Method for utilizing waste box sagger

Abstract

A method for utilizing a waste box sagger according to the present invention is characterized by comprising the steps of: preparing a crushed material of a waste box sagger; preparing an ore containing lithium; calcining the ore containing lithium to obtain a calcined material; roasting the calcined material with sulfuric acid to obtain a roasted material; and obtaining a lithium sulfate aqueous solution by water-leaching the roasted material, wherein the crushed material of the waste box sagger is introduced in the step of obtaining the lithium sulfate aqueous solution by water-leaching the roasted material.

Description

Methods of utilizing waste refractory armor

[0001] This application is an application having priority to Korean Patent Application No. 10-2024-0181454, and the contents of said priority application are all included in this specification.

[0002] The present invention relates to a method for utilizing waste refractory plates.

[0003] The positive active material of a lithium secondary battery is manufactured by firing a salt containing lithium, cobalt, nickel, manganese, etc., at a high temperature in a refractory container mainly composed of silicon, aluminum, and magnesium oxide.

[0004] At this time, the raw material of the positive electrode active material may react with the surface of the refractory case, and as the refractory case is repeatedly used, the surface of the refractory case is eroded and deteriorated by the raw material of the positive electrode active material, so it must be discarded after a certain number of uses.

[0005] Waste box saggers, which are inevitably generated after use, are currently being disposed of due to a lack of recycling technology, and the amount of waste box saggers generated is expected to increase rapidly due to the rapid demand for secondary batteries. Therefore, there is a need to develop methods to recycle waste box saggers.

[0006] The present invention aims to provide a method for utilizing waste refractory casings that can be recycled by using the waste refractory casings, which were previously discarded, as a precipitating agent in a process for producing an aqueous lithium sulfate solution from lithium-containing ore.

[0007] In addition, the present invention aims to provide a method for utilizing waste refractory plates to recover lithium by replacing a portion of the lithium-containing ore.

[0008] The present invention provides a method for utilizing waste refractory armor, comprising the steps of: preparing a crushed waste refractory armor; preparing an ore containing lithium; calcining the ore containing lithium to obtain a calcined product; mixing the calcined product with sulfuric acid and then roasting it to obtain a roasted product; and leaching the roasted product with water to obtain an aqueous lithium sulfate solution, wherein, in the step of leaching the roasted product with water to obtain an aqueous lithium sulfate solution, the crushed waste refractory armor is introduced.

[0009] The method of utilizing waste refractory casings according to the present invention has excellent environmental advantages in that waste refractory casings, which were previously discarded, can be used as a precipitating agent in a process of producing an aqueous lithium sulfate solution from lithium-containing ore.

[0010] In addition, it can replace a portion of lithium-containing ore, offering excellent advantages in both cost and environmental aspects.

[0011] Figures 1 and 2 are figures showing a lung refractory plate.

[0012] Figure 3 is a figure showing the particle size distribution of crushed waste refractory armor according to some embodiments of the present invention.

[0013] Figure 4 is a figure showing the X-ray diffraction analysis results of crushed waste refractory armor according to some embodiments of the present invention.

[0014] Figure 5 is a figure showing the lithium concentration and lithium leaching rate relative to the amount of crushed waste refractory material input according to some embodiments of the present invention.

[0015] Hereinafter, embodiments of the present invention will be described in detail. However, these are presented as examples and are not intended to limit the present invention, and the present invention is defined only by the scope of the claims set forth below.

[0016] In the present invention, when a part is described as "comprising" a certain component, this means that, unless specifically stated otherwise, it does not exclude other components but may include additional components.

[0017]

[0018] One aspect of the present invention relates to a method for utilizing waste refractory armor, comprising the steps of: preparing a crushed waste refractory armor; preparing an ore containing lithium; calcining the ore containing lithium to obtain a calcined product; mixing the calcined product with sulfuric acid and then roasting to obtain a roasted product; and leaching the roasted product with water to obtain an aqueous lithium sulfate solution, wherein, in the step of leaching the roasted product with water to obtain an aqueous lithium sulfate solution, the crushed waste refractory armor is introduced.

[0019] In the present invention, the waste refractory container is a ceramic container used for firing a positive electrode active material for a secondary battery, and may contain compounds such as Li-Al2O3, Li-SiO2, etc.

[0020]

[0021] A method for utilizing waste refractory armor according to the present invention comprises the step of preparing crushed waste refractory armor.

[0022]

[0023] In the present invention, “Dv50” refers to the particle size corresponding to when the cumulative volume distribution percentage of the crushed waste refractory material reaches 50% in the particle size distribution curve of the crushed waste refractory material. The Dv50 can be measured, for example, using a laser diffraction method. FIG. 3 is a figure showing the particle size distribution of the crushed waste refractory material according to some embodiments of the present invention.

[0024]

[0025] In one embodiment of the present invention, the crushed waste refractory material may have a Dv50 of 3 to 15 μm.

[0026] In another embodiment of the present invention, the crushed waste refractory material may have a Dv50 of 5 to 10 μm.

[0027] Specifically, the above-mentioned crushed waste refractory material may have a Dv50 of 8 to 10 μm.

[0028] If the Dv50 of the above-mentioned crushed waste refractory material satisfies the above range, there is an advantage in maximizing the leaching efficiency in the step of obtaining an aqueous lithium sulfate solution by leaching the roasted material described later.

[0029] The method of obtaining the above-mentioned crushed waste refractory material is not limited in the present invention. For example, the waste refractory material can be obtained by crushing it using a jaw crusher, hammer mill, ball mill, roller mill, jet mill, etc., and classifying it using a classifier, vibrating screen, etc., if necessary.

[0030]

[0031] In another embodiment of the present invention, the crushed waste refractory material may comprise one or more selected from the group consisting of an attachment layer, a modified layer, and a raw layer of the waste refractory.

[0032] Referring to Fig. 1, it can be seen that the waste refractory plate has layers of different properties. Specifically, the waste refractory plate can be divided into a primary layer, a modified layer formed by the diffusion or penetration of a substance such as lithium into the waste refractory plate, and an attachment layer formed on top of the modified layer.

[0033] Preferably, after crushing the above waste refractory plate, the altered layer can be separated and used.

[0034]

[0035] In another embodiment of the present invention, the crushed waste refractory material may have a lithium content of 1.7 parts by weight or more per 100 parts by weight of the total.

[0036] In another embodiment of the present invention, the crushed waste refractory material may have a lithium content of 2.5 parts by weight or more per 100 parts by weight of the total. Specifically, when the step of preparing the crushed waste refractory material further includes the step of separating the lithium-containing layer, the lithium content may be 2.5 parts by weight or more per 100 parts by weight of the total waste refractory material.

[0037] The above-mentioned crushed waste refractory material is not only useful as a precipitating agent, but also has the advantage of being able to replace a portion of the lithium-containing ore because it has the aforementioned lithium content.

[0038]

[0039] In another embodiment of the present invention, the crushed waste refractory material may contain LiAlO2.

[0040]

[0041] A method for utilizing waste refractory plates according to the present invention comprises the step of preparing an ore containing lithium.

[0042] The above lithium-containing ore may include one or more selected from the group consisting of spodumene, petalite, lepidolite, hectorite, eucryptite, jadarite, zinnwaldite, and amblygonite.

[0043] Specifically, the above lithium-containing ore may be spodumene.

[0044]

[0045] The method of utilizing waste refractory plates according to the present invention has the advantage of reducing costs while securing an excellent lithium leaching rate by using crushed waste refractory plates as a precipitating agent in the process of obtaining an aqueous lithium sulfate solution using spodumene.

[0046] Although I do not wish to be limited by theory, when lithium-containing ore, such as spodumene ore, is leached after calcination and roasting, impurities such as Al, Si, and Fe are dissolved. To remove these impurities, alkali is added to raise the pH, thereby causing them to precipitate as hydroxides, etc.

[0047] Since the above-mentioned crushed waste refractory material has a relatively high pH, ​​when the above-mentioned crushed waste refractory material is added, there is an advantage in that the pH of the leaching solution of spodumene ore is raised, thereby easily removing impurities leached from spodumene ore.

[0048]

[0049] The step of preparing the lithium-containing ore; may include the step of crushing the lithium-containing ore.

[0050] Specifically, the lithium-containing ore may be processed using a crusher so that the average particle size of the ore is 150 μm or less, preferably 100 μm or less, and more preferably 50 to 100 μm, but is not limited thereto.

[0051] If the average particle size of the lithium-containing ore is crushed to satisfy the above range, it is desirable to minimize the process time in the calcination process and sulfuric acid roasting process described later.

[0052]

[0053] A method for utilizing waste refractory armor according to the present invention comprises the step of obtaining a calcined product by calcining the lithium-containing ore.

[0054] In the step of obtaining the above calcined material, the calcination time may be performed for 5 minutes to 5 hours, preferably 10 minutes to 3 hours.

[0055] When the above calcination time satisfies the above range, the phase transition from the α phase to the β phase of the lithium-containing ore is sufficient, and it is desirable to suppress the phenomenon in which the lithium leaching rate decreases due to under-calcination or under-calcination.

[0056] The above calcination may be performed through a box furnace, but is not limited thereto.

[0057] The above calcination can be performed at 800 to 1,500°C, preferably 800 to 1,300°C, and more preferably 800 to 1,100°C.

[0058] When the above calcination is performed within the above temperature range, it is desirable that the phase transition from the α phase to the β phase of the lithium-containing ore can be sufficiently achieved while saving energy.

[0059]

[0060] The method for utilizing crushed waste refractory material according to the present invention comprises the step of obtaining a roasted material by mixing the above-mentioned calcined material with sulfuric acid and then roasting it.

[0061] By mixing the above-mentioned calcined material, that is, the above-mentioned lithium-containing ore that has been calcined, with sulfuric acid and then roasting it, the lithium within the lithium-containing ore can be transformed into a water-soluble substance.

[0062] Specifically, the above lithium-containing ore can be mixed with sulfuric acid, homogenized, and then roasted.

[0063] The equivalent ratio of lithium to sulfuric acid in the above calcined product may be 1:1.0 to 1:1.8. It is desirable that the equivalent ratio of lithium to sulfuric acid in the above calcined product satisfies the above range, as this can reduce process costs.

[0064] The concentration of the above sulfuric acid may be 95% or higher.

[0065] The above roasting can be performed at a temperature range of 175 to 250°C, preferably 200 to 250°C, for 30 minutes to 2 hours, preferably 30 minutes to 1 hour.

[0066] It is desirable that the roasting time and energy consumption be minimized when the roasting is performed within the above-mentioned time range at the above-mentioned roasting temperature range.

[0067]

[0068] A method for utilizing crushed waste refractory material according to the present invention comprises the step of obtaining an aqueous lithium sulfate solution by leaching the roasted material with water; wherein, in the step of obtaining an aqueous lithium sulfate solution by leaching the roasted material with water, the crushed waste refractory material is introduced.

[0069] Although it is not desired to be limited by theory, when the above-mentioned crushed waste refractory material is introduced, the basic oxide contained in the above-mentioned crushed waste refractory material reacts with water to produce a hydroxide, and as a result, the pH of the above-mentioned lithium sulfate aqueous solution may increase.

[0070] In other words, it can be usefully utilized as a precipitating agent that performs the role of precipitating impurities and raising the pH. Specifically, a portion of the above precipitating agent can be replaced with the above crushed waste refractory material.

[0071] In addition, there is also the advantage that the lithium contained in the crushed waste refractory armor is leached out.

[0072]

[0073] In another embodiment of the present invention, the crushed waste refractory material may be added in an amount of 50 parts by weight or less, preferably 40 parts by weight or less, and more preferably 30 parts by weight or less, based on 100 parts by weight of the total roasted material.

[0074] When the above-mentioned crushed waste refractory material is included within the above range, it is desirable to maximize the lithium leaching rate and minimize the leaching amount of impurities.

[0075] In the present invention, “impurities” may contain one or more elements selected from the group consisting of Al, Si, Fe, Mg, Ca, Na, K, Ni, Co, and Mn.

[0076]

[0077] In the step of obtaining an aqueous lithium sulfate solution by leaching the above-mentioned roasted product with water; the leaching water for leaching may be pure water or distilled water, but is not limited thereto.

[0078] It is desirable that the above leachate does not contain acidic substances such as sulfuric acid. It is desirable that the above leachate does not contain acidic substances such as sulfuric acid because it is environmentally friendly.

[0079]

[0080] The weight ratio of the roasted material to the leachate may be 1:1 to 1:4, preferably 1:1.5 to 1:3, and more preferably 1:2 to 1:3. When the weight ratio of the roasted material to the leachate satisfies the above range, it is desirable to minimize the content of the leachate while maintaining excellent lithium leaching efficiency, thereby reducing process costs.

[0081]

[0082] In another embodiment of the present invention, in the step of obtaining an aqueous lithium sulfate solution by leaching the roasted product with water, an auxiliary precipitating agent may be further added.

[0083] The lithium leaching solution, in short, the above-mentioned aqueous lithium sulfate solution, exhibits acidity. Generally, the lithium leaching solution may contain impurities leached along with lithium, and most of these impurities are removed from the solution by raising the pH and causing precipitation.

[0084] Typically, in most primary purifications, the pH is adjusted to between 5 and 8.5, but using additional auxiliary precipitating agents makes it easier to adjust the pH, which is desirable.

[0085] In another embodiment of the present invention, the auxiliary precipitating agent may include one or more selected from the group consisting of Ca(OH)2 and CaCO3.

[0086] The above Ca(OH)2 and CaCO3 are desirable because they have the advantage of being relatively inexpensive compared to other auxiliary precipitating agents.

[0087] The above auxiliary precipitating agent may be added to satisfy the pH range described below.

[0088]

[0089] In another embodiment of the present invention, the step of leaching the roasted product to obtain an aqueous lithium sulfate solution may be performed at a pH of 5 or higher.

[0090] In another embodiment of the present invention, the step of leaching the roasted product with water to obtain an aqueous lithium sulfate solution may be performed at a pH of 5 to 8.5.

[0091] Although I do not wish to be limited by theory, generally, when lithium-containing ore is mixed with sulfuric acid and then roasted and leached with water, the pH of the lithium sulfate aqueous solution is somewhat low at 1-2, so impurities can be precipitated by adjusting the pH to the above range.

[0092] Specifically, in the present invention, the crushed waste refractory armor is used as a precipitating agent, and the pH can be adjusted to the above range by additionally using an auxiliary precipitating agent.

[0093]

[0094] In another embodiment of the present invention, the step of leaching the roasted product with water to obtain an aqueous lithium sulfate solution may be performed for 10 to 120 minutes, preferably 10 to 90 minutes, more preferably 10 to 60 minutes.

[0095] When the step of obtaining an aqueous lithium sulfate solution by leaching the above-mentioned roasted product with water is performed within the above time range, it is desirable to increase the lithium leaching rate while minimizing the water leaching time. Additionally, it is desirable to reduce energy consumption.

[0096]

[0097] The step of obtaining an aqueous lithium sulfate solution by leaching the above-mentioned roasted product with water can be performed at room temperature, for example, at a temperature of 20 to 25°C.

[0098]

[0099] The step of obtaining an aqueous lithium sulfate solution by leaching the above-mentioned roasted product with water can be performed while stirring at 50 to 500 RPM, preferably 100 to 400 RPM, more preferably 200 to 300 RPM.

[0100] When the step of obtaining an aqueous lithium sulfate solution by leaching the above-mentioned roasted product with water is performed while stirring at the above-mentioned stirring speed, it is desirable to maximize the lithium leaching efficiency while minimizing the lithium leaching time.

[0101]

[0102] Subsequently, the above lithium sulfate aqueous solution is purified to remove impurities present in the above lithium sulfate aqueous solution, and then solid-liquid separation is performed to obtain a purified lithium sulfate solution, specifically a lithium sulfate solution from which impurities such as Si, Al, and Fe have been removed.

[0103] The above purification may be performed two or more times, but is not limited thereto. Specifically, the purification step may include a first purification step and a second purification step.

[0104] The above purification can be performed by a method conventionally carried out in the industry using purification auxiliary materials, and the present invention does not limit the purification method.

[0105]

[0106] The above-mentioned solid-liquid separation can be performed, for example, using a microfilter, but is not limited thereto, and can be performed by conventional methods used in the industry.

[0107]

[0108] The method of utilizing waste refractory casings according to the present invention has excellent environmental advantages, as it allows waste refractory casings that were previously discarded to be used as a precipitating agent in a process of producing an aqueous lithium sulfate solution from lithium-containing ore.

[0109] In addition, since the lithium contained in the crushed waste refractory material is leached out together during the process of preparing the above-mentioned lithium sulfate aqueous solution, it is desirable to have the advantage of recovering the lithium within the crushed waste refractory material that was previously discarded, thereby partially replacing the lithium-containing ore.

[0110]

[0111] Preferred embodiments and comparative examples of the present invention are described below. However, the following examples are merely preferred embodiments of the present invention, and the present invention is not limited to the following examples.

[0112]

[0113] Preparation Example: Crushed waste refractory material

[0114] The waste refractory material used was the one used in the process of manufacturing the N86-based cathode active material (which has a Ni content of 86% among NCM-based cathode active materials) (see Figures 1 and 2).

[0115] After crushing the waste refractory with a jaw crusher and manually separating the altered layer, crushed waste refractory was obtained using a ball mill.

[0116]

[0117] Experimental Example 1: Measurement of particle size of crushed waste refractory armor

[0118] The particle size of the crushed waste refractory material was measured (Malvern Panalytical (manufacturer), Mastersizer 3000 (model name)), and the results are shown in Table 1 and Figure 3 below.

[0119]

[0120] Dv10Dv50Dv902.2㎛8.9㎛20.7㎛

[0121] Experimental Example 2: Component Analysis of Crushed Waste Refractory Material

[0122] The compositional analysis of the crushed waste refractory material was performed using an X-ray diffractometer (XRD) (SmartLab, X-Rigaku), and the X-ray diffraction analysis results are shown in Figure 4.

[0123] Examples and Comparative Examples

[0124] The spodumene concentrate used was a concentrate of 75 µm or less, with a lithium content of 2.7%.

[0125] The prepared spodumene concentrate was subjected to a calcination-sulfurized roasting-water leaching process, at which time the amount of crushed waste refractory material added per 100g of roasted material according to the examples and comparative examples is shown in Tables 2 and 3.

[0126] Specifically, a box furnace was used for calcination, and a heating rate of 5 K / min was applied. The sample was obtained by maintaining the temperature at 1,100°C for 1 hour and then cooling the furnace. The obtained sample was homogeneously mixed with 98% pure sulfuric acid, at a mass ratio of 30% relative to the amount of the calcined mixed sample. Homogenization was performed by mixing with a glass rod at least 200 times.

[0127] The mixed sample was roasted in a box furnace. The temperature was increased at a rate of 5 K / min, maintained at 250°C for 1 hour, and then cooled in the furnace to obtain the sample.

[0128] A slurry was prepared by using a dilution of DI water (Deionized water) based on the mass of the secured sample, and then the crushed waste refractory material was added. After adding the crushed material, the mixture was stirred at room temperature for 30 minutes. A lithium sulfate aqueous solution was obtained by continuously stirring at 250 RPM using a magnetic bar.

[0129]

[0130] Input amount of crushed waste refractory material (g / 100g roasted ore) LiS PC a Mg K Na Si Comparative Example 0 1 1.39 3 0.4 1 0.0 3 0 0.45 9 0.0 19 0.14 3 0.69 7 0.0 3 0 Example 1 5 1 1.5 1 3 0.6 6 0.0 2 9 0.45 8 0.0 9 6 0.14 8 0.70 0 0.2 4 7 Example 2 1 0 1 1.9 1 3 1.2 4 0.0 2 7 0.45 0 0.14 4 0.16 7 0.75 0 0.3 9 8 Example 3 3 0 1 3.0 6 3 2.5 2 0.0 9 0.46 3 0.2 2 0 0.15 0 0.80 5 0.2 5 0 Example 45014.0034.25<0.0030.4220.2260.1530.8660.057

[0131] Input amount of crushed waste refractory material (g / 100g roasted ore) AlFeNiMnTiZnpHLi Leaching rate (%) Comparative Example 0 0.60 0 0.200 Non-detectable 0.031 Non-detectable <0.003 1.48 - Example 1 5 0.94 5 0.29 8 0.003 0.03 5 0.004 <0.003 2.10 9 1.0 Example 2 1 0 1.28 9 0.36 7 0.005 0.04 2 0.005 0.004 3.41 9 1.3 Example 3 3 0 0.67 4 0.160 Non-detectable 0.046 Non-detectable 0.005 4.16 9 7.7 Example 4 5 0 Non-detectable 0.040 Non-detectable 0.047 Non-detectable Non-detectable 5.53 9 1.6

[0132] Experimental Example 3: Component Analysis of Lithium Sulfate Aqueous Solution

[0133] The main components (g / L) in the aqueous lithium sulfate solution obtained according to the examples and comparative examples were obtained through ICP-OES analysis, and the results are shown in Tables 2 and 3 above, and the ratio of impurities to Li is shown in Table 4 below.

[0134] In addition, the lithium concentration and lithium leaching rate relative to the amount of crushed waste refractory material input are shown in Figure 5.

[0135] Specifically, in FIG. 5, “Li concentration, calculated value” represents the theoretically calculated lithium concentration when 100% of lithium is leached from the lithium content of the lithium-containing ore and the lithium content of the crushed waste refractory armor, “Li concentration, measured value” represents the lithium concentration analyzed by an analyzer, and “lithium leaching rate (%)” represents (measured value / calculated value) × 100.

[0136]

[0137] Input amount of crushed waste refractory material (g / 100g roasted ore) Li / Mg Li / Si Li / Al Li / Mn Comparative Example 01.01.01.01.0 Example 1 55.08.11.6 1.1 Example 2 107.2 12.7 2.11.3 Example 3 30 10.17.3 1.01.3 Example 4 50 9.7 1.5 -1.2

[0138] Referring to Tables 2 to 4 above, it can be seen that the lithium sulfate aqueous solution prepared according to the example has an excellent lithium leaching rate and a low amount of impurities.

[0139] Therefore, it is expected that a high-purity aqueous lithium sulfate solution can be easily produced by using the method for utilizing crushed waste refractory materials according to the present invention.

[0140]

[0141] The present invention is not limited to the above embodiments and can be manufactured in various different forms, and those skilled in the art will understand that the invention can be implemented in other specific forms without changing the technical concept or essential features of the invention. Therefore, the embodiments described above should be understood as illustrative in all respects and not restrictive.

Claims

1. Step of preparing crushed waste refractory material; Step of preparing lithium-containing ore; A step of obtaining a calcined product by calcining the above lithium-containing ore; A step of obtaining a calcined product by mixing the above calcined product with sulfuric acid and then calcining it; and A step of obtaining an aqueous lithium sulfate solution by leaching the above-mentioned calcined product with water; Includes, In the step of obtaining an aqueous lithium sulfate solution by leaching the above-mentioned roasted material with water; wherein the crushed waste refractory material is introduced, Method of utilizing lung refractory armor.

2. In Paragraph 1, A method for utilizing waste refractory ash, wherein the above-mentioned crushed waste refractory ash has a Dv50 of 3 to 15 μm.

3. In Paragraph 2, A method for utilizing waste refractory ash, wherein the above-mentioned crushed waste refractory ash has a Dv50 of 5 to 10 μm.

4. In Paragraph 1, A method for utilizing waste refractory materials in which the crushed waste refractory material is added in an amount of 50 parts by weight or less per 100 parts by weight of the total roasted material.

5. In Paragraph 4, A method for utilizing waste refractory materials in which the crushed waste refractory material is added in an amount of 40 parts by weight or less per 100 parts by weight of the total roasted material.

6. In Paragraph 1, A method for utilizing waste refractory armor, wherein the above-mentioned crushed waste refractory armor comprises one or more selected from the group consisting of an attachment layer, a modified layer, and a base layer of the waste refractory armor.

7. In Paragraph 1, A method for utilizing waste refractory ash, wherein the above-mentioned crushed waste refractory ash has a lithium content of 1.7 parts by weight or more per 100 parts by weight of the total.

8. In Paragraph 1, A method for utilizing waste refractory materials in which the above-mentioned crushed waste refractory material contains LiAlO2.

9. In Paragraph 1, A method for utilizing waste refractory plates, wherein, in the step of obtaining an aqueous lithium sulfate solution by leaching the above-mentioned roasted product with water, an auxiliary precipitating agent is further added.

10. In Paragraph 9, A method for utilizing waste refractory plates, wherein the above auxiliary precipitating agent comprises one or more selected from the group consisting of Ca(OH)2 and CaCO3.

11. In Paragraph 1, A method for utilizing waste refractory plates, wherein the step of obtaining an aqueous lithium sulfate solution by leaching the above-mentioned roasted product is performed at a pH of 5 or higher.

12. In Paragraph 11, A method for utilizing waste refractory plates, wherein the step of obtaining an aqueous lithium sulfate solution by leaching the above-mentioned roasted product is performed at a pH of 5 to 8.

5.

13. In Paragraph 1, A method for utilizing waste refractory plates, wherein the step of obtaining an aqueous lithium sulfate solution by leaching the above-mentioned roasted material with water is performed for 10 to 120 minutes.

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