JP2021155762A - Method for recovering valuable metal, and magnesia refractory material - Google Patents

Abstract

To provide a method for inexpensively recovering valuable metal by using a long-life refractory material, and a long-life refractory material that is used when recovering valuable metal.SOLUTION: A method for recovering valuable metal including the following processes: a process of preparing a charging material including at least valuable metal and lithium (Li); and a process of applying oxidation treatment and reducing/melting treatment to the charging material to obtain a reduced object including molten alloy and slag, in which an object to be treated is heated in a heating furnace when performing the reducing/melting treatment, and the heating furnace has a magnesia refractory material containing a boron component.SELECTED DRAWING: Figure 1

Description

The present invention relates to a method for recovering valuable metals and a magnesia refractory.

In recent years, a lithium ion battery (hereinafter, may be referred to as "LiB") has become widespread as a lightweight and high output battery. 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 sealed 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 made of a negative electrode active material (graphite or the like) fixed to a negative electrode current collector (copper foil or the like). The positive electrode material is made of a positive electrode active material (lithium nickel oxide, lithium cobalt oxide, etc.) fixed to a positive electrode current collector (aluminum foil, etc.). The separator is made of a polypropylene porous resin film or the like. The electrolytic solution contains an electrolyte such as lithium hexafluorophosphate (LiPF _6).

One of the main applications of lithium-ion batteries is hybrid vehicles and electric vehicles. Therefore, it is expected that a large amount of lithium-ion batteries to be installed will be discarded in the future according to the life cycle of the automobile. There are also lithium-ion batteries that are discarded as defective products during manufacturing. It is required to reuse such used batteries and defective batteries generated during manufacturing (hereinafter, "waste lithium ion batteries" or "waste batteries") as resources.

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

In the recovery of valuable metals by the pyrometallurgical process, a refractory material such as a magnesia crucible with high corrosion resistance is used for melting treatment. For example, Patent Document 1 describes a method for recovering a valuable metal from a waste lithium ion battery by adding graphite powder (reducing agent) to the obtained oxidized roasted product in a reduction melting step, mixing the mixture, and oxidizing the crucible made of magnesia. It is described that a valuable metal is alloyed by charging with a physical flux and heating by resistance heating to perform a reduction melting treatment (Patent Document 1 [0057]).

Further, although the purpose is not to recover valuable metals from waste lithium ion batteries, a crucible having a laminated structure of a carbonaceous component and ceramics such as magnesia has been proposed. For example, Patent Document 2 discloses a crucible for an induction heating furnace including an inner layer made of a refractory material mainly containing magnesia and the like and an outer layer made of a conductive material such as carbon (Patent Document 2). 1, 2 and [0021]). Further, Patent Document 3 discloses a carbon crucible in which a molten metal is ejected from a tip by gas pressure and is characterized by being coated with ceramic (claim 1 of Patent Document 3). ). Further, Patent Document 4 describes a crucible for arc melting of a highly active metal, which is characterized by being formed from an inner crucible made of a non-reactive material such as graphite and an outer crucible made of an insulating and heat insulating material such as magnesia. Is disclosed.

International Publication No. 2019/135321 JP-A-2015-55462 Japanese Unexamined Patent Publication No. 3-1354 Japanese Unexamined Patent Publication No. 64-67590

In this way, when recovering valuable metals from waste lithium-ion batteries in the pyrometallurgical process, melting treatment is performed using a crucible such as a magnesia crucible with high corrosion resistance. Further, although it is not intended to recover valuable metals, a crucible having a laminated structure of a carbonaceous component and ceramics such as magnesia has been proposed.

However, as a result of investigation by the present inventors, when recovering valuable metals in a pyrometallurgical process, if a melting process is performed using a magnesia crucible as disclosed in Patent Document 1, there is a problem that the life of the crucible is short. It turned out that there was. Therefore, when the melting (melting) process is repeated, the melt (melt) may leak from the crucible into the melting furnace. More specifically, when the alloy melt obtained from the waste lithium ion battery is held in the crucible and melted, it is separated into slag and metal, and lithium (Li) is distributed to the slag. The lithium-containing slag melt is extremely corrosive, and even a single batch of treatment will corrode the crucible just before it breaks, centering on the slight width of the slag liquid level. In addition, the crucible may be damaged during the test due to slight fluctuations in the test conditions, and the melt may leak into the melting furnace. Therefore, it is necessary to replace each batch of the melting process with a new crucible, which causes major problems in terms of operation efficiency and material cost.

Further, the crucible having a laminated structure of a carbonaceous component and ceramics proposed in Patent Documents 2 to 4 is not used when recovering a valuable metal in a pyrometallurgical process. In fact, the crucible of Patent Document 2 is intended for melting high melting point metals such as cast iron, cast steel, special steel, and copper alloys, and low melting point metals such as aluminum and zinc, and is corrosive to lithium-containing slag melts. It does not focus on improving sex (Patent Document 2 [0016]). Therefore, it is unclear whether these crucibles can be used for valuable metal recovery.

The present inventors have conducted diligent studies in view of such circumstances, and conducted tests using refractories composed of various corrosion-resistant materials. As a result, the magnesia refractory containing a boron component has excellent corrosion resistance to a slag melt containing lithium (Li), and by using this refractory, valuable metals can be recovered at low cost. I got the knowledge.

The present invention has been completed based on such knowledge, and is a method capable of recovering valuable metals at low cost by using a refractory having a long life, and a refractory having a long life used at the time of recovering valuable metals. The issue is the provision of goods.

The present invention includes the following aspects (1) to (7). In the present specification, the expression "-" includes the numerical values at both ends thereof. That is, "X to Y" is synonymous with "X or more and Y or less".

(1) A method for recovering valuable metals, which is the following step;
The process of preparing a charge containing at least valuable metal and lithium (Li), and
Including a step of subjecting the charged material to an oxidation treatment and a reduction melting treatment to obtain a reduced product containing a fusion metal and slag.
A method in which an object to be treated is heat-treated in a heating furnace during the reduction melting treatment, and the heating furnace contains a magnesia refractory containing a boron component.

(2) The method of (1) above, wherein the magnesia refractory is a furnace wall material, a hearth material and / or a crucible.

(3) The method according to (1) or (2) above, wherein the magnesia refractory further contains a carbonaceous component.

(4) The method according to (3) above, wherein the magnesia refractory contains a carbonaceous component and a boron component in a total amount of 9.0 to 15.0% by mass.

(5) The magnesia refractory contains a carbonaceous component and a boron component so that the ratio of the boron component / (carbonaceous component + boron component) is 0.5 to 0.9. Method of 4).

(6) The method according to any one of (1) to (5) above, wherein the charge includes a waste lithium ion battery.

(7) A magnesia refractory used in the method of recovering valuable metals.
The magnesia refractory is contained in a heating furnace used for reducing and melting a charge containing at least valuable metal and lithium (Li).
A magnesia refractory in which the magnesia refractory contains a boron component.

According to the present invention, there is provided a method capable of recovering a valuable metal at low cost by using a refractory having a long life, and a refractory having a long life used at the time of recovering the valuable metal.

An example of a method for recovering valuable metals is shown.

A specific embodiment of the present invention (hereinafter, referred to as “the present embodiment”) will be described. The present invention is not limited to the following embodiments, and various modifications can be made without changing the gist of the present invention.

1. 1. Method of recovering valuable metal The method of recovering the valuable metal of the present embodiment is as follows: a step of preparing a charge containing at least valuable metal and lithium (Li) (preparation step), and an oxidation of the charge. The process includes a step of obtaining a reduced product containing a fusion metal and slag (oxidation-reduction melting step) by performing a treatment and a reduction melting treatment. Further, during the reduction melting treatment, the object to be treated is heat-treated in a heating furnace, and this heating furnace contains a magnesia refractory containing a boron component.

The method of the present embodiment is a method of recovering valuable metal from a charge containing at least valuable metal and lithium (Li). Here, the valuable metal is to be recovered, and is at least one kind of metal or alloy selected from the group consisting of copper (Cu), nickel (Ni), cobalt (Co) and combinations thereof. Further, the present embodiment is mainly a recovery method by a pyrometallurgical process. However, it may consist of a pyrometallurgical process and a hydrometallurgical process. Details of each step will be described below.

<Preparation process>
In the preparatory step, a charge is prepared to obtain a molten raw material. The charged material is to be processed for recovering valuable metals, and is at least one kind of valuable metal selected from the group consisting of copper (Cu), nickel (Ni), cobalt (Co) and a combination thereof, and lithium ( Li) and. The charge may contain these components (Cu, Ni, Co, Li) in the form of a metal or a compound such as an oxide. Further, the charged material may contain other inorganic components and organic components other than these components (Cu, Ni, Co, Li).

The target of the charged material is not particularly limited, and examples thereof include waste lithium ion batteries, dielectric materials (capacitors), and magnetic materials. Further, the form is not limited as long as it is suitable for the treatment in the subsequent redox melting step. In the preparatory step, the charged material may be subjected to a treatment such as crushing to obtain a suitable form. Further, in the preparatory step, the charged material may be subjected to a treatment such as a heat treatment or a sorting treatment to remove unnecessary components such as water and organic substances.

<Redox melting process>
In the redox melting step, the prepared charge is subjected to an oxidation treatment and a reduction melting treatment to obtain a reduced product. This reduced product contains the fused metal and the slag separately. The fused gold contains a valuable metal. Therefore, it is possible to separate the component containing a valuable metal (fused gold) and other components in the reduced product. This is because metals with low added value (Al, etc.) have high oxygen affinity, whereas valuable metals have low oxygen affinity. For example, aluminum (Al), lithium (Li), carbon (C), manganese (Mn), phosphorus (P), iron (Fe), cobalt (Co), nickel (Ni) and copper (Cu) are generally used. It is 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 least easily oxidized. Therefore, low-value-added metals (Al, etc.) are easily oxidized to slag, and valuable metals (Cu, Ni, Co) are reduced to molten metals (alloys). In this way, the metal having low added value and the valuable metal can be separated into the slag and the fused metal.

In the redox melting step, the oxidation treatment and the reduction melting treatment may be performed at the same time or separately. As a method to be performed at the same time, there is a method of injecting an oxidizing agent into the melt obtained by the reduction melting treatment. Specifically, a metal tube (lance) may be inserted into the melt, and an oxidizing agent may be blown by bubbling. In this case, a gas containing oxygen such as air, pure oxygen, and an oxygen-enriched gas can be used as the oxidizing agent. However, it is preferable that the redox melting step includes the oxidation roasting step and the reduction melting step separately. As such a method, a method in which the prepared molten material is oxidatively roasted to obtain an oxidative roasted product during the oxidation treatment, and the obtained oxidative roasted product is reduced and melted to be a reduced product during the reduction melting treatment. Can be mentioned. The details of the oxidative roasting step and the reduction melting step will be described below.

<Oxidation roasting process>
The oxidative roasting step is a step of oxidatively roasting (oxidizing treatment) the charged material to obtain an oxidative roasted product. By providing the oxidative roasting step, even if the charged material contains carbon, the carbon can be oxidized and removed, and as a result, the alloy integration of the valuable metal in the subsequent reduction melting step can be promoted. .. That is, in the reduction melting step, the valuable metal is reduced to local molten fine particles. Carbon becomes a physical obstacle when molten fine particles (valuable metals) agglomerate. Therefore, if the oxidative roasting step is not provided, carbon hinders the agglutination and integration of the molten fine particles and the resulting separability of the metal (fused metal) and the slag, which may reduce the valuable metal recovery rate. On the other hand, by removing carbon in the oxidative roasting process in advance, the coagulation and integration of the molten fine particles (valuable metal) in the reduction melting process progresses, and the recovery rate of the valuable metal is further increased. Becomes possible.

Moreover, by providing the oxidation roasting step, it is possible to suppress the variation in oxidation. In the oxidative roasting step, it is desirable to perform treatment (oxidative roasting) at an oxidation degree capable of oxidizing a metal (Al or the like) having a low added value contained in a molten material (charged material or the like). On the other hand, the degree of oxidation can be easily controlled by adjusting the processing temperature, time and / or atmosphere of oxidative roasting. Therefore, the degree of oxidation can be adjusted more strictly by the oxidation roasting step, and the variation 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, it is oxidized in the order of Al> Li> C> Mn> P> Fe> Co> Ni> Cu. In the oxidative roasting step, the oxidation proceeds until the entire amount of aluminum (Al) is oxidized. Oxidation may be promoted until a part of iron (Fe) is oxidized, but the degree of oxidation is maintained to such an extent that cobalt (Co) is not oxidized and recovered as slag.

In adjusting the degree of oxidation in the oxidation roasting step, it is preferable to introduce an appropriate amount of an oxidizing agent. In particular, when the charged material contains a waste lithium ion battery, it is preferable to introduce an oxidizing agent. Lithium-ion batteries contain metals such as aluminum and iron as exterior materials. It also contains aluminum foil and carbon material as the positive electrode material and the negative electrode material. Furthermore, in the case of collective batteries, plastic is used as an external package. All of these are materials that act as reducing agents. By introducing an oxidizing agent, the degree of oxidation in the oxidative roasting process can be adjusted within an appropriate range.

The oxidizing agent is not particularly limited as long as it can oxidize carbon or a metal having low added value (Al or the like). However, oxygen-containing gases such as air, pure oxygen, and oxygen-enriched gas, which are easy to handle, are preferable. As a guide, the amount of the oxidizing agent introduced is about 1.2 times (for example, 1.15 to 1.25 times) the amount (chemical equivalent) required for oxidation of each substance to be oxidized.

The heating temperature for oxidative roasting (oxidation treatment) is preferably 700 ° C. or higher and 1100 ° C. or lower, and more preferably 800 ° C. or higher and 1000 ° C. or lower. At 700 ° C. or higher, the carbon oxidation efficiency can be further increased and the oxidation time can be shortened. Further, at 1100 ° C. or lower, the heat energy cost can be suppressed and the efficiency of oxidative roasting can be improved.

Oxidation roasting (oxidation treatment) can be performed using a known roasting furnace. Further, it is preferable to use a furnace (preliminary furnace) different from the melting furnace used in the subsequent reduction melting step and perform the process in the preliminary furnace. As the roasting furnace, any type of furnace can be used as long as it is a furnace capable of supplying an oxidizing agent (oxygen or the like) while roasting the charged material and performing an oxidation treatment inside the furnace. As an example, a conventionally known rotary kiln and tunnel kiln (Haas furnace) can be mentioned.

<Reduction melting process>
The reduction melting step is a step of heating the obtained oxidized roasted product to reduce and melt it to obtain a reduced product. The purpose of this step is to maintain the low value-added metals (Al, etc.) oxidized in the oxidation roasting step as oxides, while reducing and melting the oxidized valuable metals (Cu, Ni, Co). It is to recover as a converted alloy. The material obtained after the reduction treatment is called a "reduced product", and the alloy obtained as a melt is called a "fused gold".

During the reduction melting treatment, the object to be treated (oxidized roasted product) is heat-treated in a heating furnace. The heating furnace may be a known melting furnace. A furnace different from the roasting furnace used in the oxidative roasting step is preferable, but the same furnace may be used. As the heating furnace (melting furnace), any type of furnace can be used as long as it is a furnace capable of performing reduction melting treatment. Examples thereof include conventionally known induction heating electric furnaces, arc heating electric furnaces, and Joule heating electric furnaces.

The heating furnace used in the reduction melting treatment contains a magnesia refractory, and this magnesia refractory contains a carbonaceous component. As described above, when the melting treatment is performed using the conventional magnesia crucible, the crucible is corroded even in one batch of treatment. In addition, the crucible may be damaged and the melt (melt) may leak into the melting furnace, and it is necessary to replace the crucible with a new crucible for each batch of the melting process. On the other hand, the magnesia crucible containing a boron component has excellent corrosion resistance to a lithium-containing slag melt. Therefore, it is possible to suppress the occurrence of the problem that the melt leaks into the melting furnace, and the life is long. For example, a conventional crucible needs to be replaced for each batch, whereas a crucible containing a boron component can extend its life up to 80 times.

The magnesia refractory of the present embodiment contains a boron component. Specifically, it is composed of magnesia grains and a boron component dispersed at the grain boundaries so as to cover the magnesia grains. Magnesia grains are crystal grains composed of magnesia (MgO). The average particle size (D ₅₀ ) is not particularly limited, but is, for example, 70 to 130 μm. Further, the refractory may contain additives and impurities other than the magnesia and boron components as long as the corrosion resistance is maintained. For example, the magnesia refractory may contain a carbonaceous component as described below. However, the smaller the proportion of the components other than the magnesia, the boron component and the carbonaceous component, the more preferable, for example, it may be 10% by mass or less, 5% by mass or less, or 1% by mass or less. The magnesia refractory may contain a magnesia refractory, a boron component and, if present, a carbonaceous component, the balance of which may be composed of unavoidable impurities.

The boron component is mainly composed of boron (B) and is typically boron (B) or boron oxide (B ₂ O ₃ ). The boron component may be crystalline or amorphous. It may also contain components other than boron. For example, in addition to boron, magnesium (Mg) and oxygen (O) diffused from crystal grains may be contained. The amount of the boron component may be, for example, 1.0 to 15.0% by mass, and may be 9.0 to 15.0% by mass. The amount of the boron component is a value in terms of boron (B). That is, when the boron component is boron oxide, it is the content of boron alone contained in boron oxide.

The magnesia refractory preferably consists of a sintered body containing magnesia and a boron component. Such a sintered body can be produced, for example, by mixing and molding magnesia powder and boron powder or boron oxide powder, and sintering in an atmosphere such as an inert atmosphere. Further, in order to obtain a dense sintered body, an additive such as a sintering aid may be added.

The magnesia refractory is preferably a furnace wall material, a hearth material and / or a crucible, and particularly preferably a crucible. Here, the furnace wall material and the hearth material are members used for the inner wall and the floor of the heating furnace, and are typically bricks (fireproof bricks for furnace construction). The crucible is a member that is used in a state of being arranged in a heating furnace and that houses an object to be processed inside the crucible. As described above, the magnesium crucible containing a boron component has excellent corrosion resistance to a lithium-containing slag melt. Therefore, when the magnesia refractory of the present embodiment is applied to the crucible, it is possible to suppress the occurrence of the problem that the melt leaks into the melting furnace (heating furnace). Further, when the magnesia refractory of the present embodiment is applied to the furnace wall material and the hearth material, even if the lithium-containing slag melt leaks into the melting furnace, it is possible to suppress the further progress of the melt leakage. .. Further, the furnace wall material and the hearth material are excellent in corrosion resistance not only to lithium-containing slag but also to lithium vapor. Therefore, even if the valuable metal recovery is repeated, there is little damage due to lithium vapor.

The magnesia crucible preferably further contains a carbonaceous component. A magnesia refractory containing a carbonaceous component as well as a boron component is particularly excellent in corrosion resistance to a lithium-containing slag melt. Therefore, the occurrence of the problem that the melt leaks into the melting furnace can be suppressed more remarkably, and the life is further extended. A magnesia crucible containing a carbonaceous component in addition to a boron component is composed of magnesia grains and a boron component and a carbonaceous component dispersed at grain boundaries so as to cover the magnesia grains. The amount of carbonaceous component may be, for example, 1.0 to 15.0% by mass.

The carbonaceous component is mainly composed of carbon (C) and is typically carbon (C). The carbon constituting the carbonaceous component may be either crystalline or amorphous. Examples of carbon include graphite, amorphous carbon, fullerenes, and carbon nanotubes. Further, as the amorphous carbon, carbon black such as furnace black, channel black, acetylene black, and thermal black can be mentioned. The average particle size of the carbon fine particles is not particularly limited, but is, for example, 2 to 8 μm.

The magnesia refractory preferably contains a carbonaceous component and a boron component in a total amount of 9.0 to 15.0% by mass. In a refractory based on magnesia, the amount of wear decreases as the total content of the carbonaceous component and the boron component is gradually increased. For example, when the refractory is a crucible, the total amount of carbonaceous component and boron component is 9.0% by mass or more, and the life is 6 times or more longer than that of a crucible with magnesia alone, and 13.0% by mass. With the above, the life is extended by 12 times or more. However, when the total amount is 19.0% by mass, the amount of wear bottoms out (the lowest), and even if the content is increased further, the effect does not increase. Therefore, when the total amount of the carbonaceous component and the boron component is within the above range, the corrosion resistance is further improved, and the life of the refractory can be further extended.

The magnesia refractory preferably contains a carbonaceous component and a boron component so that the ratio of the boron component / (carbonaceous component + boron component) is 0.5 to 0.9. If the total content of the carbonaceous component and the boron component is the same, the amount of wear is further reduced when the proportion of the boron component is in the above range.

It is preferable to introduce a reducing agent during the reduction melting treatment. It is preferable to use carbon and / or carbon monoxide 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.). Further, the reduction method using carbon or carbon monoxide is extremely safer than 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 carbon, and coal or coke can be used if there is no risk of impurity contamination.

The heating temperature of the reduction melting treatment is not particularly limited. However, the heating temperature is preferably 1300 ° C. or higher and 1450 ° C. or lower, and more preferably 1350 ° C. or higher and 1400 ° C. or lower. At temperatures above 1450 ° C, heat energy is wasted and productivity may decline. On the other hand, if the temperature is less than 1300 ° C., there is a problem that the separability of the slag and the fused metal deteriorates and the recovery rate decreases. The reduction melting treatment may be carried out by a known method. For example, a method of charging an oxidized roasted product into a crucible and heating it by resistance heating or the like can be mentioned. In addition, harmful substances such as dust and exhaust gas may be generated during the reduction melting treatment, but the harmful substances can be detoxified by performing a treatment such as a known exhaust gas treatment.

When the oxidation roasting step is provided, it is not necessary to perform the oxidation treatment in the reduction melting step. However, if the oxidation in the oxidation roasting step is insufficient, or if the purpose is to further adjust the degree of oxidation, an additional oxidation treatment may be performed in the reduction melting step. By performing an additional oxidation treatment, it is possible to adjust the degree of oxidation more precisely.

<Slag separation process>
A slag separation step may be provided if necessary. In the slag separation step, the slag is separated from the reduced product obtained in the redox melting step, and the fused gold is recovered. Slag and fused gold have different specific densities. Since the slag, which has a smaller specific gravity than the fused metal, collects on the upper part of the fused metal, it can be separated and recovered by the specific gravity separation.

After the slag separation step, a sulfurization step of sulfurizing the obtained alloy or a pulverization step of pulverizing a mixture of the obtained sulfide and the alloy may be provided. Further, a hydrometallurgical process may be performed on the valuable metal alloy obtained through such a pyrometallurgical process. Impurity components can be removed by a hydrometallurgy process, and valuable metals (Cu, Ni, Co) can be separated and purified to recover each of them. Examples of the treatment in the hydrometallurgy process include known methods such as neutralization treatment and solvent extraction treatment.

According to the method for recovering valuable metals of the present embodiment, problems in operation efficiency and material cost are solved by using a boron-containing magnesia refractory having excellent corrosion resistance to the lithium-containing slag melt and having a long life. , It becomes possible to recover valuable metals at low cost.

As far as the present inventors know, such a recovery method has not been known conventionally. For example, in Patent Document 1, regarding a method of recovering a valuable metal from a waste lithium ion battery, a reduction melting treatment is performed using a crucible manufactured by Magnesia, and a specific description teaching that the crucible contains a boron component is described. There is no teaching or suggestion that it will improve corrosion resistance and longevity. Further, the crucible proposed in Patent Documents 2 to 4 is composed of a laminated structure of a carbonaceous component and ceramics, and has a structure different from that of the crucible of the present embodiment. Further, the crucibles of Patent Documents 2 to 4 are not used when recovering valuable metals in a pyrometallurgical process, much less for the purpose of improving the corrosiveness of a lithium-containing slag melt.

2. Recovery from Waste Lithium Ion Battery The charge of this embodiment is not limited as long as it contains a valuable metal and lithium (Li). However, the charge preferably contains a waste lithium ion battery. The waste lithium ion battery contains valuable metals (Cu, Ni, Co) and lithium (Li), and also contains low value-added metals (Al, Fe) and carbon components. Therefore, by using the waste lithium ion battery as a charge, the valuable metal can be efficiently separated and recovered. The waste lithium-ion battery is not only a used lithium-ion battery, but also a lithium-ion battery such as defective products generated in the manufacturing process of the positive electrode material constituting the battery, residues inside the manufacturing process, and generated waste. It is a concept that includes waste materials in the process. Therefore, the waste lithium ion battery can also be called a lithium ion battery waste material.

A method of recovering valuable metals from a waste lithium ion battery will be described with reference to FIG. FIG. 1 is a process diagram showing an example of a recovery method. As shown in FIG. 1, this method includes a waste battery pretreatment step (S1) for removing the electrolytic solution and the outer can of the waste lithium ion battery, and a first method of crushing the contents of the waste battery into a crushed product. It has a crushing step (S2), an oxidative roasting step (S3) in which the crushed product is oxidatively roasted, and a reduction melting step (S4) in which the oxidative roasted product is reduced and melted to form an alloy. Further, although not shown, a sulfurization step of sulfurizing the obtained alloy and a second grinding step of grinding the mixture of the obtained sulfide and the alloy may be provided after the reduction melting step (S4). .. Details of each step will be described below.

<Waste battery pretreatment process>
The waste battery pretreatment step (S1) is performed for the purpose of preventing the waste lithium ion battery from exploding, detoxifying it, and removing the outer can. Since the lithium ion battery is a closed system, it has an electrolytic solution and the like inside. Therefore, if the crushing process is performed as it is, there is a risk of explosion, which is dangerous. It is preferable to perform a discharge treatment or an electrolytic solution removal treatment by some method. Further, the outer can is often composed of metal aluminum (Al) or iron (Fe), and it is relatively easy to recover the metal outer can as it is. By removing the electrolytic solution and the outer can in the waste battery pretreatment step (S1), it is possible to improve the safety and the recovery rate of valuable metals (Cu, Ni, Co).

The specific method of waste battery pretreatment is not particularly limited. For example, a method of physically opening a waste battery with a needle-shaped cutting edge to remove an electrolytic solution can be mentioned. Another method is to heat the waste battery and burn the electrolytic solution to make it harmless.

When recovering aluminum (Al) and iron (Fe) contained in the outer can in the waste battery pretreatment step (S1), the removed outer can is crushed and then the crushed material is sieved using a sieve. It may be sieved. Since aluminum (Al) is easily powdered by light pulverization, it can be efficiently recovered. Further, iron (Fe) contained in the outer can may be recovered by magnetic force sorting.

<First crushing process>
In the first pulverization step (S2), the contents of the waste lithium ion battery are pulverized to obtain a pulverized product. This process aims 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. The specific pulverization method is not particularly limited. It can be crushed using a conventionally known crusher such as a cutter mixer. The waste battery pretreatment step and the first crushing step together correspond to the preparatory steps described above.

<Oxidation roasting process>
In the oxidative roasting step (S3), the pulverized product obtained in the first pulverization step (S2) is oxidatively roasted to obtain an oxidative roasted product. The details of this process are as described above.

<Reduction melting process>
In the reduction melting step (S4), the oxidative roasted product obtained in the oxidative roasting step (S3) is reduced to obtain a reduced product. The details of this process are as described above.

<Slag separation process>
In the slag separation step, the slag is separated from the reduced product obtained in the reduction melting step (S4), and the molten metal is recovered. The details of this process are as described above.

A sulfurization step or a pulverization step may be provided after the slag separation step. Further, a wet smelting process may be performed on the obtained valuable metal alloy. The details of the sulfurization step, the pulverization step and the hydrometallurgy process are as described above.

3. 3. Magnesia refractory The magnesia refractory of this embodiment is used as a method for recovering valuable metals. This magnesia refractory is contained in a heating furnace used when reducing and melting a charge containing at least valuable metal and lithium (Li). In addition, this magnesia refractory contains a boron component. The details of the method for recovering valuable metals and the magnesia refractory are as described above.

The present invention will be described in more detail with reference to the following examples and comparative examples. However, the present invention is not limited to the following examples.

(1) Creation of Magnesia Crucible Example 1
In Example 1, a magnesia crucible containing carbon in an amount of 8.0% by mass and boron in an amount of 1.0% by mass was prepared. Specifically, magnesia powder, carbon powder (graphite fine powder) and boron oxide powder were sufficiently mixed so that a crucible having the above composition could be obtained, and the powder mixture was formed by a rubber press method. The obtained molded product was fired at a high temperature of 1800 ° C. or higher to prepare a magnesia crucible made of a sintered body. The obtained crucible had a hollow cylindrical shape with an open top surface having a thickness of 40 mm and a height of 230 mm.

Example 2
In Example 2, the amount of carbon was changed to 4.5% by mass and the amount of boron was changed to 4.5% by mass. A crucible was prepared in the same manner as in Example 1 except for the above.

Example 3
In Example 3, the amount of carbon was changed to 1.0% by mass and the amount of boron was changed to 8.0% by mass. A crucible was prepared in the same manner as in Example 1 except for the above.

Example 4
In Example 4, carbon was not added (carbon content was 0% by mass), and the amount of boron was changed to 9.0% by mass. A crucible was prepared in the same manner as in Example 1 except for the above.

Example 5
In Example 5, the amount of carbon was changed to 11.5% by mass and the amount of boron was changed to 1.5% by mass. A crucible was prepared in the same manner as in Example 1 except for the above.

Example 6
In Example 6, the amount of carbon was changed to 7.0% by mass and the amount of boron was changed to 6.0% by mass. A crucible was prepared in the same manner as in Example 1 except for the above.

Example 7
In Example 7, the amount of carbon was changed to 1.0% by mass and the amount of boron was changed to 12.0% by mass. A crucible was prepared in the same manner as in Example 1 except for the above.

Example 8
In Example 8, carbon was not added (carbon content was 0% by mass), and the amount of boron was changed to 13.0% by mass. A crucible was prepared in the same manner as in Example 1 except for the above.

Example 9
In Example 9, the amount of carbon was changed to 13.0% by mass and the amount of boron was changed to 2.0% by mass. A crucible was prepared in the same manner as in Example 1 except for the above.

Example 10
In Example 10, the amount of carbon was changed to 7.5% by mass and the amount of boron was changed to 7.5% by mass. A crucible was prepared in the same manner as in Example 1 except for the above.

Example 11
In Example 11, the amount of carbon was changed to 2.0% by mass and the amount of boron was changed to 13.0% by mass. A crucible was prepared in the same manner as in Example 1 except for the above.

Example 12
In Example 12, carbon was not added (carbon content was 0% by mass), and the amount of boron was changed to 15.0% by mass. A crucible was prepared in the same manner as in Example 1 except for the above.

Comparative Example 1
In Comparative Example 1, the carbon content was changed to 9.0% by mass, and boron was not added (boron content 0% by mass). A crucible was prepared in the same manner as in Example 1 except for the above.

Comparative Example 2
In Comparative Example 2, the carbon content was changed to 13.0% by mass, and boron was not added (boron content 0% by mass). A crucible was prepared in the same manner as in Example 1 except for the above.

Comparative Example 3
In Comparative Example 3, the carbon content was changed to 15.0% by mass, and boron was not added (boron content 0% by mass). A crucible was prepared in the same manner as in Example 1 except for the above.

Comparative Example 4
In Comparative Example 4, neither carbon nor boron was added (carbon content: 0% by mass, boron amount: 0% by mass). A crucible was prepared in the same manner as in Example 1 except for the above.
(2) Evaluation

The crucibles obtained in Examples 1 to 6 and Comparative Examples 1 to 4 were evaluated for various characteristics as shown below.

<Amount of slag level wear>
The amount of slag level (SL) wear on the crucible was examined. Specifically, a test was conducted in which the amounts of LiB raw material and slag shown below were charged into the crucible prepared in each Example and Comparative Example, and kept in a nitrogen atmosphere in the heating furnace and heating temperature shown below for 8 hours. rice field.

-Induction heating furnace: diameter 205 mm, depth 230 mm
-Slug level (SL): 150mm
-Test temperature: 1600 ° C
-Test time: 8 hours-LiB raw metal: 10 kg
-Slag: 800g
-Atmosphere: Nitrogen

<Tissue observation>
After evaluating the amount of slag level wear, the crucible cross section was observed with a scanning electron microscope (SEM-EDX) equipped with an energy dispersive X-ray spectrometer to examine the microstructure. In addition, elemental analysis of the cross section was performed using the attached energy dispersive X-ray spectrometer (EDX). The magnification at the time of observation was 100 times.

(3) Result <Slag level wear amount>
The amount of slag level (SL) wear of the crucibles obtained in Examples 1 to 12 and Comparative Examples 1 to 4 is shown in Tables 1-1 to 1-4. The crucibles of Comparative Examples 1 to 4 containing no boron component had a large slag level (SL) wear amount of 4.1 mm at the minimum. In particular, the crucible of Comparative Example 4 containing neither a carbon component nor a boron component had a very large wear amount of 40.0 mm or more, and was damaged during the test. On the other hand, the crucibles of Examples 1 to 12 containing a boron component had a small wear amount of 30 mm at the maximum. In particular, the crucibles of Examples 2, 3, 6, 7, 10 and 11 contain a carbonaceous component together with a boron component and have a boron component / (carbonous component + boron component) ratio of 0.5 to 0.9. The amount of wear was as small as 1.0 mm or less.

<Tissue observation>
In Example 9, from the cross-sectional SEM photograph of the crucible after the evaluation of the amount of slag level wear and the elemental analysis image, relatively coarse magnesia (MgO) grains and fine boron (B) and carbon (C) existing at the grain boundaries were found. And turned out to exist. It is thought that the boron component and carbonaceous component diffused to the grain boundaries of the magnesia grains before the slag invaded, and the magnesia grains were coated with carbon and boron, which extended the life without causing structural failure. Be done. Therefore, the present inventors presume that the life span is up to about 50 times longer than that of the conventional crucible.

Claims (7)

A method for recovering valuable metals, which is the following process;
The process of preparing a charge containing at least valuable metal and lithium (Li), and
Including a step of subjecting the charged material to an oxidation treatment and a reduction melting treatment to obtain a reduced product containing a fusion metal and slag.
A method in which an object to be treated is heat-treated in a heating furnace during the reduction melting treatment, and the heating furnace contains a magnesia refractory containing a boron component. The method according to claim 1, wherein the magnesia refractory is a furnace wall material, a hearth material and / or a crucible. The method according to claim 1 or 2, wherein the magnesia refractory further contains a carbonaceous component. The method according to claim 3, wherein the magnesia refractory contains a carbonaceous component and a boron component in a total amount of 9.0 to 15.0% by mass. The method according to claim 3 or 4, wherein the magnesia refractory contains a carbonaceous component and a boron component so that the ratio of the boron component / (carbonic component + boron component) is 0.5 to 0.9. .. The method according to any one of claims 1 to 5, wherein the charge includes a waste lithium ion battery. A magnesia refractory used in the method of recovering valuable metals.
The magnesia refractory is contained in a heating furnace used for reducing and melting a charge containing at least valuable metal and lithium (Li).
A magnesia refractory in which the magnesia refractory contains a boron component.

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