CN115490246A - Impurity removing equipment and method for preparing high-end lithium battery positive electrode material from salt lake brine - Google Patents
Impurity removing equipment and method for preparing high-end lithium battery positive electrode material from salt lake brine Download PDFInfo
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Abstract
The application relates to the technical field of preparing a high-end lithium battery from salt lake brine, in particular to impurity removing equipment and method for preparing a high-end lithium battery positive electrode material from salt lake brine, and the impurity removing equipment comprises the following steps: s1, filtering a brine filter to obtain lithium-rich brine with a magnesium-lithium ratio of 1: 10-1: 1; s2, separating cations and anions in the solution obtained in the S1; s3, removing calcium and magnesium in the mixed solution obtained in the step S2; s5, processing the solution obtained in the previous step to obtain a lithium carbonate product, and further removing impurities in the lithium carbonate product through steps of secondary countercurrent washing, centrifugal drying, airflow crushing, magnetism removal and the like.
Description
Technical Field
The invention belongs to the technical field of preparing a high-end lithium battery from salt lake brine, and relates to impurity removal equipment and a method for preparing a high-end lithium battery positive electrode material from salt lake brine.
Background
The lithium salt lake resources in China are abundant, and the salt lake brine resources account for 90 percent and are mainly concentrated in Qinghai and Tibet regions. The annual lithium extraction yield of the salt lake in China is low and the domestic market demand cannot be met due to the restriction of various factors such as incomplete production environment and production equipment, high magnesium-lithium ratio, high lithium extraction technical difficulty, large investment scale, high production cost and the like in the plateau area.
Along with the promotion of domestic and foreign requirement to the capacity density and the security performance of lithium cell, the requirement to lithium carbonate product quality is more and more high, and current battery level lithium carbonate can't satisfy high-end lithium electricity cathode material field application requirement completely. In recent gradual industrialization of power lithium batteries, the demand of lithium battery anode materials is rapidly amplified, and the investment value of upstream mineral resources is highlighted due to the trend that the demand acceleration is larger than the supply acceleration. With the application of lithium ion batteries in the fields of electronic products, new energy electric vehicles and the like, the demand of battery-grade lithium carbonate, which is an important basic raw material of lithium ion batteries, is rapidly increasing. The battery-grade lithium carbonate is a key raw material for producing the positive electrode material of the lithium ion battery, and the battery-grade lithium carbonate is used as an electrolyte additive of the lithium ion battery, so that the safety performance of the battery can be obviously improved, and the service life of the battery can be prolonged.
Disclosure of Invention
The invention aims to provide impurity removing equipment and method for preparing a high-end lithium battery positive electrode material by using salt lake brine.
In order to realize the purpose of the invention, the technical scheme adopted by the invention is as follows:
an impurity removal method for preparing a high-end lithium battery positive electrode material by using salt lake brine comprises the following steps:
s1, old brine treatment: the bittern is naturally concentrated by solarization and concentration in multi-stage evaporation and grading, potash salt system is used to prepare potash magnesium sulphate fertilizer, the tail liquid after potassium extraction is solarized in carnallite pond and then enters into old bittern storage pond, and impurity Fe affecting the separation of Mg and Li in bittern is removed by settling and filtering 2+ The turbidity of the filtered brine is less than or equal to 0.3NTU 2+ The content is less than or equal to 0.01mg/L, the pH value is 3-3.5, and lithium-rich brine with the magnesium-lithium ratio of 1: 10-1: 1 is obtained after two-stage selective separation;
s2, magnesium and lithium separation: placing cations and anion exchange membranes in the separated filtrate in the step S1, wherein the cations pass through the cation exchange membranes under the action of an electric field, the anions migrate to the electrode through the anion exchange membranes, monovalent cations migrate through the monovalent selective cation exchange membranes, and secondary and trivalent cations are blocked, so that lithium-containing brine is obtained;
s3, refining to remove calcium and magnesium: adding caustic soda solution into the lithium-containing brine obtained in the step S2, adding a small amount of soda ash solution in the reaction process, separating the slurry solution after the reaction, wherein the solid-phase product obtained by separation is magnesium hydroxide, the separated liquid phase is refined filtrate, the pH value in the reaction process is controlled to be 12-13, and the reaction is carried out for 45min;
s4, evaporating mother liquor to remove calcium and magnesium: adding 31% hydrochloric acid into the refined filtrate obtained in the step S3, evaporating, performing three-stage evaporation to obtain a concentrated solution with a magnesium content of 15ppm, adding excessive EDTA into the evaporated concentrated solution, and smashing and homogenizing the reacted materials;
s5, precipitating lithium and converting: adding soda ash into the solution treated in the step S4, wherein an EDTA solution and a polyhydric hydroxyl alcohol mixed solution are added in the preparation process of the soda ash during the solution preparation process, so as to obtain a lithium carbonate product, wherein the EDTA solution and the polyhydric hydroxyl alcohol mixed solution are required to be added in an excessive amount, and the excessive coefficient is 1.25%;
s6, secondary countercurrent washing: partial sodium impurity is still contained in the lithium carbonate produced in the step S5, the direct stirring and washing method of the condensed water has the advantages of easy control and adjustment of product quality, high first-pass percent of the product and the like, and the secondary countercurrent washing is adopted to remove the soluble sodium and chlorine impurities in the lithium carbonate;
s7, centrifugal drying: performing centrifugal dehydration and drying on the product lithium carbonate obtained in the step S6;
s8, airflow crushing: and (4) performing air flow grinding on the product lithium carbonate subjected to the step S7, wherein the median particle diameter D50 is 3.0-8.0 microns.
Preferably, the lithium-containing brine obtained by magnesium-lithium separation in the step S2 has a lithium content of 9.5-10g/L and a magnesium content of 2.5-3.5g/L.
Preferably, the magnesium content of the separated liquid-phase refined filtrate obtained in the refining calcium and magnesium removal process in the step S3 is less than 2 ppm.
Preferably, the solution is concentrated by three-stage evaporation in step S4 until the lithium content of the evaporation mother liquor is 25 +/-1 g/L, and the pH value of the reaction process is controlled to be 6.5-7.0 during the calcium and magnesium removal of the evaporation mother liquor.
Preferably, scrap iron removal is simultaneously carried out in the secondary countercurrent washing process, and demagnetization is simultaneously carried out in the centrifugal drying and airflow crushing processes, so that the magnetic substance of the demagnetized material of the final product lithium carbonate is less than 100ppb, and the magnetic metal particles are less than or equal to 130PCS/Kg.
The utility model provides an edulcoration equipment of high-end lithium electricity cathode material is prepared to salt lake brine, includes old bittern processing system, magnesium lithium piece-rate system, degaussing system, and old bittern processing system, magnesium lithium piece-rate system, degaussing system connect gradually, old bittern processing system includes salt pan reservoir, swash plate subsider, sedimentation tank, brine filter shop, multi-media filter, plate and frame filter press, and loops through the pipeline connection, connects basic magnesium carbonate production system and lithium carbonate production system behind the material process plate and frame filter press.
Preferably, the magnesium lithium separation system comprises a plurality of cation and anion exchange membranes alternately arranged.
Preferably, the demagnetizing system comprises a soda ash filtering unit, a compressed air filtering unit, workshop RO water, a condensed water filtering unit, a steam filtering unit, a centrifugal separation unit, a slurry demagnetizing unit, a powder demagnetizing unit and a liquid iron remover.
Preferably, the liquid de-ironing separator is fluid type de-ironing separator, fluid type de-ironing separator includes framework 1, a plurality of bar magnets 2, feed inlet 3, discharge gate 4, the upper portion of framework 1 is the opening, and is equipped with lid 5 and is connected through a plurality of fixed subassemblies 8 with the opening, a plurality of bar magnets 2 are vertical to be fixed in framework 1 and align to grid, export 6 has been seted up to the side of framework 1, lid 5 deviates from open-ended one end and is equipped with handle 7, a plurality of bar magnets 2 are arranged in 1 round shape of framework, be equipped with the ball valve on the export 6.
1. Preferably, 10 the fixing assembly 8 comprises a clamping nut 9, a flat washer 10, a loose joint bolt 11, a B-shaped pin shaft 12 and a baffle 13, the clamping nut 9 penetrates through the edge of the cover body 5 and the edge of the frame body 1 to be in threaded connection with the loose joint bolt 11, the loose joint bolt 11 is fixedly provided with two baffles 13, the clamping nut 9 is connected to the middle positions of the two baffles 13, and the loose joint bolt 11 and the baffles 13 are limited and fixed through the B-shaped pin shaft 12.
Compared with the prior art, the invention has the following technical effects:
1. the invention realizes the innovation and the upgrade of impurity removal technologies such as a high magnesium-lithium ratio salt lake brine integrated membrane separation method, a chelation method, a precipitation method and the like, optimizes the process and introduces new equipment, adopts the corresponding impurity removal technology in each process to reduce the content of impurity ions in the product, systematically reduces the content of each impurity ion in the product by the method, and achieves the application requirement of lithium carbonate in the field of high-end lithium battery cathode materials by one-time off-line lithium carbonate product quality.
2. The salt lake brine has complex components and various types of ions, so that the conventional method for improving the product quality by adopting various impurity removal technologies dispersedly in the production process of a salt lake lithium extraction enterprise is difficult to comprehensively and systematically control and reduce the content of various impurity ions required by national standards.
3. In the process of preparing the calcium and magnesium removal solution from the soda ash, the EDTA solution and the polyhydric hydroxyl alcohol solution are excessively added, so that the width of a metastable zone is increased, the lithium-containing brine and the soda ash are fully chelated, and the calcium, magnesium and boron content of the product is greatly reduced.
4. The process comprises the steps of adding a mixed solution (EDTA solution and polyhydric hydroxyl alcohol solution) in the preparation process of the soda ash solution, wherein the addition excess coefficient of an additive is 1.25%, the mixed solution (the EDTA solution and the polyhydric hydroxyl alcohol solution) is fully mixed with the soda ash solution through a plunger pump, and then the mixed solution is left in a precision filter to enter a conversion reaction kettle for conversion and lithium precipitation reaction.
5. The invention introduces the process suitable for the existing production line, has reasonable process and simple operation, well controls the particle size of the product through simple process steps, and is suitable for industrial production.
6. Magnetic impurities in the material can be removed by arranging the fluid iron remover, so that the product quality of lithium carbonate is effectively improved.
Drawings
FIG. 1 is a process flow diagram of impurity removal equipment and a method for preparing a high-end lithium battery positive electrode material by using salt lake brine;
FIG. 2 is a schematic diagram of a secondary counter-current washing process according to the present invention;
fig. 3 is a distribution diagram of impurity removal equipment and magnetic removal equipment of the impurity removal equipment and the method for preparing the high-end lithium battery positive electrode material from the salt lake brine.
FIG. 4 is a schematic structural diagram of a fluid-type iron remover in the impurity removal equipment and method for preparing a high-end lithium battery cathode material from salt lake brine according to the invention;
FIG. 5 is a side view of a fluid iron remover in an impurity removal device and method for preparing a high-end lithium battery positive electrode material from salt lake brine according to the invention;
FIG. 6 is a top view of a fluid-type iron remover in an apparatus and a method for removing impurities in a high-end lithium battery positive electrode material prepared from salt lake brine according to the present invention;
fig. 7 is an enlarged schematic view of a fluid-type iron remover fixing assembly 8 in the impurity removal equipment and method for preparing the high-end lithium battery positive electrode material from salt lake brine.
Wherein, 1, a frame body; 2. a magnetic bar; 3. a feed inlet; 4. a discharge port; 5. a cover body; 6. a lead-out port; 7. a handle; 8. a fixing assembly; 9. comprises a snap nut; 10. a flat washer; 11. a slipknot bolt; 12. b-shaped pin shafts; 13. and a baffle plate.
Detailed Description
In order to make the objects, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are some embodiments of the present invention, but not all embodiments.
Example 1
An impurity removal method for preparing a high-end lithium battery positive electrode material by using salt lake brine comprises the following steps:
s1, old brine treatment: the brine is concentrated by multistage evaporation and grading natural beach solarization, potash salt system is used for preparing potash magnesium sulphate fertilizer, the tail liquid after potassium extraction is tedded in a carnallite pond and then enters an old brine storage pond, and impurity Fe influencing the separation of magnesium and lithium in the brine is removed by sedimentation and filtration 2+ The turbidity of the filtered brine is less than or equal to 0.3NTU 2+ The content is less than or equal to 0.01mg/L, the pH value is 3-3.5, and lithium-rich brine with the magnesium-lithium ratio of 1: 10-1: 1 is obtained after two-stage selective separation;
s2, magnesium and lithium separation: placing a plurality of alternately placed cation and anion exchange membranes in the separated filtrate in the step S1, wherein cations pass through the cation exchange membranes under the action of an electric field, anions migrate to an electrode through the anion exchange membranes, monovalent cations migrate through a monovalent selective cation exchange membrane, and secondary and trivalent cations are blocked, so that lithium-containing brine is obtained, and the lithium content of the lithium-containing brine obtained through magnesium-lithium separation is 9.5-10g/L and the magnesium content is 2.5-3.5g/L;
s3, refining to remove calcium and magnesium: adding caustic soda solution into the lithium-containing brine obtained in the step S2, adding a small amount of soda ash solution in the reaction process, separating the slurry solution after the reaction, wherein the solid-phase product obtained by separation is magnesium hydroxide, the separated liquid phase is refined filtrate, the pH value in the reaction process is controlled to be 12-13, the reaction is carried out for 45min, and the magnesium content in the refined filtrate of the separated liquid phase obtained in the refined calcium and magnesium removal process is within 2 ppm;
s4, evaporating mother liquor to remove calcium and magnesium: adding 31% hydrochloric acid into the refined filtrate obtained in the step S3, evaporating, carrying out three-stage evaporation until the magnesium content in the concentrated solution reaches 15ppm, adding excessive EDTA into the evaporated concentrated solution, smashing and homogenizing the reacted materials, concentrating the solution through three-stage evaporation until the lithium content of the evaporation mother solution is 25 +/-1 g/L, and removing calcium and magnesium from the evaporation mother solution, wherein the pH value of the reaction process is controlled to be 6.5-7.0;
s5, lithium deposition and conversion: adding soda ash into the solution treated in the step S4, wherein an EDTA solution and a polyhydric hydroxyl alcohol mixed solution are added in the preparation process of the soda ash during the solution preparation process, so as to obtain a lithium carbonate product, wherein the EDTA solution and the polyhydric hydroxyl alcohol mixed solution are required to be added in an excessive amount, and the excessive coefficient is 1.25%;
s6, secondary countercurrent washing: partial sodium impurity is still contained in the lithium carbonate produced in the step S5, the direct stirring and washing method of the condensed water has the advantages of easy control and adjustment of product quality, high first-pass percent of the product and the like, and the secondary countercurrent washing is adopted to remove the soluble sodium and chlorine impurities in the lithium carbonate;
s7, centrifugal drying: performing centrifugal dehydration and drying on the product lithium carbonate obtained in the step S6;
s8, airflow crushing: and (4) performing air flow grinding on the product lithium carbonate subjected to the step S7, wherein the median particle diameter D50 is 3.0-8.0 microns.
Removing iron filings in the process of secondary counter-current washing, and removing magnetism in the processes of centrifugal drying and air flow crushing, wherein the magnetic substance of the material after the magnetism of the final product lithium carbonate is removed is less than 100ppb, and the magnetic metal particles are less than or equal to 130PCS/Kg. The lithium carbonate product in the field of producing high-end lithium battery positive electrode materials meets the requirements of non-ferrous metal industry standard battery-grade lithium carbonate YS/T582-2013 in indexes: the lithium carbonate content is 99.87%; impurity content: na150ppm, mg4.8ppm, ca4.9 ppm, B15ppm, K9.5 ppm, fe < 0.003%, zn < 0.006%, cu < 0.006%, pb < 0.006%, si < 0.005%, al < 0.004%, mn < 0.006%, ni < 0.006%, SO42-17 ppm, cl-17ppm, magnetic substance 130ppb, water 0.3%, median particle size 5.6 μm.
Example 2
Auxiliary materials for producing battery-grade lithium carbonate products: hydrochloric acid, nitric acid, sodium nitrate, sodium carbonate, sodium hydroxide and additives are all bulk chemical products, are not special raw materials directly produced by lithium ion battery raw material production enterprises, and the content of magnetic substances cannot directly reach the requirement of battery-grade lithium carbonate production. The sodium carbonate and sodium hydroxide powder magnetic substance content is detected and analyzed by a production line, and the magnetic substance content is shown in the following table:
TABLE 1 analysis of sodium carbonate and caustic soda magnetic materials
Because of the magnetic substances in the raw materials and the magnetic substances introduced in the subsequent process flow and equipment, the content of the magnetic substances far exceeds the standard value required by national standards and battery enterprises.
TABLE 2 analysis of magnetic materials at key control points of production line
Through the data, the content of the magnetic substance in the lithium carbonate product is higher than 300ppb, so the research and the improvement of the demagnetization process are carried out on the existing production line in a conversion lithium deposition workshop.
Referring to fig. 3, the improved demagnetizing device for the lithium carbonate production process further comprises a soda ash filtering unit, a compressed air filtering unit, plant RO water, a refined calcium and magnesium removing unit, a sodium precipitation unit, a lithium precipitation conversion unit and a demagnetizing unit, wherein processes comprising condensed water filtering, steam filtering, centrifugal separation, drying, air flow crushing and the like are further provided.
The magnetic substance introduction source is analyzed through the production line, and a proper demagnetizing process and proper equipment are selected to reduce the content of the magnetic substance in the product. The fluid pipeline type iron remover and the electromagnetic iron remover are added in each process of the production line to reduce the content of magnetic substances in the lithium carbonate product, and after multi-stage demagnetization, the content of the magnetic substances in the lithium carbonate product is less than 300ppb, thereby meeting the requirement of battery-grade lithium carbonate in the non-ferrous metal industry standard of China.
Example 3
Referring to fig. 2, a part of sodium ions as impurities are still contained in lithium carbonate produced by the reaction of adding alkali for precipitation,the sodium ion content of impurities in the product is higher due to the surface adsorption of the solid and the entrainment of the adsorption liquid, the traditional washing method is a condensed water direct churning method, and the method has the advantages of easy control and adjustment of product quality, high first-pass yield of the product and the like, so that the soluble sodium and chlorine impurities in the lithium carbonate are removed by adopting secondary countercurrent washing. Filtering a solid phase of the lithium precipitation conversion reaction to remove a mother solution to obtain a solid phase lithium carbonate crude product, and washing solid phase lithium carbonate separated by a filter press after precipitation, wherein the washing water temperature is 70 ℃; washing lithium carbonate with equal mass of RO water slurry for 1 time, wherein the water consumption for washing is 3m 3 And t is the product. The process mainly removes soluble impurities which come into a lithium carbonate solid phase from the accompanying liquid by washing, and further reduces the content of impurity sodium.
After separation, adding equal mass of wet lithium carbonate solid phase into RO water with the temperature of 85 ℃ for 1 time of slurry washing, stirring for 30min, then performing centrifugal separation, and measuring the concentration of Na + and K + in the wet lithium carbonate solid phase.
TABLE 3 concentration of Na + and K + in the wet lithium carbonate solid phase after slurry washing at 85 deg.C
According to the table, the wet lithium carbonate solid phase with equal mass is added into distilled water with the temperature of 85 ℃ for 1 time of pulp washing, and good Na + and K + impurity removal effects can be achieved.
(1) Removing easily soluble Na + and K + impurities in the lithium carbonate solid phase by adopting primary stirring and washing;
(2) The temperature of washing water is 85 ℃; the stirred washing water quantity and the lithium carbonate solid phase have the same quality, namely the total washing water quantity is 3.5m3/t product.
After slurry washing separation, the wet lithium carbonate solid phase is washed for 2 times by using distilled water with the mass of 2 times and the temperature of 85 ℃, then centrifugal separation is carried out, a shear pump is added in the secondary process of washing more fully so as to ensure that the materials are washed, and the concentration of Na + and K + in the wet lithium carbonate solid phase is measured.
TABLE 4 concentration of Na + and K + in the wet lithium carbonate solid phase after 85 ℃ washing
According to the table, when the washing times are more than 2 times, good impurity removal effect can be achieved, and the dissolution loss of the product is small.
(1) 2 times of washing is adopted to remove soluble impurities in the solid phase of the lithium carbonate;
(2) The temperature of washing water is 85 ℃; the amount of the eluting water is 2 times of the solid phase mass of the lithium carbonate, namely the total amount of the washing water is 6m 3 T product.
Compared with the pure agitation washing, the washing method greatly saves the washing water consumption, lightens the pressure of subsequent treatment and has good washing effect. In addition, the washing water can be recycled, so that the purposes of comprehensive utilization and cost saving are achieved.
Example 4
The utility model provides an edulcoration equipment of high-end lithium electricity cathode material is prepared to salt lake brine, includes old bittern processing system, magnesium lithium piece-rate system, removes the magnetism system, and old bittern processing system, magnesium lithium piece-rate system, except that the magnetism system connects gradually, old bittern processing system includes salt pan reservoir, swash plate subsider, sedimentation tank, brine filter shop, multi-media filter, plate and frame filter press, and loops through pipeline and connect, connect basic magnesium carbonate production system and lithium carbonate production system respectively behind the plate and frame filter press.
The demagnetizing system comprises a soda ash filtering unit, a compressed air filtering unit, workshop RO water, a condensed water filtering unit, a steam filtering unit, a centrifuge, a slurry demagnetizing unit, a powder demagnetizing unit and a liquid iron remover.
Refer to figure 4, figure 5 and the illustrated edulcoration equipment of high-end lithium electricity cathode material of salt lake brine preparation, liquid de-ironing separator includes framework 1, a plurality of bar magnet 2, feed inlet 3, discharge gate 4, the upper portion of framework 1 is the opening, and is equipped with lid 5 and is connected through a plurality of fixed subassembly 8 with the opening, a plurality of bar magnet 2 are vertical be fixed in framework 1 and align to grid, export 6 has been seted up to the side of framework 1, lid 5 deviates from open-ended one end and is equipped with handle 7, a plurality of bar magnets 2 are arranged at the interior circle of framework 1, be equipped with the ball valve on the export 6.
Referring to fig. 7, the fixing assembly 8 includes a clip nut 9, a flat washer 10, a slipknot bolt 11, a B-shaped pin shaft 12 and a baffle 13, the clip nut 9 penetrates through the edge of the cover body 5 and the edge of the frame body 1 to be in threaded connection with the slipknot bolt 11, two baffles 13 are fixed on the slipknot bolt 11, the clip nut 9 is connected to the middle positions of the two baffles 13, and the slipknot bolt 11 and the baffles 13 are fixed in a limiting manner through the B-shaped pin shaft 12.
Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that changes, modifications, substitutions and alterations can be made in these embodiments without departing from the principles and spirit of the invention, the scope of which is defined in the appended claims and their equivalents.
Claims (10)
1. An impurity removal method for preparing a high-end lithium battery positive electrode material by using salt lake brine is characterized by comprising the following steps of: the method comprises the following steps:
s1, old brine treatment: the bittern is naturally concentrated by solarization and concentration in multi-stage evaporation and grading, potash salt system is used to prepare potash magnesium sulphate fertilizer, the tail liquid after potassium extraction is solarized in carnallite pond and then enters into old bittern storage pond, and Fe impurity affecting the separation of Mg and Li in bittern is removed by settling and filtering 2 + The turbidity of the filtered brine is less than or equal to 0.3NTU 2+ The content is less than or equal to 0.01mg/L, the pH value is 3-3.5, and lithium-rich brine with the magnesium-lithium ratio of 1: 10-1: 1 is obtained after two-stage selective separation;
s2, magnesium and lithium separation: placing cations and anion exchange membranes in the separated filtrate in the step S1, wherein the cations pass through the cation exchange membranes under the action of an electric field, the anions migrate to the electrode through the anion exchange membranes, monovalent cations migrate through the monovalent selective cation exchange membranes, and secondary and trivalent cations are blocked, so that lithium-containing brine is obtained;
s3, refining to remove calcium and magnesium: adding caustic soda solution into the lithium-containing brine obtained in the step S2, adding a small amount of soda ash solution in the reaction process, separating the slurry solution after the reaction, wherein the solid-phase product obtained by separation is magnesium hydroxide, the separated liquid phase is refined filtrate, the pH value in the reaction process is controlled to be 12-13, and the reaction is carried out for 45min;
s4, evaporating mother liquor to remove calcium and magnesium: adding 31% hydrochloric acid into the refined filtrate obtained in the step S3, evaporating, performing three-stage evaporation to obtain a concentrated solution with a magnesium content of 15ppm, adding excessive EDTA into the evaporated concentrated solution, and smashing and homogenizing the reacted materials;
s5, lithium deposition and conversion: adding soda ash into the solution treated in the step S4, wherein an EDTA solution and a polyhydric hydroxyl alcohol mixed solution are added in the preparation process of the soda ash during the solution preparation process, so as to obtain a lithium carbonate product, wherein the EDTA solution and the polyhydric hydroxyl alcohol mixed solution are required to be added in an excessive amount, and the excessive coefficient is 1.25%;
s6, secondary countercurrent washing: partial sodium impurity still remains in the lithium carbonate produced in the step S5, the direct stirring and washing method of the condensed water has the advantages of easy control and adjustment of product quality, high first-time qualification rate of the product and the like, and the secondary countercurrent washing is adopted to remove the soluble sodium and chlorine impurities in the lithium carbonate;
s7, centrifugal drying: performing centrifugal dehydration and drying on the product lithium carbonate obtained in the step S6;
s8, airflow crushing: and (4) performing air flow grinding on the product lithium carbonate subjected to the step S7, wherein the median particle diameter D50 is 3.0-8.0 microns.
2. The impurity removal method for preparing the high-end lithium battery positive electrode material from the salt lake brine according to claim 1, which is characterized by comprising the following steps of: the lithium-containing brine obtained by magnesium-lithium separation in the step S2 has the lithium content of 9.5-10g/L and the magnesium content of 2.5-3.5g/L.
3. The impurity removal method for preparing the high-end lithium battery positive electrode material from the salt lake brine according to claim 1, which is characterized by comprising the following steps of: and (4) the magnesium content of the separated liquid-phase refined filtrate obtained in the refining calcium and magnesium removing process in the step (S3) is within 2 ppm.
4. The impurity removal method for preparing the high-end lithium battery positive electrode material from the salt lake brine according to claim 1, which is characterized by comprising the following steps of: and S4, concentrating the solution through three-stage evaporation until the lithium content of the evaporation mother liquor is 25 +/-1 g/L, and removing calcium and magnesium from the evaporation mother liquor, wherein the pH value in the reaction process is controlled to be 6.5-7.0.
5. The impurity removal method for preparing the high-end lithium battery positive electrode material from the salt lake brine according to claim 1, which is characterized by comprising the following steps of: and removing iron filings in the process of secondary counter-current washing, and removing magnetism in the processes of centrifugal drying and air flow crushing, wherein the magnetic substance of the material after the demagnetization of the final product lithium carbonate is less than 100ppb, and the magnetic metal particles are less than or equal to 130PCS/Kg.
6. The utility model provides an impurity removing equipment of high-end lithium electricity cathode material is prepared to salt lake brine, includes old brine processing system, magnesium lithium piece-rate system, demagnetization system, and it is specially lieing in: old bittern processing system, magnesium lithium separation system, except that the magnetism system connects gradually, old bittern processing system includes salt pan reservoir, swash plate subsider, settling basin, brine filtration workshop, multi-media filter, plate and frame filter press, and loops through the pipeline and connect, connects basic magnesium carbonate production system and lithium carbonate production system behind the material through the plate and frame filter press.
7. The impurity removing equipment for preparing the high-end lithium battery positive electrode material from the salt lake brine according to claim 6, is characterized in that: the magnesium-lithium separation system comprises a plurality of cation and anion exchange membranes which are alternately arranged.
8. The impurity removing equipment for preparing the high-end lithium battery positive electrode material from the salt lake brine according to claim 6, is characterized in that: the demagnetizing system comprises a soda ash filtering unit, a compressed air filtering unit, workshop RO water, a condensed water filtering unit, a steam filtering unit, centrifugal separation, a slurry demagnetizing unit, a powder demagnetizing unit and a liquid iron remover.
9. The impurity removing equipment for preparing the high-end lithium battery cathode material from the salt lake brine according to claim 8, wherein the impurity removing equipment comprises: the liquid de-ironing separator comprises a frame body (1), a plurality of magnetic rods (2), a feeding port (3) and a discharging port (4), wherein the upper portion of the frame body (1) is provided with an opening, a cover body (5) is arranged to be connected with the opening through a plurality of fixing assemblies (8), the magnetic rods (2) are vertically fixed in the frame body (1) and are uniformly arranged, a leading-out port (6) is formed in the side face of the frame body (1), a handle (7) is arranged at one end, deviating from the opening, of the cover body (5), the magnetic rods (2) are arranged in the frame body (1) in a circular mode, and a ball valve is arranged on the leading-out port (6).
10. The impurity removing equipment for preparing the high-end lithium battery cathode material from the salt lake brine according to claim 9, characterized in that: fixed subassembly (8) are including cassette nut (9), plain washer (10), slipknot bolt (11), B type round pin axle (12), baffle (13), cassette nut (9) run through lid (5) border and framework (1) border and slipknot bolt (11) threaded connection, two fixed baffles (13) are gone up in slipknot bolt (11), and connect cassette nut (9) in two baffles (13) intermediate position, slipknot bolt (11) are spacing fixed through B type round pin axle (12) with baffle (13).
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