Valuable metal recovery method

Abstract

Provided is a method for reducing recovery loss of a valuable metal due to entrainment occurring during treatment of a mixed powder of a positive electrode active material and a negative electrode active material, which are raw materials for treatment in a valuable metal recovery method, by suppressing the generation of dust during operation. The present invention is a method for recovering a valuable metal, the method comprising a preparation step (S1) for preparing a raw material including a waste lithium ion battery, and in the preparation step (S1), a preliminary kneading step (S13) and a granulation step (S14) are performed to prepare a granulated material comprising a mixed powder, and a preliminary kneading step (S13) in which water is added to a mixed powder containing a positive electrode active material and a negative electrode active material constituting the waste lithium ion battery and preliminary kneading is performed, and a granulation step (S14) in which the preliminary kneaded product is further kneaded and granulated. The amount of water added in the preliminary kneading step (S13) is preferably adjusted to 0.14-0.16 in terms of the weight ratio with respect to the mixed powder. Furthermore, in the granulation step (S14), it is preferable to use a double-shaft paddle granulator, and the circumferential speed at the tip of the paddle is set to 50 m / min to 90 m / min.

Description

Technical Field

[0001] The invention relates to a method for recovering valuable metals from waste lithium ion batteries and other raw materials. Background Art

[0002] In recent years, lithium-ion batteries have become popular as lightweight and high-output 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. For example, the outer can is made of metals such as iron (Fe) and aluminum (Al). The negative electrode material is composed of a negative electrode active material (graphite, etc.) fixed to a negative electrode collector (copper foil, etc.). The positive electrode material is composed 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 composed of a porous resin film of polypropylene, etc. The electrolyte contains electrolytes such as lithium hexafluorophosphate (LiPF6).

[0003] 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.

[0004] As a method of recycling, for example, there is a dry smelting process in which the waste lithium-ion batteries are completely melted using a high-temperature furnace (melting furnace). In addition, there is a wet smelting process, that is, after the valuable metal-containing substances obtained from the waste lithium-ion batteries are mixed in an acidic solution and dissolved, a neutralizing agent is added to the obtained leachate to separate it into a neutralized final solution and a neutralized precipitate, and the obtained neutralized final solution is subjected to solvent extraction using, for example, an acidic extractant, and the extracted organic solvent is stripped with a sulfuric acid solution.

[0005] When the waste lithium-ion batteries are reused by the above-mentioned dry smelting process and wet smelting process, if the waste lithium-ion batteries are directly subjected to pulverization, there is a possibility of explosion and danger. Therefore, the waste lithium-ion batteries to be treated are usually subjected to pre-treatment. As a pre-treatment, for example, a method of physically opening a hole in the waste lithium-ion battery with a needle-shaped knife tip to remove the electrolyte can be cited. In addition, a method of harmlessly burning the electrolyte by heating the waste lithium-ion battery can be cited. Then, a pulverization process is carried out, and after being classified into an outer can, copper foil, aluminum foil, and a mixed powder of a positive electrode active material and a negative electrode active material, the components obtained respectively are operated as recycled raw materials.

[0006] Here, the mixed powder of the positive electrode active material and the negative electrode active material (hereinafter also referred to as "black mass") is in the form of a powder of, for example, several μm to several hundred μm. Therefore, dust may be generated during operation, or during recycling, for example, carry-over may occur due to reaction gas or convection generated during redox melting treatment, which may sometimes deteriorate production efficiency.

[0007] For example, Patent Document 1 describes that dust generated in the oxidation roasting step is discharged outside the furnace for disposal. Since the dust contains black matter carried along, it is seen that the risk of loss of recovery of valuable metals due to dust generation increases.

[0008] Prior art literature

[0009] Patent Literature

[0010] Patent document 1: Japanese Patent Application Publication No. 2021-161455. Summary of the invention

[0011] Problems to be solved by the invention

[0012] The present invention is proposed in view of the above-mentioned actual situation, and its purpose is to provide a method for suppressing dust generation during operation of the mixed powder of positive electrode active material and negative electrode active material contained in waste lithium-ion batteries, which is a raw material for treatment in dry smelting process and wet smelting process, and reducing the recovery loss of valuable metals caused by carryover during oxidation roasting treatment, reduction melting treatment, etc.

[0013] Means for solving problems

[0014] The inventors of the present invention have conducted careful research to solve the above-mentioned problems. As a result, they have found that when a mixed powder (black matter) of a positive electrode active material and a negative electrode active material is subjected to an oxidation roasting treatment, a reduction melting treatment, etc., by granulating the mixed powder under prescribed conditions, the operability can be improved and the generation of dust and carryover can be effectively suppressed, thereby completing the present invention.

[0015] (1) The first invention of the present invention is a method for recovering valuable metals, which is a method for recovering valuable metals, wherein the method comprises a preparation step, in which a raw material containing waste lithium ion batteries is prepared, wherein the waste lithium ion batteries contain valuable metals, and in the preparation step, a granulated material is prepared by performing a preliminary mixing step and a granulation step, wherein the preliminary mixing step is to add water to a mixed powder containing a positive electrode active material and a negative electrode active material constituting the waste lithium ion batteries for preliminary mixing, and the granulation step is to further mix the obtained preliminary mixing material to granulate, and the granulated material is composed of the mixed powder.

[0016] (2) A second aspect of the present invention is a method for recovering valuable metals, wherein in the first aspect, in the preliminary kneading step, the amount of water added is adjusted to be 0.14 or more and 0.16 or less in terms of a weight ratio relative to the mixed powder.

[0017] (3) The third invention of the present invention is a method for recovering valuable metals, wherein in the first invention or the second invention, in the granulation step, a double-shaft paddle granulator is used, and the peripheral speed of the front end of the paddle of the granulator is set to be greater than 50 m / min and less than 90 m / min, and the pre-mixed material is mixed and granulated.

[0018] (4) The fourth invention of the present invention is a method for recovering valuable metals, wherein in any one of the first to third inventions, the method for recovering valuable metals is composed of a dry smelting process further comprising a reduction step, wherein the reduction step is a step of subjecting the granulated material obtained through the preparation step to a reduction melting treatment to obtain a reduced molten material containing an alloy and slag, wherein the alloy contains valuable metals, and in the preliminary mixing step in the preparation step, a flux used in the reduction melting treatment is added to the mixed powder for preliminary mixing.

[0019] (5) The fifth invention of the present invention is a method for recovering valuable metals, wherein in the fourth invention, in the preliminary kneading step, the flux having a particle size of 5 mm or less is used, and the amount of the flux added is adjusted to be greater than 0.1 and less than 0.2 in terms of the weight ratio relative to the mixed powder.

[0020] Effects of the Invention

[0021] According to the present invention, for the processing raw material in the method for recovering valuable metals, i.e., the mixed powder of positive electrode active material and negative electrode active material contained in the waste lithium-ion battery, the dust generation during its operation can be suppressed, and the recovery loss of valuable metals caused by carryover when the mixed powder is subjected to oxidative roasting treatment, reduction melting treatment, etc. can be reduced. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 This is a process diagram showing the flow of a method for recovering valuable metals based on a dry smelting process. DETAILED DESCRIPTION

[0023] Hereinafter, a specific embodiment of the present invention (hereinafter referred to as "this embodiment") will be described in detail. 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 present invention.

[0024] The method for recovering valuable metals according to the present embodiment is a method for recovering valuable metals from waste lithium ion batteries containing lithium (Li) and valuable metals (Cu, Ni, Co, etc.).

[0025] Waste lithium-ion batteries are a concept that includes waste materials in the manufacturing process of lithium-ion batteries, including used lithium-ion batteries, defective products generated in the manufacturing process of positive electrode materials constituting secondary batteries, residues within the manufacturing process, and scraps. In addition, waste lithium-ion batteries contain valuable metals such as copper (Cu), nickel (Ni), and cobalt (Co).

[0026] Specifically, the method of this embodiment includes a preparation step, which prepares a raw material containing waste lithium ion batteries, and the waste lithium ion batteries contain valuable metals. Moreover, the preparation step is characterized in that a granulated material composed of a mixed powder is prepared by performing a process including a preliminary mixing step and a granulation step, wherein the preliminary mixing step is to add water to the mixed powder containing the positive electrode active material and the negative electrode active material constituting the waste lithium ion battery for preliminary mixing, and the granulation step further mixes the obtained preliminary mixed material to granulate.

[0027] The granulated material prepared in this way, which is a processing raw material for the valuable metal recovery method, is supplied to a dry smelting process or a wet smelting process, or a process combining these processes, and the valuable metals are recovered by each treatment process.

[0028] Figure 1 This is a process diagram showing an example of a process flow of a method for recovering valuable metals based on a dry smelting process. Figure 1 As shown, the method comprises: a preparation step S1, in which a raw material containing waste lithium-ion batteries is prepared; an oxidative roasting step S2, in which the raw material is oxidatively roasted; a reduction step S3, in which the obtained oxidative roasted product is reduced and melted to obtain a reduced melt containing an alloy containing valuable metals and slag; and a slag separation step S4, in which the slag is separated from the reduced melt and the alloy is recovered.

[0029] (1) Preparation process

[0030] In the preparation step S1, raw materials containing waste lithium ion batteries containing valuable metals are prepared. Waste lithium ion batteries contain Li, valuable metals (Cu, Ni, Co, etc.) as described above, and contain metals with low added value (Al, Fe, etc.) and carbon components. In addition, waste lithium ion batteries sometimes also contain phosphorus (P). By using such waste lithium ion batteries as raw materials, valuable metals can be effectively recovered. It should be noted that the valuable metals that become the recycling object are at least one metal or alloy selected from the group consisting of Cu, Ni, Co and a combination thereof.

[0031] The waste lithium ion battery may be in any form as long as it is suitable for the treatment in the steps described below. In the preparation step S1, the waste lithium ion battery may be subjected to a treatment such as pulverization to obtain a suitable form. In addition, in the preparation step S1, the waste lithium ion battery may be subjected to a treatment such as heat treatment or classification to remove unnecessary components such as moisture and organic matter.

[0032] The preparation step S1 is a step of preparing a raw material including waste lithium-ion batteries, and is a step of preparing a treatment raw material (an object to be charged into a treatment furnace) to be treated in a subsequent step.

[0033] For example, Figure 1 As shown, the preparation step S1 includes: a waste battery pretreatment step S11, in which the waste lithium-ion batteries are pretreated; a crushing step S12, in which the crushing treatment is performed; a preliminary mixing step S13, in which water is added to the mixed powder containing the positive electrode active material and the negative electrode active material constituting the waste lithium-ion batteries obtained by the crushing treatment, and mixed; and a granulation step S14, in which the obtained preliminary mixed material is further mixed to granulate.

[0034] [About the pre-treatment process of waste batteries]

[0035] The waste battery pre-treatment step S11 is a treatment step performed for the purpose of preventing the waste lithium-ion batteries from exploding, rendering them harmless, and removing the outer cans.

[0036] Since lithium-ion batteries are closed systems, they contain electrolytes and the like. Therefore, if they are crushed in this state, they may explode and be dangerous. Therefore, it is preferred to use any method to implement discharge treatment or electrolyte removal treatment. The specific treatment method in the waste battery pretreatment step S11 is not particularly limited. For example, a method of physically opening a hole in the waste battery with a needle-shaped knife tip to remove the electrolyte can be cited. In addition, a method of heating the waste lithium-ion battery to burn the electrolyte for harmlessness can be cited.

[0037] In addition, the outer cans constituting waste lithium-ion batteries are often made of aluminum (Al) and iron (Fe) which are metals, and such metal outer cans can be directly recycled relatively easily.

[0038] As described above, in the waste battery pre-treatment step S11, by removing the electrolyte and the outer can, safety can be improved, and the recovery rate of valuable metals (Cu, Ni, Co, etc.) can be increased. In addition, it is preferred that the waste lithium ion battery is separated into a metal outer can and other battery contents, and the aluminum outer can is recovered from the metal outer can. The recovered aluminum outer can can also be used as a reducing agent in the subsequent reduction step S3.

[0039] In addition, in the waste battery pre-treatment step S11, when the Al and Fe contained in the outer can are recovered, the removed outer can can be crushed and then the crushed material can be screened using a vibrating screen. Al is easily powdered by slight crushing, so it can be effectively recovered. In addition, the Fe contained in the outer can can be recovered by magnetic separation. In addition, it is preferred that the recovered aluminum outer can can be crushed into at least one form of blocks, particles, powder and foil.

[0040] [About the crushing process]

[0041] In the pulverizing step S12, the contents of the waste lithium-ion battery are pulverized to obtain a pulverized product. The pulverizing process in the pulverizing step S12 is for the purpose of improving the reaction efficiency. By improving the reaction efficiency of the processed raw materials, the recovery rate of the valuable metals (Cu, Ni, Co, etc.) contained in the raw materials can be improved.

[0042] By performing a pulverization process in the pulverization step S12, for example, a mixed powder (black matter) containing the positive electrode active material and the negative electrode active material constituting the waste lithium ion battery is obtained. The mixed powder is a powder containing the valuable metals contained in the positive electrode active material and the negative electrode active material, also known as black matter. It should be noted that for the mixed powder, the valuable metals contained in the positive electrode active material and the negative electrode active material are concentrated through the screening process in the above-mentioned waste battery pre-treatment step S11, and in addition to the valuable metals, impurity element components such as aluminum, iron, and carbon are also included.

[0043] The specific method of the pulverization treatment (pulverization method) is not particularly limited. For example, the pulverization can be performed using a conventionally known pulverizer such as a cutter mixer.

[0044] [About the preliminary kneading process and granulation process]

[0045] The mixed powder containing the positive electrode active material and the negative electrode active material constituting the waste lithium ion battery obtained through the above-mentioned pulverization step S12 is in the form of a powder with a size of about several μm to several hundred μm. Therefore, dust is easily generated during operation. In addition, in the subsequent steps, carryover due to reactive gas and convection occurs, which sometimes causes the recovery loss of valuable metals contained in the mixed powder.

[0046] Therefore, in the method of this embodiment, in the preparation step S1, there are: a preliminary kneading step S13, in which water is added to the mixed powder containing the positive electrode active material and the negative electrode active material for preliminary kneading; and a granulation step S14, in which the preliminary kneaded material is further kneaded to granulate. In the method of this embodiment, by performing such a treatment step, a granulated material composed of the mixed powder containing the positive electrode active material and the negative electrode active material is prepared.

[0047] In the method of this embodiment, by preparing granules with this structure, when supplying raw materials (granules of mixed powder) to the treatment in the oxidation roasting step S2 and the reduction step S3 described later, dust generation during operation can be prevented. In addition, losses caused by carryover can be suppressed. Thus, recovery losses can be reduced, and effective recovery of valuable metals can be achieved.

[0048] (Preliminary mixing process)

[0049] In the preliminary kneading step S13, water is added to the mixed powder containing the positive electrode active material and the negative electrode active material to perform preliminary kneading, thereby obtaining a preliminary kneaded product in which water is uniformly dispersed in the mixed powder.

[0050] The negative electrode active material contained in the mixed powder usually contains a large amount of graphite. Therefore, when granulation is performed without the preliminary mixing process in the preliminary mixing step S13, the granulation is likely to become insufficient, and dust generation from the obtained granules may not be fully suppressed. Therefore, before the main mixing and granulation of the mixed powder, by providing the preliminary mixing step S13, water is added to the mixed powder for preliminary mixing, so that good granulation of the mixed powder is possible, and dust generation can be effectively suppressed.

[0051] The mixing in the pre-mixing process can be carried out using a batch kneading machine such as a Brabender mixer, a Banbury mixer, a Henschel mixer, a screw rotor, a roller, a single-shaft mixer, a double-shaft mixer, a double-shaft paddle mixer, etc. By using such a mixer, a shear force can be effectively applied to the mixed powder, which is not only easy to mix evenly, but also can improve the adhesion of each particle. In addition, since the gap can be reduced due to the improved adhesion, the granulation property in the granulation step S14 can be improved.

[0052] In the preliminary kneading step S13, the amount of water added to the mixed powder (addition amount) is not particularly limited, and is preferably adjusted to a range of 0.14 to 0.16 in terms of weight ratio relative to the mixed powder. Thus, the added water can be more effectively dispersed in the mixed powder, and the granulation property in the granulation step S14 described later can be further improved.

[0053] It should be noted that the treatment time of the preliminary kneading can be appropriately set according to the amount of the mixed powder to be kneaded, and is not particularly limited, but is more preferably set to a time of 3 minutes or more. This allows the water to be reliably dispersed in the mixed powder, preventing insufficient kneading.

[0054] In addition, in the preliminary kneading step S13, a flux may be added to the mixed powder. The added flux is a flux used in the reduction melting treatment in the reduction step S3 described later in the method for recovering valuable metals based on the dry smelting process. Such a flux may be added at the stage of preliminary kneading the mixed powder in the preliminary kneading step S13, and a granulated material containing the flux may be prepared through the subsequent granulation step S14.

[0055] As the flux, for example, calcium carbonate (CaCO 3 ), calcium oxide (CaO), aluminum oxide (Al 2 O 3 ), silicon oxide (SiO 2 ), magnesium oxide (MgO), iron oxide (Fe 2 O 3 , etc.) and the like can be arbitrarily used.

[0056] In addition, the particle size of the flux is not particularly limited, and is preferably 5 mm or less. In addition, the amount of flux added is not particularly limited, and is preferably adjusted to a range of 0.1 or more and 0.2 or less in terms of weight ratio relative to the mixed powder. Thus, it can be well mixed with the mixed powder, and the particle size of the granulated material obtained by the granulation step S14 can be easily set to a size of 4 mm or more. By increasing the proportion of granulated materials with a particle size of 4 mm or more in this way, the operability can be further improved, dust generation can be more effectively suppressed, and the loss caused by carrying can be further reduced.

[0057] (Granulation process)

[0058] In the granulation step S14, the pre-kneaded product obtained in the pre-kneading step S13 is further kneaded and granulated, thereby preparing a granulated product composed of a mixed powder containing a positive electrode active material and a negative electrode active material.

[0059] The kneading (main kneading) and granulation operations in the granulation step S14 can be preferably performed using, for example, a twin-shaft paddle granulator. The twin-shaft paddle granulator has a structure in which paddles are helically embedded in a rotating shaft that rotates at high speed inside a housing.

[0060] Here, the kneading and granulation using a twin-shaft paddle granulator are described. First, in the initial stage of granulation, a water film is formed on the surface of the powder particles constituting the preliminary kneaded product by the stirring action of the paddles, and other powder particles are captured by the surface tension of the water film. As a result, a granulation core is formed. Then, when the stirring action of the paddles is further applied, the water is evenly diffused between the powder particles, and the formed granulation core grows significantly. Then, the growing granulation core rotates on the paddles, and with this, the powder particles are compressed with each other and granulated into a spherical shape.

[0061] In the operation of mixing and granulation using a twin-shaft paddle granulator, it is preferred that the peripheral speed of the front end of the blade is set to be greater than 50 m / min and less than 90 m / min, without particular limitation. When the peripheral speed of the front end of the blade is less than 50 m / min, the compression of the powder particles is insufficient, and the strength of the granules is insufficient and may disintegrate during operation. In addition, when the granules disintegrate, it is difficult to suppress dust generation. On the other hand, when the peripheral speed of the front end of the blade is greater than 90 m / min, although a stronger granule can be formed, the risk of equipment failure increases due to the increased load on the equipment.

[0062] In addition, a binder such as starch may be further added during kneading and granulation, thereby improving the granulation properties and obtaining a stronger granulated product.

[0063] In addition, the kneading and granulation treatment time can be appropriately set according to the amount of the pre-kneaded material to be treated, and is not particularly limited, but it is more preferably set to a time of 2 minutes or more. In this way, the ratio of granules below 1 mm in the granules can be suppressed from increasing (for example, granules below 1 mm account for more than 10%), and it is possible to avoid deterioration of operability and difficulty in suppressing dust generation.

[0064] As described above, in the method of this embodiment, there is a preparation step S1, which prepares a raw material (processing raw material) containing waste lithium ion batteries for treatment based on, for example, a dry smelting process described later, and in the preparation step S1, a preliminary mixing step S13 and a granulation step S14 are performed, wherein water is added to a mixed powder containing a positive electrode active material and a negative electrode active material constituting the waste lithium ion batteries for preliminary mixing, and the granulation step S14 further mixes the obtained preliminary mixing material for granulation. Thus, a granulated material of a predetermined size composed of the mixed powder is prepared.

[0065] By preparing such a granulated material composed of mixed powder, and subjecting the granulated material to the treatment in the oxidation roasting step S2 (oxidation roasting treatment) and the treatment in the reduction step S3 (reduction melting treatment), dust generation during operation in the treatment can be effectively suppressed, and a highly safe treatment can be achieved. In addition, in the treatment, the raw material powder can be suppressed from being carried by the reactive gas and convection, and the recovery loss of valuable metals can be reduced.

[0066] It should be noted that, hereinafter, the oxidizing roasting step S2 and the reducing step S3 in the method for recovering valuable metals by the dry smelting process will be described in order.

[0067] (2) Oxidation roasting process

[0068] The oxidation roasting step S2 is a step of performing oxidation roasting (oxidation treatment) on the treatment raw material (the material charged into the treatment furnace) to obtain an oxidation roasted product.

[0069] In the method of this embodiment, the granulated material of the mixed powder obtained through the above-mentioned preparation step S1 is loaded into a treatment furnace such as a roasting furnace and subjected to oxidation roasting treatment. In this embodiment, the mixed powder constituting the loaded material is not in a powdery form, but in the form of a granulated material to be granulated, so that dust generation can be effectively suppressed during the operation of loading into the treatment furnace and until loading. In addition, not only can the loss of valuable metals caused by dust collection be reduced, but also the carrying of valuable metals in the exhaust gas during the oxidation roasting treatment can be prevented.

[0070] In the oxidation roasting step S2, carbon (C) contained in the contents of the waste lithium ion battery is oxidized and removed, and the waste lithium ion battery is treated at an oxidation degree that can at least oxidize aluminum. The main elements constituting the waste lithium ion battery are generally easily oxidized in the order of aluminum (Al)>lithium (Li)>carbon (C)>manganese (Mn)>phosphorus (P)>iron (Fe)>cobalt (Co)>nickel (Ni)>copper (Cu) according to their differences in affinity with oxygen.

[0071] In this way, in the oxidation roasting process S2, by oxidizing roasting the granulated material of the mixed powder, the carbon contained in the granulated material can be removed. As a result, the particles of the valuable metals produced locally in the subsequent reduction process S3 can agglomerate without physical obstacles caused by carbon, and can be recovered as an integrated alloy. That is, by the reduction melting treatment in the reduction process S3 described later, the valuable metals are reduced to form local molten particles. At this time, the carbon remaining in the raw material can become a physical obstacle when the molten particles agglomerate. Therefore, in the case where the oxidation roasting treatment is not performed to remove carbon, the remaining carbon can hinder the agglomeration integration of the molten particles and the separability of the metal and slag brought by it, and sometimes reduce the recovery rate of the valuable metals. In contrast, before the reduction melting treatment, by pre-oxidizing roasting treatment to remove carbon, the agglomeration integration of the molten particles can be carried out, and the recovery rate of the valuable metals is further improved.

[0072] Furthermore, by removing carbon in advance through oxidative roasting treatment, it is possible to suppress the reduction of phosphorus (P) contained in the contents of the spent lithium ion battery by carbon in the reduction step S3, thereby suppressing the distribution of phosphorus into the alloy of valuable metals.

[0073] In addition, in the oxidation roasting step S2, it is preferred to perform the oxidation roasting treatment at an oxidation degree that can oxidize the metal (such as Al) with low added value contained in the granulated material as the processing raw material. On the other hand, by adjusting the treatment temperature, time and / or environment of the oxidation roasting, it is easy to control the oxidation degree. Therefore, by strictly adjusting the oxidation degree in the oxidation roasting treatment, the deviation of oxidation can be suppressed.

[0074] The degree of oxidation is adjusted as follows. As described above, aluminum (Al), lithium (Li), carbon (C), manganese (Mn), phosphorus (P), iron (Fe), cobalt (Co), nickel (Ni) and copper (Cu) are usually oxidized in the order of Al>Li>C>Mn>P>Fe>Co>Ni>Cu. In the oxidation roasting treatment, oxidation is performed until all Al is oxidized. Oxidation can be promoted until a portion of Fe is oxidized, but the degree of oxidation is limited to a degree that Co, which is a valuable metal, is not oxidized and recovered as slag.

[0075] When adjusting the degree of oxidation in the oxidative roasting treatment, an appropriate amount of oxidant can be introduced. In particular, in the case of a treatment raw material containing waste lithium-ion batteries, it is preferred to introduce an oxidant. As described above, waste lithium-ion batteries contain metals such as Al and Fe in the outer packaging material, and 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. These are all materials that act as a reducing agent, and therefore, by introducing an oxidant for treatment in the oxidative roasting treatment, the degree of oxidation can be adjusted to a more appropriate range.

[0076] The oxidant is not particularly limited as long as it is an oxidant that can oxidize carbon and metals with low added value (such as Al). Among them, 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., 1.15 to 1.25 times) the amount required for oxidation of each substance to be oxidized (chemical equivalent).

[0077] The heating temperature of the oxidative 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. When the temperature is 700° C. or higher, the oxidation efficiency of carbon can be further improved, and the oxidation time can be shortened. In addition, when the temperature is 1100° C. or lower, the thermal energy cost can be suppressed, and the efficiency of the oxidative roasting treatment can be improved.

[0078] The oxidation roasting treatment can be performed 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 in the reduction step S3 described later, and perform the treatment in the preparatory furnace. As a roasting furnace, all types of furnaces can be used as long as it can roast the charged material while supplying an oxidant (oxygen, etc.) and perform oxidation treatment inside it. As an example, a rotary kiln and a tunnel kiln (hearth furnace) known in the past can be cited.

[0079] It should be noted that, in the reduction step S3 described later, the oxidizing roasting step S2 is not necessarily provided as long as an oxidation treatment is performed in the same furnace before the reduction melting treatment.

[0080] (3) Reduction process

[0081] In the reduction step S3, the oxidized roasted product obtained by the oxidizing roasting step S2 is heated to be reduced and melted to obtain a reduced melt containing an alloy containing valuable metals and slag. The purpose of the reduction step S3 is to keep the metals with low added value (such as Al) oxidized in the treatment of the oxidizing roasting step S2 in the state of oxides, and to reduce and melt the oxidized valuable metals (Cu, Ni, Co) to recover them as an integrated alloy.

[0082] In the method of the present embodiment, the granulated material of the mixed powder obtained by the above-mentioned preparation step S1 is subjected to oxidation roasting treatment (oxidation roasting step S2) to obtain an oxidation roasted material. Therefore, the processing raw material provided for the reduction melting treatment is not in a powdery state. Therefore, dust generation can be effectively suppressed during the operation of loading into the treatment furnace and until loading. In addition, not only can the loss of valuable metals caused by dust collection be reduced, but also the carrying of valuable metals in the exhaust gas during the oxidation roasting treatment can be prevented.

[0083] In the reduction melting treatment, a reducing agent is preferably introduced. As the reducing agent, carbon and / or carbon monoxide are preferably used. Carbon has the ability to easily reduce the valuable metals (Cu, Ni, Co, etc.) to be recovered. For example, 1 mole of carbon can reduce 2 moles of valuable metal oxides (copper oxides, nickel oxides, etc.). In addition, compared with the method using a metal reducing agent (for example, the aluminothermic reaction method using aluminum), the reduction method using carbon and carbon monoxide is extremely safe.

[0084] As for carbon as a reducing agent, in addition to artificial graphite and natural graphite, coal, coke, etc. can also be used as long as the impurity level can be tolerated in the product and subsequent processes. In addition, ammonia and carbon monoxide can be added as a reducing agent in the reduction melting treatment.

[0085] The amount of the reducing agent introduced is preferably 0.5 mol or more and 1 mol or less, and more preferably 0.6 mol or more and 0.8 mol or less, in terms of carbon content, per mol of the oxidized valuable metal (Cu, Ni, Co).

[0086] The heating temperature of the reduction melting treatment is not particularly limited, but is preferably 1300°C or higher and 1550°C or lower, and more preferably 1350°C or higher and 1450°C or lower. At a temperature higher than 1550°C, heat energy is wasted, and the loss of refractory materials such as crucibles becomes severe, and productivity may decrease. On the other hand, at a temperature lower than 1300°C, the separability of slag and alloy deteriorates, and the recovery rate of valuable metals may decrease.

[0087] In addition, it is preferred to add a flux during the reduction melting treatment. It should be noted that when the flux is added in the preliminary kneading step S13 of the preparation step S1 to prepare a granulated material containing the flux, it is sufficient to add an insufficient amount. By using the flux for reduction melting in this way, the slag containing oxides such as Al can be dissolved in the flux and removed.

[0088] As a flux, it is preferred that the melting point is close to the melting point of the alloy and the solubility of Al is high. For example, as a flux, calcium carbonate (CaCO3), calcium oxide (CaO), aluminum oxide (Al2O3), silicon oxide (SiO2), magnesium oxide (MgO), iron oxide (Fe2O3, etc.) with a melting point of 1500°C or less can be cited. Furthermore, during the reduction melting treatment, calcium fluoride (CaF2) or the like can be added, thereby making it possible to more effectively reduce the melting point of the slag and achieve a reduction in energy costs.

[0089] The reduction melting treatment can be carried out using a known method. For example, a method in which the oxidized roasted product to be treated is placed in a crucible and heated by resistance heating or the like can be cited. It should be noted that, in the reduction melting treatment, harmful substances such as dust and exhaust gas are sometimes generated, but by implementing known exhaust gas treatment and the like, the harmful substances can be rendered harmless.

[0090] It should be noted that, when the oxidizing roasting step S2 is provided before the reducing step S3 to perform oxidizing roasting on the granulated material composed of the mixed powder, it is not necessary to perform oxidizing treatment in the reducing step S3. However, even if the oxidizing roasting step S2 is provided, when the oxidation by the oxidizing roasting treatment is insufficient, or when the purpose is to further adjust the oxidation degree, an additional oxidizing treatment may be performed in the reducing step S3.

[0091] When oxidation treatment is performed in the reduction step S3, that is, when reduction melting treatment and oxidation treatment are performed simultaneously, as a method thereof, for example, a method of blowing an oxidant into the reduction melt obtained by the reduction melting treatment can be cited. Specifically, it is set to insert a metal pipe (blowgun) into the reduction melt and blow the oxidant into it by bubbling. It should be noted that as the oxidant at this time, a gas containing oxygen such as air, pure oxygen, and oxygen-enriched gas can be used.

[0092] (4) Slag separation process

[0093] In the slag separation step S4, slag is separated from the reduced melt obtained by the reduction melting treatment in the reduction step S3 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 in the reduced melt, so it can be easily separated and recovered by specific gravity separation.

[0094] In this manner, in the slag separation step S4 , by separating the slag from the reduced melt, an alloy containing valuable metals can be recovered.

[0095] It should be noted that after the treatment in the slag separation process, a sulfidation process for sulfiding the obtained alloy and a pulverization process for pulverizing the obtained sulfide or alloy can be provided. Furthermore, a wet smelting process can be applied to the alloy containing valuable metals obtained by such a dry smelting process. Through the wet smelting process, impurity components can be removed, and valuable metals (Cu, Ni, Co, etc.) can be separated and purified and recovered respectively. As the treatment in the wet smelting process, known methods such as neutralization treatment and solvent extraction treatment can be cited.

[0096] Example

[0097] 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.

[0098] [Preparation of Granulated Powder Comprising a Mixed Powder Containing a Positive Electrode Active Material and a Negative Electrode Active Material]

[0099] First, water was added to the mixed powder (containing the mixed powder of the positive electrode active material and the negative electrode active material) having the composition shown in Table 1 below and obtained by crushing the waste lithium ion battery in the amount shown in Table 2 below, and pre-mixed using a DAW mixer (manufactured by Shin Nichinan Co., Ltd., Model PX0309) to obtain a pre-mixed product. In addition, in Examples 5 to 6, calcium carbonate of 5 mm or less was added as a flux during the pre-mixing. In Table 2, the amount of flux added and the amount of water added are expressed as a weight ratio relative to the mixed powder.

[0100] It should be noted that the mixed powder subjected to preliminary kneading is in the form of fine powder.

[0101] Table 1

[0102]

[0103] Then, the obtained pre-kneaded product was further kneaded and granulated using a DAW pelletizer (manufactured by Shin Nichinan Co., Ltd., PT0412 model) at a speed set so that the peripheral speed of the outer periphery of the blade tip becomes the speed shown in the following Table 2, to prepare a granulated product. It should be noted that the kneading time during granulation was set to 2 minutes.

[0104] In Examples 1 to 8, the proportion of the obtained granules with a diameter of 1 mm or less was determined. In Examples 4 to 6, the proportion of the granules with a diameter of 4 mm or more was further determined. In Comparative Example 1, granulation was not performed.

[0105] Table 2

[0106]

[0107] As shown in Table 2, in Examples 1 to 8, after the mixed powder was pre-kneaded, the pre-kneaded material was granulated to prepare granules, thereby obtaining larger granules than the mixed powder before pre-kneading (Comparative Example 1), and the workability was improved. In particular, in Examples 1 to 6, the proportion of granules with a particle size of 1 mm or less was less than 10%, and the workability was further improved. Furthermore, in Examples 4 to 6, the proportion of granules with a particle size of 4 mm or more was more than 30%, and the workability was further improved.

[0108] [Prepared granules are supplied to dry smelting process]

[0109] The granulated products of Examples 1 to 8 and the mixed powder of Comparative Example 1 obtained in this manner were subjected to oxidation roasting treatment and reduction melting treatment in a method for recovering valuable metals by a dry smelting process.

[0110] As a result, in Comparative Example 1, the mixed powder containing the positive electrode active material and the negative electrode active material is directly supplied to the dry smelting process, that is, the mixed powder is supplied without granulation, so a lot of dust is generated by the oxidation roasting treatment and the reduction melting treatment. It can be considered that this is because when the mixed powder is charged into the treatment furnace, a large amount of dust is generated during operation, and the dust-generating substances are carried by the reaction gas or convection in the furnace and attracted to the exhaust dust, resulting in a large amount of carryover.

[0111] In contrast, in Examples 1 to 8, granules as shown in Table 2 were prepared and supplied, and therefore, the amount of dust generated by the oxidative roasting treatment and the reduction melting treatment was significantly reduced compared to Comparative Example 1. This is considered to be because the supply of granules improved operability and effectively suppressed the generation of dust and carryover.

[0112] It should be noted that the amount of dust generated can be reduced in Examples 7 and 8 compared to Comparative Example 1. However, the amount of dust is increased compared to Examples 1 to 6.

Claims

1. A method for recovering valuable metals, which is a method for recovering valuable metals, wherein: The method for recovering valuable metals comprises a preparation step of preparing a raw material comprising waste lithium-ion batteries, wherein the waste lithium-ion batteries contain valuable metals, In the preparation step, a preliminary kneading step and a granulation step are performed to prepare a granulated material. The preliminary kneading step is to add water to the mixed powder containing the positive electrode active material and the negative electrode active material constituting the waste lithium ion battery for preliminary kneading. The granulation step is to further knead the obtained pre-mixed material to granulate it. The granulated material is composed of the mixed powder.

2. The method for recovering valuable metals according to claim 1, wherein: In the preliminary kneading step, the amount of water added is adjusted to be 0.14 or more and 0.16 or less in terms of weight ratio relative to the mixed powder.

3. The method for recovering valuable metals according to claim 1 or 2, wherein: In the granulation step, the pre-kneaded product is kneaded and granulated using a twin-shaft paddle granulator with the peripheral speed of the blade tip of the granulator set to 50 m / min to 90 m / min.

4. The method for recovering valuable metals according to claim 1 or 2, wherein: The method for recovering valuable metals comprises a dry smelting process further comprising a reduction step, wherein the granulated material obtained in the preparation step is subjected to a reduction melting treatment to obtain a reduced molten material containing an alloy and slag, wherein the alloy contains valuable metals. In the preliminary kneading step in the preparation step, a flux used in the reduction melting treatment is added to the mixed powder and preliminary kneaded.

5. The method for recovering valuable metals according to claim 4, wherein: In the preliminary kneading step, the flux having a particle size of 5 mm or less is used, and the amount of the flux added is adjusted to be 0.1 or more and 0.2 or less in terms of weight ratio relative to the mixed powder.

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