Valuable metal recovery method

Abstract

Provided is a method for inexpensively recovering a valuable metal from a spent lithium ion battery 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) in which the obtained oxidized roasted product is reduced in the presence of carbon. In the oxidizing roasting step (S3), calcium carbonate and a raw material containing the waste lithium ion battery are charged into a furnace together, and the treatment temperature of the oxidizing roasting treatment is controlled.

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 in which a negative electrode active material such as graphite is fixed to a negative electrode collector composed of copper foil, a positive electrode material in which a positive electrode active material such as lithium nickelate or lithium cobaltate is fixed to 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 a metal outer can 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 be discarded in large quantities. Many proposals have been made to recycle 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 in which waste batteries are completely melted in a high-temperature furnace has been proposed (for example, refer to Patent Document 1).

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

[0005] In the electrolyte of commercially available lithium ion batteries, lithium hexafluoride phosphate is used as described above. Lithium hexafluoride phosphate is widely used for reasons such as high solubility in carbonates commonly used as electrolytes, high lithium ion dissociation, and low cost. In the waste lithium ion batteries formed by roasting the so-called 18650 type batteries as common cylindrical lithium ion batteries, phosphorus (P) is contained at a ratio of about 0.2 mass %, and in the waste lithium ion batteries formed by roasting the square type batteries for vehicles, phosphorus (P) is contained at a ratio of about 0.1 mass %. Moreover, the phosphorus content in the battery contents when the iron outer can is removed in the case of the 18650 type, and the phosphorus content in the battery contents when the aluminum outer can is removed in the case of the square type batteries is higher.

[0006] When waste lithium-ion batteries containing phosphorus are put into a high-temperature environment where alloys are always present, such as in a copper refining furnace, 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 electrolytic treatment of crude copper based on a wet smelting process, about 70% of the phosphorus is distributed into the electrolyte. Therefore, when the electrolysis is carried out, there is a problem of an increase in the phosphorus concentration in the electrolyte. In order to reduce the phosphorus concentration in the electrolyte, it is necessary to newly set up a clean liquid process for removing phosphorus in the wet smelting process. However, in the wet smelting process, it is not enough to just collect copper. It is not easy to add a process in a way that does not affect the recovery rate of other recovery target elements, both technically and cost-wise. 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 oxidative roasting and reduction is partially sulfided, thereby, even if the contents contain a high concentration of phosphorus, phosphorus can be distributed to the residual alloy, and valuable metals such as copper, nickel, and cobalt can be recovered as sulfides with a low phosphorus content. However, when the oxidative roasting treatment is carried out near the lower limit of the temperature range specified by the method, the oxidation removal of carbon (C) in the oxidative roasting treatment is insufficient due to the grade of the waste lithium-ion battery to be treated. As a result, the separation of metal and slag in the reduction melting treatment is hindered, and the recovery rate of valuable metals sometimes decreases. Furthermore, since impurities such as iron and phosphorus are also reduced, the cost of removing impurities through subsequent processes becomes worse.

[0008] In order to avoid such a problem, it is effective to perform oxidation roasting near the upper limit of the temperature range specified by the method described in Patent Document 2, but this not only consumes thermal energy costs, but also sometimes makes temperature control difficult. As a result, the oxidation roasted product is sintered, and sometimes an efficient roasting process cannot be performed.

[0009] This tendency becomes particularly significant when the amount of carbon contained in the waste lithium-ion battery is excessive. It is believed that the reason is that the excessive carbon contained causes excessive heat generation, which cannot be adjusted by fuel. In order to avoid the situation where the heat becomes excessive, for example, there is a method of reducing the processing amount of waste lithium-ion batteries. However, this method will deteriorate production efficiency and is therefore difficult to adopt.

[0010] As described above, in the prior art, it is difficult to achieve both the quality of the oxidative roasting product and the processing efficiency of the oxidative roasting process.

[0011] Prior art literature

[0012] Patent Literature

[0013] Patent document 1: Japanese Patent No. 5818798.

[0014] Patent document 2: Japanese Patent Application Publication No. 2018-197385. Summary of the invention

[0015] Problems to be solved by the invention

[0016] The present invention is proposed in view of the above-mentioned actual situation, and its object is to provide a method for recovering valuable metals from waste lithium-ion batteries at low cost through a dry smelting process.

[0017] Means for solving problems

[0018] The inventors have conducted intensive research to solve the above-mentioned problems. As a result, it was found that in the oxidation roasting treatment of raw materials containing waste lithium ion batteries, calcium carbonate is loaded into a furnace together with the raw materials containing waste lithium ion batteries for treatment, thereby controlling the treatment temperature (oxidation roasting temperature) of the oxidation roasting treatment and effectively removing carbon, thus completing the present invention.

[0019] (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, comprising: 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 calcium carbonate is loaded into a furnace together with the raw material containing the waste lithium-ion batteries, and the treatment temperature of the oxidative roasting treatment is controlled.

[0020] (2) The second invention of the present invention is a method for recovering valuable metals, wherein in the first invention, in the oxidizing roasting step, the charging amount of the calcium carbonate is adjusted to a mass ratio of calcium oxide (CaO) / aluminum oxide (Al2O3) converted into calcium oxide and aluminum oxide to be greater than 1.0 and less than 2.0 relative to the aluminum content contained in the raw material.

[0021] (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 oxidizing 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 oxidizing roasting treatment is carried out under treatment temperature conditions selected within the range of 600°C to 900°C, and the carbon grade of the obtained oxidizing roasted product is set to less than 1.0% by mass.

[0022] Effects of the Invention

[0023] According to the present invention, it is possible to provide a method for recovering valuable metals from waste lithium-ion batteries at low cost by a dry smelting process. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 This is a process diagram showing an example of the flow of a valuable metal recovery method. DETAILED DESCRIPTION

[0025] 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.

[0026] 《1. Overview of methods for recovering valuable metals》

[0027] 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.

[0028] Waste lithium-ion batteries (hereinafter also referred to as "waste batteries") are a concept of 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).

[0029] Figure 1 This is a process diagram showing an example of the flow of a valuable metal recovery method. Figure 1 As shown, the method for recovering valuable metals of this embodiment comprises: 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 to make a crushed material; an oxidizing roasting step S3, which oxidizes and roasts the crushed material; and a reducing step S4, which reduces the oxidized roasted material and alloys the valuable metals.

[0030] In particular, the method of the present embodiment is characterized in that, in the oxidative roasting step S3, calcium carbonate is charged into the furnace together with the raw material including the waste lithium-ion battery, and the treatment temperature of the oxidative roasting treatment is controlled.

[0031] By using such a method, carbon contained in waste lithium-ion batteries 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 inexpensively and efficiently.

[0032] 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, compared with the amount of waste lithium-ion batteries put into the dry smelting process, the amount of processing in the wet smelting process can be reduced to about 1 / 4 to 1 / 3 in terms of mass ratio, which can simplify the wet smelting process. Therefore, by setting the dry smelting process (waste battery pretreatment process S1 to reduction process S4) as a pretreatment in a broad sense, an alloy with less impurities (phosphorus) is obtained, and the processing amount is greatly reduced, thereby making it possible to combine the dry smelting process and the wet smelting process in industry.

[0033] It should be noted that by performing a wet smelting process on an alloy containing valuable metals obtained by a dry smelting process, impurity components can be removed, and valuable metals such as copper, nickel, and cobalt can be separated and purified, and each can be recovered. As a treatment in a wet smelting process, it can be carried out by known methods such as neutralization treatment and solvent extraction treatment. For example, in the case of an alloy composed of copper, nickel, and cobalt, after leaching the valuable metals with an acid such as sulfuric acid (leaching process), copper, for example, is extracted by solvent extraction (extraction process), and the solution containing the residual nickel and cobalt is supplied to the positive electrode active material manufacturing process in the battery manufacturing process.

[0034] 《2. About each step of the recycling method》

[0035] Hereinafter, each step of the valuable metal recovery method according to the present embodiment will be described in detail.

[0036] [Waste battery pre-treatment process]

[0037] The waste battery pre-treatment step S1 is carried out for the purpose of preventing the explosion of waste lithium-ion batteries or making them harmless, removing the outer can, etc. That is, the waste lithium-ion battery is a closed system with an electrolyte, etc. inside. Therefore, if it is crushed in this state, it is possible to explode and there is a danger. Therefore, it is necessary to implement a discharge treatment or an electrolyte removal treatment by any method. In addition, the outer can is mostly made of metal aluminum (Al) and iron (Fe), and this metal outer can can be relatively easily directly recovered as a valuable metal. In this way, by removing the electrolyte and the outer can in the waste battery pre-treatment step S1, safety can be improved, and the recovery productivity of valuable metals such as copper, nickel, and cobalt can be improved.

[0038] The specific method of the treatment in the waste battery pre-treatment step S1 is not particularly limited. 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. Alternatively, the waste battery can be directly heated to burn the electrolyte for harmlessness.

[0039] When recycling aluminum and iron contained in the outer cans constituting waste batteries, the outer cans can be crushed and then sieved using a vibrating screen. In the case of aluminum, even light crushing can easily turn it into powder and can be efficiently recycled. In addition, the iron contained in the outer can can be recovered by magnetic separation.

[0040] [Crushing process]

[0041] 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.

[0042] The specific pulverization method in the pulverization step S2 is not particularly limited, and the pulverization can be performed using a conventionally known pulverizer such as a cutter mixer.

[0043] [Oxidation roasting process]

[0044] In the oxidation roasting step S3, the crushed material is subjected to oxidation roasting to obtain an oxidation roasted material. In the oxidation roasting step S3, carbon (C) contained in the contents of the waste battery is oxidized and removed, and the crushed material is treated at an oxidation degree that can oxidize at least 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 their affinity with oxygen.

[0045] In this way, in the oxidation roasting step S3, the carbon contained in the contents of the waste battery can be removed by oxidizing and roasting the crushed material. As a result, the molten particles of the reduced valuable metals locally generated in the subsequent reduction step S4 can be agglomerated without physical obstacles caused by carbon, and can be recovered as an integrated alloy. In addition, in the reduction step S4, the phosphorus contained in the contents of the waste battery can be suppressed from being reduced by carbon, and the phosphorus can be effectively oxidized and removed, and the distribution into the alloy of the valuable metal can be suppressed.

[0046] That is, in the oxidation roasting step S3, the carbon content contained in the obtained oxidation roasted product is set to less than 1.0 mass%. In this way, by removing carbon in a manner that makes the carbon content almost 0 mass%, phosphorus can be effectively oxidized and removed, and the amount of carbon used for efficiently reducing and alloying the valuable metals in the subsequent reduction step S4 can be easily adjusted.

[0047] Assuming that no oxidative roasting treatment is performed, that is, when the crushed material of the waste battery content is directly put into the furnace for reduction melting treatment, the carbon contained in the waste battery will hinder the separation of the metal and slag generated by the reduction melting treatment, resulting in a decrease in the recovery rate of valuable metals (or the slag cannot be fully removed). In addition, even if oxidation is performed together with the reduction melting treatment, it is difficult to make a more rigorous adjustment of the degree of oxidation, based on this point, the recovery rate of valuable metals will also decrease. In addition, when the removal of carbon in the oxidative roasting treatment is insufficient, and carbon more than the chemical equivalent of nickel, cobalt, and copper remains, even impurities such as iron and phosphorus contained in the crushed material are reduced, which will lead to a deterioration in the cost of impurity removal in the wet smelting process.

[0048] In the method of this embodiment, when the waste lithium ion battery is subjected to oxidative roasting treatment, calcium carbonate is loaded into the roasting furnace together with the raw materials containing the waste lithium ion battery. In this way, the oxidative roasting treatment is carried out by loading calcium carbonate, so that the treatment temperature of the oxidative roasting treatment can be effectively controlled.

[0049] When the carbon grade in the waste lithium-ion battery to be treated is significantly high (for example, when the carbon grade is 30% by mass or more), it is particularly effective to load calcium carbonate to implement oxidative roasting treatment. That is, when the carbon grade in the waste lithium-ion battery is significantly high, the combustion reaction of carbon becomes more active than usual, so the heat generation tends to become excessive. Therefore, even if the supply of fuel burned in the roasting furnace is adjusted to reduce the amount of fuel supplied, the treatment temperature (oxidative roasting temperature) of the oxidative roasting treatment is sometimes greater than 900°C. At this time, by loading calcium carbonate into the roasting furnace together with the waste lithium-ion battery for treatment, since the thermal decomposition reaction of the calcium carbonate is an endothermic reaction, the rise in the oxidative roasting temperature caused by the activated combustion reaction can be effectively suppressed. Moreover, the thermal decomposition temperature of calcium carbonate is near 800°C, so no endothermic reaction occurs in the temperature region below the thermal decomposition temperature. Therefore, the oxidative roasting treatment implemented in this temperature region will not be hindered. In other words, the loaded calcium carbonate only acts as a gate for preventing the treatment temperature of the oxidative roasting treatment from exceeding 900°C.

[0050] As described above, in the present embodiment, even when there is a possibility that the combustion reaction of carbon becomes more active than usual, efficient oxidation roasting treatment can be performed without making adjustments to reduce the amount of waste lithium-ion batteries to be treated.

[0051] Note that calcium carbonate is converted into calcium oxide by thermal decomposition, and therefore the generated calcium oxide can effectively function as a flux for the reaction in the reduction step S4 described later.

[0052] The amount of calcium carbonate charged is not particularly limited, but preferably, the mass ratio expressed as calcium oxide (CaO) / aluminum oxide (Al2O3) converted into calcium oxide and aluminum oxide is adjusted to be 1.0 or more and 2.0 or less relative to the amount of aluminum contained in the raw material. By charging calcium carbonate with such a charge amount for treatment, even when the carbon grade in the waste lithium ion battery to be treated is high (for example, when the carbon grade is 30% by mass or more), the increase in the treatment temperature of the oxidative roasting treatment can be efficiently suppressed.

[0053] The optimum value of the amount of calcium carbonate charged (ratio of calcium oxide (CaO) / aluminum oxide (Al2O3)) can be specifically determined, for example, by conducting preliminary tests to determine the carbon grade in waste lithium-ion batteries and the relationship between the amount of calcium carbonate charged and the treatment temperature of the oxidative roasting treatment, as shown in the embodiments described below.

[0054] In the oxidation roasting treatment, it is preferred 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 (the amount required to oxidize the carbon). In addition, the amount of the oxidant introduced is more preferably set to be 2.0 times or more and 3.0 times or less of the chemical equivalent of carbon in the raw material. The oxidant is not particularly limited, and air is preferably used from the perspective of easy operation and the purpose of cooling the remaining oxidation heat.

[0055] By introducing the oxidizing agent under the above-mentioned conditions, the oxidizing roasting treatment can be completed in a short time, and the carbon contained in the waste lithium ion battery to be oxidized can be easily oxidized and removed.

[0056] Furthermore, in the oxidation roasting treatment, it is preferred that an oxidant is introduced under the above-mentioned conditions, and the oxidation roasting treatment is performed under the treatment temperature condition of 600° C. or higher and 900° C. or lower. Thus, compared with the past, 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 past, the carbon in the raw material can be easily oxidized and removed.

[0057] That is, by introducing an oxidant under the above conditions and setting the temperature condition of the oxidation roasting treatment to 600°C or more, the carbon contained in the waste lithium-ion battery can be effectively oxidized and removed by a treatment time shorter than before. Furthermore, by setting the temperature condition of the oxidation roasting temperature to 900°C or less, the thermal energy cost can be suppressed and the temperature control can be easily performed. In this way, by performing the oxidation roasting treatment at a treatment temperature of 600°C or more and 900°C or less, the efficiency of the oxidation roasting treatment can be improved compared with the past.

[0058] 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 to perform the oxidation roasting treatment stably and uniformly.

[0059] In addition, in the method of the present embodiment, it is preferred to set the processing time of the oxidation roasting treatment so that the carbon grade (carbon content) of the obtained oxidation roasting product is less than 1.0 mass%. Here, for the specific processing time, the test of the relationship between the charging amount of calcium carbonate, the processing temperature in the oxidation roasting treatment and the introduction amount of the oxidant and the carbon content contained in the obtained oxidation roasting product is implemented, and it is set based on the test result. 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 prevented from taking more than necessary processing time to carry out oxidation roasting treatment, so the processing efficiency can be further improved.

[0060] Here, regarding the treatment temperature of the oxidation roasting treatment, when the treatment temperature is less than 600°C, even if the oxidant is introduced under the above conditions, the carbon will not decompose and will easily remain, and the oxidation of aluminum will only stay on the surface. In the subsequent reduction step S4, aluminum is easy to diffuse in the alloy. In addition, the residual carbon probably contains phosphorus. Therefore, when the residual carbon becomes more, the phosphorus that is more easily reduced will be reduced by carbon to a degree that cannot be ignored. In the subsequent reduction step S4, the phosphorus may be distributed to the alloy, which is not preferred. Moreover, in this series of processes, phosphorus cannot be effectively removed. Therefore, after the alloy is recovered, it is necessary to perform a separate treatment to remove phosphorus from the alloy through a dephosphorization process. In addition, when the temperature condition of the oxidation roasting treatment is less than 600°C, the oxidation removal of carbon takes a long time, so the processing time becomes too long, which may cause obstacles to the operation.

[0061] On the other hand, when the treatment temperature of the oxidation roasting treatment is greater than 900°C, the oxidation roasted product is easily sintered, which sometimes causes obstacles to the operability of the treatment in the subsequent reduction step S4. In addition, when a known rotary kiln is used in the oxidation roasting treatment, the roasted product adheres to the refractory in the furnace and grows, sometimes causing clogging in the furnace, and the treatment efficiency in the reduction step S4 becomes easy to decrease. Further, the furnace manufacturing cost and thermal energy cost for maintaining the temperature become extremely high, and efficient treatment cannot be performed.

[0062] In addition, the oxidation roasting treatment can be carried out using, for example, a known roasting furnace. In addition, it is preferred that a furnace (preparatory furnace) different from the melting furnace used in the reduction melting treatment in the reduction step S4 is set, and the treatment is carried out in the preparatory furnace. As a roasting furnace, all forms of furnaces and kilns that can roast the crushed material while supplying oxygen so as to carry out oxidation treatment inside it can be used. As an example, it is preferred to use a rotary kiln, a tunnel kiln (open hearth: Hearthfurnace) and the like that are known in the past.

[0063] [Reduction process]

[0064] In the reduction step S4, the oxidized roasted product obtained by the oxidizing roasting step S3 is reduced to obtain a reduced product. The purpose of the reduction step S4 is to keep the unnecessary oxides such as aluminum oxidized in the oxidizing roasting process as oxides, reduce and melt the oxides of valuable metals such as copper oxidized in the oxidizing roasting process, and recover the reduced product as an integrated alloy.

[0065] Here, in the reduction step S4, a reduction melting treatment is performed at least in the presence of carbon. By such a reduction melting treatment, a melt containing slag and an alloy containing valuable metals is obtained.

[0066] 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 and nickel oxides with 1 mole of carbon can be cited. In addition, hydrocarbons that can reduce 2 to 4 moles with 1 mole of carbon can be used as a carbon supply source. In this way, by performing a reduction melting treatment in 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, compared with the case of using aluminothermic reaction in which metal powder such as aluminum is used as a reducing agent for reduction, it has the advantage of extremely high safety.

[0067] In addition, as for carbon as a reducing agent, besides artificial graphite and natural graphite, coal, coke, etc. can also be used as long as the impurity level is acceptable in the product and subsequent processes. It should be noted that ammonia and carbon monoxide can be added in the reduction melting treatment.

[0068] At this time, it is preferred to moderately adjust the amount of carbon. When the amount of carbon is too much, in the case of containing phosphorus in the oxidation roasted product, most of the phosphorus is reduced by the carbon, and is distributed in the alloy containing the valuable metals such as copper, nickel, cobalt, and can not be effectively removed, becoming an alloy with a high phosphorus grade. On the other hand, when the amount of carbon is too little, although phosphorus is effectively removed and an alloy with a low phosphorus grade is obtained, the valuable metals are not effectively reduced, and the recovery rate of the valuable metals decreases. It should be noted that for the amount of carbon, in addition to considering the content of phosphorus remaining in the oxidation roasted product, it is also possible to consider that the price of the carbon (carbon supply source) used as a reducing agent and the difference (price difference) of the price of the valuable metals recovered are increased or decreased.

[0069] Specifically, in the reduction melting treatment in the reduction step S4, it is preferred to treat in the presence of carbon in an amount greater than 7.5% by mass and less than 10% by mass, more preferably in an amount greater than 8.0% by mass and less than 9.0% by mass, relative to 100% by mass of the oxidized roasted product to be treated. By controlling the amount of carbon in this way, the valuable metals can be effectively reduced to improve the recovery rate, and on the other hand, the reduction of phosphorus can be suppressed and phosphorus can be effectively separated to obtain an alloy with a low phosphorus grade.

[0070] The amount of carbon present can be adjusted by adding graphite etc. in the reduction melting treatment as described above. Here, preferably, the amount of carbon not oxidized and removed by the oxidation roasting treatment in the oxidation roasting process S3 is also included for adjustment. That is, the amount of carbon present is not only included in the amount of carbon added in the reduction melting treatment, but also included in the amount of carbon remaining in the oxidation roasted product. However, as described above, in the oxidation roasting process S3, a specific amount of oxidant is introduced, and the oxidation roasting treatment is carried out under the conditions of a specific temperature range, so the carbon contained in the raw material is effectively removed, and carbon is hardly included in the oxidation roasted product obtained. Therefore, about the amount of carbon in the reduction melting treatment, the amount of carbon added is a substantial amount, which can be freely adjusted by the added carbon.

[0071] 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 set to a range of 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 about 1380°C or more, and if it is a copper alloy containing more than 50% by mass of nickel, the melting point is about 1320°C or more. Therefore, by reducing and melting at a temperature above 1320°C, it is easy to recover valuable metals such as copper, nickel, and cobalt as alloys. In addition, if the reduction melting is carried out under conditions above 1450°C, the fluidity of the obtained alloy becomes very good, and the separation efficiency of impurity components and valuable metals is improved, which is more preferred. On the other hand, when the melting temperature is greater than 1600°C, the heat energy is consumed in vain, the consumption of refractory materials such as crucibles and furnace walls becomes intense, and the productivity may decrease. Therefore, as the melting temperature, it is preferably set to 1600°C or less.

[0072] In the reduction melting treatment, it is preferable to use a flux. By performing the reduction melting using a flux, slag containing oxides such as aluminum can be dissolved in the flux and removed.

[0073] As a flux, a flux containing calcium (Ca) as a main component is preferred. For example, calcium oxide and calcium carbonate can be used. When phosphorus is oxidized, it becomes an acidic oxide. Therefore, the more alkaline the composition of the slag is, the easier it is to distribute phosphorus to the slag for removal. Therefore, it is better when there is more calcium that becomes an alkaline oxide in the slag, and it is better when there is less silicon (Si) that becomes an acidic oxide. In particular, it is preferred to add a flux for treatment in a manner that the mass ratio of silicon dioxide (SiO2) / calcium oxide (CaO) in the generated slag becomes 0.5 or less. In addition, when the proportion of aluminum oxide (Al2O3) is large, the melting point of the slag rises. Therefore, in order to melt the aluminum oxide, a sufficient amount of calcium is required. In particular, it is preferred to add a flux for treatment in a manner 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.

[0074] During the reduction melting treatment, dust, exhaust gas, etc. may be generated. However, these can be rendered harmless by performing conventionally known exhaust gas treatment.

[0075] In addition, sulfur can be added to the alloy obtained by the reduction melting treatment in the reduction step S4 before recovery, thereby making the alloy brittle and easy to crush. By crushing the alloy, the specific surface area can be increased, thereby improving the leaching property in the wet smelting process.

[0076] It should be noted that the above describes a method of reducing and melting the oxidized calcined product obtained in the oxidizing calcining step S3 to recover the reduced product as an integrated alloy. However, the reduction and melting do not necessarily have to be performed simultaneously, and each step may be performed independently.

[0077] 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 are kept as oxides, and oxides of valuable metals such as copper oxidized in the oxidizing roasting treatment are reduced, and the reduced product is recovered as an integrated alloy in the subsequent melting step.

[0078] In the reduction process, for example, the oxidized calcined product is heated and reduced at a temperature of 500°C to 1000°C (reduction temperature) 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, the thermal energy cost can be suppressed, and the reduction treatment efficiency can be improved. It should be noted that when the reduction temperature is less than 500°C, the reduction reaction efficiency becomes low and the treatment requires a long time. On the other hand, when the reduction temperature is greater than 1000°C, sintering is likely to occur before the oxidized calcined product is reduced.

[0079] 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.

[0080] Then, in the melting step, the reduction product obtained in the reduction step is melted to be alloyed. By melting the reduction product in this way, a molten material is obtained, which contains slag and an alloy, wherein the slag contains oxides such as aluminum, and the alloy contains copper, nickel, cobalt, etc. as valuable metals.

[0081] 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 and calcium carbonate is preferably used. It should be noted that dust, exhaust gas, etc. may sometimes be generated in the melting process, but they can be rendered harmless by implementing conventionally known exhaust gas treatment.

[0082] Example

[0083] 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 at all.

[0084] When recovering an alloy containing valuable metals from a raw material including waste lithium-ion batteries, conditions for a treatment (oxidative roasting treatment) for removing carbon (C) contained in the raw material by oxidative roasting the raw material were verified.

[0085] (Waste battery pre-treatment process)

[0086] First, the waste lithium-ion batteries to be processed include 18650 cylindrical batteries, used batteries of vehicle-mounted square batteries, and defective batteries recovered in the battery manufacturing process. Then, the waste lithium-ion batteries are immersed in salt water to discharge them, and the water is dispersed. They are then roasted in the air at a temperature of 260°C to decompose and remove the electrolyte and the outer can to obtain the battery contents.

[0087] (Crushing process)

[0088] Then, the battery contents were pulverized by a pulverizer (trade name: Good Cutter: manufactured by Ujiie Seisakusho Co., Ltd.) The carbon content in the pulverized product (pulverized product of the waste battery) was 26% by mass.

[0089] (Oxidation roasting process)

[0090] Then, the obtained pulverized product was subjected to oxidative roasting treatment under the conditions shown in Table 1 below (carbon grade in the raw material, amount of calcium carbonate charged based on the mass ratio of calcium oxide (CaO) / aluminum oxide (Al2O3), and roasting treatment temperature). The oxidative roasting treatment was carried out by operating a rotary kiln in the atmosphere. In addition, air was introduced as an oxidant.

[0091] Table 1 below shows the conditions of the oxidation calcination treatment and the results of measuring the treatment temperature (oxidation calcination temperature) of the oxidation calcination treatment.

[0092] Table 1

[0093]

[0094] According to the results in Table 1, in Examples 1 to 2 and Reference Example 1, raw materials with the same carbon grade were used as the objects, but the oxidation roasting temperature in Examples 1 to 2 was lower than the oxidation roasting temperature in Reference Example 1 in which calcium carbonate was not charged. It can be further known that, with respect to the amount of calcium carbonate charged, the higher the mass ratio of calcium oxide (CaO) / alumina (Al2O3), the lower the oxidation roasting temperature. According to this result, it can be confirmed that the charged calcium carbonate helps to suppress the oxidation roasting temperature.

[0095] In addition, in Example 3, a raw material with a higher carbon grade (39 mass %) than the raw material used in Reference Example 1 and Examples 1 to 2 was used as the object. However, it can be seen that even so, when the carbon grade in the waste lithium-ion batteries is significantly high, by adding calcium carbonate and setting its loading amount to a loading amount with a mass ratio of calcium oxide (CaO) / aluminum oxide (Al2O3) of more than 1.0, the increase in the oxidative roasting temperature can be suppressed.

[0096] Based on such results, it can be confirmed that even when the carbon grade in the waste lithium-ion batteries is high, by adding calcium carbonate, and preferably setting its loading amount to a mass ratio of calcium oxide (CaO) / aluminum oxide (Al2O3) of 1.0 or more, the oxidation roasting temperature can be suppressed to below 900°C.

[0097] On the other hand, in Comparative Example 1, a raw material having the same high carbon grade as in Example 3 was used, but calcium carbonate was not added, so the oxidation roasting temperature exceeded 900°C and increased to 1000°C.

[0098] In addition, Comparative Example 2 is an example in which the loading amount (processing amount) of waste lithium-ion batteries is set to 80% of the processing amount in Comparative Example 1. Although the oxidation roasting temperature can be controlled to be below 900°C, it is 65°C higher than the oxidation roasting temperature in Example 3. It can be seen that in order to suppress the oxidation roasting temperature to the same level as Example 3, the processing amount of waste lithium-ion batteries needs to be further reduced. That is, it is confirmed that the method of Comparative Example 2 is an inefficient method.

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 of reducing the obtained oxidized roasted product in the presence of carbon, In the oxidation roasting step, calcium carbonate is charged into a furnace together with the raw material containing the waste lithium-ion battery, and the treatment temperature of the oxidation roasting treatment is controlled.

2. The method for recovering valuable metals according to claim 1, wherein: In the oxidation roasting step, the amount of calcium carbonate charged is adjusted to a mass ratio of calcium oxide CaO / aluminum oxide Al2O3 in terms of the amount of calcium oxide and aluminum oxide relative to the amount of aluminum contained in the raw material to be greater than 1.0 and less than 2.

0.

3. The method for recovering valuable metals according to claim 1 or 2, wherein: 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 within the range of 600° C. to 900° C., so that the carbon grade of the obtained oxidative roasted product is set to less than 1.0 mass %.

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