JP2022167755A - Method for producing valuable metal - Google Patents

Abstract

To provide a method for producing, from a raw material containing an oxide containing nickel and cobalt, a valuable metal containing the nickel and the cobalt, the method capable of appropriately and efficiently adjusting a reduction degree of an alloy obtained through a melting treatment.SOLUTION: The method for producing a valuable metal from a raw material containing an oxide containing nickel and cobalt includes: a melting step of applying a melting treatment to the raw material to obtain a melt; and a slag separation step of separating a slag from the melt and recovering an alloy containing a valuable metal. In the melting step, a reduction degree at the melting step is determined according to a rate (a cobalt recovery rate) of a cobalt amount of the alloy to be produced to a cobalt amount in the raw material, and if it is determined that the reduction degree is excessive, the raw material containing an oxide containing nickel and cobalt is added as an oxidizer.SELECTED DRAWING: Figure 4

Description

TECHNICAL FIELD The present invention relates to a method for producing valuable metals from raw materials containing oxides containing nickel and cobalt, such as waste lithium ion batteries.

In recent years, lithium-ion batteries have become popular as lightweight, high-output secondary batteries. As a lithium-ion battery, a negative electrode material in which a negative electrode current collector made of copper foil is adhered to a negative electrode active material such as graphite, and a positive electrode current collector made of aluminum foil is coated with nickel in an outer can made of metal such as aluminum or iron. A positive electrode material to which a positive electrode active material such as lithium oxide or lithium cobalt oxide is adhered, a separator made of a polypropylene porous resin film, etc., and an electrolytic solution containing an electrolyte such as lithium hexafluorophosphate (LiPF ₆ ) is enclosed. It has been known.

One of the main applications of lithium ion batteries is hybrid vehicles and electric vehicles, and it is expected that a large amount of lithium ion batteries installed in such vehicles will be discarded in the future along with the life cycle of the vehicles. Many proposals have been made to reuse such used batteries and defective products produced during manufacture (hereinafter referred to as "waste lithium ion batteries") as resources. For example, as a method for recycling waste lithium ion batteries, a pyrometallurgical refining process has been proposed in which waste lithium ion batteries are completely melted in a high-temperature furnace.

In waste lithium-ion batteries, in addition to valuable metals such as nickel (Ni), cobalt (Co), and copper (Cu), carbon (C), aluminum (Al), fluorine (F), phosphorus (P), etc. Contains impurities. Therefore, in recovering valuable metals from waste lithium ion batteries, it is necessary to remove these impurity components.

In the pyrometallurgical process, raw materials including waste lithium-ion batteries are melted at a temperature of about 1500° C. and then separated into metal and slag. In this treatment, valuable substances contained in the raw material can be reduced and recovered as metals, and impurities can be removed by oxidation and separation into slag.

However, if the degree of reduction is adjusted too strongly in order to increase the recovery rate of valuable metals such as cobalt, impurities such as phosphorus remain in the metal without being oxidized and removed. On the other hand, if the degree of reduction is adjusted too weakly, even valuable metals are oxidized, resulting in a lower recovery rate. Further, for example, in the case of super-reduction, it is conceivable to adjust the degree of reduction by blowing in a gas such as oxygen to oxidize the molten material, but this requires equipment for blowing the gas into the melt, which is costly.

Therefore, in the melting process, in order to recover valuable metals at a high recovery rate while effectively removing impurities, the degree of reduction of the resulting alloy (metal) can be adjusted appropriately and economically and efficiently. It is desired that

In addition, in Patent Document 1, in a valuable metal recovery process for recovering valuable metals including nickel and cobalt from waste lithium ion batteries, etc., dephosphorization treatment is performed without adversely affecting the recovery rate of valuable metals. Techniques for recovering valuable metals with a high recovery rate have been disclosed. However, there is no disclosure of adjusting the degree of reduction of the resulting alloy.

JP 2013-091826 A

The present invention has been proposed in view of such circumstances, and extracts valuable metals containing nickel and cobalt from raw materials containing oxides containing nickel and cobalt, such as waste lithium ion batteries as described above. An object of the present invention is to provide a manufacturing method capable of appropriately and efficiently adjusting the degree of reduction of an alloy obtained through a melting treatment.

The present inventors have made extensive studies to solve the above-described problems. As a result, in the process of melting raw materials containing oxides containing nickel and cobalt such as waste lithium ion batteries to obtain a melt, the degree of reduction in the melting process is determined based on the cobalt recovery rate. When it is judged to be excessive, the addition of a raw material containing oxides containing nickel and cobalt as an oxidizing agent finds that the degree of reduction can be adjusted appropriately and efficiently. Arrived.

(1) A first aspect of the present invention is a method for producing a valuable metal from a raw material containing oxides containing nickel and cobalt, wherein the raw material is subjected to a melting treatment to obtain a melt. and a slag separation step of separating slag from the molten material and recovering an alloy containing valuable metals, and in the melting step, the amount of cobalt in the alloy to be produced is reduced with respect to the amount of cobalt in the raw material. The degree of reduction in the melting treatment is determined based on the ratio (cobalt recovery rate), and when the degree of reduction is determined to be excessive, the raw material containing oxides containing nickel and cobalt is added as an oxidizing agent. It is a method for producing valuable metals.

(2) A second aspect of the present invention is the method for producing a valuable metal according to the first aspect, wherein in the melting step, the cobalt recovery rate is calculated based on the analysis result of the quality of cobalt in the slag. .

(3) A third aspect of the present invention is a valuable A metal manufacturing method.

(4) A fourth aspect of the present invention is a method according to any one of the first to third aspects of the invention, wherein the melting process is performed when the cobalt recovery rate is 98% or more, and the degree of reduction in the melting process is excessive. It is a method for producing valuable metals.

(5) A fifth aspect of the present invention is a valuable metal in any one of the first to fourth aspects, wherein the raw material containing an oxide containing nickel and cobalt is a raw material containing a waste lithium ion battery. is a manufacturing method.

(6) In a sixth aspect of the present invention, in any one of the first to fifth aspects, the raw material contains phosphorus, and the phosphorus content of the alloy recovered through the slag separation step is 0.1% by mass or less, a method for producing a valuable metal.

(7) A seventh aspect of the present invention is a method for producing a valuable metal according to any one of the first to sixth aspects, wherein in the melting step, the raw material is melted at a heating temperature of 1300° C. or more and 1600° C. or less. is.

ADVANTAGE OF THE INVENTION According to this invention, the reduction degree of the alloy obtained through a fusion process can be adjusted appropriately and efficiently.

It is process drawing which shows an example of the flow of the manufacturing method of a valuable metal. It is a graph showing the relationship between the quality of cobalt in slag and the recovery rate of cobalt. It is a graph chart which shows the relationship between the oxygen partial pressure in a molten material, and a cobalt recovery rate. FIG. 4 is a graph showing the relationship between the recovery rate of cobalt and the grade of phosphorus in the metal, and is a diagram for explaining the adjustment of the degree of reduction in the melting process.

An embodiment of the present invention (hereinafter referred to as "this embodiment") 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 for producing valuable metals according to the present embodiment is a method for separating and recovering valuable metals from raw materials containing oxides containing at least nickel and cobalt. Therefore, it can also be called a recovery method for 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.

Examples of "raw materials containing oxides containing nickel and cobalt" include raw materials containing waste lithium ion batteries. A positive electrode material that constitutes a lithium ion battery contains oxides of nickel and cobalt. "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.

In addition, "valuable metals" that can be recovered from raw materials containing oxides containing nickel and cobalt refer to at least nickel (Ni) and cobalt (Co). For example, when the raw material is a raw material containing waste lithium ion batteries, examples of valuable metals include nickel, cobalt, copper (Cu), and the like, and alloys made of a combination of nickel, cobalt, and copper. be done. The content of each valuable metal contained in the waste lithium ion battery is not particularly limited. For example, it may contain 10% by mass or more of copper.

Specifically, the method for producing a valuable metal according to the present embodiment includes a melting step of performing a melting process on raw materials containing oxides containing nickel and cobalt to obtain a melt, and a step of separating slag from the melt. and a slag separation step for recovering an alloy containing valuable metals. In this method, the degree of reduction in the melting process is determined based on the recovery rate of cobalt in the melting step, and if the degree of reduction is determined to be excessive, the raw material containing oxides containing nickel and cobalt is added as an oxidizing agent. Here, "cobalt recovery rate" refers to the ratio (percentage) of the amount of cobalt in the alloy produced and recovered by the treatment to the amount of cobalt in the raw material.

The cobalt recovery rate can be calculated, for example, based on the analytical results of cobalt quality in slag. Alternatively, it can also be calculated based on the measurement result of the oxygen partial pressure in the melt produced by melting the raw materials.

As described above, in the method according to the present embodiment, the cobalt recovery rate is calculated from the slag or alloy obtained by the melting process, or the melt containing them, and the degree of reduction is determined based on the cobalt recovery rate. ing.

In this method, when the degree of reduction that can be determined based on the grade of cobalt in the slag is excessive, that is, when it is determined to be over-reduction, an oxidizing agent is added to adjust the degree of reduction. As a reducing agent to be added to , a raw material containing an oxide containing nickel and cobalt, which is the raw material to be treated, is used. Specifically, for example, when a raw material containing a waste lithium ion battery is used as a raw material for melting treatment, the raw material containing the waste lithium ion battery is used as an oxidizing agent to be added when it is determined that over-reduction is occurring.

According to such a method, the degree of reduction can be appropriately determined in the melting process, and the degree of reduction can be adjusted by appropriately adding an oxidizing agent based on the degree of reduction. As a result, valuable metals can be recovered at a high recovery rate, and metals with effectively reduced contents of impurities such as phosphorus can be obtained. In addition, as an oxidizing agent added when adjusting the degree of reduction, a raw material containing oxides containing nickel and cobalt (for example, raw materials containing waste lithium ion batteries) is added, so the degree of reduction can be effectively adjusted. In addition, since it is an oxidizing agent containing valuable metals to be recovered, the recovery amount of metals can be increased.

In the following, the method for producing a valuable metal will be described more specifically, taking as an example a case where a raw material containing waste lithium ion batteries is used as a raw material containing oxides containing nickel and cobalt.

≪2. About each step of the manufacturing method≫
FIG. 1 is a process diagram showing an example of the flow of a method for producing valuable metals according to the present embodiment. As shown in FIG. 1, the method for producing valuable metals is a method for producing valuable metals from raw materials including waste lithium-ion batteries, and includes a waste battery pretreatment step of removing electrolyte and outer cans from waste lithium-ion batteries. S1, a pulverizing step S2 of pulverizing the contents of the battery to obtain a pulverized product, a preheating step S3 of preheating the pulverized product as necessary (also referred to as an “oxidizing roasting step”), and melting the pulverized product. a melting step (also referred to as a “reduction melting step”) S4 for obtaining a molten material, and a slag separation step S5 for separating slag from the molten material and recovering an alloy containing valuable metals.

[Waste battery pretreatment process]
The waste battery pretreatment step S1 is performed for the purpose of preventing the waste lithium ion battery from exploding or rendering it harmless, removing the outer can, etc., when recovering valuable metals from the waste lithium ion battery.

That is, for example, waste lithium-ion batteries such as used lithium-ion batteries are closed systems and contain electrolytic solution, etc., so if pulverization is performed in that state, there is a risk of explosion and is dangerous. be. Therefore, it is necessary to perform discharge treatment and electrolyte removal treatment in some way. By removing the electrolytic solution and the outer can in the waste battery pretreatment step S1 in this way, safety can be improved, and the recovery productivity of valuable metals such as copper, nickel, and cobalt can be improved.

A specific pretreatment method is not particularly limited, but for example, by physically opening the battery with a needle-like cutting edge, the electrolytic solution inside can be drained and removed. Alternatively, the waste lithium ion battery may be heated as it is and the electrolyte may be burned to render it harmless.

It should be noted that the exterior cans that make up the battery are often made of metals such as aluminum and iron. It is possible to For example, when recovering aluminum or iron contained in the outer can, the removed outer can can be pulverized and then sieved using a sieve shaker. In the case of aluminum, even light pulverization easily turns into powder and can be efficiently recovered. It is also possible to recover the iron contained in the outer can by magnetic sorting.

[Pulverization process]
In the pulverization step S2, the battery content obtained through the waste battery pretreatment step S1 is pulverized to obtain a pulverized material. The treatment in the pulverization step S2 is performed for the purpose of increasing the reaction efficiency in the pyrometallurgical process in the subsequent steps, and by increasing the reaction efficiency, the recovery rate of valuable metals such as copper, nickel, and cobalt can be increased. can be done.

The method of pulverizing is not particularly limited, but the content of the battery can be pulverized using a conventionally known pulverizer such as a cutter mixer.

[Preheating step]
A preheating step S3 can be provided as necessary for the pulverized waste lithium ion battery that has undergone the pulverizing step S2, and heat treatment (oxidizing roasting treatment) can be performed. By performing the heat treatment in the preheating step S3, impurities contained in the contents of the battery can be volatilized or thermally decomposed and removed.

In the preheating step S3, for example, it is preferable to perform heating at a temperature of 700° C. or higher (preheating temperature). By setting the preheating temperature to 700° C. or higher, the efficiency of removing impurities contained in the battery can be enhanced. On the other hand, the upper limit of the preheating temperature is preferably 900° C. or less, which can reduce heat energy costs and improve processing efficiency.

Heat treatment is preferably performed in the presence of an oxidizing agent. This makes it possible to oxidize and remove carbon among the impurities contained in the content of the battery, and to oxidize aluminum. In particular, by removing carbon by oxidation, the molten fine particles of the valuable metal that are locally generated in the subsequent melting step S4 can be aggregated without being physically hindered by carbon, so the alloy obtained as a melt can be integrated to facilitate recovery. In general, the main elements constituting the waste lithium-ion battery are easily oxidized in the order of aluminum>lithium>carbon>manganese>phosphorus>iron>cobalt>nickel>copper due to the difference in affinity with oxygen.

Although the oxidizing agent is not particularly limited, it is preferable to use an oxygen-containing gas such as air, pure oxygen, oxygen-enriched gas, etc. from the viewpoint of ease of handling. Also, the amount of the oxidizing agent to be introduced can be, for example, about 1.2 times the chemical equivalent required for oxidizing each substance to be oxidized.

[Melting process]
In the melting step (reduction melting step) S4, the pulverized waste lithium-ion battery is melted together with the flux to obtain a melted material composed of an alloy containing valuable metals and slag. As a result, impurity elements such as aluminum are included in the slag as oxides, and phosphorus is also taken into the flux and included in the slag. On the other hand, valuable metals such as copper, which are difficult to form oxides, can be melted and recovered from the melt as an integral alloy.

The flux preferably contains an element that takes in impurity elements to form a basic oxide with a low melting point. Among these, it is more preferable to contain a calcium compound because it is inexpensive and stable at room temperature. Phosphorus, which is an impurity element, becomes an acidic oxide when oxidized. Therefore, the more basic the slag formed by the melting treatment, the easier it is to be incorporated into the slag.

As a calcium compound, for example, calcium oxide or calcium carbonate can be added. As for the amount of calcium to be added, since the Al ₂ O ₃ —CaO—Li ₂ O system is used as the slag system, an appropriate amount for melting the alumina in the sample by eutecticization, that is, the weight ratio of CaO/ It is preferable to add an amount such that (Al ₂ O ₃ +CaO)=0.15 or more.

The melting step S4 may be performed in the presence of an oxidizing agent or a reducing agent in order to appropriately adjust the degree of oxidation-reduction when melting the waste lithium ion battery.

A known oxidizing agent can be used, and a solid oxidizing agent may be added, or a gaseous oxidizing agent may be introduced into the furnace. Also, a known reducing agent can be used, but a reducing agent containing carbon atoms is preferable. By adding a reducing agent containing carbon atoms to waste lithium-ion batteries, it is possible to easily reduce oxides of valuable metals such as copper, nickel, and cobalt contained in waste lithium-ion batteries that are to be recovered. .

A specific example of a reducing agent containing carbon atoms is graphite, which can reduce 2 mol of oxides of valuable metals such as copper oxide and nickel oxide with 1 mol of carbon. In addition, hydrocarbons capable of reducing 2 mol to 4 mol of valuable metal oxide per 1 mol, carbon monoxide capable of reducing 1 mol of valuable metal oxide per mol, etc. are used as carbon supply sources. It can also be added. By performing the reduction melting treatment in the presence of carbon as a reducing agent in this manner, the valuable metal can be efficiently reduced, and an alloy containing the valuable metal can be obtained more effectively. Moreover, the reduction treatment using carbon has the advantage of being extremely safe compared to the case of using the thermite reaction in which metal powder such as aluminum is used as a reducing agent.

In addition, when carbon is added as a reducing agent, an excessive amount of carbon may be added. If the amount of carbon added is too large, phosphorus may also be reduced by the carbon and included in the alloy phase if the waste lithium-ion battery contains a phosphorus compound. By melting the waste lithium ion battery in the presence of the flux while adding the phosphorus, the phosphorus can be taken into the flux and removed.

At the time of heating in the melting process, the fluidity of the melted material is low at the stage of reaching the heating temperature, and there is unmelted residue. Finally, it is preferable to observe the inside of the crucible and check whether it is completely melted with an iron measuring rod. After melting, the molten alloy with increased fluidity and the slag are separated in the crucible according to their specific gravities, such as a lower layer of metal and an upper layer of slag. Also at this time, the supernatant slag is sampled using an iron measuring rod, and then cooled and pulverized.

Here, in the method for producing a valuable metal according to the present embodiment, the reduction in the melting process is performed based on the ratio of the amount of cobalt in the alloy generated and recovered by the treatment to the amount of cobalt in the raw material, that is, the cobalt recovery rate. judge the degree. Then, for example, when the cobalt recovery rate is 98% or more, it can be determined that the degree of reduction in the melting process is excessive.

(First aspect regarding calculation of cobalt recovery rate)
As a first aspect, the cobalt recovery rate can be calculated based on the analysis result of the quality of cobalt in the produced slag.

FIG. 2 is a graph showing the relationship between the quality of cobalt in slag and the recovery rate of cobalt. As shown in the graph of FIG. 2, there is a proportional relationship between the quality of cobalt in slag and the recovery rate of cobalt. The amount of flux, such as calcium, to be added to the composition of the waste lithium-ion battery as the raw material is determined as an appropriate amount for melting, so if the composition of the waste lithium-ion battery as the raw material is determined, the amount of slag generated is determined, and the slope and intercept of the proportional relationship are also determined. Therefore, based on such a proportional relationship, the cobalt recovery rate can be effectively calculated from the analysis result of the cobalt quality in the slag.

Using the slag produced by the melting process in this manner, the quality of cobalt in the slag is quickly (for example, within 8 minutes) analyzed by an analysis device such as a fluorescent X-ray analyzer. Thereby, the cobalt recovery rate can be calculated.

Alternatively, the amount of cobalt in the metal is obtained from the amount of cobalt in the slag obtained from the amount of cobalt in the waste lithium-ion battery that is the raw material that is input, the quality of cobalt in the slag generated by the melting process, and the amount of slag generated, The cobalt recovery rate can also be calculated from this. Note that the amount of slag is calculated by subtracting nickel, cobalt, and copper from the amount of waste lithium-ion batteries that were put in, assuming that these are all distributed to metal, the remaining elements become oxides, and the added flux is added to the amount of slag as calcium oxide. Assuming that it will join.

(Second aspect regarding calculation of cobalt recovery rate)
As a second aspect, the cobalt recovery rate can be calculated based on the measurement result of the oxygen partial pressure of the melt (melt) produced by the melting process.

FIG. 3 is a graph showing the relationship between the oxygen partial pressure in the melt and the cobalt recovery rate. As a result of research by the present inventors, it was found that there is a one-to-one correspondence between the oxygen partial pressure in the melt and the cobalt recovery rate, as shown in FIG. It was found that the cobalt recovery rate corresponding to the oxygen partial pressure can be obtained by measuring the oxygen partial pressure of .

The method of measuring the oxygen partial pressure in the melt is not particularly limited as long as it is a method that can directly measure the oxygen partial pressure in the melt. For example, an oxygen analyzer equipped with an oxygen sensor (oxygen probe) is used, and a method of inserting the sensor so that the tip of the oxygen sensor is immersed in the melt for measurement can be used. As the oxygen sensor, a known sensor such as a zirconia solid electrolytic sensor can be used.

For example, referring to FIG. 3, when the oxygen partial pressure in the melt is 10 ⁻¹⁴ atm or less, the cobalt recovery rate exceeds 98%, and when the oxygen partial pressure in the melt is 10 ⁻¹² atm or more. yields less than 95% cobalt recovery.

For this reason, the degree of reduction should be adjusted based on the cobalt recovery rate so that the oxygen partial pressure in the molten body is controlled within a range of more than 10 ⁻¹² atm and less than 10 ⁻¹⁴ atm. So, as shown in the relationship shown in FIG. 4, which will be described later, phosphorus can be removed effectively and efficiently while cobalt is recovered at a high recovery rate. Alloy can be recovered. From the relationship as described above, it is also possible to effectively obtain the target metal by controlling the oxygen partial pressure in the melt.

(Judgment and control of degree of reduction based on calculated cobalt recovery rate)
In this way, when the cobalt recovery rate is calculated from the measurement result of the cobalt grade in the slag and the measurement result of the oxygen partial pressure in the melt, the degree of reduction in the melting process is determined based on the cobalt recovery rate. Specifically, for example, whether the cobalt recovery rate is in the range of 95% or more and 98% or less is confirmed to determine the degree of reduction.

As a result of research by the present inventors, it was found that there is a relationship between the recovery rate of cobalt from raw materials including waste lithium-ion batteries and the grade of phosphorus (P), an impurity contained in the recovered alloy (metal). was done. Specifically, FIG. 4 is a graph showing the relationship between the cobalt recovery rate and the phosphorus grade in the metal (alloy). As shown in the graph of FIG. 4, it can be seen that when the cobalt recovery rate exceeds 98%, the phosphorus grade in the recovered metal rises sharply. The recovery rate of cobalt, which is a valuable metal, is preferably 95% or more.

From this, it is confirmed whether the calculated cobalt recovery rate is in the range of 95% or more and 98% or less. The phosphorus content in the alloy (metal) can be set to 0.1% by mass or less. As a result, phosphorus can be removed effectively and efficiently while cobalt is recovered at a high recovery rate without providing a step of performing a separate dephosphorization treatment after recovering the alloy, and the phosphorus content can be reduced. A reduced high-quality alloy can be recovered.

On the other hand, when the calculated cobalt recovery rate is 98% or more, it can be determined that the degree of reduction in the melting process is excessive, that is, over-reduction. When the cobalt recovery rate is 98% or higher, as indicated by the numerical value, the recovery of cobalt is good, but the proportion of impurities such as phosphorus distributed to the metal increases.

In the method according to the present embodiment, it is thus important to determine the degree of reduction in the melting process based on the obtained cobalt recovery rate. Then, for example, when the calculated cobalt recovery rate is 98% or more, it can be determined that the degree of reduction is excessive, and based on that determination, the degree of reduction in the melting process can be appropriately adjusted. becomes.

Specifically, when the calculated cobalt recovery rate deviates from the range of 95% or more and 98% or less, or even within the range of 95% or more and 98% or less, there is a deviation from the predetermined target value. If the cobalt content of the slag is low, by adding an oxidizing agent as necessary, some of the cobalt in the metal is distributed to the slag, but phosphorus in the metal can be distributed to the slag. Conversely, if the quality of cobalt in the slag is high, by adding a reducing agent, some of the phosphorus in the slag is distributed to the metal, but the cobalt in the slag is distributed to the metal to increase the recovery rate. can.

Thus, it is possible to effectively determine whether the degree of reduction is appropriate or not from the cobalt recovery rate, and to control the melting process by adding an oxidizing agent and a reducing agent as necessary.

Here, when the calculated cobalt recovery rate is 98% or more, the degree of reduction is excessive, that is, the obtained metal is overreduced, and the phosphorus content in the metal increases. Therefore, it is necessary to adjust the degree of reduction by adding an oxidizing agent. At this time, in the method according to the present embodiment, a raw material containing oxides of nickel and cobalt is used as the oxidizing agent. Specifically, as a raw material containing oxides of nickel and cobalt, a raw material containing waste lithium ion batteries is used as an oxidizing agent.

As a result, impurities such as phosphorus in the metal can be effectively oxidized and removed by slag by appropriately adjusting the degree of reduction. And cobalt can be recovered by being reduced to the form of metal.

Generally, in the melting process, an excessive amount of carbon is added as described above, so the frequency of adding an oxidizing agent increases when adjusting the degree of reduction. At this time, by using a raw material containing oxides of nickel and cobalt as an oxidizing agent, it is possible to appropriately adjust the degree of reduction, and the nickel and cobalt contained in the oxidizing agent can also be recovered. can increase the amount of metal recovered.

As the amount of oxidizing agent used for adjusting the degree of reduction, for example, the phosphorus quality in the metal is predicted from the cobalt recovery rate calculated from the cobalt quality in the slag, and the amount of phosphorus required to oxidize all the phosphorus in the metal is Just set the amount and put it in.

Specifically, for example, when the amount of metal is 100 g and the phosphorus grade is estimated to be 0.2% by mass _, the amount of phosphorus in the metal is _0.2 g. is 100%, the reaction formula of P+5/6Ni ₂ O ₃ =1/2P ₂ O ₅ +5/3Ni holds, so the amount of the oxidizing agent Ni ₂ O ₃ added is 0.89 g. Further, if the oxidizing agent is Co ₂ O ₃ and the oxidation efficiency is 100%, the reaction formula of P+5/6Co ₂ O ₃ =1/2P ₂ O ₅ +5/3Co holds, so the oxidizing agent Co ₂ O ₃ added amount is 0.89 g. The exemplified amount of addition is the amount when the reaction efficiency is 100%, but since there is also an oxidation reaction of cobalt in the metal, the reaction of 2P + 5/2O ₂ ⇒ P ₂ O ₅ with respect to phosphorus in the metal It is preferable to set the actual addition amount so that the efficiency is determined to be 30% or more and 90% or less and the holding time is 5 minutes or more and 30 minutes or less. In addition, regarding the amount of the reducing agent to be added, when a reducing agent containing carbon atoms is used, the phosphorus in the slag is also reduced, so the reaction efficiency of 2CoO + C ⇒ 2Co + CO ₂ can be determined as 30% or more and 70% or less. preferable.

As described above, as the oxidizing agent used for adjusting the degree of reduction, raw materials containing oxides of nickel and cobalt, that is, raw materials containing waste lithium ion batteries are used. In this case, an oxide obtained by oxidizing and roasting waste lithium ion batteries at 700° C. to 900° C. (oxide derived from waste lithium ion batteries) is used. The Ni ₂ O ₃ contained in the oxide derived from the waste lithium ion battery is 0% or more and 85% or less, and the Co ₂ O ₃ is 0% or more and 85% or less, and actually contained in the oxide It is preferable to set the amount of oxides to be added based on the analytical values of Ni ₂ O ₃ and Co ₂ O ₃ .

As the oxidizing agent, instead of waste lithium ion batteries, positive electrode materials obtained by sorting waste lithium ion batteries (for example, NCA (nickel-cobalt-aluminum lithium ion battery) scrap) can be used. Ni ₂ O ₃ contained in the positive electrode material is 0% or more and 85% or less, and Co ₂ O ₃ is 0% or more and 85% or less. In this case, the amount of impurities such as aluminum and phosphorus mixed from raw materials other than the positive electrode material can be suppressed, which is preferable.

The adjustment of the degree of reduction is not limited to the use of an oxidizing agent as described above, and may be combined with the addition of a reducing agent. Specifically, the reducing agent can be adjusted by using a material with high carbon grade (graphite powder, graphite granules, coal, coke, etc.) or carbon monoxide. Also, as the reducing agent, a component of the raw material having a high carbon quality can be used.

The heating temperature (melting temperature) in the melting treatment is not particularly limited, but is preferably 1300° C. or higher, more preferably 1350° C. or higher. By performing the melting treatment at a temperature of 1300° C. or higher, valuable metals such as copper, cobalt, and nickel are efficiently melted, and an alloy is formed with sufficiently enhanced fluidity. Therefore, it is possible to improve the separation efficiency between the valuable metal and the impurity component in the slag separation step S5, which will be described later. If the heating temperature is less than 1300° C., the separation efficiency between valuable metals and impurities may be insufficient.

Moreover, the upper limit of the heating temperature in the melting treatment is preferably 1600° C. or less. If the heating temperature exceeds 1600° C., thermal energy is wasted and refractories such as crucibles and furnace walls are consumed rapidly, possibly reducing productivity.

In the melting process, dust, exhaust gas, etc. may be generated, but it can be rendered harmless by applying a conventionally known exhaust gas treatment.

[Slag separation process]
In the slag separation step S5, after solidifying the melt obtained in the melting step S4, the slag is separated from the solidified melt to recover the alloy containing the valuable metal. Since the slag and the alloy contained in the solidified melt are separated due to the difference in their specific gravities, the slag and the alloy can be recovered respectively.

Here, the treatment in the smelting process when producing each valuable metal from an alloy containing valuable metals can be performed by a known method such as neutralization treatment or solvent extraction treatment, and is not particularly limited. For example, in the case of an alloy composed of cobalt, nickel, and copper, after the valuable metal is leached with an acid such as sulfuric acid (leaching step), for example, copper is extracted by solvent extraction (extraction step), and the remaining nickel The solution of cobalt and cobalt can be used by paying out to the positive electrode active material manufacturing process in the battery manufacturing process.

In the method according to the present embodiment, as described above, in the melting step S4, the degree of reduction of the melting process is based on the ratio of the amount of cobalt in the alloy to be produced relative to the amount of cobalt in the raw material (cobalt recovery rate). to confirm. Then, for example, when it is confirmed that the calculated cobalt recovery rate is 95% or more and 98% or less, the melting process is finished, and then the slag is separated in the slag separation step S5 to recover the alloy (metal). . As a result, an alloy with an effectively reduced phosphorus content, specifically, an alloy with a phosphorus content of 0.1% by mass or less can be recovered.

On the other hand, when the melting treatment is determined to be overreduction based on the cobalt quality in the slag, for example, the cobalt recovery rate calculated from the cobalt quality is 98% or more, and it is determined to be overreduction. In some cases, a raw material containing oxides containing nickel and cobalt (raw material containing waste lithium ion batteries) is added as an oxidizing agent to adjust the degree of reduction.

The cobalt recovery rate can be calculated based on the analytical results of the quality of cobalt in the slag. Also, the cobalt recovery rate can be calculated based on the measurement result of the oxygen partial pressure in the melt generated by the melting process.

According to the method according to the present embodiment, in the step of melting waste lithium ion batteries, an alloy containing a valuable metal from which phosphorus has been removed can be efficiently obtained. can simplify the smelting process in producing valuable metals. That is, there is no need to provide a step of performing a dephosphorization treatment on the obtained alloy containing valuable metals. In addition, since the raw material is used as an oxidizing agent that is added when the degree of reduction is excessive, the valuable metal contained in this raw material can also be recovered. That is, valuable metals can be recovered with higher efficiency.

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.

[Recovery processing of valuable metals]
(Waste battery pretreatment process)
First, as waste lithium ion batteries, 18650-type cylindrical batteries, used rectangular batteries for vehicles, and defective products collected in the battery manufacturing process were prepared. Then, after the waste lithium ion batteries are collectively immersed in salt water and discharged, the moisture is removed, and the electrolyte and the outer can are decomposed and removed by roasting in the air at a temperature of 260 ° C., and the contents of the battery are obtained. got stuff The major elemental composition of the battery contents was as shown in Table 1 below.

(Pulverization process)
Next, the battery content was pulverized with a pulverizer (Good Cutter, manufactured by Ujiie Seisakusho Co., Ltd.) to obtain a pulverized product.

(Preheating step)
Next, the pulverized material thus obtained was put into a rotary kiln and preheated in the atmosphere at a preheating temperature of 800° C. for 180 minutes.

(Melting process)
The obtained oxide of the waste lithium ion battery was melted under the conditions shown in Table 2 below. Then, from the cobalt content of 0.01% by mass in the slag obtained in the first run, a cobalt recovery rate of 99.9% was estimated, and from the estimated cobalt recovery rate, the phosphorus content of the metal was 0.6% by mass. was estimated.

Also, the partial pressure of oxygen in the melt at this time was measured. As a result, the measured value of the oxygen partial pressure was 10 ^-15 atm, and the cobalt recovery rate of 99.9% could be estimated from the result of the oxygen partial pressure as well. In the measurement of the oxygen partial pressure, an oxygen analyzer equipped with an oxygen probe (OXT-O manufactured by Kawaso Denki Kogyo Co., Ltd.) was used, and the probe was positioned so that the tip of the oxygen probe was directly immersed in the melt. I plugged it in, waited for the reading to settle, then read it. The oxygen probe was equipped with a zirconia solid electrolytic sensor.

From the estimated phosphorus content in the metal, 0.89 g of Ni ₂ O ₃ and 0.89 g of Co ₂ O ₃ are required as oxidizing agents for every 0.2 mass % of phosphorus content per 100 g of metal. With respect to the amount of 2120 g, the oxide derived from NCA (nickel-cobalt-aluminum lithium ion battery) scrap contains 77% by mass of Ni ₂ O ₃ and 8% by mass of Co ₂ O ₃ . When the oxidation efficiency is assumed to be 100%, the required amount of NCA scrap-derived oxides is 66.6 g. Here, when adjusting the actual degree of reduction, considering the oxidation efficiency, in order to reliably remove phosphorus, 2.4 times the amount, that is, 160 g of NCA scrap-derived oxide with a reaction efficiency of 42% was used as an oxidizing agent. was added to adjust the degree of reduction.

(Slag separation process)
The melt after the melting treatment was cast into a mold by utilizing the difference in specific gravity, and then separated into metal and slag, and the slag was separated from the solidified melt to recover the alloy.

The slag after collecting the alloy was subjected to elemental analysis using an ICP analyzer (Agilent 5100SUDV, manufactured by Agilent Technologies), and the amounts of cobalt and phosphorus were determined as a ratio (% by mass) to the total mass of the slag. .

In addition, the alloy after the slag was separated was also subjected to elemental analysis using an ICP analyzer (Agilent 5100SUDV, manufactured by Agilent Technologies) to measure the amounts of cobalt and phosphorus, and the recovery rate of cobalt from the battery. , determined the phosphorus grade in the alloy.

[result]
Table 2 below shows the recovery rate of cobalt from waste lithium-ion batteries and the phosphorus grade in the alloy relative to the total mass of slag.

As can be seen from the results shown in Table 2, the alloys obtained in Examples have a recovery rate of cobalt, which is a valuable metal contained in the battery, of 95% or more, and the phosphorus content in the obtained alloy is 0. A favorable result of 0.01% by mass or less was obtained. In other words, the degree of reduction during reduction melting can be appropriately adjusted based on the cobalt recovery rate calculated from the result of the cobalt grade in the slag of the waste lithium ion battery in the molten state, and the desired metal can be obtained. rice field.

Further, when the oxygen partial pressure is 10 ⁻¹⁵ atm, the cobalt recovery rate is 99.9%, and when the oxygen partial pressure is 10 ^−12.8 atm, the cobalt recovery rate is 96.4%. As a result, it was shown that there is a relationship between the oxygen partial pressure and the cobalt recovery rate. Moreover, this result was consistent with the graph shown in FIG. Therefore, it has become clear that the cobalt recovery rate can be obtained based on the oxygen partial pressure of the melt, and that the target metal can be obtained based on the cobalt recovery rate. From these results, it was found that the desired metal can be obtained also by controlling the partial pressure of oxygen.

At this time, since NCA scrap was used as an oxidizing agent for adjusting the degree of reduction, it was possible to increase the amount of metal recovered.

Claims (7)

A method for producing a valuable metal from a raw material containing oxides containing nickel and cobalt, comprising:
a melting step of obtaining a melt by subjecting the raw material to a melting process;
A slag separation step of separating slag from the melt and recovering an alloy containing valuable metals;
has
In the melting step, the degree of reduction in the melting process is determined based on the ratio of the amount of cobalt in the alloy to be produced to the amount of cobalt in the raw material (cobalt recovery rate),
If the degree of reduction is determined to be excessive, the raw material containing oxides containing nickel and cobalt is added as an oxidizing agent.
A method for producing valuable metals. In the melting step, the cobalt recovery rate is calculated based on the analysis result of the cobalt grade in the slag.
The method for producing a valuable metal according to claim 1. In the melting step, the cobalt recovery rate is calculated based on the measurement result of the oxygen partial pressure in the melt generated by the melting process.
The method for producing a valuable metal according to claim 1. In the melting step, when the cobalt recovery rate is 98% or more, the degree of reduction in the melting process is judged to be excessive.
4. The method for producing a valuable metal according to any one of claims 1 to 3. The raw material containing an oxide containing nickel and cobalt is a raw material containing a waste lithium ion battery,
5. The method for producing a valuable metal according to any one of claims 1 to 4. The raw material contains phosphorus,
The phosphorus content of the alloy recovered through the slag separation step is 0.1% by mass or less,
A method for producing a valuable metal according to any one of claims 1 to 5. In the melting step, the raw material is melted at a heating temperature of 1300° C. or higher and 1600° C. or lower.
7. The method for producing a valuable metal according to any one of claims 1 to 6.

Images