JP2023028122A - Manufacturing method of valuable metal - Google Patents

Abstract

To provide a method capable of performing efficient treatment while suppressing damage to a furnace for performing melting treatment to raw materials, in a method of manufacturing a valuable metal from a raw material containing waste lithium ion secondary batteries.SOLUTION: The present invention relates to a method for manufacturing valuable metals from raw materials containing waste lithium ion batteries, including a reduction-melting process of charging the raw materials into a melting furnace, and applying reduction-melting treatment to the raw materials to obtain a reduction material including alloys containing valuable metals and a slag, and a slag separation process of separating the slag from the reduction material to recover the alloy. In the reduction-melting process, an electric furnace having an electrode inside is used as the melting furnace to apply the reduction-melting treatment. In the slag separation process, the alloy is discharged from a tap hole provided in the electric furnace, and the slag is discharged by tilting an electric furnace body through a gutter provided at a furnace body upper edge of the electric furnace.SELECTED DRAWING: Figure 1

Description

The present invention relates to a method for producing valuable metals from raw materials including waste lithium ion batteries.

In recent years, lithium-ion batteries have become popular as lightweight, high-output secondary batteries. A well-known lithium-ion battery has a structure in which a negative electrode material, a positive electrode material, a separator, and an electrolytic solution are enclosed in an outer can.

For example, the outer can is made of metal such as aluminum (Al) or iron (Fe). The negative electrode material is composed of a negative electrode active material (graphite, etc.) adhered to a negative electrode current collector (copper foil, etc.). The positive electrode material is composed of a positive electrode active material (lithium nickelate, lithium cobaltate, etc.) adhered to a positive electrode current collector (aluminum foil, etc.). The separator is made of a polypropylene porous resin film or the like. Electrolyte solutions include electrolytes such as lithium hexafluorophosphate (LiPF ₆ ).

One of the major uses of lithium-ion batteries is hybrid and electric vehicles. Therefore, it is expected that a large amount of lithium-ion batteries installed in automobiles will be discarded in the future in accordance with the life cycle of automobiles. Also, there are lithium ion batteries that are discarded as defective during manufacturing. It is desired to reuse such used batteries and defective batteries produced during manufacturing (hereinafter referred to as "waste lithium ion batteries") as resources.

As a recycling method, a pyrometallurgical refining process has been proposed in which the entire amount of waste lithium-ion batteries is melted in a high-temperature furnace. In the pyrometallurgical process, crushed waste lithium-ion batteries are melted, and valuable metals to be recovered, represented by cobalt (Co), nickel (Ni), and copper (Cu), iron (Fe) and aluminum This is a method of separating and recovering a low value-added metal represented by (Al) by utilizing the difference in oxygen affinity between them. In this method, metals with low added value are oxidized as much as possible to form slag, while the oxidation of valuable metals is suppressed as much as possible and recovered as alloys.

Patent Document 1 discloses a technique using such a pyrometallurgical process. Specifically, a method for recovering cobalt from a lithium ion battery containing aluminum and carbon comprising the steps of providing a bath furnace equipped with means for injecting oxygen and adding CaO as a slag forming agent and the lithium ion battery. providing a feedstock containing oxygen and feeding the feedstock to a furnace whereby at least some of the cobalt is reduced and collected in the metal phase; and tapping to remove slag from the metal phase. A method including a separating step is disclosed (Claim 1 of Patent Document 1).

Japanese Patent No. 5818798

Waste lithium-ion batteries contain various components, some of which have high melting points. Therefore, in order to melt a waste lithium ion battery, it is necessary to treat it at a high temperature, for example, a temperature of 1500° C. or higher.

Also, in order to efficiently recover valuable metals, it is important to control the degree of redox during the melting process. For example, waste lithium-ion batteries contain large amounts of impurities such as carbon (C), aluminum (Al), fluorine (F), and phosphorus (P). Of these, carbon (C) acts as a reducing agent, so if it remains in excess, it will hinder the removal of other impurities by oxidation. Also, excessive residual carbon interferes with the separation of alloy (metal) and slag. Furthermore, phosphorus (P) is an element that is relatively easily reduced. Therefore, unless the degree of redox is strictly controlled, the recovery rate of valuable metals is lowered. That is, if the degree of reduction is excessively high, phosphorus will not be removed by oxidation and will be mixed into the metal together with the valuable metal. On the other hand, if the degree of reduction is excessively low, even valuable metals are oxidized and cannot be recovered as alloys (metals).

Under these circumstances, conventional melting processes for waste lithium-ion batteries have used induction furnaces (induction heating furnaces), in particular, indirect heating induction furnaces, which can be maintained at high temperatures and can easily control the degree of oxidation-reduction. . An induction furnace is a heating furnace that utilizes electromagnetic induction, and is composed of a coil and a crucible provided inside the coil. In an induction furnace, passing an alternating current through a coil produces an alternating magnetic field that induces currents in the crucible or in the workpieces contained therein. The crucible or the workpiece is heated by the Joule heat of the induced current.

When a waste lithium ion battery is melted, a double crucible in which an oxide crucible is placed inside a graphite crucible is used, and the waste lithium ion battery is charged into the oxide crucible. When an electric current is applied to the coil, the graphite crucible is induction-heated, and the generated heat is transmitted to the waste lithium-ion battery via the oxide-based crucible. Since the induction furnace utilizes an external heating system using induction heating, it is not necessary to provide a graphite electrode inside the crucible. From this, it is possible to suppress the contamination of carbon as much as possible. In addition, since heating can be performed in a relatively closed atmosphere, the degree of redox can be controlled by adjusting the atmospheric gas components and pressure.

However, there are problems with the melting process using an induction furnace. That is, in order to melt a charged material containing valuable metals such as waste lithium-ion batteries, it is necessary to maintain the charged material at a high temperature, for example, 1500° C. or higher. However, since the induction furnace uses an external heating method, heat transfer loss occurs. For example, in order to maintain the charge at the melting temperature (for example, 1500° C. or higher), the temperature of the refractory (oxide crucible) containing the charge is set at the melting temperature or higher, specifically 1600° C. or higher. and maintained at that temperature. At such a high temperature, the slag erodes the refractory more intensely, making it difficult to suppress the melting damage of the refractory. In addition, the service life of the refractory (crucible) is also shortened.

As a result of investigations by the present inventors regarding such problems, a submerged arc furnace (hereinafter also simply referred to as an "electric furnace") provided with electrodes inside is used as a melting furnace, and the heat generated by the arc itself and It was found that by melting raw materials such as waste lithium-ion batteries with Joule heat, the melting damage of refractories can be significantly suppressed compared to the case of using an induction furnace. In addition, even if a graphite electrode is used as the electrode, by controlling the degree of oxidation-reduction in consideration of the amount of inflow from the electrode, valuable metals such as cobalt can be obtained at a high recovery rate, and at the same time phosphorus, manganese, etc. It was confirmed that the impurities of

However, when slag generated by melting waste lithium-ion batteries in an electric furnace is discharged from the electric furnace by tapping with a general slag hole, lithium is especially contained in the slag. There is a problem that the slag hole is easily damaged because the slag hole becomes damaged. If the slag hole is damaged, it is necessary to replace the slag hole bricks, which is costly and requires a considerable amount of work time for the replacement, resulting in a significant decrease in the operating rate.

The present invention has been proposed in view of such circumstances. It is an object of the present invention to provide a method that enables the processing of

As a result of extensive studies, the present inventors have found that when reducing and melting the raw material, an electric furnace equipped with an electrode inside is used, and the alloy (metal) obtained by the reduction melting process is discharged electrically. It was found that the above-mentioned problems can be solved by discharging the slag from the tap hole (metal hole) provided in the furnace and tilting the electric furnace main body from the gutter provided at the upper edge of the furnace body. , have completed the present invention.

(1) The first invention of the present invention is a method for producing valuable metals from raw materials including waste lithium ion batteries, wherein the raw materials are charged into a melting furnace and the raw materials are subjected to reduction melting treatment. and a slag separation step of separating the slag from the reduced product to recover the alloy, wherein the reducing melting step includes , reducing melting treatment is performed using an electric furnace having an electrode inside as the melting furnace, and in the slag separation step, the alloy is discharged from a tap hole provided in the electric furnace, and the furnace of the electric furnace This is a method for producing valuable metals, in which the slag is discharged by tilting the electric furnace body from a gutter provided on the upper edge of the body.

(2) A second aspect of the present invention is the method for producing a valuable metal according to the first aspect, wherein the electric furnace is a submerged arc furnace.

(3) A third aspect of the present invention is the method for producing a valuable metal according to the first or second aspect, wherein the slag temperature is set to 1500° C. or higher in the reduction melting step.

(4) A fourth invention of the present invention is the method for producing valuable metals according to any one of the first to third inventions, wherein the charging of the raw material into the electric furnace is performed by a batch system.

(5) A fifth aspect of the present invention is the method for producing a valuable metal according to any one of the first to fourth aspects, wherein the furnace wall of the electric furnace is made of a refractory containing carbon. be.

According to the present invention, in a method for producing valuable metals from raw materials including waste lithium-ion batteries, a method is provided in which damage to the furnace for melting the raw materials is suppressed and the processing can be performed efficiently. can provide.

It is a cross-sectional schematic diagram of a submerged arc furnace. BRIEF DESCRIPTION OF THE DRAWINGS It is process drawing which shows an example of the flow of the method of manufacturing a valuable metal from a waste lithium ion battery.

Specific embodiments of the present invention (hereinafter referred to as "present embodiments") will be described below. In addition, the present invention is not limited to the following embodiments, and various modifications are possible without changing the gist of the present invention.

≪1. Methods for producing valuable metals≫
The method of producing valuable metals according to the present embodiment is a method of separating and recovering valuable metals (Cu, Ni, Co) contained in waste lithium-ion batteries from raw materials including at least waste lithium-ion batteries. Therefore, this method can also be called a method for recovering valuable metals. The method according to the present embodiment is mainly a method by a pyrometallurgical process, but may be composed of a pyrometallurgical process and a hydrometallurgical process.

The method according to the present embodiment includes the following steps: a step of preparing raw materials including waste lithium ion batteries (preparing step); and a step of reducing, heating and melting the prepared raw materials to obtain a reduced product containing an alloy and slag. (Reduction melting step) and a step of separating the obtained slag to recover an alloy containing valuable metals (slag separation step). Here, in the reduction heating step, when heating and melting the raw material, an electric furnace having an electrode inside is used, and the raw material is charged into the electric furnace. In the electric furnace, the electrode is energized with the tip of the electrode immersed in the slag, and the raw material is heated and melted by heating due to arc discharge and Joule heat.

As described above, the method according to the present embodiment is a method for producing valuable metals from raw materials including at least waste lithium-ion batteries, and the valuable metals are recoverable objects such as copper (Cu), nickel (Ni), cobalt (Co), and at least one metal or alloy selected from the group consisting of combinations thereof.

[Preparation process]
In the preparation step, raw materials are prepared. The raw material includes at least waste lithium ion batteries, and is a processing target for recovering valuable metals. Valuable metals include at least one selected from the group consisting of copper (Cu), nickel (Ni), cobalt (Co), and combinations thereof. The raw material may contain these components (Cu, Ni, Co) in the form of metals or alloys, or in the form of compounds such as oxides. In addition to these components (Cu, Ni, Co) contained in the waste lithium ion battery, the raw material may contain other inorganic components and organic components.

The raw material may also contain other materials as long as it contains at least waste lithium ion batteries. For example, in addition to waste lithium ion batteries, raw materials may include electronic components, electronic devices, etc. containing dielectric materials or magnetic materials. Moreover, the form of the raw material is not limited as long as it is suitable for treatment in the subsequent steps. Furthermore, in the preparation process, the raw material may be subjected to a treatment such as pulverization to make it into a suitable form, or the raw material may be subjected to heat treatment, separation treatment, or the like to remove unnecessary components such as moisture and organic matter. good.

"Waste lithium-ion batteries" refers not only to used lithium-ion batteries, but also to defective products such as positive electrode materials that make up the battery during the manufacturing process, residues inside the manufacturing process, and lithium-ion waste such as generated scraps. This is a concept that includes waste materials in the battery manufacturing process. Therefore, waste lithium ion batteries can also be called lithium ion battery waste materials.

[Reduction melting process]
In the reduction melting process, raw materials including waste lithium ion batteries prepared in the preparation process are charged into the melting furnace, heated and subjected to reduction melting treatment to form a melt, and then the melt is made into an alloy (metal ) and slag.

The melt contains the alloy and slag in a molten state. Since the alloy and the slag have different specific gravities, the alloy and the slag positioned above the alloy are contained in the melt in a separated state. Also, the alloy mainly contains valuable metals, and the slag contains other components including impurity elements. Therefore, it becomes possible to separate the valuable metals and the other components respectively as the alloy and the slag. This is because metals with low added value (such as Al) have high affinity for oxygen, whereas valuable metals have low affinity for oxygen.

For example, aluminum (Al), lithium (Li), carbon (C), manganese (Mn), phosphorus (P), iron (Fe), cobalt (Co), nickel (Ni), and copper (Cu) are commonly Generally, they are oxidized in the order of Al>Li>C>Mn>P>Fe>Co>Ni>Cu. That is, aluminum (Al) is most easily oxidized, and copper (Cu) is most difficult to oxidize. Therefore, metals with low added value (such as Al) are easily oxidized into slag, and valuable metals (Cu, Ni, Co) are reduced into alloys. In this way, valuable metals and low value-added metals can be separated in the form of alloys and slag, respectively.

Here, the waste lithium ion battery contained in the raw material to be processed contains lithium (Li) derived from, for example, the positive electrode material of the battery. Lithium, as described above, has the property of being relatively easily oxidized among the elements constituting the waste lithium-ion battery. Therefore, lithium is easily oxidized and included in the slag by the reduction melting treatment of the raw material.

Now, in the method according to the present embodiment, reduction melting treatment is performed in an electric furnace having electrodes inside. In the reduction melting process, raw materials including waste lithium ion batteries are charged into an electric furnace, and then the electrodes are energized to melt the raw materials by heating by arc discharge and/or Joule heat. In this way, by using an electric furnace having electrodes inside and adopting an internal heating method in which heating is performed by the electrodes in the furnace, it is possible to prevent the refractory material forming the furnace wall from being damaged by melting.

That is, in the internal heating method, the temperature of the melt (melted raw material) located in the vicinity of the electrode becomes the highest. Therefore, the furnace wall of the electric furnace is maintained at a lower temperature than the melt. On the other hand, the conventional method using an induction furnace, for example, utilizes an external heating method in which raw materials are heated by heat transfer from a crucible that constitutes the induction furnace. In the external heating method, it is necessary to maintain the crucible at a higher temperature than the molten material, so there is a problem that the melting damage of the crucible refractory is large.

It is particularly preferable to use a submerged arc furnace as the electric furnace which is used in the reduction melting treatment and has electrodes therein. A submerged arc furnace is a type of arc furnace. An arc furnace is a furnace that utilizes the heat generated by the arc itself, and can achieve localized heating and rapid heating using ultra-high temperatures and high energy densities. Among arc furnaces, in a direct arc furnace, an electrode is installed above an object to be heated with a gap therebetween, and an arc is generated in the gap to heat the object to be heated. In an indirect arc furnace, an arc is generated between a plurality of electrodes to heat an object to be heated mainly by radiant heat. On the other hand, in a submerged arc furnace, a plurality of electrodes are buried (submerged) in an object to be heated, and Joule heat (electric resistance heat) is used together with heating by arc discharge. Specifically, in a submerged arc furnace, an arc discharge is generated between an electrode tip and an object to be heated, and the object (raw material) is heated by the arc. At the same time, a current flows between the electrodes (between the electrodes, the object to be heated, and the electrodes) through the object to be heated, and the object to be heated (slag) is also heated by Joule heat.

FIG. 1 is a schematic cross-sectional view of a submerged arc furnace. A submerged arc furnace 1 is composed of a furnace wall and hearth 11 made of refractory material, an electrode 12 and a throwing tube (raw material charging tube) 13 . In the submerged arc furnace 1, the raw material 2 is charged from the projection tube 13, the tip of the electrode 12 is immersed in the surface of the charged raw material 2, and the electrode 12 is energized. Then, the raw material 2 is melted by arc heating and Joule heat, and separated into a slag (slag layer) 3 and an alloy (alloy layer) 4 . In this way, by maintaining the state in which the tip of the electrode 12 is immersed in the slag 3, the slag 3 can be continuously heated, and the alloy 4 located below the slag 3 is heated by heat transfer from the slag 3. heated.

Thus, the submerged arc furnace has the feature of being able to efficiently heat with a small input power. In direct arc furnaces and indirect arc furnaces, since arc discharge occurs above the object to be heated, most of the generated heat is released into the atmosphere, resulting in large energy loss and uneconomical. In addition, dust is likely to be generated from the object to be heated due to the impact of the arc, so it is necessary to provide a dust disposal means or the like. Furthermore, when the electrodes are close to the furnace wall, the furnace wall refractory is susceptible to thermal damage, which may adversely affect the durability of the refractory. On the other hand, in the submerged arc furnace, the electrodes are covered with the object to be heated, so less heat is released into the atmosphere. In addition, since dust generation and thermal damage to the refractory are reduced, the cost of dust disposal and refractory replacement can be reduced. For these reasons, it becomes possible to recover valuable metals with high efficiency and low cost.

In particular, when processing raw materials including waste lithium ion batteries, the amount of slag generated is about three times as large as the amount of alloy generated in volume ratio. Ensuring heat transfer to the alloy through the slag is important in maintaining the alloy in a molten state. In addition, since the lithium component contained in the waste lithium-ion battery becomes slag as described above, it has a strong effect of eroding the refractory at high temperatures, and it is important to suppress this erosion. In this regard, in direct arc heating furnaces and indirect arc heating furnaces, only the slag surface is locally heated by arc discharge, and therefore, it is necessary to increase the input power in order to melt the entire alloy. In contrast, the submerged arc furnace uses not only arc discharge but also Joule heat, so heat is effectively conducted to the alloy through the slag, enabling efficient heating even with a small amount of input power. becomes. In addition, in the submerged arc furnace, since the electrode tip is buried in the slag, the heat distribution is relatively uniform and heat spots are less likely to occur. Even if it is contained, it is possible to suppress refractory melting damage.

Further, in the method according to the present embodiment, when the molten alloy and slag obtained by the reduction melting treatment are discharged and recovered, the metal is discharged from the electric furnace through the tap hole, and the metal is discharged from the electric furnace. The slag is discharged from the furnace by tilting the furnace body through a gutter provided at the upper edge of the furnace body.

As described above, when melting raw materials including waste lithium ion batteries, it is necessary to operate at a high temperature. Also, the raw material contains lithium, which is distributed to the slag at a rate of almost 100%. In this way, the operating temperature is high (for example, the operation is performed so that the slag temperature is 1500 ° C. or higher), and the slag contains lithium and produces slag with a high basicity. Melting damage of the refractory becomes very large. Therefore, in the method according to the present embodiment, instead of discharging the slag generated by the reduction melting process from the electric furnace by tapping from the slag hole as in the conventional method, a This is done by tilting the electric furnace (furnace body) through the gutter. In addition, in the configuration diagram of FIG. 1, the gutter provided on the upper edge portion 11a of the furnace body is denoted by reference numeral "14".

As a result, it is possible to more effectively suppress the melting damage of the refractory when the slag is discharged. In addition, the wear and tear of the refractory can be easily dealt with by performing minor repairs such as regular maintenance of the gutter 14, thereby effectively suppressing deterioration in operating efficiency. As for the maintenance of the gutter 14, for example, easy maintenance such as repairing a portion where wear has occurred using a monolithic refractory material for repair can be mentioned. Also, such slag discharge is particularly preferred if the bricks forming the gutter for slag discharge do not have a cooling structure.

Since the slag is discharged by tilting the furnace body 1A through the gutter 14 provided on the upper edge portion 11a of the furnace body, it is preferable to charge the raw material into the electric furnace 1 in a batch manner. . That is, as shown in FIG. 1, after the raw material 2 is charged on the upper surface of the slag 3 layer, the raw material is melted, and the metal 4 contained in the melted raw material is transferred to the metal 4 layer located below the slag 3 layer. It is preferable to operate in a cycle in which the slag 3 is discharged after the metal 4 has settled.

On the other hand, the alloy (metal) is discharged by tapping from a metal hole (tap hole) 15 provided in the electric furnace. When discharging the metal separated from the slag to the lower layer, if the furnace body is tilted and discharged in the same way as the slag, the electric furnace will run out of slag and the electric furnace will not be able to supply power after that, and it will be necessary to restart the furnace. becomes. On the other hand, the metal is discharged from the tap hole (metal hole 15), and the slag is discharged from the gutter provided at the upper edge of the furnace body by tilting the furnace body as described above. can be left in the furnace, which enables energization by the graphite electrodes and enables continuous operation.

Also, by discharging the metal through the metal hole 15, it is possible to prevent slag from being mixed in during the discharge.

The installation position of the metal hole 15 is not particularly limited, but for example, it corresponds to the side wall of the electric furnace and the height position where the molten material obtained by the reduction melting process is separated by specific gravity and the metal layer is formed. It can be prepared in a position to do so.

In the reduction melting process, it is preferable to provide a covering layer made of the additional raw material by charging additional raw material onto the generated slag (open chalk feed). As a result, the raw materials are efficiently heated and melted. That is, high-temperature gas is generated when the raw material is heated and melted, but by forming a covering layer made of the raw material on the upper surface of the slag, heat exchange occurs between the high-temperature gas and the raw material, and the generated heat can be effectively used for melting the raw material.

Moreover, in the reduction melting treatment, it is preferable to adjust the immersion depth of the electrode according to the melting point of the alloy to be produced. When the melting point of the alloy is very close to the melting point of the slag, or when the melting point of the alloy is higher than the melting point of the slag, it becomes difficult for the alloy to remain molten. For example, in such a case, the electrodes are immersed deep inside the slag. As a result, the Joule heat generated at the tip of the electrode is easily transmitted to the alloy, so that the alloy can be easily maintained in a molten state. On the other hand, when the melting point of the alloy is lower than the melting point of the slag, the alloy can be sufficiently maintained in a molten state even if the electrode is immersed in a shallow depth.

A graphite electrode can be used as the electrode of the electric furnace. According to the inventors' investigation, even with internal heating using graphite electrodes, the amount of carbon taken into the object to be heated (raw material) is not so large, and there is no problem in controlling the degree of oxidation reduction. . Further, by investigating in advance the amount of carbon taken into the object to be heated, the carbon taken in from the electrode can be used as a reducing agent. As a result, when a reducing agent such as carbon is added to adjust the degree of reduction, the amount of the reducing agent used can be reduced.

Further, if necessary, an electrode control device for adjusting the vertical position of the electrode, that is, a device for controlling the electrode position so that the applied current value is constant may be provided. As a result, even if the surface position of the raw material (or the molten body in which it is melted) fluctuates up and down during the operation of the electric furnace, the distance between the electrode tip and the surface of the object to be heated can be maintained at a constant distance, or the electrode tip can be The state of being immersed at a certain distance from the surface of the object to be heated can be maintained, and stable heating becomes possible.

In the reduction melting treatment, a reducing agent may be introduced (added) to the raw material. Carbon and/or carbon monoxide is preferably used as the reducing agent. Carbon has the ability to easily reduce valuable metals (Cu, Ni, Co) to be recovered. For example, 1 mol of carbon can reduce 2 mol of valuable metal oxides (copper oxide, nickel oxide, etc.). Therefore, by introducing an appropriate amount of carbon, the degree of redox can be strictly adjusted. In addition, the reduction method using carbon or carbon monoxide is extremely safe compared to the method using a metal reducing agent (for example, the thermite reaction method using aluminum). Artificial graphite and/or natural graphite can be used as the carbon, and coal or coke can also be used if there is no risk of impurity contamination.

In addition, in the reduction melting treatment, flux may be introduced (added) to the raw material. By adding flux, the melting temperature can be lowered and the removal of phosphorus (P) can be further promoted. The flux preferably contains an element that takes in impurity elements to form a basic oxide with a low melting point. Phosphorus becomes an acidic oxide when oxidized. Therefore, the more basic the slag produced by the reduction melting treatment, the easier it is to incorporate phosphorus into the slag and remove it. Among them, those containing calcium compounds that are inexpensive and stable at room temperature are more preferable. Examples of calcium compounds include calcium oxide (CaO) and calcium carbonate (CaCO ₃ ).

The heating temperature in the reduction melting treatment is not particularly limited, but it is preferable to set the slag temperature (slag heating temperature) to 1500° C. or higher. By setting the heating temperature as such, the slag and the metal can be efficiently separated from the molten raw material (melt).

Regarding the electric furnace that performs reduction melting treatment, the material of the refractory in contact with the melt inside the furnace is preferably MgO—C refractory containing carbon at a ratio of more than 0% and 20% or less. Preferably, by using such a MgO-C refractory, it can withstand operation at high temperatures and has high thermal conductivity. Slag coating can be easily made on the wall, and the furnace wall can be effectively protected.

[Preheating step (oxidizing roasting step)]
In the method according to the present embodiment, if necessary, a step of preheating (oxidizing roasting) the raw material to obtain a preheated product (oxidizing roasting product) prior to the reduction melting treatment (treatment in the melting step). (Preheating step) can be provided.

In the preheating step, by preheating the raw material to be supplied to the melting step, the amount of carbon contained in the raw material is reduced. By providing such a preheating step, even if the raw material to be subjected to the melting step contains excessive carbon, the carbon can be effectively oxidized and removed, and the heating and melting in the subsequent melting step can be performed. can promote alloy integration of valuable metals in the processing of

More specifically, in the heating and melting process in the melting process, the valuable metal is reduced and becomes locally molten fine particles. It can be a physical obstacle. If the agglomeration and integration of molten fine particles is hindered, the separation of the produced alloy and slag may be hindered, resulting in a decrease in the recovery rate of valuable metals. On the other hand, by preheating the raw material in the preheating process to remove the carbon prior to the heat melting process, the aggregation and integration of the molten fine particles can be efficiently advanced, and the recovery rate of the valuable metal can be improved. It is possible to raise it further. In addition, since phosphorus is an impurity element that is relatively easily reduced, if carbon is excessively present in the raw material, phosphorus may be reduced and incorporated into the alloy together with the valuable metal. In this respect as well, by removing excess carbon in the raw material in advance by preheating, it is possible to prevent phosphorus from being mixed into the alloy.

The carbon content of the preheated product (oxidized roasted product) obtained by the preheating treatment is preferably less than 1% by mass.

In addition, by providing a preheating step, variations in oxidation can be suppressed. The preheating treatment in the preheating step can be performed at an oxidation degree (oxidative roasting) that can oxidize low-value-added metals (such as Al) contained in the raw material to be subjected to the melting step. desirable. On the other hand, the degree of oxidation can be easily controlled by adjusting the treatment temperature, time and/or atmosphere of preheating. Therefore, in the preheating process, the degree of oxidation can be adjusted more strictly, and variations in oxidation can be suppressed.

The degree of oxidation is adjusted as follows. As mentioned above, aluminum (Al), lithium (Li), carbon (C), manganese (Mn), phosphorus (P), iron (Fe), cobalt (Co), nickel (Ni) and copper (Cu) are , generally in the order of Al>Li>C>Mn>P>Fe>Co>Ni>Cu. In the preheating step, if aluminum (Al) is contained in the raw material, oxidation is allowed to progress until all of the Al is oxidized. Oxidation may be accelerated until some of the iron (Fe) is oxidized, but it is preferable to limit the degree of oxidation to such an extent that cobalt (Co) is not oxidized and distributed to the slag.

The preheating treatment is preferably performed in the presence of an oxidizing agent. As a result, carbon (C), which is an impurity element, can be efficiently removed by oxidation. The oxidizing agent is not particularly limited, but an oxygen-containing gas (air, pure oxygen, oxygen-enriched gas, etc.) is preferable because it is easy to handle. Moreover, the amount of the oxidizing agent to be introduced is preferably, for example, about 1.2 times the chemical equivalent required for oxidizing each substance to be oxidized.

The heating temperature for preheating is preferably 700° C. or higher and 1100° C. or lower. If the temperature is 700° C. or higher, the oxidation efficiency of carbon can be further increased, and the oxidation time can be shortened. Further, by setting the temperature to 1100° C. or less, the thermal energy cost can be suppressed and the efficiency of preheating can be improved. Also, the preheating temperature may be 800° C. or higher or 900° C. or lower.

The preheating treatment can be performed using a known roasting furnace. Moreover, it is preferable to use a furnace (preliminary furnace) different from the melting furnace used in the subsequent melting process, and to carry out the treatment in the preliminarily furnace. As the preheating furnace, any type of furnace can be used as long as it is a furnace capable of performing an oxidation treatment inside by supplying an oxidizing agent (such as oxygen) while roasting the raw material to be treated. Examples include conventionally known rotary kilns and tunnel kilns (Haas furnaces).

[Slag separation process]
In the slag separation step, slag is separated from the melt obtained by heating and melting in the melting step to recover an alloy containing valuable metals. In the melt, the alloy and slag have different specific gravities. Therefore, the slag having a lower specific gravity than the alloy gathers in the upper part of the alloy, and the slag can be easily separated and recovered by specific gravity separation.

In the method according to the present embodiment, in the slag separation step, as described above, the alloy is discharged from the tap hole provided in the electric furnace, and the alloy is discharged from the gutter provided at the upper edge of the furnace body of the electric furnace. Slag is discharged by tilting the electric furnace body. By doing so, it is possible to effectively suppress the melting damage of the refractory material forming the furnace wall when the slag is discharged. In addition, the wear and tear of the refractory can be easily dealt with by performing minor repairs such as periodic maintenance of the gutter, effectively suppressing a decline in operating efficiency.

After the slag is separated in the slag separation step, a sulfurization step of sulfurizing the obtained alloy or a pulverization step of pulverizing the obtained sulfide or alloy may be provided. Further, alloys of valuable metals obtained through such pyrometallurgical processes may be subjected to hydrometallurgical processes. By the hydrometallurgical process, impurity components can be further removed, valuable metals (eg, Cu, Ni, Co) can be separated and refined, and each of them can be recovered. Examples of treatments in the hydrometallurgical process include known techniques such as neutralization treatment and solvent extraction treatment.

≪2. Method for producing valuable metals from waste lithium-ion batteries>>
FIG. 2 is a process chart showing an example of the flow of a method for producing valuable metals from waste lithium ion batteries. As shown in FIG. 2, this method includes a step of removing the electrolytic solution and outer can of the waste lithium ion battery to obtain the waste battery contents (waste battery pretreatment step S1), and pulverizing the waste battery contents. A step of forming a pulverized product (pulverizing step S2), a step of preheating the pulverized product to obtain a preheated product (preheating step S3), and a step of melting the preheated product to obtain a melt (reduction melting step S4 ) and a step of separating slag from the melt to recover the alloy (slag separation step S5).

Moreover, although not shown, a sulfurization step of sulfurizing the obtained alloy and a pulverizing step of pulverizing the obtained sulfide or alloy may be provided after the slag separation step S5.

[Waste battery pretreatment process]
The waste battery pretreatment step S1 is performed for the purpose of preventing the waste lithium ion battery from exploding and rendering it harmless. Since the lithium ion battery is a closed system, it contains an electrolytic solution and the like inside. Therefore, if the pulverization treatment is performed as it is, there is a risk of explosion, which is dangerous. It is preferable to perform discharge treatment or electrolytic solution removal treatment by some method. In this manner, by removing the electrolytic solution in the waste battery pretreatment step S1, it is possible to perform treatment with improved safety.

A specific method for the waste battery pretreatment is not particularly limited. For example, there is a method of physically piercing the waste battery with a needle-like cutting edge and removing the electrolyte. Another method is to heat the waste battery and burn the electrolytic solution to render it harmless.

[Pulverization process]
In the pulverization step S2, the content of the waste lithium ion battery is pulverized to obtain a pulverized material. The purpose of the pulverization step S2 is to increase the reaction efficiency in the pyrometallurgical process. By increasing the reaction efficiency, the recovery rate of valuable metals (Cu, Ni, Co) can be increased. A specific pulverization method is not particularly limited. It can be pulverized using a conventionally known pulverizer such as a cutter mixer.

Aluminum (Al) and iron (Fe), which are metals constituting the outer can, can be easily physically sorted by an aluminum sorter using an eddy current, a magnetic sorter, or the like. In addition, using a shaking sieve machine or the like, a foil-shaped negative electrode current collector (copper foil, etc.) or a positive electrode current collector (aluminum foil, etc.) (hereinafter also referred to as "foil material") is sieved as a sieve. As a powdery negative electrode active material (graphite, etc.) or a positive electrode active material (lithium nickelate, lithium cobaltate, etc.) (hereinafter also referred to as “powder”) can be obtained.

The waste battery pretreatment process and the crushing process together correspond to the preparatory process described above.

[Preheating step]
In the preheating step (oxidizing roasting step) S3, at least the powdery material obtained in the pulverizing step S2 is preheated (oxidizing roasting) to obtain a preheated product (oxidizing roasting product). The details of this step are as described above, and by preheating in the preheating step, even if the raw material to be subjected to the reduction melting step S4 contains excessive carbon, the carbon can be effectively oxidized. It can be removed and can promote the alloying integration of valuable metals in the process of heat melting.

[Reduction melting process]
In the reduction melting step S4, the preheated material obtained in the preheating step S3 is heated and melted to obtain a molten material composed of the alloy and slag. The details of this step are as described above.

In particular, in the method according to the present embodiment, reduction melting is performed using an electric furnace having electrodes inside. In the reduction melting treatment, a preheated material is charged into an electric furnace, and then the electrode is energized to melt the preheated material (charged material) by heating by arc discharge and/or Joule heat. In this way, by using an electric furnace having electrodes inside and adopting an internal heating method in which heating is performed by the electrodes in the furnace, it is possible to prevent the refractory material forming the furnace wall from being damaged by melting. In particular, it is preferable to use a submerged arc furnace as an electric furnace having electrodes inside.

[Slag separation process]
In the slag separation step S5, slag is separated from the melt obtained in the reduction melting step S4 to recover the alloy. The details of this step are as described above.

In particular, in the method according to the present embodiment, when the molten alloy and slag obtained by the reduction melting treatment are discharged and recovered, the metal is discharged from the electric furnace through the tap hole, and the metal is discharged from the electric furnace. The slag is discharged from the inside by tilting the furnace body through a gutter provided at the upper edge of the furnace body. As a result, it is possible to effectively suppress the melting damage of the refractory material forming the furnace wall when discharging the slag. In addition, the wear and tear of the refractory can be easily dealt with by performing minor repairs such as periodic maintenance of the gutter, effectively suppressing a decline in operating efficiency.

In addition, you may provide a sulfuration process and a grinding|pulverization process after a slag separation process. Further, a hydrometallurgical process may be performed on the obtained alloy of valuable metals.

EXAMPLES 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.

(1) Production of valuable metal <<Example 1>>
Using a waste lithium ion battery as a raw material, the following steps were sequentially performed to produce a valuable metal. The raw material was heated and melted using an electric furnace (submerged arc furnace) equipped with electrodes inside.

[Waste battery pretreatment process, pulverization process (preparation process)]
After detoxifying the raw material waste lithium ion battery, it is roughly crushed using a crusher to a size of 5 mm or less, and the aluminum (Al) and iron (Fe) that make up the outer can are separated by an aluminum sorter and a magnetic force sorter. After that, a shaking sieve machine was used to obtain a foil-like substance above the sieve and a powdery substance below the sieve.

[Preheating step]
The resulting powdery material was preheated at 800° C. (oxidizing roasting) to remove carbon, thereby obtaining a preheated material (oxidizing roasting material). The carbon content of the preheated product was less than 1% by mass.

[Reduction melting process]
1.14 kg of carbon powder was added as a reducing agent, and 7.52 kg of calcium carbonate (CaCO ₃ ) was added as a flux to a total of 50 kg of the obtained preheated material and foil-like material. The amount of the reducing agent added was adjusted so as to be an appropriate amount for reducing copper (Cu), nickel (Ni), and cobalt (Co) in the preheated material. The amount of flux added was adjusted so that the calcium oxide and alumina eutecticized to lower the melting point of the slag.

Next, the mixture of the preheated material, the reducing agent, and the flux is charged into an electric furnace (submerged arc furnace) as shown in FIG. It was heated and melted under the conditions. A slag and an alloy were thus obtained.

Here, the electric furnace had a side wall (furnace wall) in the furnace made of heat-insulating bricks and had an inner diameter of 800 mm. The electric furnace had three graphite electrodes inside, and had a rated output of 199 kVA and a maximum voltage of 228V. Furthermore, the treatment was performed by arranging the electrodes so that the tips of the graphite electrodes did not come into contact with the molten alloy. Furthermore, tap holes for discharging metal by tapping are provided in the side wall of the electric furnace, and a gutter for discharging slag is provided at the upper edge of the furnace body.

[Slag separation process]
After the reduction melting treatment, the produced slag was separated and the alloy was recovered. At this time, the metal was discharged from the electric furnace through a tap hole, and the slag was discharged by tilting the furnace body through a gutter provided at the upper edge of the furnace body.

<<Comparative Example 1>>
A mixture of a preheated material, a reducing agent, and a flux was used as a raw material, and an electric furnace different from the electric furnace used in Example 1 was used to heat and melt this raw material. Specifically, an electric furnace having a metal hole for discharging metal and a slag hole for discharging slag on the side wall of the furnace is used, and metal and slag are discharged from the electric furnace. was performed by tapping through each tap hole. Valuable metals were produced in the same manner as in Examples except for the above.

(2) Evaluation Various properties of the treatments in Example 1 and Comparative Example 1 were evaluated as follows.

[Component analysis]
The preheated material and the alloy and slag after cooling were pulverized, and component analysis was performed on each of them by fluorescent X-rays. Also, from the content of each element, the distribution ratio to each of the alloy and slag was calculated.

[Amount of refractory melt]
The amount of melt loss of the refractory material constituting the furnace wall of the electric furnace used in the reduction melting process (reduction melting process) was visually evaluated.

(3) Results Table 1 below shows the compositions of the preheated materials obtained in Example 1 and Comparative Example 1. The preheated material mainly contains copper (Cu), nickel (Ni), cobalt (Co), aluminum (Al), lithium (Li), iron (Fe), and manganese (Mn), and a small amount of It contained phosphorus (P) and silicon (Si). The composition shown in Table 1 is a value in "% by mass".

Table 2 below shows the distribution ratio of each element to the alloy and slag. As shown in Table 2, the valuable metals copper (Cu), nickel (Ni), and cobalt (Co) were partitioned into the alloy (metal) at high partition ratios. In contrast, manganese (Mn), phosphorus (P), aluminum (Al), lithium (Li), silicon (Si), and calcium (Ca) were mostly partitioned into the slag. From this, the recovery rate of copper (Cu), nickel (Ni), and cobalt (Co) is all high, and the components to be removed such as manganese (Mn) and phosphorus (P) can be almost removed from the alloy. confirmed.

Table 3 below shows the content of phosphorus (P) in the alloy, the distribution ratio of cobalt (Co) to the alloy, and the amount of refractory melt loss for each of Example 1 and Comparative Example 1. As shown in Table 3, in both the electric furnace used in Example 1 and the electric furnace used in Comparative Example 1, the cobalt (Co) recovery rate was as high as over 95%, and Phosphorus (P) grade was less than 0.001% by mass, and good results were obtained.

On the other hand, with respect to the melting damage of the refractory, in the electric furnace used in Comparative Example 1, the melting damage inside the hole of the slag hole bricks was 4 mm after processing 50 kg in total 6 times. On the other hand, in the electric furnace used in Example 1, the melting damage of the magnesia in the gutter provided at the upper edge of the furnace body of the electric furnace was as small as 1 mm after processing 50 kg in total 6 times. rice field. Regarding the extent of this wear and tear, in Comparative Example 1, the slag hole bricks need to be reloaded after a total of 50 kg x 30 treatments. The damage was such that only minor repairs were necessary.

As described above, according to the method of Example 1, it was found that valuable metals can be produced effectively while effectively suppressing the wear and tear of the electric furnace for performing the reduction melting treatment.

1 electric furnace (submerged arc furnace)
1A Furnace body 11 Furnace wall and hearth 11a Furnace body upper edge 12 Electrode 13 Throw tube (raw material input tube)
14 gutter 15 metal hole 2 raw material 3 slag 4 metal (alloy)

Claims (5)

A method for producing valuable metals from raw materials including waste lithium ion batteries, comprising:
a reduction melting step of charging the raw material into a melting furnace and subjecting the raw material to a reduction melting treatment to obtain a reduced product containing an alloy containing a valuable metal and slag;
a slag separation step of separating slag from the reduced product and recovering the alloy;
In the reduction melting step, an electric furnace having an electrode inside is used as the melting furnace to perform reduction melting treatment,
In the slag separation step, the alloy is discharged from a tap hole provided in the electric furnace, and the electric furnace body is tilted from a gutter provided at the upper edge of the furnace body of the electric furnace. discharge slag,
A method for producing valuable metals. The electric furnace is a submerged arc furnace,
The method for producing a valuable metal according to claim 1. In the reduction melting step, the slag temperature is treated to be 1500 ° C. or higher.
3. The method for producing a valuable metal according to claim 1 or 2. The charging of the raw material into the electric furnace is performed by a batch method,
4. The method for producing a valuable metal according to any one of claims 1 to 3. The electric furnace has a furnace wall made of a refractory containing carbon,
5. The method for producing a valuable metal according to any one of claims 1 to 4.

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