Method for producing valuable metal

Abstract

Provided is a method whereby valuable metals can be safely and efficiently recovered from raw materials including waste lithium ion batteries and the like, while suppressing the loss of a treatment furnace. The present invention is a method for producing a valuable metal from a starting material containing the valuable metal, the method comprising: a preparation step for preparing a starting material containing at least lithium (Li), aluminum (Al), and the valuable metal; a reduction-melting step in which the raw material is subjected to a reduction-melting treatment to obtain a reduced product containing a slag and an alloy containing a valuable metal; and a slag separation step for separating slag from the reduction product and recovering an alloy, in which a flux containing calcium (Ca) is added to the raw material and magnesium oxide (MgO) is added in either or both of the preparation step and the reduction-melting step.

Description

Technical Field

[0001] The present invention relates to a method for producing valuable metals from raw materials such as waste lithium ion batteries. Background Art

[0002] In recent years, lithium ion batteries have become popular as lightweight and high-power secondary batteries. Well-known lithium ion batteries have a structure in which a negative electrode material, a positive electrode material, a separator, and an electrolyte are sealed in an outer can.

[0003] For example, the outer can is made of metal such as aluminum (Al) and iron (Fe). The negative electrode material is made of a negative electrode active material (graphite, etc.) fixed to a negative electrode collector (copper foil, etc.). The positive electrode material is made of a positive electrode active material (lithium nickel oxide, lithium cobalt oxide, etc.) fixed to a positive electrode collector (aluminum foil, etc.). The separator is made of a porous resin film of polypropylene, etc. The electrolyte contains lithium hexafluorophosphate (LiPF 6 ) and other electrolytes.

[0004] One of the main uses of lithium-ion batteries is hybrid vehicles or electric vehicles. Therefore, it is foreseeable that as the life cycle of the car, the lithium-ion batteries carried will be discarded in large quantities. In addition, there are lithium-ion batteries that are discarded as defective products during manufacturing. It is required to reuse such used batteries or defective batteries generated during manufacturing (hereinafter referred to as "waste lithium-ion batteries") as resources.

[0005] As a method of recycling, a dry smelting process using a high-temperature furnace to melt all the waste lithium-ion batteries has been proposed. The dry smelting process is a method of melting crushed waste lithium-ion batteries and separating and recovering valuable metals represented by cobalt (Co), nickel (Ni) and copper (Cu) and metals with lower added value represented by iron (Fe) and aluminum (Al) by using the difference in oxygen affinity between them. In this method, the metals with lower added value are oxidized as much as possible to form slag, while the oxidation of valuable metals is suppressed as much as possible and recovered in the form of alloys.

[0006] For example, Patent Document 1 discloses a method for recovering valuable metals containing nickel and cobalt from waste batteries of lithium-ion batteries containing nickel and cobalt. Specifically, a process for recovering valuable metals has been proposed, which comprises: a melting step in which the waste batteries are melted to obtain a melt; an oxidation step in which the melt or the waste batteries before the melting step are subjected to oxidation treatment; and a slag separation step in which slag is separated from the melt and an alloy containing valuable metals is recovered, and calcium oxide is added in the melting step to reduce the liquidus temperature of the slag to recover the valuable metals.

[0007] Prior art literature

[0008] Patent Literature

[0009] Patent document 1: Japanese Patent No. 6819827. Summary of the invention

[0010] Problems to be solved by the invention

[0011] However, there are also problems in the technology disclosed in Patent Document 1. For example, in the method disclosed in Patent Document 1, if the slag liquidus temperature is excessively lowered by adding flux, there is a problem that the refractory of the furnace wall of the treatment furnace is corroded. If such erosion occurs, there is a risk that the treated material leaks to the outside of the furnace, which is a problem in terms of safety. In addition, the cost required for the maintenance of the refractory of the furnace wall becomes huge, and it is impossible to recover valuable metals at a low cost.

[0012] The present invention has been proposed in view of the above-mentioned actual situation, and its object is to provide a method for safely and efficiently recovering valuable metals from raw materials including waste lithium-ion batteries, etc., which can suppress the wear of a processing furnace.

[0013] Means for solving problems

[0014] The inventors have repeatedly conducted intensive research and found that when the raw material is subjected to reduction melting treatment, by adding a flux and magnesium oxide (MgO) for treatment, a slag coating can be effectively formed on the furnace wall of the treatment furnace, the loss of the furnace can be suppressed, and a safe and effective treatment can be performed, thus completing the present invention.

[0015] (1) The first invention of the present invention is a method for producing a valuable metal, which is a method for producing the valuable metal from a raw material containing the valuable metal, wherein the method for producing the valuable metal comprises: a preparation step, in which a raw material containing at least lithium (Li), aluminum (Al) and the valuable metal is prepared; a reduction melting step, in which the raw material is subjected to a reduction melting treatment to obtain a reduction product containing an alloy and slag, wherein the alloy contains the valuable metal; and a slag separation step, in which the slag is separated from the reduction product to recover the alloy, and in either or both of the preparation step and the reduction melting step, a flux containing calcium (Ca) is added to the raw material, and magnesium oxide (MgO) is added.

[0016] (2) The second invention of the present invention is a method for producing valuable metals, wherein in the first invention, in the reduction melting step, the mass ratio of calcium oxide / (aluminum oxide + calcium oxide) in the generated slag is set to be greater than 0.25 and less than 0.33, and the mass ratio of lithium oxide / (lithium oxide + aluminum oxide) is set to be greater than 0.25 and less than 0.32, and the slag heating temperature is set to be greater than 1400°C and less than 1600°C to implement reduction melting treatment.

[0017] (3) A third aspect of the present invention is a method for producing a valuable metal, wherein in the first aspect or the second aspect, the raw material includes waste lithium-ion batteries.

[0018] (4) The fourth invention of the present invention is a method for producing valuable metals, wherein in any one of the first to third inventions, a mechanism for cooling the furnace wall from the outside is provided in the melting furnace used for the treatment in the reduction melting step, and the reduction melting treatment is carried out while the furnace wall is cooled by the mechanism.

[0019] (5) The fifth invention of the present invention is a method for producing valuable metals, wherein, in any one of the first to fourth inventions, there is also an oxidation roasting step before the reduction melting treatment, in which the raw material is subjected to oxidation roasting to produce an oxidized roasted product, and the obtained oxidized roasted product is subjected to the reduction melting treatment.

[0020] (6) A sixth aspect of the present invention is a method for producing a valuable metal, wherein in any one of the first to fifth aspects, a refractory material formed in a melting furnace used in the reduction melting step contains magnesium oxide (MgO).

[0021] Effects of the Invention

[0022] According to the present invention, it is possible to safely and efficiently recover valuable metals from raw materials including waste lithium-ion batteries and the like while suppressing wear and tear of a processing furnace. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 This is a process diagram showing an example of the flow of a method for producing valuable metals from waste lithium-ion batteries.

[0024] Figure 2 The Al content in the slag is 5% by mass when magnesium oxide (MgO) is added. 2 O 3 -CaO-Li 2 The state diagram of O-based slag is a diagram in which the formation results of the slag coating obtained in the examples are plotted. DETAILED DESCRIPTION

[0025] Hereinafter, a specific embodiment 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 embodiment, and various modifications can be made within the scope of the gist of the present invention.

[0026] 《1. Method for producing valuable metals》

[0027] The method for producing valuable metals in the present embodiment is a method for separating and recovering valuable metals from a raw material containing at least lithium (Li), aluminum (Al) and valuable metals. Therefore, it can also be called a method for recovering valuable metals. The method in the present embodiment is mainly based on a dry smelting process, but can also be composed of a dry smelting process and a wet smelting process.

[0028] Specifically, the method of this embodiment includes: a process of preparing raw materials containing at least lithium, aluminum and valuable metals (preparation process); a process of performing reduction melting treatment on the prepared raw materials to obtain a reduction product (melt) containing an alloy containing valuable metals and slag (reduction melting process); and a process of separating the slag from the obtained reduction product to recover the alloy (slag separation process).

[0029] Furthermore, this method is characterized in that, in either or both of the preparation step and the reduction melting step, a flux containing calcium (Ca) is added to the raw material, and magnesium oxide (MgO) is added.

[0030] In addition, it is preferred that, in the reduction melting process, the mass ratio of calcium oxide / (aluminum oxide + calcium oxide) in the generated slag is set to be greater than 0.25 and less than 0.33, the mass ratio of lithium oxide / (lithium oxide + aluminum oxide) is set to be greater than 0.25 and less than 0.32, and the slag heating temperature is set to be greater than 1400°C and less than 1600°C to implement reduction melting treatment.

[0031] Here, the valuable metals to be recycled are, for example, copper (Cu), nickel (Ni), cobalt (Co), and combinations thereof, and are at least one metal or alloy selected from the group consisting of copper, nickel, cobalt, and combinations thereof. It should be noted that, hereinafter, copper, nickel, and cobalt are used as examples of valuable metals for description.

[0032] [Preparation process]

[0033] In the preparation step, a raw material to be processed is prepared. The raw material is a processing object for manufacturing a valuable metal, and as described above, it contains lithium and aluminum, and contains at least one valuable metal selected from the group consisting of copper, nickel and cobalt. The raw material may contain these components (Li, Al, Cu, Ni, Co) in the form of metals, or may contain these components (Li, Al, Cu, Ni, Co) in the form of compounds such as oxides. In addition, the raw material may also contain inorganic components or organic components other than these components.

[0034] As raw materials, there is no particular limitation on the object, and waste lithium ion batteries, dielectric materials (capacitors), magnetic materials, etc. can be cited. In addition, as long as it is suitable for the treatment in the reduction melting process described later, its form is not limited. In addition, in the preparation process, the raw materials can also be subjected to treatments such as pulverization to make them into an appropriate form. Furthermore, in the preparation process, the raw materials can also be subjected to treatments such as heat treatment and classification treatment to remove unnecessary components such as moisture and organic matter.

[0035] In addition, in the preparation process, a flux containing calcium (Ca) can be added to the raw material. The added flux will be described in detail later. It should be noted that in the method of this embodiment, the flux is added in either or both of the preparation process and the reduction melting process.

[0036] In the method of this embodiment, magnesium oxide (MgO) is added to the raw material in addition to the flux. It should be noted that magnesium oxide can be added in any one or both of the preparation step and the reduction melting step, similarly to the addition of the flux. The details of adding magnesium oxide will be described later.

[0037] [Reduction melting process]

[0038] In the reduction melting step, the prepared raw materials are charged into a melting furnace, and the raw materials are heated to perform a reduction melting treatment, thereby obtaining a reduction product. The reduction product contains the alloy and the slag separately.

[0039] Reduction melting treatment is to heat the raw material in a melting furnace to reduce and melt the process of making a reduced product. The purpose of this treatment is to make the metal (Al etc.) with lower added value contained in the raw material into oxides, on the other hand, the valuable metal (Cu, Ni, Co) is reduced and melted and recovered as an integrated alloy. After the reduction melting treatment, the alloy in a molten state is obtained. It should be noted that, in the case of the treatment of oxidative roasting described later before the reduction melting treatment, the oxidative roasted product obtained is loaded into a melting furnace, heated and reduced and melted. Thus, the metal (Al etc.) with lower added value oxidized by oxidative roasting treatment is maintained as an oxide state, on the other hand, the valuable metal (Cu, Ni, Co) is reduced and melted and recovered as an integrated alloy.

[0040] In the reduction melting treatment, a reducing agent is preferably introduced. In addition, as a reducing agent, carbon and / or carbon monoxide are preferably used. Carbon has the ability to easily reduce the valuable metals (Cu, Ni, Co) that are the object of recovery. For example, 2 moles of valuable metal oxides (copper oxides, nickel oxides, etc.) can be reduced with 1 mole of carbon. In addition, the reduction method using carbon or carbon monoxide is extremely safe compared to the method using a metal reducing agent (for example, the aluminothermic reaction method using aluminum).

[0041] As carbon, artificial graphite and / or natural graphite can be used. In addition, coal and coke can be used as long as there is no risk of contamination by impurities.

[0042] The alloy generated by the reduction melting treatment contains valuable metals as described above. Therefore, it is possible to separate the components (alloys) containing valuable metals from other components in the reduction product. This is because the oxygen affinity of metals with lower added value (such as Al) is high, and in contrast, the oxygen affinity of valuable metals is low. For example, aluminum (Al), lithium (Li), carbon (C), manganese (Mn), phosphorus (P), iron (Fe), cobalt (Co), nickel (Ni) and copper (Cu) are generally oxidized in the order of Al>Li>C>Mn>P>Fe>Co>Ni>Cu. That is, aluminum is most easily oxidized and copper is most difficult to oxidize. Therefore, metals with lower added value (such as Al) are easily oxidized to become slag, and valuable metals (Cu, Ni, Co) are reduced to become metals (alloys). As described above, metals with lower added value and valuable metals can be efficiently separated into slag and alloys.

[0043] Here, during the reduction melting process, a flux containing calcium (Ca) can be added to the raw material. In the method of this embodiment, the flux is added in either or both of the preparation process and the reduction melting process. The flux is a flux containing calcium (Ca) as a main component, for example, calcium oxide (CaO), calcium carbonate (CaCO 3 However, when the raw material to be processed contains a required amount of calcium, it is not necessary to add flux.

[0044] In addition, the method of this embodiment is characterized in that, in addition to adding flux, magnesium oxide (MgO) is added to the raw material and a reduction melting treatment is performed. It should be noted that the addition of magnesium oxide (MgO) can also be added in either or both of the preparation step and the reduction melting step.

[0045] Magnesium oxide (MgO) is mainly used as a material for the refractory material constituting the side wall (furnace wall) of the furnace. Magnesium oxide can increase the melting point of slag and increase the viscosity of slag, so it is possible to deteriorate the separation of slag and metal. Therefore, it is a raw material that would not be added in the past. However, based on the results of the inventor's research, by adding magnesium oxide to the raw material to implement a reduction melting treatment, although the melting point of the slag increases, it works in a way that the operating temperature increases, and the slag containing the magnesium oxide (MgO) can be generated. As a result, the slag can be attached to the surface of the refractory material constituting the side wall of the melting furnace in the form of a coating (slag coating), and the erosion and loss of the refractory material of the furnace wall can be suppressed, and a high-safety treatment can be performed. In addition, the life of the refractory material can be significantly extended.

[0046] In particular, in the method of this embodiment, since the raw material containing lithium is used as the object, the generated slag contains lithium oxide (Li 2 O), the refractory material that constitutes the melting furnace is worn out at a very high rate. This is because the raw material also contains aluminum, and lithium oxide (Li 2 O) and aluminum oxide (Al 2 O 3 ) is composed of low melting point lithium aluminate (LiAlO 2 Furthermore, when the refractory is composed of magnesium oxide, magnesium oxide is easily distributed from the refractory to the slag, causing the refractory to be further consumed.

[0047] In contrast, according to the method of this embodiment, since flux and magnesium oxide are added to the raw materials to perform a reduction melting treatment, the distribution of magnesium oxide from the refractory to the slag can be suppressed, especially when the refractory in the melting furnace is composed of magnesium oxide, and the loss of the refractory can be more effectively prevented.

[0048] The amount of magnesium oxide added is not particularly limited, but is preferably added in an amount such that the content of magnesium oxide in the generated slag is about 1 mass % to 10 mass %, more preferably about 3 mass % to 7 mass %.

[0049] In addition, the magnesium oxide is not particularly limited as long as it is magnesium oxide (MgO), and a clinker (magnesium oxide clinker) as a sintered product may be used. It should be noted that the magnesium oxide clinker is a material used directly as a refractory material of a furnace.

[0050] In addition, in the method of the present embodiment, it is preferred to carry out a reduction melting treatment so that the mass ratio of calcium oxide / (aluminum oxide + calcium oxide) in the generated slag becomes greater than 0.25 and less than 0.33, and the mass ratio of lithium oxide / (lithium oxide + aluminum oxide) becomes greater than 0.25 and less than 0.32.

[0051] Lithium (Li) and calcium (Ca) contribute to the decrease of the melting temperature of the slag. Therefore, in addition to adding magnesium oxide, it is preferred to control the composition of the generated slag to the above range, thereby enabling the melting temperature of the slag to be set to, for example, 1600° C. or less. Thus, the coating of the slag can be formed more effectively, and the treatment can be performed with greater safety.

[0052] In addition, by preventing the melting point of the slag from being excessively lowered, a slag coating can be more effectively formed between the slag and the refractory of the furnace wall, which protects the refractory of the furnace wall and enables stable operation with higher safety.

[0053] Furthermore, for example, when the melting temperature (melting point) of the slag is 1500°C, by setting the slag heating temperature to 1600°C, a slag with sufficiently low viscosity can be obtained, the slag and the metal can be efficiently separated, and the recovery rate of alloys containing valuable metals can be improved.

[0054] It should be noted that when there is a lot of calcium (Ca) in the slag, it becomes easy to remove phosphorus when the raw material contains phosphorus. This is because phosphorus is oxidized to become acidic oxides, while calcium (Ca) is oxidized to become basic oxides. Therefore, the more calcium (Ca) there is in the generated slag, the more basic the slag composition is, and as a result, it is easy to remove phosphorus by including it in the slag.

[0055] Regarding the composition of the generated slag, when the mass ratio of calcium oxide / (aluminum oxide + calcium oxide) is greater than 0.33, or when the mass ratio of lithium oxide / (lithium oxide + aluminum oxide) is greater than 0.32, the liquidus temperature of the slag drops excessively, and the melting point is, for example, less than 1400°C, and it becomes difficult to form a coating of the slag even if the furnace wall is cooled. Here, the melting point of the alloy composed of copper, nickel and cobalt obtained is about 1300°C to 1400°C, so, for example, in order to work in a manner such that the metal temperature becomes 1400°C to 1500°C, that is, in order to give heat to the metal by the slag, it is necessary to set the slag temperature to 1500°C to 1600°C. However, when the melting point of the slag is less than 1400°C, the coating cannot be effectively formed.

[0056] It should be noted that, in order to impart heat to the metal by the slag as described above, the temperature of the slag layer located on the upper side of the molten material generated by the reduction melting treatment needs to be set higher than that of the metal layer located on the lower side. For this reason, as a melting furnace, it is preferred to use a submerged arc furnace that can maintain the operating temperature of the slag layer at the highest level, that is, can make the slag layer itself heat by immersing the electrode in the slag to maintain a high temperature for treatment.

[0057] In addition, when the mass ratio represented by calcium oxide / (aluminum oxide + calcium oxide) or lithium oxide / (lithium oxide + aluminum oxide) is too low, specifically, when the mass ratios are each less than 0.25, the liquidus temperature of the slag becomes high, the raw materials for the molten material cannot be fully melted, and sometimes the valuable metals cannot be effectively recovered.

[0058] Therefore, when performing the reduction melting treatment, it is preferred to perform the treatment so that the mass ratio of calcium oxide / (aluminum oxide+calcium oxide) of the slag is 0.25 to 0.33, and the mass ratio of lithium oxide / (lithium oxide+aluminum oxide) is 0.25 to 0.32. Thus, the erosion of the refractory constituting the side wall of the melting furnace can be more effectively suppressed during the reduction melting treatment, the treatment can be performed with high safety, and valuable metals can be recovered at a high recovery rate.

[0059] The amount of slag components (e.g., Al, Li, Ca) can be easily controlled by adjusting the composition of the raw materials or the amount of flux added to the raw materials. Specifically, for example, in order to adjust the amount of calcium (Ca) in the slag, a flux containing calcium can be added to the processed material and the amount of flux added can be controlled. It should be noted that, as described above, examples of flux containing calcium include calcium oxide (CaO), calcium carbonate (CaCO 3 ). In addition, the amounts of lithium and aluminum in the slag can be adjusted by controlling the composition of the raw materials prepared in the preparation step.

[0060] In addition, in the reduction melting treatment, it is preferred to set the heating temperature (slag heating temperature) to 1400°C or more and 1600°C or less. In addition, it is more preferred to set the slag heating temperature to 1500°C or more and 1600°C or less. When the slag heating temperature is higher than 1600°C, heat energy is wasted, and the loss of refractory materials such as crucibles, bricks, and casters constituting the melting furnace becomes severe, and productivity may decrease. On the other hand, when the slag heating temperature is lower than 1400°C, the separability of the generated slag and the alloy deteriorates, and the recovery rate of valuable metals may decrease.

[0061] As the melting furnace, it is preferred to use a melting furnace equipped with a mechanism for cooling the furnace wall from the outside by water cooling or the like. While the furnace wall is cooled from the outside by the cooling mechanism, a reduction melting treatment is performed, thereby reducing the temperature of the slag in contact with the refractory surface inside the furnace to a temperature lower than the liquidus temperature of the slag, and effectively forming a coating (solidified layer) of the slag on the refractory surface. When the slag coating is formed in this way, the refractory is protected, and erosion of the refractory can be more effectively prevented.

[0062] In addition, as a melting furnace, it is preferred that the melting furnace contains magnesium oxide (MgO) in the refractory constituting the furnace wall. The furnace wall of most melting furnaces is composed of refractory containing magnesium oxide (MgO). In the method of this embodiment, since magnesium oxide is added to the raw material to implement the reduction melting treatment, the generated slag contains magnesium oxide. Therefore, when a melting furnace containing magnesium oxide in the refractory is used, the distribution of magnesium oxide from the refractory to the slag can be greatly suppressed, that is, the loss of the refractory can be more effectively suppressed.

[0063] In the reduction melting process, oxidation treatment can be performed as needed. It should be noted that, when the oxidation roasting process described later is set before the reduction melting process, and the raw material is subjected to oxidation roasting treatment, it is not necessary to perform oxidation treatment in the reduction melting process. However, when the oxidation in the oxidation roasting treatment is insufficient or the purpose is to further adjust the degree of oxidation, additional oxidation treatment can be performed in the reduction melting process or after the reduction melting process. By performing additional oxidation treatment, a more rigorous adjustment of the degree of oxidation becomes possible.

[0064] As a method for additionally performing oxidation treatment, for example, a method of blowing an oxidant into the molten material generated in the reduction melting treatment can be cited. Specifically, a metal pipe (blowgun) is inserted into the molten material generated in the reduction melting treatment, and the oxidant is blown into the molten material by bubbling to perform oxidation treatment. In this case, an oxygen-containing gas such as air, pure oxygen, or oxygen-enriched gas can be used as the oxidant.

[0065] During the reduction melting treatment, harmful substances such as dust and exhaust gas may be generated. However, by performing a known exhaust gas treatment or the like, the harmful substances can be rendered harmless.

[0066] [Oxidation roasting process]

[0067] In the method of the present embodiment, as required, a step (oxidation roasting step) of oxidizing and roasting the raw materials to obtain an oxidized roasted product can be further provided before the reduction melting treatment. It should be noted that when the oxidization roasting step is provided to oxidize and roast the raw materials, the obtained oxidized roasted product is provided to the reduction melting treatment for reduction melting.

[0068] Oxidation roasting treatment (oxidation treatment) is a treatment in which the raw material is oxidized and roasted to form an oxidized roasted product. When the raw material contains carbon, the carbon can also be effectively oxidized and removed, which can promote the alloy integration of the valuable metals in the reduction melting treatment. More specifically, in the above-mentioned reduction melting treatment, the valuable metals are reduced to become local molten particles. At this time, when carbon is contained in the raw material, the carbon becomes a physical obstacle, hindering the agglomeration of the molten particles (valuable metals), damaging the agglomeration integration of the molten particles and the resulting separation of the metal (alloy) and the slag, and sometimes reducing the recovery rate of the valuable metals. In view of this, by pre-processing the raw material with oxidation roasting before the reduction melting treatment, the carbon in the raw material can be effectively oxidized and removed, thereby promoting the agglomeration integration of the molten particles generated in the reduction melting treatment, and can further improve the recovery rate of the valuable metals.

[0069] In the oxidation roasting treatment, the adjustment of the oxidation degree can be carried out as follows. That is, as described above, 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 treatment, the treatment is carried out until all aluminum is oxidized. The treatment can also be accelerated until a part of iron (Fe) is oxidized, but it is preferred to limit the oxidation degree to a degree that the oxidation of cobalt is suppressed to a minimum so that the cobalt is not recovered as slag.

[0070] When adjusting the degree of oxidation in the oxidation roasting treatment, it is preferred to introduce an appropriate amount of oxidant. In particular, when using a raw material containing waste lithium-ion batteries, it is preferred to introduce an oxidant for treatment. Lithium-ion batteries contain metals such as aluminum and iron as outer packaging materials. In addition, aluminum foil and carbon materials are included as positive electrode materials and negative electrode materials. Furthermore, in the case of a battery assembly, plastic is used as an external package. Since they are all materials that act as a reducing agent, the degree of oxidation can be adjusted to an appropriate range by introducing an oxidant.

[0071] As the oxidant, there is no particular limitation as long as it can oxidize carbon and metals (such as Al) with low added value, and oxygen-containing gases such as air, pure oxygen, and oxygen-enriched gas that are easy to handle are preferred. The amount of the oxidant introduced is based on about 1.2 times (e.g., about 1.15 to 1.25 times) the amount (chemical equivalent) required for the oxidation of each substance to be treated by the oxidative roasting process.

[0072] The heating temperature of the oxidation roasting treatment is preferably 700° C. or higher and 1100° C. or lower, and more preferably 800° C. or higher and 1000° C. or lower. By setting the heating temperature to 700° C. or higher, the oxidation efficiency of carbon can be further improved and the oxidation time can be shortened. In addition, by setting the heating temperature to 1100° C. or lower, the thermal energy cost can be suppressed and the efficiency of the oxidation roasting can be improved.

[0073] The oxidation roasting treatment can be carried out using a known roasting furnace. In addition, it is preferred to use a furnace (preparatory furnace) different from the melting furnace used in the reduction melting treatment, and carry out the treatment in the preparatory furnace. As a roasting furnace, all types of furnaces can be used as long as it is possible to roast the crushed material while supplying an oxidant (oxygen, etc.) and treat it inside. As an example, a rotary kiln furnace and a tunnel kiln (hearth furnace) known in the past can be cited.

[0074] [Slag separation process]

[0075] In the slag separation process, slag is separated from the reduction product obtained by the reduction melting process to recover the alloy containing valuable metals. The specific gravity of the slag and the alloy is different. The slag with a smaller specific gravity than the alloy is concentrated on the upper part of the alloy. Therefore, it can be efficiently separated and recovered by specific gravity separation.

[0076] It should be noted that after separating the slag from the reduction product and recovering the alloy in the slag separation process, a sulfiding process for sulfiding the obtained alloy and a pulverizing process for pulverizing the mixture of the sulfide and the alloy obtained in the sulfiding process may also be provided. Furthermore, a wet smelting process may also be performed on the alloy of the valuable metals obtained by this dry smelting process. By means of the wet smelting process, impurity components can be removed, and the valuable metals (Cu, Ni, Co) can be separated, purified and recovered respectively. As treatments in the wet smelting process, known methods such as neutralization treatment and solvent extraction treatment may be cited.

[0077] As described above, the method of this embodiment is characterized in that, in either or both of the preparation step and the reduction melting step, a flux containing calcium (Ca) is added to the raw material, and magnesium oxide (MgO) is added to reduce and melt the raw material. By such a method, the working temperature is increased, and slag containing magnesium oxide can be generated.

[0078] Thus, the slag can be attached to the surface of the refractory material constituting the furnace wall of the melting furnace in the form of a coating (slag coating), which can inhibit the erosion and loss of the refractory material of the furnace wall and perform a highly safe treatment. In addition, the life of the refractory material can be significantly extended.

[0079] In addition, when a furnace composed of refractory materials containing magnesium oxide is used as a melting furnace to carry out reduction melting treatment, magnesium oxide is added to the raw materials to generate slag containing magnesium oxide, which can suppress the distribution of magnesium oxide from the refractory materials in the melting furnace to the slag, that is, the loss of refractory materials can be more effectively suppressed.

[0080] In addition, in the reduction melting treatment, it is preferred that the mass ratio of calcium oxide / (aluminum oxide+calcium oxide) in the obtained slag is set to be 0.25 or more and 0.33 or less, and the mass ratio of lithium oxide / (lithium oxide+aluminum oxide) is set to be 0.25 or more and 0.32 or less. Thus, the melting temperature of the slag is at least 1600°C or less, for example, 1500°C or less, and the viscosity of the slag can be reduced. In addition, the slag heating temperature is set to be 1400°C or more and 1600°C or less, preferably 1500°C or more and 1600°C or less, and the reduction melting treatment is performed.

[0081] By doing so, for example, when the melting temperature (melting point) of the slag is 1500° C., by setting the slag heating temperature to 1600° C., a sufficiently low-viscosity slag can be obtained, and the slag and metal can be efficiently separated. In addition, by preventing the melting point of the slag from being excessively lowered, a slag coating can be more effectively formed between the slag and the refractory of the furnace wall, which protects the refractory of the side wall of the melting furnace, and stable operations can be performed with high safety.

[0082] At this time, the slag heating temperature is preferably above 1500°C, so the metal temperature is about 1400°C or above, which can ensure that the working temperature of the metal is above the melting point of the metal and maintain the fluidity of the metal. It should be noted that as the alloy to be obtained, it is preferred that the alloy has a melting point of 1400°C or below.

[0083] 《2. Method for producing valuable metals from waste lithium-ion batteries》

[0084] In the method of this embodiment, the raw material to be processed is not limited as long as it contains at least lithium (Li), aluminum (Al) and valuable metals. Among them, the raw material is preferably a raw material containing waste lithium ion batteries.

[0085] Waste lithium-ion batteries contain lithium (Li) and valuable metals (Cu, Ni, Co), and contain metals (Al, Fe) and carbon (C) components with lower added value. Therefore, by using waste lithium-ion batteries as raw materials, valuable metals can be efficiently separated and recovered. It should be noted that waste lithium-ion batteries refer to the concept of waste materials in the manufacturing process of lithium-ion batteries, including not only used lithium-ion batteries, but also defective products generated in the manufacturing process of the positive electrode materials constituting the battery, residues within the manufacturing process, and waste generated. Therefore, waste lithium-ion batteries can also be called lithium-ion battery waste.

[0086] Figure 1 FIG. 1 is a process diagram showing an example of a process flow of a method for producing valuable metals from waste lithium-ion batteries. Figure 1 As shown, the method comprises: a waste battery pretreatment step S1, which removes the electrolyte and the outer can of the waste lithium-ion battery; a crushing step S2, which crushes the contents of the waste battery to prepare a crushed product; an oxidative roasting step S3, which oxidatively roasts the crushed product; a reduction melting step S4, which reduces and melts the oxidative roasted product to perform alloying; and a slag separation step S5, which separates slag from the reduction product obtained by the reduction melting treatment to recover the alloy.

[0087] Although not shown in the figure, a sulfidation step of sulfiding the obtained alloy and a pulverization step of pulverizing the mixture of the sulfide and the alloy obtained in the sulfidation step may be provided after the slag separation step S5. The details of each step will be described below.

[0088] (Waste battery pre-treatment process)

[0089] The waste battery pre-treatment step S1 is carried out for the purpose of preventing the explosion of the waste lithium ion battery of the raw material, making it harmless, and removing the outer can. Since the lithium ion battery is a closed system, it has an electrolyte and the like inside. If the pulverization process is carried out in this state, there is a possibility of explosion and there is a danger. Therefore, it is preferred to implement a discharge process or an electrolyte removal process by any method. In addition, the outer can is mostly composed of aluminum and iron as metals, and such a metal outer can is relatively easy to directly recycle. As described above, by removing the electrolyte and the outer can in the waste battery pre-treatment step S1, safety can be improved and the recovery rate of valuable metals (Cu, Ni, Co) can be improved.

[0090] The specific method of the treatment in the waste battery pretreatment step S1 is not particularly limited, and for example, a method of physically opening holes in the waste battery with a needle-shaped knife tip to remove the electrolyte or a method of calcining the waste battery to render it harmless can be cited.

[0091] (Crushing process)

[0092] In the pulverizing step S2, the contents of the waste lithium-ion battery are pulverized to obtain a pulverized product. The pulverizing process in the pulverizing step S2 is aimed at improving the reaction efficiency in the dry smelting process. By improving the reaction efficiency, the recovery rate of valuable metals (Cu, Ni, Co) can be improved.

[0093] The specific pulverization method is not particularly limited, and the pulverization can be performed using a conventionally known pulverizer such as a cutter mixer.

[0094] It should be noted that when recycling aluminum and iron contained in the outer can, the crushed material can be screened using a vibrating screen. Aluminum is easily converted into powder by light crushing, so it can be efficiently recycled. In addition, the iron contained in the outer can can also be recovered by magnetic separation.

[0095] The waste battery pre-treatment step S1 and the crushing step S2 combined together are equivalent to the above-mentioned "preparation step".

[0096] (Oxidation roasting process)

[0097] In the oxidative calcination step S3, the pulverized product obtained in the pulverizing step S2 is oxidatively calcined to obtain an oxidatively calcined product. This step is a step corresponding to the above-mentioned "oxidative calcination step", and the details are as described there.

[0098] (Reduction Melting Process)

[0099] In the reduction melting step S4, the oxidatively calcined product obtained in the oxidatively calcined step S3 is subjected to a reduction melting treatment to obtain a reduced product. This step is equivalent to the above-mentioned "reduction melting step", and the details are as described there.

[0100] In particular, the method of the present embodiment is characterized in that a flux containing calcium (Ca) is added to the raw material, and magnesium oxide (MgO) is added to reduce and melt the raw material. By such a method, a slag containing the magnesium oxide can be generated in a manner that increases the operating temperature. Thus, the slag can be attached to the surface of the refractory material constituting the furnace wall of the melting furnace in the form of a coating (slag coating), and the erosion and loss of the refractory material of the furnace wall can be suppressed, and a highly safe treatment can be performed. In addition, the life of the refractory material can be significantly extended.

[0101] In addition, in the reduction melting treatment, it is preferred that the mass ratio of calcium oxide / (aluminum oxide+calcium oxide) in the obtained slag is made to be greater than 0.25 and less than 0.33, and the mass ratio of lithium oxide / (lithium oxide+aluminum oxide) is made to be greater than 0.25 and less than 0.32. Thus, the melting temperature of the slag is at least 1600°C or less, for example, less than 1500°C, which can make the slag less viscous. Moreover, the slag heating temperature is set to be greater than 1400°C and less than 1600°C, preferably to be greater than 1500°C and less than 1600°C, and the reduction melting treatment is performed. Thus, the erosion of the refractory can be more effectively suppressed, the treatment can be performed more safely, and the valuable metals can be recovered at a high recovery rate.

[0102] (Slag separation process)

[0103] In the slag separation step S5, slag is separated from the reduction product obtained in the reduction melting step S4 to recover the alloy. This step corresponds to the above-mentioned "slag separation step", and the details are as described there.

[0104] It should be noted that a sulfiding step and a pulverizing step may be provided after the slag separation step. Furthermore, the obtained valuable metal alloy may be subjected to a wet smelting process. The details of the sulfiding step, the pulverizing step and the wet smelting process are as described above.

[0105] Example

[0106] Hereinafter, the present invention will be described in more detail with reference to examples, but the present invention is not limited to the following examples.

[0107] [Regarding the Flow of Valuable Metal Recovery Processing (Operations of Each Step)]

[0108] Waste lithium-ion batteries containing lithium (Li), aluminum (Al) and valuable metals (Cu, Ni, Co) are used as raw materials to recover valuable metals.

[0109] (Waste battery pre-treatment and crushing process)

[0110] First, as waste lithium-ion batteries, used batteries of 18650 cylindrical batteries, vehicle-mounted square batteries, and defective batteries recovered in the battery manufacturing process were prepared. Then, the waste lithium-ion batteries were immersed in salt water to discharge, and the water was removed. They were then roasted in the air at a temperature of 260°C to decompose and remove the electrolyte, thereby obtaining the battery contents.

[0111] Then, the battery contents were pulverized using a pulverizer (trade name: Good Cutter, manufactured by Ujiie Manufacturing Co., Ltd.) to obtain a pulverized product.

[0112] (Oxidation roasting process)

[0113] Then, the obtained pulverized product was oxidatively calcined in a rotary kiln at a heating temperature of 900° C. for 180 minutes in the atmosphere.

[0114] (Reduction Melting Process)

[0115] Then, the obtained oxidized calcined product was prepared so that the mass ratio of lithium oxide / (lithium oxide+aluminum oxide) became the value shown in the following Table 1, and only graphite powder in an amount of 0.6 times the total molar number of the valuable metals (Cu, Ni, Co) (i.e., 1.2 times the molar number of graphite powder required for reducing the valuable metals) was added as a reducing agent, and calcium oxide (CaO) was further added as a flux. The flux was added in an amount such that the mass ratio of calcium oxide / (aluminum oxide+calcium oxide) in the slag generated by the reduction melting treatment became the value shown in the following Table 1, and mixed.

[0116] Then, magnesium oxide (MgO) was further added to the raw material (oxidatively roasted product) in such an amount that the content of the generated slag became 5% by mass, and the mixture was mixed.

[0117] As a melting furnace for performing the reduction melting treatment, a submerged arc furnace whose furnace wall can be cooled from the outside by a water cooling jacket is used. In addition, the melting furnace has a furnace wall composed of a refractory containing magnesium oxide (MgO).

[0118] Each test sample was heated to a predetermined reduction melting temperature (slag heating temperature) shown in Table 1 below, and subjected to reduction melting treatment to alloy the valuable metals, thereby obtaining a reduction product containing an alloy and slag.

[0119] (Slag separation process)

[0120] The slag is separated from the obtained reduction product, and the alloy is recovered as a recovered alloy.

[0121] [About slag composition analysis]

[0122] The components of the slag separated from the reduction product were analyzed as follows: That is, the obtained slag was cooled and then pulverized, and analyzed by fluorescent X-ray.

[0123] (Valuable metal recovery rate)

[0124] The recovery rate of the valuable metal (Co) was calculated based on the following formula 1. It should be noted that the component analysis of the recovered alloy was performed using fluorescent X-rays.

[0125] Recovery rate of valuable metals (%) = (weight of Co in recovered alloy) ÷ (weight of Co in recovered alloy + weight of Co in slag) × 100 (Formula 1)

[0126] [About the evaluation results]

[0127] The following Table 1 shows the evaluation results of the degree of loss of the refractory constituting the side wall of the melting furnace caused by the addition of magnesium oxide (MgO) to the raw material when the raw material (oxidized roasted product) is heated at the slag heating temperature. In addition, the results of the cobalt recovery rate when the mass ratios of lithium oxide / (lithium oxide + aluminum oxide) and calcium oxide / (aluminum oxide + calcium oxide) in the obtained slag are changed are also shown.

[0128] It should be noted that the degree of refractory wear was confirmed by visual inspection after the completion of these tests and after the submerged arc furnace was powered off. In addition, the presence or absence of slag coating was also confirmed at this time.

[0129] in addition, Figure 2 The Al content in the slag is 5% by mass when magnesium oxide (MgO) is added. 2 O 3 -CaO-Li 2 The state diagram of O-series slag shows the formation results of slag coating obtained in this experiment. Figure 2 The dotted line in the state diagram represents the liquidus line calculated by thermodynamic calculation software (FactSage).

[0130] Table 1

[0131]

[0132] The results in Table 1 show that no loss of the refractory was observed in Examples 1 to 15. In addition, a slag coating was formed on the furnace wall of the melting furnace, and the refractory was protected.

[0133] On the other hand, in Comparative Examples 1 to 3, no slag coating was formed, the refractory was not protected, and significant loss of refractory was observed. This can be inferred that the liquidus temperature of the slag in this composition is too low, and the estimated slag melting point (estimated slag melting point) is 1326°C in Comparative Example 1, 1295°C in Comparative Example 2, and 1250°C in Comparative Example 3. Therefore, even if the furnace wall is cooled, the slag is almost not solidified, so it can be considered that the slag coating is almost not formed.

[0134] From these results, it can be seen that by adding magnesium oxide to the raw material and performing a reduction melting treatment, slag containing magnesium oxide can be generated, and increasing the slag heating temperature can effectively form a slag coating on the surface of the refractory, thereby suppressing the loss of the refractory.

[0135] In addition, in the examples, in Examples 1 to 12, the separation of slag and metal was also good, and a good result of 95% or more of cobalt recovery was obtained. It should be noted that in Examples 13 to 15, the results were lower than the cobalt recovery of Examples 1 to 12. This can be inferred that in Examples 13 to 15, since the estimated slag melting point in the composition of the generated slag became higher, the slag was not completely melted, and the viscosity of the slag was high, so the separation of slag and metal was slightly reduced. As a result, it can be considered that there are many small metal particles in the slag, so the cobalt recovery rate is reduced.

Claims

1. A method for producing a valuable metal, which is a method for producing the valuable metal from a raw material containing the valuable metal, wherein: The method for producing the valuable metal comprises: A preparation step of preparing a raw material containing at least lithium Li, aluminum Al and a valuable metal; A reduction melting step, in which the raw material is subjected to a reduction melting treatment to obtain a reduction product including an alloy and slag, wherein the alloy contains valuable metals; as well as a slag separation step, in which slag is separated from the reduction product to recover the alloy, In either or both of the preparation step and the reduction melting step, a flux containing calcium Ca is added to the raw material, and magnesium oxide MgO is added.

2. The method for producing a valuable metal according to claim 1, wherein: In the reduction melting process, the mass ratio of calcium oxide / (aluminum oxide + calcium oxide) in the generated slag is set to be greater than 0.25 and less than 0.33, and the mass ratio of lithium oxide / (lithium oxide + aluminum oxide) is set to be greater than 0.25 and less than 0.32, and the slag heating temperature is set to be greater than 1400°C and less than 1600°C to implement reduction melting treatment.

3. The method for producing a valuable metal according to claim 1, wherein: The raw material comprises spent lithium-ion batteries.

4. The method for producing a valuable metal according to claim 1, wherein: The melting furnace used in the reduction melting step is provided with a mechanism for cooling the furnace wall from the outside. While the furnace wall is cooled by the above mechanism, reduction melting treatment is carried out.

5. The method for producing a valuable metal according to claim 1, wherein: Prior to the reduction melting treatment, there is also an oxidation roasting step, in which the raw material is subjected to oxidation roasting to obtain an oxidation roasted product. The obtained oxidatively calcined product is subjected to the above-mentioned reduction melting treatment.

6. The method for producing a valuable metal according to claim 1, wherein: The refractory material formed in the melting furnace used in the reduction melting step contains magnesium oxide MgO.

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