Low-temperature evaporation and pyrolysis system for lithium bicarbonate solution

Abstract

The utility model discloses a lithium bicarbonate solution low-temperature evaporation pyrolysis system, which belongs to the technical field of lithium carbonate preparation, and comprises a feeding unit, an evaporation crystallization unit, a centrifugal separation unit and a steam treatment unit, and the evaporation crystallization unit is respectively connected with the feeding unit, the centrifugal separation unit and the steam treatment unit; the evaporative crystallization unit comprises a crystallizer, an evaporation chamber communicated with the crystallizer and a forced circulation pump; the steam treatment unit comprises a condenser and a vacuum system. The lithium bicarbonate solution is pyrolyzed by adopting negative-pressure low-temperature pyrolysis, so that the pyrolysis temperature is reduced, on one hand, the energy consumption in the pyrolysis process can be reduced, and the use amount of circulating water in the cooling process is reduced; on the other hand, the pyrolysis temperature is reduced, the solubility of lithium carbonate is increased, and scaling in a pyrolysis system can be reduced.

Description

Technical Field

[0001] This invention belongs to the field of lithium carbonate preparation technology and relates to a low-temperature evaporation pyrolysis system for lithium bicarbonate solution. Background Technology

[0002] Lithium carbonate is the most important lithium salt among lithium compounds and a major raw material for preparing other high-purity lithium compounds and lithium alloys. As a core raw material for lithium-ion batteries, battery-grade lithium carbonate (purity ≥99.5%) is used to prepare cathode materials such as lithium cobalt oxide and ternary materials. Its high energy density (170mAh / g) and thermal stability support the development of new energy vehicles and energy storage systems. Lithium carbonate also has wide applications in industrial manufacturing. Glass and ceramics industry: Lithium carbonate can be used to manufacture high borosilicate glass and high-temperature stable ceramics, improving the strength, thermal stability, and optical properties of glass and ceramics. Metallurgical industry: In the aluminum smelting process, lithium carbonate can be used as an additive in the electrolytic bath and can also be used to produce aluminum-lithium alloys, significantly improving the mechanical properties and corrosion resistance of the metal, enabling aluminum alloys to be more widely used in aerospace and other fields. Lithium carbonate can be used to produce acoustic-grade single crystals and optical-grade single crystals, and also has applications in synthetic rubber, dyes, semiconductors, military and defense industries, televisions, and atomic energy.

[0003] Lithium carbonate preparation methods can be categorized according to the source of its raw materials: lithium ore preparation, brine preparation, and other methods. Lithium ore preparation methods can be further divided into spodumene sintering and sulfuric acid processes, while brine preparation methods can be further divided into precipitation, adsorption, extraction, membrane separation, and other methods.

[0004] CN110656239B discloses an extraction-back-extraction separation and purification method for lithium extraction, comprising the following steps: (1) using an extraction system containing a composite extractant, extracting and separating a lithium-containing solution under pH = 10-13 conditions to obtain a lithium-loaded organic phase; (2) subjecting the lithium-loaded organic phase obtained in step (1) to gas-liquid-liquid three-stage back-extraction to obtain a lithium-loaded back-extraction solution; (3) subjecting the back-extraction solution obtained in step (2) to heat treatment and separation to obtain a lithium product and a separated mother liquor.

[0005] CN118724028A discloses a method for preparing lithium carbonate using lepidolite, comprising: S1, mixing lepidolite with sulfate, and sequentially calcining, grinding, drying, and countercurrent leaching to obtain a lepidolite leachate; S2, mixing the lepidolite leachate with water in a set ratio and adding calcium hydroxide to obtain a mixed solution; S3, filtering calcium and magnesium ions from the mixed solution; S4, mixing the mixed solution obtained in step S3 with a lithium extraction organic extractant, and then extracting to obtain a lithium-loaded extractant; S5, mixing the lithium-loaded extractant with water and washing to obtain a clean lithium-loaded extractant; S6, combining the lithium-loaded extractant obtained in step S5 with water and carbon dioxide, and then back-extracting to obtain a lithium bicarbonate solution; S7, removing oil and calcium and magnesium ions from the lithium bicarbonate solution with resin, then pyrolyzing the pyrolysis solution, and then centrifuging to obtain lithium carbonate.

[0006] CN118754166A discloses a method for leaching battery-grade lithium carbonate. The preparation steps include: (1) grinding lithium mica into powder, sieving, keeping the sieved powder at 600°C for 2 hours in a mixed atmosphere of hydrogen and argon, cooling, adding potassium fluoride powder, calcining, leaching with sulfuric acid solution, and separating the solid and liquid to obtain leaching solution and leaching residue; (2) adding C-undecylcathoxyresorcinol[4]hydrocarbon resorcinol and valamicin dimethyl sulfoxide composite solution to the leaching solution, adding anhydrous sodium carbonate to obtain crude lithium carbonate; (3) adding the crude lithium carbonate to deionized water, stirring evenly to form a suspension, passing carbon dioxide gas through, filtering to obtain clear liquid, evaporating and crystallizing the clear liquid in an evaporating dish at 80°C to obtain the battery-grade lithium carbonate.

[0007] CN119911941A discloses a novel process for preparing battery-grade lithium carbonate from lithium precipitation mother liquor, comprising: mixing quicklime and lithium precipitation mother liquor to adjust alkali and remove fluoride; filtering calcium ions from the mixture, calcining the filtered calcium slag, and then adding quicklime and carbon dioxide; mixing the obtained filtrate with an organic extractant for extraction; washing the obtained loaded organic phase with pure water; back-extracting the obtained washed loaded organic phase; degreasing the obtained back-extract; passing the degreased back-extract through a resin to remove calcium; and pyrolyzing the obtained back-extract and filtering and drying it to obtain battery-grade lithium carbonate.

[0008] Lithium carbonate aqueous solution can be converted into lithium bicarbonate upon the introduction of carbon dioxide. Lithium bicarbonate is unstable and exists only in solution. Heating the lithium bicarbonate solution precipitates lithium carbonate. This reversible reaction is used in lithium carbonate purification processes. The existing technical solutions all ultimately obtain lithium carbonate through the pyrolysis of lithium bicarbonate solution. In current solutions, the pyrolysis of lithium bicarbonate solution is carried out under normal pressure at a temperature of approximately 90°C. This high pyrolysis temperature leads to high energy consumption, requiring a large amount of circulating water for cooling after pyrolysis. Simultaneously, the solubility of lithium carbonate decreases with increasing temperature, and high-temperature pyrolysis easily leads to scaling in the pyrolysis vessel. There is an urgent need to improve the pyrolysis system of lithium bicarbonate solution to solve these technical problems. Summary of the Invention

[0009] The purpose of this invention is to provide a low-temperature evaporation pyrolysis system for lithium bicarbonate solution. This system employs negative pressure and low-temperature pyrolysis of the lithium bicarbonate solution, lowering the pyrolysis temperature. This reduces energy consumption during the pyrolysis process and decreases the amount of circulating water used for cooling. Furthermore, the lower pyrolysis temperature increases the solubility of lithium carbonate, which helps reduce scaling within the pyrolysis system and results in larger lithium carbonate solid crystals. The pyrolysis system provided by this invention is applicable whether preparing lithium carbonate from various raw materials such as brine, lithium ore, or spent lithium batteries, or from the purification of crude lithium carbonate to produce high-purity lithium carbonate, as long as the final product is lithium carbonate obtained through the pyrolysis of lithium bicarbonate solution. This invention achieves its purpose through the following technical solutions.

[0010] A low-temperature evaporation pyrolysis system for lithium bicarbonate solution includes a feeding unit, an evaporation and crystallization unit, a centrifugal separation unit, and a steam treatment unit. The evaporation and crystallization unit is connected to the feeding unit, the centrifugal separation unit, and the steam treatment unit, respectively. The evaporation and crystallization unit includes a crystallizer, an evaporation chamber connected to the crystallizer, and a forced circulation pump. The steam treatment unit includes a condenser and a vacuum system. The low-temperature evaporation pyrolysis system for lithium bicarbonate solution provided by this invention maintains the pressure in the evaporation chamber at 20-90 kPa through the vacuum system, enabling the pyrolysis of lithium bicarbonate solution at low temperatures (40-70℃), reducing energy consumption, and avoiding scaling caused by high temperatures. The forced circulation pump partially circulates the lithium bicarbonate solution and the pyrolyzed lithium carbonate slurry within the evaporation chamber and the crystallizer, ensuring complete pyrolysis of lithium bicarbonate and achieving continuous production.

[0011] Furthermore, the vacuum system includes at least one of a water ring pump, a screw vacuum pump, or a Roots blower. The vacuum system provides a stable negative pressure environment, reducing the pyrolysis temperature and accelerating the decomposition of lithium bicarbonate.

[0012] Furthermore, the outlet of the forced circulation pump is connected to the bottom of the crystallizer, forming a closed circulation loop.

[0013] Furthermore, the vacuum system outlet is connected to a carbon dioxide compression and recovery device to achieve closed-loop CO2 circulation, thereby reducing raw material costs and carbon emissions.

[0014] Furthermore, the liquid phase outlet of the condenser is connected to a condensate recovery pipe, allowing the condensate to be reused and reducing production costs.

[0015] Furthermore, the evaporation crystallization unit uses a multi-effect evaporator or an MVR compressor to provide a heat source, thereby further reducing energy consumption.

[0016] Furthermore, the feeding unit includes an oil removal device and a calcium and magnesium removal device to prevent impurities from interfering with the pyrolysis crystallization process and affecting product purity.

[0017] This invention has the following beneficial technical effects: lowering the pyrolysis temperature reduces energy consumption in the pyrolysis process and decreases the amount of circulating water used in the cooling process; furthermore, lower pyrolysis temperature increases the solubility of lithium carbonate, which helps reduce scaling in the pyrolyzer and forms larger solid lithium carbonate crystals; it is highly applicable, suitable for preparing lithium carbonate from various raw materials such as brine, lithium ore, and waste lithium batteries, as well as for purifying crude lithium carbonate to prepare high-purity lithium carbonate, as long as lithium carbonate is ultimately prepared by pyrolysis of lithium bicarbonate solution. Attached Figure Description

[0018] Figure 1 This is a schematic diagram of the main components of a low-temperature evaporation pyrolysis system for lithium bicarbonate solution provided by this utility model.

[0019] Figure reference numerals: 1-Crystallizer, 2-Evaporation chamber, 3-Forced circulation pump, 4-Condenser, 5-Vacuum system. Detailed Implementation

[0020] The technical solution of this utility model will now be clearly and completely described with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of this utility model, and not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of this utility model without creative effort are within the protection scope of this utility model.

[0021] In the description of this utility model, it should be understood that the terms "center," "longitudinal," "lateral," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," and "outer," etc., indicating the orientation or positional relationship, are based on the orientation or positional relationship shown in the accompanying drawings and are only for the convenience of describing this utility model and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this utility model. Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance, quantity, or position.

[0022] In the description of this utility model, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "joining" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this utility model according to the specific circumstances.

[0023] A low-temperature evaporation pyrolysis system for lithium bicarbonate solution, the main components of which are structured as follows: Figure 1 The diagram shows a feeding unit (not shown), an evaporation and crystallization unit, a centrifugal separation unit (not shown), and a steam treatment unit. The evaporation and crystallization unit is connected to the feeding unit, centrifugal separation unit, and steam treatment unit. The evaporation and crystallization unit includes a crystallizer 1 with an internal heat exchanger, an evaporation chamber 2 connected to the crystallizer, and a forced circulation pump 3. The steam treatment unit includes a condenser 4 and a vacuum system 5. The outlet of the forced circulation pump 3 is connected to the bottom of the crystallizer 1, forming a closed loop. The outlet of the vacuum system 5 is connected to a carbon dioxide compression and recovery device, and the liquid phase outlet of the condenser 4 is connected to a condensate recovery pipe. The feeding unit includes an oil removal device and a calcium and magnesium removal device to prevent impurities from interfering with the pyrolysis crystallization process and affecting product purity.

[0024] The working process of the low-temperature evaporation pyrolysis system for lithium bicarbonate solution provided by this utility model is as follows: The feeding unit continuously feeds the lithium bicarbonate solution, after removing oil and calcium / magnesium, into the evaporation chamber 2. Inside the evaporation chamber 2, the lithium bicarbonate solution is heated to 40-70°C, while the vacuum system 5 maintains the pressure inside the evaporation chamber 2 at 20-90 kPa. Under the above temperature and pressure, the lithium bicarbonate undergoes low-temperature pyrolysis, generating lithium carbonate slurry and a CO2-containing gas phase. The lithium carbonate slurry is continuously collected by the forced circulation pump 3 and enters the crystallizer 1. A portion of the collected slurry returns to the evaporation chamber 2, while the remainder enters the centrifugal separation unit for liquid-solid separation to obtain the lithium carbonate product. The CO2-containing gas phase enters the condenser 4, where the water vapor condenses to form condensate, which enters the condensate recovery pipe. The CO2 gas enters the carbon dioxide compression and recovery device.

[0025] Although embodiments of the present invention have been shown and described above, it is understood that these embodiments are exemplary and should not be construed as limiting the present invention. Those skilled in the art can make changes, modifications, substitutions, and alterations to the above embodiments within the scope of the present invention without departing from its principles and spirit. The scope of protection of the present invention is defined by the claims and their equivalents.

Claims

1. A low temperature evaporation pyrolysis system for lithium bicarbonate solution, characterized in that, The system comprises a feeding unit, an evaporative crystallization unit, a centrifugal separation unit and a steam treatment unit, the evaporative crystallization unit is connected with the feeding unit, the centrifugal separation unit and the steam treatment unit respectively; the evaporative crystallization unit comprises a crystallizer, an evaporation chamber communicated with the crystallizer and a forced circulation pump; the steam treatment unit comprises a condenser and a vacuum system.

2. A system for the low temperature evaporation and pyrolysis of a lithium bicarbonate solution according to claim 1, wherein, The vacuum system comprises at least one of a water ring pump, a screw vacuum pump or a Roots blower.

3. A system for the low temperature evaporation and pyrolysis of a lithium bicarbonate solution according to claim 1, wherein, The outlet of the forced circulation pump is communicated with the bottom of the crystallizer to form a closed circulation loop.

4. A system for the low temperature evaporation and pyrolysis of a lithium bicarbonate solution according to claim 1, wherein, The outlet of the vacuum system is connected with a carbon dioxide compression recovery device.

5. A system for the low temperature evaporation and pyrolysis of a lithium bicarbonate solution as claimed in claim 1, wherein, The liquid phase outlet of the condenser is connected with a condensate water recovery pipe.

6. A system for the low temperature evaporation and pyrolysis of a lithium bicarbonate solution according to claim 1, wherein, The evaporative crystallization unit adopts multi-effect evaporation or an MVR compressor to provide a heat source.

7. A system for the low temperature evaporation and pyrolysis of a lithium bicarbonate solution according to claim 1, wherein, The feeding unit comprises an oil removal device and a calcium and magnesium removal device.

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