CN115536045B - Method for efficiently and continuously preparing ultrapure lithium carbonate with uniform granularity - Google Patents
Method for efficiently and continuously preparing ultrapure lithium carbonate with uniform granularity Download PDFInfo
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Abstract
The invention discloses a method for efficiently and continuously preparing ultrapure lithium carbonate with uniform granularity, belongs to the field of lithium carbonate production, and solves the problems of low purity and granularity existing in the existing ultrapure lithium carbonate production processUneven and unstable degree and low production efficiency. The method comprises the following steps: preparing lithium bicarbonate solution; purifying the lithium bicarbonate solution; carrying out continuous pyrolysis by using a continuous pyrolysis device; washing with water; and (5) calcining. The invention designs a method for continuously producing ultrapure lithium carbonate, and liquid in each pyrolysis kettle continuously enters and exits in the production process, so that continuous production of lithium carbonate is truly realized, the reaction period is greatly shortened, and the production efficiency is improved. In the invention, the Li concentration of the liquid in each stage of pyrolysis kettle is reduced to the same degree, so that Li in unit time 2 CO 3 The precipitation rate and the crystallization growth rate are the same, the precipitation of the ultrapure lithium carbonate is reduced according to the concentration gradient, and the purity and the granularity of the obtained ultrapure lithium carbonate are stable and uniform.
Description
Technical Field
The invention belongs to the field of lithium carbonate production, and particularly relates to a method for efficiently and continuously preparing ultrapure lithium carbonate with uniform granularity.
Background
With the progress of the age and the development of science and technology, li 2 CO 3 The method is widely applied to the fields of ceramics, glass, atomic energy, aerospace, lithium batteries, lithium alloys, medicines and the like, and is also a raw material for preparing various lithium compounds. The purity and particle size of lithium carbonate may also be different due to the different uses. 99.9% of high-purity lithium carbonate is used as a positive electrode material of a lithium ion battery; 99.99% of high-purity lithium carbonate is used for the electrolyte of lithium ion batteries; 99.999% of ultrapure lithium carbonate is used in medicine and surface elastic wave element materials. Along with the continuous expansion of the application range of lithium products in the high-tech field, the demand of lithium salt is increased at home and abroad, the purity requirement of the product is higher and higher, and the requirement of granularity is also more and more severe, so that the development of high-added-value ultra-pure lithium salt products with different granularities is imperative.
Disclosure of Invention
The invention aims to provide a method for efficiently and continuously preparing ultrapure lithium carbonate with uniform granularity, so as to solve the problems of low purity, uneven granularity, instability and low production efficiency in the existing ultrapure lithium carbonate production process.
The technical scheme of the invention is as follows: a method for efficiently and continuously preparing ultrapure lithium carbonate with uniform granularity, which comprises the following steps:
A. preparation of lithium bicarbonate solution: injecting pure water into a carbonization reaction kettle, starting stirring, then adding lithium carbonate into the carbonization reaction kettle, then introducing carbon dioxide, fully reacting to prepare a lithium bicarbonate solution, and testing the Li content in the lithium bicarbonate solution to obtain a qualified lithium bicarbonate solution, wherein the Li content is between 7.5 and 8g/L;
B. purifying lithium bicarbonate solution: purifying the qualified lithium bicarbonate solution prepared in the step A to obtain a purified lithium bicarbonate solution;
C. continuous pyrolysis using a continuous pyrolysis apparatus: the continuous pyrolysis device comprises a high-level reserve tank and a plurality of pyrolysis kettles which are sequentially arranged from top to bottom, wherein the high-level reserve tank is sequentially communicated with each pyrolysis kettle through pipelines, and each pipeline is provided with a control valve;
the specific operation method is as follows: b, placing the purified lithium bicarbonate solution prepared in the step B into a high-level storage tank; sequentially opening all control valves from top to bottom to enable purified lithium bicarbonate solution to flow downwards and flow into all pyrolysis kettles in sequence, closing all control valves, heating the pyrolysis kettles, starting pyrolysis reaction in all pyrolysis kettles, controlling the reaction to enable the Li content of liquid in all pyrolysis kettles to gradually decrease from top to bottom to form a gradient, sequentially opening all control valves from top to bottom to enable liquid in all reaction kettles to carry out pyrolysis reaction while discharging liquid, enabling liquid in the lowest pyrolysis kettle to discharge liquid to a centrifugal machine for centrifugation, monitoring the Li content of liquid in all pyrolysis kettles in the continuous reaction process, enabling the Li content in all pyrolysis kettles to keep the gradient by controlling the opening degree of all control valves and the heating degree of all pyrolysis kettles, continuously feeding and discharging the purified lithium bicarbonate solution in all pyrolysis kettles and keeping the pyrolysis reaction, and continuously pyrolyzing to produce lithium carbonate;
D. washing: washing wet lithium carbonate after centrifugation by a centrifuge, wherein the washing temperature is more than or equal to 90 ℃, centrifuging the wet lithium carbonate while the wet lithium carbonate is hot after washing, and controlling the water content in the centrifuged lithium carbonate to be less than or equal to 5%;
E. calcining: calcining for 4-6h at 400-450 ℃ to obtain qualified ultra-pure lithium carbonate, wherein the purity of the ultra-pure lithium carbonate is more than or equal to 99.999%.
As a further improvement of the invention, in the step C, the continuous pyrolysis device is provided with three pyrolysis kettles, namely a first pyrolysis kettle, a second pyrolysis kettle and a third pyrolysis kettle, a first valve is arranged between the high-level reserve tank and the first pyrolysis kettle, a second valve is arranged between the first pyrolysis kettle and the second pyrolysis kettle, a third valve is arranged between the second pyrolysis kettle and the third pyrolysis kettle, the third pyrolysis kettle is connected with a centrifuge, and a liquid outlet valve is arranged between the third pyrolysis kettle and the centrifuge.
As a further improvement of the invention, in the step A, the Li content of the qualified lithium bicarbonate solution is 8g/L; in the step C, the Li content in the first pyrolysis kettle, the second pyrolysis kettle and the third pyrolysis kettle is controlled to be 6g/L, 4g/L and 2g/L respectively.
As a further improvement of the present invention, in step B, the method of the purification treatment includes the steps of:
s1, four-stage precise filtration: firstly, passing a qualified lithium bicarbonate solution through a filter bag with the diameter of 0.5 mu m, filtering out impurities with larger particles, then passing through a filter core with the diameter of 0.05 mu m, continuously filtering out small particle impurities, and finally continuously passing through a filter core with the diameter of 2 channels and 0.01 mu m;
s2, ion exchange impurity removal: removing impurity ions by using ion exchange resin;
s3, fine filtering again: the ion-exchanged lithium bicarbonate solution was filtered through a 0.01 μm filter cartridge.
In the purification treatment method, the effect of ion exchange is directly affected by multistage fine filtration, and whether the lithium bicarbonate solution which is qualified in purification can be obtained or not is judged, if small particle matters which are invisible to naked eyes cannot be filtered out in the fine filtration step, the small particle matters enter the ion exchange part and can enter microporous channels of the ion exchange resin to block the channels, so that the capability of removing impurity ions of the ion exchange resin is greatly reduced. The index of the purified lithium bicarbonate solution is as follows:Al≤0.0003g/L、As≤0.00001g/L、Ca≤0.0001g/L、Cu≤0.00001g/L、Fe≤0.0001g/L、K≤0.0009g/L、Mg≤0.00045g/L、Mn≤0.000004g/L、Na≤0.0003g/L、Ni≤0.000005g/L、Pb≤0.000001g/L、Si≤0.00048g/L、Zn≤0.000001g/L、Co≤0.000005g/L、SO 4 2- ≤0.001g/L、Cl≤0.0002g/L。
as a further improvement of the invention, in the step D, the solid-liquid mass ratio during water washing is 1:4-7.
As a further improvement of the invention, in the step C, each pyrolysis kettle is heated by steam, so that the heating efficiency is high.
As a further improvement of the invention, the first pyrolysis kettle, the second pyrolysis kettle and the third pyrolysis kettle are respectively provided with a stirring device so as to ensure uniform heating and uniform crystallization.
As a further improvement of the invention, the bottoms of the first pyrolysis kettle, the second pyrolysis kettle and the third pyrolysis kettle are tapered. Aiming at the characteristic that lithium carbonate is easy to scar, the conical design can weaken the lithium carbonate from scarring, and is more beneficial to continuous production.
As a further improvement of the invention, the outer walls of the first pyrolysis kettle, the second pyrolysis kettle and the third pyrolysis kettle are respectively provided with an insulating layer.
The beneficial effects of the invention are as follows: the invention designs a method for continuously producing ultrapure lithium carbonate, wherein liquid in each pyrolysis kettle continuously enters and exits simultaneously in the production process, so that continuous production of lithium carbonate is truly realized, the reaction period is greatly shortened, and the production efficiency is improved. In the invention, the Li concentration of the liquid in each stage of pyrolysis kettle is reduced to the same degree, so that Li in unit time 2 CO 3 The precipitation rate and the crystallization growth rate of the ultra-pure lithium carbonate are the same, the precipitation rate of the ultra-pure lithium carbonate is reduced according to the concentration gradient, and the purity and the granularity of the obtained ultra-pure lithium carbonate are stable and uniform and all meet the industry standard. The method is simple, easy to operate and has good popularization value.
Drawings
FIG. 1 is a schematic view of the structure of a continuous pyrolysis apparatus according to the present invention.
In the figure: 1-a first pyrolysis kettle; 11-a first valve; 2-a second pyrolysis kettle; 21-a second valve; 3-a third pyrolysis kettle; 31-a third valve; 32-a liquid outlet valve; 4-high-order reserve tank; 5-a centrifuge; 6-steam pipe; 7-stirring device; 8-an insulating layer.
Detailed Description
The present invention will be described in further detail with reference to the following specific embodiments.
In the following embodiments 1 to 6, the adopted continuous pyrolysis device is shown in fig. 1, and comprises a high-level reserve tank 4 and three pyrolysis kettles which are sequentially arranged from top to bottom, wherein the high-level reserve tank 4, the first pyrolysis kettle 1, the second pyrolysis kettle 2 and the third pyrolysis kettle 3 are sequentially communicated, a first valve 11 is arranged between the high-level reserve tank 4 and the first pyrolysis kettle 1, a second valve 21 is arranged between the first pyrolysis kettle 1 and the second pyrolysis kettle 2, a third valve 31 is arranged between the second pyrolysis kettle 2 and the third pyrolysis kettle 3, the third pyrolysis kettle 3 is connected with a centrifuge 5, and a liquid outlet valve 32 is arranged between the third pyrolysis kettle 3 and the centrifuge 5. The first valve 11, the second valve 21, the third valve 31 and the liquid outlet valve 32 all adopt electromagnetic valves. The first pyrolysis kettle 1, the second pyrolysis kettle 2 and the third pyrolysis kettle 3 are respectively internally provided with a steam pipe 6 and a stirring device 7. The bottoms of the first pyrolysis kettle 1, the second pyrolysis kettle 2 and the third pyrolysis kettle 3 are conical.
Example 1,
A method for efficiently and continuously preparing ultrapure lithium carbonate with uniform granularity, which comprises the following steps:
A. preparation of lithium bicarbonate solution: 1000L of pure water is injected into a 1500L carbonization reaction kettle, stirring is started, 42.77kg of battery grade lithium carbonate (purity is 99.5%) is taken (the dosage of the lithium carbonate is calculated in advance before the charging) for accurate charging, a small amount of the lithium carbonate is added into the carbonization reaction kettle for many times, then carbon dioxide is introduced for full reaction for 4 hours, a lithium bicarbonate solution is prepared, when the solution becomes clear and transparent, the Li content in the lithium bicarbonate solution is tested by hydrochloric acid titration or atomic absorption, and when the Li content is 8g/L, carbonization is completed, and a qualified lithium bicarbonate solution is obtained. The charging calculation formula is as follows: lithium carbonate amount = deionized water volume per 0.188/0.995 of lithium content in lithium bicarbonate solution, wherein the lithium carbonate amount unit is kg, the deionized water volume unit is m, the lithium content unit in lithium bicarbonate solution is kg/m, 0.188 is mass fraction of lithium in lithium carbonate, and 0.995 is main content 99.5% of battery grade lithium carbonate.
B. Purifying lithium bicarbonate solution: and C, purifying the qualified lithium bicarbonate solution prepared in the step A, wherein the purifying method comprises the following steps of:
four-stage precise filtration: firstly, passing a qualified lithium bicarbonate solution through a filter bag with the diameter of 0.5 mu m, filtering out impurities with larger particles, then passing through a filter core with the diameter of 0.05 mu m, continuously filtering out small particle impurities, and finally continuously passing through a filter core with the diameter of 2 channels and 0.01 mu m;
ion exchange impurity removal: firstly, cation exchange resin is mixed with several resins with strong specific ion exchange capacity and added into ion exchange column to remove Ca 2+ 、Mg 2+ And the like, and then removing SO by anion exchange resin 4 2- ；
And (3) fine filtering again: and (3) carrying out precise filtration on the lithium bicarbonate solution subjected to ion exchange through a filter element with the diameter of 0.01 mu m to obtain a purified lithium bicarbonate solution.
C. Continuous pyrolysis using a continuous pyrolysis apparatus: placing the purified lithium bicarbonate solution prepared in the step B into a high-level reserve tank 4; sequentially opening a first valve 11, a second valve 21 and a third valve 31 from top to bottom to enable the purified lithium bicarbonate solution to flow downwards automatically and sequentially flow into a first pyrolysis kettle 1, a second pyrolysis kettle 2 and a third pyrolysis kettle 3, wherein the liquid level in each pyrolysis kettle is about two thirds of the kettle body, and closing the first valve 11, the second valve 21 and the third valve 31; introducing high-temperature steam into the first pyrolysis kettle 1, the second pyrolysis kettle 2 and the third pyrolysis kettle 3 for heating, starting pyrolysis reaction in each pyrolysis kettle, and controlling the reaction to ensure that the Li content of the liquid in the first pyrolysis kettle 1 reaches 6g/L, the Li content of the liquid in the second pyrolysis kettle 2 reaches 4g/L and the Li content of the liquid in the third pyrolysis kettle 3 reaches 2g/L; then, the first valve 11, the second valve 21, the third valve 31 and the liquid outlet valve 32 are sequentially opened from top to bottom, so that liquid in each reaction kettle is discharged while carrying out pyrolysis reaction while feeding liquid, and liquid in the third pyrolysis kettle 3 is discharged to the centrifugal machine 5 for centrifugation. The purified lithium bicarbonate solution is continuously produced by continuous pyrolysis from the high-level reserve tank 4 to the first pyrolysis kettle 1, from the first pyrolysis kettle 1 to the second pyrolysis kettle 2, from the second pyrolysis kettle 2 to the third pyrolysis kettle 3 and from the third pyrolysis kettle 3 to the centrifugal machine 5, and the Li content of liquid in each pyrolysis kettle is monitored in the continuous reaction process, and the Li content in each pyrolysis kettle is kept at the gradient by controlling the opening degree of the first valve 11, the second valve 21, the third valve 31 and the liquid outlet valve 32 and the heating degree of each pyrolysis kettle.
D. Washing: washing wet lithium carbonate after centrifugation by a centrifuge 5 with water, wherein the solid-liquid mass ratio is 1:5, the washing temperature is more than or equal to 90 ℃, the washing time is 30min, centrifuging the wet lithium carbonate after washing while the wet lithium carbonate is hot, and controlling the water content in the centrifuged lithium carbonate to be less than or equal to 5%.
E. Calcining: calcining for 5 hours at 400 ℃ to obtain qualified ultra-pure lithium carbonate.
Purity test results: 99.99915%. Particle size test results: d10:1.7 μm, D50:6 μm, D90:14 μm.
The experimental data of this example 5 set was repeated and shown in Table 1.
As can be seen from Table 1, the prepared ultrapure lithium carbonate has very stable purity and granularity by continuous pyrolysis in a mode of entering and exiting at the same time with the concentration being reduced according to a gradient of 2g/L, and the prepared ultrapure lithium carbonate not only meets the YS/T582-2013 standard of industry, but also has very small floating of purity and granularity and is very stable.
EXAMPLE 2,
This embodiment differs from embodiment 1 in that: in the step D, the solid-liquid mass ratio during water washing was 1:4, and the other steps were the same as in example 1. Purity test results: 99.998%. Particle size test results: d10:1.9 μm, D50:5 μm, D90:13 μm.
EXAMPLE 3,
This embodiment differs from embodiment 1 in that: in the step D, the solid-liquid mass ratio during water washing was 1:6, and the other steps were the same as in example 1. Purity test results: 99.99914%. Particle size test results: d10:1.9 μm, D50:5.1 μm, D90:13 μm.
EXAMPLE 4,
This embodiment differs from embodiment 1 in that: in the step D, the solid-liquid mass ratio during water washing was 1:7, and the other steps were the same as in example 1. Purity test results: 99.99917%. Particle size test results: d10:1.8 μm, D50:6 μm, D90:13 μm.
In examples 1-4, the mass ratio of the solid to the liquid in the water washing is adjusted from 1:5 to 1:4, 1:6 and 1:7, the purity of the ultrapure lithium carbonate after adjustment is unchanged after the rising of the washing water amount, and the particle size index is not changed greatly. Considering that the water washing ratio is too large in industrial production, the requirement on the liquid treatment capacity of the production system is increased and the purity requirement is increased. Therefore, the solid-liquid ratio of 1:5 is preferably selected as the mass ratio of water washing solid-liquid of the ultrapure lithium carbonate.
EXAMPLE 5,
A method for efficiently and continuously preparing ultrapure lithium carbonate with uniform granularity, which comprises the following steps:
A. preparation of lithium bicarbonate solution: injecting 1500L pure water into a 2000L pyrolysis reaction kettle, starting stirring, taking 64.15kg of battery-grade lithium carbonate (purity is 99.5%), accurately feeding the lithium carbonate, calculating the dosage of the lithium carbonate in advance before feeding, adding a small amount of the lithium carbonate into the carbonization reaction kettle for multiple times, introducing carbon dioxide, and fully reacting for 4 hours to prepare the lithium bicarbonate solution. When the solution becomes clear and transparent, the lithium bicarbonate solution is tested by a titration method to obtain the qualified lithium bicarbonate solution, wherein the Li content is 8 g/L.
The other steps were the same as in example 1.
Purity test results: 99.99917%. Particle size test results: d10:2.4 μm, D50:7 μm, D90:14 μm.
EXAMPLE 6,
This embodiment differs from embodiment 5 in that: in step E, the calcination temperature was 450℃and the other steps were the same as in example 1. In examples 5 and 6, the calcination temperature was increased from 400 to 450 ℃, and the purity of the ultrapure lithium carbonate was not greatly changed, and 400 ℃ was preferably selected as the drying temperature in view of energy saving and production cost.
Purity test results: 99.99914%. Particle size test results: d10:2.3 μm, D50:7.2 μm, D90:14 μm.
EXAMPLE 7,
The continuous pyrolysis device that this embodiment adopted is equipped with two pyrolysis kettles, and last pyrolysis kettle connects centrifuge.
The procedure of step C of this example was similar to that of example 1, except that during the reaction, the Li content of the liquid in the first pyrolysis reactor was kept at 5g/L and the Li content of the liquid in the second pyrolysis reactor was kept at 2g/L. The other steps were the same as in example 1.
Purity test results: 99.9986%. Particle size test results: d10:4 μm, D50:13 μm, D90:21 μm.
EXAMPLE 8,
The continuous pyrolysis device that this embodiment adopted is equipped with six pyrolysis cauldron, and centrifuge is connected to last pyrolysis cauldron.
The procedure of step C of this example was similar to that of example 1, except that during the reaction, the Li content of the liquid in the first pyrolysis tank was maintained at 7g/L, the Li content of the liquid in the second pyrolysis tank was maintained at 6g/L, the Li content of the liquid in the third pyrolysis tank was maintained at 5g/L, the Li content of the liquid in the fourth pyrolysis tank was maintained at 4g/L, the Li content of the liquid in the fifth pyrolysis tank was maintained at 3g/L, and the Li content of the liquid in the sixth pyrolysis tank was maintained at 2g/L. The other steps were the same as in example 1.
Purity test results: 99.99911%. Particle size test results: d10:2 μm, D50:4.4 μm, D90:11.5 μm.
In the case of the continuous step pyrolysis of example 1, the Li content in the solution was decreased by 2g/L, the Li content in the solution of example 7 was decreased by 3g/L, and the Li content in the solution of example 8 was decreased by 1 g/L. The purity and particle size data pairs for examples 1, 7 and 8 are shown in table 2.
As can be seen from Table 2, the Li content in the solution is reduced according to 3g/L during continuous step pyrolysis, the purity of the prepared lithium carbonate is less than 99.999%, and the granularity index does not meet YS/T582-2013 standard. The Li content is reduced according to 1g/L and 2g/L, the purity of the prepared lithium carbonate is more than 99.999 percent, the granularity also accords with YS/T582-2013 standard, the two modes can be used for producing the ultrapure lithium carbonate, but the process route for preparing the ultrapure lithium carbonate according to the reduction of 1g/L is longer, a pyrolysis kettle is more, when the self-flowing is used, the requirements on the height of a factory building are met, and the comprehensive consideration of the reduction according to 2g/L is better.
Comparative example 1,
The difference between this comparative example and example 1 is that: in the step C, a single kettle intermittent pyrolysis method is adopted, rather than a continuous process, 1000L of purified lithium bicarbonate solution prepared in the step B is injected into a 1200L pyrolysis kettle, stirring is started, heating is started, the heating speed is 1 ℃/min, after the temperature of pyrolysis liquid is increased to be more than 90 ℃, the heat is preserved for 30min, pyrolysis is finished, and lithium carbonate slurry is discharged from a bottom valve of the pyrolysis kettle to a centrifuge for centrifugation. The other steps were the same as in example 1.
The comparative example was repeated 5 times, and experimental data are shown in table 3.
As can be seen from Table 3, the continuous gradient pyrolysis and the discontinuous single-kettle pyrolysis are contrasted, and the granularity and the purity of the ultrapure lithium carbonate obtained by the continuous gradient pyrolysis meet YS/T582-2013 standard and are very stable. The impurity of the ultrapure lithium carbonate obtained by discontinuous single-kettle pyrolysis is seriously wrapped, the chemical index is less than 99.999 percent, and in addition, the granularity of the ultrapure lithium carbonate prepared each time has large fluctuation and does not accord with YS/T582-2013 standard. The continuous gradient concentration control method for preparing the ultrapure lithium carbonate is more controllable and stable in purity and granularity, and chemical indexes and physical indexes of the product meet industry standards and meet the requirement of the market on stability.
Claims (9)
1. The method for efficiently and continuously preparing the ultrapure lithium carbonate with uniform granularity is characterized by comprising the following steps of:
A. preparation of lithium bicarbonate solution: injecting pure water into a carbonization reaction kettle, starting stirring, then adding lithium carbonate into the carbonization reaction kettle, then introducing carbon dioxide, fully reacting to prepare a lithium bicarbonate solution, and testing the Li content in the lithium bicarbonate solution to obtain a qualified lithium bicarbonate solution, wherein the Li content is between 7.5 and 8g/L;
B. purifying lithium bicarbonate solution: purifying the qualified lithium bicarbonate solution prepared in the step A to obtain a purified lithium bicarbonate solution;
C. continuous pyrolysis using a continuous pyrolysis apparatus: the continuous pyrolysis device comprises a high-level reserve tank (4) and a plurality of pyrolysis kettles which are sequentially arranged from top to bottom, wherein the high-level reserve tank (4) is sequentially communicated with the pyrolysis kettles through pipelines, and a control valve is arranged on each pipeline;
the specific operation method is as follows: b, placing the purified lithium bicarbonate solution prepared in the step B into a high-level reserve tank (4); sequentially opening all control valves from top to bottom to enable purified lithium bicarbonate solution to flow downwards and flow into all pyrolysis kettles in turn, closing all control valves, heating the pyrolysis kettles, starting pyrolysis reaction in all pyrolysis kettles, controlling the reaction to enable the Li content of liquid in all pyrolysis kettles to gradually decrease from top to bottom to form a gradient, taking 1g/L or 2g/L as the gradient, enabling the Li concentration of liquid in each pyrolysis kettle to decrease to the same extent, sequentially opening all control valves from top to bottom, enabling liquid in each reaction kettle to carry out pyrolysis reaction while liquid is discharged, enabling liquid in the pyrolysis kettle at the lowest layer to discharge to a centrifugal machine (5) for centrifugation, monitoring the Li content of liquid in each pyrolysis kettle in the continuous reaction process, enabling the Li content in each pyrolysis kettle to keep the gradient by controlling the opening degree of all control valves and the heating degree of each pyrolysis kettle, enabling the purified lithium bicarbonate solution in each pyrolysis kettle to continuously enter and exit and keep the pyrolysis reaction, and continuously producing lithium carbonate by pyrolysis;
D. washing: washing wet lithium carbonate after the centrifugation of the centrifuge (5) with water, wherein the washing temperature is more than or equal to 90 ℃, centrifuging the wet lithium carbonate after the washing while the wet lithium carbonate is hot, and controlling the water content in the centrifuged lithium carbonate to be less than or equal to 5%;
E. calcining: calcining for 4-6h at 400-450 ℃ to obtain qualified ultra-pure lithium carbonate, wherein the purity of the ultra-pure lithium carbonate is more than or equal to 99.999%.
2. The method for efficiently and continuously preparing ultrapure lithium carbonate with uniform particle size according to claim 1, which is characterized in that: in step C, continuous pyrolysis device is equipped with three pyrolysis kettle, be first pyrolysis kettle (1), second pyrolysis kettle (2) and third pyrolysis kettle (3) respectively, be equipped with first valve (11) between high-order reserve tank (4) and first pyrolysis kettle (1), be equipped with second valve (21) between first pyrolysis kettle (1) and second pyrolysis kettle (2), be equipped with third valve (31) between second pyrolysis kettle (2) and third pyrolysis kettle (3), centrifuge (5) are connected in third pyrolysis kettle (3), be equipped with play liquid valve (32) between third pyrolysis kettle (3) and centrifuge (5).
3. The method for efficiently and continuously preparing ultrapure lithium carbonate with uniform particle size according to claim 2, which is characterized in that: in the step A, the Li content in the qualified lithium bicarbonate solution is 8g/L; in the step C, the Li content in the first pyrolysis kettle (1), the second pyrolysis kettle (2) and the third pyrolysis kettle (3) is controlled to be 6g/L, 4g/L and 2g/L respectively.
4. A method for the efficient continuous production of ultrapure lithium carbonate of uniform particle size according to any one of claims 1 to 3, characterized in that: in step B, the method of the purification treatment includes the steps of:
s1, four-stage precise filtration: firstly, passing a qualified lithium bicarbonate solution through a filter bag with the diameter of 0.5 mu m, filtering out impurities with larger particles, then passing through a filter core with the diameter of 0.05 mu m, continuously filtering out small particle impurities, and finally continuously passing through a filter core with the diameter of 2 channels and 0.01 mu m;
s2, ion exchange impurity removal: removing impurity ions by using ion exchange resin;
s3, fine filtering again: the ion-exchanged lithium bicarbonate solution was filtered through a 0.01 μm filter cartridge.
5. The method for efficiently and continuously preparing ultrapure lithium carbonate with uniform particle size according to claim 4, which is characterized in that: in the step D, the solid-liquid mass ratio during water washing is 1:4-7.
6. The method for efficiently and continuously preparing ultrapure lithium carbonate with uniform particle size according to claim 5, which is characterized in that: in step C, each pyrolysis kettle is heated by steam.
7. The method for efficiently and continuously preparing ultrapure lithium carbonate with uniform particle size according to claim 2, which is characterized in that: and stirring devices (7) are respectively arranged in the first pyrolysis kettle (1), the second pyrolysis kettle (2) and the third pyrolysis kettle (3).
8. The method for efficiently and continuously preparing ultrapure lithium carbonate having uniform particle size according to claim 1 or 7, wherein: the bottoms of the first pyrolysis kettle (1), the second pyrolysis kettle (2) and the third pyrolysis kettle (3) are conical.
9. The method for efficiently and continuously preparing ultrapure lithium carbonate with uniform particle size according to claim 8, which is characterized in that: the outer walls of the first pyrolysis kettle (1), the second pyrolysis kettle (2) and the third pyrolysis kettle (3) are respectively provided with an insulating layer (8).
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