Process and apparatus for producing lithium carbonate from a lithium-containing solution

Abstract

The proposed invention relates to a process for producing lithium carbonate from a lithium-containing solution and to an apparatus for carrying out same. What is proposed is a process for producing lithium carbonate from a lithium-containing solution which comprises the steps of: (a) sorbing and desorbing a lithium-containing solution to obtain an eluate; (b) obtaining from the eluate a concentrate that is purified of impurities; (c) precipitating the concentrate after step (b) to obtain a precipitate and a mother liquor, and separating the precipitate and the mother liquor. The mother liquor from step (c) is fed for mixing with a lithium-containing solution before the latter is fed to step (a). The technical result of the invention is an increase in the efficiency of the lithium production process, high lithium recovery from lithium-containing solutions, and also from solid lithium recovery process waste, and the production of battery-grade lithium carbonate, as well as longer term sorbent efficiency, i.e. an increase in the service life of the sorbent.

Description

[0001] METHOD FOR PRODUCING LITHIUM CARBONATE FROM A LITHIUM-CONTAINING SOLUTION AND AN APPARATUS FOR IMPLEMENTING THE SAME Technical Field The proposed invention relates to a method for extracting lithium from lithium-containing solutions, including natural brines and waters, process solutions, and wastewater from various industries. Prior Art Patent RU2763955, published on January 11, 2022, discloses a method for the sorption extraction of lithium from lithium-containing brines, which includes feeding the initial lithium-containing brine into a sorption-desorption enrichment module, which is at least one vertically installed column filled with an inorganic granular sorbent, which is a chlorine-containing double hydroxide of aluminum and lithium. After the sorption stage, before washing, the remaining lithium-containing brine is drained from the column; washing is carried out at a rate of at least 6 column volumes per hour, in a volumeEqual to 150-250% of the column's sorbent volume, in the same direction as the initial lithium-containing brine flow. Lithium is then desorbed from the sorbent using demineralized water in the same direction as the initial lithium-containing brine flow, producing a lithium-enriched solution. The resulting solution, containing virtually pure lithium chloride, is then evaporated or otherwise concentrated. A disadvantage of the above-mentioned invention is its insufficient lithium recovery; in particular, the problem of lithium removal from the process via solid waste remains unresolved. Patent RU2816073, published on March 26, 2024, discloses a method for the sorption production of lithium concentrate from a lithium-containing solution, which includes: a sorption stage, including passing a lithium-containing solution through a sorbent to extract lithium, a stage of washing said sorbent,A desorption stage. During the washing stage of said sorbent, a washing liquid containing depleted raffinate and / or depleted eluate is used for washing. The depleted raffinate is a solution collected from the first 0.4-1.5 column volumes of the solution obtained in the sorption stage as a result of contact between the lithium-containing brine and said sorbent. The depleted eluate is a solution collected from any of the 4th, 5th, 6th, 7th, or 8th column volumes of the solution obtained in the desorption stage as a result of contact between the desorbing solution and said sorbent. A disadvantage of the above invention is insufficient lithium recovery; in particular, the problem of lithium removal from the process with solid waste remains unresolved. The closest analogue is patent RU2720420C1, published on April 29, 2020, which discloses a method for the sorption extraction of lithium from lithium-containing brines,in which: - a lithium concentrate is obtained by sorption enrichment of brine for lithium in a sorption-desorption enrichment module using a granular sorbent based on a chlorine-containing variety of double aluminum and lithium hydroxide; - the granular sorbent saturated with lithium chloride is washed from the brine; - lithium chloride is desorbed from the sorbent to obtain a primary lithium concentrate - a solution of lithium chloride with impurities of magnesium and calcium; - the primary lithium concentrate is sent to a nanofiltration unit selective with respect to magnesium and calcium; - the concentrate after the nanofiltration unit is re-directed into the flow of the original lithium-containing brine. The filtrate after the nanofiltration unit is sent for subsequent concentration for lithium chloride. The disadvantage of the above invention is an insufficiently high extraction of lithium,Since in the known scheme the nanofiltration concentrate stream contains not only calcium and magnesium, but also a lot of lithium, in fact 40-50% of the lithium obtained after the sorption stage is returned back as the input stream to sorption after passing the nanofiltration stage, which significantly reduces the efficiency of lithium extraction, creating an additional load on the sorption module. Also, additional disadvantages of the above invention are the limited service life of the nanofiltration membranes, increased costs for their washing and regeneration. Disclosure of the invention In the present application: mixing (blending) is the addition of one component to another; mother liquor is the liquid phase (liquid) after separating the precipitate from it; eluate is a solution obtained during the desorption process of the extracted component (lithium); raffinate is a solution obtained during the sorption process of the extracted component (lithium); permeate (filtrate) is a stream of substance,passing through a semipermeable membrane during membrane separation; concentrate – a solution having a lithium concentration higher than the lithium concentration in the solution at the previous technological stage; purification of concentrate from impurities – at least partial removal of impurities from the concentrate. After such a procedure, the concentrate is considered to be purified from impurities, even if some impurities remain in it; purification of eluate from impurities – at least partial removal of impurities from the eluate. After such a procedure, the eluate is considered to be purified from impurities, even if some impurities remain in it; solution – a homogeneous mixture of substances, while incomplete dissolution of one substance in another does not exclude the fact that the solution is obtained in relation to the part that is completely dissolved. Thus, a solution containing a precipitate can be in a container simultaneously with undissolved precipitate,this does not exclude the fact of the presence of a solution and its direction to the appropriate stages. The objective and technical result of the present invention is to increase the efficiency of the lithium production process, high extraction of lithium from lithium-containing solutions, including from solid waste of the lithium extraction process, production of battery-grade lithium carbonate, as well as an increase in the effective service life of the sorbent (increase in the service life of the sorbent). To solve the stated problem and achieve the technical result, a method for producing lithium carbonate from a lithium-containing solution is proposed, comprising the stages of: (a) sorption and desorption of the lithium-containing solution to obtain an eluate; (b) obtaining a concentrate purified from impurities from the eluate; (c) precipitating the concentrate after step (b) to obtain a precipitate and a mother liquor, and separating the precipitate and the mother liquor; characterized in that,that the mother liquor from step (c) is fed for mixing with the lithium-containing solution before feeding it to step (a). The above conditions made it possible to increase the efficiency of the lithium production process, ensure high lithium extraction from lithium-containing solutions, produce battery-grade lithium carbonate, and extend the effective service life of the sorbent (increase the service life of the sorbent). Directing the above mother liquor for mixing with the lithium-containing solution fed to the sorption and desorption stage makes it possible to increase the degree of lithium extraction while maintaining a long service life of the sorbent. The above stages themselves are known in the prior art and are therefore described in general terms. The present invention consists in implementing such a sequence of actions using known units, which leads to an increase in the efficiency of the lithium production process,unexpected and not anticipated in the prior art. The above steps can be carried out by means known to a person skilled in the art, while particular embodiments of the steps indicated below make it possible to achieve the claimed technical result in the most effective way. Preferably, before feeding the mother liquor from step (c) for mixing with the lithium-containing solution, the pH of the mother liquor is adjusted to 1.01-3, preferably to 1.3-2.5, more preferably to 1.4-2.0, most preferably to 1.9. When the pH of the mother liquor is less than 1.01, there is an excessive consumption of acid used to regulate (adjust) the pH of the mother liquor. At a pH greater than 1.01 and less than 3, precipitation during mixing of the concentrate with hydromineral raw materials is eliminated, and the service life of the sorbent is additionally increased. The authors of the invention associate the above effect with a decrease in the residual carbonate and bicarbonate anions,insoluble salts of which can precipitate in the pores of the sorbent, which allows for a further increase in the service life of the sorbent and an increase in the degree of lithium extraction. The above-mentioned preferred pH ranges allow for a further increase in the service life of the sorbent and an increase in the degree of lithium extraction. Preferably, the pH of the mother liquor from step (c) is adjusted to the specified value by adding hydrochloric acid. The pH can be adjusted (adjusted to the specified value) by any means known in the prior art, but it is preferable to use hydrochloric acid for this purpose. Preferably, in step (c), the precipitation of the concentrate is carried out in a reactor, wherein the concentrate is heated to 75°-95°, preferably to 80°-95°, most preferably to 85°-95°, and maintained with stirring for 20-60 minutes, preferably 30-50 minutes,most preferably 30-40 minutes. Heating the concentrate to the specified temperature and holding it under stirring further increases the degree of lithium extraction and increases the equipment utilization rate. Preferably, in step (c), the separation of the precipitate and the mother liquor is carried out in a centrifuge. Instead of a centrifuge, a Nutsche filter, press filters, a combination of these, or any other filter equipment for solid-liquid systems can be used. However, the use of centrifuges allows for further improvement of the efficiency of the lithium extraction process. Preferably, in step (a), a sorbent based on a chlorine-containing variety of double aluminum and lithium hydroxide is used. This allows for maximum utilization of all the advantages of the claimed invention. In the first (best) embodiment,Step (b) comprises the steps of: (b1) reverse osmosis concentration of the eluate to obtain a concentrate and permeate; (b2) purification of the concentrate from impurities. In the first (best) embodiment, after step (b1) and before step (b2), the concentrate is preferably evaporated, and the distillate obtained during evaporation is used to prepare the reagents used in step (c) and / or step (b2). Evaporation means reducing the amount (volume) of the concentrate by evaporating excess liquid. Directing the distillate to prepare the reagents used in step (c) and / or step (b2) makes it possible to further increase the efficiency of the lithium production process by reducing water consumption and energy consumption of the technology. In the first (best) variant, preferably, the permeate from step (b1) is collected in a container until its conductivity reaches a value in the range of 10-600 μS / cm, preferably 20-600 μS / cm, most preferably 40-600 μS / cm,and then the permeate is sent for desorption at stage (a). This allows for an additional increase in the service life of the sorbent by reducing the degree of lithium leaching from the upper part of the working zone of the columns with the sorbent, thereby preventing the leaching effect from occurring below the critical limit, which does not lead to its degradation. In the first (best) variant, it is preferable that the permeate from stage (b1) is collected in a tank until the lithium salt concentration in it reaches a range of 0.01-50 mg / L in terms of elemental lithium, preferably 0.1-50 mg / L in terms of elemental lithium, most preferably 10-50 mg / L in terms of elemental lithium, and then the permeate is sent for desorption at stage (a). This allows for an additional increase in the service life of the sorbent by reducing the degree of lithium leaching from the upper part of the working zone of the columns with the sorbent, thereby preventing the leaching effect from occurring below the critical limit, which does not lead to its degradation. In the first (best) option, it is preferable,at step (b1), a concentrate having an electrical conductivity of 16,000-60,000 μS / cm is obtained. This makes it possible to obtain a given lithium concentration with a lower load on the evaporator and thereby saves energy costs. In the first (best) embodiment, preferably, at step (b2), a precipitate containing impurities is separated from the concentrate and a solution containing said precipitate is obtained, wherein the pH of said solution is adjusted to 1-3, preferably 1.01-2, most preferably 1.01-1.3, and this solution is fed for mixing with the lithium-containing solution before feeding it to step (a). At a pH of less than 1, excessive consumption of acid occurs. At a pH of less than 3, precipitation during mixing of the concentrate with hydromineral raw materials is eliminated, and the service life of the sorbent is additionally increased. The authors of the invention associate this effect with a decrease in the residual carbonate and bicarbonate anions,insoluble salts of which can precipitate in the pores of the sorbent. The above-mentioned narrower pH ranges allow for an additional increase in the service life of the sorbent. This also allows for an additional increase in the throughput of lithium extraction and the elimination of solid production waste. In the first (best) embodiment, it is preferable that at step (b2), before separating the precipitate containing impurities from the concentrate, a sodium hydroxide solution is added to the concentrate until a pH value in the range of 10-12 is achieved, and sodium carbonate is also added and mixed. The eluate can be purified from Ca and Mg impurities by any known methods or combinations thereof, including using sorption technologies for the removal of Ca, Mg, or using reagents for the removal of Ca, Mg impurities, including through ion binding processes; however, the above method allows for an additional increase in the throughput of lithium extraction and the elimination of solid production waste. In the first (best) embodiment, it is preferable that,The pH of the solution obtained by dissolving the precipitate in step (b2) is adjusted to the specified value by adding hydrochloric acid. The pH can be adjusted by any means known in the art, but it is preferable to use hydrochloric acid for this. In the second embodiment, step (b) before step (b1) includes the step of: (b1a) purifying the eluate from impurities. In the second embodiment, preferably, in step (b1a), the precipitate containing impurities is separated from the eluate and a solution containing the said precipitate is obtained, wherein the pH of the said solution is adjusted to 1-3, preferably 1.01-2, most preferably 1.01-1.3, and this solution is fed for mixing with the lithium-containing solution before feeding it to step (a). At a pH of less than 1, excessive consumption of acid occurs. At a pH of less than 3, precipitation is excluded when mixing the concentrate with the hydromineral raw material,and also additionally increases the service life of the sorbent. The authors of the invention associate this effect with a decrease in the residual carbonate and bicarbonate anions, the insoluble salts of which can precipitate in the pores of the sorbent. The above-mentioned narrower pH ranges make it possible to further increase the service life of the sorbent. This also makes it possible to further increase the through extraction rate of lithium and eliminate solid production waste. In the second variant, preferably, at step (b1a), before separating the precipitate containing impurities from the eluate, a sodium hydroxide solution is added to the eluate until a pH value in the range of 10-12 is achieved, and sodium carbonate is also added and mixed. The eluate can be purified from Ca and Mg impurities by any known methods or their combinations, including using sorption technologies for the removal of Ca, Mg, or using reagents for the removal of Ca, Mg impurities, including through ion binding processes,However, the above method allows for an additional increase in the through lithium recovery rate and the elimination of solid production waste. In the second embodiment, preferably, at step (b1a), a precipitate containing impurities is separated from the eluate, while at step (b2), a precipitate containing impurities is separated from the concentrate, said precipitates being dissolved to obtain a mixed solution whose pH is adjusted to 1-3, preferably 1.01-2, most preferably 1.01-1.3, and this mixed solution is fed for mixing with the lithium-containing solution before feeding it to step (a). At a pH of less than 1, excessive acid consumption occurs. At a pH of less than 3, precipitation is eliminated when mixing the concentrate with the hydromineral raw material, and the service life of the sorbent is further increased. The authors of the invention attribute this effect to a decrease in the residual carbonate and bicarbonate anions,insoluble salts of which can precipitate in the pores of the sorbent. The above-mentioned narrower pH ranges allow for an additional increase in the service life of the sorbent. This also allows for an additional increase in the throughput of lithium extraction and the elimination of solid production waste. In the second embodiment, it is preferable that at step (b1a), before separating the precipitate containing impurities from the eluate, a sodium hydroxide solution is added to the eluate until a pH value in the range of 10-12 is achieved, and sodium carbonate is also added and mixed, while at step (b2), before separating the precipitate containing impurities from the concentrate, a sodium hydroxide solution is added to the concentrate until a pH value in the range of 10-12 is achieved, and sodium carbonate is also added and mixed. The eluate and concentrate can be purified from Ca and Mg impurities by any known methods or combinations thereof, including using sorption technologies for removing Ca, Mg, or using reagents for removing Ca, Mg impurities,including through ion binding processes, however, the above method allows for an additional increase in the throughput of lithium extraction and the elimination of solid production waste. In the second embodiment, it is preferable that after step (b1) and before step (b2), the concentrate is evaporated, and the distillate obtained during evaporation is used to prepare the reagents used in step (c) and / or step (b1a) and / or step (b2). Directing the distillate for the preparation of the reagents used in step (c) and / or step (b1a) and / or step (b2) allows for an additional increase in the efficiency of the lithium production process by reducing water consumption and energy consumption of the technology. In the second embodiment, it is preferable that the pH of the solution obtained by dissolving the precipitate is adjusted to the specified value by adding hydrochloric acid. The pH can be adjusted by any means known in the art,but it is preferable to use hydrochloric acid for this. In order to solve the stated problem and achieve the technical result, a plant for producing lithium carbonate from a lithium-containing solution is proposed, comprising: (a) a unit for sorption and desorption of a lithium-containing solution, configured to remove the eluate; (b) a unit for obtaining a concentrate purified from impurities from the eluate; (c) a concentrate precipitation unit, configured to separate the precipitate and the mother liquor; characterized in that the plant is configured to feed the mother liquor from unit (c) for mixing with the lithium-containing solution fed to unit (a). Preferably, the plant is configured to regulate the pH of the mother liquor from unit (c) before feeding it for mixing with the lithium-containing solution fed to unit (a). Preferably, in unit (c), the separation of the precipitate and the mother liquor is carried out in a centrifuge. Preferably,Block (a) comprises a column with a sorbent based on a chlorine-containing variety of double aluminum and lithium hydroxide. In the first (best) embodiment, block (b) includes: (b1) a unit for reverse osmosis concentration of the eluate to obtain a concentrate and a permeate; (b2) a unit for purifying the concentrate from impurities. In the first (best) embodiment, block (b2) preferably includes a unit for evaporating the concentrate before purifying it from impurities, wherein the evaporation unit is configured to feed the distillate obtained during evaporation to a unit for preparing the reagents used in block (b2) and / or block (c). In the first (best) variant, it is preferable that the installation is configured to collect permeate from block (b1) in a container until its conductivity reaches a value in the range of 10-600 μS / cm, preferably 20-600 μS / cm, most preferably 40-600 μS / cm, and then feed the permeate for desorption to block (a). In the first (best) variant, it is preferable thatthe installation is configured to collect permeate from the unit (b1) in a container until the concentration of lithium salts in it reaches a range of 0.01-50 mg / l calculated as elemental lithium, preferably 0.1-50 mg / l calculated as elemental lithium, most preferably 10-50 mg / l calculated as elemental lithium, and then feed the permeate for desorption to the unit (a). In the first (best) embodiment, the installation is preferably configured to control the electrical conductivity of the concentrate obtained in the unit (b1). In the first (best) embodiment, the unit (b2) is configured to separate a precipitate containing impurities from the concentrate, obtain a solution containing said precipitate, regulate the pH of said solution, and feed this solution for mixing with the lithium-containing solution fed to the unit (a). In the second embodiment, the unit (b) includes: (b1) a unit for purifying the eluate from impurities. In the second embodiment, it is preferable,the installation includes a unit (b2) for purifying the concentrate from impurities, comprising a unit for evaporating the concentrate before purifying it from impurities, wherein the evaporation unit is configured to feed the distillate obtained during evaporation into a unit for preparing the reagents used in unit (b1a) and / or unit (b1) and / or unit (c). In the second variant, preferably, the unit (b1a) is configured to separate the precipitate containing impurities from the eluate, to obtain a solution containing said precipitate, to regulate the pH of said solution, and to feed this solution for mixing with a lithium-containing solution fed to unit (a). In the second variant, preferably, the unit (b1a) is configured to separate the precipitate containing impurities from the eluate and to obtain a solution containing said precipitate, wherein the unit (b2) is configured to separate the precipitate containing impurities from the concentrate, to obtain a solution containing said precipitate, wherein the installation includes a unit,configured to mix said solutions to obtain a mixed solution, adjust the pH of the mixed solution, and feed this mixed solution for mixing with a lithium-containing solution fed to unit (a). All the advantages of the claimed installation are similar to the advantages of the claimed method indicated above, and all statements regarding the claimed method are fully applicable to the claimed installation. Brief description of the drawings The drawings are presented for a better understanding of the invention, however, it will be obvious to a person skilled in the art that the disclosed invention is not limited to the embodiment shown in them. Fig. 1 shows a block diagram of the first (best) embodiment of the invention. Figs. 2-4 show a block diagram of the second embodiment of the invention. Embodiments of the invention. The best embodiment of the invention The described embodiments are given for illustrative purposes only. It will be obvious to a person skilled in the art,that other embodiments are possible without changing the essence of the invention. Fig. 1 shows a block diagram of the best embodiment of the invention, Figs. 2-4 show a block diagram of a second embodiment of the invention. The plant for producing lithium carbonate from a lithium-containing solution contains the following interconnected units and lines: 1 - hydromineral raw material feed line (lithium-containing solution) 2 - tank with hydromineral raw material (lithium-containing solution) prepared for the sorption process 2a - hydromineral raw material feed line to the sorption unit 3 - sorption unit 3a - eluate discharge line 3b - raffinate discharge line 4 - reverse osmosis unit 4a - concentrate discharge line 4b - permeate discharge line 5 - evaporation unit 5a - evaporation concentrate discharge line 5b - distillate discharge line 6-1 - unit for removing Ca, Mg from the eluate 6a - purified eluate discharge line 6b - discharge line of sediment separated from the eluate 6-2 - unit for removing Ca,Mg from concentrate 6c – purified concentrate withdrawal line 6d – concentrate separated sediment withdrawal line 7 – technical lithium carbonate precipitation unit 7a – sediment withdrawal line 7b – mother liquor withdrawal line 7c – wash solution (washing solution) withdrawal line 8 – carbonation unit 8a – withdrawal line 9 – ion exchange unit 9a – withdrawal line 10 – decarbonation unit 10a – lithium carbonate withdrawal line 11 – reagent preparation unit 11a – sodium hydroxide solution feed line 11b – sodium carbonate feed line 12 – mother liquor neutralization unit 12a – neutralized mother liquor withdrawal line 13 – Ca, Mg sediment neutralization unit 13a – sediment-containing solution withdrawal line 14 – tank for liquid fed to desorption 14a – liquid drain line,fed to desorption 15 - demineralized water feed line 16a - hydrochloric acid feed line 16b - hydrochloric acid feed line The functional units themselves are known from the prior art and are therefore described in general terms. The present invention consists in implementing such a sequence of actions using known units that leads to an increase in the efficiency of the lithium production process, unexpected and not anticipated in the prior art. The plant operates and the method is carried out as follows Stage (a) of sorption and desorption of a lithium-containing solution A hydromineral raw material (lithium-containing solution) is fed to the plant for producing lithium carbonate from a lithium-containing solution, which is fed through line 1 to tank 2 for preliminary treatment of the hydromineral raw material. Then, the hydromineral raw material is fed through line 2a to the sorption unit 3, which contains columns,filled with a sorbent based on a chlorine-containing variety of double aluminum and lithium hydroxide – AXIONIT Li-sorb for lithium sorption (DGAL-Cl (LiCl 2Al(OH)3 mH2O). After the sorption and desorption cycles, the eluate is removed from sorption unit 3 through line 3a, and the raffinate is removed through line 3b. The eluate is a solution obtained during the desorption process of the extracted component (lithium). The raffinate is a solution obtained during the sorption process of the extracted component (lithium). Stage (b) of obtaining a concentrate purified from impurities from the eluate can be carried out in two ways. Option 1 (the best) Stage (b1) of reverse osmosis concentration of the eluate The eluate is fed through line 3a to the reverse osmosis unit 4,Designed for reverse osmosis concentration of the eluate. From the reverse osmosis unit 4, the concentrate is withdrawn through line 4a, and the permeate is withdrawn through line 4b. Stage (b2) of purification of the concentrate from impurities. The concentrate is fed through line 4a to the evaporation unit 5. From the evaporation unit 5, the concentrate is withdrawn through line 5a, and the distillate is withdrawn through line 5b. The evaporation concentrate is fed through line 5a to the unit 6-2 for removing Ca, Mg from the concentrate, where the concentrate is purified from calcium and magnesium. From the unit 6-2 for removing Ca, Mg, the filtrate, which is lithium-containing concentrate purified from calcium and magnesium, is withdrawn through line 6c, and the precipitate is withdrawn (unloaded) through line 6d. Option 2 Stage (b1a) of cleaning the eluate from impurities The eluate is fed through line 3a to block 6-1 for removing impurities, designed to clean the eluate from impurities such as Ca, Mg. From block 6-1, the eluate, cleaned from impurities, is discharged through line 6a,The sediment is removed (unloaded) through line 6b. Stage (b1) of reverse osmosis concentration of the eluate The purified eluate is fed through line 6a to the reverse osmosis unit 4. From the reverse osmosis unit 4, the concentrate is removed through line 4a, and the permeate is removed through line 4b. The concentrate is fed through line 4a to the evaporation unit 5. From the evaporation unit 5, the evaporation concentrate is removed through line 5a, and the distillate is removed through line 5b. Stage (b2) of purification of the concentrate from impurities The concentrate is fed through line 5a to the impurity removal unit 6-2, designed to purify the concentrate from impurities such as Ca, Mg. From the Ca, Mg removal unit 6-2, the filtrate, which is a lithium-containing concentrate purified from calcium and magnesium, is removed through line 6c, and the sediment is removed (unloaded) through line 6d. Stage (c) of precipitation of the concentrate after stage (b) to obtain a precipitate and a mother liquor,and separation of precipitate and mother liquor. The purified concentrate is fed through line 6c to block 7 for precipitation of technical lithium carbonate. From block 7 for precipitation of technical lithium carbonate, precipitate is removed through line 7a, mother liquor is removed through line 7b, and washing solution is removed through line 7c. The precipitate is fed through line 7a to block 8 of carbonation, from which it is fed through line 8a to block 9 of ion exchange, from which it is fed through line 9a to block 10 of decarbonation. From block 10 of decarbonation, battery-grade lithium carbonate is removed through line 10a. To increase the efficiency of the process of obtaining lithium carbonate from lithium-containing solutions, the following additional operations are carried out. The specified operations can be used separately with the achievement of the technical result, in preferred embodiments they are used in any combination, which allows for the claimed technical result to be achieved more efficiently, in the most preferred embodiment they are used all together,To achieve the highest results. 1. Feeding permeate from reverse osmosis unit 4 for desorption to sorption unit 3. In reverse osmosis unit 4, the eluate fed through line 3a is directed using a centrifugal pump through a bag filter with a pore size of no more than 5 microns onto sequentially located reverse osmosis membranes, the process pressure is 20-60 bar. This results in permeate and concentrate flows. Next, in reverse osmosis unit 4, the concentrate obtained from the previous osmosis stages is fed using a pump to the reverse osmosis membrane with a maximum pressure of one or more stages of 60-150 bar, preferably 80-120, most preferably 100-120 bar. Operation of the reverse osmosis unit continues until the concentrate reaches an electrical conductivity of 16,000-60,000 μS / cm. Permeate (filtrate) is a stream of substance passing through a semipermeable membrane during membrane separation. Concentrate is a solution with a higher lithium concentration.than the concentration of lithium in the solution at the previous process stage. The resulting permeate is withdrawn through line 4b and collected in tank 14 until a predetermined range of electrical conductivity of the collected permeate is achieved, monitoring the conductivity in the range of 10-600 μS / cm, preferably 20-600 μS / cm, most preferably 40-600 μS / cm using a conductometer. The above conductivity is ensured by the presence of lithium salts in the range of 0.01-50 mg / l lithium, preferably 0.1-50 mg / l, most preferably 10-50 mg / l, which are monitored by sample analysis methods using inductively coupled plasma spectrometry or other analytical research methods that allow the analysis of the elemental composition. After reaching the specified range of electrical conductivity of the collected permeate, it is sent through line 14a to sorption unit 3 for desorption of columns filled with AXIONIT Li-sorb sorbent, which allows to increase the service life of the sorbent,and also to increase the degree of lithium extraction and to reduce the water consumption of the technology. 2. Feeding the solution from the neutralized sediment from the Ca, Mg removal unit 6 for mixing with the initial hydromineral raw material Option 1 (the best) As shown in Fig. 1, the concentrate is fed through line 4a to the evaporation unit 5, where the concentrate is evaporated. Evaporation can be omitted, but it allows to further increase the efficiency of the process. The evaporation concentrate is withdrawn from the evaporation unit 5 through line 5a, and the distillate is withdrawn through line 5b to the reagent preparation unit 11, which allows to further reduce water consumption. The evaporation concentrate is fed through line 5a to the Ca, Mg removal unit 6-2. The concentrate fed through line 5a is purified from calcium and magnesium in the Ca, Mg removal unit 6-2, which contains an interconnected sedimentation reactor, a centrifuge, a Nutsche filter, pipes and pumps (not shown). The evaporation concentrate (obtained after evaporation) is poured into the reactor using a pump,fed through line 5a, and switching on the mixing. During mixing, sodium hydroxide solution is introduced from reagent preparation unit 11 through line 11a using a pump until a pH of (10.75±0.25) units is reached in order to remove magnesium from the solution. When mixing the sodium hydroxide solution with the concentrate, a gel-like precipitate of magnesium hydroxide is formed. Next, the calculated amount of sodium carbonate is poured into the reactor (the maximum permissible excess of sodium carbonate is no more than 10%) and the resulting pulp is mixed for 15 minutes. After mixing is complete, the pulp is discharged from the sedimentation reactor into a centrifuge and centrifuged for 30 minutes at 300 rpm, 20 minutes at 450 rpm, 10 minutes at 600 rpm, and 10 minutes at 900 rpm. Instead of a centrifuge, you can use: press filters, Nutsche filters,A combination of a thickener and a centrifuge / press filter / nutsche filter, etc. The centrifugal effluent flows by gravity into a drainage pump, from where it is then fed to a nutsche filter. After centrifugation, 2 liters of distilled water are added to the centrifuge and the sediment is washed. The wash water is also fed to a nutsche filter. The solution is filtered on a nutsche filter and sent to a filtrate receiver / collector, from where it is then pumped into a storage tank. The resulting filtrate, a lithium-containing concentrate purified from calcium and magnesium, is discharged through line 6c. The precipitate obtained after centrifugation and filtration is discharged via line 6d into the Ca, Mg precipitate neutralization unit 13, and hydrochloric acid is added via line 16a so that the pH of the solution is 1-3, preferably 1.01-2, most preferably 1.01-1,3. After complete dissolution of the precipitate, the resulting solution is fed via line 13a for mixing with the initial hydromineral raw material in tanks 2 for mixing flows, which makes it possible to increase the through degree of lithium extraction, as well as to eliminate solid production waste. Variant 2 In the Ca, Mg removal unit 6-1, the eluate is purified from calcium and magnesium in the same way as for the concentrate in variant 1. In the Ca, Mg removal unit 6-2, the concentrate is purified from calcium and magnesium in the same way as for the concentrate in variant 1. In one variant (a), shown in Fig. 2, the precipitate containing impurities from the eluate purification, discharged from the unit 6-1 via line 6b, is discharged into the Ca, Mg precipitate neutralization unit 13 and hydrochloric acid is added via line 16a so that the pH of the solution is 1-3, preferably 1.01-2, most preferably 1.01-1.3. After the sediment has completely dissolved, the resulting solution is fed through line 13a for mixing with the initial hydromineral raw material in tank 2 for mixing the flows,which makes it possible to increase the throughput degree of lithium extraction, as well as to eliminate solid production waste. In another embodiment (b), shown in Fig. 4, the sediment containing impurities from concentrate purification, withdrawn from block 6-2 via line 6d, is discharged into block 13 for neutralizing the Ca, Mg sediment, and hydrochloric acid is added via line 16a so that the pH of the solution is 1-3, preferably 1.01-2, most preferably 1.01 - 1.3. After complete dissolution of the sediment, the resulting solution is fed via line 13a for mixing with the initial hydromineral raw material in tank 2 for mixing the flows, which makes it possible to increase the throughput degree of lithium extraction, as well as to eliminate solid production waste. In the preferred embodiment (c), shown in Fig. 3, the sediment containing impurities from the purification of the eluate, removed from block 6-1 via line 6b, as well as the sediment containing impurities from the purification of the concentrate, removed from block 6-2 via line 6d, are discharged into the sediment neutralization block 13 Ca,Mg. Hydrochloric acid is added to block 13 via line 16a with stirring to obtain a mixed solution, and hydrochloric acid is added so that the pH of the mixed solution is 1-3, preferably 1.01-2, most preferably 1.01 - 1.3. After complete dissolution of the precipitate, the resulting mixed solution is fed via line 13a for mixing with the initial hydromineral raw material in tanks 2 for mixing flows, which makes it possible to increase the through degree of lithium extraction, as well as to eliminate solid production waste. 3. Feeding neutralized mother liquor from block 7 for precipitation of technical lithium carbonate for mixing with the initial hydromineral raw material. Lithium-containing concentrate, purified from calcium and magnesium, is fed via line 6c to block 7 for precipitation of technical lithium carbonate,A reactor and centrifuge are connected. To obtain lithium carbonate (technical grade), the concentrate, purified from calcium and magnesium, is treated with a sodium carbonate solution. The precipitation process occurs according to the reaction: 2LiCl + Na2CO3 = Li2CO3 ↓ + 2NaCl. Lithium carbonate (technical grade) precipitation is carried out in a reactor included in unit 7 for precipitation of technical lithium carbonate. In the reactor of unit 11 for preparation of reagents, a sodium carbonate solution is prepared and fed through line 11b to the lithium carbonate precipitation reactor of unit 7 for precipitation of technical lithium carbonate. Through line 6a, lithium-containing concentrate purified from calcium and magnesium is fed into the reactor using a pump, the solution is heated to 75°-95°, preferably 80°-95°, most preferably 85°-95°, and maintained with stirring for 20-60 minutes, preferably 30-50 minutes, most preferably 30-40 minutes, resulting in a hot pulp. The hot pulp is then discharged into a centrifuge,where it is separated into a precipitate and a mother liquor. Other filtering equipment known from the prior art can be used instead of a centrifuge. The mother liquor is collected and discharged via line 7b to the mother liquor neutralization unit 12, where it is acidified to a pH of 1.01-3, preferably to 1.3-2.5, more preferably to 1.4-2.0, and most preferably to 1.9 with hydrochloric acid supplied via line 16b. The resulting mother liquor is fed via line 12a for mixing with the initial hydromineral raw material in the flow mixing tank 2, which allows for an increase in the lithium extraction rate of the process. The precipitate, which is wet technical lithium carbonate, is filtered from the technical lithium carbonate precipitation unit 7, washed, and discharged via line 7a. Through line 7a, the sediment is fed to the carbonation unit 8, the ion exchange unit 9 and the decarbonation unit 10 for additional removal of Na, K, Ca, Mg, from the commercial product.B. Battery-grade lithium carbonate is removed from decarbonization unit 10 via line 10a. The test results of the claimed method and installation are presented in Tables 1 and 2 below.

[0002] Table 1 Parameters Prot Examples of implementing the invention method type 1 2 3 4 5 6 7 8 9 10 (best) 1. Feeding - yes yes yes - - - - - - yes permeate from reverse osmosis unit 4 for desorption in sorption unit 3 concentration - 0.01 30 50 - - - - - - 50 lithium in the range in the liquid fed for desorption in sorption unit 3, mg / l concentration - 10 100 600 - - - - - - 600 lithium in the range in the liquid fed for desorption in sorption unit 3, μS / cm 2. (First - - - - yes yes yes - - - yes option) Feeding solution from sediment from unit 6-2 for removing Ca, Mg from concentrate for mixing with the initial hydromineral raw material pH of the solution from - - - - 1 1.5 3 - - - 1.3 sediment from block 6 for removing Ca, Mg 3.Feeding - - - - - - - yes yes yes yes of neutralized mother liquor from technical lithium carbonate precipitation unit 7 for mixing with the initial hydromineral raw material pH of the mother liquor - - - - - - - 1.01 1.5 3 1.9 Service life up to up to up to up to up to up of the sorbent, 1000 5000 over 7500 5000 5000 5000 5000 5000 5000 over number 5000 7500 cycles of uninterrupted operation Increase 0% 0% +7% +12.5 +5% +5% +5% +8% +8% +8% +25 degree % % of through lithium extraction Table 2 Method parameters Examples of implementing the invention 11 12 13 14 15 16 17 18 19 20 1. Feeding permeate from - - - - - - - - - yes block 4 of reverse osmosis for desorption in sorption block 3 lithium concentration in - - - - - - - - - 600 range in (50) liquid fed for desorption in sorption block 3, µS / cm (mg / l) 2.(Second option, yes yes yes - - - - - - - a) Feeding the solution from the sediment from unit 6-1 for removing Ca, Mg from the eluate for mixing with the initial hydromineral raw material pH of the solution from the sediment 1 1.5 3 - - - - - - - from unit 6-1 2. (Second option, - - - yes yes yes - - - - b) Feeding the solution from the sediment from unit 6-2 for removing Ca, Mg from the concentrate for mixing with the initial hydromineral raw material pH of the solution from the sediment - - - 1 1.5 3 - - - - from unit 6-2 2. (Second option, - - - - - - yes yes yes yes c) Feeding the mixed solution obtained from the sediment from unit 6-1 for removing Ca, Mg from the eluate and the sediment from unit 6-2 for removing Ca, Mg from the concentrate for mixing with the initial hydromineral raw material pH of the mixed - - - - - - 1 1.5 3 3 solution from the sediment from block 6-1 and from the sediment from block 6-2 3.Feeding - - - - - - - - - yes neutralized mother liquor from technical lithium carbonate precipitation unit 7 for mixing with the initial hydromineral raw material pH of the mother liquor - - - - - - - - 1.9 Service life up to up to up to up to up to up to up of sorbent, quantity 5000 5000 5000 5000 5000 5000 5000 5000 5000 more cycles 7500 of uninterrupted operation Increase in the degree of +1% +1% +1% +2% +2% +2% +3% +3% +3% +23 through extraction % of lithium Thus, the claimed invention ensured: ^ increased efficiency of the lithium production process, ^ high extraction of lithium from lithium-containing solutions, including from solid waste of the lithium extraction process, ^ production of battery-grade lithium carbonate, ^ increased service life of the effective operation sorbent (increasing the service life of the sorbent), ^ absence of solid production waste in the form of calcium and magnesium salts, ^ reduction of water consumption and energy consumption of the technology.

Claims

Claims of the invention 1. A method for producing lithium carbonate from a lithium-containing solution, comprising the steps of: (a) sorption and desorption of the lithium-containing solution to obtain an eluate; (b) obtaining a concentrate purified from impurities from the eluate; (c) precipitating the concentrate after step (b) to obtain a precipitate and a mother liquor, and separating the precipitate and the mother liquor; characterized in that the mother liquor from step (c) is fed for mixing with the lithium-containing solution before feeding it to step (a).

2. The method according to claim 1, characterized in that before feeding the mother liquor from step (c) for mixing with the lithium-containing solution, the pH of the mother liquor is adjusted to 1.01-3, preferably to 1.3-2.5, more preferably to 1.4-2.0, most preferably to 1.

9.

3. The method according to claim 2, characterized in that the pH of the mother liquor from step (c) is adjusted to the specified value by adding hydrochloric acid.

4. The method according to claim1, characterized in that in step (c) the precipitation of the concentrate is carried out in a reactor, wherein the concentrate is heated to 75°-95°, preferably to 80°-95°, most preferably to 85°-95°, and maintained with stirring for 20-60 minutes, preferably 30-50 minutes, most preferably 30-40 minutes.

5. The method of claim 1, characterized in that in step (c) the separation of the precipitate and the mother liquor is carried out in a centrifuge.

6. The method of claim 1, characterized in that in step (a) a sorbent based on a chlorine-containing variety of double aluminum and lithium hydroxide is used.

7. The method of claim 1, characterized in that step (b) includes the steps of: (b1) reverse osmosis concentration of the eluate to obtain a concentrate and a permeate; (b2) purifying the concentrate from impurities.

8. The method according to claim 7, characterized in that after step (b1) and before step (b2), the concentrate is evaporated, and the distillate obtained during evaporation is used to prepare the reagents used in step (c) and / or step (b2).

9. The method according to claim 7, characterized in that the permeate from step (b1) is collected in a container until its conductivity reaches a value in the range of 10-600 μS / cm, preferably 20-600 μS / cm, most preferably 40-600 μS / cm, and then the permeate is sent for desorption in step (a).

10. The method according to claim 7, characterized in that the permeate from step (b1) is collected in a container until the concentration of lithium salts in it is in the range of 0.01-50 mg / l calculated as elemental lithium, preferably 0.1-50 mg / l calculated as elemental lithium, most preferably 10-50 mg / l calculated as elemental lithium, and then the permeate is sent for desorption in step (a).

11. The method according to claim7, characterized in that in step (b1) a concentrate is obtained having an electrical conductivity value of 16,000-60,000 μS / cm.

12. The method of claim 7, characterized in that in step (b2) a precipitate containing impurities is separated from the concentrate and a solution containing said precipitate is obtained, wherein the pH of said solution is adjusted to 1-3, preferably 1.01-2, most preferably 1.01-1.3, and this solution is fed for mixing with the lithium-containing solution before feeding it to step (a).

13. The method of claim 12, characterized in that in step (b2) before separating the precipitate containing impurities from the concentrate, a sodium hydroxide solution is added to the concentrate until a pH value in the range of 10-12 is achieved, and sodium carbonate is also added and mixed.

14. The method according to claim 13, characterized in that the pH of the solution obtained by dissolving the precipitate in step (b2) is adjusted to the specified value by adding hydrochloric acid.

15. The method according to claim 1, characterized in that step (b) before step (b1) includes the step:.(b1a) purifying the eluate from impurities.

16. The method of claim 15, characterized in that in step (b1a) a precipitate containing impurities is separated from the eluate and a solution containing said precipitate is obtained, wherein the pH of said solution is adjusted to 1-3, preferably 1.01-2, most preferably 1.01-1.3, and this solution is fed for mixing with the lithium-containing solution before feeding it to step (a).

17. The method of claim 16, characterized in that in step (b1a) before separating the precipitate containing impurities from the eluate, a sodium hydroxide solution is added to the eluate until a pH value in the range of 10-12 is achieved, and sodium carbonate is also added and mixed.

18. The method of claim7, characterized in that in step (b1a) a precipitate containing impurities is separated from the eluate, while in step (b2) a precipitate containing impurities is separated from the concentrate, wherein said precipitates are dissolved to obtain a mixed solution, the pH of which is adjusted to 1-3, preferably 1.01-2, most preferably 1.01-1.3, and this mixed solution is fed for mixing with the lithium-containing solution before feeding it to step (a).

19. The method according to claim 18, characterized in that at step (b1a), before separating the precipitate containing impurities from the eluate, a sodium hydroxide solution is added to the eluate until a pH value in the range of 10-12 is achieved, and sodium carbonate is also added and mixed, while at step (b2), before separating the precipitate containing impurities from the concentrate, a sodium hydroxide solution is added to the concentrate until a pH value in the range of 10-12 is achieved, and sodium carbonate is also added and mixed.

20. The method according to claim21, characterized in that after step (b1) and before step (b2), the concentrate is evaporated, and the distillate obtained during evaporation is used to prepare the reagents used in step (c) and / or step (b1a) and / or step (b2).

21. The method according to claim 16 or claim 18, characterized in that the pH of the solution obtained by dissolving the precipitate is brought to the specified value by adding hydrochloric acid.

22. An installation for producing lithium carbonate from a lithium-containing solution, comprising: (a) a unit for sorption and desorption of the lithium-containing solution, configured to remove the eluate; (b) a unit for obtaining a concentrate purified from impurities from the eluate; (c) a concentrate precipitation unit, configured to separate the precipitate and the mother liquor; characterized in that the installation is configured to feed the mother liquor from unit (c) for mixing with the lithium-containing solution fed to unit (a).

23. The installation according to claim 22, characterized in that the installation is configured to regulate the pH of the mother liquor from unit (c) before feeding it for mixing with the lithium-containing solution fed to unit (a).

24. The installation according to claim22, characterized in that in block (c) the separation of the sediment and the mother liquor is carried out in a centrifuge.

25. The plant according to claim 22, characterized in that block (a) contains a column with a sorbent based on a chlorine-containing variety of double hydroxide of aluminum and lithium.

26. The plant according to claim 22, characterized in that block (b) includes: (b1) a unit for reverse osmosis concentration of the eluate to obtain a concentrate and a permeate; (b2) a unit for purifying the concentrate from impurities.

27. The plant according to claim 26, characterized in that block (b2) includes a unit for evaporating the concentrate before purifying it from impurities. wherein the evaporation unit is configured to feed the distillate obtained during evaporation into the unit for preparing the reagents used in block (b2) and / or block (c).

28. The plant according to claim 26, characterized in that the plant is configured to collect the permeate from block (b1) in a container until its conductivity reaches a value in the range of 10-600 μS / cm, preferably 20-600 μS / cm, most preferably 40-600 μS / cm, and then feed the permeate for desorption into block (a).

29. The plant according to claim 26, characterized in that the plant is designed with the possibility of collecting permeate from the unit (b1) in a container until the concentration of lithium salts in it is in the range of 0.01-50 mg / l in terms of elemental lithium, preferably 0.1-50 mg / l in terms of elemental lithium, most preferably 10-50 mg / l in terms of elemental lithium, and then feeding the permeate for desorption to the unit (a).

30. The plant according to claim26, characterized in that the installation is configured to control the electrical conductivity of the concentrate obtained in the block (b1).

31. The installation according to claim 26, characterized in that the block (b2) is configured to separate from the concentrate a precipitate containing impurities, to obtain a solution containing the said precipitate, to regulate the pH of the said solution, and to feed this solution for mixing with the lithium-containing solution fed to the block (a).

32. The installation according to claim 26, characterized in that the block (b) includes: (b1) a unit for purifying the eluate from impurities.

33. The installation according to claim 32, characterized in that the block (b2) includes a unit for evaporating the concentrate before purifying it from impurities, comprising a unit for evaporating the concentrate before purifying it from impurities, 34. The installation according to claim 32, characterized in that the block (b1a) is configured to separate from the eluate a precipitate containing impurities, to obtain a solution containing said precipitate, to regulate the pH of said solution, and to feed this solution for mixing with the lithium-containing solution fed to the block (a).

35. The installation according to claim32, characterized in that the block (b1a) is configured to separate from the eluate a precipitate containing impurities and to obtain a solution containing said precipitate, wherein the block (b2) is configured to separate from the concentrate a precipitate containing impurities and to obtain a solution containing said precipitate, wherein the installation comprises a block configured to mix said solutions to obtain a mixed solution, to regulate the pH of the mixed solution, and to feed this mixed solution for mixing with a lithium-containing solution fed to the block (a).

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