Method for recovering nickel, cobalt and lithium from waste refractory saggers

Abstract

The present invention has an advantage in that after crushing the discarded refractory sacks, nickel oxide and cobalt oxide, which are positive active materials, are recovered using wet magnetic separation, and impurities are removed through Al, Si precipitation reaction and evaporation concentration to recover high purity lithium hydroxide. Therefore, by using the method for recovering positive active materials and lithium hydroxide from the discarded refractory sacks of the present invention, it is possible to recover and reuse high value-added lithium and positive active materials from the discarded refractory sacks discarded in the manufacturing process of lithium secondary batteries, and therefore it is expected that the manufacturing cost of lithium secondary batteries can be reduced.

Description

[Technical field]

[0001] The present invention relates to a method for recovering active cathode material and lithium hydroxide from discarded saggers. [Background technology]

[0002] The positive electrode active material of a lithium ion secondary battery is synthesized by a method of firing a lithium-containing composite oxide at a high temperature. If the lithium-containing composite oxide comes into direct contact with flames, ash smoke, or the like during the high-temperature firing process, the quality of the synthesized positive electrode active material will be degraded. Therefore, the lithium-containing composite oxide is produced by a method of placing it in a fireproof sagger, which is a fireproof container with excellent thermal conductivity, and then firing it at a high temperature.

[0003] The fireproof sagger for producing the positive electrode active material is made of ceramic oxide mainly composed of SiO2, Al2O3, MgO, etc. When the fireproof sagger for producing the positive electrode active material is repeatedly subjected to high-temperature firing of the lithium-containing composite oxide, the surface of the fireproof sagger for producing the positive electrode active material is corroded by lithium hydroxide or lithium carbonate produced in the high-temperature firing process, and the positive electrode active material synthesized together with the lithium hydroxide and lithium carbonate is deposited at the corroded site. As a result, the heat durability of the fireproof sagger corroded by the lithium hydroxide or lithium carbonate is reduced, and the fireproof sagger is eventually discarded as a waste fireproof sagger.

[0004] The amount of waste fireproof sacks generated in Korea is said to be about 30,000 tons per year, but with the recent dramatic increase in demand for lithium-ion secondary batteries coupled with the popularization of mobile devices and electric vehicles, the amount of waste fireproof sacks generated is expected to increase sharply.

[0005] Therefore, if it is possible to recover positive electrode active materials such as high-value nickel and cobalt deposited in eroded areas and lithium from used refractory saggers that are discarded due to reduced thermal durability caused by repeated high-temperature firing of lithium-containing composite oxides, it is expected that the recovered materials can be recycled for the production of lithium-ion secondary batteries, thereby reducing production costs.

[0006] All patents and references mentioned in this specification are herein incorporated by reference to the same extent as if each individual publication was individually and specifically indicated by reference. Summary of the Invention [Problem to be solved by the invention]

[0007] An object of the present invention is to provide an economical and effective method for recovering high-value compounds such as lithium, nickel, and cobalt from waste refractory sacks used in the manufacture of positive electrode active materials, which are discarded due to corrosion caused by lithium hydroxide, lithium carbonate, and the like with repeated use.

[0008] Other objects and technical features of the present invention will be more specifically presented in the following detailed description of the invention, the claims and the drawings. [Means for solving the problem]

[0009] The present invention provides a method for recovering a positive electrode active material and lithium hydroxide from a used refractory saggers, the method comprising: a first step of wet-pulverizing the used refractory saggers to separate solid from liquid; a second step of applying wet magnetic separation to the solid obtained by the solid-liquid separation to recover a positive electrode active material; and a third step of subjecting the filtrate obtained by the solid-liquid separation to a precipitation reaction of Al and Si and evaporation and concentration to recover lithium hydroxide.

[0010] The wet grinding is characterized in that the waste refractory saggers are dry-ground (dry-grinded) and then wet-ball milled (wet-ball mill grinding) to finely grind them to a particle size of 200 mesh or less.

[0011] The wet magnetic separation is characterized in that iron oxide and iron scale as magnetized matter are removed using primary wet magnetic separation, and then secondary wet magnetic separation is carried out on the non-magnetized matter of the primary wet magnetic separation, thereby recovering the positive electrode active material as a magnetized matter. The precipitation reaction of Al and Si is characterized in that an alkaline earth metal hydroxide and an additive are mixed with the filtrate obtained using the solid-liquid separation, to precipitate water-soluble aluminum compounds such as aluminates as poorly soluble substances such as calcium aluminum silicate hydrate or ettringite, and to precipitate water-soluble silicon-containing compounds as poorly soluble substances such as calcium silicate hydrate.

[0012] The evaporation concentration is characterized in that the filtrate obtained by the solid-liquid separation is subjected to a precipitation reaction of Al and Si, and the filtrate obtained by solid-liquid separation is subjected to evaporation concentration to recover lithium hydroxide, and is characterized in that the atmosphere is adjusted with an inert gas such as nitrogen in order to prevent lithium carbonate from being generated by reaction with carbon dioxide gas in the air, thereby decreasing the purity. Effect of the Invention

[0013] The present invention has an advantage in that after crushing the discarded used refractory sacks, nickel oxide and cobalt oxide, which are positive electrode active materials, are recovered using wet magnetic separation, and impurities are removed through a precipitation reaction of Al and Si and evaporation concentration to recover high purity lithium hydroxide. Therefore, by using the method of recovering positive electrode active materials and lithium hydroxide from the used refractory sacks of the present invention, it is possible to recover and reuse high value-added lithium and positive electrode active materials from the used refractory sacks discarded in the manufacturing process of lithium secondary batteries, and therefore it is expected that the manufacturing cost of lithium secondary batteries can be reduced. [Brief description of the drawings]

[0014] [Figure 1] 1 is a schematic diagram showing a method for recovering positive electrode active material and lithium hydroxide from a waste refractory sagger of the present invention. [Diagram 2] The mineral phase analysis of the erosion layer of the waste refractory sagger used in the sintering of NCA (LiNi0.8Co0.15Al0.05) of the present invention shows that the erosion layer is mainly composed of Li4SiO4, LiAlO2, LiAlSi2O6 and Li2CO3. [Diagram 3] The mineral phases of the crushed waste refractory saggers used in the sintering of the NCA (LiNi0.8Co0.15Al0.05) of the present invention were analyzed, and the results show that the waste refractory saggers are mainly composed of Al2O3, and also contain mineral phases such as Li0.6Al0.6Si2.4O6, Al6Si2O13, SiO2, MgAl2O4, and Mg2Al4Si5O18. [Figure 4] 1 shows scanning electron micrographs of the refractory sagger mill and erosion layer of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0015] The present invention provides a method for recovering a positive electrode active material and lithium hydroxide from a used refractory saggers, the method including: a first step of wet-pulverizing the used refractory saggers and performing solid-liquid separation; a second step of applying wet magnetic separation to the solid obtained by the solid-liquid separation to recover a positive electrode active material; and a third step of subjecting the filtrate obtained by the solid-liquid separation to a precipitation reaction of Al and Si and evaporation and concentration to recover lithium hydroxide.

[0016] The waste refractory sagger is a refractory sagger for firing and synthesizing a positive electrode active material, and is a ceramic mainly composed of SiO2, Al2O3, and MgO.

[0017] The wet pulverization is preferably performed after the refractory sagger is coarsely pulverized to a level of 0.5 to 10 mm using dry pulverization. The wet pulverization is preferably performed by finely pulverizing the refractory sagger to a level of 200 mesh or less using ball milling, and the wet pulverized material is separated into a solid and a liquid using solid-liquid separation.

[0018] The solid obtained by the solid-liquid separation is subjected to wet magnetic separation to recover the positive electrode active material. The positive electrode active material includes an oxide of lithium-nickel-cobalt. The wet magnetic separation includes a primary wet magnetic separation and a secondary wet magnetic separation, and the primary wet magnetic separation has a magnetic flux density of 100 to 500 gauss to remove iron, iron oxide, iron scale, and the like as magnetic substances. Preferably, the primary wet magnetic separation has a magnetic flux density of 100 to 200 gauss to remove iron, iron oxide, and iron scale as magnetic substances. The secondary wet magnetic separation has a magnetic density of 25,000 to 30,000 gauss to recover the positive electrode active material as a magnetic substance and recover alumina, aluminosilicate, and the like as non-magnetic substances, and is preferably performed using a separator having a magnetic density of 20,000 gauss or more.

[0019] In the present invention, the filtrate obtained by the solid-liquid separation is subjected to a precipitation reaction of Al and Si and evaporation and concentration to recover lithium hydroxide. The Al and Si precipitation reaction is carried out by mixing an alkaline earth metal hydroxide and gypsum with the filtrate obtained by the solid-liquid separation to recover lithium hydroxide. - is precipitated as poorly soluble calcium aluminum silicate hydrate or ettringite, and water-soluble SiO4 2- is precipitated as poorly soluble calcium silicate hydrate.

[0020] The evaporation concentration of the present invention is characterized in that a filtrate obtained by the solid-liquid separation is subjected to a precipitation reaction of Al and Si, and the filtrate obtained by the solid-liquid separation is subjected to evaporation concentration to recover lithium hydroxide.

[0021] The evaporation concentration includes primary, secondary, and tertiary evaporation concentration. First, the primary evaporation concentration is a process for removing impurities including calcium hydroxide, calcium carbonate, aluminum hydroxide, and silicon dioxide, and may include some lithium hydroxide and lithium carbonate. The primary evaporation concentration is preferably carried out until 0.5 to 5% of lithium hydroxide is precipitated.

[0022] The secondary evaporation concentration is a process for precipitating lithium hydroxide, and is preferably carried out until 50 to 80% of the lithium hydroxide is precipitated by using a liquid obtained by solid-liquid separation of the concentrated liquid produced by the primary evaporation concentration. The precipitated lithium hydroxide is washed, filtered and dried, and the lithium hydroxide recovered using this has a purity of 99.9% or more.

[0023] The tertiary evaporation concentration is a process for improving the recovery rate of lithium hydroxide by reintroducing lithium hydroxide that has not been precipitated in the secondary evaporation concentration process into the primary evaporation concentration process. The tertiary evaporation concentration is preferably carried out using a liquid obtained by solid-liquid separation of the concentrated liquid produced by the secondary evaporation concentration, until 90 to 95% of the lithium hydroxide is precipitated. Since the lithium hydroxide obtained as a solid by solid-liquid separation after the secondary evaporation concentration may contain impurities and have a low purity, it is dissolved again in the filtrate for the primary evaporation concentration so that it is precipitated as high-purity lithium hydroxide in the secondary evaporation concentration process. In addition, the filtrate obtained as a liquid by solid-liquid separation after being used for washing the high-purity lithium hydroxide obtained after the secondary evaporation concentration is introduced into the precipitation reaction solution of Al and Si and reused in the lithium hydroxide recovery process.

[0024] <Mode for carrying out the invention> The method for recovering the positive electrode active material and lithium hydroxide from the waste refractory sacks of the present invention will be described in detail below.

[0025] 1) Analysis of used fireproof sacks The fireproof sagger of the present invention may be a fireproof sagger that is discarded after being used to sinter a positive electrode active material for a secondary battery, or may be a container for sintering a positive electrode active material and may be a ceramic mainly composed of SiO2, Al2O3, and MgO.

[0026] Table 1 shows the NCA (LiNi 0.8 Co 0.15 Al 0.05 The composition of the waste refractory saggers used in the sintering of the 1990s was analyzed by X-ray fluorescence spectrometry (XRF) and atomic absorption spectrometry.

[0027] [Table 1]

[0028] Analysis showed that the lithium (Li) content was on the high side at 1.5%, which is equivalent to about 8.0% lithium carbonate content. The cobalt content was also about 0.2%, making it deemed that it is well worth recovering.

[0029] Figures 2 and 3 show the NCA (LiNi 0.8 Co 0.15 Al 0.05 2 shows the results of an X-ray diffraction analysis of the mineral phase of a used fireproof sagger used in the sintering of the positive electrode active material. Figure 2 shows the analysis results for the surface portion of the fireproof sagger, i.e., the portion that had been in contact with the positive electrode active material. Although the diffraction lines for lithium silicate, lithium aluminum oxide, lithium aluminum silicate, lithium carbonate, etc. were clearly observed, no clear diffraction lines were observed for the positive electrode active material, due to its small amount and poor crystallinity.

[0030] Figure 3 shows an X-ray diffraction pattern of a sample that was completely crushed and mixed from a used fireproof sagger, that is, an analysis of the entire mineral phase of the used fireproof sagger. The inside of the fireproof sagger is composed of mullite, cordierite, alumina, quartz, and spinel, which are the raw materials of the fireproof sagger, and diffraction lines of lithium aluminum silicate, which is thought to have been produced by a reaction with lithium that has penetrated from the surface, were also observed.

[0031] 2) Waste fireproof sack processing process 1 shows a process for separating iron oxide, iron scale, positive electrode active material, aluminosilicate, and lithium hydroxide from a used refractory sagger of the present invention. In particular, the use of the treatment process for a used refractory sagger of the present invention has the advantage of being able to obtain high-purity lithium hydroxide monohydrate with a purity of 99.9% or more.

[0032] (1) Crushing process of used fireproof sacks First, the waste refractory sacks (S1) are crushed into powder of 200# or less. Since pulverizing the waste refractory sacks in bulk has the problem of low crushing efficiency, it is preferable to perform dry crushing (S2) to roughly crush the waste refractory sacks to 1mm or less in step 1, and then wet crushing (S3) to finely crush the waste refractory sacks to 200# or less in step 2. In a mass processing process where crushing efficiency is more important than initial investment cost, it is preferable to arrange a jaw crusher and an impact mill (or hammer mill) in series and reduce the particle size of the crushed product to 1mm or less.

[0033] The waste refractory sacks have a relatively high compressive strength, but are weak against impact. If only the crushing efficiency is taken into consideration, it is possible to use only an impact crusher such as an impact crusher without going through various steps. However, the impact crusher has a problem that the crushed particles have sharp surfaces with high hardness, so that the parts are easily worn by crushing, which may increase the crushing cost.

[0034] Therefore, in the present invention, dry crushing (S2) is performed using a jaw crusher, which is easy to replace parts and is inexpensive, in step 1, and then finely crushing is performed using wet ball milling in step 2. In particular, the wet ball milling has an advantage that lithium can be extracted during the fine crushing process of the waste refractory saggers.

[0035] The ball milling machine used in the wet grinding (S3) is preferably structured such that a coarsely ground slurry of the used refractory saggers, which is a mixture of the coarsely ground material of the used refractory saggers and water, is fed from one end, and overflow (overflow water) containing particles finely ground by ball milling flows out from the other end. In addition, it is preferable that the overflowed slurry is passed through a 200# sieve, and particles having a particle size of 200# or more are conveyed to the feed port.

[0036] The coarsely pulverized waste refractory sack slurry is preferably produced by mixing 100 parts by weight of coarsely pulverized waste refractory sacks with 100 to 1000 parts by weight of water. If the amount of water contained in the coarsely pulverized waste refractory sack slurry is less than 100 parts by weight, the viscosity of the slurry is too high, which not only reduces the efficiency of fine pulverization using ball milling, but also reduces the lithium leaching rate. If the amount of water contained in the coarsely pulverized waste refractory sack slurry exceeds 1000 parts by weight, there is a problem that the energy cost of the subsequent concentration process increases. The coarsely pulverized waste refractory sack slurry is preferably produced by mixing 200 to 500 parts by weight of water with 100 parts by weight of coarsely pulverized waste refractory sacks. The residence time of the coarsely pulverized waste refractory sack slurry in the ball mill is preferably 10 to 120 minutes. If the residence time is less than 10 minutes, the lithium leaching rate will be low and the pulverization efficiency will be reduced, while if the residence time is more than 120 minutes, this will result in an unnecessary increase in energy costs.

[0037] (2) Solid-liquid separation process of the waste refractory sagger mill slurry The finely pulverized waste refractory sagger slurry is subjected to solid-liquid separation (S4) to separate it into a solid (S5) and a filtrate (S6). The solid (S5) contains a refractory composition containing a positive electrode active material, iron oxide, iron scale, aluminosilicate, alumina, etc., and the filtrate (S6) corresponds to a lithium leachate in which lithium, aluminum, and silicon are dissolved. The solid-liquid separation can be performed using a settling tank, a filter press, a screw filter, a centrifuge, etc., and the efficiency can be improved by combining two or more of these. There is a possibility that some lithium has been leached into the solid (S5). Therefore, the solid (S5) is washed with clean water to minimize the amount of lithium lost, and the water used for the washing (washing water) is reused as water for ball milling in the wet grinding (S3).

[0038] (3) Wet magnetic separation process The solid (S5) contains a positive electrode active material (S13) and a refractory composition (S11) (S14), and the filtrate contains lithium and aluminum silicon as Li + , O.H. - , Al(OH)4 - , SiO4 2- From the solid (S5), iron oxide, iron scale, and positive electrode active material are recovered through magnetic separation (S8 and S12), and alumina and aluminosilicate, which are the composition of the refractory sagger, are left behind as residue, and the filtrate (S6) is passed through an Al and Si precipitation removal step (S15) to recover lithium hydroxide.

[0039] The magnetic separation is composed of a primary wet separation step (S8) and a secondary wet magnetic separation step (S12). The water used in the wet magnetic separation step may be of industrial water quality, and the water used in the process may be reused. The solid (S5) obtained in the solid-liquid separation step (S4) is made into a solid slurry by adding water to the solid concentration of 1 to 10%, and the solid slurry is introduced into the primary wet magnetic separation step (S8).

[0040] The purpose of the primary wet magnetic separation process (S8) is to remove iron oxide, iron chips, iron scale, etc., which are mixed in due to wear of the crusher. The magnetic material (S9) in the primary wet magnetic separation process (S8) is iron oxide and iron scale. These have a very strong tendency to be attracted to magnets, so they can be sufficiently removed even with a magnet having a magnetic flux density of about 100 to 500 gauss. In this case, the magnetic material (S9) recovered at 200 gauss or less is mostly iron oxide and iron scale, but when the magnetic flux density exceeds 200 gauss, the ratio of the positive electrode active material (S13) mixed in the magnetic material (S9) may be high. The iron oxide and iron scale (S11) recovered using the primary wet magnetic separation process (S8) are stored in a separate place after dehydration.

[0041] The purpose of the secondary wet magnetic separation step (S12) of the present invention is to recover a positive electrode active material (S13) containing nickel oxide, cobalt oxide, etc. from the non-magnetic material (S10) of the primary wet magnetic separation step (S8). The positive electrode active material (S13) corresponds to a weak magnetic material or a paramagnetic material, so a magnet having a high magnetic flux density is required to recover these as magnetic materials. It is preferable to recover the positive electrode active material (S13) in the secondary wet magnetic separation step (S12) of the present invention using a magnetic medium having a magnetic flux density of 10,000 to 30,000 gauss. However, some positive electrode active materials such as LCO (lithium cobalt dioxide) and NCM (nickel cobalt manganese oxide) have a strong tendency to be attracted to magnets, so when trying to recover only these, a magnet having a magnetic flux density of about 2,000 gauss may be sufficient for recovery.

[0042] The magnetic separator used in the secondary wet magnetic separation step (S12) preferably has a structure that allows a slurry containing particles to be separated to flow out between magnetized magnetic media. In this case, the solids (S5) and non-magnetic materials (S10) are preferably produced and used as a slurry having a concentration of 1 to 10%. If the solid concentration of the slurry is less than 1%, an additional storage tank is required as the amount of water used increases, resulting in a problem of rising energy costs. If the concentration exceeds 10%, there is a problem of a significant decrease in separation efficiency.

[0043] (4) Al(OH)4 - and SiO4 2- Precipitation process The filtrate (S6) obtained by solid-liquid separation (S4) of the crushed refractory sagger crushed material contains Li + , O.H. - , Al(OH)4 - , SiO4 2- Therefore, if the filtrate (S6) is mixed with alkaline earth metal hydroxides such as calcium hydroxide and magnesium hydroxide and gypsum, water-soluble Al(OH)4 - and SiO42- However, the Al,Si precipitates as poorly soluble calcium silicate hydrate (CSH) and calcium aluminum silicate hydrate (CASH), as well as ettringite. The Al,Si precipitation reaction (S15) is preferably carried out at a temperature of 50 to 80°C for a reaction time of 30 to 120 minutes. The Al,Si precipitation reaction (S15) is very sensitive to the reaction temperature, and the higher the temperature, the higher the reaction rate. For example, if the Al,Si precipitation reaction (S15) is carried out at a temperature of 20°C or lower, it takes 6 hours or more to complete, and the particle size of the product is very fine, which causes difficulties in solid-liquid separation. At 50°C, the Al,Si precipitation reaction (S15) is completed within 2 hours, and at 80°C, the reaction is completed within 30 minutes. When the Al, Si precipitation reaction (S15) is carried out at a temperature close to 100° C., the reaction is completed within 10 minutes, but energy loss occurs due to evaporation of water.

[0044] The precipitant (S16) used in the precipitation reaction of the Al, Si precipitation reaction (S15) is an alkaline earth metal hydroxide, preferably calcium hydroxide. The amount of the precipitant (S16) added is determined based on the amount of Al(OH)4 - and SiO4 2- The amount of calcium hydroxide added is determined by the amount of calcium silicate hydrate (CSH) and calcium aluminum silicate hydrate (CASH), and it is preferable to add calcium hydroxide equivalent to 1 to 2 times the equivalent amount required to produce calcium silicate hydrate (CSH) and calcium aluminum silicate hydrate (CASH). If the calcium hydroxide is added in an amount less than the equivalent amount, the amount of unremoved Al(OH)4 in the solution will be reduced. - and SiO4 2- If more than 2 equivalents are used, the process cost will increase. The amount of gypsum added is preferably 0.5 to 1 times the amount of calcium hydroxide added.

[0045] Addition of additives such as calcium hydroxide and gypsum can be performed in the wet ball milling process, which has the advantage of increasing the lithium leaching rate and simplifying the process, but can reduce the magnetic separation efficiency and harden the sludge, making processing difficult.

[0046] (5) Solid-liquid separation process for Al and Si precipitates The reaction product of the Al, Si precipitation reaction (S15) is subjected to solid-liquid separation (S17) to separate a solid (S18) and a filtrate (S19). The solid (S18) contains poorly soluble calcium silicate hydrate (CSH), calcium aluminum silicate hydrate (CASH), and ettringite, which are reaction products of the Al, Si precipitation reaction (S15), and the filtrate (S19) is a lithium leachate containing lithium. A settling tank, a filter press, a screw filter, a centrifuge, etc. can be used for the solid-liquid separation (S17), and two or more of these can be combined to increase the efficiency. The solid (S18) is washed with clean water to minimize the amount of lithium contained therein and lost, and the washing water can be mixed with the filtrate (S6) used for the Al, Si precipitation reaction (S15) to reuse it.

[0047] The filtrate (S19) separated using the solid-liquid separation (S17) is mostly water and lithium hydroxide, and contains less than 100 ppm of calcium (Ca 2+ ), Aluminum (Al(OH)4 - ), silicon (SiO4 2- ) is contained in the filtrate (S19). Carbon dioxide (S20) is injected to remove impurities from the filtrate (S19). When the carbon dioxide (S20) (S20) is injected into the filtrate (S19), the calcium is precipitated as calcium carbonate. The precipitated calcium carbonate can be produced by further performing solid-liquid separation, but this can be omitted since it can be separated as a solid using solid-liquid separation (S22) in the evaporation and concentration process described below.

[0048] (6) Evaporation and concentration process The filtrate (S19) from which the impurities have been precipitated is subjected to evaporation concentration steps (S21), (S24), and (S26). The evaporation concentration steps (S21), (S24), and (S26) are steps for increasing the lithium concentration of the filtrate (S19) and removing remaining impurities such as magnesium hydroxide and calcium carbonate by precipitating them, and are preferably composed of a first evaporation concentration step (S21), a second evaporation concentration step (S24), and a third evaporation concentration step (S26).

[0049] The primary evaporation concentration step (S21) refers to subjecting the filtrate (S19) to reduced pressure evaporation at 70 to 95° C. The primary evaporation concentration step (S21) can also be performed under atmospheric pressure at 100° C., but in this case, it is essential to purge with nitrogen or argon gas to prevent carbon dioxide (S20) from coming into contact with the evaporated concentrated liquid.

[0050] The primary evaporation concentration step (S21) is preferably carried out from the time when lithium hydroxide starts to be precipitated until about 0.5 to 5% of the total lithium hydroxide is precipitated. If the primary evaporation concentration step (S21) is terminated before the amount of lithium hydroxide precipitated reaches 0.5%, the removal rate of impurities including magnesium hydroxide, calcium carbonate, etc. decreases, and if the concentration is continued until an amount higher than 5% is precipitated, lithium hydroxide is precipitated in excess, and the lithium hydroxide is returned to step (S6) together with the impurities, resulting in a decrease in process efficiency.

[0051] The lithium hydroxide concentrate produced by carrying out the primary evaporation concentration step (S21) is subjected to solid-liquid separation (S22). The solid-liquid separation (S22) is a step of separating impurities such as magnesium hydroxide and calcium carbonate precipitated in the primary evaporation concentration step (S21) from the concentrate, and some lithium hydroxide can be precipitated together with the impurities. A settling tank, a filter press, a screw filter, a centrifuge, etc. can be used for the solid-liquid separation (S22), and the efficiency can be increased by combining two or more of these.

[0052] The solid (S23) obtained by the solid-liquid separation (S22) is mixed with the filtrate (S6) obtained by the solid-liquid separation (S4) of the pulverized waste refractory sack material and reused, so that it is possible to recover a larger amount of lithium hydroxide contained in the impurities.

[0053] The secondary evaporation concentration step (S24) is carried out under the same conditions as the primary evaporation concentration step for the filtrate obtained by the primary evaporation concentration step (S21) and the solid-liquid separation (S22), and is carried out until 50 to 80% of the lithium hydroxide in the filtrate is precipitated. If the concentration is terminated before the amount of lithium hydroxide precipitated reaches 50%, the recovery rate of lithium hydroxide decreases and the process cost rises, and if the concentration is carried out so that the amount of lithium hydroxide precipitated exceeds 80%, the purity of the recovered lithium hydroxide decreases. The concentrated liquid subjected to the secondary evaporation concentration step (S24) is subjected to solid-liquid separation (S25) to separate lithium hydroxide as a solid (S28) phase. For the solid-liquid separation (S25), a settling tank, a filter press, a screw filter, a centrifuge, etc. can be used, and the efficiency can be increased by combining two or more of these.

[0054] The tertiary evaporation concentration step (S26) is a step for maximizing the recovery rate of lithium hydroxide by further concentrating the filtrate from the secondary evaporation concentration step (S24) and the solid-liquid separation (S25) and then reintroducing it into the evaporation concentration process. The tertiary evaporation concentration step (S26) is carried out in the same manner as the primary and secondary evaporation concentration steps (S21) (S24), but is continued until 90 to 95% of the lithium hydroxide in the concentrated liquid is precipitated. The solid produced using the tertiary evaporation concentration step (S26) is lithium hydroxide containing a small amount of the impurities, and is mixed and dissolved in the filtrate (S19) obtained by the solid-liquid separation (S17) after the Al, Si precipitation reaction (S15), and then reintroduced into the primary evaporation concentration step. The liquid produced using the tertiary evaporation concentration step (S26) contains a small amount of aluminum and silicon, but is input into the Al, Si precipitation reaction (S15) to remove them. If the concentration is terminated before the amount of lithium hydroxide precipitated reaches 90%, the process cost of the Al, Si precipitation reaction (S15) will rise, and if the concentration is performed so that the amount of lithium hydroxide precipitated exceeds 95%, the purity of lithium hydroxide that should be mixed and dissolved in the filtrate (S19) obtained by solid-liquid separation (S17) after the Al, Si precipitation reaction (S15) will be excessively reduced. The solid-liquid separation (S27) is a process for separating the lithium hydroxide produced in the tertiary evaporation concentration process (S26) from the aqueous solution. In general, a settling tank, a filter press, a screw filter, a centrifuge, etc. can be used, and two or more of these can be combined to increase the efficiency. The series of concentration steps that follow the primary, secondary, and tertiary stages may be performed in separate concentration tanks, or may be performed sequentially in a single concentration tank.

[0055] (7) Obtaining high-purity lithium hydroxide The high purity lithium hydroxide of the present invention is lithium hydroxide monohydrate having a purity of 99.9% or more, and is produced by washing the solid (S28) obtained by the solid-liquid separation (S25) performed after the second evaporation concentration step (S24), filtering (S29) and drying (S30) the solid obtained at 80 to 100°C until the content of attached moisture is 1% or less. The washing and filtering (S29) are performed by washing with a saturated solution of high purity lithium hydroxide and then filtering, and the process is repeated about three times. The filtrate obtained in the three washing and filtering (S29) processes is mixed with the filtrate (S19) obtained by the solid-liquid separation (S17) after the Al, Si precipitation reaction (S15) and is re-introduced into the first, second and third evaporation concentration steps (S21) (S24) (S26).

[0056] The specific embodiments described herein are merely meant to represent preferred aspects or examples of the present invention, and are not intended to limit the scope of the present invention. Modifications and other applications of the present invention will be apparent to those skilled in the art without departing from the scope of the invention as set forth in the claims of this specification. [Industrial Applicability]

[0057] By utilizing the method of the present invention for recovering positive electrode active material and lithium hydroxide from used fireproof sacks, it is possible to recover and reuse high-value added lithium and positive electrode active material from used fireproof sacks discarded in the manufacturing process of lithium secondary batteries.

Claims

1. A first step of wet-grinding the waste refractory saggers and separating the solid and liquid; A second step of recovering a positive electrode active material by applying wet magnetic separation to the solid obtained by the solid-liquid separation; A third step of recovering lithium hydroxide by subjecting the filtrate obtained by the solid-liquid separation to an Al and Si precipitation reaction and evaporation and concentration; A method for recovering positive electrode active material and lithium hydroxide from a waste refractory sagger, comprising:

2. 2. The method for recovering positive electrode active material and lithium hydroxide from used refractory sacks according to claim 1, wherein the wet pulverization comprises dry pulverizing the used refractory sacks and then wet ball milling the pulverized material to a particle size of 200 mesh or less.

3. 2. The method for recovering positive electrode active material and lithium hydroxide from waste refractory saggers according to claim 1, characterized in that the wet magnetic separation is performed by using a primary wet magnetic separation to remove iron oxide and iron scale as magnetized matter, and then performing a secondary wet magnetic separation on the non-magnetized matter of the primary wet magnetic separation to recover the positive electrode active material as the magnetized matter.

4. The Al, Si precipitation reaction is carried out by mixing the filtrate obtained by the solid-liquid separation with an alkaline earth metal hydroxide and gypsum to obtain water-soluble Al(OH). ４ － is precipitated as poorly soluble ettringite and calcium aluminum silicate hydrate, and water-soluble SiO ４ ２－ 2. The method for recovering positive electrode active material and lithium hydroxide from the waste refractory saggers according to claim 1, characterized in that the above is precipitated as sparingly soluble calcium silicate hydrate.

5. The method for recovering a positive electrode active material and lithium hydroxide from a waste refractory sagger according to claim 1, characterized in that the evaporation and concentration comprises subjecting a filtrate obtained by the solid-liquid separation to the Al, Si precipitation reaction, and then subjecting the filtrate obtained by solid-liquid separation to evaporation and concentration to recover lithium hydroxide.

6. 6. The method for recovering positive electrode active material and lithium hydroxide from waste refractory sacks according to claim 5, wherein the lithium hydroxide has a purity of 99.9% or more.

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