Method for preparing high-purity lithium carbonate from waste saggar

Abstract

The invention provides an optimized method for recovering high-purity lithium carbonate from lithium-containing composite oxides, such as lithium silicate, lithium aluminum oxide, lithium aluminum silicate and the like, which are deposited on an erosion surface of a waste sagger. The invention provides an optimized method for recovering high-purity lithium carbonate from the lithium-containing composite oxides, such as lithium silicate, lithium aluminum oxide, lithium aluminum silicate and the like. Therefore, it is expected that the method for preparing the high-purity lithium carbonate from the waste saggar can be used for preparing the high-purity lithium carbonate capable of being used for preparing the lithium secondary battery by recycling the waste saggar; and moreover, positive active substances, iron oxide, aluminum oxide, silicate, calcium carbonate and the like which are added in the preparation process can be recycled.

Description

Technical Field

[0001] The invention relates to a method for preparing high-purity lithium carbonate from waste saggers. Background Art

[0002] The positive electrode active material of lithium secondary batteries is composed of SiO 2 、Al 2 O 3 , MgO as the main component of oxide ceramic saggers (sagger) through high temperature firing. The above-mentioned sagger is used for repeated high-temperature firing of lithium-containing composite oxides (as raw materials for positive electrode active materials), so its surface is eroded over time, and lithium compounds such as lithium hydroxide and lithium carbonate and positive electrode active materials are deposited at the above-mentioned eroded parts. The saggers whose surfaces are eroded by the above-mentioned lithium hydroxide, lithium carbonate, etc. are eventually discarded due to reduced heat resistance. It is understood that South Korea produces about 9,000 tons of waste saggers each year, but with the rapid increase in demand for lithium secondary batteries due to the popularity of mobile devices and electric vehicles, the production of waste saggers is expected to increase rapidly. The positive electrode active material for lithium secondary batteries uses lithium carbonate and lithium hydroxide as lithium sources, which are generally produced from nature, such as ores or brine, or produced by recycling from discarded waste secondary batteries.

[0003] As mentioned above, the sagger is used to prepare the positive electrode active material, and during the high-temperature sintering process, it is corroded by the lithium-containing composite oxide, resulting in the loss of its function. Therefore, if lithium can be recovered and purified from the lithium-containing material deposited in the eroded part of the waste sagger that has been discarded due to the reduction of heat resistance caused by repeated high-temperature sintering of the lithium-containing composite oxide, it is expected to contribute to the effective utilization of lithium resources. However, a method for recovering high-purity lithium carbonate from waste saggers has not yet been disclosed.

[0004] Patent documents and reference documents mentioned in the present specification are hereby incorporated by reference into the present specification to the same extent as if the respective documents were expressly designated individually by reference.

[0005] Patent documents and reference documents mentioned in the present specification are hereby incorporated by reference into the present specification to the same extent as if the respective documents were expressly designated individually by reference. Summary of the invention

[0006] Problems to be solved by the invention

[0007] The object of the present invention is to provide a method for recovering high-purity lithium carbonate from waste saggers discarded after high-temperature sintering when preparing positive electrode active materials for lithium secondary batteries.

[0008] Other objects and technical features of the present invention will be more specifically presented through the detailed description of the invention, the claims and the accompanying drawings.

[0009] Solutions for solving problems

[0010] The present invention provides a method for preparing high-purity lithium carbonate from waste saggers, comprising: a first step of preparing a waste sagger crushed material by crushing the waste saggers; a second step of adding an alkali leaching agent and water to the waste sagger crushed material and reacting to prepare a dissolution reaction slurry of the waste sagger crushed material; a third step of performing a first solid-liquid separation on the dissolution reaction slurry of the waste sagger crushed material; a fourth step of performing evaporation and concentration on a liquid phase filtrate obtained by the first solid-liquid separation; and a fifth step of performing a second solid-liquid separation on a concentrated liquid obtained by the evaporation and concentration.

[0011] The sixth step is to perform a carbonation reaction on the liquid phase filtrate obtained by the second solid-liquid separation to prepare a carbonation reaction liquid; the seventh step is to perform a third solid-liquid separation on the carbonation reaction liquid; water is added to the solid phase first lithium carbonate obtained by the third solid-liquid separation to prepare a first lithium carbonate suspension, and carbon dioxide (CO 2 ) the eighth step of dissolving the first lithium carbonate; the ninth step of performing the fourth solid-liquid separation on the aqueous solution containing the first lithium carbonate; the tenth step of heating and recrystallizing the liquid filtrate obtained by the fourth solid-liquid separation to precipitate the second lithium carbonate; and the eleventh step of performing the fifth solid-liquid separation on the filtrate from which the second lithium carbonate is precipitated to obtain a high-purity second lithium carbonate in the solid phase, and drying it.

[0012] Furthermore, the present invention provides a method for preparing high-purity lithium carbonate from waste saggers, comprising: a twelfth step of preparing a waste sagger crushed material by crushing the waste sagger; a thirteenth step of adding an alkali leaching agent and water to the waste sagger crushed material and reacting to prepare a dissolution reaction slurry of the waste sagger crushed material; a fourteenth step of performing a first solid-liquid separation on the dissolution reaction slurry of the waste sagger crushed material; a fifteenth step of preparing a suspension of the solid phase obtained by the first solid-liquid separation and performing a first wet magnetic separation to obtain a first magnetic adsorbent and a first non-magnetic adsorbent; a sixteenth step of preparing a suspension of the first non-magnetic adsorbent and performing a second wet magnetic separation to obtain a second magnetic adsorbent and a second non-magnetic adsorbent. ; the seventeenth step of adding water and a leaching agent into the second non-magnetic adsorbent and reacting them to prepare a lithium leaching reaction solution; the eighteenth step of performing a sixth solid-liquid separation on the lithium leaching reaction solution; the nineteenth step of evaporating and concentrating the liquid phase filtrate obtained by the sixth solid-liquid separation; the twentieth step of performing a second solid-liquid separation on the concentrated solution obtained by the evaporation and concentration; the twenty-first step of performing a carbonation reaction on the liquid phase filtrate obtained by the second solid-liquid separation to prepare a carbonation reaction solution; the twenty-second step of performing a third solid-liquid separation on the carbonation reaction solution; adding water to the solid first lithium carbonate obtained by the third solid-liquid separation to prepare a first lithium carbonate suspension, and injecting carbonic acid gas (CO 2 ) a twenty-third step of dissolving the first lithium carbonate; a twenty-fourth step of performing a fourth solid-liquid separation on the aqueous solution in which the first lithium carbonate is dissolved; a twenty-fifth step of heating and recrystallizing the liquid filtrate obtained by the fourth solid-liquid separation to precipitate the second lithium carbonate; and

[0013] The filtrate from which the second lithium carbonate is precipitated is subjected to a fifth solid-liquid separation to obtain a high-purity second lithium carbonate in a solid phase, and then dried in the twenty-sixth step.

[0014] The above-mentioned waste sagger crushed material dissolution reaction slurry is characterized in that it is prepared by adding one or more alkalis including alkali metal hydroxide, alkali metal carbonate, or alkaline earth metal hydroxide and water to the above-mentioned waste sagger crushed material and then heating it.

[0015] The first magnetic adsorbent is characterized in that it contains iron oxide and iron scale, the second magnetic adsorbent is characterized in that it contains positive electrode active material, the solid phase of the sixth solid-liquid separation is characterized in that it contains aluminum oxide and silicate, the lithium leaching reaction solution is characterized in that it is prepared by adding alkaline earth metal hydroxide or oxide and water as leaching agents into the second non-magnetic adsorbent and reacting them in a pressure reaction vessel at a temperature of 100°C to 200°C and a reaction time of less than 3 hours, and the reaction slurry concentration of the lithium leaching reaction solution is 10wt% to 50wt%.

[0016] The above-mentioned evaporation concentration is characterized in that it is carried out by evaporating under reduced pressure at 70°C to 95°C, or by purging nitrogen or argon at atmospheric pressure, and heating to 100°C in an atmosphere where carbon dioxide cannot come into contact with the concentrated solution, and is carried out until the lithium concentration in the concentrated solution reaches 0.5% to 5%.

[0017] The carbonation reaction is characterized in that any one or more selected from carbon dioxide, carbonated water and lithium bicarbonate aqueous solution is injected into the liquid filtrate obtained by the second solid-liquid separation to react until the pH reaches 8 to 10, and the liquid filtrate obtained by the third solid-liquid separation is characterized in that it is added to the dissolution reaction slurry of the waste sagger crushed material to further recover the unreacted lithium hydroxide that did not participate in the carbonation reaction.

[0018] The reaction of injecting carbon dioxide into the above-mentioned first lithium carbonate suspension to dissolve the above-mentioned first lithium carbonate is characterized in that it is carried out at a temperature of 0°C to 20°C, and the pH of the reaction liquid reaches 6 to 8 at the end of the reaction. The liquid filtrate obtained by the above-mentioned fourth solid-liquid separation is characterized in that it is heated to a temperature of 80°C to 100°C.

[0019] The lithium carbonate (second lithium carbonate) prepared by the preparation method of the present invention is characterized in that the purity is above 99.9%.

[0020] Effects of the Invention

[0021] The present invention provides an optimized method for recovering high-purity lithium carbonate from lithium hydroxide, lithium carbonate, lithium silicate, lithium aluminum oxide, lithium aluminum silicate and other lithium-containing compounds deposited on the eroded surface of the waste sagger discarded after use. Therefore, it is expected that the method for preparing high-purity lithium carbonate from waste saggers of the present invention can not only prepare high-purity lithium carbonate that can be used for preparing lithium secondary batteries by recycling the discarded waste saggers, but also recycle the positive electrode active material, iron oxide, aluminum oxide, silicate and calcium carbonate obtained in the preparation process. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 The method for preparing high-purity lithium carbonate from waste saggers of the present invention is schematically shown in FIG.

[0023] Figure 2 2 shows the XRD analysis results of the constituent minerals of the waste sagger of the present invention.

[0024] Figure 3 This is a scanning electron microscope (SEM) photograph of the crushed waste sagger, showing the distribution of the overall particle size and the structure of the surface of the individual particles. DETAILED DESCRIPTION

[0025] The present invention relates to a method for recovering high-purity lithium carbonate from a sagger (waste sagger) discarded after firing of a positive electrode active material for a secondary battery. With repeated use of the sagger, the sagger is damaged by corrosion based on lithium hydroxide or lithium carbonate, etc., and is discarded without being recycled. The purpose of the present invention is to recover high-value-added lithium compounds from waste saggers that are discarded without being recycled. The waste sagger is a ceramic container used for firing a positive electrode active material for a secondary battery, and its main component is SiO 2 、Al 2 O 3 ,MgO.

[0026] Table 1 shows the compositions of the used saggers used for sintering NCA (sample name: SG1) and NCM (sample name: SG2) as positive electrode materials.

[0027]

Table 1

[0028] composition SG1(NCA) SG2(NCM) <![CDATA[Li 2 O(as Li)]]> 4.52(2.1)％ 1.89(0.88)％ NiO 0.13％ 0.16％ <![CDATA[Co 3 THE 4 ]]> 0.01％ 0.02％ <![CDATA[SiO 2 ]]> 49.38％ 30.73％ <![CDATA[Al 2 THE 3 ]]> 38.25％ 51.38％ CaO 0.48％ 0.52％ MgO 5.37％ 13.63％ <![CDATA[Fe 2 THE 3 ]]> 0.33％ 0.54％ <![CDATA[Na 2 The]]> 0.32％ 0.12％ <![CDATA[K 2 The]]> 0.30％ 0.19％ Others 0.91％ 0.82％

[0029] The analysis results confirmed that the lithium (Li) content of SG1 and SG2 was high, 2.1% and 0.88% respectively. When converted into lithium carbonate content, it was confirmed that SG1 = 11.17% and SG2 = 4.68%. In addition, the nickel and cobalt contents were confirmed to be 0.13% to 0.16% and 0.01% to 0.02% respectively, which have sufficient recovery value.

[0030] The above-mentioned waste sagger is composed of mullite, cordierite, alumina, quartz, spinel, lithium silicate, lithium aluminum oxide, lithium aluminum silicate, etc. Among the components of the above-mentioned waste sagger, the substances causing the sagger to be destroyed are lithium silicate, lithium aluminum oxide, lithium aluminum silicate, etc.

[0031] The present invention provides a method for preparing high-purity lithium carbonate from waste saggers, comprising: a first step of preparing a waste sagger crushed material by crushing the waste saggers; a second step of adding an alkali leaching agent and water to the waste sagger crushed material and reacting to prepare a dissolution reaction slurry of the waste sagger crushed material; a third step of performing a first solid-liquid separation on the dissolution reaction slurry of the waste sagger crushed material; a fourth step of performing evaporation and concentration on a liquid phase filtrate obtained by the first solid-liquid separation; and a fifth step of performing a second solid-liquid separation on a concentrated liquid obtained by the evaporation and concentration.

[0032] The sixth step is to perform a carbonation reaction on the liquid phase filtrate obtained by the second solid-liquid separation to prepare a carbonation reaction liquid; the seventh step is to perform a third solid-liquid separation on the carbonation reaction liquid; water is added to the solid phase first lithium carbonate obtained by the third solid-liquid separation to prepare a first lithium carbonate suspension, and carbon dioxide (CO 2 ) the eighth step of dissolving the first lithium carbonate; the ninth step of performing the fourth solid-liquid separation on the aqueous solution containing the first lithium carbonate; the tenth step of heating and recrystallizing the liquid filtrate obtained by the fourth solid-liquid separation to precipitate the second lithium carbonate; and the eleventh step of performing the fifth solid-liquid separation on the filtrate from which the second lithium carbonate is precipitated to obtain a high-purity second lithium carbonate in the solid phase, and drying it.

[0033] Furthermore, the present invention provides a method for preparing high-purity lithium carbonate from waste saggers, comprising: a twelfth step of preparing a waste sagger crushed material by crushing the waste sagger; a thirteenth step of adding an alkali leaching agent and water to the waste sagger crushed material and reacting to prepare a dissolution reaction slurry of the waste sagger crushed material; a fourteenth step of performing a first solid-liquid separation on the dissolution reaction slurry of the waste sagger crushed material; a fifteenth step of preparing a suspension of the solid phase obtained by the first solid-liquid separation and performing a first wet magnetic separation to obtain a first magnetic adsorbent and a first non-magnetic adsorbent; a sixteenth step of preparing a suspension of the first non-magnetic adsorbent and performing a second wet magnetic separation to obtain a second magnetic adsorbent and a second non-magnetic adsorbent. ; the seventeenth step of adding water and a leaching agent into the second non-magnetic adsorbent and reacting them to prepare a lithium leaching reaction solution; the eighteenth step of performing a sixth solid-liquid separation on the lithium leaching reaction solution; the nineteenth step of evaporating and concentrating the liquid phase filtrate obtained by the sixth solid-liquid separation; the twentieth step of performing a second solid-liquid separation on the concentrated solution obtained by the evaporation and concentration; the twenty-first step of performing a carbonation reaction on the liquid phase filtrate obtained by the second solid-liquid separation to prepare a carbonation reaction solution; the twenty-second step of performing a third solid-liquid separation on the carbonation reaction solution; adding water to the solid first lithium carbonate obtained by the third solid-liquid separation to prepare a first lithium carbonate suspension, and injecting carbonic acid gas (CO 2 ) a twenty-third step of dissolving the first lithium carbonate; a twenty-fourth step of performing a fourth solid-liquid separation on the aqueous solution in which the first lithium carbonate is dissolved; a twenty-fifth step of heating and recrystallizing the liquid filtrate obtained by the fourth solid-liquid separation to precipitate the second lithium carbonate; and

[0034] The filtrate from which the second lithium carbonate is precipitated is subjected to a fifth solid-liquid separation to obtain a high-purity second lithium carbonate in a solid phase, and then dried in the twenty-sixth step.

[0035] The above-mentioned waste sagger crushed material dissolution reaction slurry is characterized in that it is prepared by adding one or more alkalis including alkali metal hydroxide, alkali metal carbonate, or alkaline earth metal hydroxide and water to the above-mentioned waste sagger crushed material and then heating it.

[0036] The first magnetic adsorbent is characterized in that it contains iron oxide and iron scale, the second magnetic adsorbent is characterized in that it contains positive electrode active material, the solid phase of the sixth solid-liquid separation is characterized in that it contains aluminum oxide and silicate, the lithium leaching reaction solution is characterized in that it is prepared by adding alkaline earth metal hydroxide or oxide and water as leaching agents into the second non-magnetic adsorbent and reacting them in a pressure reaction vessel at a temperature of 100°C to 200°C and a reaction time of less than 3 hours, and the reaction slurry concentration of the lithium leaching reaction solution is 10wt% to 50wt%.

[0037] The above-mentioned evaporation concentration is characterized in that it is carried out by evaporating under reduced pressure at 70°C to 95°C, or by purging nitrogen or argon at atmospheric pressure, and heating to 100°C in an atmosphere where carbon dioxide cannot come into contact with the concentrated solution, and is carried out until the lithium concentration in the concentrated solution reaches 0.5% to 5%.

[0038] The carbonation reaction is characterized in that any one or more selected from carbon dioxide, carbonated water and lithium bicarbonate aqueous solution is injected into the liquid filtrate obtained by the second solid-liquid separation to react until the pH reaches 8 to 10, and the liquid filtrate obtained by the third solid-liquid separation is characterized in that it is added to the dissolution reaction slurry of the waste sagger crushed material to further recover the unreacted lithium hydroxide that did not participate in the carbonation reaction.

[0039] The reaction of injecting carbon dioxide into the above-mentioned first lithium carbonate suspension to dissolve the above-mentioned first lithium carbonate is characterized in that it is carried out at a temperature of 0°C to 20°C, and the pH of the reaction liquid reaches 6 to 8 at the end of the reaction. The liquid filtrate obtained by the above-mentioned fourth solid-liquid separation is characterized in that it is heated to a temperature of 80°C to 100°C.

[0040] The lithium carbonate (second lithium carbonate) prepared by the preparation method of the present invention is characterized in that the purity is above 99.9%.

[0041] Best Mode for Carrying Out the Invention

[0042] Hereinafter, the steps of the above-mentioned preparation method are described in detail according to the process.

[0043] 1) The first process: waste sagger crushing process

[0044] The waste sagger is crushed into powder of less than 200#. When the above-mentioned waste sagger is micronized at one time, there is a problem of too low crushing efficiency. Therefore, preferably, after being coarsely crushed to less than 1mm by the first crushing, it is crushed to less than 200# (mesh) by the second crushing. The above-mentioned waste sagger has a high compression strength, but weak impact resistance. An impact crusher can be used to crush the above-mentioned waste sagger, but since it will produce crushed particles with high hardness and sharp surface, there is a problem of increased wear of crusher parts and increased costs.

[0045] Therefore, in the present invention, a jaw crusher with easy replacement of parts and low cost is used in the first crushing process, and a ball mill is used in the second crushing process. Preferably, in order to improve the crushing efficiency, a medium crusher such as an impact crusher can be configured before the second crushing process.

[0046] 2) Second process: Dissolution process of crushed waste saggers

[0047] The waste sagger pulverized by the first process includes lithium-containing substances such as lithium hydroxide, lithium carbonate, lithium silicate, lithium aluminum oxide, or lithium aluminum silicate. Although most of the above lithium-containing substances are water-soluble, lithium aluminum silicate and the like have low solubility in water and are difficult to dissolve with water alone. In order to solve the above problem, the present invention uses a method of heating the above waste sagger pulverized material with a base selected from the group consisting of any one or two or more of alkali hydroxides, alkali carbonates, or alkaline earth metal hydroxides. The pulverized material dissolving process of the present invention uses a method of heating with the above alkaline leaching agent to dissolve the above waste sagger pulverized material, so that lithium aluminum silicate and the like with low solubility in water can also be decomposed, thereby having the advantage of increasing the recovery rate of lithium. The decomposition reaction of the above lithium-containing substance with low solubility has a tendency to increase the reactivity in proportion to the concentration and temperature of the alkali. However, when an alkaline aqueous solution prepared from an alkali metal salt is used as a leaching agent, the concentration of silicon and aluminum will increase, so there is a defect that a separate process is required to remove them. In contrast, when a leaching agent prepared from an alkaline earth metal oxide or hydroxide is used, soluble silicon or aluminum and insoluble salts are formed, so that while it helps to promote the decomposition of lithium aluminum silicate, it maintains a lower silicon and aluminum concentration in the solution, and reacts with lithium carbonate with lower solubility to generate lithium hydroxide and insoluble carbonate with higher solubility, thereby helping to improve the leaching rate of lithium. Therefore, in the waste sagger crushing material dissolution process of the present invention, as an additive to promote lithium extraction, calcium hydroxide, calcium oxide, or magnesium hydroxide is preferably used, and the amount thereof added is 5 to 50 parts by weight based on 100 parts by weight of the sagger. The above-mentioned waste sagger crushing material dissolution process requires more than 6 hours to terminate the reaction at a temperature below 20°C, and the particle size of the product is very fine, making it difficult to achieve solid-liquid separation. In addition, the reaction is terminated within 2 hours at a temperature of 50°C, and within 30 minutes at a temperature of 80°C. Moreover, at about 100°C, the reaction is terminated within 10 minutes, but there is a problem of a large amount of energy loss due to the evaporation of water. Therefore, the preferred waste sagger crushing material dissolution process reaction temperature of the present invention is 50°C to 80°C, and the reaction time is 30 minutes to 120 minutes.

[0048] In summary, in the preferred waste sagger crushing material dissolution process of the present invention, the waste sagger crushing material dissolution reaction liquid is heated at a temperature of 50°C to 80°C and reacted for 30 minutes to 120 minutes, wherein the waste sagger crushing material dissolution reaction liquid contains 5 to 50 parts by weight of calcium hydroxide, calcium oxide, or magnesium hydroxide as a reaction accelerator relative to 100 parts by weight of the waste sagger crushing material crushed to 200# (mesh) or less. And, under the same conditions, if an alkali metal hydroxide equivalent to 5% to 50% of its usage amount is further added together with the alkaline earth metal hydroxide (or oxide), the leaching rate and leaching rate of lithium will increase by about 5%. If the increase in process costs can be accepted, it can be a preferred method.

[0049] 3) The third process: the first solid-liquid separation process

[0050] The suspension containing the above-mentioned waste sagger crushed material is subjected to solid-liquid separation (first solid-liquid separation). The first solid-liquid separation can be performed using a sedimentation tank, a filter press, a spiral filter, a centrifuge, etc., or a combination of two or more thereof to improve its efficiency. The solid phase obtained by the first solid-liquid separation contains the positive electrode active material and the refractory composition, while the liquid phase (filtrate) contains lithium (Li + ), aluminum (aluminate ion), silicon (silicate ion).

[0051] 4) The fourth process: evaporation concentration process

[0052] The filtrate obtained by the first solid-liquid separation is mostly a lithium hydroxide aqueous solution, and contains less than 200 ppm of calcium, aluminum, silicon, etc. as impurities. The purpose of the evaporation concentration process of the present invention is to increase the lithium concentration by evaporating water in the lithium hydroxide aqueous solution and to precipitate and remove the calcium, aluminum, or silicon compounds as impurities.

[0053] Preferably, the evaporation concentration process of the present invention is carried out under reduced pressure at a temperature of 70° C. to 95° C., and when evaporation is carried out under atmospheric pressure, evaporation can be carried out under atmospheric pressure of 100° C. However, when evaporation is carried out under atmospheric pressure, nitrogen or argon gas needs to be purged to prevent carbon dioxide from contacting the concentrated liquid.

[0054] Preferably, the evaporation concentration process of the present invention is carried out until the lithium concentration in the solution reaches 0.5% to 5%. If the evaporation concentration is terminated before the lithium concentration reaches 0.5%, impurities may not be removed, and if the evaporation concentration exceeds 5%, the process efficiency will decrease and the process cost will increase.

[0055] 5) The fifth process: the second solid-liquid separation process

[0056] The above-mentioned concentrated solution (which has been evaporated and concentrated) is subjected to solid-liquid separation (second solid-liquid separation). The solid phase of calcium hydroxide, calcium carbonate, aluminum hydroxide, silicon dioxide, hydrated calcium silicate and lithium carbonate, etc., which are the precipitate of the evaporation and concentration process, are obtained by the above-mentioned second solid-liquid separation, and the lithium hydroxide aqueous solution of the solution phase is separated. The above-mentioned second solid-liquid separation process can generally use a sedimentation tank, a filter press, a spiral filter, a centrifuge, etc., or combine two or more of them to improve its efficiency. The solid phase obtained by the above-mentioned second solid-liquid separation includes lithium carbonate, so it is re-invested in the dissolution process of the above-mentioned waste sagger crushed material, thereby further recovering lithium.

[0057] 6) The sixth process: carbonation reaction process

[0058] Since the filtrate obtained by the second solid-liquid separation process is a lithium hydroxide aqueous solution, lithium carbonate (Li 2 CO 3 The carbonation reaction can be carried out by injecting carbon dioxide (CO) into the lithium hydroxide aqueous solution. 2 ) gas to achieve the first carbonation method (refer to Chemical Formula 1); the second carbonation method (refer to Chemical Formula 2) achieved by mixing a lithium hydroxide aqueous solution and carbonated water; the third carbonation method (refer to Chemical Formula 3) achieved by mixing a lithium hydroxide aqueous solution and a lithium bicarbonate aqueous solution; the fourth carbonation method (refer to Chemical Formula 4) achieved by mixing a lithium hydroxide aqueous solution and a sodium carbonate aqueous solution; or the fifth carbonation method (refer to Chemical Formula 5) achieved by mixing a lithium hydroxide aqueous solution and a potassium carbonate aqueous solution.

[0059]

Chemical formula 1

[0060] 2LiOH+CO 2 →Li 2 CO 3 +H 2 O

[0061]

Chemical formula 2

[0062] 2LiOH+H 2 CO 3 →Li 2 CO 3 +2H 2 O

[0063]

Chemical formula 3

[0064] LiOH+LiHCO 3 →Li 2 CO 3 +H 2 O

[0065]

Chemical formula 4

[0066] 2LiOH+Na 2 CO 3 →Li 2 CO 3 +2NaOH

[0067]

Chemical formula 5

[0068] 2LiOH+K 2 CO 3 →Li 2 CO 3 +2KOH

[0069] The 4th carbonating method and the 5th carbonating method in the above-mentioned carbonating method may respectively have the risk of impurities such as sodium and potassium being mixed in, therefore, there is the problem of needing to remove the above-mentioned impurities by an additional process. Therefore, in the present invention, the first carbonating method, the second carbonating method or the third carbonating method without the risk of the above-mentioned impurities being mixed in are used, preferably, the first carbonating method of injecting carbon dioxide gas is used.

[0070] In the first carbonation method of the present invention, preferably, the carbonation 3 The capacity of the reaction tank with 2% LiOH solution ranges from 3.12 to 12.48 x 10 3 l / min flow rate of carbon dioxide gas is blown in, and the carbonation reaction is terminated between 30 minutes and 120 minutes. If the amount greater than the above flow range is injected, the amount of gas that does not participate in the carbonation reaction and is lost will increase. If the amount less than the above flow range is injected, the time required for the carbonation reaction becomes longer, resulting in reduced production efficiency. In the first carbonation method of the present invention, when the exothermic reaction starts to react at 20°C, the temperature at the end of the reaction is about 30°C. Therefore, no separate heating operation is required during the reaction, but if the temperature becomes higher, the solubility of carbon dioxide will decrease, resulting in an increase in the amount of unreacted carbonic acid gas, and therefore, it is necessary to reduce the gas injection flow rate. In contrast, if the reaction temperature increases, the solubility of lithium carbonate will decrease, which can not only improve the yield of lithium carbonate, but also the crystal growth rate becomes faster, which has the effect of improving purity by recrystallization. Therefore, in the present invention, at room temperature, the first carbonation method is used for carbonation (10m 3 Capacity 20℃ reaction tank, 2% LiOH solution, carbon dioxide injection volume 3.12 to 12.48x10 3 l / min), and after the carbonation reaction is completed, the carbonation reaction solution is heated to 100°C.

[0071] The carbonation reaction liquid of the present invention is in a strongly alkaline state of more than pH 12 at the initial stage of the reaction. As the reaction proceeds, the pH gradually decreases and converges to pH 7. When the pH is about pH 9, the generation of lithium carbonate is completed. When the pH is lower than pH 9, the lithium carbonate is dissolved into lithium bicarbonate again. Therefore, preferably, the carbonation reaction is terminated when the pH is pH 8 to pH 10. If the reaction is terminated when the pH exceeds pH 10, silicon and aluminum as impurities exist in the ionic state of silicate ions or aluminate ions, etc. If the reaction is terminated when the pH is less than pH 8, the impurities are present as SiO 2 or Al(OH) 3 The above substances are co-precipitated with lithium carbonate, so there is a problem that the purity of lithium carbonate is reduced.

[0072] In the second carbonation method of the present invention, carbonated water prepared by injecting carbonic acid gas at a pressure of 5 bar to 20 bar at a temperature below 5°C to 10°C can be used. Preferably, carbonated water prepared by injecting carbonic acid gas at a pressure of 10 bar at a temperature below 5°C can be used. Carbonated water prepared by injecting carbonic acid gas at a pressure of 10 bar at a temperature below 5°C contains about 0.68 mol of carbon dioxide. According to an embodiment of the present invention, if 1l of the above carbonated water and 500ml of 2.72 mol of lithium hydroxide aqueous solution are mixed, reacted at a temperature of 20°C for 30 minutes, then heated to 100°C and filtered after aging for 10 minutes, high-purity lithium carbonate, i.e., about 39g of high-purity lithium carbonate, can be obtained. In the second carbonation method of the present invention, preferably, at the end of the reaction, the pH of the reaction solution is maintained at more than 8, and the concentration of LiOH is increased to 1.01 to 1.1 times of the theoretical equivalent to prevent the mixing of silicon and aluminum.

[0073] The third carbonation method of the present invention is to use lithium bicarbonate (LiHCO 3 ) aqueous solution, a lithium bicarbonate aqueous solution prepared by reacting lithium carbonate and carbonated water or a lithium bicarbonate aqueous solution prepared by reacting lithium carbonate and carbon dioxide in a pressure vessel can be used. As the above-mentioned lithium bicarbonate aqueous solution, it is preferred to use a lithium bicarbonate aqueous solution prepared by reacting lithium carbonate and carbon dioxide in a pressure vessel, because reacting lithium carbonate and carbon dioxide in a pressure vessel can quickly increase the concentration of lithium bicarbonate in the aqueous solution. In the above-mentioned method of reacting lithium carbonate and carbon dioxide, preferably, the carbonic acid gas pressure is maintained at 2 bar (bar) to 20 bar in a pressure reaction vessel below 20° C. In this reaction, in order to prevent the mixing of silicon and aluminum, it is also preferred to react when the concentration of LiOH is 1.01 to 1.1 times the theoretical equivalent.

[0074] 7) The seventh process: the third solid-liquid separation process

[0075] The reaction solution (having undergone the above-mentioned carbonation reaction process) is subjected to a third solid-liquid separation. The first lithium carbonate of the solid phase is obtained by the above-mentioned third solid-liquid separation, and an aqueous solution containing unreacted lithium hydroxide and impurity ions of the liquid phase (filtrate) is obtained. The above-mentioned first lithium carbonate is put into the carbonic acid dissolution process to improve the purity, and the above-mentioned filtrate is re-put into the dissolution process of the above-mentioned waste sagger crushed material, so as to further recover the lithium in the unreacted lithium hydroxide and remove impurities. The above-mentioned filtrate can be put into the waste sagger crushed material together with an additive (calcium hydroxide, calcium oxide or magnesium hydroxide) for promoting lithium extraction.

[0076] 8) The eighth process: pressurized carbonic acid dissolution process

[0077] After adding water to the solid phase first lithium carbonate obtained by the third solid-liquid separation process, carbon dioxide gas (CO 2 ) to perform the pressurized carbonic acid dissolution process, so the purity is improved by re-dissolving the lithium carbonate. If lithium carbonate and carbonic acid gas come into contact, the pH of the reaction solution converges to 6 to 8 over time, and the lithium carbonate is converted into lithium bicarbonate and dissolved. At this time, the undissolved aluminum component (Al(OH) 3 ), silicon component (SiO 2 ) and calcium carbonate (CaCO 3 ) can be removed as a solid phase by the fourth solid-liquid separation process. In order to realize the above-mentioned pressurized carbonic acid dissolution process, the slurry concentration can be adjusted to contain 2 to 12 parts by weight of lithium carbonate relative to 100 parts by weight of water. If the lithium carbonate of the above-mentioned slurry is less than 2 parts by weight, the process efficiency will be reduced. If the lithium carbonate of the above-mentioned slurry is more than 12 parts by weight, the time required for the complete dissolution of the lithium carbonate becomes longer, and the incompletely dissolved lithium carbonate is removed together with the impurities, thereby causing the problem of reduced yield. The lower the temperature, the higher the solubility of lithium carbonate in carbonated water. Preferably, the pressurized carbonic acid dissolution process of the present invention is carried out at a temperature of 0°C to 20°C.

[0078] 9) Ninth process: the fourth solid-liquid separation process

[0079] The pressurized carbonic acid dissolution process is used to obtain a liquid lithium bicarbonate aqueous solution, and the solid aluminum component (Al(OH) 3 ), silicon component (SiO 2 ) and calcium content (CaCO 3 The lithium bicarbonate in the lithium bicarbonate aqueous solution obtained by the fourth solid-liquid separation process is converted into lithium carbonate by recrystallization.

[0080] 10) The tenth process: heating recrystallization process

[0081] The filtrate (lithium bicarbonate aqueous solution) obtained in the fourth solid-liquid separation process is heated to precipitate lithium bicarbonate as lithium carbonate (second lithium carbonate). The precipitation process is represented by Chemical Formula 6.

[0082]

Chemical formula 6

[0083]

[0084] If the reaction temperature is low and the pressure is high, the lithium carbonate dissolution reaction is carried out to generate lithium bicarbonate; if the reaction temperature is high and the pressure is low, the lithium bicarbonate is precipitated as lithium carbonate. The above-mentioned decomposition reaction of lithium bicarbonate can precipitate lithium carbonate by simple vigorous stirring or aeration, but it has the disadvantage that its speed is very slow. Therefore, the most economical and easy way to precipitate lithium bicarbonate as lithium carbonate in the above reaction is to heat the reaction solution to 80°C to 100°C while stirring the reaction solution. The precipitation reaction rate of lithium carbonate varies according to temperature and pressure. The higher the temperature and the lower the pressure, the faster the precipitation reaction rate of lithium carbonate. According to the embodiment, if LiHCO 3 When a 2 mol / l aqueous solution is heated to 100°C, the precipitation reaction of lithium carbonate will be completed within 20 minutes. The aqueous solution of the liquid phase (filtrate) obtained in the reaction solution of the above-mentioned heating recrystallization process is reused as the dissolving process water of the above-mentioned waste sagger crushed material.

[0085] 11) Eleventh process: Fifth solid-liquid separation process and drying process

[0086] When the reaction liquid of the above-mentioned heating recrystallization process is subjected to solid-liquid separation, the precipitated lithium carbonate is in a solid phase, and high-purity lithium carbonate (purity of 99.9% or more) is obtained by drying the above-mentioned precipitated lithium carbonate.

[0087] 12) Process 12: First wet magnetic separation process

[0088] The solid phase obtained by the first solid-liquid separation is subjected to wet magnetic separation (first wet magnetic separation). Preferably, the first wet magnetic separation process is carried out after water is added to the solid phase to prepare a slurry. The water is sufficient as long as it reaches the water quality of industrial water, and the water used in the process can also be reused. The purpose of the first wet magnetic separation is to remove iron flakes or iron scales mixed in due to wear when crushing waste saggers. Since the iron flakes or iron scales have very strong magnetization ability, they can be removed as magnetic adsorbents at a magnetic flux density of 100 to 500 gauss. When it is below 200 gauss, most of the iron flakes and iron scales are removed as magnetic adsorbents, but when it exceeds 200 gauss, the mixing rate of the positive active material mixed in the iron flakes and iron scales as magnetic adsorbents will increase. Therefore, when wet magnetic separation is carried out under the condition of exceeding 200 gauss, separate magnetic separation for the mixed positive active material may be required. The magnetically adsorbed materials separated by the first wet magnetic separation process are iron flakes (iron oxide) and iron scales, and the non-magnetically adsorbed materials are positive electrode active materials, aluminum oxide, and silicates.

[0089] 13) The thirteenth process: the second wet magnetic separation process

[0090] The purpose of the second wet magnetic separation process of the present invention is to recover positive electrode active materials containing nickel oxide and cobalt oxide from the non-magnetic adsorbents of the first wet magnetic separation process. The positive electrode active materials contained in the above non-magnetic adsorbents are equivalent to weak magnetic or paramagnetic substances. In order to recover them as magnetic adsorbents, a magnet with a high magnetic flux density is required.

[0091] The second wet magnetic separation process of the present invention can use a high gradient magnetic separator with a magnetic flux density of more than 10,000 Gauss, and preferably, a high gradient magnetic separator with a magnetic flux density of more than 30,000 Gauss can be used. And, preferably, the above-mentioned high gradient magnetic separator has a structure in which the slurry containing the particles to be separated flows between the magnetized magnetic media. The solid concentration of the above-mentioned slurry can be 1% to 10%. If the concentration of the above-mentioned solids is lower than 1%, unnecessary storage tanks increase with the increase in water consumption, and there is a problem of increased energy costs, and if the concentration of the above-mentioned solids exceeds 10%, there is a problem of significantly reduced separation efficiency. The positive electrode active material is separated as a magnetic adsorbent through the above-mentioned second wet magnetic separation process, and the composition of the sagger from which lithium has been removed, that is, alumina or silicate, is separated as a non-magnetic adsorbent.

[0092] 14) The fourteenth process: alkali leaching process

[0093] In the non-magnetic adsorbent of the second wet magnetic separation, there are residual insoluble lithium compounds, and the concentration of residual lithium is 1000mg / kg to 6000mg / kg. In order to recover the residual lithium, the hydroxide or oxide of alkaline earth metal represented by calcium hydroxide and the non-magnetic adsorbent are mixed with water, and when reacted at a temperature of 100°C to 200°C for more than 1 hour in a pressure reaction vessel, more than 70% of the residual insoluble lithium compounds are decomposed and lithium is leached. At this time, the longer the reaction time and the higher the reaction temperature, the higher the lithium leaching rate, but the process cost will increase. Therefore, when setting the reaction temperature and reaction time, it is preferred to consider the economic benefits based on the increase in lithium recovery rate. Preferably, the solid concentration of the reaction slurry is adjusted to 10wt.% to 50wt.%.

[0094] 15) Process 15: Sixth solid-liquid separation process

[0095] When calcium hydroxide or calcium oxide is used as an alkaline leaching agent, the leaching residue is mostly calcium silicate hydrate, magnesium aluminate, calcium aluminum hydrate (Calcium Aluminium Hydrate) and calcium aluminum silicate hydrate, and a small amount of aluminum hydroxide, silicon dioxide and calcium hydroxide also coexist. + OH - The highest concentration of Ca 2+ 、AlO 2 - , H 2 SiO 4 2- The leached residue obtained by solid-liquid separation is discharged after washing, and the liquid phase is sent to the evaporation concentration process and used as a raw material for preparing lithium carbonate.

[0096] The specific embodiments described in this specification represent preferred embodiments or examples of the present invention, and the scope of the present invention is not limited thereto. It is obvious to those skilled in the art that modifications and other uses of the present invention will not exceed the scope of the invention described in the claims herein.

[0097] Industrial Applicability

[0098] It is expected that the method for preparing high-purity lithium carbonate from waste saggers of the present invention can not only prepare high-purity lithium carbonate that can be used to prepare lithium secondary batteries by recycling discarded waste saggers, but also recycle positive electrode active materials, iron oxide, aluminum oxide, silicate and calcium carbonate obtained in the preparation process.

Claims

1. A method for preparing high-purity lithium carbonate from waste saggers, comprising: The first step of preparing the waste sagger crushed material by crushing the waste sagger; A second step of adding an alkali leaching agent and water to the crushed waste sagger and reacting them to prepare a dissolution reaction slurry of the crushed waste sagger; A third step of performing a first solid-liquid separation on the dissolution reaction slurry of the waste sagger crushed material; A fourth step of evaporating and concentrating the liquid phase filtrate obtained by the first solid-liquid separation; a fifth step of performing a second solid-liquid separation on the concentrated liquid obtained by the evaporation concentration; A sixth step of subjecting the liquid phase filtrate obtained by the second solid-liquid separation to a carbonation reaction to prepare a carbonation reaction liquid; A seventh step of performing a third solid-liquid separation on the carbonation reaction liquid; An eighth step of adding water to the solid phase first lithium carbonate obtained by the third solid-liquid separation to prepare a first lithium carbonate suspension, and injecting carbon dioxide to dissolve the first lithium carbonate; a ninth step of performing a fourth solid-liquid separation on the aqueous solution in which the first lithium carbonate is dissolved; A tenth step of heating and recrystallizing the liquid filtrate obtained by the fourth solid-liquid separation to precipitate the second lithium carbonate; as well as The filtrate from which the second lithium carbonate is precipitated is subjected to a fifth solid-liquid separation to obtain a high-purity second lithium carbonate in a solid phase, and then subjected to an eleventh step of drying.

2. The method for preparing high-purity lithium carbonate from waste sagger according to claim 1, wherein: The waste sagger pulverized material dissolution reaction slurry is prepared by adding one or more alkalis including alkali metal hydroxide, alkali metal carbonate, or alkaline earth metal hydroxide and water to the waste sagger pulverized material and then heating the sagger pulverized material.

3. The method for preparing high-purity lithium carbonate from waste sagger according to claim 1, wherein: The evaporative concentration is performed by evaporating under reduced pressure at 70° C. to 95° C., or by purging nitrogen or argon at atmospheric pressure and heating to 100° C. in an atmosphere where carbon dioxide cannot come into contact with the concentrated liquid.

4. The method for preparing high-purity lithium carbonate from waste sagger according to claim 1, wherein: The evaporation concentration is carried out until the lithium concentration in the concentrated solution reaches 0.5% to 5%.

5. The method for preparing high-purity lithium carbonate from waste sagger according to claim 1, wherein: In the carbonation reaction, any one or more selected from carbon dioxide, carbonated water and lithium bicarbonate aqueous solution are injected into the liquid phase filtrate obtained by the second solid-liquid separation to react until the pH reaches 8 to 10.

6. The method for preparing high-purity lithium carbonate from waste sagger according to claim 1, wherein: The liquid filtrate obtained by the third solid-liquid separation is added to the dissolution reaction slurry of the waste sagger crushed material to further recover the unreacted lithium hydroxide that has not participated in the carbonation reaction.

7. The method for preparing high-purity lithium carbonate from waste sagger according to claim 1, wherein: The reaction of injecting carbon dioxide into the first lithium carbonate suspension to dissolve the first lithium carbonate is carried out at a temperature of 0° C. to 20° C., and the pH of the reaction solution reaches 6 to 8 when the reaction is completed.

8. The method for preparing high-purity lithium carbonate from waste sagger according to claim 1, wherein: The liquid filtrate obtained by the fourth solid-liquid separation is heated to a temperature of 80°C to 100°C.

9. The method for preparing high-purity lithium carbonate from waste sagger according to claim 1, wherein: The purity of the second lithium carbonate is above 99.9%.

10. A method for preparing high-purity lithium carbonate from waste saggers, comprising: The twelfth step of preparing the waste sagger crushed material by crushing the waste sagger; The thirteenth step is to add an alkali leaching agent and water to the crushed waste sagger and react to prepare a dissolution reaction slurry of the crushed waste sagger; The fourteenth step of performing a first solid-liquid separation on the dissolution reaction slurry of the waste sagger crushed material; A fifteenth step of preparing the solid phase obtained by the first solid-liquid separation into a suspension, and then performing a first wet magnetic separation to obtain a first magnetically adsorbed substance and a first non-magnetic adsorbed substance; After preparing the first non-magnetic adsorbent into a suspension, performing a second wet magnetic separation to obtain a second magnetic adsorbent and a second non-magnetic adsorbent; a seventeenth step of adding water and a leaching agent into the second non-magnetic adsorbent and reacting them to prepare a lithium leaching reaction solution; An eighteenth step of performing a sixth solid-liquid separation on the lithium leaching reaction solution; A nineteenth step of evaporating and concentrating the liquid phase filtrate obtained by the sixth solid-liquid separation; a twentieth step of performing a second solid-liquid separation on the concentrated liquid obtained by the evaporation concentration; A twenty-first step of preparing a carbonation reaction liquid by subjecting the liquid phase filtrate obtained by the second solid-liquid separation to a carbonation reaction reaction; A twenty-second step of performing a third solid-liquid separation on the carbonation reaction liquid; A twenty-third step of adding water to the solid phase first lithium carbonate obtained by the third solid-liquid separation to prepare a first lithium carbonate suspension, and injecting carbonic acid gas to dissolve the first lithium carbonate; A twenty-fourth step of performing a fourth solid-liquid separation on the aqueous solution in which the first lithium carbonate is dissolved; A twenty-fifth step of heating and recrystallizing the liquid filtrate obtained by the fourth solid-liquid separation to precipitate the second lithium carbonate; as well as The filtrate from which the second lithium carbonate is precipitated is subjected to a fifth solid-liquid separation to obtain a high-purity second lithium carbonate in a solid phase, and then dried in the twenty-sixth step.

11. The method for preparing high-purity lithium carbonate from waste saggers according to claim 10, wherein: The waste sagger pulverized material dissolution reaction slurry is prepared by adding one or more alkalis including alkali metal hydroxide, alkali metal carbonate, or alkaline earth metal hydroxide and water to the waste sagger pulverized material and then heating the sagger pulverized material.

12. The method for preparing high-purity lithium carbonate from waste saggers according to claim 10, wherein: The first magnetically adsorbed substance is a magnetically adsorbed substance containing iron oxide and iron scale, the second magnetically adsorbed substance is a magnetically adsorbed substance containing a positive electrode active material, and the solid phase of the sixth solid-liquid separation contains aluminum oxide and silicate.

13. The method for preparing high-purity lithium carbonate from waste saggers according to claim 10, wherein: The lithium leaching reaction solution is prepared by adding alkaline earth metal hydroxide or oxide and water as a leaching agent into the second non-magnetic adsorbent and reacting them in a pressure reaction vessel at a temperature of 100° C. to 200° C. and a reaction time of less than 3 hours. The reaction slurry concentration of the lithium leaching reaction solution is 10wt% to 50wt%.

14. The method for preparing high-purity lithium carbonate from waste saggers according to claim 10, wherein: The evaporative concentration is performed by evaporating under reduced pressure at 70° C. to 95° C., or by purging nitrogen or argon at atmospheric pressure and heating to 100° C. in an atmosphere where carbon dioxide cannot come into contact with the concentrated liquid.

15. The method for preparing high-purity lithium carbonate from waste saggers according to claim 10, wherein: The evaporation concentration is carried out until the lithium concentration in the concentrated solution reaches 0.5% to 5%.

16. The method for preparing high-purity lithium carbonate from waste saggers according to claim 10, wherein: In the carbonation reaction, any one or more selected from carbon dioxide, carbonated water and lithium bicarbonate aqueous solution are injected into the liquid phase filtrate obtained by the second solid-liquid separation to react until the pH reaches 8 to 10.

17. The method for preparing high-purity lithium carbonate from waste saggers according to claim 10, wherein: The liquid filtrate obtained by the third solid-liquid separation is added to the dissolution reaction slurry of the waste sagger crushed material to further recover the unreacted lithium hydroxide that has not participated in the carbonation reaction.

18. The method for preparing high-purity lithium carbonate from waste saggers according to claim 10, wherein: The reaction of injecting carbon dioxide into the first lithium carbonate suspension to dissolve the first lithium carbonate is carried out at a temperature of 0° C. to 20° C., and the pH of the reaction solution reaches 6 to 8 when the reaction is completed.

19. The method for preparing high-purity lithium carbonate from waste saggers according to claim 10, wherein: The liquid filtrate obtained by the fourth solid-liquid separation is heated to a temperature of 80°C to 100°C.

20. The method for preparing high-purity lithium carbonate from waste saggers according to claim 10, wherein: The purity of the second lithium carbonate is above 99.9%.

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