Method for recovering valuable metals

Abstract

Provided is a method whereby valuable metals can be recovered more efficiently by strictly controlling the oxygen partial pressure required for melting a raw material. A method for recovering valuable metals (Cu, Ni, Co), said method comprising: a step for preparing a charge containing at least phosphorus (P) and a valuable metal as a starting material; a step in which the raw material is heated and melted to form a melt, and thereafter the melt is made into a melt containing an alloy and slag; and a step for separating slag from the melt and recovering an alloy containing a valuable metal, in which the oxygen partial pressure in the melt is directly measured using an oxygen analyzer when the raw material is heated and melted, and the oxygen partial pressure is controlled on the basis of the obtained measurement result.

Description

[0001] This application is a divisional application of the application with an application date of June 29, 2021, application number 202180046720.X, and invention name “Method for Recovering Valuable Metals”. Technical Field

[0002] The present invention relates to a method for recovering valuable metals. Background Art

[0003] 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 enclosed in an outer can. Here, the outer can is made of a metal such as iron (Fe) or 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 nickelate, lithium cobaltate, 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 an electrolyte such as lithium hexafluorophosphate (LiPF6).

[0004] One of the main uses of lithium-ion batteries is in hybrid and electric vehicles. Therefore, it is foreseeable that a large number of lithium-ion batteries will be discarded over the lifecycle of a vehicle. Furthermore, some lithium-ion batteries are discarded as defective during manufacturing. There is a demand to reuse these used batteries or defective batteries generated during manufacturing (hereinafter referred to as "waste lithium-ion batteries") as resources.

[0005] As a recycling method, a dry smelting process has been proposed, in which waste lithium-ion batteries are completely melted in a high-temperature furnace (melting furnace). This process involves melting crushed waste lithium-ion batteries and separating and recovering valuable metals, such as cobalt (Co), nickel (Ni), and copper (Cu), from low-value metals, such as iron (Fe) and aluminum (Al), by exploiting the difference in oxygen affinity between them. In this method, the low-value metals are oxidized as much as possible to form slag, while the oxidation of the valuable metals is minimized to allow them to be recovered as alloys.

[0006] As mentioned above, in dry smelting processes that utilize differences in oxygen affinity to separate and recover valuable metals, controlling the redox ratio during the melt process is crucial. In other words, inadequate control can lead to problems such as impurities being mixed into the alloy to be recovered as valuable metals, or oxidized valuable metals being mixed into the slag to be recovered as impurities, reducing the recovery rate of valuable metals. Therefore, in dry smelting processes, oxidizing agents or reducing agents such as air and oxygen are traditionally introduced into the melting furnace to control the redox ratio.

[0007] For example, Patent Document 1 describes a process for separating cobalt from lithium present in a charge containing lithium-ion batteries or battery waste, wherein the oxygen input to the bath is preferably adjusted to reach 10 -18 ~10 -14 atm target oxygen pressure, through the upper limit (10 -14 atm) to eliminate the formation and loss of cobalt oxides in the slag. In addition, the lower limit (10 -18 atm) to ensure oxidation of elements such as aluminum and carbon (claims 1 and

[0018] of patent document 1).

[0008] In addition, Patent Document 2 describes a method for recovering valuable metals from waste lithium-ion batteries containing nickel and cobalt. By adjusting the oxygen amount, oxidation time, and temperature in the preliminary oxidation step, strict adjustment of the degree of oxidation can be performed. By adjusting the degree of oxidation, the approximate total amount of aluminum oxide can be separated as slag in the slag separation step, and additional oxidation treatment can be performed for a short time in the melting step. The additional oxidation step can more finely adjust the appropriate degree of oxidation (Claims 1,

[0033] , and

[0036] of Patent Document 2).

[0009] Prior art literature

[0010] Patent Literature

[0011] Patent Document 1: Japanese Patent No. 6542354.

[0012] Patent Document 2: Japanese Patent No. 5853585. Summary of the Invention

[0013] As mentioned above, while the introduction of air or oxygen during the melt treatment to control the redox ratio has been proposed for valuable metal recovery in dry smelting processes, this method still has room for improvement. Specifically, it is important to more strictly control the redox ratio (oxygen partial pressure) in order to efficiently recover valuable metals.

[0014] For example, spent lithium-ion batteries contain large amounts of impurities such as carbon (C), aluminum (Al), fluorine (F), and phosphorus (P). Furthermore, in recent years, to improve the charge-discharge and cycle characteristics of lithium-ion batteries, some batteries have been modified to include trace amounts of tungsten (W), niobium (Nb), zirconium (Zr), and other additives to the positive electrode active material, or to include chromium (Cr) derived from the SUS used in the outer cans.

[0015] Among these, impurity elements such as phosphorus, tungsten, and chromium are relatively easily reduced. Therefore, if the redox degree is not strictly controlled, impurities such as phosphorus may be incorporated into the alloy that should be recovered as valuable metals. On the other hand, if the reduction degree is too low, valuable metals, particularly cobalt, will oxidize and cannot be recovered as alloys.

[0016] In this regard, in the methods proposed in the past, the control of the redox degree (oxygen partial pressure) is insufficient. For example, in Patent Document 1, although the material balance of Cu, Ni, Fe, Co, Al, Si, and Ca is studied (Table 1 of Patent Document 1), the problem of phosphorus mixing into the alloy is not recognized. In addition, in Patent Document 1, the oxidation level (PO2) is determined by directly analyzing the gas above the molten bath (

[0022] of Patent Document 1), but in this method, it is difficult to accurately measure the oxygen partial pressure and control it. Therefore, in particular, there is a problem that phosphorus cannot be prevented from being mixed into the alloy. In fact, after investigation, the inventors found that the preferred value of less than 10 in Patent Document 1 is less than 10 -14 Atm oxygen partial pressure conditions, phosphorus may be mixed into the alloy.

[0017] Furthermore, the method proposed in Patent Document 2 includes a dephosphorization step after the melting and slag separation steps, in which phosphorus is separated from the alloy (Claims 1 and

[0039] to

[0046] of Patent Document 2). While this method can remove phosphorus, a process that can remove phosphorus without requiring a dephosphorization step is preferred to further reduce production costs. Patent Document 2 does not disclose the solution required to implement such a process. Furthermore, Patent Document 2 does not recognize the problem of contamination of impurity elements other than phosphorus, such as tungsten and chromium.

[0018] Furthermore, methods for removing tungsten from alloys include dissolving the alloy with an acid or other agent and then neutralizing it. While this method can remove tungsten, the use of a neutralizing agent or the neutralization process can lead to the co-precipitation of valuable metals such as nickel and cobalt with the tungsten, potentially significantly increasing production costs. Furthermore, if chromium is present in the alloy, for example, during pulverization, the chromium in the alloy reacts with atmospheric oxygen to form high-melting-point oxides primarily composed of chromium, potentially hindering production and reducing production efficiency.

[0019] In light of this reality, the present inventors conducted intensive research. As a result, they discovered that by directly measuring the oxygen partial pressure in the melt using an oxygen analyzer during melting of the raw materials and controlling the oxygen partial pressure based on the measurement results, it is possible to strictly control the oxygen partial pressure, thereby preventing oxidation of valuable metals and suppressing the incorporation of phosphorus, tungsten, and chromium into the alloy. Consequently, the valuable metals can be recovered more efficiently.

[0020] The present invention has been made based on this knowledge, and an object of the present invention is to provide a method capable of strictly controlling the oxygen partial pressure required when heating and melting raw materials, thereby enabling more efficient recovery of valuable metals.

[0021] The present invention includes the following solutions (1) to (7). It should be noted that in this specification, the expression "to" includes the numerical values ​​at both ends. That is, "X to Y" has the same meaning as "X or more and Y or less".

[0022] (1) A method for recovering valuable metals, comprising the following steps: a step of preparing a charge containing at least phosphorus (P) and valuable metals as a raw material; a step of heating and melting the raw material to form a melt, and then converting the melt into a molten material containing an alloy and slag; and a step of separating the slag from the melt and recovering the alloy containing the valuable metals, wherein when the raw material is heated and melted, the oxygen partial pressure in the melt is directly measured using an oxygen analyzer, and the oxygen partial pressure is controlled based on the obtained measurement result.

[0023] (2) The method according to (1) above, wherein the charge further contains at least one element of tungsten (W) and chromium (Cr).

[0024] (3) The method of (1) or (2) above, wherein the oxygen partial pressure is controlled to 10 -14.0 (atm) and above and 10 -8.0 (atm) or less.

[0025] (4) The method according to any one of (1) to (3) above, wherein the oxygen partial pressure is controlled to be 10 -14.0 (atm) and above and 10 -11.0 (atm) or less.

[0026] (5) The method according to any one of (1) to (4) above, wherein the heating temperature when the raw material is heated and melted is set to 1300° C. or higher and 1500° C. or lower.

[0027] (6) The method according to any one of (1) to (5) above, wherein the valuable metal is composed of at least one metal or alloy selected from the group consisting of copper (Cu), nickel (Ni), cobalt (Co), and combinations thereof.

[0028] (7) The method according to any one of (1) to (6) above, wherein the loaded object includes waste lithium-ion batteries.

[0029] According to the present invention, there is provided a method capable of strictly controlling the oxygen partial pressure when heating and melting a raw material, thereby enabling more efficient recovery of valuable metals. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 An example of a method for recovering valuable metals is shown. DETAILED DESCRIPTION

[0031] A specific embodiment of the present invention (hereinafter referred to as "this embodiment") will be described. However, the present invention is not limited to the following embodiment, and various modifications are possible without departing from the spirit of the present invention.

[0032] The method for recovering valuable metals according to this embodiment comprises the following steps: preparing a charge containing at least phosphorus (P) and valuable metals as raw materials (preparation step); heating and melting the prepared raw materials to form a melt, and then converting the melt into a molten product containing an alloy and slag (melting step); and separating the slag from the resulting melt to recover the alloy containing the valuable metals (slag separation step). Furthermore, while the raw materials are being heated and melted, the oxygen partial pressure in the melt is directly measured using an oxygen analyzer, and the oxygen partial pressure is controlled based on the measurement results.

[0033] The method of this embodiment is a method for recovering valuable metals from a charge containing at least phosphorus (P) and valuable metals. Furthermore, the charge may also contain at least one of tungsten (W) and chromium (Cr). Here, the valuable metal to be recovered is, for example, at least one metal or alloy selected from the group consisting of copper (Cu), nickel (Ni), cobalt (Co), and combinations thereof. Furthermore, this embodiment is primarily a recovery method based on a dry smelting process. It should be noted that the process may also be composed of a dry smelting process and a wet smelting process. The details of each process are described below.

[0034] <Preparation process>

[0035] In the method of this embodiment, a charge is prepared in the preparation step to obtain a raw material. The charge, which is the target for valuable metal recovery, contains, in addition to phosphorus (P), at least one valuable metal selected from the group consisting of copper (Cu), nickel (Ni), cobalt (Co), and combinations thereof. Furthermore, as described above, the charge may further contain, in addition to phosphorus, at least one of tungsten (W) and chromium (Cr) as an impurity element. The charge may contain these components in the form of metals or elements, or in the form of compounds such as oxides. Furthermore, the charge may contain other inorganic and organic components in addition to these components.

[0036] There are no particular limitations on the type of material to be loaded. Examples include waste lithium-ion batteries, electronic components containing dielectric or magnetic materials, and electronic equipment. Furthermore, the material's form is also not limited, as long as it is suitable for processing in subsequent steps. Furthermore, during the preparatory process, the material may be subjected to a treatment such as pulverization to achieve a suitable form. Furthermore, during the preparatory process, the material may be subjected to a heat treatment, classification treatment, or other treatment to remove unwanted components such as moisture and organic matter.

[0037] Melting process

[0038] In the method of this embodiment, in the melting step, the prepared raw materials are heated and melted to separate them into an alloy (metal) and slag. Specifically, the raw materials are heated and melted to form a melt. This melt contains the alloy and slag in a molten state. Next, the resulting melt is formed into a molten material. This molten material contains the alloy and slag in a solidified state. The alloy primarily contains valuable metals. Therefore, the valuable metals and other components can be separated into the form of an alloy and slag, respectively.

[0039] This is because metals with low added value (such as Al) have a high affinity for oxygen, while valuable metals have a low affinity for oxygen. For example, aluminum (Al), lithium (Li), carbon (C), manganese (Mn), phosphorus (P), tungsten (W), chromium (Cr), iron (Fe), cobalt (Co), nickel (Ni), and copper (Cu) are generally oxidized in the order of Al>Li>C>Mn>P>W>Cr>Fe>Co>Ni>Cu. In other words, aluminum (Al) is most easily oxidized, and copper (Cu) is the least oxidizable. Therefore, metals with low added value (such as Al) are easily oxidized and become slag, while valuable metals (Cu, Ni, Co) are reduced and become metals (alloys). In this way, it is possible to separate metals with low added value and valuable metals into slag and alloys.

[0040] In the method for the present embodiment, when the raw material is heated and melted, the oxygen partial pressure in the melt is directly measured using an oxygen analyzer, and the oxygen partial pressure is controlled according to the measurement result obtained. Thus, the redox degree of the melt can be strictly controlled, and as a result, valuable metals and impurities can be separated with high precision. This point will be described. As long as the redox degree (carbon content, oxidation number of metal, amount) of the raw material can be grasped in advance with high precision, the amount of coordination during the raw material allocation can be used to control the redox degree of the melt in principle. However, in fact, the raw material is not uniform. Sampling error will be produced when the raw material is analyzed, and due to this error, it is difficult to control the redox degree to a target value.

[0041] In addition, Patent Document 1 proposes a method of analyzing gas above the molten pool. However, this method has a large measurement error and cannot be said to be highly reliable. That is, inside a melting furnace where oxygen is continuously introduced, the oxygen partial pressure is not in equilibrium, but is always fluctuating. Therefore, the oxygen partial pressure fluctuates greatly with location and time. In addition, when the ambient gas contains dust, the dust may adhere to the probe of the gas analyzer and hinder accurate measurement. Therefore, in the method of performing gas analysis above the molten pool, it is difficult to accurately determine the redox degree (oxygen partial pressure) of the melt.

[0042] In contrast, in the method of this embodiment, since the oxygen partial pressure of the melt is directly measured, the measured value accurately reflects the actual redox degree of the melt. Therefore, if the redox degree of the melt deviates from the target value, the redox degree of the melt can be accurately brought into line with the target value by controlling the oxygen partial pressure by introducing a reducing agent and an oxidizing agent. Furthermore, as a result, even when impurity elements such as phosphorus, tungsten, and chromium, as well as elements with similar oxygen affinities such as cobalt, are present in the melt, these elements can be separated with high precision.

[0043] There are no particular limitations on the method for measuring the oxygen partial pressure in the melt. For example, an oxygen analyzer equipped with an oxygen sensor (oxygen probe) can be used, with the tip of the oxygen sensor immersed in the melt. A known oxygen sensor, such as a zirconia solid electrolytic sensor, can be used. The method is not limited as long as it can directly measure the oxygen partial pressure in the melt.

[0044] The oxygen partial pressure can be controlled by a known method. For example, a reducing agent or an oxidizing agent can be introduced into the raw material or its melt. As the reducing agent, a material with a high carbon grade (graphite powder, graphite particles, coal, coke, etc.) or carbon monoxide can be used. In addition, a component with a high carbon grade in the raw material can also be used as a reducing agent. As the oxidizing agent, an oxidizing gas (air, oxygen, etc.) or a material with a low carbon grade can be used. In addition, a component with a low carbon grade in the raw material can also be used as an oxidizing agent.

[0045] The introduction of the reducing agent and the oxidizing agent can also be carried out by a known method. When the reducing agent and the oxidizing agent are solid substances, they can be added to the raw material or the melt. When the reducing agent and the oxidizing agent are gaseous substances, they can be introduced from an inlet such as a lance provided in the melting furnace. In addition, the timing of the introduction of the reducing agent and the oxidizing agent is also not limited. When the raw material is put into the melting furnace, the reducing agent and the oxidizing agent can be introduced at the same time, or the reducing agent and the oxidizing agent can be introduced at the stage when the raw material is melted and becomes a melt. Preferably, the reducing agent, the oxidizing agent and the raw material are introduced into the melting furnace at the same time, and the oxygen partial pressure in the melt is measured at the stage when the raw material is melted and becomes a melt. Based on the results obtained, it is determined whether to add the reducing agent and the oxidizing agent. When the measured value of the oxygen partial pressure deviates from the target value, it is sufficient to add the reducing agent and the oxidizing agent. On the other hand, when it is close to the target value, it is not necessary to add the reducing agent and the oxidizing agent.

[0046] When heating and melting the raw materials, it is preferred to control the oxygen partial pressure in the melt to 10 -14.0 (atm) and above and 10 -8.0 (atm) or less. Thus, valuable metals can be recovered more efficiently. -14.0(atm), the reducing power of the melt is too strong, and phosphorus, tungsten, and chromium, which are impurities, may be reduced and mixed into the alloy. On the other hand, when the oxygen partial pressure is greater than 10 -8.0 (atm), cobalt as a valuable metal may be oxidized and incorporated into the slag. It is more preferable to control the oxygen partial pressure to 10 -14.0 (atm) and above and 10 -11.0 (atm) or less.

[0047] During the heat-melting process in the melting process, a flux can be introduced into the raw material (added). By adding a flux, the melting process temperature can be lowered, and in addition, the removal of impurity elements such as phosphorus, tungsten, and chromium can be further promoted. As a flux, it is preferred to contain an element that forms an alkaline oxide, which can incorporate impurity elements and has a low melting point. For example, phosphorus becomes an acidic oxide when oxidized. Therefore, the more alkaline the slag formed in the melting process is, the easier it is to remove phosphorus by incorporating it into the slag. Among them, it is more preferred to contain a calcium compound that is cheap and stable under normal temperature conditions. As a calcium compound, for example, calcium oxide (CaO) and calcium carbonate (CaCO3) can be cited.

[0048] The heating temperature when heating and melting the raw materials is not particularly limited, but is preferably 1300°C or higher and 1500°C or lower. By setting the heating temperature to 1300°C or higher, the valuable metals (Cu, Co, Ni) are fully melted, and an alloy is formed in a state with improved fluidity. Therefore, the alloy and the slag can be efficiently separated in the slag separation step described later. The heating temperature is more preferably 1350°C or higher. On the other hand, when the heating temperature is higher than 1500°C, the heat energy is consumed in vain, and the consumption of refractory materials such as crucibles and furnace walls becomes intense, which may reduce productivity. In addition, the heating temperature is more preferably 1450°C or lower.

[0049] <Preheating process>

[0050] If necessary, before the melting process, a process (preheating process) may be provided in which the raw materials to be subjected to the heat and melt treatment are preheated (oxidatively roasted) to form a preheated product (oxidatively roasted product). In the preheating process (oxidatively roasted process), the raw materials are preheated to reduce the amount of carbon contained in the raw materials. By providing such a preheating process, even if the raw materials (charged materials, etc.) contain excessive carbon, the carbon can be oxidized and removed, thereby promoting the alloy integration of the valuable metals in the subsequent melting process.

[0051] That is, in the melting process, the valuable metal is reduced and becomes local molten particles, and the carbon in the raw material sometimes becomes a physical obstacle when the molten particles (valuable metal) are agglomerated. Therefore, if a preheating process is not provided, carbon will hinder the agglomeration integration of the molten particles and the separation of the alloy (metal) and the slag caused thereby, and the recovery rate of the valuable metal is sometimes reduced. In contrast, by removing carbon in advance in the preheating process and agglomerating the molten particles (valuable metal) in the melting process, the recovery rate of the valuable metal can be further improved. In addition, since phosphorus (P), tungsten (W), and chromium (Cr) are impurity elements that are relatively easy to be reduced, if carbon exists in excess, phosphorus is likely to be reduced and mixed into the alloy together with the valuable metal. In this regard, by providing a preheating process to remove excess carbon in advance, it is possible to prevent impurity elements such as phosphorus from mixing into the alloy. It should be noted that the carbon amount of the preheated object is preferably less than 1% by mass.

[0052] Furthermore, by providing a preheating step, oxidation variations can be suppressed. In the preheating step, it is preferred to perform treatment (oxidative roasting) at an oxidation level sufficient to oxidize low-value-added metals (such as Al) contained in the raw materials (charge material, etc.). On the other hand, the oxidation level can be easily controlled by adjusting the preheating temperature, time, and / or environment. Therefore, the preheating step allows for more stringent regulation of the oxidation level, thereby suppressing oxidation variations.

[0053] The degree of oxidation is adjusted as follows. As described above, aluminum (Al), lithium (Li), carbon (C), manganese (Mn), phosphorus (P), tungsten (W), chromium (Cr), iron (Fe), cobalt (Co), nickel (Ni), and copper (Cu) are generally oxidized in the order of Al > Li > C > Mn > P > W > Cr > Fe > Co > Ni > Cu. During the preheating step, oxidation is continued until the entire amount of aluminum (Al) is oxidized. Oxidation can be accelerated until a portion of the iron (Fe) is oxidized, but the degree of oxidation is limited to a level that prevents cobalt (Co) from being oxidized and distributing into the slag.

[0054] Preheating is preferably performed in the presence of an oxidizing agent. This allows efficient oxidation and removal of carbon (C) as an impurity and oxidation of aluminum (Al). The oxidizing agent is not particularly limited; however, from the perspective of ease of handling, an oxygen-containing gas (such as air, pure oxygen, or oxygen-enriched gas) is preferred. Furthermore, the amount of oxidizing agent introduced is preferably approximately 1.2 times the chemical equivalent required to oxidize the respective substances being oxidized.

[0055] The preheating temperature is preferably 700°C or higher and 1100°C or lower. Setting the preheating temperature at 700°C or higher further improves carbon oxidation efficiency and shortens oxidation time. Setting the preheating temperature at 1100°C or lower reduces thermal energy costs and improves preheating efficiency. The preheating temperature can be 800°C or higher. Alternatively, the preheating temperature can be 900°C or lower.

[0056] The preheating process in the preheating step 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 subsequent melting process and perform the process in the preparatory furnace. As a preheating furnace, any type of furnace can be used as long as it can supply an oxidant (oxygen, etc.) while roasting the charged material and perform oxidation treatment therein. As an example, a rotary kiln or a tunnel kiln (hearth furnace) known in the past can be cited.

[0057] <Slag separation process>

[0058] In the slag separation process, slag is separated from the melt obtained in the melting process to recover the alloy containing valuable metals. The slag and alloy have different specific gravities. Therefore, since the slag, with a lower specific gravity than the alloy, concentrates on the upper portion of the alloy, it can be easily separated and recovered through gravity separation.

[0059] After the slag separation step, a sulfurization step for sulfurizing the resulting alloy or a pulverization step for pulverizing the resulting sulfide or alloy can be performed. Furthermore, the valuable metal alloy obtained through this dry smelting process can also be subjected to a wet smelting process. The wet smelting process can remove impurities, separate and purify the valuable metals (Cu, Ni, Co), and recover them separately. Examples of treatments in the wet smelting process include well-known methods such as neutralization and solvent extraction.

[0060] According to the method of this present embodiment, the oxygen partial pressure of the melt can be strictly controlled, thereby being able to suppress the inclusion of impurity elements such as phosphorus, tungsten and chromium into the alloy while preventing the oxidation of valuable metals. In addition, as a result, valuable metals can be recovered more efficiently. For example, the phosphorus content (phosphorus grade in the metal) of the alloy can be set to less than 0.50 mass %, less than 0.10 mass %, less than 0.05 mass %, less than 0.03 mass % or less than 0.01 mass %. In addition, the tungsten content (tungsten grade in the metal) of the alloy can be set to less than 0.20 mass %, less than 0.02 mass % or less than 0.01 mass %. In addition, the chromium content (chromium grade in the metal) of the alloy can be set to less than 0.05 mass %, less than 0.03 mass % or less than 0.01 mass %.

[0061] Furthermore, the recovery rate of valuable metals can be set to 90.0% by mass or more, 95.0% by mass or more, 97.0% by mass or more, 99.0% by mass or more, or 99.5% by mass or more. The recovery rate of valuable metals is calculated using the content of valuable metals contained in the final alloy and slag according to the following formula (1).

[0062]

[0063] The loading materials of this embodiment are not limited as long as they contain valuable metals, and preferably include waste lithium-ion batteries. Waste lithium-ion batteries contain lithium (Li) and valuable metals (Cu, Ni, Co), and contain metals with low added value (Al, Fe, P, W, Cr) and carbon components. Therefore, by using waste lithium-ion batteries as loading materials, valuable metals can be efficiently separated and recovered. It should be noted that waste lithium-ion batteries are a concept of waste materials within the manufacturing process of lithium-ion batteries, including not only used lithium-ion batteries but also defective products generated in the manufacturing process of the positive electrode materials constituting the battery, residues in the manufacturing process, waste generated, etc. Therefore, waste lithium-ion batteries can also be referred to as lithium-ion battery waste.

[0064] use Figure 1 Describe the method for recovering valuable metals from spent lithium-ion batteries. Figure 1 This is a process diagram showing an example of a recycling method. Figure 1 As shown, the method includes: a step of removing the electrolyte and outer cans of waste lithium-ion batteries to obtain the waste battery contents (waste battery pretreatment step S1); a step of pulverizing the waste battery contents to form a pulverized product (first pulverization step S2); a step of preheating the pulverized product to form a preheated product (preheating step S3); a step of melting the preheated product to form a melt (melting step S4); and a step of separating slag from the melt to recover the alloy (slag separation step). Although not shown, after the slag separation step, a sulfidation step for sulfiding the obtained alloy and a second pulverization step for pulverizing the obtained sulfide or alloy may also be provided. Details of each step are described below.

[0065] <Waste Battery Pre-treatment Process>

[0066] The waste battery pre-treatment step (S1) is carried out for the purpose of preventing the explosion of waste lithium-ion batteries, rendering them harmless, and removing the outer cans. Since lithium-ion batteries are closed systems, they contain electrolytes and the like inside. Therefore, if they are crushed in their original state, there is a risk of explosion. It is preferred to implement discharge treatment and electrolyte removal treatment by certain methods. In addition, the outer cans are mostly made of aluminum (Al) and iron (Fe) as metals, and such metal outer cans are relatively easy to recycle directly. As described above, by removing the electrolyte and the outer cans in the waste battery pre-treatment step (S1), safety can be improved and the recovery rate of valuable metals (Cu, Ni, Co) can be increased.

[0067] There are no specific restrictions on the specific methods for pre-treating waste batteries. For example, a method using a needle-like knife tip to physically pierce the waste battery and remove the electrolyte can be used. Another method is to heat the waste lithium-ion battery and burn the electrolyte to render it harmless.

[0068] In the waste battery pre-treatment step (S1), when recovering aluminum (Al) and iron (Fe) contained in the outer cans, the removed outer cans can be crushed and then screened using a screening machine. Aluminum (Al) easily becomes powdered after light crushing, allowing for efficient recovery. Furthermore, the iron (Fe) contained in the outer cans can be recovered using magnetic screening.

[0069] <First Crushing Step>

[0070] In the first pulverization step (S2), the contents of the waste lithium-ion batteries are pulverized to obtain a pulverized product. This step is intended to improve the reaction efficiency in the dry smelting process. By improving the reaction efficiency, the recovery rate of valuable metals (Cu, Ni, Co) can be increased. There are no particular restrictions on the specific pulverization method. A conventionally known pulverizer such as a chopper mixer can be used for pulverization. It should be noted that combining the waste battery pretreatment step and the first pulverization step is equivalent to the aforementioned preparatory step.

[0071] <Preheating process>

[0072] In the preheating step (oxidation roasting step) (S3), the pulverized product obtained in the first pulverization step (S2) is preheated (oxidation roasted) to obtain a preheated product (oxidation roasted product). The details of this step are as described above.

[0073] Melting process

[0074] In the melting step (S4), the preheated product obtained in the preheating step (S3) is melted to obtain a melt. The details of this step are as described above.

[0075] <Slag separation process>

[0076] In the slag separation step, slag is separated from the melt obtained in the melting step ( S4 ) to recover the alloy. The details of this step are as described above.

[0077] A sulfurization step and a pulverization step may be performed after the slag separation step. The resulting alloy containing valuable metals may also be subjected to a wet smelting process. The details of the sulfurization step, pulverization step, and wet smelting process are as described above.

[0078] Example

[0079] The present invention will be described in more detail using the following examples and comparative examples. However, the present invention is not limited to the following examples.

[0080] (1) Recovery of valuable metals

[0081] [Example 1]

[0082] We use spent lithium-ion batteries as a feedstock to recover valuable metals. The recovery process is as follows.

[0083] <Waste Battery Pre-treatment Process (Preparatory Process)>

[0084] Used lithium-ion batteries and defective batteries recovered from the battery manufacturing process were used as waste lithium-ion batteries. The waste lithium-ion batteries were then immersed in salt water to discharge, remove moisture, and then calcined in air at 260°C to decompose and remove the electrolyte and outer cans, thereby obtaining the battery contents. The main elemental composition of the battery contents is shown in Table 1 below.

[0085] Table 1

[0086]

[0087] <Crushing process>

[0088] The obtained battery contents were pulverized using a pulverizer (trade name: GOOD CUTTER, manufactured by Ujiie Manufacturing Co., Ltd.) to obtain a pulverized product.

[0089] <Preheating process>

[0090] The obtained pulverized product was placed in a rotary kiln and preheated in the atmosphere at 800° C. for 180 minutes to obtain a raw material to be heated and melted.

[0091] Melting process

[0092] To the preheated pulverized material (the raw material for melting), calcium oxide (CaO) and silicon dioxide (SiO2) are added as flux, followed by graphite powder as a reducing agent, and mixed. The resulting mixture is placed in an alumina crucible and heated to 1400°C by resistance heating to melt it, forming a melt. This results in a melt containing the alloy and slag.

[0093] When melting the raw materials, use an oxygen analyzer to directly measure the oxygen partial pressure in the melt and control the oxygen partial pressure to 10 -13.9 (atm). Specifically, an oxygen analyzer with an oxygen probe (Kawasho Electric Industry Co., Ltd., OXT-O) at the tip was used, and the probe was inserted so that the tip of the oxygen probe was directly immersed in the melt. The oxygen probe used was an oxygen probe with a zirconium oxide solid electrolytic sensor. The measured oxygen partial pressure was then read after stabilization. The oxygen partial pressure was controlled by adjusting the amount of reducing agent (graphite powder) added.

[0094] <Slag separation process>

[0095] The alloy is recovered by separating the slag from the resulting melt using the difference in specific gravity.

[0096] [Example 2]

[0097] The amount of reducing agent (graphite powder) added was changed during the melting process, and the oxygen partial pressure was controlled to 10 -12.9 (atm). Valuable metals were recovered in the same manner as in Example 1 except for the above.

[0098] [Example 3]

[0099] The amount of reducing agent (graphite powder) added was changed during the melting process, and the oxygen partial pressure was controlled to 10 -8.0 (atm). Valuable metals were recovered in the same manner as in Example 1 except for the above.

[0100] [Example 4]

[0101] The amount of reducing agent (graphite powder) added was changed during the melting process, and the oxygen partial pressure was controlled to 10 -13.0 (atm). In addition, the heating temperature was set to 1330° C. Valuable metals were recovered in the same manner as in Example 1 except for this.

[0102] [Example 5]

[0103] The amount of reducing agent (graphite powder) added was changed during the melting process, and the oxygen partial pressure was controlled to 10 -12.0 (atm). In addition, the heating temperature was set to 1480° C. Valuable metals were recovered in the same manner as in Example 1 except for this.

[0104] [Example 6]

[0105] The amount of reducing agent (graphite powder) added was changed during the melting process, and the oxygen partial pressure was controlled to 10 -7.6 (atm). Valuable metals were recovered in the same manner as in Example 1 except for the above.

[0106] [Example 7]

[0107] The amount of reducing agent (graphite powder) added was changed during the melting process, and the oxygen partial pressure was controlled to 10 -14.9 (atm). Valuable metals were recovered in the same manner as in Example 1 except for the above.

[0108] (2) Evaluation

[0109] In Examples 1 to 7, elemental analysis of the recovered alloys (metals) was performed using an ICP analyzer (Agilent Technologies, Inc., Agilent 5100SUDV). The elements analyzed were nickel (Ni), cobalt (Co), and copper (Cu), which are valuable metals, and phosphorus (P), tungsten (W), and chromium (Cr), which are impurities difficult to remove from the metals.

[0110] The phosphorus (P) content (mass %) in the alloy (metal) is defined as the phosphorus grade, the tungsten (W) content (mass %) is defined as the tungsten grade, and the chromium (Cr) content (mass %) is defined as the chromium grade. Furthermore, the recovery rate of valuable metals is determined as follows. Specifically, the recovery rate of valuable metals (Cu, Ni, and Co) in the alloy and slag, determined by elemental analysis, is calculated according to the following formula (1).

[0111]

[0112] (3) Results

[0113] The phosphorus grade, tungsten grade, chromium grade and valuable metal recovery rate obtained for Examples 1 to 7 are shown in Table 2. The results in Table 2 show that the oxygen partial pressure of the melt can be strictly controlled within 10 by adjusting the amount of reducing agent added and the heating temperature. -14.9 ~10 -7.6 (atm) range.

[0114] Furthermore, for the alloys obtained in Examples 1 to 5, the recovery rate of valuable metals contained in the batteries was as high as over 95%. Furthermore, the phosphorus grade in the resulting alloys was less than 0.03% by mass, the tungsten grade was less than 0.01% by mass, and the chromium grade was relatively low, less than 0.02% by mass. This demonstrates that valuable metals can be obtained at a high recovery rate, and phosphorus, tungsten, and chromium can be effectively removed. On the other hand, the recovery rate of valuable metals in Example 6 was low, and in Example 7, the phosphorus, tungsten, and chromium grades were poor.

[0115] Table 2

[0116]

Claims

1. A method for recovering valuable metals, wherein: The method has the following steps: A step of preparing a charge containing at least phosphorus P and valuable metals as raw materials; A step of heating and melting the raw materials to form a melt, and then converting the melt into a molten material containing an alloy and slag; as well as a step of separating slag from the melt and recovering an alloy containing valuable metals, When the raw materials are heated and melted, the oxygen partial pressure in the melt is directly measured using an oxygen analyzer, and the oxygen partial pressure is controlled based on the obtained measurement result.

2. The method according to claim 1, wherein The charge further contains at least one element of tungsten W and chromium Cr.

3. The method according to claim 1 or 2, wherein The oxygen partial pressure was controlled to be 10 -14 . 0 ATM and above 10 -8 . 0 Within the range below atm.

4. The method according to any one of claims 1 to 3, wherein The oxygen partial pressure was controlled to be 10 -14 . 0 ATM and above 10 -11 . 0 Within the range below atm.

5. The method according to any one of claims 1 to 4, wherein The heating temperature when heating and melting the raw materials is set to 1300° C. or higher and 1500° C. or lower.

6. The method according to any one of claims 1 to 5, wherein The valuable metal is composed of at least one metal or alloy selected from the group consisting of copper (Cu), nickel (Ni), cobalt (Co), and combinations thereof.

7. The method according to any one of claims 1 to 6, wherein The load contains spent lithium-ion batteries.

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