Valuable metal recovery method

Abstract

Provided is a method for inexpensively recovering valuable metals from waste lithium ion batteries by a dry smelting process. The present invention is a method for recovering a valuable metal from a waste lithium ion battery, the method comprising: an oxidizing roasting step (S3) in which a raw material including a waste lithium ion battery is subjected to an oxidizing roasting treatment; and a reduction step (S4) for reducing the obtained oxidized roasted product in the presence of carbon. In the oxidizing roasting step (S3), an oxidizing agent that is 1.5 times or more of the stoichiometric equivalent of carbon in the raw material to be treated is introduced, and the oxidizing roasting treatment is performed under treatment temperature conditions selected in the range of 600-900 DEG C (inclusive) such that the carbon grade of the obtained oxidizing roasted product is less than 1.0 mass%.

Description

Technical Field

[0001] The invention relates to a method for recovering valuable metals contained in waste lithium-ion batteries. Background Art

[0002] In recent years, lithium-ion batteries have become popular as secondary batteries with light weight and high output. As lithium-ion batteries, it is known that a negative electrode material having a negative electrode active material such as graphite fixed on a negative electrode collector composed of copper foil, a positive electrode material having a positive electrode active material such as lithium nickelate or lithium cobaltate fixed on a positive electrode collector composed of aluminum foil, a separator composed of a porous resin film of polypropylene, and an electrolyte solution containing an electrolyte such as lithium hexafluorophosphate (LiPF6) are enclosed in an outer can made of a metal such as aluminum or iron.

[0003] One of the main uses of lithium-ion batteries is hybrid vehicles or electric vehicles. It is foreseeable that as the life cycle of the vehicle ends, the lithium-ion batteries carried by the vehicle will also be discarded in large quantities. Many proposals have been made to reuse such used batteries or defective products generated during manufacturing (hereinafter referred to as "wasted lithium-ion batteries") as resources. As a method for recycling waste lithium-ion batteries, a dry smelting process has been proposed in which a high-temperature furnace is used to melt all the waste batteries (for example, refer to Patent Document 1).

[0004] The method disclosed in Patent Document 1 is that in a reduction step after a charge (copper concentrate) and a slag forming agent are placed in a copper smelting furnace and roasted, at least a portion of the exothermic agent and / or the reducing agent is replaced by waste lithium-ion batteries containing at least one of metallic iron, metallic aluminum and carbon.

[0005] It should be noted that lithium hexafluoride phosphate is used as described above in the electrolyte of commercially available lithium ion batteries. Lithium hexafluoride phosphate is widely used due to its high solubility in carbonates often used as electrolytes and its high degree of lithium ion dissociation and low cost. The so-called 18650 type battery, which is a general cylindrical lithium ion battery, contains phosphorus (P) at a ratio of about 0.2% by mass or more in the fired waste lithium ion battery, and the square battery for vehicle use contains phosphorus (P) at a ratio of about 0.1% by mass or more in the fired waste lithium ion battery. Moreover, when the iron outer can is removed in the case of the 18650 type, and when the aluminum outer can is removed in the case of the square battery, the phosphorus content in the battery contents is further increased.

[0006] For example, in a copper refining furnace, when waste lithium-ion batteries containing phosphorus are loaded into a high-temperature environment where alloys usually exist, the phosphorus is distributed into the alloy, and eventually almost all of the phosphorus is mixed into the crude copper as an impurity. In the process of electrolyzing crude copper using a wet smelting process, since about 70% of the phosphorus is distributed in the electrolyte, there is a problem that the phosphorus concentration in the electrolyte increases as the electrolysis proceeds. In order to reduce the phosphorus concentration in the electrolyte, it is necessary to set up a new liquid purification process for removing phosphorus in the wet smelting process. However, it is not enough to only collect copper in the wet smelting process, and it is not easy to add a process without affecting the recovery rate of other elements to be recovered in terms of technology and cost. Therefore, it is required to effectively remove phosphorus in the dry smelting process, which is the front process of the wet smelting process.

[0007] For example, according to the method disclosed in Patent Document 2, the alloy obtained by melting the contents of the waste lithium ion battery through oxidation roasting and reduction is partially sulfided, so that even if the contents contain a high concentration of phosphorus, phosphorus can be distributed to the residual alloy, as a sulfide with a low phosphorus content, and valuable metals such as copper, nickel, and cobalt can be recovered. However, in the case of oxidation roasting near the lower limit of the temperature range specified in the method, due to the grade of the waste lithium ion battery to be treated, the oxidation removal of carbon (C) in the oxidation roasting process becomes insufficient. As a result, the separation of metal and slag is hindered in the reduction melting process, and the recovery rate of valuable metals is sometimes reduced. Further, since impurities such as even iron or phosphorus are reduced, the cost for removing impurities in the subsequent process may increase. On the other hand, in the case of oxidation roasting near the upper limit of the temperature range specified in the method, the oxidation removal of carbon can be reliably performed accordingly, but thermal energy costs are required, and sometimes temperature control becomes difficult. Moreover, as a result, efficient roasting treatment is sometimes not performed by sintering the oxidation roasted product.

[0008] As described above, in the conventional technology, it is difficult to achieve both the quality of the oxidative roasting product and the processing efficiency of the oxidative roasting treatment.

[0009] Prior art literature

[0010] Patent Literature

[0011] Patent document 1: Japanese Patent No. 5818798.

[0012] Patent document 2: Japanese Patent Application Publication No. 2018-197385. Summary of the invention

[0013] Problems to be solved by the invention

[0014] The present invention has been made in view of such actual conditions, and an object of the present invention is to provide a method for recovering valuable metals from waste lithium-ion batteries at low cost by a dry smelting process.

[0015] Means for solving problems

[0016] The inventors have repeatedly conducted careful research to solve the above-mentioned problems. As a result, they found that, in the oxidation roasting treatment of raw materials including waste lithium-ion batteries, a specific amount of oxidant is introduced, and the treatment temperature is set within a specific temperature range, so that the carbon grade of the obtained oxidation roasted product can be less than 1.0% by mass, and carbon can be removed efficiently, thereby completing the present invention.

[0017] (1) The first invention of the present invention is a method for recovering valuable metals, which is a method for recovering valuable metals from waste lithium-ion batteries, wherein the method comprises: an oxidative roasting step, in which a raw material containing the waste lithium-ion batteries is subjected to an oxidative roasting treatment; and a reduction step, in which the obtained oxidative roasted product is reduced in the presence of carbon, wherein in the oxidative roasting step, an oxidant of 1.5 times or more of the chemical equivalent of carbon in the raw material to be treated is introduced, and the oxidative roasting treatment is carried out under a treatment temperature condition selected within the range of 600°C to 900°C, so that the carbon grade of the obtained oxidative roasted product is less than 1.0% by mass.

[0018] (2) The second invention of the present invention is the method for recovering valuable metals according to the first invention, wherein in the reduction step, the oxidized roasted product is reduced and melted in the presence of carbon to obtain a molten material containing slag and an alloy, wherein the alloy contains valuable metals.

[0019] (3) The third invention of the present invention is that in the method for recovering valuable metals of the first invention or the second invention, the carbon grade of the raw material containing the waste lithium-ion battery is less than 26 mass%, and in the oxidizing roasting step, the introduction amount of the oxidant is set to be greater than 2.0 times and less than 3.0 times the chemical equivalent of the carbon in the raw material to be processed, and the processing time of the oxidizing roasting treatment is set to be greater than 2 hours and less than 3 hours.

[0020] Effects of the Invention

[0021] According to the present invention, a method for recovering valuable metals from waste lithium-ion batteries at low cost by a dry smelting process can be provided. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 This is a process diagram showing an example of the flow of a valuable metal recovery method. 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 gist of the present invention.

[0024] 《1. Overview of methods for recovering valuable metals》

[0025] The method for recovering valuable metals of the present embodiment is a method for recovering valuable metals contained in waste lithium-ion batteries containing phosphorus (P). When recovering valuable metals from waste lithium-ion batteries, a dry smelting process and a wet smelting process are performed. The method for recovering valuable metals of the present embodiment mainly involves a dry smelting process.

[0026] Waste lithium-ion batteries (hereinafter referred to as "waste batteries") refer to the concept of waste materials in the manufacturing process of lithium-ion batteries, including used lithium-ion batteries or 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).

[0027] Figure 1 FIG. 1 is a process diagram showing an example of a process flow of a valuable metal recovery method. Figure 1 As shown, the method for recovering valuable metals of this embodiment includes: a waste battery pretreatment step S1, which removes the electrolyte and outer can of the waste lithium-ion battery; a crushing step S2, which crushes the contents of the battery as a crushed product; an oxidizing roasting step S3, which oxidizes and roasts the crushed product; and a reducing step S4, which reduces the oxidized roasted product to alloy the valuable metals.

[0028] In particular, the method of this embodiment is characterized in that, in the oxidative roasting step S3, an oxidant of 1.5 times or more of the chemical equivalent of carbon in the raw material containing waste lithium-ion batteries to be treated is introduced, and oxidative roasting treatment is carried out under treatment temperature conditions selected within the range of not less than 600°C and not more than 900°C, so that the carbon grade of the obtained oxidative roasted product is less than 1.0% by mass.

[0029] According to this method, carbon contained in the waste lithium ion battery can be efficiently and effectively oxidized and removed, and as a result, phosphorus as an impurity can be removed, and valuable metals can be recovered at low cost.

[0030] In addition, since phosphorus can be effectively removed, the wet smelting process after the dry smelting process in the recovery of valuable metals can be simplified. Specifically, as the processing amount in the wet smelting process, the mass ratio can be reduced to about 1 / 4 to 1 / 3 compared with the amount of waste lithium-ion batteries put into the dry smelting process, thereby simplifying the wet smelting process. Therefore, the dry smelting process (waste battery pretreatment process S1 to reduction process S4) is used as a general pretreatment, and the processing amount is greatly reduced while obtaining an alloy with less impurities (phosphorus), so that the combination of dry smelting process and wet smelting process can be realized industrially.

[0031] It should be noted that by performing a wet smelting process on the alloy containing valuable metals obtained by the dry smelting process, impurity components are removed, and valuable metals such as copper, nickel, and cobalt are separated and purified, so that they can be recovered separately. As a treatment in the wet smelting process, it can be carried out by a known method such as a neutralization treatment or a solvent extraction treatment. To give an example, in the case of an alloy composed of copper, nickel, and cobalt, after the valuable metals are leached with an acid such as sulfuric acid (leaching process), copper, for example, is extracted by solvent extraction (extraction process), and the remaining solution containing nickel and cobalt is used in the positive electrode active material manufacturing process in the battery manufacturing process.

[0032] 《2. About each process of recycling method》

[0033] Hereinafter, each step of the valuable metal recovery method according to the present embodiment will be described in detail.

[0034] [Waste battery pre-treatment process]

[0035] The waste battery pre-treatment process S1 is carried out for the purpose of preventing explosion or harmlessness of waste lithium-ion batteries, removing outer cans, etc. That is, since waste lithium-ion batteries are closed systems with electrolytes, etc. inside, if they are crushed in the original state, there is a concern and danger of explosion. Therefore, it is necessary to implement discharge treatment or electrolyte removal treatment in some way. In addition, the outer cans are mostly metal aluminum (Al) or iron (Fe), and such metal outer cans can be recovered as valuable metals more easily. In this way, in the waste battery pre-treatment process S1, by removing the electrolyte and the outer cans, safety can be improved, and the recovery productivity of valuable metals such as copper, nickel, and cobalt can be improved.

[0036] The specific method of the treatment in the waste battery pre-treatment step S1 is not particularly limited, but for example, the waste battery can be physically perforated with a needle-shaped knife tip to allow the electrolyte inside to flow out and be removed. In addition, the waste battery can be heated as it is to burn the electrolyte to render it harmless.

[0037] When recycling aluminum or iron contained in the outer can of waste batteries, the outer can can be crushed and then screened using a sieve shaker. In the case of aluminum, even a slight crushing can easily turn it into powder, which can be efficiently recycled. In addition, the iron contained in the outer can can be recycled by magnetic selection.

[0038] [Crushing process]

[0039] In the pulverizing step S2, the contents of the waste battery are pulverized to obtain a pulverized product. The treatment in the pulverizing step S2 is performed for the purpose of improving the reaction efficiency in the dry smelting process. By improving the reaction efficiency, the recovery rate of valuable metals such as copper, nickel, and cobalt can be increased.

[0040] The specific pulverization method in the treatment in the pulverization step S2 is not particularly limited, but pulverization can be performed using a conventionally known pulverizer such as a cutter mixer.

[0041] [Oxidation roasting process]

[0042] In the oxidation roasting step S3, the crushed material is oxidized and roasted to obtain an oxidized roasted material. In the oxidation roasting step S3, the carbon (C) included in the contents of the waste battery is oxidized and removed, and the treatment is performed at an oxidation degree that can at least oxidize the aluminum contained in the crushed material. It should be noted that 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 the difference in affinity with oxygen.

[0043] Thus, in the oxidation roasting step S3, the carbon contained in the contents of the waste battery can be removed by oxidation roasting the crushed material. And, as a result, in the subsequent reduction step S4, the molten particles of the reduced valuable metals generated locally can be aggregated due to the absence of physical barriers caused by carbon, and can be recovered as an integrated alloy. In addition, the phosphorus contained in the contents of the waste battery can be suppressed from being reduced by carbon in the reduction step S4, and the phosphorus can be effectively oxidized and removed, and can be suppressed from being distributed in the alloy of the valuable metal.

[0044] That is, in the oxidation roasting step S3, the carbon content contained in the obtained oxidation roasting product is made less than 1.0 mass%. In this way, by removing carbon in a manner that the carbon content becomes almost 0 mass%, phosphorus can be effectively oxidized and removed, and in the subsequent reduction step S4, the carbon amount for efficiently reducing the valuable metals and performing alloying can be easily adjusted.

[0045] Assuming that no oxidative roasting treatment is performed, that is, the crushed material of the waste battery content is put into the furnace as it is and subjected to reduction melting treatment, the carbon contained in the waste battery hinders the separation of the metal generated by the reduction melting treatment from the slag, resulting in a reduction in the recovery rate of the valuable metal (or the slag cannot be fully removed). In addition, even if oxidation is performed simultaneously with the reduction melting treatment, it is difficult to adjust the degree of oxidation more strictly, which also reduces the recovery rate of the valuable metal. In addition, the removal of carbon in the oxidative roasting treatment becomes insufficient. If more than the chemical equivalent of nickel, cobalt, and copper carbon remains, impurities such as iron or phosphorus contained in the crushed material are also reduced, resulting in an increase in the cost of removing impurities in the wet smelting process.

[0046] Then, in the method of this embodiment, it is characterized in that, in the oxidation roasting step S3, an oxidant of 1.5 times or more of the chemical equivalent (the amount required to oxidize carbon) of the carbon in the raw material containing the waste lithium ion battery is introduced, and the oxidation roasting treatment is performed under the treatment temperature condition of 600° C. to 900° C. Thus, compared with the existing situation, the oxidation roasting treatment can be completed efficiently and effectively in a short time, and even if the treatment temperature is not set to a high temperature as in the existing situation, the carbon in the raw material can be easily oxidized and removed.

[0047] That is, by introducing an oxidant under the above conditions and setting the temperature condition of the oxidation roasting treatment to 600°C or above, the carbon contained in the waste lithium-ion battery can be effectively oxidized and removed by treatment in a shorter time than in the prior art. Furthermore, by setting the temperature condition of the oxidation roasting temperature to 900°C or below, the thermal energy cost can be suppressed and the temperature control can be easily performed. In this way, by performing the oxidation roasting treatment under the treatment temperature condition of 600°C or above and 900°C or below, the efficiency of the oxidation roasting treatment can be improved compared with the prior art.

[0048] Furthermore, when the oxidation roasting treatment is performed using a known rotary kiln or the like, by controlling the oxidation roasting temperature to 900° C. or less, it is possible to suppress the adhesion of furnace agglomerates to the inner wall of the kiln, and the oxidation roasting treatment can be performed stably and uniformly.

[0049] In addition, in the method of the present embodiment, it is preferred to set the processing time of the oxidation roasting treatment in a manner that the carbon grade (carbon content) of the obtained oxidation roasting product is less than 1.0 mass %. Here, the specific processing time is set based on the test results by implementing a test to find the relationship between the processing temperature in the oxidation roasting treatment, the amount of the oxidant introduced, and the carbon content contained in the obtained oxidation roasting product. For example, by setting the processing time of the oxidation roasting treatment to more than 2 hours, the carbon grade in the obtained oxidation roasting product is easily less than 1.0 mass %. Further, by setting the processing time to less than 3 hours, it is possible to prevent the oxidation roasting treatment from requiring more than the processing time, so that the processing efficiency can be further improved.

[0050] Here, regarding the treatment temperature of the oxidation roasting treatment, if the treatment temperature is less than 600°C, even if an oxidant is introduced under the above conditions, carbon will not decompose and will easily remain, and the oxidation of aluminum will only stay on the surface, and aluminum will easily diffuse into the alloy in the subsequent reduction process S4. In addition, since the residual carbon generally contains phosphorus, the phosphorus that is relatively easy to be reduced when the residual carbon becomes more is reduced by carbon to a non-negligible degree, and in the subsequent reduction process S4, the phosphorus may be distributed to the alloy, so it is not preferred. Moreover, since phosphorus cannot be effectively removed in this series of processes, after the alloy is recovered, it is necessary to perform a process of removing phosphorus from the alloy in the dephosphorization process. In addition, when the temperature condition of the oxidation roasting treatment is less than 600°C, since a long time is required in the oxidation removal of carbon, the processing time is too long, and there is a concern that it will cause obstacles to the operation.

[0051] On the other hand, if the treatment temperature of the oxidation roasting treatment is greater than 900°C, the oxidation roasted product is easily sintered, which may cause obstacles to the operation of the treatment in the subsequent reduction step S4. In addition, when a known rotary kiln is used for the oxidation roasting treatment, the roasted product adheres and grows on the refractory in the furnace, causing clogging in the furnace, and the treatment efficiency in the reduction step S4 is easily reduced. Furthermore, the furnace manufacturing cost and thermal energy cost for maintaining this temperature become extremely high, and efficient treatment cannot be performed.

[0052] Then, as described above, it is a necessary condition to introduce an oxidant of 1.5 times or more of the chemical equivalent of carbon in the raw material containing the waste lithium ion battery to be processed, but the amount of the oxidant introduced is preferably 2.0 times or more and 3.0 times or less of the chemical equivalent in the raw material. In addition, the oxidant is not particularly limited, and air is preferably used from the perspective of easy operation and cooling of excess oxidation heat.

[0053] In addition, the oxidation roasting treatment can be carried out using, for example, a known roasting furnace. In addition, a furnace (preparatory furnace) different from the melting furnace used in the reduction melting treatment in the reduction step S4 is preferably provided, and carried out in the preparatory furnace. As a roasting furnace, all forms of kilns that are oxidized by supplying oxygen while roasting the crushed material can be used. As an example, existing known rotary kiln, tunnel kiln (hearth furnace) etc. can be suitably used.

[0054] [Reduction process]

[0055] In the reduction step S4, the oxidized roasted product obtained in the oxidizing roasting step S3 is reduced to obtain a reduced product. In the reduction step S4, the purpose is to reduce and melt the oxides of valuable metals such as copper oxidized in the oxidizing roasting process as oxides, and to recover the reduced product as an alloy integrating the reduced product.

[0056] Here, in the reduction step S4, a reduction melting treatment is performed at least in the presence of carbon. Through this reduction melting treatment, a melt containing slag and an alloy containing valuable metals is obtained.

[0057] Carbon is a reducing agent that has the ability to easily reduce valuable metals such as copper, nickel, and cobalt that are the objects of recovery. For example, graphite that can reduce 2 moles of oxides of valuable metals such as copper oxides or nickel oxides with 1 mole of carbon can be cited. In addition, hydrocarbons that can reduce 2 to 4 moles per mole of carbon can be used as a carbon supply source. In this way, by performing a reduction melting treatment under the condition of the presence of carbon as a reducing agent, valuable metals can be efficiently reduced, and alloys containing valuable metals can be obtained more effectively. In addition, in the reduction using carbon, for example, compared with the case of using aluminothermic reaction in which metal powder such as aluminum is reduced as a reducing agent, it also has the advantage of extremely high safety.

[0058] In addition, as the reducing agent, i.e., carbon, in addition to artificial graphite or natural graphite, coal or coke etc. may also be used as long as the impurities in the product or the subsequent process are tolerable. It should be noted that ammonia or carbon monoxide may also be added in the reduction melting treatment.

[0059] At this time, it is preferred to appropriately adjust the amount of carbon. If the amount of carbon is too much, then in the case of containing phosphorus in the oxidation roasted product, most phosphorus is reduced by the carbon, is distributed in the alloy of the valuable metals including copper, nickel, cobalt, etc., and cannot be effectively removed, becoming an alloy with a high phosphorus grade. On the other hand, if the amount of carbon is too little, phosphorus is effectively removed, and an alloy with a low phosphorus grade is obtained, but valuable metals will not be effectively reduced, and the recovery rate of valuable metals is reduced. It should be noted that the amount of carbon, except the content of phosphorus remaining in the oxidation roasted product, can also be considered to increase or decrease the price of the carbon (carbon supply source) used as a reducing agent and the price difference (price difference) of the valuable metals recovered.

[0060] Specifically, in the reduction melting treatment of the reduction step S4, it is preferred to perform the treatment under the condition that there is carbon in an amount of more than 7.5% by mass and less than 10% by mass relative to 100% by mass of the oxidized roasted product of the treatment object, and more preferably, perform the treatment under the condition that there is carbon in an amount of more than 8.0% by mass and less than 9.0% by mass. By controlling the amount of carbon in this way, the valuable metals are effectively reduced and the recovery rate is improved, and on the other hand, phosphorus is effectively separated while suppressing the reduction of phosphorus, so that an alloy with a low phosphorus grade can be obtained.

[0061] The amount of carbon present, as mentioned above, can be adjusted by adding graphite etc. in the reduction melting process. Here, strictly speaking, preferably, the amount of carbon not oxidized and removed by the oxidation roasting process in the oxidation roasting process S3 is also included to be adjusted. That is, the amount of carbon present refers to not only the amount of carbon added in the reduction melting process, but also the amount of carbon remaining in the oxidation roasting product. However, as mentioned above, in the oxidation roasting process S3, a specific amount of oxidant is introduced, and the oxidation roasting process is carried out under the conditions of a specific temperature range, so that the carbon contained in the raw material is effectively removed, and the obtained oxidation roasting product hardly contains carbon. Thus, about the carbon amount in the reduction melting process, the addition of carbon becomes the amount of carbon present in fact, and can be freely adjusted by the carbon added.

[0062] As the temperature condition (melting temperature) in the reduction melting treatment, it is not particularly limited, and it is preferably set to a range of 1320°C or more and 1600°C or less, and more preferably 1450°C or more and 1550°C or less. For example, if it is a copper alloy containing more than 50% by mass of cobalt, the melting point is approximately 1380°C or more, and if it is a copper alloy containing more than 50% by mass of nickel, the melting point is approximately 1320°C or more. Therefore, by reducing and melting at a temperature above 1320°C, valuable metals such as copper, nickel, and cobalt can be easily recovered as alloys. In addition, when the reduction melting is performed at more than 1450°C, the fluidity of the obtained alloy is very good, and the separation efficiency of impurity components and valuable metals is improved and more preferred. On the other hand, if the melting temperature exceeds 1600°C, heat energy is wasted, and the consumption of refractory materials such as crucibles or furnace walls also becomes intense, which may reduce productivity. Therefore, it is preferably below 1600°C as the melting temperature.

[0063] It is preferable to use a flux in the reduction melting treatment. By performing the reduction melting using a flux, slag containing oxides such as aluminum can be dissolved in the flux and removed.

[0064] As a flux, calcium (Ca) is preferably contained as a main component. For example, calcium oxide or calcium carbonate can be used. Since phosphorus becomes an acidic oxide when oxidized, the more alkaline the composition of the slag is, the easier it is to distribute phosphorus into the slag for removal. Therefore, the more calcium that becomes an alkaline oxide in the slag, the better, and the less silicon (Si) that becomes an acidic oxide, the better. In particular, it is preferred to add a flux and treat it in a manner such that the mass ratio of silicon dioxide (SiO2) / calcium oxide (CaO) in the generated slag becomes 0.5 or less. In addition, since the melting point of the slag rises when the proportion of aluminum oxide (Al2O3) is large, a sufficient amount of calcium is required to melt the aluminum oxide, and it is particularly preferred to add a flux and treat it in a manner such that the mass ratio of calcium oxide (CaO) / aluminum oxide (Al2O3) in the slag becomes 0.3 or more and 2.0 or less. As a result, the slag becomes alkaline, and phosphorus that generates acidic oxides can be effectively removed.

[0065] During the reduction melting treatment, dust, exhaust gas, and the like may be generated, but these can be rendered harmless by performing conventionally known exhaust gas treatment.

[0066] In addition, sulfur may be added to the alloy obtained through the reduction melting treatment in the reduction step S4 before recovery, thereby making the alloy brittle and easy to crush. Crushing the alloy can increase the specific surface area, thereby improving the leaching property in the wet smelting process.

[0067] It should be noted that, although the above description describes the method of recovering the alloy integrating the reduced product by reducing and melting the oxidized calcined product obtained through the oxidizing calcining step S3, the reduction and melting do not necessarily have to be performed simultaneously, and each step may be performed independently.

[0068] Specifically, first, as a reduction step, the oxidized roasted product obtained by the oxidizing roasting step S3 is reduced to obtain a reduced product. In this reduction step, unnecessary oxides such as aluminum oxidized in the oxidizing roasting treatment remain as oxides, and oxides of valuable metals such as copper oxidized in the oxidizing roasting treatment are reduced, and recovered as an alloy integrating the reduced product in the subsequent melting step.

[0069] In the reduction process, the oxidized calcined product is heated and reduced at a temperature (reduction temperature) of, for example, 500°C to 1000°C and in the presence of carbon. The reduction temperature is not particularly limited, but by setting it in the range of 500°C to 1000°C, the reduction time can be shortened, and the thermal energy cost can be suppressed, thereby improving the reduction treatment efficiency. It should be noted that if the reduction temperature is less than 500°C, the reduction reaction efficiency becomes low, and a long time is required in the treatment. On the other hand, if the reduction temperature exceeds 1000°C, sintering is easily caused before the oxidized calcined product is reduced.

[0070] The reduction treatment can be performed using a reduction furnace, and the interior of the reduction furnace is heated to a desired temperature using a burner or the like, and the oxidized roasted product placed in the furnace is heated and reduced.

[0071] Next, in the melting step, the reduced product obtained in the reduction step is melted and alloyed. In this way, the reduced product is melted to obtain a molten product, which contains slag and an alloy, wherein the slag contains oxides such as aluminum, and the alloy contains valuable metals such as copper, nickel, and cobalt.

[0072] In the melting process, the temperature condition (melting temperature) in the melting process is not particularly limited, but is preferably set to a temperature of 1320° C. or more and 1600° C. or less. In addition, in the melting process, a flux such as calcium oxide or calcium carbonate is preferably used. It should be noted that dust or exhaust gas may sometimes be generated in the melting process, but these can be rendered harmless by implementing conventionally known exhaust gas treatment.

[0073] Example

[0074] Hereinafter, the present invention will be described in further detail using Examples and Comparative Examples, but the present invention is not limited to the following Examples.

[0075] When recovering an alloy containing valuable metals from a raw material containing waste lithium ion batteries, conditions for a treatment (oxidative roasting treatment) of removing carbon (C) contained in the raw material by oxidative roasting the raw material were verified.

[0076] (Waste battery pre-treatment process)

[0077] First, the waste lithium-ion batteries to be processed include 18650 cylindrical batteries, used prismatic batteries for vehicles, and defective batteries recovered in the battery manufacturing process. Then, the waste lithium-ion batteries were immersed in salt water to discharge, the water was volatilized, and they were roasted in the air at a temperature of 260°C to decompose and remove the electrolyte and the outer can, thereby obtaining the battery contents.

[0078] (Crushing process)

[0079] Next, the battery contents were pulverized by a pulverizer (trade name: Good Cutter: manufactured by Ujiie Manufacturing Co., Ltd.) The carbon content in the pulverized product (pulverized product of the waste battery) was 26% by mass.

[0080] (Oxidation roasting process)

[0081] Next, the obtained pulverized product was subjected to oxidative roasting treatment under the conditions (treatment temperature, treatment time, amount of oxidant added (chemical equivalent)) shown in Table 1 below. The oxidative roasting treatment was carried out by operating a rotary kiln in the atmosphere. In addition, air was introduced as an oxidant.

[0082] Regarding the treatment time, preliminary tests for oxidative roasting treatment were conducted with the heating temperature fixed at 750°C and the amount of oxidant added fixed at 2.0 times the chemical equivalent of carbon in the raw material (crushed waste batteries), and the treatment time was determined to be 1.8 hours or longer.

[0083] Table 1 below shows the conditions of the oxidation roasting treatment and the results of measuring the carbon grade (residual carbon content) in the oxidation roasted product obtained by the treatment.

[0084] [Table 1]

[0085]

[0086] From the results in Table 1, it can be seen that the carbon content in the oxidized roasted products obtained in Examples 1 to 5 was less than 1.0%, which was effectively removed. Furthermore, by subjecting the oxidized roasted products from which carbon was effectively removed to reduction treatment, it is presumed that an alloy containing valuable metals with a reduced content of impurity phosphorus can be recovered.

[0087] On the other hand, in Comparative Example 1, where the amount of oxidant added was set to 1.0 times the chemical equivalent of carbon in the raw material, the oxidation treatment of carbon became insufficient, probably because the amount of oxidant introduced was insufficient, and the carbon grade in the oxidative roasted product exceeded 2.0%. In addition, in Comparative Example 2, where the heating temperature was set to 1000°C, the crushed product became a semi-molten state during the oxidative roasting process, and therefore could not be further processed.

Claims

1. A method for recovering valuable metals, which is a method for recovering valuable metals from waste lithium-ion batteries, wherein: The method for recovering the valuable metals comprises: an oxidative roasting step, in which the raw material containing the waste lithium-ion battery is subjected to an oxidative roasting treatment; and a reduction step, in which the obtained oxidized roasted product is reduced in the presence of carbon, In the oxidative roasting step, an oxidant of 1.5 times or more the chemical equivalent of carbon in the raw material to be treated is introduced, and the oxidative roasting treatment is carried out under treatment temperature conditions selected in the range of 600° C. to 900° C., so that the carbon grade of the obtained oxidative roasted product is less than 1.0 mass %.

2. The method for recovering valuable metals according to claim 1, wherein: In the reduction step, the oxidized roasted product is reduced and melted in the presence of carbon to obtain a melt containing slag and an alloy containing valuable metals.

3. The method for recovering valuable metals according to claim 1 or 2, wherein: The carbon grade of the raw material containing the waste lithium-ion battery is 26% by mass or less, In the oxidizing calcination step, the amount of the oxidant introduced is set to be 2.0 times or more and 3.0 times or less of the chemical equivalent of carbon in the raw material to be treated, and the treatment time of the oxidizing calcination treatment is set to be 2 hours or more and less than 3 hours.

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