Lithium recovery system for black substances

Abstract

Disclosed is a lithium recovery system for a black substance, the lithium recovery system including: a heat treatment unit performing heat treatment to convert the black substance into a soluble substance and an insoluble substance; a water leaching unit that leaches the heat-treated black substance with water to separate the heat-treated black substance into a water leach solution containing lithium ions and carbonate ions and an insoluble substance; and an impurity removal unit that removes impurities contained in the water leach solution by supplying a gas containing carbon dioxide to the water leach solution to reduce the pH.

Description

[0001] Cross - reference to related applications

[0002] This application claims priority to Korean Patent Application No. 10 - 2023 - 0161085, filed on November 20, 2023, the entire contents of which are incorporated herein by reference for all purposes. Technical field

[0003] The present disclosure relates to a system for recovering lithium from black mass, and more particularly, to a lithium recovery system for black mass that recovers high - purity lithium by removing impurities present in the black mass. Background art

[0004] Generally, black mass refers to waste materials, i.e., waste generated during the battery manufacturing process, and powders obtained by collecting waste batteries and pulverizing them.

[0005] Black mass contains various impurities because it contains not only cathode materials but also anode materials, binders, and electrolytes. Specifically, black mass can contain various metals such as aluminum (Al), copper (Cu), iron (Fe), and fluorine (F). In particular, black mass contains a large amount of aluminum (Al) and a large amount of fluorine (F), with aluminum (Al) as the base material and fluorine (F) contained in the electrolyte and binder. Since these impurities have an adverse effect on the purity of lithium carbonate or lithium hydroxide, an impurity removal step is required during the lithium recovery process to recover high - purity lithium from black mass. Summary of the invention

[0006] One aspect of the present disclosure is to provide a lithium recovery system for black mass that recovers high - purity lithium by removing impurities present in the black mass.

[0007] The technical problems to be solved in the present disclosure are not limited to the foregoing technical problems, and other unmentioned technical problems can be clearly understood by those of ordinary skill in the art to which the present disclosure pertains from the following description.

[0008] According to an embodiment of the present disclosure, there is provided a lithium recovery system for black mass, the lithium recovery system including: a heat treatment unit that performs heat treatment to convert black mass into soluble substances and insoluble substances; a water leaching unit that leaches the heat - treated black mass with water to separate the heat - treated black mass into a water leaching solution and insoluble substances, the water leaching solution containing lithium ions and carbonate ions; and an impurity removal unit that removes impurities contained in the water leaching solution by supplying a carbon dioxide - containing gas to the water leaching solution to lower the pH.

[0009] According to one embodiment, aluminum ions can precipitate in the impurity removal unit.

[0010] According to one embodiment, calcium hydroxide (Ca(OH) 2 ) can be supplied to the impurity removal unit and react with fluoride ions to precipitate calcium fluoride (CaF 2 ).

[0011] According to one embodiment, a carbon dioxide-containing gas can be supplied continuously or intermittently to keep the pH of the water leaching solution in the impurity removal unit below 8.

[0012] According to one embodiment, the pH of the water leaching solution in the impurity removal unit can be maintained at 6 or greater and 7 or less.

[0013] According to one embodiment, the carbon dioxide-containing gas can be the exhaust gas discharged after combustion in the heat treatment unit.

[0014] According to one embodiment, the exhaust gas can be supplied to the water leaching solution after passing through a dust collector.

[0015] According to one embodiment, the molar concentration of calcium hydroxide supplied to the impurity removal unit can be 1.2 times to 2 times the molar concentration of fluoride ions in the water leaching solution separated from the water leaching unit.

[0016] According to one embodiment, the lithium recovery system can further include: a reverse osmosis (RO) concentration unit that concentrates the water leaching solution from which impurities have been removed in the impurity removal unit using reverse osmosis; and a crystallization unit that crystallizes lithium carbonate by raising the temperature of the concentrated water concentrated in the RO concentration unit.

[0017] According to one embodiment, the RO concentration unit can include a first RO device and a second RO device, and while reverse osmosis is performed in one of the first RO device and the second RO device, flushing is performed in the other.

[0018] According to one embodiment, the treated water used for reverse osmosis in the RO concentration unit can be supplied to the water leaching unit.

[0019] According to one embodiment, the uncrystallized crystallization filtrate in the crystallization unit can be merged with the water leaching solution from which impurities have been removed in the impurity removal unit and then supplied to the RO concentration unit.

[0020] According to one embodiment, the lithium recovery system can further include a heat exchange unit that exchanges heat between the crystallization filtrate and the concentrated water.

[0021] According to one embodiment, the lithium recovery system may further include a separation unit that separates the lithium carbonate crystallized in the crystallization unit and the crystallization filtrate into a solid and a liquid, where a main channel and a bypass channel branched from the main channel are provided, the crystallization filtrate flows from the separation unit to the confluence part for confluent water leaching solution through the main channel, and where an ion exchange resin is provided in the bypass channel.

[0022] According to another embodiment of the present disclosure, there is provided a lithium recovery method for black substances, the lithium recovery method including: a heat treatment step of performing heat treatment to convert black substances into soluble substances and insoluble substances; a water leaching step of water leaching the heat-treated black substances to separate the heat-treated black substances into a water leaching solution and insoluble substances, the water leaching solution containing lithium ions and carbonate ions; and an impurity removal step of supplying a carbon dioxide-containing gas to the water leaching solution to reduce the pH, where aluminum ions or fluoride ions contained in the water leaching solution can be removed through the impurity removal step.

[0023] According to the present disclosure, a carbon dioxide-containing gas is supplied to the water leaching solution to reduce the pH of the water leaching solution and remove impurities contained in the water leaching solution, particularly aluminum ions and fluoride ions, so as to recover high-purity lithium from black substances.

[0024] In addition, an RO concentration method is used to concentrate the water leaching solution, thereby reducing energy consumption and increasing the lithium recovery rate. In particular, aluminum ions and fluoride ions are removed in advance. Preferably, the concentration of aluminum ions is reduced to 1 ppm or less and the concentration of fluoride ions is reduced to 10 ppm or less, so as to use the RO concentration method without causing fouling problems.

[0025] In addition, the RO concentration unit includes a first RO device and a second RO device that operate alternately, thereby preventing fouling of the RO membrane. In addition, the pH of the water leaching solution is reduced as described above to increase the concentration multiple in the RO concentration unit, thereby preventing fouling of the RO membrane.

[0026] In addition, a heat exchange unit is provided for heat exchange between the crystallization filtrate and the concentrated water, so that the crystallization filtrate can be cooled before entering the RO concentration unit to meet the required temperature conditions, and the concentrated water can be heated to reduce the energy required for crystallization.

[0027] In addition, at least some of the crystallization filtrate passes through the ion exchange resin and then flows into the RO concentration unit, thereby suppressing an increase in impurities due to repeated use.

[0028] It should be understood that the effects of the present disclosure are not limited to the foregoing effects, but include all effects that can be inferred from the configurations of the present disclosure described in the detailed description or the appended claims. Description of the Drawings

[0029] Figure 1 FIG. is a diagram showing the configuration of a lithium recovery system for black substances according to a first embodiment of the present disclosure.

[0030] Figure 2 is a diagram showing Figure 1 the detailed configuration of the reverse osmosis (RO) concentration unit in

[0031] Figure 3 FIG. is a diagram showing the configuration of a lithium recovery system for black substances according to a second embodiment of the present disclosure. DETAILED DESCRIPTION

[0032] Hereinafter, embodiments of a system and method for recovering lithium from black substances according to the present disclosure will be described with reference to the accompanying drawings.

[0033] Terms to be described later are defined in consideration of the functions in the present disclosure and may be changed according to the intention or habit of a user or an operator. The following embodiments do not limit the scope of the present disclosure, but merely illustrate the features disclosed in the appended claims.

[0034] To clearly describe the present disclosure, elements irrelevant to the description are omitted, and throughout the specification, the same reference numerals refer to the same elements. Throughout the specification, when a part is referred to as "including" a certain element, unless otherwise specified, this means that other elements are not excluded, but other elements may be additionally included.

[0035] In the present disclosure, regarding elements represented as "units", two or more elements may be integrated into a single element, or according to the subdivided functions, one element may be divided into two or more elements. In addition, each element to be described later may additionally perform some or all of the functions performed by another element in addition to its main function, and some of the main functions of each element may be completely performed by another component.

[0036] First, with reference to Figure 1 and Figure 2 a lithium recovery system for black substances according to a first embodiment of the present disclosure will be described.

[0037] The lithium recovery system according to the present disclosure may include a heat treatment unit 100, a water leaching unit 200, an impurity removal unit 300, a reverse osmosis (RO) concentration unit 400, a crystallization unit 500, a separation unit 600, a heat exchange unit 700, and an ion exchange resin 800.

[0038] The heat treatment unit 100 performs heat treatment to convert black substances into soluble substances and insoluble substances. Here, the black substances refer to waste materials, i.e., waste generated during the battery manufacturing process, and powders obtained by collecting waste batteries and pulverizing them.

[0039] By subjecting the black substances to heat treatment, lithium carbonate (Li 2 CO 3 ), lithium oxide (Li 2 O), lithium hydroxide (LiOH), etc. may be generated as soluble substances, and Ni oxide, Co oxide, Mn oxide, etc. may be generated as insoluble substances. The content of each component may vary depending on the heat treatment method and conditions. In addition, the black substances contain various impurities because they contain not only cathode materials but also anode materials, binders, and electrolytes. In particular, the black substances contain a large amount of aluminum (Al) and a large amount of fluorine (F), with aluminum (Al) being the base material and fluorine (F) being contained in the electrolyte and the binder.

[0040] The heat treatment unit 100 includes, for example, a heat treatment furnace, and a hydrocarbon fluid can be burned inside the heat treatment furnace. The inside of the heat treatment furnace is heated by burning the hydrocarbon fluid to have a carbon dioxide atmosphere based on carbon dioxide in the exhaust gas generated due to the combustion of the hydrocarbon fluid. Therefore, the carbon dioxide in the exhaust gas can react with the black substances introduced into the heat treatment furnace. However, the carbon dioxide gas can be injected into the heat treatment furnace alone without limitation.

[0041] The water leaching unit 200 leaches the heat-treated black substances with water to separate the heat-treated black substances into a water leaching solution and insoluble particles, and the water leaching solution contains lithium ions and carbonate ions. In other words, when the soluble substances dissolve in water, they are leached from the heat-treated black substances. The separated water leaching solution is supplied to the RO concentration unit 400 via the impurity removal unit 300 (to be described later). Distilled water can be used for the leaching process.

[0042] In this case, the concentration of lithium ions in the water leaching solution separated from the water leaching unit 200 can be 2,000 ppm or less because the maximum amount of lithium is eluted when the concentration of lithium ions is less than 2,000 ppm. The concentration of lithium ions in the water leaching solution can vary depending on the weight ratio of water and the heat-treated black substances subjected to water-based leaching in the water leaching unit 200.

[0043] According to the present disclosure, a carbon dioxide-containing gas can be supplied to the water leaching solution in the impurity removal unit 300 to lower the pH of the water leaching solution. Therefore, the impurities contained in the water leaching solution are removed in the impurity removal unit 300.

[0044] Generally, the pH of the water leaching solution separated from the water leaching unit 200 is from 10 to 11. However, a carbon dioxide-containing gas is continuously or intermittently supplied to the impurity removal unit 300 such that the pH of the water leaching solution can be 8 or less. In particular, it is preferable to maintain the pH of the water leaching solution in the impurity removal unit 300 at 6 or greater and 7 or less.

[0045] Specifically, in the impurity removal unit 300, as the pH of the water leaching solution decreases, aluminum ions precipitate and are removed. The solubility of aluminum tends to decrease from pH 11 towards pH 6. Therefore, when the pH of the water leaching solution decreases, particularly to pH 6 to 7, the solubility of aluminum greatly decreases, and the aluminum ions precipitate as aluminum hydroxide (Al(OH) 3 ), such that the aluminum ions can be removed from the water leaching solution. Generally, the concentration of aluminum ions in the water leaching solution separated from the water leaching unit 200 is from 5 ppm to 10 ppm. However, when the pH of the water leaching solution is decreased to 6.5 to 8 in the impurity removal unit 300, the concentration of aluminum ions is less than 1 ppm.

[0046] In addition, calcium hydroxide (Ca(OH) 2 ) can be supplied to the impurity removal unit 300. Therefore, calcium hydroxide reacts with fluoride ions together to precipitate calcium fluoride (CaF 2 ), thereby enabling the removal of fluoride ions from the water leaching solution.

[0047] When the pH of the water leaching solution is from 8 to 11, the reaction between calcium hydroxide and carbonate ions (Reaction formula (1)) is superior to the reaction between calcium hydroxide and fluoride ions (Reaction formula (2)). Therefore, calcium carbonate precipitates, and the fluoride ions are not removed.

[0048] Reaction formula (1)-----Ca(OH) 2 +CO 3 2- →CaCO 3 +2OH -

[0049] Reaction formula (2)-----Ca(OH) 2 +2F - →CaF 2 +2OH -

[0050] However, when the pH of the water leaching solution is reduced to 8 or less, the precipitation amount of calcium carbonate decreases due to the conversion of carbonate ions dissolved in water to bicarbonate ions, and the reaction between calcium hydroxide and fluoride ions (Reaction Formula (2)) predominates, thereby effectively achieving the removal of fluoride ions. In particular, when the pH of the water leaching solution is less than 7, the formation of calcium fluoride is most likely to occur. When the pH is 7 to 8, calcium carbonate may precipitate along with the formation of calcium fluoride. In this case, hydroxide ions are generated based on Reaction Formula (2) to increase the pH of the water leaching solution. In order to keep the pH of the water leaching solution below 8, even while removing impurities, a gas containing carbon dioxide is supplied continuously or intermittently.

[0051] In this case, the molar concentration of calcium hydroxide supplied to the impurity removal unit 300 can be 1.2 times to 2 times the molar concentration of fluoride ions in the water leaching solution separated from the water leaching unit 200. When the pH of the water leaching solution is reduced to 7 or less in the impurity removal unit 300, there is no significant difference in the removal of fluoride ions regardless of whether the molar concentration of calcium hydroxide is 1.2 times or 2 times the molar concentration of fluoride ions. However, when the pH of the water leaching solution is reduced to 7 to 8 in the impurity removal unit 300, some calcium ions may react with carbonate ions, so it is preferable to supply calcium hydroxide with a molar concentration of 2 times the molar concentration of fluoride ions.

[0052] Meanwhile, generally, the concentration of fluoride ions in the water leaching solution separated from the water leaching unit 200 is about 300 ppm, and the maximum level at which fluoride ions can be removed varies according to the pH of the water leaching solution. Specifically, when the pH of the water leaching solution is 6.8, the concentration of fluoride ions is reduced to 20 ppm, and at a pH of 6.5 or less, the concentration of fluoride ions is reduced to 10 ppm or less. In this way, as the pH decreases, the solubility of calcium hydroxide (Ca(OH) 2 ) increases, thereby increasing the concentration of calcium ions in the water leaching solution. Therefore, based on the reaction equation Ksp = [Ca][F] 2 , in the equilibrium state, the concentration of fluoride ions decreases as the concentration of calcium ions increases.

[0053] In addition, when the reaction is carried out at a pH of 6.5, the concentration of fluoride ions can be reduced to 10 ppm or less, but the concentration of dissolved calcium ions increases to 100 ppm or more. Therefore, after filtering and removing calcium fluoride (CaF 2 ), by adding additional calcium hydroxide to increase the pH to 7.5 or higher, the concentration of dissolved calcium ions can also be reduced to less than 5 ppm.

[0054] In this way, impurities contained in the water leaching solution, particularly aluminum ions and fluoride ions, are removed by supplying a carbon dioxide-containing gas to the water leaching solution to lower the pH of the water leaching solution, thereby obtaining a clean aqueous lithium carbonate solution. Finally, high-purity lithium is recovered from the black substance.

[0055] The RO concentration unit 400 uses reverse osmosis (RO) to concentrate the water leaching solution from which impurities have been removed by the impurity removal unit 300. As Figure 2 shown, the RO concentration unit 400 according to this embodiment includes a first RO device 420 and a second RO device 440, and the first RO device 420 and the second RO device 440 operate alternately to prevent fouling of the RO membrane.

[0056] Specifically, the first RO device 420 includes a first concentration chamber 422 to which the water leaching solution is supplied, a first treatment chamber 426 to which treated water is supplied, and a first RO membrane 424 disposed between the first concentration chamber 422 and the first treatment chamber 426. Although not shown, the first RO device 420 further includes a pressurizing device for pressurizing the water leaching solution in the first concentration chamber 422. Therefore, when the water leaching solution is pressurized by the pressurizing device after the water leaching solution is supplied to the first concentration chamber 422 and the treated water is supplied to the first treatment chamber 426, the water in the first concentration chamber 422 moves to the first treatment chamber 426, thereby concentrating the water leaching solution in the first concentration chamber 422. For example, the treated water may be distilled water.

[0057] Similarly, the second RO device 440 includes a second concentration chamber 442 to which the water leaching solution is supplied, a second treatment chamber 446 to which treated water is supplied, and a second RO membrane 444 disposed between the second concentration chamber 442 and the second treatment chamber 446. Although not shown, the second RO device 440 further includes a pressurizing device for pressurizing the water leaching solution in the second concentration chamber 442.

[0058] In this case, when reverse osmosis is performed in one of the first RO device 420 and the second RO device 440, flushing is performed in the other. In other words, when reverse osmosis is performed while supplying the water leaching solution to the first RO device 420, pure water or a flushing agent is supplied to the second RO device 440 instead of the water leaching solution, thereby flushing the RO membrane. The reverse osmosis process and the flushing process of the first RO device 420 and the second RO device 440 are performed alternately, so that metals and other impurities attached to the surface of the RO membrane can be periodically cleaned to prevent fouling.

[0059] In addition, the solubility of lithium is increased by lowering the pH of the water leaching solution in the impurity removal unit 300, thereby increasing the concentration multiple in the RO concentration unit 400 and preventing fouling of the RO membrane. When the pH of the water leaching solution is high, the solubility of lithium is low, so the final concentration that can be concentrated in the RO concentration unit 400 is limited to a low concentration due to fouling problems. In other words, as the pH of the water leaching solution decreases, the final concentration that can be concentrated in the RO concentration unit 400 increases, thereby improving the efficiency of the RO concentration process. Specifically, the pH of the water leaching solution can be lowered to increase the solubility of lithium carbonate (which is about 13 g / L at 20 °C) to more than twice, so that the water leaching solution can be further concentrated more than twice in the RO concentration unit 400. In this way, a high-concentration lithium aqueous solution is produced using RO concentration, which consumes less energy than evaporation concentration.

[0060] According to one embodiment, the treated water used for reverse osmosis in the RO concentration unit 400 can be supplied to the water leaching unit 200 and used for water-based leaching. Therefore, the amount of water additionally supplied for water-based leaching is reduced.

[0061] The crystallization unit 500 crystallizes lithium carbonate by raising the temperature of the concentrated water concentrated in the RO concentration unit 400. The crystallization unit 500 can crystallize lithium carbonate by heating the concentrated water at about 60 °C to 80 °C.

[0062] The separation unit 600 separates the lithium carbonate crystallized in the crystallization unit 500 and the uncrystallized crystallization filtrate into solid and liquid. In this case, in order to reuse the lithium ions in the crystallization filtrate, the crystallization filtrate can be merged with the water leaching solution from which impurities have been removed in the impurity removal unit 300, and then supplied to the RO concentration unit 400. For this purpose, a main channel 610 is provided, and the crystallization filtrate flows through the main channel 610 from the separation unit 600 to the merging part 630 for merging the water leaching solution.

[0063] Typically, a temperature of 40 °C or lower is allowed in the RO concentration unit 400. Therefore, the high-temperature crystallization filtrate needs to be cooled to 40 °C or lower before entering the RO concentration unit 400. According to one embodiment, the crystallization filtrate can be cooled using the concentrated water. For this purpose, a heat exchange unit 700 can be further provided to exchange heat between the crystallization filtrate and the concentrated water. For example, the temperature of the crystallization filtrate separated in the separation unit 600 is about 80 °C, and the temperature of the concentrated water discharged from the RO concentration unit 400 is about 20 °C. Since heat is exchanged between the crystallization filtrate and the concentrated water in the heat exchange unit 700, heat can be transferred from the crystallization filtrate to the concentrated water. Therefore, the temperature of the crystallization filtrate is reduced to meet the temperature conditions required for entering the RO concentration unit 400, and the temperature of the concentrated water is increased to reduce the energy cost required for later crystallization. For example, the temperature of the crystallization filtrate is reduced from about 80 °C to 20 °C, and the temperature of the concentrated water is increased from about 20 °C to 70 °C.

[0064] According to one embodiment, a bypass channel 620 branched from the main channel 610 can be further provided, and an ion exchange resin 800 can be provided in the bypass channel 620. The bypass channel 620 can branch out from the main channel 610 and then rejoin the main channel 610, or join the water leaching solution at the confluence 630. At least some, preferably 10% to 30%, of the crystallization filtrate separated in the separation unit 600 is supplied to the bypass channel 620 and passes through the ion exchange resin 800. Therefore, an increase in impurities due to the repeated use of the crystallization filtrate is suppressed. As the number of times the crystallization filtrate is reused increases, the concentration of ionic impurities (e.g., calcium ions, magnesium ions, etc.) in the crystallization filtrate increases. In this case, some of the crystallization filtrate is reused after being treated with a weakly acidic cation exchange resin, thereby effectively controlling the concentration of impurities.

[0065] According to one embodiment, an aqueous lithium hydroxide solution can be prepared by reacting crystalline lithium carbonate with a hydroxide salt (e.g., calcium hydroxide, sodium hydroxide, barium hydroxide, etc.), and then lithium hydroxide (LiOH) can be produced by evaporation concentration crystallization or ethanol mixing crystallization.

[0066] Furthermore, according to one embodiment, lithium hydroxide (LiOH) can be produced by reacting the concentrated water with a hydroxide salt to form an aqueous lithium hydroxide solution without crystallizing lithium carbonate in the crystallization unit 500 after the RO concentration unit 400, and by evaporation concentration crystallization or ethanol mixing crystallization.

[0067] Next, reference will be made to Figure 3 Describe a lithium recovery system for black substances according to a second embodiment of the present disclosure.

[0068] The lithium recovery system according to this embodiment has the same asFigure 1 The same configuration as shown, except that the carbon dioxide-containing gas supplied to the impurity removal unit 300 is the exhaust gas discharged after combustion in the heat treatment unit 100. In other words, when a hydrocarbon fluid is burned in the heat treatment furnace of the heat treatment unit 100, the exhaust gas discharged from the heat treatment unit 100 contains carbon dioxide. Therefore, by using the carbon dioxide in the exhaust gas, there is no need to separately supply a carbon dioxide-containing gas.

[0069] In this case, the exhaust gas can be supplied to the water leaching solution after passing through the dust collector 900. The dust collector 900 can be separately installed between the heat treatment unit 100 and the impurity removal unit 300. However, in some cases, the dust collector already installed inside the heat treatment unit 100 can be used.

[0070] Finally, a lithium recovery method for black substances according to the present disclosure will be described.

[0071] The lithium recovery method according to the present disclosure includes: a heat treatment step of performing heat treatment to convert black substances into soluble substances and insoluble substances; a water leaching step of water-leaching the heat-treated black substances to separate the heat-treated black substances into a water leaching solution and insoluble substances, the water leaching solution containing lithium ions and carbonate ions; and an impurity removal step of reducing the pH by supplying a carbon dioxide-containing gas to the water leaching solution. In this case, as described above, fluoride ions or aluminum ions contained in the water leaching solution can be removed through the impurity removal step.

[0072] The present disclosure is not limited to the foregoing exemplary embodiments and descriptions, and various modifications can be made by any ordinary person skilled in the art to which the present disclosure pertains without departing from the subject matter of the disclosure claimed in the appended claims. Such modifications fall within the scope of the present disclosure.

[0073] Description of Reference Numerals

[0074] 100: Heat treatment unit

[0075] 200: Water leaching unit

[0076] 300: Impurity removal unit

[0077] 400: RO concentration unit

[0078] 420: First RO device

[0079] 422: First concentration chamber

[0080] 424: First RO membrane

[0081] 426: First treatment chamber

[0082] 440: Second RO device

[0083] 442: Second concentration chamber

[0084] 444: Second RO membrane

[0085] 446: Second treatment chamber

[0086] 500: Crystallization unit

[0087] 600: Separation unit

[0088] 610: Main channel

[0089] 620: Bypass channel

[0090] 630: Confluence part

[0091] 700: Heat exchange unit

[0092] 800: Ion exchange resin

[0093] 900: Dust collector

Claims

1. A lithium recovery system for black matter, comprising: a heat treatment unit that performs heat treatment to convert the black matter into soluble matter and insoluble matter; a water leaching unit, the water leaching unit leaching the heat-treated black matter with water to separate the heat-treated black matter into a water leaching solution and an insoluble matter, the water leaching solution comprising lithium ions and carbonate ions; and An impurity removal unit removes impurities contained in the water leaching solution by supplying a gas containing carbon dioxide to the water leaching solution to reduce pH.

2. The lithium recovery system according to claim 1, wherein aluminum ions are precipitated in the impurity removal unit.

3. The lithium recovery system according to claim 1, wherein calcium hydroxide (Ca(OH)2) is supplied to the impurity removal unit and reacts with fluoride ions to precipitate calcium fluoride (CaF2).

4. The lithium recovery system according to claim 1, wherein the carbon dioxide containing gas is supplied continuously or intermittently to maintain the pH of the water leaching solution in the impurity removal unit below 8.

5. The lithium recovery system according to claim 4, wherein the pH of the water leaching solution in the impurity removal unit is maintained at 6 or more and 7 or less. 6 . The lithium recovery system according to claim 1 , wherein the gas containing carbon dioxide is exhaust gas exhausted after combustion in the thermal treatment unit. 7 . The lithium recovery system according to claim 6 , wherein the exhaust gas is supplied to the water leaching solution after passing through a dust collector.

8. The lithium recovery system according to claim 3, wherein the molar concentration of calcium hydroxide supplied to the impurity removal unit is 1.2 to 2 times the molar concentration of fluoride ions in the water leaching solution separated from the water leaching unit.

9. The lithium recovery system according to claim 1, further comprising: a reverse osmosis (RO) concentration unit that uses reverse osmosis to concentrate the water leachate solution from which impurities have been removed in the impurity removal unit; and A crystallization unit that crystallizes lithium carbonate by increasing the temperature of the concentrated water concentrated in the RO concentration unit.

10. The lithium recovery system according to claim 9, wherein The RO concentration unit includes a first RO device and a second RO device, and While the reverse osmosis is being performed in one of the first RO device and the second RO device, flushing is performed in the other one.

11. The lithium recovery system according to claim 9, wherein treated water used for the reverse osmosis in the RO concentration unit is supplied to the water leaching unit.

12. The lithium recovery system according to claim 9, wherein the crystallization filtrate that has not been crystallized in the crystallization unit is combined with the water leaching solution from which impurities have been removed in the impurity removal unit and then supplied to the RO concentration unit. 13 . The lithium recovery system according to claim 12 , further comprising a heat exchange unit that exchanges heat between the crystallization filtrate and the concentrated water.

14. The lithium recovery system according to claim 12, further comprising: A separation unit, wherein the separation unit separates the lithium carbonate crystallized in the crystallization unit and the crystallization filtrate into solid and liquid, A main channel and a bypass channel branching from the main channel are provided, the crystallization filtrate flows from the separation unit to a confluence portion for confluence with the water leaching solution through the main channel, and an ion exchange resin is provided in the bypass channel.

15. A lithium recovery method for black matter, comprising: A heat treatment step of heat-treating the black matter to convert the black matter into soluble matter and insoluble matter; a water leaching step of leaching the heat-treated black matter with water to separate the heat-treated black matter into a water leaching solution and an insoluble matter, wherein the water leaching solution contains lithium ions and carbonate ions; as well as an impurity removal step of supplying a gas containing carbon dioxide to the aqueous leachate solution to lower the pH, The aluminum ions or fluoride ions contained in the water leaching solution can be removed by the impurity removing step.

Images