Methods for producing valuable metals

Abstract

To provide a method capable of effectively and stably removing impurities in recovering valuable metals from a raw material containing a waste lithium-ion battery.SOLUTION: A method for producing valuable metals from a raw material containing at least a waste lithium-ion battery includes a melting step for loading the raw material in a melting furnace, introducing a reducer containing carbon for reduction melting treatment, and thus separating slag and an alloy containing the valuable metals to recover the valuable metals. In the melting step, an induction furnace is used as the melting furnace for the reduction melting treatment. The induction furnace has a fire-resistant lining formed inside an induction heated crucible made of graphite.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a method for producing valuable metals, which separates and recovers valuable metals from raw materials including at least discarded lithium batteries. [Background technology]

[0002] In recent years, lithium batteries (also called "lithium ion batteries") have become popular as lightweight, high-power secondary batteries. Lithium batteries are generally made of a metal exterior can made of aluminum (Al) or iron (Fe), and are made up of a negative electrode material in which a negative electrode active material such as graphite is fixed to a negative electrode current collector made of copper foil, a positive electrode material in which a positive electrode active material such as lithium nickel oxide or lithium cobalt oxide is fixed to a positive electrode current collector made of aluminum foil, a separator made of a porous resin film such as polypropylene, and lithium hexafluorophosphate (LiPF 6 In the prior art, there are known electrolytes such as ethylene glycol, propylene glycol, propylene glycol stearate, propylene glycol terephthalate, propylene glycol fluoride ...

[0003] One of the main uses of lithium-ion batteries is in hybrid and electric vehicles. For this reason, it is expected that a large amount of lithium-ion batteries installed in these vehicles will be discarded in the future according to their life cycle. In addition, some lithium-ion batteries are discarded as defective products during manufacturing. There is a demand for recycling such used batteries and defective batteries generated during manufacturing (hereinafter referred to as "waste lithium-ion batteries") as resources.

[0004] As a method of recycling, a pyrometallurgical process has been proposed in which all used lithium-ion batteries are melted in a high-temperature furnace. In this process, crushed used lithium-ion batteries are melted in a high-temperature furnace, and valuable metals such as nickel (Ni), cobalt (Co), and copper (Cu) are recovered as metals while controlling oxidation-reduction.

[0005] Now, waste lithium-ion batteries contain impurities such as carbon (C), aluminum (Al), fluorine (F), and phosphorus (P) in addition to valuable metals such as nickel, cobalt, and copper. Therefore, in order to recover valuable metals from waste lithium-ion batteries, it is necessary to remove these impurities.

[0006] For example, Patent Document 1 discloses a process for recovering cobalt from used lithium-ion batteries by pyrometallurgy, in which used lithium-ion batteries are fed into a melting furnace and oxidized with oxygen. Although this process can recover cobalt at a high recovery rate, it does not disclose the removal of impurities such as phosphorus and manganese. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] Special Publication No. 2013-506048 Summary of the Invention [Problem to be solved by the invention]

[0008] The present invention has been proposed in consideration of the above-mentioned circumstances, and aims to provide a method for effectively and stably removing impurities when recovering valuable metals from raw materials including waste lithium-ion batteries. [Means for solving the problem]

[0009] The present inventors conducted extensive research and found that the above-mentioned problems could be solved by using an induction furnace in which a refractory lining is formed on the inside of a graphite induction heater crucible as a melting furnace for melting raw materials, and thus completed the present invention.

[0010] (1) A first aspect of the present invention is a method for producing valuable metals from raw materials including at least waste lithium-ion batteries, the method including a melting step of separating and recovering slag and an alloy including valuable metals by charging the raw materials into a melting furnace and introducing a reducing agent including carbon to perform a reducing melting process, the melting step being performed using an induction furnace as the reducing melting process, and the induction furnace has a graphite induction heater crucible with a refractory lining formed on the inside.

[0011] (2) A second aspect of the present invention is a method for producing valuable metals according to the first aspect of the present invention, wherein the refractory lining is made of a material that does not contain carbon.

[0012] (3) The third invention of the present invention is the first or second invention, wherein a gas analyzer is provided in the induction furnace, and carbon dioxide (CO 2 The method for producing valuable metals further comprises monitoring the change over time in the concentration of valuable metal in the refractory lining to detect damage to the refractory lining.

[0013] (4) The fourth aspect of the present invention is the third aspect of the present invention, wherein after the reaction of the reducing melting treatment is completed, the CO in the gas discharged from the induction furnace is 2 When the concentration exceeds 3%, it is determined that the refractory lining is damaged. Effect of the Invention

[0014] According to the present invention, impurities can be effectively and stably removed when valuable metals are recovered from raw materials including waste lithium ion batteries. [Brief description of the drawings]

[0015] [Figure 1] FIG. 2 is a cross-sectional view showing the configuration of an induction furnace, illustrating a structure in which a refractory lining is formed. [Diagram 2] 1 is a graph showing changes over time in furnace temperature and CO2 concentration in exhaust gas in Test Example 1. FIG. [Diagram 3] FIG. 13 is a graph showing the change over time in the furnace temperature and the CO2 concentration in the exhaust gas in Test Example 2. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0016] The method for producing valuable metals according to the present embodiment is a method for separating and recovering valuable metals from raw materials including at least waste lithium ion batteries. Therefore, it can also be said to be a method for recovering valuable metals. The method according to the present embodiment is mainly a method using a dry smelting process, but may be composed of a dry smelting process and a wet smelting process.

[0017] The concept of a waste lithium ion battery includes not only used lithium ion batteries, but also defective products generated during the manufacturing process of the positive electrode material constituting the battery, residues in the manufacturing process, scraps, and other waste materials generated during the manufacturing process of lithium ion batteries. Therefore, waste lithium ion batteries can also be called lithium ion battery waste. Valuable metals are nickel (Ni), cobalt (Co), copper (Cu), and combinations thereof, and are at least one metal or alloy selected from the group consisting of nickel (Ni), cobalt (Co), copper (Cu), and combinations thereof.

[0018] Specifically, the method according to the present embodiment includes a melting step in which raw materials including waste lithium ion batteries are charged into a melting furnace, and a reducing agent including carbon is introduced to perform a reduction melting process, thereby separating and recovering slag and an alloy including valuable metals. In the melting step, an induction furnace is used as the melting furnace for the melting process, and the induction furnace is characterized by using an induction heater crucible made of graphite with a refractory lining formed on the inside.

[0019] Here, as described above, waste lithium-ion batteries contain impurities such as carbon (C), aluminum (Al), fluorine (F), and phosphorus (P) in addition to valuable metals such as nickel (Ni), cobalt (Co), and copper (Cu). Therefore, in order to recover valuable metals from waste lithium-ion batteries, it is necessary to remove these impurities. Among these impurities, carbon (C) impedes the separation of metal and slag if it remains. In addition, carbon (C) contributes as a reducing agent, and may hinder the proper oxidative removal of other substances. In particular, among the above-mentioned impurities, phosphorus (P) has a relatively easily reduced property, so if the degree of reduction is adjusted too strongly to increase the recovery rate of valuable metals such as cobalt (Co), phosphorus (P) will not be oxidized and will remain in the metal. On the other hand, if the degree of reduction is adjusted too weakly, even the valuable metals will be oxidized, and the recovery rate will decrease. Therefore, in order to stably recover valuable metals and remove the impurity phosphorus (P), it is necessary to stably control the amount of carbon so that the degree of oxidation and reduction is appropriate.

[0020] In order to efficiently carry out the oxidation-reduction reaction of such waste lithium-ion batteries, it is necessary to be able to freely adjust the heat treatment atmosphere to an oxidizing atmosphere or a reducing atmosphere according to the step of the reaction process. For this reason, materials with high melting points and chemically stable properties, such as aluminum oxide, magnesium oxide, calcium oxide, etc., are used as crucible materials, and the atmosphere is controlled by adjusting the composition and pressure of the atmospheric gas in a relatively sealed furnace.

[0021] In addition, a high temperature of 1400°C or higher is required to melt the oxides contained in waste lithium-ion batteries, but when using an externally heated resistance heating electric furnace, a heater such as fragile silicon carbide or molybdenum disilicide must be used. In addition, in order to remove the molten material, the crucible must be removed from the furnace and then tilted, or a melt outlet must be provided at the bottom of the crucible and the plug must be removed to drain the molten material, which not only requires large-scale equipment, but also limits the size of the crucible due to the size of the heater.

[0022] In addition, although internally heated arc furnaces can produce a large amount of melt, they have a strong reducing effect due to the use of graphite electrodes, which reduces the metals contained in the furnace, such as phosphorus (P) and manganese (Mn), increasing the level of impurities and deteriorating the quality of the valuable metals obtained.

[0023] Furthermore, when copper smelting is carried out using converters that utilize the heat generated by oxidation, although copper and nickel can be recovered, cobalt is easily oxidized and distributed into the slag, making it impossible to recover the cobalt.

[0024] In contrast, induction furnaces that use induction heating can process large amounts of several tons, and the melting amount is not a problem for commercial use. However, there is a problem when performing processing to obtain valuable metals from waste lithium-ion batteries. That is, in the case of indirect heating furnaces that use induction heaters, a melting temperature of 1400°C or more is required, so graphite crucibles and carbon bond crucibles containing silicon carbide are generally used as induction heaters. By heating such crucibles to 1400°C or more, it becomes possible to easily melt the oxides of the insulators in the waste lithium-ion batteries. However, since the molten material comes into contact with graphite, oxides such as phosphorus (P) and manganese (Mn) are also reduced and alloyed into the valuable metals, which results in a decrease in the quality of the valuable metals.

[0025] Therefore, in the method according to the present embodiment, an induction furnace in which a refractory lining is formed on the inside of an induction heater crucible made of graphite is used.

[0026] This allows the degree of oxidation-reduction to be stably controlled while heating, making it possible to recover valuable metals at a high recovery rate and effectively remove impurities.

[0027] Fig. 1 is a cross-sectional view showing the configuration of an induction furnace, and is a diagram for explaining a structure in which a refractory lining is formed. As shown in Fig. 1, the induction furnace 1 is configured by including an induction heating crucible 11 made of graphite, and a refractory lining 12 formed on the inside thereof. The induction furnace 1 is a heating furnace that utilizes electromagnetic induction, and is configured by a coil (not shown) and a crucible (induction heating crucible 11) provided inside the coil.

[0028] The induction heater crucible 11 is a crucible made of graphite, which is a conductive material. A refractory lining 12, which will be described later, is formed on the inside of the induction heater crucible 11, and the material to be treated, i.e., raw materials including waste lithium-ion batteries, are placed inside the induction heater crucible 11, sandwiching the refractory lining 12. In other words, the graphite constituting the induction heater crucible 11 is not in contact with the raw materials including the waste lithium-ion batteries, which are the material to be treated.

[0029] When an AC magnetic field is generated by an AC current flowing through a coil (not shown) provided around the induction heater crucible 11, the induction heater crucible 11 is inductively heated by the AC magnetic field. The heat generated in the induction heater crucible 11 is transferred to the material to be treated (raw materials including waste lithium-ion batteries) contained inside.

[0030] The refractory lining 12 is a lining material formed on the inner surface of the graphite induction heater crucible 11. The refractory lining 12 is preferably made of a refractory material that does not contain carbon. For example, a carbon-free amorphous refractory material can be used. Specifically, the refractory lining 12 can be made of an oxide-based refractory material such as alumina, magnesia, or calcia.

[0031] As described above, in the induction furnace 1, heat generated by the induction current from the induction heater crucible 11 is transferred, and the heat from the induction heater crucible 11 is transferred to the material to be treated housed therein via the refractory lining 12, causing it to melt. Since the induction furnace 1 uses an external heating method that utilizes induction heating, it is not necessary to provide a graphite electrode inside the crucible, and it is possible to suppress the inclusion of carbon. In addition, heating can be performed in a relatively sealed atmosphere, and it is possible to stably control the degree of oxidation-reduction by adjusting the atmospheric gas components and pressure.

[0032] Here, in the melting process of raw materials including waste lithium-ion batteries in the induction furnace 1, the materials to be treated are those that can undergo a reduction reaction when they come into contact with carbon, such as iron oxide, silicon dioxide, and manganese oxide, so that if the induction furnace 1 provided with the refractory lining 12 is continuously used, the melting loss of the refractory lining 12 will gradually progress. Eventually, damage such as holes will occur in the refractory lining 12, and a reaction with the graphite constituting the induction heater crucible 11 on the outside will progress. This will disrupt the degree of reduction in the reduction melting reaction in the induction furnace 1, and the impurity grade in the valuable metals to be recovered will increase, which may result in a decrease in quality.

[0033] In addition, since the refractory lining 12 is provided inside the induction heater crucible 11, when it is heated to 1400°C or higher, the difference in thermal expansion coefficient causes distortion at the bonding surface between the refractory lining 12 and the induction heater crucible 11. This causes a problem that cracks are likely to occur at the bonding surface due to repeated heating and cooling. Furthermore, if the molten slag reacts with the graphite that constitutes the induction heater crucible 11 and creates a hole in the induction heater crucible 11, for example, the coil located on the back side may melt, and the cooling water flowing through the coil may react with the molten slag, causing a steam explosion.

[0034] Therefore, in the method according to the present embodiment, a gas analyzer is provided in the induction furnace 1, and the amount of carbon dioxide (CO 2 It is preferable to detect damage to the refractory lining 12 by monitoring the change in concentration of fluorine with time.

[0035] Nickel (Ni) and cobalt (Co) in the cathode material contained in the waste lithium-ion batteries are recovered as metals by reducing them as shown below. At this time, the reaction shown in the following reaction formula proceeds, and carbon dioxide (CO 2 )Gas is generated. 2LiNiO 2 +2C → Li 2 O+2Ni+CO 2 +CO 2LiCoO 2 +2C → Li 2 O+2Co+CO 2 +CO

[0036] In order to melt the raw materials and recover the metals, it is necessary to remove the impurities as oxides, and in order to separate and remove them as molten slag, it is preferable to add a flux such as calcium oxide and melt the slag at a temperature close to the melting temperature of the metals. The calcium oxide flux can be added as calcium carbonate, which has the advantage that it is inexpensive, and the following decomposition reaction occurs: CaCO 3 → CaO+CO 2

[0037] The completion of the reduction melting reaction in the induction furnace 1 can be confirmed by visually checking the state of the material being treated in the furnace. 2 Since this reaction involves CO 2 When almost no gas is generated, it can be determined that the reaction that should be proceeding in the furnace is almost complete, and the melting process is also being carried out properly. Therefore, after the reduction melting reaction is complete, CO 2 Gas generation is almost eliminated.

[0038] However, in the process of reduction melting, as the melting damage of the refractory lining 12 as described above occurs and progresses, the slag containing iron oxide, silicon dioxide, manganese oxide, etc. reaches and comes into contact with the graphite constituting the induction heater crucible 11, causing a reaction involving carbon, i.e., CO 2 A reaction occurs which produces gas.

[0039] From this, the CO in the gas discharged from the induction furnace 1 2 By monitoring the concentration and observing the change over time, damage to the refractory lining 12 can be detected, and it can be determined early on whether the refractory lining 12 is in a state where it needs repair or not.

[0040] More specifically, in a normal state where the refractory lining 12 is not damaged, such as having holes, after the reduction melting reaction is completed, CO 2 There is almost no gas generation. Therefore, the CO in the exhaust gas from induction furnace 1 2 Continuous monitoring of concentrations, e.g. CO 2 When the concentration becomes equal to or lower than a predetermined threshold value, the reaction end point of the reducing melting treatment can be determined, and it can also be determined that no damage has occurred to the refractory lining 12.

[0041] FIG. 2 shows the amount of CO in the exhaust gas accompanying the reduction melting reaction, as measured in the examples described later. 2 A graph showing the transition of CO concentration. 2 Regarding the transition of concentration, the reduction melting reaction starts and ends rapidly, so as shown in Figure 2, 2 The concentration increases rapidly from the start of the reaction, remains at almost the same value due to the rate-limiting movement at the reaction interface, and then rapidly decreases at the end, making it easy to determine the end of the reaction.

[0042] On the other hand, when the refractory lining 12 is damaged (for convenience, this is called an "abnormal state"), a reaction occurs between the slag and the graphite of the induction heater crucible 11 through the damaged portion, and CO 2 CO in the exhaust gas is generated.2 By continuously monitoring the concentration, it is possible to detect sufficient CO in the exhaust gas even after the reduction melting reaction has finished. 2 If the concentration does not decrease, it can be determined that damage such as holes has occurred in the refractory lining 12. By making such a determination, repair work for the refractory lining 12 can be carried out quickly before the next batch is made, and the problem can be easily dealt with by repair work alone without replacing the induction heater crucible 11.

[0043] FIG. 3, like FIG. 2, shows the amount of CO in the exhaust gas accompanying the reduction melting reaction, measured in the Examples described later. 2 3 is a graph showing the transition of the concentration of CO 2 The graph shows the transition of CO concentration in the exhaust gas, and except for the presence or absence of damage, the treatment was carried out under the same conditions as the treatment test shown in Figure 2. As shown in Figure 2, during the reduction and melting reaction, the CO concentration in the exhaust gas changes in the same way as in the graph in Figure 2. 2 The concentration of CO increases rapidly from the start of the reaction, remains almost constant due to the rate-limiting movement at the reaction interface, and then decreases rapidly. 2 However, the CO concentration shown in Figure 2 is the lowest. 2 As is clear from the comparison with the concentration behavior of CO 2 The rate of decline in concentration gradually weakens, e.g. CO 2 The concentration remains in the range above 3%.

[0044] This means that although the reduction melting reaction has ended, the refractory lining 12 is in an abnormal state of being damaged, and the slag in the induction furnace 1 comes into contact with the graphite constituting the induction heater crucible 11, causing a reaction involving carbon, i.e., CO 2 A gas-evolving reaction occurs, which results in CO 2 This can be attributed to the fact that the concentration was not sufficiently reduced.

[0045] Therefore, the CO in the exhaust gas 2By continuously monitoring the concentration, it is possible to easily and accurately judge from the change over time whether or not damage such as holes has occurred in the refractory lining 12. This enables more stable processing operations, and more effectively removes impurities such as phosphorus and manganese, enabling valuable metals to be recovered from waste lithium-ion batteries.

[0046] CO in exhaust gas 2 Measurement of concentration can be done, for example, with CO 2 This can be done using a gas analyzer capable of analyzing the concentration. The gas analyzer may be installed inside the induction furnace 1, for example, near the gas exhaust port that exhausts the gas in the induction furnace 1, or in an exhaust gas duct that is provided next to the gas exhaust port.

[0047] Regarding the determination of damage to the refractory lining 12, when the reduction melting reaction is completed, for example, the CO 2 The occurrence of damage can be judged by the concentration being preferably more than 3%, more preferably more than 4%. 2 A range of concentrations, e.g. CO 2 Damage may be determined to have occurred if the concentration remains above 3% for approximately 30 minutes and does not decrease.

[0048] In addition, CO in the exhaust gas 2 The judgment is not limited to the threshold value of the concentration. For example, the normal CO concentration as shown in Fig. 2 2 The concentration behavior may be stored in a database and compared with the behavior under normal conditions. 2 The transition of the decrease in concentration may be determined by calculating the difference in the rate of decrease, for example.

[0049] In addition, the CO in the exhaust gas 2 Prior to judging the occurrence of damage based on the change in concentration over time, the completion of the reduction melting reaction can be judged by visually checking the state (melting state) of the molten mass in the induction furnace 1. Alternatively, it can be confirmed by using a measuring stick.

[0050] CO in exhaust gas 2 If it is determined based on the concentration monitoring that the refractory lining 12 has been damaged, such as a hole, the damaged portion of the refractory lining 12 is confirmed after the induction furnace 1 is cooled, and the damaged portion is repaired with a monolithic refractory. For example, a repair work is performed by applying a monolithic refractory of the same material to the portion where the refractory lining 12 is missing. An example of the monolithic refractory is a castable refractory. In addition, when the CO 2 If the concentration remains in the range of 10% or more, it can be determined that the extent and degree of damage to the refractory lining 12 is large. Therefore, preparations are made to replace the induction furnace 1.

[0051] As shown in the above reaction formula, carbon monoxide (CO) is also generated in the reduction melting reaction. When some of the CO gas comes into contact with the raw materials charged into the induction furnace 1 or the slag, which is the oxide that is generated, it becomes CO. 2 Therefore, the CO concentration and CO 2 Comparing the concentrations, CO 2 Therefore, in another embodiment, a gas analyzer capable of analyzing the CO concentration may be provided in the induction furnace 1 to monitor the CO concentration to detect damage to the refractory lining 12. 2 It is more preferable to detect and determine the concentration by monitoring.

[0052] As described above, in the method according to the present embodiment, in the melting step in which raw materials including waste lithium-ion batteries are charged into a melting furnace and melted, an induction furnace 1 having a refractory lining 12 formed on the inside of a graphite induction heater crucible 11 is used as the melting furnace. This makes it possible to stably control the degree of oxidation-reduction while heating, recover valuable metals at a high recovery rate, and effectively remove impurities.

[0053] In addition, it is preferable to provide a gas analyzer in the induction furnace 1 and measure the amount of carbon dioxide (CO2 ) concentration over time is monitored to detect damage to the refractory lining. This makes it possible to easily and accurately determine the occurrence of damage to the refractory lining, such as holes that may occur due to repeated heating, and makes it possible to immediately carry out repair work, etc. The processing efficiency of the operation of recovering valuable metals while removing impurities can be improved. In other words, it is possible to more effectively and stably remove impurities such as phosphorus and manganese and recover valuable metals from waste lithium-ion batteries. EXAMPLES

[0054] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to the following examples in any way.

[0055] [Test Example 1] An externally heated high-frequency induction furnace was used, in which a refractory lining made of magnesia-based castable refractory material (material that does not contain carbon) was applied to the inside of a graphite induction heating crucible, and 50 kg of oxide powder particles, the mass ratio of which for the main elements is shown in Table 1 below, were placed in the induction heating crucible, and a reducing agent and flux were added to carry out a reduction melting test. Specifically, the reducing agent was an appropriate amount of reducing agent for reducing Cu, Ni, and Co, namely NiO 2 , CoO 2 2.35 kg of graphite powder was added in an amount equivalent to 1.1 times the amount of Al. 2 O 3 -CaO-Li 2 The amount of calcium carbonate in the sample was adjusted to 0.0 to melt the alumina in the sample by eutectic formation, i.e., the molar ratio was adjusted to CaCO 3 :Al 2 O 3 9.63 kg was added to give a ratio of 1:1.

[0056] [Table 1]

[0057] A lid was placed on the top of the induction furnace to prevent free air from entering from the outside, and a 5mm inner diameter, 8mm outer diameter alumina N 2 The gas supply pipe was attached so that its end was about 5 cm from the top of the crucible, which was 100 cm deep. 2 The gas was continuously supplied to the crucible from the time the temperature was raised to the time the molten metal was poured out at a flow rate of 30 L / min. This allowed the inert atmosphere to be maintained. 2 The gas supply rate was set to 30 L / min so that the gas inside the crucible with a capacity of 90 L could be replaced every 3 min.

[0058] In order to suck up the exhaust gas generated by the reaction, a suction tube was inserted into the furnace so that its end was 20 to 30 cm from the top of the MgO-based crucible, and connected to a gas analyzer (PG330P, manufactured by Horiba, Ltd.) and sucked in at 1 L / min. so that the fluctuations could be constantly monitored. A thermometer for controlling the inside of the furnace was placed so that it was in contact with the outside of the graphite crucible.

[0059] In Test Example 1, the carbon dioxide (CO 2 The concentration of fluorine was monitored and the presence or absence of damage to the refractory lining of the induction furnace was determined from the change over time.

[0060] [Test Example 2] In Test Example 2, a magnesia-based castable refractory running was used in which a hole was formed, and the surface of the graphite induction heater crucible was visually observed. The test was carried out under the same conditions as Test Example 1.

[0061] [result] Figure 2 (Test Example 1) and Figure 3 (Test Example 2) show the relationship between the temperature inside the furnace and the CO in the exhaust gas. 2 The change in concentration over time is shown.

[0062] As shown in FIG. 2, in Test Example 1, the reduction melting reaction was completed by visual inspection inside the furnace. After 10 hours from the start, the CO2 The occurrence of was rarely confirmed.

[0063] In contrast, as shown in FIG. 3, in Test Example 2, even after 10 hours from the start, the CO 2 The concentration has stopped decreasing at about 5%, and CO 2 Gas generation was observed. This was because the material being treated was completely melted in the furnace and the reduction melting reaction was completed, and the refractory lining was melted and the slag came into contact with the graphite and reacted, resulting in the generation of CO 2 It is believed that gas was generated.

[0064] In this way, the CO in the exhaust gas 2 It was found that by monitoring the concentration and checking the changes over time, it is possible to easily and accurately determine whether the refractory lining is being properly maintained. [Explanation of symbols]

[0065] 1 induction furnace 11 Induction heating crucible 12 Fire-resistant lining

Claims

1. A method for producing valuable metals from raw materials including at least waste lithium ion batteries, The method includes a melting step of charging the raw material into a melting furnace, introducing a reducing agent containing carbon to perform a reduction melting process, and separating and recovering slag and an alloy containing valuable metals, In the melting step, the reduction melting treatment is performed using an induction furnace as the melting furnace, The induction furnace has a graphite induction heater crucible with a refractory lining on the inside, a gas analyzer is provided in the induction furnace and a change over time in the concentration of carbon dioxide (CO 2 ) in the gas discharged from the induction furnace is monitored to detect damage to the refractory lining; A method for producing valuable metals.

2. The refractory lining is made of a material that does not contain carbon. The method for producing valuable metals according to claim 1.

3. After the reaction of the reduction melting treatment is completed, the CO in the gas discharged from the induction furnace ２ When the concentration is more than 3%, it is determined that the refractory lining is damaged. The method for producing valuable metals according to claim 1 or 2.

Images