A lithium carbonate carbonization thermal desorption apparatus

Abstract

This utility model relates to the field of lithium salt production technology, specifically to a lithium carbonate carbonation thermal precipitation apparatus. The apparatus includes a carbonation tank, a thermal precipitation tank, a thickener, and a solid-liquid separator connected in sequence. The mother liquor outlet of the solid-liquid separator is connected to the inlet of the thermal precipitation tank via a mother liquor pipe. The mother liquor pipe is used to guide the mother liquor into the thermal precipitation tank, utilizing the small-diameter crystals in the mother liquor as seed crystals for the thermal precipitation reaction. This utility model solves the technical problems of low thermal precipitation efficiency and difficulty in controlling crystal particle size during the lithium carbonate carbonation thermal precipitation process. It allows the mother liquor from the solid-liquid separation to carry small-diameter extracts into the thermal precipitation process as seed crystals, thereby not only increasing the crystal particle size in the thermal precipitation reaction but also improving the thickening and sedimentation efficiency.

Description

Technical Field

[0001] This utility model relates to the field of lithium salt production technology, specifically to a lithium carbonate carbonation thermal precipitation device. Background Technology

[0002] With the rapid development of the global new energy industry, the demand for battery-grade lithium carbonate has increased dramatically, and the purity requirements for lithium salts have become increasingly stringent. Traditional lithium carbonate purification methods (such as recrystallization and acid-base dissolution) suffer from problems such as high energy consumption, complex processes, and incomplete impurity removal, making it difficult to meet the production needs of high-purity lithium salts.

[0003] The carbonation pyrolysis method is a highly efficient lithium carbonate purification technology. Its principle involves dissolving crude lithium carbonate in a CO2 atmosphere, carbonizing it to generate soluble lithium bicarbonate (LiHCO3), filtering to remove insoluble impurities, and then pyrolyzing the LiHCO3 to reprecipitate high-purity lithium carbonate crystals. This method has advantages such as mild reaction conditions, high impurity removal rate, and recyclable CO2, aligning with the development trend of green chemistry.

[0004] Currently, the main process route for lithium carbonate purification via the carbonation pyrolysis method includes a carbonation tank, a pyrolysis tank, a thickener, and a solid-liquid separator connected in sequence, such as... Figure 1 As shown, this process has the following main drawbacks: 1. The mother liquor separated by the solid-liquid separator is buffered in the mother liquor buffer tank and then returned to the thickener. This causes small-diameter lithium carbonate crystals in the mother liquor to continuously accumulate in the thickener and solid-liquid separator, which not only easily increases the number of small-diameter lithium carbonate crystals in the supernatant of the thickener, but also results in a wide particle size distribution of the lithium carbonate crystals obtained from solid-liquid separation; 2. The thickening process is time-consuming and inefficient; 3. The decomposition of lithium bicarbonate in the thermal precipitation tank involves the spontaneous formation of crystal nuclei. This process is highly random and inefficient, easily forming a large number of fine crystal nuclei. Lithium carbonate crystals easily form micron- or even nano-sized grains, making filtration and washing difficult. The small grains have a large specific surface area and easily adsorb Na from the mother liquor. + K + SO4 2- Impurities such as these affect product purity, necessitate more washing cycles, exacerbate lithium loss, and impact the processing performance of downstream cathode materials and the electrochemical performance of the battery. Utility Model Content

[0005] This invention provides a lithium carbonate carbonation pyrolysis device, which solves the technical problems of low pyrolysis efficiency and difficulty in controlling crystal particle size in the lithium carbonate carbonation pyrolysis process. It allows the mother liquor from solid-liquid separation to carry small-diameter extracts into the pyrolysis process as seed crystals, which not only increases the crystal particle size of the pyrolysis reaction, but also improves the concentration sedimentation efficiency.

[0006] A lithium carbonate carbonization thermal precipitation apparatus includes a carbonization tank, a thermal precipitation tank, a thickener, and a solid-liquid separator connected in sequence. The mother liquor outlet of the solid-liquid separator is connected to the inlet of the thermal precipitation tank through a mother liquor pipeline, and the mother liquor pipeline is used to introduce the mother liquor into the thermal precipitation tank.

[0007] In one specific embodiment of this utility model, a solid-liquid separation mother liquor tank is provided on the mother liquor pipeline between the mother liquor outlet of the solid-liquid separator and the heat treatment tank.

[0008] In one specific embodiment of this utility model, the solid-liquid separation mother liquor tank is equipped with a mother liquor stirrer.

[0009] In one specific embodiment of this utility model, a mother liquor pump is provided at the outlet of the solid-liquid separation mother liquor tank.

[0010] In one specific embodiment of this utility model, a regulating valve is provided at the output end of the mother liquor pump.

[0011] In one specific embodiment of this utility model, the solid-liquid separator is either a centrifuge or a filter press.

[0012] In one specific embodiment of this utility model, the thickener is provided with a supernatant outlet, which is connected to a supernatant tank.

[0013] In one specific embodiment of this utility model, the outlet of the supernatant tank is connected to a supernatant cooling heat exchanger.

[0014] In one specific embodiment of this utility model, the heat treatment tank is equipped with a heat treatment stirrer.

[0015] In one specific embodiment of this utility model, the carbonization tank is equipped with a carbonization stirrer.

[0016] The beneficial effects of this utility model are:

[0017] 1. This utility model introduces a mother liquor containing small-diameter crystals obtained from solid-liquid separation in a solid-liquid separator into a thermal precipitation tank via a mother liquor pipeline to participate in thermal precipitation, thus solving the problem of low efficiency in thermal precipitation of lithium carbonate carbonization.

[0018] 2. This utility model uses small-diameter crystals in the mother liquor from solid-liquid separation in a solid-liquid separator as seed crystals to participate in the thermal precipitation reaction of lithium carbonate, which can increase the particle size of the thermally precipitated crystals and promote and improve the thickening and settling efficiency of lithium carbonate slurry in a thickener.

[0019] 3. In this invention, the mother liquor of the solid-liquid separator is mixed with lithium bicarbonate and enters the thermal precipitation tank, providing seed crystals for the thermal precipitation reaction. This changes the crystal growth method to induced growth, resulting in crystals with uniform shape and narrow particle size, reducing the formation of fine crystals. Simultaneously, fine crystals in the centrifugal mother liquor do not enter the thickener, reducing the thickener load and improving sedimentation efficiency. The narrower particle size distribution of the thermally precipitated crystals reduces the crystal specific surface area, and Na+ adheres to the crystal surface. + K + SO4 2- When impurities are reduced;

[0020] 4. After implementing the improvements of this utility model, the crystal grain size D10 (cumulative particle size distribution reaches 10%) obtained by the thermal precipitation reaction is 7-8 μm, which is higher than the crystal grain size D10 of spontaneously formed crystal nuclei in the traditional thermal precipitation tank: 5-8 μm.

[0021] 5. The mother liquor from the solid-liquid separation of this invention can avoid directly entering the thickener, thus reducing the load on the concentration meter.

[0022] 6. This utility model uses small-diameter lithium carbonate crystals produced within the device as seed crystals for thermal precipitation, thereby increasing the proportion of large-diameter lithium carbonate crystals in the thickener and improving the efficiency of solid-liquid separation. Attached Figure Description

[0023] Figure 1 This is a schematic diagram of a traditional lithium carbonate carbonation thermal desorption apparatus.

[0024] Figure 2 This is a schematic diagram of the structure of the lithium carbonate carbonation pyrolysis apparatus of this utility model.

[0025] The attached diagram lists the components represented by each number as follows:

[0026] 1. Carbonization tank; 2. Heat exchange tank; 3. Thickener; 4. Solid-liquid separator; 5. Supernatant tank; 6. Supernatant cooling heat exchanger; 7. Solid-liquid separation mother liquor tank; 8. Mother liquor pipeline; 9. Mother liquor pump; 10. Control valve; 11. Mother liquor agitator; 12. Heat exchange agitator; 13. Carbonization agitator. Detailed Implementation

[0027] Example

[0028] like Figure 2 As shown, a lithium carbonate carbonization thermal precipitation apparatus includes a carbonization tank 1, a thermal precipitation tank 2, a thickener 3, and a solid-liquid separator 4 connected in sequence. The mother liquor outlet of the solid-liquid separator 4 is connected to the inlet of the thermal precipitation tank 2 through a mother liquor pipe 8. The mother liquor pipe 8 is used to introduce the mother liquor into the thermal precipitation tank 2 and to use the small-diameter crystals in the mother liquor as seed crystals for the thermal precipitation reaction crystallization.

[0029] It should be noted that excess carbon dioxide is introduced into the lithium carbonate slurry in carbonation tank 1 to react and generate lithium bicarbonate; lithium bicarbonate is thermally decomposed into lithium carbonate crystals in thermal precipitation tank 2, resulting in lithium carbonate slurry containing lithium carbonate crystals; the lithium carbonate slurry is then subjected to sedimentation in thickener 3, and the supernatant is separated to increase the solid content of the lithium carbonate crystals; solid-liquid separator 4 is used for solid-liquid separation of lithium carbonate crystals; since the mother liquor of small-diameter lithium carbonate crystals is returned to thermal precipitation tank 2 through mother liquor pipe 8 as seed crystals, it promotes the increase of the particle size of lithium carbonate crystals generated by thermal precipitation reaction, thereby reducing the proportion of small-diameter lithium carbonate crystals and increasing the proportion of large-diameter lithium carbonate crystals in thickener 3. After solid-liquid separation, the specific surface area of ​​lithium carbonate crystals is small, reducing the washing time and number of times for solid-liquid separation, and also improving the efficiency of solid-liquid separation.

[0030] In some instances, the mother liquor outlet of the solid-liquid separator 4 is also connected to a solid-liquid separation mother liquor tank 7, and the outlet of the solid-liquid separation mother liquor tank 7 is connected to one end of the mother liquor pipeline 8; the solid-liquid separation mother liquor tank 7 is used to collect the mother liquor containing small-diameter lithium carbonate crystals generated by solid-liquid separation.

[0031] In some instances, to prevent small-diameter lithium carbonate crystals from aging and settling in the solid-liquid separation mother liquor tank 7, a mother liquor stirrer 11 is installed in the solid-liquid separation mother liquor tank 7 to ensure that the small-diameter lithium carbonate crystals in the solid-liquid separation mother liquor are suspended and dispersed in the mother liquor.

[0032] In some instances, a mother liquor pump 9 is installed on the mother liquor pipeline 8 to facilitate the input of the solid-liquid separation mother liquor into the hot precipitation tank 2.

[0033] In some instances, to ensure that the carbonized lithium bicarbonate and the seed crystals are mixed in the correct proportion, the output end of the mother liquor pump 9 is equipped with a regulating valve 10, which is used to adjust the mixing ratio of the carbonized lithium bicarbonate solution and the solid-liquid separation mother liquor.

[0034] In some instances, the solid-liquid separator 4 is either a centrifuge or a filter press; preferably, the solid-liquid separator 4 is a centrifuge.

[0035] In some instances, to facilitate the discharge of the supernatant from the thickener 3 system during the thickening process, the thickener 3 is provided with a supernatant outlet, which is connected to a supernatant tank 5 for storing the supernatant discharged from the thickener 3.

[0036] By adding a mother liquor pipe 8 to the inlet of the hot precipitation tank 2, this invention reduces the amount of small-diameter lithium carbonate crystals in the supernatant, thereby extending the cycle of crystal accumulation and recovery at the bottom of the supernatant tank 5 from 2 days / time to 4 days / time.

[0037] It should be noted that the bottom of the thickener 3 is conical, and the supernatant outlet is located on the top side of the thickener 3.

[0038] In some instances, the outlet of the supernatant tank 5 is connected to a supernatant cooling heat exchanger 6 for cooling the supernatant.

[0039] In some instances, a thermal agitator 12 is provided in the thermal precipitation tank 2 to promote thorough mixing of the carbonized lithium bicarbonate solution with the solid-liquid separation mother liquor.

[0040] In other instances, a static mixer may be installed at the inlet of the thermal desorption tank 2 to promote thorough mixing of the carbonized lithium bicarbonate solution with the solid-liquid separation mother liquor.

[0041] It should be noted that the hot precipitation tank 2 is equipped with a heating jacket or heating coil to heat lithium bicarbonate to react and generate lithium carbonate crystals; a mother liquor heat exchanger can be installed on the mother liquor pipeline 8 to heat the solid-liquid separation mother liquor and improve the heating efficiency of hot precipitation; the mother liquor heat exchanger can be the aforementioned supernatant cooling heat exchanger 6 to improve the thermal energy utilization rate of the hot precipitation process.

[0042] In some instances, a carbonation agitator 13 is provided in the carbonation tank 1 to promote the carbonation reaction of lithium carbonate slurry with carbon dioxide to lithium bicarbonate.

[0043] It should be noted that the agitators of carbonization tank 1, hot precipitation tank 2, supernatant tank 5 and solid-liquid separation mother liquor tank 7 are all fixed by brackets, and the agitator shafts of the agitators extend into the interior of carbonization tank 1, hot precipitation tank 2, supernatant tank 5 and solid-liquid separation mother liquor tank 7.

[0044] The working principle of this novel lithium carbonate carbonation pyrolysis device is as follows:

[0045] The centrifuged mother liquor is mixed with lithium bicarbonate and fed into the thermal precipitation tank 2, providing seed crystals for the thermal precipitation reaction. This changes the crystal growth mode to induced growth, resulting in crystals with uniform shape and narrow particle size, reducing the formation of fine crystals. Simultaneously, fine crystals from the centrifuged mother liquor do not enter the thickener 3, reducing the load on the thickener 3 and improving sedimentation efficiency. The narrower particle size distribution of the thermally precipitated crystals reduces the crystal specific surface area, and Na+ adheres to the crystal surface. + K + SO4 2- After impurities are reduced, the pyrolyzed lithium carbonate slurry enters thickener 3 for thickening, and solid-liquid separation is achieved by centrifugation.

Claims

1. A lithium carbonate carbonization pyrolysis apparatus, comprising a carbonization tank (1), a pyrolysis tank (2), a thickener (3), and a solid-liquid separator (4) connected in sequence, characterized in that, The mother liquor outlet of the solid-liquid separator (4) is connected to the inlet of the heat treatment tank (2) through the mother liquor pipe (8), and the mother liquor pipe (8) is used to introduce the mother liquor separated from the solid into the heat treatment tank (2).

2. The lithium carbonate carbonation pyrolysis apparatus according to claim 1, characterized in that: A solid-liquid separation mother liquor tank (7) is provided on the mother liquor pipeline between the mother liquor outlet of the solid-liquid separator (4) and the heat treatment tank (2).

3. The lithium carbonate carbonation pyrolysis apparatus according to claim 2, characterized in that: The solid-liquid separation mother liquor tank (7) is equipped with a mother liquor stirrer (11).

4. The lithium carbonate carbonation pyrolysis apparatus according to claim 2, characterized in that: The outlet of the solid-liquid separation mother liquor tank (7) is equipped with a mother liquor pump (9).

5. The lithium carbonate carbonation pyrolysis apparatus according to claim 4, characterized in that: The output end of the mother liquor pump (9) is equipped with a regulating valve (10).

6. The lithium carbonate carbonation pyrolysis apparatus according to claim 1 or 2, characterized in that: The solid-liquid separator (4) can be any one of a centrifuge or a filter press.

7. The lithium carbonate carbonation pyrolysis apparatus according to claim 1, characterized in that: The thickener (3) is provided with a supernatant outlet, which is connected to the inlet of the supernatant tank (5).

8. The lithium carbonate carbonation pyrolysis apparatus according to claim 7, characterized in that: The outlet of the supernatant tank (5) is connected to a supernatant cooling heat exchanger (6).

9. The lithium carbonate carbonation pyrolysis apparatus according to claim 1, characterized in that: The heat treatment tank (2) is equipped with a heat treatment stirrer (12).

10. The lithium carbonate carbonation pyrolysis apparatus according to claim 1, characterized in that: The carbonization tank (1) is equipped with a carbonization stirrer (13).

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