by removing the electrolyte and packaging canisters in the waste battery pretreatment process (S1), safety can be improved, and the recovery rate of valuable metals (Cu, Ni, Co) can be increased.

[0076] There are no particular limitations on the specific method for the pretreatment step (S1) of waste batteries. For example, a method of physically opening the waste battery with a needle-shaped blade and removing the electrolyte can be given. Alternatively, a method of rendering waste batteries harmless by incineration can be given.

[0077] Furthermore, when recovering aluminum (Al) and iron (Fe) contained in the packaging cans, the removed packaging cans can be crushed, and the crushed material can be sieved using a vibrating screen. Light crushing easily turns aluminum (Al) into powder, thus enabling efficient recovery. Alternatively, iron (Fe) contained in the packaging cans can also be recovered using magnetic screening.

[0078] [Grinding Process]

[0079] In the crushing step (S2), the contents of the waste lithium-ion batteries are crushed to obtain crushed material. The crushing process in step (S2) aims to improve the reaction efficiency in the dry smelting process. By improving the reaction efficiency, the recovery rate of valuable metals (Cu, Ni, Co) can be increased.

[0080] There are no particular limitations on the specific crushing method. Commonly known crushers such as cutting mixers can be used. It should be noted that the waste battery pretreatment process (S1) and the crushing process (S2) are combined and equivalent to the aforementioned "preparation process".

[0081] [Oxidative roasting process]

[0082] In the oxidative roasting step (S3), the pulverized material obtained in the pulverizing step (S2) is oxidatively roasted to obtain an oxidized roasted material. This step is equivalent to the oxidation treatment (oxidative roasting treatment) in the above-mentioned "oxidation-reduction melting step", and the details are as follows.

[0083] [Reduction Melting Process]

[0084] In the reduction melting step (S4), the oxidized roasted product obtained in the oxidation roasting step (S3) is reduced to obtain a reduced product. This step is equivalent to the reduction melting treatment in the above-mentioned "oxidation-reduction melting step", and the details are as follows.

[0085] [Slag Separation Process]

[0086] In the slag separation process (S5), slag is separated from the reduced material obtained in the reduction melting process (S4), thereby recovering the molten alloy. This process is equivalent to the "slag separation process" described above, and details are as follows.

[0087] It should be noted that a sulfidation process and a crushing process can also be set up after the slag separation process. Furthermore, the obtained valuable metal alloy can also be subjected to a wet smelting process. The details of the sulfidation process, the crushing process, and the wet smelting process are as described above.

[0088] Example

[0089] The present invention is further described in detail below with examples and comparative examples, but the present invention is not limited to any of the following examples.

[0090] 1. Examples of Reagent Use

[0091] (raw material)

[0092] As part of an experiment to investigate the effects of lithium (Li) and manganese (Mn) on the slag melting temperature, the reagents used were Al2O3, CaO, LiCO3, MnO2, and Mn. For MnO2 and Mn, it was assumed that they were converted to MnO through reduction melting treatment, and they were added in a molar ratio of MnO2:Mn = 1:1.

[0093] (Experimental setup)

[0094] Figure 2 The diagram shows the configuration of the apparatus used in the experiment. In this embodiment, 20g of a mixture of reagents Al2O3, CaO, LiCO3, MnO2, and Mn in a specified ratio was placed in a 30ml alumina crucible and heated to 1873K using a small muffle furnace and held for 60 seconds. Quantitative analysis was performed using inductively coupled plasma optical emission spectrometry, and the melting temperatures of each component were determined by thermocouple method.

[0095] (Experimental Results)

[0096] Figure 3 A phase diagram of the Al₂O₃-CaO-Li₂O system (MnO = 0 wt%) is shown, plotting the results of the melting temperature determination. (See diagram for example.) Figure 3 As shown, in compositions with a weight ratio of CaO / (CaO+Al2O3) of approximately 0.2 or 0.3, where Li2O accounts for 5% to 10% by mass, the melting temperature decreases compared to the case where Li2O accounts for 0% by mass. On the other hand, when Li2O is increased to 15% by mass, the melting temperature tends to increase compared to the case where Li2O accounts for 5% to 10% by mass. It should be noted that... Figure 3 And as will be discussed later Figure 4 The dashed line in the figure represents the liquidus line calculated using the thermodynamic calculation software (FactSage).

[0097] Based on these results, it can be seen that by increasing Li₂O by 5% by mass under the condition of CaO / (CaO+Al₂O₃) = 0.3, the melting temperature decreases by more than 100 K. Furthermore, if Li₂O is increased to 15% by mass, the melting temperature increases; however, if Li₂O is further increased, the melting temperature tends to decrease again.

[0098] in addition, Figure 4 A phase diagram of the Al₂O₃-CaO-Li₂O₁₀ (mass %) MnO system, plotted based on the measured melting temperature, is shown. Figure 4 As shown, a tendency to approach approximately 0% by mass is observed. It should be noted that a slight expansion of the melting range at 1773 K was confirmed. Based on this result, it is inferred that the same tendency can be observed when the MnO in the slag is around 15% by mass or less.

[0099] 2. Examples of using spent lithium-ion batteries

[0100] Next, an embodiment of processing waste lithium-ion batteries containing lithium (Li) and valuable metals is shown.

[0101] [Process for recycling and processing valuable metals (operation of each step)]

[0102] (Pre-processing of waste batteries)

[0103] First, as waste lithium-ion batteries, we prepare used 18650 cylindrical batteries, automotive square batteries, and defective products recycled during the battery manufacturing process. Then, we immerse these waste lithium-ion batteries in salt water to discharge them, remove the moisture, and roast them in the atmosphere at 260°C to decompose and remove the electrolyte and packaging container, thus obtaining the battery contents.

[0104] (Grinding process)

[0105] Then, the battery contents are crushed using a shredder (product name: Good Cutter: manufactured by Ujiie Manufacturing Co., Ltd.).

[0106] (Oxidative roasting process)

[0107] The resulting pulverized material was then oxidized and roasted in a rotary kiln at 900°C for 180 minutes in the atmosphere.

[0108] (Reduction melting process)

[0109] Then, graphite powder as a reducing agent was added to the obtained calcined oxide at a molar ratio of 0.6 times the total molar number of valuable metals (Cu, Ni, Co), and calcium oxide (CaO) as a flux was mixed in to make the Li / Al ratio (molar ratio) and Ca / Al ratio (molar ratio) in the generated slag the values ​​in Table 1 below, and then the slag was placed in an alumina crucible. For each sample, alloying was carried out by resistance heating to the reduction melting temperature (Table 1) for 60 minutes to obtain molten alloy and slag.

[0110] (Slag separation process)

[0111] The slag is separated from the obtained reduced material, and the molten alloy is recovered as a recycled alloy.

[0112] [Compositional Analysis of Furnace Slag]

[0113] The following is a compositional analysis of the slag separated from the reducing agent. Specifically, the obtained slag was cooled, pulverized, and analyzed using fluorescent X-ray diffraction.

[0114] (Recovery rate of valuable metals)

[0115] The recovery rate of the valuable metal (Co) is calculated as follows.

[0116] That is, it is calculated as (weight of Co in the recovered alloy) ÷ (weight of Co in the recovered alloy + weight of Co in the slag) × 100. It should be noted that the compositional analysis of the recovered alloy was performed using fluorescent X-rays.

[0117] [Regarding the evaluation results]

[0118] Table 1 below shows the results of cobalt recovery when the Li / Al and Ca / Al molar ratios of the obtained slag were varied and melted at melting temperatures of 1450 °C and 1550 °C.

[0119] Table 1

[0120]

[0121] According to the results in Table 1, the slag and metal separation in Examples 1 to 5 were also good, and a good result of over 95% cobalt recovery was obtained in all samples.

[0122] On the other hand, in Comparative Examples 1 to 3, the cobalt recovery rate was lower than that in the Example. That is, the slag was not completely melted, the slag was highly viscous, and therefore it was inferred that the slag-metal separation was poor, and a large number of small metal particles were present in the slag, resulting in a low cobalt recovery rate.

Claims

1. A method for recycling valuable metals, wherein, The process includes the following steps: Preparation process: Prepare a container containing at least lithium (Li) and valuable metals; The oxidation-reduction melting process involves oxidizing and reducing the charge to obtain a reduced product containing a molten alloy with valuable metals and slag. as well as The slag separation process separates the slag from the reduced material to recover the molten alloy. The molar ratio of lithium (Li) to aluminum (Al) in the slag is set to be greater than 0.15 and less than 0.

38. The molar ratio of calcium (Ca) to aluminum (Al) in the slag is set to be greater than 0.20 and less than 0.

57. In any one or both of the preparation and redox melting processes, a flux containing calcium (Ca) is added to the charge and / or the processed material. The flux does not contain silicon.

2. The method as described in claim 1, wherein, During the oxidation treatment, the contents are oxidized and calcined to form an oxidized and calcined product. During the reduction melting process, the oxidized roasted product is reduced and melted to form a reduced product.

3. The method as described in claim 1, wherein, During the reduction melt treatment, a reducing agent is introduced.

4. The method of claim 1, wherein, The heating temperature for the reduction melting treatment is above 1300℃ and below 1575℃.

5. The method of claim 4, wherein, The heating temperature for the reduction melting treatment is above 1350°C and below 1450°C.

6. The method of claim 1, wherein, The contents include waste lithium-ion batteries.

7. The method of claim 1, wherein, The slag contains less than 15% by mass of manganese oxide (MnO).

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