A method for producing high-purity lithium carbonate from discarded refractory saggars.

Abstract

The present invention provides an optimized method for recovering high-purity lithium carbonate from lithium-containing compounds such as lithium silicate, lithium aluminum oxide, and lithium aluminum silicate deposited on the eroded surface of waste refractory crucibles to be discarded. Therefore, by using the method for producing high-purity lithium carbonate from waste refractory crucibles of the present invention, not only can the waste refractory crucibles to be discarded be recycled to produce high-purity lithium carbonate that can be used in the production of lithium secondary batteries, but it is also expected that the positive electrode active material, iron oxide, alumina, silicate, calcium carbonate, etc. obtained incidentally in the production process can also be recycled.

Description

[Technical Field]

[0001] This invention relates to a method for producing high-purity lithium carbonate from waste refractory saggars. [Background technology]

[0002] The positive electrode active material for lithium secondary batteries is manufactured by firing at high temperatures in refractory saggers (also known as firing saggers) made from oxide ceramics mainly composed of SiO2, Al2O3, and MgO. Because these refractory saggers are repeatedly used for high-temperature firing of lithium-containing composite oxides, which are the raw materials for the positive electrode active material, their surfaces are eroded over time, and lithium compounds such as lithium hydroxide and lithium carbonate, along with the positive electrode active material, are deposited in the eroded areas. Refractory saggers whose surfaces are eroded by lithium hydroxide, lithium carbonate, etc., lose their heat resistance and are eventually discarded. It is said that approximately 9,000 tons of waste refractory saggers are generated annually in South Korea, but with the recent surge in demand for lithium-ion secondary batteries, coupled with the popularization of mobile devices and electric vehicles, the amount of waste refractory saggers is expected to increase sharply. The positive electrode active materials used in lithium secondary batteries utilize lithium carbonate and lithium hydroxide as lithium sources. These were typically produced from natural sources such as ore or saltwater, or recovered from discarded secondary batteries.

[0003] As described above, refractory saggars are used in the manufacture of positive electrode active materials, and during the high-temperature firing process, they are eroded by lithium-containing composite oxides and lose their function. Therefore, if lithium can be recovered and purified from lithium-containing materials deposited in the eroded areas of discarded refractory saggars, which are discarded after repeated high-temperature firing of lithium-containing composite oxides reduces their heat resistance, it is expected that this will contribute to the effective utilization of lithium resources. However, there is absolutely no known method for recovering high-purity lithium carbonate from discarded refractory saggars.

[0004] All references cited herein, including publications, patent applications, and patents, are incorporated herein by reference to the same extent as each individual reference is specifically identified and referred to, and to the same extent as all of its contents are described herein.

[0005] All references cited herein, including publications, patent applications, and patents, are incorporated herein by reference to the same extent as each individual reference is specifically identified and referred to, and to the same extent as all of its contents are described herein. [Overview of the project] [Problems that the invention aims to solve]

[0006] The present invention aims to provide a method for recovering high-purity lithium carbonate from waste refractory saggars that are discarded after being used in high-temperature firing during the production of positive electrode active materials for lithium secondary batteries.

[0007] Other objects and technical features of the present invention are presented more specifically in the following detailed description of the invention, claims, and drawings. [Means for solving the problem]

[0008] The present invention comprises the first step of crushing waste refractory saggars to produce waste refractory saggar pulverized material, the second step of adding an alkaline leaching agent and water to the waste refractory saggar pulverized material and reacting them to produce a waste refractory saggar pulverized material dissolution reaction slurry, the third step of primary solid-liquid separation of the waste refractory saggar pulverized material dissolution reaction slurry, the fourth step of evaporating and concentrating the filtrate obtained as a liquid phase using the primary solid-liquid separation, the fifth step of secondary solid-liquid separation of the concentrated liquid obtained using the evaporation and concentration, the sixth step of performing a carbonation reaction on the filtrate obtained as a liquid phase using the secondary solid-liquid separation to produce a carbonation reaction solution, and the seventh step of tertiary solid-liquid separation of the carbonation reaction solution. The present invention provides a method for producing high-purity lithium carbonate from waste refractory saggars, comprising: an eighth step of adding water to a first lithium carbonate obtained as a solid phase using solid-liquid separation to produce a first lithium carbonate suspension, and injecting carbon dioxide (CO2) to dissolve the first lithium carbonate; a ninth step of performing quaternary solid-liquid separation on the aqueous solution in which the first lithium carbonate is dissolved; a tenth step of heating and recrystallizing the filtrate obtained as a liquid phase using the quaternary solid-liquid separation to precipitate a second lithium carbonate; and an eleventh step of performing quintuple solid-liquid separation on the filtrate in which the second lithium carbonate has been precipitated to obtain high-purity second lithium carbonate as a solid phase, and drying it.

[0009] Furthermore, the present invention comprises a 12th step of crushing waste refractory saggars to produce waste refractory saggar pulverized material, a 13th step of adding an alkaline leaching agent and water to the waste refractory saggar pulverized material and then reacting them to produce a waste refractory saggar pulverized material dissolution reaction slurry, a 14th step of performing primary solid-liquid separation of the waste refractory saggar pulverized material dissolution reaction slurry, and after producing a suspension from the solid phase obtained using the primary solid-liquid separation, performing primary wet magnetic separation to obtain a first magnetic material and a first non-magnetic material. Step 15; Step 16: After producing the first non-magnetic material as a suspension, perform secondary wet magnetic separation to obtain a second magnetic material and a second non-magnetic material; Step 17: Add water and a leaching agent to the second non-magnetic material and react them to produce a lithium leaching reaction solution; Step 18: Perform sixth-order solid-liquid separation of the lithium leaching reaction solution; Step 19: Evaporate and concentrate the filtrate obtained as a liquid phase using the sixth-order solid-liquid separation; The present invention provides a method for producing high-purity lithium carbonate from waste refractory saggars, comprising: a 20th step of performing secondary solid-liquid separation of the concentrated liquid obtained by the secondary solid-liquid separation; a 21st step of performing a carbonation reaction on the filtrate obtained as a liquid phase using the secondary solid-liquid separation to produce a carbonation reaction solution; a 22nd step of performing tertiary solid-liquid separation of the carbonation reaction solution; a 23rd step of adding water to the first lithium carbonate obtained as a solid phase using the tertiary solid-liquid separation to produce a first lithium carbonate suspension, and injecting carbon dioxide (CO2) to dissolve the first lithium carbonate; a 24th step of performing quaternary solid-liquid separation of the aqueous solution in which the first lithium carbonate is dissolved; a 25th step of heating the filtrate obtained as a liquid phase using the quaternary solid-liquid separation to recrystallize and precipitate a second lithium carbonate; and a 26th step of performing quintuple solid-liquid separation of the filtrate in which the second lithium carbonate has precipitated to obtain high-purity second lithium carbonate as a solid phase, and drying it.

[0010] The aforementioned slurry for dissolving the pulverized waste refractory saggar is characterized by being produced by adding one or more alkalis, including alkali metal hydroxides, alkali metal carbonates, or alkali earth metal hydroxides, to the pulverized waste refractory saggar together with water, and then heating it.

[0011] The first magnetic deposit is a magnetic deposit containing iron oxide and iron scale, the second magnetic deposit is a magnetic deposit containing a positive electrode active material, the solid phase of the sixth solid-liquid separation is characterized by containing alumina and silicate, the lithium leaching reaction solution is produced by adding alkali earth metal hydroxide or oxide and water as a leaching agent to the second non-magnetic deposit, and then reacting it in a pressure reaction vessel at a temperature of 100 to 200°C for a reaction time of no more than 3 hours, and the reaction slurry concentration of the lithium leaching reaction solution is characterized by being 10 to 50 wt%.

[0012] The aforementioned evaporation concentration is characterized by being carried out under reduced pressure evaporation conditions at a temperature of 70 to 95°C, or by purging with nitrogen or argon gas under atmospheric pressure to prevent contact between carbon dioxide and the concentrate, while heating to 100°C, and the evaporation concentration is carried out until the lithium concentration in the concentrate reaches 0.5 to 5%.

[0013] The carbonation reaction is characterized by injecting one or more of the following into the filtrate obtained as a liquid phase using the secondary solid-liquid separation: carbon dioxide, carbonated water, and lithium bicarbonate aqueous solution, and allowing the reaction to proceed until the pH reaches 8 to 10. The filtrate obtained as a liquid phase using the tertiary solid-liquid separation is then added to the slurry of the waste refractory saggar pulverization reaction to further recover unreacted lithium hydroxide that could not participate in the carbonation reaction.

[0014] The reaction to dissolve the first lithium carbonate by injecting carbon dioxide into the first lithium carbonate suspension is carried out under temperature conditions of 0 to 20°C, characterized in that the pH of the reaction solution becomes 6 to 8 at the end of the reaction, and the filtrate obtained as the liquid phase using the quaternary solid-liquid separation is heated to a temperature of 80 to 100°C.

[0015] The lithium carbonate (second lithium carbonate) produced by the manufacturing method of the present invention is characterized by having a purity of 99.9% or higher. [Effects of the Invention]

[0016] This invention relates to the deposition of lithium hydroxide, lithium carbonate, lithium silicate, and lithium aluminum oxide (lithi) on the eroded surface of discarded refractory saggars after use. u This invention provides an optimized method for recovering high-purity lithium carbonate from lithium-containing compounds such as aluminum oxide and lithium aluminum silicate. Therefore, by utilizing the method for producing high-purity lithium carbonate from waste refractory saggars of the present invention, it is expected that not only can discarded waste refractory saggars be reused to produce high-purity lithium carbonate that can be used in the manufacture of lithium secondary batteries, but also positive electrode active materials, iron oxide, alumina, silicate, and calcium carbonate incidentally obtained during the manufacturing process can be reused. [Brief explanation of the drawing]

[0017] [Figure 1] The present invention schematically illustrates the method for producing high-purity lithium carbonate from waste refractory saggars. [Figure 2] The results of analyzing the constituent minerals of the waste refractory saggar of the present invention by X-ray diffraction (XRD) are shown. [Figure 3] This is a scanning electron microscope (SEM) image of pulverized waste refractory saggars, showing the overall particle size distribution and the surface structure of independent particles. [Modes for carrying out the invention]

[0018] This invention relates to a method for recovering high-purity lithium carbonate from refractory saggers (waste refractory saggers) that are discarded after being used in the firing of positive electrode active materials for secondary batteries. These refractory saggers are destroyed by erosion from lithium hydroxide, lithium carbonate, etc., with repeated use and are discarded without being reused. This invention aims to recover high-value lithium compounds from waste refractory saggers that are discarded without being reused. The waste refractory saggers are ceramic containers used in the firing of positive electrode active materials for secondary batteries, and their main components are SiO2, Al2O3, and MgO.

[0019]

Table 1

[0020] As a result of the analysis, it was confirmed that the lithium (Li) contents of SG1 and SG2 were 2.1% and 0.88% respectively, and were the higher ones. When these were converted to the lithium carbonate content, it was confirmed that they corresponded to SG1 = 11.17% and SG2 = 4.68%. Also, it was confirmed that the nickel and cobalt contents were 0.13 - 0.16% and 0.01 - 0.02% respectively, and it was confirmed that the value to be recovered was sufficiently high.

[0021] The waste refractory box furnace is composed of mullite, cordierite, alumina, quartz, spinel, lithium silicate, lithium aluminum oxide, lithium aluminum silicate, etc. Among the constituent components of the waste refractory box furnace, the substances causing the destruction of the refractory box furnace are lithium silicate, lithium aluminum oxide, lithium aluminum silicate, etc.

[0022] The present invention comprises the first step of crushing waste refractory saggars to produce waste refractory saggar pulverized material, the second step of adding an alkaline leaching agent and water to the waste refractory saggar pulverized material and reacting them to produce a waste refractory saggar pulverized material dissolution reaction slurry, the third step of primary solid-liquid separation of the waste refractory saggar pulverized material dissolution reaction slurry, the fourth step of evaporating and concentrating the filtrate obtained as a liquid phase using the primary solid-liquid separation, the fifth step of secondary solid-liquid separation of the concentrated liquid obtained using the evaporation and concentration, the sixth step of performing a carbonation reaction on the filtrate obtained as a liquid phase using the secondary solid-liquid separation to produce a carbonation reaction solution, and the seventh step of tertiary solid-liquid separation of the carbonation reaction solution. The present invention provides a method for producing high-purity lithium carbonate from waste refractory saggars, comprising: an eighth step of adding water to a first lithium carbonate obtained as a solid phase using solid-liquid separation to produce a first lithium carbonate suspension, and injecting carbon dioxide (CO2) to dissolve the first lithium carbonate; a ninth step of performing quaternary solid-liquid separation on the aqueous solution in which the first lithium carbonate is dissolved; a tenth step of heating and recrystallizing the filtrate obtained as a liquid phase using the quaternary solid-liquid separation to precipitate a second lithium carbonate; and an eleventh step of performing quintuple solid-liquid separation on the filtrate in which the second lithium carbonate has been precipitated to obtain high-purity second lithium carbonate as a solid phase, and drying it.

[0023] Furthermore, the present invention comprises a 12th step of crushing waste refractory saggars to produce waste refractory saggar pulverized material, a 13th step of adding an alkaline leaching agent and water to the waste refractory saggar pulverized material and then reacting them to produce a waste refractory saggar pulverized material dissolution reaction slurry, a 14th step of performing primary solid-liquid separation of the waste refractory saggar pulverized material dissolution reaction slurry, and after producing a suspension from the solid phase obtained using the primary solid-liquid separation, performing primary wet magnetic separation to obtain a first magnetic material and a first non-magnetic material. Step 15; Step 16: After producing the first non-magnetic material as a suspension, perform secondary wet magnetic separation to obtain a second magnetic material and a second non-magnetic material; Step 17: Add water and a leaching agent to the second non-magnetic material and react them to produce a lithium leaching reaction solution; Step 18: Perform sixth-order solid-liquid separation of the lithium leaching reaction solution; Step 19: Evaporate and concentrate the filtrate obtained as a liquid phase using the sixth-order solid-liquid separation; The present invention provides a method for producing high-purity lithium carbonate from waste refractory saggars, comprising: a 20th step of performing secondary solid-liquid separation of the concentrated liquid obtained by the secondary solid-liquid separation; a 21st step of performing a carbonation reaction on the filtrate obtained as a liquid phase using the secondary solid-liquid separation to produce a carbonation reaction solution; a 22nd step of performing tertiary solid-liquid separation of the carbonation reaction solution; a 23rd step of adding water to the first lithium carbonate obtained as a solid phase using the tertiary solid-liquid separation to produce a first lithium carbonate suspension, and injecting carbon dioxide (CO2) to dissolve the first lithium carbonate; a 24th step of performing quaternary solid-liquid separation of the aqueous solution in which the first lithium carbonate is dissolved; a 25th step of heating the filtrate obtained as a liquid phase using the quaternary solid-liquid separation to recrystallize and precipitate a second lithium carbonate; and a 26th step of performing quintuple solid-liquid separation of the filtrate in which the second lithium carbonate has precipitated to obtain high-purity second lithium carbonate as a solid phase, and drying it.

[0024] The aforementioned slurry for dissolving the pulverized waste refractory saggar is characterized by being produced by adding one or more alkalis, including alkali metal hydroxides, alkali metal carbonates, or alkali earth metal hydroxides, to the pulverized waste refractory saggar together with water, and then heating it.

[0025] The first magnetic deposit is a magnetic deposit containing iron oxide and iron scale, the second magnetic deposit is a magnetic deposit containing a positive electrode active material, the solid phase of the sixth solid-liquid separation is characterized by containing alumina and silicate, the lithium leaching reaction solution is produced by adding alkali earth metal hydroxide or oxide and water as a leaching agent to the second non-magnetic deposit, and then reacting it in a pressure reaction vessel at a temperature of 100 to 200°C for a reaction time of no more than 3 hours, and the reaction slurry concentration of the lithium leaching reaction solution is characterized by being 10 to 50 wt%.

[0026] The aforementioned evaporation concentration is characterized by being carried out under reduced pressure evaporation conditions at a temperature of 70 to 95°C, or by purging with nitrogen or argon gas under atmospheric pressure to prevent contact between carbon dioxide and the concentrate, while heating to 100°C, and the evaporation concentration is carried out until the lithium concentration in the concentrate reaches 0.5 to 5%.

[0027] The carbonation reaction is characterized by injecting one or more of the following into the filtrate obtained as a liquid phase using the secondary solid-liquid separation: carbon dioxide, carbonated water, and lithium bicarbonate aqueous solution, and allowing the reaction to proceed until the pH reaches 8 to 10. The filtrate obtained as a liquid phase using the tertiary solid-liquid separation is then added to the slurry of the waste refractory saggar pulverization reaction to further recover unreacted lithium hydroxide that could not participate in the carbonation reaction.

[0028] The reaction to dissolve the first lithium carbonate by injecting carbon dioxide into the first lithium carbonate suspension is carried out under temperature conditions of 0 to 20°C, characterized in that the pH of the reaction solution becomes 6 to 8 at the end of the reaction, and the filtrate obtained as the liquid phase using the quaternary solid-liquid separation is heated to a temperature of 80 to 100°C.

[0029] The lithium carbonate (second lithium carbonate) produced by the manufacturing method of the present invention is characterized by having a purity of 99.9% or higher.

[0030] The lithium carbonate produced by the manufacturing method of the present invention is characterized by having a purity of 99.9% or higher.

[0031] The following describes the steps of the manufacturing method in order of process.

[0032] 1) First process: Crushing of waste refractory saggars The waste refractory saggars are pulverized to a powder of 200# or less. However, pulverizing all the waste refractory saggars at once presents a problem: the pulverization efficiency is too low. Therefore, it is preferable to first coarsely pulverize them to 1 mm or less using primary pulverization, and then pulverize them to 200# (mesh) or less using secondary pulverization. The waste refractory saggars have high compressive strength but are susceptible to impact. While an impact crusher can be used to crush the waste refractory saggars, it produces crushed particles with sharp, hard surfaces, leading to increased wear on the crusher's parts and higher costs. Therefore, in this invention, a jaw crusher, which has easily replaceable and inexpensive parts, is used in the primary crushing process, and a ball mill is used in the secondary crushing process. Preferably, to improve pulverization efficiency, a medium crusher such as an impact crusher may be placed before the secondary crushing process.

[0033] 2) Second process: Dissolution process of crushed waste refractory saggars The pulverized waste refractory saggar material obtained using the first step contains lithium-containing substances such as lithium hydroxide, lithium carbonate, lithium silicate, lithium aluminum oxide, or lithium aluminum silicate. Most of these lithium-containing substances are water-soluble, but lithium aluminum silicate and others have low solubility in water and are difficult to dissolve with water alone. To solve this problem, the present invention uses a method in which the pulverized waste refractory saggar material is mixed with water and an alkali selected from the group consisting of alkali metal hydroxides, alkali metal carbonates, or alkaline earth metal hydroxides, and then heated. The pulverization step of the present invention dissolves the pulverized waste refractory saggar material by heating it together with the alkali leaching agent, which has the advantage of decomposing lithium aluminum silicate and other substances with low solubility in water, resulting in a high lithium recovery rate. The decomposition reaction of lithium-containing substances with low solubility tends to increase in reactivity in proportion to the alkali concentration and temperature. However, when using an alkaline aqueous solution produced from alkali metal salts as a leaching agent, the concentrations of silicon and aluminum become high, which has the disadvantage of requiring a separate process to remove them. Conversely, when using a leaching agent produced from an alkali earth metal oxide or hydroxide, it forms sparingly soluble salts with soluble silicon and aluminum, thereby promoting the decomposition of lithium aluminum silicate and helping to maintain low concentrations of silicon and aluminum in the solution. Furthermore, it reacts with lithium carbonate, which has relatively low solubility, to produce lithium hydroxide, which has high solubility, and sparingly soluble carbonates, thus helping to improve the lithium leaching rate. Therefore, in the waste refractory saggar dissolution process of the present invention, it is preferable to use calcium hydroxide, calcium oxide, or magnesium hydroxide as an additive to promote lithium extraction, and the amount added is preferably 5 to 50 parts by weight based on 100 parts by weight of waste refractory saggars.The aforementioned dissolution process of pulverized waste refractory saggars takes more than 6 hours to complete at temperatures below 20°C, and the particle size of the product is very fine, making solid-liquid separation difficult. At 50°C, the reaction is completed within 2 hours, and at 80°C, it is completed within 30 minutes. Furthermore, at temperatures close to 100°C, the reaction is completed within 10 minutes, but there is a problem in that a significant energy loss occurs due to the evaporation of water. Therefore, the preferred reaction temperature for the dissolution process of pulverized waste refractory saggars of the present invention is 50 to 80°C, and the reaction time is 30 to 120 minutes.

[0034] In short, the preferred waste refractory saggar dissolution process of the present invention involves heating a waste refractory saggar dissolution reaction solution containing 5 to 50 parts by weight of calcium hydroxide, calcium oxide, or magnesium hydroxide as a reaction accelerator to 100 parts by weight of waste refractory saggar dissolution material ground to 200# (mesh) or less, to a temperature of 50 to 80°C and reacting for 30 to 120 minutes. Furthermore, by adding alkali metal hydroxide water equivalent to 5 to 50% of the amount used, along with alkaline earth metal hydroxide (or oxide), under the same conditions, the leaching rate and leaching rate of lithium can be increased by approximately 5%. This method is suitable when the increased process cost is acceptable.

[0035] 3) Third step: Primary solid-liquid separation step The dissolved suspension of the pulverized waste refractory saggar is subjected to solid-liquid separation (primary solid-liquid separation). A sedimentation tank, filter press, screw filter, centrifuge, etc., can be used for this primary solid-liquid separation, and two or more of these can be combined to increase efficiency. The solid phase obtained by the primary solid-liquid separation contains a positive electrode active material and a refractory composition, and the liquid phase (filtrate) is lithium (Li + It contains aluminum (aluminate ions) and silicon (silicate ions).

[0036] 4) Fourth step: Evaporation and concentration step The filtrate obtained using the primary solid-liquid separation described above is mostly an aqueous lithium hydroxide solution, containing impurities such as calcium, aluminum, and silicon at concentrations of 200 ppm or less. The purpose of the evaporation concentration step of the present invention is to increase the lithium concentration by evaporating the water in the aqueous lithium hydroxide solution, and to precipitate and remove the impurities such as calcium, aluminum, or silicon compounds.

[0037] The evaporation and concentration process of the present invention is preferably carried out under reduced pressure evaporation conditions at a temperature of 70 to 95°C, and if carried out under atmospheric pressure, it can be carried out under atmospheric pressure conditions at 100°C. However, when carried out under atmospheric pressure, nitrogen or argon gas must be purged to prevent carbon dioxide from coming into contact with the concentrate.

[0038] In the present invention, the evaporation and concentration process is preferably carried out until the lithium concentration in the solution reaches 0.5 to 5%. If the evaporation and concentration is terminated before the lithium concentration reaches 0.5%, there is a risk that impurities will not be removed. If the evaporation and concentration is carried out to more than 5%, the process efficiency will decrease, and the process cost will increase.

[0039] 5) Fifth step: Secondary solid-liquid separation step Solid-liquid separation (secondary solid-liquid separation) is performed on the concentrated liquid obtained by the evaporation concentration process. Using this secondary solid-liquid separation, calcium hydroxide, calcium carbonate, aluminum hydroxide, silicon dioxide, calcium silicate hydrate, and lithium carbonate, which are precipitates from the evaporation concentration process, are obtained as solid phases, and an aqueous lithium hydroxide solution is separated as a solution phase. The efficiency of this secondary solid-liquid separation process can usually be increased by using a sedimentation tank, filter press, screw filter, centrifuge, or a combination of two or more of these. Since the solid phase obtained using this secondary solid-liquid separation contains lithium carbonate, it is reintroduced into the dissolution process of the pulverized waste refractory saggar to further recover lithium.

[0040] 6) Sixth step: Carbonation reaction step Since the filtrate obtained using the secondary solid-liquid separation step is an aqueous lithium hydroxide solution, a carbonation reaction is performed to precipitate lithium carbonate (Li2CO3). The carbonation reaction can be carried out by any of the following methods: a first carbonation method (see Chemical Formula 1) in which carbon dioxide (CO2) gas is injected into the aqueous lithium hydroxide solution; a second carbonation method (see Chemical Formula 2) in which the aqueous lithium hydroxide solution is mixed with carbonated water; a third carbonation method (see Chemical Formula 3) in which the aqueous lithium hydroxide solution is mixed with an aqueous lithium bicarbonate solution; a fourth carbonation method (see Chemical Formula 4) in which the aqueous lithium hydroxide solution is mixed with an aqueous sodium carbonate solution; or a fifth carbonation method (see Chemical Formula 5) in which the aqueous lithium hydroxide solution is mixed with an aqueous potassium carbonate solution.

[0041] [ka]

[0042] [ka]

[0043] [ka]

[0044] [ka]

[0045] [ka]

[0046] The fourth and fifth carbonation methods described above have the problem that impurities such as sodium and potassium may be introduced, respectively, requiring further steps to remove these impurities. Therefore, in the present invention, the first, second, or third carbonation method, which does not have the concern of introducing such impurities, is used, and preferably the first carbonation method, which involves injecting carbon dioxide gas, is used.

[0047] The first carbonation method of the present invention is 10m 3 Add 3.12-12.48 x 10 to a 2% LiOH solution in a reaction vessel of the specified volume. 3 It is preferable to inject carbon dioxide gas at a flow rate of L / min so that the carbonation reaction is completed within 30 to 120 minutes. If the amount injected is greater than the aforementioned flow rate range, a large amount of gas will be lost without being able to participate in the carbonation reaction, and if the amount injected is less than the aforementioned flow rate range, the time required for the carbonation reaction will be prolonged, reducing production efficiency. In the first carbonation method of the present invention, if the reaction starts at 20°C as an exothermic reaction, the temperature at the end of the reaction will be approximately 30°C. Therefore, no additional heating operation is required during the reaction period, but as the temperature rises, the solubility of carbon dioxide decreases and the amount of unreacted carbon dioxide increases, so it is necessary to reduce the gas injection flow rate. Conversely, as the reaction temperature rises, the solubility of lithium carbonate decreases, which not only improves the yield rate of lithium carbonate, but also speeds up the crystal growth rate, resulting in an increase in purity due to recrystallization. Therefore, in the present invention, carbonation is performed using the first carbonation method at room temperature (10m 3 A reaction vessel with a capacity of 20°C, 2% LiOH solution, and carbon dioxide injection volume: 3.12~12.48 x 10 3 After the carbonation reaction is complete, the carbonation reaction solution is heated to 100°C at a rate of L / min.

[0048] The carbonation reaction solution of the present invention is strongly alkaline with a pH of 12 or higher at the beginning of the reaction, and as the reaction progresses, the pH gradually decreases and converges to pH 7. The formation of lithium carbonate ends at around pH 9, and at pH levels lower than pH 9, lithium carbonate is redissolved as lithium bicarbonate. Therefore, it is preferable that the carbonation reaction ends when the pH is in the range of 8 to 10.

[0049] If the reaction is terminated when the pH exceeds 10, the impurities silicon and aluminum will exist in ionic states such as silicate ions and aluminate ions. If the reaction is terminated when the pH is below 8, the lithium carbonate will co-precipitate with SiO2 or Al(OH)3, resulting in a decrease in the purity of the lithium carbonate.

[0050] The second carbonation method of the present invention can use carbonated water produced by injecting carbon dioxide gas at a pressure of 5 to 20 bar at a temperature of 5 to 10°C or lower, preferably carbonated water produced by injecting carbon dioxide gas at a pressure of 10 bar at a temperature of 5°C or lower. Carbonated water produced by injecting carbon dioxide gas at a pressure of 10 bar at a temperature of 5°C or lower contains approximately 0.68 mol of dissolved carbon dioxide. According to an embodiment of the present invention, 1 L of the carbonated water and 500 mL of 2.72 mol of lithium hydroxide aqueous solution are mixed and reacted at 20°C for 30 minutes, then heated to 100°C, aged for 10 minutes, and filtered to obtain approximately 39 g of high-purity lithium carbonate. In the second carbonation method of the present invention, it is preferable to maintain the pH of the reaction solution at 8 or higher at the end of the reaction and to increase the concentration of LiOH to 1.01 to 1.1 times the theoretical equivalent before adding it to prevent contamination with silicon and aluminum.

[0051] The third carbonation method of the present invention is a method using an aqueous lithium bicarbonate (LiHCO3) solution, and can be an aqueous lithium bicarbonate solution produced by reacting lithium carbonate with carbonated water or an aqueous lithium bicarbonate solution produced by reacting lithium carbonate with carbon dioxide in a pressure vessel. It is preferable to use an aqueous lithium bicarbonate solution produced by reacting lithium carbonate with carbon dioxide in a pressure vessel, because reacting lithium carbonate with carbon dioxide in a pressure vessel allows for a rapid increase in the concentration of lithium bicarbonate in the aqueous solution. In the method of reacting lithium carbonate with carbon dioxide, it is preferable to maintain the carbon dioxide gas pressure in the pressure reaction vessel at 20°C or below at 2 to 20 bar, and in this reaction as well, in order to prevent contamination with silicon and aluminum, it is preferable to carry out the reaction so that the concentration of LiOH is 1.01 to 1.1 times the theoretical equivalent.

[0052] 7) Seventh step: Tertiary solid-liquid separation step A tertiary solid-liquid separation is performed on the reaction solution obtained in the carbonation reaction step. Using this tertiary solid-liquid separation, a first lithium carbonate is obtained as the solid phase, and an aqueous solution containing unreacted lithium hydroxide and impurity ions is obtained as the liquid phase (filtrate). The first lithium carbonate is added to a carbonation dissolution step to improve its purity, and the filtrate is reintroduced to the dissolution step of the waste refractory saggar to further recover lithium from the unreacted lithium hydroxide and remove impurities. The filtrate may be added to the waste refractory saggar with an additive (calcium hydroxide, calcium oxide, or magnesium hydroxide) to promote lithium extraction.

[0053] 8) Eighth step: Pressurized carbon dioxide dissolution step After adding water to the first solid phase lithium carbonate obtained using the tertiary solid-liquid separation process, carbon dioxide (CO2) is injected to perform a pressurized carbon dioxide dissolution process, thereby improving the purity of the lithium carbonate through a redissolution process. When lithium carbonate and carbon dioxide come into contact, the pH of the reaction solution converges to 6-8 over time, and the lithium carbonate dissolves as lithium bicarbonate. At this time, undissolved aluminum components (Al(OH)3), silicon components (SiO2), and calcium carbonate (CaCO3) can be removed as solid phase using the quaternary solid-liquid separation process. For the pressurized carbon dioxide dissolution process, the slurry concentration can be adjusted so that the amount of lithium carbonate is 2-12 parts by weight per 100 parts by weight of water. If the amount of lithium carbonate in the slurry is less than 2 parts by weight, the process efficiency decreases, and if the amount of lithium carbonate in the slurry is more than 12 parts by weight, the time required for the lithium carbonate to dissolve completely increases, and the incompletely dissolved lithium carbonate is removed along with impurities, resulting in a decrease in the yield rate. The solubility of lithium carbonate in carbonated water increases as the temperature decreases. The pressurized carbon dioxide dissolution process of the present invention is preferably carried out under temperature conditions of 0 to 20°C.

[0054] 9) 9th step: Quaternary solid-liquid separation step Using the aforementioned pressurized carbonic acid dissolution step, an aqueous lithium bicarbonate solution is obtained as the liquid phase, and impurities such as aluminum (Al(OH)3), silicon (SiO2), and calcium (CaCO3) are separated as the solid phase. The lithium bicarbonate in the aqueous lithium bicarbonate solution obtained using the aforementioned fourth solid-liquid separation step is converted to lithium carbonate by recrystallization.

[0055] 10) Step 10: Heating and recrystallization step The filtrate (aqueous solution of lithium bicarbonate) obtained in the fourth solid-liquid separation step is heated to precipitate lithium bicarbonate as lithium carbonate (second lithium carbonate). The precipitation process is represented by chemical formula 6.

[0056] [ka]

[0057] When the reaction temperature is low and the pressure is high, the dissolution reaction of lithium carbonate proceeds and lithium bicarbonate is produced, and when the reaction temperature is high and the pressure is low, lithium bicarbonate precipitates as lithium carbonate. The decomposition reaction of lithium bicarbonate can precipitate lithium carbonate even with just vigorous stirring or aeration, but it has the disadvantage that the rate is very slow. Therefore, the most economical and simple method for precipitating lithium bicarbonate as lithium carbonate in the above reaction is to heat the reaction solution to 80-100°C while stirring. The precipitation reaction rate of lithium carbonate differs depending on the temperature and pressure, and it is faster the higher the temperature and the lower the pressure. According to the embodiment, if an aqueous solution with a concentration of LiHCO3 of 2 mol / L is heated to 100°C, the precipitation reaction of lithium carbonate is completed within 20 minutes. The aqueous solution obtained as the liquid phase (filtrate) from the reaction solution in the heating and recrystallization step is reused as water for the dissolution step of the waste refractory saggar pulverized material.

[0058] 11) Eleventh step: Fifth solid-liquid separation step and drying step When the reaction solution from the heating and recrystallization step is separated into solid and liquid phases, precipitated lithium carbonate is obtained as a solid phase, and the precipitated lithium carbonate is dried to obtain high-purity lithium carbonate (purity of 99.9% or higher).

[0059] 12) Step 12: Primary wet magnetic separation process Wet magnetic separation (primary wet magnetic separation) is performed on the solid phase obtained using the primary solid-liquid separation described above. The primary wet magnetic separation step is preferably performed after adding water to the solid phase to produce a slurry. The water can be of industrial quality, and the water used in the process can be reused. The purpose of the primary wet magnetic separation is to remove iron fragments and iron scale that have been mixed in by abrasion during the crushing of the waste refractory saggars. Since the iron fragments and iron scale have very strong magnetizing ability, they can be removed as magnetic deposits at a magnetic flux density of approximately 100 to 500 gauss. Below 200 gauss, most of the iron fragments and iron scale are removed as magnetic deposits, but above 200 gauss, the inclusion rate of positive electrode active material increases along with the iron fragments and iron scale as magnetic deposits. Therefore, when wet magnetic separation is performed above 200 gauss, a separate magnetic separation may be necessary for the mixed positive electrode active material. The magnetic deposits separated using the aforementioned primary wet magnetic separation process are iron pieces (iron oxide) and iron scale, while the non-magnetic deposits are positive electrode active material, alumina, and silicate.

[0060] 13) Step 13: Secondary wet magnetic separation process The secondary wet magnetic separation process of the present invention aims to recover positive electrode active materials, including nickel oxide and cobalt oxide, from the non-magnetic material obtained in the primary wet magnetic separation process. Since the positive electrode active materials contained in the non-magnetic material are weakly magnetic or paramagnetic, a magnet with a high magnetic flux density is required to recover them as magnetic material.

[0061] The secondary wet magnetic separation step of the present invention can use a high-gradient magnetic separator having a magnetic flux density of 10,000 gauss or more, preferably a high-gradient magnetic separator having a magnetic flux density of 30,000 gauss or more. Furthermore, it is preferable that the high-gradient magnetic separator has a structure in which a slurry containing the particles to be separated is flowed between magnetized magnetic media. The concentration of solid matter in the slurry may be 1 to 10%. If the concentration of solid matter is less than 1%, the amount of water used increases, leading to an increase in unnecessary storage tanks and a problem of soaring energy costs. If the concentration of solid matter exceeds 10%, the separation efficiency decreases significantly. The material separated as magnetic material using the secondary wet magnetic separation step is the positive electrode active material, and the material separated as non-magnetic material is the composition of the refractory saggar from which lithium has been removed, and is alumina or silicate.

[0062] 14) Step 14: Alkali leaching step The non-magnetic material obtained from the secondary wet magnetic separation contains residual, sparingly soluble lithium compounds, with a residual lithium concentration of 1,000 mg / kg to 6,000 mg / kg. To recover this residual lithium, the non-magnetic material is mixed with an alkali earth metal hydroxide or oxide, such as calcium hydroxide, along with water, and reacted in a pressure reaction vessel at a temperature of 100 to 200°C for at least one hour. This decomposes more than 70% of the residual sparingly soluble lithium compounds, leaching out lithium. While longer reaction times and higher reaction temperatures increase the lithium leaching rate, they also increase process costs. Therefore, it is preferable to determine the reaction temperature and time considering the economic gain associated with the increased lithium recovery rate. The solid concentration of the reaction slurry is preferably adjusted to 10 to 50 wt.%.

[0063] 15) 15th step: Sixth solid-liquid separation step When calcium hydroxide or calcium oxide is used as an alkali leaching agent, the leaching residue consists mostly of calcium silicate hydrate, magnesium aluminate, calcium aluminum hydrate, and calcium aluminum silicate hydrate, with a small amount of aluminum hydroxide, silicon dioxide, and calcium hydroxide also coexisting. The liquid phase has the highest concentration of Li + , OH - , and also contains a small amount of Ca 2+ , AlO2 - , H2SiO4 2- , etc. The leaching residue obtained by solid-liquid separation is discharged after washing, and the liquid phase is sent to an evaporation concentration process and used as a raw material for the production of lithium carbonate.

[0064] The specific embodiments described in this specification are merely meant to represent preferred modes or exemplifications of the present invention, and thus do not limit the scope of the present invention. It is obvious to those skilled in the art that modifications and other uses of the present invention do not depart from the scope of the invention described in the claims of this specification.

Industrial Applicability

[0065] By using the method for producing high-purity lithium carbonate from waste refractory crucibles of the present invention, not only can the discarded waste refractory crucibles be recycled to produce high-purity lithium carbonate that can be used in the production of lithium secondary batteries, but it is also expected that the positive electrode active material, iron oxide, alumina, silicate, calcium carbonate, etc. obtained incidentally in the production process can be recycled.

Claims

1. A first step of producing a waste refractory saggar pulverized material by crushing waste refractory saggars used in high-temperature firing of lithium-containing composite oxides, which are raw materials for the positive electrode active material of a lithium secondary battery, A second step involves adding an alkaline leaching agent and water to the aforementioned pulverized waste refractory saggar and then reacting them to produce a slurry of dissolved waste refractory saggar, A third step involves primary solid-liquid separation of the slurry from the dissolved waste refractory saggar. A fourth step involves evaporating and concentrating the filtrate obtained as a liquid phase using the primary solid-liquid separation described above, A fifth step involves performing a secondary solid-liquid separation on the concentrated liquid obtained using the aforementioned evaporation concentration, A sixth step involves carrying out a carbonation reaction on the filtrate obtained as a liquid phase using the aforementioned secondary solid-liquid separation to produce a carbonation reaction solution. A seventh step involves tertiary solid-liquid separation of the carbonation reaction solution, The first lithium carbonate obtained as a solid phase using the aforementioned tertiary solid-liquid separation is mixed with water to produce a first lithium carbonate suspension, and carbon dioxide (CO2) is added. 2 The eighth step involves injecting ) to dissolve the first lithium carbonate, A ninth step involves performing a quaternary solid-liquid separation on the aqueous solution in which the first lithium carbonate is dissolved, A tenth step involves heating the filtrate obtained as a liquid phase using the aforementioned quaternary solid-liquid separation to recrystallize it, thereby precipitating a second lithium carbonate. The 11th step involves performing a quintuple solid-liquid separation on the filtrate from which the second lithium carbonate has precipitated to obtain a second lithium carbonate with a purity of 99.9% or higher as a solid phase, and then drying it. A method for producing high-purity lithium carbonate from waste refractory saggars, including [the specified material].

2. The method for producing high-purity lithium carbonate from waste refractory saggars according to claim 1, characterized in that the slurry for dissolving waste refractory saggars is produced by adding one or more alkalis, including alkali metal hydroxides, alkali metal carbonates, or alkalis containing alkali earth metal hydroxides, to the waste refractory saggars together with water and then heating it.

3. The method for producing high-purity lithium carbonate from waste refractory saggars according to claim 1, characterized in that the evaporation and concentration is carried out under reduced pressure evaporation conditions at a temperature of 70 to 95°C, or under atmospheric pressure with purging of nitrogen or argon gas, while heating to 100°C in an atmosphere that prevents contact between carbon dioxide and the concentrate.

4. The method for producing high-purity lithium carbonate from a waste refractory saggar according to claim 1, characterized in that the evaporation and concentration is carried out until the lithium concentration in the concentrated liquid reaches 0.5 to 5%.

5. The method for producing high-purity lithium carbonate from a waste refractory saggar according to claim 1, characterized in that the carbonation reaction involves injecting one or more selected from carbon dioxide, carbonated water, and lithium bicarbonate aqueous solution into the filtrate obtained as a liquid phase using the secondary solid-liquid separation, and reacting until the pH reaches 8 to 10.

6. A method for producing high-purity lithium carbonate from waste refractory saggars according to claim 1, characterized in that the filtrate obtained as a liquid phase using the tertiary solid-liquid separation is added to the slurry of the dissolution reaction of the pulverized waste refractory saggars to further recover unreacted lithium hydroxide that could not participate in the carbonation reaction.

7. A method for producing high-purity lithium carbonate from a waste refractory saggar according to claim 1, characterized in that the reaction of injecting carbon dioxide into the first lithium carbonate suspension to dissolve the first lithium carbonate is carried out under temperature conditions of 0 to 20°C, and the pH of the reaction solution is set to 6 to 8 at the end of the reaction.

8. A method for producing high-purity lithium carbonate from waste refractory saggars according to claim 1, characterized in that the filtrate obtained as a liquid phase using the quaternary solid-liquid separation is heated to a temperature of 80 to 100°C.

9. A 12th step of producing a waste refractory saggar pulverized product by crushing waste refractory saggars used in high-temperature firing of lithium-containing composite oxides, which are raw materials for the positive electrode active material of a lithium secondary battery, A thirteenth step involves adding an alkaline leaching agent and water to the aforementioned pulverized waste refractory saggar and then reacting them to produce a slurry of dissolved waste refractory saggar, A 14th step involves primary solid-liquid separation of the slurry from the dissolved waste refractory saggar. Step 15 involves preparing a suspension from the solid phase obtained using the primary solid-liquid separation, and then performing primary wet magnetic separation to obtain a first magnetic material and a first non-magnetic material. A 16th step involves producing the first non-magnetic material as a suspension, followed by secondary wet magnetic separation to obtain a second magnetic material and a second non-magnetic material. A 17th step involves adding water and a leaching agent to the second non-magnetic material and then reacting them to produce a lithium leaching reaction solution, The eighteenth step is to perform a sixth solid-liquid separation of the lithium leaching reaction solution, A 19th step involves evaporating and concentrating the filtrate obtained as a liquid phase using the aforementioned sixth-order solid-liquid separation, A 20th step involves performing a secondary solid-liquid separation on the concentrated liquid obtained using the aforementioned evaporation concentration, A 21st step involves carrying out a carbonation reaction on the filtrate obtained as a liquid phase using the aforementioned secondary solid-liquid separation to produce a carbonation reaction solution, A 22nd step involves tertiary solid-liquid separation of the carbonation reaction solution, Water is added to the first lithium carbonate obtained as a solid phase using the tertiary solid-liquid separation described above to produce a first lithium carbonate suspension, and carbon dioxide (CO2) is produced. 2 A 23rd step involves injecting ) to dissolve the first lithium carbonate, A 24th step involves performing a quaternary solid-liquid separation on the aqueous solution in which the first lithium carbonate is dissolved, A 25th step involves heating the filtrate obtained as a liquid phase using the aforementioned quaternary solid-liquid separation to recrystallize it, thereby precipitating a second lithium carbonate. The 26th step involves performing a quintuple solid-liquid separation on the filtrate from which the second lithium carbonate has precipitated to obtain a second lithium carbonate with a solid phase having a purity of 99.9% or higher, and then drying it. A method for producing high-purity lithium carbonate from waste refractory saggars, including [the specified material].

10. The method for producing high-purity lithium carbonate from waste refractory saggars according to claim 9, characterized in that the slurry for dissolving waste refractory saggars is produced by adding one or more alkalis, including alkali metal hydroxides, alkali metal carbonates, or alkalis containing alkali earth metal hydroxides, to the waste refractory saggars together with water and then heating it.

11. A method for producing high-purity lithium carbonate from a waste refractory saggar according to claim 9, characterized in that the first magnetic deposit is a magnetic deposit containing iron oxide and iron scale, the second magnetic deposit is a magnetic deposit containing a positive electrode active material, and the solid phase of the sixth solid-liquid separation contains alumina and silicate.

12. The method for producing high-purity lithium carbonate from a waste refractory saggar according to claim 9, characterized in that the lithium leaching reaction solution is produced by adding an alkali earth metal hydroxide or oxide and water as a leaching agent to the second non-magnetic material, and then reacting it in a pressure reaction vessel at a temperature of 100 to 200°C for a reaction time of no more than 3 hours, and the reaction slurry concentration of the lithium leaching reaction solution is 10 to 50 wt%.

13. The method for producing high-purity lithium carbonate from waste refractory saggars according to claim 9, characterized in that the evaporation and concentration is carried out under reduced pressure evaporation conditions at a temperature of 70 to 95°C, or under atmospheric pressure with nitrogen or argon gas purging, while heating to 100°C in an atmosphere that prevents contact between carbon dioxide and the concentrate.

14. The method for producing high-purity lithium carbonate from a waste refractory saggar according to claim 9, characterized in that the evaporation and concentration is carried out until the lithium concentration in the concentrated liquid reaches 0.5 to 5%.

15. The method for producing high-purity lithium carbonate from a waste refractory saggar according to claim 9, characterized in that the carbonation reaction involves injecting one or more selected from carbon dioxide, carbonated water, and lithium bicarbonate aqueous solution into the filtrate obtained as a liquid phase using the secondary solid-liquid separation, and reacting until the pH reaches 8 to 10.

16. A method for producing high-purity lithium carbonate from waste refractory saggars according to claim 9, characterized in that the filtrate obtained as a liquid phase using the tertiary solid-liquid separation is added to the slurry of the dissolution reaction of the pulverized waste refractory saggars to further recover unreacted lithium hydroxide that could not participate in the carbonation reaction.

17. A method for producing high-purity lithium carbonate from waste refractory saggars according to claim 9, characterized in that the reaction of injecting carbon dioxide into the first lithium carbonate suspension to dissolve the first lithium carbonate is carried out under temperature conditions of 0 to 20°C, and the pH of the reaction solution is set to 6 to 8 at the end of the reaction.

18. A method for producing high-purity lithium carbonate from a waste refractory saggar according to claim 9, characterized in that the filtrate obtained as a liquid phase using the quaternary solid-liquid separation is heated to a temperature of 80 to 100°C.

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