Process and system for closed-loop recycling of secondary batteries without wastewater generation

Abstract

The present invention relates to a process and a system that recover sulfuric acid and lithium hydroxide through electrodialysis and reintroducing same into the process, thereby generating no wastewater and allowing for closed-loop recycling in a secondary battery recycling process, and thus enable resources from lithium secondary battery waste to be recovered in an eco-friendly and economical manner.

Description

A complete regeneration process and system for secondary batteries that does not generate wastewater

[0001] The present invention relates to a process and system capable of recovering resources from lithium secondary battery waste in an environmentally friendly and economical manner by recovering sulfuric acid and lithium hydroxide through electrodialysis and reintroducing them into the process, thereby completely circulating them within the secondary battery recycling process without generating wastewater.

[0002] Lithium secondary batteries are being used in a variety of applications, from individual cell batteries used in IT devices such as smartphones and laptops to large modular batteries used in electric vehicles (EVs) and energy storage systems (ESS), and battery production is on the rise worldwide.

[0003] As the production of lithium secondary batteries increases, the amount of waste lithium secondary batteries generated also increases every year, and technology is needed to recover and recycle valuable metals from these waste lithium secondary batteries.

[0004] Previous research has focused on recovering valuable metals such as cobalt, nickel, and manganese from spent lithium secondary battery cathode materials. The process for recovering valuable metals from spent lithium secondary batteries involves first leaching the lithium battery cathode material with sulfuric acid, then recovering components such as cobalt and nickel through solvent extraction. Ultimately, a lithium-containing waste solution (Li2SO4) is generated.

[0005] However, these waste liquids contain about 2.5 to 3.0 g / L of lithium, which is higher in concentration than the lithium contained in brine (about 0.3 to 1.0 g / L), making them worth recovering and reusing.

[0006] Methods for recovering lithium from such lithium-containing waste liquid include fractional crystallization, solvent extraction, ion exchange resin, and electrodialysis. Some of the lithium was recovered in the form of lithium phosphate, lithium sulfate, and lithium carbonate, and then manufactured into lithium hydroxide (LiOH) through a subsequent process and reused as a secondary battery raw material.

[0007] However, when manufacturing lithium hydroxide through a series of unit processes, the process is complex and by-products are generated, which can cause waste disposal and environmental pollution, so there is a need to develop a more environmentally friendly recovery process.

[0008] The present invention is intended to solve the above-mentioned problem, and the purpose of the present invention is to provide an environmentally friendly and economical metal recovery system for lithium secondary battery waste by recovering metals with high purity from wastewater or waste generated from waste lithium secondary batteries and secondary battery manufacturing processes, and by completely circulating wastewater generated from a secondary battery recycling process within the process.

[0009] In order to solve the above technical problem, the present invention

[0010] (i) A step of producing lithium carbonate by concentrating and carbonating secondary battery waste;

[0011] (ii) a step of producing lithium hydroxide and sulfuric acid by electrodialyzing lithium sulfate produced in the lithium carbonate production step; and

[0012] (iii) a step of adding sulfuric acid to secondary battery waste to leach it and adding lithium hydroxide to neutralize it to produce nickel sulfate and cobalt sulfate;

[0013] Some of the lithium hydroxide solution and sulfuric acid solution recovered through the above electrodialysis are reused within the process.

[0014] The above secondary battery waste is continuously input into the process, while the resources within the process are completely recycled and recovered without generating discharged wastewater, thereby providing a secondary battery complete circulation regeneration process without generating wastewater.

[0015] In one embodiment of the present invention, the process is characterized in that it can be reused by heating the high-temperature carbon dioxide gas generated in the carbonation process during the production of lithium carbonate without using a separate heat source, or by changing the temperature to a low temperature and reintroducing it into the process.

[0016] In addition, the present invention

[0017] (i) A reduction and combustion step of mixing secondary battery waste and activated carbon and then calcining them to produce carbon dioxide gas;

[0018] (ii) A lithium separation step of producing lithium carbonate by cooling and blowing carbon dioxide gas into a lithium leaching tank containing a mixed solution of pulverized material and water after calcination, then applying heat to the lithium leaching tank to change it into a solid state, and then filtering and drying through solid-liquid separation;

[0019] (iii) A step of manufacturing iron and manganese by adding a sulfuric acid (H2SO4) solution and a neutralizing agent to the above-mentioned solid-liquid separated solution, heating to remove impurities, injecting ozone (O3) to generate iron oxide and manganese dioxide (MnO2) solids, and then performing solid-liquid separation filtration;

[0020] (iv) a solvent extraction step in which an extractant is added to a solution containing Li, Ni, Co and residual impurities from which iron and manganese have been removed to remove the residual impurities;

[0021] (v) A metal separation step in which a solution from which residual impurities have been removed is subjected to a neutralization reaction using a regenerative neutralizing agent to extract nickel hydroxide (Ni(OH)2) and cobalt hydroxide (Co(OH)2) solids and separated from a lithium sulfate (Li2SO4) solution through solid-liquid separation;

[0022] (vi) an electrodialysis step of decomposing the lithium sulfate solution into a lithium hydroxide (LiOH) solution and a sulfuric acid (H2SO4) solution through electrodialysis;

[0023] (vii) a nickel separation step in which a sulfuric acid (H2SO4) solution is added to the nickel hydroxide (Ni(OH)2) and cobalt hydroxide (Co(OH)2) solids, impurities are removed by filtering, an extractant is added to extract the solvent, and Ni(OH)2 is added to produce nickel sulfate (NiSO4); and

[0024] (viii) A cobalt separation step in which an extractant, dilute sulfuric acid, and concentrated sulfuric acid are added to a solution in which Ni is removed and Co remains to produce cobalt sulfate (CoSO4), is provided. The present invention provides a secondary battery complete cycle regeneration process without generating wastewater, characterized by including:

[0025] In one embodiment of the present invention, the process is characterized in that it can be reused by heating the high-temperature carbon dioxide gas generated in the reduction and oxidation step without using a separate heat source or by changing the temperature to a low temperature and reintroducing it into the process.

[0026] In one embodiment of the present invention, the sulfuric acid is separated as a sulfuric acid solution by a lithium sulfate decomposition device, which is an electrodialysis device, and is reintroduced into the process without being discarded, thereby implementing an environmentally friendly process that does not generate wastewater.

[0027] In one embodiment of the present invention, the neutralizing agent is characterized in that it is a lithium hydroxide (LiOH) solution separated by the electrodialysis machine.

[0028] In one embodiment of the present invention, the extractant is characterized in that it is a liquid of oil component having a lower specific gravity than the solution, and is one selected from the group consisting of di-2-ethylhexylphosphoric acid (D2EHPA), 2-ethylhexyl phosphonic acid mono-2-ethylhexyl ester (PC88A), a mixture of di-2-ethylhexylphosphoric acid and tri-butyl-phosphate (TBP), and a mixture of 2-ethylhexyl phosphonic acid mono-2-ethylhexyl ester and tri-butyl-phosphate (TBP).

[0029] In one embodiment of the present invention, in step (vii), a cake containing nickel hydroxide (Ni(OH)2) discarded after the manufacturing process of a lithium secondary battery is additionally added to separate the metal.

[0030] In addition, the present invention

[0031] Lithium recovery unit for concentrating and carbonizing secondary battery waste;

[0032] An electrodialysis unit that electrodialyzes lithium sulfate generated in the lithium recovery unit to produce lithium hydroxide and sulfuric acid;

[0033] A metal separation unit that separates nickel and cobalt by adding a neutralizing agent to the residual solution generated through the lithium recovery unit; and

[0034] A secondary battery complete circulation regeneration system without wastewater generation is provided, characterized by including a nickel and cobalt recovery unit that neutralizes leaching light by adding sulfuric acid and lithium hydroxide to the solution generated in the metal separation unit.

[0035] According to the present invention, the secondary battery waste is continuously input into the process, while resources within the process are completely recycled and recovered without generating discharged wastewater.

[0036] In addition, the sulfuric acid solution and lithium hydroxide solution used as a neutralizing agent according to the present invention are separated by an electrodialyzer and are reintroduced into the process without being discarded, so there is an effect of being able to implement an environmentally friendly process that does not generate wastewater.

[0037] FIG. 1 is a diagram illustrating a flow diagram of a secondary battery complete circulation regeneration process without wastewater generation according to one embodiment of the present invention.

[0038] FIG. 2 is a cross-sectional view showing the configuration of a solvent extractor constituting a lithium recovery system according to one embodiment of the present invention.

[0039] Fig. 3 is a cross-sectional view showing the configuration of an electrocatalyst according to an embodiment of the present invention.

[0040] Hereinafter, preferred embodiments of the present invention will be described in more detail with reference to the attached drawings. Prior to this, it should be noted that the terms and words used in this specification and claims should not be construed as limited to their conventional or dictionary meanings. Based on the principle that the inventor can appropriately define the concepts of terms to best explain his or her invention, they should be interpreted in a way that aligns with the technical spirit of the present invention.

[0041] Therefore, the embodiments described in this specification and the configurations illustrated in the drawings are only the most preferred embodiments of the present invention and do not represent all of the technical ideas of the present invention. Therefore, it should be understood that there may be various equivalents and modified examples that can replace them at the time of filing this application.

[0042] Hereinafter, embodiments of the present invention will be described in detail with reference to the attached drawings.

[0043] Figure 1 illustrates a flow chart of a basic process representing one embodiment of the present invention.

[0044] The solution to be treated according to the present invention may be, but is not limited to, process wastewater containing lithium, nickel, cobalt, etc., or a solution (lithium waste liquid) generated during the manufacturing process of a used lithium ion secondary battery or a lithium ion secondary battery, or black powder, black mass, etc.

[0045] The solution (lithium waste liquid) discharged during the manufacturing process of waste lithium secondary batteries contains, in addition to lithium, various metal ions such as magnesium, calcium, cobalt, nickel, manganese, sodium, potassium, sulfate ions, and phosphate ions, but the content is not high. Therefore, the impact on the process of recovering lithium hydroxide and lithium carbonate from the waste liquid is not significant.

[0046] Additionally, monovalent ions such as sodium and potassium can be completely removed by hydrothermal washing after lithium carbonate production.

[0047] Magnesium and calcium ions precipitate as metal hydroxides during the subsequent electrodialysis process, causing membrane contamination and serious problems such as reduced membrane life and current efficiency. Furthermore, sulfate ions react with calcium ions to readily precipitate as calcium sulfate (gypsum), so they must be separated and removed before the electrodialysis process begins.

[0048] In the recycling process for spent lithium secondary batteries (wet process), cobalt, nickel, manganese, etc. are recovered, but the waste liquid containing low concentrations of lithium is discharged after undergoing a wastewater treatment process. The present invention relates to a method for recovering low concentrations of lithium in the waste liquid, and can obtain high-purity lithium hydroxide and lithium carbonate by removing sulfate ions, magnesium ions, and calcium ions, which are major causes of membrane fouling in the electrodialysis process.

[0049] Below, the process and each process step are categorized and explained in detail.

[0050] Step 1: Lithium carbonate production reaction

[0051] In general, when lithium sulfate (Li2SO4) is carbonated using sodium carbonate (Na2CO3) (pH 13-14), solid lithium carbonate (Li2CO3)(s) is produced, which may be in a crude lithium carbonate state (containing many impurities such as Ca, Mg, Na, SO4, etc.).

[0052] To purify this, if carbon dioxide gas is blown into (water solution) under cold conditions (below about 15℃), LiHCO3(l) is generated and the pH can be around 8~9. Therefore, lithium bicarbonate in liquid state is generated from lithium carbonate and impurities such as SiO2, CaSO4, MgSO4, etc. are precipitated as solids and can be filtered. In addition, Na + , SO4 2- is still dissolved in the liquid state solution. When it is later changed to hot condition (about 80℃ or higher), it changes back to solid state as purified lithium carbonate (Li2CO3)(s), and Na + , SO4 2- It is separated from the back and can produce high-purity lithium carbonate.

[0053] Carbon dioxide generated in the reduction and roasting process carbonates Li in the lithium secondary battery waste to become lithium carbonate (Li2CO3), and the high-temperature residual carbon dioxide discharged is cooled through a heat exchanger and then discharged into a <lithium bicarbonate leaching reactor> in which the lithium secondary battery waste discharged after reduction and roasting is mixed with water, so that lithium and lithium carbonate in the lithium secondary battery waste can be leached into lithium bicarbonate under cold conditions.

[0054] This is filtered to separate lithium bicarbonate and solids (lithium secondary battery waste from which lithium has been removed), and the lithium bicarbonate solution can be produced as lithium carbonate ((Li2CO3) powder in a boiler equipped with a heat exchanger through which the carbon dioxide gas passes.

[0055] The above separated solid matter (lithium secondary battery waste from which lithium has been removed) can be fed into a mixed solution generator to leach nickel, cobalt, manganese and impurities.

[0056] In the present invention, the purity of the lithium carbonate is improved because the recrystallization and leaching processes can be performed simultaneously by implementing high-temperature and low-temperature conditions using the carbon dioxide gas.

[0057] Step 1: Reduction and oxidation stage (reduction and oxidation section)

[0058] To proceed with the wet process, it's desirable to remove some organic matter. Most of the materials from spent secondary batteries are oxides, which exist in an unbalanced state (mixed +3 and +2) due to repeated charging and discharging. Therefore, using activated carbon as a reducing agent is desirable to transform this unbalanced state into a stable one.

[0059] When black powder, black mass, and activated carbon are fed into a screw feeder and mixed, and then calcined using a rotary kiln at a temperature of approximately 500°C or higher, carbon (C) changes into carbon dioxide (CO2). At this time, the oxide is reduced, so it is called reduction roasting, and lithium carbonate (Li2CO3)(s) is produced during this reduction roasting process.

[0060] The solids to be treated that have undergone a reduction and roasting process in a calcination reactor such as a rotary kiln may harden as the materials that have been changed to a stable state solidify, so it is preferable to crush them using a crusher and then mix them with water in a lithium leaching tank (heating reactor).

[0061] It is preferable that the content ratio of the above black powder and black mass and activated carbon is 90:10 to 70:30 (% by weight).

[0062] Step 2: Lithium leaching stage (lithium leaching section)

[0063] When the high-temperature carbon dioxide gas generated in the rotary kiln is cooled and then injected into the lithium leaching tank mixed with the above-mentioned crushed material (cold condition), lithium hydrogen carbonate (LiHCO3)(l) is leached and formed with reference to the formula below.

[0064] Li2CO3+ H2O + CO2→ 2LiHCO3[1]

[0065] Impurities such as SiO2, CaSO4, MgSO4, etc., along with lithium bicarbonate in a liquid state, precipitate as solids and can be filtered.

[0066] Afterwards, the impurities generated in this step are filtered using a filter (screw press), and lithium hydrogen carbonate (LiHCO3) is moved to the next reactor.

[0067] It is preferable that the amount of carbon dioxide gas injected is 3 to 6 NL / min or 180 to 300 wt% relative to 100 wt% of the lithium carbonate (crude).

[0068] The specific carbon dioxide gas input amounts are as shown in Table 1 below.

[0069] CO2 input amountLithium carbonate weight400 gPressure0.1Mpa(1atm)Temp.0℃CO2 input amount3-5 NL / minCO2 weight707.2 ~ 1178.7 gCO2 weight%176.8 ~ 294.7 %Temp.25℃CO2 input amount3.27-5.45 NL / minCO2 weight706.2 ~ 1177 gCO2 weight%176.6 ~ 294.3 %

[0070] Step 3: Lithium recrystallization stage (lithium recrystallization zone)

[0071] Thereafter, the high-temperature carbon dioxide gas generated from the rotary kiln passes through the lithium leaching tank, applying heat of about 80°C or higher to the lithium bicarbonate solution.

[0072] Here, Na + , SO4 2- is still dissolved in the liquid state solution, and when changed to the above hot condition (about 80℃ or higher), the lithium bicarbonate changes back to a solid state into purified lithium carbonate (Li2CO3)(s), and Na + , SO4 2- It is separable from the back.

[0073] In addition, by filtering through a solid-liquid separator (centrifugal dehydrator) and drying using the high-temperature carbon dioxide gas, high-purity lithium carbonate (Li2CO3)(s) in a solid state is produced.

[0074] The high-temperature carbon dioxide gas used in this step is the high-temperature carbon dioxide gas generated in the previous reduction and oxidation process, and a heat exchanger (heat exchange unit) through which the gas passes may be additionally provided. It is preferable that the heat exchanger be configured so that the high-temperature carbon dioxide gas passing through it and the solution can exchange heat.

[0075] In one embodiment of the present invention, by heating the leaching tank to a predetermined temperature using high-temperature carbon dioxide gas generated in the reduction and roasting process without using a separate heat source, there is an advantage in that an eco-friendly lithium recovery process can be achieved by preventing environmental pollution due to carbon emissions while also being economically efficient.

[0076] Step 4: Regeneration of sulfuric acid and carbon dioxide reuse stage (reuse section)

[0077] In addition, in the leaching or recrystallization step, solid impurities filtered through a filter are introduced into a reaction tank, sulfuric acid (H2SO4) is introduced, and the high-temperature carbon dioxide gas is allowed to pass through a pipe provided on one side of the reaction tank, so that the heat of the carbon dioxide gas is exchanged with the solution in the reaction tank, thereby lowering the temperature of the carbon dioxide gas, and the carbon dioxide gas can be re-injected into the lithium leaching tank solution for use.

[0078] In one embodiment of the present invention, the sulfuric acid used in the step is characterized in that it separates components such as Li, Ni, Co, and Mn from lithium secondary battery waste, and the solution generated during the separation process is recycled to the separation process without being discarded.

[0079] In addition, the sulfuric acid used in the above step is sulfuric acid formed using a BPED electrodialyzer, which is a lithium sulfate decomposition device, and the formation process will be described below.

[0080] Step 2: Lithium hydroxide production reaction

[0081] In one embodiment of the present invention, the reaction tank is characterized in that Ni Cake (a cake containing nickel hydroxide) (Ni(OH)2) is used as a neutralizing agent to further increase the recycling effect of resources.

[0082] The above Ni Cake may include sludge generated during a nickel smelting process, sludge generated during a secondary battery recycling process, sludge generated during an electronic plating process, etc., and the above Ni Cake may contain a large amount of impurities such as Al, Ca, and Cu.

[0083] Typically, sulfuric acid remains in the reactor, and any remaining sulfuric acid must be neutralized with caustic soda to be used in the subsequent wet process. This process presents a problem: large quantities of caustic soda are used.

[0084] Therefore, in the present invention, Ni Cake can be used as a neutralizing agent while raising the pH in the reaction tank to 5 to 5.5, preferably to 5.

[0085] Step 1: Impurity and manganese removal step

[0086] The solids to be processed in this step may contain some impurities such as lithium carbonate (LiCO3), cobalt (Co), nickel (Ni), manganese (Mn), aluminum (Al), iron (Fe), calcium (Ca), magnesium (Mg), copper (Cu), and silicon (Si).

[0087] The reaction occurring in this step is that the excess sulfuric acid can dissolve nickel hydroxide, but impurities may remain in solid form up to pH 5, and most of the impurities contained in BM can also change to solid state up to pH 5.5.

[0088] When the above solid material is fed into a mixed solution generator, a regenerated sulfuric acid (H2SO4) solution and a neutralizing agent are fed and mixed at a predetermined pH and temperature, the Li, Ni, Co, and Mn components of the solid material to be treated are dissolved in the sulfuric acid solution, and other impurities such as aluminum (Al), iron (Fe), calcium (Ca), chromium (Cr), magnesium (Mg), copper (Cu), and silicon (Si) of the solid material to be treated are precipitated as solids. At this time, the pH within the mixed solution generator (100) is preferably 4.5 to 5.5.

[0089] Therefore, in this step, when the Ni Cake is used as a neutralizing agent to adjust the pH to 4.5 to 5.5, the solid metals Al, Fe, Cu, and Cr are filtered through the first solid-liquid separation, and since Ni, Co, Mn, and Li are still dissolved, the liquid after filtering is moved to the next reactor.

[0090] The above reactor contains Li, Ni, Co, Mn, Fe, and other (Ca, Mg) impurities. At this time, in order to remove Mn and Fe, ozone (O3) is injected into the reactor and stirred, which oxidizes into iron oxide and manganese dioxide (MnO2) and changes into a solid state. Afterwards, Mn and Fe can be removed by secondary solid-liquid separation and centrifugal dehydration.

[0091] At this time, since FeSO4 and MnSO4 are oxidized by ozone to generate sulfuric acid, the pH of the solution is lowered, slowing down the oxidation reaction by ozone. However, by simultaneously adding nickel hydroxide cake to maintain the pH of the solution at 4.5 to 5.5, the iron-manganese reaction can be induced quickly. In addition, since the pH of the solution is 4.5 to 5.5, there is no need for a separate pH adjustment in the solvent extraction process, and since iron, manganese, and other impurities are filtered out once more, only the extremely small amount of remaining impurities is subject to solvent extraction, making the solvent extraction process easier.

[0092] The above ozone injection rate is preferably 1 to 3 NL / min, and the injection amount is preferably 5 to 10 wt% based on 100 wt% of the solid matter to be treated.

[0093] The specific ozone dosage is as shown in Table 2 below.

[0094] O3 input amountBM, BP leaching weight100 gPressure0.05Mpa(0.5atm)Temp.0℃O3 input amount1.5 NL / minO3 weight8.004 gO3 weight%8.004 %Temp.25℃O3 input amount1.65 NL / minO3 weight8.737 gO3 weight%8.737 %

[0095] Step 2: Solvent extraction step

[0096] In the aqueous solution from which iron and manganese have been removed, only Li, Ni, Co, Al, and Cu remain. It is desirable to perform primary solvent extraction to remove Al, Cu, etc.

[0097] At this time, it is preferable to use an oil component extractant (organic solvent) when performing the solvent extraction step, and the extractant and the mixed solution are temporarily mixed together and then separated by the difference in specific gravity, and other residual impurities such as Al and Cu in the mixed solution are captured and separated by the extractant.

[0098] The above extractant is a liquid containing an oil component having a lower specific gravity than the mixed solution, and may be, for example, one selected from the group consisting of di-2-ethylhexylphosphoric acid (D2EHPA), 2-ethylhexyl phosphonic acid mono-2-ethylhexyl ester (PC88A), a mixture of di-2-ethylhexylphosphoric acid and tri-butyl-phosphate (TBP), and a mixture of 2-ethylhexyl phosphonic acid mono-2-ethylhexyl ester and tri-butyl-phosphate (TBP). It is preferable to use di-2-ethylhexylphosphoric acid (D2EHPA).

[0099] In one embodiment of the present invention, the equilibrium pH (final pH of the solution) of the aqueous solution in the solvent extractor after solvent extraction is preferably 3 to 4, and more preferably 3.5. If the above range is not satisfied, the amount of metal extracted by the extractant is reduced, and impurities such as Al and Cu in the solution cannot be sufficiently separated.

[0100] Specifically, when the extractant and the mixed solution containing impurities in the solvent extractor are temporarily mixed, the hydrogen ions (H) of the extractant are +) is transferred to the mixed solution, and as the equilibrium pH of the mixed solution is adjusted to 3 to 4, other residual impurities in the solution except Li, Ni, and Co are transferred to the extractant and captured.

[0101] In one embodiment of the present invention, in order to further improve the impurity removal performance and at the same time significantly reduce the machine installation area for the solvent extraction process, as illustrated in FIG. 2, the solvent extractor (400) may have a structure in which a plurality of porous mixing induction plates (402) are arranged at a predetermined interval inside a column (401) having a long column shape to increase the contact area between the mixed solution and the extractant.

[0102] Specifically, the solvent extractor (400) of this embodiment may include a column (401) having a vertically elongated columnar shape, a plurality of porous mixing induction plates (402) arranged vertically at predetermined intervals inside the column (401), and an extractant outlet (406) and a solution outlet (405) formed at the upper and lower ends of the column (401), respectively.

[0103] The column (401) may have a vertically elongated column shape, having a solution inlet (403) at the top into which the aqueous solution is injected, and an extractant inlet (404) at the bottom into which the extractant is injected. The solution inlet (403) of the column (401) is connected to a reactor via a solution supply pump (not shown) so that a mixed solution containing Li, Ni, Co, and other impurities such as Al and Cu is injected into the top of the column (401). In addition, the extractant inlet (404) of the column (401) is connected to an extractant storage tank (not shown) storing an extractant such as 'D2EHPA' via an extractant supply pump (not shown) so that the extractant is injected into the bottom of the column (401).

[0104] The porous mixing induction plate (402) is arranged vertically between the solution inlet (403) and the extractant inlet (404) at a predetermined interval, and may be formed as a plate body having a plurality of holes formed therein so that the mixed solution and the extractant can pass through while being split into several branches. For example, the porous mixing induction plate (402) may be formed of a mesh, or may be formed as a porous plate in which a plurality of holes are arranged in a grid shape or radially.

[0105] The extractant discharge port (406) is positioned above the solution inlet (403) of the column (401) and is connected to the extractant recovery tank (420) provided outside the column (401), so that the extractant floating to the upper part of the column (401) due to the specific gravity difference is discharged to the extractant recovery tank (not shown) provided outside the column (401).

[0106] The solution discharge port (405) is positioned at the lower side of the extractant injection port (404) and is connected to a solution recovery tank (not shown) provided outside the column (401) to discharge the solution that has flowed to the lower part of the column (401) due to the specific gravity difference into the solution recovery tank provided outside the column (401).

[0107] In the solvent extractor (400) having such a configuration, a mixed solution is injected from the solution injection port (403) at the top of the column (401) and flows from the top to the bottom, and an extractant is injected from the extractant injection port (404) at the bottom of the column (401) and flows from the bottom to the top. The mixed solution injected into the top of the column (401) flows downward and passes through the porous mixing guide plate (402), and the extractant injected into the bottom of the column (401) flows upward and passes through the porous mixing guide plate (402), and they are mixed in the space between the plurality of porous mixing guide plates (402). At this time, since the extractant has oil-like properties, the mixed solution and the extractant do not dissolve in each other, but in this process, the hydrogen ions (H) of the extractant +) is transferred to the mixed solution, and as the equilibrium pH of the mixed solution is adjusted to 3 to 4, other residual impurities except Li, Ni, and Co in the solution are transferred to the extractant and captured. In addition, since the specific gravity of the extractant is lower than that of the mixed solution, the extractant flows to the upper side of the column (401), and the mixed solution flows to the lower side of the column (401).

[0108] The extractant flowing to the upper part of the column (401) is discharged to the extractant recovery tank (not shown) through the extractant discharge port (406) in a state where impurities such as Al and Cu in the mixed solution are captured and stored. Then, the mixed solution from which impurities have been removed while flowing to the lower part of the column (401) is discharged to the solution recovery tank through the solution discharge port (405) and stored.

[0109] Meanwhile, in order to further improve mixing performance when mixing with a mixed solution by injecting an extractant into the lower part of the column (401), the solvent extractor (400) may further include a pulse generation unit that generates pulses in the extractant when injecting the extractant into the column (401).

[0110] The pulse generating unit may be configured to generate pulses by oscillating at a certain cycle and placed at the lower part of the column (401), but the extractant supply pump, which is placed between the extractant storage tank and the extractant injection port (404) and supplies the extractant of the extractant storage tank, may be configured as a pulse-type pump that generates pulses.

[0111] In this way, when pulses are generated at regular intervals in the extractant injected into the column (401) by the pulse generating unit, when the extractant flows upward while passing through the porous mixing induction plate (402), the mixing of the mixed solution and the extractant is more actively promoted by vibration, so that the contact area between the mixed solution and the extractant increases, and the advantage of impurities in the mixed solution being more actively transferred to the extractant can be obtained.

[0112] The solvent extractor (400) having the configuration described above has the advantage of being able to significantly reduce the installation area compared to existing solvent extractors because the column (401) has a vertically long column shape, and simplifying the configuration because it does not require a rotating stirring device and a driving device for stirring, and also being able to significantly reduce manufacturing costs and maintenance costs.

[0113] The mixed solution discharged to the solution recovery tank through the solution discharge port (405) of the above solvent extractor (400) mainly contains Li, Ni, and Co components, but may also contain trace amounts of dissolved impurities. In order to extract components other than the Li component from the mixed solution in the solution recovery tank, the mixed solution in the solution recovery tank and a neutralizing agent are added and stirred to make the pH 8 to 9, thereby generating nickel hydroxide (Ni(OH)2) and cobalt hydroxide (Co(OH)2) solids.

[0114] Step 3: Li, Ni, Co separation step

[0115] It is preferable to introduce the aqueous solution from which the above impurities have been removed into a neutralization reactor to raise the pH from 3.5 to 8-9.

[0116] In one embodiment of the present invention, the neutralizing agent fed into the neutralization reactor may be a lithium hydroxide (LiOH) solution. Initially, fresh lithium hydroxide (LiOH) is used, but after lithium hydroxide (LiOH) is produced by an electrodialyzer described below, the lithium hydroxide (LiOH) solution separated by the electrodialyzer is used, thereby increasing the recyclability.

[0117] In this case, Ni and Co change into nickel hydroxide (Ni(OH)2) and cobalt hydroxide (Co(OH)2) and are filterable, and Li is dissolved in the aqueous solution and is thus separable.

[0118] The nickel hydroxide (Ni(OH)2) and cobalt hydroxide (Co(OH)2) solids generated in the neutralization reactor are separated through a third solid-liquid separation. At this time, in order to recover even trace amounts of lithium attached to the nickel hydroxide (Ni(OH)2) and cobalt hydroxide (Co(OH)2) solids separated in the third solid-liquid separator, the separated nickel hydroxide (Ni(OH)2) and cobalt hydroxide (Co(OH)2) solids are washed with wash water, and the wash water containing the Li component is transferred to a wash water recovery tank and stored. At this time, the wash water stored in the wash water recovery tank exists in the state of a very dilute lithium sulfate (Li2SO4) solution.

[0119] And, the solution from which nickel hydroxide (Ni(OH)2) and cobalt hydroxide (Co(OH)2) solids are separated in the third solid-liquid separator is in the state of a lithium sulfate (Li2SO4) solution and is transferred to and stored in a lithium sulfate solution storage tank.

[0120] The lithium sulfate (Li2SO4) solution in the above-mentioned wash water recovery tank is supplied to a reverse osmosis (SWRO) unit, concentrated, and then transferred to the lithium sulfate solution storage tank and stored.

[0121] The lithium sulfate (Li2SO4) solution in the lithium sulfate solution storage tank may contain trace amounts of impurities and floating organic matter in addition to lithium sulfate (Li2SO4), and if it is supplied to the electrodialysis machine (700) with trace amounts of impurities and floating organic matter, it may cause problems such as a decrease in electrodialysis efficiency, an increase in power consumption, and an increase in process time.

[0122] Accordingly, before feeding the lithium sulfate (Li2SO4) solution into the electrodialysis machine, the lithium sulfate (Li2SO4) solution is supplied to the pretreatment module to remove trace impurities and floating organic matter contained in the lithium sulfate (Li2SO4) solution.

[0123] The pretreatment module may include an organic matter remover containing activated carbon that removes organic matter as lithium sulfate (Li2SO4) solution supplied from a lithium sulfate solution storage tank passes through it, and an ion exchanger that separates residual impurities such as Ca, Mg, Si, Ni, Co, and Mn from the lithium sulfate (Li2SO4) solution that has passed through the organic matter remover.

[0124] The lithium sulfate (Li2SO4) solution, from which organic matter and impurities have been almost completely removed, is stored in an electrodialysis solution supply tank (710) and then fed into an electrodialysis machine (700).

[0125] In one embodiment of the present invention, the strongly alkaline lithium hydroxide (LiOH) is used as a neutralizing agent to prevent impurities such as Na from being mixed into the final product, and further, the high-purity lithium hydroxide directly purified through the process of the present invention is reused in the reaction, which is economical.

[0126] It is desirable to wash the above filtered Ni(OH)2, Co(OH)2 by adding a large amount of water so that no Li remains at all.

[0127] Step 4: Electrodialysis stage

[0128] Li separated through the above steps can be separated by using activated carbon (C) to remove organic substances contained in lithium sulfate (Li2SO4), and then using the ion exchanger to separate Ca, Mg, Si, etc. In this case, lithium sulfate with a high concentration remains, and if a BPED electrodialyzer, which is a lithium sulfate decomposition device, is used, 10% sulfuric acid (H2SO4) can be generated at the anode, and lithium hydroxide (LiOH)(l) can be generated at the cathode.

[0129] Below, the BPED electrodialysis device (700), which is a lithium sulfate decomposition device, is described in detail.

[0130] The above electrodialysis device may be configured as a bipolar electrodialysis device using a bipolar membrane, which is a combination of an anion exchange layer and a cation exchange layer. For example, the electrodialysis device may be configured with a configuration in which an anode cell including an anode, a first bipolar membrane, an anion exchange membrane, a cation exchange membrane, a second bipolar membrane, and a cathode cell including a cathode are sequentially arranged. Such a bipolar electrodialysis device may operate as follows.

[0131] Lithium sulfate (Li2SO4) solution is injected between the cation exchange membrane and the anion exchange membrane, water is injected between the first bipolar membrane and the anion exchange membrane, and between the cation exchange membrane and the second bipolar membrane, respectively, and electrode solution is injected between the anode cell and the first bipolar membrane and between the second bipolar membrane and the cathode cell, respectively, and when voltage is applied, Li2SO4 is injected through the cation exchange membrane and the anion exchange membrane, respectively. + and SO4 2- , and water is separated from the hydrophilic interface, which is the middle interface of the bipolar membrane. + Wow OH - It is very quickly dissociated and can be moved from the bipolar membrane interface to the surrounding solution by a strong electric field and recovered as a lithium hydroxide (LiOH) solution and a sulfuric acid (H2SO4) solution.

[0132] Referring to FIG. 3, in order to recover a large amount of lithium hydroxide (LiOH) solution and sulfuric acid (H2SO4) solution through an electrodialyzer (700), the electrodialyzer (700) has tens to hundreds of anion exchange membranes (710), cation exchange membranes (720), and bipolar membranes (730) arranged horizontally, and support plates (750) having predetermined passages formed therein are placed between the membranes to allow lithium sulfate (Li2SO4) solution, electrode solution, and water to pass through between the cation exchange membranes, anion exchange membranes, and bipolar membranes, and are in close contact with each other. At this time, the support plates (750) and the anion exchange membranes (710), cation exchange membranes (720), and bipolar membranes (730) must be in close contact with each other without being spaced apart from each other so that the reaction can proceed smoothly and other fluids do not leak between the membranes.

[0133] In order to press the laminate of a plurality of anion exchange membranes (710), cation exchange membranes (720), bipolar membranes (730), and support plates (750) together with a predetermined pressure, a fixed frame (761) may be arranged on one side of the laminate, and a pressure plate (762) that presses the laminate against the fixed frame (761) to pressurize the laminate into a pressed state, and a pressure unit (763) that horizontally moves the pressure plate (762) may be configured on the other side of the laminate.

[0134] The above pressurizing unit (763) can be configured using a linear motion device. For example, the pressurizing unit (763) can be configured using a linear motion device including a screw shaft having screw threads formed on the outer surface and a motor for rotating the screw shaft. However, alternatively, the pressurizing unit (763) can be configured using a linear motion device including a hydraulic cylinder, a belt wound around a plurality of pulleys and transmitting the rotational force of the pulleys, and a motor for rotating one of the pulleys.

[0135] Some of the lithium hydroxide (LiOH) solution recovered from the electrodialysis machine is used as a neutralizing agent fed into the neutralization reactor, and the remainder is made into solid lithium hydroxide crystals (LiOH·H2O)(s) through a crystallization device (MVR) and can be reused in the manufacturing process of lithium secondary batteries.

[0136] In addition, some of the sulfuric acid (H2SO4) solution recovered from the electrodialysis machine can be used to dissolve the solid to be treated, as in the reaction of step 3 of the first process of the present invention and the second process, and the remaining part can be used in the process of recovering other components (e.g., Ni, Co, etc.) of lithium secondary battery waste.

[0137] The lithium recovery system of the present invention for lithium secondary battery waste as described above can recover major components such as manganese (Mn), nickel (Ni) and cobalt (Co) from lithium secondary battery waste containing lithium, and then generate a lithium hydroxide (LiOH) solution and a sulfuric acid (H2SO4) solution using an electrodialyzer to recover lithium (Li).

[0138] At this time, some of the lithium hydroxide (LiOH) solution recovered from the electrodialysis machine is used as a neutralizing agent in the neutralization reactor, and some of the sulfuric acid (H2SO4) solution is injected into the mixed solution generator to be recycled to recover manganese (Mn), nickel (Ni), cobalt (Co), and lithium (Li) from lithium secondary battery waste.

[0139] Referring to Figure 3 and Table 3 below, the principle of producing lithium hydroxide and sulfuric acid from a lithium sulfate aqueous solution using an electrodialyzer is as follows.

[0140]

[0141] Step 3: Nickel sulfate and cobalt sulfate production reaction

[0142] Step 1: Solvent extraction step

[0143] When dissolving Ni Cake (nickel hydroxide) using fresh sulfuric acid, it is desirable to add sulfuric acid only until the pH becomes 5 to 5.5, preferably about 5, and then Al, Fe, and Cu can be removed during filtration.

[0144] Specifically, when sulfuric acid is mixed and leached into secondary battery waste, the pH changes to a state of 1 or less without solids. At this time, when the nickel hydroxide cake is added again to adjust the pH until the pH becomes 5.5, a nickel sulfate solution is generated, and a significant portion of the Ni, Co, and Mn impurities, along with the Al, Cu, etc. contained in the cake, become solids, making filtration possible.

[0145] After filtration, Ni, Co, Mn, and Fe remain in the solution, and by adding ozone and stirring, iron oxide and MnO2 can be removed. In addition, the solution from which Mn and Fe have been removed can be obtained as a solution containing Ni and Co, specifically a NiSO4 and CoSO4 solution, using a solvent extractor, column, and extractant in the same manner as the solvent extraction method described above.

[0146] In addition, when new sulfuric acid is added to the Ni(OH)2, Co(OH)2 filtered in step 3 of the second process, it changes into a NiSO4, CoSO4 solution and can be used together with the solution obtained by the solvent extraction.

[0147] Step 2: Ni, Co separation step

[0148] As a method for separating Ni and Co from the NiSO4, CoSO4 solution prepared in the above step 1, the pH should be adjusted to 5 to 6, preferably 5.5, and it is preferable not to use caustic soda at this time.

[0149] Therefore, a portion of the final product, NiSO4, is neutralized with wash water and LiOH to generate Li2SO4(l) and Ni(OH)2(s), and the Li2SO4 generated at this time can be fed into the wash water Li2SO4 tank of step 3 of the second process.

[0150] It is preferable to add Ni(OH)2 to the NiSO4, CoSO4 solution prepared in step 1 above until the pH becomes 5 to 5.5, preferably 5, and then filter using a filter press.

[0151] In one embodiment of the present invention, in order to adjust the pH, it is preferable to perform solvent extraction in two stages.

[0152] First, Ni is extracted through primary extraction, and Co is extracted through secondary extraction. Since there will be some extractant in the solution, the extractant is removed using a centrifuge. Then, by passing a nickel sulfate (NiSO4) solution through a tank filled with activated carbon, the oil remaining in the nickel sulfate can be completely removed.

[0153] The above activated carbon is used to remove residual oil, and it is desirable to perform the same process on the cobalt sulfate (CoSO4) solution generated after cobalt extraction.

[0154] It is preferable to use the extractant described in the second process above as the extractant.

[0155] In addition, the moment the extractant is injected from the bottom of the column, it contains Co and Ni, and as the extractant rises to the top, it continuously contains Co. Therefore, it is desirable to install a control valve and a flow meter at the top outside the column to input the L value per minute (l / min) to control the injected amount.

[0156] If the mixing of the oil and aqueous solution in the column is too strong, they may mix with each other, making separation difficult.

[0157] In one embodiment of the present invention, the mixing (retention) time within the column is characterized by being as long as possible and the separation time is as short as possible. The mixing time is preferably 30 to 60 minutes, and the separation time is preferably 10 to 15 minutes.

[0158] Step 3: Washing and back-extraction stage

[0159] After the above first and second extractions, it is preferable to perform a scrubbing operation using the column again. Specifically, the scrubbing operation is performed by adding dilute sulfuric acid (5% sulfuric acid) to the oil to adjust the pH to 4 to 5, preferably 4, so that the oil continues to contain Co, and a small amount of Ni is transferred to the dilute sulfuric acid.

[0160] Afterwards, it is desirable to perform a stripping reaction using a column. Specifically, when concentrated sulfuric acid (10% sulfuric acid) is added, Co can move from the oil, producing cobalt sulfate (CoSO4)(l).

[0161] It is also desirable to centrifuge the cobalt sulfate solution produced through the above-described reverse extraction, then filter it through activated carbon. Furthermore, the oil that overflows during reverse extraction can be purified using concentrated sulfuric acid, allowing for continued reuse.

[0162] It is preferable that the solution containing the above Co and Ni be moved to the reaction tank of step 1 and the extraction reaction be repeated.

[0163] In one embodiment of the present invention, the activated carbon is not discarded after use in this step, but can be reused when mixed with BP and BM in the first step of the first process, and thereafter, the activated carbon can be oxidized and used as carbon dioxide.

[0164] Hereinafter, the present invention will be described in more detail by way of examples. These examples are intended solely to illustrate the present invention, and it will be apparent to those skilled in the art that the scope of the present invention is not limited to these examples.

[0165] Example: Recovery and removal rates

[0166] The recovery rates of Li, Ni, and Co and the removal rates of Al, Cu, and Mn were confirmed according to each reaction time, reaction temperature, and pH, and the results are shown in Tables 4 and 5 below.

[0167] ClassificationLiRecovery rate(%)ClassificationNiRecovery rate(%)CoRecovery rate(%)Reaction time(hr)(Temperature 80℃)182.0Reaction time(hr)(pH 5.0)196.794.5295.4298.598.2395.5398.798.2Reaction temperature(℃)(Reaction time 2hr)6077.8pH(Reaction time 2hr)4.093.289.98095.45.098.598.210095.66.098.198.2

[0168] ClassificationAl removal rate (%)Cu removal rate (%)ClassificationMn removal rate (%)Reaction time (hr)(pH 5.0)198.093.8Reaction time (hr)(pH 6.0)178.2299.599.6299.5399.699.5399.6pH(Reaction time 2hr)4.080.488.1pH(Reaction time 2hr)4.083.95.099.599.65.088.96.099.799.66.099.5

[0169] The above description exemplifies the present invention, and the embodiments disclosed in the specification are intended to illustrate rather than limit the technical spirit of the present invention. Therefore, those skilled in the art will appreciate that various modifications and variations can be made without departing from the scope of the present invention. Therefore, the scope of protection of the present invention should be interpreted based on the matters set forth in the claims, and technical matters within a scope equivalent thereto should also be interpreted as being included within the scope of the rights of the present invention.

[0170] The secondary battery complete circulation regeneration process and system according to the present invention can implement an environmentally friendly and economical metal recovery process for lithium secondary battery waste, as secondary battery waste is continuously introduced into the process and completely recycled without generating discharged wastewater.

Claims

1. (i) A step of producing lithium carbonate by concentrating and carbonating secondary battery waste; (ii) a step of producing lithium hydroxide and sulfuric acid by electrodialyzing lithium sulfate produced in the lithium carbonate production step; and (iii) a step of adding sulfuric acid to secondary battery waste to leach it and adding lithium hydroxide to neutralize it to produce nickel sulfate and cobalt sulfate; Some of the lithium hydroxide solution and sulfuric acid solution recovered through the above electrodialysis are reused within the process. A secondary battery complete circulation regeneration process without wastewater generation, characterized in that the secondary battery waste is continuously input into the process, while resources within the process are completely recycled and recovered without generating discharged wastewater.

2. In the first paragraph, the process is characterized in that it is possible to recycle and reuse secondary battery complete circulation regeneration process without generating wastewater by heating using high-temperature carbon dioxide gas generated in the carbonation process when producing lithium carbonate without using a separate heat source or by changing the temperature to low temperature and reintroducing it into the process. 3.(i) A reduction and combustion step of mixing secondary battery waste and activated carbon and then calcining to produce carbon dioxide gas; (ii) A lithium separation step of producing lithium carbonate by cooling and blowing carbon dioxide gas into a lithium leaching tank containing a mixed solution of pulverized material and water after calcination, then applying heat to the lithium leaching tank to change it into a solid state, and then filtering and drying through solid-liquid separation; (iii) A step of manufacturing iron and manganese by adding a sulfuric acid (H2SO4) solution and a neutralizing agent to the above-mentioned solid-liquid separated solution, heating to remove impurities, injecting ozone (O3) to generate iron oxide and manganese dioxide (MnO2) solids, and then performing solid-liquid separation filtration; (iv) a solvent extraction step in which an extractant is added to a solution containing Li, Ni, Co and residual impurities from which iron and manganese have been removed to remove the residual impurities; (v) A metal separation step in which a solution from which residual impurities have been removed is subjected to a neutralization reaction using a regenerative neutralizing agent to extract nickel hydroxide (Ni(OH)2) and cobalt hydroxide (Co(OH)2) solids and separated from a lithium sulfate (Li2SO4) solution through solid-liquid separation; (vi) an electrodialysis step of decomposing the lithium sulfate solution into a lithium hydroxide (LiOH) solution and a sulfuric acid (H2SO4) solution through electrodialysis; (vii) a nickel separation step in which a sulfuric acid (H2SO4) solution is added to the nickel hydroxide (Ni(OH)2) and cobalt hydroxide (Co(OH)2) solids, impurities are removed by filtering, an extractant is added to extract the solvent, and Ni(OH)2 is added to produce nickel sulfate (NiSO4); and (viii) A secondary battery complete cycle regeneration process without wastewater generation, characterized in that it includes a cobalt separation step in which an extractant, dilute sulfuric acid, and concentrated sulfuric acid are added to a solution in which Ni is removed and Co remains to produce cobalt sulfate (CoSO4).

4. In the third paragraph, the process is characterized in that it is possible to recycle secondary batteries by heating using high-temperature carbon dioxide gas generated in the reduction and oxidation step without using a separate heat source or by changing the temperature to low temperature and reintroducing it into the process, thereby enabling regeneration. A wastewater-free secondary battery complete circulation regeneration process.

5. In the third paragraph, the sulfuric acid is a sulfuric acid solution separated by a lithium sulfate decomposition device, which is an electrodialysis device, and is not discarded but reintroduced into the process, thereby implementing an eco-friendly process that does not generate wastewater, a secondary battery complete circulation regeneration process characterized by not generating wastewater.

6. A secondary battery complete circulation regeneration process without wastewater generation, characterized in that in the third paragraph, the neutralizing agent is a lithium hydroxide (LiOH) solution separated by the electrodialysis machine.

7. In the third paragraph, the extractant is a liquid of oil component having a lower specific gravity than the solution, and is characterized in that it is one selected from the group consisting of di-2-ethylhexylphosphoric acid (D2EHPA), 2-ethylhexyl phosphonic acid mono-2-ethylhexyl ester (PC88A), a mixture of di-2-ethylhexylphosphoric acid and tri-butyl-phosphate (TBP), and a mixture of 2-ethylhexyl phosphonic acid mono-2-ethylhexyl ester and tri-butyl-phosphate (TBP), wherein the process for completely circulating regeneration of a secondary battery without generating wastewater is performed.

8. A secondary battery complete circulation regeneration process without wastewater generation, characterized in that in the third paragraph, a cake containing nickel hydroxide (Ni(OH)2) discarded after the manufacturing process of a lithium secondary battery is additionally added to separate the metal in step (vii).

9. Lithium recovery unit that concentrates and carbonizes secondary battery waste; An electrodialysis unit that electrodialyzes lithium sulfate generated in the lithium recovery unit to produce lithium hydroxide and sulfuric acid; A metal separation unit that separates nickel and cobalt by adding a neutralizing agent to the residual solution generated through the lithium recovery unit; and A secondary battery complete circulation regeneration system without wastewater generation, characterized in that it includes a nickel and cobalt recovery unit that neutralizes leaching light by adding sulfuric acid and lithium hydroxide to the solution generated in the metal separation unit.

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