Methods for recovering valuable materials

Abstract

To provide a method for recovering a valuable substance with a high recovery rate.SOLUTION: A method for recovering a valuable substance includes a physical sorting step for separating a part of C from a valuable substance-containing material, which derives from a secondary battery and includes Ni, Co, and C, by physical sorting, and a reduction step that is performed after the physical sorting step, for heating the valuable substance-containing material for reduction.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present disclosure relates to a method for recovering valuable substances, and more particularly to a method for recovering valuable substances from recovered secondary batteries. [Background technology]

[0002] In recent years, the demand for secondary batteries such as nickel-metal hydride batteries and lithium-ion batteries has increased dramatically due to the increasing demand for mobile phones and computers, and the electrification of automobiles. These secondary batteries contain valuable metals such as cobalt, nickel, and manganese in the positive electrode and graphite in the negative electrode, and recovering valuable metals from used secondary batteries is extremely important from the perspective of effective resource utilization.

[0003] Furthermore, with the increase in demand for secondary batteries, the number of defective secondary batteries generated during the manufacturing process is also on the rise, and recovery of valuable metals from these defective products is also extremely important.

[0004] Therefore, methods for recovering valuable metals from used secondary batteries and defective secondary batteries (these are called "secondary battery waste") are being studied. For example, a method is known in which lithium cobalt oxide or lithium manganese oxide contained in a secondary battery is reduced and roasted using a reducing agent (hydrogen or carbon), and then the roasted product is leached with water to elute the lithium content in the roasted product and distribute valuable metals (cobalt, manganese) into the residue, thereby recovering the respective metals (e.g., Patent Documents 1 and 2). [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2004-11010 [Patent Document 2] Japanese Patent Application Laid-Open No. 2011-094227 Summary of the Invention [Problem to be solved by the invention]

[0006] Conventional recovery methods do not provide sufficient recovery rates for valuable metals and valuable metal compounds (collectively referred to as "valuable substances"), and further improvements in recovery rates are required. Therefore, an object of an embodiment of the present invention is to provide a method for recovering valuable substances that can achieve a high recovery rate. [Means for solving the problem]

[0007] Aspect 1 of the present invention is a physical separation step of separating a portion of C from a valuable substance-containing material obtained from a secondary battery and containing Ni, Co, and C by physical separation; The valuable substance recovery method further comprises a reduction step, which is carried out after the physical separation step, of heating and reducing the valuable substance-containing material.

[0008] Aspect 2 of the present invention is In the method for recovering a valuable substance according to aspect 1, the valuable substance-containing material after the physical separation step has a carbon content of 1.5 to 10.0 mass %.

[0009] Aspect 3 of the present invention is In the method for recovering a valuable substance according to aspect 1 or 2, the physical separation is carried out by one selected from the group consisting of a separation method using a hydrocyclone device, a flotation method, a separation method using a dry cyclone device, and an air classification method.

[0010] A fourth aspect of the present invention is The physical separation step using the hydrocyclone device includes: a slurry preparation step of mixing the valuable substance-containing material with a liquid containing water to prepare a slurry having a solid concentration of 20% by mass or less; a slurry treatment step of separating a portion of C from the slurry using the hydrocyclone device.

[0011] A fifth aspect of the present invention is In the method for recovering a valuable substance according to aspect 4, the slurry preparation step prepares the slurry having a solid concentration of 10% by mass or less. [Effects of the Invention]

[0012] According to the method for recovering valuable substances of the embodiment of the present invention, a high recovery rate can be achieved. [Brief explanation of the drawings]

[0013] [Figure 1] FIG. 1 is a flowchart illustrating a valuable substance recovery method according to an embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0014] When recovering valuable materials such as Ni and Co from secondary battery waste, the valuable material-containing material obtained by crushing the secondary battery waste is roasted together with a reducing agent (reduction treatment). Valuable metal compounds contained in the valuable material are reduced to obtain valuable metals. During this process, the valuable metals aggregate, making it easier to separate them from other substances and allowing the valuable metals to be recovered efficiently. However, depending on the type of secondary battery waste, the valuable metals do not aggregate after reduction treatment, which reduces the recovery rate of the valuable metals.

[0015] The inventors conducted extensive research to improve the recovery rate of valuable substances (especially valuable metals), and discovered that in valuable substance-containing materials for secondary batteries that use graphite as the negative electrode material, the valuable metals do not agglomerate after reduction treatment. Further research led them to discover for the first time that when the content of graphite (component C) in the valuable substance-containing material significantly exceeds the amount consumed as a reducing agent in the reduction treatment, the valuable metals do not agglomerate after reduction treatment, but become powdered metals. Based on this finding, the inventors have completed a new valuable substance recovery method with a high recovery rate of valuable substances.

[0016] The method for recovering valuable substances according to an embodiment of the present invention includes: a physical separation step of separating a portion of C from a valuable substance-containing material obtained from a secondary battery and containing Ni, Co, and C by physical separation; The method includes a reduction step after the physical separation step, in which the valuable substance-containing material is heated and reduced. The collection method is optional. A step of preparing a valuable substance-containing material from secondary battery waste prior to the physical sorting step; A process in which flux is mixed with valuable substance-containing materials after the physical separation process and before the reduction process. may further include one or more of:

[0017] Each step will be described below with reference to FIG.

[0018] [Step S110 of preparing valuable substance-containing materials] In the valuable substance-containing material preparation step S110, the secondary battery waste is subjected to processing such as heating, crushing, sieving, magnetic separation, etc. to prepare a powdered material containing valuable substances (valuable substance-containing material). The procedure for preparing valuable substance-containing materials includes crushing secondary battery waste into powder. The resulting powder of secondary battery waste contains oxides of valuable metals such as Co, Ni, Mn, and Li, as well as C (graphite). It may also contain compounds containing at least one of Li and F (e.g., LiF, AlF). If necessary, the secondary battery waste may be heated before crushing to combust combustible materials, such as separators, contained in the secondary battery waste. In this case, it is desirable to stop heating once the separator combustion is complete. This prevents C (graphite) from being burned and removed. If necessary, powdered elemental metals (e.g., Cu, Fe, Al, etc.) may be separated from the powder of secondary battery waste by sorting methods such as magnetic separation or winnowing after crushing. In this way, a powdered valuable substance-containing material is prepared.

[0019] [Physical sorting process S120] In the physical separation step S120, a portion of the C is separated from the valuable substance-containing material by physical separation. This reduces the C content in the valuable substance-containing material, allowing the metallic Ni and metallic Co formed in the reduction step S140 to be obtained in an agglomerated state. The agglomerated metallic Ni and metallic Co can be recovered efficiently, thereby improving the recovery rate of valuable metals.

[0020] Furthermore, because the physical separation process reduces the C content in the valuable substance-containing material, the concentrations of Ni and Co in the valuable substance-containing material after the physical separation process increase compared to before the physical separation process (in other words, the Ni and Co components are concentrated). In other words, by performing the physical separation process, the amount of valuable metals (metallic Ni and metallic Co) obtained by reducing the valuable substance-containing material can be made greater than the amount of valuable metals obtained from the same amount of valuable substance-containing material that has not been subjected to the physical separation process. The degree of enrichment of the Ni and Co components depends on the amount of C separated from the valuable substance-containing material, but can be, for example, enriched 1.1 to 1.4 times.

[0021] In the physical separation step, it is not necessary to separate and remove all of the C from the valuable substance-containing material. The C remaining in the valuable substance-containing material functions as a reducing agent in the reduction step S140. Here, the "reducing agent" refers to a reducing agent for removing oxygen from the oxides of valuable metals (especially oxides of Co and Ni) in the valuable substance-containing material.

[0022] It is preferable that the C content remaining in the valuable substance-containing material after the physical separation process (referred to as the "residual C amount") is equal to or greater than the amount capable of reducing all of the Co and Ni oxides contained in the valuable substance-containing material (referred to as the "reduced C amount"). Furthermore, it is desirable that the amount of C remaining after the reduction treatment without being consumed in the reduction reaction is an amount that does not prevent the aggregation of metallic Ni and metallic Co (this amount is called "aggregatable C amount"). In other words, it is desirable to adjust the (amount of remaining C) to be equal to or greater than the (amount of reduced C) and equal to or less than the (amount of reduced C + amount of coagulable C).

[0023] The (reduced C amount) varies depending on the amount of Co and Ni oxides contained in the valuable substance-containing material. Therefore, the optimal (remaining C amount) differs depending on the amount of Co and Ni oxides contained in the valuable substance-containing material, but for valuable substance-containing materials obtained from general secondary batteries, it can be, for example, 1.5 to 10.0 mass %.

[0024] In conventional methods for recovering valuable substances (for example, Patent Documents 1 and 2), a reducing agent is mixed with the valuable substance-containing material before the reduction step, or the reduction step is carried out in a reducing gas atmosphere. In contrast, in the valuable substance recovery method according to the embodiment, by utilizing the reducing agent (graphite) contained in the valuable substance-containing material, there is no need to mix a reducing agent with the valuable substance-containing material or to perform a reduction process under a reducing gas atmosphere.

[0025] The sorting method used in the physical sorting step is not particularly limited as long as it can separate and remove C while leaving valuable substances (metallic Ni, Co, and their compounds) in the valuable substance-containing material. Either wet or dry sorting methods can be used as the sorting method. A selection method particularly suited to the invention according to the embodiment will be described below.

[0026] (1. Wet sorting method) Examples of wet separation methods include separation using a hydrocyclone device and flotation.

[0027] (1-1. Wet separation method using a wet cyclone device) In the physical separation process using a wet cyclone device, a slurry preparation step of mixing the valuable substance-containing material with a liquid containing water (aqueous liquid) to prepare a slurry having a solid concentration of 20% by mass or less; and a slurry treatment step of separating a portion of C from the slurry using the hydrocyclone device.

[0028] Slurry preparation process In the slurry preparation process, a slurry suitable for processing in a wet cyclone device is prepared. The slurry is prepared by mixing a valuable substance-containing material with a water-containing liquid. The solid concentration of the slurry is preferably 20% by mass or less. This ensures that the viscosity of the slurry is not too high and that it has a viscosity suitable for supplying it to a wet cyclone device by pump. It is particularly preferable that the solid concentration of the slurry is 10% by mass or less, which can reduce the amount of valuable materials discarded together with the separated graphite powder, as will be described in detail in the description of the slurry treatment step.

[0029] The solid concentration (mass%) of the slurry is calculated using the following formula (1). Solid concentration=W SOL / (W SOL +W LIQ )×100 (1) where: W SOL : mass of valuable substance-containing material contained in the slurry (kg), W LIQ : Mass (kg) of the water-containing liquid (aqueous liquid) contained in the slurry is. W SOL and W LIQ The solid concentration may be calculated as the mass of the valuable substance-containing material and the mass of the water-containing liquid mixed when preparing the slurry.

[0030] Note that reduction treatment of valuable substance-containing materials containing Li and F can sometimes generate toxic white smoke. Here, in the slurry preparation process, the valuable substance-containing material is mixed with an aqueous liquid, so the Li and F contained in the valuable substance-containing material can be dissolved in water and removed. In other words, because Li and F can be removed by the physical separation process performed before the reduction process, the generation of white smoke during the reduction process can be suppressed.

[0031] Furthermore, when Li and F are removed from the valuable substance-containing material by a wet physical separation process using a water-containing liquid, the concentrations of Ni and Co in the valuable substance-containing material after the physical separation process increase compared to before the physical separation process (in other words, the Ni and Co components are concentrated). In other words, by performing the physical separation process, the amount of valuable metals (metallic Ni and metallic Co) obtained by reducing the valuable substance-containing material can be made greater than the amount of valuable metals obtained from the same amount of valuable substance-containing material without performing the physical separation process.

[0032] The water-containing liquid used in the slurry preparation step is not particularly limited, and may be any of water, an acidic aqueous solution, an alkaline aqueous solution, and a neutral aqueous solution, with water being particularly preferred.

[0033] Slurry processing process In the slurry treatment process, a wet cyclone device is used to separate the fine particles (graphite particles) contained in the slurry from the coarse particles (materials containing valuable substances). The wet cyclone device is equipped with a cyclone body whose diameter tapers downward, and slurry is supplied at high speed from a slurry supply port at the top of the cyclone body, horizontally and tangentially to the inner wall of the cyclone body (which has a circular shape in horizontal cross section). The slurry descends while rotating at high speed within the cyclone body, during which time fine particles in the slurry are discharged from the top outlet (TOP) by an updraft generated within the cyclone body, and coarse particles are discharged from the bottom outlet (BOT). Because the graphite powder is fine, it can be recovered from the top outlet, and materials containing valuable substances can be recovered from the bottom outlet. The recovered graphite powder is discarded, and the valuable substance-containing material is further processed in the next step (reduction step S140).

[0034] The size of the particles separated into the upper and lower outlets can be changed by adjusting the slurry viscosity, the flow rate of the slurry inside the cyclone body, and the inclination angle of the cyclone body. Therefore, the slurry viscosity, etc. is basically adjusted so that graphite particles (particle size of tens of microns or less) can be collected from the upper outlet and valuable substance-containing materials can be collected from the lower outlet.

[0035] However, in order to ensure that graphite as a reducing agent is contained in the valuable substance-containing material, the slurry viscosity is adjusted so that some of the graphite remains in the valuable substance-containing material recovered from the lower outlet.

[0036] Since valuable materials contained in the graphite powder recovered from the upper outlet are discarded together with the graphite powder, it is preferable that the amount of such valuable materials be as small as possible. Here, it is preferable to set the solid concentration of the slurry to 10 mass% or less, which can reduce the amount of valuable materials recovered from the upper outlet together with the graphite powder (i.e., valuable materials to be discarded), thereby improving the recovery rate of valuable materials.

[0037] (1-2. Wet separation method using flotation) In the physical separation process using the flotation method, fine particles (graphite particles) and coarse particles (valuable substance-containing material) are separated using commonly known flotation techniques. Foam flotation is a particularly preferred flotation method. Foam flotation can be carried out using a liquid containing water (aqueous liquid). As mentioned above, using an aqueous liquid for foam flotation allows the Li and F contained in the valuable substance-containing material to be dissolved in water and removed, which has the effect of suppressing the generation of white smoke in the reduction process and increasing the amount of valuable metals (metallic Ni and metallic Co) recovered.

[0038] The aqueous liquid used in the foam flotation is not particularly limited and may be any of water, an acidic aqueous solution, an alkaline aqueous solution, and a neutral aqueous solution, with water being particularly preferred.

[0039] (2. Dry sorting method) Dry separation methods include, for example, a separation method using a dry cyclone device and an air classification method.

[0040] (2-1. Dry separation method using a dry cyclone device) As the dry cyclone device, one having the same structure as the wet cyclone device can be used. The dry cyclone device has a cyclone body with a diameter that tapers downward. Powder is supplied at high speed from a powder supply port at the top of the cyclone body in the tangential direction of the cyclone body's inner wall (which is circular in horizontal cross section). In this case, the supplied gas carrier may be air or an inert gas such as nitrogen or argon. The powder descends while rotating at high speed within the cyclone body, during which time fine powder particles are discharged from the top outlet (TOP) by the rising air current generated within the cyclone body, and coarse particles are discharged from the bottom outlet (BOT). Because the graphite powder is fine, it can be recovered from the top outlet, and materials containing valuable substances can be recovered from the bottom outlet. The recovered graphite powder is discarded, and the valuable substance-containing material is further processed in the next step (reduction step S140).

[0041] The size of the particles separated at the upper and lower outlets can be changed by the weight ratio of the gas / powder fed per unit time, the flow rate within the cyclone body, and the inclination angle of the cyclone body. Therefore, the weight ratio and speed of the gas / powder fed per unit time are adjusted so that graphite particles (particle size of several tens of microns or less) can be collected from the upper outlet and valuable substance-containing materials can be collected from the lower outlet. However, in order to ensure that graphite is contained as a reducing agent in the valuable substance-containing material, the weight ratio and speed of the gas / powder fed per unit time are adjusted so that some of the graphite remains in the valuable substance-containing material recovered from the lower outlet.

[0042] (2-2. Dry sorting method using air classification) An air classifier is a device that is equipped with a powder supply device for the inside of the flow path, a gas supply device, a mixing chamber that mixes the gas and powder to fluidize the powder (and a recovery chamber for coarse powder), and a cyclone or bag filter that collects fine powder.It is also equipped with a rotating rotor with holes that serves as a gas flow path for the mixing chamber and cyclone / bag filter. The powder is mixed with the gas and moves simultaneously with the gas, entering the rotating rotor mentioned above, with the fine powder being collected by the cyclone / bag filter at the rear of the rotor. Here, as the rotor is rotating, particles that reach the vicinity of the rotor holes are subjected to viscous forces from the gas being pushed into the rotor and centrifugal forces generated by the rotor rotation. Coarse powder, which is subjected to stronger centrifugal forces, cannot pass through the rotor and returns to the mixing chamber, where it is discharged from an outlet located below the mixing chamber. On the other hand, fine powder is collected by a cyclone or bag filter after passing through the rotor. Valuable materials are discharged into the coarse powder side, but the rotor rotation speed / gas flow rate, etc. are adjusted so that some of the graphite remains here.

[0043] [Flux mixing process S130] Optionally, a flux mixing step S130 is performed in which flux is mixed with the valuable substance-containing material after physical separation. In the flux mixing step S130, a flux for melting the recovered material is mixed. As the flux, any flux known in the art can be used, such as CaO, SiO2, FeO, MgO, steel slag, CaCo3 (e.g., limestone), dolomite, silica sand, etc.

[0044] [Reduction step S140] In the reduction step S140, the valuable substance-containing material after the physical separation step (or the optional flux mixing step) is heated and melted to reduce the valuable metal oxides contained in the valuable substance-containing material (reduction treatment). The heating temperature for the reduction treatment is sufficient to melt the valuable substance-containing material and cause a reduction reaction between the reducing agent and the valuable metal oxide, and can be set appropriately depending on the type of reducing agent, the type of target oxide, etc. The heating time is sufficient to allow the reduction reaction between the reducing agent and the valuable metal oxide to proceed sufficiently at a predetermined heating temperature, and can be set appropriately depending on the heating temperature, the type of reducing agent, the type of target oxide, etc. As a typical example, when reducing Co and Ni oxides using a carbonaceous reducing agent, the heating temperature can be 1400°C or higher and 1650°C or lower, and the heating time can be 60 minutes or shorter. The heating temperature is the temperature of the crucible (heating element). The crucible temperature is measured using a thermocouple attached to the surface of the crucible.

[0045] According to the valuable substance recovery method of the embodiment, by performing a reduction treatment after removing a portion of the excess C (graphite powder) contained in the valuable substance-containing material by physical separation, not only is the C remaining in the valuable substance-containing material used as a reducing agent for the reduction treatment, but also the aggregation of metallic Ni and metallic Co obtained by the reduction treatment is enabled. This omits the step of adding a reducing agent to the valuable substance-containing material, reducing recovery costs, and further improving the recovery rate of metallic Ni and metallic Co. [Example]

[0046] [Examples Nos. 1 to 6] In order to investigate the effect of physical separation of valuable material-containing materials, the removal rate and residual rate of various elements by physical separation were investigated.

[0047] (Preparation of Slurry) A lithium ion battery was heated and crushed to obtain powder, which was used in Examples 1 to 6 as a valuable substance-containing material. The valuable substance-containing material and water were weighed and placed in a container so as to achieve the solid concentration shown in Table 1, and then the mixture was stirred in a mixer to prepare a slurry.

[0048] (Physical sorting) The slurry was physically separated using a hydrocyclone device (SC-150 Superclone, manufactured by Murata Manufacturing Co., Ltd.). The diameter of the upper outlet (TOP) of the hydrocyclone device was 20–30 mm, and the diameter of the lower outlet (BOT) was 5–20 mm. The flow rate of the slurry supplied to the hydrocyclone device was 70–130 L / min, the inlet pressure at the slurry supply port was 0.05–0.10 MPa, and the outlet pressure at the upper and lower outlets was 0.00–0.07 MPa.

[0049] The slurry was collected from the upper outlet (TOP) and the lower outlet (BOT) of the hydrocyclone device, and the water was removed by filtration. The mass of the collected slurry after filtration (W TOP [kg]) and the filtered mass of the collected material from the lower outlet (W BOT[kg]) were measured. In addition, the components of the recovered material were analyzed, and the content of the target elements in the material recovered from the upper outlet (X TOP [mass%]) and the content of the target element in the collected material from the lower outlet (X BOT In addition, the slurry before physical separation in the hydrocyclone device was filtered to remove water, and the content of the target element (X BEF The component analysis was carried out using an ICP optical emission spectrometer SPS3500DD (manufactured by SII Corporation).

[0050] The elements measured were C, Ni, Co, Li, and F. The removal rate (%) of C, Li, and F was calculated using the following formula (2). The remaining rate (%) of Ni and Co was calculated using formula (3). Removal rate=100-X BOT ×W BOT / {X BEF ×(W BOT +W TOP )}×100 (2) Survival rate=X BOT ×W BOT / (X BOT ×W BOT +X TOP ×W TOP )×100 (3)

[0051] The removal rate defined by formula (2) is the ratio (R BOT [%]), then subtract 100[%] from R BOT The value is the difference between the two.

[0052] The residual rate defined by equation (3) is the ratio of the amount [kg] of the measured element in the valuable substance-containing material to the sum of the amount [kg] of the measured element contained in the graphite powder recovered from the upper outlet after physical separation and the amount [kg] of the measured element contained in the valuable substance-containing material recovered from the lower outlet, which is taken as 100%.

[0053] The calculation results are shown in Table 1. Note that for C, Li, and F, the higher the removal rate, the better, and for Ni and Co, the higher the remaining rate, the better. In addition, the C content in the collected material from the lower outlet (X BOT The carbon content (mass %) of the valuable substance-containing material after the physical separation process is shown in Table 2. This corresponds to the carbon content (mass %) of the valuable substance-containing material after the physical separation process.

[0054] [Table 1]

[0055] [Table 2]

[0056] In all of Examples Nos. 1 to 6, the removal rate of C was high, and it was also possible to partially remove Li and F. Therefore, it was confirmed that the wet cyclone device is suitable for the physical separation process of valuable substance-containing materials. Furthermore, it was found that in Examples 1 to 4, in which the solid concentration was 10% or less, the residual rates of Ni and Co were high, and the amounts of Ni and Co discarded together with the graphite powder could be reduced.

[0057] The reason for this result can be inferred as follows. The reason why the residual rates of Ni and Co were low in Examples 5 and 6 is thought to be that the high viscosity of the slurry prevented Ni and Co, which have high specific gravities, from reaching the lower outlet and were instead discharged from the upper outlet together with the graphite powder.

[0058] Although Examples 2 to 4 have the same solid concentration, the removal rates of C, Li, and F differ, which is thought to be due to variations in the components contained in the lithium-ion batteries from which the valuable substance-containing material was made, and the test conditions (particularly, variations in the contact conditions with water for Li and F, which dissolve in water). Compared to the differences (variations) in the removal rates in Examples 2 to 4, the differences between the removal rates in Examples 2 to 4 and those in Examples 1, 5, and 6, which have different solid concentrations, are significantly larger, making it clear that the solid concentration of the slurry affects the removal rates of C, Li, and F.

[0059] As shown in Table 2, the carbon content of the valuable substance-containing materials after the physical separation process was in the range of 1.5 to 10.0 mass % in all cases.

[0060] [Examples Nos. 7 to 10] The relationship between the carbon content after physical separation and the presence or absence of aggregation after reduction treatment was investigated.

[0061] (Materials containing valuable substances after physical sorting (before reduction process)) In Example No. 10, a valuable substance-containing material was used, which was obtained by physically separating a slurry prepared under the same conditions as in Example No. 2 under the same conditions and drying the recovered material from the lower outlet. In Examples Nos. 7 to 9, a valuable substance-containing material was used, which was obtained by mixing a predetermined amount of a carbon source (Wako Special Grade Graphite Reagent, manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) with the valuable substance-containing material obtained in Example No. 10. The amount of carbon source mixed in Examples Nos. 7 to 9 was adjusted so that the C content in the valuable substance-containing material would be close to the C content shown in Table 3.

[0062] The carbon content of the valuable substance-containing materials of Examples 7 to 10 was measured using an ICP optical emission spectrometer SPS3500DD (manufactured by SII Corporation). Note that the carbon content of Example No. 2 in Table 2 is slightly different from the carbon content of Example No. 10 in Table 3, but this is within the margin of error.

[0063] (Reduction process) 50 g of the valuable substance-containing materials of Examples 7 to 10 were placed in a graphite crucible and heated in a N2 atmosphere to carry out the reduction process. The heating furnace used was an MU αIV manufactured by SK Medical Co., Ltd., and the material was heated at a rate of 100°C / min. After reaching 1450°C, it was maintained for 10 minutes and then cooled. The obtained valuable substance was recovered together with the crucible after it had cooled sufficiently.

[0064] The recovered valuable materials were subjected to non-destructive evaluation (X-ray CT observation) while still in the crucible using a μ-focus CT scanner TXS-33000FD manufactured by Toshiba IT Control Systems Corp. Metal particles (appearing white) were identified through X-ray CT observation, and the particle diameters (equivalent spherical diameters) of the metal particles were determined through 3D image analysis, and the volume distribution for each particle diameter was obtained.

[0065] When the total amount of metals contained in the valuable substance after the reduction process was taken as 100% by volume, the content of metal particles with a diameter of 1 mm or more (considered to be "aggregates") was calculated. If the aggregate content was 10% by volume or more, it was determined that aggregation had occurred, and this was recorded as "aggregated" in Table 3. On the other hand, if no aggregates were present in the valuable substance (aggregate content was 0% by volume), or if aggregates with a diameter of 1 mm or more were present but the aggregate content was less than 10% by volume, this was recorded as "not aggregated" in Table 3.

[0066] After X-ray CT observation, the valuable substances of Examples 8 to 10 were recovered from the crucible, and the aggregates (lumps with metallic luster) were separated with tweezers and a magnet was brought close. It was confirmed that the aggregates of all of the valuable substances of Examples 8 to 10 were magnetically attracted. This indicated that the aggregates contained the target element, Ni.

[0067] [Table 3]

[0068] The results in Table 3 confirm that by reducing the C content before carrying out the reduction step, valuable metals can be agglomerated after the reduction step.

Claims

1. a physical separation step of separating a portion of C from a valuable substance-containing material obtained from a secondary battery and containing Ni, Co, and C by physical separation; a reduction step, which is performed after the physical separation step, by heating the valuable substance-containing material at a heating temperature of 1400°C or higher and 1650°C or lower to perform a reduction treatment, The method for recovering valuable substances, wherein the carbon content of the valuable substance-containing material after the physical separation step is 1.5 to 10.0 mass%.

2. 2. The method for recovering valuable substances according to claim 1, wherein the physical separation is carried out by one method selected from the group consisting of a separation method using a hydrocyclone device, a flotation method, a separation method using a dry cyclone device, and an air classification method.

3. The physical separation step using the hydrocyclone device includes: a slurry preparation step of mixing the valuable substance-containing material with a liquid containing water to prepare a slurry having a solid concentration of 20% by mass or less; The method for recovering valuable substances according to claim 2, further comprising a slurry treatment step of separating a portion of C from the slurry using the hydrocyclone device.

4. The method for recovering valuable substances according to claim 3 , wherein the slurry preparation step prepares the slurry having a solid concentration of 10% by mass or less.

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